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The Europhysical Conference on Defects in Insulating Materials, organized in the period 12–16 July 2010 in Pécs, Hungary by the Research Institute for Solid State Physics and Optics, Budapest and the Institute of Physics of the University of Pécs, was the 11th European conference in the alternate series of EURODIM and ICDIM. The first meeting in Argonne, USA in 1956 was dedicated to the field of color centers in alkali halide crystals. Since then the topic has been gradually extended to the real structure of oxides, halides, nitrides and other more complex insulators, and also to less ordered materials like glasses, ceramics and low-dimensional systems, as well as applications e.g. in radiology, non-linear optics, photonics and electronics. Recently the field covered includes the research and technology of defect-related phenomena in crystalline and amorphous wide band-gap bulk, layered and nano-materials.

More than 200 colleagues from 31 countries in Europe, Asia, Africa and the Americas have participated in the conference. The program contained in addition to seven invited and three keynote talks 67 further oral presentations as well as some 200 poster contributions.

The city of Pécs, a pearl of the Southern Danubia region, was proud of hosting the conference as one of the 2010 European Capitals of Culture, this status crowning a long urban history dating back to paleochristian times in the Roman province Pannonia.

On behalf of the Organizing Committee

László Kovács Conference Chair

Conference Chair László Kovács Crystal Physics Department Research Institute for Solid State Physics and Optics Budapest, Hungary e-mail: eurodim2010@optics.szfki.kfki.hu Program Committee Gábor Corradi (Hungary) István Földvári (Hungary) Rob A. Jackson (UK) László Kovács (Hungary) Martin Nikl (Czech Republic) Anna Vedda (Italy) Andrea Watterich (Hungary) International Advisory Committee

All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Controlling the conductivity of wide-band-gap semiconductors is key to enabling applications in electronics and optoelectronics. Many oxides exhibit unintentional n-type conductivity, and oxygen vacancies have been widely discussed as the source of this conductivity. Based on first-principles investigations we have shown that this cannot be true in ZnO and SnO₂. We suggest that the conductivity is due to unintentional incorporation of donor impurities, with hydrogen being a likely candidate. Both interstitial and substitutional hydrogen act as shallow donors in a number of oxides. The atomic and electronic structures of these centers is discussed.

Transparent conducting films are rapidly emerging as one of the most promising applications of carbon nanotubes. In these less-than-perfect materials, understanding the types of defects and their effect on the transport and optical properties plays a significant role. In this contribution, we present examples of these effects, both beneficial and adverse.

The defect formation energies of various possible defect complexes in stoichiometric LiNbO₃ are calculated and the dominant defects are predicted based on their relative stabilities. The atomistic structure of one type of ferroelectric domain wall is discussed and the width of the domain wall is identified. Based on the analysis of polarization components normal to and transverse to the domain wall plane, it is found that domain walls exhibit Bloch and Neel like characteristics. Point defects are found to have lower formation energies at domain wall. Therefore, domain walls can be considered as trap sites of point defects.

Titanium dioxide is one of the most important oxides for applications in energy and environment, such as solar cells, photocatalysis, lithium-ion batteries. In recent years, new forms of titanium dioxide with unusual structure and/or morphology have been developed, including nanocrystals, nanotubes or nanowires. We have studied in detail the point defect chemistry in nanocrystalline TiO₂ powders and ceramics. There can be a change from predominant Frenkel to Schottky disorder, depending on the experimental conditions, e.g. temperature and oxygen partial pressure.

We have also studied the local environment of various dopants with similar ion radius, but different ion charge (Zn²⁺, Y³⁺, Sn⁴⁺, Zr⁴⁺, Nb⁵⁺) in TiO₂ nanopowders and nanoceramics by Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy. Interfacial segregation of acceptors was demonstrated, but donors and isovalent ions do not segregate. An electrostatic "space charge" segregation model is applied, which explains well the observed phenomena.

We have recently described a novel method for the construction of a solid-state optical frequency reference based on doping ²²⁹Th into high energy band-gap crystals [1]. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we have argued that the ²²⁹Th optical nuclear transition may be driven inside a host crystal resulting in an optical frequency reference with a short-term stability of 3 × 10⁻¹⁷ < Δf/f < 1 × 10⁻¹⁵ at 1 s and a systematic-limited repeatability of Δf/f ∼2 × 10⁻¹⁶. Improvement by 10² – 10³ of the constraints on the variability of several important fundamental constants also appears possible. Here we present the results of the first phase of these experiments. Specifically, we have evaluated several high energy band-gap crystals (Th:NaYF, Th:YLF, Th:LiCAF, Na₂ThF₆, LiSAF) for their suitability as a crystal host by a combination of electron beam microprobe measurements, Rutherford Backscattering, and synchrotron excitation/fluorescence measurements. These measurements have shown LiCAF to be the most promising host crystal, and using a ²³²Th doped LiCAF crystal, we have performed a mock run of the actual experiment that will be used to search for the isomeric transition in ²²⁹Th. This data indicates that a measurement of the transition energy with a signal to noise ratio (SNR) greater than 30:1 can be achieved at the lowest expected fluorescence rate.

Positron annihilation lifetime spectroscopy was conducted for a synthetic saponite to investigate hydration and dehydration behaviour occurring in nanoscale interlayer spaces. Long positron lifetime of ∼ 24 ns was observed with the intensity of ∼ 8 % when the sample is evacuated at ∼ 10⁻⁵ Torr. The radius of open nanospace evaluated from the positron lifetime is ∼ 10 Å, which corresponds to the interlayer spaces of saponite. The open nanospace increases up to 13 % after baking at 423 K for 8 h under the vacuum. The present results imply that positron annihilation spectroscopy is powerful tool to investigate hydration and dehydration behavior through the local structural changes in the interlayer spaces of clay minerals.

Measurements of the characteristic luminescence green line family of Tb³⁺ embedded in magnetron sputtered and annealed Al_xIn_1−xN films (0 ≤ x ≤ 1) indicate an intensity maximum at around the composition x_Al = 0.7 (band gap energy 4.1 eV). The results are described by resonant excitation via excitons bound to the Tb atoms starting from the RESI model (Lozykowski and Jadwisienczak, phys. stat. sol. (b) 244 (2007) 2109).

We present a new method to determine the photorefraction (PR) efficiency in doped and undoped LiNbO₃ (LN) crystals. For this we study the activation of forbidden Raman lines by the nonlinear optical polarization associated with the photorefraction (PR) as a function of the wavelength of the exciting laser line. Results are plotted for various LN crystals within the same scale. The change of the PR efficiency can be related to the variations of the optical absorption and conductivity. In Hf-doped LN crystals the dependence of the PR process vs Hf content can be linked to the change in site occupation of Hf ions in the lattice.

The Mary Rose is a 16th century English warship that was sunk in 1545 in Portsmouth harbour, raised in 1982 and is currently being conserved prior to public display in a new custom-built museum. Like many water-logged ships the Mary Rose timbers are subject to the 'sulfur problem', namely the degradation of the wood by sulfuric acid. We are currently exploring the use of nanocrystalline strontium carbonate impregnation to neutralise the acid and to act as an alkaline reservoir to prevent further attack. Here we present some of the preliminary results in the characterisation of the materials and the effect of the treatment.

Single crystalline films (SCF) of Lu₂SiO₅ (LSO) and Lu₂SiO₅:Ce (LSO:Ce) silicates with thickness of 2.5-21 μm were crystallised by liquid phase epitaxy method onto undoped LSO substrates from melt-solution based on PbO-B₂O₃ flux. The luminescence and scintillation properties of LSO and LSO:Ce SCFs were compared with the properties of a reference LSO:Ce and LYSO:Ce crystals. The light yield (LY) of LSO and LSO:Ce SCF reaches up 30 % and 145 %, respectively, of that of a reference LSO:Ce crystal under excitation by α-particles of ²⁴¹Am source (5.5 MeV). We found that the luminescence spectrum of LSO:Ce SCF is red-shifted with respect to the spectrum of a reference LSO:Ce crystal. Differences in luminescence properties of LSO:Ce SCF and single crystal are explained by the different distribution of Ce³⁺ over the Lu1 and Lu2 positions of LSO host and are also due to Pb²⁺ contamination in the former.

This paper reports the results of investigation of luminescence and energy transfer processes in pure and Ce-, Gd- doped SrAlF₅ single crystals by means of time-resolved UV-VUV and XUV luminescence spectroscopy. Reliable evidence of self-trapped exciton (STE) formation was found. The complexity of STE emission and excitation bands points to the presence of several non-equivalent sites where excitons can localize. At temperatures above ∼150 K the STE emission is quenched, probably due to higher mobility and increasing probability of their interaction with defects. The role of the energy transfer of Ce³⁺ ions with lattice defects at different temperatures is discussed. For Gd³⁺:SrAlF₅ crystal no effective direct excitation of the characteristic 3.97 eV Gd³⁺ emission was found. Instead, a new PL band at 5.6 eV was revealed, which can be excited through ⁸S_7/2 - ⁶G transitions in the 4f⁷ configuration of Gd³⁺. This phenomenon is tentatively explained by high probability of energy transfer from gadolinium to nearby defects. However, efficient excitation of the characteristic Gd³⁺ emission in the range of 7-11 eV points to resonant energy transfer from growth defects to the dopants in the same manner as proposed for Ce³⁺, and this process populates directly the ⁶P_7/2 level of Gd³⁺ from which emission takes place.

Single crystalline Sc, Pr, Ce co-doped Lu₃Al₅O₁₂ garnet layers were grown by liquid phase epitaxy. The Sc doping increases the scintillation response of Pr³⁺ activator ions because of overlap of the Sc-related emission around 275 nm with the 4f→5d absorption band of Pr³⁺ centers. The radioluminescence (RL) spectra give evidence for presumed energy transfer form Sc³⁺ to Pr³⁺ activator ions. Significant increase of the RL emission output was observed when co-doping with both Pr and Sc ions compared to Sc-free samples. The maximum integral RL was noticed for samples with relatively high Sc concentration, 1.2 - 3 at %. On the contrary, an increase of the photoelectron yield, N_phe, measured under alpha particle excitation, was observed only for rather low Sc content, ∼0.6 at %, at higher Sc concentrations N_phe decreased. Nevertheless, LuAG epitaxial layers with optimal Sc and Pr contents show comparable or even a bit higher N_phe yield and energy resolution than Cz-grown Pr:LuAG single crystals. Furthermore, the slow components in photoelectron response were significantly suppressed in epitaxial layers compared to single crystals.

The most important challenge on the way to optimized solar cells is to make the thickness of the individual layers smaller than the diffusion length of the charge carriers, in order to keep the collection efficiency close to unity. Here, we propose β-SiC microcrystals grown by a sol-gel based process as a promising acceptor material. The samples are characterized by optical spectroscopy and electron paramagnetic resonance (EPR). With the help of band structures for selected surface states calculated in the framework of density functional theory (DFT) a possible scenario for the observed acceptor process is discussed.

This paper is a continuation of a comprehensive modelling study of rare earth doping in the KYF family of fluoride materials (KYF₄, KY₃F₁₀ K₂YF₅ and K₃YF₆). The morphology of the materials is predicted from surface energies, and substitution energies of rare earth dopants in the bulk material and at the dominant surfaces are used to calculate segregation energies, allowing conclusions about dopant segregation to be made.

The geometry of the most stable configuration of OH⁻ defects in nearly stoichiometric, hydrogen-contaminated, LiNbO₃ has been determined from first principles theoretical calculations. In the most stable configuration the proton is located near a bisector of an oxygen triangle and is tilted by 4.3 degrees out of the oxygen plane towards a lithium vacancy. The equilibrium length of the OH⁻ bond has been found to be 0.988 Å.

The paper presents the results of a study of the formation and decay of lattice defects in wide band-gap optical crystals of LiB₃O₅ (LBO), Li₂B₄O₇ (LTB) and Li₆Gd(BO₃)₃ (LGBO) with a sublattice of mobile lithium cations. By means of thermoluminescence techniques, and luminescent and absorption optical spectroscopy with a nanosecond time resolution under excitation with an electron beam, it was revealed that the optical absorption in these crystals in the visible and ultraviolet spectral ranges is produced by optical hole-transitions from the local defect level to the valence band states. The valence band density of the states determines mainly the optical absorption spectral profile, and the relaxation kinetics is rated by the interdefect non-radiative tunnel recombination between the trapped-hole center and the Li⁰ trapped-electron centers. At 290 K, the Li⁰ centers are subject to thermally stimulated migration. Based on experimental results, the overall picture of thermally stimulated recombination processes with the participation of shallow traps was established for these crystals.

The advanced optical and electronic characterization of primary F-defects and metallic lithium colloids in lithium fluoride thin films produced by ion-assisted thermal deposition with Xe low-energy ions (< 200 eV) on transparent amorphous substrates is presented and discussed. The volume concentrations of defects and Li nano-clusters have been estimated by applying a best-fit procedure based on a comprehensive theoretical modelling to the spectro-photometric measurements. The appreciable presence of Li metal at the film surface was clearly demonstrated by X-ray photoelectron spectra. Advanced optical microscopy confirms the negligible formation of other types of more complex luminescent colour centres.

Doubly-doped BaY₂F₈:Tm,Nd scintillation crystals were grown by modified micro-pulling-down method. Nd co-doping was chosen to enhance the energy transfer from the host lattice to the Nd³⁺ luminescence center via the 5d-levels of Tm³⁺, due to the overlap of Tm³⁺ 5d-4f emission spectrum with the Nd³⁺ 4f-5d absorption. The energy transfer was clearly evidenced in the BaY₂F₈:Tm,Nd. This process is not complicated by an energy migration to killer centers and/or cross-relaxation. The radioluminescence process is complicated by an energy transfer from the host lattice exciton states to the lower f-levels of Tm³⁺ ion.

The investigation of luminescent and scintillation properties of ⁶Li₂0-MgO-SiO₂-Ce fibers is presented. The probable mechanisms of energy transfer to activator centers are discussed. The estimation of fibers absolute scintillation efficiency was implemented. The modeling of neutron registration efficiency in substitution of monocrystalline detector by a fiber one was carried out.

We used gamma spectroscopy to study scintillation properties of the Pr³⁺-doped lutetium aluminium garnet material (LuAG:Pr). Characteristics of LuAG:Pr optical ceramic samples (0.5-5 mol % Pr³⁺ content) are compared with those of LuAG:Pr single crystal. N_phels photoelectron yield of Pr³⁺-doped optical ceramic samples reaches up to 30-40 % of that of LuAG:Pr crystal, while their energy resolution values are closer. Non-proportionality effect in optical ceramic samples is noticeably smaller with respect to single crystal below 500 keV.

Phonon spectra of BaCl₂ and BaBr₂ nanocrystals in fluorochloro- and fluorobromozirconate glasses were analyzed by Raman spectroscopy. The spectra coincide well with those from orthorhombic phase BaCl₂ and BaBr₂ bulk single crystals. Phonon frequencies for orthorhombic BaCl₂ and BaBr₂ were calculated from first-principles; a good agreement between the theoretical and the experimental data was achieved, showing a deviation of only 5 % at most in both cases.

Si ion implantation was widely used to synthesize specimens of SiO₂ containing supersaturated Si and subsequent high temperature annealing induces the formation of embedded luminescent Si nanocrystals. In this work, the potentialities of excimer UV-light (172 nm, 7.2 eV) irradiation and rapid thermal annealing (RTA) to enhance the photoluminescence and to achieve low temperature formation of Si nanocrystals have been investigated. The Si ions were introduced at acceleration energy of 180 keV to fluence of 7.5 x 10¹⁶ ions/cm². The implanted samples were subsequently irradiated with an excimer-UV lamp. After the process, the samples were rapidly thermal annealed before furnace annealing (FA). Photoluminescence spectra were measured at various stages at the process. We found that the luminescence intensity is strongly enhanced with excimer-UV irradiation and RTA. Moreover, effective visible photoluminescence is found to be observed even after FA at 900 ^oC, only for specimens treated with excimer-UV lamp and RTA. Based on our experimental results, we discuss the effects of excimer-UV lamp irradiation and RTA process on Si nanocrystals related photoluminescence.

The properties of nanocrystalline diamond (NCD) thin films are significantly affected by the defects found in the interfacial regions between the diamond crystallites (in the so called grain boundaries). Dominant sources of these defects are the sp² hybridized carbon atoms that terminate the sp³ diamond lattice and interconnect the neighboring crystallites. The detailed evaluation of these structural units is of great importance for practical applications of NCD. Since sp² hybridized C atoms have high Raman scattering cross-section, Raman spectroscopy could be a valuable method for the determination of bonding configuration of these defects. In this work near-infrared excited Raman spectroscopy and surface-enhanced Raman spectroscopy were used to investigate the sp² structural units in grain boundaries of different NCD thin films.

Electron paramagnetic resonance spectra from substitutional Mn²⁺ ions in quantum dots of cubic ZnS with tight size distribution centred at 2 nm were recorded in the 9.8 GHz and 34 GHz frequency bands. Their quantitative analysis with line shape simulation and fitting computer programs accounting for both forbidden transitions and line broadening effects demonstrate the presence of a local axial distortion attributed to a neighbouring extended planar stacking defect. The presence of such extended lattice defects, confirmed from a high resolution transmission electron microscopy study on presently investigated cubic ZnS quantum dots, seems to be essential in the incorporation and localization of Mn²⁺ activating ions in other cubic II-VI semiconductor quantum dots as well.

X-ray microscopy represents a powerful tool to obtain images of samples with very high spatial resolution. The main limitation of this technique is represented by the poor spatial resolution of standard imaging detectors. We proposed an innovative high-performance X-ray imaging detector based on the visible photoluminescence of colour centres in lithium fluoride. In this work, a confocal microscope in fluorescence mode was used to characterize LiF-based imaging detectors measuring CC integrated visible fluorescence signals of LiF crystals and films (grown on several kinds of substrates) irradiated by soft X-rays produced by a laser plasma source in different exposure conditions. The results are compared with the CC photoluminescence spectra measured on the same samples and discussed.

We investigated the assignments and characteristics of the X-ray-induced colour centres in a silver-activated radiophotoluminescent glass. The induced-absorption spectrum was decomposed into six Gaussian bands, which were, in turn, attributed to the Ag⁺, Ag₃⁺ or Ag₃²⁺, Ag₂⁺, Ag²⁺, Ag⁰ and hole-trap centres, respectively, by means of optical and thermal measurements. All components of the blue and orange radiophotoluminescence (RPL) in a silver-activated phosphate glass were confirmed to be X-ray-induced colour centres. We also proposed and constructed a new readout system for the measurement of the RPL of the glass dosimeter that considers the characteristics of the radiation-induced bands.

Ion implantation proved to be a universal technique for producing waveguides in most optical materials. Tellurite glasses are used as hosts of rare-earth elements for the development of fibre and integrated optic amplifiers and lasers covering all the main telecommunication bands. Er³⁺- doped tellurite glasses are very attractive materials for the fabrication of broadband amplifiers in wavelength division multiplexing (WDM) around 1.55 μm, as they exhibit large stimulated cross sections and broad emission bandwidth. First objective of the present research was to optimise parameters of waveguide fabrication in the Er: tellurite glass via implantation of MeV energy N⁺ ions in a wide range of implanted doses. Besides of glasses, slab optical waveguides were designed and fabricated in CaF₂, Bi₄Ge₃O₁₂ and Bi₁₂GeO₂₀ crystals, also using MeV energy N⁺ ions. Waveguides were characterised using UV/VIS and NIR absorption spectroscopy, spectroscopic ellipsometry and m-line spectroscopy. Part of the implanted samples was annealed to improve waveguide properties. We report on first working slab waveguides fabricated in CaF₂ crystals using implantation of MeV-energy medium-mass ions.

We present time-lapsed microscopy and EXAFS/XANES data on size selected ground ZnS:Cu,Cl and ZnS:Cu,Mn,Cl phosphors to probe long standing problems in using these phosphors in high brightness applications. The time-lapsed study shows that many of the individual emission centers on each particle degrade via large step decreases while < 50% have a monotonic decrease. These large steps suggest a break-up of Cu aggregate centers and this degradation mechanism is likely irreversible. The Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption near Edge Structure (XANES) studies show that during grinding, the CuS precipitates within the ZnS host become highly disordered yet the host material shows no disorder, suggesting that the ZnS:Cu,Cl materials cleave through the CuS precipitates during grinding.

Emission and excitation spectra of CaF₂, SrF₂, BaF₂ doped by PrF₃ were measured in vacuum ultraviolet region at 11 K. Emission spectra of several 5d-4f bands of CaF₂ and BaF₂ show evident vibronic structure with apparent line separated by 400 cm⁻¹ from the main zero phonon line. No such structure was observed in SrF₂-Pr. The absence of vibronic structure in SrF₂ is assumed to be caused by the closeness of a local vibronic frequency to the lattice phonon one.

Excitation spectra of 4f-4f and 5d-4f transitions are substantially different pointing on to the different excitation mechanisms of both groups of lines. The 4f-4f lines show an intense excitation peak adjacent to the exciton peak. This infers that excitons created near to Pr³⁺ ions can feed the 4f-4f transitions. The efficiency of excitation of the 4f-4f and 5d-4f emission bands is quite low in the region of band-to-band transitions. An apparent peak at 19 eV in the excitation spectrum of the BaF₂-Pr 5d-4f emission (230 nm) coincides well with that of the crossluminescence. No similar peaks were observed in CaF₂ or SrF₂ excitation spectra. We conclude that the main channel of energy transfer from the host to Pr³⁺ ions is realized resonantly through crossluminescence in BaF₂-Pr.

Improvement of the response speed during real-time holographic recoding is demonstrated in Ru-doped bismuth sillenite crystal at 1064 nm after green light pre-exposure. By using gating light significant operation speed of 60 ms is achieved.

The efficiency of F and F_n center creation in LiF crystals irradiated with 147 MeV Kr and 195 MeV ions was studied via ion fluence and flux. In the case of Kr ions with flux of 8.9×10⁹ ions/(cm²×s) saturation of F centers (∼ 10¹⁹cm⁻³) was observed at a fluence of 10¹² ions/cm². Further irradiation decrease the F center concentration. In LiF irradiated with both ions an enhancement of electron color centers (F and F_n) via flux was observed. In LiF crystals irradiated with Kr ions an enhancement of F_n centers was observed after thermal annealing up to 600 K. The mechanisms of the processes are discussed.

Biological and synthetic carbonate-containing hydroxyapatites (HAP) were exposed to γ- rays and studied by the electron paramagnetic resonance (EPR) and the electron-nuclear double resonance (ENDOR). Two types of CO₂⁻ radicals - axial and orthorhombic ones - were shown to be the dominating γ-induced paramagnetic centers in the abovementioned materials. The study of metastable radiation-induced centers allowed to identify these defects with molecular ions CO₃³⁻ in B position. The mechanism of CO₂⁻ radical formation was proposed to be CO₃²⁻→ CO₃³⁻→ CO₂⁻.

In the present work the effects produced by Eu³⁺ incorporation into sol-gel silica (doping level range: 0.001-10 mol%) are monitored by means of Fourier transform vibrational spectroscopy in the wave number range 200-3000 cm⁻¹. Complementary microreflectance, TEM, and Raman spectroscopy measurements are also performed. By increasing the Eu³⁺ concentration up to 3 mol%, the intrinsic absorption/reflectance bands related to vibrational modes of O–Si–O groups are gradually modified for what concerns the peak position and intensity, and absorption shoulders attributable to the Eu³⁺ doping appear. At 10 mol% sharp, new, Eu-related peaks grow at the expenses of the intrinsic absorptions. The results can be explained in terms of Eu-rich cluster formation, as also supported by Raman spectra analysis and TEM images. The cluster sizes increase by increasing the Eu³⁺ concentration. Their structure, in which tetrahedral (SiO₄)^4- groups are still present, remains amorphous for Eu³⁺ concentration up to 3 mol%, turning into a nearly ordered arrangement for the higher one. The spectral analysis in the regions of the weaker absorptions due to combination and overtone modes further supports the results and allows to associate the fundamental and overtone frequencies for two modes in Eu³⁺ 10 mol% doped silica. In the framework of the Morse anharmonic oscillator model, the related anharmonicity parameters and binding energies were calculated and found close to those reported for (SiO₄)^4- groups.

Tb³⁺ doped single crystals of huntite-type YAl₃(BO₃)₄ (YAB) have been characterized by means of Fourier transform absorption spectroscopy in the wave number range 500-25000 cm⁻¹ and in the temperature range 9-300 K, and by means of 9 K linear dichroism measurements. Crystal-field splitting of the fundamental ⁷F₆ and of the excited ⁷F₅, ⁷F₄, ⁷F₃, ⁷F₂, ⁷F₁, ⁷F₀, and ⁵D₄ manifolds of Tb³⁺ have been analyzed and fitted within a single ion Hamiltonian model, to obtain free-ion and crystal-field parameters. The electron-phonon interaction has been put into evidence by thermally induced line shift and discussed in the framework of a single phonon coupling model.

LiF:Pb doped crystals were successfully grown by Kyropoulos method, starting with drying powders. The presence of Pb²⁺ ions in the LiF crystals were evidenced by the absorption band at 278 nm and by 375 nm photoluminescence. The presence of some other Pb structures with oxygen compounds in the as made samples was evidenced, decreasing after some annealing procedures. The local environment and valence state of Pb in LiF were studied by X-ray Absorption Spectroscopy at the Pb L_III and L_I edges. XANES data reveal that Pb is present as Pb²⁺ whereas EXAFS data show that it is incorporated in the crystal and not forming PbF₂ precipitates. Identical spectra are obtained for samples as prepared and after thermal annealing up to 650 °C demonstrating the stability of the incorporation site. Also the concentration of Pb in the crystal has no effect on the location site of the metal as the same spectrum is obtained for specimens with different dopant concentrations.

Bismuth tellurite Bi₂TeO₅ (BTO) is a photorefractive crystal with special capability of self-fixing hologram recording. Single crystals of BTO:Tb were grown by the Czochralski technique. Five infrared transitions were identified and analyzed in the high resolution absorption spectra from the ⁷F₆ ground state to the ⁷F₄, ⁷F₃, ⁷F₂, ⁷F₁, and ⁷F₀ manifolds together with their Stark components. The features of the Tb³⁺ transitions are in accordance with the single site Tb substitution to one of the slightly different Bi-site.

The present paper reports characterization of the defects in ultrathin (∼10 nm) oxides grown by low-temperature (850°C) thermal oxidation of hydrogen plasma hydrogenated (100)Si and (111)Si substrates. Electrically active defects, studied by analyzing the frequency dispersion of the capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics are dominated by distinct defects, related to interface traps with different localized energy levels in the Si bandgap, border traps and bulk Si traps. Precursors of the trapping centers are defects in a thin, less dense Si surface region containing voids, which is formed during hydrogenation and is incorporated into the growing oxide layer. Oxidation-induced stress level, evaluated from ellipsometric and electroreflectance data analysis, is in the order of 10⁸ N/m².

Dielectric properties of Sb₂Te₃ films prepared by thermal evaporation technique onto clean glass substrates using ohmic aluminum electrodes have been investigated in the frequency range of 0.01– 100 kHz and within the temperature range of 293K– 373 K. Both the dielectric constant ε₁ and dielectric loss factor were found to depend on frequency and temperature. The activation values were evaluated and good agreement between the activation energy values obtained from capacitance and dielectric loss factor measurements were obtained.

Surface dissolution has been investigated on {100}, {010}, {001}, {110} and {101} oriented Lu_1.6Y_0.4SiO₅:Ce crystal samples by using orthophosphoric acid up to 180°C. Depending on the etching temperature and surface orientation smooth or bunched surfaces were produced. In order to study the effect of the etching process on the scintillation properties temperature dependent optical absorption measurements were carried out up to 236°C. It was found that depending on the post-growth history of the sample, etching may influence the scintillation mechanism by modifying the concentration of shallow traps.

Thin, multiphase Ti-Si-C coatings were formed by IBSD or by IBAD methods on AISI 316L steel substrates in room temperature, using single Ti₃SiC₂ target. In those methods the Ti_XSiC_Y coatings were formed from the flux of energetic atoms and ions obtained by ion sputtering of the Ti₃SiC₂ compound sample. As sputtering beam the beam of Ar⁺ ions at energy of 15keV was applied. In the IBAD method the dynamically formed coatings were additionally bombarded by beam of Ar⁺ ions at energy of 15keV. The ion beams parameters were obtained by using Monte Carlo computer simulations. The morphology (SEM, TEM), chemical (EDS/EDX) and phase composition (XRD) examinations of formed coatings were provided as well as confocal Raman microspectroscopy. Analyzed coatings were relatively thin (150nm-1μm), flat and dense. XRD analysis indicated in amorphous TiSi, the traces of Ti₅Si₃ and other phases from Ti-Si-C system (TiSi, TiSi₂,Ti₃SiC₂). For chemical bonds investigation, the laser beam with length of 532nm was used. Those analyses were performed in the low (LR) or in high (HR) resolution modes in room temperature and in 400⁰C. In the HR mode the spectral resolution was close to 2 cm⁻¹. In Raman spectra peaks at: 152cm⁻¹, 216cm⁻¹, 278cm⁻¹, 311 cm⁻¹, 608cm⁻¹, 691cm⁻¹ were recorded. Nanoindentation tests were done on coated and uncoated substrates with diamond, Berkovich-type indenter. Vickers hardness H_IT and reduced elastic modulus E_IT were calculated using Olivier& Pharr method. H_IT for coated substrates was in the range 2.7 to 5.3 GPa, E_IT was 160 GPa.

We study the influence of annealing temperature on the structural and optical properties of ZnO. Zinc oxide films were prepared by thermal oxidation of metallic Zn films. First, high quality (5N) Zn was evaporated onto sapphire substrate. Then zinc films were annealed in the oxygen atmosphere at several temperatures from 500 ^oC to 1100 ^oC. The surface was analyzed by Scanning Electron Microscopy (SEM) and structural properties were studied by XRD. Photoluminescence (PL) was measured from 350 nm to 800 nm, at two temperatures - 80 K and 300 K. Ordinary PL spectra could be divided into two parts. One band observed at ∼3.3 eV (UV PL) and second at 2.2 – 2.5 (VIS PL as "visible") - the maximum energy depends on annealing temperature. The origin of UV PL is in recombination of free excitons and bound excitons to donors and acceptors [1]. However, for VIS PL exact mechanism of emission recombination is still not fully understood. The main discussion is related to the native defects such as zinc vacancies or oxygen vacancies or oxygen antisite [2] but impurities like Cu [3] and/or hydrogen donors [4] are also candidates. Sample annealing temperature influenced the peak position of VIS PL and intensity of both part of the PL spectrum

Single crystals of Pb₃Ni_1.5Mn_5.5O₁₅ were successfully grown by the high temperature solution growth method. Their composition was determined by energy dispersive X-ray analysis. The phase homogeneity of the grown crystals was examined and confirmed by powder X-ray phase analysis. The structure was characterized by X-ray single crystal diffractometry and was indexed in the trigonal space group P-3c1 (No. 165) with lattice parameters a = 9.9142(2) Å and c = 13.4923(18) Å. The dielectric properties of Pb₃Ni_1.4Mn_5.6O₁₅ were investigated in the temperature range 150 – 500 K. The AC -measurements were carried out for 3 different frequencies: 10 kHz, 100 kHz and 1 MHz. From the DC measurements thermal activation energy was estimated.

The single crystals LiF with copper impurity were grown by Czochralski method. The concentrations of Cu in the crystals were 0,0004-0,002%. In order to determine a copper valence impurity, measurements of the ESR, emission, excitation and absorption spectra were performed. We found emission peak at 410 nm and excitation peak at 250 nm. In agreement with reference, these peaks point to presence of Cu⁺ in our samples. The mechanisms of capture and recombination providing process of thermoluminescence were recognized.

Extended positron-trapping defects in technological modified insulating nanoporous MgAl₂O₄ ceramics are characterized by positron annihilation lifetime spectroscopy. The results are achieved using three-component fitting procedure with arbitrary lifetimes applied to treatment of measured spectra. Within this approach, the first component in the lifetime spectra reflects microstructure specificity of the spinel structure, the second component responsible to extended defects near intergranual boundaries and the third component correspond to ortho-positronium "pick-off" decaying in nanopores of ceramics. It is shown that in ceramics of different technological modifications the same type of positron traps prevails.

A method of performing MD simulations of the local dynamics of 3D nonlinear crystal lattices has been presented, based on the nonlinear integral equations of the atomic motions in the site representation. The method takes into account long-range forces and has been verified on a perfect NaI crystal, where the radiation-produced recoil processes have been investigated. The energy thresholds of the defect formation have been determined to vary from 1.3 eV to 12 eV in dependence of the recoil direction. At lower recoil energies the properties of the created intrinsic localized vibrational modes (ILM) have been studied. A comparison with the traditional methods based on the clusters of nonpolarizable ions has been provided.

The paper presents the results of computer simulation of silicon wafers under scribe loading conditions. Finite Element (FE) analysis was applied to estimate a value of stresses and spread of defect zone around scratch line. It was revealed that due to impact of diamond tip, a complex stress-strain state is produced in the wafer, which is related to the appearance of defect zones in silicon. The approved methods of cutting simulation could be employed for various types of brittle materials to predict defects and damage of crystal during separation processing.

We study the interactions between Mn impurities substituting for different cations in the incipient ferroelectric perovskite SrTiO₃. Using the LSDA+U and many-body perturbation theory, we show that magnetic interactions J between off-centered Mn²⁺_A ions substituting for Sr and inducing ferroelectric instability in the system is negligible. For the nearest neighbours |J_AA/k_B| < 5 K. We show that the interactions involving Mn⁴⁺_B ions substituting for Ti are much larger (J_AA ≪ J_AB ≪ J_BB). The dependence of J_AB on Mn²⁺_A position contributes to magnetoelectricity of the system. These findings are in accordance with recent experimental observations, and provide the key for understanding microscopic mechanisms of magnetoelectricity in manganese doped incipient ferroelectrics.

The results of a computer modelling study of rare earth doping in BMF (BaMgF₄) and YLF (YLiF₄) are presented, both of which are of interest as potential laser materials when doped with rare earth ions. Solution energies are reported, which combine substitution energies with the formation energies of any charge compensating defects, and which enable the preferred substitution site and charge compensation scheme (if needed) to be predicted. Comparison of the results of a range of experimental studies is made, including a study featuring the use of Ce³⁺ doped BMF as a tuneable laser material, where the site adopted by the Ce³⁺ ion is of particular interest.

Effects of β, X, and UV radiation were studied in CaF₂: ZnO single crystals in which ZnO was embedded as nanoparticles. Absorption measurements of these crystals showed a steep increase below 250nm and a weak absorption peak at about 310nm. After prolonged β irradiation, additional absorption bands were recorded at 395 and 595nm. The irradiated samples showed during heating several thermoluminescence (TL) peaks. Samples which had been exposed to β-irradiation at RT and subsequently illuminated at LNT with 390nm light showed during re-heating to RT several TL peaks that are attributed to a process of photo-transferred TL (PTTL). Main photoluminescence (PL) emission bands were recorded at 320 and 340nm with excitation maxima near 250 and 300nm. These emission bands were also observed during X-irradiation as well as additional emission bands near 355 and 400nm. In pre-irradiated samples, a 320nm luminescence band could also be excited by 395nm light and is attributed to a process of photostimulation. The stimulation maxima of the OSL and PTTL in the 390nm region are apparently due to the observed absorption band at 395nm induced by the β-irradiation. The fact that some of the same emission bands appeared in the XL, PL, TL and OSL of this crystal indicates that the same luminescence centers are involved in these emissions.

The present work is devoted to investigation of radiation defects in chromium doped Bi₁₂GeO₂₀ (BGO) single crystals absorbing in the spectral range 0.2...1.1 μm induced under influence of the ²³⁵U ions irradiation with energy 9.35 MeV/u and a fluence 5×10¹¹ cm-². For comparison the changes of absorption spectra during irradiation by light from different sources due as radiation defects creation are studied. The effect of heating in air on the absorption spectrum of irradiated sample is also studied.

The photoluminescence emission around 1.9 eV, excited from the ultraviolet to vacuum ultraviolet was investigated in neutron irradiated silica (at 10²¹ and 10²² n/m² fluences) with different OH and impurity content: KU1 and KS-4V high purity silica and Infrasil 301. The measurements were made at different temperatures from 300K to 10K. The three irradiated silica grades show similar excitation spectra shape, although the band intensities are different depending on silica grade and temperature. Neutron irradiated KU1, with the highest OH content, shows the highest red emission attributed to nonbridging oxygen hole centers (NBOHCs). The excitation profile, from 4.0 to 8.8 eV, has two bands, which are centered around 4.85 eV and 6.5 eV. The band intensities increase with decreasing temperature from 300 to 10K for the three types of silica.

Electron paramagnetic resonance (EPR) studies have been carried out on high purity fused silica KS-4V (low OH content) and KU1 (high OH content), irradiated with fast neutrons (E > 0.1 MeV) at a high fluence of 10²² n/m². The spectrum of irradiated samples shows various well-known types of paramagnetic defects, POR, NBOHC and E'. Their thermal stability has also been studied by heating the samples in air up to 775 °C. A detailed analysis of the spectra shows that the POR spectrum of neutron-irradiated KS-4V and KU1 has two contributions from centres POR(I) and POR(II), which show very different thermal annealing behaviour. POR(I) is identified with the POR centre previously reported, whereas POR(II) is associated to the effects of fast neutrons. Moreover, a new broad line centred at g = 2.02 is reported that we suggest could be associated to oxygen-hole centres in the neighbourhood of the high amount of tracks generated by ion displacement due to fast neutrons.

Optical absorption and photoluminescence spectra were measured on gamma colored lithium fluoride crystals at five different irradiation doses. By accurate Gaussian best-fit procedures of the absorption measurements the peak intensity of F and M bands and the concentrations of F, F₂ and F₃⁺ color centers in gamma irradiated LiF crystals at different doses were obtained. A quadratic relationship between F and F₂ defect concentrations as a function of the irradiation dose was found. Photoluminescence measurements, excited by an Argon laser at 457.9 nm, were used to study the effect of the laser power on the F₂ and F₃⁺ emission spectra of gamma irradiated LiF crystals. The influence of the triplet state on the optical cicle of F₃⁺ color center was highlighted for several excitation laser power and the ratio of the transitions probability W₁ and W₂ to and from the triplet state was derived.

Defect-related instability was studied in γ-irradiated (As₂S₃)_1−x(Sb₂S₃)_x glasses (x = 0, 0.1, 0.2 and 0.3) using positron annihilation lifetime spectroscopy treated within high-measurement statistics. The observed decrease in average positron lifetime in the studied glasses is explained as a renovation of destroyed covalent chemical bonds after irradiation. This process is governed by monomolecular relaxation kinetics, being described in the framework of universal configuration-coordinate model.

The results of investigation of the photoluminescence (PL), its excitation and optical absorption of MgO crystals doped with different concentrations of transition metals exposed to fast neutron irradiation and after annealing are presented. It is suggested that the 440 nm photoluminescence band belongs to the complex V⁻_OH-Fe³⁺ center with tetragonal symmetry, the ∼730 nm PL band observed in the irradiated MgO crystals is connected with defects, generated as a result of decay of the complex V⁻_OH-Fe³⁺ centers. The near infrared luminescence bands in MgO crystals are connected with Fe³⁺-Fe³⁺ exchange coupled pairs.

Effect of radiation-induced physical ageing is investigated by differential scanning calorimetry method in As_xSe_100−x (10 ≤ x ≤ 42) and As_xS_100−x (30 ≤ x ≤ 42) glasses. Obtained results are compared with conventional physical ageing at normal conditions. Significant radiation-induced physical ageing is recorded for glassy As_xS_100−x within 30 ≤ x < 40 range, while As_xSe_100−x glasses from the same compositional interval do not show any measurable changes in DSC curves after γ-irradiation. Observed difference in radiation-induced physical ageing in arsenic-sulfide/selenide glasses is explained by a greater lifetime of γ-induced excitations within sulfur-based network in comparison with selenium-based one.

The photoluminescence spectra of as-grown and chemically reduced nominally pure LiNbO₃ crystals were measured. A powerful laser beam at 514.5 nm was used as pump to generate the small polarons, and a laser weak beam at 632.8 nm was used to probe the luminescence. The dependences of luminescence spectra on the pump beam power and crystal composition have been investigated. The luminescence intensity correlates with the so-called bipolaron absorption band in the chemically reduced crystal. We conclude that this gated luminescence at 800–950 nm is caused by the radiative transitions involving polaron states and it may be directly correlated with the two-color photorefractive sensitivity used for gated holographic recording.

The spectral properties of two-component Ca_1−xSr_xF₂:Ce³⁺(0.05 mol%) (x = 0.75, 0.41, 0.25, 0.14) crystals in UV spectral region were investigated. It was shown that spectral properties of Ca_1−xSr_xF₂:Ce³⁺(0.05 mol%) in UV spectral region have intermediate position between those for pure CaF₂ and SrF₂ crystals. The optical constants were calculated from reflectance spectrum for CaF₂, SrF₂, Ca_1−xSr_xF₂:Ce³⁺(0.05 mol%) (x = 0.75, 0.25) crystals by use of Kramers-Kronig relations for complex reflection coefficient and Fresnel formulas.

Picosecond time resolved photoluminescence (PL) spectroscopy of excitonic processes in MOCVD grown In_xG_1−xN mixed films with the In concentration in range from x=0.1 to 0.18 under the band-to-band excitation are considered. It is stated that by an In content in alloy up to 12% the band-band photo excitation at 8 K results in creating of localized excitons and biexcitons represented by close overlapping Gaussian shape luminescence bands having FWHM 27 and 8.7 meV, respectively. PL decay kinetics of both bands involves two exponential decay stages. Excitons and biexcitons in unperturbed lattice positions causes fast decay with τ∼ 10 ps, whereas their transfer to the metastable state due to relaxation of In – Ga local configuration causes slow decay τ ∼ 90 ps At increased In content up to 19% both the localized excitons and biexcitons are represented by Gaussian type luminescence bands being non-uniform broadened to the high energy side. The continuous distribution of excitons and biexcitons in transition energies is stated by analysis of the red-shift of luminescence bands during the spectra decay. An additional new narrow low energy PL band arises at low energy side expected to be caused by excitons at InN clusters.

We summarize the results of investigation of spectral-kinetic characteristics of the luminescence of F⁺ and F-centers in Al₂O₃, YAlO₃ (YAP) and Y₃Al₅O₁₂ (YAG) crystals under excitation by synchrotron radiation in the transmittance and fundamental absorption ranges of these oxides. We show that the luminescence of F⁺ and F centers in the mentioned crystals can be excited via the corresponding intrinsic 1A→2A, 2B and 3P (F⁺) and ¹S→³P, ¹P (F) transitions of these centers, as well as via the radiative relaxation of excitons localized around F⁺ and F centers. In YAG crystal fast (2.3 ns) emission in the 400 nm band, excited at 3.33, 5.37 and 6.56 eV, arises from the F⁺-type centers, localized around Y_Al antisite defects (ADs). In Al₂O₃ and YAP crystals, the luminescence of excitons localized around F⁺ centers (LE(F⁺) centers) is revealed and the energies of formation of such excitons are determined as well. In YAG crystal the observation of the luminescence of LE(F⁺) centers is obscured due to presence of the large content (∼0.2 at.%) of Y_Al ADs and formation of an excitons localized around Y_Al ADs and dimer F⁺-ADs centers.

The dynamics of the optical damage in the chemically reduced LiNbO₃ has been investigated, when a laser beam is externally focused into a bulk crystal. The temporal evolution of the transmitted power P was recorded, using the closed-aperture pseudo-Z-scan method. We define the three specific levels of the transmitted power that occur at different times during experiment: P₀ and P₁ are the initial and minimal values of the transmitted power during first stage of experiment, when the usual fast rise of optical damage causes decrease of the transmitted power due to laser beam defocusing, while P₂ is the steady-state value after the long-term exposure, when a sequent slow increase of the transmitted power is observed, indicating on the self-compensation of optical damage. This compensation becomes undetectable, when the input light intensity I within focal area is smaller than some specific value ranged from 4 to 90 W/cm² (λ = 644 nm), depending on the chemical reduction degree. At intensities above such a threshold the self-compensation increases monotonically with I.

We work out a simple, pulsed pump-probe measurement scheme to measure the homogeneous linewidth of an atomic transition in an inhomogeneously broadened spectral line in a solid state environment. We apply the theory to the ⁴I_11/2 – ⁴I_15/2 optical transition of erbium in LiNbO₃:Er³⁺ crystal. Beside obtaining the homogeneous linewidth, we have estimated the population relaxation time as well.

In this work we investigate the iron incorporation in thermally diffused Fe doped LN, by combining two experimental techniques, i.e. micro-Raman spectroscopy and proton induced X rays emission. Our results point out that in substituting for Li, Fe ions induces a decrease of Nb_Li antisite defects and rearrangement of the Nb sublattice.

The article presents the study results concerning development of methodology for measuring thermal diffusivity with the laser-flash method with special attention being paid to their repeatability. The first stage involved the literature review of the problem determining an influence of variable measurement parameters including presence of graphite coating, error correction methods and laser power. The main part of the study includes evaluation of the sample structure influence. A real ceramic mould of specific porosity and green compacts made after its grinding were examined. Influence of sample thickness and interval between individual laser shots were also determined. The analysis was performed by using the Netzsch LFA 427 instrument designed for direct measurement of thermal diffusivity with the laser-flash method. The material analysed included different types of ceramic moulds designed for manufacturing the elements made of nickel based superalloys. The preliminary study performed showed that the main factor that has an influence on obtaining correct and repeatable results of thermal diffusivity study is proper preparation of samples i.e. using them in a form of directly cut out from the mould, selection of data acquisition time and interval between individual shots. It is especially important in the case of measurements taken at high temperature when radiation mechanism of heat transfer is of basic significance.

The paper presents test results concerning characteristics of the selected thermal properties of ceramic powders of 8YSZ type on the basis of zirconium oxide modified with yttrium oxide obtained with different methods. The first of the powders was obtained with the spray drying method, the second one was characterized by a structure typical for obtaining methods from liquid phase and the third of the powders was obtained with the grinding method to get maximally broken up powder particles and similar to "nano" type structures. The scope of the tests encompassed thermal diffusivity analysis of the powders in a compressed form within temperature range 25–1500°C, and also tests of specific heat within similar temperature range. Specific heat measurements of the powders showed that the highest values within the entire test temperature range were obtained for the finest grain ("nano-sized") powder. In other two cases, the values obtained were very similar. Analogous results were found in the case of thermal diffusivity measurements. The ground powder was characterized by significantly lower thermal diffusivity value than other two types of powders, which was a result of very strong break-up of particles.

The methods of electron paramagnetic resonance and optically stimulated electron emission have been used to study the conversion of defects in samples of a nanostructured SiO₂ ceramic synthesized by the thermal decomposition of polysilazane H_xC_yN_zSi. The ceramic samples additionally underwent a thermal treatment and were exposed to accelerated electrons.

Different phases of boron nitride (BN) nano-structures are synthesized from an hBN ceramic target immersed in acetone, by ablation with a high power pulsed Nd: YAG laser. Transmission electron microscopy (TEM) and electron diffraction (ED) are used to identify the morphology and structure of the prepared colloidal suspensions. It is revealed that by varying solely a single experimental parameter, i.e. the laser pulse fluency, a large variety of BN nano-structures can be produced: nanotubes, very thin graphene-like foils, nano-curls and nano-particles, all with the hexagonal graphite-like hBN structure, as well as high pressure BN phases: orthorhombic explosion E-BN nano-rods, or cubic diamond-like cBN nano-particles.

In this work, we used Mn²⁺ as a dopant in the oxyfluoride glasses with various fluoride compounds. Electron paramagnetic resonance (EPR) measurements were carried out before and after a heat treatment of the material. In both cases, a well pronounced hyperfine (hf) structure of the EPR spectra characteristic to the Mn²⁺ ion have been observed. EPR measurements have also been studied for the separate fluoride counterparts of the oxyfluoride glasses. EPR spectra of the LaF₃:Mn²⁺ and CaF₂:Mn²⁺ powders show that Mn²⁺ ion has a strong superhyperfine (shf) interaction with surrounding fluorine nuclei, and this shf structure could be observed also in the heat treated glass samples.

Introduction of silver or copper ions in soda-lime silica glass has been investigated by studying the data obtained from optical absorption measurements and the transmission electron microscopy performances. It has been stated that the optical and structural characteristics of the doped specimens are effectively controlled by the dopant concentrations and parameters of both, the ion-exchange procedures and the annealing treatments applied afterwards. By sequential ion exchange of as received specimens in molten baths of Cu₂Cl₂ and (AgNO₃ in NaNO₃), the composition and electronic structure of the elemental-nanoclusters have been altered. Moreover, depending on the order of annealing, different microstructures were created in the fabricated composites. Like this, the two-step exchange determines a new engineering way new materials with desired optical properties could be produced.

Using optical absorption and λ-modulated differential spectroscopy we investigated non-doped and Fe-doped Bi₁₂SiO₂₀ sillenite-type crystals. The obtained results show that the doping increase absorption coefficient of the crystal shifts the absorption edge to lower photon energies, and reduce the absorption shoulder. We find out that the optical absorption spectroscopy is appropriate method for analyzing the photochromic effect, while λ-modulated differential spectroscopy is most suitable for investigation of impurity levels in the band-gap and calculation of Fe³⁺energy levels position.

The dose dependence of the concentration of point defects in alkali-halides as well as other crystals, as exhibited by the dependence of the thermoluminescence (TL), optical absorption and ESR on the dose of non-ionizing UV excitation is studied using numerical simulation. The relevant set of coupled rate equations are first written and plausible sets of trapping parameters are chosen. Instead of using simplifying assumptions previously used for reaching conclusions concerning this dose behavior, exact numerical solutions have now been reached. Depending on the parameters chosen, different dose dependencies are seen. In some cases, linear dose dependence is reached in a broad range. Sublinear dose dependence, close to a D^1/2 dependence when D is the dose of excitation can be reached when retrapping is stronger than trapping in other traps stabilizing the defects. When strong competition between stabilizing traps takes place, an initial linear range is observed followed by strong superlinearity and an approach to saturation. All these behaviors have been observed experimentally in TL measurements as well as ESR and optical absorption in different materials. Similarities and dissimilarities to linear and non-linear dose dependencies obtained experimentally and by simulations when ionizing irradiation is used for excitation are discussed.

The results of investigation of thermally stimulated recombination processes and luminescence in Li₆Gd_xY_1−x(BO₃)₃-Eu crystals are presented. The steady-state luminescence spectra under X-ray excitation (XRL), the temperature dependence of steady-state luminescence intensity and the thermally stimulated luminescence curves (TSL) were measured at 90–500 K. In the steady-state X-ray luminescence spectra the band at 312 nm related to ⁶P_J→⁸S_7/2 transitions in gadolinium ion and bands group at 580–700 nm associated with ⁵D₀→⁷F_J transitions (J = 0...4) in Eu³⁺ ion were found to be dominant. The intensity of steady-state XRL of these bands in undoped crystal is increased by 15 times as the temperature changes from 100 to 400 K. The probable mechanisms of temperature dependence of steady-state luminescence intensity and their association with energy transfer of electronic excitations in these crystals are discussed. The investigations have shown the principle complex TSL peak with maximum at 150 K and a number of weaker peaks. The thermal activation parameters (activation energy, pre-exponential factor, kinetic order) for all intense TSL peak have been determined. The origin of small trapping centres caused TSL below room temperature and their association with defects in lithium cation sublattice is discussed.

Inhomogeneous magnetoelectric effect in magnetization distribution heterogeneities (0-degree domain walls) appeared on crystal lattice defect of the multiferroic material has been investigated. Magnetic symmetry based predictions of kind of electrical polarization distribution in their volumes were used. It was found that magnetization distribution heterogeneity with any symmetry produces electrical polarization. Results were systemized in scope of micromagnetic structure chirality. It was shown that almost all 0-degree domain walls with time-noninvariant chirality have identical type of spatial distribution of the magnetization and polarization.

Ab initio calculations with the RHF/6–311G* basis set are used for geometrical optimization of regular pyramidal and defect quasi-tetrahedral clusters in binary As-S glasses. It is shown that quasi-tetrahedral S=AsS_3/2 structural units are impossible as main network-building blocks in these glasses.

Density functional theory calculations have been performed to investigate the structural and electronic properties for both unrelaxed and relaxed cases of oxygen-doped c-BN(110) surface. Oxygen atom has been substituted in a neutral charge state on both the B site (O_B) and the N site (O_N). Defect formation energies, [unrelaxed (E°_f) and relaxed (E_f)], and relaxation energies, E_r, have been calculated. It has been found that substitution O_N is more probable, moreover the O_N causes an inward relaxation of the first neighbor surface B atom.

Radioluminescence (RL) measurements of three types of silicon carbide, material considered for use in future fusion reactors, have been made to examine the potential of this technique as a possible way to evaluate in-situ the radiation damage during reactor irradiations. RL spectra taken during 1.8 MeV electron irradiation have a strong dependence on SiC type and irradiation time (dose), the intensity decreasing with irradiation dose for all samples. Reported reduction in crystallinity for HP SiC revealed by X-ray diffraction analysis following electron irradiation to 420 MGy, and the marked reduction of the main RL band by 200 MGy may be related, and that RL should be fully examined as a tool for in-situ characterization.

Lithium niobate is a resistant opto-electronic oxide material, which has close similarity with Al₂O₃ and could be a candidate for potential tritium breeding material. In this work we study the possible radiation enhanced release of He from the material and evaluate the potential to use radioluminiscence as a tool to monitor material modification and degradation. Lithium niobate samples were implanted with He⁺ ions at 45 KeV up to 5×10¹⁷ ions/cm², and Then radiation enhanced He desorption measured as a function of temperature and ionizing radiation dose in an experimental set up which permitted one to measure the release of He during 1.8 MeV electron irradiation. Radioluminiscence and optical absorption measurements show that this material is highly resistant to ionizing radiation damage.

The values of initial quantum yield of nitrite under photolysis (253.7 nm) of crystalline RbNO₃ and CsNO₃ were calculated to be 0.006 and 0.016 quantum⁻¹, respectively. Thermal annealing of UV-irradiated samples result in 3-fold decrease in the nitrite quantum yield for RbNO₃ and its 1.5-fold increase for CsNO₃. The mechanism for nitrite formation under photolysis of crystalline alkali nitrates has been discussed.

Hydrogen and tritium defects formed in LiF under the action of neutron radiation under different conditions have been studied. It is shown that U-centers are registered in LiF:OH without additional heating of the sample after irradiation. The behavior of H⁰ and T⁰ atoms in Li⁶ F irradiated at 20 K was studied, and the places of their stabilization were established.

Alumina crystals doped with Yb and Er were obtained by sol gel process and their morphologies and luminescence properties were discussed. Nanocrystals formations composed by Er₂O₃, Yb₂O₃ e Yb₃Al₅O₁₂ were observed by TEM images, EDS, electron beam diffraction and XRD, at the surface of the alumina grains. The size of the nanocrystals were of about (36±2) nm and (182±8) nm for the samples calcinated at 1200^oC and 1600^oC, respectively. The sample codoped with 1mol% of Er and 2 mol% of Yb supplied the best results for Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL). The growth intensity of dosimetric TL peak at 205^oC was linear with gamma radiation doses and the same behavior was observed in OSL results.

Tl⁺-doped lithium fluoride crystals exhibit very interesting properties concerning the formation of colour centres after X-rays irradiation. The presence of Tl⁺ ions, even in small concentrations, increases the number of traps which stabilize the H-centre aggregates. These H-centre aggregates become smaller and their number increases, inducing two sets of trapping levels. Photoluminescence measurements after subsequent thermal bleaching of the thermoluminescence peaks show a faster decreasing of the F₃⁺ centres, in three steps, compared with the F₂ ones. The F-H recombination processes may induce the excitation-emission transitions of Tl⁺-ions.

Relaxation processes in nitrogen-containing Ar solids pre-irradiated by an electron beam are studied with the focus on the interconnection of relaxation channels in system of charged and neutral species. The results of correlated in real time measurements of thermally stimulated phenomena are presented. The experiments have been performed using activation spectroscopy methods – thermally stimulated exoelectron emission (TSEE), spectrally resolved thermally stimulated luminescence (TSL) measured in visible, NUV and VUV ranges. Solid evidence of the charge relaxation cascades triggering via radiative recombination of neutral species is presented.

We measured time-resolved spectra and emission decay times under pulsed X-ray and synchrotron excitation in alkali-earth fluorides doped with Pr³⁺ ions. Two fast decay components were found in the emission spectra of BaF₂-Pr³⁺ and SrF₂-Pr³⁺ . These were 4 ns and 21 ns in BaF₂-Pr³⁺ and 8 and 24 ns in SrF₂-Pr³⁺. The intensity of the faster components 4 ns and 8 ns depended on concentration of Pr³⁺. Thus, the presence of aggregates might be the cause of such faster components.

The aim of the present paper was to investigate micro-scale spatial distribution of tetragonal and monoclinic zirconia phases by simultaneous spatial mapping of zirconia Raman scattering signal and the Sm³⁺ dopant photoluminescence. A set of 4, 8 and 10 mol% Sm³⁺ doped zirconia samples was prepared via scull-melting technique. In two samples (8 and 10 mol% Sm-doped) tetragonally stabilised zirconia is dominating, whereas in the 4 mol% doped samples a specific microscopic scale segregation of both tetragonal and monoclinic phase ZrO₂ was found.

The red emitting Y₂O₂S:Eu³⁺,Ti^IV (or Zr^IV, x_Eu: 0.01, x_Ti/Zr: 0.003/0.015/0.03) materials were prepared with a flux method. According to X-ray powder diffraction, the materials have the hexagonal crystal structure. The UV excited (λ_exc: 250 nm) emission maximum was observed at 628 nm due to the ⁵D₀→⁷F₂ transition of Eu³⁺. The excitation spectra (λ_em: 628 nm) consist of broad bands centered at 240 and 320 nm due to the charge transfer transitions O²⁻→Eu³⁺ and S²⁻→Eu³⁺, respectively. Red persistent luminescence was observed with a maximum at 628 nm, as well. Persistent luminescence was the strongest with the Ti^IV co-doping though the intensity of persistent luminescence decreased with the increasing amount of both the Ti^IV and Zr^IV co-dopants. The thermoluminescence (TL) glow curves of the Y₂O₂S:Eu³⁺,Ti^IV materials consist of bands at ca. 110 and 200 °C. In Y₂O₂S:Eu³⁺,Zr^IV, similar bands are observed at lower temperatures viz. at ca. 100 and 180 °C. TL weakens when the amount of co-dopants is increased. The Ti^IV co-doped materials have stronger TL than the Zr^IV co-doped materials. The deconvolution of TL glow curves revealed three distinct traps with depths ranging from 0.6 to 1.0 eV.

Optical absorption and luminescence spectra of yellow corundum have been analyzed, both in magmatic and metamorphic materials, looking at the role of localized electronic transitions of transition metal ions at substituted Al sites. By the aid of energy dispersed x-ray fluorescence (EDXRF) elemental analysis and electron paramagnetic resonance (EPR) measurements, the results confirm that Fe³⁺ is the dominant impurity ion. However, the results also evidence that Cr³⁺ and Ti³⁺ contribute in determining the optical absorption and emission properties of this variety of gem-quality corundum, as we have recently found in Type 1 blue sapphires of metamorphic origin. Furthermore, preferentially but not exclusively in samples of metamorphic origin, Mn plays a role never evaluated up to now. Here we show how few ppm of Mn – below the detection limit of EDXRF, not revealed in the optical absorption spectra, but barely detected by EPR spectroscopy as Mn²⁺ ion – are active in photoluminescence, showing up with the characteristic emissions of Mn²⁺, Mn³⁺ and Mn⁴⁺.

In the blue colored sapphires of metamorphic origin and Verneuil synthetic studied here, the absorption-emission properties in the VIS-NIR range are largely determined by Cr³⁺ and Ti³⁺, as we have been able to demonstrate recently. In that work a sharp radio-luminescence band occurring at 870 nm in Verneuil blue sapphires was left unattributed: here we give evidence for the attribution of that band to the ²E emission transition of V²⁺, and for the existence of such an emission also in natural samples of metamorphic origin. After such a result, we accurately evaluated by EDXRF the V concentrations in various samples and found the ion more ubiquitous than foreseen. We then searched for and found, weak but diagnostic spin forbidden transitions and phonon sequencies in the absorption spectra of samples sufficiently rich in V. The experimental results just mentioned allowed us to discuss the effects of the overlap of V³⁺ and Cr³⁺ spin-allowed absorption bands on the spectrum of the varieties of corundum under study. To complete the updating of the interpretation, we spent a further effort to strengthen the attribution of the absorption band at 14500 cm⁻¹ (currently interpreted as an IVCT (Fe²⁺ → Fe³⁺)) to the ⁵E→⁵T₂ transitions of Cr²⁺.

The experimental study of relaxation of anion and cation excitons at the selective VUV-(valence) and soft X-ray (inner-shell) excitations for binary BeO crystal and multicomponent oxide crystals Be₂SiO₄, Al₂Be₃Si₆O₁₈ and Y₂SiO₅ is presented. Results show that the relaxation during the time-scale of decay of short-living anion and cation excitations leads to creation of self-trapped excitons at the corresponding low-symmetry (tetrahedral) local structural units of crystalline lattice. This can be caused by increase of dynamical instability of such a local structural units (in comparison with high symmetry ones), which facilitates self-trapping processes in these systems.

It is the aim of this contribution to provide an overview of luminescence spectra and decay characteristics of Nd³⁺, Er³⁺ and Tm³⁺ centers in LiLuF₄ single crystal including possible energy transfer mechanisms towards and away from the Nd³⁺ 5d excited state. Single crystal doped with the mentioned RE ions were prepared by micro-pulling-down technique. Excitation and emission spectra and fast decay kinetics in VUV spectral region are completed with radio-and photoluminescence spectra and decay kinetics in UV-visible region.

Excitation spectra for the 5d → 4f emission of Ce³⁺ ions in CaGa₂S₄ crystals have been measured at 300 K by using vacuum ultraviolet (VUV) photons, together with reflectivity and absorption-edge spectra. X-ray photoelectron spectroscopy (XPS) experiment has also been performed in order to clarify the contribution of shallow core states to the excitation and reflectivity spectra. Furthermore, cluster calculation by a relativistic discrete variational Xα (DV-Xα) method has been carried out to elucidate the optical transitions resulting in the creation of multiple e-h pairs in CaGa₂S₄. The excitation processes of Ce³⁺ ions in CaGa₂S₄ by hot photocarriers are discussed on the basis of the electronic structure determined from the experiments and calculation.

Experiments on co-doped CsI:Tl,Sm suggest that samarium electron traps scavenge electrons from thallium traps and that electrons subsequently released by samarium recombine non-radiatively with trapped holes, thus suppressing afterglow. These experiments support the inference that electrons tunnel freely between samarium ions and are trapped preferentially as substitutional Sm⁺ near V_KA(Tl⁺) centers where non-radiative recombination is the rate-limiting step. Combined radioluminescence, afterglow and thermoluminescence on single-crystal samples of CsI:Tl and CsI:Tl,Sm, recorded sequentially at adjusted gain settings following low-temperature irradiation, reveal reversible radiation damage as well.

Dipole defects in gamma irradiated and thermally treated beryl (Be₃Al₂Si₆O₁₈) samples have been studied using the Thermally Stimulated Depolarization Currents (TSDC) technique. TSDC experiments were performed in pink (morganite), green (emerald), blue (aquamarine) and colourless (goshenite) natural beryl. TSDC spectra present dipole peaks at 190K, 220K, 280K and 310K that change after gamma irradiation and thermal treatments. In morganite samples, for thermal treatments between 700K and 1100K, the 280K peak increase in intensity and the band at 220K disappears. An increase of the 280K peak and a decrease of the 190K peak were observed in the TSDC spectra of morganite after a gamma irradiation of 25kGy performed after the thermal treatments. In the case of emerald samples, thermal treatments enhanced the 280K peak and gamma irradiation partially destroyed this band. The goshenite TSDC spectra present only one band at 280K that is not affected either by thermal treatments or by gamma irradiation. All the observed peaks are of dipolar origin because the intensity of the bands is linearly dependent on the polarization field, behaviour of dipole defects. The systematic study, by means of TSDC measurements, of ionizing irradiation effects and thermal treatments in these crystals makes possible a better understanding of the role played by the impurities in beryl crystals.

Although luminescence properties of Pb²⁺ and Ce³⁺ in SrHfO₃ host (SHO) have been recently studied due to various potential applications [1, 2], the mechanism of the Pb²⁺ and Ce³⁺ excited states thermal quenching has not been addressed. Both Pb²⁺ and Ce³⁺ doped SHO microcrystalline powders were prepared by multi-step solid state annealing technique. Radioluminescence and photoluminescence (PL) spectra as well as both the prompt and delayed decay kinetics were investigated in the wide temperature range (10 – 500 K) using the time-resolved luminescence spectrocopy techniques. Temperature dependences (TDs) of PL decay time and PL emission intensity of both Pb²⁺ and Ce³⁺ centres were fit by the fenomenological model. Corresponding excited state characteristics were determined. The innovative method of measuring the TD of intensity of the delayed radiative recombination was employed to better understand the origin of temperature quenching of the Pb²⁺ and Ce³⁺ decay times [3, 4]. The method put in evidence the excited state thermal ionization of both activators in the SHO host. The influence of dopant concentration and suitability of both the Pb and Ce-doped SHO for phosphor and scintillator applications are discussed.

We present numerical study of microcavity biosensor in photonic crystal (PC) with triangular lattice of air holes patterned perpendicularly to an InP-based confining heterostructure. The microcavity is formed by varying the radius of one air hole. The 2D finite difference time domain (FDTD) method algorithm (fullwave simulator) is used to compute the light transmission efficiency and the quality factor (Q) when the refractive index (RI) filled in the air holes of water and polymer. The detected spectrum has a Lorentzian line shape, and the peak occurs when the PC cavity is at resonance. The resonance wavelength of this cavity will shift accordingly due to the variation of RI. The polymer filling of photonic crystal holes can be used to measure gas, fluids, biolayers, or bound chemical.

Pure indium metal was thermally evaporated in the presence of oxygen atmosphere, with partial pressure of 6.6×10⁻² Pa, onto glass substrates and onto C-Cu grid at room temperature. The structural characteristics of these optically transparent and electrically conducting thin films were investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques and the results are discussed on the base of the differences in their morphologies and thicknesses. Cubic In₂O₃ and tetragonal In phases, with crystal structures and lattice parameters as reported in the literature, have been identified in the thinnest film having 100 nm thickness. The tendency for amorphization of the cubic and tetragonal phases becomes evident as the film thickness increases.