Table of contents

In this experiment, an electrochemical deposition process was used for creating GPL-Co-Ni coating. The conclusion of this experiment showed that synthetic coating with the addition of cobalt ions had more graphene deposits. The surface morphology of the coating were characterized by electron microscope (SEM) and super depth of field microscope. GPLs in the composite coating were characterized by Raman spectrometer. The GPL-Ni coating and GPL-Co-Ni coating were characterized by X-ray diffraction (XRD) and the Scherrer equation was used for estimating and comparing the average grain size of the cladding material. The Vickers hardness and electrochemical corrosion tests showed that GPL-Co-Ni coating had better performance in mechanical properties and corrosion resistance relative to GPL-Ni coating. Through comparison and analysis, it was found that the addition of cobalt to the composite coating increased the deposition amount of GPLs on the coating surface, and that the GPL-Co-Ni composite coating has higher microhardness and high-performance in corrosion resistance, compared with the GPL-Ni coating.

This paper presents a unique method to reduce the crosstalk noise, power consumption, power delay product (PDP) and energy delay product (EDP) in coupled multi-walled carbon nanotube (MWCNT) based through silicon vias (TSVs) with polymer liners. A novel structure of TSVs is proposed, where the MWCNT bundles are placed as conducting material and polymer liners are placed as dielectric material. The electrical equivalent model of the proposed TSVs is used and simulated in HSPICE to evaluate the performance. The performance analysis determines that there is a significant improvement in crosstalk noise, power consumption, PDP and EDP for polymer liners such as polyimide, polypropylene carbonate (PPC) and benzocyclobutene (BCB) over the conventional silicon dioxide (SiO₂) liner. Moreover, the performance is also analyzed by varying the pitch between the TSVs from 100 μm to 3000 μm. It is noted that the induced crosstalk noise issues are reduced as the TSV pitch is increased. Similarly, the power consumption, PDP and EDP of the proposed TSVs are also reduced for the high pitch value. From the simulation results, it is observed that the proposed MWCNT TSVs with BCB liner show improvements up to 18.01%, 35.37% and 49.06%, respectively in terms of power consumption, PDP and EDP over the TSVs with SiO₂ liner.

This research is focusing on the geometrical variation effects of carbon nanotube field effect transistor (CNTFET). The characteristics of the CNTFET are observed based on different CNTFET diameter, the oxide thickness and the chiral vector. The characteristics under study includes the drain current, I_ON/I_OFF, the quantum capacitance as well as the threshold voltage. The work is carried out using CNTFET labtool of nanoHUB.org includes the FETToy Simulator which based MATLAB script that calculate the ballistic I-V characteristic and MSL Nanomaterials Simulator that used to design and analyse electronic properties of various nano materials. The results show that small difference of chiral vector, (4, 0) will produce large threshold voltage. The quantum capacitance is observed to be decreased with decreasing oxide thickness as gate voltage reaches 0.5 V and above. The I_ON/I_OFF ratio will increase as the CNTFET diameter increased. As a conclusion, CNTFET is a perfect choice to substitute conventional MOSFET with their remarkable features.

Herein, graphene nanoplatelets (GNPs) are incorporated into carbon electrode to fabricate carbon-based CsPbBr₃ inorganic PSCs with the FTO/TiO₂/CsPbBr₃/carbon configuration. Steady-state photoluminescence and electrochemical impedance spectroscopy measurements indicate that the incorporation of GNPs into carbon electrode remarkably enhances the hole extraction and decreases the interfacial charge recombination in carbon-based PSCs compared with unincorporated one. Consequently, the CsPbBr₃ PSC with GNP (33.3 wt%)-incorporated electrode exhibits much higher photovoltaic performance than the device with pristine carbon electrode with the efficiency being increased from 4.84% to 6.48%. In addition, the excellent long-term stability of PSC with carbon electrode is also measured under ambient condition.

TaO_X is one of the most promising switching materials for resistive random access memory (RRAM) due to its excellent endurance. In this letter, the TaO_X-based RRAM devices with three different electrode structures were designed and fabricated to reduce its operating voltage and improve its uniformity. The ITO/TaO_X/TiN device could maintain more than ∼10⁴ cycles with high uniformity in low operating voltage (the mean voltages of set and reset were 0.036 V and −0.109 V, respectively), which could be attributed to the oxygens-rich property of ITO electrode and the TiON layer (the naturally formed layer when the TiN layer contacted with oxygens). According to X-ray photoelectron spectroscopy (XPS) characterizations and electrical results, a switching mechanism based on oxygen vacancies concentration gradient was proposed to explain the TaO_X-based ultralow operating voltage RRAM device.

Impedimetric D-Xylose and D-Arabinose sensors was development from composite electrodes of graphite and histological paraffin, modified with functionalized multi-walled carbon nanotubes (FMWCNTs) based on molecular imprinted poly-o-phenylenediamine (poly-o-PD). The contribution of this work was not only the development of a D-xylose and D-Arabinose MIP impedimetric sensor with good performance, but also the electrodeposition method for FMWCNTs onto surface of graphite composites electrodes with ease of control and reproducibility of the electrodeposition process. The sensors were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), field emission gun scanning electron microscopy (FEG-SEM) and RAMAN spectroscopy. The MIPs sensors for the pentoses have good selectivity, sensitivity in the concentration range of 1.0 × 10⁻¹¹ to 1.0 × 10⁻¹⁰ mol l⁻¹ with limit of detection (LOD) of 4.50 × 10⁻¹² mol l⁻¹ for D-Xylose and 4.25 × 10⁻¹² mol l⁻¹ for D-Arabinose. MIPs was applied to determination of pentoses in samples of sugarcane bagasse hydrolysates using the standard addition method and validated by recovery study, which presented satisfactory results between 92.9% and 115.5%.

This work focuses on characterization the performance of enhanced interface of organic light emitting diode (OLED) device by Self-assembled Monolayer (SAM) technique. SAM technique is popular in order to overcome the weak bonding at the organic/inorganic interface in OLED. New generation of SAM molecules, phenyl-benzoic-acid (PBA, 4-(9H-carbazol-9-il) benzoic acid (MZ39), 4-(2,5-di-2thienyl-1H-pyrrol-1-il) benzoic acid (MZ25) were coated on between Indium Tin Oxide (ITO). The two configuration of ITO/SAM/TPD/Al and ITO/TPD/Al diode were fabricated as hole-only device to show the contribution of SAM layer on the hole mobility calculated by Space Charge Limited Current (SCLC) technique. The optical characterization of OLED devices with configuration ITO/TPD/Alq3/Al and ITO/SAM/TPD/Alq3/Al was performed to see the effect of aromatic SAM molecules on the luminance and quantum efficiency. Especially, the SAM modified OLED has a maximum luminance of 397 cd m⁻². All devices containing SAM layer showed better performance than reference one.

Cobalt (II) phthalocyanine (CoPc) supported on graphene (CVD), carbon black (Vulcan XC72), multi walled carbon nanotube (MWCNT) and their mixtures were evaluated as electrocatalysts for oxygen reduction reaction in acid electrolytes and polymer electrolyte membrane fuel cells (PEMFC). Graphene (G) and carbon supported CoPc catalysts were prepared by impregnation method. Three different temperatures (800 °C, 650 °C and 500 °C) were studied to examine the effect of heat treatment on CoPc and the best fuel cell performance was obtained with samples heat-treated at 800 °C. Maximum power densities of CoPc/G, CoPc/Vulcan-G, CoPc/MWCNT-G, CoPc/MWCNT, CoPc/Vulcan and CoPc/Vulcan-MWCNT at 60 °C cell temperature, 100% humidity and 5 psi back pressure were found as 102, 171, 179, 189, 296, 303 mW cm⁻², respectively. CVD graphene with CoPc was forming impermeable layer-structure causing mass transport limitations and lower performance. Performance enhancements were achieved by heat-treatment of the samples, higher catalyst loading, operating at high temperatures and higher pressures under 100% humidity. Hybridization of CVD graphene with Vulcan and MWCNT led improved fuel cell performance at 25 psi back pressure compare to individual support materials.

Carbon Nanotubes (CNT) are important fillers and reinforcing agents, frequently used in polymeric composites. CNT agglomerate and entangle with each other due to the presence of strong van der Waal forces between them. This agglomeration not only results in decreased product quality but also in lower conductance of composite than expected. Deagglomeration of CNT bundles is necessary for a better dispersion either through chemical functionalization (covalent or non-covalent) or by mechanical methods (stirring, calendering and ultrasonication). This review contains different methods for chemical surface modification of CNT, which not only decrease CNT-matrix interface resistance by providing a soft interface between filler and matrix but also increases CNT dispersion in different types of matrices.

This work reports transfer curve characterization, capacitance-voltage measurement, bias stress test, bending and stretching tests of the high fidelity flexible and stretchable thin-film transistors constructed on unsorted single-walled carbon nanotubes drain-source-gate electrodes, sorted semiconducting single-walled carbon nanotubes thin film active layer, and nonpolar styrene−ethylene−butadiene−styrene (SEBS) hydrogenated elastomer dielectric and substrate. The air-stable, hysteresis-less, negligible threshold shift under bias stress test, stable performance during bending, and slightly current density changes under stretching strains of these all-carbon based thin-film transistors qualify for basic elements applicable in industrial flexible and stretchable electronics.

A surface-protected etching approach was used to synthesize monodisperse partially hollow carbon nanostructures with pseudocubic shapes. Monodisperse chemical templates (α-Fe₂O₃, MF) were synthesized by the gel-sol method and coated with a polyvinylpyrrolidone (PVP) protective layer. Pyrrole monomers were dispersed around the PVP-protected α-Fe₂O₃ templates. Upon acidic etching, Fe³⁺ ions were released to initiate in situpolymerization of pyrrole to form Fe₂O₃@PPy (MFP) core–shell intermediates. The MFP particles were calcined to obtain partially hollow 3D pseudocubic carbon nanoparticles (PCC). The PCC delivered a high specific capacitance (395 F g⁻¹ at 0.2 A g⁻¹) and enhanced cycling stability (5000 cycles at 4 A g⁻¹). The superior electrochemical properties of the PCC is attributed to its cubic and partially hollow structure, which increases electric double layer capacitance by increasing charge storage surface, facilitates effective ion diffusion by reducing interparticle distances, and buffers volumetric changes associated with ion insertion through void space/pores. The simple and highly reproducible method presented in this work can be extended to produce various hollow or yolk-shell nanostructures as high-performance supercapacitor electrode materials.

A comparative study of lead alloy electrode and carbon fibers based β-PbO₂ (CF/β-PbO₂) electrode for zinc electrowinning was discussed. The effect of electrodeposition time on the preparation and properties of the CF/β-PbO₂ electrode was firstly studied. Surface morphology, interface properties, electrochemical property and corrosion resistance of the CF/β-PbO₂ electrodes were investigated. It was found that the optimal conditions are 40 mA·cm⁻², 150 g L⁻¹ Pb(NO₃)₂ and 100 min. Under this conditions, a smooothest surface of β-PbO₂ active layer is obtained. The weightlessness rate is 0.22%. The interface resistivity of the electrode is 6.79 × 10⁻⁵ Ω·m. The oxygen evolution overpotentials of the electrode is 0.931 V. Compared to the traditional lead alloy electrode, the self-corrosion potential of the CF/β-PbO₂ electrode is 1.085 V.

Here, we demonstrate a two-step electrochemical approach for the synthesis of cobalt chalcogenides, CoQ (Q = S or Se) based on the prior modification of a substrate with S or Se, followed by electrochemical reduction in a Co²⁺-complexing electrolyte to afford CoS or CoSe in film form. The two-step strategy circumvents a common problem with the electrodeposition of metal chalcogenides, namely admixture of the target material with undesired phases such as excess metal or the chalcogen. The strategy was combined with complexation to shift the free metal deposition regime to more negative potentials. Compositional analysis showed that as-synthesized films retain a stoichiometric ratio of Co and S or Se and XPS analysis confirmed the formation of CoS and CoSe. The electrodeposited films were successfully used as electrocatalysts for the triiodide/iodide redox system and showed comparable (or even, superior) performance to a Pt electrode. As also demonstrated both by the present work and by companion studies in our laboratories, the two-step strategy is generally applicable to a variety of other metal chalcogenides.

Efficient aerobic oxidation of cyclohexene to the corresponding products catalyzed by iron (III) porphyrins in supercritical carbon dioxide (scCO₂) has been developed. Compared with the oxidation occurred in dichloroethane, the efficiency was improved significantly in scCO₂, in which the cyclohexene conversion increased from 10.5% to 22.4%. Influence of various reaction parameters including catalyst, catalyst dosage, reaction temperature and pressure on the activity and selectivity were investigated in detail. Moreover, a plausible mechanism involving free radical and high-valence iron species was proposed.

Eight microelectrodes based on carbon and diamond paste modified with zinc complexes with: tetraphenylporphyrin (ZnTPP), tetranaphtoporphyrin (ZnTNP), tetrasulphophenylporphyrin (ZnTSPP) and phtalocyanine (ZnPc), were proposed for the assay of indigo carmine in wastewaters, pharmaceutical formulations and biological samples. All measurements were performed using differential pulse voltammetry. Indigo carmine was recovered reliable from real samples in percentages higher than 90.00%. The surface of the microelectrodes can easily be renewed by simple polishing, obtaining a fresh surface ready for use in a new assay.

Alignment of liquid crystals by ion-beam (IB) irradiated bismuth-doped zinc oxide (BZO) films was investigated. The BZO alignment layer was deposited using a simple solution process, and IB irradiation of the BZO was used to induce surface-alignment of LC molecules uniformly. Solution-processed thin films have numerous advantages, including low manufacturing cost, simplicity of fabrication, and high productivity. IB irradiation of the BZO film induces a drastic improvement in the uniformity of the BZO surface and creates physico-chemical modifications that preserve the anisotropic characteristics of the surface, thereby unidirectionally aligning the LC molecules.

In this work, the charge retention properties of the thermal ALD-Al₂O₃ trapping layer with metal-oxide-oxide-oxide-silicon (MOOOS) gate stack have been investigated for non-volatile memory application. The precursor gas concentrations were changed to engineer the band gap of the Al_xO_y trapping layer and the effect of Al_xO_y post-deposition annealing on charge retention properties was studied. The Al₂O₃ layer with trimethyl aluminum (TMA): H₂O gas flow ratio of 1:1 and deposition pulse time of 1 s per each cycle showed the band gap of 4.49 eV , which is suitable for charge trapping layer. The memory retention properties of the ALD-Al₂O₃ MOOOS device was investigated by performing high-frequency capacitance-voltage measurement and compared to the device having a SiN_x charge trapping layer. The 10 nm Al_xO_y trapping layer showed the improvement in charge retention properties after low-temperature post-deposition annealing in N₂ ambient as compared to that of SiN_x trapping layer with relatively large flat band voltage shift of 2.79 V. The multilayer Al₂O₃-MOOOS gate stack is suitable for the non-volatile memory application with good retention properties as compared to different oxides non-volatile memory devices.

This article provides an overview of the published mechanical stress data for boron- and phosphorus-contained silicate glass films deposited by a variety of chemically vapor deposited (CVD) techniques, i.e. atmospheric and sub-atmospheric pressure (APCVD, SACVD), low pressure, plasma-enhanced (LPCVD, PECVD). The emphasis is done on borophosphosilicate glass films (BPSG) dedicated for the use in micro-electro-mechanical system (MEMS) and micro-opto-electro-mechanical system (MOEMS) technologies as a material with significantly higher film thickness as compared with its traditional use in microelectronics technology as a flow-able planarized interlayer dielectric. The article covers stress features of as-deposited and thermally annealed films with the boron and phosphorus concentration range in between about 1–12 wt%. Phosphorus is detected as a main film component responsible for stress type (tensile or compressive) and its particular values. Film deposition techniques strongly affect the film stress at low phosphorus content in the films, providing either tensile (APCVD, SACVD), or compressive (LPCVD, PECVD) stress types. These effects explained with differences in CVD kinetics and hydrogen-contained CVD reaction by-products formation.

Knowledge obtained on the mechanism for altering the Ce³⁺% on the ceria surface was used to create ceria slurries that polished thermal oxide with higher material removal rate (MRR) and lower post-polish roughness than slurries that are currently being used in industry. As described by the tooth-comb model, oxide removal occurs easiest at sites with fewer surface bonds. This allows for slurries to be prepared with particles of large size (68 nm) that have high MRR while obtaining roughness values that are equal to those of much smaller particles (5 nm). The addition of hydrogen peroxide initially increases the Ce³⁺% concentration on the particle surface, then decreases it. This trend is replicated by both MRR and roughness with improvements initially, until a threshold is reached, after which all of the metrics got worse. The effect of pH was more complex, as it impacts the polishing process in two ways, by governing the rate of the chemical reaction with ceria and also the rate at which silica hydrolyzes, which in turn determines the ease with which both chemical and mechanical removal occurs.

Due to its high optical permeability, excellent high temperature resistance, and chemical inertness, fused silica (FS) has been widely used in astronomical telescopes, laser systems, and optical communication. Based on the smooth surface polishing of fused silica using ceria slurry, the variations of polishing performance of fused silica in the recycling polishing were studied. Meanwhile, the variations of the ceria slurry characteristics in chemical mechanical polishing (CMP) of fused silica were investigated. The variations of the average size and the morphology of the abrasive ceria particles were measured. X-Ray photoelectron spectroscopy (XPS) measurement was used to evaluate the chemical state of the ceria slurry in different recycling polishing time. Then, elastic moduli via atomic force microscope (AFM) force curves measurement of the abrasive ceria particles were measured and analyzed. And the change of shear viscosity of the slurry was monitored. In addition, the relative removal mechanism of fused silica using ceria slurry recycling was discussed.

Following up our earlier work that highlighted the relationship between shear force (SF) and platen motor current (PMC), in parallel with the relationship between coefficient of friction (COF) and PMC for various tungsten and interlayer dielectric (ILD) chemical mechanical planarization (CMP) cases at non-steady-state conditions, we explored whether or not PMC could be used as a reliable indicator instead of SF and COF at steady-state conditions. For the 12 cases studied, 72 distinct steps were analyzed. It was determined that PMC somewhat mirrored SF and PMC for long time (i.e. 10 s or longer) intervals after data averaging and applying a trend matching algorithm. SF and PMC trends matched only about 64% of the time (ranges between 45% to 85%) for all 72 steps, while PMC and COF trends matched 62% of the time ranging between 42% and 85%. PMC-SF and PMC-COF correlations were fairly poor at 1-sec time intervals as evidenced by much lower percent match values. Such poor correlations proved that at small time intervals, PMC was not sensitive enough to capture important information regarding myriad fluid dynamics and tribological phenomena and the instantaneous stick-slip occurrences encountered in CMP.

The initial growth of a porous alumina film with a large-scale cell structure formed by galvanostatic anodizing in etidronic acid was investigated in detail by high-resolution microscopy. High-purity aluminum plates were galvanostatically anodized in etidronic acid at 2.5–20.0 Am⁻². The formation of an anodic oxide and the subsequent instability of the outer oxide simultaneously occurred at the early stage of the linear voltage increase during the anodizing process. Accordingly, a wavy interface boundary between the aluminum oxide that contained incorporated anions and the nearly pure aluminum oxide formed in the anodic oxide. The surviving pores grew as the thickness of the oxide film increased, and a clear porous alumina film with a pore at the center of each cell formed until the voltage reached its maximum value. Finally, steady-state growth of the porous alumina film occurred at the plateau voltage region after a slight voltage decrease. Eggplant-like anion distributions were measured at the head of the pores due to the viscous flow of the anodic oxide. The nanomorphology of the porous alumina film strongly depended on the current density due to the difference in the degree of oxide formation and localized oxide dissolution.

Polystyrene (PS)/CeO₂ core/shell abrasives with different shell thicknesses were synthesized and exploited to obtain high-quality 4H-SiC surface in electro-chemical mechanical polishing (ECMP). The synthesized PS/CeO₂ abrasives were observed by a scanning electron microscope (SEM); the results showed PS/CeO₂ with a similar core (200 nm) but different shell thicknesses (8.5, 15.5, 20.5 and 27.5 nm) were obtained. Young's moduli of these abrasives were measured by an atomic force microscopy (AFM) considering the bottom deformation of abrasives. The effects of shell thickness on the contact area between the abrasive and the wafer surface, and on the indentation depth of the abrasive into the wafer surface were calculated. The indentation depth, representing surface quality, was compared with the surface roughness obtained from the following ECMP verification tests. The results characterized by a microscope and an AFM showed that surface quality polished by PS/CeO₂ (little scratches; R_a: 2.388–3.181 nm) was better than that polished by CeO₂ (many scratches; R_a: 3.661 nm), and that effects of shell thickness on polishing quality agreed well with the established theoretical model. Mechanisms of improving surface quality polished by core/shell abrasives and the effects of shell thickness on polishing quality were explained by the applied elastic-contact theoretical model.

The deep levels in amorphous Ge_0.5Se_0.5 layers have been analyzed by Deep Level Transient Spectroscopy (DLTS). To that end, Metal-Insulator-Semiconductor (MIS) capacitors have been prepared by Physical Vapor Deposition of the films on p-type silicon substrates. A so-called quasi-constant capacitance procedure has been developed to account for the strong flat-band voltage shift of the capacitance-voltage characteristic with temperature. Applying this procedure to the as-deposited layers in the subthreshold regime reveals a dominant broad hole trap, with deep level parameters (trap concentration, hole capture cross section and activation energy) that strongly depend on the deposition conditions and the layer thickness. It is, finally, shown that the trap filling behavior does not follow the capture kinetics for simple point defects. Based on this observation, arguments are presented for an alternative analysis of the DLTS data.

Cobalt, the 3rd generation material for interconnect in deep nanometers' processing. Cobalt reduces the interconnect structure and process complexity compared to the dual damascene process. In this article, we investigate the effects of complexing agent L-Aspartic acid (L-Asp) and oxidant H₂O₂ for polishing Cobalt based on chemical mechanical polishing (CMP). The results show that the water-soluble Co(III)-L-Asp complex generated by adding L-Asp and H₂O₂ is beneficial to improve the Cobalt removal rate. Electrochemical measurements and X-ray photoelectron spectroscopy are ultilizd to explore the removal mechanism of Cobalt. The high removal rate of Cobalt may be attributed to the formation of [Co(C₄H₅NO₄)₂⁻] and [Co(C₄H₅NO₄)₂²⁻] complexes. The surface morphology of cobalt is observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results show that obvious corrosion phenomenon appears on the surface of cobalt after adding H₂O₂ and L-Asp, which also confirms the chemical reaction mechanism in which the removal rate is improved as previously analyzed.

We investigated the tribological, thermal and kinetic aspects of SiO₂ and Si₃N₄ polishing on blanket and patterned wafers for STI CMP. Results showed the absence of anomalous tribological vibrational behaviors thanks to synergies between the colloidal CeO₂-based slurry and application-specific conditioner. Removal rates for the two processes showed non-Prestonian behavior as both mechanical and chemical factors were at work. However, Si₃N₄ was much more non-Prestonian than SiO₂. As expected, Si₃N₄ polishing resulted in COFvalues that were approximately one-half of their SiO₂ counterparts resulting in high SiO₂-Si₃N₄ removal rate selectivity. A modified Langmuir-Hinshelwood model was used to simulate removal rates allowing us to conclude that the process was mechanically-limited for SiO₂ and highly chemically-limited for Si₃N_4. Patterned wafer polishing time traces showed that COFcould be utilized as a real-time indicator for end-point detection and that, after 6 min of polishing, we observed the total removal of SiO₂ with a hard stop on Si₃N₄. End-points reached were also consistent with our blanket wafer polishing data. Regardless of pattern density and pitch, SiO₂ removed was not proportional to polish time. This was a result of the low colloidal ceria nano-particle content in the slurry which was explained via a phenomenological model.

The end face of an optical fiber connector can be easily contaminated, the curvature radius of the end face can be difficult to guarantee, and the polishing film might not be durable during polishing. To solve these problems, a soluble fixed soft abrasive film polishing method was proposed. Through dyeing and dissolving, tensile strength, and polishing experiments, the influence of the binder and abrasive on polishing film production was studied. The results showed that when the content of each component was 15 wt% epoxy resin, 5 wt% polyacrylic resin, 75 wt% bimodal SiO₂, and 5 wt% other additives, the polishing film had superior workpiece polishing quality and durability. After polishing, the end surface of the fiber connector was smooth and clean, the surface morphology of the curved surface was complete, and the surface roughness reached Ra 5 nm.

This paper benchmarks various epitaxial growth schemes based on n-type group-IV materials as viable source/drain candidates for Ge nMOS devices. Si:P grown at low temperature on Ge, gives an active carrier concentration as high as 3.5 × 10²⁰ cm⁻³ and a contact resistivity down to 7.5 × 10⁻⁹ Ω.cm². However, Si:P growth is highly defective due to large lattice mismatch between Si and Ge. Within the material stacks assessed, one option for Ge nMOS source/drain stressors would be to stack Si:P, deposited at contact level, on top of a selectively grown n-Si_yGe_1−x−ySn_x at source/drain level, in line with the concept of Si passivation of n-Ge surfaces to achieve low contact resistivities as reported in literature (Martens et al. 2011 Appl. Phys. Lett., 98, 013 504). The saturation in active carrier concentration with increasing P (or As)-doping is the major bottleneck in achieving low contact resistivities for as-grown Ge or Si_yGe_1−x−ySn_x. We focus on understanding various dopant deactivation mechanisms in P-doped Ge and Ge_1−xSn_x alloys. First principles simulation results suggest that P deactivation in Ge and Ge_1−xSn_x can be explained both by P-clustering and donor-vacancy complexes. Positron annihilation spectroscopy analysis, suggests that dopant deactivation in P-doped Ge and Ge_1−xSn_x is primarily due to the formation of P_n-V and Sn_mP_n-V clusters.

Contact pressure at the workpiece/tin lap interface during full-aperture polishing is of great significance to workpiece's material removal process. To promote the determinacy and efficiency of polishing process, a novel wireless contact pressure measurement system is developed. Further, the contact pressure distribution map is solved by the interpolation algorithm using the acquired contact pressure data at workpiece/ tin lap interface. Subsequently, a material removal amount model within given polishing time is proposed. Based on this model, process parameters are optimized with the genetic algorithms using contact pressure distribution map under specific workpiece's initial surface figure and polishing conditions. Compared with random process parameters, the optimized process parameters can greatly improve the accuracy and convergence efficiency of workpiece's surface figure in full-aperture polishing with tin lap, which is validated by the polishing experiments.

In the present study, hydrogen water was applied to ceria abrasive removal in post-CMP cleaning. The surface of the ceria abrasive was reduced by the hydrogen water from the Ce⁴⁺ to Ce³⁺ state. Reduction of the ceria abrasive can weaken the bonding between ceria and the SiO₂ wafer surface. X-ray photoelectron spectroscopy (XPS) and UV–visible observations were utilized to reveal the reduction from Ce⁴⁺ to Ce³⁺ by hydrogen water. Thus, the remaining ceria particles and Ce-ion concentrations were reduced by 70% and 63%, respectively.

A previously developed aqueous cleaning solution (4.2 mol l⁻¹ each of H₂O₂ and NH₄OH) was found to be ineffective in cleaning oxide/nitride surfaces after contamination with ceria particles from slurries containing proline or citric acid. However, a cleaning solution consisting of 1 wt% ascorbic acid, 1 wt% ammonium carbonate and 50 ppm triton X-100 at pH 12, aided by ultrasonic cleaning, removed these ceria particles, even those as small as ∼30 nm, from both oxide and nitride surfaces with efficiencies >99% as determined by AFM imaging. Fourier transform infrared (FTIR) spectroscopy results indicated that ceria particles treated with these additives can also bind with oxide/nitride surfaces through Si–O–C and Si–O–H bonds, in addition to any Ce–O–Si, where the C and H atoms are from the additives adsorbed on the ceria particles. All these bonds are broken effectively by the nucleophilic attack of hydroxyl anions in the cleaning solution while triton X-100 in the cleaning solution reduces adhesion between the particles and the film surface and facilitates cleaning via a wetting mechanism. More importantly, ascorbic acid and ammonium carbonate prevent particle redeposition by complexing with the removed particles and blocking the active Ce³⁺ species on their surface.

As the technology node of integrated circuits (ICs) shrinks down to 7 nm and below, cobalt (Co) has been identified as the promising candidate for the interconnect/contact material. In this paper, colloidal silica was used as abrasive, potassium tartrate (PTH) was used as the promoter of TEOS and complexing agent of Co and titanium nitride (TiN), H₂O₂ was used as oxidant. The effects of PTH and H₂O₂ on the removal rate (RR) of Co/TiN/TEOS were studied. Polishing results showed that PTH can improve the RR of Co/TiN/TEOS effectively. The removal mechanism was revealed by X-ray photoelectron spectroscopy (XPS), electrochemical and UV–visible (UV-vis) spectroscopy measurements. It revealed that PTH can complex with Co(II)/Co(III) and TiO²⁺ ions produced during CMP, and formed Co(II)-PTH/Co(III)-PTH and TiO-PTH complex increases the RR of Co and TiN. The attractive force between silica abrasive and TEOS surface was improved as the concentration of PTH increased, resulting in the mechanical force increased and the RR of TEOS enhanced.

The band alignment of Atomic Layer Deposited SiO₂ on (In_xGa_1−x)₂O₃ at varying indium concentrations is reported before and after annealing at 450 °C and 600 °C to simulate potential processing steps during device fabrication and to determine the thermal stability of MOS structures in high-temperature applications. At all indium concentrations studied, the valence band offsets (VBO) showed a nearly constant decrease as a result of 450 °C annealing. The decrease in VBO was −0.35 eV for (In_0.25Ga_0.75)₂O₃, −0.45 eV for (In_0.42Ga_0.58)₂O₃, −0.40 eV for (In_0.60Ga_0.40)₂O₃, and −0.35 eV (In_0.74Ga_0.26)₂O₃ for 450 °C annealing. After annealing at 600 °C, the band alignment remained stable, with <0.1 eV changes for all structures examined, compared to the offsets after the 450 °C anneal. The band offset shifts after annealing are likely due to changes in bonding at the heterointerface. Even after annealing up to 600 °C, the band alignment remains type I (nested gap) for all indium compositions of (In_xGa_1−x)₂O₃ studied.

This paper presented a fully depleted silicon on insulator (FD-SOI) MOSFET in nano scale size with deployment the quasi two dimensional β-Ga₂O₃ material to improvement electrical properties. The main idea of the proposed structure is embedding a layer of the β-Ga₂O₃ in the drain region. Due to the β-Ga₂O₃ material features, the electric field distribution near the drain and gate side will be change and peak of the electric field of the proposed structure is diminish. The embedded layer of the β-Ga₂O₃ material in our work has an important effects on the electrical and thermal characteristics. In this paper, characteristics of the proposed structure is compared with the prevalent SOI and improvement of characteristics in our work are shown. The features such as the electric field, the potential distribution, the sub-threshold slope, the kink effect, the self-heating effect, punch through effect and DIBL effect are investigated and compared with prevalent SOI.

Films of α-Ga₂O₃ doped with Sn were grown by halide vapor phase epitaxy (HVPE) on planar and patterned sapphire substrates. For planar substrates, with the same high Sn flow, the total concentration of donors was varying from 10¹⁷ cm⁻³ to high 10¹⁸ cm⁻³. The donor centers were shallow states with activation energies 35–60 meV, centers with levels near E_c–(0.1–0.14) eV (E1), and centers with levels near E_c–(0.35–0.4) eV (E2). Deeper electron traps with levels near E_c−0.6 eV (A), near E_c−0.8 eV (B), E_c−1 eV (C) were detected in capacitance or current transient spectroscopy measurements. Annealing of heavily compensated films in molecular hydrogen flow at 500 °C for 0.5 h strongly increased the concentration of the E1 states and increased the density of the E2 and A traps. For films grown on patterned substrates the growth started by the formation of the orthorhombic α-phase in the valleys of the sapphire pattern that was overgrown by the regions of laterally propagating α-phase. No improvement of the crystalline quality of the layers when using patterned substrates was detected. The electric properties, the deep traps spectra, and the effects of hydrogen treatment were similar to the case of planar samples.

The potential of ultrawide-bandgap (UWBG) semiconductors has not been fully explored because of the difficulty of forming a p-n homojunction. In this study, a mixed-dimensional UWBG p-n heterojunction composed of a p-type diamond substrate and an n-type exfoliated β-Ga₂O₃ nanolayer has been demonstrated via a van der Waals interaction; this type of structure does not suffer from lattice mismatch. Rectifying current-voltage characteristics with a rectification ratio exceeding 10⁷ were obtained with a high reverse hard breakdown voltage of 135 V. This UWBG p-n heterojunction diode exhibited good thermal stability at elevated temperatures, retaining its high rectification ratio and low reverse leakage current. Excellent photoresponse characteristics, including responsivity (12 A W⁻¹), rejection ratio (8.5 × 10³), photo-to-dark-current ratio (3900), and fast response/decay characteristics, were observed from the diamond/β-Ga₂O₃ p-n heterojunction photodiode, showing no persistent photoconductivity. The mixed-dimensional p-n heterojunction diode based on two UWBG semiconductors (p-type diamond and n-type β-Ga₂O₃) can be used as a robust building block in next-generation power electronics and solar-blind optoelectronics.

In this study, a GaN/LiNbO₃ hybrid wafer was demonstrated using room-temperature bonding based on a surface activated bonding (SAB) method. The SAB using Fe-containing Ar ion beam bombardment achieved a strong bond between GaN and LiNbO₃ wafers. The bonded wafer made using the modified SAB method was successfully cut into 1 × 1 mm² dies using a dicing saw without interfacial debonding, and the measured tensile strength was estimated to be greater than approximately 26 MPa. These results show the presence of a strong bond that may be sufficient for device applications. In addition, TEM observation clearly indicated that the Fe-containing nanolayer deposited during ion beam bombardment appears to work well as an adhesive and form a strong bond between the negative surface of LiNbO₃ and Ga-face of GaN. These results show the potential of this room-temperature bonding method to achieve a future GaN/LiNbO₃ hybrid platform that can fully exploit the unique properties of each material.

Local plasmatic resonance existing around nanoscale metallic structures is closely related to the refractive index of the surrounding media. Gold Lamellae layers embedded in gratings are ideal to populate the plasmatic resonances locally with much higher concentration than the simple gratings, leading to enhanced sensitivity to the testing materials. Based on our earlier success in replicating dielectric lamellae layers, this paper reports our further work in converting the dielectric lamellae layers into gold ones and the study of their optical property as refractive index sensors. To prove the local surface plasmatic resonance be responsible for absorbing the light, the gratings without the lamellae layer were also tested for comparison. Both numerical simulation using the finite difference time domain method and optical measurements have demonstrated the enhanced sensitivity by the gratings with lamellae layers, although structural optimization is still needed. With the further improvement in both structural configuration, material and nanofabrication technique, it is believed that the proposed lamellae layers should be a promising candidate for highly sensitive environmental sensors.

In this work, the RF performance of proposed p-type NiO pocket based β-Ga₂O₃/graphene heterostructure MOSFET has been investigated. The figure of merits (FOMs) for its performance investigation includes transconductance (g_m), output conductance (g_d), intrinsic capacitances (gate to drain capacitance C_gd and gate to source capacitance C_gs) and cut-off frequency (f_T). The large signal CW RF performance is also investigated which includes output power (P_OUT), power-added efficiency (PAE) and power gain (G_p) as a key FOMs. The key idea behind this work is to demonstrate a device with improved RF performance and low leakages. The RF characteristics of the proposed device have been studied to show its utility in the wireless applications. The introduction of ultra-thin graphene layer beneath the channel region results in 0.85 times lower C_gs, 1.04 times improvement in f_T and 1.5 dB superior G_P in comparison to the p-type NiO pocket based β-Ga₂O₃ (NiO-GO) MOSFET. The proposed structure shows superior RF performance with low leakages.

Thermally stimulated luminescence (TSL) of β-Ga₂O₃ single crystals doped with Cr³⁺ and Mg²⁺ impurities was investigated. Based on the correlation between the Cr³⁺ concentration and light sum accumulated in the thermoluminescence (TL) glow peak at 285 K, it was concluded that doping of β-Ga₂O₃ with Cr³⁺ ions leads to the formation of electron traps manifested in this peak. The activation energy of peak at 285 K is equal to Ec-0.55 eV and close to E₁. Thus the Cr³⁺e⁻ centers can be a candidate for E₁. The high-temperature TL glow peak at 385 K (Ec-0.94 eV) is related to oxygen vacancies which are created in gallium oxide doped by Mg²⁺ ions to compensate for the negative charge formed by the substitution of gallium sites by magnesium ions.The co-doping of β-Ga₂O₃ crystals with Cr³⁺ and Mg²⁺ impurities leads to the appearance of a new TL glow peak at 320 K with an energy close to E*₂ (Ec-0.7). It is suggested that this peak is formed by defect complex, in particular, oxygen vacancies with Cr³⁺ or Fe³⁺ ions.

Tin (Sn)-doped beta phase gallium oxide (β-Ga₂O₃) nanostructures at different Sn concentrations (0 to 7.3 at%) are synthesized using a facile hydrothermal method. The Sn-doped β-Ga₂O₃ nanostructures are characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and absorbance spectroscopy. In addition, their photocatalytic activity is evaluated by observing methylene blue degradation under ultraviolet light (254 nm) irradiation. The photocatalytic activity of the Sn-doped (0.7 at%) β-Ga₂O₃ nanostructures is significantly enhanced compared to that of intrinsic β-Ga₂O₃ nanostructures due to the elevated charge separation. Excessive Sn concentrations (exceeding 2.2 at%) above the solid solubility limit of the Sn in β-Ga₂O₃ nanostructures lead to SnO₂ and SnO precipitation. The presence of SnO₂ and SnO degrades the photocatalytic efficiency in the β-Ga₂O₃ nanostructures. The results suggest new opportunities for the synthesis of highly effective β-Ga₂O₃-based photocatalysts for applications in environmental remediation, disinfection, and selective organic transformations.

One of the issues in GaN based hydrogen sensors is that the sensor signal is affected by the ambient temperature as well as hydrogen exposed to the device. This may trigger a false arm in safety system and a malfunction of hydrogen fuel cell vehicle. We demonstrate an AlGaN/GaN-based hydrogen gas sensor set with simple temperature compensation structure to overcome the effect of the ambient temperature on hydrogen sensing performance. When the sensor set is exposed to hydrogen ambient, hydrogen molecules decompose only on the Pt diode of the set, resulting in compensation of the ambient temperature effect on the output signal. The sensor set showed very stable output voltage change of 0.635 V for the temperature fluctuation from 25 °C to 200 °C at the constant input bias of 5 V. The serially-connected diode set exhibited sensitive voltage response to 500–5000 ppm hydrogen exposure at 25 °C. In addition, the diode set presented a reliable output voltage responsivity to the repeated hydrogen exposures under temperature changing condition.

We investigated the effects of etching conditions on the performance of light-emitting diodes (LEDs) of various sizes aimed at vehicle headlamp applications. Photoluminescence (PL) images showed that after wet etching, the percentage of bad LED arrays significantly increased from 75% to 94%, and the leakage current at −5 V significantly increased from 1.14 × 10⁻⁹ A to 5.02 × 10⁻⁶ A. It was shown that plasma etching turned an Ag layer into Ag particles, the size and density of which depended on the treatment time and Ag layer thickness. These Ag particles served as micro-masks during dry etching. Plasma etching produced relatively uniform hillocks of diameters 0.9–1.43 μm and heights 0.85–2.5 μm. Moreover, the PL images showed that dry etching did not degrade the LED arrays. Furthermore, the light output power of the dry-etched LEDs was higher than that of the wet-etched LEDs. For example, the output power levels of the dry-etched LEDs (chip sizes: 240 × 290 μm², 240 × 490 μm², and 490 × 1190 μm²) at 100 mA were 20.4%, 15.0%, and 11.2% higher than those of the corresponding wet-etched LEDs, respectively. Moreover, we demonstrated a vehicle headlamp unit consisting of Ag-particle-based plasma-etched LEDs.

To improve the blocking performance of Ga₂O₃ Schottky barrier diode (SBD), based on the field strength distribution at the bottom of the trench and edge effect, the impacts of structure parameter on breakdown voltage and the figure of merit (FOM) were investigated by TCAD simulation and optimization. The results indicated that the breakdown voltage raised as the corner radius of trench R and the trench length K increased in a certain range, in which K was employed to optimize the structure with a minor mesa width W. In addition, Al₂O₃ was confirmed as an appropriate dielectric layer material in Ga₂O₃ SBD. When the structure parameters were W = 1 μm, R = 0.6 μm, K = 0.8 μm–0.9 μm and Al₂O₃ was selected as dielectric layer materials, a Ga₂O₃ trench SBD with breakdown voltage of 3.4 kV and the FOM of over 1.7 GW·cm⁻² was proposed.

A high conversion efficiency of 20.2% is achieved for simple structured-Si solar cells without a conventional anti-reflection layer. The ultralow-reflectance less than ∼3% is achieved by formation of a nanocrystalline Si (nc-Si) layer using the surface structure chemical transfer (SSCT) method which takes only 15 s. The nc-Si layer is passivated by phosphosilicate glass, while the rear Si surface is passivated by boron back-surface-field (B-BSF). By optimizing diffusion conditions, a high short-circuit current density of 41.8 mAcm⁻² and improvement of an open-circuit voltage are achieved owing to enhancement of B-BSF and suppression of Auger recombination in the phosphorus-doped nc-Si layer.

In this study we compare the growth of gallium oxide films by halide vapor phase epitaxy (HVPE) on various substrates under the same growth conditions. Gallium oxide films were deposited at 500 °C–600 °C on basal plane (0001) planar and patterned sapphire substrates, (0001) 2H-GaN, 4H-SiC, and $\left(\overline{2}01\right)$ bulk β-Ga₂O₃ substrates. The layers were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and cathodoluminescence (CL) techniques. Most of the films exhibit growth features of hexagonal symmetry. Sn-doped Ga₂O₃ films exhibit n-type electrical conductivity. Heterojunctions composed of n-type hexagonal Ga₂O₃:Sn and p-type GaN:Mg demonstrate diode-like I-V characteristics and emit light under forward bias.

In the present work, effect of swift heavy ion (SHI) irradiation on structural and optical properties of β-Ga₂O₃ thin films was investigated. Different ion fluences (ϕ) of 120 MeV Ag⁹⁺ ions ranging from 1 × 10¹¹ ions-cm⁻² to 5 × 10¹² ions-cm⁻² were employed. The films were grown at room temperature (RT) using electron beam evaporation method and post-deposition annealing was done at 900 °C in oxygen atmosphere. X-ray diffraction (XRD) and UV–visible (UV-Vis) spectroscopy data confirmed the formation of polycrystalline β-Ga₂O₃ phase having a bandgap of ∼5.14 eV. An increase in the structural disorder, and decrease in the average crystallites size of β-Ga₂O₃ with increasing ϕ was also revealed by XRD. Ga₂O₃ thin films showed high transparency in the UV (upto 280 nm) and visible range with average transmittance of ∼80%. Rutherford backscattering spectrometry (RBS) revealed that the thin films were slightly O deficient. A low frequency vibration mode at 170 cm⁻¹ arising from liberation and translation of tetrahedra-octahedra chains in β-Ga₂O₃ was observed through Raman spectroscopy. Scanning electron micrograph (SEM) images suggested that the films were fairly smooth.

Beta-(Al_xGa_1−x)₂O₃ thin films were prepared on c-plane sapphire substrates by low-pressure reactive vapor deposition at different temperature. The crystal structure, surface morphology, and optical properties of β-(Al_xGa_1−x)₂O₃ films were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), and transmission spectra. The β-(Al_xGa_1−x)₂O₃ films were preferred [$\overline{2}$01] orientation. The film grown at 1400 °C has narrower full width half maximum (FWHM) than grown at 1450 °C. As the growth temperature increases, the Al group decreases. The Al content of β-(Al_xGa_1−x)₂O₃ films grown at 1400 °C and 1450 °C are x = 0.524 and x = 0.489, respectively. The SEM and AFM images showed different growth mode for β-(Al_xGa_1−x)₂O₃ films grown at 1400 °C and 1450 °C and their root-mean-square roughness (RMS) values are 5.27 nm and 5.33 nm, respectively. All the prepared β-(Al_xGa_1−x)₂O₃ films have high transmittances exceeding 90% in visible region and large optical bandgap above 6 eV. These results indicate that low-pressure reactive vapor deposition technology is a promising growth technology for a high quality β-(AlGa)₂O₃ films with tunable properties.

This paper reports pulsed DC and RF characteristics of GaN high-electron-mobility transistors (HEMTs) on a silicon substrate under external mechanical tensile strain. Tensile strain enhanced two-dimensional electron gas (2DEG) density resulted in increasing I_D, f_T and f_max at CW measurement. Eliminating self-heating by pulse measurement, DC and RF characteristics between flat and bend devices were slightly increased for small-width devices, and decreased for wide-width devices. This was because maximum electron drift velocity was reduced by a hot phonon effect while 2DEG density increased by tensile strain for wide-width devices. Results indicated that the tensile strain on thinner substrates decreased the DC and RF performances of wide-width GaN-based RF power devices. This phenomenon should be considered while using GaN-based RF power devices for compact packages, especially in high-power applications.

We report the effect of extended duration electron beam exposure on the minority carrier transport properties of 10 MeV proton irradiated (fluence ∼10¹⁴ cm⁻²) Si-doped β-Ga₂O₃ Schottky rectifiers. The diffusion length (L) of minority carriers is found to decrease with temperature from 330 nm at 21 °C to 289 nm at 120 °C, with an activation energy of ∼26 meV. This energy corresponds to the presence of shallow Si trap-levels. Extended duration electron beam exposure enhances L from 330 nm to 726 nm at room temperature. The rate of increase for L is lower with increased temperature, with an activation energy of 43 meV. Finally, a brief comparison of the effect of electron injection on proton irradiated, alpha-particle irradiated and a reference Si-doped β-Ga₂O₃ Schottky rectifiers is presented.

This research focuses on the radiation tolerance of ZnO and CuGaO₂ based semiconductor application for space borne application. In this research, n-ZnO/p-CuGaO₂ based semiconductor devices were fabricated and exposed to gamma rays with increasing total ionizing dose (TID) and neutron fluence at different flux. Based on the I-V properties, the decrease in the turn-on voltage of the diode is noticeable with increasing radiation dose for both gamma and neutron flux exposure. The maximum turn-on-voltage of the fabricated diode was shown to be 1.5 V. Exposure towards gamma, shows that the turn-on is increased to 4.7 V at 200 kGy. However, the effect of neutron flux at 6.5 × 10¹⁵ n cm⁻² shows a small significant effect on the turn on voltage of 1.7 V after irradiation. Results show moderate mitigation towards irradiation, indicating that n-ZnO/p-CuGaO₂ thin film is capable of withstanding harsh radiation environment while still retaining its semiconductor as the changes in band gap ranges between 3 eV to 4 eV at post-irradiation.

It's hard for pure perovskite quantum dots (QDs) to maintain long-term and stable optical properties in practical conditions. Here, CsPbBr₃ QDs were first stabilized in amorphous SiO₂ and crystalline hexagonal boron nitride (h-BN) nanosheets. The transmission electron microscopy (TEM) images display the laminated structure consisting of CsPbBr₃/SiO₂ nanospheres and h-BN nanosheets. Besides, the photoluminescence (PL) intensity of CsPbBr₃/SiO₂/h-BN nanohybrid only has a slight decrease than CsPbBr₃/SiO₂ nanocomposite. But, dual protection of SiO₂ and h-BN give perovskite QDs better humidity stability and thermal stability. Besides, CsPbBr₃/SiO₂/h-BN block exhibits excellent water-resistance. This work provides a novel method to accelerate the application of perovskite QDs in optoelectronic devices.

Using finite-difference time-domain method, the light extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) is investigated. Simulation results show that compared to flat sapphire substrate, the nano-patterned sapphire substrate (NPSS) expands the extraction angles of top surface and sidewalls. As a result, the LEE of transverse-magnetic (TM) polarized light is improved significantly. Roughening on the backside of n-AlGaN surface significantly enhances the LEE of top surface of thin-film flip-chip DUV LEDs. However, the LEE of sidewalls of thin-film flip-chip DUV LEDs is greatly weakened. For bare DUV LED, the LEE of flip-chip LED on NPSS is estimated to be about 15%, which is around 50% higher than that of thin-film flip-chip DUV LED with roughening on the backside of n-AlGaN surface.

This work concerns the synthesis and optical characterization of a novel Mn⁴⁺ activated luminescent material with chemical composition of [C(NH₂)₃]₂GeF₆:Mn⁴⁺. This is the first report of a Mn⁴⁺ activated fluoride comprising organic moieties. X-ray diffraction, IR transmission, differential thermal analysis/thermogravimetry and inductively coupled plasma-mass spectrometry analyses were performed to investigate the properties of the phosphor. It turns out that the material is an efficient emitter at low temperature (3 K), but the luminescence is quenched at elevated temperature. This is a rare property for Mn⁴⁺ activated fluorides and the reason for the low thermal quenching temperature is investigated. The emergence of a second zero phonon line is observed in emission spectra at temperatures higher than 10 K and a relation to spin–orbit coupling is shown. Thermal population of the higher spin–orbit level is investigated with theoretical and experimental means.

The Racah parameters in conjunction with the Tanabe—Sugano energy-level diagram are widely used as a means of describing the effects of electron—electron repulsion within the metal complexes in coordination chemistry. A determination of the excitation energy levels in the 3d³-configuration ions (Mn⁴⁺, Cr³⁺, etc.) is possible from a set of Racah parameters (B and C) and crystal-field splitting parameter (Dq), and vice versa. The Tanabe—Sugano diagram promises that the zero-phonon line ²E_g energies, E(²E_g)_ZPL, over B of the Mn⁴⁺ and Cr³⁺ ions should be nearly crystal field independent, since they are practically parallel to the horizontal axis in the whole range of Dq/B variation. However, the experimental E(²E_g)_ZPL plots showed a gradual increase with increasing Dq/B, in disagreement with the Tanabe—Sugano diagram. Therefore, a new analysis model assuming the Racah parameter ratio of C/B ∼ 4.7 has been recently proposed [ECS J. Solid State Sci. Technol., 8, R164 (2019); 8, R183 (2019)]. However, the new model has been used without rigorous validation. The present study focused on this problem and analyzed the luminescence properties of LiBaF₃:Cr³⁺ and LaGaO₃:Mn⁴⁺ phosphors. More generalized expressions were proposed for analyzing the various kinds of phosphors at an optional ratio of C/B = r.