Table of contents

A well-ordered molecular arrangement is a necessary condition for "band transport" in molecular semiconductor materials, and thus it is important for donor–acceptor molecular junctions for applications in advanced organic optoelectronic devices. In this study, the heteroepitaxial growth of an acceptor material C₆₀ on a single-crystal (001) surface of dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT), a representative high-mobility donor material, is demonstrated. Surface X-ray diffraction analysis indicated spontaneous alignment of the nearest-neighbor molecular direction of the C₆₀ crystallites uniquely to the a-axis of the DNTT.

We present the thermal conductivity (κ) of perovskite PbZr_1−xTi_xO₃ (PZT) for 0 ≤ x ≤ 1 and 300 K ≤ T ≤ 873 K, the composition and temperature ranges covering the classic phase diagram of this important piezoelectric system. The glasslike dκ/dT > 0 behavior is observed for the ferroelectric rhombohedral phases and much of the paraelectric cubic phase, implying the presence of strong phonon damping in these regions of PZT. For all the temperatures studied in this work, the κ becomes lowest at x = 0.5.

During surface-enhanced fluorescence processes, the spatial spacing layer on the surface of noble metals plays an important role in regulating the fluorescence intensity. We propose a method for regulating fluorescence intensity using the AgNPs@TA-FeIII composite nanostructured materials as the substrate and using characteristic fluorescence of graphene quantum dots as the detection signal. Tannins-FeIII (TA-FeIII) nanofilms were prepared with a one-step assembly method, which is simple, fast, green, and safe. This work is expected to help the application of polyphenol metal nanofilm technology in the field of surface enhanced fluorescence (SEF).

In the realm of ultrashort pulse laser processing, surpassing the air ionization threshold, variations in focusing characteristics due to nonlinear optical phenomena pose challenges. Particularly, suitable irradiation conditions and position control methods for high pulse energy processing around 1 mJ remain unestablished. This study explores laser divergence phenomena in several mJ pulse energy range, examining both experimental and computational data. Quantitative demonstrations of laser focusing alterations, including divergence position and fluence, were achieved. Additionally, the dry laser peening effect was enhanced by energy-specific irradiation control. Numerical simulation-based visualization facilitates precise control, advancing the processing techniques.

We report on a single-scan polarization-resolved saturated absorption spectra (SAS) method utilizing a hybridly polarized beam as the probe. Owning to the spatial-variant polarization of a hybridly polarized probe, the polarization-resolved information can be retrieved from the single signal image. Then, the polarization dependence of SAS from two transitions are investigated. Strong polarization dependence is observed from the "closed two-level transition" as |5S_1/2, F = 3> → |5P_3/2, F' = 4> of ⁸⁵Rb. By contrast, no polarization dependence is observed from "open two-level transition" as |5S_1/2, F = 3> → |5P_3/2, F' = 3>. The method would be meaningful for the samples with poor stability or the ultrafast processes.

We investigate the highly efficient terahertz nonlinearity exhibited by n-type GaAs crystals under metallic metamaterials. An intense THz field applied to the metamaterials leads to impact ionization in the GaAs substrate, which emits electroluminescence in the near-infrared region. Even for a similar THz field strength, n-type GaAs emits near-infrared photons more efficiently than semi-insulating GaAs. We analyzed the luminescence lineshapes and intensity as a function of the excitation field strength, using Fermi–Dirac statistics and the density of states in the conduction band to quantify electron density and locate the Fermi level after the relaxation of excited hot electrons.

Li₂HfBr₆ with host emission was grown as a gamma-ray- and neutron-sensitive scintillator. Decay time of Li₂HfBr₆ was estimated to be less than 5 μs, and single-photon counting is available to evaluate its light output. The emission wavelength under X-ray excitation was approximately 570 nm, which is a longer wavelength than that of commonly used neutron scintillators, e.g. Li-glass. The light output excited by thermal neutrons was estimated to be 52000 photons per thermal neutron, which is approximately eight to nine times higher than that of Li-glass. Additionally, neutrons and gamma rays were discriminated using the pulse-shaped discrimination technique for Li₂HfBr₆.

Quantum entanglement plays a crucial role in quantum information technologies. In the paper, we propose two schemes to convert from two-photon Knill–Laflamme–Milburn (KLM) entangled states to Bell states and three-photon KLM state to Greenberger–Horne–Zeilinger states based on error-detected quantum devices (EDQDs), which employ the interaction between a quantum-dot-cavity system and a photon. Moreover, the quantum circuits of EDQDs applied in the conversion processes make our schemes carry out faithfully, as the practical photon-scattering deviations are changed into heralded-failure detections. Analyses show that conversion cases have unity fidelities and high efficiencies, which encourage us to appreciate deeply fundamental properties of entanglement.

Vertical AlGaN-based UV-B laser diodes were fabricated by a laser lift-off method to exfoliate sapphire substrates. These devices were processed on 1 cm² square wafers with a polycrystalline sintered AlN substrate as a structural support for the exfoliated device. Following electrode formation and other necessary processing steps, mirrors were formed through cleavage. Subsequently, the performance of the device was evaluated by injecting a pulsed current at room temperature. Results revealed distinct characteristics, including a sharp emission at 298.1 nm, a well-defined threshold current, strong transverse-electric polarization characteristic, and a laser-specific spot-like far-field pattern, confirming the oscillation of the vertical laser diode.

A major challenge in GaN-based metal-oxide-semiconductor (MOS) devices is significant hole trapping near the oxide/GaN interface. In this study, we show that the density and energy level of the hole traps depends crucially on the concentration of magnesium (Mg) dopants in GaN layers. Although the surface potential of a conventional SiO₂/p-GaN MOS device is severely pinned by hole trapping, hole accumulation and very low interface state densities below 10¹¹ cm⁻² eV⁻¹ are demonstrated for MOS capacitors on heavily Mg-doped GaN epilayers regardless of the degree of dopant activation. These findings indicate the decisive role of Mg atoms in defect passivation.

Magnetron sputtering deposition with Zn supply was utilized to deposit Ga-doped ZnO (GZO) films to minimize acceptor-like crystalline defects. This deposition technique significantly increased the carrier concentration of GZO films. In addition, the impact of partial oxygen pressure on the deposition atmosphere on carrier concentration was remarkably reduced. As a result, the resistivity of the films decreased to as low as 4 × 10⁻⁴ Ωcm without the need for intentional substrate heating. Consequently, the deposition with Zn supply shows great potential for producing ZnO-based transparent conducting films with practically low resistivity on polymer substrates that have lower heat tolerance.

In this work, we demonstrate the first achievement in heteroepitaxial growth of β-Ga₂O₃ thin films on single crystalline diamond (111) wafers using RF magnetron sputtering. A single monoclinic (β-phase) structure with a monofamily {$\bar{2}$01} plane was obtained. XRD pole figure shows ($\mathop{2}\limits^{\unicode{x00305}}$02) and (002) textures of the ($\mathop{2}\limits^{\unicode{x00305}}$01) β-Ga₂O₃ plane parallel to (111) diamond with six distinct rotational domains, confirming successful epitaxial growth. Collectively, this research provides valuable insights into the epitaxial growth of β-Ga₂O₃ on diamond via sputtering, paving the way for scalable β-Ga₂O₃/diamond heterostructures for future electronic and optoelectronic applications with not only high performance but also effective self-thermal management.

This study investigated the crystallographic plane dependence of the reaction of AlN and AlGaN using heated-pressurized water under saturated vapor pressure. The results show that the reaction strongly depends on the crystallographic orientation plane, with no reaction in the +c-plane, the formation of an AlOOH-altered layer in the −c-plane, and etching in the a- and m-planes. These results suggest that the exfoliation mechanism of AlGaN grown on periodically formed AlN nanopillars on sapphire substrates using heated-pressurized water involves etching of a- and m-plane crystals, demonstrating that the proposed method is highly reproducible and versatile for large-diameter wafer exfoliation.

In this study, we design a hybrid BiFeO₃/SrTiO₃ p–n heterojunction to enhance the photoelectrochemical (PEC) performance of the sample. The experimental results reveal that the heterojunction can significantly improve the PEC performance. The optimized BiFeO₃/SrTiO₃ heterojunction sample shows a photocurrent density of −20.8 μA·cm⁻², which is 2.9 times higher than that of the pristine BiFeO₃ (−7.2 μA·cm⁻²). The improvement in PEC performance is attributed to the p–n heterojunction formed between BiFeO₃ and SrTiO₃, leading to the efficient separation and transport of carriers. Our work provides a promising route to develop the high-performance PEC system.

As a standard for length and angle, two-dimensional (2D) grating reference materials can be used for performance verification and calibration of various microscopes and 2D stages. This paper proposes a 2D nanoscale reference grating manufactured by combining laser-focused atomic deposition (LFAD) and extreme ultraviolet interference lithography. The theoretical pitch of the 2D grating is 150.46 nm, which is only $\frac{\sqrt{2}}{2}$ times the pitch of the Cr grating manufactured by LFAD which can be traceable to the resonance transition frequency of Cr. Moreover, the angle between two periodic directions of the 2D nanograting has natural orthogonality.

Automation is an engineering method of transforming process speed, reproducibility, and scalability from the corresponding manual process. This paper proposes a simple mechanical setup for automating the exfoliation process of two-dimensional materials constructed with simple commercial parts. Given the large shear force on the adhesive tapes, the tapes can be fixed on a mechanical bar, and the other side of the tape moves with exfoliation from the substrates. The exfoliation rate can be modulated from 2 cm min⁻¹ to 0.014 cm min⁻¹ in the setup. The developed mechanics are simple with various customizable parameters and make the exfoliation process scalable.