基于GaSe和GaSe0.7S0.3单晶的单脉冲CO2激光倍频器

描述了使用电感储能发生器和半导体转换开关泵浦的工作波长为10.6μm的高效CO2激光器。给出了激光泵浦的非线性晶体GaSe和GaSe0.7S0.3的二次谐波振荡的实验数据和理论估算结果。结果显示,GaSe晶体在输入能量为180mJ时,最大能量转换效率为0.38%,倍频激光的峰值功率为8 kW。     

基于GaSe和GaSe_(0.7)S_(0.3)单晶的单脉冲CO_2激光倍频器(英文)

描述了使用电感储能发生器和半导体转换开关泵浦的工作波长为10.6μm的高效CO2激光器。给出了激光泵浦的非线性晶体GaSe和GaSe0.7S0.3的二次谐波振荡的实验数据和理论估算结果。结果显示,GaSe晶体在输入能量为180mJ时,最大能量转换效率为0.38%,倍频激光的峰值功率为8 kW。     

Nonorganic semiconductor - Conductive polymer intercalate nanohybrids: Fabrication, properties, application

Impedance spectroscopy studies performed for intercalated multilayer structures of the type of a layered inorganic semiconductor (InSe)/conducting polymer (PEDOT:PSS) revealed low-frequency inductive response and the growth of dielectric permeability in megahertz region together with the decrease of dielectric loss angle down to one as a consequence of the conducting polymer intercalation into semiconducting layers. A model describing the unusual current-voltage characteristic is proposed.     

Atomistic study of GaSe/Ge(111) interface formed through van der Waals epitaxy

Layered materials can be grown on various substrates through van der Waals epitaxy (vdWE) regardless of lattice mismatch. The atomistic study of the film-substrate interface in vdWE is becoming increasingly important due to their expected applications as two-dimensional (2D) materials. In this contribution, we have grown GaSe thin films on Ge(111) substrates by molecular beam epitaxy and studied the GaSe/Ge(111) interface using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Cross-sectional HAADF-STEM observations revealed that the grown layers adopt predominantly the expected wurtzite-like structure and stacking, but layers with zinc-blende-like structure, similar to Ga₂Se₃ but apparently different, and other layer stacking sequences, exist locally near the film-substrate interface. These results demonstrate that even in vdWE, structural changes can occur in the grown layers adjacent to the substrate, highlighting the importance of such interface for synthesizing and applying ultimately thin 2D materials.     

First-principles calculation of the structural,electronic, elastic,and optical properties of sulfur-doping ε-GaSe crystal

The structural,electronic,mechanical properties,and frequency-dependent refractive indexes of GaSe_(1-x)S_x(x=0,0.25,and 1) are studied by using the first-principles pseudopotential method within density functional theory.The calculated results demonstrate the relationships between intralayer structure and elastic modulus in GaSe_(1-x)S_x(x=0,0.25,and 1).Doping of ε-GaSe with S strengthens the Ga-X bonds and increases its elastic moduli of C_(11) and C_(66).Born effective charge analysis provides an explanation for the modification of cleavage properties about the doping of e-GaSe with S.The calculated results of band gaps suggest that the distance between intralayer atom and substitution of S_(Se),rather than interlayer force,is a key factor influencing the electronic exciton energy of the layer semiconductor.The calculated refractive indexes indicate that the doping of ε-GaSe with S reduces its refractive index and increases its birefringence.     

AgGaS2- and Al-doped GaSe Crystals for IR Applications

We report a systematic study of AgGaS₂- and Al-doped GaSe crystals in comparison with pure GaSe and S-doped GaSe crystals. AgGaS₂-doped GaSe (GaSe:AgGaS₂) crystal was grown by Bridgman technique from the melt of GaSe:AgGaS₂ (10.6 wt.%). Its real composition was identified as GaSe:S (2 wt.%). Al-doped GaSe (GaSe:Al) crystals were grown from the melt of GaSe and 0.01, 0.05, 0.1, 0.5, 1, 2 mass % of aluminium. Al content in the grown crystals is too small to be measured. The hardness of GaSe:S (2 wt.%) crystal grown from the melt of GaSe:AgGaS₂ is 25% higher than that of GaSe:S (2 wt.%) crystal grown by a conventional S-doping technique and 1.5- to 1.9-times higher than that of pure GaSe. GaSe:Al crystals are characterized by 2.5- to 3-times higher hardness than that of pure GaSe and by extremely low conductivity of ≤ 10^− 7 Om^− 1 cm^− 1. A comparative experiment on SHG in AgGaS₂-, Al-, S-doped GaSe and pure GaSe is carried out under the pumps of 2.12-2.9 μm fs OPA and 9.2−10.8 μm ns CO₂ laser. It was found that GaSe:S crystals possess the best physical properties for mid-IR applications among these doped GaSe crystals. GaSe:Al crystals have relatively low conductivity which have strong potential for THz application.     

Al Schottky contact on p-GaSe

A new Schottky diode, Al/p-GaSe, was presented in this study. It shows an effective barrier height of 0.96 eV with an ideality factor of 1.24 over five decades and a reverse leakage current density of 4.12×10⁻⁷ A/cm² at −2 V after rapid thermal annealing at 400 C for 30 s. The generation–recombination effect of the Schottky diode was decreased as the annealing temperature was increased. The formation of Al_1.33Se₂ was observed by X-ray diffraction analysis after the diode was annealed at 400 C for 30 s. Owing to the grains’ growth, the surface morphology of the 400 C-annealed diode was rougher than that of the unannealed diode, which was observed both by the AFM and the SEM analysis.     

Refractive index,band gap and oscillator parameters of amorphous GaSe thin films

GaSe thin films are obtained by evaporating GaSe crystals onto ultrasonically cleaned glass substrates kept at room temperature under a pressure of ∼10^–5 Torr. The X‐ray analysis revealed that these films are of amorphous nature. The reflectance and transmittance of the films are measured in the incident photon energy range of 1.1–3.0 eV. The absorption coefficient spectral analysis revealed the existence of long and wide band tails of the localized states in the low absorption region. The band tails width is calculated to be 0.42 eV. The analysis of the absorption coefficient in the high absorption region revealed an indirect forbidden band gap of 1.93 eV. The transmittance analysis in the incidence photon wavelength range of 500–1100 nm allowed the determination of refractive index as function of wave length. The refractive index–wavelength variation leads to the determination of dispersion and oscillator energies as 31.23 and 3.90 eV, respectively. The static refractive index and static dielectric constant were also calculated as a result of the later data and found to be 9.0 and 3.0, respectively. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

基于GaSe和ZnGeP2晶体差频产生可调谐太赫兹辐射的理论研究

基于非线性光学频率变换理论,采用已报道的利用非线性光学差频方法产生可调谐太赫兹波的实验条件作为理论分析的实验模型,计算模拟出在不同相位匹配条件下,GaSe和ZnGeP₂晶体差频的相位匹配角、走离角、允许角和有效非线性系数,并对计算结果进行了分析比较,总结出对应输出不同太赫兹波长的最佳相位匹配方式.计算结果为利用非线性晶体差频产生可调谐太赫兹辐射的实验研究提供深入和全面的理论基础. 关键词： 太赫兹波 GaSe晶体 2晶体')" href="#">ZnGeP₂晶体 差频     

Pool-Frenkel thermoelectric modulation of exciton photoluminescence in GaSe crystals

Effect of external field on the exciton photoluminescence of GaSe crystals has been investigated and it has been observed that the PL is quenched with the applied field. The changes observed in the PL spectra have been analyzed with impact exciton, Franz-Keldysh and Pool-Frenkel effects. From the analyses of the experimental data, it has been found that the intensity of direct free, indirect free and bound exciton peaks decreased exponentially with the square root of applied field as I∼exp-β√E. The energy positions of emission peaks were found to shift to longer wavelength with the applied field as ΔE∼β√E. From these findings, the Pool-Frenkel thermoelectric field effect is seen to be the dominant mechanism in the variation of exciton PL with the applied field even though the impact exciton and Franz-Keldysh effects contribute.