Nonlinear Shift of the Raman A1 Mode in Ga-Incorporated CuInSe2 Thin Films

Composition dependence of quaternary CuIn1-x GaxSe2 films on Ga content has been systematically investigated by Raman scattering. The dominant A1 mode shifts from 174cm^-1 for CuInSe2 to 185cm^-1 for CuGaSe2 in an approximately polynomial curve other than a linear curve, indicating existence of asymmetric distribution of Ga and In on a microscopic scale in films. With Ga content x 〉 0.3, the significantly broadening and intensity decrease of A1 modes suggest the degradation of crystalline quality of chalcopyrite phase. Additionally, the quenching of additional Raman band at 183cm^-1 for the Ga-rich films reveals that CuAu-ordered phase can coexist in nominal chalcopyrite CuInSe2 films but not in CuGaSe2, due to Ga inhibition effect.     

The effect of Si content on the martensitic transformation temperature of Ni55.5Fe18Ga26.5-xSix alloys

This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry (DSC) methods. The structure type of Ni55.5Fe18Ga26.5-xSix alloys is determined by x-ray diffraction (XRD),and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite (with Si content x = 0) to body-centred cubic austenite (with x = 2) at room temperature. The martensitic transformation temperatures of the Ni55.5Fe18Ga26.5-xSix alloys decrease almost linearly with increasing Si content in the Si content range of x ≤ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga-Si alloy. The valence electronic concentrations,size factor,L21 degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.     

CuInSe2 Films Prepared by a Plasma-Assisted Selenization Process in Different Working Pressures

The effects of working pressure on the composition, structure and surface morphology properties of CuInSe2 （CIS） films selenized with a plasma-assisted selenization process is investigated. Higher selenium content, better crystalline quality and much more regular surface particles compared to the others are found in the CIS film with 40 Pa working pressure. A Cu（In,Ga）Se2 device fabricated with the optimized plasma-assisted selenization process is demonstrated to be better than our previous result. After discussion, the reason for these phenomena is attributed to the compromise of electron temperature and plasma density.     

Optical Characterization of β-FeSi2 Thin Films Prepared by Femtosecond Laser Ablation

Iron disilicide thin films are prepared on fused quartz using femtosecond laser deposition （FsPLD） with a FeSi2 alloy target. X-ray diffraction results indicate the films are single-phase, orthorhombic, β-FeSi2. Field scanning electron microscopy, high resolution transmission electron microscopy, UV-VIS-NIR spectroscopy and Raman microscope are used to characterize the structure, composition, and optical properties of the β-FeSi2 films. Normal incidence spectral transmittance and reflectance data indicate a minimum, direct energy gap of 0.85 eV. The two most intense lines of Raman scattering peaked at 181.3 cm^-1 and 235.6cm^-1 for the film on fused quartz, and at 191.2cm^-1 and 243.8cm^-1 for the film on Si （100）, are observed.     

Composition-Dependent Characterization of Sb2Te3 Thin Films Prepared by Ion Beam Sputtering Deposition

The optimization of ion beam sputtering deposition process for Sb2 Te3 thin films deposited on BK7 glass substrates is reported. The influence of composition ratio on the thermoelectric properties is investigated. X-ray diffraction shows that the major diffraction peaks of the films match with those of Sb2 Te3. Hall effect and Seebeck coefficient measurement reveal that all the samples are of p-type. The Sb2 Te3 thin films exhibit the Seebeck coefficient of 190μVk^-1 and the electrical conductivity of 1.1 × 10^3 Scm^-1 when the atomic ratio of Sb to Te is 0.65. Carrier concentration and motility of the films increase with the increasing atomic ratio of Sb to Te. The Sb2 Tea film with a maximum power factor of 2.26×10^-3 Win^-1K^-2 is achieved when annealed at 400℃. Raman measurement shows that the main peaks are at about 120 cm^-1, 252 cm^-1 and 450 cm^-1, in agreement with those of V-VI compound semiconductors.     

Epitaxial growth of Ge1-xSnx films with x up to 0.14 grown on Ge （001） at low temperature

We characterize the structures of Ge1-xSnx films with x up to 0.14 grown on Ge （001） by molecular-beam epitaxy at low temperature. The results show that Ge1-xSnx films are fully strained even at high Sn composition. The in-plane lattice parameters remain exactly the same as that of the substrate. Depth sensitivity analysis of the lattice parameters indicates that the strains of the epitaxial films are all in homogeneity. The films are fully strained. Poisson ratios, the force constants for the bonds between Ge and Sn are estimated and discussed in the present paper. Raman results show Ge-Ge, Ge-Sn, Sn-Sn vibrational modes. The Sn-Sn bond aggregation may respond to the high quality of our films. The fully strained epitaxy films with high content of Sn may be useful in designing the high quality GeSn films.     

Epitaxial growth of Ge_(1-x)Sn_x films with x up to 0.14 grown on Ge(00l) at low temperature

We characterize the structures of Ge1-xSnx films with x up to 0.14 grown on Ge(00l) by molecular-beam epitaxy at low temperature. The results show that Ge1-xSnx films are fully strained even at high Sn composition. The in-plane lattice parameters remain exactly the same as that of the substrate. Depth sensitivity analysis of the lattice parameters indicates that the strains of the epitaxial films are all in homogeneity. The films are fully strained. Poisson ratios, the force constants for the bonds between Ge and Sn are estimated and discussed in the present paper. Raman results show Ge–Ge, Ge–Sn,Sn–Sn vibrational modes. The Sn–Sn bond aggregation may respond to the high quality of our films. The fully strained epitaxy films with high content of Sn may be useful in designing the high quality GeSn films.     

Microstructure and Raman spectra of Ag-MgF_2 cermet films

Ag-MgF2 cermet films with different Ag fractions were prepared by vacuum evaporation. The micfostruc-ture of the films was examined by Raman scattering technique. The surface-enhanced Raman spectrum for MgF2 molecules in the cermet film strongly suggests the existence of Ag nanoparticles dispersed in MgFa matrix. The intensities of the Raman spectra of Ag-MgF2 cermet films increase with Ag fraction. The enhancement of Raman scattering disappears when Ag content reaches wt.20%. The analyses with the transmission electron microscopy showed that Ag-MgF2 cermet films are mainly composed of amorphous MgF2 matrix with embedded faced-center-cubic Ag nanoparticles. It suggests that the percolation threshold should be around wt.20% of Ag content.     

Observation of Shubnikov-de Haas Oscillations in Large-Scale Weyl Semimetai WTe2 Films

Topological Weyl semimetal WTe2 with large-scale Him form has a promising prospect for new-generation spintronic devices.However,it remains a hard task to suppress the defect states in large-scale WTe2 films due to the chemical nature.Here we significantly improve the crystalline quality and remove the Te vacancies in WTe2 films by post annealing.We observe the distinct Shubnikov-de Haas quantum oscillations in WTe2 films.The nontrivial Berry phase can be revealed by Landau fan diagram analysis.The Hall mobility of WTe2 films can reach 1245cm^2V^-1s^-1 and 1423cm^2V^-1s^-1 for holes and electrons with the carrier density of 5× 10^19 cm^-3 and 2 × 10^19 cm^-3,respectively.Our work provides a feasible route to obtain high-quality Weyl semimetal films for the future topological quantum device applications.     

Enhanced Raman Scattering by Quasi-phase-matched Processes in ax^（2） Photonic Crystal

An intense comb-shaped Raman spectra were obtained from a two-dimensional nonlinear x（2） photonic crystal - a hexagonally poled LiTaO3 crystal with lattice parameter 9 micros. The lowest Raman shift was down to 2 cm^-1 and the order of anti-stokes and stokes signals both achieved 11. The novel Raman spectra were mediated first by intense phonon-polariton fields, which were driven through the quasi-phase-matched coupling between the incident dual-beam both from an optical parametric oscillation laser, and further amplified greatly also by such quasi-phasematched nonlinear optical process. The dependence of the Raman spectra character on the wavelength and intensity of incident beams were studied in detail, which accordingly revealed information of the inelastic scattering and the elementary excitation in the nonlinear medium. These results on the other hand suggest technological importance for developing a novel Raman laser with the multi-wavelength output and a tunable frequency interval and for possible applications in quantum optics.     

Influence of annealing temperature on properties of Cu(In,Ga)(Se,S)2 thin films prepared by co-sputtering from quaternary alloy and In2S3 targets

Pentanary Cu(In,Ga)(Se,S)₂ (CIGSS) thin films were deposited on soda-lime glass substrate by co-sputtering quaternary alloy, and In₂S₃ targets. In this study, we investigated the influence of post-annealing temperature on structural, compositional, electrical, and optical properties of CIGSS films. Our experimental results show that the CIGS quaternary target had chalcopyrite characteristics. All CIGSS films annealed above 733 K exhibited a polycrystalline tetragonal chalcopyrite structure, with (1 1 2) preferred orientation. The carrier concentration and resistivity of the resultant CIGSS layer annealed above 763 K was 4.86×10¹⁶ cm⁻³ and 32 Ω cm, respectively, and the optical band-gap of the CIGSS absorber layer was 1.18 eV. Raman spectral analysis demonstrated the existence of many different phases, including CuInSe₂, CuGaSe₂, and CuInS₂. This may be because the vibration frequencies of In-Se, In-S bonds are similar to the Ga-Se and Ga-S bonds, causing their absorption bands overlap.     

Magnetic properties of TbMn6Sn6-xGax (x=0.0－1.2) compounds

Effects of Ga substitution for Sn on the structure and magnetic properties of TbMn₆Sn_6-xGa_x (x=0.0－1.2) compounds have been investigated by means of x-ray diffraction, magnetization measurement and ¹¹⁹Sn M?ssbauer spectroscopy. The substitution of Ga for Sn results in a decrease in lattice constants and unit-cell volumes. The magnetic ordering temperature decreases monotonically with increasing Ga content from 423 K for x=0.0 to 390 K for x=1.2. At room temperature, the easy magnetization direction changes from the c-axis to the ab-plane. This variation implies that the substitution of Ga for Sn leads to a decrease in the c-axis anisotropy of the Tb sublattice. An increase in the non-magnetic Ga concentration results in a monotonic decrease of the spontaneous magnetization M_s at room temperature. Since there are three non-equivalent Sn sites, 2c (0.33, 0.67,0), 2d (0.33, 0.67,0.5) and 2e (0,0,0.34) in the TbMn₆Sn_6-xGa_x compounds, the ¹¹⁹Sn M?ssbauer spectra of the TbMn₆Sn₆ and TbMn₆Sn_5.4Ga_0.6 compounds can be fitted by three sextets. The hyperfine fields (HFs) decrease in the order of HF(2d)>HF(2e)>HF(2c), which is in agreement with the magnetic structure.     

过渡族元素掺杂BaTiO3-Tb1-xDyxFe2-y层状复合材料中的磁电效应

用溶胶-凝胶法制备1.0%mol Mn,Cr,Co掺杂 BaTiO₃(BTO)粉体,在1350℃下烧结成多晶陶瓷样品.X射线衍射和差示扫描量热分析表明,室温下掺杂BaTiO₃具有四方钙钛矿结构;居里点和相变潜热随Cr,Mn,Co掺杂逐渐降低.将掺杂BaTiO₃与Tb_1-xDy_xFe_2-y(TDF)胶合制成双层磁电复合材料,并研究了Cr:BTO-TDF,Mn∶BTO-TDF,Co:BTO-TDF层状复合材料中的磁电效应.实验表明,在340×80 A·m^-1偏置磁场下, Cr:BTO-TDF的横向磁电电压系数达到最大值586 mV·cm^-1·(80 A·m^-1)^-1.在400×80 A·m^-1偏置磁场下,Mn∶BTO-TDF和Co:BTO-TDF的横向磁电电压系数的最大值分别为480 mV·cm^-1·(80 A·m^-1)^-1和445mV·cm^-1·(80 A·m^-1)^-1.研究表明掺杂BaTiO₃-TDF层状复合材料中具有较强的磁电耦合.作为无铅压电材料,掺杂BaTiO₃制备的磁电效应器件颇具应用前景. 关键词： 磁电效应 双层复合材料 3')" href="#">掺杂BaTiO₃ 1-xDy_xFe_2-y')" href="#">Tb_1-xDy_xFe_2-y     

InGaN薄膜的紫外共振喇曼散射

利用325nm紫外光激发,对不同组分的In_xGa_1-xN薄膜的喇曼散射谱进行了研究.在光子能量大于带隙的情况下,观察到显著增强的二阶A₁(LO)声子散射峰.二阶LO声子峰都从一阶LO声子的二倍处向高能方向移动,移动量随样品In组分的增加而增大,认为是带内Frhlich相互作用决定的多共振效应引起的.分析了一阶LO声子散射频率和峰型与In组分的关系.在喇曼谱中观察到样品存在相分离现象,并与X射线衍射的实验结果进行 关键词： xGa_1-xN合金')" href="#">In_xGa_1-xN合金 紫外共振喇曼散射 二阶声子 相分离     

类富勒烯纳米晶CNx薄膜及其场致电子发射特性

利用微波等离子体增强化学气相沉积技术制备出了CN_x薄膜,并利用x射线光电子能谱、x射线衍射、扫描电子显微镜和Raman光谱等测试手段对所制备的CN_x薄膜的微结构和成分进行了分析.研究了其场致电子发射特性.发现薄膜的结构和场发射特性与反应系中的甲烷、氮气及氢气的流量比有关,当甲烷、氢气及氮气流量比为8/50/50 sccm时,制备的薄膜具有弯曲层状的纳米石墨晶体结构（类富勒烯结构）和很好的场发射特性.场发射阈值电场降低至1.1V/μm.当电场为5.9V/μm时,平 关键词： 类富勒烯 x薄膜')" href="#">CN_x薄膜 场致电子发射 微波等离子体增强化学气相沉积     

Annealing effects on the structure and electrical characteristics of amorphous Er2O3 films

Amorphous Er 2 O 3 films are deposited on Si (001) substrates by using reactive evaporation.This paper reports the evolution of the structure,morphology and electrical characteristics with annealing temperatures in an oxygen ambience.X-ray diffraction and high resolution transimission electron microscopy measurement show that the films remain amorphous even after annealing at 700 C.The capacitance in the accumulation region of Er 2 O 3 films annealed at 450 C is higher than that of as-deposited films and films annealed at other temperatures.An Er 2 O 3 /ErO x /SiO x /Si structure model is proposed to explain the results.The annealed films also exhibit a low leakage current density (around 1.38 × 10 4 A/cm 2 at a bias of 1 V) due to the evolution of morphology and composition of the films after they are annealed.     

Study of polycrystalline bulk CuIn1-xGaxTe2

Polycrystalline CuIn_1−xGa_xTe₂ bulk films were synthesized by reacting, in stoichiometric proportions, high purity Cu, In, Ga and Te in a vacuum sealed quartz ampoule. The phase structure and composition of the bulk films were analysed by X-ray diffraction and energy-dispersive X-ray analysis, respectively. The bulk samples, of p-type conductivity, are found to be near-stoichiometric, polycrystalline, with tetragonal chalcopyrite structure, predominantly oriented along a direction perpendicular to the (1 1 2) plane. Photoluminescence spectra were recorded at 7 K and 700 mW to characterize the defects and the structural quality. The main peak as a function of composition has been studied.     

射频溅射微晶NiOxHy膜电致变色性能及其机理研究

研究了射频溅射制备的NiO_x膜的电致变色性能,发现富氧非理想化学配比的NiO _x(x>1)膜具有变色活性,这种膜出现Ni³⁺和Ni²⁺的混 合价态,当H^＋注入并占据Ni空位时,导致Ni³⁺的t_2g 能级被填满,Ni³⁺被阴极还原为Ni²⁺引起光学透明,即为漂白态; 反之,H⁺被萃取出NiO 关键词： xH_y膜')" href="#">NiO_xH_y膜 电致变色     

硒化前后电沉积贫铜和富铜的Cu(In1-xGax)Se2薄膜成分及结构的比较

采用电沉积法获得了接近化学计量比的贫铜和富铜的Cu（In_1-xGa_x）Se₂（CIGS）预置层,研究比较了两种预置层及其硒化处理后的成分和结构特性.得到了明确的实验证据证明,硒化后富铜薄膜中的Cu_xSe相会聚集凝结成结晶颗粒分散在表面.研究表明：在固态源硒化处理后,薄膜成分基本不变;当预置层中原子比Cu/（In+Ga）<11时,硒化后薄膜表面存在大量的裂纹;而当Cu/（In+Ga） >12时,可以消除裂纹的产生,形成等轴状小晶粒;富铜预置层硒化时蒸发沉积少量In,Ga和Se后,电池效率已达到68%;而贫铜预置层硒化后直接制备的电池效率大于2%,值得进一步深入研究. 关键词： 1-xGa_x）Se₂薄膜')" href="#">Cu（In_1-xGa_x）Se₂薄膜 电沉积 硒化处理 贫铜或富铜薄膜     

Structural properties of Bi1-xLaxFeO3 studied by micro-Raman scattering

This paper reports that La-doped BiFeO 3(Bi1-x La x FeO3,x = 0,0.1,0.2,0.3,0.6,0.8 and 1.0) were studied by using micro-Raman spectroscopy and x-ray diffraction(XRD).The XRD patterns indicate that the structure of Bi1-xLaxFeO 3 changes from rhombohedral BiFeO3 to orthorhombic LaFeO3.The results of Raman spectroscopy show good agreement with the XRD results.Strikingly,the phonon peak at around 610 cm-1 and the two-phonon peaks in the high frequency range exist in all compounds and enhance with increasing La substitution.The increasing intensity of the 610 cm-1 peak is attributed to the changes in the FeO 6 octahedron during the rhombohedral-orthorhombic phase transition.The enhancements of the two-phonon peaks are associated with the breakdown of the cycloid spin configuration with the appearance of the orthorhombic structure.These results indicate the existence of strong spin-phonon coupling in Bi1-xLax FeO3,which may provide useful information for understanding the effects of La content on the structural and magnetic properties of Bi1-xLaxFeO3.