Effect of concentration of cadmium sulfate solution on structural,optical and electric properties of Cd_(1-x)Zn_(x)S thin films

Cd_(1-x)Zn_(x)S thin films were deposited by chemical bath deposition(CBD)on the glass substrate to study the influence of cadmium sulfate concentration on the structural characteristics of the thin film.The SEM results show that the thin film surfaces under the cadmium sulfate concentration of 0.005 M exhibit better compactness and uniformity.The distribution diagrams of thin film elements illustrate the film growth rate changes on the trend of the increase,decrease,and increase with the increase of cadmium sulfate concentration.XRD studies exhibit the crystal structure of the film is the hexagonal phase,and there are obvious diffraction peaks and better crystallinity when the concentration is 0.005 M.Spectrophotometer test results demonstrate that the relationship between zinc content x and optical band gap value E_(g) can be expressed by the equation E_(g)(x)=0.59x^(2)+0.69x+2.43.Increasing the zinc content can increase the optical band gap,and the absorbance of the thin film can be improved by decreasing the cadmium sulfate concentration,however,all of them have good transmittance.At a concentration of 0.005 M,the thin film has good absorbance in the 300-800 nm range,80%transmittance,and band gap value of 3.24 eV,which is suitable for use as a buffer layer for solar cells.

Proposal and Achievement of a Relatively Al-rich Interlayer for In-rich Al_x In_(1-x)N Films Deposition

Ternary In-rich AlxIn1-x N films were successfully grown on Si （111） and （0001） sapphire substrates by radio-frequency magnetron sputtering on a relatively Al-rich AlxIn1-x N layer after AlN buffer. X-ray diffraction （XRD） patterns of the films indicate highly c axis-oriented wurtzite structure and the indium content of about 0.76 has been evaluated according to the Vegard＇s law. An Al-rich AlxIn1-xN transition layer was formed between the ultimate In-rich AlxIn1-x N film and the AlN buffer, which served as a further buffer to alleviate mismatch. X-ray photoelectron spectroscopy （XPS） depth profiling analyses confirm the alternative of indium and aluminum composition and the unavoidable oxygen impurities from surface to bulk. Owing to high indium content, obvious E2u and InN-like Al （LO） phonon model accompanying with slight A1N-like A1 （LO） phonon model are observed. Hall effect measurements demonstrate n-type electrical conductivity in these alloys with carrier concentrations n=1019 cm-3. The strain in In-rich AlxIn1-x N films can be significantly reduced by introducing an Al-rich interlayer, facilitating the improvement of film quality for diverse device applications.

Room-temperature ferromagnetism induced by Cu vacancies in Cu_x(Cu_2O)_(1-x) granular films

Cux（Cu2O）1-x（0.09 x 1.00） granular films with thickness about 280 nm have been fabricated by direct current reactive magnetron sputtering. The atomic ratio x can be controlled by the oxygen flow rate during Cux（Cu2O）1-x deposition. Room-temperature ferromagnetism（FM） is found in all of the samples. The saturated magnetization increases at first and then decreases with the decrease of x. The photoluminescence spectra show that the magnetization is closely correlated with the Cu vacancies in the Cux（Cu2O）1-x granular films. Fundamentally, the FM could be understood by the Stoner model based on the charge transfer mechanism. These results may provide solid evidence and physical insights on the origin of FM in the Cu2O-based oxides diluted magnetic semiconductors, especially for systems without intentional magnetic atom doping.

Nanoscale structural investigation of Zn_(1-x)Mg_(x)O alloy films on polar and nonpolar ZnO substrates with different Mg contents

Zn_(1-x)Mg_(x)O alloy films are important deep ultraviolet photoelectric materials.In this work,we used plasma-assisted molecular beam epitaxy to prepare Zn_(1-x)Mg_(x)O films with different magnesium contents on polar(0001)and nonpolar(1010)ZnO substrates.The nanoscale structural features of the grown alloy films as well as the interfaces were investigated.It was observed that the cubic phases of the alloy films emerged when the Mg content reached 20%and 37%for the alloy films grown on the(0001)and(1010)ZnO substrates,respectively.High-resolution transmission electron microscopy images revealed cubic phases without visible hexagonal phases for the alloy films with more than 70%magnesium,and the cubic phases exhibited three-fold and two-fold rotations for the alloy films on the polar(0001)and nonpolar(1010)ZnO substrates,respectively.This work aims to provide references for monitoring the Zn_(1-x)Mg_(x)O film structure with respect to different substrate orientations.

Optical study of Ba(Mn_xTi_(1-x)O_3) thin films by spectroscopic ellipsometry

Stoichiometric Ba（MnxTi（1-x）O3） （BMT） thin films with various values of x were deposited on Si（111） substrates by the sol-gel technique. The influence of Mn content on the optical properties was studied by spectroscopic ellipsometry （SE） in the UV–Vis–NIR region. By fitting the measured ellipsometric parameter （Ψ and Δ） with a four-phase model （air/BMT＋voids/BMT/Si（111））, the key optical constants of the thin films have been obtained. It was found that the refractive index n and the extinction coefficient k increase with increasing Mn content due to the increase in the packing density. Furthermore, a strong dependence of the optical band gap Eg on Mn/Ti ratios in the deposited films was observed, and it was inferred that the energy level of conduction bands decreases with increasing Mn content.

Preparation of Y_(1-x)Ho_xBa_2Cu_3O_(7-δ) Superconductive Thin Films

Y_(1-x)Ho_xBa_2Cu_3O_(7-δ)(0<x<1) sinsle crystal thin films oriented with the caxis perpendicular to the sur-face were grown by DC magnetron sputtering technique. Target was pieced together with half of YBa_2Cu_3O_(7-δ)(YBCO) and half of HoBa_2Cu_3O_(7-δ)(HBCO) superconducting materials. As the distance between HBCO targetmaterial and substrate is varied , the Ho content in material is changed respectively. When the content of Ho is0. 7 (atom ratio) , the T_c>83K.

Effects of Annealing Processes on CuxSi(1-x) Thin Films

The CuxSi（1-x） thin films have been grown by pulsed laser deposition（PLD） with in situ annealing on Si（001） and Si（111）,respectively.The transformation of phase was detected by X-ray diffraction（XRD）.The results showed that the as-deposited films were composed of Cu on both Si（001） and Si（111）.The annealed thin films consisted of Cu ＋η ＂-Cu3Si on Si（001） while Cu ＋η＇-Cu3Si on Si（111）,respectively,at annealed temperature（Ta）= 300-600℃.With the further increasing of Ta,at Ta= 700℃,there was only one main phase,η＂-Cu3Si on Si（001） while η＇-Cu3Si on Si（111）,respectively.The annealed thin films transformed from continuous dense structure to scattered-grain morphology with increasing Ta detected by field emission scanning electron microscope（FESEM）.It was also showed that the grain size would enlarge with increasing annealing time（ta）.

Polycrystalline ZnSx Se1—x thin films deposited on ITO glass by MBE

MBE growth of ZnS_xSe_1-x thin films on ITO coated glass substrate s were carried o ut using ZnS and Se sources with the substrate temperature ranging from 270℃ to 330℃. The XRD θ/2θ spectra resulted from these films indicated that the as-gro wn polycrystalline ZnS_xSe_1-x thin films had a preferred orientat ion along the (1 11) planes. The evaluated crystal sizes as deduced from the FWHM of the XRD laye r peaks showed strong growth temperature dependence, with the optimized temperat ure being about 290℃. Both AFM and TEM measurements of these thin films also in dicated a similar growth temperature dependence. High quality ZnS_xSe_1- x thin fil m grown at the optimized temperature had the smoothest surface with lowest RMS v alue of 1.2 nm and TEM cross-sectional micrograph showing a well defined column ar structure.

Optoelectronic Characterization of Chemical Bath Deposited Cd_xCo_1-xS Thin Film

Cadmium Cobalt Sulphide (CdxCo1-xS) thin film was deposited on microscopic glass substrate using chemical bath deposition technique at room temperature from aqueous solutions of Cadmium Chloride, Cobalt Chloride and Thiourea in which ammonium solution was used as complexing agents. The optical properties were characterized using the absorbance and transmission measurement from Unico UV-2102 PC spectrophotometer, at normal incidence of light in the wavelength range of 200 - 1000 nm. We report the deposition and optimization of the growth parameter with respect to time which showed that the band gap energy and the composition verified from the extended Vegard’s law are highly dependent on deposition time. The average transmittance of the film in VIS-NIR region ranges between 30% and 78% with absorbance range of 0.15 - 0.47 within the same wavelength range. The film was also observed to exhibit poor reflectance (11 x = 0.75;0.83 and 0.94), respectively. Other optical and dielectric properties of the films were also characterized. Based on the exhibited properties of the film, it can be concluded that it is a promising material for selective coatings for solar cells;effective coatings for poultry houses;use as antireflective coating materials, and for fabrication of optoelectronic devices.

磁控溅射法制备的CZGe_xT_(1-x)S薄膜的光电性能研究

用先磁控溅射多层金属膜预置层后硫化的方法成功制备出CZGe_xT_(1-x)S薄膜,并主要研究了Ge含量对于该薄膜光电学性能的影响。分别采用X射线衍射仪、X射线能量色散谱仪、拉曼光谱仪、扫描电子显微镜,紫外-可见-近红外分光光度计和霍尔效应测量仪对不同Ge含量的CZGe_xT_(1-x)S薄膜的物相结构、元素比例、表面形貌、光学带隙以及电学性能进行了表征与分析。结果表明随着Ge含量的升高,晶粒尺寸不断长大,光学带隙从1.52上升至2.12 e V。同时,Ge替换Sn可减少薄膜内的缺陷,所制备的CZGe S薄膜的载流子浓度与迁移率分别为1.99×1018cm-3与9.712 cm2/Vs。

Phase diagrams on composition-spread Fe_(y)Te_(1-x)Se_(x) films

Fe_(y)Te_(1-x)Se_(x),an archetypical iron-based high-temperature superconductor with a simple structure but rich physical properties,has attracted lots of attention because the two end compositions,Se content x=0 and 1,exhibit antiferromagnetism and nematicity,respectively,making it an ideal candidate for studying their interactions with superconductivity.However,what is clearly lacking to date is a complete phase diagram of Fe_(y)Te_(1-x)Se_(x)as functions of its chemical compositions since phase separation usually occurs from x~0.6 to 0.9 in bulk crystals.Moreover,fine control of its composition is experimentally challenging because both Te and Se are volatile elements.Here we establish a complete phase diagram of Fe_(y)Te_(1-x)Se_(x),achieved by high-throughput film synthesis and characterization techniques.An advanced combinatorial synthesis process enables us to fabricate an epitaxial composition-spread Fe_(y)Te_(1-x)Se_(x)film encompassing the entire Se content x from 0 to 1 on a single piece of CaFsubstrate.The micro-region composition analysis and X-ray diffraction show a successful continuous tuning of chemical compositions and lattice parameters,respectively.The micro-scale pattern technique allows the mapping of electrical transport properties as a function of relative Se content with an unprecedented resolution of0.0074.Combining with the spin patterns in literature,we build a detailed phase diagram that can unify the electronic and magnetic properties of Fe_(y)Te_(1-x)Se_(x).Our composition-spread Fe_(y)Te_(1-x)Se_(x) films,overcoming the challenges of phase separation and precise control of chemical compositions,provide an ideal platform for studying the relationship between superconductivity and magnetism.

Pulsed laser deposition of single-oriented superconducting Ba_(1-x)K_xBiO_3 thin films

The development of superconductor/insulator/superconductor（SIS）tunnel junctions inthe cuprate high-temperature superconductor family has been hampered by an anisotropicstructure and a coherence length ξ as short as 0.3 nm. However, the discovery of Ba1-xKx-BiO3（x≈0.4） superconductor which is an isotropic cubic structure and has a

Tunable Ba_(0.5) Sr_(0.5) TiO_3 film bulk acoustic resonators using SiO_2 /Mo Bragg reflectors

Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.