室温CdxZn1—xTe／ZnTe多量子阱光学双稳态的研究

研制了室温ＣｄｘＺｎ１－ｘＴｅ／ＺＮＴｅ多量子阱法布里－珀罗腔光双稳器件，并在该器件上观察到皮秒一级的室温激子光双稳。研究结果表明，ＣｄＺｎ１－ｘＴｅ／ＺｎＴｅ多量子阱光双稳器件的光双稳值和对比度分别为３６３ｋＷ／ｃｍ＾２和４：１。根据ＣｆｘＺｎ１－ｘＴｅ／ＺｎＴｅ多量子阱的吸收谱和激子非线性理论，归结了ＣｄｘＺｎ１－ｘＴｅ／ＺｎＴｅ多量子阱光双稳的主要非线性机理为激子的饱和和吸收。     

白宝石衬底上生长的MgxZn1-xO晶体薄膜的结构和光学性能

在白宝石 (sapphire)衬底上低温外延生长出了MgxZn1 -xO晶体薄膜 .x射线衍射 (XRD)及能量色散x射线 (EDX)分析表明 ,MgxZn1 -xO薄膜的晶体结构依赖于薄膜中Mg的组分x,随着Mg组分的增大 ,MgxZn1 -xO薄膜的结构从与ZnO晶体一致的六方结构转变为与MgO晶体一致的立方结构 .对MgxZn1 -xO薄膜的紫外透射光谱及紫外光致荧光谱 (UVPL)的分析表明 ,随着Mg组分的增大 ,光学吸收边产生明显的蓝移 ,表明MgxZn1 -xO晶体薄膜的带隙增大 ,且带隙连续可调 .吸收光谱和XRD测量显示 ,带隙高达 5 6 5eV的MgxZn1 -xO晶体薄膜与MgO之间的晶格失配仅为0 16 % .     

Band offsets engineering at Cd_xZn_(1-x)S/Cu_2ZnSnS_4 heterointerface

Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS)-based thin film solar cells usually use Cd S as a buffer layer, but due to its smaller band gap(2.4 e V), Cd S film has been replaced with higher band gap materials. The cadmium zinc sulfide(Cd Zn S) ternary compound has a higher band gap than other compounds, which leads to a decrease in window absorption loss. In this paper, the band offsets at Cd_xZn_(1-x)S/Cu_2ZnSnS_4 (CZTS) heterointerface are calculated by the first-principles, densityfunctional and pseudopotential method. The band offsets at Cd_(1-x)Zn_x S/CZTS heterointerface are tuned by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy, the calculated valence band offsets are small, which is consistent with the commonanion rule. The favorable heterointerface of type-I with a moderate barrier height( 0.3 e V) can be obtained by controlling the composition of Zn in Cd_(1-x)Zn_x S alloy between 0.25 and 0.375.     

Surface-defect-states photoluminescence in CdS nanocrystals prepared by one-step aqueous synthesis method

CdS nanocrystals were prepared by a simple one-step aqueous synthesis method using thioglycolic acid (TGA) as the capping molecule, and characterized by X-ray powder diffraction (XRD), UV-vis absorption spectra and photoluminescence (PL) emission spectroscopy. The effects of both TGA/Cd and Cd/S molar ratio on the surface-defect-state PL intensity of CdS nanocrystals have been investigated. It was found that all of the as-prepared CdS nanocrystals showed a strong broad emission in the range of 450-700 nm centered at 560 nm, which was attributed to the recombination of an electron trapped in a sulfur vacancy with a hole in the valance band of CdS. The surface-defect-states emission intensity of CdS nanocrystals significantly increased with the increase of Cd/S molar ratio, and showed a maximum when Cd/S molar ratio was 2.0. If Cd/S molar ratio continued to increase, namely more than 2.0, the surface-defect-states emission intensity would decrease. It was found that the surface-defect-states emission intensity increased with the increase the TGA/Cd molar ratio, and showed a maximum when the TGA/Cd molar ratio was equal to 1.8, and a further increase of the TGA/Cd molar ratio would lead to the decrease of the surface-defect-states emission intensity.     

Metal/semiconductor hybrids consisting of self-assembled CdS nanoparticles on Cd nanowires

We report on the synthesis and the characterisation of metal/semiconductor hybrids consisting of self-assembled CdS nanoparticles on Cd nanowires, which are grown by thermal evaporation of the mixture of CdS and Cr. The growth of the hybrids is attributed to the decomposition of CdS at high temperature and the strain relieving that arises mainly from the lattice mismatch between Cd and CdS. Temperature dependence of zero-field resistance of single nanohybrid indicates that the as-produced Cd/CdS nanohybrid undergoes a metal--semiconductor transition as a natural consequence of hybrid from metallic Cd and semiconducting CdS. The metal/semiconductor hybrid property provides a promising basis for the development of novel nanoelectronic devices.     

Analysis of Effect of Zn(O,S) Buffer Layer Properties on CZTS Solar Cell Performance Using AMPS

The Cu_2ZnSnS_4(CZTS)-based solar cell is numerically simulated by a one-dimensional solar cell simulation software analysis of microelectronic and photonic structures(AMPS-ID).The device structure used in the simulation is Al/ZnO:Al/nZn(O,S)/pCZTS/Mo.The primary motivation of this simulation work is to optimize the composition in the ZnO_(1-x)S_x buffer layer,which would yield higher conversion efRciency.By varying S/(S+0) ratio x,the conduction band offset(CBO) at CZTS/Zn(0,S) interface can range from-0.23 eV to 1.06 eV if the full range of the ratio is considered.The optimal CBO of 0.23 eV can be achieved when the ZnO_(1-x)S_x buffer has an S/(S+0) ratio of 0.6.The solar cell efRciency Rrst increases with increasing sulfur content and then decreases abruptly for x 0.6,which reaches the highest value of 17.55%by our proposed optimal sulfur content x = 0.6.Our results provide guidance in dealing with the ZnO_(1-x)S_x buffer layer deposition for high efficiency CZTS solar cells.     

(Zn、Cd)S:Cu、Br黄色交流电致发光材料的晶体结构和发光特性

本文首次提出一种制备黄色交流粉末电致发光材料的新方法.在以ZnS为基质的绿色材料的基础上,低温扩散CdS,获得系列黄材料.并测量了晶体结构和发光特性.     

Ti1-xCexO2体系纳米粉体的制备及其结构表征

 采用溶胶凝胶法制备了纳米Ti_1-xCe_xO₂系列样品。利用X射线衍射（XRD）、透射电子显微镜（TEM）、高分辨电子显微镜（HRTEM）对纳米Ti_1-xCe_xO₂系列样品颗粒尺寸、形貌以及固溶区范围和物相组成进行了研究；同时，采用Rietveld结构精修的方法研究了Ce的不同掺杂量对TiO₂晶体结构的影响。实验结果表明，Ce掺杂TiO₂能够形成Ti_1-xCe_xO₂固溶体，Ti_1-xCe_xO₂的固溶区范围在x=0～0.06之间，Ti_1-xCe_xO₂的晶粒度为5～10 nm，平均颗粒粒度约35 nm，且粒度均匀。     

CdSexS1-x电子学结构及光学性质的第一性原理研究

CdSe是Ⅱ-Ⅵ族中重要的半导体材料,一定条件下可与CdS形成无限固溶体CdSexS1-x(0≤x≤1)。CdSexS1-x在薄膜太阳电池及光电器件等领域具有重要的应用,对CdSexS1-x的电子学结构和光学性质进行研究有助于进一步提高其在光电器件等方面的应用。基于第一性原理,采用平面波超软赝势方法,计算了CdSexS1-x的电子学结构及光学性质,并将计算结果与实验进行了对比。结果表明,CdSexS1-x的晶格常数随着Se组分的增加呈线性增大趋势,态密度向低能级方向移动,禁带宽度减小,光吸收边发生一定程度的蓝移。当Se含量为0.5时,CdSexS1-x的光折射、反射和能量损失最大。除了Se和S的比例为1∶1时CdSexS1-x所属晶系为三斜晶系,其他比例下均为立方晶系。理论计算结果与实验符合。     

反应前驱物中n(S)∶n(Cd)对CdS薄膜结构及发光特性的影响

采用化学水浴以CdCl2·H2O、CS( NH2)2、NH4Cl、NH3·H2O和去离子水作为反应前驱物制备CdS纳米晶薄膜.采用扫描电镜( SEM)、X射线衍射(XRD)、透射光谱和稳态荧光光谱,研究了反应前驱物中不同的n(S)∶n(Cd)对所制备的CdS薄膜的形貌、结构和光学性能的影响.结果表明:反应前驱物中n(S...     

Phase equilibrium of Cd_(1-x)Zn_xS alloys studied by first-principles calculations and Monte Carlo simulations

The first-principles calculations based on density functional theory combined with cluster expansion techniques and Monte Carlo(MC) simulations were used to study the phase diagrams of both wurtzite(WZ) and zinc-blende(ZB)Cd_(1-x)Zn_xS alloys.All formation energies are positive for WZ and ZB Cd_(1-x)Zn_xS alloys,which means that the Cd_(1-x)Zn_xS alloys are unstable and have a tendency to phase separation.For WZ and ZB Cd_(1-x)Zn_xS alloys,the consolute temperatures are 655 K and 604 K,respectively,and they both have an asymmetric miscibility gap.We obtained the spatial distributions of Cd and Zn atoms in WZ and ZB Cd_(0.5)Zn_(0.5)S alloys at different temperatures by MC simulations.We found that both WZ and ZB phases of Cd_(0.5)Zn_(0.5)S alloy exhibit phase segregation of Cd and Zn atoms at low temperature,which is consistent with the phase diagrams.     

ZnO对硫硒化镉量子点玻璃发光性能的影响

以CdS、Se、Zn粉和玻璃基质为原料,采用高温熔融法制备了CdS_xSe_(1-x)量子点硅酸盐玻璃,研究了ZnO含量对CdS_xSe_(1-x)量子点发光玻璃微观结构及发光性能的影响。结果表明:ZnO对CdS_xSe_(1-x)量子点玻璃的发光性能有显著的影响,紫外-可见吸收光谱和荧光光谱分析结果说明在470 nm蓝光激发下,掺Zn O的CdS_xSe_(1-x)量子点玻璃中CdS_xSe_(1-x)量子点处于强限域区,出现了强烈的带边激子发射现象,证明量子点具有明显的量子尺寸效应。当样品中ZnO的质量分数为13%时,荧光光谱峰强最大,半峰宽最窄。     

Synthesis of ZnO hollow spherical structures with different surface-to-volume ratios

ZnO hollow spherical structures with different surface-to-volume ratios were prepared using solid Zn microspheres as template via a simple oxygen-controlled thermal evaporation approach. The results of scanning electron microscopy testify that ZnO hollow spherical structures with different morphologies can be realized by changing oxygen supply. The corresponding transmission electron microscopy images further reveal that the prepared spherical structures are hollow, and nanorods epitaxially grow from the surface of the sphere shell along the [0001] direction. A series of experiments indicates that the formation of hollow spherical structures involves the oxidization on the surface of Zn microspheres, sublimation of Zn, and growth of ZnO nanorods.     

CdS纳米带和纳米锯的热蒸发法的合成和光学性质研究

利用氢气辅助的一步热蒸发法,在镀有金膜的硅片上制备出大量的CdS纳米结构. CdS纳米结构由纤锌矿结构的CdS纳米带和纳米锯组成. 研究表明沉积温度对CdS纳米结构的形貌和尺寸具有重要影响. 用气-液-固和气-固复合生长机理解释了CdS纳米结构的形成过程.光致发光测试表明CdS纳米带和纳米锯均发射出波长为512 nm的很强的绿色发光峰,对应于CdS的带-带跃迁. 同时对CdS纳米结构的光波导性质也进行了观察和讨论.     

Synthesis of CdS hollow/solid nanospheres and their chain-structures by membrane technique

CdS hollow/solid nanospheres and their chain-structures were successfully synthesized through supporting liquid membrane (SLM) system with bio-membrane. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV–Vis spectroscopy, and photoluminescence (PL) spectroscopy have been used for the characterization of the products. The average diameters of CdS solid/hollow spheres are about 10, 40 nm, respectively. The wall of the hollow spheres is about 5 nm. CdS products are all cubic face-centered structure with the cell constant a = 5.830 Å. We also explore the morphology, structure and possible synthesis mechanism. A possible template mechanism has been proposed for the production of the hollow CdS nanocrystals, that is, CdS nanoparticles grow along the non-soakage interface between CHCl3 and reactant solution. During this process, the organic functional groups were crucial to the control of crystal morphologies.     

纳米二氧化钛分离富集ICP-AES测定镉、钴、锌的研究

建立了纳米二氧化钛分离富集,电感耦合等离子体原子发射光谱(ICP-AES)测定镉、钴和锌的新方法。考察了溶液pH值、洗脱条件和干扰离子等因素对分析物分离富集的影响。结果表明,在pH 9～10范围内,Cd, Co和Zn可被纳米TiO₂定量富集,吸附于纳米TiO₂上的金属离子可用0.1 mol·L-1的硝酸溶液完全解脱。在优化的实验条件下,纳米TiO₂对Cd, Co和Zn的吸附容量分别为8.1, 6.9和15.1 mg·g-1。本法对Cd, Co和Zn的检出限(3σ)分别为：5.1, 3.4和2.9 ng·mL-1,相对标准偏差(RSD)分别为4.3%, 4.6%和4.9%(n=9, c= 0.1 μg·mL-1)。该方法已成功地应用于环境样品中镉、钴和锌的测定,分析结果满意。     

Increasing the equilibrium solubility of dopants in semiconductor multilayers and alloys

We have theoretically studied the possibility to control the equilibrium solubility of dopants in semiconductor alloys, by strategic tuning of the alloy concentration. From the modeled cases of C(0) in Si(x)Ge(1-x), Zn(-) and Cd(-) in Ga(x)In(1-x)P it is seen that under certain conditions the dopant solubility can be orders of magnitude higher in an alloy or multilayer than in either of the elements of the alloy. This is found to be due to the solubility's strong dependence on the lattice constant for size mismatched dopants. The equilibrium doping concentration in alloys or multilayers could therefore be increased significantly. More specifically, Zn- in a Ga(x)In(1-x)P multilayer is found to have a maximum solubility for x = 0.9, which is 5 orders of magnitude larger than that of pure InP.     

CdxZn1-xS:SmF3的红色薄膜电致发光

本文首次报道了用CdxZn1-xS替代ZnS作为基质,改进SmF3的TFEL的实验;通过适当地在基质中掺杂CdS,在一定程度上提高了SmF3的TFEL发光亮度;分析了CdxZn1-xS基质中Cd含量对SmF3的TFEL的影响,探讨了发光亮度提高的原因.     

Zn1—xMnx／ZnSe应变超晶格分子束外延生长及光学特性研究

用分子束外延方法在ＧａＡｓ（１００）衬底上成功生长了高质量的Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ（ｘ＝０．１６），超晶格结构，用Ｘ射线衍射和低温光致发光（ＰＬ）对其结构，应变分布以及光学性能进行了研究，结果表明，２Ｋ温度下，Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ超晶格的光致发光中主发光峰对应于ＺｎＳｅ阱中基态电子和基态轻空穴之间的自由激子跃迁，而且其峰位相对于ＺｎＳｅ薄膜材料的自由激子峰有明显移动。其中，当超晶     

Large-quantity synthesis of ZnO hollow objects by thermal evaporation: Growth mechanism, structural and optical properties

Synthesis of large-quantity uniformly distributed ZnO hollow objects, i.e. cages and spheres have been performed on Si(1 0 0) and steel alloy substrates by the direct heating of metallic zinc powder in the presence of oxygen. Extensive structural observations revealed that the formed products are crystalline ZnO with the wurtzite hexagonal phases. The Raman-active optical phonon E₂ modes, attributed to wurtzite hexagonal phase of ZnO, were observed at 437 cm⁻¹ for the products grown on both the substrates. The room-temperature photoluminescence spectra showed a broad band in the visible region with a suppressed UV emission, indicating the presence of oxygen vacancies and structural defects in the as-grown structures. Additionally, post growth annealing was also carried out to further investigate the photoluminescence properties of the as-grown products. It was observed that the formation of hollow objects consists of several stages which include the formation of Zn clusters, oxidation on the sheath and sublimation/evaporation of the Zn from the interiors, resulted in the formation of hollow objects.