Fast vapor growth of cadmium telluride single crystals

Cadmium telluride single crystals were grown at growth rates of 35 mm per day by the physical vapor transport (PVT) method under high temperature gradient conditions. This is believed to be the highest PVT growth rate of CdTe reported to date. Lamellar twins are the only ones present in the CdTe crystals grown under optimal conditions in this work. At growth rates up to 15 mm per day, the crystals have a dislocation density of ∼10⁴ cm⁻². The etch pit density increases to ∼10⁵ cm⁻² with an increase of the growth rate up to 35 mm per day. Based on a uniform thermal field and high interface stability, which are established by large temperature gradients up to 40°C/cm at the growth interface, spurious nucleation and lateral twins were effectively eliminated, and the density of the lamellar twins remained low at crystal growth rates up to 35 mm per day. The major contributions of the high temperature gradients to the single crystalline growth and the apparent origin of polycrystalline grains are also discussed in this paper.     

基于弛豫铁电单晶的红外热释电探测器研究

研究了新型热释电材料驰豫铁电单晶(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMNT)的低损伤减薄工艺、电极成型和耦合封装等关键技术,研制了基于PMNT的单元热释电探测器。对减薄后约30μm晶片材料性能的测试分析表明,部分样品的热释电系数约为9.0×10-4 C/m2 K,无明显衰减。采用低噪声电路提取单元探测器的微弱热释电电流,对所研制的单元探测器性能进行了测试分析。     

Controllable molecular doping in organic single crystals toward high-efficiency light-emitting devices

Organic single-crystalline semiconductors have drawn significant attention in the area of organic electronic and optoelectronic devices due to their superiorities of highly ordered structure, high carrier mobility and low impurity content. Molecular doping technique has made great progress in improving device performance via optimizing the optical and electrical properties of organic semiconductors. In particular, this technique has been attempted by taking fluorescent dye-molecules as the emissive dopants to tune emission color and improve device performance of organic single crystals. Up to now, there are few reports about the use of molecular doping in organic single crystals to optimize their intrinsic electrical properties. Here, we have introduced the controllable molecular doping as a feasible approach toward manipulating charge carrier transport properties of organic single crystals. Upon optimization of doping concentration, balanced carrier transport can be realized in 5,5′-bis(4-trifluoromethyl phenyl) [2,2’] bithiophene (P2TCF₃)-doped 1,4-bis(4-methylstyryl) benzene (BSB–Me) crystals. Organic light-emitting devices (OLEDs) based on these doped crystals achieve a maximum luminance of 423 cd/m² and current efficiency of 0.48 cd/A. It demonstrates that high-efficiency crystal-based OLEDs are of great significance for the development of organic electronics, especially for display and lighting applications.     

配电网线路单相接地故障定位装置研究

长时间以来,配电网线路单相接地的故障定位问题,一直是国内外研究的重点对象之一,随着我国社会主义经济的不断发展以及人们生活水平的不断提高,对于供电方面的需要和要求也随之发生了变化。在供电事业的发展过程中,有一个问题已经不得不引起重视了,那便是配电网线路单相接地的故障定位问题,据不完全数据的统计,我国现阶段每年由于配电网发生单相接地故障,都会造成我国每年十几万度供电的减少,极大地影响了供电企业的经济效益和对供电指标的完成,更是从一定程度上制约了我国社会主义经济的发展步伐。为此,笔者在本文中结合自身的工作经验和对相关知识的了解,简述了单相接地故障带来的影响和危害,简要分析了我国现阶段常用的故障定位方法,并且针对配电网线路单相接地故障定位装置的研究进行了详细的探究和论述。     

Effect of rhenium doping on various physical properties of single crystals of MoSe2

正Effect of rhenium doping is examined in single crystals of MoSe_2 viz.MoRe_(0.005)Se_(1.995), MoRe_(0.001)Se_(1.999) and Mo_(0.995)Re_(0.005)Se_2,which is grown by using the direct vapor transport(DVT) technique. The grown crystals are structurally characterized by X-ray diffraction,by determining their lattice parameters a and c,and X-ray density.Also,the Hall effect and thermoelectric power(TEP) measurements show that the single crystals exhibit a p-type semiconducting nature.The direct and indirect band gap measurements are also undertaken on these semiconducting materials.     

Effect of off-orientation of seed crystal on silicon carbide (SiC) single-crystal growth on the (11 $$\bar 2$$ 0) surface0) surface

The effect of off-orientation growth has been investigated in terms of stacking fault formation during physical vapor transport (PVT) growth of silicon carbide (SiC) single crystals on the (11 0) seed crystal surface. Occurrence of stacking fault formation is largely dependent on the direction of off-orientation, and basal plane stacking fault density is significantly reduced by growing the crystals on a (11 0) seed crystal off-oriented toward 〈0001〉. The density of the basal plane stacking faults rapidly decreases from 100–150 cm⁻¹ to ∼10 cm⁻¹ as the degree of off-orientation is increased from 0 to 10 deg. The results are interpreted in the framework of microscopic facet formation during PVT growth, and the introduction of off-orientation of seed crystal is assumed to prevent (01 0) and (10 0) microfacet formation on the (11 0) growing surface through modification of the surface growth kinetics and to suppress the stacking fault formation. An erratum to this article is available at .     

Ta2O5单晶激光法生长及其介电性质研究

Ta2O5 single crystals have been grown by the laser heated pedestal growth (LHPG) technique up to several centimeters length with diameter of 1.1 mm. The crystal, characterized by X-ray diffraction, dielectric measurement, and thermal expansion analysis, has Htri-Wa2O5 symmetry. Dielectric permittivity, loss tangent along [001] and [110] direction were investigated over the temperature range from -180℃ to 100℃. Large dielectric anisotropy in 2O5 single crystal was observed. At room temperature, the dielectric permittivities (1 MHz) along [001] and [110] are 33.2 and 231.9, respectively. The reason of dielectric enhancement in Ta2O5 crystal grown by LHPG was also discussed.     

Growth and dielectric properties of Ta_2O_5 single crystals grown by laser heated pedestal growth technique

Ta2O5 single crystals have been grown by the laser heated pedestal growth (LHPG) technique up to several centimeters length with diameter of 1.1 mm. The crystal, characterized by X-ray diffraction, dielectric measurement, and thermal expansion analysis, has Htri-Ta2O5 symmetry. Dielectric permittivity, loss tangent along [001] and [110] direction were investigated over the temperature range from -80 ℃ to 100 ℃. Large dielectric anisotropy in Ta2O5 single crystal was observed. At room temperature, the dielectric permittivities (1 MHz) along [001] and [110] are 33.2 and 231.9, respectively. The reason of dielectric enhancement in Ta2O5 crystal grown by LHPG was also discussed.     

Thermal Annealing and Propagation of Shockley Stacking Faults in 4H-SiC PiN Diodes

Stacking faults within 4H-SiC PiN diodes are known to be detrimental to device operation. Here, we present electroluminescence (EL) images of 4H-SiC PiN diodes providing evidence that electrically and optically stimulated Shockley stacking fault (SSF) propagation is a reversible process at temperatures as low as 210°C. Optical beam induced current (OBIC) images taken following complete optical stressing of a PiN diode and that lead to a small number of completely propagated SSFs provide evidence that such defects propagate across the n–/p+ interface and continue to grow throughout the p+ layer. These observations bring about questions regarding the validity of the currently accepted driving force mechanism for SSF propagation.     

Defects in CdTe single crystals grown by very fast vapor growth technique

Single crystals of CdTe were obtained by the very fast vapor growth technique. The four major defects, namely, multi-grains, lamellar, lateral, and micro-twins, which are fatal to the single crystallinity, were eliminated or limited by increasing the growth stability. This investigation indicates that the latent heat under high growth rate conditions should not be neglected. A model is developed to explain the effects of latent heat on the growth stability at the interface. A relationship between crystal morphologies and growth conditions was established. It strongly suggests that the above defects are growth stability related. The origin of twinning, dominated by growth stability, is discussed in this paper.     

Effect of rhenium doping on various physical properties of single crystals of MoSe2

Effect of rhenium doping is examined in single crystals of MoSe₂ viz. MoRe_0.005Se_1.995, MoRe_0.001Se_1.999 and Mo_0.995Re_0.005Se₂, which is grown by using the direct vapor transport (DVT) technique. The grown crystals are structurally characterized by X-ray diffraction, by determining their lattice parameters a and c, and X-ray density. Also, the Hall effect and thermoelectric power (TEP) measurements show that the single crystals exhibit a p-type semiconducting nature. The direct and indirect band gap measurements are also undertaken on these semiconducting materials.     

Bulk growth of Hg0.8Cd0.2Te single crystals by a combined CVT-seeding technique

The growth of high quality Hg_0.8Cd_0.2Te bulk single crystals by CVT, combined with an in-situ seeding technique, is reported here for the first time. For this purpose, a temperature difference of 590° → 540° C with a gradient of 40°-50° C/cm at the solid-vapor interface, and about 0.1 atm of HgI₂ as a transport agent, were employed. The bulk crystals have the expected stoichiometry and compositional homogeneity. Etch pit densities of 10⁴-10⁵ cm⁻² on the (111) face and hitherto unreported etch pits on the (100) face were observed in this work. Possible origins of the sub-grain structure are discussed.     

Seeded growth of GaN at high N2 pressure on (0 0 0 1) polar surfaces of GaN single crystalline substrates

GaN single crystals obtained by the high nitrogen pressure solution method without an intentional seeding, show strong growth anisotropy which results in their platelet shape. The attempts to enhance the growth into (0 0 0 1) directions by the increase of the integral supercooling in the solution, often lead to the growth instabilities on both Ga-polar and N-polar (0 0 0 1) surfaces. This can be avoided only by the precise control of the growth conditions at the crystallization front on the particular surface.The results of the seeded growth on both Ga- and N-polar (0 0 0 1) surfaces in configuration enabling such a control is reported. It is shown that dominating mechanisms of the unstable growth such as the cellular growth or edge nucleation can be suppressed. Differences in nucleation and growth in dependence on surface polarity are discussed.     

X射线衍射形貌术在碲锌镉晶体中的应用

碲锌镉晶体中存在着各种典型晶体缺陷,X射线衍射形貌术是一种非破坏性地整体研究晶体材料结构完整性、均匀性的有效方法。本文将反射式X射线衍射形貌术应用于碲锌镉晶体质量的评价,研究了入射线狭缝宽度、积分时间、扫描步长等测试参数以及样品表面加工状态对X射线衍射形貌的影响。结果表明入射线狭缝宽度对碲锌镉晶体的X射线衍射成像及晶体质量筛选应用影响很大,积分时间、样品扫描步长等测试参数的选择与入射线狭缝宽度密切相关。     

一种改进的通信有限状态机的错误诊断方法

目前对于通信状态机的研究已经很广泛,但对于通信状态机的错误诊断方法的研究不多,已有的问题模型都是输出错误和转换错误。为了更好地将错误诊断与实际相结合,本文在一般的通信有限状态机模型上,新增了一种不可执行的情况,并在传统的问题模型中新增一种转换未执行错误的问题模型。在假设单个错误的情况下,提出了一整套新的错误诊断算法,算法通过分析症状信息进行分步检测,并利用可疑转换下一步输入输出和用例的转换序列等信息来定位出单个错误。最后,文中给出一个实例,详细描述了算法的诊断过程。     

基于声发射技术的金刚石单晶生长机理研究

作为一种动态无损检测技术,声发射在研究材料的变化机理和特殊性能表征等方面具有重要作用.本文采用声发射检测技术对高温高压下人造金刚石单晶的生长过程进行了检测与分析.并结合金刚石/金属包膜界面微观形貌的观察,讨论了声发射信号能量、幅度、振铃等参数的变化规律.实验结果表明,声发射信号的特征参数能客观反映金刚石单晶在高温高压下...     

Synthesis,growth and characterization of AgInSe2 single crystals

Single crystal of the ternary semi-conductor AgInSe₂ has been grown by Bridgman technique. The AgInSe₂ crystal crystallizes in the tetragonal chalcopyrite structure. Using melt temperature oscillation method polycrystalline charge was synthesized. The synthesized charge was subjected to powder X-ray diffraction analysis. Thermal property of AgInSe₂ was analyzed using differential scanning calorimetry (DSC) technique. The melting and solidification temperature is 777 °C and 761 °C respectively. The synthesized polycrystalline charge was employed to grow AgInSe₂ single crystals. The grown crystal was confirmed by single crystal X-ray diffraction. The crystal exhibits 60% transmission in the Infrared region. The stoichiometric composition of AgInSe₂ was confirmed by Energy dispersive X-ray analysis (EDAX). The electrical properties of the crystal were studied by Hall Effect measurements and photoconductivity.     

芯片叠层封装工艺技术研究

随着大量电子产品朝着小型化、高密度化、高可靠性、低功耗方向发展,将多种芯片封装于同一腔体内的芯片叠层封装工艺技术将得到更为广泛的应用,其封装产品的特点就是更小、更轻盈、更可靠、低功耗。芯片叠层封装是把多个芯片在垂直方向上堆叠起来,利用传统的引线封装结构,然后再进行封装。芯片叠层封装是一种三维封装技术,叠层封装不但提高了封装密度,降低了封装成本,同时也提高了器件的运行速度,且可以实现器件的多功能化。随着叠层封装工艺技术的进步及成本的降低,多芯片封装的产品将更为广泛地应用于各个领域,覆盖尖端科技产品和应用广大的消费类产品。     

Electrical transport properties of semiconducting chromium molybdenum diselenide single crystals

Mixed chromium–molybdenum diselenides (Cr_xMo_1−xSe₂ (x=0.25, 0.50, 0.75)) have been grown in single crystalline forms by the chemical vapor transport technique. Electrical transport properties like electrical resistivity (perpendicular and parallel to the c-axis), thermoelectric power measurements at high temperature and Hall effect measurements at room temperature were performed on these single crystals. Preliminary study of electrical measurements suggest a semiconducting behavior of Cr_xMo_1−xSe₂ (x=0.25, 0.50, 0.75) single crystals. Data of Hall coefficient and thermoelectric power have good agreement with each other and confirms the p-type nature of these crystals. Our findings should motivate an in-depth investigation of the underlying mechanisms.     

Multi-color light-emitting transistors composed of organic single crystals

We report a novel concept for multi-color light emission from an ambipolar organic single-crystal transistor using natural optical waveguides, the self-absorption effect, Davydov splitting and the unique alignment of the transition dipole moments. We used 9,10-bis-(2,2-diphenylvinyl)-anthracene single crystals to produce blue and green light from identical single-crystal transistors. We also observed red light, which corresponds to the emission from in-gap states that are caused by impurities. Importantly, each of these different colors corresponds to a distinguishable light polarization, which enables us to tune the emission color by using a light polarizer.