碲锌镉单晶体的(110)面蚀坑形貌观察

本文报道了一种能够在室温下择优腐蚀碲锌镉(CZT)单晶体(110)晶面的腐蚀液配方,并对富Cd生长的CZT晶体蚀坑形貌进行了扫描电镜观察.结果表明晶体(110)面腐蚀坑形状为三角形,并初步对蚀坑的成因进行了分析,估算出CZT(110)面蚀坑密度约为103～105/cm2数量级.这说明富Cd原料的改进布里奇曼法可以生长出低蚀坑密度的CZT单晶体.     

室温半导体核辐射探测器新材料及其器件研究

本文论述了室温半导体核辐射探测器新材料及其探测器的研究发展过程和最新动态,分别介绍了几种主要室温半导体核辐射探测器新材料晶体的组成、结构、性能及其探测器的制备技术,主要应用情况.结果表明:HgI2、CdZnTe和CdSe单晶体是性能优异的室温半导体核辐射探测器新材料,用其制作的探测器,可在室温下广泛用于环境监测、核医学、工业无损检测、安全检查、核武器突防、航空航天、天体物理和高能物理等领域.因此,近年来对大尺寸高质量HgI2、CdZnTe和CdSe单晶体及其室温核辐射探测器的研究,已成为高技术新材料领域的前沿研究课题.     

室温核辐射探测器用碲锌镉晶体生长研究进展

碲锌镉(CdZnTe,CZT)晶体被认为是目前最有前途的室温半导体探测器材料之一,基于该晶体的探测器件具有能量分辨率高、体积小、便携等优点.而大面积CZT像素探测器的快速发展以及对高能、大剂量X射线探测的需求,对CZT材料的质量和尺寸提出了更高的要求.本文从CZT晶体的基本物性参数入手,探讨了大尺寸CZT晶体生长的影响因素,对两种主要的CZT生长方法——布里奇曼法和移动加热器法的研究进展进行了综述.     

硒化镉单晶体的研究进展

总结了CdSe单晶体的多种生长方法,包括温度梯度熔体法,移动区熔法,助熔剂法和气相提拉法等,其中气相提拉法能有效提高CdSe单晶体的晶体纯度及光学质量.介绍了CdSe晶体用于红外非线性光学器件以及室温核辐射探测器件的研究进展,并对CdSe晶体制作中红外偏振测量用波片进行了展望.     

碘化铅单晶体生长新方法探索

本文分析了用布里奇曼法生长碘化铅单晶体的结晶过程。发现坩埚下降法生长碘化铅单晶体过程中,碘的蒸发与凝结、铅的分凝与沉淀是影响晶体质量的两个重要因素。提出了采用U型安瓿提拉方式生长碘化铅单晶体的新方法,有效抑制了碘的蒸发并排除了分凝的铅,获得了桔红色半透明的碘化铅晶体。经测试,晶体的结晶性好,红外透过率达45%,电阻率为1.7×1012Ω.cm,为制备性能优异的碘化铅室温核辐射探测器奠定了基础。     

移动加热器法生长CdMnTe和CdZnTe晶体的性能研究

采用移动加热器法生长铟惨杂浓度为5×1017 atoms/cm3的Cd0.9Mn0.1Te (CMT)和Cd0.9Zn0.1Te (CZT)单晶.生长得到的CMT晶体和CZT晶体电阻率范围为4.5×109 ～ 6.2×1010 Ω·cm.CMT晶体的成分均匀性要优于CZT晶体,拟合得到CMT和CZT晶体中Mn和Zn的分凝系数分别为0.95和1.23.富Te区在两种晶体生长过程中都具有显著的提纯作用,In惨杂的浓度范围均在6.4 ～ 14.4 ppm范围内.红外透射显微镜观察到三角形和六边形为主的Te夹杂的尺寸5 ～24 μm,浓度为105 cm-3.除最后结晶区之外,沿晶体生长方向Te夹杂的尺寸逐渐减小而浓度逐渐增大.制备的CMT和CZT探测器对59.5 keV241Am放射源均有能谱响应,能量分辨率分别为23.2;和24.6;.     

碘化汞(α-HgI2)晶体生长及其性能表征

利用垂直两温区透明油浴炉,采用升华法成功生长了α-HgI2单晶体.通过对比不同生长阶段晶体生长界面,观察到HgI2晶体在气相生长中存在界面形貌转变.晶体生长初期的生长面呈棱面,然后逐渐转变为圆滑界面.利用XRD、透射光谱以及I-V测试对所生长晶体的性能进行了表征.XRD结果表明所生长的晶体为单相的α-HgI2晶体,晶体的生长方向为[001].紫外-可见-近红外透过光谱分析发现,HgI2晶体的截至波长为580 nm,对应的禁带宽度为2.12 eV,近红外区内透过率约为45;.由于空穴的俘获及陷阱能级作用,在2307.5 nm和1731.4 nm处产生了两个明显的吸收峰.所生长的α-HgI2晶体电阻率约为1011Ω·cm,满足制作核辐射探测器的要求.     

核辐射探测单晶生长方法研究进展

核辐射探测是指用各种核辐射探测器来得到核辐射信息的过程,在军用、民用和科研等领域具有广泛的应用。作为核辐射探测核心的核辐射探测器,主要分为气体探测器、闪烁体探测器和半导体探测器。相比于气体探测器,闪烁体探测器和半导体探测器都需要晶体作为核心材料,晶体质量的品质在很大程度上决定了探测器性能的上限。为了获得性能更好的探测器,人们对探测器用单晶材料的生长方法进行了大量的研究。本文综述了近几年核辐射探测单晶生长方法研究的最新进展,总结了目前主流的晶体生长方法,包括溶液法、熔体法、气相法等,并对不同晶体的主要生长方法进行了归纳。     

移动加热器法生长CdMnTe晶体的性能研究

采用垂直布里奇曼法(VB)生长CdMnTe晶体,由于生长温度高、堆垛层错能低、热应力大等因素,晶体中存在大量孪晶、杂质、夹杂相等,限制其在核辐射探测器方面的应用.为了提高晶体的质量,本文采用移动加热器法(travelling heater method,THM)生长CdMnTe晶体,对该方法生长的晶体中Mn的轴向分布、杂质浓度、Te夹杂和电学性能进行测试分析,并与VB法生长的晶体作对比.结果表明THM法生长的CdMnTe晶体中Mn的轴向分布均匀,杂质浓度低于VB法制得的晶体,Te夹杂的尺寸5～25 μm,浓度105 cm-3,电阻率为109～1010Ω·cm,导电类型为弱n型,制备的探测器在室温下对241Am放射源有能谱响应.实验表明THM法生长的CMT晶体在晶体质量和电学性能方面明显优于VB法.     

压力引起的CdZnTe(111)表面局部形变

本文报道了在碲锌镉(CZT)晶片(111)Cd面上发现的等边三角形和四边形形变,并在CZT(111)面上做了压力实验.结果表明我们所发现的多边形是碲锌镉在压应力作用下产生的,不仅可以在(111)Cd面出现,也可以在(1 11)Te面出现.文中从经典的晶体范性形变理论和面心立方闪锌矿结构晶体所具有的滑移特性出发,阐明了出现在CZT(111)Cd面的多边形的形成机理,其内角必为60°或120°.并对磨抛工艺提出了改进意见.     

Phase diagram calculation for epitaxial growth of GaInAs on InP considering the surface, interfacial and strain energies

In order to know the effects of the surface, interfacial and strain energies on the calculation of the phase diagram, these energies were calculated for the Ga_xIn_1−xAs/InP structure and the Ga–In–As ternary phase diagram for the epitaxial growth of GaInAs on (1 1 1) InP was determined. The layer-thickness dependence of the liquidus temperature and solidus composition was determined. It was found that the liquidus and solidus phases were strongly influenced by these energies when the layer thickness was thinner than about 0.06 μm. The consideration of the effects of the surface, interfacial and strain energies is effective to explain the peculiar behavior of the experimental results near the lattice-matched composition (x=0.47), which is called the latching effect.     

Synthesis and Characterization of New Dibenzothiophene-based Host Materials for Blue Phosphorescent Organic Light-Emitting Diodes

A series of bipolar host materials containing dibenzo[b,d]thiophene (DBT) or dibenzo[b,d]thiophene 5,5-dioxide core were successfully synthesized, and their physical, photophysical, and electrochemical properties were investigated. The three host materials showed well-localized electron distribution at the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states, as evidenced by theoretical calculations. Triplet energies of the new host materials are higher than 2.6 eV, and the blend film with bis[2-(4,6-difluorophenyl)pyridinato-C² Misra, A. et al. (2006). Semicond. Sci. Technol., 21, R35.[Crossref], [Web of Science ®] , [Google Scholar],N](picolinato)iridium(III) (FIrpic) as a blue phosphorescent dopant showed highly efficient energy transfer between the host material and dopant.     

Measurement of specific surface free energy of ruby and quartz single crystals using contact angle of liquids

The specific surface free energy of ruby and quartz single crystal was experimentally obtained using contact angle of water and formamide droplets on the crystal surfaces, and compared with the morphology of each crystal. The ruby crystals satisfied Wulff's relationship even though their shape were not equilibrium form. The specific surface free energies of the growing faces of synthetic quartz crystal, ‐X, +X, Z, and S faces were obtained as 51.9, 55.6, 57.4, and 58.9 mN/m, respectively. The growth rates of these faces were 0.09, 0.23, 0.28, and 0.33 mm/day, respectively. The growth rate of each face of the quartz crystal can be regarded as a function of the experimentally obtained specific surface free energy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optic Effects of Smectic-Cholesteric Mixed Liquid-Crystals

Light transmission characteristics in optic effects of smectic-cholesteric mixed liquid-crystals are experimentally investigated. Cholesteric addition to a smectic liquid crystal changes greatly transmission characteristics in a cholesteric phase. Although a smectic liquid crystal alone is transparent, the mixed liquid crystals become opaque. However, this opaque state isconverted to the transparent state with applied fields. After the fields are removed, the transparent state is stored in case of then n-type mixture, e.g., BBBA:CN = 90:10 in weight, but returns to the original opaque state in case of thep-type mixture, e.g., C0B:CN = 90:10 in weight. In the smectic phase, the n-type mixture hardly responds to applied fields. but thep-type mixtureeasilyresponds. The response is dependent on a cell temperature: higher field is required in lower temperature. This temperature characteristic can be used for display application of liquid-crystal light valve.     

热蒸发制备CdSe薄膜及其光电特性研究

采用真空热蒸发法技术制备CdSe薄膜,通过XRD、SEM、Hall效应和分光光度计测试了薄膜的结构、表面形貌、I-V特性和光学透过率。结果表明:CdSe薄膜(100)晶面的面间距为0.369 nm,晶粒大小约为10.2 nm,薄膜表面晶粒分布较为均匀;CdSe薄膜与锡和银的肖特基势垒高度分别为0.76 V和0.69 V;CdSe薄膜的光透过率在远红外区较高,且呈上升趋势;折射率随波长增加按指数规律减小;根据Tauc关系和Urbach规则,获得能量带隙为1.79 eV和Urbach能量为0.217 eV。     

Er掺杂金刚石缺陷的第一性原理研究

本文以第一性原理计算为基础,研究了Er掺杂后金刚石的电子结构、能级跃迁及N、B原子共掺杂对金刚石Er相关缺陷的影响。首先对Er掺杂后金刚石的形成能与结合能进行计算,结果表明掺杂后的稳定结构为Er原子周围存在1个空位的结构,稳定价态为+3价。然后预测零点跃迁能(ZPL)是0.807 eV,对应激发的光子波长为1 536.289 nm。最后对N、B原子共掺杂计算,结果表明N、B原子的掺入可以使形成能降低,增加结构稳定性。Er掺杂金刚石使其在近红外光谱发光,为Er金刚石色心的应用提供了理论依据。     

Anisotropy of optical absorption in layered single crystals

The optical energy gap of Re doped MoSe₂ single crystal Mo_0.995Re_0.005Se₂ has been measured at room temperature near the fundamental absorption edge. The incident light was kept normal to the basal plane i.e. along the c‐axis of the grown crystals. Results have been given on the basis of two and three dimensional models. Both direct and indirect transitions are involved in the absorption process. The indirect transition was found to be allowed with two phonons involved in the process. The three dimensional model and not the two dimensional could be used to describe the optical properties of Re doped MoSe₂ single crystal. Also, the optical energy gaps depend upon the amount of the intercalating Re material. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Anisotropy of the optical absorption in layered single crystals of MoRe0.001Se1.999

Energy gap of MoRe_0.001Se_1.999 single crystal has been determined by fundamental absorption methods. The incident light was polarized along c‐axis of the crystals. The interpretion of the data is given within frameworks of two and three dimensional models. Both direct and indirect transitions are involved in the absorption process. The indirect transition was found to be allowed with two phonons participating in the process. The three dimensional model could be used to describe the optical properties of the single crystal. The energy gaps depend upon the amount of the intercalating Re material, which show the anisotropy of the chemical bonds. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Prediction of crystal morphology of 1,3,5-triamino-2,4,6-trinitrobenzene in dimethyl sulfoxide via modified attachment energy modeling and its experimental validation

A new computational method was established to investigate the solvent effects on the crystal morphology of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). The modified attachment energy (MAE) method was applied on TATB in dimethyl sulfoxide (DMSO). This MAE E_satt method accounting for the attachment energy effect of the solvent was proposed to replace the vacuum attachment energy using the solvent-crystal interaction energies. In our simulation study, TATB crystals in DMSO grew into a hexagonal-flake structure and are in good agreement with the experimental data.