硒化镉多晶原料的提纯

采用改进的垂直无籽晶气相法生长大尺寸高质量的CdSe单晶体要求原料的纯度高。本文根据差热(DIA)和热失重(TG)测试结果，设计出连续抽空区域升华提纯CdSe原料的新方法，用该方法提纯的原料生长出大尺寸、高质量的GtSe单晶体。等离子体质谱仪(ICP-MS)分析结果表明，新方法对CdSe的提纯是有效的，纯化后的原料可以生长出大尺寸高质量的CdSe单晶体。     

正钒酸钙晶体原料的合成与生长

本文通过固相合成方法直接合成正钒酸钙晶体原料.并用红外光谱、X射线多晶粉末衍射对所合成的原料进行表征.结果表明,固相合成法可获得纯度较高的正钒酸钙晶体原料.使用该方法合成的原料采用Czochralski高温提拉法生长出φ20mm×25mm的Ca3(VO4)2单晶.     

碳化硅单晶生长用高纯碳化硅粉体的研究进展

碳化硅(SiC)以其宽带隙、高临界击穿场强、高热导率、高载流子饱和迁移率等优点,被认为是目前较具发展前景的半导体材料之一。近年来,物理气相传输(PVT)法在制备大尺寸、高质量SiC单晶衬底方面取得了重大突破,进一步推动了SiC在高压、高频、高温电子器件领域的应用。SiC粉体是PVT法生长SiC单晶的原料,其纯度会直接影响SiC单晶的杂质含量,从而影响SiC单晶的电学性质,其中生长高质量的半绝缘SiC单晶更是直接受限于SiC粉体中N元素的含量。因此,合成高纯的SiC粉体是PVT法生长高质量SiC单晶的关键。本文主要介绍了高纯SiC粉体的合成方法及研究现状,重点对气相法和固相法合成高纯SiC粉体的优缺点进行了评述,并提出了今后高纯SiC粉体合成的发展方向。     

部分硫/硒(S/Se)红外非线性晶体原料的快速合成方法研究

含有硫/硒(S/Se)元素的部分化合物在现有中红外非线性晶体材料中占据相当重要的地位.高纯多晶原料是生长优质S/Se光学晶体的基础,但常规合成方法存在周期长、数量少等缺点.为此,针对部分S/Se化合物,我们对传统的合成方法进行优化、改进,实现GaSe,AgGaSe2,AgGaGeS4,AgGaGe5Se12等的快速合成,单次合成原料200～300 g,合成周期小于48 h,经过粉末衍射(XRD)测试表明合成的原料质量较好,能够生长出较大尺寸单晶.文中对快速合成方法的机理、存在的问题等也进行了相关讨论.     

用于SiC晶体生长的高纯原料的合成及性能研究

SiC原料的纯度、粒径和晶型直接影响生长单晶的结晶质量和电学性质,尤其是高纯半绝缘本征SiC晶体的制备需要使用高纯SiC原料.本文采用超高温真空烧结炉,选择Si粉和C粉作为反应物,通过XRD、SEM、激光粒度测试仪和GDMS等测试手段研究了合成温度、压强、时间及原料配比等工艺条件对SiC颗粒成核、生长、晶型、粒径及堆积密度等综合性能的影响.结果表明,自合成的SiC原料一致性好、颗粒度均匀、纯度达到或超过5N.最后,使用自合成原料进行晶体生长,进一步证实其完全满足高质量半绝缘SiC晶体的制备.     

大尺寸长波红外非线性晶体CdSe生长及应用

利用压力辅助法合成批量、高纯CdSe多晶原料,进行籽晶定向高压布里奇曼法生长,制备出φ(50 ～ 55) mm×(80 ～ 100) mm高品质单晶棒,加工出多相位匹配角度、多规格尺寸(6 ～8)2×(40 ～50) mm3晶体元件.元件在2.1 μm、2.6 μm、10.8 μm等多波段o、e偏振光测试下,吸收系数分别≤0.02 cm-1、≤0.02 cm-1、≤0.01 cm-1,通过光参量振荡实验,元件在10.1～10.8 μm波段实现1.05W长波红外激光输出.     

CdSe晶体及掺Cr2+激光器的研究进展

以CdSe晶体光参量振荡器为代表的中红外激光器在生物、医疗和军事等诸多领域有着广泛的应用前景.本文总结了生长CdSe单晶的工艺方法包括熔体法、熔剂法和气相法等,其中常用的为气相法,近年来高压垂直梯度冷凝(HPVGF)技术也逐渐被采用.国内外将本征CdSe晶体用于光参量振荡器件(OPO),适用于多种激光器泵浦源,且输出功率不断提高.而Cr2+的掺杂能有效提高泵浦效率,实现波长的连续可调.     

双折射YVO4晶体原料的合成及最佳制备工艺的探讨

本文介绍了液相法合成用于双折射单晶生长的钒酸钇原料的工艺。着重讨论了制备条件对原料纯度的影响,确定了最佳合成方案。为了适应工业化生产的需要,探讨了原料合成的规范化(以保证保纯性,均匀性,重复性),合成出的原料已成功生长出φ42×42mm的大尺寸优质钒酸钇单晶,且剩料可重复使用10次左右。     

红外LED用掺硅HB-GaAs单晶纵向载流子浓度分布研究

GaAs单晶作为一种重要的LED衬底材料在光电器件中应用十分广泛,但载流子浓度(C.C.)分布不均、杂质浓度过高等缺陷会严重影响相关器件的性能.为制备纵向载流子浓度分布均匀的掺硅HB-GaAs单晶,本文探讨了单晶生长过程中熔区长度对纵向载流子浓度分布的影响.以高纯GaAs多晶为原料,设定不同的拉晶温度曲线,采用窄熔区技术进行晶体生长研究,最终生长出C.C.值分布更均匀、位错密度低(EPD≤10 000 cm-2)的<111>向N型掺硅GaAs单晶.利用辉光放电质谱法(GDMS)和范德堡法霍尔效应测试对晶体进行了表征,单晶纯度达到5N且无硼杂质沾污.     

CdSe单晶体的生长及其特性研究

本文报道了用改进的垂直气相法(多级提纯垂直气相法)生长富Cd的CdSe单晶体,并对晶体的性能进行了观测,其电阻率为107Ωcm量级,电子陷阱浓度为108cm-3量级,第一次报道了(110)面的腐蚀形貌。结果表明：采用这种方法制备CdSe单晶,设备简单,易于操作,在提纯和生长过程中不需要转移原料,有利于减少晶体中的杂质含量,降低位错密度,改善晶体的电学性能。多级提纯垂直气相法是一种有前途的CdSe单晶体生长的新方法。     

Growth of single crystals of B28 at high pressures and high temperatures

A method of the high-pressure high-temperature synthesis of single crystals of orthorhombic high-pressure boron B₂₈ from metal solutions is presented. The method is based on the high-pressure multi-anvil technique. The feasibility of single-crystal growth was demonstrated in a number of experiments conducted at various pressure–temperature conditions with various precursors including β-boron of 99.99% purity and various metals (Cu, Au, and Pt) used as fluxes and capsule materials. It was found that after dissolution in metals at high pressures and high temperatures, boron crystallizes in the form of single crystals at low temperature. The process is accompanied by chemical reactions resulting in the formation of borides. The maximum length of the B₂₈ crystals achieved is ∼100 μm.     

The melt growth of semicircular crystals of the pure Pb and its dilute alloys

Semicircular crystals of Pb were grown from the melt by a rotational operation so as to change the orientation of the solid-liquid interface during crystallization. In pure Pb, specimens grew as polycrystals with grain boundaries developed transversely to the growth direction. According to the decrease in purity, the grown crystals consisted of several long grains along the circular arc. A competitive growth between grains was inhibited by a small amount of impurity and then the mode of growth approached to the complete adhesive one.     

Growth and characterization of CdSe single crystals by modified vertical vapor phase method

Good quality, large single crystals of CdSe were grown by the modified growth method (i.e., vertical unseeded vapor phase growth with multi-step purification of the starting material in the same quartz ampoule without any manual transfer between the steps). Lower temperature gradients (8–9°C/cm) at the growth interface were used for the crystal growth. As-grown CdSe crystals was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive analyzer of X-rays, high-resistance instrument measurement, and etch-pit observation. It is found that there are two cleavage faces of (1 0 0) and (1 1 0) orientations on the crystal, the resistivity is about 10⁸ Ω cm, and the density of etch pits is about 10^3–4/cm². The crystal was cut into wafers and was fabricated into detectors. The detectors were tested using an ²⁴¹Am radiation source. γ-ray spectra at 59.5 keV were obtained. The results demonstrated that the quality of the as-grown crystals was good. The crystals were useful for fabrication of room-temperature-operating nuclear radiation detectors. Therefore, the modified growth technique is a promising, convenient, new method for the growth of high-quality CdSe single crystals.     

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.     

Production of high purity TeO2 single crystals for the study of neutrinoless double beta decay

High purity TeO₂ crystals are produced to be used for the search for the neutrinoless double beta decay of ¹³⁰Te. Dedicated production lines for raw material synthesis, crystal growth, and surface processing were built compliant with radio-purity constraints specific to rare event physics experiments. High sensitivity measurements of radio-isotope concentrations in raw materials, reactants, consumables, ancillaries, and intermediary products used for TeO₂ crystals production are reported. Indications are given on the crystals perfection and how it is achieved and maintained in a large scale production process. Production and certification protocols are presented and resulting ready-to-use TeO₂ crystals are described.     

Study of the metastable region in the growth of GaN using the Na flux method

It was revealed that the metastable region, in which liquid phase epitaxy (LPE) of GaN single crystals proceeds without the generation of polycrystals, expands with growth temperature in the Na flux method. The metastable region appears when LPE growth proceeds at temperatures above 1073 K, although generation of polycrystals inevitably occurs on a crucible at temperatures less than 1073 K. The highest growth rate of 14 μm/h in a small experimental setup was achieved at a temperature of 1163 K with a nitrogen pressure of 5.5 MPa due to complete suppression of the growth of polycrystals on a crucible, even though the supersaturation at this condition reached a fairly high level.Also, an LPE crystal with a flat surface could easily be obtained under high-temperature conditions.     

The defects and spectral properties of sapphire grown by melting methods

The paper is devoted to the study of the spectral properties of the sapphire single crystals grown by Verneuil, Czochralski, Cyropulos, Stepanov and horizontal directed crystallization methods. Varing the methods, parameters of growth and starting material purity, one can control the concentration of electronic and hole centers in wide range and spectral properties of sapphire up to the irradiation.