开放体系优化ZnSe多晶原料化学计量比

本文采用开放体系对两单质加反应促进剂I2合成的ZnSe多晶原料进行了提纯.以高纯氩气为保护气体,提纯温度分别为500 ℃、550 ℃和800 ℃.能谱分析(EDS)和热重图谱(TG)结果表明:800 ℃处理后的ZnSe多晶原料,其化学计量比与理想化学计量比非常接近,而且升华开始温度提高到了850 ℃以上.运用化学气相输运(CVT)法进行晶体生长结果进一步表明,以800 ℃处理后的ZnSe多晶为原料时,消除了单质Se在生长区沉积对晶体成核生长的影响,达到了CVT法晶体生长对原料的要求.此外,以混合气体(H210;+Ar 90;)作为保护气时,在同等条件下处理后的ZnSe多晶原料,其化学计量比更加接近理想化学计量比,较氩气保护下的处理效果要好.     

两温区气相输运和机械振荡合成ZnGeP2多晶材料

ZnGeP2多晶的合成是其单晶生长的前提和基础,多晶材料的质量是生长高质量单晶的关键.因此,要获得高质量的ZnGeP2单晶体,必须提供高质量的ZnGeP2多晶材料.对两温区气相输运机械振荡法合成ZnGeP2多晶材料的工艺进行了研究,利用高纯(6N)P、Ge、Zn单质为原料,采用两温区气相输运和机械振荡合成出了ZnGeP2多晶材料.合成出的多晶材料经比重测试和X射线粉末衍射测试证明与标准值一致.采用改进的布里奇曼法生长出外观完整、无裂纹的φ15 mm × 25 mm单晶体,在2.5～10 μm范围内红外透过率达50;以上.     

高纯MgSe多晶的化学气相合成及特性研究

以高纯Mg、Se单质为原料,NH4Cl作反应促进剂,温度为999～992℃,采用化学气相输运法(CVT)成功合成出MgSe多晶.采用X射线粉末衍射仪、紫外-可见-近红外分光光度计、傅立叶变换红外光谱仪以及光致发光测试系统研究了MgSe多晶的结构和光学特性.结果表明:合成物为MgSe多晶,具有NaCl型结构,禁带宽度Eg为1.98eV,在1.6eV附近内存在与施主-受主对辐射复合发光相关的发光带.研究证明由Mg、Se单质在促进剂NH4Cl辅助下直接合成MgSe多晶是一种较好的方法.     

新型红外晶体硫锗镓银的多晶合成

本文直接使用高纯Ag,Ga,Ge,S单质作为原料合成AgGaGeS4多晶.为防止S蒸气高压使多晶合成管炸裂,采用双温区气相输运的合成方法.对合成的多晶作粉末衍射(XRD)分析,衍射图谱与标准JC-PDF卡片上峰值位置一致,表明样品为高纯单相AgGaGeS4多晶.使用该多晶原料成功生长出了优质单晶,并对合成工艺中存在的关键问题进行了讨论.     

AgGaS2多晶合成工艺改进研究

按同成分熔化点配料,采用改进了合成温控条件的双温区气相输运法成功合成出AgGaS2多晶原料,通过精确控温,有效避免了反应过程中由S蒸汽压过大引发的合成石英安瓿炸裂,提高了AgGaS2多晶合成的质量和成功率.经过XRD、DSC测试分析,结果表明:经改进方法合成的AgGaS2多晶材料是高纯单相、均匀致密的,为高质量AgGaS2单晶的生长提供了优质原料.     

磷锗锌多晶合成过程的中间生成物研究

两温区气相输运法合成ZnGeP2多晶过程中,易生成一些高熔点的杂质,导致合成材料的纯度较低.选取ZnGeP2多晶合成过程中几个重要温度的合成产物,进行X射线衍射(XRD)和能谱色散分析(EDS),结果表明:ZnGeP2多晶合成过程的中间生成物主要为Zn3P2、ZnP2和GeP等.根据分析结果,对合成工艺进行了改进,合成出外观完整、内部致密的ZnGeP2多晶锭.用XRD进行分析,结果表明:改进工艺后合成的是高纯单相ZnGeP2多晶材料,为高质量单晶体生长奠定了可靠基础.     

低位错ZnSe单晶的生长

采用化学气相输运法(CVT)在适合的温度和I2含量的条件下,生长出了25mm×3mm的ZnSe单晶,位错密度为6.5×103个/cm2.对ZnSe单晶进行光学性能分析,在10.6μm处的透过率超过70;,在10.6μm处的吸收系数为7.72×10-4/cm.     

点状籽晶法生长KDP晶体中散射颗粒分布

在不同的溶液pH值条件下进行了点状籽晶法慢速和快速生长KDP晶体实验,发展了观察晶体中散射颗粒分布的激光层析技术,通过图像处理得到了KDP晶体内部(100)面完整的散射颗粒分部图,对不同生长速度、不同pH值条件下点状籽晶法生长的KDP晶体的散射颗粒分部做了对比.利用表面光学投影技术观察了晶体表面宏观形貌,并由此分析了不同生长条件下生长机制对散射颗粒分布的影响.测定了散射颗粒密度不同部位的晶体透过率.     

CdSiP2多晶杂相分析与合成工艺改进

以高纯(6N) Cd、Si、P单质为原料,按CdSiP2化学计量比并适当富磷配料,采用传统气相输运法合成出CdSiP2多晶.X射线衍射(XRD)分析及Rietveld全谱拟合精修结果表明合成产物中含有微量SiP和CdP2杂相,分析了杂相产生的原因.针对存在的问题改进合成工艺,引入高温熔体机械和温度振荡以及分步控温冷却等新工艺,获得了外观完整、内部致密均匀的CdSiP2多晶.XRD及能量色散谱仪(EDS)分析结果表明,合成产物为高纯单相CdSiP2多晶,为高质量单晶体的生长奠定了可靠基础.以改进工艺获得的CdSiP2多晶为原料生长出质量较好的单晶体,厚度为2mm的晶片样品在1500 ～ 7000 cm-1范围内的红外透过率在45;以上,计算出晶体的禁带宽度为2.09 eV.     

富铅配料合成PbI2多晶及其熔体分层研究

富Pb配料、采用两温区气相输运法合成了单相的PbI2多晶材料,实验中出现熔体分层的现象.对合成结果的X射线衍射分析(XRD)和能量色散X射线微区分析(EDX)结果表明:富余的Pb沉积于石英安瓿的底部,与合成的单相PbI2多晶材料分离.根据富Pb配料的范围,结合文献的实验数据,可以确定在Pb-I相图中存在一个新的液相分层区域L2+L3,该区域对PbI2多晶合成和晶体生长具有指导作用.以合成的单相PbI2多晶为原料,采用垂直布里奇曼法生长出了尺寸为φ15mm×30mm、外观完整、呈桔红色的PbI2晶体.     

Photographic observation of the growth of GaP-Needles from the wet hydrogen process

GaP-needles were grown by the transport of GaP material with hydrogen in an open tube system. The needle growth was observed with a camera. Some needles were discovered whic grew without a visible Ga-droplet on their tips. It is assumed that these needles grew by the surface diffussion of GaP-complexes along the side planes of the needles.     

Vapour-phase epitaxial growth of ZnS on GaP

Single crystal layers of ZnS about 100 μm thick were grown epitaxially on GaP substrates in an open tube system using source ZnS powder and a flowing hydrogen atmosphere. The growth rate for different substrate temperatures increases with increasing hydrogen flow rate, but the growth rate profiles resemble each other in shape. The profile shifts towards the low temperature side as the source temperature is decreased. The (111)B substrate orientation is found to be preferable to the (111)A or the (100) with respect to surface morphology and crystal quality. X-ray diffraction investigations and luminescent properties show that the (111)B grown layers are of high quality. All ZnS layers grown on GaP substrates are craked on cooling, which may be due to the thermal expansion mismatch between the layer and the substrate. Heat-treatment of the grown layer does not reduce the resistivity, but increases the photoluminescence intensity markedly. Selective vapour-phase epitaxial growth has been successfully applied resulting in crack-free ZnS layers on GaP substrates.     

CVT一步生长的ZnSe单晶的光电特性研究

本文采用化学气相输运(CVT)法,由Zn(5N)和Se(5N)一步直接生长了片状ZnSe单晶,并对其结构特性和光电性能进行分析。研究表明,生长出的ZnSe单晶仅显露(111)面,红外透过率约为40%～42%,具有较高的结晶质量。该ZnSe单晶可与In电极形成良好的欧姆接触,其体电阻率约为7.3×109Ω.cm。     

Growth of high-quality ZnO single crystals by seeded CVT using the newly designed ampoule

The high-quality ZnO single crystals were grown by seeded chemical vapor transport (CVT) in a newly designed ampoule using carbon as a transport agent. The well-faceted crystal of about 5×5×5 mm³ can be grown reproducibly. Secondary ion mass spectroscopy (SIMS) analysis, X-ray rocking curve (XRC) and photoluminescence (PL) measurements demonstrate that the grown single crystal is of high purity and high crystallinity.     

Ihnomogeneous Distribution of Doping Elements in Polycrystalline GaP

The distribution of Te and Zn in polycrystalline GaP ingots grown by SSD method was studied by means of the contact resistance measurements between a tungsten carbide probe and a lapped sample surface. The differencies in carrier concentrations measured in differently oriented GaP :Te crystal grains were found as high as one order of magnitude. In GaP: Zn crystals the constant Zn concentration throughout the sample was observed.     

单质直接气相生长ZnMgSe单晶

采用高纯Zn、Mg、Se2单质为原料,以NH4Cl作为反应输运剂,用化学气相输运(CVT)的方法一步成功生长出ZnMgSe单晶。通过XRD、RO-XRD、EDS、紫外可见分光光度计和光致发光(PL)技术研究了ZnMgSe晶体的结构、成份以及光学特性。结果表明:ZnMgSe单晶具有良好的结晶性能,在400～800 nm范围内透过率达到40%～50%,在2.2～2.6 eV范围内存在与深能级电子复合相关的发光带。研究证明由Zn、Mg、Se2单质在输运剂NH4Cl辅助下一步直接合成ZnMgSe单晶是可行的。     

Vapour growth and epitaxy of minerals and synthetic crystals

Surface microtopographs of the following crystals, both natural and synthetic, grown from pure vapour phase (PV), by chemical vapour transport (CVT), from high temperature solution (HTS) and hydrothermal solution (HS) are compared according to the criteria of (1) whether spirals are circular or polygonal and (2) how wide is the step separation of the spiral; SiC (PV, CVT, both synthetic), hematite (CVT, HTS, natural and synthetic), corundum (CVT, HTS, synthetic), mica minerals (PV, CVT, HS, natural and synthetic) and beryl (CVT, HTS, HS, natural and synthetic). Clear differences in morphology and step separation were found between crystals grown from vapour phase and solutions, between PV and CVT, as well as between natural and synthetic crystals. The differences are analysed in conjunction with the recent developments of computer simulations on spiral morphology. The results show interaction between solid and fluid plays very important role in determining the spiral morphology. Oriented intergrowth between different crystals well known among minerals, such as epitaxy, topotaxy, co-axial intergrowth, exsolution etc. are briefly summarized. It is also briefly explained how these relations are used in understand the growth or cooling histories of natural minerals.     

The heteroepitaxial growth of vacuum-deposited GaP thin films on Si substrates

Heteroepitaxial GaP thin films were grown on (100) and (111)Si substrates by vacuum evaporation of the compound GaP and their structural characteristics were compared with homoepitaxial GaP films grown by the same technique on (100)GaP substrates. Nearly monocrystalline GaP thin films were deposited reproducibly on (100)Si substrates at the optimum substrate temperature of about 680–700°C and the deposition rate of 0.1 nms⁻¹. The structure of such films was comparable in quality to homoepitaxial GaP/GaP films. No monocrystalline films could be deposited on (111)Si substrates.     

Growth and Characterization of GaP Substrates for Liquid Phase Epitaxy

GaP light-emitting diodes were prepared by a single LPE process on LEC and SSD substrates. Red LEDs with a maximal efficiency of 5% could be grown reproducibly on SSD substrates with grains. The effciency of the best LEDs on substrates grown by the conventional LEC method is essentially lower (0.5%) but it can be improved considerably by a modification of the growth conditions. The substrates were characterized by structural, chemical, electrical and optical measurements and the observed differences in the luminescence efficiency between the LEDs grown on LEC and SSD subtrates, respectively, were discussed under consideration of these investigations.     

Ionized-cluster beam epitaxial growth of GaP films on GaP and Si substrates

Epitaxial films of GaP on GaP and Si substrates are grown by the Ionized-Cluster Beam Technology. The doping of Zn and N during the growth of the film are also discussed. A p-type epitaxial film doped by Zn and N shows an absorption spectrum similar to that of a direct transition type semiconductor. P-n junction LEDs are fabricated by depositing p-type GaP on n-type substrate. The luminescence from the device was observed.