温梯法Al2O3晶体位错形貌分析

用温度梯度法(Temperature Gradient Technique,简称温梯法或TGT法),定向籽晶[0001]方向,生长出φ110mm×80mm Al2O3单晶,晶体完整、透明.采用硼酸钠玻璃液作为Al2O3晶体的化学抛光和化学腐蚀剂,观察了晶体不同部位处(0001)、(112-0)晶片的化学腐蚀形貌相,(0001)切片的位错腐蚀坑呈三角形,位错密度为2×103～3×103/cm2;(112-0)切片位错腐蚀坑呈菱形,位错密度为7×103～8×103/cm2;而且等径生长部位的完整性比放肩处高.利用同步辐射X射线白光衍射实验分析了(0001)晶片的(2-021),(11-01)和(112-0)衍射面内的位错组态.确定了两组位错线的Burgers矢量,温梯法生长的Al2O3晶体中的位错主要是刃型位错.     

沿[1-100]方向升华法生长6H-SiC单晶

本文采用升华法沿着垂直于c轴方向的[1-100]方向生长6H-SiC单晶.利用光学显微镜对晶体表面及腐蚀后的晶片进行观察,发现沿[1-100]方向生长出的单晶与传统方法沿[0001]方向生长单晶有很多的不同之处,多型对于籽晶的继承性非常强,但是在生长过程中多型夹杂不会发生,该方法生长的晶体中没有发现螺位错(微管)缺陷.     

常压化学气相输运法合成Zn1-xCoxO晶体

本文采用高温化学气相输运法,温度970℃,在蓝宝石和石英基片上制备Zn1-xCoxO晶体.电子扫描显微镜(SEM)观察发现,蓝宝石晶片上的晶体形貌较SiO2 晶片上的规整,晶体呈现六棱柱或六棱锥体,一般显露柱面m{101-0}、正锥面p{101-1}、负极面c{0001-}和正极面c{0001},晶体表面光滑.在石英基片上得到的Zn1-xCoxO晶体生长的棱面较模糊,基片的部分晶体非定向密集生长,连续形成薄膜结构.X衍射证实晶体为ZnO纤锌矿结构.X光能谱﹙EDS﹚测量表明 ZnO 晶体有钴离子的存在,且浓度随原料中的Co2O3:ZnO的比值增大而增加 .     

沿[1 ■00]方向升华法生长6H-SiC单晶

本文采用升华法沿着垂直于c轴方向的[1 ■00]方向生长6H-SiC单晶。利用光学显微镜对晶体表面及腐蚀后的晶片进行观察,发现沿[1 ■00]方向生长出的单晶与传统方法沿[0001]方向生长单晶有很多的不同之处,多型对于籽晶的继承性非常强,但是在生长过程中多型夹杂不会发生,该方法生长的晶体中没有发现螺位错(微管)缺陷。     

泡生法高质量蓝宝石晶体的研究

报道了泡生法生长[0001]方向的高质量蓝宝石晶体技术.经测量晶体位错密度为2×103～1.3×104/cm2之间,并利用激光剥蚀等离子体质谱仪(LA-ICP-MS)进行晶体杂质含量准确测量与分析.在600～1200 am范围内,晶体透过率均在80;以上;在1200～3000 nm范围内,晶体透过率均在85;以上.目前使用泡生法制作的蓝宝石晶体在商业产品使用中表现出良好性能.     

化学气相输运法制备ZnO晶体

采用化学气相输运法在常压开放系统中,以ZnO粉体为原料,HCl和NH3为输运气体,O2和H2O为反应气体,适度过量的HCl作为刻蚀性气体,在(0001)方向的蓝宝石籽晶片上制备了(0002)方向定向生长的ZnO晶体,且a、b轴生长速度明显高于c轴方向.以(0002)方向的ZnO籽晶片作基片,制备了ZnO单晶厚膜,晶体呈螺旋状外延生长,正极面的单晶摇摆曲线半高宽为543.6弧秒.     

c向提拉法生长的四英寸蓝宝石单晶缺陷研究

采用提拉法沿[0001]方向成功生长出了四英寸蓝宝石单晶。X射线摇摆曲线测试结果表明晶体具有较好的晶格完整性。采用化学腐蚀法并借助光学显微镜观察了(0001)面的位错及形貌。研究了腐蚀温度、腐蚀时间、机械抛光和化学抛光对位错密度及形貌的影响。计算得到平均位错密度为6190 cm-2,优于一般提拉法生长的蓝宝石单晶。     

导模法蓝宝石单晶的位错缺陷及其力学性能的研究

采用导模法生长了a向,尺寸为60 mm ×5 mm ×300 mm的蓝宝石单晶片,采用化学腐蚀-金相显微镜法观测了其(0001)晶面的位错特征,并且采用INSTRON-1195万能试验机测试了抛光样品的弯曲强度.结果显示:当晶体中位错缺陷分布均匀时,在外部弯曲应力下,蓝宝石晶体发生特定晶面的高强解理断裂,位错密度的升高对蓝宝石弯曲强度没有明显损害作用.然而当晶体中出现位错密排结构时,蓝宝石单晶常温弯曲强度迅速下降.     

温梯法白宝石晶体的缺陷研究

采用导向温梯法(TGT)生长出[0001]方向直径为76mm的白宝石晶体.利用扫描电子显微镜(SEM)观察晶体(0001)面的腐蚀坑形态,并对晶体内部的包裹物进行了能谱(EDS)分析.白宝石晶体中的生长缺陷主要为位错和包裹体等.Al2O3晶体(0001)面的位错腐蚀坑呈六角形,并且有台阶状结构.分析了(0001)面内的位错类型.确定了TGT法生长的白宝石内部的包裹物的主要成分为碳.     

常压化学水解反应生长氧化锌晶体

采用ZnCl2·2H2O在常压下高温水解反应生长ZnO晶体,反应温度为500℃.当以SiC为衬底时,可以获得六棱柱形氧化锌晶体,直径约为10μm,长为30～100 μm.当衬底为蓝宝石时,氧化锌沿[0001]呈定向柱状生长,柱的直径为5～10 μm,柱之间具有较多的内部缺陷.当以ZnO为衬底时,在{0001}面,形成连续膜,表面扫描电镜分析表明,晶体具有明显的极性生长特征,[0001]方向呈螺旋柱状生长.在{0001}面,晶体的平整性较好,呈现台阶性生长.     

Dislocations of salol crystals grown by the Czochralski method

Crystals of salol were grown by the Czochralski method in three different pulling directions to examine the crystallographic orientation effect of the seed. They were characterized by the etch pit method and X-ray projection topography. It was found that the dislocation density was 2 × 10³−1 × 10⁴/cm² and that the configuration of dislocations was straight. The running directions of dislocations strongly depend on the pulling directions; i.e., [11 0] and [1 10] for the crystal grown in [100] axis, [11 0], [1 10] and [110] for the crystal pulled along [112] axis and [010] for [010] axis crystal.     

Low-angle boundary investigation in silicon single crystals

Low-angle boundaries in Si single crystals grown from the melt in [111], [100], [112], [110], [118] and [115] directions were investigated by chemical etching, copper decoration technique and X-ray topography. — LAB of four types were found in planes parallel to the crystal growth axes. Rearrangement of dislocations from slip bands into LAB was observed in heavily-doped Si crystals. The origin of LAB in melt grown Si crystals is discussed. It is shown that these boundaries are well interpreted in terms of dislocation alignment formation in the thermal stress field of the growing crystal.     

Edge-Defined Film-Fed (EFG) Growth of Rare-Earth Orthovanadates REVO4 (RE=Y,Gd): Approaches to Attain High-Quality Shaped Growth

In spite of their superior laser and polarizer properties rare-earth orthovanadates (REVO₄) single crystals have not been adopted yet into extensive industrial applications because of crystal growth difficulties. The main problems of CZ technique are compositional change and diameter instability. This work presents the first attempt to apply the edge-defined film-fed growth (EFG) technique by which well-shaped REVO₄crystals have been grown directly. The capillary properties of YVO₄ and GdVO₄ melt have been measured. The applicability of shaped growth for rare-earth orthovanadate family was approved by successful EFG growth of transparent rod-like macro-defect-free single crystals of YVO₄ and GdVO₄. We address two main approaches to enhance the quality of EFG crystals: (i) meniscus and crystal shape stability dependence on die top shape and (ii) the strategy of effective operating control. Concave die top was found to be the best choice for high-quality EFG growth of REVO₄ along [001] direction. The spectral analysis of weight signal from growing crystal was shown to be a useful feedforward clue to prevent crystallinity degradation at a very early stage. A reasonable stability of the EFG process was achieved using [211], [101], [001] and [100] pulling directions.     

Anisotropy effect of high-momentum of ADAP in diamond-like semiconductors

A high-momentum component of angular distributions of annihilation photons (HMC ADAP) has been studied experimentally and theoretically in single crystals of germanium, silicon and gallium arsenide and in a single crystal and polycrystal silicon. The model oe the process of positron annihilation with electrons of ion cores has been suggested and the calculations of HMC ADAP curves have been performed for crystallographic directions [111], [110] and [100] of a dimond-like lattice. It has been established that ADAP anisotropy characteristics in a single crystal of germanium are slightly dependent on the temperature in the range of ΔT = 300÷930 K. It has been concluded that HMC ADAP anisotropy is caused by annihilation of thermalizod positrons with electrons of outer shells of ion cores in crystal lattices of dimond-like semiconductors.     

LPE生长GaN的不同极性面的光学性质

极化效应会导致GaN基发光器件的效率降低,因此关于非极性和半极性GaN单晶的研究受到了广泛关注.为了进一步探究不同极性GaN的发光特性和杂质掺入的内在机理,本文利用钠助熔剂法侧向生长出的不同极性面的GaN单晶作为研究对象,对比了不同极性面的光学性质及杂质掺入特点,讨论了黄光带(YL)峰的起源及其影响因素.首先利用阴极荧...     

Epitaxial Overgrowth of LiKSO4 on β–K2SO4 Single Crystals

Nucleation of LiKSO₄ (LKS) crystals from non-equimolar solutions may occur epitaxially on the surface of previously nucleated β-K₂SO₄ (KS) crystals. Both compounds evince a profound hexagonal substructure, and have common topological features and similar coordination schemes. Moreover, they may be related by quantitative similarities between their translation parameters and by correspondence between their bond chains along the directions of epitaxy. The planes of epitaxy are (001)_KS, and (0001)_LKS' and on these planes [010]_KS is always parallel to [010]_LKS' with a misfit of 12.19%. Another pair of directions, [11 0]_KS and [100]_LKS' showing a small angular misfit (0.18°), exhibit an even lower linear misfit (3.09%).     

Low temperature epitaxial growth of Ge on CaF2 buffered cube-textured Ni

Quasi-single crystal Ge films were grown on cube textured Ni substrate at a temperature of 350 °C using an insulating buffer layer of CaF₂. A direct deposition of Ge on Ni at 350 °C was shown to alloy with Ni. From x-ray pole figure analysis, it was shown that Ge grew epitaxially with the same orientation as CaF₂ and the dispersions in the out-of-plane and in-plane directions were found to be 1.7±0.1° and 6±1°, respectively. In the out-of-plane direction, Ge[111]6CaF₂[111]6Ni[001]. In addition, the Ge consisted of four equivalent in-plane oriented domains such that two mutually orthogonal directions: Ge〈2?11〉 and Ge〈01?1〉 are parallel to mutually orthogonal directions: Ni〈1?10〉 and Ni〈1?1?0〉, respectively, of the Ni(001) surface. This was shown to originate from the four equivalent in-plane oriented domains of CaF₂ created to minimize the mismatch strain between CaF₂ and Ni in those directions.     

Strong biaxial texture and polymorph nature in TiO2 thin film formed by ex-situ annealing on c-plane Al2O3 surface

Many applications based on TiO₂ thin films are strongly influenced by the film crystalline quality, microstructure and surface morphology. We have utilized x-ray scattering methods for crystal structure study of TiO₂ films, grown by DC reactive magnetron sputtering without heating. We have observed the formation of ordered phases after post-deposition ex-situ annealing in air at 600 °C. The distinct biaxial texture with respect to the c-plane (0001) Al₂O₃ substrate surface, which developed during heating, shows remarkable patterns in pole figures. We have identified epitaxial relationships of anatase A(001)[110]6sub(001)[11?00] and rutile R(100)[001]6sub(0001)[100] within single TiO₂ layer. In addition, within the same sample, we have observed the anatase in (112) orientation with two in-plane relationship options A(112)[11?0]6sub(0001)[21?1?0] and A(112)[11?0]6sub(0001)[11?00].