PbFe_(12)O_(19)单晶体中的位错蚀斑研究

应用50％HCl作为浸蚀剂,对助熔法生长的PbFe_(12)O_(19)单晶体的(0001)解理面进行了浸蚀,以显示位错蚀斑。根据蚀斑所具有的形态,将其进行了分类,并确定了各自对应的位错类型。应用Mathews等人提出的机制,解释了在(0001)基面上所观察到的位错蚀斑阵列。     

Bi12GeO20晶体的位错蚀斑与对称群

用化学浸蚀法系统的研究了Bi₁₂GeO₂₀晶体{100},{100},{111}等晶面独特浸蚀斑规律并用对称群理论进行分析.理论预示的蚀斑形态与实验结果符合很好.显示位错蚀斑是由{112}晶面组成,即晶体的惯态面为{112}.     

C2H4在清洁和有Cs覆盖的Ru(0001)表面吸附的TDS研究

用热脱附谱(TDS)方法研究了乙烯(C₂H₄)在Ru(0001)表面上的吸附.在低温下(200K以下)乙烯可以在清洁及有Cs的Ru(0001)表面上以分子状态稳定吸附,在衬底温度升高至200K以上时,乙烯发生了脱氢分解反应,乙烯分解后的主要产物为乙炔(C₂H₂).在清洁的Ru(0001)表面,乙烯有两种吸附状态,脱附温度分别为275K和360K.而乙炔的脱附温度为350K.在Ru(0001)表面有Cs的存在时,乙烯分解 关键词： 乙烯 钌(0001)表面 铯钌(0001)表面乙烯 钌(0001)表面 铯钌(0001)表面     

α-Al2O3(0001)基片表面结构与能量研究

对α-Al₂O₃(0001)晶体表层三种不同终止原子结构的计算模型， 在三维周期边界条件下 的κ空间中，采用超软赝势平面波函数描述多电子体系.应用基于密度泛函理论的局域密度 近似，计算了不同表层结构的体系能量，表明最表层终止原子为单层Al的表面结构最稳定. 对由10个原子组成的菱形原胞进行了结构优化，得到晶胞参数值(a₀＝0.48178n m)与实验 报道值误差小于1.3%.进一步计算了超晶胞(2×2)表面弛豫，弛豫后原第2层O原子层成为最 表层； 对不同表层O，Al原子最外层电子进行了布居分析，表面电子有更大的概率被定域在 O原子的周围，表面明显地表现出O原子的电子表面态. 关键词： 2O₃(0001)')" href="#">α-Al₂O₃(0001) 超软赝势 表面结构 表面态     

温度对ZnO/Al2O3(0001)界面的吸附、扩散及生长初期模式的影响

构建了一个ZnO沉积在α-Al₂O₃(0001)表面生长初期的模型，采用基于密度泛函理论的平面波超软赝势法进行了动力学模拟.发现在400，600和800℃的条件下界面原子有不同的扩散能力，因此温度对ZnO/α-Al₂O₃(0001)表面界面结构以及ZnO薄膜生长初期模式有决定性的影响.在整个ZnO吸附生长过程中，O原子的扩散系数大于Zn原子的扩散系数，O原子的层间扩散对薄膜的均匀生长起着重要作用.进一步从理论计算上证实了ZnO在蓝宝石(0001)上两种生长模式的存在，400℃左右生长模式主要是Zn螺旋扭曲生长，具有Zn六角平面对称特征，且有利于Zn原子位于最外表面.600℃左右呈现为比较规则的层状生长，且有利于O原子位于最外表面.模拟观察到在ZnO薄膜临近Al₂O₃基片表面处，Zn的空位缺陷明显多于O的空位缺陷. 关键词： 扩散 薄膜生长 2O₃(0001)')" href="#">α-Al₂O₃(0001) ZnO     

Si(111)表面在NH3气氛下形成Si3N4薄膜的STM研究

利用扫描隧道显微镜(STM)对Si(111)在氨气气氛下进行氮化所获得的氮化硅薄膜形貌和表面结构进行了系统分析,结果表明在1075—1275K的温度下对Si(111)进行氮化可以获得较平整的晶态βSi3N4薄膜,并在氮化膜表面观察到了Si3N4(0001)表面的(4×4)再构. 关键词：     

钼晶体中存在有柏格斯矢量为〈100〉的位错的实验证据

实验结果表明:以乙二酸水溶液为电解浸蚀液,可以在钼单晶体表面上显示位错的浸蚀斑。选{100}面为观察面,沿三叉亚晶界定出了浸蚀斑密度。观测结果证实了不对称倾侧晶界的Read-shockley公式,由此确定了沿亚晶界排列的浸蚀斑与柏格斯矢量为<100>的刃型位错间的一一对应关系。 关键词：     

K5Bi0.9Er0.1(MoO4)4的晶体生长和光学性质

在化学计量的熔料里,用提拉法生长了K₅Bi_0.9Er_0.1(MoO₄)₄单晶。该晶体属于三方晶系,空间群为R3m,z=1.5,晶胞参数为a=6.029?,c=20.823?(六方表示)。晶体具有层状结构,沿着(0001)面容易解理。晶体在室温下的吸收光谱包括有若干条吸收带,它们是稀土离子所特有的。其中三个主要的吸收峰分别相当于从Er³⁺离子的基态 ⁴I_15/2向 ⁴G_11/2, ²H_11/2和 ⁴I_13/2能级的跃迁。本文还给出晶体中相当于 ⁴I_13/2→ ⁴I_15/2跃迁的荧光发射光谱。 关键词：     

蓝宝石衬底上Gd2O3掺杂CeO2氧离子导体电解质薄膜的生长及电学性能

采用反应磁控溅射方法,在(0001)蓝宝石单晶衬底上,制备了纳米多晶Gd₂O₃掺杂CeO₂(GDC)氧离子导体电解质薄膜,采用X射线衍射仪(XRD)、原子力显微镜(AFM)对薄膜物相、结构、粗糙度、表面形貌等生长特性进行了表征,利用交流阻抗谱仪测试了GDC薄膜不同温度下的电学性能;实验结果表明,GDC薄膜为面心立方结构,在所研究的衬底温度范围内,均呈强(111)织构生长;薄膜表面形貌随衬底温度发生阶段性变化：衬底温度由室温升高到300℃时, 关键词： 2O₃掺杂CeO₂电解质薄膜')" href="#">Gd₂O₃掺杂CeO₂电解质薄膜 反应磁控溅射 生长特性 电学性能     

直拉法生长的YAG单晶体中组分过冷引起的针状应力区和位错

本文研究了掺钕的YAG(Y₃Al₅O₁₂)晶体在组分过冷条件下,固液界面的形态演变以及产生的钕离子的富集区。该富集区在正交偏光下表现为针状应力区。利用光弹方法确定了该应力为压应力,且应力分布具有圆柱对称性。通过浸蚀法和双折射貌相法观察到在钕富集区边界处存在位错列,并测定了位错的线密度。其结果与根据钕的浓度差值估计的密度大体符合。故认为这些位错是钕富集区边界处点阵失配所引起的。 关键词：     

Morphologies of latent and etched heavy-ion tracks in {111} CaF2

Structure details of latent tracks created by U, Pb and Au ions (energies 6.9, 28.7 and 11.1?MeV/A, respectively) in {111} CaF₂ have been extracted by means of scanning force microscopy and transmission electron microscopy. The revealed structure has assisted in the interpretation of the etching behaviour of tracks created in {111} CaF₂ by 9.2?MeV/A Bi ions. In the latter experiments, irradiated fragments were immersed for short durations in a 3:1 10% HCl/96% H₂SO₄ solution and the morphology of the formed etch pits was derived by high-resolution scanning electron microscopy and scanning force microscopy. Three conclusions emerged. First, ion-induced surface hillocks exhibit no resistance against etchant attack. Second, the primary etching diameter of the track coincides with the nanometric width of the structurally altered track core. Third, the structure of the etch pits, 3-faced symmetric pyramidal depressions with {122} faces, indicates that etching across the track halo, a few tens of nanometers wide strained crystal, is dominated by surface energies of crystal faces.     

C60单晶的表面形貌与生长缺陷

用气相法生长出了毫米尺寸的具有规则晶面和金属光泽的高质量的纯C₆₀单晶.X射线衍射分析表明,C₆₀单晶在室温下具有面心立方(fcc)结构,晶格常数为α=1.4199(4)nm。用扫描电子显微镜和光学显微镜观察了C₆₀单晶的形貌,除观察到fcc结构的晶体所特有的{111}和{200}两种稳定晶面以及非常容易形成的孪晶之外,还发现了在{111}面上的树枝状、垄状和生长丘以及在{200}面上的树枝状、游泳池状和生长丘的生长缺陷。对C_{60 关键词：}     

α—SiC晶体中的位错

用腐蚀法和X射线形貌术研究了α-SiC晶体中的位错。所用的腐蚀剂为熔融氢氧化钾。证实了尖底蚀坑与位错的一一对应关系。由于[0001]方向的螺型位错的Burgers矢量比刃型位错的Burgers矢量大得多,故可从蚀坑的深浅来判别螺型位错和刃型位错。给出了蚀坑形状和多型体晶体结构的对应关系。研究了表面生长蜷线的形态与SiC晶体中的位错及位错运动的关系。X射线形貌图显示了α-SiC晶体中相当数量的位错处于基面C面上。生长位错从晶体“根部”成核并随着晶体生长前沿的向前推进而延伸,因而位错线的方向常常沿[101O]和[1120]方向。将腐蚀法和X射线形貌术结合起来才能全面显示α-SiC晶体中的位错。 关键词：     

Polare Eigenschaften von Zinkoxid-Kristallen

A polarc-axis must be attributed to the wurtzite structure of zinc oxide. The sign of thec-axis can be determined by cleaving perpendicular to this axis and subsequent etching of the exposed {0001} surfaces. The present paper reports how this can be achieved without cleavage, merely by etching the prism faces {10¯10} which are the principal surfaces of hexagonal needles and of thin platelets. The etch patterns unambiguously point into the direction of the positivec-axis. This method is applied not only to the prism faces but also to cleaved surfaces of the same orientation. A close relation between etch patterns and lattice defects is apparent.     

Crystallographic effects on the photoelectrochemical etching of CdTe

Photoelectrochemical etching of CdTe produces etch pits of the same shape as obtained by selective chemical defect etching on the {111}, {100} and {110} faces. Their geometry is explained by atomic models of the surfaces. These new results extend our understanding of photoelectrochemical etching. They suggest that the interpretation of surface morphology should consider, in addition to the nonuniform charge flow through the semiconductor junction, the crystallographic effects on the development of the etch pits.     

Dislocation formation and twinning from the crack tip in Ni3Al: molecular dynamics simulations

The mechanism of low-temperature deformation in a fracture process of L12 Ni3Al is studied by molecular dynamic simulations.Owing to the unstable stacking energy,the [01ˉ1] superdislocation is dissociated into partial dislocations separated by a stacking fault.The simulation results show that when the crack speed is larger than a critical speed,the Shockley partial dislocations will break forth from both the crack tip and the vicinity of the crack tip;subsequently the super intrinsic stacking faults are formed in adjacent {111} planes,meanwhile the super extrinsic stacking faults and twinning also occur.Our simulation results suggest that at low temperatures the ductile fracture in L12 Ni3Al is accompanied by twinning,which is produced by super-intrinsic stacking faults formed in adjacent {111} planes.     

Growth and piezoelectric characterisation of GeO2 single crystals with quartz structure

Abstract

The first results for growth of germanium dioxide single crystals with the crquartz type structure (α-GeO₂) from refluxed hydrothermal solutions are reported. The success of this method is due to the existence of metastable α-GeO₂ in aqueous solutions at relatively low temperature and to the structural similarity between α-GeO₂ and α-SiO₂. The continuous partial evaporation of the heated solvent, vapour condensation, saturation of the condensate by nutrient α-GeO₂ and growth of α -GeO₂ single crystals on quartz seeds are considered as the successive stages of the process. Mzre homogeneous crystals of α -GeO₂ were obtained on seeds parallel to {0001}, {1120} and {1121} faces using sodium hydroxide and ammonium fluoride solutions in the range of temperature 90-130°C and at pressure equivalent to the fugacity of saturated vapor.

Piezoelectric, elastic and dielectric properties of the mentioned above crystals for the first time were studied.     

KTiOPO4晶体理论习性

为了解决复杂结构离子晶体接触能E_att计算上的困难,本文给出了按PBC(periodic bond chain)理论导出的公式,并将其编成计算机程序。应用PBC理论,从KTiOPO₄晶体结构,对其界面进行分类表明,{100},{011}为F单形;{210},{101}和{010}为较重要的S单形;而{001}单形的晶面,属K面。根据以上公式及程序对各单形E_att进行了计算,得出了各晶面的相对重要性,其结果与观测结果符合得很好。文中提出的公式 关键词：     

TiN/TiB2异结构纳米多层膜的共格生长与力学性能

采用多靶磁控溅射法制备了一系列具有不同TiB₂调制层厚度的TiN/TiB_{2纳米多层膜.利用x射线衍射仪、高分辨电子显微镜和微力学探针研究了TiB2层厚变化对多层膜生长结构和力学性能的影响.结果表明，在fcc-TiN层(111)生长面的模板 作用下，原为非晶态的TiB2层在厚度小于2.9nm时形成hcp晶体态，并与fcc-TiN 形成共格外延生长；其界面共格关系为{111}TiN//{0001}TiB2，〈110〉TiN//〈1120〉TiB2.由于共格界面存在晶格失配 度，多层膜中形成拉、压交变的应力场，导致多层膜产生硬度和弹性模量升高的超硬效应， 最高硬度和弹性模量分别达到46.9GPa和465GPa.继续增加TiB2层的厚度，TiB2形成非晶态并破坏了与TiN层的共格外延生长，多层膜形成非晶TiN层和非晶TiB< sub>2层交替的调制结构，其硬度和弹性模量相应降低. 关键词： 2}纳米多层膜')" href="#">TiN/TiB₂纳米多层膜 共格生长 晶体化 力学性能