Defect generation on mechanical surface defects before and after the oxidation (I). TEM investigations on the nucleation of oxidation stacking faults at mechanically induced weak surface defects

In order to obtain information on the nucleation mechanism of oxidation stacking faults, mechanically induced weak surface defects as simulated by low-load scratches were investigated with TEM before and after a short-time wet oxidation at 1050 °C. The experimental results could not confirm the existing models which explain stacking fault nucleation by the splitting of complete dislocations. Rather it was found that clusters of silicon interstitials are generated due to strong local compression during scratching, which then act as nuclei for stacking faults in the subsequent oxydation process.     

Defect Structure in Te-doped GaAs Single Crystals after Plastic Deformation (II). Dislocation Slip and Cell Formation

At temperatures above the brittle-to-ductile transition (490 °C) in Te-doped GaAs three types of predominant defect configurations have been observed after uniaxial compression along a [001] direction: (i) twins and stacking faults (500 … 520 °C), (ii) slip zones of dislocations (≈550 °C) and (iii) dislocation cells (580 … 590 °C). In Part II quantitative details of the appearance of slip and cell formation are given. Leading segments of gliding half loops are mainly of 60° type. Cell walls were formed by multiple slip of perfect dislocations.     

Defect Structure in Te-doped GaAs single Crystals after Plastic Deformation (I). Twins and Stacking Faults

At temperatures above the brittle-to-ductile transition (490 °C) in Te-doped GaAs three types of predominant defect configurations have been observed after uniaxial compression along a [001] direction: (i) twins and stacking faults (500 … 520 °C), (ii) slip zones of dislocations (≈ 550 °C) and (iii) dislocation cells (580 … 590 °C). In Part I quantitative details of the appearance of twins and stacking faults are given. Most frequently found were 30° partials in twins and stacking faults.     

On the characterization of electrically active inhomogeneities in semiconductor silicon by charge collection at schottky barriers using the SEM-EBIC (II). Contrast due to defects

The influence of the control variables (E₀, I_b, U_r) as well as the semiconductor parameters (ϱ, L) on the defect contrast of direct irradiated Schottky barriers is investigated. The resolution of the subsurface regions is enhanced by increasing the primary beam energy E₀. The sharply imaged region can be extended into the depth of the crystal by applying a reverse bias U_r. Contrast width broadenings are observed in high-ohmic material, if increasing the beam current I_b, which may be annuled by switching on U_r. Against the generally held view the diffusion-induced contrast width broadening of defects (or parts of them) located outside the depletion layer was found as an extremely small fraction of the diffusion length L. Thus in rough approximation the contrasts can be interpreted as a superposition of the in general club-shaped generation volume and the defect shape.     

On the kinetic of crystallization of zinc oxalate (II). Determination of the specific surface energy at the crystal solution interface by kinetic studies

An apparatus based on turbidimetry was constructed for studying the kinetics of crystallization of sparingly soluble salts. The kinetics of crystallization of zinc oxalate was investigated at various supersaturations and pHs of the medium. The specific surface energy at the crystal-solution interface was determined from the induction periods of the S-shaped curves by means of the classical theory of nucleation. The calculations were made using the slope of the logarithmic dependence of I or τ, respectively, on supersaturation (equations 1 and 2) and the critical supersaturation which was also determined on the basis of kinetic data. Various values of σ were found for the different supersaturations. Different values for this quantity were also obtained when supersaturation was presented by the concentration ratio (S = C/C₀) or by the ratio of the product of the two ions concentrations in the supersaturated solution to that in the saturated one (S = ab/L_p). These σ values were lower than those obtained using the critical supersaturations at the two different solution pHs. For the present it is impossible to give a definite explanation of the results obtained. The experiments for determining the specific surface energy at the crystal-solution interface will be continued.     

On the correlation of lattice defects to HUBER-etch pit morphologies on (001) surface of InP

Various analytical techniques (defect etching, optical microscopy, X-ray topography (XRT), cathodoluminescence (CL) were combined to get information about the real structure of Sn- and S-doped LEC InP. The S-pits, produced by the HUBER -etch, were not only caused by microdefects, as it was described in literature. We found a correlation between S-pits and special types of dislocations.     

Studies on Epitaxial Growth of Organic Compounds on Sucrose by the Fourier Transform Method (II). Iso- and Heteroepitaxy

Iso-epitaxial growth (twinning, parallel growth) of sucrose, β-succinic acid, anthraquinone and isatin can be explained by a good fit of the energetic structures of both partners. The symmetry operations result from the pseudo-symmetries of the reciprocal crystals. In all cases possible planes favoured for the formation of twins or parallel grown individuals can be predicted. Heteroepitaxial growth of β-succinic acid, hexachlorobenzene, anthraquinone and isatin on (100)-oriented sucrose has been observed. It is possible to explain the growth mechanisms by symmetry considerations of the energetic structures.     

Study of PbO films on sodium borate glasses part II: Formation of interdiffusion layers at the glass surface

By selecting carefully controlled conditions for the thermal treatment of sodium borate glasses coated with PbO films, it is possible to prevent Pb²⁺ ions from penetrating deeply into the glass. For low alkali glasses, an interdiffusion layer can be formed, which sub-surface cation profiling (by ion beam induced radiation) shows is a solid solution of Na₂O and B₂O₃ in PbO which acts as solvent. Experiments with 18.0 mol-% Na₂O glass show that it is possible to transform such an interdiffusion layer into a second type in which Na₂O and B₂O₃ together act as solvent and the concentration of PbO solute varies through the layer. For both types of layer the Na₂O : B₂O₃ ratio is different from that of the glass substrate, and for the production of the second type of layer it is shown that an important factor connected with penetration of PbO into the glass surface is a “sweating” process in which thermal treatment of the glass, even in the absence of PbO, results in migration of Na⁺ ions so that the glass surface has a Na₂O content higher than that of the bulk glass. Changes in the UV spectra of the Pb²⁺ ion are correlated with the formation of the interdiffusion layers, and results show that types of layer have optical basicities significantly greater than that of the glass substrate, through either the high PbO or high Na₂O content.     

6H-SiC成核表面形貌与缺陷产生的研究

利用光学显微镜观察了6H-SiC晶体成核表面形貌,并使用高分辨X射线衍射法检测了不同区域的结晶质量.根据表面形貌的不同将成核表面分为三个区域:平台区、斜坡区、凹坑区.平台区的结晶质量最好,斜坡区和凹坑区由于缺陷(例如微管、小角晶界和多型夹杂等)的存在导致结晶质量变差.依据温场分布以及籽晶的固定分析了凹坑产生的可能原因.根据观察纵切片发现源于斜坡区以及凹坑区的缺陷随着晶体的生长继承到晶体内部导致后期生长的晶体质量变差.最后我们提出了通过优化成核温场分布以及改善籽晶固定方法来提高晶体成核质量的思路.     

Structure and morphology of metal oxide depositions on SiO2(II). Structural aspects of the intergrowth of metal oxides on quartz

The oxides (TiO₂, SnO₂, GeO₂) were deposited on the surfaces of quartz crystals ((101 0), (101 0), (011 1), (0001)) and investigated by RHEED. Anatase and rutile were found for TiO₂, the quartzisomorphous structure for GeO₂ and for SnO₂ apart from cassiterite a structure which was hitherto unknown. The epitaxy relations were derived and discussed from the aspect of structural chemistry.     

Raman spectroscopic investigation of the structure of silicate glasses (II). Soda-alkaline earth-alumina ternary and quaternary glasses

Raman spectra of some ternary and quaternary glasses in the system Na₂OCaOMgOAl₂O₃SiO₂ are presented. The spectra are interpreted in terms of the structural alteration of the glass as the composition is altered from the binary end members to more complicated glasses. Addition of CaO and MgO to soda-silica glasses act only to increase the disorder of the network slightly. Addition of Al₂O₃ greatly modifies the network. In some soda-lime-aluminosiliscate compositions an estimate can be made of the amount of aluminum in four- and six-fold coordination. It is shown that the amounts of four- and sixfold coordinated aluminum depend on the glass composition.     

Growth Mechanism in Atomic Layer Epitaxy (II). A Model of the Growth Process of CdTe on CdTe (111) Substrates

A realistic model of CdTe growth by atomic layer epitaxy (ALE) has been proposed. This model is based on experimental studies concerning the isothermal re-evaporation rates of elemental Cd and Te deposits on the (lll)A and (lll)B surfaces of CdTe substrates, on a study of surface morphology and crystal structure of CdTe single crystal overlayers grown by ALE on CdTe(lll)B substrates under various crystallization conditions as well as on the existing theories related to the interaction of thermally activated atoms or molecules with hot solid surfaces. This model includes: (i) an existence of transition layers of both Cd and Te₂ species, intermediate between a chemisorbed and a bulk-like film, which create reaction zones 3–4 monolayers thick near the substrate surface, and (ii) partial re-evaporation of the first, chemisorbed monolayer of the deposited constituent elements.     

Estimation of point defect parameters of solids on the basis of a defect formation model of melting (III). Formation entropy and concentration of schottky defects (vacancies)

The formation entropy of Schottky defects (vacancies) is calculated from the entropy of fusion and the concentration x_L = 0.125 of vacancies within the melt at melting point T_m. The formation of vacancies is connected with a decrease of the vibrational frequency of those lattice forming particles (atoms, ions, molecules) being neighbours of the vacancies. Theoretical values of the vacancy concentrations x_s agree with those x_s obtained with the help of experimentally determined free formation enthalpies of the defects.     

Influence of the spectator cation on the structure of anionic pyridine-2,6-dicarboxylato complexes of cobalt(II), nickel(II), and copper(II)

The structures of anionic pyridine-2,6-dicarboxylato (pdc^2–) complexes of cobalt, nickel, and copper have been studied. The stoichiometries and structures are very much dependent on whether KOH, Et₄NOH, or NaOH is used in the synthesis to deprotonate the H₂pdc ligand. Crystallographic results are: (1) K₂[Co(pdc)₂] · 7H₂O, orthorhombic, Pnna, Z = 4, a = 20.637(2)Å, b = 13.480(1)Å, c = 8.200(1)Å (2) K₂[Ni(pdc)₂] · 7H₂O, orthorhombic, Pnna, Z = 4, a = 20.648(1)Å, b = 13.375(1)Å, c = 8.2393(8)Å (3) [Co₂(H₂O)₅(pdc)₂] · 2H₂O, monoclinic, P2₁/c, Z = 4, a = 8.3880(6)Å, b = 27.384(2)Å, c = 9.6110(8)Å, = 98.271(6)° (4) [Ni(Hpdc)₂] · 3H₂O, monoclinic, P2₁/c, Z = 4, a = 13.679(1)Å, b = 10.0450(9)Å, c = 13.767(2)Å, = 115.184(7)° (5) Na₆[Co(H₂O)₆][Co(pdc)₂]₄ · 28H₂O, monoclinic, P2₁/n, Z = 2, a = 13.363(1)Å, b = 8.437(1)Å, c = 40.689(3)Å, = 91.288(5)° (6) Na[Ni(Hpdc)(pdc)] · 11.5H₂O, monoclinic, C2/m, Z = 4, a = 15.200(2)Å, b = 22.299(2)Å, c = 8.3596(7)Å, = 118.894(7)° (7) Na[Cu(Hpdc)(pdc)] · 3H₂O, monoclinic, P2₁/n, Z = 4, a = 9.516(4)Å, b = 14.917(6)Å, c = 12.247(5)Å, = 92.00(5)°. The potassium and sodium complexes have extensive K⁺—H₂O and Na⁺—H₂O networks. The fact the Et₄N⁺ ion does not appear in any of the complexes is likely due to the fact that it is incapable of forming the intricate cation—water and hydrogen-bonding networks observed in all of the other structures.     

The influence of the dislocation density on the sulphur segregation at the Ni(110) surface in the course of heating

The segregation of sulphur of the surface from Ni(110) monocrystals has been studied by LEED and AES. We have founded that the diffusion is dependent to the temperature and the dislocation density and we interpret this observation with the diffusion along the dislocations and the volume diffusion.     

The current understanding of epitaxial CVD silicon doping in the light of modelling and theory development (II). Theoretical foundations and incorporation equations

Theoretical foundations selected from related fields of science (thermodynamic and chemical equilibria, kinetics of surface-catalized reactions, open systems and steady-state equilibria, solid-state physics of semiconductors) are applied to epitaxial silicon layer doping to reveal the doping process mechanism. In this way it is shown how the empirically based relationships between the controlling parameters of the process and the doping effect (c.f. part I) can be explained by theory. In the course followed, the historical evolution is neglected in favour of the logical interconnection between the empirical and theoretical foundations.     

不同pH值下ZTS晶体(100)面台阶生长动力学规律和位错缺陷的研究

通过利用光学显微镜,对不同pH值下ZTS晶体(100)面的台阶推移过程进行了实时观察,发现在同一过饱和度下,调高生长溶液的pH值会导致台阶推移速率降低;而调低pH值时,台阶的平均推移速率增大,当pH =4.2时,(100)面生长速度最快.计算出不同pH值下的台阶动力学系数βl和台阶活化能E的数值.对不同pH值下生长出的ZTS晶体的(100)面进行了位错缺陷观察,发现pH =4.2时,位错密度较低,有利于晶体生长质量的提高.     

Morphology of SiC epitaxial layers grown by temperature gradient zone melting (II). The dependence of the structural properties of the epitaxial layers on the growth conditions

In the present paper the relationships between the structural perfection of the layer, represented by the Tb average integral concentration (which is a criterion for the second phase quantity), the rocking curve half-width (a criterion for the general structural perfection of the layer) and the layer growth conditions, represented by the quantity, which is the most important characteristic of the growth process, namely the supersaturation are discussed. The considered model allows to conclude, that a optimal value of the supersaturation exists, at which the structural perfection is maximal.     

Effect of fictive temperature on the optical absorption of cobalt (II) and nickel (II) in some phosphate glasses

The optical absorption of cobalt (II) in Na₂O, 4P₂O₅ melts and in H₂ONaCl mixtures has been studied at different temperatures; the equilibrium: octahedral ? tetrahedral shifted towards the right with increasing temperature in both solvents. The optical absorption of cobalt (II) and nickel (II) has been studied in a series of metaphosphate glasses: Na₂OCaOP₂O₅, and it has been shown that the equilibrium octahedral/tetrahedral ratio of these ions measured at room temperature can be correlated with the transformation temperature of these glasses. The colour of cobalt (II) or nickel (II) containing CaO·P₂O₅ glasses has been found to be significantly dependent on thermal history; the intensity of optical absorption changed reversibly on heat treatment at the transformation range of the glass.