Growth and structure of epitaxial diamond films grown on Si(111) single crystals

Experiments on growing single-crystal diamond films on silicon crystals with (111) surface orientation have been performed. Results attesting to the possibility of obtaining thin heteroepitaxial films are presented. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 414–418 (10 March 1997)     

Nonrelativistic dispersional equations for crystals of sphalerite and diamond structure

The tenth- and eleventh-order dispersion equations obtained for sphalerite and diamond structures in previous works are reduced to algebraic form and compared. The dispersion equation for the sphalerite structure is factorized at the axes and in the planes of symmetry. At the axes and the factorization is complete; the zones of heavy and light holes are the same as in the diamond structure. At the axes gS only a zone of heavy holes is isolated, which is again no different from that obtained from the diamond structure. Factorization of the equations for both structures in the whole of the (110) plane is performed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 3–6, November, 1982.     

Photonic crystals of diamond spheres with the opal structure

Opal samples consisting of diamond spheres have been synthesized by chemical deposition in microwave plasma from a CH₄/H₂ mixture using templates of silicon inverse opal. The optical investigations have confirmed that the periodic structures prepared are structurally perfect three-dimensional photonic crystals.     

Si基Sc膜的制备及结构分析

采用电子束镀膜方法在Si基底上制备了Sc膜,利用XRD,SEM分析了不同镀膜工艺条件下制备的Sc膜的形貌和结构。结果表明:基底温度在350～550 ℃时,薄膜主要由单质Sc组成,而且随着基底温度的升高,膜的颗粒尺寸增大,膜也变得更加致密;基底温度提高至650 ℃时,膜全部由ScSi化合物组成,膜变成颗粒状结构。沉积速率对低温时Sc膜的形貌与结构的影响不明显,颗粒尺寸随沉积速率的增大而增大,但物相结构基本没有发生变化;而在高温650 ℃时,沉积速率对膜的形貌与结构产生了很大的影响,随着沉积速率的增大,膜表面出现了大量微裂纹,而且较低的沉积速率有利于获得衍射峰单一的膜,增大沉积速率将会导致衍射峰数量明显增加。     

Si基Sc膜的制备及结构分析

采用电子束镀膜方法在Si基底上制备了Sc膜,利用XRD,SEM分析了不同镀膜工艺条件下制备的Sc膜的形貌和结构。结果表明：基底温度在350～550 ℃时,薄膜主要由单质Sc组成,而且随着基底温度的升高,膜的颗粒尺寸增大,膜也变得更加致密;基底温度提高至650 ℃时,膜全部由ScSi化合物组成,膜变成颗粒状结构。沉积速率对低温时Sc膜的形貌与结构的影响不明显,颗粒尺寸随沉积速率的增大而增大,但物相结构基本没有发生变化;而在高温650 ℃时,沉积速率对膜的形貌与结构产生了很大的影响,随着沉积速率的增大,膜表面出现了大量微裂纹,而且较低的沉积速率有利于获得衍射峰单一的膜,增大沉积速率将会导致衍射峰数量明显增加。     

Nonrelative dispersion relation in crystals with a diamond structure

The dispersion equations introduced in a previous paper are solved and the analytical expression of the dispersion relations thus obtained are investigated. The latter is in fair agreement with experiment for the heavy and light hole bands in the <100>, <110> directions and for electrons of the lower conduction band in the <100> directions. An iteration procedure is proposed for the solution of the dispersion equations in arbitrary directions of the wave vector up to the Brillouin zone boundary.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–6, July, 1982.     

Studies of interface structures of W films grown on patterned and bare Si(100) by TEM

+ Si(100) and bare Si(100) wafers by low pressure chemical vapour deposition (LPCVD) at 230–280 °C. The films were investigated by transmission electron microscopy (TEM). The cross-sectional TEM samples of W/Si(100) exhibited a fine scale interface roughness, which was attributed to the surface preparation. Irregular W plug structures were observed depending on the predeposition procedures. It was observed that an insufficient deposition of W films on the contact surface leads to the presence of aluminium around and underneath the plugs. This was observed by energy dispersive X-ray spectrometry (EDX). A study, using conventional electron diffraction, confirmed that no silicides formed at the interfaces of W-bare Si(l00) wafers. Received: 16 December 1996/Accepted: 6 May 1997     

On the born relation for crystals with diamond and sphalerite structure

The experimental data on the elastic constants C_ij for crystals with diamond and sphalerite structure at T=293 K were used to check the Born relation Δ4C₁₁(C₁₁?C₄₄)/(C₁₁+C₁₂)²=1. The relation was shown to be satisfied with a low accuracy for diamond due to a large scatter in the C_ij experimental values and with accuracies of 8.3, 7.6, 1.6, and 1.0% for Si, SiC, Ge, and α-Sn, respectively. For II–VI, III–V, and I–VII compounds with sphalerite structure, Λ was found to systematically deviate from unity toward lower values, and it was shown that the quantity (1-Λ) can be used to estimate the bond ionicity in these crystals. The effect of anharmonicity on the Λ values for Ge, Si, GaAs, InAs, and ZnSe was estimated; this effect was found to be insignificant.     

Fractal structure formation in GaSe crystals grown from melt

The structure of GaSe single crystals prepared by rapid cooling of melt has been studied. These crystals are shown to contain dendrites due to the nonequilibrium conditions of single-crystal preparation. Dendrites have a fractal structure with the Hausdorff measure equal to 1.7.     

Hard-sphere crystals with hcp and non-close-packed structure grown by colloidal epitaxy

We demonstrate the epitaxial growth of a metastable (with respect to the bulk) hcp crystal as well as any other close-packed stacking sequence of colloidal hard spheres. At certain stretched and compressed lattices we furthermore observed growth of a non-close-packed superstructure and of a perfect (100)-aligned fcc crystal. Perfect template-induced hcp-crystal growth occurs at lattice spacings that are larger than for bulk crystallization, indicative of prefreezing. Small mismatches lead to increased out-of-plane displacements. Large mismatches prevent crystallization in the surface layers.     

Defect structure in EuS single crystals grown from the melt

The defect structure in EuS single crystals grown form the melt is studied by etch pitting, scanning and high-voltage electron microscopy. Circular and square etch pits and a second phase in the shape of thin hexagonal platelets are observed by etching. Microprobe analysis indicates the platelets to consist of Eu metal. In the transmission electron microscope, smoothly curved dislocations and helical dislocations, small dislocation loops and inclusions associated with dislocations are observed. The possible origin of the detected dislocation structure is considered with reference to climb and glide processes occurring during cooling down the grown crystals. The results corroborate the glide geometry of the NaCl lattice for EuS. On leave from Institute of Physics, Academic Sinica, Peking, VR China     

Dislocation structure of kcl crystals grown with vibration of the melt

Summary The amplitude at all frequencies was 0.04 mm. Three crystals were grown at each frequency, with seeds of dislocation density D = 6 × 10⁴ cm^–2. Figure 1 shows the frequency dependence of the final D. Each point in Figs. 1 and 2 is the mean from 50 measurements (50 fields of view). At all frequencies except 180 Hz, D was 2–4 times less than that without vibration, while at 100 and 160 Hz it was less by nearly an order of magnitude.The effects of amplitude (0.02 to 0.2 mm) were examined at 100 Hz, the minimum D occurring at 0.1 mm (Fig. 2). At 0.04–0.08 mm, D was less by a factor 3–4 than for crystals grown without vibration, while at 0.1 mm it was less by an order of magnitude, being 2 × 10^–4 cm^–2. The size of the etch pits on crystals grown at amplitudes up to 0.1 mm did not differ from that for crystals grown at rest, but above 0.1 mm the size increased, by more than a factor 3 at 0.2 mm. Figure 3 illustrates these effects.Optimal vibration reduces D by improving the growth conditions (reduction of temperature gradients by mixing, more uniform impurity distribution).     

Electronic structure of Si (111) interface between diamond and hexagonal phases

The electronic structure of the Si (111) interface between the diamond and hexagonal wurtzite structure is studied by first-principles LCAO method. No gap interfacial states or resonances are found; instead, the calculated density of states curve shows an oscillatory redistribution of electron states and a reduction of band gap of about 10%. It is concluded that the electronic structure of this interface can be approximated as the average of that of the bulk diamond and the hexagonal Si.     

Self-consistent electronic structure of Si,Ge and diamond by the LMTO-ASA method

We have investigated the accuracy of the self-consistent LMTO-ASA method with interstitial spheres for open structure materials by studying the electronic structure of Si, Ge and diamond. Our band structures agree in detail with the results of the best state of the art self-consistent calculations. In addition we obtain quantitative agreement with the observed cohesive properties for all three systems. The success of these calculations suggests that the method should be useful for other open structure materials.     

TEM study of the structure of gallium nitride epitaxial films grown on substrates with different interface morphologies

The structure of gallium nitride epitaxial layers grown on patterned substrates was studied by transmission electron microscopy. The engraving of a substrate surface with pits or pyramids undoubtedly leads to structural improvement. The best results are obtained at a pattern density of about 10⁷ cm^?2.     

KDP晶体金刚石车削参数对晶体雾化的影响

安装在高功率激光系统中的KDP晶体,其表面质量是一个很重要的问题。单点金刚石车削是唯一获得透射波前误差和激光损伤阈值的方法,尤其是在紫外UV波段。KDP晶体表面雾化与金刚石车削参数有关。研究金刚石车削参数主要是为了提高KDP晶体的频率转化效率。研究结果表明,在金刚石切削中使用一种纯净的切削油和适宜的加工参数能大大地减少晶体表面的雾化。     

ZnO/Diamond/Si结构中声表面波传播特性分析

基于递归刚度矩阵方法, 建立了多层结构声表面波表面有效介电常数模型, 计算出了ZnO/Si结构声表面波的相速度频散特性, 与实验结果符合较好, 表明本文所建模型的准确性和有效性. 进一步计算得到了三层结构(ZnO/Diamond/Si)声表面波的相速度和机电耦合系数的频散规律, 获得此结构最优的高波速和高机电耦合系数组合及达到最优组合所需控制的变量, 为高频高性能声表面波器件设计和优化提供了有益参考. 关键词： 声表面波 多层结构 递归刚度矩阵 表面有效介电常数     

The unoccupied electronic structure characterization of hydrothermally grown ThO2 single crystals

Single crystals of thorium dioxide ThO₂, grown by the hydrothermal growth technique, have been investigated by ultraviolet photoemission spectroscopy (UPS), inverse photoemission spectroscopy (IPES), and L₃, M₃, M₄, and M₅ X‐ray absorption near edge spectroscopy (XANES). The experimental band gap for large single crystals has been determined to be 6 eV to 7 eV, from UPS and IPES, in line with expectations. The combined UPS and IPES, place the Fermi level near the conduction band minimum, making these crystals n‐type, with extensive band tailing, suggesting an optical gap in the region of 4.8 eV for excitations from occupied to unoccupied edge states. Hybridization between the Th 6d/5f bands with O 2p is strongly implicated. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)