The orientation and morphology of chromium deposits on hot Cu{111} substrates

Chromium (1.5–20 nm thick) was vapour deposited in ultrahigh vacuum (2×10^-9 Torr) onto single-crystal Cu{111} films. The copper substrate temperatures T_s were in the range 75–256 °C. Transmission electron microscopy and electron diffraction were used to study the orientation and morphology of the deposits. For T_s ≲ °C the electron diffraction patterns showed arced chromium reflections consistent with a distribution of orientations between Nishiyama- Wassermann (NW) and Kurdjumov-Sachs (KS) at ±5° 16′ from NW. A greater tendency towards KS was observed as T_s increased to about 130 °C. For T_s = 190 and 256 °C relatively well-defined KS orientations occured. These results are interpreted in terms of various geometric models of f.c.c.-b.c.c. interfaces. At T_s ≲ 85 °C the morphology was qualitatively similar to that observed for room temperature substrates: flat irregularly shaped crystals within which a substructure of parallel-oriented crystallites with elongated shape existed. For T_s ≲ 130 °C the morphology changed from the flat irregularly shaped crystals to isolated three- dimensional crystals with an elongated shape. The long direction of the crystals was approximately parallel to the direction of least misfit, i.e. Cr〈111〉  Cu〈110〉.     

Mechanism of SiC crystals growth on {100} and {111} diamond surfaces upon microwave heating

The subject of this work is focused on characterization of the microstructures and orientations of SiC crystals synthesized in diamond–SiC–Si composites using reactive microwave sintering. The SiC crystals grown on the surfaces of diamonds have either shapes of cubes or hexagonal prisms, dependent on crystallographic orientation of diamond. The selection of a specified plane in diamond lattice for the TEM investigations enabled a direct comparison of SiC orientations against two types of diamond facets. On the {111} diamond faces a 200 nm layer of 30–80 nm flat β-SiC grains was found having a semi-coherent interface with diamond at an orientation: (111)[112]SiC║(111)[110]C. On the {100} diamond faces β-SiC forms a 300 nm intermediate layer of 20–80 nm grains and an outer 1.2 µm layer on top of it. Surprisingly, the SiC lattice of the outer layer is aligned with the diamond lattice: (111)[110]SiC║(111)[110]C.     

Initial epitaxial growth of (111) Au/(111) Cu and (111) Cu/(111) Au

The room temperature modes of growth of Au/(111) Cu and Cu/(111) Au are described. For the former growth mode initial deposits (2.4 Å) of gold on copper form smooth flat islands delineated by coincidence lattice misfit dislocations. For 6.0 Å of gold deposit, both thick and thin gold areas were observed with almost complete substrate coverage. For a 10 Å deposit, surface coverage was complete. Strain measurements and dislocation densities obtained on the (111) Au/(111) Cu films suggest the presence of two separate misfit dislocation networks at the interface. The coincidence lattice networks were large enough for transmission electron microscopy observation but contributed little to total overlayer strain. The (van der Merwe) natural lattice misfit dislocations were too closely spaced for direct observation but their presence was inferred because of the strain measurements. The initial epitaxy of Cu/(111) Au was similar to the Stranski-Krastanov model: the initial monolayer of copper (also delineated by coincidence misfit dislocations) grew smoothly on the gold; additional copper formed essentially stress-free “nuclei” on top of the initial copper layer.     

Superconducting epitaxial $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\delta }$$ on $$\hbox {SrTiO}_{3}$$SrTiO3-buffered Si(001)

Thin films of optimally doped(001)-oriented \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) are epitaxially integrated on silicon(001) through growth on a single crystalline \(\hbox {SrTiO}_{3}\) buffer. The former is grown using pulsed-laser deposition and the latter is grown on Si using oxide molecular beam epitaxy. The single crystal nature of the \(\hbox {SrTiO}_{3}\) buffer enables high quality \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) films exhibiting high transition temperatures to be integrated on Si. For a 30-nm thick \(\hbox {SrTiO}_{3}\) buffer, 50-nm thick \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) films that exhibit a transition temperature of \(\sim \)93 K, and a narrow transition width (<5 K) are achieved. The integration of single crystalline \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\updelta }\) on Si(001) paves the way for the potential exploration of cuprate materials in a variety of applications.     

Silica based polishing of {100} and {111} single crystal diamond

Diamond is one of the hardest and most difficult to polish materials. In this paper, the polishing of {111} and {100} single crystal diamond surfaces by standard chemical mechanical polishing, as used in the silicon industry, is demonstrated. A Logitech Tribo Chemical Mechanical Polishing system with Logitech SF1 Syton and a polyurethane/polyester polishing pad was used. A reduction in roughness from 0.92 to 0.23 nm root mean square and 0.31 to 0.09 nm rms for {100} and {111} samples respectively was observed.     

Effect of Hafnium Impurities on the Magnetoresistance of $$\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\delta }$$

In the present study, we investigate the influence of the hafnium (Hf) impurities on the magnetoresistance of \(\hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\delta }\) ceramic samples in the temperature interval of the transition to the superconducting state in constant magnetic field up to 12 T. The cause of the appearance of low- temperature “tails” (paracoherent transitions) on the resistive transitions, corresponding to different phase regimes of the vortex matter state is discussed. At temperatures higher than the critical temperature (T > \(T_\mathrm{c})\), the temperature dependence of the excess paraconductivity can be described within the Aslamazov–Larkin theoretical model of the fluctuation conductivity for layered superconductors.     

Yield Vertices for Symmetric Slip on {110}<111> and Asymmetric Slip on {112}<111> Systems

The single crystal yield surfaces (SCYS) of bcc metals for symmetric slip on {110}＜111＞ and asymmetric slip on {112}＜111＞ systems have been analyzed and deduced. The complete SCYS have been derived when their critical resolved shear stresses (CRSS) are specified in a particular case (such as for Mo metal). The results showed that there are 600 stress states that can be classified into 35 groups according to the crystal symmetry. Each group activates eight, six or five {110}＜111＞ and {112}＜111＞ slip systems depending on crystallographically nonequivalent slip systems groups. Among all these stress states, three groups activate eight systems, there are 24 stress states; four groups activate six systems, there are 48 ones; the remaining twenty-eight groups activate five systems, there are 528 ones. In this case, the fraction of vertices for which there is slip ambiguity (more than five active systems) is reduced considerably compared with pure {110}＜111＞ slip.     

The structure of epitaxial overgrowths of Cu2S formed on (111) Cu

Overgrowths of Cu₂S were formed on (111) single-crystal films of copper by exposing them to sulfur vapor in the temperature range 25–300 °C. Reflection high energy electron diffraction (RHEED) analysis revealed that the resultant overgrowths were epitaxial and of various structural forms depending predominantly on the duration of exposure and not on the temperature. The overgrowth started as a cubic form of Cu₂S but transformed to the hexagonal form and finally to the orthorhombic form. The morphology of the Cu₂S indicated by RHEED, scanning electron microscopy and transmission electron microscopy proceeds from a smooth flat structure to an island-type formation.     

The growth of epitaxial ZnSe upon germanium substrates

This paper reports the growth conditions controlling the deposition by vacuum evaporation of epitaxial layers of n-type zinc selenide upon oriented p-type germanium substrates. The study has been performed in both conventional and ultra-high vacuum systems, with the growth proceeding from the vapour phase. The degree of ordering, growth rate and surface morphology of the zinc selenide layers has been systematically investigated as a function of the orientation and temperature of the germanium substrate and of the degree of residual vacuum in which the growth occurs. The influence that the source has in controlling epitaxy has also been observed. The growth techniques utilized in these studies are reported in detail and the underlying mechanisms controlling the growth process of ordered epitaxial layers are discussed.     

Microstructural and electrical transport properties of uniaxially pressed $$\text {Bi}_{1.65}\text {Pb}_{0.35}\text {Sr}_2\text {Ca}_{2.5}\text {Cu}_{3.5}\text {O}_{10+\delta }$$ ceramic superconductors

We have studied the effect of the pelletization pressure on microstructural and electrical transport properties of superconducting ceramics with starting composition given by the formula \(\text {Bi}_{1.65}\text {Pb}_{0.35}\text {Sr}_2\text {Ca}_{2.5}\text {Cu}_{3.5}\text {O}_{10+\delta }\). The experimental data of electrical measurements was processed in order to obtain the weak-link resistivity, the orientation probability of the grains’ a-axes along a certain preferential direction, the slope of the linear part in the temperature dependence of the ab-planes resistivity, and the intrinsic effective anisotropy of the grains, of each sample. In contrast with the behaviour of \(\text {Bi}_{1.65}\text {Pb}_{0.35}\text {Sr}_2\text {Ca}_{2}\text {Cu}_{3}\text {O}_{10+\delta }\) ceramics, the Ca, Cu enriched samples exhibit a reduction of their effective anisotropy at sample level and weak links resistivity with increasing compacting pressures. In addition, a compacting pressure of around 488 MPa may affect considerably the electrical and structural parameters of the material. The results suggest that a combined effect of the pelletization pressure and the doping with Ca and Cu can be used to improve the electrical transport properties of these materials for technological applications.     

Formation of {111} fibre texture in recrystallised aluminium sheet

Abstract

The deep drawability of commercial purity aluminium sheets is improved by introducing a (in fcc materials rather unusual) {111} fibre texture in the sheet surface layers. An additional step of warm rolling after the conventional hot and cold rolling leads to the formation of a pronounced shear texture in the sheet surface layers. During the final recrystallisation annealing, the desired {111} texture prevails at the expense of the other shear texture components. The present paper aims to clarify the mechanisms of the formation of {111}∥ND orientations during both warm rolling and recrystallisation. The effect of the {111} surface texture on the plastic anisotropy of the resulting sheets is discussed.     

深冲IF钢再结晶{111}纤维织构形成机制探讨

为了探讨深冲IF钢再结晶织构与退火温度之间的关系及{111}再结晶织构形成机制,采用X射线衍射三维取向(ODF)和背散射电子衍射(EBSD)分析技术并结合金相组织观察,利用Gibbs-Thom son方程对冷轧IF钢在不同退火温度下的再结晶织构演变规律及形成机制进行研究.实验结果表明:随着退火温度的增加,再结晶量逐渐增多,γ纤维织构强度亦相应增强,同时,α纤维织构强度则逐渐降低;冷轧IF钢再结晶初期的织构转变主要发生在γ纤维织构之间.研究表明,再结晶核心的形成主要以"显微择优形核"为主,晶核的长大则主要以择优生长为主,而Σ重位点阵晶界在再结晶γ纤维织构形成过程中起着重要作用.     

Effect of some growth parameters on vacuum-deposited CulnSe2 films

P-type copper indoselenide (CulnSe₂) thin films were vacuum-deposited on glass substrates by a single-source thermal evaporation technique under different conditions of preparation. The structural properties of the films were investigated by X-ray diffraction and transmission electron microscopy and diffraction techniques. The dark resistivity of the deposited films was investigated as a function of film thickness, deposition rate and substrate temperature. The conductivity activation energy ranges from 0.851 to 1.01 eV depending on the deposition rate. Single-phase and stoichiometric CulnSe₂ films could be deposited at low deposition rates (less than 4 nms^–1). Higher deposition rates led to multiphase films containing InSe, ln₂Se₃, CuSe and Cu₃Se₂ in addition to CulnSe₂.