No abstract available

[en] The disclosure relates to a plasma etch chemistry which allows a near perfectly anisotropic etch of silicon. A Cl-containing compound such as HCl has HBr added thereto, readily allowing the anisotropic etching of silicon. This is due to the low volatility of SiBr₄. The silicon surface facing the discharge is subjected to ion bombardment, allowing the volatilization (etching) of silicon as a Si-Cl-Br compound. The Br which adsorbs on the sidewalls of the etched silicon passivates them from the etching. This new plasma etch chemistry yields a very smooth etched surface, and the etch rate is relatively insensitive to the electrical conductivity of the silicon

[en] Short communication

[en] Dissociative electron attachment (DEA) is the major process where molecules are destroyed in low-energy plasmas. DEA cross sections are therefore important for a whole variety of applications but are both hard to measure or compute accurately. A method for estimating DEA cross sections based a simple resonance plus survival model is presented. Test results are presented for DEA of molecular oxygen and molecular chlorine, for which experimental measurements are available for comparison, and SiBr and SiBr₂, for which no previous data is available. The estimator has been implemented as part of Quantemol-N expert system which uses the R-matrix method to predict resonance positions and widths.

No abstract available

[en] Recently it was pointed out that transition frequencies in certain diatomic molecules have an enhanced sensitivity to variations in the fine-structure constant α and the proton-to-electron mass ratio m_p/m_e due to a near cancellation between the fine structure and vibrational interval in a ground electronic multiplet [V. V. Flambaum and M. G. Kozlov, Phys. Rev. Lett. 99, 150801 (2007)]. One such molecule possessing this favorable quality is silicon monobromide. Here we take a closer examination of SiBr as a candidate for detecting variations in α and m_p/m_e. We analyze the rovibronic spectrum by employing the most accurate experimental data available in the literature and perform ab initio calculations to determine the precise dependence of the spectrum on variations in α. Furthermore, we calculate the natural linewidths of the rovibronic levels, which place a fundamental limit on the accuracy to which variations may be determined.

[en] In recent years double core-hole states are intensively studied since their chemical shifts provide detailed information about initial-state and relaxation effects in a molecule. We derived the Si 1s"−"1, 2s"−"1, and 2p"−"1 binding energies as well as the Si 2s"−"2, 2s"−"1, 2p"−"1, and 2p"−"2 double-core hole binding energies of different SiX_4 systems in order to derive the chemical shifts. Based on these results we created Wagner plots, which give insight in the initial state and the relaxation effects in the different molecules. (paper)

[en] Highlights: • A SiB_6–MoSi_2 coating was prepared by pulse arc discharge deposition (PADD). • The coating can protect C/C composites from oxidation at 1773 K for 168 h. • Influence of iodine concentration on oxidation resistance was investigated. • The failure of the oxidation resistant coating was investigated. - Abstract: To improve the oxidation resistance of carbon/carbon (C/C) composites, a SiB_6–MoSi_2 coating was prepared by a novel pulse arc discharge deposition (PADD). The influence of iodine concentration on thickness, compactness and oxidation resistance of the multilayer coatings were investigated. Results show that the oxidation resistance of the multilayer coatings was improved with the increase of iodine concentration from 2.0 to 3.0 g L"−"1. The SiB_6–MoSi_2 coating prepared at iodine concentration of 3.0 g L"−"1 can protect C/C composites from oxidation at 1773 K in air for 168 h with a weight loss of 1.98%. The failure of the multilayer coatings is due to the volatilization of the multilayer coatings and the escape of CO and CO_2

[en] Cross section calculations of low energy e^- -molecule scattering have been limited to targets with few electrons. We show that the use of soft norm-conserving pseudopotentials in the target description and in the scattering calculations makes possible the study of the low-energy electron scattering by many-electron molecules. We present results for C F₄, C Cl₄, Si Cl₄, Si Br₄ and Si L₄ with 42, 74, 82, 154, and 226 electrons respectively. The pseudopotentials replace the nucleus and the core electrons of each atom so that only the valence is described in a many-body framework. Our calculated cross sections are in good qualitative agreement wit experiment. Except for C F₄, we show theoretical cross sections for these molecules for the first time. For the C F₄ molecule our results are in excellent agreement with the theoretical data available in the literature [8], which is an all-electron calculation, and also with the experimental results [11]. (author)

[en] Efficient vapor source Si doping of InP and In_0.53Ga_0.47As have been demonstrated using SiBr₄ as the Si source for both gas source (GSMBE) and metalorganic molecular beam epitaxy (MOMBE). Net electron concentrations ranging from n=2x10¹⁷ to 6.8x10¹⁹ cm^-3 and from 9x10¹⁶ to 3x10¹⁹ cm^-3 have been obtained for InP and In_0.53Ga_0.47As, respectively. Comparison of these data with those for Si₂H₆ indicate that the Si incorporation efficiency with SiBr₄ is more than 10 000 times greater than with Si₂H₆ for substrate temperatures in the range of 475≤T_s≤500 degree C. Specular surface morphologies were obtained, even for the most heavily doped samples. While [Si] as high as 1.8x10²⁰ cm^-3 was obtained in InP, the net electron concentrations and 300 K Hall mobilities decrease with increasing [Si] for [Si]>6.8x10¹⁹ cm^-3. Contact resistances as low as R_c=3x10^-8 Ω cm² were obtained using a nonalloyed Ti/Pt/Au contact to InP layers doped to n=6.3x10¹⁹ cm^-3. During GSMBE growth, an increased Si background concentration ([Si]∼2x10¹⁷ cm^-3) was observed after extended use of the SiBr₄ source for these heavy doping concentrations. This increased background was not observed in MOMBE-grown material. Depth profiles of pulse-doped structures indicate the absence of memory effects for structures grown by MOMBE