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The present study deals with the interaction of C-terminated c(2×2) and Si-rich 3×2 3C-SiC (100) reconstructed surfaces with a microwave plasma chemical vapor deposition used for diamond growth. Pure hydrogen and hydrogen/methane exposures have been carried out. Their effects on the atomic ordering and the stoichiometry within the first planes have been studied in situ using low energy electron diffraction and electron spectroscopies: x-ray photoelectron spectroscopy, x-ray Auger electron spectroscopy, and ultraviolet photoelectron spectroscopy. 5 min plasma exposures result in a lost of the initial reconstructions, a postplasma oxygen contamination, and strong modifications of the stoichiometry within the first planes. Indeed, the stability of well defined 3C-SiC surfaces depends strongly on their termination: C-terminated surface exhibits a high inertia while the Si-rich surface undergoes partial etching. The three first silicon atomic planes involved in the 3×2 reconstruction are removed upon pure hydrogen plasma while a monolayer is preserved after hydrogen/methane exposure. [ABSTRACT FROM AUTHOR]

Elucidation of a complex defect configuration arising from the interaction between eight first-order twin boundaries in a diamond thin film prepared by chemical vapour deposition on a silicon substrate is reported. The defect has been identified by ultrahigh-resolution electron microscopy at 0.12 nm resolution. It is shown to consist of a nearly perfect fivefold twin centre closely connected to two small portions of original Σ = 9, {122} and Σ = 27, {255} grain boundaries (GBs). Extensive image simulation has been used to deduce the detailed core structure and to propose a plausible three-dimensional atomicscale model, which contains no dangling bonds. The observed σ bond stretching and bond bending are found to be remarkably consistent with recent ab initio calculations of minimum-energy configurations for related defect structures in diamond and in silicon carbide. Moreover, the core structure of the two particular GBs, which consists of alternating columns of five- and seven-membered rings of carbon atoms, is perfectly consistent with the structures at present known to be the most stable forms of such second-order and third-order GBs in diamond and cubic diamond materials. [ABSTRACT FROM AUTHOR]

Abstract: There is a great interest for multilayer hard coatings because they exhibit enhanced properties resulting from their nanostructuration. Such coatings are frequently constituted of carbide and nitride and are generally deposited under very low pressure by plasma and PVD processes. These vacuum techniques enable the growth of heterostructures with nanometric thick individual layers and sharp interfaces, which are two requirements for advanced performances. However, both to develop more economical processes and with the goal of continuous deposition applications, the CVD processes operating under atmospheric pressure are particularly attractive. In this paper we show that the combination of pulsed direct liquid injection and the use of metalorganic precursor (DLI-MOCVD) is a promising route for the growth of nanostructured multilayer coatings under atmospheric pressure. Chromium metal as well as chromium carbide and nitrides monolithic coatings have been deposited at 773 K by this process using liquid solution of bis(benzene)chromium as Cr molecular precursor. Then, CrC x /CrN nanostructured multilayer coatings with a bilayer period as low as 50 nm have been grown. Structural characterizations and preliminary mechanical properties of these metallurgical coatings are discussed. [Copyright &y& Elsevier]

Abstract: The mechanisms involved in the diamond nucleation on 3C–SiC surfaces have been investigated using a sequential in situ approach using electron spectroscopies (XPS, XAES and ELS). Moreover, diamond crystals have been studied by HRSEM. The in situ nucleation treatment allows a high diamond nucleation density close to 4×1010 cm− 2. During the in situ enhanced nucleation treatment under plasma, a negative bias was applied to the sample. The formation of an amorphous carbon phase and the roughening of the 3C–SiC surface have been observed. The part of these competing mechanisms in diamond nucleation is discussed. [Copyright &y& Elsevier]

Two 3C-SiC(100) reconstructed surfaces have been exposed to bias enhanced nucleation (BEN) treatments performed in a microwave plasma chemical vapor deposition reactor. For both BEN steps, a significant enhancement of the diamond nucleation density has been observed on the initial C-terminated surface compared to the Si-rich surface. Samples have been characterized by in situ surface analysis, namely, x-ray photoelectron spectroscopy and x-ray Auger electron spectroscopy, and by field emission gun scanning electron microscopy. [ABSTRACT FROM AUTHOR]