Molecular-dynamics study of diamond/silicon (001) interfaces with and without graphitic interface layers

Abstract

A theoretical study of diamond/silicon ͑001͒ interface structures with and without graphitic interlayers using a density-functional based tight-binding molecular-dynamics method is presented. The study is motivated by recent progress towards diamond heteroepitaxy on Si ͑001͒ using the bias technique. The proposal by Robertson that an initial graphitic deposit with the graphite planes normal to the Si surface ͑resulting from carbon subplantation͒ provides a well matched compliant buffer layer and hence may lower the interface energy is examined. It is found here that the models with ''graphitic'' or sp 2 bonded interlayers have, in fact, higher energy than those without and that the energy increases with the number of graphitic layers. Residual strain in the graphite planes is found to be one of the reasons for this energetic disadvantage. Si surface dimerization was assumed in the initial structures. The diamond surface layer is found to dimerize spontaneously in both cases ͑with and without graphite interlayers͒. In models with an odd number of sp 2 layers, the last sp 2 bonded atoms next to diamond become the diamond dimerized termination layer. Because of the dimerization, compatibility is required between the 3-on-2 epitaxy and the (2ϫ1) dimerizations of both the Si and C surfaces joined together at the interface. The various ways in which the diamond and Si dimer arrays can be juxtaposed are analyzed and structural relaxation calculations are carried out for each to determine the optimum energy interface structure. The relative energies of the various structures are tentatively explained in terms of favorable and unfavorable local structural units. The optimum structure found has a stepped diamond surface with the lowermost carbon layer dimers orthogonal to the Si dimers.

Theoretical analysis of the diffusive ion in biased plasma enhanced diamond chemical vapor deposition

“…Thus the voltage bias is effective for reactions between carbon and hydrogen or between carbon and carbon. 11,12,31 A detailed calculation of the dynamical chemical reaction for various kinetic energies of hydrogen ions is required for the further discussion of nucleus formation of diamond in the microwave CVD process.…”

“…11,12 A variety of the interface structures between the Si substrate and diamond layers formed during the bias pretreatment, such as SiC, 13,14 amorphous carbon, 15 and nanographite, 16 are directly observed by highresolution transmission electron microscopy ͑HRTEM͒. 17 The formed structures may essentially depend on the kinetic energy of the ions on the substrate surface which is dependent on the plasma parameters.…”

Thermal properties of Si(Al)/diamond composites prepared by in situ reactive sintering

“…The Gibbs free-energy DG 0 in the formation of SiC is calculated to be À63 kJ at 1643 K. Some researches, which relate to moleculardynamics of diamond/Si composites [15] and kinetics of the reaction of diamond/Si composites [16], have been reported. TEM study of the structure and chemistry of a diamond/silicon interface showed the evidence of b-SiC [17].…”

Study on the Interface Structure: Diamond Thin Film Epitaxy on (001) Silicon Substrate

“…The ultimate goal of the diamond synthesis for the application in microelectronics would be the deposition of single-crystal diamond films in a large area on a low cost substrate such as silicon. In order to realize this aim, a lot of experimental and theoretical works [4][5][6][7][8][9][10][11][12] have been done. Especially, using the bias-enhanced nucleation (BEN) method, heteroepitaxial growth of diamond thin film has been made a great progress, [13][14][15][16] For example, oriented diamond films were synthesized on silicon substrates 12,13 and the interface structure between silicon and diamond [14][15][16] was observed directly with high resolution transmission electronic microscope (HRTEM).…”