Systematic studies of the nucleation and growth of ultrananocrystalline diamond films on silicon substrates coated with a tungsten layer

Abstract

We report on effects of a tungsten layer deposited on silicon surface on the effectiveness for diamond nanoparticles to be seeded for the deposition of ultrananocrystalline diamond (UNCD). Rough tungsten surface and electrostatic forces between nanodiamond seeds and the tungsten surface layer help to improve the adhesion of nanodiamond seeds on the tungsten surface. The seeding density on tungsten coated silicon thus increases. Tungsten carbide is formed by reactions of the tungsten layer with carbon containing plasma species. It provides favorable (001) crystal planes for the nucleation of (111) crystal planes by Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) in argon diluted methane plasma and further improves the density of diamond seeds/nuclei. UNCD films grown at different gas pressures on tungsten coated silicon which is pre-seeded by nanodiamond along with heteroepitaxially nucleated diamond nuclei were characterized by Raman scattering, field emission-scanning electron microscopy, and high resolution-transmission electron microscopy.

Metallic Seed Nanolayers for Enhanced Nucleation of Nanocrystalline Diamond Thin Films

“…50 It has been speculated that the introduction of surface nano-asperities by substrate coating could thus promote the seed adhesion and thus enhance the seeding density of ND particles on silicon substrates. 35,38 This effect is rather small for most of the sputter-coated metallic surfaces under investigation in this study, since relatively comparable values of the number density of ND particle seeds on the various metallic surfaces and the pristine silicon surface have been derived (in the order of about 1 × 10 10 cm -2 ). In fact, electrostatic interactions between the substrate surface and the ND particles, rather than van der Waals interactions, appear to dominate the embedding (adhesion and aggregation) of the ND seeds.…”

“…28−32 In addition, it has long been known that under conventional pretreatment conditions, such as manual scratching, the diamond nucleation densities on carbide-forming substrates (Si, Mo, W) are typically 1−2 orders of magnitude higher than those on substrates that do not form carbides (Cu, Au). 33 In this view, a number of recent studies focused on a precoating of silicon with thin (≤50 nm) metallic seed layers such as W, 34,35 Cr 36 and Mo 37,38 followed by ultrasonic agitation with ND powders. These studies demonstrated a more uniform and denser nucleation of diamond during CVD.…”

“…In numerous studies devoted to the growth of diamond thin films on ferrous and cemented carbide substrates, metallic interlayers were effectively employed to suppress the large uptake of carbon, to suppress the out-diffusion of highly reactive Fe and Co atoms, and to improve the adhesion of the diamond films on the substrate. − In addition, it has long been known that under conventional pretreatment conditions, such as manual scratching, the diamond nucleation densities on carbide-forming substrates (Si, Mo, W) are typically 1–2 orders of magnitude higher than those on substrates that do not form carbides (Cu, Au) . In this view, a number of recent studies focused on a precoating of silicon with thin (≤50 nm) metallic seed layers such as W, , Cr and Mo , followed by ultrasonic agitation with ND powders. These studies demonstrated a more uniform and denser nucleation of diamond during CVD.…”

Tribological and Grinding Properties of Spherical Diamond Grown on a Rough Discontinuous Surface

“…Generally, the CVD diamond had a columnar shape with {111} crystalline face after a deposition time of several hours, while the spherical diamond grains commonly appeared at the initial stage of CVD deposition and only discretely distributed on the substrate surface at nanometric scale size [10]. Hence, it was significant to research the deposition process of large spherical diamond for the tribological applications of CVD diamond [11,12].…”

A novel Mo-W interlayer approach for CVD diamond deposition on steel

“…In order to tackle the adhesion problem different types of interlayers have been used on ferrous substrates such as chromium (Cr), titanium (Ti), Mo, W, nitrides, carbides and multi-structured interlayers, 2,4-11 among which, W interlayers as well as Mo interlayers have demonstrated exceptionally promising properties. However, most of the research on tungsten interlayer was reported on silicon substrates [12][13][14] and little on metallic substrates. 15 W is a very effective diffusion barrier against Fe 8 and C 7 and a strong carbide forming material.…”