C. Speisser

HFCVD diamond growth on Cu(111). Evidence for carbon phase transformations by in situ AES and XPS

Abstract Polycrystalline diamond has been deposited on monocrystalline Cu(111) via the hot filament chemical vapour process. The diamond growth was studied by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), directly connected to the growth chamber. Shape analysis of the AES C KVV line and C 1s relative intensity both suggest the following three-step process: first the formation of two graphite layers, then the very slow growth of graphitic layers, more and more distorted when going away from the copper surface and finally, when a critical size corresponding to ca five to six layers is reached, diamond nucleation and growth. A very long induction time (> 10 h) is observed before the growth of graphitic layers. This is ascribed to the strong interaction of the graphite layer with the copper surface. Transmission electron microscopy and selected area diffraction confirm this process, but in addition reveal the presence of small spherulitic (onions) and polyhedral graphite-like aggregates. This nucleation process is roughly in agreement with the recrystallization model of diamond nucleation from amorphous carbon proposed by Singh and Vellaikal, J. Appl. Phys. 73 (1993) 2831.

Mechanisms of CVD diamond nucleation and growth on mechanically scratched and virgin Si(100) surfaces

Abstract The diamond nucleation and growth processes on a scratched and a virgin Si(100) surface were studied by both electron spectroscopies (XPS) and microstructural probes (SEM, TEM) in order to connect the nature of surface species with the structural changes. We have shown that a preliminary scratching of the substrate surface hugely enhances the nucleation kinetics relative to the virgin sample. This is explained by the much faster formation of stable diamond nuclei in correspondence of suitable nucleation sites. The results have been modeled, considering the covered surface S as the unique parameter. S obeys an Avrami plot of the form S=1−exp(−ktn) where the exponent n ≈ 2.5±0.4 over a wide range of deposition is indicative of a constant linear growth rate with decreasing nucleation rate.