Loss of epitaxy during diamond film growth on ordered Ni(100)

Abstract

Filament assisted diamond film growth was studied on a clean and highly oriented Ni(100) substrate using x-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), x-ray excited Auger electron spectroscopy (XAES), and low-energy electron diffraction (LEED) to examine the sample at selected intervals in the growth process. The sample was transferred between the growth chamber and the ultrahigh vacuum analytical chamber without exposure to air. Scanning electron microscopy (SEM) was also used to characterize the sample; however, this required exposing the sample to air. Prior to growth the Ni(100) crystal was cleaned and ordered with a combination of Ar-ion bombardment, oxygen/hydrogen treatments, and annealing. After 2 min growth, microcrystalline graphite islands formed on top of a c(2×2) carbon layer. Later, LEED showed a graphite surface with very poor azimuthal orientation. This surface developed into a disordered nondiamond surface that we assign as glassy carbon. Next, EELS and XAES showed new features due to diamond. Growth was stopped when a continuous diamond film was formed. SEM confirmed the presence of well-faceted diamond crystals on a disordered and highly three-dimensional surface. These experiments show that the graphite and glassy carbon layers, formed prior to diamond, are poorly oriented with respect to the Ni(100) surface. Since these intermediate layers are not in registry with the Ni(100) surface, subsequent diamond growth is not epitaxial.