Photoelectron Spectroscopy Study of Natural (100), (110), (111) and CVD Diamond Surfaces

Abstract

Natural type IIb diamond surfaces of (IOO), (110), and (111) orientation, as well as chemical vapor deposited (CVD) diamond thin films with (IOO), (110), or mixed orientation are probed by photoelectron spectroscopy in the ultraviolet (UPS) and X-ray (XPS) energy regimes. Dramatic changes can be observed in the valence band and core level spectra of these surfaces upon annealing, hydrogen-plasma exposure, or pulsed dye laser irradiation. The observed changes can be reversed by the exposure of the surfaces to atomic hydrogen (deuterium). The valence band spectra reveal specific surface reconstructions for all three surface preparation methods and moreover a cleaning effect is observed following laser irradiation of CVD diamond surfaces. A comparison to a multitude of theoretical and experimental studies on diamond surface reconstruction is made to elucidate the connection between electronic properties and atomic surface structures. I )

Thermal boundary conductance between refractory metal carbides and diamond

“…The observed energy values do not correspond exactly to the cited reference peaks, but subpeaks observed below the main diamond peak cannot be attributed to other species often observed on a diamond surface, i.e. hydrogen [50][51][52][53] or oxygen [37,38], since these species are known to shift the binding energy towards higher values [37,38,50,51]. On the other hand, bonding with transition metals produces peaks at lower energies than the sp 3 peak of carbon e.g.…”

Influence of diamond surface termination on thermal boundary conductance between Al and diamond

“…One peak is identified at lower energies than the main peak, at 284.4 eV and is attributed to sp 2 surface termination 27,32,34,35 . This peak was found to be shifted to 284.0 eV for the case of the Ar:O plasma treated samples.…”

“…The main peak at 285.5 eV is taken to be sp 3 carbon. Three peaks were identified at higher energies; one at 286.2 eV, attributed to C-O surface termination 27,32 , one at 286.7, attributed to C-H surface termination 25,26,34,35 , and one above 288 eV, attributed to C=O bonds. This last peak disappeared once the sample had been subjected to a bakeout at 300 • C for 10 min, thus we attribute it to surface contaminations.…”

Effect of diamond surface orientation on the thermal boundary conductance between diamond and aluminum

“…[100] surface exposed to hydrogen is 2x1:H with 4 H atoms on 2 classic [100] cubic unit cell [20,43,44], while the 1x1:2H unit cell is unstable due to mutual steric repulsion between the hydrogen atoms. The stable structure of the [111] surface is the 1x1:H and can be terminated either by C-H groups [20,44] or by C-H 3 methyl groups [45,46], increasing substantially the hydrogen surface density.…”