CHARACTERIZATION OF ION BEAM-INDUCED SURFACE MODIFICATION OF DIAMOND FILMS BY REAL-TIME SPECTROSCOPIC ELLIPSOMETRY

Real time spectroscopic ellipsometry from 1.5 to 4.0 eV has been applied to monitor surfaces of optical quality diamond thin films during exposure to low energy Ar and H ion beams, and atomic H. Monolayer-level sensivity to the conversion of diamond to optically absorbing sp2 bonded carbon upon ion impact is demonstrated. For Ar ions, a beam voltage of 50 V is found to be sufficient to convert the surface to the equivalent of a single monolayer of sp2 bonded carbon, whereas the topmost 12-16 angstrom is converted at the threshold for sputter etching, between 100 and 150 V. Atomic H and low energy H ion treatments (less-than-or-equal-to 50 V) are found to eliminate optically absorbing defects within 15 angstrom of the surface. The overall results provide optimism that real time spectroscopic ellipsometry will be a highly sensitive real time probe of diamond surface and bulk microstructure in the reactive environments of enhanced chemical vapor deposition.