AVS 49th International Symposium
    Processing at the Nanoscale Thursday Sessions
       Session PN-ThA

Paper PN-ThA8
Evolution of Surface Morphology and Microstructure during Ion Sputtering of Diamond

Thursday, November 7, 2002, 4:20 pm, Room C-109

Session: Charged Particle Patterning and Emission
Presenter: D.P. Adams, Sandia National Laboratories
Authors: D.P. Adams, Sandia National Laboratories
T.M. Mayer, Sandia National Laboratories
M.J. Vasile, Sandia National Laboratories
Correspondent: Click to Email
This work investigates the morphology and structure of diamond surfaces that evolve during focused ion beam (FIB) sputtering and chemically amplified processes. We include a detailed study of morphology for a broad range of ion incidence angles (0-88 deg) and dose. A single ion (Ga) and incident energy (20keV) are used. For incidence angles between 30-75 degrees referenced from substrate normal, we observe the formation of ripple patterns. Ripples form with a wavevector aligned to the incident beam direction over this range of angles, similar to that predicted by Bradley-Harper for small theta. In order to develop an understanding of the mechanisms underlying a rippled topography, we analyze the evolution of morphology for increasing dose. AFM is used to quantify changes in ripple wavelength and amplitude, while TEM and Raman spectroscopy probe the structure in the near surface region. Beginning at 75 and continuing to 87 degrees, a step/terrace morphology forms during sputtering. Microfacets develop at the earliest stages (lowest dose) indicating a role of initial surface topography. Obvious changes in terrace length over this range of angles suggest that morphology is affected by shadowing between neighboring features. In general, a decrease in yield is discovered with increasing dose over this entire range of angles (30-87 deg). The presence of ripples/microfacets and, more specifically, their evolving shape influence the number of sputtered atoms per ion. Dramatic effects on yield (200% decrease) with increasing dose are observed at angles >80 degrees. Additional research investigates the effects of chemical environment on morphology. Experiments involve ion bombardment in the presence of H2O, methanol and H2O2. When sputtering in the presence of these gases, dramatic changes in morphology result as a function of dose and incidence angle. Changes in sputter yield due to the presence of a gas are also quantified as a function of incidence angle from 0-88 degrees.