Scanning tunnelling microscopy characterization of gold film surfaces processed using an argon radio frequency (RF) plasma

STM investigation has revealed that the initially hat topography of gold fi lm surfaces as-deposited on mica substrates at an elevated temperature (sim ilar to 440 degrees C) is changed substantially by argon RF plasma processi ng at various power levels fur a short period (5 min). When the power level is relatively low (less than or equal to 20 W). the processed gold film su rfaces show a ell defined, uniformly distributed, dome-shaped mounds with s imilar lateral dimensions. When plasma processing is conducted at higher po wer levels (e.g. 30 and 50 W), the modified gold surfaces still exhibit mou nded topographical features but now these are less uniformly distributed an d of slightly smaller size, showing less will defined boundaries. Moreover, plasma processing can roughen the surfaces of gold, i.e. the value of FWHM (full-width-half-maximum) obtained from the height histogram is in the ran ge similar to 10-similar to 24 Angstrom for the plasma processed surfaces w ith power levels between 10-50 W. Whereas, it is only similar to 5.6 Angstr om for the initially flat and unprocessed surface of the gold film studied. All the phenomena observed can be attributed to a mechanism involving the local redeposition of the gold atoms sputtered by argon ions in the plasma and the reorganization of the plasma-disturbed surfaces via plasma-induced diffusion processes. (C) 1999 Elsevier Science S.A. All rights reserved.