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Metal clustering during depth profiling of thin films

Thin metallic layers of Cu, Cr, or Ag were deposited on Si substrates and then sputtered as in a standard depth profiling mode. The etching was completed by using 1–5 keV Ar+ beam, scanned over the surface. The composition of the exposed etched surface was monitored by X‐ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES). When the metal‐silicon interface was approached, the etching was stopped and the sample surface was analyzed by scanning electron microscopy (SEM) and scanning Auger microscopy (SAM). We observed clusters of metal on the Si substrate. Their characteristic sizes were 30–60 nm for Cu, 60–90 nm for Cr, and 100–200 nm for Ag. The patterns were sensitive to the ion energy—at 1 keV the Cu network was well defined, whereas at 3–5 keV energy the patterns become fuzzy without clear boundaries. The clustering of thin films near the interface can affect the depth profiles in surface analytical techniques, and can be used as a tool to create clusters in nanotechnology. Copyright © 2006 John Wiley & Sons, Ltd.