THIN-FILM GROWTH OF SN ON CU(100)

The deposition of Sn on a Cu(100) surface has been investigated as a function of layer thickness, deposition temperature and subsequent anneal treatment, using a combination of RBS/channeling, LEED and Auger spectroscopy measurements. No evidence of pseudomorphic Sn growth could be detected. At Sn coverages up to about one monolayer, RBS/channeling data indicate that Sn atoms displace a comparable number of Cu atoms from their regular lattice sites, even at the lowest (170 K) deposition temperature studied. LEED studies show evidence of two-dimensional commensurable phase formation whose structure depends strongly on anneal temperature and Sn coverage. Copper-rich phases such as the ε{lunate}-phase (Cu3Sn) are not observed at submonolayer Sn coverage, even after a 525 K anneal treatment. Thicker Sn layers exhibit two major anneal stages: formation of the η′-phase (Cu6Sn5) around 265 K and its subsequent conversion into the ε{lunate}-phase (Cu3Sn) around 420 K. An isochronal anneal measurement yielded activation energies of 0.65 ± 0.05 and 1.07 ± 0.08 eV for interdiffusion of Sn and Cu in the η′- and ε{lunate}-phases, respectively. RBS/channeling data indicate that the resulting η′-phase is partially (10%-20%) aligned with the Cu(100) substrate. No preferential orientation was observed for the ε{lunate}-phase. © 1990.