Ultra-thin epitaxial Al and Cu films on CaF2/Si(111)

In this work, smooth epitaxial films of Al and Cn with thickness between 5 and 20 nm have been grown by molecular beam epitaxy (MBE). This was done in order to study the surface contribution to scattering of conduction electr ons, without masking effects of grain boundary scattering. Aluminum epitaxy on CaF2/Si(1 1 1) was confirmed by reflection high energy electron diffrac tion (RHEED). The surface and interface rms roughness below 0.3 nm was achi eved for 10 nm-thick Al films, as measured by atomic force microscopy (AFM) . Threading screw dislocations but no grain boundaries were observed in the se films by scanning tunneling microscopy (STM). Preliminary resistivity me asurements on the films between 4 and 20 nm thick agreed qualitatively with the Fuchs-Sondheimer model of resistivity size effect due to diffuse elect ron scattering from surfaces. For Cu, the epitaxial growth was obtained whe n depositing on a 3 nm-rhick Al seed layer. (C) 2001 Elsevier Science B.V. All rights reserved.