The growth and structure of copper films on (0001) ruthenium surfaces

Abstract

The structural and electronic properties of clean evaporated copper films on (0001) Ru surfaces were studied by low energy electron diffraction, Auger electron spectroscopy and thermal desorption and work function measurements. Two-dimensional epitaxial growth and three-dimensional epitaxial growth are clearly discernible from “extra” spots in the low energy electron diffraction patterns and from Auger spectroscopy as well as from thermal desorption measurements which show the formation of two states β 1 and β 2. The β 2 state is identified as arising from two-dimensional copper growth and is almost saturated after the deposition of about 5 × 10 14 Cu atoms cm -2; the β 1 state is caused by the three-dimensional growth of copper. The binding energies of the two states were evaluated from the maximum desorption temperatures; we found that the binding energy of β 2 exceeds that of β 1 (which is identical with the sublimation energy of copper) by about 3–4 kcal mol -1. The work function increases up to 800 meV; an intermediate maximum indicates a small charge transfer from ruthenium to copper.