Morphology and microstructure of epitaxial Cu(001) films grown by primary ion deposition on Si and Ge substrates

A low-energy, high-brightness, broad beam Cu ion source is used to study the effects of self-ion energy E(i) on the deposition of epitaxial Cu films in ultrahigh vacuum. Atomically flat Ge(001) and Si(001) substrates are verified by in situ scanning tunneling microscopy (STM) prior to deposition of 300 nm Cu films with E(i) ranging from 20 to 100 eV. Film microstructure, texture, and morphology are characterized using x-ray diffraction omega-rocking curves, pole figure analyses, and STM. Primary ion deposition produces significant improvements in both the surface morphology and mosaic spread of the films: At E(i)>37 eV the surface roughness decreases by nearly a factor of 2 relative to evaporated Cu films, and at E(i) similar or equal to 35 eV the mosaic spread of Cu films grown on Si substrates is only i similar or equal to 2 degrees, nearly a factor of 2 smaller than that of evaporated Cu. During deposition with E(i) similar or equal to 25 eV on Ge substrates, the film coherently relaxes the 10% misfit strain by formation of a tilt boundary which is fourfold symmetric toward(lll). The films have essentially bulk resistivity with rho=1.9+/-0.1 mu Omega cm at room temperature but the residual resistance at 10 K, rho(0), shows a broad maximum as a function of E(i), e.g., at E(i) similar or equal to 30 eV, rho(0)=0.5 mu Omega cm. (C) 1996 American Institute of Physics.