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 stu dy 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) subs trates are verified by in situ scanning tunneling microscopy (STM) pri or to deposition of 300 nm Cu films with E(i) ranging from 20 to 100 e V. Film microstructure, texture, and morphology are characterized usin g x-ray diffraction omega-rocking curves, pole figure analyses, and ST M. Primary ion deposition produces significant improvements in both th e 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 evapo rated Cu films, and at E(i) similar or equal to 35 eV the mosaic sprea d of Cu films grown on Si substrates is only i similar or equal to 2 d egrees, nearly a factor of 2 smaller than that of evaporated Cu. Durin g 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 essen tially bulk resistivity with rho=1.9+/-0.1 mu Omega cm at room tempera ture but the residual resistance at 10 K, rho(0), shows a broad maximu m 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.