Quantitative understanding of the growth of Cu/Cu(001) including the determination of the Ehrlich-Schwoebel barrier at straight steps and kinks

Abstract

The initial stages of homoepitaxial growth of Cu(001) have been studied by combining experiments and simulations. The investigated temperature window ranges from 200 to 300 K, the deposition rates vary from about 0.5 to 5 monolayer (ML)/min, and the coverage ranges up to about 10 ML. The simulated data have been extracted from a kinematic Monte Carlo approach using a bulk-continued fcc lattice and energetic activation barriers taken from recent literature. The experimental data are thermal energy helium-uptake curves measured in situ during growth. The Ehrlich-Schwoebel barriers for descent from ⟨110⟩-oriented and ⟨100⟩-oriented steps have been used as fitting parameters for the heights of the first and second maxima of the temporal oscillations in the He-uptake curves. Remarkable agreement has been achieved in the entire parameter space except for temperatures below about 230 K. The deviations in the latter range are attributed to failure of the bulk-continued fcc lattice due to, e.g., contraction, etc., becoming of importance for small adatom islands. This result allows an unequivocal determination of the Ehrlich-Schwoebel barrier associated with interlayer mass transport via a kink site (i.e., a ⟨100⟩ segment) in otherwise straight ⟨110⟩ steps, amounting to EES⟨100⟩=−5±3 meV. The Ehrlich-Schwoebel barrier associated ith ⟨110⟩ is determined at EES⟨110⟩=120 meV or higher. The perfect agreement between simulated and the experimental data in the wide range of parameter space also permits a quantitative evaluation of both coarsening, i.e., the increase in the lateral length scale of the structures and the kinetic roughening during growth. The lateral length scale varies with time to the power n=0.22±0.01 in perfect agreement with experimental literature data. Roughening exponents β=0.5 and 0.25 have been obtained for 250 and 290 K, respectively, also in very good agreement with previous experimental findings.