W. C. Elliott

Orientation dependence of homoepitaxy: An in situ X-ray scattering study of Ag

Abstract We have investigated the homoepitaxial growth of Ag(111) and Ag(100) using X-ray specular reflectivity measured near the Bragg positions. At a growth temperature of 200 K, we observe that the root-mean-square roughness, σ, evolves as a power law in the deposited thickness for both crystal orientations. However, the growth kinetics of these surfaces are vastly different, leading to exponents of β = 0.5 ± 0.05 for Ag(111) and β = 0.28 ± 0.03 for Ag(100). The differences in growth are attributed to the diffusion barrier at step ledges.

Vacancy trapping and annealing in noble-metal films grown at low temperature

We have used synchrotron x-ray diffraction to study the homoepitaxial growth on Cu(001), Ag(001), and Ag(111), at temperatures between 300 and 65 K. The growth on all of these surfaces exhibits a consistent trend towards a large compressive strain that is attributed to the incorporation of vacancies into the growing film below 160 K. In each case, the vacancy concentration is ∼2% at 110 K and we have measured the temperature dependence for incorporation on the (001) surfaces as well as the annealing behavior for Cu(001). These results, which suggest new kinetic mechanisms, have important implications for understanding epitaxial crystal growth.

Kinetic Roughening During Ag Homoepitaxy

Kinetic roughening during homoepitaxial growth was studied for Ag(111) and Ag(001) where the two orientations represent opposite limits of step-ledge barrier effects. We summarize recent x-ray specular reflectivity studies of the rms surface roughness which was investigated as a function of thickness and temperature. In addition to exponents, the roughness magnitude, its relationship to step-ledge barrier effects, and the absence of noise in the deposition flux are discussed. Preliminary results are also reported for the lateral coarsening of Ag(111) at 200K.