Critical Nucleus Phase Diagram for the Cu(100) Surface
Joshua M. Pomeroy, Joel D. Brock
An experimental exploration of island nucleation dynamics during epitaxial film growth on the Cu(100) surface is presented that connects previous results from other groups at low temperatures with the room temperature regime. The steady-state balance of various atomistic processes during the island nucleation process has direct impact on the physical properties of epitaxial films, e.g. greater nucleation densities allow layer-by-layer growth to be achieved at lower temperatures. Within many theoretical frameworks, the critical nuclei size i (the largest assembly of atoms with a higher probability for decay than growth) plays a major role in determining island nuclei densities, and, by extension, the physics of film growth. This paper presents island density and distribution results from recent STM studies and analysis that allows for accurate determination of the critical nuclei size at various deposition rates and temperatures near room temperature and the i=1 to i=3 boundary (dimer to tetramer). This is accomplished by using the scaling behavior of coarsening to develop statistical weight by rescaling individual distributions and summing them. The results of this study are then combined with previously published results from other researchers to empirically determine the structure of the phase boundary from i=1 to i=3 as a function of temperature and deposition rate. At low temperatures and fluxes, the position of the phase boundary agress with expected position when only adatom mobility is considered. Deviations at higher temperatures suggest that the mobility of dimers and other small islands may be important in determining the effective critical nucleus near room temperature.
Physical Review B (Condensed Matter and Materials Physics)
coarsening, critical island size, diffusion, homoepitaxy, mean-field, nucleation dynamics, scanning tunneling microscope, thin films
and Brock, J.
Critical Nucleus Phase Diagram for the Cu(100) Surface, Physical Review B (Condensed Matter and Materials Physics)
(Accessed June 10, 2023)