We develop and analyze 1+1-and 2+1-dimensional (d) models for multilayer homoepitaxial growth of metal films at low temperatures (T), where intralayer terrace diffusion is inoperative. This work is motivated by recent variable-temperature scanning tunneling microscopy studies of Ag/Ag(100) homoepitaxy down to 50 K. Adsorption sites are bridge sites in our 1+1d models, and fourfold hollow sites in our 2+1d models for fcc(100) or bcc(100) surfaces. For growth at 0 K, we introduce a "restricted downward funneling" model, wherein deposited atoms can be trapped on the sides of steep nanoprotrusions rather than always funneling down to lower adsorption sites. This leads to the formation of overhangs and internal defects (or voids), and associated "rough" growth. Upon increasing T, we propose that a series of interlayer diffusion processes become operative, with activation barriers below that for terrace diffusion. This leads to "smooth" growth of the film for higherT (but still within the regime where terrace diffusion is absent), similar to that observed in models incorporating "complete downward funneling. "
Disciplines
Chemistry | Mathematics | Physical Chemistry
CommentsThis article is from Physical Review B 64 (2001) We develop and analyze 1ϩ1-and 2ϩ1-dimensional ͑d͒ models for multilayer homoepitaxial growth of metal films at low temperatures (T), where intralayer terrace diffusion is inoperative. This work is motivated by recent variable-temperature scanning tunneling microscopy studies of Ag/Ag͑100͒ homoepitaxy down to 50 K. Adsorption sites are bridge sites in our 1ϩ1d models, and fourfold hollow sites in our 2ϩ1d models for fcc͑100͒ or bcc͑100͒ surfaces. For growth at 0 K, we introduce a ''restricted downward funneling'' model, wherein deposited atoms can be trapped on the sides of steep nanoprotrusions rather than always funneling down to lower adsorption sites. This leads to the formation of overhangs and internal defects ͑or voids͒, and associated ''rough'' growth. Upon increasing T, we propose that a series of interlayer diffusion processes become operative, with activation barriers below that for terrace diffusion. This leads to ''smooth'' growth of the film for higher T ͑but still within the regime where terrace diffusion is absent͒, similar to that observed in models incorporating ''complete downward funneling.''