Over the past several years we have been investigating the fundamental aspects of thin film growth using energetic neutral molecular beams produced by supersonic expansions as sources. Our focus has been on Group IV systems-- Si, Ge and Si@sub 1-x@Ge@sub x@. This work has ranged from detailed investigations of the gas-surface chemical dynamics of dissociative adsorption, to thin film deposition and growth emphasizing morphological aspects, to computer simulations of both the thin film morphology and gas-surface fluid dynamics. We will present an overview of this work, focusing on more recent developments, which will include (i) the growth of thin films at grazing angles of incidence; (ii) the selectivity of growth (e.g., Si vs. SiO@sub 2@) as a function of beam energy, beam composition and substrate temperature; and (iii) the exploration of scale-up strategies (experiment and computer simulation) for deposition over large areas.