Interfacial effect on the formation and properties of stable glasses

Abstract

An in-depth understanding of the relationship between the structure and properties of physical vapor deposited (PVD) glass films is crucial for their applications at the nanoscale within industrial contexts. This study employs a coarse-grained simulation methodology to model PVD films composed of N,N-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) molecules with varying thicknesses. The findings indicate that, in contrast to liquid-quenched glasses (LQG), PVD glasses exhibit a higher elastic modulus and a lower loss modulus in the bulk, corroborating previous research that highlights enhanced mechanical stability. This work also shows that a region adjacent to the substrate of the PVD films has an exceptionally elevated elastic modulus that is correlated with changes in loss modulus, molecular orientation, and out-of-plane mobility. This phenomenon may be attributed to the surface-substrate effect resulting from the PVD process, and this effect may facilitate incoming molecule to a deeper energy state, resulting in a remarkable thermal and mechanical stability of ultrathin films.