Why are thin films different from the bulk?

This review discusses three fundamental factors that foster film-bulk differences, namely: (1) unusually varied microstructures produced by serial atomistic deposition and subsequent nucleation and growth processes, (2) the effect of interfaces on either film surface, and in particular, the nature and implications of the film/substrate interface, and (3) arbitrary thinness in one dimension which enables unique size effect phenomena (e.g., optical interference, quantum effects, nonlinear mass transport) to be exhibited in single film or multilayer structures.