Lattice Orientations of Evaporated Metals onto Uniaxially Oriented, Semicrystalline, Ultra thin Polymer Films

Abstract

ABSTRACTThe textured oriented overgrowth (epitaxy) of certain metals evaporated onto substrates consisting of highly oriented ultra thin polymer films of polyethylene (PE), polypropylene (PP) and polybutene-1 (PB-1) has been well known since a few years. However, the origin of the observed epitaxy is not clear at all: graphoepitaxy (i. e. orientation induced by nucleation onto oriented topographic features of the substrate), the formation of a chemical layer (i. e. of metal-methyl groups building up the polymer-metal interface, or simply classic epitaxy (i.e. lattice matching) seem all to be possible explanations for the observed orientations. Here, we used Transmission Electron Microscopy (TEM) and Scanning Force Microscopy (SFM) to investigate the possibility of graphoepitaxial growth on polymeric surfaces. Our investigations show that the morphology of polymeric bulk material determine the topographic properties observed at the polymer surface. The semicrystalline nature of the polymer films leads to polymeric surface steps which are suitable as locations for graphoepitaxial growth. Artificial epitaxy (graphoepitaxy) seems to be the most likely orientation mechanism.