Formation of amorphous interlayers by solid-state diffusion in ultrahigh-vacuum-deposited polycrystalline Nb and Ta thin films on (111)Si

Abstract

The formation of amorphous interlayers (a-interlayers) in ultrahigh-vacuum-deposited polycrystalline Nb and Ta thin films on (111)Si has been studied by cross-sectional transmission electron microscopy. The growth of a interlayers was found to follow a linear growth law initially in samples annealed at 450–500 °C and 550–625 °C for Nb/Si and Ta/Si, respectively. The growth then slows down and deviates from a linear growth behavior as a critical thickness of the a interlayer was reached. The a interlayer/crystalline Si interface was found to be rather smooth. The roughness of the interface between the Nb layer and a interlayer was observed to decrease with annealing temperature and time. The observation suggested that the growth of the a interlayer was interface reaction controlled initially.