Mechanisms of epitaxy and defects at the interface in ultrathin YSZ films on Si(001)

Abstract

Ultrathin YSZ epitaxial films have been deposited by pulsed laser deposition under ultra-high vacuum on Si(001) without removing its native oxide. It is found that YSZ grows amorphously while producing a progressive reduction of native SiO_x, and above a thickness of 1.0–1.5, nm the whole YSZ film crystallises. Nanometric SiO_x-free regions act as seeds for epitaxy and subsequent lateral crystallisation of the rest of the amorphous YSZ. With further YSZ deposition, SiO_x is totally reduced with concomitant formation of a new interface between already existing crystalline YSZ film and Si substrate. Defective regions, with lattice parameter intermediate between Si and bulk YSZ, are periodically distributed along the SiO_x-free interface.