Mechanical Stability of Ultra Thin Ge/Si Film on SiO$_2$:the Effect of Si/SiO$_2$ Interface

We perform two-dimensional linear elastic finite element analysis to investigate mechanical stability of ultra-thin Ge/Si film grown on or bonded to SiO$_2$, using imperfect interface elements between Si and SiO$_2$ to model Si/SiO$_2$ interfacial slippage. We show that the overall composite film is stable when only the tangential slippage is allowed. But it becomes unstable when normal slippage is allowed: the coherently strained Ge island induces a large local bending of Si layer, and debonds the Si layer from the underlying SiO$_2$ forming a void at the Si/SiO$_2$ interface. Thus, the quality of Si/SiO$_2$ interface is expected to play an important role in controlling the stability of those device structures employing the strained Si/SiO$_2$ film. *This work is supported by DOE.