Epitaxy of Si nanocrystals by molecular beam epitaxy on a crystalline insulator LaAlO3(0 0 1)

Abstract

We have studied the Si initial growth mechanisms on LaAlO3(001), a crystalline oxide with a high dielectric constant (high-κ material). The clean LaAlO3(001) substrate exhibits a c(2×2) reconstruction that can be attributed to surface O vacancies.Si deposit by molecular beam epitaxy was studied as a function of both deposition temperature and thickness. Epitaxy was obtained only above 550°C. In this case, a Volmer–Weber mode is observed. The associated nanodots are relaxed and formed by pure Si as ascertained by the Si2s XPS peak, which remains for 1 and 10ML at the binding energy corresponding to Si–Si bonds. Moreover the islands have an abrupt interface with the LaAlO3(001) substrate without the formation of silicate or silica. A unique epitaxial relationship between LaAlO3 and the crystallized Si islands is pointed out by RHEED and confirmed by HRTEM, where the Si(001) planes are parallel to the LaAlO3(001) ones, but rotated by 45° in the [001] direction. This orientation leads to mismatch and strain minimization of the Si film.