X-ray photoelectron diffraction study of thin Al2 O3 films grown on Si(111) by molecular beam epitaxy

Abstract

The in-plane and out-of-plane crystallographic orientations of Al2 O3 films grown by molecular beam epitaxy on Si(111) have been determined by combining x-ray photoelectron diffraction (XPD) with transmission electron microscopy (TEM). On the one hand, polar and azimuth XPD curves for Al2p, O1s, and Si2p core levels (recorded on a 6-nm-thick film) clearly indicate that Al2 O3 grows (111) oriented on Si(111) but with two in-plane orientations: a "direct" one, i.e., [11 2̄] Al2 O3 // [11 2̄] Si (111) and a "mirror" one, i.e., [1̄ 1̄ 2] Al2 O3 (111) // [11 2̄] Si (111). On the other hand, a close inspection of the 40 4̄ Al2 O3 TEM diffraction spots (recorded on a 2-nm-thick film) reveals that these two in-plane orientations are slightly rotated with respect to the Si(111) orientations. These two results are consistent with an oxygen plane as the interfacial plane between Al2 O3 (111) and Si(111). © 2009 The American Physical Society.