Surface atom dynamics in epitaxial growth studied by RHEED-TRAXS

Abstract

The intensity of X-ray emission during RHEED observation changes with many parameters. The glancing angle (θ g) dependence of the X-ray emission is approximated by 1 sin θ g , when the atoms emitting the X-rays are confined at the surface. With increasing θ g, the X-ray emission from the nth layer below the surface increases at first, makes a peak at θ n and then decreases according to 1 sin θ g . The peak position θ n shifts to a higher angle with increasing depth. Thus, we can measure the depths of specific atom layers by measuring the θ g dependence of the characteristic X-ray emission. The experimental results can be explained by a Monte Carlo electron trajectory simulation. It was shown that the depth resolution is better than 1 ML near the surface. Applying this new method, surface atom dynamics in the epitaxial growth of Ag, Au, Sn, Ga and In on the metal-induced Si(111) surface structures (Si(111)- n × m-M) were investigated in detail. Epitaxial growth processes observed are classified into five growth modes. Normal growth mode (N) was observed for the system of Ag/Si-Au. Substitution-atom growth mode (S) and floating-atom growth mode (F) were observed for the systems of (Au, Sn, In)/Si-Ag, Au/Si-Sn, Au/Si-In, Ag/Si-Ga. Alloying growth mode (A) was observed for the systems of (Sn, Ga, In)/Si-Au, (Ag, Ga, In)/Si-Sn, Au/Si-Ga, and (Ag, Sn, Ga)/Si-In. For the systems of Ga/Si-Ag and (Sn, In)/Si-Ga. complex growth modes (C) were observed. The latter four growth modes, S, F, A and C are newly characterized growth modes.