In-situ probing of near and below sputter-threshold ion-induced nanopatterning on GaSb(1 0 0)

Abstract

This work presents in-situ near and below sputter-threshold studies for GaSb(1 0 0) at energies 50, 100 and 200 eV and current densities near 50 μAcm −2. Variation of incident particle energy probes the energy deposition distribution and its relation to surface composition. In-situ analysis is conducted over irradiation modification using Ar singly-charged ions at normal incidence of the surface using complementary techniques including: X-ray photoelectron spectroscopy (XPS) and ion-scattering spectroscopy (LEISS). The former probes 1–3 nm and the latter technique probes the first 1–2 ML or 0.3–0.6 nm. Ex-situ analysis includes HR–SEM to correlated surface morphology with surface composition studied in-situ during irradiation. Results indicate ordering of nanodot formation at fluence threshold of about 10 17 cm −2. Both XPS and LEISS identify Ga 2O 3 islands formation due to GaSb chemical affinity for oxygen followed by an initial enhancement of Ga/Sb = 1.20 ratio and then a sharp drop in Ga relative concentration with LEISS reaching a Sb-dominated terminating 1–2 nm region corresponding to the implantation depth between 50 and 200 eV. XPS shows a slight enrichment of Ga in sub-surface layers that levels to a 1:1 stoichiometry of the crystalline GaSb(1 0 0) surface.