Production of nanohole/nanodot patterns on Si(001) by ion beam sputtering withsimultaneous metal incorporation

Abstract

We have established the conditions for which nanohole and nanodot patterns are produced on Si(001) surfacesby 1 keV Ar+ ion beam sputtering (IBS) at normal incidence with an alternating cold cathode ion source(ACC-IS). Nanohole patterns are produced within a narrow IBS window for low ion fluxes (<100 µA cm−2) and relativelylow ion fluences (<1018 ions cm−2) whereas nanodot morphologies are produced above this window. The nanohole pattern isnot stable after prolonged irradiation since it evolves to a nanodot morphology. Rutherfordbackscattering spectrometry (RBS) measurements show that nanohole patterns areproduced when the metal content on the irradiated surfaces is higher (within (2.5–3.5 × 1015) atoms cm−2) than in the caseof nanodots (<2.5 × 1015 atoms cm−2). The different metal content is related to the ACC-IS operation, since the set-up providessimultaneous incorporation of Fe and Mo on the target surface from the erosion of thecathodes and sample holder, respectively. The role of metal incorporation on patternselectivity has been corroborated qualitatively by extending the results obtained with theACC-IS to a standard Kaufman-type source. In order to gain further information on themetal effects, chemical analysis of the surface has been performed to complement thecompositional RBS results, showing for the first time the relevant participation of metalsilicides. Further outlook and a discussion regarding the role of metal incorporation are alsogiven.