The evolution of Si-capped Ge islands on Si (1 0 0) by RF magnetron sputtering and rapid thermal processing: The role of annealing times

Abstract

Germanium (Ge) nanocrystals were synthesized by rapid thermal processing (RTP) of radio frequency sputtered Ge on silicon (100) substrate. A Si capping layer of 185nm thickness was deposited onto the 225nm Ge layer. The layered samples subsequently underwent annealing during RTP at 900°C for 30, 45, and 60s to subsequently evolve into Ge islands. Scanning electron microscopy (SEM) showed that as the annealing time increased, the Ge islands’ size increased from 100nm to 500nm, and they became more uniform and dense. Atomic force microscopy (AFM) indicated that the increase in annealing time reduced the surface roughness by approximately 50%. Raman spectra showed that good crystalline nanostructures of the Ge peaks were obtained for all samples, with increased annealing time improving the crystallinity. A visible broad band photoluminescence was observed from UV to green with blue shift as nanocrystallite size decreases. High resolution X-ray diffraction (HR-XRD) revealed cubic and tetragonal Ge phases in the samples with low tensile strain around the Ge islands. The results indicated that both annealing ambient temperature and time do significantly influence the formation and evolution of the Ge islands on Si.