Ion beam synthesis of germanium nanostructures

Si and Ge nanocrystals embedded in SiO(2) have attracted much attention due to their possible application in integrated optoelectronic devices. Ion beam mixing of Ge film into fused silica to form Ge nanoparticles is one of the possible methods to controllably produce embedded nanoclusters. In this work, Ge nanocrystals in fused silica were formed by defect induced nucleation and ion beam mixing. In our experiment, we have created defects in fused silica using 200 keV Ar ions with different fluences ranging from 1 x 10(15) to 2 x 10(16) ions/cm(2) (pre-mixing irradiation). Ce film (20 nm) was then deposited on it and ion beam mixed using 230 keV Ar ions at a fluence of 2 x 10(16) ions/cm(2). The Ge-SiO(2) composite films were characterized using UV-visible and Micro-Raman spectroscopy. UV-visible spectra showed variation in absorption band gap with ion beam fluence used for pre-mixing irradiation. Micro-Raman spectra showed formation of Ge nanoparticles in SiO(2). (C) 2009 Elsevier B.V. All rights reserved

Role of rapid thermal annealing in the formation of crystalline SiGe nanoparticles

In the present work, we report the formation of SiGe nanoparticles embedded in SiO(2) film by atom beam sputtering method in conjunction with Rapid Thermal Annealing (RTA). Crystalline SiGe nanoparticles in the co-sputtered films are formed after rapid thermal annealing at 900 degrees C and 1000 degrees C for 1 min in N(2) gas ambient. These nanoparticles were characterized using UV-vis absorption, GXRD, FTIR and Raman measurements. UV-vis spectra show blue shift of absorption edge with the increase in annealing temperature. GXRD pattern shows that particles formed are crystalline. The average size of the nanoparticle estimated from GXRD is 15 nm to 30 nm for the films annealed at temperatures 800 degrees C and 1000 degrees C respectively. FTIR spectra show the phase separation between SiGe nanoparticles and SiO(2) matrix after RTA. Raman spectra show that SiGe phase is formed with c-Ge as core and c-SiGe as shell in the SiO(2) matrix. (C) 2009 Elsevier B.V. All rights reserved