Ion beam irradiation effects on Ge nanocrystals synthesized by using RF sputtering followed by RTA

Here we report the effects of ion beam irradiation on Ge nanocrystals (NCs) embedded in SiO2 matrix. The Ge NCs embedded in silicon oxide matrix have been synthesized using RF magnetron co-sputtering technique followed by rapid thermal annealing. Eventually, Ge NCs were irradiated by 120 MeV Ag ions with various fluences at room temperature. X-ray diffraction patterns indicate the decrease in average size of Ge NCs with increase in irradiation fluence. Raman scattering spectra showed a peak of Ge-Ge optical phonon vibrational mode shifted towards lower wavenumber side upon irradiation with respect to its bulk value, which is due to quantum confinement of optical phonons in the NCs. This blue shift also reflects decrease in the size of NCs upon irradiation. Change of NC size with the increase of irradiation fluence can be explained on the basis of energy deposited by incident ion inside the target material.