|Track||Date and time||Hall||Duration|
|Invited Lectures||Monday, 15. June 2015., 10:30||Mimoza II Hall||30’|
Debdulal Kabiraj (1), Sonu Hooda (1), Sunil Ojha (1), Shramana Mishra (2), Anushree Roy (2), D. Kanjilal (1)
Studies of structural modification in GaAs, InP, Ge single crystal wafer irradiated by swift heavy ions (SHI) and pre-damaged Ge single crystal wafer on further irradiation with SHI are reported in detail. The irradiation by 100 MeV Ag was performed at room temperature with ion fluence ranging from 1012 to 1014 ions/cm2 at beam current of 1-2 pnA. The damage evolution of irradiated samples was studied by Rutherford back scattering channeling (c-RBS) technique. In all the materials electronic energy loss (Se) of 100 MeV Ag is approximately same, ranging between 16-14 keV/nm and nuclear energy loss (Sn) is approximately 0.1% of Se. We observe negligible damage formation in single crystal GaAs  and Ge whereas InP undergo heavy damage at higher fluences as detected by c-RBS measurement.
Three sets of Ge samples with sub-threshold, at threshold and above threshold fluences of amorphization, as estimated by c-RBS were prepared by 100 keV Ar irradiation. After SHI irradiation of these samples, it is observed that first set of samples (sub-threshold amorphization) has undergone substantial recrystallization whereas in the second set of samples recrystallization is restricted to the region close to amorphous-to-crystalline boundary. Apart from results of c-RBS, Raman spectroscopy, high resolution transmission electron microscopy (HRTEM) and associated Fast Fourier transform (FFT) pattern studies confirm recrystallization. In the case of heavily damaged samples no change in amorphous phase is recorded. However, the instead swelling of the sample is observed after Ag irradiation. The relative swelling is found to increase steadily with increasing ion fluence up to 3×1013 ions cm-2 and then to saturate at a maximum value of 20% at highest fluence of 1×1014 ions cm-2. The results are explained on the basis of thermal spike model.
 Shramana Mishra, Sudipta Bhaumik, Jaya Kumar Panda, Sunil Ojha, Achintya Dhar, D. Kabiraj, Anushree Roy. Nucl. Instr. Meth. Phys. Res. B 316 (2013) 192.