V.S. Vendamani

Three-dimensional hybrid silicon nanostructures for surface enhanced Raman spectroscopy based molecular detection

Three-dimensional silver nanoparticles decorated vertically aligned Si nanowires (Si NWs) are effective surface-enhanced Raman spectroscopy (SERS) substrates for molecular detection at low concentration levels. The length of Si NWs prepared by silver assisted electroless etching is increased with an increase in etching time, which resulted in the reduced optical reflection in the visible region. These substrates were tested and optimized by measuring the Raman spectrum of standard dye Rhodamine 6G (R6G) of 10 nM concentration. Further, effective SERS enhancements of ∼105 and ∼104 were observed for the cytosine protein (concentration of 50 μM) and ammonium perchlorate (oxidizer used in explosives composition with a concentration of 10 μM), respectively. It is established that these three-dimensional SERS substrates yielded considerably higher enhancement factors for the detection of R6G when compared to previous reports. The sensitivity can further be increased and optimized since the Raman enhancement was...

Ion Beam Studies Of Semiconductor Nanoparticles For The Integration Of Optoelectronic Devices

Radiation hardened microelectronics compatible and tunable light emitting devices are essential for the integration of electronic and optoelectronic devices. Porous or nano‐crystalline silicon seems to be a promising material for accomplishing this task. Ion beam patterned structures of light emitting silicon nanoparticles can be used for achieving multiple wavelength emission. Here we present a study on the influence of oxidation, pre and post anodization irradiation on emission parameters and on the stability of passivating bonds of porous silicon.

Ion induced effects on the dissociation of silicon nanoparticles

We report a detailed study on the dissociation of isolated silicon nanoparticles under high energy ion irradiation. Ultra-small (1-10 nm) colloidal silicon nanoparticles (Si NPs) have been synthesized by ablating porous silicon (pSi) in acetone using femtosecond laser pulses. Porous silicon was ablated, considering the fact that it contains a large number of light emitting silicon nanoparticles. The shape and size distribution of Si NPs was investigated by Transmission Electron Microscopy (TEM). The crystallinity of spherical Si NPs was confirmed by Selective Area Electron Diffraction (SAED).

Anharmonic effects on positron channeling angular scans and dechanneling due to stacking faults and platelets

Energy dependence studies of channeling angular scans and dechanneling probabilities are essential for defect analysis. We have recently shown that the dechanneling probability of positrons due to stacking faults need not necessarily be independent of incident energy. Here we study the energy dependence relations for positron channeling angular scans and dechanneling probability due to stacking faults and platelets under the influence of anharmonic continuum potential. The anharmonic term in the transverse potential is considered as perturbation to harmonic approximation. Energy dependence relations obtained in this study are found to be consistent with those obtained in harmonic approximation. Further, the dechanneling probability due to platelets is found to increase with the increase in energy and saturates for higher energies. This study further suggests that the dechanneling probability due to platelets is also independent of energy in classical regime as is known for simple stacking faults.