Effect of Swift Heavy Ions on Pulsed Laser Deposited Ag Doped CdS Nanocrystalline Thin Films

A new tool for modification of the materials by swift heavy ions is investigated. The role of ion velocity is explored on various properties of 1 at.% Ag doped CdS nanocrystalline thin films. Ag doping in CdS is carried out by chemical co-precipitation method. Thin films of 1% Ag doped CdS are grown by pulsed laser deposition at a substrate temperature of 200 degrees C in vacuum using a target prepared by pressing and sintering the chemically synthesized powder. The Ag doping in CdS is confirmed by X-ray photoelectron spectroscopy studies carried out for 5% Ag doped CdS sample. Thin films of 1% Ag doped CdS are further irradiated using 70 MeV and 160 MeV Ni+6 ions at varying fluence. The velocity of 160 MeV Ni ions is root 2 times than that of 70 MeV Ni ions while electronic energy loss remains almost same at the two energies. GAXRD results reveals that the film irradiated with the higher ion velocity at fluence 1 x 10(14) ions/cm(2) is highly textured. It is observed that diffraction peaks are shifted toward higher angle with increase in ion fluence for either of the ion energy, however in case of 160 MeV Ni+6 ion irradiation shifting is comparatively less. Raman spectra show four optical phonon modes viz. fundamental (1LO), multiphonon scattering (1LO + 2E(2)), first over tone (2LO) and multiphonon scattering (2LO+2E(2)) modes at 302, 400, 603 and 702 cm(-1), respectively. The intensity and asymmetry variation exhibits by Raman active mode is not same for the films irradiated by the ions of different ion velocities. UV-Visible absorption spectra show a systematic reduction in band gap i.e., increment in particle size with increase in ions fluence at both energies. The photoluminescence studies further suggest that ion beam irradiation is a powerful tool to enhance the quantum efficiency.