Pragati Kumar; Nupur Saxena; Avinash Agarwal; Vinay Gupta
Abstract
Influence of growth temperature on swift heavy ion (SHI) induced structural and optical functionality in CdS thin films is explored for photonic applications. Intense green emission is observed in nanocrystalline CdS thin films grown by pulsed laser deposition (PLD) at two different substrate temperatures ...
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Influence of growth temperature on swift heavy ion (SHI) induced structural and optical functionality in CdS thin films is explored for photonic applications. Intense green emission is observed in nanocrystalline CdS thin films grown by pulsed laser deposition (PLD) at two different substrate temperatures (Ts): room temperature (RT) and 200 ºC. The role of Ts and its implications on the effect of dense electronic excitation provoked by swift heavy ion irradiation (SHII) on various optical and structural properties of CdS films is investigated under the influence of 70 MeV 58 Ni +6 ion beam. It reveals from the present studies that Ts may crucially affect the crystalline structure, vibrational and electronic states of the film and thereafter the functionality induced by ion beam. It is found that ion beam is capable to transform structural phase from mixed phase of cubic and hexagonal structure to either pure cubic or pure hexagonal phase of CdS depending upon the pre-existing preferred orientation in pristine film. The modification in crystallite size and band gap due to impact of ion beam is found to be strongly dependent on pre-existing structural phase, as determined by Ts. The studies presented here confirm that initial growth conditions play a key role even after post deposition SHII treatment in selecting precisely the functional behavior of the films.
S. Pal; A. Sarkar; D. Sanyal; T. Rakshit; D. Kanjilal; P. Kumar; S. K. Ray; D. Jana
Abstract
1.2 MeV Argon (Ar) ion irradiation turns white coloured ZnO to yellowish (fluence 1 × 10 14 ions/cm 2 ) and then reddish brown (1 × 10 14 ions/cm 2 ). At the same time the material becomes much more conducting and purely blue luminescent for the highest fluence of irradiation. To get ...
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1.2 MeV Argon (Ar) ion irradiation turns white coloured ZnO to yellowish (fluence 1 × 10 14 ions/cm 2 ) and then reddish brown (1 × 10 14 ions/cm 2 ). At the same time the material becomes much more conducting and purely blue luminescent for the highest fluence of irradiation. To get insight on the defects in the irradiated samples Ultraviolet-visible (UV-vis) absorption, Raman, and photoluminescence (PL) spectroscopy and Glancing Angle X-Ray Diffraction (GAXRD) measurements have been carried out. Enhancement of overall disorder in the irradiated samples is reflected from the GAXRD peak broadening. UV-vis absorption spectra of the samples shows new absorption bands due to irradiation. Complete absorption in the blue region of the spectrum and partial absorption in the green and red region changes the sample colour from white to reddish brown. The Raman peak representing wurtzite structure of the ZnO material (~ 437 cm -1 ) has decreased monotonically with the increase of irradiation fluence. At the same time, evolution of the 575 cm -1 Raman mode in the irradiated samples shows the increase of oxygen deficient disorder like zinc interstitials (IZn) and/or oxygen vacancies (VO) in ZnO. PL spectrum of the yellow coloured sample shows large reduction of overall luminescence compared to the unirradiated one. Further increase of fluence causes an increase of luminescence in the blue region of the spectrum. The blue-violet emission can be associated with the interstitial Zn (IZn) related optical transition. The results altogether indicates IZn type defects in the highest fluence irradiated sample. Large changes in the electrical resistance and luminescent features of ZnO using Ar ion beam provides a purposeful way to tune the optoelectronic properties of ZnO based devices.