Native defects and optical properties of Ar ion irradiated ZnO

Native Defects And Optical Properties Of Ar Ion Irradiated ZnO

S. Pal¹, A. Sarkar², D. Sanyal³, T. Rakshit⁴, D. Kanjilal⁵, P. Kumar⁵, S. K. Ray⁴, D. Jana^1*

¹Department of Physics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700 009, India

²Department of Physics, Bangabasi Morning College, 19, R. C. Sarani, Kolkata 700 009, India

³Variable Energy Cyclotron Centre (VECC), 1/AF, Bidhannagar, Kolkata 700 064, India

⁴Department of Physics and Materials Science, Indian Institute of Technology, Kharagpur 721302, India

⁵Inter-University Accelerator Centre, P.O. Box 10502, Aruna Asaf Ali Marg, New Delhi 110067, India

Adv. Mater. Lett., 2015, 6 (4), pp 365-369

DOI: 10.5185/amlett.2015.5730

Publication Date (Web): Mar 21, 2015

E-mail: djphy@caluniv.ac.in

Full Article

Abstract

1.2 MeV Argon (Ar) ion irradiation turns white coloured ZnO to yellowish (fluence 1 × 10¹⁴ ions/cm²) and then reddish brown (1 × 10¹⁴ ions/cm²). 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.