Defect engineering and opto electronic property modifications by 1.5 MeV Li+ implantation on nano crystalline MgIn2O4 thin films

Author： Moses Ezhil Raj A. Som T. Jayachandran M. Sanjeeviraja C.

Publisher： Taylor & Francis Ltd

ISSN： 1042-0150

Source： Radiation Effects and Defects in Solids, Vol.165, Iss.4, 2010-04, pp. : 265-276

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Abstract

Spinel MgIn2O4 thin films were deposited on quartz substrates by the chemical spray pyrolysis technique using metal organic precursors at 450°C. Energetic 1.5 MeV Li+ ions were implanted to various fluences of 1013, 1014 and 1015 ions/cm2 onto insulating MgIn2O4 films using a 9 SDH-2, NEC, 3MV accelerator to modify the material properties and surface nature. X-ray diffraction analysis was carried out to identify the changes in the crystallinity and grain orientations before and after implantations. Before implantation, the grains of polycrystalline MgIn2O4 were randomly oriented [(222), (311), (442) and (511)], and after implantation they exhibited a tendency to realign the crystallites along the even (hkl) planes [(222) and (442)]. On the Li+-implanted sample, one or more grains combine together and form bigger grains along with shallow pits, as observed through the atomic force micrographs. The as-deposited films have a percentage transmittance of 70-80% in the wavelength range 400-800 nm and the observed optical transmittance was less in Li+-implanted MgIn2O4 films. The index of refraction and the extinction co-efficient values were respectively n=1.98 and k=10-2 in the visible region. However, the DC electrical conductivity of Li+-implanted films to a fluence of 1015 ions/cm2 was nearly 0.7 S/cm at room temperature. The efficiency of the carrier generation was increased from 13.41% to 26.81% on annealing the implanted sample to lower fluence (1013 ions/cm2).