Effect of growth temperature on structural, electrical and optical properties of dual ion beam sputtered ZnO thin films

ZnO epitaxial thin films were grown on p-type Si(100) substrates by dual ion beam sputtering deposition system. The crystalline quality, surface morphology, optical and electrical properties of as-deposited ZnO thin films at different growth temperatures were studied. Substrate temperature was varied from 100 to 600 degrees C at constant oxygen percentage O-2/(O-2 + Ar) % of 66.67 % in a mixed gas of Ar and O-2 with constant chamber pressure of 2.75 x 10(-4) mBar. X-Ray diffraction analyses revealed that all the films had (002) preferred orientation. The minimum value of stress was reported to be -0.32 x 10(10) dyne/cm(2) from ZnO film grown at 200 degrees C. Photoluminescence measurements demonstrated sharp near-band-edge emission (NBE) was observed at similar to 375 nm along with deep level emission (DLE) in the visible spectral range at room temperature. The DLE Peak was found to have decrement as ZnO growth temperature was increased from 200 to 600 degrees C. The minimum FWHM of the NBE peak of 16.76 nm was achieved at 600 degrees C growth temperature. X-Ray photoelectron spectroscopy study revealed presence of oxygen interstitials and vacancies point defects in ZnO film grown at 400 degrees C. The ZnO thin film was found to be highly resistive when grown at 100 degrees C. The ZnO films were found to be n-type conducting with decreasing resistivity on increasing substrate temperature from 200 to 500 degrees C and again increased for film grown at 600 degrees C. Based on these studies a correlation between native point defects, optical and electrical properties has been established.