Structural, morphological and optical properties of nanocrystalline ZnO films deposited by RF sputtering at different bias voltages

In the present study high optical transmittance ZnO thin films were deposited by RF magnetron sputtering on p- type (100) silicon and glass substrates by varying the substrate bias voltages ranging from 0 to -120 V. The effect of substrate bias voltage on the structural, morphological and optical properties was studied by using X-ray diffraction, scanning electron microscope, atomic force microscope, and UV-Vis-NIR spectrophotometer. The X-ray diffraction results confirmed that the films consists of ZnO peaks of (100), (002) and (110). The Fourier transform infrared spectrum confirms the presence of Zn-O bonding at wave number of 409 cm(-1). The optical transmittance data reveals the average transmittance in the visible range more than 80% for all films. Optical band gap of ZnO films first increased from 3.14 to 3.16 eV and then decreased to 3.10 eV at higher substrate bias voltages.