Influence of rf power on growth, structural and optical properties of ZnO synthesized via vapor transport in inductively coupled plasma

Abstract

The aim of this work was to examine the influence of radio frequency (rf) power on ZnO films synthesized by means of chemical vapor transport technique in inductively coupled plasma (ICP). As the rf power increased, with a fixed processing time of only 8 min, the temperature inside the reactor tube, the thickness and surface roughness of the formed polycrystalline ZnO films increased. The morphology of the ZnO films changed to oblate, webby like cloud-grains, nanoslices, and a mixture of nanorods and nanograins with changing the rf power from 300 to 500 W. Mixed phases of hexagonal ZnO and hexagonal Zn were found for samples synthesized at 300 and 500 W whereas single hexagonal ZnO was synthesized at 350, 400 and 450 W. The optical band gap decreased from 3.35 eV to 3.05 eV with increasing the rf power from 300 W to 500 W. The refractive index and extinction coefficient values were mainly increased with increasing the rf power. The electrical resistivity was generally decreased with increasing rf power and has values between 1.38 × 10−2 - 2.83 × 10−3 Ωcm. The obtained results might be important for useful applications of ZnO films grown by chemical vapor transport with the assistance of ICP.