The effect of thickness on optical, structural and growth mechanism of ZnO thin film prepared by magnetron sputtering

Highlights: •Oriented ZnO thin films were grown on glass substrate by RF-sputtering. •There are three different growth mechanisms that are changed with the thickness. •Films with thickness above 90 nm have a loss of preferential orientation. •The bandgap energy increases with the thickness. -- Abstract: In this contribution we discuss the structural, morphological and optical properties of ZnO thin films deposited on glass substrates by radio frequency magnetron sputtering technique. Our results indicate that an increase in deposition time leads to a change in the film growth mechanism. Three different growth regimes can be observed when the deposition time changes. Islands initially start to nucleate and grow into rough and highly stressed films. Increasing the surface population leads to island coalescence compatible with a planar architecture, where the stress is relieved, and the roughness is minimized. Longer still deposition times induce the growth of columnar structures. The increase in deposition time brings about a stress relaxation and grain growth together with a reduction of the texture coefficient, c-lattice contraction and an increase of band gap values.