Microscopic investigations of morphology and thermal properties of ZnO thin films grown by atomic layer deposition method

Abstract

This work presents the study of morphology and thermal properties of thin ZnO films fabricated by atomic layer deposition. The layers were deposited on n-Si(100) wafers at 200 °C. X-ray diffraction measurements showed the polycrystalline structure of the thin films with preferred (100) orientation. The thinner ZnO layers were fine grained, while the thicker films were formed with larger, elongated grains. Surface morphology parameters and the thermal conductivities were obtained from microscopic measurements. Thermal properties correlated with surface roughness of the ZnO thin films. Variations in thermal conductivity followed the changes in morphology of the layers. The mean surface roughness depended on the number of deposition cycles and varied from 1.1-2.6 nm. Thermal conductivity varied from 0.28 to 4.29 Wm^-1K^-1 and increased also with an increase of average crystallite size. The possible correlations between electrical conductivity and thermal conductivity were also analyzed. The phonon contribution to total thermal conductivity dominates over the electron thermal conductivity.

Keywords: Electrical conductivity; Scanning Probe Microscopy; Thermal conductivity; ZnO thin films.