S. Christoulakis

Surface characterization of ZnO transparent thin films

Zinc oxide transparent thin films (ZnO) with different thickness were prepared by dc magnetron sputtering and pulsed laser deposition (PLD) techniques using metallic and ceramic targets onto silicon and Corning glass substrates. Structural investigations carried out by Optical Microscopy (OM), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) have shown a strong influence of the target and deposition technique on the film surface topography. Film roughness (RMS), grain shape and dimensions were found to correlate with the applied deposition technique. On the films grown by PLD high oriented nanostructures were identified and XRD measurements proved that they have a polycrystalline structure following the characteristic zincite XRD spectrum, while the dc magnetron sputtered films were amorphous. Results revealed also that the target composition has a radical effect on film characteristics. In the case of thin films sputtered from a ceramic target AFM analysis has shown the presence of hexagonal shaped grains exhibiting a different surface behavior compared with the films grown from metallic target, the first being also the case of the PLD grown film surfaces. This work indicates that the film surface characteristics are strongly influenced by the deposition technique and conditions applied, thus providing a tool for the enhancement of the film sensing capabilities.

Surface characteristics and tribology study of metal oxide thin films

Abstract Microcrystalline high quality undoped ZnO thin films were deposited on Si(100) and Corning 1737F glass substrates by a dc magnetron sputtering system. Surface and mechanical properties of ZnO thin films deposited under different deposition conditions (thickness, deposition rate and plasma composition) were investigated. Atomic force microscopy, nanoindentation techniques and scratch tests have been carried out. The lateral grain radius was between 50 and 160 nm. Surface roughness was found to vary from 1·3 to 10·3. In order to measure the real hardness of ZnO thin films grown on Si(100) and glass Continuous Stiffness Measurement technique was used. The hardness was found to be between 11 and 13 GPa for the polycrystalline ZnO almost five times larger than for the corresponding single crystalline material, while scratch tests verified a film structure, thickness, and surface morphology dependency on the mechanical properties for these metal oxide thin films.