Hydrogen effect on structure and mechanical properties of ZnO films deposited in Ar/H_2 plasma

摘要

In the present work the mechanical properties of ZnO thin films, deposited on Si (100) substrates, were studied using the nanoindentation technique. ZnO thin films were deposited by radiofrequency sputtering from a ZnO target with different H_2/Ar gas mixtures. During the deposition the plasma species were in-situ monitored using optical emission spectroscopy (OES). The results showed that the introduction of H_2 in the plasma phase had a strong effect on the material's hardness and elastic modulus. The measured elastic modulus values were then related to the material density to estimate the porosity of the ZnO films. We found an increased film porosity when H_2 was added to the sputtering gas, from 6% to 18% in volume. Moreover we found that the porosity was correlated by the emission intensity ratio of atomic Argon on atomic Hydrogen.