Nanoindentation measurements of combustion CVD Al2O3 and YSZ films

Combustion chemical vapor deposition (combustion CVD) was used to deposit thin films of yttria stabilized zirconia (YSZ) and alumina (Al2O3). Nanoindentation analysis for hardness, modulus and fracture toughness of the films as well as several bulk materials, including single crystal Al2O3, MgO, SiO2, YSZ and polycrystalline Al2O3 was conducted. YSZ films that were produced with a total cation molarity of 0.005 M possessed significant surface roughness that was not conducive to nanoindentation measurements. The lower concentration investigated, 0.002 M provided a repeatable deposition condition that produced thin films with consistent hardness and modulus values. Load-displacement measurements at very low loads (up to total displacements of 200 nm) showed that the Al2O3 films tended to plastically deform, whereas the YSZ films showed less of a tendency to do so. For Al2O3 films that were 0.38±0.09 μm thick, the modulus, hardness and fracture toughness values were 28.6±1.6 GPa, 479±15 GPa and 2.22±0.31 MPa m0.5, respectively; for YSZ films that were 0.65±0.05 μm thick, the values were 16.1±4.6 GPa, 388±89 GPa and 1.67±0.46 MPa m0.5, respectively. These values were found to be consistent with the values measured via nanoindentation in this work for bulk samples of Al2O3 and YSZ, as well as to those reported in the literature.