Hardness of Cr(N,O) thin films on (001)-, (011)-, and (111)-oriented MgO substrates

The epitaxial growth of Cr(N, O) thin films on (001)- and (011)-oriented MgO substrates as well as a (200)-oriented polycrystalline Cr(N, O) thin film on MgO(111) were performed using pulsed laser deposition. Data obtained from Rutherford backscattering spectroscopy and electron energy loss spectroscopy indicated that Cr(N, O) on (001)-, (011)-, and (111)-oriented MgO substrates contained chromium, nitrogen and oxygen. Nano-indentation showed negligible differences in the hardness values of Cr(N, O) films on (001)-, (011)-, and (111)-oriented MgO substrates, the two former having values of approximately 36 GPa. These results indicate that the hardness of Cr(N, O) is independent of both the growth morphology brought about by the substrate orientation and grain boundary effects. Finally, Cr(N, O) films on all substrates exhibited greater hardness than a comparison specimen consisting of epitaxial CrN on MgO(001). (C) 2016 The Japan Society of Applied Physics