Nanoindentation studies of single-crystal (001)-, (011)-, and (111)-oriented TiN layers on MgO

Abstract

The mechanical properties of (001)-, (011)-, and (111)-oriented MgO wafers and 1-μm-thick TiN overlayers, grown simultaneously by dc magnetron sputter deposition at 700 °C in a mixed N2 and Ar discharge, were investigated using nanoindentation. A combination of x-ray-diffraction (XRD) pole figures, high-resolution XRD analyses, and Auger electron spectroscopy was used to show that all TiN films were single crystals with N/Ti ratios of 1.0±0.05. The nanoindentation measurements were carried out using a three-sided pyramidal Berkovich diamond indentor tip operated at loads ranging from 0.4 to 40 mN. All three orientations of MgO substrates, as-received, exhibited identical hardness values as determined using the Oliver and Pharr method. After a 1 h anneal at 800 °C, corresponding to the thermal treatment received prior to film growth, the measured hardness of MgO(001) was 9.0±0.3 GPa. All TiN films displayed a completely elastic response at low loads. Measured hardness values, which decreased with increasing loads, increased in the order (011)<(001)<(111). After a 30 s postdeposition anneal at 1000 °C, however, hardness was found to be independent of load except at displacements >100 nm where substrate effects were apparent. TiN(001) and (111) films had hardnesses of 20±0.8 and 21±1 GPa, respectively, while data obtained from (011) layers exhibited large scatter due to surface roughness effects. Young’s moduli for annealed samples, calculated from the elastic unloading curves, were found to be 307±15 GPa for MgO (001) and 445±38 and 449±28 GPa for TiN (001) and TiN (111), respectively.