Titanium Nitride as a Strain Gauge Material.

The performance of titanium nitride (Ti-N) thin films deposited by reactive magnetron sputtering for use as a strain gauge material was investigated. Films of different composition ranging from pure titanium to over-stoichiometric Ti-N were prepared by varying the nitrogen flow to total flow ratio ( $\alpha )$ . The atomic composition was measured using Rutherford backscattering spectrometry and energy-dispersive X-ray spectroscopy. The structure of the films was studied using X-ray diffraction and scanning electron microscopy, revealing the formation of a columnar film morphology consisting of cubic-Ti-N grains with preferential crystal orientations depending on the flow ratio $\alpha $ . The stability of the film resistivity was studied at 200 °C for 360 h. Films deposited at low ( $\alpha \leq 0.08$ ) and high ( $\alpha = 0.60$ ) nitrogen flows exhibited a stable behavior relative to films deposited with intermediate nitrogen flows. The longitudinal piezoresistive gauge factor was found to increase with increasing nitrogen flow before settling at values of 6–6.35. Finally, the temperature coefficient of resistivity was found to be less than 300 ppm/°C for the films with the highest gauge factors. The results demonstrate that the Ti-N films have a good potential as a strain gauge material, especially due to the relatively high gauge factor. [2016-0040] [ABSTRACT FROM PUBLISHER]