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 (α). 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 cubicTi-N grains with preferential crystal orientations depending on the flow ratio α. The stability of the film resistivity was studied at 200 °C for 360 h. Films deposited at low (α ≤ 0.08) and high (α = 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.