Tunable phase and electrical characteristics induced by Al content in Zr1<b>−</b> <i>x</i>Al<i>x</i>N films for temperature sensors with wide temperature range

Transition metal nitride (TMN) films hold great promise in temperature sensing due to their excellent stability, but the decreased sensitivity with increasing temperature has limited their adaptability to various temperature scenarios. In this paper, a method for regulating the high-sensitivity temperature range (HSTR) of the temperature sensors based on the zirconium aluminum nitride (Zr1−xAlxN) films by adjusting the Al content is proposed. According to the resistance–temperature (R–T) curves from 4.2 to 300 K, the metal-to-semiconductor transition was observed when Al atoms were doped in ZrN. Moreover, the semiconductor R–T curve gradually shifts to 300 K and then backs to cryogenics by continuously increasing the Al content in Zr1−xAlxN. Interestingly, the phase transition from cubic (c)-ZrN to cubic (c)-Zr1−xAlxN, then to the mixed phases of c-Zr1−xAlxN and wurtzite aluminum nitride (w-AlN), and, finally, to the hexagonal close packed-zirconium (α-Zr) precipitation was observed with increasing Al content, which shows high consistency with R–T characteristics. Moreover, the bandgap energy initially increases and then decreases, which matches well with the phase and electrical transitions. Based on the experimental results, we build a physical model that can clarify the above phase and electrical transition when the Al content in Zr1−xAlxN films changes, proposing that the effect of Al content on the phase and electrical characteristics can realize the control of the HSTR of Zr1−xAlxN films. These findings suggest ideas for developing temperature sensors based on TMN films with high sensitivity across a wide temperature range.