Boltzmann thermometer with broadband emission in Mn4+-Doped -Ga2O3 crystals

The luminescence properties of Mn4+-doped beta-Ga2O3 are strongly affected by the surrounding crystal field within the [MnO6] octahedral site, which is substitute for GaII site, as determined through the first-principles calcula-tions. The crystal field strength parameters Dq, B, and C are computed, and the Tanabe-Sugano diagram is redrawn for C/B = 6.7. The temperature dependence of the optical spectra is thoroughly examined, revealing the thermal quenching mechanisms involving the thermal activation energy of 2Eg and 4T2g, which are 378 +/- 26 cm-1 and 3527 +/- 25 cm-1, respectively. In order to further investigate the temperature sensing characteristics, the absolute (Sa) and relative (Sr) sensitivities are obtained. At 303 K, the Sr is determined to be 0.72 %K-1, while Sa is estimated to be in the range of 10-2 (below 0.05 K-1) for the Mn4+ doped beta-Ga2O3 thermometers. The thermal resolution delta T is demonstrated to be below 0.1 K, surpassing that of traditional Nd3+ and Er3+-doped thermometers. Moreover, a linear relationship between the energy separation Delta E of the thermally coupled 2Eg-4T2g energy levels and the crystal field strength Dq is observed in numerous materials. With this consider-ation, the nature of the thermometer, along with its Sa and Sr, can be roughly predicted and designed for various operational conditions.