Au -Ge Alloys for Wide-Range Low-Temperature On-Chip Thermometry

We present results for a Au -Ge alloy that is useful as a resistance-based thermometer from room temperature down to at least 0.2 K. Over a wide range, the electrical resistivity of the alloy shows a logarithmic temperature dependence, which simultaneously retains the sensitivity required for practical thermometry while also maintaining a relatively modest and easily measurable value of resistivity. We characterize the sensitivity of the alloy as a possible thermometer and show that it compares favorably with commercially available temperature sensors. We experimentally identify that the characteristic logarithmic temperature dependence of the alloy stems from Kondo-like behavior induced by the specific heat treatment it undergoes.