Publication
The need for new accurate temperature monitoring is becoming high, especially with the proliferation of IoT monitoring and biological applications. In this work, we report the design, fabrication and electrical characterization results of a new type of resonant RF sensors that can be used as RF temperature tags, exploiting the high temperature sensitivity of reversible insulator-metal transition in VO2. We have explored split-ring resonator transducers on 40 nm thick undoped VO2 and on 2.3% Ge-doped VO2 ALD thin films below coplanar waveguide (CPW). The temperature sensing principle is based on the non-linear dielectric constant variation of VO2 around its transition temperature. We demonstrate two regions with very contrasted temperature sensitivities in insulator-phase and near-transition temperature. For the Ge-doped VO2 resonator, the experimental temperature sensitivity is higher than for the VO2 resonator, reaching 6.9 MHz/degrees C between 25 and 78 degrees C and a record high value of 463 MHz/degrees C between 78 and 95 degrees C, respectively. This shows that doping plays an important role in controlling both transition temperature and temperature sensitivity.