Temperature sensor for scanning thermal microscopy based on photoluminescence of microcrystal

A new sensor is developed for measuring local temperatures. This sensor is based on a thermal-resistive probe and on photoluminescence of crystal. The final purpose is to develop a device calibrated in temperature and capable of acquiring images of local temperature at sub-micrometric scale. Indeed, the sensor temperature can be obtained in two distinct ways: one from the thermal probe parameters and the other from the green photoluminescence generated in the anti-Stokes mode by the Er ions directly excited by a red laser. The thermal probe is in Wollaston wire whose thermal-resistive element is in platinum/rhodium. Its temperature is estimated from the probe electrical characteristics and a modelling. A microcrystal of Cd0.7Sr0.3F2: Er3+(4%)-Yb3+(6%) about 25 mu m in diameter is glued at the probe extremity. This luminescent material has the particularity to give an emission spectrum with intensities sensitive to small temperature variations. The crystal temperature is estimated from the intensity measurements at 522, 540 and 549 nm by taking advantage of particular optical properties due to the crystalline nature of Cd0.7Sr0.3F2: Er3+-Yb3+. The temperature of probe microcrystal is then assessed as a function of electric current in the thermal probe by applying the Boltzmann's equations. The first results will be presented and discussed.