Nanoscale thermal imaging of active devices by fluorescent SThM

We describe a scanning thermal microscope that uses a fluorescent nanocrystal as a temperature probe. The nanocrystal is made of an inorganic fluoride material doped with erbium ions. The temperature is determined by measuring the fluorescence intensity ratio between two adjacent fluorescence lines. We first visualized the heating of a Cr stripe, and observed two different heat transfer channels, by direct contact between the tip and the device and by conduction through the air gap. We then measured the temperature map of a Joule heated submicron wide Pt wire and observed that the temperature elevation is uniform all along the wire. The measured images are obtained with a submicron lateral resolution and demonstrate the good reliability of the technique for characterizing the thermal properties of nanoscale devices and structures.