Calibration of a scanning Joule expansion microscope (SJEM)

Scanning thermal microscopy (SThM) is a scanning probe technique based on atomic force microscopy (AFM) enabling high-resolution topographical imaging together with visualization of the temperature distribution in the studied sample. For the thermal mapping, rather expensive, micro-fabricated cantilevers with integrated thermocouples have to be used. The spatial resolution is typically limited to 100 nm. Scanning Joule expansion microscopy (SJEM) uses an alternative approach to detect the temperature of the sample with a regular silicon cantilever and lock-in detection. By monitoring the thermal expansion of the sample (due to Joule heating), the local temperature can be monitored. The resolution of SJEM is comparable to that of contact AFM, which is an order of magnitude better than for SThM. Our research involves implementing a SJEM for the study of heating phenomena in mesoscopic structures prepared by electron beam lithography and lift-off techniques. In particular, we calibrated our SJEM in order to make quantitative temperature maps of the studied samples.