Quantitative thermal measurement by the use of scanning thermal microscope and resistive thermal probes

Scanning thermal microscopy (SThM) is the only method for thermal measurements providing spatial resolution in the nanometer range. The method combines the topographical imaging of atomic force microscopy (AFM) with the thermal characterization of samples by the use of specially designed AFM probes having a temperature sensor near the apex. Measurements can be carried out in two modes: the temperature contrast (or passive) mode and the conductance contrast (or active) mode. In the first mode, the probe is not heated and the temperature distribution on the sample surface is measured. In the second mode, there are no heat sources in the sample and the probe is heated. The probe temperature depends on the thermal conductance for the heat exchange between the probe and the sample. This thermal conductance depends on the sample thermal conductivity and probe-sample interfacial thermal resistance. If the latter is constant, the distribution of the thermal conductivity on the sample surface can be obtained. The principle of qualitative SThM is quite simple. However, quantitative measurements require rigorous analysis of temperature distribution and heat fluxes in the probe-sample system. This paper provides basic information about SThM starting from first principles, through instrumentation, characterization of probes used for measurements, general theory of the temperature, and the thermal conductivity measurements, to a few examples of practical applications of this method. Finally, perspectives and challenges for SThM based measurements are discussed.