Lock-in thermographic investigation of probe-sample interaction in scanning thermal microscopy (SThM)

Thermographic lock-in investigation of thermal interaction between a thermal probe used in scanning thermal microscopy and a thin composite sample is used for estimating the relative fraction of heat flux transferred to the sample by conduction through the air and by direct local contact. The latter is determined by vector subtraction of out-of-contact data from in-contact data, for different modulation frequencies. It represents only 8% of the total modulated heat flux dissipated by the probe, and is frequency-independent. The heat transfer by air conduction varies between 23% and 6% for f = 0.2 ... 40 Hz with a broad equivalent heat source radius of r 0.2 mm.