Heat transfer in ultrahigh vacuum scanning thermal microscopy

We report investigations of the heat transfer in scanning tunneling microscopy and scanning thermal microscopy under ultrahigh vacuum conditions. The distance dependence of the heat transfer is found to increase significantly for tip-sample distances smaller than several 10 nm, indicating the existence of a proximity effect in heat transfer between tip and sample. Upon scanning the thermal probe over the sample, topographic features of the sample can be clearly seen in the thermal image with down to 10 nm size.