SUBSURFACE IMAGING BY SCANNING THERMAL MICROSCOPY

Scanning probe thermal microscopy has been used to achieve sub-surface imaging of metallic particles embedded in a polymer matrix, using a p robe which can act as both ohmic heater and thermometer. A lateral res olution of the order of a micron and a depth detection of a few micron s were achieved. Together with the description of the technique and th e experimental results obtained, a basic theoretical framework is pres ented which describes heat flow and temperature distributions within a sample consisting of inclusions buried within a bulk material. Comput er models have been developed to give theoretical heat flows and tempe rature profiles: these are compared here with the experimental data. T he theoretical lateral resolution was found to be in good agreement wi th the experimental observation. We show that theoretical modelling ca n be used to calibrate the instrument for specific investigations. For example, the technique could be used quantitatively to determine and map thermal conductivity variations across heterogeneous samples, or t o determine the depth at which inclusions are located in the case wher e the thermal conductivities of both the inclusions and the enclosing material are known as well as the geometry of the inclusions.