3D thermal wave scattering on buried inhomogeneities in ac thermal microscopy

The scattering of the thermal waves on buried small thermal resistances is theoretically studied in the framework of conductive thermal modelling of the coupling between a SThM probe and a sample. Lateral resolutions for the amplitude and phase of the probe's ac thermal response are obtained. The modelling, using an iterative method, goes beyond the usual first Born approximation results. Technically, the ac temperature field in the entire geometry is expressed in terms of two-dimensional plane wave spectra which permit direct use of fast Fourier transform algorithms. The various analytical results are easily obtained via a multilayer treatment of the probe and of the sample.