Françoise Depasse

D.C. scanning thermal microscopy : Characterisation and interpretation of the measurement

Abstract The used Scanning Thermal Microscopy (SThM) probe is a thin Pt resistance wire acting as a heat source and as a detector simultaneously. Its energetic balance is investigated by the study of the temperature profile along the probe. A theoretical approach of the measurement, based on this investigation, is then proposed. Simulations with this modelling are shown to predict how the heat, electrically produced in the probe, is dissipated in the probe-sample system. In particular, it is shown that the steady-state of conduction losses to the thermal element support varies versus the thermal conductivity of the sample and can lead to bad interpretations of the measurement.

AC thermal microscopy: a probe - sample thermal coupling model

A simple model of the thermal coupling between a probe tip and a sample is given, assuming an exchange through a thermal conductive medium. Comparisons between one-dimensional and three-dimensional calculations show the near-field character of the ac exchange. The coupling is analysed according to the different important parameters: probe - surface distances, sample thermal conductivity and diffusivity.

A.C. scanning thermal microscopy: Tip–sample interaction and buried defects modellings

Abstract Modellings describing the different thermal interactions between a sample surface and a probe in case of modulated heated probe are given and analysed. To obtain more reliable thermal data for a full calibration of thermal microscope or quantitative interpretations, these models are developed in three dimensions. The scattering of the thermal waves on buried small thermal resistances is theoretically studied. Lateral resolutions for the amplitude and phase of the probes a.c. thermal response are obtained.

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 probes 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.

Sample tip thermal coupling in modulated laser surface excitation

A model of the a.c. thermal coupling between a sample surface and a non-contact material probe, in the case of a modulated heated sample, is analyzed. The temperature field of the sample surface is obtained in using approximated self-consistent perturbation from the heat losses via the probe channel. Numerical estimation is given for uniform and local heat sources highlighting the roles of the modulation frequency and the probe dimensions.

Plane-wave spectrum approach for the AC thermal analysis of vertical thermal resistance on sample surface

The perturbation caused by a vertical thermal resistance to the alternating current temperature field in a homogeneous sample is analysed by using a plane-wave spectrum for which the reference plane is perpendicular to the crack. This unusual Fourier analysis gives rapid access to the temperature field in the frequency domain at any place in the sample. This can thus furnish the source term for a complete thermoelastic local response and complete the available surface temperature data.