We present the theoretical and experimental calibrations of a scanning thermal microscope (SThM) based on a hot anemometer wire probe. Under ac heating and due to the linear dependence of the probe electrical resistance to temperature, the third harmonic of the tip voltage is also linear to the temperature. This method called “3-ω” is currently used to estimate the thermal properties with a hot strip deposited on the sample surface. However, in this last technique, the sensor size allows one to reach the sample transient thermal behavior whereas the SThM tip does not. We propose a thermal model showing what information can in fact be obtained by using the microscope under the 3ω mode. We finally report an experimental calibration providing the tip/sample contact thermal parameters.

Thermal conductivity characterization with nanoscale spatial resolution can be performed by contact probe techniques only. The technique based on a hot anemometer wire probe mounted in an atomic force microscope is now a standard setup. However, no rigorous calibration procedure is provided so far in basic dc mode. While in contact with the sample surface, the electrical current I injected into the probe is controlled so that electrical resistance or the wire temperature is maintained by the Joule effect. The variation in current is assumed to be linearly related to the heat flux lost towards the sample and traditional calibration is carried out by relating the thermal conductivity of a set of samples to the measured current I. We provide analytical and numerical thermal modeling of the tip and sample to estimate the key heat transfer in a conductivity calibration procedure. A simple calibration expression is established that provides thermal conductivity as a function of the probe current or voltage measured. Finally, experimental data allow us to determine the unknown quantities of the parametric form obtained, i.e., the mean tip-sample contact radius and conductance.

Hot tips are used either for characterizing nanostructures by using Scanning Thermal Microscopes or for local heating to assist data writing. The tip-sample thermal interaction involves conduction at solid-solid contact as well as conduction through the ambient gas and through the water meniscus. We analyze those three heat transfer modes with experimental data and modeling. We conclude that the three modes contribute in a similar manner to the thermal contact conductance but they have distinct contact radii ranging from 30nm to 1micron. We also show that any scanning thermal microscope has a 1 to 3 microns resolution when used in ambient air.

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