Opracowanie metod pomiaru lokalnych właściwości cieplnych wykorzystujących skaningowy mikroskop cieplny

Abstract

The aim of the thesis was to develop a new method of measurement, enabling the study of local thermal properties of solids with high spatial resolution. To develop the new method of measurement the scanning thermal microscope was utilized. Research carried out in the framework of this study included theoretical and numerical analysis as well as experimental work. In the first part of the thesis a model of the probe - sample system is presented, created basing on the finite element method. The model allows a comprehensive analysis of the physical processes occurring in the probe - sample system during the measurement. Numerical analysis allowed to determine the optimal conditions for experimental research, estimate the maximum probe sensitivity to thermal properties and model different modes of quantitative measurements. An important result of this part of research was developing a correction procedure for determining the thermal conductivity of a thin film. In the next part of the thesis a model of heat transport processes in the probe - sample system, which based on electro-thermal analogies, was proposed and experimentally verified. It was shown that the developed model allows to achieve better compliance with the measurement results than the models used so far and that it is helpful in the analysis and interpretation of the results obtained in different modes of measurement. The main goal of the work was to propose a new method of measurement. It utilizes the dc biased probe with small ac current superimposed to it. The static and dynamic resistance of the probe are measured. The method combines the advantages of both dc and ac excitation, such as: mechanical stability of the probe, average temperature control, lock-in signal processing, higher signal to noise ratio. A new way of analyzing the results of the measurements was proposed, in which the difference between dynamic and static resistance of the probe is calculated. It was shown that it is directly proportional to the thermal resistance of the probe, which contains information about the thermal conductivity of the sample. Utilizing the probe signal measured in air is a reference, minimizes the influence of the instability of ambient conditions. It was shown that the sensitivity to the thermal properties is higher than in the standard measurement methods. Experimental studies included the verification of the correctness of proposed measurement method and its use to investigate thermal properties of selected micro- and nanostructures. The results of investigations of multi-layer photonic structures, TSV structures and thin SiO2 and BaTiO3 layers were presented. It was shown that the proposed method of signal detection and analysis can be used both in the classical methods of thermal imaging as well as in the quantitative measurements. Results of research carried out in the framework of this thesis and utilizing the developed measurement method were published in 7 scientific papers. The results of the research were presented at several presentations at international conferences.