Institute of Solid State Physics
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SS22 WS22 SS23 WS23 SS24 WS24 Guidelines for Master Students
Modelling and measuring of thermal transport in stacked thin layers – optimisation, implementation and experimental validation Measuring thermophysical properties of thin film systems in the micro-/nanometer range is an important field of material science. Its area of applications ranges from thermal simulations of high-speed machining tools to thermal design of power electronics. Measuring the thermal properties of thin layers in the ranges of tens to a few hundred nanometer and the interfaces between them is difficult due to their dimensions, but they are of particular interest, as they are needed for example for chip design or protective coatings. Time-domain Thermo-Reflectance (TDTR) is a pump-probe technique that utilizes the constant thermoreflectance coefficient of some material to measure the thermophysical properties of layered samples in a non-destructive manner. It uses a model-fitting approach, which allows determining the properties of individual layers and interfaces. The aim of this thesis is to develop an analysis procedure for TDTR measurements of layered samples. To that end, a heat transfer model, that was developed by Cahill was implemented in Python. The effect of different numerical integration schemes onto the model was investigated. Several data pre-processing steps and a sensitivity analysis were developed and implemented. Two different minimization method for the model fitting process were examined and uncertainty analysis of the fitting results was done and implemented. A graphical user interface (GUI) that provided easy access to the implemented methods was developed. To validate the used approach 4 samples with various layers of Mo, Al and SiO2 have been measured with the PicoTR of Netzsch and analyzed with the developed procedure. The measured samples include a 421 nm Mo layer on a quartz substrate used as a standard by the National Institute of Advanced Industrial Science and Technology (AIST, Japan). Taking thickness (d) and layer deposition method into account, all measured values are reasonably close to literature values. E.g. molybdenum: thermal conductivity: 129.2 Wm-1K-1 (d=421 nm), 65.5 Wm-1K-1 (d=116 nm), 68.2 Wm-1K-1 (d=100 nm), volumetric heat capacity: 2.6*106 Jm-3K-1 (d=421 nm), 1.0*106 Jm-3K-1 (d=116 nm), 3.0*106 Jm-3K-1 (d=100 nm). The developed software can be used to analyse TDTR measurements of stacked samples. It allows determining the thermal conductivity and volumetric heat capacity of the individual layers and thermal interface resistances. Due to the model fitting approach the determination of multiple unknown parameters is also possible, but multiparameter-fitting proofed to require knowledge of the sample. |
