Thermal conductivity measurement methods

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Table of contents

Introduction
Chapter 1 Thermoelectric materials and devices 
1.1 Introduction
1.2 Thermoelectric effect
1.2.1 Seebeck effect
1.2.2 Peltier effect
1.2.3 Thomson effect
1.3 Thermoelectric figure of merit
1.3.1 Seebeck Coefficient
1.3.1.1 Seebeck coefficient measurement methods
1.3.2 Thermal conductivity
1.3.2.1 Thermal conductivity measurement methods
1.3.3 Electrical conductivity
1.3.3.1 Electrical conductivity measurement methods
1.4 Optimization of the thermoelectric performance of a material
1.4.1 State-of-the-art thermoelectric materials
1.5 Si-based thermoelectrics
1.5.1 State-of-the-art Si-based thermoelectric materials
1.6 Thermoelectric applications
1.6.1 Thermoelectric generator
1.6.2 Thermoelectric cooling
1.6.3 Sensing
1.7 Conclusions
Chapter 2 Formation and Properties of Porous Silicon 
2.1 Introduction
2.2 Porous Si formation
2.2.1 Porous Si formation by electrochemical etching of bulk c-Si
2.2.1.1 Fundamentals of electrochemical etching of c-Si
2.2.1.2 I-V Curves and formation conditions
2.2.1.3 Anodization cells
2.2.2 Porous Silicon formation by electroless etching
2.2.2.1 Stain etching
2.2.2.2 Galvanic etching
2.2.2.3 Metal-Assisted Chemical Etching (MACE)
2.2.3 Local porous Si formation
2.2.3.1 Local anodization through mask
2.2.3.2 Local anodization using etch stops
2.2.4 Free standing porous Si membranes (FSPSi)
2.3 Porous Si morphology and structure
2.4 Porosity and thickness measurements
2.5 Conclusions
Chapter 3 Porous Si thermal conductivity in the tPorous Si thermal conductivity in the temperature range 4.2emperature range 4.2–350K350K
3.1 Introduction
3.2 Thermal transport at the nanoscale
3.3 Temperature dependence of thermal conductivity
3.3.1 Crystalline materials
3.3.2 Amorphous materials and glasses
3.4 Porous Si layers studied in this thesis
3.4.1 Isotropic Porous Si
3.4.2 Anisotropic Porous Si
3.4.3 Test structure
3.5 DC method with consequent FEM analysis
3.5.1 Finite Element Method (FEM) simulations – General considerations
3.5.1.1 Heat transfer
3.5.2 Implementation of the method
3.5.3 Experimental results – Temperature dependence of porous Si Thermal resistance
3.5.4 Experimental results – Temperature dependence of Porous Si thermal conductivity
3.5.5 Comparison with other materials and theory
3.6 3ω method
3.6.1 General assumptions and considerations
3.6.1.1 One – dimensional Line heater
3.6.1.2 Infinite heat source at the surface
3.6.1.3 Effect of finite thickness of the substrate
3.6.1.4 Finite width of the heater
3.6.1.5 Approximate solution to the exact equation
3.6.2 Experimental setup
3.6.3 Data analysis
3.6.3.1 The slope method
3.6.3.2 Extracting thermal conductivity using Cahill’s integral form – Approach1
3.6.3.3 3ω method with consequent FEM analysis – Approach 2
3.6.4 Experimental results
3.6.4.1 Bulk c-Si covered with a thin TEOS oxide
3.6.4.2 Anisotropic porous Si – 70% porosity
3.6.4.3 Isotropic porous Si – 63% porosity
3.7 Conclusions
Chapter 4 Thermal conductivity of PSi in the temperature range 4.2Thermal conductivity of PSi in the temperature range 4.2–20K 20K –– Interpretation of the plateauInterpretation of the platea
4.1 Introduction
4.2 Fractals and their physical properties
4.2.1 Fractal dimension
4.2.2 Methods of measuring fractal dimension
4.2.2.1 Scattering experiment
4.2.2.2 Image analysis
4.3 Fractons
4.4 Fractal nature of porous Si
4.4.1 Porous Si fractal dimension
4.4.1.1 Isotropic Porous Si
4.4.1.2 Anisotropic porous Si
4.5 Plateau-like behavior of porous Si thermal conductivity at cryogenic temperatures – Interpretation based on its fractal geometry
4.6 Conclusions
Chapter 5 Effectiveness of porous Si as a thermal insulating platform on the Si wafer Effectiveness of porous Si as a thermal insulating platform on the Si wafer 
5.1 Introduction
5.2 Temperature distribution in a test device incorporating a thermal insulating porous Si layer
5.3 Effect of applied power
5.4 Effect of porous Si layer thickness
5.5 Comparison to bulk c-Si and other CMOS compatible thermal insulators
5.6 Conclusions
Chapter 6 Seebeck coefficient of porous Si as a function of porositySeebeck coefficient of porous Si as a function of porosity
6.1 Introduction
6.2 Study of porous Si free standing membranes
6.2.1 Fabrication process
6.2.2 SEM and TEM characterization
6.2.3 PL measurements
6.3 Seebeck coefficient measurements
6.3.1 Home-built setup description
6.3.2 Data analysis
6.3.3 Validity of the measurements
6.3.3.1 Seebeck coefficient of highly doped p-type Si
6.3.3.2 Diagnostic test measurements for hysteretic behavior
6.3.3.3 Comparison with simulations
6.4 Experimental results – Porosity dependence of porous Si Seebeck coefficient
6.5 Conclusions
Chapter 7 Thermoelectric performance of LPCVD polycryThermoelectric performance of LPCVD polycrystalline Si thin filmsstalline Si thin films
7.1 Introduction
7.2 Polycrystalline Silicon
7.2.1 Low Pressure Chemical Vapor Deposition (LPCVD)
7.2.2 Microstructure of undoped polysilicon films deposited by LPCVD
7.2.3 Microstructure of doped polysilicon films deposited by LPCVD
7.2.4 Polysilicon grain growth
7.3 Polycrystalline Si thin films studied in this thesis
7.3.1 Structural characterization
7.4 Electrical resistivity and TCR
7.4.1 Test structure
7.4.2 Measurement method
7.4.3 Experimental results
7.4.3.1 Electrical resistivity
7.4.3.2 TCR
7.4.3.3 Comparison with theory
7.5 Seebeck coefficient
7.5.1 Test structure
7.5.2 Measurement method
7.5.3 Experimental results
7.5.3.1 Comparison with theory
7.6 Thermal conductivity
7.6.1 Test structure
7.6.2 Measurement method
7.6.3 Experimental results
7.6.4 Comparison with theory
7.7 Power factor & Figure of merit
7.8 Comparison with other works on polysilicon films found in the literature
7.9 Conclusions
Conclusions
Perspectives