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<p><b>Chapter 1 8</b></p> <p>Bottom-up growth methods 8</p> <p>Abstract 8</p> <p>1.1. Introduction 9</p> <p>1.2. Bottom-up growth mechanisms 10</p> <p>1.2.1. Vapor-liquid-solid growth mechanism 10</p> <p>1.2.2. Vapor-solid-solid growth mechanism 16</p> <p>1.2.3. Vapor-solid growth mechanism 22</p> <p>1.2.4. Solution-liquid-solid growth mechanism 26</p> <p>1.3. Bottom-up growth techniques 29</p> <p>1.3.1. Chemical Vapor Deposition 29</p> <p>1.3.2. Metal-organic chemical vapor deposition 33</p> <p>1.3.3. Plasma-enhanced chemical vapor deposition 36</p> <p>1.3.4. Hydride vapor phase epitaxy 38</p> <p>1.3.5. Molecular Beam Epitaxy 41</p> <p>1.3.6. Laser ablation 44</p> <p>1.3.7. Thermal evaporation 46</p> <p>1.3.8. Carbothermal reduction 48</p> <p>References 51</p> <p><b>Chapter 2 65</b></p> <p>Top-down fabrication processes 65</p> <p>Abstract 65</p> <p>2.1. Introduction 66</p> <p>2.2. Top-down fabrication techniques 68</p> <p>2.2.1. Focused ion beam 68</p> <p>2.2.2. Electron beam lithography 69</p> <p>2.2.3. Reactive ion etching 72</p> <p>2.2.4. Combined lithography techniques 74</p> <p>References 76</p> <p><b>Chapter 3 81</b></p> <p>Hybrid fabrication techniques and nanowire heterostructures 81</p> <p>Abstract 81</p> <p>3.1. Introduction 82</p> <p>3.2. Bottom-up meets top-down approaches 84</p> <p>3.3. Integration of nanowires onto unconventional substrates 86</p> <p>3.3.1. Transferring nanowires onto flexible substrates 86</p> <p>3.3.2. Growing nanowires on graphene and layered material substrates 92</p> <p>3.4. Synthesis of nanowire heterostructures 95</p> <p>3.4.1. Synthesis of one-dimensional heterostructures 95</p> <p>3.4.2. Synthesis of mixed dimensional heterostructures 98</p> <p>References 101</p> <p><b>Chapter 4 108</b></p> <p>Electrical properties of wide bandgap nanowires 108</p> <p>Abstract 108</p> <p>4.1. Electrical properties 109</p> <p>4.2. Measurement of electrical conductivity 109</p> <p>4.3. Fundamental electrical properties of nanowires 112</p> <p>4.3.1 Effect of doping on electrical properties 113</p> <p>4.3.2 Mobility 115</p> <p>4.3.3 Activation/ionization energy 116</p> <p>4.3.4 Dependence of activation/ionization energy on NW dimensions 118</p> <p>4.4 Electrical properties of wide bandgap nanowire based devices 118</p> <p>4.4.1 Single NW electrical sensing devices 118</p> <p>4.4.2 Field-effect transistors (FETs) 120</p> <p>References 129</p> <p><b>Chapter 5 132</b></p> <p>Mechanical properties of wide bandgap nanowires 132</p> <p>Abstract 132</p> <p>5.1. Characterization techniques 133</p> <p>5.1.1 Bending and buckling methods 133</p> <p>5.1.2 Nano indenting method 138</p> <p>5.1.3 Resonance testing method 139</p> <p>5.2. Impact of defects and microstructures on mechanical properties of NWs 140</p> <p>5.2.1. Defects 140</p> <p>5.2.2 Effect of structures, dimensions and temperatures 143</p> <p>5.3. Anelasticity and plasticity properties 148</p> <p>5.3.1 Anelasticity 148</p> <p>5.3.2 Plasticity 148</p> <p>5.3.3 Brittle to ductile transition 150</p> <p>References 152</p> <p><b>Chapter 6 155</b></p> <p>Optical properties of wide bandgap nanowires 155</p> <p>Abstract 155</p> <p>6.1 Optical properties of WBG NWs 156</p> <p>6.1.1 Photoluminescence characterization of NWs 156</p> <p>6.1.2 Size-dependent optical properties 157</p> <p>6.1.3 Shape/morphology-dependent optical properties 158</p> <p>6.1.4 Effect of crystal orientation 159</p> <p>6.1.5 Tuning optical properties of NWs 160</p> <p>6.2 Wide bangap nanowire light-emitting diodes (LEDs) 164</p> <p>6.2.1 GaN nanowire based LEDs 164</p> <p>6.2.2 GaN nanowire UV LEDs 169</p> <p>6.2.3 ZnO nanowire based LEDs 172</p> <p>References 175</p> <p><b>Chapter 7 180</b></p> <p>Thermal properties of wide bandgap nanowires 180</p> <p>Abstract 180</p> <p>7.1. Thermal conductivity 181</p> <p>7.1.1 Fundamental of thermal transport and thermal conductivity 181</p> <p>7.1.2 Measurement of thermal conductivity 182</p> <p>7.1.3 Effect of diameters on thermal properties 183</p> <p>7.1.4 Effect of orientation on thermal properties 186</p> <p>7.1.5 Tenability of thermal properties 187</p> <p>7.2 Thermoelectric properties 190</p> <p>7.2.1 Fundamental thermoelectric properties 190</p> <p>7.2.2 Thermoelectric properties of ZnO and GaN NWs 191</p> <p>7.2.3 Thermoelectric properties of SiC NWs 193</p> <p>7.2.4 Optimisation of the thermoelectric properties 194</p> <p>References 196</p> <p><b>Chapter 8 200</b></p> <p>Ultraviolet sensors 200</p> <p>Abstract 200</p> <p>8.1. Introduction 201</p> <p>8.2. Sensing mechanism 201</p> <p>8.2.1. Photoconductor architectures 202</p> <p>8.2.2. Schottky diode photo sensors 204</p> <p>8.2.3. Semiconductor p-n junction 206</p> <p>8.2.4. Field effect transistor-based UV sensors 208</p> <p>8.3. Device development technologies 210</p> <p>8.3.1. The choice of wide band gap materials for UV sensing 210</p> <p>8.3.2 Top down fabrication of wide band gap nanowire UV sensors 216</p> <p>8.3.4. Transfer process for nanowires 219</p> <p>8.4. Applications of nanowire UV sensors 222</p> <p>8.4.1 Flame sensors 222</p> <p>8.4.2. Environmental monitoring 224</p> <p>8.4.4 Biological sensors and health care applications 225</p> <p>References 227</p> <p><b>Chapter 9 233</b></p> <p>Mechanical Sensors 233</p> <p>Abstract 233</p> <p>9.1. Introduction 234</p> <p>9.2. Sensing mechanisms and corresponding materials 234</p> <p>9.2.1. The piezoresistive effect 234</p> <p>9.2.2. Piezotronics effect in nanowires 239</p> <p>9.2.3 Capacitive sensing 243</p> <p>9.3. Transducer configurations and fabrication technologies 244</p> <p>9.3.1. Strain sensors 244</p> <p>9.3.2. Pressure sensors 248</p> <p>9.3.3 Tactile sensors 253</p> <p>9.3.4. Acceleration and vibration sensors 256</p> <p>9.3.5. Energy harvesting devices 257</p> <p>9.4. Applications of mechanical sensors using wide band gap materials 261</p> <p>9.4.1. Structural heath monitoring 261</p> <p>9.4.2. Advanced health care 262</p> <p>9.4.3 Robotics 265</p> <p>References 267</p> <p><b>Chapter 10 273</b></p> <p>Gas sensors 273</p> <p>Abstract 273</p> <p>10.1. Introduction 274</p> <p>10.2. Principle of gas sensing 274</p> <p>10.2.1. Transconductance sensing mechanism 274</p> <p>10.2.2. Field effect transistor-based gas sensors 276</p> <p>10.2.3. Metal-semiconductor Schottky contact based gas sensors 277</p> <p>10.2.4. Integration of nanowires with micro heaters 278</p> <p>10.3. Standard physical parameters for gas sensors 280</p> <p>10.3.1. Sensitivity 280</p> <p>10.3.2. Selectivity 281</p> <p>10.3.3. Response time 282</p> <p>10.4. Materials for different types of gases 284</p> <p>10.4.1 Oxygen sensors 284</p> <p>10.4.2 Carbon dioxide 285</p> <p>10.4.3 Organic gases 287</p> <p>10.4.4 Hydrogen gas 290</p> <p>References 301</p> <p><b>Chapter 11 308</b></p> <p>Wide band gap nanoresonators 308</p> <p>Abstract 308</p> <p>11.1. Introduction 309</p> <p>11.2. Principle of nanoresonators 310</p> <p>11.3. Actuation and measurement techniques 316</p> <p>11.3.1 Electrostatic actuation 316</p> <p>11.3.2 Piezoelectric actuation 318</p> <p>11.3.3 Magnetomotive actuation 320</p> <p>11.3.4. Thermal actuator 323</p> <p>11.4. Engineering the performance of nanoresonators using wide band gap materials 325</p> <p>11.4.1. Residual stress 325</p> <p>11.4.2 Mechanical clamping enhancement 329</p> <p>11.4.3 Tunning resonant frequency using electrically driven forces 331</p> <p>11.5. Applications of nanoresonators 334</p> <p>11.5.1 Logic Circuit at high temperatures 334</p> <p>11.5.2 Mass sensing applications 337</p> <p>11.5.3 Biosensors 338</p> <p>11.5.4 Mechanical sensing 339</p> <p>11.5.5 Optical devices 341</p> <p>References 343</p> <p> </p>

<p><b>Tuan Anh Pham</b> is a research assistant as well as a process engineer at the Queensland Micro- and Nanotechnology Centre, Griffith University, Australia. Dr. Pham’s longstanding research interests have been focused on various fields of condensed matter physics and materials science, including 1D/2D materials, topological insulators, wide bandgap semiconductors, surface science, and wearable technology.</p> <p><b>Toan Dinh</b> is a Senior Lecturer in the School of Engineering, University of Southern Queensland, Australia. Dr. Dinh’s research interests include micro/nano-electromechanical systems (MEMS/NEMS), physics of semiconductors, sensors for harsh environments, soft robotics, and advanced materials for healthcare and wearable applications. <p><b>Nam-Trung Nguyen</b> is a Professor and the Director of Queensland Micro- and Nanotechnology Centre at Griffith University in Brisbane, Australia, and leads a research group of over 20 postgraduate and postdoctoral researchers. Research themes of the group include micro- and nanofluidics, micro- and nanofabrication; as well as micro- electromechanical systems (MEMS). <p><b>Hoang-Phuong Phan</b> is currently an ARC DECRA Fellow at Queensland Micro- and Nanotechnology Centre, Griffith University. He will join the University of New South Wales (UNSW), Sydney, Australia from March 2022 as a Senior Lecturer. The Phan Lab’s research interest covers a broad range of semiconductor devices and applications, including MEMS/NEMS, integrated sensors, flexible electronics, and bio-sensing applications.

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