1 MOLECULAR MODELING:APPLICATION TO HYDROGEN INTERACTION WITH CARBON-SUPPORTED TRANSITION METAL SYSTEMS&Samir H.Mushrif Gilles H.Peslherbe Alejandro D.Rey 1
1 Introduction 1
2 Molecular Modeling Methods 7
2.1 Molecular Mechanics 7
2.2 Electronic Structure Theory 11
2.3 Density Functional Theory 14
2.4 Plane-Wave Pseudo-Potential Methods 19
2.5 Optimization Techniques 22
3 Modeling Hydrogen Interaction with Doped Transition Metal Carbon Materials Using Car-Parrinello Molecular Dynamics and Metadynamics 30
3.1 Dissociative Chemisorption 33
3.2 Spillover and Migration of Hydrogen 35
4 Summary 42
References 43
2 SURFACE MODIFICATION OF DIAMOND FOR CHEMICAL SENSOR APPLICATIONS:SIMULATION AND MODELING&Karin Larsson 51
1 Introduction 51
2 Factors Influencing Surface Reactivity 52
3 Diamond as a Sensor Material 52
3.1 Background 52
3.2 Electrochemical Properties of Diamond Surfaces 54
4 Theory and Methodology 55
4.1 Density Functional Theory 55
4.2 Force-Field Methods 62
5 Diamond Surface Chemistry 63
5.1 Electron Transfer from an H-Terminated Diamond (100)Surface to an Atmospheric Water Adlayer;a Quantum Mechanical Study 63
5.2 Effect of Partial Termination with Oxygen-Containing Species on the Electron-Transfer Processes 66
5.3 The Energetic Possibility to Completely Oxygen-Terminate a Diamond Surface 70
5.4 Effect on Electron-Transfer Processes of Complete Termination with Oxygen-Containing Species 76
5.5 Biosensing 78
5.6 Simulation of the Pluronic F108 Adsorption Layer on F-,H-,O-,and OH-Terminated NCD Surfaces 80
References 81
3 GENERAL APPROACH TO DESIGN AND MODELING OF NANOSTRUCTURE-MODIFIED SEMICONDUCTOR AND NANOWIRE INTERFACES FOR SENSOR AND MICROREACTOR APPLICATIONS&J.L.Gole W.Laminack 87
1 Introduction:The IHSAB Model for Porous Silicon Sensors and Microreactors 87
2 The Interface on Extrinsic Semiconductors 89
3 The IHSAB Concept as the Basis for Nanostructure-Directed Physisorption(Electron Transduction)at Sensor Interfaces 94
4 The Extrinsic Semiconductor Framework 97
5 Physisorption(Electron Transduction)and the Response of a Nanostructure-Modified Sensor Platform 100
6 The Underlying IHSAB Principle 114
7 Application to Nanowire Configurations 116
8 Application to Additional Semiconductors 119
9 Time-Varying Operation and False-Positives;Sensing in an Unsaturated Mode 119
10 Sensor Rejuvenation 122
11 Summary of Sensor Attributes 123
12 Extension to Phytocatalysis-Enhanced System 123
13 Mixed Gas Format 125
14 Comparison to Alternative Technologies 126
15 Chemisorption and the Analog of the HSAB Principle 127
16 Physisorption(Electron Transduction)versus Chemisorption 129
17 Outlook 130
Acknowledgments 132
References 132
4 DETECTION MECHANISMS AND PHYSICO-CHEMICAL MODELS OF SOLID-STATE HUMIDITY SENSORS&V.K.Khanna 137
1 Introduction 137
2 Humidity-Sensitive Materials 138
3 Resistive and Capacitive Humidity-Sensing Configurations,and Other Structures 139
4 Equivalent Circuit Modeling of Humidity Sensors 141
5 General Approaches to the Formulation of Humidity Sensor Models 143
6 Theories of Adsorption of Water on the Surfaces of Solids 143
6.1 Hydroxylation of the Surface by Chemisorption of Water 143
6.2 Mono-and Multilayer Physisorption and Brunauer-Emmett-Teller(BET)Theory 144
6.3 Capillary Condensation of Water Vapor 146
7 Modeling the Kinetics of Diffusion of Water in Solids 146
8 Surface Conduction Mechanisms on Solids and Humidity-Induced Surface Conductivity Modulation 147
9 Dielectric Properties of Solids Containing Adsorbed Water 148
9.1 The Modified Clausius-Mosotti Equation in the Presence of Moisture 148
9.2 Maxwell-Wagner Effect in Heterogeneous Binary Systems 148
9.3 Sillars's Theory for Spheroidal Particles Sparsely Distributed in an Insulator 149
10 Fleming's Approach:Surface Electrostatic Field Model 150
11 Theory of the Porous Alumina Humidity Sensor,and Simulation of Its Capacitance and Resistance Characteristics 152
11.1 Microstructure of Porous Anodic Alumina 152
11.2 Water Vapor Adsorption on Porous Alumina 155
11.3 Adsorption Isotherm on Porous Alumina 156
11.4 Surface Conduction Mechanisms on Porous Alumina and Their Correlation with Surface Conductivity Variation with Humidity 157
11.5 Statistical Distribution of Humidity-Dependent Surface Conductivity of Alumina Among Pores 159
11.6 Response of Dielectric Properties of Alumina to Humidity Changes 160
11.7 Influence of Pore Shape Parameter(λ)on Capacitance and Resistance Variation 166
12 Dynamic Behavior and Transient Response Modeling of Humidity Sensors 167
12.1 The Tetelin-Pellet Model 167
12.2 Designing a Short-Response-Time Humidity Sensor Structure 169
13 Modeling the Diffusion Kinetics of Cylindrical Film and Cylindrical Body Structures for Enhanced-Speed Humidity Sensing 170
14 Effect of Ionic Doping on Humidity Sensor Performance 173
14.1 Anionic Doping in Al2O3 Humidity Sensors 173
14.2 Alternative Doping Techniques 175
15 Modeling the Drift and Ageing of Humidity Sensors 175
16 Artificial Neural Network (ANN)-Based Behavioral Modeling of Humidity Sensors 177
17 Modeling Other Types of Humidity Sensors 179
17.1 Microgravimetric Humidity Sensors:The Sauerbrey Equation 179
17.2 Surface Acoustic Wave(SAW) Delay-Line Humidity Sensors Using Velocity and Attenuation Changes 180
17.3 Microcantilever Stress-Based Humidity Sensors:Stoney's formula 181
17.4 Field-Effect Humidity Sensors 182
18 Discussion of Humidity Sensor Models 184
19 Conclusions and Outlook 184
Dedication 186
Acknowledgments 186
References 186
5 THE SENSING MECHANISM AND RESPONSE SIMULATION OF THE MIS HYDROGEN SENSOR&Linfeng Zhang 191
1 Introduction 191
2 Sensors and Their Sensing Mechanisms 192
2.1 Metal-Semiconductor Sensors 192
2.2 Metal-Semiconductor-Metal Sensors 194
2.3 Metal-Insulator-Semiconductor Sensors 197
3 Gas Diffusion 200
4 Kinetics of Surface and Interface Adsorption 205
5 Simulations 209
5.1 MS Sensors 209
5.2 MIS Sensors 212
6 Conclusions 219
Appendix 219
References 228