Growth and Transport in Nanostructured Materials: Reactive Transport in PVD, CVD, and ALD (SpringerBriefs in Materials)

This book will address the application of gas phase thin film methods, including techniques such as evaporation, sputtering, CVD, and ALD to the synthesis of materials on nanostructured and high aspect-ratio high surface area materials. We have chosen to introduce these topics and the different application fields from a chronological perspective: we start with the early concepts of step coverage and later conformality in semiconductor manufacturing, and how later on the range of application branched out to include others such as energy storage, catalysis, and more broadly nanomaterials synthesis. The book will describe the ballistic and continuum descriptions of gas transport on nanostructured materials and then will move on to incorporate the impact of precursor-surface interaction. We will finally conclude approaching the subjects of feature shape evolution and the connection between nano and reactor scales and will briefly present different advanced algorithms that can be used to effectively compute particle transport, in some cases borrowing from other disciplines such as radiative heat transfer. The book gathers in a single place information scattered over thirty years of scientific research, including the most recent results in the field of Atomic Layer Deposition. Besides a mathematical description of the fundamentals of thin film growth in nanostructured materials, it includes analytic expressions and plots that can be used to predict the growth using gas phase synthesis methods in a number of ideal approximations. The focus on the fundamental aspects over particular processes will broaden the appeal and the shelf lifetime of this book. The reader of this book will gain a thorough understanding on the coating of high surface area and nanostructured materials using gas phase thin film deposition methods, including the limitations of each technique. Those coming from the theoretical side will gain the knowledge required to model the growth process, while those readers more interested in the process development will gain the theoretical understanding will be useful for process optimization. Preface 7 Contents 9 1 Introduction 12 1.1 Introduction 12 1.2 Vapor Phase Thin Film Deposition Techniques 14 1.2.1 Conformality of Vapor Phase Deposition Techniques 14 1.2.2 Sticking Probability 16 1.2.3 Knudsen Number 17 1.3 Substrates and Scaffolds 19 1.3.1 Deterministic Substrates 20 1.3.2 Porous and Disordered Substrates 22 1.4 Historical Overview 23 1.4.1 Conformality in Semiconductor Manufacturing 23 1.4.2 Chemical Vapor Infiltration 25 1.4.3 Chemical Engineering and Heterogeneous Catalysis 26 1.5 Summary 27 References 27 2 Physical and Chemical Vapor Deposition Techniques 30 2.1 Physical Vapor Deposition Methods: Evaporation and Sputtering 30 2.1.1 Evaporation 31 2.1.2 Sputtering 32 2.1.3 Approaches to Improve Step Coverage in PVD Methods 34 2.2 Chemical Vapor Deposition 34 2.2.1 Impact of Kinetics on the Conformality of CVD Processes 35 2.2.2 Strategies to Improve Conformality in CVD 40 2.3 Atomic Layer Deposition 41 2.3.1 Introduction 41 2.3.2 Models of ALD Surface Kinetics 42 2.3.3 Application of ALD to High Surface Area Materials 45 2.4 Summary 46 References 47 3 Fundamentals of Gas Phase Transport in Nanostructured Materials 49 3.1 Ballistic Models 51 3.1.1 Fundamental Equations 51 3.1.2 Source Gas Distribution 53 3.1.3 Particle Reemission Model 54 3.1.4 View Factors 55 3.2 Single Particle Approaches to Ballistic Transport 60 3.2.1 Kinetic Monte Carlo Simulations 61 3.2.2 Markov Chain Formulation 63 3.3 Continuum Description: Diffusion-Based Models 66 3.3.1 Knudsen Diffusion Coefficient 67 3.3.2 Transitional Flow 71 3.3.3 Diffusion in Micropores 72 3.3.4 Diffusion in Polymers 74 3.3.5 Transport in Presence of Reversible Adsorption/Desorption 75 3.4 Summary 77 References 77 4 Thin Film Growth in Nanostructured Materials 78 4.1 PVD and Early Line of Sight Approximations 78 4.1.1 Directed Flow 79 4.1.2 Isotropic Case 80 4.2 Constant Sticking Probability 81 4.2.1 Diffusion-Based Model 83 4.2.2 Impact of Reaction Probability on Film Conformality 84 4.3 Pressure-Dependent Kinetics 88 4.3.1 Conformal Zone for Single-Source Precursors 90 4.3.2 Superconformal Processes and Conformality Enhancement 94 4.4 Self-limited Surface Kinetics: Atomic Layer Deposition 99 4.4.1 Infiltration Kinetics 99 4.4.2 Non-ideal ALD Processes 106 4.5 Summary 107 References 107 5 Advanced Concepts 109 5.1 Predicting Shape Evolution 109 5.1.1 Lagrangian Methods 110 5.1.2 Eulerian Methods 111 5.1.3 String Methods 111 5.1.4 Method of Characteristics 114 5.1.5 Cell or Volume of Fluid Methods 122 5.1.6 Level Set Methods 123 5.1.7 Pore Constriction Models 127 5.2 Bridging Feature and Reactor Scales 128 5.2.1 Effective Reactivity Approach 129 5.2.2 Mesoscale Model Approach 130 5.2.3 Effective Reaction Probability of High Surface Area Materials 132 5.3 Summary 132 References 133 Index 134 Front Matter....Pages i-xi Introduction....Pages 1-18 Physical and Chemical Vapor Deposition Techniques....Pages 19-37 Fundamentals of Gas Phase Transport in Nanostructured Materials....Pages 39-67 Thin Film Growth in Nanostructured Materials....Pages 69-99 Advanced Concepts....Pages 101-125 Back Matter....Pages 127-128