Supervisor's Foreword; Abstract; List of Publications; Acknowledgements; Contents; 1 An Introduction to Security Based on Physical Disorder; 1.1 Motivation; 1.2 The Need for a New Era of Authenticity; 1.3 Using Hardware as a Basis of Trust; 1.3.1 Employing Physical Disorder; 1.3.2 Physically Unclonable Functions; 1.3.3 Unique Objects; 1.3.4 Physical Disorder at the Extreme; Bibliography; 2 An Introduction to Semiconductors and Quantum Confinement; 2.1 Introduction; 2.2 Semiconducting Materials; 2.2.1 The Basics; 2.2.2 Doping in Semiconductors; 2.2.3 Semiconductor Band Structure

2.2.4 Direct Versus Indirect Semiconductors2.2.5 Compound Semiconductors; 2.3 The Effects of Confinement; 2.3.1 The 'Particle in a Box' Approximation; 2.3.2 Beyond 1 Dimension of Confinement; 2.3.3 Excitons; 2.4 Aim of This Work: The Sensitivity to Imperfections; 2.5 Thesis Outline; Bibliography; 3 Sample Preparation and Experimental Techniques; 3.1 Introduction; 3.2 Production of Resonant Tunneling Diodes; 3.2.1 Molecular Beam Epitaxy Growth; 3.2.2 Device Fabrication; 3.2.3 Probe Station Measurements; 3.3 The Langmuir-Blodgett Technique; 3.3.1 Background; 3.3.2 The Langmuir-Blodgett Trough

3.3.3 A Typical Isotherm Experiment3.3.4 The Mixing Problem; 3.3.5 The Case for Electrospray; 3.4 Characterisation Techniques; 3.4.1 Brewster Angle Microscopy (BAM); 3.4.2 Scanning Probe Microscopies (SPM); 3.4.3 Scanning Electron Microscopy (SEM); 3.4.4 Photoluminescence, Raman and Fluorescence Spectroscopies; Bibliography; 4 Unique Identification with Resonant Tunneling Diodes; 4.1 Introduction; 4.2 Uniqueness in Semiconductor Nanostructures; 4.2.1 A Sensitivity to Quantum Confinement; 4.2.2 Imperfections and Defects in Nanostructures; 4.2.3 Quantum Dots as an Example System

4.3 Electronic Unique Identification Using Quantum Confinement4.3.1 Resonant Tunneling Diodes; 4.4 Testing RTD Characteristics; 4.4.1 Stabilisation of RTDs; 4.4.2 Size Selection of RTDs; 4.5 Resonant Tunneling Diodes as Unique Identifiers; 4.5.1 Testing the Uniqueness; 4.5.2 Testing the Robustness; 4.5.3 Implementation Considerations; 4.6 Summary; Bibliography; 5 Langmuir-Blodgett Deposition of 2D Materials for Unique Identification; 5.1 Introduction; 5.2 Unique Properties of 2D Materials; 5.2.1 An Introduction to 2D Materials; 5.2.2 Effects of Confinement in 2D Materials

5.3 Langmuir-Blodgett Films of 2D Materials5.3.1 A Brief Comparison of Fabrication Methods; 5.3.2 Thin Films of Liquid Exfoliated 2D Materials; 5.3.3 Creating a Langmuir Film of MoS2; 5.3.4 MoS2 at the Air-Water Interface; 5.3.5 Deposition of a Langmuir-Blodgett Film; 5.3.6 Creating Optical Identification Devices; 5.4 Analysis of Deposited Langmuir-Blodgett Films of MoS2; 5.4.1 Quenched Photoluminescence of MoS2 Films; 5.4.2 Investigation of Possible Quenching Mechanisms; 5.4.3 A Different Source of MoS2; 5.5 Summary; Bibliography