METAL-OXIDE-BASED ELECTRONIC DEVICES A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Engineering and Physical Sciences 2013 JIDONG JIN SCHOOL OF ELECTRICAL AND ELECTRONIC ENGINEERING Contents List of Figures ................................................................................................................ 5 List of Tables ................................................................................................................ 10 Abbreviations ............................................................................................................... 11 Abstract ........................................................................................................................ 14 Declaration ................................................................................................................... 15 Copyright Statement ..................................................................................................... 15 Acknowledgments ........................................................................................................ 17 1 Introduction ............................................................................................................. 18 1.1 Overview .......................................................................................................... 18 1.2 Thesis Layout ................................................................................................... 21 References ................................................................................................................ 22 2 Literature Review .................................................................................................... 26 2.1 Metal-Semiconductor Junctions ....................................................................... 26 2.1.1 Schottky Contact ....................................................................................... 27 2.1.2 Ohmic Contact........................................................................................... 30 2.2 Metal-Oxide Semiconductors ........................................................................... 34 2.2.1 ZnO............................................................................................................ 34 2.2.2 Tin Oxide ................................................................................................... 35 2.3 Metal-Oxide Thin-Film Transistors.................................................................. 37 2.3.1 Device Structures ...................................................................................... 38 2.3.2 Basic Device Operation ............................................................................. 38 2.3.3 Effect of Dielectric Layer .......................................................................... 41 2.4 Metal-Oxide Resistance Random Access Memory .......................................... 42 2.4.1 Basic Working Principle ............................................................................ 43 2.4.2 Resistive Switching Mechanisms .............................................................. 44 2.4.3 Device Performance Metrics ..................................................................... 47 1 2.5 Planar Nano-Electronic Devices ...................................................................... 49 2.5.1 Side-Gated Transistor ................................................................................ 49 2.5.2 Self-Switching Diode ................................................................................ 50 References ................................................................................................................ 53 3 Experimental Techniques ........................................................................................ 64 3.1 Thin-Film Deposition ....................................................................................... 64 3.1.1 Sputter Deposition ..................................................................................... 64 3.1.2 Atomic Layer Deposition .......................................................................... 67 3.1.3 Anodisation ............................................................................................... 69 3.2 Electron-Beam Lithography ............................................................................. 73 3.2.1 EBL System ............................................................................................... 73 3.2.2 Electron-Solid Interactions ........................................................................ 77 3.3 Thin-Film Characterisation .............................................................................. 78 3.3.1 Atomic-Force Microscope......................................................................... 78 3.3.2 X-Ray Diffraction ..................................................................................... 81 3.4 Electrical Characterisation of Devices ............................................................. 83 3.4.1 Electrical Characterisation of Thin-Film Transistors ................................ 84 3.4.2 Electrical Characterisation of Resistance Random Access Memory ........ 87 References ................................................................................................................ 89 4 Tuning the Electrical Properties of ZnO Thin-Film Transistors.............................. 93 4.1 Introduction ...................................................................................................... 93 4.2 Experiment ....................................................................................................... 94 4.3 Results and Discussion ..................................................................................... 95 4.3.1 Temperature-Dependence Assessment ...................................................... 95 4.3.2 Time-Dependence Assessment .................................................................. 99 4.3.3 Influence of Annealing ............................................................................ 101 4.3.4 Stability Assessment ................................................................................ 102 4.4 Conclusions .................................................................................................... 103 2 References .............................................................................................................. 104 5 Optimisation of ZnO Thin-Film Deposition Processes ......................................... 109 5.1 Introduction .................................................................................................... 109 5.2 Experiment ..................................................................................................... 111 5.3 Results and Discussion ................................................................................... 112 5.4 Conclusions .................................................................................................... 120 References .............................................................................................................. 121 6 Metal-Oxide Thin-Films for Non-Volatile Memory Applications ........................ 124 6.1 Introduction .................................................................................................... 124 6.2 SnOx Based Memory Devices ........................................................................ 125 6.2.1 Experiment .............................................................................................. 126 6.2.2 Results and Discussion ............................................................................ 127 6.3 Resistive Switching in Anodic Oxide Films .................................................. 132 6.3.1 Experiment .............................................................................................. 133 6.3.2 Results and Discussion ............................................................................ 134 6.4 Conclusions .................................................................................................... 138 References .............................................................................................................. 140 7 ZnO-Based Nano-Devices ..................................................................................... 146 7.1 Introduction .................................................................................................... 146 7.2 Fabrication of Nano-Devices.......................................................................... 147 7.3 Results and Discussion ................................................................................... 149 7.3.1 ZnO-Based Side-Gated Transistor .......................................................... 149 7.3.2 ZnO-Based Self-Switching Diode ........................................................... 151 7.3.3 ZnO-Based Planar Inverter...................................................................... 152 7.4 Conclusions .................................................................................................... 153 References .............................................................................................................. 154 3 8 Conclusions and Future Outlook ........................................................................... 158 8.1 Conclusions ...................................................................................................