Abstract The search for nanoscale active electronic devices has been an important objective in nanoscience and nanotechnology. In this study, the electronic and transport properties of the benzene-1,4-dithiol-molecule (BDT) and Au-atom-S-benzene-ring-O-(SBO)-Au-atom junctions and the Au-AlN(0001)-Au polar semiconductor junction have been calculated using the first-principles calculation method and a new integrated piecewise thermal equilibrium approach for the current. The current-voltage (I-V) and conductance-voltage (C-V) characteristic curves obtained for the Au-BDT-Au molecular junction agreed reasonably well with experimental ones. The study of Au-BDT-Au identifies that treating Au 5d electrons as core electrons and letting the S end of BDT be bonded to the Au surface directly overestimated the current. Calculated I-V characteristic curve revealed that the asymmetric Au-SBO-Au molecular junction has a pulse-like I-V characteristic curve with dual differential conductance, which resembled well the one observed experimentally. The analysis of the electronic structures showed that this dual differential conductance transport property was due to a subtle charge transfer at the electrode-molecule contacts. The calculated J-V characteristic curve of the Au-Al(0001)-Au junction shows coexistence of ohmic, switching effect and negative differential conductance. The electronic structure calculations show the existence of an intrinsic band tilt due to the polar nature of the AlN(0001) film, which gives rise to an asymmetric transport property of the junction and the presence of hole states at the N-surface side and interface states at the Al-surface side of the AlN film. The bias induced changes of the hole states, interface states and the states of the Al and N ions in central layers in the vicinity of the local chemical potential give rise to the interesting transport property of the Au-AlN(0001)-Au junction.

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This thesis concentrates on advancing the thermal atom layer deposition (ALD) of Sb2Te3 and related multilayered metal chalcogenide thin films. It involves depositing a sub-monolayer of the target compound during each ALD cycle through successive, separated, and self-limiting gas-solid reactions between typically two gaseous reactants. The low deposition temperatures facilitate the creation of unconventional combinations of multilayers in distinct thermodynamic regimes. The well-defined chemical reactions inherent in ALD processes yield layers with ideal stoichiometry, and subsequent heat treatment enhances crystallite size and interface quality. Various methodologies have been explored to manipulate the optical and electrical properties of these thin films, demonstrating the capacity to tune their electrical and thermal transport properties using ALD.:Abstract Table of Contents Acknowledgments 1. Introduction 2. Background and Motivation 2.1. Basic Features of ALD 2.2. ALD of Metal Chalcogenides 2.3. Functional Properties 2.3.1. Photoresponse Effect 2.3.2. Thermoelectric Effect 2.4. State-of-art in Sb2Te3 and Related Multilayers 3. Experimental Techniques 3.1. Thin Films and Devices Preparation 3.2. Transport Property Evaluation 4. Wafer-Scale Growth of Sb2Te3 for Photodetectors 4.1. Microstructure Characterization 4.2. Rectifying Behaviour 4.3. Photoresponse Behaviour 4.4. DFT Calculation 4.5. High Yield Integration 4.6. Conclusion 5. Sb2Te3 with Insulator SbOx Layer 5.1. Microstructure Characterization 5.2. Sb2Te3 with Single-cycle of SbOx 5.3. Sb2Te3 with Multi-cycles of SbOx 5.4. Comparison of TE Performance 5.5. Conclusion 6. Sb2Te3 with Semiconductor Sb2Se3 Layer 6.1. Microstructure Characterization 6.2. Transport Properties 6.3. Thermal Conductivity and zT Values 6.4. Conclusion 7. Conclusion and Outlook Appendix: Wafer-Scale Growth of Sb2Te3 for Photodetectors Bibliography