Energy Level Alignment and Electron Transport Through Metal/Organic Contacts: From Interfaces to Molecular Electronics

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Springer Science & Business Media, Sep 15, 2012 - Science - 198 pages

In recent years, ever more electronic devices have started to exploit the advantages of organic semiconductors. The work reported in this thesis focuses on analyzing theoretically the energy level alignment of different metal/organic interfaces, necessary to tailor devices with good performance. Traditional methods based on density functional theory (DFT), are not appropriate for analyzing them because they underestimate the organic energy gap and fail to correctly describe the van der Waals forces.

Since the size of these systems prohibits the use of more accurate methods, corrections to those DFT drawbacks are desirable. In this work a combination of a standard DFT calculation with the inclusion of the charging energy (U) of the molecule, calculated from first principles, is presented. Regarding the dispersion forces, incorrect long range interaction is substituted by a van der Waals potential. With these corrections, the C60, benzene, pentacene, TTF and TCNQ/Au(111) interfaces are analyzed, both for single molecules and for a monolayer. The results validate the induced density of interface states model.

 

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Contents

1 General Introduction
1
2 Theoretical Foundation
17
3 Further Developments in IDIS Model
63
4 The IDIS Model at the Molecular Limit
94
5 Results for Various Interfaces C60 Benzene TTF TCNQ and Pentacene over Au111
115
6 General Conclusions and Future Work
159
Appendix A Introduction to Second Quantization
163
Appendix B Different Approximations for a Simple Benzene Model Hybrid Functionals
176
Appendix C Spin Dependent Extension of McWEDA and Hybrid Functionals
189
Curriculum Vitae
195
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