The physical limitations of miniaturization of the traditional silicon-based electronic devices have motivated growing interest in molecular electronics due to its promising potential in transcending Moore's Law. Since the concept of molecular rectifier was first proposed by Ratner and Aviram in 1974, a lot of efforts have been devoted to realizing nondestructive electrical contacts to the individual or ensemble molecules, such as liquid metal contact, break junctions, cross wire junctions, etc. Among them, rolled-up nanotechnology is compatible with the conventional photolithography processes and can provide an efficient strategy to fabricate fully integrated functional molecular devices on a chip via an array of damage-free soft contacts. This nanotechnology takes an important step towards implementing the miniaturization of molecular devices and promotes the development of molecular electronics.
In this doctoral thesis, rolled-up nanotechnology is employed to develop functional molecular devices on chips. Enabled by these rolled-up soft contacts, fully integrated molecular rectifiers based on ultrathin molecular heterojunctions are developed for the first time, and they are able to convert alternating current to direct current with frequencies up to 10 MHz. This is also the first time that a nanoscale organic rectifier with an operating frequency exceeding 1 MHz has been fabricated. The remarkable unidirectional current behavior of the molecular devices mainly originates from the intrinsically different surfaces of bottom planar and top microtubular gold electrodes. While the excellent high-frequency response is guaranteed by the charge accumulation in the phthalocyanine molecular heterojunction, which not only improves the charge injection but also increases the carrier density.
Then this rolled-up nanotechnology is further employed to explore multi-functional molecular devices. In this thesis, fully integrated process-programmable molecular devices are achieved for the first time, which can switch between photomultiplication photodiodes and bipolar memristors. The transition depends on the release of mobile ions initially stored in the bottom polymeric electrode and can be controlled by modulating the local electric field at the interface between the ultrathin molecular layer and the bottom electrode. Photogenerated-carrier trapping at a low interfacial electric field leads to photomultiplication with an ultrahigh external quantum efficiency (up to 104%). In contrast, mobile-ion polarization triggered by a high interfacial electric field results in ferroelectric-like memristive behaviour with both remarkable resistive on/off ratios and rectification ratios. The combination of the “soft-contact” enabled by rolled-up nanotechnology and the “ion reservoir” provided by the polymeric electrode opens up a novel strategy for integrating multi-functional molecular devices based on the synergistic electronic-ionic reaction to various stimuli.:List of abbreviations 6
Chapter 1 Introduction 8
1.1 Molecular electronics: a brief history 8
1.2 Motivation: why molecular electronics? 9
1.3 Objectives: developing integrated functional molecular devices 14
1.4 Dissertation structure 15
Chapter 2 Fabrication and characterization methods 17
2.1 Core nanotechnology adopted in this thesis: rolled-up nanomembrane contacts 17
2.2 Fabrications 18
2.2.1 Photolithography 18
2.2.2 Spin-coating 23
2.2.3 Electron-beam deposition 24
2.2.4 Sputter deposition 25
2.2.5 Atomic layer deposition 27
2.2.6 Low-temperature evaporation 28
2.3 Characterizations 30
2.3.1 Atomic force microscopy 30
2.3.2 Photoelectron spectroscopy 32
2.3.3 X-ray diffraction 35
Chapter 3 Integrated molecular rectifiers 37
3.1 Introduction 37
3.2 Construction of the organic heterojunction 39
3.3 Microfabrication of the molecular diode 46
3.4 Origination of the rectification 54
3.5 Frequency performance 61
3.6 Discussion 63
Chapter 4 Integrated process-programmable molecular devices 66
4.1 Introduction 66
4.2 Design and microfabrication of the molecular devices 69
4.2.1 Top tubular metallic electrodes 69
4.2.2 Bottom finger polymer electrodes 71
4.3 Function I: Molecular photomultiplication photodiodes 75
4.3.1 Traditional photodiodes and photomultiplication photodiodes 75
4.3.2 Performance of molecular photomultiplication photodiodes 78
4.3.3 Transition voltage spectroscopy 84
4.4 Function II: Molecular bipolar memristors 86
4.4.1 Ion doping-assisted injection 86
4.4.2 Performance of the molecular bipolar memristors 88
4.4.3 Mechanism of the resistance switching 97
4.5 Mechanism of the electric-field-driven transition 106
4.6 Conclusions 108
Chapter 5 Conclusions and outlook 110
5.1 Conclusions 110
5.1.1 Fully integrated molecular rectifiers 110
5.1.2 Fully integrated process-programmable molecular devices 111
5.2 Outlook 111
5.2.1 Improve the yield of the integrated molecular devices 111
5.2.2 Develop integrated molecular functional devices 112
References 113
List of figures and tables 129
Selbständigkeitserklärung 134
Theses 135
Acknowledgments 138
Research achievements 140
Curriculum-vitae 142
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:80593 |
| Date | 09 September 2022 |
| Creators | Li, Tianming |
| Contributors | Schmidt, Oliver G., Schmidt, Oliver G., Zhu, Feng, Technische Universtität Chemnitz |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/acceptedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | https://doi.org/10.1038/s41467-020-17352-9, https://doi.org/10.1038/s41467-022-30498-y |
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