Electronic and optoelectronic devices based on 2-dimensional crystals
<p>Two dimensional (2D) crystals including graphene and monolayer transition metal dichalcogenides (TMD) such as molybdenum disulphide (MoS<sub>2</sub>) and tungsten disulphide (WS<sub>2</sub>) have attracted widespread attention for both basic scientific interest and p...
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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2017
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| _version_ | 1797102583135862784 |
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| author | Tan, H |
| author2 | Warner, J |
| author_facet | Warner, J Tan, H |
| author_sort | Tan, H |
| collection | OXFORD |
| description | <p>Two dimensional (2D) crystals including graphene and monolayer transition metal dichalcogenides (TMD) such as molybdenum disulphide (MoS<sub>2</sub>) and tungsten disulphide (WS<sub>2</sub>) have attracted widespread attention for both basic scientific interest and potential in device applications. In this thesis, we investigate the electronic and optoelectronic devices based on 2D crystals grown using chemical vapour deposition (CVD).</p> <p>In our study on graphene transistors, we show that surface charge transfer between graphene and vertically stacked WS<sub>2</sub> causes local modulation to doping levels of graphene, and can be further stimulated by photo-irradiation. We demonstrate the formation of an isotype junction in graphene, where two lateral sections of a graphene ribbon contain different dopant concentrations.</p> <p>Ultrathin lateral photodetectors of 2 nm thickness are made by incorporating graphene as electrodes and WS<sub>2</sub> as active semiconductor. We show that graphene is different to conventional metal electrodes due to the finite density of states from the Dirac cones of the valence and conduction bands, which enables modulation of photoresponsivity through electrostatic gating and light input control.</p> <p>We demonstrate photodetectors with laterally spaced graphene electrodes and vertically stacked WS<sub>2</sub>/MoS<sub>2</sub> as active light-adsorbing component, achieving photoresponsivity as high as 2340 A W<sup>-1</sup>. We observe in hybrid WS<sub>2</sub>/MoS<sub>2</sub> photodetector massive enhancements in photogain compared to homobilayer and monolayer devices of MoS<sub>2</sub> or WS<sub>2</sub> due to efficient charge transfer between WS<sub>2</sub> and MoS<sub>2</sub> and long carrier lifetimes. Our results show that high performance photodetectors using all 2D materials can be realized using graphene electrodes and TMD heterostructures with type II band alignment.</p> |
| first_indexed | 2024-03-07T06:07:58Z |
| format | Thesis |
| id | oxford-uuid:ee7ee222-be0a-4d64-a7dd-bbb54da3cb49 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T06:07:58Z |
| publishDate | 2017 |
| record_format | dspace |
| spelling | oxford-uuid:ee7ee222-be0a-4d64-a7dd-bbb54da3cb492022-03-27T11:33:09ZElectronic and optoelectronic devices based on 2-dimensional crystalsThesishttp://purl.org/coar/resource_type/c_db06uuid:ee7ee222-be0a-4d64-a7dd-bbb54da3cb49EnglishORA Deposit2017Tan, HWarner, J<p>Two dimensional (2D) crystals including graphene and monolayer transition metal dichalcogenides (TMD) such as molybdenum disulphide (MoS<sub>2</sub>) and tungsten disulphide (WS<sub>2</sub>) have attracted widespread attention for both basic scientific interest and potential in device applications. In this thesis, we investigate the electronic and optoelectronic devices based on 2D crystals grown using chemical vapour deposition (CVD).</p> <p>In our study on graphene transistors, we show that surface charge transfer between graphene and vertically stacked WS<sub>2</sub> causes local modulation to doping levels of graphene, and can be further stimulated by photo-irradiation. We demonstrate the formation of an isotype junction in graphene, where two lateral sections of a graphene ribbon contain different dopant concentrations.</p> <p>Ultrathin lateral photodetectors of 2 nm thickness are made by incorporating graphene as electrodes and WS<sub>2</sub> as active semiconductor. We show that graphene is different to conventional metal electrodes due to the finite density of states from the Dirac cones of the valence and conduction bands, which enables modulation of photoresponsivity through electrostatic gating and light input control.</p> <p>We demonstrate photodetectors with laterally spaced graphene electrodes and vertically stacked WS<sub>2</sub>/MoS<sub>2</sub> as active light-adsorbing component, achieving photoresponsivity as high as 2340 A W<sup>-1</sup>. We observe in hybrid WS<sub>2</sub>/MoS<sub>2</sub> photodetector massive enhancements in photogain compared to homobilayer and monolayer devices of MoS<sub>2</sub> or WS<sub>2</sub> due to efficient charge transfer between WS<sub>2</sub> and MoS<sub>2</sub> and long carrier lifetimes. Our results show that high performance photodetectors using all 2D materials can be realized using graphene electrodes and TMD heterostructures with type II band alignment.</p> |
| spellingShingle | Tan, H Electronic and optoelectronic devices based on 2-dimensional crystals |
| title | Electronic and optoelectronic devices based on 2-dimensional crystals |
| title_full | Electronic and optoelectronic devices based on 2-dimensional crystals |
| title_fullStr | Electronic and optoelectronic devices based on 2-dimensional crystals |
| title_full_unstemmed | Electronic and optoelectronic devices based on 2-dimensional crystals |
| title_short | Electronic and optoelectronic devices based on 2-dimensional crystals |
| title_sort | electronic and optoelectronic devices based on 2 dimensional crystals |
| work_keys_str_mv | AT tanh electronicandoptoelectronicdevicesbasedon2dimensionalcrystals |