III-VI metal chalcogenide semiconductor nanosheets and heterostructures
This thesis presents an investigation into the properties of III-VI metal chalcogenide semiconductor nanosheets and demonstrates their capability to enhance graphene-based optoelectronics. Strong quantization effects and tunable near-infrared-to-visible (NIR-to-VIS) photoluminescence emission are re...
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| Format: | Thesis (University of Nottingham only) |
| Language: | English |
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2016
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| Online Access: | https://eprints.nottingham.ac.uk/33512/ |
| _version_ | 1848794647873191936 |
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| author | Mudd, Garry William |
| author_facet | Mudd, Garry William |
| author_sort | Mudd, Garry William |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | This thesis presents an investigation into the properties of III-VI metal chalcogenide semiconductor nanosheets and demonstrates their capability to enhance graphene-based optoelectronics. Strong quantization effects and tunable near-infrared-to-visible (NIR-to-VIS) photoluminescence emission are reported in mechanically exfoliated crystals of gamma-rhombohedral semiconducting InSe at room temperature. The optical properties of InSe nanosheets differ qualitatively from those reported for transition metal dichalcogenides and indicate a crossover from a direct-to-indirect band gap semiconductor when the InSe nanosheet thickness, L, is reduced to a few nanometres, corresponding to the emergence of a ‘Mexican hat’ energy dispersion for the valence band.
At low temperature, radiative recombination of photoexcited carriers bound at native donors and acceptors in nominally undoped InSe nanosheets is observed. A two-dimensional hydrogenic model for impurities is used to describe the increase in binding energy with decreasing L and reveals a strong sensitivity of the binding energy on the position of the impurities within the nanolayer.
The application of a magnetic field, B, perpendicular to the plane of InSe nanosheets induces a marked change of the observed optical spectrum. A transfer of intensity from a low-to-high energy component at high B corresponds to an indirect-to-direct band gap crossover, which arises from the Landau quantisation of the in-plane carrier motion and crossover between hole cyclotron orbits centred on closed edges of the valence band.
High broad-band (NIR-to-VIS) photoresponsivity is achieved in mechanically formed InSe–graphene van der Waals heterostructures, which exploit the broad-band transparency of graphene, the direct bandgap of InSe, and the favourable band line up of n-InSe with graphene. The photoresponse is dependent on the electron transit time through the InSe layer, as evaluated by a semiclassical model. |
| first_indexed | 2025-11-14T19:19:31Z |
| format | Thesis (University of Nottingham only) |
| id | nottingham-33512 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-14T19:19:31Z |
| publishDate | 2016 |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-335122025-02-28T11:48:44Z https://eprints.nottingham.ac.uk/33512/ III-VI metal chalcogenide semiconductor nanosheets and heterostructures Mudd, Garry William This thesis presents an investigation into the properties of III-VI metal chalcogenide semiconductor nanosheets and demonstrates their capability to enhance graphene-based optoelectronics. Strong quantization effects and tunable near-infrared-to-visible (NIR-to-VIS) photoluminescence emission are reported in mechanically exfoliated crystals of gamma-rhombohedral semiconducting InSe at room temperature. The optical properties of InSe nanosheets differ qualitatively from those reported for transition metal dichalcogenides and indicate a crossover from a direct-to-indirect band gap semiconductor when the InSe nanosheet thickness, L, is reduced to a few nanometres, corresponding to the emergence of a ‘Mexican hat’ energy dispersion for the valence band. At low temperature, radiative recombination of photoexcited carriers bound at native donors and acceptors in nominally undoped InSe nanosheets is observed. A two-dimensional hydrogenic model for impurities is used to describe the increase in binding energy with decreasing L and reveals a strong sensitivity of the binding energy on the position of the impurities within the nanolayer. The application of a magnetic field, B, perpendicular to the plane of InSe nanosheets induces a marked change of the observed optical spectrum. A transfer of intensity from a low-to-high energy component at high B corresponds to an indirect-to-direct band gap crossover, which arises from the Landau quantisation of the in-plane carrier motion and crossover between hole cyclotron orbits centred on closed edges of the valence band. High broad-band (NIR-to-VIS) photoresponsivity is achieved in mechanically formed InSe–graphene van der Waals heterostructures, which exploit the broad-band transparency of graphene, the direct bandgap of InSe, and the favourable band line up of n-InSe with graphene. The photoresponse is dependent on the electron transit time through the InSe layer, as evaluated by a semiclassical model. 2016-07-20 Thesis (University of Nottingham only) NonPeerReviewed application/pdf en arr https://eprints.nottingham.ac.uk/33512/1/GWMUDD_Thesis_2016.pdf Mudd, Garry William (2016) III-VI metal chalcogenide semiconductor nanosheets and heterostructures. PhD thesis, University of Nottingham. Indium Selenide III-VI metal chalcogenides graphene InSe heterostructures van der Waals crystals. |
| spellingShingle | Indium Selenide III-VI metal chalcogenides graphene InSe heterostructures van der Waals crystals. Mudd, Garry William III-VI metal chalcogenide semiconductor nanosheets and heterostructures |
| title | III-VI metal chalcogenide semiconductor nanosheets and heterostructures |
| title_full | III-VI metal chalcogenide semiconductor nanosheets and heterostructures |
| title_fullStr | III-VI metal chalcogenide semiconductor nanosheets and heterostructures |
| title_full_unstemmed | III-VI metal chalcogenide semiconductor nanosheets and heterostructures |
| title_short | III-VI metal chalcogenide semiconductor nanosheets and heterostructures |
| title_sort | iii-vi metal chalcogenide semiconductor nanosheets and heterostructures |
| topic | Indium Selenide III-VI metal chalcogenides graphene InSe heterostructures van der Waals crystals. |
| url | https://eprints.nottingham.ac.uk/33512/ |