| dc.contributor |
Craciun, Monica |
|
| dc.creator |
Alkhalifa, Saad Fadhil Ramadhan |
|
| dc.date |
2018-12-03T11:35:45Z |
|
| dc.date |
2018-07-27 |
|
| dc.date.accessioned |
2023-02-23T10:11:05Z |
|
| dc.date.available |
2023-02-23T10:11:05Z |
|
| dc.identifier |
http://hdl.handle.net/10871/34955 |
|
| dc.identifier.uri |
http://localhost:8080/xmlui/handle/CUHPOERS/257368 |
|
| dc.description |
In the last decade, the emerging classes of two-dimensional (2D) materials have been
studied as potential candidates for various sensing technologies, including magnetic
and optoelectronic detectors. Within the quickly growing portfolio of 2D materials,
graphene and semiconducting transition metal dichalcogenides (TMDs) have
emerged as attractive candidates for various sensor applications because of their
unique properties such as extreme thickness, excellent electrical and optical
properties.
In this thesis, I have exploited the unique properties of graphene and TMDs materials
to develop 2D detectors based on field effect transistors for sensing magnetic field
and light. In the first part of this thesis I have shown how the sensitivity of the
properties of 2D materials to their surrounding environment can be turned into a
feature useful to create new types of magnetic field sensors. The first experimental
demonstration of this concept involved the use of graphene deposited on hexagonal
Boron Nitride (h-BN), where the inevitable contaminations occurring at the interface
of the two materials was used to generate a large magnetoresistance (MR) for a
magnetic field sensor. Specifically, I have demonstrated that the contaminations
generate an inhomogeneity in the carrier mobility throughout the channel, which is
a required ingredient for magnetic field sensing based on linear magnetoresistance
(LMR). Another approach I used to make a LMR sensor was by exploiting the large
dependence of the mobility in graphene on the Fermi level position. This concept
was used to generate two parallel electron gases with different mobility by tuning
the Fermi level with an electrical field employing a field effect transistor. The second
part of the thesis is focussed on strategies to reduce the impact of the surrounding
environment on the properties of 2D materials in order to improve their performance.
In particular, I used a 2D heterostructure encapsulated in an ionic polymer to makeii
a highly responsive graphene-TMD photodetector. In this device, the ionic polymer
covering the heterostructure was employed to screen the long-lived charge traps that
limit the speed of such detectors, resulting in a drastic improvement of the detector
responsivity properties. Finally, some of the 2D materials properties are very
sensitive to the configuration of the electronics measurement setup. For example,
effects behind spintronic and valleytronic concepts require non-local electrical
transport measurement. We built a novel circuit that enables the detection of such
effects without concern about the spurious contributions. |
|
| dc.description |
The Higher Committee For Education Development in Iraq (HCED) |
|
| dc.language |
en |
|
| dc.publisher |
University of Exeter |
|
| dc.publisher |
Physics |
|
| dc.rights |
An embargo of 18 months has been applied so that the author may pursue opportunities to publish their research. The embargo is due to lift on 03/Jun/2020. |
|
| dc.rights |
2019-11-19 |
|
| dc.rights |
Object: supervisor letter supporting the 18 months embargo on the thesis of SAAD FADHIL RAMADHAN ALKHALIFA
I am writing this letter to confirm that I wish to place an embargo on the thesis of SAAD FADHIL RAMADHAN ALKHALIFA to be made universally accessible via ORE, the online institutional repository, for a standard period of 18 months. This embargo is because we wish to publish papers using material that is substantially drawn from this thesis. |
|
| dc.subject |
2D material |
|
| dc.subject |
magnetoresistance |
|
| dc.subject |
Graphene |
|
| dc.subject |
optoelectronic |
|
| dc.title |
2D materials for Magnetic and Optoelectronic Sensing Applications |
|
| dc.type |
Thesis or dissertation |
|
| dc.type |
PhD in Physics |
|
| dc.type |
Doctoral |
|
| dc.type |
PhD |
|