Nanostructured Materials Group Department of Materials

Nanotube and Graphene DPhil Projects Available

We are always looking for highly talented and motivated students wishing to undertake a PhD (Dphil) in nanomaterial science. Below is a list of current projects on offer, with a focus on 2D materials.

Information about how to apply

UK students:

http://www.materials.ox.ac.uk/admissions/postgraduate/uk.html

EU students

http://www.materials.ox.ac.uk/admissions/postgraduate/eu.html

Overseas students:

http://www.materials.ox.ac.uk/admissions/postgraduate/overseas.html

For further information email: jamie.warner@materials.ox.ac.uk

Projects:

1. Synthesis of large area graphene sheets using chemical vapour deposition for electronic applications

Supervisor: Dr Jamie Warner

The 2D crystalline nature of graphene makes it suitable for large area transparent conducting electrodes and in nanoelectronics. The biggest challenge in synthetic graphene is achieving large single crystals of graphene and uniformity in the layer number on the centimeter scale. We have recently shown how chemical vapour deposition (CVD) can be used to grow centimeter scale continuous films of pure monolayer graphene with graphene crystal grain sizes approaching the millimeter scale. This project will extend this body of work to focus on understanding the growth mechanisms behind CVD grown graphene and then developing approaches to improve the atomic structure and electronic properties. Techniques to transfer the sheets to transparent substrates, such as glass or flexible polymers will be examined and the sheet resistance determined. Nanoelectronic devices such as field effect transistors and Hall bar structures will be fabricated using lithography in order to evaluate the electronic properties of the synthetic graphene. Methods to incorporate dopants into the CVD growth process will be pursued with the aim of improving conductivity. Controlling the number of graphene layers grown by CVD will be investigated. The material produced in this project will underpin a wide range of applications based on graphene and has the potential for significant impact.

2. Sensor Technology Based on Large Area Synthetic Graphene

Supervisor: Dr Jamie Warner

Sensor technology, such as touch screen displays and pressure/strain sensors, will be developed using graphene. The graphene will be synthetic and of large area, produced using metal catalyst assisted chemical vapour deposition. Processing methods for transferring the graphene onto transparent flexible polymer substrates will be developed. This project aims at bringing graphene into application and will utilize recent advances within the group for producing outstanding synthetic graphene material. Optical and electron beam lithography will be used to pattern the graphene and metal electrodes for devices. Interfacing with computer hardware will be undertaken to achieve functioning sensor technology.

3. Atomic Resolution Imaging of Defects and Grain Boundaries in Graphene

Supervisors: Dr Jamie Warner and Prof. Angus Kirkland

Graphene is a 2D crystal only one atom thick and is ideal for studying individual carbon atoms using transmission electron microscopy. This project will focus on understanding fundamental crystal defects in graphene, such as edge dislocations (both glide and shuffle), mono-vacancies and the other non-6 member ring structures that exist in the unique 2D crystal. It will also investigate the grain boundary interface between two graphene domains with the aim of mapping out the unique atomic stitching that occurs. Graphene will be grown by chemical vapour deposition. This project will use Oxford's state-of-the-art aberration-corrected high resolution transmission electron microscope, equipped with a monochromator for the electron beam to give unprecedent spatial resolution at a low accelerating voltage of 80 kV. Advanced image analysis techniques, such as exit-wave reconstruction, and comparison to image simulations will be utilized for a deeper understanding of the atomic structure.

4. Chemical Functionalization of Graphene

Supervisor: Dr Jamie Warner and Dr Kyriakos Porfyrakis

Graphene holds a lot of promise for electronic applications, such as electrically detecting chemical sensing. The large surface area of graphene makes it highly sensitive to doping, which modifies the conductivity. Improving the selectivity of the doping sensitivity requires chemical functionalization of graphene surfaces to produce desired functional groups that are suitable for attaching other molecules, atoms or nanoparticles.

This project will focus on direct chemical reactions involving modification of sp2 carbon bonds within graphene sheets. The modified bonds will be used as reaction sites for the attachment of molecules such as fullerenes or porphyrins. The changes in the conductivity will be monitored using 4-probe electrical measurements and micron scale devices will be fabricated using photolithography. Graphene films up to 4 inches will be grown by chemical vapour deposition on metal catalysts and then transferred onto silicon wafers for further processing. Narrow graphene ribbon devices will be fabricated and utilized as chemical sensors. The ability to modulate the electronic properties of graphene and tailor their sensitivity to doping from different species will open up new areas in chemical sensors and electrical read-out of molecular interactions.

5. Insulating and Semiconducting 2D crystals for electronic applications

Supervisor: Dr Jamie Warner

Graphene is a semi-metal 2D crystal, Boron Nitride (BN) an insulating 2D crystal, and MoS2/WS2 are semiconducting 2D crystals. Realizing the potential of 2D crystals in electronic applications requires all 3 of these variants. We have undertaken years of research in growing graphene crystals by chemical vapour deposition and can now produce high quality materials. However, further improvement is needed to advanced the synthesis of BN and MoS2/WS2 2D crystals to obtain similar quality films. In this project 2D crystals will be synthesized by chemical vapour deposition to produce materials with varying band structure. New synthetic strategies will be developed in order to produce large single crystal structures on a variety of substrates compatible with device processing.

The atomic structure of the new 2D crystals will be characterized using advanced electron microscopy (scanning electron microscopy and transmission electron microscopy). The electronic properties of the new materials will be analysed by fabricating nanoelectronic devices such as transistors. This is a unique opportunity to undertake a project involving new materials synthesis, characterization of the atomic structure, and implementation in nanoelectronic transistor arrays. The project is well integrated into the group's goals by developing new 2D crystals that will have large up-take amongst other researchers for a applications ranging from flexible electronics, pressure sensors, optical detectors, LEDs and solar cells.

6. Graphene electrodes for nanocrystal solar cells

Supervisor: Dr Jamie Warner and Dr Andrew Watt

Graphene is an ideal 2D material for utilization as a transparent conducting electrode in photovoltaics (solar cells). High efficiency photovoltaic devices will require the effective integration of other nanomaterials with graphene to produce hybrid nanosystems. Inorganic nanocrystals such as PbS, ZnSe, TiO2 and Si, have unique semiconducting properties with band gaps that span from the near-IR to UV. This project will focus on synthesizing inorganic nanocrystals using solution-phase chemistry. Control over the shape to tailor spherical, rod and branched structures will be investigated. Variation of surface state morphology will be conducted through various chemical approachs to control the inter-nanocrystal interactions. Synthetic graphene will be produced using chemical vapour deposition. Composite hybrid devices will be fabricated that use synthetic graphene as a working transparent conducting electrode and the inorganic nanocrystal as the active functional nanomaterial.

7. Graphene-based Spintronic Devices

Supervisor: Dr Jamie Warner

Spintronics is an emerging technology that seeks to utilize both the spin and charge of an electron in a device. Graphene is highly suited for this area of research due to its small spin-orbit coupling and low natural abundance of a the C13 isotope. The extremely high electron velocities and moderate spin coherence lifetimes in graphene have the potential for long spin coherence lengths. This project will focus on building devices, such as lateral spin valves that exploit spin and charge properties of graphene. High quality single crystal graphene will be produced using well-established chemical vapour deposition methods within the group. The graphene will then be transferred to silicon wafers for device fabrication using electron beam lithography. Ferromagnetic electrodes will be deposited onto graphene and magnetoresistance measurements performed at cryogenic temperatures in magnetic fields. This project will lay the foundations for future extensions of the work involving manipulation of electron spin in solid-state electronic devices.