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dc.contributor.authorDong, Tianqi
dc.date.accessioned2018-05-09T09:04:17Z
dc.date.available2018-05-09T09:04:17Z
dc.date.issued2018-05-19
dc.date.submitted2018-01-02
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/275642
dc.description.abstractGraphene is a single hexagonal atomic carbon layer. Since its discovery, graphene is emerging as an exciting and promising new material to impact various areas of fundamental research and technology. It has potentially useful electrical properties for device applications such as graphene photodetectors and graphene-based sensors. This thesis focuses on the femtosecond laser processing of graphene from both scientific and industrial points of view. Started from the manufacturing process, a new manufacturing route for graphene devices based on a femtosecond laser system is explored. In this thesis, the graphene ablation threshold was determined in the range of 100 mJ/cm2. In this deposited fluence range, selective removal of graphene was achieved using femtosecond laser processing with little damage to the SiO2 /Si substrate. This finding supports the feasibility of direct patterning of graphene for silicon-substrate field effect transistors (FETs) as the gate dielectric, silicon dioxide is only negligibly removed (2~10 nm) and no damage occurs to the silicon. Beyond the selective removal of graphene, the effects of exposing femtosecond laser pulses on a monolayer of graphene deposited on a SiO2/Si substrate is also studied under subthreshold irradiation conditions. It has been demonstrated that a femtosecond laser can induce defects on exposure. The dependence of the D, G, and 2D Raman spectrum lines on various laser pulse energies was evaluated using Raman Spectroscopy. The I (D)/I (G) ratio was seen to increase with increasing laser energy. The increase in the D’ (intravalley phonon and defect scattering) peak at 1620 cm-1 appeared as defective graphene. These findings provide an opportunity for tuning graphene properties locally by applying femtosecond laser pulses. Applications might include p-n junctions, and the graphene doping process. To explore the power absorption process in graphene and the SiO2/Si substrate, a theoretical model was developed based on the transfer-matrix method. The results revealed that the most significant absorption was in the silicon substrate. The light reflection form each layer was considered. The model shows the temperature oscillations are more significant in the silicon layer compared to the silicon dioxide which can provide a theoretical rationale for the swelling effect observed in the experiments. This model can assist in the choice of laser parameters chosen for future laser systems used in the production of graphene devices.
dc.language.isoen
dc.rightsAll rights reserved
dc.rightsAll Rights Reserveden
dc.rights.urihttps://www.rioxx.net/licenses/all-rights-reserved/en
dc.subjectfemtosecond laser
dc.subjectgraphene
dc.subjectlaser-matter interactions
dc.subjectmicromachining
dc.titleA Study of Infrared Femtosecond Laser Irradiation on Monolayer Graphene on SiO2/Si Substrate
dc.typeThesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridge
dc.publisher.departmentEngineering
dc.date.updated2018-05-08T16:07:38Z
dc.identifier.doi10.17863/CAM.22894
dc.type.qualificationtitlePhD in Engineering
cam.supervisorO'Neill, Bill
cam.thesis.fundingfalse
rioxxterms.freetoread.startdate2019-05-09


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