Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/121348
Title: GRAPHENE ON FUNCTIONAL SUBSTRATE
Authors: ORHAN KAHYA
Keywords: Graphene, P(VDF-TrFE), Ferroelectric, Polymer, Sheet Resistance, SrTiO3
Issue Date: 21-Aug-2014
Source: ORHAN KAHYA (2014-08-21). GRAPHENE ON FUNCTIONAL SUBSTRATE. ScholarBank@NUS Repository.
Abstract: In this dissertation, we have explored use of various functional substrates for electronic applications of graphene. We have used SrTiO3 to have large doping level for low voltage electronics. However unexpected interface effects such as anti-ferroelectric type hysteresis and decreased doping constantly limit the doping level. We have demonstrated that use of ultra- thin hydrophobic octyltrichlorosilane substrates successfully reverse unexpected and undesired anti-ferroelectric hysteresis. P(VDF-TrFE) polymeric gate dielectric is later used both as a substrate and top gate (depending on the thickness of the film) for low sheet resistance applications. We choose this material due to its high remnant polarization. However major challenge is to overcome stability issues which are an area that was not explored previously. We have found that the stability depends on various factors such as flatness of the substrate, purity of the interface, and quality of the graphene. By using other 2D materials such as WS2 and h-BN to enhance all the three properties of graphene. Interestingly, we have found an anomalous doping effect of unpolarized P(VDF-TrFE) films on graphene leading to reduction of sheet resistance. This effect allowed us to investigate the use of graphene as a growth layer for polymer films. Results show that one atom thick graphene layer on SiO2 drastically change the surface morphology of the P(VDF-TrFE) films. Piezo-response force microscopy measurements show total shift of the hysteresis curves which is in literature speculated by existence of a self-polarized polymer layer at the substrate vicinity. Finally, we have investigated both PET and self-standing P(VDF-TrFE) substrates which enables flexible and transparent electronic applications such as touchscreens, nanogenerators, acoustic actuators.
URI: http://scholarbank.nus.edu.sg/handle/10635/121348
Appears in Collections:Ph.D Theses (Restricted)

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