Study of Flexoelectricity in Graphene Composite Structures
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Study of Flexoelectricity in Graphene Composite Structures Mohamed Serry and Mahmoud A. Sakr MRS Advances / FirstView Article / August 2016, pp 1 - 7 DOI: 10.1557/adv.2016.547, Published online: 05 August 2016
Link to this article: http://journals.cambridge.org/abstract_S2059852116005478 How to cite this article: Mohamed Serry and Mahmoud A. Sakr Study of Flexoelectricity in Graphene Composite Structures. MRS Advances, Available on CJO 2016 doi:10.1557/adv.2016.547 Request Permissions : Click here
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MRS Advances © 2016 Materials Research Society DOI: 10.1557/adv.2016.547
Study of Flexoelectricity in Graphene Composite Structures Mohamed Serry, Mahmoud A. Sakr Department of Mechanical Engineering, The American University in Cairo, AUC Avenue, 11835, New Cairo, Egypt ABSTRACT This paper introduces the theoretical and experimental investigation of flexoelectric behavior in a graphene composite structure consisting of multilayer CVD-graphene deposited on an ALD-platinum catalyst layer deposited on top of n-silicon substrate. The polarization induced by varying the radius of curvature from 200–1500 mm by applying bending stresses was investigated experimentally. Meanwhile, due to the cluster-growth nature of the ALD-platinum catalyst layer, a strong correlation was observed between the resulting number of graphene layers and the Pt catalyst layer thickness, which subsequently had a strong impact on the induced polarization. A polarization current of up to 7.4 mA was detected when the composite structure was bent through a 600-mm radius of curvature. Residual stresses at the interface of the different layers were estimated experimentally in the order of 85–217 MPa. The effect of thermallyinduced stresses, residual stresses at the interface layers, thickness of graphene layers, and radius of curvature were investigated theoretically using the finite element method (FEM) and firstprinciple analyses. Theoretically, it was confirmed that non-uniform strain results in an appreciable non-uniform graphene band gap opening, in addition to non-uniform change of the band structure across the surface and thickness which results in increasing the potential energy difference between the graphene layers. FEM confirmed that thermally induced strains could further enhance the power output of the device by inducing a flexoelectric current combined with the thermionic response. This is verified by estimating a lattice displacement up to 0.31 Å in response to 2-mW heat flux, which corresponds to an appreciable graphene band opening and a potential energy difference across the graphene layers in the order of 1.23 eV, as estimated by the tight binding model. 1 INTRODUCTION Recently, there has been a growing trend for the usage of graphene in energy conversion applications [1, 2]. However, recent efforts have mainly focused on t
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