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Title:Substrate-mediated modulations of graphene’s electronic properties
Author(s):Hinnefeld, John H
Director of Research:Mason, Nadya
Doctoral Committee Chair(s):Cooper, S. Lance
Doctoral Committee Member(s):van der Zande, Arend; Weaver, Richard
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:As a perfectly two-dimensional material graphene is exceptionally susceptible to its environment. In particular, the substrate used to support graphene can dramatically alter its electrical and mechanical properties. In this thesis we investigate the interactions between graphene and three distinct types of substrate. First we consider graphene on flexible substrates and the interaction between the strain induced by the substrate and graphene's mechanical integrity. Next we consider ferroelectric substrates, the doping effect of the substrate polarization, and the effects of that polarization on polar adsorbates. Finally we consider topographically patterned substrates and the effects of local variations in strain and doping on the transport properties of graphene. We explore these three topics using optical measurements, atomic force microscopy, and electrical transport measurements. We first find that graphene on flexible substrates undergoes partial mechanical failure when the substrate is stretched, but that graphene is robust to subsequent applications of strain provided the applied strain does not exceed the maximum strain previously applied. This result extends our understanding of graphene's mechanical failure to the non-suspended case, and is directly applicable to technological applications which use graphene as a flexible conductor. We next find that ferroelectric substrates can affect the orientation of polar dopants adsorbed on graphene, and that different orientations contribute different degrees of doping. This result illuminates the subtleties of doping graphene via polarizable mediums. Finally, we find that local variations in doping can create quantum dot regions in graphene which are characterized by quasi-bound states rather than the fully bound states typically found in quantum dot systems. This result provides experimental verification of theoretical predictions and presents an experimental paradigm with which to further explore the interactions between local strain and doping and graphene's electric properties. We discuss these findings in detail, and conclude by proposing future experiments which expand on the results presented here.
Issue Date:2017-02-09
Rights Information:Copyright 2017 John Hinnefeld
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05

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