TAILIEUCHUNG - A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy

In ME it is hard to distinguish between expenditure on research and development and the costs incurred for the current output. The reason is that in a process with a high share of made-to-measure products, some research and a lot of development may be undertaken in connection with special orders. That is especially the case for small and medium-sized firms. Thus it is true that the available figures for research and development in ME do not reflect all the efforts taken by firms to find new technical solutions and to optimize products as well as clients’ processes. However, all of. | MECHANICAL AND ELECTRICAL PROPERTIES OF GRAPHENE SHEETS A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Joseph Scott Bunch May 2008 2008 Joseph Scott Bunch MECHANICAL AND ELECTRICAL PROPERTIES OF GRAPHENE SHEETS Joseph Scott Bunch Ph. D. Cornell University 2008 This thesis examines the electrical and mechanical properties of graphene sheets. We perform low temperature electrical transport measurements on gated quasi-2D graphite quantum dots. In devices with low contact resistances we use longitudinal and Hall resistances to extract a carrier density of 2-6 x 1011 holes per sheet and a mobility of 200-1900 cm2 V-s. In devices with high resistance contacts we observe Coulomb blockade phenomena and infer the charging energies and capacitive couplings. These experiments demonstrate that electrons in mesoscopic graphite pieces are delocalized over nearly the whole graphite piece down to low temperatures. We also fabricate nanoelectromechanical systems NEMS from ultra thin graphite and graphene by mechanically exfoliating thin sheets over trenches in SiO2. Vibrations with fundamental resonant frequencies in the MHz range are actuated either optically or electrically and detected optically by interferometry. We demonstrate room temperature charge sensitivities down to 2x10-3 e Hz . The thinnest resonator consists of a single suspended layer of atoms and represents the ultimate limit of a two dimensional NEMS. In addition to work on doubly clamped beams and cantilevers we also investigate the properties of resonating drumheads which consist of graphene sealed microchambers containing a small volume of trapped gas. These experiments allow us to probe the membrane properties of single atomic layers of graphene. We show .

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