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Special Seminar: Electronic Properties & Atomic Scale Microscopy of 2D Nanoscale Materials: Graphene & MoS2

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Jyoti Katoch, University of Central Florida
24 April 2014 from 11:00 AM to 12:00 PM
339 Davey Laboratory
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Novel two dimensional nanoscale materials like graphene and metal dichalcogenides

(MX2) have attracted the attention of the scientific community, due to their rich physics

and wide range of potential applications.

It has been shown that novel graphene based transparent conductors and radiofrequency

transistors are competitive with the existing technologies. Graphene’s properties are

influenced sensitively by adsorbates and substrates. As such not surprisingly, physical

properties of graphene are found to have a large variability, which cannot be controlled at

the synthesis level, reducing the utility of graphene. I have developed atomic hydrogen as

a novel technique to count the scatterers responsible for limiting the carrier mobility of

graphene field effect transistors on silicon oxide (SiO2) and identified that charged

impurities in SiO2 to be the most dominant scatterer. This result enables systematic

reduction of the detrimental variability in device performance of graphene. Such

sensitivity to substrates also gives an opportunity for engineering device properties of

graphene using substrate interaction and atomic scale vacancies. Stacking graphene on

hexagonal boron-nitride (h-BN) gives rise to nanoscale periodic potential, which

influences its electronic graphene. Using state-of-the-art atomic-resolution scanning

probe microscope, I correlated the observed transport properties to the substrate induced

extrinsic potentials.

On the other hand, molybdenum disulfide (MoS2) exhibits thickness dependent bandgap.

Transistors fabricated from single layer MoS2 have shown a high on/off ratio. It is

expected that ad-atom engineering can be used to induce on demand a metalsemiconductor

transition in MoS2. In this direction, I have explored controlled/reversible

fluorination and hydrogenation of monolayer MoS2 to potentially derive a full range of

integrated circuit technology. The in-depth characterization of the samples is carried out

by Raman/photoluminescence spectroscopy and scanning tunneling microscopy.