Professor Subhasis Ghosh | WIN Seminar Series

Описание: On September 20 2018, Subhasis – Professor in the Department of Physics at the School of Physical Sciences, Jawaharlal Nehru University, New Delhi – visited WIN as a part of the WIN Seminar Series.

“Charge Transport in Doped Graphene”

Graphene is considered as one of the most promising materials for future electronics. Extremely high carrier mobility has been achieved. However, zero band gap and difficulty in doping are two issues that limit the successful application of graphene in electronic devices. It is believed that functionalization of graphene with organic molecules could solve both these problems.
First, we present how to dope large area graphene monolayers by trapping organic molecules between graphene and substrate. Combinations of Raman, IR and UV-Vis absorption spectroscopic studies reveal the microscopic origin of n-type and p-type doping which was further corroborated with electrical characteristics of graphene field effect transistor. In second part, a systematic investigation on various possible scattering mechanisms responsible for limiting the carrier mobility in doped graphene on a solid substrate, like SiO2. Correlation between the results obtained from electrical measurements and Raman spectra revealed different scattering mechanisms responsible for deciding the carrier mobility. It has been shown that remote interfacial phonons in SiO2 are responsible for limiting the mobility at room temperature whereas, substrate impurities and Raman active point defects in the graphene lattice are the dominant scatterers for limiting mobility at low temperatures.
Further, we show that monolayer graphene based transistor exhibit suppressed electron conduction compared to hole conduction due to presence of donor impurities which scatter electrons more efficiently. This is explained by the relativistic nature of charge carriers in graphene monolayer and can be reconciled with the fact that in relativistic quantum system scattering cross section depends on sign of scattering potential in contrast to non-relativistic quantum system.

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