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11:00-11:30Invited: Emanuel TutucElectron Interaction & Tunneling in Graphene-Based Heterostructures
Co-authors: Kayoung Lee, Stefano Larentis, Babak Fallahazad
Vertical heterostructures consisting of atomic layers separated by insulators can enable novel tunneling devices, and also open a window to explore electron interaction effect in these materials, otherwise not accessible in single layer devices. In this presentation we discuss two examples of vertical heterostructures of atomic layer materials, where electron interaction plays a key role.
We examine the electron transport in graphene-MoS2 heterostructures, fabricated using a layer-by-layer transfer approach. Four point conductivity measurements of the heterostructure as a function of back-gate bias show ambipolar characteristics, with a clear conductivity saturation on the electron branch. Magnetotransport measurements reveal that the conductivity saturation marks the onset of MoS2 being populated with electrons. Most surprisingly, once the MoS2 becomes populated with electrons the carrier density in graphene decreases with increasing gate bias, a finding indicating that the MoS2 electrons have a negative quantum capacitance .
A second type of heterostructure examined here are double bilayer heterostructures, consisting of two bilayer graphene flakes separated by hexagonal boron-nitride. Using the top layer as a resistively detected Kelvin probe we map the chemical potential of the bottom bilayer graphene as a function of electron density, perpendicular magnetic field, and transverse electric field. At zero magnetic field the chemical potential reveals a strongly non-linear dependence on density, with an electric field induced energy gap at charge neutrality. The data allow a direct measurement of the electric field-induced bandgap at zero magnetic field, the orbital Landau level energies, and the broken symmetry quantum Hall state gaps at high magnetic fields . The interlayer transport shows a gate tunable negative differential resistance suggestive of momentum conserving tunneling.
 S. Larentis, et al., “Band Offset and Negative Compressibility in Graphene-MoS2 Heterostructures”,Nano Letters14, 2039 (2014).
 K. Lee, et al., “Chemical potential and quantum Hall ferromagnetism in bilayer graphene mapped using double bilayer heterostructures”, Science 345, 58 (2014).11:30-1145Oral: Andrew O'HaraTheoretical Investigation of the Hafnia-Hafnium Interface in RRAM Devices11:45-12:00Oral: Antonio Claudio Padilha
A Study of TiO Magneli Phases Using Density Functional Theory
Co-authors: Alexandre Reily Rocha, Jorge Osorio-Guillén, Gustavo Dalpian12:00-12:15
Oral: Roderick Melnik
Coupled Dynamic Effects in Shape Memory Alloy Nanostructures
Co-authors: Rakesh Dhote12:15-12:30Oral: Matthew Grayson
p x n Transverse Thermoelectrics: A Novel Paradigm for Thermoelectric Materials
Co-authors: Chuanle Zhou, S. Birner, Yang Tang, Karen Heinselman, Boya Cui12:30-12:45Oral: Stefano RoddaroAchieving Millivolt Range Thermovoltages from a Single Nanowire
Co-authors: Daniele Ercolani, Mian Akif Safeen, Francesco Rossella, Vincenzo Piazza, Francesco Giazotto, Lucia Sorba, Fabio Beltram 12:45-13:00Open