RESUMO
We demonstrate a graphene-MoS2 architecture integrating multiple field-effect transistors (FETs), and we independently probe and correlate the conducting properties of van der Waals coupled graphene-MoS2 contacts with those of the MoS2 channels. Devices are fabricated starting from high-quality single-crystal monolayers grown by chemical vapor deposition. The heterojunction was investigated by scanning Raman and photoluminescence spectroscopies. Moreover, transconductance curves of MoS2 are compared with the current-voltage characteristics of graphene contact stripes, revealing a significant suppression of transport on the n-side of the transconductance curve. On the basis of ab initio modeling, the effect is understood in terms of trapping by sulfur vacancies, which counterintuitively depends on the field effect, even though the graphene contact layer is positioned between the backgate and the MoS2 channel.
RESUMO
One fundamental challenge in biophysics is to understand the connection between protein dynamics and its function. Part of the difficulty arises from the fact that proteins often present local atomic motions and collective dynamics on the same time scales, and challenge the experimental identification and quantification of different dynamic modes. Here, by taking lyophilized proteins as the example, we combined deuteration technique and neutron scattering to separate and characterize the self-motion of hydrogen and the collective interatomic motion of heavy atoms (C, O, N) in proteins on the pico-to-nanosecond time scales. We found that hydrogen atoms present an instrument-resolution-dependent onset for anharmonic motions, which can be ascribed to the thermal activation of local side-group motions. However, the protein heavy atoms exhibit an instrument-resolution-independent anharmonicity around 200 K, which results from unfreezing of the relaxation of the protein structures on the laboratory equilibrium time (100-1000 s), softening of the entire bio-macromolecules.
