14:00 〜 14:15
▲ [15p-A33-4] Signature of individual Gas Molecules Absorbed on Graphene
キーワード：van der Waals interaction, CO2 gas sensing
van der Waals (vdW) interaction plays a central role in molecules adsorption on to a surface. External tuning of this interaction is crucial to bring out the desirable features and functionalities in surface science. The charge fluctuations associated with the molecules adsorption is electro-dynamically correlated with the charge fluctuations in the adsorbed surface, which can be modified external electric field. Electronically, the graphene is an exceptionally low-noise material and the charge transfer between the graphene and the gas molecules can be accurately traced from the Dirac point monitoring under a range of electric field. Thus, physisorption of gas molecules on to the graphene is a unique platform to explore the tuning of vdW interaction in order to identify the individual gas molecules.
The tunable charge transfer of the vdW complex, if any, could be measured as the easily detectable doping concentration in graphene. Hence, to verify the theory, we measure doping concentrations, nd, in graphene with adsorptions formed at different VT . Fig. 1A illustrates the device and measurement setup. The doping concentrations are monitored along with the time (Fig. 2B), the values are extracted from gate modulation curves. At VT from -20 V to 40 V, positively increased doping concentrations uncover the role of adsorbed CO2 molecules as an acceptor. Moreover, deeper doping is observed at larger VT, which is considered as an evidence of the tuned charge transfers. In contrast, VT of -40 V causes negative doping, showing CO2 as a donor. These results demonstrate the tunability of the charge transfer of molecules in the electric field, substantiating the prediction of the first-principles calculations (Fig. 1C). Details will be presented in the conference.
The tunable charge transfer of the vdW complex, if any, could be measured as the easily detectable doping concentration in graphene. Hence, to verify the theory, we measure doping concentrations, nd, in graphene with adsorptions formed at different VT . Fig. 1A illustrates the device and measurement setup. The doping concentrations are monitored along with the time (Fig. 2B), the values are extracted from gate modulation curves. At VT from -20 V to 40 V, positively increased doping concentrations uncover the role of adsorbed CO2 molecules as an acceptor. Moreover, deeper doping is observed at larger VT, which is considered as an evidence of the tuned charge transfers. In contrast, VT of -40 V causes negative doping, showing CO2 as a donor. These results demonstrate the tunability of the charge transfer of molecules in the electric field, substantiating the prediction of the first-principles calculations (Fig. 1C). Details will be presented in the conference.