Tomáš Šikola - Electronic transport properties of graphene doped by gallium

Описание: This talk was part of the Workshop “Modeling of Crystalline Interfaces and Thin Film Structures: A Joint Mathematics-Physics Symposium” held November 11 - 15, 2019 at the ESI.

In this work we present the effect of low dose gallium (Ga) deposition (4ML) performed in UHV (10−7 Pa) on electronic doping and charge carrier scattering in graphene grown by chemical vapor deposition. In situ graphene transport measurements performed with a graphene field-effect transistor structure show that at low Ga coverages a graphene layer tends to be strongly n-doped with an efficiency of 0.64 electrons per one Ga atom, while the further deposition and Ga cluster formation results in removing electrons from graphene (less n- doping) [1]. These experimental results are supported by density functional theory (DFT) calculations and explained as a consequence of distinct interaction between graphene and Ga atoms in case of individual atoms, layers, or clusters. We will present application of DFT for calculations of Ga atom clustering on graphene. According to DFT simulations, gallium starts to form stable clusters from three atoms. However, when the van der Waals correction is involved, a parallel geometry up to size of four atoms is preferred. This leads to an increase of absolute values of doping of graphene by electrons from Ga atoms. In addition, we will show that gallium atoms can diffuse along the graphene sheet across a small diffusion barrier of 0.11 eV. This barrier can be additionally reduced by application of external electric field, which was simulated by ionization of the simulated structure. The work is a joint collaboration with David Nezval, Miroslav Barto\v{s}\'{i}k, Jind\v{r}ich Mach, Jakub Piastek, Pavel Proch\'{a}zka, Vojt\v{e}ch \v{S}varc, Miroslav Kone\v{c}n\'{y},
The work is a joint collaboration with David Nezval, Miroslav Barto\v{s}\'{i}k, Jind\v{r}ich Mach, Jakub Piastek, Pavel Proch\'{a}zka, Vojt\v{e}ch \v{S}varc, and Miroslav Kone\v{c}n\'{y}.
References

[1] J. Mach, P. Proch\'{a}zka, M Barto\v{s}\'{i}k, D. Nezval, J. Piastek, J. Hulva, V. \v{S}varc, M. Kone\v{c}n\'{y}, L. Kormo\v{s}, and T. \v{S}ikola, Electronic transport properties of graphene doped by gallium. Nanotechnology
28 (2017), 415203.