Orateur
Description
The quantum Hall resistance standard is a key element for the dissemination of electrical units within the International System of Units (SI). Currently, the realization of this resistance standard at the best level of uncertainty $\left(10^{-9}\right.$ in relative value) mainly relies on the use of GaAs-based quantum Hall effect (QHE) devices , which requires demanding operating conditions, namely high magnetic induction $(B=10 \mathrm{~T})$, low temperature $(T=1.5 \mathrm{~K})$, and low measurement current $(I<100 \mu \mathrm{A})$. With the goal to obtain easier-to-implement quantum Hall resistance standard, graphene on $\mathrm{SiC}(\mathrm{G} / \mathrm{SiC})$ is promising as it has shown QHE in much more relaxed conditions (respectively at $3.5 \mathrm{~T}, 10 \mathrm{~K}$ and $0.5 \mathrm{~mA}$ ) without degrading the level of accuracy[1]. However, the control of doping in G/SiC to achieve the emergence of the quantization of the QHE at low magnetic field is still a major challenge.
In this work, we have explored molecular doping in $\mathrm{G} / \mathrm{SiC}$, following precursor works using F4-TCNQ molecule as a stable electron acceptor under ambient conditions [2, 3]. We study the thickness effect of the spacer layer - between the graphene and the dopant layer - on the graphene carrier concentration. Our preliminary results indicate different doping regimes depending on the spacer layer thickness (50 $\mathrm{nm}$ to $500 \mathrm{~nm}$ ), which strongly influences the carrier density and mobility, as well as their temperature dependence. Importantly, we achieved hole density as low as $3.7 .10^{10} \mathrm{~cm}^{-2}$ at $T=5 \mathrm{~K}$, while mobility is $21000 \mathrm{~cm}^{2} \mathrm{~V}^{-1} \mathrm{~s}^{-1}$. Our work aims to provide a simple, reliable and reproducible method to engineer graphene devices with the electronic desired properties.
| Affiliation de l'auteur principal | LNE/C2N |
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