High-quality Graphene p-n-p junctions through controlled metallic diffusion
Cheng-Hua Liu1,2, Min-Ken, Li3, Shih-Ching, Liou1,2, Fu-Yu Shih1,2, Po-Hsun Ho3, Chun-Wei Chen3, Chi-Te Liang1, Wei-Hua Wang2*
1Department of physics, National Taiwan University, Taipei, Taiwan
2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
3Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan
* presenting author:劉承華, email:tasieio@gmail.com
We report high-quality graphene p-n-p junctions achieved by controlled metallic diffusion. Generally, metal deposition on graphene surface introduces substantial carrier scattering, which undermines the high mobility of intrinsic graphene. However, we discover a weakly functionalized regime with small carrier scattering, while p-type doping of graphene is achieved due to the metal deposition. Consequently, the graphene p-n-p junctions are composed of p-type doping regions with metallic diffusion and an intrinsic graphene region. This technique enables a one-step and resist-free method to fabricate the graphene p-n-p junctions. The high-quality graphene p-n-p junctions is evidenced by a pronounced quantum Hall effect. We also observed insulating temperature dependence over the entire bipolar junction regime, and metal-insulator transition in the unipolar regime of the graphene p-n-p junctions. We performed Raman spectroscopy and confirmed p-type doping regions which corresponding to the metallic diffusion. Finally, we demonstrated high-quality graphene p-n junctions by utilizing same technique but with asymmetric metallic diffusion.

Keywords: graphene, p-n-p junctions, quantum hall effect