VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Tuesday 6
Poster Session

› 21:00 - 23:00 (2h)
Focused-Laser-Enabled p-n Junctions in Graphene Field-Effect Transistors
Young Duck Kim  1@  , Myung Rae Cho  1@  , Jae-Hyun Lee  1@  , Kim Pilkwang  1@  , Soo Ung Hwang  1@  , Sung Wan Cho  1@  , Myung-Ho Bae  2@  , Jung-Tak Seo  3@  , Yong Seung Kim  4@  , Jae Hong Lee  4@  , Joung Real Ahn  3@  , Seung-Hyun Chun  4@  , Yun Daniel Park  1, *@  
1 : Department of Physics & Astronomy Seoul National University  (SNU)
Department of Physics & Astronomy NS50 Seoul National University -  South Korea
2 : Korea Research Institute of Standards & Science  (KRISS)
267 Gajeong-ro, Yuseong-gu, Daejeon, 305-340, -  South Korea
3 : Department of Physics Sungkyunkwan University  (SKKU)
300 Cheoncheon-dong, Jangan-gu, Suwon, 440-746 -  South Korea
4 : Department of Physics and Graphene Research Institute, Sejong University  (SU)
209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747 -  South Korea
* : Corresponding author

We demonstrate that laser irradiation can induce spatially controllable p-n junctions in graphene devices without additional structures, such as extra local gates, chemical dopants. The focused laser ejects the trapped-charge carriers in the gate oxide and modifies the electrostatic potential of the substrate. We manipulate the location, segment size (0.5 - 10 µm length) and number of p-n junctions in graphene by controlling the electrical gate stress and the position, intensity, irradiation time and wavelength of the focused laser. From the electrical measurements, we observe the effects that range from large shifts in the Dirac voltage (ΔVDirac $\sim$ -60 V) to the double Dirac peak in graphene. Furthermore, from the gate-dependent scanning photocurrent microscopy (SPM), we verify the formation of a p-n-p and p-n-p-n-p junction and observe that the stable and sharp p-n junctions formed by laser irradiation in the graphene due to the deep energy levels ($\sim$ 2.64 eV) of the trap-sites in the gate oxide. Focused-laser manipulation of the induced p-n junctions in graphene with nanoscale floating gates can be applied to produce more stable and efficient graphene-based opto-electronic devices but also in fundamental studies, such as periodic potential-induced quantum behavior in graphene. 

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