Twisted bilayer graphene shedding light on new generation photodetector

MAR . 22 2016
Peking University, March. 22, 2016: Graphene has been a star material since it was born. Until now most researches have focused on graphene’s application in electronic area. In recent years scientists also draw their attention to its use in ultrafast photodetection. This is attributed to graphene’s impressive optical properties: it has surprisingly high carrier mobility, and it shows ultra-short photoresponse time.
However, it is not easy to achieve high responsivity and selectivity with graphene detector. The challenge is graphene’s weak and broadband absorption of photons.Now Professor Liu Zhongfan and Professor Peng Hailin’s group has found a way to address this problem, giving insight into making sensitive graphene photodetector.
Their solution relies on twisted bilayer graphene (tBLG), a two-layer graphene structure with one layer rotated by a certain angle relative to the other. This new structure introduces a physical feature called van Hove singularity (VHS). The teams finds out that these VHSs enhance photocurrent generation in tBLG for up to 80 times, which means great improvement in photoresponsivity. Moreover, when researchers rotate one graphene layer with different angles, the tBLG shows preference for different wavelengths of light. This makes it possible to develop high-selectivity photodetectors.

Schematic illustration of a tBLG photodetection device
From Jianbo Yin et al.; “Selectively enhanced photocurrent generation in twisted bilayer graphene with van Hove singularity”, Nature communications. 2016, 7, 10699. DOI: 10.1038/ncomms10699.
Their findings are published in Nano Letter and Nature Communications. The team hopes their work could give new ideas for designing unconventional graphene photodetectors.
These projects are supported by National Basic Research Program of China, the National Natural Science Foundation of China, the National Program for Support of Top-Notch Young Professionals and Beijing Municipal Science and Technology Commission.
For the original Nano Letter and Nature Communicationspapers, please click:

Written By: Li Yike
Edited By: Xiao Yunyun
Source: College of Chemistry and Molecular Engineering