Selectively enhanced photocurrent generation in twisted bilayer graphene with van Hove singularity.

Jianbo Yin,Xiao Sun,Li Lin,Yulin Chen,Han Peng,Zhenjun Tan,Ai Leen Koh,Huan Wang,Lei Liao,Zhongfan Liu,Hailin Peng

doi:10.1038/ncomms10699

Abstract

Graphene with ultra-high carrier mobility and ultra-short photoresponse time has shown remarkable potential in ultrafast photodetection. However, the broad and weak optical absorption (∼2.3%) of monolayer graphene hinders its practical application in photodetectors with high responsivity and selectivity. Here we demonstrate that twisted bilayer graphene, a stack of two graphene monolayers with an interlayer twist angle, exhibits a strong light–matter interaction and selectively enhanced photocurrent generation. Such enhancement is attributed to the emergence of unique twist-angle-dependent van Hove singularities, which are directly revealed by spatially resolved angle-resolved photoemission spectroscopy. When the energy interval between the van Hove singularities of the conduction and valance bands matches the energy of incident photons, the photocurrent generated can be significantly enhanced (up to ∼80 times with the integration of plasmonic structures in our devices). These results provide valuable insight for designing graphene photodetectors with enhanced sensitivity for variable wavelength.

Highlights

Graphene with ultra-high carrier mobility and ultra-short photoresponse time has shown remarkable potential in ultrafast photodetection
Structure and Raman spectra. twisted bilayer graphene (tBLG) samples were grown on copper foil via chemical vapour deposition (CVD) method and transferred to heavily doped Si substrate, which was capped with 90 nm SiO2
The interlayer twist angle can be measured from the relative misalignment of the straight edges, which is consistent with the observation by transmission electron microscopy (TEM) (Supplementary Fig. 1 and Supplementary Note 1). tBLG domains with different twist angles can be readily obtained in our samples (Fig. 1d), which provide a platform for the study of y-dependent light–matter interactions

Summary

Introduction

Graphene with ultra-high carrier mobility and ultra-short photoresponse time has shown remarkable potential in ultrafast photodetection. When the energy interval between the van Hove singularities of the conduction and valance bands matches the energy of incident photons, the photocurrent generated can be significantly enhanced (up to B80 times with the integration of plasmonic structures in our devices) These results provide valuable insight for designing graphene photodetectors with enhanced sensitivity for variable wavelength. The rapid cooling process of photoexcited carriers (Bpicoseconds) in the monolayer graphene results in a quick annihilation of photoelectrical signal in the electric circuit[5,6,7,8,9,10,11,12] These advantages of the monolayer graphene facilitate its applications associated with ultrafast photodetection, such as high-speed optical communications[13,14,15,16,17] and terahertz oscillators[18]. We report that the VHSs in tBLG leads to a prominent photocurrent enhancement of tBLG photodetectors with a wavelength selectivity under incident light irradiation

Methods

Results

Conclusion