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Photo-induced Doping in Graphene/BN Heterostructures

(a) Optical micrograph of a 2D heterostructure composed of graphene and boron nitride layers contacted by gold electrodes. (b) Optical excitation can lead to stable photo-induced doping in graphene, which show gate-dependent electrical transport with remarkable carrier mobility.

Scientific Achievement
Developed photo-induced doping in van der Waals coupled graphene/BN heterostructures with high carrier mobility.

Significance and Impact
The photo-doping in G/BN could enable novel high-quality graphene electronic devices using a photoresist-free photolithography, where the BN substrate itself acts as the photosensitive media.

The design of stacks of layered materials in which adjacent layers interact by van der Waals forces has enabled the combination of various two-dimensional crystals with different electrical, optical and mechanical properties, and the emergence of novel physical phenomena and device functionality. Feng Wang and colleagues have demonstrated photo-induced doping in van der Waals heterostructures consisting of graphene and boron nitride layers (G/BN). The doping effect arises from microscopically coupled optical and electrical responses of G/BN, including optical excitation of defect transitions in boron nitride, electrical transport in graphene, and charge transfer between boron nitride and graphene. It enables flexible and repeatable writing and erasing of charge doping features in graphene with visible light. Not only does the photo-induced doping maintain the high carrier mobility of G/BN, but it can be used to generate spatially varying doping profiles such as p–n junctions.

This photoinduced ‘modulation’ doping in G/BN heterostructures is qualitatively different from photoinduced effects previously observed in graphene on SiO2, which originates from interfacial charge traps in the amorphous oxide, and it leads to an electron mobility more than an order of magnitude higher and along with superior stability and reversibility. This effect could enable flexible fabrication of novel high-quality graphene devices through controlled light exposure.

L. Ju et al. Nature Nanotech doi:10.1038/NNANO.2014.60 (2014)