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Cyclical Thinning of Black Phosphorus with High Spatial Resolution for Heterostructure Devices
Matthew C Robbins1, Seon Namgung1, Sang-Hyun Oh1
1Department of Electrical and Computer Engineering, University of Minnesota-Twin Cities , 200 Union Street SE, Minneapolis, Minnesota 55455, United States.
Abstract:
A high spatial resolution, cyclical thinning method for realizing black phosphorus (BP) heterostructures is reported. This process utilizes a cyclic technique involving BP surface oxidation and vacuum annealing to create BP flakes as thin as 1.6 nm. The process also utilizes a spatially patternable mask created by evaporating Al that oxidizes to form Al2O3, which stabilizes the unetched BP regions and enables the formation of lateral heterostructures with spatial resolution as small as 150 nm. This thinning/patterning technique has also been used to create the first-ever lateral heterostructure BP metal oxide semiconductor field-effect transistor (MOSFET), in which half of a BP flake was thinned in order to increase its band gap. This heterostructure MOSFET showed an ON/OFF current ratio improvement of 1000× compared to homojunction MOSFETs.
