Stabilizing ultra-thin black phosphorus with <i>in-situ</i>-grown 1 nm-Al2O3 barrier

Abstract

Exfoliated black phosphorus is a 2D semiconductor with promising properties for electronics, spintronics, and optoelectronics. Nevertheless, its rapid degradation in air renders its integration and use in devices particularly challenging—even more so for smaller thicknesses for which the degradation rate is tremendously enhanced. In order to effectively protect the thinnest flakes, we present here an approach based on an in-situ dielectric capping to avoid all contact with air. Optical microscopy, Raman spectroscopy, and atomic force microscopy studies confirm that 1 nm of Al2O3 efficiently passivates exfoliated black phosphorus (below 5 layers) on Si/SiO2 substrates. Such an ultrathin and transparent passivation layer can act as a tunnel barrier allowing for black phosphorus devices processing without passivation layer removal.