Near-infrared Emission from Defect States in Few-layer Phosphorene (1706.10189v1)

Abstract: Atomically-thin films of phosphorene (also known as black phosphorus) are a low dimensional optical material with direct exciton emission, whose wavelength is tunable by controlling the number of layers. In addition to this excitonic emission, recent works revealed the existence of emissions from defect states and described new methods to manipulate them. Monolayer phosphorene exhibits emission from localized defect states at wavelengths near 920 nm. Increasing the number of layers should shift the defect emission to longer wavelengths, enabling the material to span a broader spectral range. However, defect emission from few-layer phosphorene has not yet been reported. In this paper, we demonstrate the existence of a new class of near-infrared emission from defect states in few-layer phosphorene. Photoluminescence measurements show a bright emission around 1240 nm with a sublinear growth of emission intensity when the excitation intensity is linearly increased, confirming the defect-based nature of this emission. From time-resolved lifetime measurements we determine an emission lifetime of 1.1 ns, in contrast with the exciton lifetime from phosphorene, which has been previously reported to be in the range of a few hundred picoseconds. This work shows that phosphorene defects can act as a source of infrared light with potential applications in optoelectronics.