Light response and adsorption interaction of black phosphorus quantum dots and single-layer graphene phototransistor

Black phosphorus quantum dots (BPQDs) are synthesized and combined with graphene sheet. The fabricated BPQDs/graphene devices are capable of detecting visible and near infrared radiation. The adsorption effect of BPQDs in graphene is clarified by the relationship of the photocurrent and the shift of the Dirac point with different substrate. The Dirac point moves toward a neutral point under illumination with both SiO₂/Si and Si₃N₄/Si substrates, indicating an anti-doped feature of photo-excitation. To our knowledge, this provides the first observation of photoresist induced photocurrent in such systems. Without the influence of the photoresist the device can respond to infrared light up to 980 nm wavelength in vacuum in a cryostat, in which the photocurrent is positive and photoconduction effect is believed to dominate the photocurrent. Finally, the adsorption effect is modeled using a first-principle method to give a picture of charge transfer and orbital contribution in the interaction of phosphorus atoms and single-layer graphene.