Scanning Tunneling Microscopy Studies On The Electronic Structure Of Doped Defects In Black Phosphorus Surfaces

Black phosphorus(BP),a layered allotropic form of elemental phosphorus,has attracted increasing attention from researchers because of its layer-dependent bandgap over a wide energy range from the visible up to the infrared light.Understanding the local electronic properties of individual defects and dopants in black phosphorus is great importance for both fundamental research and technological applications.In this thesis,by utilizing a combination of scanning tunneling microscopy/spectroscopy(STM/STS),density functional theory calculations and model simulations,we characterize the electronic properties of single atomic P vacancy,substitution dopant(Co)and adsorption dopant(Fe cluster)on BP surface.Co-doped BP is atomic substitution doping,similar to the intrinsic vacancy of BP,which induces a strongly anisotropic electron scattering,known as Friedl Oscillation,around the defect.This causes a highly delocalized dumbbell-like contrast in the STM image.By contrast,Fe-doped BP is atomic adsorption doping and this introduces a gap state in the BP band gap because of the weak couplings between Fe and BP.As a result,the charge state of the Fe atoms can be reversibly switched by manipulating the bias voltage through the tip-induced band bending(TIBB).The rich and intriguing properties shown by the defects on BP surface suggest their potential applications in protootype storage electronic devices and in model atomic catalysis.