Interface Electronic Structure Of PTCDI And Its Derivatives With Black Phosphorus

Black phosphorus(BP)has attracted extensive attention due to its excellent and unique structure and properties.However,the surface of BP is easily oxidized and its performance is degraded,which has become an urgent problem to be solved on the road to practical application of BP.In this dissertation,the feasibility of vacuum deposition of organic molecular PTCDI and its derivatives(PTCDIs)thin films on BP surface against air oxidation was explored.The electronic structure,film morphology and passivation mechanism of PTCDIs/BP interface were systematically analyzed by photoelectron spectroscopy(PES),atomic force microscopy(AFM)and density functional theory(DFT)calculations.The conclusions are as follows:(1)The adsorption of PTCDI,PTCDI-Ph and PTCDI-C8 molecules did not affect the intrinsic electronic structure of BP,and the shift of the vacuum energy level is constituted by the interface dipole and the band bending on the PTCDIs side.A large electron injection barrier and hole injection barrier are formed at the interface between PTCDIs and BP,and the energy level arrangement of the PTCDIs/BP interface is Straddling Gap,which proves that PTCDIs can act as a blocking layer to prevent the outflow of carriers in BP.(2)PTCDI,PTCDI-Ph and PTCDI-C8 molecules were physically adsorbed on the surface of BP.The X-ray Photoelectron Spectroscopy results showed that the chemical environment of various atoms changed as a whole during the deposition of PTCDIs,but the relative peak positions between different atoms remained unchanged,and the intramolecular chemical bonds did not change.AFM morphology study showed that PTCDIs molecules were all condensed to form films on the surface of BP,and the different substituents resulted in different film morphologies.Within the experimental thickness(4.8 nm),the growth pattern of PTCDI and PTCDI-C8 molecules on the BP surface is Frankvan der Merwe,while that of the PTCDI-Ph molecules is Stranski-Krastanov.(3)PTCDI,PTCDI-Ph and PTCDI-C8 molecular layers have good passivation effect on BP.The PES and AFM results showed that PTCDI had the best passivation effect after 10 days of exposure in air,and the intrinsic electronic structure and chemical properties of the underlying BP were effectively protected.DFT calculations show that the total amount of electrons transferred from BP to adsorbed oxygen molecules in the presence of PTCDI molecules is reduced from 1.213 e/molecule to 0.208 e/molecule,effectively preventing the formation of surface phosphorus oxides.