Optical Properties Of The Thin Black Phosphorus By Uniaxial Strain

After the single-layer graphene was successfully exfoliated in 2004,because of its the high mobility and high thermal conductivity,graphene have been considered to be with great development potential in the field of optoelectronics.Two dimensional materials have become a research hotspot in the fields of materials,physics,and chemistry.Although the two-dimensional material of graphene has good electric properties,its zero band gap limits its application in the field of optoelectronics.Black phosphorus is a two-dimensional material emerging in recent years.It is the most stable allotrope of phosphorus in the present.Black phosphorus has a honeycomb-like crystal structure,and its unique crystal structure makes black phosphorus exhibit strong anisotropy in different crystal directions.This anisotropy is also manifested in the optical and electrical properties of black phosphorus.The fact that black phosphorus has both a direct band gap and high electron mobility greatly compensates for the drawbacks of other two-dimensional materials such as graphene(no bandgap)and molybdenum disulfide(low mobility),which also makes black phosphorus a promising materials in optoelectronics application.This thesis mainly discusses the optical properties of thin black phosphorus under strain control,and the cellular pleated crystal structure of black phosphorus,so that the photoelectric properties of black phosphorus show anisotropy along the two crystal directions.The Raman spectrum and Photoluminescence spectrum of the thin black phosphorus were studied by applying strain in different crystal directions of black phosphorus.The main contents of this article include:(1)Preparation and characterization of thin black phosphorus samples.Thin black phosphorus samples were prepared by mechanical exfoliation method and were characterized by AFM and Raman spectroscopy.(2)Low-temperature Raman measurement of thin black phosphorus samples.The Raman spectra of the thin black phosphorus from 20 K to 300 K were studied by using 633 nm laser as the excitation source.(3)Strain-controlled Raman spectroscopy and PL spectroscopy measurements.The 532 nm laser was used as the excitation source to study the changes of Raman and PL spectra of black phosphorus after applying different strains on the thin black phosphorus along the ZZ crystal direction.