| The rapid development of the information age will inevitably put forward higher requirements for data computing capabilities and storage reliability.However,silicon-based semiconductor technology has reached its physical limit,and the emergence of atomically thin 2D materials is expected to continue and expand the Moore's law in the“post-silicon”era.The interlayer interaction force of 2D materials is weak van der Waals force,and its unique physical and chemical properties have attracted extensive attention from the semiconductor industry and academia,such as graphene,Mo S2,Bi2Se3,and so on.Since the successful synthesis of ultrathin Bi2O2Se in 2017,this kind of quasi-2D materials high-symmetry oxyselenides has been a research hotspot,its marvelous material properties are conductive to improving the functional performances of next-generation electronic products based on functional devices such as field effect transistors and photodetectors.The preparation method of atomically thin and high-quality epitaxial films is the preconception of further research on Bi2O2Se.Based on Pulsed Laser Deposition and thin film characterization technique,the epitaxial growth mechanism and related physical properties of Bi2O2Se were studied in this thesis.(1)The effects of laser parameters,growth parameters and geometric parameters on the epitaxial growth of Bi2O2Se thin films were researched,and the“growth window”of high-quality Bi2O2Se films was explored.Bi2O2Se can achieve a typical“cube-on-cube”mode of crystal epitaxy growth on Sr Ti O3(001)substrate with Ti O2 termination.According to the crystallinity,the growth temperature“window”is determined to be400°C?510°C,in which the relatively high temperature is beneficial to the migration and arrangement of grains on the substrate surface.At 510°C,the growth mode of the Bi2O2Se thin film realizes a transition from a 3D“island-like”growth mode(film thickness<44 nm)to an“island-like/layered”composite growth mode,and the 147 nm thin film still has a smooth surface.According to the surface topography,a higher growth frequency(9 Hz)can effectively improve the crystal quality and surface topography.The lower energy density(0.5 J/cm~2?1 J/cm~2)can moderately reduce the surface roughness of the films,and the lower oxygen pressure(?1×10-1 Pa)can realize 2D“layered”growth mode of Bi2O2Se on Sr Ti O3(001)substrate.(2)According to the influence of process parameters on film growth,the growth parameters such as growth temperature,growth frequency,energy density,and oxygen pressure were optimized.After systematic experimental exploration,high-quality atomically smooth Bi2O2Se/Sr Ti O3(001)epitaxy film was achieved under the growth conditions of growth temperature of 450°C,growth frequency of 9 Hz,energy density of0.5 J/cm~2,and oxygen pressure of 3.7×10-1 Pa.High-quality Bi2O2Se nucleates along the surface steps of Sr Ti O3 in a 2D growth mode,with a surface roughness as low as 0.28nm,and clear Kessig fringes are observed.(3)Based on high-quality Bi2O2Se films,their chemical bonding properties,electron transport properties and Raman mode were researched.The experiment results of XPS and Raman spectroscopy indicated that the chemical bonding properties and Raman activity of Bi2O2Se nanoplates are accordance with the theoretical values,and the electron transport properties of Bi2O2Se exhibit strong thickness-dependent and temperature-dependent properties. |
PDF Full Text Request