Preparation And Infrared Photodetection Of Two-dimensional Bi₂Se₃ Flakes And Their Heterojunctions

Infrared photodetector is one of the core components of the modern electronics industry and plays a vital role in many fields such as military defense,industrial production,and medical diagnosis.With the rapid development of information technology and the increasing demand for life,infrared photodetector is developing in the direction of small size,high sensitivity and high flexibility.However,traditional infrared photodetectors are difficult to achieve miniaturization,flexibility,and portability due to complex preparation,low performance,and high brittleness.In recent years,two-dimensional(2D)materials have attracted wide attention from researchers due to their ultrathin thickness,strong light-matter interaction,and excellent mechanical flexibility,which have brought opportunities for the development of next-generation infrared photodetectors.Among 2D materials,the2D Bi₂Se₃ possesses a narrow band gap,high carrier mobility and high environmental stability,which is considered to have great application potential in the field of infrared photodetection.However,current infrared photodetectors based on 2D Bi₂Se₃ flakes still exist many problems such as small material size,high dark current,and low responsivity.Based on these,this paper starts from the preparation of large-size 2D Bi₂Se₃ flakes,then explores its intrinsic infrared photodetection performance,and further optimizes its performance by virtue of van der Waals heterojunction engineering and recombination with photosensitive material.The works are listed as follows:(1)Van der Waals epitaxial growth of large-size 2D Bi₂Se₃ flakes.By using layered mica without suspension bond as substrates to reduce the lateral growth energy barriers,and adjusting the evaporation temperature of precursor to balance the relationship between nucleation density and growth size,the large-size 2D Bi₂Se₃ flakes were obtained via van der Waals epitaxial growth.The lateral size and thickness of an individual 2D Bi₂Se₃ flake can reach up to 0.4 mm and 2 nm,respectively.The TEM characterization results proved that the as-grown 2D Bi₂Se₃ flakes have high crystal quality,which lays the material foundation for the construction of high-performance infrared photodetectors.(2)Research on the infrared photodetection performace of 2D Bi₂Se₃ flakes.The optoelectronic devices based on the as-grown 2D Bi₂Se₃ flakes were fabricated,and their electronic and optoelectronic performaces were systematically investagted.The as-grown2D Bi₂Se₃ flakes demonstrate competitive field-effect mobility of 39.4 cm² V^-1 s^-1 and excellent photoresponse to near-infrared light of 1456 nm.At room temperature,the responsivity and detectivity are 2.7 A W^-1 and 3.3×10¹⁰ Jones,respectively.When the temperature drops to 80 K,the infrared photodetection performance can be increased by about 10 times due to the reduction of Coulomb scattering and phonon scattering.(3)Preparation and infrared photodetection of 2D Bi₂Se₃/WSe₂ van der Waals heterojunction.A type-III broken-gap 2D Bi₂Se₃/WSe₂ van der Waals tunneling heterojunction was designed based on the band structure engineering.And the heterojunction was constructed by mechanical exfoliation and deterministic transfer method.The non-overlapping band structure causes high interfacial barriers,which makes the dark current of the heterojunction reduce to the picoamp level.And the strong interfacial coupling between 2D Bi₂Se₃ flake and 2D WSe₂ flake promotes carriers to enter the channel via quantum tunneling throght the interface barrier,resulting in highly sensitive infrared photodetection.The resultant photodetector exhibits a high on/off ratio of 3.5×10⁴ and a fast response rate of 4 ms.(4)Preparation and infrared photodetection of 2D Bi₂Se₃/Ni-CAT-1 hybird heterojunctions.The 2D layered MOF(Ni-CAT-1)with high infrared absorption efficiency was combined with the high-mobility 2D Bi₂Se₃ flakes.The 2D Bi₂Se₃/Ni-CAT-1 hybird heterojunctions with complementary advantages is preparaed via solution process.The heterojunction exhibited enhanced optical absorption and broadened absorption range,which demonstrated high-performance and broadband infrared photodetection.The responsivity and detectivity of the 2D Bi₂Se₃/Ni-CAT-1 hybird heterojunction to near-infrared light 1500 nm can reach up to 4725 A W^-1 and 3.5×10¹³ Jones.And its detection range can be extended to 2000 nm due to the broad optical absorption range of Ni-CAT-1.