Preparation And Optoelectronic Properties Of SnO₂ Nanocomposites

SnO₂ is an n-type wide band gap semiconductor,which not only has good chemical stability,but also has high electrical conductivity and high visible light transmittance.Therefore,it is widely used in the field of transparent conductive films.Although the SnO₂ single crystal is a direct bandgap semiconductor,due to the limitation of the band structure symmetry,the transition of electrons between the conduction band bottom and the valence band top is prohibited?forbidden transition?,as a result,the bulk SnO₂ single crystal cannot emit band edge ultraviolet light.However,recent domestic and foreign studies have shown that through the two methods of nano-engineering and doping engineering,the limitation of the forbidden transition rule of SnO₂ single crystal can be broken,and the band edge ultraviolet luminescence is restored.In this thesis,combined with doping engineering and nanotechnology,the following researches were carried out:?1?Ag-doped SnO₂ nanocomposite films?SnO₂:Ag/Ag nanocomposites?were prepared,and Ag-doped and surface-plasma synergistically enhanced films were developed.The UV photoelectric properties of the device were studied.?2?The SnO₂ nanostructure/ZnO:Li heterojunction light-emitting diode?LED?was fabricated.The effect of the morphology of the SnO₂nanostructure on the LED luminescence performance was studied.The above research has achieved the following results:1.SnO₂:Ag/Ag nanocomposite film was prepared by laser rapid annealing.The phenomenon of red band shift of optical band gap,increase in resistivity,decrease in carrier concentration and mobility due to Ag doping was observed.2.The SnO₂:Ag/Ag nanocomposite film was prepared by a simple two-step method.The nanocomposite films were annealed at 500°C and 900°C,and then combined with photolithography to prepare the photodetector based on nanocomposite film.The peak reflectance of the photodetector based on the SnO₂:Ag/Ag nanocomposite film is enhanced by about four times compared to the undoped film.3.A SnO₂ nanostructure/ZnO:Li heterojunction light emitting diode was prepared.A light-emitting diode device was prepared by vapor deposition method using a nanostructured SnO₂ and a P-type ZnO:Li prepared by a high pressure method.Under current excitation,the SnO₂ nanobelt/ZnO:Li heterojunction LED produced a broad blue light emission,while the SnO2 nanowire/ZnO:Li heterojunction LED observed a narrow UV luminescence peak.