Research On Fabrication And Properties Of SrTiO₃ Thin Films And Relevant Light-emitting Diodes

At present,environmental and energy issues are becoming increasingly important,and the development of environmental protection materials has also attracted much attention.Among them,perovskite materials have become the focus of recent research due to their excellent properties.Among these perovskite materials,Sr TiO₃(STO),as a typical metal oxide,is an electronic functional ceramic material with low dielectric loss,high dielectric constant and thermal stability.It is widely applied in electronic,mechanical and ceramic industries.Recent decades,with the rapid development of the preparation process of nanomaterials,novel methods have emerged to synthesize functional materials based on STO,which has stimulated people's interest in its research,thereby promoting a wider application range of STO materials.STO materials with cubic perovskite structure are considered as potential materials in the optoelectronic field because of their excellent physical properties such as superconductivity and huge magnetoresistance.However,there are few reports on STO materials in the field of LED.In recent years,researchers have found that the blue light emission of STO is associated with oxygen deficiency,which indicates that STO materials have potential applications in light-emitting devices.However,no STO-based electroluminescence(EL)of light-emitting diodes is available so far.Here we prepared STO and Nb:STO films by RF magnetron sputtering.On this basis,we prepared a heterojunction light-emitting diode that can achieve white light emission at room temperature,and investigated the photoelectric properties and luminescent source of the white light-emitting diode.The research results obtained are as follows:1.The STO films were successfully fabricated on soda–lime glass(SLG)substrates by RF magnetron sputtering and then annealed at different temperatures.We found that when the annealing temperature is below 500?,the films are amorphous.But when the annealing temperature reaches 600?,the films exhibit a single cubic perovskite structure.Further study found that with the increase of annealing temperature,the transmittance of the film increased,and the band gap also changed,so by adjusting the annealing temperature to achieve the purpose of adjusting the STO band gap.Then the results of Hall effect test show that the carrier concentration of STO film decreases with the increase of annealing temperature.2.The STO film was deposited on the p-type GaN substrate to prepare an n-STO/p-GaN heterojunction light-emitting diode.The pn junction shows remarkable rectification characteristics in current-voltage(I-V)measurements.We found that as the excitation current increased,the EL spectrum showed a change from yellow-green to white light.Combining with PL measurements,we found that the n-STO films have an emission band from ultraviolet(UV)to blue(375-450 nm),which is associated with near band-edge emission and defect-related radiation recombination,and p-GaN layer with the emission bands from green to red(centered at 550 nm).The white emission in the EL spectrum comes from the combination of the blue emission from the STO layer and the green to red emission from the GaN layer.3.Nb:STO films with various Nb doping concentrations were prepared on quartz substrates by RF magnetron sputtering.The experimental results indicate that Nb impurities are doped into the STO lattice and all the films have a single cubic perovskite structure.It was found by UV-Vis absorption spectrum that the optical band gap of the Nb:STO films gradually become wider and the transmittance of the films gradually increase with the increase of the Nb concentration.More importantly,the resistivity of the films decreases with the increase of the Nb concentration by Hall effect measurements.