| The research on properties of the interface between different materials has been the hotspot in the study of physics,chemistry and materials recently.The discontinuity of electronic structure of different interface materials will bring some unusual novelty.The La Al O3/Sr Ti O3 polar-nonpolar oxide heterostructure interface has attracted a lot of attention since it was found two-dimensional electron gas(2DEG)at the interface.The high mobility 2DEG and rich physical properties of La Al O3/Sr Ti O3 heterostructure,such as magnetic and superconductivity,make it possible to be the next generation of new oxide electronic device materials.With the background of the existing research results of La Al O3/Sr Ti O3,the La BO3/KNb O3(B = Al,Ga)oxide heterostructures were studied by first-principles calculations,in order to improve the interface carriers density and mobility,as well as the further exploring of the photocatalytic of the system,Firstly,three structures of parent bulk perovskite crystals were optimized,and the lattice mismatch and the position of band edge were analyzed,where it is found that the conditions of making up the heterostructure are satisfied.Then the La BO3/KNb O3 heterostructures were built.After geometry optimization,cleavage energies,bond length and the average electrostatic potential of the heterostructures were calculated to study the stability and geometric properties.It is found that there exists opposite direction of the polarization field on both sides of the interface,which makes the carriers more evenly distributed in the heterostructures.Secondly,the electrical conductivity and transport properties of La BO3/KNb O3 heterostructures were discussed.From the electronic structure analysis,the studied heterostructures all show n-type metallic state without critical thickness.As the increase of La BO3 layer thickness,the pseudo band gap tends to close.This process is more sensitive to La Al O3 than La Ga O3,and the relaxation of ions is found to be equivalent to the effect of depolarization fields.The interfacial carrier density of studied heterostructures perform one order of magnitude larger than La Al O3/Sr Ti O3 because of the increased intrinsic carrier limit.With the increase of La BO3 layer thickness,the interfacial carrier density rises up to 1.26 × 1014 cm-2,and the electron effective mass decrease monotonically,resulting in higher carrier mobility and about 6 times larger electrical conductivity.Finally,the photocatalytic properties of La BO3/KNb O3 heterostructures interface were investigated,and a sandwich-like p-n type heterostructures were built.Through the analysis of band alignment,the studied heterostructures with KO-KO terminal,KO-Nb O2 terminal,Nb O2-KO terminal and Nb O2-Nb O2 terminal can all be used as reduction in photocatalytic,but none of them can be used as catalyst for oxidation.The absorption spectrum of KO-KO terminal heterostructure and Nb O2-Nb O2 terminal heterostructure show obvious absorption peaks in IR-visible region.Increasing KNb O3 layer thicknesses results in the red shift of the absorption peak position,while the optical absorption characteristics are not sensitive to the change of the interlayer La BO3.The trend of optical absorption can be related to the band structure of heterostructures.The property of optical absorption mainly depends on the direct band gap of the system.With the decrease of the width of the pseudo band gap,the position of the absorption peak gets red-shifted. |
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