Study On The Structural And Electronic Properties Of LiAlO₂/SrTiO₃ And LiAlO₂/LaAlO₃ Heterostructures

Recently metal oxide heterostructures have received a great deal of attention because their novel properties and potential applications.We study the electronic properties of nonpolar/nonpolar LiAlO2/SrTiO3 heterostructures with oxygen vacancies and polar/nonpolar LiAlO2/LaAlO3 heterostructures by using first principles calculations,and obtain some innovation achievements.The main results are listed as below:1.We obtain the most stable stacking configurations for LiAlO2/SrTiO3 and LiAlO2/LaAlO3 heterostructures.The most stable stacking configurations are determined by comparing the adhesion energy of high symmetry stacking configurations.We find that the layer distances of LiAlO2 in LiAlO2/LaAlO3 heterostructures are obviously larger than in LiAlO2 bulk along the direction perpendicular to interfaces,due to the big pressure stress in LiAlO2.The tensile stress in LiAlO2/SrTiO3 is little,so the layer distances of LiAlO2 in LiAlO2/LaAlO3 heterostructures are close to layer distances in LiAlO2 bulk.2.The density of states(DOS)are changed by induced oxygen vacancies.ADOS peak appears in the bandgap of LiAlO2/SrTiO3 heterostructures with oxygen vacancies.There are no DOS at the chemical potential for electrons in perfect LiAlO2/SrTiO3 heterostructures,the upper valence band is mainly derived from O-2p states while the lower conduction band is mainly derived from Ti-3d states.For the SrO/LiAlO2 interface with oxygen vacancies,a DOS peak appears at the chemical potential and the band gap still exists.3.The semiconductor-metal transition happens in LiAlO2/LaAlO3 heterostructures with thicker LaAlO3.LiAlO2/LaAlO3 heterostructures with AlO2/LiAlO2 interface and LaO/LiAlO2 interface have no DOS at the chemical potential for electrons.When LaAlO3 has fewer layers.However,the bandgaps of both interfaces become smaller and smaller with more LaAlO3 layers,and at last the heterostructures possess metallic states.From the layer-projected DOS of LiAlO2/LaAlO3 heterostructures with 16 layer LaAlO3,we find that the states at Fermi level are mainly derived from the surface and interface layer of LaAlO3 and LiAlO2 layers for AlO2/LiAlO2 interface.For LaO/LiAlO2 interface,the states at Fermi level are only derived from the surface layer of LaAlO3.