Investigations On Electron Energy-Loss Spectrum And Electronic Structure Of Semiconductor Materials（GaN、TiO₂）

Semiconductor materials have attracted extensive attention due to their rich physical phenomena.In this paper,the electronic structure characteristics of several semiconductor materials are studied by using density functional theory and electron energy loss spectroscopy.The main research contents are as follows.The effect of electronic structure of Zn doped Ga N on the basic physical properties of the material was investigated.The calculated atomic density of States is used to analyze the low-energy part of the electron energy loss spectrum,distinguish the loss peak formed by the plasma oscillation,and reasonably allocate other loss peaks caused by the single electron transition.It is found that the plasma peak moves to the low-energy region and the inter band transition intensity increases after Zn doping.The impurity level is introduced into the density of States,and the hybrid orbitals of N 2p and Zn 3d are formed near the Fermi level.For the high energy loss spectrum at N-K edge,an additional peak of donor defect state is observed.The experimental and theoretical results show that the nuclear hole effect is accurate in the simulation.The effect of Zn doping on the electronic structure of Ga N is studied.It is found that with the increase of Zn concentration,the band gap decreases gradually.The top of the valence band passes through the Fermi surface and moves in the direction of the guide band.The optical properties are calculated and the conductivity and dielectric function are obtained.The peak value is also due to the interband transition.The new peak value at 0～2 e V is due to the doping of Zn,the generation of new energy levels and the formation of Zn 3d and N.The imaginary part of the dielectric function corresponds to the conductivity curve,and there is a peak at 0～2 e V.The relationship between electronic structure and physical properties of Ti O₂was studied.Firstly,we have carried out the substitution of Sn and N with different concentrations of cations Ti and anion O.the doping of Sn will be introduced into Sn 5s and 5p states by the band structure and DOS analysis,and the hybrid effect can occur between Sn 5s and 5p States and Ti 3d states.N 2p state is introduced into n dopant,which makes some electrons change to N 2p-Ti 3d.Because the N 2p state was near Fermi surface,the band gap will be reduced and the transition behavior of electrons will be more easily occurred.The results show that the absorption edge of titanium dioxide will be red shifted by the introduction of Sn and N in optical properties.The red shift effect becomes obvious with the increase of doping amount,and the absorption of the material in visible light region is enhanced.The atomic spacing of different Sn and N reflects the effect of the interaction between atoms on photocatalytic activity.The band is always a direct band gap semiconductor,but with the increase of the spacing between the two Sn atoms and the two N atoms,the interaction force between atoms decrease,and the hybridization effect will be weakened due to the far atomic spacing.From the optical properties,the absorption capacity of light becomes weaker and the photocatalytic effect becomes worse.