The influence of oxygen defects upon the electronic properties of Nb-doped TiO2 has been studied by using the general gradient approximation （GGA）＋U method. Four independent models （i.e., an undoped anatase cell, ...The influence of oxygen defects upon the electronic properties of Nb-doped TiO2 has been studied by using the general gradient approximation （GGA）＋U method. Four independent models （i.e., an undoped anatase cell, an anatase cell with a Nb dopant at Ti site （NbTi）, an anatase cell with a Nb-dopant and an oxygen vacancy （NbTi＋Vo）, and an anatase cell with a Nb-dopant and an interstitial oxygen （NbTi＋Oi）） were considered. The density of states, effective mass, Bader charge, charge density, and electron localization function were calcul^ited. The results show that in the NbTi＋Vo cell both eg and t2g levels of Ti 3d orbits make contributions to the electronic conductivity, and the oxygen vacancies （Vo） collaborate with Nb-dopants to favor the high electrical conductivity by inducing the Nb-dopants to release more excess charges. In NbTi＋Oi, an unoccupied impurity level appears in the band gap, which served as an acceptor level and suppressed the electronic conductivity. The results qualitatively coincide with experimental results and possibly provide insights into the preparation of TCOs with desirable conductivity.展开更多
The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-...The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-Ga_2O_3 are in good agreement with experimental results. Si-and Sn-doped β-Ga_2O_3 tend to form under O-poor conditions, and the formation energy of Si-doped β-Ga_2O_3 is larger than that of Sn-doped β-Ga_2O_3 because of the large bond length variation between Ga–O and Si–O. Si-and Sn-doped β-Ga_2O_3 have wider optical gaps than β-Ga_2O_3, due to the Burstein–Moss effect and the bandgap renormalization effect. Si-doped β-Ga_2O_3 shows better electron conductivity and a higher optical absorption edge than Sn-doped β-Ga_2O_3, so Si is more suitable as a dopant of n-type β-Ga_2O_3, which can be applied in deep-UV photoelectric devices.展开更多
The prospect ofα-Ga2O3 in optical and electrical devices application is fascinating.In order to obtain better performance,Ge and F elements with similar electronegativity and atomic size are selected as dopants.Based...The prospect ofα-Ga2O3 in optical and electrical devices application is fascinating.In order to obtain better performance,Ge and F elements with similar electronegativity and atomic size are selected as dopants.Based on density functional theory(DFT),we systematically research the electronic structure and optical properties of dopedα-Ga2O3 by GGA+U calculation method.The results show that Ge atoms and F atoms are effective n-type dopants.For Ge-dopedα-Ga2O3,it is probably obtained under O-poor conditions.However,for F-dopedα-Ga2O3,it is probably obtained under O-rich conditions.The doping system of F element is more stable due to the lower formation energy.In this investigation,it is found that two kinds of doping can reduce theα-Ga2O3 band gap and improve the conductivity.What is more,it is observed that the absorption edge after doping has a blue shift and causes certain absorption effect on the visible region.Through the whole scale of comparison,Ge doping is more suitable for the application of transmittance materials,yet F doping is more appropriate for the application of deep ultraviolet devices.We expect that our research can provide guidance and reference for preparation ofα-Ga2O3 thin films and photoelectric devices.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51002135 and 51172200)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.2013QNA4011)
文摘The influence of oxygen defects upon the electronic properties of Nb-doped TiO2 has been studied by using the general gradient approximation （GGA）＋U method. Four independent models （i.e., an undoped anatase cell, an anatase cell with a Nb dopant at Ti site （NbTi）, an anatase cell with a Nb-dopant and an oxygen vacancy （NbTi＋Vo）, and an anatase cell with a Nb-dopant and an interstitial oxygen （NbTi＋Oi）） were considered. The density of states, effective mass, Bader charge, charge density, and electron localization function were calcul^ited. The results show that in the NbTi＋Vo cell both eg and t2g levels of Ti 3d orbits make contributions to the electronic conductivity, and the oxygen vacancies （Vo） collaborate with Nb-dopants to favor the high electrical conductivity by inducing the Nb-dopants to release more excess charges. In NbTi＋Oi, an unoccupied impurity level appears in the band gap, which served as an acceptor level and suppressed the electronic conductivity. The results qualitatively coincide with experimental results and possibly provide insights into the preparation of TCOs with desirable conductivity.
基金Project supported by the Science and Technology Program of Guangdong Province,China(Grant No.2015B010112002)the Science and Technology Project of Guangzhou City,China(Grant No.201607010250)
文摘The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-Ga_2O_3 are in good agreement with experimental results. Si-and Sn-doped β-Ga_2O_3 tend to form under O-poor conditions, and the formation energy of Si-doped β-Ga_2O_3 is larger than that of Sn-doped β-Ga_2O_3 because of the large bond length variation between Ga–O and Si–O. Si-and Sn-doped β-Ga_2O_3 have wider optical gaps than β-Ga_2O_3, due to the Burstein–Moss effect and the bandgap renormalization effect. Si-doped β-Ga_2O_3 shows better electron conductivity and a higher optical absorption edge than Sn-doped β-Ga_2O_3, so Si is more suitable as a dopant of n-type β-Ga_2O_3, which can be applied in deep-UV photoelectric devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.51302215)the Natural Science Basic Research Program of Shaanxi Province,China(Grant Nos.2018JQ6084 and 2019JQ-860).
文摘The prospect ofα-Ga2O3 in optical and electrical devices application is fascinating.In order to obtain better performance,Ge and F elements with similar electronegativity and atomic size are selected as dopants.Based on density functional theory(DFT),we systematically research the electronic structure and optical properties of dopedα-Ga2O3 by GGA+U calculation method.The results show that Ge atoms and F atoms are effective n-type dopants.For Ge-dopedα-Ga2O3,it is probably obtained under O-poor conditions.However,for F-dopedα-Ga2O3,it is probably obtained under O-rich conditions.The doping system of F element is more stable due to the lower formation energy.In this investigation,it is found that two kinds of doping can reduce theα-Ga2O3 band gap and improve the conductivity.What is more,it is observed that the absorption edge after doping has a blue shift and causes certain absorption effect on the visible region.Through the whole scale of comparison,Ge doping is more suitable for the application of transmittance materials,yet F doping is more appropriate for the application of deep ultraviolet devices.We expect that our research can provide guidance and reference for preparation ofα-Ga2O3 thin films and photoelectric devices.
