锐钛矿相和金红石相Nb:TiO_2电学性质的GGA(+U)法研究

采用基于密度泛函理论第一性原理GGA和GGA+U相结合的方法研究了不同掺杂浓度下锐钛矿相和金红石相Nb:TiO2的晶体结构、电子结构以及稳定性.结果表明:锐钛矿相Nb:TiO2能带结构与简并半导体类似,呈类金属导电机理.金红石相Nb:TiO2呈半导体导电机理.Nb原子比Ti原子电离产生出更多的电子.锐钛矿相Nb:TiO2中Nb原子的电离率比金红石相Nb:TiO2的大.以上结果说明锐钛矿相Nb:TiO2比金红石相Nb:TiO2更适宜用作TCO材料;掺杂浓度对其杂质能级,费米能级和有效质量都有影响.Nb原子掺杂浓度越高,材料电离率呈降低趋势;形成能计算结果显示:在富钛条件下不利于Nb原子的掺杂,而在富氧条件下有利于Nb原子的掺杂.对于金红石相和锐钛矿相Nb:TiO2,不论是在贫氧或富氧条件下,随着Nb原子掺杂浓度的提高,形成能均增大.

Investigation on the electrical properties of anatase and rutile Nb-doped TiO2 by GGA(+U)

Crystal structure, electronic properties, and stability of anatase and rutile Nb-doped TiO₂ (Nb:TiO₂) compounds with different doping concentrations are studied by the combination of GGA and GGA+U methods within the density functional theory based first-principle calculation. And the main research work and contents are listed as follows: The anatase Nb:TiO₂ appears as a degenerated semiconductor which behaves as an intrinsic metal. Its metallic property arises from Nb substitution into the Ti site, providing electrons to the conduction band. In contrast, the rutile Nb:TiO₂ shows insulating behaviors. Ionization efficiency of Nb in anatase Nb:TiO₂ is higher than that in rutile. We expect that anatase Nb:TiO₂ is a potential material for transparent conducting oxide (TCO) while rutile Nb:TiO₂ is not. The doped systems show different electronic characteristics, such as band structure, Fermi energy, and effective mass of carriers at different doping levels. In higher dopant concentration n_Nb, the ionization efficiency decreases slightly. Calculated defect-formation energy shows that Ti-rich material growth conditions are not in favor of the introduction of Nb while Nb can be easily doped in Nb:TiO₂ under O-rich growth conditions. Nb dopant is difficult to be doped at higher doping level for both anatase and rutile Nb:TiO₂.
Keywords：first principle calculationelectronic structurestability2')" href="#">Nb：TiO₂