锰氮共掺锐钛矿型二氧化钛的电子性质和光学性质研究

Study on Optical and Electronic Properties of Anatase TiO_2 with Mn-N Co-Doping

利用金属与非金属共掺TiO2半导体提高对可见光的利用率是近期研究的一个热点。通过基于密度泛函理论的平面波超软赝势方法,计算了Mn掺杂、N掺杂、Mn-N共掺杂TiO2晶体的能带、态密度、分态密度和光学性质。通过对比,发现单一N掺杂使TiO2的禁带宽度从3.2eV减小到2.83eV;单一Mn掺杂在禁带中产生了三条杂质能级,减小了电子从价带往导带跃迁的能量;而Mn-N共掺杂TiO2锐钛矿晶体后,费米能级偏离价带向导带方向移动,既在价带顶部形成杂质能级,又减小了禁带宽度,电子从杂质能级跃迁到导带仅需要2.1eV(对应波长为590nm)的能量,该能量恰好对应吸收谱中的吸收峰,相比单一掺杂,更加有效地利用了可见光。

Recently, improving the visible-light utilization ratio by the metal and non-metallic impurities co-doped TiO2 semiconductor is a research focus. The band structure, density of states, partial density of states and optical properties of Mn-doped, N-doped and Mn-N co-doped anatase TiO2 are studied by plane-wave supersoft pseudopotential method based on the density functional theory. Contrasting Mn, N, Mn-N doped anatase TiO2, the results show that N single doped TiO2 effectively makes the band gap decrease from 3.2 eV to 2.83 eV and a Mn single doping results in three impurity levels in the band gap, which reduces the electron transition energy from the valence band to conduction band. While Mn-N co-doped anatase TiO2 crystals lead the Fermi level to move to the conduction band, simultaneously forming impurity level in the valence band top and reducing the band gap. The electronic transition energy is about 2.1 eV （wavelength is 590 nm） from impurity levels to the conduction band, which exactly corresponds to the absorption peak in the absorption spectrum. This will more effectively improve the utilization of the visible light.