四角晶相HfO_2(001)表面原子和电子结构研究

Geometries and the electronic structures of t-HfO-2 (001) surface

采用基于第一性原理的密度泛函理论研究了四角晶相二氧化铪(t-HfO2)体相及其(001)表面的原子几何与电子结构.理论计算结果表明,t-HfO2(001)表面不会产生重构现象.与体相电子结构相比,t-HfO2(001)表面态密度明显高于体相态密度.其次,表面原子的态密度更靠近费米能级(EF),价带往低能量处移动,并有表面态产生.计算结果表明了t-HfO2表面禁带宽度明显低于体相的禁带宽度.t-HfO2(001)的表面态产生以及表面禁带宽度减小是由于Hf原子与O原子的配位数减少,表面原子周围的环境发生变化而引起的.

The geometries and the electronic structures of t-HfO2 and its （001） surface have been studied by first-principle calculations usingthe density functional theory （DFT）. The optimized results show that the t-HfO2 （001） surface has no surface reconstruction. Compared with the bulk electronic structure, the density of states （DOS） of t＇HfO2 （001） surface is higher than that of the bulk. In addition, the DOS of t-HfO2 （001） surface is closer to the Fermi level. The valence band has the tendency to move toward the lower energy, resulting in the formation of a new surface state. The band gap of t-HfO2 （001） surface is much smaller than that of bulk band gap. The existence of a new surface state and the reduction of band gap are due to the reduction of the Hf and O surface coordination which are different from the bulk atoms.