论文标题
BI $ _2 $ SE $ _3 $拓扑绝缘子的氮气表面掺杂的证据
Evidence for nitrogen gas surface doping of the Bi$_2$Se$_3$ topological insulator
论文作者
论文摘要
使用扫描隧道光谱法，我们研究了氮气暴露对状态二晶型硒化密度的影响。我们观察到狄拉克点的转移，这与氮结合与硒空位的理论建模一致。在经过精心控制的测量中，Bi $ _2 $ SE $ _3 $晶体最初在氦气环境中裂解，然后暴露于22 scfh超高纯度n $ _2 $气体的22 SCFH流动。我们观察到频谱曲线的发生变化，大约50分钟后的暴露效果饱和，最终使Dirac点更接近Fermi水平。将这些结果与密度功能理论计算进行了比较，该计算支持$ n_2 $分子的图像在SE空位附近进行物理，并分离为单个N原子，然后将其强烈结合到SE空位。在这种解释中，n原子与SE空位位点的结合消除了空位所产生的表面缺陷，并改变了费米能量相对于狄拉克点的位置。
Using scanning tunneling spectroscopy we have studied the effects of nitrogen gas exposure on the bismuth selenide density of states. We observe a shift in the Dirac point which is qualitatively consistent with theoretical modeling of nitrogen binding to selenium vacancies. In carefully controlled measurements, Bi$_2$Se$_3$ crystals were initially cleaved in a helium gas environment and then exposed to a 22 SCFH flow of ultra-high purity N$_2$ gas. We observe a resulting change in the spectral curves, with the exposure effect saturating after approximately 50 minutes, ultimately bringing the Dirac point about 50 meV closer to the Fermi level. These results are compared to density functional theoretical calculations, which support a picture of $N_2$ molecules physisorbing near Se vacancies and dissociating into individual N atoms which then bind strongly to Se vacancies. In this interpretation, the binding of the N atom to a Se vacancy site removes the surface defect state created by the vacancy and changes the position of the Fermi energy with respect to the Dirac point.
