抄録
Theoretical studies on the local tunneling barrier height on an Al(100) surface are presented. First, the effect of localized states on the local tunneling barrier height (LBH) is discussed. The bias polarity dependence of LBH on the Al(100) surface, containing a vacancy cluster in the layer next to the surface, is studied. It is found that the bias polarity dependence of the LBH can be attributed to the reduction in the effective potential and the change in the surface electron states by the applied bias voltage. Second, the effect of tip atomic species on the LBH is discussed. It is found that, for the tip-sample distance dependence of the LBH, the difference between measurements with the two atomic species is larger in the LBH than in the maximum barrier height evaluated from the calculated potential profile. Furthermore, it is found that the bias polarity dependence of the LBH measured with the Na tip shows behavior opposite to that measured with the Al tip. Finally, the difference in LBH by the approach and modulation methods is discussed. It is found that the change in modulation amplitude, which is caused by the force acting on the tip atom due to the applied bias voltage, can account for the observation that the modulation method provides smaller LBH values than approach method.
