کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5425857 | 1395868 | 2007 | 7 صفحه PDF | دانلود رایگان |
We have studied the influence of oxygen pressure during the cyclic annealing used for the cleaning of W(1Â 1Â 0) surfaces. For this purpose the surface morphology and electronic properties are measured by means of scanning tunneling microscopy (STM) and spectroscopy (STS), respectively. It is found that the surfaces with impurity atom densities as low as 2Â ÃÂ 10â3 can be obtained by gradually reducing the oxygen pressure between subsequent annealing cycles down to about 2Â ÃÂ 10â8Â mbar in the final cycle. Only on the clean surface a bias-dependent spatial modulation of the local density of states (LDOS) is observed at step edges and around impurity sites by STS. In addition, we find a pronounced peak in the occupied states. In combination with density functional theory calculations these features can be traced back to a dispersive pz-dxz-type surface resonance band and the lower band edge of a surface state, respectively.
Journal: Surface Science - Volume 601, Issue 16, 15 August 2007, Pages 3308-3314