Local Tunneling Barrier Height Imaging on Si(111) Surface

We measured the spatial distribution of a local tunneling barrier height by means of the AC height modulation method. We performed this measurement on clean Si(111)7×7 surfaces and the surfaces exposed to O2 gas. On clean surfaces, 7×7 structures, which are the same as those in topographic images, were observed in the tunneling barrier height mode. It was found that the spatial distribution of local tunneling barrier height was modified along a step. It was also found that the topography and the spatial distribution of local tunneling barrier height were modified by exposure to O2 gas.