Local Tunneling Barrier Height Image of the Si(111)-(7×7) Surface

The local tunneling barrier height (LBH) image of Si(111)-(7×7) surface is compared with the corresponding scanning tunneling microscope (STM) image. At a negative sample bias voltage, while the faulted half adatoms in the 7×7 unit cell in the STM image are observed to be 0.24 Å higher than the unfaulted half adatoms, there exists no difference in the LBH image contrast between faulted and unfaulted halves. At a positive sample bias voltage, we observe no difference between the faulted and unfaulted halves both in the STM and LBH images. The results suggest that there exists an unexpected mechanism which determines the STM and LBH images.