We report standing waves observed on Si(100) and Ge(100) surfaces by means of scanning tunneling microscopy at $79\mathrm{K}$. Differential conductance $(dI∕dV)$ imaging with atomic resolution enabled observation of spatial oscillations in the local density of states corresponding to the empty dangling bond state $\left({\pi }^{*}\right)$. Applying Fourier transform (FT) to standing wave images, we confirmed that the ${\pi }^{*}$ state has a strong anisotropy between the dimer row and dimer bond directions. This suggests that the ${\pi }^{*}$ state is likely a one-dimensional electronic band along the dimer row. Furthermore, through the FT analysis, we determined the energy dispersions of the ${\pi }^{*}$ state on both the Si(100) and Ge(100) surfaces.

• Received 23 May 2005

DOI:https://doi.org/10.1103/PhysRevB.72.235327