Structure of GaAs(001)(2×4)−c(2×8)Determined by Scanning Tunneling Microscopy

The scanning tunneling microscope (STM) has been used to study the $(2\mathrm{}\times 4)-c(2\mathrm{}\times 8)$ reconstruction on the arsenic-rich surface of GaAs(001). The STM images show that the 4× periodicity is due to a regular array of missing arsenic dimers. The (2×4) units are arranged so as to give small domains of either (2×4) or $c(2\mathrm{}\times 8)$ reconstructions. These images are the first high-resolution STM images obtained from a surface grown by molecular-beam epitaxy. Features are seen which may be important in the mechanism of growth.