Atomic-scale control of surface reconstruction on Ge(001) by scanning tunneling microscopy at 80 K

The reconstruction of a clean Ge(001) surface is controlled at the atomic scale by the temporal change in the sample bias voltage during scanning tunneling microscopy (STM) observation at 80K. A positive voltage pulse on the c(4 x 2)-reconstructed region flips the buckled dimers only in the dimer row right under the STM tip apex, and creates a wire of p(2 x 2) reconstruction extending along the dimer row. An artificial superstructure is made on the c(4 x 2) surface by inverting the buckling of the target dimer rows periodically and forming p(2 x 2) wires side by side. A negative voltage pulse on the p(2 x 2) region creates a local c(4 x 2)-reconstructed area near the point of pulse. Its size can be reduced to 1.6 nm x 2.8 nm by manipulating the voltage of the pulse.