Extrinsic structure changes by STM at 65 K on Si(001)

Using variable-temperature scanning tunneling microscopy to image buckled dimers in a C(4 x 2) phase on Si(001) at 65 K under conventional scanning conditions, we have observed symmetric dimers in the P(2 x 1) phase and the flip-flop motion of dimers at the boundary of two different phases. Careful investigation shows that higher tunneling currents produce larger areas of P(2 x 1) phase and higher flip-flop rates of individual dimers. We have measured and plotted the flip-flop rate as a function of current. The origin of the phase transition and the flip-flop dimer motion are discussed.