We perform density-functional calculations on the influence of external electric fields and electrons or holes injected into surface states on the relative stability of $c(4\times 2)$ and $p(2\times 2)$ reconstructed Si(001) surfaces. It is shown that an electric field parallel to the $\left[001\right]$ direction or the insertion of electrons into surface states favors the formation of $p(2\times 2)$ periodicities. Our results explain recent experimental studies reporting changes of surface reconstruction of Si and Ge(001) surfaces induced by the scanning tunneling microscope and the occurrence of $p(2\times 2)$ reconstructions on $\left(001\right)$ surfaces of $n$-doped Si.

• Received 27 February 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.036101