Anomalous surface reconstruction: Observation of Si(111) 2×1 on sputtered and annealed Si(111) surfaces

The 2×1 π-bonded chain reconstruction of cleaved Si(111) is observed on sputtered and annealed Si(111) surfaces after thermal quenching. Several terraces of 2×1 comprising all three principle domains are seen in a region ∼2000×700 A${\mathrm{̊}}^2$, noncontiguous with domains of 7×7 reconstruction that surround the 2×1 area. Phase boundaries between 2×1 domains are observed both on terraces (intraterrace) and between terraces (interterrace) at double-layer step transitions. I-V characteristics acquired over the 2×1 terraces show good overall agreement with previous work, but differ by 0.1–0.4 V in the energy position of features in the normalized differential conductivity. This may be due to the variability in electronic structure for typical high-resolution tunneling tips, bringing into question the use of such tips for electronic-structure analysis. The presence of this phase on an otherwise 7×7 surface is interpreted in terms of thermal-stress cleavage of the sample during the quench.