Scanning tunneling microscopy study of Si (001) and Si (110) surface structures resulting from different thermal cleaning treatments

We have studied the morphology and distribution of atomic steps on Si (001) and Si (110) with scanning tunneling microscopy. We find that native oxide removal at temperatures up to 1350 K leads to step pinning and bunching on Si (001) and to facetting on Si (110). Cleaning at temperatures in excess of 1450 K leads to regular step distributions. For both types of surfaces, the average step direction and step density reflect the macroscopic misorientation of the sample. However, locally the step edges tend to follow directions determined by surface reconstructions.