ETCHING OF SI(100)-2X1 WITH CHLORINE - REACTION PATHWAYS, ENERGY ANISOTROPIES, AND ATOMIC-SCALE PHENOMENA

Rate constants for growth of Cl-induced etch pits on Si(100)-2X1 have been evaluated using data obtained with scanning tunneling microscopy. Etch pits are produced via the removal of a single dimer from a terrace and they grow by removal of adjacent dimers. Two growth modes have been identified, namely, linear growth, where dimer removal occurs along the dimer row direction, and branch formation, where a dimer is removed from an adjacent row. Analysis of the lengths of linear etch pits shows that they follow the most probable Flory-Schulz size distribution. We deduce that the rate constant for linear growth is 4.7+/-1 times that for branch creation because the energy barrier for dimer removal along the dimer row direction is 0.11+/-0.02 eV less than that for branch formation. Once a branch is created, its rate constant for linear growth is 2.2+/-0.5 times greater than along the parent pit since no net step addition is involved. The energy difference for these two types of growth involving a branched pit is 0.06+/-0.02 eV.