Dynamics of surface roughening of Cl-terminated Si(100)-(2×1) at 700 K

Abstract

The dynamics of surface roughening and healing induced by Cl on Si͑100͒-͑2ϫ1͒ were studied with variable-temperature scanning tunneling microscopy. Clean samples were exposed to Cl 2 at room temperature, heated to as high as 700 K, and imaged for periods that exceeded 20 h. Chlorine caused surface roughening via a Cl recycling pathway that created pits and regrowth islands with minimal desorption of SiCl 2. This reaction pathway is accessible at ϳ675 K if the surface is not saturated with Cl. Images showed dimer vacancy creation and pit growth, together with vacancy capture by pits. They also showed dimer vacancy escape from pits and pit annihilation, which had not been reported previously. When the terrace coverage was 0.93 ML, the diffusivity of dimer vacancies along the dimer rows was ϳ0.7 Å 2 /sec, about three orders-of-magnitude lower than that on clean Si͑100͒. Single Si adatoms were created on terraces and bonded to Si dimers that were Cl-free. They could form new regrowth dimers or they could be accommodated at the ends of existing islands. Adatoms could also be released from regrowth islands. Pairs of atom vacancy lines separated by one or two Si dimers were observed and the transition between those lines and dimer vacancy lines was recorded. Local areas with ͑3ϫ2͒ symmetry were created from the latter. These dynamic changes all require Cl-free Si dimers, and the rate of change of the surface morphology reflects the surface concentration. The rate of change increases with time as the density of bare dimers increases due to the creation of new sites for Cl on an increasingly rough surface and limited desorption.

Dimer-Anticorrelation-Induced Stabilization of Adsorbate Clustering on theSi(100)−(2×1)Surface

“…These insights have important implications for Si(100) processing chemistry where defects of this kind are common. In particular, these results are not consistent with a recent claim regarding the distribution of Cl atoms on etched Si(100) surfaces [23].…”

Equilibrium morphologies for Cl-roughened Si(100) at 700–750 K: Dependence on Cl concentration

“…This surface is far from equilibrium in that subsequent scans showed changes in average sizes for pits and RIs, as well as their surface areas. 10 Figure 5 shows the combined pit and RI areas as a function of time at 700 K for Cl-terminated Si͑100͒ surfaces. For i (Cl)ϭ0.3 and 0.5 ML, the combined area first increased quickly but it saturated after ϳ4 and ϳ8 h, respectively, as the surfaces reached dynamic equilibrium.…”

Atom vacancy lines and surface patterning: The role of stress for Br-Si(100)-(2×1)at 700 K

“…It has been reported that dimer vacancy lines of odd lengths, 2Nϩ1 dimer vacancies, greatly outnumber those of even lengths, 2N, because odd lengths offer a rebonded symmetric redimerization configuration for the second-layer Si atoms and are energetically favorable. 25 This Comparison shows that the two BD's that were gray in ͑a͒ were dark in ͑b͒. ͑d͒ Schematic of the initial and final Br configurations in box II showing that electron injection perturbed the system and caused Br atoms to hop.…”

“…24 In turn, elongation is assisted by the high surface stress at the ends of the atom vacancy lines. The atom vacancy line formation mechanism is the same as that for Cl-Si͑100͒, 25 but the atom vacancy lines are more numerous here because the Br-Br steric repulsion is stronger. 26 Thus, stress both lowers the barrier for dimer vacancy creation and is important in atom vacancy line formation.…”