Step free energies, surface stress, and adsorbate interactions for Cl-Si(100) at 700 K

Abstract

The evolution and equilibrium morphology of Si͑100͒ with 0.1 monolayer of adsorbed Cl was studied at 700 K with variable temperature scanning tunneling microscopy. Chlorine caused surface roughening with monolayer pits and regrowth islands. The aspect ratio of these features then increased with their size because of the surface-stress anisotropy. By analyzing the equilibrium feature shape as a function of size, we found that the ratio of step free energies for A-and B-type steps was F b /F a ϭ2.44 for regrowth islands and 3.33 for pits. These ratios are higher than for clean Si͑100͒, F b /F a ϭ2.13, because the steps are destabilized.

Crossover energetics for halogenated Si(100): Vacancy line defects, dimer vacancy lines, and atom vacancy lines

“…The presence of I alters the energies, but not the relative magnitudes, as was shown for Cl-Si͑100͒. 8 It is important to note that the vacancy line defects reported here are thermodynamically favored for a surface with high I concentration and bond strain. These vacancy line defects are analogous to those observed on Ge-covered Si͑100͒, where the larger lattice constant of Ge led to compressive strain ͑i.e., repulsive interactions͒.…”

“…The shape of two-dimensional islands is determined by both step free energies and surface strain energy. 8,13,14 Regrowth then follows the scheme observed previously in etching by hydrogen, 15 oxygen, 16 and halogens, 7 as well as during Si homoepitaxy. 17,18 Intriguingly, the image in Fig.…”

“…1,3,5,7 Variable temperature scanning tunneling microscopy ͑STM͒ studies then revealed the dynamics of those changes as terrace vacancies formed and the released Si atoms produced islands on the terrace. [2][3][4][5]8 The underlying driving force for roughening can be traced in large measure to the repulsive interactions among the halogen atoms, and halogenated Si͑100͒ is an ideal system for investigations of the effects of adsorbates on intrinsic surface energetics. 2,4,6,8 Chlorine roughening is characterized by the production of dimer vacancy lines ͑DVLs͒ with the elongation of onelayer-deep pits along the dimer row direction, as depicted in Fig.…”

Monte Carlo modeling of Si(100) roughening due to adsorbate–adsorbate repulsion

“…Furthermore, beyond a critical size, the strain energy decreases with feature size, and this favors the formation of large features. Detailed analysis of the equilibrium morphology of Si(1 0 0) with 0.1 ML of Cl shows that strain energy plays a similar role in this system as for bare Si(1 0 0) [18].…”

Energy scaling and surface patterning of halogen-terminated Si(001) surfaces

“…During the last few years this process is also extensively studied experimentally with scanning tunneling microscopes (STM) [1][2][3][4][5][6]. However, the science governing this process and the associated surface rearrangements are not well understood, in spite of the fact that on a Si surface halogen-halogen interactions are extremely short-ranged and dominated mostly by the nearest-neighbor intra-and inter-row repulsions (denoted by a and b, respectively).…”