Terrace ledge kink model

In chemistry, the terrace ledge kink (TLK) model, which is also referred to as the terrace step kink (TSK) model, describes the thermodynamics of crystal surface formation and transformation, as well as the energetics of surface defect formation.

Figure 1 illustrates the names for the atomic positions and point defects on a surface for a simple cubic lattice.

These bonds are grouped in such a way in order to create a concave structure, which naturally accommodates the incoming building unit.

This unique arrangement not only minimizes the system's free energy but also aligns the new unit with the symmetry of the underlying lattice.

This subtle yet fundamental mechanism distinguishes kink-mediated growth from other aggregation processes and underscores its critical role in maintaining the uniformity and symmetry of growing crystals.

For a simple cubic lattice in this model, each atom is treated as a cube and bonding occurs at each face, giving a coordination number of 6 nearest neighbors.

This can be envisioned as the surface being disassembled one terrace at a time by removing atoms from the edge of each step, which is the kink position.

Figure 1: The names for the various atomic positions in the TLK model. This graphic representation is for a simple cubic lattice.
Figure 2: A scanning tunneling microscope image of a clean silicon (100) surface showing a step edge as well as many surface vacancies. Many kink sites are visible along the terrace edge. The rows visible are dimer rows in a 2x1 reconstruction.
Figure 3: Ball model representation of a real (atomically rough) crystal surface with steps, kinks, adatoms, and vacancies in a closely packed crystalline material. Adsorbed molecules, substitutional and interstitial atoms are also illustrated. [ 3 ]