Fluctuations and Growth Phenomena in Surface Diffusion

Microscopic Dynamics of Li+ in Rutile TiO2 Revealed by 8Li β-Detected Nuclear Magnetic Resonance

“…This may also explain the LiF prefactor, but it clearly does not apply to the extrinsic implanted 8 Li + in the dilute limit. With the advent of sensitive atomic resolution probes of surfaces in the past few decades, a very detailed picture of diffusion on crystal surfaces has emerged, , which can help to refine our ideas about bulk diffusion. For example, in some cases, the Arrhenius prefactor of adatoms diffusing along a step edge is significantly enhanced over a flat terrace .…”

Surface diffusion experiments with STM: equilibrium correlations and non-equilibrium low temperature growth

“…Coverage gradients in an overlayer can exist under nonequilibrium conditions when imposed as initial conditions, i.e. at t = 0 the coverage θ(r, t) has an externally imposed value θ 0 (r, 0) (different from its average equilibrium value θ ) [11,12]. For example, in non-equilibrium one-dimensional step profile experiments the coverage has a value θ 1 for r < 0 and a different value θ 2 for r > 0.…”

“…As shown by equation (11), equilibrium diffusion measurements can be carried out from the decay of concentration fluctuations within a probe area A. An area is naturally defined in the STM geometry because the tunneling current depends exponentially on the tip-surface separation and most of the current (more than 90%) is confined within the projection of the approximately 'hemispherically' shaped tip to the planar surface.…”

“…Figure 4 shows power spectra for H/Si(111) close to saturation θ → 1 as a function of temperature T = 500-730 K, showing that the mean square fluctuations δ N 2 (0) increase while the spectral content shifts to higher frequencies with increasing temperature [11]…”

“…In principle, A can be estimated from the solution of the Schrodinger equation to match the measured tunneling current i (V ) at a given voltage V . Since this requires knowing the exact 3-d shape of the tip, we suggest [11] an experimental method to measure A which avoids the uncertainty of the tip shape.…”