High-resolution LEED profile analysis and diffusion barrier estimation for submonolayer homoepitaxy of Ag/Ag(100)

Abstract

We present a high-resolution low-energy electron diffraction study of two-dimensional island distributions formed by depositing 0.3 ML of Ag on Ag(100). The substrate temperature ranged between 170 and 295 K. From the ring structure or "splitting" of the diffraction profiles, we determine the behavior of the spatial correlation length characterizing the island distribution. The precise relationship between this correlation length and the mean island separation is also determined via an analysis of kinematic diffraction from island distributions in a realistic model of nucleation and growth. Resulting estimates of this separation are consistent with those based on results from a previous scanning tunneling microscopy study at 295 K. From the Arrhenius behavior of the correlation length, we estimate a terrace diffusion barrier for Ag on Ag (100) We present a high-resolution low-energy electron diffraction study of two-dimensional island distributions formed by depositing 0.3 ML of Ag on Ag͑100͒. The substrate temperature ranged between 170 and 295 K. From the ring structure or ''splitting'' of the diffraction profiles, we determine the behavior of the spatial correlation length characterizing the island distribution. The precise relationship between this correlation length and the mean island separation is also determined via an analysis of kinematic diffraction from island distributions in a realistic model of nucleation and growth. Resulting estimates of this separation are consistent with those based on results from a previous scanning tunneling microscopy study at 295 K. From the Arrhenius behavior of the correlation length, we estimate a terrace diffusion barrier for Ag on Ag͑100͒ of 0.40 Ϯ0.04 eV, with a vibrational prefactor of about 3ϫ10 13 s Ϫ1 . ͓S0163-1829͑98͒08819-5͔

Formation and morphological evolution of self-similar 3D nanostructures on weakly interacting substrates

“…Moreover, BCS values are also compared to experimental results [16,54,69,[71][72][73][74][75][76][77][78], as well as barriers obtained from our nudged-elasticband (NEB) calculations using an embedded atom method interatomic potential [79]. Activation barriers for selected processes are listed in Table I.…”

Nucleation, Growth, and Relaxation of Thin Films: Metal(100) Homoepitaxial Systems

“…From KMC-simulated films for Ag(100), we find that L av ≈ L c /λ(θ), where λ(θ) increases with θ, and λ(0.3) ≈ 1.7. 7 However, proportionality between L av and L c (for fixed θ) is sufficient to determine E d . As shown in Table 2, L c increases as T increases, reflecting again a decrease in N av .…”

“…In the HRLEED analysis, 7 an Ag crystal with typical terrace widths of L terr ≈ 1000 Å was used for studies at 295 K, and a poorer quality crystal with L terr ≈ 600 Å was used for 280-170 K. In all cases, terrace widths are far larger than island separations. HRLEED intensities were obtained near an outof-phase condition for destructive interference between scattering from successive layers in Ag/Ag(100).…”

Kimet al.Reply:

“…First of all, it is noteworthy that experiments on the Ag(001) surface, in contrast to Pd(001), produce holelike patterns [4] even though Ag and Pd have similar atomic numbers and the same crystal structure, and thus the simulated results are almost the same. One clue to this difference in surface morphology is that diffusion barriers for Ag are lower than Pd [5,6]. There is a more direct indication showing diffusion kinetics plays an important role in the morphology of ionsputtered surfaces.…”