Volume 79, Number 1, July 2007
Article Number 16001
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 11 June 2007
EPL, 79 (2007) 16001
DOI: 10.1209/0295-5075/79/16001

Mesoscopic mismatch as a driving force for modified morphology above percolation

R. Dana and Y. Manassen

Department of Physics, Ben-Gurion University of the Negev - P.O. Box 653, Beer Sheva, 84105, Israel

received 15 November 2006; accepted in final form 21 May 2007; published July 2007
published online 11 June 2007

The steady-state morphology of submonolayer Si/Si(111)$7\times 7$ islands is characterized by a size-dependent transition from compact through ramified to 1D-like forms. The transition is described by the linear-chain model (LCM), which explains this shape transition in strained heteroepitaxial layers, as a mechanism for strain relaxation without dislocations. We found that above the percolation coverage $\theta _{c}$, the entire structure adopts new steady-state morphology and reduces its typical width by a factor of e, to its optimal-energy value. The LCM predicts this value as the asymptotic behavior for infinite elongated islands. Our experimental results, which are supported by energy calculations, confirm the LCM predictions for the first time in homoepitaxy. These results are explained by a size-dependent mesoscopic mismatch between the islands and the substrate.

68.35.Gy - Mechanical properties; surface strains .
68.37.Ef - Scanning tunneling microscopy (including chemistry induced with STM) .
68.65.-k - Low-dimensional, mesoscopic, and nanoscale systems: structure and nonelectronic properties .

© Europhysics Letters Association 2007