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Title: Delayed plastic relaxation limit in SiGe islands grown by Ge diffusion from a local source

The hetero-epitaxial strain relaxation in nano-scale systems plays a fundamental role in shaping their properties. Here, the elastic and plastic relaxation of self-assembled SiGe islands grown by surface-thermal-diffusion from a local Ge solid source on Si(100) are studied by atomic force and transmission electron microscopies, enabling the simultaneous investigation of the strain relaxation in different dynamical regimes. Islands grown by this technique remain dislocation-free and preserve a structural coherence with the substrate for a base width as large as 350 nm. The results indicate that a delay of the plastic relaxation is promoted by an enhanced Si-Ge intermixing, induced by the surface-thermal-diffusion, which takes place already in the SiGe overlayer before the formation of a critical nucleus. The local entropy of mixing dominates, leading the system toward a thermodynamic equilibrium, where non-dislocated, shallow islands with a low residual stress are energetically stable. These findings elucidate the role of the interface dynamics in modulating the lattice distortion at the nano-scale, and highlight the potential use of our growth strategy to create composition and strain-controlled nano-structures for new-generation devices.
Authors:
; ;  [1] ;  [2] ;  [3] ; ; ; ;  [4] ;  [5] ;  [6] ;  [7]
  1. CNISM-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)
  2. IMM-CNR, Stradale Primosole 50, I-95121 Catania (Italy)
  3. CNR-IFN, LNESS, Via Anzani 42, I-22100 Como (Italy)
  4. Dipartimento di Scienza dei Materiali and L-NESS, Università Milano-Bicocca, via Cozzi 53, I-20125 Milano (Italy)
  5. Department of Sciences at the Università Roma Tre, Via Vasca Navale 79, 00146 Roma (Italy)
  6. CNISM, LNESS, Dipartimento di Fisica, Politecnico di Milano (Polo di Como), Via Anzani 42, I-22100 Como (Italy)
  7. ICFO–The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, 3, E-08860 Castelldefels (Barcelona) (Spain)
Publication Date:
OSTI Identifier:
22399259
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DISLOCATIONS; ENTROPY; EPITAXY; GERMANIUM SILICIDES; INTERFACES; LAYERS; NANOSTRUCTURES; PLASTICITY; RELAXATION; RESIDUAL STRESSES; SOLIDS; STRAINS; SUBSTRATES; SURFACES; THERMAL DIFFUSION; TRANSMISSION ELECTRON MICROSCOPY