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Title: Programming the Shape of Highly Ordered Ge Islands on Si: from Dots to Rods

Abstract

In the Ge on Si model heteroepitaxial system, we show that metal patterns on the Si surface induce the assembly of deposited Ge atoms into highly ordered islands whose shapes are programmed by a combination of metal species and substrate orientation. The island shapes including truncated pyramids and nanorods are radically different from those grown on metal-free surfaces and arise by a process whereby intermixing between deposited Ge and substrate Si atoms from the onset of island formation facilitate the island shape evolution.

Authors:
; ;  [1];  [2];  [3]
  1. Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States)
  2. (United States)
  3. Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
21055055
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 893; Journal Issue: 1; Conference: ICPS 2006: 28. international conference on the physics of semiconductors, Vienna (Austria), 24-28 Jul 2006; Other Information: DOI: 10.1063/1.2729758; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMS; EPITAXY; GERMANIUM; NANOSTRUCTURES; ORIENTATION; SILICON; SUBSTRATES; SURFACES

Citation Formats

Dubon, O. D., Robinson, J. T., Cao, Y., Lawrence Berkeley National Laboratory, Berkeley, CA 94720, and Liddle, J. A. Programming the Shape of Highly Ordered Ge Islands on Si: from Dots to Rods. United States: N. p., 2007. Web. doi:10.1063/1.2729758.
Dubon, O. D., Robinson, J. T., Cao, Y., Lawrence Berkeley National Laboratory, Berkeley, CA 94720, & Liddle, J. A. Programming the Shape of Highly Ordered Ge Islands on Si: from Dots to Rods. United States. doi:10.1063/1.2729758.
Dubon, O. D., Robinson, J. T., Cao, Y., Lawrence Berkeley National Laboratory, Berkeley, CA 94720, and Liddle, J. A. Tue . "Programming the Shape of Highly Ordered Ge Islands on Si: from Dots to Rods". United States. doi:10.1063/1.2729758.
@article{osti_21055055,
title = {Programming the Shape of Highly Ordered Ge Islands on Si: from Dots to Rods},
author = {Dubon, O. D. and Robinson, J. T. and Cao, Y. and Lawrence Berkeley National Laboratory, Berkeley, CA 94720 and Liddle, J. A.},
abstractNote = {In the Ge on Si model heteroepitaxial system, we show that metal patterns on the Si surface induce the assembly of deposited Ge atoms into highly ordered islands whose shapes are programmed by a combination of metal species and substrate orientation. The island shapes including truncated pyramids and nanorods are radically different from those grown on metal-free surfaces and arise by a process whereby intermixing between deposited Ge and substrate Si atoms from the onset of island formation facilitate the island shape evolution.},
doi = {10.1063/1.2729758},
journal = {AIP Conference Proceedings},
number = 1,
volume = 893,
place = {United States},
year = {Tue Apr 10 00:00:00 EDT 2007},
month = {Tue Apr 10 00:00:00 EDT 2007}
}
  • The critical volume for the onset of plastic strain relaxation in SiGe islands on Si(001) is computed for different Ge contents and realistic shapes by using a three-dimensional model, with position-dependent dislocation energy. It turns out that the critical bases for dome- and barnlike islands are different for any composition. By comparison to extensive atomic force microscopy measurements of the footprints left on the Si substrates by islands grown at different temperatures (and compositions), we conclude that, in contrast with planar films, dislocation nucleation in 3D islands is fully thermodynamic.
  • Strained Ge islands have been grown on fully relaxed Si{sub 0.5}Ge{sub 0.5} substrate by pulsed laser ablation technique. The formation of strained Ge islands has been found for film with higher thickness following StranskiÔÇôKrastanov growth mechanism. The variation of strain with changing Ge layer thickness has been analyzed using Raman spectroscopy and high-resolution X-ray diffraction techniques. X-ray photoelectron spectra have shown the absence of any Si-Ge intermixing and oxidation of Ge films. A strong no-phonon photoluminescence emission from Ge islands has been observed, showing the superior optical characteristics of the islands grown on relaxed substrate.
  • The shape evolution of Ge/Si(001) islands grown by ultrahigh vacuum chemical vapor deposition were investigated by atomic force microscopy at different deposition rates. We find that, at low deposition rates, the evolution of islands follows the conventional pathway by which the islands form the pyramid islands, evolve into dome islands, and dislocate at a superdome shape with increasing coverage. While at a high deposition rate of 3 monolayers per minute, the dome islands evolve towards the pyramids by a reduction of the contact angle. The presence of the atomic intermixing between the Ge islands and Si substrate at high depositionmore » rate is responsible for the reverse evolution. {copyright} 2001 American Institute of Physics.« less
  • Ge islands were grown on Si(001) and then annealed at 650 degree sign C for 0, 20, 40, and 60 min in a chemical-vapor deposition reactor following Ge deposition. This letter confirms the previous observations directly. By combining the ability to quantify strain with the ability to measure island dimensions in a transmission electron microscope, we were able to plot strain versus aspect ratio for the various annealing times. The islands first relax strain because of Si intermixing with the Ge epilayer causes the lattice mismatch to be lowered. Once the mismatch is sufficiently reduced, and thus the strain energymore » sufficiently reduced, it becomes favorable for the islands to reverse their shape back from domes to pyramids, thus reducing surface energy. This confirms the reversibility of island shape and thus the thermodynamics of the transition. (c) 2000 American Institute of Physics.« less
  • In the Ge on Si model heteroepitaxial system, metal patterns on the silicon surface provide unprecedented control over the morphology of highly ordered Ge islands. Island shape including nanorods and truncated pyramids is set by the metal species and substrate orientation. Analysis of island faceting elucidates the prominent role of the metal in promoting growth of preferred facet orientations while investigations of island composition and structure reveal the importance of Si-Ge intermixing in island evolution. These effects reflect a remarkable combination of metal-mediated growth phenomena that may be exploited to tailor the functionality of island arrays in heteroepitaxial systems.