Crystallization of Amorphous Si0.6Ge0.4 Nanoparticles Embedded in SiO2: Crystallinity Versus Compositional Stability Articles uri icon

authors

  • RODRIGUEZ, A
  • RODRIGUEZ, T
  • PRIETO, A.C
  • JIMÉNEZ, J
  • KLING, A
  • BALLESTEROS PEREZ, CARMEN INES
  • SANGRADOR, J

publication date

  • August 2010

start page

  • 1194

end page

  • 1202

issue

  • 8

volume

  • 39

International Standard Serial Number (ISSN)

  • 0361-5235

Electronic International Standard Serial Number (EISSN)

  • 1543-186X

abstract

  • Si0.6Ge0.4 nanocrystals, of diameter <5 nm, embedded in SiO2 in the form of single layers (2.1 × 1012 nanoparticles cm&-2) and five-period multilayers (above 1013 nanoparticles cm&-2) have been fabricated using a low-thermal-budget process consisting of deposition by low-pressure chemical vapor deposition
    and crystallization by rapid thermal annealing at several
    temperatures and for different times. The crystallization process
    was monitored by Raman spectroscopy and transmission
    electron microscopy. The loss of integrity and compositional changes
    of the nanoparticles during the annealing process were
    characterized by Rutherford backscattering spectrometry. During the
    annealing process, crystallization and Ge out-diffusion have
    been observed to compete with each other. Annealing of samples
    with nanoparticles of 4.6 nm diameter at low temperature
    (750°C) yields poor crystallization of the nanoparticles and causes
    the Ge to leave them by a pure diffusive mechanism, thus
    destroying their integrity. At higher temperatures (≥800°C),
    crystallization
    takes place in a short period of time (<30 s) and
    diffusion from the crystallized material is initially hindered. For
    samples
    with nanoparticles of 3.3 nm diameter, partial
    crystallization is detected at 800°C and 900°C and the crystalline
    quality
    is improved in both cases as the annealing time increases.
    Also, the detection capabilities of the Raman spectroscopy system
    for the detection of a certain density of SiGe nanocrystals
    of given diameter and composition have been explored and the lower
    limit estimated.