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Title: Silicon nanocrystals in SiN{sub x}/SiO{sub 2} hetero-superlattices: The loss of size control after thermal annealing

Superlattices containing 3 nm thick silicon rich silicon nitride sublayers and 3 nm and 10 nm thick SiO{sub 2} barriers were prepared by plasma enhanced chemical vapor deposition. Despite the as-prepared samples represented a well-kept multilayer structure with smooth interfaces, the high temperature annealing resulted in the total destruction of multilayer structure in the samples containing 3 nm SiO{sub 2} barriers. Energy-filtered transmission electron microscopy images of these samples indicated a silicon nanoclusters formation with sizes of 2.5–12.5 nm, which were randomly distributed within the structure. Although in the sample with 10 nm SiO{sub 2} barriers some fragments of the multilayer structure could be still observed after thermal annealing, nevertheless, the formation of large nanocrystals with diameters up to 10 nm was confirmed by dark field transmission electron microscopy. Thus, in contrast to the previously published results, the expected size control of silicon nanocrystals was lost. According to the FTIR results, the thermal annealing of SiN{sub x}/SiO{sub 2} superlattices led to the formation of silicon nanocrystals in mostly oxynitride matrix. Annealed samples demonstrated a photoluminescence peak at 885 nm related to the luminescence of silicon nanocrystals, as confirmed by time-resolved photoluminescence measurements. The loss of nanocrystals size control is discussed in terms of the migration of oxygen atomsmore » from the SiO{sub 2} barriers into the silicon rich silicon nitride sublayers. A thermodynamic mechanism responsible for this process is proposed. According to this mechanism, the driving force for the oxygen migration is the gain in the configuration entropy related to the relative arrangements of oxygen and nitrogen atoms.« less
Authors:
;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ; ;  [5] ; ;  [6] ;  [6] ;  [7] ;  [8]
  1. Faculty of Engineering, IMTEK, Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 103, Freiburg 79110 (Germany)
  2. (Ukraine)
  3. Faculty of Physics, M.V. Lomonosov Moscow State University, Leninskie Gory 1, Moscow 119991 (Russian Federation)
  4. Fraunhofer-Institut für Solare Energiesysteme ISE, Heidenhofstr. 2, Freiburg 79110 (Germany)
  5. Max-Planck-Institute of Microstructure Physics, Weinberg 2, Halle 06120 (Germany)
  6. MIND-IN2UB, Departament d'Electrònica, Universitat de Barcelona, C/Martí i Franquès, 1, Barcelona 08028 (Spain)
  7. (Spain)
  8. Optics and Photonics, School of Information and Communication Technology, Royal Institute of Technology (KTH), Electrum 229, Kista SE-16440 (Sweden)
Publication Date:
OSTI Identifier:
22304498
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 24; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; CHEMICAL VAPOR DEPOSITION; DIFFUSION BARRIERS; ENTROPY; FOURIER TRANSFORMATION; INFRARED SPECTRA; INTERFACES; LAYERS; NANOMATERIALS; NANOSTRUCTURES; OXYGEN; PHOTOLUMINESCENCE; PLASMA; RANDOMNESS; SILICON; SILICON NITRIDES; SILICON OXIDES; SUPERLATTICES; TIME RESOLUTION; TRANSMISSION ELECTRON MICROSCOPY