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Title: Absorption and emission of silicon nanocrystals embedded in SiC: Eliminating Fabry-Pérot interference

Silicon nanocrystals embedded in SiC are studied by spectrophotometry and photoluminescence (PL) spectroscopy. Absorptivities are found to be affected by residual Fabry-Pérot interference arising from measurements of reflection and transmission at locations of different film thickness. Multiple computational and experimental methods to avoid these errors in thin film measurements, in general, are discussed. Corrected absorptivity depends on the quantity of Si embedded in the SiC but is independent of the Si crystallinity, indicating a relaxation of the k-conservation criterion for optical transitions in the nanocrystals. Tauc gaps of 1.8–2.0 and 2.12 eV are determined for Si nanoclusters and SiC, respectively. PL spectra exhibit a red-shift of ∼100 nm per nm nominal Si nanocluster diameter, which is in agreement with quantum confinement but revealed to be an artifact entirely due to Fabry-Pérot interference. Several simple experimental methods to diagnose or avoid interference in PL measurements are developed that are applicable to all thin films. Corrected PL is rather weak and invariant with passivation, indicating that non-paramagnetic defects are responsible for rapid non-radiative recombination. They are also responsible for the broad, sub-gap PL of the SiC, and can wholly account for the form of the PL of samples with Si nanoclusters. The PL intensitymore » of samples with Si nanoclusters, however, can only be explained with an increased density of luminescent defects in the SiC due to Si nanoclusters, efficient tunneling of photogenerated carriers from Si nanoclusters to SiC defects, or with emission from a-Si nanoclusters. Films prepared on Si exhibit much weaker PL than the same films prepared on quartz substrates.« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [4] ;  [5] ; ;  [1] ;  [6]
  1. Fraunhofer-Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany)
  2. (United Kingdom)
  3. Consiglio Nazionale delle Richerche—Istituto per e i Microsistemi, Via Gobetti 101, 40129 Bologna (Italy)
  4. Department of Materials and Nano Physics, School of Information and Communication Technology, Royal Institute of Technology, Electrum 229, 16440 Kista (Sweden)
  5. MIND–IN2UB, Electronics Department, University of Barcelona, Martí i Franquès 1, E–08028 Barcelona (Spain)
  6. Department of Materials, University of Oxford, Parks Rd., Oxford OX1 3PH (United Kingdom)
Publication Date:
OSTI Identifier:
22413014
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 4; Other Information: (c) 2015 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; ABSORPTION; ABSORPTIVITY; EMISSION SPECTROSCOPY; FABRY-PEROT INTERFEROMETER; INTERFERENCE; NANOSTRUCTURES; PARAMAGNETISM; PHOTOLUMINESCENCE; QUARTZ; RECOMBINATION; RED SHIFT; REFLECTION; RELAXATION; SILICON; SILICON CARBIDES; SPECTROPHOTOMETRY; SUBSTRATES; THIN FILMS; TUNNEL EFFECT