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Title: Expansion and melting of Xe nanocrystals in Si

Abstract

Xe agglomerates confined in a Si matrix by ion implantation were synthesized with different size depending on the implantation process and/or the thermal treatment. At low temperature Xe nanocrystals are formed, whose expansion and melting were studied in the range 15-300 K. Previous high resolution x-ray diffraction spectra were corroborated with complementary techniques such as two-dimensional imaging plate patterns and transmission electron microscopy. We detected fcc Xe nanocrystals whose properties were size dependent. The experiments showed that in annealed samples epitaxial condensation of small Xe clusters, on the cavities of the Si matrix, gave in fact expanded and oriented Xe, suggesting a possible preferential growth of Xe (311) planes oriented orthogonally to the Si[02-2] direction. On the contrary, small Xe clusters in an amorphous Si matrix have a fcc lattice contracted as a consequence of surface tension. Furthermore, a solid-to-liquid phase transition size dependent was found. Expansion of fcc Xe lattice was accurately determined as a function of the temperature. Overpressurized nanocrystals and/or binary size distributions were disproved.

Authors:
; ; ; ;  [1];  [2];  [3]
  1. Dipartimento di Fisica e Astronomia, Universita di Catania, MATIS-Istituto Nazionale di Fisica della Materia, Via Santa Sofia 64, 95123 Catania (Italy)
  2. (France)
  3. (United States)
Publication Date:
OSTI Identifier:
20853977
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 74; Journal Issue: 23; Other Information: DOI: 10.1103/PhysRevB.74.235436; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; DISTRIBUTION; EPITAXY; EXPANSION; FCC LATTICES; ION IMPLANTATION; LIQUIDS; MELTING; NANOSTRUCTURES; PLATES; SEMICONDUCTOR MATERIALS; SILICON; SOLIDS; SURFACE TENSION; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; XENON

Citation Formats

Faraci, Giuseppe, Pennisi, Agata R., Zontone, Federico, Li, Boquan, Petrov, Ivan, ESRF, European Synchrotron Research Facility, Boite Postale 220, F-38043 Grenoble Cedex, and CMM-Center for Microanalysis of Materials, University of Illinois, Urbana, Illinois 61801. Expansion and melting of Xe nanocrystals in Si. United States: N. p., 2006. Web. doi:10.1103/PHYSREVB.74.235436.
Faraci, Giuseppe, Pennisi, Agata R., Zontone, Federico, Li, Boquan, Petrov, Ivan, ESRF, European Synchrotron Research Facility, Boite Postale 220, F-38043 Grenoble Cedex, & CMM-Center for Microanalysis of Materials, University of Illinois, Urbana, Illinois 61801. Expansion and melting of Xe nanocrystals in Si. United States. doi:10.1103/PHYSREVB.74.235436.
Faraci, Giuseppe, Pennisi, Agata R., Zontone, Federico, Li, Boquan, Petrov, Ivan, ESRF, European Synchrotron Research Facility, Boite Postale 220, F-38043 Grenoble Cedex, and CMM-Center for Microanalysis of Materials, University of Illinois, Urbana, Illinois 61801. Fri . "Expansion and melting of Xe nanocrystals in Si". United States. doi:10.1103/PHYSREVB.74.235436.
@article{osti_20853977,
title = {Expansion and melting of Xe nanocrystals in Si},
author = {Faraci, Giuseppe and Pennisi, Agata R. and Zontone, Federico and Li, Boquan and Petrov, Ivan and ESRF, European Synchrotron Research Facility, Boite Postale 220, F-38043 Grenoble Cedex and CMM-Center for Microanalysis of Materials, University of Illinois, Urbana, Illinois 61801},
abstractNote = {Xe agglomerates confined in a Si matrix by ion implantation were synthesized with different size depending on the implantation process and/or the thermal treatment. At low temperature Xe nanocrystals are formed, whose expansion and melting were studied in the range 15-300 K. Previous high resolution x-ray diffraction spectra were corroborated with complementary techniques such as two-dimensional imaging plate patterns and transmission electron microscopy. We detected fcc Xe nanocrystals whose properties were size dependent. The experiments showed that in annealed samples epitaxial condensation of small Xe clusters, on the cavities of the Si matrix, gave in fact expanded and oriented Xe, suggesting a possible preferential growth of Xe (311) planes oriented orthogonally to the Si[02-2] direction. On the contrary, small Xe clusters in an amorphous Si matrix have a fcc lattice contracted as a consequence of surface tension. Furthermore, a solid-to-liquid phase transition size dependent was found. Expansion of fcc Xe lattice was accurately determined as a function of the temperature. Overpressurized nanocrystals and/or binary size distributions were disproved.},
doi = {10.1103/PHYSREVB.74.235436},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 23,
volume = 74,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • The structural configuration of Xe clusters, obtained by ion implantation in a Si matrix, has been investigated as a function of the temperature by x-ray absorption fine structure spectroscopy. In contrast with previous results, we demonstrate that an accurate analysis of the data, using high order cumulants, gives evidence of Xe fcc nanocrystals at low temperature, even in the as-implanted Si; expansion of the Xe lattice is always found as a function of the temperature, with no appreciable overpressure. We point out that a dramatic modification of these conclusions can be induced by an incorrect analysis using standard symmetrical pairmore » distribution function G(r); for this reason, all the results were checked by x-ray diffraction measurements.« less
  • The structure of the ternary system U-- Zr-- B was studied by means of x- ray investigations. No ternary compounds are present, but UB 12 and ZrB 12 form a continuous mixed series. UB 2 dissolves about 10 mole% ZrB 2. The thermal expansion coefficients of TaB 2, MoAlSi, Mo(Al,Si) 2, and Mo 3(Al,Si) were determined by measurement of the lattice parameters.
  • The structural characterization, electronic spectroscopy, and excited-state dynamics of surface-oxidized Si nanocrystals, prepared in a high-temperature aerosol apparatus, are studied to gain insight into the emission mechanism of visible light from these systems. The results are compared with direct-gap CdSe nanocrystals, indirect-gap AgBr nanocrystals, bulk crystalline silicon, and porous silicon thin films. As the size of the Si crystallites decreases to 1-2 nm in diameter, the band gap and luminescence energy correspondingly increase to near 2.0 eV, or 0.9 eV above the bulk 1.1-eV band gap. The absorption and luminescence spectra remain indirect-gap-like with strong transverse optical vibronic origins. Themore » quantum yield increases to about 5% at room temperature, but the unimolecular radiative rate remains quite long, approximately 10{sup {minus}3}-10{sup {minus}4} s{sup {minus}1}. The luminescence properties of Si nanocrystals and porous Si are consistent, in most respects, with simple emission from size-dependent, volume-quantum-confined nanocrystal states. Room-temperature quantum yields increase not because coupling to the radiation field is stronger in confined systems, but because radiationless processes, which dominate bulk Si emission, are significantly weaker in nanocrystalline Si. An analogous series of changes occurs in nanocrystalline AgBr. 42 refs., 8 figs.« less
  • An imaging technique to determine in situ the shape and atomic structure of nanosized Xe crystals embedded in Al is described using high-resolution transmission electron microscopy (HRTEM). The Xe nanocrystals, with sizes less than 5 nm were prepared by the implantation of 30 keV Xe+ into Al at room temperature. The fcc Xe nanocrystals are mesotactic with the Al lattice and have a lattice parameter [almost equal to]50% larger than that of Al. HRTEM images of the Xe were not clear in [110] zone axis illumination because of the small number of Xe atoms relative to Al atoms in anymore » atom column. An off-axial imaging technique that consists of tilting the specimen several degrees from a zone axis and defocusing to suppress the Al lattice fringes is employed for the 110 projection of the Xe/Al system and the structure of the Xe nanocrystals is successfully imaged. The Xe images clearly represent projections of cuboctahedra with faces parallel to eight Al {l_brace}111{r_brace} planes truncated by six {l_brace}100{r_brace} planes. The results of multislice image simulations using a three-dimensional atomic model agreed well with the results obtained by the off-axial imaging technique. The usefulness of the technique is demonstrated with observations of crystal defects introduced into the Xe under intense 1000 keV electron irradiation.« less
  • Defect introduction processes in two differently sized Xe nanocrystals embedded in Al were observed with in situ high-resolution electron microscopy. The imaging conditions made it possible to follow the apparent movement of Xe atom columns within a nanocrystal. The positions of individual atom columns were measured on captured video images, before and after defect introduction, from intensity traces along the rows of atom columns. For each of these precipitates, a planar defect appears on {l_brace}1 1 1{r_brace}. The observed displacement of Xe atom columns approximately corresponds to the projected displacement produced by a Shockley partial dislocation, bounding an intrinsic stackingmore » fault. Comparison of the displacements of atoms in the two nanocrystals shows that the displacements are reduced at the precipitate/matrix interfaces. This implies that there will be a displacement at interfaces that represents some compromise between the strain field of the partial dislocation and the interface compatibility requirement.« less