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Title: Si and Ge nanocluster formation in silica matrix

Abstract

High resolution transmission electron microscopy, scanning transmission electron microscopy, and cathodoluminescence have been used to investigate Si and Ge cluster formation in amorphous silicon-dioxide layers. Commonly, cathodoluminescence emission spectra of pure SiO{sub 2} are identified with particular defect centers within the atomic network of silica including the nonbridging oxygen hole center associated with the red luminescence at 650 nm (1.9 eV) and the oxygen deficient centers with the blue (460 nm; 2.7 eV) and ultraviolet band (295 nm; 4.2 eV). In Ge{sup +} ion-implanted SiO{sub 2}, an additional violet emission band appears at 410 nm (3.1 eV). The strong increase of this violet luminescence after thermal annealing is associated with formation of low-dimension Ge aggregates such as dimers, trimers, and higher formations, further growing to Ge nanoclusters. On the other hand, pure silica layers were modified by heavy electron beam irradiation (5 keV; 2.7 A/cm{sup 2}), leading to electronic as well as thermal dissociation of oxygen and the appearance of under-stoichiometric SiO{sub x}. This SiO{sub x} will undergo a phase separation and we observe Si cluster formation with a most probable cluster diameter of 4 nm. Such largely extended Si clusters will diminish the SiO{sub 2}-related luminescence and Si-crystal-related luminescencemore » in the near IR.« less

Authors:
 [1];  [2]; ; ;  [3];  [4];  [1]
  1. University of Rostock, Institute of Physics (Germany)
  2. Cornell University, School of Applied and Engineering Physics (United States)
  3. Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)
  4. Institute of Ion Beam Physics and Materials Research, Research Center Rossendorf (Germany)
Publication Date:
OSTI Identifier:
21088092
Resource Type:
Journal Article
Resource Relation:
Journal Name: Semiconductors; Journal Volume: 41; Journal Issue: 4; Other Information: DOI: 10.1134/S1063782607040033; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Ltd; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; CATHODOLUMINESCENCE; CRYSTAL DEFECTS; CRYSTALS; DISSOCIATION; ELECTRON BEAMS; EMISSION SPECTRA; EV RANGE 01-10; GERMANIUM IONS; ION IMPLANTATION; IRRADIATION; KEV RANGE 01-10; LAYERS; NANOSTRUCTURES; OXYGEN; SILICA; SILICON OXIDES; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Salh, Roushdey, Fitting, L., Kolesnikova, E. V., Sitnikova, A. A., Zamoryanskaya, M. V., Schmidt, B., and Fitting, H.-J.. Si and Ge nanocluster formation in silica matrix. United States: N. p., 2007. Web. doi:10.1134/S1063782607040033.
Salh, Roushdey, Fitting, L., Kolesnikova, E. V., Sitnikova, A. A., Zamoryanskaya, M. V., Schmidt, B., & Fitting, H.-J.. Si and Ge nanocluster formation in silica matrix. United States. doi:10.1134/S1063782607040033.
Salh, Roushdey, Fitting, L., Kolesnikova, E. V., Sitnikova, A. A., Zamoryanskaya, M. V., Schmidt, B., and Fitting, H.-J.. Sun . "Si and Ge nanocluster formation in silica matrix". United States. doi:10.1134/S1063782607040033.
@article{osti_21088092,
title = {Si and Ge nanocluster formation in silica matrix},
author = {Salh, Roushdey and Fitting, L. and Kolesnikova, E. V. and Sitnikova, A. A. and Zamoryanskaya, M. V. and Schmidt, B. and Fitting, H.-J.},
abstractNote = {High resolution transmission electron microscopy, scanning transmission electron microscopy, and cathodoluminescence have been used to investigate Si and Ge cluster formation in amorphous silicon-dioxide layers. Commonly, cathodoluminescence emission spectra of pure SiO{sub 2} are identified with particular defect centers within the atomic network of silica including the nonbridging oxygen hole center associated with the red luminescence at 650 nm (1.9 eV) and the oxygen deficient centers with the blue (460 nm; 2.7 eV) and ultraviolet band (295 nm; 4.2 eV). In Ge{sup +} ion-implanted SiO{sub 2}, an additional violet emission band appears at 410 nm (3.1 eV). The strong increase of this violet luminescence after thermal annealing is associated with formation of low-dimension Ge aggregates such as dimers, trimers, and higher formations, further growing to Ge nanoclusters. On the other hand, pure silica layers were modified by heavy electron beam irradiation (5 keV; 2.7 A/cm{sup 2}), leading to electronic as well as thermal dissociation of oxygen and the appearance of under-stoichiometric SiO{sub x}. This SiO{sub x} will undergo a phase separation and we observe Si cluster formation with a most probable cluster diameter of 4 nm. Such largely extended Si clusters will diminish the SiO{sub 2}-related luminescence and Si-crystal-related luminescence in the near IR.},
doi = {10.1134/S1063782607040033},
journal = {Semiconductors},
number = 4,
volume = 41,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • Si nanocrystals with face-centered-cubic (fcc) structure were fabricated using common sputtering technique, but applying bias on the substrate, the thermodynamic calculation indicates that the bombardment of Ar{sup +} ions arising from the bias should be responsible for the crystallization and phase transition of Si nanocrystals. The silica films containing fcc-Si nanocrystals give strong blue and ultraviolet light emissions, which suggest that the band structure of Si material could be modified by changing the crystal structure.
  • The Si{sub 2}{sup +} and Ge{sub 2}{sup +} cation radicals were generated by pulsed laser vaporization and isolated in rare-gas matrices at 4 K for electron spin resonance (ESR) investigations. The electronic ground states were established as X{sup 4}{Sigma} for both cations with the three unpaired electrons occupying predominantly valence p-type orbitals. In the case of {sup 29}Si{sub 2}{sup +}, the observed nuclear hyperfine interaction (A tensor) was compared with that computed in an ab initio configuration interaction type calculation. The dependence of the hyperfine parameters on internuclear distance was also investigated. For comparison purposes, all diatomic and triatomic cationsmore » studied in the gas phase and in rare-gas matrices at sufficiently high resolution to observe nuclear hyperfine interaction are listed. For {sup 29}Si{sub 2}{sup +} in neon, g{sub {perpendicular}} = 1.993 (1), {vert bar}A{sub {perpendicular}}{vert bar} = 52.4 (5) MHz, and D = 27.6 (8) GHz; for {sup 73}Ge{sub 2}{sup +}, g{sub {perpendicular}} = 1.939 (1) and {vert bar}A{sub {perpendicular}}{vert bar} = 10 (3) MHz.« less
  • Longitudinal photoconductivity spectra of Si/Ge multilayer structures with Ge quantum dots grown pseudomorphically to the Si matrix are studied. Lines of optical transitions between hole levels of quantum dots and Si electronic states are observed. This allowed us to construct a detailed energy-level diagram of electron-hole levels of the structure. It is shown that hole levels of pseudomorphic Ge quantum dots are well described by the simplest 'quantum box' model using actual sizes of Ge islands. The possibility of controlling the position of the long-wavelength photosensitivity edge by varying the growth parameters of Si/Ge structures with Ge quantum dots ismore » determined.« less
  • Using magnetron cosputtering of SiO{sub 2}, Ge, and Si targets, Si-based SiO{sub 2}:Ge:Si films were fabricated for exploring the influence of Si target proportion (P{sub Si}) and annealing temperature (Ta) on formation, local structure, and phonon properties of nanocrystalline Si{sub 1-x}Ge{sub x} (nc-Si{sub 1-x}Ge{sub x}). At low P{sub Si} and Ta higher than 800 deg. C, no nc-Si{sub 1-x}Ge{sub x} but a kind of composite nanocrystal consisting of a Ge core, GeSi shell, and amorphous Si outer shell is formed in the SiO{sub 2} matrix. At moderate P{sub Si}, nc-Si{sub 1-x}Ge{sub x} begins to be formed at Ta=800 deg. Cmore » and coexists with nc-Ge at Ta=1100 deg. C. At high P{sub Si}, it was disclosed that both optical phonon frequency and lattice spacing of nc-Si{sub 1-x}Ge{sub x} increase with raising Ta. The possible origin of this phenomenon is discussed by considering three factors, the phonon confinement, strain effect, and composition variation of nc-Si{sub 1-x}Ge{sub x}. This work will be helpful in understanding the growth process of ternary GeSiO films and beneficial to further investigations on optical properties of nc-Ge{sub 1-x}Si{sub x} in the ternary matrix.« less
  • The capability to fabricate Ge/Si quantum dots with small dot size and high dot density uniformly over a large area is crucial for many applications. In this work, we demonstrate that this can be achieved by scanning a pre-deposited Ge thin layer on Si substrate with a line-focused pulsed laser beam to induce formation of quantum dots. With suitable setting, Ge/Si quantum dots with a mean height of 2.9 nm, a mean diameter of 25 nm, and a dot density of 6×10{sup 10} cm{sup −2} could be formed over an area larger than 4 mm{sup 2}. The average size ofmore » the laser-induced quantum dots is smaller while their density is higher than that of quantum dots grown by using Stranski-Krastanov growth mode. Based on the dependence of the characteristics of quantum dots on the laser parameters, a model consisting of laser-induced strain, surface diffusion, and Ostwald ripening is proposed for the mechanism underlying the formation of the Ge/Si quantum dots. The technique demonstrated could be applicable to other materials besides Ge/Si.« less