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  • AIP Publishing  (10)
  • 1
    Online Resource
    Online Resource
    Role of intericosahedral chains on the hardness of sputtered boron carbide films
    AIP Publishing ; 2004
    In:  Applied Physics Letters Vol. 84, No. 21 ( 2004-05-24), p. 4173-4175
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 84, No. 21 ( 2004-05-24), p. 4173-4175
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.1755841
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2004
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 2
    Online Resource
    Online Resource
    Synthesis, structure, and scintillation of Ce-doped gadolinium oxyorthosilicate nanoparticles prepared by solution combustion synthesis
    AIP Publishing ; 2011
    In:  Journal of Applied Physics Vol. 110, No. 8 ( 2011-10-15)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 110, No. 8 ( 2011-10-15)
    Abstract: The synthesis of Ce-doped Gd oxyorthosilicate nanoparticles using the solution combustion synthesis (SCS) method was investigated as a function of the amount of SiO2 in the precursor mixture. The SCS product consists of mixtures of Ce-doped Gd2SiO5, Gd4.67(SiO4)3O, and Gd2O3, whose relative concentrations depend on the amount of SiO2 in the precursor mixture; the synthesis of GSO:Ce was obtained with a reduction by 30% of the SiO2 content. Accordingly, this is the brightest material produced, with a photoluminescence signal that is comparable to that obtained from the bulk sample. Thermoluminescence (TL) results showed a considerably lower concentration of trapping defects in the nanoparticles than in the bulk sample. A previous study [E. G. Yukihara, L. G. Jacobsohn, M. W. Blair, B. L. Bennett, S. C. Tornga, and R. E. Muenchausen, J. Lumin. 130, 2309-2316 (2010)] reporting a comparison between photoluminescence and scintillation measurements, coupled to the TL characterization, suggests that surfaces play a major role in decreasing the scintillation efficiency of the nanoparticles. These results show that it is possible to prepare relatively bright scintillator powders using the SCS method.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.3647304
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2011
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 3
    Online Resource
    Online Resource
    Luminescent properties and reduced dimensional behavior of hydrothermally prepared Y2SiO5:Ce nanophosphors
    AIP Publishing ; 2006
    In:  Applied Physics Letters Vol. 88, No. 10 ( 2006-03-06)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 88, No. 10 ( 2006-03-06)
    Abstract: Hydrothermally prepared nanophosphor Y2SiO5:Ce crystallizes in the P21∕c structure, rather than the B2∕b structure observed in bulk material. Relative to bulk powder, nanophosphors of particle size ∼25–100nm diameter exhibit redshifts of the photoluminescence excitation and emission spectra, reduced self absorption, enhanced light output, and medium-dependent radiative lifetime. Photoluminescence data are consistent with reduced symmetry of the P21∕c structure and are not necessarily related to reduced dimensionality of the nanophosphor. In contrast, medium-dependent lifetime and enhanced light output are attributed to nanoscale behavior. Perturbation of the Ce ion electric field is responsible for the variable lifetime.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.2183737
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2006
    detail.hit.zdb_id: 211245-0
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  • 4
    Online Resource
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    Synthesis of cobalt nanoparticles by ion implantation and effects of postimplantation annealing
    AIP Publishing ; 2004
    In:  Journal of Applied Physics Vol. 96, No. 8 ( 2004-10-15), p. 4444-4450
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 96, No. 8 ( 2004-10-15), p. 4444-4450
    Abstract: A study of the synthesis of Co nanoparticles by ion implantation and the effects of postimplantation annealing was carried out. Silica was implanted with 35keV Co+ ion beams to doses ranging from 8×1015to1×1017atoms∕cm2. Nanoparticle size, distribution, and structure were ascertained via transmission electron microscopy measurements, which reveal the presence of spherical nanoparticles in both as-implanted and annealed samples. X-ray photoelectron spectroscopy show the chemical state of the nanoparticles in both as-implanted and annealed samples to be metallic. Temperature-dependent field-cooled and zero-field-cooled, susceptibility measurements indicated superparamagnetic behavior, which is analyzed by accounting for the size dispersion of the nanoparticles. Results showed that the magnetic properties of the specimen can be tailored by implantation conditions. Annealing in vacuum at 900°C for up to 10h leads to an increase of the average nanoparticle size and a broader size distribution. Mie scattering and magnetic force microscopy measurements provide evidence of a strong interaction among the nanoparticles in the annealed samples. The feasibility of obtaining small-dispersion size-controlled synthesis of Co nanoparticles at room temperature is illustrated.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1787143
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2004
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 5
    Online Resource
    Online Resource
    Y 2 O 3 : Bi nanophosphor: Solution combustion synthesis, structure, and luminescence
    AIP Publishing ; 2008
    In:  Journal of Applied Physics Vol. 104, No. 12 ( 2008-12-15)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 104, No. 12 ( 2008-12-15)
    Abstract: Photoluminescence (PL), radioluminescence (RL), and thermoluminescence (TL) investigation of Y2O3:Bi nanophosphors prepared by solution combustion synthesis using urea, glycine, and hexamethylenetetramine (HMT) as fuels was carried out. The as-prepared nanopowders have increasing crystallinity and average crystallite sizes for urea, glycine, and HMT, respectively. Luminescence is composed of two emission bands centered at 408 and 505 nm due to two nonequivalent Bi3+ sites with symmetry S6 and C2, respectively. The occupancy of these sites depends on the synthesis conditions, in agreement with theoretical predictions. Annealing at 1000 °C for 1 h improves PL and RL efficiency due to enhanced crystallinity of the nanopowders and activation of recombination centers (Bi3+ ions). No shift in the PL peak position was observed as a function of average crystallite size. The concentration quenching was experimentally determined to have a maximum emission of around 3 mol % of the dopant. TL spectra present several peaks between 50 and 300 °C, and the total TL signal is correlated with the heat of combustion of the fuel and thus crystallinity increases. Most likely, increases in RL and TL are also due to the increase in the concentration of recombination centers.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.3042223
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 6
    Online Resource
    Online Resource
    Multifunction Gd2O3:Eu nanocrystals produced by solution combustion synthesis: Structural, luminescent, and magnetic characterization
    AIP Publishing ; 2008
    In:  Journal of Applied Physics Vol. 103, No. 10 ( 2008-05-15)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 103, No. 10 ( 2008-05-15)
    Abstract: The synthesis, structural, luminescent, and magnetic properties of multifunction 8 at. % Eu-doped Gd2O3 nanocrystals were investigated. The material was synthesized by the solution combustion technique and characterized by x-ray diffraction (XRD), transmission electron microscopy, and photoluminescence and magnetization measurements. The as-prepared material presents predominant base-centered monoclinic structure with average crystallite size of 35 nm. Isothermal annealing at 1000 °C for up to 152 h induced gradual structural transition toward the body-centered cubic structure. Debye–Scherrer analysis of XRD results showed that annealing did not induce grain growth of monoclinic nanocrystals, while cubic nanocrystals reached 47 nm after annealing for 152 h. The luminescent behavior was monitored as a function of annealing time and related to the structural transformation. In particular, an inversion of the predominant photoluminescence emission line from 621.4 to 609.5 nm was observed and related to changes in the crystalline field resultant to phase transformation from cubic to monoclinic. Magnetic measurements revealed the paramagnetic nature of the material, much insensitive to the crystallographic structure.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.2931024
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
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  • 7
    Online Resource
    Online Resource
    Array of cobalt nanoparticles in silica: Synthesis and effects of thermal annealing
    AIP Publishing ; 2006
    In:  Journal of Applied Physics Vol. 99, No. 10 ( 2006-05-15)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 99, No. 10 ( 2006-05-15)
    Abstract: The synthesis, characterization, and the effects of isochronal annealing of nearly monodispersive three-dimensional arrays of Co nanoparticles are presented. Samples were obtained by alternating electron beam evaporation of Co and SiO2 layers 0.5 and 20nm thick, respectively, onto fused silica. Transmission electron microscopy (TEM) revealed the presence of 3.2nm diameter Co particles with a size dispersion standard deviation of 16%. Annealing at temperatures up to 800°C was carried out in vacuum for 5min. Field and zero-field cooled measurements of the magnetic susceptibility monitored the effects of annealing on the magnetic behavior. Two temperature regimes were observed. One, up to 700°C with an activation energy of 0.062eV where no significant particle size change was observed, was tentatively related to bonding ordering within the particles. The other regime, with an activation energy of 0.67eV, was attributed to Co diffusion and reflected particle growth as observed by TEM. These results were supported by exchange bias anisotropy and x-ray photoelectron spectroscopy measurements.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.2199982
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2006
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 8
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    Online Resource
    Quantum confinement contribution to porous silicon photoluminescence spectra
    AIP Publishing ; 2004
    In:  Journal of Applied Physics Vol. 96, No. 1 ( 2004-07-01), p. 197-203
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 96, No. 1 ( 2004-07-01), p. 197-203
    Abstract: Photoluminescence (PL) spectra of freshly etched and ambient-aged porous silicon specimens have been measured and analyzed to extract spectral contributions due to quantum confinement (QC) and non-QC effects. It is shown that all spectra can be deconvolved into five Gaussian bands with typical peak energies 1.59, 1.76, 1.84, 1.94, and 2.07 eV. Ambient aging induces ∼0.1 eV blueshift in each of the three highest energy peaks, which is attributed to QC effects. In contrast, the two lowest energy peaks remain unshifted as expected for non-QC effects. Because size of the porous silicon nanoparticles is deduced from the magnitude of blueshift, it is imperative to correctly identify the spectral components associated solely with QC. The three closely spaced Gaussian bands are summed and the resulting single Gaussian band is analyzed with the model of Islam and Kumar [J. Appl. Phys. 93, 1753 (2003)]. Results show that peak energy of the freshly etched sample is 1.86 eV with average nanoparticle size L0=3.90 nm and dispersion σ=0.065 nm. Ambient aging for 40 days causes this peak to blueshift to 2.07 eV and reduces the nanoparticle size to L0=3.37 nm with dispersion σ=0.088 nm. The reduction in particle size (ΔL=0.53 nm) is attributed to oxidation of the nanocrystalline surface, and corresponds to approximately 2 monolayers of oxide growth.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1756217
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2004
    detail.hit.zdb_id: 220641-9
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  • 9
    Online Resource
    Online Resource
    The role of the chemical nature of implanted species on quenching and recovery of photoluminescence in ion-irradiated porous silicon
    AIP Publishing ; 2005
    In:  Journal of Applied Physics Vol. 98, No. 7 ( 2005-10-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 98, No. 7 ( 2005-10-01)
    Abstract: The effects of ion irradiation on porous Si (po-Si) photoluminescence (PL) have been investigated. Specimens were progressively irradiated with H+ and He+ ions followed by PL measurements. After the final irradiation, which resulted in total PL quenching, PL recovery was monitored for more than 200 days. The behavior of both PL quenching and recovery was correlated to the amount of retained irradiation-induced damage, determined by channeling spectrometry measurements, and to the chemical nature of the implanted species. Quenching was attributed to the generation of defects that create nonradiative states within the gap, while recovery was attributed to the passivation of these defects by atmospheric exposure. H+ irradiation is approximately five times more efficient in quenching PL and leads to approximately four times lower recovery rate than He+ irradiation. This behavior is attributed to the formation of stable H-defect complexes.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.2081118
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2005
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 10
    Online Resource
    Online Resource
    The effects of ion irradiation on porous silicon photoluminescence
    AIP Publishing ; 2005
    In:  Journal of Applied Physics Vol. 97, No. 3 ( 2005-02-01)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 97, No. 3 ( 2005-02-01)
    Abstract: The effects of ion irradiation on porous Si (po-Si) photoluminescence (PL) are investigated to gain insight into the emission mechanism. Po-Si was obtained by standard electrochemical etching of p-doped Si(100) and the samples were aged for several weeks to achieve stability of the PL intensity. Specimens were progressively irradiated with H+, He+, or Ne++ ions followed by PL measurements. PL spectra were obtained as a function of the displacement per atom (DPA) parameter up to a DPA level of ∼10−2, which was sufficient to nearly extinguish PL. The quenching behavior showed a strong dependence on the chemical nature of the implanted species. Within experimental error, the quenching efficiency was equivalent for He+ and Ne++ irradiations, but was considerably higher for H+ irradiation. Channeling spectrometry showed the efficiency to be correlated with the self-recovery of defects generated during irradiation. The observed PL quenching is associated with the creation of nonradiative recombination sites within the band gap, but not with Si nanostructure amorphization and∕or surface oxygen removal. Significant recovery of quenched PL occurs over a period of 120days for specimens that are stored in air, but not for samples that are stored in vacuum. These results demonstrate the importance and complexity of surface oxidation on the po-Si luminescence mechanism.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.1849434
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2005
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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