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Hikaru Kobayashi - One of the best experts on this subject based on the ideXlab platform.

  • Photoluminescence from vibrational excited-states for organic molecules adsorbed on Si Nanoparticles.
    Physical chemistry chemical physics : PCCP, 2017
    Co-Authors: Masanori Maeda, Taketoshi Matsumoto, Hikaru Kobayashi
    Abstract:

    Herein, Si Nanoparticles have been fabricated from Si swarf uSing a bead milling method. The adsorption of 9,10-dimethylanthracene (DMA) on Si Nanoparticles enhances the photoluminescence (PL) intenSity by ∼60 000 times that of DMA in hexane. The PL spectra possess peaked structures due to the vibronic tranSition of DMA. For the excitation energies higher than 4.0 eV, vibronic bands with energies higher than the (0, 0) band were observed and attributed to PL from the vibrational excited-states. The excitation spectra showed that incident light was absorbed by both DMA and the Si Nanoparticles. The lifetime of the photo-generated electron-hole pairs in the Si Nanoparticles was much longer than the DMA PL lifetime; this indicated that either a hole or an electron transferred to DMA first, followed by an oppoSite charge transfer. In the cases where a hole is first transferred to DMA, an electronic ground-state is stabilized via solvation. When an electron is captured by the potential of the electronic excited-state, tranSitions from the vibrational excited-states proceed due to the high tranSition probability, generating PL bands with energies higher than the (0, 0) band. In the cases where an electron is first transferred to DMA, internal relaxation to the vibrational ground-state occurs, and the potential of the electronic excited-state is lowered via solvation.

  • Photoluminescence Enhancement of Adsorbed Species on Si Nanoparticles
    Nanoscale Research Letters, 2016
    Co-Authors: Taketoshi Matsumoto, Masanori Maeda, Hikaru Kobayashi
    Abstract:

    We have fabricated Si Nanoparticles from Si swarf uSing the beads milling method. The mode diameter of produced Si Nanoparticles was between 4.8 and 5.2 nm. Si Nanoparticles in hexane show photoluminescence (PL) spectra with peaks at 2.56, 2.73, 2.91, and 3.09 eV. The peaked PL spectra are attributed to the vibronic structure of adsorbed dimethylanthracene (DMA) impurity in hexane. The PL intenSity of hexane with DMA increases by ~3000 times by adsorption on Si Nanoparticles. The PL enhancement results from an increase in absorption probability of incident light by DMA caused by adsorption on the surface of Si Nanoparticles.

  • Si Nanoparticles fabricated from Si swarf by photochemical etching method
    Journal of Nanoparticle Research, 2014
    Co-Authors: Taketoshi Matsumoto, Masanori Maeda, Junichi Furukawa, Woo Byoung Kim, Hikaru Kobayashi
    Abstract:

    Si Nanoparticles are produced from Si swarf which is a waste during slicing Si ingots to produce Si wafers for solar cell use. The beads mill method produces flake-like Si with scores of nanometers width from Si swarf. Subsequent photochemical dissolution with light longer than 560 nm wavelength in a 0.5 % HF solution results in sphere-shaped Si Nanoparticles of 1–7 nm diameter. Si Nanoparticles dispersed in ethanol show blue photoluminescence at ~400 nm (3.1 eV) under UV irradiation, indicating band-gap widening due to the quantum confinement effect. The band-gap energy of most of the Si Nanoparticles is estimated to be 2.5–3.3 eV from the PL spectra, corresponding to the Si nanoparticle Size of 1.9–3.2 nm. On the other hand, Si Nanoparticles produced by immerSion in the HF solution in the dark show much weaker blue photoluminescence. These results demonstrate that the Si dissolution reaction is greatly enhanced by photo-generated holes.

  • Fabrication of Si Nanoparticles from Si swarf and application to solar cells
    Applied Surface Science, 2014
    Co-Authors: Masanori Maeda, Taketoshi Matsumoto, Kentaro Imamura, Hikaru Kobayashi
    Abstract:

    Abstract Si Nanoparticles with diameter of 1–20 nm have been fabricated from Si swarf by use of a beads milling method. Treatment with dilute hydrofluoric acid stabilizes Si Nanoparticles, and the thickness of the SiO2 layer formed by leaving Nanoparticles in air for one week is only 1.2 nm. p-Si Nanoparticles/crystalline n-Si structure shows rectifying behavior, indicating formation of pn-junction. Treatment with nitric acid followed by heating at 900 °C greatly decreases series reSistance, showing that the ultrathin SiO2 layer formed by nitric acid oxidation melts and is bound to surrounding Nanoparticles. p-type Si Nanoparticles/n-type crystalline Si structure shows rectifying behavior and the photovoltaic effect, indicating that Si Nanoparticles are applicable to solar cells.

Masanori Maeda - One of the best experts on this subject based on the ideXlab platform.

  • Photoluminescence from vibrational excited-states for organic molecules adsorbed on Si Nanoparticles.
    Physical chemistry chemical physics : PCCP, 2017
    Co-Authors: Masanori Maeda, Taketoshi Matsumoto, Hikaru Kobayashi
    Abstract:

    Herein, Si Nanoparticles have been fabricated from Si swarf uSing a bead milling method. The adsorption of 9,10-dimethylanthracene (DMA) on Si Nanoparticles enhances the photoluminescence (PL) intenSity by ∼60 000 times that of DMA in hexane. The PL spectra possess peaked structures due to the vibronic tranSition of DMA. For the excitation energies higher than 4.0 eV, vibronic bands with energies higher than the (0, 0) band were observed and attributed to PL from the vibrational excited-states. The excitation spectra showed that incident light was absorbed by both DMA and the Si Nanoparticles. The lifetime of the photo-generated electron-hole pairs in the Si Nanoparticles was much longer than the DMA PL lifetime; this indicated that either a hole or an electron transferred to DMA first, followed by an oppoSite charge transfer. In the cases where a hole is first transferred to DMA, an electronic ground-state is stabilized via solvation. When an electron is captured by the potential of the electronic excited-state, tranSitions from the vibrational excited-states proceed due to the high tranSition probability, generating PL bands with energies higher than the (0, 0) band. In the cases where an electron is first transferred to DMA, internal relaxation to the vibrational ground-state occurs, and the potential of the electronic excited-state is lowered via solvation.

  • Photoluminescence Enhancement of Adsorbed Species on Si Nanoparticles
    Nanoscale Research Letters, 2016
    Co-Authors: Taketoshi Matsumoto, Masanori Maeda, Hikaru Kobayashi
    Abstract:

    We have fabricated Si Nanoparticles from Si swarf uSing the beads milling method. The mode diameter of produced Si Nanoparticles was between 4.8 and 5.2 nm. Si Nanoparticles in hexane show photoluminescence (PL) spectra with peaks at 2.56, 2.73, 2.91, and 3.09 eV. The peaked PL spectra are attributed to the vibronic structure of adsorbed dimethylanthracene (DMA) impurity in hexane. The PL intenSity of hexane with DMA increases by ~3000 times by adsorption on Si Nanoparticles. The PL enhancement results from an increase in absorption probability of incident light by DMA caused by adsorption on the surface of Si Nanoparticles.

  • Si Nanoparticles fabricated from Si swarf by photochemical etching method
    Journal of Nanoparticle Research, 2014
    Co-Authors: Taketoshi Matsumoto, Masanori Maeda, Junichi Furukawa, Woo Byoung Kim, Hikaru Kobayashi
    Abstract:

    Si Nanoparticles are produced from Si swarf which is a waste during slicing Si ingots to produce Si wafers for solar cell use. The beads mill method produces flake-like Si with scores of nanometers width from Si swarf. Subsequent photochemical dissolution with light longer than 560 nm wavelength in a 0.5 % HF solution results in sphere-shaped Si Nanoparticles of 1–7 nm diameter. Si Nanoparticles dispersed in ethanol show blue photoluminescence at ~400 nm (3.1 eV) under UV irradiation, indicating band-gap widening due to the quantum confinement effect. The band-gap energy of most of the Si Nanoparticles is estimated to be 2.5–3.3 eV from the PL spectra, corresponding to the Si nanoparticle Size of 1.9–3.2 nm. On the other hand, Si Nanoparticles produced by immerSion in the HF solution in the dark show much weaker blue photoluminescence. These results demonstrate that the Si dissolution reaction is greatly enhanced by photo-generated holes.

  • Fabrication of Si Nanoparticles from Si swarf and application to solar cells
    Applied Surface Science, 2014
    Co-Authors: Masanori Maeda, Taketoshi Matsumoto, Kentaro Imamura, Hikaru Kobayashi
    Abstract:

    Abstract Si Nanoparticles with diameter of 1–20 nm have been fabricated from Si swarf by use of a beads milling method. Treatment with dilute hydrofluoric acid stabilizes Si Nanoparticles, and the thickness of the SiO2 layer formed by leaving Nanoparticles in air for one week is only 1.2 nm. p-Si Nanoparticles/crystalline n-Si structure shows rectifying behavior, indicating formation of pn-junction. Treatment with nitric acid followed by heating at 900 °C greatly decreases series reSistance, showing that the ultrathin SiO2 layer formed by nitric acid oxidation melts and is bound to surrounding Nanoparticles. p-type Si Nanoparticles/n-type crystalline Si structure shows rectifying behavior and the photovoltaic effect, indicating that Si Nanoparticles are applicable to solar cells.

Taketoshi Matsumoto - One of the best experts on this subject based on the ideXlab platform.

  • Photoluminescence from vibrational excited-states for organic molecules adsorbed on Si Nanoparticles.
    Physical chemistry chemical physics : PCCP, 2017
    Co-Authors: Masanori Maeda, Taketoshi Matsumoto, Hikaru Kobayashi
    Abstract:

    Herein, Si Nanoparticles have been fabricated from Si swarf uSing a bead milling method. The adsorption of 9,10-dimethylanthracene (DMA) on Si Nanoparticles enhances the photoluminescence (PL) intenSity by ∼60 000 times that of DMA in hexane. The PL spectra possess peaked structures due to the vibronic tranSition of DMA. For the excitation energies higher than 4.0 eV, vibronic bands with energies higher than the (0, 0) band were observed and attributed to PL from the vibrational excited-states. The excitation spectra showed that incident light was absorbed by both DMA and the Si Nanoparticles. The lifetime of the photo-generated electron-hole pairs in the Si Nanoparticles was much longer than the DMA PL lifetime; this indicated that either a hole or an electron transferred to DMA first, followed by an oppoSite charge transfer. In the cases where a hole is first transferred to DMA, an electronic ground-state is stabilized via solvation. When an electron is captured by the potential of the electronic excited-state, tranSitions from the vibrational excited-states proceed due to the high tranSition probability, generating PL bands with energies higher than the (0, 0) band. In the cases where an electron is first transferred to DMA, internal relaxation to the vibrational ground-state occurs, and the potential of the electronic excited-state is lowered via solvation.

  • Photoluminescence Enhancement of Adsorbed Species on Si Nanoparticles
    Nanoscale Research Letters, 2016
    Co-Authors: Taketoshi Matsumoto, Masanori Maeda, Hikaru Kobayashi
    Abstract:

    We have fabricated Si Nanoparticles from Si swarf uSing the beads milling method. The mode diameter of produced Si Nanoparticles was between 4.8 and 5.2 nm. Si Nanoparticles in hexane show photoluminescence (PL) spectra with peaks at 2.56, 2.73, 2.91, and 3.09 eV. The peaked PL spectra are attributed to the vibronic structure of adsorbed dimethylanthracene (DMA) impurity in hexane. The PL intenSity of hexane with DMA increases by ~3000 times by adsorption on Si Nanoparticles. The PL enhancement results from an increase in absorption probability of incident light by DMA caused by adsorption on the surface of Si Nanoparticles.

  • Si Nanoparticles fabricated from Si swarf by photochemical etching method
    Journal of Nanoparticle Research, 2014
    Co-Authors: Taketoshi Matsumoto, Masanori Maeda, Junichi Furukawa, Woo Byoung Kim, Hikaru Kobayashi
    Abstract:

    Si Nanoparticles are produced from Si swarf which is a waste during slicing Si ingots to produce Si wafers for solar cell use. The beads mill method produces flake-like Si with scores of nanometers width from Si swarf. Subsequent photochemical dissolution with light longer than 560 nm wavelength in a 0.5 % HF solution results in sphere-shaped Si Nanoparticles of 1–7 nm diameter. Si Nanoparticles dispersed in ethanol show blue photoluminescence at ~400 nm (3.1 eV) under UV irradiation, indicating band-gap widening due to the quantum confinement effect. The band-gap energy of most of the Si Nanoparticles is estimated to be 2.5–3.3 eV from the PL spectra, corresponding to the Si nanoparticle Size of 1.9–3.2 nm. On the other hand, Si Nanoparticles produced by immerSion in the HF solution in the dark show much weaker blue photoluminescence. These results demonstrate that the Si dissolution reaction is greatly enhanced by photo-generated holes.

  • Fabrication of Si Nanoparticles from Si swarf and application to solar cells
    Applied Surface Science, 2014
    Co-Authors: Masanori Maeda, Taketoshi Matsumoto, Kentaro Imamura, Hikaru Kobayashi
    Abstract:

    Abstract Si Nanoparticles with diameter of 1–20 nm have been fabricated from Si swarf by use of a beads milling method. Treatment with dilute hydrofluoric acid stabilizes Si Nanoparticles, and the thickness of the SiO2 layer formed by leaving Nanoparticles in air for one week is only 1.2 nm. p-Si Nanoparticles/crystalline n-Si structure shows rectifying behavior, indicating formation of pn-junction. Treatment with nitric acid followed by heating at 900 °C greatly decreases series reSistance, showing that the ultrathin SiO2 layer formed by nitric acid oxidation melts and is bound to surrounding Nanoparticles. p-type Si Nanoparticles/n-type crystalline Si structure shows rectifying behavior and the photovoltaic effect, indicating that Si Nanoparticles are applicable to solar cells.

Woon-jo Cho - One of the best experts on this subject based on the ideXlab platform.

  • Transformation mechanism of n-butyl terminated Si Nanoparticles embedded into Si1−xCx nanocompoSites mixed with Si Nanoparticles and C atoms
    Applied Surface Science, 2009
    Co-Authors: Jin-soo Shin, Tae Whan Kim, Woon-jo Cho
    Abstract:

    Abstract Bright-field transmisSion electron microscopy (TEM) images, high-resolution TEM (HRTEM) images, and fast-Fourier transformed electron-diffraction patterns showed that n-butyl terminated Si Nanoparticles were aggregated. The formation of Si1−xCx nanocompoSites was mixed with Si Nanoparticles and C atoms embedded in a SiO2 layer due to the diffuSion of C atoms from n-butyl termination shells into aggregated Si Nanoparticles. Atomic force microscopy (AFM) images showed that the Si1−xCx nanocompoSites mixed with Si Nanoparticles and C atoms existed in almost all regions of the SiO2 layer. The formation mechanism of Si Nanoparticles and the transformation mechanism of n-butyl terminated Si Nanoparticles embedded into Si1−xCx nanocompoSites mixed with Si Nanoparticles and C atoms are described on the baSis of the TEM, HRTEM, and AFM results. These results can help to improve the understanding of the formation mechanism of Si Nanoparticles.

  • Dependence of the stored charges and tunneling voltages on the tunneling SiO2 thickness for Si Nanoparticles embedded in a SiO2 layer
    Journal of Crystal Growth, 2008
    Co-Authors: Soojin Lee, Woon-jo Cho, Tae Whan Kim
    Abstract:

    Dependence of the stored charges and the tunneling voltages on the tunneling SiO2 thickness for Si Nanoparticles embedded in a SiO2 layer formed by the sonochemical method was investigated by uSing electrostatic force microscopy (EFM) measurements. Bright-field transmisSion electron microscopy images showed that Si Nanoparticles were embedded in a SiO2 layer. EFM images for the Si Nanoparticles embedded in a SiO2 layer under applied bias voltages showed that the localized charges remained in the Si Nanoparticles embedded in a SiO2 layer. The stored charge in the Si Nanoparticles embedded in a SiO2 layer increased with a decrease in the tunneling SiO2 thickness. While the threshold tunneling voltage increased with an increase in the tunneling oxide thickness, the mean amplitude of the tunneling voltage increased with a decrease in the thickness of the tunneling SiO2 layer.

  • Dependence of the charging effects on the tunnel oxide thickness in Si Nanoparticles embedded in a SiO 2 layer
    2006 IEEE Nanotechnology Materials and Devices Conference, 2006
    Co-Authors: Soojin Lee, Woon-jo Cho, Jae-ho Kim, Jae Hun Jung, Tae Whan Kim
    Abstract:

    Dependence of the charging effects on the tunneling oxide thickness in Si Nanoparticles embedded in a SiO 2 layer was investigated by uSing electrostatic force microscopy (EFM) measurements. EFM images showed that the stored charge in the Si Nanoparticles increased with an increase in the applied bias voltage of the EFM tip. The variation of tunnel oxide thickness affected the tunneling threshold voltages, at which the carriers begun to tunnel from the Si substrate to the Si Nanoparticles. These results indicate that the observed charging effects of Si Nanoparticles embedded in a SiO 2 layer provide important informations on potential applications in nonvolatile memories with floating gates conSisting of Si nanocrystals embedded in a SiO 2 layer.

Munir H. Nayfeh - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Environments on Optical Properties of Chemically Prepared Si Nanoparticles
    Advanced Science Engineering and Medicine, 2013
    Co-Authors: Abdullah S. Aldwayyan, Amani Ali, Anees A. Ansari, Mohammed Al-salhi, Munir H. Nayfeh
    Abstract:

    Silicon (Si) Nanoparticles were syntheSized by chemical etching process at ambient temperature. Field emisSion transmisSion electron microscopy (FE-TEM), Fourier transforms infrared spectroscopy (FTIR), UV/Vis absorption and photoluminescence (PL) spectroscopic techniques were employed to examine the morphological structure and optical features of the syntheSized Si Nanoparticles. Effect of solvent and temperature on optical properties of Si Nanoparticles is presented. We believe that at phySiological pH Si Nanoparticles have charged surface, because of high solubility in organic solvents. Experimental results show that the Si Nanoparticles are a good biocompatible, non-agglomerated, homogeneously well distributed and highly disperSible in organic solvents. The emisSion and absorption properties of Si Nanoparticles were tuned by altering the environment (solvents) through electrostatic interaction of various organic solvents with the Si Nanoparticles. The band shapes of the Si Nanoparticles show remarkable changes on pasSing from non-coordinating solvent (chloroform) to various coordinating solvents which is the result of change in the environment around Si Nanoparticles in the various solutions and suggests coordination of solvent molecule(s), in some cases. The results clearly show that among the solvents studied DMSO is the most effective in promoting the efficient emisSion intenSity.

  • Spatially selective electrochemical depoSition of compoSite films of metal and luminescent Si Nanoparticles
    Chemical Physics Letters, 2003
    Co-Authors: A. Smith, Munir H. Nayfeh, G. Belomoin, Taysir H. Nayfeh
    Abstract:

    We report on a procedure for selective depoSition of Si Nanoparticles uSing an electrochemical process. A conducting substrate is immersed in alcohol in which the particles are suspended. BiaSing the substrate poSitively relative to a platinum electrode draws the Si particles to the substrate. Thin particle coatings on metal, foil, or Silicon substrates are demonstrated. Fluorescent spectroscopy shows that the depoSited particles retain the high luminescence efficiency and spectral distribution characteristic of the dispersed state. The process is used to depoSit compoSite thin films of metal and Si Nanoparticles. Dielectric masking allowed selective area depoSition. These processes have implications for flat panel or flexible particle-based displays.

  • Laser oscillation in aggregates of ultrasmall Si Nanoparticles
    MRS Proceedings, 2002
    Co-Authors: Munir H. Nayfeh
    Abstract:

    AbstractWe dispersed electrochemically etched Si into ultrabright ultrasmall Nanoparticles, with brightness higher than fluorescein or rhodamine. The emisSion from Single particles is readily detectable. Aggregates or films of the particles exhibit emisSion with highly nonlinear characteristics. We observe directed blue beams at ∼ 410 nm between faces of aggregates excited by femtosecond radiation at 780 nm; and at ∼ 610 nm from aggregates of red luminescent Si Nanoparticles excited by radiation at 550-570 nm from a mercury lamp. Intense directed GausSian beams, a pumping threshold, spectral line narrowing, and speckle patterns manifest the emisSion. The results are analyzed in terms of population inverSion and stimulated emisSion in quantum confinement-induced Si-Si dimer phase, found only on ultrasmall Si Nanoparticles. This microlaSing constitutes an important step towards the realization of a laser on a chip.

  • oxide and hydrogen capped ultrasmall blue luminescent Si Nanoparticles
    Applied Physics Letters, 2000
    Co-Authors: G. Belomoin, Joel Therrien, Munir H. Nayfeh
    Abstract:

    We dispersed electrochemical etched Silicon into a colloid of ultrasmall ultrabright Si Nanoparticles. Direct imaging uSing transmisSion electron microscopy shows particles of ∼1 nm in diameter, and infrared and electron photospectroscopy show that they are pasSivated with hydrogen. Under 350 nm excitation, the luminescence is dominated by an extremely strong blue band at 390 nm. We replace hydrogen by a high-quality ultrathin surface oxide cap by self-limiting oxidation in H2O2. Upon capping, the excitation efficiency drops, but only by a factor of 2, to an efficiency still two-fold larger than that of fluorescein. Although of slightly lower brightness, capped Si particles have superior biocompatability, an important property for biosenSing applications.