WorldWideScience

Sample records for sio2 gate insulators

  1. Investigation of pentacene growth on SiO2 gate insulator after photolithography for nitrogen-doped LaB6 bottom-contact electrode formation

    Science.gov (United States)

    Maeda, Yasutaka; Hiroki, Mizuha; Ohmi, Shun-ichiro

    2018-04-01

    Nitrogen-doped (N-doped) LaB6 is a candidate material for the bottom-contact electrode of n-type organic field-effect transistors (OFETs). However, the formation of a N-doped LaB6 electrode affects the surface morphology of a pentacene film. In this study, the effects of surface treatments and a N-doped LaB6 interfacial layer (IL) were investigated to improve the pentacene film quality after N-doped LaB6 electrode patterning with diluted HNO3, followed by resist stripping with acetone and methanol. It was found that the sputtering damage during N-doped LaB6 deposition on a SiO2 gate insulator degraded the crystallinity of pentacene. The H2SO4 and H2O2 (SPM) and diluted HF treatments removed the damaged layer on the SiO2 gate insulator surface. Furthermore, the N-doped LaB6 IL improved the crystallinity of pentacene and realized dendritic grain growth. Owing to these surface treatments, the hole mobility improved from 2.8 × 10-3 to 0.11 cm2/(V·s), and a steep subthreshold swing of 78 mV/dec for the OFET with top-contact configuration was realized in air even after bottom-contact electrode patterning.

  2. Plasma Deposited SiO2 for Planar Self-Aligned Gate Metal-Insulator-Semiconductor Field Effect Transistors on Semi-Insulating InP

    Science.gov (United States)

    Tabory, Charles N.; Young, Paul G.; Smith, Edwyn D.; Alterovitz, Samuel A.

    1994-01-01

    Metal-insulator-semiconductor (MIS) field effect transistors were fabricated on InP substrates using a planar self-aligned gate process. A 700-1000 A gate insulator of Si02 doped with phosphorus was deposited by a direct plasma enhanced chemical vapor deposition at 400 mTorr, 275 C, 5 W, and power density of 8.5 MW/sq cm. High frequency capacitance-voltage measurements were taken on MIS capacitors which have been subjected to a 700 C anneal and an interface state density of lxl0(exp 11)/eV/cq cm was found. Current-voltage measurements of the capacitors show a breakdown voltage of 107 V/cm and a insulator resistivity of 10(exp 14) omega cm. Transistors were fabricated on semi-insulating InP using a standard planar self-aligned gate process in which the gate insulator was subjected to an ion implantation activation anneal of 700 C. MIS field effect transistors gave a maximum extrinsic transconductance of 23 mS/mm for a gate length of 3 microns. The drain current drift saturated at 87.5% of the initial current, while reaching to within 1% of the saturated value after only 1x10(exp 3). This is the first reported viable planar InP self-aligned gate transistor process reported to date.

  3. Total Ionizing Dose Effects of Si Vertical Diffused MOSFET with SiO2 and Si3N4/SiO2 Gate Dielectrics

    Directory of Open Access Journals (Sweden)

    Jiongjiong Mo

    2017-01-01

    Full Text Available The total ionizing dose irradiation effects are investigated in Si vertical diffused MOSFETs (VDMOSs with different gate dielectrics including single SiO2 layer and double Si3N4/SiO2 layer. Radiation-induced holes trapping is greater for single SiO2 layer than for double Si3N4/SiO2 layer. Dielectric oxidation temperature dependent TID effects are also studied. Holes trapping induced negative threshold voltage shift is smaller for SiO2 at lower oxidation temperature. Gate bias during irradiation leads to different VTH shift for different gate dielectrics. Single SiO2 layer shows the worst negative VTH at VG=0 V, while double Si3N4/SiO2 shows negative VTH shift at VG=-5 V, positive VTH shift at VG=10 V, and negligible VTH shift at VG=0 V.

  4. Improving thermal insulation of TC4 using YSZ-based coating and SiO2 aerogel

    OpenAIRE

    Jin, Lei; Li, Peizhong; Zhou, Haibin; Zhang, Wei; Zhou, Guodong; Wang, Chun

    2015-01-01

    In this paper, air plasmas spray (APS) was used to prepare YSZ and Sc2O3–YSZ (ScYSZ) coating in order to improve the thermal insulation ability of TC4 alloy. SiO2 aerogel was also synthesized and affixed on TC4 titanium alloy to inhabit thermal flow. The microstructures, phase compositions and thermal insulation performance of three coatings were analyzed in detail. The results of thermal diffusivity test by a laser flash method showed that the thermal diffusivities of YSZ, Sc2O3–YSZ and SiO2...

  5. Improving thermal insulation of TC4 using YSZ-based coating and SiO2 aerogel

    Directory of Open Access Journals (Sweden)

    Lei Jin

    2015-04-01

    Full Text Available In this paper, air plasmas spray (APS was used to prepare YSZ and Sc2O3–YSZ (ScYSZ coating in order to improve the thermal insulation ability of TC4 alloy. SiO2 aerogel was also synthesized and affixed on TC4 titanium alloy to inhabit thermal flow. The microstructures, phase compositions and thermal insulation performance of three coatings were analyzed in detail. The results of thermal diffusivity test by a laser flash method showed that the thermal diffusivities of YSZ, Sc2O3–YSZ and SiO2 aerogel are 0.553, 0.539 and 0.2097×10−6 m2/s, respectively. Then, the thermal insulation performances of three kinds of coating were investigated from 20 °C to 400 °C using high infrared radiation heat flux technology. The experimental results indicated that the corresponding temperature difference between the top TC4 alloy (400 °C and the bottom surface of YSZ is 41.5 °C for 0.6 mm thickness coating. For 1 mm thickness coating, the corresponding temperature difference between the top TC4 alloys (400 °C and the bottom surface of YSZ, ScYSZ, SiO2 aerogel three specimens is 54, 54.6 and 208 °C, respectively. The coating thickness and species were found to influence the heat insulation ability. In these materials, YSZ and ScYSZ exhibited a little difference for heat insulation behavior. However, SiO2 aerogel was the best one among them and it can be taken as protection material on TC4 alloys. In outer space, SiO2 aerogel can meet the need of thermal insulation of TC4 of high-speed aircraft.

  6. SiO2/AlON stacked gate dielectrics for AlGaN/GaN MOS heterojunction field-effect transistors

    Science.gov (United States)

    Watanabe, Kenta; Terashima, Daiki; Nozaki, Mikito; Yamada, Takahiro; Nakazawa, Satoshi; Ishida, Masahiro; Anda, Yoshiharu; Ueda, Tetsuzo; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2018-06-01

    Stacked gate dielectrics consisting of wide bandgap SiO2 insulators and thin aluminum oxynitride (AlON) interlayers were systematically investigated in order to improve the performance and reliability of AlGaN/GaN metal–oxide–semiconductor (MOS) devices. A significantly reduced gate leakage current compared with that in a single AlON layer was achieved with these structures, while maintaining the superior thermal stability and electrical properties of the oxynitride/AlGaN interface. Consequently, distinct advantages in terms of the reliability of the gate dielectrics, such as an improved immunity against electron injection and an increased dielectric breakdown field, were demonstrated for AlGaN/GaN MOS capacitors with optimized stacked structures having a 3.3-nm-thick AlON interlayer.

  7. Experimental and theoretical investigation of the effect of SiO2 content in gate dielectrics on work function shift induced by nanoscale capping layers

    KAUST Repository

    Caraveo-Frescas, J. A.; Wang, H.; Schwingenschlö gl, Udo; Alshareef, Husam N.

    2012-01-01

    The impact of SiO2 content in ultrathin gate dielectrics on the magnitude of the effective work function (EWF) shift induced by nanoscale capping layers has been investigated experimentally and theoretically. The magnitude of the effective work function shift for four different capping layers (AlN, Al2O3, La2O3, and Gd2O3) is measured as a function of SiO2 content in the gate dielectric. A nearly linear increase of this shift with SiO2 content is observed for all capping layers. The origin of this dependence is explained using density functional theory simulations.

  8. Experimental and theoretical investigation of the effect of SiO2 content in gate dielectrics on work function shift induced by nanoscale capping layers

    KAUST Repository

    Caraveo-Frescas, J. A.

    2012-09-10

    The impact of SiO2 content in ultrathin gate dielectrics on the magnitude of the effective work function (EWF) shift induced by nanoscale capping layers has been investigated experimentally and theoretically. The magnitude of the effective work function shift for four different capping layers (AlN, Al2O3, La2O3, and Gd2O3) is measured as a function of SiO2 content in the gate dielectric. A nearly linear increase of this shift with SiO2 content is observed for all capping layers. The origin of this dependence is explained using density functional theory simulations.

  9. Radiation-induced interface state generation in MOS devices with reoxidised nitrided SiO2 gate dielectrics

    International Nuclear Information System (INIS)

    Lo, G.Q.; Shih, D.K.; Ting, W.; Kwong, D.L.

    1989-01-01

    In this letter, the radiation-induced interface state generation ΔD it in MOS devices with reoxidised nitrided gate oxides has been studied. The reoxidised nitrided oxides were fabricated by rapid thermal reoxidation (RTO) of rapidly thermal nitrided (RTN) SiO 2 . The devices were irradiated by exposure to X-rays at doses of 0.5-5.0 Mrad (Si). It is found that the RTO process improves the radiation hardness of RTN oxides in terms of interface state generation. The enhanced interface ''hardness'' of reoxidised nitrided oxides is attributed to the strainless interfacial oxide regrowth or reduction of hydrogen concentration during RTO of RTN oxides. (author)

  10. Memory and learning behaviors mimicked in nanogranular SiO2-based proton conductor gated oxide-based synaptic transistors.

    Science.gov (United States)

    Wan, Chang Jin; Zhu, Li Qiang; Zhou, Ju Mei; Shi, Yi; Wan, Qing

    2013-11-07

    In neuroscience, signal processing, memory and learning function are established in the brain by modifying ionic fluxes in neurons and synapses. Emulation of memory and learning behaviors of biological systems by nanoscale ionic/electronic devices is highly desirable for building neuromorphic systems or even artificial neural networks. Here, novel artificial synapses based on junctionless oxide-based protonic/electronic hybrid transistors gated by nanogranular phosphorus-doped SiO2-based proton-conducting films are fabricated on glass substrates by a room-temperature process. Short-term memory (STM) and long-term memory (LTM) are mimicked by tuning the pulse gate voltage amplitude. The LTM process in such an artificial synapse is due to the proton-related interfacial electrochemical reaction. Our results are highly desirable for building future neuromorphic systems or even artificial networks via electronic elements.

  11. Lateral protonic/electronic hybrid oxide thin-film transistor gated by SiO2 nanogranular films

    International Nuclear Information System (INIS)

    Zhu, Li Qiang; Chao, Jin Yu; Xiao, Hui

    2014-01-01

    Ionic/electronic interaction offers an additional dimension in the recent advancements of condensed materials. Here, lateral gate control of conductivities of indium-zinc-oxide (IZO) films is reported. An electric-double-layer (EDL) transistor configuration was utilized with a phosphorous-doped SiO 2 nanogranular film to provide a strong lateral electric field. Due to the strong lateral protonic/electronic interfacial coupling effect, the IZO EDL transistor could operate at a low-voltage of 1 V. A resistor-loaded inverter is built, showing a high voltage gain of ∼8 at a low supply voltage of 1 V. The lateral ionic/electronic coupling effects are interesting for bioelectronics and portable electronics

  12. The effect of the gate electrode on the C-V- characteristics of the structure M-TmF3-SiO2-Si

    International Nuclear Information System (INIS)

    Basily, R.R.

    1979-09-01

    The C-V characteristics of the structure M-TmF 3 -SiO 2 -Si, thermally treated at a temperature of 300 0 C for 15 minutes, were investigated. At higher temperatures to about 150 0 C, the hysteresis of the C-V characteristics is completely absent, whereas at room temperature hysteresis depends on the applied voltage and on the material of the gate electrode. The dependence of the flat band voltage shift on the applied voltage, the thickness of SiO 2 layer and the material of the gate electrode were measured. (author)

  13. Improved linearity and reliability in GaN metal-oxide-semiconductor high-electron-mobility transistors using nanolaminate La2O3/SiO2 gate dielectric

    Science.gov (United States)

    Hsu, Ching-Hsiang; Shih, Wang-Cheng; Lin, Yueh-Chin; Hsu, Heng-Tung; Hsu, Hisang-Hua; Huang, Yu-Xiang; Lin, Tai-Wei; Wu, Chia-Hsun; Wu, Wen-Hao; Maa, Jer-Shen; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

    2016-04-01

    Improved device performance to enable high-linearity power applications has been discussed in this study. We have compared the La2O3/SiO2 AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) with other La2O3-based (La2O3/HfO2, La2O3/CeO2 and single La2O3) MOS-HEMTs. It was found that forming lanthanum silicate films can not only improve the dielectric quality but also can improve the device characteristics. The improved gate insulation, reliability, and linearity of the 8 nm La2O3/SiO2 MOS-HEMT were demonstrated.

  14. Thermal response of Ru electrodes in contact with SiO2 and Hf-based high-k gate dielectrics

    International Nuclear Information System (INIS)

    Wen, H.-C.; Lysaght, P.; Alshareef, H.N.; Huffman, C.; Harris, H.R.; Choi, K.; Senzaki, Y.; Luan, H.; Majhi, P.; Lee, B.H.; Campin, M. J.; Foran, B.; Lian, G.D.; Kwong, D.-L.

    2005-01-01

    A systematic experimental evaluation of the thermal stability of Ru metal gate electrodes in direct contact with SiO 2 and Hf-based dielectric layers was performed and correlated with electrical device measurements. The distinctly different interfacial reactions in the Ru/SiO 2 , Ru/HfO 2 , and Ru/HfSiO x film systems were observed through cross-sectional high-resolution transmission electron microscopy, high angle annular dark field scanning transmission electron microscopy with electron-energy-loss spectra, and energy dispersive x-ray spectra analysis. Ru interacted with SiO 2 , but remained stable on HfO 2 at 1000 deg. C. The onset of Ru/SiO 2 interfacial interactions is identified via silicon substrate pitting possibly from Ru diffusion into the dielectric in samples exposed to a 900 deg. C/10-s anneal. The dependence of capacitor device degradation with decreasing SiO 2 thickness suggests Ru diffuses through SiO 2 , followed by an abrupt, rapid, nonuniform interaction of ruthenium silicide as Ru contacts the Si substrate. Local interdiffusion detected on Ru/HfSiO x samples may be due to phase separation of HfSiO x into HfO 2 grains within a SiO 2 matrix, suggesting that SiO 2 provides a diffusion pathway for Ru. Detailed evidence consistent with a dual reaction mechanism for the Ru/SiO 2 system at 1000 deg. C is presented

  15. Surface properties of SiO2 with and without H2O2 treatment as gate dielectrics for pentacene thin-film transistor applications

    Science.gov (United States)

    Hung, Cheng-Chun; Lin, Yow-Jon

    2018-01-01

    The effect of H2O2 treatment on the surface properties of SiO2 is studied. H2O2 treatment leads to the formation of Si(sbnd OH)x at the SiO2 surface that serves to reduce the number of trap states, inducing the shift of the Fermi level toward the conduction band minimum. H2O2 treatment also leads to a noticeable reduction in the value of the SiO2 capacitance per unit area. The effect of SiO2 layers with H2O2 treatment on the behavior of carrier transports for the pentacene/SiO2-based organic thin-film transistor (OTFT) is also studied. Experimental identification confirms that the shift of the threshold voltage towards negative gate-source voltages is due to the reduced number of trap states in SiO2 near the pentacene/SiO2 interface. The existence of a hydrogenated layer between pentacene and SiO2 leads to a change in the pentacene-SiO2 interaction, increasing the value of the carrier mobility.

  16. Nonvolatile Memories Using Quantum Dot (QD) Floating Gates Assembled on II-VI Tunnel Insulators

    Science.gov (United States)

    Suarez, E.; Gogna, M.; Al-Amoody, F.; Karmakar, S.; Ayers, J.; Heller, E.; Jain, F.

    2010-07-01

    This paper presents preliminary data on quantum dot gate nonvolatile memories using nearly lattice-matched ZnS/Zn0.95Mg0.05S/ZnS tunnel insulators. The GeO x -cladded Ge and SiO x -cladded Si quantum dots (QDs) are self-assembled site-specifically on the II-VI insulator grown epitaxially over the Si channel (formed between the source and drain region). The pseudomorphic II-VI stack serves both as a tunnel insulator and a high- κ dielectric. The effect of Mg incorporation in ZnMgS is also investigated. For the control gate insulator, we have used Si3N4 and SiO2 layers grown by plasma- enhanced chemical vapor deposition.

  17. Temperature-dependent field-effect carrier mobility in organic thin-film transistors with a gate SiO2 dielectric modified by H2O2 treatment

    Science.gov (United States)

    Lin, Yow-Jon; Hung, Cheng-Chun

    2018-02-01

    The effect of the modification of a gate SiO2 dielectric using an H2O2 solution on the temperature-dependent behavior of carrier transport for pentacene-based organic thin-film transistors (OTFTs) is studied. H2O2 treatment leads to the formation of Si(-OH) x (i.e., the formation of a hydroxylated layer) on the SiO2 surface that serves to reduce the SiO2 capacitance and weaken the pentacene-SiO2 interaction, thus increasing the field-effect carrier mobility ( µ) in OTFTs. The temperature-dependent behavior of carrier transport is dominated by the multiple trapping model. Note that H2O2 treatment leads to a reduction in the activation energy. The increased value of µ is also attributed to the weakening of the interactions of the charge carriers with the SiO2 dielectric that serves to reduce the activation energy.

  18. Top-gate pentacene-based organic field-effect transistor with amorphous rubrene gate insulator

    Science.gov (United States)

    Hiroki, Mizuha; Maeda, Yasutaka; Ohmi, Shun-ichiro

    2018-02-01

    The scaling of organic field-effect transistors (OFETs) is necessary for high-density integration and for this, OFETs with a top-gate configuration are required. There have been several reports of damageless lithography processes for organic semiconductor or insulator layers. However, it is still difficult to fabricate scaled OFETs with a top-gate configuration. In this study, the lift-off process and the device characteristics of the OFETs with a top-gate configuration utilizing an amorphous (α) rubrene gate insulator were investigated. We have confirmed that α-rubrene shows an insulating property, and its extracted linear mobility was 2.5 × 10-2 cm2/(V·s). The gate length and width were 10 and 60 µm, respectively. From these results, the OFET with a top-gate configuration utilizing an α-rubrene gate insulator is promising for the high-density integration of scaled OFETs.

  19. Silicon dioxide with a silicon interfacial layer as an insulating gate for highly stable indium phosphide metal-insulator-semiconductor field effect transistors

    Science.gov (United States)

    Kapoor, V. J.; Shokrani, M.

    1991-01-01

    A novel gate insulator consisting of silicon dioxide (SiO2) with a thin silicon (Si) interfacial layer has been investigated for high-power microwave indium phosphide (InP) metal-insulator-semiconductor field effect transistors (MISFETs). The role of the silicon interfacial layer on the chemical nature of the SiO2/Si/InP interface was studied by high-resolution X-ray photoelectron spectroscopy. The results indicated that the silicon interfacial layer reacted with the native oxide at the InP surface, thus producing silicon dioxide, while reducing the native oxide which has been shown to be responsible for the instabilities in InP MISFETs. While a 1.2-V hysteresis was present in the capacitance-voltage (C-V) curve of the MIS capacitors with silicon dioxide, less than 0.1 V hysteresis was observed in the C-V curve of the capacitors with the silicon interfacial layer incorporated in the insulator. InP MISFETs fabricated with the silicon dioxide in combination with the silicon interfacial layer exhibited excellent stability with drain current drift of less than 3 percent in 10,000 sec, as compared to 15-18 percent drift in 10,000 sec for devices without the silicon interfacial layer. High-power microwave InP MISFETs with Si/SiO2 gate insulators resulted in an output power density of 1.75 W/mm gate width at 9.7 GHz, with an associated power gain of 2.5 dB and 24 percent power added efficiency.

  20. Structural Evaluation of 5,5′-Bis(naphth-2-yl)-2,2′-bithiophene in Organic Field-Effect Transistors with n-Octadecyltrichlorosilane Coated SiO2 Gate Dielectric

    DEFF Research Database (Denmark)

    Lauritzen, Andreas E.; Torkkeli, Mika; Bikondoa, Oier

    2018-01-01

    We report on the structure and morphology of 5,5′-bis(naphth-2-yl)-2,2′-bithiophene (NaT2) films in bottom-contact organic field-effect transistors (OFETs) with octadecyltrichlorosilane (OTS) coated SiO2 gate dielectric, characterized by atomic force microscopy (AFM), grazing-incidence X......-ray diffraction (GIXRD), and electrical transport measurements. Three types of devices were investigated with the NaT2 thin-film deposited either on (1) pristine SiO2 (corresponding to higher surface energy, 47 mJ/m2) or on OTS deposited on SiO2 under (2) anhydrous or (3) humid conditions (corresponding to lower...... surface energies, 20–25 mJ/m2). NaT2 films grown on pristine SiO2 form nearly featureless three-dimensional islands. NaT2 films grown on OTS/SiO2 deposited under anhydrous conditions form staggered pyramid islands where the interlayer spacing corresponds to the size of the NaT2 unit cell. At the same time...

  1. Magnetic gating of a 2D topological insulator

    Science.gov (United States)

    Dang, Xiaoqian; Burton, J. D.; Tsymbal, Evgeny Y.

    2016-09-01

    Deterministic control of transport properties through manipulation of spin states is one of the paradigms of spintronics. Topological insulators offer a new playground for exploring interesting spin-dependent phenomena. Here, we consider a ferromagnetic ‘gate’ representing a magnetic adatom coupled to the topologically protected edge state of a two-dimensional (2D) topological insulator to modulate the electron transmission of the edge state. Due to the locked spin and wave vector of the transport electrons the transmission across the magnetic gate depends on the mutual orientation of the adatom magnetic moment and the current. If the Fermi energy matches an exchange-split bound state of the adatom, the electron transmission can be blocked due to the full back scattering of the incident wave. This antiresonance behavior is controlled by the adatom magnetic moment orientation so that the transmission of the edge state can be changed from 1 to 0. Expanding this consideration to a ferromagnetic gate representing a 1D chain of atoms shows a possibility to control the spin-dependent current of a strip of a 2D topological insulator by magnetization orientation of the ferromagnetic gate.

  2. Fabrication of amorphous InGaZnO thin-film transistor with solution processed SrZrO3 gate insulator

    Science.gov (United States)

    Takahashi, Takanori; Oikawa, Kento; Hoga, Takeshi; Uraoka, Yukiharu; Uchiyama, Kiyoshi

    2017-10-01

    In this paper, we describe a method of fabrication of thin film transistors (TFTs) with high dielectric constant (high-k) gate insulator by a solution deposition. We chose a solution processed SrZrO3 as a gate insulator material, which possesses a high dielectric constant of 21 with smooth surface. The IGZO-TFT with solution processed SrZrO3 showed good switching property and enough saturation features, i.e. field effect mobility of 1.7cm2/Vs, threshold voltage of 4.8V, sub-threshold swing of 147mV/decade, and on/off ratio of 2.3×107. Comparing to the TFTs with conventional SiO2 gate insulator, the sub-threshold swing was improved by smooth surface and high field effect due to the high dielectric constant of SrZrO3. These results clearly showed that use of solution processed high-k SrZrO3 gate insulator could improve sub-threshold swing. In addition, the residual carbon originated from organic precursors makes TFT performances degraded.

  3. Molecular dynamics simulations of the effect of shape and size of SiO2 nanoparticle dopants on insulation paper cellulose

    Directory of Open Access Journals (Sweden)

    Chao Tang

    2016-12-01

    Full Text Available The effect of silica nanoparticle (Nano-SiO2 dopants on insulation paper cellulose, and the interaction between them, was investigated using molecular dynamics simulations. The mechanical properties, interactions, and cellulose-Nano-SiO2 compatibility of composite models of cellulose doped with Nano-SiO2 were studied. An increase in Nano-SiO2 size leads to a decrease in the mechanical properties, and a decrease in the anti-deformation ability of the composite model. The binding energies and bond energies per surface area of the composite models indicate that the bonding interaction between spherical Nano-SiO2 and cellulose is the strongest among the four different Nano-SiO2 shapes that are investigated. The solubilities of the four composite models decrease with increasing Nano-SiO2 size, and the difference between the solubility of pure cellulose and those of the composite models increases with increasing Nano-SiO2 size. Good doping effects with the highest cellulose-Nano-SiO2 compatibility are achieved for the cellulose model doped with spherical Nano-SiO2 of 10 Å in diameter. These findings provide a method for modifying the mechanical properties of cellulose by doping, perhaps for improving insulation dielectrics.

  4. Nonvolatile Solid-State Charged-Polymer Gating of Topological Insulators into the Topological Insulating Regime

    Science.gov (United States)

    Ireland, R. M.; Wu, Liang; Salehi, M.; Oh, S.; Armitage, N. P.; Katz, H. E.

    2018-04-01

    We demonstrate the ability to reduce the carrier concentration of thin films of the topological insulator (TI) Bi2 Se3 by utilizing a nonvolatile electrostatic gating via corona charging of electret polymers. Sufficient electric field can be imparted to a polymer-TI bilayer to result in significant electron density depletion, even without the continuous connection of a gate electrode or the chemical modification of the TI. We show that the Fermi level of Bi2 Se3 is shifted toward the Dirac point with this method. Using terahertz spectroscopy, we find that the surface chemical potential is lowered into the bulk band gap (approximately 50 meV above the Dirac point and 170 meV below the conduction-band minimum), and it is stabilized in the intrinsic regime while enhancing electron mobility. The mobility of surface state electrons is enhanced to a value as high as approximately 1600 cm2/V s at 5 K.

  5. Gas-controlled dynamic vacuum insulation with gas gate

    Science.gov (United States)

    Benson, D.K.; Potter, T.F.

    1994-06-07

    Disclosed is a dynamic vacuum insulation comprising sidewalls enclosing an evacuated chamber and gas control means for releasing hydrogen gas into a chamber to increase gas molecule conduction of heat across the chamber and retrieving hydrogen gas from the chamber. The gas control means includes a metal hydride that absorbs and retains hydrogen gas at cooler temperatures and releases hydrogen gas at hotter temperatures; a hydride heating means for selectively heating the metal hydride to temperatures high enough to release hydrogen gas from the metal hydride; and gate means positioned between the metal hydride and the chamber for selectively allowing hydrogen to flow or not to flow between said metal hydride and said chamber. 25 figs.

  6. Low-voltage organic field-effect transistors based on novel high-κ organometallic lanthanide complex for gate insulating materials

    Directory of Open Access Journals (Sweden)

    Qi Liu

    2014-08-01

    Full Text Available A novel high-κ organometallic lanthanide complex, Eu(tta3L (tta=2-thenoyltrifluoroacetonate, L = 4,5-pinene bipyridine, is used as gate insulating material to fabricate low-voltage pentacene field-effect transistors (FETs. The optimized gate insulator exhibits the excellent properties such as low leakage current density, low surface roughness, and high dielectric constant. When operated under a low voltage of −5 V, the pentacene FET devices show the attractive electrical performance, e.g. carrier mobility (μFET of 0.17 cm2 V−1 s−1, threshold voltage (Vth of −0.9 V, on/off current ratio of 5 × 103, and subthreshold slope (SS of 1.0 V dec−1, which is much better than that of devices obtained on conventional 300 nm SiO2 substrate (0.13 cm2 V−1 s−1, −7.3 V and 3.1 V dec−1 for μFET, Vth and SS value when operated at −30 V. These results indicate that this kind of high-κ organometallic lanthanide complex becomes a promising candidate as gate insulator for low-voltage organic FETs.

  7. Metal-oxide assisted surface treatment of polyimide gate insulators for high-performance organic thin-film transistors.

    Science.gov (United States)

    Kim, Sohee; Ha, Taewook; Yoo, Sungmi; Ka, Jae-Won; Kim, Jinsoo; Won, Jong Chan; Choi, Dong Hoon; Jang, Kwang-Suk; Kim, Yun Ho

    2017-06-14

    We developed a facile method for treating polyimide-based organic gate insulator (OGI) surfaces with self-assembled monolayers (SAMs) by introducing metal-oxide interlayers, called the metal-oxide assisted SAM treatment (MAST). To create sites for surface modification with SAM materials on polyimide-based OGI (KPI) surfaces, the metal-oxide interlayer, here amorphous alumina (α-Al 2 O 3 ), was deposited on the KPI gate insulator using spin-coating via a rapid sol-gel reaction, providing an excellent template for the formation of a high-quality SAM with phosphonic acid anchor groups. The SAM of octadecylphosphonic acid (ODPA) was successfully treated by spin-coating onto the α-Al 2 O 3 -deposited KPI film. After the surface treatment by ODPA/α-Al 2 O 3 , the surface energy of the KPI thin film was remarkably decreased and the molecular compatibility of the film with an organic semiconductor (OSC), 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C 10 ), was increased. Ph-BTBT-C 10 molecules were uniformly deposited on the treated gate insulator surface and grown with high crystallinity, as confirmed by atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis. The mobility of Ph-BTBT-C 10 thin-film transistors (TFTs) was approximately doubled, from 0.56 ± 0.05 cm 2 V -1 s -1 to 1.26 ± 0.06 cm 2 V -1 s -1 , after the surface treatment. The surface treatment of α-Al 2 O 3 and ODPA significantly decreased the threshold voltage from -21.2 V to -8.3 V by reducing the trap sites in the OGI and improving the interfacial properties with the OSC. We suggest that the MAST method for OGIs can be applied to various OGI materials lacking reactive sites using SAMs. It may provide a new platform for the surface treatment of OGIs, similar to that of conventional SiO 2 gate insulators.

  8. Effects of (NH4)2S x treatment on the surface properties of SiO2 as a gate dielectric for pentacene thin-film transistor applications

    Science.gov (United States)

    Hung, Cheng-Chun; Lin, Yow-Jon

    2018-01-01

    The effect of (NH4)2S x treatment on the surface properties of SiO2 is studied. (NH4)2S x treatment leads to the formation of S-Si bonds on the SiO2 surface that serves to reduce the number of donor-like trap states, inducing the shift of the Fermi level toward the conduction band minimum. A finding in this case is the noticeably reduced value of the SiO2 capacitance as the sulfurated layer is formed at the SiO2 surface. The effect of SiO2 layers with (NH4)2S x treatment on the carrier transport behaviors for the pentacene/SiO2-based organic thin-film transistor (OTFT) is also studied. The pentacene/as-cleaned SiO2-based OTFT shows depletion-mode behavior, whereas the pentacene/(NH4)2S x -treated SiO2-based OTFT exhibits enhancement-mode behavior. Experimental identification confirms that the depletion-/enhancement-mode conversion is due to the dominance competition between donor-like trap states in SiO2 near the pentacene/SiO2 interface and acceptor-like trap states in the pentacene channel. A sulfurated layer between pentacene and SiO2 is expected to give significant contributions to carrier transport for pentacene/SiO2-based OTFTs.

  9. Novel Quantum Dot Gate FETs and Nonvolatile Memories Using Lattice-Matched II-VI Gate Insulators

    Science.gov (United States)

    Jain, F. C.; Suarez, E.; Gogna, M.; Alamoody, F.; Butkiewicus, D.; Hohner, R.; Liaskas, T.; Karmakar, S.; Chan, P.-Y.; Miller, B.; Chandy, J.; Heller, E.

    2009-08-01

    This paper presents the successful use of ZnS/ZnMgS and other II-VI layers (lattice-matched or pseudomorphic) as high- k gate dielectrics in the fabrication of quantum dot (QD) gate Si field-effect transistors (FETs) and nonvolatile memory structures. Quantum dot gate FETs and nonvolatile memories have been fabricated in two basic configurations: (1) monodispersed cladded Ge nanocrystals (e.g., GeO x -cladded-Ge quantum dots) site-specifically self-assembled over the lattice-matched ZnMgS gate insulator in the channel region, and (2) ZnTe-ZnMgTe quantum dots formed by self-organization, using metalorganic chemical vapor-phase deposition (MOCVD), on ZnS-ZnMgS gate insulator layers grown epitaxially on Si substrates. Self-assembled GeO x -cladded Ge QD gate FETs, exhibiting three-state behavior, are also described. Preliminary results on InGaAs-on-InP FETs, using ZnMgSeTe/ZnSe gate insulator layers, are presented.

  10. Simulation of Heating of an Oil-Cooled Insulated Gate Bipolar Transistors Converter Model

    National Research Council Canada - National Science Library

    Ovrebo, Gregory

    2004-01-01

    I used SolidWorks a three-dimensional modeling software, and FloWorks, a fluid dynamics analysis tool, to simulate oil flow and heat transfer in a heat sink structure attached to three insulated gate bipolar transistors...

  11. Physical and Electrical Properties of SiO2 Layer Synthesized by Eco-Friendly Method

    Science.gov (United States)

    Kim, Jong-Woong; Kim, Young-Seok; Hong, Sung-Jei; Hong, Tae-Hwan; Han, Jeong-In

    2010-05-01

    SiO2 thin film has a wide range of applications, including insulation layers in microelectronic devices, such as semiconductors and flat panel displays, due to its advantageous characteristics. Herein, we developed a new eco-friendly method for manufacturing SiO2 nanoparticles and, thereby, SiO2 paste to be used in the digital printing process for the fabrication of SiO2 film. By excluding harmful Cl- and NO3- elements from the SiO2 nanoparticle synthetic process, we were able to lower the heat treatment temperature for the SiO2 precursor from 600 to 300 °C and the diameter of the final SiO2 nanoparticles to about 14 nm. The synthesized SiO2 nanoparticles were dispersed in an organic solvent with additives to make a SiO2 paste for feasibility testing. The SiO2 paste was printed onto a glass substrate to test the feasibility of using it for digital printing. The insulation resistance of the printed film was high enough for it to be used as an insulation layer for passivation.

  12. Photoemission study on electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces

    International Nuclear Information System (INIS)

    Fujimura, Nobuyuki; Ohta, Akio; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

    2017-01-01

    Electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces have been investigated by X-ray photoelectron spectroscopy (XPS) under monochromatized Al Kα radiation. From the analysis of the cut-off energy for secondary photoelectrons measured at each thinning step of a dielectric layer by wet-chemical etching, an abrupt potential change caused by electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces has been clearly detected. Al-gate MOS capacitors with thermally-grown SiO_2 and a HfO_2/SiO_2 dielectric stack were fabricated to evaluate the Al work function from the flat band voltage shift of capacitance-voltage (C-V) characteristics. Comparing the results of XPS and C-V measurements, we have verified that electrical dipole formed at the interface can be directly measured by photoemission measurements. (author)

  13. Development of insulated gate bipolar transistor-based power ...

    Indian Academy of Sciences (India)

    [5] S V Nakhe et al, National Laser Symposium, 81–82 (2001). [6] E G Cook et al, 8th IEEE Pulsed Power Conference, June 1991. [7] L Druckmann et al, IEEE Power Modulator Symposium, 213–216 (1992). [8] Hybrid gate drivers and gate drive power supplies, M57962L datasheet from Mitsubishi. Electric Corpn. Pramana ...

  14. Processing and performance of organic insulators as a gate layer in ...

    Indian Academy of Sciences (India)

    Fabrication of organic thin film transistor (OTFT) on flexible substrates is a challenge, because of its low softening temperature, high roughness and flexible nature. Although several organic dielectrics have been used as gate insulator, it is difficult to choose one in absence of a comparative study covering processing of ...

  15. Processing and performance of organic insulators as a gate layer in ...

    Indian Academy of Sciences (India)

    Abstract. Fabrication of organic thin film transistor (OTFT) on flexible substrates is a challenge, because of its low softening temperature, high roughness and flexible nature. Although several organic dielectrics have been used as gate insulator, it is difficult to choose one in absence of a comparative study covering ...

  16. HfO2 and SiO2 as barriers in magnetic tunneling junctions

    Science.gov (United States)

    Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

    2017-05-01

    SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

  17. Silicon-on-Insulator Lateral-Insulated-Gate-Bipolar-Transistor with Built-in Self-anti-ESD Diode

    Directory of Open Access Journals (Sweden)

    Xiaojun Cheng

    2014-05-01

    Full Text Available Power SOI (Silicon-On-Insulator devices have an inherent sandwich structure of MOS (Metal-Oxide-Semiconductor gate which is very easy to suffer ESD (Electro-Static Discharge overstress. To solve this reliability problem, studies on design and modification of a built-in self-anti-ESD diode for a preliminarily optimized high voltage SOI LIGBT (Lateral-Insulated-Gate-Bipolar-Transistor were carried out on the Silvaco TCAD (Technology-Computer-Aided-Design platform. According to the constrains of the technological process, the new introduction of the N+ doped region into P-well region that form the built-in self-anti-ESD diode should be done together with the doping of source under the same mask. The modifications were done by adjusting the vertical impurity profile in P-well into retrograde distribution and designing a cathode plate with a proper length to cover the forward depletion terminal and make sure that the thickness of the cathode plate is the same as that of the gate plate. The simulation results indicate that the modified device structure is compatible with the original one in process and design, the breakdown voltage margin of the former was expanded properly, and both the transient cathode voltages are clamped low enough very quickly. Therefore, the design and optimization results of the modified device structure of the built-in self-anti-ESD diode for the given SOI LIGBT meet the given requirements.

  18. The Microwave Noise Behaviour Of Dual Material Gate Silicon On Insulator

    Science.gov (United States)

    Jafar, N.; Soin, N.

    2009-06-01

    This work presents the noise behaviour due to the applied Dual Material Gate (DMG) on the 75 nm n-channel Silicon On Insulator (SOI) device operating in the fully depletion mode, particularly for microwave circuit design. Influences of DMG properties namely the gate length ratio (L1:L2) and gate material workfunction difference (ΔΦM) as well as structural and operational parameters which are silicon thickness (TSi) and threshold voltage (VTH) setting variation on the noise performance were carried out on simulation basis using ATLAS 2D. Results show better noise performance in DMG as compare to the standard gate structure of FD-SOI devices. Higher VTH for DMG design is recommended for minimized noise figure in line with the advantage of inverse VTH roll-off characteristics for short channel effects suppression.

  19. Fringing field effects in negative capacitance field-effect transistors with a ferroelectric gate insulator

    Science.gov (United States)

    Hattori, Junichi; Fukuda, Koichi; Ikegami, Tsutomu; Ota, Hiroyuki; Migita, Shinji; Asai, Hidehiro; Toriumi, Akira

    2018-04-01

    We study the effects of fringing electric fields on the behavior of negative-capacitance (NC) field-effect transistors (FETs) with a silicon-on-insulator body and a gate stack consisting of an oxide film, an internal metal film, a ferroelectric film, and a gate electrode using our own device simulator that can properly handle the complicated relationship between the polarization and the electric field in ferroelectric materials. The behaviors of such NC FETs and the corresponding metal-oxide-semiconductor (MOS) FETs are simulated and compared with each other to evaluate the effects of the NC of the ferroelectric film. Then, the fringing field effects are evaluated by comparing the NC effects in NC FETs with and without gate spacers. The fringing field between the gate stack, especially the internal metal film, and the source/drain region induces more charges at the interface of the film with the ferroelectric film. Accordingly, the function of the NC to modulate the gate voltage and the resulting function to improve the subthreshold swing are enhanced. We also investigate the relationships of these fringing field effects to the drain voltage and four design parameters of NC FETs, i.e., gate length, gate spacer permittivity, internal metal film thickness, and oxide film thickness.

  20. Controlled fabrication of Si nanocrystal delta-layers in thin SiO2 layers by plasma immersion ion implantation for nonvolatile memories

    International Nuclear Information System (INIS)

    Bonafos, C.; Ben-Assayag, G.; Groenen, J.; Carrada, M.; Spiegel, Y.; Torregrosa, F.; Normand, P.; Dimitrakis, P.; Kapetanakis, E.; Sahu, B. S.; Slaoui, A.

    2013-01-01

    Plasma Immersion Ion Implantation (PIII) is a promising alternative to beam line implantation to produce a single layer of nanocrystals (NCs) in the gate insulator of metal-oxide semiconductor devices. We report herein the fabrication of two-dimensional Si-NCs arrays in thin SiO 2 films using PIII and rapid thermal annealing. The effect of plasma and implantation conditions on the structural properties of the NC layers is examined by transmission electron microscopy. A fine tuning of the NCs characteristics is possible by optimizing the oxide thickness, implantation energy, and dose. Electrical characterization revealed that the PIII-produced-Si NC structures are appealing for nonvolatile memories

  1. Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module

    Science.gov (United States)

    2015-02-01

    executed with SolidWorks Flow Simulation , a computational fluid-dynamics code. The graph in Fig. 2 shows the timing and amplitudes of power pulses...defined a convective flow of air perpendicular to the bottom surface of the mounting plate, with a velocity of 10 ft/s. The thermal simulations were...Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module by Gregory K Ovrebo ARL-TR-7210

  2. A novel double gate MOSFET by symmetrical insulator packets with improved short channel effects

    Science.gov (United States)

    Ramezani, Zeinab; Orouji, Ali A.

    2018-03-01

    In this article, we study a novel double-gate SOI MOSFET structure incorporating insulator packets (IPs) at the junction between channel and source/drain (S/D) ends. The proposed MOSFET has great strength in inhibiting short channel effects and OFF-state current that are the main problems compared with conventional one due to the significant suppressed penetrations of both the lateral electric field and the carrier diffusion from the S/D into the channel. Improvement of the hot electron reliability, the ON to OFF drain current ratio, drain-induced barrier lowering, gate-induced drain leakage and threshold voltage over conventional double-gate SOI MOSFETs, i.e. without IPs, is displayed with the simulation results. This study is believed to improve the CMOS device reliability and is suitable for the low-power very-large-scale integration circuits.

  3. Characterization of a vertically movable gate field effect transistor using a silicon-on-insulator wafer

    Science.gov (United States)

    Song, In-Hyouk; Forfang, William B. D.; Cole, Bryan; You, Byoung Hee

    2014-10-01

    The vertically movable gate field effect transistor (VMGFET) is a FET-based sensing element, whose gate moves in a vertical direction over the channel. A VMGFET gate covers the region between source and drain. A 1 μm thick air layer separates the gate and the substrate of the VMGFET. A novel fabrication process to form a VMGFET using a silicon-on-insulator (SOI) wafer provides minimal internal stress of the gate structure. The enhancement-type n-channel VMGFET is fabricated with the threshold voltage of 2.32 V in steady state. A non-inverting amplifier is designed and integrated on a printable circuit board (PCB) to characterize device sensitivity and mechanical properties. The VMGFET is mechanically coupled to a speaker membrane to apply mechanical vibration. The oscillated drain current of FET are monitored and sampled with NI LabVIEW. The frequency of the output signal correlates with that of the input stimulus. The resonance frequency of the fabricated VMGFET is measured to be 1.11 kHz. The device sensitivity linearly increases by 0.106 mV/g Hz in the range of 150 Hz and 1 kHz.

  4. Characterization of a vertically movable gate field effect transistor using a silicon-on-insulator wafer

    International Nuclear Information System (INIS)

    Song, In-Hyouk; Forfang, William B D; Cole, Bryan; Hee You, Byoung

    2014-01-01

    The vertically movable gate field effect transistor (VMGFET) is a FET-based sensing element, whose gate moves in a vertical direction over the channel. A VMGFET gate covers the region between source and drain. A 1 μm thick air layer separates the gate and the substrate of the VMGFET. A novel fabrication process to form a VMGFET using a silicon-on-insulator (SOI) wafer provides minimal internal stress of the gate structure. The enhancement-type n-channel VMGFET is fabricated with the threshold voltage of 2.32 V in steady state. A non-inverting amplifier is designed and integrated on a printable circuit board (PCB) to characterize device sensitivity and mechanical properties. The VMGFET is mechanically coupled to a speaker membrane to apply mechanical vibration. The oscillated drain current of FET are monitored and sampled with NI LabVIEW. The frequency of the output signal correlates with that of the input stimulus. The resonance frequency of the fabricated VMGFET is measured to be 1.11 kHz. The device sensitivity linearly increases by 0.106 mV/g Hz in the range of 150 Hz and 1 kHz. (paper)

  5. The InP - SiO2 interface: Electron tunneling into oxide traps

    International Nuclear Information System (INIS)

    Prasad, S.J.; Owen, S.J.T.

    1985-01-01

    Indium Phosphide is an attractive material for high-speed devices. Though many successful devices have been built and demonstrated, InP MISFET's still suffer from drain current drift. From the data current drift measurements, the shift in the threshold voltage ΔV was computed for different times. It was found that a linear relationship exists between √ΔV and log(t). When a positive bias-stress was applied to the gate of an MIS capacitor for a time t, the C-V cure shifted by an amount ΔV and again, a linear relationship was observed between √ΔV and log(t). This was verified on four different gate insulators: pyrolytic SiO 2 at 320 0 C and 360 0 C, plasma oxide at 300 0 C and photo CVD oxide at 225 0 C. These results can only be explained by a model in which electrons tunnel from the substrate into oxide traps

  6. Duo gating on a 3D topological insulator - independent tuning of both topological surface states

    Science.gov (United States)

    Li, Chuan; de Ronde, Bob; Snelder, Marieke; Stehno, Martin; Huang, Yingkai; Golden, Mark; Brinkman, Alexander; ICE Team; IOP Collaboration

    ABSTRACT: Topological insulators are associated with a trove of exciting physics, such as the ability to host robust anyons, Majorana Bound States, which can be used for quantum computation. For future Majorana devices it is desirable to have the Fermi energy tuned as close as possible to the Dirac point of the topological surface state. Based on previous work on gating BSTS, we report the experimental progress towards gate-tuning of the top and bottom topological surface states of BiSbTeSe2 crystal flakes. When the Fermi level is moved across the Dirac point conduction is shown to change from electron dominated transport to hole dominated transport independently for either surface. In the high magnetic field, one can tune the system precisely between the different landau levels of both surfaces, thus a full gating map of the possible landau levels combination is established. In addition, we provide a simple capacitance model to explain the general hysteresis behaviors in topological insulator systems.

  7. MIS field effect transistor with barium titanate thin film as a gate insulator

    Energy Technology Data Exchange (ETDEWEB)

    Firek, P., E-mail: pfirek@elka.pw.edu.p [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Werbowy, A.; Szmidt, J. [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland)

    2009-11-25

    The properties of barium titanate (BaTiO{sub 3}, BT) like, e.g. high dielectric constant and resistivity, allow it to find numerous applications in field of microelectronics. In this work silicon metal insulator semiconductor field effect transistor (MISFET) structures with BaTiO{sub 3} (containing La{sub 2}O{sub 3} admixture) thin films in a role of gate insulator were investigated. The films were produced by means of radio frequency plasma sputtering (RF PS) of sintered BaTiO{sub 3} + La{sub 2}O{sub 3} (2 wt.%) target. In the paper transfer and output current-voltage (I-V), transconductance and output conductance characteristics of obtained transistors are presented and discussed. Basic parameters of these devices like, e.g. threshold voltage (V{sub TH}), are determined and discussed.

  8. Versatile sputtering technology for Al2O3 gate insulators on graphene

    Directory of Open Access Journals (Sweden)

    Miriam Friedemann, Mirosław Woszczyna, André Müller, Stefan Wundrack, Thorsten Dziomba, Thomas Weimann and Franz J Ahlers

    2012-01-01

    Full Text Available We report a novel, sputtering-based fabrication method of Al2O3 gate insulators on graphene. Electrical performance of dual-gated mono- and bilayer exfoliated graphene devices is presented. Sputtered Al2O3 layers possess comparable quality to oxides obtained by atomic layer deposition with respect to a high relative dielectric constant of about 8, as well as low-hysteresis performance and high breakdown voltage. We observe a moderate carrier mobility of about 1000 cm2 V− 1 s−1 in monolayer graphene and 350 cm2 V− 1 s−1 in bilayer graphene, respectively. The mobility decrease can be attributed to the resonant scattering on atomic-scale defects, likely originating from the Al precursor layer evaporated prior to sputtering.

  9. PECVD SiO2 dielectric for niobium Josephson IC process

    International Nuclear Information System (INIS)

    Lee, S.Y.; Nandakumar, V.; Murdock, B.; Hebert, D.

    1991-01-01

    PECVD SiO 2 dielectric has been evaluated as an insulator for a Nb-based, all-refractory Josephson integrated circuit process. First, the properties of PECVD SiO 2 films were measured and compared with those of evaporated SiO films. Second, the PECVD SiO 2 dielectric film was used in our Nb-based Josephson integrated circuit process. The main problem was found to be the deterioration of the critical temperature of the superconducting niobium adjacent to the SiO 2 . The cause and a solution of the problem were investigated. Finally, a Josephson integrated sampler circuit was fabricated and tested. This paper shows acceptable junction I-V characteristics and a measured time resolution of a 4.9 ps pulse in liquid helium

  10. Vortices and gate-tunable bound states in a topological insulator coupled to superconducting leads

    Science.gov (United States)

    Finck, Aaron; Kurter, C.; Hor, Y. S.; van Harlingen, D. J.

    2014-03-01

    It has been predicted that zero energy Majorana bound states can be found in the core of vortices within topological superconductors. Here, we report on Andreev spectroscopy measurements of the topological insulator Bi2Se3 with a normal metal lead and one or more niobium leads. The niobium induces superconductivity in the Bi2Se3 through the proximity effect, leading to both signatures of Andreev reflection and a prominent re-entrant resistance effect. When a large magnetic field is applied perpendicular to the surface of the Bi2Se3, we observe multiple abrupt changes in the subgap conductance that are accompanied by sharp peaks in the dynamical resistance. These peaks are very sensitive to changes in magnetic field and disappear at temperatures associated with the critical temperature of the induced superconductivity. The appearance of the transitions and peaks can be tuned by a top gate. At high magnetic fields, we also find evidence of gate-tunable states, which can lead to stable zero-bias conductance peaks. We interpret our results in terms of a transition occurring within the proximity effect region of the topological insulator, likely due to the formation of vortices. We acknowledge support from Microsoft Project Q.

  11. Highly stable piezo-immunoglobulin-biosensing of a SiO2/ZnO nanogenerator as a self-powered/active biosensor arising from the field effect influenced piezoelectric screening effect.

    Science.gov (United States)

    Zhao, Yayu; Fu, Yongming; Wang, Penglei; Xing, Lili; Xue, Xinyu

    2015-02-07

    Highly stable piezo-immunoglobulin-biosensing has been realized from a SiO2/ZnO nanowire (NW) nanogenerator (NG) as a self-powered/active biosensor. The piezoelectric output generated by the SiO2/ZnO NW NG can act not only as a power source for driving the device, but also as a sensing signal for detecting immunoglobulin G (IgG). The stability of the device is very high, and the relative standard deviation (RSD) ranges from 1.20% to 4.20%. The limit of detection (LOD) of IgG on the device can reach 5.7 ng mL(-1). The response of the device is in a linear relationship with IgG concentration. The biosensing performance of SiO2/ZnO NWs is much higher than that of bare ZnO NWs. A SiO2 layer uniformly coated on the surface of the ZnO NW acts as the gate insulation layer, which increases mechanical robustness and protects it from the electrical leakages and short circuits. The IgG biomolecules modified on the surface of the SiO2/ZnO NW act as a gate potential, and the field effect can influence the surface electron density of ZnO NWs, which varies the screening effect of free-carriers on the piezoelectric output. The present results demonstrate a feasible approach for a highly stable self-powered/active biosensor.

  12. High performance top-gated indium–zinc–oxide thin film transistors with in-situ formed HfO{sub 2} gate insulator

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yang, E-mail: yang_song@brown.edu [Department of Physics, Brown University, 182 Hope Street, Providence, RI 02912 (United States); Zaslavsky, A. [Department of Physics, Brown University, 182 Hope Street, Providence, RI 02912 (United States); School of Engineering, Brown University, 184 Hope Street, Providence, RI 02912 (United States); Paine, D.C. [School of Engineering, Brown University, 184 Hope Street, Providence, RI 02912 (United States)

    2016-09-01

    We report on top-gated indium–zinc–oxide (IZO) thin film transistors (TFTs) with an in-situ formed HfO{sub 2} gate dielectric insulator. Building on our previous demonstration of high-performance IZO TFTs with Al{sub 2}O{sub 3}/HfO{sub 2} gate dielectric, we now report on a one-step process, in which Hf is evaporated onto the 20 nm thick IZO channel, forming a partially oxidized HfO{sub x} layer, without any additional insulator in-between. After annealing in air at 300 °C, the in-situ reaction between partially oxidized Hf and IZO forms a high quality HfO{sub 2} gate insulator with a low interface trapped charge density N{sub TC} ~ 2.3 × 10{sup 11} cm{sup −2} and acceptably low gate leakage < 3 × 10{sup −7} A/cm{sup 2} at gate voltage V{sub G} = 1 V. The annealed TFTs with gate length L{sub G} = 50 μm have high mobility ~ 95 cm{sup 2}/V ∙ s (determined via the Y-function technique), high on/off ratio ~ 10{sup 7}, near-zero threshold voltage V{sub T} = − 0.02 V, and a subthreshold swing of 0.062 V/decade, near the theoretical limit. The on-current of our proof-of-concept TFTs is relatively low, but can be improved by reducing L{sub G}, indicating that high-performance top-gated HfO{sub 2}-isolated IZO TFTs can be fabricated using a single-step in-situ dielectric formation approach. - Highlights: • High-performance indium–zinc–oxide (IZO) thin film transistors (TFTs). • Single-step in-situ dielectric formation approach simplifies fabrication process. • During anneal, reaction between HfO{sub x} and IZO channel forms a high quality HfO{sub 2} layer. • Gate insulator HfO{sub 2} shows low interface trapped charge and small gate leakage. • TFTs have high mobility, near-zero threshold voltage, and a low subthreshold swing.

  13. Selective SiO2 etching in three dimensional structures using parylene-C as mask

    NARCIS (Netherlands)

    Veltkamp, Henk-Willem; Zhao, Yiyuan; de Boer, Meint J.; Wiegerink, Remco J.; Lötters, Joost Conrad

    2017-01-01

    This abstract describes an application of an easy and straightforward method for selective SiO2 etching in three dimensional structures, which is developed by our group. The application in this abstract is the protection of the buried-oxide (BOX) layer of a silicon-on-insulator (SOI) wafer against

  14. Valence band variation in Si (110) nanowire induced by a covered insulator

    International Nuclear Information System (INIS)

    Hong-Hua, Xu; Xiao-Yan, Liu; Yu-Hui, He; Gang, Du; Ru-Qi, Han; Jin-Feng, Kang; Chun, Fan; Ai-Dong, Sun

    2010-01-01

    In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si (110) nanowire via the simulation of strain distribution and the calculation of a generalized 6×6k·p strained valence band. The nanowire is surrounded by the gate dielectric. Our simulation indicates that the strain of the amorphous SiO 2 insulator is negligible without considering temperature factors. On the other hand, the thermal residual strain in a nanowire with amorphous SiO 2 insulator which has negligible lattice misfit strain pushes the valence subbands upwards by chemical vapour deposition and downwards by thermal oxidation treatment. In contrast with the strain of the amorphous SiO 2 insulator, the strain of the HfO 2 gate insulator in Si (110) nanowire pushes the valence subbands upwards remarkably. The thermal residual strain by HfO 2 insulator contributes to the up-shifting tendency. Our simulation results for valence band shifting and warping in Si nanowires can provide useful guidance for further nanowire device design. (classical areas of phenomenology)

  15. Improvements in the reliability of a-InGaZnO thin-film transistors with triple stacked gate insulator in flexible electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hua-Mao [Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Chang, Ting-Chang, E-mail: tcchang3708@gmail.com [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Advanced Optoelectronics Technology Center, National Cheng Kung University, Taiwan (China); Tai, Ya-Hsiang [Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Chen, Kuan-Fu [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Chiang, Hsiao-Cheng [Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Liu, Kuan-Hsien [Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan (China); Lee, Chao-Kuei [Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan (China); Lin, Wei-Ting; Cheng, Chun-Cheng; Tu, Chun-Hao; Liu, Chu-Yu [Advanced Technology Research Center, AU Optronics Corp, Hsinchu, Taiwan (China)

    2015-11-30

    This study examined the impact of the low-temperature stacking gate insulator on the gate bias instability of a-InGaZnO thin film transistors in flexible electronics applications. Although the quality of SiN{sub x} at low process/deposition temperature is better than that of SiO{sub x} at similarly low process/deposition temperature, there is still a very large positive threshold voltage (V{sub th}) shift of 9.4 V for devices with a single low-temperature SiN{sub x} gate insulator under positive gate bias stress. However, a suitable oxide–nitride–oxide-stacked gate insulator exhibits a V{sub th} shift of only 0.23 V. This improvement results from the larger band offset and suitable gate insulator thickness that can effectively suppress carrier trapping behavior. - Highlights: • The cause of the bias instability for a low-temperature gate insulator is verified. • A triple-stacked gate insulator was fabricated. • A suitable triple stacked gate insulator shows only 0.23 V threshold voltage shift.

  16. Positron annihilation in SiO 2-Si studied by a pulsed slow positron beam

    Science.gov (United States)

    Suzuki, R.; Ohdaira, T.; Uedono, A.; Kobayashi, Y.

    2002-06-01

    Positron and positronium (Ps) behavior in SiO 2-Si have been studied by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The PALS study of SiO 2-Si samples, which were prepared by a dry-oxygen thermal process, revealed that the positrons implanted in the Si substrate and diffused back to the interface do not contribute to the ortho-Ps long-lived component, and the lifetime spectrum of the interface has at least two components. From the AMOC study, the momentum distribution of the ortho-Ps pick-off annihilation in SiO 2, which shows broader momentum distribution than that of crystalline Si, was found to be almost the same as that of free positron annihilation in SiO 2. A varied interface model was proposed to interpret the results of the metal-oxide-semiconductor (MOS) experiments. The narrow momentum distribution found in the n-type MOS with a negative gate bias voltage could be attributed to Ps formation and rapid spin exchange in the SiO 2-Si interface. We have developed a two-dimensional positron lifetime technique, which measures annihilation time and pulse height of the scintillation gamma-ray detector for each event. Using this technique, the positronium behavior in a porous SiO 2 film, grown by a sputtering method, has been studied.

  17. Experimental study on short-circuit characteristics of the new protection circuit of insulated gate bipolar transistor

    International Nuclear Information System (INIS)

    Ji, In-Hwan; Choi, Young-Hwan; Ha, Min-Woo; Han, Min-Koo; Choi, Yearn-Ik

    2006-01-01

    A new protection circuit employing the collector to emitter voltage (V CE ) sensing scheme for short-circuit withstanding capability of the insulated gate bipolar transistor (IGBT) is proposed and verified by experimental results. Because the current path between the gate and collector can be successfully eliminated in the proposed protection circuit, the power consumption can be reduced and the gate input impedance can be increased. Previous study is limited to dc characteristics. However, experimental results show that the proposed protection circuit successfully reduces the over-current of main IGBT by 80.4% under the short-circuit condition

  18. Chemical Gating of a Weak Topological Insulator: Bi14Rh3I9.

    Science.gov (United States)

    Ghimire, Madhav Prasad; Richter, Manuel

    2017-10-11

    The compound Bi 14 Rh 3 I 9 has recently been suggested as a weak three-dimensional topological insulator on the basis of angle-resolved photoemission and scanning-tunneling experiments in combination with density functional (DF) electronic structure calculations. These methods unanimously support the topological character of the headline compound, but a compelling confirmation could only be obtained by dedicated transport experiments. The latter, however, are biased by an intrinsic n-doping of the material's surface due to its polarity. Electronic reconstruction of the polar surface shifts the topological gap below the Fermi energy, which would also prevent any future device application. Here, we report the results of DF slab calculations for chemically gated and counter-doped surfaces of Bi 14 Rh 3 I 9 . We demonstrate that both methods can be used to compensate the surface polarity without closing the electronic gap.

  19. On the stability of silicon field effect capacitors with phosphate buffered saline electrolytic gate and self assembled monolayer gate insulator

    International Nuclear Information System (INIS)

    Hemed, Nofar Mintz; Inberg, Alexandra; Shacham-Diamand, Yosi

    2013-01-01

    We herein report on the stability of Electrolyte/Insulator/Semiconductor (EIS) devices with Self-Assembled Monolayer (SAM) gate insulator layers, i.e. Electrolyte/SAM/Semiconductor (ESS) devices. ESS devices can be functionalized creating highly specific sensors that can be integrated on standard silicon platform. However, biosensors by their nature are in contact with biological solutions that contain ions and molecules that may affect the device characteristics and cause electrical instability. In this paper we present a list of potential hazards to ESS devices and a study of the device stability under common testing conditions analyzing possible causes for the instabilities. ESS capacitors under open circuit conditions (i.e. open circuit bias of ∼0.6 V vs. Ag/AgCl reference electrode) were periodically characterized. We measured the complex impedance of the capacitors versus bias and extracted the effective capacitance vs. voltage (C–V) curves using two methods. We observed a parallel shift of the C–V curves toward negative bias; showing an effective accumulation of positive charge. The quantitative analysis of the drift vs. time was found to depend on the effective capacitance evaluation method. This effect is discussed and a best-known method is proposed. The devices surface composition was tested before and after the stress experiment by X-ray Photoelectron Spectroscopy (XPS) and sodium accumulation was observed. To further explore the flat-band voltage drift effect and to challenge the assumption that alkali ions are involved in the drift we conceived a novel alkali-free phosphate buffer saline (AF-PBS) where the sodium and potassium ions are replaced by ammonium ion and tested the capacitor under similar conditions to standard PBS. We found that the drift of the AF-PBS solution was much less at the first hour but was similar to that of the conventional PBS for longer stress times; hence, AF-PBS does not solve the long-term instability problem

  20. Development and characterization of ultrathin hafnium titanates as high permittivity gate insulators

    Science.gov (United States)

    Li, Min

    High permittivity or high-kappa materials are being developed for use as gate insulators for future ultrascaled metal oxide semiconductor field effect transistors (MOSFETs). Hafnium containing compounds are the leading candidates. Due to its moderate permittivity, however, it is difficult to achieve HfO2 gate structures with an EOT well below 1.0 nm. One approach to increase HfO2 permittivity is combining it with a very high-kappa material, such as TiO2. In this thesis, we systematically studied the electrical and physical characteristics of high-kappa hafnium titanates films as gate insulators. A series of HfxTi1-xO2 films with well-controlled composition were deposited using an MOCVD system. The physical properties of the films were analyzed using a variety of characterization techniques. X-ray micro diffraction indicates that the Ti-rich thin film is more immune to crystallization. TEM analysis showed that the thick stoichiometric HfTiO 4 film has an orthorhombic structure and large anisotropic grains. The C-V curves from the devices with the hafnium titanates films displayed relatively low hysteresis. In a certain composition range, the interfacial layer (IL) EOT and permittivity of HfxTi1-x O2 increases linearly with increasing Ti. The charge is negative for HfxTi1-xO2/IL and positive for Si/IL interface, and the magnitude increases as Hf increases. For ultra-thin films (less than 2 nm EOT), the leakage current increases with increasing HE Moreover, the Hf-rich sample has weaker temperature dependence of the current. In the MOSFET devices with the hafnium titanates films, normal transistor characteristics were observed, also electron mobility degradation. Next, we investigated the effects that different pre-deposition surface treatments, including HF dipping, NH3 surface nitridation, and HfO2 deposition, have on the electrical properties of hafnium titanates. Surface nitridation shows stronger effect than the thin HfO2 layer. The nitrided samples displayed a

  1. Modeling small-signal response of GaN-based metal-insulator-semiconductor high electron mobility transistor gate stack in spill-over regime: Effect of barrier resistance and interface states

    International Nuclear Information System (INIS)

    Capriotti, M.; Fleury, C.; Oposich, M.; Bethge, O.; Strasser, G.; Pogany, D.; Lagger, P.; Ostermaier, C.

    2015-01-01

    We provide theoretical and simulation analysis of the small signal response of SiO 2 /AlGaN/GaN metal insulator semiconductor (MIS) capacitors from depletion to spill over region, where the AlGaN/SiO 2 interface is accumulated with free electrons. A lumped element model of the gate stack, including the response of traps at the III-N/dielectric interface, is proposed and represented in terms of equivalent parallel capacitance, C p , and conductance, G p . C p -voltage and G p -voltage dependences are modelled taking into account bias dependent AlGaN barrier dynamic resistance R br and the effective channel resistance. In particular, in the spill-over region, the drop of C p with the frequency increase can be explained even without taking into account the response of interface traps, solely by considering the intrinsic response of the gate stack (i.e., no trap effects) and the decrease of R br with the applied forward bias. Furthermore, we show the limitations of the conductance method for the evaluation of the density of interface traps, D it , from the G p /ω vs. angular frequency ω curves. A peak in G p /ω vs. ω occurs even without traps, merely due to the intrinsic frequency response of gate stack. Moreover, the amplitude of the G p /ω vs. ω peak saturates at high D it , which can lead to underestimation of D it . Understanding the complex interplay between the intrinsic gate stack response and the effect of interface traps is relevant for the development of normally on and normally off MIS high electron mobility transistors with stable threshold voltage

  2. Dielectric strength of SiO2 in a CMOS transistor structure

    International Nuclear Information System (INIS)

    Soden, J.M.

    1979-01-01

    The distribution of experimental dielectric strengths of SiO 2 gate dielectric in a CMOS transistor structure is shown to be composed of a primary, statistically-normal distribution of high dielectric strength and a secondary distribution spread through the lower dielectric strength region. The dielectric strength was not significantly affected by high level (1 x 10 6 RADS (Si)) gamma radiation or high temperature (200 0 C) stress. The primary distribution breakdowns occurred at topographical edges, mainly at the gate/field oxide interface, and the secondary distribution breakdowns occurred at random locations in the central region of the gate

  3. PAC study in the HfO2-SiO2 system

    International Nuclear Information System (INIS)

    Chain, C.Y.; Damonte, L.C.; Ferrari, S.; Munoz, E.; Torres, C. Rodriguez; Pasquevich, A.F.

    2010-01-01

    A high-k HfO 2 /SiO 2 gate stack is taking the place of SiO 2 as a gate dielectric in field effect transistors. This fact makes the study of the solid-state reaction between these oxides very important. Nanostructure characterization of a high-energy ball milled and post-annealed equimolar HfO 2 and amorphous SiO 2 powder mixture has been carried out by perturbed angular correlations (PAC) technique. The study was complemented with X-ray diffraction and positron annihilation lifetime spectroscopy (PALS). The experimental results revealed that the ball milling of equimolar mixtures increases the defects concentration in hafnium oxide. No solid-state reaction occurred even after 8 h of milling. The formation of HfSiO 4 (hafnon) was observed in the milled blends annealed at high temperatures.The PAC results of the milled samples are compared with those obtained for pure m-ZrO 2 subjected to high-energy ball milling and with reported microstructure data for the system ZrO 2 -SiO 2 .

  4. Radiation Effects in Advanced Multiple Gate and Silicon-on-Insulator Transistors

    Science.gov (United States)

    Simoen, Eddy; Gaillardin, Marc; Paillet, Philippe; Reed, Robert A.; Schrimpf, Ron D.; Alles, Michael L.; El-Mamouni, Farah; Fleetwood, Daniel M.; Griffoni, Alessio; Claeys, Cor

    2013-06-01

    The aim of this review paper is to describe in a comprehensive manner the current understanding of the radiation response of state-of-the-art Silicon-on-Insulator (SOI) and FinFET CMOS technologies. Total Ionizing Dose (TID) response, heavy-ion microdose effects and single-event effects (SEEs) will be discussed. It is shown that a very high TID tolerance can be achieved by narrow-fin SOI FinFET architectures, while bulk FinFETs may exhibit similar TID response to the planar devices. Due to the vertical nature of FinFETs, a specific heavy-ion response can be obtained, whereby the angle of incidence becomes highly important with respect to the vertical sidewall gates. With respect to SEE, the buried oxide in the SOI FinFETs suppresses the diffusion tails from the charge collection in the substrate compared to the planar bulk FinFET devices. Channel lengths and fin widths are now comparable to, or smaller than the dimensions of the region affected by the single ionizing ions or lasers used in testing. This gives rise to a high degree of sensitivity to individual device parameters and source-drain shunting during ion-beam or laser-beam SEE testing. Simulations are used to illuminate the mechanisms observed in radiation testing and the progress and needs for the numerical modeling/simulation of the radiation response of advanced SOI and FinFET transistors are highlighted.

  5. Simulation of dual-gate SOI MOSFET with different dielectric layers

    Science.gov (United States)

    Yadav, Jyoti; Chaudhary, R.; Mukhiya, R.; Sharma, R.; Khanna, V. K.

    2016-04-01

    The paper presents the process design and simulation of silicon-on-insulator (SOI)-based dual-gate metal oxide field-effect transistor (DG-MOSFET) stacked with different dielectric layers on the top of gate oxide. A detailed 2D process simulation of SOI-MOSFETs and its electrical characterization has been done using SILVACO® TCAD tool. A variation in transconductance was observed with different dielectric layers, AlN-gate MOSFET having the highest tranconductance value as compared to other three dielectric layers (SiO2, Si3N4 and Al2O3).

  6. Densification of ∼5 nm-thick SiO_2 layers by nitric acid oxidation

    International Nuclear Information System (INIS)

    Choi, Jaeyoung; Joo, Soyeong; Park, Tae Joo; Kim, Woo-Byoung

    2017-01-01

    Highlights: • Leakage current density of the commercial PECVD grown ∼5 nm SiO_2 layer has been decreased about three orders of magnitude by densification. • The densification of SiO_2 layer is achieved by high oxidation ability of O·. • Densities of suboxide, fixed charge (N_f) and defect state (N_d) in SiO_2/Si interface are decreased by NAOS and PMA. • Tunneling barrier height (Φ_t) is increased because of the increase of atomic density in SiO_2 layer. - Abstract: Low-temperature nitric acid (HNO_3) oxidation of Si (NAOS) has been used to improve the interface and electrical properties of ∼5 nm-thick SiO_2/Si layers produced by plasma-enhanced chemical vapor deposition (PECVD). Investigations of the physical properties and electrical characteristics of these thin films revealed that although their thickness is not changed by NAOS, the leakage current density at a gate bias voltage of −1 V decreases by about two orders of magnitude from 1.868 × 10"−"5 A/cm"2. This leakage current density was further reduced by post-metallization annealing (PMA) at 250 °C for 10 min in a 5 vol.% hydrogen atmosphere, eventually reaching a level (5.2 × 10"−"8 A/cm"2) approximately three orders of magnitude less than the as-grown SiO_2 layer. This improvement is attributed to a decrease in the concentration of suboxide species (Si"1"+, Si"2"+ and Si"3"+) in the SiO_2/Si interface, as well as a decrease in the equilibrium density of defect sites (N_d) and fixed charge density (N_f). The barrier height (Φ_t) generated by a Poole-Frenkel mechanism also increased from 0.205 to 0.371 eV after NAOS and PMA. The decrease in leakage current density is therefore attributed to a densification of the SiO_2 layer in combination with the removal of OH species and increase in interfacial properties at the SiO_2/Si interface.

  7. Thermally tunable VO2-SiO2 nanocomposite thin-film capacitors

    Science.gov (United States)

    Sun, Yifei; Narayanachari, K. V. L. V.; Wan, Chenghao; Sun, Xing; Wang, Haiyan; Cooley, Kayla A.; Mohney, Suzanne E.; White, Doug; Duwel, Amy; Kats, Mikhail A.; Ramanathan, Shriram

    2018-03-01

    We present a study of co-sputtered VO2-SiO2 nanocomposite dielectric thin-film media possessing continuous temperature tunability of the dielectric constant. The smooth thermal tunability is a result of the insulator-metal transition in the VO2 inclusions dispersed within an insulating matrix. We present a detailed comparison of the dielectric characteristics of this nanocomposite with those of a VO2 control layer and of VO2/SiO2 laminate multilayers of comparable overall thickness. We demonstrated a nanocomposite capacitor that has a thermal capacitance tunability of ˜60% between 25 °C and 100 °C at 1 MHz, with low leakage current. Such thermally tunable capacitors could find potential use in applications such as sensing, thermal cloaks, and phase-change energy storage devices.

  8. N-channel thin-film transistors based on 1,4,5,8-naphthalene tetracarboxylic dianhydride with ultrathin polymer gate buffer layer

    International Nuclear Information System (INIS)

    Tanida, Shinji; Noda, Kei; Kawabata, Hiroshi; Matsushige, Kazumi

    2009-01-01

    N-channel operation of thin-film transistors based on 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) with a 9-nm-thick poly(methyl methacrylate) (PMMA) gate buffer layer was examined. The uniform coverage of the ultrathin PMMA layer on an SiO 2 gate insulator, verified by X-ray reflectivity measurement, caused the increase of electron field-effect mobility because of the suppression of electron traps existing on the SiO 2 surface. In addition, air stability for n-channel operation of the NTCDA transistor was also improved by the PMMA layer which possibly prevented the adsorption of ambient water molecules onto the SiO 2 surface.

  9. Preparation and Characterization of Fluorescent SiO2 Microspheres

    Science.gov (United States)

    Xu, Cui; Zhang, Hao; Guan, Ruifang

    2018-01-01

    Fluorescent compound without typical fluorophores was synthesized with citric acid (CA) and aminopropyltriethoxysilane (APTS) firstly, and then it was grafted to the surface of the prepared SiO2 microspheres by chemical reaction. The fluorescent SiO2 microspheres with good fluorescent properties were obtained by optimizing the reaction conditions. And the morphology and structure of the fluorescent SiO2 microspheres have been characterized by scanning electron microscopy (SEM) and fourier transform infrared (FTIR) spectroscopy. The results showed that the preparation of fluorescent SiO2 microspheres have good monodispersity and narrow particle size distribution. Moreover, the fluorescent SiO2 microspheres can be applied to detect Fe3+ in aqueous solution, prepare fluorescent SiO2 rubber, and have potential to be applied in the fluorescent labeling and fingerprint appearing technique fields.

  10. Pentacene based thin film transistors with high-k dielectric Nd2O3 as a gate insulator

    International Nuclear Information System (INIS)

    Sarma, R.; Saikia, D.

    2010-01-01

    We have investigated the pentacene based Organic Thin Film Transistors (OTFTs) with high-k dielectric Nd 2 O 3 . Use of high dielectric constant (high-k) gate insulator Nd 2 O 3 reduces the threshold voltage and sub threshold swing of the OTFTs. The calculated threshold voltage -2.2V and sub-threshold swing 1V/decade, current ON-OFF ratio is 1.7 X 10 4 and mobility is 0.13cm 2 /V.s. Pentacene film is deposited on Nd 2 O 3 surface using two step deposition method. Deposited pentacene film is found poly crystalline in nature. (author)

  11. Unified analytical threshold voltage model for non-uniformly doped dual metal gate fully depleted silicon-on-insulator MOSFETs

    Science.gov (United States)

    Rao, Rathnamala; Katti, Guruprasad; Havaldar, Dnyanesh S.; DasGupta, Nandita; DasGupta, Amitava

    2009-03-01

    The paper describes the unified analytical threshold voltage model for non-uniformly doped, dual metal gate (DMG) fully depleted silicon-on-insulator (FDSOI) MOSFETs based on the solution of 2D Poisson's equation. 2D Poisson's equation is solved analytically for appropriate boundary conditions using separation of variables technique. The solution is then extended to obtain the threshold voltage of the FDSOI MOSFET. The model is able to handle any kind of non-uniform doping, viz. vertical, lateral as well as laterally asymetric channel (LAC) profile in the SOI film in addition to the DMG structure. The analytical results are validated with the numerical simulations using the device simulator MEDICI.

  12. Quantum and Classical Magnetoresistance in Ambipolar Topological Insulator Transistors with Gate-tunable Bulk and Surface Conduction

    Science.gov (United States)

    Tian, Jifa; Chang, Cuizu; Cao, Helin; He, Ke; Ma, Xucun; Xue, Qikun; Chen, Yong P.

    2014-01-01

    Weak antilocalization (WAL) and linear magnetoresistance (LMR) are two most commonly observed magnetoresistance (MR) phenomena in topological insulators (TIs) and often attributed to the Dirac topological surface states (TSS). However, ambiguities exist because these phenomena could also come from bulk states (often carrying significant conduction in many TIs) and are observable even in non-TI materials. Here, we demonstrate back-gated ambipolar TI field-effect transistors in (Bi0.04Sb0.96)2Te3 thin films grown by molecular beam epitaxy on SrTiO3(111), exhibiting a large carrier density tunability (by nearly 2 orders of magnitude) and a metal-insulator transition in the bulk (allowing switching off the bulk conduction). Tuning the Fermi level from bulk band to TSS strongly enhances both the WAL (increasing the number of quantum coherent channels from one to peak around two) and LMR (increasing its slope by up to 10 times). The SS-enhanced LMR is accompanied by a strongly nonlinear Hall effect, suggesting important roles of charge inhomogeneity (and a related classical LMR), although existing models of LMR cannot capture all aspects of our data. Our systematic gate and temperature dependent magnetotransport studies provide deeper insights into the nature of both MR phenomena and reveal differences between bulk and TSS transport in TI related materials. PMID:24810663

  13. Poly(4-vinylphenol gate insulator with cross-linking using a rapid low-power microwave induction heating scheme for organic thin-film-transistors

    Directory of Open Access Journals (Sweden)

    Ching-Lin Fan

    2016-03-01

    Full Text Available A Microwave-Induction Heating (MIH scheme is proposed for the poly(4-vinylphenol (PVP gate insulator cross-linking process to replace the traditional oven heating cross-linking process. The cross-linking time is significantly decreased from 1 h to 5 min by heating the metal below the PVP layer using microwave irradiation. The necessary microwave power was substantially reduced to about 50 W by decreasing the chamber pressure. The MIH scheme is a good candidate to replace traditional thermal heating for cross-linking of PVP as the gate insulator for organic thin-film-transistors.

  14. Poly(4-vinylphenol) gate insulator with cross-linking using a rapid low-power microwave induction heating scheme for organic thin-film-transistors

    Science.gov (United States)

    Fan, Ching-Lin; Shang, Ming-Chi; Hsia, Mao-Yuan; Wang, Shea-Jue; Huang, Bohr-Ran; Lee, Win-Der

    2016-03-01

    A Microwave-Induction Heating (MIH) scheme is proposed for the poly(4-vinylphenol) (PVP) gate insulator cross-linking process to replace the traditional oven heating cross-linking process. The cross-linking time is significantly decreased from 1 h to 5 min by heating the metal below the PVP layer using microwave irradiation. The necessary microwave power was substantially reduced to about 50 W by decreasing the chamber pressure. The MIH scheme is a good candidate to replace traditional thermal heating for cross-linking of PVP as the gate insulator for organic thin-film-transistors.

  15. Passivation of pigment-grade TiO2 particles by nanothick atomic layer deposited SiO2 films

    International Nuclear Information System (INIS)

    King, David M; Liang Xinhua; Weimer, Alan W; Burton, Beau B; Akhtar, M Kamal

    2008-01-01

    Pigment-grade TiO 2 particles were passivated using nanothick insulating films fabricated by atomic layer deposition (ALD). Conformal SiO 2 and Al 2 O 3 layers were coated onto anatase and rutile powders in a fluidized bed reactor. SiO 2 films were deposited using tris-dimethylaminosilane (TDMAS) and H 2 O 2 at 500 deg. C. Trimethylaluminum and water were used as precursors for Al 2 O 3 ALD at 177 deg. C. The photocatalytic activity of anatase pigment-grade TiO 2 was decreased by 98% after the deposition of 2 nm SiO 2 films. H 2 SO 4 digest tests were performed to exhibit the pinhole-free nature of the coatings and the TiO 2 digest rate was 40 times faster for uncoated TiO 2 than SiO 2 coated over a 24 h period. Mass spectrometry was used to monitor reaction progress and allowed for dosing time optimization. These results demonstrate that the TDMAS-H 2 O 2 chemistry can deposit high quality, fully dense SiO 2 films on high radius of curvature substrates. Particle ALD is a viable passivation method for pigment-grade TiO 2 particles

  16. Suspended graphene devices with local gate control on an insulating substrate

    International Nuclear Information System (INIS)

    Ong, Florian R; Cui, Zheng; Vojvodin, Cameron; Papaj, Michał; Deng, Chunqing; Bal, Mustafa; Lupascu, Adrian; Yurtalan, Muhammet A; Orgiazzi, Jean-Luc F X

    2015-01-01

    We present a fabrication process for graphene-based devices where a graphene monolayer is suspended above a local metallic gate placed in a trench. As an example we detail the fabrication steps of a graphene field-effect transistor. The devices are built on a bare high-resistivity silicon substrate. At temperatures of 77 K and below, we observe the field-effect modulation of the graphene resistivity by a voltage applied to the gate. This fabrication approach enables new experiments involving graphene-based superconducting qubits and nano-electromechanical resonators. The method is applicable to other two-dimensional materials. (paper)

  17. Thickness and composition of ultrathin SiO2 layers on Si

    International Nuclear Information System (INIS)

    Marel, C. van der; Verheijen, M.A.; Tamminga, Y.; Pijnenburg, R.H.W.; Tombros, N.; Cubaynes, F.

    2004-01-01

    investigated [D. A. Muller, T. Sorsch, S. Moccio, F. H. Baumann, K. Evans-Lutterodt, and G. Timp, Nature (London) 399, 758 (1999); D. A. Muller and J. B. Neaton, Structure and Energetics of the Interface Between Si and Amorphous SiO 2 in Fundamental Aspects of Silicon Oxidation, edited by Y. J. Chabal (Springer, Berlin, 2001), pp. 219-246.] by means of high-resolution electron energy loss spectroscopy measurements of the O K edge in ultrathin gate oxides of SiO 2

  18. Electrical analysis of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors on flexible bulk mono-crystalline silicon

    KAUST Repository

    Ghoneim, Mohamed T.; Rojas, Jhonathan Prieto; Young, Chadwin D.; Bersuker, Gennadi; Hussain, Muhammad Mustafa

    2015-01-01

    We report on the electrical study of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors (MOSCAPs) on a flexible ultra-thin (25 μm) silicon fabric which is peeled off using a CMOS compatible process from a standard

  19. Solid-gate control of insulator to 2D metal transition at SrTiO3 surface

    Science.gov (United States)

    Schulman, Alejandro; Stoliar, Pablo; Kitoh, Ai; Rozenberg, Marcelo; Inoue, Isao H.

    As miniaturization of the semiconductor transistor approaches its limit, semiconductor industries are facing a major challenge to extend information processing beyond what can be attainable by conventional Si-based transistors. Innovative combinations of new materials and new processing platforms are desired. Recent discovery of the 2D electron gas (2DEG) at the surface of SrTiO3 (STO) and its electrostatic control, have carried it to the top of promising materials to be utilized in innovative devices. We report an electrostatic control of the carrier density of the 2DEG formed at the channel of bilayer-gated STO field-effect devices. By applying a gate electric field at room temperature, its highly insulating channel exhibits a transition to metallic one. This transition is accompanied by non-monotonic voltage-gain transfer characteristic with both negative and positive slope regions and unexpected enhancement of the sheet carrier density. We will introduce a numerical model to rationalize the observed features in terms of the established physics of field-effect transistors and the physics of percolation. Furthermore, we have found a clear signature of a Kondo effect that arises due to the interaction between the dilute 2DEG and localized Ti 3d orbitals originated by oxygen vacancies near the channel. On leave from CIC nanoGUNE, Spain.

  20. Fluorinated copper-phthalocyanine-based n-type organic field-effect transistors with a polycarbonate gate insulator

    International Nuclear Information System (INIS)

    Sethuraman, Kunjithapatham; Kumar, Palanisamy; Santhakumar, Kannappan; Ochiai, Shizuyasu; Shin, Paikkyun

    2012-01-01

    Fluorinated copper-phthalocyanine (F 16 CuPc) thin films were prepared by using a vacuum evaporation technique and were applied to n-type organic field-effect transistors (OFETs) as active channel layers combined with a spin-coated polycarbonate thin-film gate insulator. The output characteristics of the resulting n-type OFET devices with bottom-gate/bottom-contact structures were investigated to evaluate the performances such as the field effect mobility (μ FE ), the on/off current ratio (I on/off ), and the threshold voltage (V th ). A relatively high field effect mobility of 6.0 x 10 -3 cm 2 /Vs was obtained for the n-type semiconductor under atmospheric conditions with an on/off current ratio of 1 x 10 4 and a threshold voltage of 5 V. The electron mobility of the n-type semiconductor was found to depend strongly on the growth temperature of the F 16 CuPc thin films. X-ray diffraction profiles showed that the crystallinity and the orientation of the F 16 CuPc on a polycarbonate thin film were enhanced with increasing growth temperature. Atomic force microscopy studies revealed various surface morphologies of the active layer. The field effect mobility of the F 16 CuPc-OFET was closely related to the crystallinity and the orientation of the F 16 CuPc thin film.

  1. Study of SiO2-Si and metal-oxide-semiconductor structures using positrons

    Science.gov (United States)

    Leung, T. C.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K. G.

    1993-01-01

    Studies of SiO2-Si and metal-oxide-semiconductor (MOS) structures using positrons are summarized and a concise picture of the present understanding of positrons in these systems is provided. Positron annihilation line-shape S data are presented as a function of the positron incident energy, gate voltage, and annealing, and are described with a diffusion-annihilation equation for positrons. The data are compared with electrical measurements. Distinct annihilation characteristics were observed at the SiO2-Si interface and have been studied as a function of bias voltage and annealing conditions. The shift of the centroid (peak) of γ-ray energy distributions in the depletion region of the MOS structures was studied as a function of positron energy and gate voltage, and the shifts are explained by the corresponding variations in the strength of the electric field and thickness of the depletion layer. The potential role of the positron annihilation technique as a noncontact, nondestructive, and depth-sensitive characterization tool for the technologically important, deeply buried interface is shown.

  2. Study of SiO2-Si and metal-oxide-semiconductor structures using positrons

    International Nuclear Information System (INIS)

    Leung, T.C.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K.G.

    1993-01-01

    Studies of SiO 2 -Si and metal-oxide-semiconductor (MOS) structures using positrons are summarized and a concise picture of the present understanding of positrons in these systems is provided. Positron annihilation line-shape S data are presented as a function of the positron incident energy, gate voltage, and annealing, and are described with a diffusion-annihilation equation for positrons. The data are compared with electrical measurements. Distinct annihilation characteristics were observed at the SiO 2 -Si interface and have been studied as a function of bias voltage and annealing conditions. The shift of the centroid (peak) of γ-ray energy distributions in the depletion region of the MOS structures was studied as a function of positron energy and gate voltage, and the shifts are explained by the corresponding variations in the strength of the electric field and thickness of the depletion layer. The potential role of the positron annihilation technique as a noncontact, nondestructive, and depth-sensitive characterization tool for the technologically important, deeply buried interface is shown

  3. SiO 2/SiC interface proved by positron annihilation

    Science.gov (United States)

    Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Itoh, H.

    2003-06-01

    We have studied positron annihilation in a Silicon carbide (SiC)-metal/oxide/semiconductor (MOS) structure using a monoenergetic positron beam. The Doppler broadening of annihilation quanta were measured as functions of the incident positron energy and the gate bias. Applying negative gate bias, significant increases in S-parameters were observed. This indicates the migration of implanted positrons towards SiO 2/SiC interface and annihilation at open-volume type defects. The behavior of S-parameters depending on the bias voltage was well correlated with the capacitance-voltage ( C- V) characteristics. We observed higher S-parameters and the interfacial trap density in MOS structures fabricated using the dry oxidation method as compared to those by pyrogenic oxidation method.

  4. SiO2/SiC interface proved by positron annihilation

    International Nuclear Information System (INIS)

    Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Itoh, H.

    2003-01-01

    We have studied positron annihilation in a Silicon carbide (SiC)-metal/oxide/semiconductor (MOS) structure using a monoenergetic positron beam. The Doppler broadening of annihilation quanta were measured as functions of the incident positron energy and the gate bias. Applying negative gate bias, significant increases in S-parameters were observed. This indicates the migration of implanted positrons towards SiO 2 /SiC interface and annihilation at open-volume type defects. The behavior of S-parameters depending on the bias voltage was well correlated with the capacitance-voltage (C-V) characteristics. We observed higher S-parameters and the interfacial trap density in MOS structures fabricated using the dry oxidation method as compared to those by pyrogenic oxidation method

  5. High performance organic field-effect transistors with ultra-thin HfO2 gate insulator deposited directly onto the organic semiconductor

    International Nuclear Information System (INIS)

    Ono, S.; Häusermann, R.; Chiba, D.; Shimamura, K.; Ono, T.; Batlogg, B.

    2014-01-01

    We have produced stable organic field-effect transistors (OFETs) with an ultra-thin HfO 2 gate insulator deposited directly on top of rubrene single crystals by atomic layer deposition (ALD). We find that ALD is a gentle deposition process to grow thin films without damaging rubrene single crystals, as results these devices have a negligibly small threshold voltage and are very stable against gate-bias-stress, and the mobility exceeds 1 cm 2 /V s. Moreover, the devices show very little degradation even when kept in air for more than 2 months. These results demonstrate thin HfO 2 layers deposited by ALD to be well suited as high capacitance gate dielectrics in OFETs operating at small gate voltage. In addition, the dielectric layer acts as an effective passivation layer to protect the organic semiconductor

  6. Flexible high-κ/Metal gate metal/insulator/metal capacitors on silicon (100) fabric

    KAUST Repository

    Rojas, Jhonathan Prieto

    2013-10-01

    Implementation of memory on bendable substrates is an important step toward a complete and fully developed notion of mechanically flexible computational systems. In this paper, we have demonstrated a simple fabrication flow to build metal-insulator-metal capacitors, key components of dynamic random access memory, on a mechanically flexible silicon (100) fabric. We rely on standard microfabrication processes to release a thin sheet of bendable silicon (area: 18 {\\ m cm}2 and thickness: 25 \\\\mu{\\ m m}) in an inexpensive and reliable way. On such platform, we fabricated and characterized the devices showing mechanical robustness (minimum bending radius of 10 mm at an applied strain of 83.33% and nominal strain of 0.125%) and consistent electrical behavior regardless of the applied mechanical stress. Furthermore, and for the first time, we performed a reliability study suggesting no significant difference in performance and showing an improvement in lifetime projections. © 1963-2012 IEEE.

  7. Association behaviour of 241Am(III) on SiO2(amorphous) and SiO2(quartz) colloids

    International Nuclear Information System (INIS)

    Degueldre, C.; Wernli, B.

    1993-01-01

    SiO 2 colloids have been identified as a potential vector for enhancing radionuclide transport in granitic groundwater and in concrete pore water. The sorption behaviour of 241 Am(III) on SiO 2 colloids was studied as a function of americium concentration pH (5-12), colloid concentration, ionic strength, temperature and SiO 2 allotropic species. The Am(III) sorption mechanism on amorphous silica is different from that on quartz. For SiO 2(amorphous) solution, the variation of log K p (ml g -1 ) with pH is linear (pH=5-9) with a slope of +1 indicating a one proton exchange mechanism. The colloid concentration (ppm) affects the sorption and log K p 3.7-0.67 log [SiO 2 ] (pH = 6). K p increases insignificantly when the ionic strength decreases. It shows no significant variation, however, with the Am concentration. On amorphous silica, the Am(III) sorption is driven by proton exchange from the silanol groups. For SiO 2 (quartz), log K p is constant over a large range of quartz concentration in suspension and the variation of log K p with pH is about linear (pH = 5-12), with a slope of 0.28, indicating a more complex exchange mechanism. Reactions taking into account the interaction of positive Am(OH) w (3-w)+ species on to the negatively charged quartz surface are suggested. (author)

  8. High performance a-IGZO thin-film transistors with mf-PVD SiO2 as an etch-stop-layer

    NARCIS (Netherlands)

    Nag, M.; Steudel, S.; Bhoolokam, A.; Chasin, A.; Rockele, M.; Myny, K.; Maas, J.; Fritz, T.; Trube, J.; Groeseneken, G.; Heremans, P.

    2014-01-01

    In this work, we report on high-performance bottom-gate top-contact (BGTC) amorphous-Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistor (TFT) with SiO2 as an etch-stop-layer (ESL) deposited by medium frequency physical vapor deposition (mf-PVD). The TFTs show field-effect mobility (μFE) of

  9. Diffusive charge transport in graphene on SiO 2

    Science.gov (United States)

    Chen, J.-H.; Jang, C.; Ishigami, M.; Xiao, S.; Cullen, W. G.; Williams, E. D.; Fuhrer, M. S.

    2009-07-01

    We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO 2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density ( σ(n)∝n) in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates; increased dielectric screening reduces the scattering from charged impurities, but increases the scattering from short-range scatterers. We evaluate the effects of the corrugations (ripples) of graphene on SiO 2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity that is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO 2 substrate give rise to an activated, carrier density-dependent resistivity. Together the results paint a complete picture of charge carrier transport in graphene on SiO 2 in the diffusive regime.

  10. In-Ga-Zn-oxide thin-film transistors with Sb2TeOx gate insulators fabricated by reactive sputtering using a metallic Sb2Te target

    International Nuclear Information System (INIS)

    Cheong, Woo-Seok

    2011-01-01

    Using reactive sputtering, we made transparent amorphous Sb 2 TeO x thin films from a metallic Sb 2 Te target in an oxidizing atmosphere. In-Ga-Zn-oxide thin-film transistors (IGZO TFTs) with Sb 2 TeO x gate insulators deposited at room temperature showed a large hysteresis with a counter clockwise direction, which was caused by mobile charges in the gate insulators. The problems of the mobile charges was solved by using Sb 2 TeO x films formed at 250 .deg. C. After the IGZO TFT had been annealed at 200 .deg. C for 1 hour in an O 2 ambient, the mobility of the IGZO TFT was 22.41 cm 2 /Vs, and the drain current on-off ratio was ∼10 8 .

  11. Low-voltage organic field-effect transistors based on novel high-κ organometallic lanthanide complex for gate insulating materials

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qi; Li, Yi; Zhang, Yang; Song, You, E-mail: wangxzh@nju.edu.cn, E-mail: yli@nju.edu.cn, E-mail: yousong@nju.edu.cn; Wang, Xizhang, E-mail: wangxzh@nju.edu.cn, E-mail: yli@nju.edu.cn, E-mail: yousong@nju.edu.cn; Hu, Zheng [Key Laboratory of Mesoscopic Chemistry of MOE, Jiangsu Provincial Lab for Nanotechnology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China. High-Tech Research Institute of Nanjing University (Suzhou), Suzhou 215123 (China); Sun, Huabin; Li, Yun, E-mail: wangxzh@nju.edu.cn, E-mail: yli@nju.edu.cn, E-mail: yousong@nju.edu.cn; Shi, Yi [School of Electronic Science and Engineering and Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials, Nanjing University, Nanjing 210093 (China)

    2014-08-15

    A novel high-κ organometallic lanthanide complex, Eu(tta){sub 3}L (tta=2-thenoyltrifluoroacetonate, L = 4,5-pinene bipyridine), is used as gate insulating material to fabricate low-voltage pentacene field-effect transistors (FETs). The optimized gate insulator exhibits the excellent properties such as low leakage current density, low surface roughness, and high dielectric constant. When operated under a low voltage of −5 V, the pentacene FET devices show the attractive electrical performance, e.g. carrier mobility (μ{sub FET}) of 0.17 cm{sup 2} V{sup −1} s{sup −1}, threshold voltage (V{sub th}) of −0.9 V, on/off current ratio of 5 × 10{sup 3}, and subthreshold slope (SS) of 1.0 V dec{sup −1}, which is much better than that of devices obtained on conventional 300 nm SiO{sub 2} substrate (0.13 cm{sup 2} V{sup −1} s{sup −1}, −7.3 V and 3.1 V dec{sup −1} for μ{sub FET}, V{sub th} and SS value when operated at −30 V). These results indicate that this kind of high-κ organometallic lanthanide complex becomes a promising candidate as gate insulator for low-voltage organic FETs.

  12. The ceramic SiO2 and SiO2-TiO2 coatings on biomedical Ti6Al4VELI titanium alloy

    International Nuclear Information System (INIS)

    Surowska, B.; Walczak, M.; Bienias, J.

    2004-01-01

    The paper presents the study of intermediate SiO 2 and SiO 2 -TiO 2 sol-gel coatings and dental porcelain coatings on Ti6Al4VELI titanium alloy. Surface microstructures and wear behaviour by pin-on-disc method of the ceramic coatings were investigated. The analysis revealed: (1) a compact, homogeneous SiO 2 and SiO 2 -TiO 2 coating and (2) that intermediate coatings may provide a durable joint between metal and porcelain, and (3) that dental porcelain on SiO 2 and TiO 2 coatings shows high wear resistance. (author)

  13. Cylindrical gate all around Schottky barrier MOSFET with insulated shallow extensions at source/drain for removal of ambipolarity: a novel approach

    Science.gov (United States)

    Kumar, Manoj; Pratap, Yogesh; Haldar, Subhasis; Gupta, Mridula; Gupta, R. S.

    2017-12-01

    In this paper TCAD-based simulation of a novel insulated shallow extension (ISE) cylindrical gate all around (CGAA) Schottky barrier (SB) MOSFET has been reported, to eliminate the suicidal ambipolar behavior (bias-dependent OFF state leakage current) of conventional SB-CGAA MOSFET by blocking the metal-induced gap states as well as unwanted charge sharing between source/channel and drain/channel regions. This novel structure offers low barrier height at the source and offers high ON-state current. The I ON/I OFF of ISE-CGAA-SB-MOSFET increases by 1177 times and offers steeper subthreshold slope (~60 mV/decade). However a little reduction in peak cut off frequency is observed and to further improve the cut-off frequency dual metal gate architecture has been employed and a comparative assessment of single metal gate, dual metal gate, single metal gate with ISE, and dual metal gate with ISE has been presented. The improved performance of Schottky barrier CGAA MOSFET by the incorporation of ISE makes it an attractive candidate for CMOS digital circuit design. The numerical simulation is performed using the ATLAS-3D device simulator.

  14. Demonstration of AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors with silicon-oxy-nitride as the gate insulator

    International Nuclear Information System (INIS)

    Balachander, K.; Arulkumaran, S.; Egawa, T.; Sano, Y.; Baskar, K.

    2005-01-01

    AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs) were fabricated with plasma enhanced chemical vapor deposited silicon oxy-nitride (SiON) as an insulating layer. The compositions of SiON thin films were confirmed using X-ray photoelectron spectroscopy. The fabricated MOSHEMTs exhibited a very high saturation current density of 1.1 A/mm coupled with high positive operational gate voltage up to +7 V. The MOSHEMTs also exhibited four orders of low gate leakage current and high forward-on voltage when compared with the conventional HEMTs. The drain current collapse using gate pulse measurements showed only a negligible difference in the saturation current density revealing the drastic improvement in passivation of the surface states due to the high quality of dielectric thin films deposited. Thus, based on the improved direct-current operation, SiON can be considered to be a potential gate oxide comparable with other dielectric insulators

  15. Thin-barrier enhancement-mode AlGaN/GaN MIS-HEMT using ALD Al2O3 as gate insulator

    International Nuclear Information System (INIS)

    Wang Zheli; Zhou Jianjun; Kong Yuechan; Kong Cen; Dong Xun; Yang Yang; Chen Tangsheng

    2015-01-01

    A high-performance enhancement-mode (E-mode) gallium nitride (GaN)-based metal–insulator–semiconductor high electron mobility transistor (MIS-HEMT) that employs a 5-nm-thick aluminum gallium nitride (Al 0.3 Ga 0.7 N) as a barrier layer and relies on silicon nitride (SiN) passivation to control the 2DEG density is presented. Unlike the SiN passivation, aluminum oxide (Al 2 O 3 ) by atomic layer deposition (ALD) on AlGaN surface would not increase the 2DEG density in the heterointerface. ALD Al 2 O 3 was used as gate insulator after the depletion by etching of the SiN in the gate region. The E-mode MIS-HEMT with gate length (L G ) of 1 μm showed a maximum drain current density (I DS ) of 657 mA/mm, a maximum extrinsic transconductance (g m ) of 187 mS/mm and a threshold voltage (V th ) of 1 V. Comparing with the corresponding E-mode HEMT, the device performances had been greatly improved due to the insertion of Al 2 O 3 gate insulator. This provided an excellent way to realize E-mode AlGaN/GaN MIS-HEMTs with both high V th and I DS . (paper)

  16. Graphene-insulator-semiconductor capacitors as superior test structures for photoelectric determination of semiconductor devices band diagrams

    Directory of Open Access Journals (Sweden)

    K. Piskorski

    2018-05-01

    Full Text Available We report on the advantages of using Graphene-Insulator-Semiconductor (GIS instead of Metal-Insulator-Semiconductor (MIS structures in reliable and precise photoelectric determination of the band alignment at the semiconductor-insulator interface and of the insulator band gap determination. Due to the high transparency to light of the graphene gate in GIS structures large photocurrents due to emission of both electrons and holes from the substrate and negligible photocurrents due to emission of carriers from the gate can be obtained, which allows reliable determination of barrier heights for both electrons, Ee and holes, Eh from the semiconductor substrate. Knowing the values of both Ee and Eh allows direct determination of the insulator band gap EG(I. Photoelectric measurements were made of a series of Graphene-SiO2-Si structures and an example is shown of the results obtained in sequential measurements of the same structure giving the following barrier height values: Ee = 4.34 ± 0.01 eV and Eh = 4.70 ± 0.03 eV. Based on this result and results obtained for other structures in the series we conservatively estimate the maximum uncertainty of both barrier heights estimations at ± 0.05 eV. This sets the SiO2 band gap estimation at EG(I = 7.92 ± 0.1 eV. It is shown that widely different SiO2 band gap values were found by research groups using various determination methods. We hypothesize that these differences are due to different sensitivities of measurement methods used to the existence of the SiO2 valence band tail.

  17. Graphene-insulator-semiconductor capacitors as superior test structures for photoelectric determination of semiconductor devices band diagrams

    Science.gov (United States)

    Piskorski, K.; Passi, V.; Ruhkopf, J.; Lemme, M. C.; Przewlocki, H. M.

    2018-05-01

    We report on the advantages of using Graphene-Insulator-Semiconductor (GIS) instead of Metal-Insulator-Semiconductor (MIS) structures in reliable and precise photoelectric determination of the band alignment at the semiconductor-insulator interface and of the insulator band gap determination. Due to the high transparency to light of the graphene gate in GIS structures large photocurrents due to emission of both electrons and holes from the substrate and negligible photocurrents due to emission of carriers from the gate can be obtained, which allows reliable determination of barrier heights for both electrons, Ee and holes, Eh from the semiconductor substrate. Knowing the values of both Ee and Eh allows direct determination of the insulator band gap EG(I). Photoelectric measurements were made of a series of Graphene-SiO2-Si structures and an example is shown of the results obtained in sequential measurements of the same structure giving the following barrier height values: Ee = 4.34 ± 0.01 eV and Eh = 4.70 ± 0.03 eV. Based on this result and results obtained for other structures in the series we conservatively estimate the maximum uncertainty of both barrier heights estimations at ± 0.05 eV. This sets the SiO2 band gap estimation at EG(I) = 7.92 ± 0.1 eV. It is shown that widely different SiO2 band gap values were found by research groups using various determination methods. We hypothesize that these differences are due to different sensitivities of measurement methods used to the existence of the SiO2 valence band tail.

  18. Stability Study of Flexible 6,13-Bis(triisopropylsilylethynylpentacene Thin-Film Transistors with a Cross-Linked Poly(4-vinylphenol/Yttrium Oxide Nanocomposite Gate Insulator

    Directory of Open Access Journals (Sweden)

    Jin-Hyuk Kwon

    2016-03-01

    Full Text Available We investigated the electrical and mechanical stability of flexible 6,13-bis(triisopropylsilylehtynylpentacene (TIPS-pentacene thin-film transistors (TFTs that were fabricated on polyimide (PI substrates using cross-linked poly(4-vinylphenol (c-PVP and c-PVP/yttrium oxide (Y2O3 nanocomposite films as gate insulators. Compared with the electrical characteristics of TIPS-pentacene TFTs with c-PVP insulators, the TFTs with c-PVP/Y2O3 nanocomposite insulators exhibited enhancements in the drain current and the threshold voltage due to an increase in the dielectric capacitance. In electrical stability experiments, a gradual decrease in the drain current and a negative shift in the threshold voltage occurred during prolonged bias stress tests, but these characteristic variations were comparable for both types of TFT. On the other hand, the results of mechanical bending tests showed that the characteristic degradation of the TIPS-pentacene TFTs with c-PVP/Y2O3 nanocomposite insulators was more critical than that of the TFTs with c-PVP insulators. In this study, the detrimental effect of the nanocomposite insulator on the mechanical stability of flexible TIPS-pentacene TFTs was found to be caused by physical adhesion of TIPS-pentacene molecules onto the rough surfaces of the c-PVP/Y2O3 nanocomposite insulator. These results indicate that the dielectric and morphological properties of polymeric nanocomposite insulators are significant when considering practical applications of flexible electronics operated at low voltages.

  19. Observing the semiconducting band-gap alignment of MoS2 layers of different atomic thicknesses using a MoS2/SiO2/Si heterojunction tunnel diode

    NARCIS (Netherlands)

    Nishiguchi, K.; Castellanos-Gomez, A.; Yamaguchi, H.; Fujiwara, A.; Van der Zant, H.S.J.; Steele, G.A.

    2015-01-01

    We demonstrate a tunnel diode composed of a vertical MoS2/SiO2/Si heterostructure. A MoS2 flake consisting four areas of different thicknesses functions as a gate terminal of a silicon field-effect transistor. A thin gate oxide allows tunneling current to flow between the n-type MoS2 layers and

  20. Synthesis of metallic nanoparticles in SiO2 matrices

    International Nuclear Information System (INIS)

    Gutierrez W, C.; Mondragon G, G.; Perez H, R.; Mendoza A, D.

    2004-01-01

    Metallic nanoparticles was synthesized in SiO 2 matrices by means of a process of two stages. The first one proceeded via sol-gel, incorporating the metallic precursors to the reaction system before the solidification of the matrix. Later on, the samples underwent a thermal treatment in atmosphere of H 2 , carrying out the reduction of the metals that finally formed to the nanoparticles. Then it was detected the presence of smaller nanoparticles than 20 nm, dispersed and with the property of being liberated easily of the matrix, conserving a free surface, chemically reactive and with response to external electromagnetic radiation. The system SiO 2 -Pd showed an important thermoluminescent response. (Author)

  1. Positive magnetoresistance in Co40Fe40B20/SiO2/Si heterostructure

    KAUST Repository

    Zhang, Y.

    2016-07-20

    Current-perpendicular-to-plane electronic transport properties and magnetoresistance of amorphous Co40Fe40B20/SiO2/Si heterostructures are investigated systematically. A backward diode-like rectifying behavior was observed due to the formation of a Schottky barrier between Co40Fe40B20 and Si. The junction resistance shows a metal-insulator transition with decreasing temperature in both the forward and reverse ranges. A large positive magnetoresistance (MR) of ∼2300% appears at 200 K. The positive MR can be attributed to the magnetic-field-controlled impact ionization process of carriers. MR shows a temperature-peak-type character under a constant bias current, which is related to the spin-dependent barrier in the Si near the interface. © CopyrightEPLA, 2016.

  2. Positive magnetoresistance in Co40Fe40B20/SiO2/Si heterostructure

    KAUST Repository

    Zhang, Y.; Mi, W. B.; Zhang, Xixiang

    2016-01-01

    Current-perpendicular-to-plane electronic transport properties and magnetoresistance of amorphous Co40Fe40B20/SiO2/Si heterostructures are investigated systematically. A backward diode-like rectifying behavior was observed due to the formation of a Schottky barrier between Co40Fe40B20 and Si. The junction resistance shows a metal-insulator transition with decreasing temperature in both the forward and reverse ranges. A large positive magnetoresistance (MR) of ∼2300% appears at 200 K. The positive MR can be attributed to the magnetic-field-controlled impact ionization process of carriers. MR shows a temperature-peak-type character under a constant bias current, which is related to the spin-dependent barrier in the Si near the interface. © CopyrightEPLA, 2016.

  3. Adsorption of uranyl in SiO2 porous glass

    International Nuclear Information System (INIS)

    Benedetto, F. E.; Prado, M. O.

    2013-01-01

    Vitreous SiO 2 porous matrices can be used in many applications involving the uptake of chemical species on its solid surface. In this work, vitreous silica sponges were prepared from a sodium borosilicate glass manufactured in our laboratory. The product obtained was then separated into phases with subsequent leaching of the soluble phase rich in B and Na. The resulting porous matrices have a specific surface of 35 m2/gr. Adsorption of uranyl ions onto the SiO 2 porous surface was studied to evaluate the use of this material as a filter for treatment of uranium containing water. The effects of contact time, adsorbent mass and equilibrium concentration of solution were studied. The porous adsorbent exhibits a pseudo-second-order kinetic behavior. The sponges with adsorbed uranium were thermally sealed as a way of U immobilization. Retention of uranium was confirmed during the matrix sealing by TGA. Uranium concentration before and after adsorption tests were made by means of ICP-OES. For uranium concentration of 800 ppm, 72 hours contact time and pH of 3.5, the amount of uranium adsorbed was 21.06 ± 0.02 mg U per gram of vitreous porous SiO 2 . (author)

  4. Poly(4-vinylphenol-co-methyl methacrylate) / titanium dioxide nanocomposite gate insulators for 6,13-bis(triisopropylsilylethynyl)-pentacene thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xue; Park, Jiho; Baang, Sungkeun; Park, Jaehoon [Hallym University, Chuncheon (Korea, Republic of); Piao, Shanghao; Kim, Sohee; Choi, Hyoungjin [Inha University, Incheon (Korea, Republic of)

    2014-12-15

    Poly(4-vinylphenol-co-methyl methacrylate) / titanium dioxide (TiO{sub 2}) nanocomposite insulators were fabricated for application in 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn) thin-film transistors (TFTs). The capacitance of the fabricated capacitors with this nanocomposite insulator increased with increasing content of the high-dielectric-constant TiO{sub 2} nanoparticles. Nonetheless, particle aggregates, which were invariably produced in the insulator at higher TiO{sub 2} contents, augmented gate-leakage currents during device operation while the rough surface of the insulator obstructed charge transport in the conducting channel of the TIPS-Pn TFTs. These results suggest a significant effect of the morphological characteristics of nanocomposite insulators on TFT performance, as well as on their dielectric properties. Herein, the optimal particle composition was determined to be approximately 1.5 wt%, which contributed to characteristic improvements in the drain current, field-effect mobility, and threshold voltage of TIPS-Pn TFTs.

  5. Ultra-thin films of polysilsesquioxanes possessing 3-methacryloxypropyl groups as gate insulator for organic field-effect transistors

    International Nuclear Information System (INIS)

    Nakahara, Yoshio; Kawa, Haruna; Yoshiki, Jun; Kumei, Maki; Yamamoto, Hiroyuki; Oi, Fumio; Yamakado, Hideo; Fukuda, Hisashi; Kimura, Keiichi

    2012-01-01

    Polysilsesquioxanes (PSQs) possessing 3-methacryloxypropyl groups as an organic moiety of the side chain were synthesized by sol–gel condensation copolymerization of the corresponding trialkoxysilanes. The ultra-thin PSQ film with a radical initiator and a cross-linking agent was prepared by a spin-coating method, and the film was cured integrally at low temperatures of less than 120 °C through two different kinds of polymeric reactions, which were radical polymerization of vinyl groups and sol–gel condensation polymerization of terminated silanol and alkoxy groups. The obtained PSQ film showed the almost perfect solubilization resistance to acetone, which is a good solvent of PSQ before polymerization. It became clear by atomic force microscopy observation that the surface of the PSQ film was very smooth at a nano-meter level. Furthermore, pentacene-based organic field-effect transistor (OFET) with the PSQ film as a gate insulator showed typical p-channel enhancement mode operation characteristics and therefore the ultra-thin PSQ film has the potential to be applicable for solution-processed OFET systems. - Highlights: ► Polysilsesquioxanes (PSQs) possessing 3-methacryloxypropyl groups were synthesized. ► The ultra-thin PSQ film could be cured at low temperatures of less than 120 °C. ► The PSQ film showed the almost perfect solubilization resistance to organic solvent. ► The surface of the PSQ film was very smooth at a nano-meter level. ► Pentacene-based organic field-effect transistor with the PSQ film was fabricated.

  6. Ultra-thin films of polysilsesquioxanes possessing 3-methacryloxypropyl groups as gate insulator for organic field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Nakahara, Yoshio; Kawa, Haruna [Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University, 930 Sakae-dani, Wakayama 640-8510 (Japan); Yoshiki, Jun [Division of Information and Electronic Engineering, Faculty of Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran 050-8585 (Japan); Kumei, Maki; Yamamoto, Hiroyuki; Oi, Fumio [Konishi Chemical IND. Co., LTD., 3-4-77 Kozaika, Wakayama 641-0007 (Japan); Yamakado, Hideo [Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University, 930 Sakae-dani, Wakayama 640-8510 (Japan); Fukuda, Hisashi [Division of Engineering for Composite Functions, Faculty of Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran 050-8585 (Japan); Kimura, Keiichi, E-mail: kkimura@center.wakayama-u.ac.jp [Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University, 930 Sakae-dani, Wakayama 640-8510 (Japan)

    2012-10-01

    Polysilsesquioxanes (PSQs) possessing 3-methacryloxypropyl groups as an organic moiety of the side chain were synthesized by sol-gel condensation copolymerization of the corresponding trialkoxysilanes. The ultra-thin PSQ film with a radical initiator and a cross-linking agent was prepared by a spin-coating method, and the film was cured integrally at low temperatures of less than 120 Degree-Sign C through two different kinds of polymeric reactions, which were radical polymerization of vinyl groups and sol-gel condensation polymerization of terminated silanol and alkoxy groups. The obtained PSQ film showed the almost perfect solubilization resistance to acetone, which is a good solvent of PSQ before polymerization. It became clear by atomic force microscopy observation that the surface of the PSQ film was very smooth at a nano-meter level. Furthermore, pentacene-based organic field-effect transistor (OFET) with the PSQ film as a gate insulator showed typical p-channel enhancement mode operation characteristics and therefore the ultra-thin PSQ film has the potential to be applicable for solution-processed OFET systems. - Highlights: Black-Right-Pointing-Pointer Polysilsesquioxanes (PSQs) possessing 3-methacryloxypropyl groups were synthesized. Black-Right-Pointing-Pointer The ultra-thin PSQ film could be cured at low temperatures of less than 120 Degree-Sign C. Black-Right-Pointing-Pointer The PSQ film showed the almost perfect solubilization resistance to organic solvent. Black-Right-Pointing-Pointer The surface of the PSQ film was very smooth at a nano-meter level. Black-Right-Pointing-Pointer Pentacene-based organic field-effect transistor with the PSQ film was fabricated.

  7. Nonvolatile memory thin-film transistors using biodegradable chicken albumen gate insulator and oxide semiconductor channel on eco-friendly paper substrate.

    Science.gov (United States)

    Kim, So-Jung; Jeon, Da-Bin; Park, Jung-Ho; Ryu, Min-Ki; Yang, Jong-Heon; Hwang, Chi-Sun; Kim, Gi-Heon; Yoon, Sung-Min

    2015-03-04

    Nonvolatile memory thin-film transistors (TFTs) fabricated on paper substrates were proposed as one of the eco-friendly electronic devices. The gate stack was composed of chicken albumen gate insulator and In-Ga-Zn-O semiconducting channel layers. All the fabrication processes were performed below 120 °C. To improve the process compatibility of the synthethic paper substrate, an Al2O3 thin film was introduced as adhesion and barrier layers by atomic layer deposition. The dielectric properties of biomaterial albumen gate insulator were also enhanced by the preparation of Al2O3 capping layer. The nonvolatile bistabilities were realized by the switching phenomena of residual polarization within the albumen thin film. The fabricated device exhibited a counterclockwise hysteresis with a memory window of 11.8 V, high on/off ratio of approximately 1.1 × 10(6), and high saturation mobility (μsat) of 11.5 cm(2)/(V s). Furthermore, these device characteristics were not markedly degraded even after the delamination and under the bending situration. When the curvature radius was set as 5.3 cm, the ION/IOFF ratio and μsat were obtained to be 5.9 × 10(6) and 7.9 cm(2)/(V s), respectively.

  8. Insulator-semiconductor interface fixed charges in AlGaN/GaN metal-insulator-semiconductor devices with Al2O3 or AlTiO gate dielectrics

    Science.gov (United States)

    Le, Son Phuong; Nguyen, Duong Dai; Suzuki, Toshi-kazu

    2018-01-01

    We have investigated insulator-semiconductor interface fixed charges in AlGaN/GaN metal-insulator-semiconductor (MIS) devices with Al2O3 or AlTiO (an alloy of Al2O3 and TiO2) gate dielectrics obtained by atomic layer deposition on AlGaN. Analyzing insulator-thickness dependences of threshold voltages for the MIS devices, we evaluated positive interface fixed charges, whose density at the AlTiO/AlGaN interface is significantly lower than that at the Al2O3/AlGaN interface. This and a higher dielectric constant of AlTiO lead to rather shallower threshold voltages for the AlTiO gate dielectric than for Al2O3. The lower interface fixed charge density also leads to the fact that the two-dimensional electron concentration is a decreasing function of the insulator thickness for AlTiO, whereas being an increasing function for Al2O3. Moreover, we discuss the relationship between the interface fixed charges and interface states. From the conductance method, it is shown that the interface state densities are very similar at the Al2O3/AlGaN and AlTiO/AlGaN interfaces. Therefore, we consider that the lower AlTiO/AlGaN interface fixed charge density is not owing to electrons trapped at deep interface states compensating the positive fixed charges and can be attributed to a lower density of oxygen-related interface donors.

  9. Electrical analysis of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors on flexible bulk mono-crystalline silicon

    KAUST Repository

    Ghoneim, Mohamed T.

    2015-06-01

    We report on the electrical study of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors (MOSCAPs) on a flexible ultra-thin (25 μm) silicon fabric which is peeled off using a CMOS compatible process from a standard bulk mono-crystalline silicon substrate. A lifetime projection is extracted using statistical analysis of the ramping voltage (Vramp) breakdown and time dependent dielectric breakdown data. The obtained flexible MOSCAPs operational voltages satisfying the 10 years lifetime benchmark are compared to those of the control MOSCAPs, which are not peeled off from the silicon wafer. © 2014 IEEE.

  10. Study of an Insulated Gate Bipolar Transistor (IGBT) and its connection in series. Application at a chopper 1500V-5A-10kHz

    International Nuclear Information System (INIS)

    Gros, P.

    1993-01-01

    In the frame of the tokamak ITER (International Thermonuclear Experimental Reactor) we have studied, for neutral particle injection, a converter with at least two static interrupters by Mosfet transistor, bipolar transistor or Insulated Gate Bipolar Transistor (IGBT). After a comparison between these three types of transistors, by the simulating software MICROCAP, a serial of tests has shown the advantages of the IGBT. A command, associated with two IGBT of equivalent characteristics, has given a simple and efficacious solution. The performances are: (1) between two blockages: 50 ns without overvoltage, (2) between two cut-off: 60 ns. 40 figs; 30 refs; 10 annexes

  11. Electro-Thermo-Mechanical Analysis of High-Power Press-Pack Insulated Gate Bipolar Transistors under Various Mechanical Clamping Conditions

    DEFF Research Database (Denmark)

    Hasmasan, Adrian Augustin; Busca, Cristian; Teodorescu, Remus

    2014-01-01

    With the continuously increasing demand for energy and the limited supply of fossil fuels, renewable power sources are becoming ever more important. Knowing that future energy demand will grow, manufacturers are increasing the size of new wind turbines (WTs) in order to reduce the cost of energy...... production. The reliability of the components has a large impact on the overall cost of a WT, and press-pack (PP) insulated gate bipolar transistors (IGBTs) could be a good solution for future multi-megawatt WTs because of advantages like high power density and reliability. When used in power converters, PP...

  12. Investigation of Rapid Low-Power Microwave-Induction Heating Scheme on the Cross-Linking Process of the Poly(4-vinylphenol) for the Gate Insulator of Pentacene-Based Thin-Film Transistors

    Science.gov (United States)

    Fan, Ching-Lin; Shang, Ming-Chi; Wang, Shea-Jue; Hsia, Mao-Yuan; Lee, Win-Der; Huang, Bohr-Ran

    2017-01-01

    In this study, a proposed Microwave-Induction Heating (MIH) scheme has been systematically studied to acquire suitable MIH parameters including chamber pressure, microwave power and heating time. The proposed MIH means that the thin indium tin oxide (ITO) metal below the Poly(4-vinylphenol) (PVP) film is heated rapidly by microwave irradiation and the heated ITO metal gate can heat the PVP gate insulator, resulting in PVP cross-linking. It is found that the attenuation of the microwave energy decreases with the decreasing chamber pressure. The optimal conditions are a power of 50 W, a heating time of 5 min, and a chamber pressure of 20 mTorr. When suitable MIH parameters were used, the effect of PVP cross-linking and the device performance were similar to those obtained using traditional oven heating, even though the cross-linking time was significantly decreased from 1 h to 5 min. Besides the gate leakage current, the interface trap state density (Nit) was also calculated to describe the interface status between the gate insulator and the active layer. The lowest interface trap state density can be found in the device with the PVP gate insulator cross-linked by using the optimal MIH condition. Therefore, it is believed that the MIH scheme is a good candidate to cross-link the PVP gate insulator for organic thin-film transistor applications as a result of its features of rapid heating (5 min) and low-power microwave-irradiation (50 W). PMID:28773101

  13. Investigation of Rapid Low-Power Microwave-Induction Heating Scheme on the Cross-Linking Process of the Poly(4-vinylphenol for the Gate Insulator of Pentacene-Based Thin-Film Transistors

    Directory of Open Access Journals (Sweden)

    Ching-Lin Fan

    2017-07-01

    Full Text Available In this study, a proposed Microwave-Induction Heating (MIH scheme has been systematically studied to acquire suitable MIH parameters including chamber pressure, microwave power and heating time. The proposed MIH means that the thin indium tin oxide (ITO metal below the Poly(4-vinylphenol (PVP film is heated rapidly by microwave irradiation and the heated ITO metal gate can heat the PVP gate insulator, resulting in PVP cross-linking. It is found that the attenuation of the microwave energy decreases with the decreasing chamber pressure. The optimal conditions are a power of 50 W, a heating time of 5 min, and a chamber pressure of 20 mTorr. When suitable MIH parameters were used, the effect of PVP cross-linking and the device performance were similar to those obtained using traditional oven heating, even though the cross-linking time was significantly decreased from 1 h to 5 min. Besides the gate leakage current, the interface trap state density (Nit was also calculated to describe the interface status between the gate insulator and the active layer. The lowest interface trap state density can be found in the device with the PVP gate insulator cross-linked by using the optimal MIH condition. Therefore, it is believed that the MIH scheme is a good candidate to cross-link the PVP gate insulator for organic thin-film transistor applications as a result of its features of rapid heating (5 min and low-power microwave-irradiation (50 W.

  14. Formation of SiO2/polytetrafluoroethylene hybrid superhydrophobic coating

    International Nuclear Information System (INIS)

    Zheng Yansheng; He Yi; Qing Yongquan; Zhuo Zhihao; Mo Qian

    2012-01-01

    Highlights: ► The coating showed the water contact angle of 165° and the water sliding angle of 6°. ► The hierarchical structure with the low surface energy leads to surface superhydrophobicity. ► We demonstrated a simple yet efficient approach to preparing superhydrophobic surface. - Abstract: Superhydrophobic coating has been fabricated on the glass substrates with modified SiO 2 sol and polytetrafluoroethylene emulsion through a sol–gel process. SiO 2 sol was modified with γ-glycidoxypropyl trimethoxysilane. The coatings were characterized by water contact angle measurement, Scanning electron microscope, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy and thermal synthetic analysis. The experimental results show that coatings exhibited superhydrophobic and heat-resistant property with a water average contact angle of 156° and sliding angle of 6°, coating has a rough surface with both micro- and nanoscale structures, γ-glycidoxypropyl trimethoxysilane enhanced the hydrophobicity of the coatings. Low surface energy of polymer and special structure of the coatings were responsible for the hydrophobic of the surfaces.

  15. Interactions of atomic hydrogen with amorphous SiO2

    Science.gov (United States)

    Yue, Yunliang; Wang, Jianwei; Zhang, Yuqi; Song, Yu; Zuo, Xu

    2018-03-01

    Dozens of models are investigated by the first-principles calculations to simulate the interactions of an atomic hydrogen with a defect-free random network of amorphous SiO2 (a-SiO2) and oxygen vacancies. A wide variety of stable configurations are discovered due to the disorder of a-SiO2, and their structures, charges, magnetic moments, spin densities, and density of states are calculated. The atomic hydrogen interacts with the defect-free a-SiO2 in positively or negatively charged state, and produces the structures absent in crystalline SiO2. It passivates the neutral oxygen vacancies and generates two neutral hydrogenated E‧ centers with different Si dangling bond projections. Electron spin resonance parameters, including Fermi contacts, and g-tensors, are calculated for these centers. The atomic hydrogen interacts with the positive oxygen vacancies in dimer configuration, and generate four different positive hydrogenated defects, two of which are puckered like the Eγ‧ centers. This research helps to understand the interactions between an atomic hydrogen, and defect-free a-SiO2 and oxygen vacancies, which may generate the hydrogen-complexed defects that play a key role in the degeneration of silicon/silica-based microelectronic devices.

  16. Stability of trapped electrons in SiO2

    International Nuclear Information System (INIS)

    Fleetwood, D.M.; Winokur, P.S.; Flament, O.; Leray, J.L.

    1998-01-01

    Electron trapping near the Si/SiO 2 interface plays a crucial role in mitigating the response of MOS devices to ionizing radiation or high-field stress. These electrons offset positive charge due to trapped holes, and can be present at densities exceeding 10 12 cm -2 in the presence of a similar density of trapped positive charge. The nature of the defects that serve as hosts for trapped electrons in the near-interfacial SiO 2 is presently unknown, although there is compelling evidence that these defects are often intimately associated with trapped holes. This association is depicted most directly in the model of Lelis et al., which suggests that trapped electrons and holes occupy opposite sides of a compensated E center in SiO 2 . Charge exchange between electron traps and the Si can occur over a wide range of time scales, depending on the trap depth and location relative to the Si/SiO 2 interface. Here the authors report a detailed study of the stability of electron traps associated with trapped holes near the Si/SiO 2 interface

  17. Effect of Commercial SiO2 and SiO2 from rice husk ash loading on biodegradation of Poly (lactic acid) and crosslinked Poly (lactic acid)

    Science.gov (United States)

    Prapruddivongs, C.; Apichartsitporn, M.; Wongpreedee, T.

    2017-09-01

    In this work, biodegradation behavior of poly (lactic acid) (PLA) and crosslinked PLA filled with two types of SiO2, precipitated SiO2 (commercial SiO2) and SiO2 from rice husk ash, were studied. Rice husks were first treated with 2 molar hydrochloric acid (HCl) to produce high purity SiO2, before burnt in a furnace at 800°C for 6 hours. All components were melted bending by an internal mixer then hot pressed using compression molder to form tested specimens. FTIR spectra of SiO2 and PLA samples were investigated. The results showed the lack of silanol group (Si-OH) of rice husk ash after steric acid surface modification, while the addition of particles can affect the crosslinking of the PLA. For biodegradation test by evaluating total amount of carbon dioxide (CO2) evolved during 60 days incubation at a controlled temperature of 58±2°C, the results showed that the biodegradation of crosslinked PLA occurred slower than the neat PLA. However, SiO2 incorporation enhanced the degree of biodegradation In particular, introducing commercial SiO2 in PLA and crosslinked PLA tended to clearly increase the degree of biodegradation as a consequence of the more accelerated hydrolysis degradation.

  18. Do SiO 2 and carbon-doped SiO 2 nanoparticles melt? Insights from QM/MD simulations and ramifications regarding carbon nanotube growth

    Science.gov (United States)

    Page, Alister J.; Chandrakumar, K. R. S.; Irle, Stephan; Morokuma, Keiji

    2011-05-01

    Quantum chemical molecular dynamics (QM/MD) simulations of pristine and carbon-doped SiO 2 nanoparticles have been performed between 1000 and 3000 K. At temperatures above 1600 K, pristine nanoparticle SiO 2 decomposes rapidly, primarily forming SiO. Similarly, carbon-doped nanoparticle SiO 2 decomposes at temperatures above 2000 K, primarily forming SiO and CO. Analysis of the physical states of these pristine and carbon-doped SiO 2 nanoparticles indicate that they remain in the solid phase throughout decomposition. This process is therefore one of sublimation, as the liquid phase is never entered. Ramifications of these observations with respect to presently debated mechanisms of carbon nanotube growth on SiO 2 nanoparticles will be discussed.

  19. Interfacial, Electrical, and Band Alignment Characteristics of HfO2/Ge Stacks with In Situ-Formed SiO2 Interlayer by Plasma-Enhanced Atomic Layer Deposition

    Science.gov (United States)

    Cao, Yan-Qiang; Wu, Bing; Wu, Di; Li, Ai-Dong

    2017-05-01

    In situ-formed SiO2 was introduced into HfO2 gate dielectrics on Ge substrate as interlayer by plasma-enhanced atomic layer deposition (PEALD). The interfacial, electrical, and band alignment characteristics of the HfO2/SiO2 high-k gate dielectric stacks on Ge have been well investigated. It has been demonstrated that Si-O-Ge interlayer is formed on Ge surface during the in situ PEALD SiO2 deposition process. This interlayer shows fantastic thermal stability during annealing without obvious Hf-silicates formation. In addition, it can also suppress the GeO2 degradation. The electrical measurements show that capacitance equivalent thickness of 1.53 nm and a leakage current density of 2.1 × 10-3 A/cm2 at gate bias of Vfb + 1 V was obtained for the annealed sample. The conduction (valence) band offsets at the HfO2/SiO2/Ge interface with and without PDA are found to be 2.24 (2.69) and 2.48 (2.45) eV, respectively. These results indicate that in situ PEALD SiO2 may be a promising interfacial control layer for the realization of high-quality Ge-based transistor devices. Moreover, it can be demonstrated that PEALD is a much more powerful technology for ultrathin interfacial control layer deposition than MOCVD.

  20. Silicon (100)/SiO2 by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, David S.; Kanyal, Supriya S.; Madaan, Nitesh; Vail, Michael A.; Dadson, Andrew; Engelhard, Mark H.; Linford, Matthew R.

    2013-09-25

    Silicon (100) wafers are ubiquitous in microfabrication and, accordingly, their surface characteristics are important. Herein, we report the analysis of Si (100) via X-ray photoelectron spectroscopy (XPS) using monochromatic Al K radiation. Survey scans show that the material is primarily silicon and oxygen, and the Si 2p region shows two peaks that correspond to elemental silicon and silicon dioxide. Using these peaks the thickness of the native oxide (SiO2) was estimated using the equation of Strohmeier.1 The oxygen peak is symmetric. The material shows small amounts of carbon, fluorine, and nitrogen contamination. These silicon wafers are used as the base material for subsequent growth of templated carbon nanotubes.

  1. Nucleation of C60 on ultrathin SiO2

    Science.gov (United States)

    Conrad, Brad; Groce, Michelle; Cullen, William; Pimpinelli, Alberto; Williams, Ellen; Einstein, Ted

    2012-02-01

    We utilize scanning tunneling microscopy to characterize the nucleation, growth, and morphology of C60 on ultrathin SiO2 grown at room temperature. C60 thin films are deposited in situ by physical vapor deposition with thicknesses varying from <0.05 to ˜1 ML. Island size and capture zone distributions are examined for a varied flux rate and substrate deposition temperature. The C60 critical nucleus size is observed to change between monomers and dimers non-monotonically from 300 K to 500 K. Results will be discussed in terms of recent capture zone studies and analysis methods. Relation to device fabrication will be discussed. doi:10.1016/j.susc.2011.08.020

  2. Surface spins disorder in uncoated and SiO2 coated maghemite nanoparticles

    International Nuclear Information System (INIS)

    Zeb, F.; Nadeem, K.; Shah, S. Kamran Ali; Kamran, M.; Gul, I. Hussain; Ali, L.

    2017-01-01

    We studied the surface spins disorder in uncoated and silica (SiO 2 ) coated maghemite (γ-Fe 2 O 3 ) nanoparticles using temperature and time dependent magnetization. The average crystallite size for SiO 2 coated and uncoated nanoparticles was about 12 and 29 nm, respectively. Scanning electron microscopy (SEM) showed that the nanoparticles are spherical in shape and well separated. Temperature scans of zero field cooled (ZFC)/field cooled (FC) magnetization measurements showed lower average blocking temperature (T B ) for SiO 2 coated maghemite nanoparticles as compared to uncoated nanoparticles. The saturation magnetization (M s ) of SiO 2 coated maghemite nanoparticles was also lower than the uncoated nanoparticles and is attributed to smaller average crystallite size of SiO 2 coated nanoparticles. For saturation magnetization vs. temperature data, Bloch's law (M(T)= M(0).(1− BT b )) was fitted well for both uncoated and SiO 2 coated nanoparticles and yields: B =3×10 −7 K -b , b=2.22 and B=0.0127 K -b , b=0.57 for uncoated and SiO 2 coated nanoparticles, respectively. Higher value of B for SiO 2 coated nanoparticles depicts decrease in exchange coupling due to enhanced surface spins disorder (broken surface bonds) as compared to uncoated nanoparticles. The Bloch's exponent b was decreased for SiO 2 coated nanoparticles which is due to their smaller average crystallite size or finite size effects. Furthermore, a sharp increase of coercivity at low temperatures (<25 K) was observed for SiO 2 coated nanoparticles which is also due to contribution of increased surface anisotropy or frozen surface spins in these smaller nanoparticles. The FC magnetic relaxation data was fitted to stretched exponential law which revealed slower magnetic relaxation for SiO 2 coated nanoparticles. All these measurements revealed smaller average crystallite size and enhanced surface spins disorder in SiO 2 coated nanoparticles than in uncoated γ-Fe 2 O 3 nanoparticles. - Highlights: • Surface effects in SiO 2 coated and uncoated γ-Fe 2 O 3 nanoparticles were studied. • Average crystallite size was decreased for SiO 2 coated nanoparticles. • Average blocking temperature of SiO 2 coated nanoparticles is decreased. • SiO 2 coated nanoparticles showed enhanced surface spins disordered • SiO 2 coated nanoparticles showed slow magnetic relaxation.

  3. Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm3+ and SiO2:Ho3+, Tm3+ systems

    CSIR Research Space (South Africa)

    Dhlamini, MS

    2012-05-01

    Full Text Available .physb.2011.09.091 Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm 3+ and SiO2:Ho 3+, Tm3+ systems M.S. Dhlamini, G.H. Mhlongo, H.C. Swart, O.M. Ntwaeaborwa, K.T. Hillie ABSTRACT: Cathodoluminescence (CL) properties of Si...O2 powders activated with thulium (Tm3+) and holmium (Ho3+) ions prepared by a sol–gel process were investigated. Different molar concentrations of Tm3+ co-doped with Ho3+ were studied. The 460 nm peak was monitored and the influence of the beam...

  4. Processing of SiO2 protective layer using HMDS precursor by combustion CVD.

    Science.gov (United States)

    Park, Kyoung-Soo; Kim, Youngman

    2011-08-01

    Hexamethyldisilazane (HMDS, [(CH3)3Si]2NH) was used as a precursor to form SiO2 protective coatings on IN738LC alloys by combustion chemical vapor deposition (CCVD). SEM and XPS showed that the processed coatings were composed mainly of SiO2. The amount of HMDS had the largest effect on the size of the SiO2 agglomerates and the thickness of the deposited coatings. The specimens coated with SiO2 using the 0.05 mol/l HMDS solution showed a significantly higher temperature oxidation resistance than those deposited under other conditions.

  5. Magnetic SiO2/Fe3O4 colloidal crystals

    International Nuclear Information System (INIS)

    Huang, C-K; Hou, C-H; Chen, C-C; Tsai, Y-L; Chang, L-M; Wei, H-S; Hsieh, K-H; Chan, C-H

    2008-01-01

    We proposed a novel technique to fabricate colloidal crystals by using monodisperse SiO 2 coated magnetic Fe 3 O 4 (SiO 2 /Fe 3 O 4 ) microspheres. The magnetic SiO 2 /Fe 3 O 4 microspheres with a diameter of 700 nm were synthesized in the basic condition with ferric sulfate, ferrous sulfate, tartaric acid and tetraethyl orthosilicate (TEOS) in the reaction system. Monodisperse SiO 2 /Fe 3 O 4 superparamagnetic microspheres have been successfully used to fabricate colloidal crystals under the existing magnetic field

  6. Adsorption of cationic dye on a biohybrid SiO2-alginate

    International Nuclear Information System (INIS)

    Barrón Zambrano, J A; Ávila Ortega, A; Muñoz Rodríguez, D; Carrera Figueiras, C; López-Pérez, A J

    2013-01-01

    In this work, a biohybrid material based on SiO 2 -alginate was obtained and its properties of adsorption evaluated using methylene blue as a model dye. The experimental results showed that the biohybrid SiO 2 -alginate has a higher adsorption ability compared to their base compounds (SiO 2 and alginate). Methylene blue adsorption is pH dependent, resulting in a maximum adsorption at pH = 8. The sorption kinetics rate is similar to SiO 2 . Kinetic data were fitted to a model of pseudosecond order. The experimental isotherms fit well the Langmuir model.

  7. Preliminary study in development of glass-ceramic based on SiO2-LiO2 system, starting of different SiO2 starting powders

    International Nuclear Information System (INIS)

    Daguano, J.K.M.F.; Santos, F.A.; Santos, C.; Marton, L.F.M.; Conte, R.A.; Rodrigues Junior, D.; Melo, F.C.L.

    2009-01-01

    In this work, lithium disilicate glass-ceramics were developed starting of the rice ash- SiO 2 and Li 2 CO 3 powders. The results were compared with glass ceramics based on the lithium disilicate obtained by commercial SiO 2 powders. Glass were melted at 1580 deg C, and annealed at 850 deg C. X-Ray diffraction and scanning electron microscopy were used for characterization of the materials, and hardness and fracture toughness were evaluated using Vickers indentation method. Glasses with amorphous structure were obtained in both materials. After annealing, 'rice-ash' samples presented Li 2 SiO 3 and residual SiO 2 as crystalline phases. On the other side, commercial SiO 2 - Samples presented only Li 2 Si 2 O 5 as crystalline phases and the better results of hardness and fracture toughness. (author)

  8. Phonon spectra in SiO2 glasses

    International Nuclear Information System (INIS)

    Perez R, J.F.; Jimenez S, S.; Gonzalez H, J.; Vorobiev, Y.V.; Hernandez L, M.A.; Parga T, J.R.

    1999-01-01

    Phonon spectra in SiO 2 sol-gel made glasses annealed under different conditions are investigated using infrared absorption and Raman scattering. These data are compared with those obtained in commercial optical-quality quartz. All the materials exhibit the same phonon bands, the exact position and the intensity depend on the measuring technique and on the sample preparation method. The phonon spectra in this material are interpreted on the basis of a simple quasi-linear description of elastic waves in an O-Si-O chain. It is shown that the main features observed in the range 400-1400 cm -1 can be predicted using a quasi-linear chain model in which the band at 1070 cm -1 is assigned to the longitudinal optical waves in the O-Si-O chain with the smallest possible wavelength at the Brillouin zone boundary, the band located around 450 cm -1 is assigned to the transversal optical waves and the band at 800 cm -1 to the longitudinal acoustical waves with the same wavelength. The degree of structural disorder can be also deduced within the framework of the proposed model. (Author)

  9. Functionalized sio2 microspheres for extracting oil from produced water

    KAUST Repository

    Mishra, Himanshu

    2017-03-16

    Functionalized material, methods of producing the functionalized material, and use thereof for separation processes such as but not limited to use for separating and extracting a dissolved organic foulant, charged contaminant or oily matter or any combination thereof from water, such as produced water, are provided. In an embodiment, the functionalized material is a mineral material, such as mica, silica (e.g. an SiO2 microsphere) or a metal oxide, and the outer surface of the material is functionalized with an alkyl chain or a perfluorinated species. In an embodiment, the method of making the functionalized material, includes: a) providing a mineral material; b) providing an alkyl chain and/or a perfluorinated species, the alkyl chain or perfluorinated species selected to dissolve organic foulants, charged contaminants or oily matter from water or any combination thereof; c) hydroxylating the material via a concentrated acid solution or a basic solution; and d) grafting the alkyl chain and/or the perfluorinated species onto the material via a silanation reaction.

  10. Gate-controlled metal-insulator transition in the LaAlO{sub 3}/SrTiO{sub 3} system with sub-critical LaAlO{sub 3} thickness

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Joon Sung; Lee, Seung Ran; Chang, Jung-Won; Noh, Hyunho; Baasandorj, Lkhagvasuren; Shim, Seung-Bo; Kim, Jinhee [Korea Research Institute of Standards and Science, Daejeon 305-600 (Korea, Republic of); Seung, Sang Keun; Shin, Hyun Sup; Song, Jonghyun [Department of Physics, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

    2012-12-15

    We studied the electrical conduction in the LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) interface electron system with a sub-critical LAO layer thickness of {proportional_to}3.5 unit cells (uc). It was found that the true dividing point between metallic and insulating behaviour without gating lies near the LAO thickness of 3.5 uc. Our marginally metallic 3.5 uc sample showed a sharp transition to insulating state at temperatures which strongly depended on the applied negative back-gate voltage. The superior gate-controllability of the sample was attributed to its sheet carrier density which was an order of magnitude lower than those of conducting LAO/STO samples with 4 uc or more of LAO layers. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Poole Frenkel current and Schottky emission in SiN gate dielectric in AlGaN/GaN metal insulator semiconductor heterostructure field effect transistors

    Science.gov (United States)

    Hanna, Mina J.; Zhao, Han; Lee, Jack C.

    2012-10-01

    We analyze the anomalous I-V behavior in SiN prepared by plasma enhanced chemical vapor deposition for use as a gate insulator in AlGaN/GaN metal insulator semiconductor heterostructure filed effect transistors (HFETs). We observe leakage current across the dielectric with opposite polarity with respect to the applied electric field once the voltage sweep reaches a level below a determined threshold. This is observed as the absolute minimum of the leakage current does not occur at minimum voltage level (0 V) but occurs earlier in the sweep interval. Curve-fitting analysis suggests that the charge-transport mechanism in this region is Poole-Frenkel current, followed by Schottky emission due to band bending. Despite the current anomaly, the sample devices have shown a notable reduction of leakage current of over 2 to 6 order of magnitudes compared to the standard Schottky HFET. We show that higher pressures and higher silane concentrations produce better films manifesting less trapping. This conforms to our results that we reported in earlier publications. We found that higher chamber pressure achieves higher sheet carrier concentration that was found to be strongly dependent on the trapped space charge at the SiN/GaN interface. This would suggest that a lower chamber pressure induces more trap states into the SiN/GaN interface.

  12. High fluence swift heavy ion structure modification of the SiO{sub 2}/Si interface and gate insulator in 65 nm MOSFETs

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yao [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Gao, Bo, E-mail: gaobo@scu.edu.cn [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Gong, Min [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Willis, Maureen [College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Yang, Zhimei [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); Guan, Mingyue [College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Li, Yun [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China)

    2017-04-01

    In this work, a study of the structure modification, induced by high fluence swift heavy ion radiation, of the SiO{sub 2}/Si structures and gate oxide interface in commercial 65 nm MOSFETs is performed. A key and novel point in this study is the specific use of the transmission electron microscopy (TEM) technique instead of the conventional atomic force microscope (AFM) or scanning electron microscope (SEM) techniques which are typically performed following the chemical etching of the sample to observe the changes in the structure. Using this method we show that after radiation, the appearance of a clearly visible thin layer between the SiO{sub 2} and Si is observed presenting as a variation in the TEM intensity at the interface of the two materials. Through measuring the EDX line scans we reveal that the Si:O ratio changed and that this change can be attributed to the migration of the Si towards interface after the Si-O bond is destroyed by the swift heavy ions. For the 65 nm MOSFET sample, the silicon substrate, the SiON insulator and the poly-silicon gate interfaces become blurred under the same irradiation conditions.

  13. Synthesis of TiO2-doped SiO2 composite films and its applications

    Indian Academy of Sciences (India)

    Wintec

    structure of the titanium oxide species in the TiO2-doped SiO2 composite films and the photocatalytic reactiv- ity in order to ... gaku D-max γA diffractometer with graphite mono- chromized ... FT–IR absorption spectra of TiO2-doped SiO2 com-.

  14. Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

    Indian Academy of Sciences (India)

    Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres. K C BARICK and D BAHADUR*. Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay,. Mumbai 400 076, India. Abstract. The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 ...

  15. Excimer laser crystallization of InGaZnO4 on SiO2 substrate

    NARCIS (Netherlands)

    Chen, T.; Wu, M.Y.; Ishihara, R.; Nomura, K.; Kamiya, T.; Hosono, H.; Beenakker, C.I.M.

    2011-01-01

    In this paper, we were able to crystallize InGaZnO4 (IGZO) by excimer laser on SiO2 substrate. It was observed that uniform [0001] textured polycrystalline IGZO film has been obtained without any grain boundaries and oxygen vacancies on SiO2 substrate. This process is very promising in fabricating

  16. Water droplet behavior on superhydrophobic SiO2 nanocomposite films during icing/deicing cycles

    NARCIS (Netherlands)

    Lazauskas, A.; Guobiene, A.; Prosycevas, I.; Baltrusaitis, V.; Grigaliunas, V.; Narmontas, P.; Baltrusaitis, Jonas

    2013-01-01

    This work investigates water droplet behavior on superhydrophobic (water contact angle value of 162 ± 1°) SiO2 nanocomposite films subjected to repetitive icing/deicing treatments, changes in SiO2 nanocomposite film surface morphology and their non-wetting characteristics. During the experiment,

  17. Tunable graphene doping by modulating the nanopore geometry on a SiO2/Si substrate

    KAUST Repository

    Lim, Namsoo; Yoo, Tae Jin; Kim, Jin Tae; Pak, Yusin; Kumaresan, Yogeenth; Kim, Hyeonghun; Kim, Woochul; Lee, Byoung Hun; Jung, Gun Young

    2018-01-01

    A tunable graphene doping method utilizing a SiO2/Si substrate with nanopores (NP) was introduced. Laser interference lithography (LIL) using a He–Cd laser (λ = 325 nm) was used to prepare pore size- and pitch-controllable NP SiO2/Si substrates

  18. Positron Annihilation in Insulating Materials

    International Nuclear Information System (INIS)

    Asoka-Kumar, P; Sterne, PA

    2002-01-01

    We describe positron results from a wide range of insulating materials. We have completed positron experiments on a range of zeolite-y samples, KDP crystals, alkali halides and laser damaged SiO 2 . Present theoretical understanding of positron behavior in insulators is incomplete and our combined theoretical and experimental approach is aimed at developing a predictive understanding of positrons and positronium annihilation characteristics in insulators. Results from alkali halides and alkaline-earth halides show that positrons annihilate with only the halide ions, with no apparent contribution from the alkali or alkaline-earth cations. This contradicts the results of our existing theory for metals, which predicts roughly equal annihilation contributions from cation and anion. We also present result obtained using Munich positron microprobe on laser damaged SiO 2 samples

  19. Precipitation of amorphous SiO2 particles and their properties

    Directory of Open Access Journals (Sweden)

    S. Musić

    2011-03-01

    Full Text Available The experimental conditions were optimized for the synthesis of amorphous SiO2 particles by the reaction of neutralization of sodium silicate solution with H2SO4 solution. Amorphous SiO2 particles were characterized by XRD, FT-IR, FE-SEM, EDS and microelectrophoresis. The amorphous peak was located at 2θ = 21.8º in the XRD pattern. Primary SiO2 particles were ~ 15 to ~ 30 nm in size and they aggregated into bigger particles. Amorphous SiO2 particles showed a specific surface area up to 130 m²g-1, dependent on the parameters of the precipitation process. The EDS spectrum of amorphous SiO2 particles did not show contamination with sulfate or other ions, which cannot be excluded in traces. pHzpc =1.7 was obtained by microelectrophoresis.

  20. Pulsed ion-beam assisted deposition of Ge nanocrystals on SiO2 for non-volatile memory device

    International Nuclear Information System (INIS)

    Stepina, N.P.; Dvurechenskii, A.V.; Armbrister, V.A.; Kirienko, V.V.; Novikov, P.L.; Kesler, V.G.; Gutakovskii, A.K.; Smagina, Z.V.; Spesivtzev, E.V.

    2008-01-01

    A floating gate memory structure, utilizing Ge nanocrystals (NCs) deposited on tunnel SiO 2 , have been fabricated using pulsed low energy ion-beam induced molecular-beam deposition (MBD) in ultra-high vacuum. The ion-beam action is shown to stimulate the nucleation of Ge NCs when being applied after thin Ge layer deposition. Growth conditions for independent change of NCs size and array density were established allowing to optimize the structure parameters required for memory device. Activation energy E = 0.25 eV was determined from the temperature dependence of NCs array density. Monte Carlo simulation has shown that the process, determining NCs array density, is the surface diffusion. Embedding of the crystalline Ge dots into silicon oxide was carried out by selective oxidation of Si(100)/SiO 2 /Ge(NCs)/poly-Si structure. MOS-capacitor obtained after oxidation showed a hysteresis in its C-V curves attributed to charge retention in the Ge dots

  1. Passivation of Flexible YBCO Superconducting Current Lead With Amorphous SiO2 Layer

    Science.gov (United States)

    Johannes, Daniel; Webber, Robert

    2013-01-01

    across a thermal gradient with as little flow of heat as possible to make an efficient current lead. By protecting YBCO on a flexible substrate of low thermal conductivity with SiO2, a thermally efficient and flexible current lead can be fabricated. The technology is also applicable to current leads for 4 K superconducting electronics current biasing. A commercially available thin-film YBCO composite tape conductor is first stripped of its protective silver coating. It is then mounted on a jig that holds the sample flat and acts as a heat sink. Silicon dioxide is then deposited onto the YBCO to a thickness of about 1 micron using PECVD (plasma-enhanced chemical vapor deposition), without heating the YBCO to the point where degradation occurs. Since SiO2 can have good high-frequency electrical properties, it can be used to coat YBCO cable structures used to feed RF signals across temperature gradients. The prime embodiment concerns the conduction of DC current across the cryogenic temperature gradient. The coating is hard and electrically insulating, but flexible.

  2. Fabrication and properties of highly luminescent materials from Tb(OH)3-SiO2 and Tb(OH)3-SiO2:Eu3+ nanotubes

    International Nuclear Information System (INIS)

    Tran Thu Huong; Tran Kim Anh; Le Quoc Minh

    2009-01-01

    Luminescent nanomaterials with one-dimensional (1D) structures have attracted much attention due to their unique properties and potential applications in nanophotonics and nanobiophotonics. In this paper, we report a synthesis of terbium - hydroxide - at - silica Tb(OH) 3 -SiO 2 and Tb(OH) 3 -SiO 2 :Eu 3+ nanotubes. Terbium - hydroxide tubes were synthesized by soft template method. The size of the tubes can be controlled precisely and have outer diameters ranging from 80 to 120 nm, wall thickness of about 30 nm, and lengths ranging from 300 to 800 nm. To fabricate core/shell materials, the seed growth method is used. FESEM, X-ray diffraction, Raman spectra of Tb(OH) 3 and Tb(OH) 3 -SiO 2 nanotubes were investigated. The photoluminescence (PL) spectrum of Tb(OH) 3 under 325 nm excitation consists of four main peaks at 488, 542, 582, and 618 nm. Furthermore, a preliminary suggestion for the mechanism of growth of the Tb(OH) 3 nanotubes using the soft - template synthesis technique has been proposed. The PL intensity from Tb(OH) 3 -SiO 2 or Tb(OH) 3 -SiO 2 :Eu 3+ nanotubes is much stronger than that of Tb(OH) 3 .

  3. Enhanced antioxidation and microwave absorbing properties of SiO2-coated flaky carbonyl iron particles

    Science.gov (United States)

    Zhou, Yingying; Xie, Hui; Zhou, Wancheng; Ren, Zhaowen

    2018-01-01

    SiO2 was successfully coated on the surface of flaky carbonyl iron particles using a chemical bath deposition method in the presence of 3-aminopropyl triethoxysilane (APTES). The morphologies, composition, valence states of elements, as well as antioxidation and electromagnetic properties of the samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and microwave network analyzer. TG curve shows the obvious weight gain of carbonyl iron was deferred to 360 °C after SiO2-coated, which can be ascribed to the exits of SiO2 overlayer. Compared with the raw carbonyl iron, SiO2-coated sample shows good wave absorption performance due to its impedance matching. The electromagnetic properties of raw and SiO2-coated carbonyl iron particles were characterized in X band before and after heat treatment at 250 °C for 10 h. It was established that SiO2-coated carbonyl iron demonstrate good thermal stability, indicating SiO2-coating is useful in the usage of microwave absorbers operating at temperature up to 250 °C.

  4. Preparation and Characterization of SiO2/SiCN Core-shell Ceramic Microspheres

    Directory of Open Access Journals (Sweden)

    ZHANG Hai-yuan

    2017-05-01

    Full Text Available The SiO2/PSN core-shell microspheres were prepared via an emulsion reaction combined with the polymer-derived ceramics (PDCs method using polysilazane (PSN in situ polymerization on the surface of SiO2 modified by silane coupling agents MPS, followed by pyrolysis process to obtain SiO2/SiCN core-shell ceramic microspheres. The effects of raw mass ratio, curing time and pyrolysis temperature on the formation and the morphology of core-shell microspheres were studied. The morphology, chemical composition and phase transformation were characterized by SEM, EDS, TEM, FT-IR and XRD. The results show that after reaction for 4h at 200℃, SiO2 completely coated PSN forms a core-shell microsphere with rough surface when the mass ratio of SiO2 and PSN is 1:4; when pyrolysis temperature is at 800-1200℃, amorphous SiO2/SiCN core-shell ceramic microspheres are prepared; at 1400℃, the amorphous phase partially crystallizes to produce SiO2, SiC and Si3N4 phase.

  5. Effect of SiO2 addition and gamma irradiation on the lithium borate glasses

    Science.gov (United States)

    Raut, A. P.; Deshpande, V. K.

    2018-01-01

    The physical properties like density, glass transition temperature (Tg), and ionic conductivity of lithium borate (LB) glasses with SiO2 addition were measured before and after gamma irradiation. Remarkable changes in properties have been obtained in the physical properties of LB glasses with SiO2 addition and after gamma irradiation. The increase in density and glass transition temperature of LB glasses with SiO2 addition has been explained with the help of increase in density of cross linking due to SiO4 tetrahedra formation. The increase in ionic conductivity with SiO2 addition was explained with the help of ‘mixed glass former effect’. The increase in density and Tg of LB glasses with SiO2 addition after gamma irradiation has been attributed to fragmentation of bigger ring structure into smaller rings, which increases the density of cross linking and hence compaction. The exposure of gamma irradiation has lead to decrease in ionic conductivity of LB glasses with SiO2 addition. The atomic displacement caused by gamma irradiation resulted in filling of interstices and decrease in trapping sites. This explains the obtained decrease in ionic conductivity after gamma irradiation of glasses. The obtained results of effect of SiO2 addition and gamma irradiation on the density, Tg and ionic conductivity has been supported by FTIR results.

  6. Stability analysis of SiO2/SiC multilayer coatings

    International Nuclear Information System (INIS)

    Fu Zhiqiang; Jean-Charles, R.

    2006-01-01

    The stability behaviours of SiC coatings and SiO 2 /SiC coatings in helium with little impurities are studied by HSC Chemistry 4.1, the software for analysis of Chemical reaction and equilibrium in multi-component complex system. It is found that in helium with a low partial pressure of oxidative impurities under different total pressure, the key influence factor controlling T cp of SiC depends is the partial pressure of oxidative impurities; T cp of SiC increases with the partial pressure of oxidative impurities. In helium with a low partial pressure of different impurities, the key influence factor of T cs of SiO 2 are both the partial pressure of impurities and the amount of impurities for l mol SiO 2 ; T cs of SiO 2 increases with the partial pressure of oxidative impurities at the same amount of the impurities for 1 mol SiO 2 while it decreases with the amount of the impurities for 1 mm SiO 2 at the same partial pressure of the impurities. The influence of other impurities on T cp of SiC in He-O 2 is studied and it is found that CO 2 , H 2 O and N-2 increase T cp of SiC in He-O 2 while H 2 , CO and CH 4 decrease T cp of SiC He-O 2 . When there exist both oxidative impurities and reductive impurities, their effect on T cs of SiO 2 can be suppressed by the other. In HTR-10 operation atmosphere, SiO 2 /SiC coatings can keep stable status at higher temperature than SiC coatings, so SiO 2 /SiC coatings is more suitable to improve the oxidation resistance of graphite in HTR-10 operation atmosphere compared with SiC coatings. (authors)

  7. Self-Ordered Voids Formation in SiO2 Matrix by Ge Outdiffusion

    OpenAIRE

    B. Pivac; P. Dubček; J. Dasović; H. Zorc; S. Bernstorff; J. Zavašnik; B. Vlahovic

    2018-01-01

    The annealing behavior of very thin SiO2/Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800°C) in inert atmosphere, Ge is completely outdiffused from the SiO2 matrix leaving small (about 3 nm) spherical voids embedded in the SiO2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction) and self-organization ...

  8. Formation of radiative centers in SiO2 by tin high-dose implantation

    International Nuclear Information System (INIS)

    Komarov, F.F.; Parkhomenko, I.N.; Vlasukova, L.A.; Mil'chanin, O.V.; Mokhovikov, M.A.; Wendler, E.; Wesch, W.

    2013-01-01

    The structural transformations in SiO 2 layers implanted with high fluence of Sn ions have been investigated. It has been found that post-implantation annealing results in the β-Sn precipitation as well as the formation of SnO 2 -enriched regions in SiO 2 :Sn matrix. The intensive emission in the range of photon energies 1.5 – 3.5 eV is registered for the implanted and annealed samples. We attribute it to the oxygen deficiency centers created in the SiO 2 :Sn matrix and at the 'nanocluster/SiO 2 ' interfaces. (authors)

  9. Cytotoxicity and effect on GJIC of SiO2 nanoparticles in HL-7702 cells

    International Nuclear Information System (INIS)

    Pan Tao; Jin Minghua; Liu Xiaomei; Du Zhongjun; Zhou Xianqing; Huang Peili; Sun Zhiwei

    2013-01-01

    Objective: To study the cytotoxicity and effect on gap junction intracellular communication (GJIC) of SiO 2 nanoparticles in HL-7702 cells, and to provide experimental basis for toxicity assessment and the security applications of SiO 2 nanoparticles. Methods: Transmission electron microscope (TEM) was used to characterize two kinds of SiO 2 nanoparticles, verifying their size, dispersion and shape; dynamic light scattering (DLS) method was used to analyze the water dispersion and culture medium dispersion of the SiO 2 nanoparticles; MTT assay was carried out to examine the cytotoxicities of the two sizes SiO 2 nanoparticles on the cells; lactate dehydrogenase (LDH) release assay was performed to examine the integrity nano of the cell membrane; Scrape-loading and dye transfer assay was performed to examine the effect of SiO 2 nanoparticles on GJIC. Results: Based on the result of TEM, two kinds of SiO 2 nanoparticles were spherically shaped, uniformly sized and sporadically dispersed; the statistical analysis results showed the diameters of the two nanoparticles were (447.60±20.78) nm and (67.42±5.69) nm, respectively, thus they could be categorized as submicron scale and nano scale. The DLS method results manifested that the hydration nanoparticle sizes of the two SiO 2 nanoparticles were (684.37±18.76) nm, (128.31±7.64) nm in high purity water and (697.02±19.57) nm, (133.74±8.97) nm in RPMI-1640 solution, all the two nanoparticles were well dispersed without aggregation. MTT assay indicated that 24 h after treatment of SiO 2 nanoparticles, the cell viabilities were affected by both the size and the dose of the SiO 2 nanoparticles; the higher the dose was, the less viability the cells exhibited. Moreover, the nano scale particles inflicted more damage to the cells. LDH release assay indicated that the SiO 2 particles could also damage the cell membrane in a dose-dependent and size-dependent way. Scrape-loading and dye transfer assay indicated that the nano scale particles could cause GJIC inhibition in a dose-dependent way; and when at the same dose, the nanoparticles could cause a more obvious inhibition of GJIC than the submicron particles. Conclusion: SiO 2 nanoparticles have cytotoxicity on HL-7702 cells, and would cause GJIC inhibition. (authors)

  10. Si nanocrystals embedded in SiO2: Optical studies in the vacuum ultraviolet range

    DEFF Research Database (Denmark)

    Pankratov, V.; Osinniy, Viktor; Kotlov, A.

    2011-01-01

    done. It is demonstrated that the experimentally determined blueshift of the photoluminescence excitation and absorption spectra is larger than the theoretical predictions. The influence of point defects in the SiO2 matrix on the optical and luminescence properties of the embedded Si nanocrystals...... is discussed. Moreover, it is demonstrated that no energy transfer takes place between the SiO2 and Si nanocrystals when the excitation energy is higher than the band-to-band transition energy in SiO2....

  11. Facile synthesis of microporous SiO2/triangular Ag composite nanostructures for photocatalysis

    Science.gov (United States)

    Sirohi, Sidhharth; Singh, Anandpreet; Dagar, Chakit; Saini, Gajender; Pani, Balaram; Nain, Ratyakshi

    2017-11-01

    In this article, we present a novel fabrication of microporous SiO2/triangular Ag nanoparticles for dye (methylene blue) adsorption and plasmon-mediated degradation. Microporous SiO2 nanoparticles with pore size aminopropyl) trimethoxysilane) to introduce amine groups. Amine-functionalized microporous silica was used for adsorption of triangular silver (Ag) nanoparticles. The synthesized microporous SiO2 nanostructures were investigated for adsorption of different dyes including methylene blue, congo red, direct green 26 and curcumin crystalline. Amine-functionalized microporous SiO2/triangular Ag nanostructures were used for plasmon-mediated photocatalysis of methylene blue. The experimental results revealed that the large surface area of microporous silica facilitated adsorption of dye. Triangular Ag nanoparticles, due to their better charge carrier generation and enhanced surface plasmon resonance, further enhanced the photocatalysis performance.

  12. Efficient photocatalytic activity with carbon-doped SiO2 nanoparticles

    KAUST Repository

    Zhang, Dongen; Wu, Jinbo; Zhou, Bingpu; Hong, Yaying; Li, Shunbo; Wen, Weijia

    2013-01-01

    by thermogravimetric analysis, X-ray diffraction, standard and high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The C-doped SiO2 displayed outstanding photocatalytic properties, as evidenced by its catalysis of Rhodamine B

  13. Characterization of the implantation damage in SiO2 with x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Ajioka, T.; Ushio, S.

    1986-01-01

    X-ray photoelectron spectroscopy (XPS) has been applied to characterize the damage introduced into SiO 2 by ion implantation. By measuring the peak width of Si/sub 2p/ from SiO 2 which corresponds to perturbation of the SiO 2 network, good depth profiles of the damage have been obtained for implanted samples and subsequently annealed samples. The results show that the damage distributed more widely than that calculated from energy deposition and that the perturbation of the network is caused not only by radiation damage but also by the existence of impurities in the network. It has been found that the XPS method is effective to understand the atomic structure, and thus, electrical properties of SiO 2

  14. Synthesis of unidirectional structures of SiO2-Ag using Au nanoparticles as nucleation centers

    International Nuclear Information System (INIS)

    Villa S, G.; Mendoza A, D.; Gutierrez W, C.; Perez H, R.

    2008-01-01

    This paper reports a method to synthesize Ag unidirectional structures covered with SiO 2 by sol-gel technique using Au nanoparticles as nucleation centers of the unidirectional structures. In the first phase unidirectional structures of SiO 2 -Ag CI are obtained by sol-gel, using TEOS as a precursor of metallic structures (Ag) and the incorporation of Au nanoparticles as nucleation centers for growth of unidirectional structures. In the second stage, one-way systems are subjected to thermal treatment in H 2 atmosphere for obtain AG 0 particles through mechanisms that diffusion and coalescence of silver to form structures that have a thin cover of SiO 2 . Analysis by scanning electron microscopy, transmission and atomic force microscopy allowed to determine the chemical composition and microstructural properties of unidirectional systems SiO 2 -Ag. (Author)

  15. Experimental determination of nanofluid specific heat with SiO2 nanoparticles in different base fluids

    Science.gov (United States)

    Akilu, S.; Baheta, A. T.; Sharma, K. V.; Said, M. A.

    2017-09-01

    Nanostructured ceramic materials have recently attracted attention as promising heat transfer fluid additives owing to their outstanding heat storage capacities. In this paper, experimental measurements of the specific heats of SiO2-Glycerol, SiO2-Ethylene Glycol, and SiO2-Glycerol/Ethylene Glycol mixture 60:40 ratio (by mass) nanofluids with different volume concentrations of 1.0-4.0% have been carried out using differential scanning calorimeter at temperatures of 25 °C and 50 °C. Experimental results indicate lower specific heat capacities are found with SiO2 nanofluids compared to their respective base fluids. The specific heat was decreasing with the increase of concentration, and this decrement depends on upon the type of the base fluid. It is observed that temperature has a positive impact on the specific heat capacity. Furthermore, the experimental values were compared with the theoretical model predictions, and a satisfactory agreement was established.

  16. Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

    KAUST Repository

    Munirasu, Selvaraj; Nunes, Suzana Pereira

    2014-01-01

    of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material

  17. Analysis of SiO2 nanoparticles binding proteins in rat blood and brain homogenate

    Directory of Open Access Journals (Sweden)

    Shim KH

    2014-12-01

    Full Text Available Kyu Hwan Shim,1 John Hulme,1 Eun Ho Maeng,2 Meyoung-Kon Kim,3 Seong Soo A An1 1Department of Bionano Technology, Gachon Medical Research Institute, Gachon University, Sungnam-si, 2Department of Analysis, KTR, Kimpo, Gyeonggi-do, 3Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, South Korea Abstract: A multitude of nanoparticles, such as titanium oxide (TiO2, zinc oxide, aluminum oxide, gold oxide, silver oxide, iron oxide, and silica oxide, are found in many chemical, cosmetic, pharmaceutical, and electronic products. Recently, SiO2 nanoparticles were shown to have an inert toxicity profile and no association with an irreversible toxicological change in animal models. Hence, exposure to SiO2 nanoparticles is on the increase. SiO2 nanoparticles are routinely used in numerous materials, from strengthening filler for concrete and other construction composites, to nontoxic platforms for biomedical application, such as drug delivery and theragnostics. On the other hand, recent in vitro experiments indicated that SiO2 nanoparticles were cytotoxic. Therefore, we investigated these nanoparticles to identify potentially toxic pathways by analyzing the adsorbed protein corona on the surface of SiO2 nanoparticles in the blood and brain of the rat. Four types of SiO2 nanoparticles were chosen for investigation, and the protein corona of each type was analyzed using liquid chromatography-tandem mass spectrometry technology. In total, 115 and 48 plasma proteins from the rat were identified as being bound to negatively charged 20 nm and 100 nm SiO2 nanoparticles, respectively, and 50 and 36 proteins were found for 20 nm and 100 nm arginine-coated SiO2 nanoparticles, respectively. Higher numbers of proteins were adsorbed onto the 20 nm sized SiO2 nanoparticles than onto the 100 nm sized nanoparticles regardless of charge. When proteins were compared between the two charges, higher numbers of proteins were found for arginine-coated positively charged SiO2 nanoparticles than for the negatively charged nanoparticles. The proteins identified as bound in the corona from SiO2 nanoparticles were further analyzed with ClueGO, a Cytoscape plugin used in protein ontology and for identifying biological interaction pathways. Proteins bound on the surface of nanoparticles may affect functional and conformational properties and distributions in complicated biological processes. Keywords: silica, nanoparticles, protein corona, plasma, brain homogenate, nanotoxicity

  18. Three-dimensional fabrication and characterisation of core-shell nano-columns using electron beam patterning of Ge-doped SiO2

    DEFF Research Database (Denmark)

    Gontard, Lionel C.; Jinschek, Joerg R.; Ou, Haiyan

    2012-01-01

    electron tomography. The results show that transformations in insulators that have been subjected to intense irradiation using charged particles can be studied directly in three dimensions. The fabricated structures include core-shell nano-columns, sputtered regions, voids, and clusters. (C) 2012 American......A focused electron beam in a scanning transmission electron microscope (STEM) is used to create arrays of core-shell structures in a specimen of amorphous SiO2 doped with Ge. The same electron microscope is then used to measure the changes that occurred in the specimen in three dimensions using...

  19. The Fault Detection, Localization, and Tolerant Operation of Modular Multilevel Converters with an Insulated Gate Bipolar Transistor (IGBT Open Circuit Fault

    Directory of Open Access Journals (Sweden)

    Wei Li

    2018-04-01

    Full Text Available Reliability is one of the critical issues for a modular multilevel converter (MMC since it consists of a large number of series-connected power electronics submodules (SMs. In this paper, a complete control strategy including fault detection, localization, and tolerant operation is proposed for the MMC under an insulated gate bipolar transistor (IGBT open circuit fault. According to the output characteristics of the SM with the open-circuit fault of IGBT, a fault detection method based on the circulating current and output current observation is used. In order to further precisely locate the position of the faulty SM, a fault localization method based on the SM capacitor voltage observation is developed. After the faulty SM is isolated, the continuous operation of the converter is ensured by adopting the fault-tolerant strategy based on the use of redundant modules. To verify the proposed fault detection, fault localization, and fault-tolerant operation strategies, a 900 kVA MMC system under the conditions of an IGBT open circuit is developed in the Matlab/Simulink platform. The capabilities of rapid detection, precise positioning, and fault-tolerant operation of the investigated detection and control algorithms are also demonstrated.

  20. Development of nano SiO2 incorporated nano zinc phosphate coatings on mild steel

    International Nuclear Information System (INIS)

    Tamilselvi, M.; Kamaraj, P.; Arthanareeswari, M.; Devikala, S.; Selvi, J. Arockia

    2015-01-01

    Highlights: • Nano SiO 2 incorporated nano zinc phosphate coating on mild steel was developed. • Coatings showed enhanced corrosion resistance. • The nano SiO 2 is adsorbed on mild steel surface and become nucleation sites. • The nano SiO 2 accelerates the phosphating process. - Abstract: This paper reports the development of nano SiO 2 incorporated nano zinc phosphate coatings on mild steel at low temperature for achieving better corrosion protection. A new formulation of phosphating bath at low temperature with nano SiO 2 was attempted to explore the possibilities of development of nano zinc phosphate coatings on mild steel with improved corrosion resistance. The coatings developed were studied by Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Electrochemical measurements. Significant variation in the coating weight, morphology and corrosion resistance was observed as nano SiO 2 concentrations varied from 0.5–4 g/L. The results showed that, the nano SiO 2 in the phosphating solution changed the initial potential of the interface between mild steel substrate and phosphating solution and reduce the activation energy of the phosphating process, increase the nucleation sites and yielded zinc phosphate coatings of higher coating weight, greater surface coverage and enhanced corrosion resistance. Better corrosion resistance was observed for coatings derived from phosphating bath containing 1.5 g/L nano SiO 2 . The new formulation reported in the present study was free from Ni or Mn salts and had very low concentration of sodium nitrite (0.4 g/L) as accelerator

  1. Nano-Ticl 4 .SiO 2 : a Versatile and Efficient Catalyst for Synthesis of ...

    African Journals Online (AJOL)

    Nano-TiCl4.SiO2 has been found to be an extremely efficient catalyst for the preparation of 3,4-dihydropyrimidinones/thiones via three-component reactions of an aldehyde, β-ketoester or β-diketone and urea or thiourea under mild conditions. Nano-TiCl4.SiO2 as a solid Lewis acid has been synthesized by reaction of ...

  2. Physical and Chemical Properties of TiOxNy Prepared by Low-Temperature Oxidation of Ultrathin Metal Nitride Directly Deposited on SiO2

    Institute of Scientific and Technical Information of China (English)

    HAN Yue-Ping; HAN Yan

    2009-01-01

    Physical and chemical properties of titanium oxynitride (TiOxNy) formed by low-temperature oxidation of titanium nitride (TIN) layer are investigated for advanced metal-oxide--semiconductor (MOS) gate dielectric application.TiOx Ny exhibits polycrystalline properties after the standard thermal process for MOS device fabrication,showing the preferred orientation at [200].Superior electrical properties of TiOxNy can be maintained before and after the annealing,probably due to the nitrogen incorporation in the oxide bulk and at the interface.Naturally formed transition layer between TiOxNy and SiO2 is also confirmed.

  3. Potential energy landscape of an interstitial O2 molecule in a SiO2 film near the SiO2/Si(001) interface

    Science.gov (United States)

    Ohta, Hiromichi; Watanabe, Takanobu; Ohdomari, Iwao

    2008-10-01

    Potential energy distribution of interstitial O2 molecule in the vicinity of SiO2/Si(001) interface is investigated by means of classical molecular simulation. A 4-nm-thick SiO2 film model is built by oxidizing a Si(001) substrate, and the potential energy of an O2 molecule is calculated at Cartesian grid points with an interval of 0.05 nm in the SiO2 film region. The result shows that the potential energy of the interstitial site gradually rises with approaching the interface. The potential gradient is localized in the region within about 1 nm from the interface, which coincides with the experimental thickness of the interfacial strained layer. The potential energy is increased by about 0.62 eV at the SiO2/Si interface. The result agrees with a recently proposed kinetic model for dry oxidation of silicon [Phys. Rev. Lett. 96, 196102 (2006)], which argues that the oxidation rate is fully limited by the oxidant diffusion.

  4. Surface modification of polyimide gate insulators for solution-processed 2,7-didecyl[1]benzothieno[3,2-b][1]benzothiophene (C10-BTBT) thin-film transistors.

    Science.gov (United States)

    Jang, Kwang-Suk; Kim, Won Soo; Won, Jong-Myung; Kim, Yun-Ho; Myung, Sung; Ka, Jae-Won; Kim, Jinsoo; Ahn, Taek; Yi, Mi Hye

    2013-01-21

    The surface property of a polyimide gate insulator was successfully modified with an n-octadecyl side-chain. Alkyl chain-grafted poly(amic acid), the polyimide precursor, was synthesized using the diamine comonomer with an alkyl side-chain. By adding a base catalyst to the poly(amic acid) coating solution, the imidization temperature of the spin-coated film could be reduced to 200 °C. The 350 nm-thick polyimide film had a dielectric constant of 3.3 at 10 kHz and a leakage current density of less than 8.7 × 10(-10) A cm(-2), while biased from 0 to 100 V. To investigate the potential of the alkyl chain-grafted polyimide film as a gate insulator for solution-processed organic thin-film transistors (TFTs), we fabricated C(10)-BTBT TFTs. C(10)-BTBT was deposited on the alkyl chain-grafted polyimide gate insulator by spin-coating, forming a well-ordered crystal structure. The field-effect mobility and the on/off current ratio of the TFT device were measured to be 0.20-0.56 cm(2) V(-1) s(-1) and >10(5), respectively.

  5. SiO2@TiO2 Coating: Synthesis, Physical Characterization and Photocatalytic Evaluation

    Directory of Open Access Journals (Sweden)

    A. Rosales

    2018-03-01

    Full Text Available Use of silicon dioxide (SiO2 and titanium dioxide (TiO2 have been widely investigated individually in coatings technology, but their combined properties promote compatibility for different innovative applications. For example, the photocatalytic properties of TiO2 coatings, when exposed to UV light, have interesting environmental applications, such as air purification, self-cleaning and antibacterial properties. However, as reported in different pilot projects, serious durability problems, associated with the adhesion between the substrate and TiO2, have been evidenced. Thus, the aim of this work is to synthesize SiO2 together with TiO2 to increase the durability of the photocatalytic coating without affecting its photocatalytic potential. Therefore, synthesis using sonochemistry, synthesis without sonochemistry, physical characterization, photocatalytic evaluation, and durability of the SiO2, SiO2@TiO2 and TiO2 coatings are presented. Results indicate that using SiO2 improved the durability of the TiO2 coating without affecting its photocatalytic properties. Thus, this novel SiO2@TiO2 coating shows potential for developing long-lasting, self-cleaning and air-purifying construction materials.

  6. Effect of SiO2 passivation overlayers on hillock formation in Al thin films

    International Nuclear Information System (INIS)

    Kim, Deok-kee

    2012-01-01

    Hillock formation in Al thin films with varying thicknesses of SiO 2 as a passivation layer was investigated during thermal cycling. Based on the stress measurements and the number of hillocks, 250 nm thick SiO 2 was thick enough to suppress the hillock formation and the suppression of hillock at 250 nm passivation and the lack of suppression at thinner passivation is related to the presence/absence of protection against the diffusive flow of atoms from the surrounding area to the surface due to the biaxial compressive stresses present in the film through the weak spots in the passivation layer. The stress state of Al films measured during annealing (the driving force for hillock formation) did not vary much with SiO 2 thickness. A small number of hillocks formed during the plasma enhanced chemical vapor deposition of SiO 2 overlayers at 300 °C. - Highlights: ► We examined the effect of SiO 2 overlayers on hillock formation in Al thin films. ► Thin overlayers were not effective in suppressing diffusive flow to the surface. ► A thick overlayer suppressed the diffusive flow from the interior to the surface. ► The stress state of Al films did not vary much with SiO 2 passivation thickness. ► High mechanical strength provided a large driving force for the large grain growth.

  7. Screen-Printed Photochromic Textiles through New Inks Based on SiO2@naphthopyran Nanoparticles.

    Science.gov (United States)

    Pinto, Tânia V; Costa, Paula; Sousa, Céu M; Sousa, Carlos A D; Pereira, Clara; Silva, Carla J S M; Pereira, Manuel Fernando R; Coelho, Paulo J; Freire, Cristina

    2016-10-26

    Photochromic silica nanoparticles (SiO 2 @NPT), fabricated through the covalent immobilization of silylated naphthopyrans (NPTs) based on 2H-naphtho[1,2-b]pyran (S1, S2) and 3H-naphtho[2,1-b]pyran (S3, S4) or through the direct adsorption of the parent naphthopyrans (1, 3) onto silica nanoparticles (SiO 2 NPs), were successfully incorporated onto cotton fabrics by a screen-printing process. Two aqueous acrylic- (AC-) and polyurethane- (PU-) based inks were used as dispersing media. All textiles exhibited reversible photochromism under UV and solar irradiation, developing fast responses and intense coloration. The fabrics coated with SiO 2 @S1 and SiO 2 @S2 showed rapid color changes and high contrasts (ΔE* ab = 39-52), despite presenting slower bleaching kinetics (2-3 h to fade to the original color), whereas the textiles coated with SiO 2 @S3 and SiO 2 @S4 exhibited excellent engagement between coloration and decoloration rates (coloration and fading times of 1 and 2 min, respectively; ΔE* ab = 27-53). The PU-based fabrics showed excellent results during the washing fastness tests, whereas the AC-based textiles evidenced good results only when a protective transfer film was applied over the printed design.

  8. Coupling between Ge-nanocrystals and defects in SiO2

    International Nuclear Information System (INIS)

    Skov Jensen, J.; Franzo, G.; Leervad Petersen, T.P.; Pereira, R.; Chevallier, J.; Christian Petersen, M.; Bech Nielsen, B.; Nylandsted Larsen, A.

    2006-01-01

    Room temperature photoluminescence (PL) at around 600 nm from magnetron-sputtered SiO 2 films co-doped with Ge is reported. The PL signal is observed in pure SiO 2 , however, its intensity increases significantly in the presence of Ge-nanocrystals (Ge-nc). The PL intensity has been optimized by varying the temperature of heat treatment, type of gas during heat treatment, concentration of Ge in the SiO 2 films, and gas pressure during deposition. Maximum intensity occurs when Ge-nc of around 3.5 nm are present in large concentration in SiO 2 layers deposited at fairly high gas pressure. Based on time resolved PL, and PL measurements after α-particle irradiation or H passivation, we attribute the origin of the PL to a defect in SiO 2 (probably an O deficiency) that is excited through an energy transfer from Ge-nc. There is no direct PL from the Ge-nc; however, there is a strong coupling between excitons created in the Ge-nc and the SiO 2 defect

  9. SiO2 stabilized Pt/C cathode catalyst for proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Zhu Tong; Du Chunyu; Liu Chuntao; Yin Geping; Shi Pengfei

    2011-01-01

    This paper describes the preparation of SiO 2 stabilized Pt/C catalyst (SiO 2 /Pt/C) by the hydrolysis of alkoxysilane, and examines the possibility that the SiO 2 /Pt/C is used as a durable cathode catalyst for proton exchange membrane fuel cells (PEMFCs). TEM and XRD results revealed that the hydrolysis of alkoxysilane did not significantly change the morphology and crystalline structure of Pt particles. The SiO 2 /Pt/C catalyst exhibited higher durability than the Pt/C one, due to the facts that the silica layers covered were beneficial for reducing the Pt aggregation and dissolution as well as increasing the corrosion resistance of supports, although the benefit of silica covering was lower than the case of Pt/CNT catalyst. Also, it was observed that the activity of the SiO 2 /Pt/C catalyst for the oxygen reduction reaction was somewhat reduced compared to the Pt/C one after the silica covering. This reduction was partially due to the low oxygen kinetics as revealed by the rotating-disk-electrode measurement. Silica covering by hydrolysis of only 3-aminopropyl trimethoxysilane is able to achieve a good balance between the durability and activity, leading to SiO 2 /Pt/C as a promising cathode catalyst for PEMFCs.

  10. Band alignments and improved leakage properties of (La2O3)0.5(SiO2)0.5/SiO2/GaN stacks for high-temperature metal-oxide-semiconductor field-effect transistor applications

    Science.gov (United States)

    Gao, L. G.; Xu, B.; Guo, H. X.; Xia, Y. D.; Yin, J.; Liu, Z. G.

    2009-06-01

    The band alignments of (La2O3)0.5(SiO2)0.5(LSO)/GaN and LSO/SiO2/GaN gate dielectric stacks were investigated comparatively by using x-ray photoelectron spectroscopy. The valence band offsets for LSO/GaN stack and LSO/SiO2/GaN stack are 0.88 and 1.69 eV, respectively, while the corresponding conduction band offsets are found to be 1.40 and 1.83 eV, respectively. Measurements of the leakage current density as function of temperature revealed that the LSO/SiO2/GaN stack has much lower leakage current density than that of the LSO/GaN stack, especially at high temperature. It is concluded that the presence of a SiO2 buffer layer increases band offsets and reduces the leakage current density effectively.

  11. Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

    Science.gov (United States)

    Marszałek, Konstanty; Winkowski, Paweł; Jaglarz, Janusz

    2014-01-01

    Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

  12. Effect of ZnO channel thickness on the device behaviour of nonvolatile memory thin film transistors with double-layered gate insulators of Al2O3 and ferroelectric polymer

    International Nuclear Information System (INIS)

    Yoon, Sung-Min; Yang, Shin-Hyuk; Ko Park, Sang-Hee; Jung, Soon-Won; Cho, Doo-Hee; Byun, Chun-Won; Kang, Seung-Youl; Hwang, Chi-Sun; Yu, Byoung-Gon

    2009-01-01

    Poly(vinylidene fluoride trifluoroethylene) and ZnO were employed for nonvolatile memory thin film transistors as ferroelectric gate insulator and oxide semiconducting channel layers, respectively. It was proposed that the thickness of the ZnO layer be carefully controlled for realizing the lower programming voltage, because the serially connected capacitor by the formation of a fully depleted ZnO channel had a critical effect on the off programming voltage. The fabricated memory transistor with Al/P(VDF-TrFE) (80 nm)/Al 2 O 3 (4 nm)/ZnO (5 nm) exhibits encouraging behaviour such as a memory window of 3.8 V at the gate voltage of -10 to 12 V, and 10 7 on/off ratio, and a gate leakage current of 10 -11 A.

  13. Neutron-irradiation effects on SiO2 and SiO2-based glass ceramics

    International Nuclear Information System (INIS)

    Porter, D.L.; Pascucci, M.R.; Olbert, B.H.

    1981-01-01

    A preliminary data base to assess the radiation-damage resistance of some glass ceramic materials has been gathered. These are rather complex materials, both in structure and composition, but possess many of those properties required for structural, insulator applications in fusion-reactor design. Property measurements were made after fast (E > 0.1 MeV) neutron irradiations of approx. 2.4 x 10 22 n/cm 2 at 400 0 C and 550 0 C. The results have shown general resistance to changes in thermal expansion and most did not eperience severe loss of mechanical integrity. The maximum volume expansion occurred in several of the fluorophlogapite-based glass ceramics (approx. 3.0%). Several observations demonstrated differences between the effects of neutron and electron irradiation; irradiation conditions proptotypic of projected reactor uses need be considered for optimum materials selection

  14. A facile approach to fabricate Au nanoparticles loaded SiO2 microspheres for catalytic reduction of 4-nitrophenol

    International Nuclear Information System (INIS)

    Tang, Mingyi; Huang, Guanbo; Li, Xianxian; Pang, Xiaobo; Qiu, Haixia

    2015-01-01

    Hydrophilic and biocompatible macromolecules were used to improve and simplify the process for the fabrication of core/shell SiO 2 @Au composite particles. The influence of polymers on the morphology of SiO 2 @Au particles with different size of SiO 2 cores was analyzed by transmission electron microscopy and scanning electron microscopy. The optical property of the SiO 2 @Au particles was studied with UV–Vis spectroscopy. The results indicate that the structure and composition of macromolecules affect the morphology of Au layers on SiO 2 microspheres. The SiO 2 @Au particles prepared in the presence of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) have thin and complete Au nanoshells owing to their inducing act in preferential growth of Au nanoparticles along the surface of SiO 2 microspheres. SiO 2 @Au particles can be also prepared from SiO 2 microspheres modified with 3-aminopropyltrimethoxysilane in the presence of PVA or PVP. This offers a simple way to fabricate a Au layer on SiO 2 or other microspheres. The SiO 2 @Au particles demonstrated high catalytic activity in the reduction of 4-nitrophenol. - Highlights: • Facile direct deposition method for Au nanoparticles on silica microspheres. • Influence of different types of macromolecule on the formation of Au shell. • High catalytic performance of Au nanoparticles on silica microspheres

  15. Tunable graphene doping by modulating the nanopore geometry on a SiO2/Si substrate

    KAUST Repository

    Lim, Namsoo

    2018-02-28

    A tunable graphene doping method utilizing a SiO2/Si substrate with nanopores (NP) was introduced. Laser interference lithography (LIL) using a He–Cd laser (λ = 325 nm) was used to prepare pore size- and pitch-controllable NP SiO2/Si substrates. Then, bottom-contact graphene field effect transistors (G-FETs) were fabricated on the NP SiO2/Si substrate to measure the transfer curves. The graphene transferred onto the NP SiO2/Si substrate showed relatively n-doped behavior compared to the graphene transferred onto a flat SiO2/Si substrate, as evidenced by the blue-shift of the 2D peak position (∼2700 cm−1) in the Raman spectra due to contact doping. As the porosity increased within the substrate, the Dirac voltage shifted to a more positive or negative value, depending on the initial doping type (p- or n-type, respectively) of the contact doping. The Dirac voltage shifts with porosity were ascribed mainly to the compensation for the reduced capacitance owing to the SiO2–air hetero-structured dielectric layer within the periodically aligned nanopores capped by the suspended graphene (electrostatic doping). The hysteresis (Dirac voltage difference during the forward and backward scans) was reduced when utilizing an NP SiO2/Si substrate with smaller pores and/or a low porosity because fewer H2O or O2 molecules could be trapped inside the smaller pores.

  16. SiO2-induced release of sVEGFRs from pulmonary macrophages.

    Science.gov (United States)

    Chao, Jie; Lv, Yan; Chen, Jin; Wang, Jing; Yao, Honghong

    2018-01-01

    The inhalation of silicon dioxide (SiO 2 ) particles causes silicosis, a stubborn pulmonary disease that is characterized by alveolar inflammation during the early stage. Soluble cytokine receptors (SCRs) play important roles in regulating inflammation by either attenuating or promoting cytokine signaling. However, the role of SCRs in silicosis remains unknown. Luminex assays revealed increased soluble vascular endothelial growth factor receptor (sVEGFR) family levels in the plasma of silicosis patients. In an enzyme-linked immunosorbent assay (ELISA), cells from the differentiated human monocytic cell line U937 released sVEGFR family proteins after exposure to SiO 2 (50μg/cm 2 ). Further Western blot experiments revealed that VEGFR expression was also elevated in U937 cells. In contrast, levels of sVEGFR family members did not change in the supernatants of human umbilical vein endothelial cells (HUVECs) after exposure to SiO 2 (50μg/cm 2 ). Interestingly, VEGFR expression in HUVECs decreased after SiO 2 treatment. In a scratch assay, HUVECs exhibited cell migration ability, indicating the acquisition of mesenchymal properties. Our findings highlight the important role of sVEGFRs in both inflammation and fibrosis induced by SiO 2 , suggesting a possible mechanism for the fibrogenic effects observed in pulmonary diseases associated with fibrosis. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Transfer free graphene growth on SiO2 substrate at 250 °C

    Science.gov (United States)

    Vishwakarma, Riteshkumar; Rosmi, Mohamad Saufi; Takahashi, Kazunari; Wakamatsu, Yuji; Yaakob, Yazid; Araby, Mona Ibrahim; Kalita, Golap; Kitazawa, Masashi; Tanemura, Masaki

    2017-03-01

    Low-temperature growth, as well as the transfer free growth on substrates, is the major concern of graphene research for its practical applications. Here we propose a simple method to achieve the transfer free graphene growth on SiO2 covered Si (SiO2/Si) substrate at 250 °C based on a solid-liquid-solid reaction. The key to this approach is the catalyst metal, which is not popular for graphene growth by chemical vapor deposition. A catalyst metal film of 500 nm thick was deposited onto an amorphous C (50 nm thick) coated SiO2/Si substrate. The sample was then annealed at 250 °C under vacuum condition. Raman spectra measured after the removal of the catalyst by chemical etching showed intense G and 2D peaks together with a small D and intense SiO2 related peaks, confirming the transfer free growth of multilayer graphene on SiO2/Si. The domain size of the graphene confirmed by optical microscope and atomic force microscope was about 5 μm in an average. Thus, this approach will open up a new route for transfer free graphene growth at low temperatures.

  18. Thermodynamics of Bi2O3-SiO2 system

    Directory of Open Access Journals (Sweden)

    Onderka B.

    2017-01-01

    Full Text Available Thermodynamic properties of the liquid Bi2O3-SiO2 solutions were determined from the results of the electrochemical measurements by use of the solid oxide galvanic cells with YSZ (Yttria-Stabilized-Zirconia electrolyte. Activities of Bi2O3 in the solutions were determined for 0.2, 0.3, 0.4, and 0.5 SiO2 mole fractions in the temperature range 1073-1293 K from measured electromotive force (e.m.f of the solid electrolyte galvanic cell: Bi, Bi2O3-SiO2 | YSZ | air (pO2 = 0.213 bar Additionally, heat capacity data obtained for two solid phases 6Bi2O3•SiO2 and 2Bi2O3•3SiO2 were included into optimization of thermodynamic properties of the system. Optimization procedure was supported by differential thermal analysis (DTA data obtained in this work as well as those accepted from the literature. Using the data obtained in this work, and the information about phase equilibria found in the literature, binary system Bi2O3-SiO2 was assessed with the ThermoCalc software.

  19. Comparisons between TiO2- and SiO2-flux assisted TIG welding processes.

    Science.gov (United States)

    Tseng, Kuang-Hung; Chen, Kuan-Lung

    2012-08-01

    This study investigates the effects of flux compounds on the weld shape, ferrite content, and hardness profile in the tungsten inert gas (TIG) welding of 6 mm-thick austenitic 316 L stainless steel plates, using TiO2 and SiO2 powders as the activated fluxes. The metallurgical characterizations of weld metal produced with the oxide powders were evaluated using ferritoscope, optical microscopy, and Vickers microhardness test. Under the same welding parameters, the penetration capability of TIG welding with TiO2 and SiO2 fluxes was approximately 240% and 292%, respectively. A plasma column made with SiO2 flux exhibited greater constriction than that made with TiO2 flux. In addition, an anode root made with SiO2 flux exhibited more condensation than that made with TiO2 flux. Results indicate that energy density of SiO2-flux assisted TIG welding is higher than that of TiO2-flux assisted TIG welding.

  20. The improvement of SiO2 nanotubes electrochemical behavior by hydrogen atmosphere thermal treatment

    Science.gov (United States)

    Spataru, Nicolae; Anastasescu, Crina; Radu, Mihai Marian; Balint, Ioan; Negrila, Catalin; Spataru, Tanta; Fujishima, Akira

    2018-06-01

    Highly defected SiO2 nanotubes (SiO2-NT) were obtained by a simple sol-gel procedure followed by calcination. Boron-doped diamond (BDD) polycrystalline films coated with SiO2-NT were used as working electrodes and, unexpectedly, cyclic voltammetric experiments have shown that the concentration of both positive and negative defects at the surface is high enough to enable redox processes involving positively charged Ru(bpy)32+/3+ to occur. Conversely, no electrochemical activity was put into evidence for Fe(CN)63-/4- species, most likely as a result of the strong electrostatic repulsion exerted by the negatively charged SiO2 surface. The concentration of surface defects was further increased by a subsequent thermal treatment in a hydrogen atmosphere which, as EIS measurements have shown, significantly promotes Ru(bpy)32+ anodic oxidation. Digital simulation of the voltammetric responses demonstrated that this treatment does not lead to a similar increase of the number of electron-donor sites. It was also found that methanol anodic oxidation at hydrogenated SiO2-NT-supported platinum results in Tafel slopes of 116-220 mV decade-1, comparable to those reported for both conventional PtRu and Pt-oxide catalysts.

  1. Dependence of Photocatalytic Activity of TiO2-SiO2 Nanopowders

    Directory of Open Access Journals (Sweden)

    M. Riazian

    2014-10-01

    Full Text Available Structural properties and chemical composition change the photocatalytic activity in TiO2-SiO2 nanopowder composite. The SiO2-TiO2 nanostructure is synthesized based on sol–gel method. The nanoparticles are characterized by x-ray fluorescents (XRF, x- ray diffraction (XRD, tunneling electron microscopy (TEM, field emission scanning electron microscopy (FE-SEM, UV-vis. Spectrophotometer and furrier transmission create infrared absorption (FTIR techniques. The rate constant k for the degradation of methylen blue in its aqueous solution under UV irradiation is determined as a measure of photocatalytic activity. Dependence between photocatalytic activity and SiO2 content in the composite is determined. Rate constant k is found dependent on the content of SiO2 in the composite that calcined at 900 oC. The addition of low composition SiO2 to the TiO2 matrix (lower than 45% enhances the photocatalytic activity due to thermal stability and increasing in the surface area. The effects of chemical compositions on the surface topography and the crystallization of phases are studied.

  2. UV-VUV laser induced phenomena in SiO2 glass

    International Nuclear Information System (INIS)

    Kajihara, Koichi; Ikuta, Yoshiaki; Oto, Masanori; Hirano, Masahiro; Skuja, Linards; Hosono, Hideo

    2004-01-01

    Creation and annihilation of point defects were studied for SiO 2 glass exposed to ultraviolet (UV) and vacuum UV (VUV) lights to improve transparency and radiation toughness of SiO 2 glass to UV-VUV laser light. Topologically disordered structure of SiO 2 glass featured by the distribution of Si-O-Si angle is a critical factor degrading transmittance near the fundamental absorption edge. Doping with terminal functional groups enhances the structural relaxation and reduces the number of strained Si-O-Si bonds by breaking up the glass network without creating the color centers. Transmittance and laser toughness of SiO 2 glass for F 2 laser is greatly improved in fluorine-doped SiO 2 glass, often referred as 'modified silica glass'. Interstitial hydrogenous species are mobile and reactive at ambient temperature, and play an important role in photochemical reactions induced by exposure to UV-VUV laser light. They terminate the dangling-bond type color centers, while enhancing the formation of the oxygen vacancies. These findings are utilized to develop a deep-UV optical fiber transmitting ArF laser photons with low radiation damage

  3. Integrated nanophotonic hubs based on ZnO-Tb(OH3/SiO2 nanocomposites

    Directory of Open Access Journals (Sweden)

    Lin Yu

    2011-01-01

    Full Text Available Abstract Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH3/SiO2 as well as SnO2-Tb(OH3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

  4. Microwave electromagnetic and absorption properties of SiO2/C core/shell composites plated with metal cobalt

    Science.gov (United States)

    Shen, Guozhu; Fang, Xumin; Wu, Hongyan; Wei, Hongyu; Li, Jingfa; Li, Kaipeng; Mei, Buqing; Xu, Yewen

    2017-04-01

    A facile method has been developed to fabricate magnetic core/shell SiO2/C/Co sub-microspheres via the pyrolysis of SiO2/PANI (polyaniline) and electroless plating method. The electromagnetic parameters of these SiO2/C and SiO2/C/Co composites were measured and the microwave reflection loss properties were evaluated in the frequency range of 2-18 GHz. The results show that the dielectric loss of SiO2/C composite increases with the increase of carbonization temperature and the magnetic loss enhances due to the deposition of cobalt on the SiO2/C sub-microspheres. The reflection loss results exhibit that the microwave absorption properties of the SiO2/C/Co composites are more excellent than those of SiO2/C composites for each thickness. The maximum effective absorption bandwidth (reflection loss ≤ -10 dB) arrives at 5.0 GHz (13.0-18 GHz) for SiO2/C/Co composite with 1.5 mm of thickness and the minimum reflection loss value is -24.0 dB at 5.0 GHz with 4.0 mm of thickness. The microwave loss mechanism of the SiO2/C/Co composites was also discussed in this paper.

  5. Semiconductor nanocrystals formed in SiO2 by ion implantation

    International Nuclear Information System (INIS)

    Zhu, J.G.; White, C.W.; Budai, J.D.; Withrow, S.P.; Chen, Y.

    1994-11-01

    Nanocrystals of group IV (Si, Ge and SiGe), III-V (GaAs), and II-VI (CdSe) semiconductor materials have been fabricated inside SiO 2 by ion implantation and subsequent thermal annealing. The microstructure of these nanocrystalline semiconductor materials has been studied by transmission electron microscopy (TEM). The nanocrystals form in near-spherical shape with random crystal orientations in amorphous SiO 2 . Extensive studies on the nanocrystal size distributions have been carried out for the Ge nanocrystals by changing the implantation doses and the annealing temperatures. Remarkable roughening of the nanocrystals occurs when the annealing temperature is raised over the melting temperature of the implanted semiconductor material. Strong red photoluminescence peaked around 1.67 eV has been achieved in samples with Si nanocrystals in SiO 2

  6. Positron annihilation spectroscopy of the interface between nanocrystalline Si and SiO2

    International Nuclear Information System (INIS)

    Pi, X.D.; Coleman, P.G.; Harding, R.; Davies, G.; Gwilliam, R.M.; Sealy, B.J.

    2003-01-01

    Positron annihilation spectroscopy has been employed to study changes in the interface region between nanocrystalline Si and SiO 2 , following annealing between 400 deg. C and 900 deg. C in nitrogen or oxygen. With the support of photoluminescence spectroscopy we find that nitrogen and oxygen are trapped in voids at the interface at low temperatures. At temperatures above 700 deg. C both nitrogen and oxygen react with Si nanocrystals, and the resulting volume increase introduces stress in the SiO 2 matrix which is relaxed by the shrinkage of its intrinsic open volume. Oxygen appears to enhance Si diffusion in SiO 2 so that the agglomeration of Si nanocrystals occurs more readily during annealing in oxygen than in nitrogen

  7. Investigation of luminescence properties in SiO2: Tb, Yb upconversion inverse opal

    International Nuclear Information System (INIS)

    Yang Zhengwen; Yan Dong; Song Zhiguo; Zhou Dacheng; Yu Xue; Yang Yong; Yin Zhaoyi; Yan Lei; Wang Rongfei; Wu Hangjun; Qiu Jianbei

    2012-01-01

    The SiO 2 : Tb, Yb inverse opals with photonic band gap at 465 or 543 nm were prepared, and an effect of photonic band gap on upconversion spontaneous emission from Tb 3+ was investigated. The results show that the photonic band gap has a significant influence on the upconversion emission of the SiO 2 : Tb, Yb inverse opals. The upconversion luminescence of the Tb 3+ ions is suppressed in the inverse opal compared with the luminescence of that of the reference sample. - Highlights: ► Upconversion emission from Tb 3+ was observed in the SiO 2 : Tb, Yb inverse opal. ► UC emission of Tb 3+ was modulated by controlling the structure of inverse opal. ► UC emission of Tb 3+ was depressed in the inverse opal.

  8. Self-Ordered Voids Formation in SiO2 Matrix by Ge Outdiffusion

    Directory of Open Access Journals (Sweden)

    B. Pivac

    2018-01-01

    Full Text Available The annealing behavior of very thin SiO2/Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800°C in inert atmosphere, Ge is completely outdiffused from the SiO2 matrix leaving small (about 3 nm spherical voids embedded in the SiO2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction and self-organization (in horizontal direction. The formed films produce intensive photoluminescence (PL with a peak at 500 nm. The explored dynamics of the PL decay show the existence of a very rapid process similar to the one found at Ge/SiO2 defected interface layers.

  9. Ion assisted deposition of SiO2 film from silicon

    Science.gov (United States)

    Pham, Tuan. H.; Dang, Cu. X.

    2005-09-01

    Silicon dioxide, SiO2, is one of the preferred low index materials for optical thin film technology. It is often deposited by electron beam evaporation source with less porosity and scattering, relatively durable and can have a good laser damage threshold. Beside these advantages the deposition of critical optical thin film stacks with silicon dioxide from an E-gun was severely limited by the stability of the evaporation pattern or angular distribution of the material. The even surface of SiO2 granules in crucible will tend to develop into groove and become deeper with the evaporation process. As the results, angular distribution of the evaporation vapor changes in non-predicted manner. This report presents our experiments to apply Ion Assisted Deposition process to evaporate silicon in a molten liquid form. By choosing appropriate process parameters we can get SiO2 film with good and stable property.

  10. The hydrophobic and omnidirectional antireflection coating of SiO2 nanospheres with C18-TEOS

    Science.gov (United States)

    Hsu, Cheng-Chih; Lan, Wen-Lin; Chen, Nien-Po; Wu, Chyan-Chyi

    2014-06-01

    This paper demonstrates the antireflection coating of SiO2 nanospheres applied to cover glass by using the optimal spin-coating method. Because of the hydrolysis and condensation reactions between the SiO2 nanosphere antireflection (AR) coating and n-octadecyltriethoxysilane solution (C18-TEOS), the contact angle of the AR coating with hydrophobic treatment is improved approximately 38%, and the moisture-resistance remains unchanged, which preserved similar transmittance for six weeks. Furthermore, the AR coating with hydrophobic treatment exhibits approximately 3% and 7% improvement in the transmittance at normal and oblique incidence, respectively. The hydrophobic and omnidirectional AR coating with nanoscale SiO2 particles can be fabricated using the proposed simple and economical method.

  11. Effect of water layer at the SiO2/graphene interface on pentacene morphology.

    Science.gov (United States)

    Chhikara, Manisha; Pavlica, Egon; Matković, Aleksandar; Gajić, Radoš; Bratina, Gvido

    2014-10-07

    Atomic force microscopy has been used to examine early stages of pentacene growth on exfoliated single-layer graphene transferred to SiO2 substrates. We have observed 2D growth with mean height of 1.5 ± 0.2 nm on as-transferred graphene. Three-dimensional islands of pentacene with an average height of 11 ± 2 nm were observed on graphene that was annealed at 350 °C prior to pentacene growth. Compellingly similar 3D morphology has been observed on graphene transferred onto SiO2 that was treated with hexamethyldisilazane prior to the transfer of graphene. On multilayer graphene we have observed 2D growth, regardless of the treatment of SiO2. We interpret this behavior of pentacene molecules in terms of the influence of the dipolar field that emerges from the water monolayer at the graphene/SiO2 interface on the surface energy of graphene.

  12. SiO2 coating of silver nanoparticles by photoinduced chemical vapor deposition

    International Nuclear Information System (INIS)

    Boies, Adam M; Girshick, Steven L; Roberts, Jeffrey T; Zhang Bin; Nakamura, Toshitaka; Mochizuki, Amane

    2009-01-01

    Gas-phase silver nanoparticles were coated with silicon dioxide (SiO 2 ) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO 2 precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO 2 coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 0 C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10 7 particles cm -3 .

  13. Study on the technique for precision measurement of density of SiO_2 foam shells

    International Nuclear Information System (INIS)

    Ma Xiaojun; Gao Dangzhong; Meng Jie

    2013-01-01

    The measuring method based on vertical scanning interference and combined with the relation between refraction index and density of SiO_2 foam shells is introduced, and the relation is analyzed according to formulas of Lorentz-Lorenz and Gladstone-Dale. The experimental result and measuring uncertainty evaluation indicate that the precision measurement of density of low density SiO_2 foam shells can be realized by using the vertical scanning interference technique and combining with Gladstone and Dale analysis method, and the measuring uncertainty is about 5%. (authors)

  14. A microbiological evaluation of SiO2-coated textiles in hospital interiors

    DEFF Research Database (Denmark)

    Mogensen, Jeppe; Jørgensen, Poul-Erik; Thomsen, Trine Rolighed

    2016-01-01

    . From this perspective, the purpose of this paper is therefore to address focus on alternative passive coatings that without actively killing the bacteria provide a hydrophobic and easy-to-clean textile surface. The paper relates to an in-situ study evaluating the effect and cleaning potential of SiO2...... contact plates through a three-week period. By determining the level of contamination on these surfaces, the study illustrates that the SiO2-coated textile is possible to clean to an acceptable level below the critical limit value of 2,5 Colony Forming Units (CFU) per cm2. In comparison, the traditional...

  15. Bond length contraction in Au nanocrystals formed by ion implantation into thin SiO2

    International Nuclear Information System (INIS)

    Kluth, P.; Johannessen, B.; Giraud, V.; Cheung, A.; Glover, C.J.; Azevedo, G. de M; Foran, G.J.; Ridgway, M.C.

    2004-01-01

    Au nanocrystals (NCs) fabricated by ion implantation into thin SiO 2 and annealing were investigated by means of extended x-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy. A bond length contraction was observed and can be explained by surface tension effects in a simple liquid-drop model. Such results are consistent with previous reports on nonembedded NCs implying a negligible influence of the SiO 2 matrix. Cumulant analysis of the EXAFS data suggests surface reconstruction or relaxation involving a further shortened bond length. A deviation from the octahedral closed shell structure is apparent for NCs of size 25 A

  16. Structural colors of the SiO2/polyethyleneimine thin films on poly(ethylene terephthalate) substrates

    International Nuclear Information System (INIS)

    Jia, Yanrong; Zhang, Yun; Zhou, Qiubao; Fan, Qinguo; Shao, Jianzhong

    2014-01-01

    The SiO 2 /polyethyleneimine (PEI) films with structural colors on poly(ethylene terephthalate) (PET) substrates were fabricated by an electrostatic self-assembly method. The morphology of the films was characterized by Scanning Electron Microscopy. The results showed that there was no distinguishable multilayered structure found of SiO 2 /PEI films. The optical behaviors of the films were investigated through the color photos captured by a digital camera and the color measurement by a multi-angle spectrophotometer. Different hue and brightness were observed at various viewing angles. The structural colors were dependent on the SiO 2 particle size and the number of assembly cycles. The mechanism of the structural colors generated from the assembled films was elucidated. The morphological structures and the optical properties proved that the SiO 2 /PEI film fabricated on PET substrate formed a homogeneous inorganic/organic SiO 2 /PEI composite layer, and the structural colors were originated from single thin film interference. - Highlights: • SiO 2 /PEI thin films were electrostatic self-assembled on PET substrates. • The surface morphology and optical behavior of the film were investigated. • The structural colors varied with various SiO 2 particle sizes and assembly cycles. • Different hue and lightness of SiO 2 /PEI film were observed at various viewing angles. • Structural color of the SiO 2 /PEI film originated from single thin film interference

  17. More accurate definition of liquation dome in Na2O-B2O3-SiO2 system

    International Nuclear Information System (INIS)

    Alekseeva, Z.D.; Mazurin, O.V.; Aver'yanov, V.I.; Galakhov, F.Ya.

    1977-01-01

    The liquation region in the system Na 2 O-B 2 O 3 -SiO 2 was investigated. The liquation temperatures were determined by the boundary of disappearance of opalescence in specimens with pre-induced opalescence. Extrapolation of the concentration dependences of the liquation temperature along sections with a constant SiO 2 content to a point indicates that with a SiO 2 content of 20-40% the liquation boundary in the system B 2 O 3 -SiO 2 hardly lies above 450 deg C

  18. Thickness and composition of ultrathin SiO2 layers on Si

    NARCIS (Netherlands)

    van der Marel, C; Verheijen, M.A.; Tamminga, Y; Pijnenburg, RHW; Tombros, N; Cubaynes, F

    2004-01-01

    Ultrathin SiO2 layers are of importance for the semiconductor industry. One of the techniques that can be used to determine the chemical composition and thickness of this type of layers is x-ray photoelectron spectroscopy (XPS). As shown by Seah and Spencer [Surf. Interface Anal. 33, 640 (2002)], it

  19. Enhanced Photocatalytic Activity of ZrO2-SiO2 Nanoparticles by Platinum Doping

    Directory of Open Access Journals (Sweden)

    Mohammad W. Kadi

    2013-01-01

    Full Text Available ZrO2-SiO2 mixed oxides were prepared via the sol-gel method. Photo-assisted deposition was utilized for doping the prepared mixed oxide with 0.1, 0.2, 0.3, and 0.4 wt% of Pt. XRD spectra showed that doping did not result in the incorporation of Pt within the crystal structure of the material. UV-reflectance spectrometry showed that the band gap of ZrO2-SiO2 decreased from 3.04 eV to 2.48 eV with 0.4 wt% Pt doping. The results show a specific surface area increase of 20%. Enhanced photocatalysis of Pt/ZrO2-SiO2 was successfully tested on photo degradation of cyanide under illumination of visible light. 100% conversion was achieved within 20 min with 0.3 wt% of Pt doped ZrO2-SiO2.

  20. Defect layer in SiO2-Sic interface proved by a slow positron beam

    International Nuclear Information System (INIS)

    Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Miyashita, A.; Suzuki, R.; Ohdaira, T.

    2006-01-01

    The structure of the SiO 2 -4ph-SiC interface layer produced by dry oxidation has been studied by positron annihilation spectroscopy using slow positron beams. From Doppler broadening measurements, the interface layer was clearly distinguished from the SiO 2 and SiC layers and was observed to be defective. At the interface layer, a single long positron lifetime of 451 ps, which is close to the second lifetime in the SiO 2 layer, was obtained, thus suggesting that the structure of the interface layer resembles an amorphous SiO 2 network. A comparison was made between the obtained electron momentum distribution at the interface layer and the theoretical calculation. It was found that positrons annihilate with oxygen valence electrons. By annealing after the oxidation, the annihilation probability of the positrons with oxygen valence electrons and the number of interface traps decreased in the same temperature range, thus suggesting a correlation between interface traps and positron annihilation sites

  1. Hazards of TiO2 and amorphous SiO2 nanoparticles

    NARCIS (Netherlands)

    Reijnders, L.; Kahn, H.A.; Arif, I.A.

    2012-01-01

    TiO2 and amorphous SiO2 nanoparticles have been described as ‘safe’, ‘non-toxic’ and ‘environment friendly’ in scientific literature. However, though toxicity data are far from complete, there is evidence that these nanoparticles are hazardous. TiO2 nanoparticles have been found hazardous to humans

  2. Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

    DEFF Research Database (Denmark)

    Leervad Pedersen, T.P.; Skov Jensen, J.; Chevallier, J.

    2005-01-01

    The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO2 thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can...

  3. Preparation of TiO2-SiO2 composite photocatalysts for environmental applications

    Czech Academy of Sciences Publication Activity Database

    Paušová, Š.; Krýsa, J.; Jirkovský, Jaromír; Prevot, V.; Mailhot, G.

    2014-01-01

    Roč. 89, č. 8 (2014), s. 1129-1135 ISSN 0268-2575 Institutional support: RVO:61388955 Keywords : photocatalysis * TiO2/SiO2 * composite Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.349, year: 2014

  4. Catalytic combustion of trichloroethylene over TiO2-SiO2 supported catalysts

    NARCIS (Netherlands)

    Kulazynski, M.; van Ommen, J.G.; Trawczynski, J.; Walendziewski, J.

    2002-01-01

    Combustion of trichloroethylene (TCE) on Cr2O3, V2O5, Pt or Pd catalysts supported on TiO2-SiO2 as a carrier has been investigated. It was found that oxide catalysts are very active but their activity quickly diminishes due to loss of the active component, especially at higher reaction temperatures

  5. Electrocatalytic oxidation of alcohols on single gold particles in highly ordered SiO2 cavities

    International Nuclear Information System (INIS)

    Li, Na; Zhou, Qun; Tian, Shu; Zhao, Hong; Li, Xiaowei; Adkins, Jason; Gu, Zhuomin; Zhao, Lili; Zheng, Junwei

    2013-01-01

    In the present work, we report a new and simple approach for preparing a highly ordered Au (1 1 1) nanoparticle (NP) array in SiO 2 cavities on indium-doped tin oxide (ITO) electrodes. We fabricated a SiO 2 cavity array on the surface of an ITO electrode using highly ordered self-assembly of polystyrene spheres as a template. Gold NPs were electrodeposited at the bottom of the SiO 2 cavities, and single gold NPs dominated with (1 1 1) facets were generated in each cavity by annealing the electrode at a high temperature. Such (1 1 1) facets were the predominate trait of the single gold particle which exhibited considerable electrocatalytic activity toward oxidation of methanol, ethanol, and glycerol. This has been attributed to the formation of incipient hydrous oxides at unusually low potential on the specific (1 1 1) facet of the gold particles. Moreover, each cavity of the SiO 2 possibly behaves as an independent electrochemical cell in which the methanol molecules are trapped; this produces an environment advantageous to catalyzing electrooxidation. The oxidation of methanol on the electrodes is a mixed control mechanism (both by diffusion and electrode kinetics). This strategy both provided an approach to study electrochemical reactions on a single particle in a microenvironment and may supply a way to construct alcohols sensors

  6. FeCl3.nano SiO2: An Efficient Heterogeneous Nano Catalyst for the ...

    African Journals Online (AJOL)

    NICO

    2012-05-28

    May 28, 2012 ... low cost, ease of preparation, and catalyst recycling.3,4 Among various solid .... FeCl3-SiO2 (np) to produce 1,8-dioxo-octahydro-xanthenes. RESEARCH ..... 38 G. Song, B. Wang, H. Luo and L. Yang, Catal. Commun., 2007, 8 ...

  7. Enhanced field emission properties of carbon nanotube bundles confined in SiO2 pits

    Science.gov (United States)

    Lim, Yu Dian; Grapov, Dmitry; Hu, Liangxing; Kong, Qinyu; Tay, Beng Kang; Labunov, Vladimir; Miao, Jianmin; Coquet, Philippe; Aditya, Sheel

    2018-02-01

    It has been widely reported that carbon nanotubes (CNTs) exhibit superior field emission (FE) properties due to their high aspect ratios and unique structural properties. Among the various types of CNTs, random growth CNTs exhibit promising FE properties due to their reduced inter-tube screening effect. However, growing random growth CNTs on individual catalyst islands often results in spread out CNT bundles, which reduces overall field enhancement. In this study, significant improvement in FE properties in CNT bundles is demonstrated by confining them in microfabricated SiO2 pits. Growing CNT bundles in narrow (0.5 μm diameter and 2 μm height) SiO2 pits achieves FE current density of 1-1.4 A cm-2, which is much higher than for freestanding CNT bundles (76.9 mA cm-2). From the Fowler Nordheim plots, confined CNT bundles show a higher field enhancement factor. This improvement can be attributed to the reduced bundle diameter by SiO2 pit confinement, which yields bundles with higher aspect ratios. Combining the obtained outcomes, it can be conclusively summarized that confining CNTs in SiO2 pits yields higher FE current density due to the higher field enhancement of confined CNTs.

  8. SiO2 Glass Density to Lower-Mantle Pressures

    DEFF Research Database (Denmark)

    Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste

    2017-01-01

    and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range...... for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60...... GPa. The density data present two discontinuities at similar to 17 and similar to 60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at similar to 40 GPa, and its density...

  9. Theory of Al2O3 incorporation in SiO2

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2002-01-01

    Different possible forms of Al2O3 units in a SiO2 network are studied theoretically within the framework of density-functional theory. Total-energy differences between the various configurations are obtained, and simple thermodynamical arguments are used to provide an estimate of their relative...

  10. Crystallization kinetics of BaO-Al2O3-SiO2 glasses

    Science.gov (United States)

    Bansal, Narottam P.; Hyatt, Mark J.

    1989-01-01

    Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.

  11. CoFe2O4-SiO2 Composites: Preparation and Magnetodielectric Properties

    Directory of Open Access Journals (Sweden)

    T. Ramesh

    2016-01-01

    Full Text Available Cobalt ferrite (CoFe2O4 and silica (SiO2 nanopowders have been prepared by the microwave hydrothermal (M-H method using metal nitrates as precursors of CoFe2O4 and tetraethyl orthosilicate as a precursor of SiO2. The synthesized powders were characterized by XRD and FESEM. The (100-x (CoFe2O4 + xSiO2 (where x = 0%, 10%, 20%, and 30% composites with different weight percentages have been prepared using ball mill method. The composite samples were sintered at 800°C/60 min using the microwave sintering method and then their structural and morphological studies were investigated using X-ray diffraction (XRD, Fourier transformation infrared (FTIR spectra, and scanning electron microscopy (SEM, respectively. The effect of SiO2 content on the magnetic and electrical properties of CoFe2O4/SiO2 nanocomposites has been studied via the magnetic hysteresis loops, complex permeability, permittivity spectra, and DC resistivity measurements. The synthesized nanocomposites with adjustable grain sizes and controllable magnetic properties make the applicability of cobalt ferrite even more versatile.

  12. Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

    Science.gov (United States)

    Gasvoda, Ryan J; van de Steeg, Alex W; Bhowmick, Ranadeep; Hudson, Eric A; Agarwal, Sumit

    2017-09-13

    Surface phenomena during atomic layer etching (ALE) of SiO 2 were studied during sequential half-cycles of plasma-assisted fluorocarbon (CF x ) film deposition and Ar plasma activation of the CF x film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CF x deposition half-cycle from a C 4 F 8 /Ar plasma show that an atomically thin mixing layer is formed between the deposited CF x layer and the underlying SiO 2 film. Etching during the Ar plasma cycle is activated by Ar + bombardment of the CF x layer, which results in the simultaneous removal of surface CF x and the underlying SiO 2 film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CF x deposition, which combined with an ultrathin CF x layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CF x film, ∼3-4 Å of SiO 2 was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CF x layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CF x on reactor walls leads to a gradual increase in the etch per cycle.

  13. Efficient photocatalytic activity with carbon-doped SiO2 nanoparticles

    KAUST Repository

    Zhang, Dongen

    2013-01-01

    Photocatalysis provides a \\'green\\' approach to completely eliminate various kinds of contaminants that are fatal for current environmental and energy issues. Semiconductors are one of the most frequently used photocatalysts as they can absorb light over a wide spectral range. However, it is also well known that naked SiO2 is not an efficient photocatalyst due to its relatively large band gap, which could only absorb shortwave ultraviolet light. In this report, nanoscale particles of carbon-doped silicon dioxide (C-doped SiO2) for use in photocatalysis were successfully prepared by a facile one-pot thermal process using tetraethylorthosilicate (TEOS) as the source of both silicon and carbon. These particles were subsequently characterized by thermogravimetric analysis, X-ray diffraction, standard and high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The C-doped SiO2 displayed outstanding photocatalytic properties, as evidenced by its catalysis of Rhodamine B degradation under near-UV irradiation. We propose that carbon doping of the SiO2 lattice creates new energy states between the bottom of the conduction band and the top of the valence band, which narrows the band gap of the material. As a result, the C-doped SiO2 nanoparticles exhibit excellent photocatalytic activities in a neutral environment. The novel synthesis reported herein for this material is both energy efficient and environmentally friendly and as such shows promise as a technique for low-cost, readily scalable industrial production. © 2013 The Royal Society of Chemistry.

  14. Ultrathin Microporous SiO2 Membranes Photodeposited on Hydrogen Evolving Catalysts Enabling Overall Water Splitting

    KAUST Repository

    Bau, Jeremy A.

    2017-10-17

    Semiconductor systems for photocatalytic overall water splitting into H2 and O2 gases typically require metal cocatalyst particles, such as Pt, to efficiently catalyze H2 evolution. However, such metal catalyst surfaces also serve as recombination sites for H2 and O2, forming H2O. We herein report the photon-induced fabrication of microporous SiO2 membranes that can selectively restrict passage of O2 and larger hydrated ions while allowing penetration of protons, water, and H2. The SiO2 layers were selectively photodeposited on Pt nanoparticles on SrTiO3 photocatalyst by using tetramethylammonium (TMA) as a structure-directing agent (SDA), resulting in the formation of core–shell Pt@SiO2 cocatalysts. The resulting photocatalyst exhibited both improved overall water splitting performance under irradiation and with no H2/O2 recombination in the dark. The function of the SiO2 layers was investigated electrochemically by fabricating the SiO2 layers on a Pt electrode via an analogous cathodic deposition protocol. The uniform, dense, yet amorphous layers possess microporosity originating from ring structures formed during the hydrolysis of the silicate precursor in the presence of TMA, suggesting a double-role for TMA in coordinating silicate to cathodic surfaces and in creating a microporous material. The resulting layers were able to function as a molecular sieve, allowing for exclusive H2 generation while excluding unwanted side reactions by O2 or ferricyanide. The SiO2 layer is stable for extended periods of time in photocatalytic conditions, demonstrating promise as a nontoxic material for selective H2 evolution.

  15. Ultrathin Microporous SiO2 Membranes Photodeposited on Hydrogen Evolving Catalysts Enabling Overall Water Splitting

    KAUST Repository

    Bau, Jeremy A.; Takanabe, Kazuhiro

    2017-01-01

    Semiconductor systems for photocatalytic overall water splitting into H2 and O2 gases typically require metal cocatalyst particles, such as Pt, to efficiently catalyze H2 evolution. However, such metal catalyst surfaces also serve as recombination sites for H2 and O2, forming H2O. We herein report the photon-induced fabrication of microporous SiO2 membranes that can selectively restrict passage of O2 and larger hydrated ions while allowing penetration of protons, water, and H2. The SiO2 layers were selectively photodeposited on Pt nanoparticles on SrTiO3 photocatalyst by using tetramethylammonium (TMA) as a structure-directing agent (SDA), resulting in the formation of core–shell Pt@SiO2 cocatalysts. The resulting photocatalyst exhibited both improved overall water splitting performance under irradiation and with no H2/O2 recombination in the dark. The function of the SiO2 layers was investigated electrochemically by fabricating the SiO2 layers on a Pt electrode via an analogous cathodic deposition protocol. The uniform, dense, yet amorphous layers possess microporosity originating from ring structures formed during the hydrolysis of the silicate precursor in the presence of TMA, suggesting a double-role for TMA in coordinating silicate to cathodic surfaces and in creating a microporous material. The resulting layers were able to function as a molecular sieve, allowing for exclusive H2 generation while excluding unwanted side reactions by O2 or ferricyanide. The SiO2 layer is stable for extended periods of time in photocatalytic conditions, demonstrating promise as a nontoxic material for selective H2 evolution.

  16. A novel fabrication of a high performance SiO(2)-graphene oxide (GO) nanohybrids: Characterization of thermal properties of epoxy nanocomposites filled with SiO(2)-GO nanohybrids.

    Science.gov (United States)

    Haeri, S Z; Ramezanzadeh, B; Asghari, M

    2017-05-01

    In this study it has been aimed to enhance the thermal resistance of epoxy coating through incorporation of SiO 2 -GO nanohybrids. SiO 2 -GO nanohybrids were synthesized through one-step sol-gel route using a mixture of Tetraethylorthosilane (TEOS) and 3-Aminopropyl triethoxysilane (APTES) silanes. The SiO 2 -GO nanohybrids were prepared at various hydrolysis times of 24, 48 and 72h. Then 0.2wt.% of GO and SiO 2 -GO nanohybrids were separately incorporated into the epoxy coating. Results revealed that amino functionalized SiO 2 nanoparticles with particle size around 20-30nm successfully synthesized on the basal plane of GO. Results showed significant improvement of dispersion and interfacial interactions between nanohybrids and epoxy composite arising from covalent bonding between the SiO 2 -GO and the epoxy matrix. It was found that the thermal resistance of SiO 2 -GO nanohybrids and SiO 2 -GO/Epoxy nanocomposite was noticeably higher than GO and epoxy matrix, respectively. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Printing Semiconductor-Insulator Polymer Bilayers for High-Performance Coplanar Field-Effect Transistors.

    Science.gov (United States)

    Bu, Laju; Hu, Mengxing; Lu, Wanlong; Wang, Ziyu; Lu, Guanghao

    2018-01-01

    Source-semiconductor-drain coplanar transistors with an organic semiconductor layer located within the same plane of source/drain electrodes are attractive for next-generation electronics, because they could be used to reduce material consumption, minimize parasitic leakage current, avoid cross-talk among different devices, and simplify the fabrication process of circuits. Here, a one-step, drop-casting-like printing method to realize a coplanar transistor using a model semiconductor/insulator [poly(3-hexylthiophene) (P3HT)/polystyrene (PS)] blend is developed. By manipulating the solution dewetting dynamics on the metal electrode and SiO 2 dielectric, the solution within the channel region is selectively confined, and thus make the top surface of source/drain electrodes completely free of polymers. Subsequently, during solvent evaporation, vertical phase separation between P3HT and PS leads to a semiconductor-insulator bilayer structure, contributing to an improved transistor performance. Moreover, this coplanar transistor with semiconductor-insulator bilayer structure is an ideal system for injecting charges into the insulator via gate-stress, and the thus-formed PS electret layer acts as a "nonuniform floating gate" to tune the threshold voltage and effective mobility of the transistors. Effective field-effect mobility higher than 1 cm 2 V -1 s -1 with an on/off ratio > 10 7 is realized, and the performances are comparable to those of commercial amorphous silicon transistors. This coplanar transistor simplifies the fabrication process of corresponding circuits. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Effects of Mev Si Ions and Thermal Annealing on Thermoelectric and Optical Properties of SiO2/SiO2+Ge Multi-nanolayer thin Films

    Science.gov (United States)

    Budak, S.; Alim, M. A.; Bhattacharjee, S.; Muntele, C.

    Thermoelectric generator devices have been prepared from 200 alternating layers of SiO2/SiO2+Ge superlattice films using DC/RF magnetron sputtering. The 5 MeV Si ionsbombardmenthasbeen performed using the AAMU Pelletron ion beam accelerator to formquantum dots and / or quantum clusters in the multi-layer superlattice thin films to decrease the cross-plane thermal conductivity, increase the cross-plane Seebeck coefficient and increase the cross-plane electrical conductivity to increase the figure of merit, ZT. The fabricated devices have been annealed at the different temperatures to tailor the thermoelectric and optical properties of the superlattice thin film systems. While the temperature increased, the Seebeck coefficient continued to increase and reached the maximum value of -25 μV/K at the fluenceof 5x1013 ions/cm2. The decrease in resistivity has been seen between the fluence of 1x1013 ions/cm2 and 5x1013 ions/cm2. Transport properties like Hall coefficient, density and mobility did not change at all fluences. Impedance spectroscopy has been used to characterize the multi-junction thermoelectric devices. The loci obtained in the C*-plane for these data indicate non-Debye type relaxation displaying the presence of the depression parameter.

  19. Ethanol-to-Butadiene Conversion over SiO2-MgO Catalysts: Synthesis-Structure-Performance Relationships

    NARCIS (Netherlands)

    Angelici, C.

    2015-01-01

    The work presented in this PhD Thesis provides new insights into the underlying reasons that make SiO2-MgO materials excellent catalysts for the ethanol-to-butadiene Lebedev process. In particular, the preparation technique of choice affects the structural properties of the resulting SiO2-MgO

  20. Sensitizing effects of ZnO quantum dots on red-emitting Pr3+-doped SiO2 phosphor

    CSIR Research Space (South Africa)

    Mbule, PS

    2012-05-01

    Full Text Available In this study, red cathodoluminescence (CL) ( emission=614 nm) was observed from Pr3+ ions in a glassy (amorphous) SiO2 host. This emission was enhanced considerably when ZnO quantum dots (QDs) were incorporated in the SiO2:Pr3+ suggesting...

  1. Preparation of Raspberry-like Superhydrophobic SiO2 Particles by Sol-gel Method and Its Potential Applications

    Directory of Open Access Journals (Sweden)

    Xu Gui-Long

    2011-12-01

    Full Text Available Raspberry‐like SiO2 particles with a nano‐micro‐binary structure were prepared by a simple sol‐gel method using tetraethoxysilane (TEOS and methyltriethoxysilane (MTES as precursors. The chemical components and morphology of the SiO2 particles were characterized by Fourier transform infrared spectroscopy (FT‐IR and a Transmission electron microscope (TEM. The surface topography and wetting behaviour of the raspberry‐like SiO2 surface were observed with a Scanning electron microscope (SEM and studied by the water/oil contact angle (CA, respectively. The thermal stability of the prepared SiO2 particles was characterized by TGA analysis. The results show that the highly dispersed SiO2 particles initially prepared by the sol‐gel method turn into raspberry‐like particles with during the aging process. The raspberry‐like SiO2 particles show superhydrophobicity and superoleophilicity across a wide range of pH values. The SiO2 particles were thermally stable up to 475°C, while above this temperature the hydrophobicity decreases and finally becomes superhydrophobic when the temperature reaches 600°C. The raspberry‐like SiO2 particles which were prepared have potential applications in the fields of superhydrophobic surfaces, water‐oil separation, anti‐corrosion and fluid transportation.

  2. The electrorheological properties of nano-sized SiO2 particle materials doped with rare earths

    International Nuclear Information System (INIS)

    Liu Yang; Liao Fuhui; Li Junran; Zhang Shaohua; Chen Shumei; Wei Chenguan; Gao Song

    2006-01-01

    Electrorheological (ER) materials of pure SiO 2 and SiO 2 doped with rare earths (RE = Ce, Gd, Y) (non-metallic glasses (silicates)) were prepared using Na 2 SiO 3 and RECl 3 as starting materials. The electrorheological properties are not enhanced by all rare earth additions. The material doped with Ce exhibits the best ER performance

  3. Room-Temperature Voltage Stressing Effects on Resistive Switching of Conductive-Bridging RAM Cells with Cu-Doped SiO2 Films

    Directory of Open Access Journals (Sweden)

    Jian-Yang Lin

    2014-01-01

    Full Text Available SiO2 or Cu-doped SiO2 (Cu:SiO2 insulating films combined with Cu or W upper electrodes were constructed on the W/Si substrates to form the conductive-bridging RAM (CB-RAM cells. The CB-RAMs were then subjected to a constant-voltage stressing (CVS at room temperature. The experimental results show that the room-temperature CVS treatment can effectively affect the current conduction behavior and stabilize the resistive switching of the memory cells. After the CVS, the current conduction mechanisms in the high resistance state during the set process of the Cu/Cu:SiO2/W cell can be changed from Ohm’s law and the space charge limited conduction to Ohm’s law, the Schottky emission, and the space charge limited conduction. Presumably, it is due to the breakage of the conduction filaments during the CVS treatment that the conduction electrons cannot go back to the back electrode smoothly.

  4. Cleaning Challenges of High-κ/Metal Gate Structures

    KAUST Repository

    Hussain, Muhammad Mustafa; Shamiryan, Denis G.; Paraschiv, Vasile; Sano, Kenichi; Reinhardt, Karen A.

    2010-01-01

    High-κ/metal gates are used as transistors for advanced logic applications to improve speed and eliminate electrical issues associated with polySi and SiO2 gates. Various integration schemes are possible and will be discussed, such as dual gate, gate-first, and gate-last, both of which require specialized cleaning and etching steps. Specific areas of discussion will include cleaning and conditioning of the silicon surface, forming a high-quality chemical oxide, removal of the high-κ dielectric with selectivity to the SiO2 layer, cleaning and residue removal after etching, and prevention of galvanic corrosion during cleaning. © 2011 Scrivener Publishing LLC. All rights reserved.

  5. Cleaning Challenges of High-κ/Metal Gate Structures

    KAUST Repository

    Hussain, Muhammad Mustafa

    2010-12-20

    High-κ/metal gates are used as transistors for advanced logic applications to improve speed and eliminate electrical issues associated with polySi and SiO2 gates. Various integration schemes are possible and will be discussed, such as dual gate, gate-first, and gate-last, both of which require specialized cleaning and etching steps. Specific areas of discussion will include cleaning and conditioning of the silicon surface, forming a high-quality chemical oxide, removal of the high-κ dielectric with selectivity to the SiO2 layer, cleaning and residue removal after etching, and prevention of galvanic corrosion during cleaning. © 2011 Scrivener Publishing LLC. All rights reserved.

  6. On the Evaluation of Gate Dielectrics for 4H-SiC Based Power MOSFETs

    Directory of Open Access Journals (Sweden)

    Muhammad Nawaz

    2015-01-01

    Full Text Available This work deals with the assessment of gate dielectric for 4H-SiC MOSFETs using technology based two-dimensional numerical computer simulations. Results are studied for variety of gate dielectric candidates with varying thicknesses using well-known Fowler-Nordheim tunneling model. Compared to conventional SiO2 as a gate dielectric for 4H-SiC MOSFETs, high-k gate dielectric such as HfO2 reduces significantly the amount of electric field in the gate dielectric with equal gate dielectric thickness and hence the overall gate current density. High-k gate dielectric further reduces the shift in the threshold voltage with varying dielectric thicknesses, thus leading to better process margin and stable device operating behavior. For fixed dielectric thickness, a total shift in the threshold voltage of about 2.5 V has been observed with increasing dielectric constant from SiO2 (k=3.9 to HfO2 (k=25. This further results in higher transconductance of the device with the increase of the dielectric constant from SiO2 to HfO2. Furthermore, 4H-SiC MOSFETs are found to be more sensitive to the shift in the threshold voltage with conventional SiO2 as gate dielectric than high-k dielectric with the presence of interface state charge density that is typically observed at the interface of dielectric and 4H-SiC MOS surface.

  7. Ultra-low power thin film transistors with gate oxide formed by nitric acid oxidation method

    International Nuclear Information System (INIS)

    Kobayashi, H.; Kim, W. B.; Matsumoto, T.

    2011-01-01

    We have developed a low temperature fabrication method of SiO 2 /Si structure by use of nitric acid, i.e., nitric acid oxidation of Si (NAOS) method, and applied it to thin film transistors (TFT). A silicon dioxide (SiO 2 ) layer formed by the NAOS method at room temperature possesses 1.8 nm thickness, and its leakage current density is as low as that of thermally grown SiO 2 layer with the same thickness formed at ∼900 deg C. The fabricated TFTs possess an ultra-thin NAOS SiO 2 /CVD SiO 2 stack gate dielectric structure. The ultrathin NAOS SiO 2 layer effectively blocks a gate leakage current, and thus, the thickness of the gate oxide layer can be decreased from 80 to 20 nm. The thin gate oxide layer enables to decrease the operation voltage to 2 V (cf. the conventional operation voltage of TFTs with 80 nm gate oxide: 12 V) because of the low threshold voltages, i.e., -0.5 V for P-ch TFTs and 0.5 V for N-ch TFTs, and thus the consumed power decreases to 1/36 of that of the conventional TFTs. The drain current increases rapidly with the gate voltage, and the sub-threshold voltage is ∼80 mV/dec. The low sub-threshold swing is attributable to the thin gate oxide thickness and low interface state density of the NAOS SiO 2 layer. (authors)

  8. Enhanced formation of Ge nanocrystals in Ge : SiO2 layers by swift heavy ions

    International Nuclear Information System (INIS)

    Antonova, I V; Volodin, V A; Marin, D M; Skuratov, V A; Smagulova, S A; Janse van Vuuren, A; Neethling, J; Jedrzejewski, J; Balberg, I

    2012-01-01

    In this paper we report the ability of swift heavy Xe ions with an energy of 480 MeV and a fluence of 10 12 cm -2 to enhance the formation of Ge nanocrystals within SiO 2 layers with variable Ge contents. These Ge-SiO 2 films were fabricated by the co-sputtering of Ge and quartz sources which followed various annealing procedures. In particular, we found that the irradiation of the Ge : SiO 2 films with subsequent annealing at 500 °C leads to the formation of a high concentration of nanocrystals (NCs) with a size of 2-5 nm, whereas without irradiation only amorphous inclusions were observed. This effect, as evidenced by Raman spectra, is enhanced by pre-irradiation at 550 °C and post-irradiation annealing at 600 °C, which also leads to the observation of room temperature visible photoluminescence. (paper)

  9. Pulsed ion-beam induced nucleation and growth of Ge nanocrystals on SiO2

    International Nuclear Information System (INIS)

    Stepina, N. P.; Dvurechenskii, A. V.; Armbrister, V. A.; Kesler, V. G.; Novikov, P. L.; Gutakovskii, A. K.; Kirienko, V. V.; Smagina, Zh. V.; Groetzschel, R.

    2007-01-01

    Pulsed low-energy (200 eV) ion-beam induced nucleation during Ge deposition on thin SiO 2 film was used to form dense homogeneous arrays of Ge nanocrystals. The ion-beam action is shown to stimulate the nucleation of Ge nanocrystals when being applied after thin Ge layer deposition. Temperature and flux variation was used to optimize the nanocrystal size and array density required for memory device. Kinetic Monte Carlo simulation shows that ion impacts open an additional channel of atom displacement from a nanocrystal onto SiO 2 surface. This results both in a decrease in the average nanocrystal size and in an increase in nanocrystal density

  10. Refractories in the Al2O3-ZrO2-SiO2 system

    International Nuclear Information System (INIS)

    Banerjee, S.P.; Bhadra, A.K.; Sircar, N.R.

    1978-01-01

    The effect of addition of ZrO 2 in different proportions in the refractories of the Al 2 O 3 -SiO 2 system was studied. The investigation was confined to two broad ranges of compositions incorporating zirconia (15-30 percent and 80-85 percent) in the Al 2 O 3 -ZrO 2 -SiO 2 system. The overall attainment of properties is dependent upon the mode of fabrication and firing, and bears a relationship with the phase assemblages and the relative proportion thereof. Of the different characteristics, the trend of dissociation of zircon has been found to be specially significant vis-a-vis the temperature of firing and thermal shock resistance. Reassociation of the dissociated products has been ascribed to bring forth improved resistance to thermal spalling. The different products developed during this investigation are considered to be very promising which find useful applications in view of the properties attained by them. (auth.)

  11. Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium

    Directory of Open Access Journals (Sweden)

    Liliana Kotte

    2014-12-01

    Full Text Available This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al in comparison to an anodizing process (NaTESi process. The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

  12. Electron irradiation response on Ge and Al-doped SiO 2 optical fibres

    Science.gov (United States)

    Yaakob, N. H.; Wagiran, H.; Hossain, I.; Ramli, A. T.; Bradley, D. A.; Hashim, S.; Ali, H.

    2011-05-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  13. Formation of nucleoplasmic protein aggregates impairs nuclear function in response to SiO2 nanoparticles

    International Nuclear Information System (INIS)

    Chen Min; Mikecz, Anna von

    2005-01-01

    Despite of their exponentially growing use, little is known about cell biological effects of nanoparticles. Here, we report uptake of silica (SiO 2 ) nanoparticles to the cell nucleus where they induce aberrant clusters of topoisomerase I (topo I) in the nucleoplasm that additionally contain signature proteins of nuclear domains, and protein aggregation such as ubiquitin, proteasomes, cellular glutamine repeat (polyQ) proteins, and huntingtin. Formation of intranuclear protein aggregates (1) inhibits replication, transcription, and cell proliferation; (2) does not significantly alter proteasomal activity or cell viability; and (3) is reversible by Congo red and trehalose. Since SiO 2 nanoparticles trigger a subnuclear pathology resembling the one occurring in expanded polyglutamine neurodegenerative disorders, we suggest that integrity of the functional architecture of the cell nucleus should be used as a read out for cytotoxicity and considered in the development of safe nanotechnology

  14. Fourier transform infrared spectroscopic study of gamma irradiated SiO2 nanoparticles

    Science.gov (United States)

    Huseynov, Elchin; Garibov, Adil; Mehdiyeva, Ravan; Huseynova, Efsane

    2018-03-01

    In the present work, nano SiO2 particles are investigated before and after gamma irradiation (25, 50, 75, 100 and 200 kGy) using Fourier transform infrared (FTIR) spectroscopy method for the wavenumber between 400-4000 cm-1. It is found that as a result of spectroscopic analysis, five new peaks have appeared after gamma radiation. Two of new obtained peaks (which are located at 687 cm-1 and 2357 cm-1 of wavenumber) were formed as a result of gamma radiation interaction with Si-O bonds. Another three new peaks (peaks appropriate to 941, 2052 and 2357 cm-1 values of wavenumber) appear as a result of interaction of water with nano SiO2 particles after gamma irradiation. It has been defined as asymmetrical bending vibration, symmetrical bending vibration, symmetrical stretching vibration and asymmetrical stretching vibration of Si-O bonds appropriate to peaks.

  15. Annealing characteristics of SiO2-Si structures after incoherent light pulse processing

    International Nuclear Information System (INIS)

    Sieber, N.; Klabes, R.; Voelskow, M.; Fenske, F.

    1982-01-01

    The behaviour of oxide charges and interface charges in boron implanted and non-implanted SiO 2 -Si structures as well as the electrical activation of the dopants by the action of incoherent light pulses was studied. Depth profiles of electrically active boron ions are presented for different annealing conditions as measured by the pulsed C-V method. It can be concluded that exposure of MOS structures to intense radiation of flash lamps does not increase the fixed charge and the fast state density at the SiO 2 -Si interface if optimal annealing conditions (energy densities) are employed. Low dose boron implanted silicon can be electrically activated without diffusion or segregation of dopants

  16. Diffusion limited Cu and Au nanocrystal formation in thin film SiO2

    International Nuclear Information System (INIS)

    Johannessen, B.; Kluth, P.; Glover, C.J.; Foran, G.J.; Ridgway, M.C.

    2006-01-01

    Elemental Cu and Au nanocrystals (NCs) were produced by high-energy ion-implantations into amorphous silica (SiO 2 ) and subsequent thermal annealing. By a combination of X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) we confirm both NC species to have the bulk face-centered cubic phase and estimate their average diameter. We concentrate on the investigation of the concentration and size-dependent coordination number (China) of these matrix embedded NCs utilising extended X-ray absorption fine structure (EXAFS) spectroscopy. The CN is found to be suppressed compared to that of a bulk standard. The CN in Au NCs is found to be lower than that of Cu NCs in agreement with smaller average Au NC sizes. We explain this difference by the difference in diffusivity for the two atomic species in SiO 2

  17. Electron irradiation response on Ge and Al-doped SiO2 optical fibres

    International Nuclear Information System (INIS)

    Yaakob, N.H.; Wagiran, H.; Hossain, I.; Ramli, A.T.; Bradley, D.A; Hashim, S.; Ali, H.

    2011-01-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  18. Microwave absorption properties and mechanism of cagelike ZnO /SiO2 nanocomposites

    Science.gov (United States)

    Cao, Mao-Sheng; Shi, Xiao-Ling; Fang, Xiao-Yong; Jin, Hai-Bo; Hou, Zhi-Ling; Zhou, Wei; Chen, Yu-Jin

    2007-11-01

    In this paper, cagelike ZnO /SiO2 nanocomposites were prepared and their microwave absorption properties were investigated in detail. Dielectric constants and losses of the pure cagelike ZnO nanostructures were measured in a frequency range of 8.2-12.4GHz. The measured results indicate that the cagelike ZnO nanostructures are low-loss material for microwave absorption in X band. However, the cagelike ZnO /SiO2 nanocomposites exhibit a relatively strong attenuation to microwave in X band. Such strong absorption is related to the unique geometrical morphology of the cagelike ZnO nanostructures in the composites. The microcurrent network can be produced in the cagelike ZnO nanostructures, which contributes to the conductive loss.

  19. XPS studies of SiO2 surface layers formed by oxygen ion implantation into silicon

    International Nuclear Information System (INIS)

    Schulze, D.; Finster, J.

    1983-01-01

    SiO 2 surface layers of 160 nm thickness formed by 16 O + ion implantation into silicon are examined by X-ray photoelectron spectroscopy measurements into the depth after a step-by-step chemical etching. The chemical nature and the thickness of the transition layer were determined. The results of the XPS measurements show that the outer surface and the bulk of the layers formed by oxygen implantation and subsequent high temperature annealing consist of SiO 2 . There is no evidence for Si or SiO/sub x/ (0 2 and Si is similar to that of thin grown oxide layers. Only its thickness is somewhat larger than in thermal oxide

  20. Density gradient in SiO 2 films on silicon as revealed by positron annihilation spectroscopy

    Science.gov (United States)

    Revesz, A. G.; Anwand, W.; Brauer, G.; Hughes, H. L.; Skorupa, W.

    2002-06-01

    Positron annihilation spectroscopy of thermally grown and deposited SiO 2 films on silicon shows in a non-destructive manner that these films have a gradient in their density. The gradient is most pronounced for the oxide grown in dry oxygen. Oxidation in water-containing ambient results in an oxide with reduced gradient, similarly to the gradient in the deposited oxide. These observations are in accordance with earlier optical and other studies using stepwise etching or a set of samples of varying thickness. The effective oxygen charge, which is very likely one of the reasons for the difference in the W parameters of silica glass and quartz crystal, could be even higher at some localized configurations in the SiO 2 films resulting in increased positron trapping.

  1. Effect of annealing induced residual stress on the resonance frequency of SiO2 microcantilevers

    Science.gov (United States)

    Balasubramanian, S.; Prabakar, K.; Tripura Sundari, S.

    2018-04-01

    In the present work, effect of residual stress, induced due to annealing of SiO2 microcantilevers (MCs) on their resonance frequency is studied. SiO2MCs of various dimensions were fabricated using direct laser writer & wet chemical etching method and were annealed at 800 °C in oxygen environment, post release. The residual stress was estimated from the deflection profile of the MCs measured using 3D optical microscope, before and after annealing. Resonance frequency of the MCs was measured using nano-vibration analyzer and was found to change after annealing. Further the frequency shift was found to depend on the MC dimensions. This is attributed to the large stress gradients induced by annealing and associated stiffness changes.

  2. Experimental observations of the chemistry of the SiO2/Si interface

    Science.gov (United States)

    Grunthaner, F. J.; Maserjian, J.

    1977-01-01

    Changes in silicon surface preparation prior to thermal oxidation are shown to leave a signature by altering the final SiO2/Si interface structure. Surface analytical techniques, including XPS, static SIMS, ion milling, and newly developed wet-chemical profiling procedures are used to obtain detailed information on the chemical structure of the interface. The oxides are shown to be essentially SiO2 down to a narrow transitional interface layer (3-7 A). A number of discrete chemical species are observed in this interface layer, including different silicon bonds (e.g., C-, OH-, H-) and a range of oxidation states of silicon (0 to +4). The effect of surface preparation and the observed chemical species are correlated with oxide growth rate, surface-state density, and flatband shifts after irradiation.

  3. A novel growth mode of alkane films on a SiO2 surface

    DEFF Research Database (Denmark)

    Mo, H.; Taub, H.; Volkmann, U.G.

    2003-01-01

    on the SiO2 surface with the long-axis of the C32 molecules oriented parallel to the interface followed by a C32 monolayer with the long-axis perpendicular to it. Finally, preferentially oriented bulk particles nucleate having two different crystal structures. This growth model differs from that found...... previously for shorter alkanes deposited from the vapor phase onto solid surfaces....

  4. Positron mobility in thermally grown SiO2 measured by Doppler broadening technique

    International Nuclear Information System (INIS)

    Kong, Y.; Leung, T.C.; Asoka-Kumar, P.; Nielsen, B.; Lynn, K.G.

    1991-01-01

    The positron mobility in thermally grown SiO 2 is deduced from Doppler broadening lineshape data on a metal-oxide-semiconductor sample for positrons implanted into the oxide layer. The fitted mobility is ∼13(10)x10 -3 cm 2 /s V. This value is between that of the electron and hole mobilities in the same system and is two orders of magnitude smaller than the previous estimate from positron measurements

  5. Study of hydrogen interaction with SiO2/Si(100) system using positrons

    International Nuclear Information System (INIS)

    Asoka-Kumar, P.; Lynn, K.G.; Leung, T.C.; Nielsen, B.; Wu, X.Y.

    1991-01-01

    We describe positron annihilation studies of SiO 2 /Si(100) structures having 100-nm-thick oxide grown by plasma enhanced chemical vapor deposition. A normalized shape parameter is used to characterize the positron annihilation spectra. Activation and passivation of interface states by atomic hydrogen are demonstrated by repeated vacuum anneal and atomic hydrogen exposure. Hydrogen activation energy is derived for one of the samples as 2.02±0.07 eV

  6. Effect of SiO2 Overlayer on WO3 Sensitivity to Ammonia

    Directory of Open Access Journals (Sweden)

    Vibha Srivastava

    2010-06-01

    Full Text Available Ammonia gas sensing properties of tungsten trioxide thick film sensor was investigated. The doping of noble catalysts such as Pt, Pd, Au enhanced the gas sensitivity. Platinum doping was found to result in highest sensitivity. Remarkable sensitivity enhancement was realized by coating WO3 thick film sensors with SiO2 overlayer. Sol gel process derived silica overlayer increased ammonia gas sensitivity for doped as well as undoped sensor.

  7. Characterization of Ultra thin chromium layers deposited ou to SiO2 using the Le-PIXE and the RB S techniques

    International Nuclear Information System (INIS)

    Zahraman, K.; Nsouli, B.; Roumie, M.

    2007-01-01

    In this paper, we demonstrate the ability of the Le-PIXE (Low Energy PIXE) technique, using proton energies < 1 MeV, for the monitoring of the thickness and the thickness uniformity of ultra thin (0.5 nm < t < 20 nm) chromium layers deposited onto quartz substrates. Chromium is a good candidate for obtaining conductive ultra thin layers on insulator substrates such as quartz (SiO2). The resistivity of such layers is highly related to the quality of the deposited chromium film. In order to optimize the deposition process, there is a need for rapid and accurate monitoring of such films (film thickness, thickness uniformity over a big surface...). The acquisition time needed to obtain results with less than 3-4 % precision was 5 minutes for the thinnest layers. The validation for the use of the Le-PIXE technique was checked by means of conventional RB S technique.

  8. Strong piezoelectricity in single-layer graphene deposited on SiO2 grating substrates.

    Science.gov (United States)

    da Cunha Rodrigues, Gonçalo; Zelenovskiy, Pavel; Romanyuk, Konstantin; Luchkin, Sergey; Kopelevich, Yakov; Kholkin, Andrei

    2015-06-25

    Electromechanical response of materials is a key property for various applications ranging from actuators to sophisticated nanoelectromechanical systems. Here electromechanical properties of the single-layer graphene transferred onto SiO2 calibration grating substrates is studied via piezoresponse force microscopy and confocal Raman spectroscopy. The correlation of mechanical strains in graphene layer with the substrate morphology is established via Raman mapping. Apparent vertical piezoresponse from the single-layer graphene supported by underlying SiO2 structure is observed by piezoresponse force microscopy. The calculated vertical piezocoefficient is about 1.4 nm V(-1), that is, much higher than that of the conventional piezoelectric materials such as lead zirconate titanate and comparable to that of relaxor single crystals. The observed piezoresponse and achieved strain in graphene are associated with the chemical interaction of graphene's carbon atoms with the oxygen from underlying SiO2. The results provide a basis for future applications of graphene layers for sensing, actuating and energy harvesting.

  9. Slow positron studies of hydrogen activation/passivation on SiO2/Si(100) interfaces

    International Nuclear Information System (INIS)

    Lynn, K.G.; Asoka-Kumar, P.

    1991-01-01

    The hydrogen atoms are one of the most common impurity species found in semiconductor systems owing to its large diffusivity, and are easily incorporated either in a controlled process like in ion implantation or in an uncontrolled process like the one at the fabrication stage. Hydrogen can passivate dangling bonds and dislocations in these systems and hence can be used to enhance the electrical properties. In a SiO 2 /Si system, hydrogen can passivate electronic states at the interface and can alter the fixed or mobile charges in the oxide layer. Since hydrogen is present in almost all of the environments of SiO 2 /Si wafer fabrication, the activation energy of hydrogen atoms is of paramount importance to a proper understanding of SiO 2 /Si based devices and has not been measured on the technologically most important Si(100) face. There are no direct, nondestructive methods available to observe hydrogen injection into the oxide layer and subsequent diffusion. This study uses the positrons as a ''sensitive'', nondestructive probe to observe hydrogen interaction in the oxide layer and the interface region. We also describe a new way of characterizing the changes in the density of the interface states under a low-temperature annealing using positrons. 9 refs., 6 figs

  10. Slow positron studies of hydrogen activation/passivation on SiO2/Si(100) interfaces

    Science.gov (United States)

    Lynn, K. G.; Asoka-Kumar, P.

    The hydrogen atoms are one of the most common impurity species found in semiconductor systems owing to its large diffusivity, and are easily incorporated either in a controlled process like in ion implantation or in an uncontrolled process like the one at the fabrication stage. Hydrogen can passivate dangling bonds and dislocations in these systems and hence can be used to enhance the electrical properties. In a SiO2/Si system, hydrogen can passivate electronic states at the interface and can alter the fixed or mobile charges in the oxide layer. Since hydrogen is present in almost all of the environments of SiO2/Si wafer fabrication, the activation energy of hydrogen atoms is of paramount importance to a proper understanding of SiO2/Si based devices and has not been measured on the technologically most important Si(100) face. There are no direct, nondestructive methods available to observe hydrogen injection into the oxide layer and subsequent diffusion. The positrons are used as a 'sensitive', nondestructive probe to observe hydrogen interaction in the oxide layer and the interface region. A new way is described of characterizing the changes in the density of the interface states under a low temperature annealing using positrons.

  11. Improving Passivation Process of Si Nanocrystals Embedded in SiO2 Using Metal Ion Implantation

    Directory of Open Access Journals (Sweden)

    Jhovani Bornacelli

    2013-01-01

    Full Text Available We studied the photoluminescence (PL of Si nanocrystals (Si-NCs embedded in SiO2 obtained by ion implantation at MeV energy. The Si-NCs are formed at high depth (1-2 μm inside the SiO2 achieving a robust and better protected system. After metal ion implantation (Ag or Au, and a subsequent thermal annealing at 600°C under hydrogen-containing atmosphere, the PL signal exhibits a noticeable increase. The ion metal implantation was done at energies such that its distribution inside the silica does not overlap with the previously implanted Si ion . Under proper annealing Ag or Au nanoparticles (NPs could be nucleated, and the PL signal from Si-NCs could increase due to plasmonic interactions. However, the ion-metal-implantation-induced damage can enhance the amount of hydrogen, or nitrogen, that diffuses into the SiO2 matrix. As a result, the surface defects on Si-NCs can be better passivated, and consequently, the PL of the system is intensified. We have selected different atmospheres (air, H2/N2 and Ar to study the relevance of these annealing gases on the final PL from Si-NCs after metal ion implantation. Studies of PL and time-resolved PL indicate that passivation process of surface defects on Si-NCs is more effective when it is assisted by ion metal implantation.

  12. Effects of four step sintering on Y2O3: SiO2 nanocomposite

    International Nuclear Information System (INIS)

    Ahlawat, Rachna

    2015-01-01

    Need for high performance materials for advanced applications have led to the development of new concepts in materials design processing and their fabrication. The development of nanocrystalline materials with improved and novel properties is an important turning point in materials research. In present work, we report synthesis and structural characterization of Y 2 O 3 : SiO 2 nanocomposite. Sol-gel technique is being used to prepare-Y 2 O 3 SiO 2 nanocomposite due to its effectiveness in preparing samples with good mixing of starting materials and at relatively low reaction temperature. We have used Y(NO 3 ) 3 .4H 2 O and TEOS as precursors and followed usual approach of sol-gel technique, the final product of Y 2 O 3 : SiO 2 nanocomposite is obtained in the form of powder. The powder samples were sintered at different temperature for different time durations in programmable muffle furnace. The samples were characterized by complementary techniques as X-Ray Diffraction (XRD), Fourier Transforms Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). (author)

  13. Impact of SiO2 on Al–Al thermocompression wafer bonding

    International Nuclear Information System (INIS)

    Malik, Nishant; Finstad, Terje G; Schjølberg-Henriksen, Kari; Poppe, Erik U; Taklo, Maaike M V

    2015-01-01

    Al–Al thermocompression bonding suitable for wafer level sealing of MEMS devices has been investigated. This paper presents a comparison of thermocompression bonding of Al films deposited on Si with and without a thermal oxide (SiO 2 film). Laminates of diameter 150 mm containing device sealing frames of width 200 µm were realized. The wafers were bonded by applying a bond force of 36 or 60 kN at bonding temperatures ranging from 300–550 °C for bonding times of 15, 30 or 60 min. The effects of these process variations on the quality of the bonded laminates have been studied. The bond quality was estimated by measurements of dicing yield, tensile strength, amount of cohesive fracture in Si and interfacial characterization. The mean bond strength of the tested structures ranged from 18–61 MPa. The laminates with an SiO 2 film had higher dicing yield and bond strength than the laminates without SiO 2 for a 400 °C bonding temperature. The bond strength increased with increasing bonding temperature and bond force. The laminates bonded for 30 and 60 min at 400 °C and 60 kN had similar bond strength and amount of cohesive fracture in the bulk silicon, while the laminates bonded for 15 min had significantly lower bond strength and amount of cohesive fracture in the bulk silicon. (paper)

  14. Surface Modification of SiO2 Microchannels with Biocompatible Polymer Using Supercritical Carbon Dioxide

    Science.gov (United States)

    Saito, Tatsuro; Momose, Takeshi; Hoshi, Toru; Takai, Madoka; Ishihara, Kazuhiko; Shimogaki, Yukihiro

    2010-11-01

    The surface of 500-mm-long microchannels in SiO2 microchips was modified using supercritical CO2 (scCO2) and a biocompatible polymer was coated on it to confer biocompatibility to the SiO2 surface. In this method, the SiO2 surface of a microchannel was coated with poly(ethylene glycol monomethacrylate) (PEGMA) as the biocompatible polymer using allyltriethoxysilane (ATES) as the anchor material in scCO2 as the reactive medium. Results were compared with those using the conventional wet method. The surface of a microchannel could not be modified by the wet method owing to the surface tension and viscosity of the liquid, but it was modified uniformly by the scCO2 method probably owing to the near-zero surface tension, low viscosity, and high diffusivity of scCO2. The effect of the surface modification by the scCO2 method to prevent the adsorption of protein was as high as that of the modification by the wet method. Modified microchips can be used in biochemical and medical analyses.

  15. Annealing behavior of oxygen in-diffusion from SiO2 film to silicon substrate

    International Nuclear Information System (INIS)

    Abe, T.; Yamada-Kaneta, H.

    2004-01-01

    Diffusion behavior of oxygen at (near) the Si/SiO 2 interface was investigated. We first oxidized the floating-zone-grown silicon substrates, and then annealed the SiO 2 -covered substrates in an argon ambient. We examined two different conditions for oxidation: wet and dry oxidation. By the secondary-ion-mass spectrometry, we measured the depth profiles of the oxygen in-diffusion of these heat-treated silicon substrates: We found that the energy of dissolution (in-diffusion) of an oxygen atom that dominates the oxygen concentration at the Si/SiO 2 interface depends on the oxidation condition: 2.0 and 1.7 eV for wet and dry oxidation, respectively. We also found that the barrier heights for the oxygen diffusion in argon anneal were significantly different for different ambients adopted for the SiO 2 formation: 3.3 and 1.8 eV for wet and dry oxidation, respectively. These findings suggest that the microscopic behavior of the oxygen atoms at the Si/SiO 2 interface during the argon anneal depends on the ambient adopted for the SiO 2 formation

  16. Irradiation-induced hardening/softening in SiO2 studied with instrumented indentation

    International Nuclear Information System (INIS)

    Nakano, Shinsuke; Muto, Shunsuke; Tanabe, Tetsuo

    2005-01-01

    To understand the plastic deformation mechanism of SiO 2 polytypes, we measured the mechanical parameters of He + -irradiated crystalline SiO 2 (α-quartz, c-SiO 2 ) and vitreous SiO 2 (silica glass, v-SiO 2 ) as functions of the irradiation dose, by using the instrumented indentation method combined with a finite-element analysis. We extracted the effects of local rotation and bending of the SiO 4 framework (the degree of local structural freedom), which play key roles in the plastic deformation, and expressed the hardness change with a simple formula. For v-SiO 2 , the changes in the density and the number of broken bonds correlated well with the change in the degree of freedom. In contrast, for c-SiO 2 the present formulation was insufficient to fully express the hardness change in the structural disordering regime. The structure change by irradiation peculiar to this material is discussed, based on the theoretical formulation

  17. Bulk properties and near-critical behaviour of SiO2 fluid

    Science.gov (United States)

    Green, Eleanor C. R.; Artacho, Emilio; Connolly, James A. D.

    2018-06-01

    Rocky planets and satellites form through impact and accretion processes that often involve silicate fluids at extreme temperatures. First-principles molecular dynamics (FPMD) simulations have been used to investigate the bulk thermodynamic properties of SiO2 fluid at high temperatures (4000-6000 K) and low densities (500-2240 kg m-3), conditions which are relevant to protoplanetary disc condensation. Liquid SiO2 is highly networked at the upper end of this density range, but depolymerises with increasing temperature and volume, in a process characterised by the formation of oxygen-oxygen (Odbnd O) pairs. The onset of vaporisation is closely associated with the depolymerisation process, and is likely to be non-stoichiometric at high temperature, initiated via the exsolution of O2 molecules to leave a Si-enriched fluid. By 6000 K the simulated fluid is supercritical. A large anomaly in the constant-volume heat capacity occurs near the critical temperature. We present tabulated thermodynamic properties for silica fluid that reconcile observations from FPMD simulations with current knowledge of the SiO2 melting curve and experimental Hugoniot curves.

  18. Characterization of Chemical Vapor Deposited Tetraethyl Orthosilicate based SiO2 Films for Photonic Devices

    Directory of Open Access Journals (Sweden)

    Jhansirani KOTCHARLAKOTA

    2016-05-01

    Full Text Available Silicon has been the choice for photonics technology because of its cost, compatibility with mass production and availability. Silicon based photonic devices are very significant from commercial point of view and are much compatible with established technology. This paper deals with deposition and characterization of SiO2 films prepared by indigenously developed chemical vapor deposition system. Ellipsometry study of prepared films showed an increase in refractive index and film thickness with the increment in deposition temperature. The deposition temperature has a significant role for stoichiometric SiO2 films, FTIR measurement has shown the three characteristics peaks of Si-O-Si through three samples prepared at temperatures 700, 750 and 800 °C while Si-O-Si stretching peak positions were observed to be shifted to lower wavenumber in accordance to the temperature. FESEM analysis has confirmed the smooth surface without any crack or disorder while EDX analysis showed the corresponding peaks of compositional SiO2 films.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7245

  19. Fiber-optic thermometer application of thermal radiation from rare-earth end-doped SiO2 fiber

    International Nuclear Information System (INIS)

    Katsumata, Toru; Morita, Kentaro; Komuro, Shuji; Aizawa, Hiroaki

    2014-01-01

    Visible light thermal radiation from SiO 2 glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO 2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO 2 fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900 K. Peak intensities of thermal radiations from rare-earth doped SiO 2 fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO 2 fibers are smaller than those from SiO 2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO 2 are potentially applicable for the fiber-optic thermometry above 900 K

  20. Oligo- and polymeric FET devices: Thiophene-based active materials and their interaction with different gate dielectrics

    International Nuclear Information System (INIS)

    Porzio, W.; Destri, S.; Pasini, M.; Bolognesi, A.; Angiulli, A.; Di Gianvincenzo, P.; Natali, D.; Sampietro, M.; Caironi, M.; Fumagalli, L.; Ferrari, S.; Peron, E.; Perissinotti, F.

    2006-01-01

    Derivatives of both oligo- and polythiophene-based FET were recently considered for low cost electronic applications. In the device optimization, factors like redox reversibility of the molecule/polymer, electronic level compatibility with source/drain electrodes, packing closeness, and orientation versus the electrodes, can determine the overall performance. In addition, a gate insulator with a high dielectric constant, a low leakage current, and capability to promote ordering in the semiconductor is required to increase device performances and to lower the FET operating voltage. In this view, Al 2 O 3 appears a good candidate, although its widespread adoption is limited by the disorder that such oxide induces on the semiconductor with detrimental consequences on semiconductor electrical properties. In this contribution, an overview of recent results obtained on thiophene-derivative-based FET devices, fabricated by different growth techniques, and using both thermally grown SiO 2 and Al 2 O 3 from atomic layer deposition gate insulators will be reported and discussed with particular reference to organic solid state aggregation, morphology, and organic-inorganic interface

  1. Role of the interface region on the optoelectronic properties of silicon nanocrystals embedded in SiO2

    International Nuclear Information System (INIS)

    Daldosso, N.; Dalba, G.; Fornasini, P.; Grisenti, R.; Pavesi, L.; Luppi, M.; Magri, R.; Ossicini, S.; Degoli, E.; Rocca, F.; Boninelli, S.; Priolo, F.; Spinella, C.; Iacona, F.

    2003-01-01

    Light-emitting silicon nanocrystals embedded in SiO 2 have been investigated by x-ray absorption measurements in total electron and photoluminescence yields, by energy filtered transmission electron microscopy and by ab initio total energy calculations. Both experimental and theoretical results show that the interface between the silicon nanocrystals and the surrounding SiO 2 is not sharp: an intermediate region of amorphous nature and variable composition links the crystalline Si with the amorphous stoichiometric SiO 2 . This region plays an active role in the light-emission process

  2. Ultralow-density SiO2 aerogels prepared by a two-step sol-gel process

    International Nuclear Information System (INIS)

    Wang Jue; Li Qing; Shen Jun; Zhou Bin; Chen Lingyan; Jiang; Weiyang

    1996-01-01

    Low density SiO 2 gels are prepared by a two-step sol-gel process from TEOS. The influence of various solution ratios on the gelation process is investigated. The comparative characterization of gels using different solvent, such as ethanol, acetone and methyl cyanide, is also given. The ultralow-density SiO 2 aerogels with density less than 10 kg/m 3 are prepared by CO 2 supercritical drying technique. The structure difference between SiO 2 aerogels prepared by conventional single-step process and the two-step process is also presented

  3. The Role of SiO2 Gas in the Operation of Anti-Corrosion Coating Produced by PVD

    Directory of Open Access Journals (Sweden)

    Meysam Zarchi

    2015-09-01

    Full Text Available This study examined theSiO2 gas present in the coatings used in corrosion industry.These layers have been created by physical vapor deposition (PVD, with an appropriate performance. Sublimation of SiO2is used to protect PVD aluminum flakes from water corrosionand to generate highly porous SiO2 flakes with holes in the nanometer range. SiOx/Al/SiOx sandwiches were made as well as Ag loaded porous SiO2 as antimicrobial filler.

  4. Morphology of SiO2 films as a key factor in alignment of liquid crystals with negative dielectric anisotropy

    Directory of Open Access Journals (Sweden)

    Volodymyr Tkachenko

    2016-11-01

    Full Text Available Control of liquid crystal (LC orientation using a proper SiO2 alignment layer is essential for the optimization of vertically aligned nematic (VAN displays. With this aim, we studied the optical anisotropy of thin SiO2 films by generalized ellipsometry as a function of deposition angle. The columnar SiO2 structure orientation measured by a noninvasive ellipsometry technique is reported for the first time, and its morphology influence on the LC alignment is demonstrated for large deposition angles.

  5. Identification of conduction and hot electron property in ZnS, ZnO and SiO2

    International Nuclear Information System (INIS)

    Huang Jinzhao; Xu Zheng; Zhao Suling; Li Yuan; Yuan Guangcai; Wang Yongsheng; Xu Xurong

    2007-01-01

    The impact excitation and ionization is the most important process in layered optimization scheme and solid state cathodoluminescence. The conduction property (semiconductor property) of SiO 2 , ZnS and ZnO is studied based on organic/inorganic electroluminescence. The hot electron property (acceleration and multiplication property) of SiO 2 and ZnS is investigated based on the solid state cathodoluminescence. The results show that the SiO 2 has the fine hot electron property and the conduction property is not as good as ZnO and ZnS

  6. Photocatalytic Removal of Phenol under Natural Sunlight over N-TiO2-SiO2 Catalyst: The Effect of Nitrogen Composition in TiO2-SiO2

    Directory of Open Access Journals (Sweden)

    Viet-Cuong Nguyen

    2009-01-01

    Full Text Available In this present work, high specific surface area and strong visible light absorption nitrogen doped TiO2-SiO2 photocatalyst was synthesized by using sol-gel coupled with hydrothermal treatment method. Nitrogen was found to improve the specific surface area while it also distorted the crystal phase of the resulting N-TiO2-SiO2 catalyst. As the N/ (TiO2-SiO2 molar ratio was more than 10%, the derived catalyst presented the superior specific surface area up to 260 m2/g. Nevertheless, its photoactivity towards phenol removal was observed to significantly decrease, which could results from the too low crystallinity. The nitrogen content in N-TiO2-SiO2 catalyst was therefore necessary to be optimized in terms of phenol removal efficiency and found at ca. 5%. Under UVA light and natural sunlight irradiation of 80 min, N(5%-TiO2-SiO2 catalyst presented the phenol decomposition efficiencies of 68 and 100%, respectively. It was also interestingly found in this study that the reaction rate was successfully expressed using a Langmuir-Hinshelwood (L-H model, indicating the L-H nature of photocatalytic phenol decomposition reaction on the N-TiO2-SiO2 catalyst.

  7. Efficient VEGF targeting delivery of DOX using Bevacizumab conjugated SiO2@LDH for anti-neuroblastoma therapy.

    Science.gov (United States)

    Zhu, Rongrong; Wang, Zhaoqi; Liang, Peng; He, Xiaolie; Zhuang, Xizhen; Huang, Ruiqi; Wang, Mei; Wang, Qigang; Qian, Yechang; Wang, Shilong

    2017-11-01

    Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis and is highly expressed in carcinoma, which make it an important target for tumor targeting therapy. Neuroblastoma is the main cause for cancer-related death in children. Like most solid tumors, it is also accompanied with the overexpression of VEGF. Doxorubicin Hydrochloride (DOX), a typical chemotherapeutic agent, exhibits efficient anticancer activities for various cancers. However, DOX, without targeting ability, usually causes severe damage to normal tissues. To overcome the shortages, we designed a novel nano-composite, which is Bevacizumab (Bev) modified SiO 2 @LDH nanoparticles (SiO 2 @LDH-Bev), loading with DOX to achieve targeting ability and curative efficiency. SiO 2 @LDH-DOX and SiO 2 @LDH-Bev-DOX nanoparticles were synthesized and the physicochemical properties were characterized by TEM detection, Zeta potential analysis, FTIR, Raman and XPS analysis. Then in vitro and in vivo anti-neuroblastoma efficiency, targeting ability and mechanisms of anti-carcinoma and anti-angiogenesis of SiO 2 @LDH-Bev-DOX were explored. Our results indicated that we obtained the core-shell structure SiO 2 @LDH-Bev with an average diameter of 253±10nm and the amount of conjugated Bev was 4.59±0.38μg/mg SiO 2 @LDH-Bev. SiO 2 @LDH-Bev-DOX could improve the cellular uptake and the targeting effect of DOX to brain and tumor, enhance the anti-neuroblastoma and anti-angiogenesis efficiency both in vitro and in vivo, and alleviate side effects of DOX sharply, especially hepatic injury. In addition, we also demonstrated that angiogenesis inhibitory effect was mediated by DOX and VEGF triggered signal pathways, including PI3K/Akt, Raf/MEK/ERK, and adhesion related pathways. In summary, SiO 2 @LDH-Bev could be a potential VEGF targeting nanocarrier applied in VEGF positive cancer therapy. This paper explored that a novel core-shell structure nanomaterial SiO 2 @LDH and modified SiO 2 @LDH with Bevacizumab (Bev) to form a new tumor vasculature targeting nanocarrier SiO 2 @LDH-Bev as vector of DOX, which was not reported before. The results indicated that SiO 2 @LDH-Bev could improve the VEGF targeting ability, anti-neuroblastoma and anti-angiogenesis efficiency of DOX. At the same time, SiO 2 @LDH-Bev-DOX could erase the cardiac toxicity and hepatic injury coming from DOX. Tube formation showed SiO 2 @LDH-Bev-DOX had the strongest effect on inhibiting angiogenesis among all the four formulations. SiO 2 @LDH-Bev-DOX could downregulate expression of p-VEGFR and inhibit activation of the Raf/MEK/ERK, p38MAPK, PI3K/Akt and FAK signaling pathways to achieve the goal of anti-angiogenesis. This work provides a novel system for the safe and efficient use of Bev and DOX on Neuroblastoma and explores the mechanism of the function of nano carrier in cancer therapy both in vitro and in vivo. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  8. Preparation and characterization of silane-modified SiO2 particles reinforced resin composites with fluorinated acrylate polymer.

    Science.gov (United States)

    Liu, Xue; Wang, Zengyao; Zhao, Chengji; Bu, Wenhuan; Na, Hui

    2018-04-01

    A series of fluorinated dental resin composites were prepared with two kinds of SiO 2 particles. Bis-GMA (bisphenol A-glycerolate dimethacrylate)/4-TF-PQEA (fluorinated acrylate monomer)/TEGDMA (triethylene glycol dimethacrylate) (40/30/30, wt/wt/wt) was introduced as resin matrix. SiO 2 nanopartices (30nm) and SiO 2 microparticles (0.3µm) were silanized with 3-methacryloxypropyl trimethoxysilane (γ-MPS) and used as fillers. After mixing the resin matrix with 0%, 10%, 20%, 30% SiO 2 nanopartices and 0%, 10%, 20%, 30%, 40%, 50% SiO 2 microparticles, respectively, the fluorinated resin composites were obtained. Properties including double bond conversion (DC), polymerization shrinkage (PS), water sorption (W p ), water solubility (W y ), mechanical properties and cytotoxicity were investigated in comparison with those of neat resin system. The results showed that, filler particles could improve the overall performance of resin composites, particularly in improving mechanical properties and reducing PS of composites along with the addition of filler loading. Compared to resin composites containing SiO 2 microparticles, SiO 2 nanoparticles resin composites had higher DC, higher mechanical properties, lower PS and lower W p under the same filler content. Especially, 50% SiO 2 microparticles reinforced resins exhibited the best flexural strength (104.04 ± 7.40MPa), flexural modulus (5.62 ± 0.16GPa), vickers microhardness (37.34 ± 1.13 HV), compressive strength (301.54 ± 5.66MPa) and the lowest polymerization (3.42 ± 0.22%). Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

    Science.gov (United States)

    Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

    2015-01-01

    Fe3O4@SiO2-graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe3O4@SiO2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe3O4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe3O4@SiO2 NPs was 24 ± 0.3 nm, similar to that of Fe3O4@SiO2-NH2. Fe3O4@SiO2-GO composites were synthesized by linking of Fe3O4@SiO2-NH2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe3O4@SiO2-GO composite has potential applications in the production of bioethanol.

  10. Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

    International Nuclear Information System (INIS)

    Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

    2015-01-01

    Fe 3 O 4 @SiO 2 –graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe 3 O 4 @SiO 2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe 3 O 4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO 2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe 3 O 4 @SiO 2 NPs was 24 ± 0.3 nm, similar to that of Fe 3 O 4 @SiO 2 –NH 2 . Fe 3 O 4 @SiO 2 –GO composites were synthesized by linking of Fe 3 O 4 @SiO 2 –NH 2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe 3 O 4 @SiO 2 –GO composite has potential applications in the production of bioethanol

  11. Carboxylated SiO2-coated α-Fe nanoparticles: towards a versatile platform for biomedical applications.

    Science.gov (United States)

    Kohara, Kaori; Yamamoto, Shinpei; Seinberg, Liis; Murakami, Tatsuya; Tsujimoto, Masahiko; Ogawa, Tetsuya; Kurata, Hiroki; Kageyama, Hiroshi; Takano, Mikio

    2013-03-28

    Carboxylated SiO2-coated α-Fe nanoparticles have been successfully prepared via CaH2-mediated reduction of SiO2-coated Fe3O4 nanoparticles followed by surface carboxylation. These α-Fe-based nanoparticles, which are characterized by ease of coating with additional functional groups, a large magnetization of 154 emu per g-Fe, enhanced corrosion resistivity, excellent aqueous dispersibility, and low cytotoxicity, have potential to be a versatile platform in biomedical applications.

  12. Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

    Science.gov (United States)

    Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

    2015-12-30

    This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Fabrication of hierarchical structured SiO2/polyetherimide-polyurethane nanofibrous separators with high performance for lithium ion batteries

    International Nuclear Information System (INIS)

    Zhai, Yunyun; Xiao, Ke; Yu, Jianyong; Ding, Bin

    2015-01-01

    Highlights: • Electrospinning followed by dip-coating was used to fabricate SiO 2 /PEI-PU membranes. • Introducing PEI, PU and SiO 2 improved safety, tensile strength and ionic conductivity. • Coating SiO 2 also restrained the micro-shorting and migrated the self-discharge. • SiO 2 /PEI-PU membranes based cell exhibited prominent cycling and rate performance. - ABSTRACT: The performance of lithium ion battery based on electrospun nanofibrous membranes has gained a great deal of attention in the past decades, but the intrinsic low mechanical strength and large pore size of electrospun membranes limit their battery performance. To overcome this limitation, a powerful strategy for designing, fabricating and evaluating silica nanoparticles coated polyetherimide-polyurethane (SiO 2 /PEI-PU) nanofibrous composite membranes is easily developed via electrospinning followed by a dip-coating process. Benefiting from the high porosity, interpenetrating network structure and synergetic effect of PU, PEI and SiO 2 nanoparticles, the as-prepared composite membranes exhibit high ionic conductivity (2.33 mS cm −1 ), robust tensile strength (15.65 MPa) and improved safety (excellent thermal resistance and flame retardant property). Additionally, the as-prepared composite membranes possess relatively narrow pore size distribution with average pore size of 0.58 μm after coating SiO 2 nanoparticles, which plays an important role in hindering the micro-shorting and mitigating self-discharge. Significantly, the SiO 2 /PEI-PU membranes based Li/LiFePO 4 cell exhibits more excellent cycling stability with capacity retention of 98.7% after 50 cycles at 0.2 C rate and better rate capability compared with the Celgard membrane based cell. The results clearly demonstrate that this is a promising separator candidate for next-generation lithium ion batteries, which may represent a significant step toward separators with improved performance

  14. Room temperature synthesis of porous SiO2 thin films by plasma enhanced chemical vapor deposition

    OpenAIRE

    Barranco Quero, Ángel; Cotrino Bautista, José; Yubero Valencia, Francisco; Espinós, J. P.; Rodríguez González-Elipe, Agustín

    2004-01-01

    Synthesis of porous SiO2 thin films in room temperature was carried out using plasma enhanced chemical vapor deposition (CVD) in an electron cyclotron resonance microwave reactor with a downstream configuration.The gas adsorption properties and the type of porosity of the SiO2 thin films were assessed by adsorption isotherms of toluene at room temperature.The method could also permit the tailoring synthesis of thin films when both composition and porosity can be simultaneously and independent...

  15. Magnetic SiO2 gel microspheres for arterial embolization hyperthermia

    International Nuclear Information System (INIS)

    Li Zhixia; Kawashita, Masakazu; Araki, Norio; Mitsumori, Michihide; Hiraoka, Masahiro; Doi, Masaaki

    2010-01-01

    We have prepared magnetic SiO 2 microspheres with a diameter of 20-30 μm as thermoseeds for hyperthermia of cancer. These were prepared by directly introducing preformed magnetic iron oxide nanoparticles (IONPs) into microspheres of a SiO 2 gel matrix derived from the hydrolysis of tetramethoxysilane (TMOS) in a water-in-oil (W/O) emulsion. Dimethylformamide (DMF) was used as a stabilizer, methanol (CH 3 OH) as a dispersant and ammonia (NH 4 OH) as the catalyst for the formation of the spherical particles in the aqueous phase of the W/O emulsion. The magnetic IONPs were synthesized hydrochemically in an aqueous system composed of ferrous chloride, sodium nitrate and sodium hydroxide. Mono-dispersed magnetic SiO 2 gel microspheres with a diameter of approximately 20 μm were successfully obtained by adding a determined amount of solution with a molar ratio of TMOS/DMF/CH 3 OH/H 2 O/NH 4 OH = 1:1.4:9:20:0.03 to kerosene with a surfactant (sorbitan monooleate/sorbitan monostearate = 3:1 by weight ratio) that was 30 wt% of the total amount of the oil phase. These were estimated to contain up to 60 wt% of IONPs that consisted mainly of Fe 3 O 4 and showed a higher specific absorption rate (SAR = 27.9-43.8 W g -1 ) than that of the starting IONPs (SAR = 25.3 W g -1 ) under an alternating current magnetic field of 300 Oe and 100 kHz.

  16. Voltage-Controlled Spray Deposition of Multiwalled Carbon Nanotubes on Semiconducting and Insulating Substrates

    Science.gov (United States)

    Maulik, Subhodip; Sarkar, Anirban; Basu, Srismrita; Daniels-Race, Theda

    2018-05-01

    A facile, cost-effective, voltage-controlled, "single-step" method for spray deposition of surfactant-assisted dispersed carbon nanotube (CNT) thin films on semiconducting and insulating substrates has been developed. The fabrication strategy enables direct deposition and adhesion of CNT films on target samples, eliminating the need for substrate surface functionalization with organosilane binder agents or metal layer coatings. Spray coating experiments on four types of sample [bare silicon (Si), microscopy-grade glass samples, silicon dioxide (SiO2), and polymethyl methacrylate (PMMA)] under optimized control parameters produced films with thickness ranging from 40 nm to 6 μm with substantial surface coverage and packing density. These unique deposition results on both semiconducting and insulator target samples suggest potential applications of this technique in CNT thin-film transistors with different gate dielectrics, bendable electronics, and novel CNT-based sensing devices, and bodes well for further investigation into thin-film coatings of various inorganic, organic, and hybrid nanomaterials on different types of substrate.

  17. SiO2-supported Pt particles studied by electron microscopy

    International Nuclear Information System (INIS)

    Wang, D.; Penner, S.; Su, D.S.; Rupprechter, G.; Hayek, K.; Schloegl, R.

    2003-01-01

    Regularly grown Pt particles supported by amorphous SiO 2 were heated in hydrogen at 873 K after an oxidising treatment. The morphological and structural changes were studied by electron microscopy. Platinum silicides Pt 3 Si with L1 2 (Cu 3 Au) structure, monoclinic Pt 3 Si and tetragonal Pt 12 Si 5 were identified after the treatment. The mechanisms of coalescence of the particles and the formation of irregular large particles are suggested. A topotactic structural transformation accompanied with the migration of Si from the substrate to the particles are suggested to take place during Pt 3 Si formation

  18. Disordered electrical potential observed on the surface of SiO2 by electric field microscopy

    International Nuclear Information System (INIS)

    GarcIa, N; Yan Zang; Ballestar, A; Barzola-Quiquia, J; Bern, F; Esquinazi, P

    2010-01-01

    The electrical potential on the surface of ∼300 nm thick SiO 2 grown on single-crystalline Si substrates has been characterized at ambient conditions using electric field microscopy. Our results show an inhomogeneous potential distribution with fluctuations up to ∼0.4 V within regions of 1 μm. The potential fluctuations observed at the surface of these usual dielectric holders of graphene sheets should induce strong variations in the graphene charge densities and provide a simple explanation for some of the anomalous behaviors of the transport properties of graphene.

  19. Friction and wear properties of ZrO2/SiO2 composite nanoparticles

    International Nuclear Information System (INIS)

    Li Wei; Zheng Shaohua; Cao Bingqiang; Ma Shiyu

    2011-01-01

    In this article, the lubrication properties of ZrO 2 /SiO 2 composite nanoparticles modified with aluminum zirconium coupling agent as additives in lubricating oil under variable applied load and concentration fraction were reported. It was demonstrated that the modified nanoparticles as additives in lubrication can effectively improve the lubricating properties. Under an optimized concentration of 0.1 wt%, the average friction coefficient was reduced by 16.24%. This was because the nanoparticles go into the friction zone with the flow of lubricant, and then the sliding friction changed to rolling friction with a result of the reduction of the friction coefficient.

  20. Hydrogen and chlorine detection at the SiO2/Si interface

    International Nuclear Information System (INIS)

    Tsong, I.S.T.; Monkowski, M.D.; Monkowski, J.R.; Wintenberg, A.L.; Miller, P.D.; Moak, C.D.

    1981-01-01

    Hydrogen and chlorine depth profiles were obtained on a series of silicon oxides thermally grown in HCl/O 2 and Cl 2 /O 2 ambients at 1100 0 C for 15 minutes using the 19 F nuclear reaction and SIMS techniques. The data show close correlation between the H and Cl profiles in both the HCl/O 2 and Cl 2 /O 2 oxides. While the H and Cl appear to be enriched at the SiO 2 /Si interface of the HCl/O 2 oxides, they are higher in concentration and more evenly distributed in the oxide bulk of the Cl 2 /O 2 oxides

  1. Experimental study of viscosity properties of emulsion system with SiO2 nanoparticles.

    Directory of Open Access Journals (Sweden)

    ZEIGMAN Yury Veniaminovich,

    2017-04-01

    Full Text Available When oil production is increasing due to intensive oilfield development methods supporting seam pressure by water injection oil producers face the problem of displacement agent break in more permeable intervals of petroleum reservoir. That leads to dramatic increase of product inundation for well stock and decrease of economic efficiency for well performance. Nowadays the petroleum engineers have proposed more than 100 technologies designed to restrict water inflows and flooding agent to bottom-hole zone of the production wells. The water inflows restriction technologies are distinguished by the type of applied chemical compositions and the way how the chemical compositions are delivered to bottom-hole zone. The analysis of the currently applied chemical compositions has allowed authors to reveal the common feature. The common feature is that the currently applied chemical compositions are non-selective and they produce isolating or blocking effect onto water-saturated and oil-saturated zones of the petroleum reservoir. The application of the nonselective high-stability chemical compositions leads to uncontrolled colmatation of all treated intervals and makes it difficult to involve them into filtration process in future. This work presents the technology for the selective reservoir stimulation based on emulsion systems with SiO2 nanoparticles content and gelling acid composition. The technology was developed for complex impact on formation system, that achieved by blocking water-saturated intervals of reservoir and stimulation of less permeable oil-saturated intervals of reservoir. The paper shows the results of complex laboratory experiments to study viscosity parameters of emulsion systems with SiO2 nanoparticles content. The results of the experiments revealed the ability of the SiO2 nanoparticles to rise dynamic viscosity of the different type of emulsion systems: oil in water and water in oil. Test for thermostability of the modified emulsion systems showed stability of the systems under 80о C. In addition, the modified emulsion systems kept the ability to decrease significantly viscosity in the reaction with hydrocarbons, i.e. the emulsion systems with SiO2 nanoparticles are selective compositions for the water-inflows restriction.

  2. Internal Friction of (SiO2)1-x (GeO2)x Glasses

    OpenAIRE

    Kosugi , T.; Kobayashi , H.; Kogure , Y.

    1996-01-01

    Internal friction of (SiO2)1-x (GeO2)x glasses (x = 0, 5, 10, 24 and 100 mole%) is measured at temperatures between 1.6 and 280 K. The data are filted with the equations for thermally activated relaxation with distributing activation energies in symmetrical double-well potentials. From the determined relaxation strength spectra for each sample, the contributions from each type of microscopic structural units are calculated assuming that transverse motion of the bridging O atom in Si-O-Si, Si-...

  3. Tetrahedral ↔ octahedral network structure transition in simulated vitreous SiO2

    International Nuclear Information System (INIS)

    Vo Van Hoang; Nguyen Trung Hai; Hoang Zung

    2006-01-01

    By using molecular dynamics (MD) simulations we found a transition from a tetrahedral to an octahedral network structure in an amorphous SiO 2 model under compression from 2.20 to 5.35 g/cm 3 . And on heating of a high density amorphous (hda) model of 5.35 g/cm 3 at zero pressure, the structure transforms to a low density amorphous (lda) form. Simulations were done in a model containing 3000 particles under periodic boundary conditions with interatomic potentials which have a weak Coulomb interaction and a Morse type short-range interaction

  4. Ordering at Si(111)/o-Si and Si(111)/SiO2 Interfaces

    DEFF Research Database (Denmark)

    Robinson, I. K.; Waskiewicz, W. K.; Tung, R. T.

    1986-01-01

    X-ray diffraction has been used to measure the intensity profile of the two-dimensional rods of scattering from a single interface buried inside a bulk material. In both Si(111)/a-Si and Si(111)/SiO2 examples there are features in the perpendicular-momentum-transfer dependence which are not expec...... are not expected from an ideal sharp interface. The diffraction profiles are explained by models with partially ordered layers extending into the amorphous region. In the Si(111)/a-Si case there is clear evidence of stacking faults which are attributed to residual 7×7 reconstruction....

  5. Measurement of nanosize etched pits in SiO2 optical fiber conduit using AFM

    International Nuclear Information System (INIS)

    Espinosa, G.; Golzarri, J.I.; Vazquez, C.; Fragoso, R.

    2003-01-01

    Fission fragment tracks from 252 Cf have been observed in SiO 2 optical fiber, using an atomic force microscope (AFM), after a very short chemical etching in hydrofluoric acid solution at normal temperature. The nuclear track starting and evolution process is followed by the AFM direct measurements on the material surface and beyond a fine layer of the surface material. The images of the scanned cones were determined observing the two predominant energies from 252 Cf fission fragments and the development of the tracks in the 150 μm diameter optical fiber conduit

  6. High refractive index modification of SiO2 created by femtosecond laser nanostructuring

    International Nuclear Information System (INIS)

    Barillot, T; Grojo, D; Gertsvolf, M; Rayner, D M; Corkum, P B; Lei, S

    2010-01-01

    By comparing simulations with experiment, we show that the effective refractive index of fused SiO 2 can be locally reduced by (1.8 ± 0.2)% by femtosecond laser nanostructuring. We create a microlens of material containing a planar array of nanocracks embedded inside fused silica and probe how it refracts or absorbs light as a function of pulse energy. The self-generated microlens lowers the peak light intensity by deflecting the light around the focus. We obtain the refractive index by simulating the beam transport using the 3D wave equation in conjunction with the measured dimensions of the modified material.

  7. Ultrasensitive spectroscopy based on photonic waveguides on Al2O3/SiO2 platform

    Science.gov (United States)

    Heidari, Elham; Xu, Xiaochuan; Tang, Naimei; Mokhtari-Koushyar, Farzad; Dalir, Hamed; Chen, Ray T.

    2018-02-01

    Here a photonic waveguide on Al2O3/SiO2 platform is proposed to cover the 240 320 nm wavelength-range, which is of paramount significance in protein and nuclei acid quantification. Our optical waveguide increases path-length and overlap integration for light-matter interaction with proteins. The proposed system detects one order less proteins concentration as low as 12.5 μg/ml compared with NanoDropTM that detects Beer-Lambert-law.

  8. Positron trap centers in x-ray and γ-ray irradiated SiO2

    International Nuclear Information System (INIS)

    Khatri, R.; Asoka-Kumar, P.; Nielsen, B.; Roellig, L.O.; Lynn, K.G.

    1993-01-01

    Using Doppler broadening annihilation spectroscopy, we investigated the properties of irradiated samples of SiO 2 /Si(100) with 117 nm thick oxide layer, grown in dry O 2 on p- and n-type substrates. These samples were irradiated with γ rays and x rays at doses in the range of 7x10 4 --9x10 6 rad and 50--2000 mJ/cm 2 , respectively. The changes observed in the Doppler broadening line shape parameter after irradiation and its recovery during isochronal annealing were used to obtain an activation energy of 1.48--1.61 eV required for annealing the defects

  9. SiO2 Antireflection Coatings Fabricated by Electron-Beam Evaporation for Black Monocrystalline Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Minghua Li

    2014-01-01

    Full Text Available In this work we prepared double-layer antireflection coatings (DARC by using the SiO2/SiNx:H heterostructure design. SiO2 thin films were deposited by electron-beam evaporation on the conventional solar cell with SiNx:H single-layer antireflection coatings (SARC, while to avoid the coverage of SiO2 on the front side busbars, a steel mask was utilized as the shelter. The thickness of the SiNx:H as bottom layer was fixed at 80 nm, and the varied thicknesses of the SiO2 as top layer were 105 nm and 122 nm. The results show that the SiO2/SiNx:H DARC have a much lower reflectance and higher external quantum efficiency (EQE in short wavelengths compared with the SiNx:H SARC. A higher energy conversion efficiency of 17.80% was obtained for solar cells with SiO2 (105 nm/SiNx:H (80 nm DARC, an absolute conversion efficiency increase of 0.32% compared with the conventional single SiNx:H-coated cells.

  10. A new cataluminescence gas sensor based on SiO2 nanotubes fabricated using carbon nanotube templates.

    Science.gov (United States)

    Wang, Yali; Cao, Xiaoan; Li, Jinwen; Chen, Nan

    2011-05-15

    In the present work, two morphologies of SiO(2) nanomaterials (SiO(2) nanotubes and nanoparticles) have been successfully synthesized in supercritical fluids (SCFs). The cataluminescence (CTL) features of the two SiO(2) nanomaterials to some common harmful gases were compared, and the results showed that SiO(2) nanotubes had better CTL sensing characteristic to some common harmful gases. The SiO(2) nanotubes not only had uniform size and shape with a high specific surface area, but also exhibited superior sensitivity and selectivity to ethyl acetate vapor. Using the SiO(2) nanotubes as sensing material, a CTL sensor for ethyl acetate vapor was developed. The proposed sensor showed high sensitivity and specificity to ethyl acetate at optimal temperature of 293°C, a wavelength of 425 nm and a flow rate of 345 mL/min. With a detection limit of 0.85 ppm, the linear range of CTL intensity versus concentrations of ethyl acetate vapor was 2.0-2000 ppm. None or only very low levels of interference were observed while the foreign substances such as acetone, acetaldehyde, acetic acid, formaldehyde, ammonia, ethanol, benzene and methanol were passing through the sensor. This method allows rapid determination of gaseous ethyl acetate at workshop. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. Synergetic scattering of SiO2 and Ag nanoparticles for light-trapping enhancement in organic bulk heterojunction

    Science.gov (United States)

    Yang, Huan; Ding, Qiuyu; Li, Ben Q.; Jiang, Xinbing; Zhang, Manman

    2018-02-01

    Though noble metal nanoparticles have been explored to enhance the performance of the organic solar cell, effect of dielectric nanoparticles, and coupled effect of dielectric and metal nanoparticles, have rarely been reported, if at all, on organic solar cell. This work reports an experimental study on synergetic scattering of SiO2 and Ag nanoparticles in a bulk organic heterojunction for the broadband light absorption enhancement. The wavelength scale SiO2 particles were arranged as a monolayer on the surface of the solar cell to guide incident light into the active layer and prolong the effective optical length of the entered energy. This is achieved by the excitation of whispering gallery modes in SiO2 nanoparticles and by leaky mode radiation. When small size Ag particles were incorporated into the transport layer of the solar cell, synergetic scattering of SiO2 and Ag nanoparticles is formed by coupling of the whispering gallery mode of closely arranged SiO2 particles atop and collaborative localized surface plasma resonance scattering of Ag nanoparticles dispersed in the transport layer. As a result, the performance of the organic solar cell is greatly enhanced and the short-circuit current density has an improvement of 42.47%. Therefore, the organic solar cell incorporated with SiO2 and Ag particles presents a meaningful strategy to achieve high energy-harvesting performance. [Figure not available: see fulltext.

  12. Realization of Colored Multicrystalline Silicon Solar Cells with SiO2/SiNx:H Double Layer Antireflection Coatings

    Directory of Open Access Journals (Sweden)

    Minghua Li

    2013-01-01

    Full Text Available We presented a method to use SiO2/SiNx:H double layer antireflection coatings (DARC on acid textures to fabricate colored multicrystalline silicon (mc-Si solar cells. Firstly, we modeled the perceived colors and short-circuit current density (Jsc as a function of SiNx:H thickness for single layer SiNx:H, and as a function of SiO2 thickness for the case of SiO2/SiNx:H (DARC with fixed SiNx:H (refractive index n=2.1 at 633 nm, and thickness = 80 nm. The simulation results show that it is possible to achieve various colors by adjusting the thickness of SiO2 to avoid significant optical losses. Therefore, we carried out the experiments by using electron beam (e-beam evaporation to deposit a layer of SiO2 over the standard SiNx:H for 156×156 mm2 mc-Si solar cells which were fabricated by a conventional process. Semisphere reflectivity over 300 nm to 1100 nm and I-V measurements were performed for grey yellow, purple, deep blue, and green cells. The efficiency of colored SiO2/SiNx:H DARC cells is comparable to that of standard SiNx:H light blue cells, which shows the potential of colored cells in industrial applications.

  13. High ink absorption performance of inkjet printing based on SiO2@Al13 core-shell composites

    Science.gov (United States)

    Chen, YiFan; Jiang, Bo; Liu, Li; Du, Yunzhe; Zhang, Tong; Zhao, LiWei; Huang, YuDong

    2018-04-01

    The increasing growth of the inkjet market makes the inkjet printing more necessary. A composite material based on core-shell structure has been developed and applied to prepare inkjet printing layer. In this contribution, the ink printing record layers based on SiO2@Al13 core-shell composite was elaborated. The prepared core-shell composite materials were characterized by X-ray photoelectron spectroscopy (XPS), zeta potential, X-ray diffraction (XRD), scanning electron microscopy (SEM). The results proved the presence of electrostatic adsorption between SiO2 molecules and Al13 molecules with the formation of the well-dispersed system. In addition, based on the adsorption and the liquid permeability analysis, SiO2@Al13 ink printing record layer achieved a relatively high ink uptake (2.5 gmm-1) and permeability (87%), respectively. The smoothness and glossiness of SiO2@Al13 record layers were higher than SiO2 record layers. The core-shell structure facilitated the dispersion of the silica, thereby improved its ink absorption performance and made the clear printed image. Thus, the proposed procedure based on SiO2@Al13 core-shell structure of dye particles could be applied as a promising strategy for inkjet printing.

  14. Improvement in negative bias illumination stress stability of In-Ga-Zn-O thin film transistors using HfO2 gate insulators by controlling atomic-layer-deposition conditions

    Science.gov (United States)

    Na, So-Yeong; Kim, Yeo-Myeong; Yoon, Da-Jeong; Yoon, Sung-Min

    2017-12-01

    The effects of atomic layer deposition (ALD) conditions for the HfO2 gate insulators (GI) on the device characteristics of the InGaZnO (IGZO) thin film transistors (TFTs) were investigated when the ALD temperature and Hf precursor purge time were varied to 200, 225, and 250 °C, and 15 and 30 s, respectively. The HfO2 thin films showed low leakage current density of 10-8 A cm-2, high dielectric constant of over 20, and smooth surface roughness at all ALD conditions. The IGZO TFTs using the HfO2 GIs showed good device characteristics such as a saturation mobility as high as 11 cm2 V-1 s-1, a subthreshold swing as low as 0.10 V/dec, and all the devices could be operated at a gate voltage as low as  ±3 V. While there were no marked differences in transfer characteristics and PBS stabilities among the fabricated devices, the NBIS instabilities could be improved by increasing the ALD temperature for the formation of HfO2 GIs by reducing the oxygen vacancies within the IGZO channel.

  15. Scratch resistance of SiO2 and SiO2 - ZrO2 sol-gel coatings on glass-ceramic obtained by sintering

    International Nuclear Information System (INIS)

    Soares, V. O.; Soares, P.; Peitl, O.; Zanotto, E. D.; Duran, A.; Castro, Y.

    2013-01-01

    The sol-gel process is widely used to obtain coatings on glass-ceramic substrates in order to improve the scratch and abrasion resistance, also providing a bright and homogeneous appearance of a glaze avoiding expensive final polishing treatments. This paper describes the preparation of silica and silica / zirconia coatings by sol-gel method on Li 2 O-Al 2 O3-SiO 2 (LAS) glassceramic substrates produced by sintering. The coatings were deposited by dip-coating on LAS substrates and characterized by optical microscopy and spectral ellipsometry. On the other hand, hardness and elastic modulus, coefficient of friction and abrasion and scratch resistance of the coatings were determined and compared with the substrate properties. Coatings deposited on LAS glass-ceramic confere the substrate a bright and homogeneous aspect, similar to a glaze, improving the appearance and avoiding the final polishing. However these coatings do not increase the scratch resistance of the substrate only equaling the properties of the glass-ceramic. (Author)

  16. Trapping time of excitons in Si nanocrystals embedded in a SiO2 matrix

    Science.gov (United States)

    de Jong, E. M. L. D.; de Boer, W. D. A. M.; Yassievich, I. N.; Gregorkiewicz, T.

    2017-05-01

    Silicon (Si) nanocrystals (NCs) are of great interest for many applications, ranging from photovoltaics to optoelectonics. The photoluminescence quantum yield of Si NCs dispersed in SiO2 is limited, suggesting the existence of very efficient processes of nonradiative recombination, among which the formation of a self-trapped exciton state on the surface of the NC. In order to improve the external quantum efficiency of these systems, the carrier relaxation and recombination need to be understood more thoroughly. For that purpose, we perform transient-induced absorption spectroscopy on Si NCs embedded in a SiO2 matrix over a broad probe range for NCs of average sizes from 2.5 to 5.5 nm. The self-trapping of free excitons on surface-related states is experimentally and theoretically discussed and found to be dependent on the NC size. These results offer more insight into the self-trapped exciton state and are important to increase the optical performance of Si NCs.

  17. Self assembly of SiO2-encapsulated carbon microsphere composites

    International Nuclear Information System (INIS)

    Yang Yongzhen; Song Jingjing; Han Yanxing; Guo Xingmei; Liu Xuguang; Xu Bingshe

    2011-01-01

    SiO 2 was firstly coated onto the surface of carbon microspheres (CMSs) using tetraethyl orthosilicate (TEOS) as precursor by Stoeber method. Then SiO 2 -encapsulated CMS (CMS-SiO 2 ) composites were self-assembled by vertical deposition, in which the effects of deposition temperature and suspension concentration on the quality of self-assembling film were investigated. Morphologies and structures of the samples were characterized by field emission scanning electron microscopy, Fourier transformation infrared spectrometry, X-ray diffraction and thermogravimetry. The results show that uniform CMS-SiO 2 composites with good mono-dispersion were prepared by Stober method with 0.5 g of CMSs, 2 mL of TEOS, 30 mL of ammonia and 12 h of reaction time, the CMSs-based films with ordered and denser structure were prepared by vertical deposition using CMS-SiO 2 composites as monodipersion spheres under suspension concentration of 1 wt% and deposition temperature of 50 deg. C. The ultraviolet-visible absorption measurement shows that the absorbance of CMS-SiO 2 composite films grew steadily with increasing suspension concentration.

  18. Photon Irradiation Response on Ge and Al-Doped SiO2 Optical Fibres

    Science.gov (United States)

    Yaakob, Nor Haliza; Wagiran, Husin; Ramli, Ahmad Termizi; Ali, Hassan; Asni, Hazila

    2010-07-01

    Recently, research groups have reported a number of radiation effects on the applications of SiO2 optical fibres with possible use as dosimeter material because these optical fibre provide a good basis for medical radiation dosimetry. The objective of this study is to investigate the thermoluminescence response and fading characteristic for germanium and aluminium doped SiO2 optical fibres with photon irradiation. These optical fibres are placed in solid phantom and irradiated to 6 and 10 MV photon beam at dose ranging from 0.06 Gy to 0.24 Gy using Primus MLC 3339 linear accelerator at Hospital Sultan Ismail, Johor Bahru. In fading studies, the TL measurements were continued up to 14 days period. The optical fibres will produce glow curves whereby the information is then analyzed. Al and Ge-doped optical fibres have a linear dose-TL signal relationship that is proportionality between the TL signal and the doses. Comparison for TL response between different linear accelerator showed a good agreement because these optical fibres also have a linear dose-TL signal relationship even using different equipments.

  19. Laser conditioning effect on HfO2/SiO2 film

    International Nuclear Information System (INIS)

    Wei Yaowei; Zhang Zhe; Liu Hao; Ouyang Sheng; Zheng Yi; Tang Gengyu; Chen Songlin; Ma Ping

    2013-01-01

    Laser conditioning is one of the important methods to improve the laser damage threshold of film optics. Firstly, a large aperture laser was used to irradiate the HfO 2 /SiO 2 reflectors, which were evaporated from hafnia and silica by e-beam. Secondly, a laser calorimeter was used to test the film absorption before and after laser irradiation. Focused ion beam (FIB) was few reported using on laser film, it was used to study the damage morphology and explore the cause of damage. The shooting of the partial ejection on nodule was obtained for the first time, which provided the basis for study the damage process. The results show that film absorption was decreased obviously after the laser irradiation, laser conditioning can raise the laser damage threshold by the 'cleaning mechanism'. For the HfO 2 /SiO 2 reflectors, laser conditioning was effective to eject the nodules on substrate. It resulted from the nodule residue not to affect the subsequent laser. In addition, laser conditioning was not effective to the nodule in the film, which might be from the material spatter in coating process. In this case, other method could be used to get rid of the nodules. (authors)

  20. Translocation of SiO2-NPs across in vitro human bronchial epithelial monolayer

    International Nuclear Information System (INIS)

    George, I; Vranic, S; Boland, S; Borot, M C; Marano, F; Baeza-Squiban, A

    2013-01-01

    Safe development and application of nanotechnologies in many fields require better knowledge about their potential adverse effects on human health. Evidence of abilities of nanoparticles (NPs) to cross epithelial barriers and reach secondary organs via the bloodstream led us to investigate the translocation of SiO 2 NPs of 50 nm (50 nm-SiO 2 -NPs) across human bronchial epithelial cells that are primary targets after exposure to inhaled NPs. We quantified the translocation of fluorescently labelled SiO 2 NPs at non-cytotoxic concentrations (5 and 10 μg/cm 2 ) across Calu-3 epithelial monolayer. After 14 days in culture Calu-3 cells seeded onto 3 μm-polycarbonate Transwell membranes formed an efficient bronchial barrier assessed by measurement of the transepithelial electric resistance and quantification of the permeability of the monolayer. After 24 hours of exposure, we observed a significant translocation of NPs that was more important when the initial NP concentration decreased. Confocal microscopy observations revealed NP uptake by cells and an important NP retention inside the porous membrane. In conclusion, 50 nm-SiO 2 -NPs can cross the human bronchial epithelial barrier without affecting the integrity of the epithelial cell monolayer.

  1. Wrinkling instability in graphene supported on nanoparticle-patterned SiO2

    Science.gov (United States)

    Cullen, William; Yamamoto, Mahito; Pierre-Louis, Olivier; Einstein, Theodore; Fuhrer, Michael

    2012-02-01

    Atomically-thin graphene is arguably the thinnest possible mechanical membrane: graphene's effective thickness (the thickness of an isotropic continuum slab which would have the same elastic and bending stiffness) is significantly less than 1 å, indicating that graphene can distort out-of-plane to conform to sub-nanometer features. Here we study the elastic response of graphene supported on a SiO2 substrate covered with SiO2 nanoparticles. At a low density of nanoparticles, graphene is largely pinned to the substrate due to adhesive interaction. However, with increasing nanoparticle density, graphene's elasticity dominates adhesion and strain is relieved by the formation of wrinkles which connect peaks introduced by the supporting nanoparticles. At a critical density, the wrinkles percolate, resulting in a wrinkle network. We develop a simple elastic model allowing for adhesion which accurately predicts the critical spacing between nanoparticles for wrinkle formation. This work has been supported by the University of Maryland NSF-MRSEC under Grant No. DMR 05-20471 with supplemental funding from NRI, and NSF-DMR 08-04976.

  2. Study of SiO2/PMMA/CE tri-component interpenetrating polymer network composites

    International Nuclear Information System (INIS)

    Wang Junlong; Wang Chuang; Jiao Gengsheng; Wang Qiuya

    2010-01-01

    A technology of conjugated tri-component interpenetrating polymer networks was applied to synthesize a nano-SiO 2 /polymethylmethacrylate (PMMA)/cyanate (CE) composite through an asynchronous synthesis way. The microstructure of the composite was characterized using infrared spectroscopy (IR) and transmission electron microscopy (TEM). The mechanical properties were measured in German-made DL-1000B and XCL-40 universal material test machines, respectively. Results showed that both the impact strength and the flexural strength were in the optimum status when 3% SiO 2 /PMMA/CE was chosen as a sample with the PMMA/CE ratio of 20/80. Compared with the strengths of pure cyanate, those of the composite were raised by 137.28% and 31.29%, respectively. When 3% nano-SiO 2 was added, the impact strength was increased by 29.96% and the flexural strength by 20.05%, compared with the strengths of polymers without SiO 2 . Analysis and measurements by IR and TEM indicated that no chemical reactions took place among components in the composite. The interpenetration of the conjugated tri-component improved the loading capacity of the polymer, hence the toughness enhancement of cyanate.

  3. Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

    Directory of Open Access Journals (Sweden)

    Giyjaz E. Bekmukhamedov

    2016-10-01

    Full Text Available Due to the continuously rising demand for C3–C5 olefins it is important to improve the performance of catalysts for dehydrogenation of light alkanes. In this work the effect of modification by SiO2 on the properties of the alumina support and the chromia-alumina catalyst was studied. SiO2 was introduced by impregnation of the support with a silica sol. To characterize the supports and the catalysts the following techniques were used: low-temperature nitrogen adsorption; IR-spectroscopy; magic angle spinning 29Si nuclear magnetic resonance; temperature programmed desorption and reduction; UV-Vis-, Raman- and electron paramagnetic resonance (EPR-spectroscopy. It was shown that the modifier in amounts of 2.5–7.5 wt % distributed on the support surface in the form of SiOx-islands diminishes the interaction between the alumina support and the chromate ions (precursor of the active component. As a result, polychromates are the compounds predominantly stabilized on the surface of the modified support; under thermal activation of the catalyst and are reduced to the amorphous Cr2O3. This in turn leads to an increase in the activity of the catalyst in the dehydrogenation of isobutane.

  4. Structure and magnetic properties of granular NiZn-ferrite - SiO2

    Directory of Open Access Journals (Sweden)

    Albuquerque Adriana Silva de

    1999-01-01

    Full Text Available Granular systems composed by nanostructured magnetic materials embedded in a non-magnetic matrix present unique physical properties that depend crucially on their nanostructure. In this work, we have studied the structural and magnetic properties of NiZn-ferrite nanoparticles embedded in SiO2, a granular system synthesized by sol-gel processing. Samples with ferrite volumetric fraction x ranging from 6% to 78% were prepared, and characterized by X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometry. Our results show the formation of pure stoichiometric NiZn-ferrite in the SiO2 matrix for x < 34%. Above these fraction, our samples presented also small amounts of Fe2O3. Mössbauer spectroscopy revealed the superparamagnetic behaviour of the ferrimagnetic NiZn-ferrite nanoparticles. The combination of different ferrite concentration and heat treatments allowed the obtaintion of samples with saturation magnetization between 1.3 and 68 emu/g and coercivity ranging from 0 to 123 Oe, value which is two orders of magnitude higher than the coercivity of bulk NiZn-ferrite.

  5. Amorphous Ge quantum dots embedded in SiO2 formed by low energy ion implantation

    International Nuclear Information System (INIS)

    Zhao, J. P.; Huang, D. X.; Jacobson, A. J.; Chen, Z. Y.; Makarenkov, B.; Chu, W. K.; Bahrim, B.; Rabalais, J. W.

    2008-01-01

    Under ultrahigh vacuum conditions, extremely small Ge nanodots embedded in SiO 2 , i.e., Ge-SiO 2 quantum dot composites, have been formed by ion implantation of 74 Ge + isotope into (0001) Z-cut quartz at a low kinetic energy of 9 keV using varying implantation temperatures. Transmission electron microscopy (TEM) images and micro-Raman scattering show that amorphous Ge nanodots are formed at all temperatures. The formation of amorphous Ge nanodots is different from reported crystalline Ge nanodot formation by high energy ion implantation followed by a necessary high temperature annealing process. At room temperature, a confined spatial distribution of the amorphous Ge nanodots can be obtained. Ge inward diffusion was found to be significantly enhanced by a synergetic effect of high implantation temperature and preferential sputtering of surface oxygen, which induced a much wider and deeper Ge nanodot distribution at elevated implantation temperature. The bimodal size distribution that is often observed in high energy implantation was not observed in the present study. Cross-sectional TEM observation and the depth profile of Ge atoms in SiO 2 obtained from x-ray photoelectron spectra revealed a critical Ge concentration for observable amorphous nanodot formation. The mechanism of formation of amorphous Ge nanodots and the change in spatial distribution with implantation temperature are discussed

  6. Anomalous defect processes in Si implanted amorphous SiO2, II

    International Nuclear Information System (INIS)

    Fujita, Tetsuo; Fukui, Minoru; Okada, Syunji; Shimizu-Iwayama, Tsutomu; Hioki, Tatsumi; Itoh, Noriaki

    1994-01-01

    Aanomalous features of the defects in Si implanted amorphous SiO 2 are reported. The numbers of E 1 prime centers and B 2 centers are found to increase monotonically with implanted Si dose, in contrast to the saturating feature of these numbers in Ar implanted samples. Moreover, when H ions are implanted in amorphous SiO 2 predamaged by Si implantation, both of the density and the number of E 1 prime centers increase and they reach a constant value at a small H dose. We point out that these anomalies can be explained in terms of the difference in the cross-section for defect annihilation in the specimens implanted with Si ions and other ions, in accordance with the homogeneous model proposed by Devine and Golanski. We consider that the main mechanism of defect annihilation is the recombination of an E 1 prime center and an interstitial O, which is stabilized by an implanted Si, reducing the cross-section in Si-implanted specimens. ((orig.))

  7. Beyond sixfold coordinated Si in SiO2 glass at ultrahigh pressures.

    Science.gov (United States)

    Prescher, Clemens; Prakapenka, Vitali B; Stefanski, Johannes; Jahn, Sandro; Skinner, Lawrie B; Wang, Yanbin

    2017-09-19

    We investigated the structure of SiO 2 glass up to 172 GPa using high-energy X-ray diffraction. The combination of a multichannel collimator with diamond anvil cells enabled the measurement of structural changes in silica glass with total X-ray diffraction to previously unachievable pressures. We show that SiO 2 first undergoes a change in Si-O coordination number from fourfold to sixfold between 15 and 50 GPa, in agreement with previous investigations. Above 50 GPa, the estimated coordination number continuously increases from 6 to 6.8 at 172 GPa. Si-O bond length shows first an increase due to the fourfold to sixfold coordination change and then a smaller linear decrease up to 172 GPa. We reconcile the changes in relation to the oxygen-packing fraction, showing that oxygen packing decreases at ultrahigh pressures to accommodate the higher than sixfold Si-O coordination. These results give experimental insight into the structural changes of silicate glasses as analogue materials for silicate melts at ultrahigh pressures.

  8. Crack-resistant Al2O3-SiO2 glasses.

    Science.gov (United States)

    Rosales-Sosa, Gustavo A; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki

    2016-04-07

    Obtaining "hard" and "crack-resistant" glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3-(100-x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3-SiO2 glasses. In particular, the composition of 60Al2O3 • 40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses.

  9. Effect of SiO2 coating in bolometric Ge light detectors for rare event searches

    International Nuclear Information System (INIS)

    Beeman, J.W.; Gentils, A.; Giuliani, A.; Mancuso, M.; Pessina, G.; Plantevin, O.; Rusconi, C.

    2013-01-01

    In germanium-based light detectors for scintillating bolometers, a SiO 2 anti-reflective coating is often applied on the side of the germanium wafer exposed to light with the aim to improve its light collection efficiency. In this paper, we report about a measurement, performed in the temperature range 25–35 mK, of the light-collection increase obtained thanks to this method, which resulted to be of the order of 20%. The procedure followed has been carefully selected in order to minimize systematic effects. The employed light sources have the same spectral features (peaking at ∼630nm wavelength) that will characterize future neutrinoless double beta decay experiments on the isotope 82 Se and based on ZnSe crystals, such as LUCIFER. The coupling between source and light detector reproduces the configuration used in scintillating bolometers. The present measurement clarifies the role of SiO 2 coating and describes a method and a set-up that can be extended to the study of other types of coatings and luminescent materials

  10. Effect of SiO2 coating in bolometric Ge light detectors for rare event searches

    Science.gov (United States)

    Beeman, J. W.; Gentils, A.; Giuliani, A.; Mancuso, M.; Pessina, G.; Plantevin, O.; Rusconi, C.

    2013-05-01

    In germanium-based light detectors for scintillating bolometers, a SiO2 anti-reflective coating is often applied on the side of the germanium wafer exposed to light with the aim to improve its light collection efficiency. In this paper, we report about a measurement, performed in the temperature range 25-35 mK, of the light-collection increase obtained thanks to this method, which resulted to be of the order of 20%. The procedure followed has been carefully selected in order to minimize systematic effects. The employed light sources have the same spectral features (peaking at ˜630 nm wavelength) that will characterize future neutrinoless double beta decay experiments on the isotope 82Se and based on ZnSe crystals, such as LUCIFER. The coupling between source and light detector reproduces the configuration used in scintillating bolometers. The present measurement clarifies the role of SiO2 coating and describes a method and a set-up that can be extended to the study of other types of coatings and luminescent materials.

  11. Location of trapped charge in aluminum-implanted SiO2

    International Nuclear Information System (INIS)

    DiMaria, D.J.; Young, D.R.; Hunter, W.R.; Serrano, C.M.

    1978-01-01

    The position of the centroid of electrons trapped on sites resulting from aluminum implantation into SiO 2 is measured by using the photo I-V technique for energies from 15 to 40 keV, oxide thicknesses from 49 to 140 nm, and post-implant annealing temperature from 600 to 1050 0 C in N 2 for 30 min. The centroid of the trapped electrons is found to be identical to that of the implanted aluminum from SIMS measurements, regardless of annealing temperature from 600 to 1050 0 C, and located closer (by less than 9 nm) to the Al--SiO 2 interface than predicted from the Lindhard-Scharff-Schott (LSS) calculations of Gibbons, Johnson, and Mylroie. Comparison of centroids determined from photo I-V and SIMS measurements as a function of SiO 2 thickness also implies that the distributions of the ions and negative trapped charge are the same. The trapping behavior of these sites is discussed in the accompanying paper by Young et al

  12. Electronic transport in bismuth selenide in the topological insulator regime

    Science.gov (United States)

    Kim, Dohun

    The 3D topological insulators (TIs) have an insulating bulk but spin-momentum coupled metallic surface states stemming from band inversion due to strong spin-orbit interaction, whose existence is guaranteed by the topology of the band structure of the insulator. While the STI surface state has been studied spectroscopically by e.g. photoemission and scanned probes, transport experiments have failed to demonstrate clear signature of the STI due to high level of bulk conduction. In this thesis, I present experimental results on the transport properties of TI material Bi2Se3 in the absence of bulk conduction (TI regime), achieved by applying novel p-type doping methods. Field effect transistors consisting of thin (thickness: 5-17 nm) Bi2Se3 are fabricated by mechanical exfoliation of single crystals, and a combination of conventional dielectric (300 nm thick SiO2) and electrochemical or chemical gating methods are used to move the Fermi energy through the surface Dirac point inside bulk band gap, revealing the ambipolar gapless nature of transport in the Bi2Se3 surface states. The minimum conductivity of the topological surface state is understood within the self-consistent theory of Dirac electrons in the presence of charged impurities. The intrinsic finite-temperature resistivity of the topological surface state due to electron-acoustic phonon scattering is measured to be 60 times larger than that of graphene largely due to the smaller Fermi and sound velocities in Bi2Se 3, which will have implications for topological electronic devices operating at room temperature. Along with semi-classical Boltzmann transport, I also discuss 2D weak anti-localization (WAL) behavior of the topological surface states. By investigating gate-tuned WAL behavior in thin (5-17 nm) TI films, I show that WAL in the TI regime is extraordinarily sensitive to the hybridization induced quantum mechanical tunneling between top and bottom topological surfaces, and interplay of phase coherence

  13. Silicon on insulator self-aligned transistors

    Science.gov (United States)

    McCarthy, Anthony M.

    2003-11-18

    A method for fabricating thin-film single-crystal silicon-on-insulator (SOI) self-aligned transistors. Standard processing of silicon substrates is used to fabricate the transistors. Physical spaces, between the source and gate, and the drain and gate, introduced by etching the polysilicon gate material, are used to provide connecting implants (bridges) which allow the transistor to perform normally. After completion of the silicon substrate processing, the silicon wafer is bonded to an insulator (glass) substrate, and the silicon substrate is removed leaving the transistors on the insulator (glass) substrate. Transistors fabricated by this method may be utilized, for example, in flat panel displays, etc.

  14. Superhydrophobic coatings fabricated with polytetrafluoroethylene and SiO2 nanoparticles by spraying process on carbon steel surfaces

    International Nuclear Information System (INIS)

    Wang, Haibin; Chen, Eryu; Jia, Xianbu; Liang, Lijun; Wang, Qi

    2015-01-01

    Graphical abstract: - Highlights: • The SiO 2 and PTFE NP-filled coatings exhibit excellent superhydrophobicity. • PTFE-filled coatings show denser structures and better liquid resistance than SiO 2 . • Air pocket of Wentzel model explains the difference in the superhydrophobicity. - Abstract: Superhydrophobicity is extensively investigated because of the numerous methods developed for water-repellant interface fabrication. Many suitable functional materials for the production of superhydrophobic surfaces on various substrates are still being explored. In this study, inorganic SiO 2 and organic polytetrafluoroethylene (PTFE) nanoparticles (NPs) are used for a comparative study on the performance of superhydrophobic coating on carbon steel surfaces. The NPs are added to PTFE coating emulsions by physical blending to form coating mixtures. Raw SiO 2 NPs are then hydrophobized using KH-570 and validated by Fourier transform-infrared spectroscopy (FT-IR) and Dynamic Laser Scattering (DLS) grain size analyses. The microstructures of the surfaces are characterized by contact angle (CA) measurements and field emission-scanning electron microscope (FE-SEM) images. The prepared surfaces are subjected to adhesion, hardness, water resistance, and acid/alkali erosion tests. Hydrophobized SiO 2 -filled coating surfaces are found to have better uniformity than raw SiO 2 regardless of their similar maximum static contact angles (SCAs) about 150°. A SCA of 163.1° is obtained on the PTFE NP-filled coating surfaces that have a considerably denser structure than SiO 2 . Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses reveal that all fabricated surfaces have good thermal stability and tolerate temperatures up to 550 °C. The PTFE NP-filled coating surfaces also exhibit excellent water and acid resistance. A possible mechanism concerning the amount of trapped air is proposed in relation to practical superhydrophobic surface fabrication

  15. Microstructural, thermal, physical and mechanical behavior of the self compacting concrete containing SiO2 nanoparticles

    International Nuclear Information System (INIS)

    Nazari, Ali; Riahi, Shadi

    2010-01-01

    Research highlights: → TiO 2 nanoparticles effects on flexural strength of self compacting concrete. → Physical and microstructural consideration. → Mechanical tests. → Thermal analysis. → Porosimetry. - Abstract: In the present study, flexural strength, thermal properties and microstructure of self compacting concrete with different amount of SiO 2 nanoparticles has been investigated. SiO 2 nanoparticles with the average particle size of 15 nm were partially added to self compacting concrete and various behaviors of the specimens have been measured. The results indicate that SiO 2 nanoparticles are able to improve the flexural strength of self compacting concrete and recover the negative effects of superplasticizer on flexural strength of the specimens. SiO 2 nanoparticle as a partial replacement of cement up to 4 wt% could accelerate C-S-H gel formation as a result of the increased crystalline Ca(OH) 2 amount at the early ages of hydration. The increased the SiO 2 nanoparticles' content more than 4 wt%, causes the reduced the flexural strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all also indicate that SiO 2 nanoparticles up to 4 wt% could improve the mechanical and physical properties of the specimens. Finally, SiO 2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.

  16. Physicochemical characterization of Fe3O4/SiO2/Au multilayer nanostructure

    International Nuclear Information System (INIS)

    Khosroshahi, Mohammad E.; Ghazanfari, Lida

    2012-01-01

    Highlights: ► The purpose of the research was to synthesize and characterize Fe 3 O 4 /SiO 2 /Au NPs. ► Uncoated MNPs showed an Ms range of 80–100 emu g −1 for particles between 35–96 nm. ► The magnetic NPs were modified with a thin layer of silica using Stober method. ► Small gold colloids (1–3 nm) were covered the amino functionalized particle surface. ► An absorption peak of 550 nm was obtained for a gold thickness of about 35 nm. - Abstract: The purpose of this research was to synthesize and characterize gold-coated Fe 3 O 4 /SiO 2 nanoshells for biomedical applications. Magnetite nanoparticles (NPs) were prepared using co-precipitation method. Smaller particles were synthesized by decreasing the NaOH concentration, which in our case this corresponded to 35 nm using 0.9 M of NaOH at 750 rpm with a specific surface area of 41 m 2 g −1 . For uncoated Fe 3 O 4 NPs, the results showed an octahedral geometry with saturation magnetization range of 80–100 emu g −1 and coercivity of 80–120 Oe for particles between 35 and 96 nm, respectively. The magnetic NPs were modified with a thin layer of silica using Stober method. Small gold colloids (1–3 nm) were synthesized using Duff method and covered the amino functionalized particle surface. Magnetic and optical properties of gold nanoshells were assessed using Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM), UV–Vis spectrophotometer, atomic and magnetic force microscope (AFM, MFM), and transmission electron microscope (TEM). Based on the X-ray diffraction (XRD) results, three main peaks of Au (1 1 1), (2 0 0) and (2 2 0) were identified. The formation of each layer of a nanoshell is also demonstrated by Fourier transform infrared (FTIR) results. The Fe 3 O 4 /SiO 2 /Au nanostructures, with 85 nm as particle size, exhibited an absorption peak at ∼550 nm with a magnetization value of 1.3 emu g −1 with a specific surface area of 71 m 2 g −1 .

  17. Formation of thin DLC films on SiO2/Si substrate using FCVAD technique

    International Nuclear Information System (INIS)

    Bootkul, D.; Intarasiri, S.; Aramwit, C.; Tippawan, U.; Yu, L.D.

    2013-01-01

    Diamond-like carbon (DLC) films deposited on SiO 2 /Si substrate are attractive for novel sensitive and selective chemical sensors. According to the almost never ending of size reduction, a nm-thickness layer of the film is greatly required. However, formation of such a very thin DLC film on SiO 2 /Si substrate is challenging. In this experiment, DLC films were formed using our in-house Filtered Cathodic Vacuum Arc Deposition (FCVAD) facility by varying the bias voltage of 0 V, −250 V and −450 V with the arc voltage of 350 V, 450 V, 550 V, 650 V and 750 V for 10 min. Raman spectroscopy was applied for characterization of the film qualities and Transmission Electron Microscopy (TEM) was applied for cross sectional analysis. Results showed that films of thickness ranging from 10–50 nm were easily acquired depending on deposition conditions. Deconvolution of Raman spectra of these samples revealed that, when fixing the substrate bias but increasing the arc voltage from 350 to 750 V, the ratio between D-peak and G-peak intensity, namely I D /I G ratio, tended to reduce up to the arc voltage of 450 V, then increased up to the arc voltage of 650 V and finally decreased again. On the other hand, when fixing the arc voltage, the I D /I G ratio tended to decrease continuously as the increasing of bias voltage. It can be concluded that the bonding structure would evolve from a graphitic-like structure to a diamond-like structure as the substrate bias increases. Additionally, the sp 3 site should be maximized at the arc voltage ∼450 V for fixed bias voltage. It is expected that, at −450 V bias and 450 V arc, sp 3 fractions could be higher than 60%. However, in some cases, e.g. at low arc voltages, voids formed between the film and the amorphous SiO 2 substrate. Electron energy loss spectroscopy (EELS) of the C edge across the DLC indicated that the thicker DLC film had uniform chemistry and structure, whereas the thin DLC film showed changes in the edge shape, indicating a gradual change in its properties between the edges and the core

  18. Low-voltage high-speed programming gate-all-around floating gate memory cell with tunnel barrier engineering

    Science.gov (United States)

    Hamzah, Afiq; Ezaila Alias, N.; Ismail, Razali

    2018-06-01

    The aim of this study is to investigate the memory performances of gate-all-around floating gate (GAA-FG) memory cell implementing engineered tunnel barrier concept of variable oxide thickness (VARIOT) of low-k/high-k for several high-k (i.e., Si3N4, Al2O3, HfO2, and ZrO2) with low-k SiO2 using three-dimensional (3D) simulator Silvaco ATLAS. The simulation work is conducted by initially determining the optimized thickness of low-k/high-k barrier-stacked and extracting their Fowler–Nordheim (FN) coefficients. Based on the optimized parameters the device performances of GAA-FG for fast program operation and data retention are assessed using benchmark set by 6 and 8 nm SiO2 tunnel layer respectively. The programming speed has been improved and wide memory window with 30% increment from conventional SiO2 has been obtained using SiO2/Al2O3 tunnel layer due to its thin low-k dielectric thickness. Furthermore, given its high band edges only 1% of charge-loss is expected after 10 years of ‑3.6/3.6 V gate stress.

  19. Charge trapping/de-trapping in nitrided SiO2 dielectrics and its influence on device reliability

    Science.gov (United States)

    Kambour, Kenneth; Hjalmarson, Harold; Nguyen, Duc; Kouhestani, Camron; Devine, Roderick

    2012-02-01

    Field effect devices with insulator gate dielectrics are excellent test vehicles to probe the physics of defects and charge trapping in the insulator/ semiconductor structure. p-channel field effect device reliability under negative bias stressing has been identified to originate from at least two terms: a) charged defect generation at the Si substrate/SiOxNy interface and b) charge trapping at neutral defect pre-cursors in the ``bulk'' of the SiOxNy beyond the interface. Measurements of transistor characteristics enable extraction of the two terms. We report the results of such measurements and demonstrate that short time effects are associated primarily with electric field assisted tunneling of holes from the inversion layer to neutral traps. This is confirmed by bias stressing measurements at different frequencies in the range 1 Hz to 2 MHz. First principles modeling of the tunneling/trapping phenomena is presented. K.Kambour worked under contract FA9453-08-C-0245 with the Air Force Research Laboratory/RVSE. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  20. Potentiodynamical deposition of nanostructured MnO2 film at the assist of electrodeposited SiO2 as template

    International Nuclear Information System (INIS)

    Wu, Lian-Kui; Xia, Jie; Hou, Guang-Ya; Cao, Hua-Zhen; Tang, Yi-Ping; Zheng, Guo-Qu

    2016-01-01

    Highlights: • MnO 2 -SiO 2 composite film is prepared by potentiodynamical deposition. • Hierarchical porous MnO 2 films is obtained after the etching of SiO 2 . • The obtained MnO 2 film electrode exhibit high specific capacitance. - Abstract: We report a novel silica co-electrodeposition route to prepare nanostructured MnO 2 films. Firstly, MnO 2 -SiO 2 composite film was fabricated on a stainless steel substrate by potentiodynamical deposition, i.e. cyclic deposition, and then the SiO 2 template was removed by simple immersion in concentrated alkaline solution, leading to the formation of a porous MnO 2 (po-MnO 2 ) matrix. The structure and morphology of the obtained films were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties of the po-MnO 2 film were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). Results showed that this porous MnO 2 derived from the MnO 2 -SiO 2 composite film exhibits good electrochemical performance for potential use as a supercapacitor material.

  1. Synthesis and Characterization of Ti-Phenyl at SiO2 Core-Shell Nanoparticles Catalyst

    International Nuclear Information System (INIS)

    Syamsi Aini; Jon Efendi; Syamsi Aini; Jon Efendi

    2012-01-01

    This study highlights the potential use of Ti-Phenyl at SiO 2 core-shell nanoparticles as heterogeneous catalysis in oxidation reaction. The Ti-Phenyl at SiO 2 was synthesized by reduction of TiCl 4 and diazonium salt with sodium borohydride to produce phenyl titanium nanoparticles (Ti-Phenyl), followed by the silica shell coating using tetraethyl orthosilicate (TEOS). The Ti-Phenyl at SiO 2 nanoparticles were characterized by Fourier transform infrared (FTIR) spectrometer, diffuse reflectance (DR) UV-visible spectrometer, thermogravimetric analyzer (TGA), X-ray diffraction (XRD) spectrometer, field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The core-shell size of Ti-Phenyl at SiO 2 was in the range of 40 to 100 nm with its core composed with an agglomeration of Ti-Phenyl. The Ti-Phenyl at SiO 2 was active as a catalyst in the liquid phase epoxidation of 1-octene with aqueous hydrogen peroxide as an oxidant. (author)

  2. Effect of SiO2, PVA and glycerol concentrations on chemical and mechanical properties of alginate-based films.

    Science.gov (United States)

    Yang, Manli; Shi, Jinsheng; Xia, Yanzhi

    2018-02-01

    Sodium alginate (SA)/polyvinyl alcohol (PVA)/SiO 2 nanocomposite films were prepared by in situ polymerization through solution casting and solvent evaporation. The effect of different SA/PVA ratios, SiO 2 , and glycerol content on the mechanical properties, water content, water solubility, and water vapor permeability were studied. The nanocomposite films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal stability (thermogravimetric analysis/differential thermogravimetry) analyses. The nanocomposites showed the highest values of mechanical properties, such as SA/PVA ratio, SiO 2 , and glycerol content was 7:3, 6wt.%, and 0.25g/g SA, respectively. The tensile strength and elongation at break (E%) of the nanocomposites increased by 525.7% and 90.7%, respectively, compared with those of the pure alginate film. The Fourier transform infrared spectra showed a new SiOC band formed in the SA/PVA/SiO 2 nanocomposite film. The scanning electron microscopy image revealed good adhesion between SiO 2 and SA/PVA matrix. After the incorporation of PVA and SiO 2 , the water resistance of the SA/PVA/SiO 2 nanocomposite film was markedly improved. Transparency decreased with increasing PVA content but was enhanced by adding SiO 2 . Copyright © 2017. Published by Elsevier B.V.

  3. INVESTIGATION ON PHYSICAL AND ELECTRICAL PROPERTIES OF THE SiO2-ZnO NANOCOMPOSITE AT DIFFERENT COMPOSITION MIXINGS

    Directory of Open Access Journals (Sweden)

    Moh. Sinol

    2018-01-01

    Full Text Available Physical and electrical properties of The SiO2-ZnO mixing at different compositions were investigated. The experiment used simple mixing method at the sintering temperature 600oC. It was used the composition mixing ratio of SiO2:ZnO ie. 0:10; 7:3; 5:5; 3:7; and 10:0 (%Wt. Based on X-Ray Diffraction (XRD results, it obtained that a new phase in each sample was not formed even though having different diffraction peak. The mixing ratio of SiO2: ZnO nanocomposite (7:3 %wt had the biggest grain size (77,92 nm, the highest dielectric constant (3.00E+05 and the smallest conductivity (0,726549 (Ωm-1. On the other side, the mixing ratio of SiO2: ZnO nanocomposite (5:5 %wt had the smallest grain size (35.42nm, dielectric constant (3.00E+2 and the highest conductivity (25.36729  (Ωm-1. It can be concluded that the difference of composition ratio offered the change on both physical and electrical properties of SiO2-ZnO nanocomposite.

  4. Thickness measurement of SiO2 films thinner than 1 nm by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Joong Kim, Kyung; Park, Ki Tae; Lee, Jong Wan

    2006-01-01

    The thickness measurement of ultra-thin SiO 2 films thinner than 1 nm was studied by X-ray photoelectron spectroscopy (XPS). Amorphous SiO 2 thin films were grown on amorphous Si films to avoid the thickness difference due to the crystalline structure of a substrate. SiO 2 thin films were grown by ion beam sputter deposition under oxygen gas flow and the thickness was measured by in situ XPS. The attenuation length was determined experimentally by a SiO 2 film with a known thickness. The straight line fit between the measured thickness using XPS and the nominal thickness showed a good linear relation with a gradient of 0.969 and a small offset of 0.126 nm. The gradient measured at the range of 3.4-0.28 nm was very close to that measured at sub-nanometer range of 1.13-0.28 nm. This result means that the reliable measurement of SiO 2 film thickness below 1 nm is possible by XPS

  5. Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

    Directory of Open Access Journals (Sweden)

    Ling Wang

    2017-02-01

    Full Text Available Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms, the highest gain coefficient (1.10 ms·pm2, the maximum Stark splitting manifold of 2F7/2 level (781 cm−1, and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers.

  6. Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

    DEFF Research Database (Denmark)

    Abel, Brett M.; Morgan, James M.; Mauro, John C.

    2013-01-01

    . In the composition range of interest for industrial glasses, Tliq tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO2, SiO2+Al2O3, and SrO contents, respectively. By comparison...... with the phase diagrams for CaO-Al2O3-SiO2 and MgO-Al2O3-SiO2 systems, we have found that for the highest [RO]/[Al2O3] ratios, Tliq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging...... to the SrO-Al2O3-SiO2 family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature....

  7. Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

    Science.gov (United States)

    Wang, Ling; Zeng, Huidan; Yang, Bin; Ye, Feng; Chen, Jianding; Chen, Guorong; Smith, Andew T.; Sun, Luyi

    2017-01-01

    Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms), the highest gain coefficient (1.10 ms·pm2), the maximum Stark splitting manifold of 2F7/2 level (781 cm−1), and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers. PMID:28772601

  8. Magnesium Removal from an Aluminum A-332 Molten Alloy Using Enriched Zeolite with Nanoparticles of SiO2

    Directory of Open Access Journals (Sweden)

    R. Muñoz-Arroyo

    2014-01-01

    Full Text Available In order to improve the Mg removal from an A-380 molten alloy, mixtures of zeolite and SiO2 nanoparticles (SiO2(NPs were tested. Zeolite was enriched with 2.5, 5, 7.5, 10, or 12.5 wt-% of amorphous SiO2(NPs. The SiO2(NPs and zeolite were mixed for 30 min in ethanol for each experiment and then dried in a furnace at 80°C for 12 h. The enriched zeolites were analyzed by scanning electron microscopy, transmission electron microscopy, and N2 gas adsorption analysis. The Mg removal was carried out injecting each mixture into the molten aluminum alloy at 750°C using argon. The Mg content of the molten alloy was measured after different periods of the injection time. Zeolites enriched with 2.5 and 5 wt-% of SiO2(NPs were demonstrated to be the better mixtures, removing Mg from an initial content of 1.6 to a final content of 0.0002 and 0.0101 wt-%, respectively, in 45 min of injection.

  9. VO x /SiO 2 Catalyst Prepared by Grafting VOCl 3 on Silica for Oxidative Dehydrogenation of Propane

    KAUST Repository

    Zhu, Haibo; Ould-Chikh, Samy; Dong, Hailin; Llorens, Isabelle; Saih, Youssef; Anjum, Dalaver H.; Hazemann, Jean Louis; Basset, Jean-Marie

    2015-01-01

    The VOx/SiO2 catalysts for oxidative dehydrogenation of propane were synthesized by a simple grafting method. The VOCl3 was first grafted at the surface of SiO2, which was dehydrated at different temperature (from 200 to 1000°C). The formed grafted complexes were then calcined in air, leading to the formation of VOx/SiO2 catalysts. The synthesized catalysts were characterized by nitrogen adsorption, SEM, Raman spectroscopy, temperature-programmed reduction, and extended X-ray absorption fine structure analysis. The SiO2 pretreatment temperature has an evident effect on the loading and dispersion of VOx on SiO2, which finally affects their catalytic performance. High SiO2 treatment temperature is beneficial to dispersing the vanadium oxide species at the SiO2 surface. These materials are efficient catalysts for the catalytic oxidative dehydrogenation of propane to propylene. The best selectivity to propylene is achieved on the VOx/SiO2-(1000) catalyst. The high selectivity and activity are well maintained for three days catalytic reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. VO x /SiO 2 Catalyst Prepared by Grafting VOCl 3 on Silica for Oxidative Dehydrogenation of Propane

    KAUST Repository

    Zhu, Haibo

    2015-09-07

    The VOx/SiO2 catalysts for oxidative dehydrogenation of propane were synthesized by a simple grafting method. The VOCl3 was first grafted at the surface of SiO2, which was dehydrated at different temperature (from 200 to 1000°C). The formed grafted complexes were then calcined in air, leading to the formation of VOx/SiO2 catalysts. The synthesized catalysts were characterized by nitrogen adsorption, SEM, Raman spectroscopy, temperature-programmed reduction, and extended X-ray absorption fine structure analysis. The SiO2 pretreatment temperature has an evident effect on the loading and dispersion of VOx on SiO2, which finally affects their catalytic performance. High SiO2 treatment temperature is beneficial to dispersing the vanadium oxide species at the SiO2 surface. These materials are efficient catalysts for the catalytic oxidative dehydrogenation of propane to propylene. The best selectivity to propylene is achieved on the VOx/SiO2-(1000) catalyst. The high selectivity and activity are well maintained for three days catalytic reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Optical properties of ZrO2, SiO2 and TiO2-SiO2 xerogels and coatings doped with Eu3+ and Eu2+

    Directory of Open Access Journals (Sweden)

    Gonçalves Rogéria R.

    1999-01-01

    Full Text Available Eu3+ doped bulk monoliths and thin films were obtained by sol-gel methods in the ZrO2, SiO2 and SiO2-TiO2 systems. Eu3+ 5D0 ® 7FJ emission and decay time characteristics were measured during the entire experimental preparation route from the initial sol to the final xerogels. The crystalline phases identified were tetragonal ZrO2 and mixtures of rutile and anatase TiO2 at high temperature treatments in bulk samples. Good quality thin films were obtained for all systems by dip-coating optical glasses (Schott BK270. The same spectroscopic features were observed either for the bulk monoliths or the films. By appropriate heat treatments under H2 atmosphere Eu2+ containing samples could be obtained in the SiO2-TiO2 system.

  12. A Grand Challenge for CMOS Scaling: Alternate Gate Dielectrics

    Science.gov (United States)

    Wallace, Robert M.

    2001-03-01

    Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.13 um complementary metal oxide semiconductor (CMOS) technology. The prospect of replacing SiO2 is a formidable task because the alternate gate dielectric must provide many properties that are, at a minimum, comparable to those of SiO2 yet with a much higher permittivity. A systematic examination of the required performance of gate dielectrics suggests that the key properties to consider in the selection an alternative gate dielectric candidate are (a) permittivity, band gap and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. We will review the performance requirements for materials associated with CMOS scaling, the challenges associated with these requirements, and the state-of-the-art in current research for alternate gate dielectrics. The requirements for process integration compatibility are remarkably demanding, and any serious candidates will emerge only through continued, intensive investigation.

  13. On formation of silicon nanocrystals under annealing SiO2 layers implanted with Si ions

    International Nuclear Information System (INIS)

    Kachurin, G.A.; Yanovskaya, S.G.; Volodin, V.A.; Kesler, V.G.; Lejer, A.F.; Ruault, M.-O.

    2002-01-01

    Raman scattering, X-ray photoelectron spectroscopy, and photoluminescence have been used to study the formation of silicon nanocrystals in SiO 2 implanted with Si ions. Si clusters have been formed at once in the postimplanted layers, providing the excessive Si concentration more ∼ 3 at. %. Si segregation with Si-Si 4 bonds formation is enhanced as following annealing temperature increase, however, the Raman scattering by Si clusters diminishes. The effect is explained by a transformation of the chain-like Si clusters into compact phase nondimensional structures. Segregation of Si nanoprecipitates had ended about 1000 deg C, but the strong photoluminescence typical for Si nanocrystals manifested itself only after 1100 deg C [ru

  14. Infrared spectroscopic ellipsometry of micrometer-sized SiO2 line gratings

    Science.gov (United States)

    Walder, Cordula; Zellmeier, Matthias; Rappich, Jörg; Ketelsen, Helge; Hinrichs, Karsten

    2017-09-01

    For the design and process control of periodic nano-structured surfaces spectroscopic ellipsometry is already established in the UV-VIS spectral regime. The objective of this work is to show the feasibility of spectroscopic ellipsometry in the infrared, exemplarily, on micrometer-sized SiO2 line gratings grown on silicon wafers. The grating period ranges from 10 to about 34 μm. The IR-ellipsometric spectra of the gratings exhibit complex changes with structure variations. Especially in the spectral range of the oxide stretching modes, the presence of a Rayleigh singularity can lead to pronounced changes of the spectrum with the sample geometry. The IR-ellipsometric spectra of the gratings are well reproducible by calculations with the RCWA method (Rigorous Coupled Wave Analysis). Therefore, infrared spectroscopic ellipsometry allows the quantitative characterization and process control of micrometer-sized structures.

  15. Incorporation of sol-gel SnO2:Sb into nanoporous SiO2

    International Nuclear Information System (INIS)

    Canut, B.; Blanchin, M.G.; Ramos-Canut, S.; Teodorescu, V.; Toulemonde, M.

    2006-01-01

    Silicon oxide films thermally grown on Si(1 0 0) wafers were irradiated with 200 MeV 197 Au ions in the 10 9 -10 1 cm -2 fluence range. The targets were then etched at room temperature in aqueous HF solution (1 vol.%) for various durations. Atomic force microscopy (AFM) in the tapping mode was used to probe the processed surfaces. Conical holes with a low size dispersion were evidenced. Their surface diameter varies between 20 and 70 nm, depending on the etching time. Sol-gel dip coating technique, associated with a further annealing treatment performed at 500 o C for 15 min, was used to fill the nanopores created in SiO 2 with a transparent conductive oxide (SnO 2 doped with antimony). Transmission electron microscopy (TEM) performed on cross-sectional specimen showed that SnO 2 :Sb crystallites of ∼5 nm mean size are trapped in the holes without degrading their geometry

  16. Lateral spread of P+ ions implanted in silicon through the SiO2 mask window

    International Nuclear Information System (INIS)

    Sakurai, T.; Kawata, H.; Sato, T.; Hisatsugu, T.; Hashimoto, H.; Furuya, T.

    1979-01-01

    The lateral spread of implanted P + ions and the shape of the mask window have been observed simultaneously using the technique of staining the cleaved surface and scanning electron microscopy for the Si samples with the SiO 2 mask window with a tapered edge. The mask edge with a gradient of 45 0 or 78 0 to the Si surface and the implanted n-type region with a carrier concentration higher than 2 x 10 17 /cm 3 are observed in the same photograph. The observed maximum lateral spread when the gradient of the mask edge is 45 0 is about 1.6 times larger than that when the gradient is 78 0 . The calculated results of the lateral spread agree relatively well with the experimental data although the precise analysis based on the definite basis is necessary

  17. Potassium ions in SiO2: electrets for silicon surface passivation

    Science.gov (United States)

    Bonilla, Ruy S.; Wilshaw, Peter R.

    2018-01-01

    This manuscript reports an experimental and theoretical study of the transport of potassium ions in thin silicon dioxide films. While alkali contamination was largely researched in the context of MOSFET instability, recent reports indicate that potassium ions can be embedded into oxide films to produce dielectric materials with permanent electric charge, also known as electrets. These electrets are integral to a number of applications, including the passivation of silicon surfaces for optoelectronic devices. In this work, electric field assisted migration of ions is used to rapidly drive K+ into SiO2 and produce effective passivation of silicon surfaces. Charge concentrations of up to ~5  ×  1012 e cm-2 have been achieved. This charge was seen to be stable for over 1500 d, with decay time constants as high as 17 000 d, producing an effectively passivated oxide-silicon interface with SRV  industrial manufacture of silicon optoelectronic devices.

  18. Ge nanocrystals embedded in ultrathin Si3N4 multilayers with SiO2 barriers

    Science.gov (United States)

    Bahariqushchi, R.; Gundogdu, Sinan; Aydinli, A.

    2017-04-01

    Multilayers of germanium nanocrystals (NCs) embedded in thin films of silicon nitride matrix separated with SiO2 barriers have been fabricated using plasma enhanced chemical vapor deposition (PECVD). SiGeN/SiO2 alternating bilayers have been grown on quartz and Si substrates followed by post annealing in Ar ambient from 600 to 900 °C. High resolution transmission electron microscopy (HRTEM) as well as Raman spectroscopy show good crystallinity of Ge confined to SiGeN layers in samples annealed at 900 °C. Strong compressive stress for SiGeN/SiO2 structures were observed through Raman spectroscopy. Size, as well as NC-NC distance were controlled along the growth direction for multilayer samples by varying the thickness of bilayers. Visible photoluminescence (PL) at 2.3 and 3.1 eV with NC size dependent intensity is observed and possible origin of PL is discussed.

  19. An algorithm for the calculation of heavy ion ranges in SiO2

    International Nuclear Information System (INIS)

    Kabadayi, Oe.; Guemues, H.

    2003-01-01

    The heavy ion ranges in amorphous SiO 2 have been calculated by using a technique based on solution of first order ODE's. Br, Au, Hg, Bi projectiles have been chosen as incident ions. Since the target is assumed to be amorphous, Bragg's rule can be used to calculate electronic and nuclear stopping powers in the compound. Numerical solutions have ben performed by using Fuhlberg fourth-fifth order Runge-Kutta method. The results are compared with experimental data, as well as with the result of Monte Carlo program SRIM and other standard procedures such as PRAL and WS. It is found that the agreement between our method and the experiment is good and within 10%. (author)

  20. Investigation of hydrogen and chlorine at the SiO2/Si interface

    International Nuclear Information System (INIS)

    Tsong, I.S.T.; Monkowski, M.D.; Monkowski, J.R.; Miller, P.D.; Moak, C.D.; Appleton, B.R.; Wintenberg, A.L.

    1980-01-01

    Silicon oxides thermally grown in H 2 O, O 2 , HCl/O 2 and Cl 2 /O 2 ambients were analyzed, via 1 H( 19 F,αγ) 16 O nuclear reaction and SIMS, for the presence of hydrogen. In addition, those oxides grown in HCl/O 2 and Cl 2 /O 2 ambients were analyzed with SIMS for the presence of chlorine. The SIMS data show that the hydrogen levels in these oxides were below the limit of detection for nuclear reaction experiments. The 35 Cl + depth-profiles show that chlorine is enriched at the SiO 2 interface for the HCl/O 2 grown oxides while it is more evenly distributed in oxide bulk in the Cl 2 /O 2 grown samples

  1. Defects in electron irradiated vitreous SiO2 probed by positron annihiliation

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro; Kawano, Takao; Itoh, Hisayoshi

    1994-01-01

    Defects in 3 MeV electron irradiated vitreous SiO 2 (v-SiO 2 ) were probed by the positron annihilation technique. For unirradiated v-SiO 2 specimens, almost all positrons were found to annihilate from positronium (Ps) states. This high formation probability of Ps was attributed to the trapping of positrons by open-space defects. The formation probability of Ps was decreased by the electron irradiation. The observed inhibition of the Ps formation was attributed to the trapping of positrons by point defects introduced and/or activated by the irradiation. From measurements of the lifetime distribution of Ps, it was found that, by the electron irradiation, the mean size of open-space defects was decreased and the size distribution of such defects was broadened. (Author)

  2. Defects in SiO2 crystals after neutron irradiations at 20 K and 360 K

    International Nuclear Information System (INIS)

    Nakagawa, M.; Okada, M.; Kawabata, Y.; Atobe, K.; Itoh, H.; Nakanishi, S.

    1994-01-01

    The synthetic silicon dioxide (SiO 2 ), cut parallel (x-plate) or perpendicular (z-plate) to c-axis, are irradiated by reactor neutrons at 360 K (2.8x10 18 n/cm 2 ) or at 20 K (8.0x10 16 n/cm 2 ). After neutron irradiation at 360 K, the main absorption peak can be observed at 212 nm (5.84 eV) for z-plate and 217 nm (5.71 eV) for x-plate. After irradiation at 20 K a new band at 250 nm (4.96 eV) can be observed in addition to the band at about 220 nm. The 250 nm band having FWHM similar 0.44 eV disappears at 300-340 K. Thermoluminescences are also observed between 80 to 400 K; which show some difference between x-plate and z-plate. ((orig.))

  3. Investigation of SiO2 thin films dielectric constant using ellipsometry technique

    Directory of Open Access Journals (Sweden)

    P Sangpour

    2014-11-01

    Full Text Available In this paper, we studied the optical behavior of SiO2 thin films prepared via sol-gel route using spin coating deposition from tetraethylorthosilicate (TEOS as precursor. Thin films were annealed at different temperatures (400-600oC. Absorption edge and band gap of thin layers were measured using UV-Vis spectrophotometery. Optical refractive index and dielectric constant were measured by ellipsometry technique. Based on our atomic force microscopic (AFM and ellipsometry results, thin layers prepared through this method showed high surface area, and high porosity ranging between 4.9 and 16.9, low density 2 g/cm, and low dielectric constant. The dielectric constant and porosity of layers increased by increasing the temperature due to the changes in surface roughness and particle size.

  4. Stability and kinetics of point defects in SiO2 and in SiC

    International Nuclear Information System (INIS)

    Roma, G.

    2012-01-01

    This document is conceived as an overview of Guido Roma's research achievements on defects stability and kinetics in two materials of interest in nuclear science and for many other application domains: silicon dioxide and silicon carbide. An extended summary in french is followed by the main document, in english. Chapter 1 describes the context, introduces the approach and explains the choice of silicon dioxide and silicon carbide. Chapter 2 discusses several approximations and specific issues of the application of Density Functional Theory to point defects in non-metallic materials for the study of defects energetics and diffusion. Chapter 3 is devoted to native defects in silicon dioxide and the understanding of self-diffusion in crystalline and amorphous SiO 2 . Chapter 4 summarises the results on native defects and palladium impurities in silicon carbide. A conclusion, including suggestions for future developments, closes the main part of the document. (author) [fr

  5. Emission Mechanisms of Si Nanocrystals and Defects in SiO2 Materials

    Directory of Open Access Journals (Sweden)

    José Antonio Rodríguez

    2014-01-01

    Full Text Available Motivated by the necessity to have all silicon optoelectronic circuits, researchers around the world are working with light emitting silicon materials. Such materials are silicon dielectric compounds with silicon content altered, such as silicon oxide or nitride, enriched in different ways with Silicon. Silicon Rich Oxide or silicon dioxide enriched with silicon, and silicon rich nitride are without a doubt the most promising materials to reach this goal. Even though they are subjected to countless studies, the light emission phenomenon has not been completely clarified. So, a review of different proposals presented to understand the light emission phenomenon including emissions related to nanocrystals and to point defects in SiO2 is presented.

  6. Orientation of pentacene molecules on SiO2: From a monolayer to the bulk

    International Nuclear Information System (INIS)

    Zheng, Fan; Park, Byoung-Nam; Seo, Soonjoo; Evans, Paul G.; Himpsel, F. J.

    2007-01-01

    Near edge x-ray absorption fine structure (NEXAFS) spectroscopy is used to study the orientation of pentacene molecules within thin films on SiO 2 for thicknesses ranging from monolayers to the bulk (150 nm). The spectra exhibit a strong polarization dependence of the π * orbitals for all films, which indicates that the pentacene molecules are highly oriented. At all film thicknesses the orientation varies with the rate at which pentacene molecules are deposited, with faster rates favoring a thin film phase with different tilt angles and slower rates leading to a more bulklike orientation. Our NEXAFS results extend previous structural observations to the monolayer regime and to lower deposition rates. The NEXAFS results match crystallographic data if a finite distribution of the molecular orientations is included. Damage to the molecules by hot electrons from soft x-ray irradiation eliminates the splitting between nonequivalent π * orbitals, indicating a breakup of the pentacene molecule

  7. Visible light emission from silicon implanted and annealed SiO2layers

    International Nuclear Information System (INIS)

    Ghislotti, G.; Nielsen, B.; Asoka-Kumar, P.; Lynn, K.G.; Di Mauro, L.F.; Bottani, C.E.; Corni, F.; Tonini, R.; Ottaviani, G.P.

    1997-01-01

    Silicon implanted and annealed SiO 2 layers are studied using photoluminescence (PL) and positron annihilation spectroscopy (PAS). Two PL emission bands are observed. A band centered at 560 nm is present in as-implanted samples and it is still observed after 1,000 C annealing. The emission time is fast. A second band centered at 780 nm is detected after 1,000 C annealing. The intensity of the 780 nm band further increased when hydrogen annealing was performed. The emission time is long (1 micros to 0.2 ms). PAS results show that defects produced by implantation anneal at 600 C. Based on the annealing behavior and on the emission times, the origin of the two bands is discussed

  8. SiO2 sol-gel films after ammonia and heat two-step treatments

    International Nuclear Information System (INIS)

    Zhang Chunlai; Wang Biyi; Tian Dongbin; Yin Wei; Jiang Xiaodong; Yuan Xiaodong; Yan Lianghong; Zhang Hongliang; Zhao Songnan; Lv Haibing

    2008-01-01

    SiO 2 thin films were deposited using tetraethoxylsilane as precursor, ammonia as catalyst on K9 glass by sol-gel method. These films were post-treated by ammonia and heat. The properties of the coatings were characterized by ellipsometer, UV-vis spectrophotometry, FTIR-spectroscopy, scanning probe microscope and contact angle measurement apparatus. The resuits indicate that the thickness of the films with ammonia and heat treatment tend to decrease. Both the refractive index and water contact angle increase after ammonia treatment. However, they both decrease after heat treatment. The former increases by 0.236 for the first step, then decreases by 0.202 for the second. The latter increases to 58.92 degree, then decreases to 38.07 degree. The transmittance of the coatings turn to be better and continuously shift to short wave by UV-vis spectrophotometry. The surface becomes smoother by AFM after the two-step treatment. (authors)

  9. Space charge limitation of the current in implanted SiO2 layers

    International Nuclear Information System (INIS)

    Szydlo, N.; Poirier, R.

    1974-01-01

    Metal-oxide-semiconductor capacitors were studied where the metal is a semitransparent gold layer of 5mm diameter, the oxide is thermal silica whose, thickness depends on the nature of the implant, and the semiconductor is N-type silicon of 5 ohms/cm. The SiO 2 thickness was chosen in such a way that the maximum of the profile of the implanted substance is in the medium of the oxide layer. In the case of virgin silica, the oscillations in the photocurrent versus energy and exponential variations versus the applied voltage show that the photoconduction obeys the model of injection limited current. In the case of the oxide after ion bombardment, the photocurrent similarity, independent of the direction of the electric field in silica, shows that volume transport phenomena become preponderent [fr

  10. Channel mobility degradation and charge trapping in high-k/metal gate NMOSFETs

    International Nuclear Information System (INIS)

    Mathew, Shajan; Bera, L.K.; Balasubramanian, N.; Joo, M.S.; Cho, B.J.

    2004-01-01

    NMOSFETs with Metalo-Organic Chemical Vapor Deposited (MOCVD) HfAlO gate dielectric and TiN metal gate have been fabricated. Channel electron mobility was measured using the split-CV method and compared with SiO 2 devices. All high-k devices showed lower mobility compared with SiO 2 reference devices. High-k MOSFETs exhibited significant charge trapping and threshold instability. Threshold voltage recovery with time was studied on devices with oxide/nitride interfacial layer between high-k film and silicon substrate

  11. In-situ grown CNTs modified SiO2/C composites as anode with improved cycling stability and rate capability for lithium storage

    Science.gov (United States)

    Wang, Siqi; Zhao, Naiqin; Shi, Chunsheng; Liu, Enzuo; He, Chunnian; He, Fang; Ma, Liying

    2018-03-01

    Silica (SiO2) is regarded as one of the most promising anode materials for lithium ion batteries owing to its high theoretical specific capacity, relatively low operation potentials, abundance, environmental benignity and low cost. However, the low intrinsic electrical conductivity and large volume change of SiO2 during the discharge/charge cycles usually results in poor electrochemical performance. In this work, carbon nanotubes (CNTs) modified SiO2/C composites have been fabricated through an in-situ chemical vapor deposition method. The results show that the electrical conductivity of the SiO2/C/CNTs is visibly enhanced through a robust connection between the CNTs and SiO2/C particles. Compared with the pristine SiO2 and SiO2/C composites, the SiO2/C/CNTs composites display a high initial capacity of 1267.2 mA h g-1. Besides, an excellent cycling stability with the capacity of 315.7 mA h g-1 is achieved after 1000th cycles at a rate of 1 A g-1. The significantly improved electrochemical properties of the SiO2/C/CNTs composites are mainly attributed to the formation of three dimensional CNT networks in the SiO2/C substrate, which can not only shorten the Li-ion diffusion path but also relieve the volume change during the lithium-ion insertion/extraction processes.

  12. Photoluminescent characteristics of ion beam synthesized Ge nanoparticles in thermally grown SiO2 films

    International Nuclear Information System (INIS)

    Yu, C.F.; Chao, D.S.; Chen, Y.-F.; Liang, J.H.

    2013-01-01

    Prospects of developing into numerous silicon-based optoelectronic applications have prompted many studies on the optical properties of Ge nanoparticles within a silicon oxide (SiO 2 ) matrix. Even with such abundant studies, the fundamental mechanism underlying the Ge nanoparticle-induced photoluminescence (PL) is still an open question. In order to elucidate the mechanism, we dedicate this study to investigating the correlation between the PL properties and microstructure of the Ge nanoparticles synthesized in thermally grown SiO 2 films. Our spectral data show that the peak position, at ∼3.1 eV or 400 nm, of the PL band arising from the Ge nanoparticles was essentially unchanged under different Ge implantation fluences and the temperatures of the following annealing process, whereas the sample preparation parameters modified or even fluctuated (in the case of the annealing temperature) the peak intensity considerably. Given the microscopically observed correlation between the nanoparticle structure and the sample preparation parameters, this phenomenon is consistent with the mechanism in which the oxygen-deficiency-related defects in the Ge/SiO 2 interface act as the major luminescence centers; this mechanism also successfully explains the peak intensity fluctuation with the annealing temperature. Moreover, our FTIR data indicate the formation of GeO x upon ion implantation. Since decreasing of the oxygen-related defects by the GeO x formation is expected to be correlated with the annealing temperature, presence of the GeO x renders further experimental support to the oxygen defect mechanism. This understanding may assist the designing of the manufacturing process to optimize the Ge nanoparticle-based PL materials for different technological applications

  13. Exploring the Phase Diagram SiO2-CO2 at High Pressures and Temperatures

    Science.gov (United States)

    Kavner, A.

    2015-12-01

    CO2 is an important volatile system relevant for planetary sciences and fundamental chemistry. Molecular CO2 has doubly bonded O=C=O units but high pressure-high temperature (HP-HT) studies have recently shown its transformation into a three-dimensional network of corner-linked [CO4] units analogous to the silica mineral polymorphs, through intermediate non-molecular phases. Here, we report P-V-T data on CO2-IV ice from time-of-flight neutron diffraction experiments, which allow determining the compressibility and thermal expansivity of this intermediate molecular-to-non-molecular phase.1 Aditionally, we have explored the SiO2-CO2 phase diagram and the potential formation of silicon carbonate compounds. New data obtained by laser-heating diamond-anvil experiments in CO2-filled microporous silica polymorphs will be shown. In particular, these HP-HT experiments explore the existence of potential CO2/SiO2 compounds with tetrahedrally-coordinated C/Si atoms by oxygens, which are predicted to be stable (or metastable) by state-of-the-art ab initio simulations.2,3 These theoretical predictions were supported by a recent study that reports the formation of a cristobalite-type Si0.4C0.6O2 solid solution at high-pressures and temperatures, which can be retained as a metastable solid down to ambient conditions.4 Entirely new families of structures could exist based on [CO4]4- units in various degrees of polymerisation, giving rise to a range of chain, sheet and framework solids like those found in silicate chemistry. References[1] S. Palaich et al., Am. Mineral. Submitted (2015) [2] A. Morales-Garcia et al., Theor. Chem. Acc. 132, 1308 (2013) [3] R. Zhou et al., Phys. Rev. X, 4, 011030 (2014) [4] M. Santoro et al. Nature Commun. 5, 3761 (2014)

  14. Fluorescence of Pentavalent Chromium in SiO2 Sol-Gel Glasses

    Science.gov (United States)

    Jia, Weiyi; Castro, Lymari; Wang, Yanyun; Liu, Huimin

    1998-01-01

    Chromium ions are very attractive to optical spectroscopy and laser physics. It is well known that the first laser in the history is a ruby laser activated with Cr(3+). It was found in early nineties that Cr(4+) was also an interesting lasing ion in the near infrared, and various Cr(4+) lasers have been developed. Very recently, it was reported that Cr(2+) doped in CdSe crystals showed lasing action in the infrared. The above achievement have stimulated an interest in searching for Cr(5+) and investigating its optical properties. Cr(5+) is isoelectronic with Ti(3+) and V(4+), having electron configuration 3d1. Ti(3+) is the active center of commercial cw and femtosecond sapphire lasers, tunable in the range 680-1100 nm. V(4+) doped in YAlO3 and Al2O3 showed broad band emission near 635 nm. Although EPR results of Cr(5+) were reported, the optical properties were less studied. Herren et al. reported an observation of luminescence from Cr doped in SiO2 sol-gel glass. The luminescence spectrum was assigned to pentavalent ions in their first paper, and later it was identified to be the emission from the charge transfer transition of Cr(6+). The first observation of photoluminescence from octahedrally coordinated Cr(5+) in BaCaMg aluminate glasses was reported very recently. In this work, we report luminescence results of Cr doped SiO2 sol-gel glasses. The fluorescence spectra are very different from Herrens' results, and we believe it originates from pentavalent Cr.

  15. Suppression of dewetting phenomena during excimer laser melting of thin metal films on SiO2

    International Nuclear Information System (INIS)

    Kline, J.E.; Leonard, J.P.

    2005-01-01

    Pulsed excimer laser irradiation has been used to fully melt 200 nm films of elemental Au and Ni on SiO 2 substrates. With the use of a capping layer of SiO 2 and line irradiation via projection optics, the typical liquid-phase dewetting processes associated with these metals on SiO 2 has been suppressed. In a series of experiments varying line widths and fluence, a process region is revealed immediately above the complete melting threshold for which the films remain continuous and smooth after melting and resolidification. Simple energetic arguments for mechanisms leading to initiation of dewetting support these observations, and a gas-mediated model is proposed to describe the process conditions that are necessary for the suppression of dewetting

  16. Silver nanoparticle deposition on inverse opal SiO2 films embedded in protective polypropylene micropits for SERS applications

    Science.gov (United States)

    Ammosova, Lena; Ankudze, Bright; Philip, Anish; Jiang, Yu; Pakkanen, Tuula T.; Pakkanen, Tapani A.

    2018-01-01

    Common methods to fabricate surface enhanced Raman scattering (SERS) substrates with controlled micro-nanohierarchy are often complex and expensive. In this study, we demonstrate a simple and cost effective method to fabricate SERS substrates with complex geometries. Microworking robot structuration is used to pattern a polypropylene (PP) substrate with micropits, facilitating protective microenvironment for brittle SiO2 inverse opal (IO) structure. Hierarchical SiO2 IO patterns were obtained using polystyrene (PS) spheres as a sacrificial template, and were selectively embedded into the hydrophilized PP micropits. The same microworking robot technique was subsequently used to deposit silver nanoparticle ink into the SiO2 IO cavities. The fabricated multi-level micro-nanohierarchy surface was studied to enhance Raman scattering of the 4-aminothiophenol (4-ATP) analyte molecule. The results show that the SERS performance of the micro-nanohierarchical substrate increases significantly the Raman scattering intensity compared to substrates with structured 2D surface geometries.

  17. Site-specific Pt deposition and etching on electrically and thermally isolated SiO2 micro-disk surfaces

    International Nuclear Information System (INIS)

    Saraf, Laxmikant V

    2010-01-01

    Electrically and thermally isolated surfaces are crucial for improving the detection sensitivity of microelectronic sensors. The site-specific in situ growth of Pt nano-rods on thermally and electrically isolated SiO 2 micro-disks using wet chemical etching and a focused ion/electron dual beam (FIB-SEM) is demonstrated. Fabrication of an array of micro-cavities on top of a micro-disk is also demonstrated. The FIB source is utilized to fabricate through-holes in the micro-disks. Due to the amorphous nature of SiO 2 micro-disks, the Ga implantation possibly modifies through-hole sidewall surface chemistry rather than affecting its transport properties. Some sensor design concepts based on micro-fabrication of SiO 2 micro-disks utilizing thermally and electrically isolated surfaces are discussed from the viewpoint of applications in photonics and bio-sensing.

  18. Determining oxide trapped charges in Al2O3 insulating films on recessed AlGaN/GaN heterostructures by gate capacitance transients measurements

    Science.gov (United States)

    Fiorenza, Patrick; Greco, Giuseppe; Schilirò, Emanuela; Iucolano, Ferdinando; Lo Nigro, Raffaella; Roccaforte, Fabrizio

    2018-05-01

    This letter presents time-dependent gate-capacitance transient measurements (C–t) to determine the oxide trapped charges (N ot) in Al2O3 films deposited on recessed AlGaN/GaN heterostructures. The C–t transients acquired at different temperatures under strong accumulation allowed to accurately monitor the gradual electron trapping, while hindering the re-emission by fast traps that may affect conventional C–V hysteresis measurements. Using this method, an increase of N ot from 2 to 6 × 1012 cm‑2 was estimated between 25 and 150 °C. The electron trapping is ruled by an Arrhenius dependence with an activation energy of 0.12 eV which was associated to points defects present in the Al2O3 films.

  19. Influence of the charge trap density distribution in a gate insulator on the positive-bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eungtaek; Kim, Choong-Ki; Lee, Myung Keun; Bang, Tewook; Choi, Yang-Kyu; Choi, Kyung Cheol, E-mail: shkp@kaist.ac.kr, E-mail: kyungcc@kaist.ac.kr [School of Electrical Engineering, KAIST, Daejeon 34141 (Korea, Republic of); Park, Sang-Hee Ko, E-mail: shkp@kaist.ac.kr, E-mail: kyungcc@kaist.ac.kr [Department of Material Science and Engineering, KAIST, Daejeon 34141 (Korea, Republic of)

    2016-05-02

    We investigated the positive-bias stress (PBS) instability of thin film transistors (TFTs) composed of different types of first-gate insulators, which serve as a protection layer of the active surface. Two different deposition methods, i.e., the thermal atomic layer deposition (THALD) and plasma-enhanced ALD (PEALD) of Al{sub 2}O{sub 3}, were applied for the deposition of the first GI. When THALD was used to deposit the GI, amorphous indium-gallium-zinc oxide (a-IGZO) TFTs showed superior stability characteristics under PBS. For example, the threshold voltage shift (ΔV{sub th}) was 0 V even after a PBS time (t{sub stress}) of 3000 s under a gate voltage (V{sub G}) condition of 5 V (with an electrical field of 1.25 MV/cm). On the other hand, when the first GI was deposited by PEALD, the ΔV{sub th} value of a-IGZO TFTs was 0.82 V after undergoing an identical amount of PBS. In order to interpret the disparate ΔV{sub th} values resulting from PBS quantitatively, the average oxide charge trap density (N{sub T}) in the GI and its spatial distribution were investigated through low-frequency noise characterizations. A higher N{sub T} resulted during in the PEALD type GI than in the THALD case. Specifically, the PEALD process on a-IGZO layer surface led to an increasing trend of N{sub T} near the GI/a-IGZO interface compared to bulk GI owing to oxygen plasma damage on the a-IGZO surface.

  20. Influence of the charge trap density distribution in a gate insulator on the positive-bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors

    International Nuclear Information System (INIS)

    Kim, Eungtaek; Kim, Choong-Ki; Lee, Myung Keun; Bang, Tewook; Choi, Yang-Kyu; Choi, Kyung Cheol; Park, Sang-Hee Ko

    2016-01-01

    We investigated the positive-bias stress (PBS) instability of thin film transistors (TFTs) composed of different types of first-gate insulators, which serve as a protection layer of the active surface. Two different deposition methods, i.e., the thermal atomic layer deposition (THALD) and plasma-enhanced ALD (PEALD) of Al_2O_3, were applied for the deposition of the first GI. When THALD was used to deposit the GI, amorphous indium-gallium-zinc oxide (a-IGZO) TFTs showed superior stability characteristics under PBS. For example, the threshold voltage shift (ΔV_t_h) was 0 V even after a PBS time (t_s_t_r_e_s_s) of 3000 s under a gate voltage (V_G) condition of 5 V (with an electrical field of 1.25 MV/cm). On the other hand, when the first GI was deposited by PEALD, the ΔV_t_h value of a-IGZO TFTs was 0.82 V after undergoing an identical amount of PBS. In order to interpret the disparate ΔV_t_h values resulting from PBS quantitatively, the average oxide charge trap density (N_T) in the GI and its spatial distribution were investigated through low-frequency noise characterizations. A higher N_T resulted during in the PEALD type GI than in the THALD case. Specifically, the PEALD process on a-IGZO layer surface led to an increasing trend of N_T near the GI/a-IGZO interface compared to bulk GI owing to oxygen plasma damage on the a-IGZO surface.

  1. Enhanced the hydrophobic surface and the photo-activity of TiO2-SiO2 composites

    Science.gov (United States)

    Wahyuni, S.; Prasetya, A. T.

    2017-02-01

    The aim of this research is to develop nanomaterials for coating applications. This research studied the effect of various TiO2-SiO2 composites in acrylic paint to enhance the hydrophobic properties of the substrate. Titanium dioxide containing silica in the range 20-35 mol% has been synthesized using sol-gel route. The XRD’s spectra show that increasing SiO2 content in the composite, decreasing its crystalline properties but increasing the surface area. TiO2-SiO2 composite was dispersed in acrylic paint in 2% composition by weight. The largest contact angle was 70, which produced by the substrate coated with TS-35-modified acrylic paint. This study also investigated the enhanced photo-activity of TiO2-SiO2 modified with poly-aniline. The XRD spectra show that the treatment does not change the crystal structure of TiO2. The photo-activity of the composite was evaluated by degradation of Rhodamine-B with visible light. The best performance of the degradation process was handled by the composite treated with 0.1mL anilines per gram of TiO2-SiO2 composite (TSP-A). On the other side, the contact angle 70 has not shown an excellent hydrophobic activity. However, the AFM spectra showed that nanoroughness has started to form on the surface of acrylic paint modified with TiO2-SiO2 than acrylic alone.

  2. A comparative study on omnidirectional anti-reflection SiO2 nanostructure films coating by glancing angle deposition

    Science.gov (United States)

    Prachachet, R.; Samransuksamer, B.; Horprathum, M.; Eiamchai, P.; Limwichean, S.; Chananonnawathorn, C.; Lertvanithphol, T.; Muthitamongkol, P.; Boonruang, S.; Buranasiri, P.

    2018-02-01

    Fabricated omnidirectional anti-reflection nanostructure films as a one of the promising alternative solar cell applications have attracted enormous scientific and industrial research benefits to their broadband, effective over a wide range of incident angles, lithography-free and high-throughput process. Recently, the nanostructure SiO2 film was the most inclusive study on anti-reflection with omnidirectional and broadband characteristics. In this work, the three-dimensional silicon dioxide (SiO2) nanostructured thin film with different morphologies including vertical align, slant, spiral and thin films were fabricated by electron beam evaporation with glancing angle deposition (GLAD) on the glass slide and silicon wafer substrate. The morphological of the prepared samples were characterized by field-emission scanning electron microscope (FE-SEM) and high-resolution transmission electron microscope (HRTEM). The transmission, omnidirectional and birefringence property of the nanostructure SiO2 films were investigated by UV-Vis-NIR spectrophotometer and variable angle spectroscopic ellipsometer (VASE). The spectrophotometer measurement was performed at normal incident angle and a full spectral range of 200 - 2000 nm. The angle dependent transmission measurements were investigated by rotating the specimen, with incidence angle defined relative to the surface normal of the prepared samples. This study demonstrates that the obtained SiO2 nanostructure film coated on glass slide substrate exhibits a higher transmission was 93% at normal incident angle. In addition, transmission measurement in visible wavelength and wide incident angles -80 to 80 were increased in comparison with the SiO2 thin film and glass slide substrate due to the transition in the refractive index profile from air to the nanostructure layer that improve the antireflection characteristics. The results clearly showed the enhanced omnidirectional and broadband characteristic of the three dimensional SiO2 nanostructure film coating.

  3. Effect of SiO2 concentration in silica sol on interface reaction during titanium alloy investment casting

    Directory of Open Access Journals (Sweden)

    Ya-meng Wei

    2018-01-01

    Full Text Available Using silica sol as a binder for titanium investment casting is very attractive due to its good stability and reasonable cost as compared with yttrium sol and zirconium sol. However, the mechanism of interface reaction in the related system remains unclear. In this investigation, the interface reaction between Y2O3-SiO2 (Y-Si shell mold and titanium alloys was studied. A group of shell molds were prepared by using Y2O3 sand and silica sol with different contents of SiO2. Ti-6Al-4V alloy was cast under vacuum by gravity casting through cold crucible induction melting (CCIM method. Scanning electron microscopy (SEM and energy dispersive x-ray spectroscopy (EDS were employed to characterize the micromorphology and composition of the reaction area, respectively. X-ray photoelectron spectroscopy (XPS was used to confirm the valence state of relevant elements. White light interferometer (WLI was used to obtain the surface topography of Y-Si shells. The results show that the thickness of reaction layers is below 3 μm when the SiO2 content of silica sol is below 20wt.%. Whereas, when the SiO2 content increases to 25wt.%, the thickness of the reaction layer increases sharply to about 15 μm. There is a good balance between chemical inertness and mechanical performance when the SiO2 content is between 15 and 20wt.%. Moreover, it was found that the distribution of SiO2 and the roughness at the surface of the shell are the key factors that determine the level of reaction.

  4. Osteoblast interaction with laser cladded HA and SiO2-HA coatings on Ti-6Al-4V

    International Nuclear Information System (INIS)

    Yang Yuling; Serpersu, Kaan; He Wei; Paital, Sameer R.; Dahotre, Narendra B.

    2011-01-01

    In order to improve the bioactivity and biocompatibility of titanium endosseous implants, the morphology and composition of the surfaces were modified. Polished Ti-6Al-4V substrates were coated by a laser cladding process with different precursors: 100 wt.% HA and 25 wt.% SiO 2 -HA. X-ray diffraction of the laser processed samples showed the presence of CaTiO 3 , Ca 3 (PO 4 ) 2 , and Ca 2 SiO 4 phases within the coatings. From in vitro studies, it was observed that compared to the unmodified substrate all laser cladded samples presented improved cellular interactions and bioactivity. The samples processed with 25 wt.% SiO 2 -HA precursor showed a significantly higher HA precipitation after immersion in simulated body fluid than 100 wt.% HA precursor and titanium substrates. The in vitro biocompatibility of the laser cladded coatings and titanium substrate was investigated by culturing of mouse MC3T3-E1 pre-osteoblast cell line and analyzing the cell viability, cell proliferation, and cell morphology. A significantly higher cell attachment and proliferation rate were observed for both laser cladded 100 wt.% HA and 25 wt.% SiO 2 -HA samples. Compared to 100 wt.% HA sample, 25 wt.% SiO 2 -HA samples presented a slightly improved cellular interaction due to the addition of SiO 2 . The staining of the actin filaments showed that the laser cladded samples induced a normal cytoskeleton and well-developed focal adhesion contacts. Scanning electron microscopic image of the cell cultured samples revealed better cell attachment and spreading for 25 wt.% SiO 2 -HA and 100 wt.% HA coatings than titanium substrate. These results suggest that the laser cladding process improves the bioactivity and biocompatibility of titanium. The observed biological improvements are mainly due to the coating induced changes in surface chemistry and surface morphology. Highlights: → Laser cladding of Ti alloys with bioceramics creates new phases. → Laser cladded samples with SiO 2 -doped bioceramics show higher mineralization in vitro. → Addition of SiO 2 improves surface wettability. → Significantly better osteoblast growth was observed for laser cladded samples.

  5. Facile preparation of polyethylenimine-tannins coated SiO2 hybrid materials for Cu2+ removal

    Science.gov (United States)

    Huang, Qiang; Liu, Meiying; Zhao, Jiao; Chen, Junyu; Zeng, Guangjian; Huang, Hongye; Tian, Jianwen; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2018-01-01

    Polyethylenimine-tannins coated SiO2 (SiO2@PEI-TA) hybrid materials have been prepared via a single-step multifunctional coating with polyethylenimine (PEI) and tannins (TA), and characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The as-prepared SiO2@PEI-TA composites were examined as adsorbents to remove the Cu2+ from aqueous solution. The effects of contact time, initial Cu2+ concentration, solution pH and temperature, on Cu2+ adsorption have been investigated. The results show that the adsorption of Cu2+ onto SiO2@PEI-TA is dependent on the contact time, Cu2+ concentration, pH and temperature. The SiO2@PEI-TA composites show a 2.4-fold increase in adsorption capacity, implying that the introduction of PEI-TA coating is in favor of the Cu2+ adsorption. Based on the analysis of kinetic data, the kinetics of Cu2+ adsorption is more accurately described by the pseudo-second-order model. The equilibrium data are analyzed by Langmuir and Freundlich isotherms. Results of isotherms show that the better agreement is Freundlich isotherm model with correlation coefficient of 0.9914, which suggests that the adsorption of Cu2+ onto SiO2@PEI-TA is mainly a heterogeneous adsorption process. Thermodynamic analyses show that the adsorption interaction is actually a spontaneous and endothermic chemical process, which might involve the chemical chelation between Cu2+ and functional groups (amine and carboxyl groups) on the surface of SiO2@PEI-TA. In addition, the Cu2+ ions could desorb from SiO2@PEI-TA by using acid solution and the adsorption efficiency remains at high level after five adsorption-desorption recycles. These results provide potential applications of these novel adsorbents for the removal of heavy metal Cu2+ from aqueous solution and also provide strong evidence to support the adsorption mechanism proposed in the study.

  6. High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Volkmann, U.G.; Pino, M.; Altamirano, L.A.

    2002-01-01

    -crystal substrates. Our results suggest a model of a solid dotriacontane film that has a phase closest to the SiO2 surface in which the long-axis of the molecules is oriented parallel to the interface. Above this "parallel film" phase, a solid monolayer adsorbs in which the molecules are oriented perpendicular...... at higher coverages. In addition, we have performed high-resolution ellipsometry and stray-light measurements on dotriacontane films deposited from solution onto highly oriented pyrolytic graphite substrates. After film deposition, these substrates proved to be less stable in air than SiO2....

  7. The investigation of influence of accelerated electrons on SiO2 used in silicon solar cells

    International Nuclear Information System (INIS)

    Abdullaev, G.B.; Bakirov, M.Ya; Akhmedov, G.M.; Safarov, N.A.; Safarova, F.D.

    1994-01-01

    The process of radiation defects production in enlightened SiO 2 layers coated on silicon solar cells was studied. During irradiation the silicon solar cells with enlightened layers radiation defects are formed both in silicon and SiO 2 thus making worse photo energetic parameters of cells. For investigation of radiation effects formed under irradiation by electrons with 5 MeV energy and cobalt-60 gamma-rays photoluminescence, absorption spectra and electron spin resonance methods were used. It is supposed that main radiation defects in silicon dioxide are E'-centers and oxygen vacancies. (A.D. Avezov). 10 refs.; 2 figs

  8. Volume labeling with Alexa Fluor dyes and surface functionalization of highly sensitive fluorescent silica (SiO2) nanoparticles

    Science.gov (United States)

    Wang, Wei; Nallathamby, Prakash D.; Foster, Carmen M.; Morrell-Falvey, Jennifer L.; Mortensen, Ninell P.; Doktycz, Mitchel J.; Gu, Baohua; Retterer, Scott T.

    2013-10-01

    A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems. Electronic supplementary information (ESI) available: Cell culture preparation for dose/response imaging experiments. See DOI: 10.1039/c3nr02639f

  9. Positron annihilation studies of silicon-rich SiO2 produced by high dose ion implantation

    International Nuclear Information System (INIS)

    Ghislotti, G.; Nielsen, B.; Asoka-Kumar, P.; Lynn, K.G.; Di Mauro, L.F.; Corni, F.; Tonini, R.

    1997-01-01

    Positron annihilation spectroscopy (PAS) is used to study Si-rich SiO 2 samples prepared by implantation of Si (160 keV) ions at doses in the range 3x10 16 endash 3x10 17 cm -2 and subsequent thermal annealing at high temperature (up to 1100 degree C). Samples implanted at doses higher than 5x10 16 cm -2 and annealed above 1000 degree C showed a PAS spectrum with an annihilation peak broader than the unimplanted sample. We discuss how these results are related to the process of silicon precipitation inside SiO 2 . copyright 1997 American Institute of Physics

  10. THE THERMODYNAMIC PROPERTIES OF MELTS OF DOUBLE SYSTEM MgO – Al2O3, MgO – SiO2, MgO – CaF2, Al2O3 – SiO2, Al2O3 – CaF2, SiO2 – CaF2

    Directory of Open Access Journals (Sweden)

    В. Судавцова

    2012-04-01

    Full Text Available Methodology of prognostication of thermodynamics properties of melts is presented from the coordinatesof liquidus of diagram of the state in area of equilibria a hard component is solution, on which energies ofmixing of Gibbs are expected in the double border systems of MgO – Al2O3, MgO – SiO2, MgO – CaF2,Al2O3 – SiO2, Al2O3 - CaF2, SiO2 - CaF2. For the areas of equilibrium there is quasibinary connection(MgAl2O4, Mg2SiO4, Al6Si2O13 – a grout at calculations was used equalization of Hauffe-Wagner. Theobtained data comport with literary

  11. Selenide isotope generator for the Galileo Mission: SIG thermal insulation evaluaion tests

    International Nuclear Information System (INIS)

    1979-06-01

    Since the SIG program required the use of very high performance thermal insulation materials in rather severe thermal and environmental conditions, a thorough screening and testing program was performed. Several types of materials were included in the preliminary survey. Most promising were oxide and carbonaceous fibrous insulations, oxide and carbonaceous foamed materials, and multilayer materials with both powder and cloth spacers. The latter were only viable for the vacuum option. In all, over one hundred materials from more than sixty manufacturers were evaluated from literature and manufacturers' data. The list was pared to eighteen candidates in seven basic types, i.e., fibrous microporous SiO 2 , fibrous SiO 2 /Al 2 O 3 , fibrous ZrO 2 , fibrous carbon, foamed SiO 2 , foamed carbon, and multilayer. Test results are presented

  12. Remaining Useful Life Estimation of Insulated Gate Biploar Transistors (IGBTs Based on a Novel Volterra k-Nearest Neighbor Optimally Pruned Extreme Learning Machine (VKOPP Model Using Degradation Data

    Directory of Open Access Journals (Sweden)

    Zhen Liu

    2017-11-01

    Full Text Available The insulated gate bipolar transistor (IGBT is a kind of excellent performance switching device used widely in power electronic systems. How to estimate the remaining useful life (RUL of an IGBT to ensure the safety and reliability of the power electronics system is currently a challenging issue in the field of IGBT reliability. The aim of this paper is to develop a prognostic technique for estimating IGBTs’ RUL. There is a need for an efficient prognostic algorithm that is able to support in-situ decision-making. In this paper, a novel prediction model with a complete structure based on optimally pruned extreme learning machine (OPELM and Volterra series is proposed to track the IGBT’s degradation trace and estimate its RUL; we refer to this model as Volterra k-nearest neighbor OPELM prediction (VKOPP model. This model uses the minimum entropy rate method and Volterra series to reconstruct phase space for IGBTs’ ageing samples, and a new weight update algorithm, which can effectively reduce the influence of the outliers and noises, is utilized to establish the VKOPP network; then a combination of the k-nearest neighbor method (KNN and least squares estimation (LSE method is used to calculate the output weights of OPELM and predict the RUL of the IGBT. The prognostic results show that the proposed approach can predict the RUL of IGBT modules with small error and achieve higher prediction precision and lower time cost than some classic prediction approaches.

  13. PENGUJIAN AKTIVITAS KOMPOSIT Fe2O3-SiO2 SEBAGAI FOTOKATALIS PADA FOTODEGRADASI 4-KLOROFENOL (The Activity Test of Fe2O3-SiO2 Composite As Photocatalyst on 4-Chlorophenol Photodegradation

    Directory of Open Access Journals (Sweden)

    Eko Sri Kunarti

    2009-03-01

    Full Text Available ABSTRAK  Pada penelitian ini telah dilakukan pengujian aktivitas komposit Fe2O3-SiO2 sebagai fotokatalis pada fotodegradasi 4-klorofenol. Penelitian diawali dengan preparasi dan karakterisasi fotokatalis Fe2O3-SiO2. Preparasi dilakukan dengan metode sol-gel pada temperatur kamar menggunakan tetraetil ortosilikat (TEOS dan besi (III nitrat sebagai prekursor diikuti dengan perlakuan termal pada temperature 500 oC. Karakterisasi dilakukan dengan metode spektrometri inframerah, difraksi sinar-X dan spektrometri fluoresensi sinar-X. Uji aktivitas komposit untuk fotodegradasi 4-klorofenol dilakukan dalam reaktor tertutup yang dilengkapi dengan lampu UV. Pada uji ini telah dipelajari pengaruh waktu penyinaran dan pH larutan terhadap efektivitas fotodegradasi 4-klorofenol. Hasil penelitian menunjukkan bahwa komposit Fe2O3-SiO2 dapat dipreparasi dengan metode sol-gel pada temperatur kamar diikuti perlakuan termal. Komposit Fe2O3-SiO2 dapat meningkatkan efektivitas fotodegradasi 4-klorofenol dari 11,86 % menjadi 55,38 %. Efektivitas fotodegradasi 4- klorofenol dipengaruhi waktu penyinaran dan pH larutan yang semakin lama waktu penyinaran efektifitas fotodegradasi semakin tinggi, namun waktu penyinaran yang lebih lama dari 4 jam dapat menurunkan efektivitasnya. pH larutan memberikan pengaruh yang berbeda-beda pada efektivitas fotodegradasi 4-klorofenol.   ABSTRACT The activity test of Fe2O3-SiO2 composite as photocatalyst on 4-chlorophenol photodegradation has been studied. The research was initiated by preparation of Fe2O3-SiO2 photocatalyst and followed by characterization. The preparation was conducted by sol-gel method at room temperature using tetraethylorthosilicate (TEOS and iron (III nitrate as precursors followed by thermal treatment at a temperature of 500oC. The characterizations were performed by X-ray Diffraction (XRD, Infrared and X-ray Fluorescence Spectrophotometry. The photocatalytic activity test of composites for 4 chlorophenol degradation was carried out in a closed reactor equipped with UV light. In this test, the influences of irradiation time and 4-chlorophenol pH were studied.  Results showed that the composite could be prepared through sol-gel method. The Fe2O3-SiO2 composite could increase activity of 4-chlorophenol photodegradation from 11.86 % to 55.38 %. The photodegradation effectiveness was influenced by irradiating time and pH of solution. The pH of solution gave different 4-chlorophenol photodegradation effectiveness.

  14. The influence of SiO2 Addition on 2MgO-Al2O3-3.3P2O5 Glass

    DEFF Research Database (Denmark)

    Larsen, P.H.; Poulsen, F.W.; Berg, Rolf W.

    1999-01-01

    2MgO-Al2O3-3.3P2O5 glasses with increasing amounts of SiO2 are considered for sealing applications in Solid Oxide Fuel Cells (SOFC). The change in chemical durability under SOFC anode conditions and the linear thermal expansion is measured as functions of the SiO2 concentration. Raman spectroscopy...... analysis of the glasses reveals no sign of important changes in the glass structure upon SiO2 addition. Some increase in glass durability with SiO2 concentration is reported and its cause is discussed....

  15. Atomic force microscopy measurements of topography and friction on dotriacontane films adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Trogisch, S.; Simpson, M.J.; Taub, H.

    2005-01-01

    We report comprehensive atomic force microscopy (AFM) measurements at room temperature of the nanoscale topography and lateral friction on the surface of thin solid films of an intermediate-length normal alkane, dotriacontane (n-C32H66), adsorbed onto a SiO2 surface. Our topographic and frictional...

  16. Flexible SiO2 cantilevers for torsional self-aligning micro scale four-point probes

    DEFF Research Database (Denmark)

    Kjær, Daniel; Gammelgaard, Lauge; Bøggild, Peter

    2007-01-01

    In order to successfully measure the conductivity of a sample with a four- point probe, good alignment of the electrodes to the sample is important to establish even contact pressure and contact areas of the electrodes. By incorporating a hinge in a microfabricated SiO2 mono- cantilever the ability...

  17. Composite SiOx/hydrocarbon plasma polymer films prepared by RF magnetron sputtering of SiO2 and polyimide

    Czech Academy of Sciences Publication Activity Database

    Drabik, M.; Kousal, J.; Pinosh, Y.; Choukourov, A.; Biederman, H.; Slavínská, D.; Macková, Anna; Boldyryeva, Hanna; Pešička, J.

    2007-01-01

    Roč. 81, č. 7 (2007), s. 920-927 ISSN 0042-207X Institutional research plan: CEZ:AV0Z10480505 Keywords : composite films * magnetron * sputtering * polyimide * SiO2 Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.881, year: 2007

  18. Fixed-bed adsorption separation of xylene isomers over sio2/silicallite-1 core-shell adsorbents

    KAUST Repository

    Khan, Easir A.; Rajendran, Arvind; Lai, Zhiping

    2013-01-01

    SiO2/Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin

  19. Enhanced Visible Transmittance of Thermochromic VO2 Thin Films by SiO2 Passivation Layer and Their Optical Characterization

    Directory of Open Access Journals (Sweden)

    Jung-Hoon Yu

    2016-07-01

    Full Text Available This paper presents the preparation of high-quality vanadium dioxide (VO2 thermochromic thin films with enhanced visible transmittance (Tvis via radio frequency (RF sputtering and plasma enhanced chemical vapor deposition (PECVD. VO2 thin films with high Tvis and excellent optical switching efficiency (Eos were successfully prepared by employing SiO2 as a passivation layer. After SiO2 deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO2 coating, the phase transition temperature (Tc of the prepared films was not affected. Compared with pristine VO2, the total layer thickness after SiO2 coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO2 thin films showed a higher Tvis value (λ 650 nm, 58% compared with the pristine samples (λ 650 nm, 43%. This enhancement of Tvis while maintaining high Eos is meaningful for VO2-based smart window applications.

  20. FTIR and Raman spectroscopy of carbon nanoparticles in SiO2, ZnO and NiO matrices

    CSIR Research Space (South Africa)

    Katumba, G

    2008-11-01

    Full Text Available Coatings of carbon nanoparticles dispersed in SiO2, ZnO and NiO matrices on aluminium substrates have been fabricated by a sol–gel technique. Spectrophotometry was used to determine the solar absorptance and the thermal emittance of the composite...

  1. Porous SiO2/HAp Coatings on Cp-Titanium Grade 1 Surfaces Produced by Electrophoretic Deposition

    Directory of Open Access Journals (Sweden)

    Moskalewicz T.

    2016-12-01

    Full Text Available Porous hydroxyapatite doped SiO2 coatings were electrophoretically deposited (EPD on commercially pure titanium. The influence of EPD parameters on coatings quality was investigated. Microstructural observation was done using transmission and scanning electron microscopy as well as X-ray diffractometry.

  2. Light coupling and distribution for Si3N4/SiO2 integrated multichannel single-mode sensing system

    Science.gov (United States)

    Kaźmierczak, Andrzej; Dortu, Fabian; Schrevens, Olivier; Giannone, Domenico; Bouville, David; Cassan, Eric; Gylfason, Kristinn B.; Sohlström, Hans; Sanchez, Benito; Griol, Amadeu; Hill, Daniel

    2009-01-01

    We present an efficient and highly alignment-tolerant light coupling and distribution system for a multichannel Si3N4/SiO2 single-mode photonics sensing chip. The design of the input and output couplers and the distribution splitters is discussed. Examples of multichannel data obtained with the system are given.

  3. Influence of SiO2 Addition on Properties of PTFE/TiO2 Microwave Composites

    Science.gov (United States)

    Yuan, Ying; Wang, Jie; Yao, Minghao; Tang, Bin; Li, Enzhu; Zhang, Shuren

    2018-01-01

    Composite substrates for microwave circuit applications have been fabricated by filling polytetrafluoroethylene (PTFE) polymer matrix with ceramic powder consisting of rutile TiO2 ( D 50 ≈ 5 μm) partially substituted with fused amorphous SiO2 ( D 50 ≈ 8 μm) with composition x vol.% SiO2 + (50 - x) vol.% TiO2 ( x = 0, 3, 6, 9, 12), and the effects of SiO2 addition on characteristics such as the density, moisture absorption, microwave dielectric properties, and thermal properties systematically investigated. The results show that the filler was well distributed throughout the matrix. High dielectric constant ( ɛ r > 7.19) and extremely low moisture absorption (ceramic particles served as barriers and improved the thermal stability of the PTFE polymer, retarding its decomposition. The temperature coefficient of dielectric constant ( τ ɛ ) of the composites shifted toward the positive direction (from - 309 ppm/°C to - 179 ppm/°C) as the SiO2 content was increased, while the coefficient of thermal expansion remained almost unchanged (˜ 35 ppm/°C).

  4. Deposition of conductive TiN shells on SiO2 nanoparticles with a fluidized bed ALD reactor

    NARCIS (Netherlands)

    Didden, A.; Hillebrand, P.; Wollgarten, M.; Dam, B.; Van de Krol, R.

    2016-01-01

    Conductive TiN shells have been deposited on SiO2 nanoparticles (10–20 nm primary particle size) with fluidized bed atomic layer deposition using TDMAT and NH3 as precursors. Analysis of the powders confirms that shell growth saturates at approximately 0.4 nm/cycle at TDMAT doses of >1.2 mmol/g of

  5. Matrix solid-phase dispersion extraction of organophosphorus pesticide using SiO2-poly(N-vinylimidazole)

    International Nuclear Information System (INIS)

    Gutiérrez-Solís, M C; Muñoz-Rodríguez, D; Carrera-Figueiras, C; Ávila-Ortega, A; Medina-Peralta, S

    2013-01-01

    A sorbent material based on silica particles modified with poly(N-vinylimidazole) (SiO 2 -PVI) has been evaluated for the treatment of samples by matrix solid-phase dispersion (MSPD). The extraction of four organophosphorus pesticides was done from a spiked tomato and the extracts were analyzed by gas chromatography coupled to mass spectrometry. Six elution solvents were evaluated and acetone was selected due to better recovery of the four pesticides and low background signal in the chromatograms. A factorial design 2 4 was used for selection of extraction conditions. The factors were contact time, acetone volume, treatment (with or without freeze-drying) and adsorbent (SiO 2 or SiO 2 -PVI). The best recoveries were obtained using 15 minutes of contact, 2 mL of solvent and sorbent without freeze-drying. The recoveries were between 60 and 83% for SiO 2 -PVI in spiked tomato with 0.2 and 0.8μg/g.

  6. Wear and friction performance of PTFE filled epoxy composites with a high concentration of SiO2 particles

    NARCIS (Netherlands)

    Shen, J.T.; Top, M.; Pei, Y.T.; de Hosson, Jeff

    2015-01-01

    In this work, the tribological performance of PTFE filled SiO2 particles–epoxy composites is investigated. Under a load of 60 N (~140 MPa contact pressure), the optimum content of PTFE lies between 10 and 15 wt%, which yields an ultralow coefficient of friction (CoF) in conjunction with a low wear

  7. Effects of SiO2 and TiO2 fillers on thermal and dielectric properties ...

    Indian Academy of Sciences (India)

    Administrator

    eco-friendly bismuth glass microcomposites of plasma display panels. SHIV PRAKASH SINGH ... MS received 12 November 2008; revised 18 March 2009. Abstract. The effects .... In view of above, in this paper we report the effects of. SiO2 (amorphous) ..... mic Membrane Sections of this institute for carrying out the XRD and ...

  8. Raman and optical absorption spectroscopic investigation of Yb-Er codoped phosphate glasses containing SiO2

    Institute of Scientific and Technical Information of China (English)

    Youkuo Chen; Lei Wen; Lili Hu; Wei Chen; Y. Guyot; G. Boulon

    2009-01-01

    Yb-Er codoped Na2O-Al2O3-P2Os-xSiO2 glasses containing 0 鈥? 20 mol% SiO2 were prepared successfully. The addition of SiO2 to the phosphate glass not only lengthens the bond between P5+ and non-bridging oxygen but also reduces the number of P=O bond. In contrast with silicate glass in which there is only four-fold coordinated Si4+, most probably there coexist [SiO4] tetrahedron and [SiO6] octahedron in our glasses. Within the range of 0 鈥? 20 mol% SiO2 addition, the stimulated emission cross-section of Er3+ ion only decreases no more than 10%. The Judd-Ofelt intensity parameters of Er3+, 惟.2 does not change greatly, but 惟74 and 惟6 decrease obviously with increasing SiO2 addition, because the bond between Er + and O2- is more strongly covalently bonded.

  9. Highly transparent and UV-resistant superhydrophobic SiO2-coated ZnO nanorod arrays

    KAUST Repository

    Gao, Yangqin; Gereige, Issam; El Labban, Abdulrahman; Cha, Dong Kyu; Isimjan, Tayirjan T.; Beaujuge, Pierre

    2014-01-01

    Highly transparent and UV-resistant superhydrophobic arrays of SiO 2-coated ZnO nanorods are prepared in a sequence of low-temperature (<150 C) steps on both glass and thin sheets of PET (2 × 2 in. 2), and the superhydrophobic nanocomposite

  10. An SFG study of interfacial amino acids at the hydrophilic SiO2 and hydrophobic deuterated polystyrene surfaces.

    Science.gov (United States)

    Holinga, George J; York, Roger L; Onorato, Robert M; Thompson, Christopher M; Webb, Nic E; Yoon, Alfred P; Somorjai, Gabor A

    2011-04-27

    Sum frequency generation (SFG) vibrational spectroscopy was employed to characterize the interfacial structure of eight individual amino acids--L-phenylalanine, L-leucine, glycine, L-lysine, L-arginine, L-cysteine, L-alanine, and L-proline--in aqueous solution adsorbed at model hydrophilic and hydrophobic surfaces. Specifically, SFG vibrational spectra were obtained for the amino acids at the solid-liquid interface between both hydrophobic d(8)-polystyrene (d(8)-PS) and SiO(2) model surfaces and phosphate buffered saline (PBS) at pH 7.4. At the hydrophobic d(8)-PS surface, seven of the amino acids solutions investigated showed clear and identifiable C-H vibrational modes, with the exception being l-alanine. In the SFG spectra obtained at the hydrophilic SiO(2) surface, no C-H vibrational modes were observed from any of the amino acids studied. However, it was confirmed by quartz crystal microbalance that amino acids do adsorb to the SiO(2) interface, and the amino acid solutions were found to have a detectable and widely varying influence on the magnitude of SFG signal from water at the SiO(2)/PBS interface. This study provides the first known SFG spectra of several individual amino acids in aqueous solution at the solid-liquid interface and under physiological conditions.

  11. High thermal stability of abrupt SiO2/GaN interface with low interface state density

    Science.gov (United States)

    Truyen, Nguyen Xuan; Taoka, Noriyuki; Ohta, Akio; Makihara, Katsunori; Yamada, Hisashi; Takahashi, Tokio; Ikeda, Mitsuhisa; Shimizu, Mitsuaki; Miyazaki, Seiichi

    2018-04-01

    The effects of postdeposition annealing (PDA) on the interface properties of a SiO2/GaN structure formed by remote oxygen plasma-enhanced chemical vapor deposition (RP-CVD) were systematically investigated. X-ray photoelectron spectroscopy clarified that PDA in the temperature range from 600 to 800 °C has almost no effects on the chemical bonding features at the SiO2/GaN interface, and that positive charges exist at the interface, the density of which can be reduced by PDA at 800 °C. The capacitance-voltage (C-V) and current density-SiO2 electric field characteristics of the GaN MOS capacitors also confirmed the reduction in interface state density (D it) and the improvement in the breakdown property of the SiO2 film after PDA at 800 °C. Consequently, a high thermal stability of the SiO2/GaN structure with a low fixed charge density and a low D it formed by RP-CVD was demonstrated. This is quite informative for realizing highly robust GaN power devices.

  12. Chemical gating of epitaxial graphene through ultrathin oxide layers.

    Science.gov (United States)

    Larciprete, Rosanna; Lacovig, Paolo; Orlando, Fabrizio; Dalmiglio, Matteo; Omiciuolo, Luca; Baraldi, Alessandro; Lizzit, Silvano

    2015-08-07

    We achieved a controllable chemical gating of epitaxial graphene grown on metal substrates by exploiting the electrostatic polarization of ultrathin SiO2 layers synthesized below it. Intercalated oxygen diffusing through the SiO2 layer modifies the metal-oxide work function and hole dopes graphene. The graphene/oxide/metal heterostructure behaves as a gated plane capacitor with the in situ grown SiO2 layer acting as a homogeneous dielectric spacer, whose high capacity allows the Fermi level of graphene to be shifted by a few hundreds of meV when the oxygen coverage at the metal substrate is of the order of 0.5 monolayers. The hole doping can be finely tuned by controlling the amount of interfacial oxygen, as well as by adjusting the thickness of the oxide layer. After complete thermal desorption of oxygen the intrinsic doping of SiO2 supported graphene is evaluated in the absence of contaminants and adventitious adsorbates. The demonstration that the charge state of graphene can be changed by chemically modifying the buried oxide/metal interface hints at the possibility of tuning the level and sign of doping by the use of other intercalants capable of diffusing through the ultrathin porous dielectric and reach the interface with the metal.

  13. Fully patterned p-channel SnO TFTs using transparent Al2O3 gate insulator and ITO as source and drain contacts

    Science.gov (United States)

    Guzmán-Caballero, D. E.; Quevedo-López, M. A.; De la Cruz, W.; Ramírez-Bon, R.

    2018-03-01

    SnO p-type was used as active layer to fabricate thin film transistors (TFTs) through photolithography and dry etching processes. The SnO p-type thin films (25 nm) were deposited by DC reactive sputtering with variable oxygen (O2) flow rate to then be annealed in air at 250 ◦C. Al2O3 gate dielectric (15 nm) was deposited by atomic layer deposition. Hall measurements showed p-type carrier concentration (N h ) of around 1 × 1018 cm-3 and Hall mobilities (μ Hall) between 0.35 and 2.64 cm2 V-1 s-1, depending on the O2 flow rate during deposition. The hole transport was dominated by variable-range hopping conduction. A change in the preferred crystalline orientation in the SnO films from (101) to (110) was associated with the increase in μ Hall. In addition, Raman vibrational modes at 110 and 209 cm-1 of polycrystalline SnO films showed certain dependence with the grain orientation. The SnO-based TFTs showed p-type behavior with low threshold voltages (V T ) and low sub threshold swing (SS) in the range from 1.76 to 3.50 V and 1.63 to 3.24 V/dec., respectively. The TFTs mobilities in the saturation regime (μ sat) were in the range of 0.12 and 1.32 cm2 V-1 s-1. The current on/off ratio (I ON/I OFF) was in the order of 102, approximately. The large values of the interface trap density (D IT) contributed to the high I OFF and the low I ON/I OFF of the TFTs.

  14. Oxide Structure Dependence of SiO2/SiOx/3C-SiC/n-Type Si Nonvolatile Resistive Memory on Memory Operation Characteristics

    Science.gov (United States)

    Yamaguchi, Yuichiro; Shouji, Masatsugu; Suda, Yoshiyuki

    2012-11-01

    We have investigated the dependence of the oxide layer structure of our previously proposed metal/SiO2/SiOx/3C-SiC/n-Si/metal metal-insulator-semiconductor (MIS) resistive memory device on the memory operation characteristics. The current-voltage (I-V) measurement and X-ray photoemission spectroscopy results suggest that SiOx defect states mainly caused by the oxidation of 3C-SiC at temperatures below 1000 °C are related to the hysteresis memory behavior in the I-V curve. By restricting the SiOx interface region, the number of switching cycles and the on/off current ratio are more enhanced. Compared with a memory device formed by one-step or two-step oxidation of 3C-SiC, a memory device formed by one-step oxidation of Si/3C-SiC exhibits a more restrictive SiOx interface with a more definitive SiO2 layer and higher memory performances for both the endurance switching cycle and on/off current ratio.

  15. Study of strained-Si p-channel MOSFETs with HfO2 gate dielectric

    Science.gov (United States)

    Pradhan, Diana; Das, Sanghamitra; Dash, Tara Prasanna

    2016-10-01

    In this work, the transconductance of strained-Si p-MOSFETs with high-K dielectric (HfO2) as gate oxide, has been presented through simulation using the TCAD tool Silvaco-ATLAS. The results have been compared with a SiO2/strained-Si p-MOSFET device. Peak transconductance enhancement factors of 2.97 and 2.73 has been obtained for strained-Si p-MOSFETs in comparison to bulk Si channel p-MOSFETs with SiO2 and high-K dielectric respectively. This behavior is in good agreement with the reported experimental results. The transconductance of the strained-Si device at low temperatures has also been simulated. As expected, the mobility and hence the transconductance increases at lower temperatures due to reduced phonon scattering. However, the enhancements with high-K gate dielectric is less as compared to that with SiO2.

  16. SiO2-Ta2O5 sputtering yields: simulated and experimental results

    International Nuclear Information System (INIS)

    Vireton, E.; Ganau, P.; Mackowski, J.M.; Michel, C.; Pinard, L.; Remillieux, A.

    1994-09-01

    To improve mirrors coating, we have modeled sputtering of binary oxide targets using TRIM code. First, we have proposed a method to calculate TRIM input parameters using on the one hand thermodynamic cycle and on the other hand Malherbe's results. Secondly, an iterative processing has provided for oxide steady targets caused by ionic bombardment. Thirdly, we have exposed a model to get experimental sputtering yields. Fourthly, for (Ar - SiO 2 ) pair, we have determined that steady target is a silica one. A good agreement between simulated and experimental yields versus ion incident angle has been found. For (Ar - Ta 2 O 5 ) pair, we have to introduce preferential sputtering concept to explain discrepancy between simulation and experiment. In this case, steady target is tantalum monoxide. For (Ar - Ta(+O 2 ) pair, tantalum sputtered by argon ions in reactive oxygen atmosphere, we have to take into account new concept of oxidation stimulated by ion beam. We have supposed that tantalum target becomes a Ta 2 O 5 one in reactive oxygen atmosphere. Then, following mechanism is similar to previous pair. We have obtained steady target of tantalum monoxide too. Comparison between simulated and experimental sputtering yields versus ion incident angle has given very good agreement. By simulation, we have found that tantalum monoxide target has at least 15 angstrom thickness. Those results are compatible with Malherbe's and Taglauer's ones. (authors)

  17. Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

    KAUST Repository

    Munirasu, Selvaraj

    2014-07-22

    A new kind of asymmetric organic-inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m-2 h -1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology. © 2014 Springer Science+Business Media New York.

  18. Liquid-phase-deposited SiO2 on AlGaAs and its application

    International Nuclear Information System (INIS)

    Lee, Kuan-Wei; Huang, Jung-Sheng; Lu, Yu-Lin; Lee, Fang-Ming; Lin, Hsien-Cheng; Huang, Jian-Jun; Wang, Yeong-Her

    2011-01-01

    The silicon dioxide (SiO 2 ) on AlGaAs prepared by liquid phase deposition (LPD) at 40 °C has been explored. The LPD-SiO 2 film deposition rate is about 67 nm h −1 for the first hour. The leakage current density is about 1.21 × 10 −6 A cm −2 at 1 MV cm −1 . The interface trap density (D it ) and the flat-band voltage shift (ΔV FB ) are 1.28 × 10 12 cm −2 eV −1 and 0.5 V, respectively. After rapid thermal annealing in the N 2 ambient at 300 °C for 1 min, the leakage current density, D it , and ΔV FB can be improved to 4.24 × 10 −7 A cm −2 at 1 MV cm −1 , 1.7 × 10 11 cm −2 eV −1 , and 0.2 V, respectively. Finally, this study demonstrates the application of the LPD-SiO 2 film to the AlGaAs/InGaAs pseudomorphic high-electron-mobility transistor

  19. Natural CaO-TiO2-SiO2 based ceramics

    Directory of Open Access Journals (Sweden)

    Jelena Pantić

    2011-06-01

    Full Text Available Lešnica river deposits consist of a large number of minerals of different grain sizes including sphene. Since it is very difficult to obtain pure monophase titanite by different synthetic routes (sol-gel, coprecipitation, combustion, spray pyrolysis and hydrothermal method, the aim of this work was to study the structure of the sphene from the Lešnica river deposits and possibility of using it as a natural precursor for CaO-TiO2-SiO2 based ceramics. The sphene from Lešnica was analyzed by different methods: tristimulus colorimetry, infrared spectroscopy, electron microprobe and X-ray single crystal diffraction. It was confirmed that Al, Fe, Mn and P are present in the sphene structure and proposed that corresponding structural formula could be: (Ca2+1.008 Mn2+0.0021.010(Ti4+0.901 Fe3+0.033 Al3+0.060 P5+0.0010.995 Si4+1.024 O2-5.

  20. Oxidation of atomically thin MoS2 on SiO2

    Science.gov (United States)

    Yamamoto, Mahito; Cullen, William; Einstein, Theodore; Fuhrer, Michael

    2013-03-01

    Surface oxidation of MoS2 markedly affects its electronic, optical, and tribological properties. However, oxidative reactivity of atomically thin MoS2 has yet to be addressed. Here, we investigate oxidation of atomic layers of MoS2 using atomic force microscopy and Raman spectroscopy. MoS2 is mechanically exfoliated onto SiO2 and oxidized in Ar/O2 or Ar/O3 (ozone) at 100-450 °C. MoS2 is much more reactive to O2 than an analogous atomic membrane of graphene and monolayer MoS2 is completely etched very rapidly upon O2 treatment above 300 °C. Thicker MoS2 (> 15 nm) transforms into MoO3 after oxidation at 400 °C, which is confirmed by a Raman peak at 820 cm-1. However, few-layer MoS2 oxidized below 400 °C exhibits no MoO3 Raman mode but etch pits are formed, similar to graphene. We find atomic layers of MoS2 shows larger reactivity to O3 than to O2 and monolayer MoS2 transforms chemically upon O3 treatment even below 100 °C. Work supported by the U. of Maryland NSF-MRSEC under Grant No. DMR 05-20741.

  1. Synthesis and characterization of ion-implanted Pt nanocrystals in SiO2

    International Nuclear Information System (INIS)

    Giulian, R.; Kluth, P.; Johannessen, B.; Araujo, L.L.; Llewellyn, D.J.; Cookson, D.J.; Ridgway, M.C.

    2007-01-01

    Pt nanocrystals (NCs) produced by ion implantation in SiO 2 films were investigated by Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The implantations were performed at liquid nitrogen temperature using energies between 3.4 and 5.6 MeV and an ion fluence range of 2-30 x 10 16 cm -2 and were followed by annealing in forming gas (95% N 2 , 5% H 2 ) for one hour at temperatures between 500 and 1100 deg. C. TEM analysis revealed that the NCs are spherical in shape. The mean size of the NCs annealed at 1100 deg. C varied between 2.8 and 3.6 nm for the highest and lowest fluences, respectively, as determined with both TEM and SAXS. In contrast to previous studies on ion implanted metal NCs, larger Pt NCs are located far beyond the Pt peak concentration, potentially the result of a strongly defect mediated NC nucleation

  2. Deoxygenation of Plant Fatty Acid using NiSnK/ SiO2 as Catalyst

    International Nuclear Information System (INIS)

    Chiam, L.T.; Tye, C.T.

    2013-01-01

    Environmental friendly bio-oil which offers supply reliability as a potential alternative fuel, has spurred to rapid development of bio fuels technology. Palm oil is a potential renewable energy source for bio fuels production in the future and Malaysia is one of the world largest palm oil producers. However, undesired oxygen content in the plant fatty acid that contributes to low energy density, high viscosity, and low stability, makes the palm oil not effective to be used as bio fuels directly. In the present study, the performance of silica supported trimetal catalyst, NiSnK/ SiO 2 , on deoxygenation of used palm oil was evaluated. In addition, the effects of operating parameters, such as reaction temperature and weight hourly space velocity were investigated. Conversion of palmitic acid as high as 90 % was achieved in deoxygenation of used palm oil at reaction temperature 350 degree Celsius. In order to have a better understanding on the deoxygenation reaction, model compound system using the major saturated fatty acid in the used palm oil, palmitic acid was also carried out. Palmitic acid was found mainly decarboxylated into n-pentadecane with some decarboxylation and isomerization products. (author)

  3. Non-iridescent structural colors from uniform-sized SiO2 colloids

    Science.gov (United States)

    Topçu, Gökhan; Güner, Tuğrul; Demir, Mustafa M.

    2018-05-01

    Structural colors have recently attracted interest from diverse fields of research due to their ease of fabrication and eco-friendliness. These types of colors are, in principle, achieved by periodically arranged submicron-diameter colloidal particles. The interaction of light with a structure containing long-range ordered colloidal particles leads to coloration; this usually varies depending on the angle of observation (iridescence). However, the majority of the applications demand constant color that is independent of the viewing angle (non-iridescence). In this work, silica colloids were obtained using the Stöber method at different sizes from 150 to 300 nm in an alcoholic dispersion. The casting of the dispersion on a substrate leaves behind a photonic crystal showing a colorful iridescent film. However, centrifugation and redispersion of the SiO2 particles into fresh solvent may cause the formation of small, aggregated silica domains in the new dispersion. The casting of this dispersion allows for the development of photonic glass, presumably due to the accumulation of aggregates showing stable colloidal film independent of viewing angle. Moreover, depending on the size of the silica colloids, non-iridescent photonic glasses with various colors (violet, blue, green, and orange) are obtained.

  4. Configuration of organic dye excimers in nanoporous SiO2 matrices

    International Nuclear Information System (INIS)

    Sorokin, A.V.; Gnap, B.A.; Bespalova, I.I.; Yefimova, S.L.; Malyukin, Yu.V.

    2016-01-01

    The effect of cyanine dye 3,3′-dioctadecyloxacarbocyanine perchlorate (DiO) and benzimidazole dye 4-dimethylamino-1,8-naphthoylene-1′,2′-benzimidazole (DNBI) accumulation in nanoporous silica matrices on the dyes luminescence properties has been studied. For both dyes, ground state dimer formation with perpendicular transition dipoles at high dye concentrations has been considered as a result of restricted geometry of the nanoscale pores. The dimer excitation leads to excimer formation revealing by appearance of new long-wavelength luminescence band and shortening the dye luminescence lifetime. In the excimer luminescence excitation spectra two additional bands have been observed, one of which is bathochromically shifted relatively to the absorption band and another one is hypsocromically shifted. Using the Kasha exciton model it was shown that the excimers possess oblique transition dipoles configuration. - Highlights: • Organic dye molecules are efficiently accumulated in nanoporous silica matrices. • Restricted geometry of SiO 2 nanopores provokes excimerization of both cyanine and benzimidazole dyes. • The excimers reveal configuration of oblique dimers. • The excimers are originated from ground state dimers with a perpendicular arrangement of transition dipoles.

  5. Turbidimetric Measurement for On-line Monitoring of SiO2 Particles

    International Nuclear Information System (INIS)

    Kim, In Sook; Lim, H. B.; Kim, Yang Sun

    2004-01-01

    In this work, the fundamental study of on-line monitoring of SiO 2 particles in the size range of 40 nm to 725 nm was carried out using turbidimetry. The size of particle was measured using a field emission scanning electron microscope (FE-SEM). The factors affecting on the turbidity were discussed, for example, wavelength, size, and concentration. In order to observe the dependence of turbidity on the wavelength, a turbidimetric system equipped with charged coupled detector (CCD) was built. The shape of the transmitted peak was changed and the peak maximum was shifted to the red when the concentration of particle was increased. This result indicates that the turbidity is related to the wavelength, which corresponds to the characteristic of the Mie extinction coefficient, Q, that is a function of not only particle diameter and refractive index but also wavelength. It is clear that a linear calibration curve for each particle in different size can be obtained at an optimized wavelength

  6. Moessbauer studies of magnetic Fe2O3/SiO2 nanocomposite

    International Nuclear Information System (INIS)

    Lancok, A.; Zaveta, K.; Savii, C.; Barcova, K.

    2006-01-01

    Fe 2 O 3 /SiO 2 magnetic nanocomposites rich in Fe 2 O 3 have been obtained by annealing at 1000 grad C the xerogel samples, prepared under various conditions. The target concentrations of iron oxide in inert matrix were 20% and 30%. As mesoporous matrices both silica and polyvinyl alcohol - silica hybrid ones were used. The xerogel nanocomposite samples were obtained in situ and by impregnation under ultrasonic activation. All obtained samples were annealed under moderate oxidation conditions (air) and inert atmosphere such as vacuum or nitrogen. Moessbauer spectra were obtained using a conventional Moessbauer spectrometer with a 57 Co/Rh source and constant acceleration. Velocity calibration was done using α-iron, and the Moessbauer parameters are given relative to this standard at room temperature. The Moessbauer spectra contained the sextets of ε-Fe 2 O 3 , hematite, and superparamagnetic component. The content of various phases in the samples depends on the conditions of preparation. In one of the samples also magnetite was present. The ranges of the ε-Fe 2 O 3 area of the samples are 39-76%. The hematite phase is only residual, after transformation due to heat treatment. (authors)

  7. Regulating effect of SiO2 interlayer on optical properties of ZnO thin films

    International Nuclear Information System (INIS)

    Xu, Linhua; Zheng, Gaige; Miao, Juhong; Su, Jing; Zhang, Chengyi; Shen, Hua; Zhao, Lilong

    2013-01-01

    ZnO/SiO 2 nanocomposite films with periodic structure were prepared by electron beam evaporation technique. Regulating effect of SiO 2 interlayer with various thicknesses on the optical properties of ZnO/SiO 2 thin films was investigated deeply. The analyses of X-ray diffraction show that the ZnO layers in ZnO/SiO 2 nanocomposite films have a wurtzite structure and are preferentially oriented along the c-axis while the SiO 2 layers are amorphous. The scanning electron microscope images display that the ZnO layers are composed of columnar grains and the thicknesses of ZnO and SiO 2 layers are all very uniform. The SiO 2 interlayer presents a significant modulation effect on the optical properties of ZnO thin films, which is reflected in the following two aspects: (1) the transmittance of ZnO/SiO 2 nanocomposite films is increased; (2) the photoluminescence (PL) of ZnO/SiO 2 nanocomposite films is largely enhanced compared with that of pure ZnO thin films. The ZnO/SiO 2 nanocomposite films have potential applications in light-emitting devices and flat panel displays. -- Highlights: ► ZnO/SiO 2 nanocomposite films with periodic structure were prepared by electron beam evaporation technique. ► The SiO 2 interlayer presents a significant modulation effect on the optical properties of ZnO thin films. ► The photoluminescence of ZnO/SiO 2 nanocomposite films is largely enhanced compared with that of pure ZnO thin films. ► The ZnO/SiO 2 nanocomposite films have potential applications in light-emitting devices and flat panel displays

  8. Rapid removal of uranium from aqueous solutions using magnetic Fe3O4@SiO2 composite particles.

    Science.gov (United States)

    Fan, Fang-Li; Qin, Zhi; Bai, Jing; Rong, Wei-Dong; Fan, Fu-You; Tian, Wei; Wu, Xiao-Lei; Wang, Yang; Zhao, Liang

    2012-04-01

    Rapid removal of U(VI) from aqueous solutions was investigated using magnetic Fe(3)O(4)@SiO(2) composite particles as the novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, shaking time and initial U(VI) concentrations on uranium sorption efficiency as well as the desorbing of U(VI). The sorption of uranium on Fe(3)O(4)@SiO(2) composite particles was pH-dependent, and the optimal pH was 6.0. In kinetics studies, the sorption equilibrium can be reached within 180 min, and the experimental data were well fitted by the pseudo-second-order model, and the equilibrium sorption capacities calculated by the model were almost the same as those determined by experiments. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 20-200 mg/L. The maximum uranium sorption capacity onto magnetic Fe(3)O(4)@SiO(2) composite particles was estimated to be about 52 mg/g at 25 °C. The highest values of uranium desorption (98%) was achieved using 0.01 M HCl as the desorbing agent. Fe(3)O(4)@SiO(2) composite particles showed a good selectivity for uranium from aqueous solution with other interfering cation ions. Present study suggested that magnetic Fe(3)O(4)@SiO(2) composite particles can be used as a potential adsorbent for sorption uranium and also provided a simple, fast separation method for removal of heavy metal ion from aqueous solution. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Assembly of Ge nanocrystals on SiO2 via a stress-induced dewetting process

    International Nuclear Information System (INIS)

    Sutter, E; Sutter, P

    2006-01-01

    We use epitaxial Ge islands on silicon-on-insulator (001) to initiate and drive the dewetting of the ultrathin ( 2 layer and transforms the Ge islands into oxide-supported, electrically isolated, Ge-rich nanocrystals. We investigate the process of dewetting and demonstrate that it can be used for the controlled assembly of nanocrystals-from isolated single ones to dense arrays

  10. Photocatalytic hydrogen production using visible-light-responsive Ta 3N5 photocatalyst supported on monodisperse spherical SiO2 particulates

    KAUST Repository

    Liu, Xiaoming; Zhao, Lan; Domen, Kazunari; Takanabe, Kazuhiro

    2014-01-01

    Fine nanoparticles of Ta3N5 (10-20 nm) were synthesized on the surfaces of SiO2 spheres with a diameter of ∼550 nm. A sol-gel method was used to modify the surface of SiO2 with Ta2O5 from TaCl5 dissolved in ethanol in the presence of citric acid

  11. Dehydration of glucose to 5-hydroxymethylfurfural by a core-shell Fe3O4@SiO2-SO3H magnetic nanoparticle catalyst

    Science.gov (United States)

    This paper discusses the potential use of (Fe3O4@SiO2-SO3H) nanoparticle catalyst for the dehydration of glucose into 5-hydroxymethylfurfural (HMF). A magnetically recoverable (Fe3O4@SiO2-SO3H) nanoparticle catalyst was successfully prepared by supporting sulfonic acid groups (SO3H) on the surface o...

  12. Influence of Poly (Ethylene Glycol) and Oleylamine on the Formation of Nano to Micron Size Spherical SiO2 Particles

    Science.gov (United States)

    We report an eco-friendly synthesis of well–controlled, nano-to-micron-size, spherical SiO2 particles using non-hazardous solvent and a byproducts-producing system. It was found that the morphology and size of spherical SiO2 particles are controlled by adjusting the concentration...

  13. In-situ synthesis of SiO2@MOF composites for high-efficiency removal of aniline from aqueous solution

    Science.gov (United States)

    Han, Tongtong; Li, Caifeng; Guo, Xiangyu; Huang, Hongliang; Liu, Dahuan; Zhong, Chongli

    2016-12-01

    A series of SiO2@aluminum-MOF(MIL-68) composites with different SiO2 loadings have been synthesized by a simple and mild compositing strategy for high-efficiency removal of aniline. As evidenced from SEM and TEM images as well as the particle size distribution, the incorporation of SiO2 can improve the dispersity of MIL-68(Al) in composites, and result in the smaller particle size than that of pristine MIL-68(Al). Besides, the adsorption of aniline over SiO2, MIL-68(Al), the physical mixture of these two materials, and SiO2@MIL-68(Al) composites was investigated comparatively, demonstrating a relatively high adsorption capacity (531.9 mg g-1) of 7% SiO2@MIL-68(Al) towards aniline. Combining the ultrafast adsorption dynamics (reaching equilibrium within 40 s) and great reusability, 7% SiO2@MIL-68(Al) shows excellent adsorption performance. This indicates that the SiO2@MIL-68(Al) composites possess great potential applications as a kind of fascinating adsorbent in water pollution protection.

  14. Luminescence dependence of Pr3+ activated SiO2 nanophosphor on Pr3+ concentration, temperature, and ZnO incorporation

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2011-08-01

    Full Text Available Green-emitting ZnO nanoparticles were successfully embedded in Pr3+-doped SiO2 by a sol–gel method resulting in a red-emitting ZnO·SiO2:Pr3+ nanocomposite phosphor. The particle morphology and luminescent properties of SiO2:Pr3+ phosphor powders...

  15. Electronic and surface properties of pentacene films deposited on SiO2 prepared by the sol–gel and thermally grown methods

    International Nuclear Information System (INIS)

    Dai, Chi-Jie; Tsao, Hou-Yen; Lin, Yow-Jon; Liu, Day-Shan

    2014-01-01

    This study investigates the effect of different types of SiO 2 on the electronic and surface properties of pentacene films. Developing better contacts on dielectrics is one of the main challenges for pentacene-based transistor technology. The water contact angle variation indicates more hydrophobic thermally grown SiO 2 surfaces than sol–gel SiO 2 surfaces, suggesting that the thermally grown SiO 2 dielectric enables a better molecular arrangement as the pentacene layer is deposited. It is found that the carrier mobility in pentacene on thermally grown SiO 2 dielectrics is higher than that in pentacene on sol–gel SiO 2 dielectrics. The Hall-effect analysis by using the polaron theory revealed that the enhanced carrier mobility is due to the increased spacing between molecules. - Highlights: • The carrier mobility of pentacene on thermally grown and sol–gel SiO 2 was researched. • The enhanced carrier mobility of pentacene on thermally grown SiO2 was observed. • The dominance of tunneling (hopping) at low (high) temperatures was observed. • The carrier mobility is correlated with the morphology of pentacene films

  16. Molecular dewetting on insulators

    International Nuclear Information System (INIS)

    Burke, S A; Topple, J M; Gruetter, P

    2009-01-01

    Recent attention given to the growth and morphology of organic thin films with regard to organic electronics has led to the observation of dewetting (a transition from layer(s) to islands) of molecular deposits in many of these systems. Dewetting is a much studied phenomenon in the formation of polymer and liquid films, but its observation in thin films of the 'small' molecules typical of organic electronics requires additional consideration of the structure of the interface between the molecular film and the substrate. This review covers some key concepts related to dewetting and molecular film growth. In particular, the origins of different growth modes and the thickness dependent interactions which give rise to dewetting are discussed in terms of surface energies and the disjoining pressure. Characteristics of molecular systems which may lead to these conditions, including the formation of metastable interface structures and commensurate-incommensurate phase transitions, are also discussed. Brief descriptions of some experimental techniques which have been used to study molecular dewetting are given as well. Examples of molecule-on-insulator systems which undergo dewetting are described in some detail, specifically perylene derivatives on alkali halides, C 60 on alkali halides, and the technologically important system of pentacene on SiO 2 . These examples point to some possible predicting factors for the occurrence of dewetting, most importantly the formation of an interface layer which differs from the bulk crystal structure. (topical review)

  17. Molecular dewetting on insulators.

    Science.gov (United States)

    Burke, S A; Topple, J M; Grütter, P

    2009-10-21

    Recent attention given to the growth and morphology of organic thin films with regard to organic electronics has led to the observation of dewetting (a transition from layer(s) to islands) of molecular deposits in many of these systems. Dewetting is a much studied phenomenon in the formation of polymer and liquid films, but its observation in thin films of the 'small' molecules typical of organic electronics requires additional consideration of the structure of the interface between the molecular film and the substrate. This review covers some key concepts related to dewetting and molecular film growth. In particular, the origins of different growth modes and the thickness dependent interactions which give rise to dewetting are discussed in terms of surface energies and the disjoining pressure. Characteristics of molecular systems which may lead to these conditions, including the formation of metastable interface structures and commensurate-incommensurate phase transitions, are also discussed. Brief descriptions of some experimental techniques which have been used to study molecular dewetting are given as well. Examples of molecule-on-insulator systems which undergo dewetting are described in some detail, specifically perylene derivatives on alkali halides, C(60) on alkali halides, and the technologically important system of pentacene on SiO(2). These examples point to some possible predicting factors for the occurrence of dewetting, most importantly the formation of an interface layer which differs from the bulk crystal structure.

  18. Formation of metallic Si and SiC nanoparticles from SiO2 particles by plasma-induced cathodic discharge electrolysis in chloride melt

    International Nuclear Information System (INIS)

    Tokushige, M.; Tsujimura, H.; Nishikiori, T.; Ito, Y.

    2013-01-01

    Silicon nanoparticles are formed from SiO 2 particles by conducting plasma-induced cathodic discharge electrolysis. In a LiCl–KCl melt in which SiO 2 particles were suspended at 450 °C, we obtained Si nanoparticles with diameters around 20 nm. During the electrolysis period, SiO 2 particles are directly reduced by discharge electrons on the surface of the melt just under the discharge, and the deposited Si atom clusters form Si nanoparticles, which leave the surface of the original SiO 2 particle due to free spaces caused by a molar volume difference between SiO 2 and Si. We also found that SiC nanoparticles can be obtained using carbon anode. Based on Faraday's law, the current efficiency for the formation of Si nanoparticles is 70%

  19. Implantation of P ions in SiO2 layers with embedded Si nanocrystals

    International Nuclear Information System (INIS)

    Kachurin, G.A.; Cherkova, S.G.; Volodin, V.A.; Kesler, V.G.; Gutakovsky, A.K.; Cherkov, A.G.; Bublikov, A.V.; Tetelbaum, D.I.

    2004-01-01

    The effect of 10 13 -10 16 cm -2 P ions implantation and of subsequent annealing on Si nanocrystals (Si-ncs), formed preliminarily in SiO 2 layers by the ion-beam synthesis, has been studied. Photoluminescence (PL), Raman spectroscopy, high resolution electron microscopy (HREM), X-Ray Photoelectron Spectroscopy (XPS) and optical absorption were used for characterizations. The low fluence implantations have shown even individual displacements in Si-ncs quench their PL. Restoration of PL from partly damaged Si-ncs proceeds at annealing less than 1000 deg. C. In the low fluence implanted and annealed samples an increased Si-ncs PL has been found and ascribed to the radiation-induced shock crystallization of stressed Si nanoprecipitates. Annealing at temperatures under 1000 deg. C are inefficient when P ion fluences exceed 10 14 cm -2 , thus becoming capable to amorphize Si-ncs. High crystallization temperature of the amorphized Si-ncs is attributed to a counteraction of their shell layers. After implantation of the highest P fluences an enhanced recovery of PL was found from P concentration over 0.1 at.%. Raman spectroscopy and HREM showed an increased Si-ncs number in such layers. The effect resembles the impurity-enhanced crystallization, known for heavily doped bulk Si. This effect, along with the data obtained by XPS, is considered as an indication P atoms are really present inside the Si-ncs. However, no evidence of free electrons appearance has been observed. The fact is explained by an increased interaction of electrons with the donor nuclei in Si-ncs

  20. Superheating and supercooling of Ge nanocrystals embedded in SiO2

    International Nuclear Information System (INIS)

    Xu, Q; Sharp, I D; Yuan, C W; Yi, D O; Liao, C Y; Glaeser, A M; Minor, A M; Beeman, J W; Ridgway, M C; Kluth, P; Iii, J W Ager; Chrzan, D C; Haller, E E

    2007-01-01

    Free-standing nanocrystals exhibit a size-dependant thermodynamic melting point reduction relative to the bulk melting point that is governed by the surface free energy. The presence of an encapsulating matrix, however, alters the interface free energy of nanocrystals and their thermodynamic melting point can either increase or decrease relative to bulk. Furthermore, kinetic contributions can significantly alter the melting behaviours of embedded nanoscale materials. To study the effect of an encapsulating matrix on the melting behaviour of nanocrystals, we performed in situ electron diffraction measurements on Ge nanocrystals embedded in a silicon dioxide matrix. Ge nanocrystals were formed by multi-energy ion implantation into a 500 nm thick silica thin film on a silicon substrate followed by thermal annealing at 900 deg. C for 1 h. We present results demonstrating that Ge nanocrystals embedded in SiO 2 exhibit a 470 K melting/solidification hysteresis that is approximately symmetric about the bulk melting point. This unique behaviour, which is thought to be impossible for bulk materials, is well described using a classical thermodynamic model that predicts both kinetic supercooling and kinetic superheating. The presence of the silica matrix suppresses surface pre-melting of nanocrystals. Therefore, heterogeneous nucleation of both the liquid phase and the solid phase are required during the heating and cooling cycle. The magnitude of melting hysteresis is governed primarily by the value of the liquid Ge/solid Ge interface free energy, whereas the relative values of the solid Ge/matrix and liquid Ge/matrix interface free energies govern the position of the hysteresis loop in absolute temperature

  1. Growth and structure of hyperthin SiO2 coatings on polymers

    International Nuclear Information System (INIS)

    Dennler, G.; Houdayer, A.; Segui, Y.; Wertheimer, M.R.

    2001-01-01

    Transparent inorganic oxide coatings on polymers are playing an increasingly important role in pharmaceutical, food, and beverage packaging, and more recently in encapsulation of organic, light-emitting display devices. Such coatings are being prepared by physical or by chemical vacuum-deposition methods. They possess barrier properties against permeation of gases or vapors when they are thicker than a certain critical thickness, d c ; for d c , the 'oxygen transmission rate' (in standard cm 3 /m 2 /day/bar), for example, is roughly the same as that of the uncoated polymer. This fact is commonly attributed in the literature to a 'nucleation' phase of the coating's growth, during which it is thought to present an island-like structure. In order to test this hypothesis, we have deposited hyperthin SiO 2 coatings on various flexible polymeric substrates using plasma-enhanced chemical vapor deposition. The film thicknesses investigated here, well below d c (typically in the range 1-10 nm), were determined by Rutherford backscattering spectroscopy, which allows us to determine the surface concentration of silicon. This was found to be a linear function of the deposition time, t, for t≥0.5 s. Then, combining reactive ion etching in oxygen plasma with scanning electron and optical microscopy, we have been able to characterize the structure of the coatings: even for d≤2 nm, no island structure has been observed. Instead, we found continuous coatings which contain large concentrations, n, of tiny pinhole defects (with typical radii in the range of tens of nanometers), where n increases with decreasing d. These assertions are confirmed by grazing angle (80 deg. ) angle-resolved x-ray photoelectron spectroscopy, which shows that even for d=2 nm, the structural features of the polymer substrate cannot be detected

  2. Magnetic properties of Mn-oxide nanoparticles dispersed in an amorphous SiO2 matrix

    Science.gov (United States)

    Milivojević, D.; Babić-Stojić, B.; Jokanović, V.; Jagličić, Z.; Makovec, D.

    2011-03-01

    Samples of Mn-oxide nanoparticles dispersed in an amorphous SiO2 matrix with manganese concentration 0.7 and 3 at% have been synthesized by a sol-gel method. Transmission electron microscopy analysis has shown that the samples contain agglomerates of amorphous silica particles 10-20 nm in size. In silica matrix two types of Mn-rich particles are dispersed, smaller nanoparticles with dimensions between 3 and 10 nm, and larger crystalline areas consisting of aggregates of the smaller nanoparticles. High-temperature magnetic susceptibility study reveals that dominant magnetic phase at higher temperatures is λ-MnO2. At temperatures below TC=43 K strong ferrimagnetism originating from the minor Mn3O4 phase masks the relatively weak magnetism of λ-MnO2 with antiferromagnetic interactions. Magnetic field dependence of the maximum in the zero-field-cooled magnetization for both the samples in the vicinity of 40 K, and a frequency shift of the real component of the ac magnetic susceptibility in the sample with 3 at% Mn suggest that the magnetic moments of the smaller Mn3O4 nanoparticles with dimensions below 10 nm are exposed to thermally activated blocking process just below the Curie temperature TC. Appearance of a maximum in the zero-field-cooled magnetization for both the samples below 10 K indicates possible spin glass freezing of the magnetic moments at low temperatures which might occur in the geometrically frustrated Mn sublattice of the λ-MnO2 crystal structure.

  3. B2O3/SiO2 substitution effect on structure and properties of Na2O-CaO-SrO-P2O5-SiO2 bioactive glasses from molecular dynamics simulations.

    Science.gov (United States)

    Ren, Mengguo; Lu, Xiaonan; Deng, Lu; Kuo, Po-Hsuen; Du, Jincheng

    2018-05-23

    The effect of B2O3/SiO2 substitution in SrO-containing 55S4.3 bioactive glasses on glass structure and properties, such as ionic diffusion and glass transition temperature, was investigated by combining experiments and molecular dynamics simulations with newly developed potentials. Both short-range (such as bond length and bond angle) and medium-range (such as polyhedral connection and ring size distribution) structures were determined as a function of glass composition. The simulation results were used to explain the experimental results for glass properties such as glass transition temperature and bioactivity. The fraction of bridging oxygen increased linearly with increasing B2O3 content, resulting in an increase in overall glass network connectivity. Ion diffusion behavior was found to be sensitive to changes in glass composition and the trend of the change with the level of substitution is also temperature dependent. The differential scanning calorimetry (DSC) results show a decrease in glass transition temperature (Tg) with increasing B2O3 content. This is explained by the increase in ion diffusion coefficient and decrease in ion diffusion energy barrier in glass melts, as suggested by high-temperature range (above Tg) ion diffusion calculations as B2O3/SiO2 substitution increases. In the low-temperature range (below Tg), the Ea for modifier ions increased with B2O3/SiO2 substitution, which can be explained by the increase in glass network connectivity. Vibrational density of states (VDOS) were calculated and show spectral feature changes as a result of the substitution. The change in bioactivity with B2O3/SiO2 substitution is discussed with the change in pH value and release of boric acid into the solution.

  4. The Effect of SiO2 Shell on the Suppression of Photocatalytic Activity of TiO2 and ZnO Nanoparticles

    International Nuclear Information System (INIS)

    Lee, Min Hee; Lee, Choon Soo; Patil, Umakant Mahadev; Kochuveedu, Saji Thomas

    2012-01-01

    In this study, we investigate the potential use of TiO 2 SiO 2 and ZnO SiO 2 core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, SiO 2 was coated over different types of TiO 2 (anatase and rutile) and ZnO by sol-gel method. The synthesized TiO 2 SiO 2 and ZnO SiO 2 Nps were characterized by UV-Vis, XRD, Sem and TEM. The UV-vis absorbance and transmittance spectra of core shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous SiO 2 coated over the TiO 2 and ZnO NPs. The FESEM and TEM images shows that coating of SiO 2 over the surface of anatase, rutile TiO 2 and ZnO NPs resulted in the increase in particle size by ∼30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on TiO 2 SiO 2 and ZnO SiO 2 NPs was performed. Photocatalytic activity for both types of TiO 2 NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the SiO 2 coating

  5. Photocatalytic application of TiO2/SiO2-based magnetic nanocomposite (Fe3O4@SiO2/TiO2 for reusing of textile wastewater

    Directory of Open Access Journals (Sweden)

    Laleh Enayati Ahangar

    2016-01-01

    Full Text Available In this research we have developed a treatment method for textile wastewater by TiO2/SiO2-based magnetic nanocomposite. Textile wastewater includes a large variety of dyes and chemicals and needs treatments. This manuscript presents a facile method for removing dyes from the textile wastewater by using TiO2/SiO2-based nanocomposite (Fe3O4@SiO2/TiO2 under UV irradiation. This magnetic nanocomposite, as photocatalytically active composite, is synthesized via solution method in mild conditions. A large range of cationic, anionic and neutral dyes including: methyl orange, methylene blue, neutral red, bromocresol green and methyl red are used for treatment investigations. Neutral red and bromocresol green have good results in reusing treatment. The high surface area of nanocomposites improve the kinetic of wastewater treatment. In this method, by using the magnetic properties of Fe3O4 nanoparticles, TiO2-based photocatalyst could be separated and reused for 3 times. The efficiency of this method is respectively 100% and 65% for low concentration (10 ppm and high concentration (50 ppm of neutral red and bromocrosol green after 3 h treatment. The efficiency of treatment using the second used nanocomposite was 90% for 10 ppm of the same dyes.

  6. Determination of phosphorus distribution in the region of a SiO2-Si interface by substoichiometric analysis

    International Nuclear Information System (INIS)

    Shigematsu, T.; Yonezawa, H.

    1994-01-01

    A simplified method for the substoichiometric analysis of phosphorus has been developed and applied to determine the concentration distribution of phosphorus in the region of a SiO 2 -Si interface in order to explain why phosphorus is lost from the ion-implanted silicon surface throughout the oxidation and oxide removal processes. It is revealed that phosphorus piles up on the SiO 2 side at the interface by the thermal oxidation of silicon surface and is removed with the oxide by wet etching and with the resulting silicon by RCA cleaning. This results in a total loss of ion-implanted phosphorus of 3.5%. (author) 11 refs.; 2 figs.; 3 tabs

  7. Biocomposite of Cassava Starch Reinforced with Cellulose Pulp Fibers Modified with Deposition of Silica (SiO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Joabel Raabe

    2015-01-01

    Full Text Available Eucalyptus pulp cellulose fibers were modified by the sol-gel process for SiO2 superficial deposition and used as reinforcement of thermoplastic starch (TPS. Cassava starch, glycerol, and water were added at the proportion of 60/26/14, respectively. For composites, 5% and 10% (by weight of modified and unmodified pulp fibers were added before extrusion. The matrix and composites were submitted to thermal stability, tensile strength, moisture adsorption, and SEM analysis. Micrographs of the modified fibers revealed the presence of SiO2 nanoparticles on fiber surface. The addition of modified fibers improved tensile strength in 183% in relation to matrix, while moisture adsorption decreased 8.3%. Such improvements were even more effective with unmodified fibers addition. This result was mainly attributed to poor interaction between modified fibers and TPS matrix detected by SEM analysis.

  8. Spontaneous emission of semiconductor quantum dots in inverse opal SiO2 photonic crystals at different temperatures.

    Science.gov (United States)

    Yang, Peng; Yang, Yingshu; Wang, Yinghui; Gao, Jiechao; Sui, Ning; Chi, Xiaochun; Zou, Lu; Zhang, Han-Zhuang

    2016-02-01

    The photoluminescence (PL) characteristics of CdSe quantum dots (QDs) infiltrated into inverse opal SiO2 photonic crystals (PCs) are systemically studied. The special porous structure of inverse opal PCs enhanced the thermal exchange rate between the CdSe QDs and their surrounding environment. Finally, inverse opal SiO2 PCs suppressed the nonlinear PL enhancement of CdSe QDs in PCs excited by a continuum laser and effectively modulated the PL characteristics of CdSe QDs in PCs at high temperatures in comparison with that of CdSe QDs out of PCs. The final results are of benefit in further understanding the role of inverse opal PCs on the PL characteristics of QDs. Copyright © 2015 John Wiley & Sons, Ltd.

  9. Effect of re-oxidation annealing process on the SiO2/SiC interface characteristics

    International Nuclear Information System (INIS)

    Yan Hongli; Jia Renxu; Tang Xiaoyan; Song Qingwen; Zhang Yuming

    2014-01-01

    The effect of the different re-oxidation annealing (ROA) processes on the SiO 2 /SiC interface characteristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric charge density and interface trap density are obtained from the capacitance—voltage curves. It is found that the lowest interface trap density is obtained by the wet-oxidation annealing process at 1050 °C for 30 min, while a large number of effective dielectric charges are generated. The components at the SiO 2 /SiC interface are analyzed by X-ray photoelectron spectroscopy (XPS) testing. It is found that the effective dielectric charges are generated due to the existence of the C and H atoms in the wet-oxidation annealing process. (semiconductor technology)

  10. Silicon electrodeposition from chloride-fluoride melts containing K2SiF6 and SiO2

    Directory of Open Access Journals (Sweden)

    Zhuk Sergey I.

    2017-01-01

    Full Text Available Silicon electrodeposition on glassy carbon from the KF-KCl-K2SiF6, KF-KCl-K2SiF6-KOH and KF-KCl-K2SiF6-SiO2 melts was studied by the cyclic voltammetry. Тhe electroreduction of Si(IV to metallic Si was observed as a single 4-electron wave under all considered conditions. The reactions of cathode reduction of silicon from fluoride and oxyfluoride complexes were suggested. It was shown that the process can be controlled by the preliminary transformation of SiO44- to SiF62- and SiOxFyz-. The influence of the current density on structure and morphology of silicon deposits obtained during galvanostatic electrolysis of the KF-KCl-K2SiF6-SiO2 melt was studied.

  11. Nanocrystal in Er3+-doped SiO2-ZrO2 Planar Waveguide with Yb3+ Sensitizer

    International Nuclear Information System (INIS)

    Razaki, N. Iznie; Jais, U. Sarah; Abd-Rahman, M. Kamil; Bhaktha, S. N. B.; Chiasera, A.; Ferrari, M.

    2010-01-01

    Higher doping of Er 3+ in glass ceramic waveguides would cause concentration and pair-induced quenching which lead to inhomogeneous line-width of luminescence spectrum thus reduce output intensity. Concentration quenching can be overcome by introducing ZrO 2 in the glass matrix while co-doping with Yb 3+ which acts as sensitizer would improve the excitation efficiency of Er 3+ . In this study, SiO 2 -ZrO 2 planar waveguides having composition in mol percent of 70SiO 2 -30ZrO 2 doped with Er 3+ and co-doped with Yb 3+ , were prepared via sol-gel route. Narrower and shaper peaks of PL and XRD shows the formation of nanocrystals. Intensity is increase with addition amount of Yb 3+ shows sensitizing effect on Er 3+ .

  12. Crystallization behaviour of nanostructured hybrid SiO2-TiO2 gel glasses to nanocomposites.

    Science.gov (United States)

    Tsvetelina, Gerganova; Yordanka, Ivanova; Yuliya, Vueva; Miranda, Salvado Isabel M; Helena, Fernandes Maria

    2010-04-01

    The crystallization behaviour of hybrid SiO2-TiO2 nanocomposites derived from titanosiloxanes by sol-gel method has been investigated depending on the type of siloxane precursor and the pirolysis temperature. The resulting hybrid titanosiloxanes, crosslinked with trimethylsilil isocyanate (nitrogen-modified) or methyltrietoxisilane (carbon-modified), were pirolyzed in an inert atmosphere in the temperature range between 600 to 1100 degrees C in order to form C-(N)-Si-O-TiO2 nanocomposites. By means of XRD, FTIR, 29Si NMR, SEM, TEM and AFM investigations have been established that the transformation of the nanostructured SiO2-TiO2 hybrid materials into nanocomposites as well as the crystalline size depend on the titanium content and the type of cross-linking agents used in the synthesizes.

  13. Photochemical process of divalent germanium responsible for photorefractive index change in GeO2-SiO2 glasses.

    Science.gov (United States)

    Sakoh, Akifumi; Takahashi, Masahide; Yoko, Toshinobu; Nishii, Junji; Nishiyama, Hiroaki; Miyamoto, Isamu

    2003-10-20

    The photoluminescence spectra of the divalent Ge (Ge2+) center in GeO2-SiO2 glasses with different photosensitivities were investigated by means of excitation-emission energy mapping. The ultraviolet light induced photorefractivity has been correlated with the local structure around the Ge2+ centers. The glasses with a larger photorefractivity tended to exhibit a greater band broadening of the singlet-singlet transition on the higher excitation energy side accompanied by an increase in the Stokes shifts. This strongly suggests the existence of highly photosensitive Ge2+ centers with higher excitation energies. It is also found that the introduction of a hydroxyl group or boron species in GeO2-SiO2 glasses under appropriate conditions modifies the local environment of Ge2+ leading to an enhanced photorefractivity.

  14. Crystallization and chemical durability of glasses in the system Bi2O3-SiO2

    International Nuclear Information System (INIS)

    Fredericci, C.

    2011-01-01

    The crystallization of the Bi 2 O 3 -SiO 2 -TiO 2 -Al 2 O 3 -Na 2 O-K 2 O and Bi 2 O 3 -SiO 2 -ZnO-Al 2 O 3 -B 2 O 3 -Na 2 O glasses was studied using glass samples prepared by traditional melt-quench method. Differential thermal analysis (DTA) curves suggested that surface crystallization played a major role in the crystallization of the glass samples. X-ray diffraction (XRD) analysis revealed the crystallization of bismuth silicate for both glasses and bismuth silicate and zinc silicate for the glass containing ZnO. Through scanning electron microscopy (MEV) and energy dispersive spectroscopy (EDS), it was possible to observe that the crystals of zinc silicate (Zn 2 SiO 4 ) were readily attacked by hot 0,1 N sulfuric acid, whereas bismuth silicate crystals were more resistant to acidic attack etching. (author)

  15. Nanoparticles of Pt and Ag supported in meso porous SiO2: characterization and catalytic applications

    International Nuclear Information System (INIS)

    Espinosa, M.E.; Perez H, R.; Perez A, M.; Mondragon G, G.; Arenas A, J.

    2004-01-01

    The surface properties of catalysts of Pt and Ag supported in conventional SiO 2 hey have been studied through reduction reactions of N 2 O with H 2 which is a sensitive reaction to the structure. In our case it was used a meso porous ceramic support of SiO 2 of great surface area (1100 m 2 /gr), where it is caused a high dispersion of the metallic nanoparticles of Pt and Ag, the total charge of the active phase in the meso porous support was of 3% in weight. The catalysts show a variation in the percentages of conversion of N 2 O depending on the size and dispersion of the metallic phases. (Author)

  16. Estimation of the depth resolution of secondary ion mass spectrometry at the interface SiO2/Si

    Science.gov (United States)

    Kocanda, J.; Fesič, V.; Veselý, M.; Breza, J.; Kadlečíková, M.

    1995-08-01

    Similarities between the processes that occur during sputtering of monocrystalline Si by reactive O2+ primary ions and the interface SiO2/monocrystalline Si by noble gas ions (e.g., by Ar+) have motivated us to utilize the semiempirical model of P. C. Zalm and C. J. Vriezema [Nucl. Instrum. Methods B 67, 495 (1992)], modified later by M. Petravić, B. G. Svensson, and J. S. Williams [Appl. Phys. Lett. 62, 278 (1993)] to calculate the decay length λb, as defined by J. B. Clegg [Surf. Interface Anal. 10, 322 (1987)], at the SiO2/Si interface. The measured and calculated results agree remarkably well. Inconsistency observed to be larger than 100% for glancing incidence angles confirms limitations of this model that were admitted already by its authors.

  17. Effect of hydrostatic pressure on photoluminescence spectra from structures with Si nanocrystals fabricated in SiO2 matrix

    International Nuclear Information System (INIS)

    Zhuravlev, K.S.; Tyschenko, I.E.; Vandyshev, E.N.; Bulytova, N.V.; Misiuk, A.; Rebohle, L.; Skorupa, W.

    2002-01-01

    The effect of hydrostatic pressure applied at high temperature on photoluminescence of Si-implanted SiO 2 films was studied. A 'blue'-shift of PL spectrum from the SiO 2 films implanted with Si + ions to total dose of 1.2x10 17 cm -2 with increase in hydrostatic pressure was observed. For the films implanted with Si + ions to a total dose of 4.8x10 16 cm -2 high temperature annealing under high hydrostatic pressure (12 kbar) causes a 'red'-shift of photoluminescence spectrum. The 'red' photoluminescence bands are attributed to Si nanocrystals while the 'blue' ones are related to Si nanocrystals of reduced size or chains of silicon atoms or Si-Si defects. A decrease in size of Si nanocluster occurs in result of the pressure-induced decrease in the diffusion of silicon atoms. (author)

  18. Formation of Pentacene wetting layer on the SiO2 surface and charge trap in the wetting layer

    International Nuclear Information System (INIS)

    Kim, Chaeho; Jeon, D.

    2008-01-01

    We studied the early-stage growth of vacuum-evaporated pentacene film on a native SiO 2 surface using atomic force microscopy and in-situ spectroscopic ellipsometry. Pentacene deposition prompted an immediate change in the ellipsometry spectra, but atomic force microscopy images of the early stage films did not show a pentacene-related morphology other than the decrease in the surface roughness. This suggested that a thin pentacene wetting layer was formed by pentacene molecules lying on the surface before the crystalline islands nucleated. Growth simulation based on the in situ spectroscopic ellipsometry spectra supported this conclusion. Scanning capacitance microscopy measurement indicated the existence of trapped charges in the SiO 2 and pentacene wetting layer

  19. Characterisation of NdFeB thin films prepared on (100)Si substrates with SiO2 barrier layers

    International Nuclear Information System (INIS)

    Sood, D.K.; Muralidhar, G.K.

    1998-01-01

    This work presents a systematic study of the deposition and characterization of NdFeB films on substrates of Si(100) and of SiO2 layer thermally grown on Si(100) held at RT, 360 deg C or 440 deg C. The post-deposition annealing is performed at 600 or 800 deg C in vacuum. The films are characterised using the analytical techniques of RBS, SIMS, XRD, OM and SEM. Results indicate that SiO2 is, in deed, an excellent diffusion barrier layer till 600 deg C but becomes relatively less effective at 800 deg C. Without this barrier layer, interdiffusion at the Si-NdFeB film interface leads to formation of iron silicides, α-Fe and B exclusion from the diffusion zone, in competition with the formation of the magnetic NdFeB phase. (authors)

  20. BF3.SiO2: an efficient catalyst for the synthesis of azo dyes at room temperature

    Directory of Open Access Journals (Sweden)

    Bi Bi Fatemeh Mirjalili

    2012-07-01

    Full Text Available A rapid one-pot method has been developed for the synthesis of azo dyes via ‎sequential diazotization–diazo coupling of aromatic amines with coupling agents at room ‎temperature in the presence of BF3.SiO2 as acidic catalyst. The obtained aryl diazonium salts bearing silica supported boron tri-flouride counter ion‎ was sufficiently stable to be kept at room ‎temperature in the dry state.‎

  1. Plasma-assisted ALD for the conformal deposition of SiO2 : process, material and electronic properties

    NARCIS (Netherlands)

    Dingemans, G.; Helvoirt, van C.A.A.; Pierreux, D.; Keuning, W.; Kessels, W.M.M.

    2012-01-01

    Plasma-assisted atomic layer deposition (ALD) was used to deposit SiO2 films in the temperature range of Tdep = 50–400°C on Si(100). H2Si[N(C2H5)2]2 and an O2 plasma were used as Si precursor and oxidant, respectively. The ALD growth process and material properties were characterized in detail.

  2. Network rigidity and properties of SiO2 and GeO2 glasses under pressure.

    Science.gov (United States)

    Trachenko, Kostya; Dove, Martin T; Brazhkin, Vadim; El'kin, F S

    2004-09-24

    We report in situ studies of SiO2 glass under pressure and find that temperature-induced densification takes place in a pressure window. To explain this effect, we study how rigidity of glasses changes under pressure, with rigidity percolation affecting the dynamics of local relaxation events. We link rigidity percolation in glasses to other effects, including a large increase of crystallization temperature and logarithmic relaxation under pressure.

  3. Studying of Nano SiO2 Preparation from Rice Husk Ash by Using High Gravity Reaction Precipitation Technology

    International Nuclear Information System (INIS)

    Nguyen Thanh Chung; Tran Ngoc Ha; Hoang Van Duc

    2013-01-01

    A novel method (High-gravity reactive precipitation - HGRP) was developed to prepare nano-SiO 2 from rice husk ash using gas-liquid reaction system. The precipitated silica produced by our proposed method had average size of 20 nm with narrow size distribution and purity of SiO 2 was approximately 99.2%. The principles of the method as well as experimental conditions were also described. (author)

  4. Study of sputtered ZnO thin films on SiO2 and GaP substrates

    International Nuclear Information System (INIS)

    Brath, T.; Buc, D.; Kovac, J.; Hrnciar, V.; Caplovic, L.

    2011-01-01

    We have investigated n-ZnO polycrystalline thin films prepared on SiO 2 and p-GaP substrate using magnetron sputtering technique. The structural and electrical properties of these structures were studied. The measured parameters give promising results with a possibility to utilize n-ZnO/p-GaP heterostructure for application in the solar cells development especially in the field of nanostructures. The prepared structures will be a subject of further research. (authors)

  5. Angular dependence of the redeposition rates during SiO2 etching in a CF4 plasma

    International Nuclear Information System (INIS)

    Cho, Byeong-Ok; Hwang, Sung-Wook; Lee, Gyeo-Re; Moon, Sang Heup

    2001-01-01

    The angular dependence of the redeposition rates during SiO 2 etching in a CF 4 plasma was studied using three types of Faraday cages located in a transformer coupled plasma etcher. The SiO 2 substrates were fixed on sample holder slopes that have different angles to the cathode. The substrate was subjected to one of three processes depending on the design of the Faraday cage, i.e., redeposition of sputtered particles from the SiO 2 bottom surface (case I), substrate etching by incident ions (case II), or simultaneous etching and redeposition (case III). Both the redeposition and the etch rates were measured by changing the substrate-surface angle and the self-bias voltage in the range of -100 to -800 V. The redeposition-only rates (case I) at -450 and -800 V closely followed the quadratic curve of the angle whereas the rates at -100 V followed the cubic curve, indicating different mechanisms of the bottom SiO 2 etching depending on the energy regimes. The steep increase of the redeposition rate with the angle was attributed to three factors: the substrate-bottom distance, the angular distribution of emitted particles from the bottom surface, and the particle incident angle on the substrate surface. The etch-only rate curves (case II) closely followed the cosine of the surface angle. The etch-rate curve changed into a reverse-S shape when the substrate was subjected to simultaneous etching and redeposition (case III). The net etch rate for case III decreased drastically above 60 deg. , showing a negative value, i.e., a net redeposition, beyond 75 deg. . The drastic decrease in the net etch rate coincided with the steep increase in the redeposition rate, implying the significant effect of redeposition

  6. Influence of ion bombardment on structural and electrical properties of SiO2 thin films deposited from O2/HMDSO inductively coupled plasmas under continuous wave and pulsed modes

    International Nuclear Information System (INIS)

    Bousquet, A.; Goullet, A.; Leteinturier, C.; Granier, A.; Coulon, N.

    2008-01-01

    Low pressure Plasma Enhanced Chemical Vapour Deposition is commonly used to deposit insulators on temperature sensitive substrates. In these processes, the ion bombardment experienced by films during its growth is known to have benefits but also some disadvantages on material properties. In the present paper, we investigate the influence of this bombardment on the structure and the electrical properties of SiO 2 -like film deposited from oxygen/hexa-methyl-di-siloxane radiofrequency plasma in continuous and pulsed modes. First, we studied the ion kinetics thanks to time-resolved measurements by Langmuir probe. After, we showed the ion bombardment in such plasma controls the OH bond content in deposited films. Finally, we highlight the impressive reduction of fixed charge and interface state densities in films obtained in pulsed mode due to a lower ion bombardment. (authors)

  7. Thermal insulation

    International Nuclear Information System (INIS)

    Aspden, G.J.; Howard, R.S.

    1988-01-01

    The patent concerns high temperature thermal insulation of large vessels, such as the primary vessel of a liquid metal cooled nuclear reactor. The thermal insulation consists of multilayered thermal insulation modules, and each module comprises a number of metal sheet layers sandwiched between a back and front plate. The layers are linked together by straps and clips to control the thickness of the module. (U.K.)

  8. Accessing the application of in situ cosmogenic 14C to surface exposure dating of amorphous SiO2

    Science.gov (United States)

    Cesta, J. M.; Goehring, B. M.; Ward, D. J.

    2017-12-01

    We assess the feasibility and utility of in situ cosmogenic 14C as a geochronometer for landforms composed of amorphous SiO2 through the comparison of 14C surface exposure ages to independently determined eruption ages on Obsidian Dome, California. Landforms composed of amorphous SiO2 phases are difficult to date by conventional cosmogenic nuclide methods due to several complications that may arise (e.g., inability to remove meteoric contamination). The onset of an increased understanding of production rates and analytical measurement of in situ 14C in SiO2 provides an opportunity to address this limitation. Obsidian Dome is a 600-year-old phreatomagmatic dome of the Mono-Inyo Craters located in Inyo County, California, and consists of vesicular pumice, obsidian, and rhyolite. Exposure ages from eight obsidian and banded pumice and obsidian surface samples range from 3947 ± 678 to 914 ± 134 years, all significantly older than the accepted radiocarbon age of 650-550 years. δ13C values for the samples range between +2.65‰ and +1.34‰ and show a negative correlation with CO2 yield. The `too old' exposure ages coupled with this negative correlation between δ13C and CO2 yield suggests the incorporation of an atmospheric component of 14C. Measurement of 14C concentrations in shielded, subsurface samples will assist in isolating the atmospheric 14C component and aid in correcting the surface exposure ages.

  9. Suppressing Structural Colors of Photocatalytic Optical Coatings on Glass: The Critical Role of SiO2.

    Science.gov (United States)

    Li, Ronghua; Boudot, Mickael; Boissière, Cédric; Grosso, David; Faustini, Marco

    2017-04-26

    The appearance of structural colors on coated-glass is a critical esthetical drawback toward industrialization of photocatalytic coatings on windows for architecture or automobile. Herein we describe a rational approach to suppress the structural color of mesoporous TiO 2 -based coatings preserving photoactivity and mechanical stiffness. Addition of SiO 2 as third component is discussed. Ti x Si (1-x) O 2 mesoporous coatings were fabricated by one-step liquid deposition process through the evaporation induced self-assembling and characterized by GI-SAXS, GI-WAXS, electron microscopies, and in situ Environmental Ellipsometry Porosimetry. Guided by optical simulation, we investigated the critical role of SiO 2 on the optical responses of the films but also on the structural, mechanical, and photocatalytic properties, important requirements to go toward real applications. We demonstrate that adding SiO 2 to porous TiO 2 allows tuning and suppression of structural colors through refractive index matching and up to 160% increase in mechanical stiffening of the films. This study leads us to demonstrate an example of "invisible" coating, in which the light reflection is angle- and thickness-independent, and exhibiting high porosity, mechanical stiffness, and photoactivity.

  10. Study on adsorption of rhodamine B onto Beta zeolites by tuning SiO2/Al2O3 ratio.

    Science.gov (United States)

    Cheng, Zhi-Lin; Li, Yan-Xiang; Liu, Zan

    2018-02-01

    The exploration of the relationship between zeolite composition and adsorption performance favored to facilitate its better application in removal of the hazardous substances from water. The adsorption capacity of rhodamine B (RB) onto Beta zeolite from aqueous solution was reported. The relationship between SiO 2 /Al 2 O 3 ratio and adsorption capacity of Beta zeolite for RB was explored. The structure and physical properties of Beta zeolites with various SiO 2 /Al 2 O 3 ratios were determined by XRD, FTIR, TEM, BET, UV-vis and so on characterizations. The adsorption behavior of rhodamine B onto Beta zeolite matched to Langmuir adsorption isotherm and more suitable description for the adsorption kinetics was a pseudo-second-order reaction model. The maximum adsorption capacity of the as-prepared Beta zeolite with SiO 2 /Al 2 O 3 = 18.4 was up to 27.97mg/g. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Argon-plasma-controlled optical reset in the SiO2/Cu filamentary resistive memory stack

    Science.gov (United States)

    Kawashima, T.; Yew, K. S.; Zhou, Y.; Ang, D. S.; Zhang, H. Z.; Kyuno, K.

    2018-05-01

    We show that resistive switching in the SiO2/Cu stack can be modified by a brief exposure of the oxide to an Ar plasma. The set voltage of the SiO2/Cu stack is reduced by 33%, while the breakdown voltage of the SiO2/Si stack (control) is almost unchanged. Besides, the Ar plasma treatment suppresses the negative photoconductivity or optical resistance reset effect, where the electrically formed filamentary conductive path consisting of Cu-ion and oxygen-vacancy clusters is disrupted by the recombination of the oxygen vacancies with nearby light-excited oxygen ions. From the enhanced O-H peak in the Fourier-transform infrared spectrum of the plasma-treated oxide, it is proposed that the Ar plasma has created more oxygen vacancies in the surface region of the oxide. These vacancies in turn adsorb water molecules, which act as counter anions (OH-) promoting the migration of Cu cations into the oxide and forming a more complete Cu filament that is less responsive to light. The finding points to the prospect of a control over the optical resistance reset effect by a simple surface treatment step.

  12. Sol-gel synthesis of TiO2-SiO2 photocatalyst for β-naphthol photodegradation

    International Nuclear Information System (INIS)

    Qourzal, S.; Barka, N.; Tamimi, M.; Assabbane, A.; Nounah, A.; Ihlal, A.; Ait-Ichou, Y.

    2009-01-01

    Silica gel supported titanium dioxide particles (TiO 2 -SiO 2 ) prepared by sol-gel method was as photocatalyst in the degradation of β-naphthol in water under UV-illumination. The prepared sample has been characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The supported catalyst had large surface area and good sedimentation ability. The photodegradation rate of β-naphthol under UV-irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The experiments were measured by high performance liquid chromatography (HPLC). The photodegradation rate of β-naphthol using 60% TiO 2 -SiO 2 particles was faster than that using TiO 2 'Degussa P-25', TiO 2 'PC-50' and TiO 2 'Aldrich' as photocatalyst by 2.7, 4 and 7.8 times, respectively. The kinetics of photocatalytic β-naphthol degradation was found to follow a pseudo-first-order rate law. The effect of the TiO 2 loading on the photoactivity of TiO 2 -SiO 2 particles was also discussed. With good photocatalytic activity under UV-irradiation and the ability to be readily separated from the reaction system, this novel kind of catalyst exhibited the potential effective in the treatment of organic pollutants in aqueous systems.

  13. Viscosity of SiO2-"FeO"-Al2O3 System in Equilibrium with Metallic Fe

    Science.gov (United States)

    Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

    2013-08-01

    The present study delivered the measurements of viscosities in SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe. The rotational spindle technique was used in the measurements at the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The Fe saturation condition was maintained by an iron plate placed at the bottom of the crucible. The equilibrium compositions of the slags were measured by EPMA after the viscosity measurements. The effect of up to 20 mol. pct Al2O3 on the viscosity of the SiO2-"FeO" slag was investigated. The "charge compensation effect" of the Al2O3 and FeO association has been discussed. The modified quasi-chemical viscosity model has been optimized in the SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe to describe the viscosity measurements of the present study.

  14. Viscosity Measurements of SiO2-"FeO"-MgO System in Equilibrium with Metallic Fe

    Science.gov (United States)

    Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

    2014-01-01

    The present study delivers the measurements of viscosities in the SiO2-"FeO"-MgO system in equilibrium with metallic Fe. The rotational spindle technique was used for the measurements at the temperature range of 1523 K to 1773 K (1250 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The viscosity measurements were carried out at 31 to 47 mol pct SiO2 and up to 18.8 mol pct MgO. Analysis of the quenched sample by Electron probe X-ray microanalysis after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. The replacement of "FeO" by MgO was found to increase viscosity and activation energy of the SiO2-"FeO"-MgO slags. The modified Quasi-chemical Viscosity Model was further optimized in this system based on the current viscosity measurements.

  15. Metal dioxides as analogue of SiO2 under strong compression studied by synchrotron XRD and simulations

    Science.gov (United States)

    Liu, H.; Liu, L. L.

    2017-12-01

    The phase transition sequence of SiO2 inducing by high pressure was theoretically predicted as coordination number (CN=6) structures (rutile, pyrite), CN=8 (Pnma) and CN=9 (P-62m) structures, but only the phases up to pyrite structure in SiO2 were observed experimentally up to now. The CN8 phase and CN9 phases of SiO2 were predicted to be stable at least 650 GPa, which is challenging to achieve in the static DAC experiment at present. In other metal dioxide systems, such as TiO2, the ambient rutile and anatase phases first transform to pyrite (CN6), then to the baddeleyite (CN7) phase, to a Pnma (CN8) phase and P-62m(CN9) phase. In this report, under strong compression at room temperature, several metal dioxides were studied experimentally and theoretically, to verify whether this theoretical predicted trend is common transition path under strong compression. This work was supported by Natural Science Foundation of China (11374075), Heilongjiang Province Science Fund for Distinguished Young Scholars (JC201005), Longjiang Scholar, the Fundamental Research Funds for the Central Universities (HIT. BRET1.2010002, HIT. IBRSEM.A.201403).

  16. Toluene and chlorobenzene dinitration over solid H3PO4/MoO3/SiO2 catalyst

    International Nuclear Information System (INIS)

    Adamiak, Joanna; Kalinowska-Alichnewicz, Dorota; Szadkowski, Michal; Skupinski, Wincenty

    2011-01-01

    Highlights: → A novel catalyst H 3 PO 4 /MoO 3 /SiO 2 was characterized and used in nitration. → On the surface domains of phosphomolybdic acid (HPM) are obtained. → Dinitrotoluene is obtained with very high yield i.e. 96 wt.% in mild conditions. → Dinitrochlorobenzene is obtained with only twelve-fold excess of nitric acid. → It is sulfuric acid free and solvent free nitration of aromatic compounds. - Abstract: A new catalyst, H 3 PO 4 /MoO 3 /SiO 2 , was prepared by modification of MoO 3 /SiO 2 using phosphoric acid. The characterization of the catalyst was performed using Infrared and Raman Spectroscopy, potentiometric titration and nitrogen adsorption-desorption methods. Molybdenum oxides were identified along with phosphomolybdic acid and polymolybdates on the modified surface. The suitability of the catalysts for toluene and chlorobenzene nitration in continuous process was examined. Toluene is effectively nitrated to dinitrotoluene (DNT) in one-stage process (96 wt.% of DNT in the product) and in mild conditions i.e. at room temperature and only with ten-fold excess of nitric acid. In chlorobenzene nitration only twelve-fold excess of nitric acid is needed to obtain as high yield as 95 wt.%. Most importantly, the novel catalysts we have developed, provide the opportunity for sulfuric acid- free nitration of aromatic compounds.

  17. Improving Passivation Process of Si Nano crystals Embedded in SiO2 Using Metal Ion Implantation

    International Nuclear Information System (INIS)

    Bornacelli, J.; Esqueda, J.A.R.; Fernandez, L.R.; Oliver, A.

    2013-01-01

    We studied the photoluminescence (PL) of Si nano crystals (Si-NCs) embedded in SiO 2 obtained by ion implantation at MeV energy. The Si-NCs are formed at high depth (1-2 μm) inside the SiO 2 achieving a robust and better protected system. After metal ion implantation (Ag or Au), and a subsequent thermal annealing at 600°C under hydrogen-containing atmosphere, the PL signal exhibits a noticeable increase. The ion metal implantation was done at energies such that its distribution inside the silica does not overlap with the previously implanted Si ion . Under proper annealing Ag or Au nanoparticles (NPs) could be nucleated, and the PL signal from Si-NCs could increase due to plasmonic interactions. However, the ion-metal-implantation-induced damage can enhance the amount of hydrogen, or nitrogen, that diffuses into the SiO 2 matrix. As a result, the surface defects on Si-NCs can be better passivated, and consequently, the PL of the system is intensified. We have selected different atmospheres (air, H 2 /N 2 and Ar) to study the relevance of these annealing gases on the final PL from Si-NCs after metal ion implantation. Studies of PL and time-resolved PL indicate that passivation process of surface defects on Si-NCs is more effective when it is assisted by ion metal implantation.

  18. ZnO nanowire co-growth on SiO2 and C by carbothermal reduction and vapour advection

    International Nuclear Information System (INIS)

    Vega, N C; Caram, J; Grinblat, G; Comedi, D; Wallar, R; LaPierre, R R; Tirado, M

    2012-01-01

    Vertically aligned ZnO nanowires (NWs) were grown on Au-nanocluster-seeded amorphous SiO 2 films by the advective transport and deposition of Zn vapours obtained from the carbothermal reaction of graphite and ZnO powders. Both the NW volume and visible-to-UV photoluminescence ratio were found to be strong functions of, and hence could be tailored by, the (ZnO+C) source–SiO 2 substrate distance. We observe C flakes on the ZnO NWs/SiO 2 substrates which exhibit short NWs that developed on both sides. The SiO 2 and C substrates/NW interfaces were studied in detail to determine growth mechanisms. NWs on Au-seeded SiO 2 were promoted by a rough ZnO seed layer whose formation was catalysed by the Au clusters. In contrast, NWs grew without any seed on C. A correlation comprising three orders of magnitude between the visible-to-UV photoluminescence intensity ratio and the NW volume is found, which results from a characteristic Zn partial pressure profile that fixes both O deficiency defect concentration and growth rate. (paper)

  19. Synthesis and Luminescence Properties of Yellow-emitting SiO2/Zn2SiO4: Mn Nanocomposite

    Directory of Open Access Journals (Sweden)

    Karim OMRI

    2014-05-01

    Full Text Available Yellow light emitting Mn2+-doped b-Zn2SiO4 phosphor nanoparticles embedded in SiO2 host matrix, were prepared by a simple solid-phase reaction under natural atmosphere at 1500 °C for 2 hours after the incorporation of manganese doped zinc oxide nanoparticles in silica using sol-gel method. The SiO2/Zn2SiO4:Mn nanocomposite was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM and photoluminescence (PL. The nanopowder was crystallized in triclinic b-Zn2SiO4 phase with a particles size varies between 70 nm and 84 nm. The SiO2/b-Zn2SiO4:Mn nanocomposite exhibited a broad yellow emission band at 575 nm under UV excitation light. The dependence of the intensity and energy position of the obtained PL band on measurement temperature and power excitation will be discussed.

  20. Theoretical prediction of Grüneisen parameter for SiO_2.TiO_2 bulk metallic glasses

    International Nuclear Information System (INIS)

    Singh, Chandra K.; Pandey, Brijesh K.; Pandey, Anjani K.

    2016-01-01

    The Grüneisen parameter (γ) is very important to decide the limitations for the prediction of thermoelastic properties of bulk metallic glasses. It can be defined in terms of microscopic and macroscopic parameters of the material in which former is based on vibrational frequencies of atoms in the material while later is closely related to its thermodynamic properties. Different formulation and equation of states are used by the pioneer researchers of this field to predict the true sense of Gruneisen parameter for BMG but for SiO_2.TiO_2 very few and insufficient information is available till now. In the present work we have tested the validity of two different isothermal EOS viz. Poirrior-Tarantola EOS and Usual-Tait EOS to predict the true value of Gruneisen parameter for SiO_2.TiO_2 as a function of compression. Using different thermodynamic limitations related to the material constraints and analyzing obtained result it is concluded that the Poirrior-Tarantola EOS gives better numeric values of Grüneisen parameter (γ) for SiO_2.TiO_2 BMG.

  1. Preparation and characterization of Sio2CaCl2 nanocomposite by the sol-gel method

    International Nuclear Information System (INIS)

    Tohidi, S. H.; Ziaie, F.; Abdolmaleki, A.

    2009-01-01

    The SiO 2 CaCl 2 hybrid porous materials were prepared by the sol-gel method. This process was conducted by the hydrolysis and condensation of Tetraethyl orthosilicate by replacement of ethanol from alcogel and drying at the ambient temperature to obtain xerogel structure. The alcogel samples were synthesized from Tetraethyl orthosilicate, EtOH, H 2 O, HCl, NH 4 OH and CaCl 2 , while the total molar ratio of the compounds was 1: 9: 4: 8 x 10 -4 , 8 x 10 -3 , respectively. Xerogel containing 30 wt % of CaCl 2 (dry matter) was prepared and characterized by Scanning Electron Microscopy, Transmission Electron Microscopy, Fourier Transmittance Infra Red spectrum, Energy Dispersive X-ray and Thermal Gravimetric Analysis systems. The results obtained from Scanning Electron Microscopy and Energy Dispersive X-ray showed the micrograph of CaCl 2 on the silica and chemical elemental analysis, respectively. On the other hand, The Transmission Electron Microscopy micrograph confirmed average particle size of SiO 2 -CaCl 2 about 50 nm and Fourier Transmittance Infra Red spectrum described the functional groups of the nano composite. The thermal analysis of SiO 2 -CaCl 2 nano composite was performed using Thermal Gravimetric Analysis system and the results showed that the suitable temperature for initial thermal treatment was about 200 d eg C .

  2. Synthesis and effect of copper incorporation on the thermoluminescence and structural properties of SiO2 particles

    International Nuclear Information System (INIS)

    Burruel I, S. E.; Cruz V, C.; Salas J, Ch. J.; Bernal, R.; Garcia H, A. R.; Castano, V. M.

    2015-10-01

    Full text: In this work, we evaluated the effect of Cu-dopant concentration in SiO 2 particles on structural and thermoluminescence (Tl) properties, prepared by the sol-gel technique. Tl studies in silica samples containing Cu show an important enhancement of their Tl response when compared with pure silica samples. In the copper doped silica a prominent Tl peak is observed, the glow curve was observed between 70 and 450 degrees C after exposure to beta irradiation. The maximum temperature of the glow peak centered at around 140 degrees C shifts to higher values and the intensity enhancement with increasing Cu content, this glow curve is surely composed of several overlapped individual Tl peaks. Also, the particle size is affected by the concentration of Cu dopant. In the case SiO 2 , only is observed a glow peak centered to 95 degrees C, which is interesting for non-Tl dosimetry of ionizing radiation, which is based in detecting the afterglow response following exposure to radiation. The dose response of SiO 2 :Cu showed a linear behaviour in the interval studied with no saturation evidence until 6.4 kGy, which makes this material suitable and promising for medical, industrial and also space dosimetry applications. (Author)

  3. Influence of radiation-damages on parameters of lattice oscillations in crystalline and vitreous SiO2

    International Nuclear Information System (INIS)

    Abdukadyrova, I.Kh.

    2008-01-01

    Using IR reflection spectroscopy, the influence of radiation-induced disturbances on a number of parameters of lattice oscillations in two SiO 2 modifications was investigated. Radiation kinetics of changes in spectral characteristics of fundamental oscillations in SiO 2 crystalline and glassy states was determined. Dose dependences of both reflectivity and degenerate mode vibrational frequency were found to show minima whose locations were governed by a type of a sample. Under higher doses of neutron radiation (10 21 cm -2 ), certain characteristics of bands were observed to be of the same values for the both materials modified. The features of radiation kinetics were found for dynamic parameters of the samples. It was deduced that specific character of radiation-induced changes observed in spectral and dynamic parameters of oscillations in the region of degenerate modes was due to both the accumulation of radiation damages and a change in the force field surrounding bridge-type bonds which was related with the change in the SiO 2 structure. (authors)

  4. Fixed-bed adsorption separation of xylene isomers over sio2/silicallite-1 core-shell adsorbents

    KAUST Repository

    Khan, Easir A.

    2013-12-29

    SiO2/Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin polycrystalline silicalite-1 shell which was synthesized via a self-assembly of silicalite-1 nanocrystals on core silica surface followed by a secondary seeded growth method. The core materials, SiO2 used in this study has mesoporosity with an average pore diameter of 60Å and hence offers no shape selectivity for xylene isomers. However, the shell, silicalite-1 contains rigid pore structures and preferentially adsorbs p-xylene from their isomers mixtures. A series of adsorption fixed bed breakthrough adsorption/desorption experiment was performed to obtain the equilibrium isotherms and adsorption isotherm parameters of xylene isomers. The equilibrium isotherms of xylene isomers follow the Langmuir\\'s model. A chromatographic adsorption model has been used to describe the fixed-bed breakthrough profiles of xylene isomers. The model has successfully predicted the responses of the binary mixtures of p/o-xylene isomers. The SiO2/silicalite-1 core-shell adsorbents have shown para-selectivity as high as 15. © Bangladesh Uni. of Engg. & Tech.

  5. Synthesis of ZnFe2O4/SiO2 composites derived from a diatomite template.

    Science.gov (United States)

    Liu, Zhaoting; Fan, Tongxiang; Zhou, Han; Zhang, Di; Gong, Xiaolu; Guo, Qixin; Ogawa, Hiroshi

    2007-03-01

    A novel porous ZnFe2O4/SiO2 composite product has been generated with a template-directed assembly method from porous diatomite under different synthesis conditions, such as precursor concentrations (metallic nitrates), calcination temperature and diatomite type. The phase composition and morphology of all the materials were examined by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results indicated that an inherited hierarchical porous structure from the diatomite template can be obtained, and the synthesis conditions were found to have clear effects on the formation of the ZnFe2O4/SiO2 composite. The ideal composite of ZnFe2O4/SiO2 can be obtained through optimization of diatomite template type, precursor solution and calcination temperature. Furthermore, the adsorption abilities of two types of diatomites were analyzed in detail using FTIR spectra and nitrogen adsorption measurements etc, which proved that A-diatomite (Shengzhou-diatomite) is better than B-diatomite (Changbai-diatomite) on the aspect of adsorbing Zn and Fe ions, and of forming the ZnFe2O4.

  6. Cellulose Insulation

    Science.gov (United States)

    1980-01-01

    Fire retardant cellulose insulation is produced by shredding old newspapers and treating them with a combination of chemicals. Insulating material is blown into walls and attics to form a fiber layer which blocks the flow of air. All-Weather Insulation's founders asked NASA/UK-TAP to help. They wanted to know what chemicals added to newspaper would produce an insulating material capable of meeting federal specifications. TAP researched the query and furnished extensive information. The information contributed to successful development of the product and helped launch a small business enterprise which is now growing rapidly.

  7. Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents

    Directory of Open Access Journals (Sweden)

    Wang C

    2017-04-01

    Full Text Available Chongwen Wang,1,2,* Kehan Zhang,2,* Zhe Zhou,2,* Qingjun Li,2 Liting Shao,2 Rong Zhang Hao,3 Rui Xiao,2 Shengqi Wang1,2 1College of Life Sciences & Bio-Engineering, Beijing University of Technology, 2Beijing Key Laboratory of New Molecular Diagnosis Technologies for Infectious Diseases, Beijing Institute of Radiation Medicine, Beijing, 3Institute for Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, People’s Republic of China *These authors contributed equally to this work Abstract: Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe3O4@SiO2@Ag microflowers were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe3O4@SiO2@Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe3O4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe3O4@SiO2@Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 20 µg mL-1, respectively. The microflowers also showed enhanced effect compared with bare Fe3O4@SiO2@Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe3O4@SiO2@Ag microflowers exhibit promising applications in the antibacterial fields. Keywords: antibiotic-resistant bacteria, surface area, biological properties, magnetic composites, Ag shell

  8. Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

    Science.gov (United States)

    Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

    2017-06-01

    We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

  9. Synthesis, structural characterization and dielectric properties of Nb doped BaTiO3/SiO2 core–shell heterostructure

    International Nuclear Information System (INIS)

    Cernea, M.; Vasile, B.S.; Boni, A.; Iuga, A.

    2014-01-01

    Highlights: • Optimal parameters for preparation by sol–gel of core–shell (BT-Nb 0.005 )/SiO 2 are presented in this paper. • Single crystalline BT-Nb 0.005 /SiO 2 core–shell composite with ∼34 nm shell thick was prepared. • The core–shell ceramic exhibits good dielectric properties and ferroelectric characteristics. -- Abstract: Perovskite complex ceramic oxides, BaTiO 3 doped with 0.5 mol%Nb 2 O 5 and then nanocoated with SiO 2 (abbreviated as BT-Nb 0.005 /SiO 2 ) was successful prepared using conventional sol–gel processing. Phase composition, particle morphology, structure, and electric properties of BT-Nb 0.005 core and BT-Nb 0.005 /SiO 2 core–shell were examined and compared, using X-ray diffraction, transmission electron microscopy and, dielectric and ferroelectric measurements. Core–shell composite with well-defined perovskite tetragonal phase of BaTiO 3 was achieved. Furthermore, single crystalline BT-Nb 0.005 /SiO 2 core–nanoshell heterostructure with ∼34 nm shell thick was prepared, which is a novelty in ferroelectrics field. The ferroelectric quality of BT-Nb 0.005 has suffered an alteration when the (BT-Nb 0.005 )/SiO 2 core–shell heterostructure was realized. One-dimensional BT-Nb 0.005 /SiO 2 core–shell heterostructure exhibits an improvement of dielectric losses and a decrease of dielectric constant, compared to uncoated BT-Nb 0.005 . The (BT-Nb 0.005 )/SiO 2 core–shell material could be interesting for application in the composite capacitors

  10. Thermal insulation

    International Nuclear Information System (INIS)

    Pinsky, G.P.

    1977-01-01

    Thermal insulation for vessels and piping within the reactor containment area of nuclear power plants is disclosed. The thermal insulation of this invention can be readily removed and replaced from the vessels and piping for inservice inspection, can withstand repeated wettings and dryings, and can resist high temperatures for long periods of time. 4 claims, 3 figures

  11. Study of SiO2 surface sputtering by a 250-550 keV He+ ion beam during high-resolution Rutherford backscattering measurements

    International Nuclear Information System (INIS)

    Kusanagi, Susumu; Kobayashi, Hajime

    2006-01-01

    Decreases in oxygen signal intensities in spectra of high-resolution Rutherford backscattering spectrometry (HRBS) were observed during measurements on a 5-nm thick SiO 2 layer on a Si substrate when irradiated by 250-550 keV He + ions. Shifts in an implanted arsenic profile in a 5-nm thick SiO 2 /Si substrate were also observed as a result of He + ion irradiation. These results lead to the conclusion that the SiO 2 surface was sputtered by He + ions in this energy range

  12. Shift in room-temperature photoluminescence of low-fluence Si+-implanted SiO2 films subjected to rapid thermal annealing

    International Nuclear Information System (INIS)

    Fu Mingyue; Tsai, J.-H.; Yang, C.-F.; Liao, C.-H.

    2008-01-01

    We experimentally demonstrate the effect of the rapid thermal annealing (RTA) in nitrogen flow on photoluminescence (PL) of SiO 2 films implanted by different doses of Si + ions. Room-temperature PL from 400-nm-thick SiO 2 films implanted to a dose of 3x10 16 cm -2 shifted from 2.1 to 1.7 eV upon increasing RTA temperature (950-1150 deg. C) and duration (5-20 s). The reported approach of implanting silicon into SiO 2 films followed by RTA may be effective for tuning Si-based photonic devices.

  13. Optical Properties of Malachite Green Dye Doped SiO2 Glasses: Effect of Transition Metal (Fe-I Used as a Codopant

    Directory of Open Access Journals (Sweden)

    Dulen Bora

    2014-01-01

    Full Text Available Enhanced luminescence properties of Malachite Green (MG (oxalate in Fe-MG codoped SiO2 glasses compared to its values in MG doped SiO2 glasses are reported here. The enhancement is chiefly attributed to a resonance nonradiative energy transfer between Fe and MG. The quantum yield of Malachite Green (MG, in presence of Iron, trapped in sol-gel derived SiO2 glass increases by an order of ~103 compared to that in low viscous solvent while a lifetime of 3.29 ns is reported.

  14. Fabrication of GaAs nanowire devices with self-aligning W-gate electrodes using selective-area MOVPE

    International Nuclear Information System (INIS)

    Ooike, N.; Motohisa, J.; Fukui, T.

    2004-01-01

    We propose and demonstrate a novel self-aligning process for fabricating the tungsten (W) gate electrode of GaAs nanowire FETs by using selective-area metalorganic vapor phase epitaxy (SA-MOVPE) where SiO 2 /W composite films are used to mask the substrates. First, to study the growth process and its dependence on mask materials, GaAs wire structures were grown on masked substrates partially covered with a single W layer or SiO 2 /W composite films. We found that lateral growth over the masked regions could be suppressed when a wire along the [110] direction and a SiO 2 /W composite mask were used. Using this composite mask, we fabricated GaAs narrow channel FETs using W as a Schottky gate electrode, and we were able to observe FET characteristics at room temperature

  15. Exploration of porous SiC nanostructures as thermal insulator with high thermal stability and low thermal conductivity

    Institute of Scientific and Technical Information of China (English)

    Peng; WAN; Jingyang; WANG

    2016-01-01

    The crucial challenge for current nanoscale thermal insulation materials,such as Al2O3 and SiO2 aerogel composites,is to solve the trade-off between extremely low thermal conductivity and unsatisfied thermal stability.Typical high-temperature ceramic SiC possesses excellent mechanical properties and

  16. Synthesis and characterization of erbium-doped SiO2 nanoparticles fabricated by using reverse micelle and sol-gel processing

    International Nuclear Information System (INIS)

    Park, Hoyyul; Bae, Dongsik

    2012-01-01

    Erbium-doped SiO 2 nanoparticles have been synthesized using a reverse micelle technique combined with metal-alkoxide hydrolysis and condensation. The sizes and the morphologies of the erbium-doped SiO 2 nanoparticles could be changed by varying the molar ratio of water to surfactant. The sizes and the morphologies of the erbium-doped SiO 2 nanoparticles were examined by using a transmission electron microscope. The average size of synthesized erbium-doped SiO 2 nanoparticles was approximately 20 - 25 nm and that of the erbium particles was 3 - 5 nm. The effects of the synthesis parameters, such as the molar ratio of water to surfactant, are discussed.

  17. Ag-Decorated Fe3O4@SiO2 Nanorods: Synthesis, Characterization, and Applications in Degradation of Organic Dyes

    Directory of Open Access Journals (Sweden)

    Chao Li

    2016-01-01

    Full Text Available Well-dispersed Ag nanoparticles (NPs are successfully decorated on Fe3O4@SiO2 nanorods (NRs via a facile step-by-step strategy. This method involves coating α-Fe2O3 NRs with uniform silica layer, reduction in 10% H2/Ar atmosphere at 450°C to obtain Fe3O4@SiO2 NRs, and then depositing Ag NPs on the surface of Fe3O4@SiO2 NRs through a sonochemical step. It was found that the as-prepared Ag-decorated magnetic Fe3O4@SiO2 NRs (Ag-MNRs exhibited a higher catalytic efficiency than bare Ag NPs in the degradation of organic dye and could be easily recovered by convenient magnetic separation, which show great application potential for environmental protection applications.

  18. The Fate and Transport of the SiO2 Nanoparticles in a Granular Activated Carbon Bed and Their Impact on the Removal of VOCs

    Science.gov (United States)

    Adsorption isotherm, adsorption kinetics and column breakthrough experiments evaluating trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) were conducted in the presence and absence of silica nanoparticles (SiO2 NPs). Zeta potential of the SiO

  19. Effects of SiO2 encapsulation and laser processing on single CdTe/ZnTe quantum dots grown on Si (001) substrates

    International Nuclear Information System (INIS)

    Lee, Hong Seok; Rastelli, Armando; Schmidt, Oliver G.; Kim, Tae Whan; Lee, In Won

    2011-01-01

    Micro-photoluminescence (μ-PL) measurements are carried out to investigate the effects of SiO 2 encapsulation and laser processing of single CdTe/ZnTe quantum dots (QDs) grown on Si (001) substrates by using molecular beam epitaxy and atomic layer epitaxy. After laser processing, the μ-PL peak shift for the 200-nm SiO 2 capped single QD is larger than that of the as-grown sample. The large μ-PL peak shift in the 200-nm SiO 2 capped sample is related to the compressive stress induced by the ZnTe cap layer during laser processing. These results indicate that SiO 2 encapsulation and laser processing represent effective methods for achieving local wavelength tuning in single QDs.

  20. Activation of stress-related signalling pathway in human cells upon SiO2 nanoparticles exposure as an early indicator of cytotoxicity

    LENUS (Irish Health Repository)

    Mohamed, Bashir M

    2011-07-29

    Abstract Background Nanomaterials such as SiO2 nanoparticles (SiO2NP) are finding increasing applications in the biomedical and biotechnological fields such as disease diagnostics, imaging, drug delivery, food, cosmetics and biosensors development. Thus, a mechanistic and systematic evaluation of the potential biological and toxic effects of SiO2NP becomes crucial in order to assess their complete safe applicability limits. Results In this study, human monocytic leukemia cell line THP-1 and human alveolar epithelial cell line A549 were exposed to a range of amorphous SiO2NP of various sizes and concentrations (0.01, 0.1 and 0.5 mg\\/ml). Key biological indicators of cellular functions including cell population density, cellular morphology, membrane permeability, lysosomal mass\\/pH and activation of transcription factor-2 (ATF-2) were evaluated utilizing quantitative high content screening (HCS) approach and biochemical techniques. Despite the use of extremely high nanoparticle concentrations, our findings showed a low degree of cytotoxicity within the panel of SiO2NP investigated. However, at these concentrations, we observed the onset of stress-related cellular response induced by SiO2NP. Interestingly, cells exposed to alumina-coated SiO2NP showed low level, and in some cases complete absence, of stress response and this was consistent up to the highest dose of 0.5 mg\\/ml. Conclusions The present study demonstrates and highlights the importance of subtle biological changes downstream of primary membrane and endocytosis-associated phenomena resulting from high dose SiO2NP exposure. Increased activation of transcription factors, such as ATF-2, was quantitatively assessed as a function of i) human cell line specific stress-response, ii) SiO2NP size and iii) concentration. Despite the low level of cytotoxicity detected for the amorphous SiO2NP investigated, these findings prompt an in-depth focus for future SiO2NP-cell\\/tissue investigations based on the combined analysis of more subtle signalling pathways associated with accumulation mechanisms, which is essential for establishing the bio-safety of existing and new nanomaterials.

  1. Activation of stress-related signalling pathway in human cells upon SiO2 nanoparticles exposure as an early indicator of cytotoxicity

    Directory of Open Access Journals (Sweden)

    Mohamed Bashir

    2011-07-01

    Full Text Available Abstract Background Nanomaterials such as SiO2 nanoparticles (SiO2NP are finding increasing applications in the biomedical and biotechnological fields such as disease diagnostics, imaging, drug delivery, food, cosmetics and biosensors development. Thus, a mechanistic and systematic evaluation of the potential biological and toxic effects of SiO2NP becomes crucial in order to assess their complete safe applicability limits. Results In this study, human monocytic leukemia cell line THP-1 and human alveolar epithelial cell line A549 were exposed to a range of amorphous SiO2NP of various sizes and concentrations (0.01, 0.1 and 0.5 mg/ml. Key biological indicators of cellular functions including cell population density, cellular morphology, membrane permeability, lysosomal mass/pH and activation of transcription factor-2 (ATF-2 were evaluated utilizing quantitative high content screening (HCS approach and biochemical techniques. Despite the use of extremely high nanoparticle concentrations, our findings showed a low degree of cytotoxicity within the panel of SiO2NP investigated. However, at these concentrations, we observed the onset of stress-related cellular response induced by SiO2NP. Interestingly, cells exposed to alumina-coated SiO2NP showed low level, and in some cases complete absence, of stress response and this was consistent up to the highest dose of 0.5 mg/ml. Conclusions The present study demonstrates and highlights the importance of subtle biological changes downstream of primary membrane and endocytosis-associated phenomena resulting from high dose SiO2NP exposure. Increased activation of transcription factors, such as ATF-2, was quantitatively assessed as a function of i human cell line specific stress-response, ii SiO2NP size and iii concentration. Despite the low level of cytotoxicity detected for the amorphous SiO2NP investigated, these findings prompt an in-depth focus for future SiO2NP-cell/tissue investigations based on the combined analysis of more subtle signalling pathways associated with accumulation mechanisms, which is essential for establishing the bio-safety of existing and new nanomaterials.

  2. The structure of well defined SiO2 supported MoO3 clusters during sulfidation : an in situ EXAFS-study

    NARCIS (Netherlands)

    Boer, de M.; Dillen, van A.J.; Koningsberger, D.C.; Geus, J.W.; Kuroda, H.; Ohta, T.

    1993-01-01

    The sulfidation of a well defined MoO3/SiO2 catalyst has been examd. by means of TPS, EXAFS, and TEM. The oxidic clusters in a 5.6 wt% MoO3/SiO2 catalyst are transformed into almost completely sulfided particles (MoOxSy) by O-S exchange at RT. A molybdenum-sulfido particle that resembles the MoS3

  3. The influence of Pr3+ co-doping on the photoluminescence and cathodoluminescence properties of SiO2:Eu3+/Tb3+

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2011-07-01

    Full Text Available Tb3+-Pr3+, and Eu3+-Pr3+ ion pairs co-doped in a SiO2 matrix were prepared by a sol-gel method. Co-doping of Eu3+ and Tb3+ ions with Pr3+ in SiO2 resulted in the quenching of Eu3+ and Tb3+ emissions with increasing Pr3+ concentrations. The quenching...

  4. Transport and abatement of fluorescent silica nanoparticle (SiO_2 NP) in granular filtration: effect of porous media and ionic strength

    International Nuclear Information System (INIS)

    Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

    2017-01-01

    The extensive production and application of engineered silica nanoparticles (SiO_2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO_2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO_2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO_2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO_2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO_2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO_2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO_2 NP filtration.

  5. Transport and abatement of fluorescent silica nanoparticle (SiO2 NP) in granular filtration: effect of porous media and ionic strength

    Science.gov (United States)

    Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

    2017-03-01

    The extensive production and application of engineered silica nanoparticles (SiO2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO2 NP filtration.

  6. Silver nanoparticles embedded mesoporous SiO_2 nanosphere: an effective anticandidal agent against Candida albicans 077

    International Nuclear Information System (INIS)

    Qasim, M; Paik, P; Das, D; Singh, Braj R; Naqvi, A H

    2015-01-01

    Candida albicans is a diploid fungus that causes common infections such as denture stomatitis, thrush, urinary tract infections, etc. Immunocompromised patients can become severely infected by this fungus. Development of an effective anticandidal agent against this pathogenic fungus, therefore, will be very useful for practical application. In this work, Ag-embedded mesoporous silica nanoparticles (mSiO_2@AgNPs) have successfully been synthesized and their anticandidal activities against C. albicans have been studied. The mSiO_2@AgNPs nanoparticles (d ∼ 400 nm) were designed using pre-synthesized Ag nanoparticles and tetraethyl orthosilicate (TEOS) as a precursor for SiO_2 in the presence of cetyltrimethyl ammonium bromide (CTAB) as an easily removable soft template. A simple, cost-effective, and environmentally friendly approach has been adopted to synthesize silver (Ag) nanoparticles using silver nitrate and leaf extract of Azadirachta indica. The mesopores, with size-equivalent diameter of the micelles (d = 4–6 nm), were generated on the SiO_2 surface by calcination after removal of the CTAB template. The morphology and surface structure of mSiO_2@AgNPs were characterized through x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), particle size analysis (PSA), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller (BET) and high-resolution transmission electron microscopy (HRTEM). The HRTEM micrograph reveals the well-ordered mesoporous structure of the SiO_2 sphere. The antifungal activities of mSiO_2@AgNPs on the C. albicans cell have been studied through microscopy and are seen to increase with increasing dose of mSiO_2@AgNPs, suggesting mSiO_2@AgNPs to be a potential antifungal agent for C. albicans 077. (paper)

  7. Cathodic Potential Dependence of Electrochemical Reduction of SiO2 Granules in Molten CaCl2

    Science.gov (United States)

    Yang, Xiao; Yasuda, Kouji; Nohira, Toshiyuki; Hagiwara, Rika; Homma, Takayuki

    2016-09-01

    As part of an ongoing fundamental study to develop a new process for producing solar-grade silicon, this paper examines the effects of cathodic potential on reduction kinetics, current efficiency, morphology, and purity of Si product during electrolysis of SiO2 granules in molten CaCl2 at 1123 K (850 °C). SiO2 granules were electrolyzed potentiostatically at different cathodic potentials (0.6, 0.8, 1.0, and 1.2 V vs Ca2+/Ca). The reduction kinetics was evaluated based on the growth of the reduced Si layer and the current behavior during electrolysis. The results suggest that a more negative cathodic potential is favorable for faster reduction. Current efficiencies in 60 minutes are greater than 65 pct at all the potentials examined. Si wires with sub-micron diameters are formed, and their morphologies show little dependence on the cathodic potential. The impurities in the Si product can be controlled at low level. The rate-determining step for the electrochemical reduction of SiO2 granules in molten CaCl2 changes with time. At the initial stage of electrolysis, the electron transfer is the rate-determining step. At the later stage, the diffusion of O2- ions is the rate-determining step. The major cause of the decrease in reduction rate with increasing electrolysis time is the potential drop from the current collector to the reaction front due to the increased contact resistance among the reduced Si particles.

  8. Sol-gel synthesis and characterization of single-phase Ni ferrite nanoparticles dispersed in SiO2 matrix

    International Nuclear Information System (INIS)

    Nadeem, K.; Traussnig, T.; Letofsky-Papst, I.; Krenn, H.; Brossmann, U.; Wuerschum, R.

    2010-01-01

    Nanoparticles of NiFe 2 O 4 dispersed in SiO 2 (25 wt%) matrix were synthesized by sol-gel method using tetraethyl orthosilicate (TEOS), as a precursor for SiO 2 . The sol-gel method for nanocomposites normally provides multi-phase nanoparticles. We investigated by a synopsis of different analysis methods, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SQUID-magnetometry, how the various chemical phases are transformed to a single-phase spinel structure during the various stages of annealing from 300 to 900 o C. We have developed a full phase diagram of chemical phases as a function of annealing temperature. The average particle size lies in the range 16-27 nm. The chemical phases formed below 900 o C are NiFe, NiO, γ-Fe 2 O 3 , α-Fe 2 O 3 , and NiFe 2 O 4 , respectively. The role of the TEOS prepared SiO 2 matrix is to restrict the particle size in a small range in order to rule out particle size effects. In the mid-infrared, a shift of the vibrational Fe-O bond is observed from 568 to 586 cm -1 for annealing between 500 and 700 o C which indicates an increasing NiFe 2 O 4 phase formation. A systematic study of coercivity field (ranging from 32 to 200 Oe) and saturation magnetic moment (ranging from 12.2 to 32.1 emu/g) for differently annealed samples supports our findings about the evolution of single-phase NiFe 2 O 4 at 900 o C. The opposite trend of saturation magnetic moment and coercivity with respect to annealing temperature clearly separates the different phases of metallic, antiferromagnetic, and finally single-phase spinel NiFe 2 O 4 .

  9. The solubility limit of SiO2 in α-alumina at 1600 °C

    International Nuclear Information System (INIS)

    Moshe, Ruth; Berner, Alex; Kaplan, Wayne D.

    2014-01-01

    The solubility limit of Si in α-alumina was measured using wavelength-dispersive spectroscopy on a scanning electron microscope. Samples were doped with Si such that the equilibrated material would contain two phases: mullite (3Al 2 O 3 ·2SiO 2 ) and alumina saturated with Si. Thus the amount of Si measured in the alumina grains represents the solubility limit. Measurements were conducted on water-quenched and furnace-cooled samples. For the quenched samples the Si solubility limit in Al 2 O 3 was found to be 188 ± 7 ppm at 1600 °C

  10. Microstructure and magnetic properties of FePt:Ag nanocomposite films on SiO2/Si(1 0 0)

    International Nuclear Information System (INIS)

    Wang Hao; Yang, F.J.; Wang, H.B.; Cao, X.; Xue, S.X.; Wang, J.A.; Gao, Y.; Huang, Z.B.; Yang, C.P.; Chiah, M.F.; Cheung, W.Y.; Wong, S.P.; Li, Q.; Li, Z.Y.

    2006-01-01

    FePt:Ag nanocomposite films were prepared by pulsed filtered vacuum arc deposition system and subsequent rapid thermal annealing on SiO 2 /Si(1 0 0) substrates. The microstructure and magnetic properties were investigated. A strong dependence of coercivity and ordering of the face-central tetragonal structure on both Ag concentration and annealing temperature was observed. With Ag concentration of 22% in atomic ratio, the coercivity got to 6.0 kOe with a grain size of 6.7 nm when annealing temperature was 400 deg. C

  11. Cathodoluminescence properties of SiO2:Pr3+and ZnO.SiO2:Pr3+ phosphor nanopowders

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2010-10-01

    Full Text Available regardless of the incorporation of Pr3+ and nanocrystalline ZnO or annealing at 600 °C. The particles were mostly spherical and agglomerated as confirmed by Field Emission Scanning Electron Microscopy. Thermogravimetric analysis of dried gels performed... Science, vol. 45(19): 5228-5236 Cathodoluminescence properties of SiO2:Pr 3+and ZnO·SiO2:Pr 3+ phosphor nanopowders G. H. Mhlongo, O. M. Ntwaeaborwa, M. S. Dhlamini, H. C. Swart, K. T. Hillie ABSTRACT: The successful incorporation of Zn...

  12. Chemical states of piled-up phosphorus and arsenic atoms at the SiO2/Si interface

    International Nuclear Information System (INIS)

    Yoshimura, Yusuke; Ono, Kanta; Fujioka, Hiroshi; Hayakawa, Shinjiro; Sato, Yoshiyuki; Uematsu, Masashi; Baba, Yuji; Hirose, Kazuyuki; Oshima, Masaharu

    1999-01-01

    We have investigated the positions of the piled-up phosphorus atoms at the SiO 2 /Si interface using the extended X-ray absorption fine structure (EXAFS) and X-ray photoelectron spectroscopy (XPS). The EXAFS and XPS data can be well explained on the assumption that the piled-up arsenic atoms exist at the tetrahedral sites. On the contrary, phosphorus atoms exist not at the tetrahedral sites but at the denser sites. The depth profile measurements of XPS have revealed that the piled-up arsenic and phosphorus atoms exist within 20A from the interface. (author)

  13. Using Apatite to Model Chlorine Contents of High SiO2 Magmas: An Enhanced Methodological Approach

    Science.gov (United States)

    Flesch, R.; Webster, J. D.; Nadeau, P. A.

    2015-12-01

    Hydrothermal experiments were conducted on high-silica (73-75 wt% SiO2), fluid-saturated melts at 844-862°C and ca. 50 MPa using crushed glass of the Los Posos rhyolite. Water and salts including NaCl, KCl, Ca(OH)2, and CaHPO4 and HCl were added proportionally to the experiments to restrict the variability of the aluminosity of the melt. The Durango apatite, which contains 3.53 wt% F and 0.41% Cl, was added as "seeds"bearing magmatic systems.

  14. FE3O4@SIO2-OSO3H NANOCOMPOSITE AS AN EFFICIENT CATALYST FOR THE PREPARATION OF TRICARBOXAMIDES

    Directory of Open Access Journals (Sweden)

    Mohammad Ali Ghasemzadeh

    Full Text Available In this research a highly efficient one-pot preparation of tricarboxamide derivatives via five-component reactions of isocyanides, aldehydes Meldrum's acid and 2equiv. of amines have been developed in the presence of Fe3O4@SiO2-OSO3H nanocomposite. Nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid was readily recovered using an external magnet and could be reused several times without significant loss of reactivity. The catalyst was fully characterized by VSM, FT-IR, SEM, XRD, EDX and TEM analysis.

  15. Atomic force microscopy investigation of growth process of organic TCNQ aggregates on SiO2 and mica substrates

    Science.gov (United States)

    Huan, Qing; Hu, Hao; Pan, Li-Da; Xiao, Jiang; Du, Shi-Xuan; Gao, Hong-Jun

    2010-08-01

    Deposition patterns of tetracyanoquinodimethane (TCNQ) molecules on different surfaces are investigated by atomic force microscopy. A homemade physical vapour deposition system allows the better control of molecule deposition. Taking advantage of this system, we investigate TCNQ thin film growth on both SiO2 and mica surfaces. It is found that dense island patterns form at a high deposition rate, and a unique seahorse-like pattern forms at a low deposition rate. Growth patterns on different substrates suggest that the fractal pattern formation is dominated by molecule-molecule interaction. Finally, a phenomenal “two-branch" model is proposed to simulate the growth process of the seahorse pattern.

  16. Atomic force microscopy investigation of growth process of organic TCNQ aggregates on SiO2 and mica substrates

    International Nuclear Information System (INIS)

    Qing, Huan; Hao, Hu; Li-Da, Pan; Jiang, Xiao; Shi-Xuan, Du; Hong-Jun, Gao

    2010-01-01

    Deposition patterns of tetracyanoquinodimethane (TCNQ) molecules on different surfaces are investigated by atomic force microscopy. A homemade physical vapour deposition system allows the better control of molecule deposition. Taking advantage of this system, we investigate TCNQ thin film growth on both SiO 2 and mica surfaces. It is found that dense island patterns form at a high deposition rate, and a unique seahorse-like pattern forms at a low deposition rate. Growth patterns on different substrates suggest that the fractal pattern formation is dominated by molecule–molecule interaction. Finally, a phenomenal “two-branch” model is proposed to simulate the growth process of the seahorse pattern. (general)

  17. Structural and optical characterization of Mn doped ZnS nanocrystals elaborated by ion implantation in SiO2

    International Nuclear Information System (INIS)

    Bonafos, C.; Garrido, B.; Lopez, M.; Romano-Rodriguez, A.; Gonzalez-Varona, O.; Perez-Rodriguez, A.; Morante, J.R.; Rodriguez, R.

    1999-01-01

    Mn doped ZnS nanocrystals have been formed in SiO 2 layers by ion implantation and thermal annealing. The structural analysis of the processed samples has been performed mainly by Secondary Ion Mass Spectroscopy (SIMS) and Transmission Electron Microscopy (TEM). The data show the precipitation of ZnS nanocrystals self-organized into two layers parallel to the free surface. First results of the optical analysis of samples co-implanted with Mn show the presence of a yellow-green photoluminescence depending on the Mn concentration and the size of the nanocrystals, suggesting the doping with Mn of some precipitates

  18. Laser-controlled stress of Si nanocrystals in a free-standing Si /SiO2 superlattice

    Science.gov (United States)

    Khriachtchev, Leonid; Räsänen, Markku; Novikov, Sergei

    2006-01-01

    We report laser manipulations with stress at the nanoscale level. The continuous-wave Ar+ laser radiation melts Si nanocrystals in a free-standing Si /SiO2 superlattice. Silicon crystallization from the liquid phase leads to a compressive stress, which can be accurately tuned in the 3GPa range using laser annealing below the Si melting temperature and then recovered by laser annealing above the melting temperature. This allows investigations of various phenomena as a function of stress and makes a case of Si-nanocrystal memory with very long retention time, which can be written, erased, and read by optical means.

  19. Nonlinear X-ray production of defect spins in vitreous SiO2: the roles of creation and activation

    International Nuclear Information System (INIS)

    Galeener, F.L.; Kerwin, D.B.; Miller, A.J.

    1992-01-01

    The dependence of spin concentration on X-ray dose is shown to be nonlinear in distinctive ways for the three most common defect structures in vitreous SiO 2 . We fit the data with a model invoking two concurrent simple processes: creation of new defects and activation of preexisting ones. The resultant fit parameters show dependencies on hydroxyl concentration and fictive temperature that shed new light on the processes, the defects, their origins and the radiation hardness of v-SiO 2 . (author)

  20. Formation and relaxation processes of photoinduced defects in a Ge-doped SiO2 glass

    International Nuclear Information System (INIS)

    Yamaguchi, M.; Saito, K.; Ikushima, A.J.

    2002-01-01

    The defect centers induced by ArF laser irradiation in Ge-doped SiO 2 have been investigated by the electron-spin resonance method. In order to observe formation and relaxation processes of the defects, step annealing has been carried out after the irradiation at 77 K. The thermally induced decay of the self-trapped hole (STH) and formation of the so-called Ge(2) centers have been observed with increasing temperature. The result suggests that the holes are transferred from the STH to the Ge(2)