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)

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

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

Nanoscale gadolinium oxide capping layers on compositionally variant gate dielectrics

KAUST Repository

Alshareef, Husam N.

2010-11-19

Metal gate work function enhancement using nanoscale (1.0 nm) Gd2O3 interfacial layers has been evaluated as a function of silicon oxide content in the HfxSiyOz gate dielectric and process thermal budget. It is found that the effective work function tuning by the Gd2O3 capping layer varied by nearly 400 mV as the composition of the underlying dielectric changed from 0% to 100% SiO2, and by nearly 300 mV as the maximum process temperature increased from ambient to 1000 °C. A qualitative model is proposed to explain these results, expanding the existing models for the lanthanide capping layer effect.

Nanoscale gadolinium oxide capping layers on compositionally variant gate dielectrics

KAUST Repository

Alshareef, Husam N.; Caraveo-Frescas, J. A.; Cha, D. K.

2010-01-01

Metal gate work function enhancement using nanoscale (1.0 nm) Gd2O3 interfacial layers has been evaluated as a function of silicon oxide content in the HfxSiyOz gate dielectric and process thermal budget. It is found that the effective work function tuning by the Gd2O3 capping layer varied by nearly 400 mV as the composition of the underlying dielectric changed from 0% to 100% SiO2, and by nearly 300 mV as the maximum process temperature increased from ambient to 1000 °C. A qualitative model is proposed to explain these results, expanding the existing models for the lanthanide capping layer effect.

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)

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.

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.

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.

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

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.

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.

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...

Plasma-Induced Damage on the Reliability of Hf-Based High-k/Dual Metal-Gates Complementary Metal Oxide Semiconductor Technology

International Nuclear Information System (INIS)

Weng, W.T.; Lin, H.C.; Huang, T.Y.; Lee, Y.J.; Lin, H.C.

2009-01-01

This study examines the effects of plasma-induced damage (PID) on Hf-based high-k/dual metal-gates transistors processed with advanced complementary metal-oxide-semiconductor (CMOS) technology. In addition to the gate dielectric degradations, this study demonstrates that thinning the gate dielectric reduces the impact of damage on transistor reliability including the positive bias temperature instability (PBTI) of n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) and the negative bias temperature instability (NBTI) of p-channel MOSFETs. This study shows that high-k/metal-gate transistors are more robust against PID than conventional SiO 2 /poly-gate transistors with similar physical thickness. Finally this study proposes a model that successfully explains the observed experimental trends in the presence of PID for high-k/metal-gate CMOS technology.

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.

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.

Interface Study on Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Using High-k Gate Dielectric Materials

Directory of Open Access Journals (Sweden)

Yu-Hsien Lin

2015-01-01

Full Text Available We investigated amorphous indium gallium zinc oxide (a-IGZO thin film transistors (TFTs using different high-k gate dielectric materials such as silicon nitride (Si3N4 and aluminum oxide (Al2O3 at low temperature process (<300°C and compared them with low temperature silicon dioxide (SiO2. The IGZO device with high-k gate dielectric material will expect to get high gate capacitance density to induce large amount of channel carrier and generate the higher drive current. In addition, for the integrating process of integrating IGZO device, postannealing treatment is an essential process for completing the process. The chemical reaction of the high-k/IGZO interface due to heat formation in high-k/IGZO materials results in reliability issue. We also used the voltage stress for testing the reliability for the device with different high-k gate dielectric materials and explained the interface effect by charge band diagram.

Interface Study on Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Using High-k Gate Dielectric Materials

International Nuclear Information System (INIS)

Lin, Y. H.; Chou, J. C.

2015-01-01

We investigated amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFT_s) using different high-Κ gate dielectric materials such as silicon nitride (Si_3N_4) and aluminum oxide (Al_2O_3) at low temperature process (<300 degree) and compared them with low temperature silicon dioxide (SiO_2). The IGZO device with high-Κ gate dielectric material will expect to get high gate capacitance density to induce large amount of channel carrier and generate the higher drive current. In addition, for the integrating process of integrating IGZO device, post annealing treatment is an essential process for completing the process. The chemical reaction of the high-κ/IGZO interface due to heat formation in high-Κ/IGZO materials results in reliability issue. We also used the voltage stress for testing the reliability for the device with different high-Κ gate dielectric materials and explained the interface effect by charge band diagram.

Gate-stack engineering for self-organized Ge-dot/SiO2/SiGe-shell MOS capacitors

Directory of Open Access Journals (Sweden)

Wei-Ting eLai

2016-02-01

Full Text Available We report the first-of-its-kind, self-organized gate-stack heterostructure of Ge-dot/SiO2/SiGe-shell on Si fabricated in a single step through the selective oxidation of a SiGe nano-patterned pillar over a Si3N4 buffer layer on a Si substrate. Process-controlled tunability of the Ge-dot size (7.5−90 nm, the SiO2 thickness (3−4 nm, and as well the SiGe-shell thickness (2−15 nm has been demonstrated, enabling a practically-achievable core building block for Ge-based metal-oxide-semiconductor (MOS devices. Detailed morphologies, structural, and electrical interfacial properties of the SiO2/Ge-dot and SiO2/SiGe interfaces were assessed using transmission electron microscopy, energy dispersive x-ray spectroscopy, and temperature-dependent high/low-frequency capacitance-voltage measurements. Notably, NiGe/SiO2/SiGe and Al/SiO2/Ge-dot/SiO2/SiGe MOS capacitors exhibit low interface trap densities of as low as 3-5x10^11 cm^-2·eV^-1 and fixed charge densities of 1-5x10^11 cm^-2, suggesting good-quality SiO2/SiGe-shell and SiO2/Ge-dot interfaces. In addition, the advantage of having single-crystalline Si1-xGex shell (x > 0.5 in a compressive stress state in our self-aligned gate-stack heterostructure has great promise for possible SiGe (or Ge MOS nanoelectronic and nanophotonic applications.

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.

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

Graphene-graphite oxide field-effect transistors.

Science.gov (United States)

Standley, Brian; Mendez, Anthony; Schmidgall, Emma; Bockrath, Marc

2012-03-14

Graphene's high mobility and two-dimensional nature make it an attractive material for field-effect transistors. Previous efforts in this area have used bulk gate dielectric materials such as SiO(2) or HfO(2). In contrast, we have studied the use of an ultrathin layered material, graphene's insulating analogue, graphite oxide. We have fabricated transistors comprising single or bilayer graphene channels, graphite oxide gate insulators, and metal top-gates. The graphite oxide layers show relatively minimal leakage at room temperature. The breakdown electric field of graphite oxide was found to be comparable to SiO(2), typically ~1-3 × 10(8) V/m, while its dielectric constant is slightly higher, κ ≈ 4.3. © 2012 American Chemical Society

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

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.

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.

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).

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.

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.

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

Electrical characteristics of AlO sub x N sub y prepared by oxidation of sub-10-nm-thick AlN films for MOS gate dielectric applications

CERN Document Server

Jeon, S H; Kim, H S; Noh, D Y; Hwang, H S

2000-01-01

In this research, the feasibility of ultrathin AlO sub x N sub y prepared by oxidation of sub 100-A-thick AlN thin films for metal-oxide-semiconductor (MOS) gate dielectric applications was investigated. Oxidation of 51-A-and 98-A-thick as-deposited AlN at 800 .deg. C was used to form 72-A-and 130-A-thick AlO sub x N sub y , respectively. Based on the capacitance-voltage (C-V) measurements of the MOS capacitor, the dielectric constants of 72 A-thick and 130 A-thick Al-oxynitride were 5.15 and 7, respectively. The leakage current of Al-oxynitride at low field was almost the same as that of thermal SiO sub 2. based on the CV data, the interface state density of Al-oxynitride was relatively higher than that of SiO sub 2. Although process optimization is still necessary, the Al-oxynitride exhibits some possibility for future MOS gate dielectric applications.

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.

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)

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)

Self-aligned indium–gallium–zinc oxide thin-film transistors with SiNx/SiO2/SiNx/SiO2 passivation layers

International Nuclear Information System (INIS)

Chen, Rongsheng; Zhou, Wei; Zhang, Meng; Kwok, Hoi-Sing

2014-01-01

Self-aligned top-gate amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) with SiN x /SiO 2 /SiN x /SiO 2 passivation layers are developed in this paper. The resulting a-IGZO TFT exhibits high reliability against bias stress and good electrical performance including field-effect mobility of 5 cm 2 /Vs, threshold voltage of 2.5 V, subthreshold swing of 0.63 V/decade, and on/off current ratio of 5 × 10 6 . With scaling down of the channel length, good characteristics are also obtained with a small shift of the threshold voltage and no degradation of subthreshold swing. The proposed a-IGZO TFTs in this paper can act as driving devices in the next generation flat panel displays. - Highlights: • Self-aligned top-gate indium–gallium–zinc oxide thin-film transistor is proposed. • SiN x /SiO 2 /SiN x /SiO 2 passivation layers are developed. • The source/drain areas are hydrogen-doped by CHF3 plasma. • The devices show good electrical performance and high reliability against bias stress

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.

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.

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

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.

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.

Role of the SiO2 buffer layer thickness in the formation of Si/SiO2/nc-Ge/SiO2 structures by dry oxidation

International Nuclear Information System (INIS)

Kling, A.; Ortiz, M.I.; Prieto, A.C.; Rodriguez, A.; Rodriguez, T.; Jimenez, J.; Ballesteros, C.; Soares, J.C.

2006-01-01

Nanomemories, containing Ge-nanoparticles in a SiO 2 matrix, can be produced by dry thermal oxidation of a SiGe layer deposited onto a Si-wafer with a barrier SiO 2 layer on its top. Rutherford backscattering spectrometry has been used to characterize the kinetics of the oxidation process, the composition profile of the growing oxide, the Ge-segregation and its diffusion into the barrier oxide in samples with thin and thick barrier oxide layers. The Ge segregated during the oxidation of the SiGe layer diffuses into the barrier oxide. In the first case the diffusion through the thin oxide is enhanced by the proximity of the substrate that acts as a sink for the Ge, resulting in the formation of a low Ge concentration SiGe layer in the surface of the Si-wafer. In the second case, the Ge-diffusion progresses as slowly as in bulk SiO 2 . Since barrier oxide layers as thin as possible are favoured for device fabrication, the structures should be oxidized at lower temperatures and the initial SiGe layer thickness reduced to minimize the Ge-diffusion

Metabolomic effects of CeO2, SiO2 and CuO metal oxide nanomaterials on HepG2 cells

Data.gov (United States)

U.S. Environmental Protection Agency — The data set is a matrix of cellular biochemical (metabolites) in HepG2 cells treated with various metal oxide nanomaterials composed of CeO2, SiO2 and CuO. This...

Study of bulk Hafnium oxide (HfO2) under compression

Science.gov (United States)

Pathak, Santanu; Mandal, Guruprasad; Das, Parnika

2018-04-01

Hafnium oxide (HfO2) is a technologically important material. This material has K-value of 25 and band gap 5.8 eV. A k value of 25-30 is preferred for a gate dielectric [1]. As it shows good insulating and capacitive properties, HfO2 is being considered as a replacement to SiO2 in microelectronic devices as gate dielectrics. On the other hand because of toughening mechanism due to phase transformation induced by stress field observed in these oxides, HFO2 has been a material of investigations in various configurations for a very long time. However the controversies about phase transition of HfO2 under pressure still exists. High quality synchrotron radiation has been used to study the structural phase transition of HfO2 under pressure.

Interfacial microstructure of NiSi x/HfO2/SiO x/Si gate stacks

International Nuclear Information System (INIS)

Gribelyuk, M.A.; Cabral, C.; Gusev, E.P.; Narayanan, V.

2007-01-01

Integration of NiSi x based fully silicided metal gates with HfO 2 high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi x film. Ni content varies near the NiSi/HfO x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi x /HfO 2 interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi x /HfO x was found higher than that of poly-Si/HfO 2 , likely due to compositional non-uniformity of NiSi x . No intermixing between Hf, Ni and Si beyond interfacial roughness was observed

Effect of oxide charge trapping on x-ray photoelectron spectroscopy of HfO2/SiO2/Si structures

International Nuclear Information System (INIS)

Abe, Yasuhiro; Miyata, Noriyuki; Suzuki, Haruhiko; Kitamura, Koji; Igarashi, Satoru; Nohira, Hiroshi; Ikenaga, Eiji

2009-01-01

We examined the effects of interfacial SiO 2 layers and a surface metal layer on the photoelectron spectra of HfO 2 /SiO 2 /Si structures by hard X-ray photoemission spectroscopy with synchrotron radiation as well as conventional X-ray photoelectron spectroscopy (XPS). The Hf 4f and Hf 3d photoelectron peaks broadened and shifted toward a higher binding energy with increasing thickness of the interfacial SiO 2 layer, even though photoelectrons may have been emitted from the HfO 2 layer with the same chemical composition. Thinning the interfacial Si oxide layer to approximately one monolayer and depositing a metal layer on the HfO 2 surface suppressed these phenomena. The O 1s photoelectron spectra revealed marked differences between the metal- and nonmetal-deposited HfO 2 /SiO 2 /Si structures; HfO 2 and SiO 2 components in the O 1s photoelectron spectra for the metal-deposited structures were observed at reasonably separated binding energies, but those for the nonmetal-deposited structures were not separated clearly. From this behavior concerning the effects of interfacial SiO 2 and surface metal layers, we concluded that the Hf 4f, Hf 3d, and O 1s spectra measured from the HfO 2 /SiO 2 /Si structures did not reflect actual chemical bonding states. We consider that potential variations in the HfO 2 film owing to charge trapping strongly affect the measured photoelectron spectra. On the basis of angle-resolved XPS measurements, we propose that positive charges are trapped at the HfO 2 surface and negative charges are trapped inside the HfO 2 layer. (author)

Electrical and materials properties of ZrO2 gate dielectrics grown by atomic layer chemical vapor deposition

Science.gov (United States)

Perkins, Charles M.; Triplett, Baylor B.; McIntyre, Paul C.; Saraswat, Krishna C.; Haukka, Suvi; Tuominen, Marko

2001-04-01

Structural and electrical properties of gate stack structures containing ZrO2 dielectrics were investigated. The ZrO2 films were deposited by atomic layer chemical vapor deposition (ALCVD) after different substrate preparations. The structure, composition, and interfacial characteristics of these gate stacks were examined using cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy. The ZrO2 films were polycrystalline with either a cubic or tetragonal crystal structure. An amorphous interfacial layer with a moderate dielectric constant formed between the ZrO2 layer and the substrate during ALCVD growth on chemical oxide-terminated silicon. Gate stacks with a measured equivalent oxide thickness (EOT) of 1.3 nm showed leakage values of 10-5 A/cm2 at a bias of -1 V from flatband, which is significantly less than that seen with SiO2 dielectrics of similar EOT. A hysteresis of 8-10 mV was seen for ±2 V sweeps while a midgap interface state density (Dit) of ˜3×1011 states/cm eV was determined from comparisons of measured and ideal capacitance curves.

Energy stored in BeO, MgO, Al2O3 and SiO2 oxides irradiated with neutrons

International Nuclear Information System (INIS)

Roux, Andre

1969-01-01

Within the field of researches on refractory oxides which may be used in structure materials in atomic pile, the objective of this research thesis has been the measurement of the energy stored in some specific oxides (BeO, MgO, Al 2 O 3 and SiO 2 ) after their irradiation in a nuclear reactor. This measurement is performed by 'healing' the irradiated substance by means of thermal treatments during which sample initial mass and morphologies are preserved. The measurement of the Wigner energy is then performed by differential enthalpy analysis. The first part reports the experimental determination of Wigner energies (measurement apparatus, method of ballistic differential enthalpy analysis, thermo-gram compensation). The second part presents the Wigner energies obtained for the sintered BeO, the sintered MgO, the sintered Al 2 O 3 , and the vitreous SiO 2 . The third part reports the result interpretation

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.

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

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

Low-temperature formation of high-quality gate oxide by ultraviolet irradiation on spin-on-glass

International Nuclear Information System (INIS)

Usuda, R.; Uchida, K.; Nozaki, S.

2015-01-01

Although a UV cure was found to effectively convert a perhydropolysilazane (PHPS) spin-on-glass film into a dense SiO x film at low temperature, the electrical characteristics were never reported in order to recommend the use of PHPS as a gate-oxide material that can be formed at low temperature. We have formed a high-quality gate oxide by UV irradiation on the PHPS film, and obtained an interface midgap trap density of 3.4 × 10 11  cm −2 eV −1 by the UV wet oxidation and UV post-metallization annealing (PMA), at a temperature as low as 160 °C. In contrast to the UV irradiation using short-wavelength UV light, which is well known to enhance oxidation by the production of the excited states of oxygen, the UV irradiation was carried out using longer-wavelength UV light from a metal halide lamp. The UV irradiation during the wet oxidation of the PHPS film generates electron-hole pairs. The electrons ionize the H 2 O molecules and facilitate dissociation of the molecules into H and OH − . The OH − ions are highly reactive with Si and improve the stoichiometry of the oxide. The UV irradiation during the PMA excites the electrons from the accumulation layer, and the built-in electric field makes the electron injection into the oxide much easier. The electrons injected into the oxide recombine with the trapped holes, which have caused a large negative flat band voltage shift after the UV wet oxidation, and also ionize the H 2 O molecules. The ionization results in the electron stimulated dissociation of H 2 O molecules and the decreased interface trap density

Simulation of atomistic processes during silicon oxidation

OpenAIRE

Bongiorno, Angelo

2003-01-01

Silicon dioxide (SiO2) films grown on silicon monocrystal (Si) substrates form the gate oxides in current Si-based microelectronics devices. The understanding at the atomic scale of both the silicon oxidation process and the properties of the Si(100)-SiO2 interface is of significant importance in state-of-the-art silicon microelectronics manufacturing. These two topics are intimately coupled and are both addressed in this theoretical investigation mainly through first-principles calculations....

TiO2, SiO2 and ZrO2 Nanoparticles Synergistically Provoke Cellular Oxidative Damage in Freshwater Microalgae

Directory of Open Access Journals (Sweden)

Yinghan Liu

2018-02-01

Full Text Available Metal-based nanoparticles (NPs are the most widely used engineered nanomaterials. The individual toxicities of metal-based NPs have been plentifully studied. However, the mixture toxicity of multiple NP systems (n ≥ 3 remains much less understood. Herein, the toxicity of titanium dioxide (TiO2 nanoparticles (NPs, silicon dioxide (SiO2 NPs and zirconium dioxide (ZrO2 NPs to unicellular freshwater algae Scenedesmus obliquus was investigated individually and in binary and ternary combination. Results show that the ternary combination systems of TiO2, SiO2 and ZrO2 NPs at a mixture concentration of 1 mg/L significantly enhanced mitochondrial membrane potential and intracellular reactive oxygen species level in the algae. Moreover, the ternary NP systems remarkably increased the activity of the antioxidant defense enzymes superoxide dismutase and catalase, together with an increase in lipid peroxidation products and small molecule metabolites. Furthermore, the observation of superficial structures of S. obliquus revealed obvious oxidative damage induced by the ternary mixtures. Taken together, the ternary NP systems exerted more severe oxidative stress in the algae than the individual and the binary NP systems. Thus, our findings highlight the importance of the assessment of the synergistic toxicity of multi-nanomaterial systems.

Lowered operation voltage in Pt/SBi2Ta2O9/HfO2/Si ferroelectric-gate field-effect transistors by oxynitriding Si

International Nuclear Information System (INIS)

Horiuchi, Takeshi; Takahashi, Mitsue; Li, Qiu-Hong; Wang, Shouyu; Sakai, Shigeki

2010-01-01

Oxynitrided Si (SiON) surfaces show smaller subthreshold swings than do directly nitrided Si (SiN) surfaces when used in ferroelectric-gate field-effect transistors (FeFETs) having the following stacked-gate structure: Pt/SrBi 2 Ta 2 O 9 (SBT)/HfO 2 /Si. SiON/Si substrates for FeFETs were prepared by rapid thermal oxidation (RTO) in O 2 at 1000 °C and subsequent rapid thermal nitridation (RTN) in NH 3 at various temperatures in the range 950–1150 °C. The electrical properties of the Pt/SBT/HfO 2 /SiON/Si FeFET were compared with those of reference FETs, i.e. Pt/SBT/HfO 2 gate stacks formed on Si substrates subjected to various treatments: SiN x /Si formed by RTN, SiO 2 /Si formed by RTO and untreated Si. The Pt/SBT/HfO 2 /SiON/Si FeFET had a larger memory window than all the other reference FeFETs, particularly at low operation voltages when the RTN temperature was 1050 °C

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.

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.

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.

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.

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

Thermodynamics of Bi2O3-SiO2 system

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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.

Removal of Hazardous Pollutants from Wastewaters: Applications of TiO2-SiO2 Mixed Oxide Materials

Directory of Open Access Journals (Sweden)

Shivatharsiny Rasalingam

2014-01-01

Full Text Available The direct release of untreated wastewaters from various industries and households results in the release of toxic pollutants to the aquatic environment. Advanced oxidation processes (AOP have gained wide attention owing to the prospect of complete mineralization of nonbiodegradable organic substances to environmentally innocuous products by chemical oxidation. In particular, heterogeneous photocatalysis has been demonstrated to have tremendous promise in water purification and treatment of several pollutant materials that include naturally occurring toxins, pesticides, and other deleterious contaminants. In this work, we have reviewed the different removal techniques that have been employed for water purification. In particular, the application of TiO2-SiO2 binary mixed oxide materials for wastewater treatment is explained herein, and it is evident from the literature survey that these mixed oxide materials have enhanced abilities to remove a wide variety of pollutants.

ZnO nanowire-based nano-floating gate memory with Pt nanocrystals embedded in Al2O3 gate oxides

International Nuclear Information System (INIS)

Yeom, Donghyuk; Kang, Jeongmin; Lee, Myoungwon; Jang, Jaewon; Yun, Junggwon; Jeong, Dong-Young; Yoon, Changjoon; Koo, Jamin; Kim, Sangsig

2008-01-01

The memory characteristics of ZnO nanowire-based nano-floating gate memory (NFGM) with Pt nanocrystals acting as the floating gate nodes were investigated in this work. Pt nanocrystals were embedded between Al 2 O 3 tunneling and control oxide layers deposited on ZnO nanowire channels. For a representative ZnO nanowire-based NFGM with embedded Pt nanocrystals, a threshold voltage shift of 3.8 V was observed in its drain current versus gate voltage (I DS -V GS ) measurements for a double sweep of the gate voltage, revealing that the deep effective potential wells built into the nanocrystals provide our NFGM with a large charge storage capacity. Details of the charge storage effect observed in this memory device are discussed in this paper

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-.

Nondegradative Dielectric Coating of Graphene using Thermal Evaporation of SiO

Science.gov (United States)

Suzuki, Seiya; Lee, Chien-Chung; Nagamori, Takashi; Schibli, Thomas; Yoshimura, Masamichi

2013-03-01

Deposition of dielectrics onto graphene is a challenging technique due to the difficulties of fabricating high quality oxide on pristine graphene without introducing atomic defects. Here we report on a novel method to fabricate silicon oxide layer on graphene by vacuum thermal evaporation of silicon monoxide (SiO). Raman spectroscopy and mapping showed the present method did not degrade graphene, in contrast to the e-beam evaporated SiO2 coating method previously reported. We fabricated graphene field effect transistor devices with four metal electrodes to measure gate voltage dependence of sheet resistance of the graphene, and deposited a top coating of SiO on the graphene channel. The electrical measurements before and after the top-coating revealed that the top coating suppressed chemical shift of the graphene from strong p-dope to nearly undoped. Since SiO is transparent for visible and infrared light, the coating can be available as a protection layer for optical devices of graphene such as photodetectors and electro-optic modulators. Since the SiO top coating is a simple vacuum evaporation, it is much easier than atomic-layer-deposition which requires additional functionalization of graphene, and compatible with industrial use. This research was supported in part by Toyoaki Scholarship Foundation

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

Synthesis of LiFePO4/Li2SiO3/reduced Graphene Oxide (rGO) Composite via Hydrothermal Method

Science.gov (United States)

Arifin, M.; Iskandar, F.; Aimon, A. H.; Munir, M. M.; Nuryadin, B. W.

2016-08-01

LiFePO4 is a type of cathode active material used for lithium ion batteries. It has a high electrochemical performance. However, it suffers from certain disadvantages such as a very low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to increase the conductivity of LiFePO4. We have investigated the addition of Li2SiO3 and reduced graphene oxide (rGO) to LiFePO4. The objective of this research was to synthesize LiFePO4/Li2SiO3/rGO via hydrothermal method. Fourier transform infrared spectroscopy (FTIR) measurement showed that the peaks corresponded to the vibration of LiFePO4/Li2SiO3. Further, X-ray diffraction (XRD) measurement confirmed a single phase of LiFePO4. Finally, scanning electron microscopy (SEM) images showed that rGO was distributed on the LiFePO4/Li2SiO3 structure.

Synthesis of LiFePO4/Li2SiO3/reduced Graphene Oxide (rGO) Composite via Hydrothermal Method

International Nuclear Information System (INIS)

Arifin, M; Iskandar, F; Aimon, A H; Munir, M M; Nuryadin, B W

2016-01-01

LiFePO 4 is a type of cathode active material used for lithium ion batteries. It has a high electrochemical performance. However, it suffers from certain disadvantages such as a very low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to increase the conductivity of LiFePO4. We have investigated the addition of Li2SiO3 and reduced graphene oxide (rGO) to LiFePO4. The objective of this research was to synthesize LiFePO 4 /Li 2 SiO 3 /rGO via hydrothermal method. Fourier transform infrared spectroscopy (FTIR) measurement showed that the peaks corresponded to the vibration of LiFePO 4 /Li 2 SiO 3 . Further, X-ray diffraction (XRD) measurement confirmed a single phase of LiFePO4. Finally, scanning electron microscopy (SEM) images showed that rGO was distributed on the LiFePO 4 /Li 2 SiO 3 structure. (paper)

Mechanistic analysis of temperature-dependent current conduction through thin tunnel oxide in n+-polySi/SiO2/n+-Si structures

Science.gov (United States)

Samanta, Piyas

2017-09-01

We present a detailed investigation on temperature-dependent current conduction through thin tunnel oxides grown on degenerately doped n-type silicon (n+-Si) under positive bias ( VG ) on heavily doped n-type polycrystalline silicon (n+-polySi) gate in metal-oxide-semiconductor devices. The leakage current measured between 298 and 573 K and at oxide fields ranging from 6 to 10 MV/cm is primarily attributed to Poole-Frenkel (PF) emission of trapped electrons from the neutral electron traps located in the silicon dioxide (SiO2) band gap in addition to Fowler-Nordheim (FN) tunneling of electrons from n+-Si acting as the drain node in FLOating gate Tunnel OXide Electrically Erasable Programmable Read-Only Memory devices. Process-induced neutral electron traps are located at 0.18 eV and 0.9 eV below the SiO2 conduction band. Throughout the temperature range studied here, PF emission current IPF dominates FN electron tunneling current IFN at oxide electric fields Eox between 6 and 10 MV/cm. A physics based new analytical formula has been developed for FN tunneling of electrons from the accumulation layer of degenerate semiconductors at a wide range of temperatures incorporating the image force barrier rounding effect. FN tunneling has been formulated in the framework of Wentzel-Kramers-Brilloiun taking into account the correction factor due to abrupt variation of the energy barrier at the cathode/oxide interface. The effect of interfacial and near-interfacial trapped-oxide charges on FN tunneling has also been investigated in detail at positive VG . The mechanism of leakage current conduction through SiO2 films plays a crucial role in simulation of time-dependent dielectric breakdown of the memory devices and to precisely predict the normal operating field or applied floating gate (FG) voltage for lifetime projection of the devices. In addition, we present theoretical results showing the effect of drain doping concentration on the FG leakage current.

The effect on phase separation of the oxidation state of molybdenum in a Na2O-B2O3-SiO2 glass

International Nuclear Information System (INIS)

Kawamoto, Y.; Clemens, K.; Tomozawa, M.; Warden, J.T.

1981-01-01

The effect of oxidation state on phase separation was studied for 13Na 2 O, 49B 2 O 3 , 38SiO 2 (mol%) glasses containing 1 mol% Mo oxide. The glasses were melted under various conditions to vary the oxidation states of Mo ions. The oxidation states of Mo ions were determined by chemical analysis and ESR. The crystallisation tendency, the immiscibility temperature, and the phase separation morphology of the glasses were examined by DTA, x-ray diffraction, opalescence method, and replica electron microscopy. Glasses containing Mo 4+ ions have a great tendency to precipitate MoO 2 crystals. The immiscibility temperature of glass goes through a minimum when the oxidation states of Mo ions are changed. It was suggested that there is an optimum oxidation state to prevent crystallisation and to suppress the phase separation tendency of this system. (author)

ZnO nanowire-based nano-floating gate memory with Pt nanocrystals embedded in Al{sub 2}O{sub 3} gate oxides

Energy Technology Data Exchange (ETDEWEB)

Yeom, Donghyuk; Kang, Jeongmin; Lee, Myoungwon; Jang, Jaewon; Yun, Junggwon; Jeong, Dong-Young; Yoon, Changjoon; Koo, Jamin; Kim, Sangsig [Department of Electrical Engineering and Institute for Nano Science, Korea University, Seoul 136-701 (Korea, Republic of)], E-mail: sangsig@korea.ac.kr

2008-10-01

The memory characteristics of ZnO nanowire-based nano-floating gate memory (NFGM) with Pt nanocrystals acting as the floating gate nodes were investigated in this work. Pt nanocrystals were embedded between Al{sub 2}O{sub 3} tunneling and control oxide layers deposited on ZnO nanowire channels. For a representative ZnO nanowire-based NFGM with embedded Pt nanocrystals, a threshold voltage shift of 3.8 V was observed in its drain current versus gate voltage (I{sub DS}-V{sub GS}) measurements for a double sweep of the gate voltage, revealing that the deep effective potential wells built into the nanocrystals provide our NFGM with a large charge storage capacity. Details of the charge storage effect observed in this memory device are discussed in this paper.

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.

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....

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.

Large-Area CVD-Grown Sub-2 V ReS2 Transistors and Logic Gates.

Science.gov (United States)

Dathbun, Ajjiporn; Kim, Youngchan; Kim, Seongchan; Yoo, Youngjae; Kang, Moon Sung; Lee, Changgu; Cho, Jeong Ho

2017-05-10

We demonstrated the fabrication of large-area ReS 2 transistors and logic gates composed of a chemical vapor deposition (CVD)-grown multilayer ReS 2 semiconductor channel and graphene electrodes. Single-layer graphene was used as the source/drain and coplanar gate electrodes. An ion gel with an ultrahigh capacitance effectively gated the ReS 2 channel at a low voltage, below 2 V, through a coplanar gate. The contact resistance of the ion gel-gated ReS 2 transistors with graphene electrodes decreased dramatically compared with the SiO 2 -devices prepared with Cr electrodes. The resulting transistors exhibited good device performances, including a maximum electron mobility of 0.9 cm 2 /(V s) and an on/off current ratio exceeding 10 4 . NMOS logic devices, such as NOT, NAND, and NOR gates, were assembled using the resulting transistors as a proof of concept demonstration of the applicability of the devices to complex logic circuits. The large-area synthesis of ReS 2 semiconductors and graphene electrodes and their applications in logic devices open up new opportunities for realizing future flexible electronics based on 2D nanomaterials.

Synthesis of mesoporous TS-1 using a hybrid SiO2–TiO2 xerogel for catalytic oxidative desulfurization

International Nuclear Information System (INIS)

Yang, Seung-Tae; Jeong, Kwang-Eun; Jeong, Soon-Yong; Ahn, Wha-Seung

2012-01-01

Graphical abstract: Display Omitted Highlights: ► Meso-TS-1 catalyst was synthesized using a SiO 2 –TiO 2 xerogel with an organosilane precursor. ► Hierarchical pore structure was confirmed by characterization of the materials. ► Catalytic activity was tested using oxidative desulfurization of the model sulfur compounds. ► Meso-TS-1 demonstrated significantly improved catalytic activity than TS-1. -- Abstract: Mesoporous TS-1 (M-TS-1) was synthesized using a hybrid SiO 2 –TiO 2 xerogel combined with an organosilane precursor. Prepared samples were characterized by XRD, UV–vis spectroscopy, SEM, and N 2 adsorption–desorption measurement. M-TS-1, prepared in 2 days, showed high crystallinity and the best textural properties among the samples. The N 2 adsorption–desorption isotherms of M-TS-1 exhibited a hysteresis loop at pressure higher than P/P 0 = 0.4, clearly indicating the existence of mesopores. M-TS-1 has significantly larger mesopore volume (0.48 cm 3 /g) than that of conventional TS-1 (0.07 cm 3 /g), and showed a narrow peak centered at ca. 6.3 nm. In the oxidative desulfurization reaction, M-TS-1 was more active than conventional TS-1 at the same Ti-loading; M-TS-1 produced a dibenzothiophene (DBT) conversion of 96%, whereas conventional TS-1 produced a final DBT conversion of 5.6% after a reaction time of 180 min. Oxidative desulfurization over TS-1 was influenced both by electron density and steric hindrance in the sulfur compounds tested.

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.

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)

Characterization, integration and reliability of HfO2 and LaLuO3 high-κ/metal gate stacks for CMOS applications

International Nuclear Information System (INIS)

Nichau, Alexander

2013-01-01

The continued downscaling of MOSFET dimensions requires an equivalent oxide thickness (EOT) of the gate stack below 1 nm. An EOT below 1.4 nm is hereby enabled by the use of high-κ/metal gate stacks. LaLuO 3 and HfO 2 are investigated as two different high-κ oxides on silicon in conjunction with TiN as the metal electrode. LaLuO 3 and its temperature-dependent silicate formation are characterized by hard X-ray photoemission spectroscopy (HAXPES). The effective attenuation length of LaLuO 3 is determined between 7 and 13 keV to enable future interface and diffusion studies. In a first investigation of LaLuO 3 on germanium, germanate formation is shown. LaLuO 3 is further integrated in a high-temperature MOSFET process flow with varying thermal treatment. The devices feature drive currents up to 70μA/μm at 1μm gate length. Several optimization steps are presented. The effective device mobility is related to silicate formation and thermal budget. At high temperature the silicate formation leads to mobility degradation due to La-rich silicate formation. The integration of LaLuO 3 in high-T processes delicately connects with the optimization of the TiN metal electrode. Hereby, stoichiometric TiN yields the best results in terms of thermal stability with respect to Si-capping and high-κ oxide. Different approaches are presented for a further EOT reduction with LaLuO 3 and HfO 2 . Thereby the thermodynamic and kinetic predictions are employed to estimate the behavior on the nanoscale. Based on thermodynamics, excess oxygen in the gate stack, especially in oxidized metal electrodes, is identified to prevent EOT scaling below 1.2 nm. The equivalent oxide thickness of HfO 2 gate stacks is scalable below 1 nm by the use of thinned interfacial SiO 2 . The prevention of oxygen incorporation into the metal electrode by Si-capping maintains the EOT after high temperature annealing. Redox systems are employed within the gate electrode to decrease the EOT of HfO 2 gate stacks

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.

Composited reduced graphene oxide into LiFePO4/Li2SiO3 and its electrochemical impedance spectroscopy properties

Science.gov (United States)

Arifin, M.; Rus, Y. B.; Aimon, A. H.; Iskandar, F.; Winata, T.; Abdullah, M.; Khairurrijal, K.

2017-03-01

LiFePO4 is commonly used as cathode material for Li-ion batteries due to its stable operational voltage and high specific capacity. However, it suffers from certain disadvantages such as low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to analyse the effect of reduced graphene oxide (rGO) on the electrochemical properties of LiFePO4/Li2SiO3 composite. This composite was synthesized by a hydrothermal method. Fourier transform infrared spectroscopy measurement identified the O-P-O, Fe-O, P-O, and O-Si-O- bands in the LiFePO4/Li2SiO3 composite. X-ray diffraction measurement confirmed the formation of LiFePO4. Meanwhile, Raman spectroscopy confirmed the number of rGO layers. Further, scanning electron microscopy images showed that rGO was distributed around the LiFePO4/Li2SiO3 particles. Finally, the electrochemical impedance spectroscopy results showed that the addition of 1 wt% of rGO to the LiFePO4/Li2SiO3 composite reduced charge transfer resistance. It may be concluded that the addition of 1 wt% rGO to LiFePO4/Li2SiO3 composite can enhance its electrochemical performance as a cathode material.

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

Selective Dispersive Solid Phase Extraction of Ser-traline Using Surface Molecularly Imprinted Polymer Grafted on SiO2/Graphene Oxide

Directory of Open Access Journals (Sweden)

Faezeh Khalilian

2017-01-01

Full Text Available A surface molecularly imprinted dispersive solid phase extraction coupled with liquid chromatography–ultraviolet detection is proposed as a selective and fast clean-up technique for the determination of sertraline in biological sample. Surface sertraline-molecular imprinted polymer was grafted and synthesized on the SiO2/graphene oxide surface. Firstly SiO2 was coated on synthesized graphene oxide sheet using sol-gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO2/graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross-linker and progen, respectively. Non-imprinted polymer was also prepared for comparing purposes. The properties of the molecular imprinted polymer were characterized using field emission-scanning electron microscopy and Fourier transform infrared spectroscopy methods. The surface molecular imprinted polymer was utilized as an adsorbent of dispersive solid phase extraction for separation and preconcentration of sertraline. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the non-imprinted polymer was examined in absence and presence of competitive drugs. Sertraline calibration curve showed linearity in the ranges 1–500 µg L-1. The limits of detection and quantification under optimized conditions were obtained 0.2 and 0.5 µg L-1. The within-day and between-day relative standard deviations (n=3 were 4.3 and 7.1%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 92%.

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.

SiO mass spectrometry and Si-2p photoemission spectroscopy for the study of oxidation reaction dynamics of Si(001) surface by supersonic O sub 2 molecular beams under 1000K

CERN Document Server

Teraoka, Y; Moritani, K

2003-01-01

The Si sup 1 sup 8 O desorption yield was measured in the Si(001) surface temperature region from 900K to 1300K at the sup 1 sup 8 O sub 2 incident energies of 0.7eV, 2.2eV and 3.3eV. The Si sup 1 sup 8 O desorption yield in a surface temperature region higher than 1000K increased with increasing incident energy, indicating the incident-energy-induced oxidation and the variation of angular distribution of Si sup 1 sup 8 O desorption. Inversely, the Si sup 1 sup 8 O desorption yield decreased with increasing incident energy in the region from 900K to 1000K, indicating the coexistence of the passive and the active oxidation. In order to clarify the reaction mechanisms of the later phenomenon, real-time in-situ Si-2p photoemission spectroscopy has been performed. The obtained Si-2p spectra showed the variation of the oxide-nuclei quality from the sub-oxide-rich structure to the SiO sub 2 -rich structure. The formation of the SiO sub 2 structure suppresses the SiO desorption due to the enhanced O sub 2 sticking a...

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.

Comparison of interfaces for (Ba,Sr)TiO3 films deposited on Si and SiO2/Si substrates

International Nuclear Information System (INIS)

Suvorova, N.A.; Lopez, C.M.; Irene, E.A.; Suvorova, A.A.; Saunders, M.

2004-01-01

(Ba,Sr)TiO 3 (BST) thin films were deposited by ion sputtering on both bare and oxidized Si. Spectroscopic ellipsometry results have shown that a SiO 2 underlayer of nearly the same thickness (2.6 nm in average) is found at the Si interface for BST sputter depositions onto nominally bare Si, 1 nm SiO 2 on Si or 3.5 nm SiO 2 on Si. This result was confirmed by high-resolution electron microscopy analysis of the films, and it is believed to be due to simultaneous subcutaneous oxidation of Si and reaction of the BST layer with SiO 2 . Using the conductance method, capacitance-voltage measurements show a decrease in the interface trap density D it of an order of magnitude for oxidized Si substrates with a thicker SiO 2 underlayer. Further reduction of D it was achieved for the capacitors grown on oxidized Si and annealed in forming gas after metallization

Comparison of interfaces for (Ba,Sr)TiO3 films deposited on Si and SiO2/Si substrates

Science.gov (United States)

Suvorova, N. A.; Lopez, C. M.; Irene, E. A.; Suvorova, A. A.; Saunders, M.

2004-03-01

(Ba,Sr)TiO3(BST) thin films were deposited by ion sputtering on both bare and oxidized Si. Spectroscopic ellipsometry results have shown that a SiO2 underlayer of nearly the same thickness (2.6 nm in average) is found at the Si interface for BST sputter depositions onto nominally bare Si, 1 nm SiO2 on Si or 3.5 nm SiO2 on Si. This result was confirmed by high-resolution electron microscopy analysis of the films, and it is believed to be due to simultaneous subcutaneous oxidation of Si and reaction of the BST layer with SiO2. Using the conductance method, capacitance-voltage measurements show a decrease in the interface trap density Dit of an order of magnitude for oxidized Si substrates with a thicker SiO2 underlayer. Further reduction of Dit was achieved for the capacitors grown on oxidized Si and annealed in forming gas after metallization.

TiN/Al2O3/ZnO gate stack engineering for top-gate thin film transistors by combination of post oxidation and annealing

Science.gov (United States)

Kato, Kimihiko; Matsui, Hiroaki; Tabata, Hitoshi; Takenaka, Mitsuru; Takagi, Shinichi

2018-04-01

Control of fabrication processes for a gate stack structure with a ZnO thin channel layer and an Al2O3 gate insulator has been examined for enhancing the performance of a top-gate ZnO thin film transistor (TFT). The Al2O3/ZnO interface and the ZnO layer are defective just after the Al2O3 layer formation by atomic layer deposition. Post treatments such as plasma oxidation, annealing after the Al2O3 deposition, and gate metal formation (PMA) are promising to improve the interfacial and channel layer qualities drastically. Post-plasma oxidation effectively reduces the interfacial defect density and eliminates Fermi level pinning at the Al2O3/ZnO interface, which is essential for improving the cut-off of the drain current of TFTs. A thermal effect of post-Al2O3 deposition annealing at 350 °C can improve the crystalline quality of the ZnO layer, enhancing the mobility. On the other hand, impacts of post-Al2O3 deposition annealing and PMA need to be optimized because the annealing can also accompany the increase in the shallow-level defect density and the resulting electron concentration, in addition to the reduction in the deep-level defect density. The development of the interfacial control technique has realized the excellent TFT performance with a large ON/OFF ratio, steep subthreshold characteristics, and high field-effect mobility.

Novel Dry-Type Glucose Sensor Based on a Metal-Oxide-Semiconductor Capacitor Structure with Horseradish Peroxidase + Glucose Oxidase Catalyzing Layer

Science.gov (United States)

Lin, Jing-Jenn; Wu, You-Lin; Hsu, Po-Yen

2007-10-01

In this paper, we present a novel dry-type glucose sensor based on a metal-oxide-semiconductor capacitor (MOSC) structure using SiO2 as a gate dielectric in conjunction with a horseradish peroxidase (HRP) + glucose oxidase (GOD) catalyzing layer. The tested glucose solution was dropped directly onto the window opened on the SiO2 layer, with a coating of HRP + GOD catalyzing layer on top of the gate dielectric. From the capacitance-voltage (C-V) characteristics of the sensor, we found that the glucose solution can induce an inversion layer on the silicon surface causing a gate leakage current flowing along the SiO2 surface. The gate current changes Δ I before and after the drop of glucose solution exhibits a near-linear relationship with increasing glucose concentration. The Δ I sensitivity is about 1.76 nA cm-2 M-1, and the current is quite stable 20 min after the drop of the glucose solution is tested.

Gate tunneling current and quantum capacitance in metal-oxide-semiconductor devices with graphene gate electrodes

Science.gov (United States)

An, Yanbin; Shekhawat, Aniruddh; Behnam, Ashkan; Pop, Eric; Ural, Ant

2016-11-01

Metal-oxide-semiconductor (MOS) devices with graphene as the metal gate electrode, silicon dioxide with thicknesses ranging from 5 to 20 nm as the dielectric, and p-type silicon as the semiconductor are fabricated and characterized. It is found that Fowler-Nordheim (F-N) tunneling dominates the gate tunneling current in these devices for oxide thicknesses of 10 nm and larger, whereas for devices with 5 nm oxide, direct tunneling starts to play a role in determining the total gate current. Furthermore, the temperature dependences of the F-N tunneling current for the 10 nm devices are characterized in the temperature range 77-300 K. The F-N coefficients and the effective tunneling barrier height are extracted as a function of temperature. It is found that the effective barrier height decreases with increasing temperature, which is in agreement with the results previously reported for conventional MOS devices with polysilicon or metal gate electrodes. In addition, high frequency capacitance-voltage measurements of these MOS devices are performed, which depict a local capacitance minimum under accumulation for thin oxides. By analyzing the data using numerical calculations based on the modified density of states of graphene in the presence of charged impurities, it is shown that this local minimum is due to the contribution of the quantum capacitance of graphene. Finally, the workfunction of the graphene gate electrode is extracted by determining the flat-band voltage as a function of oxide thickness. These results show that graphene is a promising candidate as the gate electrode in metal-oxide-semiconductor devices.

Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

International Nuclear Information System (INIS)

Xu, J.L.; Xiao, Q.F.; Mei, D.D.; Zhong, Z.C.; Tong, Y.X.; Zheng, Y.F.; Li, L.

2017-01-01

Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the “coral reef” like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 µm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO 2 and a few amorphous Fe 2 O 3 and Nd 2 O 3 . The amorphous SiO 2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees. - Highlights: • Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation. • The coatings presented excellent thermal shock resistance. • The corrosion resistance could be enhanced by one order of magnitude. • The MAO coatings slightly decreased the magnetic properties of the NdFeB samples.

Analysis of chemical bond states and electrical properties of stacked AlON/HfO{sub 2} gate oxides formed by using a layer-by-layer technique

Energy Technology Data Exchange (ETDEWEB)

Choi, Wonjoon; Lee, Jonghyun; Yang, Jungyup; Kim, Chaeok; Hong, Jinpyo; Nahm, Tschanguh; Byun, Byungsub; Kim, Moseok [Hanyang University, Seoul (Korea, Republic of)

2006-06-15

Stacked AlON/HfO{sub 2} thin films for gate oxides in metal-oxide-semiconductor devices are successfully prepared on Si substrates by utilizing a layer-by-layer technique integrated with an off-axis RF remote plasma sputtering process at room temperature. This off-axis structure is designed to improve the uniformity and the quality of gate oxide films. Also, a layer-by-layer technique is used to control the interface layer between the gate oxide and the Si substrate. The electrical properties of our stacked films are characterized by using capacitance versus voltage and leakage current versus voltage measurements. The stacked AlON/HfO{sub 2} gate oxide exhibits a low leakage current of about 10{sup -6} A/cm{sup 2} and a high dielectric constant value of 14.26 by effectively suppressing the interface layer between gate oxide and Si substrate. In addition, the chemical bond states and the optimum thickness of each AlON and HfO{sub 2} thin film are analyzed using X-ray photoemission spectroscopy and transmission electron microscopy measurement.

Investigation of thin oxide layer removal from Si substrates using an SiO2 atomic layer etching approach: the importance of the reactivity of the substrate

International Nuclear Information System (INIS)

Metzler, Dominik; Oehrlein, Gottlieb S; Li, Chen; Lai, C Steven; Hudson, Eric A

2017-01-01

The evaluation of a plasma-based atomic layer etching (ALE) approach for native oxide surface removal from Si substrates is described. Objectives include removal of the native oxide while minimizing substrate damage, surface residues and substrate loss. Oxide thicknesses were measured using in situ ellipsometry and surface chemistry was analyzed by x-ray photoelectron spectroscopy. The cyclic ALE approach when used for removal of native oxide SiO 2 from a Si substrate did not remove native oxide to the extent required. This is due to the high reactivity of the silicon substrate during the low-energy (<40 eV) ion bombardment phase of the cyclic ALE approach which leads to reoxidation of the silicon surface. A modified process, which used continuously biased Ar plasma with periodic CF 4 injection, achieved significant oxygen removal from the Si surface, with some residual carbon and fluorine. A subsequent H 2 /Ar plasma exposure successfully removed residual carbon and fluorine while passivating the silicon surface. The combined treatment reduced oxygen and carbon levels to about half compared to as received silicon surfaces. The downside of this process sequence is a net loss of about 40 Å of Si. A generic insight of this work is the importance of the substrate and final surface chemistry in addition to precise etch control of the target film for ALE processes. By a fluorocarbon-based ALE technique, thin SiO 2 layer removal at the Ångstrom level can be precisely performed from an inert substrate, e.g. a thick SiO 2 layer. However, from a reactive substrate, like Si, complete removal of the thin SiO 2 layer is prevented by the high reactivity of low energy Ar + ion bombarded Si. The Si surfaces are reoxidized during the ALE ion bombardment etch step, even for very clean and ultra-low O 2 process conditions. (paper)

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.

The gate oxide integrity of CVD tungsten polycide

International Nuclear Information System (INIS)

Wu, N.W.; Su, W.D.; Chang, S.W.; Tseng, M.F.

1988-01-01

CVD tungsten polycide has been demonstrated as a good gate material in recent very large scale integration (VLSI) technology. CVD tungsten silicide offers advantages of low resistivity, high temperature stability and good step coverage. On the other hand, the polysilicon underlayer preserves most characteristics of the polysilicon gate and acts as a stress buffer layer to absorb part of the thermal stress origin from the large thermal expansion coefficient of tungsten silicide. Nevertheless, the gate oxide of CVD tungsten polycide is less stable or reliable than that of polysilicon gate. In this paper, the gate oxide integrity of CVD tungsten polycide with various thickness combinations and different thermal processes have been analyzed by several electrical measurements including breakdown yield, breakdown fluence, room temperature TDDB, I-V characteristics, electron traps and interface state density

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.

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

A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Binary Systems

Science.gov (United States)

Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

2016-04-01

A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

Design of Higher-k and More Stable Rare Earth Oxides as Gate Dielectrics for Advanced CMOS Devices

Directory of Open Access Journals (Sweden)

Yi Zhao

2012-08-01

Full Text Available High permittivity (k gate dielectric films are widely studied to substitute SiO₂ as gate oxides to suppress the unacceptable gate leakage current when the traditional SiO₂ gate oxide becomes ultrathin. For high-k gate oxides, several material properties are dominantly important. The first one, undoubtedly, is permittivity. It has been well studied by many groups in terms of how to obtain a higher permittivity for popular high-k oxides, like HfO₂ and La₂O₃. The second one is crystallization behavior. Although it’s still under the debate whether an amorphous film is definitely better than ploy-crystallized oxide film as a gate oxide upon considering the crystal boundaries induced leakage current, the crystallization behavior should be well understood for a high-k gate oxide because it could also, to some degree, determine the permittivity of the high-k oxide. Finally, some high-k gate oxides, especially rare earth oxides (like La₂O₃, are not stable in air and very hygroscopic, forming hydroxide. This topic has been well investigated in over the years and significant progresses have been achieved. In this paper, I will intensively review the most recent progresses of the experimental and theoretical studies for preparing higher-k and more stable, in terms of hygroscopic tolerance and crystallization behavior, Hf- and La-based ternary high-k gate oxides.

High-κ gate dielectrics: Current status and materials properties considerations

Science.gov (United States)

Wilk, G. D.; Wallace, R. M.; Anthony, J. M.

2001-05-01

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal-oxide-semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric 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. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward successful integration into the expected processing conditions for future CMOS technologies, especially due to their tendency to form at interfaces with Si (e.g. silicates). These pseudobinary systems also thereby enable the use of other high-κ materials by serving as an interfacial high-κ layer. While work is ongoing, much research is still required, as it is clear that any material which is to replace SiO2 as the gate dielectric faces a formidable challenge. The requirements for process integration compatibility are remarkably demanding, and any serious candidates will emerge only through continued, intensive investigation.

Temperature dependence of the work function of ruthenium-based gate electrodes

International Nuclear Information System (INIS)

Alshareef, H.N.; Wen, H.C.; Luan, H.F.; Choi, K.; Harris, H.R.; Senzaki, Y.; Majhi, P.; Lee, B.H.; Foran, B.; Lian, G.

2006-01-01

The effect of device fabrication temperature on the work function of ruthenium (Ru) metal gate and its bilayers was investigated. The work function shows strong temperature dependence when Ru electrodes are deposited on silicon oxide, SiO 2 , but not on hafnium silicates (HfSiO x ). Specifically, the work function of Ru on SiO 2 increased from 4.5 eV at 500 deg. C to 5.0 eV at 700 deg. C. On further annealing to 900 deg. C or higher, the work function dropped to about 4.4 eV. In the case of HfSiO x , the work function of Ru changed by less than 100 mV over the same temperature range. Identical temperature dependence was observed using hafnium (Hf)/Ru and tantalum (Ta)/Ru bilayers. However, the peak values of the work function decreased with increasing Hf/Ru and Ta/Ru thickness ratios. Materials analysis suggests that these trends are driven by interactions at the Ru metal gate-dielectric interface

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.

High-Mobility 6,13-Bis(triisopropylsilylethynyl) Pentacene Transistors Using Solution-Processed Polysilsesquioxane Gate Dielectric Layers.

Science.gov (United States)

Matsuda, Yu; Nakahara, Yoshio; Michiura, Daisuke; Uno, Kazuyuki; Tanaka, Ichiro

2016-04-01

Polysilsesquioxane (PSQ) is a low-temperature curable polymer that is compatible with low-cost plastic substrates. We cured PSQ gate dielectric layers by irradiation with ultraviolet light at ~60 °C, and used them for 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) thin film transistors (TFTs). The fabricated TFTs have shown the maximum and average hole mobility of 1.3 and 0.78 ± 0.3 cm2V-1s-1, which are comparable to those of the previously reported transistors using single-crystalline TIPS-pentacene micro-ribbons for their active layers and thermally oxidized SiO2 for their gate dielectric layers. Itis therefore demonstrated that PSQ is a promising polymer gate dielectric material for low-cost organic TFTs.

Memory characteristics of Au nanocrystals embedded in metal-oxide-semiconductor structure by using atomic-layer-deposited Al2O3 as control oxide

International Nuclear Information System (INIS)

Wang, C.-C.; Chiou, Y.-K.; Chang, C.-H.; Tseng, J.-Y.; Wu, L.-J.; Chen, C.-Y.; Wu, T.-B.

2007-01-01

The nonvolatile memory characteristics of metal-oxide-semiconductor (MOS) structures containing Au nanocrystals in the Al 2 O 3 /SiO 2 matrix were studied. In this work, we have demonstrated that the use of Al 2 O 3 as control oxide prepared by atomic-layer-deposition enhances the erase speed of the MOS capacitors. A giant capacitance-voltage hysteresis loop and a very short erase time which is lower than 1 ms can be obtained. Compared with the conventional floating-gate electrically erasable programmable read-only memories, the erase speed was promoted drastically. In addition, very low leakage current and large turn-around voltage resulting from electrons or holes stored in the Au nanocrystals were found in the current-voltage relation of the MOS capacitors

Flexible Proton-Gated Oxide Synaptic Transistors on Si Membrane.

Science.gov (United States)

Zhu, Li Qiang; Wan, Chang Jin; Gao, Ping Qi; Liu, Yang Hui; Xiao, Hui; Ye, Ji Chun; Wan, Qing

2016-08-24

Ion-conducting materials have received considerable attention for their applications in fuel cells, electrochemical devices, and sensors. Here, flexible indium zinc oxide (InZnO) synaptic transistors with multiple presynaptic inputs gated by proton-conducting phosphorosilicate glass-based electrolyte films are fabricated on ultrathin Si membranes. Transient characteristics of the proton gated InZnO synaptic transistors are investigated, indicating stable proton-gating behaviors. Short-term synaptic plasticities are mimicked on the proposed proton-gated synaptic transistors. Furthermore, synaptic integration regulations are mimicked on the proposed synaptic transistor networks. Spiking logic modulations are realized based on the transition between superlinear and sublinear synaptic integration. The multigates coupled flexible proton-gated oxide synaptic transistors may be interesting for neuroinspired platforms with sophisticated spatiotemporal information processing.

Photolithographically Patterned TiO2 Films for Electrolyte-Gated Transistors.

Science.gov (United States)

Valitova, Irina; Kumar, Prajwal; Meng, Xiang; Soavi, Francesca; Santato, Clara; Cicoira, Fabio

2016-06-15

Metal oxides constitute a class of materials whose properties cover the entire range from insulators to semiconductors to metals. Most metal oxides are abundant and accessible at moderate cost. Metal oxides are widely investigated as channel materials in transistors, including electrolyte-gated transistors, where the charge carrier density can be modulated by orders of magnitude upon application of relatively low electrical bias (2 V). Electrolyte gating offers the opportunity to envisage new applications in flexible and printed electronics as well as to improve our current understanding of fundamental processes in electronic materials, e.g. insulator/metal transitions. In this work, we employ photolithographically patterned TiO2 films as channels for electrolyte-gated transistors. TiO2 stands out for its biocompatibility and wide use in sensing, electrochromics, photovoltaics and photocatalysis. We fabricated TiO2 electrolyte-gated transistors using an original unconventional parylene-based patterning technique. By using a combination of electrochemical and charge carrier transport measurements we demonstrated that patterning improves the performance of electrolyte-gated TiO2 transistors with respect to their unpatterned counterparts. Patterned electrolyte-gated (EG) TiO2 transistors show threshold voltages of about 0.9 V, ON/OFF ratios as high as 1 × 10(5), and electron mobility above 1 cm(2)/(V s).

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

Study of the tunnelling initiated leakage current through the carbon nanotube embedded gate oxide in metal oxide semiconductor structures

International Nuclear Information System (INIS)

Chakraborty, Gargi; Sarkar, C K; Lu, X B; Dai, J Y

2008-01-01

The tunnelling currents through the gate dielectric partly embedded with semiconducting single-wall carbon nanotubes in a silicon metal-oxide-semiconductor (MOS) structure have been investigated. The application of the gate voltage to such an MOS device results in the band bending at the interface of the partly embedded oxide dielectric and the surface of the silicon, initiating tunnelling through the gate oxide responsible for the gate leakage current whenever the thickness of the oxide is scaled. A model for silicon MOS structures, where carbon nanotubes are confined in a narrow layer embedded in the gate dielectric, is proposed to investigate the direct and the Fowler-Nordheim (FN) tunnelling currents of such systems. The idea of embedding such elements in the gate oxide is to assess the possibility for charge storage for memory device applications. Comparing the FN tunnelling onset voltage between the pure gate oxide and the gate oxide embedded with carbon nanotubes, it is found that the onset voltage decreases with the introduction of the nanotubes. The direct tunnelling current has also been studied at very low gate bias, for the thin oxide MOS structure which plays an important role in scaling down the MOS transistors. The FN tunnelling current has also been studied with varying nanotube diameter

Ordered micro/macro porous K-OMS-2/SiO2 nanocatalysts: Facile synthesis, low cost and high catalytic activity for diesel soot combustion

Science.gov (United States)

Yu, Xuehua; Zhao, Zhen; Wei, Yuechang; Liu, Jian

2017-04-01

A series of novel oxide catalysts, which contain three-dimensionally ordered macroporous (3DOM) and microporous structure, were firstly designed and successfully synthesized by simple method. In the as-prepared catalysts, 3DOM SiO2 is used as support and microporous K-OMS-2 oxide nanoparticles are supported on the wall of SiO2. 3DOM K-OMS-2/SiO2 oxide catalysts were firstly used in soot particle oxidation reaction and they show very high catalytic activities. The high activities of K-OMS-2/SiO2 oxide catalysts can be assigned to three possible reasons: macroporous effect of 3DOM structure for improving contact between soot and catalyst, microporous effect of K-OMS-2 for adsorption of small gas molecules and interaction of K and Mn for activation of gas molecules. The catalytic activities of catalysts are comparable to or even higher than noble metal catalyst in the medium and high temperature range. For example, the T50 of K-OMS-2/SiO2-50, 328 °C, is much lower than those of Pt/Al2O3 and 3DOM Au/LaFeO3, 464 and 356 °C,respectively. Moreover, catalysts exhibited high catalytic stability. It is attributed to that the K+ ions are introduced into the microporous structure of OMS-2 and stabilized in the catalytic reaction. Meanwhile, the K+ ions play an important role in templating and stabilizing the tunneled framework of OMS-2.

Carbon nanotube transistors with graphene oxide films as gate dielectrics

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

Carbon nanomaterials,including the one-dimensional(1-D) carbon nanotube(CNT) and two-dimensional(2-D) graphene,are heralded as ideal candidates for next generation nanoelectronics.An essential component for the development of advanced nanoelectronics devices is processing-compatible oxide.Here,in analogy to the widespread use of silicon dioxide(SiO2) in silicon microelectronic industry,we report the proof-of-principle use of graphite oxide(GO) as a gate dielectrics for CNT field-effect transistor(FET) via a fast and simple solution-based processing in the ambient condition.The exceptional transistor characteristics,including low operation voltage(2 V),high carrier mobility(950 cm2/V-1 s-1),and the negligible gate hysteresis,suggest a potential route to the future all-carbon nanoelectronics.

Pseudo 2-transistor active pixel sensor using an n-well/gate-tied p-channel metal oxide semiconductor field eeffect transistor-type photodetector with built-in transfer gate

Science.gov (United States)

Seo, Sang-Ho; Seo, Min-Woong; Kong, Jae-Sung; Shin, Jang-Kyoo; Choi, Pyung

2008-11-01

In this paper, a pseudo 2-transistor active pixel sensor (APS) has been designed and fabricated by using an n-well/gate-tied p-channel metal oxide semiconductor field effect transistor (PMOSFET)-type photodetector with built-in transfer gate. The proposed sensor has been fabricated using a 0.35 μm 2-poly 4-metal standard complementary metal oxide semiconductor (CMOS) logic process. The pseudo 2-transistor APS consists of two NMOSFETs and one photodetector which can amplify the generated photocurrent. The area of the pseudo 2-transistor APS is 7.1 × 6.2 μm2. The sensitivity of the proposed pixel is 49 lux/(V·s). By using this pixel, a smaller pixel area and a higher level of sensitivity can be realized when compared with a conventional 3-transistor APS which uses a pn junction photodiode.

Phosphorus oxide gate dielectric for black phosphorus field effect transistors

Science.gov (United States)

Dickerson, W.; Tayari, V.; Fakih, I.; Korinek, A.; Caporali, M.; Serrano-Ruiz, M.; Peruzzini, M.; Heun, S.; Botton, G. A.; Szkopek, T.

2018-04-01

The environmental stability of the layered semiconductor black phosphorus (bP) remains a challenge. Passivation of the bP surface with phosphorus oxide, POx, grown by a reactive ion etch with oxygen plasma is known to improve photoluminescence efficiency of exfoliated bP flakes. We apply phosphorus oxide passivation in the fabrication of bP field effect transistors using a gate stack consisting of a POx layer grown by reactive ion etching followed by atomic layer deposition of Al2O3. We observe room temperature top-gate mobilities of 115 cm2 V-1 s-1 in ambient conditions, which we attribute to the low defect density of the bP/POx interface.

Heterogeneous Ag-TiO2-SiO2 composite materials as novel catalytic systems for selective epoxidation of cyclohexene by H2O2.

Directory of Open Access Journals (Sweden)

Xin Wang

Full Text Available TiO2-SiO2 composites were synthesized using cetyl trimethyl ammonium bromide (CTAB as the structure directing template. Self-assembly hexadecyltrimethyl- ammonium bromide TiO2-SiO2/(CTAB were soaked into silver nitrate (AgNO3 aqueous solution. The Ag-TiO2-SiO2(Ag-TS composite were prepared via a precipitation of AgBr in soaking process and its decomposition at calcination stage. Structural characterization of the materials was carried out by various techniques including X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, N2 adsorption-desorption and ultraviolet visible spectroscopy (UV-Vis. Characterization results revealed that Ag particles were incorporated into hierarchical TiO2-SiO2 without significantly affecting the structures of the supports. Further heating-treatment at 723 K was more favorable for enhancing the stability of the Ag-TS composite. The cyclohexene oxide was the major product in the epoxidation using H2O2 as the oxidant over the Ag-TS catalysts. Besides, the optimum catalytic activity and stability of Ag-TS catalysts were obtained under operational conditions of calcined at 723 K for 2 h, reaction time of 120 min, reaction temperature of 353 K, catalyst amount of 80 mg, aqueous H2O2 (30 wt.% as oxidant and chloroform as solvent. High catalytic activity with conversion rate up to 99.2% of cyclohexene oxide could be obtainable in water-bathing. The catalyst was found to be stable and could be reused three times without significant loss of catalytic activity under the optimized reaction conditions.

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

Unraveling the role of SiC or Si substrates in water vapor incorporation in SiO 2 films thermally grown using ion beam analyses

Science.gov (United States)

Corrêa, S. A.; Soares, G. V.; Radtke, C.; Stedile, F. C.

2012-02-01

The incorporation of water vapor in SiO 2 films thermally grown on 6H-SiC(0 0 0 1) and on Si (0 0 1) was investigated using nuclear reaction analyses. Water isotopically enriched in deuterium ( 2H or D) and in 18O was used. The dependence of incorporated D with the water annealing temperature and initial oxide thickness were inspected. The D amount in SiO 2/SiC structures increases continuously with temperature and with initial oxide thickness, being incorporated in the surface, bulk, and interface regions of SiO 2 films. However, in SiO 2/Si, D is observed mostly in near-surface regions of the oxide and no remarkable dependence with temperature or initial oxide thickness was observed. At any annealing temperature, oxygen from water vapor was incorporated in all depths of the oxide films grown on SiC, in contrast with the SiO 2/Si.

The far infrared radiation characteristics for Li2O.Al2O3.4SiO2(LAS) glass-ceramics and transition-metal oxide

International Nuclear Information System (INIS)

Huh, Nam Jung; Yang, Joong Sik

1991-01-01

The far infrared radiation characteristic for Li 2 O.Al 2 O 3 .4SiO 2 (LAS) glass, the LAS glass-ceramic and sintered transition metal oxides such as CuO, Fe 2 O 3 and Co 3 O 4 , were investigated. LAS glass and LAS glass-ceramic was higher than that of the LAS glass. Heat-treated CuO and Co 3 o 4 had radiation characteristic of high efficiency infrared radiant, and heat-treated Fe 2 O 3 had radiation characteristic that infrared emissivity decreased in higher was length above 15μm. (Author)

The comparison of gamma-radiation and electrical stress influences on oxide and interface defects in power VDMOSFET

Directory of Open Access Journals (Sweden)

Đorić-Veljković Snežana M.

2013-01-01

Full Text Available The behaviour of oxide and interface defects in n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors, firstly degraded by the gamma-irradiation and electric field and subsequently recovered and annealed, is presented. By analyzing the transfer characteristic shifts, the changes of threshold voltage and underlying changes of gate oxide and interface trap densities during the stress (recovery, annealing of investigated devices, it is shown that these two types of stress influence differently on the gate oxide and the SiO2-Si interface. [Projekat Ministarstva nauke Republike Srbije, br. OI171026

Ni nanoparticles decorated onto graphene oxide with SiO2 as interlayer for high performance on histidine-rich protein separation

Science.gov (United States)

Yang, Xiaodan; Zhang, Min; Zheng, Jing; Li, Weizhen; Gan, Wenjun; Xu, Jingli; Hayat, Tasawar; Alharbi, Njud S.; Yang, Fan

2018-05-01

Sandwich-like structure of graphene oxide (GO) @SiO2@C-Ni nanosheets were prepared by combining an extended stöber method with subsequent carbonization treatment, in which polydopamine was used as reducing agent and carbon source. Firstly, the GO nanosheets were covered with SiO2 interlayer and finally coated with a outer shell of nickel ion doped polydopamine (PDA-Ni2+) with an extended stöber method. Followed by a carbonization to produce the GO@SiO2@C-Ni sheets with metallic nickel nanoparticles embedded in PDA-derived thin graphic carbon layer. Notably, silica interlayer played a vital role in the formation of such GO@SiO2@C-Ni sheets. Without the protection of SiO2, the hydrophobic graphene@C-Ni composites were obtained instead. While with silica layer as the spacer, the obtained hydrophilic GO@SiO2@C-Ni composites were not only well dispersed in the solution, but also can be adjusted in terms of the size and density of Ni nanoparticles (NPs) on surface by changing the calcination temperature or the molar ratio between dopamine and nickel salt. Furthermore, nickel nanoparticles decorated on GO@SiO2 sheets were employed to enrich His-rich proteins (BHb and BSA) via specific metal affinity force between polyhistidine groups and nickel nanoparticles.

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.

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.

Synthesis of Y2O3-ZrO2-SiO2 composite coatings on carbon fiber reinforced resin matrix composite by an electro-plasma process

Science.gov (United States)

Zhang, Yuping; Lin, Xiang; Chen, Weiwei; Cheng, Huanwu; Wang, Lu

2016-05-01

In the present paper the Y2O3-ZrO2-SiO2 composite coating was successfully synthesized on carbon fiber reinforced resin matrix composite by an electro-plasma process. The deposition process, microstructures and oxidation resistance of the coatings with different SiO2 concentrations were systematically investigated. A relatively dense microstructure was observed for the Y2O3-ZrO2-SiO2 composite coating with the SiO2 concentration above 5 g/L. The coating exhibited very good oxidation resistance at 1273 K with the mass loss rate as low as ∼30 wt.%, compared to 100 wt.% of the substrate. The formation of the ceramic composites was discussed in detail based on the electrochemical mechanism and the deposition dynamics in order to explain the effect of the plasma discharge. We believe that the electro-plasma process will find wide applications in preparing ceramics and coatings in industries.

Characterization, modeling and physical mechanisms of different surface treatment methods at room temperature on the oxide and interfacial quality of the SiO2 film using the spectroscopic scanning capacitance microscopy

Directory of Open Access Journals (Sweden)

Kin Mun Wong

Full Text Available In this article, a simple, low cost and combined surface treatment method [pre-oxidation immersion of the p-type silicon (Si substrate in hydrogen peroxide (H2O2 and post oxidation ultra-violet (UV irradiation of the silicon-dioxide (SiO2 film] at room temperature is investigated. The interface trap density at midgap [Dit(mg] of the resulting SiO2 film (denoted as sample 1A is quantified from the full width at half-maximum of the scanning capacitance microscopy (SCM differential capacitance (dC/dV characteristics by utilizing a previously validated theoretical model. The Dit(mg of sample 1A is significantly lower than the sample without any surface treatments which indicates that it is a viable technique for improving the interfacial quality of the thicker SiO2 films prepared by wet oxidation. Moreover, the proposed combined surface treatment method may possibly complement the commonly used forming gas anneal process to further improve the interfacial quality of the SiO2 films. The positive shift of the flatband voltage due to the overall oxide charges (estimated from the probe tip dc bias at the peak dC/dV spectra of sample 1A suggests the presence of negative oxide fixed charge density (Nf in the oxide. In addition, an analytical formula is derived to approximate the difference of the Nf values between the oxide samples that are immersed in H2O2 and UV irradiated from their measured SCM dC/dV spectra. Conversely, some physical mechanisms are proposed that result in the ionization of the SiO− species (which are converted from the neutral SiOH groups that originate from the pre-oxidation immersion in H2O2 and ensuing wet oxidation during the UV irradiation as well as the UV photo-injected electrons from the Si substrate (which did not interact with the SiOH groups. They constitute the source of mobile electrons which partially passivate the positively charged empty donor-like interface traps at the Si-SiO2 interface. Keywords: Dielectrics

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.

Near interface traps in SiO{sub 2}/4H-SiC metal-oxide-semiconductor field effect transistors monitored by temperature dependent gate current transient measurements

Energy Technology Data Exchange (ETDEWEB)

Fiorenza, Patrick; La Magna, Antonino; Vivona, Marilena; Roccaforte, Fabrizio [Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM), Strada VIII 5, Zona Industriale 95121 Catania (Italy)

2016-07-04

This letter reports on the impact of gate oxide trapping states on the conduction mechanisms in SiO{sub 2}/4H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs). The phenomena were studied by gate current transient measurements, performed on n-channel MOSFETs operated in “gate-controlled-diode” configuration. The measurements revealed an anomalous non-steady conduction under negative bias (V{sub G} > |20 V|) through the SiO{sub 2}/4H-SiC interface. The phenomenon was explained by the coexistence of a electron variable range hopping and a hole Fowler-Nordheim (FN) tunnelling. A semi-empirical modified FN model with a time-depended electric field is used to estimate the near interface traps in the gate oxide (N{sub trap} ∼ 2 × 10{sup 11} cm{sup −2}).

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.

Inorganic proton conducting electrolyte coupled oxide-based dendritic transistors for synaptic electronics.

Science.gov (United States)

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

2014-05-07

Ionic/electronic hybrid devices with synaptic functions are considered to be the essential building blocks for neuromorphic systems and brain-inspired computing. Here, artificial synapses based on indium-zinc-oxide (IZO) transistors gated by nanogranular SiO2 proton-conducting electrolyte films are fabricated on glass substrates. Spike-timing dependent plasticity and paired-pulse facilitation are successfully mimicked in an individual bottom-gate transistor. Most importantly, dynamic logic and dendritic integration established by spatiotemporally correlated spikes are also mimicked in dendritic transistors with two in-plane gates as the presynaptic input terminals.

Inhibitory Effect of Dissolved Silica on the H2O2 Decomposition by Iron(III) and Manganese(IV) Oxides: Implications for H2O2-based In Situ Chemical Oxidation

Science.gov (United States)

Pham, Anh Le-Tuan; Doyle, Fiona M.; Sedlak, David L.

2011-01-01

The decomposition of H2O2 on iron minerals can generate •OH, a strong oxidant that can transform a wide range of contaminants. This reaction is critical to In Situ Chemical Oxidation (ISCO) processes used for soil and groundwater remediation, as well as advanced oxidation processes employed in waste treatment systems. The presence of dissolved silica at concentrations comparable to those encountered in natural waters decreases the reactivity of iron minerals toward H2O2, because silica adsorbs onto the surface of iron minerals and alters catalytic sites. At circumneutral pH values, goethite, amorphous iron oxide, hematite, iron-coated sand and montmorillonite that were pre-equilibrated with 0.05 – 1.5 mM SiO2 were significantly less reactive toward H2O2 decomposition than their original counterparts, with the H2O2 loss rates inversely proportional to the SiO2 concentration. In the goethite/H2O2 system, the overall •OH yield, defined as the percentage of decomposed H2O2 producing •OH, was almost halved in the presence of 1.5 mM SiO2. Dissolved SiO2 also slows the H2O2 decomposition on manganese(IV) oxide. The presence of dissolved SiO2 results in greater persistence of H2O2 in groundwater, lower H2O2 utilization efficiency and should be considered in the design of H2O2-based treatment systems. PMID:22129132

Negative charge induced degradation of PMOSFETs with BF2-implanted p+-poly gate

International Nuclear Information System (INIS)

Lu, C.Y.; Sung, J.M.

1989-01-01

A new degradation phenomenon on thin gate oxide PMOS-FETs with BF 2 implanted p + -poly gate has been demonstrated and investigated. The cause of this type of degradation is a combination of the boron penetration through the gate oxide and charge trap generation due to the presence of fluorine in the gate oxide and some other processing-induced effects. The negative charge-induced degradation other than enhanced boron diffusion has been studied in detail here. The impact of this process-sensitive p + -poly gate structure on deep submicron CMOS process integration has been discussed. (author)

Electronic states of SiO2-MxOy (MxOy=P205, TiO2 and ZrO2) glasses

Energy Technology Data Exchange (ETDEWEB)

Kowada, Y [Hyogo Univ. of Teacher Education, Hyogo (Japan); Adachi, H [Kyoto Univ. (Japan). Faculty of Engineering; Minami, T [Univ. of Osaka Prefecture, Osaka (Japan). Faculty of Engineering

1993-12-01

Using the sol-gel method the surface of metal and glass substrates can be modified. For example, stainless steel sheets coated with the SiO2-ZrO2 glass films have higher resistance to corrosion and oxidation. The coating films contain high concentration of alkali ions diffusing from the glass substrates. It suggests that the sodium ions are trapped strongly within the coating films and are blocked to further diffuse to the surface. This behavior must be associated with the chemical bonding around the sodium ions in the SiO2-TiO2 and SiO2-ZrO2 films. For better understanding of the chemical bonding in the glasses, the electronic states of the SiO2-MxOy glasses were calculated by means of the DV-Xa cluster method. In this paper, the calculation method is explained, the results are discussed and the conclusion is stated. 17 refs., 6 figs.

Fe3O4@SiO2@CS-TETA functionalized graphene oxide for the adsorption of methylene blue (MB) and Cu(II)

Science.gov (United States)

Wang, Fan; Zhang, Lijuan; Wang, Yeying; Liu, Xijian; Rohani, Sohrab; Lu, Jie

2017-10-01

The graphene oxide (GO) functionalized by Fe3O4@SiO2@CS-TETA nanoparticles, Fe3O4@SiO2@CS-TETA-GO, was firstly fabricated in a mild way as a novel adsorbent for the removal of Cu(II) ions and methylene blue (MB) from aqueous solutions. The magnetic composites showed a good dispersity in water and can be conveniently collected for reuse through magnetic separation due to its excellent magnetism. When the Fe3O4@SiO2@CS- TETA-GO was used as an absorbent for the absorption of MB and Cu(II), the adsorption kinetics and isotherms data well fitted the pseudo-second-order model and the Langmuir model, respectively. Under the optimized pH and initial concentration, the maximum adsorption capacity was about 529.1 mg g-1 for MB in 20 min and 324.7 mg g-1 for Cu(II) in 16 min, respectively, exhibiting a better adsorption performance than other GO-based adsorbents reported recently. More importantly, the synthesized adsorbent could be effectively regenerated and repeatedly utilized without significant capacity loss after six times cycles. All the results demonstrated that Fe3O4@SiO2@CS-TETA-GO could be used as an excellent adsorbent for the adsorption of Cu(II) and MB in many fields.

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)

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

Effect of interfacial SiO2- y layer and defect in HfO2- x film on flat-band voltage of HfO2- x /SiO2- y stacks for backside-illuminated CMOS image sensors

Science.gov (United States)

Na, Heedo; Lee, Jimin; Jeong, Juyoung; Kim, Taeho; Sohn, Hyunchul

2018-03-01

In this study, the effect of oxygen gas fraction during deposition of a hafnium oxide (HfO2- x ) film and the influence of the quality of the SiO2- y interlayer on the nature of flat-band voltage ( V fb) in TiN/HfO/SiO2- y /p-Si structures were investigated. X-ray photoemission spectroscopy analysis showed that the non-lattice oxygen peak, indicating an existing oxygen vacancy, increased as the oxygen gas fraction decreased during sputtering. From C- V and J- E analyses, the V fb behavior was significantly affected by the characteristics of the SiO2- y interlayer and the non-lattice oxygen fraction in the HfO2- x films. The HfO2- x /native SiO2- y stack presented a V fb of - 1.01 V for HfO2- x films with an oxygen gas fraction of 5% during sputtering. Additionally, the V fb of the HfO2- x /native SiO2- y stack could be controlled from - 1.01 to - 0.56 V by changing the deposition conditions of the HfO2- x film with the native SiO2- y interlayer. The findings of this study can be useful to fabricate charge-accumulating layers for backside-illuminated image sensor devices.

Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

Science.gov (United States)

Xu, J. L.; Xiao, Q. F.; Mei, D. D.; Zhong, Z. C.; Tong, Y. X.; Zheng, Y. F.; Li, L.

2017-03-01

Amorphous SiO2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the "coral reef" like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 μm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO2 and a few amorphous Fe2O3 and Nd2O3. The amorphous SiO2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees.

Functionalization of 2D macroporous silicon under the high-pressure oxidation

Science.gov (United States)

Karachevtseva, L.; Kartel, M.; Kladko, V.; Gudymenko, O.; Bo, Wang; Bratus, V.; Lytvynenko, O.; Onyshchenko, V.; Stronska, O.

2018-03-01

Addition functionalization after high-pressure oxidation of 2D macroporous silicon structures is evaluated. X-ray diffractometry indicates formation of orthorhombic SiO2 phase on macroporous silicon at oxide thickness of 800-1200 nm due to cylindrical symmetry of macropores and high thermal expansion coefficient of SiO2. Pb center concentration grows with the splitting energy of LO- and TO-phonons and SiO2 thickness in oxidized macroporous silicon structures. This increase EPR signal amplitude and GHz radiation absorption and is promising for development of high-frequency devices and electronically controlled elements.

Impact of metal-ion contaminated silica particles on gate oxide integrity

NARCIS (Netherlands)

Rink, Ingrid; Wali, F.; Knotter, D.M.

2009-01-01

The impact of metal-ion contamination (present on wafer surface before oxidation) on gate oxide integrity (GOI) is well known in literature, which is not the case for clean silica particles [1, 2]. However, it is known that particles present in ultra-pure water (UPW) decrease the random yield in

Self-aligned top-gate InGaZnO thin film transistors using SiO{sub 2}/Al{sub 2}O{sub 3} stack gate dielectric

Energy Technology Data Exchange (ETDEWEB)

Chen, Rongsheng; Zhou, Wei; Zhang, Meng; Wong, Man; Kwok, Hoi Sing

2013-12-02

Self-aligned top-gate amorphous indium–gallium–zinc oxide (a-IGZO) thin film transistors (TFTs) utilizing SiO{sub 2}/Al{sub 2}O{sub 3} stack thin films as gate dielectric are developed in this paper. Due to high quality of the high-k Al{sub 2}O{sub 3} and good interface between active layer and gate dielectric, the resulting a-IGZO TFT exhibits good electrical performance including field-effect mobility of 9 cm{sup 2}/Vs, threshold voltage of 2.2 V, subthreshold swing of 0.2 V/decade, and on/off current ratio of 1 × 10{sup 7}. With scaling down of the channel length, good characteristics are also obtained with a small shift of the threshold voltage and no degradation of subthreshold swing. - Highlights: • Self-aligned top-gate indium–gallium–zinc oxide thin-film transistor is proposed. • SiO{sub 2}/Al{sub 2}O{sub 3} stack gate dielectric is proposed. • The source/drain areas are hydrogen-doped by CHF{sub 3} plasma. • The devices show good electrical performance and scaling down behavior.

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 .

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

First-principles simulations of the leakage current in metal-oxide-semiconductor structures caused by oxygen vacancies in HfO2 high-K gate dielectric

International Nuclear Information System (INIS)

Mao, L.F.; Wang, Z.O.

2008-01-01

HfO 2 high-K gate dielectric has been used as a new gate dielectric in metal-oxide-semiconductor structures. First-principles simulations are used to study the effects of oxygen vacancies on the tunneling current through the oxide. A level which is nearly 1.25 eV from the bottom of the conduction band is introduced into the bandgap due to the oxygen vacancies. The tunneling current calculations show that the tunneling currents through the gate oxide with different defect density possess the typical characteristic of stress-induced leakage current. Further analysis shows that the location of oxygen vacancies will have a marked effect on the tunneling current. The largest increase in the tunneling current caused by oxygen vacancies comes about at the middle oxide field when defects are located at the middle of the oxide. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Performance of organic field effect transistors with high-k gate oxide after application of consecutive bias stress

Energy Technology Data Exchange (ETDEWEB)

Lee, Sunwoo; Choi, Changhwan; Lee, Kilbock [Department of Materials Science and Engineering, Hanyang University, Seoul, 133-791 (Korea, Republic of); Cho, Joong Hwee [Department of Embedded Systems Engineering,University of Incheon, Incheon 406-722 (Korea, Republic of); Ko, Ki-Young [Korea Institute of Patent Information, Seoul, 146-8 (Korea, Republic of); Ahn, Jinho, E-mail: jhahn@hanyang.ac.kr [Department of Materials Science and Engineering, Hanyang University, Seoul, 133-791 (Korea, Republic of)

2012-10-30

We report the effect of consecutive electrical stress on the performance of organic field effect transistors (OFETs). Sputtered aluminum oxide (Al{sub 2}O{sub 3}) and hafnium oxide (HfO{sub 2}) were used as gate oxide layers. After the electrical stress, the threshold voltage, which strongly depends on bulk defects, was remarkably shifted to the negative direction, while the other performance characteristics of OFETs such as on-current, transconductance and mobility, which are sensitive to interface defects, were slightly decreased. This result implies that the defects in the bulk layer are significantly affected compared to the defects in the interface layer. Thus, it is important to control the defects in the pentacene bulk layer in order to maintain the good reliabilities of pentacene devices. Those defects in HfO{sub 2} gate oxide devices were larger compared to those in Al{sub 2}O{sub 3} gate oxide devices.

Magnetic interactions in high-energy ball-milled NiZnFe2O4/SiO2 composites

International Nuclear Information System (INIS)

Pozo Lopez, G.; Silvetti, S.P.; Urreta, S.E.; Cabanillas, E.D.

2007-01-01

Composites Ni 0.5 Zn 0.5 Fe 2 O 4 /SiO 2 are obtained after high-energy ball milling precursor oxides, in stoichiometric proportions, for 200 h at room temperature and further isothermal annealing for 1 h at 1273 K, under air and argon atmosphere, respectively. After 200 h grinding, a complex microstructure develops with small hematite crystals mixed with SiO 2 and remanent NiO and ZnO particles, and very small NiZn ferrite clusters, reaching a mean size of ∼9 nm. The high temperature treatments remove the hematite grains from the powder and promote the growth of NiZn ferrite grains to reach mean sizes nearly ∼20 nm. For treatments in oxidizing atmospheres, the major phases are SiO 2 and NiZn ferrite, while for annealing in Ar a new phase appears, fayalite, which is paramagnetic at room temperature. The M-H loops are all well described by the sum of a ferromagnetic and a superparamagnetic-like contribution. The observed properties are interpreted considering the different magnetic phases obtained, their crystal sizes and their mutual interactions

Formation and electrical characteristics of silicon dioxide layers by use of nitric acid oxidation method

International Nuclear Information System (INIS)

Imal, S.; Takahashi, M.; Matsuba, K.; Asuha; Ishikawa, Y.; Kobayashi, Hikaru

2005-01-01

SiO 2 /Si structure can be formed at low temperatures by use of nitric acid (HNO 3 ) oxidation of Si (NAOS) method. When Si wafers are immersed in ∼ 40 wt% HNO 3 solutions at 108 deg C, ∼ 1 nm SiO 2 layers are formed. The subsequent immersion in 68 wt% HNO 3 (i.e., azeotropic mixture of HNO 3 with water) at 121 deg C increases the SiO 2 thickness. The 3,5 nm-thick SiO 2 layers produced by this two-step NAOS method possess a considerably low leakage current density (e.g. 1 x 10 2 A/cmi 2 at the forward gate bias, V G , of 1.5 V), in spite of the low temperature oxidation, and further decreased (e.g., 8 x 10 4 A/cm 2 at V G = 1.5 V) by post-metallization annealing at 250 deg C in hydrogen atmosphere. In order to increase the SiO 2 thickness, a bias voltage is applied during the NAOS method. When 10 V is applied to Si with respect to a Pt counter electrode both immersed in 1 M HNO 3 solutions at 25 deg C, SiO 2 layers with 8 nm thickness can be formed for 1 h(Authors)

Interface passivation and trap reduction via hydrogen fluoride for molybdenum disulfide on silicon oxide back-gate transistors

Science.gov (United States)

Hu, Yaoqiao; San Yip, Pak; Tang, Chak Wah; Lau, Kei May; Li, Qiang

2018-04-01

Layered semiconductor molybdenum disulfide (MoS2) has recently emerged as a promising material for flexible electronic and optoelectronic devices because of its finite bandgap and high degree of gate control. Here, we report a hydrogen fluoride (HF) passivation technique for improving the carrier mobility and interface quality of chemical vapor deposited monolayer MoS2 on a SiO2/Si substrate. After passivation, the fabricated MoS2 back-gate transistors demonstrate a more than double improvement in average electron mobility, a reduced gate hysteresis gap of 3 V, and a low interface trapped charge density of ˜5.8 × 1011 cm-2. The improvements are attributed to the satisfied interface dangling bonds, thus a reduction of interface trap states and trapped charges. Surface x-ray photoelectron spectroscopy analysis and first-principles simulation were performed to verify the HF passivation effect. The results here highlight the necessity of a MoS2/dielectric passivation strategy and provides a viable route for enhancing the performance of MoS2 nano-electronic devices.

Influence of implantation energy on the electrical properties of ultrathin gate oxides grown on nitrogen implanted Si substrates

International Nuclear Information System (INIS)

Kapetanakis, E.; Skarlatos, D.; Tsamis, C.; Normand, P.; Tsoukalas, D.

2003-01-01

Metal-oxide-semiconductor tunnel diodes with gate oxides, in the range of 2.5-3.5 nm, grown either on 25 or 3 keV nitrogen-implanted Si substrates at (0.3 or 1) x10 15 cm -2 dose, respectively, are investigated. The dependence of N 2 + ion implant energy on the electrical quality of the growing oxide layers is studied through capacitance, equivalent parallel conductance, and gate current measurements. Superior electrical characteristics in terms of interface state trap density, leakage current, and breakdown fields are found for oxides obtained through 3 keV nitrogen implants. These findings together with the full absence of any extended defect in the silicon substrate make the low-energy nitrogen implantation technique an attractive option for reproducible low-cost growth of nanometer-thick gate oxides

Positron annihilation in a metal-oxide semiconductor studied by using a pulsed monoenergetic positron beam

Science.gov (United States)

Uedono, A.; Wei, L.; Tanigawa, S.; Suzuki, R.; Ohgaki, H.; Mikado, T.; Ohji, Y.

1993-12-01

The positron annihilation in a metal-oxide semiconductor was studied by using a pulsed monoenergetic positron beam. Lifetime spectra of positrons were measured as a function of incident positron energy for a polycrystalline Si(100 nm)/SiO2(400 nm)/Si specimen. Applying a gate voltage between the polycrystalline Si film and the Si substrate, positrons implanted into the specimen were accumulated at the SiO2/Si interface. From the measurements, it was found that the annihilation probability of ortho-positronium (ortho-Ps) drastically decreased at the SiO2/Si interface. The observed inhibition of the Ps formation was attributed to an interaction between positrons and defects at the SiO2/Si interface.

Effect of top gate potential on bias-stress for dual gate amorphous indium-gallium-zinc-oxide thin film transistor

Energy Technology Data Exchange (ETDEWEB)

Chun, Minkyu; Um, Jae Gwang; Park, Min Sang; Chowdhury, Md Delwar Hossain; Jang, Jin, E-mail: jjang@khu.ac.kr [Advanced Display Research Center and Department of Information Display, Kyung Hee University, Seoul 02447 (Korea, Republic of)

2016-07-15

We report the abnormal behavior of the threshold voltage (V{sub TH}) shift under positive bias Temperature stress (PBTS) and negative bias temperature stress (NBTS) at top/bottom gate in dual gate amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). It is found that the PBTS at top gate shows negative transfer shift and NBTS shows positive transfer shift for both top and bottom gate sweep. The shift of bottom/top gate sweep is dominated by top gate bias (V{sub TG}), while bottom gate bias (V{sub BG}) is less effect than V{sub TG}. The X-ray photoelectron spectroscopy (XPS) depth profile provides the evidence of In metal diffusion to the top SiO{sub 2}/a-IGZO and also the existence of large amount of In{sup +} under positive top gate bias around top interfaces, thus negative transfer shift is observed. On the other hand, the formation of OH{sup −} at top interfaces under the stress of negative top gate bias shows negative transfer shift. The domination of V{sub TG} both on bottom/top gate sweep after PBTS/NBTS is obviously occurred due to thin active layer.

Origin of the n -type and p -type conductivity of MoS 2 monolayers on a SiO 2 substrate

KAUST Repository

Dolui, Kapildeb

2013-04-02

Ab initio density functional theory calculations are performed to study the electronic properties of a MoS2 monolayer deposited over a SiO 2 substrate in the presence of interface impurities and defects. When MoS2 is placed on a defect-free substrate, the oxide plays an insignificant role since the conduction band top and the valence band minimum of MoS2 are located approximately in the middle of the SiO2 band gap. However, if Na impurities and O dangling bonds are introduced at the SiO2 surface, these lead to localized states, which modulate the conductivity of the MoS2 monolayer from n- to p-type. Our results show that the conductive properties of MoS2 deposited on SiO 2 are mainly determined by the detailed structure of the MoS 2/SiO2 interface, and suggest that doping the substrate can represent a viable strategy for engineering MoS2-based devices. © 2013 American Physical Society.

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

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.

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.

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

Temperature Effects on a-IGZO Thin Film Transistors Using HfO2 Gate Dielectric Material

Directory of Open Access Journals (Sweden)

Yu-Hsien Lin

2014-01-01

Full Text Available This study investigated the temperature effect on amorphous indium gallium zinc oxide (a-IGZO thin film transistors (TFTs using hafnium oxide (HfO2 gate dielectric material. HfO2 is an attractive candidate as a high-κ dielectric material for gate oxide because it has great potential to exhibit superior electrical properties with a high drive current. In the process of integrating the gate dielectric and IGZO thin film, postannealing treatment is an essential process for completing the chemical reaction of the IGZO thin film and enhancing the gate oxide quality to adjust the electrical characteristics of the TFTs. However, the hafnium atom diffused the IGZO thin film, causing interface roughness because of the stability of the HfO2 dielectric thin film during high-temperature annealing. In this study, the annealing temperature was optimized at 200°C for a HfO2 gate dielectric TFT exhibiting high mobility, a high ION/IOFF ratio, low IOFF current, and excellent subthreshold swing (SS.

Depth-resolved detection and process dependence of traps at ultrathin plasma-oxidized and deposited SiO2/Si interfaces

International Nuclear Information System (INIS)

Brillson, L. J.; Young, A. P.; White, B. D.; Schaefer, J.; Niimi, H.; Lee, Y. M.; Lucovsky, G.

2000-01-01

Low-energy electron-excited nanoluminescence spectroscopy reveals depth-resolved optical emission associated with traps near the interface between ultrathin SiO 2 deposited by plasma-enhanced chemical vapor deposition on plasma-oxidized crystalline Si. These near-interface states exhibit a strong dependence on local chemical bonding changes introduced by thermal/gas processing, layer-specific nitridation, or depth-dependent radiation exposure. The depth-dependent results provide a means to test chemical and structural bond models used to develop advanced dielectric-semiconductor junctions. (c) 2000 American Vacuum Society

Comparative studies of MOS-gate/oxide-passivated AlGaAs/InGaAs pHEMTs by using ozone water oxidation technique

International Nuclear Information System (INIS)

Lee, Ching-Sung; Hung, Chun-Tse; Chou, Bo-Yi; Hsu, Wei-Chou; Liu, Han-Yin; Ho, Chiu-Sheng; Lai, Ying-Nan

2012-01-01

Al 0.22 Ga 0.78 As/In 0.24 Ga 0.76 As pseudomorphic high-electron-mobility transistors (pHEMTs) with metal-oxide-semiconductor (MOS)-gate structure or oxide passivation by using ozone water oxidation treatment have been comprehensively investigated. Annihilated surface states, enhanced gate insulating property and improved device gain have been achieved by the devised MOS-gate structure and oxide passivation. The present MOS-gated or oxide-passivated pHEMTs have demonstrated superior device performances, including superior breakdown, device gain, noise figure, high-frequency characteristics and power performance. Temperature-dependent device characteristics of the present designs at 300–450 K are also studied. (paper)

Investigation of interface property in Al/SiO2/ n-SiC structure with thin gate oxide by illumination

Science.gov (United States)

Chang, P. K.; Hwu, J. G.

2017-04-01

The reverse tunneling current of Al/SiO2/ n-SiC structure employing thin gate oxide is introduced to examine the interface property by illumination. The gate current at negative bias decreases under blue LED illumination, yet increases under UV lamp illumination. Light-induced electrons captured by interface states may be emitted after the light sources are off, leading to the recovery of gate currents. Based on transient characteristics of gate current, the extracted trap level is close to the light energy for blue LED, indicating that electron capture induced by lighting may result in the reduction of gate current. Furthermore, bidirectional C- V measurements exhibit a positive voltage shift caused by electron trapping under blue LED illumination, while a negative voltage shift is observed under UV lamp illumination. Distinct trapping and detrapping behaviors can be observed from variations in I- V and C- V curves utilizing different light sources for 4H-SiC MOS capacitors with thin insulators.

High permittivity materials for oxide gate stack in Ge-based metal oxide semiconductor capacitors

Energy Technology Data Exchange (ETDEWEB)

Molle, Alessandro, E-mail: alessandro.molle@mdm.infm.i [Laboratorio Nazionale MDM, CNR-INFM, via C. Olivetti 2, 20041 Agrate Brianza, Milano (Italy); Baldovino, Silvia [Laboratorio Nazionale MDM, CNR-INFM, via C. Olivetti 2, 20041 Agrate Brianza, Milano (Italy); Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano Bicocca, Milano (Italy); Spiga, Sabina [Laboratorio Nazionale MDM, CNR-INFM, via C. Olivetti 2, 20041 Agrate Brianza, Milano (Italy); Fanciulli, Marco [Laboratorio Nazionale MDM, CNR-INFM, via C. Olivetti 2, 20041 Agrate Brianza, Milano (Italy); Dipartimento di Scienza dei Materiali, Universita degli Studi di Milano Bicocca, Milano (Italy)

2010-01-01

In the effort to ultimately shrink the size of logic devices towards a post-Si era, the integration of Ge as alternative channel material for high-speed p-MOSFET devices and the concomitant coupling with high permittivity dielectrics (high-k) as gate oxides is currently a key-challenge in microelectronics. However, the Ge option still suffers from a number of unresolved drawbacks and open issues mainly related to the thermodynamic and electrical compatibility of Ge substrates with high-k gate stack. Strictly speaking, two main concerns can be emphasized. On one side is the dilemma on which chemical/physical passivation is more suitable to minimize the unavoidable presence of electrically active defects at the oxide/semiconductor interface. On the other side, overcoming the SiO{sub 2} gate stack opens the route to a number of potentially outperforming high-k oxides. Two deposition approaches were here separately adopted to investigate the high-k oxide growth on Ge substrates, the molecular beam deposition (MBD) of Gd{sub 2}O{sub 3} and the atomic layer deposition (ALD) of HfO{sub 2}. In the MBD framework epitaxial and amorphous Gd{sub 2}O{sub 3} films were grown onto GeO{sub 2}-passivated Ge substrates. In this case, Ge passivation was achieved by exploiting the Ge{sup 4+} bonding state in GeO{sub 2} ultra-thin interface layers intentionally deposited in between Ge and the high-k oxide by means of atomic oxygen exposure to Ge. The composition of the interface layer has been characterized as a function of the oxidation temperature and evidence of Ge dangling bonds at the GeO{sub 2}/Ge interface has been reported. Finally, the electrical response of MOS capacitors incorporating Gd{sub 2}O{sub 3} and GeO{sub 2}-passivated Ge substrates has been checked by capacitance-voltage measurements. On the other hand, the structural and electrical properties of HfO{sub 2} films grown by ALD on Ge by using different oxygen precursors, i.e. H{sub 2}O, Hf(O{sup t}Bu){sub 2}(mmp

Hydrogen-terminated diamond vertical-type metal oxide semiconductor field-effect transistors with a trench gate

Energy Technology Data Exchange (ETDEWEB)

Inaba, Masafumi, E-mail: inaba-ma@ruri.waseda.jp; Muta, Tsubasa; Kobayashi, Mikinori; Saito, Toshiki; Shibata, Masanobu; Matsumura, Daisuke; Kudo, Takuya; Hiraiwa, Atsushi [Graduate School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kawarada, Hiroshi [Graduate School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, 2-8-26 Nishiwaseda, Shinjuku, Tokyo 169-0051 (Japan)

2016-07-18

The hydrogen-terminated diamond surface (C-H diamond) has a two-dimensional hole gas (2DHG) layer independent of the crystal orientation. A 2DHG layer is ubiquitously formed on the C-H diamond surface covered by atomic-layer-deposited-Al{sub 2}O{sub 3}. Using Al{sub 2}O{sub 3} as a gate oxide, C-H diamond metal oxide semiconductor field-effect transistors (MOSFETs) operate in a trench gate structure where the diamond side-wall acts as a channel. MOSFETs with a side-wall channel exhibit equivalent performance to the lateral C-H diamond MOSFET without a side-wall channel. Here, a vertical-type MOSFET with a drain on the bottom is demonstrated in diamond with channel current modulation by the gate and pinch off.

Temperature Effects on a-IGZO Thin Film Transistors Using HfO2 Gate Dielectric Material

OpenAIRE

Lin, Yu-Hsien; Chou, Jay-Chi

2014-01-01

This study investigated the temperature effect on amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) using hafnium oxide (HfO2) gate dielectric material. HfO2 is an attractive candidate as a high-κ dielectric material for gate oxide because it has great potential to exhibit superior electrical properties with a high drive current. In the process of integrating the gate dielectric and IGZO thin film, postannealing treatment is an essential process for completing the chem...

Preparation, characterization and catalytic behavior of hierachically porous CuO/α-Fe2O3/SiO2 composite material for CO and o-DCB oxidation

Institute of Scientific and Technical Information of China (English)

Xiaodong Ma; Xi Feng; Xuan He; Hongwen Guo; Lu Lü

2011-01-01

Hierachically porous (HP) CuO/α-Fe2O3/SiO2 composite material was fabricated by sol-gel method and multi-hydrothermal processes using HP-SiO2 as support.The resulting material was characterized by N2 adsorption-desorption,X-ray diffraction and scanning electron microscopy.The as-prepared CuO/Fe2O3/HP-SiO2 sample,with α-Fe2O3 and CuO nanocrystals,possessed a co-continuous skeleton,through-macroporous and mesoporous structure.Its catalytic behavior for CO and o-DCB oxidation was investigated.The result showed that CuO/Fe2O3/HP-SiO2 catalyst exhibited high catalytic activity for both CO and o-DCB oxidation,indicating its potential application in combined abatement of CO and chlorinated volatile organic compounds.

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)

Chemical vapor deposited monolayer MoS2 top-gate MOSFET with atomic-layer-deposited ZrO2 as gate dielectric

Science.gov (United States)

Hu, Yaoqiao; Jiang, Huaxing; Lau, Kei May; Li, Qiang

2018-04-01

For the first time, ZrO2 dielectric deposition on pristine monolayer MoS2 by atomic layer deposition (ALD) is demonstrated and ZrO2/MoS2 top-gate MOSFETs have been fabricated. ALD ZrO2 overcoat, like other high-k oxides such as HfO2 and Al2O3, was shown to enhance the MoS2 channel mobility. As a result, an on/off current ratio of over 107, a subthreshold slope of 276 mV dec-1, and a field-effect electron mobility of 12.1 cm2 V-1 s-1 have been achieved. The maximum drain current of the MOSFET with a top-gate length of 4 μm and a source/drain spacing of 9 μm is measured to be 1.4 μA μm-1 at V DS = 5 V. The gate leakage current is below 10-2 A cm-2 under a gate bias of 10 V. A high dielectric breakdown field of 4.9 MV cm-1 is obtained. Gate hysteresis and frequency-dependent capacitance-voltage measurements were also performed to characterize the ZrO2/MoS2 interface quality, which yielded an interface state density of ˜3 × 1012 cm-2 eV-1.

Effects of Gate Stack Structural and Process Defectivity on High-k Dielectric Dependence of NBTI Reliability in 32 nm Technology Node PMOSFETs

Directory of Open Access Journals (Sweden)

H. Hussin

2014-01-01

Full Text Available We present a simulation study on negative bias temperature instability (NBTI induced hole trapping in E′ center defects, which leads to depassivation of interface trap precursor in different geometrical structures of high-k PMOSFET gate stacks using the two-stage NBTI model. The resulting degradation is characterized based on the time evolution of the interface and hole trap densities, as well as the resulting threshold voltage shift. By varying the physical thicknesses of the interface silicon dioxide (SiO2 and hafnium oxide (HfO2 layers, we investigate how the variation in thickness affects hole trapping/detrapping at different stress temperatures. The results suggest that the degradations are highly dependent on the physical gate stack parameters for a given stress voltage and temperature. The degradation is more pronounced by 5% when the thicknesses of HfO2 are increased but is reduced by 11% when the SiO2 interface layer thickness is increased during lower stress voltage. However, at higher stress voltage, greater degradation is observed for a thicker SiO2 interface layer. In addition, the existence of different stress temperatures at which the degradation behavior differs implies that the hole trapping/detrapping event is thermally activated.

Degradation of ultra-thin gate oxide LDD NMOSFET under GIDL stress

International Nuclear Information System (INIS)

Hu Shigang; Hao Yue; Cao Yanrong; Ma Xiaohua; Wu Xiaofeng; Chen Chi; Zhou Qingjun

2009-01-01

The degradation of device under GIDL (gate-induced drain leakage current) stress has been studied using LDD NMOSFETs with 1.4 nm gate oxides. Experimental result shows that the degradation of device parameters depends more strongly on V d than on V g . The characteristics of the GIDL current are used to analyze the damage generated during the stress. It is clearly found that the change of GIDL current before and after stress can be divided into two stages. The trapping of holes in the oxide is dominant in the first stage, but that of electrons in the oxide is dominant in the second stage. It is due to the common effects of edge direct tunneling and band-to-band tunneling. SILC (stress induced leakage current) in the NMOSFET decreases with increasing stress time under GIDL stress. The degradation characteristic of SILC also shows saturating time dependence. SILC is strongly dependent on the measured gate voltage. The higher the measured gate voltage, the less serious the degradation of the gate current. A likely mechanism is presented to explain the origin of SILC during GIDL stress.

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

Solvothermal synthesis of gallium-indium-zinc-oxide nanoparticles for electrolyte-gated transistors.

Science.gov (United States)

Santos, Lídia; Nunes, Daniela; Calmeiro, Tomás; Branquinho, Rita; Salgueiro, Daniela; Barquinha, Pedro; Pereira, Luís; Martins, Rodrigo; Fortunato, Elvira

2015-01-14

Solution-processed field-effect transistors are strategic building blocks when considering low-cost sustainable flexible electronics. Nevertheless, some challenges (e.g., processing temperature, reliability, reproducibility in large areas, and cost effectiveness) are requirements that must be surpassed in order to achieve high-performance transistors. The present work reports electrolyte-gated transistors using as channel layer gallium-indium-zinc-oxide nanoparticles produced by solvothermal synthesis combined with a solid-state electrolyte based on aqueous dispersions of vinyl acetate stabilized with cellulose derivatives, acrylic acid ester in styrene and lithium perchlorate. The devices fabricated using this approach display a ION/IOFF up to 1 × 10(6), threshold voltage (VTh) of 0.3-1.9 V, and mobility up to 1 cm(2)/(V s), as a function of gallium-indium-zinc-oxide ink formulation and two different annealing temperatures. These results validates the usage of electrolyte-gated transistors as a viable and promising alternative for nanoparticle based semiconductor devices as the electrolyte improves the interface and promotes a more efficient step coverage of the channel layer, reducing the operating voltage when compared with conventional dielectrics gating. Moreover, it is shown that by controlling the applied gate potential, the operation mechanism of the electrolyte-gated transistors can be modified from electric double layer to electrochemical doping.

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.

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.

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.

Pd/Nb2O5/SiO2 catalyst for the direct hydrodeoxygenation of biomass-related compounds to liquid alkanes under mild conditions.

Science.gov (United States)

Shao, Yi; Xia, Qineng; Liu, Xiaohui; Lu, Guanzhong; Wang, Yanqin

2015-05-22

A simple Pd-loaded Nb2 O5 /SiO2 catalyst was prepared for the hydrodeoxygenation of biomass-related compounds to alkanes under mild conditions. Niobium oxide dispersed in silica (Nb2 O5 /SiO2 ) as the support was prepared by the sol-gel method and characterized by various techniques, including N2 adsorption, XRD, NH3 temperature-programmed desorption (TPD), TEM, and energy-dispersive X-ray spectroscopy (EDAX) atomic mapping. The characterization results showed that the niobium oxide species were amorphous and well dispersed in silica. Compared to commercial Nb2 O5 , Nb2 O5 /SiO2 has significantly more active niobium oxide species exposed on the surface. Under mild conditions (170 °C, 2.5 MPa), Pd/10 %Nb2 O5 /SiO2 was effective for the hydrodeoxygenation reactions of 4-(2-furyl)-3-buten-2-one (aldol adduct of furfural with acetone), palmitic acid, tristearin, and diphenyl ether (model compounds of microalgae oils, vegetable oils, and lignin), which gave high yields (>94 %) of alkanes with little CC bond cleavage. More importantly, owing to the significant promotion effect of NbOx species on CO bond cleavage and the mild reaction conditions, the CC cleavage was considerably restrained, and the catalyst showed an excellent activity and stability for the hydrodeoxygenation of palmitic acid with almost no decrease in hexadecane yield (94-95 %) in a 150 h time-on-stream test. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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)

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.

Comparison of electron transmittances and tunneling currents in an anisotropic TiNx/HfO2/SiO2/p-Si(100) metal-oxide-semiconductor (MOS) capacitor calculated using exponential- and Airy-wavefunction approaches and a transfer matrix method

International Nuclear Information System (INIS)

Noor, Fatimah A.; Abdullah, Mikrajuddin; Sukirno; Khairurrijal

2010-01-01

Analytical expressions of electron transmittance and tunneling current in an anisotropic TiN x /HfO 2 /SiO 2 /p-Si(100) metal-oxide-semiconductor (MOS) capacitor were derived by considering the coupling of transverse and longitudinal energies of an electron. Exponential and Airy wavefunctions were utilized to obtain the electron transmittance and the electron tunneling current. A transfer matrix method, as a numerical approach, was used as a benchmark to assess the analytical approaches. It was found that there is a similarity in the transmittances calculated among exponential- and Airy-wavefunction approaches and the TMM at low electron energies. However, for high energies, only the transmittance calculated by using the Airy-wavefunction approach is the same as that evaluated by the TMM. It was also found that only the tunneling currents calculated by using the Airy-wavefunction approach are the same as those obtained under the TMM for all range of oxide voltages. Therefore, a better analytical description for the tunneling phenomenon in the MOS capacitor is given by the Airy-wavefunction approach. Moreover, the tunneling current density decreases as the titanium concentration of the TiN x metal gate increases because the electron effective mass of TiN x decreases with increasing nitrogen concentration. In addition, the mass anisotropy cannot be neglected because the tunneling currents obtained under the isotropic and anisotropic masses are very different. (semiconductor devices)

Electrical and physical characterizations of the effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and (000\\bar{1})

Science.gov (United States)

Shiomi, Hiromu; Kitai, Hidenori; Tsujimura, Masatoshi; Kiuchi, Yuji; Nakata, Daisuke; Ono, Shuichi; Kojima, Kazutoshi; Fukuda, Kenji; Sakamoto, Kunihiro; Yamasaki, Kimiyohi; Okumura, Hajime

2016-04-01

The effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and (000\\bar{1}) were investigated using both electrical and physical characterization methods. Hall measurements and split capacitance-voltage (C-V) measurements revealed that the difference in field-effect mobility between wet oxide and dry oxynitride interfaces was mainly attributed to the ratio of the mobile electron density to the total induced electron density. The surface states close to the conduction band edge causing a significant trapping of inversion carriers were also evaluated. High-resolution Rutherford backscattering spectroscopy (HR-RBS) analysis and high-resolution elastic recoil detection analysis (HR-ERDA) were employed to show the nanometer-scale compositional profile of the SiC-MOS interfaces for the first time. These analyses, together with cathode luminescence (CL) spectroscopy and transmission electron microscopy (TEM), suggested that the deviations of stoichiometry and roughness at the interface defined the effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and (000\\bar{1}).

Direct deposition of aluminum oxide gate dielectric on graphene channel using nitrogen plasma treatment

International Nuclear Information System (INIS)

Lim, Taekyung; Kim, Dongchool; Ju, Sanghyun

2013-01-01

Deposition of high-quality dielectric on a graphene channel is an essential technology to overcome structural constraints for the development of nano-electronic devices. In this study, we investigated a method for directly depositing aluminum oxide (Al 2 O 3 ) on a graphene channel through nitrogen plasma treatment. The deposited Al 2 O 3 thin film on graphene demonstrated excellent dielectric properties with negligible charge trapping and de-trapping in the gate insulator. A top-gate-structural graphene transistor was fabricated using Al 2 O 3 as the gate dielectric with nitrogen plasma treatment on graphene channel region, and exhibited p-type transistor characteristics

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.

Photoluminescence analysis of Ce3+:Zn2SiO4 & Li++ Ce3+:Zn2SiO4: phosphors by a sol-gel method

Science.gov (United States)

Babu, B. Chandra; Vandana, C. Sai; Guravamma, J.; Rudramadevi, B. Hemalatha; Buddhudu, S.

2015-06-01

Here, we report on the development and photoluminescence analysis of Zn2SiO4, Ce3+:Zn2SiO4 & Li+ + Ce3+: Zn2SiO4 novel powder phosphors prepared by a sol-gel technique. The total amount of Ce3+ ions was kept constant in this experiment at 0.05 mol% total doping. The excitation and emission spectra of undoped (Zn2SiO4) and Ce3+ doped Zn2SiO4 and 0.05 mol% Li+ co-doped samples have been investigated. Cerium doped Zn2SiO4 powder phosphors had broad blue emission corresponding to the 2D3/2→2FJ transition at 443nm. Stable green-yellow-red emission has been observed from Zn2SiO4 host matrix and also we have been observed the enhanced luminescence of Li+ co-doped Zn2SiO4:Ce3+. Excitation and emission spectra of these blue luminescent phosphors have been analyzed in evaluating their potential as luminescent screen coating phosphors.

Analyzing nitrogen concentration using carrier illumination (CI) technology for DPN ultra-thin gate oxide

International Nuclear Information System (INIS)

Li, W.S.; Wu, Bill; Fan, Aki; Kuo, C.W.; Segovia, M.; Kek, H.A.

2005-01-01

Nitrogen concentration in the gate oxide plays a key role for 90 nm and below ULSI technology. Techniques like secondary ionization mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS) are commonly used for understanding N concentration. This paper describes the application of the carrier illuminationTM (CI) technique to measure the nitrogen concentration in ultra-thin gate oxides. A set of ultra-thin gate oxide wafers with different DPN (decoupled plasma nitridation) treatment conditions were measured using the CI technique. The CI signal has excellent correlation with the N concentration as measured by XPS

Surface Preparation and Deposited Gate Oxides for Gallium Nitride Based Metal Oxide Semiconductor Devices

Directory of Open Access Journals (Sweden)

Paul C. McIntyre

2012-07-01

Full Text Available The literature on polar Gallium Nitride (GaN surfaces, surface treatments and gate dielectrics relevant to metal oxide semiconductor devices is reviewed. The significance of the GaN growth technique and growth parameters on the properties of GaN epilayers, the ability to modify GaN surface properties using in situ and ex situ processes and progress on the understanding and performance of GaN metal oxide semiconductor (MOS devices are presented and discussed. Although a reasonably consistent picture is emerging from focused studies on issues covered in each of these topics, future research can achieve a better understanding of the critical oxide-semiconductor interface by probing the connections between these topics. The challenges in analyzing defect concentrations and energies in GaN MOS gate stacks are discussed. Promising gate dielectric deposition techniques such as atomic layer deposition, which is already accepted by the semiconductor industry for silicon CMOS device fabrication, coupled with more advanced physical and electrical characterization methods will likely accelerate the pace of learning required to develop future GaN-based MOS technology.

The effects of gate oxide thickness on radiation damage in MOS system

International Nuclear Information System (INIS)

Zhu Hui; Yan Rongliang; Wang Yu; He Jinming

1988-01-01

The dependences of the flatband voltage shift (ΔV FB ) and the threshold voltage shift (ΔV TH ) in MOS system on the oxide thickness (T ox ) and on total irradiated dose (D) of electron-beam and 60 Co γ-ray have been studied. It has been found that ΔV FB ∝ T ox 3 , with +10V of gate bias during irradiation for n-Si substrate MOS capacitors; ΔV TH ∝ T ox 3 D 2/3 , with 'on' gate bias during irradiation for n- and P-channel MOS transistors; ΔV TP ∝ T ox 2 D 2/3 , with 'off' gate bias during irradiation for P-channel MOS transistors. These results are explained by Viswanathan model. According to ∼T ox 3 dependence, the optimization of radiation hardening process for MOS system is also simply discussed

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.

Compositional and optical properties of SiO x films and (SiO x /SiO y ) junctions deposited by HFCVD

Science.gov (United States)

2014-01-01

In this work, non-stoichiometric silicon oxide (SiO x ) films and (SiO x /SiO y ) junctions, as-grown and after further annealing, are characterized by different techniques. The SiO x films and (SiO x /SiO y ) junctions are obtained by hot filament chemical vapor deposition technique in the range of temperatures from 900°C to 1,150°C. Transmittance spectra of the SiO x films showed a wavelength shift of the absorption edge thus indicating an increase in the optical energy band gap, when the growth temperature decreases; a similar behavior is observed in the (SiO x /SiO y ) structures, which in turn indicates a decrease in the Si excess, as Fourier transform infrared spectroscopy (FTIR) reveals, so that, the film and junction composition changes with the growth temperature. The analysis of the photoluminescence (PL) results using the quantum confinement model suggests the presence of silicon nanocrystal (Si-nc) embedded in a SiO x matrix. For the case of the as-grown SiO x films, the absorption and emission properties are correlated with quantum effects in Si-nc and defects. For the case of the as-grown (SiO x /SiO y ) junctions, only the emission mechanism related to some kinds of defects was considered, but silicon nanocrystal embedded in a SiO x matrix is present. After thermal annealing, a phase separation into Si and SiO2 occurs, as the FTIR spectra illustrates, which has repercussions in the absorption and emission properties of the films and junctions, as shown by the change in the A and B band positions on the PL spectra. These results lead to good possibilities for proposed novel applications in optoelectronic devices. PACS 61.05.-a; 68.37.Og; 61.05.cp; 78.55.-m; 68.37.Ps; 81.15.Gh PMID:25342935

Structural aspects of B2O3-substituted (PbO)0.5(SiO2)0.5 glasses

International Nuclear Information System (INIS)

Sudarsan, V.; Kulshreshtha, S.K.; Shrikhande, V.K.; Kothiyal, G.P.

2002-01-01

Lead borosilicate glasses having general formulae (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x with 0.0≤x≤0.4 and (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y with 0.0≤y≤0.5 have been prepared by a conventional melt-quench method and characterized by 29 Si, 11 B magic angle spinning (MAS) NMR techniques and infrared spectroscopy, as regards their structural features. From 29 Si NMR results, it has been inferred that with increasing concentration of boron oxide, (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 )x glasses exhibit a systematic increase in the number of Q 4 structural units of Si at the expense of Q 2 structural units, along with the formation of Si-O-B linkages. On the other hand, for (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y glasses, there is no direct interaction between SiO 2 and B 2 O 3 in the glass network, as revealed by the 29 Si MAS NMR studies. Boron exists in both trigonal and tetrahedral configurations for these two series of glasses and for the (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y series of glasses; the relative concentration of these two structural units remains almost constant with increasing B 2 O 3 concentration. In contrast, for (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x glasses, there is a slight increase in the number of BO 3 structural units above x = 0.2, as there is a competition between SiO 2 and B 2 O 3 for interaction with Pb 2+ , thereby leading to the formation of BO 3 structural units. For both series of glasses, the thermal expansion coefficient is found to decrease with increasing B 2 O 3 concentration, the effect being more pronounced for the (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x series of glasses due to the increased concentration of Q 4 structural units of silicon and better cross-linking as a result of the formation of Si-O-B-type linkages. (author)

Influence of gate recess on the electronic characteristics of β-Ga2O3 MOSFETs

Science.gov (United States)

Lv, Yuanjie; Mo, Jianghui; Song, Xubo; He, Zezhao; Wang, Yuangang; Tan, Xin; Zhou, Xingye; Gu, Guodong; Guo, Hongyu; Feng, Zhihong

2018-05-01

Gallium oxide (Ga2O3) metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated with gate recess depths of 110 nm and 220 nm, respectively. The gate recess was formed by dry plasma etching with Cr metal as the mask. The fabricated devices with a 25-nm HfO2 gate dielectric both showed a low off-state drain current of about 1.8 × 10-10 A/mm. The effects of recess depth on the electronic characteristics of Ga2O3 MOSFETs were investigated. Upon increasing the recess depth from 110 nm to 220 nm, the saturated drain current decreased from 20.7 mA/mm to 2.6 mA/mm, while the threshold voltage moved increased to +3 V. Moreover, the breakdown voltage increased from 122 V to 190 V. This is mainly because the inverted-trapezoidal gate played the role of a gate-field plate, which suppressed the peak electric field close to the gate.

Gel electrolytes based on poly(acrylonitrile)/sulpholane with hybrid TiO2/SiO2 filler for advanced lithium polymer batteries

International Nuclear Information System (INIS)

Kurc, Beata

2014-01-01

Highlights: • Paper describes properties of gel electrolyte based on PAN with TMS and TiO 2 -SiO 2 . • The TiO 2 -SiO 2 oxide composite was precipitated in the emulsion system and used as the fillers. • The capacity of the graphite anode depends on the current rate and the amount of TiO 2 -SiO 2 . • For PE3 electrolyte was obtained practical capacity more than 90% of the theoretical capacity. - Abstract: This paper describes the synthesis and properties of a new type of ceramic fillers for composite polymer gel electrolytes. Hybrid TiO 2 -SiO 2 ceramic powders have been obtained by co-precipitation from titanium(IV) sulfate solution using sodium silicate as the precipitating agent. The resulting submicron-size powders have been applied as fillers for composite polymer gel electrolytes for Li-ion batteries based on polyacrylonitrile (PAN) membranes. The powders and gel electrolytes have been examined structurally and electrochemically, showing favorable properties in terms of electrolyte uptake and electrochemical characteristics in Li-ion cells

Quantitative analysis of crystalline and remaining glass phases in CaO-B2O3-SiO2 ternary system glass ceramics

International Nuclear Information System (INIS)

He Ming; Wu Mengqiang; Zhang Shuren; Zhou Xiaohua; Zhang Ting; Chen Song

2010-01-01

Research highlights: → As for CBS ternary system glass ceramics, due to the complex phase compositions, many methods could be difficult to determine quantitatively the absolute amounts of crystalline and remaining oxides. In this study, an available method based on the Rietveld method was used to quantitatively analyze the relative weight fraction and densities of crystalline phases. These above data are used to obtain a table of both relative weight fraction of crystalline phases and densities of all phases including CBS LTCC. Using volume additivity rule, it is possible to analysis quantitatively the absolute weight fraction of crystalline phases and also the oxides molar content in the remaining glass. - Abstract: Based on Rietveld method of X-ray techniques and volume additivity rule, a new method was developed to quantitatively analyze the phase composition of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics. Lattice parameters, densities and relative weight fractions of crystalline phases in CaO-B 2 O 3 -SiO 2 ternary system were obtained by X-ray diffraction (XRD) refinement. According to the relative weight fraction of crystalline phases and densities of various components, the volume additivity rule was revealed by calculating the absolute weight fraction of crystalline phases of CaO-B 2 O 3 -SiO 2 glass ceramics. In addition, molar contents of the oxides in the remaining glass can also be determined by this method. Comparing this method with internal standard method, it is found that the maximum deviations of the crystallinity and the absolute weight fraction of crystalline phases are less than 2.6% and 2.9%, respectively. As a result, quantitative evaluation of CaO-B 2 O 3 -SiO 2 ternary system glass ceramics can be achieved using this method.

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

Paired-pulse facilitation achieved in protonic/electronic hybrid indium gallium zinc oxide synaptic transistors

Directory of Open Access Journals (Sweden)

Li Qiang Guo

2015-08-01

Full Text Available Neuromorphic devices with paired pulse facilitation emulating that of biological synapses are the key to develop artificial neural networks. Here, phosphorus-doped nanogranular SiO2 electrolyte is used as gate dielectric for protonic/electronic hybrid indium gallium zinc oxide (IGZO synaptic transistor. In such synaptic transistors, protons within the SiO2 electrolyte are deemed as neurotransmitters of biological synapses. Paired-pulse facilitation (PPF behaviors for the analogous information were mimicked. The temperature dependent PPF behaviors were also investigated systematically. The results indicate that the protonic/electronic hybrid IGZO synaptic transistors would be promising candidates for inorganic synapses in artificial neural network applications.

Electrical and structural properties of CaF sub 2 films

CERN Document Server

Kim, D Y; Yi, J S

1999-01-01

Fluoride films have many practical applications such as gate insulators for thin-film transistors(TFTs), anti-reflection coatings, and optical waveguides. We have investigated fluoride films as gate insulators for TFT applications. Most of gate oxide films of TFTs, like SiO sub 2 , Ta sub 2 O sub 5 , Al sub 2 O sub 3 , and SiO sub x , exhibited problems with the trap charge density, lattice mismatch, and interface states, As a way of circumventing these problems in conventional gate insulators, we investigated CaF sub 2 which has a low interface trap charge density and lattice constant similar to that of the Si surface. We were able to achieve almost epitaxial CaF sub 2 film growth in the (200) plane on a (100) p-type Si substrate. Investigations of the structural properties of CaF sub 2 films for various substrate temperatures resulted in the best lattice mismatch of 0.7 % and an average surface roughness of 8.4 A. The C-V results for the Metal-Insulator-Semiconductor (MIS) structure of the CaF sub 2 films s...

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

Capacitance-voltage characterization of fully silicided gated MOS capacitor

International Nuclear Information System (INIS)

Wang Baomin; Ru Guoping; Jiang Yulong; Qu Xinping; Li Bingzong; Liu Ran

2009-01-01

This paper investigates the capacitance-voltage (C-V) measurement on fully silicided (FUSI) gated metal-oxide-semiconductor (MOS) capacitors and the applicability of MOS capacitor models. When the oxide leakage current of an MOS capacitor is large, two-element parallel or series model cannot be used to obtain its real C-V characteristic. A three-element model simultaneously consisting of parallel conductance and series resistance or a four-element model with further consideration of a series inductance should be used. We employed the three-element and the four-element models with the help of two-frequency technique to measure the Ni FUSI gated MOS capacitors. The results indicate that the capacitance of the MOS capacitors extracted by the three-element model still shows some frequency dispersion, while that extracted by the four-element model is close to the real capacitance, showing little frequency dispersion. The obtained capacitance can be used to calculate the dielectric thickness with quantum effect correction by NCSU C-V program. We also investigated the influence of MOS capacitor's area on the measurement accuracy. The results indicate that the decrease of capacitor area can reduce the dissipation factor and improve the measurement accuracy. As a result, the frequency dispersion of the measured capacitance is significantly reduced, and real C-V characteristic can be obtained directly by the series model. In addition, this paper investigates the quasi-static C-V measurement and the photonic high-frequency C-V measurement on Ni FUSI metal gated MOS capacitor with a thin leaky oxide. The results indicate that the large tunneling current through the gate oxide significantly perturbs the accurate measurement of the displacement current, which is essential for the quasi-static C-V measurement. On the other hand, the photonic high-frequency C-V measurement can bypass the leakage problem, and get reliable low-frequency C-V characteristic, which can be used to

Ultrathin silicon dioxide layers with a low leakage current density formed by chemical oxidation of Si

Science.gov (United States)

Asuha,; Kobayashi, Takuya; Maida, Osamu; Inoue, Morio; Takahashi, Masao; Todokoro, Yoshihiro; Kobayashi, Hikaru

2002-10-01

Chemical oxidation of Si by use of azeotrope of nitric acid and water can form 1.4-nm-thick silicon dioxide layers with a leakage current density as low as those of thermally grown SiO2 layers. The capacitance-voltage (C-V) curves for these ultrathin chemical SiO2 layers have been measured due to the low leakage current density. The leakage current density is further decreased to approx1/5 (cf. 0.4 A/cm2 at the forward gate bias of 1 V) by post-metallization annealing at 200 degC in hydrogen. Photoelectron spectroscopy and C-V measurements show that this decrease results from (i) increase in the energy discontinuity at the Si/SiO2 interface, and (ii) elimination of Si/SiO2 interface states and SiO2 gap states.

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.

High performance GaN-based LEDs on patterned sapphire substrate with patterned composite SiO2/Al2O3 passivation layers and TiO2/Al2O3 DBR backside reflector.

Science.gov (United States)

Guo, Hao; Zhang, Xiong; Chen, Hongjun; Zhang, Peiyuan; Liu, Honggang; Chang, Hudong; Zhao, Wei; Liao, Qinghua; Cui, Yiping

2013-09-09

GaN-based light-emitting diodes (LEDs) on patterned sapphire substrate (PSS) with patterned composite SiO(2)/Al(2)O(3) passivation layers and TiO(2)/Al(2)O(3) distributed Bragg reflector (DBR) backside reflector have been proposed and fabricated. Highly passivated Al(2)O(3) layer deposited on indium tin oxide (ITO) layer with excellent uniformity and quality has been achieved with atomic layer deposition (ALD) technology. With a 60 mA current injection, an enhancement of 21.6%, 59.7%, and 63.4% in the light output power (LOP) at 460 nm wavelength was realized for the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers, the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers and Ag mirror + 3-pair TiO(2)/SiO(2) DBR backside reflector, and the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layer and Ag mirror + 3-pair ALD-grown TiO(2)/Al(2)O(3) DBR backside reflector as compared with the conventional LED only with a single SiO(2) passivation layer, respectively.

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

Sustainable synthesis of magnetically separable SiO2/Co@Fe2O4 nanocomposite and its catalytic applications for the benzimidazole synthesis

Science.gov (United States)

Jithendra Kumara, K. S.; Krishnamurthy, G.; Sunil Kumar, N.; Naik, Nagaraja; Praveen, T. M.

2018-04-01

The Co(II) and Fe(III) centres magnetically separable two new mesoporous nanocatalyst were synthesised via chemical synthesis method. The transmission electron microscopic studies (TEM) show that, the particles are spherical shape with mean size of 20 nm. The Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals that SiO2 is coating on the surface of the cobalt ferrate nanoparticle (CoFe2O4). The SiO2 coating is efficiently preventing the aggregated collision of nanoparticles. Magnetic measurements show that diamagnetic character of the SiO2 is unaffected to the coercivity of SiO2 coated CoFe2O4 particles. In addition, these nanoparticles are used as nanocatalyst for high yielding, facile and expeditious synthesis of various functionalized 2-arylbenzimidazoles via one-pot condensation. The cascade including imine formation, cyclization, condensation, and aromatization occurs, without addition of any reducing or oxidizing agents. In all situations, the desired product was synthesised with excellent yield. The shorter reaction time, mild reaction condition, simplicity, non-toxicity, safe reaction and easy workup are the impotent merits of this protocol.

Al2O3 nanocrystals embedded in amorphous Lu2O3 high-k gate dielectric for floating gate memory application

International Nuclear Information System (INIS)

Yuan, C L; Chan, M Y; Lee, P S; Darmawan, P; Setiawan, Y

2007-01-01

The integration of nanoparticles has high potential in technological applications and opens up possibilities of the development of new devices. Compared to the conventional floating gate memory, a structure containing nanocrystals embedded in dielectrics shows high potential to produce a memory with high endurance, low operating voltage, fast write-erase speeds and better immunity to soft errors [S. Tiwari, F. Rana, H. Hanafi et al. 1996 Appl.Phys. Lett. 68, 1377]. A significant improvement on data retention [J. J. Lee, X. Wang et al. 2003 Proceedings of the VLSI Technol. Symposium, p33] can be observed when discrete nanodots are used instead of continuous floating gate as charge storage nodes because local defect related leakage can be reduced efficiently. Furthermore, using a high-k dielectric in place of the conventional SiO2 based dielectric, nanodots flash memory is able to achieve significantly improved programming efficiency and data retention [A. Thean and J. -P. Leburton, 2002 IEEE Potentials 21, 35; D. W. Kim, T. Kim and S. K. Banerjee, 2003 IEEE Trans. Electron Devices 50, 1823]. We have recently successfully developed a method to produce nanodots embedded in high-k gate dielectrics [C. L. Yuan, P. Darmawan, Y. Setiawan and P. S. Lee, 2006 Electrochemical and Solid-State Letters 9, F53; C. L. Yuan, P. Darmawan, Y. Setiawan and P. S. Lee, 2006 Europhys. Lett. 74, 177]. In this paper, we fabricated the memory structure of Al 2 O 3 nanocrystals embedded in amorphous Lu 2 O 3 high k dielectric using pulsed laser ablation. The mean size and density of the Al 2 O 3 nanocrystals are estimated to be about 5 nm and 7x1011 cm -2 , respectively. Good electrical performances in terms of large memory window and good data retention were observed. Our preparation method is simple, fast and economical

High-current and low acceleration voltage arsenic ion implanted polysilicon-gate and source-drain electrode Si mos transistor

International Nuclear Information System (INIS)

Saito, Yasuyuki; Sugimura, Yoshiro; Sugihara, Michiyuki

1993-01-01

The fabrication process of high current arsenic (As) ion implanted polysilicon (Si) gate and source drain (SD) electrode Si n-channel metal oxide-semiconductor field effect transistor (MOSFET) was examined. Poly Si film n-type doping was performed by using high current (typical current: 2mA) and relatively low acceleration voltage (40keV) As ion implantation technique (Lintott series 3). It was observed that high dose As implanted poly Si films as is show refractoriness against radical fluorine excited by microwave. Using GCA MANN4800 (m/c ID No.2, resist: OFPR) mask pattern printing technique, the high current As ion implantation technique and radical fluorine gas phase etching (Chemical dry etching: CDE) technique, the n-channel Poly Si gate (ρs = ≅100Ω/□) enhancement MQSFETs(ρs source drain = ≅50Ω/□, SiO 2 gate=380 angstrom) with off-leak-less were obtained on 3 inch Czochralski grown 2Ωcm boron doped p type wafers (Osaka titanium). By the same process, a 8 bit single chip μ-processor with 26MHz full operation was performed

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

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

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

Si-O compound formation by oxygen ion implantation into silicon

International Nuclear Information System (INIS)

Hensel, E.; Wollschlaeger, K.; Kreissig, U.; Skorupa, W.; Schulze, D.; Finster, J.

1985-01-01

High dose oxygen ion implantation into silicon at 30 keV was performed to produce understoichiometric and stoichiometric surface oxide layers of approx. 160 nm thickness. The oxygen depth profile and oxide stoichiometry was determined by RBS and XPS. Si-O compound formation was found by IR spectroscopy and XPS in the unannealed samples as well as after target heating, furnace or flash lamp annealing. As implanted understoichiometric layers consist of random bonding like SiOsub(x) (O 2 after annealing. Unannealed stoichiometric layers are bond strained SiO 2 . The activation energies of demixing and of the annealing of bond strains are determined to 0.19 and 0.13 eV, respectively. The removing of bond strains occurs at temperatures >= 800 C in a time shorter than 1 s. The SiO 2 /Si transition region of unannealed stoichiometric layers consists of SiOsub(x) with an extent of about 10 nm. After annealing this extent diminishes to 0.8 to 1 nm in consequence of oxidation by excess oxygen from the overstoichiometric oxide region. This thickness is comparable with that of thermal oxide. (author)

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

Investigation on the utilization of ZrO2-SiO2 composite microspheres for Sr+2 sorption synthesized via sol-gel method

International Nuclear Information System (INIS)

Sert, S.; Tel, H.; Altas, Y.; Eral, M.; Cetinkaya, B.; Inan, S.; Kasap, S.

2009-01-01

Multivalence metal ion's oxides and hydro oxides show high adsorption capacity. These are selective to some kind of ions and show thermal, chemical and radiation resistance. Because of these properties they can be used as a adsorbent for radioactive waste management. It is known that the mix oxide's acidic and basic surface sides and textural (surface area, por side and volume) properties related to mix oxide composition. The previously works shown that the ZrO 2 have high adsorption capacity for Sr + 2. Additionally ZrO 2 is used in production of heat resistance materials, glass and ceramic industries due to it's high melting point. Generally inorganic adsorbents which are crystal forms have low surface area. It is needed that the materials have high surface area and appropriate por size to targeted molecules for take inside adsorbent, in the practical adsorption proses. It is thought that the addition of oxide which has high surface area ( SiO 2 etc.) to between material layer increase it's surface area. Some works showed that the silica increase surface area when mixed Ti in materials structure. Sol-jell proses is a method which is show homogen hetero metal oxide bounds distribution and give advantages to prepare multicomponent oxide materials. In this study, ZrO 2 -SiO 2 -TiO 2 composite microspheres were synthesized by sol-gel method. In synthesis proses; peristaltic pump, nozzle-vibrator system and glass column were used. The optimum Sr 2 + adsorption conditions were determined by 'Central Composite Design' (CCD). Thermodynamic parameters related to adsorption such as ΔHo, ΔSo and ΔGo were calculated. The adsorption data have been interpreted in terms of Langmuir, Freundlich and D-R isotherms.

Non-volatile nano-floating gate memory with Pt-Fe{sub 2}O{sub 3} composite nanoparticles and indium gallium zinc oxide channel

Energy Technology Data Exchange (ETDEWEB)

Hu, Quanli [Myongji University, Department of Nano Science and Engineering (Korea, Republic of); Lee, Seung Chang; Baek, Yoon-Jae [Myongji University, Department of Materials Science and Engineering (Korea, Republic of); Lee, Hyun Ho [Myongji University, Department of Chemical Engineering (Korea, Republic of); Kang, Chi Jung [Myongji University, Department of Nano Science and Engineering (Korea, Republic of); Kim, Hyun-Mi; Kim, Ki-Bum [Seoul National University, Department of Materials Science and Engineering (Korea, Republic of); Yoon, Tae-Sik, E-mail: tsyoon@mju.ac.kr [Myongji University, Department of Nano Science and Engineering (Korea, Republic of)

2013-02-15

Non-volatile nano-floating gate memory characteristics with colloidal Pt-Fe{sub 2}O{sub 3} composite nanoparticles with a mostly core-shell structure and indium gallium zinc oxide channel layer were investigated. The Pt-Fe{sub 2}O{sub 3} nanoparticles were chemically synthesized through the preferential oxidation of Fe and subsequent pileup of Pt into the core in the colloidal solution. The uniformly assembled nanoparticles' layer could be formed with a density of {approx}3 Multiplication-Sign 10{sup 11} cm{sup -2} by a solution-based dip-coating process. The Pt core ({approx}3 nm in diameter) and Fe{sub 2}O{sub 3}-shell ({approx}6 nm in thickness) played the roles of the charge storage node and tunneling barrier, respectively. The device exhibited the hysteresis in current-voltage measurement with a threshold voltage shift of {approx}4.76 V by gate voltage sweeping to +30 V. It also showed the threshold shift of {approx}0.66 V after pulse programming at +20 V for 1 s with retention > {approx}65 % after 10{sup 4} s. These results demonstrate the feasibility of using colloidal nanoparticles with core-shell structure as gate stacks of the charge storage node and tunneling dielectric for low-temperature and solution-based processed non-volatile memory devices.

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.

SiO2 decoration dramatically enhanced the stability of PtRu electrocatalysts with undetectable deterioration in fuel cell performance

Science.gov (United States)

Yu, Xinxin; Xu, Zejun; Yang, Zehui; Xu, Sen; Zhang, Quan; Ling, Ying; Zhang, Yunfeng; Cai, Weiwei

2018-06-01

Prevention of Ru dissolution is essential for steady CO tolerance of anodic electrocatalysts in direct methanol fuel cells. Here, we demonstrate a facile way to stabilize Ru atoms by decorating commercial CB/PtRu with SiO2, which shows a six-fold higher stability and similar activity toward a methanol oxidation reaction leading to no discernible degradation in fuel cell performance compared to commercial CB/PtRu electrocatalysts. The higher stability and stable CO tolerance of SiO2-decorated electrocatalysts originate from the SiO2 coating, since Ru atoms are partially ionized during SiO2 decorating, resulting in difficulties in dissolution; while, in the case of commercial CB/PtRu, the dissolved Ru offers active sites for Pt coalescences and CO species resulting in the rapid decay of the electrochemical surface area and fuel cell performance. To the best of our knowledge, this is the first study about the stabilization of Ru atoms by SiO2. The highest stability is obtained for a PtRu electrocatalyst with negligible effect on the electrochemical properties.

High performance solution processed zirconium oxide gate dielectric appropriate for low temperature device application

Energy Technology Data Exchange (ETDEWEB)

Hasan, Musarrat; Nguyen, Manh-Cuong; Kim, Hyojin; You, Seung-Won; Jeon, Yoon-Seok; Tong, Duc-Tai; Lee, Dong-Hwi; Jeong, Jae Kyeong; Choi, Rino, E-mail: rino.choi@inha.ac.kr

2015-08-31

This paper reports a solution processed electrical device with zirconium oxide gate dielectric that was fabricated at a low enough temperature appropriate for flexible electronics. Both inorganic dielectric and channel materials were synthesized in the same organic solvent. The dielectric constant achieved was 13 at 250 °C with a reasonably low leakage current. The bottom gate transistor devices showed the highest mobility of 75 cm{sup 2}/V s. The device is operated at low voltage with high-k dielectric with excellent transconductance and low threshold voltage. Overall, the results highlight the potential of low temperature solution based deposition in fabricating more complicated circuits for a range of applications. - Highlights: • We develop a low temperature inorganic dielectric deposition process. • We fabricate oxide semiconductor channel devices using all-solution processes. • Same solvent is used for dielectric and oxide semiconductor deposition.

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.

Reaction analysis of initial oxidation of silicon by UV-light-excited ozone and the application to rapid and uniform SiO2 film growth

International Nuclear Information System (INIS)

Tosaka, Aki; Nonaka, Hidehiko; Ichimura, Shingo; Nishiguchi, Tetsuya

2007-01-01

UV-light-excited O 3 prepared by irradiation of nearly 100% pure O 3 with a KrF excimer laser (λ=248 nm, irradiated area=30x10 mm 2 ) was utilized for low-temperature Si oxidation. The initial oxidation rate was determined, and the activation energy was shown to be almost zero (0.049 eV). To clarify the optimum oxidation conditions, the dependence of the SiO 2 film growth rate on the total photon number and the photon density was investigated. The evolution of O 3 density after UV-light irradiation was experimentally measured, and the O( 1 D) density change is discussed. O( 1 D) density changes are successfully explained by using a second-order reaction model, indicating that a pulse supply of oxygen atoms is essential in the initial oxidation process. The uniform oxidation of 8 in. Si wafer has been carried out using a wafer-transfer type chamber by irradiating the wafer with KrF excimer laser light expanded linearly to the wafer width by a concave lens

Indium-gallium-zinc-oxide thin-film transistor with a planar split dual-gate structure

Science.gov (United States)

Liu, Yu-Rong; Liu, Jie; Song, Jia-Qi; Lai, Pui-To; Yao, Ruo-He

2017-12-01

An amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) with a planar split dual gate (PSDG) structure has been proposed, fabricated and characterized. Experimental results indicate that the two independent gates can provide dynamical control of device characteristics such as threshold voltage, sub-threshold swing, off-state current and saturation current. The transconductance extracted from the output characteristics of the device increases from 4.0 × 10-6S to 1.6 × 10-5S for a change of control gate voltage from -2 V to 2 V, and thus the device could be used in a variable-gain amplifier. A significant advantage of the PSDG structure is its flexibility in controlling the device performance according to the need of practical applications.

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.

Fracto- mechanoluminescence and thermoluminescence properties of orange-red emitting Eu3+ doped Ca2Al2SiO7 phosphors

International Nuclear Information System (INIS)

Tiwari, Geetanjali; Brahme, Nameeta; Sharma, Ravi; Bisen, D.P.; Sao, Sanjay K.; Khare, Ayush

2017-01-01

The suitability of nano-structured Ca 2 Al 2 SiO 7 :Eu 3+ phosphors for thermoluminescence and mechanoluminescence dosimeter were investigated. Europium doped di-calcium di-aluminum silicate phosphor was synthesised by the combustion assisted method and annealed at 1100 °C for 4 h in reducing and oxidizing environments. The prepared Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDX), photoluminescence (PL) and decay characteristics. The phase structure of sintered phosphor has akermanite type which belongs to the tetragonal crystallography; this structure is a member of the melilite group and forms a layered compound. The chemical composition of the sintered Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was confirmed by EDX spectra. Mechanoluminescence (ML) and thermoluminescence (TL) studies revealed that the ML and TL intensity increases with activator concentration. Optimum ML was observed for the sample having 2 mol% of Eu ions. The TL intensity of Ca 2 Al 2 SiO 7 :Eu 3+ was recorded for different exposure times of γ -irradiation and it was observed that TL intensity is maximum for γ dose of 1770 Gy. The PL spectra indicated that Ca 2 Al 2 SiO 7 :Eu 3+ could be excited effectively by near ultraviolet (NUV) light and exhibited bright orange-red emission with excellent colour stability. CIE colour coordinates of the prepared Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was found suitable as orange-red light emitting phosphor with a CIE value of (x=0.6142, y=0.3849) and correlated colour temperature (CCT) is 1250 K. Therefore, it is considered to be a new promising orange-red emitting phosphor for white light emitting diode (LED) application.

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.

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.

GaN MOSHEMT employing HfO2 as a gate dielectric with partially etched barrier

Science.gov (United States)

Han, Kefeng; Zhu, Lin

2017-09-01

In order to suppress the gate leakage current of a GaN high electron mobility transistor (GaN HEMT), a GaN metal-oxide-semiconductor high electron mobility transistor (MOSHEMT) is proposed, in which a metal-oxide-semiconductor gate with high-dielectric-constant HfO2 as an insulating dielectric is employed to replace the traditional GaN HEMT Schottky gate. A 0.5 μm gate length GaN MOSHEMT was fabricated based on the proposed structure, the {{{Al}}}0.28{{{Ga}}}0.72{{N}} barrier layer is partially etched to produce a higher transconductance without deteriorating the transport characteristics of the two-dimensional electron gas in the channel, the gate dielectric is HfO2 deposited by atomic layer deposition. Current-voltage characteristics and radio frequency characteristics are obtained after device preparation, the maximum current density of the device is 900 mA mm-1, the source-drain breakdown voltage is 75 V, gate current is significantly suppressed and the forward gate voltage swing range is about ten times higher than traditional GaN HEMTs, the GaN MOSHEMT also demonstrates radio frequency characteristics comparable to traditional GaN HEMTs with the same gate length.

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.

Effective surface modification of MnFe2O4@SiO2@PMIDA magnetic nanoparticles for rapid and high-density antibody immobilization

Science.gov (United States)

Rashid, Zahra; Soleimani, Masoud; Ghahremanzadeh, Ramin; Vossoughi, Manouchehr; Esmaeili, Elaheh

2017-12-01

The present study is aimed at the synthesis of MnFe2O4@SiO2@PMIDA in terms of highly efficient sensing platform for anti-prostate specific membrane antigen (PSMA) immobilization. Superparamagnetic manganese ferrite nanoparticles were synthesized following co-precipitation method and then SiO2 shell was coated on the magnetic core with tetraethyl orthosilicate (TEOS) through a silanization reaction to prevent oxidation, agglomeration and, increase the density of OH groups on the surface of MnFe2O4. Subsequently, MnFe2O4@SiO2@PMIDA obtained as a result of the reaction between N-(phosphonomethyl)iminodiacetic acid (PMIDA) and MnFe2O4@SiO2. The reactive carboxyl groups on the surface of magnetic nanoparticles can efficiently conjugate to a monoclonal antibody, specific to PSMA, which was confirmed by enzyme-linked immune sorbent assay (ELISA). Thus, this kind of functionalized magnetic nanoparticles is promising to be utilized in the improvement of ELISA-based biosensors and also will be effective in a variety of biomedical applications such as cell separation, diagnosis, and monitoring of human diseases.

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.

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

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

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

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.

Multifunctional Roles of TiO 2 Nanoparticles for Architecture of Complex Core−Shells and Hollow Spheres of SiO 2 −TiO 2 −Polyaniline System

KAUST Repository

Wang, Dan Ping; Zeng, Hua Chun

2009-01-01

to prepare inorganic-polymer nanocomposites. In this work, we explore the roles of metal-oxide nanoparticles (anatase TiO2) in the area of constructional synthesis of highly complex core-shell and hollow sphere nanostructures comprising SiO2, TiO2

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

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

LEACHABILITY OF CHROME FROM MAGNESIA-CHROMITE REFRACTORY BRICKS CORRODED BY Cu/CuO- Na2O.2SiO2 SLAGS

Directory of Open Access Journals (Sweden)

David Medved

2015-06-01

Full Text Available The interactions of magnesia-chromite refractory brick with Cu-Na2O.2SiO2 and CuO-Na2O.2SiO2 melts are studied and the chemical durability of corrosion products in water is evaluated. The corrosion tests confirm intensive infiltration of the slag melts into the tested refractory bricks and formation of Cr(6+ compounds. The molten copper partially oxidizes during corrosion test by air and penetrates into bricks. Interactions among periclase (MgO and chromite (FeCr2O4 grains with the melt Na2O.2SiO2 and copper oxides makes possible to form several compounds (e.g. Cu2MgO3, CuCrO4, CaCrO4, Na2CrO4, MgCrO4. Just the marked yellow spots, which were observed on the corroded brick surface after 30 days of free storage, suggest hydration of the high-temperature corrosion products. The yellow color of spots points out to chromates as Na2CrO4 and MgCrO4, which are well soluble in water. The leaching of corroded bricks in water (batch leaching test of a ratio of S (solid : W (water = 0.1 taking up to 28 days confirmed the Cr, Na, Mg and Ca ions leach-out. The pH value of solution increased up to 9 during leaching mainly as a consequence of elevated Na+ ion concentration. The Cr ion concentration rises in the solution up to 1 mmol.l-1. The observed moderate decrease of Cr ion concentration in the solution with the length of leaching indicates super-saturation of the solution and precipitation of the products.

Nonvolatile memory characteristics in metal-oxide-semiconductors containing metal nanoparticles fabricated by using a unique laser irradiation method

International Nuclear Information System (INIS)

Yang, JungYup; Yoon, KapSoo; Kim, JuHyung; Choi, WonJun; Do, YoungHo; Kim, ChaeOk; Hong, JinPyo

2006-01-01

Metal-oxide-semiconductor (MOS) capacitors with metal nanoparticles (Co NP) were successfully fabricated by utilizing an external laser exposure technique for application of non-volatile memories. Images of high-resolution transmission electron microscopy reveal that the spherically shaped Co NP are clearly embedded in the gate oxide layer. Capacitance-voltage measurements exhibit typical charging and discharging effects with a large flat-band shift. The effects of the tunnel oxide thickness and the different tunnel materials are analyzed using capacitance-voltage and retention characteristics. In addition, the memory characteristics of the NP embedded in a high-permittivity material are investigated because the thickness of conventionally available SiO 2 gates is approaching the quantum tunneling limit as devices are scaled down. Finally, the suitability of NP memory devices for nonvolatile memory applications is also discussed. The present results suggest that our unique laser exposure technique holds promise for the NP formation as floating gate elements in nonvolatile NP memories and that the quality of the tunnel oxide is very important for enhancing the retention properties of nonvolatile memory.

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

Physical and electrical characteristics of AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors with rare earth Er2O3 as a gate dielectric

International Nuclear Information System (INIS)

Lin, Ray-Ming; Chu, Fu-Chuan; Das, Atanu; Liao, Sheng-Yu; Chou, Shu-Tsun; Chang, Liann-Be

2013-01-01

In this study, the rare earth erbium oxide (Er 2 O 3 ) was deposited using an electron beam onto an AlGaN/GaN heterostructure to fabricate metal-oxide-semiconductor high-electron-mobility transistors (MOS–HEMTs) that exhibited device performance superior to that of a conventional HEMT. Under similar bias conditions, the gate leakage currents of these MOS–HEMT devices were four orders of magnitude lower than those of conventional Schottky gate HEMTs. The measured sub-threshold swing (SS) and the effective trap state density (N t ) of the MOS–HEMT were 125 mV/decade and 4.3 × 10 12 cm −2 , respectively. The dielectric constant of the Er 2 O 3 layer in this study was 14, as determined through capacitance–voltage measurements. In addition, the gate–source reverse breakdown voltage increased from –166 V for the conventional HEMT to –196 V for the Er 2 O 3 MOS–HEMT. - Highlights: ► GaN/AlGaN/Er 2 O 3 metal-oxide semiconductor high electron mobility transistor ► Physical and electrical characteristics are presented. ► Electron beam evaporated Er 2 O 3 with excellent surface roughness ► Device exhibits reduced gate leakage current and improved I ON /I OFF ratio

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

Nanogranular SiO{sub 2} proton gated silicon layer transistor mimicking biological synapses

Energy Technology Data Exchange (ETDEWEB)

Liu, M. J.; Huang, G. S., E-mail: gshuang@fudan.edu.cn, E-mail: pfeng@nju.edu.cn; Guo, Q. L.; Tian, Z. A.; Li, G. J.; Mei, Y. F. [Department of Materials Science, Fudan University, Shanghai 200433 (China); Feng, P., E-mail: gshuang@fudan.edu.cn, E-mail: pfeng@nju.edu.cn; Shao, F.; Wan, Q. [School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

2016-06-20

Silicon on insulator (SOI)-based transistors gated by nanogranular SiO{sub 2} proton conducting electrolytes were fabricated to mimic synapse behaviors. This SOI-based device has both top proton gate and bottom buried oxide gate. Electrical transfer properties of top proton gate show hysteresis curves different from those of bottom gate, and therefore, excitatory post-synaptic current and paired pulse facilitation (PPF) behavior of biological synapses are mimicked. Moreover, we noticed that PPF index can be effectively tuned by the spike interval applied on the top proton gate. Synaptic behaviors and functions, like short-term memory, and its properties are also experimentally demonstrated in our device. Such SOI-based electronic synapses are promising for building neuromorphic systems.

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.

Reliability study of ultra-thin gate oxides on strained-Si/SiGe MOS structures

International Nuclear Information System (INIS)

Varzgar, John B.; Kanoun, Mehdi; Uppal, Suresh; Chattopadhyay, Sanatan; Tsang, Yuk Lun; Escobedo-Cousins, Enrique; Olsen, Sarah H.; O'Neill, Anthony; Hellstroem, Per-Erik; Edholm, Jonas; Ostling, Mikael; Lyutovich, Klara; Oehme, Michael; Kasper, Erich

2006-01-01

The reliability of gate oxides on bulk Si and strained Si (s-Si) has been evaluated using constant voltage stressing (CVS) to investigate their breakdown characteristics. The s-Si architectures exhibit a shorter life time compared to that of bulk Si, which is attributed to higher bulk oxide charges (Q ox ) and increased surface roughness in the s-Si structures. The gate oxide in the s-Si structure exhibits a hard breakdown (HBD) at 1.9 x 10 4 s, whereas HBD is not observed in bulk Si up to a measurement period of 1.44 x 10 5 s. The shorter lifetime of the s-Si gate oxide is attributed to a larger injected charge (Q inj ) compared to Q inj in bulk Si. Current-voltage (I-V) measurements for bulk Si samples at different stress intervals show an increase in stress induced leakage current (SILC) of two orders in the low voltage regime from zero stress time to up to 5 x 10 4 s. In contrast, superior performance enhancements in terms of drain current, maximum transconductance and effective channel mobility are observed in s-Si MOSFET devices compared to bulk Si. The results from this study indicate that further improvement in gate oxide reliability is needed to exploit the sustained performance enhancement of s-Si devices over bulk Si

Impact of oxide thickness on gate capacitance – Modelling and ...

Indian Academy of Sciences (India)

Department of Electronics and Communication Engineering, National ... conventional HEMT, Schottky barrier diode is formed at the gate electrode. .... term corresponds to the energy required for the electric field in the oxide layer and the.

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)

Low-power DRAM-compatible Replacement Gate High-k/Metal Gate Stacks

Science.gov (United States)

Ritzenthaler, R.; Schram, T.; Bury, E.; Spessot, A.; Caillat, C.; Srividya, V.; Sebaai, F.; Mitard, J.; Ragnarsson, L.-Å.; Groeseneken, G.; Horiguchi, N.; Fazan, P.; Thean, A.

2013-06-01

In this work, the possibility of integration of High-k/Metal Gate (HKMG), Replacement Metal Gate (RMG) gate stacks for low power DRAM compatible transistors is studied. First, it is shown that RMG gate stacks used for Logic applications need to be seriously reconsidered, because of the additional anneal(s) needed in a DRAM process. New solutions are therefore developed. A PMOS stack HfO2/TiN with TiN deposited in three times combined with Work Function metal oxidations is demonstrated, featuring a very good Work Function of 4.95 eV. On the other hand, the NMOS side is shown to be a thornier problem to solve: a new solution based on the use of oxidized Ta as a diffusion barrier is proposed, and a HfO2/TiN/TaOX/TiAl/TiN/TiN gate stack featuring an aggressive Work Function of 4.35 eV (allowing a Work Function separation of 600 mV between NMOS and PMOS) is demonstrated. This work paves the way toward the integration of gate-last options for DRAM periphery transistors.

Wannier–Stark electro-optical effect, quasi-guided and photonic modes in 2D macroporous silicon structures with SiO_2 coatings

International Nuclear Information System (INIS)

Karachevtseva, L.; Goltviansky, Yu.; Sapelnikova, O.; Lytvynenko, O.; Stronska, O.; Bo, Wang; Kartel, M.

2016-01-01

Highlights: • The IR absorption spectra of oxidized macroporous silicon were studied. • The Wannier–Stark electro-optical effect on Si-SiO_2 boundary was confirmed. • An additional electric field of quasi-guided optical modes was evaluated. • The photonic modes and band gaps were measured as peculiarities in absorption spectra. - Abstract: Opportunities to enhance the properties of structured surfaces were demonstrated on 2D macroporous silicon structures with SiO_2 coatings. We investigated the IR light absorption oscillations in macroporous silicon structures with SiO2 coatings 0–800 nm thick. The Wannier–Stark electro-optical effect due to strong electric field on Si-SiO_2boundary and an additional electric field of quasi-guided optical modes were taken into account. The photonic modes and band gaps were also considered as peculiarities in absorbance spectra of macroporous silicon structures with a thick SiO_2 coating. The photonic modes do not coincide with the quasi-guided modes in the silicon matrix and do not appear in absorption spectra of 2D macroporous silicon structures with surface nanocrystals.

The TDDB Characteristics of Ultra-Thin Gate Oxide MOS Capacitors under Constant Voltage Stress and Substrate Hot-Carrier Injection

Directory of Open Access Journals (Sweden)

Jingyu Shen

2018-01-01

Full Text Available The breakdown characteristics of ultra-thin gate oxide MOS capacitors fabricated in 65 nm CMOS technology under constant voltage stress and substrate hot-carrier injection are investigated. Compared to normal thick gate oxide, the degradation mechanism of time-dependent dielectric breakdown (TDDB of ultra-thin gate oxide is found to be different. It is found that the gate current (Ig of ultra-thin gate oxide MOS capacitor is more likely to be induced not only by Fowler-Nordheim (F-N tunneling electrons, but also by electrons surmounting barrier and penetrating electrons in the condition of constant voltage stress. Moreover it is shown that the time to breakdown (tbd under substrate hot-carrier injection is far less than that under constant voltage stress when the failure criterion is defined as a hard breakdown according to the experimental results. The TDDB mechanism of ultra-thin gate oxide will be detailed. The differences in TDDB characteristics of MOS capacitors induced by constant voltage stress and substrate hot-carrier injection will be also discussed.

Contribution to the study of metal-oxide-semiconductor devices with optical access. In2O3-SiO2-Si structure

International Nuclear Information System (INIS)

Thenoz, Yves.

1974-01-01

A general study of the fabrication of the structure In 2 O 3 /SiO 2 /Si was made encompassing the problems posed during the realization of these structures. The sputtering study enabled the influence of the main parameters on layer properties to be determined. The decisive importance of clean conditions throughout fabrication (especially during sputtering) on the properties of In 2 O 3 layers and on those of the structure and its stability was revealed. However, the problem of ageing of the structure were not investigated. Finally, the construction of MOS capacitors and transistors showed that In 2 O 3 /SiO 2 /Si structures can be used in MOS circuits [fr

Metabolomic effects of CeO2, SiO2 and CuO metal oxide nanomaterials on HepG2 cells

Science.gov (United States)

To better assess potential hepatotoxicity of nanomaterials, human liver HepG2 cells were exposed for 3 days to five different CeO2 (either 30 or 100 μg/ml), 3 SiO2 based (30 μg/ml) or 1 CuO (3 μg/ml) nanomaterials with dry primary particle sizes ranging from 15 to 213 nm. Metabol...

Impacts of oxidants in atomic layer deposition method on Al2O3/GaN interface properties

Science.gov (United States)

Taoka, Noriyuki; Kubo, Toshiharu; Yamada, Toshikazu; Egawa, Takashi; Shimizu, Mitsuaki

2018-01-01

The electrical interface properties of GaN metal-oxide-semiconductor (MOS) capacitors with an Al2O3 gate insulator formed by atomic layer deposition method using three kinds of oxidants were investigated by the capacitance-voltage technique, Terman method, and conductance method. We found that O3 and the alternate supply of H2O and O3 (AS-HO) are effective for reducing the interface trap density (D it) at the energy range of 0.15 to 0.30 eV taking from the conduction band minimum. On the other hand, we found that surface potential fluctuation (σs) induced by interface charges for the AS-HO oxidant is much larger than that for a Si MOS capacitor with a SiO2 layer formed by chemical vapor deposition despite the small D it values for the AS-HO oxidant compared with the Si MOS capacitor. This means that the total charged center density including the fixed charge density, charged slow trap density, and charged interface trap density for the GaN MOS capacitor is higher than that for the Si MOS capacitor. Therefore, σs has to be reduced to improve the performances and reliability of GaN devices with the Al2O3/GaN interfaces.

Pulsed laser deposition of oxide gate dielectrics for pentacene organic field-effect transistors

International Nuclear Information System (INIS)

Yaginuma, S.; Yamaguchi, J.; Itaka, K.; Koinuma, H.

2005-01-01

We have fabricated Al 2 O 3 , LaAlO 3 (LAO), CaHfO 3 (CHO) and CaZrO 3 (CZO) thin films for the dielectric layers of field-effect transistors (FETs) by pulsed laser deposition (PLD). The films exhibited very smooth surfaces with root-mean-squares (rms) roughnesses of ∼1.3 A as evaluated by using atomic force microscopy (AFM). The breakdown electric fields of Al 2 O 3 , LAO, CHO and CZO films were 7, 6, 10 and 2 MV/cm, respectively. The magnitude of the leak current in each film was low enough to operate FET. We performed a comparative study of pentacene FET fabricated using these oxide dielectrics as gate insulators. High field-effect mobility of 1.4 cm 2 /V s and on/off current ratio of 10 7 were obtained in the pentacene FET using LAO gate insulating film. Use of the LAO films as gate dielectrics has been found to suppress the hysteresis of pentacene FET operations. The LAO films are relevant to the dielectric layer of organic FETs

Investigation of Electrical and Optical Characteristics of Nanohybride Composite (Polyvinyl Alcohol / Nickel Oxide

Directory of Open Access Journals (Sweden)

A. Hayati

2014-01-01

Full Text Available Some issues; leakage, tunneling currents, boron diffusion are threatening SiO2 to be used as a good gate dielectric for the future of the CMOS (complementary metal- oxide- semiconductor transistors. For finding an alternative and novel gate dielectric, the NiO (Nickel oxide and PVA (polyvinyl alcohol nano powders were synthesized with the sol-gel method and their nano structural properties were studied using the X-ray diffraction (XRD, Atomic force microscopy (AFM, Scanning electron microscopy (SEM, UV-Vis spectrophotometer and GPS 132 techniques. The obtained results indicated that the sample (5 g NiO and 0.02g PVA prepared at 30˚C, annealed in an oven at a temperature of 80˚C can fill this gap due to its higher dielectric constant, better morphology, less rough surface and less leakage current.

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.

Structured-gate organic field-effect transistors

International Nuclear Information System (INIS)

Aljada, Muhsen; Pandey, Ajay K; Velusamy, Marappan; Burn, Paul L; Meredith, Paul; Namdas, Ebinazar B

2012-01-01

We report the fabrication and electrical characteristics of structured-gate organic field-effect transistors consisting of a gate electrode patterned with three-dimensional pillars. The pillar gate electrode was over-coated with a gate dielectric (SiO 2 ) and solution processed organic semiconductors producing both unipolar p-type and bipolar behaviour. We show that this new structured-gate architecture delivers higher source-drain currents, higher gate capacitance per unit equivalent linear channel area, and enhanced charge injection (electrons and/or holes) versus the conventional planar structure in all modes of operation. For the bipolar field-effect transistor (FET) the maximum source-drain current enhancements in p- and n-channel mode were >600% and 28%, respectively, leading to p and n charge mobilities with the same order of magnitude. Thus, we have demonstrated that it is possible to use the FET architecture to manipulate and match carrier mobilities of material combinations where one charge carrier is normally dominant. Mobility matching is advantageous for creating organic logic circuit elements such as inverters and amplifiers. Hence, the method represents a facile and generic strategy for improving the performance of standard organic semiconductors as well as new materials and blends. (paper)

Structured-gate organic field-effect transistors

Science.gov (United States)

Aljada, Muhsen; Pandey, Ajay K.; Velusamy, Marappan; Burn, Paul L.; Meredith, Paul; Namdas, Ebinazar B.

2012-06-01

We report the fabrication and electrical characteristics of structured-gate organic field-effect transistors consisting of a gate electrode patterned with three-dimensional pillars. The pillar gate electrode was over-coated with a gate dielectric (SiO2) and solution processed organic semiconductors producing both unipolar p-type and bipolar behaviour. We show that this new structured-gate architecture delivers higher source-drain currents, higher gate capacitance per unit equivalent linear channel area, and enhanced charge injection (electrons and/or holes) versus the conventional planar structure in all modes of operation. For the bipolar field-effect transistor (FET) the maximum source-drain current enhancements in p- and n-channel mode were >600% and 28%, respectively, leading to p and n charge mobilities with the same order of magnitude. Thus, we have demonstrated that it is possible to use the FET architecture to manipulate and match carrier mobilities of material combinations where one charge carrier is normally dominant. Mobility matching is advantageous for creating organic logic circuit elements such as inverters and amplifiers. Hence, the method represents a facile and generic strategy for improving the performance of standard organic semiconductors as well as new materials and blends.

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)

An oxide filled extended trench gate super junction MOSFET structure

International Nuclear Information System (INIS)

Cai-Lin, Wang; Jun, Sun

2009-01-01

This paper proposes an oxide filled extended trench gate super junction (SJ) MOSFET structure to meet the need of higher frequency power switches application. Compared with the conventional trench gate SJ MOSFET, new structure has the smaller input and output capacitances, and the remarkable improvements in the breakdown voltage, on-resistance and switching speed. Furthermore, the SJ in the new structure can be realized by the existing trench etching and shallow angle implantation, which offers more freedom to SJ MOSFET device design and fabrication. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Transfer-free graphene synthesis on sapphire by catalyst metal agglomeration technique and demonstration of top-gate field-effect transistors

International Nuclear Information System (INIS)

Miyoshi, Makoto; Arima, Yukinori; Kubo, Toshiharu; Egawa, Takashi; Mizuno, Masaya; Soga, Tetsuo

2015-01-01

Transfer-free graphene synthesis was performed on sapphire substrates by using the catalyst metal agglomeration technique, and the graphene film quality was compared to that synthesized on sputtered SiO 2 /Si substrates. Raman scattering measurements indicated that the graphene film on sapphire has better structural qualities than that on sputtered SiO 2 /Si substrates. The cross-sectional transmission microscopic study also revealed that the film flatness was drastically improved by using sapphire substrates instead of sputtered SiO 2 /Si substrates. These quality improvements seemed to be due the chemical and thermal stabilities of sapphire. Top-gate field-effect transistors were fabricated using the graphene films on sapphire, and it was confirmed that their drain current can be modulated with applied gate voltages. The maximum field-effect mobilities were estimated to be 720 cm 2 /V s for electrons and 880 cm 2 /V s for holes, respectively

SEMICONDUCTOR DEVICES: Structural and electrical characteristics of lanthanum oxide gate dielectric film on GaAs pHEMT technology

Science.gov (United States)

Chia-Song, Wu; Hsing-Chung, Liu

2009-11-01

This paper investigates the feasibility of using a lanthanum oxide thin film (La2O3) with a high dielectric constant as a gate dielectric on GaAs pHEMTs to reduce gate leakage current and improve the gate to drain breakdown voltage relative to the conventional GaAs pHEMT. An E/D mode pHEMT in a single chip was realized by selecting the appropriate La2O3 thickness. The thin La2O3 film was characterized: its chemical composition and crystalline structure were determined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. La2O3 exhibited good thermal stability after post-deposition annealing at 200, 400 and 600 °C because of its high binding-energy (835.6 eV). Experimental results clearly demonstrated that the La2O3 thin film was thermally stable. The DC and RF characteristics of Pt/La2O3/Ti/Au gate and conventional Pt/Ti/Au gate pHEMTs were examined. The measurements indicated that the transistor with the Pt/La2O3/Ti/Au gate had a higher breakdown voltage and lower gate leakage current. Accordingly, the La2O3 thin film is a potential high-k material for use as a gate dielectric to improve electrical performance and the thermal effect in high-power applications.

Research on total-dose hardening for H-gate PD NMOSFET/SIMOX by ion implanting into buried oxide

International Nuclear Information System (INIS)

Qian Cong; Zhang Zhengxuan; Zhang Feng; Lin Chenglu

2008-01-01

In this work, we investigate the back-gate I-V characteristics for two kinds of NMOSFET/SIMOX transistors with H gate structure fabricated on two different SOI wafers. A transistors are made on the wafer implanted with Si + and then annealed in N 2 , and B transistors are made on the wafer without implantation and annealing. It is demonstrated experimentally that A transistors have much less back-gate threshold voltage shift ΔV th than B transistors under X-ray total close irradiation. Subthreshold charge separation technique is employed to estimate the build-up of oxide charge and interface traps during irradiation, showing that the reduced ΔV th for A transistors is mainly due to its less build-up of oxide charge than B transistors. Photo-luminescence (PL) research indicates that Si implantation results in the formation of silicon nanocrystalline (nanocluster) whose size increases with the implant dose. This structure can trap electrons to compensate the positive charge build-up in the buried oxide during irradiation, and thus reduce the threshold voltage negative shift. (authors)

Comparison Study on the Microstructure of Nanocrystalline TiO2 in Different Ti-Si Binary Oxides

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

Three different Ti-Si oxide structuares, silica supported titania, silica coated titania and intimately mixed silicatitania, containing 10%-40% SiO2, were made by sol-gel process. The variations of microstructure parameters of nanocrystalline (nc) TiO2-anatase in the three kirds of binary oxides, including in-plane spacing d, cell constants (a0, CQ), cell volume V, cell axial ratio c0/a0 and crystal grain size, were comparatively investigated by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). It is found that the microstructure parameters vary remarkably with increasing SiO2 content and annealing temperature. Different structured Ti-Si binary oxides lead to different variation tendencies of microstructure parameters. The more SiO2 the binary oxide contains, the more lattice defects of nc TiO2-anatase appear; diffusion or migration of Si cations could be an important influential factor in the variations of microstructure. The grain size of nc TiO2 in the three kinds of binary oxides not only depends on SiO2 content and annealing temperature but also on the degree of lattice microstrain and distortion of nc TiO2-anatase. Both grain size and phase transformation of nc TiO2-anatase are effectively inhibited with increasing SiOa content.

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...

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...

In2Ga2ZnO7 oxide semiconductor based charge trap device for NAND flash memory

Science.gov (United States)

Hwang, Eun Suk; Kim, Jun Shik; Jeon, Seok Min; Lee, Seung Jun; Jang, Younjin; Cho, Deok-Yong; Hwang, Cheol Seong

2018-04-01

The programming characteristics of charge trap flash memory device adopting amorphous In2Ga2ZnO7 (a-IGZO) oxide semiconductors as channel layer were evaluated. Metal-organic chemical vapor deposition (MOCVD) and RF-sputtering processes were used to grow a 45 nm thick a-IGZO layer on a 20 nm thick SiO2 (blocking oxide)/p++-Si (control gate) substrate, where 3 nm thick atomic layer deposited Al2O3 (tunneling oxide) and 5 nm thick low-pressure CVD Si3N4 (charge trap) layers were intervened between the a-IGZO and substrate. Despite the identical stoichiometry and other physicochemical properties of the MOCVD and sputtered a-IGZO, a much faster programming speed of MOCVD a-IGZO was observed. A comparable amount of oxygen vacancies was found in both MOCVD and sputtered a-IGZO, confirmed by x-ray photoelectron spectroscopy and bias-illumination-instability test measurements. Ultraviolet photoelectron spectroscopy analysis revealed a higher Fermi level (E F) of the MOCVD a-IGZO (∼0.3 eV) film than that of the sputtered a-IGZO, which could be ascribed to the higher hydrogen concentration in the MOCVD a-IGZO film. Since the programming in a flash memory device is governed by the tunneling of electrons from the channel to charge trapping layer, the faster programming performance could be the result of a higher E F of MOCVD a-IGZO.

Low-temperature formation of high-quality gate oxide by ultraviolet irradiation on spin-on-glass

Energy Technology Data Exchange (ETDEWEB)

Usuda, R.; Uchida, K.; Nozaki, S., E-mail: nozaki@ee.uec.ac.jp [Graduate School of Informatics and Engineering, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182-1515 (Japan)

2015-11-02

Although a UV cure was found to effectively convert a perhydropolysilazane (PHPS) spin-on-glass film into a dense SiO{sub x} film at low temperature, the electrical characteristics were never reported in order to recommend the use of PHPS as a gate-oxide material that can be formed at low temperature. We have formed a high-quality gate oxide by UV irradiation on the PHPS film, and obtained an interface midgap trap density of 3.4 × 10{sup 11 }cm{sup −2} eV{sup −1} by the UV wet oxidation and UV post-metallization annealing (PMA), at a temperature as low as 160 °C. In contrast to the UV irradiation using short-wavelength UV light, which is well known to enhance oxidation by the production of the excited states of oxygen, the UV irradiation was carried out using longer-wavelength UV light from a metal halide lamp. The UV irradiation during the wet oxidation of the PHPS film generates electron-hole pairs. The electrons ionize the H{sub 2}O molecules and facilitate dissociation of the molecules into H and OH{sup −}. The OH{sup −} ions are highly reactive with Si and improve the stoichiometry of the oxide. The UV irradiation during the PMA excites the electrons from the accumulation layer, and the built-in electric field makes the electron injection into the oxide much easier. The electrons injected into the oxide recombine with the trapped holes, which have caused a large negative flat band voltage shift after the UV wet oxidation, and also ionize the H{sub 2}O molecules. The ionization results in the electron stimulated dissociation of H{sub 2}O molecules and the decreased interface trap density.

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.

Bias-induced migration of ionized donors in amorphous oxide semiconductor thin-film transistors with full bottom-gate and partial top-gate structures

Directory of Open Access Journals (Sweden)

Mallory Mativenga

2012-09-01

Full Text Available Bias-induced charge migration in amorphous oxide semiconductor thin-film transistors (TFTs confirmed by overshoots of mobility after bias stressing dual gated TFTs is presented. The overshoots in mobility are reversible and only occur in TFTs with a full bottom-gate (covers the whole channel and partial top-gate (covers only a portion of the channel, indicating a bias-induced uneven distribution of ionized donors: Ionized donors migrate towards the region of the channel that is located underneath the partial top-gate and the decrease in the density of ionized donors in the uncovered portion results in the reversible increase in mobility.

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

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.

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

Lateral protonic/electronic hybrid oxide thin-film transistor gated by SiO{sub 2} nanogranular films

Energy Technology Data Exchange (ETDEWEB)

Zhu, Li Qiang, E-mail: lqzhu@nimte.ac.cn; Chao, Jin Yu; Xiao, Hui [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

2014-12-15

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{sub 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.

Material parameters from frequency dispersion simulation of floating gate memory with Ge nanocrystals in HfO2

Science.gov (United States)

Palade, C.; Lepadatu, A. M.; Slav, A.; Lazanu, S.; Teodorescu, V. S.; Stoica, T.; Ciurea, M. L.

2018-01-01

Trilayer memory capacitors with Ge nanocrystals (NCs) floating gate in HfO2 were obtained by magnetron sputtering deposition on p-type Si substrate followed by rapid thermal annealing at relatively low temperature of 600 °C. The frequency dispersion of capacitance and resistance was measured in accumulation regime of Al/HfO2 gate oxide/Ge NCs in HfO2 floating gate/HfO2 tunnel oxide/SiOx/p-Si/Al memory capacitors. For simulation of the frequency dispersion a complex circuit model was used considering an equivalent parallel RC circuit for each layer of the trilayer structure. A series resistance due to metallic contacts and Si substrate was necessary to be included in the model. A very good fit to the experimental data was obtained and the parameters of each layer in the memory capacitor, i.e. capacitances and resistances were determined and in turn the intrinsic material parameters, i.e. dielectric constants and resistivities of layers were evaluated. The results are very important for the study and optimization of the hysteresis behaviour of floating gate memories based on NCs embedded in oxide.

Epitaxial ZnO gate dielectrics deposited by RF sputter for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors

Science.gov (United States)

Yoon, Seonno; Lee, Seungmin; Kim, Hyun-Seop; Cha, Ho-Young; Lee, Hi-Deok; Oh, Jungwoo

2018-01-01

Radio frequency (RF)-sputtered ZnO gate dielectrics for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) were investigated with varying O2/Ar ratios. The ZnO deposited with a low oxygen content of 4.5% showed a high dielectric constant and low interface trap density due to the compensation of oxygen vacancies during the sputtering process. The good capacitance-voltage characteristics of ZnO-on-AlGaN/GaN capacitors resulted from the high crystallinity of oxide at the interface, as investigated by x-ray diffraction and high-resolution transmission electron microscopy. The MOS-HEMTs demonstrated comparable output electrical characteristics with conventional Ni/Au HEMTs but a lower gate leakage current. At a gate voltage of -20 V, the typical gate leakage current for a MOS-HEMT with a gate length of 6 μm and width of 100 μm was found to be as low as 8.2 × 10-7 mA mm-1, which was three orders lower than that of the Ni/Au Schottky gate HEMT. The reduction of the gate leakage current improved the on/off current ratio by three orders of magnitude. These results indicate that RF-sputtered ZnO with a low O2/Ar ratio is a good gate dielectric for high-performance AlGaN/GaN MOS-HEMTs.

Ambipolar transport in CVD grown MoSe2 monolayer using an ionic liquid gel gate dielectric

Directory of Open Access Journals (Sweden)

Deliris N. Ortiz

2018-03-01

Full Text Available CVD grown MoSe2 monolayers were electrically characterized at room temperature in a field effect transistor (FET configuration using an ionic liquid (IL as the gate dielectric. During the growth, instead of using MoO3 powder, ammonium heptamolybdate was used for better Mo control of the source and sodium cholate added for lager MoSe2 growth areas. In addition, a high specific capacitance (∼7 μF/cm2 IL was used as the gate dielectric to significantly reduce the operating voltage. The device exhibited ambipolar charge transport at low voltages with enhanced parameters during n- and p-FET operation. IL gating thins the Schottky barrier at the metal/semiconductor interface permitting efficient charge injection into the channel and reduces the effects of contact resistance on device performance. The large specific capacitance of the IL was also responsible for a much higher induced charge density compared to the standard SiO2 dielectric. The device was successfully tested as an inverter with a gain of ∼2. Using a common metal for contacts simplifies fabrication of this ambipolar device, and the possibility of radiative recombination of holes and electrons could further extend its use in low power optoelectronic applications.

Development of III-V p-MOSFETs with high-kappa gate stack for future CMOS applications

Science.gov (United States)

Nagaiah, Padmaja

As the semiconductor industry approaches the limits of traditional silicon CMOS scaling, non-silicon materials and new device architectures are gradually being introduced to improve Si integrated circuit performance and continue transistor scaling. Recently, the replacement of SiO2 with a high-k material (HfO2) as gate dielectric has essentially removed one of the biggest advantages of Si as channel material. As a result, alternate high mobility materials are being considered to replace Si in the channel to achieve higher drive currents and switching speeds. III-V materials in particular have become of great interest as channel materials, owing to their superior electron transport properties. However, there are several critical challenges that need to be addressed before III-V based CMOS can replace Si CMOS technology. Some of these challenges include development of a high quality, thermally stable gate dielectric/III-V interface, and improvement in III-V p-channel hole mobility to complement the n-channel mobility, low source/drain resistance and integration onto Si substrate. In this thesis, we would be addressing the first two issues i.e. the development high performance III-V p-channels and obtaining high quality III-V/high-k interface. We start with using the device architecture of the already established InGaAs n-channels as a baseline to understand the effect of remote scattering from the high-k oxide and oxide/semiconductor interface on channel transport properties such as electron mobility and channel electron concentration. Temperature dependent Hall electron mobility measurements were performed to separate various scattering induced mobility limiting factors. Dependence of channel mobility on proximity of the channel to the oxide interface, oxide thickness, annealing conditions are discussed. The results from this work will be used in the design of the p-channel MOSFETs. Following this, InxGa1-xAs (x>0.53) is chosen as channel material for developing p

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.

In vitro cytotoxicity of SiO2 or ZnO nanoparticles with different sizes and surface charges on U373MG human glioblastoma cells

Directory of Open Access Journals (Sweden)

Kim JE

2014-12-01

Full Text Available Jung-Eun Kim,1,* Hyejin Kim,1,* Seong Soo A An,2 Eun Ho Maeng,3 Meyoung-Kon Kim,4 Yoon-Jae Song1 1Department of Life Science, 2Department of Bionano Technology, Gachon University, Seongnam-Si, South Korea; 3Korea Testing and Research Institute, Seoul, South Korea; 4Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, South Korea *These authors contributed equally to this work Abstract: Silicon dioxide (SiO2 and zinc oxide (ZnO nanoparticles are widely used in various applications, raising issues regarding the possible adverse effects of these metal oxide nanoparticles on human cells. In this study, we determined the cytotoxic effects of differently charged SiO2 and ZnO nanoparticles, with mean sizes of either 100 or 20 nm, on the U373MG human glioblastoma cell line. The overall cytotoxicity of ZnO nanoparticles against U373MG cells was significantly higher than that of SiO2 nanoparticles. Neither the size nor the surface charge of the ZnO nanoparticles affected their cytotoxicity against U373MG cells. The 20 nm SiO2 nanoparticles were more toxic than the 100 nm nanoparticles against U373MG cells, but the surface charge had little or no effect on their cytotoxicity. Both SiO2 and ZnO nanoparticles activated caspase-3 and induced DNA fragmentation in U373MG cells, suggesting the induction of apoptosis. Thus, SiO2 and ZnO nanoparticles appear to exert cytotoxic effects against U373MG cells, possibly via apoptosis. Keyword: apoptosis

Magnetic nanoparticles induced dielectric enhancement in (La, Gd)2O3: SiO2 composite systems

Science.gov (United States)

Kao, T. H.; Mukherjee, S.; Yang, H. D.

2013-11-01

Magnetic Gd2O3 and non-magnetic La2O3 nanoparticles (NPs) have been synthesized together with different doping concentrations in SiO2 matrix via sol-gel route calcination at 700 °C and above. Properly annealed NP-glass composite systems show enhancement of dielectric constant and magnetodielectric effect (MDE) near room temperature, depending on superparamagnetic NPs concentrations. From application point of view, the enhancement of dielectric constant along with MDE can be achieved by tuning the NPs size through varying calcination temperature and/or increasing the doping concentration of magnetic rare earth oxide.

Reaction mechanisms at 4H-SiC/SiO2 interface during wet SiC oxidation

Science.gov (United States)

Akiyama, Toru; Hori, Shinsuke; Nakamura, Kohji; Ito, Tomonori; Kageshima, Hiroyuki; Uematsu, Masashi; Shiraishi, Kenji

2018-04-01

The reaction processes at the interface between SiC with 4H structure (4H-SiC) and SiO2 during wet oxidation are investigated by electronic structure calculations within the density functional theory. Our calculations for 4H-SiC/SiO2 interfaces with various orientations demonstrate characteristic features of the reaction depending on the crystal orientation of SiC: On the Si-face, the H2O molecule is stable in SiO2 and hardly reacts with the SiC substrate, while the O atom of H2O can form Si-O bonds at the C-face interface. Two OH groups are found to be at least necessary for forming new Si-O bonds at the Si-face interface, indicating that the oxidation rate on the Si-face is very low compared with that on the C-face. On the other hand, both the H2O molecule and the OH group are incorporated into the C-face interface, and the energy barrier for OH is similar to that for H2O. By comparing the calculated energy barriers for these reactants with the activation energies of oxide growth rate, we suggest the orientation-dependent rate-limiting processes during wet SiC oxidation.

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

Effects of Na2WO4 and Na2SiO3 additives in electrolytes on microstructure and properties of PEO coatings on Q235 carbon steel

International Nuclear Information System (INIS)

Wang Yunlong; Jiang Zhaohua; Yao Zhongping

2009-01-01

Ceramic coatings were achieved on Q235 carbon steel by plasma electrolytic oxidation in aluminate system with and without Na 2 WO 4 and Na 2 SiO 3 additives in electrolyte. Influence of Na 2 WO 4 and Na 2 SiO 3 on surface morphology, phase and elemental composition of PEO coatings were examined by means of scanning electron microscope (SEM), thin-film X-ray diffraction (TF-XRD) and energy dispersive X-ray spectroscopy (EDS). Effects of the two additives on the properties of the coatings including surface roughness, surface micro hardness and friction coefficient were studied. The results showed that W from Na 2 WO 4 and Si from Na 2 SiO 3 in electrolytes entered into the coatings. Na 2 WO 4 additive had no evident effect on phase composition of the coating, while Na 2 SiO 3 additive resulted in the coating changing from crystalline state to amorphous state and increased the content of P in the coating. Both additives reduced the surface roughness of the coatings. With Na 2 WO 4 or Na 2 SiO 3 into the electrolytes, the surface micro hardness of the coating was enhanced to 1433 and 1478, respectively, and the friction coefficients were also decreased to below 0.1.

Investigation of 6T SRAM memory circuit using high-k dielectrics based nano scale junctionless transistor

Science.gov (United States)

Charles Pravin, J.; Nirmal, D.; Prajoon, P.; Mohan Kumar, N.; Ajayan, J.

2017-04-01

In this paper the Dual Metal Surround Gate Junctionless Transistor (DMSGJLT) has been implemented with various high-k dielectric. The leakage current in the device is analysed in detail by obtaining the band structure for different high-k dielectric material. It is noticed that with increasing dielectric constant the device provides more resistance for the direct tunnelling of electron in off state. The gate oxide capacitance also shows 0.1 μF improvement with Hafnium Oxide (HfO2) than Silicon Oxide (SiO2). This paved the way for a better memory application when high-k dielectric is used. The Six Transistor (6T) Static Random Access Memory (SRAM) circuit implemented shows 41.4% improvement in read noise margin for HfO2 than SiO2. It also shows 37.49% improvement in write noise margin and 30.16% improvement in hold noise margin for HfO2 than SiO2.

Rat Aquaporin-5 Is pH-Gated Induced by Phosphorylation and Is Implicated in Oxidative Stress

Directory of Open Access Journals (Sweden)

Claudia Rodrigues

2016-12-01

Full Text Available Aquaporin-5 (AQP5 is a membrane water channel widely distributed in human tissues that was found up-regulated in different tumors and considered implicated in carcinogenesis in different organs and systems. Despite its wide distribution pattern and physiological importance, AQP5 short-term regulation was not reported and mechanisms underlying its involvement in cancer are not well defined. In this work, we expressed rat AQP5 in yeast and investigated mechanisms of gating, as well as AQP5’s ability to facilitate H2O2 plasma membrane diffusion. We found that AQP5 can be gated by extracellular pH in a phosphorylation-dependent manner, with higher activity at physiological pH 7.4. Moreover, similar to other mammalian AQPs, AQP5 is able to increase extracellular H2O2 influx and to affect oxidative cell response with dual effects: whereas in acute oxidative stress conditions AQP5 induces an initial higher sensitivity, in chronic stress AQP5 expressing cells show improved cell survival and resistance. Our findings support the involvement of AQP5 in oxidative stress and suggest AQP5 modulation by phosphorylation as a novel tool for therapeutics.

Electrical Performance and Reliability Improvement of Amorphous-Indium-Gallium-Zinc-Oxide Thin-Film Transistors with HfO2 Gate Dielectrics by CF4 Plasma Treatment

Science.gov (United States)

Fan, Ching-Lin; Tseng, Fan-Ping; Tseng, Chiao-Yuan

2018-01-01

In this work, amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a HfO2 gate insulator and CF4 plasma treatment was demonstrated for the first time. Through the plasma treatment, both the electrical performance and reliability of the a-IGZO TFT with HfO2 gate dielectric were improved. The carrier mobility significantly increased by 80.8%, from 30.2 cm2/V∙s (without treatment) to 54.6 cm2/V∙s (with CF4 plasma treatment), which is due to the incorporated fluorine not only providing an extra electron to the IGZO, but also passivating the interface trap density. In addition, the reliability of the a-IGZO TFT with HfO2 gate dielectric has also been improved by the CF4 plasma treatment. By applying the CF4 plasma treatment to the a-IGZO TFT, the hysteresis effect of the device has been improved and the device’s immunity against moisture from the ambient atmosphere has been enhanced. It is believed that the CF4 plasma treatment not only significantly improves the electrical performance of a-IGZO TFT with HfO2 gate dielectric, but also enhances the device’s reliability. PMID:29772767

Electrical Performance and Reliability Improvement of Amorphous-Indium-Gallium-Zinc-Oxide Thin-Film Transistors with HfO2 Gate Dielectrics by CF4 Plasma Treatment

Directory of Open Access Journals (Sweden)

Ching-Lin Fan

2018-05-01

Full Text Available In this work, amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs with a HfO2 gate insulator and CF4 plasma treatment was demonstrated for the first time. Through the plasma treatment, both the electrical performance and reliability of the a-IGZO TFT with HfO2 gate dielectric were improved. The carrier mobility significantly increased by 80.8%, from 30.2 cm2/V∙s (without treatment to 54.6 cm2/V∙s (with CF4 plasma treatment, which is due to the incorporated fluorine not only providing an extra electron to the IGZO, but also passivating the interface trap density. In addition, the reliability of the a-IGZO TFT with HfO2 gate dielectric has also been improved by the CF4 plasma treatment. By applying the CF4 plasma treatment to the a-IGZO TFT, the hysteresis effect of the device has been improved and the device’s immunity against moisture from the ambient atmosphere has been enhanced. It is believed that the CF4 plasma treatment not only significantly improves the electrical performance of a-IGZO TFT with HfO2 gate dielectric, but also enhances the device’s reliability.

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....

Physical and electrical properties of bilayer CeO{sub 2}/TiO{sub 2} gate dielectric stack

Energy Technology Data Exchange (ETDEWEB)

Chong, M.M.V. [School of Materials Science and Engineering, Nanyang Technological University of Singapore, Block N 4.1Nanyang Avenue, Singapore 639798 (Singapore); GlobalFoundries Singapore Private Limited, 60 Woodlands Industrial Park D Street 2, Singapore 738406 (Singapore); Lee, P.S. [School of Materials Science and Engineering, Nanyang Technological University of Singapore, Block N 4.1Nanyang Avenue, Singapore 639798 (Singapore); Tok, A.I.Y., E-mail: MIYTOK@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University of Singapore, Block N 4.1Nanyang Avenue, Singapore 639798 (Singapore)

2016-08-15

Highlights: • A bilayer gate dielectric stack of CeO{sub 2}/TiO{sub 2} to study the dependency of film growth with varying annealing temperatures is proposed. • The study demonstrates CeO{sub 2}/TiO{sub 2} bilayer stack with comparable κ-value as that of HfO{sub 2} but with reduced leakage current density of 4 orders of magnitude. • Schottky emission is the dominant leakage conduction mechanism of annealed CeO{sub 2}/TiO{sub 2} stack due to thermionic effect of interface properties. - Abstract: This study demonstrates a bilayer gate oxide structure of cerium oxide deposited via pulsed laser deposition and titanium oxide using conventional atomic layer deposition. Samples were deposited on p-type Si (100) substrate and exhibit interesting physical and electrical properties such that 600 °C annealed CeO{sub 2}/TiO{sub 2} samples having κ-value of 18 whereas pure CeO{sub 2} deposited samples have dielectric constant of 17.1 with leakage current density of 8.94 × 10{sup −6} A/cm{sup 2} at 1 V applied voltage. The result shows promising usage of the synthesized rare earth oxides as gate dielectric where ideal κ-value and significant reduction of the leakage current by 5 orders of magnitude is achieved. Leakage current conduction mechanism for as-deposited sample is found to be dominated by Poole–Frenkel (PF) emission; the trap level is found to be at 1.29 eV whereas annealed samples (600 °C and 800 °C) exhibited Schottky emission with trap levels at 1.45 eV and 0.81 eV, respectively.

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 .

Synthesis and cathodoluminescent properties of Y2SiO5:Tb3+ phosphors prepared from uniform precursor

International Nuclear Information System (INIS)

Fan Deyong; Yang Sen; Wang Jieqiong; Zheng Aqun; Song Xiaoping; Yu Demei

2012-01-01

The luminescent properties of phosphors are sensitive to the size of phosphor particles. The commercial Y 2 SiO 5 :Tb 3+ phosphors usually show relatively larger particle size (5–10 μm) due to the irregular morphology of rare earth oxide precursor and thus degrade the luminescent properties. In this paper, we report the Y 2 SiO 5 :Tb 3+ phosphors synthesized from the uniform Tb-doped Y 2 O 3 precursor by a homogeneous precipitation method. Compared with the commercial phosphors, the obtained Y 2 SiO 5 :Tb 3+ phosphors manifest the uniform morphology with much smaller particles distributing from 0.8 μm to 1.9 μm. Consequently, the cathodoluminescent intensity under low excitation voltage (1–5 kV) was increased, demonstrating a strong green emission with a dominant wavelength of 545 nm. Our results indicate an effective way to develop the high-quality phosphors for field emission display. - Highlights: ► The Y 2 SiO 5 :Tb 3+ phosphors are synthesized by a homogeneous precipitation method. ► They manifest the uniform morphology with much smaller particles than commercial one. ► The corresponding cathodoluminescent intensity of green emission is greatly enhanced. ► Our results indicate an effective way to develop the high-quality phosphors for FED.

Long lasting yellow phosphorescence and photostimulated luminescence in Sr3SiO5 : Eu2+ and Sr3SiO5 : Eu2+, Dy3+ phosphors

International Nuclear Information System (INIS)

Sun Xiaoyuan; Zhang Jiahua; Zhang Xia; Luo Yongshi; Wang Xiaojun

2008-01-01

We report the observation of long lasting yellow phosphorescence and photostimulated luminescence (PSL) in Sr 3 SiO 5 : Eu 2+ and Sr 3 SiO 5 : Eu 2+ , Dy 3+ phosphors. The decay patterns of phosphorescence and thermoluminescence curves demonstrate that introduction of Dy 3+ into Sr 3 SiO 5 : Eu 2+ can generate a large number of shallow traps and deep traps. The generated deep traps prolong the phosphorescence up to 6 h after UV irradiation. The PSL is studied under 808 nm excitation. Slow rising and falling edges of the emission in Sr 3 SiO 5 : Eu 2+ , Dy 3+ are observed, showing a retrapping process by the generated shallow traps due to co-doping Dy 3+ .

Fabrication and electrical properties of metal-oxide semiconductor capacitors based on polycrystalline p-Cu{sub x}O and HfO{sub 2}/SiO{sub 2} high-{kappa} stack gate dielectrics

Energy Technology Data Exchange (ETDEWEB)

Zou Xiao [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China); Department of Electromachine Engineering, Jianghan University, Wuhan, 430056 (China); Fang Guojia, E-mail: gjfang@whu.edu.c [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China); Yuan Longyan; Liu Nishuang; Long Hao; Zhao Xingzhong [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China)

2010-05-31

Polycrystalline p-type Cu{sub x}O films were deposited after the growth of HfO{sub 2} dielectric on Si substrate by pulsed laser deposition, and Cu{sub x}O metal-oxide-semiconductor (MOS) capacitors with HfO{sub 2}/SiO{sub 2} stack gate dielectric were primarily fabricated and investigated. X-ray diffraction and X-ray photoelectron spectroscopy were applied to analyze crystalline structure and Cu{sup +}/Cu{sup 2+} ratios of Cu{sub x}O films respectively. SiO{sub 2} interlayer formed between the high-{kappa} dielectric and substrate was estimated by the transmission electron microscope. Results of electrical characteristic measurement indicate that the permittivity of HfO{sub 2} is about 22, and the gate leakage current density of MOS capacitor with 11.3 nm HfO{sub 2}/SiO{sub 2} stack dielectrics is {approx} 10{sup -4} A/cm{sup 2}. Results also show that the annealing in N{sub 2} can improve the quality of Cu{sub x}O/HfO{sub 2} interface and thus reduce the gate leakage density.

Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors.

Science.gov (United States)

Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

2016-12-01

In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade(-1) and 3.62 × 10(11) eV(-1) cm(-2), respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT.

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)

Atomic-Layer-Deposited SnO2 as Gate Electrode for Indium-Free Transparent Electronics

KAUST Repository

Alshammari, Fwzah Hamud

2017-08-04

Atomic-layer-deposited SnO2 is used as a gate electrode to replace indium tin oxide (ITO) in thin-film transistors and circuits for the first time. The SnO2 films deposited at 200 °C show low electrical resistivity of ≈3.1 × 10−3 Ω cm with ≈93% transparency in most of the visible range of the electromagnetic spectrum. Thin-film transistors fabricated with SnO2 gates show excellent transistor properties including saturation mobility of 15.3 cm2 V−1 s−1, a low subthreshold swing of ≈130 mV dec−1, a high on/off ratio of ≈109, and an excellent electrical stability under constant-voltage stressing conditions to the gate terminal. Moreover, the SnO2-gated thin-film transistors show excellent electrical characteristics when used in electronic circuits such as negative channel metal oxide semiconductor (NMOS) inverters and ring oscillators. The NMOS inverters exhibit a low propagation stage delay of ≈150 ns with high DC voltage gain of ≈382. A high oscillation frequency of ≈303 kHz is obtained from the output sinusoidal signal of the 11-stage NMOS inverter-based ring oscillators. These results show that SnO2 can effectively replace ITO in transparent electronics and sensor applications.

Facile fabrication of nanofluidic diode membranes using anodic aluminium oxide

Science.gov (United States)

Wu, Songmei; Wildhaber, Fabien; Vazquez-Mena, Oscar; Bertsch, Arnaud; Brugger, Juergen; Renaud, Philippe

2012-08-01

Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al2O3/SiO2 (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al2O3 (positive) and SiO2 (negative), the membrane exhibits clear rectification of ion current in electrolyte solutions with very low aspect ratios compared to previous approaches. Our hetero-structured nanopore arrays provide a valuable platform for high throughput applications such as molecular separation, chemical processors and energy conversion.Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al2O3/SiO2 (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al2O3

Analytical drain current formulation for gate dielectric engineered dual material gate-gate all around-tunneling field effect transistor

Science.gov (United States)

Madan, Jaya; Gupta, R. S.; Chaujar, Rishu

2015-09-01

In this work, an analytical drain current model for gate dielectric engineered (hetero dielectric)-dual material gate-gate all around tunnel field effect transistor (HD-DMG-GAA-TFET) has been developed. Parabolic approximation has been used to solve the two-dimensional (2D) Poisson equation with appropriate boundary conditions and continuity equations to evaluate analytical expressions for surface potential, electric field, tunneling barrier width and drain current. Further, the analog performance of the device is studied for three high-k dielectrics (Si3N4, HfO2, and ZrO2), and it has been investigated that the problem of lower ION, can be overcome by using the hetero-gate architecture. Moreover, the impact of scaling the gate oxide thickness and bias variations has also been studied. The HD-DMG-GAA-TFET shows an enhanced ION of the order of 10-4 A. The effectiveness of the proposed model is validated by comparing it with ATLAS device simulations.

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.

Degradation of Ultra-Thin Gate Oxide NMOSFETs under CVDT and SHE Stresses

International Nuclear Information System (INIS)

Shi-Gang, Hu; Yan-Rong, Cao; Yue, Hao; Xiao-Hua, Ma; Chi, Chen; Xiao-Feng, Wu; Qing-Jun, Zhou

2008-01-01

Degradation of device under substrate hot-electron (SHE) and constant voltage direct-tunnelling (CVDT) stresses are studied using NMOSFET with 1.4-nm gate oxides. The degradation of device parameters and the degradation of the stress induced leakage current (SILC) under these two stresses are reported. The emphasis of this paper is on SILC and breakdown of ultra-thin-gate-oxide under these two stresses. SILC increases with stress time and several soft breakdown events occur during direct-tunnelling (DT) stress. During SHE stress, SILC firstly decreases with stress time and suddenly jumps to a high level, and no soft breakdown event is observed. For DT injection, the positive hole trapped in the oxide and hole direct-tunnelling play important roles in the breakdown. For SHE injection, it is because injected hot electrons accelerate the formation of defects and these defects formed by hot electrons induce breakdown. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

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.

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.

Tungsten trioxide as high-{kappa} gate dielectric for highly transparent and temperature-stable zinc-oxide-based thin-film transistors

Energy Technology Data Exchange (ETDEWEB)

Lorenz, Michael; Wenckstern, Holger von; Grundmann, Marius [Universitaet Leipzig, Fakultaet fuer Physik und Geowissenschaften, Institut fuer Experimentelle Physik II, Linnestr. 5, 04103 Leipzig (Germany)

2012-07-01

We demonstrate metal-insulator-semiconductor field-effect transistors with high-{kappa}, room-temperature deposited, highly transparent tungsten trioxide (WO{sub 3}) as gate dielectric. The channel material consists of a zinc oxide (ZnO) thin-film. The transmittance and resistivity of WO{sub 3} films was tuned in order to obtain a highly transparent and insulating WO{sub 3} dielectric. The devices were processed by standard photolithography using lift-off technique. On top of the WO{sub 3} dielectric a highly transparent and conductive oxide consisting of ZnO: Al 3% wt. was deposited. The gate structure of the devices exhibits an average transmittance in the visible spectral range of 86%. The on/off-current ratio is larger than 10{sup 8} with off- and gate leakage-currents below 3 x 10{sup -8} A/cm{sup 2}. Due to the high relative permittivity of {epsilon}{sub r} {approx} 70, a gate voltage sweep of only 2 V is necessary to turn the transistor on and off with a minimum subthreshold swing of 80 mV/decade. The channel mobility of the transistors equals the Hall-effect mobility with a value of 5 cm{sup 2}/Vs. It is furthermore shown, that the devices are stable up to operating temperatures of at least 150 C.