WorldWideScience

Sample records for al2o3 thin films

  1. Research on oxidation resistance of Al2O3 thin film prepared by electrodeposition-pyrolysis

    Directory of Open Access Journals (Sweden)

    Jing MA

    2015-08-01

    Full Text Available Al2O3 thin films are deposited on the surface of 304 stainless steel by electrodeposition-pyrolysis, and the effects of electrolyte concentration and electro-deposition voltage on the oxidation behavior of Al2O3 thin film at 900 ℃ are investigated. Macroscopic surface morphologies, XRD analysis and oxidation kinetics curves show that the electrodeposition-Al2O3 thin films reduce the partial pressure of oxygen at the initial oxidation stage on the substrate surface, promoting the selective oxidation, thus the oxidation resistance of 304 stainless steel is significantly improved. The high temperature oxidation resistance of Al2O3 film prepared under voltage of 25 V and aluminum nitrate alcohol solution of 0.10 mol/L is the best.

  2. The chemisorption of H2O, HCOOH and CH3COOH on thin amorphous films of Al2O3

    Science.gov (United States)

    Lewis, B. F.; Weinberg, W. H.; Mosesman, M.

    1974-01-01

    Investigation of the irreversible chemisorption of water, formic acid and acetic acid on a thin amorphous aluminum oxide film, using inelastic tunneling spectroscopy. All of the tunnel junctions employed were Al-Al2O3-Pb junctions with the adsorbate on the Al2O3 surface between the Al2O3 and the Pb electrode. The results obtained include the finding that all Al2O3 surfaces prepared by oxidation of Al have free CH groups present on them.

  3. Characterization of Al2O3 Thin Films on GaAs Substrate Grown by Atomic Layer Deposition

    Institute of Scientific and Technical Information of China (English)

    LU Hong-Liang; LI Yan-Bo; XU Min; DING Shi-Jin; SUN Liang; ZHANG Wei; WANG Li-Kang

    2006-01-01

    @@ Al2O3 thin films are grown by atomic layer deposition on GaAs substrates at 300℃. The structural properties of the Al2O3 thin film and the Al2O3/GaAs interface are characterized using x-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM), and x-ray photoelectron spectroscopy (XPS). The XRD results show that the as-deposited Al2O3 film is amorphous. For 30 atomic layer deposition growth cycles, the thicknesses of the Al2O3 thin film and the interface layer from the HRTEM are 3.3nm and 0.5nm, respectively.XPS analyses reveal that the Al2O3/GaAs interface is almost free from As2O3.

  4. Growth of highly oriented γ- and α-Al2O3 thin films by pulsed laser deposition

    Science.gov (United States)

    Balakrishnan, G.; Babu, R. Venkatesh; Shin, K. S.; Song, J. I.

    2014-03-01

    Highly oriented aluminum oxide (Al2O3) thin films were grown on SrTiO3 (100), α-Al2O3 (11¯02), α-Al2O3 (0001) and MgO (100) single crystal substrates at an optimized oxygen partial pressure of 3.5×10-3 mbar and 700 °C by pulsed laser deposition. The films were characterized by X-ray diffraction and atomic force microscopy. The X-ray diffraction studies indicated the highly oriented growth of γ-Al2O3 (400) ǁ SrTiO3 (100), α-Al2O3 (024) ǁ α-Al2O3 (11¯02), α-Al2O3 (006) ǁ α-Al2O3 (0001) and α-Al2O3 (006) ǁ MgO (100). Formation of nanostructures with dense and smooth surface morphology was observed using atomic force microscopy. The root mean square surface roughness of the films were 0.2 nm, 0.5 nm, 0.7 nm and 0.3 nm on SrTiO3 (100), α-Al2O3 (11¯02), α-Al2O3 (0001) and MgO (100) substrates, respectively.

  5. Atomic Layer Deposition Al2O3 Thin Films in Magnetized Radio Frequency Plasma Source

    Science.gov (United States)

    Li, Xingcun; Chen, Qiang; Sang, Lijun; Yang, Lizhen; Liu, Zhongwei; Wang, Zhenduo

    Self-limiting deposition of aluminum oxide (Al2O3) thin films were accomplished by the plasma-enhanced chemical vapor deposition using trimethyl aluminum (TMA) and O2 as precursor and oxidant, respectively, where argon was kept flowing in whole deposition process as discharge and purge gas. In here we present a novel plasma source for the atomic layer deposition technology, magnetized radio frequency (RF) plasma. Difference from the commercial RF source, magnetic coils were amounted above the RF electrode, and the influence of the magnetic field strength on the deposition rate and morphology are investigated in detail. It concludes that a more than 3 Å/ purging cycle deposition rate and the good quality of ALD Al2O3 were achieved in this plasma source even without extra heating. The ultra-thin films were characterized by including Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectric spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The high deposition rates obtained at ambient temperatures were analyzed after in-situ the diagnostic of plasmas by Langmuir probe.

  6. Experiment and prediction on thermal conductivity of Al2O3/ZnO nano thin film interface structure

    Indian Academy of Sciences (India)

    Ping Yang; Liqiang Zhang; Haiying Yang; Dongjing Liu; Xialong Li

    2014-05-01

    We predict that there is a critical value of Al2O3/ZnO nano thin interface thickness based on two assumptions according to an interesting phenomenon, which the thermal conductivity (TC) trend of Al2O3/ZnO nano thin interface is consistent with that of relevant single nano thin interface when the nano thin interface thickness is > 300 nm; however, TC of Al2O3/ZnO nano thin interface is higher than that of relevant single nano thin interface when the thin films thickness is < 10 nm. This prediction may build a basis for the understanding of interface between two different oxide materials. It implies an idea for new generation of semiconductor devices manufacturing.

  7. Studies on the properties of Al2O3:Cr2O3 (50:50) thin film

    Science.gov (United States)

    Ponmudi, S.; Sivakumar, R.; Sanjeeviraja, C.

    2016-05-01

    Aluminium oxide (Al2O3) and chromium oxide (Cr2O3) thin films have received great attention of researchers because of their unique properties of corrosion/oxidation resistance and high dielectric constant. In addition, chromium aluminium oxide has been considered as a best candidate for deep-ultraviolet optical masks. In the present work, thin films of Al2O3:Cr2O3 (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.

  8. Nano porous Al2O3-TiO2 thin film based humidity sensor prepared by spray pyrolysis technique

    Science.gov (United States)

    Chandrashekara, H. D.; Angadi, Basavaraj; Ravikiran, Y. T.; Poornima, P.; Shashidhar, R.; Murthy, L. C. S.

    2016-05-01

    The nano porous surface structured TiO2 and Al2O3-TiO2 thin films were prepared using spray pyrolysis technique at 350°C. The XRD pattern of Al2O3-TiO2 film shows anatase phase and mixed phase of Al2TiO5. The surface morphology of films show a uniformly distributed nano porous structure. The elemental analysis through EDAX shows good stoichiometry. The sensitivity for humidity sensing were determined for both films of TiO2 and Al2O3-TiO2 and corresponding values are found to be 74.2% and 84.02%, this result reveal that Al2O3-TiO2 films shows higher sensing percent than the TiO2 due to the nano porous surface nature. The Al2O3-TiO2 film shows fast response time and long recovery time than the TiO2 film, this may be due to the meso-porous morphology of these films.

  9. The enhanced conductivity of AZO thin films on soda lime glass with an ultrathin Al2O3 buffer layer

    International Nuclear Information System (INIS)

    Aluminum doped zinc oxide (AZO) films were deposited by radio frequency (RF) magnetron sputtering on the Al2O3-coated and bare soda lime glass substrates, respectively. The properties of AZO films were analyzed using X-ray diffraction (XRD), atomic force microscope (AFM), Hall effect measurement and ultraviolet-visible (UV-vis) spectrophotometer. The results of XRD measurement showed that all the AZO thin films had a preferentially oriented (0 0 2) peak and the intensity of (0 0 2) peak decreased with increase in the thickness of the Al2O3 buffer layer. The Hall measurement results showed that the conductivity of the AZO film with a 3 nm Al2O3 buffer layer had a remarkable 41.3% increase when compared with that of the single AZO film. The figures of merit from optical transmittance and electrical conductivity for AZO films on the 3 nm Al2O3-coated and bare glass substrates were 5466 and 3772 S cm-1, respectively. All the results suggested that the use of an ultrathin Al2O3 buffer layer effectively improved the quality of AZO film on the glass substrate.

  10. Oxygen partial pressure dependence of memory effect of sputtered nc-Al/α-Al2O3 thin films

    International Nuclear Information System (INIS)

    Nanocrystalline aluminum embedded in amorphous dielectric alumina matrix thin films (nc-Al/α-Al2O3) was synthesized via reactive magnetron sputtering. The nc-Al/α-Al2O3 films at different oxygen partial pressures were sputtered on p-type Si substrates from a pure Al target in the mixed ambient of Ar and O2. Both deposition rate and aluminum concentration increase as the oxygen partial pressure decreases. X-ray photoelectron spectroscopy and high-resolution transmission electron microscope studies give the confirmation of nanocrystalline Al embedded in amorphous Al2O3 matrix. This nanocomposite thin film exhibits memory effect as a result of charge trapping. The flat band voltage value depends on the Al nanocrystal concentration which is related to oxygen partial pressure

  11. Electron Cyclotron Resonance Plasma-Assisted Atomic Layer Deposition of Amorphous Al2O3 Thin Films

    International Nuclear Information System (INIS)

    Without extra heating, Al2O3 thin films were deposited on a hydrogen-terminated Si substrate etched in hydrofluoric acid by using a self-built electron cyclotron resonance (ECR) plasma-assisted atomic layer deposition (ALD) device with Al(CH3)3 (trimethylaluminum; TMA) and O2 used as precursor and oxidant, respectively. During the deposition process, Ar was introduced as a carrier and purging gas. The chemical composition and microstructure of the as-deposited Al2O3 films were characterized by using X-ray diffraction (XRD), an X-ray photoelectric spectroscope (XPS), a scanning electron microscope (SEM), an atomic force microscope (AFM) and a high-resolution transmission electron microscope (HRTEM). It achieved a growth rate of 0.24 nm/cycle, which is much higher than that deposited by thermal ALD. It was found that the smooth surface thin film was amorphous alumina, and an interfacial layer formed with a thickness of ca. 2 nm was observed between the Al2O3 film and substrate Si by HRTEM. We conclude that ECR plasma-assisted ALD can grow Al2O3 films with an excellent quality at a high growth rate at ambient temperature.

  12. Working Pressure Dependence of Properties of Al2O3 Thin Films Prepared by Electron Beam Evaporation

    Institute of Scientific and Technical Information of China (English)

    ZHAN Mei-Qiong; Wu Zhong-Lin; FAN Zheng-xiu

    2008-01-01

    The effects of working pressure of Al2O3 thin films are investigated.Transmittance of the Al2Oa thin film is measured by a Lambda 900 spectrometer.Laser-induced damage threshold(LIDT)is measured by a Nd:YAG laser at 355nm with 8 pulse width of 7ns.Microdefects were observed under a Nomarski microscope.The samples are characterized by optical properties and defect,as well as LIDT under the 355nm Nd:YAG laser radiation.It js found that the working pressure has fundamental effect on the LIDT.It is the absorption rather than the microdefect that plays an important role on the LIDT of Al2O3 thin film.

  13. Molecular beam epitaxy and characterization of thin Bi2Se3 films on Al2O3 (110)

    Science.gov (United States)

    Tabor, Phillip; Keenan, Cameron; Urazhdin, Sergei; Lederman, David

    2011-07-01

    The structural and electronic properties of thin Bi2Se3 films grown on Al2O3 (110) by molecular beam epitaxy are investigated. The epitaxial films grow in the Frank-van der Merwe mode and are c-axis oriented. They exhibit the highest crystallinity, the lowest carrier concentration, and optimal stoichiometry at a substrate temperature of 200 °C determined by the balance between surface kinetics and desorption of Se. The crystallinity of the films improves with increasing Se/Bi flux ratio. Our results enable studies of thin topological insulator films on inert, non-conducting substrates that allow optical access to both film surfaces.

  14. Enhanced carrier mobility of multilayer MoS2 thin-film transistors by Al2O3 encapsulation

    Science.gov (United States)

    Kim, Seong Yeoul; Park, Seonyoung; Choi, Woong

    2016-10-01

    We report the effect of Al2O3 encapsulation on the carrier mobility and contact resistance of multilayer MoS2 thin-film transistors by statistically investigating 70 devices with SiO2 bottom-gate dielectric. After Al2O3 encapsulation by atomic layer deposition, calculation based on Y-function method indicates that the enhancement of carrier mobility from 24.3 cm2 V-1 s-1 to 41.2 cm2 V-1 s-1 occurs independently from the reduction of contact resistance from 276 kΩ.μm to 118 kΩ.μm. Furthermore, contrary to the previous literature, we observe a negligible effect of thermal annealing on contact resistance and carrier mobility during the atomic layer deposition of Al2O3. These results demonstrate that Al2O3 encapsulation is a useful method of improving the carrier mobility of multilayer MoS2 transistors, providing important implications on the application of MoS2 and other two-dimensional materials into high-performance transistors.

  15. Nanovoid formation by change in amorphous structure through the annealing of amorphous Al2O3 thin films

    International Nuclear Information System (INIS)

    The formation mechanism of a high density of nanovoids by annealing amorphous Al2O3 thin films prepared by an electron beam deposition method was investigated. Transmission electron microscopy observations revealed that nanovoids ∼1-2 nm in size were formed by annealing amorphous Al2O3 thin films at 973 K for 1-12 h, where the amorphous state was retained. The elastic stiffness, measured by a picosecond laser ultrasound method, and the density, measured by X-ray reflectivity, increased drastically after the annealing process, despite nanovoid formation. These increases indicate a change in the amorphous structure during the annealing process. Molecular dynamics simulations indicated that an increase in stable AlO6 basic units and the change in the ring distribution lead to a drastic increase in both the elastic stiffness and the density. It is probable that a pre-annealed Al2O3 amorphous film consists of unstable low-density regions containing a low fraction of stable AlO6 units and stable high-density regions containing a high fraction of stable AlO6 units. Thus, local density growth in the unstable low-density regions during annealing leads to nanovoid formation (i.e., local volume shrinkage).

  16. Strain Distribution of Au and Ag Nanoparticles Embedded in Al2O3 Thin Film

    Directory of Open Access Journals (Sweden)

    Honghua Huang

    2014-01-01

    Full Text Available Au and Ag nanoparticles embedded in amorphous Al2O3 matrix are fabricated by the pulsed laser deposition (PLD method and rapid thermal annealing (RTA technique, which are confirmed by the experimental high-resolution transmission electron microscope (HRTEM results, respectively. The strain distribution of Au and Ag nanoparticles embedded in the Al2O3 matrix is investigated by the finite-element (FE calculations. The simulation results clearly indicate that both the Au and Ag nanoparticles incur compressive strain by the Al2O3 matrix. However, the compressive strain existing on the Au nanoparticle is much weaker than that on the Ag nanoparticle. This phenomenon can be attributed to the reason that Young’s modulus of Au is larger than that of Ag. This different strain distribution of Au and Ag nanoparticles in the same host matrix may have a significant influence on the technological potential applications of the Au-Ag alloy nanoparticles.

  17. α-Cr2O3 template-texture effect on α-Al2O3 thin-film growth

    OpenAIRE

    Eklund, Per; Sridharan, Madanagurusamy; Sillassen, Michael; Böttiger, Jörgen

    2008-01-01

    We employ textured α-Cr2O3 thin films as templates for growth of α-Al2O3 by reactive inductively coupled plasma magnetron sputtering. The texture of the template has a strong influence on the nucleation and growth of α-Al2O3. Extended growth of α-Al2O3 at a substrate temperature of 450 °C is obtained using a predominantly [101̄4]-textured α-Cr2O3 template layer, while only limited α-Al2O3 nucleation is seen on a [0001]-textured α-Cr2O3 template.

  18. The effects of amorphous Al2O3 underlayer on the microstructure and magnetic properties of BaFe12O19 thin films

    International Nuclear Information System (INIS)

    Single phase nanostructured BaFe12O19 thin films have been deposited on Si(110) substrate and Si(110) substrate with amorphous Al2O3 underlayer by a sol–gel method. The effects of the amorphous Al2O3 underlayer on the composition, microstructure and magnetic properties were explored by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometery techniques. The results revealed that the amorphous Al2O3 underlayer promoted some perpendicular c-axis orientation with ΔHc=Hcperpendicular−Hc∥=300 Oe. - Highlights: • The BaFe12O19 film fabricated by the Pechini method, deposited on Si(110), Si(110)/Al2O3 substrates. • The Al2O3 underlayer induced some c-axis perpendicular orientation. • Out-of-plane magnetic properties of the film with underlayer are better than those of in-plane orientation

  19. Synthesis of Al2O3 thin films using laser assisted spray pyrolysis (LASP)

    International Nuclear Information System (INIS)

    Highlights: ► Alumina thin films were made by laser assisted spray pyrolysis at various laser powers. ► The particle size was found to increase with laser power. ► The refractive index of the films was studied using ellipsometry. ► The film stoichiometry was studied using X-ray photoelectron spectroscopy. ► The film/substrate interface was studied using ellipsometer and secondary ion mass spectrometer. - Abstract: The present study reports the development of a laser assisted ultrasonic spray pyrolysis technique and synthesis of dense optical alumina films using the same. In this technique ultrasonically generated aerosols of aluminum acetylacetonate dissolved in ethanol and a laser beam (Nd:YAG, CW, 1064 nm) were fed coaxially and concurrently through a quartz tube on to a hot substrate mounted on an X–Y raster stage. At the laser focused spot the precursor underwent solvent evaporation and solute sublimation followed by precursor vapor decomposition giving rise to oxide coating, the substrate is rastered to get large surface area coating. The surface morphology revealed coalescence of particles with increase in laser power. The observed particle sizes were 17 nm for films synthesized without laser and 18, 21 and 25 nm for films made with laser at 25, 38 and 50 W, respectively. Refractive index of the films synthesized increased from 1.56 to 1.62 as the laser power increased from 0 to 50 W. The stoichiometry of films was studied using XPS and the increase in interfacial layer thickness with laser power was observed from dynamic SIMS depth profiling and ellipsometry.

  20. Interface Properties of Atomic-Layer-Deposited Al2O3 Thin Films on Ultraviolet/Ozone-Treated Multilayer MoS2 Crystals.

    Science.gov (United States)

    Park, Seonyoung; Kim, Seong Yeoul; Choi, Yura; Kim, Myungjun; Shin, Hyunjung; Kim, Jiyoung; Choi, Woong

    2016-05-11

    We report the interface properties of atomic-layer-deposited Al2O3 thin films on ultraviolet/ozone (UV/O3)-treated multilayer MoS2 crystals. The formation of S-O bonds on MoS2 after low-power UV/O3 treatment increased the surface energy, allowing the subsequent deposition of uniform Al2O3 thin films. The capacitance-voltage measurement of Au-Al2O3-MoS2 metal oxide semiconductor capacitors indicated n-type MoS2 with an electron density of ∼10(17) cm(-3) and a minimum interface trap density of ∼10(11) cm(-2) eV(-1). These results demonstrate the possibility of forming a high-quality Al2O3-MoS2 interface by proper UV/O3 treatment, providing important implications for their integration into field-effect transistors.

  1. Effect of Trimethyl Aluminium Surface Pretreatment on Atomic Layer Deposition Al2O3 Ultra-Thin Film on Si Substrate

    Institute of Scientific and Technical Information of China (English)

    XU Min; LU Hong-Liang; DING Shi-Jin; SUN Liang; ZHANG Wei; WANG Li-Kang

    2005-01-01

    @@ Ultra-thin Al2O3 dielectric films have been deposited on Si substrates by using trimethyl aluminium (TMA)and water as precursors in an atomic layer deposition (ALD) system. Growth of the interfacial layer between ultra-thin Al2O3 and the Si substrate is effectively suppressed by a long-time TMA surface pretreatment of the Si substrate prior to Al2O3 atomic layer deposition. High resolution transmission electron microscopy (TEM) images show that the thickness of the interfacial layer is reduced to be 0.5nm for the sample with TMA pretreatment lasting 3600s. The x-ray photoelectron spectroscopy results indicate that the Al2O3 film deposited on the TMApretreated Si surface exhibits very good thermal stability. However, a hysteresis of about 50mV is observed in the C-V curve of the samples with the TMA pretreatment.

  2. Synthesis of Al2O3 thin films using laser assisted spray pyrolysis (LASP)

    Science.gov (United States)

    Dhonge, Baban P.; Mathews, Tom; Tripura Sundari, S.; Krishnan, R.; Balamurugan, A. K.; Kamruddin, M.; Subbarao, R. V.; Dash, S.; Tyagi, A. K.

    2013-01-01

    The present study reports the development of a laser assisted ultrasonic spray pyrolysis technique and synthesis of dense optical alumina films using the same. In this technique ultrasonically generated aerosols of aluminum acetylacetonate dissolved in ethanol and a laser beam (Nd:YAG, CW, 1064 nm) were fed coaxially and concurrently through a quartz tube on to a hot substrate mounted on an X-Y raster stage. At the laser focused spot the precursor underwent solvent evaporation and solute sublimation followed by precursor vapor decomposition giving rise to oxide coating, the substrate is rastered to get large surface area coating. The surface morphology revealed coalescence of particles with increase in laser power. The observed particle sizes were 17 nm for films synthesized without laser and 18, 21 and 25 nm for films made with laser at 25, 38 and 50 W, respectively. Refractive index of the films synthesized increased from 1.56 to 1.62 as the laser power increased from 0 to 50 W. The stoichiometry of films was studied using XPS and the increase in interfacial layer thickness with laser power was observed from dynamic SIMS depth profiling and ellipsometry.

  3. Superconducting MgB2 thin films grown by pulsed laser deposition on Al2O3(0001) and MgO(100) substrates

    Science.gov (United States)

    Wang, S. F.; Dai, S. Y.; Zhou, Y. L.; Chen, Z. H.; Cui, D. F.; Xu, J. D.; He, M.; Lu, H. B.; Yang, G. Z.; Fu, G. S.; Han, L.

    2001-11-01

    Superconducting MgB2 thin films were fabricated on Al2O3(0001) and MgO(100) substrates by a two-step method. Boron thin films were deposited by pulsed laser deposition followed by an ex-situ annealing process. Resistance measurements of the deposited MgB2 films show a Tc of 38.6 K for MgB2/Al2O3 and 38.1 K for MgB2/MgO. Atomic force microscopy, scanning electron microscopy and x-ray diffraction were used to study the properties of the films. The results indicate that the MgB2/Al2O3 films consist of well-crystallized grains with a highly c-axis-oriented structure while the MgB2/MgO films have a dense uniform appearance with an unfixed orientation.

  4. Behaviour of Parallel Coupled Microstrip Band Pass Filter and Simple Microstripline due to Thin-Film Al2O3 Overlay

    Directory of Open Access Journals (Sweden)

    S. B. Rane

    1996-01-01

    Full Text Available The X-band behaviour of a seven-section parallel-coupled microstrip band pass filter and microstripline due to thin-film Al2O3 overlay of different thickness is reported in this paper. This Al2O3 film can give a homogeneous overlay structure. There is a substantial increase in the bandwidth due to the overlay, the pass band extending towards higher frequency side. In most of the cases, an increase in the pass band transmittance of a microstripline also increases due to a thin-film Al2O3 overlay, especially for frequencies less than 9.0 GHz. At higher frequencies, random variations are observed. It is felt that thin-film overlays can be used to modify the microstripline circuit properties, thereby avoiding costly and time consuming elaborate design procedures.

  5. Al2O3衬底上多晶硅薄膜的外延和区熔再结晶%Polycrystalline Silicon Thin Films on Al2O3 Substrates for Solar Cells

    Institute of Scientific and Technical Information of China (English)

    励旭东; 许颖; 顾亚华; 李艳; 王文静; 赵玉文

    2003-01-01

    研究了陶瓷衬底上多晶硅薄膜的生长和区熔再结晶.利用快速热化学气相沉积(RTCVD)方法,在低成本的Al2O3衬底上沉积了重掺杂的致密多晶硅薄膜,薄膜的晶粒尺寸在微米级.经区熔再结晶(ZMR)后,薄膜的晶粒尺寸有了较大的提高,而且迁移率较高,这样的薄膜可以用作晶体硅薄膜太阳电池的籽晶层.最大的晶粒达到毫米量级,空穴迁移率超过50 cm2·V-1·s-1.在籽晶层上外延的活性层形貌与此类似.这些结果显示这种薄膜在光伏应用方面有较大的潜力.%In this paper, growth and recrystallization of silicon films on ceramic substrates were studied. Heavily doped polycrystalline silicon thin films were deposited on low cost Al2O3 by thermal rapid chemical vapor deposition (RTCVD). Compact and uniform films with grain size in the order of some micrometers were fabricated. By means of zone melting recrystallization (ZMR) method, polycrystalline silicon thin films with large grains and relative high carrier mobility were obtained, which could act as a seeding layer. The maximum grain of these films was about one millimeter in width and some millimeters in length, and hole mobility exceeded 50 cm2·V-1·s-1. Active silicon films deposited on these seeding layers showed the same morphologies. These results showed that these films have great potential for photovoltaic applications.

  6. Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Rizwan Ali

    2015-05-01

    Full Text Available We investigate the optical and thermo-optical properties of amorphous TiO\\(_2\\–Al\\(_2\\O\\(_3\\ thin-film bilayers fabricated by atomic layer deposition (ALD. Seven samples of TiO\\(_2\\–Al\\(_2\\O\\(_3\\ bilayers are fabricated by growing Al\\(_2\\O\\(_3\\ films of different thicknesses on the surface of TiO\\(_2\\ films of constant thickness (100 nm. Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE\\textsuperscript{\\textregistered}. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO\\(_2\\ films. The effects of TiO\\(_2\\ surface defects on the films' thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al\\(_2\\O\\(_3\\ diffusion barrier layers. Increasing the ALD-Al\\(_2\\O\\(_3\\ thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO\\(_2\\. The thermo-optic coefficients of the 100 nm-thick ALD-TiO\\(_2\\ film and 30 nm-thick ALD-Al\\(_2\\O\\(_3\\ film in a bilayer are (0.048 \\(\\pm\\ 0.134 \\(\\times 10 ^{-4} {^\\circ}\\mathrm {C}^{-1}\\ and (0.680 \\(\\pm\\ 0.313 \\(\\times 10^{-4} {^\\circ} \\mathrm {C}^{-1}\\, respectively, at a temperature \\(T = 62 ^\\circ \\mathrm{C}\\.

  7. A light-stimulated synaptic transistor with synaptic plasticity and memory functions based on InGaZnOx-Al2O3 thin film structure

    Science.gov (United States)

    Li, H. K.; Chen, T. P.; Liu, P.; Hu, S. G.; Liu, Y.; Zhang, Q.; Lee, P. S.

    2016-06-01

    In this work, a synaptic transistor based on the indium gallium zinc oxide (IGZO)-aluminum oxide (Al2O3) thin film structure, which uses ultraviolet (UV) light pulses as the pre-synaptic stimulus, has been demonstrated. The synaptic transistor exhibits the behavior of synaptic plasticity like the paired-pulse facilitation. In addition, it also shows the brain's memory behaviors including the transition from short-term memory to long-term memory and the Ebbinghaus forgetting curve. The synapse-like behavior and memory behaviors of the transistor are due to the trapping and detrapping processes of the holes, which are generated by the UV pulses, at the IGZO/Al2O3 interface and/or in the Al2O3 layer.

  8. Electrically programmable-erasable In-Ga-Zn-O thin-film transistor memory with atomic-layer-deposited Al2O3/Pt nanocrystals/Al2O3 gate stack

    Science.gov (United States)

    Qian, Shi-Bing; Zhang, Wen-Peng; Liu, Wen-Jun; Ding, Shi-Jin

    2015-12-01

    Amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistor (TFT) memory is very promising for transparent and flexible system-on-panel displays; however, electrical erasability has always been a severe challenge for this memory. In this article, we demonstrated successfully an electrically programmable-erasable memory with atomic-layer-deposited Al2O3/Pt nanocrystals/Al2O3 gate stack under a maximal processing temperature of 300 oC. As the programming voltage was enhanced from 14 to 19 V for a constant pulse of 0.2 ms, the threshold voltage shift increased significantly from 0.89 to 4.67 V. When the programmed device was subjected to an appropriate pulse under negative gate bias, it could return to the original state with a superior erasing efficiency. The above phenomena could be attributed to Fowler-Nordheim tunnelling of electrons from the IGZO channel to the Pt nanocrystals during programming, and inverse tunnelling of the trapped electrons during erasing. In terms of 0.2-ms programming at 16 V and 350-ms erasing at -17 V, a large memory window of 3.03 V was achieved successfully. Furthermore, the memory exhibited stable repeated programming/erasing (P/E) characteristics and good data retention, i.e., for 2-ms programming at 14 V and 250-ms erasing at -14 V, a memory window of 2.08 V was still maintained after 103 P/E cycles, and a memory window of 1.1 V was retained after 105 s retention time.

  9. Electrically programmable-erasable In-Ga-Zn-O thin-film transistor memory with atomic-layer-deposited Al2O3/Pt nanocrystals/Al2O3 gate stack

    Directory of Open Access Journals (Sweden)

    Shi-Bing Qian

    2015-12-01

    Full Text Available Amorphous indium-gallium-zinc oxide (a-IGZO thin-film transistor (TFT memory is very promising for transparent and flexible system-on-panel displays; however, electrical erasability has always been a severe challenge for this memory. In this article, we demonstrated successfully an electrically programmable-erasable memory with atomic-layer-deposited Al2O3/Pt nanocrystals/Al2O3 gate stack under a maximal processing temperature of 300 oC. As the programming voltage was enhanced from 14 to 19 V for a constant pulse of 0.2 ms, the threshold voltage shift increased significantly from 0.89 to 4.67 V. When the programmed device was subjected to an appropriate pulse under negative gate bias, it could return to the original state with a superior erasing efficiency. The above phenomena could be attributed to Fowler-Nordheim tunnelling of electrons from the IGZO channel to the Pt nanocrystals during programming, and inverse tunnelling of the trapped electrons during erasing. In terms of 0.2-ms programming at 16 V and 350-ms erasing at −17 V, a large memory window of 3.03 V was achieved successfully. Furthermore, the memory exhibited stable repeated programming/erasing (P/E characteristics and good data retention, i.e., for 2-ms programming at 14 V and 250-ms erasing at −14 V, a memory window of 2.08 V was still maintained after 103 P/E cycles, and a memory window of 1.1 V was retained after 105 s retention time.

  10. Fabrication and characterization of Al2O3 /Si composite nanodome structures for high efficiency crystalline Si thin film solar cells

    Directory of Open Access Journals (Sweden)

    Ruiying Zhang

    2015-12-01

    Full Text Available We report on our fabrication and characterization of Al2O3/Si composite nanodome (CND structures, which is composed of Si nanodome structures with a conformal cladding Al2O3 layer to evaluate its optical and electrical performance when it is applied to thin film solar cells. It has been observed that by application of Al2O3thin film coating using atomic layer deposition (ALD to the Si nanodome structures, both optical and electrical performances are greatly improved. The reflectivity of less than 3% over the wavelength range of from 200 nm to 2000 nm at an incident angle from 0° to 45° is achieved when the Al2O3 film is 90 nm thick. The ultimate efficiency of around 27% is obtained on the CND textured 2 μm-thick Si solar cells, which is compared to the efficiency of around 25.75% and 15% for the 2 μm-thick Si nanodome surface-decorated and planar samples respectively. Electrical characterization was made by using CND-decorated MOS devices to measure device’s leakage current and capacitance dispersion. It is found the electrical performance is sensitive to the thickness of the Al2O3 film, and the performance is remarkably improved when the dielectric layer thickness is 90 nm thick. The leakage current, which is less than 4x10−9 A/cm2 over voltage range of from -3 V to 3 V, is reduced by several orders of magnitude. C-V measurements also shows as small as 0.3% of variation in the capacitance over the frequency range from 10 kHz to 500 kHz, which is a strong indication of surface states being fully passivated. TEM examination of CND-decorated samples also reveals the occurrence of SiOx layer formed between the interface of Si and the Al2O3 film, which is thin enough that ensures the presence of field-effect passivation, From our theoretical and experimental study, we believe Al2O3 coated CND structures is a truly viable approach to achieving higher device efficiency.

  11. Fabrication and characterization of Al2O3 /Si composite nanodome structures for high efficiency crystalline Si thin film solar cells

    International Nuclear Information System (INIS)

    We report on our fabrication and characterization of Al2O3/Si composite nanodome (CND) structures, which is composed of Si nanodome structures with a conformal cladding Al2O3 layer to evaluate its optical and electrical performance when it is applied to thin film solar cells. It has been observed that by application of Al2O3thin film coating using atomic layer deposition (ALD) to the Si nanodome structures, both optical and electrical performances are greatly improved. The reflectivity of less than 3% over the wavelength range of from 200 nm to 2000 nm at an incident angle from 0° to 45° is achieved when the Al2O3 film is 90 nm thick. The ultimate efficiency of around 27% is obtained on the CND textured 2 μm-thick Si solar cells, which is compared to the efficiency of around 25.75% and 15% for the 2 μm-thick Si nanodome surface-decorated and planar samples respectively. Electrical characterization was made by using CND-decorated MOS devices to measure device’s leakage current and capacitance dispersion. It is found the electrical performance is sensitive to the thickness of the Al2O3 film, and the performance is remarkably improved when the dielectric layer thickness is 90 nm thick. The leakage current, which is less than 4x10−9 A/cm2 over voltage range of from -3 V to 3 V, is reduced by several orders of magnitude. C-V measurements also shows as small as 0.3% of variation in the capacitance over the frequency range from 10 kHz to 500 kHz, which is a strong indication of surface states being fully passivated. TEM examination of CND-decorated samples also reveals the occurrence of SiOx layer formed between the interface of Si and the Al2O3 film, which is thin enough that ensures the presence of field-effect passivation, From our theoretical and experimental study, we believe Al2O3 coated CND structures is a truly viable approach to achieving higher device efficiency

  12. Characteristics of Sputter-deposited Gadolinia-doped Ceria Thin Films on Al2O3/SiO2/Si Systems

    Institute of Scientific and Technical Information of China (English)

    KUO Yulin; LEE Chiapyng; CHEN Yongsiou; SU Yuming; LIANG Hsuang

    2009-01-01

    Metal oxide films prepared by thin film technology have been reported for the potential applications on thin solid electrolyte layers for solid oxide fuel cells(SOFCs). Gadolinia-doped ceria(GDC) thin films and Al2O3 layers on SiO2/Si substrates are successively deposited by RF reactive magnetron sputtering from a cerium-gadolinium (90:10 at.%) alloy target and Al target in O2/Ar gas mixture and then perform post-thermal treatments at 300-700 ℃ and 900 ℃ for 2 h, respectively. Materials characteristics and chemical compositions of GDC films and Al2O3 layers are investigated by X-ray photoelectron spectroscopy(XPS), cross-sectional scanning electron microscopy(SEM), X-ray diffraction(XRD), and atomic force microscopy(AFM). Stoichiometric Al2O3 layers with polycrystalline structures are firstly prepared onto SiO2/Si substrates. A cubic fluorite structure with columnar crystallites of GDC films is successfully deposited on Al2O3/SiO2/Si systems. The chemical composition of 700 ℃-annealed GDC films is (Ce0.91Gd0.09)O1.94 and possesses a higher film density of 7.257 g/cm3. As a result, GDC thin films prepared by RF reactive magnetron sputtering and post-thermal treatments can be used as thin solid electrolyte layers for intermediate temperature SOFCs system as compared to the well-known yttria-stabilized zirconia(YSZ).

  13. Atomic layer deposition for fabrication of HfO2/Al2O3 thin films with high laser-induced damage thresholds.

    Science.gov (United States)

    Wei, Yaowei; Pan, Feng; Zhang, Qinghua; Ma, Ping

    2015-01-01

    Previous research on the laser damage resistance of thin films deposited by atomic layer deposition (ALD) is rare. In this work, the ALD process for thin film generation was investigated using different process parameters such as various precursor types and pulse duration. The laser-induced damage threshold (LIDT) was measured as a key property for thin films used as laser system components. Reasons for film damaged were also investigated. The LIDTs for thin films deposited by improved process parameters reached a higher level than previously measured. Specifically, the LIDT of the Al2O3 thin film reached 40 J/cm(2). The LIDT of the HfO2/Al2O3 anti-reflector film reached 18 J/cm(2), the highest value reported for ALD single and anti-reflect films. In addition, it was shown that the LIDT could be improved by further altering the process parameters. All results show that ALD is an effective film deposition technique for fabrication of thin film components for high-power laser systems.

  14. Temperature-dependent structuring of Au-Pt bimetallic nanoclusters on a thin film of Al2O3/NiAl(100).

    Science.gov (United States)

    Luo, Meng-Fan; Wang, Chao-Chuan; Chao, Chen-Sheng; Ho, Chiun-Yu; Wang, Cheng-Ting; Lin, Won-Ru; Lin, Yin-Chang; Lai, Yu-Lin; Hsu, Yao-Jane

    2011-01-28

    Au-Pt bimetallic nanoclusters on a thin film of Al(2)O(3)/NiAl(100) undergo significant structural evolution on variation of the temperature. Au and Pt deposited sequentially from the vapor onto thin-film Al(2)O(3)/NiAl(100) at 300 K form preferentially bimetallic nanoclusters (diameter ≦ 6.0 nm and height ≦ 0.8 nm) with both Au and Pt coexisting at the cluster surface, despite the order of metal deposition. These bimetallic clusters are structurally ordered, have a fcc phase and grow with their facets either (111) or (001) parallel to the θ-Al(2)O(3)(100) surface. Upon annealing the clusters to 400-500 K, the Au atoms inside the clusters migrate toward the surface, resulting in formation of a structure with a Pt core and an Au shell. Annealing the sample to 500-650 K reorients the bimetallic clusters--all clusters have their (001) facets parallel to the oxide surface--and induces oxidation of Pt. Such annealed bimetallic clusters become encapsulated with the aluminium-oxide materials and a few Au remain on the surface. PMID:21116540

  15. Preparation and Characterization of Ca3Co4O9 Thin Films on Polycrystalline Al2O3 Substrates by Chemical Solution Deposition

    Institute of Scientific and Technical Information of China (English)

    Yankun Fu; Xianwu Tang; Jie Yang; Hongbin Jian; Xuebin Zhu; Yuping Sun

    2013-01-01

    Ca3Co4O9 thin films have been first prepared on polycrystalline Al2O3 substrates using chemical solution deposition method by multiple annealing processing.It is observed that the derived thin films are c-axis oriented although the substrates are polycrystalline Al2O3 substrates,suggesting the self-assembled c-axis orientation.The annealing temperature effects on the properties are investigated and discussed.The best performances are attributed to the 850 ℃-annealed sample,whose resistivity,Seebeck coefficient and power factor at 300 K are 7.4 mΩ cm,117 μV/K and 0.18 mW/m K-2 respectively,which is even better than those of the thin films deposited on single crystal substrates.The results will provide an effective route to optimize the properties of Ca3Co4O9 thin films using chemical solution deposition by multiple annealing processing even the substrates are polycrystalline.

  16. Methanol-driven structuring of Au-Pt bimetallic nanoclusters on a thin film of Al2O3/NiAl(100)

    Science.gov (United States)

    Ho, Chiun-Yu; Patil, Rahul B.; Wang, Chao-Chuan; Chao, Chen-Sheng; Li, Yu-Da; Hsu, Hsing-Chung; Luo, Meng-Fan; Lin, Yin-Chang; Lai, Yu-Lin; Hsu, Yao-Jane

    2012-08-01

    The adsorption of methanol altered structures of Au-Pt bimetallic nanoclusters on a thin film of Al2O3/NiAl(100). Methanol adsorbed on the Au-Pt intermixed bimetallic clusters, of which the surfaces consist of both Au and Pt, induced a segregation of Au from Pt. This segregation state was unstable, as the clusters returned to the initial Au-Pt intermixed state upon desorption or decomposition of adsorbed methanol. Ethanol and cyclohexene were adsorbed on Au-Pt bimetallic clusters for comparisons, indicating that the interaction of the hydroxyl group of methanol with the clusters accounts for the structural modifications.

  17. Data storage applications based on LiCoO2 thin films grown on Al2O3 and Si substrates

    Science.gov (United States)

    Svoukis, E.; Mihailescu, C. N.; Mai, V. H.; Schneegans, O.; Breza, K.; Lioutas, C.; Giapintzakis, J.

    2016-09-01

    In this study, LiCoO2 thin films were investigated for data storage applications based on scanning probe mediated approaches. LiCoO2, compared to other materials proposed for scanning probe mediated nanoscale patterning, is highly stable and exhibits reversible electrochemical surface modifications. LiCoO2 thin films have been grown by pulsed laser deposition on Al2O3 and Si substrates over a range of deposition temperatures. The crystal structure and the microstructure of the films has been inferred through in- and out-of-plane X-ray diffraction studies and high-resolution transmission electron microscopy, respectively. The influence of the film deposition temperature on the surface electrical properties of the LiCoO2 films is discussed along with the relevant mechanism of surface resistance modification.

  18. Surface plasmon coupled emission studies on engineered thin film hybrids of nano α-Al2O3 on silver

    Science.gov (United States)

    Mulpur, Pradyumna; Lingam, Kiran; Chunduri, Avinash; Rattan, Tanu Mimani; Rao, Apparao M.; Kamisetti, Venkataramaniah

    2014-01-01

    We report the first time engineering and fabrication of a novel thin film hybrid of nano α-alumina doped in a polyvinyl alcohol (PVA) matrix along with rhodamine b (Rh.B) on a silver thin film. Silver films of 50 nm thickness on glass slides were fabricated by thermal evaporation. Nano α-alumina was synthesized through the combustion route and characterized by XRD. The α-alumina was dispersed in the PVA-Rh.B matrix by tip sonication. The resultant solution was spin coated on the Ag thin film at 3000 rpm to generate an overcoat of ˜30 nm. We have designed and constructed an opto-mechanical setup for performing the SPCE studies. Excitation with a 532 nm continuous laser, led to the coupling of the energy of Rh.B emission to the surface plasmon modes of silver. The emission @ 580 nm was recorded using an Ocean Optics{copyright, serif} fiber optic spectrometer. Calculation of the ratio of signal intensity between the directional SPCE and isotropic fluorescence gives us the factor of signal enhancements which SPCE offers. We report an '8 fold' signal enhancement attributed to SPCE arising from the metal oxide doped thin film hybrid. We observed only a '5 fold' signal enhancement in the case of a thin film hybrid without α-alumina. The emission was also 92% P-polarized which is in coherence with the theory of SPCE. The greater degree of signal enhancement observed in the α-alumina doped thin film substrate can be attributed to the surface roughness which alumina offers to silver, which along with the porous nature of alumina enables a greater degree of adsorption of Rh.B which results in a higher emission intensity. Computational modeling was also performed, based on surface plasmon resonance (SPR) calculations to provide theoretical background to observed experimental data. The α-alumina thin film hybrid can be extended as an economical sensing platform towards the high sensitive detection of analytes.

  19. Fabrication and characterization of highly luminescent Er3+:Al2O3 thin films with optimized growth parameters

    Science.gov (United States)

    Nayar, Priyanka; Zhu, Xue-Yi; Yang, Fuyi; Lu, Minghui; Lakshminarayana, G.; Liu, Xiao Ping; Chen, Yan-Feng; Kityk, I. V.

    2016-10-01

    Erbium doped amorphous alumina thin films were fabricated using Co-sputtering technique in various depositions runs with varying parameters for optimizing the deposition parameters to obtain the films with best optical performance. The main subject of investigation includes the effects of change in various deposition parameters such as substrate heating, radio frequency (RF) power and oxygen pressure inside the chamber while deposition. High quality as-deposited films with various Er concentrations and low carbon content have been confirmed by XPS. Substrate heating ∼500 °C was found to be very effective in getting highly dense films with high refractive index of 1.70 at 1530-1570 nm emission band. The Er3+-doped films showed very intense near-infrared luminescence peak at 1550 nm even without any post-deposition annealing treatment.

  20. Electroless Plating of Thin Silver Films on Porous Al2O3 Substrate and the Study of Deposition Kinetics

    Institute of Scientific and Technical Information of China (English)

    Fang Mei; Donglu Shi

    2005-01-01

    A novel concept has been developed to coat the inner pore surfaces of reticulated alumina with a thin silver film by an electroless-plating method. As a result of coating, the porous alumina sample exhibits a sharp transition from insulating to conducting due to a thin silver layer on the inner pore surfaces. Systematic studies have been carried out to investigate the coating kinetics by employment of scanning electron microscope (SEM), X-ray diffraction (XRD), and computer simulation. Both coating procedures and effects of processing parameters on the quality of films are reported. Also, this paper presents the film bonding strength to the substrate, effects of sintering, and conduction mechanism of coated composite. The fundamental silver electroless-plating mechanism has been identified based on computer modeling. The simulation results indicate an excellent agreement between the silver deposition behavior and the physical model applied.

  1. Effect of Tm-Er concentration ratio on the photoluminescence of Er-Tm: Al2O3 thin films fabricated by pulsed laser deposition

    Institute of Scientific and Technical Information of China (English)

    Bo Zhou; Zhisong Xiao; Anping Huang; Lu Yan; Fang Zhu; Jinliang Wang; Penggang Yin; Hao Wang

    2008-01-01

    Er-Tm codoped amorphous aluminum oxide (a-Al2O3) thin films have been prepared by an alternative pulsed laser deposition. The phase structure and the surface of the deposited thin films were characterized by the X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Effective photoluminescence (PL) in the region of 350-900nm was observed when pumped at 325nm, and the PL performance has been improved by modifying the Tm3+ concentration. With the increasing of [Tm]/[Er] concentration ratio, the intensity of emission of 382nm and 500nm bands was improved effectively while that of 76Snm band increased smoothly. Our results suggest that the resonant energy transfer and cross relaxation between Tm3+ and Er3+ play an important role in the evolution of the luminescent response.

  2. Enhanced photoelectrocatalytic performance of α-Fe2O3 thin films by surface plasmon resonance of Au nanoparticles coupled with surface passivation by atom layer deposition of Al2O3

    Science.gov (United States)

    Liu, Yuting; Xu, Zhen; Yin, Min; Fan, Haowen; Cheng, Weijie; Lu, Linfeng; Song, Ye; Ma, Jing; Zhu, Xufei

    2015-09-01

    The short lifetime of photogenerated charge carriers of hematite (α-Fe2O3) thin films strongly hindered the PEC performances. Herein, α-Fe2O3 thin films with surface nanowire were synthesized by electrodeposition and post annealing method for photoelectrocatalytic (PEC) water splitting. The thickness of the α-Fe2O3 films can be precisely controlled by adjusting the duration of the electrodeposition. The Au nanoparticles (NPs) and Al2O3 shell by atom layer deposition were further introduced to modify the photoelectrodes. Different constructions were made with different deposition orders of Au and Al2O3 on Fe2O3 films. The Fe2O3-Au-Al2O3 construction shows the best PEC performance with 1.78 times enhancement by localized surface plasmon resonance (LSPR) of NPs in conjunction with surface passivation of Al2O3 shells. Numerical simulation was carried out to investigate the promotion mechanisms. The high PEC performance for Fe2O3-Au-Al2O3 construction electrode could be attributed to the Al2O3 intensified LSPR, effective surface passivation by Al2O3 coating, and the efficient charge transfer due to the Fe2O3-Au Schottky junctions.

  3. A novel p-type and metallic dual-functional Cu-Al2O3 ultra-thin layer as the back electrode enabling high performance of thin film solar cells.

    Science.gov (United States)

    Lin, Qinxian; Su, Yantao; Zhang, Ming-Jian; Yang, Xiaoyang; Yuan, Sheng; Hu, Jiangtao; Lin, Yuan; Liang, Jun; Pan, Feng

    2016-09-14

    Increasing the open-circuit voltage (Voc) along with the fill factor (FF) is pivotal for the performance improvement of solar cells. In this work, we report the design and construction of a new structure of CdS/CdTe/Al2O3/Cu using the atomic layer deposition (ALD) method, and then we control Cu diffusion through the Al2O3 atomic layer into the CdTe layer. Surprisingly, this generates a novel p-type and metallic dual-functional Cu-Al2O3 atomic layer. Due to this dual-functional character of the Cu-Al2O3 layer, an efficiency improvement of 2% in comparison with the standard cell was observed. This novel dual-functional back contact structure could also be introduced into other thin film solar cells for their efficiency improvement. PMID:27384986

  4. Al2O3/Au/Al2O3 layered films as tritium permeation barrier%Al2O3/Au/Al2O3层状阻氚薄膜

    Institute of Scientific and Technical Information of China (English)

    汤波楷; 何业东; 曹江利; 唐涛; 饶咏初

    2012-01-01

    Single Al2O3 films, single Au films and Al2O3/Au/Al2O3 layered films were prepared on 316L stainless steel substrate by megnetron sputtering. Then vapour phase permeation experiment of deuterium through 316L substrate and its film materials were carried out at 500℃ with a partial pressure of deuterium 0. 06 MPa. The results indicate that morphology of the three films is good and no phenomenon of cracking and spalling is found after deuterium permeation. Deuterium permeation reduction factors (PRF) of these films are over one order of magnitude relative to clean 316L. The performance of barrying deuterium increases progressively in the order of single Al2O3 films, single Au films and Al2O3/Au/Al2O3 ayered films. Al2O3/Au/Al2O3 layered films exhibit excellent performance of barrying deuterium because the mechanical properties of the layered films are improved visibly by the ductile interlayer Au and the interdiffusion between Au and 316L substratc is hindered by Al2O3 layer, so Au can give full play to barry deuterium. The study shows that layered films like precious metal integrated with ceramics is a new way in the domain of tritium permeation barrier development.%采用磁控溅射法在316L不锈钢基体上分别沉积单层Al2O3,膜、单层Au膜以及Al2O3/Au/Al2O3层状薄膜。采用气相渗透法在500℃,氘分压为0.06MPa条件下测试了薄膜的阻氘性能。结果表明,3种薄膜氘渗透后,薄膜的形貌良好,无开裂、无剥落的现象,氘渗透率减低因子均比316L不锈钢基材增大一个数量级以上,阻氘效能按单层Al2O3,膜、单层Au膜以及Al2O3/Au/Al2O3层状薄膜依次递升。Al2O3/Au/Al2O3层状薄膜的优异阻氘效能可归因于,延性的Au夹层使层状薄膜的力学性能得到显著提高;Al2O3层能阻止Au与基体间互扩散,使Au能充分发挥阻氘效能。本研究表明,由贵金属与陶瓷阻氚材料构成的层状薄膜是发展阻氚涂层的新途径。

  5. Surface structures of Au-Pt bimetallic nanoclusters on thin film Al2O3/NiAl(100) probed with CO

    Science.gov (United States)

    Li, Y. D.; Hong, T. C.; Liao, T. W.; Luo, M. F.

    2013-12-01

    With infrared reflection absorption spectra and temperature-programmed desorption of CO as a probe molecule, we investigated the surface structure of Au-Pt bimetallic nanoclusters on thin-film Al2O3/NiAl(100) under ultrahigh vacuum conditions. Vapor Au and Pt (0.0-2.0 ML) were sequentially deposited onto Al2O3/NiAl(100) at 300 K to form bimetallic clusters; under the kinetic constraint, the order of the metal deposition made a variation in the surface structure of the grown clusters. For the deposition of Au onto Pt clusters (first Pt and then Au), the deposited Au decorated preferentially and then aggregated the edge sites of Pt clusters, instead of decorating the rest of Pt surface. For the metal deposition in the reverse order, the deposited Pt covered uniformly the surface of existing Au clusters and no preferential adsorption site was indicated. The infrared absorption for CO on Au sites was significantly enhanced when alloying occurred; this enhancement is primarily a local field effect depending on the coordination of CO-binding Au, and hence provides additional structural characterization of the grown clusters.

  6. Decomposition of methanol on partially alumina-encapsulated Pt nanoclusters supported on thin film Al2O3/NiAl(1 0 0)

    Science.gov (United States)

    Chao, C. S.; Li, Y. D.; Liao, T. W.; Hung, T. C.; Luo, M. F.

    2014-08-01

    Various surface probe techniques were applied to investigate the decomposition of methanol on partially alumina-encapsulated Pt nanoclusters on an ordered thin film of Al2O3/NiAl(1 0 0). The alumina-encapsulated Pt clusters were prepared on annealing Pt clusters (grown by vapor deposition onto the Al2O3/NiAl(1 0 0) at 300 K) to 650 K under UHV conditions. The annealed cluster became a Pt1+-Pt2+ state and partially encapsulated with inert alumina. Methanol on the partially encapsulated Pt clusters decomposed only on the uncovered Pt sites, and through both dehydrogenation to CO and scission of the C-O bond. In comparison to the reactions on Pt clusters, the C-O bond scission was altered little on the partially encapsulated clusters whereas the dehydrogenation was hindered to a certain extent. The quantities of CO and hydrogen produced from the dehydrogenation per surface Pt on the partially encapsulated clusters amounted to only half those on Pt clusters. The altered methanol decomposition was correlated to both electronic and ensemble effects.

  7. Microstructure and dielectric properties of (Ba 0.6Sr 0.4)TiO 3 thin films grown on super smooth glazed-Al 2O 3 ceramics substrate

    Science.gov (United States)

    Chen, Hongwei; Yang, Chuanren; Zheng, Shanxue; Zhang, Jihua; Zhang, Qiaozhen; Lei, Guanhuan; Lou, Feizhi; Yang, Lijun

    2011-12-01

    Modified substrates with nanometer scale smooth surface were obtained via coating a layer of CaO-Al2O3-SiO2 (CaAlSi) high temperature glaze with proper additives on the rough-95% Al2O3 ceramics substrates. (Ba0.6Sr0.4)TiO3 (BST) thin films were deposited on modified Al2O3 substrates by radio-frequency magnetron sputtering. The microstructure, dielectric, and insulating properties of BST thin films grown on glazed-Al2O3 substrates were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), and dielectric properties measurement. These results showed that microstructure and dielectric properties of BST thin films grown on glazed-Al2O3 substrates were almost consistent with that of BST thin films grown on LaAlO3 (1 0 0) single-crystal substrates. Thus, the expensive single-crystal substrates may be substituted by extremely cheap glazed-Al2O3 substrates.

  8. Effect of Al2O3 insulator thickness on the structural integrity of amorphous indium-gallium-zinc-oxide based thin film transistors.

    Science.gov (United States)

    Kim, Hak-Jun; Hwang, In-Ju; Kim, Youn-Jea

    2014-12-01

    The current transparent oxide semiconductors (TOSs) technology provides flexibility and high performance. In this study, multi-stack nano-layers of TOSs were designed for three-dimensional analysis of amorphous indium-gallium-zinc-oxide (a-IGZO) based thin film transistors (TFTs). In particular, the effects of torsional and compressive stresses on the nano-sized active layers such as the a-IGZO layer were investigated. Numerical simulations were carried out to investigate the structural integrity of a-IGZO based TFTs with three different thicknesses of the aluminum oxide (Al2O3) insulator (δ = 10, 20, and 30 nm), respectively, using a commercial code, COMSOL Multiphysics. The results are graphically depicted for operating conditions. PMID:25971080

  9. Morphological and optical properties of sol-gel derived 6SrO.6BaO.7Al2O3 thin films

    International Nuclear Information System (INIS)

    A novel 6SrO.6BaO.7Al2O3 (S6B6A7) thin film deposited onto soda lime float glass via sol-gel dip coating technique is reported. The morphological and compositional properties of the S6B6A7 thin films have been investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) revealing that the films were composed of S6B6A7 nanoparticles. The optical properties of the S6B6A7 films are affected by sol concentration, film thickness and annealing temperature as revealed by UV-vis transmittance. The transparency of S6B6A7 films improved on increasing annealing temperature up to 450 deg. C in air. The S6B6A7 films prepared using 2, 5, and 8 (wt.%) sols and annealed at 450 deg. C exhibit an average transmittance of over ∼91% in wide visible range.

  10. Hydrogen–argon plasma pre-treatment for improving the anti-corrosion properties of thin Al2O3 films deposited using atomic layer deposition on steel

    International Nuclear Information System (INIS)

    The effect of H2–Ar plasma pre-treatment prior to thermal atomic layer deposition (ALD) and plasma-enhanced atomic layer deposition (PEALD) of Al2O3 films on steel for corrosion protection was investigated. Time-of-flight secondary ion mass spectrometry and transmission electron microscopy were used to observe the changes in the interface. The electrochemical properties of the samples were studied with polarization measurements, and the coating porosities were calculated from the polarization results for easier comparison of the coatings. Prior to thermal ALD the plasma pre-treatment was observed to reduce the amount of impurities at the interface and coating porosity by 1–3 orders of magnitude. The anti-corrosion properties of the PEALD coatings could also be improved by the pre-treatment. However, exposure of the pre-treatment plasma activated steel surface to oxygen plasma species in PEALD led to facile oxide layer formation in the interface. The oxide layer formed this way was thicker than the native oxide layer and appeared to be detrimental to the protective properties of the coating. The best performance for PEALD Al2O3 coatings was achieved when, after the plasma pre-treatment, the surface was given time to regrow a thin protective interfacial oxide prior to exposure to the oxygen plasma. The different effects that thermal and plasma-enhanced ALD have on the substrate-coating interface were compared. The reactivity of the oxygen precursor was shown to have a significant influence on substrate surface in the early stages of film growth and thereafter also on the overall quality of the protective film. - Highlights: • Influence of H2–Ar plasma pre-treatment to ALD coatings on steel was studied. • The pre-treatment modified the coating–substrate interface composition and thickness. • The pre-treatment improved the barrier properties of the coatings

  11. Low-temperature multi-layer Al2 O3/TiO2 composite encapsulation thin film by atomic layer deposition%原子层沉积方法制备低温多层Al2 O3/TiO2复合封装薄膜的研究

    Institute of Scientific and Technical Information of China (English)

    周忠伟; 李民; 徐苗; 邹建华; 王磊; 彭俊彪

    2016-01-01

    Atomic layer deposition (ALD)is considered as one of the most promising thin-film encap-sulation technologies for flexible organic light-emitting diode (OLED)device because of high-quality films formed.In this work,different laminated structures of Al2 O3/TiO2 composite film were pre-pared at low temperature (80 ℃)by ALD method.The growth mechanism of Al2 O3 and TiO2 film was studied.The water vapor barrier properties of the different stacked structures of composite Al2 O3/TiO2 thin film were studied by the calcium film,which were analyzed by water vapor transmission rate (WVTR)test and contact angle measurements.The WVTR of the 5 nm/5 nm×8 dyads Al2 O3/TiO2 composite thin film was 2.1×10-5 g/m2/day and the OLED devices encapsulated by this optimized Al2 O3/TiO2 structure exhibited better lifetime characteristics in high temperature and high humidity test.%原子层沉积(ALD)方法可以制备出高质量薄膜,被认为是可应用于柔性有机电致发光器件(OLED)最有发展前景的薄膜封装技术之一.本文采用原子层沉积(ALD)技术,在低温(80℃)下,研究了 Al2 O3及TiO2薄膜的生长规律,通过钙膜水汽透过率(WVTR)、薄膜接触角测试等手段,研究了不同堆叠结构的多层 Al2 O3/TiO2复合封装薄膜的水汽阻隔特性,其中5 nm/5 nm×8 dyads(重复堆叠次数)的Al2 O3/TiO2叠层结构薄膜的WVTR达到2.1×10-5 g/m2/day.采用优化后的 Al2 O3/TiO2叠层结构薄膜对 OLED器件进行封装,实验发现封装后的 OLED 器件在高温高湿条件下展现了较好的寿命特性.

  12. Obstruction by CO of the decomposition of methanol on Pt nanoclusters on a thin film of Al2O3/NiAl(1 0 0)

    Science.gov (United States)

    Chao, C.-S.; Liao, T.-W.; Wang, C. X.; Li, Y.-D.; Hung, T.-C.; Luo, M.-F.

    2014-02-01

    Obstructed decomposition of methanol by CO on Pt nanoclusters deposited from the vapor onto thin-film Al2O3/NiAl(1 0 0) was studied with various surface probe techniques. The Pt clusters had mean diameter about 2.3 nm and height about 0.4 nm, and grew with phase fcc and primarily in the (1 1 1) orientation. CO adsorbed molecularly on the Pt clusters to saturate the sites atop Pt, and methanol was subsequently adsorbed for the reactions. The probability of dehydrogenation of methanol co-adsorbed with CO on the clusters was about half that of methanol not so co-adsorbed; CO molecules produced from dehydrogenated methanol adsorbed in a conformation with the CO bond nearly parallel to the surface. In contrast, the CO obstructed less effectively the scission of the CO bond of methanol: the probability of that scission was decreased only 20-30%. CO with atomic hydrogen produced from dehydrogenated methanol on the clusters exhibited a comparable obstructive effect, even though the produced CO occupied only the reactive sites on the clusters. The comparison indicates also that the inactive sites of the clusters comprise primarily terrace Pt.

  13. Epitaxial Growth of V2O3 Thin Films on c-Plane Al2O3 in Reactive Sputtering and Its Transformation to VO2 Films by Post Annealing

    Science.gov (United States)

    Okimura, Kunio; Suzuki, Yasushi

    2011-06-01

    Epitaxial growth of thin vanadium sesquioxide (V2O3) films on c-plane sapphire (c-Al2O3) substrates was achieved with reactive magnetron sputtering under restricted oxygen flow. Even with a film thickness of approximately 12 nm, highly c-axis textured growth of corundum V2O3 was realized because of the smaller mismatch of V2O3 against corundum Al2O3. Post annealing in O2 atmosphere for as-grown V2O3 films caused phase transformation to oxidized crystalline phases. At a moderate annealing temperature of 450 °C, the V2O3 thin films transformed to VO2 films, which show a resistivity change of over three orders of magnitude. The X-ray photoelectron spectroscopy spectra for the annealed VO2 film showed a single charge state of V4+, indicating a homogeneous crystalline structure, in contrast to the inhomogeneous feature with mixed charge states of V in addition to V3+ for as-grown V2O3 film. This method is promising to prepare thin VO2 films with metal-insulator transition in productive reactive sputtering and to examine crystalline phase transformation mechanisms, including phase coexistence.

  14. Enhanced photoelectrocatalytic performance of α-Fe2O3 thin films by surface plasmon resonance of Au nanoparticles coupled with surface passivation by atom layer deposition of Al2O3

    OpenAIRE

    Liu, Yuting; Xu, Zhen; Yin, Min; Fan, Haowen; Cheng, Weijie; Lu, Linfeng; SONG, YE; Ma, Jing; Zhu, Xufei

    2015-01-01

    The short lifetime of photogenerated charge carriers of hematite (α-Fe2O3) thin films strongly hindered the PEC performances. Herein, α-Fe2O3 thin films with surface nanowire were synthesized by electrodeposition and post annealing method for photoelectrocatalytic (PEC) water splitting. The thickness of the α-Fe2O3 films can be precisely controlled by adjusting the duration of the electrodeposition. The Au nanoparticles (NPs) and Al2O3 shell by atom layer deposition were further introduced to...

  15. 原子层沉积Al2O3薄膜钝化n型单晶硅表面的研究%n-type Crystalline Si Surface Passivated by Al2O3 Thin Films Synthesized by Atomic Layer Deposition

    Institute of Scientific and Technical Information of China (English)

    李想; 颜钟惠; 刘阳辉; 竺立强

    2013-01-01

    以三甲基铝(TMA)和水为反应源,采用原子层沉积(ALD)技术在n型单晶硅表面沉积15 nm、30 nm和100 nm的Al2O3薄膜,并对样品进行快速退火(RTA)处理.采用少子寿命测试仪测试样品的有效少子寿命,获得了表面复合速率(SRV),通过X射线光电子能谱(XPS)分析了薄膜的化学成分,在此基础上研究了薄膜厚度及退火条件对钝化效果的影响,并分析了钝化机理.结果表明:ALD技术制备的Al2O3薄膜经退火后可使n型单晶硅SRV值降低到7 cm/s,表面钝化效果显著.%A12O3 thin films with the thickness of 15 ran, 30 nm and 100 nm were synthesized by thermal atomic layer deposition (ALD) using A1(CH3 )3 and H2O as sources. The surface passivation of n-type monocrystalline silicon was studied. After receiving rapid thermal annealing, the impact of film thickness and annealing conditions on the passivation performance was investigated. The passivation mechanism was analyzed through characterizing the effective minority carrier lifetime, surface recombination velocities and X-ray photoelectron spectroscopy (XPS). It is shown that a high level surface passivation was addressed by post-deposition annealed AI2O3 thin films with an effective surface recombination velocity of 7 cm/s.

  16. Role of Ge and Si substrates in higher-k tetragonal phase formation and interfacial properties in cyclical atomic layer deposition-anneal Hf1-xZrxO2/Al2O3 thin film stacks

    Science.gov (United States)

    Dey, Sonal; Tapily, Kandabara; Consiglio, Steven; Clark, Robert D.; Wajda, Cory S.; Leusink, Gert J.; Woll, Arthur R.; Diebold, Alain C.

    2016-09-01

    Using a five-step atomic layer deposition (ALD)-anneal (DADA) process, with 20 ALD cycles of metalorganic precursors followed by 40 s of rapid thermal annealing at 1073 K, we have developed highly crystalline Hf1-xZrxO2 (0 ≤ x ≤ 1) thin films (<7 nm) on ˜1 nm ALD Al2O3 passivated Ge and Si substrates for applications in higher-k dielectric metal oxide semiconductor field effect transistors below 10 nm technology node. By applying synchrotron grazing incidence x-ray d-spacing maps, x-ray photoelectron spectroscopy (XPS), and angle-resolved XPS, we have identified a monoclinic to tetragonal phase transition with increasing ZrO2 content, elucidated the role of the Ge vs Si substrates in complete tetragonal phase formation (CTPF), and determined the interfacial characteristics of these technologically relevant films. The ZrO2 concentration required for CTPF is lower on Ge than on Si substrates (x ˜ 0.5 vs. x ˜ 0.86), which we attribute as arising from the growth of an ultra-thin layer of metal germanates between the Hf1-xZrxO2 and Al2O3/Ge, possibly during the first deposition and annealing cycle. Due to Ge-induced tetragonal phase stabilization, the interfacial metal germanates could act as a template for the subsequent preferential growth of the tetragonal Hf1-xZrxO2 phase following bottom-up crystallization during the DADA ALD process. We surmise that the interfacial metal germanate layer also function as a diffusion barrier limiting excessive Ge uptake into the dielectric film. An ALD Al2O3 passivation layer of thickness ≥1.5 nm is required to minimize Ge diffusion for developing highly conformal and textured HfO2 based higher-k dielectrics on Ge substrates using the DADA ALD process.

  17. The investigation of ZnO:Al2O3/metal composite back reflectors in amorphous silicon germanium thin film solar cells

    Institute of Scientific and Technical Information of China (English)

    Wang Guang-Hong; Zhao Lei; Yan Bao-Jun; Chen Jing-Wei; Wang Ge; Diao Hong-Wei; Wang Wen-Jing

    2013-01-01

    Different aluminum-doped ZnO (AZO)/metal composite thin films,including AZO/Ag/Al,AZO/Ag/nickelchromium alloy (NiCr),and AZO/Ag/NiCr/Al,are utilized as the back reflectors of p-i-n amorphous silicon germanium thin film solar cells.NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion,which increases the short circuit current density of solar cell.NiCr and NiCr/Al layers are used as protective layers of Ag layer against oxidation and sulfurization,the higher efficiency of solar cell is achieved.The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best.The initial conversion efficiency is achieved to be 8.05%.

  18. Structural, optical, and magnetic properties of Zn0.93Mn0.07O thin films grown on Al2O3 (0001) by r.f. magnetron sputtering

    International Nuclear Information System (INIS)

    Zn1-xMnxO thin films were grown on Al2O3 (0001) substrates by an r.f. magnetron sputtering method. The films grown without buffer layer showed the columnar-structured configuration. In contrast, the films grown by employing a 40-nm-thick buffer layer showed a significantly clean surface with mirror-like morphology. From the results of photoluminescence measurements at room temperature, UV emission originating from near-band -edge emission was observed for the mirror-like Zn0.93Mn0.07O thin films, while the columnar-structured Zn0.93Mn0.07O thin films were optically poor. The mirror-like Zn0.93Mn0.07O thin films clearly showed a hysteretic behavior for the measurement of magnetization, which is obvious evidence of ferromagnetism. The columnar-structured Zn0.93Mn0.07O thin films revealed a step-like curve around 20 ∼ 50 K in the characteristic of temperature-dependent magnetization, which might be attributed to the solid solution of Mn3O4 observed in X-ray diffraction patterns.

  19. Controlled direct growth of Al2O3-doped HfO2 films on graphene by H2O-based atomic layer deposition.

    Science.gov (United States)

    Zheng, Li; Cheng, Xinhong; Yu, Yuehui; Xie, Yahong; Li, Xiaolong; Wang, Zhongjian

    2015-02-01

    Graphene has been drawing worldwide attention since its discovery in 2004. In order to realize graphene-based devices, thin, uniform-coverage and pinhole-free dielectric films with high permittivity on top of graphene are required. Here we report the direct growth of Al2O3-doped HfO2 films onto graphene by H2O-based atom layer deposition (ALD). Al2O3-onto-HfO2 stacks benefited the doping of Al2O3 into HfO2 matrices more than HfO2-onto-Al2O3 stacks did due to the micro-molecular property of Al2O3 and the high chemical activity of trimethylaluminum (TMA). Al2O3 acted as a network modifier, maintained the amorphous structure of the film even to 800 °C, and made the film smooth with a root mean square (RMS) roughness of 0.8 nm, comparable to the surface of pristine graphene. The capacitance and the relative permittivity of Al2O3-onto-HfO2 stacks were up to 1.18 μF cm(-2) and 12, respectively, indicating the high quality of Al2O3-doped HfO2 films on graphene. Moreover, the growth process of Al2O3-doped HfO2 films introduced no detective defects into graphene confirmed by Raman measurements. PMID:25519447

  20. Luminescent properties of Al2O3:Ce single crystalline films under synchrotron radiation excitation

    Science.gov (United States)

    Zorenko, Yu.; Zorenko, T.; Gorbenko, V.; Savchyn, V.; Voznyak, T.; Fabisiak, K.; Zhusupkalieva, G.; Fedorov, A.

    2016-09-01

    The paper is dedicated to study the luminescent and scintillation properties of the Al2O3:Ce single crystalline films (SCF) grown by LPE method onto saphire substrates from PbO based flux. The structural quality of SCF samples was investigated by XRD method. For characterization of luminescent properties of Al2O3:Ce SCFs the cathodoluminescence spectra, scintillation light yield (LY) and decay kinetics under excitation by α-particles of Pu239 source were used. We have found that the scintillation LY of Al2O3:Ce SCF samples is relatively large and can reach up to 50% of the value realized in the reference YAG:Ce SCF. Using the synchrotron radiation excitation in the 3.7-25 eV range at 10 K we have also determined the basic parameters of the Ce3+ luminescence in Al2O3 host.

  1. Growth and characterization of Al2O3 films on fluorine functionalized epitaxial graphene

    Science.gov (United States)

    Robinson, Zachary R.; Jernigan, Glenn G.; Wheeler, Virginia D.; Hernández, Sandra C.; Eddy, Charles R.; Mowll, Tyler R.; Ong, Eng Wen; Ventrice, Carl A.; Geisler, Heike; Pletikosic, Ivo; Yang, Hongbo; Valla, Tonica

    2016-08-01

    Intelligent engineering of graphene-based electronic devices on SiC(0001) requires a better understanding of processes used to deposit gate-dielectric materials on graphene. Recently, Al2O3 dielectrics have been shown to form conformal, pinhole-free thin films by functionalizing the top surface of the graphene with fluorine prior to atomic layer deposition (ALD) of the Al2O3 using a trimethylaluminum (TMA) precursor. In this work, the functionalization and ALD-precursor adsorption processes have been studied with angle-resolved photoelectron spectroscopy, low energy electron diffraction, and X-ray photoelectron spectroscopy. It has been found that the functionalization process has a negligible effect on the electronic structure of the graphene, and that it results in a twofold increase in the adsorption of the ALD-precursor. In situ TMA-dosing and XPS studies were also performed on three different Si(100) substrates that were terminated with H, OH, or dangling Si-bonds. This dosing experiment revealed that OH is required for TMA adsorption. Based on those data along with supportive in situ measurements that showed F-functionalization increases the amount of oxygen (in the form of adsorbed H2O) on the surface of the graphene, a model for TMA-adsorption on graphene is proposed that is based on a reaction of a TMA molecule with OH.

  2. Enhancing the thermal conductivity of polymer-assisted deposited Al2O3 film by nitrogen doping

    Institute of Scientific and Technical Information of China (English)

    Huang Jiang; Zhang Yin; Pan Tai-Song; Zeng Bo; Hu Guo-Hua; Lin Yuan

    2012-01-01

    Polymer-assisted deposition technique has been used to deposit Al2O3 and N-doped Al2O3 (AlON) thin films on Si(100) substrates.The chemical compositions,crystallinity,and thermal conductivity of the as-grown films have been characterized by X-ray photoelectron spectroscopy (XPS),X-ray diffraction (XRD),and 3-omega method,respectively.Amorphous and polycrystalline Al2O3 and AlON thin films have been formed at 700 ℃ and 1000 ℃.The thermal conductivity results indicated that the effect of nitrogen doping on the thermal conductivity is determined by the competition of the increase of Al-N bonding and the suppression of crystallinity.A 67% enhancement in thermal conductivity has been achieved for the samples grown at 700 ℃,demonstrating that the nitrogen doping is an effective way to improve the thermal performance of polymer-assisted-deposited Al2O3 thin films at a relatively low growth temperature.

  3. Comparative Study of Properties of ZnO/GaN/Al2O3 and ZnO/Al2O3 Films Grown by Low-Pressure Metal Organic Chemical Vapour Deposition

    Institute of Scientific and Technical Information of China (English)

    赵佰军; 杨洪军; 杜国同; 缪国庆; 杨天鹏; 张源涛; 高仲民; 王金忠; 方秀军; 刘大力; 李万成; 马燕; 杨晓天; 刘博阳

    2003-01-01

    ZnO films were deposited by low-pressure metal organic chemical vapour deposition on epi-GaN/Al2O3 films and c-Al2O3 substrates.The structure and optical properties of the ZnO/GaN/Al2O3 and ZnO/Al2O3 films have been investigated to determine the differences between the two substrates.ZnO films on GaN/Al2O3 show very strong emission features associated with exciton transitions,just as ZnO films on Al2O3,while the crystalline structural qualities for ZnO films on GaN/Al2O3 are much better than those for ZnO films directly grown on Al2O3 substrates.Zn and O elements in the deposited ZnO/GaN/Al2O3 and ZnO/Al2O3 films are investigated and compared by x-ray photoelectron spectroscopy.According to the statistical results,the Zn/O ratio changes from Zn-rich for ZnO/Al2O3 films to O-rich for ZnO/GaN/Al2O3 films.

  4. A thin layer fiber-coupled luminescence dosimeter based on Al2O3:C

    DEFF Research Database (Denmark)

    Klein, F.A.; Greilich, Steffen; Andersen, Claus Erik;

    2011-01-01

    In this paper we present a fiber-coupled luminescent Al2O3:C dosimeter probe with high spatial resolution (0.1 mm). It is based on thin layers of Al2O3:C crystal powder and a UV-cured acrylate monomer composition. The fabrication of the thin layers is described in detail. No influence of the intr......In this paper we present a fiber-coupled luminescent Al2O3:C dosimeter probe with high spatial resolution (0.1 mm). It is based on thin layers of Al2O3:C crystal powder and a UV-cured acrylate monomer composition. The fabrication of the thin layers is described in detail. No influence...... without sensitivity corrections. For protons, a relative luminescence efficiency hHCP of 0.715 0.014 was found in the Bragg peak. For carbon ions, a value of 0.498 0.001 was found in the entrance channel, 0.205 0.015 in the Bragg peak, and a mean of 0.413 0.050 in the tail region. The mean range...

  5. Antireflective bilayer coatings based on Al2O3 film for UV region

    OpenAIRE

    Marszałek Konstanty; Winkowski Paweł; Marszałek Marta

    2015-01-01

    Bilayer antireflective coatings consisting of aluminium oxide Al2O3/MgF2 and Al2O3/SiO2 are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5 × 10-3 Pa in the presence of oxygen, and magnesium fluoride was prepared by thermal evaporation on heated optical lenses made from quartz glass (Corning HPFS). Substrate temperature was maintained at 250 _C during the deposition. Thickness and deposition rate were controlled with a thickness measuring syste...

  6. Structural Characteristics and Magnetic Properties of Al2O3 Matrix-Based Co-Cermet Nanogranular Films

    Directory of Open Access Journals (Sweden)

    Giap Van Cuong

    2015-01-01

    Full Text Available Magnetic micro- and nanogranular materials prepared by different methods have been used widely in studies of magnetooptical response. However, among them there seems to be nothing about magnetic nanogranular thin films prepared by a rf cosputtering technique for both metals and insulators till now. This paper presented and discussed preparation, structural characteristics, and magnetic properties of alumina (Al2O3 matrix-based granular Co-cermet thin films deposited by means of the cosputtering technique for both Co and Al2O3. By varying the ferromagnetic (Co atomic fraction, x, from 0.04 to 0.63, several dominant features of deposition for these thin films were shown. Structural characteristics by X-ray diffraction confirmed a cermet-type structure for these films. Furthermore, magnetic behaviours presented a transition from paramagnetic- to superparamagnetic- and then to ferromagnetic-like properties, indicating agglomeration and growth following Co components of Co clusters or nanoparticles. These results show a typical granular Co-cermet feature for the Co-Al2O3 thin films prepared, in which Co magnetic nanogranules are dispersed in a ceramic matrix. Such nanomaterials can be applied suitably for our investigations in future on the magnetooptical responses of spinplasmonics.

  7. Antireflective bilayer coatings based on Al2O3 film for UV region

    Directory of Open Access Journals (Sweden)

    Marszałek Konstanty

    2015-03-01

    Full Text Available Bilayer antireflective coatings consisting of aluminium oxide Al2O3/MgF2 and Al2O3/SiO2 are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5 × 10-3 Pa in the presence of oxygen, and magnesium fluoride was prepared by thermal evaporation on heated optical lenses made from quartz glass (Corning HPFS. Substrate temperature was maintained at 250 _C during the deposition. Thickness and deposition rate were controlled with a thickness measuring system Inficon XTC/2. The experimental results of the optical measurements carried out during and after the deposition process have been presented. Physical thickness measurements were made during the deposition process and resulted in 44 nm/52 nm for Al2O3/MgF2 and 44 nm/50 nm for Al2O3/SiO2 system. Optimization was carried out for ultraviolet region with minimum of reflectance at 300 nm. The influence of post deposition annealing on the crystal structure was determined by X-ray measurements. In the range from ultraviolet to the beginning of visible region, the reflectance of both systems decreased and reached minimum at 290 nm. The value of reflectance at this point, for the coating Al2O3/MgF2 was equal to R290nm = 0.6 % and for Al2O3/SiO2R290nm = 1.1 %. Despite the difference between these values both are sufficient for applications in the UV optical systems for medicine and UV laser technology.

  8. The impact of ultrathin Al2O3 films on the electrical response of p-Ge/Al2O3/HfO2/Au MOS structures

    Science.gov (United States)

    Botzakaki, M. A.; Skoulatakis, G.; Kennou, S.; Ladas, S.; Tsamis, C.; Georga, S. N.; Krontiras, C. A.

    2016-09-01

    It is well known that the most critical issue in Ge CMOS technology is the successful growth of high-k gate dielectrics on Ge substrates. The high interface quality of Ge/high-k dielectric is connected with advanced electrical responses of Ge based MOS devices. Following this trend, atomic layer deposition deposited ultrathin Al2O3 and HfO2 films were grown on p-Ge. Al2O3 acts as a passivation layer between p-Ge and high-k HfO2 films. An extensive set of p-Ge/Al2O3/HfO2 structures were fabricated with Al2O3 thickness ranging from 0.5 nm to 1.5 nm and HfO2 thickness varying from 2.0 nm to 3.0 nm. All structures were characterized by x-ray photoelectron spectroscopy (XPS) and AFM. XPS analysis revealed the stoichiometric growth of both films in the absence of Ge sub-oxides between p-Ge and Al2O3 films. AFM analysis revealed the growth of smooth and cohesive films, which exhibited minimal roughness (~0.2 nm) comparable to that of clean bare p-Ge surfaces. The electrical response of all structures was analyzed by C-V, G-V, C-f, G-f and J-V characteristics, from 80 K to 300 K. It is found that the incorporation of ultrathin Al2O3 passivation layers between p-Ge and HfO2 films leads to superior electrical responses of the structures. All structures exhibit well defined C-V curves with parasitic effects, gradually diminishing and becoming absent below 170 K. D it values were calculated at each temperature, using both Hill-Coleman and Conductance methods. Structures of p-Ge/0.5 nm Al2O3/2.0 nm HfO2/Au, with an equivalent oxide thickness (EOT) equal to 1.3 nm, exhibit D it values as low as ~7.4  ×  1010 eV-1 cm-2. To our knowledge, these values are among the lowest reported. J-V measurements reveal leakage currents in the order of 10-1 A cm-2, which are comparable to previously published results for structures with the same EOT. A complete mapping of the energy distribution of D its into the energy bandgap of p-Ge, from the valence band

  9. Application of Al2O3-based polyimide composite thick films to integrated substrates using aerosol deposition method

    International Nuclear Information System (INIS)

    Al2O3-based polyimide composite thick films were successfully fabricated with reduction of residual stress and improvement in plasticity for integrated substrates at room temperature by aerosol deposition method. Scanning electron microscopy and energy dispersive spectroscopy mappings exhibited a high content of Al2O3 evenly distributed in the composite thick films. The relative dielectric permittivity and loss tangent of Al2O3-based polyimide composite thick films were 7.6 and 0.007, respectively. There was almost no change in the crystallite size of Al2O3-based polyimide composite thick films compared with that of starting powder due to the reduction of kinetic energy by polyimide during collision on the substrates. Moreover, it was confirmed that the residual stress of Al2O3-based polyimide composite thick films remarkably decreased compared with that of Al2O3 thick films.

  10. Enhanced water vapor barrier properties for biopolymer films by polyelectrolyte multilayer and atomic layer deposited Al 2 O 3 double-coating

    Science.gov (United States)

    Hirvikorpi, Terhi; Vähä-Nissi, Mika; Harlin, Ali; Salomäki, Mikko; Areva, Sami; Korhonen, Juuso T.; Karppinen, Maarit

    2011-09-01

    Commercial polylactide (PLA) films are coated with a thin (20 nm) non-toxic polyelectrolyte multilayer (PEM) film made from sodium alginate and chitosan and additionally with a 25-nm thick atomic layer deposited (ALD) Al 2O 3 layer. The double-coating of PEM + Al 2O 3 is found to significantly enhance the water vapor barrier properties of the PLA film. The improvement is essentially larger compared with the case the PLA film being just coated with an ALD-grown Al 2O 3 layer. The enhanced water vapor barrier characteristics of the PEM + Al 2O 3 double-coated PLA films are attributed to the increased hydrophobicity of the surface of these films.

  11. Electrical characteristics of SrTiO3/Al2O3 laminated film capacitors

    Science.gov (United States)

    Peng, Yong; Yao, Manwen; Chen, Jianwen; Xu, Kaien; Yao, Xi

    2016-07-01

    The electrical characteristics of SrTiO3/Al2O3 (160 nm up/90 nm down) laminated film capacitors using the sol-gel process have been investigated. SrTiO3 is a promising and extensively studied high-K dielectric material, but its leakage current property is poor. SrTiO3/Al2O3 laminated films can effectively suppress the demerits of pure SrTiO3 films under low electric field, but the leakage current value reaches to 0.1 A/cm2 at higher electric field (>160 MV/m). In this study, a new approach was applied to reduce the leakage current and improve the dielectric strength of SrTiO3/Al2O3 laminated films. Compared to laminated films with Au top electrodes, dielectric strength of laminated films with Al top electrodes improves from 205 MV/m to 322 MV/m, simultaneously the leakage current maintains the same order of magnitude (10-4 A/cm2) until the breakdown occurs. The above electrical characteristics are attributed to the anodic oxidation reaction in origin, which can repair the defects of laminated films at higher electric field. The anodic oxidation reactions have been confirmed by the corresponding XPS measurement and the cross sectional HRTEM analysis. This work provides a new approach to fabricate dielectrics with high dielectric strength and low leakage current.

  12. Influence of Content of Al2O3 on Structure and Properties of Nanocomposite Nb-B-Al-O films.

    Science.gov (United States)

    Liu, Na; Dong, Lei; Dong, Lei; Yu, Jiangang; Pan, Yupeng; Wan, Rongxin; Gu, Hanqing; Li, Dejun

    2015-12-01

    Nb-B-Al-O nanocomposite films with different power of Al2O3 were successfully deposited on the Si substrate via multi-target magnetron co-sputtering method. The influences of Al2O3's content on structure and properties of obtained nanocomposite films through controlling Al2O3's power were investigated. Increasing the power of Al2O3 can influence the bombarding energy and cause the momentum transfer of NbB2. This can lead to the decreasing content of Al2O3. Furthermore, the whole films showed monocrystalline NbB2's (100) phase, and Al2O3 shaded from amorphous to weak cubic-crystalline when decreasing content of Al2O3. This structure and content changes were proof by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). When NbB2 grains were far from each other in lower power of Al2O3, the whole films showed a typical nanocomposite microstructure with crystalline NbB2 grains embedded in a matrix of an amorphous Al2O3 phase. Continuing increasing the power of Al2O3, the less content of Al2O3 tended to cause crystalline of cubic-Al2O3 between the close distances of different crystalline NbB2 grains. The appearance of cubic-crystallization Al2O3 can help to raise the nanocomposite films' mechanical properties to some extent. The maximum hardness and elastic modulus were up to 21.60 and 332.78 GPa, which were higher than the NbB2 and amorphous Al2O3 monolithic films. Furthermore, this structure change made the chemistry bond of O atom change from the existence of O-Nb, O-B, and O-Al bonds to single O-Al bond and increased the specific value of Al and O. It also influenced the hardness in higher temperature, which made the hardness variation of different Al2O3 content reduced. These results revealed that it can enhance the films' oxidation resistance properties and keep the mechanical properties at high temperature. The study highlighted the importance of controlling the Al2O3's content to prepare

  13. Stabilization of Hydrogen Production via Methanol Steam Reforming in Microreactor by Al2O3 Nano-Film Enhanced Catalyst Adhesion.

    Science.gov (United States)

    Jeong, Heondo; Na, Jeong-Geol; Jang, Min Su; Ko, Chang Hyun

    2016-05-01

    In hydrogen production by methanol steam reforming reaction with microchannel reactor, Al2O3 thin film formed by atomic layer deposition (ALD) was introduced on the surface of microchannel reactor prior to the coating of catalyst particles. Methanol conversion rate and hydrogen production rate, increased in the presence of Al2O3 thin film. Over-view and cross-sectional scanning electron microscopy study showed that the adhesion between catalyst particles and the surface of microchannel reactor enhanced due to the presence of Al2O3 thin film. The improvement of hydrogen production rate inside the channels of microreactor mainly came from the stable fixation of catalyst particles on the surface of microchannels. PMID:27483762

  14. Stabilization of Hydrogen Production via Methanol Steam Reforming in Microreactor by Al2O3 Nano-Film Enhanced Catalyst Adhesion.

    Science.gov (United States)

    Jeong, Heondo; Na, Jeong-Geol; Jang, Min Su; Ko, Chang Hyun

    2016-05-01

    In hydrogen production by methanol steam reforming reaction with microchannel reactor, Al2O3 thin film formed by atomic layer deposition (ALD) was introduced on the surface of microchannel reactor prior to the coating of catalyst particles. Methanol conversion rate and hydrogen production rate, increased in the presence of Al2O3 thin film. Over-view and cross-sectional scanning electron microscopy study showed that the adhesion between catalyst particles and the surface of microchannel reactor enhanced due to the presence of Al2O3 thin film. The improvement of hydrogen production rate inside the channels of microreactor mainly came from the stable fixation of catalyst particles on the surface of microchannels.

  15. Ethanol gas sensing properties of Al2O3-doped ZnO thick film resistors

    Indian Academy of Sciences (India)

    D R Patil; L A Patil; D P Amalnerkar

    2007-12-01

    The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ethanol vapours at 300°C. Aluminium oxide grains dispersed around ZnO grains would result into the barrier height among the grains. Upon exposure of ethanol vapours, the barrier height would decrease greatly leading to drastic increase in conductance. It is reported that the surface misfits, calcination temperature and operating temperature can affect the microstructure and gas sensing performance of the sensor. The efforts are, therefore, made to create surface misfits by doping Al2O3 into zinc oxide and to study the sensing performance. The quick response and fast recovery are the main features of this sensor. The effects of microstructure and additive concentration on the gas response, selectivity, response time and recovery time of the sensor in the presence of ethanol vapours were studied and discussed.

  16. Structure and micro-tribologicai properties of PTFE/Al2O3 micro-assembling film

    Institute of Scientific and Technical Information of China (English)

    汤卉; 贾会娟; 邵俊鹏

    2003-01-01

    In order to improve the wear resistance of elastic metallic-plastic thrust bearing pad,micro-assembling PTFE/Al2O3 multi-layer film was developed by alternating radio frequency(RF)magnetron sputtering PTFE and Al2O3 targets.For enhancing the adhesion of the interfaces between PTFE and Al2O3 film,N+ implantation was employed.The structure,mechanical and micro-tribological properties were studied by XPS,X-ray photoelectron spectrometer and atomic force and friction force microscope(AFM/FFM).The results show that the multi-layer consists of Al2O3 component and crystalline PTFE.The hardness of the multi-layer modified by ion implantation is less than that of Al2O3,but its toughness is greatly improved.The friction coefficient of PTFE/ Al2 O3 multi-layer modified by ion implantation is much lower than that of Al2 O3 film,and its resistance to wear is much greater than that of PTFE film.Therefore the wear resistance of elastic metallic-plastic thrust bearing pad is greatly improved.

  17. Properties of Ultrathin Al2O3-TiO2 Nanolaminate Films for Gate Dielectric Applications Deposited by Plasma-Assisted Atomic Layer Deposition

    Science.gov (United States)

    Garces, Nelson; Meyer, David; Nepal, Neeraj; Wheeler, Virginia; Eddy, Charles

    2012-02-01

    High permittivity dielectrics such as Al2O3, HfO2, Ta2O5, TiO2, etc., are an essential component of aggressively-scaled III-V and graphene field effect transistors (FETs) where insulators are necessary to reduce gate leakage current while maintaining high gate capacitance and charge control of the channel. Atomic layer deposition (ALD) has the capability to deposit hybrid films, or nanolaminates, of two or more dielectrics that have unique properties. Thin [Al2O3+TiO2] nanolaminates with varying TiO2 and Al2O3 content were deposited on n-Si substrates at ˜225-300 C using ALD. A nanolaminate is composed of bilayers, defined as the sum of (x)Al2O3 and (y)TiO2, where x, and y indicate the number of times a component monolayer is repeated. While the overall thickness of the dielectric was held at ˜ 17-20 nm, the relative ratio of Al2O3 to TiO2 in the bilayer stack was varied to evaluate changes in the material properties and electrical performance of the oxides. C-V and I-V measurements on various [(x)TiO2+(y)Al2O3] MOS capacitors were taken. The high-TiO2-content films show limited evidence of oxide charge trapping and relatively large dielectric constants (κ˜15), whereas the high-Al2O3-content films offer a larger optical bandgap and improved suppression of leakage current. We will discuss the properties of very thin nanolaminates and their possible use as gate oxides. Morphological, electrical, and XPS composition assessments will be presented.

  18. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    Science.gov (United States)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-06-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage (C-V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage (R-V) characteristics of variable-area photodiodes. The minority carrier lifetime, C-V characteristics, and R-V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  19. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    Science.gov (United States)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-09-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  20. Photoluminescence enhancement in porous SiC passivated by atomic layer deposited Al2O3 films

    DEFF Research Database (Denmark)

    Lu, Weifang; Iwasa, Yoshimi; Ou, Yiyu;

    2016-01-01

    Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved.......Porous SiC co-doped with B and N was passivated by atomic layer deposited (ALD) Al2O3 films to enhance the photoluminescence. After optimizing the deposition conditions, as high as 14.9 times photoluminescence enhancement has been achieved....

  1. Formation of Al2O3-HfO2 Eutectic EBC Film on Silicon Carbide Substrate

    Directory of Open Access Journals (Sweden)

    Kyosuke Seya

    2015-01-01

    Full Text Available The formation mechanism of Al2O3-HfO2 eutectic structure, the preparation method, and the formation mechanism of the eutectic EBC layer on the silicon carbide substrate are summarized. Al2O3-HfO2 eutectic EBC film is prepared by optical zone melting method on the silicon carbide substrate. At high temperature, a small amount of silicon carbide decomposed into silicon and carbon. The components of Al2O3 and HfO2 in molten phase also react with the free carbon. The Al2O3 phase reacts with free carbon and vapor species of AlO phase is formed. The composition of the molten phase becomes HfO2 rich from the eutectic composition. HfO2 phase also reacts with the free carbon and HfC phase is formed on the silicon carbide substrate; then a high density intermediate layer is formed. The adhesion between the intermediate layer and the substrate is excellent by an anchor effect. When the solidification process finished before all of HfO2 phase is reduced to HfC phase, HfC-HfO2 functionally graded layer is formed on the silicon carbide substrate and the Al2O3-HfO2 eutectic structure grows from the top of the intermediate layer.

  2. Ellipsometry and XPS comparative studies of thermal and plasma enhanced atomic layer deposited Al2O3-films

    Directory of Open Access Journals (Sweden)

    Jörg Haeberle

    2013-11-01

    Full Text Available We report on results on the preparation of thin (2O3 films on silicon substrates using thermal atomic layer deposition (T-ALD and plasma enhanced atomic layer deposition (PE-ALD in the SENTECH SI ALD LL system. The T-ALD Al2O3 layers were deposited at 200 °C, for the PE-ALD films we varied the substrate temperature range between room temperature (rt and 200 °C. We show data from spectroscopic ellipsometry (thickness, refractive index, growth rate over 4” wafers and correlate them to X-ray photoelectron spectroscopy (XPS results. The 200 °C T-ALD and PE-ALD processes yield films with similar refractive indices and with oxygen to aluminum elemental ratios very close to the stoichiometric value of 1.5. However, in both also fragments of the precursor are integrated into the film. The PE-ALD films show an increased growth rate and lower carbon contaminations. Reducing the deposition temperature down to rt leads to a higher content of carbon and CH-species. We also find a decrease of the refractive index and of the oxygen to aluminum elemental ratio as well as an increase of the growth rate whereas the homogeneity of the film growth is not influenced significantly. Initial state energy shifts in all PE-ALD samples are observed which we attribute to a net negative charge within the films.

  3. Microwave Band-Pass Filter with Aerosol-Deposited Al2O3-Polytetrafluoroethylene Composite Thick Films.

    Science.gov (United States)

    Lee, Ji-Won; Koh, Jung-Hyuk

    2015-03-01

    Fabrication of microwave band-pass filter with coplanar waveguide with ground structure was realized by employing Al2O3-polytetrafluoroethylene (Al2O3-PTFE) composite thick films for integrated substrates produced by aerosol deposition (AD). In order to predict the performance of the band-pass filter, 3-D electromagnetic simulations were performed by high-frequency structure analysis. The thick Al2O3-PTFE composite films prepared by the AD process had submicron-sized Al2O3 crystallites due to the shock-absorbing effect of PTFE during the film growth. The thick films were characterized by X-ray diffraction and scanning electron microscopy. The Cu transmission lines with the thickness of 300 nm were deposited by electron-beam evaporation to form the band-pass filter. The fabricated band-pass filter showed similar characteristics to the simulation results. The insertion loss and resonance frequency were 9.5 dB and 2.3 GHz, respectively. PMID:26413656

  4. Photoluminescence Enhancement in Nanotextured Fluorescent SiC Passivated by Atomic Layer Deposited Al2O3 Films

    DEFF Research Database (Denmark)

    Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas;

    2016-01-01

    The influence of thickness of atomic layer deposited Al2O3 films on nano-textured fluorescent 6H-SiC passivation is investigated. The passivation effect on the light emission has been characterized by photoluminescence and time-resolved photoluminescence at room temperature. The results show...

  5. Impact of graphene–graphite films on electrical properties of Al2O3 metal–insulator–semiconductor structure

    Science.gov (United States)

    Choi, Kyeong-Keun; Kee, Jong; Park, Chan-Gyung; Kim, Deok-kee

    2016-08-01

    The diffusion barrier property of directly grown graphene–graphite films between Al2O3 films and Si substrates was evaluated using metal–insulator–semiconductor (MIS) structures. The roughness, morphology, sheet resistance, Raman spectrum, chemical composition, and breakdown field strength of the films were investigated after rapid thermal annealing. About 2.5-nm-thick graphene–graphite films effectively blocked the formation of the interfacial layer between Al2O3 films and Si, which was confirmed by the decreased breakdown field strength of graphene–graphite film structures. After annealing at 975 °C for 90 s, the increase in the mean breakdown field strength of the structure with the ∼2.5-nm-thick graphene–graphite film was about 91% (from 8.7 to 16.6 MV/cm), while that without the graphene–graphite film was about 187% (from 11.2 to 32.1 MV/cm). Si atom diffusion into Al2O3 films was reduced by applying the carbon-based diffusion barrier.

  6. Giant Hall Effect of Fe45.51(Al2O3)54.49 Nano-granular Film

    Institute of Scientific and Technical Information of China (English)

    XU Qing-Yu; NI Gang; SANG Hai; DU You-Wei

    2000-01-01

    A series of Fe45.51(Al2O3)54.49 nano-granular films were prepared using ion-beam sputtering technique. A saturated hall resistivity of about 12.5μΩ.cm at room temperature was observed. The transmission electron microscopy image showed that very small Fe particles of smaller than 1 nm are embedded in Al2Os matrix, and connected into network. The measured ρ- T curve indicated that this giant Hall effect may originate from the percolation phenomenon. With different annealing temperature (TA) up to 300℃, the saturated Hall resistivity decreased only a little. The good thermal stability of Fe45.51 (Al2O3)54.49 nano-granular Films showed potential application for magnetic sensor.

  7. Effects of starting powder on the growth of Al2O3 films on Cu substrates using the aerosol deposition method

    International Nuclear Information System (INIS)

    The origin of craters on the surfaces of aerosol deposited ceramic thick films has been ascribed to the mechanical impact of large and hard ceramic particles; however, the main cause of craters has not been fully clarified. To determine the fundamental cause of the craters, three types of α-Al2O3 powders, with particles of different sizes and shapes, were prepared; Al2O3 thick films were deposited on Cu substrates using these powders, and aspects of deposition were observed. The surfaces of the aerosol-deposited Al2O3 films showed considerably different morphologies, depending on the starting powder. In the case of large and agglomerated Al2O3 starting powders, the surface roughness of the deposited films increased and the deposition rate decreased compared with that of standard Al2O3 powder having particles with an average size of 0.5-μm. In addition, we confirmed an increase in the crater size when using the large and agglomerated particles. For Al2O3 starting powder with 0.5-μm particles, the relative permittivity and loss tangent of the deposited Al2O3 films were 9.8 and 0.013, respectively; however, large and agglomerated Al2O3 powders produced film with a significant increase in dielectric loss. As a result, the agglomerated and large particles were confirmed to particles adversely affected the surface morphology and the dielectric properties.

  8. Enhancement of ferromagnetic resonance in Al2O3-doped Co2FeAl Heusler alloy film prepared by oblique sputtering

    Science.gov (United States)

    Li, Shan-Dong; Cai, Zhi-Yi; Xu, Jie; Cao, Xiao-Qin; Du, Hong-Lei; Xue, Qian; Gao, Xiao-Yang; Xie, Shi-Ming

    2014-10-01

    Large and variable in-plane uniaxial magnetic anisotropy in a nanocrystalline (Co2FeAl)97.8(Al2O3)2.2 soft magnetic thin film is obtained by an oblique sputtering method without being induced by magnetic field or post annealing. The in-plane uniaxial magnetic anisotropy varies from 50 Oe to 180 Oe (1 Oe = 79.5775 Am-1) by adjusting the sample's position. As a result, the ferromagnetic resonance frequency of the film increases from 1.9 GHz to 3.75 GHz.

  9. Synthesis of Vertically-Aligned Carbon Nanotubes from Langmuir-Blodgett Films Deposited Fe Nanoparticles on Al2O3/Al/SiO2/Si Substrate.

    Science.gov (United States)

    Takagiwa, Shota; Kanasugi, Osamu; Nakamura, Kentaro; Kushida, Masahito

    2016-04-01

    In order to apply vertically-aligned carbon nanotubes (VA-CNTs) to a new Pt supporting material of polymer electrolyte fuel cell (PEFC), number density and outer diameter of CNTs must be controlled independently. So, we employed Langmuir-Blodgett (LB) technique for depositing CNT growth catalysts. A Fe nanoparticle (NP) was used as a CNT growth catalyst. In this study, we tried to thicken VA-CNT carpet height and inhibit thermal aggregation of Fe NPs by using Al2O3/Al/SiO2/Si substrate. Fe NP LB films were deposited on three typed of substrates, SiO2/Si, as-deposited Al2O3/Al/SiO2/Si and annealed Al2O3/Al/SiO2/Si at 923 K in Ar atmosphere of 16 Pa. It is known that Al2O3/Al catalyzes hydrocarbon reforming, inhibits thermal aggregation of CNT growth catalysts and reduces CNT growth catalysts. It was found that annealed Al2O3/Al/SiO2/Si exerted three effects more strongly than as-deposited Al2O3/Al/SiO2/Si. VA-CNTs were synthesized from Fe NPs-C16 LB films by thermal chemical vapor deposition (CVD) method. As a result, at the distance between two nearest CNTs 28 nm or less, VA-CNT carpet height on annealed Al2O3/Al/SiO2/Si was about twice and ten times thicker than that on SiO2/Si and that on as-deposited Al2O3/Al/SiO2/Si, respectively. Moreover, distribution of CNT outer diameter on annealed Al2O3/Al/SiO2/Si was inhibited compared to that on SiO2/Si. These results suggest that since thermal aggregation of Fe NPs is inhibited, catalyst activity increases and distribution of Fe NP size is inhibited.

  10. Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

    Science.gov (United States)

    Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

    1990-01-01

    An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

  11. Influence of deposition temperature of thermal ALD deposited Al2O3 films on silicon surface passivation

    Directory of Open Access Journals (Sweden)

    Neha Batra

    2015-06-01

    Full Text Available The effect of deposition temperature (Tdep and subsequent annealing time (tanl of atomic layer deposited aluminum oxide (Al2O3 films on silicon surface passivation (in terms of surface recombination velocity, SRV is investigated. The pristine samples (as-deposited show presence of positive fixed charges, QF. The interface defect density (Dit decreases with increase in Tdep which further decreases with tanl up to 100s. An effective surface passivation (SRV<8 cm/s is realized for Tdep ≥ 200 °C. The present investigation suggests that low thermal budget processing provides the same quality of passivation as realized by high thermal budget process (tanl between 10 to 30 min.

  12. Oxidation Resistance of Fe-13Cr Alloy with Micro-Laminated (ZrO2-Y2O3)/(Al2O3-Y2O3) Films

    Institute of Scientific and Technical Information of China (English)

    Yao Mingming; He Yedong; Wang Deren; Gao Wei

    2005-01-01

    The micro-laminated (ZrO2-Y2O3)/(Al2O3-Y2O3) composite films were prepared on the surface of Fe-13Cr alloy by an electrochemical process and a sintering process alternately. High-resolution field emission scanning electron microscopy (FE-SEM) was used to characterize the laminated films, indicating that the micro-laminated (ZrO2-Y2O3)/(Al2O3-Y2O3) films have nano-structures. SEM, EDS and mass gain measurement were adopted to study the oxidation resistance of films on Fe-13Cr alloy. It is proved that such micro-laminated films are more effective than ZrO2-Y2O3 or Al2O3-Y2O3 films to resist the oxidation of the alloy, and the oxidation resistance is increased with increasing layers in micro-laminated films. These beneficial effects can be contributed to the mechanism, by which such micro-laminated (ZrO2-Y2O3)/(Al2O3-Y2O3) composite film combines all the beneficial effects and overcomes all the disadvantages of both ZrO2-Y2O3 film and Al2O3-Y2O3 film during oxidation of alloy.

  13. Effect of atomic layer deposition temperature on current conduction in Al2O3 films formed using H2O oxidant

    Science.gov (United States)

    Hiraiwa, Atsushi; Matsumura, Daisuke; Kawarada, Hiroshi

    2016-08-01

    To develop high-performance, high-reliability gate insulation and surface passivation technologies for wide-bandgap semiconductor devices, the effect of atomic layer deposition (ALD) temperature on current conduction in Al2O3 films is investigated based on the recently proposed space-charge-controlled field emission model. Leakage current measurement shows that Al2O3 metal-insulator-semiconductor capacitors formed on the Si substrates underperform thermally grown SiO2 capacitors at the same average field. However, using equivalent oxide field as a more practical measure, the Al2O3 capacitors are found to outperform the SiO2 capacitors in the cases where the capacitors are negatively biased and the gate material is adequately selected to reduce virtual dipoles at the gate/Al2O3 interface. The Al2O3 electron affinity increases with the increasing ALD temperature, but the gate-side virtual dipoles are not affected. Therefore, the leakage current of negatively biased Al2O3 capacitors is approximately independent of the ALD temperature because of the compensation of the opposite effects of increased electron affinity and permittivity in Al2O3. By contrast, the substrate-side sheet of charge increases with increasing ALD temperature above 210 °C and hence enhances the current of positively biased Al2O3 capacitors more significantly at high temperatures. Additionally, an anomalous oscillatory shift of the current-voltage characteristics with ALD temperature was observed in positively biased capacitors formed by low-temperature (≤210 °C) ALD. This shift is caused by dipoles at the Al2O3/underlying SiO2 interface. Although they have a minimal positive-bias leakage current, the low-temperature-grown Al2O3 films cause the so-called blisters problem when heated above 400 °C. Therefore, because of the absence of blistering, a 450 °C ALD process is presently the most promising technology for growing high-reliability Al2O3 films.

  14. Preparation and characterization of α-Al2O3 film by low temperature thermal oxidation of Al8Cr5 coating

    Science.gov (United States)

    Zhang, Min; Xu, Bajin; Ling, Guoping

    2015-03-01

    In this paper, α-Al2O3 film was prepared by low temperature thermal oxidation of Al8Cr5 coating. The Al8Cr5 alloy coating was prepared on SUS430 stainless steel through a two-step approach including electrodepositing Cr/Al composite coating and subsequent heat treatment at 740 °C for 16 h. After mechanical polishing removal of voids on the surface, the Al8Cr5 coating was thermal oxidized at 720 °C in argon for 100 h. The samples were characterized by SEM, EDX, XRD, XPS and TEM. XPS detection on the surface of oxidized Al8Cr5 coating showed that the oxide film mainly consisted of Al2O3. TEM characterization of the oxide film showed that it was α-Al2O3 films ca. 110 nm. The formation of α-Al2O3 films at low temperature can be attributed to the formation of Cr2O3 nuclei at the initial stage of oxidation which lowers the nucleation energy barrier of α-Al2O3.

  15. Consideration of the formation mechanism of an Al2O3-HfO2 eutectic film on a SiC substrate

    Science.gov (United States)

    Seya, Kyosuke; Ueno, Shunkichi; Nishimura, Toshiyuki; Jang, Byung-Koog

    2016-01-01

    An Al2O3-HfO2 eutectic EBC film was prepared on a SiC substrate by using the electric furnace heating and the optical zone melting methods. All of Al2O3 phase disappeared during the heating step at a temperature below the melting point, and all of the HfO2 phase reacted with the carbon and boron, which are included in SiC bulk as sintering agents, during the heating step at a temperature below the melting point. The thermal decomposition of the SiC phase, the reduction reaction of Al2O3 phase, the vaporization of the Al2O3 component, the reduction reaction of HfO2 and the formation of the HfC phase occurred at a temperature below the melting point. However, a highly dense HfC phase was formed on the SiC substrate. A rapid heating process becomes possible by using the optical zone melting method. A solidified film that was composed of a highly dense HfC layer as the intermediate layer and the Al2O3-HfO2 eutectic structure layer as the top coat was obtained by using the optical zone melting method.

  16. The Dielectic Properties of Polyimide/Nano-Al2O3 Composites Films%聚酰亚胺/纳米Al2O3复合薄膜的介电性能

    Institute of Scientific and Technical Information of China (English)

    李鸿岩; 郭磊; 刘斌; 陈维; 陈寿田

    2006-01-01

    为了提高聚酰亚胺(PI)的耐电晕性能,采用原位分散聚合法制备了聚酰亚胺/纳米Al2O3复合材料,并采用透射电子显微镜(TEM)对纳米Al2O3的分散状态进行了表征.研究了纳米Al2O3填加量对该复合材料耐电晕性能和其它介电性能的影响,结果表明,随着纳米Al2O3含量的增加,材料的耐电晕性能显著增强,在±910V(双极性)、15kHz条件下,纳米Al2O3质量分数为20%的PI薄膜的耐电晕寿命达到极大值,为纯PI薄膜寿命的25倍,聚酰亚胺/纳米Al2O3复合材料的体积电阻率和击穿场强没有明显的劣化,而相对介电常数和损耗角正切有所增加.

  17. Effect of annealing temperature on the structural reorganization of Eu3+ optical centers in Al2O3-Eu2O3-BiOF gel films

    Science.gov (United States)

    Malashkevich, G. E.; Kornienko, A. A.; Dunina, E. B.; Prusova, I. V.; Shevchenko, G. P.; Bokshits, Yu. V.

    2007-06-01

    The dependence of the structural reorganization of Eu3+ optical centers in Al2O3-Eu2O3-BiOF films on the annealing temperature has been investigated. It is shown by the methods of crystal field theory and computer simulation that the increase in the annealing temperature from 700 to 1100 °C leads to removal of bismuth from Eu-O-Bi complex centers with the C 3V symmetry in the Al2O3 structure and the change in symmetry from D 3 to O h for a large fraction of EuAlO3 centers.

  18. Static compression of Al2O3 to 1.2 Mbars /120 GPa/

    Science.gov (United States)

    Gupta, M. C.; Ruoff, A. L.

    1979-01-01

    Pressures up to 120 GPa were generated when a diamond indentor of radius 10.0 micrometers was pressed against a very thin sample of Al2O3 on a diamond flat. The thin film of Al2O3 was prepared by sputtering of aluminum in an oxygen atmosphere. From the measurement of the electrical resistance of Al2O3 as a function of pressure it was found that Al2O3 remains an insulator at the highest pressure studied, namely, 120 GPa.

  19. Modification of metal–InGaAs Schottky barrier behaviour by atomic layer deposition of ultra-thin Al2O3 interlayers

    International Nuclear Information System (INIS)

    The effect of inserting ultra-thin atomic layer deposited Al2O3 dielectric layers (1 nm and 2 nm thick) on the Schottky barrier behaviour for high (Pt) and low (Al) work function metals on n- and p-doped InGaAs substrates has been investigated. Rectifying behaviour was observed for the p-type substrates (both native oxide and sulphur passivated) for both the Al/p-InGaAs and Al/Al2O3/p-InGaAs contacts. The Pt contacts directly deposited on p-InGaAs displayed evidence of limited rectification which increased with Al2O3 interlayer thickness. Ohmic contacts were formed for both metals on n-InGaAs in the absence of an Al2O3 interlayer, regardless of surface passivation. However, limited rectifying behaviour was observed for both metals on the 2 nm Al2O3/n-InGaAs samples for the sulphur passivated InGaAs surface, indicating the importance of both surface passivation and the presence of an ultra-thin dielectric interlayer on the current–voltage characteristics displayed by these devices. - Highlights: • Investigation of the modification of metal–InGaAs Schottky barrier (SB) behaviour • Improving metal–InGaAs interface by sulphur passivation and ultrathin interlayer • Examine the effect of low work function and high work function metals on SB • Different SB behaviours observed on both n-type InGaAs and p-type InGaAs • Metal/n-InGaAs interface is more strongly pinned than the metal/p-InGaAs interface

  20. Effect of O2 gas partial pressure on mechanical properties of Al2O3 films deposited by inductively coupled plasma-assisted radio frequency magnetron sputtering

    International Nuclear Information System (INIS)

    The effect of O2 partial pressure on the mechanical properties of Al2O3 films is studied. Using films prepared by inductively coupled plasma-assisted radio frequency magnetron sputtering, the deposition rate of Al2O3 decreases rapidly when oxygen is added to the argon sputtering gas. The internal stresses in the films are compressive, with magnitude decreasing steeply from 1.6 GPa for films sputtered in pure argon gas to 0.5 GPa for films sputtered in argon gas at an O2 partial pressure of 0.89 × 10−2 Pa. Stress increases gradually with increasing O2 partial pressure. Using a nanoindentation tester with a Berkovich indenter, film hardness was measured to be about 14 GPa for films sputtered in pure argon gas. Hardness decreases rapidly on the addition of O2 gas, but increases when the O2 partial pressure is increased. Adhesion, measured using a Vickers microhardness tester, increases with increasing O2 partial pressure. Electron probe microanalyzer measurements reveal that the argon content of films decreases with increasing O2 partial pressure, whereas the O to Al composition ratio increases from 1.15 for films sputtered in pure argon gas to 1.5 for films sputtered in argon gas at O2 partial pressures over 2.4 × 10−2 Pa. X-ray diffraction measurements reveal that films sputtered in pure argon gas have an amorphous crystal structure, whereas γ-Al2O3 is produced for films sputtered in argon gas with added O2 gas. Atomic force microscopy observations reveal that the surface topography of sputtered Al2O3 films changes from spherical to needlelike as O2 partial pressure is increased. Fracture cross sections of the films observed by scanning electron microscopy reveal that the film morphology exhibits no discernible features at all O2 partial pressures.

  1. On the reliability of nanoindentation hardness of Al2O3 films grown on Si-wafer by atomic layer deposition

    International Nuclear Information System (INIS)

    The interest in applying thin films on Si-wafer substrate for microelectromechanical systems devices by using atomic layer deposition (ALD) has raised the demand on reliable mechanical property data of the films. This study aims to find a quick method for obtaining nanoindentation hardness of thin films on silicon with improved reliability. This is achieved by ensuring that the film hardness is determined under the condition that no plastic deformation occurs in the substrate. In the study, ALD Al2O3 films having thickness varying from 10 to 600 nm were deposited on a single-side polished silicon wafer at 300 °C. A sharp cube-corner indenter was used for the nanoindentation measurements. A thorough study on the Si-wafer reference revealed that at a specific contact depth of about 8 nm the wafer deformation in loading transferred from elastic to elastic–plastic state. Furthermore, the occurrence of this transition was associated with a sharp increase of the power-law exponent, m, when the unloading data were fitted to a power-law relation. Since m is only slightly material dependent and should fall between 1.2 and 1.6 for different indenter geometry having elastic contact to common materials, it is proposed that the high m values are the results from the inelastic events during unloading. This inelasticity is linked to phase transformations during pressure releasing, a unique phenomenon widely observed in single crystal silicon. Therefore, it is concluded that m could be used to monitor the mechanical state of the Si substrate when the whole coating system is loaded. A suggested indentation depth range can then be assigned to each film thickness to provide guidelines for obtaining reliable property data. The results show good consistence for films thicker than 20 nm and the nanoindentation hardness is about 11 GPa independent of film thickness

  2. Comparison of the microstructure and magnetic properties of strontium hexaferrite films deposited on Al2O3(0001), Si(100)/Pt(111) and Si(100) substrates by pulsed laser technique

    International Nuclear Information System (INIS)

    Strontium hexaferrite SrFe12O19 (SrM) films have been deposited on Al2O3(0001), Si(100)/Pt(111) and Si(100) substrates. The (001) oriented SrFe12O19 films deposited on the Al2O3(0001) and Si(100)/Pt(111) substrates have been confirmed by X-ray diffraction patterns. Higher coercivity in perpendicular direction rather than in-plane direction of the SrM/Al2O3(0001) and SrM/Pt(111) films showed that the films had perpendicular magnetic anisotropy. The (001) orientation and similar microstructure and magnetic properties of the SrM/Al2O3(0001) and SrM/Pt(111) films show the Al2O3(0001) substrate can be replaced by the Si(100)/Pt(111) substrate. - Highlights: • The SrFe12O19 film deposited on different Si(100), Si(100)/Pt(111) and Al2O3(0001) substrates by PLD. • The SrM/Pt(111) and SrM/Al2O3(0001) films showed the c-axis perpendicular orientation. • The SrM/Al2O3(0001) films exhibited more perpendicular magnetic anisotropy than SrM/Pt(111) films. • The Al2O3(0001) substrate can be replaced by the Si(100)/Pt(111) substrate

  3. Study of a high-temperature and high-pressure FBG sensor with Al2O3 thin-wall tube substrate

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hong; QIAO Xue-guang; WANG Hong-liang; FENG De-quan; WANG Wei

    2008-01-01

    A fiber Bragg grating (FBG) high-temperature and high pressure sensor has been designed and fabricated by using the Al2O3 thin-wall tube as a substrate. The test results show that the sensor can withstand a pressure range of 0-45 MPa and a temperature range of-10-300℃, and has a pressure sensitivity of 0.0426 nm/MPa and a temperature sensitivity of 0.0112nm/℃

  4. GaN MOS-HEMT Using Ultra-Thin Al2O3 Dielectric Grown by Atomic Layer Deposition

    Institute of Scientific and Technical Information of China (English)

    YUE Yuan-Zheng; HAO Yue; FENG Qian; ZHANG Jin-Cheng; MA Xiao-Hua; NI Jin-Yu

    2007-01-01

    @@ We report a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) with atomic layer deposited (ALD) Al2O3 gate dielectric. Based on the previous work [Appl. Phys. Lett. 86 (2005) 063501] of Ye et al. By decreeing the thickness of the gate oxide to 3.5nm and optimizing the device fabrication process, the device with maximum transconductance of 150mS/mm is produced and discussed in comparison with the result of 100mS/mm of Ye et al. The corresponding drain current density in the 0.8-μm-gate-length MOS-HEMT is 800mA/mm at the gate bias of 3.0 V. The gate leakage is two orders of magnitude lower than that of the conventional AlGaN/GaN HEMT. The excellent characteristics of this novel MOS-HEMT device structure with ALD Al2O3 gate dielectric are presented.

  5. Dielectric and ferroelectric properties of highly (100)-oriented (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 thin films grown on LaNiO 3/γ-Al 2O 3/Si substrates by chemical solution deposition

    Science.gov (United States)

    Guo, Yiping; Akai, Daisuke; Sawada, Kazauki; Ishida, Makoto

    2008-07-01

    A (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 chemical solution was prepared by using barium acetate, nitrate of sodium, nitrate of bismuth, and Ti-isopropoxide as raw materials. A white precipitation appeared during the preparation was analyzed to be Ba(NO 3) 2. We found that ethanolamine is a very effective coordinating ligand of Ba 2+. A transparent and stable (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 precursor chemical solution has been achieved by using ethanolamine as a ligand of Ba 2+. (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 films were grown on LaNiO 3/γ-Al 2O 3/Si substrates. Highly (100)-oriented (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 films were obtained in this work due to lattice match growth. The dielectric, ferroelectric and insulative characteristics against applied field were studied. The conduction current shows an Ohmic conduction behavior at lower voltages and space-charge-limited behavior at higher voltages, respectively. These results indicate that, the (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 film is a promising lead-free ferroelectric film.

  6. Influence of Nano-Al2O3 Powder on Micro-arc Anodic Oxidation Film of Magnesium Alloy%Al2O3纳米粉体对镁合金微弧氧化陶瓷膜性能的影响

    Institute of Scientific and Technical Information of China (English)

    包晗; 邵忠财; 刘鹏

    2013-01-01

    Nano-Al2O3 powder are added into magnesium alloy during melting process,then the prepared composite material are treated by micro-arc oxidation; also the magnesium alloy are treated by micro-arc oxidation with nano-Al2O3 powder in the electrolyte.Scanning electron microscope (SEM),X-ray diffraction (XRD) and electrochemical tests are used to analyze the influence of nano-Al2O3 powder on micro-arc anodic oxidation film.Results show that both of the two methods of adding Al2O3 powder can improve the corrosion resistance of magnesium alloy micro-arc oxidation ceramic film,but the first one is better.%在熔炼镁合金过程中加入Al2O3纳米粉体的复合材料进行微弧氧化处理;在微弧氧化电解液中加入Al2O3粉体并对镁合金基体进行微弧氧化.采用扫描电镜、X-射线衍射和电化学测试分析Al2O3粉体对镁合金微弧氧化膜层耐蚀性的影响.结果表明,两种方式加入Al2O3粉体都会提高镁合金微弧氧化陶瓷膜的耐蚀性,而熔炼过程中加入效果更佳.

  7. Calculation Method for the Thermal Aging of Polyimide / Al2O3 Hybrid Films%聚酰亚胺/Al2O3掺杂薄膜热老化寿命计算方法研究

    Institute of Scientific and Technical Information of China (English)

    周浩然; 柳长富; 赵蕊; 崔晓禹; 孙安

    2012-01-01

    The thermal stabilization of PI / Al2 Q3 hybrid films was studied with TG. Meanwhile, the kinetics parameters (activation energy of thermal decomposition, collision coefficient and action progression) were calculated, and the upper limit temperature was predicted according to the relevant data. The experiment results showed that the order of reaction in air atmosphere was bigger than that in nitrogen atmosphere, and tended to second-order reaction. The value of E calculated by the method of Kissinger was lower than that in the method of Coats-Red fern. The collide coefficient (A) was calculated in the method of Coats-Red fern selected by contrast, and the upper limit temperatures of hybrid PI material was nearly 300 ℃ similar to those reported in previous literatures. The results have shown that Coats-Red fern method is one of the reliable methods to predict the long-term life upper limit temperature of hybrid PI materials.%利用热失重仪(TG)测定了Al2O3掺杂聚酰亚胺的热稳定性,采用Kissinger法和Coats-Red fern法计算动力学参数,预测杂化薄膜长期使用的上限温度.实验结果表明:在空气气氛中的反应级数大于氮气气氛中的反应级数,且趋于二级反应.利用Kissinger法求出的E值低于Coats-Redfern法求出的E值,选取Coats-Redfern法求取相应的碰撞系数(A)值后,预测杂化PI膜长期使用的上限温度在300℃左右,与文献报道基本相符.结果表明Coats-Red fern方法是预测杂化PI材料长期使用上限温度的可靠方法之一.

  8. Photoluminescence of Ga-doped ZnO film grown on c-Al2O3 (0001) by plasma-assisted molecular beam epitaxy

    International Nuclear Information System (INIS)

    High quality gallium doped ZnO (Ga:ZnO) thin films were grown on c-Al2O3(1000) by plasma-assisted molecular beam epitaxy, and Ga concentration NGa was controlled in the range of 1x1018-2.5x1020/cm3 by adjusting/changing the Ga cell temperature. From the low-temperature photoluminescence at 10 K, the donor bound exciton I8 related to Ga impurity was clearly observed and confirmed by comparing the calculated activation energy of 16.8 meV of the emission peak intensity with the known localization energy, 16.1 meV. Observed asymmetric broadening with a long tail on the lower energy side in the photoluminescence (PL) emission line shape could be fitted by the Stark effect and the compensation ratio was approximately 14-17% at NGa≥1x1020/cm3. The measured broadening of photoluminescence PL emission is in good agreement with the total thermal broadening and potential fluctuations caused by random distribution of impurity at NGa lower than the Mott critical density

  9. Al2O3 antireflection coatings for silicon solar cells

    OpenAIRE

    L.A. Dobrzański; M. Szindler

    2013-01-01

    Purpose: The aim of this paper was to investigate changes in surface morphology and optical properties of thin films of Al2O3. Thin films were prepared using atomic layer deposition (ALD) method.Design/methodology/approach: The microanalysis was investigated by the Energy-dispersive X-ray spectroscopy EDS. The changes in surface topography was observed by the atomic force microscope AFM XE-100 and scanning electron microscope SEM. The results of roughness was obtained by the software XEI Park...

  10. Uniform deposition of ultrathin polymer films on the surfaces of Al2O3 nanoparticles by a plasma treatment

    Science.gov (United States)

    Shi, Donglu; Wang, S. X.; van Ooij, Wim J.; Wang, L. M.; Zhao, Jiangang; Yu, Zhou

    2001-02-01

    Surface modification of nanoparticles will present great challenges due to their extremely small dimensions, high surface areas, and high surface energies. In this research, we demonstrate the uniform deposition of ultrathin polymer films of 2 nm on the surfaces of alumina nanoparticles. The deposited film can also be tailored to multilayers. Time-of-flight secondary ion mass spectroscopy was used to confirm the pyrrole thin film on the nanoparticle surfaces. Using such a nanocoating, it is possible to alter the intrinsic properties of materials that cannot be achieved by conventional methods and materials.

  11. IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

    Energy Technology Data Exchange (ETDEWEB)

    Scott X. Mao

    2003-03-10

    In order to improve the hot corrosion resistance of conventional YSZ TBC system, a thin and dense {alpha}-Al{sub 2}O{sub 3} overlay has been deposited on the YSZ surface by the composite-sol-gel route (CSG). The YSZ substrates were dipped with boehmite sol containing calcined {alpha}-Al{sub 2}O{sub 3} particles, dried to form a gel film and calcined at 1200 C to form {alpha}-Al{sub 2}O{sub 3} overlay. Hot corrosion tests were carried out on the TBCs with and without Al{sub 2}O{sub 3} coating in molten salt mixtures (Na{sub 2}SO{sub 4} + 5% V{sub 2}O{sub 5}) at 950 C for 10 hours. The results showed that besides a thin and dense alumina overlay with the thickness of about 100-500 nm formed on the YSZ surface, the microcracks and porous near the surface in YSZ was also occupied by alumina because of penetration of the low viscosity precursor. As a result, the Al{sub 2}O{sub 3} overlay remarkably refrained the infiltration of the molten salt into the YSZ coating. The amount of M-phase in the TBC coating with Al{sub 2}O{sub 3} overlay was substantially reduced comparing to that without alumina overlay. In the next reporting period, we will prepare the alumina overlay by CSG route with different thickness and study the hot corrosion mechanism of YSZ TBC with thin Al{sub 2}O{sub 3} overlay coating produced by CSG.

  12. Epitaxial Al2O3 capacitors for low microwave loss superconducting quantum circuits

    Directory of Open Access Journals (Sweden)

    K.-H. Cho

    2013-10-01

    Full Text Available We have characterized the microwave loss of high-Q parallel plate capacitors fabricated from thin-film Al/Al2O3/Re heterostructures on (0001 Al2O3 substrates. The superconductor-insulator-superconductor trilayers were grown in situ in a hybrid deposition system: the epitaxial Re base and polycrystalline Al counterelectrode layers were grown by sputtering, while the epitaxial Al2O3 layer was grown by pulsed laser deposition. Structural analysis indicates a highly crystalline epitaxial Al2O3 layer and sharp interfaces. The measured intrinsic (low-power, low-temperature quality factor of the resonators is as high as 3 × 104. These results indicate that low-loss grown Al2O3 is an attractive candidate dielectric for high-fidelity superconducting qubit circuits.

  13. Optimization of Wet or Dry Micro-blasting on PVD Films by Various Al2O3 Grain Sizes for Improving the Coated Tools' Cutting Performance

    Directory of Open Access Journals (Sweden)

    K. -D. Bouzakis

    2011-06-01

    Full Text Available Micro-blasting on PVD coated tools is an effective technology for improving their cutting performance. Through micro-blasting, compressive stresses are induced into the film, thus increasing the coating hardness, but its brittleness too. Simultaneously, abrasion phenomena are activated, which may lead to roughness augmentation, film thickness decrease and substrate revelation. In this way, for a successful process conduct, it is pivotal to adapt, among others, the applied micro-blasting pressure to the employed medium, air or water. The paper deals with the optimization of wet or dry micro-blasting pressure by various Al2O3 grain sizes for improving the coated tool’s wear resistance. The wear behaviour of coated and variously dry or wet micro-blasted tools was investigated in milling. Considering the grains’ penetration kinematics into the coated tool surface and the film deformation mechanisms during dry or wet microblasting by fine or coarse sharp–edged Al2O3 grains, optimum process pressures can be determined.

  14. IMPERMEABLE THIN AL2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

    Energy Technology Data Exchange (ETDEWEB)

    Scott X. Mao

    2003-12-16

    To improve the hot corrosion resistance of YSZ thermal barrier coatings, a 25 {micro}m and a 2 {micro}m thick Al{sub 2}O{sub 3} overlay were deposited by HVOF thermal spray and by sol-gel coating method, respectively, onto to the surface of YSZ coating. Indenter test was employed to investigate the spalling of YSZ with and without Al{sub 2}O{sub 3} overlay after hot corrosion. The results showed that Al{sub 2}O{sub 3} overlay acted as a barrier against the infiltration of the molten salt into the YSZ coating during exposure, thus significantly reduced the amount of M-phase of ZrO{sub 2} in YSZ coating. However, a thick Al{sub 2}O{sub 3} overlay was harmful for TBC by increasing compressive stress which causes crack and spalling of YSZ coating. As a result, a dense and thin Al{sub 2}O{sub 3} overlay is critical for simultaneously preventing YSZ from hot corrosion and spalling. In the next reporting period, we will measure or calculate the residue stress within Al{sub 2}O{sub 3} overlay and YSZ coating to study the mechanism of effect of Al{sub 2}O{sub 3} overlay on spalling of YSZ coating.

  15. IMPERMEABLE THIN Al2O3 OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES

    Energy Technology Data Exchange (ETDEWEB)

    Scott X. Mao

    2002-11-30

    In order to improve the hot corrosion resistance of conventional YSZ TBC system, the Al{sub 2}O{sub 3} overlay coating has been successfully produced on the surface of YSZ by the Sol-gel route. The YSZ substrates were coated with boehmite sol by dip coating process, dried to form a gel film and calcined at 1200 C to form {alpha}-Al{sub 2}O{sub 3} overlay. The microstructures of TBC and Al{sub 2}O{sub 3} overlay were examined by scanning electron microscopy (SEM). The results showed that micro-pores ranged from 3 {micro}m to 20 {micro}m and micro-cracks could be clearly seen on the surface of APS YSZ coating. The thickness of alumina overlay increased with increasing the number of dip coating circles. The small microcracks (0.5-1.0 {micro}m width) on the YSZ surface could be filled and blocked by calcined alumina particles, whereas large pores remained empty and the alumina overlay was un-continuous after one time dip coating circle. Alumina overlay thicker than 5 m m obtained by five times dip coating circles largely cracked after calcinations. As a result, multiple dip coatings up to three times were ideal for getting high quality, crack- free and continuous overlay. The optimal thickness of alumina overlay was in the range of 2.5-3.5 {micro}m. In the next reporting period, we will study the hot corrosion behaviors of YSZ TBC with Al{sub 2}O{sub 3} overlay coating produced by sol gel route by exposure the samples to molten salts mixtures (Na{sub 2}SO{sub 4} + 5%V{sub 2}O{sub 5}) at 950 C.

  16. Atomic layer deposition of TiO2 and Al2O3 on nanographite films: structure and field emission properties

    Science.gov (United States)

    Kleshch, Victor I.; Ismagilov, Rinat R.; Smolnikova, Elena A.; Obraztsova, Ekaterina A.; Tuyakova, Feruza; Obraztsov, Alexander N.

    2016-03-01

    Atomic layer deposition (ALD) of metal oxides (MO) was used to modify the properties of nanographite (NG) films produced by direct current plasma-enhanced chemical vapor deposition technique. NG films consist of a few layers of graphene flakes (nanowalls) and nanoscrolls homogeneously distributed over a silicon substrate with a predominantly vertical orientation of graphene sheets to the substrate surface. TiO2 and Al2O3 layers, with thicknesses in the range of 50 to 250 nm, were deposited on NG films by ALD. The obtained NG-MO composite materials were characterized by scanning electron microscopy, energy dispersive x-ray analysis, and Raman spectroscopy. It was found that ALD forms a uniform coating on graphene flakes, while on the surface of needle-like nanoscrolls it forms spherical nanoparticles. Field emission properties of the films were measured in a flat vacuum diode configuration. Analysis based on obtained current-voltage characteristics and electrostatic calculations show that emission from NG-TiO2 films is determined by the nanoscrolls protruding from the TiO2 coverage. The TiO2 layers with thicknesses of <200 nm almost do not affect the overall field emission characteristics of the films. At the same time, these layers are able to stabilize the NG films' surface and can lead to an improvement of the NG cold cathode performance in vacuum electronics.

  17. Subcutaneous oxidation of In0.53Ga0.47As(100) through ultra-thin atomic layer deposited Al2O3

    International Nuclear Information System (INIS)

    Stability of oxide/semiconductor interfaces during device fabrication is critically important, particularly for adoption of new semiconductor channel materials, such as III-V compounds. Unintentional oxidation of an underlying In0.53Ga0.47As(100) surface through atomic layer deposited (ALD) Al2O3 layers of varying thickness is investigated. Oxygen annealing of 1 ∼ 2 nm thickness Al2O3 layers at 300 °C or higher and large-dose water vapor exposure during the ALD-Al2O3 process at 300 °C produces InGaAs surface oxidation. This subcutaneous oxidation of InGaAs increases the Al2O3/InGaAs interface defect density as observed in suppressed band-edge photoluminescence and in capacitance-voltage analysis, possibly by creating As dangling bonds at the InGaAs surface

  18. Experimental determination of the oxygen K-shell fluorescence yield using thin SiO2 and Al2O3 foils

    Science.gov (United States)

    Hönicke, P.; Kolbe, M.; Krumrey, M.; Unterumsberger, R.; Beckhoff, B.

    2016-10-01

    In this work, the K-shell fluorescence yield for oxygen ωO,K-shell is determined experimentally, employing the radiometrically calibrated X-ray fluorescence instrumentation of the Physikalisch-Technische Bundesanstalt (PTB), Germany's National Metrology Institute. Four free-standing thin foils with two different thicknesses of both SiO2 and Al2O3 were used in order to derive an experimental value for this atomic fundamental parameter. Multiple excitation photon energies were applied to record fluorescence spectra of all four samples. The resulting value (ωO,K-shell = 0.00688 ± 0.00036) is almost 20 % higher than the commonly used value from the Krause tables [M. Krause, Atomic Radiative and Radiationless Yields for K and L shells, J. Phys. Chem. Ref. Data 8(2), 307-327 (1979)]. In addition, the achieved total uncertainty budget for the new experimental value is reduced significantly in comparison to available literature data. For validation purposes, thin SiO2 layers on Si samples were used. Here, the layer thicknesses derived from X-ray reflectometry are well in line with our X-ray fluorescence quantification results based on the new experimental value for the O K-shell fluorescence yield.

  19. Preparation and characterization of ultrathin [Ru(CO)3Cl2]2 and [BMIM][Tf2N] films on Al2O3/NiAl(110) under UHV conditions.

    Science.gov (United States)

    Sobota, Marek; Schernich, Stefan; Schulz, Hannes; Hieringer, Wolfgang; Paape, Natalia; Wasserscheid, Peter; Görling, Andreas; Laurin, Mathias; Libuda, Jörg

    2012-08-14

    Towards a better understanding of the interface chemistry of ionic liquid (IL) thin film catalytic systems we have applied a rigorous surface science model approach. For the first time, a model homogeneous catalyst has been prepared under ultrahigh vacuum conditions. The catalyst, di-μ-chlorobis(chlorotricarbonylruthenium) [Ru(CO)(3)Cl(2)](2), and the solvent, the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf(2)N], have been deposited by physical vapor deposition onto an alumina model support [Al(2)O(3)/NiAl(110)]. First, the interaction between thin films of [Ru(CO)(3)Cl(2)](2) and the support is investigated. Then, the ruthenium complex is co-deposited with the IL and the influence of the solvent on the catalyst is discussed. D(2)O, which is a model reactant, is further added. Growth, surface interactions, and mutual interactions in the thin films are studied with IRAS in combination with density functional (DFT) calculations. At 105 K, molecular adsorption of [Ru(CO)(3)Cl(2)](2) is observed on Al(2)O(3)/NiAl(110). The IRAS spectra of the binary [Ru(CO)(3)Cl(2)](2) + [BMIM][Tf(2)N] and ternary [Ru(CO)(3)Cl(2)](2) + [BMIM][Tf(2)N] + D(2)O show every characteristic band of the individual components. Above 223 K, partial decomposition of the ruthenium complex leads to species of molecular nature attributed to Ru(CO) and Ru(CO)(2) surface species. Formation of metallic ruthenium clusters occurs above 300 K and the model catalyst decomposes further at higher temperatures. Neither the presence of the IL nor of D(2)O prevents this partial decomposition of [Ru(CO)(3)Cl(2)](2) on alumina. PMID:22760015

  20. Effects of ozone post deposition treatment on interfacial and electrical characteristics of atomic-layer-deposited Al2O3 and HfO2 films on GaSb substrates

    International Nuclear Information System (INIS)

    Atomic-layer-deposited Al2O3 and HfO2 films on GaSb substrates were treated by in-situ ozone post deposition treatment (PDT). The effects of ozone PDT on the interfacial and electrical properties of Al2O3 and HfO2 gate dielectric films on GaSb substrates were investigated carefully. It is found that the dielectric quality and the interfacial properties of the Al2O3 and HfO2 films are improved by ozone PDT. After in-situ ozone PDT for 5 min, the Al2O3 and HfO2 films on GaSb substrates exhibit improved electrical and interfacial properties, such as reduced frequency dispersion, gate leakage current, border traps and interface traps. Interface trap density is reduced by ∼24% for the Al2O3/GaSb stacks and ∼27% for the HfO2/GaSb stacks. In-situ ozone PDT is proved to be a promising technique in improving the quality of high-k gate stacks on GaSb substrates.

  1. Reduced impurities and improved electrical properties of atomic-layer-deposited HfO2 film grown at a low temperature (100 °C) by Al2O3 incorporation

    Science.gov (United States)

    Park, Tae Joo; Byun, Youngchol; Wallace, Robert M.; Kim, Jiyoung

    2016-05-01

    The HfO2 films grown by atomic layer deposition (ALD) at a low temperature (100 °C) necessarily has a large amount of residual impurities due to lack of thermal energy for stable ALD reactions such as ligand removal and oxidation, which degrades various properties. However, Al2O3 incorporation into the film significantly decreased the residual impurities despite of a low growth temperature. The decrease in C impurity is attributed to the reduced oxygen vacancies by the incorporated Al2O3 phase or the high reactivity of Al precursor. Consequently, the electronic band structure of the film, and thereby the electrical properties were improved significantly.

  2. Growth of crystalline Al2O3 via thermal atomic layer deposition: Nanomaterial phase stabilization

    Directory of Open Access Journals (Sweden)

    S. M. Prokes

    2014-03-01

    Full Text Available We report the growth of crystalline Al2O3 thin films deposited by thermal Atomic Layer Deposition (ALD at 200 °C, which up to now has always resulted in the amorphous phase. The 5 nm thick films were deposited on Ga2O3, ZnO, and Si nanowire substrates 100 nm or less in diameter. The crystalline nature of the Al2O3 thin film coating was confirmed using Transmission Electron Microscopy (TEM, including high-resolution TEM lattice imaging, selected area diffraction, and energy filtered TEM. Al2O3 coatings on nanowires with diameters of 10 nm or less formed a fully crystalline phase, while those with diameters in the 20–25 nm range resulted in a partially crystalline coating, and those with diameters in excess of 50 nm were fully amorphous. We suggest that the amorphous Al2O3 phase becomes metastable with respect to a crystalline alumina polymorph, due to the nanometer size scale of the film/substrate combination. Since ALD Al2O3 films are widely used as protective barriers, dielectric layers, as well as potential coatings in energy materials, these findings may have important implications.

  3. Ultra-sensitive film sensor based on Al2O3-Au nanoparticles supported on PDDA-functionalized graphene for the determination of acetaminophen.

    Science.gov (United States)

    Li, Jianbo; Sun, Weiyan; Wang, Xiaojiao; Duan, Huimin; Wang, Yanhui; Sun, Yuanling; Ding, Chaofan; Luo, Chuannan

    2016-08-01

    An electrochemical sensor of acetaminophen based on poly(diallyldimethylammonium chloride) (PDDA)-functionalized reduced graphene-loaded Al2O3-Au nanoparticles coated onto glassy carbon electrode (Al2O3-Au/PDDA/reduced graphene oxide (rGO)/glass carbon electrode (GCE)) were prepared by layer self-assembly technique. The as-prepared electrode-modified materials were characterized by scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The electrocatalytic performances of Al2O3-Au/PDDA/rGO-modified glassy carbon electrode toward the acetaminophen were investigated by cyclic voltammetry and differential pulse voltammetry. The modified electrodes of graphene oxide (GO)/GCE, PDDA/rGO/GCE, and Al2O3-Au/PDDA/rGO/GCE were constructed for comparison and learning the catalytic mechanism. The research showed Al2O3-Au/PDDA/rGO/GCE having good electrochemical performance, attributing to the synergetic effect that comes from the special nanocomposite structure and physicochemical properties of Al2O3-Au nanoparticles and graphene. A low detection limit of 6 nM (S/N = 3) and a wide linear detection range from 0.02 to 200 μM (R (2) = 0.9970) was obtained. The preparation of sensor was successfully applied for the detection of acetaminophen in commercial pharmaceutical pills. Graphical abstract Schematic diagram of synthesis of Al2O3-Au/PDDA/rGO/GCE. PMID:27255103

  4. Interfacial and Electrical Characterization of HfO2 Gate Dielectric Film with a Blocking Layer of Al2O3%具有Al2O3阻挡层的HfO2栅介质膜的界面和电学性能的表征

    Institute of Scientific and Technical Information of China (English)

    程新红; 何大伟; 宋朝瑞; 俞跃辉; 沈达身

    2009-01-01

    研究了经过700℃快速热退火的并在Si界面处插入Al2O3阻挡层的HfO2栅介质膜的界面结构和电学性能.X射线光电子谱表明,退火后,界面层中的siOx转化为化学当量的SiO2,而且未发现铪基硅酸盐和铪基酸化物.由电学测试提取出等效栅氧厚度为2.5nm,固定电荷密度为-4.5×1011/cm2.发现Al2O3阻挡层能有效地阻止Si原子扩散进入HfO2薄膜,进而改善HfO2栅介质膜的界面和电学性能.%HfO2 gate dielectric films with a blocking layer of Al2O3 inserted between HfO2 layer and Si layer (HfO2/Si) were treated with rapid thermal annealing process at 700℃. The interracial structure and electrical properties were reported. The results of X-ray photoelectron spectroscopy showed that the interracial layer of SiOx transformed into SiO2 after the annealing treatment, and Hf-silicates and Hf-silicides were not detected. The results of high-resolution transmission electron microscopy indicated that the in-terracial layer was composed of SiO2 for the annealed film with blocking layer. The results of the electrical measurements indicated that the equivalent oxide thickness decreased to 2.5 nm and the fixed charge density decreased to -4.5×1011/cm2 in comparison with the same thickness of HfO2 films without the blocking layer. Al2O3 layer could effectively prevent the diffusion of Si into HfO2 film and improve the interfacial and electrical performance of HfO2 film.

  5. Atomic Structure of a Spinel-like Transition Al2O3 (100) Surface

    DEFF Research Database (Denmark)

    Jensen, Thomas Nørregaard; Meinander, Kristoffer; Helveg, Stig;

    2014-01-01

    We study a crystalline epitaxial alumina thin film with the characteristics of a spinel-type transition Al2O3(100) surface by using atom-resolved noncontact atomic force microscopy and density functional theory. It is shown that the films are terminated by an Al-O layer rich in Al vacancies...

  6. Preparation and characterization of DLC/SiO2/Al2O3 nanofiltration membrane

    Indian Academy of Sciences (India)

    Jin-Su Jeong; Churl-Hee Cho; Jong-Oh Kim; Dong-Hun Yeo; Won-Youl Choi

    2013-12-01

    High quality ceramic thin films were fabricated by thin film deposition process in semiconductor field in order to fabricate high performance carbon/SiO2/Al2O3 membrane. -Al2O3 substrate was used as a supporting material. A severe thermal stress and rough surface for active ceramic top layer such as zeolite were observed. To overcome thermal stress, intermediate layer of SiO2 and diamond-like carbon (DLC) thin films were used. SiO2 and DLC thin films on porous alumina support were deposited using plasma-enhanced chemical vapour deposition (PECVD). Homogeneous and smooth surfaces and interfaces of DLC/SiO2/Al2O3 membrane were observed by FESEM. The phases of DLC and SiO2 thin films were identified by X-ray diffraction pattern. Gas permeabilities of the nanofiltration membrane with DLC/SiO2/Al2O3 were observed at various annealing temperatures. Mixed gas permeability of the membrane with 1 m-thick SiO2 and 2 m-thick DLC thin filmannealed at 200 °C was ∼18 ccm at 1018 mb back pressure.

  7. Pt-Ti/ALD-Al2O3/p-Si MOS Capacitors for Future ULSI Technology

    OpenAIRE

    Ashok M. Mahajan; Anil G. Khairnar; Brian J. Thibeault

    2011-01-01

    The high dielectric constant (high-k) thin film of Al2O3 was deposited by using Plasma enhanced atomic layer deposition (PE-ALD) technique. The electron beam evaporation system was used to deposit the Pt-Ti metal to fabricate the Pt-Ti/Al2O3/Si MOS capacitors. Thickness measurement of Al2O3 gate dielectric was carried out with variable angle spectroscopic ellipsometry, which is measured to be 2.83 nm. The MOS capacitors were characterized to evaluate the electrical properties using capacitanc...

  8. Super Smooth Modification of Al2O3 Ceramic Substrate by High Temperature Glaze of CaO-Al2O3-SiO2 System

    Science.gov (United States)

    Zhang, Jihua; Zhen, Shanxue; Yang, Lijun; Lou, Feizhi; Chen, Hongwei; Yang, Chuanren

    2011-01-01

    The rough surface of ceramic substrate is an obstacle for the scale down of line-width for thin film passive integrated devices (PID). In this paper, a modification method for Al2O3 ceramic substrate with super smooth in surface was proposed. Coating a layer of CaO-Al2O3-SiO2 (CAS) glass was performed to flat the rough surface of alumina substrate by sol-gel method. It was found that addition of 0.06% V2O5 can inhibit the recrystallization of the glaze. The root-mean-square (RMS) roughness of the glazed substrates reached a surprising flatness as small as 0.5 nm, and its melting temperature is higher than 1300 °C. This substrate with super flatness and high temperature endurance may be promising for high performance thin film devices.

  9. Electrochemical Characterization of Al2 O3 -Ni Thin Film Selective Surface on Aluminium

    OpenAIRE

    KADIRGAN, Figen

    1999-01-01

    Solar thermal collectors represent a widely used type of system for the conversion of solar energy. In order to produce selective coatings on aluminium substrates to be used as absorber plates in high efficiency solar collectors, nickel pigmentation was applied to anodically oxidised surfaces. Electrochemical dc methods are used to study the oxidation of aluminium as functions of the following electrolysis conditions: applied current, pH, temperature and concentration of electrolyte....

  10. Electrical properties of (Al2O3)x(TiO2)1-x films deposited on a silicon substrate

    Science.gov (United States)

    Vitanov, P.; Alexieva, Z.; Harizanova, A.; Horvath, Z.; Dozsa, L.

    2008-05-01

    Direct current conductance in Al/(Al2O3)X(TiO2)1-X/silicon structure was studied, the dielectric layers being deposited by the chemical solution deposition method. The measurements were carried out at room temperature and 320, 340 and 360 K. The results correspond to bulk-limited conduction of the Poole-Frenkel type. High voltages and temperature lead to an additional current rise, explained by thermal excitation and tunneling of electrons through the lowered Poole-Frenkel barrier.

  11. Investigating the electronic properties of Al2O3/Cu(In,GaSe2 interface

    Directory of Open Access Journals (Sweden)

    R. Kotipalli

    2015-10-01

    Full Text Available Atomic layer deposited (ALD Al2O3 films on Cu(In,GaSe2 (CIGS surfaces have been demonstrated to exhibit excellent surface passivation properties, which is advantageous in reducing recombination losses at the rear metal contact of CIGS thin-film solar cells. Here, we report, for the first time, experimentally extracted electronic parameters, i.e. fixed charge density (Qf and interface-trap charge density (Dit, for as-deposited (AD and post-deposition annealed (PDA ALD Al2O3 films on CIGS surfaces using capacitance–voltage (C-V and conductance-frequency (G-f measurements. These results indicate that the AD films exhibit positive fixed charges Qf (approximately 1012 cm−2, whereas the PDA films exhibit a very high density of negative fixed charges Qf (approximately 1013 cm−2. The extracted Dit values, which reflect the extent of chemical passivation, were found to be in a similar range of order (approximately 1012 cm−2 eV−1 for both AD and PDA samples. The high density of negative Qf in the bulk of the PDA Al2O3 film exerts a strong Coulomb repulsive force on the underlying CIGS minority carriers (ns, preventing them to recombine at the CIGS/Al2O3 interface. Using experimentally extracted Qf and Dit values, SCAPS simulation results showed that the surface concentration of minority carriers (ns in the PDA films was approximately eight-orders of magnitude lower than in the AD films. The electrical characterization and estimations presented in this letter construct a comprehensive picture of the interfacial physics involved at the Al2O3/CIGS interface.

  12. Wear Behavior of Cold Pressed and Sintered Al2O3/TiC/CaF2Al2O3/TiC Laminated Ceramic Composite

    Institute of Scientific and Technical Information of China (English)

    Xuefeng YANG; Jian CHENG; Peilong SONG; Shouren WANG; Liying YANG; Yanjun WANG; Ken MAO

    2013-01-01

    A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance,such as low friction coefficient and low wear rate.Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure.Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear.Al2O3/TiC ceramic was also cold pressed and sintered for comparison.Friction analysis of the two ceramics was then conducted via a wear-and-tear machine.Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum,respectively.Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite.Under the friction load,the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits.This process formed a smooth,self-lubricating film,which led to better anti-wear properties.Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.

  13. Preparation and Properties of Diamond Abrasive Coated with Titania/Alumina Film%金刚石表面涂覆TiO2/Al2O3薄膜及性能

    Institute of Scientific and Technical Information of China (English)

    胡伟达; 万隆; 刘小磐; 陈茂开; 万众; 钱琦

    2011-01-01

    A titania/alumina (TiO2/Al2O3) film was coated on the surface of diamond abrasive by a sol-gel method. The surface morphology, structure, oxidation resistance properties and compressive strength of the film coated diamond were analyzed by environmental scaninng electron microscope, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, X-my diffractometer,thermogravimetry-differential scanning calorimetry and single particle compressive strength test. The grinding performance of a vitrified-bond grinding wheel prepared by the TiO2/Al2O3 film coated diamond was investigated. The results show that compared to the uncoated diamond, the oxidation resistance temperature of the film coated diamond is increased by 175 ℃, and the compressive strength hs increased by 26.4%. It was also found that the TiO2/Al2O3 film could give a wettability between diamond and vitrified-bond matrix at high temperatures. Compared to the uncoated diamond, the hardness of the vitrified-bond grinding wheel prepared by the TiO2/Al2O3 film coated diamond was increased by 8.7% and the grinding ratio to carbide alloy (YG8) was increased by 66.1%.%采用溶胶-凝胶法在金刚石磨料表面涂覆TiO2/Al2O3薄膜.通过环境扫描电子显微镜、能谱仪、Fourier变换红外光谱仪、X射线衍射、热重-差示扫描量热、金刚石抗压强度检测等方法,对涂膜后金刚石表面形貌、结构、抗氧化性能和抗压强度进行分析,同时研究了TiO2/Al2O3薄膜对陶瓷结合剂金刚石砂轮磨削性能的影响.结果表明:涂膜金刚石较未涂膜金刚石抗氧化温度提高了175℃,抗压强度提高26.4%; TiO2/Al2O3薄膜改善了高温状态下陶瓷熔料对金刚石的润湿性;与未涂膜金刚石陶瓷结合剂砂轮相比,涂膜金剐石砂轮表面硬度提高8.7%,对硬质合金(YG8)的磨耗比提高66.1%.

  14. Vacuum ultraviolet photochemical selective area atomic layer deposition of Al2O3 dielectrics

    Directory of Open Access Journals (Sweden)

    P. R. Chalker

    2015-01-01

    Full Text Available We report the photochemical atomic layer deposition of Al2O3 thin films and the use of this process to achieve area-selective film deposition. A shuttered vacuum ultraviolet (VUV light source is used to excite molecular oxygen and trimethyl aluminum to deposit films at 60°C. In-situ QCM and post-deposition ellipsometric measurements both show that the deposition rate is saturative as a function of irradiation time. Selective area deposition was achieved by projecting the VUV light through a metalized magnesium fluoride photolithographic mask and the selectivity of deposition on the illuminated and masked regions of the substrate is a logarithmic function of the UV exposure time. The Al2O3 films exhibit dielectric constants of 8 – 10 at 1 MHz after forming gas annealing, similar to films deposited by conventional thermal ALD.

  15. Non-polar a-plane ZnO films grown on r-Al2O3 substrates using GaN buffer layers

    Science.gov (United States)

    Xu, C. X.; Chen, W.; Pan, X. H.; Chen, S. S.; Ye, Z. Z.; Huang, J. Y.

    2016-09-01

    In this work, GaN buffer layer has been used to grow non-polar a-plane ZnO films by laser-assisted and plasma-assisted molecular beam epitaxy. The thickness of GaN buffer layer ranges from ∼3 to 12 nm. The GaN buffer thickness effect on the properties of a-plane ZnO thin films is carefully investigated. The results show that the surface morphology, crystal quality and optical properties of a-plane ZnO films are strongly correlated with the thickness of GaN buffer layer. It was found that with 6 nm GaN buffer layer, a-plane ZnO films display the best crystal quality with X-ray diffraction rocking curve full-width at half-maximum of only 161 arcsec for the (101) reflection.

  16. Radiation endurance in Al2O3 nanoceramics

    Science.gov (United States)

    García Ferré, F.; Mairov, A.; Ceseracciu, L.; Serruys, Y.; Trocellier, P.; Baumier, C.; Kaïtasov, O.; Brescia, R.; Gastaldi, D.; Vena, P.; Beghi, M. G.; Beck, L.; Sridharan, K.; Di Fonzo, F.

    2016-01-01

    The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C –namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films. PMID:27653832

  17. 聚酰亚胺纳米杂化薄膜的透光率与光击穿特性%Research on transmittance and characteristics of optical breakdown of Al2O3/PI hybrid films

    Institute of Scientific and Technical Information of China (English)

    刘晓旭; 阎凯; 朱波; 殷景华

    2011-01-01

    为了研究无机组分的添加对复合材料抗光击穿能力的影响,采用溶胶--凝胶法制备不同组分的AlO/PI复合薄膜,利用半导体激光照射不同组分的AlO/PI薄膜,研究其透光率、光击穿区域的形貌及不同区域的元素分布、击穿孔区的有效面积.数据分析表明:随AlO含量的增加,杂化薄膜的透光率、光击穿孔区的破坏程度、孔区的面积逐渐下降.实验结果表明:纳米AlO颗粒可以减小复合薄膜击穿孔的有效面积,从而提高复合薄膜耐击穿性.杂化薄膜的透光率可以表征其光击穿情况.%Aimed at investigating the effect of addition of inorganic content( Al203 ) on the anti-optical breakdown of hybrid films, this paper introduces the preparation of the Al2O3/PI composition films with different content by Sol-Gel method, the irradiation of the Al2O3/PI films using semiconductor laser,and the identification of the transmittance of hybrid films, the morphology of optical breakdown region,element distribution in different regions, and the effective area of optical breakdown hole. The data analysis show that the light transmittance of the films and the size of the breakdown hole decrease with the increase of Al2O3. The results show that the nano-Al2O3 can reduce the effective area of breakdown hole in the films, thus increasing breakdown-resistance performance, and characterizing the optical breakdown situation by transmittance of hybrid films.

  18. Surface modified Al2O3 in fluorinated polyimide/Al2O3 nanocomposites: Synthesis and characterization

    Indian Academy of Sciences (India)

    Zivar Ghezelbash; Davoud Ashouri; Saman Mousavian; Amir Hossein Ghandi; Yaghoub Rahnama

    2012-11-01

    Organic–inorganic hybrid materials consisting of inorganic materials and organic polymers are a new class of materials, which have received much attention in recent years. In the present investigation, at first, the surface of nano-alumina (Al2O3) was treated with a silane coupling agent of -aminopropyltriethoxysilane (KH550), which introduces organic functional groups on the surface of Al2O3 nanoparticles. Then fluorinated polyimide (PI) was synthesized from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride and 4,4'-diaminodiphenylsulfone. Finally, PI/modified Al2O3 nanocomposite films having 3, 5, 7 and 10% of Al2O3 were successfully prepared by an in situ polymerization reaction through thermal imidization. The obtained nanocomposites were characterized by fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray powder diffraction, UV-Vis spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The results show that the Al2O3 nanoparticles were dispersed homogeneously in PI matrix. According to thermogravimetry analysis results, the addition of these nanoparticles improved thermal stability of the obtained hybrid materials.

  19. Trapped charge densities in Al2O3-based silicon surface passivation layers

    Science.gov (United States)

    Jordan, Paul M.; Simon, Daniel K.; Mikolajick, Thomas; Dirnstorfer, Ingo

    2016-06-01

    In Al2O3-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al2O3 layers are grown by atomic layer deposition with very thin (˜1 nm) SiO2 or HfO2 interlayers or interface layers. In SiO2/Al2O3 and HfO2/Al2O3 stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured in pure Al2O3. In Al2O3/SiO2/Al2O3 or Al2O3/HfO2/Al2O3 stacks, very high total charge densities of up to 9 × 1012 cm-2 are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al2O3 layer thickness between silicon and the HfO2 or the SiO2 interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al2O3 layers opens the possibility to engineer the field-effect passivation in the solar cells.

  20. DUPLEX Al2O3/DLC COATING ON 15SiCp/2024 ALUMINUM MATRIX COMPOSITE USING COMBINED MICROARC OXIDATION AND FILTERED CATHODIC VACUUM ARC DEPOSITION

    OpenAIRE

    WENBIN XUE; HUA TIAN; JIANCHENG DU; MING HUA; XU ZHANG; YONGLIANG LI

    2012-01-01

    Microarc oxidation (MAO) treatment produces a thick Al2O3 coating on the 15SiCp/2024 aluminum matrix composite. After pretreatment of Ti ion implantation, a thin diamond-like carbon film (DLC) was deposited on the top of polished Al2O3 coating by a pulsed filtered cathodic vacuum arc (FCVA) deposition system with a metal vapor vacuum arc (MEVVA) source. The morphology and tribological properties of the duplex Al2O3/DLC multiplayer coating were investigated by Raman spectroscopy, scanning elec...

  1. Fabrication and Characteristics of AIInN/A1N/GaN MOS-HEMTs with Ultra-Thin Atomic Layer Deposited Al2O3 Gate Dielectric

    Institute of Scientific and Technical Information of China (English)

    MAO Wei; BI Zhi-Wei; LIANG Xiao-Zhen; ZHANG Jin-Feng; KUANG Xian-Wei; ZHANG Jin-Cheng; XUE Jun-Shuai; HAO Yao; MA Xiao-Hua; WANG Chong; LIU Hong-Xia; XU Sheng-Rui; YANG Lin-An

    2010-01-01

    @@ Al0.85In0.15N/AlN/GaN metal-oxide-semiconductor high electron mobility transistors(MOS-HEMTs)employing a 3-nm ultra-thin atomic-layer deposited(ALD)Al2O3 gate dielectric layer are reported.Devices with 0.6μm gate lengths exhibit an improved maximum drain current density of 1227mA/mm at a gate bias of 3 V,a peak transconductance of 328 mS/mm,a cutoff frequency fT of 16 GHz,a maximum frequency of oscillation fmax of45 GHz,as well as significant gate leakage suppression in both reverse and forward directions,compared with the conventional Al0.85In0.15N/AlN/GaN HEMT.Negligible C-V hysteresis,together with a smaller pinch-off voltage shift,is observed,demonstrating few bulk traps in the dielectric and high quality of the Al2O3/AlInN interface.It is most notable that not only the transconductance profile of the MOS-HEMT is almost the same as that of the conventional HEMT with a negative shift,but also the peak transconductance of the MOS-HEMT is increased slightly.It is an exciting improvement in the transconductance performance.

  2. PEDOT gate electrodes with PVP/Al2O3 dielectrics for stable high-performance organic TFTs

    Science.gov (United States)

    Lee, Young Kyu; Maniruzzaman, Md.; Lee, Chiyoung; Lee, Mi Jung; Lee, Eun-Gu; Lee, Jaegab

    2013-11-01

    A poly(3,4-ethylenedioxythiophene) (PEDOT) gate electrode on a polyestersulfone (PES) substrate was used to fabricate inverted staggered pentacene organic thin film transistors (OTFTs). The PEDOT gate formed on the PES substrate exhibited semi-transparency, high conductivity, and excellent adhesion to the substrate. Prior to the deposition of poly-4-vinyl phenol (PVP) dielectrics, a thin Al2O3 layer (12 nm) was coated onto a PEDOT electrode, providing an effective barrier against inter-diffusion between the PVP dielectrics and the underlying PEDOT gate electrode, and against moisture penetration through the PES substrate. This led to stable high-performance OTFTs consisting of a PEDOT gate electrode and PVP/Al2O3 dielectrics. The combined PVP/Al2O3 dielectrics with PEDOT gate electrodes were successfully implemented in flexible organic TFTs that exhibit excellent compatibility with flexible electronics.

  3. Oxidation of Al2O3-dispersion chromizing coating by pack-cementation at 800℃

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yue-bo; CHEN Hong-yu; ZHANG Hai-jun; WANG Yong-dong

    2008-01-01

    Preparation and oxidation of an Al2O3-dispersed chromizing coating were investigated by chromizing an aselectrodeposited Ni-Al2O3 nanocomposite film using a conventional pack-cementation method at a greatly decreased temperature (800℃).For comparison,chromizing was also performed with the same condition on an as-deposited Ni film without Al2O3 nanoparticles.Oxidation at 900℃ indicates that,compared with the Al2O3-free chromizing coating,the Al2O3-dispersed chromizing coating exhibits a increased oxidation resistance,due to the formation of purer and denser chromia scale.The effect of Al2O3 on the coating formation and the coating oxidation behavior was discussed in details.

  4. Investigation on the passivated Si/Al2O3 interface fabricated by non-vacuum spatial atomic layer deposition system.

    Science.gov (United States)

    Lien, Shui-Yang; Yang, Chih-Hsiang; Wu, Kuei-Ching; Kung, Chung-Yuan

    2015-01-01

    Currently, aluminum oxide stacked with silicon nitride (Al2O3/SiNx:H) is a promising rear passivation material for high-efficiency P-type passivated emitter and rear cell (PERC). It has been indicated that atomic layer deposition system (ALD) is much more suitable to prepare high-quality Al2O3 films than plasma-enhanced chemical vapor deposition system and other process techniques. In this study, an ultrafast, non-vacuum spatial ALD with the deposition rate of around 10 nm/min, developed by our group, is hired to deposit Al2O3 films. Upon post-annealing for the Al2O3 films, the unwanted delamination, regarded as blisters, was found by an optical microscope. This may lead to a worse contact within the Si/Al2O3 interface, deteriorating the passivation quality. Thin stoichiometric silicon dioxide films prepared on the Si surface prior to Al2O3 fabrication effectively reduce a considerable amount of blisters. The residual blisters can be further out-gassed when the Al2O3 films are thinned to 8 nm and annealed above 650°C. Eventually, the entire PERC with the improved triple-layer SiO2/Al2O3/SiNx:H stacked passivation film has an obvious gain in open-circuit voltage (V oc) and short-circuit current (J sc) because of the increased minority carrier lifetime and internal rear-side reflectance, respectively. The electrical performance of the optimized PERC with the V oc of 0.647 V, J sc of 38.2 mA/cm(2), fill factor of 0.776, and the efficiency of 19.18% can be achieved.

  5. Duplex Al2O3/DLC Coating on 15SiCp/2024 Aluminum Matrix Composite Using Combined Microarc Oxidation and Filtered Cathodic Vacuum Arc Deposition

    Science.gov (United States)

    Xue, Wenbin; Tian, Hua; Du, Jiancheng; Hua, Ming; Zhang, Xu; Li, Yongliang

    2012-08-01

    Microarc oxidation (MAO) treatment produces a thick Al2O3 coating on the 15SiCp/2024 aluminum matrix composite. After pretreatment of Ti ion implantation, a thin diamond-like carbon film (DLC) was deposited on the top of polished Al2O3 coating by a pulsed filtered cathodic vacuum arc (FCVA) deposition system with a metal vapor vacuum arc (MEVVA) source. The morphology and tribological properties of the duplex Al2O3/DLC multiplayer coating were investigated by Raman spectroscopy, scanning electron microscopy (SEM) and SRV ball-on-disk friction tester. It is found that the duplex Al2O3/DLC coating had good adhesion and a low friction coefficient of less than 0.07. As compared to a single Al2O3 or DLC coating, the duplex Al2O3/DLC coating on aluminum matrix composite exhibited a better wear resistance against ZrO2 ball under dry sliding, because the Al2O3 coating as an intermediate layer improved load support for the top DLC coating on 15SiCp/2024 composite substrate, meanwhile the top DLC coating displayed low friction coefficient.

  6. Model Research On Synthesis Of Al2O3-C Layers By MOCVD

    Directory of Open Access Journals (Sweden)

    Sawka A.

    2015-06-01

    Full Text Available These are model studies whose aim is to obtain information that would allow development of new technology for synthesizing monolayers of Al2O3-C with adjusted microstructure on cemented carbides. The Al2O3-C layer will constitute an intermediate layer on which the outer layer of Al2O3 without carbon is synthesized. The purpose of the intermediate layer is to block the cobalt diffusion to the synthesized outer layer of Al2O3 and to stop the diffusion of air oxygen to the substrate during the synthesis of the outer layer. This layer should be thin, continuous, dense and uniform in thickness.

  7. Pt-Ti/ALD-Al2O3/p-Si MOS Capacitors for Future ULSI Technology

    Directory of Open Access Journals (Sweden)

    Ashok M. Mahajan

    2011-01-01

    Full Text Available The high dielectric constant (high-k thin film of Al2O3 was deposited by using Plasma enhanced atomic layer deposition (PE-ALD technique. The electron beam evaporation system was used to deposit the Pt-Ti metal to fabricate the Pt-Ti/Al2O3/Si MOS capacitors. Thickness measurement of Al2O3 gate dielectric was carried out with variable angle spectroscopic ellipsometry, which is measured to be 2.83 nm. The MOS capacitors were characterized to evaluate the electrical properties using capacitance voltage (C-V analyzer at different measurement frequencies. Capacitance voltage measurement shows that, dielectric constant k ranges from 7.87 to 10.44. In CV curve a slight negative shift is observed in the flatband voltage because of presence of trap charges in the Al2O3 MOS capacitor. A lower equivalent oxide thickness (EOT of 1.057 nm is obtained for the fabricated Pt-Ti/ Al2O3 /Si MOS capacitors.

  8. 利用小角X射线散射技术研究组分对聚酰亚胺/Al2O3杂化薄膜界面特性与分形特征的影响%Research on interface and fractal characteristics of Pl/Al2 O3 Films by SAXS

    Institute of Scientific and Technical Information of China (English)

    刘晓旭; 殷景华; 程伟东; 卜文斌; 范勇; 吴忠华

    2011-01-01

    Inorganic nano-composite polyimide (PI) films were prepared with the method of sol-gel. The interfacial situation and the fractal characteristics of PI films were investigated by small angle X-ray scattering (SAXS) using synchrotron radiation as X-ray source. SAXS results indicated that the scattering curves in the high-angle region have a negative slope,i. e., a negative deviation from Porod's law, which suggests that there are obvious interface layers between the organic phase and the inorganic phase in the PI films. The thicknesses of interface layers are 0. 54-1. 48 nm. The interaction of the organic phase and inorganic phase becomes stronger and the thickness of interfacial layer increases with the increase of inorganic nano-components. Nano-particles have mass fractal, simultaneously have surface fractal structure, and their distribution and assemblage are nonlinear dynamic processes. With the inorganic nano-components increasing, the surface fractal dimension increases and mass fractal dimension decreases, which shows that the nano-particles structure becomes looser and mass distribution becomes more uneven. The anchoring action of polymer chains is enhanced and the number of anchored point increased respectively, the surface of the hybrid PI films becomes rougher. Finally, according to the interface characteristics of hybrid PI films, the relationship of the breakdown field strength with component is analyzed by percolation theory and polarization theory.%采用溶胶-凝胶方法制备无机纳米杂化聚酰亚胺(PI),应用同步辐射小角X射线散射(SAXS)方法研究不同组分杂化PI薄膜的界面特性与分形特征.研究结果表明:散射曲线不遵守Porod定理,形成负偏离,说明薄膜中有机相与Al2O3纳米颗粒间存在界面层,界面层厚度在0.54 nm到1.48 nm范围内;随无机纳米组分增加,界面层厚度增加,有机相与无机相作用变强;无机纳米颗粒同时具有质量分形和表面分形特征,其分

  9. Optimization of Wet or Dry Micro-blasting on PVD Films by Various Al2O3 Grain Sizes for Improving the Coated Tools' Cutting Performance

    OpenAIRE

    K.-D. Bouzakis; Tsouknidas, A.; G. Skordaris; E. Bouzakis; Makrimallakis, S.; S. Gerardis; G. Katirtzoglou

    2011-01-01

    Micro-blasting on PVD coated tools is an effective technology for improving their cutting performance. Through micro-blasting, compressive stresses are induced into the film, thus increasing the coating hardness, but its brittleness too. Simultaneously, abrasion phenomena are activated, which may lead to roughness augmentation, film thickness decrease and substrate revelation. In this way, for a successful process conduct, it is pivotal to adapt, among others, the applied micro-blasting pres...

  10. 纳米多孔Al2O3薄膜的制备及其光致发光%Preparation and Photoluminescence of Nanoporous Alumina Films

    Institute of Scientific and Technical Information of China (English)

    帖长军; 许勤芳; 王倩

    2011-01-01

    Porous alumina film was fabricated in oxalic acid electrolyte by a two-step anodization method at room temperature. The film was annealed at 600℃ in the air. The surface morphology and crystalline state of the annealed film were investigated by scanning electron microscopy and X-ray diffraction, respectively.The constituent elements on the film surface were determincd by Energy Disperse Spectroscopy. The results showed that the film was amorphous and presented highly ordered structures with uniform pore distribution. and included trace carbon. The film presented a blue-green emission band at 470nm when it was excited at 340nm. We find that the origin of the emission band was related to the Oxalate luminophore.%利用二次阳极氧化法在室温条件下制备了多孔氧化铝薄膜.采用扫描电镜、能量色散谱和X射线衍射对空气环境中600℃退火处理的多孔氧化铝薄膜进行了表面形貌、成分和结晶形式分析,结果表明多孔氧化铝薄膜孔阵排列有序、孔径大小一致,含有微量的C元素且为非晶态结构.在340nm的光激发条件下,多孔氧化铝薄膜出现峰值位于470nm的蓝绿发光带.通过分析得出,此光致发光带与草酸根离子发光基团有关.

  11. Preparation and photoluminescence of nanoporous alumina films%纳米多孔Al2O3薄膜的制备及其光致发光

    Institute of Scientific and Technical Information of China (English)

    李志军; 许勤芳; 王倩

    2011-01-01

    Porous alumina film is fabricated in oxalic acid electrolyte by a two-step anodization method at room temperature. The film is annealed at 600 ℃ in the air. The surface morphology and crystalline state of the annealed film are investigated by scanning electron microscopy and X-ray diffraction, respectively. The constituent elements on the film surface are determined by energy disperse spectroscopy. The results show that the film is amorphous and present highly ordered structures with uniform pore distribution, and includes trace carbon. The film presents a blue-green emission band at 470 nm when it is excited at 340 nm. A possible mechanism is proposed that the origin of the emission band is related to the oxalate luminophore.%利用二次阳极氧化法在室温条件下制备了多孔氧化铝薄膜.采用扫描电镜、能量色散谱和X射线衍射对空气中600℃退火处理的多孔氧化铝薄膜进行了表面形貌、成分和结晶形式分析.结果表明,多孔氧化铝薄膜孔阵排列有序,孔径大小一致,含有微量的C元素且为非晶态结构.在340 nm的光激发下,多孔氧化铝薄膜出现峰值位于470nm的蓝绿发光带,此光致发光带与草酸根离子发光基团有关.

  12. Interface sulfur passivation using H2S annealing for atomic-layer-deposited Al2O3 films on an ultrathin-body In0.53Ga0.47As-on-insulator

    International Nuclear Information System (INIS)

    Highlights: • ALD Al2O3 films were grown on ultrathin-body In0.53Ga0.47As substrates for III-V compound-semiconductor-based devices. • Interface sulfur passivation was performed with wet processing using (NH4)2S solution, and dry processing using post-deposition annealing under a H2S atmosphere. • Electrical properties of the device were better for (NH4)2S wet-treatment than the PDA under a H2S atmosphere. • PDA under a H2S atmosphere following (NH4)2S wet-treatment resulted in an increased S concentration at the interface, which improved the electrical properties of the devices. - Abstract: Atomic-layer-deposited Al2O3 films were grown on ultrathin-body In0.53Ga0.47As substrates for III-V compound-semiconductor-based devices. Interface sulfur (S) passivation was performed with wet processing using ammonium sulfide ((NH4)2S) solution, and dry processing using post-deposition annealing (PDA) under a H2S atmosphere. The PDA under the H2S atmosphere resulted in a lower S concentration at the interface and a thicker interfacial layer than the case with (NH4)2S wet-treatment. The electrical properties of the device, including the interface property estimated through frequency dispersion in capacitance, were better for (NH4)2S wet-treatment than the PDA under a H2S atmosphere. They might be improved, however, by optimizing the process conditions of PDA. The PDA under a H2S atmosphere following (NH4)2S wet-treatment resulted in an increased S concentration at the interface, which improved the electrical properties of the devices

  13. Frictional properties of CeO$_{2}$-Al$_{2}$O$_{3}$-ZrO$_{2}$ plasma-sprayed film under mixed and boundary lubricating conditions

    CERN Document Server

    Kita, H; Osumi, K; 10.2109/jcersj.112.615

    2004-01-01

    In order to find a counterpart for reducing the frictional coefficient of Al/sub 2/O/sub 3/-ZrO/sub 2/-CeO/sub 2/ plasma-sprayed film, the sliding properties in mixed and boundary lubricating conditions was investigated. It was found that combination of a CrN- coated cast iron pin and an Al/sub 2/O/sub 3/-ZrO/sub 2/-CeO/sub 2/ plasma sprayed plate provided the lowest frictional coefficient among several combinations chosen from practical materials. The coefficient of friction was much lower than that of the materials combination widely used for piston ring and cylinder liner. It was inferred that the combination of a pin made of hard materials with high density, a smooth surface such as CrN-coated cast iron and a porous plate can reduce the frictional coefficient because less sliding resistance is implemented and porosity retains oil.

  14. Microstructure and Mechanical Property of Hot-Pressed Al2O3-Ni-P Composites Using Ni-P-Coated Al2O3 Powders

    Directory of Open Access Journals (Sweden)

    Hyeong-Chul Kim

    2015-01-01

    Full Text Available Al2O3-Ni-P composite powders with Ni-P contents of 10.9, 14.4, and 20.4 wt.% were synthesized via the Ni-P electroless deposition process. The as-received Al2O3-Ni-P composite powders were composed of Ni-P particles and Ni-P coating layer. Some Ni-P particles randomly adhered to the Al2O3 powders, and their particle diameter ranged from 5 nm to 20 nm. The thin Ni-P layer had about 5 nm thick amorphous structure and directly bonded with Al2O3 powders. Using the Ni-P-coated Al2O3 powders, a dense Al2O3-Ni-P composite can be successfully obtained using the hot press process at 1,350°C for 1 hour in an Ar atmosphere under an applied pressure of 30 MPa. The hot-pressed Al2O3-15 wt.% Ni-P composite showed excellent material properties. Its relative density, Vickers hardness, and fracture toughness were comparatively high: about 99.1%, 2,360 Hv, and 6 MPa·m1/2, respectively. The fracture surface of the hot-pressed Al2O3-Ni-P composite showed a semiductile mode due to the mixed intergranular and transgranular fracture mode. In particular, the fracture toughness of the hot-pressed Al2O3-15 wt.% Ni-P composite was strongly enhanced by the combined action of the crack branching and the crack deflection.

  15. Structural, electronic structure, and band alignment properties at epitaxial NiO/Al2O3 heterojunction evaluated from synchrotron based X-ray techniques

    Science.gov (United States)

    Singh, S. D.; Nand, Mangla; Das, Arijeet; Ajimsha, R. S.; Upadhyay, Anuj; Kamparath, Rajiv; Shukla, D. K.; Mukherjee, C.; Misra, P.; Rai, S. K.; Sinha, A. K.; Jha, S. N.; Phase, D. M.; Ganguli, Tapas

    2016-04-01

    The valence band offset value of 2.3 ± 0.2 eV at epitaxial NiO/Al2O3 heterojunction is determined from photoelectron spectroscopy experiments. Pulsed laser deposited thin film of NiO on Al2O3 substrate is epitaxially grown along [111] direction with two domain structures, which are in-plane rotated by 60° with respect to each other. Observation of Pendellosung oscillations around Bragg peak confirms high interfacial and crystalline quality of NiO layer deposited on Al2O3 substrate. Surface related feature in Ni 2p3/2 core level spectra along with oxygen K-edge soft X-ray absorption spectroscopy results indicates that the initial growth of NiO on Al2O3 substrate is in the form of islands, which merge to form NiO layer for the larger coverage. The value of conduction band offset is also evaluated from the measured values of band gaps of NiO and Al2O3 layers. A type-I band alignment at NiO and Al2O3 heterojunction is also obtained. The determined values of band offsets can be useful in heterojunction based light emitting devices.

  16. Rectification and tunneling effects enabled by Al2O3 atomic layer deposited on back contact of CdTe solar cells

    Science.gov (United States)

    Liang, Jun; Lin, Qinxian; Li, Hao; Su, Yantao; Yang, Xiaoyang; Wu, Zhongzhen; Zheng, Jiaxin; Wang, Xinwei; Lin, Yuan; Pan, Feng

    2015-07-01

    Atomic layer deposition (ALD) of Aluminum oxide (Al2O3) is employed to optimize the back contact of thin film CdTe solar cells. Al2O3 layers with a thickness of 0.5 nm to 5 nm are tested, and an improved efficiency, up to 12.1%, is found with the 1 nm Al2O3 deposition, compared with the efficiency of 10.7% without Al2O3 modification. The performance improvement stems from the surface modification that optimizes the rectification and tunneling of back contact. The current-voltage analysis indicates that the back contact with 1 nm Al2O3 maintains large tunneling leakage current and improves the filled factor of CdTe cells through the rectification effect. XPS and capacitance-voltage electrical measurement analysis show that the ALD-Al2O3 modification layer features a desired low-density of interface state of 8 × 1010 cm-2 by estimation.

  17. High Temperature Mechanical Characterization and Analysis of Al2O3 /Al2O3 Composition

    Science.gov (United States)

    Gyekenyesi, John Z.; Jaskowiak, Martha H.

    1999-01-01

    Sixteen ply unidirectional zirconia coated single crystal Al2O3 fiber reinforced polycrystalline Al2O3 was tested in uniaxial tension at temperatures to 1400 C in air. Fiber volume fractions ranged from 26 to 31%. The matrix has primarily open porosity of approximately 40%. Theories for predicting the Young's modulus, first matrix cracking stress, and ultimate strength were applied and evaluated for suitability in predicting the mechanical behavior of Al2O3/Al2O3 composites. The composite exhibited pseudo tough behavior (increased area under the stress/strain curve relative to monolithic alumina) from 22 to 1400 C. The rule-of-mixtures provides a good estimate of the Young's modulus of the composite using the constituent properties from room temperature to approximately 1200 C for short term static tensile tests in air. The ACK theory provides the best approximation of the first matrix cracking stress while accounting for residual stresses at room temperature. Difficulties in determining the fiber/matrix interfacial shear stress at high temperatures prevented the accurate prediction of the first matrix cracking stress above room temperature. The theory of Cao and Thouless, based on Weibull statistics, gave the best prediction for the composite ultimate tensile strength.

  18. Bimodal substrate biasing to control \\gamma-Al2O3 deposition during reactive magnetron sputtering

    CERN Document Server

    Prenzel, Marina; Stein, Adrian; von Keudell, Achim; Nahif, Farwah; Schneider, Jochen M

    2013-01-01

    Al2O3 thin films have been deposited at substrate temperatures between 500{\\deg}C to 600{\\deg}C by reactive magnetron sputtering using an additional arbitrary substrate bias to tailor the energy distribution of the incident ions. The films were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The film structure being amorphous, nanocrystalline, or crystalline was correlated with characteristic ion energy distributions. The evolving crystalline structure is connected with different levels of displacements per atom (dpa) in the growing film as being derived from TRIM simulations. The boundary between the formation of crystalline films and amorphous or nanocrystalline films was at 0.9 dpa for a substrate temperature of 500{\\deg}C. This threshold shifts to 0.6 dpa for films grown at 550{\\deg}C.

  19. Electrical property of Al203/SiO2 multilayer films deposited by electron evaporation%电子束蒸发Al2O3/SiO2复合薄膜电学性能的研究

    Institute of Scientific and Technical Information of China (English)

    翁卫祥; 贾贞; 于光龙; 李昱; 郭太良

    2011-01-01

    利用离子辅助电子束蒸发技术,在玻璃基底上以交替沉积的方式制备了A12O3/SiO2叠层复合薄膜,单层介质膜膜厚分别选取54和16 nm,总厚度为560 nm.采用步进法测试得到金属电极/复合绝缘膜/金属电极(MIM)结构的I-V特性曲线,具体成分为CrCuCr/(Al2O3/SiO2)8/CrCuCr,相应的厚度为80 nm/560 nm/80nm,复合薄膜的平均击穿场强为2.7 MV·cm-1,较好地满足FED后栅结构中对介质膜耐压特性的要求.结合理论分析发现,Al2O3/SiO2复合薄膜在不同的场强条件下以某一种导通作为主要的导通机制,其低场强区服从准欧姆定律,随着场强升高,在不同的阶段分别以肖特基效应,普尔-弗兰凯尔效应和F-N效应为主.%The mutilayer thin films of aluminum oxide( AI2O3 ) and silicon oxide (SiO2) were alternating deposited on glass substrates by ion beam assisted electron evaporation. The thickness of the films was 560 nm, and each layer of Al2O3 and SiO2 was 54 and 16 nm. Based on the metal - insulating metal structure, the I - V curves of the CrCuCr/ (A12 O3/SiO2 )s/CrCuCr was obtained with the voltage stepping method. The breakdown field strength of the composite layer was 2.7 MV · cm-1, fulfilled the requirements of FED for its withstand voltage property. It is found that the multilayer thin films have different conduction mechanisms under the condition of various field strengths combined with theoretics, the conduction mechanism followed Ohm' s law in the low - field area, then as the field strength increases, the Schottky effect, Poole - Fulankaier effect and F - N effect are respectively regarded as the mian mechanism at different stages.

  20. Evolution of complementary resistive switching characteristics using IrOx/GdOx/Al2O3/TiN structure

    Science.gov (United States)

    Jana, Debanjan; Samanta, Subhranu; Maikap, Siddheswar; Cheng, Hsin-Ming

    2016-01-01

    The complementary resistive switching (CRS) characteristics using an IrOx/GdOx/Al2O3/TiN single cell are observed whereas the bipolar resistive switching (BRS) characteristics are observed for the IrOx/GdOx/TiN structure. Transmission electron microscope and energy dispersive X-ray spectroscopy depth profile show crystalline GdOx film and the presence of higher amount of oxygen at both IrOx/GdOx interface and Al2O3 layer. Inserting thin Al2O3 layer, the BRS is changed to CRS. This CRS has hopping distance of 0.58 nm and Poole-Frenkel current conductions for the "0" and "1" states, respectively. A schematic model using oxygen vacancy filament formation/rupture at the TE/GdOx interface and Al2O3 layer has been illustrated. This CRS device has good endurance of 1000 cycles with a pulse width of 1 μs, which is very useful for future crossbar architecture.

  1. Hydrogen Embrittlement Processes and Al/Al2O3 Hydrogen Resistance Coatings of NdFeB Magnets

    Institute of Scientific and Technical Information of China (English)

    张万里; 彭斌; 蒋洪川; 张文旭; 杨仕清

    2004-01-01

    After analyzing the phenomena and processes of hydrogen embrittlement of NdFeB permanent magnets,RF magnetron sputtering was used to fabricate Al thin films and then oxidized to form the Al/Al2O3 composite films on the magnets as the hydrogen resistance coatings.SEM and EDS were used to examine the morphology and composition respectively.Hydrogen resistance performance was tested by exposing the magnets in 10 MPa hydrogen gas at room temperature.The results show that the magnets with 8 μm Al/Al2O3 coatings can withstand hydrogen of 10 MPa for 65 min without being embrittled into powder.The samples with and without hydrogen resistance coatings have almost the same magnetic properties.

  2. Plasma-Assisted ALD of an Al2O3 Permeation Barrier Layer on Plastic

    Science.gov (United States)

    Lei, Wenwen; Li, Xingcun; Chen, Qiang; Wang, Zhengduo

    2012-02-01

    Atomic layer deposition (ALD) technique is used in the preparation of organic/inorganic layers, which requires uniform surfaces with their thickness down to several nanometers. For film with such thickness, the growth mode defined as the arrangement of clusters on the surface during the growth is of significance. In this work, Al2O3 thin film was deposited on various interfacial species of pre-treated polyethylene terephthalate (PET, 12 μm) by plasma assisted atomic layer deposition (PA-ALD), where trimethyl aluminium was used as the Al precursor and O2 as the oxygen source. The interfacial species, -NH3, -OH, and -COOH as well as SiCHO (derived from monomer of HMDSO plasma), were grafted previously by plasma and chemical treatments. The growth mode of PA-ALD Al2O3 was then investigated in detail by combining results from in-situ diagnosis of spectroscopic ellipsometry (SE) and ex-situ characterization of as-deposited layers from the morphologies scanned by atomic force microscopy (AFM). In addition, the oxygen transmission rates (OTR) of the original and treated plastic films were measured. The possible reasons for the dependence of the OTR values on the surface species were explored.

  3. Plasma-Assisted ALD of an Al2O3 Permeation Barrier Layer on Plastic

    International Nuclear Information System (INIS)

    Atomic layer deposition (ALD) technique is used in the preparation of organic/inorganic layers, which requires uniform surfaces with their thickness down to several nanometers. For film with such thickness, the growth mode defined as the arrangement of clusters on the surface during the growth is of significance. In this work, Al2O3 thin film was deposited on various interfacial species of pre-treated polyethylene terephthalate (PET, 12 μm) by plasma assisted atomic layer deposition (PA-ALD), where trimethyl aluminium was used as the Al precursor and O2 as the oxygen source. The interfacial species, -NH3, -OH, and -COOH as well as SiCHO (derived from monomer of HMDSO plasma), were grafted previously by plasma and chemical treatments. The growth mode of PA-ALD Al2O3 was then investigated in detail by combining results from in-situ diagnosis of spectroscopic ellipsometry (SE) and ex-situ characterization of as-deposited layers from the morphologies scanned by atomic force microscopy (AFM). In addition, the oxygen transmission rates (OTR) of the original and treated plastic films were measured. The possible reasons for the dependence of the OTR values on the surface species were explored.

  4. Plasma-Assisted ALD of an Al2O3 Permeation Barrier Layer on Plastic

    Institute of Scientific and Technical Information of China (English)

    雷雯雯; 李兴存; 陈强; 王正铎

    2012-01-01

    Atomic layer deposition (ALD) technique is used in the preparation of organic/inorganic layers, which requires uniform surfaces with their thickness down to several nanometers. For film with such thickness, the growth mode defined as the arrangement of clusters on the surface during the growth is of significance. In this work, Al2O3 thin film was deposited on various interfacial species of pre-treated polyethylene terephthalate (PET, 12 μm) by plasma assisted atomic layer deposition (PA-ALD), where trimethyl aluminium was used as the Al precursor and O2 as the oxygen source. The interracial species, -NH3, -OH, and -COOH as well as SiCHO (derived from monomer of HMDSO plasma), were grafted previously by plasma and chemical treatments. The growth mode of PA-ALD Al2O3 was then investigated in detail by combining results from in-situ diagnosis of spectroscopic ellipsometry (SE) and ex-situ characterization of as-deposited layers from the morphologies scanned by atomic force microscopy (AFM). In addition, the oxygen transmission rates (OTR) of the original and treated plastic films were measured. The possible reasons for the dependence of the OTR values on the surface species were explored.

  5. CoFe2/Al2O3/PMNPT multiferroic heterostructures by atomic layer deposition

    Science.gov (United States)

    Zhou, Ziyao; Grocke, Garrett; Yanguas-Gil, Angel; Wang, Xinjun; Gao, Yuan; Sun, Nianxiang; Howe, Brandon; Chen, Xing

    2016-05-01

    Multiferroic materials and applications allow electric bias control of magnetism or magnetic bias control of polarization, enabling fast, compact, energy-efficient devices in RF/microwave communication systems such as filters, shifters, and antennas; electronics devices such as inductors and capacitors; and other magnetic material related applications including sensors and memories. In this manuscript, we utilize atomic layer deposition technology to grow magnetic CoFe metallic thin films onto PMNPT, with a ˜110 Oe electric field induced ferromagnetic resonance field shift in the CoFe/Al2O3/PMNPT multiferroic heterostructure. Our work demonstrates an atomic layer deposition fabricated multiferroic heterostructure with significant tunability and shows that the unique thin film growth mechanism will benefit integrated multiferroic application in near future.

  6. Al2O3/Al2O3 Joint Brazed with Al2O3-particulate-contained Composite Ag-Cu-Ti Filler Material

    Institute of Scientific and Technical Information of China (English)

    Jianguo YANG; Hongyuan FANG; Xin WAN

    2005-01-01

    Microstructure and interfacial reactions of Al2O3 joints brazed with Al2O3-particulate-contained composite Ag-Cu-Ti filler material were researched by scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA),energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The interfacial reaction layer thickness of joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of Al2O3 particulate was also studied. The experimental results indicated although there were Al2O3 particulates added into active filler metals, the time dependence of interfacial layer growth of joints brazed with active composite filler material is t1/2 as described by Fickian law as the joints brazed with conventional active filler metal.

  7. Deposition and Properties of the Pseudobinary Alloy (Al2O3)x(TiO2)1-x and Its Application for Silicon Surface Passivation

    Science.gov (United States)

    Vitanov, P.; Harizanova, A.; Ivanova, T.; Alexieva, Z.; Agostinelli, G.

    2006-07-01

    The electrical properties of (Al2O3)x(TiO2)1-x thin films, obtained from sol solution by spin coating on Si substrates (c-Si or mc-Si), have been studied. By varying the ratios between Al2O3 and TiO2 components, the optical and dielectric characteristics can be changed. This deposition method can be used for effective engineering of physical properties of the dielectric layer. Surface recombination velocities as low as 150 cm/s have been obtained using (Al2O3)x(TiO2)1-x layers on 1 Ω\\cdotcm Czochralski (CZ) silicon wafers. Low surface recombination is achieved by field induced surface passivation due to a high density of negative fixed charges.

  8. Highly-Ordered Magnetic Nanostructures on Self-Assembled α-Al2O3 and Diblock Copolymer Templates

    International Nuclear Information System (INIS)

    This thesis shows the preparation of nanostructured systems with a high degree of morphological uniformity and regularity employing exclusively selfassembly processes, and documents the investigation of these systems by means of atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), and nuclear resonant scattering of synchrotron radiation (NRS). Whenever possible, the X-ray scattering methods are applied in-situ and simultaneously in order to monitor and correlate the evolution of structural and magnetic properties of the nanostructured systems. The following systems are discussed, where highly-ordered magnetic nanostructures are grown on α-Al2O3 substrates with topographical surface patterning and on diblock copolymer templates with chemical surface patterning: - Nanofaceted surfaces of α-Al2O3 - Magnetic nanostructures on nanofaceted α-Al2O3 substrates - Thin films of microphase separated diblock copolymers - Magnetic nanostructures on diblock copolymer thin film templates The fact that the underlying self-assembly processes can be steered by external factors is utilized to optimize the degree of structural order in the nanostructured systems. The highly-ordered systems are well-suited for investigations with X-ray scattering methods, since due to their uniformity the inherently averaged scattered signal of a sample yields meaningful information on the properties of the contained nanostructures: By means of an in-situ GISAXS experiment at temperatures above 1000 C, details on the facet formation on α-Al2O3 surfaces are determined. A novel method, merging in-situ GISAXS and NRS, shows the evolution of magnetic states in a system with correlated structural and magnetic inhomogeneity with lateral resolution. The temperature-dependence of the shape of Fe nanodots growing on diblock copolymer templates is revealed by in-situ GISAXS during sputter deposition of Fe. Combining in-situ GISAXS and NRS, the magnetization stabilization

  9. Fabrication and characterization of hydroxyapatite/Al2O3 biocomposite coating on titanium

    Institute of Scientific and Technical Information of China (English)

    WU Zhen-jun; HE Li-ping; CHEN Zong-zhang

    2006-01-01

    A novel biocomposite coating of hydroxyapatite/Al2O3 was fabricated on titanium using a multi-step technique including physical vapor deposition(PVD), anodization, electrodeposition and hydrothermal treatment. Anodic Al2O3 layer with micrometric pore diameter was formed by anodization of the PVD-deposited aluminum film on titanium and subsequent removal of part barrier Al2O3 layer. Hydroxyapatite coating was then electrodeposited onto the as-synthesized anodic Al2O3 on titanium. A hydrothermal process was finally applied to the fabricated biocomposite coating on titanium in alkaline medium. Scanning electron microscopy(SEM), energy dispersive spectrometry(EDS) and X-ray diffractometry(XRD) were employed to investigate the morphologies and compositions of the pre- and post-hydrothermally treated hydroxyapatite/Al2O3 biocomposite coatings. The results show that micrometric plate-like Ca-deficient hydroxyapatite (CDHA) coatings are directly electrodeposited onto anodic Al2O3 at constant current densities ranging from 1.2 to 2.0 mA/cm2 using NaH2PO4 as the phosphorous source. After hydrothermal treatment,the micrometric plate-like CDHA coating electrodeposited at 2.0 mA/cm2 is converted into nano-network Ca-rich hydroxyapatite (CRHA) one and the adhesion strength is improved from 9.5 MPa to 21.3 MPa. A mechanism of dissolution-recrystallization was also proposed for the formation of CRHA.

  10. ZnO/Al2O3 coatings for the photoprotection of polycarbonate

    International Nuclear Information System (INIS)

    ZnO and ZnO/Al2O3 thin films were deposited by r.f. magnetron sputtering on polycarbonate (PC) films in order to protect this polymer against photodegradation. The composition, structure and optical properties of the ceramic coatings were characterised. CO2-plasma treatments were applied to PC in order to improve the coating adhesion. The PC surface energy was characterised by wettability measurements and the chemical bonds were analysed by XPS. It was found that ZnO coatings improve the stability of PC to UV radiations and that an intermediate alumina coating inhibits the photocatalytic oxidation of PC at the PC/ZnO interface. Additionally an external alumina coating brings a high hardness to the coating

  11. SYNTHESIS AND ELECTRICAL PROPERTIES OF POLYIMIDE-Al2O3 COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Hong-yan Li; Shu-fan Ning; Hai-bing Hu; Bin Liu; Wei Chen; Shou-tian Chen

    2007-01-01

    Polyimide-alumina hybrid films were synthesized via in situ polymerization and thermal imidation process from a solution of polyimide precursor and nanosized alumina in N,N-dimethylacetamide, and the microstructure of the hybrid films was characterized by transmission electron microscope (TEM) and infra-red (IR) spectrometry. The dependence of thermal stability, tensile properties, dielectric properties and degradation endurance under corona on the nano-Al2O3 content of polyimide-alumina hybrid films was studied. The results show that with the increase of Al2O3 content, the thermal stability and the dielectric properties of the hybrids increase, while the tensile properties decrease. Better corona resistance can be achieved if the PI film is filled with α-Al2O3 nanometric particle.

  12. Reactive ion etching of low-loss channel waveguides in $Al_2O_3$ and $Y_2O_3$ layers

    NARCIS (Netherlands)

    Bradley, J.D.B.; Ay, F.; Wörhoff, K.; Pollnau, M.

    2007-01-01

    In this work, the etching behaviour of reactively co-sputtered amorphous $Al_2O_3$ and polycrystalline $Y_2O_3$ films was investigated using an inductively coupled reactive ion etch system. In $Al_2O_3$ channel waveguides were fabricated with BCl3/HBr plasma and using a standard resist mask, while i

  13. Relation of hardness and oxygen flow of Al2O3 coatings deposited by reactive bipolar pulsed magnetron sputtering

    International Nuclear Information System (INIS)

    Aluminum oxide thin films are widely used because of their excellent properties, especially in terms of chemical, thermal, abrasive and corrosive resistance. But many properties of alumina films are significantly deposition parameters dependent. Since different applications and environments demand different kind of properties in thin films, it is important to determine the influence of the deposition parameters on the alumina film properties. In this work, different alumina structures were deposited by means of reactive, bipolar, pulsed, magnetron sputtering. In order to find the appropriate parameter combination to synthesize crystalline alumina (for this investigation γ-Al2O3), substrate temperature, power density at the target and oxygen flow were varied. The γ-Al2O3 films were synthesized at 650 deg. C, 0.2 Pa, 800 W, 1:4 duty cycle, 19.2 kHz, and 11-12% oxygen flow. The structure and morphology of the deposited Al2O3 films were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Since the coating hardness is a decisive factor for many applications, the aim of this paper was to investigate the influence of the oxygen flow on the alumina hardness. It was observed that the hardness and the structure of the PVD-deposited alumina coatings are significantly oxygen flow dependent. The hardness of the alumina films was determined by nanoindentation. It varied between 1 and 25.8 GPa. The hardness increased by increasing oxygen flow until the target reached the poisoned state, where a hardness reduction was clearly observed

  14. Reduced defect density at the CZTSSe/CdS interface by atomic layer deposition of Al2O3

    Science.gov (United States)

    Erkan, Mehmet Eray; Chawla, Vardaan; Scarpulla, Michael A.

    2016-05-01

    The greatest challenge for improving the power conversion efficiency of Cu2ZnSn(S,Se)4 (CZTSSe)/CdS/ZnO thin film solar cells is increasing the open circuit voltage (VOC). Probable leading causes of the VOC deficit in state-of-the-art CZTSSe devices have been identified as bulk recombination, band tails, and the intertwined effects of CZTSSe/CdS band offset, interface defects, and interface recombination. In this work, we demonstrate the modification of the CZTSSe absorber/CdS buffer interface following the deposition of 1 nm-thick Al2O3 layers by atomic layer deposition (ALD) near room temperature. Capacitance-voltage profiling and quantum efficiency measurements reveal that ALD-Al2O3 interface modification reduces the density of acceptor-like states at the heterojunction resulting in reduced interface recombination and wider depletion width. Indications of increased VOC resulting from the modification of the heterojunction interface as a result of ALD-Al2O3 treatment are presented. These results, while not conclusive for application to state-of-the-art high efficiency CZTSSe devices, suggest the need for further studies as it is probable that interface recombination contributes to reduced VOC even in such devices.

  15. Air Plasma-Sprayed Y2O3 Coatings for Al2O3/Al2O3 Ceramic Matrix Composites

    OpenAIRE

    Mechnich, Peter; Braue, Wolfgang

    2013-01-01

    Al2O3/Al2O3 ceramic matrix composites (CMC) are candidate materials for hot-gas leading components of gas turbines. Since Al2O3/Al2O3 CMC are prone to hot-corrosion in combustion environments, the development of environmental barrier coatings (EBC) is mandatory. Owing to its favorable chemical stability and thermal properties, Y2O3 is considered a candidate EBC material for Al2O3/Al2O3 CMC. Up to one mm thick Y2O3 coatings were deposited by means of air plasma spraying (APS) on Al2O3/Al2O3 CM...

  16. Sliding Wear Behavior of Plasma Sprayed Alumina-Based Composite Coatings against Al2O3 Ball

    Institute of Scientific and Technical Information of China (English)

    Minh-quy Le; Young-hun Chae; Seock-sam Kim

    2004-01-01

    The sliding wear behaviors of a single layer Al2O3-30 wt pct ZrO2, a double layer Al2O3-30 wt pct ZrO2/Ni-Cr and a single layer Al2O3-13 wt pct TiO2 coating deposited on low carbon steel by plasma spraying were investigated under lubricated conditions with various normal loads. The plastic deformation, detachment and pull out of splats were involved in the wear process of the studied coatings under test conditions. Crack propagation was found in Al2O3-13 wt pct TiO2 under loads of 70 and 100 N and in Al2O3-30 wt pct ZrO2/Ni-Cr under a load of 130 N.While increasing the normal load, the wear rates of Al2O3-30 wt pct ZrO2 and Al2O3-30 wt pct ZrO2/Ni-Cr slightly increased, the wear rate of Al2O3-13 wt pct TiO2 increased rapidly. The results showed that the Ni-Cr bonding layer improved the wear resistance of the coating system even it is relatively thin compared with the outer coating layer.The influence of this bonding layer on wear behavior of the coating increased as increasing the normal load.

  17. The improvement of Al2O3/AlGaN/GaN MISHEMT performance by N2 plasma pretreatment

    Institute of Scientific and Technical Information of China (English)

    Feng Qian; Tian Yuan; Bi Zhi-Wei; Yue Yuan-Zheng; Ni Jin-Yu; Zhang Jin-Cheng; Hao Yue; Yang Lin-An

    2009-01-01

    This paper discusses the effect of N2 plasma treatment before dielectric deposition on the electrical performance of a Al2O3/AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MISHEMT), with Al2O3deposited by atomic layer deposition. The results indicated that the gate leakage was decreased two orders of magnitude after the Al2O3/AlGaN interface was pretreated by N2 plasma. Furthermore, effects of N2 plasma pretreatment on the electrical properties of the AlGaN/Al2O3 interface were investigated by x-ray photoelectron spectroscopy measurements and the interface quality between Al2O3 and AlGaN film was improved.

  18. The effect of thermal annealing on the adherence of $Al_2O_3$-films deposited by low-pressure, metal-organic, chemical-vapor deposition on AISI 304

    NARCIS (Netherlands)

    Haanappel, V.A.C.; Vendel, van de D.; Corbach, van H.D.; Fransen, T.; Gellings, P.J.

    1995-01-01

    Thin alumina films, deposited at 280°C by low-pressure, metal-organic, chemical-vapor deposition on stainless steel, type AISI 304, were annealed at 0.17 kPa in a nitrogen atmosphere for 2,4, and 17 hr at 600, 700, and 800°C. The effect of the annealing process on the adhesion of the thin alumina fi

  19. Rapid fabrication of Al2O3 encapsulations for organic electronic devices

    Science.gov (United States)

    Ali, Kamran; Ali, Junaid; Mehdi, Syed Murtuza; Choi, Kyung-Hyun; An, Young Jin

    2015-10-01

    Organic electronics have earned great reputation in electronic industry yet they suffer technical challenges such as short lifetimes and low reliability because of their susceptibility to water vapor and oxygen which causes their fast degradation. This paper report on the rapid fabrication of Al2O3 encapsulations through a unique roll-to-roll atmospheric atomic layer deposition technology (R2R-AALD) for the life time enhancement of organic poly (4-vinylphenol) (PVP) memristor devices. The devices were then categorized into two sets. One was processed with R2R-AALD Al2O3 encapsulations at 50 °C and the other one was kept as un-encapsulated. The field-emission scanning electron microscopy (FESEM) results revealed that pin holes and other irregularities in PVP films with average arithmetic roughness (Ra) of 9.66 nm have been effectively covered by Al2O3 encapsulation having Ra of 0.92 nm. The X-ray photoelectron spectroscopy XPS spectrum for PVP film showed peaks of C 1s and O 1s at the binding energies of 285 eV and 531 eV, respectively. The respective appearance of Al 2p, Al 2s, and O 1s peaks at the binding energies of 74 eV, 119 eV, and 531 eV, confirms the fabrication of Al2O3 films. Electrical current-voltage (I-V) measurements confirmed that the Al2O3 encapsulation has a huge influence on the performance, robustness and life time of memristor devices. The Al2O3 encapsulated memristor performed with superior stability for four weeks whereas the un-encapsulated devices could only last for one week. The performance of encapsulated device had been promising after being subjected to bending test for 100 cycles and the variations in its stability were of minor concern confirming the mechanical robustness and flexibility of the devices.

  20. Preparation and Characterization of Highly Flexible Al2O3/Al/Al2O3 Hybrid Composite

    Directory of Open Access Journals (Sweden)

    Zhijiang Wang

    2015-01-01

    Full Text Available The natural brittleness of oxide ceramics heavily inhibits their more extensive applications. In present research, a highly flexible Al2O3/Al/Al2O3 hybrid composite was fabricated by employing plasma electrolysis oxidation to in situ grow alumina layers on Al foil, in which an outside layer of nanostructured polycrystalline oxide ceramic was composed of nanosized grains with the size of around 17 nm. Due to shear band formation, nanosized circle bubbles prolonging the crack path, grain rotation, and deformation, the fabricated Al2O3/Al/Al2O3 hybrid composite contains no observable cracks even after being bent on a cylindrical bar with a curvature of 1.5 mm. The composite exhibits alumina stiffness at the elastic stage and aluminum ductility during plastic deformation, which provides high flexibility with the well-integrated properties of the components. In a synergistic interaction, the alumina on the outside exhibited a strain of 0.33% at room temperature, which was higher than optimum value of 0.25% presented by reported most flexible oxide ceramics. With the unique characteristics and properties, the Al2O3/Al/Al2O3 composite demonstrates a great potential for various engineering applications.

  1. Al2O3-Coated Nano-SiC Particles Reinforced Al2O3 Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Properties of Al2O3-coated nano-SiC have been compared with those of as-received SiC. The isoelectric point (IEP)of SiC changed from pH3.4 to pH7.3 after coating with the alumina precursor, which is close to that of alumina.Because both surfaces of coated SiC and Al2O3 possess higher positive charge at pH=4.5~5.0, they are uniformly dispersed in the two-phase aqueous suspensions, Then a mixed powder containing nano-SiC dispersed homogeneously into the Al2O3 matrix was achieved from flocculating the two-phase suspension. Finally, Al2O3/SiC nanocomposites were obtained by coating nano-SiC with Al2O3, in which the majority of SiC particles were located within the Al2O3 grains. The observation by transmission electron microscopy (TEM) and the analysis by the X-ray photoelectron spectroscopy (XPS) showed that cracks propagated towards the intragranular SiC rather than along grain boundaries.

  2. Catalytic Methane Decomposition over Fe-Al2O3

    KAUST Repository

    Zhou, Lu

    2016-05-09

    The presence of a Fe-FeAl2O4 structure over an Fe-Al2O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750°C, Fe-Al2O3 prepared by means of a fusion method, containing 86.5wt% FeAl2O4 and 13.5wt% Fe0, showed a stable CMD activity at 750°C for as long as 10h. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Capability for Fine Tuning of the Refractive Index Sensing Properties of Long-Period Gratings by Atomic Layer Deposited Al2O3 Overlays

    Directory of Open Access Journals (Sweden)

    Mateusz Śmietana

    2013-11-01

    Full Text Available This work presents an application of thin aluminum oxide (Al2O3 films obtained using atomic layer deposition (ALD for fine tuning the spectral response and refractive-index (RI sensitivity of long-period gratings (LPGs induced in optical fibers. The technique allows for an efficient and well controlled deposition at monolayer level (resolution ~ 0.12 nm of excellent quality nano-films as required for optical sensors. The effect of Al2O3 deposition on the spectral properties of the LPGs is demonstrated experimentally and numerically. We correlated both the increase in Al2O3 thickness and changes in optical properties of the film with the shift of the LPG resonance wavelength and proved that similar films are deposited on fibers and oxidized silicon reference samples in the same process run. Since the thin overlay effectively changes the distribution of the cladding modes and thus also tunes the device’s RI sensitivity, the tuning can be simply realized by varying number of cycles, which is proportional to thickness of the high-refractive-index (n > 1.6 in infrared spectral range Al2O3 film. The advantage of this approach is the precision in determining the film properties resulting in RI sensitivity of the LPGs. To the best of our knowledge, this is the first time that an ultra-precise method for overlay deposition has been applied on LPGs for RI tuning purposes and the results have been compared with numerical simulations based on LP mode approximation.

  4. Eliminated Phototoxicity of TiO2 Particles by an Atomic-Layer-Deposited Al2 O3 Coating Layer for UV-Protection Applications.

    Science.gov (United States)

    Jang, Eunyong; Sridharan, Kishore; Park, Young Min; Park, Tae Joo

    2016-08-16

    We demonstrate the conformal coating of an ultrathin Al2 O3 layer on TiO2 nanoparticles through atomic layer deposition by using a specifically designed rotary reactor to eliminate the phototoxicity of the particles for cosmetic use. The ALD reactor is modified to improve the coating efficiency as well as the agitation of the particles for conformal coating. Elemental and microstructural analyses show that ultrathin Al2 O3 layers are conformally deposited on the TiO2 nanoparticles with a controlled thickness. Rhodamine B dye molecules on Al2 O3 -coated TiO2 exhibited a long life time under UV irradiation, that is, more than 2 h, compared to that on bare TiO2 , that is, 8 min, indicating mitigation of photocatalytic activity by the coated layer. The effect of carbon impurities in the film resulting from various deposition temperatures and thicknesses of the Al2 O3 layer on the photocatalytic activity are also thoroughly investigated with controlled experimental condition by using dye molecules on the surface. Our results reveal that an increased carbon impurity resulting from a low processing temperature provides a charge conduction path and generates reactive oxygen species causing the degradation of dye molecule. A thin coated layer, that is, less than 3 nm, also induced the tunneling of electrons and holes to the surface, hence oxidizing dye molecules. Furthermore, the introduction of an Al2 O3 layer on TiO2 improves the light trapping thus, enhances the UV absorption. PMID:27405514

  5. Current Tunnelling in MOS Devices with Al2O3/SiO2 Gate Dielectric

    Directory of Open Access Journals (Sweden)

    A. Bouazra

    2008-01-01

    Full Text Available With the continued scaling of the SiO2 thickness below 2 nm in CMOS devices, a large direct-tunnelling current flow between the gate electrode and silicon substrate is greatly impacting device performance. Therefore, higher dielectric constant materials are desirable for reducing the gate leakage while maintaining transistor performance for very thin dielectric layers. Despite its not very high dielectric constant (∼10, Al2O3 has emerged as one of the most promising high-k candidates in terms of its chemical and thermal stability as its high-barrier offset. In this paper, a theoretical study of the physical and electrical properties of Al2O3 gate dielectric is reported including I(V and C(V characteristics. By using a stack of Al2O3/SiO2 with an appropriate equivalent oxide thickness of gate dielectric MOS, the gate leakage exhibits an important decrease. The effect of carrier trap parameters (depth and width at the Al2O3/SiO2 interface is also discussed.

  6. Al2O3 sintered pellets as thermoluminescent dosimeters Pastillas sinterizadas de Al2O3 como dosímetros termoluminiscentes

    Directory of Open Access Journals (Sweden)

    Amalia Osorio

    2012-06-01

    Full Text Available Verification of the radiation doses received by the area exposed during medical treatment is essential for assessing any scheme radiotherapy. This workdescribes the characteristic thermoluminescent (TL of sintered Al2O3 pellets, for its use as dosimeter dose low. Sintered Al2O3 pellets under different calcinations with a diameter of 5 mm and a thickness of 1 mm, they were irradiated to different dose using an unit of60 Co Theratron 780Cr in air to ambient temperature. The reading was carried in a Harshaw TLD 4500. Themain dosimetric properties of the material (glow curve, response reproducibility, reutilization, linearity and fading have been studied in detail. The glowcurve of the thin sintered Al2O3 pellets presents an intense peak TL to about 165◦C, which can be used for dosimetry. The results show that the pellets canbe used in quality control programs as thermoluminescent dosimeter in therapeutic dose range. The importance of this work is that the aluminum oxide (α−Al2O3 is a promising alternative in TL materials used for dosimetry “in vivo” within quality control programs.La verificación de la dosis de radiación recibida por el área expuesta durante eltratamiento médico es esencial para la evaluación de cualquier régimen de radioterapia.Este trabajo describe las caracteríısticas termoluminiscentes (TLde pastillas sinterizadas de Al2O3, para su posible uso como dosímetro TL de baja dosis. Pastillas de Al2O3 sinterizadas bajo diferentes condiciones decalcinación, con un diámetro de 5 mm y un espesor de 1 mm, fueron irradiadasa diferentes dosis usando una unidad de 60Co Theratron 780Cr enaire a temperatura ambiente. La lectura se realizó en un Harshaw TLD 4500.Las principales propiedades dosimétricas del material (curva de brillo, reproducibilidadde la respuesta, reutilización, linealidad y decaimiento térmicohan sido estudiadas en detalle. La curva de brillo de las pastillas sinterizadasde Al2O3 presenta un intenso

  7. New battery strategies with a polymer/Al2O3 separator

    Science.gov (United States)

    Park, Kyusung; Cho, Joon Hee; Shanmuganathan, Kadhiravan; Song, Jie; Peng, Jing; Gobet, Mallory; Greenbaum, Steven; Ellison, Christopher J.; Goodenough, John B.

    2014-10-01

    A low-cost, thin, flexible, and mechanically robust alkali-ion electrolyte separator is shown to allow fabrication of a safe rechargeable alkali-ion battery with alternative cathode strategies. A Na-ion battery with an insertion host as cathode and a Li-ion battery with a redox flow-through cathode are demonstrated to cycle without significant fade. The separator membrane is a composite of Al2O3 particles and cross-linked ethylene-oxide chains; it can be fabricated at low cost into a large-area thin membrane that blocks dendrites from an alkali-metal anode. To block a soluble ferrocene redox molecule from crossing from the cathode side to the anode in a Li-ion battery with a redox-flow cathode, a thin mixed Li+/electronic-conducting film has been added to the cathode side of the composite separator. An osmosis issue was minimized by balancing concentrations of solutes on the two sides of the separator where the cathode side contains a soluble redox molecule.

  8. High-temperature oxidation behavior of Al2O3/TiAl matrix composite in air

    Institute of Scientific and Technical Information of China (English)

    AI TaoTao; WANG Fen; FENG XiaoMing

    2009-01-01

    The oxidation behavior of Al2O3/TiAl in situ composites fabricated by hot-pressing technology was in-vestigated at 900℃ in static air. The results indicate that the mass gains of the composites samples decrease gradually with increasing Nb2O5 content and the inert Al2O3 dispersoids effectively increase the oxidation resistance of the composites. The higher the Al2O3 dispersoids content, the more pro-nounced the effect. The primary oxidation precesses obey approximately the linear laws, and the cyclic oxidation precesses follow the parabolic laws. The oxidized sample containing Ti2AIN and TiAI phases in the scales exhibits excellent oxidation resistance. The oxide scale formed after exposure at 900℃ for 120 h is multiple-layered, consisting mainly of an outer TiC2 layer, an intermediate Al2O3 layer, and an inner TiO2+Al2O3 mixed layer. From the outer layer to the inner layer, TiO2+Al2O3 mixed layer presents the transit of AI-rich oxide to Ti-rich oxide mixed layer. Near the substrate, cross-section micrograph shows a relatively loose layer, and micro- and macro-pores remain on this layer, which is a transition layer and transferres from Al2O3+TiO2 scale to substrate. The thickness of oxide layer is about 20 μm. It is also found that continuous protective alumina scales can not be observed on the surface of oxida-tion scales. Ti ions diffuse outwardly to form the outer TiC2 layer, while oxygen ions transport inwardly to form the inner TiO2+Al2O3 mixed layer. Under long-time intensive oxidation exposure, the internal Al2O3 scale has s good adhesiveness with the outer TiO2 scale. No obvious spallation of the oxide scales occurs. The increased oxidation resistance by the presence of in situ Al2O3 particulates is at-tributed to the enhanced alumina-forming tendency and thin and dense scale formation. Al2O3 particu-lates enhance the potential barrier of Ti ions from M/MO interface to O/MO interface, thereby the TiO2growth rate decreases, which is also beneficial to

  9. Síntese e caracterização do compósito Al2O3 -YAG e do Al2O3-YAG e Al2O3 aditivados com Nb2O5 Synthesis and characterization of Al2O3 -YAG composite and Al2O3-YAG and Al2O3 with Nb2O5 additives

    Directory of Open Access Journals (Sweden)

    R. F. Cabral

    2012-03-01

    Full Text Available O compósito Al2O3-YAG possui alta resistência à corrosão e à fluência em ambientes agressivos, o que permite vislumbrar aplicações bastante atrativas, tais como aletas de motores a jato e de turbinas a gás. Este compósito também apresenta elevada dureza e alta resistência à abrasão possibilitando o seu emprego em blindagens balísticas. Nesse estudo os pós precursores de Al2O3, Y2O3 e Nb2O5 foram homogeneizados em moinho de bolas planetário por 4 h, secados em estufa a 120 ºC por 48 h, desaglomerados e peneirados. O compósito Al2O3-YAG foi produzido a partir das misturas de Al2O3-Y2O3 a 1300 ºC por 2 h. Foram produzidas amostras de Al2O3-YAG, Al2O3-YAG com Nb2O5 e Al2O3 com Nb2O5. Posteriormente os pós foram prensados uniaxialmente a 70 MPa. A sinterização foi feita a 1400 e 1450 ºC. Os pós como recebidos e os processados foram caracterizados quanto à área de superfície específica e ao tamanho médio de partícula. Os materiais sinterizados foram caracterizados por densidade e porosidade aparente pelo método de Arquimedes e avaliados quanto à retração e à perda de massa. Os resultados mostraram que são necessários ainda ajustes nas condições de sinterização da composição Al2O3-YAG com Nb2O5 para melhorar a densificação e a retração, que foram baixas, da ordem de 60 e 3%, respectivamente. O Al2O3 aditivado com Nb2O5, por sua vez, apresentou uma densificação satisfatória, de 96% e uma retração em torno de 15%.The Al2O3-YAG composite exhibits high corrosion and creep resistance in aggressive environments, which provides quite glimpse attractive applications such as jet engine vanes and as gas turbines. This composite also shows high hardness and wear resistance allowing its use in ballistic armor. In this study, precursor powders of Al2O3, Y2O3 and Nb2O5 were homogeneously mixed in a planetary ball mill for 4 h, dried in an oven at 120 ºC for 48 h, sieved and deagglomerated. The Al2O3-YAG composite

  10. Epitaxial growth and electrochemical transfer of graphene on Ir(111)/α-Al2O3(0001) substrates

    Science.gov (United States)

    Koh, Shinji; Saito, Yuta; Kodama, Hideyuki; Sawabe, Atsuhito

    2016-07-01

    Low-pressure chemical vapor deposition growth of graphene on Iridium (Ir) layers epitaxially deposited on α-Al2O3 (0001) substrates was investigated. The X-ray diffraction, Raman and reflection high energy electron diffraction characterizations revealed that graphene films were epitaxially grown on Ir(111) layers, and the in-plane epitaxial relationship between graphene, Ir(111), and α-Al2O3(0001) was graphene ⟨ 1 1 ¯ 00 ⟩//Ir⟨ 11 2 ¯ ⟩//α-Al2O3⟨ 11 2 ¯ 0 ⟩. The graphene on Ir(111) was electrochemically transferred onto SiO2/Si substrates. We also demonstrated the reuse of the Ir(111)/α-Al2O3(0001) substrates in multiple growth and transfer cycles.

  11. DEPENDENCE OF CORROSION BEHAVIOR OF Ni–MoS2/Al2O3 COATINGS IN RELATION TO THE Al2O3 RATIO IN MoS2/Al2O3 PARTICLES

    OpenAIRE

    ZHONG-JIA HUANG; DANG-SHENG XIONG

    2009-01-01

    The MoS2 particles were coated with Al2O3 ratio varying from 5 to 50 wt.% content. Ni–MoS2/Al2O3 composite coatings were prepared by means of pulse electrodeposition. The dependence of preferential orientation index and corrosion properties of these composite coatings was investigated in relation to the Al2O3 ratio in MoS2/Al2O3 particles. Polarization measurements have been used to evaluate corrosion resistance performance of coating. The Ni–MoS2/50 wt.% Al2O3 coatings showed the highest cor...

  12. Fast neutron detection with Al 2O 3 thermoluminescence dosimeter

    Science.gov (United States)

    Ranogajec-Komor, Maria; Osvay, Margit; Dvornik, Igor; Biró, Tamàs

    1983-07-01

    The technique of thermoluminescent (TL) dosimeter activation can be used to detect any radiation making TL dosimeters radioactive. In the experiment discussed in this paper Al2O3:Mg, Y TL dosimeters were irradiated by cyclotron neutrons with 5±1 MeV mean energy and by accompanying gamma rays. The gamma and the fast neutron component can be separately measured by the same dosimeter. Because of low neutron sensitivity of Al2O3 the gamma dose can be determined by the first TL reading while the 27Al(n, α)24 Na reaction provides the possibility of fast neutron detection by the subsequent reading of thermoluminescence induced in the TL material by the decay of 24Na.

  13. Antibiotic properties of Al2O3 doping silver

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hai-bin; LIU Qing-ju; ZHU Zhong-qi; ZHANG Jin; EU Xing-hui

    2005-01-01

    The preparation technique and properties of Ag-type inorganic antibiotic material carried by Al2 O3 were studied. The results show that the material has good antibiotic and safety properties, the acute toxicity taken by stomata is LD50 > 8 000 mg/kg (little and big white rats), and the normal quantity in subacute toxicity test is the optimal sintering temperature is from 1 000 ℃ to 1 100 ℃.

  14. On the Control of the Fixed Charge Densities in Al2O3-Based Silicon Surface Passivation Schemes.

    Science.gov (United States)

    Simon, Daniel K; Jordan, Paul M; Mikolajick, Thomas; Dirnstorfer, Ingo

    2015-12-30

    A controlled field-effect passivation by a well-defined density of fixed charges is crucial for modern solar cell surface passivation schemes. Al2O3 nanolayers grown by atomic layer deposition contain negative fixed charges. Electrical measurements on slant-etched layers reveal that these charges are located within a 1 nm distance to the interface with the Si substrate. When inserting additional interface layers, the fixed charge density can be continuously adjusted from 3.5 × 10(12) cm(-2) (negative polarity) to 0.0 and up to 4.0 × 10(12) cm(-2) (positive polarity). A HfO2 interface layer of one or more monolayers reduces the negative fixed charges in Al2O3 to zero. The role of HfO2 is described as an inert spacer controlling the distance between Al2O3 and the Si substrate. It is suggested that this spacer alters the nonstoichiometric initial Al2O3 growth regime, which is responsible for the charge formation. On the basis of this charge-free HfO2/Al2O3 stack, negative or positive fixed charges can be formed by introducing additional thin Al2O3 or SiO2 layers between the Si substrate and this HfO2/Al2O3 capping layer. All stacks provide very good passivation of the silicon surface. The measured effective carrier lifetimes are between 1 and 30 ms. This charge control in Al2O3 nanolayers allows the construction of zero-fixed-charge passivation layers as well as layers with tailored fixed charge densities for future solar cell concepts and other field-effect based devices. PMID:26618751

  15. Influence of the Al2O3 partial-monolayer number on the crystallization mechanism of TiO2 in ALD TiO2/Al2O3 nanolaminates and its impact on the material properties

    Science.gov (United States)

    Testoni, G. E.; Chiappim, W.; Pessoa, R. S.; Fraga, M. A.; Miyakawa, W.; Sakane, K. K.; Galvão, N. K. A. M.; Vieira, L.; Maciel, H. S.

    2016-09-01

    TiO2/Al2O3 nanolaminates are being investigated to obtain unique materials with chemical, physical, optical, electrical and mechanical properties for a broad range of applications that include electronic and energy storage devices. Here, we discuss the properties of TiO2/Al2O3 nanolaminate structures constructed on silicon (1 0 0) and glass substrates using atomic layer deposition (ALD) by alternatively depositing a TiO2 sublayer and Al2O3 partial-monolayer using TTIP-H2O and TMA-H2O precursors, respectively. The Al2O3 is formed by a single TMA-H2O cycle, so it is a partial-monolayer because of steric hindrance of the precursors, while the TiO2 sublayer is formed by several TTIP-H2O cycles. Overall, each nanolaminate incorporates a certain number of Al2O3 partial-monolayers with this number varying from 10-90 in the TiO2/Al2O3 nanolaminate grown during 2700 total reaction cycles of TiO2 at a temperature of 250 °C. The fundamental properties of the TiO2/Al2O3 nanolaminates, namely film thickness, chemical composition, microstructure and morphology were examined in order to better understand the influence of the number of Al2O3 partial-monolayers on the crystallization mechanism of TiO2. In addition, some optical, electrical and mechanical properties were determined and correlated with fundamental characteristics. The results show clearly the effect of Al2O3 partial-monolayers as an internal barrier, which promotes structural inhomogeneity in the film and influences the fundamental properties of the nanolaminate. These properties are correlated with gas phase analysis that evidenced the poisoning effect of trimethylaluminum (TMA) pulse during the TiO2 layer growth, perturbing the growth per cycle and consequently the overall film thickness. It was shown that the changes in the fundamental properties of TiO2/Al2O3 nanolaminates had little influence on optical properties such as band gap and transmittance. However, in contrast, electrical properties as resistivity

  16. Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3

    Science.gov (United States)

    Zhang, Guozhen; Wu, Hao; Chen, Chao; Wang, Ti; Yue, Jin; Liu, Chang

    2015-02-01

    Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3 dielectrics have been fabricated on indium tin oxide-coated polyethylene naphthalate substrates by atomic layer deposition. A capacitance density of 7.8 fF/μm2 at 10 KHz was obtained, corresponding to a dielectric constant of 26.3. Moreover, a low leakage current density of 3.9 × 10-8 A/cm2 at 1 V has been realized. Bending test shows that the capacitors have better performances in concave conditions than in convex conditions. The capacitors exhibit an average optical transmittance of about 70% in visible range and thus open the door for applications in transparent and flexible integrated circuits.

  17. Thermal conductivity of amorphous Al2O3/TiO2 nanolaminates deposited by atomic layer deposition.

    Science.gov (United States)

    Ali, Saima; Juntunen, Taneli; Sintonen, Sakari; Ylivaara, Oili M E; Puurunen, Riikka L; Lipsanen, Harri; Tittonen, Ilkka; Hannula, Simo-Pekka

    2016-11-01

    The thermophysical properties of Al2O3/TiO2 nanolaminates deposited by atomic layer deposition (ALD) are studied as a function of bilayer thickness and relative TiO2 content (0%-100%) while the total nominal thickness of the nanolaminates was kept at 100 nm. Cross-plane thermal conductivity of the nanolaminates is measured at room temperature using the nanosecond transient thermoreflectance method. Based on the measurements, the nanolaminates have reduced thermal conductivity as compared to the pure amorphous thin films, suggesting that interfaces have a non-negligible effect on thermal transport in amorphous nanolaminates. For a fixed number of interfaces, we find that approximately equal material content of Al2O3 and TiO2 produces the lowest value of thermal conductivity. The thermal conductivity reduces with increasing interface density up to 0.4 nm(-1), above which the thermal conductivity is found to be constant. The value of thermal interface resistance approximated by the use of diffuse mismatch model was found to be 0.45 m(2) K GW(-1), and a comparative study employing this value supports the interpretation of non-negligible interface resistance affecting the overall thermal conductivity also in the amorphous limit. Finally, no clear trend in thermal conductivity values was found for nanolaminates grown at different deposition temperatures, suggesting that the temperature in the ALD process has a non-trivial while modest effect on the overall thermal conductivity in amorphous nanolaminates.

  18. Thermal conductivity of amorphous Al2O3/TiO2 nanolaminates deposited by atomic layer deposition.

    Science.gov (United States)

    Ali, Saima; Juntunen, Taneli; Sintonen, Sakari; Ylivaara, Oili M E; Puurunen, Riikka L; Lipsanen, Harri; Tittonen, Ilkka; Hannula, Simo-Pekka

    2016-11-01

    The thermophysical properties of Al2O3/TiO2 nanolaminates deposited by atomic layer deposition (ALD) are studied as a function of bilayer thickness and relative TiO2 content (0%-100%) while the total nominal thickness of the nanolaminates was kept at 100 nm. Cross-plane thermal conductivity of the nanolaminates is measured at room temperature using the nanosecond transient thermoreflectance method. Based on the measurements, the nanolaminates have reduced thermal conductivity as compared to the pure amorphous thin films, suggesting that interfaces have a non-negligible effect on thermal transport in amorphous nanolaminates. For a fixed number of interfaces, we find that approximately equal material content of Al2O3 and TiO2 produces the lowest value of thermal conductivity. The thermal conductivity reduces with increasing interface density up to 0.4 nm(-1), above which the thermal conductivity is found to be constant. The value of thermal interface resistance approximated by the use of diffuse mismatch model was found to be 0.45 m(2) K GW(-1), and a comparative study employing this value supports the interpretation of non-negligible interface resistance affecting the overall thermal conductivity also in the amorphous limit. Finally, no clear trend in thermal conductivity values was found for nanolaminates grown at different deposition temperatures, suggesting that the temperature in the ALD process has a non-trivial while modest effect on the overall thermal conductivity in amorphous nanolaminates. PMID:27670821

  19. Thermal conductivity of amorphous Al2O3/TiO2 nanolaminates deposited by atomic layer deposition

    Science.gov (United States)

    Ali, Saima; Juntunen, Taneli; Sintonen, Sakari; Ylivaara, Oili M. E.; Puurunen, Riikka L.; Lipsanen, Harri; Tittonen, Ilkka; Hannula, Simo-Pekka

    2016-11-01

    The thermophysical properties of Al2O3/TiO2 nanolaminates deposited by atomic layer deposition (ALD) are studied as a function of bilayer thickness and relative TiO2 content (0%–100%) while the total nominal thickness of the nanolaminates was kept at 100 nm. Cross-plane thermal conductivity of the nanolaminates is measured at room temperature using the nanosecond transient thermoreflectance method. Based on the measurements, the nanolaminates have reduced thermal conductivity as compared to the pure amorphous thin films, suggesting that interfaces have a non-negligible effect on thermal transport in amorphous nanolaminates. For a fixed number of interfaces, we find that approximately equal material content of Al2O3 and TiO2 produces the lowest value of thermal conductivity. The thermal conductivity reduces with increasing interface density up to 0.4 nm‑1, above which the thermal conductivity is found to be constant. The value of thermal interface resistance approximated by the use of diffuse mismatch model was found to be 0.45 m2 K GW‑1, and a comparative study employing this value supports the interpretation of non-negligible interface resistance affecting the overall thermal conductivity also in the amorphous limit. Finally, no clear trend in thermal conductivity values was found for nanolaminates grown at different deposition temperatures, suggesting that the temperature in the ALD process has a non-trivial while modest effect on the overall thermal conductivity in amorphous nanolaminates.

  20. Hf-Doped Ni-Al2O3 Interfaces at Equilibrium

    Energy Technology Data Exchange (ETDEWEB)

    Meltzman, Hila [Technion, Israel Institute of Technology; Besmann, Theodore M [ORNL; Kaplan, Prof. Wayne D. [Technion, Israel Institute of Technology

    2012-01-01

    In this study, a series of dewetting experiments of pure and Hf-doped Ni films on sapphire and HfO2 substrates were conducted in order to measure the change in interface energy of the Ni-Al2O3 interface in the presence of Hf, and to study Hf interfacial segregation. It was found that Hf oxidizes under the conditions of the experiment (P(O2)=10-20atm.), and that the presence of HfO2 at the Ni-Al2O3 interface increases the interface energy from 2.16 0.2 to 2.7 0.4 [J/m2]. This result contradicts several theoretical studies that predict that Hf segregates to the interface to stabilize it thermodynamically. The solubility of Hf in bulk Ni was found to be significantly lower than the value reported in the equilibrium phase diagram.

  1. Epitaxial growth of Al/Al2O3 multilayer structures

    International Nuclear Information System (INIS)

    In order to obtain Al-Al2O3 quantum effect devices, it is necessary to deposit epitaxially Al on Al2O3 and Al2O3 on Al. We have already obtained an epitaxial Al/Al2O3/Al structures on Si(111). In this paper, we have deposit Al/Al2O3/Al structures on Si(111), and investigated the crystallinity by using RBS. (author)

  2. Activity Enhancement of Pt/Ba/Al2O3 Mixed with Mn/Ba/Al2O3 for NOx Storage-reduction by Hydrogen

    Institute of Scientific and Technical Information of China (English)

    Jian Hua XIAO; Xue Hui LI; Sha DENG; Fu Rong WANG; Le Fu WANG

    2006-01-01

    Mn/Ba/Al2O3 catalyst for NO oxidation-storage and Pt/Ba/Al2O3 catalyst mixed with Mn/Ba/Al2O3 for NOx storage-reduction by hydrogen were investigated. The results showed that Mn/Ba/Al2O3 had large nitrogen oxides storage capacity (397.9 μmolg-1) under lean bum condition.When Pt/Ba/Al2O3 catalyst was mixed with Mn/Ba/Al2O3 in equal weight proportion, the NOx conversion increased between 250 ℃ and 500 ℃ under the dynamic lean-rich bum conditions, and the maximum NOx conversion increased from 95.4% to 98.2%. Mn/Ba/Al2O3 has promoted NOx storing in the lean stage and improved NOx reduction efficiency in the rich stage, these might result in higher NOx conversion over the low Pt loading content catalyst.

  3. Al2O3-based nanofluids: a review

    Directory of Open Access Journals (Sweden)

    Satapathy Lakshmi Narayan

    2011-01-01

    Full Text Available Abstract Ultrahigh performance cooling is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in heat transfer fluids such as water, oil, diesel, ethylene glycol, etc. Innovative heat transfer fluids are produced by suspending metallic or nonmetallic nanometer-sized solid particles. Experiments have shown that nanofluids have substantial higher thermal conductivities compared to the base fluids. These suspended nanoparticles can change the transport and thermal properties of the base fluid. As can be seen from the literature, extensive research has been carried out in alumina-water and CuO-water systems besides few reports in Cu-water-, TiO2-, zirconia-, diamond-, SiC-, Fe3O4-, Ag-, Au-, and CNT-based systems. The aim of this review is to summarize recent developments in research on the stability of nanofluids, enhancement of thermal conductivities, viscosity, and heat transfer characteristics of alumina (Al2O3-based nanofluids. The Al2O3 nanoparticles varied in the range of 13 to 302 nm to prepare nanofluids, and the observed enhancement in the thermal conductivity is 2% to 36%.

  4. Atomic-layer-deposited Al2O3 and HfO2 on InAlAs: A comparative study of interfacial and electrical characteristics

    Science.gov (United States)

    Wu, Li-Fan; Zhang, Yu-Ming; Lv, Hong-Liang; Zhang, Yi-Men

    2016-10-01

    Al2O3 and HfO2 thin films are separately deposited on n-type InAlAs epitaxial layers by using atomic layer deposition (ALD). The interfacial properties are revealed by angle-resolved x-ray photoelectron spectroscopy (AR-XPS). It is demonstrated that the Al2O3 layer can reduce interfacial oxidation and trap charge formation. The gate leakage current densities are 1.37 × 10-6 A/cm2 and 3.22 × 10-6 A/cm2 at +1 V for the Al2O3/InAlAs and HfO2/InAlAs MOS capacitors respectively. Compared with the HfO2/InAlAs metal-oxide-semiconductor (MOS) capacitor, the Al2O3/InAlAs MOS capacitor exhibits good electrical properties in reducing gate leakage current, narrowing down the hysteresis loop, shrinking stretch-out of the C-V characteristics, and significantly reducing the oxide trapped charge (Q ot) value and the interface state density (D it). Project supported by the National Basic Research Program of China (Grant No. 2010CB327505), the Advanced Research Foundation of China (Grant No. 914xxx803-051xxx111), the National Defense Advance Research Project, China (Grant No. 513xxxxx306), the National Natural Science Foundation of China (Grant No. 51302215), the Scientific Research Program Funded by Shaanxi Provincial Education Department, China (Grant No. 14JK1656), and the Science and Technology Project of Shaanxi Province, China (Grant No. 2016KRM029).

  5. Characterization of (Co0.45Fe0.45Zr0.10)x(Al2O3)1-x nanocomposite films applicable as spintronic materials

    International Nuclear Information System (INIS)

    Full text: The influence of composition and gas mixture during sputtering process on magnetic state and DC and AC carrier transport of composite films containing amorphous CoFeZr nanoparticles in amorphous aluminium oxide matrix has been investigated. The films with 3-5 m thicknesses and variable composition 30 at. % -s(s≤ 2) in low temperature region ( 55 at.% (over the percolative threshold) the power law R(ω)∼ ω-s is disturbed although activational character of temperature dependence of AC conductance is remained. In the samples with x > 40 % the dramatical increase (up to 2-3 orders by magnitude) of capacitance modulus occurs at achieving some threshold value of bias voltage. The obtained increase of capacitance modulus with bias voltage is always accompanied by the decrease of real part of impedance. The value of threshold bias voltage decreases with the growth of metallic component content in the studied composites

  6. Effect of Processing Parameters on Thermal Cycling Behavior of Al2O3-Al2O3 Brazed Joints

    Science.gov (United States)

    Dandapat, Nandadulal; Ghosh, Sumana; Guha, Bichitra Kumar; Datta, Someswar; Balla, Vamsi Krishna

    2016-10-01

    In the present study, alumina ceramics were active metal brazed at different temperatures ranging from 1163 K to 1183 K (890 °C to 910 °C) using TICUSIL (68.8Ag-26.7Cu-4.5Ti in wt pct) foil as filler alloy of different thicknesses. The brazed joints were subjected to thermal cycling for 100 cycles between 323 K and 873 K (50 °C and 600 °C). The microstructural and elemental composition analysis of the brazed joints were performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) before and after thermal cycling. Helium (He) leak test and brazing strength measurement were also conducted after thermal cycling for 100 cycles. The joint could withstand up to 1 × 10-9 Torr pressure and brazing strength was higher than 20 MPa. The experimental results demonstrated that joints brazed at the higher temperature with thinner filler alloy produced strong Al2O3-Al2O3 joints.

  7. Storage-Reduction of NOx over Combined Catalysts of Pt/Ba/Al2O3-Mn/Ba/Al2O3: Carbon Monoxide as Reductant

    Institute of Scientific and Technical Information of China (English)

    Sha Deng; Xuehui Li; Jianhua Xiao; Furong Wang; Lefu Wang

    2007-01-01

    Storage-reduction of NOx by carbon monoxide was investigated over combined catalysts of Mn/Ba/Al2O3-Pt/Ba/Al2O3. Combination of Mn/Ba/Al2O3 and Pt/Ba/Al2O3 catalysts in different ways showed excellent NOx storage-reduction performance and the content of Pt could be reduced by 50%.Not only the addition of 5Mn/15Ba/Al2O3 to 1Pt/15Ba/Al2O3 could improve its storage ability, but also enhance the NOx conversion consequently. NOx conversion over the combined catalysts (the combined catalysts Ⅰ and Ⅱ) was increased under dynamic lean-rich burn conditions, the maximum NOx conversion increased from 69.4% to respectively 78.8% and 75.7% over two combined catalysts.

  8. Surface chemistry of plasma-assisted atomic layer deposition of Al2O3 studied by infrared spectroscopy

    International Nuclear Information System (INIS)

    The surface groups created during plasma-assisted atomic layer deposition (ALD) of Al2O3 were studied by infrared spectroscopy. For temperatures in the range of 25-150 deg. C, -CH3 and -OH were unveiled as dominant surface groups after the Al(CH3)3 precursor and O2 plasma half-cycles, respectively. At lower temperatures more -OH and C-related impurities were found to be incorporated in the Al2O3 film, but the impurity level could be reduced by prolonging the plasma exposure. The results demonstrate that -OH surface groups rule the surface chemistry of the Al2O3 process and likely that of plasma-assisted ALD of metal oxides from organometallic precursors in general

  9. A study on Al2O3 passivation in GaN MOS-HEMT by pulsed stress

    Institute of Scientific and Technical Information of China (English)

    Yue Yuan-Zheng; Hao Yue; Zhang Jin-Cheng; Feng Qian; Ni Jin-Yu; Ma Xiao-Hua

    2008-01-01

    This paper studies systematically the drain current collapse in AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) by applying pulsed stress to the device. Low-temperature layer of Al2O3 ultrathin film used as both gate dielectric and surface paasivation layer was deposited by atomic layer deposition (ALD).For HEMT, gate turn-on pulses induced large current collapse. However, for MOS-HEMT, no significant current collapse was found in the gate turn-on pulsing mode with different pulse widths, indicating the good passivation effect of ALD Al2O3. A small increase in Id in the drain pulsing mode is due to the relieving of self-heating effect. The comparison of synchronously dynamic pulsed Id - Vds characteristics of HEMT and MOS-HEMT further demonstrated the good passivation effect of ALD Al2O3.

  10. Theoretical study of ZnO adsorption and bonding on Al2O3 (0001) surface

    Institute of Scientific and Technical Information of China (English)

    LI; Yanrong

    2004-01-01

    [1]Wang En′ge, Atomic-scales study of kinetics in film growth, Progress in Physics (in Chineses), 2003, 23(1): 1-61.[2]Harrison, N. M., First principles simulation of surfaces and interfaces, Computer Physics Communications, 2001, 137: 59-73.[3]Erwin, S. C., Lee, S. H., Scheffler, M., First principles study of nucleation, growth, and interface structure of Fe/GaAs, Phys. Rev., 2002, B65(10): 205422.[4]Yang, C., Li, Y. R., Computer simulation and modeling of thin film growth, Gongneng Cailiao, 2003, 34(3): 247-249.[5]Ohkubo, I., Matsumoto, Y., Ohtomo, A. et al., Investigation of ZnO/sapphire interface and formation of ZnO nanocrystalline by laser MBE, Appl. Surf. Sci., 2000, 159-160: 514-519.[6]Ohnishi, T., Ohtomo, A., Ohkuboa, I. et al., Coaxial impact-collision ion scattering spectroscopy analysis of ZnO thin films and single crystals, Materials Science and Engineering, 1998, B56: 256-262.[7]Millon, E., Albert, O., Loulergue, J. C. et al., Growth of heteroepitaxial ZnO thin films by femtosecond pulsed-laser deposition, J. App. Phys., 2000, 88: 6937-6939.[8]Ohkubo, I., Ohtomo, A., Ohnishi, T. et al., In-plane and polar orientations of ZnO thin films grown on atomically flat sapphire, Surf. Sci., 1999, 443: L1043-L1048.[9]Yang, C., Li, Y. R., Xue, W. D. Et al., Study on the structure and energy of the (0001) surface of α- Al2O3(0001) substrate, Acta Phys. Sin. (in Chinese), 2003, 52(9): 2268-2273.[10]Robert, W. C., Melvin, A. J., William, B. H., CRC Handbook of Chemistry and Physics, Florida: CRC Press Inc., 1993, 95-100.[11]Hanchen, H., Gilmer, G. H., Multi-lattice Monte Carlo model of thin films, Journal of Computer-Aided Materials Design, 1999, 6: 117-127.[12]Car, R., Parrinello, M., Unified approach for molecular dynamics and density-functional theory, Phys. Rev. Lett., 1985, 55: 2471-2474.[13]Vanderbilt, D., Soft self-consistent pseudopotentials in a generalized eigenvalue formalism, Phys. Rev., 1990, B41

  11. Ni/Al2O3 catalysts for CO methanation: Effect of Al2O3 supports calcined at different temperatures

    Institute of Scientific and Technical Information of China (English)

    Jiajian; Gao; Chunmiao; Jia; Jing; Li; Meiju; Zhang; Fangna; Gu; Guangwen; Xu; Ziyi; Zhong; Fabing; Su

    2013-01-01

    The correlation between phase structures and surface acidity of Al2O3 supports calcined at different temperatures and the catalytic performance of Ni/Al2O3 catalysts in the production of synthetic natural gas(SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al2O3 catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al2O3 supports were adjusted by calcining the commercial γ-Al2O3 at different temperatures(600–1200 C). CO methanation reaction was carried out in the temperature range of 300–600 C at different weight hourly space velocities(WHSV = 30000 and 120000 mL·g-1h-1) and pressures(0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al2O3 supports due to the rapid decrease of the specific surface area and acidity of Al2O3 supports. Interestingly, Ni catalysts supported on Al2O3 calcined at 1200 C(Ni/Al2O3-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al2O3-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures(600, 800 and 1000 C). These findings would therefore be helpful to develop Ni/Al2O3 methanation catalyst for SNG production.

  12. Abrasive wear characteristics and mechanisms of Al2O3/PA1010 composite coatings

    Institute of Scientific and Technical Information of China (English)

    JIA Xian; LING Xiaomei

    2004-01-01

    The abrasive wear characteristics of Al2O3/PA1010 composite coatings on the surface of quenched and low-temperature temper steel 45 were tested on the mmplate abrasive wear testing machine and the same uncoated steel 45 was used as a reference material. Experimental results showed that the abrasive wear resistance of Al2O3//PAl010 composite coatings has a good linear relationship with the volume fraction of Al2O3 particles in Al2O3/PAl010 composite coatings, and the linear correlative coefficient is 0.979. Under the experimental conditions, the size of Al2O3 particles (40.5-161.0 μm) has little influence on the abrasive wear resistance of Al2O3/PA l010 composite coatings. By treating the surface of Al2O3 particles with a suitable bonding agent, the distribution of Al2O3 particles in matrix PAl010 is more homogeneous and the bonding state between Al2O3 particles and matrix PAl010 is better. Therefore, the ml2O3 particles in Al2O3/PA1010 composite coatings make the Al2O3/PAl010 composite coatings have better abrasive wear resistance than PA1010 coatings. The wear resistance of Al2O3/PA 1010 composite coatings is about 45% compared with that of steel 45.

  13. A comparison of BCF-12 organic scintillators and Al2O3:C crystals for real-time medical dosimetry

    DEFF Research Database (Denmark)

    Beierholm, Anders Ravnsborg; Andersen, Claus Erik; Lindvold, Lars;

    2008-01-01

    Radioluminescence (RL) from aluminium oxide (Al2O3:C) crystals and organic scintillators such as the blue-emitting BCF-12 can be used for precise real-time dose rate measurements during radiation therapy of cancer patients. Attaching the dosimeters to thin light-guiding fiber cables enables in vi...

  14. Mechanical properties of thin film Parylene-metal-Parylene devices

    Directory of Open Access Journals (Sweden)

    Curtis Dixon Lee

    2015-09-01

    Full Text Available Structures and testing methods for measuring the adhesion strength, minimum bending diameter, and bending fatigue performance of thin film polymer electronic architectures were developed and applied to Parylene-metal-Parylene systems with and without the moisture barrier Al2O3 (deposited using atomic layer deposition (ALD. Parylene-metal-Parylene interfaces had the strongest average peel test strength and Parylene-Parylene interfaces had the weakest peel. Layers of ALD Al2O3 deposited within the device increased the average peel strength for Parylene-Parylene interfaces when combined with silane A-174, but did not increase the Parylene-metal-Parylene interface. Metal traces in the middle of 24 µm thick Parylene-metal-Parylene devices had a minimum bending diameter of ~130 µm before breaking and being measured as an open circuit. The addition of one layer of Al2O3 above the traces allowed them to be completely creased when bent away from the Al2O3 layer without producing an open circuit, but increased the minimum bending diameter to ~450 µm when bent away from the Al2O3. Although fatigue testing produced cracks in all devcies after 100k bends, the insulation of the Parylene-metal-Parylene devices without Al2O3 performed well with electrochemical impedance spectroscopy (EIS showing only small decreases in impedance magnitude and small increases of impedance phase at low frequencies. However, devices with Al2O3 failed during EIS due to Al2O3 being deteriorated by water.

  15. Unraveling the Origin of Structural Disorder in High Temperature Transition Al2O3: Structure of θ-Al2O3

    Energy Technology Data Exchange (ETDEWEB)

    Kovarik, Libor; Bowden, Mark E.; Shi, Dachuan; Washton, Nancy M.; Anderson, Amity; Hu, Jian Z.; Lee, Jaekyoung; Szanyi, Janos; Kwak, Ja Hun; Peden, Charles HF

    2015-09-22

    The crystallography of transition Al2O3 has been extensively studied in the past due to the advantageous properties of the oxide in catalytic and a range of other technological applications. However, existing crystallographic models are insufficient to describe the structure of many important Al2O3 polymorphs due to their highly disordered nature. In this work, we investigate structure and disorder in high-temperature treated transition Al2O3, and provide a structural description for θ-Al2O3 by using a suite of complementary imaging, spectroscopy and quantum calculation techniques. Contrary to current understanding, our high-resolution imaging shows that θ-Al2O3 is a disordered composite phase of at least two different end members. By correlating imaging and spectroscopy results with DFT calculations, we propose a model that describes θ-Al2O3 as a disordered intergrowth of two crystallographic variants at the unit cell level. One variant is based on β-Ga2O3, and the other on a monoclinic phase that is closely-related to δ-Al2O3. The overall findings and interpretations afford new insight into the origin of poor crystallinity in transition Al2O3, and also provide new perspectives on structural complexity that can emerge from intergrowth of closely related structural polymorphs.

  16. Dipole defects in Al2O3:Mg,Cr.

    Science.gov (United States)

    Blak, A R; Gobbi, V; Ayres, F

    2002-01-01

    In this work, dipole defects are investigated applying the thermally stimulated depolarisation currents (TSDC) technique. The TSDC spectra of Al2O3 doped with Mg and Cr show two bands centred at 230 K and 250 K, respectively. The maximum intensity of the bands increases linearly with the polarisation field, a typical behaviour of defects with dipole origin. An increase of the band at 250 K with gamma irradiation has been observed and a thermal decrease of the bands for heat treatments between 1000 K and 1400 K. Above this temperature the bands are partially recovered. Impurity neutron activation analysis shows that magnesium. chromium and iron content varies from 15 to 60 ppm. Optical absorption (AO) measurements show a broad band centred in 2.6 eV (21000 cm(-1)) associated with trapped holes localised on an O- ion adjacent to a cation site which is deficient in positive charge. It has been assumed that a substitutional Mg2+ ion occupies the cation site near a trapped hole on one of the six oxygen ions surrounding the magnesium impurity giving rise to the dipole responsible for the observed TSDC bands. Calculations carried out through defect simulation methods confirm that the probability of Al3+ being replaced by Mg2+ is higher than Mn2+, Co2+, Fe2+ and Cr2+. PMID:12382829

  17. High-temperature oxidation behavior of Al2O3/TiAl matrix composite in air

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The oxidation behavior of Al2O3/TiAl in situ composites fabricated by hot-pressing technology was in-vestigated at 900℃ in static air.The results indicate that the mass gains of the composites samples decrease gradually with increasing Nb2O5 content and the inert Al2O3 dispersoids effectively increase the oxidation resistance of the composites.The higher the Al2O3 dispersoids content,the more pro-nounced the effect.The primary oxidation precesses obey approximately the linear laws,and the cyclic oxidation precesses follow the parabolic laws.The oxidized sample containing Ti2AlN and TiAl phases in the scales exhibits excellent oxidation resistance.The oxide scale formed after exposure at 900 ℃ for 120 h is multiple-layered,consisting mainly of an outer TiO2 layer,an intermediate Al2O3 layer,and an inner TiO2+Al2O3 mixed layer.From the outer layer to the inner layer,TiO2+Al2O3 mixed layer presents the transit of Al-rich oxide to Ti-rich oxide mixed layer.Near the substrate,cross-section micrograph shows a relatively loose layer,and micro-and macro-pores remain on this layer,which is a transition layer and transferres from Al2O3+TiO2 scale to substrate.The thickness of oxide layer is about 20 μm.It is also found that continuous protective alumina scales can not be observed on the surface of oxida-tion scales.Ti ions diffuse outwardly to form the outer TiO2 layer,while oxygen ions transport inwardly to form the inner TiO2+Al2O3 mixed layer.Under long-time intensive oxidation exposure,the internal Al2O3 scale has a good adhesiveness with the outer TiO2 scale.No obvious spallation of the oxide scales occurs.The increased oxidation resistance by the presence of in situ Al2O3 particulates is at-tributed to the enhanced alumina-forming tendency and thin and dense scale formation.Al2O3 particu-lates enhance the potential barrier of Ti ions from M/MO interface to O/MO interface,thereby the TiO2 growth rate decreases,which is also beneficial to improve the oxidation

  18. Effect of Al2O3 on Structure and Wearability of Composite Coating

    Institute of Scientific and Technical Information of China (English)

    DING Hong-yan; ZHANG Yue

    2004-01-01

    The composite coating was prepared by thermal spray welding after making composite powder, which is composed of Ni-based self-melted alloy and Al2O3 ceramic powder including nano, sub-micron and micron powders. The influences of contents and sizes of Al2O3 on the structure and wearability were investigated. The results show that the wear resistance of the coating would be increased greatly by adding Al2O3, but the spray weldability decreases with increasing Al2O3 content. So there is an optimal content of Al2O3 powder. The composite coating with Al2O3 nano or sub-micron powder of 0.5 % has the best abrasive resistance, while the optimal content of Al2O3 micron powder is 1%.

  19. Thermodynamic modeling of the (Al2O3 + Na2O), (Al2O3 + Na2O + SiO2), and (Al2O3 + Na2O + AlF3 + NaF) systems

    International Nuclear Information System (INIS)

    Highlights: ► We modeled Al2O3–Na2O–SiO2 and Al2O3–Na2O–AlF3–NaF using the Modified Quasichemical Model in the Quadruplet Approximation. ► This assessment includes a very thorough review of all available experimental data for Al2O3–Na2O and Al2O3–Na2O–SiO2. ► The charge compensation effect in the SiO2-rich region of the (Al2O3 + Na2O + SiO2) system is modeled with a NaAl4+ cation. ► First detailed thermodynamic modeling of the (Al2O3 + Na2O + SiO2) ternary system. ► First thermodynamic modeling at all compositions and temperatures of the (Al2O3 + Na2O + AlF3 + NaF) reciprocal oxyfluoride system. - Abstract: All available thermodynamic and phase diagram data for the condensed phases of the (Al2O3 + Na2O), (Al2O3 + Na2O + SiO2), and (Al2O3 + Na2O + AlF3 + NaF) systems have been critically assessed. Model parameters for solid solutions and a single set of parameters for the liquid solution in the binary, ternary, and ternary reciprocal systems have been optimized and permit to reproduce most of the critically reviewed experimental data. The Modified Quasichemical Model in the Quadruplet Approximation was used for the oxyfluoride (mixture of molten oxides and salts) liquid solution, which exhibits strong first-nearest-neighbor and second-nearest-neighbor short-range order. This thermodynamic model takes into account both types of short-range order as well as the coupling between them. The charge compensation effect present in the (Al2O3 + Na2O + SiO2) system was taken into account by adding a (NaAl)4+ species in the liquid solution.

  20. Resistive switching characteristics in memristors with Al2O3/TiO2 and TiO2/Al2O3 bilayers

    Science.gov (United States)

    Alekseeva, Liudmila; Nabatame, Toshihide; Chikyow, Toyohiro; Petrov, Anatolii

    2016-08-01

    Differences between the resistive switching characteristics of Al2O3/TiO2 and TiO2/Al2O3 bilayer structures, fabricated by atomic layer deposition at 200 °C and post-deposition annealing, were studied in Pt bottom electrode (Pt-BE)/insulator/Pt top electrode (Pt-TE) capacitors. The Pt-BE/Al2O3/TiO2/Pt-TE capacitor exhibits stable bipolar resistive switching with an on-resistance/off-resistance ratio of ∼102 controlled by a small voltage of ±0.8 V. The forming process occurs in two steps of breaking of the Al2O3 layer and transfer of oxygen vacancies (VO) into the TiO2 layer. The capacitor showed poor endurance, particularly in the high-resistance state under vacuum conditions. This indicates that the insulating TiO2 layer without VO is not formed near the Al2O3 layer because oxygen cannot be introduced from the exterior. On the other hand, in the Pt-BE/TiO2/Al2O3/Pt-TE capacitor, multilevel resistive switching with several applied voltage-dependent nonvolatile states is observed. The switching mechanism corresponds to the Al2O3 layer’s trapped VO concentration, which is controlled by varying the applied voltage.

  1. The MgO-Al2O3-SiO2 system - Free energy of pyrope and Al2O3-enstatite. [in earth mantle formation

    Science.gov (United States)

    Saxena, S. K.

    1981-01-01

    The model of fictive ideal components is used to determine Gibbs free energies of formation of pyrope and Al2O3-enstatite from the experimental data on coexisting garnet and orthopyroxene and orthopyroxene and spinel in the temperature range 1200-1600 K. It is noted that Al2O3 forms an ideal solution with MgSiO3. These thermochemical data are found to be consistent with the Al2O3 isopleths that could be drawn using most recent experimental data and with the reversed experimental data on the garnet-spinel field boundary.

  2. Dissolution mechanism of Al2O3 in refining slags containing Ce2O3

    Directory of Open Access Journals (Sweden)

    Wang L.J.

    2016-01-01

    Full Text Available In the present work, the rate of dissolution of Al2O3 rod in CaO-SiO2-Al2O3 and CaO-SiO2-Al2O3-Ce2O3 slags were carried out in the temperature range of 1793 K (1520ºC - 1853 K (1580ºC under static conditions. The cross section of the rod and the boundary layers were identified and analyzed by SEM-EDS. The dissolution of Al2O3 was favored with the increasing CaO/Al2O3 ratio, elevating temperatures as well as the addition of Ce2O3. An intermediate product 3CaO5Al2O3Ce2O3 was detected. The mechanism of dissolution of Al2O3 in the Ce2O3 containing slag were also proposed as three steps involved: 1 the formation of calcium aluminates CaO•Al2O3 at the interface 2 the formation of 3CaO5Al2O3Ce2O3 as the reaction progresses; and 3 the dissolution of 3CaO5Al2O3Ce2O3 into the slag.

  3. Directed laser processing of compacted powder mixtures Al2O3-TiO2-Y2O3

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2013-01-01

    Full Text Available The phase formation, microstructure and surface texture of laser treated ternary powder mixtures of Al2O3-TiO2-Y2O3 had been studied. Rapid high temperature heating and subsequent rapid cooling due to the directed movement of the laser beam forms concave ceramic tracks. Phase composition and microstructure of the tracks depends on the Al2O3 content and the TiO2/Y2O3 ratio of the initial mixtures. The main phases observed are Y3Al5O12, Y2Ti2O7, Al2O3 and Al2TiO5. Due to the temperature gradient in the heating zone, complex layered structures are formed. The tracks consist of three main layers: a thin surface layer, a layer of crystallization products of eutectic alloys, and a lower sintered layer. The thickness of the crystallization layer and the shrinkage of the irradiation zone depend on the amount of Y3Al5O12 and Al2O3 crystallized from the melt.

  4. Atomic to Nanoscale Investigation of Functionalities of Al2O3 Coating Layer on Cathode for Enhanced Battery Performance

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Zhang, Xiaofeng; Xu, Rui; Amine, Khalil; Xiao, Jie; Zhang, Jiguang; Wang, Chong M.

    2016-01-06

    Surface coating of cathode has been identified as an effective approach for enhancing the capacity retention of layered structure cathode. However, the underlying operating mechanism of such a thin layer of coating, in terms of surface chemical functionality and capacity retention, remains unclear. In this work, we use aberration corrected scanning transmission electron microscopy and high efficient spectroscopy to probe the delicate functioning mechanism of Al2O3 coating layer on Li1.2Ni0.2Mn0.6O2 cathode. We discovered that in terms of surface chemical function, the Al2O3 coating suppresses the side reaction between cathode and the electrolyte upon the battery cycling. At the same time, the Al2O3 coating layer also eliminates the chemical reduction of Mn from the cathode particle surface, therefore avoiding the dissolution of the reduced Mn into the electrolyte. In terms of structural stability, we found that the Al2O3 coating layer can mitigate the layer to spinel phase transformation, which otherwise will initiate from the particle surface and propagate towards the interior of the particle with the progression of the battery cycling. The atomic to nanoscale effects of the coating layer observed here provide insight for optimized design of coating layer on cathode to enhance the battery properties.

  5. A study of GaN MOSFETs with atomic-layer-deposited Al2O3 as the gate dielectric

    Institute of Scientific and Technical Information of China (English)

    Feng Qian; Xing Tao; Wang Qiang; Feng Qing; Li Qian; Bi Zhi-Wei; Zhang Jin-Cheng; Hao Yue

    2012-01-01

    Accumulation-type GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) with atomic-layerdeposited Al2O3 gate dielectrics are fabricated.The device,with atomic-layer-deposited Al2O3 as the gate dielectric,presents a drain current of 260 mA/mm and a broad maximum transconductance of 34 mS/mm,which are better than those reported previously with Al2O3 as the gate dielectric.Furthermore,the device shows negligible current collapse in a wide range of bias voltages,owing to the effective passivation of the GaN surface by the Al2O3 film.The gate drain breakdown voltage is found to be about 59.5 V,and in addition the channel mobility of the n-GaN layer is about 380 cm2/Vs,which is consistent with the Hall result,and it is not degraded by atomic-layer-deposition Al2Oa growth and device fabrication.

  6. AlGaN/GaN high electron mobility transistor with Al2O3+BCB passivation

    Institute of Scientific and Technical Information of China (English)

    张昇; 马晓华; 孙兵; 刘新宇; 魏珂; 余乐; 刘果果; 黄森; 王鑫华; 庞磊; 郑英奎; 李艳奎

    2015-01-01

    In this paper, A12O3 ultrathin film used as the surface passivation layer for AlGaN/GaN high electron mobility transistor (HEMT) is deposited by thermal atomic layer deposition (ALD), thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition (PECVD) SiN passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency (RF) performance are achieved after applying Al2O3+BCB passivation. For the Al2O3+BCB passivated device with a 0.7 µm gate, the value of fmax reaches up to 100 GHz, but it decreases to 40 GHz for SiN HEMT. The fmax/ft ratio (≥4) is also improved after Al2O3+BCB passivation. The capacitance–voltage (C–V ) measurement demonstrates that Al2O3+BCB HEMT shows quite less density of trap states (on the order of magnitude of 1010 cm−2) than that obtained at commonly studied SiN HEMT.

  7. Alumina Thin Film Growth: Experiments and Modeling

    OpenAIRE

    Wallin, Erik

    2007-01-01

    The work presented in this thesis deals with experimental and theoretical studies related to the growth of crystalline alumina thin films. Alumina, Al2O3, is a polymorphic material utilized in a variety of applications, e.g., in the form of thin films. Many of the possibilities of alumina, and the problems associated with thin film synthesis of the material, are due to the existence of a range of different crystalline phases. Controlling the formation of the desired phase and the transformati...

  8. Surface phonon polariton characteristics of In(0.04)Al(0.06)Ga(0.90)N/AlN/Al(2)O(3) heterostructure.

    Science.gov (United States)

    Ng, S S; Lee, S C; Bakhori, S K Mohd; Hassan, Z; Abu Hassan, H; Yakovlev, V A; Novikova, N N; Vinogradov, E A

    2010-05-10

    Surface phonon polariton (SPP) characteristics of In(0.04)Al(0.06)Ga(0.90)N/AlN/Al(2)O(3) heterostructure are investigated by means of p-polarized infrared (IR) attenuated total reflection spectroscopy. Two absorption dips corresponding to In(0.04)Al(0.06)Ga(0.90)N SPP modes are observed. In addition, two prominent dips and one relatively weak and broad dip corresponding to the Al(2)O(3) SPP mode, In(0.04)Al(0.06)Ga(0.90)N/Al(2)O(3) interface mode, and Al(2)O(3) bulk polariton mode, respectively, are clearly seen. No surface mode feature originating from the AlN layer is observed because it is too thin. Overall, the observations are in good agreement with the theoretical predictions. PMID:20588890

  9. Influence of Al2O3 on the ionic conductivity of plasticized PVC-PEG blend polymer electrolytes

    Science.gov (United States)

    Ravindran, D.; Vickraman, P.

    2016-05-01

    Polymer electrolytes with PVC-PEG blend as host matrix and LiClO4 as dopant salt was prepared through conventional solution casting method. To enhance the conductivity propylene carbonate (PC) was used as plasticizer. The influence of ceramic filler Al2O3 on the conductivity of the electrolyte films were studied by varying the (PVC: Al2O3) ratio. The films were subjected to XRD, complex impedance analysis and SEM analysis. The XRD studies reveal a marginal increase in the amorphous phase of the electrolyte films due to the incorporation of filler. The AC impedance analysis shows the dependency of ionic conductivity on the content (wt %) of filler and exhibit a maximum at 4 wt% filler. The SEM analysis depicts the occurrence of phase separation in electrolyte which is attributed to the poor solubility of polymer PVC in the liquid electrolyte.

  10. Anomalous elongation of c-axis of GaN on Al2O3 grown by MBE using NH3-cluster ions

    Science.gov (United States)

    Ichinohe, Yoshihiro; Imai, Kazuaki; Suzuki, Kazuhiko; Saito, Hiroshi

    2016-02-01

    GaN thin films were grown on Al2O3 (0001) by MBE using NH3-clusters either ionized with the energy of 4-7 eV/molecule (ionized Cluster Beam, i-CB) or un-ionized with the energy of about 0.1 eV/molecule (neutral Cluster Beam, n-CB) at growth temperatures ranging from 390 to 960 °C. The c-axis is extremely elongated but the a-axis is shrunken at the initial growth stage (up to the film thickness of about 10 nm) in GaN grown by the mixture of n- and i-CB under N-rich condition. The films thicker than 30 nm have the relaxed a- and c-axis lengths close to the unstrained values and obey the Poisson relation. GaN grown by i-CB under Ga-rich condition have the relaxed lattice constants obeying the Poisson relation for the film as thin as 6 nm. In GaN grown by the cluster beam (CB) which is not ionized intentionally, both a- and c-axis lengths are almost independent of the film thickness, having nearly the same values as those of the unstrained samples. These characteristics can be ascribed to the nature of interface between the nitrided Al2O3 substrate and epilayer. It is concluded that the films grown by i-CB bond firmly to underlay AlN than the films by n-CB and CB.

  11. Photo-stability and time-resolved photoluminescence study of colloidal CdSe/ZnS quantum dots passivated in Al2O3 using atomic layer deposition

    Science.gov (United States)

    Cheng, Chih-Yi; Mao, Ming-Hua

    2016-08-01

    We report photo-stability enhancement of colloidal CdSe/ZnS quantum dots (QDs) passivated in Al2O3 thin film using the atomic layer deposition (ALD) technique. 62% of the original peak photoluminescence (PL) intensity remained after ALD. The photo-oxidation and photo-induced fluorescence enhancement effects of both the unpassivated and passivated QDs were studied under various conditions, including different excitation sources, power densities, and environment. The unpassivated QDs showed rapid PL degradation under high excitation due to strong photo-oxidation in air while the PL intensity of Al2O3 passivated QDs was found to remain stable. Furthermore, recombination dynamics of the unpassivated and passivated QDs were investigated by time-resolved measurements. The average lifetime of the unpassivated QDs decreases with laser irradiation time due to photo-oxidation. Photo-oxidation creates surface defects which reduces the QD emission intensity and enhances the non-radiative recombination rate. From the comparison of PL decay profiles of the unpassivated and passivated QDs, photo-oxidation-induced surface defects unexpectedly also reduce the radiative recombination rate. The ALD passivation of Al2O3 protects QDs from photo-oxidation and therefore avoids the reduction of radiative recombination rate. Our experimental results demonstrated that passivation of colloidal QDs by ALD is a promising method to well encapsulate QDs to prevent gas permeation and to enhance photo-stability, including the PL intensity and carrier lifetime in air. This is essential for the applications of colloidal QDs in light-emitting devices.

  12. An Investigation of Laser Assisted Machining of Al_2O_3 Particle Reinforced Aluminum Matrix Composite

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Al 2O 3 particles reinforced aluminum matrix composite (Al 2O 3p/Al) are more and more widely used for their excellent physical and chemical properties. However, their poor machinability leads to severe tool wear and bad machined surface. In this paper laser assisted machining is adopted in machining Al 2O 3p/Al composite and good result was obtained. The result of experiment shows in machining Al 2O 3p/Al composites the cutting force is reduced in 30%~50%, the tool wear is reduced in 20%~30% an...

  13. The effect of intragranular microstress in Al2O3-SiC nanocomposites

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Yuan; Wu Yu-Gong; Tong Shuai; Wu Si-Qi

    2012-01-01

    A theoretical model is established to investigate the intragranular particle residual stress in Al2O3-SiC nanocomposites.Using this model,we calculate the average compressive stress on the Al2O3 grain boundary (GB) and the average tensile stress within Al2O3 grains caused by SiC nanoparticles.The normal compressive stress strengthens the GB,and the average tensile stress weakens the grains.The model gives a reasonable interpretation of the strength changes of Al2O3-SiC nanocomposites with the number of SiC particles.

  14. Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta2O5)x(Al2O3)1-x as potential gate dielectrics for GaN/AlxGa1-xN/GaN high electron mobility transistors

    Science.gov (United States)

    Partida-Manzanera, T.; Roberts, J. W.; Bhat, T. N.; Zhang, Z.; Tan, H. R.; Dolmanan, S. B.; Sedghi, N.; Tripathy, S.; Potter, R. J.

    2016-01-01

    This paper describes a method to optimally combine wide band gap Al2O3 with high dielectric constant (high-κ) Ta2O5 for gate dielectric applications. (Ta2O5)x(Al2O3)1-x thin films deposited by thermal atomic layer deposition (ALD) on GaN-capped AlxGa1-xN/GaN high electron mobility transistor (HEMT) structures have been studied as a function of the Ta2O5 molar fraction. X-ray photoelectron spectroscopy shows that the bandgap of the oxide films linearly decreases from 6.5 eV for pure Al2O3 to 4.6 eV for pure Ta2O5. The dielectric constant calculated from capacitance-voltage measurements also increases linearly from 7.8 for Al2O3 up to 25.6 for Ta2O5. The effect of post-deposition annealing in N2 at 600 °C on the interfacial properties of undoped Al2O3 and Ta-doped (Ta2O5)0.12(Al2O3)0.88 films grown on GaN-HEMTs has been investigated. These conditions are analogous to the conditions used for source/drain contact formation in gate-first HEMT technology. A reduction of the Ga-O to Ga-N bond ratios at the oxide/HEMT interfaces is observed after annealing, which is attributed to a reduction of interstitial oxygen-related defects. As a result, the conduction band offsets (CBOs) of the Al2O3/GaN-HEMT and (Ta2O5)0.16(Al2O3)0.84/GaN-HEMT samples increased by ˜1.1 eV to 2.8 eV and 2.6 eV, respectively, which is advantageous for n-type HEMTs. The results demonstrate that ALD of Ta-doped Al2O3 can be used to control the properties of the gate dielectric, allowing the κ-value to be increased, while still maintaining a sufficient CBO to the GaN-HEMT structure for low leakage currents.

  15. Oxidation of Al2O3-30%TiCN-0.2%Y2O3 Composite

    Institute of Scientific and Technical Information of China (English)

    Li Xikun; Qiu Guanming; Xiu Zhimeng; Sun Xudong; Yan Changhao; Dai Shaojun

    2005-01-01

    The oxidation behavior of Al2O3-30%TiCN-0.2%Y2O3 composite and its effect on high temperature bending strength was studied. The result indicates that the mass gain during static oxidation of the material under normal atmosphere follows the parabolic law. Oxide increases with increasing temperature and prolonging time. It has good oxidation resistance. The product of oxidation of the material is TiO2. Therefore, the volume of the material expands. The oxide film is destroyed because residual stress inside the oxide film is released. Proper oxidation is beneficial to the improvement of bending strength of Al2O3-30%TiCN-0.2%Y2O3 composite. The strength increase is up to 4.5%.

  16. MgAl2O4–-Al2O3 solid solution interaction: mathematical framework and phase separation of -Al2O3 at high temperature

    Indian Academy of Sciences (India)

    Soumen Pal; A K Bandyopadhyay; S Mukherjee; B N Samaddar; P G Pal

    2011-07-01

    Although existence of MgAl2O4–-Al2O3 solid solution has been reported in the past, the detailed interactions have not been explored completely. For the first time, we report here a mathematical framework for the detailed solid solution interactions of -Al2O3 in MgAl2O4 (spinel). To investigate the solid solubility of -Al2O3 in MgAl2O4, Mg–Al spinel (MgO–Al2O3; = 1, 1.5, 3, 4.5 and an arbitrary high value 30) precursors have been heat treated at 1000°C. Presence of only non-stoichiometric MgAl2O4 phase up to = 4.5 at 1000°C indicates that alumina (as -Al2O3) present beyond stoichiometry gets completely accommodated in MgAl2O4 in the form of solid solution. → alumina phase transformation and its subsequent separation from MgAl2O4 has been observed in the Mg–Al spinel powders ( > 1) when the 1000°C heat treated materials are calcined at 1200°C. In the mathematical framework, unit cell of MgAl2O4 (Mg8Al16O32) has been considered for the solid solution interactions (substitution of Mg2+ ions by Al3+ ions) with -Al2O3. It is suggested that combination of unit cells of MgAl2O4 takes part in the interactions when > 5 (MgO–Al2O3).

  17. Surface Oxidation of Al2O3/SiC Nanocomposite: Phase Transformation and Microstructure

    Institute of Scientific and Technical Information of China (English)

    Cai Shu; Peng Zhenzhen; Feng Jie; Lu Feng

    2005-01-01

    The surface oxidation behavior of pressureless sintered Al2O3/SiC nanocomposite was studied from 1000 to 1400 ℃ for more than 10 h in air. Weight gain during the process of heat treatment was measured by TG analysis. Phase transformation and microstructure changes of these specimens due to oxidation were investigated with X-ray diffraction (XRD), SEM and EDX technology. Thermogravimetric analysis show that the weight gain as a result of oxidation of SiC become significant above 1200 ℃. In the range of 1000~1300 ℃, the SiC grits are usually coated with a layer of amorphous silica after oxidation. Above 1300 ℃, the amorphous silica reacted with alumina matrix and formed mullite or crystallized into cristobalite. The rate of oxidation depends on the formation of dense cristobalite film. Large amount of needle-like mullite and alumina crystals are formed on the surface after oxidation at 1400 ℃.

  18. Effect of Al 2 O 3 Recombination Barrier Layers Deposited by Atomic Layer Deposition in Solid-State CdS Quantum Dot-Sensitized Solar Cells

    KAUST Repository

    Roelofs, Katherine E.

    2013-03-21

    Despite the promise of quantum dots (QDs) as a light-absorbing material to replace the dye in dye-sensitized solar cells, quantum dot-sensitized solar cell (QDSSC) efficiencies remain low, due in part to high rates of recombination. In this article, we demonstrate that ultrathin recombination barrier layers of Al2O3 deposited by atomic layer deposition can improve the performance of cadmium sulfide (CdS) quantum dot-sensitized solar cells with spiro-OMeTAD as the solid-state hole transport material. We explored depositing the Al2O3 barrier layers either before or after the QDs, resulting in TiO2/Al2O3/QD and TiO 2/QD/Al2O3 configurations. The effects of barrier layer configuration and thickness were tracked through current-voltage measurements of device performance and transient photovoltage measurements of electron lifetimes. The Al2O3 layers were found to suppress dark current and increase electron lifetimes with increasing Al 2O3 thickness in both configurations. For thin barrier layers, gains in open-circuit voltage and concomitant increases in efficiency were observed, although at greater thicknesses, losses in photocurrent caused net decreases in efficiency. A close comparison of the electron lifetimes in TiO2 in the TiO2/Al2O3/QD and TiO2/QD/Al2O3 configurations suggests that electron transfer from TiO2 to spiro-OMeTAD is a major source of recombination in ss-QDSSCs, though recombination of TiO2 electrons with oxidized QDs can also limit electron lifetimes, particularly if the regeneration of oxidized QDs is hindered by a too-thick coating of the barrier layer. © 2013 American Chemical Society.

  19. Electrochemical promotion of propane oxidation on Pt deposited on a dense β"-Al2O3 ceramic Ag+ conductor

    Directory of Open Access Journals (Sweden)

    Michail eTsampas

    2013-08-01

    Full Text Available A new kind of electrochemical catalyst based on a Pt porous catalyst film deposited on a β"-Al2O3 ceramic Ag+ conductor was developed and evaluated during propane oxidation. It was observed that upon anodic polarization, the rate of propane combustion was significantly electropromoted up to 400%. Moreover, for the first time, exponential increase of the catalytic rate was evidenced during galvanostatic transient experiment in excellent agreement with EPOC equation.

  20. Performance and retention characteristics of nanocrystalline Si floating gate memory with an Al2O3 tunnel layer fabricated by plasma-enhanced atomic layer deposition

    Science.gov (United States)

    Ma, Zhongyuan; Wang, Wen; Yang, Huafeng; Jiang, Xiaofan; Yu, Jie; Qin, Hua; Xu, Ling; Chen, Kunji; Huang, Xinfan; Li, Wei; Xu, Jun; Feng, Duan

    2016-02-01

    The down-scaling of nanocrystal Si (nc-Si) floating gate memory must overcome the challenge of leakage current induced by the conventional ultra-thin tunnel layer. We demonstrate that an improved memory performance based on the Al/SiNx/nc-Si/Al2O3/Si structure can be achieved by adopting the Al2O3 tunnel layer fabricated by plasma-enhanced atomic layer deposition. A larger memory window of 7.9 V and better retention characteristics of 4.7 V after 105 s can be obtained compared with the devices containing a conventional SiO2 tunnel layer of equivalent thickness. The capacitance-voltage characteristic reveals that the Al2O3 tunnel layer has a smaller electron barrier height, which ensures that more electrons are injected into the nc-Si dots through the Al2O3/Si interface. The analysis of the conductance-voltage and high-resolution cross-section transmission microscopy reveals that the smaller nc-Si dots dominate in the charge injection in the nc-Si floating gate MOS device with an Al2O3 tunnel layer. With an increase of the nc-Si size, both nc-Si and the interface contribute to the charge storage capacity and retention. The introduction of the Al2O3 tunnel layer in nc-Si floating gate memory provides a method to achieve an improved performance of nc-Si floating gate memory.

  1. Properties of slow traps of ALD Al2O3/GeOx/Ge nMOSFETs with plasma post oxidation

    Science.gov (United States)

    Ke, M.; Yu, X.; Chang, C.; Takenaka, M.; Takagi, S.

    2016-07-01

    The realization of Ge gate stacks with a small amount of slow trap density as well as thin equivalent oxide thickness and low interface state density (Dit) is a crucial issue for Ge CMOS. In this study, we examine the properties of slow traps, particularly the location of slow traps, of Al2O3/GeOx/n-Ge and HfO2/Al2O3/GeOx/n-Ge MOS interfaces with changing the process and structural parameters, formed by atomic layer deposition (ALD) of Al2O3 and HfO2/Al2O3 combined with plasma post oxidation. It is found that the slow traps can locate in the GeOx interfacial layer, not in the ALD Al2O3 layer. Furthermore, we study the time dependence of channel currents in the Ge n-MOSFETs with 5-nm-thick Al2O3/GeOx/Ge gate stacks, with changing the thickness of GeOx, in order to further clarify the position of slow traps. The time dependence of the current drift and the effective time constant of slow traps do not change among the MOSFETs with the different thickness GeOx, demonstrating that the slow traps mainly exist near the interfaces between Ge and GeOx.

  2. Investigation of a 4H-SiC metal-insulation-semiconductor structure with an Al2O3/SiO2 stacked dielectric

    Institute of Scientific and Technical Information of China (English)

    Tang Xiao-Yan; Song Qing-Wen; Zhang Yu-Ming; Zhang Yi-Men; Jia Ren-Xu; Lü Hong-Liang; Wang Yue-Hu

    2012-01-01

    Atomic layer deposited (ALD) Al2O3/dry-oxidized ultrathin SiO2 films as a high-k gate dielectric grown on 8° off-axis 4H-SiC (0001) epitaxial wafers are investigated in this paper.The metal-insulation-semiconductor (MIS) capacitors,respectively with different gate dielectric stacks (Al2O3/SiO2,Al2O3,and SiO2) are fabricated and compared with each other.The I-V measurements show that the Al2O3/SiO2 stack has a high breakdown field (≥12 MV/cm)comparable to SiO2,and a relatively low gate leakage current of 1 × 10-7 A/cm2 at an electric field of 4 MV/cm comparable to Al2O3.The 1-MHz high frequency C-V measurements exhibit that the Al2O3/SiO2 stack has a smaller positive flat-band voltage shift and hysteresis voltage,indicating a less effective charge and slow-trap density near the interface.

  3. Thermally Sprayed Coatings as Interlayers for DLC-Based Thin Films

    Science.gov (United States)

    Bolelli, G.; Gualtieri, E.; Lusvarghi, L.; Pighetti Mantini, F.; Pitacco, F.; Valeri, S.; Volz, H.

    2009-06-01

    This article examines the usefulness of a thick thermally sprayed interlayer (plasma-sprayed Ni-50%Cr, plasma-sprayed Al2O3-13%TiO2, or high-velocity oxygen-fuel-sprayed WC-17%Co) for enhancing the wear resistance and the corrosion protectiveness of a diamond-like carbon (DLC)-based thin film deposited onto a carbon steel substrate. Scratch tests indicate that the Al2O3-13%TiO2 and WC-17%Co interlayers definitely increase the critical spallation load of the thin film, but the Al2O3-13%TiO2 interlayer itself undergoes brittle fracture under high-contact loads. Accordingly, during ball-on-disk tests at room temperature, no cracking and spallation occur in the DLC-based film deposited onto the WC-17%Co interlayer, whereas the one onto the Al2O3-13%TiO2 interlayer is rapidly removed because the interlayer itself is fractured. At 300 °C, by contrast, the DLC-based film on the Al2O3-13%TiO2 interlayer offers the best tribological performance, possibly thanks to the increased toughness of the ceramic interlayer at this temperature. Electrochemical polarization tests indicate that the thin film/WC-Co systems possess the lowest corrosion current density.

  4. High Elastic Moduli of a 54Al2O3-46Ta2O5 Glass Fabricated via Containerless Processing

    Science.gov (United States)

    Rosales-Sosa, Gustavo A.; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki; Yanaba, Yutaka; Mizoguchi, Teruyasu; Umada, Takumi; Okamura, Kohei; Kato, Katsuyoshi; Watanabe, Yasuhiro

    2015-10-01

    Glasses with high elastic moduli have been in demand for many years because the thickness of such glasses can be reduced while maintaining its strength. Moreover, thinner and lighter glasses are desired for the fabrication of windows in buildings and cars, cover glasses for smart-phones and substrates in Thin-Film Transistor (TFT) displays. In this work, we report a 54Al2O3-46Ta2O5 glass fabricated by aerodynamic levitation which possesses one of the highest elastic moduli and hardness for oxide glasses also displaying excellent optical properties. The glass was colorless and transparent in the visible region, and its refractive index nd was as high as 1.94. The measured Young’s modulus and Vickers hardness were 158.3 GPa and 9.1 GPa, respectively, which are comparable to the previously reported highest values for oxide glasses. Analysis made using 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy revealed the presence of a significantly large fraction of high-coordinated Al in addition to four-coordinated Al in the glass. The high elastic modulus and hardness are attributed to both the large cationic field strength of Ta5+ ions and the large dissociation energies per unit volume of Al2O3 and Ta2O5.

  5. Influences of high-temperature annealing on atomic layer deposited Al2O3/4H-SiC

    Institute of Scientific and Technical Information of China (English)

    Wang Yi-Yu; Shen Hua-Jun; Bai Yun; Tang Yi-Dan; Liu Ke-An; Li Cheng-Zhan; Liu Xin-Yu

    2013-01-01

    High-temperature annealing of the atomic layer deposition (ALD) of Al2O3 films on 4H-SiC in O2 atmosphere is studied with temperature ranging from 800 ℃ to 1000 ℃.It is observed that the surface morphology of Al2O3 films annealed at 800 ℃ and 900 ℃ is pretty good,while the surface of the sample annealed at 1000 ℃ becomes bumpy.Grazing incidence X-ray diffraction (GIXRD) measurements demonstrate that the as-grown films are amorphous and begin to crystallize at 900 ℃.Furthermore,C-V measurements exhibit improved interface characterization after annealing,especially for samples annealed at 900 ℃ and 1000 ℃.It is indicated that high-temperature annealing in O2 atmosphere can improve the interface of Al2O3/SiC and annealing at 900 ℃ would be an optimum condition for surface morphology,dielectric quality,and interface states.

  6. Influence of Al2O3 sol concentration on the microstructure and mechanical properties of Cu-Al2O3 composite coatings

    Science.gov (United States)

    Wei, Xiaojin; Yang, Zhendi; Tang, Ying; Gao, Wei

    2015-03-01

    Copper (Cu) is widely used as electrical conducting and contacting material. However, Cu is soft and does not have good mechanical properties. In order to improve the hardness and wear resistance of Cu, sol-enhanced Cu-Al2O3 nanocomposite coatings were electroplated by adding a transparent Al oxide (Al2O3) sol into the traditional electroplating Cu solution. It was found that the microstructure and mechanical properties of the nanocomposite coatings were largely influenced by the Al2O3 sol concentration. The results show that the Al2O3 nanoparticle reinforced the composite coatings, resulting in significantly improved hardness and wear resistance in comparison with the pure Cu coatings. The coating prepared at the sol concentration of 3.93 mol/L had the best microhardness and wear resistance. The microhardness has been improved by 20% from 145.5 HV (Vickers hardness number) of pure Cu coating to 173.3 HV of Cu-Al2O3 composite coatings. The wear resistance was also improved by 84%, with the wear volume loss dropped from 3.2 × 10-3 mm3 of Cu coating to 0.52 × 10-3 mm3 of composite coatings. Adding excessive sol to the electrolyte deteriorated the properties.

  7. Dissolution mechanism of Al2O3 in refining slags containing Ce2O3

    OpenAIRE

    Wang L.J.; Wang Q; Li J.M.; Chou K.C.

    2016-01-01

    In the present work, the rate of dissolution of Al2O3 rod in CaO-SiO2-Al2O3 and CaO-SiO2-Al2O3-Ce2O3 slags were carried out in the temperature range of 1793 K (1520ºC) - 1853 K (1580ºC) under static conditions. The cross section of the rod and the boundary layers were identified and analyzed by SEM-EDS. The dissolution of Al2O3 was favored with the increasing CaO/Al2O3 ratio, elevating temperatures as well as the addition of Ce2O3. An intermediate product 3...

  8. Promotion effect of iron on Mo/Al2O3 catalyst for the CAMERE process

    Directory of Open Access Journals (Sweden)

    Abolfazl Gharibi Kharaji

    2012-08-01

    Full Text Available Reverse Water Gas Shift (RWGS reaction is one of the main reactions that can be used toreduce greenhouse gases emissions. Through this reaction CO2 is converted to CO to produce beneficialchemicals such as methanol. In this paper Mo-Al2O3 catalyst was prepared and then promoted with Feions through co-impregnation method to produce Fe-Mo-Al2O3 catalyst. XRD tests were taken todetermine the structure of the catalysts. Activity, selectivity and stability of both catalysts wereinvestigated in a batch reactor and the results indicate that addition of Fe promoter to Mo-Al2O3 catalystincreased its activity and CO selectivity. Fe-Mo-Al2O3 showed acceptable catalytic stability during RWGSreaction. As a whole, Fe-Mo-Al2O3 can be a suitable candidate for RWGS reaction in CAMERE (carbondioxide hydrogenation to form methanol via a reverse-water-gas-shift reaction process.

  9. Photochemistry of the α-Al2O3-PETN Interface

    Directory of Open Access Journals (Sweden)

    Roman V. Tsyshevsky

    2016-02-01

    Full Text Available Optical absorption measurements are combined with electronic structure calculations to explore photochemistry of an α-Al2O3-PETN interface formed by a nitroester (pentaerythritol tetranitrate, PETN, C5H8N4O12 and a wide band gap aluminum oxide (α-Al2O3 substrate. The first principles modeling is used to deconstruct and interpret the α-Al2O3-PETN absorption spectrum that has distinct peaks attributed to surface F0-centers and surface—PETN transitions. We predict the low energy α-Al2O3 F0-center—PETN transition, producing the excited triplet state, and α-Al2O3 F0-center—PETN charge transfer, generating the PETN anion radical. This implies that irradiation by commonly used lasers can easily initiate photodecomposition of both excited and charged PETN at the interface. The feasible mechanism of the photodecomposition is proposed.

  10. Role of epitaxial microstructure, stress and twin boundaries in the metal–insulator transition mechanism in VO2/Al2O3 heterostructures

    International Nuclear Information System (INIS)

    The microstructures of epitaxial polycrystalline VO2 thin films grown on (0 0 1) sapphire were investigated by means of X-ray diffraction, Cs-corrected scanning transmission electron microscopy (STEM), in both plane and transverse geometry, in relation to its metal–insulator transition (MIT) properties. It is shown that the epitaxial relationship between the thin film and the substrate can be defined as out-of-plane twofold twinning symmetry {0 2 0}M//(0 0 6)S (where subscripts “M” and “S” denote the monoclinic phase of VO2 and the sapphire α-Al2O3 substrate, respectively) with in-plane threefold twinning structure (2 0 0)M//{1 1 0}S. The origin of these twinning structures is discussed: the in-plane threefold twinning structure comes from the threefold symmetry of the Al2O3 (0 0 1) plane, and the twofold twinning symmetry is induced by the MIT phase transition. The STEM planar view observations of the thin film demonstrate the presence of elongated grains down to nanoscale, with a high density of twin boundaries (TB). These TB are highly orientated into two sets of families. STEM low-angle annular dark-field imaging and STEM dark-field atomic displacement measurements evidence very different strain behaviors for these two TB families. Most of the TB and some of the smaller grains with typical dimensions of only a couple of nanometers exhibit locally an enhanced tetragonality. They are proposed to act as nucleation centers during the MIT process and then to influence the dynamics of the transition

  11. Microstructure and Properties of SCE-Al2O3/PES-MBAE Composite

    Directory of Open Access Journals (Sweden)

    Yufei Chen

    2014-01-01

    Full Text Available SCE-Al2O3 was the nano-Al2O3 modified by supercritical ethanol and the surface of SCE-Al2O3 was coated with active group. 4,4′-diaminodiphenylmethane bismaleimide (MBMI was used as matrix; 3,3′-diallyl bisphenol A (BBA and bisphenol-A diallyl ether (BBE were used as reactive diluent, polyethersulfone (PES as toughening agent, and SCE-Al2O3 as modifier; SCE-Al2O3/PES-MBAE nanocomposite was prepared through in situ sol-gel method. The mechanism of composite toughened by PES was observed and analyzed. FTIR indicated that the reaction between MBMI and allyl compound occurred and SCE-Al2O3 had doped into the polymer matrix. SEM showed that PES particle was inlaid in matrix and presented as a two-phase structure in matrix. The heat resistance, dielectric properties, and mechanical properties of SCE-Al2O3/PES-MBAE nanocomposites were evaluated. The results showed that with the incorporation of PES, although the toughness of the material improved, the heat resistance and dielectric properties of material declined, meanwhile. The adulteration of SCE-Al2O3 could remedy the harmful effect caused by PES, while the content of SCE-Al2O3 was reasonable. The decomposition temperature, dielectric constant, and dielectric loss of composite were 441.23°C, 3.63 (100 Hz, and 1.52 × 10−3 (100 Hz; the bending strength and impact strength were 129.22 MPa and 13.19 kJ/mm2, respectively, when the content of SCE-Al2O3 was 3 wt% and PES was 5 wt%.

  12. Robust Low Voltage Program-Erasable Cobalt-Nanocrystal Memory Capacitors with Multistacked Al2O3/HfO2/Al2O3 Tunnel Barrier

    Institute of Scientific and Technical Information of China (English)

    LIAO Zhong-Wei; GOU Hong-Yan; HUANG Yue; SUN Qing-Qing; DING Shi-Jin; ZHANG Wei; ZHANG Shi-Li

    2009-01-01

    An atomic-layer-deposited Al2O3/HfO2/Al2O3 (A/H/A) tunnel barrier is investigated for Co nanocrystal memory capacitors. Compared to a single Al2O3 tunnel barrier, the A/H/A barrier can significantly increase the hysteresis window, i.e., an increase by 9 V for ±12 V sweep range. This is attributed to a marked decrease in the energy barriers of charge injections for the A/H/A tunnel barrier. Further, the Co-nanocrystal memory capacitor with the A/H/A tunnel barrier exhibits a memory window as large as 4.1 V for 100 /us program/erase at a low voltage of ±7 V, which is due to fast charge injection rates, i.e., about 2.4 × 1016 cm-2s-1 for electrons and 1.9×1016 cm-2s-1 for holes.

  13. Passivation of Al2O3 / TiO2 on monocrystalline Si with relatively low reflectance

    Science.gov (United States)

    Lu, Chun-Ti; Huang, Yu-Shiang; Liu, C. W.

    2016-06-01

    Al2O3/TiO2 stack layers deposited by the plasma-enhanced atomic layer deposition enhance photoluminescence intensity by reducing effective surface recombination velocities on both n-type and p-type monocrystalline Si. The field effect of negative oxide charges in the dielectrics is responsible for the low effective surface recombination velocity. The dependence of the effective surface recombination velocity on the photoluminescence intensity is investigated by the 2D numerical simulation. The bilayer stacks without texture also reduce the AM1.5-weighted front side reflectance to 11.8%. The field-effect passivation of Al2O3/TiO2 films is further improved by a forming gas annealing due to the additional increase of the negative oxide charge density.

  14. Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates

    Directory of Open Access Journals (Sweden)

    Gema López

    2013-11-01

    Full Text Available The aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx stacks on both p-type and n-type crystalline silicon (c-Si substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD to form anti-reflection coating (ARC stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300–1200 nm without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (Seff,max was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450–1000 nm.

  15. The corrosive influence of chloride ions preference adsorption on α-Al2O3 (0 0 0 1) surface

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • The preference adsorption and interaction of Cl− at increasing monolayer coverage on Al2O3 in solution environment are modeling by DFT with COSMO. • A redefinition critical one plane monolayer of Cl− is 3/7, and the adsorption energy decrease in three steps, each adsorption energy step only relate to the adsorption site and the morphology. • The weaker interaction between Cl− and Al2O3 surface but stronger interactions between three Cl− make the electrons uniformly occupy on the energy levels of three ions. - Abstract: Conductor-like screening model (COSMO), Periodic DFT calculations have been performed on a Al2O3 surface to model the influence of preference adsorption and interaction of chloride ions at increasing monolayer coverage on undefective passive film on Aluminum in solution environment. The results evidence that the critical monolayer of Cl− is 3/7, which is redefined. With increasing Cl− adsorption, both the first and second Cl− move from Al(1) atop and bridge10 sites to O(5) sites, suggesting that the weaker interaction between Cl− and Al2O3 surface but stronger interactions between three ions make the electrons uniformly occupy on the energy levels of them. More calculations shows that the preference adsorption sites of Cl− are independent of the surface area of oxide, and the adsorption energy decrease in three steps, each adsorption energy step only relate to the adsorption site and the morphology. On undefective oxide film, low coverage Cl− adsorption would restrain surface breakdown to happen which is consistent with the experiment results

  16. Control of magnetization reversal in oriented Strontium Ferrite thin films

    OpenAIRE

    Roy, Debangsu; Kumar, P. S. Anil

    2013-01-01

    Oriented Strontium Ferrite films with the c axis orientation were deposited with varying oxygen partial pressure on Al2O3(0001) substrate using PLD technique. The angle dependent magnetic hysteresis, remanent coercivity and temperature dependent coercivity had been employed to understand the magnetization reversal of these films. It was found that the Strontium Ferrite thin film grown at lower (higher) oxygen partial pressure shows Stoner-Wohlfarth type (Kondorsky like) reversal. The relative...

  17. Pinhole Effect on the Melting Behavior of Ag@Al2O3 SERS Substrates.

    Science.gov (United States)

    Ma, Lingwei; Huang, Yu; Hou, Mengjing; Li, Jianghao; Zhang, Zhengjun

    2016-12-01

    High-temperature surface-enhanced Raman scattering (SERS) sensing is significant for practical detections, and pinhole-containing (PC) metal@oxide structures possessing both enhanced thermal stability and superior SERS sensitivity are served as promising SERS sensors at extreme sensing conditions. Through tuning the Al2O3 precursors' exposure time during atomic layer deposition (ALD), Al2O3 shells with different amount of pinholes were covered over Ag nanorods (Ag NRs). By virtue of these unique PC Ag@Al2O3 nanostructures, herein we provide an excellent platform to investigate the relationship between the pinhole rate of Al2O3 shells and the melting behavior, high-temperature SERS performances of these core-shell nanostructures. Pinhole effect on the melting procedures of PC Ag@Al2O3 substrates was characterized in situ via their reflectivity variations during heating, and the specific melting point was quantitatively estimated. It is found that the melting point of PC Ag@Al2O3 raised along with the decrement of pinhole rate, and substrates with less pinholes exhibited better thermal stability but sacrificed SERS efficiency. This work achieved highly reliable and precise control of the pinholes over Al2O3 shells, offering sensitive SERS substrates with intensified thermal stability and superior SERS performances at extreme sensing conditions. PMID:27033846

  18. Pt–Al2O3 nanocoatings for high temperature concentrated solar thermal power applications

    International Nuclear Information System (INIS)

    Nano-phased structures based on metal–dielectric composites, also called cermets (ceramic–metal), are considered among the most effective spectral selective solar absorbers. For high temperature applications (stable up to 650 °C) noble metal nanoparticles and refractory oxide host matrices are ideal as per their high temperature chemical inertness and stability: Pt/Al2O3 cermet nano-composites are a representative family. This contribution reports on the optical properties of Pt/Al2O3 cermet nano-composites deposited in a multilayered tandem structure. The radio-frequency sputtering optimized Pt/Al2O3 solar absorbers consist of stainless steel substrate/ Mo coating layer/ Pt–Al2O3/ protective Al2O3 layer and stainless steel substrate/ Mo coating layer /Pt–Al2O3 for different composition and thickness of the Pt–Al2O3 cermet coatings. The microstructure, morphology, theoretical modeling and optical properties of the coatings were analyzed by the x-ray diffraction, atomic force, microscopy, effective medium approximation and UV–vis specular and diffuse reflectance.

  19. Al2O3 on Black Phosphorus by Atomic Layer Deposition: An in Situ Interface Study.

    Science.gov (United States)

    Zhu, Hui; McDonnell, Stephen; Qin, Xiaoye; Azcatl, Angelica; Cheng, Lanxia; Addou, Rafik; Kim, Jiyoung; Ye, Peide D; Wallace, Robert M

    2015-06-17

    In situ "half cycle" atomic layer deposition (ALD) of Al2O3 was carried out on black phosphorus ("black-P") surfaces with modified phosphorus oxide concentrations. X-ray photoelectron spectroscopy is employed to investigate the interfacial chemistry and the nucleation of the Al2O3 on black-P surfaces. This work suggests that exposing a sample that is initially free of phosphorus oxide to the ALD precursors does not result in detectable oxidation. However, when the phosphorus oxide is formed on the surface prior to deposition, the black-P can react with both the surface adventitious oxygen contamination and the H2O precursor at a deposition temperature of 200 °C. As a result, the concentration of the phosphorus oxide increases after both annealing and the atomic layer deposition process. The nucleation rate of Al2O3 on black-P is correlated with the amount of oxygen on samples prior to the deposition. The growth of Al2O3 follows a "substrate inhibited growth" behavior where an incubation period is required. Ex situ atomic force microscopy is also used to investigate the deposited Al2O3 morphologies on black-P where the Al2O3 tends to form islands on the exfoliated black-P samples. Therefore, surface functionalization may be needed to get a conformal coverage of Al2O3 on the phosphorus oxide free samples.

  20. Influence of Al2O3 reinforcement on precipitation kinetic of Cu–Cr nanocomposite

    International Nuclear Information System (INIS)

    Highlights: ► Cr precipitation in Cu-1 wt.% Cr solid solution is based on nucleation and growth models. ► The overall ageing process is accelerated by the presence of Al2O3 reinforcement. ► Al2O3–Cu interfaces act as primary nucleation sites. ► Structural defects act as secondary nucleation sites. - Abstract: In this paper, the kinetic of precipitation process in mechanically alloyed Cu-1 wt.% Cr and Cu-1 wt.% Cr/3 wt.% Al2O3 solid solution was compared using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The ageing kinetics in Cu–Cr and Cu–Cr/Al2O3 can be described using Johnson–Mehl–Avrami (JMA) and Sestak–Berggren (SB) models, respectively. These different behaviors have been discussed in details. It was found that in presence of Al2O3 reinforcement, the ageing activation energy is decreased and the overall ageing process is accelerated. This behavior is probably due to higher dislocation density previously obtained during ball milling and Al2O3–Cu interface. TEM observations confirm that Al2O3–Cu interface and structural defects act as a primary and secondary nucleation sites, respectively.

  1. Aluminum induced crystallization of strongly (111) oriented polycrystalline silicon thin film and nucleation analysis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A polycrystalline silicon thin film was fabricated on glass substrate by means of aluminum induced crystallization (AIC). Al and α-Si layers were deposited by magnetron sputtering respectively and annealed at 480°C for 1 h to realize layer exchange. The polycrystalline silicon thin film was continuous and strongly (111) oriented. By analyzing the structure variation of the oxidation membrane and lattice mismatch between γ-Al2O3 and Si, it was concluded that aluminum promoted the formation of (111) oriented silicon nucleus by controlling the orientation of γ-Al2O3, which was formed at the early stage of annealing.

  2. Mechanical assessment of suspended ALD thin films by bulge and shaft-loading techniques

    International Nuclear Information System (INIS)

    We assessed mechanical properties of free-standing atomic-layer-deposited (ALD) Al2O3 thin films, mixed oxide (AlxTiyOz) films and Al2O3/TiO2 nanolaminates (75 and 200 nm). Using bulge and microelectromechanical system shaft-loading techniques, we evaluated the Young’s modulus, residual stress and ultimate tensile stress of these films and laminates. Fits to the load–displacement curves provided estimates for the residual stress and Young’s modulus. We extracted a residual stress of 347–403 MPa for Al2O3, 365–389 MPa for AlxTiyOz and 450–455 MPa for the nanolaminate. The Young’s modulus was 164–165 GPa for Al2O3, 151–154 GPa for mixed oxide and 148–169 GPa for the nanolaminate. Thin membranes exhibited an ultimate tensile strength of 1.57–2.56 GPa for Al2O3, 1.17–2.09 GPa for AlxTiyOz and 1.23–2.26 GPa for the nanolaminate. The ability to make thin, yet mechanically strong, suspended membranes is useful in micro- and nanosystem applications ranging from thermally insulated devices to large stroke mechanical actuators

  3. Hydrothermal synthesis of nanosize alpha-Al2O3 from seeded aluminum hydroxide

    OpenAIRE

    Sharma, Pramod K.; Burgard, Detlef; Nass, Rüdiger; Schmidt, Helmut K.; Jilavi, Mohammad H.

    1998-01-01

    α-Alumina and boehmite particles were synthesized by co-precipitation followed by a hydrothermal treatment. X-ray diffraction (XRD) indicated that α-Al2O3 was the major phase and coexisted with 4% of boehmite in the presence of the α-Al2O3 seeds. On the other hand, a single boehmite phase was obtained in the absence of the α-Al2O3 seed particles. The powder densified in the temperature range from 1050° to 1350°C. High-resolution transmission electron microscopy (HRTEM)...

  4. The Modification of Sodium Polyacrylate Water Solution Cooling Properties by AL2O3

    OpenAIRE

    Wojciech Gęstwa; Małgorzata Przyłęcka

    2010-01-01

    This paper presents a preliminary examination of water cooling ability as a result of its modification by the addition of sodium polyacrylate and AL2O3 nanoparticles. (AL2O3) alumina oxide was present in gamma phase as a form of nanopowder whose particle size was less than 50 nm. Cooling curves in the temperature-time system were marked for the three cooling media: water, 10% water solution of sodium polyacrylate, and 10% water solution of sodium polyacrylate with 1% addition of AL2O3 nanopar...

  5. Preparation and Characterization of Fe/Al2 O3 Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Fe2O3/Al2O3 nanocomposites prepared by using the sol-gel technique were reduced in H2 atmosphere at different temperatures, and the corresponding Fe/Al2O3 nanocomposites were obtained after the reduction of Fe2O3/Al2O3 nanocomposites at 1173 K. The structures and properties of the specimens were studied by X-ray diffraction(XRD), M(o)ssbauer spectroscopy(MS), and vibrating sample magnetometry(VSM). The results show that the reduction temperature has a significant influence on the structure, the grain size, and the magnetic properties of the specimens.

  6. In-situ Herstellung von Al2O3/SiC-Nanokompositen

    OpenAIRE

    Hopf, Jürgen

    2007-01-01

    Mittels kolloidaler Techniken wurden Pulvermischungen aus Ruß, Al2O3 und SiO2 erzeugt, wobei das SiO2 sowohl partikulär als auch als Schicht vorlag, und gefriergetrocknet. Aus diesen Pulvern wurden durch carbothermische Reduktion des SiO2 und einer nachfolgenden Mahlung homogene Al2O3/SiC Kompositpulver erhalten. Diese Pulver enthielten 5 und 10 Vol.-% SiC und wurden durch uniaxiales Heißpressen nahezu vollständig verdichtet. Die Al2O3/SiC Komposite wiesen eine homogene Verteilung der Sil...

  7. Thermoluminescence studies of γ-irradiated Al2O3:Ce3+ phosphor

    Science.gov (United States)

    Reddy, S. Satyanarayana; Nagabhushana, K. R.; Singh, Fouran

    2016-07-01

    Pure and Ce3+ doped Al2O3 phosphors were synthesized by solution combustion method. The synthesized samples were characterized by X-ray diffraction (XRD) and its shows α-phase of Al2O3. Crystallite size was estimated by Williamson-Hall (W-H) method and found to be 49, 59 and 84 nm for pure, 0.1 mol% and 1 mol% Ce3+ doped Al2O3 respectively. Trace elemental analysis of undoped Al2O3 shows impurities viz. Fe, Cr, Mn, Mg, Ti, etc. Photoluminescence (PL) spectra of Al2O3:Ce3+ shows emission at 367 nm and excitation peak at 273 nm, which are corresponding to 5D → 4F and 4F → 5D transitions respectively. PL intensity decreases with concentration up to 0.4 mol%, beyond this mol% PL intensity increases with doping concentration up to 2 mol%. Thermoluminescence (TL) studies of γ-rayed pure and Ce3+ doped Al2O3 have been studied. Two well resolved TL glow peaks at 457.5 K and 622 K were observed in pure Al2O3. Additional glow peak at 566 K was observed in Al2O3:Ce3+. Maximum TL intensity was observed for Al2O3:Ce3+ (0.1 mol%) beyond this TL intensity decreases with increasing Ce3+ concentration. Computerized glow curve deconvolution (CGCD) method was used to resolve the multiple peaks and to calculate TL kinetic parameters. Thermoluminescence emission (TLE) spectra of pure Al2O3 glow peaks (457.5 K and 622 K) shows sharp emission at 694 nm and two small humps at 672 nm and 709 nm. The sharp peak at 696 nm corresponds to Cr3+ impurity of 2Eg → 4A2g transition of R lines and 713 nm hump is undoubtedly belongs to Cr3+ emission of near neighbor pairs. The emission at 672 nm is characteristic of Mn4+ impurity ions of 2E → 4A2 transition. TLE of Al2O3:Ce3+ (0.1 mol%) shows additional broad emission at 412 nm corresponds to F-centers. Linearity is observed in the dose range 20-500 Gy in Al2O3:Ce3+ (1 mol%).

  8. Structure and properties of ceramic preforms based on Al2O3 particles

    OpenAIRE

    L.A. Dobrzański; M. Kremzer; Nagel, A.

    2009-01-01

    Purpose: The main goal of this project is to elaborate and optimize the method of manufacturing the porous, ceramic preforms based on Al2O3 particles used as the reinforcement in order to produce modern metal matrix composites by pressure infiltration method with liquid metal alloys.Design/methodology/approach: Ceramic preforms were manufactured by the sintering method of Al2O3 powder with addition of pore forming agent. The preform material consists of powder Alcoa Al2O3 CL 2500, however, as...

  9. High energy transmission of Al2O3 doped with light transition metals

    KAUST Repository

    Schuster, Cosima

    2012-01-31

    The transmission of transparent colored ceramics based on Al2O3doped with light transition metals is measured in the visible and infrared range. To clarify the role of the dopands we perform ab initiocalculations. We discuss the electronic structure and present optical spectra obtained in the independent particle approximation. We argue that the gross spectral features of Co- and Ni-doped Al2O3 samples are described by our model, while the validity of the approach is limited for Cr-doped Al2O3.

  10. Finite element analysis of WC-Al2O3 composites

    Science.gov (United States)

    Patel, Satyanarayan; Vaish, Rahul

    2014-02-01

    Object oriented finite element analysis (OOF2) is used to estimate the thermal and mechanical properties of WC-Al2O3 composites. In the present work, five compositions of 10%, 20%, 30%, 40% and 50% Al2O3 (by volume) are studied. Young's modulus, thermal conductivity and thermal expansion coefficient are estimated using OOF2 and compared with other known analytical methods. Stress and strain contours are plotted to study the thermal and mechanical behavior of composites. It is found that the stresses are largely concentrated at the interfaces of the WC-Al2O3 phases.

  11. Support Effects on Thiophene Hydrodesulfurization over Co-Mo-Ni/Al2O3 and Co-Mo-Ni/TiO2-Al2O3 Catalysts

    Institute of Scientific and Technical Information of China (English)

    刘超; 周志明; 黄永利; 程振民; 袁渭康

    2014-01-01

    Hierarchically macro-/mesoporous structured Al2O3 and TiO2-Al2O3 materials were used as supports to prepare novel Co-Mo-Ni hydrodesulfurization (HDS) catalysts. A commercial Co-Mo-Ni/Al2O3 catalyst without macroporous channels was taken as a reference. The catalysts were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive spectrometry (EDS), N2 adsorption-desorption, X-ray diffraction (XRD), and temperature programmed reduction (TPR). The apparent activities of the hierarchi-cally porous catalysts for thiophene HDS were superior to those of the commercial catalyst, which was mainly as-cribed to the diffusion-enhanced effect of the hierarchically bimodal pore structure. The addition of titania to alu-mina in the support helped to weaken the interaction between the active phase and the support, and as a result, the novel Co-Mo-Ni/TiO2-Al2O3 catalyst with a low titania loading (28%, by mass) in the support exhibited high HDS activities, even without presulfiding treatment. However, the catalyst with a high titania loading (61%, by mass) showed much lower activities, which was mostly caused by its low surface area and pore volume as well as the non-uniform distribution of titania and alumina. The kinetic analysis further demonstrated the support effects on HDS activities of the catalysts.

  12. Development of free-standing InGaN LED devices on Al2O3/Si substrate by wet etching

    International Nuclear Information System (INIS)

    Free-standing InGaN-based LEDs grown on Al2O3/Si (1 1 1) have been achieved using selective area wet etching. Conventional device design was used for LED fabrication, in which p-type and n-type contacts are located at the same side of the epilayers. These LED devices were bonded to a dual in-line package (DIP), and epoxy was used to protect the front side of the epilayers as well as the bonding wires. The silicon substrate was selectively removed by wet etching while the chip was mounted in a DIP which prevented the thin film from cracking or warping. No significant change in electrical characteristics, peak emission wavelength or EL intensity versus drive current was observed. The substrate-removal process and the challenges involved are discussed. Such packaging techniques could be beneficial for commercial-scale production of InGaN-based LEDs grown on silicon substrates.

  13. Effects of Al2O3 Particulates on the Thickness of Reaction Layer of Al2O3 Joints Brazed with Al2O3-Particulate-Contained Composite Filler Materials

    Institute of Scientific and Technical Information of China (English)

    Jianguo YANG; Jingwei WU; Hongyuan FANG

    2003-01-01

    In order to understand the rate-controlling process for the interfacial layer growth of brazing joints brazed with activecomposite filler materials, the thickness of brazing joints brazed with conventional active filler metal and activecomposite filler materials with different volume fraction of Al2O3 particulate was studied. The experimental resultsindicate although there are Al2O3 particulates added into active filler metals, the time dependence of interfacial layergrowth is t2 as described by Fickian law for the joints brazed with conventional active filler metal. It also shows thatthe key factor affecting the interfacial layer growth is the volume fraction of alumina in the composite filler materialcompared with the titanium weight fraction in the filler material.

  14. Experiments on thermal interactions: Tests with Al2O3 droplets and water

    International Nuclear Information System (INIS)

    Within the analysis of severe highly hypothetical fast breeder accidents the consequences of a fuel-coolant interaction have to be considered, i.e. the thermal interaction between hot molten fuel and sodium. To improve principal knowledge on the fragmentation process during the interaction of a hot droplet with a cold fluid, a series of experiments was performed with single droplets of molten Al2O3 as the hot liquid and water as the cold and easily volatile fluid. To initiate fragmentation of the droplet pressure pulses of up to 1 MPa were generated in the water by a magnetic hammer. The events were filmed by a high speed camera with up to 105 pictures per second. Details of the interactions can be deduced from the films and from the pressure histories. The existence of a vapour trail in all experiments indicates complex heat and mass transfer processes occurring in the vapour film spontaneously formed between droplet and cold fluid. Fragmentation was initiated by local events in the vapour trail area. (orig.)

  15. Anomalously high thermoelectric power factor in epitaxial ScN thin films

    DEFF Research Database (Denmark)

    Kerdsongpanya, Sit; Van Nong, Ngo; Pryds, Nini;

    2011-01-01

    Thermoelectric properties of ScN thin films grown by reactive magnetron sputtering on Al2O3(0001) wafers are reported. X-ray diffraction and elastic recoil detection analyses show that the composition of the films is close to stoichiometry with trace amounts (∼1 at. % in total) of C, O, and F. We...

  16. PREPARATION OF CUO/γ-Al2O3 CATALYSTS FOR CATALYTIC COMBUSTION VOCS VIA PLASMA

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    CuO/γ-Al2O3 catalysts were prepared by plasma treatment and conventional impregnation methods. The catalytic combustion of two kinds of volatile organic compounds (VOCs), toluene and benzene, were carried out over these CuO/γ-Al2O3 catalysts. The surface properties of these catalysts were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The experimental results showed that in catalytic combustion the activity of the CuO/γ-Al2O3 catalyst prepared via plasma was much higher than that of the CuO/γ-Al2O3 catalyst prepared by conventional impregnation method. XRD results showed that an enhanced dispersion had been achieved with the plasma treatment. SEM results indicated that the size became much smaller and the surface became more uniform with the plasma treatment.

  17. Thermal shock fatigue behavior of TiC/Al2O3 composite ceramics

    Institute of Scientific and Technical Information of China (English)

    SI Tingzhi; LIU Ning; ZHANG Qingan; YOU Xianqing

    2008-01-01

    The thermal shock fatigue behaviors of pure hot-pressed alumina and 30 wt. % TiC/Al2O3 composites were studied. The effect of TiC and Al2O3 starting particle size on the mechanical properties of the composites was discussed. Indentation-quench test was conducted to evaluate the effect of thermal fatigue temperature difference (ΔT) and number of thermal cycles (N) on fatigue crack growth (Δα). The mechanical properties and thermal fatigue resistance of TiC/Al2O3 composites are remarkably improved by the addition of TiC. The thermal shock fatigue of monolithic alumina and TiC/Al2O3 composites is due to a "true" cycling effect (thermal fatigue). Crack deflection and bridging are the predominant reasons for the improvement of thermal shock fatigue resistance of the composites.

  18. Magnetic Properties and Activity of Pt-Er/γ-Al2O3 Catalysts

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A series of Pt-Er/γ-Al2O3 catalysts containing 0.5%(mass fraction) platinum and 0.05%-1.5% Er were prepared by impregnation of γ-Al2O3 supported with different concentrations of erbium chloride solution. The surface properties of the catalysts were studied by methods of temperature programmed reduction and temperature programmed desorption. The magnetic behavior of Pt-Er-γ-Al2O3 catalysts were studied with a Faraday magnetic balance and the results show that the addition of Er can affect the surface properties, the catalytic activities, and magnetic behavior of the reforming catalysts. It is found that there is a corresponding relationship between the susceptibility and selectivity of Pt-Er-γ-Al2O3 catalysts. The experimental results show that Er plays the role of electron promoter.

  19. Research on Surface Modification of 96 Al2O3 by Ni Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-hong; SUN Zhi; ZHU Xin; WANG Zhen-zhong

    2006-01-01

    A matrix of 96 Al2O3 ceramics was implanted with Ni ion of different dosages and energies using a MEVVA implanter. Then metallic structures of copper were made on the implanted ceramics, by using selective electroless copper plating. In addition, the characteristics and microstructure of the implanted layer were studied by using the SEM, RBS and XPS. The results show that: 1) the implanted Ni exits as Ni0 , Ni2+, and Ni3+ in the surface of Al2O3 and metal Ni particles precipitate on ceramics during implantation; 2) the concentration of Ni submits to the Gauss distribution along the direction of implantation on the surface of Al2O3 and high Ni concentration on the surface can be obtained if the Ni is implanted with low energy and a high dosage and 3) Ni ion implantation can activate the surface of Al2O3 and induce electroless copper plating on the ceramics.

  20. Influence of Synthesized Super Al2O3 Powder on the Properties of Alumina Castable

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong; PENG Dayan; WEN Hongjie

    2003-01-01

    The influence of three different Al2O3 powder on self-flowing alumina castable was studied. Maximum compaction of sample was computed by Andresen Equation. The result showed that the Al2O3 powder, which has much smaller particle size ,could improve the microstructure and the mechanical properties of castable under room temperature and high temperature. With the same powder size,the room temperature strength of the castable added with Al2O3 powder proPerties of which were altered by adding mineralizing agent, was higher than that of the castable added with common Al2O3 powder, but the flowability of these three different castable was almost the same.

  1. Oxidation of Al2O3 continuous fiber-reinforced/NiAl composites

    Science.gov (United States)

    Doychak, J.; Nesbitt, J. A.; Noebe, R. D.; Bowman, R. R.

    1992-01-01

    The 1200 C and 1300 C isothermal and cyclic oxidation behavior of Al2O3 continuous fiber-reinforced/NiAl composites were studied. Oxidation resulted in formation of Al2O3 external scales in a similar manner as scales formed on monolithic NiAl. The isothermal oxidation of an Al2O3/NiAl composite resulted in oxidation of the matrix along the fiber/matrix interface near the fiber ends. This oxide acted as a wedge between the fiber and the matrix, and, under cyclic oxidation conditions, led to further oxidation along the fiber lengths and eventual cracking of the composite. The oxidation behavior of composites in which the Al2O3 fibers were sputter coated with nickel prior to processing was much more severe. This was attributed to open channels around the fibers which formed during processing, most likely as a result of the diffusion of the nickel coating into the matrix.

  2. Preparation and formation mechanism of Al2O3 nanoparticles by reverse microemulsion

    Institute of Scientific and Technical Information of China (English)

    HUANG Ke-long; YIN Liang-guo; LIU Su-qin; LI Chao-jian

    2007-01-01

    Al2O3 nanoparticles were prepared by polyethylene glycol octylphenyl ether(Triton X-100)/n-butyl alcohol/cyclohexane/ water W/O reverse microemulsion. The proper calcination temperature was determined at 1 150 ℃ by thermal analysis of the precursor products. The structures and morphologies of Al2O3 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy and UV-Vis spectra. The influences of mole ratio of water to surfactant on the morphologies and the sizes of the Al2O3 nanoparticles were studied. With the increase of surfactant content, the particles size becomes larger. The agglomeration of nanoparticles was solved successfully. And the formation mechanisms of Al2O3 nanoparticles in the reverse microemulsion were also discussed.

  3. Sintering densification and properties of Al2O3/PSZ(3Y) ceramic composites

    Institute of Scientific and Technical Information of China (English)

    马伟民; 修稚萌; 闻雷; 孙旭东; 铁维麟

    2004-01-01

    The content of partially stabilized zirconia has remarkable influence on densification and mechanical properties of Al2 O3/PSZ(3Y) ceramic composites. When 15%PSZ(3Y) is added to Al2 O3, after vacuum sintering for 2h at 1 550 ℃, the fracture toughness and bending strength of the Al2O3/PSZ(3Y) ceramic composite reaches 8.2properties was investigated. The change of rn-ZrO2 and t-ZrO2 phases content before and after fracture was measured by X-ray diffraction quantitative phase analysis. It is confirmed that improvement in bending strength and fracture toughness of the Al2O3/PSZ(3Y) ceramic composite is due to the phase transformation toughening mechanism of PSZ(3Y).

  4. Fabrication of Al2O3/glass/Cf Composite Substrate with High Thermal Conductivity

    Science.gov (United States)

    Wang, S. X.; Liu, G. S.; Ouyang, X. Q.; Wang, Y. D.; Zhang, D.

    2016-02-01

    In this paper, carbon fiber with high thermal conductivity was introduced into the alumina-based composites. To avoid oriented alignment of carbon fibers (Cf) and carbothermal reactions during the sintering process, the Al2O3/glass/Cf substrate was hot-pressed under a segmental-pressure procedure at 1123 K. Experimental results show that carbon fibers randomly distribute and form a bridging structure in the matrix. The three-dimensional network of Cf in Al2O3/glass/Cf substrate brings excellent heat conducting performance due to the heat conduction by electrons. The thermal conductivity of Al2O3/30%glass/30%Cf is as high as 28.98 W mK-1, which is 4.56 times larger than that of Al2O3/30%glass.

  5. Methane Coupling Using Hydrogen Plasma and Pt/γ-Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In this paper, methane coupling at ambient temperature, under atmospheric pressure and in the presence of hydrogen was firstly investigated by using pulse corona plasma and Pt/γ-Al2O3 catalyst. Experimental results showed that Pt/γ-Al2O3 catalyst has catalytic activity for methane coupling to C2H4. Over sixty percent of outcomes of C2 hydrocarbons were detected to be ethylene.

  6. Preparation of ultrafine a-Al2O3 using precipitation-azeotropic distillation method

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Ammonium aluminum carbonate hydroxide (AACH) was prepared by a precipitation-azeotropic distillation method,which uses aluminum sulfate as the Al source and ammonium carbonate as the precipitant.Then,AACH was calcined into ultrafine α-Al2O3 powder.The factors that influence the dispersion property of ultrafine α-Al2O3 powder are discussed in this paper,such as the methods of adding materials,surfactant,and drying methods.The changes of the structure and property of ultrafine alumina in the thermal treatment process are also studied.The morphological structure and properties of AACH are characterized by DTA/TGA,SEM,XRD,and ICP measurements.The results show that ultrafine α-Al2O3 powder with a uniform particle size and well-distributed property can be synthesized only after aluminum sulfate atomizes into ammonium carbonate,proper amount of PEG1000 is added as the dispersant,and the product is treated by azeotropic distillation.The phase transformation of alumina during the calcination process can be described as amorphous Al2O3→γ-Al2O3→θ-Al2O3→α-Al2O3.The crystal grain size and density of ultrafine alumina powder increase with the increase of the calcination temperature.After AACH has been calcined at 1200℃ for 2 h,the ultrafine α-Al2O3 with uniform particle size,spherical shape,and more than 99.97% purity is obtained and its powder is well dispersed.

  7. TEM study of a hot-pressed Al2O3-NbC composite material

    OpenAIRE

    Wilson Acchar; Carlos Alberto Cairo; Ana Maria Segadães

    2005-01-01

    Alumina-based composites have been developed in order to improve the mechanical properties of the monolithic matrix and to replace the WC-Co material for cutting tool applications. Al2O3 reinforced with refractory carbides improves hardness, fracture toughness and wear resistance to values suitable for metalworking applications. Al2O3-NbC composites were uniaxially hot-pressed at 1650 °C in an inert atmosphere and their mechanical properties and microstructures were analyzed. Sintered density...

  8. Equivalent oxide thickness scaling of Al2O3/Ge metal-oxide-semiconductor capacitors with ozone post oxidation

    Institute of Scientific and Technical Information of China (English)

    Sun Jia-Bao; Yang Zhou-Wei; Geng Yang; Lu Hong-Liang; Wu Wang-Ran; Ye Xiang-Dong; David Zhang Wei

    2013-01-01

    Aluminum-oxide films deposited as gate dielectrics on germanium (Ge) by atomic layer deposition were post oxidized in an ozone atmosphere.No additional interracial layer was detected by the high-resolution cross-sectional transmission electron microscopy and X-ray photoelectron spectroscopy measurements made after the ozone post oxidation (OPO) treatment.Decreases in the equivalent oxide thickness of the OPO-treated Al2O3/Ge MOS capacitors were confirmed.Furthermore,a continuous decrease in the gate leakage current was achieved with increasing OPO treatment time.The results can be attributed to the film quality having been improved by the OPO treatment.

  9. In situ fabrication and microstructure of Al2O3 particles reinforced aluminum matrix composites

    International Nuclear Information System (INIS)

    Al2O3p/Al composites were prepared by direct melt reaction process. The thermodynamics of in situ chemical reactions between molten aluminum and CeO2 powder was studied. The XRD results show that the components of the as-prepared composites consist of Al2O3 and Al phases. For the as-cast composite specimens, SEM, EDX, TEM and SAD were used to analyze the reinforcement phases and interface characters of composites. The results show that the in situ generated Al2O3 particles, whose sizes are 100-200 nm, have various irregular shapes and disperse uniformly in matrix. TEM observation shows that the interface between particle and matrix is clean. Furthermore, there is no fixed orientation relationship between Al2O3 particles and aluminum matrix. Only [12-bar 10]//[111] orientation parallel relationship with low exponent is found. Therefore, the composites have isotropic properties. Besides characters mentioned above, there are large amount of high density dislocations and the generated extensive fine subgrains around Al2O3 particles. These features are favorable for improving composite performances. As a result, the composites are comprehensively strengthened not only by Al2O3 particles, but also by the high density dislocations and fine subgrains.

  10. Characteristic evaluation of Al2O3/CNTs hybrid materials for micro-electrical discharge machining

    Institute of Scientific and Technical Information of China (English)

    Hyun-Seok TAK; Chang-Seung HA; Ho-Jun LEE; Hyung-Woo LEE; Young-Keun JEONG; Myung-Chang KANG

    2011-01-01

    The characteristic evaluation of aluminum oxide (Al2O3)/carbon nanotubes (CNTs) hybrid composites for micro-electrical discharge machining (EDM) was described. Alumina matrix composites reinforced with CNTs were fabricated by a catalytic chemical vapor deposition method. Al2O3 composites with different CNT concentrations were synthesized. The electrical characteristic of Al2O3/CNTs composites was examined. These composites were machined by the EDM process according to the various EDM parameters, and the characteristics of machining were analyzed using field emission scanning electron microscope (FESEM). The electrical conductivity has a increasing tendency as the CNTs content is increased and has a critical point at 5% Al2O3 (volume fraction). In the machining accuracy, many tangles of CNT in Al2O3/CNTs composites cause violent spark. Thus, it causes the poor dimensional accuracy and circularity. The results show that conductivity of the materials and homogeneous distribution of CNTs in the matrix are important factors for micro-EDM of Al2O3/CNTs hybrid composites.

  11. Ion conduction and relaxation in PEO-LiTFSI-Al2O3 polymer nanocomposite electrolytes

    International Nuclear Information System (INIS)

    Ion conduction and relaxation in PEO-LiTFSI-Al2O3 polymer nanocomposite electrolytes have been studied for different concentrations of Al2O3 nanoparticles. X-ray diffraction and differential scanning calorimetric studies show that the maximum amorphous phase of PEO is observed for PEO-LiTFSI embedded with 5 wt. % Al2O3. The maximum ionic conductivity ∼3.3 × 10−4 S cm−1 has been obtained for this composition. The transmission electron microscopic image shows a distribution of Al2O3 nanoparticles in all compositions with size of <50 nm. The temperature dependence of the ionic conductivity follows Vogel-Tamman-Fulcher nature, indicating a strong coupling between ionic and polymer chain segmental motions. The scaling of the ac conductivity implies that relaxation dynamics follows a common mechanism for different temperatures and Al2O3 concentrations. The imaginary modulus spectra are asymmetric and skewed toward the high frequency sides of the maxima and analyzed using Havriliak-Negami formalism. The temperature dependence of the relaxation time obtained from modulus spectra also exhibits Vogel-Tamman-Fulcher nature. The values of the stretched exponent obtained from Kohlrausch-Williams-Watts fit to the modulus data are fairly low, suggesting highly non-exponential relaxation for all concentrations of Al2O3 in these electrolytes

  12. FAST TRACK COMMUNICATION: Self-patterned aluminium interconnects and ring electrodes for arrays of microcavity plasma devices encapsulated in Al2O3

    Science.gov (United States)

    Kim, K. S.; Park, S.-J.; Eden, J. G.

    2008-01-01

    Automatic formation of Al interconnects and ring electrodes, fully encapsulated by alumina, in planar arrays of Al2O3/Al/Al2O3 microcavity plasma devices has been accomplished by electrochemical processing of Al foil. Following the fabrication of cylindrical microcavities (50-350 µm in diameter) in 127 µm thick Al foil, virtually complete anodization of the foil yields azimuthally symmetric Al electrodes surrounding each cavity and interconnects between adjacent microcavities that are produced and simultaneously buried within a transparent Al2O3 film without the need for conventional patterning techniques. The diameter and pitch of the microcavities prior to anodization, as well as the anodization process parameters, determine which of the microcavity plasma devices in a one- or two-dimensional array are connected electrically. Data presented for 200 µm diameter cavities with a pitch of 150-225 µm illustrate the patterning of the interconnects and electrode connectivity after 4-10 h of anodization in oxalic acid. Self-patterned, linear arrays comprising 25 dielectric barrier devices have been excited by a sinusoidal or bipolar pulse voltage waveform and operated in 400-700 Torr of rare gas. Owing to the electrochemical conversion of most of the Al foil into Al2O3, the self-formed arrays exhibit an areal capacitance ~82% lower than that characteristic of previous Al/Al2O3 device arrays (Park et al 2006 J. Appl. Phys. 99 026107).

  13. Nano-oxide thin films deposited via atomic layer deposition on microchannel plates.

    Science.gov (United States)

    Yan, Baojun; Liu, Shulin; Heng, Yuekun

    2015-01-01

    Microchannel plate (MCP) as a key part is a kind of electron multiplied device applied in many scientific fields. Oxide thin films such as zinc oxide doped with aluminum oxide (ZnO:Al2O3) as conductive layer and pure aluminum oxide (Al2O3) as secondary electron emission (SEE) layer were prepared in the pores of MCP via atomic layer deposition (ALD) which is a method that can precisely control thin film thickness on a substrate with a high aspect ratio structure. In this paper, nano-oxide thin films ZnO:Al2O3 and Al2O3 were prepared onto varied kinds of substrates by ALD technique, and the morphology, element distribution, structure, and surface chemical states of samples were systematically investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoemission spectroscopy (XPS), respectively. Finally, electrical properties of an MCP device as a function of nano-oxide thin film thickness were firstly studied, and the electrical measurement results showed that the average gain of MCP was greater than 2,000 at DC 800 V with nano-oxide thin film thickness approximately 122 nm. During electrical measurement, current jitter was observed, and possible reasons were preliminarily proposed to explain the observed experimental phenomenon.

  14. Electrical properties and interfacial issues of high-k/Si MIS capacitors characterized by the thickness of Al2O3 interlayer

    Science.gov (United States)

    Wang, Xing; Liu, Hongxia; Fei, Chenxi; Zhao, Lu; Chen, Shupeng; Wang, Shulong

    2016-06-01

    A thin Al2O3 interlayer deposited between La2O3 layer and Si substrate was used to scavenge the interfacial layer (IL) by blocking the out-diffusion of substrate Si. Some advantages and disadvantages of this method were discussed in detail. Evident IL reduction corroborated by the transmission electron microscopy results suggested the feasibility of this method in IL scavenging. Significant improvements in oxygen vacancy and leakage current characteristics were achieved as the thickness of Al2O3 interlayer increase. Meanwhile, some disadvantages such as the degradations in interface trap and oxide trapped charge characteristics were also observed.

  15. Determination of differential dose rates in a mixed beta and gamma field using shielded Al2O3:C : Results of Monte Carlo modelling

    DEFF Research Database (Denmark)

    Aznar, M.C.; Nathan, R.; Murray, A.S.;

    2003-01-01

    Mixed beta and gamma heterogeneous radiation fields are found in many circumstances, ranging from retrospective dosimetry to medical therapy treatments. It can be very important to provide a direct measurement of the contribution to dose rate from beta particles and gamma rays separately...... outline the results of our modelling of the most appropriate encapsulation for Al2O3: C luminescence dosimeters when used to measure the dose rate from natural radiation fields. We consider a configuration where one Al2O3: C chip of a pair is enclosed in a beta-thin light-tight package (which would allow...

  16. Electrical properties and interfacial issues of high-k/Si MIS capacitors characterized by the thickness of Al2O3 interlayer

    Directory of Open Access Journals (Sweden)

    Xing Wang

    2016-06-01

    Full Text Available A thin Al2O3 interlayer deposited between La2O3 layer and Si substrate was used to scavenge the interfacial layer (IL by blocking the out-diffusion of substrate Si. Some advantages and disadvantages of this method were discussed in detail. Evident IL reduction corroborated by the transmission electron microscopy results suggested the feasibility of this method in IL scavenging. Significant improvements in oxygen vacancy and leakage current characteristics were achieved as the thickness of Al2O3 interlayer increase. Meanwhile, some disadvantages such as the degradations in interface trap and oxide trapped charge characteristics were also observed.

  17. Impacts of Annealing Conditions on the Flat Band Voltage of Alternate La2O3/Al2O3 Multilayer Stack Structures

    Science.gov (United States)

    Feng, Xing-Yao; Liu, Hong-Xia; Wang, Xing; Zhao, Lu; Fei, Chen-Xi; Liu, He-Lei

    2016-09-01

    The mechanism of flat band voltage (VFB) shift for alternate La2O3/Al2O3 multilayer stack structures in different annealing condition is investigated. The samples were prepared for alternate multilayer structures, which were annealed in different conditions. The capacitance-voltage (C-V) measuring results indicate that the VFB of samples shift negatively for thinner bottom Al2O3 layer, increasing annealing temperature or longer annealing duration. Simultaneously, the diffusion of high- k material to interfaces in different multilayer structures and annealing conditions is observed by X-ray photoelectron spectroscopy (XPS). Based on the dipole theory, a correlation between the diffusion effect of La towards bottom Al2O3/Si interface and VFB shift is found. Without changing the dielectric constant k of films, VFB shift can be manipulated by controlling the single-layer cycles and annealing conditions of alternate high- k multilayer stack.

  18. Resistive Switching in Al/Al2O3/TiO2/Al/PES Flexible Device for Nonvolatile Memory Application.

    Science.gov (United States)

    Lin, Chun-Chieh; Lee, Wang-Ying; Lee, Han-Tang

    2016-05-01

    Resistive switching memory devices with superior properties are possibly used in next-generation nonvolatile memory to replace the flash memory. In addition, flexible electronics has also attracted much attention because of its light-weight and flexibility. Therefore, an Al/Al2O3/TiO2/Al/PES flexible resistive switching memory is employed in this study. The resistive switching characteristics and stability of the flexible device are improved by inserting the Al2O3 film. The resistive switching of the flexible device can be repeated over hundreds of times after the bending test. A possible resistive switching model of the flexible device is also proposed. In addition, the non-volatility of the flexible device is demonstrated. Based on our research results, the proposed Al2O3/TiO2-based resistive switching memory is possibly used in next-generation flexible electronics and nonvolatile memory applications. PMID:27483828

  19. Studies on oxidation and deuterium permeation behavior of a low temperature α-Al2O3-forming Fesbnd Crsbnd Al ferritic steel

    Science.gov (United States)

    Xu, Yu-Ping; Zhao, Si-Xiang; Liu, Feng; Li, Xiao-Chun; Zhao, Ming-Zhong; Wang, Jing; Lu, Tao; Hong, Suk-Ho; Zhou, Hai-Shan; Luo, Guang-Nan

    2016-08-01

    To evaluate the capability of Fesbnd Crsbnd Al ferritic steels as tritium permeation barrier in fusion systems, the oxidation behavior together with the permeation behavior of a Fesbnd Crsbnd Al steel was investigated. Gas driven permeation experiments were performed. The permeability of the oxidized Fesbnd Crsbnd Al steel was obtained and a reduced activation ferritic/martensitic steel CLF-1 was used as a comparison. In order to characterize the oxide layer, SEM, XPS, TEM, HRTEM were used. Al2O3 was detected in the oxide film by XPS, and HRTEM showed that Al2O3 in the α phase was found. The formation of α-Al2O3 layer at a relatively low temperature may result from the formation of Cr2O3 nuclei.

  20. Impacts of Annealing Conditions on the Flat Band Voltage of Alternate La2O3/Al2O3 Multilayer Stack Structures.

    Science.gov (United States)

    Feng, Xing-Yao; Liu, Hong-Xia; Wang, Xing; Zhao, Lu; Fei, Chen-Xi; Liu, He-Lei

    2016-12-01

    The mechanism of flat band voltage (VFB) shift for alternate La2O3/Al2O3 multilayer stack structures in different annealing condition is investigated. The samples were prepared for alternate multilayer structures, which were annealed in different conditions. The capacitance-voltage (C-V) measuring results indicate that the VFB of samples shift negatively for thinner bottom Al2O3 layer, increasing annealing temperature or longer annealing duration. Simultaneously, the diffusion of high-k material to interfaces in different multilayer structures and annealing conditions is observed by X-ray photoelectron spectroscopy (XPS). Based on the dipole theory, a correlation between the diffusion effect of La towards bottom Al2O3/Si interface and VFB shift is found. Without changing the dielectric constant k of films, VFB shift can be manipulated by controlling the single-layer cycles and annealing conditions of alternate high-k multilayer stack. PMID:27620192

  1. Preface: Advanced Thin Film Developments and Nano Structures

    Institute of Scientific and Technical Information of China (English)

    Ray Y.Lin

    2005-01-01

    @@ In this special issue, we invited a few leading materials researchers to present topics in thin films, coatings, and nano structures. Readers will find most recent developments in topics, including recent advances in hard, tough, and low friction nanocomposite coatings; thin films for coating nanomaterials; electroless plating of silver thin films on porous Al2O3 substrate; CrN/Nano Cr interlayer coatings; nano-structured carbide derived carbon (CDC) films and their tribology; predicting interdiffusion in high-temperature coatings; gallium-catalyzed silica nanowire growth; and corrosion protection properties of organofunctional silanes. Authors are from both national laboratories and academia.

  2. Pressure-Induced Shifts of Energy Spectra of α-Al2O3:Mn4+

    Institute of Scientific and Technical Information of China (English)

    MA Dong-Ping,; CHEN Ju-Rong; MA Ning

    2002-01-01

    By making use of the diagonalization of the complete d3 energy matrix in a trigonally distorted cubic-field and the theory of pressure-induced shifts (PS) of energy spectra, the whole energy spectrum of α-Al2 O3 :Mn4+ and PS of levels have been calculated. All the calculated results are in excellent agreement with the experimental data. The comparison between the results ofα-AlO3:Mn4+ and ruby has been made. It is found that on one hand, R1-line and R2line PS of α-Al2O3:Mn4+ and ruby are linear in pressure over 0 ~ 100 kbar, and their values of the principal parameter for PS are very close to each other. On the other hand, the sensitivities of R1-line and R2-line PS of α-Al2O3:Mn4+are higher than those of ruby respectively, which comes mainly from the difference between the values of parameters at normal pressure of two crystals; moreover, the expansion ofd-electron wavefunctions of α-Al2 O3 :Mn4+ with compression is slightly larger than the one of ruby, and the effective charge experienced by d-electrons of α-Al2O3:Mn4+ decreases with compression more rapidly than the one of ruby. In the final analysis, all these can be explained in terms of the facts that the two crystals are doped α-Al2O3 with two isoelectronic ions; the strengths of the crystal field and covalency of α-Al2O3 :Mn4+ are larger than those of ruby respectively, due to the charge of Mn4+ to be larger than that of Cr3+.

  3. Mechanical Properties and Electrical Conductivity of TiN-Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    TIN-Al2O3 composite powders with different TiN contents (0,10 vol%,20 vol%,30 vol% and 40 vol%) were prepared with micrometer TiN and α-Al2O3 powder (their purities were 99%) as starting materials by wet ball milling for 5 h.TiN-Al2O3 com-posite were then prepared by pressing the above composite powders,drying at 200 ℃ for 12 h and firing at 1 800 ℃ for 3 h in nitrogen atmosphere in hot-pressing furnace.The influences of TiN content on mechanical properties and electrical conductivity of TiN-Al2O3 com-posites were studied.The results showed that the me-chanical properties of the composite increased with TiN content increasing,while the resistivity of composites de-creased.A composite with 40% TiN had 498 MPa ben-ding strength,4.285 MPa·m1/2 fracture toughness,1.34×10-3 Ω·cm resistivity.The SEM analysis showed that the fine TiN crystals distributed among the crystal boundary of Al2O3 matrix.They bonded together forming a net-like structure which played a role of re-straining Al2O3 grains from growing up,toughening and strengthening,so the mechanical properties of TIN -Al2O3 composite were enhanced.

  4. The mechanical properties of a nanocrystalline Al2O3/a-Al2O3 composite coating measured by nanoindentation and Brillouin spectroscopy

    International Nuclear Information System (INIS)

    In this work, ellipsometry, Brillouin spectroscopy and nanoindentation are combined to assess the mechanical properties of a nanocrystalline Al2O3/a-Al2O3 composite coating with high accuracy and precision. The nanocomposite is grown by pulsed laser deposition at either room temperature or 600 °C. The adhesive strength is evaluated by nanoscratch tests. In the room temperature process the coating attains an unusual combination of compactness, strong interfacial bonding, moderate stiffness (E = 195 ± 9 GPa and ν = 0.29 ± 0.02) and significant hardness (H = 10 ± 1 GPa), resulting in superior plastic behavior and a relatively high ratio of hardness to elastic modulus (H/E = 0.049). These features are correlated to the nanostructure of the coating, which comprises a regular dispersion of ultrafine crystalline Al2O3 nanodomains (2–5 nm) in a dense and amorphous alumina matrix, as revealed by transmission electron microscopy. For the coating grown at 600 °C, strong adhesion is also observed, with an increase of stiffness and a significant enhancement of hardness (E = 277 ± 9 GPa, ν = 0.27 ± 0.02 and H = 25 ± 1 GPa), suggesting an outstanding resistance to wear (H/E = 0.091)

  5. New routes for improving adhesion at the metal/α-Al2O3(0001) interface

    OpenAIRE

    Cavallotti, Rémi,; Le, Ha-Linh Thi; Goniakowski, Jacek; Lazzari, Rémi; Jupille, Jacques; Koltsov, Alexey; Loison, Didier

    2015-01-01

    With the advent of new steel grades, the galvanic protection by zinc coating faces a new paradigm. Indeed, enrichment in strengthening elements prone to oxidation such as Al, Mn, and Si, leads to the formation of oxide films that are poorly wet by zinc. We study herein routes for improvement of adhesion at the model Zn/α-Al 2 O 3 interface by metallic additions. As a first step, with help of ab initio results on adsorption characteristics of transition metal adatoms at α-alumina surfaces, we ...

  6. Tunneling planer Hall effect in Ni81Fe19/Al2O3/Nix Fe1-x junction

    Institute of Scientific and Technical Information of China (English)

    陈慧余; 冯永嘉; 熊曹水

    1999-01-01

    Tunneling planer Hall (TPH) effect in Ni81Fe19/Al2O3/NixFe1-x trilayer junction is different from general planer Hall effect in single-layer film or two-layer junction. This effect concerns the spin-polarized transport, so that the TPH voltage depends on the angle between magnetic vectors of two ferromagnetic layers. The TPH effect is reported to be influenced by composition and magnetic properties of FM layers and the thickness of the insulating layer.

  7. Low-Temperature Process for Atomic Layer Chemical Vapor Deposition of an Al2O3 Passivation Layer for Organic Photovoltaic Cells.

    Science.gov (United States)

    Kim, Hoonbae; Lee, Jihye; Sohn, Sunyoung; Jung, Donggeun

    2016-05-01

    Flexible organic photovoltaic (OPV) cells have drawn extensive attention due to their light weight, cost efficiency, portability, and so on. However, OPV cells degrade quickly due to organic damage by water vapor or oxygen penetration when the devices are driven in the atmosphere without a passivation layer. In order to prevent damage due to water vapor or oxygen permeation into the devices, passivation layers have been introduced through methods such as sputtering, plasma enhanced chemical vapor deposition, and atomic layer chemical vapor deposition (ALCVD). In this work, the structural and chemical properties of Al2O3 films, deposited via ALCVD at relatively low temperatures of 109 degrees C, 200 degrees C, and 300 degrees C, are analyzed. In our experiment, trimethylaluminum (TMA) and H2O were used as precursors for Al2O3 film deposition via ALCVD. All of the Al2O3 films showed very smooth, featureless surfaces without notable defects. However, we found that the plastic flexible substrate of an OPV device passivated with 300 degrees C deposition temperature was partially bended and melted, indicating that passivation layers for OPV cells on plastic flexible substrates need to be formed at temperatures lower than 300 degrees C. The OPV cells on plastic flexible substrates were passivated by the Al2O3 film deposited at the temperature of 109 degrees C. Thereafter, the photovoltaic properties of passivated OPV cells were investigated as a function of exposure time under the atmosphere.

  8. Fabrication of low-loss channel waveguides in Al2O3 and Y2O3 layers by inductively coupled plasma reactive ion etching

    NARCIS (Netherlands)

    Bradley, J.D.B.; Ay, F.; Wörhoff, K.; Pollnau, M.

    2007-01-01

    Etching of amorphous Al2O3 and polycrystalline Y2O3 films has been investigated using an inductively coupled reactive ion etch system. The etch behaviour has been studied by applying various common process gases and combinations of these gases, including CF4/O2, BCl3, BCl3/HBr, Cl2, Cl2/Ar and Ar. T

  9. Low-Temperature Process for Atomic Layer Chemical Vapor Deposition of an Al2O3 Passivation Layer for Organic Photovoltaic Cells.

    Science.gov (United States)

    Kim, Hoonbae; Lee, Jihye; Sohn, Sunyoung; Jung, Donggeun

    2016-05-01

    Flexible organic photovoltaic (OPV) cells have drawn extensive attention due to their light weight, cost efficiency, portability, and so on. However, OPV cells degrade quickly due to organic damage by water vapor or oxygen penetration when the devices are driven in the atmosphere without a passivation layer. In order to prevent damage due to water vapor or oxygen permeation into the devices, passivation layers have been introduced through methods such as sputtering, plasma enhanced chemical vapor deposition, and atomic layer chemical vapor deposition (ALCVD). In this work, the structural and chemical properties of Al2O3 films, deposited via ALCVD at relatively low temperatures of 109 degrees C, 200 degrees C, and 300 degrees C, are analyzed. In our experiment, trimethylaluminum (TMA) and H2O were used as precursors for Al2O3 film deposition via ALCVD. All of the Al2O3 films showed very smooth, featureless surfaces without notable defects. However, we found that the plastic flexible substrate of an OPV device passivated with 300 degrees C deposition temperature was partially bended and melted, indicating that passivation layers for OPV cells on plastic flexible substrates need to be formed at temperatures lower than 300 degrees C. The OPV cells on plastic flexible substrates were passivated by the Al2O3 film deposited at the temperature of 109 degrees C. Thereafter, the photovoltaic properties of passivated OPV cells were investigated as a function of exposure time under the atmosphere. PMID:27483916

  10. Effect of fluoride additives on production and characterization of nano--Al2O3 particles

    Indian Academy of Sciences (India)

    F Mirjalili

    2014-12-01

    Nano--Al2O3 particles were synthesized by a sol–gel method using aqueous solutions of aluminum isopropoxide and 0.5 Maluminum nitrate. Sodium dodecylbenzenesulfonate (SDBS) was used as surfactant stabilizing agents. The solution was stirred for 48 h at 60 °C. The microstructural observation showed that surfactant with 48 h stirring time nanoscale -Al2O3 powder was produced at 1200 °C in the range of 20–30 nm in the presence of SDBS as a surfactant with 48 h stirring time. Temperature reduction of -Al2O3 formation has been achieved by introducing fluoride in the alumina precursor. The effects of ZnF2 additive and milling on the phase transformation as well as micrograph of the prepared -Al2O3 particles were investigated. The samples were characterized by different techniques such as X-ray diffraction, thermogravimetry analysis, differential scanning calorimetry, Fourier transform infrared spectra, scanning electron microscopy and transmission electron microscopy. Results indicated that using zinc fluoride (ZnF2) additive accompanied by milling led to retardation of the transformation temperature and modification of the alumina particle shape. The finest size for nonagglomerated nano-plate-like -Al2O3 particles (15–20 nm) was achieved at 950 °C.

  11. Elimination of formaldehyde over Cu-Al2O3 catalyst at room temperature

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chang-bin; SHI Xiao-yan; GAO Hong-wei; HE Hong

    2005-01-01

    Catalytic elimination of formaldehyde(HCHO) was investigated over Cu-Al2O3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface.With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD)showed that HCHO was completely oxidized into HCOOH over Cu-Al2 O3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO2 over the catalyst surface, and the deactivated Cu-Al2 O3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al2 O3, Cu dramatically lowered the decomposition temperature of HCOOH into CO2. It was shown that Cu-Al2 O3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.

  12. Synthesis, biocompatibility and mechanical properties of ZrO2-Al2O3 ceramics composites.

    Science.gov (United States)

    Nevarez-Rascon, Alfredo; González-Lopez, Santiago; Acosta-Torres, Laura Susana; Nevarez-Rascon, Martina Margarita; Orrantia-Borunda, Erasmo

    2016-01-01

    This study evaluated cell viability, microhardness and flexural strength of two ceramic composites systems (ZA and AZ), pure alumina and zirconia. There were prepared homogeneous mixtures of 78wt%Al2O3+20wt%3Y-TZP+2wt%Al2O3w (AZ) and 80wt%3YTZP+18wt%Al2O3+2wt%Al2O3w (ZA), as well as 3Y-TZP (Z), pure Al2O3 (A) and commercial monolithic 3Y-TZP (Zc). Also mouse fibroblast cells 3T3-L1 and a MTT test was carried out at 24, 48 and 72 h. The surfaces were observed with SEM and the microhardness and three-point flexural strength values were estimated. The absolute microhardness values were: A>AZ>Z>Zc>ZA. Flexural strength of Zc, Z, and ZA were around double than AZ and A. All groups showed high biocompatibility trough cell viability values at 24, 48 and 72 h. Factors like grain shape, grain size and homogeneous or heterogeneous grain distributions may play an important role in physical, mechanical and biological properties of the ceramic composites. PMID:27251994

  13. Elimination of formaldehyde over Cu-Al2O3 catalyst at room temperature.

    Science.gov (United States)

    Zhang, Chang-Bin; Shi, Xiao-Yan; Gao, Hong-Wei; He, Hong

    2005-01-01

    Catalytic elimination of formaldehyde (HCHO) was investigated over Cu-Al2O3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface. With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD) showed that HCHO was completely oxidized into HCOOH over Cu-Al2O3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO2 over the catalyst surface, and the deactivated Cu-Al2O3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al2O3, Cu dramatically lowered the decomposition temperature of HCOOH into CO2. It was shown that Cu-Al2O3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.

  14. Thin film Encapsulations of Flexible Organic Light Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Tsai Fa-Ta

    2016-01-01

    Full Text Available Various encapsulated films for flexible organic light emitting diodes (OLEDs were studied in this work, where gas barrier layers including inorganic Al2O3 thin films prepared by atomic layer deposition, organic Parylene C thin films prepared by chemical vapor deposition, and their combination were considered. The transmittance and water vapor transmission rate of the various organic and inorgabic encapsulated films were tested. The effects of the encapsulated films on the luminance and current density of the OLEDs were discussed, and the life time experiments of the OLEDs with these encapsulated films were also conducted. The results showed that the transmittance are acceptable even the PET substrate were coated two Al2O3 and Parylene C layers. The results also indicated the WVTR of the PET substrate improved by coating the barrier layers. In the encapsulation performance, it indicates the OLED with Al2O3 /PET, 1 pair/PET, and 2 pairs/PET presents similarly higher luminance than the other two cases. Although the 1 pair/PET encapsulation behaves a litter better luminance than the 2 pairs/PET encapsulation, the 2 pairs/PET encapsulation has much better life time. The OLED with 2 pairs/PET encapsulation behaves near double life time to the 1 pair encapsulation, and four times to none encapsulation.

  15. Laser diode induced white light emission of γ-Al2O3 nano-powders

    International Nuclear Information System (INIS)

    A broadband white light emission was observed ranging from 450 to 900 nm from nominally un-doped γ-Al2O3 nano-powders under 803.5 nm and 975 nm laser diode excitations. The white light emission has a strong dependence on both the environment pressure and the pumping laser power. We spectroscopically characterized this white light emission in a systematic way by collecting spectra, measuring decay- and rise patterns and changing parameters such as pumping power, pumping wavelength, environment temperature and pressure. - Highlights: • Nominally un-doped commercial γ-Al2O3 nanopowders were used. • We report the production of white light from nominally un-doped γ-Al2O3 nano-powders under laser diode excitation. • Some spectroscopic parameters of obtained white light emission were determined under a variety of conditions

  16. Corrosion behavior of Zn-Ni-Al2O3 composite coating

    Institute of Scientific and Technical Information of China (English)

    ZHENG Huanyu; AN Maozhong; LU Junfeng

    2006-01-01

    The corrosion behavior and anti-corrosion mechanism of the Zn-Ni-Al2O3 composite coating were investigated by SEM, EDS and XPS.The results indicate that the corrosion type of the Zn-Ni-Al2O3 coatings in neutral 5 wt.% NaCl solution is uniform corrosion.The presence of compact and uniformly dispersed nano alumina particles substantially inhibits the corrosion of Zn-Ni-Al2O3 composite coatings.In the initial corrosion stage, the corrosive products of Zn-Ni matrix form a compact ZnCl2·4Zn(OH)2 layer.With the development of corrosion, some nano alumina particles are embedded and form a Ni enrichment layer.In Ni enrichment layer, Ni presents as Ni and NiO.

  17. Sensitization by UV light of α-Al2O3:C polycrystalline detectors

    International Nuclear Information System (INIS)

    This paper describes an increase in sensitivity to gamma and beta radiation on α-Al2O3:C polycrystalline detector, which has been produced by a sol-gel process, following previous exposure to ultraviolet light. The increased sensitivity of the detector as a function of the exposure time and ultraviolet wavelength was studied. Since the main luminescent centers have emission peaks at different wavelengths, selective measurements of thermoluminescent emission intensity were done, in order to investigate the possible conversion of centers as a result of the exposition to ultraviolet light. Experimental results indicate that the nature and parameters of the luminescent centers in α-Al2O3:C sol-gel material can be very different of those in α-Al2O3:C single crystal. (author)

  18. FABRICATION OF Al/Al2O3 FGM ROTATING DISC

    Directory of Open Access Journals (Sweden)

    A. B. Sanuddin

    2012-06-01

    Full Text Available This study presents a method of fabricating a disc made of Al/Al2O3 functionally graded materials (FGM, using a powder metallurgy manufacturing process. The aim is to develop a processing method for a rotating disc made of FGM, by stacking the slurry, layer by layer in a radial direction. A three-layer functionally graded material of Al/Al2O3 is fabricated with compositions of 10, 20, 30 vol.% Al2O3. The ceramic composition increases from the discs inner (centre to the outer. The combination of these materials can offer the ability to withstand high temperature conditions whilst maintaining strength in extreme environments.

  19. Laser micromachining of CNT/Fe/Al2O3 nanocomposites

    Institute of Scientific and Technical Information of China (English)

    Kwang-Ryul KIM; Byoung-Deog CHOI; Jun-Sin YI; Sung-Hak CHO; Yong-Ho CHOA; Dong-Soo SHIN; Dong-Ho BAE; Myung-Chang KANG; Young-Keun JEONG

    2009-01-01

    CNT/Fe/Al2O3 mixed powders were synthesized from Fe/Al2O3 nanopowders using thermal CVD for the homogeneous dispersion of carbon nanotubes CNTs. CNTs consisted of MWNT, and the diameter was approximately 20-30 nm. After sintering, CNTs were homogenously located throughout Al2O3 grain boundary and were buckled. A femto-second laser installed with special optical systems was used for micromachining of the nanocomposites. The relationship between material ablation rate and energy fluence was theoretically investigated and compared with experimental results from cross-sectional SEM analysis. The nanocomposites which have higher content of CNT show a fairly good machining result due to its higher thermal conductivity and smaller grain size as well as lower light transmittance.

  20. Electrical conductivity studies on CuBr containing Al2O3 particles

    Science.gov (United States)

    Dubec, P. M.; Wagner, J. B., Jr.

    1984-01-01

    The conductivity of CuBr was studied and the role of a second phase, Al2O3, dispersed in CuBr was tested. CuBr melts at 493 C and exhibits three phases in the solid state. CuBr is a good ionic conductor with a transport number for copper ions of virtually unity with weighed proportions of the appropriate chemicals used. The CuBr materials were heated above melting point of CuBr, and the samples were sandwiched between copper electrodes. The ac conductivity, was determined at 1 kHz between 25 and 440 C depending on the sample. It was shown that at low temperatures, the conductivity for CuBr (Al2O3) increased by as much as 100, whereas in the beta phase the conductivity of CuBr containing Al2O3 decreased. The electrical conductivity studies are in agreement with earlier data.

  1. Synthesis of -Al2O3 nanowires through a boehmite precursor route

    Indian Academy of Sciences (India)

    Qi Yang

    2011-04-01

    Crystalline -Al2O3 nanowires with diameter, 20–40 nm, length above 600 nm and aspect ratio above 30 have been successfully synthesized by thermal decomposition of boehmite (-AlOOH) precursors obtained via hydrothermal route by using AlCl3, NaOH and NH3 as starting materials. Thermogravimetric analysis (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscope (TEM), selected area electron diffraction (SAED) and high resolution transmission electron microscope (HRTEM) were used to characterize the features of the as-made -Al2O3 nanowires and their -AlOOH precursors. The pH value of the solution and the mixed precipitant play important roles in the formation of -AlOOH nanowires. After calcination at 500°C for 2 h, the orthorhombic -AlOOH transforms to cubic -Al2O3 and retains nanowire morphology.

  2. Preparation and Properties of Plasma Spraying Cu-Al2O3 Gradient Coatings

    Institute of Scientific and Technical Information of China (English)

    Ali LEI; Nan DONG; Lajun FENG

    2007-01-01

    In order to overcome the limitations of low adhesion strength and poor thermal-shock resistance of pure ceramic coatings, Cu-Al2O3 gradient coatings were fabricated by plasma spraying. The microstructure and distribution of Cu-Al2O3 gradient coatings were analyzed. The adhesion strength, thermal-shock resistance and porosity of the coatings were tested. The results show that the composition of the gradient coatings has a gradient distribution along the thickness of coatings. As copper has a relatively low melting point and the molten copper has good wettability on the surface of Al2O3, it can be melted sufficiently and could fill the interstices and pores among the spraying particles effectively, thus improves the adhesion strength, thermal shock resistance and reduces the porosity. The adhesion strength of the gradient coating is 15.2 MPa which is two times of that of the double-layer structure coating.

  3. Laser assembly nanostructured Al2O3/TiO2 coating on cast aluminum surface

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guang-jun; DAI Jian-qiang; WANG Hui-ping; YAN Min-jie; XI Wen-long; ZOU Chang-gu; GE Da-fang

    2004-01-01

    CO2 laser quick assembly technology is adopted on the surface of cast aluminum ZL104 to form a dense ceramic coating containing a great deal of nanometer Al2O3/TiO2 particles which eliminate cracks and porosities.The major phases of the coating are α-Al2O3 andβ-TiO2. The micro-hardness distribution of the coating is 1 813,1 504, 1 485 and 1 232 (HV0.05). The bonding strength of the coating LC1 is 11.4 N, which is 7.26 times higher than that of the conventional hot-spraying Al2O3/TiO2 coating. It has been proved by analysis that the bonding strength is achieved because of the effects of both super-quick laser consolidation and the nanometer effect of nanometer ceramic material.

  4. The effective reinforcement of magnesium alloy ZK60A using Al2O3 nanoparticles

    International Nuclear Information System (INIS)

    ZK60A nanocomposite containing Al2O3 nanoparticle reinforcement (50 nm average size) was fabricated using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size to the monolithic alloy, reasonable Al2O3 nanoparticle distribution, non-dominant (0 0 0 2) texture in the longitudinal direction, and 15% higher hardness than the monolithic alloy. Compared to the monolithic alloy (in tension), the nanocomposite exhibited lower yield strength (0.2%TYS) (−4%) and higher ultimate strength (UTS), failure strain, and work of fracture (WOF) (+13%, +170%, and +200%, respectively). Compared to the monolithic alloy (in compression), the nanocomposite exhibited lower yield strength (0.2%CYS) (−5%) and higher ultimate strength (UCS), failure strain, and WOF (+6%, +41%, and +43%, respectively). The effects of Al2O3 nanoparticle addition on the enhancement of tensile and compressive properties of ZK60A are investigated in this article.

  5. Sensitivity enhancement of metal oxide thin film transistor with back gate biasing

    NARCIS (Netherlands)

    Dam, V.A.T.; Blauw, M.A.; Brongersma, S.H.; Crego-Calama, M.

    2011-01-01

    In this work, a room-temperature sensing device for detecting carbon monoxide using a ZnO thin film is presented. The ZnO layer (thickness close to the Debye length), which has a polycrystalline structure, is deposited with atomic-layer deposition (ALD) on an Al2O3/Si substrate. The operating princi

  6. Effect of AL2O3 and TiO2 nanoparticles on aquatic organisms

    Science.gov (United States)

    Gosteva, I.; Morgalev, Yu; Morgaleva, T.; Morgalev, S.

    2015-11-01

    Environmental toxicity of aqueous disperse systems of nanoparticles of binary compounds of titanium dioxides (with particle size Δ50=5 nm, Δ50=50 nm, Δ50=90 nm), aluminum oxide alpha-forms (Δ50=7 nm and Δ50=70 nm) and macro forms (TiO2 Δ50=350 nm, Al2O3 A50=4000 nm) were studied using biological testing methods. The bioassay was performed using a set of test organisms representing the major trophic levels. We found the dependence of the toxic effect concentration degree of nTiO2 and nAl2O3 on the fluorescence of the bacterial biosensor "Ekolyum", the chemotactic response of ciliates Paramecium caudatum, the growth of unicellular algae Chlorella vulgaris Beijer and mortality of entomostracans Daphnia magna Straus. We revealed the selective dependence of nTiO2 and nAl2O3 toxicity on the size, concentration and chemical nature of nanoparticles. The minimal concentration causing an organism's response on nTiO2 and nAl2O3 effect depends on the type of the test- organism and the test reaction under study. We specified L(E)C50 and acute toxicity categories for all the studied nanoparticles. We determined that nTiO2 (Δ50=5 nm) belong to the category «Acute toxicity 1», nTiO2 (A50=90 nm) and nAl2O3 (Δ50=70 nm) - to the category «Acute toxicity 2», nAl2O3 (Δ50=7 nm) - to the category «Acute toxicity 3». No acute toxicity was registered for nTiO2 (Δ50=50 nm) and macro form TiO2.

  7. Preparation and Characterization of PVC-Al2O3-LiClO4 Composite Polymeric Electrolyte

    International Nuclear Information System (INIS)

    Ionic conductivity of composite polymer electrolyte PVC-Al2O3-LiClO4 as a function of Al2O3 concentration has been studied. The electrolyte samples were prepared by solution casting technique. Their ionic conductivity was measured using impedance spectroscopy technique. It was observed that the conductivity of the electrolyte varies with Al2O3 concentration. The highest room temperature conductivity of the electrolyte of 3.43 x 10-10 S.cm-1 was obtain at 25 % by weight of Al2O3 and that without Al2O3 filler was found to be 2.43 x 10-11 S.cm-1. The glass transition temperature decreases with the increase of Al2O3 percentage due to the increasing amorphous state, meanwhile the degradation temperature increases with the increase of Al2O3 percentage. Both of these thermal properties influence the enhancement of the conductivity value. The morphology of the samples shows the even distribution of the Al2O3 filler in the samples. However, the filler starts to agglomerate in the sample when high percentage of Al2O3 is being used. In conclusion, the addition of Al2O3 filler improves the ionic conductivity of PVC- Al2O3-LiCIO4 solid polymer electrolyte. (author)

  8. Effect of Nd-doping on the Thermal Stability and Pore-structure of Al2O3 Membranes

    Institute of Scientific and Technical Information of China (English)

    YU Jian-Chang; XU Wei-Jun; HUANG Qing-Ming; HU Sheng-Wei

    2005-01-01

    Unsupported Nd-doped Al2O3 membranes have been prepared with a sol-gel treatnt by using aluminium isopropoxide and Nd(NO3)3 as the main raw materials. The properties of Nd-doped Al2O3 membranes were characterized by XRD, DTA-TG, IR and N2 adsorption. The effects of Nd-doping on the phase composition, thermal stability as well as applications of pore- structure of Nd-doped Al2O3 membranes at high temperature were discussed. The results show that Nd-doping can raise the transition temperature rom γ-Al2O3 to α-Al2O3, enhance the thermal stability of Al2O3 membranes, and evidently improve the pore-structural parameters of Al2O3 mem- branes applied at higher temperatures.

  9. Influence of Additives on Hydrodesulfurization Activity of Fe-Mo/Al2O3 Catalysts

    Institute of Scientific and Technical Information of China (English)

    Tuktin Balga T; Zakumbaeva Gaukhar D; Du Wei

    2006-01-01

    Based on the study relating to the influence of additives on the hydrodesulfurization performance of Fe-Mo-Al2O3 catalysts, it was found out that the introduction of additives could increase considerably the activity of Fe-Mo/Al2O3 catalysts in the reaction of hydrodesulfurization of gasoline and diesel fractions. The introduction of zeolites (HY, HZSM) and other additives could lead to an increase of the concentration of acid centers, which were able to react with sulfur compounds, along with an increase of total catalysts' pore volume,which could improve the capability of catalyst to adsorb the hydrogen and feed oil.

  10. The Evolution of Al2O3 Content in Ancient Chinese Glasses

    Directory of Open Access Journals (Sweden)

    Wang Cheng-yu

    2016-01-01

    Full Text Available Based on the evidence from museums, collectors, the dug out of the grave, the evolution of Al2O3 content in Chinese glasses from Western Zhou to Qing dynasty was documented in this paper in detail. It was found that Al2O3 contents in ancient Chinese glasses were relatively higher than those of outside of China in the world. This is the character of the ancient Chinese glasses which is caused by not only the high Al contents in the raw materials but also by the Chinese people’s preference of the milky glasses similar to jade

  11. Narrow in-gap states in doped Al 2 O 3

    KAUST Repository

    Casas-Cabanas, Montse

    2011-10-01

    Based on XRD data testifying that the M ions occupy substitutional sites, transmittance measurement are discussed in comparison to electronic structure calculations for M-doped Al2O3 with M = V, Mn, and Cr. The M 3d states are found approximatively 2 eV above the top of the host valence band. The fundamental band gap of Al2O3 is further reduced in the V and Mn cases due to a splitting of the narrow band at the Fermi energy. Nevertheless the measured transmittance in the visible range remains high in all three cases. © 2011 Elsevier B.V. All rights reserved.

  12. Study of the KNO3-Al2O3 system by differential scanning calorimetry

    Science.gov (United States)

    Amirov, A. M.; Gafurov, M. M.; Rabadanov, K. Sh.

    2016-09-01

    The structural and the thermodynamic properties of potassium nitrate KNO3 and its composites with nanosized aluminum oxide Al2O3 have been studied by differential scanning calorimetry. It has been found that an amorphous phase forms in composites (1- x)KNO3- x Al2O3. The thermal effect corresponding to this phase has been observed at 316°C. It has been found that the phase transition heats of potassium nitrate decreased as the aluminum oxide fraction increased.

  13. Studies on the Structure and Properties of Multiphase Al2O3 Abrasion-resistant Ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Ren-Ping; YU Yan; RUAN Yu-Zhong

    2006-01-01

    The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstructure of ceramic are characterized by means of XRD,SEM, etc., and the physical and mechanical properties are also tested. The results show that besides the phase of corundum, a little mullite, Mg-Al spinel and hyalophane phases also exist in the product. These phases are produced via reaction in-situ, which can inhibit the overgrowth of Al2O3grain in grain boundary, and improve the integral property of the material.

  14. Co2+ adsorption in porous oxides Mg O, Al2O3 and Zn O

    International Nuclear Information System (INIS)

    The porous oxides Mg O, Al2O3 and Zn O were synthesized by the chemical combustion in solution method and characterized be means of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The adsorption behavior of Co2+ ions present in aqueous solution were studied on the synthesized materials by means of experiments lots type to ambient temperature. It was found that the cobalt ions removal was of 90% in Mg O, 65% in Zn O and 72% in Al2O3 respectively, indicating that the magnesium oxide is the best material to remove Co2+ presents in aqueous solution. (Author)

  15. Manufacturing of aluminium matrix composite materials reinforced by Al2O3 particles

    OpenAIRE

    A. Włodarczyk-Fligier; L.A. Dobrzański; M. Kremzer; M. Adamiak

    2008-01-01

    Purpose: The purpose of the paper is to show and compare of modern method composite materials with aluminium alloy matrix reinforced by Al2O3 particles manufacturing.Design/methodology/approach: Material for investigation was manufactured by two methods: powder metallurgy (consolidation, pressing, hot extrusion of powder mixtures of aluminium EN AW-AlCu4Mg1(A) and ceramic particles Al2O3) and pressure infiltration of porous performs by liquid alloy EN AC AlSi12 (performs were prepared by sint...

  16. OSL response of Al2O3:C inlight dot detectors to ultraviolet radiation

    International Nuclear Information System (INIS)

    The commercial dosimeters Al2O3:C InLight Dot and the OSL microStar System reader, both developed by Landauer, were utilized in this work for the detection of ultraviolet radiation. The OSL response of Al2O3:C InLight Dots was obtained in relation to the parameters of irradiance and illumination time using an UV artificial source. The results showed an increase of the OSL response and a tendency to saturation about 1.7 W.m-2 of irradiance and 30 min of UV illumination. (author)

  17. Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

    Institute of Scientific and Technical Information of China (English)

    J.A.da Silva; B.M.Moreschi; G.C.R.Garcia; S.Ribeiro

    2013-01-01

    Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics.This work involved a study of the wetting of SiC ceramics by two oxide systems,Al2O3/Dy2O3 and Al2O3/Yb2O3,which have so far not been studied for application in the sintering of SiC ceramics.Five mixtures of each system were prepared,with different compositions close to their respective eutectic ones.Samples of the mixtures were pressed into cylindrical specimens,which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace.The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle,the parameter that measures the degree of wettability.The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading.All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere.The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX).The DRX analysis showed that Al2O3 and RE2O3 reacted and formed the Dy3Al5O12 (DyAg) and Yb3Al5O12 (YbAg) phases.The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.

  18. The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM)

    Science.gov (United States)

    Strojny-Nędza, Agata; Pietrzak, Katarzyna; Węglewski, Witold

    2016-08-01

    In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

  19. The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM)

    Science.gov (United States)

    Strojny-Nędza, Agata; Pietrzak, Katarzyna; Węglewski, Witold

    2016-07-01

    In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

  20. The electrical characteristics of a 4H-silicon carbide metal-insulator-semiconductor structure with Al2O3 as the gate dielectric

    Institute of Scientific and Technical Information of China (English)

    Liu Li; Yang Yin-Tang; Ma Xiao-Hua

    2011-01-01

    A 4H-silicon carbide metal-insulator-semiconductor structure with ultra-thin Al2O3 as the gate dielectric,deposited by atomic layer deposition on the epitaxial layer of a 4H-SiC (0001) 8(0)N-/N+ substrate,has been fabricated.The experimental results indicate that the prepared ultra-thin Al2O3 gate dielectric exhibits good physical and electrical characteristics,including a high breakdown electrical field of 25 MV/cm,excellent interface properties (1 × 1014 cm-2)and low gate-leakage current (IG =1 × 10-3 A/cm-2(o)Eox =8 MV/cm).Analysis of the current conduction mechanism on the deposited Al2O3 gate dielectric was also systematically performed.The confirmed conduction mechanisms consisted of Fowler-Nordheim (FN) tunneling,the Frenkel-Poole mechanism,direct tunneling and Schottky emission,and the dominant current conduction mechanism depends on the applied electrical field.When the gate leakage current mechanism is dominated by FN tunneling,the barrier height of SiC/Al2O3 is 1.4 eV,which can meet the requirements of silicon carbide metal-insulator-semiconductor transistor devices.

  1. Annealing behaviour of structure and morphology and its effects on the optical gain of Er3+/Yb3+ co-doped Al2O3 planar waveguide amplifier

    Institute of Scientific and Technical Information of China (English)

    Tan Na; Zhang Qing-Yu

    2006-01-01

    Using transmission electron microscopy (TEM) and x-ray diffraction analysis, we have studied the structural and morphological evolution of highly Er/Yb co-doped Al2O3 films in the temperature range from 600℃-900℃. Bycomparison with TEM observation, the annealing behaviours of photoluminescence (PL) emission and optical loss were found to have relation to the structure and morphology. The increase of PL intensity and optical loss above 800℃ might result from the crystallization of amorphous Al2O3 films. Based on the study on the structure and morphology,a rate equation propagation model of a multilevel system was used to calculate the optical gains of Er-doped Al2O3 planar waveguide amplifiers involving the variation of PL efficiency and optical loss with annealing temperature. It was found that the amplifiers had an optimized optical gain at the temperature corresponding to the minimum of optical loss, rather than at the temperature corresponding to the maximum of PL efficiency, suggesting that the optical loss is a key factor for determining the optical gain of an Er-doped Al2O3 planar waveguide amplifier.

  2. Exposure of metallic copper surface on Cu-Al2O3-carbon catalysts

    NARCIS (Netherlands)

    Menon, P.G.; Prasad, J.

    1970-01-01

    The bifunctional nature of Cu---Al2O3-on-carbon catalysts, used in the direct catalytic conversion of ethanol to ethyl acetate, prompted an examination of the dispersion of Cu on the composite catalyst. For this, the N2O-method of Osinga et al. for estimation of bare metallic copper surface on compo

  3. Thermally stimulated conductivity and thermoluminescence from Al2O3 : C

    DEFF Research Database (Denmark)

    Agersnap Larsen, N.; Bøtter-Jensen, L.; McKeever, S.W.S.

    1999-01-01

    Simultaneous measurements of thermoluminescence (TL) and thermally stimulated conductivity (TSC) are reported on single-crystal dosimetry-quality Al2O3:C following gamma irradiation at room temperature. Analysis of the data reveals a superposition of several first-order TL and TSC peaks caused...

  4. Neutron studies of nanostructured CuO-Al2O3 NOx removal catalysts

    International Nuclear Information System (INIS)

    Nanostructured powders of automotive catalytic system CuO0Al2O3, targeted for nitrogen oxides (NOx) removal under lean-burn engine conditions, were investigated using neutron diffraction and small-angle neutron scattering. The crystal phases, structural transformations and microstructure of 10 mol% Cu-Al2O3 powders are characterized according to the heat-treatment conditions. These properties are correlated with the pore structure and NOx removal efficiency determined by nitrogen adsorption isotherm, electron spin resonance, and temperature programmed reaction measurements. The γ-(Cu, Al)2O3 phase and the mass-fractal-like aggregate of particles (size ∼ 26 nm) at annealing temperatures below 900 degrees C were found to be crucial to the high NOx removal performance. The transformation to bulk crystalline phases of α-Al2O3 + CuAl2O4 spinel above ∼1050 degrees C corresponds to a drastic drop of Nox removal efficiency. The usefulness of neutron-scattering techniques as well as their complementarity with other traditional methods of catalytic research are discussed

  5. Gas-phase dehydration of glycerol over commercial Pt/γ-Al2O3 catalysts

    Institute of Scientific and Technical Information of China (English)

    Sergey Danov; Anton Esipovich; Artem Belousov; Anton Rogozhin

    2015-01-01

    Gas-phase dehydration of glycerol to produce acrolein was investigated over commercial catalysts based onγ-Al2O3, viz. A-64, A-56, I-62, AP-10, AP-56, AP-64 and KR-104. To understand the effect of Cl−anions, HCl-impregnated sup-ports have been investigated in the dehydration reaction of glycerol at 375 °C. For comparison, various H-zeolites were also examined. It was found that the glycerol conversion over the solid acid catalysts was strongly dependent on their acidity and surface area. And the relationship between the catalytic activity and the acidity of the catalysts was discussed. The outstanding properties of Pt/γ-Al2O3 catalyst systems for the dehydration of glycerol were revealed. Pt/γ-Al2O3 catalyst (AP-64) showed the highest catalytic activity after 50 h of reaction with an acrolein selectivity of 65%at a conversion of glycerol of 90%. Based on these results, catalysts based onγ-Al2O3 appear to be most promising for gas phase dehydration of glycerol.

  6. Ir-Ru/Al2O3 catalysts used in satellite propulsion

    Directory of Open Access Journals (Sweden)

    T.G. Soares Neto

    2003-09-01

    Full Text Available Ir/Al2O3, Ir-Ru/Al2O3 and Ru/Al2O3, catalysts with total metal contents of 30% were prepared using the methods of incipient wetness and incipient coimpregnation wetness and were tested in a 2N microthruster. Their performances were then compared with that of the Shell 405 commercial catalyst (30% Ir/Al2O3. Tests were performed in continuous and pulsed regimes, where there are steep temperature and pressure gradients, from ambient values up to 650 ºC and 14 bar. Performance stability, thrust produced, temperature and stagnation pressure in the chamber and losses of mass were analyzed and compared to the corresponding parameters in Shell 405 tests. It was observed that the performance of all the above-mentioned catalysts was comparable to that of the commercial one, except for in loss of mass, where the values was higher, which was attributed to the lower mechanical resistance of the support.

  7. Hydrogen generation from methanolysis of sodium borohydride over Co/Al2O3 catalyst

    Institute of Scientific and Technical Information of China (English)

    Dongyan Xu; Lin Zhao; Ping Dai; Shengfu Ji

    2012-01-01

    Co/Al2O3 catalyst is prepared with an impregnation-chemical reduction method and used to catalyze the methanolysis of sodium borohydride (NaBH4) for hydrogen generation.At solution temperature of 0℃,the methanolysis reaction can be effectively accelerated using Co/Al2O3 catalyst and provide a desirable hydrogen generation rate,which makes it suitable for apphcations under the circumstance of low environmental temperature.The byproduct of methanolysis reaction is analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).The characterization results indicate that methanol can be easily recovered after methanolysis reaction by hydrolysis of the methanolysis byproduct,NaB(OCH3)4.The catalytic activity of Co/Al2O3 towards NaBH4 methanolysis can be further improved by appropriate calcination treatment.The catalytic methanolysis kinetics and catalyst reusability are also studied over the Co/Al2O3 catalyst calcined at the optimized temperature.

  8. CW-OSL measurement protocols using optical fibre Al2O3:C dosemeters

    DEFF Research Database (Denmark)

    Edmund, J.M.; Andersen, C.E.; Marckmann, C.J.;

    2006-01-01

    A new system for in vivo dosimetry during radiotherapy has been introduced. Luminescence signals from a small crystal of carbon-doped aluminium oxide (Al2O3:C) are transmitted through an optical fibre cable to an instrument that contains optical filters, a photomultiplier tube and a green (532 nm...

  9. Focused ion beam nano-structuring of photonic Bragg gratings in $Al_2O_3$ waveguides

    NARCIS (Netherlands)

    Uranga, Amaia; Ay, Feridun; Bradley, Jonathan D.B.; Ridder, de René M.; Wörhoff, Kerstin; Pollnau, Markus; Emplit, Ph.; Delqué, M.; Gorza, S.-P.; Kockaart, P.; Leijtens, X.

    2007-01-01

    Focused ion beam (FIB) etching is receiving increasing attention for the fabrication of active integrated optical components such as waveguide amplifiers and lasers. Si-technology compatible low-loss $Al_2O_3$ channel waveguides grown on thermally oxidized silicon substrates have been reported recen

  10. Focused ion beam nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides

    NARCIS (Netherlands)

    Ay, Feridun; Uranga, Amaia; Bradley, Jonathan D.B.; Wörhoff, Kerstin; Ridder, de René M.; Pollnau, Markus; Ridder, de R.M.; Ay, F.; Kauppinen, L.J.

    2008-01-01

    We report our recent results on an optimization study of focused ion beam (FIB) nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides. By optimizing FIB milling parameters such as ion current, dwell time, loop repetitions, scanning strategy, and applying a top metal layer for reducing c

  11. Temperature dependence of the Al2O3:C response in medical luminescence dosimetry

    DEFF Research Database (Denmark)

    Edmund, Jens Morgenthaler; Andersen, Claus Erik

    2007-01-01

    Over the last years, attention has been given to applications of Al2O3:C in space and medical dosimetry. One such application is in vivo dose verification in radiotherapy of cancer patients and here we investigate the temperature effects on the radioluminescence (RL) and optically stimulated...

  12. Precipitation of ZnO in Al 2O 3-doped zinc borate glass ceramics

    Science.gov (United States)

    Masai, Hirokazu; Ueno, Takahiro; Takahashi, Yoshihiro; Fujiwara, Takumi

    2011-10-01

    Crystallization behavior of the oxide semiconductor ZnO in zinc borate glass was investigated. The precipitated crystalline phase of glass ceramics containing a small amount of Al 2O 3 was α-Zn 3B 2O 6 whereas that of the glass ceramics containing a large amount of Al 2O 3 was ZnO. It was found that the c-oriented precipitation of ZnO in a glass ceramic was brought about by the in-plane crystal growth of needle-like ZnO crystallites along the a-axis. Amount of Al 2O 3 that can make glass network affected the coordination state of B 2O 3 in the glass, and a three-coordinated BO 3 unit was preferentially formed in the glass containing a higher amount of Al 2O 3. The present results suggest that crystallization of ZnO from multi-component glass is dominated by the local coordination state of the mother glass.

  13. Al2O3/Silicon NanoISFET with Near Ideal Nernstian Response

    NARCIS (Netherlands)

    Chen, Songyue; Bomer, Johan G.; Carlen, Edwin T.; Berg, van den Albert

    2011-01-01

    Nanoscale ISFET (ion sensitive field-effect transistor) pH sensors are presented that produce the well-known sub-Nernstian pH-response for silicon dioxide (SiO2) surfaces and near ideal Nernstian sensitivity for alumina (Al2O3) surfaces. Titration experiments of SiO2 surfaces resulted in a varying p

  14. MALEIC ANHYDRIDE HYDROGENATION OF PD/AL2O3 CATALYST UNDER SUPERCRITICAL CO2 MEDIUM

    Science.gov (United States)

    Hydrogenation of maleic anhydride (MA) to either y-butyrolactone of succinic anhydride over simple Pd/Al2O3 impregnated catalyst in supercritical CO2 medium has been studied at different temperatures and pressures. A comparison of the supercritical CO2 medium reaction with the c...

  15. Theoretical investigation of the structure of κ-Al2O3

    DEFF Research Database (Denmark)

    Yourdshahyan, Y.; Engberg, U.; Bengtsson, L.;

    1997-01-01

    Using plane-wave pseudopotential calculations based on density-functional theory at the local-density-approximation level we investigate all the possible kappa-Al2O3 structures which are permitted by the known crystal symmetry. We find that structures with sixfold coordinated Al atoms are signifi...

  16. Optical observation of DNA translocation through Al2O3 sputtered silicon nanopores in porous membrane

    Science.gov (United States)

    Yamazaki, Hirohito; Ito, Shintaro; Esashika, Keiko; Taguchi, Yoshihiro; Saiki, Toshiharu

    2016-03-01

    Nanopore sensors are being developed as a platform for analyzing single DNA, RNA, and protein. In nanopore sensors, ionic current measurement is widely used and proof-of-concept of nanopore DNA sequencing by it has been demonstrated by previous studies. Recently, we proposed an alternative platform of nanopore DNA sequencing that incorporates ultraviolet light and porous silicon membrane to perform high-throughput measurement. In the development of our DNA sequencing platform, controlling nanopore size in porous silicon membrane is essential but remains a challenge. Here, we report on observation of DNA translocation through Al2O3 sputtered silicon nanopores (Al2O3 nanopores) by our optical scheme. Electromagnetic wave simulation was performed to analyze the excitation volume on Al2O3 nanopores generated by focused ultraviolet light. In the experiment, DNA translocation time through Al2O3 nanopores was compared with that of silicon nanopores and we examined the effect of nanopore density and thickness of membrane by supplementing the static electric field simulation.

  17. Corrosion behaviour of Al/SiC and Al/Al2O3 nanocomposites

    Directory of Open Access Journals (Sweden)

    Tamer Samir Mahmoud

    2012-12-01

    Full Text Available In the present investigation, the static immersion corrosion behavior of Al/Al2O3 and Al/SiC nanocomposites in 1 M HCl acidic solution was evaluated. The nanocomposites were fabricated using conventional powder metallurgy (P/M route. The effect of nanoparticulates size and volume fraction on the corrosion behavior of nanocomposites was studied. The durations of the corrosion tests ranged from 24 to 120 hours and the temperatures of the solution ranged from ambient to 75 ºC. The corrosion rates of the nanocomposites were calculated using the weight loss method. The results showed that both Al/SiC and Al/Al2O3 MMNCs have lower corrosion rates than the pure Al matrix. Such behavior was noticed at both ambient and higher temperatures. Generally, the Al/Al2O3 nanocomposites exhibited lower corrosion rates than the Al/SiC nanocomposites. The Al/Al2O3 (60 nm nanocomposites exhibited the highest corrosion resistance among all the investigated nanocomposites. The corrosion rate was found to be reduced by increasing of the exposure time and the volume fraction of the nanoparticulates, while it was found to be increased by increasing of the nanoparticulates size and the solution temperature.

  18. Thermochemical synthesis of nanostructured Cu-Al2O3 composite powder

    Directory of Open Access Journals (Sweden)

    Seyedraoufi Z.S.

    2014-01-01

    Full Text Available Synthesis of Cu-Al2O3 nanocomposite powder through a thermochemical method from the water solution of copper nitrate (Cu (NO32.3H2O and aluminum nitrate (Al (NO36.9H2O is studied in this research. X-ray diffraction (XRD technique, scanning electron microscopy (SEM and transmission electron microscopy (TEM were utilized to characterize the synthesized powder. XRD results show that γ-Al2O3 phase begins to form at the temperature ≈800°C during the heat treatment process. Studying SEM micrographs proves that the nano sized Al2O3 particles are homogenously dispersed in the copper matrix. XRD results also show that disappearing the reflects of CuO peaks after performing a reduction chemical reaction at the temperatures above 800°C in hydrogen atmosphere indicates that such chemical reaction at the temperatures above 800°C is required in order to achieve Cu-Al2O3 nanocomposite powder.

  19. In-situ RHEED and characterization of ALD Al2O3 gate dielectrics

    NARCIS (Netherlands)

    Bankras, Radko Gerard

    2006-01-01

    In-situ RHEED en karakterisatie van ALD Al2O3 gate diëlektrica Sinds de introductie van de MOSFET transistor (metaal-oxide-silicium veldeffecttransistor) in 1960, heeft de halfgeleidertechnologie een snelle ontwikkeling doorgemaakt. Deze vooruitgang bestond hoofdzakelijk uit de mogelijkheid om trans

  20. Preparation and Properties of Crystallizable Glass/Al2O3 Composites for LTCC Material

    Institute of Scientific and Technical Information of China (English)

    SHAO Hui; ZHOU Hongling; ZHU Haihui; SHEN Xiaodong

    2011-01-01

    The investigated low temperature Co fired ceramics(LTCC) composite of 60wt% CaO-Al2O3-B2O3-SiO2 glass and 40wt% α-Al2O3 as a filler is a non-reactive system,which is a critical part of the low temperature Co fired ceramics process.Through a study on densification process,the phase transformation and microstructure can be revealed.Its composites typically consist of CaO-Al2O3-B2O3-SiO2 glass and α-Al2O3 powders of average particle size (D50=3.49 μm).The sintering behavior,phase evaluation,sintered morphology,and microwave dielectric properties were investigated.In the fire range of 800 to 900 ℃,the composites were crystallized after completion of densification.It is found that the composites start to densify at 825 ℃,simultaneously,the dielectric constant (εr) reaches its maximum.With increasing heat-treatment temperatures,due to the loose microstmcture of the material,tanδ increases slightly.The last of the sintered samples were identified as partly Anorthite at 850 ℃.At that temperature it has εr of 7.9 and tanδ less than 1 x 10-3,and can be used as a promising LTCC material.

  1. Surface tension, densities and viscosities of some CaO-Al2O3 slags

    International Nuclear Information System (INIS)

    The metallurgical concepts with regard to the structures and properties of calcium aluminate melts have been based upon analogies within ternary CaO-Al2O3-SiO2 systems. In this work the results of surface tension, density and viscosity of some calcium aluminate slags, in the temperature range of 1500 to 1600 degree centigrade are presented and the results are discussed based upon recent structural characterisation results of crystalline aluminates. The compositional range investigated was from 45 to 53 weight-% alumina. The results indicate a reduction in density as the molar ratio CaO-Al2O3 decreases. Surface tension falls on increasing either the molar ratio CaO-Al2O3 or temperature. Conversely, viscosity increases with increasing molar ratio CaO-Al2O3 and decreasing temperature. The compositional dependence of both surface tension and viscosity data may be associated with the presence of some aluminium ions in octahedral co-ordination, and a concept of surface behaviour is proposed which involves surface activity of aluminate anions containing aluminium ions in a reduced valence state, such as Al''2+. (Author) 21 refs

  2. Analysis of the residual stress in Al2O3-SiC nanocomposites

    Institute of Scientific and Technical Information of China (English)

    王宏志; 高濂; 郭景坤

    1999-01-01

    The residual stress in Al2O3-SiC nanocomposites was measured by the X-ray diffraction method. A mode was established to calculate the residual stress, which accorded with the results measured by the XRD method. The strengthening and toughening mechanism was also discussed.

  3. Preliminary Study on MgO· Al2O3 Spinel Fiber

    Institute of Scientific and Technical Information of China (English)

    YANG Daoyuan; GUO Xinrong; ZHONG Xiangchong

    2004-01-01

    MgO· Al2O3 spinel fibers may be obtained by thermal treatment of pressed specimens composed of Mg-Al-O materials with appropriate oxide-metal ratio at high temperature under controlled atmosphere. Their phase composition and microstructure have been examined.

  4. Preliminary Study on MgO.Al2O3 Spinel Fiber

    Institute of Scientific and Technical Information of China (English)

    YANGDaoyuan; GUOXinrong; ZHONGXiangchong

    2004-01-01

    MgO·Al2O3 spinel fibers may be obtained by thermal treatment of pressed specimens composed of Mg-Al-O materials with appropriate oxide-metal ratio at high temperature under controlled atmosphere. Their phase composition and microsttrure have been examined.

  5. Thermal diffusivity of sintered 12CaO-7Al2O3

    OpenAIRE

    Nikolić Pantelija M.; Luković D.; Savić S.; Urošević Dragan B.; Đurić S.

    2003-01-01

    The thermal diffusivity and some electrical transport properties of sintered 12CaO-7Al2O3 were determined using a photoacoustic method with a transmission detection configuration. The thermal diffusivity, coefficient of carrier diffusion and the surface recombination velocities were determined by fitting experimental spectra and theoretical photoacoustic amplitude and phase signals.

  6. Theory of Al2O3 incorporation in SiO2

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2002-01-01

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

  7. The temperature dependence of optically stimulated luminescence from α-Al2O3:C

    DEFF Research Database (Denmark)

    Markey, B.G.; McKeever, S.W.S.; Akselrod, M.S.;

    1996-01-01

    The results of experimental measurements and computer simulations on optically stimulated luminescence (OSL) from alpha-Al2O3:C are described. The intensity of the OSL observed during illumination of irradiated specimens with visible light is temperature dependent. Optical stimulation is observed...

  8. H2 assisted NH3-SCR over Ag/Al2O3 for automotive applications

    DEFF Research Database (Denmark)

    Fogel, Sebastian

    The up-coming strict emission legislation demands new and improved catalysts for diesel vehicle deNOx. The demand for low-temperature activity is especially challenging. H2-assisted NH3-SCR over Ag/Al2O3 has shown a very promising low-temperature activity and a combination of Ag/Al2O3 and Fe...... has been the preparation of monolithic catalyst bricks for the catalyst testing. A high SBET and higher Ag loading gave a high sulphur tolerance and activity. It was believed that the high SBET is needed to give a higher NH3 adsorption capacity, necessary for the SCR reaction. A higher Ag loading....../Al2O3 if it was placed downstream or as the inner layer. Full-scale engine testing, on the other hand, showed the opposite for a dual-brick layout. High NO2 concentrations are believed to give fast-SCR over the Fe-BEA when it was placed upstream of the Ag/Al2O3. The activity of the combined catalyst...

  9. Electrochemical Impedance Studies on Tribocorrosion Behavior of Plasma-Sprayed Al2O3 Coatings

    Science.gov (United States)

    Liu, Zhe; Chu, Zhenhua; Chen, Xueguang; Dong, Yanchun; Yang, Yong; Li, Yingzhen; Yan, Dianran

    2015-06-01

    In this paper, the tribocorrosion of plasma-sprayed Al2O3 coatings in simulated seawater was investigated by electrochemical impedance spectroscopy (EIS) technique, complemented by scanning electron microscopy to observe the morphology of the tribocorrosion attack. Base on EIS of plasma-sprayed Al2O3 coatings undergoing long-time immersion in simulated seawater, the corrosion process of Al2O3 coatings can be divided into the earlier stage of immersion (up to 20 h) and the later stage (beyond 20 h). Then, the wear tests were carried out on the surface of Al2O3 coating undergoing different times of immersion to investigate the influence of wear on corrosion at different stages. The coexistence of wear and corrosion condition had been created by a boron nitride grinding head rotating on the surface of coatings corroded in simulated seawater. The measured EIS and the values of the fitting circuit elements showed that wear accelerated corrosion at the later stage, meanwhile, corrosion accelerated wear with the immersion time increasing.

  10. Inline Array Jet Impingement Cooling Using Al2O3 / Water Nanofluid In A Plate Finned Electronic Heat Sink

    Directory of Open Access Journals (Sweden)

    R. Reji Kumar

    2016-07-01

    Full Text Available - Jet impingement cooling is a technique used for cooling the electronic systems. In this work, heat transfer and pressure drop characteristics of deionized water and Al2O3/water nanofluid in an electronic heat sink having aluminium plate fins and provision for jet impingement cooling have been studied. A novel heat sink contains two rows of plate fins of size 29mm x 24mm x 0.56mm. A thin plate having 110 holes of diameter 2.5 mm is used to produce number of jets. The plate is kept inside the heat sink in such a way that H/dn is 5.2 mm and adjacent jet spacing is 2mm. The overall dimension of the heat sink is 60x60x 65 mm. For this work we prepared a Al2O3/water nanofluid by dispersing specified quantity of nanoparticles in to deionized water by using a ultrasonic bath. Experiments were conducted under constant heat flux condition and the volume flow rate of the fluid was in the range of 1.315 to 2.778. It is found from the results that the nanofluid removes heat better than water in the jet impingement cooling with very low rise in pressure drop.

  11. Atomic to Nanoscale Investigation of Functionalities of an Al2O3 Coating Layer on a Cathode for Enhanced Battery Performance

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Pengfei; Zheng, Jianming; Zhang, Xiaofeng; Xu, Rui; Amine, Khalil; Xiao, J; Zhang, Ji-Guang; Wang, Chong-Min

    2016-02-09

    Surface coating has been identified as an effective approach for enhancing the capacity retention of layered structure cathode. However, the underlying operating mechanism of such a thin coating layer, in terms of surface chemical functionality and capacity retention, remains unclear. In this work, we use aberration-corrected scanning transmission electron microscopy and high-efficiency spectroscopy to probe the delicate functioning mechanism of an Al2O3 coating layer on a Li1.2Ni0.2Mn0.6O2 cathode. We discovered that in terms of surface chemical function, the Al2O3 coating suppresses the side reaction between the cathode and the electrolyte during battery cycling. At the same time, the Al2O3 coating layer also eliminates the chemical reduction of Mn from the cathode particle surface, therefore preventing the dissolution of the reduced Mn into the electrolyte. In terms of structural stability, we found that the Al2O3 coating layer can mitigate the layer to spinel phase transformation, which otherwise will be initiated from the particle surface and propagate toward the interior of the particle with the progression of battery cycling. The atomic to nanoscale effects of the coating layer observed here provide insight into the optimized design of a coating layer on a cathode to enhance the battery properties.

  12. Swift ion irradiation effect on high-k ZrO2- and Al2O3-based MOS devices

    Science.gov (United States)

    Rao, Ashwath; Chaurasia, Priyanka; Singh, B. R.

    2016-03-01

    This paper describes the heavy ion-induced effects on the electrical characteristics of reactively sputtered ZrO2 and Al2O3 high-k gate oxides deposited in argon plus nitrogen containing plasma. Radiation-induced degradation of sputtered high-k dielectric ZrO2/Si and Al2O3/Si interface was studied using 45 MeV Li3+ ions. The devices were irradiated with Li3+ ions at various fluences ranging from 5 × 109 to 5 × 1012 ions/cm2. Capacitance-voltage and current-voltage characteristics were used for electrical characterization. Shift in flat band voltage towards negative value was observed in devices after exposure to ion radiation. Post-deposition annealing effect on the electrical behavior of high-k/Si interface was also investigated. The annealed devices showed better electrical and reliability characteristics. Different device parameters such as flat band voltage, leakage current, interface defect density and oxide-trapped charge have been extracted.The surface morphology and roughness values for films deposited in nitrogen containing plasma before and after ion radiation are extracted from Atomic Force Microscopy.

  13. Surface morphology of Al0.3Ga0.7N/Al2O3-high electron mobility transistor structure.

    Science.gov (United States)

    Cörekçi, S; Usanmaz, D; Tekeli, Z; Cakmak, M; Ozçelik, S; Ozbay, E

    2008-02-01

    We present surface properties of buffer films (AIN and GaN) and Al0.3Gao.zN/Al2O3-High Electron Mobility Transistor (HEMT) structures with/without AIN interlayer grown on High Temperature (HT)-AIN buffer/Al2O3 substrate and Al2O3 substrate. We have found that the GaN surface morphology is step-flow in character and the density of dislocations was about 10(8)-10(9) cm(-2). The AFM measurements also exhibited that the presence of atomic steps with large lateral step dimension and the surface of samples was smooth. The lateral step sizes are in the range of 100-250 nm. The typical rms values of HEMT structures were found as 0.27, 0.30, and 0.70 nm. HT-AIN buffer layer can have a significant impact on the surface morphology of Al0.3Ga0.7N/Al2O3-HEMT structures.

  14. The Influence of Na2O on the Solidification and Crystallization Behavior of CaO-SiO2-Al2O3-Based Mold Flux

    Science.gov (United States)

    Gao, Jinxing; Wen, Guanghua; Sun, Qihao; Tang, Ping; Liu, Qiang

    2015-08-01

    The reaction between [Al] and SiO2 sharply increased the Al2O3 and decreased SiO2 contents in mold flux during the continuous casting of high-Al steels. These changes converted original CaO-SiO2-based flux into CaO-SiO2-Al2O3-based flux, promoting the crystallization and deteriorating the mold lubrication. Therefore, study on the solidification and crystallization behavior of CaO-SiO2-Al2O3-based mold flux, with the applicable fluidizers, is of importance. The effect of Na2O, predominantly used as the fluidizer in mold flux, on the solidification and crystallization behavior of CaO-SiO2-Al2O3-based mold flux needs to be investigated. In this study, a CaO-SiO2-Al2O3-based mold flux containing 6.5 wt pct Li2O was designed; the effect of Na2O on the solidification and crystallization behavior of these mold fluxes was investigated using the single hot thermocouple technique (SHTT) and the double hot thermocouple technique (DHTT). Moreover, the slag film obtained by a heat flux simulator was analyzed using X-ray diffraction (XRD). The results indicate that the solid fraction of molten slag (Fs) and the crystalline fraction of solid slag (Fc) in the mold slag films decrease with increasing Na2O content from 0 to 2 wt pct. However, Fs and Fc increased when the Na2O content increased from 2 to 6 wt pct. The critical cooling rates initially decreases and then increases with increasing Na2O content. The XRD analysis results show that LiAlO2 and CaF2 were the basic crystals for all the mold fluxes. Increasing the Na2O content both inhibits the Ca2Al2SiO7 formation and promotes the production of Ca12Al14O33, indicating that the mold lubrication deteriorated because of the high melting-point phase formation of Ca2Al2SiO7 in the CaO-SiO2-Al2O3-based mold flux containing 6.5 wt pct Li2O, without Na2O. The strong crystallization tendency also deteriorated the mold lubrication for the mold flux with a higher Na2O content. Therefore, the addition of Na2O was less than 2 wt pct in

  15. Thermal stability and fracture toughness of epoxy resins modified with epoxidized castor oil and Al2O3 nanoparticles

    International Nuclear Information System (INIS)

    This study examined the effects of the epoxidized castor oil (ECO) and Al2O3 content on the thermal stability and fracture toughness of the diglycidylether of bisphenol-A (DGEBA)/ECO/Al2O3 ternary composites using a range of techniques. The thermal stability of the composites was decreased by the addition of ECO and Al2O3 nanoparticles. The fracture toughness of the composites was improved significantly by the addition of ECO and Al2O3 nanoparticles. The composite containing 3 wt % Al2O3 nanoparticles showed the maximum flexural strength. Scanning electron microscopy (SEM) revealed tortuous cracks in the DGEBA/ECO/Al2O3 composites, which prevented deformation and crack propagation

  16. Microstructure of Suspension Plasma Spray and Air Plasma Spray Al2O3-ZrO2 Composite Coatings

    Science.gov (United States)

    Chen, Dianying; Jordan, Eric H.; Gell, Maurice

    2009-09-01

    Al2O3-ZrO2 coatings were deposited by the suspension plasma spray (SPS) molecularly mixed amorphous powder and the conventional air plasma spray (APS) Al2O3-ZrO2 crystalline powder. The amorphous powder was produced by heat treatment of molecularly mixed chemical solution precursors below their crystallization temperatures. Phase composition and microstructure of the as-synthesized and heat-treated SPS and APS coatings were characterized by XRD and SEM. XRD analysis shows that the as-sprayed SPS coating is composed of α-Al2O3 and tetragonal ZrO2 phases, while the as-sprayed APS coating consists of tetragonal ZrO2, α-Al2O3, and γ-Al2O3 phases. Microstructure characterization revealed that the Al2O3 and ZrO2 phase distribution in SPS coatings is much more homogeneous than that of APS coatings.

  17. Effects of Al2O3-Particulate-Contained Composite Filler Materials on the Shear Strength of Alumina Joints

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    All2O3/Al2O3 joints were brazed with a new kind of filler materials, which were formed by adding Al2O3 particulates into Ag-Cu-Ti active filler metal. The results showed that the material parameters (the Ti content, Al2O3 particulate volume fraction) of the composite filler materials affected the shear strength of brazed joints. When the Ti content was 2 wt pct in the filler metal, the shear strength of brazing joints decreased with the increasing the volume ratio of Al2O3 particulate. When the Ti content was 3 wt pct in the filler metal, the shear strength of joints increased from 93.75 MPa(Al2O3p 0 vol. pct) to 135.32 MPa(Al2O3p 15 vol. pct).

  18. Detection of chemical substances in water using an oxide nanowire transistor covered with a hydrophobic nanoparticle thin film as a liquid-vapour separation filter

    Science.gov (United States)

    Lim, Taekyung; Lee, Jonghun; Ju, Sanghyun

    2016-08-01

    We have developed a method to detect the presence of small amounts of chemical substances in water, using a Al2O3 nanoparticle thin film covered with phosphonic acid (HDF-PA) self-assembled monolayer. The HDF-PA self-assembled Al2O3 nanoparticle thin film acts as a liquid-vapour separation filter, allowing the passage of chemical vapour while blocking liquids. Prevention of the liquid from contacting the SnO2 nanowire and source-drain electrodes is required in order to avoid abnormal operation. Using this characteristic, the concentration of chemical substances in water could be evaluated by measuring the current changes in the SnO2 nanowire transistor covered with the HDF-PA self-assembled Al2O3 nanoparticle thin film.

  19. The role of ion species on the adhesion enhancement of ion beam mixed Fe/Al2O3 systems

    International Nuclear Information System (INIS)

    The role of the ion species on the adhesion enhancement of ion beam mixed Fe/Al2O3 systems has been investigated. The ion implantations were carried out after film deposition using Cr (300 keV), Fe (320 keV), or Ni (340 keV) ions. The adhesion of the films was measured by a pull test and a scratch test. While the three types of implantation result in similar ion concentration profiles (with the peak concentration at the interface) and similar damage profiles, the three species were not equally effective in improving the adhesion. In this paper the effects are proposed to be due to changes in the interfacial energy resulting from both the damage and the presence of the ion species at the interface

  20. Innovational radiation sensor by integrating AL2O3:C optically stimulated luminescent dosemeter and GaN detectors

    International Nuclear Information System (INIS)

    We report a new dosimetry concept that is built on an earlier integrated sensor concept by our group at Univ. of Washington to integrate a radiation-dosimetry-quality Al2O3:C and a high quantum-efficiency GaN-based p-i-n photodiode on one side, and light emitting diodes (LEDs) on the opposite side as the stimulation source. The performance of the sensor has been evaluated by computer simulation, the performance of GaN photodiodes and studying the GaN films. The absorption spectrum of the GaN film was measured and indicated that the GaN photodiodes would not respond to the output wavelengths of the stimulating LEDs. The electrical properties and the performance of GaN p-i-n photodiode under irradiation were simulated. The results showed that the sensor offered comparable radiation sensitivity to current technologies and could be operated in active mode. (authors)

  1. Superconducting MgB2 Thin Films with Tc ≈ 39 K Grown by Pulsed Laser Deposition

    Institute of Scientific and Technical Information of China (English)

    王淑芳; 戴守愚; 周岳亮; 陈正豪; 崔大复; 许佳迪; 何萌; 吕惠宾; 杨国桢

    2001-01-01

    Superconducting MgB2 thin films were fabricated on Al2 O3 (0001) substrates under ex situ processing conditions.Boron thin films were deposited by pulsed laser deposition followed by a post-annealing process. Resistance measurements of the deposited MgB2 films show Tc of ~39 K, while scanning electron microscopy and x-ray vdiffraction analysis indicate that the films consist of well-crystallized grains with a highly c-axis-oriented structure.

  2. Effect of Al2O3 Binder on the Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

    Institute of Scientific and Technical Information of China (English)

    Hai-Jun Wan; Bao-Shan Wu; Xia An; Ting-Zhen Li; Zhi-Chao Tao; Hong-Wei Xiang; Yong-Wang Li

    2007-01-01

    A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N2 physical adsorption, temperature-programmed reduction/desorption (TPR/TPD) and M(o)ssbauer effect spectroscopy (MES) methods. The characterization results indicated that the BET surface area increases with increasing Al2O3 content and passes through a maximum at the Al2O3/Fe ratio of 10/100 (weight basis). After the point, it decreases with further increase in Al2O3 content. The incorporation of Al2O3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al2O3 and Fe-Al2O3 interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing Al2O3 content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR) under the reaction conditions of 260 ℃, 1.5 MPa, 1000 h-1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al2O3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al2O3 content, the FTS activity and water gas shift reaction (WGS) activity are decreased severely. The addition of appropriate Al2O3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al2O3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.

  3. Development and Application of Al2O3 - Si3N4 Refractories Used in Blast Furnace

    Institute of Scientific and Technical Information of China (English)

    LI Xianming; LI Yong; KANG Huarong; DONG Shengying; XUE Wendong; SONG Wen

    2008-01-01

    Newly developed Al2O3-Si3N4 composite refracto-ries used for blast furnace is introduced in this work.Al2O3-Si3N4 composite refractories attacked by alkali vapor and blast Jhrnace slag was investigated. High per-formance Al2O3 -Si3N4 composite refractories was pro-duced and used at both 2 560 m3 blast furnaces of Tan-gsteel and No. 5 blast furnace of Shaosteel.

  4. Promotion Effect of CaO Modification on Mesoporous Al2O3-Supported Ni Catalysts for CO2 Methanation

    Directory of Open Access Journals (Sweden)

    Wen Yang

    2016-01-01

    Full Text Available The catalysts Ni/Al2O3 and CaO modified Ni/Al2O3 were prepared by impregnation method and applied for methanation of CO2. The catalysts were characterized by N2 adsorption/desorption, temperature-programmed reduction of H2 (H2-TPR, X-ray diffraction (XRD, and temperature-programmed desorption of CO2 and H2 (CO2-TPD and H2-TPD techniques, respectively. TPR and XRD results indicated that CaO can effectively restrain the growth of NiO nanoparticles, improve the dispersion of NiO, and weaken the interaction between NiO and Al2O3. CO2-TPD and H2-TPD results suggested that CaO can change the environment surrounding of CO2 and H2 adsorption and thus the reactants on the Ni atoms can be activated more easily. The modified Ni/Al2O3 showed better catalytic activity than pure Ni/Al2O3. Ni/CaO-Al2O3 showed high CO2 conversion especially at low temperatures compared to Ni/Al2O3, and the selectivity to CH4 was very close to 1. The high CO2 conversion over Ni/CaO-Al2O3 was mainly caused by the surface coverage by CO2-derived species on CaO-Al2O3 surface.

  5. Effect of Nano-Al2O3 on the Toxicity and Oxidative Stress of Copper towards Scenedesmus obliquus

    Science.gov (United States)

    Li, Xiaomin; Zhou, Suyang; Fan, Wenhong

    2016-01-01

    Nano-Al2O3 has been widely used in various industries; unfortunately, it can be released into the aquatic environment. Although nano-Al2O3 is believed to be of low toxicity, it can interact with other pollutants in water, such as heavy metals. However, the interactions between nano-Al2O3 and heavy metals as well as the effect of nano-Al2O3 on the toxicity of the metals have been rarely investigated. The current study investigated copper toxicity in the presence of nano-Al2O3 towards Scenedesmus obliquus. Superoxide dismutase activity and concentration of glutathione and malondialdehyde in cells were determined in order to quantify oxidative stress in this study. Results showed that the presence of nano-Al2O3 reduced the toxicity of Cu towards S. obliquus. The existence of nano-Al2O3 decreased the growth inhibition of S. obliquus. The accumulation of copper and the level of oxidative stress in algae were reduced in the presence of nano-Al2O3. Furthermore, lower copper accumulation was the main factor that mitigated copper toxicity with the addition of nano-Al2O3. The decreased copper uptake could be attributed to the adsorption of copper onto nanoparticles and the subsequent decrease of available copper in water. PMID:27294942

  6. A high degree of enhancement of strength of sputter deposited Al/Al2O3 multilayers upon post annealing

    International Nuclear Information System (INIS)

    We report here an order of magnitude enhancement of strength of sputter deposited Al/Al2O3 multilayers after annealing. The increase in strength is shown to be mostly associated with the precipitation of extremely fine γ-Al2O3, 5–10 nm in diameter, in Al layers. This provides a new method of achieving high strength in Al/Al2O3 multilayers that cannot be explained by the Koehler effect or modified Hall–Petch, which will lead to the growth and development of new generation of Al/Al2O3 multilayers. We also examine the fracture behavior of the post annealed Al/Al2O3 multilayered composites with TEM and density functional theory (DFT) simulations. DFT showed that the multilayers are not likely to delaminate at the Al/Al2O3 interface, consistent with the experimental observations. The simulations are also used to determine elastic constants for the γ-Al2O3 phase and to calculate a driving force for O transport from the γ-Al2O3 to the Al layers. The formation of these precipitates is consistent with DFT calculations, which predict an energetic driving force for the dissolution of O atoms from the γ-Al2O3 layers into the Al layers

  7. Preparation and Characterization of Liquid Crystalline Polyurethane/Al2O3/Epoxy Resin Composites for Electronic Packaging

    Directory of Open Access Journals (Sweden)

    Shaorong Lu

    2012-01-01

    Full Text Available Liquid crystalline polyurethane (LCPU/Al2O3/epoxy resin composites were prepared by using LCPU as modifier. The mechanical properties, thermal stability, and electrical properties of the LCPU/Al2O3/epoxy resin composites were investigated systematically. The thermal oxidation analysis indicated that LCPU/Al2O3/epoxy resin composites can sustain higher thermal decomposition temperature. Meanwhile, coefficient of thermal expansion (CTE was also found to decrease with addition of LCPU and nano-Al2O3.

  8. Effects of Surface Treatments on the Performances of Al2 O3 Nano-Particle/Polyimide adhesive

    Institute of Scientific and Technical Information of China (English)

    MA Shi-ning; ZHANG Shi-tang; QIAO Yu-lin

    2004-01-01

    The nano-Al2O3/polyimide composite adhesive was prepared by high-energy chemical and mechanical handing in this paper. The thermally curing process was preliminary determined, furthermore, the effects of n-Al2 O3 on the performance of polyimide adhesive were investigated using SEM. The results were showed that n-Al2 O3 particles were segregated from adhesive to the interface, especially bulk structural defect, which may be the reason why the performance of n-Al2O3/PI adhesive becomes better. However, the detailed mechanism is still to be discussed.

  9. Atomic Layer Deposition of Al2O3 on WSe2 Functionalized by Titanyl Phthalocyanine.

    Science.gov (United States)

    Park, Jun Hong; Fathipour, Sara; Kwak, Iljo; Sardashti, Kasra; Ahles, Christopher F; Wolf, Steven F; Edmonds, Mary; Vishwanath, Suresh; Xing, Huili Grace; Fullerton-Shirey, Susan K; Seabaugh, Alan; Kummel, Andrew C

    2016-07-26

    To deposit an ultrathin dielectric onto WSe2, monolayer titanyl phthalocyanine (TiOPc) is deposited by molecular beam epitaxy as a seed layer for atomic layer deposition (ALD) of Al2O3 on WSe2. TiOPc molecules are arranged in a flat monolayer with 4-fold symmetry as measured by scanning tunneling microscopy. ALD pulses of trimethyl aluminum and H2O nucleate on the TiOPc, resulting in a uniform deposition of Al2O3, as confirmed by atomic force microscopy and cross-sectional transmission electron microscopy. The field-effect transistors (FETs) formed using this process have a leakage current of 0.046 pA/μm(2) at 1 V gate bias with 3.0 nm equivalent oxide thickness, which is a lower leakage current than prior reports. The n-branch of the FET yielded a subthreshold swing of 80 mV/decade. PMID:27305595

  10. Geant4 calculations for space radiation shielding material Al2O3

    Directory of Open Access Journals (Sweden)

    Capali Veli

    2015-01-01

    Full Text Available Aluminium Oxide, Al2O3 is the most widely used material in the engineering applications. It is significant aluminium metal, because of its hardness and as a refractory material owing to its high melting point. This material has several engineering applications in diverse fields such as, ballistic armour systems, wear components, electrical and electronic substrates, automotive parts, components for electric industry and aero-engine. As well, it is used as a dosimeter for radiation protection and therapy applications for its optically stimulated luminescence properties. In this study, stopping powers and penetrating distances have been calculated for the alpha, proton, electron and gamma particles in space radiation shielding material Al2O3 for incident energies 1 keV – 1 GeV using GEANT4 calculation code.

  11. [Laser Raman spectra study on Co-Mo/Al2O3 hydrodesulphurization catalysts].

    Science.gov (United States)

    Yuan, Hui; Xu, Guang-Tong; Qiherima; Li, Hui-Feng; Lu, Li-Jun; Yang, Xing-Yuan; Tana

    2014-02-01

    Due to the implementation of more stringent specifications in sulfur content for gasoline , a deep understanding of the active phase of Co-Mo/Al2O3 catalysts is necessary to the development of hydrodesulphurization (HDS) catalysts. A series of Co-Mo/Al2O3 HDS catalysts with different metal loading were studied by laser Raman spectra. The existence form and the content of the active component of the catalyst were obtained by Raman spectra. The result shows that the percentage of characteristic Raman bands 940 cm(-1) correlates linearly with the HDS selectivity, which can be used as an experimental evidence for developing industrial selective HDS catalysts. Raman spectra of sulfided catalysts show that the bands of oxidic catalysts at 839 and 940 cm(-1) disappeared, and simultaneously, the bands of Mo-S at 372 and 408 cm(-1) emerged, which indicate that the oxidic sample is sulfided completely. PMID:24822416

  12. Flexibility of Burned Al2O3-C Due to Bending Tests at Room Temperature

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Simple three-point bending test at ambient tempera-ture characterized the mechanical behavior of burned Al2O3-C refractories before and after thermal shock in association with the processing parameters (graphite con-tent and coking temperature,etc.).The results showed that non-linear plastic-elastic behavior under load lower than cold modulus of rupture (CMOR) Was registered in all specimens and real linear elastic behavior could be identified after the first load.The total deformation could be divided into two parts,plastic and elastic areas.The graphite content and joint bonding system of carbon and ceramic phases were responsible for mechanical behavior of Al2O3-C refractories.

  13. Improved real-time dosimetry using the radioluminescence signal from Al2O3:C

    DEFF Research Database (Denmark)

    Damkjær, Sidsel Marie Skov; Andersen, Claus Erik; Aznar, Marianne

    2008-01-01

    15th International Conference on Solid State Dosimetry Location: Delft Univ Technol, Delft, NETHERLANDS Date: JUL 08-13, 2007 Abstract: Carbon-doped aluminum oxide (Al2O3:C) is a highly sensitive luminescence material for ionizing radiation dosimetry, and it is well established that the optically...... to greatly reduce the influence of shallow traps in the range from 0 to 3 Gy and the RL dose-rate measurements with a time resolution of 0. 1 s closely matched dose-rate changes monitored with in ionization chamber. (c) 2007 Elsevier Ltd. All rights reserved.......15th International Conference on Solid State Dosimetry Location: Delft Univ Technol, Delft, NETHERLANDS Date: JUL 08-13, 2007 Abstract: Carbon-doped aluminum oxide (Al2O3:C) is a highly sensitive luminescence material for ionizing radiation dosimetry, and it is well established that the optically...

  14. Luminescence study of nanosized Al2O3:Tb3+ obtained by gas-dispersed synthesis

    Science.gov (United States)

    Berezovskaya, I. V.; Poletaev, N. I.; Khlebnikova, M. E.; Zatovsky, I. V.; Bychkov, K. L.; Efryushina, N. P.; Khomenko, O. V.; Dotsenko, V. P.

    2016-09-01

    Terbium-doped Al2O3 samples were obtained by gas-dispersed synthesis. It was shown that the resulting powders, with particle sizes of 10-70 nm, consist of a mixture of transition aluminas, among which the δ *-polymorph is dominant. The luminescence properties of Al2O3:Tb3+ have been studied upon excitation in the UV-visible range of the spectrum. It was found that Tb3+ ions cause several groups of inhomogeneously broadened emission bands in the range of 470-640 nm, which are characteristic for disordered materials. In addition, the emission spectra contain a broad band at about 450 nm and several narrower ones in the 680-720 nm region. These features are attributed to surface defects and impurity Cr3+ ions occupying Al3+ octahedral positions, respectively.

  15. Reaction-bonded Al2O3 containing ZrO2 (RBAO)

    International Nuclear Information System (INIS)

    The RBAO process starts from attritated Al/Al2O3 powder mixtures, which are compacted in heat treatment in an oxidising atmosphere. The metal phase is oxidized with an increase in volume, which nearly compensates the sintering shrinkage. A fine-grained Al2O3 with homogeneous pore structure, glass-phase free grain boundaries and high strength is produced. By mixing in fine ZrO2 or Zr, the time for a complete oxidation reaction of the metal phase can be reduced. By adding different additives (Si, Ti, Cr, Zr, SiC, ZrO2 etc) structures and properties can be varied and the shrinking behaviour can be stopped. Due to the high retention of shape and dimensions, the RBAO process is suitable for the production of compound materials, eg: by the insertion of reinforcing fibres and particles. (orig.)

  16. Low Temperature Preparation and Cold Manufacturing Techniques for Femoral Head of Al2O3 Ceramic

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite additives, the cold manufacturing techniques of lathe turning, grade polishing and the matching size correction of the sintered femoral head were studied. The results showed, after being pressed under 200 MPa cold isostatic pressure and being pre-sintered at 1 150 ℃, the biscuit' s strength can meet the demands of lathe turning; After being grade polished by SiC micro-powder and diamond abrading agent and being size corrected by special instruments, the femoral head prosthesis of Al2O3 ceramic has good surface degree of finish and articulates tightly with femoral handle.

  17. Fe-Al2O3 nanocomposites prepared by high-energy ball milling

    DEFF Research Database (Denmark)

    Linderoth, Søren; Pedersen, M.S.

    1994-01-01

    Nanocomposites of alpha-Fe and alpha-Al2O3, prepared by high-energy ball milling, exhibit coercivities which are enhanced by about two orders of magnitude with respect to the bulk value. The degree of enhancement depends on the volume fraction (x(upsilon)) of Fe, with a maximum for x(upsilon) alm......Nanocomposites of alpha-Fe and alpha-Al2O3, prepared by high-energy ball milling, exhibit coercivities which are enhanced by about two orders of magnitude with respect to the bulk value. The degree of enhancement depends on the volume fraction (x(upsilon)) of Fe, with a maximum for x...

  18. Strength Properties and Microstructure of Diphase β—Sialon/Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    LIYoufen; HONGYanruo; 等

    2000-01-01

    Study on modules of rupture and microstructure of xphase bearing diphase β-Sialon and diphase β-Sialon/Al2O3 composites shows that MOR increases with tempera-ture rise up to a maximum oint and then decreases,For diphase β-Sialon materials,the maximum strength reaches 130 MPa-170 MPa at 1200℃;whereas for diphase β-Sialon/Al2O3 composites,the maximum strength reaches 200MPa-300 MPa at 1000℃,In the microstructure of th composite ,oblong crystals of x-phase and hexagonal prismatic crystals of β-Sialon are interlaced in the skeleton structure of corundum.This struture creates a distinctly intensifying effect on the strength of the composite.

  19. TEM study of a hot-pressed Al2O3-NbC composite material

    Directory of Open Access Journals (Sweden)

    Wilson Acchar

    2005-03-01

    Full Text Available Alumina-based composites have been developed in order to improve the mechanical properties of the monolithic matrix and to replace the WC-Co material for cutting tool applications. Al2O3 reinforced with refractory carbides improves hardness, fracture toughness and wear resistance to values suitable for metalworking applications. Al2O3-NbC composites were uniaxially hot-pressed at 1650 °C in an inert atmosphere and their mechanical properties and microstructures were analyzed. Sintered density, average grain size, microhardness and fracture toughness measurements and microstructural features were evaluated. Results have shown that the mechanical properties of alumina-NbC are comparable to other carbide systems. Microstructural analysis has shown that the niobium carbide particles are mainly located at the grain boundaries of alumina grains, which is an evidence of the "pinning effect", produced by NbC particles.

  20. Versatile sputtering technology for Al2O3 gate insulators on graphene

    Directory of Open Access Journals (Sweden)

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

    2012-01-01

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

  1. Preparation of ZnO-Al2O3 Particles in a Premixed Flame

    DEFF Research Database (Denmark)

    Jensen, Joakim Reimer; Johannessen, Tue; Wedel, Stig;

    2000-01-01

    Zinc oxide (ZnO) and alumina (Al2O3) particles are synthesized by the combustion of their volatilized acetylacetonate precursors in a premixed air-methane flame reactor. The particles are characterized by XRD, transmission electron microscopy, scanning mobility particle sizing and by measurement...... temperature and a decreasing precursor vapour pressure. The combustion of precursor mixtures leads to composite particles consisting of zinc aluminate ZnAl2O4 intermixed with either ZnO or Al2O3 phases. The zinc aluminate particles are dendritic aggregates, resembling the alumina particles, and are evidently...... synthesized to the full extent allowed by the overall precursor composition. The addition of even small amounts of alumina to ZnO increases the specific surface area of the composites significantly, for e.g. zinc aluminate particles to approximately 150 m2/g. The gas-to-particle conversion is initiated...

  2. Ni/Al2O3 catalysts for syngas methanation: Effect of Mn promoter

    Institute of Scientific and Technical Information of China (English)

    Anmin Zhao; Weiyong Ying; Haitao Zhang; Hongfang Ma; Dingye Fang

    2012-01-01

    Ni/Al2O3 catalysts with different amounts of manganese ranging from 1 to 3 wt% as promoter were prepared by co-impregnation method.The catalysts were characterized by N2 physisorption,XRD,TPR,SEM and TEM.Their catalytic activity towards syngas methanation reaction was also investigated using a fixed-bed integral reactor.It was demonstrated that the addition of manganese to Ni/Al2O3 catalysts can increase the catalyst surface area and average pore volume,but decrease NiO crystallite size,leading to higher activity and stability.The effects of reaction temperature,pressure and weight hourly space velocity (WHSV) on carbon oxides conversion and CH4 formation rate were also studied.High carbon oxides conversion,CH4 selectivity and formation rate were achieved at the reaction temperature range of 280-300 ℃.

  3. 气相氟化四氯乙烯的ZnF_2/Al_2O_3催化剂%Study on ZnF_2/Al_2O_3 catalysts for the vapor phase hydrofluorination of tetrachloroethylene

    Institute of Scientific and Technical Information of China (English)

    程永香; 谢遵运; 彭小波; 罗孟飞

    2012-01-01

    ZnF2/Al2O3 catalysts were prepared by an impregnation method.The effect of the Al2O3 support calcination temperature on catalytic performance for the vapor phase hydrofluorination of tetrachloroethylene was studied.The catalysts were characterized by XRD,Raman,NH3-TPD and BET techniques.The results show that-Al2O3 started to transform to-Al2O3 and α-Al2O3 at 900 ℃.-Al2O3 reaches to its maximum at 1100℃.By further increasing the calcination temperature,all-Al2O3 transformed to α-Al2O3.The highest activity was obtained on a ZnF2/Al2O3 catalyst with the Al2O3 support calcined at 1110 ℃.The conversion of tetrachloroethylene was 45.7% and the selectivity to HCFC-123(2,2-dichloro-1,1,1-three ethyl fluoride) and HCFC-124(2-chloro-1,1,1,2-tetrafluoroethane) was 48.2% at a reaction temperature of 300 ℃.%采用浸渍法制备了ZnO/Al2O3催化剂,考察了载体Al2O3的焙烧温度对催化剂性能的影响。并对催化剂进行了X射线衍射(XRD)、Raman光谱、氨气程序升温脱附(NH3-TPD)和BET表征。结果表明:随着Al2O3焙烧温度升高,从900℃开始,-Al2O3逐渐向-Al2O3和α-Al2O3转变,1100℃焙烧样品中-Al2O3的XRD峰强度达到最大。当温度继续升高,-Al2O3将转变成α-Al2O3Al2O3载体经过1100℃焙烧制得的ZnF2/Al2O3催化剂催化性能最高,当反应温度为300℃时,四氯乙烯的转化率为45.7%,HCFC-123(2,2-二氯-1,1,1-三氟乙烷)和HCFC-124(2-氯-1,1,1,2-四氟乙烷)的总选择性为48.2%。

  4. Deactivation of a Co-Precipitated Co/Al2O3 Catalyst

    OpenAIRE

    YILDIZ, Meltem; AKIN, Ayşe Nilgün

    2007-01-01

    The effects of reaction temperature, feed ratio, space time, and CO percentage in feed on the deactivation conditions of a co-precipitated 36 wt% Co/Al2O3 catalyst in CO hydrogenation were investigated. Environmental-SEM-EDX and temperature-programmed reduction (TPR) studies were performed on used catalysts to investigate the effect of reaction conditions on catalyst deactivation. Intensive coke deposition on the catalyst was observed at a reaction temperature of about 573 K. Increas...

  5. Modified Mechanism of Eutectic Silicon in Al2O3/Al-Si Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Al2O3/Al-Si alloy composite was manufactured by squeeze casting. The morphology of the eutectic silicon in the composite was observed by scanning electronic microscope (SEM), and the modified mechanism of eutectic silicon in the composite was approached. The alumina fiber in the composite can trigger twin during the growth of Al-Si eutectic and lead to the modification of eutectic silicon near the fiber.

  6. Charge injection from a surface depletion region—The Al 2O 3-silicon system

    Science.gov (United States)

    Kolk, J.; Heasell, E. L.

    1980-03-01

    Electron injection from a surface depletion region, over the surface barrier at an Al 2O 3-silicon interface is studied. The current passing over the barrier is measured by observing the rate of flat-band voltage shift as charge is trapped in the oxide. The data obtained is compared with the predictions of present models for charge injection. It is found that the so-called 'lucky-electron' model gives the most generally satisfactory agreement with the observations.

  7. Radioluminescence in Al2O3: C - analytical and numerical simulation results

    DEFF Research Database (Denmark)

    Pagonis, V.; Lawless, J.; Chen, R.;

    2009-01-01

    used to provide a quantitative description of the thermoluminescence and optically stimulated luminescence processes in Al2O3 : C. Using appropriate sets of trapping parameters for the kinetic model, the RL signal along with the occupancies of the relevant traps and centres are simulated numerically...... hold during irradiation. Several experimentally observed characteristics of the RL signals are explained by using the model. Good quantitative agreement is found between the analytical expressions and the numerical solutions of the model for short irradiation pulses....

  8. KINERJA KATALIS Ag/Al2O3 UNTUK REDUKSI NOx

    Directory of Open Access Journals (Sweden)

    Rakhman Sarwono

    2012-02-01

    Full Text Available NOx merupakan hasil samping dari suatu reaksi pembakaran. NOx merupakan gas yang beracun sangat berbahaya terhadap kesehatan manusia dan hewan bila terhirup pada waktu bernafas. Untuk mengurangi kadar NOx pada gas buang, banyak penelitian diarahkan pada reduksi NOx dengan katalis secara selektif dengan hidrokarbon dan oksigen berlebihan. Katalis yang digunakan adalah katalis alumina (Al2O3 yang didapat dari katalis komersial (AlO1-7 dan katalis hasil sintesa (ALOA. Katalis Ag/Al2O3 didapat dengan memasukkan logam Ag ke dalam alumina (Al2O3 dengan cara impregnasi dengan larutan perak nitrat. Katalis diuji aktifitasnya pada reaktor fixed bed yang diluarnya terdapat pemanas yang bisa diatur suhunya. Reaktan seperti gas NO, C2H4  dan oksigen dimasukkan kedalam reaktor dengan laju yang ditentukan. Hasil reaksi dianalisa dengan gas chromatography dan dicatat pada recorder, selanjutnya bisa ditentukan kuantitas dan prosentase konversinya. Katalis alumina  ALOA mempunyai kemampuan mereduksi NO dengan konversi  sekitar 40-45% gas NO menjadi N2. Loading logam perak (Ag kedalam Al2O3 sebesar 2-3% berat menambah daya reduksi NO menjadi sekitar 45-50% pada suhu 500oC. Pada umpan NO + C2H4  + O2  reaksi reduksi terjadi pada suhu 300oC, sedangkan pada umpan NO + C2H4   (tanpa oksigen reaksi reduksi baru terjadi pada suhu 450oC, dengan demikian adanya oksigen sangat berperan dalam proses reduksi NOx. Reaksi peruraian C2H4 menjadi COx berkebalikan dengan kinerja katalis pada proses reduksi NOx

  9. Electrocatalytic oxidation of phenol using Ni-Al2O3 composite-coating electrodes

    International Nuclear Information System (INIS)

    Electrocatalytic oxidation of phenol on Ni-Al2O3 composite electrodes was investigated in wastewater. Firstly Ni-Al2O3 composite-coating electrodes was prepared by electrodeposition of Ni-Al2O3 composite on the mild steel substrates from the citrate bath containing NiSO4 as a source of nickel and alumina particles. The electrodeposited composite coating was heat treated at 400 deg. C and characterized by using different techniques such as scanning electron microscope (SEM), electron dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). On using this composite coating as electrodes it was found that the highest electrocatalytic activity was achieved in presence of [H2SO4 (2 g/l) + FeSO4 (20 mg/l)]. In presence of each of NaOH and H2SO4 the activity of the electrode was poor. The electro-Fenton's reagent was the most suitable oxidizing agent for the oxidation of phenol. The reaction between hydrogen peroxide, produced at a cathode, with ferrous sulphate produces hydroxyl radical, one of the strongest inorganic oxidants. In the presence of organic compound, the hydroxyl radical oxidizes the degradable compound to a free radicals and water. Further chain oxidation of the organic radicals leads to a total decomposition of the organic compound, leaving only carbon dioxide and water. Optimizing the conditions that ensure effective electrochemical degradation of phenol on Ni-Al2O3 composite-coating electrodes necessitates the control of all the operating factors.

  10. Corrosion Resistance of Ni/Al2O3 Nanocomposite Coatings

    OpenAIRE

    Kucharska, Beata; Agnieszka BROJANOWSKA; Karol POPŁAWSKI; Jerzy Robert SOBIECKI

    2016-01-01

    Nickel matrix composite coatings with ceramic disperse phase have been widely investigated due to their enhanced properties, such as higher hardness and wear resistance in comparison to the pure nickel. The main aim of this research was to characterize the structure and corrosion properties of electrochemically produced Ni/Al2O3 nanocomposite coatings. The coatings were produced in a Watts bath modified by nickel grain growth inhibitor, cationic surfactant and the addition of alumina particle...

  11. New experimental molecular stopping cross section data of Al2O3, for heavy ions

    International Nuclear Information System (INIS)

    Molecular stopping cross section data of Al2O3, for heavy ions of 12C, 16O, 28Si, 35Cl, 79Br within the energy range of 0.01–1.0 MeV/nucleon were measured. Both direct transmission and bulk analysis methods were applied. Stopping cross sections were calculated both with the SRIM and MSTAR codes. Evaluation and intercomparison of the new data with the calculated and previously measured ones are reported in this paper

  12. Influence of Sonication on the Stability and Thermal Properties of Al2O3 Nanofluids

    OpenAIRE

    Monir Noroozi; Shahidan Radiman; Azmi Zakaria

    2014-01-01

    Nanofluids containing Al2O3 nanoparticles (either 11 or 30 nm in size) dispersed in distilled water at low concentrations (0.125–0.5 wt%) were prepared using two different ultrasonic devices (a probe and a bath sonicator) as the dispersant. The effect of the ultrasonic system on the stability and thermal diffusivity of the nanofluids was investigated. Thermal diffusivity measurements were conducted using a photopyroelectric technique. The dispersion characteristics and morphology of the nanop...

  13. Kinetic Adsorption of Cd onto Nanometer Al2O3/Carbon Fibre

    Institute of Scientific and Technical Information of China (English)

    LI Yu; WANG Yue; HAN Wei; LI Su-wen; ZHAO Hui; ZHU Chang-yun; WANG Heng

    2005-01-01

    A new nanometer material, nano-Al2O3 with carbon fibre as the carrier, was employed for the removal of Cd with low concentrations from polluted water. The characterization of the material was carried out by means of SEM and TEM. Batch adsorption and elution experiments were carried out to determine the adsorption properties of Cd on the new adsorbent. The classical Thomas model was applied to estimating the equilibrium coefficients of Cd adsorption and the saturated adsorption ability. The results show that the Thomas model is fit for describing the kinetic adsorption process, and the maximum adsorption capacity of the nanometer Al2O3/carbon is 69.29 mg/g. The resulting information also indicates that the desorption of Cd eluted with de-ionized water at a rate of 9.8 mL/min can be neglected. With the advantage of a high adsorption capacity for removing low concentration Cd, the Al2O3/carbon fibre possesses the potentiality to be an effective adsorbent for the removal of Cd from polluted water.

  14. Insight into the effects of different ageing protocols on Rh/Al2O3 catalyst

    Science.gov (United States)

    Zhao, Baohuai; Ran, Rui; Cao, Yidan; Wu, Xiaodong; Weng, Duan; Fan, Jun; Wu, Xueyuan

    2014-07-01

    In this work, a catalyst of Rh loaded on Al2O3 was prepared by impregnating method with rhodium nitrate aqueous solution as the Rh precursor. The catalyst was aged under different protocols (lean, rich, inert and cyclic) to obtain several aged samples. All the Rh/Al2O3 samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, CO-chemisorption, H2-temperature programmed reduction (H2-TPR), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that a specific ageing treatment could strongly affect the catalytic activity. The N2 aged and the H2 aged samples had a better catalytic activity for CO + NO reaction than the fresh sample while the air aged and the cyclic aged samples exhibited much worse activity. More surface Rh content and better reducibility were obtained in the N2 and the H2 aged samples and the Rh particles existed with an appropriate size, which were all favorable to the catalytic reaction. However, the air and the cyclic ageing protocols induced a strong interaction between Rh species and the Al2O3 support, which resulted in a severe sintering of particles of Rh species and the loss of active sites. The structure evolution scheme of the catalysts aged in different protocols was also established in this paper.

  15. Fabrication of Homogenous Dispersion TiB2-Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jinyong; TANG Wenjun; FU Zhengyi; WANG Weiming; ZHANG Qingjie

    2011-01-01

    In order to get a homogenous mixture and compact of TiB2-A12O3,hybridization as a surface modification method was used to prepare nano-scale Al2O3 coated TiB2 particles.PE-wax particles were first coated onto TiB2 particles by hybridization,and then the nano-scale Al2O3 particles were coated onto the surface of TiB2 coated by PE-wax particles again.SEM,TEM and EDS were used to characterize the microstructure of as-received core/shell particles and its compacts.The experimental results show that a particle-scale homogenous dispersion of TiB2 and Al2O3 can be formed not only in mixed powder but also in dewaxed compacts.The compacts then were sintered by gas-pressing sintering(GPS).Finial products show improved mechanic properties comparing with reference samples fabricated by normal ways.

  16. Effects of drying method on preparation of nanometer α-Al2O3

    Institute of Scientific and Technical Information of China (English)

    XIAO Jin; WAN Ye; DENG Hua; LI Jie; LIU Ye-xiang

    2007-01-01

    Ammonium aluminum carbonate hydroxide (AACH) precursor was synthesized by the precipitation reaction of aluminum sulfate and ammonium carbonate. Then the precursor was dealt with five drying methods including ordinary drying, alcohol exchange, vacuum freeze-drying, glycol distillation, n-butanol azeotropic distillation respectively and calcined at 1 200 ℃ for 2 h to get α-Al2O3. The effects of drying methods on preparation of nanometer α-Al2O3 were discussed, and the optimal drying method was confirmed. The structural properties of powders were characterized by XRD, SEM and BET measurements. The results show that vacuum freeze-drying, glycol distillation and n-butanol azeotropic distillation can prevent the powders from aggregating, and among them the n-butanol azeotropic distillation is the best method. The nanometer α-Al2O3 powder with non-aggregation can be manufactured using n-butanol azeotropic distillation and the average particle size is about 40 nm.

  17. Micro mechanical properties of n-Al2O3/Ni composite coating by nanoindentation

    Institute of Scientific and Technical Information of China (English)

    WANG Hong-mei; XU Bin-shi; MA Shi-ning; DONG Shi-yun; LI Xiao-ying

    2004-01-01

    A new type of nano test system was introduced, the test principle and the indentation data analysis method were described. It was used to test the micro mechanical properties, such as hardness, elastic modulus and indentation creep property of n-Al2O3/Ni composite coating on steel prepared by brush plating, and the variety of mechanical properties with coating thickness was researched. The results show that the mechanical properties are basically identical within the whole coating, the hardness and modulus decrease in the defect fields, especially within the dendritic crystals, whereas the mechanical properties are not influenced greatly at the interspaces among dendritic crystals. The average hardness and elastic modulus of n-Al2O3/Ni coating are 6.34 GPa and 154 GPa respectively, and the hardness is 2.4 times higher than that of steel and the indentation creep curve of n-Al2O3/Ni coating is similar to that of the uniaxial compression creep, and the creep rate of steady-state is about 0. 104 nm/s. These results will supply useful data for process improvement, new type material development and application expansion.

  18. Hole centers in γ-irradiated, oxidized Al2O3

    International Nuclear Information System (INIS)

    ESR observations of centers with S = 1/2, g approximately equal to 2, S = 1, g approximately equal to 2 have been made at 77 K on oxidized Al2O3 after γ-irradiation at 300C. From the radiation growth data, it is shown that the S = 1/2 centers are precursors of the S = 1 centers. In addition, when the S = 1 centers anneal out at about 1100C, the S = 1/2 centers reappear and eventually anneal out at about 2600C. Previously Gamble (Gamble, F.T.; Ph.D. Thesis, U. of Connecticut (1963)) and Cox (Cox, R.T.; Ph.D. Thesis, U. of Grenoble (1972) unpublished), respectively, observed S = 1/2 and S = 1 paramagnetic centers in electron-irradiated nominally pure Al2O3 and γ-irradiated, oxidized, titanium-doped Al2O3. The models proposed for these centers were one hole and two holes trapped on oxygen ions adjacent to Al3+ vacancies. Our results further substantiate these models. (author)

  19. Bonding of Al2O3 ceramic and Nb using transient liquid phase brazing

    Institute of Scientific and Technical Information of China (English)

    于治水; 梁超; 李瑞峰; 吴铭方; 祁凯

    2004-01-01

    The brazing of Al2O3 to Nb was achieved by the method of transient liquid phase (TLP) bonding. Ti foil and Ni-5V alloy foil were used as interlayers for the bonding. The base materials were brazed at 1 423 - 1 573 K for 1-120 min. The results show that the shear strength of the joint first increases and then decreases with increasing holding time and brazing temperature. The joint interface microstructure and elements distribution were investigated. It can be concluded that a composite structure, in which the base metals are solid solution Nb(V) and Nb(Ti)reinforced by Ni2Ti, is formed when the brazing temperature is 1 473 K and holding time 15 min, and a satisfactory joint strength can be achieved. The interaction of Ti foil and Ni-5V foil leads to the formation of liquid eutectic phase with low melting point, at the same time the combination of Ti come from the interlayer with O atoms from Al2O3 results in the bonding of Al2 O3 and Nb.

  20. Compactibility of Al/Al2O3 Isotropic Composite with Variation of Holding Time Sintering.

    Directory of Open Access Journals (Sweden)

    Eddy S Siradj

    2008-11-01

    Full Text Available The requirement of component with structural ability, light weight and also strength is increasing base on Metal Matrix Composites (MMCs by aluminum as matrix (AMCs. A structural ability is connected to composites compactibility which is depend on quality of interfacial bounding. Powder metallurgy is one of method to produce composite with powder mixing, compacting and sintering. Volume fractions reinforced and sintering time can influence composites compactibility. Volume fractions reinforced variable can produce different reinforcement effect. Beside that, on sintering enables the formation of new phase during sintering time. In this research, Al/Al2O3 isotropic composites are made with aluminum as matrix and alumina (Al2O3 as reinforced. Volume fraction reinforced used 10%. 20%. 30% and 40%. Sintering temperature and compaction pressure are each 600oC and 15 kN. The tests that applied are compression and metallographic test. The result that obtained is optimum compactibility of Al/Al2O3 composite reached at holding time 2 hour. During sintering, new phase can occur that is aluminum oxides (alumina, with unstable properties. The best volume fraction reinforced and holding time sintering are 40% and 2 hours.

  1. Er3+–Al2O3 nanoparticles doping of borosilicate glass

    Indian Academy of Sciences (India)

    Jonathan Massera; Laeticia Petit; Joona Koponen; Benoit Glorieux; Leena Hupa; Mikko Hupa

    2015-09-01

    Novel borosilicate glasses were developed by adding in the glass batch Er3+–Al2O3 nanoparticles synthetized by using a soft chemical method. A similar nanoparticle doping with modified chemical vapour deposition (MCVD) process was developed to increase the efficiency of the amplifying silica fibre in comparison to using MCVD and solution doping. It was shown that with the melt quench technique, a Er3+–Al22O3 nanoparticle doping neither leads to an increase in the Er3+ luminescence properties nor allows one to control the rare-earth chemical environment in a borosilicate glass. The site of Er3+ in the Er3+–Al2O3 nanoparticle containing glass seems to be similar as in glasses with the same composition prepared using standard raw materials. We suspect the Er3+ ions to diffuse from the nanoparticles into the glass matrix. There was no clear evidence of the presence of Al2O3 nanoparticles in the glasses after melting.

  2. Microstructure and mechanical properties of Al2O3/TiAl composite

    Institute of Scientific and Technical Information of China (English)

    AI Tao-tao; WANG Fen; ZHU Jian-feng

    2006-01-01

    Al2O3/TiAl composites were fabricated by PAXD (pressure-assisted exothermic dispersion) method. The effects of Nb2O5 content on the microstructure and mechanical properties of the composites were investigated. The results show that the ultimate phases of the composite consist of TiAl, Ti3Al, Al2O3 and a small amount of NbAl3. SEM reveals that a submicron γ+(α2/γ) dual phases structure can be presented after sintered at 1 200 ℃. Furthermore, with the increase of Nb2O5 content, the ratio of TiAl to Ti3Al phase decreases correspondingly, the grains of the composites are remarkably refined, and the produced Al2O3 particles are uniformly dispersed. When 6% Nb2O5 is added, the composite has the best comprehensive properties. It exhibits a Vickers hardness of 4.77 GPa and a bending strength of 642 MPa. Grain-refinement and dispersion-strengthening are the main strengthening mechanisms.

  3. Fabrication and Mechanical Properties of Al_2O_3/TiAl Composites

    Institute of Scientific and Technical Information of China (English)

    AI Taotao

    2009-01-01

    Al_2O_3/TiAl composites were successfully fabricated by hot-press-assisted exother-mic dispersion method with elemental powder mixtures of Ti,Al TiO_2 and Nb_2O_5,and the micro-structure and mechanical properties were investigated.The results indicate the fine Al_2O_3 particles tend to disperse on the grain boundaries.The grain size of TiAl matrix decreases and the hardness increases with increasing Nb_2O_5 content.The bending strength and fracture toughness reach to a maximum when Nb_2O_5 content is 6 wt%,under 642 Mpa and 6.69 Mpa·m ~(1/2) ,respectively.Based on the fractography and the observation of crack propagation path,it is concluded that the strengthening and toughening of such composites at room temperature can be attributed to the refinement of the TiAl matrix,the de-flection behavior in the crack propagation and the dispersion of Al_2O_3 particles.

  4. Spectroscopy and optically stimulated luminescence of Al2O3:C using time-resolved measurements

    Science.gov (United States)

    Yukihara, E. G.; McKeever, S. W. S.

    2006-10-01

    This paper reports the observation of ultraviolet (UV) emission at 335nm in the optically stimulated luminescence (OSL) of carbon-doped aluminum oxide (Al2O3:C) and presents results on the investigation of the OSL properties of this band, including its dose response, time dependence after irradiation, and dependence of the OSL signal on the type of radiation. Time-resolved OSL measurements were used to separate the UV emission band from the dominant OSL emission band of Al2O3:C, namely, the F-center luminescence at 420nm. A comparison of the OSL properties of the UV and F-center emission bands is important for various dosimetric applications because the relative contribution of the UV and F-center emissions to the OSL signal varies with readout technique and optical filters used in the readout equipment. The UV emission band is found to show an ionization density dependence that is different from the dependence observed for the F-center emission, and an increase in intensity with time elapsed after beta irradiation. These results are relevant for OSL dosimetry of radiation fields containing heavy charged particles, such as the space radiation field and the secondary fields created by interactions of matter with energetic neutrons, as well as for understanding of the basic OSL mechanism in Al2O3:C.

  5. Growth of Epitaxial gamma-Al2O3 Films on Rigid Single-Crystal Ceramic Substrates and Flexible, Single-Crystal-Like Metallic Substrates by Pulsed Laser Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Junsoo [ORNL; Goyal, Amit [ORNL; Wee, Sung Hun [ORNL

    2009-01-01

    Epitaxial -Al2O3 thin films were grown on diverse substrates using pulsed laser deposition. The high quality of epitaxial growth and cubic structure of -Al2O3 films was confirmed by x-ray diffraction. SrTiO3 and MgO single crystal substrates were used to optimize the growth conditions for epitaxial -Al2O3 film. Under the optimized conditions, epitaxial -Al2O3 thin films were grown on flexible, single-crystal-like, metallic templates. These included untextured Hastelloy substrates with a biaxially textured MgO layer deposited using ion-beam-assisted-deposition and biaxially textured Ni-W metallic tapes with epitaxially grown and a biaxially textured, MgO buffer layer. These biaxially textured, -Al2O3 films on flexible, single-crystal-like substrates are promising for subsequent epitaxial growth of various complex oxide films used for electrical, magnetic and electronic device applications.

  6. Capacitance-voltage characteristics of (Al/Ti)/Al2O3/n-GaN MIS structures

    International Nuclear Information System (INIS)

    The capacitance-voltage characteristics of (Al/Ti)/Al2O3/n-GaN metal—insulator-semiconductor (MIS) structures are measured and analyzed. n-Type GaN films are grown on sapphire (0001) substrates by the metal-organic chemical vapor deposition method. An aluminum-oxide layer with a thickness of 60 nm is deposited onto the surface of GaN by the method of atomic-layer deposition from the gas phase. Metallic contacts are deposited by the electron-beam evaporation of titanium and aluminum in vacuum. According to the measurement results, the breakdown-field strength of the oxide, its dielectric constant, and the integrated electron density of states at the oxide-semiconductor interface are 5 × 106 V/cm, 7.5, and 3 × 1012 cm−2, respectively

  7. Preparation of Paraffin/γ-Al2O3Composites as Phase Change Energy Storage Materials%Preparation of Paraffin/γ-Al2O3 Composites as Phase Change Energy Storage Materials

    Institute of Scientific and Technical Information of China (English)

    ZHAO Liang; MARuiying; MENG Xianglan; WANG Gang; FANG Xiangchen

    2011-01-01

    Paraffin/γ-Al2O3 composites as phase change energy storage materials were prepared by absorbingparaffin in porous network of γ-Al2O3.In the composite materials,paraffin was used as a phase change material(PCM) for thermal energy storage,and γ-Al2O3 acted as supporting materials.Characterizations were conducted to evaluate the energy storage performance of the composites,and differential scanning calorimeter results showed that the PCM-3 composite has melting latent heat of 112.9 kJ/kg with a melting temperature of 62.9 ℃.Due to strong capillary force and surface tension between paraffin and γ-Al2O3,the leakage of melted paraffin from the composites can be effectively prevented.Therefore,the paraffin/γ-Al2O3 composites have a good thermal stability and can be used repeatedly.

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

    OpenAIRE

    Yu-Hsien Lin; Jay-Chi Chou

    2015-01-01

    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 (

  9. A nanoplate-like α-Al2O3 out-layered Al2O3-ZrO2 coating fabricated by micro-arc oxidation for hip joint prosthesis

    Science.gov (United States)

    Zhang, Lan; Zhang, Wenting; Han, Yong; Tang, Wu

    2016-01-01

    A nanoplate-like α-Al2O3 out-layered Al2O3-ZrO2 coating was fabricated on Zr substrate by micro-arc oxidation (MAO). The structure, formation mechanism, anti-wear property and aging behavior of the coating were explored. The obtained results show that the coating is composed of Al2O3 and ZrO2; the amount and crystallinity of Al2O3 increase gradually from inner layer to the coating surface; monoclinic ZrO2 (m-ZrO2) and tetragonal ZrO2 (t-ZrO2) are both present in the coating, and the ratio of t-ZrO2/m-ZrO2 increases with closing to the coating surface by a "constraint" mechanism of Al2O3; the coating surface mainly consists of nanoplate-like α-Al2O3, and a small amount of nanocrystallized m- and t-ZrO2. The superimposition of α-Al2O3 growth unit on {0 0 0 1} face should be prohibited by PO43- during the MAO process, resulting in the formation of nanoplate-like α-Al2O3 on the coating surface. Compared with pure Zr, the coating shows noticeable improvement in wear-resistance. For aging behavior, although more t-ZrO2 in the coating is transformed to m-ZrO2 with increasing aging time, wear loss increases slightly. It indicates that the nanoplate-like α-Al2O3 out-layered Al2O3-ZrO2 is a potential coating for articular head replacement.

  10. Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al2O3 particles

    Institute of Scientific and Technical Information of China (English)

    Shu-Huei Hsieh; Jao-Jia Horng

    2007-01-01

    Carbon nanotubes (CNTs) were grown on the surface of microsized Al2O3 particles in CH4 atmosphere at 700 ℃ under the catalysis of Fe-Ni nanoparticles.The CNTs on Al2O3 were used for adsorbing Pb2+,Cu2+,and Cd2+ from the solution and the results were compared with active carbon powders,commercial carbon nanotubes,and Al2O3 particles.The as-grown CNTs/Al2O3 have demonstrated extraordinary absorption capacity with further treatment or oxidation,as well as hydrophilic ability that other CNTs lacked.The adsorption capacity of CNTs on Al2O3 is superior to other adsorbents and the preference order of adsorption on composite Al2O3 is Pb2+>Cu2+>Cd2+.It seemed that the adsorption of those Pb2+,Cu2+,and Cd2+ did not change the surface properties of composite particles.The adsorption behaviors of Pb2+,Cu2+,and Cd2+ by CNTs on Al2O3 match well with the Langmuir isothermal adsorption model and the second order kinetic model.The calculated saturation amount adsorbed by 1 g of CNTs on Al2O3 are 67.11,26.59,and 8.89 mg/g for Pb2+,Cu2+,and Cd2+ in single adsorption test,respectively.

  11. Study on Sulfation of CeO2/γ-Al2O3 Sorbent in Simulated Flue Gas

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The sulfation of CeO2/γ-Al2O3 sorbent in simulated flue gas was studied. A series of CeO2/γ-Al2O3 sorbents with different CeO2 loadings were prepared by impregnation and characterized by X-ray diffraction. Thermogravimetric technique was used to study the sulfation of CeO2/γ-Al2O3 sorbents, mainly on the CeO2 loading, sulfation cycles, and intrinsic kinetics. The study revealed that monolayer coverage of CeO2 supported on γ-Al2O3 was 0.125 g CeO2/g (γ-Al2O3). Below monolayer coverage, CeO2 was highly dispersed on γ-Al2O3. The optimal CeO2 loading on sulfation was 0.03 g CeO2/g (γ-Al2O3). CeO2/γ-Al2O3 sorbent was recyclable by controlling sulfation time. Intrinsic kineticd equation was R=1.1394×10-4×exp (-1,508.39/T) mg·mg-1·s-1. Activation energy and reaction order were 12.54 kJ·mol-1 and first order, respectively.

  12. Formation of a 25 mol% Fe2O3-Al2O3 solid solution prepared by ball milling

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Mørup, Steen; Linderoth, Søren

    1996-01-01

    The phase transformation process of a 25 mol% Fe2O3-Al2O3 powder mixture during high-energy ball milling has been studied by x-ray diffraction and Mossbauer spectroscopy. A metastable solid solution of 25 mol % Fe2O3 in Al2O3 with corundum structure has successfully been prepared after a milling ...

  13. Structure, optical properties and thermal stability of Al2O3-WC nanocomposite ceramic spectrally selective solar absorbers

    Science.gov (United States)

    Gao, Xiang-Hu; Wang, Cheng-Bing; Guo, Zhi-Ming; Geng, Qing-Fen; Theiss, Wolfgang; Liu, Gang

    2016-08-01

    Traditional metal-dielectric composite coating has found important application in spectrally selective solar absorbers. However, fine metal particles can easily diffuse, congregate, or be oxidized at high temperature, which causes deterioration in the optical properties. In this work, we report a new spectrally selective solar absorber coating, composed of low Al2O3 ceramic volume fraction (Al2O3(L)-WC) layer, high Al2O3 ceramic volume fraction (Al2O3(H)-WC layer) and Al2O3 antireflection layer. The features of our work are: 1) compared with the metal-dielectric composites concept, Al2O3-WC nanocomposite ceramic successfully achieves the all-ceramic concept, which exhibits a high solar absorptance of 0.94 and a low thermal emittance of 0.08, 2) Al2O3 and WC act as filler material and host material, respectively, which are different from traditional concept, 3) Al2O3-WC nanocomposite ceramic solar absorber coating exhibits good thermal stability at 600 °C. In addition, the solar absorber coating is successfully modelled by a commercial optical simulation programme, the result of which agrees with the experimental results.

  14. Influence of different acid etchings on the superficial characteristics of Ti sandblasted with Al2O3

    Directory of Open Access Journals (Sweden)

    Bruno Ramos Chrcanovic

    2013-01-01

    Full Text Available Some implant manufactures use Al2O3 instead TiO2 powder to sandblast the machined dental implant, because Al2O3 powder is commercially more easily available and is cheaper than TiO2 powder. However, Al2O3 powder usually leaves aluminum oxide contamination on the surface, which is potentially toxic. In this work, we subjected Ti discs previously sandblasted with Al2O3 powder to 5 different acid etchings in order to verify which treatment is able to remove incorporated particles of Al2O3 from the surface. One group of samples were only sandblasted and served as control. The samples were analyzed by electron microscopy (SEM, EDS, scanning probe microscopy, and grazing incidence XRD. The control group showed presence of Al2O3 on the surface. Three acid etchings were efficient in removing the alumina from the tested samples. Almost all the tested samples showed higher roughness parameters values than the control samples. Titanium hydride was found in almost all test groups. Moreover, the results suggest that there is no incorporation of the whole Al2O3 particle into the titanium surface after the collision, conversely a particle fragmentation occurs and what remains on the titanium surface are Al2O3 residues.

  15. Effects of Y2O3 on Thermal Shock of Al2O3/TiCN Composites

    Institute of Scientific and Technical Information of China (English)

    Qiu Guanming; Li Xikun; Xiu Zhimeng; Sun Xudong; Yan Changhao; Dai Shaojun

    2005-01-01

    Thermal shock resistance of Al2O3-TiCN(30%)-Y2O3(0.2%) composite was studied by hot pressing(HP) method at different temperatures. The study shows that thermal shock resistance of the material is determined by its microstructure and reinforced mechanism. According to SEM and calculation of thermal shock, the fractured surface of Al2O3-30%TiCN-0.2%Y2O3 composite is undulate. The residual strength of Al2O3-30%TiCN-0.2%Y2O3 is higher than Al2O3-30%TiCN at 200~800 ℃ after thermal shock. Cracks initiation resistance (R')and cracks propagation resistance (R″″)of Al2O3-30%TiCN-0.2%Y2O3 composite increases 12% and 5% respectively compared with that of Al2O3-30%TiCN. It matches with experimental results. The addition of Y2O3 forms YAG that inhibits crystal growth, and increases fracture stress, fracture toughness, cracks initiation resistance and cracks propagation resistance. Therefore, thermal shock resistance increases. The fracture work of Al2O3-30%TiCN and Al2O3-30%TiCN-0.2%Y2O3 composites are 132 and 148 J·m-2 respectively.

  16. Deposition of BaFe12O19 Thin Films by a New Injection-CVD Method

    OpenAIRE

    Pignard, S.; SÉnateur, J.; Vincent, H.; Kreisel, J.; Abrutis, A.

    1997-01-01

    A new process of injection-MOCVD has been used to synthesize barium hexaferrite thin films on Al2O3 (0001) substrates. This new technique uses a liquid source of precursors dissolved in a convenient solvent. X-ray diffraction measurements have been performed to observe thin films lattices with respect to the orientation of the substrate : hexaferrite film epitaxy is observed with c-axis perpendicular to the substrate. Magnetic measurements have been performed in the plane and perpendicular to...

  17. The effect of precursors salts on surface state of Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts

    Directory of Open Access Journals (Sweden)

    André L. Guimarães

    2004-12-01

    Full Text Available The influence of the precursors on the promoting effect of ceria on Pd/Al2O3 catalyst, when ceria is coated over alumina was studied. The reaction of propane oxidation proceeded under different feed conditions and the surface active sites were characterized by X-ray photoelectron spectroscopy (XPS and in situ diffuse reflectance spectroscopy (DRS. XPS and DRS results show that PdO/Pd0 interface are the active sites independent of the precursor, while the catalysts containing CeO2 showed formation of palladium species in the highest oxidation state, probably PdO2 (338 eV after the oxidation of propane. Besides, the O/Al and O/Ce ratios evidenced the increase of oxygen storage in the presence of CeO2. In addition, the precursor acetylacetonate favors the oxygen storage in the lattice.Estudo da influência dos precursores sobre os catalisadores de Pd/Al2O3 promovidos com céria ancorado sobre a alumina. A oxidação do propano foi feita sob diferentes condições de alimentação sendo caracterizados os sítios superficiais por Espectroscopia Fotoeletrônica de raios X (XPS e por Refletância Difusa em ''situ''. Resultados de XPS e DRS mostraram a formação de interfaces de PdO/Pd0 como sendo os sítios ativos, independentes do precursor utilizado na preparação, enquanto que os catalisadores contendo CeO2 mostraram a formação de espécies de paládio com estado de oxidação mais altos, provavelmente PdO2 (338 eV após a oxidação do propano. Além disso, as razões O/Al e O/Ce evidenciaram um aumento de oxigênio armazenado na presença de CeO2. O precursor acetilacetonato favoreceu o armazenamento de oxigênio na rede.

  18. Research on microcracks avoidance in processing of α-Al2O3 by ultrashort laser pulses

    Science.gov (United States)

    Wang, Cheng-Wei; Zhao, Quan-Zhong

    2013-07-01

    The optical crystal α-Al2O3 has been widely used as the matrix of ruby and blue sapphire for its wide transparency, high thermal conductivity, big scale and low cost. α-Al2O3 is so hard that cutter is easily abraded. Micromachining of α-Al2O3 by ultrashort pulsed laser is superior to the traditional mechanical approach as its non-contact and cold machining features. However, unexpected cracks on the surface of α-Al2O3 are observed after femtosecond laser machining. In order to hinder the crack source from stretching, we optimize the laser parameters accompanied with annealing. The crack-free machining can be achieved. Three-dimensional α-Al2O3 microstructures free from fracture, such as cylinder, barrel and sphere are demonstrated.

  19. The Influence of Nano-Al2O3 Additive on the Adhesion between Epoxy Resin and Steel Substrate

    Institute of Scientific and Technical Information of China (English)

    ZHAI Lan-lan; LING Guo-ping

    2004-01-01

    The influence of nano-Al2O3 additive on the adhesion between epoxy resin and steel substrate has been investigated. The results of tensile testing indicated that the adhesion strength was increased dramatically by addition of Al2O3 nanoparticles in epoxy resin compared with that of the unmodified resin. The highest adhesion strength was obtained with 1 wt% nano-Al2O3 added in epoxy adhesive, more than two times higher than that of the unmodified. Scanning electronic microscope (SEM) revealed that a boundary layer exists between epoxy and steel substrate, energy spectrum analysis indicates there is enrichment of the nano-Al2O3 particle. Those results confirmed that the nano-Al2O3 additive was closely related to the change of interface morphology and the improvement of adhesion strength. The reason for adhesion improvement was also be discussed.

  20. Synthesis and characterization of PMMA/Al2O3 composite particles by in situ emulsion polymerization

    Institute of Scientific and Technical Information of China (English)

    Hui Liu; Hongqi Ye; Tianquan Lin; Tao Zhou

    2008-01-01

    In order to improve its dispersibility, superfine alumina (Al2O3) was encapsulated with poly (methyl methacrylate) (PMMA) by in situ emulsion polymerization. It was found that only when the concentration of sodium dodecyl sulfate (SDS) was much higher than its critical micelle concentration, could PMMA/Al2O3 composite particles with high percentage of grafting (PG) be prepared. The same results were obtained between the experimental and stoichiometric amounts of tris (dodecylbenzenesulfonate) isopropoxide (NDZ), indicating that single-molecule-layer adsorption had taken place between NDZ and Al2O3. Analysis using FTIR. TEM and XPS showed that PMMA/Al2O3 composite particles with core-shell structure had been successfully synthesized by in sire emulsion polymerization. Compared to Al2O3, thermal stability and dispersibility of the composite particles showed marked improvement.

  1. Synthesis of ZrO2—Al2O3 Ultrafines Composites and Their Sintering Behavior

    Institute of Scientific and Technical Information of China (English)

    CHENZhiqiang; QINFeng

    1997-01-01

    Four kinds of ultrafies were manufac-tured by different methods,Sintering behavior,mechanical properties,thermal shock resis-tance and microstructure were studied,ZrO2 grains and Al2O3 grains can inhibit each other's growth during sintering process,ZrO2-Al2O3 comosites have higher sintering temperatures than single Y-ZrO2 or Al2O3 materials,Proper ZrO2 addition can reinforce and densify Al2O3 ultrafines material as well as improve thermal shock resistance,20wt% Al2O3 doped to 3Y-ZrO3 material is beneficial to stability of ZrO2 materials,the bend strength can reach 817.8 MPa.

  2. UV and IR laser induced ablation of Al2O3/SiN:H and a-Si:H/SiN:H

    Directory of Open Access Journals (Sweden)

    Schutz-Kuchly T.

    2014-01-01

    Full Text Available Experimental work on laser induced ablation of thin Al2O3(20 nm/SiN:H (70 nm and a-Si:H (20 nm/SiN:H (70 nm stacks acting, respectively, as p-type and n-type silicon surface passivation layers is reported. Results obtained using two different laser sources are compared. The stacks are efficiently removed using a femtosecond infra-red laser (1030 nm wavelength, 300 fs pulse duration but the underlying silicon surface is highly damaged in a ripple-like pattern. This collateral effect is almost completely avoided using a nanosecond ultra-violet laser (248 nm wavelength, 50 ns pulse duration, however a-Si:H flakes and Al2O3 lace remain after ablation process.

  3. Temperature- and frequency-dependent dielectric behaviors of insulator/semiconductor (Al2O3/ZnO) nanolaminates with various ZnO thicknesses

    Science.gov (United States)

    Li, Jin; Bi, Xiaofang

    2016-07-01

    Al2O3/ZnO nanolaminates (NLs) with various ZnO sublayer thicknesses were prepared by atomic layer deposition. The Al2O3 sublayers are characterized as amorphous and the ZnO sublayers have an oriented polycrystalline structure. As the ZnO thickness decreases to a certain value, each NL exhibits a critical temperature at which its dielectric constant starts to rise quickly. Moreover, this temperature increases as the ZnO thickness is decreased further. On the other hand, the permittivity demonstrates a large value of several hundred at a frequency  ⩽1000 Hz, followed by a steplike decrease at a higher frequency. The change in the cut-off frequency with ZnO thickness is characterized by a hook function. It is revealed that the Coulomb confinement effect becomes predominant in the dielectric behaviors of the NLs with very thin ZnO. As the ZnO thickness decreases to about the same as or even smaller than the Bohr radius of ZnO, a great change in the carrier concentration and effective mass of ZnO is induced, which is shown to be responsible for the peculiar dielectric behaviors of Al2O3/ZnO with very thin ZnO. These findings provide insight into the prevailing mechanisms to optimize the dielectric properties of semiconductor/insulator laminates with nanoscale sublayer thickness.

  4. Oxide Charge Engineering of Atomic Layer Deposited AlOxNy/Al2O3 Gate Dielectrics: A Path to Enhancement Mode GaN Devices.

    Science.gov (United States)

    Negara, M A; Kitano, M; Long, R D; McIntyre, P C

    2016-08-17

    Nitrogen incorporation to produce negative fixed charge in Al2O3 gate insulator layers is investigated as a path to achieve enhancement mode GaN device operation. A uniform distribution of nitrogen across the resulting AlOxNy films is obtained using N2 plasma enhanced atomic layer deposition (ALD). The flat band voltage (Vfb) increases to a significantly more positive value with increasing nitrogen concentration. Insertion of a 2 nm thick Al2O3 interlayer greatly decreases the trap density of the insulator/GaN interface, and reduces the voltage hysteresis and frequency dispersion of gate capacitance compared to single-layer AlOxNy gate insulators in GaN MOSCAPs.

  5. Oxide Charge Engineering of Atomic Layer Deposited AlOxNy/Al2O3 Gate Dielectrics: A Path to Enhancement Mode GaN Devices.

    Science.gov (United States)

    Negara, M A; Kitano, M; Long, R D; McIntyre, P C

    2016-08-17

    Nitrogen incorporation to produce negative fixed charge in Al2O3 gate insulator layers is investigated as a path to achieve enhancement mode GaN device operation. A uniform distribution of nitrogen across the resulting AlOxNy films is obtained using N2 plasma enhanced atomic layer deposition (ALD). The flat band voltage (Vfb) increases to a significantly more positive value with increasing nitrogen concentration. Insertion of a 2 nm thick Al2O3 interlayer greatly decreases the trap density of the insulator/GaN interface, and reduces the voltage hysteresis and frequency dispersion of gate capacitance compared to single-layer AlOxNy gate insulators in GaN MOSCAPs. PMID:27459343

  6. Effect of 10Ce-TZP/Al2O3 nanocomposite particle amount and sintering temperature on the microstructure and mechanical properties of Al/(10Ce-TZP/Al2O3) nanocomposites

    International Nuclear Information System (INIS)

    Highlights: • Increasing the 10Ce-TZP/Al2O3 content up to 7 wt.%, enhanced composites’ hardness. • Significant enhancement in compressive strength is obtained with 7% 10Ce-TZP/Al2O3. • Sintering at 450 °C, hardness and compressive strength are higher than at 400 °C. - Abstract: A zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite) can be a good substitute as reinforcement in metal matrix composites. In the present study, the effect of the amount of 10Ce-TZP/Al2O3 particles on the microstructure and properties of Al/(10Ce-TZP/Al2O3) nanocomposites was investigated. For this purpose, aluminum powders with average size of 30 μm were ball-milled with 10Ce-TZP/Al2O3 nanocomposite powders (synthesized by aqueous combustion) in varying amounts of 1, 3, 5, 7, and 10 wt.%. Cylindrical-shape samples were prepared by pressing the powders at 600 MPa for 60 min while heating at 400–450 °C. The specimens were then characterized by scanning and transmission electron microscopy (SEM and TEM) in addition to different physical and mechanical testing methods in order to establish the optimal processing conditions. The highest compression strength was obtained in the composite with 7 wt.% (10Ce-TZP/Al2O3) sintered at 450 °C

  7. 超声波在γ-Al2O3载体制备中的应用%Application of Ultrasonic in Preparation ofγ-Al2O3 Carrier

    Institute of Scientific and Technical Information of China (English)

    张鹏飞; 庞晨

    2014-01-01

    介绍了γ-Al2O3作为催化剂载体的优点和最新研究迚展,同时介绍了超声波在化学合成领域中的収展过程以及超声波在γ-Al2O3载体制备过程中的作用机理。经过不同超声波反应条件制备的γ-Al2O3载体,其团聚程度,孔结构等性质均会収生不同程度的变化,能够对所制备载体的性质起到优化作用,仍而提高催化剂的性能。%Advantages ofγ-Al2O3 as catalyst carrier were introduced as well as its latest research progress. Application of ultrasonic wave in the field of chemical synthesis was described as well as the function mechanism of ultrasonic in preparation process ofγ-Al2O3.γ-Al2O3 carriers which were synthesized in different ultrasonic reaction conditions had different degrees of change in agglomeration and pore structure. The ultrasonic can optimize the properties of theγ-Al2O3 carrier, and improve the performance of catalyst.

  8. PROPERTIES OF TiC-Al2O3/Fe COMPOSITES PREPARED BY SHS/PHIP%SHS/PHIP制备TiC-Al2O3/Fe复合材料的性能

    Institute of Scientific and Technical Information of China (English)

    张卫方; 韩杰才; 杜善义; 习年生; 陶春虎

    2001-01-01

    对SHS/PHIP技术制备出的TiC-Al2O3/Fe复合材料的性能进行了测试和分析.结果表明,TiC-Al2O3/Fe复合材料具有良好的综合力学性能.材料具有很高的比刚度.金属Fe相的加入,较大地提高了材料的抗弯强度和断裂韧性.TiC-Al2O3复相陶瓷为典型的脆性断裂;随着Fe含量的增加,材料具有明显韧性断裂的特征.%The influence of Fe content on the properties of TiC-Al2O3/Fe composites prepared by SHS/PHIP was studied. The results show that the TiC-Al2O3/Fe cermets prepared by SHS/PHIP possess high mechanical properties such as well-improved flexural strength and fracture toughness owing to the addition of Fe, and highly special stiffness. The TiC-Al2O3 ceramic exhibits the typical brittle fracture behavior. However, the TiC-Al2O3/Fe cermets exhibit obvious characteristic of tough fracture with Fe content increasing.

  9. DFT Study of the Effect of Temperature on ZnO Adsorbed on α-Al2O3(0001) Surface%温度对α-Al2O3(0001)表面吸附生长ZnO影响的DFT研究

    Institute of Scientific and Technical Information of China (English)

    杨春; 余毅; 李来才

    2006-01-01

    The adsorption and the growth of ZnO on α-Al2O3(0001) surface at various temperatures were theoretically calculated by using a plane wave pseudopotentials (USP) method based on density functional theory.The average adsorption energy of ZnO at 400, 600 and 800 ℃ is 4.16±0.08, 4.25±0.11 and 4.05±0.23 eV respectively. Temperature has a remarkable effect on the structure of the surface and the interface of ZnO/α-Al2O3(0001). It is found that the Zn-hexagonal symmetry deflexion does not appear during the adsorption growth of ZnO at 400 ℃, and that the ZnO[10-10] is parallel with the [10-10] of the α-Al2O3(0001), which is favorable for forming ZnO film with the Zn-terminated surface. It is observed from simulation that there are two kinds of surface structures in the adsorption of ZnO at 600 ℃: one is the ZnO surface that has the Zn-terminated structure, and whose [10-10] parallels the [10-10] of the substrate surface, and the other is the ZnO[10-10] //sapphire [11-10] with the O-terminated surface. The energy barrier of the phase transition between these two different surface structures is about 1.6 eV, and the latter is more stable. Therefore,the suitable temperature for the thin film growth of ZnO on sapphire is about 600 ℃, and it facilitates the formation of wurtzite structure containing Zn-O-Zn-O-Zn-O double-layers as a growth unit-cell. At 600 ℃, the average bond length of Zn-O is 0.190±0.01 nm, and the ELF value indicates that the bond of (substrate)-O-Zn-O has a distinct covalent character, whereas the (Zn)O-Al (substrate) shows a clear character of ionic bond. However, at a temperature of 800 ℃, the dissociation of Al and O atoms on the surface of the α-Al2O3(0001) leads to a disordered surface and interface structure. Thus, the Zn-hexagonal symmetry structure of the ZnO film is not observed under this condition.%用密度泛函理论的平面波赝势法对ZnO在α-Al2O3(0001)表面吸附生长进行了动力学计算.400、600、800℃

  10. Strength and thermal stability of Cu-Al2O3 composite obtained by internal oxidation

    Directory of Open Access Journals (Sweden)

    Jovanovic, M. T.

    2010-12-01

    Full Text Available The objective of the work is to study the effects of the high-energy milling on strengthening, thermal stability and electrical conductivity of Cu-Al2O3 composite. The prealloyed copper powders, atomized in inert gas and containing 3 wt. % Al, were milled up to 20 h in the planetary ball mill to oxidize in situ aluminium with oxygen from the air. Composite compacts were obtained by hot-pressing in an argon atmosphere at 800 °C for 3 h under the pressure of 35MPa. The microstructural characterization was performed by the optical microscope, scanning electron microscope (SEM, transmission electron microscope (TEM and X-ray diffraction analysis (XRD. The microhardness, electrical conductivity and density measurements were also carried out. The effect of internal oxidation and high-energy milling on strengthening of Cu-Al2O3 composite was significant, The increase of the microhardness of composite compacts (292 HV is almost threefold comparing to compacts processed from the as-received Cu-3 wt. % Al powder (102 HV. The grain size of Cu-Al2O3 compacts processed from 5 and 20 h-milled powders was 75 and 45 nm, respectively. The small increase in the grain size and the small microhardness drop indicate the high thermal stability of Cu-Al2O3 composite during high-temperature exposure at 800 °C.El objetivo del trabajo es el estudio de los efectos de la pulverización con altas energías sobre la resistencia, estabilidad térmica y conductividad eléctrica del compuesto Cu-Al2O3. El polvo pre-aleado de cobre, obtenido a través de la atomización con gas inerte y con un contenido de 3wt. % Al, se molió durante 20 h en el molino planetario de bolas dando lugar a la oxidación in situ del aluminio con el oxígeno del aire. El compuesto compactado se ha obtenido mediante prensado en caliente en atmósfera de argón a 800 °C durante 3 h y a una presión de 35MPa. La caracterización microestructural se hizo a través de microscopia óptica, microscopia

  11. Sulfation and Desulfation Behavior of Pt-BaO/MgO-Al2O3 NOx Storage Reduction Catalyst.

    Science.gov (United States)

    Jeong, Soyeon; Kim, Do Heui

    2016-05-01

    The comparative study between Pt-BaO/Al2O3 and Pt-BaO/MgO-Al2O3 gives the information about the effect of MgO addition to Al2O3 support on the sulfation and desulfation behavior of Pt-BaO/MgO-Al2O3 NOx storage reduction catalyst. The sulfated two samples were analyzed by using element analysis (EA), X-ray diffraction (XRD), H2 temperature programmed reaction (H2 TPRX) and NOx uptake measurement. The amount of sulfur uptake on 2 wt% Pt-20 wt% BaO/Al2O3 and 2 wt% Pt-20 wt% BaO/MgO-Al2O3 are almost identical as 0.45 and 0.40 of S/Ba, respectively, which yields the drastic decrease in NOx uptake for both sulfated samples. However, after desulfa- tion with H2 at 600 degrees C, the residual sulfur amount on MgO-Al2O3 supported catalyst is three times larger than that on Al2O3 supported one, indicating that sulfur species formed on the former are more stable than those on the latter. It is also well corresponding to the H2 TPRX results where the main H2S peak from MgO-Al2O3 supported sample is observed at higher temperature than Al2O3 supported one, resulting in the lower NOx uptake activity of former sample than the latter one. Meanwhile, after desulfation of MgO-Al2O3 supported sample at 700 degrees C and 800 degrees C, the activity is recovered more significantly due to the removal of the large amount of sulfur while Al2O3 supported one decreases monotonically due to the sintering of Pt crystallite and the formation of BaAl2O4 phase. It is summarized that MgO-Al2O3 supported catalyst enhances the thermal stability of the catalyst, however, forms the stable sulfate species, which needs to be improved to develop the more sulfur resistant NSR catalyst system.

  12. Sulfation and Desulfation Behavior of Pt-BaO/MgO-Al2O3 NOx Storage Reduction Catalyst.

    Science.gov (United States)

    Jeong, Soyeon; Kim, Do Heui

    2016-05-01

    The comparative study between Pt-BaO/Al2O3 and Pt-BaO/MgO-Al2O3 gives the information about the effect of MgO addition to Al2O3 support on the sulfation and desulfation behavior of Pt-BaO/MgO-Al2O3 NOx storage reduction catalyst. The sulfated two samples were analyzed by using element analysis (EA), X-ray diffraction (XRD), H2 temperature programmed reaction (H2 TPRX) and NOx uptake measurement. The amount of sulfur uptake on 2 wt% Pt-20 wt% BaO/Al2O3 and 2 wt% Pt-20 wt% BaO/MgO-Al2O3 are almost identical as 0.45 and 0.40 of S/Ba, respectively, which yields the drastic decrease in NOx uptake for both sulfated samples. However, after desulfa- tion with H2 at 600 degrees C, the residual sulfur amount on MgO-Al2O3 supported catalyst is three times larger than that on Al2O3 supported one, indicating that sulfur species formed on the former are more stable than those on the latter. It is also well corresponding to the H2 TPRX results where the main H2S peak from MgO-Al2O3 supported sample is observed at higher temperature than Al2O3 supported one, resulting in the lower NOx uptake activity of former sample than the latter one. Meanwhile, after desulfation of MgO-Al2O3 supported sample at 700 degrees C and 800 degrees C, the activity is recovered more significantly due to the removal of the large amount of sulfur while Al2O3 supported one decreases monotonically due to the sintering of Pt crystallite and the formation of BaAl2O4 phase. It is summarized that MgO-Al2O3 supported catalyst enhances the thermal stability of the catalyst, however, forms the stable sulfate species, which needs to be improved to develop the more sulfur resistant NSR catalyst system. PMID:27483765

  13. Testing of Flame Sprayed Al2O3 Matrix Coatings Containing TiO2

    Directory of Open Access Journals (Sweden)

    Czupryński A.

    2016-09-01

    Full Text Available The paper presents the results of the properties of flame sprayed ceramic coatings using oxide ceramic materials coating of a powdered aluminium oxide (Al2O3 matrix with 3% titanium oxide (TiO2 applied to unalloyed S235JR grade structural steel. A primer consisting of a metallic Ni-Al-Mo based powder has been applied to plates with dimensions of 5×200×300 mm and front surfaces of Ø40×50 mm cylinders. Flame spraying of primer coating was made using a RotoTec 80 torch, and an external coating was made with a CastoDyn DS 8000 torch. Evaluation of the coating properties was conducted using metallographic testing, phase composition research, measurement of microhardness, substrate coating adhesion (acc. to EN 582:1996 standard, erosion wear resistance (acc. to ASTM G76-95 standard, and abrasive wear resistance (acc. to ASTM G65 standard and thermal impact. The testing performed has demonstrated that flame spraying with 97% Al2O3 powder containing 3% TiO2 performed in a range of parameters allows for obtaining high-quality ceramic coatings with thickness up to ca. 500 µm on a steel base. Spray coating possesses a structure consisting mainly of aluminium oxide and a small amount of NiAl10O16 and NiAl32O49 phases. The bonding primer coat sprayed with the Ni-Al-Mo powder to the steel substrate and external coating sprayed with the 97% Al2O3 powder with 3% TiO2 addition demonstrates mechanical bonding characteristics. The coating is characterized by a high adhesion to the base amounting to 6.5 MPa. Average hardness of the external coating is ca. 780 HV. The obtained coatings are characterized by high erosion and abrasive wear resistance and the resistance to effects of cyclic thermal shock.

  14. Coking-resistant Ni-ZrO2/Al2O3 catalyst for CO methanation

    Institute of Scientific and Technical Information of China (English)

    Qing Liu; Fangna Gu; Jiajian Gao; Huifang Li; Guangwen Xu∗; Fabing Su∗

    2014-01-01

    Highly coke-resisting ZrO2-decorated Ni/Al2O3 catalysts for CO methanation were prepared by a two-step process. The support was first loaded with NiO by impregnating method and then modified with ZrO2 by deposition-precipitation method (IM-DP). Nitrogen adsorption-desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, H2 temperature-programmed reduction and desorption, NH3 temperature-programmed desorption, and zeta potential analysis were employed to characterize the samples. The results revealed that, compared with the catalysts with the same composition prepared by co-impregnation (CI) and sequential impregnation (SI) methods, the Ni/Al2O3 catalyst prepared by IM-DP showed much enhanced catalytic performance for syngas methanation under the condition of atmospheric pressure and a high weight hourly space velocity of 120000 mL·g−1·h−1. In a 80 h life time test under the condition of 300–600◦C and 3.0 MPa, this catalyst showed high stability and resistance to coking, and the amount of deposited carbon was only 0.4 wt%. On the contrary, the deposited carbon over the catalyst without ZrO2 reached 1.5 wt%after a 60 h life time test. The improved catalytic performance was attributed to the selective deposition of ZrO2 nanoparticles on the surface of NiO rather than Al2O3, which could be well controlled via changing the electrostatic interaction in the DP procedure. This unique structure could enhance the dissociation of CO2 and generate surface oxygen intermediates, thus preventing carbon deposition on the Ni particles in syngas methanation.

  15. Synthesis of γ-Al2O3 nanoparticles by chemical precipitation method

    Institute of Scientific and Technical Information of China (English)

    SONG Xiao-lan; QU Peng; YANG Hai-pin; HE Xi; QIU Guan-zhou

    2005-01-01

    Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor Al(OH)3 sols are produced by using 0.1 mol/L Al(NO3)3 ·9H2O and 0.16 mol/L (NH4)2CO3·H2O reaction solutions, according to the volume ratio 1.33, adding 0.024% (volume fraction) surfactant PEG600, and reacting at 40 ℃, 1 000 r/min stirring rate for 15 min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80 ℃ for 8 h, final calcined at 800 ℃ for 1 h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, O7H-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131.35 m2/g in BET specific surface area, 7-11 nm in pore diameter, and not lower than 99.93% in purity.

  16. A novel Al 2O 3 fluorescent nuclear track detector for heavy charged particles and neutrons

    Science.gov (United States)

    Akselrod, G. M.; Akselrod, M. S.; Benton, E. R.; Yasuda, N.

    2006-06-01

    A novel Al2O3 fluorescent nuclear track detector (FNTD), recently developed by Landauer, Inc., has demonstrated sensitivity and functionality superior to that of existing nuclear track detectors. The FNTD is based on single crystals of aluminum oxide doped with carbon and magnesium, and having aggregate oxygen vacancy defects (Al2O3:C,Mg). Radiation-induced color centers in the new material have an absorption band at 620 nm and produce fluorescence at 750 nm with a high quantum yield and a short, 75 ± 5 ns, fluorescence lifetime. Non-destructive readout of the detector is performed using a confocal fluorescence microscope. Scanning of the three-dimensional spatial distribution of fluorescence intensity along the track of a heavy charged particle (HCP) permits reconstruction of particle trajectories through the crystal and the LET can be determined as a function of distance along the trajectory based on the fluorescence intensity. Major advantages of Al2O3:C,Mg FNTD over conventionally processed CR-39 plastic nuclear track detector include superior spatial resolution, a wider range of LET sensitivity, no need for post-irradiation chemical processing of the detector and the capability to anneal and reuse the detector. Preliminary experiments have demonstrated that the material possesses a low-LET threshold of <1 keV/μm, does not saturate at LET in water as high as 1800 keV/μm, and is capable of irradiation to fluences in excess of 106 cm-2 without saturation (track overlap).

  17. Preparation of SiCp/Al2O3-Al Composites by Directed Metal Oxidation

    Institute of Scientific and Technical Information of China (English)

    LIN Ying; YANG Hai-bo; WANG Fen; ZHU Jian-feng

    2006-01-01

    SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and metallurgical microscope. The effects of technical parameters on the properties of the product were analyzed. The results indicate that the composite possesses a dense microstructure, composed of three interpenetrated phases. Of them, SiO2 layer prohibits the powdering of the composites; Mg promotes the wetting and infiltration of the system and Si restricts the interfacial reaction while improving the wetting ability between reinforcement and matrix.

  18. Lanthanum Modified Ni/γ-Al2O3 Catalysts for Partial Oxidation of Methane

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    La modified Ni/γ-Al2O3 catalysts prepared by co-precipitation method using NaOH-Na2CO3 as a precipitator show high activity and selectivity for the partial oxidation of methane (POM). Meanwhile, the addition of La is beneficial for the formation of an active component and stability of support. We investigated some factors including calcining temperature, nickel content, and space velocity, which turned out to have a strong influence on catalytic activity and selectivity. By XRD and TPR, it is concluded that Ni0 reduced from amorphous NiAl2O4 is the major active component for POM.

  19. Defect formation in MgOxnAl2O3 at gamma-neutron irradiation

    International Nuclear Information System (INIS)

    Optical and mechanical characteristics of spinel crystals after reactor irradiation are investigated. The comparison of the concentrations of radiation-induced anion vacancies and stable F-centers has shown that less than one tenth of the point defects is stabilized at room temperature. The annealing of these vacancies occurs at 800 K. The vacancy formation during gamma-neutron irradiation of nominally pure spinel crystals improves the crack resistance. The irradiation of Fe- and Mn ion-doped crystals MgOxnAl2O3, is accompanied by the coagulation stresses and crack resistance decrease

  20. Ni/Al2O3 xerogel catalysts for biogas cleaning

    OpenAIRE

    Claude, Vincent; Heinrichs, Benoît; Lambert, Stéphanie

    2013-01-01

    This poster summarize the firsts results of the PhD project started on October 2012 about the catalytic purification of biogas. The aim of this project consists in the development of Ni/Al2O3 catalyst in order to reform the tars present in the outlet gas of biomass gasifier. In order to obtain catalysts with high performance and lifetime, materials need to have optimized specific surface and metal particle dispersion. This poster investigate the effect of different surfactants (Pluronic P123;...

  1. Texture Analyses of Ti/Al2O3 Nanocomposite Produced Using Friction Stir Processing

    Science.gov (United States)

    Shafiei-Zarghani, Aziz; Kashani-Bozorg, Seyed Farshid; Gerlich, Adrian P.

    2016-11-01

    The texture evolution of Ti/Al2O3 nanocomposite fabricated using friction stir processing (FSP) was investigated at both macroscopic and microscopic levels employing X-ray diffraction and electron backscattering diffraction techniques. The developed textures were compared with ideal shear textures of hexagonal close-packed (hcp) structure, revealing that the fabricated nanocomposite is dominated by the P 1 hcp (fiber { 10bar{1}1} continuous dynamic recrystallization as well as increasing the fraction of high-angle grain boundaries within the developed microstructure.

  2. Pt-Rh/g Al2O3 Benzene Hydrogenation Reaction as a Characterization Technique

    Directory of Open Access Journals (Sweden)

    N.M. da Fonseca

    1998-06-01

    Full Text Available Pt-Rh/Al2O3 catalysts prepared by successive incipient impregnations and coimpregnation were characterized by H2 chemisorption, temperature programmed reduction and benzene hydrogenation reaction in the vapor phase. The results showed that Rh plays the role of Pt reducting agent, which is very different from the effects of metal-metal interaction which appear mainly in solids with the highest metal contents. The most important parameter that results in bimetallic particles in the catalyst prepared by successive impregnation is the sequence of metal addition.

  3. The anomalous behaviour of Ag-Al2O3 Cermet electroformed devices

    International Nuclear Information System (INIS)

    Cermet coating consisting of silver particles in an aluminium oxide matrix were prepared on glass substrates by vacuum deposition. Variation of the circulating current with potential difference was obtained in evaporated Al/Ag-Al2O3/Cu sandwich structures, 100 to 200 nm thick containing 10 wt % Ag. It was observed that the investigated sandwich structures exhibit anomalous behaviour such as electroforming with Voltage-Controlled-Negative Resistance (VCNR) in vacuo of ∼ 4 x 10-6 torr. The formed characteristics were explained on the basis of filamentary model. (author)

  4. Hydrogen Production via Glycerol Dry Reforming over La-Ni/Al2O3 Catalyst

    Directory of Open Access Journals (Sweden)

    Kah Weng Siew

    2013-12-01

    Full Text Available Glycerol (a bio-waste generated from biodiesel production has been touted as a promising bio-syngas precursor via reforming route. Previous studies have indicated that carbon deposition is the major performance-limiting factor for nickel (Ni catalyst during glycerol steam reforming. In the current paper, dry (CO2-reforming of glycerol, a new reforming route was carried out over alumina (Al2O3-supported non-promoted and lanthanum-promoted Ni catalysts. Both sets of catalysts were synthesized via wet co-impregnation procedure. The physicochemical characterization of the catalyst showed that the promoted catalyst possessed smaller metal crystallite size, hence higher metal dispersion compared to the virgin Ni/Al2O3 catalyst. This was also corroborated by the surface images captured by the FESEM analysis. In addition, BET surface area measurement gave 92.05m²/g for non-promoted Ni catalyst whilst promoted catalysts showed an average of 1 to 6% improvement depending on the La loading. Reaction studies at 873 K showed that glycerol dry reforming successfully produced H2 with glycerol conversion and H2 yield that peaked at 9.7% and 25% respectively over 2wt% La content. The optimum catalytic performance by 2%La-Ni/Al2O3 can be attributed to the larger BET surface area and smaller crystallite size that ensured accessibility of active catalytic sites.  © 2013 BCREC UNDIP. All rights reservedReceived: 12nd May 2013; Revised: 7th October 2013; Accepted: 16th October 2013[How to Cite: Siew, K.W., Lee, H.C., Gimbun, J., Cheng, C.K. (2013. Hydrogen Production via Glycerol Dry Reforming over La-Ni/Al2O3 Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (2: 160-166. (doi:10.9767/bcrec.8.2.4874.160-166][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.2.4874.160-166

  5. Microstructure Evolution of Defect Clusters in Neutron Irradiated MgO・nAl_2O_3

    OpenAIRE

    Fukumoto, K.; Kinoshita, C.; Maeda, S; Y. Watanuki; Nakai, K.

    1994-01-01

    The formation process of defect clusters in MgO・nAl_2O_3 has been studied not only for understanding the mechanism of the nucleation and growth process of defect clusters but also for getting insights into the reason why this material shows radiation resistance. Defect analysis was performed to determine the following sequential change of dislocation loops under irradiation with fission neutrons in Joyo and JMTR; 1/6[111](111)→1/4[110](111)→1/4[110](101)→1/4[110](110)→1/2[110](110). Effective...

  6. Study on void reduction in direct wafer bonding using Al2O3/HfO2 bonding interface for high-performance Si high-k MOS optical modulators

    Science.gov (United States)

    Han, Jae-Hoon; Takenaka, Mitsuru; Takagi, Shinichi

    2016-04-01

    We have investigated the direct wafer bonding (DWB) method with a thin bonding dielectric interface to fabricate Si high-k MOS optical modulators with a thin equivalent oxide thickness (EOT). To suppress void generation on the bonded wafer during high-temperature annealing, we examined the high-k dielectric bonding interfacial layers, such as Al2O3 and HfO2. We found that the Al2O3/HfO2 bilayer enables void-less wafer bonding in conjunction with pre-bonding annealing at 700 °C. By using the 0.5-nm Al2O3/2.0-nm HfO2 bonding interface, the density of voids is reduced by three orders of magnitude as compared with that in the case of using the Al2O3 bonding interface. We achieved a density of voids of approximately 2 × 10-3 cm-2 even when the bonded wafer is annealed at 700 °C. By thermal desorption spectroscopy (TDS), we found that degassing from the bonding interface is successfully suppressed by the introduction of the HfO2 layer and the pre-bonding annealing at 700 °C, which are considered to suppress void generation. Wafer bonding with thin Al2O3/HfO2 high-k bonding interface is promising for Si high-k MOS optical modulators.

  7. Structure and Mechanical Properties of Ni-P-Nano Al2O3 Composite Coatings Synthesized by Electroless Plating

    Institute of Scientific and Technical Information of China (English)

    ZHOU Guang-hong; DING Hong-yan; ZHOU Fei; ZHANG Yue

    2008-01-01

    Ni-P-nano Al2O3 composite coatings were deposited by electroless plating, and their microstructures were observed by SEM (scanning electron microscope). The microhardness and the wear resistance of the Ni-P-nano Al2O3 composite coatings were measured using microhardness tester and block-on-ring tribometer, respectively, and the comparison with those of Ni-P coatings or Ni-P-micro Al2O3 coating was given. The influences of aging temperature on their hardness and wear resistance were analyzed. The results showed that the nano Al2O3 particles were distributed uniformly in the Ni-P-Al2O3 coatings. Among three kinds of Ni-P based coatings, the hardness and wear resistance of Ni-P-nano Al2O3 coatings were largest, and the maximum values could be obtained at 400 ℃. This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the Ni-P coatings.

  8. Fabrication and mechanical properties of WC-Co-Al2O3 nanocomposites by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    SHEN Jun; ZHANG Fa-ming; SUN Jian-fei

    2005-01-01

    Small amounts of nanocrystalline Al2 O3 particles were doped in WC-Co nanocrystalline powders to study their reinforcing effects, and spark plasma sintering technique was used to fabricate the WC-Co-Al2 O3 nanocomposites. Experimental results show that the use of Al2 O3 nanoparticles as dispersions to reinforce WC-Co composites can increase the hardness, especially the transverse rupture strength of the WC-Co hardmetal. With addition of 0.5%(mass fraction) Al2O3 nanoparticles, the spark plasma sintered WC-7Co-0.5Al2O3 nanocomposites exhibit hardness of 21.22 GPa and transverse rupture strength of 3 548 MPa. The fracture surface of the WC-7Co-0.5Al2O3 nanocomposites mainly fracture with transcrystalline rupture mode. The reinforcing mechanism is maybe related to the hindrance effect of microcracks propagation and the pinning effect for the dislocations movement, as well as the residual compressive strength due to the Al2 O3 nanoparticles doped.

  9. Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

    Institute of Scientific and Technical Information of China (English)

    Xirong Chen; Hanbo Zou; Shengzhou Chen; Xinfa Dong; Weiming Lin

    2007-01-01

    The RU/Al2O3 catalysts modified with metal oxide (K2O and La2Os) were prepared via incipient wetness impregnation method from RUCl3.nH2O mixed with nitrate loading on Al2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX) from the hydrogen-rich gas streams produced by reforming gas, and the performances of catalysts were investigated by XRD and TPR. The results showed that the activity temperature of the modified catalysts RU-K2O/Al2O3 and Ru-La2Oa/Al2O3 were lowered approximately 30 ℃ compared with pure RU/AI2O3, and the activity temperature range was widened. The conversion of CO on RU-K2O/Al2O3 and Ru-La2O3/Al2O3 was above 99% at 140-160 ℃, suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La2O3/Al2O3 was higher than that of RU-K2O/AI2O3 in the active temperature range. Slight methanation reaction was detected at 220 ℃ and above.

  10. Fluência em filtros cerâmicos de Al2O3 Creep in Al2O3 ceramic filters

    Directory of Open Access Journals (Sweden)

    V. R. Salvini