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. Effects of the interfacial layer on electrical characteristics of Al 2O 3/TiO 2/Al 2O 3 thin films for gate dielectrics

    Science.gov (United States)

    Kim, Chang Eun; Yun, Ilgu

    2012-01-01

    Effects of thermal annealing on the electrical properties of Al2O3/TiO2/Al2O3 (ATA) dielectric thin films prepared by atomic layer deposition are investigated. The structural properties and chemical states in the interfacial layer are analyzed with varying the annealing temperature. The dielectric constant and leakage current are affected by the formation of Al2O3-TiO2 composite and interfacial layer including SiOx in the interface by the annealing. The transformation of interfacial layer at the interface of the ATA/Si substrate due to the annealing is a critical point to apply ATA thin films as gate dielectric layers.

  3. Scattering of light molecules from thin Al2O3 films

    International Nuclear Information System (INIS)

    Molecular oxygen and hydrogen ions were scattered at grazing incidence from various thin Al2O3 films. The energy of incident particles was varied from 390 to 1000 eV. For scattered positive oxygen ions, negative ion fractions of up to 17% were recorded. For scattered positive hydrogen ions, the negative ion fractions reached up to 2%. These findings qualify thin films of Al2O3 as possible candidates for use as charge state conversion surfaces in neutral particle sensing instruments, which will work in space.

  4. 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.

  5. Comparison of dielectric dispersion of Al2O3 and Se thin films

    International Nuclear Information System (INIS)

    We investigate the frequency and temperature dependence of the dielectric conductivity and dielectric constant of Al2O3 thin films having ionic structure and compare the results with those obtained for Se thin films having homopolar structure in the 0.1 - 100 kHz frequency range and in the 100 - 400 K temperature range. Our samples have a metal - insulator - metal configuration. Oxide-layer thickness ranges between 50 and 1550 Aa for Al2O3 films and 150 and 8500 Aa for Se films. The existence of a minimum in the imaginary part of dielectric constant versus frequency curves for each thickness of Al2O3 films leads us to conclude that two types of polarization mechanisms are dominant in different frequency regions, depending on the structure of Al2O3 samples, but that only one mechanism dominates in Se samples, which do not have such minima in the imaginary part of their dielectric constant versus frequency curves. [copyright] 2001 American Institute of Physics

  6. Dielectric properties of DC reactive magnetron sputtered Al2O3 thin films

    International Nuclear Information System (INIS)

    Alumina (Al2O3) thin films were sputter deposited over well-cleaned glass and Si substrates by DC reactive magnetron sputtering under various oxygen gas pressures and sputtering powers. The composition of the films was analyzed by X-ray photoelectron spectroscopy and an optimal O/Al atomic ratio of 1.59 was obtained at a reactive gas pressure of 0.03 Pa and sputtering power of 70 W. X-ray diffraction results revealed that the films were amorphous until 550 °C. The surface morphology of the films was studied using scanning electron microscopy and the as-deposited films were found to be smooth. The topography of the as-deposited and annealed films was analyzed by atomic force microscopy and a progressive increase in the rms roughness of the films from 3.2 nm to 4.53 nm was also observed with increase in the annealing temperature. Al-Al2O3-Al thin film capacitors were then fabricated on glass substrates to study the effect of temperature and frequency on the dielectric property of the films. Temperature coefficient of capacitance, AC conductivity and activation energy were determined and the results are discussed. - Highlights: ► Al2O3 thin films were deposited by DC reactive magnetron sputtering. ► The films were found to be amorphous up to annealing temperature of 550 C. ► An increase in rms roughness of the films was observed with annealing. ► Al-Al2O3-Al thin film capacitors were fabricated and dielectric constant was 7.5. ► The activation energy decreased with increase in frequency.

  7. Enhanced Barrier Performance of Engineered Paper by Atomic Layer Deposited Al2O3 Thin Films.

    Science.gov (United States)

    Mirvakili, Mehr Negar; Van Bui, Hao; van Ommen, J Ruud; Hatzikiriakos, Savvas G; Englezos, Peter

    2016-06-01

    Surface modification of cellulosic paper is demonstrated by employing plasma assisted atomic layer deposition. Al2O3 thin films are deposited on paper substrates, prepared with different fiber sizes, to improve their barrier properties. Thus, a hydrophobic paper is created with low gas permeability by combining the control of fiber size (and structure) with atomic layer deposition of Al2O3 films. Papers are prepared using Kraft softwood pulp and thermomechanical pulp. The cellulosic wood fibers are refined to obtain fibers with smaller length and diameter. Films of Al2O3, 10, 25, and 45 nm in thickness, are deposited on the paper surface. The work demonstrates that coating of papers prepared with long fibers efficiently reduces wettability with slight enhancement in gas permeability, whereas on shorter fibers, it results in significantly lower gas permeability. Wettability studies on Al2O3 deposited paper substrates have shown water wicking and absorption over time only in papers prepared with highly refined fibers. It is also shown that there is a certain fiber size at which the gas permeability assumes its minimum value, and further decrease in fiber size will reverse the effect on gas permeability. PMID:27165172

  8. 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.

  9. 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.

  10. Vanadium dioxide film protected with an atomic-layer-deposited Al2O3 thin film

    International Nuclear Information System (INIS)

    A VO2 film exposed to ambient air is prone to oxidation, which will degrade its thermochromic properties. In this work, the authors deposited an ultrathin Al2O3 film with atomic layer deposition (ALD) to protect the underlying VO2 film from degradation, and then studied the morphology and crystalline structure of the films. To assess the protectiveness of the Al2O3 capping layer, the authors performed a heating test and a damp heating test. An ultrathin 5-nm-thick ALD Al2O3 film was sufficient to protect the underlying VO2 film heated at 350 °C. However, in a humid environment at prolonged durations, a thicker ALD Al2O3 film (15 nm) was required to protect the VO2. The authors also deposited and studied a TiO2/Al2O3 bilayer, which significantly improved the protectiveness of the Al2O3 film in a humid environment

  11. Vanadium-Al2O3 nanostructured thin films prepared by pulsed laser deposition: Optical switching

    International Nuclear Information System (INIS)

    The formation and optical response of VO x nanoparticles embedded in amorphous aluminium oxide (Al2O3) thin films by pulsed laser deposition is studied. The thin films have been grown by alternate laser ablation of V and Al2O3 targets, which has resulted in a multilayer structure with embedded nanoparticles. The V content has been varied by changing the number of pulses on the V target. It is found that VO x nanoparticles with dimensions around 5 nm have been formed. The structural analysis shows that the vanadium nanoparticles are oxidized, although probably there is not a unique oxide phase for each sample. The films show a different optical response depending on their vanadium content. Optical switching as a function of temperature has been observed for the two films with the highest vanadium content, at transition temperatures of about -20 deg. C and 315 deg. C thus suggesting the presence of nanoparticles with compositions V4O7 and V2O5, respectively

  12. Deposition of alumina thin film by dual magnetron sputtering: Is it γ-Al2O3?

    International Nuclear Information System (INIS)

    Alumina thin films were deposited by reactive dual magnetron sputtering at 550 °C on cemented carbide substrates. A Young’s modulus of 315 GPa and a Vickers hardness of 2348 were determined by nanoindentation and were compared to reference materials. The crystal structure of such films is usually referred to as γ-Al2O3; however, the crystal structure of cubic γ-Al2O3 is not well defined, not even for bulk materials. The alumina grain size of the films was about 50 nm as measured by dark-field imaging in a transmission electron microscope. The energy-filtered electron diffraction patterns were segmented: one part showed an amorphous intensity distribution, not known for γ-Al2O3, the other part contained reflections arranged in rings, the brightest of which had lattice spacings of the (4 0 0) and (4 4 0) reflections of γ-Al2O3. Therefore, the structure of the thin films is referred to as pseudo γ-Al2O3. This nomenclature expresses that this phase is different from γ-Al2O3 but among the Al2O3 phases is most closely related to this phase. Differences between the two crystal structures are highlighted and discussed with respect to lattice spacings, intensities of the various reflections, chemical composition and other physical properties. The pseudo γ-Al2O3 films contained an Al/Ar mole fraction ratio of about 17 as determined by energy-dispersive X-ray spectroscopy.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. Production and study of mixed Al-Al2O3 thin films for passive electronic circuits

    International Nuclear Information System (INIS)

    A new vacuum deposition process, named reactive evaporation, is used to realize passive thin film circuits. Using aluminium, oxidized at various steps in its vapor phase, we obtain: - Al-Al2O3 cermet resistors (R□ = 10000 Ω□, CTR 2O3 capacitors (C□ = 60000 pf/cm2, tg δ < 0.5 per cent). These thin film components present good electrical behaviour and should find interesting applications in integrated circuits. (author)

  20. Physical characterization of thin ALD-Al2O3 films

    International Nuclear Information System (INIS)

    Aluminum oxide was deposited using atomic layer deposition on either a silicon oxide or a silicon nitride interface. Water vapor or ozone were used as oxidation precursors. The structural properties of these films were investigated by time-of-flight secondary-ion-mass-spectroscopy (ToF-SIMS), X-ray photoelectron spectroscopy (XPS) and elastic recoil detection (ERD). Special attention was given to contamination issues of the film and the interface, bonding conditions and temperature influence on diffusion. The results suggest that the silicon most likely diffused along grain boundaries of polycrystalline Al2O3. Carbon and hydrogen were located at the interface and furthermore hydrogen diffused out of the film to some extent due to anneal. Carbon content in the layer was reduced when using O3 as an oxidant. The formation of metallic aluminum clusters was not observed for any of the investigated process conditions

  1. 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).

  2. 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.

  3. 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.

  4. Twin symmetry texture of energetically condensed niobium thin films on sapphire substrate (a-plane Al2O3)

    Science.gov (United States)

    Zhao, X.; Phillips, L.; Reece, C. E.; Seo, Kang; Krishnan, M.; Valderrama, E.

    2011-08-01

    An energetic condensation technique, cathodic arc discharge deposition, is used to grow epitaxial Niobium (Nb) thin films on a-plane sapphire (hexagonal-closed-packed Al2O3) at moderate substrate heating temperature (RRR) value 214, despite using a reactor-grade Nb cathode source whose RRR was only 30. The measurements suggest that the film's density of impurities and structural defects are lower when compared to Nb films produced by other techniques, such as magnetron sputtering, e-beam evaporation or molecular-beam-epitaxy. At lower substrate temperature, textured polycrystalline Nb thin films were created, and the films might have twin symmetry grains with {110} orientations in-plane. The texture was revealed by x-ray diffraction pole figures. The twin symmetry might be caused by a combination effect of the Nb/Al2O3 three-dimensional epitaxial relationship ("3D-Registry" Claassen's nomenclature) and the "Volmer-Weber" (Island) growth model. However, pole figures obtained by electron backscattering diffraction (EBSD) found no twin symmetry on the thin films' topmost surface (˜50 nm in depth). The EBSD pole figures showed only one Nb{110} crystal plane orientation. A possible mechanism is suggested to explain the differences between the bulk (XRD) and surface (EBSD) pole figures.

  5. 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

  6. Structural and mechanical characterization of Al/Al2O3 nanotube thin film on TiV alloy

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • To construct Al2O3 nanotube on Ti–6Al–4V. • To investigate adhesion strength of coating to the substrate. • To evaluate the effect of plasma annealing on adhesion strength of coating. • To characterize the Al2O3 nanotube coating on substrate by FESEM. - Abstract: In this study, the fabrication and characterization of Al/Al2O3 nanotubular arrays on Ti–6Al–4V substrate were carried out. To this end, aluminum thin films were deposited as a first coating layer by direct current (DC) magnetron sputtering with the coating conditions of 300 W, 150 °C and 75 V substrate bias voltage. Al2O3 nanotube array as a second layer was grown on the Al layer by electrochemical anodisation at the constant potential of 20 V within different time periods in an electrolyte solution. For annealing the coated substrates, plasma treatment (PT) technique was utilized under various conditions to get the best adhesion strength of coating to the substrate. To characterize the coating layers, micro scratch test, Vickers hardness and field emission of scanning electron microscopy (FESEM) were used. Results show that after the deposition of pure aluminum on the substrate the scratch length, load and failure point were 794.37 μm, 1100 mN and 411.43 μm, respectively. After PT, the best adhesion strength (2038 mN) was obtained at RF power of 60 W. With the increase of the RF power up to 80 W, a reduction in adhesion strength was observed (1525.22 mN). From the microstructural point of view, a homogenous porous structure with an average pore size of 40–60 nm was formed after the anodisation for 10–45 min. During PT, the porous structure was converted to dense alumina layer when the RF power rose from 40 to 80 W. This led to an increase in hardness value from 2.7 to 3.4 GPa. Based on the obtained data, the RF power of 60 W was the optimum condition for plasma treatment of Al/Al2O3 nanotubular arrays on Ti–6Al–4V substrate

  7. 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.

  8. Growth and characterization of ceria thin films and Ce-doped γ-Al2O3 nanowires using sol-gel techniques

    International Nuclear Information System (INIS)

    γ-Al2O3 is a well known catalyst support. The addition of Ce to γ-Al2O3 is known to beneficially retard the phase transformation of γ-Al2O3 to α-Al2O3 and stabilize the γ-pore structure. In this work, Ce-doped γ-Al2O3 nanowires have been prepared by a novel method employing an anodic aluminium oxide (AAO) template in a 0.01 M cerium nitrate solution, assisted by urea hydrolysis. Calcination at 500 deg. C for 6 h resulted in the crystallization of the Ce-doped AlOOH gel to form Ce-doped γ-Al2O3 nanowires. Ce3+ ions within the nanowires were present at a concentration of 2 thin film was deposited with a cubic fluorite structure and a crystallite size of 6-7 nm. Characterization of the nanowires and thin films was performed using scanning electron microscopy, transmission electron microscopy, electron energy loss spectroscopy, x-ray photoelectron spectroscopy and x-ray diffraction. The nanowire formation mechanism and urea hydrolysis kinetics are discussed in terms of the pH evolution during the reaction. The Ce-doped γ-Al2O3 nanowires are likely to find useful applications in catalysis and this novel method can be exploited further for doping alumina nanowires with other rare earth elements.

  9. 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.

  10. Preparation and characterization of thin films of MgO, Al2O3 and MgAl2O4 by atomic layer deposition

    Science.gov (United States)

    Huang, Ron; Kitai, Adrian H.

    1993-02-01

    MgO, Al2O3 and MgAl2O4 thin films were deposited on silicon substrates at various temperatures by the atomic layer deposition (ALD) method using bis(cyclopentadienyl)magnesium, triethylaluminum, and H2O and were characterized systematically. High-quality polycrystalline MgO films were deposited for a substrate temperature above 500°C, and amorphous thin films were deposited around 400°C. The deposited Al2O3 and MgAl2O4 thin films were characterized as amorphous in structure. Applicability of ALD to complex oxides is discussed.

  11. Electrical mechanism analysis of Al2O3 doped zinc oxide thin films deposited by rotating cylindrical DC magnetron sputtering

    International Nuclear Information System (INIS)

    Cost efficient and large area deposition of superior quality Al2O3 doped zinc oxide (AZO) films is instrumental in many of its applications, including solar cell fabrication due to its numerous advantages over indium tin oxide (ITO) films. In this study, AZO films were prepared by a highly efficient rotating cylindrical direct current (DC) magnetron sputtering system using an AZO target, which has a target material utilization above 80%, on glass substrates in argon (Ar) ambient. A detailed analysis on the electrical, optical, and structural characteristics of AZO thin films was performed for the solar cell, as well as display applications. The properties of films were found to critically depend on deposition parameters, such as sputtering power, substrate temperature, working pressure, and film thickness. A low resistivity of ∼ 5.5 x 10-4 Ω cm was obtained for films deposited at 2 kW, keeping the pressure, substrate temperature and thickness constant at 3 mTorr, 230 deg. C and ∼ 1000 nm respectively. This was due to an increase in carrier mobility and large grain size. Mobility is found to be controlled by ionized impurity scattering within the grains, since the mean free path of carriers is much smaller than the grain size of the films. The AZO films showed a high transparency of ∼ 90% in the long wavelength region. Our results offer a cost-efficient AZO film deposition method that can fabricate films with significant low resistivity and high transmittance that can be applied in thin-film solar cells, as well as thin film transistor (TFT) and non-volatile memory (NVM).

  12. 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.

  13. 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.

  14. 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.

  15. Photocatalytic activity of Al2O3-doped TiO2 thin films activated with visible light on the bacteria Escherichia coli

    International Nuclear Information System (INIS)

    Al2O3-doped TiO2 thin films were prepared by combining electrophoretic deposition (EPD) with sputtering. A Corning* glass was used as a substrate, in which a titanium film was deposited by sputtering. Then, a precursor sol was prepared with Ti(n-OBu)4 and Al(s-OBu)3 and used as the medium for EPD. Next, the thin films were sintered and, finally, characterised by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Several cultures of Escherichia coli, strain XL1-Blue, were prepared. Nine experiments were carried out. In three of them, an inoculum (a low amount of a product that contains bacteria) was prepared without a film; in the other six Al2O3-doped TiO2 film-coated glass substrates were irradiated with visible light before they were introduced in the inoculum. The SEM and EDS results showed that TiO2-Al2O3 films were obtained, covering all the glass substrate and with uniform size of particles forming them, and that the aluminium was distributed uniformly on the film. XRD results showed that rutile phase was obtained. By TEM, the structure of TiO2 was demonstrated. Al2O3-doped TiO2 thin films were successful at eliminating E. coli.

  16. Barrier properties of Al2O3 and alucone coatings and nanolaminates on flexible biopolymer films

    International Nuclear Information System (INIS)

    Thin atomic layer deposited (ALD) Al2O3 coatings are efficient barriers against gases and vapors. Al2O3 coatings are, however, brittle and straining them generates defects that impair barrier properties. Flexibility of ALD-grown Al2O3 coatings on biopolymer substrates can be improved by separating thinner Al2O3 layers with inorganic–organic alucone layers. The number and size of defects were smaller for these nanolaminates compared to the thick Al2O3 films after straining, and hence straining deteriorated the oxygen barrier properties less when applied to the laminates than when applied to the Al2O3 coatings. - Highlights: ► Al2O3, alucone and five-layer nanolaminates were deposited on biopolymers. ► Straining of Al2O3 coating generated defects that impaired barrier properties. ► Nanolaminates with thin Al2O3 layers and alucone were less sensitive to straining.

  17. Influence of Al2O3 layer insertion on the electrical properties of Ga-In-Zn-O thin-film transistors

    International Nuclear Information System (INIS)

    To investigate the influence of ionic/covalent interface of Al2O3/SiO2 gate insulator on the electrical properties of thin-film transistors (TFTs) with ionic Ga-In-Zn-O (GIZO) semiconducting channel layers, Al2O3 layers of different thickness were introduced between SiO2 and GIZO using plasma-enhanced atomic layer deposition. The GIZO layers were obtained by DC magnetron sputtering using a GIZO target (Ga:In:Zn = 1:1:1 mol. %). The GIZO TFTs with an Al2O3/SiO2 gate insulator exhibited positive threshold voltage (Vth) shift (about 1.1 V), Vth hysteresis suppression (0.23 V), and electron mobility degradation (about 13%) compared with those of a GIZO TFT with SiO2 gate insulator by the influence of ionic/ionic and ionic/covalent interface at Al2O3/GIZO and Al2O3/SiO2, respectively. To clarify the origin of the positive Vth shift, the authors estimated the shifts of flatband voltage (0.4 V) due to the dipole and the fixed charge (−1.1 × 1011/cm2) at Al2O3/SiO2 interface, from capacitance–voltage data for Pt/Al2O3/SiO2/p-Si capacitors. Based on these experimental data, the authors found that the positive Vth shift (1.1 V) could be divided into three components: the dipole (−0.4 V) and fixed charge (0.15 V) at the SiO2/Al2O3 interface, and the fixed charge (1.35 V) at the Al2O3/GIZO interface. Finally, it is noted that heterointerface of SiO2/Al2O3/GIZO stacks is important not only to recognize mechanism of Vth shift but also to design future TFTs with high-k dielectrics and low operating voltage

  18. Understanding time-resolved processes in atomic-layer etching of ultra-thin Al2O3 film using BCl3 and Ar neutral beam

    International Nuclear Information System (INIS)

    We scrutinize time-resolved processes occurring in atomic-layer etching (ALET) of ultra-thin Al2O3 film using BCl3 gas and Ar neutral beam by employing density functional theory calculations and experimental measurements. BCl3 gas is found to be preferentially chemisorbed on Al2O3(100) in trans form with the surface atoms creating O-B and Al-Cl contacts. We disclose that the most likely sequence of etching events involves dominant detachment of Al-associated moieties at early etching stages in good agreement with our concurrent experiments on tracking Al2O3 surface compositional variations during Ar bombardment. In this etching regime, we find that ALET requires half the maximum reaction energy of conventional plasma etching, which greatly increases if the etching sequence changes.

  19. 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.

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

    International Nuclear Information System (INIS)

    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

  1. 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.

  2. 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.

  3. Dip coated 12CaO.7Al2O3 thin films through sol-gel process using metal alkoxide

    International Nuclear Information System (INIS)

    Transparent nanostructured 12CaO.7Al2O3 thin films with cubic structure have been prepared on soda lime glass substrates via the sol-gel dip coating using the precursor sol solution at low temperature. The structural, compositional, morphological and optical properties of the 12CaO.7Al2O3 films and powder were studied using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy. Optical properties of 12CaO.7Al2O3 films have been investigated using UV-visible spectroscopy. Two different precursor sols were prepared using calcium-2-ethyl hexonate and aluminium isopropoxide as precursor materials in isopropanol and ethylene glycol monomethyl ether solvents. Dip coated gel like films were dried at 120 oC for 15 min and subsequently heat-treated at 450 oC for 1 h in air atmosphere. The influence of films thickness and optical transparency with use of different solvent and sol concentration on microstructure of the films were established. In addition, XRD patterns revealed that 12CaO.7Al2O3 films have been composed of cubic phase. SEM observations exhibited that the films structure becomes more homogeneous using isopropanol as compared to ethylene glycol monomethyl ether solvent. The 12CaO.7Al2O3 films prepared using 2 (wt.%) sol in isopropanol had high transparency nearly 88% in wide visible range with maximum of 90% at 600 nm wavelength.

  4. 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

  5. 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.

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

    Science.gov (United States)

    Zhang, Ruiying; Zhu, Jian; Zhang, Zhen; Wang, Yanyan; Qiu, Bocang; Liu, Xuehua; Zhang, Jinping; Zhang, Yi; Fang, Qi; Ren, Zhong; Bai, Yu

    2015-12-01

    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.

  7. 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. PMID:27117229

  8. 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).

  9. Self-aligned top-gate InGaZnO thin film transistors using SiO2/Al2O3 stack gate dielectric

    International Nuclear Information System (INIS)

    Self-aligned top-gate amorphous indium–gallium–zinc oxide (a-IGZO) thin film transistors (TFTs) utilizing SiO2/Al2O3 stack thin films as gate dielectric are developed in this paper. Due to high quality of the high-k Al2O3 and good interface between active layer and gate dielectric, the resulting a-IGZO TFT exhibits good electrical performance including field-effect mobility of 9 cm2/Vs, threshold voltage of 2.2 V, subthreshold swing of 0.2 V/decade, and on/off current ratio of 1 × 107. With scaling down of the channel length, good characteristics are also obtained with a small shift of the threshold voltage and no degradation of subthreshold swing. - Highlights: • Self-aligned top-gate indium–gallium–zinc oxide thin-film transistor is proposed. • SiO2/Al2O3 stack gate dielectric is proposed. • The source/drain areas are hydrogen-doped by CHF3 plasma. • The devices show good electrical performance and scaling down behavior

  10. Low-temperature atomic layer deposited Al2O3 thin film on layer structure cathode for enhanced cycleability in lithium-ion batteries

    International Nuclear Information System (INIS)

    The deposition of Al2O3 on LiCoO2 electrodes using a low-temperature atomic layer deposition has been investigated. Scanning electron microscopy confirms that Al2O3 films can be homogeneously deposited on LiCoO2 particles of porous electrodes at 120 deg. C. The results of X-ray photoelectron spectroscopy show that the Al2O3 preferentially deposits on the LiCoO2. Furthermore, the results of cycling stability tests show that the cells with Al2O3-coated LiCoO2 electrodes have enhanced performance.

  11. Resistive switching characteristics of multilayered (HfO2/Al2O3)n n = 19 thin film

    International Nuclear Information System (INIS)

    A transparent resistive random access memory used as Indium Tin Oxide (ITO) electrode, ITO/HfO2/Al2O3/…/HfO2/Al2O3/ITO capacitor structure is fabricated on glass substrate by atomic layer deposition. The unipolar resistive switching characteristics can be performed by applying the positive- or negative-bias through top electrode, however, the differences of switching and stability in the two different operations can be observed. The diversities of electrical property are attributed to different oxide/ITO interface materials, which influence the current flow of the injected electrons.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

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

    International Nuclear Information System (INIS)

    Highlights: • Methanol on partially alumina-encapsulated Pt clusters decomposed on the uncovered Pt sites. • Methanol decomposition occurs via dehydrogenation to CO and scission of the C–O bond. • The dehydrogenation on partially encapsulated Pt clusters was hindered to some extent. • The C–O bond scission on partially encapsulated Pt clusters was altered little in comparison to that on Pt clusters. - Abstract: 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

  19. 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

  20. 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.

  1. Comparison of Multilayer Dielectric Thin Films for Future Metal-Insulator-Metal Capacitors: Al2O3/HfO2/Al2O3 versus SiO2/HfO2/SiO2

    Science.gov (United States)

    Park, Sang-Uk; Kwon, Hyuk-Min; Han, In-Shik; Jung, Yi-Jung; Kwak, Ho-Young; Choi, Woon-Il; Ha, Man-Lyun; Lee, Ju-Il; Kang, Chang-Yong; Lee, Byoung-Hun; Jammy, Raj; Lee, Hi-Deok

    2011-10-01

    In this paper, two kinds of multilayered metal-insulator-metal (MIM) capacitors using Al2O3/HfO2/Al2O3 (AHA) and SiO2/HfO2/SiO2 (SHS) were fabricated and characterized for radio frequency (RF) and analog mixed signal (AMS) applications. The experimental results indicate that the AHA MIM capacitor (8.0 fF/µm2) is able to provide a higher capacitance density than the SHS MIM capacitor (5.1 fF/µm2), while maintaining a low leakage current of about 50 nA/cm2 at 1 V. The quadratic voltage coefficient of capacitance, α gradually decreases as a function of stress time under constant voltage stress (CVS). The parameter variation of SHS MIM capacitors is smaller than that of AHA MIM capacitors. The effects of CVS on voltage linearity and time-dependent dielectric breakdown (TDDB) characteristics were also investigated.

  2. 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

  3. Cathode encapsulation of organic light emitting diodes by atomic layer deposited Al2O3 films and Al2O3/a-SiNx:H stacks

    International Nuclear Information System (INIS)

    Al2O3 thin films synthesized by plasma-enhanced atomic layer deposition (ALD) at room temperature (25 deg. C) have been tested as water vapor permeation barriers for organic light emitting diode devices. Silicon nitride films (a-SiNx:H) deposited by plasma-enhanced chemical vapor deposition served as reference and were used to develop Al2O3/a-SiNx:H stacks. On the basis of Ca test measurements, a very low intrinsic water vapor transmission rate of ≤ 2 x 10-6 g m-2 day-1 and 4 x 10-6 g m-2 day-1 (20 deg. C/50% relative humidity) were found for 20-40 nm Al2O3 and 300 nm a-SiNx:H films, respectively. The cathode particle coverage was a factor of 4 better for the Al2O3 films compared to the a-SiNx:H films and an average of 0.12 defects per cm2 was obtained for a stack consisting of three barrier layers (Al2O3/a-SiNx:H/Al2O3).

  4. Mechanical stress in ALD-Al2O3 films

    International Nuclear Information System (INIS)

    Mechanical stress in atomic-layer deposition (ALD)-Al2O3 films was investigated at room temperature and during thermal cycling up to 870 deg. C. The films were generally under tensile stress. Thicker films (25-60 nm) showed a sharp stress increase at about 780-790 deg. C. X-ray diffraction (XRD)-, X-ray reflectance (XRR)- and X-ray photoelectron spectroscopy (XPS)-measurements indicate an irreversible phase transition from amorphous AlO(OH) to a mixture of different crystalline Al2O3-phases. Annealing at higher temperatures leads to a stress reduction as a result of diffusion and recovery processes. The stress behaviour of thinner films (<20 nm) during thermal cycling is quite different. Tensile stress increases with increasing temperature and decreases to nearly the same value during cooling down. The process is continuous and reversible

  5. Low-loss optical waveguides for the near ultra-violet and visible spectral regions with Al2O3 thin films from atomic layer deposition

    International Nuclear Information System (INIS)

    In this work, we report low-loss single-mode integrated optical waveguides in the near ultra-violet and visible spectral regions with aluminum oxide (Al2O3) films using an atomic layer deposition (ALD) process. Alumina films were deposited on glass and fused silica substrates by the ALD process at substrate/chamber temperatures of 200 oC and 300 oC. Transmission spectra and waveguide measurements were performed in our alumina films with thicknesses in the range of 210-380 nm for the optical characterization. Those measurements allowed us to determine the optical constants (nw and kw), propagation loss, and thickness of the alumina films. The experimental results from the applied techniques show good agreement and demonstrate a low-loss optical waveguide. Our alumina thin-film waveguides are well transparent in the whole visible spectral region and also in an important region of the UV; the measured propagation loss is below 4 dB/cm down to a wavelength as short as 250 nm. The low propagation loss of these alumina guiding films, in particular in the near ultra-violet region which lacks materials with high optical performance, is extremely useful for several integrated optic applications.

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

    International Nuclear Information System (INIS)

    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 C-O bond nearly parallel to the surface. In contrast, the CO obstructed less effectively the scission of the C-O 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.

  7. Leakage spot evolution in thin (ZrO2)0.8(Al2O3)0.2 -films observed by conductive atomic force microscopy (CAFM)

    International Nuclear Information System (INIS)

    A change from amorphous to nanocrystalline dielectric layers is necessary to achieve dielectric constants >30 as required for future technology nodes. This often leads to significantly higher leakage currents. These were measured in such inhomogeneous samples with a spatial resolution on the nanoscale. CAFM was used to characterize 20 nm-thin (ZrO2)0.8(Al2O3)0.2-films grown by molecular beam deposition. In nanocrystalline samples, there are hillocks at the surface with typical diameters and heights of 30 nm and 3 nm, respectively. An investigation by transmission electron microscopy implies that these hillocks are crystallites that protrude from the surface. CAFM current maps show leakage spots in which the current is significantly higher than in the surrounding matrix. These leakage spots are strongly correlated with the hillocks on the corresponding morphology images, indicating that the formation of crystallites really leads to leakage paths. To distinguish between different transport mechanisms, multiple images of the same area were taken, while the bias-voltage was changed consecutively. By using the entire set of images, IV-curves can be assigned to each location. These show a hysteretic behaviour for all leakage spots. Also, the voltage at which the strong increase in current occurs varies significantly for different leakage spots, i.e. between -1 V and -4 V

  8. New half-film method for measuring Al2O3 film MTF of 3rd generation image intensifier

    Science.gov (United States)

    Cheng, Yaojin; Shi, Feng; Bai, Xiaofeng; Zhu, Yufeng; Yan, Lei; Liu, Feng; Li, Min

    2012-10-01

    In 3rd generation image intensifier, Al2O3 film on the input of MCP is a serious influence factor on device MTF due to its electron scattering process. There are no reportes about how to measure the MTF of Al2O3 film. In this paper a new Half-film comparssion test method is creatively established for determing the film MTF, which overcomes the difficulty of measuring super thin film less than a few nm. In this way, the MTF curves of 10nm Al2O3 film can be accurately obtained. The measurement results show that 10nm Al2O3 film obviously decay the MTF performance of the 3rd generation image intensifier and take an important role in the improvement work of 3rd generation image intensifier MTF and resolution performances.

  9. 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.

  10. Chemical, morphological and nano-mechanical characterizations of Al2O3 thin films deposited by metal organic chemical vapour deposition on AISI 304 stainless steel

    International Nuclear Information System (INIS)

    Amorphous alumina coatings of different thickness have been deposited on AISI 304 stainless steel substrates by MOCVD in a hot wall reactor at 380 deg. C under O2/H2O atmosphere. The used aluminium precursor was the high volatile and easy to prepare dimethyl-aluminum-isopropoxide. Selected films were annealed in N2 and O2 atmosphere at 500 and 700 deg. C to evaluate the effects of the thermal treatments on the morphology and on the nano-mechanical properties of the coatings. X-ray diffraction and Rutherford backscattering spectroscopy measurements indicated that both the as grown and annealed films were amorphous and very pure with the correct Al2O3 stoichiometry. The surface morphology, investigated by atomic force microscopy, was free of cracks with a roughness of the films that increases with deposition time and with annealing in oxygen atmosphere. The hardness and the elastic modulus of the films and of the AISI 304 stainless steel substrate were measured by load-depth nano-indentation tests. The results highlighted a significant increase in the Berkovich hardness of the coated samples compared to that of the bulk AISI 304 stainless steel

  11. 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...

  12. Structures of Co and Pt nanoclusters on a thin film of Al 2O 3/NiAl(1 0 0) from reflection high-energy electron diffraction and scanning-tunnelling microscopy

    Science.gov (United States)

    Luo, M. F.; Wen, W. H.; Lin, C. S.; Chiang, C. I.; Sartale, S. D.; Zei, M. S.

    2007-05-01

    With reflection high-energy electron diffraction (RHEED) and scanning-tunnelling microscopy (STM), we made measurements on Co and Pt nanoclusters grown by vapour deposition on a thin film of Al 2O 3/NiAl(1 0 0). The results show that the annealed Co nanoclusters (with mean diameters 2.5, 3.4, 5.8 nm and heights 0.7, 1.5, 1.5 nm, respectively) and Pt nanoclusters (with mean diameter 2.25 nm and height 0.4 nm) are highly crystalline and that their structures are significantly affected by the oxide substrate. Structural analysis based on the RHEED patterns indicates that both Co and Pt clusters have a fcc phase and grow with their (0 0 1) facets parallel to the θ-Al 2O 3(1 0 0) surfaces, and with their [1 1 0] and [-1 1 0] axes along the [0 1 0] and [0 0 1] directions of the oxide surface, respectively, so (Co(0 0 1)[1 1 0]∥Al 2O 3(1 0 0)[0 1 0] and Pt(0 0 1)[1 1 0]∥Al 2O 3(1 0 0)[0 1 0]). This growth is optimal as the Co and Pt fcc (0 0 1) facets match well with the oxygen mesh. To minimize the lattice mismatch, the lattice parameter of the Co clusters expands 4-5% relative to fcc Co bulk, whereas the lattice parameter of the Pt clusters remains near the bulk value, as the Pt fcc (0 0 1) plane has a close lattice match with the oxide surface.

  13. Structural and optical properties of ZrO2 and Al2O3 thin films and Bragg reflectors grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    Our objective is to build a threshold-less laser based on the emission from a Bose-Einstein condensate of exciton-polaritons in a semiconductor microcavity-resonator. For this purpose, high reflective mirrors with smooth boundaries are necessary. The aspired resonator structure consists of a half-wavelength ZnO cavity embedded between two ZrO2/Al2O3 Bragg reflectors. We present high-reflective ZrO2/Al2O3 Bragg reflectors grown by pulsed laser deposition on c-plane sapphire and silicon substrates. For ZrO2/Al2O3 Bragg reflectors with a layer pair number of 12.5, reflectivity values of 99.8% at 3.3 eV and smooth surfaces have been reached. As preceding investigations, the optical and structural properties as the refractive indices, the crystal structure, and the surface properties of the used materials have been determined and optimised. It was found that these properties depend on the substrate and the position in the Bragg reflector layer stack. The optical and structural properties of the single layers and Bragg reflectors have been gained from spectroscopic ellipsometry in the energy range (1.0-4.5) eV, X-ray diffraction measurements, atomic force microscopy, and transmission scanning electron microscopy

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

    International Nuclear Information System (INIS)

    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

  15. Novel silicon surface passivation by Al2O3/ZnO/Al2O3 films deposited by thermal atomic layer deposition

    Science.gov (United States)

    Jeong, Kwang-Seok; Oh, Sung-Kwen; Shin, Hong-Sik; Yun, Ho-Jin; Kim, Seong-Hyeon; Lee, Ho-Ryeong; Han, Kyu-Min; Park, Ho-Yun; Lee, Hi-Deok; Lee, Ga-Won

    2014-01-01

    In this paper, a novel Al2O3/ZnO/Al2O3 stack is proposed as the silicon passivation layer for c-Si solar cell application. Recently, the Al2O3 film has been proved to be effective for passivating the p-type c-Si surface by forming the negative fixed oxide charge. It is confirmed by this experiment that the amount of negative fixed oxide charge can be controlled by inserting a ZnO interlayer (IL), which is explained by acceptor-like defect (VZn, Oi, and OZn) formation determined by the room-temperature photoluminescence (RTPL) analysis. The effect of ZnO IL is investigated using Al2O3 bottom layers of various thicknesses by electrical and physical analyses. The effective lifetime measurement shows that the electronic recombination losses at the silicon surface are reduced effectively by optimizing the Al2O3/ZnO/Al2O3 stack.

  16. 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%.

  17. 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.

  18. Surface passivation and antireflectance performances for atomic-layer-deposited Al2O3 films

    International Nuclear Information System (INIS)

    Al2O3 films were deposited on single crystalline silicon wafers by atomic layer deposition. Both passivation and antireflectance performances are studied in detail. 30 nm Al2O3 passivated n-type and p-type Si shows a maximum effective minority carrier lifetime (τeff) of ∼5.2 ms and ∼4.7 ms, corresponding to a low surface recombination velocity of ∼3.8 cm s−1 and ∼4.2 cm s−1, respectively. By drawing a contour map of post-deposition annealing (PDA) temperature, PDA time and τeff, a wide PDA window is obtained for obtaining good passivation performances. The excellent passivation performances are related to the large, negative fixed charge density within Al2O3 films and the formation of interfacial SiO2 layer at the Al2O3/Si interface. Antireflectance performances are also studied in detail for Al2O3 and Al2O3/SiNx double-layer on textured Si. For obtaining a low average reflectance between 2.6% and 3%, a wide film-thickness window of ∼30 nm for Al2O3 and SiNx layer is observed for Al2O3/SiNx double-layer on textured Si. Our results indicate that Al2O3 films have excellent surface passivation and antireflectance performances with a wide processing window, which is favorable for c-Si solar cell applications. (paper)

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

    International Nuclear Information System (INIS)

    Poly(vinylidene fluoride trifluoroethylene) and ZnO were employed for nonvolatile memory thin film transistors as ferroelectric gate insulator and oxide semiconducting channel layers, respectively. It was proposed that the thickness of the ZnO layer be carefully controlled for realizing the lower programming voltage, because the serially connected capacitor by the formation of a fully depleted ZnO channel had a critical effect on the off programming voltage. The fabricated memory transistor with Al/P(VDF-TrFE) (80 nm)/Al2O3 (4 nm)/ZnO (5 nm) exhibits encouraging behaviour such as a memory window of 3.8 V at the gate voltage of -10 to 12 V, and 107 on/off ratio, and a gate leakage current of 10-11 A.

  1. Pulsed Laser Deposition and Reflection High-Energy Electron Diffraction studies of epitaxial long range order, nano- and microstructured Ag thin films grown on MgO, Al2 O3 , STO and Si

    Science.gov (United States)

    Velazquez, Daniel; Seibert, Rachel; Man, Hamdi; Spentzouris, Linda; Terry, Jeff

    2015-03-01

    Pulsed Laser Deposition is a state-of-the-art technique that allows for the fine tunability of the deposition rate, highly uniform and epitaxial sample growth, the ability to introduce partial pressures of gases into the experimental chamber for growth of complex materials without interfering with the energy source (laser). An auxiliary in situ technique for growth monitoring, Reflection High-Energy Electron Diffraction, is a powerful characterization tool for predictability of the surface physical structure both, qualitatively and quantitatively. RHEED patterns during and post deposition of Ag thin films on MgO, Al2O3, Si and STO substrtates are presented and their interpretations are compared with surface imaging techniques (SEM, STM) to evidence the usefulness of the technique.

  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. Angular properties of pure and Ca-substituted YBa2Cu3O7-δ superconducting thin films grown on SrTiO3 and CeO2 buffered Al2O3 substrates

    International Nuclear Information System (INIS)

    In this work transport properties of superconducting 10 at.% Ca-substituted YBCO thin films grown on (1 0 0)-SrTiO3 single crystal substrate (STO) and superconducting pure and 10 at.% Ca-substituted YBCO thin films grown on CeO2 buffered Al2O3 substrates (CAO) have been analyzed as a function of the temperature, applied magnetic field and angle between magnetic field direction and the direction normal to the film surfaces. Particularly, the angular analysis provides an easy way to discriminate between isotropic point defects and correlated pinning sites. Despite the intragrain pinning mechanisms remained unaffected by Ca substitution, a detrimental effect on grain boundary properties clearly emerged for 10 at.% Ca concentration. This effect is enhanced in sample grown on CeO2 buffered sapphire where a more disturbed grain boundary is expected resulting in an enhancement of the correlated pinning, already observed in pure YBCO films grown on CAO, and in a reduction of the intrinsic pinning efficiency

  4. Epitaxially grown L10-FePt/(C, SiO2, and Al2O3) granular films

    International Nuclear Information System (INIS)

    Additive effects of C, SiO2, and Al2O3 on L10-FePt epitaxial thin film were studied. Samples were fabricated by co-sputtering of FePt and (C, SiO2, and Al2O3) on MgO (1 0 0) substrate at 973 K. These additives effectively reduce the particle size of FePt. C additive deteriorates the crystal orientation, while Al2O3 additive gradually degrades the L10 ordering. On the other hand, SiO2 additive can reduce the particle size while keeping the high c-axis orientation and higher degree of L10 ordering

  5. 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.

  6. Thermal stability of atomic layer deposition Al2O3 film on HgCdTe

    Science.gov (United States)

    Zhang, P.; Sun, C. H.; Zhang, Y.; Chen, X.; He, K.; Chen, Y. Y.; Ye, Z. H.

    2015-06-01

    Thermal stability of Atomic Layer Deposition Al2O3 film on HgCdTe was investigated by Al2O3 film post-deposition annealing treatment and Metal-Insulator-Semiconductor device low-temperature baking treatment. The effectiveness of Al2O3 film was evaluated by measuring the minority carrier lifetime and capacitance versus voltage characteristics. After annealing treatment, the minority carrier lifetime of the HgCdTe sample presented a slight decrease. Furthermore, the fixed charge density and the slow charge density decreased significantly in the annealed MIS device. After baking treatment, the fixed charge density and the slow charge density of the unannealed and annealed MIS devices decreased and increased, respectively.

  7. 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...

  8. 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...

  9. 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.

  10. Spatial ALD Al2O3 film integrated in low-cost, high-performance bifacial solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Vermont, P.; Granneman, E.; Ernst, M.A. [Levitech BV, Versterkerstraat 10, 1322 AP, Almere (Netherlands); Cesar, I.; Mewe, A.A.; Weeber, A.W. [ECN Solar Energy, Petten (Netherlands)

    2012-09-15

    ALD (Atomic Layer Deposition) Al2O3 films have been integrated in an open rear-side p-PASHA (Passivated All Sides and H-pattern) type solar cell. The manufacturing of this cell is cost-effective as it uses a single dielectric Al2O3 layer (i.e. no SiNx capping layer), partial (30-50%) coverage of metal paste on the rear side, no laser opening or laser firing required, and co-firing of the Ag and Al pastes. The spatial ALD deposition is carried out in the Levitrack system which is characterized by a high throughput (up to 3600 wafers/hr) and strict separation of H2O and TMA compounds (tetramethacrylate) in the system. The Al2O3 film was thin enough to allow effective firing through, while avoiding the formation of defects (blisters) upon high-temperature firing. On p-type Cz and multi-crystalline material, the p-PASHA cell was superior to the reference full-BSF (back surface field) cell in J{sub sc} x V{sub oc} by 1% and 2.5% respectively. Local IQE (Iterative Query Expansion) mapping indicates that the Al2O3 passivation performance is maintained after firing.

  11. 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.

  12. Molecular dynamics simulations on the direct sputtering of Al2O3 insulating film in a magnetic tunneling junction

    International Nuclear Information System (INIS)

    The molecular dynamics (MD) simulation is used to study the direct deposition of aluminum-oxide (Al2O3) to grow an insulating thin film on cobalt substrate in a magnetic tunneling junction (MTJ). The direct deposition of Al2O3 may produce a very thin film with very smooth surface and form an averagely oxidized insulator. A high magnetoresistance ratio is desired in an MTJ device, so that smooth surface and good structural integrity for the insulating thin film is anticipated. The MD simulation is an effective way in determining optimal processing parameters that can be used to fabricate high-quality MTJ devices. The Buckingham and many-body tight-binding potentials are applied in the MD simulations for different interactions between particles. The effects of the cluster size and the incident energy on the thin film's surface morphology and Al2O3 purity are investigated. Some optimal parameters that could be used as the reference for practical processing purposes are derived

  13. 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.

  14. Enhanced water vapor barrier properties for biopolymer films by polyelectrolyte multilayer and atomic layer deposited Al2O3 double-coating

    International Nuclear Information System (INIS)

    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) Al2O3 layer. The double-coating of PEM + Al2O3 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 Al2O3 layer. The enhanced water vapor barrier characteristics of the PEM + Al2O3 double-coated PLA films are attributed to the increased hydrophobicity of the surface of these films.

  15. 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.

  16. 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.

  17. Nanostructured Er3+-doped SiO2-TiO2 and SiO2-TiO2-Al2O3 sol-gel thin films for integrated optics

    Science.gov (United States)

    Predoana, Luminita; Preda, Silviu; Anastasescu, Mihai; Stoica, Mihai; Voicescu, Mariana; Munteanu, Cornel; Tomescu, Roxana; Cristea, Dana

    2015-08-01

    The nanostructured multilayer silica-titania or silica-titania-alumina films doped with Er3+ were prepared by sol-gel method. The sol-gel method is a flexible and convenient way to prepare oxide films on several types of substrates, and for this reason it was extensively investigated for optical waveguides fabrication. The selected molar composition was 90%SiO2-10%TiO2 or 85%SiO2-10%TiO2-5% Al2O3 and 0.5% Er2O3. The films were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Spectroellipsometry (SE), as well as by Atomic Force Microscopy (AFM) and photoluminescence (PL). The films deposited on Si/SiO2 substrate by dip-coating or spin-coating, followed by annealing at 900 °C, presented homogenous and continuous surface and good adherence to the substrate. Differences were noticed in the structure and properties of the prepared films, depending on the composition and the number of deposited layers. Channel optical waveguides were obtained by patterning Er3+-doped SiO2-TiO2 and SiO2-TiO2-Al2O3 sol-gel layers deposited on oxidized silicon wafers.

  18. Space-charge-controlled field emission model of current conduction through Al2O3 films

    Science.gov (United States)

    Hiraiwa, Atsushi; Matsumura, Daisuke; Kawarada, Hiroshi

    2016-02-01

    This study proposes a model for current conduction in metal-insulator-semiconductor (MIS) capacitors, assuming the presence of two sheets of charge in the insulator, and derives analytical formulae of field emission (FE) currents under both negative and positive bias. Since it is affected by the space charge in the insulator, this particular FE differs from the conventional FE and is accordingly named the space-charge-controlled (SCC) FE. The gate insulator of this study was a stack of atomic-layer-deposition Al2O3 and underlying chemical SiO2 formed on Si substrates. The current-voltage (I-V) characteristics simulated using the SCC-FE formulae quantitatively reproduced the experimental results obtained by measuring Au- and Al-gated Al2O3/SiO2 MIS capacitors under both biases. The two sheets of charge in the Al2O3 films were estimated to be positive and located at a depth of greater than 4 nm from the Al2O3/SiO2 interface and less than 2 nm from the gate. The density of the former is approximately 1 × 1013 cm-2 in units of electronic charge, regardless of the type of capacitor. The latter forms a sheet of dipoles together with image charges in the gate and hence causes potential jumps of 0.4 V and 1.1 V in the Au- and Al-gated capacitors, respectively. Within a margin of error, this sheet of dipoles is ideally located at the gate/Al2O3 interface and effectively reduces the work function of the gate by the magnitude of the potential jumps mentioned above. These facts indicate that the currents in the Al2O3/SiO2 MIS capacitors are enhanced as compared to those in ideal capacitors and that the currents in the Al-gated capacitors under negative bias (electron emission from the gate) are more markedly enhanced than those in the Au-gated capacitors. The larger number of gate-side dipoles in the Al-gated capacitors is possibly caused by the reaction between the Al and Al2O3, and therefore gate materials that do not react with underlying gate insulators should be chosen

  19. Comparative measurements on atomic layer deposited Al2O3 thin films using ex situ table top and mapping ellipsometry, as well as X-ray and VUV reflectometry

    International Nuclear Information System (INIS)

    In this study we compare the thicknesses and optical properties of atomic layer deposited (ALD) Al2O3 films measured using table top and mapping ellipsometry as well as X-ray and optical reflectometry. The thickness of the films is varied in the range of 1–50 nm. ALD samples are used as references with well-controlled composition and thickness, as well as with a good lateral homogeneity. The homogeneity is checked using mapping ellipsometry. Optical models of increasing complexity were developed to take into account both the top (surface roughness on the nanometer scale) and bottom interfaces (buried silicon oxide and interface roughness). The best ellipsometric model was the one using a single interface roughness layer. Since the techniques applied in this work do not measure in vacuum, organic surface contamination even in the sub-nanometer thickness range may cause an offset in the measured layer thicknesses that result in significant systematic errors. The amount of surface contamination is estimated by in situ reflectometry measurement during removal by UV radiation. Taking into account the surface contamination the total thicknesses determined by the different methods were consistent. The linearity of the total thickness with the number of atomic layer deposition cycles was good, with an offset of 1.5 nm, which is in good agreement with the sum of thicknesses of the interface layer, surface nanoroughness, and contamination layer. - Highlights: ► Improved X-ray and optical methods for atomic layer deposited Al2O3 films ► Mapping ellipsometry to check inhomogeneity for the comparative investigations ► Best fit ellipsometric model includes a single interface roughness layer. ► Consistent thickness values from the different methods ► Surface contamination effect on the different methods compared

  20. nc-VO2/Al2O3 nanocomposite films prepared by dual target magnetron sputtering

    International Nuclear Information System (INIS)

    A dual target magnetron sputtering system was used to synthesize nanocomposite films with VO2 nanocrystals embedded in Al2O3 matrix. Glancing incidence X-ray diffraction and high-resolution transmission electron microscopy reveal the formation of VO2 nanocrystallites with monoclinic structure. X-ray photoemission analysis confirmed that oxide particles predominantly possess VO2 stoichiometry. Valence band spectra acquired below and above transition temperature demonstrate that embedded VO2 particles exhibit a first-order monoclinic-to-tetragonal phase transition, however the band shape in a metallic state exhibits feature that is not characteristic for bulk material

  1. Preparation and characterization of carbonate terminated polycrystalline Al2O3/Al films

    International Nuclear Information System (INIS)

    X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface reactivity of polycrystalline Al films in contact with a gas mixture of carbon dioxide and oxygen at room temperature. Based on the characterization of interactions between these substrates and the individual gases at selected exposures, various surface functionalities were identified. Simultaneously dosing both carbon dioxide and oxygen is shown to create surface-terminating carbonate species, which contribute to inhibiting the formation of an Al2O3 layer. Finally, a reaction scheme is suggested to account for the observed dependence of surface group formation on the dosing conditions

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Role of Al2O3 intermediate layer for improving the quality of polycrystalline-silicon film in inverted aluminum-induced layer exchange

    International Nuclear Information System (INIS)

    Highlights: • Al2O3 intermediate layer deposited by ALD was introduced in inverted-ALILE process. • Poly-Si with 93% (1 0 0)-oriented crystals fraction and 28-μm average grain size was achieved at 4-nm Al2O3 intermediate layer. • Smooth surface morphology and lower defects of poly-Si was achieved. • An a-AlOx layer exists at the poly-Si/Al interface after inverted-ALILE process. - Abstract: A thin Al2O3 intermediate layer prepared by atomic layer deposition was introduced into inverted aluminum-induced layer exchange (inverted-ALILE) to form high-quality polycrystalline silicon (poly-Si) thin layer. It was demonstrated that the continuity and quality of poly-Si were obviously improved by the Al2O3 layer. The fraction of (1 0 0)-oriented crystals reached 93%, and the average grain size of 28 μm with uniform surface morphology and low defect density were achieved at the optimal Al2O3 thickness of 4 nm. It was also found that an a-AlOx layer always existed at the poly-Si/Al interface after inverted-ALILE process, which is independent on the original surface states. The results suggested that the thin poly-Si layer would be a promising epitaxial template for Si based thin film solar cells

  7. A study of Al2O3 films on CLAM substrate

    International Nuclear Information System (INIS)

    Full text of publication follows: The Dual-Functional Lithium-Lead Blanket Module (DFLL-TBM) system is designed to demonstrate and validate the technologies of both the helium-cooled blanket and the helium/lithium-lead dual-cooled blanket, and there will be several relevant concept designs in China. Considering the fugacity of the tritium and its very low solubility in liquid LiPb, tritium is very easy to permeate out of the blanket, and this will result in the losing of nuclear fuel and the potential radioactive hazard to the circumstance. Additional liquid LiPb flowing in the blanket will produce serious MHD effects and corrupt the structural material. After many years of research in this field, it's considered possible to produce a coating on the structural materials which have advantages such as anti-irradiation-swelling, low thermal expansion coefficient and higher thermal conductance, to reduce tritium permeation, mitigate MHD effects and corrosion by the liquid LiPb. Chinese Low Activation Martensitic (CLAM) Steel was designed to be used as the structural material in the DFLL-TBM and the future DEMO reactor because of its high quality. It is recognized that large quantities of ceramics will be needed in the future for the fabrication of ITER test blanket modules and the ITER driver blanket. Aluminum oxide (Al2O3) ceramic has long been recognized as a promising tritium-breeding material for fusion reactor blankets. Al2O3 films were prepared on CLAM Substrate with the ratio of O2/Ar from 0.1 to 1.2 by RF Magnetron Sputtering method, and the base and the sputtering pressure are 2 x 10-4 Pa and 1 Pa respectively. The existence of nano-scale Al2O3 grains was observed by the Scanning Electronic Microscope(SEM); the structure of the films was investigated by means of X-Ray Diffraction (XRD); the samples were submitted to hydrogen permeation; the resistivity was calculated according to the resistance and the thickness which was measured by interferometer. In this

  8. 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.

  9. 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.

  10. Nanocrystal and interface defects related photoluminescence in silicon-rich Al2O3 films

    International Nuclear Information System (INIS)

    In this study, silicon nanocrystal-rich Al2O3 film has been prepared by co-sputtering a silicon and alumina composite target and subsequent annealing in N2 atmosphere. The microstructure of the film has been characterized by infrared (IR) absorption, Raman spectra and UV-absorption spectra. Typical nanocrystal and interface defects related photoluminescence with the photon energy of 1.54 (IR band) and 1.69 eV (R band) has been observed by PL spectrum analysis. A post-annealing process in oxygen atmosphere has been carried out to clarify the emission mechanism. Despite the red shift of the spectra, enhanced emission of the 1.69 eV band together with the weak emission phenomenon of the 1.54 eV band has been found after the post-annealing. The R band is discussed to originate from silicon nanocrystal interface defects. The IR band is concluded to be a coupling effect between electronic and vibrational emissions

  11. Nanoindentation investigation of mechanical properties of ZrO2, ZrO2–Y2O3, Al2O3 and TiO2 thin films deposited on stainless steel OC 404 substrate by spray pyrolysis

    International Nuclear Information System (INIS)

    Highlights: • ZrO2, ZrO2–Y2O3, Al2O3 and TiO2 films were deposited by spray pyrolysis. • Surface morphology and structure of the films were characterized via SEM and X-ray. • Mechanical properties of films were investigated by nanoindentation and was established that their values exceed these for pure metals. - Abstract: Thin ZrO2, ZrO2–Y2O3, Al2O3 and TiO2 films were deposited by spray pyrolysis method on stainless steel OC 404 substrate with thickness 50 μm. The thicknesses of obtained films varied from 0.50 to 0.64 μm. The surface morphology and structure of the films were characterized by scanning electron microscopy in secondary electron imaging mode. The X-ray diffraction measurements for determination of the lattice parameters, the average crystallite size and the sample strain were performed. Mechanical properties of investigated films and substrate were investigated by nanoindentation experiments, using Nano Indenter G200 (Agilent Technologies). As a result of nanoindentation experiments, load–displacement curves were obtained and two mechanical characteristics of the substrate and investigated films – indentation hardness (HIT) and indentation modulus (EIT) – were calculated using Oliver and Pharr approximation method. Dependence of indentation modulus and indentation hardness on depth of indentation was investigated as well

  12. 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....

  13. 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.

  14. 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.

  15. 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

  16. 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 that...... passivation in fluorescent SiC based white LEDs applications....

  17. Development of nano-sized α-Al2O3:C films for application in digital radiology

    International Nuclear Information System (INIS)

    Ceramic materials are widely used as sensors for ionizing radiation. In nuclear applications, the alpha-alumina doped with carbon (α-Al2O3:C) is the most widely ceramic used because of its excellent optically stimulated luminescence (OSL) and thermoluminescent (TL) properties applied to detection of ionizing radiation. Another application of OSL and TL materials are in Digital Radiography, with ceramic/polymeric film composites. Recently, Computed Radiography (CR) devices based on OSL materials are replacing the old conventional film radiography. In this study we investigate the thermoluminescence of nano-sized α-Al2O3 samples doped with different percentages of carbon, sintered in reducing atmospheres at temperatures ranging from 1300 to 1750 deg C. The results indicate that the nano-sized α-Al2O3:C materials have a luminescent response that could be due to both OSL and RPL properties, but without application to radiation dosimetry. Moreover, the results indicate that micro-sized α-Al2O3:C, doped with 0.5% carbon, and nano-sized ones doped with 2% of carbon, present thermoluminescent signal around 30 to 100 times the TL output signal of commercial TLD-100, the most used TL dosimeter in the world. The results indicate that these ceramic nano-particles have great potential for use in Digital Radiography based on thermoluminescent film imaging, being able to provide image resolutions much higher than the micro-sized α-Al2O3:C, in view of their improved resolution provided by nano-particulates. (author)

  18. Synthesis and characterization of CuO/ZnO-Al2O3 catalyst washcoat thin films with ZrO2 sols for steam reforming of methanol in a microreactor

    International Nuclear Information System (INIS)

    Inner surface and the fine structure of the microchannel reactor using porous alumina support CuO/ZnO mixed with ZrO2 sol washcoat catalyst for autothermal reforming of methanol have been synthesized and characterized. Experimentally, catalyst slurries have been dried at 298 K for 5 h and then calcined at 623 K for 2 h to increase the surface area and specific pore structures of washcoat catalysts. Intensities of Cu content from XRD patterns indicate that Al2O3 assign with Cu(0) to from CuAl2O4. The EXAFS data reveals that the Cu species in washcoat have a Cu-O bonding with a bond distance of 1.96 A and a coordination number of 2.95, respectively.

  19. 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.

  20. Growth of ¦�Al2O3¡ Crystal by Edge-Defined, Film-Fed Growth Technique

    Directory of Open Access Journals (Sweden)

    YANG Xin-Bo,LI Hong-Jun,BI Qun-Yu,CHENG Yan,SU Liang-Bi,TANG Qiang,XU Jun

    2009-03-01

    Full Text Available ¦�Al2O3¡ crystal was grown by Edge-Defined, Film-Fed Growth Technique (EFG in which graphite heating unit and shield acted as the carbon source and high purity Al2O3 was used as the raw material. Thermoluminescence (TL and optically stimulated luminescence (OSL properties of as-grown crystal after annealing in H2 were investigated. The crystal shows a single one-order kinetic glow peak at 460K and blue emission band at 415nm. OSL decay curve of ¦�Al2O3¡ crystal shows exponential characteristic. The decay curve is made up of two components, i.e. the faster component and the slower component. The TL and OSL responses of ¦�Al2O3¡ crystal show linearª²sublinearª²saturation characteristics. The TL exhibits good linear dose response in the dose range from 5¡�0-6 to 0.2Gy and saturation is about 10Gy. The OSL exhibits good linear dose response in the dose range from 5¡�0-6 to 10Gy and saturation is about 30Gy.

  1. 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.

  2. Interfacial study and energy-band alignment of annealed Al2O3 films prepared by atomic layer deposition on 4H-SiC

    International Nuclear Information System (INIS)

    Al2O3 films were prepared by atomic layer deposition using trimethylaluminum and H2O at 250 °C on 4H-SiC substrates and annealed at 1000 °C in N2. The as-deposited and annealed Al2O3 films were measured and analyzed near the Al2O3/SiC interfaces by using an X-ray photoelectron spectroscopy (XPS) with etching processing. The XPS results showed that as-deposited Al2O3 films were O-rich and converted to anhydride Al2O3 films after annealed at 1000 °C in N2. Si suboxides were found both at as-deposited and annealed Al2O3/SiC interfaces. Energy band shift between Al2O3 and 4H-SiC was found after annealing. The conduction band offsets of as-grown and annealed Al2O3/SiC were 1.90 and 1.53 eV, respectively. These results demonstrated that Al2O3 can be a good candidate to be applied in SiC metal-oxide-semiconductor devices.

  3. Filling performance and electrical characteristics of Al2O3 films deposited by atomic layer deposition for through-silicon via applications

    International Nuclear Information System (INIS)

    We have evaluated the conformality and electrical properties of Al2O3 films deposited by atomic layer deposition at temperatures below 300 °C for through-silicon via (TSV) applications. Al2O3 films were able to be conformally deposited on the scallops of 50-μm-wide, 100-μm-deep TSV at the temperature range between 200 and 300 °C. The median breakdown fields of the metal–insulator–metal device with 30-nm-thick Al2O3 layer were above 6 MV/cm for the films deposited at 250 and 300 °C, while that at 200 °C was inferior due to residual carbon impurities in the oxide layer. - Highlights: • Filling performance and electrical properties of Al2O3 films were evaluated. • Al2O3 films were conformally deposited on the scallops of through-silicon via holes. • The median breakdown field of 30-nm-thick Al2O3 layer was above 6 MV/cm. • The Al2O3 film deposited at 200 °C was inferior due to the residual carbon impurities. • Al2O3 films showed a promise as the dielectric for through-silicon via application

  4. 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.

  5. Barrier properties of plastic films coated with an Al2O3 layer by roll-to-toll atomic layer deposition

    International Nuclear Information System (INIS)

    Thin (30–40 nm) and highly uniform Al2O3 coatings have been deposited at relatively low temperature of 100 °C onto various polymeric materials employing the atomic layer deposition (ALD) technique, both batch and roll-to-roll (R2R) mode. The applications for ALD have long been limited those feasible for batch processing. The work demonstrates that R2R ALD can deposit thin films with properties that are comparable to the film properties fabricated by in batch. This accelerates considerably the commercialization of many products, such as flexible, printed electronics, organic light-emitting diode lighting, third generation thin film photovoltaic devices, high energy density thin film batteries, smart textiles, organic sensors, organic/recyclable packaging materials, and flexible displays, to name a few. - Highlights: • Thin and uniform Al2O3 coatings have been deposited onto polymers materials. • Batch and roll-to-roll (R2R) atomic layer deposition (ALD) have been employed. • Deposition with either process improved the barrier properties. • Sensitivity of coated films to defects affects barrier obtained with R2R ALD

  6. Microstructure and transport properties of epitaxial topological insulator Bi2Se3 thin films grown on MgO (100), Cr2O3 (0001), and Al2O3 (0001) templates

    Science.gov (United States)

    Lee, Y. F.; Kumar, R.; Hunte, F.; Narayan, J.; Schwartz, J.

    2015-09-01

    We report the epitaxial integration of defect-induced room temperature ferromagnetic insulators, Cr2O3 and MgO, with topological insulators Bi2Se3 on c-sapphire substrate by pulsed laser deposition. The structural, magnetic, and magnetotransport properties of ˜15 nm Bi2Se3 thin films are investigated on each template. The lattice misfits of Cr2O3/Bi2Se3 and MgO/Bi2Se3 are ˜16% and ˜39%, respectively, where the critical thickness for pseudomorphic growth is less than one monolayer. The insulating behavior is more pronounced due to the additional scattering of the surface states of the Bi2Se3 layer by interfacing with MgO and Cr2O3. The weak antilocalization effect from the surface states is clearly suppressed, accounting for the presence of magnetic bottom layers. This work demonstrates an effective way to study the emergence of a ferromagnetic phase in topological insulators by the magnetic proximity effect in Bi2Se3, a step toward unveiling their exotic properties.

  7. 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.

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

    International Nuclear Information System (INIS)

    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. (condensed matter: structural, mechanical, and thermal properties)

  9. Influence of RF-sputtering power on formation of vertically stacked Si1−xGex nanocrystals between ultra-thin amorphous Al2O3 layers: structural and photoluminescence properties

    International Nuclear Information System (INIS)

    In this work, we investigate the structural and photoluminescence (PL) properties of (SiGe+Al2O3)/Al2O3 multi-layer films with layer thicknesses in the range of a few nanometres. The films were prepared by magnetron sputtering deposition at room temperature followed by an annealing process to promote the formation of small SiGe nanocrystals (NCs) (∼3 to 5 nm) embedded between ultra-thin (∼6 nm thickness) Al2O3 layers. Our results show that the structural and compositional properties of the films can be tuned by changing the RF-power. It is found that nearly spherical and well confined isolated SiGe NCs (∼5 nm) are obtained for an RF-power value of 80 W. The PL properties of the films were studied and optical emission in the blue visible wavelength region was observed. (paper)

  10. Electrochemical properties of estradiol at glassy carbon electrode modified with nano-Al2O3 film

    International Nuclear Information System (INIS)

    Nano-Al2O3 is dispersed onto the surface of the glassy carbon electrode (GCE). This nanostructured film modified GCE exhibits a great enhancement to the oxidation of estradiol (E2), especially when adequate concentration of cationic surfactant such as cetyltrimethylammonium bromide (CTAB) is added into the sample solution. Due to the nanoparticle's unique properties and its inclination to selectively combine with some groups of bimolecules, as well as synergistic adsorption of E2 and CTAB on the electrode surface, E2 gives a more sensitive voltammetric response compared with bare GCE performed in the absence of CTAB. The lowest detectable concentration (3σ) of E2 is estimated to be 8x10-8 mol l-1 (accumulation for 2 min). The linear relationship between peak current and concentration of E2 holds in the range 4x10-7-4x10-5 mol l-1 (R=0.9932). The electrochemical properties of E2 on this modified electrode are investigated by linear scan voltammetry and cyclic voltammetry. Scanning electron microscope (SEM) and BET are employed to characterize the surface of the electrode modified with nano-Al2O3 film

  11. The structure and optical characters of the ZnO film grown on GaAs/Al2O3 substrate

    International Nuclear Information System (INIS)

    In this paper ZnO films are grown on GaAs/Al2O3 substrates at different temperature by metal-organic chemical vapor deposition (MOCVD). The GaAs/Al2O3 substrates are formed by depositing GaAs layer (∼35 nm) on the Al2O3 substrate. The results of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) demonstrate that most of the Ga and As atoms form Ga-As bond and the GaAs layer does not present any orientation. The characters of the ZnO films grown on GaAs/Al2O3 substrates are investigated by XRD, photoluminescence (PL), atomic force microscopy (AFM) and Raman scattering. Compared with ZnO film grown on Al2O3 substrate, ZnO film prepared by our fabrication scheme has good crystal and optical quality. Meanwhile its grain size becomes bigger according to the AFM image. Raman analysis indicates that the intrinsic defects and the in-plane tensile stress are obviously reduced in ZnO/GaAs/Al2O3 samples.

  12. Low Surface Recombination Velocity on P-Type Cz-Si Surface by Sol-Gel Deposition of Al2O3 Films for Solar Cell Applications.

    Science.gov (United States)

    Balaji, Nagarajan; Park, Cheolmin; Raja, Jayapal; Ju, Minkyu; Venkatesan, Muthukumarasamy Rangaraju; Lee, Haeseok; Yi, Junsin

    2015-07-01

    High quality surface passivation has gained a significant importance in photovoltaic industry for fabricating low cost and high efficiency solar cells using thinner and lower cost wafers. The passivation property of spin coated Al2O3 films with a thickness of about 50 nm on p-type Cz-Si wafers has been investigated as a function of annealing temperatures. An effective surface recombination velocity of 55 cm/s was obtained for the films annealed at 500 °C. The chemical and field effect passivation was analyzed by C-V measurements. A high density of negative fixed charges (Qf) in the order of 9 x 10(11) cm(-2) was detected in Al2O3 films and its impact on the level of surface passivation was demonstrated experimentally. The C-V curves show density of the interface state (Dit) of 1 x 10(12) eV(-1)cm(-2) at annealing temperature of 500 °C. During annealing, a thin interfacial SiOx is formed, and this interfacial layer is supposed to play a vital role in the origin of negative QF and Dit. The homogeneous SiOx interlayer result in higher passivation performance due to both the increase of negative Qf and the decrease of Dit. PMID:26373089

  13. Magnetic properties and anisotropic coercivity in nanogranular films of Co/Al2O3 above the percolation limit

    Science.gov (United States)

    Kulyk, M. M.; Kalita, V. M.; Lozenko, A. F.; Ryabchenko, S. M.; Stognei, O. V.; Sitnikov, A. V.; Korenivski, V.

    2014-08-01

    Magnetic properties of nanogranular ferromagnetic Co/Al2O3 films with 74.5 at% Co, which is above the percolation limit, are investigated. It is established that the films have perpendicular magnetic anisotropy and a weaker in-plane anisotropy. The magnetization curves show that the film consists of two magnetic components: a dominating contribution from magneto-anisotropic isolated grains with the anisotropy axis perpendicular to the film plane and a weaker contribution from the percolated part of the film. This two-component magnetic composition of the films, with the dominating contribution from the nanograins, is confirmed by transmission electron microscopy as well as by ferromagnetic resonance spectroscopy. It is further established that the coercive field of the film is almost entirely determined by the percolated part of the film. In this, the angular dependence of the coercive force, Hc (θH), is essentially proportional to sin-1θH, where θH is the angle between the applied field and the film's normal. However, for θH → 0, Hc (θH) there is a narrow minimum with Hc approaching zero. Such non-linear dependence agrees well with our modelling results for a two-component magnetic system of the film, where the non-percolated nanograins have a distinct perpendicular anisotropy. The reported results should be important for in-depth characterization and understanding the magnetism and anisotropy in inhomogeneous systems as well as for applications, specifically in perpendicular magnetic recording.

  14. 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.

  15. 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.

  16. Studies on hydrogen loaded V-Fe8 at% films on Al2O3 substrate

    International Nuclear Information System (INIS)

    Hydride formation of V-Fe8 at% films with different microstructures was investigated by measuring the electromotoric force (EMF), in-plane stress and, additionally, the local chemistry by performing tomographic atom probe (TAP). The phase boundaries of the films were found to be microstructure dependent: the α-phase solubility limit was found to be cH,α = 0.1 H/V and cH,β = 0.45 ± 0.02 H/V for films with small-domain size, and cH,α = 0.1 H/V and cH,β = 0.6 ± 0.02 H/V for films with large domain size. Stress release also depends on the microstructure; it is more efficient for small-domain samples resulting in smaller total stress. It is shown that the plateau pressure and the plateau slope of the films increase with hydrogen-induced in-plane compressive stress increase. TAP analysis at about 20 K monitors the occurrence of a plate-like hydride VD0.65-precipitate at the V/Pd interface. The detected concentrations are in good agreement with those expected at low temperatures

  17. 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.

  18. Magnetic properties and anisotropic coercivity in nanogranular films of Co/Al2O3 above the percolation limit

    International Nuclear Information System (INIS)

    Magnetic properties of nanogranular ferromagnetic Co/Al2O3 films with 74.5 at% Co, which is above the percolation limit, are investigated. It is established that the films have perpendicular magnetic anisotropy and a weaker in-plane anisotropy. The magnetization curves show that the film consists of two magnetic components: a dominating contribution from magneto-anisotropic isolated grains with the anisotropy axis perpendicular to the film plane and a weaker contribution from the percolated part of the film. This two-component magnetic composition of the films, with the dominating contribution from the nanograins, is confirmed by transmission electron microscopy as well as by ferromagnetic resonance spectroscopy. It is further established that the coercive field of the film is almost entirely determined by the percolated part of the film. In this, the angular dependence of the coercive force, Hc (θH), is essentially proportional to sin−1θH, where θH is the angle between the applied field and the film's normal. However, for θH → 0, Hc (θH) there is a narrow minimum with Hc approaching zero. Such non-linear dependence agrees well with our modelling results for a two-component magnetic system of the film, where the non-percolated nanograins have a distinct perpendicular anisotropy. The reported results should be important for in-depth characterization and understanding the magnetism and anisotropy in inhomogeneous systems as well as for applications, specifically in perpendicular magnetic recording. (paper)

  19. Atomic layer deposition of Al2O3 on V2O5 xerogel film for enhanced lithium-ion intercalation stability

    International Nuclear Information System (INIS)

    V2O5 xerogel films were fabricated by casting V2O5 sols onto fluorine-doped tin oxide glass substrates at room temperature. Five, ten and twenty atomic layers of Al2O3 were grown onto as-fabricated films respectively. The bare film and Al2O3-deposited films all exhibited hydrous V2O5 phase only. Electrochemical impedance spectroscopy study revealed increased surface charge-transfer resistance of V2O5 films as more Al2O3 atomic layers were deposited. Lithium-ion intercalation tests at 600 mAg-1 showed that bare V2O5 xerogel film possessed high initial discharge capacity of 219 mAhg-1 but suffered from severe capacity degradation, i.e., having only 136 mAhg-1 after 50 cycles. After deposition of ten atomic layers of Al2O3, the initial discharge capacity was 195 mAhg-1 but increased over cycles before stabilizing; after 50 cycles, the discharge capacity was as high as 225 mAhg-1. The noticeably improved cyclic stability of Al2O3-deposited V2O5 xerogel film could be attributed to the improved surface chemistry and enhanced mechanical strength. During repeated lithium-ion intercalation/de-intercalation, atomic layers of Al2O3 which were coated onto V2O5 surface could prevent V2O5 electrode dissolution into electrolyte by reducing direct contact between active electrode and electrolyte while at the same time acting as binder to maintain good mechanical contact between nanoparticles inside the film.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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

  6. 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/℃

  7. 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.

  8. 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.

  9. 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.

  10. 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...

  11. 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

  12. Structural, optical, and acoustic characterization of high-quality AlN thick films sputtered on Al2O3(0001) at low temperature for GHz-band electroacoustic devices applications

    International Nuclear Information System (INIS)

    Aluminum nitride thin and thick films were grown on Al2O3(0001) substrates by reactive radio frequency-sputtering technique at 180 deg. C. The AlN films, 0.022-6.2 μm thick, were stress-free, uniform, transparent, and extremely adhesive to the substrate. Their structural properties were investigated by x-ray diffraction measurements: the resulting films were highly c-axis oriented, with a full width at half maximum of the (0002) rocking curve in the range from 1.6 deg. to 1.0 deg. for AlN film thickness ranging between 0.022 and 6.2 μm. The crystalline quality of AlN films was extremely good even at high thicknesses, as shown by the presence of the AlN(0004) reflection and by the narrow (0.12 deg. -0.20 deg.) diffraction peaks. Optical measurements of the transmission in the visual and infrared region demonstrated that the AlN films have low absorption and scattering. The extinction and the absorption coefficients, α and Ke, were estimated at λ≥600 nm (α=850±50 cm-1,Ke=0.0040±0.0005). The piezoelectric strain constant d33 was measured for all the sputtered films: the mean d33 value was (4.2±0.7)x10-12 C/N, which is very close to the value of the AlN single crystal. Surface acoustic wave (SAW) delay lines were photolithographically defined on the free surface of the AlN films grown on bare or metallized Al2O3(0001) substrates. Harmonic modes operating at frequencies up to about 2.4 GHz were obtained just by using a conventional photolithographic technique with 7.5 μm linewidth. The phase and group velocities of SAWs propagating in AlN/Al/Al2O3 and in AlN/Al2O3 structures, along and normal to the Al2O3 a axis, were estimated for different AlN thicknesses. The experimental measurements were compared with the theoretical data and found to be in good agreement

  13. 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.

  14. Low-pressure chemical vapour deposition growth of high-quality ZnO films on epi-GaN/α-Al2O3

    International Nuclear Information System (INIS)

    We present the first results on (0001) ZnO/(0001) epi-GaN/(0001) α-Al2O3 heterostructure fabrication combining metal-organic vapour phase epitaxy and low-pressure chemical vapour deposition methods. The surface morphologies of the films were studied, and x-ray and reflection high-energy electron diffraction measurements were made, which showed a high degree of structural perfection of the ZnO films, with crystallite misorientation as low as 21'. The measured photoluminescence spectra of the films featured prevailingly emission within the excitonic region. (author). Letter-to-the-editor

  15. 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.

  16. Formation and properties of Bi-Sr-Ca-Cu-O/ZrO2/Si(Al2O3) high temperature superconductive films

    International Nuclear Information System (INIS)

    Films in Bi-Sr-Ca-Cu-O/ZrO2/Si(Al2O3), Bi-Sr-Ca-Cu-O/(ZrO2 + 10%Y2O5)/Si systems are produced, investigation into their composition and interaction between their components by the methods of X-ray electron spectrometry is conducted, resistance temperature progress is measured, superconducting transition temperature is determined. It is shown that films produced in the course of spray coating are characterized by a uniform distribution of film elements by depth, presence of a clear boundary between the film and sublayer and absence of mutual diffusion of film and substrate elements. The film annealing leads to a notable sublayer broadening, erosion of its boundaries and a partial penetration of film elements to the substrate. An increase of annealing time amplifies, and introduction of stabilizing Y2O3 additions weakens these processes

  17. 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.

  18. Monolayer FePt nanocrystal self-assembly embedded into atomic-layer-deposited Al2O3 films for nonvolatile memory applications

    International Nuclear Information System (INIS)

    Highlights: • Memory cells containing chemically-synthesized FePt nanocrystals are fabricated. • A hexagonal arrangement monolayer is self-assembled on alumina by dip-coating. • The core–shell structure is formed with alloy core and amorphous iron oxide shell. • The MOS capacitors are electrically measured exhibiting obvious memory effects. -- Abstract: A simple approach is developed to fabricate oxide/FePt nanocrystals/oxide composite films by a combination of chemically-synthesized FePt nanocrystals’ self-assembly and atomic layer deposition for ultrahigh-density nonvolatile memory applications. A hexagonally arranged monolayer of well-monodispersed FePt nanocrystals with a grain size of 4.5 nm has been assembled onto atomic-layer-deposited Al2O3 oxide by solution-based dip-coating. The lattice constant of this two-dimensional pattern is about 8 nm with the high density of 1.8 × 1012/cm2. A fraction of the Fe is oxidized during annealing at 500 °C for 5 min in O2 atmosphere, and the core–shell structure is formed with fcc-Fe0.75Pt nanocrystal core and amorphous Fe2O3 shell. The metal–oxide–Si capacitors with unannealed and annealed FePt nanocrystals embedded into Al2O3 films are electrically measured, and exhibit obvious memory effects with a hysteresis memory window of 4.1 and 8.1 V at the sweeping gate voltage of ±8 V, respectively. The enhanced memory window of samples with annealed FePt nanocrystals can be attributed to the existence of the Fe2O3 shell, which introduces additional interface and provides more trap sites for charge trapping storage

  19. 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.

  20. 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

  1. 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.

  2. Enhanced photoluminescence response of Er3+-Si nanoparticle codoped Al2O3 films by controlled synthesis in the nanoscale and thermal processing

    International Nuclear Information System (INIS)

    Nanostructured Er3+-Si nanoparticles (NPs) codoped Al2O3 films were synthesized by a one step laser based deposition process which allows to form the Si NPs in situ at room temperature, and to control their size and separation with the Er ions in the nanoscale. Two different thermal annealing treatments are studied in order to optimize the photoluminescence (PL) emission: rapid thermal annealing (RTA) at 900 oC during 2 min, and conventional furnace step annealing at different temperatures up to 750 oC for 1 h. After RTA process the films show an important enhancement on the photoluminescence lifetime values which is related to a reduction of the non-radiative decay channels. Nevertheless, the Si NPs to Er ions energy transfer is strongly reduced. In contrast after conventional furnace annealing up to 700 oC, although there is only a moderate increase of the photoluminescence lifetime values, the excitation of Er ions through Si NPs is still active and as a consequence a large enhancement of the photoluminescence intensity with respect to the Er-only doped film is achieved. These different behaviours are most likely related to structural and chemical changes in the Er environment upon the different annealing processes.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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...

  9. A Pt/Al2O3-supported metal-organic framework film as the size-selective core-shell hydrogenation catalyst.

    Science.gov (United States)

    Aguado, Sonia; El-Jamal, Sawsan; Meunier, Frederic; Canivet, Jerome; Farrusseng, David

    2016-06-01

    The substituted imidazolate-based MOF (SIM-1) easily forms a homogeneous layer at the surface of millimetric platinum-loaded alumina beads. This new core-shell SIM-1@Pt/Al2O3 catalyst shows the fine molecular sieving effect for the Pt-catalyzed hydrogenation of carbon-carbon double bonds. PMID:27172134

  10. Thin layer a-Al2O3:C beta dosemeters for the assessment of current dose rate in teeth due to 90Sr intake and comparison with electron paramagnetic resonance dosimetry

    International Nuclear Information System (INIS)

    The use of thin-layer a-Al2O3:C thermoluminescence detectors (TLDs) for the assessment of current beta dose rate in human teeth due to 90Sr intake is investigated. The teeth used in this study were collected from members of the Techa river population who were exposed to radiation as a result of releases of the Mayak plutonium production facilities (Southern Urals-Russia) between 1949 and 1956. The beta dose rates from different parts of the tooth (enamel, crown dentine, and root) were determined by storing the detectors over the samples in a shielded environment. The cumulative dose measured by electron paramagnetic resonance (EPR) in different dental tissues is found to be proportional to the current dose rate obtained from a-Al2O3:C thermoluminescence dosemeters. The retention of 90Sr in various parts of the teeth is discussed. (author)

  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. Investigating the electronic properties of Al2O3/Cu(In,Ga)Se2 interface

    Science.gov (United States)

    Kotipalli, R.; Vermang, B.; Joel, J.; Rajkumar, R.; Edoff, M.; Flandre, D.

    2015-10-01

    Atomic layer deposited (ALD) Al2O3 films on Cu(In,Ga)Se2 (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.

  13. 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.

  14. Charge trapping characteristics of Au nanocrystals embedded in remote plasma atomic layer-deposited Al2O3 film as the tunnel and blocking oxides for nonvolatile memory applications

    International Nuclear Information System (INIS)

    Remote plasma atomic layer deposited (RPALD) Al2O3 films were investigated to apply as tunnel and blocking layers in the metal-oxide-semiconductor capacitor memory utilizing Au nanocrystals (NCs) for nonvolatile memory applications. The interface stability of an Al2O3 film deposited by RPALD was studied to observe the effects of remote plasma on the interface. The interface formed during RPALD process has high oxidation states such as Si+3 and Si+4, indicating that RPALD process can grow more stable interface which has a small amount of fixed oxide trap charge. The significant memory characteristics were also observed in this memory device through the electrical measurement. The memory device exhibited a relatively large memory window of 5.6 V under a 10/-10 V program/erase voltage and also showed the relatively fast programming/erasing speed and a competitive retention characteristic after 104 s. These results indicate that Al2O3 films deposited via RPALD can be applied as the tunnel and blocking oxides for next-generation flash memory devices.

  15. TEM and AFM study of WO3 nanosize growth on α-Al2O3

    International Nuclear Information System (INIS)

    WO3 thin films have been deposited by thermal evaporation on (0001) and (1012 ) planes of alumina oxide single crystal and annealed either in Oxygen or in air atmosphere. The morphology and crystallographic structure of films (as-deposited and annealed films) have been characterized by Atomic Force Microscope (AFM), transmission electron microscope (TEM), and transmission electron diffraction (TED). During annealing, the films undergo important morphological and structural changes. The annealed films exhibit large grains. These grains have the monoclinic structure in epitaxial orientations. The grains are made of twinned microdomains elongated in the [100] direction resulting of a preferential growth. The microdomains are along the three different directions on the (0001) α-Al2O3 surface and only one direction on the (1012 ) α-Al2O3 one.(author)

  16. 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%.

  17. Interface properties of atomic layer deposited TiO2/Al2O3 films on In(0.53)Ga(0.47)As/InP substrates.

    Science.gov (United States)

    Mukherjee, C; Das, T; Mahata, C; Maiti, C K; Chia, C K; Chiam, S Y; Chi, D Z; Dalapati, G K

    2014-03-12

    Electrical and interfacial properties of metal-oxide-semiconductor (MOS) capacitors fabricated using atomic layer deposited bilayer TiO2/Al2O3 films on In0.53Ga0.47As/InP substrates are reported. Vacuum annealing at 350 °C is shown to improve the interface quality. Capacitance-voltage (C-V) characteristics with higher accumulation capacitance, negligible frequency dispersion, small hysteresis and low interface state density (∼1.5 × 10(11) cm(-2) eV(-1)) have been observed for MOS capacitors. Low frequency (1/f) noise characterization and inelastic electron tunneling spectroscopy (IETS) studies have been performed to determine defects and interface traps and explain the lattice dynamics and trap state generation mechanisms. Both the IETS and 1/f noise studies reveal the spatial locations of the traps near the interface and also the nature of the traps. The IETS study further revealed the dynamic evolution of trap states related to low frequency noise sources in the deposited TiO2/Al2O3 stacks. It is shown that deposition of an ultrathin layer of TiO2 on Al2O3 can effectively control the diffusion of As in the dielectric and the oxidation states of In and Ga at the In0.53Ga0.47As surface. PMID:24472090

  18. Epitaxial growth of γ-Al2O3 on Ti2AlC(0001 by reactive high-power impulse magnetron sputtering

    Directory of Open Access Journals (Sweden)

    Per Eklund

    2014-01-01

    Full Text Available Al2O3 was deposited by reactive high-power impulse magnetron sputtering at 600 °C onto pre-deposited Ti2AlC(0001 thin films on α-Al2O3(0001 substrates. The Al2O3 was deposited to a thickness of 65 nm and formed an adherent layer of epitaxial γ-Al2O3(111 as shown by transmission electron microscopy. The demonstration of epitaxial growth of γ-Al2O3 on Ti2AlC(0001 open prospects for growth of crystalline alumina as protective coatings on Ti2AlC and related nanolaminated materials. The crystallographic orientation relationships are γ-Al2O3(111//Ti2AlC(0001 (out-of-plane and γ- Al 2O3(22¯0// Ti 2 AlC (112¯0 (in-plane as determined by electron diffraction. Annealing in vacuum at 900 °C resulted in partial decomposition of the Ti2AlC by depletion of Al and diffusion into and through the γ-Al2O3 layer.

  19. 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.

  20. 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.

  1. 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.

  2. Nanopore patterning using Al2O3 hard masks on SOI substrates

    Science.gov (United States)

    Wang, Xiaofeng; Goryll, Michael

    2015-07-01

    Aluminum oxide Al2O3, deposited using amorphous atomic layer deposition (ALD), is a very promising material to be utilized as a hard mask for nano-patterning. We used an aluminum oxide hard mask on a silicon-on-insulator (SOI) substrate to implement a sub-100 nm nanopore process. The transfer of nanoscale patterns via dry etching of the Al2O3 thin film was investigated by comparing etch profiles, etch rates, and selectivity of Al2O3 over PMMA resist, using different gas chemistries such as Cl2, Ar, Ar/BCl3 mixtures, and BCl3 plasma. A selectivity of 1:4 was observed using an inductively coupled plasma reactive ion etching (ICP-RIE) tool with BCl3 plasma, and the sub-100 nm nanopore patterns were anisotropically transferred to the alumina layer from a 250 nm PMMA layer. The dense and inert Al2O3 hard mask showed exceptional etch selectivity to Si and SiO2, which allowed the subsequent transfer of the nanopore patterns into the 340 nm-thick Si device layer and made it possible to attempt etching the 1 μm-thick buried oxide (BOX) layer. Using chlorine chemistry, nanopores patterned in the Si device layer showed excellent anisotropy while preserving the original pattern dimensions. The process demonstrated is ideally suited for patterning high aspect ratio nanofluidic structures.

  3. 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...

  4. Determination of the band gap of TiO2-Al2O3 films as a function of processing parameters

    International Nuclear Information System (INIS)

    In this work the study of band gap is based on the processing parameters and was calculated using the Indirect Transition Model. An experimental design was done, in order to have a sequence of 18 samples to analyze. The alumina doped titania thin films were prepared by combining electrophoretic deposition (EPD) with sputtering. The addition of alumina to the titania was with the purpose to reduce the band gap of the semiconductor. Several researches have tried to dope titania with other materials, because it has photocatalytic activity only in the UV spectrum. Then, reducing the band gap of the titania, it will have activity in the entire visible spectrum, and its applications increase considerably. Comparing with the adsorption line in the ultraviolet region for all the samples, the results show the adsorption edge for samples doped with fewer amounts of alumina shifts a little toward a lower energy region, leading to a band gap reduction.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Optical studies of amorphous Ge nanostructures in Al2O3 produced by pulsed laser deposition

    International Nuclear Information System (INIS)

    Thin films with embedded amorphous Ge nanostructures are characterised by in-situ and post-deposition techniques in order to study their size-dependent properties. The films are multilayer structures in which Ge nanostructured layers with effective thickness are separated by amorphous aluminium oxide layers (Al2O3). During deposition in-situ reflectivity measurements are used to achieve information on the amount of Ge deposited and on the Al2O3 coverage. The effective optical properties of the films were obtained from spectroscopic ellipsometry measurement analysis. Our results suggest a topological evolution of the Ge nanostructures as a function of the Ge content and the existence of size-dependent quantum confinement effects in the nanostructures. - Highlights: ► Amorphous Ge nanostructures with tunable optical band-gap embedded in Al2O3 matrix ► In-situ reflectivity characterisation of amorphous Ge nanostructure ► Ex-situ spectroscopic ellipsometry characterisation of amorphous Ge nanostructures ► Size-dependent optical band-gap study of amorphous Ge nanostructures

  10. 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

  11. Fabrication and characterization of TS-1 films on α-Al 2O 3 substrates using TiCl 3 as titanium source

    Science.gov (United States)

    Wang, Xiaodong; Zhang, Pingping; Liu, Xiufeng; Zhang, Baoquan

    2007-11-01

    The continuous and highly intergrown anatase-free TS-1 film was fabricated with TiCl 3 as the titanium source for the first time. The in situ nucleation and secondary growth method was employed to synthesize the TS-1 film. By means of scanning electron microscopy (SEM) images, X-ray diffraction (XRD) patterns, and FT-IR and UV-vis spectra measurements, the resulting film was observed to be anatase-free, continuous and highly intergrown with the MFI-type structure, and the Ti atoms existed only in tetrahedral coordination.

  12. Fabrication and characterization of TS-1 films on α-Al2O3 substrates using TiCl3 as titanium source

    International Nuclear Information System (INIS)

    The continuous and highly intergrown anatase-free TS-1 film was fabricated with TiCl3 as the titanium source for the first time. The in situ nucleation and secondary growth method was employed to synthesize the TS-1 film. By means of scanning electron microscopy (SEM) images, X-ray diffraction (XRD) patterns, and FT-IR and UV-vis spectra measurements, the resulting film was observed to be anatase-free, continuous and highly intergrown with the MFI-type structure, and the Ti atoms existed only in tetrahedral coordination

  13. 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...

  14. 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.

  15. 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.

  16. 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

  17. Gas diffusion ultrabarriers on polymer substrates using Al2O3 atomic layer deposition and SiN plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Thin films grown by Al2O3 atomic layer deposition (ALD) and SiN plasma-enhanced chemical vapor deposition (PECVD) have been tested as gas diffusion barriers either individually or as bilayers on polymer substrates. Single films of Al2O3 ALD with thicknesses of ≥10 nm had a water vapor transmission rate (WVTR) of ≤5x10-5 g/m2 day at 38 deg. C/85% relative humidity (RH), as measured by the Ca test. This WVTR value was limited by H2O permeability through the epoxy seal, as determined by the Ca test for the glass lid control. In comparison, SiN PECVD films with a thickness of 100 nm had a WVTR of ∼7x10-3 g/m2 day at 38 deg. C/85% RH. Significant improvements resulted when the SiN PECVD film was coated with an Al2O3 ALD film. An Al2O3 ALD film with a thickness of only 5 nm on a SiN PECVD film with a thickness of 100 nm reduced the WVTR from ∼7x10-3 to ≤5x10-5 g/m2 day at 38 deg. C/85% RH. The reduction in the permeability for Al2O3 ALD on the SiN PECVD films was attributed to either Al2O3 ALD sealing defects in the SiN PECVD film or improved nucleation of Al2O3 ALD on SiN.

  18. 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.

  19. 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.

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

    International Nuclear Information System (INIS)

    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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

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

    International Nuclear Information System (INIS)

    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

  6. Interface behavior of Al2O3/Ti joints produced by liquid state bonding

    International Nuclear Information System (INIS)

    In this work we study brazing of Al2O3 to Ti with biocompatibility properties, using a Au-foil as joining element. Al2O3 was produced by sintering of powder at 1550 °C. Al2O3 samples were coated with a 2 and 4 μm thick of Mo layer and then stacked with Ti. Al2O3–Mo/Au/Ti combinations were joined at 1100 °C in vacuum. Successful joining of Mo–Al2O3 to Ti was observed. Interface shows the formation of a homogeneous diffusion zone. Mo diffused inside Au forming a concentration line. Ti3Au and TiAu phases were observed. - Highlights: • The interface behavior of Al2O3–Mo/Au/Ti joints was studied. • Al2O3–Mo/Au/Ti combinations were produced by brazing at 1100 °C in vacuum. • Defect-free interfaces and continuous thin reaction layers of Ti3Au and TiAu phases were obtained. • SEM images revealed an homogenous diffusion zone on the metal side of the joint

  7. The AC conduction in Ag - Al2O3 cermet sandwich structures

    International Nuclear Information System (INIS)

    We have prepared cermet thin ms of Ag - Al2O3 sandwiched between Al electrodes by evaporation of the elements onto glass substrates in vacuo of 10-6 torr. Conductance and loss factor were obtained in evaporated Al/Ag - Al2O3/Al sandwich structures for m thickness ∼ 100 to 200nm containing 5 to 20 wt % Ag in the Al2O3 matrix at room temperature. The ac conductivity of Ag-Al2O3 cermet thin ms can be presented by the form AωS. The losses are discussed on the basis of concept of Goswami and Goswami model and are found to be in conformity with this model. (author)

  8. Cathodic electrochemiluminescence at double barrier Al/Al2O3/Al/Al2O3 tunnel emission electrodes

    International Nuclear Information System (INIS)

    Double insulating barrier tunnel emission electrodes were fabricated by adding a new pure aluminum layer upon oxidized aluminum electrodes by vacuum evaporation and thermally oxidizing the new aluminum layer in air at room temperature. Resulting Al/Al2O3/Al/Al2O3 electrodes allow the use of various aluminum alloys in the electrode body necessary for hardness or shaping ability of the electrode while obtaining the luminescence properties of pure aluminum oxide. During electrical excitation of luminescent labels by cathodic hot electron injection into aqueous electrolyte solution, the background noise is mainly based on high-field-induced solid-state electroluminescence and F-center luminescence of the outer aluminum oxide film. The more defect states and/or impurity centers the outer oxide film contains, the higher is the background emission intensity. The present electrode fabrication method provides a considerable improvement in signal-to-noise ratio for time-resolved electrochemiluminescence (TR-ECL) measurements when the original native oxide film of the electrode body contains luminescence centers displaying long-lived luminescence. The excellent performance of the present electrodes is demonstrated by extremely low-level detection of Tb(III) chelates, luminol, Pt(II) coproporphyrin and Tb(III) labels in an immunometric immunoassay by time-resolved electrochemiluminescence

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Monocrystalline silicon surface passivation by Al2O3/porous silicon combined treatment

    International Nuclear Information System (INIS)

    In this paper, we report on the effect of Al2O3/porous silicon combined treatment on the surface passivation of monocrystalline silicon (c-Si). Al2O3 films with a thickness of 5, 20 and 80 nm are deposited by pulsed laser deposition (PLD). It was demonstrated that Al2O3 coating is a very interesting low temperature solution for surface passivation. The level of surface passivation is determined by techniques based on photoconductance and FTIR. As a result, the effective minority carrier lifetime increase from 2 μs to 7 μs at a minority carrier density (Δn) of 1 × 1015 cm−3 and the reflectivity reduce from 28% to about 7% after Al2O3/PS coating

  15. Border trap reduction in Al2O3/InGaAs gate stacks

    Science.gov (United States)

    Tang, Kechao; Winter, Roy; Zhang, Liangliang; Droopad, Ravi; Eizenberg, Moshe; McIntyre, Paul C.

    2015-11-01

    The effect of Al2O3 atomic layer deposition (ALD) temperature on the border trap density (Nbt) of Al2O3/InGaAs gate stacks is investigated quantitatively, and we demonstrate that lowering the trimethylaluminum (TMA)/water vapor ALD temperature from 270 °C to 120 °C significantly reduces Nbt. The reduction of Nbt coincides with increased hydrogen incorporation in low temperature ALD-grown Al2O3 films during post-gate metal forming gas annealing. It is also found that large-dose (˜6000 L) exposure of the In0.53Ga0.47As (100) surface to TMA immediately after thermal desorption of a protective As2 capping layer is an important step to guarantee the uniformity and reproducibility of high quality Al2O3/InGaAs samples made at low ALD temperatures.

  16. 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

  17. 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.

  18. Crystalline gamma-Al2O3 physical vapour deposition-coating for steel thixoforging tools.

    Science.gov (United States)

    Bobzin, K; Hirt, G; Bagcivan, N; Khizhnyakova, L; Ewering, M

    2011-10-01

    The process of thixoforming, which has been part of many researches during the last decades, combines the advantages of forging and casting for the shaping of metallic components. But due to the high temperatures of semi-solid steel alloys high demands on the tools are requested. To resists the thermal and mechanical loads (wear, friction, thermal and thermomechanical fatigue) protecting thin films are necessary. In this regard crystalline gamma-Al2O3 deposited via Physical Vapour Deposition (PVD) is a promising candidate: It exhibits high thermal stability, high oxidation resistance and high hot hardness. In the present work the application of a (Ti, Al)N/gamma-Al2O3 coating deposited by means of Magnetron Sputter Ion Plating in an industrial coating unit is presented. The coating was analysed by means of Rockwell test, nanoindentation, and Scanning Electron Microscopy (SEM). The coated tool was tested in thixoforging experiments with steel grade X210CrW12 (AlSI D6). The surface of the coated dies was examined with Scanning Electron Microscope (SEM) after 22, 42, 90 and 170 forging cycles. PMID:22400259

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. Optically stimulated luminescence response to Al2O3 to beta radiation

    DEFF Research Database (Denmark)

    Akselrod, A.; Akselrod, M.S.; Agersnap Larsen, N.;

    1999-01-01

    High sensitivity dosemeters based on Al2O3:C have been prepared and tested for use as beta dosemeters using optically stimulated luminescence (OSL). Two types of sample were prepared and tested, namely unpolished thick, single crystal chips and thin powder layers on aluminium substrates. The samp......High sensitivity dosemeters based on Al2O3:C have been prepared and tested for use as beta dosemeters using optically stimulated luminescence (OSL). Two types of sample were prepared and tested, namely unpolished thick, single crystal chips and thin powder layers on aluminium substrates...

  4. Electrowetting properties of atomic layer deposited Al2O3 decorated silicon nanowires

    International Nuclear Information System (INIS)

    This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al2O3 as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al2O3 films of 10nm thickness were conformally deposited over silicon nanowires. Al2O3 dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°. Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air

  5. 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.

  6. 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...

  7. Development of Al2O3/Cu functionally gradient material

    International Nuclear Information System (INIS)

    In order to insure reliability of the thermoelectric module, we had applied FGM layer with composition of Cu and Si3N4 to the bonding parts in the module and decided the functionally graded compositional profile based on thermal stress analysis. And the Si3N4/Cu FGM had been fabricated by the hot press based on the analysis results. But many cracks initiated in FGM after sintering process with dependence of compositional profile and specimen geometries and bonding strength was very low because of a large difference of sintering temperature between Cu and Si3N4. In this study, Al2O3/Cu FGM was developed based on residual stress analysis by using high-purity Al2O3 particle with character of very small particle radius and low sintering temperature. Obtained results are summarized as follow, (1) Al2O3/Cu composites could be fabricated under low sintering temperature (1473 K). And temperature dependence of mechanical properties of the Al2O3/Cu composites was measured. (2) In order to minimize residual stress in the FGM after sintering process, functionally graded profile of Al2O3/Cu FGM was examined based on finite element analysis using the mechanical properties of Al2O3/Cu composites. (3) Al2O3/Cu FGM was fabricated based on the above residual stress analysis results. It was found that the FGM could be fabricated if residual stress in the FGM was lower than the bending strength the Al2O3/Cu composites. (author)

  8. 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.

  9. 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.

  10. 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.

  11. A short-time fading study of Al2O3:C

    International Nuclear Information System (INIS)

    This paper studies the short-time fading from Al2O3:C by measuring optically stimulated luminescence (OSL) signals (Total OSL: TOSL, and Peak OSL: POSL) from droplets and Luxel™ pellets. The influence of various bleaching regimes (blue, green and white) and light power is compared. The fading effect is the decay of the OSL signal in the dark at room temperature. Al2O3:C detectors were submitted to various bleaching regimes, irradiated with a reference dose and read out after different time spans. Investigations were carried out using 2 mm size droplet detectors, made of thin Al2O3:C powder mixed with a photocured polymer. Tests were compared to Luxel™-type detectors (Landauer Inc.). Short-time post-irradiation fading is present in OSL results (TOSL and POSL) droplets for time spans up to 200 s. The effect of short-time fading can be lowered/removed when treating the detectors with high-power and/or long time bleaching regimes; this result was observed in both TOSL and POSL from droplets and Luxel™. - Highlights: • Droplet composed of thin powder of Al2O3:C was prepared using a photo-curable polymer. • Powder grain sizes ranged from 5 μm to 35 μm. • Short-time fading was measured for irradiated samples. • Various bleaching regimes and light power was tested. • Droplets were compared to a commercially dosimeter, Luxel™

  12. 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

  13. 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.

  14. 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

  15. 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

  16. Effect of the addition of Al2O3 nanoparticles on the magnetic properties of Fe soft magnetic composites

    Science.gov (United States)

    Peng, Yuandong; Nie, Junwu; Zhang, Wenjun; Ma, Jian; Bao, Chongxi; Cao, Yang

    2016-02-01

    We investigated the effect of the addition of Al2O3 nanoparticles on the permeability and core loss of Fe soft magnetic composites coated with silicone. Fourier transform infra-red spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis revealed that the surface layer of the powder particles consisted of a thin insulating Al2O3 layer with uniform surface coverage. The permeability and core loss of the composite with the Al2O3 addition annealed at 650 °C were excellent. The results indicated that the Al2O3 nanoparticle addition increases the permeability stablility with changing frequency and decreases the core loss over a wide range of frequencies.

  17. 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

  18. 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.

  19. 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...

  20. Dynamical heterogeneities in supercooled Al2O3

    International Nuclear Information System (INIS)

    Dynamical heterogeneities in supercooled Al2O3 models have been investigated. We evaluated the non-Gaussian parameter for the self-part of the van Hove correlation function and cluster size distributions of the most mobile or most immobile particles in the model. We compared the partial radial distribution functions for the 10% most mobile or 10% most immobile Al particles with the corresponding mean ones. We have found that mean cluster size grows with decreasing temperature

  1. Optically stimulated luminescence of Al2O3

    International Nuclear Information System (INIS)

    Anion-deficient aluminum oxide doped with carbon (Al2O3:C) is not only an extremely sensitive thermoluminescence (TL) material, but is well suited to optically stimulated luminescence OSL applications due to a high cross-section for interaction of light with radiation-induced trapped charge. Several different OSL readout protocols have been suggested, including pulsed OSL (POSL), and 'delayed' OSL (DOSL). This paper examines the properties of Al2O3:C for application using these two readout protocols. The POSL technique utilizes the prompt luminescence that results from the direct recombination of released charge carriers at luminescence sites (F-centers in Al2O3:C). Following a pulse of stimulation light using a laser, the POSL signal is observed to decay with a temperature-independent lifetime of ∼35-36 ms. The DOSL signal, on the other hand, utilizes the temperature-dependent signal resulting from the capture of released charge carriers by shallow traps. The decay of the luminescence component after the stimulating pulse has a lifetime of several hundred ms, depending upon temperature. The dependence of the DOSL signal on readout temperature can be explained in terms of the involvement of the shallow traps in the process. However, the intensity (not the lifetime) of the POSL signal is also slightly temperature dependent. It is conjectured that this may be caused by a thermally assisted optical detrapping process involving localized excited states. Different forms of Al2O3:C are examined. By modifying both the concentration and energy distribution of the shallow traps material optimized for DOSL applications can be engineered. In contrast, the best material for POSL is grown with no shallow traps. The integrated light output in a typical POSL measurement is approximately a factor of 7-8 greater than that of DOSL, even for a DOSL-quality sample

  2. 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

  3. Microstructure and spectral selectivity of Mo-Al2O3 solar selective absorbing coatings after annealing

    International Nuclear Information System (INIS)

    Mo, Al2O3 single layer, Mo-Al2O3 granular cermet layer, Mo/Al2O3 tandem and an optimized Mo-Al2O3 multilayer coating with a double cermet layer configuration were deposited on stainless steel substrates by magnetron sputtering technique. The samples were annealed in vacuum at different temperatures ranging from 350 deg. C to 1000 deg. C for 2-5 h to evaluate their thermal stability. The spectral absorbance and thermal emissivity for the multi-layer selective coatings in the region of 1.3-25 μm were 0.91-0.93 and 0.19-0.27, respectively, depending on heat treatment temperature. Increasing annealing temperature has more obvious influence on the rise of emissivity than the drop of spectral absorbance. The microstructure, surface morphology, composition distribution and diffusion for various films before and after high temperature aging were investigated employing scanning electronic microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Fe2O3, as a diffusion barrier between Mo layer and SS substrate, effectively holds back the presence of Mo2C and Fe2MoC complex phases. Al2O3 is a stable phase even at 1000 deg. C for 3 h. However, defects such as widened boundaries, cracks and holes, which could appear in Al2O3 layer when heated at higher temperature than 650 deg. C, will provide the paths of Mo diffusion. Two diffusion modes of Mo, including inner self-congregation of Mo inside the cermet layer and Mo infiltration through the Al2O3 layer in Mo/Al2O3 tandem at 800 deg. C for 5 h, were observed after annealing

  4. Fast spatial atomic layer deposition of Al2O3 at low temperature (<100 °C) as a gas permeation barrier for flexible organic light-emitting diode displays

    International Nuclear Information System (INIS)

    The authors developed a high throughput (70 Å/min) and scalable space-divided atomic layer deposition (ALD) system for thin film encapsulation (TFE) of flexible organic light-emitting diode (OLED) displays at low temperatures (<100 °C). In this paper, the authors report the excellent moisture barrier properties of Al2O3 films deposited on 2G glass substrates of an industrially relevant size (370 × 470 mm2) using the newly developed ALD system. This new ALD system reduced the ALD cycle time to less than 1 s. A growth rate of 0.9 Å/cycle was achieved using trimethylaluminum as an Al source and O3 as an O reactant. The morphological features and step coverage of the Al2O3 films were investigated using field emission scanning electron microscopy. The chemical composition was analyzed using Auger electron spectroscopy. These deposited Al2O3 films demonstrated a good optical transmittance higher than 95% in the visible region based on the ultraviolet visible spectrometer measurements. Water vapor transmission rate lower than the detection limit of the MOCON test (less than 3.0 × 10−3 g/m2 day) were obtained for the flexible substrates. Based on these results, Al2O3 deposited using our new high-throughput and scalable spatial ALD is considered a good candidate for preparation of TFE films of flexible OLEDs

  5. 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)

  6. Probing the stability of Al2O3/Ge structures with ion beams

    International Nuclear Information System (INIS)

    Al2O3 films were deposited on Ge substrates by reactive sputtering. Resulting samples were submitted to different post-deposition annealings (PDAs) in order to probe composition modifications induced by such treatments. Nuclear reaction profiling (NRP) revealed that O incorporation depends on PDA temperature and on the employed atmosphere (water or oxygen). We also found that O from the gas phase strongly interacts with the Ge semiconductor substrate when PDA is performed with water at 500 °C. Ion scattering analyses evidenced an increase of Ge concentration throughout the Al2O3 dielectric layer and on the sample surface associated with the oxidation of the Ge substrate. These findings are explained by GeO desorption resulting from chemical reactions occurring at the dielectric/Ge interface.

  7. Probing the stability of Al 2O 3/Ge structures with ion beams

    Science.gov (United States)

    Bom, N. M.; Soares, G. V.; Krug, C.; Baumvol, I. J. R.; Radtke, C.

    2012-02-01

    Al 2O 3 films were deposited on Ge substrates by reactive sputtering. Resulting samples were submitted to different post-deposition annealings (PDAs) in order to probe composition modifications induced by such treatments. Nuclear reaction profiling (NRP) revealed that O incorporation depends on PDA temperature and on the employed atmosphere (water or oxygen). We also found that O from the gas phase strongly interacts with the Ge semiconductor substrate when PDA is performed with water at 500 °C. Ion scattering analyses evidenced an increase of Ge concentration throughout the Al 2O 3 dielectric layer and on the sample surface associated with the oxidation of the Ge substrate. These findings are explained by GeO desorption resulting from chemical reactions occurring at the dielectric/Ge interface.

  8. Rise and fall of ferromagnetism in O-irradiated Al2O3 single crystals

    International Nuclear Information System (INIS)

    In dilute magnetic semiconductors studies, sapphire was usually used as non-magnetic substrate for films. We observed weak ferromagnetic component in Al2O3 single crystal substrate, and excluded the possibility of ferromagnetic contaminations carefully by inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. The ferromagnetism rise and fall during the process of annealing-oxygen irradiation-annealing of the sapphire. The ferromagnetic changes are consistent with Al-vacancy related defects detected by positron annihilation spectroscopy. With first-principle calculations, we confirm that Al-vacancy can introduce magnetic moment for 3 μB in Al2O3 crystal and form stable VAl-VAl ferromagnetic coupling at room temperature

  9. Microstructural Analysis of Al/Al2O3/Gr Powder Composites Produced by Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    Gheorghe Iacob

    2011-09-01

    Full Text Available Powder samples of Al/Al2O3/Gr hybrid composites with different weight percents were obtained by mechanical alloying in a high energy ball mill. The aim of this study is to investigate the effect of alumina and graphite particles content on the microstructure of Al/Al2O3/Gr hybrid composites. Results obtained using Scanning Electron Microscopy (SEM as well as Energy-Dispersive X-ray Spectroscopy (EDS show that the addition of alumina particles as the reinforcement has a drastic effect on the size and morphology of the composite powders. Also, the addition of graphite particles as one of the reinforcing components is presumed to improve tribological properties by forming a graphite-rich lubricant film between the sliding surfaces.

  10. 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.

  11. 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.

  12. A short-time fading study of Al2O3:C

    Science.gov (United States)

    Nascimento, L. F.; Vanhavere, F.; Silva, E. H.; Deene, Y. De

    2015-01-01

    This paper studies the short-time fading from Al2O3:C by measuring optically stimulated luminescence (OSL) signals (Total OSL: TOSL, and Peak OSL: POSL) from droplets and Luxel™ pellets. The influence of various bleaching regimes (blue, green and white) and light power is compared. The fading effect is the decay of the OSL signal in the dark at room temperature. Al2O3:C detectors were submitted to various bleaching regimes, irradiated with a reference dose and read out after different time spans. Investigations were carried out using 2 mm size droplet detectors, made of thin Al2O3:C powder mixed with a photocured polymer. Tests were compared to Luxel™-type detectors (Landauer Inc.). Short-time post-irradiation fading is present in OSL results (TOSL and POSL) droplets for time spans up to 200 s. The effect of short-time fading can be lowered/removed when treating the detectors with high-power and/or long time bleaching regimes; this result was observed in both TOSL and POSL from droplets and Luxel™.

  13. 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%.

  14. High-κ Al2O3/WOx Bilayer Dielectrics for Low-Power Resistive Switching Memory Applications

    Science.gov (United States)

    Banerjee, Writam; Ziaur Rahaman, Sheikh; Prakash, Amit; Maikap, Siddheswar

    2011-10-01

    A bipolar resistive switching memory device using high-κ Al2O3/WOx bilayer dielectrics in an IrOx/Al2O3/WOx/W structure with a small device area of 8 ×8 µm2 is investigated for the first time. A high hole trapping density of ˜1.76 ×1018 cm-3 in a high-κ Al2O3 film with a thickness of 5 nm is investigated using IrOx/Al2O3/SiO2/p-Si capacitors. The thickness and chemical bonding of the high-κ Al2O3/WOx films in a resistive memory device are investigated by both high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The resistive switching memory device with a low power operation of 0.7 mW and a low current compliance of 500 µA has a reasonable SET/RESET voltage of -1.4 V/+1.0 V, a high resistance ratio of >103, an excellent read endurance of >105 times at a large read voltage of -0.5 V, and 10 years of data retention at 85 °C.

  15. 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

  16. Electron paramagnetic resonance evaluation of defects at the (100)Si/Al2O3 interface

    OpenAIRE

    Jones, Benjamin; Barklie, R.C.

    2005-01-01

    Electron paramagnetic resonance (EPR) was conducted on aluminium oxide films deposited by atomic layer deposition on (100)Si. Multiplet spectra are observed, which can be consistently decomposed assuming the presence of only Pb0 and Pb1 centres, which are well known in Si/SiO2 structures. Al2O3 films deposited on HF-treated (100)Si exhibit unpassivated Pb0 and Pb1 centres, with concentrations of (7.7±1.0)x1011 cm-2 and (8±3)x1010 cm-2 respectively. Rapid thermal annealing of the substrate ...

  17. Al2O3-SrCo0.6Fe0.4O3 Membrane Coated on a Meso-Porous Al2O3 Support

    International Nuclear Information System (INIS)

    In this work, a membrane for oxygen separation from air was a composite system with a mesoporous alumina support and a thin layer with microporous structures. The support was formed into a disc shape using alumina powder following a press-calcination process and subsequently, a nanoscale pore membrane with narrow pore size distribution was infused following a sol-gel approach. The sol-gel method entailed the use of a stable sol prepared from an organo-metallic oxide precursor, followed by deposition of the sol onto the porous support via dip coating. The sol hardened upon drying, and forms thin Al2O3-SrCo0.6Fe0.4O3 active layer after sintering.

  18. Charge trapping behavior of rare-earth ion-doped Al2O3 and its application to nonvolatile memories

    International Nuclear Information System (INIS)

    We investigated the charge trapping properties of rare-earth(RE)-Yb-doped Al2O3 in view of their potential application to nonvolatile memories. The as-grown, low-temperature annealed Yb-doped Al2O3 film showed a dominant hole trapping behavior, but it changed to mostly electron trapping after high temperature annealing. No correlation was found between the Yb charge state and the reduction of hole traps, excluding the Yb ion itself as the hole trap. As-grown annealed Yb-doped Al2O3 showed a defect-related below-bandgap optical absorption. Since the oxygen vacancy is a charge trap in Al2O3 among all the intrinsic defects, we attribute the observed hole trap to the oxygen vacancy. On the other hand, the energy levels of the Yb3+ ion in Al2O3 make it the most likely electron trap. In addition, the large Yb ion strains the nearby bonds to make it vulnerable to defect formation during an external stress. We found that hot electron injection actually created addition electron traps. Yb ions and/or defect complexes including Yb ions seem to be responsible for the observed electron trapping. Our experimental results show that RE ion doping may be a new method for realizing a nonvolatile memory device.

  19. 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

  20. 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.

  1. Thermal conductivities of thin, sputtered optical films

    International Nuclear Information System (INIS)

    The normal component of thin-film thermal conductivity has been measured for the first time, to the best of our knowledge, for several advanced sputtered optical materials. Included are data for single layers of boron nitride, silicon aluminum nitride, silicon aluminum oxynitride, silicon carbide, and for dielectric-enhanced metal reflectors of the form Al(SiO2/Si3N4)n and Al(Al2O3/AlN)n. Sputtered films of more conventional materials such as SiO2, Al2O3, Ta2O5, Ti, and Si have also been measured. The data show that thin-film thermal conductivities are typically 10 to 100 times lower than conductivities for the same materials in bulk form. Structural disorder in the amorphous or fine-grained films appears to account for most of the conductivity difference. Conclusive evidence for a film--substrate interface contribution is presented

  2. Nucleation of ordered Fe islands on Al2O3/Ni3Al(111)

    OpenAIRE

    Lehnert, A.; Krupski, A.; Degen, S.; Franke, K.; Decker, R.; Rusponi, S.; Kralj, M.; Becker, C.; Brune, H.; Wandelt, K

    2006-01-01

    Scanning tunneling microscopy (STM) has been used to investigate the nucleation and stability of iron clusters on the Al2O3/Ni3Al (111) surface as a function of coverage and annealing temperature. We show that atomic beam deposition of iron leads to hexagonally ordered cluster arrangements with a distance of 24 angstrom between the clusters evidencing the template effect of the alumina film. The shape of the iron clusters is two-dimensional (2D) at deposition temperatures from 130 K to 160 K ...

  3. 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.

  4. 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

  5. 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%.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. The effect of oxygen source on atomic layer deposited Al2O3 as blocking oxide in metal/aluminum oxide/nitride/oxide/silicon memory capacitors

    International Nuclear Information System (INIS)

    This work explores the electrical properties of Al2O3 films formed by atomic layer deposition (ALD) using different oxygen sources (water and ozone) and trimethylaluminium (TMA). The as-deposited Al2O3 layers were used as blocking oxides in metal (Pt)–alumina–nitride–oxide–silicon memory capacitors. The capacitance–voltage characteristics of the devices with Al2O3 deposited with the ozone–TMA and water–TMA processes showed almost identical capacitance equivalent thicknesses in accordance with transmission electron microscopy imaging which revealed similar dielectric layer thicknesses between the two gate stacks. At high negative gate voltages the water-TMA devices exhibited higher leakage currents than the ozone-TMA devices. This effect had a direct impact on the attainable memory window, due to the limited erase performance of the capacitors and the extended erase-saturation effect. These findings indicate that the ALD chemistry and in particular the oxygen source is a crucial factor which determines the electrical behavior of the as-deposited Al2O3 films, and therefore the performance of the memory stacks. These differences are attributed to the different trap distributions either in space or energy within the Al2O3 layers. - Highlights: ► Al2O3 films were formed by atomic layer deposition using H2O and O3 as oxygen sources. ► Al2O3 layers were used as blocking oxides in charge trapping memory capacitors. ► At high negative voltages, H2O-based samples exhibit higher leakage current density. ► The H2O-based samples have a limited ability to remove trapped electrons. ► Oxygen source differentiates the electrical behavior of as-deposited Al2O3 layers

  11. 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

  12. 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...

  13. 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

    International Nuclear Information System (INIS)

    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

  14. 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.

  15. 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.

  16. 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...

  17. Ir-Ru/Al2O3 catalysts used in satellite propulsion

    OpenAIRE

    T.G. Soares Neto; J. Gobbo-Ferreira; A.J.G. Cobo; G.M. Cruz

    2003-01-01

    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 ...

  18. Quasi-two-dimensional electron gas at the interface of γ-Al2O3/SrTiO3 heterostructures grown by atomic layer deposition

    International Nuclear Information System (INIS)

    We report the formation of a quasi-two-dimensional electron gas (2-DEG) at the interface of γ-Al2O3/TiO2-terminated SrTiO3 (STO) grown by atomic layer deposition (ALD). The ALD growth of Al2O3 on STO(001) single crystal substrates was performed at temperatures in the range of 200–345 °C. Trimethylaluminum and water were used as co-reactants. In situ reflection high energy electron diffraction, ex situ x-ray diffraction, and ex situ cross-sectional transmission electron microscopy were used to determine the crystallinity of the Al2O3 films. As-deposited Al2O3 films grown above 300 °C were crystalline with the γ-Al2O3 phase. In situ x-ray photoelectron spectroscopy was used to characterize the Al2O3/STO interface, indicating that a Ti3+ feature in the Ti 2p spectrum of STO was formed after 2–3 ALD cycles of Al2O3 at 345 °C and even after the exposure to trimethylaluminum alone at 300 and 345 °C. The interface quasi-2-DEG is metallic and exhibits mobility values of ∼4 and 3000 cm2 V−1 s−1 at room temperature and 15 K, respectively. The interfacial conductivity depended on the thickness of the Al2O3 layer. The Ti3+ signal originated from the near-interfacial region and vanished after annealing in an oxygen environment

  19. Electrochemical anticorrosion performance evaluation of Al2O3 coatings deposited by MOCVD on an industrial brass substrate

    International Nuclear Information System (INIS)

    Alumina (Al2O3) coatings of different thickness were deposited on OT59 brass substrate (BS) using the metal organic chemical vapour deposition (MOCVD) technique to evaluate the corrosion performance by EIS measurements. The used precursor was dimethyl-aluminium-isopropoxide. Electrochemical characterizations of the deposited films were performed in a standard very aggressive acidic solution (aerated 1N H2SO4 at 25 deg. C up to 168 h of immersion time) by means of direct current method (Tafel curves) and electrochemical impedance spectroscopy (EIS). The Rutherford backscattering spectroscopy (RBS) indicated that the films are very pure with the correct Al2O3 stoichiometry, while the IR absorption spectra showed that the films did not contain any -O-H groups. The surface film morphology was investigated by atomic force microscopy (AFM) and displayed a globular texture. The films were very smooth, with a maximum root mean square roughness, for example, of 14 nm for a 0.96 μm thick coating. The EIS data confirmed, as expected, that a 2.40 μm Al2O3 layer ensures the best corrosion protection after 168 h of immersion in the very acidic environment used

  20. 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%.

  1. 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.

  2. 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.

  3. 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.

  4. 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).

  5. 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 ℃.

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

    Directory of Open Access Journals (Sweden)

    PhilippeVernoux

    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.

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

    Science.gov (United States)

    Tsampas, Michail; Kambolis, Anastasios; Obeid, Emil; Lizarraga, Leonardo; Sapountzi, Foteini; Vernoux, Philippe

    2013-08-01

    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.

  8. Design and fabrication of compositionally graded inorganic oxide thin films: Mechanical, optical and permeation characteristics

    International Nuclear Information System (INIS)

    Different types of inorganic oxide films composed of a chemical composition gradient single layer were designed, fabricated and characterized. Compositionally graded thin films were created by power-controlled co-sputtering of alumina (Al2O3) and silica (SiO2) at room temperature, allowing the structural design of the film to be tailored at the nanometer scale. Two distinct graded thin films were fabricated: one with a compositionally asymmetric structure consisting of a SiO2-rich bottom interface and a Al2O3-rich top surface, and the other with a compositionally balanced sandwich structure consisting of both the top surface and bottom interface rich in SiO2 and a core rich in Al2O3 (referred to as SGS for 'sandwich graded structure'). Smoothly graded thin films without interfacial boundaries were verified by Auger electron spectroscopy profiles. X-ray photoelectron spectroscopy demonstrated that the Al2O3/SiO2 graded structures consisted of Si-O and Al-O bonds, as well as Al-O-Si bonds in the transition layer. Neat Al2O3 or SiO2 and their graded ones were all investigated for their mechanical, optical and permeation properties. A SGS thin film presented the best mechanical stability (i.e., about three times improved film toughness of a neat Al2O3 single layer), demonstrating that balanced internal stresses and alternating bonding structures, achieved via a graded structure without interfaces, are crucial for enhancing mechanical stability. Furthermore, neat and graded thin films exhibited the similar level of optical transmittance and the permeation properties for the graded films were well matched with the behaviors of mechanical stability.

  9. Transmissionselektronenmikroskopische Untersuchungen von undotierten und Si-dotierten Al2O3-Beschichtungen und von Al2O3-Faser-Matrix-Verbundwerkstoffen

    OpenAIRE

    Müller, Merlin Garde Jana

    2015-01-01

    In the first part of this thesis the influence of silicon (Si) alloying on the thermal stability of alumina thin films was investigated by means of transmission electron microscopy (TEM). These alumina thin films were deposited by filtered cathodic arc (FCA) and by magnetron sputter ion plating (MSIP). Amorphous and crystalline FCA alumina thin films were deposited on Si wafers, and crystalline MSIP alumina thin films were deposited on Si wafers and on cemented carbide cutting tools. The thin...

  10. 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.

  11. 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.

  12. 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.

  13. High temperature oxidation-sulfidation behavior of Cr-Al2O3 and Nb-Al2O3 composites densified by spark plasma sintering

    International Nuclear Information System (INIS)

    The high temperature oxidation-sulfidation behavior of Cr-Al2O3 and Nb-Al2O3 composites prepared by mechanical alloying (MA) and spark plasma sintering (SPS) has been studied. These composite powders have a particular metal-ceramic interpenetrating network and excellent mechanical properties. Oxidation-sulfidation tests were carried out at 900 deg. C, in a 2.5%SO2 + 3.6%O2 + N2(balance) atmosphere for 48 h. The results revealed the influence of the sintering conditions on the specimens corrosion resistance, i.e. the Cr-Al2O3 and Nb-Al2O3 composite sintered at 1310 deg. C/4 min showed better corrosion resistance (lower weight gains) compared with those found for the 1440 deg. C/5 min conditions. For the former composite, a protective Cr2O3 layer immediately forms upon heating, whereas for the later pest disintegration was noted. Thus, under the same sintering conditions the Nb-Al2O3 composites showed the highest weight gains. The oxidation products were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy

  14. 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.

  15. 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...

  16. 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.

  17. Sterilisation of Al2O3 for production of /sup 99m/Tc generators

    International Nuclear Information System (INIS)

    The effect of sterilization of Al2O3 (by radiation, thermal treatment or in the autoclave) on its adsorption capacity and efficiency of elution of /sup 99m/Tc has been investigated. No difference has been observed in the adsorption capacity of sterilized and unsterilized Al2O3 samples. However, the efficiency of elution of /sup 99m/Tc differed in sterilized and unsterilized samples, and even depended on the sterilization procedure used. The highest elution efficiency was found with unsterilized Al2O3 (94%), somewhat lower with thermally sterilized (90%) and the lowest with 60Co gamma radiation sterilized Al2O3 (85%). Al2O3 sterilized at 300 0C has slightly higher adsorption capacity with respect to molybdenum. (author)

  18. Effects of Al2O3 phase and Cl component on dehydrogenation of propane

    Science.gov (United States)

    Liu, Jie; Liu, Changcheng; Ma, Aizeng; Rong, Junfeng; Da, Zhijian; Zheng, Aiguo; Qin, Ling

    2016-04-01

    The effects of two Al2O3 phases, γ- and θ-Al2O3, and Cl component on the performances of Pt-Al2O3 catalysts in the dehydrogenation of propane were investigated in this work. The catalysts were systematically characterized by various techniques, such as scanning transmission electron microscopy (STEM), temperature-programmed desorption with ammonia as probe molecules (NH3-TPD) and temperature-programmed oxidation (TPO). The characterizations and catalytic results show that: (i) the pore structures and acid properties of the two Al2O3 phases can change the quantity, location and property of the carbon deposition, (ii) the existence of Cl plays a significant role on the agglomeration of Pt particles and carbon deposition, which further influence the catalytic performances of Pt-Al2O3 catalysts with different support phases for propane dehydrogenation.

  19. 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

  20. 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%.

  1. 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.

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

    Science.gov (United States)

    López, Gema; Ortega, Pablo R; Voz, Cristóbal; Martín, Isidro; Colina, Mónica; Morales, Anna B; Orpella, Albert; Alcubilla, Ramón

    2013-01-01

    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 (S eff,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. PMID:24367740

  3. 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.

  4. 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

  5. The influence of Ni-P layer deposited onto Al2O3 on structure and properties of Al-Al2O3 composite materials

    OpenAIRE

    L.A. Dobrzański; M. Kremzer; J. Konieczny

    2011-01-01

    Purpose: The purpose of this work is to present the influence of wettability improvement of sintered Al2O3 particles by deposition of Ni-P coating.Design/methodology/approach: The material for investigations was manufactured by pressure infiltration method of ceramic porous preforms. The eutectic aluminium alloy EN AC - AlSi12 was use as a matrix while as reinforcement were used ceramic preforms manufactured by sintering of Al2O3 Alcoa CL 2500 powder with addition of pore forming agents as ca...

  6. 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...

  7. 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.

  8. 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

  9. Interface behaviour of Al2O3/Ti joints produced by liquid state bonding

    International Nuclear Information System (INIS)

    The main objective of this work was to determine various aspects during brazing of Al2O3 samples to commercially titanium alloy grade 4 with biocompatibility properties, using a Au-foil as joining element. Al2O3 ceramic was previously produced by sintering of powder cylindrical shape at 1550 grades C for 120 minutes. Previously to joining experiments, the surface of Al2O3 samples were coating, by chemical vapor depositions (CVD) process, with a Mo layer of 2 and 4 μm thick and then stacked together with the Ti samples. Joining experiments were carried out on Al2O3-Mo/Au/Ti combinations at temperature of 1100 grades C using different holding times under vacuum atmosphere. The experimental results show a successful joining Mo-Al2O3 to Ti. Analysis by scanning electron microscopy (Sem) revealed that joining of Al2O3 to metal occurred by the formation of a homogeneous diffusion zone with no interfacial cracking or porosity at the interface. Results by electron probe micro analysis (EPMA) of Al2O3-Mo/Au/Ti combinations revealed that Mo traveled inside the joining elements and remained as solid solutions, however during cooling process Mo had a tendency to stay as a precipitate phase and atomic distributions of elements show a concentration line of Mo inside the joining element Au. On the other hand, well interaction of Ti with Au form different phases; like Ti3Au and Ti Au. (author)

  10. 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.

  11. 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

  12. 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)...

  13. 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...

  14. 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.

  15. 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...

  16. 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...

  17. 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.

  18. Selective-area growth and magnetic characterization of MnAs/AlGaAs nanoclusters on insulating Al2O3 layers crystallized on Si(111) substrates

    International Nuclear Information System (INIS)

    We report on selective-area metal-organic vapor phase epitaxy and magnetic characterization of coupled MnAs/AlGaAs nanoclusters formed on thin Al2O3 insulating layers crystallized on Si(111) substrates. Cross-sectional transmission electron microscopy reveals that poly-crystalline γ-Al2O3 grains are formed after an annealing treatment of the amorphous Al2O3 layers deposited by atomic layer deposition on Si(111) substrates. The 〈111〉 direction of the γ-Al2O3 grains tends to be oriented approximately parallel to the 〈111〉 direction of the Si substrate. We observe that hexagonal MnAs nanoclusters on AlGaAs buffer layers grown by selective-area metal-organic vapor phase epitaxy on partially SiO2-masked Al2O3 insulator crystallized on Si(111) substrates are oriented with the c-axis along the 〈111〉 direction of the substrates, but exhibit a random in-plane orientation. A likely reason is the random orientation of the poly-crystalline γ-Al2O3 grains in the Al2O3 layer plane. Magnetic force microscopy studies at room temperature reveal that arrangements of coupled MnAs nanoclusters exhibit a complex magnetic domain structure. Such arrangements of coupled MnAs nanoclusters may also show magnetic random telegraph noise, i.e., jumps between two discrete resistance levels, in a certain temperature range, which can be explained by thermally activated changes of the complex magnetic structure of the nanocluster arrangements

  19. 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.

  20. 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...

  1. 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.

  2. 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.)

  3. Crystallisation of Al2O3 - ZrO2 - SiO2 gels

    International Nuclear Information System (INIS)

    Glassy and crystalline fibres, including SiO2, SiO2-10-50 mole%TiO2, SiO2-10-30 moles Al2O3 ,SiO2-10-33 moles ZrO2 , SiO2-ZrO2-N/A, have been prepared by drawing from a viscous gel followed by heat treatment. A wide variety of optical, dielectric, diffusion/oxidation barriers and other types of coating have also been prepared from gels by a dipping or spinning process. Dipping has been used commercially for the large scale coating of sheet glass since the l.'s. The forming process differs significantly from bulk gel formation because the rapid increase in concentration resulting from evaporation forces the precursors into close proximity, significantly increasing reaction rate. The structure of the initial film is strongly influenced by the degree of branching of precursors and the rates of condensation and evaporation. Shear stresses arising from fluid flow and film attachment are also applied to the depositing film during deposition so that aggregation gelation and drying occur in seconds rather than days or months. The gel initially shrinks as liquid evaporates but, as it stiffens, shrinkage stops and very fine porosity is introduced. The porosity can be reduced or eliminated by heating at relatively low temperatures (sintering), at higher temperatures crystalline phases may nucleate and grow. (author)

  4. Participation of Al2O3 hydroxyl-shell oxygen in the catalytic oxidation of carbon monoxide over Pd/Al2O3 and Pd.Cu/Al_2O_3 catalysts

    International Nuclear Information System (INIS)

    This paper studies the mechanism of low temperature CO oxidation over catalysts of 0.003%-0.1 wt.% palladium supported on gamma-Al2O3, and over a solid solution of copper in gamma-Al2O3 (0.5-3.0 wt.% CuO). In order to obtain information about the reactive forms of oxygen in CO oxidation over these catalysts, the authors used tagged oxygen (ca 80 atom %) and secondary ion mass spectrometry. To confirm the effect of oxygen isotope exchange on the tracer content of the CO2, CO oxidation was carried out with CO2 freeze-out in the cycle. CO oxidation over supported palladium, under conditions of reduction or of catalysis, can go via reaction with OH oxygen atoms, but the temperature ranges of these conditions differ by more than 250 degrees. It is noted that over Pd.Cu/Al_2O_3 catalysts the mechanism represented is only partly realized. Along with OH oxygen, an adsorbed form of oxygen evidently also contributes to CO formation over these catalysts

  5. 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.

  6. Tensile deformation behavior of a sub-micrometer Al2O3/6061Al composite

    International Nuclear Information System (INIS)

    A 0.3 μm Al2O3/6061Al composite with 33% volume fraction of Al2O3 was fabricated by the patented squeeze-casting technology. The tensile properties were studied, and the dynamic tensile deformation behavior was investigated by an in situ TEM tensile technique. The as-cast composite exhibits excellent tensile properties with a fracture strength of 504 MPa, and the strength increases to 579 MPa after a T6 treatment. The high strength is mainly attributed to the dispersion strengthening effect of the finer sub-micrometer Al2O3 particles. Dynamic transmission electron microscopy indicates that micro-cracks initiate and propagate mainly in the matrix. The Al2O3 particles can hinder the growth and deflect the cracks, but the resistance of the particles to crack propagation is small. The propagation stage is accordingly short, leading to the fracture of the composite

  7. 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.

  8. 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.

  9. 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.

  10. 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).

  11. 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.

  12. Neutron diffraction residual stress analysis of Al2O3/Y-TZP ceramic composites

    International Nuclear Information System (INIS)

    Residual stress measurements were conducted by time-of-flight neutron diffraction and Rietveld analysis method in Al2O3/Y-TZP ceramic composites fabricated by different green processing techniques (a novel tape casting and conventional slip casting) and with different Y-TZP content (5 and 40 vol.% Y-TZP). The results show that the residual stresses in Y-TZP particulates are tensile and the ones in Al2O3 matrix are compressive, with almost flat through-thickness residual stress profiles in all bulk samples. As Y-TZP content increased, tension in Y-TZP phase was decreased but compression in Al2O3 matrix was increased (in absolute value). The values of residual stresses for both phases were mainly dependent on the Y-TZP content in the studied Al2O3/Y-TZP composites, irrespective of sample orientation and fabrication processes (a novel tape casting and conventional slip casting). (Author)

  13. Effect of rhodium precursor on Rh/Al2O3 catalysts

    International Nuclear Information System (INIS)

    The infrared spectra of the CO/Rh/Al2O3 system have been examined following several different means of preparing the supported rhodium catalyst. Rhodium precursor materials including RhCl3 x 3H2O, Rh(NO3)3 x 2H2O, Rh6(CO)16, [Rh(OCOCH3)2]2, and Rh2(SO4)3 have been compared as to their tendencies to produce upon reduction the various CO/Rh/Al2O3 species generally attributed to this catalytic system. The nitrate and carbonyl precursors are most easily reduced to rhodium metal. The acetate and sulfate anions poison the Rh/Al2O3 surface through decomposition during reduction leading to very minimal CO adsorption. The catalytic properties of Rh/Al2O3 could be quite dependent upon the nature of rhodium precursor chosen

  14. 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.

  15. 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.

  16. Properties of electrodeposited Ni–B–Al2O3 composite coatings

    International Nuclear Information System (INIS)

    Highlights: • Alteration of metallic luster and chemical composition. • Modification of crystal structure, surface roughness and texture. • Significant improvement in mechanical properties. • A decent improvement in corrosion behavior. - Abstract: Ni–B coatings have gained a great deal of attraction due to their promising mechanical properties. Owing to tempting properties, Ni–B coatings have succeeded to find their applications in automotive, aerospace, petrochemical, plastic, optics, nuclear, electronics, computer, textile, paper, food and printing industries. Despite having promising properties, further improvement in their properties is essential so that more challenging requirements and new developments can be successfully addressed. In the present study, novel Ni–B–Al2O3 composite coatings have been synthesized through electrodeposition process by reinforcing Ni–B matrix with Al2O3 particles. A comparison of properties of Ni–B and Ni–B–Al2O3 coatings in their as deposited states is presented to elucidate the beneficial role of Al2O3 addition. The structural analyses indicate that Ni–B coatings exhibit a single broad peak indicative of an amorphous structure. However, the addition of Al2O3 into Ni–B matrix considerably improves the crystallinity of the deposit. The surface morphology study reveals the formation of uniform, dense and fine-grained deposit in both Ni–B and Ni–B–Al2O3 composite coatings. However, addition of Al2O3 particles into Ni–B coatings results in high surface roughness. The nanoindentation results demonstrates that the addition of Al2O3 into Ni–B matrix results in significant improvement in mechanical properties (hardness and modulus of elasticity) which may be attributed to dispersion hardening of Ni–B matrix by hard Al2O3 particles. The linear polarization tests confirm that the addition of Al2O3 improves the corrosion resistance of Ni–B coatings. This improvement in corrosion behavior may be

  17. High-stability 5 V spinel LiNi0.5Mn1.5O4 sputtered thin film electrodes by modifying with aluminium oxide

    International Nuclear Information System (INIS)

    Aluminium oxide (Al2O3)-modified LiNi0.5Mn1.5O4 (LNMO) thin-film electrodes were prepared by pulsed laser deposition and effects of surface modification on interfacial reactions of LNMO were studied. The modification by Al2O3 was carried out successively after the deposition of LNMO thin-film. Field-emission Scanning Electron Microscope results show that Al2O3 disperses uniformly in nano-scale on the film electrodes. Charge/discharge behavior of the batteries under a high cutoff voltage of 4.9 V vs. Li is highly improved by using Al2O3 modification, especially at elevated temperature. The electrochemical properties of LNMO thin-film electrodes are also affected by the thickness of coating. It is found that 20 nm thick Al2O3 coating layer improves thermal stability most obviously among them. At 55 °C, 84.1% of its initial capacity at 1C-rate can be retained after 100 cycles, and as the rate increases from 0.2 to 10 C the reversible capacity can still maintain 80.7mAhg−1, which are greatly improved compared to pristine, 6 and 40 nm thick Al2O3 modified samples

  18. PROPERTIES OF Al2O3 FOAMS OPTIMIZED BY FACTORIAL DESIGN

    OpenAIRE

    JÁN LOKAJ; VLADIMÍR KOVÁR; LADISLAV PACH; ZORA BAZELOVÁ

    2011-01-01

    Alumina foam was prepared by the direct foaming method. The foam was stabilized by in situ partially hydrophobized particles of Al2O3. Dodecylbenzenesulphonic acid was used for hydrophobization and it also acted as a foaming agent. The composition of the starting suspensions (Al2O3, boehmite, dodecylbenzenesulphonic acid and water) were varied according to factorial design. The resulting properties observed were: foam ratio, foam shrinkage on drying and sintering, bulk density and porosity of...

  19. Synthesis of MgO nanoparticle loaded mesoporous Al2O3 and its defluoridation study

    International Nuclear Information System (INIS)

    Highlights: • Simple and cost effective preparation of MgO nanoparticles loaded mesoporous Al2O3. • Adsorbents possess high surface area and mesoporous structure. • Higher fluoride removal capacity of MgO loaded Al2O3 than that of pure Al2O3. • Faster fluoride adsorption kinetics of MgO loaded Al2O3 from water. - Abstract: MgO nanoparticle loaded mesoporous alumina has been synthesized using a simple aqueous solution based cost effective method for removal of fluoride from water. Wide angle powder X-ray diffraction, nitrogen adsorption desorption analysis, transmission electron microscopy techniques and energy dispersive X-ray spectroscopy were used to characterize the synthesized adsorbents. Synthesized adsorbents possess high surface area with mesoporous structure. The adsorbents have been thoroughly investigated for the adsorption of F− using batch adsorption method. MgO nanoparticle loading on mesoporous Al2O3 enhances the F− adsorption capacity of Al2O3 from 56% to 90% (initial F− concentration = 10 mg L−1). Kinetic study revealed that adsorption kinetics follows the pseudo-second order model, suggesting the chemisorption mechanism. The F− adsorption isotherm data was explained by both Langmuir and Freundlich model. The maximum adsorption capacity of 40MgO@Al2O3 was 37.35 mg g−1. It was also observed that, when the solutions having F− concentration of 5 mg L−1 and 10 mg L−1 was treated with 40MgO@Al2O3, the F− concentration in treated water became <1 mg L−1, which is well below the recommendation of WHO

  20. 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.

  1. 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...

  2. Determination of transmission factors for beta radiation using Al 2O 3:C commercial OSL dosimeters

    Science.gov (United States)

    Pinto, T. N. O.; Caldas, L. V. E.

    2010-07-01

    In recent years, the optically stimulated luminescence (OSL) technique has been used in personal dosimetry, and aluminum oxide (Al 2O 3:C) has become a very useful material for this technique. The objective of this work was the determination of the transmission factors for beta radiation using Al 2O 3:C commercial dosimeters and the OSL method. The obtained results were similar to the transmission factors reported in the beta source calibration certificates.

  3. Effect of the thickness on properties of Al2O3 coatings deposited by plasma spraying

    International Nuclear Information System (INIS)

    Al2O3 coatings with different thicknesses (160, 320, 480 and 640 μm) were deposited on stainless steel substrate by plasma spraying. The variation in microstructural characteristics and properties of coatings with various thicknesses was investigated. Powders morphology and the microstructure of as-sprayed coatings were characterized by scanning electron microscopy and optical microscopy. The microhardness was measured using a Vickers' indentor. The corrosion behaviour of plasma-sprayed Al2O3 coatings in 1 N H2SO4 solution at a temperature of 25 deg. C was evaluated by electrochemistry method. Experimental results indicated that surface roughness showed no obvious dependence on the coating thickness. However, the porosity of Al2O3 coating was increased with increased thickness. The enhanced coating thickness also resulted in decreasing microhardness and reduced corrosion resistance. In this study, the Al2O3 coating with thickness of 160 μm possesses the lowest porosity, the highest hardness and superior corrosion resistance. Research Highlights: → Increase of coating thickness shows no obvious effect on phase composition and surface roughness of plasma sprayed Al2O3 coatings. → Variation of porosity and microhardness presents dependence on coating thickness parameter. → Increasing coating thickness leads to reduced corrosion resistance of plasma sprayed Al2O3 coating.

  4. Enhancement of nanovoid formation in annealed amorphous Al2O3 including W

    Science.gov (United States)

    Nakamura, R.; Ishimaru, M.; Hirata, A.; Sato, K.; Tane, M.; Kimizuka, H.; Shudo, T.; Konno, T. J.; Nakajima, H.

    2011-09-01

    The effect of W on the nanovoid formation in annealed amorphous Al2O3 was studied by transmission electron microscopy and molecular dynamics simulations. A comparison of the void formation behavior in electron-beam deposited Al2O3 (without W) and resistance-heating deposited Al2O3 (with 10 at. % W) revealed that W enhances the formation and growth of nanovoids. An analysis of the pair distribution function (PDF) in both types of amorphous Al2O3 showed that the introduction of W into amorphous Al2O3 brings about a significant change in the amorphous structure. Furthermore, it was found by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) that sub-nm sized W clusters exist in as-deposited Al2O3 prepared by resistance-heating and then dissolve in the amorphous matrix with annealing. The combination of PDF analysis and HAADF-STEM observation provides evidence that the enhancement of void formation originates in the heterogeneous short-range atomic configurations induced by the addition of W.

  5. 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.

  6. Improvement compressive strength of concrete in different curing media by Al2O3 nanoparticles

    International Nuclear Information System (INIS)

    Research highlights: → Al2O3 nanoparticles. → Mechanical properties. → Physical properties. → Thermal properties. → Microstructure. - Abstract: In the present work, the effect of curing medium on microstructure together with physical, mechanical and thermal properties of concrete containing Al2O3 nanoparticles has been investigated. Portland cement was partially replaced by Al2O3 nanoparticles with the average particle size of 15 nm and the specimens were cured in water and saturated limewater for specific ages. The results indicate that Al2O3 nanoparticles up to maximum of 2.0% produces concrete with improved compressive strength and setting time when the specimens cured in saturated limewater. The optimum level of replacement for cured specimens in water is 1.0 wt%. Although the limewater reduces the strength of concrete without nanoparticles when it is compared with the specimens cured in water, curing the specimens bearing nanoparticles in saturated limewater results in more strengthening gel formation around Al2O3 nanoparticles causes more rapid setting time together with high strength. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all indicate that Al2O3 nanoparticles could improve mechanical and physical properties of the specimens.

  7. 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.

  8. 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

  9. The effects of RF power on the interfacial property between Al2O3 and Si3N4 and on the memory property in a MANOS structure

    International Nuclear Information System (INIS)

    The interface stability and memory properties of an Al2O3 blocking oxide deposited using remote plasma atomic layer deposition (RPALD) at various RF powers were investigated. The plasma density increased with an increase in radio frequency (RF) power from 50 to 300 W due to increased neutral impact excitation rate. Based on x-ray photoelectron spectroscopy and auger electron spectroscopy, an oxygen-deficient interfacial layer was formed for Al2O3 film deposition at 50 W. In addition, increased migrations of Si and N atoms were observed at low power due to the formation of fewer oxygen radicals. While reduced migrations of Si and N atoms from Si3N4 to Al2O3 were observed when the RF power was sufficient due to the sufficient oxygen radicals. Therefore, the interfacial reaction between Al2O3 and Si3N4 is dependent on the RF power. After applying 18 V, the program speed of Al2O3 with 100 W, 200 W and 300 W were 10-2 s, 10-5 s and 10-6 s, respectively.

  10. 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.

  11. 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.

  12. 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.

  13. 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+.

  14. Thermal conductivity and viscosity of Al2O3 nanofluid based on car engine coolant

    International Nuclear Information System (INIS)

    Various suspensions containing Al2O3 nanoparticles (2O3 nanoparticles as well as temperature between 10 and 80 0C. The prepared nanofluid, containing only 0.035 volume fraction of Al2O3 nanoparticles, displays a fairly higher thermal conductivity than the base fluid and a maximum enhancement (knf/kbf) of ∼10.41% is observed at room temperature. The thermal conductivity enhancement of the Al2O3 nanofluid based on engine coolant is proportional to the volume fraction of Al2O3. The volume fraction and temperature dependence of the thermal conductivity of the studied nanofluids present excellent correspondence with the model proposed by Prasher et al (2005 Phys. Rev. Lett. 94 025901), which takes into account the role of translational Brownian motion, interparticle potential and convection in fluid arising from Brownian movement of nanoparticles for thermal energy transfer in nanofluids. Viscosity data demonstrate transition from Newtonian characteristics for the base fluid to non-Newtonian behaviour with increasing content of Al2O3 in the base fluid (coolant). The data also show that the viscosity increases with an increase in concentration and decreases with an increase in temperature. An empirical correlation of the type log(μnf) = A exp(-BT) explains the observed temperature dependence of the measured viscosity of Al2O3 nanofluid based on car engine coolant. We further confirm that Al2O3 nanoparticle concentration dependence of the viscosity of nanofluids is very well predicted on the basis of a recently reported theoretical model (Masoumi et al 2009 J. Phys. D: Appl. Phys. 42 055501), which considers Brownian motion of nanoparticles in the nanofluid.

  15. 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.

  16. 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 vivo...... can be circumvented for pulsed beams due to the long life-time of the main luminescence center. In contrast, chromatic removal seems to be the most effective method for organic scintillators, but is found to yield some experimental complexities. In this paper, we report on dose rate measurements using...

  17. Atomic-layer-deposited Al2O3-HfO2-Al2O3 dielectrics for metal-insulator-metal capacitor applications

    Science.gov (United States)

    Ding, Shi-Jin; Zhu, Chunxiang; Li, Ming-Fu; Zhang, David Wei

    2005-08-01

    Atomic-layer-deposited Al2O3-HfO2-Al2O3 dielectrics have been investigated to replace conventional silicon oxide and nitride for radio frequency and analog metal-insulator-metal capacitors applications. In the case of 1-nm-Al2O3, sufficiently good electrical performances are achieved, including a high dielectric constant of ˜17, a small dissipation factor of 0.018 at 100kHz, an extremely low leakage current of 7.8×10-9A/cm2 at 1MV/cm and 125°C, perfect voltage coefficients of capacitance (74ppm/V2 and 10ppm/V). The quadratic voltage coefficient of capacitance decreases with the applied frequency due to the change of relaxation time with different carrier mobility in insulator, and correlates with the dielectric composition and thickness, which is of intrinsic property owing to electric field polarization. Furthermore, the conduction mechanism of the AHA dielectrics is also discussed, indicating the Schottky emission dominated at room temperature.

  18. The influence of Ni-P layer deposited onto Al2O3 on structure and properties of Al-Al2O3 composite materials

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2011-06-01

    Full Text Available Purpose: The purpose of this work is to present the influence of wettability improvement of sintered Al2O3 particles by deposition of Ni-P coating.Design/methodology/approach: The material for investigations was manufactured by pressure infiltration method of ceramic porous preforms. The eutectic aluminium alloy EN AC - AlSi12 was use as a matrix while as reinforcement were used ceramic preforms manufactured by sintering of Al2O3 Alcoa CL 2500 powder with addition of pore forming agents as carbon fibres Sigrafil C10 M250 UNS, SGL Carbon Group Company. The Al2O3 was coated with the Ni-P alloy to improve the wettability of sintered particles. Metallographic examinations were made in the transmission electron microscope (TEM.Findings: The obtained results indicate the possibility of obtaining new materials with all advantageous properties of the particular composite constituents by infiltration of the ceramics with the liquid aluminium alloy.Practical implications: The composite materials made by the developed method can find application as the alternative material for elements fabricated from conventional materials.Originality/value: The obtained results show the possibility of manufacturing the composite materials by the pressure infiltration method of porous sintered preforms based on the ceramic particles with liquid aluminium alloy being a cheaper alternative for materials reinforced by fibres.

  19. 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)

  20. 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 ...

  1. 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.

  2. Epitaxial growth and electrical transport properties of Cr2GeC thin films

    International Nuclear Information System (INIS)

    Cr2GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr2GeC was grown directly onto Al2O3(0001) at temperatures of 700-800 deg. C. These films have an epitaxial component with the well-known epitaxial relationship Cr2GeC(0001)//Al2O3(0001) and Cr2GeC(1120)//Al2O3(1100) or Cr2GeC(1120)//Al2O3(1210). There is also a large secondary grain population with (1013) orientation. Deposition onto Al2O3(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr2GeC(0001) with a virtually negligible (1013) contribution. In contrast to the films deposited at 700-800 deg. C, the ones grown at 500-600 deg. C are polycrystalline Cr2GeC with (1010)-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53-66 μΩcm. Temperature-dependent resistivity measurements from 15-295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.

  3. 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

  4. 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.

  5. 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.

  6. Influence of mechanical activation of AL2O3 on synthesis of magnesium aluminate spinel

    Directory of Open Access Journals (Sweden)

    Zhihui Zhang

    2004-01-01

    Full Text Available Magnesium aluminate (MA spinel is synthesized by reaction sintering from alumina and magnesia. The effects of mechanical activation of Al2O3 on reaction sintering were investigated. Non-milled a - Al2O3 and a - Al2O3 high-energy ball milled for 12h, 24h and 36h were mixed with a MgO analytical reagent according to the stoichiometric MA ratio, respectively and pressed into billets with diameters of 20mm and height of 15mm. The green-body billets were then sintered at high temperature in an air atmosphere. The results show that bulk density, relative content of MA and grain size of MA increase with increasing high-energy ball milling time of Al2O3. However prolonged milling time over 24h has a small beneficial effect on the densification of MA. Bulk density and grain size of a sample of a- Al2O3 milled for 24h are 3.30g/cm3 and 4-5 mm, respectively.

  7. 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.

  8. 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

  9. 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

  10. Microstructural characterization of Al2O3: Eu with dosimetric purposes

    International Nuclear Information System (INIS)

    In this work a microstructural analysis is presented, through Sem, EDS and XRD, of the alumina with Europium (Al2O3: Eu) synthesized by the sol gel method. According to those obtained results, a previous thermal treatment to 1000 C to the samples, induces the formation of the γ-alumina phase for the samples that does not contain Eu; however when there is presence of this element, the θ alumina phase is obtained. Likewise, it was observed that the particle size is increased with the presence of Eu. When analyzing the thermoluminescent response (TL) induced by the gamma radiation, it was observed that the pure Al2O3 presents an intense TL sign; while the Al2O3: Eu, the sign suffers a marked decrement. (Author)

  11. 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.

  12. 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)

  13. 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.

  14. Growth, Quantitative Growth Analysis, and Applications of Graphene on γ-Al2O3 catalysts

    Science.gov (United States)

    Park, Jaehyun; Lee, Joohwi; Choi, Jung-Hae; Hwang, Do Kyung; Song, Yong-Won

    2015-07-01

    The possibilities offered by catalytic γ-Al2O3 substrates are explored, and the mechanism governing graphene formation thereon is elucidated using both numerical simulations and experiments. The growth scheme offers metal-free synthesis at low temperature, grain-size customization, large-area uniformity of electrical properties, single-step preparation of graphene/dielectric structures, and readily detachable graphene. We quantify based on thermodynamic principles the activation energies associated with graphene nucleation/growth on γ-Al2O3, verifying the low physical and chemical barriers. Importantly, we derive a universal equation governing the adsorption-based synthesis of graphene over a wide range of temperatures in both catalytic and spontaneous growth regimes. Experimental results support the equation, highlighting the catalytic function of γ-Al2O3 at low temperatures. The synthesized graphene is manually incorporated as a ‘graphene sticker’ into an ultrafast mode-locked laser.

  15. 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.

  16. 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.

  17. Dependence of phase composition on nuclei available in SiO2--Al2O3

    International Nuclear Information System (INIS)

    Phase equilibria in the system SiO2--Al2O3 were studied. Data obtained by conventional static quenching and phase analysis are difficult to interpret due to persistent metastability in silicate systems. Aksay and Pask, using a diffusion couple technique to determine stable phase equilibria, proposed the stable and metastable phase equilibrium boundaries to explain experimentally observed behavior. The major area of difference in phase equilibria studies is in the nature of the stable equilibria in the high alumina portion of the diagram, i.e., the melting behavior of mullite and the extent of the α-Al2O3 primary phase field. Results are reported of an experiment designed to seek improved resolution in these areas and to clarify the phase behavior in the system SiO2--Al2O3

  18. 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.

  19. 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.

  20. 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)

  1. 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.

  2. Study on aluminum phosphate binder and related Al2O3-SiC ceramic coating

    International Nuclear Information System (INIS)

    Refractory and wear-resistant Al2O3-SiC ceramic coatings have been fabricated on A3 steel using alumina (Al2O3), silicon carbide (SiC), aluminum phosphate binder (inorganic binder), and other additives as starting materials. The powder X-ray diffraction (XRD), thermogravimetric analysis/differential thermal analysis (TG/DTA), and scanning electron microscopy (SEM) techniques are applied to investigate the chemical compositions of the in-house synthesized aluminum phosphate binder and the morphologies of the fabricated ceramic coatings after abrasion test. The XRD results indicate that monoaluminum phosphate (Al(H2PO4)3) is the most effective binding phase in the synthesized aluminum phosphate binder. The TG/DTA analysis shows that two phase transformations occur at 100.7 and 217.7 deg. C when the synthesized aluminum phosphate binder is heated in a range 60-1000 deg. C and the binder after heat treatment is a mixture of several phases. The wear test results show that the wear durability of the A3 steel covered with Al2O3-SiC ceramic coatings is about two times that of the uncoated A3 steel. The results also indicate that the wear properties of Al2O3-SiC ceramic coatings are dependent on fabrication conditions such as the weight ratio of ceramics (Al2O3 and SiC) to the binder (RCB), the distribution of particle size of ceramics, the density of the aluminum phosphate binder, and the Al/P atomic ratio in the aluminum phosphate binder. Upon the above results, optimal fabrication conditions for achieving good wear resistance of Al2O3-SiC ceramic coatings are suggested in this paper

  3. 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.

  4. Depth profiling of Al2O3 + TiO2 nanolaminates by means of a time-of-flight energy spectrometer

    International Nuclear Information System (INIS)

    Atomic layer deposition (ALD) is currently a widespread method to grow conformal thin films with a sub-nm thickness control. By using ALD for nanolaminate oxides, it is possible to fine tune the electrical, optical and mechanical properties of thin films. In this study the elemental depth profiles and surface roughnesses were determined for Al2O3 + TiO2 nanolaminates with nominal single-layer thicknesses of 1, 2, 5, 10 and 20 nm and total thickness between 40 nm and 60 nm. The depth profiles were measured by means of a time-of-flight elastic recoil detection analysis (ToF-ERDA) spectrometer recently installed at the University of Jyväskylä. In TOF-E measurements 63Cu, 35Cl, 12C and 4He ions with energies ranging from 0.5 to 10 MeV, were used and depth profiles of the whole nanolaminate film could be analyzed down to 5 nm individual layer thickness.

  5. 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)

  6. 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...

  7. 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

  8. The uses and enigmas of the Al2O3-Y2O3 phase system

    International Nuclear Information System (INIS)

    The uses of the five compounds, namely Al2O3, Y3Al5O12, YAlO3, Y4Al2O9 and Y2O3, which occur in the Al2O3-Y2O3 phase system are reviewed and the uncertainties which have pervaded the existence and stability of the three intermediate phases are discussed. It is shown that the major factor which has resolved these uncertainties is the correlation achieved between phase studies and single-crystal growth data, the latter being prompted by the increased device use of the compounds within in this phase system. (orig.)

  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. 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)

  11. TEM characterization of Al-C-Cu-Al2O3 composites produced by mechanical milling

    International Nuclear Information System (INIS)

    Novel Al-based composites (Al-C-Cu-Al2O3) obtained by mechanical milling (MM), were characterized by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Analyses of composites were carried out in both, the as-milled and the as-sintered conditions. C nanoparticles were found in the as-milled condition and Al2O3 nanofibers were found in as-sintered products, as determined by EELS. C and Cu react with Al to crystallize in Al3C4 and Al2Cu structures, respectively

  12. 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.

  13. 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.

  14. Solidification processing of Al-Al2O3 composite using turbine stirrer

    Science.gov (United States)

    Al-Jarrah, J. A.; Ray, S.; Ghosh, P. K.

    1998-06-01

    Solidification processing of Al-Al2O3 composites involves mixing of nonwetting alumina particles in molten aluminum alloy resulting in a slurry where the particles are often attached to bubbles sucked at the center of vortex below the stirrer. The internal surface of bubbles is eventually oxidized by oxygen from air entrapped in it. These bubble-particle combines may float or settle during casting depending on the overall density influencing the particle and porosity distribution in a cast composite ingot where the performance of a stirrer may be evaluated under a given condition of processing. Particle incorporation is more for turbine stirrers instead of flat blade stirrers, but the porosity also increases. Flotation of bubble-particle combines during casting of ingot results in higher particle content at the top. Microstructure shows clusters of particles along circular boundaries of thin oxides at the top of the ingot and sometimes at the bottom. This may be a consequence of filling of bubbles to different extents by surrounding liquid puncturing the oxide layer, if necessary, during solidification. When the manner of stirring is changed to 2 minutes of stirring of particles into molten alloy with an intermediate 2-minute period of no stirring before stirring the slurry again for 2 minutes, relatively uniform particle incorporation results along the height of cast ingot compared to that obtained by continuous stirring. This difference in particle distribution may be attributed to flotation of bubble-particle combines to release the particles on the top of the slurry when stirring ceases and its remixing into the slurry when it is stirred again. However, an increase in the intermediate period of no stirring and a higher processing temperature result in enhanced porosity and a more inhomogeneous particle distribution along the height of the ingot.

  15. Characterization of ZrO2 buffer layers for sequentially evaporated Y-Ba-CuO on Si and Al2O3 substrates

    Science.gov (United States)

    Valco, George J.; Rohrer, Norman J.; Pouch, John J.; Warner, Joseph D.; Bhasin, Kul B.

    1988-01-01

    Thin film high temperature superconductors have the potential to change the microwave technology for space communications systems. For such applications it is desirable that the films be formed on substrates such as Al2O3 which have good microwave properties. The use of ZrO2 buffer layers between Y-Ba-Cu-O and the substrate has been investigated. These superconducting films have been formed by multilayer sequential electron beam evaporation of Cu, BaF2 and Y with subsequent annealing. The three layer sequence of Y/BaF2/Cu is repeated four times for a total of twelve layers. Such a multilayer film, approximately 1 micron thick, deposited directly on SrTiO3 and annealed at 900 C for 45 min produces a film with a superconducting onset of 93 K and critical temperature of 85 K. Auger electron spectroscopy in conjunction with argon ion sputtering was used to obtain the distribution of each element as a function of depth for an unannealed film, the annealed film on SrTiO3 and annealed films on ZrO2 buffer layers. The individual layers were apparent. After annealing, the bulk of the film on SrTiO3 is observed to be fairly uniform while films on the substrates with buffer layers are less uniform. The Y-Ba-Cu-O/ZrO2 interface is broad with a long Ba tail into the ZrO2, suggesting interaction between the film and the buffer layer. The underlying ZrO2/Si interface is sharper. The detailed Auger results are presented and compared with samples annealed at different temperatures and durations.

  16. Crack-resistant Al2O3–SiO2 glasses

    Science.gov (United States)

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

    2016-04-01

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

  17. Positron Annihilation Lifetime Study of Pure and Doped Polyvinyl Chloride with Al2O3

    International Nuclear Information System (INIS)

    Positron annihilation lifetime of pure and doped polyvinyl chloride (PVC) with Al2O3 reflect the effect of concentration as well as temperature on free volume. Therefore, variations of the ortho-positronium (o-Ps) lifetime and its intensity have been correlated with changes in the dielectric properties of the pure and doped PVC. The o-Ps lifetime and its intensity show a linear dependence with a discontinuity at 20 % concentration of Al2O3. The size and the fractional of the o-Ps hole volume were estimated from the positron annihilation parameters. Therefore, the temperature dependence of the electrical conductivity and the positron annihilation parameters on pure and doped PVC with 20 % Al2O3 were studied in the range from 20 to 140 degree C. The shift of the glass transition temperature to lower temperature for the 20 % Al2O3 doped PVC might explain the increase in the electrical conductivity with the concentration of the additive

  18. 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...

  19. Preparation of Al2O3/Mo nanocomposite powder via chemical route and spray drying

    International Nuclear Information System (INIS)

    A route to prepare nanometer-sized Mo particulates in Al2O3 was attempted by a combination of solution reactions in molecular scale and forcing precipitation by a spray-drying technique. MoO3 was first dissolved in ammonia water and then added in the slurry with high purity, submicrometer Al2O3 powder. Mixed suspension was spray-dried, and then the dried granules were reduced by hydrogen gas and further hot-pressing to a bulky composite at various temperatures. Dissolution of Mo oxide, adsorption reactions on alumina surface, and surface potential of alumina particles in homogeneous ammonia suspension were studied. Characterization of the granules, including compactability, flowing properties, surface morphology, grain growth of Mo and Al2O3, and mixing homogeneity, were examined. Homogeneity of the spray-dried granules was determined by the calculation of mixing index and the observation of the microstructure of sintered body. The existence of intergranular, intragranular, and nanosized Mo particulates within Al2O3 grains was observed by transmission electron microscopy (TEM). All the evidences revealed that homogeneous composites with nanometer-sized Mo had been successfully prepared by this attempt with the proposed chemical route and following spray-drying process. copyright 1996 Materials Research Society

  20. 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.

  1. Crystallization kinetics of BaO-Al2O3-SiO2 glasses

    Science.gov (United States)

    Bansal, Narottam P.; Hyatt, Mark J.

    1989-01-01

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

  2. Crack-resistant Al2O3-SiO2 glasses.

    Science.gov (United States)

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

    2016-01-01

    Obtaining "hard" and "crack-resistant" glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3-(100-x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3-SiO2 glasses. In particular, the composition of 60Al2O3•40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses. PMID:27053006

  3. Crack-resistant Al2O3–SiO2 glasses

    Science.gov (United States)

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

    2016-01-01

    Obtaining “hard” and “crack-resistant” glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3–(100–x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3–SiO2 glasses. In particular, the composition of 60Al2O3•40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses. PMID:27053006

  4. Modification of the optical properties of Al2O3 by ion implantation

    International Nuclear Information System (INIS)

    The implantation of Au into Al2O3 followed by thermal annealing at 1100 degrees C leads to dramatic changes in the optical properties. In this paper the linear and nonlinear optical properties are correlated to the presence of small Au precipitates which form during annealing

  5. Plasma etching behavior of Y2O3 ceramics: Comparative study with Al2O3

    Science.gov (United States)

    Cao, Yu-Chao; Zhao, Lei; Luo, Jin; Wang, Ke; Zhang, Bo-Ping; Yokota, Hiroki; Ito, Yoshiyasu; Li, Jing-Feng

    2016-03-01

    The plasma etching behavior of Y2O3 coating was investigated and compared with that of Al2O3 coating under various conditions, including chemical etching, mixing etching and physical etching. The etching rate of Al2O3 coating declined with decreasing CF4 content under mixing etching, while that of Y2O3 coating first increased and then decreased. In addition, the Y2O3 coating demonstrated higher erosion-resistance than Al2O3 coating after exposing to fluorocarbon plasma. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formations of YF3 and AlF3 on the Y2O3 and Al2O3 coatings, respectively, which acted as the protective layer to prevent the surface from further erosion with fluorocarbon plasma. It was revealed that the etching behavior of Y2O3 depended not only on the surface fluorination but also on the removal of fluoride layer. To analyze the effect of porosity, Y2O3 bulk samples with high density were prepared by spark plasma sintering, and they demonstrated higher erosion-resistances compared with Y2O3 coating.

  6. 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...

  7. Radioluminescence in Al2O3: C - analytical and numerical simulation results

    DEFF Research Database (Denmark)

    Pagonis, V.; Lawless, J.; Chen, R.; Andersen, Claus Erik

    2009-01-01

    The phenomenon of radioluminescence (RL) has been reported in a number of materials including Al2O3 : C, which is one of the main dosimetric materials. In this work, we study RL using a kinetic model involving two trapping states and two kinds of recombination centres. The model has been previous...

  8. 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

  9. 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.

  10. 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...

  11. 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.

  12. 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.

  13. 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 of...

  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. 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.

  16. Theoretical investigation of the structure of κ-Al2O3

    DEFF Research Database (Denmark)

    Yourdshahyan, Y.; Engberg, U.; Bengtsson, L.; Lundqvist, B.I.; Hammer, Bjørk

    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...

  17. Distinctive electrical properties in sandwich-structured Al2O3/low density polyethylene nanocomposites

    Science.gov (United States)

    Wang, Si-Jiao; Zha, Jun-Wei; Li, Wei-Kang; Dang, Zhi-Min

    2016-02-01

    The sandwich-structured Al2O3/low density polyethylene (Al2O3/LDPE) nanocomposite dielectrics consisting of layer-by-layer with different concentration Al2O3 loading were prepared by melt-blending and following hot pressing method. The space charge distribution from pulsed electro-acoustic method and breakdown strength of the nanocomposites were investigated. Compared with the single-layer Al2O3/LDPE nanocomposites, the sandwich-structured nanocomposites remarkably suppressed the space charge accumulation and presented higher breakdown strength. The charges in the sandwich-structured nanocomposites decayed much faster than that in the single-layer nanocomposites, which was attributed to an effective electric field caused by the formation of the interfacial space charges. The energy depth of shallow and deep traps was estimated as 0.73 eV and 1.17 eV in the sandwich-structured nanocomposites, respectively, according to the thermal excitation theoretical model we proposed. This work provides an attractive strategy of design and fabrication of polymer nanocomposites with excellent space charge suppression.

  18. 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

  19. 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.

  20. 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

  1. 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.

  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. 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.

  4. MgO-Al2O3-ZrO2 Amorphous Ternary Composite: A Dense and Stable Optical Coating

    Science.gov (United States)

    Shaoo, Naba K.; Shapiro, Alan P.

    1998-01-01

    The process-parameter-dependent optical and structural properties of MgO-Al2O3-ZrO2 ternary mixed-composite material were investigated. Optical properties were derived from spectrophotometric measurements. The surface morphology, grain size distributions, crystallographic phases, and process- dependent material composition of films were investigated through the use of atomic force microscopy, x-ray diffraction analysis, and energy-dispersive x-ray analysis. Energy-dispersive x-ray analysis made evident the correlation between the optical constants and the process-dependent compositions in the films. It is possible to achieve environmentally stable amorphous films with high packing density under certain optimized process conditions.

  5. Sputtering-deposition of Ru nanoparticles onto Al2O3 modified with imidazolium ionic liquids: synthesis, characterisation and catalysis.

    Science.gov (United States)

    Foppa, Lucas; Luza, Leandro; Gual, Aitor; Weibel, Daniel E; Eberhardt, Dario; Teixeira, Sérgio R; Dupont, Jairton

    2015-02-14

    Well-distributed Ru nanoparticles (Ru-NPs) were produced over Al(2)O(3) supports modified with covalently anchored imidazolium ionic liquids (ILs) containing different anions and cation lateral alkyl chain lengths by simple sputtering from a Ru foil. These Ru-NPs were active catalysts for the hydrogenation of benzene. Furthermore, depending on the nature of the IL used to modify the support (hydrophilic or hydrophobic), different catalytic behaviours were observed. Turnover numbers (TON) as high as 27 000 with a turnover frequency (TOF) of 2.73 s(-1) were achieved with Ru-NPs of 6.4 nm supported in Al(2)O(3) modified with an IL containing the N(SO(2)CF(3))2(-) anion, whereas higher initial cyclohexene selectivities (ca. 20% at 1% benzene conversion) were attained for Ru-NPs of 6.6 nm in the case where Cl(-) and BF(4)(-) anions were used. Such observations strongly suggest that thin layers of ILs surround the NP surface, modifying the reactivity of these catalytic systems. These findings open a new window of opportunity in the development of size-controlled Ru-NPs with tuneable reactivity. PMID:25531917

  6. 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.

  7. Surface Tension of the System NaF -AlF3-Al2O3 and Surface Adsorption of Al2O3

    Science.gov (United States)

    Kucharík, Marián; Vasiljev, Roman

    2006-08-01

    Part of the molten system NaF-AlF3-Al2O3 was studied by surface tension measurements, which were performed at cryolite ratios (CR) between 1.5 and 3 [CR = n(NaF)/n(AlF3)]. The maximal bubble pressure method was applied. The surface adsorption of alumina (Al2O3) was also calculated. The obtained results were discussed in terms of the anionic composition of the melt. The addition of AlF3 to melt with CR= 3 decreases the surface tension, as AlF3 is surface-active in molten Na3AlF6. The concentration dependence of the surface tension and the surface adsorption of alumina in the title system are influenced by the formation of surface-active oxofluoroaluminates. An increase of the difference between the surface tension of NaF-AlF3 mixtures and the surface tension of pure alumina was observed with decreasing cryolite ratio.

  8. Structural optical correlated properties of SnO2/Al2O3 core@ shell heterostructure

    Science.gov (United States)

    Heiba, Zein K.; Imam, N. G.; Bakr Mohamed, Mohamed

    2016-07-01

    Nano size polycrystalline samples of the core@shell heterostructure of SnO2 @ xAl2O3 (x = 0, 25, 50, 75 wt.%) were synthesized by sol-gel technique. The resulting samples were characterized with fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and X-ray powder diffraction (XRD). The XRD patterns manifest diffraction peaks of SnO2 as main phase with weak peaks corresponding to Al2O3 phase. The formation of core@ shell structure is confirmed by TEM images and Rietveld quantitative phase analysis which revealed that small part of Al2O3 is incorporated into the SnO2 lattice while the main part (shell) remains as a separate phase segregated on the grain boundary surface of SnO2 (core). It is found that the grain size of the mixed oxides SnO2 @ xAl2O3 is below 10 nm while for pure SnO2 it is over 41 nm, indicating that alumina can effectively prevent SnO2 from further growing up in the process of calcination. This is confirmed by the large increase in the specific surface area for mixed oxide samples. The PL emission showed great dependence on the structure properties analyzed by XRD and FTIR. The PL results recommend Al2O3@SnO2 core@shell heterostructure to be a promising short-wavelength luminescent optoelectronic devices for blue, UV, and laser light-emitting diodes.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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)

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. Effect of gamma irradiation on the surface and catalytic properties of Al2O3 and NiO-Al2O3 catalysts

    International Nuclear Information System (INIS)

    Pure alumina and NiO-Al2O3 catalysts of varying NiO content were prepared and irradiated with γ-rays. The textural properties of of non-irradiated and γ-irradiated catalysts were determined by low temperature nitrogen adsorption. The surface acidities were determined from the chemisorption of pyridine. The catalytic conversion of isopropanol at 2800C was followed on non-irradiated and γ-irradiated catalysts. γ-Irradiation with > 45 M rad brought about significant changes in the textural properties (surface area decrease and pore widening). Irradiation with such high doses removed a considerable fraction of the surface acidity. Dehydration of isopropanol is related to th number of acid sites per unit surface area while dehydrogenation of this alcohol is related to the degree of the dispersion of NiO on the surface

  20. Pseudo-hexagonal in-plane alignment of rutile (100)Nb:TiO2 on hexagonal (0001)Al2O3 plane

    Science.gov (United States)

    Wang, Chaojun; Dho, Joonghoe; Geul Lee, Sang

    2013-10-01

    Nb-doped TiO2 (Nb:TiO2) films were grown on a hexagonal (0001)Al2O3 substrate at 650 °C and ∼10-5 Torr. The Nb:TiO2 film had a small resistivity of ∼8×10-4 Ω cm at room temperature and a behavior of a slightly increasing resistance upon cooling. In addition, the Nb:TiO2 film had an optical transmittance of about 60% in the visible range. A careful analysis of the in-plane atomic structure suggests that the rutile Nb:TiO2 film on the hexagonal (0001)Al2O3 can be re-interpreted by a certain pseudo-hexagonal structure, which is discriminated from the in-plane rectangular one of the tetragonal (100)Nb:TiO2. The pseudo-hexagonal properties of the Nb:TiO2 film were characterized by negligible mosaic structure at the interface, the same electron diffraction pattern as the hexagonal Al2O3 substrate, and perfect six-fold symmetries in the pole figure and ϕ-scan XRD patterns.

  1. Geant4 calculations for space radiation shielding material Al2O3

    Science.gov (United States)

    Capali, Veli; Acar Yesil, Tolga; Kaya, Gokhan; Kaplan, Abdullah; Yavuz, Mustafa; Tilki, Tahir

    2015-07-01

    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.

  2. 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.

  3. 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.)

  4. Fabrication of porous Al2O3-based ceramics using combustion synthesized powders

    Directory of Open Access Journals (Sweden)

    Jiahai Bai

    2012-03-01

    Full Text Available Porous Al2O3-based ceramics were fabricated from powders synthesized via a solution combustion process using starch and urea as fuels. Effects of the relative fuel-to-oxidant ratio (φe = 1.4, 1.6, 1.8 and 2.0, respectively on open porosity, pore size distribution and flexural strength of the as-prepared porous Al2O3-based ceramics were investigated. Experimental results revealed that the densification ability of the as-synthesized powders increased significantly as φe increased, and open porosity, pore size distribution and flexural strength of the porous ceramics exhibited remarkable dependence on the densification ability of the powders instead of the weight fraction of the charred organic residuals in the powders. SEM micrographs disclosed that the porous ceramics from the precursors with φe = 1.8 or 2.0 exhibited significantly homogenous microstructures including pore size and pore distribution.

  5. Al2 O3/Si C powders synthesis from natural precursors

    International Nuclear Information System (INIS)

    Al2 O3/Si C composites can be prepared by sintering reactive powders produced by carbothermical reduction of different aluminum-silicates (kaolin, kianite and pyrophillite) by a rich carbon agent, as carbon black. The composite is prepared by the mixture such of natural precursors, following stoichiometric quantities, in a furnace with controlled atmosphere in a temperature range of 1400 to 1500 deg C. This work presents the first results of batch of experiments carried out to obtain reactive Al2 O3/SiC powders, suitable for the processing of ceramic nano composites. X-ray diffraction and transmission electronic microscopy analysis showed that the phases and the ratio between them was readily obtained. However, the morphology and particle size control was more difficult to achieve. (author)

  6. 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 ℃.

  7. Pressureless infiltration of porous Al2O3 preform in molten 6061 commercial aluminium alloy

    International Nuclear Information System (INIS)

    This paper presents an infiltration study of Al2O3 samples containing, approximately, 40% of pores with 1μ average radios. These samples were totally infiltrated with Al-6061 at 1100 deg C for 24 hs in air. Microstructural analysis showed the presence of an alumina matrix infiltrated through mechanisms that combine reactive processes and capillarity, and thus being coherent with the presence of open and closed porosity. The metallographic analysis showed open porosity infiltrated with Al-6061 by capillarity, while SEM micrographs corresponding to this system also showed closed pores filled with metal, that was transported into the ceramic matrix through a reactivate infiltration mechanism. The EDAX analysis for the Al2O3/Al 6061 system showed areas rich in silicon and copper at the metal-ceramic interface, while the ceramic phase showed the presence of Mg. XRD identified the presence of the MgAl2O4 spinel in the ceramic phase

  8. Preparation of nano-sized α-Al2O3 from oil shale ash

    International Nuclear Information System (INIS)

    Oil shale ash (OSA), the residue of oil shale semi-coke roasting, was used as a raw material to synthesize nano-sized α-Al2O3. Ultrasonic oscillation pretreatment followed by azeotropic distillation was employed for reducing the particle size of α-Al2O3. The structural characterization at molecular and nanometer scales was performed using X-ray diffraction (XRD), transmission electron microscopy (TEM), respectively. The interaction between alumina and n-butanol was characterized by Fourier transform infrared spectroscopy (FT-IR). The results revealed that the crystalline phase of alumina nanoparticles was regular and the well dispersed alumina nanoparticles had a diameter of 50-80 nm. In addition, the significant factors including injection rate of carbon oxide (CO2), ultrasonic oscillations, azeotropic distillation and surfactant were investigated with respect to their effects on the size of the alumina particles.

  9. 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.

  10. 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.

  11. Laser annealing of Al2O3 containing copper nanoparticles formed by implantation

    International Nuclear Information System (INIS)

    Al2O3 with Cu nanoparticles synthesized by ion implantation at energy of 40 keV, dose of 1·1017 ion/cm2 and current density from 2.5 to 12.5 μA/cm2 were annealed using several pulses of the high-power Kr F excimer laser with the single pulse fluence of 0.3 J/cm2. The formation and modification of metal nanoparticles after laser treatment were studied by optical reflectance, Rutherford backscattering and energy dispersive X-ray analysis. Generally, changes induced by laser pulses suggest there is reduction of the size of the nanoparticles without diffusion of metal atoms inward the Al2O3. The particle sizes and oxidation of copper particles were estimated in the framework on the Mie theory. The presented calculations assumes that during excimer laser treatment metal Cu nanoparticles endure more obviously the redaction of the particle sizes then the their oxidation

  12. Optical-fiber guided Al2O3:C radioluminescence dosimetry for external beam radiotherapy

    International Nuclear Information System (INIS)

    Small luminescence point-detectors coupled to optical-fiber cables (typically 1 mm diameter and 15 m length) may be used for medical dosimetry. Currently, the main luminescence materials are Al2O3:C and organic scintillator materials. The potential applications include, for example, online in vivo dose verification during remotely afterloaded brachytherapy, in vivo time-resolved IMRT dosimetry and dose-per-pulse measurements in megavolt x-ray beams. In the present work, we specifically explored the use of a new readout protocol for Al2O3:C for accelerator characterization measurements, and eventually, small-field dosimetry in external beam radiotherapy. Al2O3:C can in principle be used for radioluminescence (RL) dosimetry as well as optically stimulated luminescence (OSL) dosimetry. In the new readout protocol, however, we have eliminated the OSL readout. The main advantage of this so-called saturated RL protocol compared with the combined RL/OSL readout protocol is that it provides an RL sensitivity which is almost constant. Furthermore, the new readout protocol is much simpler and faster to use in the clinic. In contract to the main organic scintillators, it is noteworthy that the RL signal from Al2O3:C has a long luminescence life-time which allows for almost complete removal of any interference from light generated in the optical fiber cable due to stray radiation from pulsed beams. Measurements were conducted in a 6 MV beam (Varian iX linear accelerator, USA) using a solid- water phantom (type 457, Gammex, USA) and a 2 mg Al2O3:C crystal (Landauer Inc, USA) attached to a PMMA optical-fiber cable. The data acquisition system recorded both the RL signal from the Al2O3:C and the number of accelerator gun pulses (deduced from the so-called target current signal). The new RL-protocol with saturated Al2O3:C was found to be highly sensitive (-5x106 counts pr. Gy) and doses in the range from 10 mGy to above 15 Gy could be measured using a single calibration factor

  13. The effect of crystal orientation on damage accumulation in chromium-implanted Al2O3

    International Nuclear Information System (INIS)

    Chromium-implantation of single crystal aluminium oxide (Al2O3) has been shown to be anisotropic with respect to damage accumulation. Ultra-low load indentation and Rutherford Backscattering Spectroscopy (RBS) have been used to demonstrate the dependence of radiation damage on fluence and crystal orientation. Single crystal Al2O3 specimens of c-axis ([0001] normal to the surface) and a-axis ([1120] normal to the surface) orientations were ion-implanted simultaneously and found to possess different near-surface mechanical properties. Subsequent RBS-ion channeling examination indicated different amounts of disorder in both the aluminum and oxygen sublattices for the two orientations. These results imply a higher amorphization threshold in terms of implantation fluence for the a-axis oriented samples. 15 refs., 6 figs

  14. 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.

  15. 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

  16. X-ray imaging using the thermoluminescent properties of commercial Al2O3 ceramic plates.

    Science.gov (United States)

    Shinsho, Kiyomitsu; Kawaji, Yasuyuki; Yanagisawa, Shin; Otsubo, Keisuke; Koba, Yusuke; Wakabayashi, Genichiro; Matsumoto, Kazuki; Ushiba, Hiroaki

    2016-05-01

    This research demonstrated that commercially available alumina is well-suited for use in large area X-ray detectors. We discovered a new radiation imaging device that has a high spatial resolution, high sensitivity, wide dynamic range, large imaging area, repeatable results, and low operating costs. The high thermoluminescent (TL) properties of Al2O3 ceramic plates make them useful for X-ray imaging devices. PMID:26972627

  17. 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...

  18. 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.

  19. Tribological properties of Al 7075 alloy based composites strengthened with Al2O3 fibres

    OpenAIRE

    K. Naplocha; J.W. Kaczmar

    2011-01-01

    Wear resistance of 7075 aluminium alloy based composite materials reinforced with Al2O3 Saffil fibres was investigated. The measurementsof wear were performed applying the pin-on-disc method at dry friction conditions with the gray iron counterpart. The effects ofpressure of composite samples on the counterpart made of gray iron and the orientation of fibers in relation to the friction surface on wear rate were determined. The materials were produced by squeeze casting method where 80-90% por...

  20. Corrosion Resistance of Ni/Al2O3 Nanocomposite Coatings

    OpenAIRE

    Beata KUCHARSKA; 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...

  1. Washcoated Pd/Al2O3 monoliths for the liquid phase hydrodechlorination of dioxins

    OpenAIRE

    Cobo, Martha; Orrego, Andrés; Conesa Ferrer, Juan Antonio

    2012-01-01

    The catalytic activity and durability of 2 wt.% Pd/Al2O3 in powder and washcoated on cordierite monoliths were examined for the liquid phase hydrodechlorination (LPHDC) of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs), also known as dioxins. NaOH was employed as a neutralizing agent, and 2-propanol was used as a hydrogen donor and a solvent. Fresh and spent powder and monolith samples were characterized by elemental analysis, surface area, hydrogen chemisorption, s...

  2. 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.

  3. Preparation of porous Al2O3-Ti-C perform by combustion synthesis

    OpenAIRE

    Granat, K.; K. Naplocha

    2009-01-01

    Using combustion synthesis porous ceramic preforms for composite reinforcing were produced. Prepared mixture of alumina Saffilfibres, Ti powder and graphite flakes, after drying were placed in waveguide of microwave reactor. Supplied with constant power of 540Wmagnetron ignited and maintained reaction in flowing stream of CO2 gas. Al2O3 fibres should improve preliminary endurance of perform,whereas Ti powder processed to hard titanium carbides and oxides. During microwave heating ignited plas...

  4. Structure of amorphous Al2O3 produced by ion implantation

    International Nuclear Information System (INIS)

    The amorphous state can be produced in α-Al2O3 by ion beam induced displacements at 77 K or by displacements combined with chemical effects at room temperature. Progress toward understanding the amorphization process has been made from studies of the short-range order, electronic charge on implanted species, and the critical composition for amorphization. Results are presented for implantation of Al + O in the stoichiometric ratio, zirconium, iron, and tin. 10 refs., 6 figs

  5. 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

  6. In-situ RHEED and characterization of ALD Al2O3 gate dielectrics

    OpenAIRE

    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 transistoren met steeds kleinere afmetingen te maken en resulteerde in geïntegreerde circuits zoals de huidige Intel Pentium 4 processor, waarop 178 miljoen transistoren te vinden zijn. Niet alleen de c...

  7. 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.

  8. 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...

  9. 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

  10. Solid state reduction of chromium (VI) pollution for Al2O3-Cr metal ceramics application

    Science.gov (United States)

    Zhu, Hekai; Fang, Minghao; Huang, Zhaohui; Liu, Yangai; Tang, Hao; Min, Xin; Wu, Xiaowen

    2016-04-01

    Reduction of chromium (VI) from Na2CrO4 through aluminothermic reaction and fabrication of metal-ceramic materials from the reduction products have been investigated in this study. Na2CrO4 could be successfully reduced into micrometer-sized Cr particles in a flowing Ar atmosphere in presence of Al powder. The conversion ratio of Na2CrO4 to metallic Cr attained 96.16% efficiency. Al2O3-Cr metal-ceramic with different Cr content (5 wt%, 10 wt%, 15 wt%, 20 wt%) were further prepared from the reduction product Al2O3-Cr composite powder, and aluminum oxide nanopowder via pressure-less sintering. The phase composition, microstructure and mechanical properties of metal-ceramic composites were characterized to ensure the potential of the Al2O3-Cr composite powder to form ceramic materials. The highest relative density and bending strength can reach 93.4% and 205 MP, respectively. The results indicated that aluminothermic reduction of chromium (VI) for metal-ceramics application is a potential approach to remove chromium (VI) pollutant from the environment.

  11. 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.

  12. 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.

  13. Insight into the effects of different ageing protocols on Rh/Al2O3 catalyst

    International Nuclear Information System (INIS)

    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.

  14. 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)

  15. 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.

  16. Tribological Behavior of A356/Al2O3 Surface Nanocomposite Prepared by Friction Stir Processing

    Science.gov (United States)

    Mazaheri, Y.; Karimzadeh, F.; Enayati, M. H.

    2014-04-01

    Surface A356 aluminum alloy matrix composites containing micro and nanosized Al2O3 are prepared by a new approach utilizing high-velocity oxy-fuel spraying and friction stir processing (FSP). Optical and scanning electron microscopy, microhardness, and wear tests were used to characterize the surface composites. Results indicated that, the presence of Al2O3 in matrix can improve the mechanical properties of specimens. The microhardness of surface composites containing micro and nanosized Al2O3 were 89.8 ± 2.6 HV and 109.7 ± 2.5 HV, respectively, which were higher than those for the as-received (79.6 ± 1.1 HV) and the FSPed A356-T6 with no alumina powder (66.8 ± 0.9 HV). Surface composites revealed low friction coefficients and wear rates, which were significantly lower than those obtained for substrate. The wear mass losses of the as-received, the FSPed, and surface micro and nanocomposite specimens after 500-m sliding distance were 50.5, 55.6, 31, and 17.2 mg, respectively. Scanning electron microscopy tests revealed different wear mechanisms on the surface of the wear test specimens.

  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