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Sample records for annealing temperature dependence

  1. Annealing and Test Temperature Dependence of Tensile Properties of UNS N04400 Alloy

    NASA Astrophysics Data System (ADS)

    Afzal, Naveed; Ahmad, R.; Akhtar, Tanveer; Ayub, R.; Ghauri, I. M.

    2013-07-01

    Effects of annealing and test temperatures on the tensile behavior of UNS N04400 alloy have been examined. The specimens were annealed at 800, 1000, and 1200 °C for 4 h under vacuum in a muffle furnace. Stress-strain curves of the specimens were obtained in the temperature range 25-300 °C using a universal testing machine fitted with a thermostatic chamber. The results indicate that the yield strength (YS), ultimate tensile strength (UTS), and percentage elongation of the specimens decrease with increase of annealing temperature. By increasing the test temperature, the YS and UTS decrease, whereas the percentage elongation initially decreases with increase of test temperature from 25 to 100 °C and then increases with further increasing the temperature up to 300 °C. The changes in the tensile properties of the alloy are associated with the post-annealing microstructure and modes of fracture.

  2. Temperature- and roughness- dependent permittivity of annealed/unannealed gold films.

    PubMed

    Shen, Po-Ting; Sivan, Yonatan; Lin, Cheng-Wei; Liu, Hsiang-Lin; Chang, Chih-Wei; Chu, Shi-Wei

    2016-08-22

    Intrinsic absorption and subsequent heat generation have long been issues for metal-based plasmonics. Recently, thermo-plasmonics, which takes the advantage of such a thermal effect, is emerging as an important branch of plasmonics. However, although significant temperature increase is involved, characterization of metal permittivity at different temperatures and corresponding thermo-derivative are lacking. Here we measure gold permittivity from 300K to 570K, which the latter is enough for gold annealing. More than one order difference in thermo-derivative is revealed between annealed and unannealed films, resulting in a large variation of plasmonic properties. In addition, an unusual increase of imaginary permittivity after annealing is found. Both these effects can be attributed to the increased surface roughness incurred by annealing. Our results are valuable for characterizing extensively used unannealed nanoparticles, or annealed nanostructures, as building blocks in future thermo-nano-plasmonic systems. PMID:27557205

  3. Annealing temperature dependency of ZnO thin films memristive behavior

    NASA Astrophysics Data System (ADS)

    Shaari, N. A. A.; Kasim, S. M. M.; Rusop, M.; Herman, S. H.

    2016-07-01

    The work focuses on the effect of different annealing temperature on the ZnO-based memristive device. Zinc oxide was deposited on the ITO substrate by sol-gel spincoating technique. The deposited ZnO thin films were then annealed from 50°C to 450°C in a furnace for 60 minutes each. The electrodes Platinum (Pt) were sputtered by using JEOL JFC-1600 Auto Fine Coater. The thin film thicknesses were measured by Veeco Dektak 150 Surface Profiler. The thickness of the thin film annealed at 350°C is the thinnest, which is 54.78nm and from the electrical characterization it also shown the switching characteristic behavior. The surface morphology and topology to examine the existence of nanoparticles

  4. Temperature dependence and annealing effects of absorption edges for selenium quantum dots formed by ion implantation in silica glass

    SciTech Connect

    Ueda, A.; Wu, M.; Mu, R.

    1998-12-31

    The authors have fabricated Se nanoparticles in silica substrates by ion implantation followed by thermal annealing up to 1000 C, and studied the Se nanoparticle formation by optical absorption spectroscopy, Rutherford backscattering spectrometry, X-ray diffraction, and transmission electron microscopy. The sample with the highest dose (1 {times} 10{sup 17} ions/cm{sup 2}) showed the nanoparticle formation during the ion implantation, while the lower dose samples (1 and 3 {times} 10{sup 16} ions/cm{sup 2}) required thermal treatment to obtain nano-sized particles. The Se nanoparticles in silica were found to be amorphous. After thermal annealing, the particle doses approached the value of bulk after thermal annealing. The temperature dependent absorption spectra were also measured for this system in a temperature range from 15 to 300 K.

  5. Temperature dependence of electrical properties of gallium-nitride bulk single crystals doped with Mg and their evolution with annealing

    SciTech Connect

    Litwin-Staszewska, E.; Suski, T.; Piotrzkowski, R.; Grzegory, I.; Bockowski, M.; Robert, J. L.; Konczewicz, L.; Wasik, D.; Kaminska, E.; Cote, D.

    2001-06-15

    Comprehensive studies of the electrical properties of Mg-doped bulk GaN crystals, grown by high-pressure synthesis, were performed as a function of temperature up to 750{degree}C. Annealing of the samples in nitrogen ambient modifies qualitatively their resistivity values {rho} and the {rho}(T) variation. It was found that our material is characterized by a high concentration of oxygen-related donors and that the charge transport in the studied samples is determined by two types of states, one of shallow character (Mg-related state, E{sub A}{approximately}0.15eV), and the second one much more deep, E{sub 2}{approximately}0.95eV (above the valence band). Depending on the effective concentration of either states, different resistivities {rho} can be observed: lower resistivity ({rho}{lt}10{sup 4}{Omega}cm at ambient temperature) in samples with dominant E{sub A} states and very high resistivity ({rho}{gt}10{sup 6}{Omega}cm at ambient temperature) in samples with dominant E{sub 2} states. For the first type of samples, annealing at T{sub ann}{lt}500{degree}C leads to a decrease of their resistivity and is associated with an increase of the effective concentration of the shallow Mg acceptors. Annealing of both types of samples at temperatures between 600 and 750{degree}C leads to an increase of the deep state concentration. The presence of hydrogen ambient during annealing of the low-resistivity samples strongly influences their properties. The increase of the sample resistivity and an appearance of a local vibrational mode of hydrogen at 3125 cm{minus}1 were observed. These effects can be removed by annealing in hydrogen-free ambient. {copyright} 2001 American Institute of Physics.

  6. Temperature-dependent current-voltage characteristics in thermally annealed ferromagnetic Co/n-GaN Schottky contacts

    NASA Astrophysics Data System (ADS)

    Ejderha, Kadir; Yıldırm, N.; Turut, A.

    2014-11-01

    Co/n-GaN SDs has been prepared by magnetron DC sputtering technique. The Co/n-GaN SDs have annealed at 600 °C after a post-deposition. The diode parameters such as the ideality factor, barrier height and Richardson constant have been determined by thermionic emission (TE) equation within the measurement temperature range 60-320 K by the steps of 20 K in the dark. It has been seen that the parameters depend on the measurement temperature indicating the presence of a lateral inhomogeneity in the Schottky barrier. Therefore, it has been modified the experimental data by the thermionic emission (TE) mechanism with Gaussian distribution of the barrier heights by using Tung's theoretical approach that the Schottky barrier consists of laterally inhomogeneous patches of different barrier heights. Thus, the modified Richardson plot according to Tung's barrier inhomogeneity model [8] has given a Richardson constant of 27.66 A/(cm2 K2).

  7. Annealing temperature and thickness dependencies of structural and magnetic properties of Co2FeAl thin films

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Gabor, M. S.; Zighem, F.; Roussigné, Y.; Faurie, D.; Tiusan, C.

    2016-09-01

    Co2FeAl (CFA) thin films, of various thicknesses (3 nm≤t ≤50 nm ), have been grown by sputtering on (001) MgO single-crystal substrates and annealed at different temperatures (RT≤Ta≤600 ∘C , where RT is the room temperature). The influence of the CFA thickness (t ), as well as ex situ annealing temperature (Ta), on the magnetic and structural properties has been investigated by x-ray diffraction (XRD), vibrating sample magnetometry, and broadband microstrip ferromagnetic resonance (MS-FMR). The XRD revealed an epitaxial growth of the films with the cubic [001] CFA axis normal to the substrate plane and that the chemical order varies from the B 2 phase to the A 2 phase when decreasing t or Ta. The deduced lattice parameters showed an in-plane tetragonal distortion and in-plane and out-plane strains that increase with Ta and 1 /t . For all Ta values, the variation of the effective magnetization, deduced from the fit of MS-FMR measurements, shows two different regimes separated by a critical thickness, which is Ta dependent. It decreases (increases) linearly with the inverse thickness (1 /t ) in the first (second) regime due to the contribution of the magnetoelastic anisotropy to surface (to volume) anisotropy. The observed behavior has been analyzed through a model allowing for the separation of the magnetocrystalline, magnetoelastic, and Néel-type interface anisotropy constants to the surface and the volume anisotropies. Similar behavior has been observed for the effective fourfold anisotropy field which governs the in-plane anisotropy present in all the samples. Finally, the MS-FMR data also allow one to conclude that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with Ta.

  8. The effects of incomplete annealing on the temperature dependence of sheet resistance and gage factor in aluminum and phosphorus implanted silicon on sapphire

    NASA Technical Reports Server (NTRS)

    Pisciotta, B. P.; Gross, C.

    1976-01-01

    Partial annealing of damage to the crystal lattice during ion implantation reduces the temperature coefficient of resistivity of ion-implanted silicon, while facilitating controlled doping. Reliance on this method for temperature compensation of the resistivity and strain-gage factor is discussed. Implantation conditions and annealing conditions are detailed. The gage factor and its temperature variation are not drastically affected by crystal damage for some crystal orientations. A model is proposed to account for the effects of electron damage on the temperature dependence of resistivity and on silicon piezoresistance. The results are applicable to the design of silicon-on-sapphire strain gages with high gage factors.

  9. Post-deposition annealing temperature dependence TiO2-based EGFET pH sensor sensitivity

    NASA Astrophysics Data System (ADS)

    Zulkefle, M. A.; Rahman, R. A.; Yusoff, K. A.; Abdullah, W. F. H.; Rusop, M.; Herman, S. H.

    2016-07-01

    EGFET pH sensor is one type of pH sensor that is used to measure and determine pH of a solution. The sensing membrane of EGFET pH sensor plays vital role in the overall performance of the sensor. This paper studies the effects of different annealing temperature of the TiO2 sensing membranes towards sensitivity of EGFET pH sensor. Sol-gel spin coating was chosen as TiO2 deposition techniques since it is cost-effective and produces thin film with uniform thickness. Deposited TiO2 thin films were then annealed at different annealing temperatures and then were connected to the gate of MOSFET as a part of the EGFET pH sensor structure. The thin films now act as sensing membranes of the EGFET pH sensor and sensitivity of each sensing membrane towards pH was measured. From the results it was determined that sensing membrane annealed at 300 °C gave the highest sensitivity followed by sample annealed at 400 °C and 500 °C.

  10. Temperature Dependence and High-Temperature Stability of the Annealed Ni/Au Ohmic Contact to p-Type GaN in Air

    NASA Astrophysics Data System (ADS)

    Zhao, Shirong; McFavilen, Heather; Wang, Shuo; Ponce, Fernando A.; Arena, Chantal; Goodnick, Stephen; Chowdhury, Srabanti

    2016-04-01

    We report on the temperature-dependent contact resistivity and high-temperature stability of the annealed Ni/Au ohmic contacts to p-type GaN in air. As the measure temperature increases from 25°C to 390°C, both the specific contact resistivity (ρ c) and sheet resistance (R sh) decrease by factors ˜10, contributing to the 10-fold increase in current at 390°C compared with that at 25°C. It was also observed that the ρ c was further reduced by 36%, i.e., from 2.2 × 10-3 Ω cm2 to 1.4 × 10-3 Ω cm2, during the 48-h high-temperature stability test at 450°C in air, showing excellent stability of the contacts. An increase in ρ c was observed after the contacts were subjected to 500°C in air. Higher temperature stress led to a significant increase in ρ c. The contacts show rectifying I-V characteristics after being subjected to 700°C for 1 h. The degradation mechanics were analyzed with the assistance of transmission electron microscopy and energy dispersive x-ray spectroscopy.

  11. Iron phthalocyanine on Cu(111): Coverage-dependent assembly and symmetry breaking, temperature-induced homocoupling, and modification of the adsorbate-surface interaction by annealing

    NASA Astrophysics Data System (ADS)

    Snezhkova, Olesia; Bischoff, Felix; He, Yuanqin; Wiengarten, Alissa; Chaudhary, Shilpi; Johansson, Niclas; Schulte, Karina; Knudsen, Jan; Barth, Johannes V.; Seufert, Knud; Auwärter, Willi; Schnadt, Joachim

    2016-03-01

    We have examined the geometric and electronic structures of iron phthalocyanine assemblies on a Cu(111) surface at different sub- to mono-layer coverages and the changes induced by thermal annealing at temperatures between 250 and 320 °C by scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. The symmetry breaking observed in scanning tunneling microscopy images is found to be coverage dependent and to persist upon annealing. Further, we find that annealing to temperatures between 300 and 320 °C leads to both desorption of iron phthalocyanine molecules from the surface and their agglomeration. We see clear evidence of temperature-induced homocoupling reactions of the iron phthalocyanine molecules following dehydrogenation of their isoindole rings, similar to what has been observed for related tetrapyrroles on transition metal surfaces. Finally, spectroscopy indicates a modified substrate-adsorbate interaction upon annealing with a shortened bond distance. This finding could potentially explain a changed reactivity of Cu-supported iron phthalocyanine in comparison to that of the pristine compound.

  12. High temperature annealing of ion irradiated tungsten

    SciTech Connect

    Ferroni, Francesco; Yi, Xiaoou; Fitzgerald, Steven P.; Edmondson, Philip D.; Roberts, Steve G.

    2015-03-21

    In this study, transmission electron microscopy of high temperature annealing of pure tungsten irradiated by self-ions was conducted to elucidate microstructural and defect evolution in temperature ranges relevant to fusion reactor applications (500–1200°C). Bulk isochronal and isothermal annealing of ion irradiated pure tungsten (2 MeV W+ ions, 500°C, 1014 W+/cm2) with temperatures of 800, 950, 1100 and 1400°C, from 0.5 to 8 h, was followed by ex situ characterization of defect size, number density, Burgers vector and nature. Loops with diameters larger than 2–3 nm were considered for detailed analysis, among which all loops had View the MathML source and were predominantly of interstitial nature. In situ annealing experiments from 300 up to 1200°C were also carried out, including dynamic temperature ramp-ups. These confirmed an acceleration of loop loss above 900°C. At different temperatures within this range, dislocations exhibited behaviour such as initial isolated loop hopping followed by large-scale rearrangements into loop chains, coalescence and finally line–loop interactions and widespread absorption by free-surfaces at increasing temperatures. An activation energy for the annealing of dislocation length was obtained, finding Ea=1.34±0.2 eV for the 700–1100°C range.

  13. High temperature annealing of ion irradiated tungsten

    DOE PAGES

    Ferroni, Francesco; Yi, Xiaoou; Arakawa, Kazuto; Fitzgerald, Steven P.; Edmondson, Philip D.; Roberts, Steve G.

    2015-03-21

    In this study, transmission electron microscopy of high temperature annealing of pure tungsten irradiated by self-ions was conducted to elucidate microstructural and defect evolution in temperature ranges relevant to fusion reactor applications (500–1200°C). Bulk isochronal and isothermal annealing of ion irradiated pure tungsten (2 MeV W+ ions, 500°C, 1014 W+/cm2) with temperatures of 800, 950, 1100 and 1400°C, from 0.5 to 8 h, was followed by ex situ characterization of defect size, number density, Burgers vector and nature. Loops with diameters larger than 2–3 nm were considered for detailed analysis, among which all loops had View the MathML source andmore » were predominantly of interstitial nature. In situ annealing experiments from 300 up to 1200°C were also carried out, including dynamic temperature ramp-ups. These confirmed an acceleration of loop loss above 900°C. At different temperatures within this range, dislocations exhibited behaviour such as initial isolated loop hopping followed by large-scale rearrangements into loop chains, coalescence and finally line–loop interactions and widespread absorption by free-surfaces at increasing temperatures. An activation energy for the annealing of dislocation length was obtained, finding Ea=1.34±0.2 eV for the 700–1100°C range.« less

  14. Dual N/Pb ion-implanted Si: Temperature dependence of the novel shift of the Pb peak under electron beam annealing

    NASA Astrophysics Data System (ADS)

    Markwitz, Andreas; Fang, Fang; Johnson, Peter B.

    2011-03-01

    (1 0 0) Si was dual ion-implanted with 24 keV N and 7 keV Pb to peak concentrations ˜10 at.%. Implanted samples were then electron beam annealed (EBA) at a peak temperature T for 30 s with T ranging from 100 °C to 900 °C and for 15 s at 1000 °C. Pb profiles were measured using RBS and surfaces characterised by AFM. For T up to 500 °C there was no shift in the profile from the implanted depth ˜10 nm. For higher values of T a striking feature was the large movement of the Pb profile away from the surface without a significant change in width or Pb content. The profile depths were: ˜40 nm for 600 °C, ˜68 nm for 700-900 °C and ˜80 nm for 1000 °C. The response to EBA was found to be strongly dependent on both ion implantation order and Si starting structure. For (1 0 0) Si nanowhiskers formed on the treated surfaces for T = 900 °C and 1000 °C. A model is developed based on the restructuring of the amorphous implanted layer under EBA. It is proposed that a compaction starting at the surface sweeps the Pb before it via a stress interaction as it advances into the Si.

  15. Thermal annealing as a method to predict results of high temperature irradiation embrittlement

    NASA Astrophysics Data System (ADS)

    Kryukov, A.; Debarberis, L.; Hähner, P.; Gillemot, F.; Oszvald, F.

    2013-01-01

    In order to assess the validity of post-irradiation annealing as a method to predict results of high temperature irradiation a new analysis of experimental data has been performed revealing the combined influence of annealing temperature and impurities content on residual embrittlement after annealing. For 2CrMoV (WWER-440 reactor pressure vessel) steel with low contents of copper and phosphorus, the comparison of two embrittlement dependencies has been done: on irradiation temperature and post-irradiation annealing temperature. It is demonstrated that data for both the transition temperature shift after irradiation, ΔTk, and the residual transition temperature shift after post-irradiation annealing, ΔTres, fall within the same scatter band. A similarly close correlation is observed by comparison of yield strength increases after irradiation and after post-irradiation annealing.

  16. Thermoelectric properties by high temperature annealing

    NASA Technical Reports Server (NTRS)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Kumar, Shankar (Inventor); Lee, Hohyun (Inventor)

    2009-01-01

    The present invention generally provides methods of improving thermoelectric properties of alloys by subjecting them to one or more high temperature annealing steps, performed at temperatures at which the alloys exhibit a mixed solid/liquid phase, followed by cooling steps. For example, in one aspect, such a method of the invention can include subjecting an alloy sample to a temperature that is sufficiently elevated to cause partial melting of at least some of the grains. The sample can then be cooled so as to solidify the melted grain portions such that each solidified grain portion exhibits an average chemical composition, characterized by a relative concentration of elements forming the alloy, that is different than that of the remainder of the grain.

  17. Annealing dependence of giant magnetoresistance in CuFeNi alloys

    NASA Astrophysics Data System (ADS)

    Martins, C. S.; Missell, F. P.

    2000-05-01

    Giant magnetoresistance (GMR) in granular CuFeNi alloys is comparable in magnitude to that observed in CuCo. Here we study magnetization M and GMR (0annealed Cu80Fe20-xNix (x=0, 2.5, 5, 10, and 15) as a function of annealing temperature Tan<500 °C, using a superconducting quantum interference device (SQUID) magnetometer. A wide variety of granular structures characterized by different average values of the particle sizes is obtained for different Fe/Ni ratios and annealing conditions. For Cu80Fe10Ni10, neither M nor GMR exhibit static hysteresis for T>50 K. At this temperature, the largest GMR value (19%) was obtained for a sample annealed at 400 °C for 2 h. In Cu80Fe5Ni15, on the other hand, the microstructure and magnetic properties of the alloy are much more sensitive to annealing. The magnetoresistence is strongly dependent upon both the annealing and the measuring temperatures. For Fe-rich Cu80Fe20-xNix, the magnetic properties other alloys show a weak dependence upon annealing temperature. Magnetization curves for both as-cast and annealed alloys indicate many large particles which saturate at low magnetic fields. GMR versus alloy composition is presented for two annealing temperatures.

  18. Annealing temperature dependence of local atomic and electronic structure of polycrystalline La0.5Sr0.5MnO3

    NASA Astrophysics Data System (ADS)

    Zhang, Hong-Guang; Li, Yong-Tao; Xie, Liang; Dong, Xue-Guang; Li, Qi

    2015-10-01

    The local atomic and electronic structure of La0.5Sr0.5MnO3 was investigated at different annealing temperatures (TA) by X-ray absorption spectroscopy (XAS) and photoemission spectroscopy (XPS). The extended X-ray absorption fine structure indicates that the MnO6 octahedral distortion is reduced by increasing TA. The chemical shift for the sample with TA = 1350°C measured by XPS of Mn 2p core level demonstrates the increasing of Mn3+ ions content. From the deconvolution of valence band photoemission spectra, the number of eg electron is also proved to increase with increasing TA. It is also demonstrated that there is a strongest hybridization between O 2p and surrounding atomic orbital states in sample with TA = 1350°C, which is consistent with valence band photoemission.

  19. Selective aspect ratio of CNTs based on annealing temperature by TCVD method

    NASA Astrophysics Data System (ADS)

    Yousefi, Amin Termeh; Mahmood, Mohamad Rusop; Ikeda, Shoichiro

    2016-07-01

    Various aspect ratios of CNTs reported based on alteration of annealing temperature using thermal-chemical vapor deposition (TCVD) method. Also the growth dependent and independent parameters of the carbon nanotube (CNTs) array were studied as a function of synthesis method. The FESEM images indicate that the nanotubes are approximately perpendicular to the surface of the silicon substrate and form carbon nanotubes in different aspect ratios according to the applied annealing temperature. Furthermore, due to the optimized results it can be observed that, the mechanism of the CNTs growth is still present in the annealing step as well as deposition process and the most CNTs with crystalline aspect, produced in the annealing temperature, which was optimized at 700 - 900 ˚C. This result demonstrates that the growth rate, mass production, diameter, density, and crystallinity of CNT can be controlled by the annealing temperature.

  20. Correlation between microstructure and temperature dependent electrical behavior of annealed Ti/Al/Ni/Au Ohmic contacts to AlGaN/GaN heterostructures

    SciTech Connect

    Iucolano, Ferdinando; Greco, Giuseppe; Roccaforte, Fabrizio

    2013-11-11

    This letter reports on the temperature behavior of the structural and electrical properties of Ti/Al/Ni/Au contacts to AlGaN/GaN heterostructures. While Ohmic contacts formed at 750 °C showed a decreasing temperature behavior of the specific contact resistance ρ{sub C}, which was explained by a thermionic field emission mechanism, an increasing trend is observed in the contacts formed at 850 °C. In this case, ρ{sub C} exhibits a “metal-like” behavior, i.e., describable by a T{sup 1.8} dependence. The microstructural analysis of the interfacial region allowed to explain the results with the formation of metallic intrusions contacting directly the two dimensional electron gas.

  1. Temperature, stress, and annealing effects on the luminescence from electron-irradiated silicon

    NASA Technical Reports Server (NTRS)

    Jones, C. E.; Johnson, E. S.; Compton, W. D.; Noonan, J. R.; Streetman, B. G.

    1973-01-01

    Low-temperature photoluminescence spectra are presented for Si crystals which have been irradiated with high-energy electrons. Studies of isochronal annealing, stress effects, and the temperature dependences of the luminescence are used to discuss the nature of the luminescent transitions and the properties of defects. Two dominant bands present after room-temperature anneal of irradiated material are discussed, and correlations of the properties of these bands are made with known Si defects. A band between 0.8 and 1.0 eV has properties which are related to those of the divacancy, and a band between 0.6 and 0.8 eV has properties related to those of the Si-G15(K) center. Additional peaks appear in the luminescence after high-temperature anneal; the influence of impurities and the effects of annealing of these lines are discussed.

  2. Low temperature magnetothermoelectric effect and magnetoresistance in Te vapor annealed Bi2Te3.

    PubMed

    Hor, Y S; Qu, D; Ong, N P; Cava, R J

    2010-09-22

    The electrical properties of single crystals of p-type Bi(2)Te(3) are shown to be tuned by annealing as-grown crystals in elemental Te vapor at temperatures in the range of 400-420 °C. While as-grown nominally stoichiometric Bi(2)Te(3) has p-type conductivity below room temperature, Te vapor annealed Bi(2)Te(3) shows a cross over from p- to n-type behavior. The temperature dependent resistivity of the Te annealed crystals shows a characteristic broad peak near 100 K. Applied magnetic fields give rise to a large low temperature magnetothermoelectric effect in the Te annealed samples and enhance the low temperature peak in the resistivity. Further, Te annealed Bi(2)Te(3) shows a large positive magnetoresistance, ∼ 200% at 2 K, and ∼ 15% at room temperature. The annealing procedure described can be employed to optimize the properties of Bi(2)Te(3) for study as a topological insulator.

  3. Radiation damage annealing mechanisms and possible low temperature annealing in silicon solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.

    1980-01-01

    Deep level transient spectroscopy and the Shockley-Read-Hall recombination theory are used to identify the defect responsible for reverse annealing in 2 ohm-cm n+/p silicon solar cells. This defect, with energy level at Ev + 0.30 eV, has been tentatively identified as a boron-oxygen-vacancy complex. It has been also determined by calculation that the removal of this defect could result in significant annealing at temperatures as low as 200 C for 2 ohm-cm and lower resistivity cells.

  4. Effect of annealing temperature on titania nanoparticles

    SciTech Connect

    Manikandan, K. Arumugam, S.; Chandrasekaran, G.

    2014-04-24

    Titania polycrystalline samples are prepared by using sol-gel route hydrolyzing a alkoxide titanium precursor under acidic conditions. The as prepared samples are treated with different calcination temperatures. The anatase phase of titania forms when treated below 600°C, above that temperature the anatase phase tends to transform into the rutile phase of titania. The experimental determination of average grain size, phase formation, lattice parameters and the crystal structures of titania samples at different calcinations is done using X-ray diffraction (XRD). Fourier Transform Infra-red Spectroscopy (FTIR), UV-vis-NIR spectroscopy and Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis X-ray are used to characterize the samples to bring impact on the respective properties.

  5. High temperature annealing studies of strontium ion implanted glassy carbon

    NASA Astrophysics Data System (ADS)

    Odutemowo, O. S.; Malherbe, J. B.; Prinsloo, L.; Langa, D. F.; Wendler, E.

    2016-03-01

    Glassy carbon samples were implanted with 200 keV strontium ions to a fluence of 2 × 1016 ions/cm2 at room temperature. Analysis with Raman spectroscopy showed that ion bombardment amorphises the glassy carbon structure. Partial recovery of the glassy carbon structure was achieved after the implanted sample was vacuum annealed at 900 °C for 1 h. Annealing the strontium ion bombarded sample at 2000 °C for 5 h resulted in recovery of the glassy carbon substrate with the intensity of the D peak becoming lower than that of the pristine glassy carbon. Rutherford backscattering spectroscopy (RBS) showed that the implanted strontium diffused towards the surface of the glassy carbon after annealing the sample at 900 °C. This diffusion was also accompanied by loss of the implanted strontium. Comparison between the as-implanted and 900 °C depth profiles showed that less than 30% of the strontium was retained in the glassy carbon after heat treatment at 900 °C. The RBS profile after annealing at 2000 °C indicated that no strontium ions were retained after heat treatment at this temperature.

  6. Sign change in the tunnel magnetoresistance of Fe{sub 3}O{sub 4}/MgO/Co-Fe-B magnetic tunnel junctions depending on the annealing temperature and the interface treatment

    SciTech Connect

    Marnitz, L. Rott, K.; Niehörster, S.; Klewe, C.; Meier, D.; Fabretti, S.; Thomas, A.; Reiss, G.; Kuschel, T.; Witziok, M.; Krampf, A.; Kuschel, O.; Schemme, T.; Kuepper, K.; Wollschläger, J.

    2015-04-15

    Magnetite (Fe{sub 3}O{sub 4}) is an eligible candidate for magnetic tunnel junctions (MTJs) since it shows a high spin polarization at the Fermi level as well as a high Curie temperature of 585°C. In this study, Fe{sub 3}O{sub 4}/MgO/Co-Fe-B MTJs were manufactured. A sign change in the TMR is observed after annealing the MTJs at temperatures between 200°C and 280°C. Our findings suggest an Mg interdiffusion from the MgO barrier into the Fe{sub 3}O{sub 4} as the reason for the change of the TMR. Additionally, different treatments of the magnetite interface (argon bombardment, annealing at 200°C in oxygen atmosphere) during the preparation of the MTJs have been studied regarding their effect on the performance of the MTJs. A maximum TMR of up to -12% could be observed using both argon bombardment and annealing in oxygen atmosphere, despite exposing the magnetite surface to atmospheric conditions before the deposition of the MgO barrier.

  7. Effective dopant activation via low temperature microwave annealing of ion implanted silicon

    NASA Astrophysics Data System (ADS)

    Zhao, Zhao; David Theodore, N.; Vemuri, Rajitha N. P.; Das, Sayantan; Lu, Wei; Lau, S. S.; Alford, T. L.

    2013-11-01

    Susceptor-assisted microwave annealing enables effective dopant activation, at low temperatures, in ion-implanted Si. Given similar thermal budgets for microwave annealing and rapid thermal annealing (RTA), sheet resistances of microwave annealed Si, with either B+ or P+ implants, are lower than the values obtained using RTA. The fraction of dopants activated is as high as 18% for B+ implants and 64% for P+ implants. Dopant diffusion is imperceptible after microwave annealing, but significant after RTA, for P+ implanted Si samples with the same dopant activation. Microwave annealing achieves such properties using shorter anneal times and lower peak temperatures compared to RTA.

  8. Luminescence characteristics of nanoporous anodic alumina annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Ilin, D. O.; Vokhmintsev, A. S.; Weinstein, I. A.

    2016-09-01

    Anodic aluminum oxide (AAO) membranes with 100 µm thickness were synthesized in oxalic acid solution under constant current density. Grown samples were annealed in 500-1250 °C range for 5 h in air. Average pore diameter was evaluated using quantitative analysis of SEM images and appeared to be within 78-86 nm diapason. It was found there was a broad emission band in the 350-620 nm region of photoluminescence (PL) spectra in amorphous membranes which is attributed to F-type oxygen deficient centers or oxalic ions. It was shown that intensive red emission caused by Cr3+ (696 nm) and Mn4+ (680 nm) impurities dominates in PL of AAO samples with crystalline α- and δ-phases after annealing at 1100-1250 °C temperatures.

  9. Surface self-diffusion of silicon during high temperature annealing

    NASA Astrophysics Data System (ADS)

    Acosta-Alba, Pablo E.; Kononchuk, Oleg; Gourdel, Christophe; Claverie, Alain

    2014-04-01

    The atomic-scale mechanisms driving thermally activated self-diffusion on silicon surfaces are investigated by atomic force microscopy. The evolution of surface topography is quantified over a large spatial bandwidth by means of the Power Spectral Density functions. We propose a parametric model, based on the Mullins-Herring (M-H) diffusion equation, to describe the evolution of the surface topography of silicon during thermal annealing. Usually, a stochastic term is introduced into the M-H model in order to describe intrinsic random fluctuations of the system. In this work, we add two stochastic terms describing the surface thermal fluctuations and the oxidation-evaporation phenomenon. Using this extended model, surface evolution during thermal annealing in reducing atmosphere can be predicted for temperatures above the roughening transition. A very good agreement between experimental and theoretical data describing roughness evolution and self-diffusion phenomenon is obtained. The physical origin and time-evolution of these stochastic terms are discussed. Finally, using this model, we explore the limitations of the smoothening of the silicon surfaces by rapid thermal annealing.

  10. Surface self-diffusion of silicon during high temperature annealing

    SciTech Connect

    Acosta-Alba, Pablo E.; Kononchuk, Oleg; Gourdel, Christophe; Claverie, Alain

    2014-04-07

    The atomic-scale mechanisms driving thermally activated self-diffusion on silicon surfaces are investigated by atomic force microscopy. The evolution of surface topography is quantified over a large spatial bandwidth by means of the Power Spectral Density functions. We propose a parametric model, based on the Mullins-Herring (M-H) diffusion equation, to describe the evolution of the surface topography of silicon during thermal annealing. Usually, a stochastic term is introduced into the M-H model in order to describe intrinsic random fluctuations of the system. In this work, we add two stochastic terms describing the surface thermal fluctuations and the oxidation-evaporation phenomenon. Using this extended model, surface evolution during thermal annealing in reducing atmosphere can be predicted for temperatures above the roughening transition. A very good agreement between experimental and theoretical data describing roughness evolution and self-diffusion phenomenon is obtained. The physical origin and time-evolution of these stochastic terms are discussed. Finally, using this model, we explore the limitations of the smoothening of the silicon surfaces by rapid thermal annealing.

  11. Power change in amorphous silicon technology by low temperature annealing

    NASA Astrophysics Data System (ADS)

    Mittal, Ankit; Rennhofer, Marcus; Dangel, Angelika; Duman, Bogdan; Schlosser, Victor

    2015-07-01

    Amorphous silicon (a-Si) is one of the best established thin-film solar-cell technologies. Despite its long history of research, it still has many critical issues because of its defect rich material and its susceptibility to degrade under light also called as Staebler-Wronski effect (SWE). This leads to an increase in the defect density of a-Si, but as a metastable effect it can be completely healed at temperatures above 170 °C. Our study is focused on investigating the behavior of annealing of different a-Si modules under low temperature conditions below 80 °C indicated by successive change of module power. These conditions reflect the environmental temperature impact of the modules in the field, or integrated in buildings as well. The power changes were followed by STC power rating and investigation of module-power evolution under low irradiance conditions at 50 W/m2. Our samples were recovered close to their initial state of power, reaching as high as 99% from its degraded value. This shows the influence of low temperature annealing and light on metastable module behavior in a-Si thin-film modules.

  12. Structural transformation of implanted diamond layers during high temperature annealing

    NASA Astrophysics Data System (ADS)

    Rubanov, S.; Fairchild, B. A.; Suvorova, A.; Olivero, P.; Prawer, S.

    2015-12-01

    In the recent years graphitization of ion-beam induced amorphous layers became the basic tool for device fabrication in diamond. The etchable graphitic layers can be removed to form free-standing membranes into which the desired structures can be sculpted using FIB milling. The optical properties of the devices fabricated using this method are assumed on the model of sharp diamond-air interface. The real quality of this interface could depend on degree of graphitization of the amorphous damage layers after annealing. In the present work the graphitization process was studied using conventional and analytical TEM. It was found that annealing at 550 °C results in a partial graphitization of the implanted volume with formation of the nano-crystalline graphitic phase sandwiched between layers of tetrahedral amorphous carbon. Annealing at 1400 °C resulted in complete graphitization of the amorphous layers. The average size of graphite nano-crystals did not exceed 5 nm with predominant orientation of c-planes normal to the sample surface.

  13. The Giant Magnetostriction of [Fe/Tb/Fe/Dy]n Multilayer Films Under Different Annealing Temperature

    NASA Astrophysics Data System (ADS)

    Li, X. D.; Zhao, Z. J.; Feng, T.; Pan, L. K.; Huang, S. M.; Chen, Y. W.; Sun, Z.

    The effect of annealing temperature on the magnetic and giant magnetostriction (GMS) of [Fe/Tb/Fe/Dy]n multilayer films were investigated. X-ray diffraction showed that the multilayer films' microstructures were still in amorphous at annealing temperature 300°C. The multilayer films began to crystalline at annealing temperature 400°C. The saturation magnetization of multilayer films increased by the increasing annealed temperature. The coercivity first decreased at annealing temperature 300°C and then increased when the annealing temperature was higher than 400°C. The multilayer films had good low-field GMS, and the magnetostriction of the multilayer films increased by the increasing annealing temperature.

  14. Photoluminescence of new Tb3+-intercalated octosilicates depending on phase transition caused by annealing

    NASA Astrophysics Data System (ADS)

    Chen, Yufeng; Yan, Yudong; Bao, Yao; Zou, Yan

    2016-08-01

    A new Tb3+-intercalated layered octosilicate (Tb-Oct) was prepared through protonation, exfoliation and intercalation processing. Photoluminescence of the Tb-Oct silicates dependant of phase transition has been investigated in detail. The emissions attributed to 5D4-7FJ (J = 3, 4, 5, 6) transition of Tb3+were observed from the emission spectra of the as-prepared Tb-Oct silicates. After the as-prepared Tb-Oct silicates thermal treatment at 200 °C, all diffraction peaks disappeared, suggesting the collapse of layered structure. With the increase in the annealing temperature from 200 to 1000 °C, no diffraction peaks appeared in all the annealed samples. Photoluminescence spectra show that the green emission ascribed to 5D4-7F5 transition of Tb3+ markedly increased as the sample was annealed at 800 °C. However, this green emission disappeared while the sample was annealed at 400, 600, and 1000 °C, which may relate to actual surroundings of Tb3+ ions. That is, the amorphous phase formed at 800 °C is more favorable for the green emission of Tb3+.

  15. Post-deposition annealing of praseodymia films on Si(111) at low temperatures

    NASA Astrophysics Data System (ADS)

    Gevers, S.; Weisemoeller, T.; Bruns, D.; Giussani, A.; Schroeder, T.; Wollschläger, J.

    2011-03-01

    Thin heteroepitaxial praseodymia films with fluorite structure on Si(111) were annealed under ultra-high vacuum conditions at temperatures in the region of 100 up to 300 °C. Afterward investigations by x-ray diffraction, grazing incidence x-ray diffraction and x-ray reflectometry were performed to obtain information about structural changes of the film during the annealing process. For this reason, praseodymia Bragg peaks were carefully analyzed within the kinematic diffraction theory. This analysis demonstrates the coexistence of different praseodymia phases depending on the conditions of preparation. Here, annealing of the samples up to 150 °C leads to a homogeneous film with a PrO1.833 phase and with negligible strain since both the lateral and vertical lattice parameters nearly match the corresponding bulk praseodymia phase. Further annealing leads to oxygen loss accompanied by significantly increased lattice parameters. Since the lateral lattice parameter is pinned at the interface, the vertical lattice constant has to increase considerably due to the tetragonal distortion of the film. This causes the decomposition of the film into two oxide species with significantly different oxygen contents. Annealing at 300 °C reduces the film almost completely to PrO1.5 which has the minimum content of oxygen.

  16. Ferromagnetism in Semiconductor C-Ni Films at Different Annealing Temperature

    NASA Astrophysics Data System (ADS)

    Dalouji, Vali; Elahi, Smohammad

    2016-02-01

    In this work, the microstructure and magnetic properties of carbon-nickel (C-Ni) composite films annealed at different temperatures (300-1000∘C) were investigated. The films were grown by radio frequency magnetron sputtering on quartz substrates at room temperature. The nickel concentration in the films are affected by changing of the value of evaporation nickel atoms and measured by Rutherford backscattering spectroscopy (RBS). Values of coercive field were measured under both increasing and decreasing applied magnetic field. It is shown that the coercive field of films strongly dependent on the annealing temperature and at 500∘C films has maximum value of 93.67Oe. The difference in the coercive fields increased for films annealed from 300 to 500∘C and then decreased from 500 to 1000∘C. The ID/IG ratio of Raman spectra would indicate the presence of higher sp2 bonded carbon in the films annealed at 800∘C.

  17. The effect of annealing temperature on the electrical characterization of Co/n type GaP Schottky diode

    SciTech Connect

    Orak, İ.; Ejderha, K.; Sönmez, E.; Alanyalıoğlu, M.; Turut, A.

    2015-01-15

    The Co/n-GaP nano-Schottky diodes have been fabricated to investigate effect of annealing temperature on the characteristics of the device. DC Magnetron sputtering technique has been used for Co metallic contact. The samples have been annealed for three minutes at 400 °C and 600 °C. XRD analyzes of the devices subjected to thermal annealing process have been investigated. Surface images have been taken with atomic force microscopy (AFM) in order to examine the morphology of the surface of the metal layer before and after the annealing the sample. The current–voltage (I–V) measurements taken at room temperature have shown that the ideality factor and series resistance decrease with the increasing annealing temperature. The ideality factor was found to be 1.02 for sample annealed at 400 °C. Before and after annealing, depending on the temperature measurement, the capacitance–frequency (C–f), and conductance–frequency (G–f) have been measured, and graphs have been plotted.

  18. Composition dependent thermal annealing behaviour of ion tracks in apatite

    NASA Astrophysics Data System (ADS)

    Nadzri, A.; Schauries, D.; Mota-Santiago, P.; Muradoglu, S.; Trautmann, C.; Gleadow, A. J. W.; Hawley, A.; Kluth, P.

    2016-07-01

    Natural apatite samples with different F/Cl content from a variety of geological locations (Durango, Mexico; Mud Tank, Australia; and Snarum, Norway) were irradiated with swift heavy ions to simulate fission tracks. The annealing kinetics of the resulting ion tracks was investigated using synchrotron-based small-angle X-ray scattering (SAXS) combined with ex situ annealing. The activation energies for track recrystallization were extracted and consistent with previous studies using track-etching, tracks in the chlorine-rich Snarum apatite are more resistant to annealing than in the other compositions.

  19. Low-temperature electron irradiation and annealing in pure magnesium

    SciTech Connect

    Simester, J.H.

    1982-01-01

    In this study of magnesium after 1.0 MeV electron irradiations at 1.55/sup 0/K, it has been observed that the damage production rate in Mg is (3.57 +- 0.03) x 10/sup -26/ ..cap omega..cm/(e/sup -/ cm/sup 2/). There is no evidence for thermal annealing up to 4/sup 0/K. The low temperature recovery in magnesium is found to consist of two broad substages between 4 to 14/sup 0/K, both of which exhibit evidence for correlated and uncorrelated recovery processes. The two substages are found to have very different frequency factors for annealing, and there is evidence that the recovery processes in the second substage are influenced by those in the first. A model for recovery is proposed using the split configuration in the plane which explains the first substage as being due to interstitial migration in the basal plane and the second to migration perpendicular to the plane.

  20. Magnetic properties of hexagonal barium ferrite films on Pt/MgO(111) substrates annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Han, Mangui; Zheng, Liang; Deng, Jiangxia; Zheng, Peng; Wu, Qiong; Deng, Longjiang; Qin, Huibin

    2016-09-01

    In this work, hexagonal barium ferrite thin films have been deposited on Pt/MgO(111) substrates by pulsed laser deposition. The anneal temperature dependence of crystal structures, extents of diffusion and magnetic properties have been studied. X-ray diffraction patterns reveal that the crystal structure changes from the hexagonal to the spinel when the anneal temperature increases. The texture with c-axis perpendicular to the film plane and the small c-axis dispersion angles (△ɵc) have been obtained in the film annealed at 950 °C for 10 h. Both the X-ray photoelectron spectroscopy profiles and energy dispersive spectrometer show that the diffusions of Mg2+and Fe3+cations are more obvious when the annealing temperature is higher than 950 °C. The film annealed at 950 °C show anisotropic and hard magnetic properties. The magnetic properties of film annealed at 1050 °C are soft. In order to study the cation diffusions between thin film and substrate, the concentration profiles of cations (Ba2+, Fe3+, Mg2+) have been measured by XPS for a thin film with a thickness of 130 nm annealed at 950°C and 1050°C, as shown in Fig. 3. When Ta is 950°C, as shown in Fig. 3(a), diffusions between the film and the substrate are scarcely detected. However, obvious inter-diffusions have been found for Mg2+ cation and Fe3+ cation when it is annealed at 1050°C. An obvious diffusion has not been found for Ba2+ cation at both annealing temperatures.

  1. Coupled annealing temperature and layer thickness effect on strengthening mechanisms of Ti/Ni multilayer thin films

    NASA Astrophysics Data System (ADS)

    Yang, Zhou; Wang, Junlan

    2016-03-01

    A systematic study was performed on mechanical and microstructural properties of Ti/Ni multilayers with layer thickness from 200 nm to 6 nm and annealing temperature from room temperature to 500 °C. Based on the observed hardness evolution, a coupled layer-thickness and annealing-temperature dependent strengthening mechanism map is proposed. For as-deposited films, the deformation behavior follows the traditional trend of dislocation mediated strengthening to grain boundary mediated softening with decreasing layer thickness. For annealed films, grain boundary relaxation is considered to be the initial strengthening mechanism with higher activation temperature required for thicker layers. Under further annealing, solid solution hardening, intermetallic precipitation hardening, and fully intermixed alloy structure continue to strengthen the thin layered films, while recrystallization and grain-growth lead to the eventual softening of thick layered films. For the films with intermediate layer thickness, a strong orientation dependent hardness behavior is exhibited under high temperature annealing due to mechanism switch from grain growth softening to intermetallic precipitation hardening when changing the loading orientation from perpendicular to parallel to the layer interfaces.

  2. Influence of Annealing Temperature on CZTS Thin Film Surface Properties

    NASA Astrophysics Data System (ADS)

    Feng, Wenmei; Han, Junfeng; Ge, Jun; Peng, Xianglin; Liu, Yunong; Jian, Yu; Yuan, Lin; Xiong, Xiaolu; Cha, Limei; Liao, Cheng

    2016-08-01

    In this work, copper zinc tin sulfide (CZTS) films were deposited by direct current sputtering and the samples were annealed in different oven-set temperatures and atmosphere (Ar and H2S). The surface evolution was investigated carefully by using scanning electron microscopy (SEM), Raman spectroscopy and x-ray photoelectron spectroscopy. The surface of the as-sputtered precursor contained little Cu and large amounts of Zn and Sn. The metallic precursor was continuous and compact without pinholes or cracks. With the increase of the temperature from room temperature to 250°C, Cu atoms diffused to the film surface to form Cu1-x S and covered other compounds. Some small platelets were smaller than 500 nm spreading randomly in the holes of the film surfaces. When the temperature reached 350°C, Zn and Sn atoms began to diffuse to the surface and react with S or Cu1-x S. At 400°C, SEM showed the melting of large particles and small particles with a size from 100 nm to 200 nm in the background of the film surface. Excess Zn segregated towards the surface regions and formed ZnS phase on the surface. In addition, the signal of sodium in the CZTS surface was observed above 400°C. At 600°C, a large amount of regular structures with clear edges and corners were observed in the film surface in SEM images. A clear recrystallized process on the surface was assumed from those observations.

  3. Lateral Temperature-Gradient Method for High-Throughput Characterization of Material Processing by Millisecond Laser Annealing.

    PubMed

    Bell, Robert T; Jacobs, Alan G; Sorg, Victoria C; Jung, Byungki; Hill, Megan O; Treml, Benjamin E; Thompson, Michael O

    2016-09-12

    A high-throughput method for characterizing the temperature dependence of material properties following microsecond to millisecond thermal annealing, exploiting the temperature gradients created by a lateral gradient laser spike anneal (lgLSA), is presented. Laser scans generate spatial thermal gradients of up to 5 °C/μm with peak temperatures ranging from ambient to in excess of 1400 °C, limited only by laser power and materials thermal limits. Discrete spatial property measurements across the temperature gradient are then equivalent to independent measurements after varying temperature anneals. Accurate temperature calibrations, essential to quantitative analysis, are critical and methods for both peak temperature and spatial/temporal temperature profile characterization are presented. These include absolute temperature calibrations based on melting and thermal decomposition, and time-resolved profiles measured using platinum thermistors. A variety of spatially resolved measurement probes, ranging from point-like continuous profiling to large area sampling, are discussed. Examples from annealing of III-V semiconductors, CdSe quantum dots, low-κ dielectrics, and block copolymers are included to demonstrate the flexibility, high throughput, and precision of this technique. PMID:27385487

  4. Effects of annealing temperature on the properties of Ga-doped In2O3 Thin Films

    NASA Astrophysics Data System (ADS)

    Cho, Shinho

    2015-10-01

    Ga-doped In2O3 (GIO) thin films were deposited on glass substrates at a growth temperature of 300 °C by using radio-frequency magnetron sputtering. The deposited films were then subjected to rapid thermal annealing (RTA) at various temperatures. The annealed films were characterized by using X-ray diffraction (XRD), ultraviolet-visible spectrophotometry, scanning electron microscopy, and Hall-effect measurements. The optical bandgap, electrical resistivity, and figure of merit of the GIO thin films were found to depend significantly on the RTA temperature. The XRD patterns of the films indicated that all the films had a body-centered cubic structure, with the primary peak being the (222) diffraction peak. The average optical transmittance of the GIO thin films for wavelengths of 500 - 1100 nm increased from 44.5% before annealing to 87.2% after annealing at 450 °C; the figure of merit was also the highest after annealing at this temperature. These results indicate that the properties of GIO thin films can be varied by controlling the RTA temperature.

  5. Thermal annealing of radiation damage in CMOS ICs in the temperature range -140 C to +375 C

    NASA Technical Reports Server (NTRS)

    Danchenko, V.; Fang, P. H.; Brashears, S. S.

    1982-01-01

    Annealing of radiation damage was investigated in the commercial, Z- and J-processes of the RCA CD4007A ICs in the temperature range from -140 C to +375 C. Tempering curves were analyzed for activation energies of thermal annealing, following irradiation at -140 C. It was found that at -140 C, the radiation-induced shifts in the threshold potentials were similar for all three processes. The radiation hardness of the Z- and J-process is primarily due to rapid annealing of radiation damage at room temperature. In the region -140 to 20 C, no dopant-dependent charge trapping is seen, similar to that observed at higher temperatures. In the unbiased Z-process n-channels, after 1 MeV electron irradiation, considerable negative charge remains in the gate oxide.

  6. Structure and stress studies of low temperature annealed W/Si multilayers for the X-ray telescope.

    PubMed

    Huang, Qiushi; Zhang, Jinshuai; Qi, Runze; Yang, Yang; Wang, Fengli; Zhu, Jie; Zhang, Zhong; Wang, Zhanshan

    2016-07-11

    Low stress W/Si multilayer mirrors are demanded in the hard X-ray telescopes to achieve the high angular resolution. To reduce the stress of the as-deposited multilayer and maintain a high reflectivity, two groups of low-temperature annealing experiments were performed on the periodic multilayers with a d-spacing of ~3.8 nm. The temperature-dependent experiments show that the 150 °C annealing can slightly increase the reflectivity while the stress reduced only by 24%. Higher temperature annealing induced a larger reduction of the stress and the multilayer reached an almost zero stress state at 250 °C. The stress relaxation was accompanied by a small drop of reflectivity of ≤5% and a period compaction of <0.02 nm. The time-dependent experiments indicate that most of the stress changes occurred within the first 10 minutes while a prolonged annealing is not useful. The X-ray scattering and transmission electron microscopy were further used to study the microstructure changes of the multilayers. It is found that the W/Si multilayer exhibits an amorphous structure before and after annealing, while an enhanced diffusion and intermixing is the main reason for the stress relaxation and structure changes. PMID:27410835

  7. Structure and stress studies of low temperature annealed W/Si multilayers for the X-ray telescope.

    PubMed

    Huang, Qiushi; Zhang, Jinshuai; Qi, Runze; Yang, Yang; Wang, Fengli; Zhu, Jie; Zhang, Zhong; Wang, Zhanshan

    2016-07-11

    Low stress W/Si multilayer mirrors are demanded in the hard X-ray telescopes to achieve the high angular resolution. To reduce the stress of the as-deposited multilayer and maintain a high reflectivity, two groups of low-temperature annealing experiments were performed on the periodic multilayers with a d-spacing of ~3.8 nm. The temperature-dependent experiments show that the 150 °C annealing can slightly increase the reflectivity while the stress reduced only by 24%. Higher temperature annealing induced a larger reduction of the stress and the multilayer reached an almost zero stress state at 250 °C. The stress relaxation was accompanied by a small drop of reflectivity of ≤5% and a period compaction of <0.02 nm. The time-dependent experiments indicate that most of the stress changes occurred within the first 10 minutes while a prolonged annealing is not useful. The X-ray scattering and transmission electron microscopy were further used to study the microstructure changes of the multilayers. It is found that the W/Si multilayer exhibits an amorphous structure before and after annealing, while an enhanced diffusion and intermixing is the main reason for the stress relaxation and structure changes.

  8. Estimation of effective temperatures in a quantum annealer: Towards deep learning applications

    NASA Astrophysics Data System (ADS)

    Realpe-Gómez, John; Benedetti, Marcello; Perdomo-Ortiz, Alejandro

    Sampling is at the core of deep learning and more general machine learning applications; an increase in its efficiency would have a significant impact across several domains. Recently, quantum annealers have been proposed as a potential candidate to speed up these tasks, but several limitations still bar them from being used effectively. One of the main limitations, and the focus of this work, is that using the device's experimentally accessible temperature as a reference for sampling purposes leads to very poor correlation with the Boltzmann distribution it is programmed to sample from. Based on quantum dynamical arguments, one can expect that if the device indeed happens to be sampling from a Boltzmann-like distribution, it will correspond to one with an instance-dependent effective temperature. Unless this unknown temperature can be unveiled, it might not be possible to effectively use a quantum annealer for Boltzmann sampling processes. In this work, we propose a strategy to overcome this challenge with a simple effective-temperature estimation algorithm. We provide a systematic study assessing the impact of the effective temperatures in the quantum-assisted training of Boltzmann machines, which can serve as a building block for deep learning architectures. This work was supported by NASA Ames Research Center.

  9. Implantation activation annealing of Si-implanted gallium nitride at temperatures > 1,100 C

    SciTech Connect

    Zolper, J.C.; Han, J.; Biefeld, R.M.

    1997-06-01

    The activation annealing of Si-implanted GaN is reported for temperatures from 1,100 to 1,400 C. Although previous work has shown that Si-implanted GaN can be activated by a rapid thermal annealing at {approximately}1,100 C, it was also shown that significant damage remained in the crystal. Therefore, both AlN-encapsulated and uncapped Si-implanted GaN samples were annealed in a metal organic chemical vapor deposition system in a N{sub 2}/NH{sub 3} ambient to further assess the annealing process. Electrical Hall characterization shows increases in carrier density and mobility for annealing up to 1,300 C before degrading at 1,400 C due to decomposition of the GaN epilayer. Rutherford backscattering spectra show that the high annealing temperatures reduce the implantation induced damage profile but do not completely restore the as-grown crystallinity.

  10. Effect of Solution Annealing Temperatures on the Crevice Corrosion Mode of Alloy 22

    SciTech Connect

    El-Dasher, B S; Etien, R; Torres, S G

    2005-10-31

    The effect of solution annealing temperature on the observed corrosion attack mode in Alloy 22 welds was assessed. Three types of specimens were examined, including the as-welded state, solution annealed for 20 minutes at 1121 C, and solution annealed for 20 minutes at 1200 C. The microstructures of the specimens were first mapped using electron backscatter diffraction to determine the grain structure evolution due to solution annealing. The specimens were then subjected to electrochemical testing in a 6 molal NaCl + 0.9 molal KNO{sub 3} environment to initiate crevice corrosion. Examination of the specimen surfaces after corrosion testing showed that in the as-welded specimen, corrosion was present in both the weld dendrites as well as around the secondary phases. However, the specimen solution annealed at 1121 C showed corrosion only at secondary phases and the specimen annealed at 1200 C showed pitting corrosion only in a handful of grains.

  11. Temperature Driven Annealing of Perforations in Bicellar Model Membranes

    SciTech Connect

    Nieh, Mu-Ping; Raghunathan, V.A.; Pabst, Georg; Harroun, Thad; Nagashima, K; Morales, H; Katsaras, John; Macdonald, P

    2011-01-01

    Bicellar model membranes composed of 1,2-dimyristoylphosphatidylcholine (DMPC) and 1,2-dihexanoylphosphatidylcholine (DHPC), with a DMPC/DHPC molar ratio of 5, and doped with the negatively charged lipid 1,2-dimyristoylphosphatidylglycerol (DMPG), at DMPG/DMPC molar ratios of 0.02 or 0.1, were examined using small angle neutron scattering (SANS), {sup 31}P NMR, and {sup 1}H pulsed field gradient (PFG) diffusion NMR with the goal of understanding temperature effects on the DHPC-dependent perforations in these self-assembled membrane mimetics. Over the temperature range studied via SANS (300-330 K), these bicellar lipid mixtures exhibited a well-ordered lamellar phase. The interlamellar spacing d increased with increasing temperature, in direct contrast to the decrease in d observed upon increasing temperature with otherwise identical lipid mixtures lacking DHPC. {sup 31}P NMR measurements on magnetically aligned bicellar mixtures of identical composition indicated a progressive migration of DHPC from regions of high curvature into planar regions with increasing temperature, and in accord with the 'mixed bicelle model' (Triba, M. N.; Warschawski, D. E.; Devaux, P. E. Biophys. J.2005, 88, 1887-1901). Parallel PFG diffusion NMR measurements of transbilayer water diffusion, where the observed diffusion is dependent on the fractional surface area of lamellar perforations, showed that transbilayer water diffusion decreased with increasing temperature. A model is proposed consistent with the SANS, {sup 31}P NMR, and PFG diffusion NMR data, wherein increasing temperature drives the progressive migration of DHPC out of high-curvature regions, consequently decreasing the fractional volume of lamellar perforations, so that water occupying these perforations redistributes into the interlamellar volume, thereby increasing the interlamellar spacing.

  12. Arsenic ambient conditions preventing surface degradation of GaAs during capless annealing at high temperatures

    NASA Technical Reports Server (NTRS)

    Kang, C. H.; Kondo, K.; Lagowski, J.; Gatos, H. C.

    1987-01-01

    Changes in surface morphology and composition caused by capless annealing of GaAs were studied as a function of annealing temperature, T(GaAs), and the ambient arsenic pressure controlled by the temperature, T(As), of an arsenic source in the annealing ampul. It was established that any degradation of the GaAs surface morphology could be completely prevented, providing that T(As) was more than about 0.315T(GaAs) + 227 C. This empirical relationship is valid up to the melting point temperature of GaAs (1238 C), and it may be useful in some device-processing steps.

  13. Effect of annealing temperature on PL spectrum and surface morphology of zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Zendehnam, A.; Mirzaee, M.; Miri, S.

    2013-04-01

    Zinc oxide (ZnO) thin films were produced by thermal oxidation of Zn layers (200 nm thickness) which were coated on Si (1 0 0) substrate by DC magnetron sputtering. In order to study the effect of annealing temperature on photoluminescence (PL) properties and the surface morphology of the ZnO samples, the annealing temperature range of 500-700 °C was employed. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) for investigation of surface morphology of the ZnO samples were carried out. The surface statistical characteristics of these ZnO thin films are then evaluated against data which outcome from AFM. SEM and AFM results indicated that the annealing temperature produces larger grains and rough surfaces at higher temperatures. The results of PL spectra represent an increase in interstitial zinc with increasing annealing temperature.

  14. Temperature dependent BRDF facility

    NASA Astrophysics Data System (ADS)

    Airola, Marc B.; Brown, Andrea M.; Hahn, Daniel V.; Thomas, Michael E.; Congdon, Elizabeth A.; Mehoke, Douglas S.

    2014-09-01

    Applications involving space based instrumentation and aerodynamically heated surfaces often require knowledge of the bi-directional reflectance distribution function (BRDF) of an exposed surface at high temperature. Addressing this need, the Johns Hopkins University Applied Physics Laboratory (JHU/APL) developed a BRDF facility that features a multiple-port vacuum chamber, multiple laser sources covering the spectral range from the longwave infrared to the ultraviolet, imaging pyrometry and laser heated samples. Laser heating eliminates stray light that would otherwise be seen from a furnace and requires minimal sample support structure, allowing low thermal conduction loss to be obtained, which is especially important at high temperatures. The goal is to measure the BRDF of ceramic-coated surfaces at temperatures in excess of 1000°C in a low background environment. Most ceramic samples are near blackbody in the longwave infrared, thus pyrometry using a LWIR camera can be very effective and accurate.

  15. High temperature annealing of fission tracks in fluorapatite, Santa Fe Springs oil field, Los Angeles Basin, California

    USGS Publications Warehouse

    Naeser, Nancy D.; Crowley, Kevin D.; McCulloh, Thane H.; Reaves, Chris M.; ,

    1990-01-01

    Annealing of fission tracks is a kinetic process dependent primarily on temperature and to a laser extent on time. Several kinetic models of apatite annealing have been proposed. The predictive capabilities of these models for long-term geologic annealing have been limited to qualitative or semiquantitative at best, because of uncertainties associated with (1) the extrapolation of laboratory observations to geologic conditions, (2) the thermal histories of field samples, and (3) to some extent, the effect of apatite composition on reported annealing temperatures. Thermal history in the Santa Fe Springs oil field, Los Angeles Basin, California, is constrained by an exceptionally well known burial history and present-day temperature gradient. Sediment burial histories are continuous and tightly constrained from about 9 Ma to present, with an important tie at 3.4 Ma. No surface erosion and virtually no uplift were recorded during or since deposition of these sediments, so the burial history is simple and uniquely defined. Temperature gradient (???40??C km-1) is well established from oil-field operations. Fission-track data from the Santa Fe Springs area should thus provide one critical field test of kinetic annealing models for apatite. Fission-track analysis has been performed on apatites from sandstones of Pliocene to Miocene age from a deep drill hole at Santa Fe Springs. Apatite composition, determined by electron microprobe, is fluorapatite [average composition (F1.78Cl0.01OH0.21)] with very low chlorine content [less than Durango apatite; sample means range from 0.0 to 0.04 Cl atoms, calculated on the basis of 26(O, F, Cl, OH)], suggesting that the apatite is not unusually resistant to annealing. Fission tracks are preserved in these apatites at exceptionally high present-day temperatures. Track loss is not complete until temperatures reach the extreme of 167-178??C (at 3795-4090 m depth). The temperature-time annealing relationships indicated by the new data

  16. Annealing temperature influence on the degree of inhomogeneity of the Schottky barrier in Ti/4H—SiC contacts

    NASA Astrophysics Data System (ADS)

    Han, Lin-Chao; Shen, Hua-Jun; Liu, Ke-An; Wang, Yi-Yu; Tang, Yi-Dan; Bai, Yun; Xu, Heng-Yu; Wu, Yu-Dong; Liu, Xin-Yu

    2014-12-01

    Tung's model was used to analyze anomalies observed in Ti/SiC Schottky contacts. The degree of the inhomogeneous Schottky barrier after annealing at different temperatures is characterized by the ‘T0 anomaly’ and the difference (△Φ) between the uniformly high barrier height (ΦB0) and the effective barrier height (ΦBeff). Those two parameters of Ti Schottky contacts on 4H—SiC were deduced from I-V measurements in the temperature range of 298 K-503 K. The increase in Schottky barrier (SB) height (ΦB) and decrease in the ideality factor (n) with an increase measurement temperature indicate the presence of an inhomogeneous SB. The degree of inhomogeneity of the Schottky barrier depends on the annealing temperature, and it is at its lowest for 500-°C thermal treatment. The degree of inhomogeneity of the SB could reveal effects of thermal treatments on Schottky contacts in other aspects.

  17. Temperature-dependent μ-Raman investigation of struvite crystals

    NASA Astrophysics Data System (ADS)

    Prywer, Jolanta; Kasprowicz, D.; Runka, T.

    2016-04-01

    The effect of temperature on the vibrational properties of struvite crystals grown from silica gels was systematically studied by μ-Raman spectroscopy. The time-dependent Raman spectra recorded in the process of long time annealing of struvite crystal at 353 K do not indicate structural changes in the struvite crystal with the time of annealing. The temperature-dependent Raman spectra recorded in the range 298-423 K reveal a phase transition in struvite at about 368 K. Above this characteristic temperature, some of bands assigned to vibrations of the PO4 and NH4 tetrahedra and water molecules observed in the Raman spectra in low temperatures (orthorhombic phase) change their spectral parameters or disappear, which indicates a transition to a higher symmetry structure of struvite in the range of high temperatures.

  18. Effect of annealing temperature on the microstructure and optical-electrical properties of Cu-Al-O thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Y. J.; Liu, Z. T.; Zang, D. Y.; Che, X. S.; Feng, L. P.; Bai, X. X.

    2013-12-01

    We have successfully prepared Cu-Al-O thin films on silicon (100) and quartz substrates by radio frequency (RF) magnetron sputtering method. The as-deposited Cu-Al-O film is amorphous in nature and post-annealing treatment in argon ambience results in crystallization of the films and the formation of CuAlO2. The annealing temperature plays an important role in the surface morphology, phase constitution and preferred growth orientation of CuAlO2 phase, thus affecting the properties of the film. The film annealed at 900 °C is mainly composed of CuAlO2 phase and shows smooth surface morphology with well-defined grain boundaries, thus exhibiting the optimum optical-electrical properties with electrical resistivity being 79.7 Ω·cm at room temperature and optical transmittance being 80% in visible region. The direct optical band gaps of the films are found in the range of 3.3-3.8 eV depending on the annealing temperature.

  19. Effect of the annealing temperature on dynamic and structural properties of Co2FeAl thin films

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Tuzcuoglu, H.; Gabor, M.; Petrisor, T.; Tiusan, C.; Zighem, F.; Chérif, S. M.; Moch, P.

    2014-07-01

    10 nm and 50 nm thick Co2FeAl (CFA) thin films have been deposited on thermally oxidized Si(001) substrates by magnetron sputtering using a Tantalum cap layer and were then ex-situ annealed at 415°C, 515°C and 615°C during 15 minutes in vacuum. X-rays diffraction indicates that films CFA are polycrystalline and exhibit an in-plane isotropy growth. Ferromagnetic resonance measurements, using a microstrip line (MS-FMR), reveal a huge interfacial perpendicular magnetic anisotropy and small in-plane uniaxial anisotropy both annealing temperature-dependent. The MS-FMR data also allow concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with annealing temperature. Finally, the FMR linewidth decreases with increasing annealing temperature due to the enhancement of the chemical order, and allow deriving a very low intrinsic damping parameter (1.3×10-3 at 615°C).

  20. Rapid thermal annealing and modulation-doping effects on InAs/GaAs quantum dots photoluminescence dependence on excitation power

    NASA Astrophysics Data System (ADS)

    Chaâbani, W.; Melliti, A.; Maaref, M. A.; Testelin, C.; Lemaître, A.

    2016-07-01

    The optical properties of p-doped and annealed InAs/GaAs quantum dots (QDs) was investigated by photoluminescence (PL) as a function of temperature and excitation power density (Pexc). At low-T, PL spectra of rapid thermal annealing (RTA) and p-modulation doped QDs show an energy blueshift and redshift, respectively. A superlinear dependence of integrated PL intensity on Pexc at high-T was found only for undoped QD. The superlinearity was suppressed by modulation-doping and RTA effects. A linear dependence of IPL at all temperatures and a decrease of the carrier-carrier Coulomb interaction at high-T was found after RTA.

  1. Effect of annealing temperature on the pitting corrosion resistance of super duplex stainless steel UNS S32750

    SciTech Connect

    Tan Hua; Jiang Yiming; Deng Bo; Sun Tao; Xu Juliang; Li Jin

    2009-09-15

    The pitting corrosion resistance of commercial super duplex stainless steels SAF2507 (UNS S32750) annealed at seven different temperatures ranging from 1030 deg. C to 1200 deg. C for 2 h has been investigated by means of potentiostatic critical pitting temperature. The microstructural evolution and pit morphologies of the specimens were studied through optical/scanning electron microscope. Increasing annealing temperature from 1030 deg. C to 1080 deg. C elevates the critical pitting temperature, whereas continuing to increase the annealing temperature to 1200 deg. C decreases the critical pitting temperature. The specimens annealed at 1080 deg. C for 2 h exhibit the best pitting corrosion resistance with the highest critical pitting temperature. The pit morphologies show that the pit initiation sites transfer from austenite phase to ferrite phase as the annealing temperature increases. The aforementioned results can be explained by the variation of pitting resistance equivalent number of ferrite and austenite phase as the annealing temperature changes.

  2. The optical functions of silicon at elevated temperatures and their application to pulsed laser annealing

    SciTech Connect

    Jellison, G.E. Jr.; Lowndes, D.H.; Wood, R.F.

    1993-06-01

    The results of measurements of the optical functions of silicon at elevated temperatures are reviewed and the results applied to pulsed laser annealing of silicon. Several optical experiments which were performed to understand the physics of pulsed laser annealing are described, and related to detailed thermal modeling. The fabrication of silicon solar cells using both thermal and laser processing is described, both of which give very goods results.

  3. Effect of annealing temperature on the structure and optical parameters of Ge{sub 20}Se{sub 50}Te{sub 30} thin films

    SciTech Connect

    Mohamed, Mansour

    2015-05-15

    Highlights: • The amorphous nature of as prepared Ge{sub 20}Se{sub 50}Te{sub 30} films was confirmed by XRD. • The thermal annealing was found to affect the structure and optical parameter. • Thermal annealing resulted in an appearance of crystalline phases in studied films. • The average particle size increased with increasing the annealing temperature. • The indirect band gap was found to decrease with increasing annealing temperature. - Abstract: Bulk glasses and thin films of Ge{sub 20}Se{sub 50}Te{sub 30} were prepared by melt-quenching and thermal evaporation technique, respectively. The stoichiometry of the composition was checked by energy dispersive X-ray diffraction (EDX), whereas the crystallization was investigated using differential scanning calorimetery (DSC). The effect of heat treatment on the structure transformation of Ge{sub 20}Se{sub 50}Te{sub 30} films was determined by X-ray diffraction (XRD). The XRD results reveal that the as-prepared films are amorphous in nature while the annealed ones show crystalline phases. Further, the average crystallite size, strain, and dislocation density were found to depend on the annealing temperature. The optical transmittance and reflectance of the studied films at different annealing temperatures were measured using spectrophotometer. The optical parameters were calculated as a function of annealing temperature. The optical transition was found to be allowed indirect transition with optical band gap decreases from 1.69 to 1.41 eV with increasing the annealing temperature from 553 to 633 K.

  4. Ambient dependence of the phase of nanowires grown by annealing brass

    SciTech Connect

    Srivastava, Himanshu; Ganguli, Tapas; Tiwari, Pragya; Srivastava, A. K.; Deb, S. K.

    2012-06-05

    The growth of oxide nanowires has been studied by the annealing of brass (Cu 65%, Zn 35%) at different annealing temperatures and in different ambient. The annealing temperature was varied from 400 deg. C to 650 deg. C. Scanning Electron Microscope (SEM) results showed that the temperature has a significant effect on the density and size of the nanowires. The annealing temperature of 600 deg. C was found to be optimum for the growth of nanowires. The growth at 600 deg. C was observed in two ambient-air and moist nitrogen. Selected Area Electron Diffraction (SAED) and Energy Dispersive Spectroscopy (EDS) results on Transmission Electron Microscope (TEM) showed that with changing the ambient from air to moist nitrogen, the phase of the nanowires changed from Zn doped CuO to Cu doped ZnO. This result can be of significance importance as it suggests the use of ambient for the tuning of phase of oxide nanowires and in turn for the tuning of their physical properties.

  5. Effect of deposition and annealing temperature on mechanical properties of TaN film

    NASA Astrophysics Data System (ADS)

    Liu, X.; Ma, G. J.; Sun, G.; Duan, Y. P.; Liu, S. H.

    2011-11-01

    Tantalum nitride films (TaN) were synthesized by microwave ECR-DC sputtering. The effects of deposition and annealing temperature on mechanical properties of TaN films were investigated. Cross-section pattern, microstructure and binding energy of the films were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Mechanical properties were evaluated using nano-indentation and scratch tester. The results showed that the maximal hardness value of approximately 40 GPa was deposited in the TaN sample at 573 K. While the preparation temperature decreased, the hardness, modulus and adhesion of TaN film also decreased. Hardness and modulus also decreased with the increase in annealing temperature. Meanwhile the adhesion strength was also sensitive to the annealing temperature, with a maximum adhesion strength of 40 N measured in the TaN film annealed at 448 K. The results demonstrated that a desirable mechanical property of TaN films deposited by DC reactive magnetron sputtering can be obtained by controlling the deposition and annealing temperature.

  6. Investigation the cause of plasma treatment for low temperature annealed dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zen, Shungo; Komatsu, Yuta; Ono, Ryo

    2015-09-01

    Dye-sensitized solar cells (DSSCs) require annealing of TiO2photoelectrodes at 450 C to 550 C. However, such high-temperature annealing is unfavorable because it limits the use of materials that cannot withstand high temperatures, such as plastic substrates. In our previous paper, a low temperature annealing technique of TiO2 photoelectrodes using ultraviolet light and dielectric barrier discharge treatments was proposed to reduce the annealing temperature from 450 C to 150 C for a TiO2 paste containing an organic binder. Here, we investigated the cause of plasma treatment via the Nyquist diagram (Cole-Cole plot) of DSSCs. The Nyquist diagram was masured with a frequency response analyzer (NF Corporation, FRA5022) under 100 mW/cm2 illumination of a calibrated xenon lamp (Hamamatsu L2274, 150W). The lifetime of the electrons, the effective electron diffusion coefficient, and the electron diffusion length of TiO2 photoelectrodes were determined by analyzing the Nyquist diagrams. As a result of analyzing the Nyquist diagrams, it was shown that plasma treatment can reduce the electron transport resistance and promote the necking of Hot UV annealed TiO2 nanoparticles. This work was supported by Grant-in-Aid for JSPS Fellows.

  7. Influence of annealing temperature on the phase transformation of Al2O3

    NASA Astrophysics Data System (ADS)

    Mahat, Annie Maria; Mastuli, Mohd Sufri; Kamarulzaman, Norlida

    2016-02-01

    In the present study, Al2O3 powders were prepared via a self-propagating combustion method using citric acid as a combustion agent. Effects of annealing temperature on the phase transformation of the prepared powders were studied on samples annealed at 800 °C and 1000 °C. The Al2O3 samples were characterized using X-Ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and N2 adsorption-desorption measurements. The XRD results showed that pure η-phase and pure α-phase of Al2O3 were obtained at 800 °C and 1000 °C, respectively. Their crystallite sizes are totally different as can be seen clearly from the FESEM micrographs. The η-Al2O3 sample annealed at low temperature has crystallite size smaller than 10 nm compared to the α-Al2O3 sample annealed at higher temperature which has crystallites from few microns to hundreds microns in size. From the BET (Brunauer-Emmett-Teller) method, the specific surface area for both samples are 59.4 m2g-1 and 3.1 m2g-1, respectively. It is proposed that the annealing temperature less pronounced for the morphology, but, it is significant for the phase transitions as well as the size and the specific surface area of the Al2O3 samples.

  8. High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films

    SciTech Connect

    R. Farrell; V. R. Pagan; A. Kabulski; Sridhar Kuchibhatl; J. Harman; K. R. Kasarla; L. E. Rodak; P. Famouri; J. Peter Hensel; D. Korakakis

    2008-05-01

    A Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.

  9. High Temperature Annealing Studies on the Piezoelectric Properties of Thin Aluminum Nitride Films

    SciTech Connect

    Farrell, R.; Pagan, V.R.; Kabulski, A.; Kuchibhatla, S.; Harman, J.; Kasarla, K.R.; Rodak, L.E.; Hensel, J.P.; Famouri, P.; Korakakis, D.

    2008-01-01

    A Rapid Thermal Annealing (RTA) system was used to anneal sputtered and MOVPE-grown Aluminum Nitride (AlN) thin films at temperatures up to 1000°C in ambient and controlled environments. According to Energy Dispersive X-Ray Analysis (EDAX), the films annealed in an ambient environment rapidly oxidize after five minutes at 1000°C. Below 1000°C the films oxidized linearly as a function of annealing temperature which is consistent with what has been reported in literature [1]. Laser Doppler Vibrometry (LDV) was used to measure the piezoelectric coefficient, d33, of these films. Films annealed in an ambient environment had a weak piezoelectric response indicating that oxidation on the surface of the film reduces the value of d33. A high temperature furnace has been built that is capable of taking in-situ measurements of the piezoelectric response of AlN films. In-situ d33 measurements are recorded up to 300°C for both sputtered and MOVPE-grown AlN thin films. The measured piezoelectric response appears to increase with temperature up to 300°C possibly due to stress in the film.

  10. Estimation of effective temperatures in quantum annealers for sampling applications: A case study with possible applications in deep learning

    NASA Astrophysics Data System (ADS)

    Benedetti, Marcello; Realpe-Gómez, John; Biswas, Rupak; Perdomo-Ortiz, Alejandro

    2016-08-01

    An increase in the efficiency of sampling from Boltzmann distributions would have a significant impact on deep learning and other machine-learning applications. Recently, quantum annealers have been proposed as a potential candidate to speed up this task, but several limitations still bar these state-of-the-art technologies from being used effectively. One of the main limitations is that, while the device may indeed sample from a Boltzmann-like distribution, quantum dynamical arguments suggest it will do so with an instance-dependent effective temperature, different from its physical temperature. Unless this unknown temperature can be unveiled, it might not be possible to effectively use a quantum annealer for Boltzmann sampling. In this work, we propose a strategy to overcome this challenge with a simple effective-temperature estimation algorithm. We provide a systematic study assessing the impact of the effective temperatures in the learning of a special class of a restricted Boltzmann machine embedded on quantum hardware, which can serve as a building block for deep-learning architectures. We also provide a comparison to k -step contrastive divergence (CD-k ) with k up to 100. Although assuming a suitable fixed effective temperature also allows us to outperform one-step contrastive divergence (CD-1), only when using an instance-dependent effective temperature do we find a performance close to that of CD-100 for the case studied here.

  11. Structural phase transition of as-synthesized Sr-Mn nanoferrites by annealing temperature

    NASA Astrophysics Data System (ADS)

    Amer, M. A.; Meaz, T. M.; Attalah, S. S.; Ghoneim, A. I.

    2015-11-01

    The Sr0.2Mn0.8Fe2O4 nanoparticle ferrites were synthesized by the co-precipitation method and annealed at different temperatures T. XRD, TEM, FT-IR, VSM and Mössbauer techniques were used to characterize the samples. This study proved that the structural phase of nanoferrites was transformed from cubic spinel for T≤500 °C to Z-type hexagonal for T≥700 °C. The structural transformation was attributed to Jahn-Teller effect of the Mn3+ ions and/or atomic disorder existed in the crystal lattice. The obtained spectra and parameters for the samples were affected by the transformation process. The lattice constant a showed a splitting to a and c for T>500 °C. The lattice constant c, grain and crystallite size R, strain, octahedral B-site band position and force constant, Debye temperature, coercivity Hc, remnant magnetization, squareness and magnetic moment, spontaneous magnetization and hyperfine magnetic fields showed increase against T. The lattice constant a, distortion and dislocation parameters, specific surface area, tetrahedral A-site band position and force constant, threshold frequency, Young's and bulk moduli, saturation magnetization Ms, area ratio of B-/A-sites, A-site line width were decreased with T. Experimental and theoretical densities, porosity, Poison ratio, stiffness constants, rigidity modulus, B-site line width and spontaneous magnetization showed dependence on T, whereas Ms and Hc proved dependence on R.

  12. Temperature effects on failure and annealing behavior in dynamic random access memories

    NASA Astrophysics Data System (ADS)

    Wilkin, N. D.; Self, C. T.

    1982-12-01

    Total dose failure levels and long time anneal characteristics of dynamic random access memories are measured while the devices are exercised under actual use conditions. These measurements were performed over the temperature range of -60 C to +70 C. The total dose failure levels are shown to decrease with increasing temperature. The anneal characteristics are shown to result in both an increase and decrease in the measured number of errors as a function of time. Finally a description of the test instrumentation and irradiation procedures are given.

  13. Room-temperature simultaneously enhanced magnetization and electric polarization in BiFeO3 ceramic synthesized by magnetic annealing

    NASA Astrophysics Data System (ADS)

    Luo, Wanju; Wang, Dongliang; Wang, Fangwei; Liu, Tao; Cai, Jianwang; Zhang, Liyan; Liu, Yulong

    2009-05-01

    Multiferroic BiFeO3 ceramics were synthesized by high temperature magnetic annealing using nanosized precursor powders prepared through microwave combustion. Simultaneously enhanced magnetization and electric polarization were observed at room temperature in the sample annealed under an external magnetic field of 10 T. These enhanced properties might be originated from a spin structure severely modulated or the low temperature magnetic phase driven up to room temperature and above by the large external annealing magnetic fields. These results demonstrate that the strong magnetic annealing method is an alternative way to synthesize high performance BiFeO3 materials.

  14. Effect of annealing temperature on wettability of TiO2 nanotube array films

    PubMed Central

    2014-01-01

    Highly ordered TiO2 nanotube array (TN) films were prepared by anodization of titanium foil in a mixed electrolyte solution of glycerin and NH4F and then annealed at 200°C, 400°C, 600°C, and 800°C, respectively. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), water contact angle (WCA), and photoluminescence (PL). It was found that low temperature (below 600°C) has no significant influence on surface morphology, but the diameter of the nanotube increases from 40 to 50 nm with increasing temperature. At 800°C, the nanotube arrays are completely destroyed and only dense rutile film is observed. Samples unannealed and annealed at 200°C are amorphous. At 400°C, anatase phase appears. At 600°C, rutile phase appears. At 800°C, anatase phase changes into rutile phase completely. The wettability of the TN films shows that the WCAs for all samples freshly annealed at different temperatures are about 0°. After the annealed samples have been stored in air for 1 month, the WCAs increase to 130°, 133°, 135°, 141°, and 77°, respectively. Upon ultraviolet (UV) irradiation, they exhibit a significant transition from hydrophobicity to hydrophilicity. Especially, samples unannealed and annealed at 400°C show high photoinduced hydrophilicity. PMID:25426006

  15. High-temperature annealing of proton irradiated beryllium - A dilatometry-based study

    NASA Astrophysics Data System (ADS)

    Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; Ghose, Sanjit; Savkliyildiz, Ilyas

    2016-08-01

    Ssbnd 200 F grade beryllium has been irradiated with 160 MeV protons up to 1.2 1020 cm-2 peak fluence and irradiation temperatures in the range of 100-200 °C. To address the effect of proton irradiation on dimensional stability, an important parameter in its consideration in fusion reactor applications, and to simulate high temperature irradiation conditions, multi-stage annealing using high precision dilatometry to temperatures up to 740 °C were conducted in air. X-ray diffraction studies were also performed to compliment the macroscopic thermal study and offer a microscopic view of the irradiation effects on the crystal lattice. The primary objective was to qualify the competing dimensional change processes occurring at elevated temperatures namely manufacturing defect annealing, lattice parameter recovery, transmutation 4He and 3H diffusion and swelling and oxidation kinetics. Further, quantification of the effect of irradiation dose and annealing temperature and duration on dimensional changes is sought. The study revealed the presence of manufacturing porosity in the beryllium grade, the oxidation acceleration effect of irradiation including the discontinuous character of oxidation advancement, the effect of annealing duration on the recovery of lattice parameters recovery and the triggering temperature for transmutation gas diffusion leading to swelling.

  16. Structure and infrared photoluminescence of GeSi nanocrystals formed by high temperature annealing of GeOx/SiO2 multilayers

    NASA Astrophysics Data System (ADS)

    Volodin, V. A.; Gambaryan, M. P.; Cherkov, A. G.; Stoffel, M.; Rinnert, H.; Vergnat, M.

    2016-08-01

    Germanium and GeSi nanocrystals were synthesized in SiGeO2 glass by high temperature annealings of GeOx(5 nm)/SiO2(5 nm) multilayers. According to electron microscopy data, the size distribution and stoichiometry of the nanocrystals depend on the annealing temperature (700, 800, or 900 °C). Spatial redistribution of Ge with the formation of large faceted nanocrystals located near the Si substrate and GeSi intermixing at the substrate/film interface were observed. In the case of the 900 °C annealed sample, we note that some nanocrystals have a pyramid-like shape. Infrared absorption spectroscopy demonstrates that intermixing takes place between the GeOx and SiO2 layers leading to the formation of SiGeO2 glass. Raman spectroscopy confirms the formation of Ge nanocrystals after annealing at 700 °C and GeSi nanocrystals after annealing at 800 and 900 °C. For all annealed samples, we report the observation of infrared photoluminescence (PL) at low temperatures in the spectral range 1300-2100 nm. The observation of PL at wavelengths close to 2000 nm may be due to defect-induced radiative transitions in the nanocrystals.

  17. Carrier capture efficiency in InGaN/GaN LEDs: Role of high temperature annealing

    SciTech Connect

    Vinattieri, A.; Batignani, F.; Bogani, F.; Meneghini, M.; Meneghesso, G.; Zanoni, E.; Zhu, D.; Humphreys, C. J.

    2014-02-21

    By means of time integrated (TI), time-resolved (TR) photoluminescence (PL) and PL excitation spectra, we investigate the role of an high temperature post-growth thermal annealing (TA) on a set of InGaN/GaN LED structures with different dislocation densities. We provide evidence of the nature of the radiative recombination from a wide distribution of non-interacting localised states and we show the beneficial effect of thermal annealing in reducing the contribution of non-radiative recombination in the well region.

  18. High dopant activation of phosphorus in Ge crystal with high-temperature implantation and two-step microwave annealing

    NASA Astrophysics Data System (ADS)

    Shih, Tzu-Lang; Su, Yin-Hsien; Lee, Wen-Hsi

    2016-09-01

    In this letter, high-temperature ion implantation and low-temperature microwave annealing were employed to achieve high n-type active concentrations, approaching the solid solubility limit, in germanium. To use the characteristics of microwave annealing more effectively, a two-step microwave annealing process was employed. In the first annealing step, a high-power (1200 W; 425 °C) microwave was used to achieve solid-state epitaxial regrowth and to enhance microwave absorption. In the second annealing step, contrary to the usual process of thermal annealing with higher temperature, a lower-power (900 W; 375 °C) microwave process was used to achieve a low sheet resistance, 78Ω/◻, and a high carrier concentration, 1.025 × 1020 P/cm3, which is close to the solid solubility limit of 2 × 1020 P/cm3.

  19. Impact of annealing temperature on the mechanical and electrical properties of sputtered aluminum nitride thin films

    SciTech Connect

    Gillinger, M.; Schneider, M.; Bittner, A.; Schmid, U.; Nicolay, P.

    2015-02-14

    Aluminium nitride (AlN) is a promising material for challenging sensor applications such as process monitoring in harsh environments (e.g., turbine exhaust), due to its piezoelectric properties, its high temperature stability and good thermal match to silicon. Basically, the operational temperature of piezoelectric materials is limited by the increase of the leakage current as well as by enhanced diffusion effects in the material at elevated temperatures. This work focuses on the characterization of aluminum nitride thin films after post deposition annealings up to temperatures of 1000 °C in harsh environments. For this purpose, thin film samples were temperature loaded for 2 h in pure nitrogen and oxygen gas atmospheres and characterized with respect to the film stress and the leakage current behaviour. The X-ray diffraction results show that AlN thin films are chemically stable in oxygen atmospheres for 2 h at annealing temperatures of up to 900 °C. At 1000 °C, a 100 nm thick AlN layer oxidizes completely. For nitrogen, the layer is stable up to 1000 °C. The activation energy of the samples was determined from leakage current measurements at different sample temperatures, in the range between 25 and 300 °C. Up to an annealing temperature of 700 °C, the leakage current in the thin film is dominated by Poole-Frenkel behavior, while at higher annealing temperatures, a mixture of different leakage current mechanisms is observed.

  20. Influence of rapid thermal vacuum annealing and high temperature treatment on the properties of PSG films

    NASA Astrophysics Data System (ADS)

    Beschkov, G.; Bakardjieva, V.; Alexieva, Z.

    2008-05-01

    The effect is presented of rapid thermal annealing (RTA) in vacuum and thermal annealing in water vapor at 850 °C on the properties of phosphosilicate glass (PSG) films deposited in PECVD and μPCVD reactors. The films were characterized by etch rates and XPS and AES analyses. The RTA was carried out at 800 - 1400 °C at annealing times varying from 15 to 180 sec. The RTA caused a significant decrease in the etch rate, which is indicative of structural changes. The XPS and AES analyses showed that the PECVD PSG films contain excess Si due to the lower oxidation activity of N2O. The excess Si can be oxidized in water vapor at high temperatures. The excess Si leads to a decrease in the etching rate of the PECVD PSG layers as compared to that of the μPCVD films.

  1. High temperature annealing effects on low energy iron implanted SiO 2

    NASA Astrophysics Data System (ADS)

    Kennedy, J.; Leveneur, J.; Markwitz, A.

    2012-02-01

    15 keV Fe ions were implanted into a thermally grown silica film with a fluence of 1 × 10 16 at./cm 2 resulting in a near Gaussian concentration profile peaking at 8 at.% about 15 nm under the surface. High vacuum (˜10 -7 mbar) furnace annealing and electron beam annealing at high temperature resulted in diffusion of Fe inside the oxide film. Segregation of Fe atoms at the SiO 2 surface and SiO 2/Si interface was observed in both cases. EBA resulted in faster precipitation and lower out-diffusion of Fe. In-situ Rutherford Backscattering Spectrometry was performed during high vacuum annealing and is shown to be an appropriate method to investigate the diffusion rate. The differences observed between the methods are explained by the effect of excess electrons and ionization induced by the electron beam on the oxygen-vacancy mediated displacement mechanism and on the reduction of Fe oxides.

  2. Enhanced photocurrent density of hematite thin films on FTO substrates: effect of post-annealing temperature.

    PubMed

    Cho, Eun Soo; Kang, Myung Jong; Kang, Young Soo

    2015-06-28

    Fluorine doped tin oxide (FTO) is widely used as a substrate in the synthesis of a photo-reactive semiconductor electrode for solar water splitting. The hematite film on the surface of the FTO substrate annealed at 700 °C showed an enhanced photocurrent value with a maximum photocurrent of 0.39 mA cm(-2) at 1.23 V vs. RHE under 1 sun illumination. This is a much enhanced photocurrent value of the hematite films than that of those annealed at temperatures lower than 700 °C. This is a promising approach for the enhancement of the photoelectrochemical properties of metal oxide thin films. This work reports on the mechanism of the annealing process of the synthesized hematite film to enhance the photocurrent value. Furthermore, this can be used for the enhanced efficiency of the solar water splitting reaction. PMID:26032403

  3. Microstructural Changes upon Milling of Graphite in Water and Subsequent MWCNT Formation During High Temperature Annealing

    SciTech Connect

    Milev, Adriyan; Tran, Nguyen; Kamali Kannangara, G. S.; Wilson, Michael

    2007-01-19

    The method of preparing carbon nanotube (CNT) by milling of graphite particles in water followed by high temperature annealing is proposed and the mechanism discussed. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) line broadening analysis reveal that cleavage of the graphite particles occurs preferentially along the out-of-plane {pi} bonds. Carbon K-edge near edge X-ray absorption fine structure (NEXAFS) of the milled graphite shows an increased sp3 character of the C=C bonds, but no major bonds rupture in the graphene sheets. The annealing at 1400 deg. C for 4 h of the milled graphite in argon results in formation of multiwalled carbon nanotubes accompanied with a number of coiled and twisted stacks of graphene sheets. The increased structural disorder of the milled graphite and presence of iron contaminations facilitate the rolling up of the cleaved graphene sheets during annealing.

  4. Microstructural Changes upon Milling of Graphite in Water and Subsequent MWCNT Formation During High Temperature Annealing

    NASA Astrophysics Data System (ADS)

    Milev, Adriyan; Tran, Nguyen; Kamali Kannangara, G. S.; Wilson, Michael

    2007-01-01

    The method of preparing carbon nanotube (CNT) by milling of graphite particles in water followed by high temperature annealing is proposed and the mechanism discussed. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) line broadening analysis reveal that cleavage of the graphite particles occurs preferentially along the out-of-plane π bonds. Carbon K-edge near edge X-ray absorption fine structure (NEXAFS) of the milled graphite shows an increased sp3 character of the C=C bonds, but no major bonds rupture in the graphene sheets. The annealing at 1400 °C for 4 h of the milled graphite in argon results in formation of multiwalled carbon nanotubes accompanied with a number of coiled and twisted stacks of graphene sheets. The increased structural disorder of the milled graphite and presence of iron contaminations facilitate the rolling up of the cleaved graphene sheets during annealing.

  5. Microstructure of V-based ohmic contacts to AlGaN/GaN heterostructures at a reduced annealing temperature

    SciTech Connect

    Schmid, A. Schroeter, Ch.; Otto, R.; Heitmann, J.; Schuster, M.; Klemm, V.; Rafaja, D.

    2015-02-02

    Ohmic contacts with V/Al/Ni/Au and V/Ni/Au metalization schemes were deposited on AlGaN/GaN heterostructures. The dependence of the specific contact resistance on the annealing conditions and the V:Al thickness ratio was shown. For an optimized electrode stack, a low specific contact resistance of 8.9 × 10{sup −6} Ω cm{sup 2} was achieved at an annealing temperature of 650 °C. Compared to the conventional Ti/Al/Ni/Au contact, this is a reduction of 150 K. The microstructure and contact formation at the AlGaN/metal interface were investigated by transmission electron microscopy including high-resolution micrographs and energy dispersive X-ray analysis. It was shown that for low-resistive contacts, the resistivity of the metalization has to be taken into account. The V:Al thickness ratio has an impact on the formation of different intermetallic phases and thus is crucial for establishing ohmic contacts at reduced annealing temperatures.

  6. Microwave annealing

    NASA Astrophysics Data System (ADS)

    Lee, Yao-Jen; Cho, T.-C.; Chuang, S.-S.; Hsueh, F.-K.; Lu, Y.-L.; Sung, P.-J.; Chen, S.-J.; Lo, C.-H.; Lai, C.-H.; Current, Michael I.; Tseng, T.-Y.; Chao, T.-S.; Yang, F.-L.

    2012-11-01

    Microwave annealing of dopants in Si has been reported to produce highly activated junctions at temperatures far below those needed for comparable results using conventional thermal processes. However the details of the kinetics and mechanisms for microwave annealing are far from well understood. Comparisons between MWA and RTA of dopants in implanted Si has been investigated to produce highly activated junctions. First, As, 31P, and BF 2 implants in Si substrate were annealed by MWA at temperatures below 550 °C.

  7. Thermal stress modification in regenerated fiber Bragg grating via manipulation of glass transition temperature based on CO₂-laser annealing.

    PubMed

    Lai, Man-Hong; Lim, Kok-Sing; Gunawardena, Dinusha S; Yang, Hang-Zhou; Chong, Wu-Yi; Ahmad, Harith

    2015-03-01

    In this work, we have demonstrated thermal stress relaxation in regenerated fiber Bragg gratings (RFBGs) by using direct CO₂-laser annealing technique. After the isothermal annealing and slow cooling process, the Bragg wavelength of the RFBG has been red-shifted. This modification is reversible by re-annealing and rapid cooling. It is repeatable with different cooling process in the subsequent annealing treatments. This phenomenon can be attributed to the thermal stress modification in the fiber core by means of manipulation of glass transition temperature with different cooling rates. This finding in this investigation is important for accurate temperature measurement of RFBG in dynamic environment. PMID:25723423

  8. Low Temperature, Rapid Thermal Cycle Annealing of HgCdTe Grown on CdTe/Si

    NASA Astrophysics Data System (ADS)

    Simingalam, Sina; Brill, Gregory; Wijewarnasuriya, Priyalal; Rao, Mulpuri V.

    2015-05-01

    The HgCdTe(MCT) grown on CdTe/Si substrate has a high dislocation density due to lattice mismatch. Thermal cycle annealing (TCA) is effective in reducing the dislocation density. The TCA at high temperatures results in inter-diffusion of the constituent elements across the MCT/CdTe interface. In this study, we observed a reduction in dislocation density with good surface morphology due to proper design of the TCA system, low annealing temperature, and large number of annealing cycles. The ampoule containing the samples is placed in direct contact with the graphite heating tube which helps in increasing the heating and cooling rates of the annealing cycle. To maintain Hg overpressure, Hg is placed in the sample holder, instead of in the ampoule to avoid Hg condensation. The best results were obtained by cycling the annealing temperature between 290°C and 350°C. Anneals were performed by using 32, 64, 128 and 256 cycles. We obtained an etch pit density (EPD) as low as 1 × 106 cm-2. Lower EPD was not achieved either by increasing annealing temperature or number of annealing cycles. Through secondary ion mass spectroscopy analysis, we observed very little inter-diffusion of Cd across the MCT/CdTe interface for the 128 cycle annealing. These results show promise in bridging the gap in the device performance between the MCT material grown on CdTe/Si and CdZnTe substrates.

  9. Effect of low temperature anneals and nonthermal treatments on the properties of gap fill oxides used in SiGe and III-V devices

    NASA Astrophysics Data System (ADS)

    Ryan, E. Todd; Morin, Pierre; Madan, Anita; Mehta, Sanjay

    2016-07-01

    Silicon dioxide is used to electrically isolate CMOS devices such as fin field effect transistors by filling gaps between the devices (also known as shallow trench isolation). The gap fill oxide typically requires a high temperature anneal in excess of 1000 °C to achieve adequate electrical properties and oxide densification to make the oxide compatible with subsequent fabrication steps such as fin reveal etch. However, the transition from Si-based devices to high mobility channel materials such as SiGe and III-V semiconductors imposes more severe thermal limitations on the processes used for device fabrication, including gap fill oxide annealing. This study provides a framework to quantify and model the effect of anneal temperature and time on the densification of a flowable silicon dioxide as measured by wet etch rate. The experimental wet etch rates allowed the determination of the activation energy and anneal time dependence for oxide densification. Dopant and self-diffusion can degrade the channel material above a critical temperature. We present a model of self-diffusion of Ge and Si in SiGe materials. Together these data allowed us to map the thermal process space for acceptable oxide wet etch rate and self-diffusion. The methodology is also applicable to III-V devices, which require even lower thermal budget. The results highlight the need for nonthermal oxide densification methods such as ultraviolet (UV) and plasma treatments. We demonstrate that several plasma treatments, in place of high temperature annealing, improved the properties of flowable oxide. In addition, UV curing prior to thermal annealing enables acceptable densification with dramatically reduced anneal temperature.

  10. Role of annealing temperatures on the evolution of microstructure and properties of Cr2O3 films

    NASA Astrophysics Data System (ADS)

    He, Nairu; Ji, Li; Liu, Xiaohong; Li, Hongxuan; Zhou, Huidi; Chen, Jianmin

    2015-12-01

    Cr2O3 films were deposited on Ni-based high-temperature alloy substrates by using a cathodic arc ion plating system and then annealed in air at different temperatures. The effects of different annealing temperatures on the microstructure, mechanical and tribological properties of the films were examined. Results showed that the as-deposited Cr2O3 films were primarily amorphous with crystallization and vaporization temperatures of 360 °C and 940 °C, respectively. Annealing above the crystallization temperature improved the hardness, adhesion, and wear life of the Cr2O3 films. A mesh-like heave structure comprising Cr2O3 and Cr2Ti7O17 phases formed on the film surface after annealing above the vaporization temperature. The mesh-like heave structure endued the film with excellent tribological properties in a wide temperature range from room temperature (RT) to 1000 °C.

  11. An investigation of temperature measurement methods in nuclear power plant reactor pressure vessel annealing

    SciTech Connect

    Acton, R.U.; Gill, W.; Sais, D.J.; Schulze, D.H.; Nakos, J.T.

    1996-05-01

    The objective of this project was to provide an assessment of several methods by which the temperature of a commercial nuclear power plant reactor pressure vessel (RPV) could be measured during an annealing process. This project was a coordinated effort between DOE`s Office of Nuclear Energy, Science and Technology; DOE`s Light Water Reactor Technology Center at Sandia National Laboratories; and the Electric Power Research Institute`s Non- Destructive Evaluation Center. Ball- thermocouple probes similar to those described in NUREG/CR-5760, spring-loaded, metal- sheathed thermocouple probes, and 1778 air- suspended thermocouples were investigated in experiments that heated a section of an RPV wall to simulate a thermal annealing treatment. A parametric study of ball material, emissivity, thermal conductivity, and thermocouple function locations was conducted. Also investigated was a sheathed thermocouple failure mode known as shunting (electrical breakdown of insulation separating the thermocouple wires). Large errors were found between the temperature as measured by the probes and the true RPV wall temperature during heat-up and cool-down. At the annealing soak temperature, in this case 454{degrees}C [850`F], all sensors measured the same temperature within about {plus_minus}5% (23.6{degrees}C [42.5{degrees}F]). Because of these errors, actual RPV wall heating and cooling rates differed from those prescribed (by up to 29%). Shunting does not appear to be a problem under these conditions. The large temperature measurement errors led to the development of a thermal model that predicts the RPV wall temperature from the temperature of a ball- probe. Comparisons between the model and the experimental data for ball-probes indicate that the model could be a useful tool in predicting the actual RPV temperature based on the indicated ball- probe temperature. The model does not predict the temperature as well for the spring-loaded and air suspended probes.

  12. Temperature Dependence of Cesium Iodine

    NASA Astrophysics Data System (ADS)

    Valentine, John David

    The gamma-ray excited, temperature dependent scintillation characteristics of CsI(T1) are reported over the temperature range of -100 to +50^circ C. The modified Bollinger-Thomas and shaped square wave methods were used to measure the rise and decay times. Emission spectra were measured using a monochromator and corrected for monochromator and photocathode spectral efficiencies. The shaped square wave method was also used to determine the scintillation yield as was a current mode method. The thermoluminescence emission of CsI(T1) were measured using the same current mode method. At room temperature, CsI(T1) was found to have two primary decay components with decay time constants of tau_1 = 679 +/- 9 ns (63.7%) and tau_2 = 3.34 +/- 0.10 mus (36.1%), an absolute scintillation yield of 65,500 +/- 4,100 photons/MeV, and emission bands at about 400 and 560 nm. The tau_1 luminescent state was observed to be populated by an exponential process with a resulting rise time constant of 19.6 +/- 1.9 ns at room temperature. An ultra-fast decay component with a <0.5 ns decay time was found to emit about 0.2% of the total scintillation light (about 100 photons/MeV). Except for the ultra-fast decay time, the rise and decay time constants were observed to increase exponentially with inverse temperature. At -80 ^circC, tau_1 and tau_2 were determined to be 2.22 +/- 0.31 mu s and 18.0 +/- 1.44 mus, respectively, while the 400 nm emission band was not observed below -50 ^circC. At +50^circ C, the decay constants were found to be 628 +/- 3 ns (70.5%) and 2.63 +/- 0.03 mus (29.3%) and both emission bands are present. The scintillation yield of CsI(T1) was observed to be only slightly temperature dependent between -40 and +50^circ C, peaking at about -30 ^circC (about 6% above the room temperature yield). Four different commercially-available CsI(T1) crystals were used. Minimal variations in the measured scintillation characteristics were observed among these four crystals

  13. Luminescence Studies of Residual Damage in Low-Dose Arsenic Implanted Silicon after High-Temperature Annealing

    NASA Astrophysics Data System (ADS)

    Sagara, Akihiko; Hiraiwa, Miori; Shibata, Satoshi; Sugie, Ryuichi; Yamada, Keiichi

    2011-01-01

    In order to prevent the degradation of device performance, it is necessary to detect and reduce residual damage remaining after ion implantation and annealing. In this study, we focused on the high-temperature annealing process after low-dose arsenic (As) implantation in silicon (Si) and evaluated the correlation of annealing conditions and damage by cathodoluminescence (CL) compared to Secondary Ion Mass Spectrometry (SIMS) and Junction Photo-Voltage (JPV) results. Increasing the annealing temperature with the high-heat-up rate, As profile and the sheet resistance didn't change. However, the intensity of the band-to-band transition increased with temperature. This implies the some kind of residual damage remains after low-temperature annealing and it is removed with increasing annealing temperature. On the other hand, with increasing the annealing time at 1200 °C, more As was piled-up at the SiO2/Si interface and the luminescence intensity decreased. We guess this piled-up As is inactive and it may create some kind of damage combined with the defects around the interface, and these damage types cause the suppression of the luminescence intensity. We concluded that the luminescence intensity reflects the various kinds of damage and optical characterization methods have a potential to evaluate defect evolution in annealing process.

  14. Temperature dependence of basalt weathering

    NASA Astrophysics Data System (ADS)

    Li, Gaojun; Hartmann, Jens; Derry, Louis A.; West, A. Joshua; You, Chen-Feng; Long, Xiaoyong; Zhan, Tao; Li, Laifeng; Li, Gen; Qiu, Wenhong; Li, Tao; Liu, Lianwen; Chen, Yang; Ji, Junfeng; Zhao, Liang; Chen, Jun

    2016-06-01

    The homeostatic balance of Earth's long-term carbon cycle and the equable state of Earth's climate are maintained by negative feedbacks between the levels of atmospheric CO2 and the chemical weathering rate of silicate rocks. Though clearly demonstrated by well-controlled laboratory dissolution experiments, the temperature dependence of silicate weathering rates, hypothesized to play a central role in these weathering feedbacks, has been difficult to quantify clearly in natural settings at landscape scale. By compiling data from basaltic catchments worldwide and considering only inactive volcanic fields (IVFs), here we show that the rate of CO2 consumption associated with the weathering of basaltic rocks is strongly correlated with mean annual temperature (MAT) as predicted by chemical kinetics. Relations between temperature and CO2 consumption rate for active volcanic fields (AVFs) are complicated by other factors such as eruption age, hydrothermal activity, and hydrological complexities. On the basis of this updated data compilation we are not able to distinguish whether or not there is a significant runoff control on basalt weathering rates. Nonetheless, the simple temperature control as observed in this global dataset implies that basalt weathering could be an effective mechanism for Earth to modulate long-term carbon cycle perturbations.

  15. Effect of annealing temperature on structure and electrical properties of topological insulator Bi2Te3

    NASA Astrophysics Data System (ADS)

    Urkude, R. R.; Palikundwar, U. A.

    2016-05-01

    Bi2Te3 samples were prepared by precipitation method. The samples were annealed in evacuated quartz tubes and were treated at different temperature for different duration of time. Effects of annealing temperature and time on the structure of Bi2Te3 were studied in detail. The Bi2Te3 samples annealed at temperature 300°C and 450°C for 48Hrs, 72Hrs and 96Hrs were selected for the present study. The structure of Bi2Te3 and related phases were investigated by the X-ray powder diffraction technique. Morphology and chemical compositions of the samples were investigated by scanning electron microscope and energy dispersive X-ray spectroscopy respectively. All the samples were indexed in rhombohedral crystal structure, with a space group R-3m. The structure consists of repeated quintuple layers of atoms, Te2-Bi-Te1-Bi-Te2 stacking along the z-axis of the unit cell. Electrical properties of the sample annealed at 300°C for 96Hrs was evaluated by measurements of the electrical resistivity and magnetoresistance. The magnetoresistance data at low temperature (1.5 to 50 K) were analyzed to investigate weak antilocalization (WAL) effect. MR data followed the Hikami-Larkin-Nagaoka (HLN) equation with a fit parameter α close to -1 as expected for topological surface states at 1.5 K, but for other temperatures the small oscillations were observed which may be due to the phenomena like Shubnikov-de Hass effect.

  16. SURFACE TEMPERATURE OF PROTOPLANETARY DISKS PROBED BY ANNEALING EXPERIMENTS REFLECTING SPITZER OBSERVATIONS

    SciTech Connect

    Roskosz, Mathieu; Gillot, Jessy; Leroux, Hugues; Capet, Frederic; Roussel, Pascal

    2009-12-20

    Pyroxenes and olivines are the dominant crystalline silicates observed in protoplanetary disks. Recent spectral observations from the Spitzer Space Telescope indicate that the abundance of olivine, generally associated with silica polymorphs, relative to pyroxene is higher in the outer cold part of the disk than in the inner warmer part. The interpretation of these unexpected results requires a comprehensive knowledge of the thermal processing of Mg-rich silicate dust. In this respect, amorphous analogs were thermally annealed to identify microscopic crystallization mechanisms. We show that pyroxenes are not produced in significant proportions below the glass transition temperature of the amorphous precursor. The annealing of amorphous enstatite leads to a mineralogical assemblage dominated by forsterite, with only minute amounts of pyroxenes at temperatures as high as the glass transition temperature of enstatite (1050 K). The decoupling of cation mobility in amorphous silicates, favors the crystallization of the most Mg-enriched silicates. These results are consistent with Spitzer observations of silicate dust and also with the documented mineralogy of presolar silicates, making the low-temperature annealing a likely formation process for these objects. Based on these laboratory experiments and Spitzer observations, it appears that the reported zoned mineralogy may directly records and calibrates the thermal gradient at the scale of protoplanetary disks.

  17. Tuning phase transition temperature of VO2 thin films by annealing atmosphere

    NASA Astrophysics Data System (ADS)

    Liu, Xingxing; Wang, Shao-Wei; Chen, Feiliang; Yu, Liming; Chen, Xiaoshuang

    2015-07-01

    A simple new way to tune the optical phase transition temperature of VO2 films was proposed by only controlling the pressure of oxygen during the annealing process. Vanadium films were deposited on glass by a large-scale magnetron sputtering coating system and then annealed in appropriate oxygen atmosphere to form the VO2 films. The infrared transmission change (at 2400 nm) is as high as 58% for the VO2 thin film on the glass substrate, which is very good for tuning infrared radiation and energy saving as smart windows. The phase transition temperature of the films can be easily tuned from an intrinsic temperature to 44.7 °C and 40.2 °C on glass and sapphire by annealing oxygen pressure, respectively. The mechanism is: V3+ ions form in the film when under anaerobic conditions, which can interrupt the V4+ chain and reduce the phase transition temperature. The existence of V3+ ions has been observed by x-ray photoelectron spectroscopy (XPS) experiments as proof.

  18. Dielectric relaxation and conduction mechanisms in sprayed TiO2 thin films as a function of the annealing temperature

    NASA Astrophysics Data System (ADS)

    Juma, Albert; Acik, Ilona Oja; Mere, Arvo; Krunks, Malle

    2016-04-01

    The electrical properties of TiO2 thin films deposited by chemical spray pyrolysis onto Si substrates were investigated in the metal-oxide-semiconductor (MOS) configuration using current-voltage characteristics and impedance spectroscopy. The electrical properties were analyzed in relation to the changes in microstructure induced during annealing in air up to a temperature of 950 °C. Anatase to rutile transformation started after annealing at 800 °C, and at 950 °C, only the rutile phase was present. The dielectric relaxation strongly depended upon the microstructure of TiO2 with the dielectric constant for the anatase phase between 45 and 50 and that for the rutile phase 123. Leakage current was reduced by three orders of magnitude after annealing at 700 °C due to the densification of the TiO2 film. A double-logarithmic plot of the current-voltage characteristics showed a linear relationship below 0.12 V consistent with Ohmic conduction, while space-charge-limited conduction mechanism as described by Child's law dominated for bias voltages above 0.12 V.

  19. A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures

    SciTech Connect

    Pristavu, G.; Brezeanu, G.; Badila, M.; Pascu, R.; Danila, M.; Godignon, P.

    2015-06-29

    Ni Schottky contacts on SiC have a nonideal behavior, with strong temperature dependence of the electrical parameters, caused by a mixed barrier on the contact area and interface states. A simple analytical model that establishes a quantitative correlation between Schottky contact parameter variation with temperature and barrier height non-uniformity is proposed. A Schottky contact surface with double Schottky barrier is considered. The main model parameters are the lower barrier (Φ{sub Bn,l}) and a p factor which quantitatively evaluates the barrier non-uniformity on the Schottky contact area. The model is validated on Ni/4H-SiC Schottky contacts, post metallization sintered at high temperatures. The measured I{sub F}–V{sub F}–T characteristics, selected so as not to be affected by interface states, were used for model correlation. An inhomogeneous double Schottky barrier (with both nickel silicide and Ni droplets at the interface) is formed by a rapid thermal annealing (RTA) at 750 °C. High values of the p parameter are obtained from samples annealed at this temperature, using the proposed model. A significant improvement in the electrical properties occurs following RTA at 800 °C. The expansion of the Ni{sub 2}Si phase on the whole contact area is evinced by an X-Ray diffraction investigation. In this case, the p factor is much lower, attesting the uniformity of the contact. The model makes it possible to evaluate the real Schottky barrier, for a homogenous Schottky contact. Using data measured on samples annealed at 800 °C, a true barrier height of around 1.73 V has been obtained for Ni{sub 2}Si/4H-SiC Schottky contacts.

  20. Pressure dependencies of magnetostrictive strain and d coefficient in Terfenol-D after thermal or magnetic annealing

    NASA Astrophysics Data System (ADS)

    Galloway, N.; Greenough, R. D.; Jenner, A. G. I.; Schulze, M. P.

    1994-11-01

    The pressure dependence of the magnetostrictive strain coefficient, d(sub 33), and maximum strains in applied fields of 120 kA/m have been measured in samples of Terfenol-D before and after thermal or magnetic annealing. Application of an annealing field, H(sub a), parallel to the (111) axes which are normal to grains oriented along the (11-2) axis, leads to an increase in d(sub 33) of as much as 81%, with applied uniaxial prestresses as low as 3 MPa. The variation of optimum d(sub 33) values as a function of stress applied along the (11-2) axis shows anomalous oscillations after magnetic annealing. The thermal and magnetic effects of the annealing are discussed and a mechanism to explain magnetic annealing is proposed.

  1. The stability of tin silicon oxide thin-film transistors with different annealing temperatures

    NASA Astrophysics Data System (ADS)

    Yang, Jianwen; Fu, Ruofan; Han, Yanbing; Meng, Ting; Zhang, Qun

    2016-07-01

    The influence of annealing temperature on the electrical properties of tin silicon oxide (TSO) thin-film transistors (TFTs) and the corresponding bias stress stability have been investigated. With increasing annealing temperature, the TSO films present a structure which is closer to crystallization, and it is conducive to the improvement of the mobility of TSO TFTs. Meanwhile, the positive bias stress (PBS) stability of TSO TFTs is ameliorated due to the decreasing traps at the interface of dielectric layer and channel layer. The threshold voltage shifts in opposite direction after being stressed under negative bias stress (NBS), which is due to the competition between electrons captured by defects related to oxygen vacancies in the channel layer and water molecule adsorption on the back channel.

  2. Effect of solution annealing temperature on precipitation in 2205 duplex stainless steel

    SciTech Connect

    Kashiwar, A.; Vennela, N. Phani; Kamath, S.L.; Khatirkar, R.K.

    2012-12-15

    In the present study, effect of solution annealing temperature (1050 Degree-Sign C and 1100 Degree-Sign C) and isothermal ageing (700 Degree-Sign C: 15 min to 6 h) on the microstructural changes in 2205 duplex stainless steel has been investigated systematically. Scanning electron microscopy and X-ray diffraction were adopted to follow the microstructural evolution, while an energy dispersive spectrometer attached to scanning electron microscope was used to obtain localised chemical information of various phases. The ferritic matrix of the two phase 2205 duplex stainless steel ({approx} 45% ferrite and {approx} 55% austenite) undergoes a series of metallurgical transformations during ageing-formation of secondary austenite ({gamma}{sub 2}) and precipitation of Cr and Mo rich intermetallic (chi-{chi} and sigma-{sigma}) phases. For solution annealing at 1050 Degree-Sign C, significant amount of carbides were observed in the ferrite grains after 1 h of ageing at 700 Degree-Sign C. {chi} Phase precipitated after the precipitation of carbides-preferentially at the ferrite-ferrite and also at the ferrite-austenite boundaries. {sigma} Phase was not observed in significant quantity even after 6 h of ageing. The sequence of precipitation in samples solution annealed at 1050 Degree-Sign C was found to be carbides {yields} {chi} {yields} {sigma}. On the contrary, for samples solution annealed at 1100 Degree-Sign C, the precipitation of {chi} phase was negligible. {chi} Phase precipitated before {sigma} phase, preferentially along the ferrite-ferrite grain boundaries and was later consumed in the {sigma} phase precipitation. The {sigma} phase precipitated via the eutectoid transformation of ferrite to yield secondary austenite {gamma}{sub 2} and {sigma} phase in the ferrite and along the ferrite-austenite grain boundaries. An increase in the volume fraction of {gamma}{sub 2} and {sigma} phase with simultaneous decrease in the ferrite was evidenced with ageing. - Highlights

  3. Effects of Annealing Temperature on Microstructure and Tensile Properties in Ferritic Lightweight Steels

    NASA Astrophysics Data System (ADS)

    Han, Seung Youb; Shin, Sang Yong; Lee, Hyuk-Joong; Lee, Byeong-Joo; Lee, Sunghak; Kim, Nack J.; Kwak, Jai-Hyun

    2012-03-01

    An investigation was conducted into the effects of annealing temperature on microstructure and tensile properties of ferritic lightweight steels. Two steels were fabricated by varying the C content, and were annealed at 573 K to 1173 K (300 °C to 900 °C) for 1 hour. According to the microstructural analysis results, κ-carbides were formed at about 973 K (700 °C), which was confirmed by equilibrium phase diagrams calculated from a THERMO-CALC program. In the steel containing low carbon content, needle-shaped κ-carbides were homogeneously dispersed in the ferrite matrix, whereas bulky band-shaped martensites were distributed in the steel containing high carbon content. In the 973 K (700 °C)-annealed specimen of the steel containing high carbon content, deformation bands were formed throughout the specimen, while fine carbides were sufficiently deformed inside the deformation bands, thereby resulting in the greatest level of strength and ductility. These results indicated that the appropriate annealing treatment of steel containing high carbon content was useful for the improvement of both strength and ductility over steel containing low carbon content.

  4. Post-Growth Annealing of Bridgman-grown CdZnTe and CdMnTe Crystals for Room-temperature Nuclear Radiation Detectors

    DOE PAGES

    Egarievwe, Stephen U.; Yang, Ge; Egarievwe, Alexander; Okwechime, Ifechukwude O.; Gray, Justin; Hales, Zaveon M.; Hossain, Anwar; Camarda, Guiseppe S.; Bolotnikov, Aleksey E.; James, Ralph B.

    2015-02-11

    Bridgman-grown cadmium zinc telluride (CdZnTe or CZT) and cadmium manganese telluride (CdMnTe or CMT) crystals often have Te inclusions that limit their performances as X-ray- and gamma-ray-detectors. We present here the results of post-growth thermal annealing aimed at reducing and eliminating Te inclusions in them. In a 2D analysis, we observed that the sizes of the Te inclusions declined to 92% during a 60-h annealing of CZT at 510 °C under Cd vapor. Further, tellurium inclusions were eliminated completely in CMT samples annealed at 570 °C in Cd vapor for 26 h, whilst their electrical resistivity fell by an ordermore » of 102. During the temperature-gradient annealing of CMT at 730 °C and an 18 °C/cm temperature gradient for 18 h in a vacuum of 10-5 mbar, we observed the diffusion of Te from the sample, causing a reduction in size of the Te inclusions. For CZT samples annealed at 700 °C in a 10 °C/cm temperature gradient, we observed the migration of Te inclusions from a low-temperature region to a high one at 0.022 μm/s. During the temperature-gradient annealing of CZT in a vacuum of 10-5 mbar at 570 °C and 30 °C/cm for 18 h, some Te inclusions moved toward the high-temperature side of the wafer, while other inclusions of the same size, i.e., 10 µm in diameter, remained in the same position. These results show that the migration, diffusion, and reaction of Te with Cd in the matrix of CZT- and CMT-wafers are complex phenomena that depend on certain conditions.« less

  5. Post-Growth Annealing of Bridgman-grown CdZnTe and CdMnTe Crystals for Room-temperature Nuclear Radiation Detectors

    SciTech Connect

    Egarievwe, Stephen U.; Yang, Ge; Egarievwe, Alexander; Okwechime, Ifechukwude O.; Gray, Justin; Hales, Zaveon M.; Hossain, Anwar; Camarda, Guiseppe S.; Bolotnikov, Aleksey E.; James, Ralph B.

    2015-02-11

    Bridgman-grown cadmium zinc telluride (CdZnTe or CZT) and cadmium manganese telluride (CdMnTe or CMT) crystals often have Te inclusions that limit their performances as X-ray- and gamma-ray-detectors. We present here the results of post-growth thermal annealing aimed at reducing and eliminating Te inclusions in them. In a 2D analysis, we observed that the sizes of the Te inclusions declined to 92% during a 60-h annealing of CZT at 510 °C under Cd vapor. Further, tellurium inclusions were eliminated completely in CMT samples annealed at 570 °C in Cd vapor for 26 h, whilst their electrical resistivity fell by an order of 102. During the temperature-gradient annealing of CMT at 730 °C and an 18 °C/cm temperature gradient for 18 h in a vacuum of 10-5 mbar, we observed the diffusion of Te from the sample, causing a reduction in size of the Te inclusions. For CZT samples annealed at 700 °C in a 10 °C/cm temperature gradient, we observed the migration of Te inclusions from a low-temperature region to a high one at 0.022 μm/s. During the temperature-gradient annealing of CZT in a vacuum of 10-5 mbar at 570 °C and 30 °C/cm for 18 h, some Te inclusions moved toward the high-temperature side of the wafer, while other inclusions of the same size, i.e., 10 µm in diameter, remained in the same position. These results show that the migration, diffusion, and reaction of Te with Cd in the matrix of CZT- and CMT-wafers are complex phenomena that depend on certain conditions.

  6. The influence of temperature on fatigue-crack growth in a mill-annealed Ti-6Al-4V alloy

    NASA Technical Reports Server (NTRS)

    Wei, R. P.; Ritter, D. L.

    1971-01-01

    To understand the influence of temperature on the rate of fatigue crack growth in high strength metal alloys, constant load amplitude fatigue crack growth experiments were carried out using a 1/4 inch thick (6.35 mm) mill-annealed Ti-6Al-4V alloy plate as a model material. The rates of fatigue crack growth were determined as a function of temperature, ranging from room temperature to about 290 C and as a function of the crack tip, stress intensity factor K, in dehumidified high purity argon environment. The dependence of the rate of fatigue crack growth on K appears to be separable into two regions. The transition correlates with changes in both the microscopic and macroscopic appearances of the fracture surfaces, and suggests a change in the mechanism and the influence of microstructure on fatigue crack growth.

  7. Effect of annealing temperature on the optical property of high Cd content CdZnO films

    NASA Astrophysics Data System (ADS)

    Liu, Teren; Wang, Dongbo; Guo, Fengyun; Jiao, Shujie; Wang, Jinzhong; Liu, Yuhang; Luan, Chunyang; Cao, Wenwu; Zhao, Liancheng

    2016-09-01

    CdZnO films with high Cd contents (59%) have been deposited on quartz substrate by radio-frequency (RF) magnetron sputtering. The as-deposited CdZnO films can hardly show detectable photoluminescence (PL). However, once subjected to suitable annealing temperature, the CdZnO films exhibit pronounced PL. Furthermore, when the annealing temperature at 300 °C and above, that the CdZnO are changed from the single phase of the rs structure to involving w, zb, and rs phases. Consequently, reliable formation and optical property improvement of the CdZnO layers are achieved through annealing temperature at 300 °C.

  8. Preparation of nickel oxide thin films at different annealing temperature by sol-gel spin coating method

    NASA Astrophysics Data System (ADS)

    Abdullah, M. A. R.; Mamat, M. H.; Ismail, A. S.; Malek, M. F.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

    2016-07-01

    Preparation of NiO thin films at different annealing temperature by sol-gel method was conducted to synthesize the quality of the surface thin films. The effects of annealing temperature on the surface topology were systematically investigated. Our studies confirmed that the surface roughness of the thin films was increased whenever annealing temperature was increase. NiO thin films morphology structure analysis was confirmed by field emission scanning electron microscope. Surface roughness of the thin films was investigated by atomic force microscopy.

  9. The role of annealing temperature on the structural and magnetic consequences of Ta/PrFeB/Ta thin films processed by rapid thermal annealing

    NASA Astrophysics Data System (ADS)

    Ghasemi, Ali

    2016-04-01

    Ta/PrFeB/Ta thin films were deposited on CORNING 7059 by sputtering technique followed by rapid thermal annealing (RTA). The thickness of PrFeB was kept constant at 50 nm. The role of annealing temperature from 450 to 700 °C in a step of 50 °C for constant heating time of 60 s on the structural and magnetic consequences of thin films was studied by means of X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy and vibrating sample magnetometer. The (00l) texture was almost fully developed at temperature of 650 °C and with an increase in temperature up to 700 °C the (105) peaks was also appeared in the patterns. The grains size and surface roughness of PrFeB films were increased by an increase in temperature. It was found that with an increase in temperature up to 500 °C the coercivity was developed and enhanced to 0.75 MA/m by further increasing of temperature to 650 °C. The maximum remanent-magnetization ratio and coercivity were obtained at temperature of 650 °C. The magnetization reversal process is accompanied by the combination of domain wall motion (DWM) and Stoner-Wohlfarth (S-W) rotation. However, for PrFeB films annealed at 550-700 °C it is closer to the S-W model than DWM modes.

  10. Evolution of Self-Assembled Au NPs by Controlling Annealing Temperature and Dwelling Time on Sapphire (0001).

    PubMed

    Lee, Jihoon; Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kunwar, Sundar

    2015-12-01

    Au nanoparticles (NPs) have been utilized in a wide range of device applications as well as catalysts for the fabrication of nanopores and nanowires, in which the performance of the associated devices and morphology of nanopores and nanowires are strongly dependent on the size, density, and configuration of the Au NPs. In this paper, the evolution of the self-assembled Au nanostructures and NPs on sapphire (0001) is systematically investigated with the variation of annealing temperature (AT) and dwelling time (DT). At the low-temperature range between 300 and 600 °C, three distinct regimes of the Au nanostructure configuration are observed, i.e., the vermiform-like Au piles, irregular Au nano-mounds, and Au islands. Subsequently, being provided with relatively high thermal energy between 700 and 900 °C, the round dome-shaped Au NPs are fabricated based on the Volmer-Weber growth model. With the increased AT, the size of the Au NPs is gradually increased due to a more favorable surface diffusion while the density is gradually decreased as a compensation. On the other hand, with the increased DT, the size and density of Au NPs decrease due to the evaporation of Au at relatively high annealing temperature at 950 °C.

  11. Evolution of Self-Assembled Au NPs by Controlling Annealing Temperature and Dwelling Time on Sapphire (0001).

    PubMed

    Lee, Jihoon; Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kunwar, Sundar

    2015-12-01

    Au nanoparticles (NPs) have been utilized in a wide range of device applications as well as catalysts for the fabrication of nanopores and nanowires, in which the performance of the associated devices and morphology of nanopores and nanowires are strongly dependent on the size, density, and configuration of the Au NPs. In this paper, the evolution of the self-assembled Au nanostructures and NPs on sapphire (0001) is systematically investigated with the variation of annealing temperature (AT) and dwelling time (DT). At the low-temperature range between 300 and 600 °C, three distinct regimes of the Au nanostructure configuration are observed, i.e., the vermiform-like Au piles, irregular Au nano-mounds, and Au islands. Subsequently, being provided with relatively high thermal energy between 700 and 900 °C, the round dome-shaped Au NPs are fabricated based on the Volmer-Weber growth model. With the increased AT, the size of the Au NPs is gradually increased due to a more favorable surface diffusion while the density is gradually decreased as a compensation. On the other hand, with the increased DT, the size and density of Au NPs decrease due to the evaporation of Au at relatively high annealing temperature at 950 °C. PMID:26704710

  12. Effects of Low Temperature Anneal on the Interface Properties of Thermal Silicon Oxide for Silicon Surface Passivation.

    PubMed

    Balaji, Nagarajan; Park, Cheolmin; Chung, Sungyoun; Ju, Minkyu; Raja, Jayapal; Yi, Junsin

    2016-05-01

    High quality surface passivation has gained a significant importance in photovoltaic industry for reducing the surface recombination and hence fabricating low cost and high efficiency solar cells using thinner wafers. The formation of good-quality SiO2 films and SiO2/Si interfaces at low processing temperatures is a prerequisite for improving the conversion efficiency of industrial solar cells with better passivation. High-temperature annealing in inert ambient is promising to improve the SiO2/Si interface. However, annealing treatments could cause negative effects on SiO2/Si interfaces due to its chemical at high temperatures. Low temperature post oxidation annealing has been carried out to investigate the structural and interface properties of Si-SiO2 system. Quasi Steady State Photo Conductance measurements shows a promising effective carrier lifetime of 420 μs, surface recombination velocity of 22 cm/s and a low interface trap density (D(it)) of 4 x 10(11) states/cm2/eV after annealing. The fixed oxide charge density was reduced to 1 x 10(11)/cm2 due to the annealing at 500 degrees C. The FWHM and the Si-O peak wavenumber corresponding to the samples annealed at 500 degrees C reveals that the Si dangling bonds in the SiO2 films due to the oxygen defects was reduced by the low temperature post oxidation annealing. PMID:27483822

  13. Effects of annealing on the polymorphic structure of starches from sweet potatoes (Ayamurasaki and Sunnyred cultivars) grown at various soil temperatures.

    PubMed

    Genkina, Natalia K; Wasserman, Lyubov A; Noda, Takahiro; Tester, Richard F; Yuryev, Vladimir P

    2004-04-28

    Starches extracted from the sweet potato cultivars Sunnyred and Ayamurasaki grown at 15 or 33 degrees C (soil temperature) were annealed in excess water (3 mg starch/mL water) for different times (1, 4, 8 or 10h) at the temperatures 2-3 degrees K below the onset melting temperature. The structures of annealed starches, as well as their gelatinisation (melting) properties, were studied using high-sensitivity differential scanning calorimetry (HSDSC). In excess water, the single endothermic peak shifted to higher temperatures, while the melting (gelatinisation) enthalpy changed only very slightly, if any. The elevation of gelatinisation temperature was associated with increasing order/thickness of the crystalline lamellae. The only DSC endotherm identified in 0.6 M KCl for Sunnyred starch grown at 33 degrees C was attributed to A-type polymorphic structure. The multiple endothermic forms observed by DSC performed in 0.6M KCl for annealed starches from both cultivars grown at 15 degrees C provided evidence of a complex C-type (A- plus B-type) polymorphic structure of crystalline lamellae. The A:B-ratio of two polymorphic forms increased upon annealing due to partial transformation of B- to A-polymorph, which was time dependent. Long heating periods facilitated the maximal transformation of B- to A-polymorph associated with limited A:B ratio.

  14. Effects of annealing on the polymorphic structure of starches from sweet potatoes (Ayamurasaki and Sunnyred cultivars) grown at various soil temperatures.

    PubMed

    Genkina, Natalia K; Wasserman, Lyubov A; Noda, Takahiro; Tester, Richard F; Yuryev, Vladimir P

    2004-04-28

    Starches extracted from the sweet potato cultivars Sunnyred and Ayamurasaki grown at 15 or 33 degrees C (soil temperature) were annealed in excess water (3 mg starch/mL water) for different times (1, 4, 8 or 10h) at the temperatures 2-3 degrees K below the onset melting temperature. The structures of annealed starches, as well as their gelatinisation (melting) properties, were studied using high-sensitivity differential scanning calorimetry (HSDSC). In excess water, the single endothermic peak shifted to higher temperatures, while the melting (gelatinisation) enthalpy changed only very slightly, if any. The elevation of gelatinisation temperature was associated with increasing order/thickness of the crystalline lamellae. The only DSC endotherm identified in 0.6 M KCl for Sunnyred starch grown at 33 degrees C was attributed to A-type polymorphic structure. The multiple endothermic forms observed by DSC performed in 0.6M KCl for annealed starches from both cultivars grown at 15 degrees C provided evidence of a complex C-type (A- plus B-type) polymorphic structure of crystalline lamellae. The A:B-ratio of two polymorphic forms increased upon annealing due to partial transformation of B- to A-polymorph, which was time dependent. Long heating periods facilitated the maximal transformation of B- to A-polymorph associated with limited A:B ratio. PMID:15063196

  15. Excitation intensity dependent photoluminescence of annealed two-dimensional MoS2 grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kaplan, D.; Mills, K.; Lee, J.; Torrel, S.; Swaminathan, V.

    2016-06-01

    Here, we present detailed results of Raman and photoluminescence (PL) characterization of monolayers of MoS2 grown by chemical vapor deposition (CVD) on SiO2/Si substrates after thermal annealing at 150 °C, 200 °C, and 250 °C in an argon atmosphere. In comparison to the as-grown monolayers, annealing in the temperature range of 150-250 °C brings about significant changes in the band edge luminescence. It is observed that annealing at 150 °C gives rise to a 100-fold increase in the PL intensity and produces a strong band at 1.852 eV attributed to a free-to-bound transition that dominates over the band edge excitonic luminescence. This band disappears for the higher annealing temperatures. The improvement in PL after the 200 °C anneal is reduced in comparison to that obtained after the 150 °C anneal; this is suggested to arise from a decrease in the non-radiative lifetime caused by the creation of sulfur di-vacancies. Annealing at 250 °C degrades the PL in comparison to the as-grown sample because of the onset of disorder/decomposition of the sample. It is clear that the PL features of the CVD-grown MoS2 monolayer are profoundly affected by thermal annealing in Ar atmosphere. However, further detailed studies are needed to identify, unambiguously, the role of native defects and/or adsorbed species in defining the radiative channels in annealed samples so that the beneficial effect of improvement in the optical efficiency of the MoS2 monolayers can be leveraged for various device applications.

  16. Thermally activated decomposition of (Ga,Mn)As thin layer at medium temperature post growth annealing

    NASA Astrophysics Data System (ADS)

    Melikhov, Y.; Konstantynov, P.; Domagala, J.; Sadowski, J.; Chernyshova, M.; Wojciechowski, T.; Syryanyy, Y.; Demchenko, I. N.

    2016-05-01

    The redistribution of Mn atoms in Ga1-xMnxAs layer during medium-temperature annealing, 250-450 oC, by Mn K-edge X-ray absorption fine structure (XAFS) recorded at ALBA facility, was studied. For this purpose Ga1-xMnxAs thin layer with x=0.01 was grown on AlAs buffer layer deposited on GaAs(100) substrate by molecular beam epitaxy (MBE) followed by annealing. The examined layer was detached from the substrate using a “lift-off” procedure in order to eliminate elastic scattering in XAFS spectra. Fourier transform analysis of experimentally obtained EXAFS spectra allowed to propose a model which describes a redistribution/diffusion of Mn atoms in the host matrix. Theoretical XANES spectra, simulated using multiple scattering formalism (FEFF code) with the support of density functional theory (WIEN2k code), qualitatively describe the features observed in the experimental fine structure.

  17. Finding Low-Temperature States with Parallel Tempering, Simulated Annealing and Simple Monte Carlo

    NASA Astrophysics Data System (ADS)

    Moreno, J. J.; Katzgraber, Helmut G.; Hartmann, Alexander K.

    Monte Carlo simulation techniques, like simulated annealing and parallel tempering, are often used to evaluate low-temperature properties and find ground states of disordered systems. Here we compare these methods using direct calculations of ground states for three-dimensional Ising diluted antiferromagnets in a field (DAFF) and three-dimensional Ising spin glasses (ISG). For the DAFF, we find that, with respect to obtaining ground states, parallel tempering is superior to simple Monte Carlo and to simulated annealing. However, equilibration becomes more difficult with increasing magnitude of the externally applied field. For the ISG with bimodal couplings, which exhibits a high degeneracy, we conclude that finding true ground states is easy for small systems, as is already known. But finding each of the degenerate ground states with the same probability (or frequency), as required by Boltzmann statistics, is considerably harder and becomes almost impossible for larger systems.

  18. The effects of cluster carbon implantation at low temperature on damage recovery after annealing

    NASA Astrophysics Data System (ADS)

    Onoda, Hiroshi; Nakashima, Yoshiki; Hamamoto, Nariaki; Nagayama, Tsutomu; Koga, Yuji; Umisedo, Sei; Kawamura, Yasunori; Hashimoto, Masahiro

    2012-11-01

    Amorphous Si layer formation with cluster carbon ion implantations at low substrate temperature and its effects on damage recovery and diffusion suppression have been discussed. Cluster carbon molecule species (C3Hx˜C7Hx), implantation temperature (RT ˜ -60°C), implantation dose and energy were used as parameters. Amorphous Si formation by cluster carbon implantation is more effective compared with monomer carbon implantation. Low temperature cluster carbon implantations increase amorphous Si thickness far beyond monomer carbon implantation even at very low temperature. Amorphous-crystal interface smoothness was characterized by Rutherford Backscattering Spectroscopy, and is improved by lower temperature implantations. The smoothness improvement affects the residual damage, End of Range Defects, after annealing. Thicker amorphous Si over 100 nm depth can be formed with light Cn+ molecule implantations. That makes it possible to suppress wide distributed phosphorus diffusion.

  19. Sub-surface oxide features at the aluminum-sapphire interface after low temperature annealing

    NASA Astrophysics Data System (ADS)

    Dutta, Sreya

    This work focuses on the formation of sub-surface oxide features that form at the aluminum-sapphire interface during a low temperature heat-treatment. The features consist of two parts, stable alpha-alumina ridges on the substrate, and faceted pyramidal structures composed of thin, low-temperature oxide shells that are bounded by the ridges. It is surprising to observe the formation of thermodynamically stable alpha-alumina at a low temperature. The ridges are epitaxial with the (0001) sapphire substrate and the overlying metal. The pyramidal features resemble closely the Wulff shape in aluminum. Experiments show that these features are underlying the annealing hillocks. This work is a detailed study of such oxide interfacial features associated with hollow hillocks. At the annealing temperatures (below the melting point of aluminum), the aluminum thin film is subjected to compressive stresses arising from the thermal expansion coefficient mismatch and this is aided by dewetting at the aluminum-sapphire interface. Creep cavitation and grain boundary sliding are postulated to help in the cavity formation. Annealing holes are also observed in the thin films. Two different types of holes are seen: dendritic branched holes and hexagonal faceted holes (drums). At lower temperature and thickness, dendritic holes are seen to be formed at the grain boundaries. The drums form within the grains at higher temperatures and in thicker films. The drums have a surface oxide layer suspended on the top. It is postulated that clustering of vacancies due to the presence of irregularities, defects, and dislocations at the interface as well as dewetting causes the nucleation of the drums at the interface. Numerous hillock-hole couples were seen. Thinning of the metal in areas near the hillocks could possibly aid in the hole formation process. It is speculated that the hole growth occurred during the cooling stage when the film was subjected to tensile stresses. Another interesting

  20. Effect of annealing temperature on structural, morphological and electrical properties of nanoparticles TiO2 thin films by sol-gel method

    NASA Astrophysics Data System (ADS)

    Muaz, A. K. M.; Hashim, U.; Arshad, M. K. Md.; Ruslinda, A. R.; Ayub, R. M.; Gopinath, Subash C. B.; Voon, C. H.; Liu, Wei-Wen; Foo, K. L.

    2016-07-01

    In this paper, the sol-gel method is used to prepare nanoparticles titanium dioxide (TiO2) thin films at different annealing temperature. The prepared sol was deposited on the p-SiO2 substrates by spin coating technique under room temperature. The nanoparticles TiO2 solution was synthesized using Ti{OCH(CH3)2}4 as a precursor with an methanol solution at a molar ratio 1:10. The prepared TiO2 sols will further validate through structural, morphological and electrical properties. From the X-ray diffraction (XRD) analysis, as-deposited films was found to be amorphous in nature and tend to transform into tetragonal anatase and rutile phase as the films annealed at 573 and 773 K, respectively. The diversification of the surface roughness was characterized by atomic force microscopy (AFM) indicated the roughness and thickness very dependent on the annealing temperature. The two-point probe electrical resistance and conductance of nanoparticles TiO2 thin films were determined by the DC current-voltage (IV) analysis. From the I-V measurement, the electrical conductance increased as the films annealed at higher temperature.

  1. Temperature dependent magnetic coupling between ferromagnetic FeTaC layers in multilayer thin films

    NASA Astrophysics Data System (ADS)

    Singh, Akhilesh Kumar; Hsu, Jen-Hwa; Perumal, Alagarsamy

    2016-11-01

    We report systematic investigations on temperature dependent magnetic coupling between ferromagnetic FeTaC layers and resulting magnetic properties of multilayer structured [FeTaC (~67 nm)/Ta(x nm)]2/FeTaC(~67 nm)] thin films, which are fabricated directly on thermally oxidized Si substrate. As-deposited amorphous films are post annealed at different annealing temperatures (TA=200, 300 and 400 °C). Structural analyzes reveal that the films annealed at TA≤200 °C exhibit amorphous nature, while the films annealed above 200 °C show nucleation of nanocrystals at TA=300 °C and well-defined α-Fe nanocrystals with size of about 9 nm in amorphous matrix for 400 °C annealed films. Room temperature and temperature dependent magnetic hysteresis (M-H) loops reveal that magnetization reversal behaviors and magnetic properties are strongly depending on spacer layer thickness (x), TA and temperature. A large reduction in coercivity (HC) was observed for the films annealed at 200 °C and correlated to relaxation of stress quenched in during the film deposition. On the other hand, the films annealed at 300 °C exhibit unusual variation of HC(T), i.e., a broad minimum in HC(T) vs T curve. This is caused by change in magnetic coupling between ferromagnetic layers having different microstructure. In addition, the broad minimum in the HC(T) curve shifts from 150 K for x=1 film to 80 K for x=4 film. High-temperature thermomagnetization data show a strong (significant) variation of Curie temperature (TC) with TA (x). The multilayer films annealed at 200 °C exhibit low value of TC with a minimum of 350 K for x=4 film. But, the films annealed at 400 °C show largest TC with a maximum of 869 K for x=1 film. The observed results are discussed on the basis of variations in magnetic couplings between FeTaC layers, which are majorly driven by temperature, spacer layer thickness, annealing temperature and nature of interfaces.

  2. Effect of annealing on the nonequilibrium carrier lifetime in GaAs grown at low temperatures

    SciTech Connect

    Pastor, A. A.; Prokhorova, U. V.; Serdobintsev, P. Yu.; Chaldyshev, V. V. Yagovkina, M. A.

    2013-08-15

    GaAs samples grown by molecular-beam epitaxy at low (230 Degree-Sign C) temperatures are investigated. One of the samples is subjected to aftergrowth annealing at 600 Degree-Sign C. Using an unconventional pump-probe scheme for measuring the dynamic variation in the light refractive index, the nonequilibrium charge-carrier lifetime (275 {+-} 30 fs before annealing) is determined. Such a short carrier lifetime in the unannealed material is due to the high concentration of point defects, mainly As{sub Ga} antisite defects. According to X-ray diffraction and steady-state optical absorption data, the As{sub Ga} concentration in the samples is 3 Multiplication-Sign 10{sup 19} cm{sup -3}, which corresponds to an arsenic excess of 0.26 at %. Upon annealing at 600 Degree-Sign C, the superstoichiometric As defects self-organize and form As nanoinclusions in the GaAs crystal matrix. It is shown that in this case the nonequilibrium charge-carrier lifetime increases to 452 {+-} 5 fs. This lifetime is apparently ensured by the capture of non-equilibrium charge carriers at metal As nanoinclusions.

  3. Influence of annealing temperature on the structural, optical and electrical properties of amorphous Zinc Sulfide thin films

    NASA Astrophysics Data System (ADS)

    Göde, F.; Güneri, E.; Kariper, A.; Ulutaş, C.; Kirmizigül, F.; Gümüş, C.

    2011-11-01

    Zinc sulfide films have been deposited on glass substrates at room temperature by the chemical bath deposition technique. The growth mechanism is studied using X-ray diffraction, scanning electron microscopy, optical absorption spectra and electrical measurements. The as-deposited film was given thermal annealing treatment in air atmosphere at various temperatures (100, 200, 300 400 and 500 °C) for 1 h. The annealed film was also characterized by structural, optical and electrical studies. The structural analyses revealed that the as-deposited film was amorphous, but after being annealed at 500 °C, it changed to polycrystalline. The optical band gap is direct with a value of 4.01 eV, but this value decreased to 3.74 eV with annealing temperature, except for the 500 °C anneal where it only decreased to 3.82 eV. The refractive index (n), extinction coefficient (k), and real (ɛ1) and imaginary (ɛ2) parts of the dielectric constant are evaluated. Raman peaks appearing at ~478 cm-1, ~546 cm-1, ~778 cm-1 and ~1082 cm-1 for the annealed film (500 °C) were attributed to [TOl+LAΣ, 2TOΓ, 2LO, 3LO phonons of ZnS. The electrical conductivities of both as-deposited and annealed films have been calculated to be of the order of ~10-10 (Ω cm)-1 .

  4. High temperature annealing of minority carrier traps in irradiated MOCVD n(+)p InP solar cell junctions

    NASA Technical Reports Server (NTRS)

    Messenger, S. R.; Walters, R. J.; Summers, G. P.

    1993-01-01

    Deep level transient spectroscopy was used to monitor thermal annealing of trapping centers in electron irradiated n(+)p InP junctions grown by metalorganic chemical vapor deposition, at temperatures ranging from 500 up to 650K. Special emphasis is given to the behavior of the minority carrier (electron) traps EA (0.24 eV), EC (0.12 eV), and ED (0.31 eV) which have received considerably less attention than the majority carrier (hole) traps H3, H4, and H5, although this work does extend the annealing behavior of the hole traps to higher temperatures than previously reported. It is found that H5 begins to anneal above 500K and is completely removed by 630K. The electron traps begin to anneal above 540K and are reduced to about half intensity by 630K. Although they each have slightly different annealing temperatures, EA, EC, and ED are all removed by 650K. A new hole trap called H3'(0.33 eV) grows as the other traps anneal and is the only trap remaining at 650K. This annealing behavior is much different than that reported for diffused junctions.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  6. Effect of annealing temperature on the morphology and optical properties of PMMA films by spin-coating method

    NASA Astrophysics Data System (ADS)

    Aadila, A.; Afaah, A. N.; Asib, N. A. M.; Mohamed, R.; Rusop, M.; Khusaimi, Z.

    2016-07-01

    Poly(methyl methacrylate) (PMMA) films were deposited on glass substrate by sol-gel spin-coating method. The films were annealed for 10 minutes in furnace at different annealing temperature of room temperature, 50, 100, 150 and 200 °C. The effect of annealing temperatures to the surface and optical properties of PMMA films spin-coated on the substrate were investigated by Atomic Force Microscope (AFM) and Ultraviolet-Visible (UV-Vis) Spectroscopy. It was observed in AFM analysis all the annealed films show excellent smooth surface with zero roughness. All the samples demonstrate a high transmittance of 80% in UV region as shown in UV-Vis measurement. Highly transparent films indicate the films are good optical properties and could be applied in various optical applications and also in non-linear optics.

  7. Structure and microhardness of Al-Si-Cu-Ni alloy after severe plastic deformation and high-temperature annealing

    NASA Astrophysics Data System (ADS)

    Shvets, Karina; Khalikova, Gulnara; Korznikova, Elena; Trifonov, Vadim

    2015-10-01

    The effect of severe plastic deformation by high-pressure torsion (HPT) and subsequent annealing on the microstructure and microhardness of squeeze casting Al-22%Si-3%Cu-1.7%Ni alloy was investigated. HPT was performed at room temperature with 5 rotations under the pressure of 4 GPa. Annealing temperature range varied from 300 to 500°C for 5 min. HPT resulted in refinement and partial dissolution of the primary silicon and intermetallic particles in aluminum matrix and structure fragmentation that caused the microhardness increase. Subsequent annealing lead to the decomposition of the supersaturated solid solution that took place simultaneously with recovery and recrystallization of the fragmented structure. Increase of annealing temperature resulted in decrease of microhardness values.

  8. Role of annealing temperatures on structure polymorphism, linear and nonlinear optical properties of nanostructure lead dioxide thin films

    NASA Astrophysics Data System (ADS)

    Zeyada, H. M.; Makhlouf, M. M.

    2016-04-01

    The powder of as synthesized lead dioxide (PbO2) has polycrystalline structure β-PbO2 phase of tetragonal crystal system. It becomes nanocrystallites α-PbO2 phase with orthorhombic crystal system upon thermal deposition to form thin films. Annealing temperatures increase nanocrystallites size from 28 to 46 nm. The optical properties of α-PbO2 phase were calculated from absolute values of transmittance and reflectance at nearly normal incidence of light by spectrophotometer measurements. The refractive and extinction indices were determined and showed a response to annealing temperatures. The absorption coefficient of α-PbO2 films is >106 cm-1 in UV region of spectra. Analysis of the absorption coefficient spectra near optical edge showed indirect allowed transition. Annealing temperature decreases the value of indirect energy gap for α-PbO2 films. The dispersion parameters such as single oscillator energy, dispersion energy, dielectric constant at high frequency and lattice dielectric constant were calculated and its variations with annealing temperatures are reported. The nonlinear refractive index (n2), third-order nonlinear susceptibility (χ(3)) and nonlinear absorption coefficient (βc) were determined. It was found that χ(3), n2 and β increase with increasing photon energy and decrease with increasing annealing temperature. The pristine film of α-PbO2 has higher values of nonlinear optical constants than for annealed films; therefore it is suitable for applications in manufacturing nonlinear optical devices.

  9. Study of the Temperature Dependence of Coercivity in MnBi

    NASA Astrophysics Data System (ADS)

    Curcio, C.; Olivetti, E. S.; Martino, L.; Küpferling, M.; Basso, V.

    Two set of polycrystalline MnBi bulk samples, as-annealed and compacted powders, with different grain size, were prepared through powder metallurgy. Coercivity mechanisms were investigated by Kronmüller plot analysis, evaluating α and Neff parameters, which take into account the effect of microstructure. The temperature dependence of coercivity of the as-annealed sample (α= 0.31) is compatible with pinning-type mechanisms, while that of the compacted powders (α= 0.41) indicates nucleation-type processes. Irreversible effects of temperature dependence of coercivity have been investigated.

  10. Photoluminescence of monocrystalline and stain-etched porous silicon doped with high temperature annealed europium

    NASA Astrophysics Data System (ADS)

    Guerrero-Lemus, R.; Montesdeoca-Santana, A.; González-Díaz, B.; Díaz-Herrera, B.; Velázquez, J. J.; Hernández-Rodríguez, C.; Jiménez-Rodríguez, E.

    2011-08-01

    In this work, for the first time, the photoluminescent emission and excitation spectra of non-textured layers and stain-etched porous silicon layers (PSLs) doped with high temperature annealed europium (Eu) are evaluated. The PSLs are evaluated as a host for rare earth ions and as an antireflection coating. The applied doping process, which consists in a simple impregnation method followed by a high-temperature annealing step, is compatible with the standard processes in the fabrication of solar cells. The results show down-shifting processes with a maximum photoluminescent intensity at 615 nm, related to the transition 5D0 → 7F2. Different initial concentrations of Eu(NO3)3 are evaluated to study the influence of the rare earth concentration on the photoluminescent intensity. The chemical composition and the morphology of Eu-doped PSLs are examined by means of x-ray dispersion spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. These Eu-doped layers are considered to be applied as energy converters in silicon-based third generation solar cells.

  11. Field emission behavior of carbon nanotube field emitters after high temperature thermal annealing

    SciTech Connect

    Sun, Yuning; Shin, Dong Hoon; Yun, Ki Nam; Leti, Guillaume; Hwang, Yeon Mo; Song, Yenan; Saito, Yahachi; Lee, Cheol Jin

    2014-07-15

    The carbon nanotube (CNT) field emitters have been fabricated by attaching a CNT film on a graphite rod using graphite adhesive material. The CNT field emitters showed much improved field emission properties due to increasing crystallinity and decreasing defects in CNTs after the high temperature thermal annealing at 900 °C in vacuum ambient. The CNT field emitters showed the low turn-on electric field of 1.15 V/μm, the low threshold electric field of 1.62 V/μm, and the high emission current of 5.9 mA which corresponds to a current density of 8.5 A/cm{sup 2}. In addition, the CNT field emitters indicated the enhanced field emission properties due to the multi-stage effect when the length of the graphite rod increases. The CNT field emitter showed good field emission stability after the high temperature thermal annealing. The CNT field emitter revealed a focused electron beam spot without any focusing electrodes and also showed good field emission repeatability.

  12. Structural and magnetic properties of Zn0.95Cr0.05O annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Heiba, Zein K.; Arda, L.; Mohamed, Mohamed Bakr

    2015-09-01

    The doped ZnO system Zn0.95Cr0.05O (ZCO) was prepared as nano-polycrystalline by a simple sol-gel process and annealed at different temperatures. Structural and microstructure analyses are performed by applying x-ray diffraction (XRD) and Rietveld method. Results showed that Cr ions reside in the ZnO lattice substitutionally for Zn yielding ZCO single phase. The Rietveld refined u-fractional coordinate of Zn/Cr decreased with the annealing temperature from 0.3879 Å at 400 °C to 0.3740 Å at 600 °C. The Zn tetrahedrons become more symmetric and the distortion is gradually relieved by annealing. The field cooled (FC) and zero field cooled (ZFC) magnetization versus temperature and the magnetization versus applied field at different temperatures were carried out. Measurements indicated that the absence of ferromagnetic behavior with magnetization slightly changed by changing the annealing temperature and no saturation. The Curie-Weiss paramagnetic temperature θ for annealed samples is negative indicating the antiferromagnetic nature of the samples.

  13. Overcoming Zn segregation in CdZnTe with the temperature gradient annealing

    NASA Astrophysics Data System (ADS)

    Kim, K.; Bolotnikov, A. E.; Camarda, G. S.; Hossain, A.; James, R. B.

    2016-05-01

    The availability of large volume crystals with the same energy gap in melt-grown CdZnTe (CZT) is restricted due to the Zn segregation in CdTe hosts. We observed the migration of Zn in the solid phase along the positive temperature gradient direction both in situ and post-growth temperature gradient annealing (TGA) of CZT. Diffusivity of Zn obtained from the in situ TGA was approximately 10-5 cm2/s order and completely different mechanism with that of post-growth. The CZT ingots obtained through in situ TGA have uniform Zn and resistivity of 1010 Ω cm orders. The CZT detectors fabricated from in situ TGA applied ingots exhibit 10% of energy resolution for 59.5 keV peak of 241Am.

  14. Effects of high-temperature annealing on ESR properties of solid solutions of garnet minerals

    NASA Astrophysics Data System (ADS)

    Gundu Rao, T. K.; Cano, Nilo F.; Chubaci, Jose F. D.; Watanabe, S.

    2016-04-01

    A garnet (G7) silicate mineral belonging to pyralspite subgroup was studied using the technique of electron spin resonance (ESR). This study shows that iron is present in G7 as isolated species as well as species coupled by dipolar interactions. The ESR data shows a gradual increase of cluster of Fe3+ ions accompanied by decrease of dipolar interactions and increase of possible exchange interactions at high temperature. The Fe2+→Fe3+ oxidation process occurs in the garnets as a function of annealing temperature. Thermoluminescence (TL) peaks at approximately 190 and 340 °C are observed in the irradiated G7 garnet. Investigations using the technique of ESR were carried out to identify the centers involved in the TL process.

  15. Annealing temperature and environment effects on ZnO nanocrystals embedded in SiO2: a photoluminescence and TEM study

    PubMed Central

    2013-01-01

    We report on efficient ZnO nanocrystal (ZnO-NC) emission in the near-UV region. We show that luminescence from ZnO nanocrystals embedded in a SiO2 matrix can vary significantly as a function of the annealing temperature from 450°C to 700°C. We manage to correlate the emission of the ZnO nanocrystals embedded in SiO2 thin films with transmission electron microscopy images in order to optimize the fabrication process. Emission can be explained using two main contributions, near-band-edge emission (UV range) and defect-related emissions (visible). Both contributions over 500°C are found to be size dependent in intensity due to a decrease of the absorption cross section. For the smallest-size nanocrystals, UV emission can only be accounted for using a blueshifted UV contribution as compared to the ZnO band gap. In order to further optimize the emission properties, we have studied different annealing atmospheres under oxygen and under argon gas. We conclude that a softer annealing temperature at 450°C but with longer annealing time under oxygen is the most preferable scenario in order to improve near-UV emission of the ZnO nanocrystals embedded in an SiO2 matrix. PMID:24314071

  16. Effects of rolling temperature and subsequent annealing on mechanical properties of ultrafine-grained Cu–Zn–Si alloy

    SciTech Connect

    Zhang, Xiangkai; Yang, Xuyue; Chen, Wei; Qin, Jia; Fouse, Jiaping

    2015-08-15

    The effects of rolling temperature and subsequent annealing on mechanical properties of Cu–Zn–Si alloy were investigated by using X-ray diffraction, transmission electron microscope, electron back scattered diffraction and tensile tests. The Cu–Zn–Si alloy has been processed at cryogenic temperature (approximately 77 K) and room temperature up to different rolling strains. It has been identified that the cryorolled Cu–Zn–Si alloy samples show a higher strength compared with those room temperature rolled samples. The improved strength of cryorolled samples is resulted from grain size effect and higher densities of dislocations and deformation twins. And subsequent annealing, as a post-heat treatment, enhanced the ductility. An obvious increase in uniform elongation appears when the volume fraction of static recrystallization grains exceeds 25%. The strength–ductility combination of the annealed cryorolled samples is superior to that of annealed room temperature rolled samples, owing to the finer grains, high fractions of high angle grain boundaries and twins. - Highlights: • An increase in hardness of Cu–Zn–Si alloy is noticed during annealing process. • Thermal stability is reduced in Cu–Zn–Si alloy by cryorolling. • An obvious enhancement in UE is noticed when fraction of SRX grains exceeds 25%. • A superior strength–ductility combination is achieved in the cryorolling samples.

  17. The stress corrosion resistance and the cryogenic temperature mechanical properties of annealed Nitronic 60 bar material

    NASA Technical Reports Server (NTRS)

    Montano, J. W. L.

    1977-01-01

    Ambient and cryogenic temperature mechanical properties and the ambient temperature stress corrosion properties of annealed, straightened, and centerless ground Nitronic 60 stainless steel alloy bar material are presented. The mechanical properties of longitudinal specimens were evaluated at test temperatures from ambient to liquid hydrogen. The tensile test data indicated increasing strength with decreasing temperature to -196 C. Below liquid nitrogen temperature the smooth tensile and notched tensile strengths decreased slightly while the elongation and reduction of area decreased drastically. The Charpy V-notched impact energy decreased steadily with decreasing test temperature. Stress corrosion tests were performed on longitudinal tensile specimens and transverse C-ring specimens exposed to: alternate immersion in a 3.5% NaCl bath; humidity cabinet; and a 5% salt spray atmosphere. The longitudinal tensile specimens experienced no corrosive attack. Approximately 3/4 of the transverse C-rings exposed to alternate immersion and to salt spray experienced a pitting attack on the top and bottom ends. Additional stress corrosion tests were performed on transverse tensile specimens. No failures occurred in the 90% stressed specimens exposed for 90 days in the alternate immersion and salt spray environments

  18. Energy dependence of defects in a-Si:H solar cells during degradation and annealing processes

    SciTech Connect

    Caputo, D.; Lemmi, F.; Palma, F.

    1997-07-01

    In this work the authors report on the effect of current-induced degradation and annealing on p-i-n amorphous silicon solar cells. Current-voltage curves and capacitance measurements under forward bias have been used to monitor the current-induced changes as a function of time. They found that the recovery rate increases with the annealing current, while the stabilized value of efficiency decreases. Comparison of short circuit current and capacitance evolution suggests that defect kinetics in the electronic gap occurs in a different way during degradation and annealing. This behavior can be modeled assuming a faster annealing of defects closest to the extended band and a slower annealing of mid-gap defects.

  19. Annealing dependence of residual stress and optical properties of TiO2 thin film deposited by different deposition methods.

    PubMed

    Chen, Hsi-Chao; Lee, Kuan-Shiang; Lee, Cheng-Chung

    2008-05-01

    Titanium oxide (TiO(2)) thin films were prepared by different deposition methods. The methods were E-gun evaporation with ion-assisted deposition (IAD), radio-frequency (RF) ion-beam sputtering, and direct current (DC) magnetron sputtering. Residual stress was released after annealing the films deposited by RF ion-beam or DC magnetron sputtering but not evaporation, and the extinction coefficient varied significantly. The surface roughness of the evaporated films exceeded that of both sputtered films. At the annealing temperature of 300 degrees C, anatase crystallization occurred in evaporated film but not in the RF ion-beam or DC magnetron-sputtered films. TiO(2) films deposited by sputtering were generally more stable during annealing than those deposited by evaporation.

  20. Annealing dependence of residual stress and optical properties of TiO2 thin film deposited by different deposition methods.

    PubMed

    Chen, Hsi-Chao; Lee, Kuan-Shiang; Lee, Cheng-Chung

    2008-05-01

    Titanium oxide (TiO(2)) thin films were prepared by different deposition methods. The methods were E-gun evaporation with ion-assisted deposition (IAD), radio-frequency (RF) ion-beam sputtering, and direct current (DC) magnetron sputtering. Residual stress was released after annealing the films deposited by RF ion-beam or DC magnetron sputtering but not evaporation, and the extinction coefficient varied significantly. The surface roughness of the evaporated films exceeded that of both sputtered films. At the annealing temperature of 300 degrees C, anatase crystallization occurred in evaporated film but not in the RF ion-beam or DC magnetron-sputtered films. TiO(2) films deposited by sputtering were generally more stable during annealing than those deposited by evaporation. PMID:18449260

  1. Passivation mechanism of thermal atomic layer-deposited Al2O3 films on silicon at different annealing temperatures

    PubMed Central

    2013-01-01

    Thermal atomic layer-deposited (ALD) aluminum oxide (Al2O3) acquires high negative fixed charge density (Qf) and sufficiently low interface trap density after annealing, which enables excellent surface passivation for crystalline silicon. Qf can be controlled by varying the annealing temperatures. In this study, the effect of the annealing temperature of thermal ALD Al2O3 films on p-type Czochralski silicon wafers was investigated. Corona charging measurements revealed that the Qf obtained at 300°C did not significantly affect passivation. The interface-trapping density markedly increased at high annealing temperature (>600°C) and degraded the surface passivation even at a high Qf. Negatively charged or neutral vacancies were found in the samples annealed at 300°C, 500°C, and 750°C using positron annihilation techniques. The Al defect density in the bulk film and the vacancy density near the SiOx/Si interface region decreased with increased temperature. Measurement results of Qf proved that the Al vacancy of the bulk film may not be related to Qf. The defect density in the SiOx region affected the chemical passivation, but other factors may dominantly influence chemical passivation at 750°C. PMID:23452508

  2. Microstructure evolution of a ZrC coating layer in TRISO particles during high-temperature annealing

    NASA Astrophysics Data System (ADS)

    Kim, Daejong; Chun, Young Bum; Ko, Myeong Jin; Lee, Hyeon-Geun; Cho, Moon-Sung; Park, Ji Yeon; Kim, Weon-Ju

    2016-10-01

    The influence of high-temperature annealing on the microstructure of zirconium carbide (ZrC) was investigated in relation to its application as a coating layer of a nuclear fuel in a very high temperature gas cooled reactor. ZrC was deposited as a constituent coating layer of TRISO coated particles by a fluidized bed chemical vapor deposition method using a ZrCl4-CH4-Ar-H2 system. The grain growth of ZrC during high-temperature annealing was strongly influenced by the co-deposition of free carbon. Sub-stoichiometric ZrC coatings have experienced a significant grain growth during high-temperature annealing at 1800 °C and 1900 °C for 1 h. On the other hand, a dual phase of stoichiometric ZrC and free carbon experienced little grain growth. It was revealed that the free carbon of the as-deposited ZrC was primarily distributed within the ZrC grains but was redistributed to the grain boundaries after annealing. Consequently, carbon at the grain boundary retarded the grain growth of ZrC. Electron backscatter diffraction (EBSD) results showed that as-deposited ZrC had (001) a preferred orientation that kept its favored direction after significant grain growth during annealing. The hardness slightly decreased as the grain growth progressed.

  3. Effect of annealing temperature on gelatinization of rice starch suspension as studied by rheological and thermal measurements.

    PubMed

    Tsutsui, Kazumi; Katsuta, Keiko; Matoba, Teruyoshi; Takemasa, Makoto; Nishinari, Katsuyoshi

    2005-11-16

    The effect of annealing temperature (Ta) on the rheological behavior of 10 wt % rice starch suspension was investigated by the dynamic viscoelasticity, the differential scanning calorimetry (DSC), and the amount of leached out amylose and the swelling ratio of starch suspension. The rheological behaviors of the annealed samples are classified into three types in terms of Ta: Ta1, 48 and 55 degrees C, which are much lower than the gelatinization temperature, Tgel (=62 degrees C); Ta2, 58, 60, and 62 degrees C, which are almost the same as Tgel; and Ta3, 65, 68, 70, and 73 degrees C, which are much higher than Tgel. For the samples annealed at Ta2, the onset temperature of the storage and the loss moduli, G' and G'', increased with increasing T(a), and G' and G" in the temperature range from 65 to 90 degrees C gradually increased though smaller than those for the nonannealed sample, the control. This can be understood by the partial gelatinization; i.e., the leached out amylose prevents further amylose from leaching out. The rheological property of the samples annealed at Ta1 is not so different from that of the control, and the samples annealed at Ta3 are almost gelatinized. The rheological behavior of starch suspension can be controlled by Ta.

  4. Detection of nitrogen dioxide down to ppb levels using flower-like tungsten oxide nanostructures under different annealing temperatures.

    PubMed

    Wang, Chong; Ding, Mengdi; Kou, Xueying; Guo, Lanlan; Feng, Changhao; Li, Xin; Zhang, Hong; Sun, Peng; Sun, Yanfeng; Lu, Geyu

    2016-12-01

    3D hierarchical flower-like WO3·0.33H2O nanostructures were synthesized via a facile solvothermal method without using any template or surfactant. After annealed at high temperature, the as-prepared WO3·0.33H2O would partly or fully transform into monoclinic WO3 with the morphology almost unchanged. Gas sensing properties of the sensor based on these flower-like nanostructures with the relationship of annealing temperature were also investigated systematically. The experiment results indicate the sensor shows highest response to NO2 when the annealing temperature is 500°C. At the same time, the detection limit can be as low as ∼5ppb level. Thus, the novel flower-like nanostructures might be a promising material for designing NO2 gas sensor with high performance. PMID:27565963

  5. Photoluminescenceof magnetron sputtered CdTe films: dependence on target purity, substrate, and annealing conditions

    NASA Astrophysics Data System (ADS)

    Hinko, Kathleen

    2002-03-01

    We have altered several parameters relating to the CdTe layer in CdTe-based solar cells and have analyzed the effects of these changes on low-temperature photoluminescence (PL). Polycrystalline CdTe films were grown by radio frequency magnetron sputtering from two targets purchased from commercial vendors and one pressed at the University of Toledo (UT). We observed substantial differences related to the targets and to the soda lime and borosilicate glass substrates. Parts of each film were annealed at 387 C and 400 C in the presence of CdCl2. The intensity and the spectrum of the PL suggest that films grown from the homemade UT target were of comparable quality to those grown from the commercial target. We found much weaker PL for films grown on borosilicate glass than for soda-lime glass. This may indicate that sodium from the soda-lime glass may leach into the films producing a shallow donor and enhancing the donor-acceptor pair luminescence. Work supported by NREL and NSF.

  6. Change in the magnetic properties of nanoferrihydrite with an increase in the volume of nanoparticles during low-temperature annealing

    NASA Astrophysics Data System (ADS)

    Balaev, D. A.; Krasikov, A. A.; Stolyar, S. V.; Iskhakov, R. S.; Ladygina, V. P.; Yaroslavtsev, R. N.; Bayukov, O. A.; Vorotynov, A. M.; Volochaev, M. N.; Dubrovskiy, A. A.

    2016-09-01

    The results of the investigation into the effect of low-temperature annealing of a powder of nanoparticles of bacterial ferrihydrite on its magnetic properties have been presented. It has been found that an increase in the time (up to 240 h) and temperature (in the range from 150 to 200°C) of annealing leads to a monotonic increase in the superparamagnetic blocking temperature, the coercive force, and the threshold field of the opening of the magnetic hysteresis loop (at liquid-helium temperatures), as well as to an increase in the magnetic resonance line width at low temperatures and in the magnetic susceptibility at room temperature. At the same time, according to the results of the analysis of the Mössbauer spectra, the annealing of ferrihydrite does not lead to the formation of new iron oxide phases. Most of these features are well consistent with the fact that the low-temperature annealing of ferrihydrite causes an increase in the size of nanoparticles, which is confirmed by the results of transmission electron microscopy studies.

  7. Proton irradiation of a swept charge device at cryogenic temperature and the subsequent annealing

    NASA Astrophysics Data System (ADS)

    Gow, J. P. D.; Smith, P. H.; Pool, P.; Hall, D. J.; Holland, A. D.; Murray, N. J.

    2015-01-01

    A number of studies have demonstrated that a room temperature proton irradiation may not be sufficient to provide an accurate estimation of the impact of the space radiation environment on detector performance. This is a result of the relationship between defect mobility and temperature, causing the performance to vary subject to the temperature history of the device from the point at which it was irradiated. Results measured using Charge Coupled Devices (CCD) irradiated at room temperature therefore tend to differ from those taken when the device was irradiated at a cryogenic temperature, more appropriate considering the operating conditions in space, impacting the prediction of in-flight performance. This paper describes the cryogenic irradiation, and subsequent annealing of an e2v technologies Swept Charge Device (SCD) CCD236 irradiated at -35.4°C with a 10 MeV equivalent proton fluence of 5.0 × 108 protons · cm-2. The CCD236 is a large area (4.4 cm2) X-ray detector that will be flown on-board the Chandrayaan-2 and Hard X-ray Modulation Telescope spacecraft, in the Chandrayaan-2 Large Area Soft X-ray Spectrometer and the Soft X-ray Detector respectively. The SCD is readout continually in order to benefit from intrinsic dither mode clocking, leading to suppression of the surface component of the dark current and allowing the detector to be operated at warmer temperatures than a conventional CCD. The SCD is therefore an excellent choice to test and demonstrate the variation in the impact of irradiation at cryogenic temperatures in comparison to a more typical room temperature irradiation.

  8. Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

    NASA Technical Reports Server (NTRS)

    Rai, Amarendra K.; Schmitt, Michael P.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

    2014-01-01

    Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating.

  9. Infrared mediated production of C-Co-Pd nanocomposites under different annealing temperature and it's structural and phase composition analysis

    NASA Astrophysics Data System (ADS)

    Kurtsova, A. S.

    2016-08-01

    In the present study C-Co-Pd nanocomposites were prepared via Infrared annealing mediated method using precursor such as polyacrylonitrile (PAN), CoCl2 • 6H2O and PdCl2. In addition the effect annealing temperatures such as 200, 250, 300, 400, 500, 600, 700, 800 and 900 °C on phase composition and structural characterization was analyzed using X-ray diffractometry (XRD) and transmission electron microscopy (TEM). Results reveals that the increase in temperature drastically influenced the phase and size of the C-Co-Pd nanocomposites.

  10. Structural features and mechanical properties of austenitic Hadfield steel after high-pressure torsion and subsequent high-temperature annealing

    NASA Astrophysics Data System (ADS)

    Tukeeva, M. S.; Melnikov, E. V.; Maier, H. J.; Astafurova, E. G.

    2012-06-01

    Mechanisms of structure fragmentation and strengthening of single crystals of a Hadfield steel after warm torsion under high-pressure torsion (HPT) and subsequent annealing in a temperature range of 400-800°C have been studied. Multiple twinning and formation of ultrafine carbides upon HPT at 400°C ( P = 5 GPa) promote rapid fragmentation of the microstructure. They are responsible for the high mechanical properties of the steel after HPT and the thermal stability of the microstructure up to an annealing temperature of 500°C.

  11. Wide Temperature Core Loss Characteristics of Transverse Magnetically Annealed Amorphous Tapes for High Frequency Aerospace Magnetics

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.; Schwarze, Gene E.

    1999-01-01

    100 kHz core loss properties of sample transverse magnetically annealed, cobalt-based amorphous and iron-based nanocrystalline tape wound magnetic cores are presented over the temperature range of -150 C to 150 C, at selected values of B(sub peak). For B-fields not close to saturation, the core loss is not sensitive to temperature in this range and is as low as seen in the best MnZn power ferrites at their optimum temperatures. Frequency resolved characteristics are given over the range of 50 kHz to 1 MHz, but at B(sub peak) = 0.1 T and 50 C only. For example, the 100 kHz specific core loss ranged from 50 - 70 mW/cubic cm for the 3 materials, when measured at 0.1 T and 50 C. This very low high frequency core loss, together with near zero saturation magnetostriction and insensitivity to rough handling, makes these amorphous ribbons strong candidates for power magnetics applications in wide temperature aerospace environments.

  12. Temperature dependence of the electrical properties of hydrogen titanate nanotubes

    SciTech Connect

    Alves, Diego C. B.; Brandão, Frederico D.; Krambrock, Klaus; Ferlauto, Andre S.; Fonseca, Fabio C.

    2014-11-14

    The temperature dependence of the electrical properties of hydrogen-rich titanate nanotubes (H-TNTs) in the 90–270 °C range was investigated by impedance spectroscopy. Three types of dominant conduction were found which depend on the previous thermal treatment of the samples. For untreated samples, at low temperatures (T < 100 °C), electrical conductivity is relatively high (>10{sup −4} S/cm at T ≈ 90 °C) and is dominated by protonic transport within structural water molecules. For thermal annealing in inert atmosphere up to 150 °C, water molecules are released from the nanotube structure resulting in a dehydrated H{sub 2}Ti{sub 3}O{sub 7} phase. Such phase has a low, thermally-dependent, electrical conductivity (10{sup −8} S/cm at T ≈ 90 °C) with activation energy of 0.68 eV. For samples annealed up to 260 °C, loss of OH groups, and consequent generation of oxygen vacancies, occurs that result in the non-stoichiometric H{sub 2(1−z)}Ti{sub 3}O{sub 7−z} phase. This phase has much higher conductivity (10{sup −5} S/cm at T ≈ 90 °C) and lower associated activation energy (0.40 eV). The generation of oxygen vacancies is confirmed by electron paramagnetic resonance measurements at room temperature, which revealed the presence of single-electron-trapped oxygen vacancies. The activation energy value found is consistent with the thermal ionization energy of the oxygen vacancies. Such defect formation represents the initial stage of the phase transformation from titanate to TiO{sub 2} (B). X-ray diffraction and Raman spectroscopy measurements also support such interpretation.

  13. Structure, optical, and electrical properties of indium tin oxide thin films prepared by sputtering at room temperature and annealed in air or nitrogen

    SciTech Connect

    Guillen, C.; Herrero, J.

    2007-04-01

    Indium tin oxide (ITO) thin films have been grown onto soda-lime glass substrates by sputtering at room temperature with various oxygen to argon partial pressure ratios. After deposition, the samples have been annealed at temperatures ranging from 100 to 500 degree sign C in nitrogen or in air. The structure, optical, and electrical characteristics of the ITO coatings have been analyzed as a function of the deposition and the annealing parameters by x-ray diffraction, spectrophotometry, and Hall effect measurements. It has been found that the as-grown amorphous layers crystallize in the cubic structure by heating above 200 degree sign C. Simultaneously, the visible optical transmittance increases and the electrical resistance decreases, in proportions that depend mainly on the sputtering conditions. The lowest resistivity values have been obtained by annealing at 400 degree sign C in nitrogen, where the highest carrier concentrations are achieved, related to oxygen vacancy creation. Some relationships between the analyzed properties have been established, showing the dependence of the cubic lattice distortion and the infrared optical characteristics on the carrier concentration.

  14. Structural transformations and hardness of electrodeposited Ni-P and Co-P coatings subjected to low-temperature annealing

    NASA Astrophysics Data System (ADS)

    Kukareko, V. A.

    2015-11-01

    The structural state and durometric properties of electrodeposited Ni-P and Co-P coatings subjected to low-temperature annealing at 520-540 K have been investigated. It has been shown that the low-temperature annealing of crystalline Ni-P and Co-P coatings is accompanied by a substantial increase in the parameters of crystal lattices of the solid solutions of phosphorus in nickel and cobalt, and also by an increase in the hardness of coatings. The conclusion has been drawn that an increase in the hardness and in the lattice parameters of Ni-P and Co-P solid solutions upon annealing is connected with the passage of phosphorus atoms from the substitutional into interstitial positions by the Frank-Turnbull dissociative mechanism.

  15. Effects of High-Temperature Annealing in Air on Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    2008-01-01

    BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites (CMC) were annealed for 100 h in air at various temperatures to 1200 C, followed by flexural strength measurements at room temperature. Values of yield stress and strain, ultimate strength, and composite modulus remain almost unchanged for samples annealed up to 1100 C. A thin porous layer formed on the surface of the 1100 C annealed sample and its density decreased from 3.09 to 2.90 g/cu cm. The specimen annealed at 1200 C gained 0.43 wt%, was severely deformed, and was covered with a porous layer of thick shiny glaze which could be easily peeled off. Some gas bubbles were also present on the surface. This surface layer consisted of elongated crystals of monoclinic celsian and some amorphous phase(s). The fibers in this surface ply of the CMC had broken into small pieces. The fiber-matrix interface strength was characterized through fiber push-in technique. Values of debond stress, alpha(sub d), and frictional sliding stress, tau(sub f), for the as-fabricated CMC were 0.31+/-0.14 GPa and 10.4+/-3.1 MPa, respectively. These values compared with 0.53+/-0.47 GPa and 8.33+/-1.72 MPa for the fibers in the interior of the 1200 C annealed sample, indicating hardly any change in fiber-matrix interface strength. The effects of thermal aging on microstructure were investigated using scanning electron microscopy. Only the surface ply of the 1200 C annealed specimens had degraded from oxidation whereas the bulk interior part of the CMC was unaffected. A mechanism is proposed explaining the various steps involved during the degradation of the CMC on annealing in air at 1200 C.

  16. Wide Temperature Characteristics of Transverse Magnetically Annealed Amorphous Tapes for High Frequency Aerospace Magnetics

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    1999-01-01

    100 kHz core loss and magnetization properties of sample transverse magnetically annealed, cobalt-based amorphous and iron-based nanocrystalline tape wound magnetic cores are presented over the temperature range of -150 to 150 C, at selected values of B(sub peak). For B-fields not close to saturation, the core loss is not sensitive to temperature in this range and is as low as seen in the best MnZn power ferrites at their optimum temperatures. Frequency resolved characteristics are given over the range of 50 kHz to 1 MHz, at B(sub peak) = 0.1 T and 50 C only. A linear permeability model is used to interpret and present the magnetization characteristics and several figures of merit applicable to inductor materials arc reviewed. This linear modeling shows that, due to their high permeabilities, these cores must he gapped in order to make up high Q or high current inductors. However, they should serve well, as is, for high frequency, anti ratcheting transformer applications.

  17. 454-Pyrosequencing Analysis of Bacterial Communities from Autotrophic Nitrogen Removal Bioreactors Utilizing Universal Primers: Effect of Annealing Temperature.

    PubMed

    Gonzalez-Martinez, Alejandro; Rodriguez-Sanchez, Alejandro; Rodelas, Belén; Abbas, Ben A; Martinez-Toledo, Maria Victoria; van Loosdrecht, Mark C M; Osorio, F; Gonzalez-Lopez, Jesus

    2015-01-01

    Identification of anaerobic ammonium oxidizing (anammox) bacteria by molecular tools aimed at the evaluation of bacterial diversity in autotrophic nitrogen removal systems is limited by the difficulty to design universal primers for the Bacteria domain able to amplify the anammox 16S rRNA genes. A metagenomic analysis (pyrosequencing) of total bacterial diversity including anammox population in five autotrophic nitrogen removal technologies, two bench-scale models (MBR and Low Temperature CANON) and three full-scale bioreactors (anammox, CANON, and DEMON), was successfully carried out by optimization of primer selection and PCR conditions (annealing temperature). The universal primer 530F was identified as the best candidate for total bacteria and anammox bacteria diversity coverage. Salt-adjusted optimum annealing temperature of primer 530F was calculated (47°C) and hence a range of annealing temperatures of 44-49°C was tested. Pyrosequencing data showed that annealing temperature of 45°C yielded the best results in terms of species richness and diversity for all bioreactors analyzed.

  18. Temperature dependence of the deformation behavior of 316 stainless steel after low temperature neutron irradiation

    SciTech Connect

    Pawel-Robertson, J.E.; Rowcliffe, A.F.; Grossbeck, M.L.

    1996-10-01

    The effects of low temperature neutron irradiation on the tensile behavior of 316 stainless steel have been investigated. A single heat of solution annealed 316 was irradiated to 7 and 18 dpa at 60, 200, 330, and 400{degrees}C. The tensile properties as a function of dose and as a function of temperature were examined. Large changes in yield strength, deformation mode, strain to necking, and strain hardening capacity were seen in this irradiation experiment. The magnitudes of the changes are dependent on both irradiation temperature and neutron dose. Irradiation can more than triple the yield strength over the unirradiated value and decrease the strain to necking (STN) to less than 0.5% under certain conditions. A maximum increase in yield strength and a minimum in the STN occur after irradiation at 330{degrees}C but the failure mode remains ductile.

  19. Rapid low-temperature processing of metal-oxide thin film transistors with combined far ultraviolet and thermal annealing

    SciTech Connect

    Leppäniemi, J. Ojanperä, K.; Kololuoma, T.; Huttunen, O.-H.; Majumdar, H.; Alastalo, A.; Dahl, J.; Tuominen, M.; Laukkanen, P.

    2014-09-15

    We propose a combined far ultraviolet (FUV) and thermal annealing method of metal-nitrate-based precursor solutions that allows efficient conversion of the precursor to metal-oxide semiconductor (indium zinc oxide, IZO, and indium oxide, In{sub 2}O{sub 3}) both at low-temperature and in short processing time. The combined annealing method enables a reduction of more than 100 °C in annealing temperature when compared to thermally annealed reference thin-film transistor (TFT) devices of similar performance. Amorphous IZO films annealed at 250 °C with FUV for 5 min yield enhancement-mode TFTs with saturation mobility of ∼1 cm{sup 2}/(V·s). Amorphous In{sub 2}O{sub 3} films annealed for 15 min with FUV at temperatures of 180 °C and 200 °C yield TFTs with low-hysteresis and saturation mobility of 3.2 cm{sup 2}/(V·s) and 7.5 cm{sup 2}/(V·s), respectively. The precursor condensation process is clarified with x-ray photoelectron spectroscopy measurements. Introducing the FUV irradiation at 160 nm expedites the condensation process via in situ hydroxyl radical generation that results in the rapid formation of a continuous metal-oxygen-metal structure in the film. The results of this paper are relevant in order to upscale printed electronics fabrication to production-scale roll-to-roll environments.

  20. Microstructural changes to AlCu6Ni1 alloy after prolonged annealing at elevated temperature.

    PubMed

    Wierzbińska, M; Sieniawski, J

    2010-03-01

    This work presents results of microstructure examination of AlCu(6)Ni(1) aluminium alloy. The commercial AlCu(4)Ni(2)Mg(2) (M-309) alloy is widely used for elements of aircraft and automotive engines. Modification its chemical composition was aimed at improving the stability of mechanical properties of the alloy subjected to long-term exposure to high temperature. The alloy after standard T6 heat treatment (solution heat treated at 818 K/10 h/water quenched followed by ageing at 498 K/8 h/air cooled) was annealed for 150 h at elevated temperature of 573 K corresponding to the maximum value at which structural elements of jet piston engines made of aluminium alloys operate. It was found that applied heat treatment caused an increasing in the particles of hardening phase (theta'-Al(2)Cu) size. The significant growth of the length of theta'-Al(2)Cu precipitations was observed in particularly. Nevertheless, it did not strongly result in change of its shape - the 'crystallites' and 'rods' were still characteristic of hardening phase morphology. The phenomena of the growth of theta'-Al(2)Cu precipitates caused decreasing the mechanical properties of the alloy, what is the subject of further investigations by the authors.

  1. Microstructural changes to AlCu6Ni1 alloy after prolonged annealing at elevated temperature.

    PubMed

    Wierzbińska, M; Sieniawski, J

    2010-03-01

    This work presents results of microstructure examination of AlCu(6)Ni(1) aluminium alloy. The commercial AlCu(4)Ni(2)Mg(2) (M-309) alloy is widely used for elements of aircraft and automotive engines. Modification its chemical composition was aimed at improving the stability of mechanical properties of the alloy subjected to long-term exposure to high temperature. The alloy after standard T6 heat treatment (solution heat treated at 818 K/10 h/water quenched followed by ageing at 498 K/8 h/air cooled) was annealed for 150 h at elevated temperature of 573 K corresponding to the maximum value at which structural elements of jet piston engines made of aluminium alloys operate. It was found that applied heat treatment caused an increasing in the particles of hardening phase (theta'-Al(2)Cu) size. The significant growth of the length of theta'-Al(2)Cu precipitations was observed in particularly. Nevertheless, it did not strongly result in change of its shape - the 'crystallites' and 'rods' were still characteristic of hardening phase morphology. The phenomena of the growth of theta'-Al(2)Cu precipitates caused decreasing the mechanical properties of the alloy, what is the subject of further investigations by the authors. PMID:20500428

  2. Effect of annealing temperatures on the secondary re-crystallization of extruded PM2000 steel bar.

    PubMed

    Chen, C-L; Tatlock, G J; Jones, A R

    2009-03-01

    The ferritic oxide dispersion-strengthened alloy PM2000 is an ideal candidate for high-temperature applications as it contains uniform nano-oxide dispersoids, which act as pinning points to obstruct dislocation and grain boundary motion and therefore impart excellent creep resistance. The development of the microstructure during re-crystallization of oxide dispersion-strengthened alloys has been discussed by a number of authors, but the precise mechanism of secondary re-crystallization still remains uncertain. Hence, this work is aimed at investigating the re-crystallization behaviour of extruded PM2000 bar for different annealing temperatures, using electron backscatter diffraction, in particular, to determine grain orientations, grain boundary misorientation angles, etc. The results show that the as-extruded bar microstructure comprises both low-angle grain boundaries pinned by oxide particles and high-angle boundaries that will have inherent boundary mobility to allow boundary migration. In addition, dynamical re-crystallization was found in the outer region of the non-heat-treated PM2000 bar, which suggested that deformation heterogeneities can be introduced during thermo-mechanical processing that enhance the nucleation of re-crystallization. Subsequent heat treatments promote and stimulate secondary re-crystallization, giving rise to large grains with few sub-grain boundaries. PMID:19250468

  3. Effect of annealing temperatures on the secondary re-crystallization of extruded PM2000 steel bar.

    PubMed

    Chen, C-L; Tatlock, G J; Jones, A R

    2009-03-01

    The ferritic oxide dispersion-strengthened alloy PM2000 is an ideal candidate for high-temperature applications as it contains uniform nano-oxide dispersoids, which act as pinning points to obstruct dislocation and grain boundary motion and therefore impart excellent creep resistance. The development of the microstructure during re-crystallization of oxide dispersion-strengthened alloys has been discussed by a number of authors, but the precise mechanism of secondary re-crystallization still remains uncertain. Hence, this work is aimed at investigating the re-crystallization behaviour of extruded PM2000 bar for different annealing temperatures, using electron backscatter diffraction, in particular, to determine grain orientations, grain boundary misorientation angles, etc. The results show that the as-extruded bar microstructure comprises both low-angle grain boundaries pinned by oxide particles and high-angle boundaries that will have inherent boundary mobility to allow boundary migration. In addition, dynamical re-crystallization was found in the outer region of the non-heat-treated PM2000 bar, which suggested that deformation heterogeneities can be introduced during thermo-mechanical processing that enhance the nucleation of re-crystallization. Subsequent heat treatments promote and stimulate secondary re-crystallization, giving rise to large grains with few sub-grain boundaries.

  4. Post-annealing effect on the room-temperature ferromagnetism in Cu-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Hu, Yu-Min; Li, Sih-Sian; Kuang, Chein-Hsiun; Han, Tai-Chun; Yu, Chin-Chung

    2015-05-01

    In this work, we investigated the structural and magnetic properties of both as-deposited and post-annealed Cu-doped ZnO thin films for better understanding the possible mechanisms of room-temperature ferromagnetism (RT-FM) in ZnO-based diluted magnetic oxides. All of the films have a c-axis-oriented wurtzite structure and display RT-FM. X-ray photoelectron spectroscopy results showed that the incorporated Cu ions in as-deposited films are in 1+ valence state merely, while an additional 2+ valence state occurs in post-annealed films. The presence of Cu2+ state in post-annealed film accompanies a higher magnetization value than that of as-deposited film and, in particular, the magnetization curves at 10 K and 300 K of the post-annealed film separate distinctly. Since Cu1+ ion has a filled 3d band, the RT-FM in as-deposited Cu-doped ZnO thin films may stem solely from intrinsic defects, while that in post-annealed films is enhanced due to the presence of CuO crystallites.

  5. Post-annealing effect on the room-temperature ferromagnetism in Cu-doped ZnO thin films

    SciTech Connect

    Hu, Yu-Min Kuang, Chein-Hsiun; Han, Tai-Chun; Yu, Chin-Chung; Li, Sih-Sian

    2015-05-07

    In this work, we investigated the structural and magnetic properties of both as-deposited and post-annealed Cu-doped ZnO thin films for better understanding the possible mechanisms of room-temperature ferromagnetism (RT-FM) in ZnO-based diluted magnetic oxides. All of the films have a c-axis-oriented wurtzite structure and display RT-FM. X-ray photoelectron spectroscopy results showed that the incorporated Cu ions in as-deposited films are in 1+ valence state merely, while an additional 2+ valence state occurs in post-annealed films. The presence of Cu{sup 2+} state in post-annealed film accompanies a higher magnetization value than that of as-deposited film and, in particular, the magnetization curves at 10 K and 300 K of the post-annealed film separate distinctly. Since Cu{sup 1+} ion has a filled 3d band, the RT-FM in as-deposited Cu-doped ZnO thin films may stem solely from intrinsic defects, while that in post-annealed films is enhanced due to the presence of CuO crystallites.

  6. Effect of annealing temperature on the supercapacitor behaviour of β-V{sub 2}O{sub 5} thin films

    SciTech Connect

    Jeyalakshmi, K.; Vijayakumar, S.; Nagamuthu, S.; Muralidharan, G.

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Structural, optical, supercapacitor properties of β-V{sub 2}O{sub 5} thin films are reported. ► Influence of annealing temperature on β-V{sub 2}O{sub 5} thin films have been studied. ► Film annealed at 300 °C exhibit lower charge transfer resistance. -- Abstract: Vanadium pentoxide thin films are prepared via sol–gel spin coating method. The films coated on FTO and glass substrates are treated at different temperatures ranging from 250 °C to 400 °C. The structural, optical and electrochemical investigations are made. X-ray diffraction analysis shows the film to be composed of V{sub 2}O{sub 5} in β-phase up to annealing temperature of 350 °C and at 400 °C the structural transformation to α-phase is observed. FTIR spectrum shows the formation of V-O bond. The SEM images reveal the formation of nanopores. Optical absorption studies indicate a band gap of 2.2–2.4 eV. The supercapacitor behaviour is studied using cyclic voltammetery technique and electrochemical impedance analysis. The vanadium pentoxide films annealed at 300 °C for an hour exhibits a maximum specific capacitance of 346 F g{sup −1} at a scan rate of 5 mV s{sup −1}.

  7. Effects of high-temperature anneals and {sup 60}Co gamma-ray irradiation on strained silicon on insulator

    SciTech Connect

    Park, K.; Canonico, M.; Celler, G. K.; Seacrist, M.; Chan, J.; Gelpey, J.; Holbert, K. E.; Nakagawa, S.; Tajima, M.; Schroder, D. K.

    2007-10-01

    Strained silicon on insulator was exposed to high-temperature annealing and high-dose {sup 60}Co gamma ({gamma})-ray irradiation to study the tenacity of the bond between the strained Si film and the underlying buried oxide. During the high-temperature anneals, the samples were ramped at a rate of 150 deg. C/s to 850 deg. C then ramped to 1200, 1250, and 1300 deg. C at a rate of approximately 5x10{sup 5} deg. C/s for millisecond duration anneals. For the irradiation experiments, the samples were irradiated with {sup 60}Co {gamma} rays to a dose of 51.5 kGy. All samples were characterized by ultraviolet (UV) Raman, pseudo metal-oxide-semiconductor field-effect transistor ({psi}-MOSFET) current voltage, Hall mobility, and photoluminescence (PL) to verify changes in strain. UV Raman, PL, and {psi}-MOSFET measurements show no strain relaxation for the high-temperature annealed samples and only very slight relaxation for the {gamma}-ray irradiated samples.

  8. Escherichia coli survival in waters: Temperature dependence

    EPA Science Inventory

    Knowing the survival rates of water-borne Escherichia coli is important in evaluating microbial contamination and making appropriate management decisions. E. coli survival rates are dependent on temperature, a dependency that is routinely expressed using an analogue of the Q10 mo...

  9. Wide Temperature Magnetization Characteristics of Transverse Magnetically Annealed Amorphous Tapes for High Frequency Aerospace Magnetics

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.; Schwarze, Gene E.

    1999-01-01

    100 kHz magnetization properties of sample transverse magnetically annealed, cobalt-based amorphous and iron-based nanocrystalline tape wound magnetic cores are presented over the temperature range of -150 C to 150 C, at selected values of B(sub peak). Frequency resolved characteristics are given over the range of 50 kHz to 1 MHz, but at B(sub peak) = 0.1 T and 50 C only. Basic exciting winding current and induced voltage data were taken on bare toroidal cores, in a standard type measurement setup. A linear permeability model, which represents the core by a parallel L-R circuit, is used to interpret and present the magnetization characteristics and several figures of merit applicable to inductor materials are reviewed. The 100 kHz permeability thus derived decreases with increasing temperature for the Fe-based, nanocrystalline material, but increases roughly linearly with temperature for the two Co-based materials, as long as B(sub peak) is sufficiently low to avoid saturation effects. Due to the high permeabilities, rather low values of the 'quality factor' Q, from about 20 to below unity, were obtained over the frequency range of 50 kHz to 1 MHz (50 C, B(sub peak) = 0.1 T). Therefore these cores must be gapped in order to make up high Q or high current inductors. However, being rugged, low core loss materials with flat B-H loop characteristics, they may provide new solutions to specialty inductor applications.

  10. Regulation of Silk Material Structure by Temperature-Controlled Water Vapor Annealing

    PubMed Central

    Hu, Xiao; Shmelev, Karen; Sun, Lin; Gil, Eun-Seok; Park, Sang-Hyug; Cebe, Peggy; Kaplan, David L.

    2011-01-01

    We present a simple and effective method to obtain refined control of the molecular structure of silk biomaterials through physical temperature-controlled water vapor annealing (TCWVA). The silk materials can be prepared with control of crystallinity, from a low content using conditions at 4°C (alpha-helix dominated silk I structure), to highest content of ~60% crystallinity at 100°C (beta-sheet dominated silk II structure). This new physical approach covers the range of structures previously reported to govern crystallization during the fabrication of silk materials, yet offers a simpler, green chemistry, approach with tight control of reproducibility. The transition kinetics, thermal, mechanical, and biodegradation properties of the silk films prepared at different temperatures were investigated and compared by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), uniaxial tensile studies, and enzymatic degradation studies. The results revealed that this new physical processing method accurately controls structure, in turn providing control of mechanical properties, thermal stability, enzyme degradation rate, and human mesenchymal stem cell interactions. The mechanistic basis for the control is through the temperature controlled regulation of water vapor, to control crystallization. Control of silk structure via TCWVA represents a significant improvement in the fabrication of silk-based biomaterials, where control of structure-property relationships is key to regulating material properties. This new approach to control crystallization also provides an entirely new green approach, avoiding common methods which use organic solvents (methanol, ethanol) or organic acids. The method described here for silk proteins would also be universal for many other structural proteins (and likely other biopolymers), where water controls chain interactions related to material properties. PMID:21425769

  11. Regulation of silk material structure by temperature-controlled water vapor annealing.

    PubMed

    Hu, Xiao; Shmelev, Karen; Sun, Lin; Gil, Eun-Seok; Park, Sang-Hyug; Cebe, Peggy; Kaplan, David L

    2011-05-01

    We present a simple and effective method to obtain refined control of the molecular structure of silk biomaterials through physical temperature-controlled water vapor annealing (TCWVA). The silk materials can be prepared with control of crystallinity, from a low content using conditions at 4 °C (α helix dominated silk I structure), to highest content of ∼60% crystallinity at 100 °C (β-sheet dominated silk II structure). This new physical approach covers the range of structures previously reported to govern crystallization during the fabrication of silk materials, yet offers a simpler, green chemistry, approach with tight control of reproducibility. The transition kinetics, thermal, mechanical, and biodegradation properties of the silk films prepared at different temperatures were investigated and compared by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), uniaxial tensile studies, and enzymatic degradation studies. The results revealed that this new physical processing method accurately controls structure, in turn providing control of mechanical properties, thermal stability, enzyme degradation rate, and human mesenchymal stem cell interactions. The mechanistic basis for the control is through the temperature-controlled regulation of water vapor to control crystallization. Control of silk structure via TCWVA represents a significant improvement in the fabrication of silk-based biomaterials, where control of structure-property relationships is key to regulating material properties. This new approach to control crystallization also provides an entirely new green approach, avoiding common methods that use organic solvents (methanol, ethanol) or organic acids. The method described here for silk proteins would also be universal for many other structural proteins (and likely other biopolymers), where water controls chain interactions related to material properties.

  12. A re-evaluation of geological timescale benchmarks and temperature sensitivity of fission-track annealing in apatites

    NASA Astrophysics Data System (ADS)

    Luijendijk, Elco; Andriessen, Paul

    2016-04-01

    Current models of the temperature sensitivity of fission track annealing in apatites have been calibrated using fission track data from boreholes, with the assumption that these samples are currently at maximum burial depth and temperatures. The most detailed data-set comes from boreholes located in the Otway basin, Australia. However, several lines of evidence suggest that these samples are not at their maximum burial depth and temperature and consequently the cooling temperature of the apatite fission track thermochronometer would then be higher than previously assumed. Significant late Cenozoic exhumation in the Otway Basin was suggested by earlier studies that document a major late-Miocene erosional unconformity, folding and trusting of underlying sediments and elevated strandlines along the coast. In addition, anomalously young apatite (U-Th)/He ages in several boreholes in the basin suggest that the basin's sediments have been exhumed and cooled in the late Cenozoic. We explore the effects of late Cenozoic exhumation on fission track data in the Otway basin using a 1D model of burial and thermal history. We show that simulating several 100s of meters of exhumation in the basin results in significant misfit between current annealing models and observed fission track data. The additional exhumation reconciles the Otway basin data with a second detailed fission track dataset from boreholes in Southern Texas with a well-constrained thermal and burial history. We combine vitrinite reflectance data and U-Th/He data from the Otway basin to recalibrate the burial history of the Otway basin. Subsequently we combine the new thermal history of the Otway basin with the Southern Texas dataset to recalibrate the fission track annealing algorithm. The results suggest that fission-track annealing in apatites is underestimated by approximately 20°C by current annealing models, with significant implications for studies that use apatite fission track thermochronology to

  13. Electrical properties of undoped zinc oxide nanostructures at different annealing temperature

    NASA Astrophysics Data System (ADS)

    Nasir, M. F.; Zainol, M. N.; Hannas, M.; Mamat, M. H.; Rahman, S. A.; Rusop, Mohamad

    2016-07-01

    This project has been focused on the electrical and optical properties respectively on the effect of Undoped zinc oxide (ZnO) thin films at different annealing temperature which is varied 400 °C, 450 °C, 500 °C, and 550 °C.Undoped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thin films were characterized using Current Voltage (I-V) measurement and UV-vis-NIR spectrophotometer for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 500 °C which its resistivity is 5.36 × 104 Ωcm-1. The absorption coefficient spectrum obtained from UV-Vis-NIR spectrophotometer measurement shows all films exhibit very low absorption in the visible (400-800nm) and near infrared (NIR) (>800nm) range but exhibit high absorption in the UV range.

  14. Effect of annealing temperature on structural and magnetic properties of strontium hexaferrite nanoparticles synthesized by sol-gel auto-combustion method

    NASA Astrophysics Data System (ADS)

    Roohani, Ebrahim; Arabi, Hadi; Sarhaddi, Reza; Sudkhah, Saeedeh; Shabani, Ameneh

    2015-10-01

    In this paper, strontium hexaferrite nanoparticles were synthesized by the sol-gel auto-combustion method. Effect of annealing temperature on crystal structure, morphology and magnetic properties of nanoparticles was investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). Also, the thermal decomposition of as-synthesized powdered samples has been studied by thermogravimetric analysis (TGA). The XRD patterns confirmed the formation of single phase M-type hexagonal crystal structure for powders annealed above 950∘C, whereas the presence of hematite (α-Fe2O3) as secondary phase was also observed for sample annealed at 900∘C. Furthermore, the crystallinity along with the crystallite size were augmented with annealing temperature. Comparison of the FT-IR spectra of the samples before and after annealing treatment showed the existence of metal-oxygen stretching modes after annealing. The thermogravimetric analysis confirmed the thermal decomposition of as-burnt powders happened in three-stage degradation process. The TEM images showed the nanoparticles like hexagonal-shaped platelets as the size of nanoparticles increases by increasing the annealing temperature. With increasing annealing temperature, the magnetic saturation and the coercivity were increased to the maximum value of 74.26 emu/g and 5.67 kOe for sample annealed at 1000∘C and then decreased.

  15. Temperature dependence of sapphire fiber Raman scattering

    DOE PAGES

    Liu, Bo; Yu, Zhihao; Tian, Zhipeng; Homa, Daniel; Hill, Cary; Wang, Anbo; Pickrell, Gary

    2015-04-27

    Anti-Stokes Raman scattering in sapphire fiber has been observed for the first time. Temperature dependence of Raman peaks’ intensity, frequency shift, and linewidth were also measured. Three anti-Stokes Raman peaks were observed at temperatures higher than 300°C in a 0.72-m-long sapphire fiber excited by a second-harmonic Nd YAG laser. The intensity of anti-Stokes peaks are comparable to that of Stokes peaks when the temperature increases to 1033°C. We foresee the combination of sapphire fiber Stokes and anti-Stokes measurement in use as a mechanism for ultrahigh temperature sensing.

  16. Effects of the annealing temperature and atmosphere on the microstructures and dielectric properties of ZnO/Al2O3 composite coatings

    NASA Astrophysics Data System (ADS)

    Wei, Ping; Zhu, Dongmei; Huang, Shanshan; Zhou, Wancheng; Luo, Fa

    2013-11-01

    ZnO/Al2O3 composite coatings were fabricated by atmospheric plasma spraying technology (APS). The effects of annealing temperature and atmospheres (in air or vacuum) on the microstructure and phase transformation of the sprayed coatings were studied by scanning electron microscope (SEM) and X-ray diffraction spectroscopy (XRD). The microwave dielectric properties of these coatings after annealing treatment were also discussed in the frequency range of 8.2-12.4 GHz. Both the real part and the imaginary part of the permittivity decreased significantly with increased annealing temperature when the annealing process is carried out in air atmosphere, while the complex permittivity of the coating annealed in vacuum atmosphere was obviously increased compared to the initial sprayed coating. The mechanism for the variation of dielectric properties of sprayed ZnO/Al2O3 composite coating caused by annealing treatment was discussed in this study.

  17. X-ray diffraction analysis of the effect of annealing temperature on the microstructure of magnesium oxide nanopowder

    NASA Astrophysics Data System (ADS)

    Soleimanian, V.; Aghdaee, S. R.

    2015-06-01

    In this study, nanocrystalline MgO powders were prepared using the sol-gel method and annealed in air over a temperature range of [400-700] °C. Various microstructural characteristics were determined using three different X-ray diffraction analysis approaches, i.e., modified Williamson-Hall, modified Warren-Averbach, and variance methods. The transmission electron microscopy micrographs were used to measure the size distributions of the MgO samples. The results obtained using the three different methods were in good agreement. At all temperatures, the main source of dislocation was edge type but as the annealing temperature increased, the crystallite size and dislocation density increased and decreased, respectively, thereby indicating that the crystal quality of the nanopowders was improved.

  18. Low resistance Ti Ohmic contacts to 4H-SiC by reducing barrier heights without high temperature annealing

    SciTech Connect

    Huang Lingqin; Liu Bingbing; Zhu Qiaozhi; Chen Suhua; Gao Mingchao; Wang Dejun; Qin Fuwen

    2012-06-25

    Ti Ohmic contacts to relatively highly doped (1 Multiplication-Sign 10{sup 18} cm{sup -3}) n-type 4H-SiC have been produced, without high temperature annealing, by means of low temperature electronic cyclotron resonance microwave hydrogen plasma pre-treatment (HPT) of the SiC surface. The as-deposited Ti/4H-SiC contacts show Ohmic properties, and the specific contact resistance obtained is as low as 2.07 Multiplication-Sign 10{sup -4}{Omega}{center_dot}cm{sup 2} after annealing at low temperatures (400 Degree-Sign C). This is achieved by low barrier height at Ti/SiC interface, which could be attributed to decrease of surface states density by the HPT releasing Fermi level pinning, and to band-gap narrowing, image-force, and thermionic-field emission at high doping.

  19. Low-temperature growth of aligned ZnO nanorods: effect of annealing gases on the structural and optical properties.

    PubMed

    Umar, Ahmad; Hahn, Yoon-Bong; Al-Hajry, A; Abaker, M

    2014-06-01

    Aligned ZnO nanorods were grown on ZnO/Si substrate via simple aqueous solution process at low-temperature of - 65 degrees C by using zinc nitrate and hexamethylenetetramine (HMTA). The detailed morphological and structural properties measured by FESEM, XRD, EDS and TEM confirmed that the as-grown nanorods are vertically aligned, well-crystalline possessing wurtzite hexagonal phase and grown along the [0001] direction. The room-temperature photoluminescence spectrum of the grown nanorods exhibited a strong and broad green emission and small ultraviolet emission. The as-prepared ZnO nanorods were post-annealed in nitrogen (N2) and oxygen (O2) environments and further characterized in terms of their morphological, structural and optical properties. After annealing the nanorods exhibit well-crystallinity and wurtzite hexagonal phase. Moreover, by annealing the PL spectra show the enhancement in the UV emission and suppression in the green emission. The presented results demonstrate that simply by post-annealing process, the optical properties of ZnO nanostructures can be controlled.

  20. Effect of Annealing Temperature on Bi3.25La0.75Ti3O12 Powders for Humidity Sensing Properties

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; He, Jinping; Yuan, Mengjiao; Jiang, Bin; Li, Peiwen; Tong, Yexing; Zheng, Xuejun

    2016-08-01

    Bi3.25La0.75Ti3O12 (BLT) powders have been synthesized via the metal-organic decomposition method with annealing of the BLT precursor solution at 350°C, 450°C, 550°C, 650°C or 750°C. The crystalline structure and morphology of the BLT powders were characterized by x-ray diffraction analysis, field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, and specific surface and pore size analyses. The humidity sensing properties of the BLT powders annealed at the five temperatures were investigated to determine the effect of annealing temperature. The annealing temperature strongly influenced the grain size, pore size distribution, and specific surface area of the BLT powders, being largely correlated to their humidity sensing properties. The specific surface area of the BLT powder annealed at 550°C was 68.2 m2/g, much larger than for the other annealing temperatures, and the majority of the pores in the BLT powder annealed at 550°C were mesoporous, significantly increasing the adsorption efficiency of water vapor onto the surface of the material. The impedance of the BLT powder annealed at 550°C varied by more than five orders of magnitude over the whole humidity range at working frequency of 100 Hz, being approximately five times greater than for BLT powders annealed at other temperatures. The response time was about 8 s, with maximum hysteresis of around 3% relative humidity. The BLT powder annealed at 550°C exhibited the best humidity sensing properties compared with the other annealing temperatures. We expect that these results will offer useful guidelines for preparation of humidity sensing materials.

  1. Dependence of the concentration of ionized donors on epitaxy temperature for Si:Er/Si layers grown by sublimation molecular-beam epitaxy

    SciTech Connect

    Kuznetsov, V. P.; Shmagin, V. B.; Drozdov, M. N.; Marychev, M. O.; Kudryavtsev, K. E.; Kuznetsov, M. V.; Andreev, B. A.; Kornaukhov, A. V.; Krasilnik, Z. F.

    2011-01-15

    The dependence of the concentrations of the Er impurity and ionized donors on the epitaxy temperature has been studied before and after annealing of Si:Er/Si layers grown by sublimation molecular-beam epitaxy. n-Si:Er layers have been grown in the temperature range 400-800 Degree-Sign C and annealed in hydrogen atmosphere at a temperature of 800 Degree-Sign C for 30 min. The possible nature of the donor centers is discussed.

  2. Investigations of Low Temperature Time Dependent Cracking

    SciTech Connect

    Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J

    2002-09-30

    The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.

  3. Temperature dependence of polymer photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Nakazawa, Yuko

    One of many steps to develop a sustainable society is to reduce the use of fossil fuels by replacing them with renewable energy sources, such as solar energy. This dissertation concerns one of the most contemporary methods to harvest solar radiation and covert it to electricity, using thin polymer films. The photovoltaic devices in this study consisted of a thin layer of p-phenylenevinylene (PPV) based semiconducting polymer sandwiched between two metals (semi-transparent ITO and evaporated metal electrode). Two modified device structures were studied, an interfacial heterojunction device, which includes an additional layer of inorganic n-type semiconductor (Ti-oxides) and a bulk heterojunction device, which is formed by blending electron-attracting materials. Both modifications resulted in higher device performances under ambient conditions due to an increased number of dissociation sites. From studies of inorganic solar cells, it is well known that temperature has a large effect on device performance. However, there are only a few studies on organic Solar cells, concerning the temperature dependence. This thesis focuses on understanding the temperature dependent behaviors of polymer photovoltaic devices. Temperature dependence study allows us to examine how the device parameters such as short circuit current (Isc) and open circuit voltage (Voc) are affected by the material properties and the device architectures. The current-voltage relationships were measured in a temperature controlled OXFORD cryostat operating between 150K and 404K. From the dark current-voltage measurements, the field-independent hole mobility (mu0) was extracted, using a space charge limited current analysis. From the photocurrent-voltage measurements, the temperature dependence on Isc, Voc, and fill factor were studied. The temperature characteristics of Isc (T) were compared to that of mu0(T), and two different dependencies were obtained for different device architectures. The temperature

  4. Annealing temperature and barrier thickness effect on the structural and optical properties of silicon nanocrystals/SiO₂ superlattices

    SciTech Connect

    López-Vidrier, J. Hernández, S.; López-Conesa, L.; Peiró, F.; Garrido, B.; Hiller, D.; Gutsch, S.; Zacharias, M.; Estradé, S.

    2014-10-07

    The effect of the annealing temperature and the SiO₂ barrier thickness of silicon nanocrystal (NC)/SiO₂ superlattices (SLs) on their structural and optical properties is investigated. Energy-filtered transmission electron microscopy (TEM) revealed that the SL structure is maintained for annealing temperatures up to 1150 °C, with no variation on the nanostructure morphology for different SiO₂ barrier thicknesses. Nevertheless, annealing temperatures as high as 1250 °C promote diffusion of Si atoms into the SiO₂ barrier layers, which produces larger Si NCs and the loss of the NC size control expected from the SL approach. Complementary Raman scattering measurements corroborated these results for all the SiO₂ and Si-rich oxynitride layer thicknesses. In addition, we observed an increasing crystalline fraction up to 1250 °C, which is related to a decreasing contribution of the suboxide transition layer between Si NCs and the SiO₂ matrix due to the formation of larger NCs. Finally, photoluminescence measurements revealed that the emission of the superlattices exhibits a Gaussian-like lineshape with a maximum intensity after annealing at 1150 °C, indicating a high crystalline degree in good agreement with Raman results. Samples submitted to higher annealing temperatures display a progressive emission broadening, together with an increase in the central emission wavelength. Both effects are related to a progressive broadening of the size distribution with a larger mean size, in agreement with TEM observations. On the other hand, whereas the morphology of the Si NCs is unaffected by the SiO₂ barrier thickness, the emission properties are slightly modified. These observed modifications in the emission lineshape allow monitoring the precipitation process of Si NCs in a direct non-destructive way. All these experimental results evidence that an annealing temperature of 1150 °C and 1-nm SiO₂ barrier can be reached whilst preserving the SL structure, being

  5. Effect of annealing temperature on the structural and optical properties of CeO2:Ni thin films

    NASA Astrophysics Data System (ADS)

    Murugan, R.; Vijayaprasath, G.; Sakthivel, P.; Mahalingam, T.; Ravi, G.

    2016-05-01

    High quality Ni-doped CeO2 (CeO2:Ni) thin films were deposited on glass substrates at room temperature by using radio frequency magnetron sputtering. The effect of annealing temperature on structural and optical properties of the CeO2:Ni films was investigated. The structural, optical and vibrational properties of the films were determined using X-ray diffraction (XRD), photoluminescence spectrometer (PL) and Raman spectrometer. It was found that the as-deposited film has a fluorite cubic structure. By increasing annealing temperature from 100°C to 300°C, the crystalline quality of the thin films could be improved. The UV and visible band emissions were observed in the photoluminescence spectra, due to exciton, defect related emissions respectively. The micro-Raman results show the characteristic peak of CeO2 F2g at 465 cm-1 and 2L0 at 1142 cm-1. Defect peaks like D and 0 bands were observed at 641 cm-1 and 548 cm-1 respectively. It is found from the spectra that the peak intensity of the films increased with increase of annealing temperature.

  6. The effect of high-temperature annealing on the structure and electrical properties of well-aligned carbon nanotubes

    SciTech Connect

    Gong Qianming . E-mail: gongqianming@mail.tsinghua.org.cn; Li Zhi; Wang Ye; Wu Bin; Zhang Zhengyi; Liang Ji

    2007-03-22

    Systematic work has been performed on the effect of high-temperature annealing on structural defects and impurities of well-aligned carbon nanotubes (ACNTs) in this paper. ACNTs had been prepared by CVD process with ferrocene as catalyst and then the as-grown samples were experienced heat treatment (HT) from 1800 to 3000 deg. C. X-ray diffraction, Raman spectroscopy and electron dispersive spectroscopy (EDS), etc., have been used to analyze the effect of annealing. Results indicate that some impurities can be removed once annealing temperature exceeds vaporization point of corresponding metal or non-metal. Desorption of O should be attributed to reduced active sites of dangling covalent bonds after heat treatment. Specious discrepancy about interlayer spacing resulted from XRD and Raman tests show that although high-temperature heat treatment can remove in-plane defects of carbon nanotubes greatly, interlayer spacing between graphene shells could not be reduced effectively because of the special concentric cylindrical structure of nanotubes. Electrical resistivity of ACNTs block is about three orders higher than that of copper even after HT at 3000 deg. C, and the anisotropy of electrical properties increased once experienced heat treatment at increased temperature.

  7. Supercooled liquid-like solvent in trypsin crystals: implications for crystal annealing and temperature-controlled X-ray radiation damage studies.

    PubMed

    Weik, M; Schreurs, A M M; Leiros, H K S; Zaccai, G; Ravelli, R B G; Gros, P

    2005-05-01

    The study of temperature-dependent physical changes in flash-cooled macromolecular crystals is pertinent to cryocrystallography and related issues such as crystal annealing, X-ray radiation damage and kinetic crystallography. In this context, the unit-cell volume of flash-cooled trigonal and orthorhombic trypsin crystals has been monitored upon warming from 100 to 200 K and subsequent re-cooling to 100 K. Crystals of both forms were obtained under the same crystallization conditions, yet they differ in solvent content and channel size. An abrupt non-reversible unit-cell volume decrease is observed at 185 K in orthorhombic and at 195 K in trigonal crystals as the temperature is increased; this result is consistent with ultra-viscous solvent leaving the crystals. Concomitant appearance of ice rings in the diffraction patterns suggests that the transported solvent forms crystalline ice. These results demonstrate that solvent in flash-cooled protein crystals is liquid-like near its crystallization temperature, as has been proposed, yet controversially discussed, for the case of pure water. The use of mineral oil prevents the unit-cell volume decrease in trigonal but not in orthorhombic crystals. The observation of liquid-like solvent has implications in the development of annealing protocols and points a way to the rational design of temperature-controlled crystallographic studies that aim either at studying specific radiation damage or at trapping enzymatic intermediate states. PMID:15840916

  8. Through-vial impedance spectroscopy of the mechanisms of annealing in the freeze-drying of maltodextrin: the impact of annealing hold time and temperature on the primary drying rate.

    PubMed

    Smith, Geoff; Arshad, Muhammad Sohail; Polygalov, Eugene; Ermolina, Irina

    2014-06-01

    The study aims to investigate the impact of annealing hold time and temperature on the primary drying rate/duration of a 10% (w/v) solution of maltodextrin with an emphasis on how the mechanisms of annealing might be understood from the in-vial measurements of the ice crystal growth and the glass transition. The electrical impedance of the solution within a modified glass vial was recorded between 10 and 10(6) Hz during freeze-drying cycles with varying annealing hold times (1-5 h) and temperatures. Primary drying times decreased by 7%, 27% and 34% (1.1, 4.3 and 5.5 h) with the inclusion of an annealing step at temperatures of -15°C, -10°C and -5°C, respectively. The glass transition was recorded at approximately -16°C during the re-heating and re-cooling steps, which is close to the glass transition (Tg ') reported for 10% (w/v) maltodextrin and therefore indicates that a maximum freeze concentration (∼86%, w/w, from the Gordon-Taylor equation) was achieved during first freezing, with no further ice being formed on annealing. This observation, coupled to the decrease in electrical resistance that was observed during the annealing hold time, suggests that the reduction in the drying time was because of improved connectivity of ice crystals because of Ostwald ripening rather than devitrification.

  9. Analyses of residual iron in carbon nanotubes produced by camphor/ferrocene pyrolysis and purified by high temperature annealing

    NASA Astrophysics Data System (ADS)

    Antunes, E. F.; de Resende, V. G.; Mengui, U. A.; Cunha, J. B. M.; Corat, E. J.; Massi, M.

    2011-07-01

    A detailed analysis of iron-containing phases in multiwall carbon nanotube (MWCNT) powder was carried out. The MWCNTs were produced by camphor/ferrocene and purified by high temperature annealing in an oxygen-free atmosphere (N2 or VC). Thermogravimetric analysis, Mössbauer spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy enabled the evaluation of the residual iron in MWCNTs after purification. The VC treatments provided MWCNTs with a purity degree higher than 99%. Moreover, Raman spectroscopy revealed a significant improvement in graphitic ordering after thermal annealing. A brief description of the mechanism of iron removal was included. We highlight the mobility of iron atoms through graphitic sheets and the large contact angle of iron clusters formed on MWCNT surfaces at high temperatures.

  10. Temperature dependence of optically induced cell deformations

    NASA Astrophysics Data System (ADS)

    Fritsch, Anatol; Kiessling, Tobias R.; Stange, Roland; Kaes, Josef A.

    2012-02-01

    The mechanical properties of any material change with temperature, hence this must be true for cellular material. In biology many functions are known to undergo modulations with temperature, like myosin motor activity, mechanical properties of actin filament solutions, CO2 uptake of cultured cells or sex determination of several species. As mechanical properties of living cells are considered to play an important role in many cell functions it is surprising that only little is known on how the rheology of single cells is affected by temperature. We report the systematic temperature dependence of single cell deformations in Optical Stretcher (OS) measurements. The temperature is changed on a scale of about 20 minutes up to hours and compared to defined temperature shocks in the range of milliseconds. Thereby, a strong temperature dependence of the mechanics of single suspended cells is revealed. We conclude that the observable differences arise rather from viscosity changes of the cytosol than from structural changes of the cytoskeleton. These findings have implications for the interpretation of many rheological measurements, especially for laser based approaches in biological studies.

  11. Temperature dependence of BCF plastic scintillation detectors

    PubMed Central

    Wootton, Landon; Beddar, Sam

    2013-01-01

    We examined temperature dependence in plastic scintillation detectors (PSDs) made of BCF-60 or BCF-12 scintillating fiber coupled to optical fiber with cyanoacrylate. PSDs were subjected to a range of temperatures using a temperature-controlled water bath and irradiated at each temperature while either the dose was measured using a CCD camera or the spectral output was measured using a spectrometer. The spectrometer was used to examine the intensity and spectral distribution of scintillation light emitted by the PSDs, Cerenkov light generated within the PSD, and light transmitted through an isolated optical coupling. BCF-60 PSDs exhibited a 0.50% decrease and BCF-12 PSDs a 0.09% decrease in measured dose per °C increase, relative to dose measured at 22°C. Spectrometry revealed that the total intensity of the light generated by BCF-60 and BCF-12 PSDs decreased by 0.32% and 0.13%, respectively, per °C increase. The spectral distribution of the light changed slightly with temperature for both PSDs, accounting for the disparity between the change in measured dose and total light output. The generation of Cerenkov light was temperature independent. However, light transmitted through optical coupling between the scintillator and the optical fiber also exhibited temperature dependence. PMID:23574889

  12. Effect of low-temperature annealing on the electronic- and band-structures of (Ga,Mn)As epitaxial layers

    SciTech Connect

    Yastrubchak, O. Gluba, L.; Żuk, J.; Wosinski, T. Andrearczyk, T.; Domagala, J. Z.; Sadowski, J.

    2014-01-07

    The effect of outdiffusion of Mn interstitials from (Ga,Mn)As epitaxial layers, caused by post-growth low-temperature annealing, on their electronic- and band-structure properties has been investigated by modulation photoreflectance (PR) spectroscopy. The annealing-induced changes in structural and magnetic properties of the layers were examined with high-resolution X-ray diffractometry and superconducting quantum interference device magnetometry, respectively. They confirmed an outdiffusion of Mn interstitials from the layers and an enhancement in their hole concentration, which were more efficient for the layer covered with a Sb cap acting as a sink for diffusing Mn interstitials. The PR results demonstrating a decrease in the band-gap-transition energy in the as-grown (Ga,Mn)As layers, with respect to that in the reference GaAs one, are interpreted by assuming a merging of the Mn-related impurity band with the GaAs valence band. Whereas an increase in the band-gap-transition energy caused by the annealing treatment of the (Ga,Mn)As layers is interpreted as a result of annealing-induced enhancement of the free-hole concentration and the Fermi level location within the valence band. The experimental results are consistent with the valence-band origin of itinerant holes mediating ferromagnetic ordering in (Ga,Mn)As, in agreement with the Zener model for ferromagnetic semiconductors.

  13. The effect of substrate on high-temperature annealing of GaN epilayers: Si versus sapphire

    SciTech Connect

    Pastor, D.; Cusco, R.; Artus, L.; Gonzalez-Diaz, G.; Iborra, E.; Jimenez, J.; Peiro, F.; Calleja, E.

    2006-08-15

    We have studied the effects of rapid thermal annealing at 1300 deg.C on GaN epilayers grown on AlN buffered Si(111) and on sapphire substrates. After annealing, the epilayers grown on Si display visible alterations with craterlike morphology scattered over the surface. The annealed GaN/Si layers were characterized by a range of experimental techniques: scanning electron microscopy, optical confocal imaging, energy dispersive x-ray microanalysis, Raman scattering, and cathodoluminescence. A substantial Si migration to the GaN epilayer was observed in the crater regions, where decomposition of GaN and formation of Si{sub 3}N{sub 4} crystallites as well as metallic Ga droplets and Si nanocrystals have occurred. The average diameter of the Si nanocrystals was estimated from Raman scattering to be around 3 nm. Such annealing effects, which are not observed in GaN grown on sapphire, are a significant issue for applications of GaN grown on Si(111) substrates when subsequent high-temperature processing is required.

  14. Effect of rapid thermal annealing temperature on the dispersion of Si nanocrystals in SiO{sub 2} matrix

    SciTech Connect

    Saxena, Nupur Kumar, Pragati; Gupta, Vinay

    2015-05-15

    Effect of rapid thermal annealing temperature on the dispersion of silicon nanocrystals (Si-NC’s) embedded in SiO{sub 2} matrix grown by atom beam sputtering (ABS) method is reported. The dispersion of Si NCs in SiO{sub 2} is an important issue to fabricate high efficiency devices based on Si-NC’s. The transmission electron microscopy studies reveal that the precipitation of excess silicon is almost uniform and the particles grow in almost uniform size upto 850 °C. The size distribution of the particles broadens and becomes bimodal as the temperature is increased to 950 °C. This suggests that by controlling the annealing temperature, the dispersion of Si-NC’s can be controlled. The results are supported by selected area diffraction (SAED) studies and micro photoluminescence (PL) spectroscopy. The discussion of effect of particle size distribution on PL spectrum is presented based on tight binding approximation (TBA) method using Gaussian and log-normal distribution of particles. The study suggests that the dispersion and consequently emission energy varies as a function of particle size distribution and that can be controlled by annealing parameters.

  15. Selective synthesis of boron nitride nanotubes by self-propagation high-temperature synthesis and annealing process

    SciTech Connect

    Wang Jilin; Zhang Laiping; Zhao Guowei; Gu Yunle; Zhang Zhanhui; Zhang Fang; Wang Weimin

    2011-09-15

    Four types of BN nanotubes are selectively synthesized by annealing porous precursor in flowing NH{sub 3} and NH{sub 3}/H{sub 2} atmosphere at temperature ranging from 1000 to 1200 deg. C in a vertical furnace. The as-synthesized BN nanotubes, including cylinder, wave-like, bamboo-like and bubble-chain, are characterized by XRD, FTIR, Raman, SEM, TEM and HRTEM. Three phenomenological growth models are proposed to interpret growth scenario and structure features of the four types of BN nanotubes. Selectivity of nanotubes formation is estimated as approximately 80-95%. The precursor containing B, Mg, Fe and O prepared by self-propagation high-temperature synthesis (SHS) method plays a key role in selective synthesis of the as-synthesized BN nanotubes. Chemical reactions are also discussed. - Graphical Abstract: Four types of BN nanotubes are selectively synthesized by annealing porous precursor prepared by self-propagation high-temperature synthesis. Three phenomenological growth models are proposed to reveal growth scenario and characteristics of the as-synthesized BN nanotubes. Highlights: > Four types of BN nanotubes are selectively synthesized by annealing porous precursor. > Selectivity of BN nanotubes formation is estimated as approximately 80-95 wt%. > Three growth models are proposed to interpret growth of the as-synthesized BN nanotubes. > The precursor prepared by SHS method plays a key role in selective synthesis process.

  16. Effects of dip-coating speed and annealing temperature on structural, morphological and optical properties of sol-gel nano-structured TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Touam, Tahar; Atoui, Mohamed; Hadjoub, Ilhem; Chelouche, Azeddine; Boudine, Boubekeur; Fischer, Alexis; Boudrioua, Azzedine; Doghmane, Abdellaziz

    2014-09-01

    We reported material characterization of the nano-structured TiO2 thin films prepared by the sol-gel dip-coating process on glass substrates. The dependence of the structural, morphological and optical properties of the synthesized films on the fabrication parameters such as withdrawal velocity and annealing temperature were investigated by the techniques of X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-visible spectrophotometry. The results indicate that for the TiO2 films annealed at 500 °C there exhibits (1 0 1) XRD peak corresponding to the anatase phase of TiO2. The latter is consistent with the recorded Raman signal observed at 142 cm-1 (Eg mode) and 391 cm-1 (B1g mode), respectively. From the analyses made on the SEM micrographs and AFM images, it was revealed that the morphology and surface roughness of the thin films would depend on the withdrawal speed and the heat treatment temperature. The UV-visible spectroscopy analyses show that all the films were transparent in the visible region with an average transmittance of more than 70%. With an increase on the dip-coating speed from 1 cm/min to 3 cm/min, we observed a spectral red shift of the absorption edge from 3.76 eV to 3.71 eV, indicating a decrease in the bandgap energy (Eg) of the films.

  17. Temperature dependence of hydrogenated amorphous silicon solar cell performances

    NASA Astrophysics Data System (ADS)

    Riesen, Y.; Stuckelberger, M.; Haug, F.-J.; Ballif, C.; Wyrsch, N.

    2016-01-01

    Thin-film hydrogenated amorphous silicon solar (a-Si:H) cells are known to have better temperature coefficients than crystalline silicon cells. To investigate whether a-Si:H cells that are optimized for standard conditions (STC) also have the highest energy yield, we measured the temperature and irradiance dependence of the maximum power output (Pmpp), the fill factor (FF), the short-circuit current density (Jsc), and the open-circuit voltage (Voc) for four series of cells fabricated with different deposition conditions. The parameters varied during plasma-enhanced chemical vapor deposition (PE-CVD) were the power and frequency of the PE-CVD generator, the hydrogen-to-silane dilution during deposition of the intrinsic absorber layer (i-layer), and the thicknesses of the a-Si:H i-layer and p-type hydrogenated amorphous silicon carbide layer. The results show that the temperature coefficient of the Voc generally varies linearly with the Voc value. The Jsc increases linearly with temperature mainly due to temperature-induced bandgap reduction and reduced recombination. The FF temperature dependence is not linear and reaches a maximum at temperatures between 15 °C and 80 °C. Numerical simulations show that this behavior is due to a more positive space-charge induced by the photogenerated holes in the p-layer and to a recombination decrease with temperature. Due to the FF(T) behavior, the Pmpp (T) curves also have a maximum, but at a lower temperature. Moreover, for most series, the cells with the highest power output at STC also have the best energy yield. However, the Pmpp (T) curves of two cells with different i-layer thicknesses cross each other in the operating cell temperature range, indicating that the cell with the highest power output could, for instance, have a lower energy yield than the other cell. A simple energy-yield simulation for the light-soaked and annealed states shows that for Neuchâtel (Switzerland) the best cell at STC also has the best energy

  18. Carbon films embedded by nickel nanoparticles: fluctuation in hopping rate and variable-range hopping with respect to annealing temperature

    NASA Astrophysics Data System (ADS)

    Dalouji, Vali; Elahi, Smohammad; Solaymani, Shahram; Ghaderi, Atefeh; Elahi, Hossein

    2016-05-01

    In this work, the electrical properties of carbon-nickel films annealed at different temperatures (573, 773, 1073 and 1273 K) in the temperature range 15-300 K were investigated. The films were grown by radio frequency magnetron co-sputtering on quartz substrates at room temperature. The multiphonon hopping conduction mechanism is found to dominate the electrical transport in the temperature range 150-300 K. It can be seen that the room-temperature hopping rate (ΓRT) at 773 K has maximum value of 56.8 × 105 s-1. Our results of conductivity measurements at high temperature are in good agreement with strong carrier-lattice coupling model; on the other hand, the conductivity in the range 15-50 K is well described in terms of variable-range hopping (VRH) conduction mechanism. The localized state density around Fermi level N( E F) and the average hopping energy W hop at low temperature for the films annealed at 773 K have maximum value of 2.23 × 1023 (cm-3 eV-1) and minimum value of 9.74 × 10-4 eV, respectively.

  19. Influence of annealing temperature and Sn doping on the optical properties of hematite thin films determined by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    de Souza, Lígia P.; Chaves, Rodrigo O. G.; Malachias, Angelo; Paniago, Roberto; Ferreira, Sukarno O.; Ferlauto, Andre S.

    2016-06-01

    Hematite (α-Fe2O3) thin films were prepared by sol-gel route and investigated for application in H2 generation by photo-assisted water splitting. The photoelectrochemical (PEC) performance was shown to increase significantly for films deposited on SnO2:F/glass subjected to high temperature (T) annealing (>750 °C). Strong correlation was found between photogenerated current, donor concentration, and Sn concentration as determined by Mott-Schottky analysis and X-ray photoelectron spectroscopy. The effects of thermal annealing and Sn addition in the resulting microstructure and optical properties of hematite films deposited on fused silica substrates were determined by a combination of structural characterization techniques and spectroscopic ellipsometry. Thermal annealing (>600 °C) induces a higher optical absorption that is associated directly to film densification and grain growth; however, it promotes no changes in the energy positions of the main Fe2O3 electronic transitions. The band gap energy was found to be 2.21 eV and independent of microstructure and of Sn concentration for all studied films. On the other hand, Sn can be incorporated in the Fe2O3 lattice for concentration up to Sn/Fe ˜2%, leading to an increase in energy split of the main absorption peak, attributed to a distortion of the Fe2O3 lattice. For higher concentrations, Sn incorporation leads to a reduction in absorption, associated with higher porosity and the formation of a secondary Sn-rich phase. In summary, the variation in the optical properties induced by thermal annealing and Sn addition cannot account for the order of magnitude increase of the current density generated by photoanodes annealed at high T (>750 °C); thus, it is concluded that the major contribution for the enhanced PEC performance comes from improved electronic properties induced by the n-type doping caused by Sn diffusion from the SnO2:F substrate.

  20. Temperature dependence of the hyperfine interaction at

    SciTech Connect

    Lopez-Garcia, Alberto; de la Presa, Patricia; Ayala, Alejandro

    2001-06-01

    The temperature dependence of the quadrupole hyperfine parameters covering the temperature range from 293 to 1173 K was measured at {sup 181}Ta probes in SrHfO{sub 3} by perturbed angular correlation spectroscopy. A fluctuating distribution of quadrupole interactions model was applied to interpret the data. At low temperatures above {approximately}300 K a static, asymmetric, and distributed electric quadrupole interaction was detected. At intermediate temperatures ({approx}600 K) a different quadrupole interaction appears, characterized by a fluctuating distribution of axially symmetric electric field gradient tensors. Above 873 K, the unique presence of a nuclear spin relaxation mechanism shows a second change in the perturbation acting on probes. These changes in the hyperfine interaction are consistent with the structural phase transitions detected by diffraction techniques. The probe effects were also analyzed, comparing {sup 181}Ta with {sup 111}Cd experiments.

  1. Effect of annealing temperature on antimicrobial and structural properties of bio-synthesized zinc oxide nanoparticles using flower extract of Anchusa italica.

    PubMed

    Azizi, Susan; Mohamad, Rosfarizan; Bahadoran, Azadeh; Bayat, Saadi; Rahim, Raha Abdul; Ariff, Arbakariya; Saad, Wan Zuhainis

    2016-08-01

    The use of nontoxic biological compounds in the synthesis of nanomaterials is an economic and eco-friendly approach. The present work was undertaken to develop zinc oxide nanoparticles (ZnO-NPs) by a green method using simple precursor from the solution consisting of zinc acetate and the flower extract of Anchusa italica (A. italica). Effect of annealing temperature on structural and antimicrobial properties was investigated. The crystalline structure of ZnO-NPs was shown using X-ray diffraction (XRD) analysis. Transmission electron microscopy (TEM) results showed that ZnO-NPs are hexagonal in shapes with mean particle size of ~8 and ~14nm at 100°C and 200°C annealing temperatures respectively. The optical band gap was increased from 3.27eV to 3.30eV with the decreasing of the particle size. The antimicrobial activity of ZnO-NPs towards Gram positive (Bacillus megaterium and Stapphylococcus aureus) and Gram negative (Escherichia coli and Salmonella typhimurium) pathogens decreased with the increasing of the heat treating temperature. In vitro cytotoxicity studies on Vero cells, a dose dependent toxicity with non-toxic effect of concentration below 142μg/mL was shown. The results indicated that A. italica is an appropriate reaction media to prepare ZnO-NPs for cosmetic and bio-medical productions. PMID:27318600

  2. Coupled temperature dependences of volume and compressibility

    NASA Astrophysics Data System (ADS)

    Lawson, A. C.; Ledbetter, H.

    2011-04-01

    We present a new method for understanding the changes with temperature of the volume and compressibility of solids. These changes depend on five parameters: V 0, B 0, Θ, γ G and δ T. V 0 and B 0 are the atomic volume and bulk modulus at T = 0 K, Θ is the Debye temperature, γ G is the Grüneisen parameter, and δ T is the Anderson-Grüneisen parameter. Equations for the temperature-dependent volume, bulk modulus and thermal expansion are given, and examples of the use of these equations are provided, with particular emphasis on the light actinides. For the elements, we examine the relationship between experimental values of γ G and δ T, and find no clear correlation. In particular, Swenson's rule, which states that the bulk modulus does not change with temperature if the volume is held constant, is a poor approximation to the data. We reveal a new useful approximate relationship between dB/dP and γ G. We find that the thermodynamic quantity q, which describes the variation in γ G with volume, distributes around 2, not around 1, as often assumed. We show that the thermal- expansion behavior of Si and Ge (including negative thermal expansion at low temperatures) are well described with the use of a two-level invar model.

  3. Electrical properties of solution-deposited ZnO thin-film transistors by low-temperature annealing.

    PubMed

    Lim, Chul; Oh, Ji Young; Koo, Jae Bon; Park, Chan Woo; Jung, Soon-Won; Na, Bock Soon; Chu, Hye Yong

    2014-11-01

    Flexible oxide thin-film transistors (Oxide-TFTs) have emerged as next generation transistors because of their applicability in electronic device. In particular, the major driving force behind solution-processed zinc oxide film research is its prospective use in printing for electronics. A low-temperature process to improve the performance of solution-processed n-channel ZnO thin-film transistors (TFTs) fabricated via spin-coating and inkjet-printing is introduced here. ZnO nanoparticles were synthesized using a facile sonochemical method that was slightly modified based on a previously reported method. The influence of the annealing atmosphere on both nanoparticle-based TFT devices fabricated via spin-coating and those created via inkjet printing was investigated. For the inkjet-printed TFTs, the characteristics were improved significantly at an annealing temperature of 150 degrees C. The field effect mobility, V(th), and the on/off current ratios were 3.03 cm2/Vs, -3.3 V, and 10(4), respectively. These results indicate that annealing at 150 degrees C 1 h is sufficient to obtain a mobility (μ(sat)) as high as 3.03 cm2/Vs. Also, the active layer of the solution-based ZnO nanoparticles allowed the production of high-performance TFTs for low-cost, large-area electronics and flexible devices. PMID:25958581

  4. Enthalpy relaxation and annealing effect in polystyrene.

    PubMed

    Sakatsuji, Waki; Konishi, Takashi; Miyamoto, Yoshihisa

    2013-07-01

    The effects of thermal history on the enthalpy relaxation in polystyrene are studied by differential scanning calorimetry. The temperature dependence of the specific heat in the liquid and the glassy states, that of relaxation time, and the exponent of the Kohlrausch-Williams-Watts function are determined by measurements of the thermal response against sinusoidal temperature variation. A phenomenological model equation previously proposed to interpret the memory effect in the frozen state is applied to the enthalpy relaxation and the evolution of entropy under a given thermal history is calculated. The annealing below the glass transition temperature produces two effects on enthalpy relaxation: the decay of excess entropy with annealing time in the early stage of annealing and the increase in relaxation time due to physical aging in the later stage. The crossover of these effects is reflected in the variation of temperature of the maximum specific heat observed in the heating process after annealing and cooling.

  5. Effects of high-temperature thermal annealing on the electronic properties of In-Ga-Zn oxide thin films

    SciTech Connect

    Li, Qin; Song, Zhong Xiao; Ma, Fei E-mail: liyhemail@gmail.com; Li, Yan Huai E-mail: liyhemail@gmail.com; Xu, Ke Wei

    2015-03-15

    Indium gallium zinc oxide (IGZO) thin films were deposited by radio-frequency magnetron sputtering at room-temperature. Then, thermal annealing was conducted to improve the structural ordering. X-ray diffraction and high-resolution transmission electron microscopy demonstrated that the as-deposited IGZO thin films were amorphous and crystallization occurred at 800 and 950 °C. As a result of crystallization at high temperature, the carrier concentration and the Hall mobility of IGZO thin films were sharply increased, which could be ascribed to the increased oxygen vacancies and improved structural ordering of the thin films.

  6. Room-temperature laser annealing for solid-phase epitaxial crystallization of β-Ga2O3 thin films

    NASA Astrophysics Data System (ADS)

    Shiojiri, Daishi; Fukuda, Daiji; Yamauchi, Ryosuke; Tsuchimine, Nobuo; Koyama, Koji; Kaneko, Satoru; Matsuda, Akifumi; Yoshimoto, Mamoru

    2016-10-01

    The epitaxial crystallization of β-Ga2O3 thin films on NiO-buffered α-Al2O3(0001) substrates via the solid-phase crystallization of amorphous Ga2O3 thin films by KrF excimer laser annealing at room temperature (RT) was examined. The results of X-ray and reflection high-energy electron diffraction measurements indicated that the epitaxial β-Ga2O3 (\\bar{2}01) thin films were fabricated by RT laser annealing. The optical bandgap of the thin films was estimated to be 4.9 eV from the results of UV/vis transmittance measurements. In the cathodoluminescence spectrum, UV-green luminescence was observed for the thin films. These optical properties are similar to those of bulk β-Ga2O3.

  7. The photoluminescence and structural properties of (Ce, Yb) co-doped silicon oxides after high temperature annealing

    SciTech Connect

    Heng, C. L. Li, J. T.; Su, W. Y.; Yin, P. G.; Finstad, T. G.

    2015-01-28

    We studied the photoluminescence (PL) and structural properties of Ce and Yb co-doped silicon oxide films after high temperature annealing. The PL spectra of Ce{sup 3+} and Yb{sup 3+} ions were sensitive to the structural variation of the films, and the Yb PL intensities were significantly enhanced especially upon 1200 °C annealing. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, indicated that rare earth silicates and the CeO{sub 2} phase had formed in the oxides. The proportions of the phases varied with the “nominal Si-richness” of the films. Energy transfer from the excited Ce{sup 3+} to Yb{sup 3+} can be inferred from both PL excitation and decay spectra.

  8. Effects of annealing temperature on the physicochemical, optical and photoelectrochemical properties of nanostructured hematite thin films prepared via electrodeposition method

    SciTech Connect

    Phuan, Yi Wen; Chong, Meng Nan; Zhu, Tao; Yong, Siek-Ting; Chan, Eng Seng

    2015-09-15

    Highlights: • Nanostructured hematite thin films were synthesized via electrodeposition method. • Effects of annealing on size, grain boundary and PEC properties were examined. • Photocurrents generation was enhanced when the thin films were annealed at 600 °C. • The highest photocurrent density of 1.6 mA/cm{sup 2} at 0.6 V vs Ag/AgCl was achieved. - Abstract: Hematite (α-Fe{sub 2}O{sub 3}) is a promising photoanode material for hydrogen production from photoelectrochemical (PEC) water splitting due to its wide abundance, narrow band-gap energy, efficient light absorption and high chemical stability under aqueous environment. The key challenge to the wider utilisation of nanostructured hematite-based photoanode in PEC water splitting, however, is limited by its low photo-assisted water oxidation caused by large overpotential in the nominal range of 0.5–0.6 V. The main aim of this study was to enhance the performance of hematite for photo-assisted water oxidation by optimising the annealing temperature used during the synthesis of nanostructured hematite thin films on fluorine-doped tin oxide (FTO)-based photoanodes prepared via the cathodic electrodeposition method. The resultant nanostructured hematite thin films were characterised using field emission-scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV-visible spectroscopy and Fourier transform infrared spectroscopy (FTIR) for their elemental composition, average nanocrystallites size and morphology; phase and crystallinity; UV-absorptivity and band gap energy; and the functional groups, respectively. Results showed that the nanostructured hematite thin films possess good ordered nanocrystallites array and high crystallinity after annealing treatment at 400–600 °C. FE-SEM images illustrated an increase in the average hematite nanocrystallites size from 65 nm to 95 nm when the annealing temperature was varied from 400 °C to 600

  9. Enhanced p-type conduction of B-doped nanocrystalline diamond films by high temperature annealing

    SciTech Connect

    Gu, S. S.; Hu, X. J.

    2013-07-14

    We report the enhanced p-type conduction with Hall mobility of 53.3 cm{sup 2} V{sup -1} s{sup -1} in B-doped nanocrystalline diamond (NCD) films by 1000 Degree-Sign C annealing. High resolution transmission electronic microscopy, uv, and visible Raman spectroscopy measurements show that a part of amorphous carbon grain boundaries (GBs) transforms to diamond phase, which increases the opportunity of boron atoms located at the GBs to enter into the nano-diamond grains. This phase transition doping is confirmed by the secondary ion mass spectrum depth profile results that the concentration of B atoms in nano-diamond grains increases after 1000 Degree-Sign C annealing. It is also observed that 1000 Degree-Sign C annealing improves the lattice perfection, reduces the internal stress, decreases the amount of trans-polyacetylene, and increases the number or size of aromatic rings in the sp{sup 2}-bonded carbon cluster in B-doped NCD films. These give the contributions to improve the electrical properties of 1000 Degree-Sign C annealed B-doped NCD films.

  10. The effect of different annealing temperatures on tin and cadmium telluride phases obtained by a modified chemical route

    SciTech Connect

    Mesquita, Anderson Fuzer; Porto, Arilza de Oliveira; Magela de Lima, Geraldo; Paniago, Roberto; Ardisson, José Domingos

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► Synthesis of cadmium and tin telluride. ► Chemical route to obtain pure crystalline cadmium and tin telluride. ► Effect of the annealing temperature on the crystalline phases. ► Removal of tin oxide as side product through thermal treatment. -- Abstract: In this work tin and cadmium telluride were prepared by a modification of a chemical route reported in the literature to obtain metallacycles formed by oxidative addition of tin-tellurium bonds to platinum (II). Through this procedure it was possible to obtain tin and cadmium telluride. X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the crystalline phases obtained as well as the presence of side products. In the case of tin telluride it was identified potassium chloride, metallic tellurium and tin oxide as contaminants. The tin oxidation states were also monitored by {sup 119}Sn Mössbauer spectroscopy. The annealing in hydrogen atmosphere was chosen as a strategy to reduce the tin oxide and promote its reaction with the excess of tellurium present in the medium. The evolution of this tin oxide phase was studied through the annealing of the sample at different temperatures. Cadmium telluride was obtained with high degree of purity (98.5% relative weight fraction) according to the Rietveld refinement of X-ray diffraction data. The modified procedure showed to be very effective to obtain amorphous tin and cadmium telluride and the annealing at 450 °C has proven to be useful to reduce the amount of oxide produced as side product.

  11. Microstructural evolution during ultra-rapid annealing of severely deformed low-carbon steel: strain, temperature, and heating rate effects

    NASA Astrophysics Data System (ADS)

    Mostafaei, M. A.; Kazeminezhad, M.

    2016-07-01

    An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200-1100°C/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. Moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.

  12. Retrieving the ground state of spin glasses using thermal noise: Performance of quantum annealing at finite temperatures

    NASA Astrophysics Data System (ADS)

    Nishimura, Kohji; Nishimori, Hidetoshi; Ochoa, Andrew J.; Katzgraber, Helmut G.

    2016-09-01

    We study the problem to infer the ground state of a spin-glass Hamiltonian using data from another Hamiltonian with interactions disturbed by noise from the original Hamiltonian, motivated by the ground-state inference in quantum annealing on a noisy device. It is shown that the average Hamming distance between the inferred spin configuration and the true ground state is minimized when the temperature of the noisy system is kept at a finite value, and not at zero temperature. We present a spin-glass generalization of a well-established result that the ground state of a purely ferromagnetic Hamiltonian is best inferred at a finite temperature in the sense of smallest Hamming distance when the original ferromagnetic interactions are disturbed by noise. We use the numerical transfer-matrix method to establish the existence of an optimal finite temperature in one- and two-dimensional systems. Our numerical results are supported by mean-field calculations, which give an explicit expression of the optimal temperature to infer the spin-glass ground state as a function of variances of the distributions of the original interactions and the noise. The mean-field prediction is in qualitative agreement with numerical data. Implications on postprocessing of quantum annealing on a noisy device are discussed.

  13. Advanced processing of gallium nitride and gallium nitride-based devices: Ultra-high temperature annealing and implantation incorporation

    NASA Astrophysics Data System (ADS)

    Yu, Haijiang

    This dissertation is focused on three fields: ultra-high temperature annealing of GaN, activation of implanted GaN and the implantation incorporation into AlGaN/GaN HEMT processing, with an aim to increase the performance, manufacturability and reliability of AlGaN/GaN HEMTs. First, the ultra high temperature (around 1500°C) annealing of MOCVD grown GaN on sapphire has been studied, and a thermally induced threading dislocation (TD) motion and reaction are reported. Using a rapid thermal annealing (RTA) approach capable of heating 2 inch wafers to around 1500°C with 100 bar N2 over-pressure, evidence of dislocation motion was first observed in transmission electron microscopy (TEM) micrographs of both planar and patterned GaN films protected by an AIN capping layer. An associated decrease in x-ray rocking curve (XRC) full-width-half-maximum (FWHM) was also observed for both the symmetric and asymmetric scans. After annealing, the AIN capping layer remained intact, and optical measurements showed no degradation of the opto-electronic properties of the films. Then activation annealing of Si implants in MOCVD grown GaN has been studied for use in ohmic contacts. Si was implanted in semi-insulating GaN at 100 keV with doses from 5 x 1014 cm-2 to 1.5 x 1016 cm-2. Rapid thermal annealing at 1500°C with 100 bar N2 over-pressure was used for dopant activation, resulting in a minimum sheet resistance of 13.9 O/square for a dose of 7 x 1015 cm-2. Secondary ion mass spectroscopy measurements showed a post-activation broadening of the dopant concentration peak by 20 nm (at half the maximum), while X-Ray triple axis o-2theta scans indicated nearly complete implant damage recovery. Transfer length method measurements of the resistance of Ti/Al/Ni/Au contacts to activated GaN:Si (5 x 1015 cm-2 at 100 keV) indicated lowest contact resistances of 0.07 Omm and 0.02 Omm for as-deposited and subsequently annealed contacts, respectively. Finally, the incorporation of Si implantation

  14. Influence of Annealing Temperature on the Photo-Electrical and Structural Disorder Characteristics of Nano-Structured Zinc Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Mamat, M. H.; Sahdan, M. Z.; Amizam, S.; Rafaie, H. A.; Khusaimi, Z.; Rusop, M.

    2009-06-01

    This paper studies the photoelectrical and structural disorder characteristic of zinc oxide thin films on glass substrates at different annealing temperatures. The ZnO thin films were prepared through cost effective sol-gel method and spin-coating technique from zinc acetate in alcoholic solution. The photoelectrical and structural disorder properties were investigated for the thin films annealed at 350˜500° C. The results indicate the improvement of both photoelectrical and structural disorder characteristics of ZnO thin films at higher annealing temperatures.

  15. Temperature dependent light transmission in ferrofluids

    NASA Astrophysics Data System (ADS)

    Brojabasi, Surajit; Mahendran, V.; Lahiri, B. B.; Philip, John

    2015-05-01

    We investigate the influence of temperature on the magnetic field induced light transmission in a kerosene based ferrofluid containing oleic acid coated Fe3O4 nanoparticles, where the direction of propagation of light is parallel to the direction of the external magnetic field. At a fixed temperature the transmitted light intensity is found to monotonically increase with incident wavelength due to reduced extinction efficiency at higher wavelength. The transmitted intensity decreases with external magnetic field due to enhanced scattering from the field induced linear chain like structures along the direction of the external magnetic field and due to the build-up of standing waves inside the scattering medium. The extinction of the field induced transmitted light intensity is found to occur at a lower external field as the sample temperature is lowered. The rate of extinction of normalized transmitted light intensity decreased linearly with increasing sample temperature due to slower field induced aggregation kinetics because of an increased Brownian motion of the suspended nanoparticles and a reduced coupling constant. The observed temperature dependent magneto-optical properties of magnetic nanofluids can be exploited for applications in optical devices.

  16. Measurement of temperature-dependent defect diffusion in proton-irradiated GaN(Mg, H)

    SciTech Connect

    Fleming, R. M.; Myers, S. M.

    2006-08-15

    Deuterated p-type GaN(Mg,{sup 2}H) films were irradiated at room temperature with 1 MeV protons to create native point defects with a concentration approximately equal to the Mg doping (5x10{sup 19} cm{sup -3}). The samples were then annealed isothermally at a succession of temperatures while monitoring the infrared absorption due to the H local mode of the MgH defect. As the samples were annealed, the MgH absorption signal decreased and a new mode at slightly higher frequency appeared, which has been associated with the approach of a mobile nitrogen interstitial. We used the time dependence of the MgH absorption to obtain a diffusion barrier of the nitrogen interstitial in p-type GaN of 1.99 eV. This is in good agreement with theoretical calculations of nitrogen interstitial motion in GaN.

  17. Measurement of temperature-dependent defect diffusion in proton-irradiated GaN(Mg, H).

    SciTech Connect

    Myers, Samuel Maxwell, Jr.; Fleming, Robert M.

    2005-06-01

    Deuterated p-type GaN(Mg,{sup 2}H) films were irradiated at room temperature with 1 MeV protons to create native point defects with a concentration approximately equal to the Mg doping (5 x 10{sup 19} cm{sup -3}). The samples were then annealed isothermally at a succession of temperatures while monitoring the infrared absorption due to the H local mode of the MgH defect. As the samples were annealed, the MgH absorption signal decreased and a new mode at slightly higher frequency appeared, which has been associated with the approach of a mobile nitrogen interstitial. We used the time dependence of the MgH absorption to obtain a diffusion barrier of the nitrogen interstitial in p-type GaN of 1.99 eV. This is in good agreement with theoretical calculations of nitrogen interstitial motion in GaN.

  18. Effects of annealing temperature on optical, morphological, and electrical characteristics of polyfluorene-derivative thin films on ITO glass substrate.

    PubMed

    Lim, Way Foong; Quah, Hock Jin; Hassan, Zainuriah

    2016-02-20

    The effects of postdeposition annealing temperature (125°C-200°C) toward optical, morphological, and electrical characteristics of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-phenylene)] end capped with dimethylphenyl group deposited on indium tin oxide glass substrates were investigated. Green and red-infrared photoluminescence emissions, originating from П-conjugation aggregates and keto-type defects did not attenuate the intensity of the blue emission peak. This suggested that the aggregates and defects might serve as local traps for radiative recombination. In samples annealed at 125°C-175°C, a decreasing optical energy gap (E(g)) that decreased barrier height as well as an increasing amount of traps have increased current conduction via thermionic emission and trap-assisted tunneling. Nonetheless, an acquisition of the largest E(g) and amount of traps testified that thermionic emission was dominating current conduction, surpassing trap-assisted tunneling in samples annealed at 200°C. PMID:26906569

  19. Effects of annealing temperature on optical, morphological, and electrical characteristics of polyfluorene-derivative thin films on ITO glass substrate.

    PubMed

    Lim, Way Foong; Quah, Hock Jin; Hassan, Zainuriah

    2016-02-20

    The effects of postdeposition annealing temperature (125°C-200°C) toward optical, morphological, and electrical characteristics of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-phenylene)] end capped with dimethylphenyl group deposited on indium tin oxide glass substrates were investigated. Green and red-infrared photoluminescence emissions, originating from П-conjugation aggregates and keto-type defects did not attenuate the intensity of the blue emission peak. This suggested that the aggregates and defects might serve as local traps for radiative recombination. In samples annealed at 125°C-175°C, a decreasing optical energy gap (E(g)) that decreased barrier height as well as an increasing amount of traps have increased current conduction via thermionic emission and trap-assisted tunneling. Nonetheless, an acquisition of the largest E(g) and amount of traps testified that thermionic emission was dominating current conduction, surpassing trap-assisted tunneling in samples annealed at 200°C.

  20. Suppression of the antiferromagnetic pseudogap in the electron-doped high-temperature superconductor by protect annealing

    NASA Astrophysics Data System (ADS)

    Horio, M.; Adachi, T.; Mori, Y.; Takahashi, A.; Yoshida, T.; Suzuki, H.; Ambolode, L. C. C.; Okazaki, K.; Ono, K.; Kumigashira, H.; Anzai, H.; Arita, M.; Namatame, H.; Taniguchi, M.; Ootsuki, D.; Sawada, K.; Takahashi, M.; Mizokawa, T.; Koike, Y.; Fujimori, A.

    2016-02-01

    In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity. In the electron-doped cuprates, on the other hand, superconductivity appears only in a narrow window of high-doped Ce concentration after reduction annealing, and strong antiferromagnetic correlation persists in the superconducting phase. Recently, Pr1.3-xLa0.7CexCuO4 (PLCCO) bulk single crystals annealed by a protect annealing method showed a high critical temperature of around 27 K for small Ce content down to 0.05. Here, by angle-resolved photoemission spectroscopy measurements of PLCCO crystals, we observed a sharp quasi-particle peak on the entire Fermi surface without signature of an antiferromagnetic pseudogap unlike all the previous work, indicating a dramatic reduction of antiferromagnetic correlation length and/or of magnetic moments. The superconducting state was found to extend over a wide electron concentration range. The present results fundamentally challenge the long-standing picture on the electronic structure in the electron-doped regime.

  1. Suppression of the antiferromagnetic pseudogap in the electron-doped high-temperature superconductor by protect annealing.

    PubMed

    Horio, M; Adachi, T; Mori, Y; Takahashi, A; Yoshida, T; Suzuki, H; Ambolode, L C C; Okazaki, K; Ono, K; Kumigashira, H; Anzai, H; Arita, M; Namatame, H; Taniguchi, M; Ootsuki, D; Sawada, K; Takahashi, M; Mizokawa, T; Koike, Y; Fujimori, A

    2016-01-01

    In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity. In the electron-doped cuprates, on the other hand, superconductivity appears only in a narrow window of high-doped Ce concentration after reduction annealing, and strong antiferromagnetic correlation persists in the superconducting phase. Recently, Pr(1.3-x)La0.7Ce(x)CuO4 (PLCCO) bulk single crystals annealed by a protect annealing method showed a high critical temperature of around 27 K for small Ce content down to 0.05. Here, by angle-resolved photoemission spectroscopy measurements of PLCCO crystals, we observed a sharp quasi-particle peak on the entire Fermi surface without signature of an antiferromagnetic pseudogap unlike all the previous work, indicating a dramatic reduction of antiferromagnetic correlation length and/or of magnetic moments. The superconducting state was found to extend over a wide electron concentration range. The present results fundamentally challenge the long-standing picture on the electronic structure in the electron-doped regime.

  2. Annealing Temperature and Initial Iron Valence Ratio Effects on the Structural Characteristics of Nanoscale Nickel Zinc Ferrite

    SciTech Connect

    Calvin, S.; Shultz, M; Glowzenski, L; Carpenter, E

    2010-01-01

    Nickel zinc ferrite (NZFO) nanoparticles were synthesized via a reverse micelle method with a nonionic surfactant. Three different initial Fe{sup 3+}/Fe{sup 2+} ratios were employed along with three different firing temperatures (200, 500, 1000 C) to investigate the effects on the NZFO system. Extended x-ray absorption fine structure (EXAFS) results reveal zinc loss at high annealing temperatures; at 1000 C, the loss is nearly total for Fe{sup 3+}/Fe{sup 2+} ratios other than 10:90. Annealing at 500 C, however, appears necessary for fully incorporating the zinc and nickel into the spinel phase. The best nanoferrite was thus obtained using an initial Fe{sup 3+}/Fe{sup 2+} ratio of 10:90 and a moderate firing temperature of 500 C. This sample exhibits a room temperature saturation magnetization of 58 emu/g as measured via vibrating sample magnetometry, comparable with bulk values and greater than that of confirmed nano-NZFOs found in the literature. EXAFS also indicates that in all cases in which the elements adopted a spinel structure, the nickel occupies only octahedral sites and the zinc primarily tetrahedral sites.

  3. Effect of the annealing temperature on the low-temperature photoluminescence in Si:Er light-emitting structures grown by molecular-beam epitaxy

    SciTech Connect

    Andreev, B. A.; Sobolev, N. A. Denisov, D. V.; Shek, E. I.

    2013-10-15

    The photoluminescence spectra of light-emitting structures based on silicon doped with erbium during the course of molecular-beam epitaxy at a temperature of 500 Degree-Sign C are studied at 4.2 K on being annealed at 800-900 Degree-Sign C. Three sets of lines belonging to the emitting centers of erbium in silicon with a low oxygen-impurity concentration are revealed.

  4. Strong, Twist-Stable Carbon Nanotube Yarns and Muscles by Tension Annealing at Extreme Temperatures.

    PubMed

    Di, Jiangtao; Fang, Shaoli; Moura, Francisco A; Galvão, Douglas S; Bykova, Julia; Aliev, Ali; de Andrade, Mônica Jung; Lepró, Xavier; Li, Na; Haines, Carter; Ovalle-Robles, Raquel; Qian, Dong; Baughman, Ray H

    2016-08-01

    A high-speed incandescent tension annealing process (ITAP) is used to increase the modulus and strength of twist-spun carbon nanotube yarns by up to 12-fold and 2.6-fold, respectively, provide remarkable resistance to oxidation and powerful protonating acids, and freeze yarn untwist. This twist stability enables torsional artificial-muscle motors having improved performance and minimizes problematic untwist during weaving nanotube yarns. PMID:27184216

  5. Effects of post-annealing temperature on the properties of ZnO nanorods grown on homogenous seed-layers by using the hydrothermal method

    NASA Astrophysics Data System (ADS)

    Yim, Kwang Gug; Kim, Min Su; Kim, Soaram; Leem, Jae-Young; Nam, Giwoong; Jeon, Su Min; Lee, Dong-Yul; Kim, Jin Soo; Kim, Jong Su; Lee, Joo In

    2012-05-01

    ZnO nanorods were grown on Si substrates by using the hydrothermal method; then, they were post-annealed at various temperatures ranging from 573 to 973 K. The effects of post-annealing temperature on the structural and the optical properties were investigated by using scanning electron microscopy (SEM), X-ray diffraction, and photoluminescence (PL). After the post-annealing process, small pores had been formed on the surface of the ZnO nanorods without any change in the shape of the ZnO nanorods. A tensile stress was observed in the as-grown and the post-annealed ZnO nanorods. The PL intensity ratio of the near-band-edge emission (NBE) to the deep-level emission (DLE) was enhanced, and the DLE peak shifted from yellow to orange emission with increasing post-annealing temperature. The activation energy of the post-annealed ZnO nanorods was increased by the post-annealing process.

  6. Temperature-dependent ion beam mixing

    SciTech Connect

    Rehn, L.E.; Alexander, D.E.

    1993-08-01

    Recent work on enhanced interdiffusion rates during ion-beam mixing at elevated temperatures is reviewed. As discussed previously, expected increase in ion-beam mixing rates due to `radiation-enhanced diffusion` (RED), i.e. the free migration of isolated vacancy and interstitial defects, is well documented in single-crystal specimens in the range of 0.4 to 0.6 of absolute melting temperature. In contrast, the increase often observed at somewhat lower temperatures during ion-beam mixing of polycrystalline specimens is not well understood. However, sufficient evidence is available to show that this increase reflects intracascade enhancement of a thermally-activated process that also occurs without irradiation. Recent evidence is presented which suggests that this process is Diffusion-induced Grain-Boundary Migration (DIGM). An important complementary conclusion is that because ion-beam mixing in single-crystal specimens exhibits no significant temperature dependence below that of RED, models that invoke only irradiation-specific phenomena, e.g., cascade-overlap, thermal-spikes, or liquid-diffusion, and hence which predict no difference in mixing behavior between single- or poly-crystalline specimens, cannot account for the existing results.

  7. Effect of Annealing Temperature on Dielectric Constant and Bonding Structure of Low-k SiCOH Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Lee, Sungwoo; Yang, Jaeyoung; Yeo, Sanghak; Lee, Jaewon; Jung, Donggeun; Boo, Jin-hyo; Kim, Hyoungsub; Chae, Heeyeop

    2007-02-01

    We investigated the effect of annealing temperature on the properties of SiCOH films deposited by plasma-enhanced chemical vapor deposition using or a mixture of Si-O containing and hydrocarbon precursors, decamethyl-cyclopentasiloxane (DMCPSO-C10H30O5Si5) and cyclohexane (CHex-C6H12). These SiCOH films were deposited at pressures of 0.6 and 1.5 Torr and the as-deposited SiCOH films were subjected to annealing temperatures from 25 to 500 °C in a furnace for 1 h in N2 ambient at a pressure of 1 atm. The relative dielectric constants, k, of the SiCOH films deposited at 0.6 and 1.5 Torr were 2.76 and 2.26, respectively, before the annealing process. The subsequent annealing of the SiCOH film at 500 °C further reduced the k values to as low as 2.31 and 1.85, respectively. Decreases in the refractive index, hardness, and modulus were observed as the annealing temperature increased to 450 °C. However, further increasing annealing temperature to 500 °C caused the refractive index, hardness, and modulus to increase again. Trends of decreases in both the hardness and modulus with increasing annealing temperature were found. The refractive index and the film thickness retention also decreased with increasing annealing temperature. The change in the k value as a function of the annealing temperature was correlated with the change in the Fourier transform infrared absorption peaks of C-Hx, Si-CH3, and Si-O related groups. As the annealing temperature increased, the intensity of both the CHx and Si-CH3 peaks decreased, respectively. In particular, the C-H2 (asymmetric and symmetric) peaks provide direct evidence of the presence of ethylene groups in the SiCOH films. Thus the decrease in intensity of the peaks corresponding to the CHx groups and Si-O cage structure in the SiCOH films was considered to be responsible for lowering they dielectric constant, refractive index, hardness and modulus of the films. The leakage current density of the SiCOH films at 1 MV/cm is obtained

  8. Low-temperature, site selective graphitization of SiC via ion implantation and pulsed laser annealing

    SciTech Connect

    Lemaitre, Maxime G.; Tongay, Sefaattin; Wang, Xiaotie; Venkatachalam, Dinesh K.; Elliman, Robert G.; Fridmann, Joel; Gila, Brent P.; Appleton, Bill R.; Hebard, Arthur F.; Ren, Fan

    2012-05-07

    A technique is presented to selectively graphitize regions of SiC by ion implantation and pulsed laser annealing (PLA). Nanoscale features are patterned over large areas by multi-ion beam lithography and subsequently converted to few-layer graphene via PLA in air. Graphitization occurs only where ions have been implanted and without elevating the temperature of the surrounding substrate. Samples were characterized using Raman spectroscopy, ion scattering/channeling, SEM, and AFM, from which the degree of graphitization was determined to vary with implantation species, damage and dose, laser fluence, and pulsing. Contrasting growth regimes and graphitization mechanisms during PLA are discussed.

  9. Effect of annealing temperature and pH on morphology and optical property of highly dispersible ZnO nanoparticles

    SciTech Connect

    Uthirakumar, Periyayya; Hong, Chang-Hee

    2009-11-15

    Highly dispersible zinc oxide nanoparticles were produced in large quantity via a simple solution method. The effect of temperature and pH impact on as-prepared ZnO nanoparticles with respect to the morphological and optical characteristics has been investigated. The average particle size of ZnO nanoparticles increased with increasing annealing temperature. A sharp UV band-edge emission was observed in as-prepared ZnO nanoparticles with negligibly less intense deep level emission. However, upon annealing at high temperature in air, UV band-edge emission disappears with an evolution of a broad deep level emission in photoluminescence spectra. Similarly, by adjusting the pH of reaction medium from 4 to pH = 8 using ammonium hydroxide solution, particle size gets bigger and bigger leads to red-shift in UV band-edge emission and an appearance of deep level emission peak. At pH = 8, well resolved sharp X-ray diffraction peaks were observed with lower FWHM values due to higher crystallite sizes.

  10. Flow rate distribution and effect of convection and radiation heat transfer on the temperature profile during a coil annealing process

    NASA Astrophysics Data System (ADS)

    Haouam, A.; Bigerelle, M.

    2015-02-01

    Determining the temperature of several steel coils, heated in a furnace with a controlled hydrogen environment is important in an annealing process. Temperatures must be defined during heat treatment in order to guarantee metallurgical properties and acceptable reduced residual stresses. In this paper we approach hydrogen flow characteristics in the furnace and through a set of coils using an annealing non-differential model. Fluid flow is schematized as a pipe network solved by the Hardy Cross method to obtain pressure drops across the various gas flow segments. A comparison is made between measured and simulated results, confirming the adequacy of adopted assumptions and the validity of proposed model. Convective and radiative exchanges between the furnace and the coils are calculated by a discretization using the finite differences method. The convection coefficients are estimated and introduced into the boundary conditions around the coil to obtain the temperature distribution in the coils and in the covering bell. Finally, heat exchanges by convection and radiation are estimated by this model and the modeling errors are <8 °C.

  11. Escherichia coli survival in waters: temperature dependence.

    PubMed

    Blaustein, R A; Pachepsky, Y; Hill, R L; Shelton, D R; Whelan, G

    2013-02-01

    Knowing the survival rates of water-borne Escherichia coli is important in evaluating microbial contamination and making appropriate management decisions. E. coli survival rates are dependent on temperature, a dependency that is routinely expressed using an analogue of the Q₁₀ model. This suggestion was made 34 years ago based on 20 survival curves taken from published literature, but has not been revisited since then. The objective of this study was to re-evaluate the accuracy of the Q₁₀ equation, utilizing data accumulated since 1978. We assembled a database of 450 E. coli survival datasets from 70 peer-reviewed papers. We then focused on the 170 curves taken from experiments that were performed in the laboratory under dark conditions to exclude the effects of sunlight and other field factors that could cause additional variability in results. All datasets were tabulated dependencies "log concentration vs. time." There were three major patterns of inactivation: about half of the datasets had a section of fast log-linear inactivation followed by a section of slow log-linear inactivation; about a quarter of the datasets had a lag period followed by log-linear inactivation; and the remaining quarter were approximately linear throughout. First-order inactivation rate constants were calculated from the linear sections of all survival curves and the data grouped by water sources, including waters of agricultural origin, pristine water sources, groundwater and wells, lakes and reservoirs, rivers and streams, estuaries and seawater, and wastewater. Dependency of E. coli inactivation rates on temperature varied among the water sources. There was a significant difference in inactivation rate values at the reference temperature between rivers and agricultural waters, wastewaters and agricultural waters, rivers and lakes, and wastewater and lakes. At specific sites, the Q₁₀ equation was more accurate in rivers and coastal waters than in lakes making the value of

  12. Effects of annealing temperature on structure and magnetic properties of CoAl0.2Fe1.8O4/SiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, L.; Li, J.; Liu, M.; Zhang, Y. M.; Lu, J. B.; Li, H. B.

    2012-12-01

    CoAl0.2Fe1.8O4/SiO2 nanocomposites were prepared by sol-gel method. The effects of annealing temperature on the structure and magnetic properties of the samples were studied by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer and Mössbauer spectroscopy. The results show that the CoAl0.2Fe1.8O4 in the samples exhibits a spinel structure after being annealed. As annealing temperature increases from 800 to 1200 °C, the average grain size of CoAl0.2Fe1.8O4 in the nanocomposites increases from 5 to 41 nm while the lattice constant decreases from 0.8397 to 0.8391 nm, the saturation magnetization increases from 21.96 to 41.53 emu/g. Coercivity reaches a maximum of 1082 Oe for the sample annealed at 1100 °C, and thereafter decreases with further increasing annealing temperature. Mössbauer spectra show that the isomer shift decreases, hyperfine field increases and the samples transfer from mixed state of superparamagnetic and magnetic order to the completely magnetic order with annealing temperature increasing from 800 to 1200 °C.

  13. Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature

    PubMed Central

    2014-01-01

    Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications. PMID:25520589

  14. Preparation of high temperature superconducting coated wires by dipping and post annealing

    SciTech Connect

    Provenzano, V.; Singh, A.K.; Imam, M.A.; Tritt, T.M.

    1992-04-14

    This patent describes a process for coating a film on a wire substrate, it comprises: melting a superconducting metal oxide mixture in a crucible to form a melt; coating the substrate with a diffusion barrier; dipping the coated wire substrate into the melt; cooling the coated wire substrate at a rate sufficiently slow to avoid thermal shock and hot cracking; and post-annealing the cooled, coated wire substrate to relieve thermal stresses in the coating, whereupon the superconducting metal-oxide mixture forms a perovskite coating upon the wire substrate.

  15. Co2FeAl Heusler thin films grown on Si and MgO substrates: Annealing temperature effect

    NASA Astrophysics Data System (ADS)

    Belmeguenai, M.; Tuzcuoglu, H.; Gabor, M. S.; Petrisor, T.; Tiusan, C.; Zighem, F.; Chérif, S. M.; Moch, P.

    2014-01-01

    10 nm and 50 nm Co2FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (Ta), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing Ta, while the uniaxial anisotropy field is nearly unaffected by Ta within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with Ta. Finally, the FMR linewidth decreases when increasing Ta, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.1×10-3 and 1.3×10-3 for films of 50 nm thickness annealed at 615 °C grown on MgO and on Si, respectively).

  16. Effects of low-temperature (120 °C) annealing on the carrier concentration and trap density in amorphous indium gallium zinc oxide thin film transistors

    SciTech Connect

    Kim, Jae-sung; Piao, Mingxing; Jang, Ho-Kyun; Kim, Gyu-Tae; Oh, Byung Su; Joo, Min-Kyu; Ahn, Seung-Eon

    2014-12-28

    We report an investigation of the effects of low-temperature annealing on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). X-ray photoelectron spectroscopy was used to characterize the charge carrier concentration, which is related to the density of oxygen vacancies. The field-effect mobility was found to decrease as a function of the charge carrier concentration, owing to the presence of band-tail states. By employing the transmission line method, we show that the contact resistance did not significantly contribute to the changes in device performance after annealing. In addition, using low-frequency noise analyses, we found that the trap density decreased by a factor of 10 following annealing at 120 °C. The switching operation and on/off ratio of the a-IGZO TFTs improved considerably after low-temperature annealing.

  17. Strain rate and temperature dependent mechanical behavior of nanocrystalline gold

    NASA Astrophysics Data System (ADS)

    Karanjgaokar, Nikhil J.

    Nanocrystalline metal films are candidate materials for microelectronics and Microelectromechanical Systems (MEMS). The long term mechanical stability of metal films requires quantitative understanding of their thermo-mechanical behavior in the large range of operating strain rates and temperatures. This dissertation research studied (a) the role of thermally activated processes based on the strain rate and temperature dependent mechanical behavior of nanocrystalline Au thin films, and (b) deformation processes at nominally elastic loads that lead to creep strain over a moderate temperature range that is relevant to MEMS applications. The rate dependent mechanical behavior of nanocrystalline Au thin films was first investigated at room temperature ~ 25 °C and at strain rates between 10-6 to 20 s-1. The use of digital image correlation (DIC) facilitated repeatable and accurate measurements of fullfield strain from free-standing nanocrystalline Au thin films. The experimental stress-strain curves were used to calculate activation volumes for two film thicknesses (0.85 mum, and 1.75 mum), which were 4.5b3 and 8.1b3, at strain rates smaller than 10-4 s-1 and 12.5b3 and 14.6b3 at strain rates higher than 10-4 s-1. The reduced activation volume and increased strain rate sensitivity at slow strain rates were attributed to grain boundary (GB) diffusional processes that result in creep strain. The room temperature strain rate results were augmented with microscale strain rate experiments at temperatures up to 110 °C. Two methods for heating free-standing microscale thin film specimens, namely uniform heating using a custom-built microheater and resistive (Joule) heating, were evaluated using a combination of full-field strain measurements by optical microscopy and full-field temperature measurements by infrared (IR) thermal imaging. It was shown for the first time that the Joule specimen heating method results in large underestimation of the inelastic material properties

  18. Investigation of isochronal annealing on the optical properties of HWCVD amorphous silicon nitride deposited at low temperatures and low gas flow rates

    NASA Astrophysics Data System (ADS)

    Muller, T. F. G.; Jacobs, S.; Cummings, F. R.; Oliphant, C. J.; Malgas, G. F.; Arendse, C. J.

    2015-06-01

    Hydrogenated amorphous silicon nitride (a-SiNx:H) is used as anti-reflection coatings in commercial solar cells. A final firing step in the production of micro-crystalline silicon solar cells allows hydrogen effusion from the a-SiNx:H into the solar cell, and contributes to bulk passivation of the grain boundaries. In this study a-SiNx:H deposited in a hot-wire chemical vapour deposition (HWCVD) chamber with reduced gas flow rates and filament temperature compared to traditional deposition regimes, were annealed isochronally. The UV-visible reflection spectra of the annealed material were subjected to the Bruggeman Effective Medium Approximation (BEMA) treatment, in which a theoretical amorphous semiconductor was combined with particle inclusions due to the structural complexities of the material. The extraction of the optical functions and ensuing Wemple-DeDomenici analysis of the wavelength-dependent refractive index allowed for the correlation of the macroscopic optical properties with the changes in the local atomic bonding configuration, involving silicon, nitrogen and hydrogen.

  19. Effects of Phosphorous-doping and High Temperature Annealing on CVD grown 3C-SiC

    SciTech Connect

    I. J. van Rooyen; J. H. Neethling; A. Henry; E. Janzen; S. M. Mokoduwe; A. Janse van Vuuren; E. Olivier

    2012-10-01

    The integrity and property behavior of the SiC layer of the Tri-isotropic (TRISO) coated particle (CP) for high temperature reactors (HTR) are very important as the SiC layer is the main barrier for gaseous and metallic fission product release. This study describes the work done on un-irradiated SiC samples prepared with varying phosphorus levels to simulate the presence of phosphorus due to transmutation. 30Si transmutes to phosphorous (31P) and other transmutation products during irradiation, which may affect the integrity of the SiC layer. The P-doping levels of the SiC samples used in this study cover the range from 1.1x1015 to 1.2x1019 at/cm3 and are therefore relevant to the PBMR operating conditions. Annealing from 1000 C to 2100 C was performed to study the possible changes in nanostructures and various properties due to temperature. Characterization results by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM), are reported in this article. As grain boundary diffusion is identified as a possible mechanism by which 110mAg, one of the fission activation products, might be released through intact SiC layer, grain size measurements is also included in this study. Temperature is evidently one of the factors/parameters amongst others known to influence the grain size of SiC and therefore it is important to investigate the effect of high temperature annealing on the SiC grain size. The ASTM E112 method as well as electron back scatter diffraction (EBSD) was used to determine the grain size of various commercial SiC samples and the SiC layer in experimental PBMR Coated Particles (CPs) after annealing at temperatures ranging from 1600 C to 2100 C. The HRTEM micrograph of the decomposition of SiC at 2100 C are shown and discussed. Nanotubes were not identified during the TEM and HRTEM analysis although graphitic

  20. Crystallization and segregation in vitreous rutile films annealed at high temperature

    SciTech Connect

    Omari, M.A.; Sorbello, R.S.; Aita, C.R.

    2005-11-15

    Vitreous titania films with rutile short-range order were sputter deposited on unheated fused silica substrates, sequentially annealed at 973 and 1273 K, and examined by Raman microscopy, scanning electron microscopy, and x-ray diffraction. A segregated microstructure developed after the 1273 K anneal. This microstructure consists of supermicron-size craters dispersed in a matrix of submicron rutile crystals. Ti-O short-range order in the craters is characteristic of a mixture of two high pressure phases, m-TiO{sub 2} (monoclinic P2{sub 1}/c space group) and {alpha}-TiO{sub 2} (tetragonal Pbcn space group). We calculated that a high average compressive stress parallel to the substrate must be accommodated in the films at 1273 K, caused by the difference in the thermal expansion coefficients of titania and fused silica. The formation of the segregated microstructure is modeled by considering two processes at work at 1273 K to lower a film's internal energy: crystallization and nonuniform stress relief. The Gibbs-Thomson relation shows that small m-TiO{sub 2} crystallites are able to form directly from vitreous TiO{sub 2} at 1273 K. However, the preferred mechanism for forming {alpha}-TiO{sub 2} is likely to be by epitaxial growth at crystalline rutile twin boundaries (secondary crystallization). Both phases are denser than crystalline rutile and reduce the average thermal stress in the films.

  1. Surface Al doping of 4H-SiC via low temperature annealing

    NASA Astrophysics Data System (ADS)

    Park, Junbo; Kim, Ki-hwan; Park, Young-rak; Kim, Minki; Lee, Hyungseok; Jun, Chi-Hoon; Koo, Sangmo; Ko, Sang Choon

    2016-07-01

    We present a method of forming shallow p-doping on a 4H-SiC surface by depositing a thin Al layer (d = 5 nm) and then thermally annealing it at 1000 °C for 10 min. A secondary ion mass spectrometry analysis of the annealed Al/SiC sample reveals an Al concentration in excess of 1017 cm-3 up to a depth of d ≤ 250 nm. I-V measurements and CV characterizations of Ti-SiC Schottky barrier diodes (SBDs) fabricated on a n-type SiC epi-wafer indicate that the shallow Al doping increases the built-in potential of the junction and the barrier height by Δ V b i = 0.51 eV and Δ ϕ B = 0.26 eV , respectively. Assuming a rectangular doping profile, calculations of the built-in voltage shift and the Schottky barrier height indicate that partial dopant activation (activation ratio ˜2%) can induce the observed barrier height shift. The shallow doping method was then used to fabricate junction terminations in SBDs which increased the breakdown voltage and reduced the reverse leakage current. Technology CAD simulations of the SBD with and without doping verify that a reduction of peak electric field can explain the improvement of the breakdown voltage.

  2. A self-propagation high-temperature synthesis and annealing route to synthesis of wave-like boron nitride nanotubes

    SciTech Connect

    Wang, Jilin; Zhang, Laiping; Gu, Yunle; Pan, Xinye; Zhao, Guowei; Zhang, Zhanhui

    2013-03-15

    Highlights: ► Large quantities of wave-like BN nanotubes were synthesized by SHS-annealing method. ► The catalytic boron-containing porous precursor was produced by self-propagation high-temperature synthesis method. ► Three growth models were proposed to explain the growth mechanism of the wave-like BN nanotubes. - Abstract: Large quantities of boron nitride (BN) nanotubes were synthesized by annealing a catalytic boron-containing porous precursor in flowing NH{sub 3} gas at 1180 °C. The porous precursor was prepared by self-propagation high-temperature synthesis (SHS) method at 800 °C using Mg, B{sub 2}O{sub 3} and amorphous boron powder (α-B) as the starting materials. The porous precursor played an important role in large quantities synthesis of BN nanotubes. The as-synthesized product was characterized by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), Raman, Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HRTEM). Characterization results indicated that the BN nanotubes displayed wave-like inner structures with diameters in the range of 50–300 nm and average lengths of more than 10 μm. The possible growth mechanism of the BN nanotubes was also discussed.

  3. Improved repetitive-element PCR fingerprinting of Salmonella enterica with the use of extremely elevated annealing temperatures.

    PubMed

    Johnson, J R; Clabots, C

    2000-03-01

    Modified thermal cycling conditions were explored in an effort to improve the reproducibility and resolving power of repetitive-element PCR (rep-PCR) fingerprinting. Assay performance was rigorously evaluated under standard and modified cycling conditions, using as a test set 12 strains putatively representing 12 serovars of Salmonella enterica. For all three fingerprint types (ERIC2, BOXA1R, and composite fingerprints), the use of extremely elevated annealing temperatures plus an initial "touchdown" cycling routine yielded significant improvements in day-to-day reproducibility and discriminating power despite the somewhat sparser appearance of the fingerprints. Modified cycling conditions markedly reduced the variability of fingerprints between cyclers, allowing fingerprints from different cyclers to be analyzed together without the degradation of assay performance that occurred with between-cycler analyses under standard cycling conditions. With modified cycling, composite fingerprints exhibited the lowest reproducibility but the highest net discriminating power of the three fingerprint types. rep-PCR fingerprints led to the discovery of a serotyping error involving one of the 12 test strains. These data demonstrate that modified cycling regimens that incorporate elevated annealing temperatures (with or without an initial touchdown routine) may markedly improve the performance of rep-PCR fingerprinting as a bacterial typing tool.

  4. Influence of substrate properties and annealing temperature on the stress state of magnetron sputtered tungsten thin films

    SciTech Connect

    Oliveira, J. C.; Cavaleiro, A.

    2006-11-15

    The influence of substrate properties and annealing temperature on the stress state of tungsten thin films deposited by dc reactive magnetron sputtering was studied using 310 steel (AISI), Fecralloy registered and Invar registered substrates. Besides elemental tungsten, only residual amounts of contamination elements (O, C, Ar, etc.) were detected by electron probe microanalysis. Only the {alpha}-W crystalline structure, with a preferential <110> orientation, was detected in all the films by x-ray diffraction. The highest lattice parameters were measured for the films deposited on 310 steel substrates, while the smallest values were obtained for the films deposited on Invar registered substrates. These results are closely related to the thermal expansion coefficients of the substrates. All the as-deposited films were in a compressive stress state independent of the substrate type (-3 GPa for 310 steel and Fecralloy registered substrates and -2 GPa for Invar registered substrates). The residual compressive stresses of the films deposited on Fecralloy registered substrates strongly decrease with annealing temperatures up to {approx_equal}-8 GPa at 1175 K. This result shows that the measured compressive stresses are not real, and they are a direct consequence of plastic deformation of the substrate. On the contrary, the compressive stresses measured in the films deposited on Invar registered and 310 steel substrates are real as plastic deformation of the substrates is not observed.

  5. The growth of ubiquitous ZnO rods on PMMA-coated substrate by solution-immersion method at different annealing temperatures

    NASA Astrophysics Data System (ADS)

    Aadila, A.; Asib, N. A. M.; Afaah, A. N.; Husairi, F. S.; Mohamed, R.; Rusop, M.; Khusaimi, Z.

    2016-07-01

    In this work, solution-immersion method was used to grow ZnO rods on PMMA-coated substrate. For this purpose, 0.15 M of zinc nitrate hexahydrate (Zn(NO3)2.6H2O) and hexamethylenetetramine (C6H12N4) were used to growth of ZnO films at different annealing temperatures (room temperature, 80, 100, 120 and 140 °C). The morphology of the films was investigated by Scanning Electron Microscope (SEM) and optical properties were studied by Ultraviolet (UV-Vis) Spectroscopy. SEM analysis showed ubiquitous growth of ZnO rods that became better aligned and more closely-packed as the annealing temperature increased. As the annealing temperature exceeds 100 °C, the rods tend to merge to adjacent particles and the UV absorption decreased for the sample at higher temperatures (120 °C and 140 °C). Good absorption and better orientation of ZnO was obtained for the sample annealed at 100 °C due to the film possess better distribution and these improved orientation of particles caused the light to be effectively scattered on the sample. Both surface morphology and UV was significantly affected by the change in annealing temperatures thus thermal effect played a dominant role in shaping and improving the orientation of ZnO rods on PMMA-coated and its UV absorption.

  6. In-situ post-deposition thermal annealing of co-evaporated Cu(InGa)Se2 thin films deposited at low temperatures

    SciTech Connect

    Wilson, James D.; McCandless, Brian E.; Birkmire, Robert W.; Shafarman, William N.

    2009-06-09

    The effects of deposition temperature and in-situ post-deposition annealing on the microstructure of coevaporated Cu(InGa)Se2 thin films and on the performance of the resulting solar cell devices have been characterized. Films were deposited at substrate temperatures of 150°C, 300°C and 400°C. Films were also deposited at these temperatures and then annealed in-situ at 550°C for 10 minutes. In as -deposited films without annealing, additional XRD reflections that may be due to a polytypic modification of the chalcopyrite phase were observed. Films deposited at 150°C were Se-rich. Post-deposition annealing caused microstructural changes in all films and improved the resulting solar cells. Only films deposited at 400°C, however, yielded high-efficiency devices after post-deposition annealing that were equivalent to devices made from films grown at 550°C. Films originally deposited at 300°C yielded devices after post-deposition annealing with VOC close to that of devices made from films grown at 550°C, despite smaller grain size.

  7. Temperature dependent nonlinear metal matrix laminae behavior

    NASA Technical Reports Server (NTRS)

    Barrett, D. J.; Buesking, K. W.

    1986-01-01

    An analytical method is described for computing the nonlinear thermal and mechanical response of laminated plates. The material model focuses upon the behavior of metal matrix materials by relating the nonlinear composite response to plasticity effects in the matrix. The foundation of the analysis is the unidirectional material model which is used to compute the instantaneous properties of the lamina based upon the properties of the fibers and matrix. The unidirectional model assumes that the fibers properties are constant with temperature and assumes that the matrix can be modelled as a temperature dependent, bilinear, kinematically hardening material. An incremental approach is used to compute average stresses in the fibers and matrix caused by arbitrary mechanical and thermal loads. The layer model is incorporated in an incremental laminated plate theory to compute the nonlinear response of laminated metal matrix composites of general orientation and stacking sequence. The report includes comparisons of the method with other analytical approaches and compares theoretical calculations with measured experimental material behavior. A section is included which describes the limitations of the material model.

  8. Zero-temperature quantum annealing bottlenecks in the spin-glass phase

    NASA Astrophysics Data System (ADS)

    Knysh, Sergey

    2016-08-01

    A promising approach to solving hard binary optimization problems is quantum adiabatic annealing in a transverse magnetic field. An instantaneous ground state--initially a symmetric superposition of all possible assignments of N qubits--is closely tracked as it becomes more and more localized near the global minimum of the classical energy. Regions where the energy gap to excited states is small (for instance at the phase transition) are the algorithm's bottlenecks. Here I show how for large problems the complexity becomes dominated by O(log N) bottlenecks inside the spin-glass phase, where the gap scales as a stretched exponential. For smaller N, only the gap at the critical point is relevant, where it scales polynomially, as long as the phase transition is second order. This phenomenon is demonstrated rigorously for the two-pattern Gaussian Hopfield model. Qualitative comparison with the Sherrington-Kirkpatrick model leads to similar conclusions.

  9. Zero-temperature quantum annealing bottlenecks in the spin-glass phase.

    PubMed

    Knysh, Sergey

    2016-01-01

    A promising approach to solving hard binary optimization problems is quantum adiabatic annealing in a transverse magnetic field. An instantaneous ground state-initially a symmetric superposition of all possible assignments of N qubits-is closely tracked as it becomes more and more localized near the global minimum of the classical energy. Regions where the energy gap to excited states is small (for instance at the phase transition) are the algorithm's bottlenecks. Here I show how for large problems the complexity becomes dominated by O(log N) bottlenecks inside the spin-glass phase, where the gap scales as a stretched exponential. For smaller N, only the gap at the critical point is relevant, where it scales polynomially, as long as the phase transition is second order. This phenomenon is demonstrated rigorously for the two-pattern Gaussian Hopfield model. Qualitative comparison with the Sherrington-Kirkpatrick model leads to similar conclusions. PMID:27491338

  10. Zero-temperature quantum annealing bottlenecks in the spin-glass phase

    PubMed Central

    Knysh, Sergey

    2016-01-01

    A promising approach to solving hard binary optimization problems is quantum adiabatic annealing in a transverse magnetic field. An instantaneous ground state—initially a symmetric superposition of all possible assignments of N qubits—is closely tracked as it becomes more and more localized near the global minimum of the classical energy. Regions where the energy gap to excited states is small (for instance at the phase transition) are the algorithm's bottlenecks. Here I show how for large problems the complexity becomes dominated by O(log N) bottlenecks inside the spin-glass phase, where the gap scales as a stretched exponential. For smaller N, only the gap at the critical point is relevant, where it scales polynomially, as long as the phase transition is second order. This phenomenon is demonstrated rigorously for the two-pattern Gaussian Hopfield model. Qualitative comparison with the Sherrington-Kirkpatrick model leads to similar conclusions. PMID:27491338

  11. Investigation of extended-gate field-effect transistor pH sensors based on different-temperature-annealed bi-layer MWCNTs-In2O3 films

    PubMed Central

    2014-01-01

    In this paper, indium (In) films were deposited on glass substrates using DC sputtering method. Multiwalled carbon nanotubes (MWCNTs) and dispersant were dissolved in alcohol, and the mixed solution was deposited on the In films using the spray method. The bi-layer MWCNTs-In2O3 films were annealed at different temperatures (from room temperature to 500°C) in O2 atmosphere. The influences of annealing temperature on the characteristics of the bi-layer MWCNTs-In2O3 films were investigated by scanning electron microscopy, X-ray diffraction pattern, Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. A separative extended-gate field-effect transistor (EGFET) device combined with a bi-layer MWCNTs-In2O3 film was constructed as a pH sensor. The influences of different annealing temperatures on the performances of the EGFET-based pH sensors were investigated. We would show that the pH sensitivity was dependent on the thermal oxygenation temperature of the bi-layer MWCNTs-In2O3 films. PMID:25288911

  12. Influence of surfactant and annealing temperature on optical properties of sol-gel derived nano-crystalline TiO2 thin films.

    PubMed

    Vishwas, M; Sharma, Sudhir Kumar; Rao, K Narasimha; Mohan, S; Gowda, K V Arjuna; Chakradhar, R P S

    2010-03-01

    Titanium dioxide thin films have been synthesized by sol-gel spin coating technique on glass and silicon substrates with and without surfactant polyethylene glycol (PEG). XRD and SEM results confirm the presence of nano-crystalline (anatase) phase at an annealing temperature of 300 degrees C. The influence of surfactant and annealing temperature on optical properties of TiO(2) thin films has been studied. Optical constants and film thickness were estimated by Swanepoel's (envelope) method and by ellipsometric measurements in the visible spectral range. The optical transmittance and reflectance were found to decrease with an increase in PEG percentage. Refractive index of the films decreased and film thickness increased with the increase in percentage of surfactant. The refractive index of the un-doped TiO(2) films was estimated at different annealing temperatures and it has increased with the increasing annealing temperature. The optical band gap of pure TiO(2) films was estimated by Tauc's method at different annealing temperature.

  13. Highest transmittance and high-mobility amorphous indium gallium zinc oxide films on flexible substrate by room-temperature deposition and post-deposition anneals

    SciTech Connect

    Gadre, Mandar J.; Alford, T. L.

    2011-08-01

    Amorphous indium gallium zinc oxide (a-IGZO) thin films of the highest transmittance reported in literature were initially deposited onto flexible polymer substrates at room temperature. The films were annealed in vacuum, air, and oxygen to enhance their electrical and optical performances. Electrical and optical characterizations were done before and after anneals. A partial reversal of the degradation in electrical properties upon annealing in oxygen was achieved by subjecting the films to subsequent vacuum anneals. A model was developed based on film texture and structural defects which showed close agreement between the measured and calculated carrier mobility values at low carrier concentrations (2-6 x 10{sup 19} cm{sup -3}).

  14. Features of the temperature dependence of pressure of solid helium at low temperatures

    NASA Astrophysics Data System (ADS)

    Lisunov, A. A.; Maidanov, V. A.; Rubanskii, V. Y.; Rubets, S. P.; Rudavskii, E. Y.; Rybalko, A. S.; Syrkin, E. S.

    2012-06-01

    A series of experiments has been performed to investigate the conditions of formation of a disordered (glass-like) state in crystals of 3He. With the help of precise measurements of pressure at constant volume it has been established that a glass phase is formed easily in rapidly cooled crystals grown under homogeneous temperature conditions in the presence of large numbers of nucleation centers. This phase can be removed only by careful annealing. This result has been found in both 3He and 4He, and is independent of type of quantum statistics and determined mainly by crystal growth conditions. An analysis of similar measurements has been performed using a different cell where during the crystal growth a directed temperature gradient was created. In this case, additional defects created as a result of deformation of the crystal were necessary to form a glass-like phase. The degree of deformation of a crystal, achievable in the experiment, was sufficient to form a glass-like phase in solid 4He, but not in a crystal of 3He where the atoms have a large amplitude of zero-point oscillations. Analyzing a temperature dependence of pressure, a study of the features of a phonon contribution to the pressure was also carried out. It was found that in both crystals 3He and 4He at different thicknesses of samples the phonon pressure differs by several times. This effect is qualitatively explained by that that in thin samples an interaction among layers of atoms becomes stronger. This leads to decreasing the phonon contribution to the thermodynamic properties of the helium crystal at low temperatures.

  15. Self-assembled Ge QDs Formed by High-Temperature Annealing on Al(Ga)As (001)

    NASA Astrophysics Data System (ADS)

    O'Brien, William A.; Qi, Meng; Yan, Lifan; Stephenson, Chad A.; Protasenko, Vladimir; Xing, Huili; Millunchick, Joanna M.; Wistey, Mark A.

    2015-05-01

    This work studies the spontaneous self-assembly of Ge QDs on AlAs, GaAs and AlGaAs by high-temperature in situ annealing using molecular beam epitaxy (MBE). The morphology of Ge dots formed on AlAs were observed by atom probe tomography, which revealed nearly spherical QDs with diameters approaching 10 nm and confirmed the complete absence of a wetting layer. Reflection high-energy electron diffraction and atomic force microscopy of Ge annealed under similar conditions on GaAs and Al0.3Ga0.7As surfaces revealed the gradual suppression of QD formation with decreasing Al-content of the buffer. To investigate the prospects of using encapsulated Ge dots for upconverting photovoltaics, in which photocurrent can still be generated from photons with energy less than the host bandgap, Ge QDs were embedded into the active region of III-V PIN diodes by MBE. It was observed that orders of magnitude higher short-circuit current is obtained at photon energies below the GaAs bandgap compared with a reference PIN diode without Ge QDs. These results demonstrate the promise of Ge QDs for upconverting solar cells and the realization of device-quality integration of group IV and III-V semiconductors.

  16. Control of antiferromagnetic domain distribution via polarization-dependent optical annealing

    PubMed Central

    Higuchi, Takuya; Kuwata-Gonokami, Makoto

    2016-01-01

    The absence of net magnetization inside antiferromagnetic domains has made the control of their spatial distribution quite challenging. Here we experimentally demonstrate an optical method for controlling antiferromagnetic domain distributions in MnF2. Reduced crystalline symmetry can couple an order parameter with non-conjugate external stimuli. In the case of MnF2, time-reversal symmetry is macroscopically broken reflecting the different orientations of the two magnetic sublattices. Thus, it exhibits different absorption coefficients between two orthogonal linear polarizations below its antiferromagnetic transition temperature under an external magnetic field. Illumination with linearly polarized laser light under this condition selectively destructs the formation of a particular antiferromagnetic order via heating. As a result, the other antiferromagnetic order is favoured inside the laser spot, achieving spatially localized selection of an antiferromagnetic order. Applications to control of interface states at antiferromagnetic domain boundaries, exchange bias and control of spin currents are expected. PMID:26911337

  17. Formation of two-dimensionally confined superparamagnetic (Mn, Ga)As nanocrystals in high-temperature annealed (Ga, Mn)As/GaAs superlattices.

    PubMed

    Sadowski, Janusz; Domagala, Jaroslaw Z; Mathieu, Roland; Kovacs, Andras; Dłużewski, Piotr

    2013-05-15

    The annealing-induced formation of (Mn, Ga)As nanocrystals in (Ga, Mn)As/GaAs superlattices was studied by x-ray diffraction, transmission electron microscopy and magnetometry. The superlattice structures with 50 Å thick (Ga, Mn)As layers separated by 25, 50 and 100 Å thick GaAs spacers were grown by molecular beam epitaxy at low temperature (250 °C), and then annealed at high temperatures of 400, 560 and 630 °C. The high-temperature annealing causes decomposition to a (Ga, Mn)As ternary alloy and the formation of (Mn, Ga)As nanocrystals inside the GaAs matrix. The nanocrystals are confined in the planes that were formerly occupied by (Ga, Mn)As layers for the up to 560 °C annealing and diffuse throughout the GaAs spacer layers at 630 °C annealing. The two-dimensionally confined nanocrystals exhibit a superparamagnetic behavior which becomes high-temperature ferromagnetism (~350 K) upon diffusion.

  18. Nonlinear temperature dependence of resistivity in Bi2Sr2CuOy crystals

    NASA Astrophysics Data System (ADS)

    Wang, N. L.; Ruan, K. Q.; Yang, L. M.; Wang, C. Y.; Cao, L. Z.; Chen, Z. J.; Wu, W. B.; Zhou, G. E.; Zhang, Y. H.

    1993-11-01

    We have measured the ab-plane resistivity on a number of Bi2Sr2CuOy crystals from 4.2 K to 300 K. The as-grown crystals usually exhibit a minimum in their normal-state resistivity. The low-temperature electronic transport can be described by a hopping conduction. As the crystals were annealed in the ambient flowing oxygen, they could become metallic over the whole temperature range. A nonlinear temperature-dependent resistivity was observed and found to be sample dependent. Some ρ(T) curves can be fitted to a power law with the exponent slightly greater than 1, while others appear with a Bloch-Grüneisen-like shape. A discussion of the experimental results is presented.

  19. High-Dose Phosphorus-Implanted 4H-SiC: Microwave and Conventional Post-Implantation Annealing at Temperatures ≥1700°C

    NASA Astrophysics Data System (ADS)

    Nipoti, R.; Nath, A.; Qadri, S. B.; Tian, Y.-L.; Albonetti, C.; Carnera, A.; Rao, Mulpuri V.

    2012-03-01

    Semi-insulating 4H-SiC ⟨0001⟩ wafers have been phosphorus ion implanted at 500°C to obtain phosphorus box depth profiles with dopant concentration from 5 × 1019 cm-3 to 8 × 1020 cm-3. These samples have been annealed by microwave and conventional inductively heated systems in the temperature range 1700°C to 2050°C. Resistivity, Hall electron density, and Hall mobility of the phosphorus-implanted and annealed 4H-SiC layers have been measured in the temperature range from room temperature to 450°C. The high-resolution x-ray diffraction and rocking curve of both virgin and processed 4H-SiC samples have been analyzed to obtain the sample crystal quality up to about 3 μm depth from the wafer surface. For both increasing implanted phosphorus concentration and increasing post-implantation annealing temperature the implanted material resistivity decreases to an asymptotic value of about 1.5 × 10-3 Ω cm. Increasing the implanted phosphorus concentration and post-implantation annealing temperature beyond 4 × 1020 cm-3 and 2000°C, respectively, does not bring any apparent benefit with respect to the minimum obtainable resistivity. Sheet resistance and sheet electron density increase with increasing measurement temperature. Electron density saturates at 1.5 × 1020 cm-3 for implanted phosphorus plateau values ≥4 × 1020 cm-3, irrespective of the post-implantation annealing method. Implantation produces an increase of the lattice parameter in the bulk 4H-SiC underneath the phosphorus-implanted layer. Microwave and conventional annealing produce a further increase of the lattice parameter in such a depth region and an equivalent recovered lattice in the phosphorus-implanted layers.

  20. Thickness-dependent crystallization on thermal anneal for titania/silica nm-layer composites deposited by ion beam sputter method.

    PubMed

    Pan, Huang-Wei; Wang, Shun-Jin; Kuo, Ling-Chi; Chao, Shiuh; Principe, Maria; Pinto, Innocenzo M; DeSalvo, Riccardo

    2014-12-01

    Crystallization following thermal annealing of thin film stacks consisting of alternating nm-thick titania/silica layers was investigated. Several prototypes were designed, featuring a different number of titania/silica layer pairs, and different thicknesses (in the range from 4 to 40 nm, for the titania layers), but the same nominal refractive index (2.09) and optical thickness (a quarter of wavelength at 1064 nm). The prototypes were deposited by ion beam sputtering on silicon substrates. All prototypes were found to be amorphous as-deposited. Thermal annealing in air at progressive temperatures was subsequently performed. It was found that the titania layers eventually crystallized forming the anatase phase, while the silica layers remained always amorphous. However, progressively thinner layers exhibited progressively higher threshold temperatures for crystallization onset. Accordingly it can be expected that composites with thinner layers will be able to sustain higher annealing temperatures without crystallizing, and likely yielding better optical and mechanical properties for advanced coatings application. These results open the way to the use of materials like titania and hafnia, that crystallize easily under thermal anneal, but ARE otherwise promising candidate materials for HR coatings necessary for cryogenic 3rd generation laser interferometric gravitational wave detectors. PMID:25606914

  1. Lithium phosphorus oxynitride solid-state thin-film electrolyte deposited and modified by bias sputtering and low temperature annealing

    SciTech Connect

    Chiu, K.-F.; Chen, C. C.; Lin, K. M.; Lo, C. C.; Lin, H. C.; Ho, W.-H.; Jiang, C. S.

    2010-07-15

    Amorphous lithium phosphorus oxynitride (LiPON) solid-state thin-film electrolyte has been deposited and characterized. The thin films were prepared by rf magnetron sputtering under various substrate biases. By fabricating under different substrate biases and applying low temperature annealing (473 K), the properties of the LiPON thin-film electrolytes and the electrolyte/cathode interfaces were modified. The ionic conductivity as high as 9.4x10{sup -4} S m{sup -1} can be obtained by depositing at optimal bias. The performances of the consequently fabricated SnO{sub 2}/LiPON/LiMn{sub 2}O{sub 4} all-solid-state lithium ion thin-film batteries were improved using the bias sputtering technique, due to the enhanced the ionic conductivity and uniform interface.

  2. Indium tin oxide films prepared by atmospheric plasma annealing and their semiconductor-metal conductivity transition around room temperature

    NASA Astrophysics Data System (ADS)

    Li, Yali; Li, Chunyang; He, Deyan; Li, Junshuai

    2009-05-01

    We report the synthesis of indium tin oxide (ITO) films using the atmospheric plasma annealing (APA) technique combined with the spin-coating method. The ITO film with a low resistivity of ~4.6 × 10-4 Ω cm and a high visible light transmittance, above 85%, was achieved. Hall measurement indicates that compared with the optimized ITO films deposited by magnetron sputtering, the above-mentioned ITO film has a higher carrier concentration of ~1.21 × 1021 cm-3 and a lower mobility of ~11.4 cm2 V-1 s-1. More interestingly, these electrical characteristics result in the semiconductor-metal conductivity transition around room temperature for the ITO films prepared by APA.

  3. Vanadium dioxide thin films prepared on silicon by low temperature MBE growth and ex-situ annealing

    NASA Astrophysics Data System (ADS)

    Homm, Pia; van Bilzen, Bart; Menghini, Mariela; Locquet, Jean-Pierre; Ivanova, Todora; Sanchez, Luis; Sanchis, Pablo

    Vanadium dioxide (VO2) is a material that shows an insulator to metal transition (IMT) near room temperature. This property can be exploited for applications in field effect devices, electro-optical switches and nonlinear circuit components. We have prepared VO2 thin films on silicon wafers by combining a low temperature MBE growth with an ex-situ annealing at high temperature. We investigated the structural, electrical and optical characteristics of films with thicknesses ranging from 10 to 100 nm. We have also studied the influence of the substrate cleaning. The films grown with our method are polycrystalline with a preferred orientation in the (011) direction of the monoclinic phase. For the films produced on silicon with a native oxide, an IMT at around 75 °C is observed. The magnitude of the resistance change across the IMT decreases with thickness while the refractive index at room temperature corresponds with values reported in the literature for thin films. The successful growth of VO2 films on silicon with good electrical and optical properties is an important step towards the integration of VO2 in novel devices. The authors acknowledge financial support from the FWO project G052010N10 and EU-FP7 SITOGA project. PH acknowledges support from Becas Chile - CONICYT.

  4. Analysis of Tensile Deformation and Failure in Austenitic Stainless Steels: Part I- Temperature Dependence

    SciTech Connect

    Kim, Jin Weon; Byun, Thak Sang

    2010-01-01

    This paper describes the temperature dependence of deformation and failure behaviors in the austenitic stainless steels (annealed 304, 316, 316LN, and 20% cold-worked 316LN) in terms of equivalent true stress-true strain curves. The true stress-true strain curves up to the final fracture were calculated from the tensile test data obtained at -150 ~ 450oC using an iterative technique of finite element simulation. Analysis was largely focused on the necking deformation and fracture: Key parameters such as the strain hardening rate, equivalent fracture stress, fracture strain, and tensile fracture energy were evaluated, and their temperature dependencies were investigated. It was shown that a significantly high strain hardening rate was still retained during unstable deformation although overall strain hardening rate beyond the onset of necking was lower than that of the uniform deformation. The values of the parameters except for fracture strain decreased with temperature up to 200oC and were saturated as the temperature came close to the maximum test temperature 450oC. The fracture strain increased and had a maximum at -50oC to 20oC before decreasing with temperature. It was explained that these temperature dependencies of fracture properties were associated with a change in the dominant strain hardening mechanism with test temperature. Also, it was seen that the pre-straining of material has little effect on the strain hardening rate during necking deformation and on fracture properties.

  5. The effect of the annealing temperature on the transition from conductor to semiconductor behavior in zinc tin oxide deposited atomic layer deposition

    SciTech Connect

    Ahn, Byung Du; Choi, Dong-won Choi, Changhwan; Park, Jin-Seong

    2014-09-01

    We investigated the electrical properties of zinc tin oxide (ZTO) films deposited via atomic layer deposition and compared them to ZnO and SnO{sub 2} films as a function of the annealing temperature. The ZTO and ZnO, except for SnO{sub 2}, films exhibited an electrical transition from a metal to semiconductor characteristics when annealed above 300 °C. The X-ray photoelectron spectroscopy analyses indicate that the relative area of the oxygen vacancy-related peak decreased from 58% to 41% when annealing at temperatures above 400 °C. Thin film transistors incorporating ZTO active layers demonstrated a mobility of 13.2 cm{sup 2}/V s and a negative bias instability of −0.2 V.

  6. Investigation of high temperature annealing effectiveness for recovery of radiation-induced structural changes and properties of 18Cr-10Ni-Ti austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Gurovich, B. A.; Kuleshova, E. A.; Frolov, A. S.; Maltsev, D. A.; Prikhodko, K. E.; Fedotova, S. V.; Margolin, B. Z.; Sorokin, A. A.

    2015-10-01

    A complex study of structural state and properties of 18Cr-10Ni-Ti austenitic stainless steel after irradiation in BOR-60 fast research reactor (in the temperature range 330-400 °C up to damaging doses of 145 dpa) and in VVER-1000 light water reactor (at temperature ∼320 °C and damaging doses ∼12-14 dpa) was performed. The possibility of recovery of structural-phase state and mechanical properties to the level almost corresponding to the initial state by the recovery annealing was studied. The principal possibility of the recovery annealing of pressurized water reactor internals that ensures almost complete recovery of its mechanical properties and microstructure was shown. The optimal mode of recovery annealing was established: 1000 °C during 120 h.

  7. Evaluation of a gate-first process for AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors with low ohmic annealing temperature

    NASA Astrophysics Data System (ADS)

    Liuan, Li; Jiaqi, Zhang; Yang, Liu; Jin-Ping, Ao

    2016-03-01

    In this paper, TiN/AlOx gated AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) were fabricated for gate-first process evaluation. By employing a low temperature ohmic process, ohmic contact can be obtained by annealing at 600 °C with the contact resistance approximately 1.6 Ω·mm. The ohmic annealing process also acts as a post-deposition annealing on the oxide film, resulting in good device performance. Those results demonstrated that the TiN/AlOx gated MOS-HFETs with low temperature ohmic process can be applied for self-aligned gate AlGaN/GaN MOS-HFETs. Project supported by the International Science and Technology Collaboration Program of China (Grant No. 2012DFG52260).

  8. Optical and electrical characterization of sputter-deposited FeSi{sub 2} and its evolution with annealing temperature

    SciTech Connect

    Tan, K. H.; Chi, D. Z.; Pey, K. L.

    2008-09-15

    Optical and electrical properties of sputter-deposited FeSi{sub 2} thin films on p-Si(100) and SiO{sub 2}/p-Si(100) substrates as well as their evolution with rapid thermal annealing (RTA) temperature have been investigated. Optical absorption measurements were carried out to determine the absorption spectra of FeSi{sub 2} based on the proposed optical absorption model for the double-layer and triple-layer structures. A direct band gap behavior was concluded for both amorphous and polycrystalline semiconducting FeSi{sub 2}. An absorption coefficient in the order of 10{sup 5} cm{sup -1} at 1 eV and a band gap value of {approx}0.86 eV were obtained for the {beta}-FeSi{sub 2}. Hall effect measurements at room temperature indicate heavily doped and n-type conductivity for the FeSi{sub 2} films on p-Si, whose residual carrier concentration was found to be closely correlated with the observed subgap optical absorption via band tailing. The carrier mobility was shown to increase with decreasing residual carrier concentration when the RTA temperature was increased.

  9. Temperature-dependent spectral mismatch corrections

    DOE PAGES

    Osterwald, Carl R.; Campanelli, Mark; Moriarty, Tom; Emery, Keith A.; Williams, Rafell

    2015-11-01

    This study develops the mathematical foundation for a translation of solar cell short-circuit current from one thermal and spectral irradiance operating condition to another without the use of ill-defined and error-prone temperature coefficients typically employed in solar cell metrology. Using the partial derivative of quantum efficiency with respect to temperature, the conventional isothermal expression for spectral mismatch corrections is modified to account for changes of current due to temperature; this modification completely eliminates the need for short-circuit-current temperature coefficients. An example calculation is provided to demonstrate use of the new translation.

  10. Water temperature dependence of single bubble sonoluminescence threshold.

    PubMed

    Germano, M; Alippi, A; Bettucci, A; Brizi, F; Passeri, D

    2010-01-01

    Water temperature dependence of single bubble sonoluminescence (SBSL) threshold has been experimentally measured to perform measurements at different temperatures on the very same bubble. Results show lower thresholds, i.e. an easier prime of mechanism, of sonoluminescence at lower water temperatures. Dependence is almost linear at lower temperatures while between 14 degrees C and about 20 degrees C the curve changes its slope reaching soon a virtual independence from water temperature above about 20 degrees C.

  11. Modeling temperature dependence of trace element concentrations in groundwater using temperature dependent distribution coefficient

    NASA Astrophysics Data System (ADS)

    Saito, H.; Saito, T.; Hamamoto, S.; Komatsu, T.

    2015-12-01

    In our previous study, we have observed trace element concentrations in groundwater increased when groundwater temperature was increased with constant thermal loading using a 50-m long vertical heat exchanger installed at Saitama University, Japan. During the field experiment, 38 degree C fluid was circulated in the heat exchanger resulting 2.8 kW thermal loading over 295 days. Groundwater samples were collected regularly from 17-m and 40-m deep aquifers at four observation wells located 1, 2, 5, and 10 m, respectively, from the heat exchange well and were analyzed with ICP-MS. As a result, concentrations of some trace elements such as boron increased with temperature especially at the 17-m deep aquifer that is known as marine sediment. It has been also observed that the increased concentrations have decreased after the thermal loading was terminated indicating that this phenomenon may be reversible. Although the mechanism is not fully understood, changes in the liquid phase concentration should be associated with dissolution and/or desorption from the solid phase. We therefore attempt to model this phenomenon by introducing temperature dependence in equilibrium linear adsorption isotherms. We assumed that distribution coefficients decrease with temperature so that the liquid phase concentration of a given element becomes higher as the temperature increases under the condition that the total mass stays constant. A shape function was developed to model the temperature dependence of the distribution coefficient. By solving the mass balance equation between the liquid phase and the solid phase for a given element, a new term describing changes in the concentration was implemented in a source/sink term of a standard convection dispersion equation (CDE). The CDE was then solved under a constant ground water flow using FlexPDE. By calibrating parameters in the newly developed shape function, the changes in element concentrations observed were quite well predicted. The

  12. The dramatic effect of the annealing temperature and dielectric functionalization on the electron mobility of indene-C60 bis-adduct thin films.

    PubMed

    Orgiu, Emanuele; Squillaci, Marco A; Rekab, Wassima; Börjesson, Karl; Liscio, Fabiola; Zhang, Lei; Samorì, Paolo

    2015-03-28

    Herein we report on the charge transport properties of spin-coated thin films of an n-type fullerene derivative, i.e. the indene-C60 bis-adduct (ICBA). In particular, the effects of annealing temperature and duration as well as surface functionalization are explored. Electron mobilities approaching 0.1 cm(2) V(-1) s(-1) are reported.

  13. Non-Stoichiometric Amorphous Indium Selenide Thin Films as a Buffer Layer for CIGS Solar Cells with Various Temperatures in Rapid Thermal Annealing.

    PubMed

    Yoo, Myoung Han; Kim, Nam-Hoon

    2016-05-01

    The conventional structure of most of copper indium gallium diselenide (Culn(1-x)Ga(x)Se2, CIGS) solar cells includes a CdS thin film as a buffer layer. Cd-free buffer layers have attracted great interest for use in photovoltaic applications to avoid the use of hazardous and toxic materials. The RF magnetron sputtering method was used with an InSe2 compound target to prepare the indium selenide precursor. Rapid thermal annealing (RTA) was conducted in ambient N2 gas to control the concentration of volatile Se from the precursor with a change in temperature. The nature of the RTA-treated indium selenide thin films remained amorphous under annealing temperatures of ≤ 700 degrees C. The Se concentration of the RTA-treated specimens demonstrated an opposite trend to the annealing temperature. The optical transmittance and band gap energies were 75.33% and 2.451-3.085 eV, respectively, and thus were suitable for the buffer layer. As the annealing temperature increased, the resistivity decreased by an order-of-magnitude from 10(4) to 10(1) Ω-cm. At lower Se concentrations, the conductivity abruptly changed from p-type to n-type without crystallite formation in the amorphous phase, with the carrier concentration in the order of 10(17) cm(-3). PMID:27483873

  14. Non-monotonic temperature dependence of radiation defect dynamics in silicon carbide

    DOE PAGES

    Bayu Aji, L. B.; Wallace, J. B.; Shao, L.; Kucheyev, S. O.

    2016-08-03

    Understanding response of solids to particle irradiation remains a major materials physics challenge. This applies even to SiC, which is a prototypical nuclear ceramic and wide-band-gap semiconductor material. The lack of predictability is largely related to the complex, dynamic nature of radiation defect formation. Here, we use a novel pulsed-ion-beam method to study dynamic annealing in 4H-SiC ion-bombarded in the temperature range of 25–250 °C. We find that, while the defect recombination efficiency shows an expected monotonic increase with increasing temperature, the defect lifetime exhibits a non-monotonic temperature dependence with a maximum at ~100 °C. This finding indicates a changemore » in the dominant defect interaction mechanism at ~100 °C. As a result, the understanding of radiation defect dynamics may suggest new paths to designing radiation-resistant materials.« less

  15. Non-monotonic temperature dependence of radiation defect dynamics in silicon carbide

    NASA Astrophysics Data System (ADS)

    Bayu Aji, L. B.; Wallace, J. B.; Shao, L.; Kucheyev, S. O.

    2016-08-01

    Understanding response of solids to particle irradiation remains a major materials physics challenge. This applies even to SiC, which is a prototypical nuclear ceramic and wide-band-gap semiconductor material. The lack of predictability is largely related to the complex, dynamic nature of radiation defect formation. Here, we use a novel pulsed-ion-beam method to study dynamic annealing in 4H-SiC ion-bombarded in the temperature range of 25–250 °C. We find that, while the defect recombination efficiency shows an expected monotonic increase with increasing temperature, the defect lifetime exhibits a non-monotonic temperature dependence with a maximum at ~100 °C. This finding indicates a change in the dominant defect interaction mechanism at ~100 °C. The understanding of radiation defect dynamics may suggest new paths to designing radiation-resistant materials.

  16. Non-monotonic temperature dependence of radiation defect dynamics in silicon carbide.

    PubMed

    Bayu Aji, L B; Wallace, J B; Shao, L; Kucheyev, S O

    2016-01-01

    Understanding response of solids to particle irradiation remains a major materials physics challenge. This applies even to SiC, which is a prototypical nuclear ceramic and wide-band-gap semiconductor material. The lack of predictability is largely related to the complex, dynamic nature of radiation defect formation. Here, we use a novel pulsed-ion-beam method to study dynamic annealing in 4H-SiC ion-bombarded in the temperature range of 25-250 °C. We find that, while the defect recombination efficiency shows an expected monotonic increase with increasing temperature, the defect lifetime exhibits a non-monotonic temperature dependence with a maximum at ~100 °C. This finding indicates a change in the dominant defect interaction mechanism at ~100 °C. The understanding of radiation defect dynamics may suggest new paths to designing radiation-resistant materials. PMID:27484358

  17. Non-monotonic temperature dependence of radiation defect dynamics in silicon carbide

    NASA Astrophysics Data System (ADS)

    Bayu Aji, L. B.; Wallace, J. B.; Shao, L.; Kucheyev, S. O.

    2016-08-01

    Understanding response of solids to particle irradiation remains a major materials physics challenge. This applies even to SiC, which is a prototypical nuclear ceramic and wide-band-gap semiconductor material. The lack of predictability is largely related to the complex, dynamic nature of radiation defect formation. Here, we use a novel pulsed-ion-beam method to study dynamic annealing in 4H-SiC ion-bombarded in the temperature range of 25-250 °C. We find that, while the defect recombination efficiency shows an expected monotonic increase with increasing temperature, the defect lifetime exhibits a non-monotonic temperature dependence with a maximum at ~100 °C. This finding indicates a change in the dominant defect interaction mechanism at ~100 °C. The understanding of radiation defect dynamics may suggest new paths to designing radiation-resistant materials.

  18. Non-monotonic temperature dependence of radiation defect dynamics in silicon carbide

    PubMed Central

    Bayu Aji, L. B.; Wallace, J. B.; Shao, L.; Kucheyev, S. O.

    2016-01-01

    Understanding response of solids to particle irradiation remains a major materials physics challenge. This applies even to SiC, which is a prototypical nuclear ceramic and wide-band-gap semiconductor material. The lack of predictability is largely related to the complex, dynamic nature of radiation defect formation. Here, we use a novel pulsed-ion-beam method to study dynamic annealing in 4H-SiC ion-bombarded in the temperature range of 25–250 °C. We find that, while the defect recombination efficiency shows an expected monotonic increase with increasing temperature, the defect lifetime exhibits a non-monotonic temperature dependence with a maximum at ~100 °C. This finding indicates a change in the dominant defect interaction mechanism at ~100 °C. The understanding of radiation defect dynamics may suggest new paths to designing radiation-resistant materials. PMID:27484358

  19. Temperature Dependence of Phonons in Pyrolitic Graphite

    DOE R&D Accomplishments Database

    Brockhouse, B. N.; Shirane, G.

    1977-01-01

    Dispersion curves for longitudinal and transverse phonons propagating along and near the c-axis in pyrolitic graphite at temperatures between 4°K and 1500°C have been measured by neutron spectroscopy. The observed frequencies decrease markedly with increasing temperature (except for the transverse optical ''rippling'' modes in the hexagonal planes). The neutron groups show interesting asymmetrical broadening ascribed to interference between one phonon and many phonon processes.

  20. Temperature dependence of interaction-induced entanglement

    SciTech Connect

    Khasin, Michael; Kosloff, Ronnie

    2005-11-15

    Both direct and indirect weak nonresonant interactions are shown to produce entanglement between two initially disentangled systems prepared as a tensor product of thermal states, provided the initial temperature is sufficiently low. Entanglement is determined by the Peres-Horodecki criterion, which establishes that a composite state is entangled if its partial transpose is not positive. If the initial temperature of the thermal states is higher than an upper critical value T{sub uc} the minimal eigenvalue of the partially transposed density matrix of the composite state remains positive in the course of the evolution. If the initial temperature of the thermal states is lower than a lower critical value T{sub lc}{<=}T{sub uc} the minimal eigenvalue of the partially transposed density matrix of the composite state becomes negative, which means that entanglement develops. We calculate the lower bound T{sub lb} for T{sub lc} and show that the negativity of the composite state is negligibly small in the interval T{sub lb}temperature T{sub lb} can be considered as the critical temperature for the generation of entanglement. It is conjectured that above this critical temperature a composite quantum system could be simulated using classical computers.

  1. Effects of post-annealing and temperature/humidity treatments on the interfacial adhesion energy of the Cu/SiN x interface for Cu interconnects

    NASA Astrophysics Data System (ADS)

    Jeong, Minsu; Bae, Byung-Hyun; Lee, Hyeonchul; Kang, Hee-Oh; Hwang, Wook-Jung; Yang, Jun-Mo; Park, Young-Bae

    2016-06-01

    The effects of 200 °C post-annealing and 85 °C and 85% relative humidity temperature and humidity (T/H) treatments on the interfacial adhesion energy of a Cu/SiN x interface were systematically investigated. The results of a four-point bending test, X-ray photoemission spectroscopy, and high-resolution transmission electron microscopy revealed that the interfacial adhesion energy during T/H treatment decreased with time faster than during annealing treatment, which is closely related to the faster Cu oxidation of SiN x /Cu interfaces.

  2. STIS CCD Hot Pixel Annealing

    NASA Astrophysics Data System (ADS)

    Hernandez, Svea

    2013-10-01

    This purpose of this activity is to repair radiation induced hot pixel damage to theSTIS CCD by warming the CCD to the ambient instrument temperature and annealing radiation damaged pixels. Radiation damage creates hot pixels in the STIS CCD Detector. Many of these hot pixels can be repaired by warming the CCD from its normal operating temperature near-83 C to the ambient instrument temperature { +5 C} for several hours. The number of hot pixels repaired is a function of annealing temperature. The effectiveness of the CCD hot pixel annealing process is assessed by measuring the dark current behavior before and after annealing and by searching for any window contamination effects.

  3. Temperature dependence of electrical conductivity and lunar temperatures

    NASA Technical Reports Server (NTRS)

    Olhoeft, G. R.; Strangway, D. W.; Sharpe, H.; Frisillo, A. L.

    1974-01-01

    Metallic conduction mechanicsms are probably not important in lunar materials because of the small amounts of free metal and metallic oxides present. This is confirmed by the extremely low conductivities measured to date and the fact that the conductivity increases with temperature. The major conduction mechanicsm appears to be ionic. This conduction mechanism is very strongly controlled by temperature, by deviations from stoichiometry, by electric field strengths, and by oxygen fugacity.

  4. Temperature dependent electrical resistivity of liquid Sn

    NASA Astrophysics Data System (ADS)

    Prajapati, A. V.; Sonvane, Y. A.; Patel, H. P.; Thakor, P. B.

    2016-05-01

    The present paper deals with the effect of temperature variation on the electrical resistivity (ρ) of liquid Sn(Tin). We have used a new parameter free pseudopotential along with screening Taylor et al and Farid et al local field correction functions. The Percus-Yevick Hard Sphere (PYHS) reference system is used to describe structural information. Zeeman formula has been used for finding resistivity with the variation of temperature. The balanced harmonies between present data and experimental data have been achieved with a minimal deviation. So, we concluded that our newly constructed model potential is an effective one to produce the data of electrical resistivity of liquid Sn(Tin) as a function of temperature.

  5. Temperature Dependent Electrical Properties of PZT Wafer

    NASA Astrophysics Data System (ADS)

    Basu, T.; Sen, S.; Seal, A.; Sen, A.

    2016-04-01

    The electrical and electromechanical properties of lead zirconate titanate (PZT) wafers were investigated and compared with PZT bulk. PZT wafers were prepared by tape casting technique. The transition temperature of both the PZT forms remained the same. The transition from an asymmetric to a symmetric shape was observed for PZT wafers at higher temperature. The piezoelectric coefficient (d 33) values obtained were 560 pc/N and 234 pc/N, and the electromechanical coupling coefficient (k p) values were 0.68 and 0.49 for bulk and wafer, respectively. The reduction in polarization after fatigue was only ~3% in case of PZT bulk and ~7% for PZT wafer.

  6. Effect of Channel Thickness, Annealing Temperature and Channel Length on Nanoscale Ga2O3-In2O3-ZnO Thin Film Transistor Performance.

    PubMed

    Kumaresan, Yogeenth; Pak, Yusin; Lim, Namsoo; Lee, Ryeri; Song, Hui; Kim, Tae Heon; Choi, Boran; Jung, Gun Young

    2016-06-01

    We demonstrated the effect of active layer (channel) thickness and annealing temperature on the electrical performances of Ga2O3-In2O3-ZnO (GIZO) thin film transistor (TFT) having nanoscale channel width (W/L: 500 nm/100 μm). We found that the electron carrier concentration of the channel was decreased significantly with increasing the annealing temperature (100 degrees C to 300 degrees C). Accordingly, the threshold voltage (V(T)) was shifted towards positive voltage (-12.2 V to 10.8 V). In case of channel thickness, the V(T) was shifted towards negative voltage with increasing the channel thickness. The device with channel thickness of 90 nm annealed at 200 degrees C revealed the best device performances in terms of mobility (10.86 cm2/Vs) and V(T) (0.8 V). The effect of channel length was also studied, in which the channel width, thickness and annealing temperature were kept constant such as 500 nm, 90 nm and 200 degrees C, respectively. The channel length influenced the on-current level significantly with small variation of V(T), resulting in lower value of on/off current ratio with increasing the channel length. The device with channel length of 0.5 μm showed enhanced on/off current ratio of 10(6) with minimum V(T) of 0.26 V. PMID:27427719

  7. Impact of low temperature annealing on structural, optical, electrical and morphological properties of ZnO thin films grown by RF sputtering for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Purohit, Anuradha; Chander, S.; Sharma, Anshu; Nehra, S. P.; Dhaka, M. S.

    2015-11-01

    This paper presents effect of low temperature annealing on the physical properties of ZnO thin films for photovoltaic applications. The thin films of thickness 50 nm were grown on glass and indium tin oxide (ITO) coated glass substrates employing radio frequency magnetron sputtering technique followed by thermal annealing within low temperature range 150-450 °C. These as-grown and annealed films were subjected to the X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) for structural, optical, electrical and surface morphological analysis respectively. The compositional analysis of the as-grown ZnO film was also carried out using energy dispersive spectroscopy (EDS). The XRD patterns reveal that the films have wurtzite structure of hexagonal phase with preferred orientation (1 0 0) and polycrystalline in nature. The crystallographic and optical parameters are calculated and discussed in detail. The optical band gap was found in the range 3.30-3.52 eV and observed to decrease with annealing temperature except 150 °C. The current-voltage characteristics show that the films exhibit approximately ohmic behavior. The SEM studies show that the films are uniform, homogeneous and free from crystal defects and voids. The experimental results reveal that ZnO thin films may be used as alternative materials for eco-friendly buffer layer to the thin film solar cell applications.

  8. Effect of annealing temperature on optical and electrical properties of ZrO{sub 2}−SnO{sub 2} based nanocomposite thin films

    SciTech Connect

    Anitha, V. S. Lekshmy, S. Sujatha Berlin, I. John Joy, K.

    2014-01-28

    Transparent nanocomposite ZrO{sub 2}−SnO{sub 2} thin films were prepared by sol-gel dip-coating technique. Films were annealed at 500°C, 800°C and 1200°C respectively. X-ray diffraction(XRD) spectra showed a mixture of three phases: tetragonal ZrO{sub 2} and SnO{sub 2} and orthorhombic ZrSnO{sub 4}. The grain size of all the three phases' increased with annealing temperature. An average transmittance greater than 85%(in UV-Visible region) is observed for all the films. The band gap for the films decreased from 4.79 eV to 4.62 eV with increase in annealing temperature from 500 to 1200 °C. The electrical resistivity increased with increase in annealing temperature. Such composite ZrO{sub 2}−SnO{sub 2} films can be used in many applications and in optoelectronic devices.

  9. Effect of Mg diffusion on photoluminescence spectra of MgZnO/ZnO bi-layers annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Das, Amit K.; Misra, P.; Ajimsha, R. S.; Bose, A.; Joshi, S. C.; Porwal, S.; Sharma, T. K.; Oak, S. M.; Kukreja, L. M.

    2013-11-01

    MgZnO/ZnO bilayers (Mg concentration of ˜30%) have been grown and subsequently annealed at different temperatures in the range of 600-900 °C with the specific interest of studying the effect of inter-diffusion of Mg on the photoluminescence (PL) properties of the bilayers. The influence of Mg diffusion and material homogenization is evaluated through absorption, PL, and secondary ion mass spectrometry (SIMS) measurements. No appreciable change in the spectral positions is seen either in PL or absorption up to an annealing temperature of 700 °C, which is also supported by SIMS. However at higher annealing temperatures, diffusion of Mg into the ZnO layer is clearly evident in SIMS profile, which results in the red-shift (blue-shift) of spectral positions of MgZnO (ZnO) layer, respectively. Finally, for the sample annealed at 900 °C, the two layers are completely merged providing a single peak at ˜3.60 eV in PL/absorption corresponding to a completely homogenized MgZnO layer. Spectroscopic results are corroborated by the numerical simulations based on a simple theoretical model, which correlates the observed PL spectra of the heterostructures with the experimental Mg diffusion profiles across the heterointerface, as measured by SIMS.

  10. Effects of air annealing on CdS quantum dots thin film grown at room temperature by CBD technique intended for photosensor applications

    SciTech Connect

    Shaikh, Shaheed U.; Desale, Dipalee J.; Siddiqui, Farha Y.; Ghosh, Arindam; Birajadar, Ravikiran B.; Ghule, Anil V.; Sharma, Ramphal

    2012-11-15

    Graphical abstract: The effect of different intensities (40, 60 100 and 200 W) of light on CdS quantum dots thin film annealed at 350 °C indicating enhancement in (a) photo-current and (b) photosensitivity. Highlights: ► The preparation of CdS nanodot thin film at room temperature by M-CBD technique. ► Study of air annealing on prepared CdS nanodots thin film. ► The optimized annealing temperature for CdS nanodot thin film is 350 °C. ► Modified CdS thin films can be used in photosensor application. -- Abstract: CdS quantum dots thin-films have been deposited onto the glass substrate at room temperature using modified chemical bath deposition technique. The prepared thin films were further annealed in air atmosphere at 150, 250 and 350 °C for 1 h and subsequently characterized by scanning electron microscopy, ultraviolet–visible spectroscopy, electrical resistivity and I–V system. The modifications observed in morphology and opto-electrical properties of the thin films are presented.

  11. Temperature dependence of soil water potential

    SciTech Connect

    Mohamed, A.M.O.; Yong, R.N. ); Cheung, S.C.H. )

    1992-12-01

    To understand the process of coupled heat and water transport, the relationship between temperature and soil water potential must be known. Two clays, Avonlea bentonite and Lake Agassiz clay, are being considered as the clay-based sealing materials for the Canadian nuclear fuel waste disposal vault. Avonlea bentonite is distinguished from Lake Agassiz clay by its high sealing potential in water. A series of experiments was performed in which the two clays were mixed with equal amounts of sand and were compacted to a dry density of 1.67 Mg/m[sup 3] under various moisture contents and temperatures. A psychrometer was placed within the compacted clay-sand to measure the soil water potential based on the electromotive force measured by the psychrometer. The results indicate that the soil water potential at a particular temperature is higher for both clay-sand mixtures than predicted by the change in the surface tension of water; this effect is much more prominent in the Avonlea bentonite and at low moisture contents. The paper presents empirical equations relating the soil water potential with the moisture content and temperature of the two clay-sand mixtures. 24 refs., 8 figs., 2 tabs.

  12. Temperature dependence of gramicidin channel conductance

    NASA Astrophysics Data System (ADS)

    Song, Hyundeok; Beck, Thomas

    2010-03-01

    The gramicidin channel is the smallest known biological ion channel, and it exhibits cation selectivity. Recently, Dr. John Cuppoletti's group at the University of Cincinnati has shown that the gramicidin channel can function at high temperatures with significant currents. This finding may have implications for fuel cell technologies. In order to explore the effect of temperature on channel conductance, we examined the gramicidin system at 300K, 330K, and 360K by computer simulation. Two forms of gramicidin, the head-to-head helical dimer and the intertwined double helix, were examined. Both the decrease of the free energy barrier and the increase of the diffusion of potassium ions inside the gramicidin channel at high temperatures imply an increase of current. We found that higher temperatures also affect the lifetime of hydrogen bonds, the distribution of the bending angle, the distribution of the distance between dimers, and the size of the pore radius for the helical dimer structure. These finding may be related to the gating of the gramicidin channel.

  13. Effect of Annealing Temperature on Hardness and Wear Resistance of Electroless Ni-B-Mo Coatings

    NASA Astrophysics Data System (ADS)

    Serin, Ihsan Gökhan; Göksenli, Ali

    2015-06-01

    Formation of nickel-boron-molybdenum (Ni-B-Mo) coating on steel by electroless plating and evaluation of their morphology, hardness and tribological properties post heat treatment at different temperatures for 1 h is investigated. The 25 μm thick coating is uniform and adhesion between the substrate and coating is good. Ni-B-Mo coating was amorphous-like structure in their as-plated condition and by 400°C heat-treated coating, nickel fully crystallized and nickel borides and molybdenum carbide were formed. All coatings exhibited higher hardness than the substrate steel. Hardness values of all coatings up to 400°C did not change distinctively but decreased partly beyond 400°C. Friction coefficient reached lowest value post heat treatment at 300°C but later increased with increasing tempering temperature. Wear resistance was lowest in as-plated coating; however it reached the highest value at 300°C. Worn surface of the coatings showed the abrasive wear as the dominant wear mechanism. An additional adhesive wear mechanism was detected in coating tempered at 550°C. Moreover, our results confirmed that the molybdenum addition improved the thermal stability of the resulting coating. Therefore, Ni-B-Mo coating has potential for application in precision mould, optical parts mould or bipolar plates, where thermal stability is essential.

  14. Mechanism of Ti/Al/Ti/W Au-free ohmic contacts to AlGaN/GaN heterostructures via pre-ohmic recess etching and low temperature annealing

    NASA Astrophysics Data System (ADS)

    Zhang, Jinhan; Huang, Sen; Bao, Qilong; Wang, Xinhua; Wei, Ke; Zheng, Yingkui; Li, Yankui; Zhao, Chao; Liu, Xinyu; Zhou, Qi; Chen, Wanjun; Zhang, Bo

    2015-12-01

    The physical mechanism of low-thermal-budget Au-free ohmic contacts to AlGaN/GaN heterostructures is systematically investigated with current-voltage, high-resolution transmission electron microscopy, and temperature-dependent contact resistivity characterizations. With a low annealing temperature of 600 °C, pre-ohmic recess etching of the AlGaN barrier down to several nanometers is demonstrated to be an effective method to reduce the contact resistance between Ti/Al/Ti/W ohmic metals and AlGaN/GaN heterostructures. However, further over recess of the AlGaN barrier leads to only sidewall contact to 2D electron gas channel and thus degraded contact performance. It is verified by temperature-dependent contact resistivity measurements that field emission (tunneling) dominates the current transport mechanism in Au-free ohmic contacts with AlGaN barrier partially and over recessed, while both field emission and thermionic emission contribute to traditional Ti/Al/Ni/Au ohmic contacts to AlGaN/GaN heterostructures that annealed at high temperature (850 °C).

  15. Mechanism of Ti/Al/Ti/W Au-free ohmic contacts to AlGaN/GaN heterostructures via pre-ohmic recess etching and low temperature annealing

    SciTech Connect

    Zhang, Jinhan; Zhou, Qi; Chen, Wanjun; Zhang, Bo; Huang, Sen Bao, Qilong; Wang, Xinhua; Wei, Ke; Zheng, Yingkui; Li, Yankui; Zhao, Chao; Liu, Xinyu

    2015-12-28

    The physical mechanism of low-thermal-budget Au-free ohmic contacts to AlGaN/GaN heterostructures is systematically investigated with current-voltage, high-resolution transmission electron microscopy, and temperature-dependent contact resistivity characterizations. With a low annealing temperature of 600 °C, pre-ohmic recess etching of the AlGaN barrier down to several nanometers is demonstrated to be an effective method to reduce the contact resistance between Ti/Al/Ti/W ohmic metals and AlGaN/GaN heterostructures. However, further over recess of the AlGaN barrier leads to only sidewall contact to 2D electron gas channel and thus degraded contact performance. It is verified by temperature-dependent contact resistivity measurements that field emission (tunneling) dominates the current transport mechanism in Au-free ohmic contacts with AlGaN barrier partially and over recessed, while both field emission and thermionic emission contribute to traditional Ti/Al/Ni/Au ohmic contacts to AlGaN/GaN heterostructures that annealed at high temperature (850 °C)

  16. Quasipermanent magnets of high temperature superconductor - Temperature dependence

    NASA Technical Reports Server (NTRS)

    Chen, In-Gann; Liu, Jianxiong; Ren, Yanru; Weinstein, Roy; Kozlowski, Gregory; Oberly, Charles E.

    1993-01-01

    We report on persistent field in quasi-permanent magnets of high temperature superconductors. Magnets composed of irradiated Y(1+)Ba2Cu3O7 trapped field Bt = 1.52 T at 77 K and 1.9 T at lower temperature. However, the activation magnet limited Bt at lower temperature. We present data on Jc(H,T) for unirradiated materials, and calculate Bt at various T. Based upon data at 65 K, we calculate Bt in unirradiated single grains at 20 K and find that 5.2 T will be trapped for grain diameter d about 1.2 cm, and 7.9 T for d = 2.3 cm. Irradiated grains will trap four times these values.

  17. The universality of enzymatic rate-temperature dependency.

    PubMed

    Elias, Mikael; Wieczorek, Grzegorz; Rosenne, Shaked; Tawfik, Dan S

    2014-01-01

    Organismal adaptation to extreme temperatures yields enzymes with distinct configurational stabilities, including thermophilic and psychrophilic enzymes, which are adapted to high and low temperatures, respectively. These enzymes are widely assumed to also have unique rate-temperature dependencies. Thermophilic enzymes, for example, are considered optimal at high temperatures and effectively inactive at low temperatures due to excess rigidity. Surveying published data, we find that thermophilic, mesophilic, and psychrophilic enzymes exhibit indistinguishable rate-temperature dependencies. Furthermore, given the nonenzymatic rate-temperature dependency, all enzymes, regardless of their operation temperatures, become >10-fold less powerful catalysts per 25 °C temperature increase. Among other factors, this loss of rate acceleration may be ascribed to thermally induced vibrations compromising the active-site catalytic configuration, suggesting that many enzymes are in fact insufficiently rigid.

  18. High temperature annealing effects on deep-level defects in a high purity semi-insulating 4H-SiC substrate

    SciTech Connect

    Iwamoto, Naoya Azarov, Alexander; Svensson, Bengt G.; Ohshima, Takeshi; Moe, Anne Marie M.

    2015-07-28

    Effects of high-temperature annealing on deep-level defects in a high-purity semi-insulating 4H silicon carbide substrate have been studied by employing current-voltage, capacitance-voltage, junction spectroscopy, and chemical impurity analysis measurements. Secondary ion mass spectrometry data reveal that the substrate contains boron with concentration in the mid 10{sup 15 }cm{sup −3} range, while other impurities including nitrogen, aluminum, titanium, vanadium and chromium are below their detection limits (typically ∼10{sup 14 }cm{sup −3}). Schottky barrier diodes fabricated on substrates annealed at 1400–1700 °C exhibit metal/p-type semiconductor behavior with a current rectification of up to 8 orders of magnitude at bias voltages of ±3 V. With increasing annealing temperature, the series resistance of the Schottky barrier diodes decreases, and the net acceptor concentration in the substrates increases approaching the chemical boron content. Admittance spectroscopy results unveil the presence of shallow boron acceptors and deep-level defects with levels in lower half of the bandgap. After the 1400 °C annealing, the boron acceptor still remains strongly compensated at room temperature by deep donor-like levels located close to mid-gap. However, the latter decrease in concentration with increasing annealing temperature and after 1700 °C, the boron acceptor is essentially uncompensated. Hence, the deep donors are decisive for the semi-insulating properties of the substrates, and their thermal evolution limits the thermal budget for device processing. The origin of the deep donors is not well-established, but substantial evidence supporting an assignment to carbon vacancies is presented.

  19. High temperature annealing effects on deep-level defects in a high purity semi-insulating 4H-SiC substrate

    NASA Astrophysics Data System (ADS)

    Iwamoto, Naoya; Azarov, Alexander; Ohshima, Takeshi; Moe, Anne Marie M.; Svensson, Bengt G.

    2015-07-01

    Effects of high-temperature annealing on deep-level defects in a high-purity semi-insulating 4H silicon carbide substrate have been studied by employing current-voltage, capacitance-voltage, junction spectroscopy, and chemical impurity analysis measurements. Secondary ion mass spectrometry data reveal that the substrate contains boron with concentration in the mid 1015 cm-3 range, while other impurities including nitrogen, aluminum, titanium, vanadium and chromium are below their detection limits (typically ˜1014 cm-3). Schottky barrier diodes fabricated on substrates annealed at 1400-1700 °C exhibit metal/p-type semiconductor behavior with a current rectification of up to 8 orders of magnitude at bias voltages of ±3 V. With increasing annealing temperature, the series resistance of the Schottky barrier diodes decreases, and the net acceptor concentration in the substrates increases approaching the chemical boron content. Admittance spectroscopy results unveil the presence of shallow boron acceptors and deep-level defects with levels in lower half of the bandgap. After the 1400 °C annealing, the boron acceptor still remains strongly compensated at room temperature by deep donor-like levels located close to mid-gap. However, the latter decrease in concentration with increasing annealing temperature and after 1700 °C, the boron acceptor is essentially uncompensated. Hence, the deep donors are decisive for the semi-insulating properties of the substrates, and their thermal evolution limits the thermal budget for device processing. The origin of the deep donors is not well-established, but substantial evidence supporting an assignment to carbon vacancies is presented.

  20. Temperature dependence of the internal friction of polycrystalline indium

    NASA Astrophysics Data System (ADS)

    Sapozhnikov, K. V.; Golyandin, S. N.; Kustov, S. B.

    2010-12-01

    The temperature dependences of the internal friction and the elastic modulus of polycrystalline indium have been investigated in the temperature range 7-320 K at oscillatory loading frequencies of approximately 100 kHz. The effect of temperature on the amplitude dependence and the effect of high-amplitude loading at 7 K on the temperature and amplitude dependences of the internal friction of indium have been analyzed. It has been demonstrated that the thermocycling leads to microplastic deformation of indium due to the anisotropy of thermal expansion and the appearance of a "recrystallization" maximum in the spectrum of the amplitude-dependent internal friction. The conclusion has been drawn that the bulk diffusion of vacancies and impurities begins at temperatures of approximately 90 K and that, at lower temperatures, the diffusion occurs in the vicinity of dislocations. It has been revealed that the high-temperature internal friction background becomes noticeable after the dissolution of Cottrell atmospheres.

  1. Effect of low temperature annealing on the wear properties of NITINOL

    NASA Astrophysics Data System (ADS)

    Mukunda, Sriram; Nath. S, Narendra; Herbert, Mervin A.; Mukunda, P. G.

    2016-02-01

    NiTi shape memory alloy is a wonder material that is a solution looking for problems. The material finds wide biomedical applications like endodontic files for root canal treatment and cardiovascular stents. This material has rendered the surgical procedure simple compared to that with the existing Stainless Steel (SS) or titanium ones. NiTi as an endodontic file would cause less discomfort to the patients in comparison to that with far stiffer SS or titanium ones. Here nearly equi-atomic 50:50 commercial NiTi rods were subjected to low temperature aging at 300 to 450°C. The wear resistance of the as-received and the heat-treated samples was studied using adhesive wear tests on hardened steel counter face. Abrasive wear tests were run against Alumina disc to simulate the working of endodontic drills and files against dental hard and soft tissues. The abrasive wear resistance is expected to be proportional to the Vickers Hardness of the material and is high for the 450°C heat-treated sample. A correlation between the mechanical properties and microstructures of this material is attempted

  2. Temperature dependence of the magnetostriction and the induced anisotropy in nanocrystalline FeCuNbSiB alloys, and their fluxgate properties

    SciTech Connect

    Nielsen, O.V.; Petersen, J.R.; Herzer, G.

    1994-03-01

    Making use of the stress induced magnetic anisotropy in some iron-rich FeCuNbSiD nanocrystalline materials the authors studied the thermal dependence of their magnetostriction which becomes zero below the Curie temperature. The choice of a suitable composition and annealing temperature results in materials with zero magnetostriction at room temperature. Due to the low magnetostriction these materials have very promising fluxgate properties which were studied as well.

  3. Enhanced electrical and optical properties of room temperature deposited Aluminium doped Zinc Oxide (AZO) thin films by excimer laser annealing

    NASA Astrophysics Data System (ADS)

    El hamali, S. O.; Cranton, W. M.; Kalfagiannis, N.; Hou, X.; Ranson, R.; Koutsogeorgis, D. C.

    2016-05-01

    High quality transparent conductive oxides (TCOs) often require a high thermal budget fabrication process. In this study, Excimer Laser Annealing (ELA) at a wavelength of 248 nm has been explored as a processing mechanism to facilitate low thermal budget fabrication of high quality aluminium doped zinc oxide (AZO) thin films. 180 nm thick AZO films were prepared by radio frequency magnetron sputtering at room temperature on fused silica substrates. The effects of the applied RF power and the sputtering pressure on the outcome of ELA at different laser energy densities and number of pulses have been investigated. AZO films deposited with no intentional heating at 180 W, and at 2 mTorr of 0.2% oxygen in argon were selected as the optimum as-deposited films in this work, with a resistivity of 1×10-3 Ω.cm, and an average visible transmission of 85%. ELA was found to result in noticeably reduced resistivity of 5×10-4 Ω.cm, and enhancing the average visible transmission to 90% when AZO is processed with 5 pulses at 125 mJ/cm2. Therefore, the combination of RF magnetron sputtering and ELA, both low thermal budget and scalable techniques, can provide a viable fabrication route of high quality AZO films for use as transparent electrodes.

  4. Effect of annealing temperature on the structural and magnetic properties of CTAB-capped SrFe12O19 platelets

    NASA Astrophysics Data System (ADS)

    Harikrishnan, V.; Saravanan, P.; Ezhil Vizhi, R.; Babu, D. Rajan; Vinod, V. T. P.; Kejzlar, Pavel; Černík, Miroslav

    2016-03-01

    The use of surfactant such as cetyl-trimethyl ammonium bromide (CTAB) in producing highly coercive SrFe12O19 platelets is presented in this study. The synthesis of SrFe12O19 was accomplished by co-precipitation in presence of 1 wt% CTAB. The CTAB-coated precipitant thus obtained was subjected to annealing at different temperatures: 700, 800, 900 and 1000 °C. The annealed counterparts were characterized with respect to their structural and magnetic properties and the results are compared with that of those processed without CTAB. Thermogravimetry analysis was employed to study the thermo-chemical behavior for the SrFe12O19 samples. The evolution of crystalline phases as a function of annealing temperature was studied using x-ray diffraction. For the SrFe12O19 samples without CTAB, formation of α-Fe2O3 secondary phases are noticed at annealing temperatures of 700 and 800 °C; while such a secondary phase formation is not evident for the CTAB-capped SrFe12O19. Fourier transform infrared spectroscopy of the samples annealed at 1000 °C showed deformation in the structure due to the splitting of the bands. Both morphology and composition of the samples were examined by a field-emission scanning electron microscope attached with energy dispersive x-ray analysis. The morphology of CTAB-capped SrFe12O19 samples showed the presence of hexagonal platelets at higher annealing temperatures. The magnetic parameters such as saturation magnetization, MS and coercivity, HC were evaluated from the magnetic hysteresis loops obtained by vibrating sample magnetometer. Maximum values of HC (6.3 kOe) and MS (42.7 emu/g) were obtained for the CTAB-capped SrFe12O19 samples annealed at 900 °C. The possible mechanism on the formation of M-type hexagonal phase with platelet morphology using minimal amount of CTAB (1 wt%) in achieving high the HC values for the SrFe12O19 is discussed.

  5. Temperature Dependence of Diffusion and Reaction at a Pd/SiC Contact

    NASA Technical Reports Server (NTRS)

    Shi, D.T.; Lu, W. J.; Bryant, E.; Elshot, K.; Lafate, K.; Chen, H.; Burger, A.; Collins, W. E.

    1998-01-01

    Schottky diodes of Palladium/SiC are good candidates for hydrogen and hydrocarbon gas sensors at elevated temperature. The detection sensibility of the diodes has been found heavily temperature dependent. In this work, emphasis has been put on the understanding of changes of physical and chemical properties of the Schottky diodes with variation of temperature. Schottky diodes were made by depositing ultra-thin palladium films onto silicon carbide substrates. The electrical and chemical properties of Pd/SiC Schottky contacts were studied by XPS and AES at different annealing temperatures. No significant change in the Schottky barrier height of the Pd/SiC contact was found in the temperature range of RT-400 C. However, both palladium diffused into SiC and silicon migrated into palladium thin film as well as onto surface were observed at room temperature. The formation of palladium compounds at the Pd/SiC interface was also observed. Both diffusion and reaction at the Pd/SiC interface became significant at 300 C and higher temperature. In addition, silicon oxide was found also at the interface of the Pd/SiC contact at high temperature. In this report, the mechanism of diffusion and reaction at the Pd/SiC interface will be discussed along with experimental approaches.

  6. Effects of oxygen partial pressure, deposition temperature, and annealing on the optical response of CdS:O thin films as studied by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Junda, Maxwell M.; Grice, Corey R.; Subedi, Indra; Yan, Yanfa; Podraza, Nikolas J.

    2016-07-01

    Ex-situ spectroscopic ellipsometry measurements are made on radio frequency magnetron sputtered oxygenated cadmium sulfide (CdS:O) thin films. Films are deposited onto glass substrates at room temperature and at 270 °C with varying oxygen to total gas flow ratios in the sputtering ambient. Ellipsometric spectra from 0.74 to 5.89 eV are collected before and after annealing at 607 °C to simulate the thermal processes during close-space sublimation of overlying cadmium telluride in that solar cell configuration. Complex dielectric function (ɛ = ɛ1 + iɛ2) spectra are extracted for films as a function of oxygen gas flow ratio, deposition temperature, and post-deposition annealing using a parametric model accounting for critical point transitions and an Urbach tail for sub-band gap absorption. The results suggest an inverse relationship between degree of crystallinity and oxygen gas flow ratio, whereas annealing is shown to increase crystallinity in all samples. Direct band gap energies are determined from the parametric modeling of ɛ and linear extrapolations of the square of the absorption coefficient. As-deposited samples feature a range of band gap energies whereas annealing is shown to result in gap energies ranging only from 2.40 to 2.45 eV, which is close to typical band gaps for pure cadmium sulfide.

  7. The influence of composition, annealing treatment, and texture on the fracture toughness of Ti-5Al-2.5Sn plate at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Vanstone, R. H.; Shannon, J. L., Jr.; Pierce, W. S.; Low, J. R., Jr.

    1977-01-01

    The plane strain fracture toughness K sub Ic and conventional tensile properties of two commercially produced one-inch thick Ti-5Al-2.5Sn plates were determined at cryogenic temperatures. One plate was extra-low interstitial (ELI) grade, the other normal interstitial. Portions of each plate were mill annealed at 1088 K (1500 F) followed by either air cooling or furnace cooling. The tensile properties, flow curves, and K sub Ic of these plates were determined at 295 K (room temperature), 77 K (liquid nitrogen temperature), and 20 K (liquid hydrogen temperature).

  8. The annealing influence onto the electrical and magnetic behavior of magnetoresistive/insulator system

    NASA Astrophysics Data System (ADS)

    Ahmed, A. M.; Mohamed, Abd El-Mo'ez A.; Mohamed, H. F.; Diab, A. K.; Mohamed, Aml M.; Mazen, A. E. A.

    2016-09-01

    This investigation is mainly concerned with the effect of annealing temperature (600, 700, 800, and 900 °C) in air for (La0.7Ba0.3MnO3)1-x/(NiO)x with x = 0 and x = 0.10 samples. It was shown that the annealing temperature does not affect the structure and parameters of rhombohedral lattice of the samples. However, it is observed that the annealing treatment has a notable effect on the electrical resistivity and the metal-semiconductor transition temperature Tms. Temperature dependent magnetization measurements showed a decrease in Curie temperature TC with annealing temperature. In the same time, annealing process decreases the magnetoresistance of La0.7Ba0.3MnO3, in contrast to (La0.7Ba0.3MnO3)0.9/(NiO)0.1 composite.

  9. Temperature dependence of heterogeneous nucleation: Extension of the Fletcher model

    NASA Astrophysics Data System (ADS)

    McGraw, Robert; Winkler, Paul; Wagner, Paul

    2015-04-01

    Recently there have been several cases reported where the critical saturation ratio for onset of heterogeneous nucleation increases with nucleation temperature (positive slope dependence). This behavior contrasts with the behavior observed in homogeneous nucleation, where a decreasing critical saturation ratio with increasing nucleation temperature (negative slope dependence) seems universal. For this reason the positive slope dependence is referred to as anomalous. Negative slope dependence is found in heterogeneous nucleation as well, but because so few temperature-dependent measurements have been reported, it is not presently clear which slope condition (positive or negative) will become more frequent. Especially interesting is the case of water vapor condensation on silver nanoparticles [Kupc et al., AS&T 47: i-iv, 2013] where the critical saturation ratio for heterogeneous nucleation onset passes through a maximum, at about 278K, with higher (lower) temperatures showing the usual (anomalous) temperature dependence. In the present study we develop an extension of Fletcher's classical, capillarity-based, model of heterogeneous nucleation that explicitly resolves the roles of surface energy and surface entropy in determining temperature dependence. Application of the second nucleation theorem, which relates temperature dependence of nucleation rate to cluster energy, yields both necessary and sufficient conditions for anomalous temperature behavior in the extended Fletcher model. In particular it is found that an increasing contact angle with temperature is a necessary, but not sufficient, condition for anomalous temperature dependence to occur. Methods for inferring microscopic contact angle and its temperature dependence from heterogeneous nucleation probability measurements are discussed in light of the new theory.

  10. The influence of internal oxidation during decarburization of a grain oriented silicon steel on the morphology of the glass film formed at high temperature annealing

    NASA Astrophysics Data System (ADS)

    Silveira, Carolina Cesconetto; da Cunha, Marco Antônio; Buono, Vicente Tadeu Lopes

    2014-05-01

    Fourier transform infrared spectroscopy (FTIR) was applied to evaluate the amount of fayalite formed during decarburization of a grain-oriented silicon steel, in order to assess its influence on the morphology of the glass film developed at the final high temperature annealing. The decarburization conditions varied within the temperature range of 740-950 °C and pH2O/pH2 from 0.28 to 0.58. The decarburized specimens were then coated with magnesia slurry and submitted to the high temperature annealing at 1200 °C for 15 h. Characterization of the oxide layer and glass film samples was performed by scanning and transmission electron microscopy. The FTIR analysis showed that the amount of fayalite increased as the temperature and the dew point increased during decarburization. The morphology of the glass film obtained after high temperature annealing was related to the amount of fayalite and silica previously formed. A higher amount of subsurface particles in the glass film, which can deteriorate magnetic properties by restraining domain wall movements, was obtained from oxide layers rich in fayalite and thus with a low amount of silica.

  11. Structural, morphological and optical properties of Ag-AgO thin films with the effect of increasing film thickness and annealing temperature

    NASA Astrophysics Data System (ADS)

    Pal, Anil Kumar; Bharathi Mohan, D.

    2015-10-01

    Ag films of thickness ranging from 5 to 60 nm were deposited by thermal evaporation technique followed by air annealing process with temperature varying from 50 to 250 °C. Morphological properties such as particle size, shape, surface roughness and number particles density were studied by atomic force microscope (AFM). The structural transition from quasi-amorphous to nanocrystalline to crystalline upon increasing film thickness and annealing temperature were studied. Ag films with smallest particle size and surface roughness were achieved up to film thickness of 7 nm. The possibility of surface oxidation of Ag on both as deposited and annealed films was studied through Raman mapping by using confocal Raman spectroscopy. Ag film was X-ray amorphous even after annealing process up to the film thickness of 7 nm and above which the crystallinity reached maximum at 250 °C. The surface plasmon resonance (SPR) with a symmetric line shape due to dipole-dipole interactions was found to be very strong for film thickness of 5 nm at 100 °C, attributed to the formation of smaller Ag NPs size of ∼22 nm with least size distribution and higher particles number density of ∼1625 μm-2 in a self-organized fashion. With an increase of film thickness and annealing temperature, an asymmetric broad absorption arose due to increase in damping of collective electron oscillation on bulky NPs. Theoretical absorption spectra were simulated using extended Maxwell garnet method showing a decent agreement with experimental data. The real and imaginary parts of dielectric constants were determined and plotted for different film thicknesses of as deposited Ag films. Even though the film is oxidized at the surface level, it still can be used for plasmonic sensor applications however the film thickness should be approximately 7 nm for the enhanced result.

  12. Crossing regimes of temperature dependence in animal movement.

    PubMed

    Gibert, Jean P; Chelini, Marie-Claire; Rosenthal, Malcolm F; DeLong, John P

    2016-05-01

    A pressing challenge in ecology is to understand the effects of changing global temperatures on food web structure and dynamics. The stability of these complex ecological networks largely depends on how predator-prey interactions may respond to temperature changes. Because predators and prey rely on their velocities to catch food or avoid being eaten, understanding how temperatures may affect animal movement is central to this quest. Despite our efforts, we still lack a mechanistic understanding of how the effect of temperature on metabolic processes scales up to animal movement and beyond. Here, we merge a biomechanical approach, the Metabolic Theory of Ecology and empirical data to show that animal movement displays multiple regimes of temperature dependence. We also show that crossing these regimes has important consequences for population dynamics and stability, which depend on the parameters controlling predator-prey interactions. We argue that this dependence upon interaction parameters may help explain why experimental work on the temperature dependence of interaction strengths has so far yielded conflicting results. More importantly, these changes in the temperature dependence of animal movement can have consequences that go well beyond ecological interactions and affect, for example, animal communication, mating, sensory detection, and any behavioral modality dependent on the movement of limbs. Finally, by not taking into account the changes in temperature dependence reported here we might not be able to properly forecast the impact of global warming on ecological processes and propose appropriate mitigation action when needed. PMID:26854767

  13. DNAzyme catalytic beacon sensors that resist temperature-dependent variations.

    PubMed

    Nagraj, Nandini; Liu, Juewen; Sterling, Stephanie; Wu, Jenny; Lu, Yi

    2009-07-21

    The temperature-dependent variability of a Pb2+-specific 8-17E DNAzyme catalytic beacon sensor has been addressed through the introduction of mismatches in the DNAzyme, and the resulting sensors resist temperature-dependent variations from 4 to 30 degrees C.

  14. A dual role for mycobacterial RecO in RecA-dependent homologous recombination and RecA-independent single-strand annealing.

    PubMed

    Gupta, Richa; Ryzhikov, Mikhail; Koroleva, Olga; Unciuleac, Mihaela; Shuman, Stewart; Korolev, Sergey; Glickman, Michael S

    2013-02-01

    Mycobacteria have two genetically distinct pathways for the homology-directed repair of DNA double-strand breaks: homologous recombination (HR) and single-strand annealing (SSA). HR is abolished by deletion of RecA and reduced in the absence of the AdnAB helicase/nuclease. By contrast, SSA is RecA-independent and requires RecBCD. Here we examine the function of RecO in mycobacterial DNA recombination and repair. Loss of RecO elicits hypersensitivity to DNA damaging agents similar to that caused by deletion of RecA. We show that RecO participates in RecA-dependent HR in a pathway parallel to the AdnAB pathway. We also find that RecO plays a role in the RecA-independent SSA pathway. The mycobacterial RecO protein displays a zinc-dependent DNA binding activity in vitro and accelerates the annealing of SSB-coated single-stranded DNA. These findings establish a role for RecO in two pathways of mycobacterial DNA double-strand break repair and suggest an in vivo function for the DNA annealing activity of RecO proteins, thereby underscoring their similarity to eukaryal Rad52. PMID:23295671

  15. A dual role for mycobacterial RecO in RecA-dependent homologous recombination and RecA-independent single-strand annealing

    PubMed Central

    Gupta, Richa; Ryzhikov, Mikhail; Koroleva, Olga; Unciuleac, Mihaela; Shuman, Stewart; Korolev, Sergey; Glickman, Michael S.

    2013-01-01

    Mycobacteria have two genetically distinct pathways for the homology-directed repair of DNA double-strand breaks: homologous recombination (HR) and single-strand annealing (SSA). HR is abolished by deletion of RecA and reduced in the absence of the AdnAB helicase/nuclease. By contrast, SSA is RecA-independent and requires RecBCD. Here we examine the function of RecO in mycobacterial DNA recombination and repair. Loss of RecO elicits hypersensitivity to DNA damaging agents similar to that caused by deletion of RecA. We show that RecO participates in RecA-dependent HR in a pathway parallel to the AdnAB pathway. We also find that RecO plays a role in the RecA-independent SSA pathway. The mycobacterial RecO protein displays a zinc-dependent DNA binding activity in vitro and accelerates the annealing of SSB-coated single-stranded DNA. These findings establish a role for RecO in two pathways of mycobacterial DNA double-strand break repair and suggest an in vivo function for the DNA annealing activity of RecO proteins, thereby underscoring their similarity to eukaryal Rad52. PMID:23295671

  16. Effects of high-temperature diluted-H2 annealing on effective mobility of 4H-SiC MOSFETs with thermally-grown SiO2

    NASA Astrophysics Data System (ADS)

    Hirai, Hirohisa; Kita, Koji

    2016-04-01

    The impact of post-oxidation annealing (POA) in diluted-H2 ambient on a 4H-SiC/SiO2 interface was investigated with a cold wall furnace. Effective mobility (μeff) was extracted from lateral metal-oxide-semiconductor field-effect transistors (MOSFETs) by applying the split capacitance-voltage (C-V) technique to the determination of charge density and a calibration technique using two MOSFETs with different gate lengths to minimize the contribution of parasitic components. POA at 1150 °C in diluted-H2 ambient resulted in an enhancement of μeff compared with that for POA in N2 ambient. It was indicated that the effects of POA in diluted H2 should be attributed to the reduction in the density of near interface traps, which disturb the electron transportation in the inversion channel, from the measurement temperature dependence of μeff as well as from the C-V curves of MOS capacitors fabricated on n-type SiC.

  17. Birefringence simulation of annealed ingot of calcium fluoride single crystal

    NASA Astrophysics Data System (ADS)

    Ogino, H.; Miyazaki, N.; Mabuchi, T.; Nawata, T.

    2008-01-01

    We developed a method for simulating birefringence of an annealed ingot of calcium fluoride single crystal caused by the residual stress after annealing process. The method comprises the heat conduction analysis that provides the temperature distribution during the ingot annealing, the elastic thermal stress analysis using the assumption of the stress-free temperature that provides the residual stress after annealing, and the birefringence analysis of an annealed ingot induced by the residual stress. The finite element method was applied to the heat conduction analysis and the elastic thermal stress analysis. In these analyses, the temperature dependence of material properties and the crystal anisotropy were taken into account. In the birefringence analysis, the photoelastic effect gives the change of refractive indices, from which the optical path difference in the annealed ingot is calculated by the Jones calculus. The relation between the Jones calculus and the approximate method using the stress components averaged along the optical path is discussed theoretically. It is found that the result of the approximate method agrees very well with that of the Jones calculus in birefringence analysis. The distribution pattern of the optical path difference in the annealed ingot obtained from the present birefringence calculation methods agrees reasonably well with that of the experiment. The calculated values also agree reasonably well with those of the experiment, when a stress-free temperature is adequately selected.

  18. Temperature Dependence of the Magnetization of the Ni52Mn24Ga24 Alloy in Various Structural States

    NASA Astrophysics Data System (ADS)

    Musabirov, I. I.; Sharipov, I. Z.; Mulyukov, R. R.

    2015-10-01

    are presented of a study of the temperature dependence of the magnetization σ(Т) of the polycrystalline Ni52Mn24Ga24 alloy in various structural states: in the initial coarse-grained state, after severe plastic deformation by high pressure torsion, and after stepped annealing of the deformed specimen at temperatures from 200 to 700°С for 30 min. As a study of the σ(Т) curve shows, in an alloy possessing a coarse-grained initial structure, a martensitic phase transition and a magnetic phase transition are observed in the room temperature interval. The martensitic transformation takes place in the ferromagnetic state of the alloy. This transformation is accompanied by an abrupt lowering of the magnetization of the material, associated with a lowering of the symmetry of the crystalline lattice and a high value of the magnetocrystalline anisotropy constant of the alloy in the martensitic phase. It is shown that as a result of plastic deformation there takes place a destruction of ferromagnetic order and a suppression of the martensitic transformation. Consecutive annealing after deformation leads to a gradual recovery of ferromagnetic order and growth of the magnetization of the material. Recovery of the martensitic transformation begins to be manifested only after annealing of the alloy at a temperature of 500°C, when the mean grain size in the recrystallized structure reaches a value around 1 μm.

  19. Temperature dependence of the excited state absorption of alexandrite

    SciTech Connect

    Shand, M.L.; Jenssen, H.P.

    1983-03-01

    The temperature dependence from 28 to 290/sup 0/C of the excited-state absorption cross section sigma /SUB 2a/ (E) in the gain wavelength region of alexandrite has been determined from the temperature dependence of the single pass gain (SPG) and of the fluorescence. sigma /SUB 2a/ (E) and the emission cross section increase with temperature at approximately the same rate.

  20. Correlation of the nanostructure with optoelectronic properties during rapid thermal annealing of Ga(NAsP) quantum wells grown on Si(001) substrates

    NASA Astrophysics Data System (ADS)

    Wegele, Tatjana; Beyer, Andreas; Gies, Sebastian; Zimprich, Martin; Heimbrodt, Wolfram; Stolz, Wolfgang; Volz, Kerstin

    2016-01-01

    Ga(NAsP) quantum wells grown pseudomorphically on Si substrate are promising candidates for optically active light sources in future optoelectronically integrated circuits on Si substrates. As the material is typically grown at low temperatures, it has to be thermally annealed after growth to remove defects and optimize optoelectronic properties. Here we show by quantitative transmission electron microscopy that two different kinds of structural development are associated with the annealing. First of all, the quantum well homogeneity improves with increasing annealing temperature. For annealing temperatures above 925 °C the composition becomes less homogeneous again. Second, voids form in the quantum well for annealing temperatures above 850 °C. Their density and size increase continuously with increasing annealing temperature. These results are correlated to the optical properties of the samples, where we find from temperature-dependent photoluminescence measurements two scales of disorder, which show the same temperature dependence as the structural properties.

  1. Impact of high-temperature annealing of AlN layer on sapphire and its thermodynamic principle

    NASA Astrophysics Data System (ADS)

    Fukuyama, Hiroyuki; Miyake, Hideto; Nishio, Gou; Suzuki, Shuhei; Hiramatsu, Kazumasa

    2016-05-01

    The N2-CO gas annealing technique was demonstrated to improve the crystalline quality of the AlN layer on sapphire. 300-nm-thick AlN layers were fabricated on sapphire substrates by a metal-organic vapor phase epitaxy method. The AlN layers were annealed in N2 and/or N2-CO gas atmosphere at 1923-1973 K for 0.5-4 h. Many pits and voids were observed on the AlN surface annealed in N2 atmosphere at 1973 K for 2 h. The rough surface was, however, much improved for the AlN annealed in N2-CO gas atmosphere. The thermodynamic principle of the N2-CO gas annealing technique is explained in this paper on the basis of the phase stability diagram of the Al2O3-AlN-C-N2-CO system. Voids and γ-aluminum oxynitride (γ-AlON) at the AlN/sapphire interface formed during the annealing, which is also explained on the basis of the phase stability diagram. The in-plane epitaxial relationships among AlN, γ-AlON, and sapphire are presented, and misfits among them are discussed.

  2. On the Debossing, Annealing and Mounting of Bells

    NASA Astrophysics Data System (ADS)

    PERRIN, R.; SWALLOWE, G. M.; CHARNLEY, T.; MARSHALL, C.

    1999-10-01

    Changes in the frequencies of the musical partials of various types of bells following debossing dismounting/mounting and annealing/quench annealing are reported. Debossing, dismounting and quench annealing lead to frequency drops, while mounting gives rises. Annealing can lead to frequency increases or decreases depending upon the maximum temperature employed and the initial residual stress. Qualitative explanations of these phenomena are given in terms of changes in crown stiffness, internal stress and alloy phase structure. These are supported by the results of X-ray diffraction measurements. Although the effects are all small they can be large enough to be detected by a reasonably musical car. This, together with the fact that the effects cannot be controlled, gives a plausible explanation of why modern bellfounders use vertical lathes for tuning, even with small carillon bells, and do not anneal bells when trying to control warble.

  3. Temperature dependence of unsaturated hydraulic conductivity of two soils.

    USGS Publications Warehouse

    Constantz, J.

    1982-01-01

    The temperature dependence of the soil water matric potential, surface tension, and diffuse double-layer thickness are discussed in terms of their possible interaction with the unsaturated conductivity values obtained. A case is presented for further study to isolate these temperature-sensitive parameters as well as additional parameters related to fluid flow path changes with temperature.-from Author

  4. Temperature dependence of conductivity measurement for conducting polymer

    NASA Astrophysics Data System (ADS)

    Gutierrez, Leandro; Duran, Jesus; Isah, Anne; Albers, Patrick; McDougall, Michael; Wang, Weining

    2014-03-01

    Conducting polymer-based solar cells are the newest generation solar cells. While research on this area has been progressing, the efficiency is still low because certain important parameters of the solar cell are still not well understood. It is of interest to study the temperature dependence of the solar cell parameters, such as conductivity of the polymer, open circuit voltage, and reverse saturation current to gain a better understanding on the solar cells. In this work, we report our temperature dependence of conductivity measurement using our in-house temperature-varying apparatus. In this project, we designed and built a temperature varying apparatus using a thermoelectric cooler module which gives enough temperature range as we need and costs much less than a cryostat. The set-up of the apparatus will be discussed. Temperature dependence of conductivity measurements for PEDOT:PSS films with different room-temperature conductivity will be compared and discussed. NJSGC-NASA Fellowship grant

  5. In-Situ Measurements of Graphene Mechanics During Annealing

    NASA Astrophysics Data System (ADS)

    Hui, Aaron; de Alba, Roberto; Sebastian, Abhilash; Parpia, Jeevak

    Graphene shows great potential as a material for a new generation of mechanical nanodevices. However, current methodologies used for fabricating graphene structures involve polymer resists for transfer and patterning, which degrades mechanical performance. To improve surface quality, high current or high temperature annealing of graphene is commonly employed. Previous studies of graphene mechanics have focused on performance after annealing or temperature-dependent behavior from 4K-300K. Here we present real-time, in-situ measurements of graphene mechanical resonance during high temperature annealing from 300K-600K. Upon heating, reversible changes in mechanical frequency are indicative of graphene thermal contraction. Discontinuous and irreversible changes are also seen, corresponding to graphene slipping and mass desorption. Both reversible and irreversible changes in quality factor are also observed. Characterizing the effects of annealing on the structural properties of graphene will enable more precise engineering for particular applications, such as mass sensing.

  6. Annealing dependence of diamond-metal Schottky barrier heights probed by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Gaowei, M.; Muller, E. M.; Rumaiz, A. K.; Weiland, C.; Cockayne, E.; Woicik, J. C.; Jordan-Sweet, J.; Smedley, J.

    2012-05-14

    Hard x-ray photoelectron spectroscopy was applied to investigate the diamond-metal Schottky barrier heights for several metals and diamond surface terminations. The position of the diamond valence-band maximum was determined by theoretically calculating the diamond density of states and applying cross section corrections. The diamond-platinum Schottky barrier height was lowered by 0.2 eV after thermal annealing, indicating annealing may increase carrier injection in diamond devices leading to photoconductive gain. The platinum contacts on oxygen-terminated diamond was found to provide a higher Schottky barrier and therefore a better blocking contact than that of the silver contact in diamond-based electronic devices.

  7. Temperature dependence of DNA condensation at high ionic concentration

    NASA Astrophysics Data System (ADS)

    Mao, Wei; Gao, Qingqing; Liu, Yanhui; Fan, Yangtao; Hu, Lin; Xu, Houqiang

    2016-08-01

    A series of experiments pointed out that compact states of DNA condensed by multivalent cation prefer higher temperature. The condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in temperature. At the same time, a recent experimental work carried out in buffer solution without multivalent cation points out that DNA persistence length strongly depends on the temperature. DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. It is necessary to revolve the effects of temperature dependence of persistence length on DNA condensation, and a model including the temperature dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the temperature dependence of toroid conformations. With an increase in temperature, the first periodic oscillation in the autocorrelation function shifts left and the number of segments containing the first periodic oscillation decreases gradually. According to the experiments mentioned above, the long-axis length is defined to estimate the temperature dependence of condensation process further. At the temperatures defined in experiments mentioned above, the relation between long-axis length and temperature matches the experimental results.

  8. Two- and multi-step annealing of cereal starches in relation to gelatinization.

    PubMed

    Shi, Yong-Cheng

    2008-02-13

    Two- and multi-step annealing experiments were designed to determine how much gelatinization temperature of waxy rice, waxy barley, and wheat starches could be increased without causing a decrease in gelatinization enthalpy or a decline in X-ray crystallinity. A mixture of starch and excess water was heated in a differential scanning calorimeter (DSC) pan to a specific temperature and maintained there for 0.5-48 h. The experimental approach was first to anneal a starch at a low temperature so that the gelatinization temperature of the starch was increased without causing a decrease in gelatinization enthalpy. The annealing temperature was then raised, but still was kept below the onset gelatinization temperature of the previously annealed starch. When a second- or third-step annealing temperature was high enough, it caused a decrease in crystallinity, even though the holding temperature remained below the onset gelatinization temperature of the previously annealed starch. These results support that gelatinization is a nonequilibrium process and that dissociation of double helices is driven by the swelling of amorphous regions. Small-scale starch slurry annealing was also performed and confirmed the annealing results conducted in DSC pans. A three-phase model of a starch granule, a mobile amorphous phase, a rigid amorphous phase, and a crystalline phase, was used to interpret the annealing results. Annealing seems to be an interplay between a more efficient packing of crystallites in starch granules and swelling of plasticized amorphous regions. There is always a temperature ceiling that can be used to anneal a starch without causing a decrease in crystallinity. That temperature ceiling is starch-specific, dependent on the structure of a starch, and is lower than the original onset gelatinization of a starch.

  9. The Effect of High Temperature Annealing on the Grain Characteristics of a Thin Chemical Vapor Deposition Silicon Carbide Layer.

    SciTech Connect

    Isabella J van Rooyen; Philippus M van Rooyen; Mary Lou Dunzik-Gougar

    2013-08-01

    The unique combination of thermo-mechanical and physiochemical properties of silicon carbide (SiC) provides interest and opportunity for its use in nuclear applications. One of the applications of SiC is as a very thin layer in the TRi-ISOtropic (TRISO) coated fuel particles for high temperature gas reactors (HTGRs). This SiC layer, produced by chemical vapor deposition (CVD), is designed to withstand the pressures of fission and transmutation product gases in a high temperature, radiation environment. Various researchers have demonstrated that macroscopic properties can be affected by changes in the distribution of grain boundary plane orientations and misorientations [1 - 3]. Additionally, various researchers have attributed the release behavior of Ag through the SiC layer as a grain boundary diffusion phenomenon [4 - 6]; further highlighting the importance of understanding the actual grain characteristics of the SiC layer. Both historic HTGR fission product release studies and recent experiments at Idaho National Laboratory (INL) [7] have shown that the release of Ag-110m is strongly temperature dependent. Although the maximum normal operating fuel temperature of a HTGR design is in the range of 1000-1250°C, the temperature may reach 1600°C under postulated accident conditions. The aim of this specific study is therefore to determine the magnitude of temperature dependence on SiC grain characteristics, expanding upon initial studies by Van Rooyen et al, [8; 9].

  10. Enhancement of dye-sensitized solar cell efficiency using carbon nanotube/TiO2 nanocomposite thin films fabricated at various annealing temperatures

    NASA Astrophysics Data System (ADS)

    Abdullah, Huda; Razali, Mohd Zikri; Shaari, Sahbudin; Taha, Mohd Raihan

    2014-05-01

    To increase energy conversion efficiency of dye-sensitized solar cells (DSSCs), carbon nanotubes (CNTs) were added to TiO2 gel-like solution. Modified acid-catalyzed sol-gel method was used with the doctor blade coating technique to obtain thin films of CNT/TiO2 nanocomposite photoanode. CNT/TiO2 paste was applied onto the conductive glass to generate a 0.25 cm2 active area which was later annealed at 350°C, 450°C, and 550°C for 60 min. Characterization of the CNT/TiO2 paste was performed using x-ray diffraction. Results showed that the crystalline phase of the particles was anatase. The micrograph obtained using field emission scanning electron microscopy demonstrated that the pastes are highly porous. Brunauer-Emmett-Teller analysis was performed to determine the CNT/TiO2 surface area and particle size. The DSSC with the CNT/TiO2 photoanodes annealed at 550°C showed the highest incident photon-to-charge carrier efficiency value of 0.95% compared with the DSSCs with photoanodes annealed at 350°C and 450°C (0.70% and 0.83%, respectively). The observed efficiencies of the DSSCs with CNT/TiO2 photoanode annealed at the three different temperatures were 2.62%, 2.65%, and 3.13%. The electrochemical impedance spectroscopy analysis showed that the DSSCs with photoanodes developed using the highest annealing temperature (550°C) have higher electron lifetime of 70.423 ms and lower effective recombination rate of 1.42 × 10-2 s-1, thereby improving the performance of CNT/TiO2 DSSCs.

  11. Effective reduction of trap density at the Y{sub 2}O{sub 3}/Ge interface by rigorous high-temperature oxygen annealing

    SciTech Connect

    Bethge, O. Zimmermann, C.; Lutzer, B.; Simsek, S.; Smoliner, J.; Bertagnolli, E.; Stöger-Pollach, M.; Henkel, C.

    2014-12-07

    The impact of thermal post deposition annealing in oxygen at different temperatures on the Ge/Y{sub 2}O{sub 3} interface is investigated using metal oxide semiconductor capacitors, where the yttrium oxide was grown by atomic layer deposition from tris(methylcyclopentadienyl)yttrium and H{sub 2}O precursors on n-type (100)-Ge substrates. By performing in-situ X-ray photoelectron spectroscopy, the growth of GeO during the first cycles of ALD was proven and interface trap densities just below 1 × 10{sup 11} eV{sup −1 }cm{sup −2} were achieved by oxygen annealing at high temperatures (550 °C–600 °C). The good interface quality is most likely driven by the growth of interfacial GeO{sub 2} and thermally stabilizing yttrium germanate.

  12. Effect of annealing temperature on photoelectrochemical properties of nanocrystalline MoBi2(Se0.5Te0.5)5 thin films

    NASA Astrophysics Data System (ADS)

    Salunkhe, Manauti; Pawar, Nita; Patil, P. S.; Bhosale, P. N.

    2014-10-01

    Nanocrystalline MoBi2(Se0.5Te0.5)5 thermoelectric thin films have been deposited on ultrasonically cleaned glass and FTO-coated glass substrates by Arrested Precipitation Technique. The change in properties of MoBi2(Se0.5Te0.5)5 thin films were examined after annealing at the temperature 473 K for 3 h. The structural, morphological, compositional and electrical properties of thin films were characterized by X-ray Diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, etc. Thermoelectric properties of the thin films have been evaluated by measurements of electrical conductivity and Seebeck coefficient in the temperature range 300-500 K. Our aim is to investigate the effect of annealing on behaviour of MoBi2(Se0.5Te0.5)5 thin films along with photoelectrochemical properties.

  13. The amorphous state of spray-dried maltodextrin: sub-sub-Tg enthalpy relaxation and impact of temperature and water annealing.

    PubMed

    Descamps, Nicolas; Palzer, Stefan; Zuercher, Ulrich

    2009-01-01

    The annealing behaviour of a spray-dried maltodextrin was investigated by differential scanning calorimetry. Special attention was paid to the effect of temperature and humidity on the annealing process. Comparison was also made with the glassy state of the same compound prepared by various cooling processes. The presence of a very pronounced sub-T(g) peak upon ageing reveals the specificities of the glass and the complexity of the relaxation spectrum of the spray-dried material. This peak seems actually to correspond to a partial ergodicity recovery that may be attributed to onset of molecular mobility occurring below T(g). The position of the sub-T(g) peak with regard to the conventional T(g) was systematically studied. It clearly showed the difference between the effect of temperature and water plasticization on the relaxations occurring in the glassy state of materials prepared by spray-drying. PMID:18977472

  14. Role of ITO electrode in the resistive switching behavior of TiN/HfO2/ITO memory devices at different annealing temperatures

    NASA Astrophysics Data System (ADS)

    Ye, Cong; Deng, Teng-fei; Wu, Jiaji; Zhan, Chao; Wang, Hao; Zhang, Jun

    2015-05-01

    TiN/HfO2/ITO memory devices were fabricated and annealed at 200, 300, and 400 °C. At room temperature (RT), 200 °C, and 300 °C, the devices show the self-compliance phenomenon and a low SET voltage of 0.2 V, while at 400 °C the SET voltage increases to 1.1 V and the low resistance state (LRS) current increases to 8 mA. We deduced that the impact of annealing temperature on the resistive switching behavior is mainly attributed to the indium tin oxide (ITO) electrode. Some Sn4+ ions in the ITO electrode drift towards the HfO2 layer owing to the electrical force, then an interfacial layer is formed and acts as an internal resistor. At 400 °C, the remarkable increase of LRS current is attributed to the decreases in both the ITO electrode resistance and the interface resistance.

  15. Temperature dependent vibrational modes of glycosidic bond in disaccharide sugars.

    PubMed

    Seo, Jeong-Ah; Kwon, Hyun-Joung; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2008-03-17

    We studied the temperature dependent vibrational modes of the glycosidic bond in trehalose, sucrose, and maltose at wavenumbers ranging from 1000 to 1200 cm(-1). We found that the slope of temperature dependent Raman shifts of the glycosidic bond in trehalose and sucrose changed at temperatures around 120 degrees C, indicating a bond length or a bond angle (dihedral and torsional angles) change. However, we did not observe any slope change in maltose because the melting temperature of maltose is very close to 120 degrees C. We also found, at temperatures below 120 degrees C, that Raman shifts of the vibrational modes of the glycosidic bond in trehalose showed the strongest temperature dependence among the three disaccharides.

  16. Effective dopant activation by susceptor-assisted microwave annealing of low energy boron implanted and phosphorus implanted silicon

    SciTech Connect

    Zhao, Zhao; Vemuri, Rajitha N. P.; Alford, T. L.; David Theodore, N.; Lu, Wei; Lau, S. S.; Lanz, A.

    2013-12-28

    Rapid processing and reduced end-of-range diffusion result from susceptor-assisted microwave (MW) annealing, making this technique an efficient processing alternative for electrically activating dopants within ion-implanted semiconductors. Sheet resistance and Hall measurements provide evidence of electrical activation. Susceptor-assisted MW annealing, of ion-implanted Si, enables more effective dopant activation and at lower temperatures than required for rapid thermal annealing (RTA). Raman spectroscopy and ion channeling analyses are used to monitor the extent of ion implantation damage and recrystallization. The presence and behavior of extended defects are monitored by cross-section transmission electron microscopy. Phosphorus implanted Si samples experience effective electrical activation upon MW annealing. On the other hand, when boron implanted Si is MW annealed, the growth of extended defects results in reduced crystalline quality that hinders the electrical activation process. Further comparison of dopant diffusion resulting from MW annealing and rapid thermal annealing is performed using secondary ion mass spectroscopy. MW annealed ion implanted samples show less end-of-range diffusion when compared to RTA samples. In particular, MW annealed P{sup +} implanted samples achieve no visible diffusion and equivalent electrical activation at a lower temperature and with a shorter time-duration of annealing compared to RTA. In this study, the peak temperature attained during annealing does not depend on the dopant species or dose, for susceptor-assisted MW annealing of ion-implanted Si.

  17. Effective dopant activation by susceptor-assisted microwave annealing of low energy boron implanted and phosphorus implanted silicon

    NASA Astrophysics Data System (ADS)

    Zhao, Zhao; David Theodore, N.; Vemuri, Rajitha N. P.; Lu, Wei; Lau, S. S.; Lanz, A.; Alford, T. L.

    2013-12-01

    Rapid processing and reduced end-of-range diffusion result from susceptor-assisted microwave (MW) annealing, making this technique an efficient processing alternative for electrically activating dopants within ion-implanted semiconductors. Sheet resistance and Hall measurements provide evidence of electrical activation. Susceptor-assisted MW annealing, of ion-implanted Si, enables more effective dopant activation and at lower temperatures than required for rapid thermal annealing (RTA). Raman spectroscopy and ion channeling analyses are used to monitor the extent of ion implantation damage and recrystallization. The presence and behavior of extended defects are monitored by cross-section transmission electron microscopy. Phosphorus implanted Si samples experience effective electrical activation upon MW annealing. On the other hand, when boron implanted Si is MW annealed, the growth of extended defects results in reduced crystalline quality that hinders the electrical activation process. Further comparison of dopant diffusion resulting from MW annealing and rapid thermal annealing is performed using secondary ion mass spectroscopy. MW annealed ion implanted samples show less end-of-range diffusion when compared to RTA samples. In particular, MW annealed P+ implanted samples achieve no visible diffusion and equivalent electrical activation at a lower temperature and with a shorter time-duration of annealing compared to RTA. In this study, the peak temperature attained during annealing does not depend on the dopant species or dose, for susceptor-assisted MW annealing of ion-implanted Si.

  18. Climate change and temperature-dependent sex determination in reptiles.

    PubMed Central

    Janzen, F J

    1994-01-01

    Despite increasing concern over the possible impact of global temperature change, there is little empirical evidence of direct temperature effects on biotic interactions in natural systems. Clear assessment of the ecological and evolutionary impact of changing climatic temperature requires a natural system in which populations exhibit a direct unambiguous fitness response to thermal fluctuation. I monitored nests of a population of painted turtles (Chrysemys picta) with temperature-dependent sex determination to investigate the causal relationship between local climatic variation in temperature and offspring sex ratio. Consistent with theoretical predictions, annual offspring sex ratio was highly correlated with mean July air temperature, validating concerns about the effect of climate change on population demography. This correlation implies that even modest increases in mean temperature (< 2 degrees C) may drastically skew the sex ratio. Statistical evaluation of the variance in climate change indicates that an increase in mean temperature of 4 degrees C would effectively eliminate production of male offspring. Quantitative genetic analyses and behavioral data suggest that populations with temperature-dependent sex determination may be unable to evolve rapidly enough to counteract the negative fitness consequences of rapid global temperature change. Populations of species with temperature-dependent sex determination may serve as ideal indicators of the biological impact of global temperature change. PMID:8052608

  19. Influence of multi-deposition multi-annealing on time-dependent dielectric breakdown characteristics of PMOS with high-k/metal gate last process

    NASA Astrophysics Data System (ADS)

    Wang, Yan-Rong; Yang, Hong; Xu, Hao; Wang, Xiao-Lei; Luo, Wei-Chun; Qi, Lu-Wei; Zhang, Shu-Xiang; Wang, Wen-Wu; Yan, Jiang; Zhu, Hui-Long; Zhao, Chao; Chen, Da-Peng; Ye, Tian-Chun

    2015-11-01

    A multi-deposition multi-annealing technique (MDMA) is introduced into the process of high-k/metal gate MOSFET for the gate last process to effectively reduce the gate leakage and improve the device’s performance. In this paper, we systematically investigate the electrical parameters and the time-dependent dielectric breakdown (TDDB) characteristics of positive channel metal oxide semiconductor (PMOS) under different MDMA process conditions, including the deposition/annealing (D&A) cycles, the D&A time, and the total annealing time. The results show that the increases of the number of D&A cycles (from 1 to 2) and D&A time (from 15 s to 30 s) can contribute to the results that the gate leakage current decreases by about one order of magnitude and that the time to fail (TTF) at 63.2% increases by about several times. However, too many D&A cycles (such as 4 cycles) make the equivalent oxide thickness (EOT) increase by about 1 Å and the TTF of PMOS worsen. Moreover, different D&A times and numbers of D&A cycles induce different breakdown mechanisms. Project supported by the National High Technology Research and Development Program of China (Grant No. SS2015AA010601) and the National Natural Science Foundation of China (Grant Nos. 61176091 and 61306129).

  20. Thermal fission rates with temperature dependent fission barriers

    NASA Astrophysics Data System (ADS)

    Zhu, Yi; Pei, J. C.

    2016-08-01

    Background: The fission processes of thermal excited nuclei are conventionally studied by statistical models which rely on inputs of phenomenological level densities and potential barriers. Therefore the microscopic descriptions of spontaneous fission and induced fission are very desirable for a unified understanding of various fission processes. Purpose: We propose to study the fission rates, at both low and high temperatures, with microscopically calculated temperature-dependent fission barriers and collective mass parameters. Methods: The fission barriers are calculated by the finite-temperature Skyrme-Hartree-Fock+BCS method. The mass parameters are calculated by the temperature-dependent cranking approximation. The thermal fission rates can be obtained by the imaginary free energy approach at all temperatures, in which fission barriers are naturally temperature dependent. The fission at low temperatures can be described mainly as a barrier-tunneling process. While the fission at high temperatures has to incorporate the reflection above barriers. Results: Our results of spontaneous fission rates reasonably agree with other studies and experiments. The temperature dependencies of fission barrier heights and curvatures have been discussed. The temperature dependent behaviors of mass parameters have also been discussed. The thermal fission rates from low to high temperatures with a smooth connection have been given by different approaches. Conclusions: Since the temperature dependencies of fission barrier heights and curvatures, and the mass parameters can vary rapidly for different nuclei, the microscopic descriptions of thermal fission rates are very valuable. Our studies without free parameters provide a consistent picture to study various fissions such as that in fast-neutron reactors, astrophysical environments, and fusion reactions for superheavy nuclei.

  1. Effects of Intercritical Annealing Temperature on Mechanical Properties of Fe-7.9Mn-0.14Si-0.05Al-0.07C Steel

    SciTech Connect

    Zhao, Xianming; Shen, Yongfeng; Qiu, Lina; Liu, Yandong; Sun, Xin; Zuo, Liang

    2014-12-09

    A medium Mn steel has been designed to achieve an excellent combination of strength and ductility based on the TRIP (Transformation Induced Plasticity) concept for automotive applications. Following six passes of hot rolling at 850 °C, the Fe-7.9Mn-0.14Si-0.05Al-0.07C (wt.%) steel was warm-rolled at 630 °C for seven passes and subsequently air cooled to room temperature. The sample was subsequently intercritically annealed at various temperatures for 30 min to promote the reverse transformation of martensite into austenite. The obtained results show that the highest volume fraction of austenite is 39% for the sample annealed at 600 °C. This specimen exhibits a yield stress of 910 MPa and a high ultimate tensile stress of 1600 MPa, with an elongation-to-failure of 0.29 at a strain rate of 1 × 10⁻³/s. The enhanced work-hardening ability of the investigated steel is closely related to martensitic transformation and the interaction of dislocations. Especially, the alternate arrangement of acicular ferrite (soft phase) and ultrafine austenite lamellae (50–200 nm, strong and ductile phase) is the key factor contributing to the excellent combination of strength and ductility. On the other hand, the as-warm-rolled sample also exhibits the excellent combination of strength and ductility, with elongation-to-failure much higher than those annealed at temperatures above 630 °C.

  2. Effects of color centers absorption on the spectrum of the temperature-dependent radiation-induced attenuation in fiber.

    PubMed

    Jin, Jing; Hou, Yunxia; Liu, Chunjing

    2015-02-01

    Spectra ranging from 800 to 1650 nm of the temperature-dependent radiation-induced attenuation (RIA) in the irradiated and sufficiently annealed fiber with germanium and phosphorous dopant has been measured. These RIA spectra were investigated based on the mechanism of color centers absorption. With the configurational coordinate model, these RIA spectra were decomposed by the absorption bands of three kinds of color centers. The effects of color centers absorption on the spectrum of temperature-dependent RIA is discussed by comparing the absorption intensity of different color centers at a same wavelength. Moreover, the temperature-dependent RIA of the fiber has been measured separately at 850, 1310, and 1550 nm. The measured results agreed well with the analysis of RIA spectra.

  3. Temperature dependent electrical transport of disordered reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Muchharla, Baleeswaraiah; Narayanan, T. N.; Balakrishnan, Kaushik; Ajayan, Pulickel M.; Talapatra, Saikat

    2014-06-01

    We report on the simple route for the synthesis of chemically reduced graphene oxide (rGO) using ascorbic acid (a green chemical) as a reducing agent. Temperature-dependent electrical transport properties of rGO thin films have been studied in a wide range (50 K T 400 K) of temperature. Electrical conduction in rGO thin films was displayed in two different temperature regimes. At higher temperatures, Arrhenius-like temperature dependence of resistance was observed indicating a band gap dominating transport behavior. At lower temperatures, the rGO sample showed a conduction mechanism consistent with Mott's two-dimensional variable range hopping (2D-VRH). An unsaturated negative magnetoresistance (MR) was observed up to 3 T field. A decrease in negative MR at high temperatures is attributed to the phonon scattering of charge carriers.

  4. Temperature dependence of the spin Hall angle and switching current in the nc-W(O)/CoFeB/MgO system with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Neumann, L.; Meier, D.; Schmalhorst, J.; Rott, K.; Reiss, G.; Meinert, M.

    2016-10-01

    We investigated the temperature dependence of the switching current for a perpendicularly magnetized CoFeB film deposited on a nanocrystalline tungsten film with large oxygen content: nc-W(O). The effective spin Hall angle | ΘSH eff | ≈ 0.22 is independent of temperature, whereas the switching current increases strongly at low temperature. The increase indicates that the current induced switching itself is thermally activated, in agreement with a recent theoretical prediction. The dependence of the switching current on the in-plane assist field suggests the presence of an interfacial Dzyaloshinskii-Moriya interaction with D ≈ 0.23 mJ/m2, intermediate between the Pt/CoFe and Ta/CoFe systems. We show that the nc-W(O) is insensitive to annealing, which makes this system a good choice for the integration into magnetic memory or logic devices that require a high-temperature annealing process during fabrication.

  5. Correlation between Pd metal thickness and thermally stable perpendicular magnetic anisotropy features in [Co/Pd]{sub n} multilayers at annealing temperatures up to 500 °C

    SciTech Connect

    An, Gwang Guk; Lee, Ja Bin; Yang, Seung Mo; Yoon, Kap Soo; Kim, Jae Hong; Chung, Woo Seong; Hong, Jin Pyo

    2015-02-15

    We examine highly stable perpendicular magnetic anisotropy (PMA) features of [Co/Pd]{sub 10} multilayers (MLs) versus Pd thickness at various ex-situ annealing temperatures. Thermally stable PMA characteristics were observed up to 500 °C, confirming the suitability of these systems for industrial applications at this temperature. Experimental observations suggest that the choice of equivalent Co and Pd layer thicknesses in a ML configuration ensures thermally stable PMA features, even at higher annealing temperatures. X-ray diffraction patterns and cross-sectional transmission electron microscopy images were obtained to determine thickness, post-annealing PMA behavior, and to explore the structural features that govern these findings.

  6. Simulated annealing versus quantum annealing

    NASA Astrophysics Data System (ADS)

    Troyer, Matthias

    Based on simulated classical annealing and simulated quantum annealing using quantum Monte Carlo (QMC) simulations I will explore the question where physical or simulated quantum annealers may outperform classical optimization algorithms. Although the stochastic dynamics of QMC simulations is not the same as the unitary dynamics of a quantum system, I will first show that for the problem of quantum tunneling between two local minima both QMC simulations and a physical system exhibit the same scaling of tunneling times with barrier height. The scaling in both cases is O (Δ2) , where Δ is the tunneling splitting. An important consequence is that QMC simulations can be used to predict the performance of a quantum annealer for tunneling through a barrier. Furthermore, by using open instead of periodic boundary conditions in imaginary time, equivalent to a projector QMC algorithm, one obtains a quadratic speedup for QMC, and achieve linear scaling in Δ. I will then address the apparent contradiction between experiments on a D-Wave 2 system that failed to see evidence of quantum speedup and previous QMC results that indicated an advantage of quantum annealing over classical annealing for spin glasses. We find that this contradiction is resolved by taking the continuous time limit in the QMC simulations which then agree with the experimentally observed behavior and show no speedup for 2D spin glasses. However, QMC simulations with large time steps gain further advantage: they ``cheat'' by ignoring what happens during a (large) time step, and can thus outperform both simulated quantum annealers and classical annealers. I will then address the question how to optimally run a simulated or physical quantum annealer. Investigating the behavior of the tails of the distribution of runtimes for very hard instances we find that adiabatically slow annealing is far from optimal. On the contrary, many repeated relatively fast annealing runs can be orders of magnitude faster for

  7. Stochastic annealing simulation of cascades in metals

    SciTech Connect

    Heinisch, H.L.

    1996-04-01

    The stochastic annealing simulation code ALSOME is used to investigate quantitatively the differential production of mobile vacancy and SIA defects as a function of temperature for isolated 25 KeV cascades in copper generated by MD simulations. The ALSOME code and cascade annealing simulations are described. The annealing simulations indicate that the above Stage V, where the cascade vacancy clusters are unstable,m nearly 80% of the post-quench vacancies escape the cascade volume, while about half of the post-quench SIAs remain in clusters. The results are sensitive to the relative fractions of SIAs that occur in small, highly mobile clusters and large stable clusters, respectively, which may be dependent on the cascade energy.

  8. Role Of Annealing Atmosphere On The Dielectric Properties Of La2NiMnO6

    NASA Astrophysics Data System (ADS)

    Sayed, Farheen N.; Achary, S. N.; Jayakumar, O. D.; Deshpande, S. K.; Shinde, A. B.; Krishna, P. S. R.; Tyagi, A. K.

    2010-12-01

    La2NiMnO6 (LNMO) was prepared by gel combustion method from nitrates using glycine as fuel followed by high temperature annealing. The prepared sample was annealed in O2, air and N2 and characterized by powder X-ray and neutron diffraction and dielectric measurements. Cation ordered monoclinic (P21/n) and rhombohedral (R-3) phases are observed in the as prepared sample and fraction of monoclinic phase increases on annealing in oxygen atmosphere. On annealing in inert atmosphere decomposition of the sample to manganese rich perovskite, La2NiO4 and NiO is observed. Temperature and frequency dependent permittivity (˜103) is observed in the sample annealed in air. The relative permittivity decreases significantly on annealing the sample in oxygen or N2.atmospher. The formation and annihilation of defects is attributed to the observed large permittivity of La2NiMnO6.

  9. Microstructure and Thermal Conductivity of the As-Cast and Annealed Al-Cu-Mg-Si Alloys in the Temperature Range from 25°C to 400° C

    NASA Astrophysics Data System (ADS)

    Zhang, Cong; Du, Yong; Liu, Shuhong; Liu, Shaojun; Jie, Wanqi; Sundman, Bosse

    2015-11-01

    Four Al-based Al-Cu-Mg-Si alloy ingots were prepared by electrical resistance furnace. Microstructures and phase identification of the alloys were investigated by using electron probe microanalysis and X-ray diffraction techniques, respectively. The temperature dependences of thermal diffusivity and thermal conductivity of the as-cast and annealed alloys were investigated within the temperature range from 25°C to 400° C, and the estimated thermal conductivity was correlated with the microstructure and (Al) matrix phase compositions of the alloys. According to the results, the thermal conductivity of Al-Cu-Mg-Si alloys increased with temperature. The formation of precipitates, which consumes solute elements in the (Al) phase, contributes to the improvement in thermal diffusivity and thermal conductivity of annealed Al-Cu-Mg-Si alloys. The complex interconnection precipitates with a lower thermal conductivity than (Al) phase may affect the continuity of the matrix phase in microstructure and decreasing the thermal conductivity of the alloys significantly.

  10. Identification of temperature-dependent thermal conductivity and experimental verification

    NASA Astrophysics Data System (ADS)

    Pan, Weizhen; Yi, Fajun; Zhu, Yanwei; Meng, Songhe

    2016-07-01

    A modified Levenberg-Marquardt method (LMM) for the identification of temperature-dependent thermal conductivity is proposed; the experiment and structure of the specimen for identification are also designed. The temperature-dependent thermal conductivities of copper C10200 and brass C28000 are identified to verify the effectiveness of the proposed identification method. The comparison between identified results and the measured data of laser flash diffusivity apparatus indicates the fine consistency and potential usage of the proposed method.

  11. Temperature Dependence of Thermopower in Strongly Correlated Multiorbital Systems

    SciTech Connect

    Sekino, M; Okamoto, Satoshi; Koshibae, W; Mori, Michiyasu; Maekawa, Sadamichi

    2014-01-01

    Temperature dependence of thermopower in the multiorbital Hubbard model is studied by using the dynamical mean-field theory with the non-crossing approximation impurity solver. It is found that the Coulomb interaction, the Hund coupling, and the crystal filed splitting bring about nonmonotonic temperature dependence of the hermopower, including its sign reversal. The implication of our theoretical results to some materials is discussed.

  12. Temperature and size-dependent Hamaker constants for metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Jiang, K.; Pinchuk, P.

    2016-08-01

    Theoretical values of the Hamaker constant have been calculated for metal nanoparticles using Lifshitz theory. The theory describes the Hamaker constant in terms of the permittivity of the interacting bodies. Metal nanoparticles exhibit an internal size effect that alters the dielectric permittivity of the particle when its size falls below the mean free path of the conducting electrons. This size dependence of the permittivity leads to size-dependence of the Hamaker constant for metal nanoparticles. Additionally, the electron damping and the plasma frequency used to model the permittivity of the particle exhibit temperature-dependence, which lead to temperature dependence of the Hamaker constant. In this work, both the size and temperature dependence for gold, silver, copper, and aluminum nanoparticles is demonstrated. The results of this study might be of interest for studying the colloidal stability of nanoparticles in solution.

  13. Temperature Dependence of Radiative and Nonradiative Rates from Time-Dependent Correlation Function Methods.

    PubMed

    Banerjee, Shiladitya; Baiardi, Alberto; Bloino, Julien; Barone, Vincenzo

    2016-02-01

    The temperature dependence of the rate constants in radiative and nonradiative decays from excited electronic states has been studied using a time-dependent correlation function approach in the framework of the adiabatic representation and the harmonic oscillator approximation. The present work analyzes the vibrational aspect of the processes, which gives rise to the temperature dependence, with the inclusion of mode-mixing, as well as of frequency change effects. The temperature dependence of the rate constants shows a contrasting nature, depending on whether the process has been addressed within the Franck-Condon approximation or beyond it. The calculation of the Duschinsky matrix and the shift vector between the normal modes of the two states can be done in Cartesian and/or internal coordinates, depending on the flexibility of the investigated molecule. A new computational code has been developed to calculate the rates of intersystem crossing, internal conversion, and fluorescence for selected molecules as functions of temperature. PMID:26683207

  14. The temperature dependence of electrical excitability in fish hearts.

    PubMed

    Vornanen, Matti

    2016-07-01

    Environmental temperature has pervasive effects on the rate of life processes in ectothermic animals. Animal performance is affected by temperature, but there are finite thermal limits for vital body functions, including contraction of the heart. This Review discusses the electrical excitation that initiates and controls the rate and rhythm of fish cardiac contraction and is therefore a central factor in the temperature-dependent modulation of fish cardiac function. The control of cardiac electrical excitability should be sensitive enough to respond to temperature changes but simultaneously robust enough to protect against cardiac arrhythmia; therefore, the thermal resilience and plasticity of electrical excitation are physiological qualities that may affect the ability of fishes to adjust to climate change. Acute changes in temperature alter the frequency of the heartbeat and the duration of atrial and ventricular action potentials (APs). Prolonged exposure to new thermal conditions induces compensatory changes in ion channel expression and function, which usually partially alleviate the direct effects of temperature on cardiac APs and heart rate. The most heat-sensitive molecular components contributing to the electrical excitation of the fish heart seem to be Na(+) channels, which may set the upper thermal limit for the cardiac excitability by compromising the initiation of the cardiac AP at high temperatures. In cardiac and other excitable cells, the different temperature dependencies of the outward K(+) current and inward Na(+) current may compromise electrical excitability at temperature extremes, a hypothesis termed the temperature-dependent depression of electrical excitation. PMID:27385752

  15. Temperature dependence of photovoltaic cells, modules, and systems

    SciTech Connect

    Emery, K.; Burdick, J.; Caiyem, Y.

    1996-05-01

    Photovoltaic (PV) cells and modules are often rated in terms of a set of standard reporting conditions defined by a temperature, spectral irradiance, and total irradiance. Because PV devices operates over a wide range of temperatures and irradiances, the temperature and irradiance related behavior must be known. This paper surveys the temperature dependence of crystalline and thin-film, state-of-the-art, research-size cells, modules, and systems measured by a variety of methods. The various error sources and measurement methods that contribute to cause differences in the temperature coefficient for a given cell or module measured with various methods are discussed.

  16. Temperature dependence of helium diffusion through common epoxies

    NASA Astrophysics Data System (ADS)

    Lovinger, D. J.; Hallock, R. B.

    2012-12-01

    Helium gas at room temperature is known to diffuse through the epoxies commonly used in various low temperature applications, which can complicate leak detection. The helium flux typically decreases with decreasing temperature. We have measured the flux of helium that passes though thin sections of as-cast clear Stycast 1266, Stycast 2850FT (black) and TRA-BOND 2151 (blue) epoxies as a function of temperature in the range 130K < T < 300K. We analyze the data to create normalized (to constant sample thickness and pressure differential) data for comparison. We report the preliminary temperature-dependent fluxes we have measured, which show significant differences among the epoxies studied.

  17. Temperature dependent droplet impact dynamics on flat and textured surfaces

    SciTech Connect

    Azar Alizadeh; Vaibhav Bahadur; Sheng Zhong; Wen Shang; Ri Li; James Ruud; Masako Yamada; Liehi Ge; Ali Dhinojwala; Manohar S Sohal

    2012-03-01

    Droplet impact dynamics determines the performance of surfaces used in many applications such as anti-icing, condensation, boiling and heat transfer. We study impact dynamics of water droplets on surfaces with chemistry/texture ranging from hydrophilic to superhydrophobic and across a temperature range spanning below freezing to near boiling conditions. Droplet retraction shows very strong temperature dependence especially for hydrophilic surfaces; it is seen that lower substrate temperatures lead to lesser retraction. Physics-based analyses show that the increased viscosity associated with lower temperatures can explain the decreased retraction. The present findings serve to guide further studies of dynamic fluid-structure interaction at various temperatures.

  18. A temperature dependent SPICE macro-model for power MOSFETs

    SciTech Connect

    Pierce, D.G.

    1991-01-01

    The power MOSFET SPICE Macro-Model has been developed suitable for use over the temperature range {minus}55 to 125 {degrees}C. The model is comprised of a single parameter set with temperature dependence accessed through the SPICE .TEMP card. SPICE parameter extraction techniques for the model and model predictive accuracy are discussed. 7 refs., 8 figs., 1 tab.

  19. Frequency and temperature dependence of dielectric properties of chicken meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric properties of chicken breast meat were measured with an open-ended coaxial-line probe between 200 MHz and 20 GHz at temperatures ranging from -20 degree C to +25 degree C. At a given temperature, the frequency dependence of the dielectric constant reveals two relaxations while those of th...

  20. Effect of the annealing temperature and ion-beam bombardment on the properties of solution-derived HfYGaO films as liquid crystal alignment layers

    SciTech Connect

    Park, Hong-Gyu; Lee, Yun-Gun; Jang, Sang Bok; Lee, Ju Hwan; Jeong, Hae-Chang; Seo, Dae-Shik; Oh, Byeong-Yun

    2015-11-15

    Hafnium yttrium gallium oxide (HfYGaO) films were applied to liquid crystal displays (LCDs) as liquid crystal (LC) alignment layers, replacing conventional polyimide (PI) layers. The HfYGaO alignment layers were prepared by fabricating solution-processed HfYGaO films, annealing them, and treating them with ion-beam (IB) irradiation. The authors studied the effects of annealing temperature and IB irradiation of the solution-derived HfYGaO films on the orientation of LC molecules. The LC molecules on the solution-derived HfYGaO films were homogeneously and uniformly aligned by IB irradiation, irrespective of the annealing temperature. Atomic force microscopy analyses revealed that the surface reformation of the HfYGaO films induced by IB irradiation strengthened the van der Waals force between the LC molecules and the HfYGaO films, leading to uniform LC alignment. Enhanced electro-optical characteristics were observed in the twisted-nematic (TN) LCDs based on IB-irradiated HfYGaO films compared with those of TN-LCDs based on PI layers, demonstrating the high application potential of the proposed solution-derived HfYGaO films as LC alignment layers.

  1. Impacts of annealing temperature on charge trapping performance in Zr0.5Hf0.5O2 for nonvolatile memory

    NASA Astrophysics Data System (ADS)

    Zhao, J. H.; Yan, X. B.; Li, Y. C.; Yang, T.; Jia, X. L.; Zhou, Z. Y.; Zhang, Y. Y.

    2016-10-01

    In this study, Zr0.5Hf0.5O2 films were fabricated on Si substrate and were annealed at different temperatures by rapid thermal annealing (RTA) process. The charge trapping memory devices based on Zr0.5Hf0.5O2/SiO2/Si simple structure were investigated in detail. The memory device annealing at 690 °C shows the best property with a memory window of 5.6 V under ±12 V sweeping voltages in its capacitance-voltage curve and a better retention property. The high resolved transmission electron microscopy shows the generated SiO2 working as tunneling layer after RTA process, whose thickness increases with the rise of temperature. Combined with the TEM results, the photoluminescence spectrum and in situ angle resolved photoemission spectroscopy results further verify that oxygen vacancies and inter-diffusion layer also play a crucial role in charge trapping performance. This work provides direct insights for the charge trapping mechanisms based on high-k Zr0.5Hf0.5O2 films devices.

  2. Low-temperature (˜180 °C) position-controlled lateral solid-phase crystallization of GeSn with laser-anneal seeding

    NASA Astrophysics Data System (ADS)

    Matsumura, Ryo; Chikita, Hironori; Kai, Yuki; Sadoh, Taizoh; Ikenoue, Hiroshi; Miyao, Masanobu

    2015-12-01

    To realize next-generation flexible thin-film devices, solid-phase crystallization (SPC) of amorphous germanium tin (GeSn) films on insulating substrates combined with seeds formed by laser annealing (LA) has been investigated. This technique enables the crystallization of GeSn at controlled positions at low temperature (˜180 °C) due to the determination of the starting points of crystallization by LA seeding and Sn-induced SPC enhancement. The GeSn crystals grown by SPC from LA seeds showed abnormal lateral profiles of substitutional Sn concentration. These lateral profiles are caused by the annealing time after crystallization being a function of distance from the LA seeds. This observation of a post-annealing effect also indicates that GeSn with a substitutional Sn concentration of up to ˜10% possesses high thermal stability. These results will facilitate the fabrication of next-generation thin-film devices on flexible plastic substrates with low softening temperatures (˜250 °C).

  3. Temperature dependence of the diffusion coefficient of nanoparticles

    NASA Astrophysics Data System (ADS)

    Rudyak, V. Ya.; Dubtsov, S. N.; Baklanov, A. M.

    2008-06-01

    The temperature dependence of the diffusion coefficient of nanoparticles in gases has been experimentally studied. It is established that this dependence significantly differs from that predicted by various correlations, in particular, by the Cunningham-Millikan-Davies correlation that is used as an instrumental basis for virtually all methods of measurement of the diffusion coefficient in aerosols.

  4. Temperature Dependence of Viscosities of Common Carrier Gases

    ERIC Educational Resources Information Center

    Sommers, Trent S.; Nahir, Tal M.

    2005-01-01

    Theoretical and experimental evidence for the dependence of viscosities of the real gases on temperature is described, suggesting that this dependence is greater than that predicted by the kinetic theory of gases. The experimental results were obtained using common modern instrumentation and could be reproduced by students in analytical or…

  5. Accumulation and annealing of radiation defects under low-temperature electron and neutron irradiation of ODS steel and Fe-Cr alloys

    NASA Astrophysics Data System (ADS)

    Arbuzov, V. L.; Goshchitskii, B. N.; Sagaradze, V. V.; Danilov, S. E.; Kar'kin, A. E.

    2010-10-01

    The processes of accumulation and annealing of radiation defects at low-temperature (77 K) electron and neutron irradiation and their effect on the physicomechanical properties of Fe-Cr alloys and oxide dispersion strengthened (ODS) steel have been studied. It has been shown that the behavior of radiation defects in ODS steel and Fe-Cr alloys is qualitatively similar. Above 250 K, radiation-induced processes of the solid solution decomposition become conspicuous. These processes are much less pronounced in ODS steel because of specific features of its microstructure. Processes related to the overlapping of displacement cascades under neutron irradiation have been considered. It has been shown that, in this case, it is the increase in the size of vacancy clusters, rather than the growth of their concentration, that is prevailing. Possible mechanisms of the radiation hardening of the ODS steel and the Fe-13Cr alloy upon irradiation and subsequent annealing have been discussed.

  6. Realization of atomically flat steps and terraces like surface of SrTiO3 (001) single crystal by hot water etching and high temperature annealing

    NASA Astrophysics Data System (ADS)

    Prakash, Bhanu; Chakraverty, S.

    2015-07-01

    We have successfully prepared atomically flat single-terminated SrTiO3(001) surface using a mild and reproducible etching technique combined with high temperature annealing. To achieve single terminated surface, deionised water at 60 °C was used to selectively etch SrO composites from the substrate surface. A clear step-and-terrace like surface morphology is observed by subsequent air annealing at 1000 °C. Atomic Force Microscopy suggests the step height (~0.4 nm) corresponding to the lattice parameter of SrTiO3, which confirms the formation of single-terminated surface. This chemical-free mild etching technique might be useful to prepare single-terminated surface, especially for the perovskites containing reactive elements.

  7. Low-temperature Raman spectroscopy of copper and silver nanoparticles ion-synthesized in a silica glass and subjected to laser annealing

    NASA Astrophysics Data System (ADS)

    Kurbatova, N. V.; Galyautdinov, M. F.; Shtyrkov, E. I.; Nuzhdin, V. I.; Stepanov, A. L.

    2010-06-01

    The modification of the shape of ion-synthesized silver and copper nanoparticles in a silica glass during laser annealing has been studied for the first time by Raman spectroscopy at a temperature of 77 K. The laser annealing has been carried out for a wavelength of 694 nm at the edge of the plasmon absorption spectrum of nanoparticles. A comparison of the experimental spectra and the calculated modes of in-phase bending vibrations of the “harmonica” type in nanostrings of the corresponding metals has demonstrated their good agreement. The effects observed have been discussed from the standpoint of the size quantization of vibrations in metal nanowires. This methodical approach has made it possible to estimate the sizes of the Ag and Cu nanoparticles under the assumption that they have an elongated form; in this case, their average lengths are equal to 2.5 and 1.4 nm, respectively.

  8. The temperature dependent amide I band of crystalline acetanilide

    NASA Astrophysics Data System (ADS)

    Cruzeiro, Leonor; Freedman, Holly

    2013-10-01

    The temperature dependent anomalous peak in the amide I band of crystalline acetanilide is thought to be due to self-trapped states. On the contrary, according to the present model, the anomalous peak comes from the fraction of ACN molecules strongly hydrogen-bonded to a neighboring ACN molecule, and its intensity decreases because, on average, this fraction decreases as temperature increases. This model provides, for the first time, an integrated and theoretically consistent view of the temperature dependence of the full amide I band and a qualitative explanation of some of the features of nonlinear pump-probe experiments.

  9. TEMPERATURE DEPENDENCE OF THERMAL NEUTRONS FROM THE MOON

    SciTech Connect

    R.C. LITTLE; W. FELDMAN; ET AL

    2000-10-01

    Planetary thermal neutron fluxes provide a sensitive proxy for mafic and feldspathic terranes, and are also necessary for translating measured gamma-ray line strengths to elemental abundances. Both functions require a model for near surface temperatures and a knowledge of the dependence of thermal neutron flux on temperature. We have explored this dependence for a representative sample of lunar soil compositions and surface temperatures using MCNP{trademark}. For all soil samples, the neutron density is found to be independent of temperature, in accord with neutron moderation theory. The thermal neutron flux, however, does vary with temperature in a way that depends on {Delta}, the ratio of macroscopic absorption to energy-loss cross sections of soil compositions. The weakest dependence is for the largest {Delta} (which corresponds to the Apollo 17 high Ti basalt in our soil selection), and the largest dependence is for the lowest {Delta} (which corresponds to ferroan anorthosite, [FAN] in our selection). For the lunar model simulated, the depth at which the thermal neutron population is most sensitive to temperature is {approx}30 g/cm{sup 2}.

  10. Temperature dependence of acoustic impedance for specific fluorocarbon liquids.

    PubMed

    Marsh, Jon N; Hall, Christopher S; Wickline, Samuel A; Lanza, Gregory M

    2002-12-01

    Recent studies by our group have demonstrated the efficacy of perfluorocarbon liquid nanoparticles for enhancing the reflectivity of tissuelike surfaces to which they are bound. The magnitude of this enhancement depends in large part on the difference in impedances of the perfluorocarbon, the bound substrate, and the propagating medium. The impedance varies directly with temperature because both the speed of sound and the mass density of perfluorocarbon liquids are highly temperature dependent. However, there are relatively little data in the literature pertaining to the temperature dependence of the acoustic impedance of these compounds. In this study, the speed of sound and density of seven different fluorocarbon liquids were measured at specific temperatures between 20 degrees C and 45 degrees C. All of the samples demonstrated negative, linear dependencies on temperature for both speed of sound and density and, consequently, for the acoustic impedance. The slope of sound speed was greatest for perfluorohexane (-278 +/- 1.5 cm/s-degrees C) and lowest for perfluorodichlorooctane (-222 +/- 0.9 cm/s-degrees C). Of the compounds measured, perfluorohexane exhibited the lowest acoustic impedance at all temperatures, and perfluorodecalin the highest at all temperatures. Computations from a simple transmission-line model used to predict reflectivity enhancement from surface-bound nanoparticles are discussed in light of these results.

  11. Temperature dependence of the electrical resistivity and the anisotropic magnetoresistance (AMR) of electrodeposited Ni-Co alloys

    NASA Astrophysics Data System (ADS)

    Tóth, B. G.; Péter, L.; Révész, Á.; Pádár, J.; Bakonyi, I.

    2010-05-01

    The electrical resistivity and the anisotropic magnetoresistance (AMR) was investigated for Ni-Co alloys at and below room temperature. The Ni-Co alloy layers having a thickness of about 2 μm were prepared by electrodeposition on Si wafers with evaporated Cr and Cu underlayers. The alloy composition was varied in the whole concentration range by varying the ratio of Ni-sulfate and Co-sulfate in the electrolyte. The Ni-Co alloy deposits were investigated first in the as-deposited state on the substrates and then, by mechanically stripping them from the substrates, as self-supporting layers both without and after annealing. According to an X-ray diffraction study, a strongly textured face-centered cubic (fcc) structure was formed in the as-deposited state with an average grain size of about 10 nm. Upon annealing, the crystal structure was retained whereas the grain size increased by a factor of 3 to 5, depending on alloy composition. The zero-field resistivity decreased strongly by annealing due to the increased grain size. The annealing hardly changed the AMR below 50 at.% Co but strongly decreased it above this concentration. The composition dependence of the resistivity and the AMR of the annealed Ni-Co alloy deposits was in good quantitative agreement with the available literature data both at 13 K and at room temperature. Both transport parameters were found to exhibit a pronounced maximum in the composition range between 20 and 30 at.% Co and the data of the Ni-Co alloys fitted well to the limiting values of the pure component metals (fcc-Ni and fcc-Co). The only theoretical calculation reported formerly on fcc Ni-Co alloys yielded at T = 0 K a resistivity value smaller by a factor of 5 and an AMR value larger by a factor of about 2 than the corresponding low-temperature experimental data, although the theoretical study properly reproduced the composition dependence of both quantities.

  12. AlN bandgap temperature dependence from its optical properties

    NASA Astrophysics Data System (ADS)

    Silveira, E.; Freitas, J. A.; Schujman, S. B.; Schowalter, L. J.

    2008-08-01

    In the present work we report on the AlN gap energy temperature dependence studied through the optical properties of high-quality large bulk AlN single crystals grown by a sublimation-recondensation technique. The cathodoluminescence, transmission/absorption as well as optical reflectance measurements at low temperature show a clear feature at about 6.03 eV, which could be attributed to the free exciton A. Even using a rather thick sample it was possible to observe the absorption due to the free exciton A in this energy range due to its large binding energy. We followed the temperature evolution of these features up to room temperature and inferred the gap energy temperature dependence using the exciton binding energy obtained by our group in the past.

  13. Controlled fabrication of Si nanostructures by high vacuum electron beam annealing

    NASA Astrophysics Data System (ADS)

    Fang, F.; Markwitz, A.

    2009-10-01

    Silicon nanostructures, called Si nanowhiskers, have been successfully synthesized on Si(1 0 0) substrate by high vacuum electron beam annealing (EBA). Detailed analysis of the Si nanowhisker morphology depending on annealing temperature, duration and the temperature gradients applied in the annealing cycle is presented. A correlation was found between the variation in annealing temperature and the nanowhisker height and density. Annealing at 935 °C for 0 s, the density of nanowhiskers is about 0.2 μm -2 with average height of 2.4 nm grow on a surface area of 5×5 μm, whereas more than 500 nanowhiskers (density up to 28 μm -2) with an important average height of 4.6 nm for field emission applications grow on the same surface area for a sample annealed at 970 °C for 0 s. At a cooling rate of -50 °C s -1 during the annealing cycle, 10-12 nanowhiskers grew on a surface area of 5×5 μm, whereas close to 500 nanowhiskers grew on the same surface area for samples annealed at the cooling rate of -5 °C s -1. An exponential dependence between the density of Si nanowhiskers and the cooling rate has been found. At 950 °C, the average height of Si nanowhiskers increased from 4.0 to 6.3 nm with an increase of annealing duration from 10 to 180 s. A linear dependence exists between the average height of Si nanowhiskers and annealing duration. Selected results are presented showing the possibility of controlling the density and the height of Si nanowhiskers for improved field emission properties by applying different annealing temperatures, durations and cooling rates.

  14. Temperature Dependence of Surface Layering in a Dielectric Liquid

    SciTech Connect

    Mo,H.; Kewalramani, S.; Evmenenko, G.; Kim, K.; Ehrlich, S.; Dutta, P.

    2007-01-01

    The temperature dependence of the density oscillations (layers) at the free surface of tetrakis(2-ethylhexoxy)silane, a nonmetallic molecular liquid, was investigated using x-ray reflectivity. Below {approx}215K , the layer parameters weakly vary with temperature, if at all. Above this temperature, the layer spacings and intrinsic layer widths increase continuously, until there is no identifiable layering above 230K . This transition occurs at T/{Tc}{approx}0.23 , a temperature region that is usually accessible in metallic liquids but is preempted by freezing in many dielectric liquids.

  15. Temperature dependence of the water retention curve for dry soils

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Goss, K.-U.

    2011-03-01

    Water retention curves (WRCs) are equivalent to water adsorption isotherms that display the soil water content as a function of water activity in the pore space. The use of water activity implies that pure (unbound) water at the given temperature is considered to be a reference state. In this study we measured the temperature dependence of WRCs for nine European soils under dry conditions (i.e., water activity < 90% relative humidity (RH), matrix tension <-1.5 MPa). The results show a significant temperature dependence of the WRCs. The absolute value of the adsorption enthalpy of water, ?, which reflects this temperature dependence, increased with decreasing water content and thus deviated from the condensation enthalpy of a pure (unbound) water phase, ?. These results are explained by the following facts: under increasingly drier conditions the interactions between water molecules and the mineral surfaces become more and more dominant because the sorbed water film becomes very thin. These interactions between water and minerals are stronger than those between pure water molecules. The observed temperature dependence of WRCs varied only a little between the studied soils. Therefore, the average equation, ?, derived from our experimental data may serve as a good approximation of ? for soils in general and thus allow the temperature extrapolation of WRCs (in the dry region down to 30% RH) between 5°C and 40°C without the need for additional experimental information.

  16. Arrhenius temperature dependence of in vitro tissue plasminogen activator thrombolysis

    NASA Astrophysics Data System (ADS)

    Shaw, George J.; Dhamija, Ashima; Bavani, Nazli; Wagner, Kenneth R.; Holland, Christy K.

    2007-06-01

    Stroke is a devastating disease and a leading cause of death and disability. Currently, the only FDA approved therapy for acute ischemic stroke is the intravenous administration of the thrombolytic medication, recombinant tissue plasminogen activator (tPA). However, this treatment has many contraindications and can have dangerous side effects such as intra-cerebral hemorrhage. These treatment limitations have led to much interest in potential adjunctive therapies, such as therapeutic hypothermia (T <= 35 °C) and ultrasound enhanced thrombolysis. Such interest may lead to combining these therapies with tPA to treat stroke, however little is known about the effects of temperature on the thrombolytic efficacy of tPA. In this work, we measure the temperature dependence of the fractional clot mass loss Δm(T) resulting from tPA exposure in an in vitro human clot model. We find that the temperature dependence is well described by an Arrhenius temperature dependence with an effective activation energy Eeff of 42.0 ± 0.9 kJ mole-1. Eeff approximates the activation energy of the plasminogen-to-plasmin reaction of 48.9 kJ mole-1. A model to explain this temperature dependence is proposed. These results will be useful in predicting the effects of temperature in future lytic therapies.

  17. Temperature dependence of proton relaxation times in vitro.

    PubMed

    Nelson, T R; Tung, S M

    1987-01-01

    Accurate measurement of tissue relaxation characteristics is dependent on many factors, including field strength and temperature. The purpose of this study was to evaluate the relationship between sample temperature, viscosity and proton spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). A review of two basic models of relaxation the simple molecular motion model and the fast exchange two state model is given with reference to their thermal dependencies. The temperature dependence for both T1 and T2 was studied on a 0.15 Tesla whole body magnetic resonance imager. Thirteen samples comprising both simple and complex materials were investigated by using a standard spin-echo (SE) technique and a modified Carr-Purcell-Meiboom-Gill (CPMG) multi-echo sequence. A simple linear relationship between T1 and temperature was observed for all samples over the range of 20 degrees C to 50 degrees C. There is an inverse relationship between viscosity and T1 and T2. A quantity called the temperature dependence coefficient (TDC) is introduced and defined as the percent rate of change of the proton relaxation time referenced to a specific temperature. The large TDC found for T1 values, e.g. 2.37%/degrees C for CuSO4 solutions and 3.59%/degrees C for light vegetable oils at 22 degrees C, indicates that a temperature correction should be made when comparing in-vivo and in-vitro T1 times. The T2 temperature dependence is relatively small. PMID:3041151

  18. Effect of the annealing temperature on the long-term thermal stability of Pt/Si/Ta/Ti/4H-SiC contacts

    NASA Astrophysics Data System (ADS)

    Cheng, Yue; Zhao, Gao-Jie; Liu, Yi-Hong; Sun, Yu-Jun; Wang, Tao; Chen, Zhi-Zhan

    2015-10-01

    The Pt/Si/Ta/Ti multilayer metal contacts on 4H-SiC are annealed in Ar atmosphere at 600 °C-1100 °C by a rapid thermal processor (RTP). The long-term thermal stability is evaluated by aging the annealed contact at 600 °C in air. The contact’s properties are determined by current-voltage measurement, and the specific contact resistance is calculated based on the transmission line model (TLM). Transmission electron microscope (TEM) and energy-dispersive x-ray spectrometry (EDX) are used to characterize the interface morphology, thickness, and composition. The results reveal that a higher annealing temperature is favorable for the formation of an Ohmic contact with a lower specific contact resistance, and causes the rapid degradation of the Ohmic contact in the aging process. Project supported by the Special Prophase Project on the National Basic Research Program of China (Grant No. 2012CB326402), the National Natural Science Found of China (Grant No. 61404085), the Innovation Program of Shanghai Municipal Education Commission, China (Grant No. 13ZZ108), and the Shanghai Science and Technology Commission, China (Grant No. 13520502700).

  19. Substrate-dependent temperature sensitivity of soil organic matter decomposition

    NASA Astrophysics Data System (ADS)

    Myachina, Olga; Blagodatskaya, Evgenia

    2015-04-01

    Activity of extracellular enzymes responsible for decomposition of organics is substrate dependent. Quantity of the substrate is the main limiting factor for enzymatic or microbial heterotrophic activity in soils. Different mechanisms of enzymes response to temperature suggested for low and high substrate availability were never proved for real soil conditions. We compared the temperature responses of enzymes-catalyzed reactions in soils. Basing on Michaelis-Menten kinetics we determined the enzymes affinity to substrate (Km) and mineralization potential of heterotrophic microorganisms (Vmax) 1) for three hydrolytic enzymes: β-1,4-glucosidase, N-acetyl- β -D-glucosaminidase and phosphatase by the application of fluorogenically labeled substrates and 2) for mineralization of 14C-labeled glucose by substrate-dependent respiratory response. Here we show that the amount of available substrate is responsible for temperature sensitivity of hydrolysis of polymers in soil, whereas monomers oxidation to CO2 does not depend on substrate amount and is mainly temperature governed. We also found that substrate affinity of enzymes (which is usually decreases with the temperature) differently responded to warming for the process of depolymerisation versus monomers oxidation. We suggest the mechanism to temperature acclimation based on different temperature sensitivity of enzymes kinetics for hydrolysis of polymers and for monomers oxidation.

  20. Temperature Dependent Constitutive Modeling for Magnesium Alloy Sheet

    SciTech Connect

    Lee, Jong K.; Lee, June K.; Kim, Hyung S.; Kim, Heon Y.

    2010-06-15

    Magnesium alloys have been increasingly used in automotive and electronic industries because of their excellent strength to weight ratio and EMI shielding properties. However, magnesium alloys have low formability at room temperature due to their unique mechanical behavior (twinning and untwining), prompting for forming at an elevated temperature. In this study, a temperature dependent constitutive model for magnesium alloy (AZ31B) sheet is developed. A hardening law based on non linear kinematic hardening model is used to consider Bauschinger effect properly. Material parameters are determined from a series of uni-axial cyclic experiments (T-C-T or C-T-C) with the temperature ranging 150-250 deg. C. The influence of temperature on the constitutive equation is introduced by the material parameters assumed to be functions of temperature. Fitting process of the assumed model to measured data is presented and the results are compared.

  1. Temperature dependence of the Soret coefficient of ionic colloids

    NASA Astrophysics Data System (ADS)

    Sehnem, A. L.; Figueiredo Neto, A. M.; Aquino, R.; Campos, A. F. C.; Tourinho, F. A.; Depeyrot, J.

    2015-10-01

    The temperature dependence of the Soret coefficient ST(T ) in electrostatically charged magnetic colloids is investigated. Two different ferrofluids, with different particles' mean dimensions, are studied. In both cases we obtain a thermophilic behavior of the Soret effect. The temperature dependence of the Soret coefficient is described assuming that the nanoparticles migrate along the ionic thermoelectric field created by the thermal gradient. A model based on the contributions from the thermoelectrophoresis and variation of the double-layer energy, without fitting parameters, is used to describe the experimental results of the colloid with the bigger particles. To do so, independent measurements of the ζ potential, mass diffusion coefficient, and Seebeck coefficient are performed. The agreement of the theory and the experimental results is rather good. In the case of the ferrofluid with smaller particles, it is not possible to get experimentally reliable values of the ζ potential and the model described is used to evaluate this parameter and its temperature dependence.

  2. On the detection of precipitation dependence on temperature

    NASA Astrophysics Data System (ADS)

    Zhou, Yu; Luo, Ming; Leung, Yee

    2016-05-01

    Employing their newly proposed interannual difference method (IADM), Liu et al. (2009) and Shiu et al. (2012) reported a shocking increase of around 100% K-1 in heavy precipitation with warming global temperature in 1979-2007. Such increase is alarming and prompts us to probe into the IADM. In this study, both analytical derivations and numerical analyses demonstrate that IADM provides no additional information to that of the conventional linear regression, and also, it may give a false indication of dependence. For clarity and simplicity, we therefore recommend linear regression analysis over the IADM for the detection of dependence. We also find that heavy precipitation decreased during the global warming hiatus, and the precipitation dependence on temperature drops by almost 50% when the study period is extended to 1979-2014 and it may keep dropping in the near future. The risk of having heavy precipitation under warming global temperature may have been overestimated.

  3. Diversity of electronic transitions and photoluminescence properties of p-type cuprous oxide films: A temperature-dependent spectral transmittance study

    SciTech Connect

    Yu, W. L. E-mail: zghu@ee.ecnu.edu.cn; Lin, Y. Z.; Zhu, X. W.; Cai, S. S.; Chen, L. L.; Shao, H. H.; Hu, Z. G. E-mail: zghu@ee.ecnu.edu.cn; Han, M. J.

    2015-01-28

    Cuprous oxide films have been deposited on quartz substrates by a sol-gel method under various annealing temperatures. The X-ray diffraction analysis and Raman scattering show that all the films are of pure Cu{sub 2}O phase. From comparison of photoluminescence with 488 and 325 nm laser excitations, the electronic transition energies and intensities present the annealing-temperature dependent behavior. The electronic band structures of the Cu{sub 2}O film annealed at 800 °C, especially for the contribution of exciton series and high energy transitions, have been investigated by temperature dependent transmittance. The extracted refraction index and the high frequency dielectric constant both abruptly decrease until the temperature rises up to 100 K. Six transitions can be clearly identified and the red shift trend of E{sub o3}-E{sub o5} transition energies with increasing the temperature can be found. Moreover, the anomalous behavior takes place at about 200 K from the E{sub o6} transition. The singularities indicate that the change in the crystalline and electronic band structure occurs as the temperature near 100 K and 200 K for the film.

  4. Annealing Mechanism and Effect of Microwave Plasma Assisted Annealing on Properties of Sputtered Pb(Zr0.52Ti0.48)O3 Thin Films.

    PubMed

    Wan, Jing; Yang, Chengtao; He, Ming

    2016-03-01

    To solve some problems existing in PZT films, such as: large residual stresses, interface diffusion, and lead loss, etc., which were caused by high post-annealing temperatures, and to obtain thin films with high-preferred orientation and uniform size grain and dense microstructure, different technological conditions of microwave plasma assisted post-annealing had been pilot studied. X-ray diffraction was used to analyze the crystal structures of the films. Transmission electronic microscope was used to analyze the surface and the interface morphology of the films. Ferroelectric properties were showed by measuring the remnant polarization and the leakage current dependence of electric field. The results indicated that it was good for reducing lead loss and annealing temperature of PZT films by microwave plasma assisted annealing. Ferroelectric properties of the film could also be enhanced by this pilot annealing method.

  5. Annealing Mechanism and Effect of Microwave Plasma Assisted Annealing on Properties of Sputtered Pb(Zr0.52Ti0.48)O3 Thin Films.

    PubMed

    Wan, Jing; Yang, Chengtao; He, Ming

    2016-03-01

    To solve some problems existing in PZT films, such as: large residual stresses, interface diffusion, and lead loss, etc., which were caused by high post-annealing temperatures, and to obtain thin films with high-preferred orientation and uniform size grain and dense microstructure, different technological conditions of microwave plasma assisted post-annealing had been pilot studied. X-ray diffraction was used to analyze the crystal structures of the films. Transmission electronic microscope was used to analyze the surface and the interface morphology of the films. Ferroelectric properties were showed by measuring the remnant polarization and the leakage current dependence of electric field. The results indicated that it was good for reducing lead loss and annealing temperature of PZT films by microwave plasma assisted annealing. Ferroelectric properties of the film could also be enhanced by this pilot annealing method. PMID:27455722

  6. A new perspective on self-reversed thermo-remanent magnetization and room-temperature magnetic exchange bias in quenched and annealed ferri-ilmenite solid solutions

    NASA Astrophysics Data System (ADS)

    Robinson, P.; Harrison, R. J.; Fabian, K.; McEnroe, S. A.; Miyajima, N.

    2012-04-01

    In the 1950's, rocks containing ferri-ilmenite solid solutions with compositions X FeTiO3 = 0.53-0.71 were discovered to self-reverse during cooling in a weak field. Such samples played a vexing early role in the history of geomagnetism, because they demonstrably acquire a thermoremanent magnetization (TRM) inverse to the external field, strengthening a common opinion, at that time, that reversed lavas result from a rock-magnetic self-reversal process, while the geomagnetic field polarity itself is constant in time. Early self-reversal models postulated two distinct phases, a subsidiary phase with weak magnetization, and higher Fe content, Curie temperature, and coercivity, referred to as "the x phase", and a dominant phase with a strong magnetization, lower Fe content, Curie T temperature, and coercivity. The "x phase" magnetizes first at higher temperature parallel to the Earth field, and the dominant phase acquires a stronger magnetization at a lower temperature in an orientation opposite to the Earth field, either by direct antiferromagnetic coupling, or as a magnetostatic response to the previously acquired mineral magnetization. Landmark work by Nord and Lawson, on quench and annealing experiments with TEM, showed that, during quench, the solid solution starts to order, but with alternate A and B positioning of Fe and Ti layers. With coarsening, the alternately and chaotically positioned domains merge along antiphase domain boundaries (APBs) that are inherently unstable. With further annealing, boundaries move and are eliminated due to coarsening of some domains and shrinking of others. They showed that quenched, or slightly annealed samples, show self-reversed TRM, but further annealing results in a coarse simple ferrimagnetic phase. They suggested that the "x phase" is represented by the disordered regions along the chemical antiphase boundaries. Harrison visualized a solid solution sample, after quench and coarsening after annealing, which consisted of two

  7. Temperature dependence of protein hydration hydrodynamics by molecular dynamics simulations.

    SciTech Connect

    Lau, E Y; Krishnan, V V

    2007-07-18

    The dynamics of water molecules near the protein surface are different from those of bulk water and influence the structure and dynamics of the protein itself. To elucidate the temperature dependence hydration dynamics of water molecules, we present results from the molecular dynamic simulation of the water molecules surrounding two proteins (Carboxypeptidase inhibitor and Ovomucoid) at seven different temperatures (T=273 to 303 K, in increments of 5 K). Translational diffusion coefficients of the surface water and bulk water molecules were estimated from 2 ns molecular dynamics simulation trajectories. Temperature dependence of the estimated bulk water diffusion closely reflects the experimental values, while hydration water diffusion is retarded significantly due to the protein. Protein surface induced scaling of translational dynamics of the hydration waters is uniform over the temperature range studied, suggesting the importance protein-water interactions.

  8. Origins of the temperature dependence of hammerhead ribozyme catalysis.

    PubMed Central

    Peracchi, A

    1999-01-01

    The difficulties in interpreting the temperature dependence of protein enzyme reactions are well recognized. Here, the hammerhead ribozyme cleavage was investigated under single-turnover conditions between 0 and 60 degrees C as a model for RNA-catalyzed reactions. Under the adopted conditions, the chemical step appears to be rate-limiting. However, the observed rate of cleavage is affected by pre-catalytic equilibria involving deprotonation of an essential group and binding of at least one low-affinity Mg2+ion. Thus, the apparent entropy and enthalpy of activation include contributions from the temperature dependence of these equilibria, precluding a simple physical interpretation of the observed activation parameters. Similar pre-catalytic equilibria likely contribute to the observed activation parameters for ribozyme reactions in general. The Arrhenius plot for the hammerhead reaction is substantially curved over the temperature range considered, which suggests the occurrence of a conformational change of the ribozyme ground state around physiological temperatures. PMID:10390528

  9. Temperature-dependent absorption cross sections for hydrogen peroxide vapor

    NASA Technical Reports Server (NTRS)

    Nicovich, J. M.; Wine, P. H.

    1988-01-01

    Relative absorption cross sections for hydrogen peroxide vapor were measured over the temperature ranges 285-381 K for lambda = 230 nm-295 nm and 300-381 K for lambda = 193 nm-350 nm. The well established 298 K cross sections at 202.6 and 228.8 nm were used as an absolute calibration. A significant temperature dependence was observed at the important tropospheric photolysis wavelengths lambda over 300 nm. Measured cross sections were extrapolated to lower temperatures, using a simple model which attributes the observed temperature dependence to enhanced absorption by molecules possessing one quantum of O-O stretch vibrational excitation. Upper tropospheric photodissociation rates calculated using the extrapolated cross sections are about 25 percent lower than those calculated using currently recommended 298 K cross sections.

  10. Temperature dependence of DNA translocations through solid-state nanopores.

    PubMed

    Verschueren, Daniel V; Jonsson, Magnus P; Dekker, Cees

    2015-06-12

    In order to gain a better physical understanding of DNA translocations through solid-state nanopores, we study the temperature dependence of λ-DNA translocations through 10 nm diameter silicon nitride nanopores, both experimentally and theoretically. The measured ionic conductance G, the DNA-induced ionic-conductance blockades [Formula: see text] and the event frequency Γ all increase with increasing temperature while the DNA translocation time τ decreases. G and [Formula: see text] are accurately described when bulk and surface conductances of the nanopore are considered and access resistance is incorporated appropriately. Viscous drag on the untranslocated part of the DNA coil is found to dominate the temperature dependence of the translocation times and the event rate is well described by a balance between diffusion and electrophoretic motion. The good fit between modeled and measured properties of DNA translocations through solid-state nanopores in this first comprehensive temperature study, suggest that our model captures the relevant physics of the process.

  11. Temperature and Depth Dependence of Order in Liquid Crystal Interfaces

    SciTech Connect

    Martinez-Miranda,L.; Hu, Y.

    2006-01-01

    We have studied the depth dependence and temperature behavior of the ordering of smectic-A films close to the smectic A-nematic transition, deposited on grated glass. X-ray grazing incidence geometry in reflection mode through the glass substrate was used to characterize the samples. Our results indicate the presence of a structure similar to the helical twist grain boundary phase. The structure has two maxima, one close to the glass-liquid crystal interface and another about 8 {mu}m above the surface. The structure at 8 {mu}m is the one that dominates at higher temperatures. In addition, we find that order is preserved to temperatures close to the nematic-isotropic transition temperature for the deeper gratings. We find also a dependence of the orientation of the structure with the depth of the grating and the elastic constant of the liquid crystal.

  12. Effect of annealing on the thermal properties of poly (lactic acid)/starch blends.

    PubMed

    Lv, Shanshan; Gu, Jiyou; Cao, Jun; Tan, Haiyan; Zhang, Yanhua

    2015-03-01

    A comparative study of the thermal behavior of PLA/starch blends annealed at different temperatures has been conducted. Annealing was found to be beneficial to weaken and even eliminate the enthalpy relaxation near Tg. The degree of crystallinity was evaluated by means of DSC, and the results showed that the crystallinity of the samples increased as the annealing temperatures were increased. It was observed that, during the annealing process, the disorder α (α') crystal modification tended to transform into the order α crystal modification. All of the PLA/starch blends showed a double melting behavior. With the increase of annealing temperatures, the lower Tm1 increased, while the Tm2 showed no evident change. The XRD patterns also showed that annealing was beneficial to the samples to form higher crystallinity. The TGA results indicated that the annealed samples did not show any higher thermal stability than the virgin samples. The activation energy calculated by the Flynn-Wall-Ozawa method at lower conversion degrees confirmed that the annealing slightly slowed the degradation. The activation energy did not show any dependence on the conversion degree, which indicated that there existed a complex degradation process of the PLA/starch blends. The average activation energy did not show obvious differences, indicating that the annealing treatment had little influence on the degradation activation energy.

  13. Temperature dependent sensor response caused by polymer-solvent interactions

    SciTech Connect

    Butler, M A

    1992-01-01

    Absorption of organic solvents by a range of polymers has been used as the chemical transduction mechanism for a variety of sensors. This paper examines the effect of the polymer-solvent interaction on the temperature dependence of the sensor response. Optical interferometric cavities are formed on the end of an optical fiber by plasma-deposition of a fluorocarbon polymer. Swelling of the polymer when exposed to various solvent vapors produces changes in the reflectivity of the fiber tip. The temperature dependence of the sensor response is related to the strength of the polymer-solvent interaction and the heat of vaporization of the solvent.

  14. Anomalous temperature dependence of the IR spectrum of polyalanine

    NASA Astrophysics Data System (ADS)

    Helenius, V.; Korppi-Tommola, J.; Kotila, S.; Nieminen, J.; Lohikoski, R.; Timonen, J.

    1997-12-01

    We have studied the temperature dependence of the infrared spectra of acetanilide (ACN), tryptophan-(alanine) 15, and tyrosine-(alanine) 15. No sidebands of the amide-I vibration were observed in the polypeptides, but two anomalous sidebands of the NH stretch with a similar temperature dependence as that of the anomalous amide-I vibrational mode at 1650 cm -1 of crystalline ACN were detected. Fermi resonance combined with the appearance of a red-shifted sideband of NH stretch through coupling to lattice modes seems to explain this band structure. Observations are indicative of excitons that may occur in polypeptides as well as in single crystals of ACN.

  15. Temperature dependence of VUV transmission of synthetic fused silica

    NASA Astrophysics Data System (ADS)

    Franke, St.; Lange, H.; Schoepp, H.; Witzke, H.-D.

    2006-07-01

    The temperature dependence of the VUV transmission of synthetic fused silica is of interest for commercial applications as well as for fundamental research. In this work the transmission properties of Suprasil 2 from Heraeus with an absorption edge at very low wavelengths is investigated. The absorption edge of this quartz glass shifts from 170 to 180 nm between 789 and 1129 K. The Urbach rule is discussed for the characterization of the temperature dependent transmission curves. The results are applied to the diagnostics of the Hg 185 nm line from a high pressure mercury discharge lamp.

  16. Effects of Intercritical Annealing Temperature on Mechanical Properties of Fe-7.9Mn-0.14Si-0.05Al-0.07C Steel

    DOE PAGES

    Zhao, Xianming; Shen, Yongfeng; Qiu, Lina; Liu, Yandong; Sun, Xin; Zuo, Liang

    2014-12-09

    A medium Mn steel has been designed to achieve an excellent combination of strength and ductility based on the TRIP (Transformation Induced Plasticity) concept for automotive applications. Following six passes of hot rolling at 850 °C, the Fe-7.9Mn-0.14Si-0.05Al-0.07C (wt.%) steel was warm-rolled at 630 °C for seven passes and subsequently air cooled to room temperature. The sample was subsequently intercritically annealed at various temperatures for 30 min to promote the reverse transformation of martensite into austenite. The obtained results show that the highest volume fraction of austenite is 39% for the sample annealed at 600 °C. This specimen exhibits amore » yield stress of 910 MPa and a high ultimate tensile stress of 1600 MPa, with an elongation-to-failure of 0.29 at a strain rate of 1 × 10⁻³/s. The enhanced work-hardening ability of the investigated steel is closely related to martensitic transformation and the interaction of dislocations. Especially, the alternate arrangement of acicular ferrite (soft phase) and ultrafine austenite lamellae (50–200 nm, strong and ductile phase) is the key factor contributing to the excellent combination of strength and ductility. On the other hand, the as-warm-rolled sample also exhibits the excellent combination of strength and ductility, with elongation-to-failure much higher than those annealed at temperatures above 630 °C.« less

  17. Temperature Dependence of Photosynthesis in Agropyron smithii Rydb. 1

    PubMed Central

    Monson, Russell K.; Stidham, Mark A.; Williams, George J.; Edwards, Gerald E.; Uribe, Ernest G.

    1982-01-01

    As part of an extensive analysis of the factors regulating photosynthesis in Agropyron smithii Rydb., a C3 grass, we have examined the response of leaf gas exchange and ribulose-1,5-bisphosphate (RuBP) carboxylase activity to temperature. Emphasis was placed on elucidating the specific processes which regulate the temperature response pattern. The inhibitory effects of above-optimal temperatures on net CO2 uptake were fully reversible up to 40°C. Below 40°C, temperature inhibition was primarily due to O2 inhibition of photosynthesis, which reached a maximum of 65% at 45°C. The response of stomatal conductance to temperature did not appear to have a significant role in determining the overall temperature response of photosynthesis. The intracellular conductance to CO2 increased over the entire experimental temperature range, having a Q10 of 1.2 to 1.4. Increases in the apparent Michaelis constant (Kc) for RuBP carboxylase were observed in both in vitro and in vivo assays. The Q10 values for the maximum velocity (Vmax) of CO2 fixation by RuBP carboxylase in vivo was lower (1.3-1.6) than those calculated from in vitro assays (1.8-2.2). The results suggest that temperature-dependent changes in enzyme capacity may have a role in above-optimum temperature limitations below 40°C. At leaf temperatures above 40°C, decreases in photosynthetic capacity were partially dependent on temperature-induced irreversible reductions in the quantum yield for CO2 uptake. PMID:16662320

  18. The temperature dependence of ponded infiltration under isothermal conditions

    USGS Publications Warehouse

    Constantz, J.; Murphy, F.

    1991-01-01

    A simple temperature-sensitive modification to the Green and Ampt infiltration equation is described; this assumes that the temperature dependence of the hydraulic conductivity is reciprocally equal to the temperature dependence of the viscosity of liquid water, and that both the transmission zone saturation and the wetting front matric potential gradient are independent of temperature. This modified Green and Ampt equation is compared with ponded, isothermal infiltration experiments run on repacked columns of Olympic Sand and Aiken Loam at 5, 25, and 60??C. Experimental results showed increases in infiltration rates of at least 300% between 5 and 60??C for both soil materials, with subsequent increases in cumulative infiltration of even greater magnitudes for the loam. There is good agreement between measured and predicted initial infiltration rates at 25??C for both soil materials, yet at 60??C, the predicted results overestimate initial infiltration rates for the sand and underestimate initial rates for the loam. Measurements of the wetting depth vs. cumulative infiltration indicate that the transmission zone saturation increased with increasing temperature for both soil materials. In spite of this increased saturation with temperature, the final infiltration rates at both 25 and 60??C were predicted accurately using the modified Green and Ampt equation. This suggests that increased saturation occurred primarily in dead-end pore spaces, so that transmission zone hydraulic conductivities were unaffected by these temperature-induced changes in saturation. In conclusion, except for initial infiltration rates at 60??C, the measured influence of temperature on infiltration rates was fully accounted for by the temperature dependence of the viscosity of liquid water. ?? 1991.

  19. Temperature dependent energy levels of methylammonium lead iodide perovskite

    SciTech Connect

    Foley, Benjamin J.; Marlowe, Daniel L.; Choi, Joshua J. E-mail: mgupta@virginia.edu; Sun, Keye; Gupta, Mool C. E-mail: mgupta@virginia.edu; Saidi, Wissam A.; Scudiero, Louis E-mail: mgupta@virginia.edu

    2015-06-15

    Temperature dependent energy levels of methylammonium lead iodide are investigated using a combination of ultraviolet photoemission spectroscopy and optical spectroscopy. Our results show that the valence band maximum and conduction band minimum shift down in energy by 110 meV and 77 meV as temperature increases from 28 °C to 85 °C. Density functional theory calculations using slab structures show that the decreased orbital splitting due to thermal expansion is a major contribution to the experimentally observed shift in energy levels. Our results have implications for solar cell performance under operating conditions with continued sunlight exposure and increased temperature.

  20. Temperature dependence of nucleation rate in a binary solid solution

    NASA Astrophysics Data System (ADS)

    Wang, H. Y.; Philippe, T.; Duguay, S.; Blavette, D.

    2012-12-01

    The influence of regression (partial dissolution) effects on the temperature dependence of nucleation rate in a binary solid solution has been studied theoretically. The results of the analysis are compared with the predictions of the simplest Volmer-Weber theory. Regression effects are shown to have a strong influence on the shape of the curve of nucleation rate versus temperature. The temperature TM at which the maximum rate of nucleation occurs is found to be lowered, particularly for low interfacial energy (coherent precipitation) and high-mobility species (e.g. interstitial atoms).

  1. Measurement of Temperature Dependent Apparent Specific Heat Capacity in Electrosurgery.

    PubMed

    Karaki, Wafaa; Akyildiz, Ali; Borca Tasciuc, Diana-Andra; De, Suvranu

    2016-01-01

    This paper reports on the measurement of temperature dependent apparent specific heat of ex-vivo porcine liver tissue during radiofrequency alternating current heating for a large temperature range. The difference between spatial and temporal evolution of experimental temperature, obtained during electrosurgical heating by infrared thermometry, and predictions based on finite element modeling was minimized to obtain the apparent specific heat. The model was based on transient heat transfer with internal heat generation considering heat storage along with conduction. Such measurements are important to develop computational models for real time simulation of electrosurgical procedures. PMID:27046573

  2. NICMOS Flats and temperature dependence of the DQE

    NASA Astrophysics Data System (ADS)

    Boeker, Torsten

    2001-07-01

    The purpose of this proposal is to obtain initial estimates of the detective quantum efficiency {DQE} of the NICMOS detectors and its temperature dependence in the previously uncharted temperature regime expected for operation under the NICMOS Cooling System {NCS}. The observations will measure the relative {via flat field morphology} and absolute DQE variation at three temperature setpoints. In addition, they will provide a monitor for particulate contamination {"Grot"} and detector lateral position {from the coronagraphic spot and FDA vignetting}. When stars are present in the field of view, they will enable a preliminary focus determination.

  3. Measurement of Temperature Dependent Apparent Specific Heat Capacity in Electrosurgery.

    PubMed

    Karaki, Wafaa; Akyildiz, Ali; Borca Tasciuc, Diana-Andra; De, Suvranu

    2016-01-01

    This paper reports on the measurement of temperature dependent apparent specific heat of ex-vivo porcine liver tissue during radiofrequency alternating current heating for a large temperature range. The difference between spatial and temporal evolution of experimental temperature, obtained during electrosurgical heating by infrared thermometry, and predictions based on finite element modeling was minimized to obtain the apparent specific heat. The model was based on transient heat transfer with internal heat generation considering heat storage along with conduction. Such measurements are important to develop computational models for real time simulation of electrosurgical procedures.

  4. The Temperature Dependence of Biological Rates from Enzymes to Ecosystems

    NASA Astrophysics Data System (ADS)

    Arcus, V. L.; Schipper, L. A.

    2014-12-01

    Can enzymology and thermodynamics shed light on the response of the biosphere to a changing climate? We have recently developed a theory describing the temperature dependence of biological rates. We have called this MacroMolecular Rate Theory (MMRT) to reflect some fundamental thermodynamic properties peculiar to biological macromolecules. This theory scales well from enzymes to ecosystems and explains the curved temperature dependence of ecosystem processes such as respiration, as described by Lloyd and Taylor 20 years ago. MMRT also accounts for temperature optima which are a feature of all biological processes including respiration, photosynthsis and net ecosystem exchange. MMRT begins with enzymes. Enzymes drive metabolism and enable life by catalysing a myraid of chemical reactions with phenomenal rate enhancements. According to the classical thermodynamics description, enzymes achieve catalysis by binding to the transition state for the reaction and thus, lowering the reaction barrier. The dissociation constant, Kd, for the enzyme-transition state complex, commensurate with the observed rate enhancements, is extreme (Kd ~ 10-22 M). Such tight binding of the transition state influences the thermodynamic parameter, Cp, the heat capacity of the molecule. The difference in heat capacity, ∆C‡P, between the enzyme-substrate complex (Kd ~ 10-5 M) and the enzyme-transition state complex (Kd ~ 10-22 M) has important implications for the temperature dependence of enzyme catalyzed rates. ∆C‡P is close to zero for reactions that involve small molecules, but is generally large and negative for reactions that involve macromolecules such as enzymes. The result is a curved temperature dependence of enzyme catalyzed rates and a temperature optimum above which, the rate decreases. This ∆C‡P signature is pervasive and scales from enzymes, to microbial growth rates, to microbial metabolism and ecosystem fluxes. It also has important implications for the temperature

  5. High temperature dependence of thermal transport in graphene foam

    NASA Astrophysics Data System (ADS)

    Li, Man; Sun, Yi; Xiao, Huying; Hu, Xuejiao; Yue, Yanan

    2015-03-01

    In contrast to the decreased thermal property of carbon materials with temperature according to the Umklapp phonon scattering theory, highly porous free-standing graphene foam (GF) exhibits an abnormal characteristic that its thermal property increases with temperature above room temperature. In this work, the temperature dependence of thermal properties of free-standing GF is investigated by using the transient electro-thermal technique. Significant increase for thermal conductivity and thermal diffusivity from ˜0.3 to 1.5 W m-1 K-1 and ˜4 × 10-5 to ˜2 × 10-4 m2 s-1 respectively is observed with temperature from 310 K to 440 K for three GF samples. The quantitative analysis based on a physical model for porous media of Schuetz confirms that the thermal conductance across graphene contacts rather than the heat conductance inside graphene dominates thermal transport of our GFs. The thermal expansion effect at an elevated temperature makes the highly porous structure much tighter is responsible for the reduction in thermal contact resistance. Besides, the radiation heat exchange inside the pores of GFs improves the thermal transport at high temperatures. Since free-standing GF has great potential for being used as supercapacitor and battery electrode where the working temperature is always above room temperature, this finding is beneficial for thermal design of GF-based energy applications.

  6. High temperature dependence of thermal transport in graphene foam.

    PubMed

    Li, Man; Sun, Yi; Xiao, Huying; Hu, Xuejiao; Yue, Yanan

    2015-03-13

    In contrast to the decreased thermal property of carbon materials with temperature according to the Umklapp phonon scattering theory, highly porous free-standing graphene foam (GF) exhibits an abnormal characteristic that its thermal property increases with temperature above room temperature. In this work, the temperature dependence of thermal properties of free-standing GF is investigated by using the transient electro-thermal technique. Significant increase for thermal conductivity and thermal diffusivity from ∼0.3 to 1.5 W m(-1) K(-1) and ∼4 × 10(-5) to ∼2 × 10(-4) m(2) s(-1) respectively is observed with temperature from 310 K to 440 K for three GF samples. The quantitative analysis based on a physical model for porous media of Schuetz confirms that the thermal conductance across graphene contacts rather than the heat conductance inside graphene dominates thermal transport of our GFs. The thermal expansion effect at an elevated temperature makes the highly porous structure much tighter is responsible for the reduction in thermal contact resistance. Besides, the radiation heat exchange inside the pores of GFs improves the thermal transport at high temperatures. Since free-standing GF has great potential for being used as supercapacitor and battery electrode where the working temperature is always above room temperature, this finding is beneficial for thermal design of GF-based energy applications.

  7. Ultra-low temperature (≤300 °C) growth of Ge-rich SiGe by solid-liquid-coexisting annealing of a-GeSn/c-Si structures

    SciTech Connect

    Sadoh, Taizoh Chikita, Hironori; Miyao, Masanobu; Matsumura, Ryo

    2015-09-07

    Ultra-low temperature (≤300 °C) growth of Ge-rich SiGe on Si substrates is strongly desired to realize advanced electronic and optical devices, which can be merged onto Si large-scale integrated circuits (LSI). To achieve this, annealing characteristics of a-GeSn/c-Si structures are investigated under wide ranges of the initial Sn concentrations (0%–26%) and annealing conditions (300–1000 °C, 1 s–48 h). Epitaxial growth triggered by SiGe mixing is observed after annealing, where the annealing temperatures necessary for epitaxial growth significantly decrease with increasing initial Sn concentration and/or annealing time. As a result, Ge-rich (∼80%) SiGe layers with Sn concentrations of ∼2% are realized by ultra-low temperature annealing (300 °C, 48 h) for a sample with the initial Sn concentration of 26%. The annealing temperature (300 °C) is in the solid-liquid coexisting temperature region of the phase diagram for Ge-Sn system. From detailed analysis of crystallization characteristics and composition profiles in grown layers, it is suggested that SiGe mixing is generated by a liquid-phase reaction even at ultra-low temperatures far below the melting temperature of a-GeSn. This ultra-low-temperature growth technique of Ge-rich SiGe on Si substrates is expected to be useful to realize next-generation LSI, where various multi-functional devices are integrated on Si substrates.

  8. [Temperature-Dependent Photoluminescence Property Studies of SiN(x) Films with nc-Si].

    PubMed

    Liu, Jian-ping; Zheng, Yan; Liu, Hai-xu; Yu, Wei; Ding, Wen-ge; Lai, Wei-dong

    2016-03-01

    Silicon nitride (SiN(x)) films containing nanocrystalline silicon (nc-Si) were deposited on crystalline silicon substrate by facing-target sputtering technique. Thermal annealing process was performed at 450 degrees C for 50 min in a conventional furnace under FG(10% H2, 90% N2) ambient. The photoluminescece (PL) properties of the SiN(x) films with nc-Si were investigated by steady/transient PL spectra measurements by Fluorescence spectrometer with different temperatures. The PL processes could be attributed to the quantum confinement effect of nc-Si and the defects in the film. The PL peak position exhibits a small blue shift with the increasing of the excitation energy, which indicates that the PL portion of the nc-Si increased with smaller size. In addition, the PL lifetime increases and the PL intensity exhibits exponential increase as a result of the decreased temperature which supressed the nonradiative recombination process and then improved the radiative recombination. The PL lifetime of the film significantly reduces with the decreasing of the detection wavelength, which indicates that the PL process related to the the quantum confinement effect strongly depends on temperature. PMID:27400499

  9. Efficiencies of thermodynamics when temperature-dependent energy levels exist.

    PubMed

    Yamano, Takuya

    2016-03-14

    Based on a generalized form of the second law of thermodynamics, in which the temperature-dependent energy levels of a system are appropriately included in entropy generation, we show that the effect reasonably appears in efficiencies of thermodynamic processes. PMID:26890276

  10. Investigation of temperature dependence of development and aging

    NASA Technical Reports Server (NTRS)

    Sacher, G. A.

    1969-01-01

    Temperature dependence of maturation and metabolic rates in insects, and the failure of vital processes during development were investigated. The paper presented advances the general hypothesis that aging in biological systems is a consequence of the production of entropy concomitant with metabolic activity.

  11. Temperature dependence of soliton diffusion in trans-polyacetylene

    SciTech Connect

    Tang, J.; Norris, J.R.; Isoya, J.

    1997-07-01

    The temperature dependence of 1-D diffusion rate of solitons in transpolyacetylene is determined by time-domain analysis of ESR measurements. The diffusion rate appears to obey a simple power law. Monte Carlo simulation of 1-D diffusion process in impure chains indicates that overall diffusion can be much slower than that without traps.

  12. Anomalous temperature dependence of the fluorescence lifetime of phycobiliproteins

    NASA Astrophysics Data System (ADS)

    Maksimov, E. G.; Schmitt, F.-J.; Hätti, P.; Klementiev, K. E.; Paschenko, V. Z.; Renger, G.; Rubin, A. B.

    2013-05-01

    Using a single photon counting technique we have investigated fluorescence decay spectra of phycobiliproteins with picosecond time resolution. The studies were performed in a wide range of temperatures—from 4 to 300 K. Comparing the fluorescence decay kinetics of samples rapidly frozen in liquid nitrogen with samples that were frozen slowly revealed that the temperature-dependent changes of phycobiliproteins fluorescence lifetime reflect the presence of three different stages, with a phase transition between 273 and 263 K that strongly depends on the rate of freezing. When the temperature decreases from 300 to 273 K, the fluorescence lifetime increases from 1.6 to 1.8 ns. In the region from 273 to 263 K we observed a decrease of the fluorescence lifetime, which strongly depends on the freezing rate: a slight decrease at high freezing rate and a drop down to 200 ps lifetime at slow freezing rate. In the low-temperature regime from 263 to 4 K a linear increase in the fluorescence lifetime was observed for all samples. It was found that the strong temperature dependence of the phycobiliprotein fluorescence, especially in the range between 263 and 273 K, is due to the interaction of the solvent with the chromophore bound to the protein. This feature is explained by a photoisomerization of the phycobiliproteins into a quenching form which is naturally prevented by the protein environment. The formation of ice microcrystals at low freezing rate eliminates this ‘protective’ effect of the protein environment.

  13. Time- and temperature-dependent failures of a bonded joint

    SciTech Connect

    Sihn, Sangwook; Miyano, Yasushi; Tsai, S.W.

    1997-07-01

    Time and temperature dependent properties of a tubular lap bonded joint are reported. The joint bonds a cast iron rod and a composite pipe together with an epoxy type of an adhesive material containing chopped glass fiber. A new fabrication method is proposed.

  14. Temperature dependence of liquid crystals electrical response by impedance analysis

    NASA Astrophysics Data System (ADS)

    Torres, J. C.; Gaona, N.; Pérez, I.; Urruchi, V.; Pena, J. M. S.

    2007-05-01

    Liquid crystals are a growing technology bringing solutions for a number of applications in high performance displays featuring video-rate, color and high resolution images, and in prototypes of photonic devices. Electrooptic response of antiferroelectric liquid crystals (AFLC) might be superior to nematic liquid crystals that are been customarily employed nowadays. AFLC show reduced time response being promising candidates for portable multimedia devices, optical routing applications, among others. In this work, temperature and frequency dependence of impedance measurements, in passive devices of commercial antiferroelectric liquid crystals, has been studied. Measurements of the temperature dependence of optical transmission have been obtained. 1Hz triangular waveforms with different amplitude have been applied to the devices to carry out such characterization. Simultaneous measurements of optical transmission and electrical impedance have been performed. Specific addressing schemes have been tested in order to obtain the optimum electrooptical performance. Display blanking takes place when a saturation pulse is applied. Results achieved show that increasing temperature shifts the dynamic range of the analogue grayscale towards lower voltages. Impedance analysis of these devices upon switching has been performed as well. Temperature and frequency dependence of the impedance measurements have been characterized. Negative phase responses show there is a combined capacitive and resistive behavior. As the frequency increases the capacitive effect grows. Magnitude shows a linear decrease on a log-log frequency scale. As temperature increases, phase profile becomes slight more complex. New capacitive effects are suggested in a model of the electric response of AFLC cells at low frequencies.

  15. Temperature dependent phonon shifts in few-layer black phosphorus.

    PubMed

    Late, Dattatray J

    2015-03-18

    Atomically thin two-dimensional (2D) sheets of black phosphorus have attracted much attention due to their potential for future nanoelectronic and photonics device applications. Present investigations deal with the temperature dependent phonon shifts in a few-layer black phosphorus nanosheet sample prepared using micromechanical exfoliation on a 300 nm SiO2/Si substrate. The temperature dependent Raman spectroscopy experiments were carried out on a few-layer black phosphorus sample, which depicts softening of Ag(1), B2g, and Ag(2) modes as temperature increases from 77 to 673 K. The calculated temperature coefficients for Ag(1), B2g, and Ag(2) modes of the few-layer black phosphorus nanosheet sample were observed to be -0.01, -0.013, and -0.014 cm(-1) K(-1), respectively. The temperature dependent softening modes of black phosphorus results were explained on the basis of a double resonance process which is more active in an atomically thin sample. This process can also be fundamentally pertinent in other promising and emerging 2D ultrathin layer and heterostructured materials.

  16. Study of the PTW microLion chamber temperature dependence.

    PubMed

    Gómez, F; González-Castaño, D; Díaz-Botana, P; Pardo-Montero, J

    2014-06-01

    The use of liquid ionization chambers in radiotherapy has grown during the past few years. While for air ionization chambers the k(TP) correction for air mass density due to pressure and temperature variations is well known, less work has been done on the case of liquid ionization chambers, where there is still the need to take into account the influence of temperature in the free ion yield. We have measured the PTW microLion isooctane-filled ionization chamber temperature dependence in a ~ ±10 °C interval around the standard 20 °C room temperature for three operation voltages, including the manufacturer recommended voltage, and two beam qualities, (60)Co and 50 kV x-rays. Within the measured temperature range, the microLion signal exhibits a positive linear dependence, which is around 0.24% K(-1) at 800 V with (60)Co irradiation. This effect is of the same order of magnitude as the T dependence found in air ionization chambers, but its nature is completely different and its sign opposite to that of an air chamber. Onsager theory has been used to model the results and is consistent with this linear behaviour. However, some inconsistencies in the modelling of the 50 kV x-ray results have been found that are attributed to the failure of Onsager's isolated pair assumption for such radiation quality.

  17. Stress versus temperature dependent activation energies in creep

    NASA Technical Reports Server (NTRS)

    Freed, A. D.; Raj, S. V.; Walker, K. P.

    1990-01-01

    The activation energy for creep at low stresses and elevated temperatures is lattice diffusion, where the rate controlling mechanism for deformation is dislocation climb. At higher stresses and intermediate temperatures, the rate controlling mechanism changes from that of dislocation climb to one of obstacle-controlled dislocation glide. Along with this change, there occurs a change in the activation energy. It is shown that a temperature-dependent Gibbs free energy does a good job of correlating steady-state creep data, while a stress-dependent Gibbs free energy does a less desirable job of correlating the same data. Applications are made to copper and a LiF-22 mol. percent CaF2 hypereutectic salt.

  18. Unconventional temperature dependence of the cuprate excitation spectrum

    NASA Astrophysics Data System (ADS)

    Sacks, William; Mauger, Alain; Noat, Yves

    2016-08-01

    Key properties of the cuprates, such as the pseudogap observed above the critical temperature Tc, remain highly debated. Given their importance, we recently proposed a novel mechanism based on the Bose-like condensation of mutually interacting Cooper pairs [W. Sacks, A. Mauger, Y. Noat, Supercond. Sci. Technol. 28, 105014 (2015)]. In this work, we calculate the temperature dependent DOS using this model for different doping levels from underdoped to overdoped. In all situations, due to the presence of excited pairs, a pseudogap is found above Tc while the normal DOS is recovered at T∗, the pair formation temperature. A similar behavior is found as a function of magnetic field, crossing a vortex, where a pseudogap exists in the vortex core. We show that the precise DOS shape depends on combined pair (boson) and quasiparticle (fermion) excitations, allowing for a deeper understanding of the SC to the PG transition.

  19. Stress versus temperature dependence of activation energies for creep

    NASA Technical Reports Server (NTRS)

    Freed, A. D.; Raj, S. V.; Walker, K. P.

    1992-01-01

    The activation energy for creep at low stresses and elevated temperatures is associated with lattice diffusion, where the rate controlling mechanism for deformation is dislocation climb. At higher stresses and intermediate temperatures, the rate controlling mechanism changes from dislocation climb to obstacle-controlled dislocation glide. Along with this change in deformation mechanism occurs a change in the activation energy. When the rate controlling mechanism for deformation is obstacle-controlled dislocation glide, it is shown that a temperature-dependent Gibbs free energy does better than a stress-dependent Gibbs free energy in correlating steady-state creep data for both copper and LiF-22mol percent CaF2 hypereutectic salt.

  20. Temperature dependence of penetration depth in thin film niobium

    NASA Technical Reports Server (NTRS)

    More, N.; Muhlfelder, B.; Lockhart, J.

    1989-01-01

    A novel technique is presented which should allow precise determination of the temperature dependence of the inductance, and hence of the penetration depth, of superconducting niobium thin-film structures. Four niobium thin-film stripline inductors are arranged in a bridge configuration, and inductance differences are measured using a potentiometric technique with a SQUID (superconducting quantum interference device) as the null detector. Numerical simulations of the stripline inductances are presented which allow the performance of the measurement technique to be evaluated. The prediction of the two-fluid model for the penetration-depth temperature dependence is given for reduced temperatures of 0.3 to 0.9. The experimental apparatus and its resolution and accuracy are discussed.

  1. Temperature dependence of angular momentum transport across interfaces

    NASA Astrophysics Data System (ADS)

    Chen, Kai; Lin, Weiwei; Chien, C. L.; Zhang, Shufeng

    2016-08-01

    Angular momentum transport in magnetic multilayered structures plays a central role in spintronic physics and devices. The angular momentum currents or spin currents are carried by either quasiparticles such as electrons and magnons, or by macroscopic order parameters such as local magnetization of ferromagnets. Based on the generic interface exchange interaction, we develop a microscopic theory that describes interfacial spin conductance for various interfaces among nonmagnetic metals, ferromagnetic insulators, and antiferromagnetic insulators. Spin conductance and its temperature dependence are obtained for different spin batteries including spin pumping, temperature gradient, and spin Hall effect. As an application of our theory, we calculate the spin current in a trilayer made of a ferromagnetic insulator, an antiferromagnetic insulator, and a nonmagnetic heavy metal. The calculated results on the temperature dependence of spin conductance quantitatively agree with the existing experiments.

  2. Co{sub 2}FeAl Heusler thin films grown on Si and MgO substrates: Annealing temperature effect

    SciTech Connect

    Belmeguenai, M. Tuzcuoglu, H.; Zighem, F.; Chérif, S. M.; Moch, P.; Gabor, M. S. Petrisor, T.; Tiusan, C.

    2014-01-28

    10 nm and 50 nm Co{sub 2}FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (T{sub a}), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing T{sub a}, while the uniaxial anisotropy field is nearly unaffected by T{sub a} within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with T{sub a}. Finally, the FMR linewidth decreases when increasing T{sub a}, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.1×10{sup −3} and 1.3×10{sup −3} for films of 50 nm thickness annealed at 615 °C grown on MgO and on Si, respectively)

  3. Sensitive Dependence of Gibbs Measures at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Coronel, Daniel; Rivera-Letelier, Juan

    2015-09-01

    The Gibbs measures of an interaction can behave chaotically as the temperature drops to zero. We observe that for some classical lattice systems there are interactions exhibiting a related phenomenon of sensitive dependence of Gibbs measures: An arbitrarily small perturbation of the interaction can produce significant changes in the low-temperature behavior of its Gibbs measures. For some one-dimensional XY models we exhibit sensitive dependence of Gibbs measures for a (nearest-neighbor) interaction given by a smooth function, and for perturbations that are small in the smooth category. We also exhibit sensitive dependence of Gibbs measures for an interaction on a classical lattice system with finite-state space. This interaction decreases exponentially as a function of the distance between sites; it is given by a Lipschitz continuous potential in the configuration space. The perturbations are small in the Lipschitz topology. As a by-product we solve some problems stated by Chazottes and Hochman.

  4. Temperature Dependence of Carbon Isotope Fractionation in CAM Plants 1

    PubMed Central

    Deleens, Eliane; Treichel, Isabel; O'Leary, Marion H.

    1985-01-01

    The carbon isotope fractionation associated with nocturnal malic acid synthesis in Kalanchoë daigremontiana and Bryophyllum tubiflorum was calculated from the isotopic composition of carbon-4 of malic acid, after appropriate corrections. In the lowest temperature treatment (17°C nights, 23°C days), the isotope fractionation for both plants is −4‰ (that is, malate is enriched in 13C relative to the atmosphere). For K. daigremontiana, the isotope fractionation decreases with increasing temperature, becoming approximately 0‰ at 27°C/33°C. Detailed analysis of temperature effects on the isotope fractionation indicates that stomatal aperture decreases with increasing temperature and carboxylation capacity increases. For B. tubiflorum, the temperature dependence of the isotope fractionation is smaller and is principally attributed to the normal temperature dependences of the rates of diffusion and carboxylation steps. The small change in the isotopic composition of remaining malic acid in both species which is observed during deacidification indicates that malate release, rather than decarboxylation, is rate limiting in the deacidification process. PMID:16664371

  5. Temperature dependence of denitrification in phototrophic river biofilms.

    PubMed

    Boulêtreau, S; Salvo, E; Lyautey, E; Mastrorillo, S; Garabetian, F

    2012-02-01

    Denitrification is an ecosystem service of nitrogen load regulation along the terrestrial-freshwater-marine continuum. The present study documents the short-term temperature sensitivity of denitrification enzyme activity in phototrophic river biofilms as a typical microbial assemblage of this continuum. Denitrification measurements were performed using the acetylene inhibition method at four incubation temperatures: 1.1, 12.1, 21.2 and 30.9°C. For this range of temperature, N(2)O production could be fitted to an exponential function of incubation temperature, yielding mean (±standard error) activation energy of 1.42 (±0.24) eV and Q(10) of 7.0 (±1.4). This first quantification of denitrification enzyme activity temperature dependence in phototrophic river biofilms compares with previous studies performed in soils and sediments. This demonstrates the high temperature dependence of denitrification as compared to other community-level metabolisms such as respiration or photosynthesis. This result suggests that global warming can unbalance natural community metabolisms in phototrophic river biofilms and affect their biogeochemical budget.

  6. TEMPERATURE-DEPENDENT INFRARED OPTICAL CONSTANTS OF OLIVINE AND ENSTATITE

    SciTech Connect

    Zeidler, S.; Mutschke, H.; Posch, Th. E-mail: harald.mutschke@uni-jena.de

    2015-01-10

    Since the Infrared Space Observatory (ISO) mission, it has become clear that dust in circumstellar disks and outflows consists partly of crystalline silicates of pyroxene and olivine type. An exact mineralogical analysis of the dust infrared emission spectra relies on laboratory spectra, which, however, have been mostly measured at room temperature so far. Given that infrared spectral features depend on the thermal excitation of the crystal's vibrational modes, laboratory spectra measured at various (low and high) temperatures, corresponding to the thermal conditions at different distances from the star, can improve the accuracy of such analyses considerably. We have measured the complex refractive index in a temperature range of 10-973 K for one mineral of each of those types of silicate, i.e., for an olivine and an enstatite of typical (terrestrial) composition. Thus, our data extend the temperature range of previous data to higher values and the compositional range to higher iron contents. We analyze the temperature dependence of oscillator frequencies and damping parameters governing the spectral characteristics of the bands and calculate absorption cross-sectional spectra that can be compared with astronomical emission spectra. We demonstrate the usefulness of our new data by comparing spectra calculated for a 100 K dust temperature with the ISO SWS spectrum of IRAS 09425-6040.

  7. Temperature dependence of single-axis acoustic levitation

    NASA Astrophysics Data System (ADS)

    Xie, W. J.; Wei, B.

    2003-03-01

    The temperature-dependent physical conditions for single-axis acoustic levitation are theoretically analyzed with consideration of the deviation of the actual acoustic field from the plane standing wave approximation. The effects of temperature variation on the resonant conditions, levitation force and threshold pressures pm (the minimum entrapping pressure) and pM (the maximum pressure to keep the integration of a liquid drop) are discussed by assuming a quasi-static heating and cooling process. The first resonant spacing H1 between the reflector and emitter is larger than that predicted for plane standing waves, and its temperature dependence comes mainly from the variation of wavelength, which is proportional to T1/2. The maximum levitation force FM has a drastic decreasing tendency with temperature rise due to its sensitivity to the ratios of the geometric parameters to wavelength. For the containerless processing of water and the Pb-Sn eutectic alloy, pm decreases whereas pM increases with the enhancement of temperature, which narrows the allowed pressure range for the safe and stable levitation of the processed drops at higher temperatures. As an experimental application of these analyses, the acoustically levitated water and the Pb-Sn eutectic alloy melt are highly undercooled by up to 24 and 38 K, respectively.

  8. On the Temperature Dependence of Enzyme-Catalyzed Rates.

    PubMed

    Arcus, Vickery L; Prentice, Erica J; Hobbs, Joanne K; Mulholland, Adrian J; Van der Kamp, Marc W; Pudney, Christopher R; Parker, Emily J; Schipper, Louis A

    2016-03-29

    One of the critical variables that determine the rate of any reaction is temperature. For biological systems, the effects of temperature are convoluted with myriad (and often opposing) contributions from enzyme catalysis, protein stability, and temperature-dependent regulation, for example. We have coined the phrase "macromolecular rate theory (MMRT)" to describe the temperature dependence of enzyme-catalyzed rates independent of stability or regulatory processes. Central to MMRT is the observation that enzyme-catalyzed reactions occur with significant values of ΔCp(‡) that are in general negative. That is, the heat capacity (Cp) for the enzyme-substrate complex is generally larger than the Cp for the enzyme-transition state complex. Consistent with a classical description of enzyme catalysis, a negative value for ΔCp(‡) is the result of the enzyme binding relatively weakly to the substrate and very tightly to the transition state. This observation of negative ΔCp(‡) has important implications for the temperature dependence of enzyme-catalyzed rates. Here, we lay out the fundamentals of MMRT. We present a number of hypotheses that arise directly from MMRT including a theoretical justification for the large size of enzymes and the basis for their optimum temperatures. We rationalize the behavior of psychrophilic enzymes and describe a "psychrophilic trap" which places limits on the evolution of enzymes in low temperature environments. One of the defining characteristics of biology is catalysis of chemical reactions by enzymes, and enzymes drive much of metabolism. Therefore, we also expect to see characteristics of MMRT at the level of cells, whole organisms, and even ecosystems. PMID:26881922

  9. On the Temperature Dependence of Enzyme-Catalyzed Rates.

    PubMed

    Arcus, Vickery L; Prentice, Erica J; Hobbs, Joanne K; Mulholland, Adrian J; Van der Kamp, Marc W; Pudney, Christopher R; Parker, Emily J; Schipper, Louis A

    2016-03-29

    One of the critical variables that determine the rate of any reaction is temperature. For biological systems, the effects of temperature are convoluted with myriad (and often opposing) contributions from enzyme catalysis, protein stability, and temperature-dependent regulation, for example. We have coined the phrase "macromolecular rate theory (MMRT)" to describe the temperature dependence of enzyme-catalyzed rates independent of stability or regulatory processes. Central to MMRT is the observation that enzyme-catalyzed reactions occur with significant values of ΔCp(‡) that are in general negative. That is, the heat capacity (Cp) for the enzyme-substrate complex is generally larger than the Cp for the enzyme-transition state complex. Consistent with a classical description of enzyme catalysis, a negative value for ΔCp(‡) is the result of the enzyme binding relatively weakly to the substrate and very tightly to the transition state. This observation of negative ΔCp(‡) has important implications for the temperature dependence of enzyme-catalyzed rates. Here, we lay out the fundamentals of MMRT. We present a number of hypotheses that arise directly from MMRT including a theoretical justification for the large size of enzymes and the basis for their optimum temperatures. We rationalize the behavior of psychrophilic enzymes and describe a "psychrophilic trap" which places limits on the evolution of enzymes in low temperature environments. One of the defining characteristics of biology is catalysis of chemical reactions by enzymes, and enzymes drive much of metabolism. Therefore, we also expect to see characteristics of MMRT at the level of cells, whole organisms, and even ecosystems.

  10. Temperature-enhanced solvent vapor annealing of a C3 symmetric hexa-peri-hexabenzocoronene: controlling the self-assembly from nano- to macroscale.

    PubMed

    Treossi, Emanuele; Liscio, Andrea; Feng, Xinliang; Palermo, Vincenzo; Müllen, Klaus; Samorì, Paolo

    2009-01-01

    Temperature-enhanced solvent vapor annealing (TESVA) is used to self-assemble functionalized polycyclic aromatic hydrocarbon molecules into ordered macroscopic layers and crystals on solid surfaces. A novel C3 symmetric hexa-peri-hexabenzocoronene functionalized with alternating hydrophilic and hydrophobic side chains is used as a model system since its multivalent character can be expected to offer unique self-assembly properties and behavior in different solvents. TESVA promotes the molecule's long-range mobility, as proven by their diffusion on a Si/SiO(x) surface on a scale of hundreds of micrometers. This leads to self-assembly into large, ordered crystals featuring an edge-on columnar type of arrangement, which differs from the morphologies obtained using conventional solution-processing methods such as spin-coating or drop-casting. The temperature modulation in the TESVA makes it possible to achieve an additional control over the role of hydrodynamic forces in the self-assembly at surfaces, leading to a macroscopic self-healing within the adsorbed film notably improved as compared to conventional solvent vapor annealing. This surface re-organization can be monitored in real time by optical and atomic force microscopy.

  11. Periodically pulsed wet annealing approach for low-temperature processable amorphous InGaZnO thin film transistors with high electrical performance and ultrathin thickness

    PubMed Central

    Kim, Ye Kyun; Ahn, Cheol Hyoun; Yun, Myeong Gu; Cho, Sung Woon; Kang, Won Jun; Cho, Hyung Koun

    2016-01-01

    In this paper, a simple and controllable “wet pulse annealing” technique for the fabrication of flexible amorphous InGaZnO thin film transistors (a-IGZO TFTs) processed at low temperature (150 °C) by using scalable vacuum deposition is proposed. This method entailed the quick injection of water vapor for 0.1 s and purge treatment in dry ambient in one cycle; the supply content of water vapor was simply controlled by the number of pulse repetitions. The electrical transport characteristics revealed a remarkable performance of the a-IGZO TFTs prepared at the maximum process temperature of 150 °C (field-effect mobility of 13.3 cm2 V−1 s−1; Ion/Ioff ratio ≈ 108; reduced I-V hysteresis), comparable to that of a-IGZO TFTs annealed at 350 °C in dry ambient. Upon analysis of the angle-resolved x-ray photoelectron spectroscopy, the good performance was attributed to the effective suppression of the formation of hydroxide and oxygen-related defects. Finally, by using the wet pulse annealing process, we fabricated, on a plastic substrate, an ultrathin flexible a-IGZO TFT with good electrical and bending performances. PMID:27198067

  12. Structural and optical properties of thermal decomposition assisted Gd2O3:Ho3 +/Yb3 + upconversion phosphor annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Tiwari, S. P.; Kumar, K.; Rai, V. K.

    2016-10-01

    The infrared to visible upconversion fluorescent nanoparticles of Ho3 +/Yb3 + codoped Gd2O3 phosphor is synthesized via thermal decomposition route. The as-synthesized sample was annealed at 800, 1000 and 1200 °C for 3 h and then structural and optical properties were studied. The Rietveld refinement of X-ray diffraction (XRD) data was analyzed to probe the effect of Ho3 +/Yb3 + dopant on the structural parameters of Gd2O3 host. The upconversion emission spectra of as-synthesized and annealed samples are compared using 980 nm diode laser excitation and five emission bands noticed at 490, 539, 550, 667 and 757 nm corresponding to the 5F3 → 5I8, 5F4 → 5I8, 5S2 → 5I8,5F5 → 5I8 and 5I4 → 5I8 manifolds, respectively. The local temperature induced by laser light is also calculated. The fluorescence intensity ratio (FIR) of two thermally coupled transitions 5F4 → 5I8 and 5S2 → 5I8 is plotted against the sample temperature and sensor sensitivity of sample is calculated.

  13. Effect of TiO2 Particles on Micro-Hardness Corrosion, Wear and Friction of Ni-P-TiO2 Composite Coatings at Different Annealing Temperatures

    NASA Astrophysics Data System (ADS)

    Gadhari, Prasanna; Sahoo, Prasanta

    2016-09-01

    The present study investigates the effect of titania particles on the micro-hardness, wear resistance, corrosion resistance and friction of electroless Ni-P-TiO2 composite coatings deposited on mild steel substrates at different annealing temperatures. The experimental results confirmed that the amount of TiO2 particles incorporated in the coatings increases with increase in the concentration of particles in the electroless bath. In presence of TiO2 particles, hardness, wear resistance and corrosion resistance of the coating improve significantly. At higher annealing temperature, wear resistance increases due to formation of hard Ni3P phase and incorporation of titania particles in the coated layer. Charge transfer resistance and corrosion current density of the coatings reduce with an increase in TiO2 particles, whereas corrosion potential increases. Microstructure changes and composition of the composite coating due to heat treatment are studied with the help of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA) and X-ray diffraction (XRD) analysis.

  14. Structural and optical properties of thermal decomposition assisted Gd2O3:Ho(3+)/Yb(3+) upconversion phosphor annealed at different temperatures.

    PubMed

    Kumar, A; Tiwari, S P; Kumar, K; Rai, V K

    2016-10-01

    The infrared to visible upconversion fluorescent nanoparticles of Ho(3+)/Yb(3+) codoped Gd2O3 phosphor is synthesized via thermal decomposition route. The as-synthesized sample was annealed at 800, 1000 and 1200°C for 3h and then structural and optical properties were studied. The Rietveld refinement of X-ray diffraction (XRD) data was analyzed to probe the effect of Ho(3+)/Yb(3+) dopant on the structural parameters of Gd2O3 host. The upconversion emission spectra of as-synthesized and annealed samples are compared using 980nm diode laser excitation and five emission bands noticed at 490, 539, 550, 667 and 757nm corresponding to the (5)F3→(5)I8, (5)F4→(5)I8, (5)S2→(5)I8,(5)F5→(5)I8 and (5)I4→(5)I8 manifolds, respectively. The local temperature induced by laser light is also calculated. The fluorescence intensity ratio (FIR) of two thermally coupled transitions (5)F4→(5)I8 and (5)S2→(5)I8 is plotted against the sample temperature and sensor sensitivity of sample is calculated. PMID:27284763

  15. Temperature dependent Raman and DFT study of creatine.

    PubMed

    Gangopadhyay, Debraj; Sharma, Poornima; Singh, Ranjan K

    2015-01-01

    Temperature dependent Raman spectra of creatine powder have been recorded in the temperature range 420-100K at regular intervals and different clusters of creatine have been optimized using density functional theory (DFT) in order to determine the effect of temperature on the hydrogen bonded network in the crystal structure of creatine. Vibrational assignments of all the 48 normal modes of the zwitterionic form of creatine have been done in terms of potential energy distribution obtained from DFT calculations. Precise analysis gives information about thermal motion and intermolecular interactions with respect to temperature in the crystal lattice. Formation of higher hydrogen bonded aggregates on cooling can be visualized from the spectra through clear signature of phase transition between 200K and 180K. PMID:26010702

  16. Temperature dependence of contact resistance at metal/MWNT interface

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Eui; Moon, Kyoung-Seok; Sohn, Yoonchul

    2016-07-01

    Although contact resistance of carbon nanotube (CNT) is one of the most important factors for practical application of electronic devices, a study regarding temperature dependence on contact resistance of CNTs with metal electrodes has not been found. Here, we report an investigation of contact resistance at multiwalled nanotube (MWNT)/Ag interface as a function of temperature, using MWNT/polydimethylsiloxane (PDMS) composite. Electrical resistance of MWNT/PDMS composite revealed negative temperature coefficient (NTC). Excluding the contact resistance with Ag electrode, the NTC effect became less pronounced, showing lower intrinsic resistivity with the activation energy of 0.019 eV. Activation energy of the contact resistance of MWNT/Ag interface was determined to be 0.04 eV, two times larger than that of MWNT-MWNT network. The increase in the thermal fluctuation assisted electron tunneling is attributed to conductivity enhancement at both MWNT/MWNT and MWNT/Ag interfaces with increasing temperature.

  17. Temperature-dependent liquid metal flowrate control device

    DOEpatents

    Carlson, Roger D.

    1978-01-01

    A temperature-dependent liquid metal flowrate control device includes a magnet and a ferromagnetic member defining therebetween a flow path for liquid metal, the ferromagnetic member being formed of a material having a curie temperature at which a change in the flow rate of the liquid metal is desired. According to the preferred embodiment the magnet is a cylindrical rod magnet axially disposed within a cylindrical member formed of a curie material and having iron pole pieces at the ends. A cylindrical iron shunt and a thin wall stainless steel barrier are disposed in the annulus between magnet and curie material. Below the curie temperature flow between steel barrier and curie material is impeded and above the curie temperature flow impedance is reduced.

  18. Temperature dependent relativistic mean field for highly excited hot nuclei

    NASA Astrophysics Data System (ADS)

    Gambhir, Y. K.; Maharana, J. P.; Lalazissis, G. A.; Panos, C. P.; Ring, P.

    2000-11-01

    The temperature dependent relativistic mean field (RMF-T) results obtained by using nonlinear Lagrangian parameter set NL3 are presented for a few selected representative spherical and deformed nuclei. The calculated total binding energy (entropy) decrease (increase) as temperature (T) increases. The depths of the potentials and the single particle (sp) energies change very little with temperature. The density slightly spreads out; as a result the radius increases as temperature rises. For well deformed nuclei the shell effects disappear at around T~3 MeV. This value of T is relatively higher as compared to the corresponding value of T (~1.8 MeV) obtained in the Strutinsky-type calculations. This difference in the value of T is shown to be due to the use of the effective nucleon mass (< the bare mass) appearing in the Skyrme III interaction or emerging from the RMF Lagrangian.

  19. Multiaxial Temperature- and Time-Dependent Failure Model

    NASA Technical Reports Server (NTRS)

    Richardson, David; McLennan, Michael; Anderson, Gregory; Macon, David; Batista-Rodriquez, Alicia

    2003-01-01

    A temperature- and time-dependent mathematical model predicts the conditions for failure of a material subjected to multiaxial stress. The model was initially applied to a filled epoxy below its glass-transition temperature, and is expected to be applicable to other materials, at least below their glass-transition temperatures. The model is justified simply by the fact that it closely approximates the experimentally observed failure behavior of this material: The multiaxiality of the model has been confirmed (see figure) and the model has been shown to be applicable at temperatures from -20 to 115 F (-29 to 46 C) and to predict tensile failures of constant-load and constant-load-rate specimens with failure times ranging from minutes to months..

  20. Multi-Relaxation Temperature-Dependent Dielectric Model of the Arctic Soil at Positive Temperatures

    NASA Astrophysics Data System (ADS)

    Savin, I. V.; Mironov, V. L.

    2014-11-01

    Frequency spectra of the dielectric permittivity of the Arctic soil of Alaska are investigated with allowance for the dipole and ionic relaxation of molecules of the soil moisture at frequencies from 40 MHz to 16 GHz and temperatures from -5 to +25°С. A generalized temperature-dependent multi-relaxation refraction dielectric model of the humid Arctic soil is suggested.

  1. A nanoscale temperature-dependent heterogeneous nucleation theory

    SciTech Connect

    Cao, Y. Y.; Yang, G. W.

    2015-06-14

    Classical nucleation theory relies on the hypothetical equilibrium of the whole nucleation system, and neglects the thermal fluctuations of the surface; this is because the high entropic gains of the (thermodynamically extensive) surface would lead to multiple stable states. In fact, at the nanometer scale, the entropic gains of the surface are high enough to destroy the stability of the thermal equilibrium during nucleation, comparing with the whole system. We developed a temperature-dependent nucleation theory to elucidate the heterogeneous nucleation process, by considering the thermal fluctuations based on classical nucleation theory. It was found that the temperature not only affected the phase transformation, but also influenced the surface energy of the nuclei. With changes in the Gibbs free energy barrier, nucleation behaviors, such as the nucleation rate and the critical radius of the nuclei, showed temperature-dependent characteristics that were different from those predicted by classical nucleation theory. The temperature-dependent surface energy density of a nucleus was deduced based on our theoretical model. The agreement between the theoretical and experimental results suggested that the developed nucleation theory has the potential to contribute to the understanding and design of heterogeneous nucleation at the nanoscale.

  2. Temperature-dependent internal photoemission probe for band parameters

    NASA Astrophysics Data System (ADS)

    Lao, Yan-Feng; Perera, A. G. Unil

    2012-11-01

    The temperature-dependent characteristic of band offsets at the heterojunction interface was studied by an internal photoemission (IPE) method. In contrast to the traditional Fowler method independent of the temperature (T), this method takes into account carrier thermalization and carrier/dopant-induced band-renormalization and band-tailing effects, and thus measures the band-offset parameter at different temperatures. Despite intensive studies in the past few decades, the T dependence of this key band parameter is still not well understood. Re-examining a p-type doped GaAs emitter/undoped AlxGa1-xAs barrier heterojunction system disclosed its previously ignored T dependency in the valence-band offset, with a variation up to ˜-10-4 eV/K in order to accommodate the difference in the T-dependent band gaps between GaAs and AlGaAs. Through determining the Fermi energy level (Ef), IPE is able to distinguish the impurity (IB) and valence bands (VB) of extrinsic semiconductors. One important example is to determine Ef of dilute magnetic semiconductors such as GaMnAs, and to understand whether it is in the IB or VB.

  3. Recovery behavior of high purity cubic SiC polycrystals by post-irradiation annealing up to 1673 K after low temperature neutron irradiation

    NASA Astrophysics Data System (ADS)

    Idris, Mohd Idzat; Yamazaki, Saishun; Yoshida, Katsumi; Yano, Toyohiko

    2015-10-01

    Two kinds of high purity cubic (β) SiC polycrystals, PureBeta-SiC and CVD-SiC, were irradiated in the BR2 reactor (Belgium) up to a fluence of 2.0-2.5 × 1024 (E > 0.1 MeV) at 333-363 K. Changes in macroscopic lengths were examined by post-irradiation thermal annealing using a precision dilatometer up to 1673 K with a step-heating method. The specimen was held at each temperature step for 6 h and the change in length of the specimen was recorded during each isothermal annealing step from 373 K to 1673 K with 50 K increments. The recovery curves were analyzed with the first order model, and rate constants at each annealing step were obtained. Recovery of defects, induced by neutron irradiation in high purity β-SiC, has four stages of different activation energies. At 373-573 K, the activation energy of PureBeta-SiC and CVD-SiC was in the range of 0.17-0.24 eV and 0.12-0.14 eV; 0.002-0.04 eV and 0.006-0.04 eV at 723-923 K; 0.20-0.27 eV and 0.26-0.31 eV at 923-1223 K; and 1.37-1.38 eV and 1.26-1.29 eV at 1323-1523 K, respectively. Below ∼1223 K the recombination occurred possibly for closely positioned C and Si Frenkel pairs, and no long range migration is deemed essential. Nearly three-fourths of recovery, induced by neutron irradiation, occur by this mechanism. In addition, at 1323-1523 K, recombination of slightly separated C Frenkel pairs and more long-range migration of Si interstitials may have occurred for PureBeta-SiC and CVD-SiC specimens. Migration of both vacancies may be restricted up to ∼1523 K. Comparing to hexagonal α-SiC, high purity β-SiC recovered more quickly in the lower annealing temperature range of less than 873 K, in particular less than 573 K.

  4. Time- and temperature-dependent failures of a bonded joint

    NASA Astrophysics Data System (ADS)

    Sihn, Sangwook

    This dissertation summarizes my study of time- and temperature-dependent behavior of a tubular lap bonded joint to provide a design methodology for windmill blade structures. The bonded joint is between a cast-iron rod and a GFRP composite pipe. The adhesive material is an epoxy containing chopped glass fibers. We proposed a new fabrication method to make concentric and void-less specimens of the tubular joint with a thick adhesive bondline to stimulate the root bond of a blade. The thick bondline facilitates the joint assembly of actual blades. For a better understanding of the behavior of the bonded joint, we studied viscoelastic behavior of the adhesive materials by measuring creep compliance at several temperatures during loading period. We observed that the creep compliance depends highly on the period of loading and the temperature. We applied time-temperature equivalence to the creep compliance of the adhesive material to obtain time-temperature shift factors. We also performed constant-rate of monotonically increased uniaxial tensile tests to measure static strength of the tubular lap joint at several temperatures and different strain-rates. We observed two failure modes from load-deflection curves and failed specimens. One is the brittle mode, which was caused by weakness of the interfacial strength occurring at low temperature and short period of loading. The other is the ductile mode, which was caused by weakness of the adhesive material at high temperature and long period of loading. Transition from the brittle to the ductile mode appeared as the temperature or the loading period increased. We also performed tests under uniaxial tensile-tensile cyclic loadings to measure fatigue strength of the bonded joint at several temperatures, frequencies and stress ratios. The fatigue data are analyzed statistically by applying the residual strength degradation model to calculate statistical distribution of the fatigue life. Combining the time-temperature

  5. Annealing of PEEK, PET and PI implanted with Co ions at high fluencies

    NASA Astrophysics Data System (ADS)

    Mackova, A.; Malinsky, P.; Miksova, R.; Pupikova, H.; Khaibullin, R. I.; Valeev, V. F.; Svorcik, V.; Slepicka, P.

    2013-07-01

    The properties of implanted polymers strongly depend on the implantation ion fluence and on the properties of the implanted atoms. The stability of synthesized nano-structures during further technological steps like annealing is of importance for their possible applications. Polyimide (PI), polyetheretherketone (PEEK), and polyethyleneterephtalate (PET) were implanted with 40 keV Co+ ions at room temperature at fluences ranging from 0.2 × 1016 cm-2 to 1.0 × 1017 cm-2 and annealed at a temperature of 200 °C. The implanted depth profiles of as-implanted and annealed samples, determined by the RBS method, were compared with the results of SRIM 2012 simulations. The structural and compositional changes of the implanted and subsequently annealed polymers were characterized by RBS and UV-vis spectroscopy. The surface morphology of as-implanted and annealed samples was examined by the AFM method and their electrical properties by sheet resistance measurement.

  6. Temperature-Dependent Giant Magnetoimpedance Effect in Amorphous Soft Magnets

    NASA Astrophysics Data System (ADS)

    Kurniawan, M.; Roy, R. K.; Panda, A. K.; Greve, D. W.; Ohodnicki, P.; McHenry, M. E.

    2014-12-01

    Giant magnetoimpedance (GMI)-based devices offer potential as next-generation low-cost, flexible, ultrasensitive sensors. They can be used in applications that include current sensors, field sensors, stress sensors, and others. Challenging applications involve operation at high temperatures, and therefore studies of GMI temperature dependence and performance of soft magnetic materials are needed. We present a high-temperature GMI study on an amorphous soft magnetic microwire from room temperature to 560°C. The GMI ratio was observed to be nearly constant at ˜86% at low temperatures and to decrease rapidly at ˜290°C, finally reaching a near-zero value at 500°C. The rapid drop in GMI ratio at 290°C is associated with a reduction in the long-range ferromagnetic order as measured by the spontaneous magnetization ( M) at the Curie temperature ( T c). We also correlated the impedance with the magnetic properties of the material. From room temperature to 290°C, the impedance was found to be proportional to the square root of the magnetization to magnetic anisotropy ratio. Lastly, M( T) has been fit using a Handrich-Kobe model, which describes the system with a modified Brillouin function and an asymmetrical distribution of exchange interactions. We infer that the structural fluctuations of the amorphous phase result in a relatively small asymmetry in the fluctuation parameters.

  7. Temperature-dependent solvation modulates the dimensions of disordered proteins

    PubMed Central

    Wuttke, René; Hofmann, Hagen; Nettels, Daniel; Borgia, Madeleine B.; Mittal, Jeetain; Best, Robert B.; Schuler, Benjamin

    2014-01-01

    For disordered proteins, the dimensions of the chain are an important property that is sensitive to environmental conditions. We have used single-molecule Förster resonance energy transfer to probe the temperature-induced chain collapse of five unfolded or intrinsically disordered proteins. Because this behavior is sensitive to the details of intrachain and chain–solvent interactions, the collapse allows us to probe the physical interactions governing the dimensions of disordered proteins. We find that each of the proteins undergoes a collapse with increasing temperature, with the most hydrophobic one, λ-repressor, undergoing a reexpansion at the highest temperatures. Although such a collapse might be expected due to the temperature dependence of the classical “hydrophobic effect,” remarkably we find that the largest collapse occurs for the most hydrophilic, charged sequences. Using a combination of theory and simulation, we show that this result can be rationalized in terms of the temperature-dependent solvation free energies of the constituent amino acids, with the solvation properties of the most hydrophilic residues playing a large part in determining the collapse. PMID:24706910

  8. Temperature-dependent solvation modulates the dimensions of disordered proteins.

    PubMed

    Wuttke, René; Hofmann, Hagen; Nettels, Daniel; Borgia, Madeleine B; Mittal, Jeetain; Best, Robert B; Schuler, Benjamin

    2014-04-01

    For disordered proteins, the dimensions of the chain are an important property that is sensitive to environmental conditions. We have used single-molecule Förster resonance energy transfer to probe the temperature-induced chain collapse of five unfolded or intrinsically disordered proteins. Because this behavior is sensitive to the details of intrachain and chain-solvent interactions, the collapse allows us to probe the physical interactions governing the dimensions of disordered proteins. We find that each of the proteins undergoes a collapse with increasing temperature, with the most hydrophobic one, λ-repressor, undergoing a reexpansion at the highest temperatures. Although such a collapse might be expected due to the temperature dependence of the classical "hydrophobic effect," remarkably we find that the largest collapse occurs for the most hydrophilic, charged sequences. Using a combination of theory and simulation, we show that this result can be rationalized in terms of the temperature-dependent solvation free energies of the constituent amino acids, with the solvation properties of the most hydrophilic residues playing a large part in determining the collapse.

  9. The mass and speed dependence of meteor air plasma temperatures.

    PubMed

    Jenniskens, Peter; Laux, Christophe O; Wilson, Michael A; Schaller, Emily L

    2004-01-01

    The speed and mass dependence of meteor air plasma temperatures is perhaps the most important data needed to understand how small meteoroids chemically change the ambient atmosphere in their path and enrich the ablated meteoric organic matter with oxygen. Such chemistry can play an important role in creating prebiotic compounds. The excitation conditions in various air plasma emissions were measured from high-resolution optical spectra of Leonid storm meteors during NASA's Leonid Multi-Instrument Aircraft Campaign. This was the first time a sufficient number and range of temperature measurements were obtained to search for meteoroid mass and speed dependencies. We found slight increases in temperature with decreasing altitude, but otherwise nearly constant values for meteoroids with speeds between 35 and 72 km/s and masses between 10(-5) g and 1 g. We conclude that faster and more massive meteoroids produce a larger emission volume, but not a higher air plasma temperature. We speculate that the meteoric plasma may be in multiphase equilibrium with the ambient atmosphere, which could mean lower plasma temperatures in a CO(2)-rich early Earth atmosphere.

  10. The mass and speed dependence of meteor air plasma temperatures

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Laux, Christophe O.; Wilson, Michael A.; Schaller, Emily L.

    2004-01-01

    The speed and mass dependence of meteor air plasma temperatures is perhaps the most important data needed to understand how small meteoroids chemically change the ambient atmosphere in their path and enrich the ablated meteoric organic matter with oxygen. Such chemistry can play an important role in creating prebiotic compounds. The excitation conditions in various air plasma emissions were measured from high-resolution optical spectra of Leonid storm meteors during NASA's Leonid Multi-Instrument Aircraft Campaign. This was the first time a sufficient number and range of temperature measurements were obtained to search for meteoroid mass and speed dependencies. We found slight increases in temperature with decreasing altitude, but otherwise nearly constant values for meteoroids with speeds between 35 and 72 km/s and masses between 10(-5) g and 1 g. We conclude that faster and more massive meteoroids produce a larger emission volume, but not a higher air plasma temperature. We speculate that the meteoric plasma may be in multiphase equilibrium with the ambient atmosphere, which could mean lower plasma temperatures in a CO(2)-rich early Earth atmosphere.

  11. A temperature dependent SPICE macro-model for power MOSFETs

    SciTech Connect

    Pierce, D.G.

    1992-05-01

    A power MOSFET macro-model for use with the circuit simulator SPICE has been developed suitable for use over the temperature range of {minus}55 to 125{degrees}C. The model is comprised of a single parameter set with the temperature dependence accessed through the SPICE TEMP card. This report describes in detail the development of the model and the extraction algorithms used to obtain model parameters. The extraction algorithms are described in sufficient detail to allow for automated measurements which in turn allows for rapid and cost effective development of an accurate SPICE model for any power MOSFET. 22 refs.

  12. Temperature-dependent dielectric properties of a thermoplastic gelatin

    NASA Astrophysics Data System (ADS)

    Landi, Giovanni; Neitzert, Heinz C.; Sorrentino, Andrea

    2016-05-01

    The frequency and the temperature dependence of the dielectric properties of a thermoplastic gelatin based bio-material have been investigated. At lower frequencies the dielectric response is strongly affected by charge carrier accumulation at the electrodes which modifies the dominating hopping conduction mechanism. The variation of the ac conductivity with frequency obeys a Jonscher type power law except for a small deviation in the low frequency range due to the electrode polarization effect. The master curve of the ac conductivity data shows that the conductivity relaxation of the gelatin is temperature independent.

  13. Temperature dependence of the thermal conductivity of thin silicon nanowires.

    PubMed

    Donadio, Davide; Galli, Giulia

    2010-03-10

    We compute the lattice thermal conductivity (kappa) of silicon nanowires as a function of temperature by molecular dynamics simulations. In wires with amorphous surfaces kappa may reach values close to that of amorphous silicon and is nearly constant between 200 and 600 K; this behavior is determined by the presence of a majority of nonpropagating vibrational modes. We develop a parameter-free model that accounts for the temperature dependence observed in our simulations and provides a qualitative explanation of recent experiments. PMID:20163124

  14. Temperature dependence of the electrical conductivity of imidazolium ionic liquids.

    PubMed

    Leys, Jan; Wübbenhorst, Michael; Preethy Menon, Chirukandath; Rajesh, Ravindran; Thoen, Jan; Glorieux, Christ; Nockemann, Peter; Thijs, Ben; Binnemans, Koen; Longuemart, Stéphane

    2008-02-14

    The electrical conductivities of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids and of 1-hexyl-3-methylimidazolium ionic liquids with different anions were determined in the temperature range between 123 and 393 K on the basis of dielectric measurements in the frequency range from 1 to 10(7) Hz. Most of the ionic liquids form a glass and the conductivity values obey the Vogel-Fulcher-Tammann equation. The glass transition temperatures are increasing with increasing length of the alkyl chain. The fragility is weakly dependent on the alkyl chain length but is highly sensitive to the structure of the anion.

  15. Temperature dependence of predation depends on the relative performance of predators and prey.

    PubMed

    Öhlund, Gunnar; Hedström, Per; Norman, Sven; Hein, Catherine L; Englund, Göran

    2015-01-22

    The temperature dependence of predation rates is a key issue for understanding and predicting the responses of ecosystems to climate change. Using a simple mechanistic model, we demonstrate that differences in the relative performances of predator and prey can cause strong threshold effects in the temperature dependence of attack rates. Empirical data on the attack rate of northern pike (Esox lucius) feeding on brown trout (Salmo trutta) confirm this result. Attack rates fell sharply below a threshold temperature of +11°C, which corresponded to a shift in relative performance of pike and brown trout with respect to maximum attack and escape swimming speeds. The average attack speed of pike was an order of magnitude lower than the escape speed of brown trout at 5°C, but approximately equal at temperatures above 11°C. Thresholds in the temperature dependence of ecological rates can create tipping points in the responses of ecosystems to increasing temperatures. Thus, identifying thresholds is crucial when predicting future effects of climate warming.

  16. Dose dependence of mechanical properties in tantalum and tantalum alloys after low temperature irradiation

    SciTech Connect

    Byun, Thak Sang

    2008-01-01

    The dose dependence of mechanical properties was investigated for tantalum and tantalum alloys after low temperature irradiation. Miniature tensile specimens of three pure tantalum metals, ISIS Ta, Aesar Ta1, Aesar Ta2, and one tantalum alloy, Ta-1W, were irradiated by neutrons in the High Flux Isotope Reactor (HFIR) at ORNL to doses ranging from 0.00004 to 0.14 displacements per atom (dpa) in the temperature range 60 C 100 oC. Also, two tantalum-tungsten alloys, Ta-1W and Ta-10W, were irradiated by protons and spallation neutrons in the LANSCE facility at LANL to doses ranging from 0.7 to 7.5 dpa and from 0.7 to 25.2 dpa, respectively, in the temperature range 50 C 160 oC. Tensile tests were performed at room temperature and at 250oC at nominal strain rates of about 10-3 s-1. All neutron-irradiated materials underwent progressive irradiation hardening and loss of ductility with increasing dose. The ISIS Ta experienced embrittlement at 0.14 dpa, while the other metals retained significant necking ductility. Such a premature embrittlement in ISIS Ta is believed to be because of high initial oxygen concentrations picked up during a pre-irradiation anneal. The Ta-1W and Ta-10W specimens irradiated in spallation condition experienced prompt necking at yield since irradiation doses for those specimens were high ( 0.7 dpa). At the highest dose, 25.2 dpa, the Ta-10W alloy specimen broke with little necking strain. Among the test materials, the Ta-1W alloy displayed the best combination of strength and ductility. The plastic instability stress and true fracture stress were nearly independent of dose. Increasing test temperature decreased strength and delayed the onset of necking at yield.

  17. Identification of a kinetic length scale which dictates alloy phase composition in Ni-Al interfaces on annealing at low temperatures

    NASA Astrophysics Data System (ADS)

    Swain, Mitali; Singh, Surendra; Basu, Saibal; Bhattacharya, Debarati; Gupta, Mukul

    2014-12-01

    Ni-aluminides are an important class of intermetallics from technological point of view. Ni-Al phase diagram has been studied in detail experimentally as well as theoretically. It is known that if annealed at low temperature, the first alloy phase is usually NiAl3 according to Bené's rule. It is also understood that heat of formation may get modified by local densities of the constituents forming the alloy. In this regard, it is important to identify a kinetic length scale for defining "local density" in a system. We have deposited ultrathin multilayers of Ni and Al of layer thickness in tens of nanometres with Ni:Al stoichiometric ratio as 3:1 and 1:3, respectively. Considering these stoichiometry, Ni3Al and NiAl3 are the thermodynamically favoured alloy phases in these samples. We used x-ray reflectivity, polarized neutron reflectivity, x-ray diffraction, and secondary ion mass spectroscopy to follow the alloy formation after annealing and identified the alloy phases at interfaces with nanometre resolution. Diffusion length of Ni and Al was obtained using Darken's law. Our results predict that `diffusion length' is the unique length scale that connects kinetics to local density. In another interesting observation, using "virtual Kirkendall markers" at the interfaces, we showed asymmetry in consumption of Al for alloy formation, at Al on Ni (Al/Ni) and Ni on Al (Ni/Al) interfaces by comparing as-deposited and annealed states with respect to the markers.

  18. The importance of temperature dependent energy gap in the understanding of high temperature thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Singh, Saurabh; Pandey, Sudhir K.

    2016-10-01

    In this work, we show the importance of temperature dependent energy band gap, E g (T), in understanding the high temperature thermoelectric (TE) properties of material by considering LaCoO3 (LCO) and ZnV2O4 (ZVO) compounds as a case study. For the fix value of band gap, E g , deviation in the values of α has been observed above 360 K and 400 K for LCO and ZVO compounds, respectively. These deviation can be overcomed by consideration of temperature dependent band gap. The change in used value of E g with respect to temperature is ∼4 times larger than that of In As. This large temperature dependence variation in E g can be attributed to decrement in the effective on-site Coulomb interaction due to lattice expansion. At 600 K, the value of ZT for n and p-doped, LCO is ∼0.35 which suggest that it can be used as a potential material for TE device. This work clearly suggest that one should consider the temperature dependent band gap in predicting the high temperature TE properties of insulating materials.

  19. Effects of implantation temperature and thermal annealing on the Ga+ ion beam induced optical contrast formation in a-SiC:H

    NASA Astrophysics Data System (ADS)

    Tsvetkova, T.; Wright, C. D.; Kitova, S.; Bischoff, L.; Zuk, J.

    2013-07-01

    The effects of implantation temperature and post-implantation thermal annealing on the Ga+ ion beam induced optical contrast formation in hydrogenated silicon-carbon alloy films have been studied. As a result of the implantation a well-expressed "darkening" effect (i.e. absorption edge shift to the longer-wavelength/lower-photon-energy region) has been registered. It is accompanied by a remarkable increase of the absorption coefficient up to 2 orders of magnitude in the measured photon energy range (1.5-3.1 eV). The optical contrast thus obtained (between implanted and unimplanted regions of the film material) has been made use of in the form of optical pattern formation by computer-operated Ga+-focused ion beam. Possible applications of this effect in the area of submicron lithography and high-density optical data storage have been suggested with regard to the most widely spread focused micro-beam systems based on Ga+ liquid metal ion sources. The fact that Ga has a very low melting point (Tm = 29.8 °C) and an unusual feature of volume contraction on melting are factors which favour Ga incorporation upon ion-implantation as dispersed clusters, or small nanoparticles. It has been previously noted that Ga precipitation into nanoparticles can vary dramatically (in terms of particle size) with Ga concentration and small changes in surface implant temperature, thus affecting the optical properties of the target. The precise role of implantation temperature effects, i.e. the target temperature during Ga+ ion irradiation, on the optical contrast obtainable, has been therefore a key part of this study. Appropriate post-implantation annealing treatments were also studied, since these are expected to offer further benefits in reducing the required ion dose and enhancing contrast, thus increasing the cost-effectiveness of the bit-writing method.

  20. Effect of Annealing on Thermal & Optical Properties of Polypyrrole

    NASA Astrophysics Data System (ADS)

    Saxena, Rashmi; Dixit, Manasvi; Sharma, Kananbala; Saxena, Narendra S.; Sharma, Thaneshwar P.

    2008-04-01

    Pure polypyrrole sample (S1) was synthesized by chemical oxidation method using NaOH as reducing agent in aqueous HCl medium. The polypyrrole pellet sample (S2) was then annealed at 200 °C for 4 hrs. The amorphous nature of both annealed and as- prepared polypyrrole samples was confirmed by XRD. FTIR spectra of both samples were taken, which indicate the significant change in annealed sample (S2) compared to as prepared sample. Temperature dependence of effective thermal conductivity of both samples (S1, S2) was studied by Transient plane source (TPS) technique. The effective thermal conductivity (λe) obtained for S1 & S2 exhibits a variation with temperature and a peak was observed for the two samples at 150 °C & 120 °C with a value 0.17 W/mK & 0.18 W/mK respectively. The shift of thermal conductivity peak of annealed sample towards the lower temperature side is explained on the basis of removal of voids and defects on annealing. The absorption spectra of these samples were recorded by USB-2000 spectrophotometer at room temperature in the wavelength range 300-800 nm. From the analysis of absorption spectra, optical band gap of S1 & S2 were determined. It was found that the values of optical band gap for sample S1 & S2 are 2.39 eV&2.24 eV respectively.

  1. Interaction of YBa2Cu3O6.8 with atmospheric moisture during low-temperature annealing

    NASA Astrophysics Data System (ADS)

    Bobylev, I. B.; Ponosov, Yu. S.; Zyuzeva, N. A.

    2014-08-01

    The interaction of YBa2Cu3O6.8 (123) with water vapors at T = 200°C and the water influence on the structure and electrophysical properties of the compound have been studied using Raman spectroscopy, magnetometry, and X-ray diffraction. It has been found that the penetration of water into the 123 structure leads to its transition to a hydride-oxyhydroxide H2 x - z YBa2Cu3O y + x - z (OH) z containing fragments of the 124-type structure and exhibiting the spectrum of two-magnon scattering characteristic of antiferromagnetic 123 á compositions; in this case, the superconducting properties of the material as a whole are conserved. After short-time recovery annealing and subsequent oxidation, the water is removed from the compound structure, which leads to the disappearance of the spectrum of spin fluctuations. A possible mechanism of change in the 123 structure upon hydrogen and water intercalation has been discussed.

  2. Temperature dependence of carrier capture by defects in gallium arsenide

    SciTech Connect

    Wampler, William R.; Modine, Normand A.

    2015-08-01

    This report examines the temperature dependence of the capture rate of carriers by defects in gallium arsenide and compares two previously published theoretical treatments of this based on multi phonon emission (MPE). The objective is to reduce uncertainty in atomistic simulations of gain degradation in III-V HBTs from neutron irradiation. A major source of uncertainty in those simulations is poor knowledge of carrier capture rates, whose values can differ by several orders of magnitude between various defect types. Most of this variation is due to different dependence on temperature, which is closely related to the relaxation of the defect structure that occurs as a result of the change in charge state of the defect. The uncertainty in capture rate can therefore be greatly reduced by better knowledge of the defect relaxation.

  3. Temperature Dependence of Internal Deformation Field in Zeolites

    NASA Astrophysics Data System (ADS)

    Cha, Wonsuk; Song, Sanghoon; Jeong, Nak Cheon; Pham, Tung; Harder, Ross; Xiong, Gang; Yoon, Kyung Byung; Robinson, Ian K.; Kim, Hyunjung

    2011-03-01

    We studied temperature dependent internal deformation field distributions in zeolite microcrystals using coherent x-ray diffraction. We measured the coherent x-ray diffraction patterns around (200) and (020) Bragg peaks of the crystals. The three-dimensional real space images were obtained by phasing and inverting the oversampled diffraction patterns using the phase retrieval algorithm combined with error reduction and hybrid input-output method. The internal deformation fields show unusual temperature dependent behaviors which might be originated from the synthesis and calcination process. This work was supported by National Research Foundation of Korea (Nos. 2010-0000112 and R15-2008-006-01001-0), Seoul Research and Business Development Program (10816), and Sogang University Research Grant (2010).

  4. Temperature dependent transport characteristics of graphene/n-Si diodes

    NASA Astrophysics Data System (ADS)

    Parui, S.; Ruiter, R.; Zomer, P. J.; Wojtaszek, M.; van Wees, B. J.; Banerjee, T.

    2014-12-01

    Realizing an optimal Schottky interface of graphene on Si is challenging, as the electrical transport strongly depends on the graphene quality and the fabrication processes. Such interfaces are of increasing research interest for integration in diverse electronic devices as they are thermally and chemically stable in all environments, unlike standard metal/semiconductor interfaces. We fabricate such interfaces with n-type Si at ambient conditions and find their electrical characteristics to be highly rectifying, with minimal reverse leakage current (<10-10 A) and rectification of more than 106. We extract Schottky barrier height of 0.69 eV for the exfoliated graphene and 0.83 eV for the CVD graphene devices at room temperature. The temperature dependent electrical characteristics suggest the influence of inhomogeneities at the graphene/n-Si interface. A quantitative analysis of the inhomogeneity in Schottky barrier heights is presented using the potential fluctuation model proposed by Werner and Güttler.

  5. Effects of the high-temperature-annealed self-buffer layer on the improved properties of ZnO epilayers grown by helicon-wave-excited-plasma sputtering epitaxy on a-plane sapphire substrates

    NASA Astrophysics Data System (ADS)

    Koyama, T.; Fouda, A. N.; Shibata, N.; Chichibu, S. F.

    2007-10-01

    The use of the high-temperature-annealed self-buffer layer (HITAB) enabled to observe free A-and B-exciton emissions at 9K from ZnO heteroepitaxial films grown by the sputtering epitaxy method using a helicon-wave-excited plasma on uniaxially nearly lattice-matched (112¯0) Al2O3 substrates. The result was correlated with a twofold decrease in the densities of threading dislocations having both the screw and edge components, according to the dislocation concealing in ZnO HITAB due to lateral mass transport of low-temperature deposited ZnO nanocrystalline grains during high temperature annealing.

  6. Time temperature-stress dependence of boron fiber deformation

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1976-01-01

    Flexural stress relaxation (FSR) and flexural internal friction (FIF) techniques were employed to measure the time-dependent deformation of boron fibers from -190 to 800 C. The principal specimens were 203 micrometers diameter fibers commercially produced by chemical vapor deposition (CVD) on a 13 micrometer tungsten substrate. The observation of complete creep strain recovery with time and temperature indicated that CVD boron fibers deform flexurally as anelastic solids with no plastic component.

  7. Temperature-Dependent Conformations of Model Viscosity Index Improvers

    SciTech Connect

    Ramasamy, Uma Shantini; Cosimbescu, Lelia; Martini, Ashlie

    2015-05-01

    Lubricants are comprised of base oils and additives where additives are chemicals that are deliberately added to the oil to enhance properties and inhibit degradation of the base oils. Viscosity index (VI) improvers are an important class of additives that reduce the decline of fluid viscosity with temperature [1], enabling optimum lubricant performance over a wider range of operating temperatures. These additives are typically high molecular weight polymers, such as, but not limited to, polyisobutylenes, olefin copolymer, and polyalkylmethacrylates, that are added in concentrations of 2-5% (w/w). Appropriate polymers, when dissolved in base oil, expand from a coiled to an uncoiled state with increasing temperature [2]. The ability of VI additives to increase their molar volume and improve the temperature-viscosity dependence of lubricants suggests there is a strong relationship between molecular structure and additive functionality [3]. In this work, we aim to quantify the changes in polymer size with temperature for four polyisobutylene (PIB) based molecular structures at the nano-scale using molecular simulation tools. As expected, the results show that the polymers adopt more conformations at higher temperatures, and there is a clear indication that the expandability of a polymer is strongly influenced by molecular structure.

  8. Temperature dependent bacteriophages of a tropical bacterial pathogen

    PubMed Central

    Shan, Jinyu; Korbsrisate, Sunee; Withatanung, Patoo; Adler, Natalie Lazar; Clokie, Martha R. J.; Galyov, Edouard E.

    2014-01-01

    There is an increasing awareness of the multiple ways that bacteriophages (phages) influence bacterial evolution, population dynamics, physiology, and pathogenicity. By studying a novel group of phages infecting a soil borne pathogen, we revealed a paradigm shifting observation that the phages switch their lifestyle according to temperature. We sampled soil from an endemic area of the serious tropical pathogen Burkholderia pseudomallei, and established that podoviruses infecting the pathogen are frequently present in soil, and many of them are naturally occurring variants of a common virus type. Experiments on one phage in the related model B. thailandensis demonstrated that temperature defines the outcome of phage-bacteria interactions. At higher temperatures (37°C), the phage predominantly goes through a lytic cycle, but at lower temperatures (25°C), the phage remains temperate. This is the first report of a naturally occurring phage that follows a lytic or temperate lifestyle according to temperature. These observations fundamentally alter the accepted views on the abundance, population biology and virulence of B. pseudomallei. Furthermore, when taken together with previous studies, our findings suggest that the phenomenon of temperature dependency in phages is widespread. Such phages are likely to have a profound effect on bacterial biology, and on our ability to culture and correctly enumerate viable bacteria. PMID:25452746

  9. Temperature dependence of the reconstruction of zigzag edges in graphene.

    PubMed

    He, Kuang; Robertson, Alex W; Fan, Ye; Allen, Christopher S; Lin, Yung-Chang; Suenaga, Kazu; Kirkland, Angus I; Warner, Jamie H

    2015-05-26

    We examine the temperature dependence of graphene edge terminations at the atomic scale using an in situ heating holder within an aberration-corrected transmission electron microscope. The relative ratios of armchair, zigzag, and reconstructed zigzag edges from over 350 frames at each temperature are measured. Below 400 °C, the edges are dominated by zigzag terminations, but above 600 °C, this changes dramatically, with edges dominated by armchair and reconstructed zigzag edges. We show that at low temperature chemical etching effects dominate and cause deviation to the thermodynamics of the system. At high temperatures (600 and 800 °C), adsorbates are evaporated from the surface of graphene and chemical etching effects are significantly reduced, enabling the thermodynamic distribution of edge types to be observed. The growth rate of holes at high temperature is also shown to be slower than at room temperature, indicative of the reduced chemical etching process. These results provide important insights into the role of chemical etching effects in the hole formation, edge sputtering, and edge reconstruction in graphene.

  10. Temperature dependence of the Soret coefficient of ionic colloids.

    PubMed

    Sehnem, A L; Figueiredo Neto, A M; Aquino, R; Campos, A F C; Tourinho, F A; Depeyrot, J

    2015-10-01

    The temperature dependence of the Soret coefficient S(T)(T) in electrostatically charged magnetic colloids is investigated. Two different ferrofluids, with different particles' mean dimensions, are studied. In both cases we obtain a thermophilic behavior of the Soret effect. The temperature dependence of the Soret coefficient is described assuming that the nanoparticles migrate along the ionic thermoelectric field created by the thermal gradient. A model based on the contributions from the thermoelectrophoresis and variation of the double-layer energy, without fitting parameters, is used to describe the experimental results of the colloid with the bigger particles. To do so, independent measurements of the ζ potential, mass diffusion coefficient, and Seebeck coefficient are performed. The agreement of the theory and the experimental results is rather good. In the case of the ferrofluid with smaller particles, it is not possible to get experimentally reliable values of the ζ potential and the model described is used to evaluate this parameter and its temperature dependence. PMID:26565244

  11. Temperature-dependent particle-number projected moment of inertia

    SciTech Connect

    Allal, N. H.; Fellah, M.; Benhamouda, N.; Oudih, M. R.

    2008-05-15

    Expressions of the parallel and perpendicular temperature-dependent particle-number projected nuclear moment of inertia have been established by means of a discrete projection method. They generalize that of the FTBCS method and are well adapted to numerical computation. The effects of particle-number fluctuations have been numerically studied for some even-even actinide nuclei by using the single-particle energies and eigenstates of a deformed Woods-Saxon mean field. It has been shown that the parallel moment of inertia is practically not modified by the use of the projection method. In contrast, the discrepancy between the projected and FTBCS perpendicular moment of inertia values may reach 5%. Moreover, the particle-number fluctuation effects vary not only as a function of the temperature but also as a function of the deformation for a given temperature. This is not the case for the system energy.

  12. Density of biogas digestate depending on temperature and composition.

    PubMed

    Gerber, Mandy; Schneider, Nico

    2015-09-01

    Density is one of the most important physical properties of biogas digestate to ensure an optimal dimensioning and a precise design of biogas plant components like stirring devices, pumps and heat exchangers. In this study the density of biogas digestates with different compositions was measured using pycnometers at ambient pressure in a temperature range from 293.15 to 313.15K. The biogas digestates were taken from semi-continuous experiments, in which the marine microalga Nannochloropsis salina, corn silage and a mixture of both were used as feedstocks. The results show an increase of density with increasing total solid content and a decrease with increasing temperature. Three equations to calculate the density of biogas digestate were set up depending on temperature as well as on the total solid content, organic composition and elemental composition, respectively. All correlations show a relative deviation below 1% compared to experimental data.

  13. Temperature dependence of the properties of vapor-deposited polyimide

    NASA Astrophysics Data System (ADS)

    Tsai, F. Y.; Blanton, T. N.; Harding, D. R.; Chen, S. H.

    2003-04-01

    The Young's modulus and helium gas permeability of vapor-deposited poly(4,4'-oxydiphenylenepyromellitimide) were measured at cryogenic and elevated temperatures (10-573 K). The Young's modulus decreased with increasing temperature from 5.5 GPa at 10 K to 1.8 GPa at 573 K. The temperature dependency of the permeability followed the Arrhenius' relationship, with different activation energy for permeation for samples imidized under different conditions. The effect of the imidization conditions on the permeation properties could be explained in terms of morphology/crystallinity as determined by x-ray diffraction techniques. Imidizing in air instead of nitrogen increased the permeability while lowering the activation energy for permeation and crystallinity. Imidizing at higher heating rates (in nitrogen) resulted in higher permeability, lower activation energy for permeation, and larger and fewer crystallites with better-aligned lattice planes.

  14. Temperature dependence of charge transport in conjugated single molecule junctions

    NASA Astrophysics Data System (ADS)

    Huisman, Eek; Kamenetska, Masha; Venkataraman, Latha

    2011-03-01

    Over the last decade, the break junction technique using a scanning tunneling microscope geometry has proven to be an important tool to understand electron transport through single molecule junctions. Here, we use this technique to probe transport through junctions at temperatures ranging from 5K to 300K. We study three amine-terminated (-NH2) conjugated molecules: a benzene, a biphenyl and a terphenyl derivative. We find that amine groups bind selectively to undercoordinate gold atoms gold all the way down to 5K, yielding single molecule junctions with well-defined conductances. Furthermore, we find that the conductance of a single molecule junction increases with temperature and we present a mechanism for this temperature dependent transport result. Funded by a Rubicon Grant from The Netherlands Organisation for Scientific Research (NWO) and the NSEC program of NSF under grant # CHE-0641523.

  15. Density of biogas digestate depending on temperature and composition.

    PubMed

    Gerber, Mandy; Schneider, Nico

    2015-09-01

    Density is one of the most important physical properties of biogas digestate to ensure an optimal dimensioning and a precise design of biogas plant components like stirring devices, pumps and heat exchangers. In this study the density of biogas digestates with different compositions was measured using pycnometers at ambient pressure in a temperature range from 293.15 to 313.15K. The biogas digestates were taken from semi-continuous experiments, in which the marine microalga Nannochloropsis salina, corn silage and a mixture of both were used as feedstocks. The results show an increase of density with increasing total solid content and a decrease with increasing temperature. Three equations to calculate the density of biogas digestate were set up depending on temperature as well as on the total solid content, organic composition and elemental composition, respectively. All correlations show a relative deviation below 1% compared to experimental data. PMID:26026294

  16. Temperature dependence of DNA translocations through solid-state nanopores

    PubMed Central

    Verschueren, Daniel V.; Jonsson, Magnus P.; Dekker, Cees

    2015-01-01

    In order to gain a better physical understanding of DNA translocations through solid-state nanopores, we study the temperature dependence of λ-DNA translocations through 10 nm-in-diameter silicon-nitride nanopores, both experimentally and theoretically. The measured ionic conductance G, the DNA-induced ionic-conductance blockades ΔG and the event frequency Γ all increase with increasing temperature while the DNA translocation time τ decreases. G and ΔG are accurately described when bulk and surface conductances of the nanopore are considered and access resistance is incorporated appropriately. Viscous drag on the untranslocated part of the DNA coil is found to dominate the temperature dependence of the translocation times and the event rate is well described by a balance between diffusion and electrophoretic motion. The good fit between modeled and measured properties of DNA translocations through solid-state nanopores in this first comprehensive temperature study, suggest that our model captures the relevant physics of the process. PMID:25994084

  17. Temperature Dependent Cyclic Deformation Mechanisms in Haynes 188 Superalloy

    NASA Technical Reports Server (NTRS)

    Rao, K. Bhanu Sankara; Castelli, Michael G.; Allen, Gorden P.; Ellis, John R.

    1995-01-01

    The cyclic deformation behavior of a wrought cobalt-base superalloy, Haynes 188, has been investigated over a range of temperatures between 25 and 1000 C under isothermal and in-phase thermomechanical fatigue (TMF) conditions. Constant mechanical strain rates (epsilon-dot) of 10(exp -3)/s and 10(exp -4)/s were examined with a fully reversed strain range of 0.8%. Particular attention was given to the effects of dynamic strain aging (DSA) on the stress-strain response and low cycle fatigue life. A correlation between cyclic deformation behavior and microstructural substructure was made through detailed transmission electron microscopy. Although DSA was found to occur over a wide temperature range between approximately 300 and 750 C the microstructural characteristics and the deformation mechanisms responsible for DSA varied considerably and were dependent upon temperature. In general, the operation of DSA processes led to a maximum of the cyclic stress amplitude at 650 C and was accompanied by pronounced planar slip, relatively high dislocation density, and the generation of stacking faults. DSA was evidenced through a combination of phenomena, including serrated yielding, an inverse dependence of the maximum cyclic hardening with epsilon-dot, and an instantaneous inverse epsilon-dot sensitivity verified by specialized epsilon-dot -change tests. The TMF cyclic hardening behavior of the alloy appeared to be dictated by the substructural changes occuring at the maximum temperature in the TMF cycle.

  18. Temperature dependence of Brewer UV measurements at Rome station

    NASA Astrophysics Data System (ADS)

    Siani, Anna M.; Benevento, Giuseppe; Casale, Giuseppe R.

    2003-11-01

    Decreasing trends of total ozone affect mainly solar ultraviolet (UV) levels at ground level with adverse effects on the biosphere. Highly accurate measurements of solar UV irradiance have become an important issue to assess UV trends. To detect these trends stations with well calibrated instruments, with long-term stability and Quality Assurance (QA)/ Quality Control (QC) carefully followed procedures, are necessary. The Solar Radiometry Observatory of Rome, University "La Sapienza" (city center) is one of the stations regularly measuring UV irradiance in Italy. Measurements of UV spectral (290-325 nm) irradiance started in 1992, using Brewer MKIV 067. Measurements of total irradiance contained in the 280 - 320 nm waveband begun in 2000 with the YES UVB-1 broad-band radiometer. An investigation of the internal temperature dependence of the spectral responsivity to improve the quality of the Brewer UV data was carried out. The study was based on the analysis of responsivity files recorded during the years 2000-2002. Responsivities are provided by specific tests through a set of five 50 W quartz tungsten-halogen lamps, traceable to the standards of the National Institute of Standards and Technology (NIST). The lamp tests allow to measure any changes in the instrument response over time. It was observed that a decrease in the instrument's responsivity resulted from an increase of the internal temperature. A methodology based on a family of responsivity files at different temperature intervals is proposed to allow correction of UV irradiances using the responsivity file at the corresponding temperatures. The mean percentage differnce between temperature corrected and non-corrected Brewer data varies from 0.8% to 1.5% over an internal temperature of 8°C-42°C. In addition the results of a field evaluation in Rome between Brewer 067 and two temperature stabilized instruments, a broad-band radiometer (YES UVB-1) and a moderate bandwidth multichannel radiometer

  19. Post-annealing of thin-film yttria stabilized zirconia electrolytes for anode-supported low-temperature solid oxide fuel cells.

    PubMed

    Bae, Jiwoong; Chang, Ikwhang; Kang, Sungmin; Hong, Soonwook; Cha, Suk Won; Kim, Young Beom

    2014-12-01

    The effects of a post-annealing treatment on the performance of low-temperature solid oxide fuel cells (LT-SOFCs) were investigated. Nickel oxide-samarium doped ceria (NiO-SDC) anodes and yttria stabilized zirconia (YSZ) electrolytes were deposited on anodized aluminum oxide (AAO) membranes by RF sputtering and DC reactive sputtering, respectively. The half-cell of YSZ/NiO-SDC was then heat-treated at 600 degrees C for 10 h, and a porous platinum (Pt) cathode was deposited on the annealed YSZ/NiO-SDC structure by DC magnetron sputtering. Electrochemical impedance spectroscopy (EIS) analysis revealed a significant decrease in the ohmic resistance and a slight increase in the cathodic impedance. Such a result may be attributed to the increased grain size and enhanced crystallinity of the YSZ electrolyte after the heat treatment. The maximum power density observed for the heat-treated cell was 35 mW/cm2 at 450 degrees C, more than three times higher than the 10 mW/cm2 value obtained for the as-deposited cell.

  20. Effect of post-annealing temperature on structure and optical properties of Zn1- x Cd x O thin films synthesized by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sui, Yingrui; Song, Yanping; Yue, Yonggao; Xiao, Li; Wu, Yanjie; Lv, Shiquan; Liu, Xiaoyan; Yao, Bin; Yang, Jinghai

    2016-08-01

    The Zn1- x Cd x O ( x = 0.5) thin film was grown on quartz by the direct current reactive magnetron sputtering and post-annealing techniques. The influence of annealing temperature ( T a) on the structure and optical properties of Zn1- x Cd x O thin film was investigated by using X-ray diffraction (XRD), photoluminescence and optical absorbance measurements. The XRD results indicate that the as-grown Zn1- x Cd x O thin film is of highly (002)-preferred orientation and possessing the hexagonal wurtzite structure of pure ZnO, as the T a increases up from 300 to 600 °C, the phase segregation as cubic CdO was observed. The detailed microstructures of the Zn1- x Cd x O thin film were investigated by transmission electron microscopy. Moreover, with the increase of T a, the optical band gap of the Zn1- x Cd x O thin films increased from 2.08 to 3.14 eV. Correspondingly, the near-band-edge photoluminescence was tuned in a wide visible region from ~588 to 403 nm.

  1. Temperature dependent deformation mechanisms in pure amorphous silicon

    SciTech Connect

    Kiran, M. S. R. N. Haberl, B.; Williams, J. S.; Bradby, J. E.

    2014-03-21

    High temperature nanoindentation has been performed on pure ion-implanted amorphous silicon (unrelaxed a-Si) and structurally relaxed a-Si to investigate the temperature dependence of mechanical deformation, including pressure-induced phase transformations. Along with the indentation load-depth curves, ex situ measurements such as Raman micro-spectroscopy and cross-sectional transmission electron microscopy analysis on the residual indents reveal the mode of deformation under the indenter. While unrelaxed a-Si deforms entirely via plastic flow up to 200 °C, a clear transition in the mode of deformation is observed in relaxed a-Si with increasing temperature. Up to 100 °C, pressure-induced phase transformation and the observation of either crystalline (r8/bc8) end phases or pressure-induced a-Si occurs in relaxed a-Si. However, with further increase of temperature, plastic flow rather than phase transformation is the dominant mode of deformation. It is believed that the elevated temperature and pressure together induce bond softening and “defect” formation in structurally relaxed a-Si, leading to the inhibition of phase transformation due to pressure-releasing plastic flow under the indenter.

  2. Temperature dependent vibration analysis of functionally graded rectangular plates

    NASA Astrophysics Data System (ADS)

    Kim, Young-Wann

    2005-06-01

    A theoretical method is developed to investigate vibration characteristics of initially stressed functionally graded rectangular plates made up of metal and ceramic in thermal environment. The temperature is assumed to be constant in the plane of the plate and to vary in the thickness direction only. Two types of thermal condition are considered. The first type is that one value of the temperature is imposed on the upper surface and the other (or same) value on the lower surface. The second is that the heat flows from the upper surface to the lower one held at a prescribed temperature. Material properties are assumed to be temperature dependent, and vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The third-order shear deformation plate theory to account for rotary inertia and transverse shear strains is adopted to formulate the theoretical model. The Rayleigh-Ritz procedure is applied to obtain the frequency equation. The analysis is based on an expansion of the displacements in the double Fourier series that satisfy the boundary conditions. The effect of material compositions, plate geometry, and temperature fields on the vibration characteristics is examined. The present theoretical results are verified by comparing with those in literature.

  3. Temperature dependence of the hydrophobic interaction in protein folding.

    PubMed Central

    Baldwin, R L

    1986-01-01

    Accurate calorimetric data for the thermodynamics of transfer of six liquid hydrocarbons to water have been combined with solubility data to provide a model for the temperature dependence of the hydrophobic interaction in protein folding. The model applies at temperatures for which the change in heat capacity (delta Cp) is constant. The extrapolated value of the temperature (Ts) at which the entropy of transfer (delta S degrees) reaches zero is strikingly similar (Ts = 112.8 degrees C +/- 2.2 degrees C) for the six hydrocarbons. This finding provides an interpretation for the empirical relation discovered by Sturtevant: the ratio delta S degrees/delta Cp measured at 25 degrees C is constant for the transfer of nonpolar substances from nonaqueous media to water. Constancy of this ratio is equivalent to Ts = constant. When applied to protein folding, the hydrocarbon model gives estimates of the contributions of the hydrophobic interaction to the entropy and enthalpy changes on unfolding and, by difference, estimates of the residual contributions from other sources. The major share of the large enthalpy change observed on unfolding at high temperatures comes from the hydrophobic interaction. The hydrophobic interaction changes from being entropy-driven at 22 degrees C to being enthalpy-driven at 113 degrees C. Finally, the hydrocarbon model predicts that plots of the specific entropy change on unfolding versus temperature should nearly intersect close to 113 degrees C, as observed by Privalov. PMID:3464944

  4. Temperature, stress, and structural-relaxation dependence of the magnetostriction in (Co0.94/BFe0.06)75/BSi15B10 glasses

    NASA Astrophysics Data System (ADS)

    Barandiarán, J. M.; Hernando, A.; Madurga, V.; Nielsen, O. V.; Vázquez, M.; Vázquez-López, M.

    1987-04-01

    High-sensitivity measurements of the magnetostriction constant λs have been performed in the nearly zero magnetostriction (Co0.94Fe0.06)75Si15B10 metallic glass as a function of the stress and temperature after pulse-annealing treatments. A stress dependence of λs in this amorphous alloy is reported for the first time. At room temperature a slope of about -2×10-7 GPa-1 has been determined leading to a change in the sign of the magnetostriction constant in some circumstances. For determination of the thermal variation of λs, the temperature was changed by means of the alternating current flowing through the sample during the measurement, which was done by the small-angle magnetization-rotation (SAMR) method. The compensation temperatures, i.e., those temperatures at which the value of λs vanishes in going from negative to positive, were determined after isochronal annealing. In this way, the evolution of the single-ion and two-ion contributions to the magneto- striction was monitored during the structural relaxation. The ratio between the two contributions follows a chemical short-range-order kinetics. The stress dependence of the single-ion and two-ion contributions was deduced from measurements of the stress dependence of the magnetostriction at different temperatures.

  5. Effects of oxygen partial pressure and annealing temperature on the residual stress of hafnium oxide thin-films on silicon using synchrotron-based grazing incidence X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Biswas, Debaleen; Sinha, Anil Kumar; Chakraborty, Supratic

    2016-10-01

    Synchrotron radiation-based grazing incidence X-ray diffraction (GI-XRD) technique is employed here to estimate the residual stress of < 10 nm thin hafnium oxide film deposited on Si (100) substrate at different argon/oxygen ratios using reactive rf sputtering. A decrease in residual stress, tensile in nature, is observed at higher annealing temperature for the samples deposited with increasing argon ratio in the Ar/O2 plasma. The residual stress of the films deposited at higher pAr (Ar:O2 = 4:1) is also found to be decreased with increasing annealing temperature. But the stress is more or less constant with annealing temperature for the films deposited at lower Ar/O2 (1:4) ratio. All the above phenomena can be explained on the basis of swelling of the interfacial layer and enhanced structural relaxation in the presence of excess Hf in hafnium oxide film during deposition.

  6. Temperature-dependent Refractive Index of Silicon and Germanium

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.; Madison, Timothy J.

    2006-01-01

    Silicon and germanium are perhaps the two most well-understood semiconductor materials in the context of solid state device technologies and more recently micromachining and nanotechnology. Meanwhile, these two materials are also important in the field of infrared lens design. Optical instruments designed for the wavelength range where these two materials are transmissive achieve best performance when cooled to cryogenic temperatures to enhance signal from the scene over instrument background radiation. In order to enable high quality lens designs using silicon and germanium at cryogenic temperatures, we have measured the absolute refractive index of multiple prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For silicon, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 1.1 to 5.6 pin, while for germanium, we cover temperatures ranging from 20 to 300 K and wavelengths from 1.9 to 5.5 microns. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. Citing the wide variety of values for the refractive indices of these two materials found in the literature, we reiterate the importance of measuring the refractive index of a sample from the same batch of raw material from which final optical components are cut when absolute accuracy greater than k5 x 10" is desired.

  7. Temperature-dependent elastic properties of Ti{sub 1−x}Al{sub x}N alloys

    SciTech Connect

    Shulumba, Nina; Hellman, Olle; Rogström, Lina; Raza, Zamaan; Tasnádi, Ferenc; Odén, Magnus; Abrikosov, Igor A.

    2015-12-07

    Ti{sub 1−x}Al{sub x}N is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the symmetry imposed force constant temperature dependent effective potential method, which include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C{sub 11} decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy.

  8. Temperature dependence of the energy gap of semiconductors in the low-temperature limit.

    PubMed

    Cardona, Manuel; Meyer, T A; Thewalt, M L W

    2004-05-14

    The temperature dependence of the electronic states and energy gaps of semiconductors is an old but still important experimental and theoretical topic. Remarkably, extant results do not clarify the asymptotic T-->0 behavior. Recent breakthroughs in the spectroscopy of enriched 28Si allow us to measure changes in the band gap over the liquid 4He temperature range with an astounding precision of one part in 10(8), revealing a T4.0+/-0.2 decrease with increasing T. This is in excellent agreement with a theoretical argument predicting an exponent of 4. This power law should apply, in the low temperature limit, to the temperature dependence of the energies of all electronic states in semiconductors and insulators.

  9. Temperature dependence and shape effect in high-temperature microwave heating of nickel oxide powders

    NASA Astrophysics Data System (ADS)

    Sugawara, H.; Kashimura, K.; Hayashi, M.; Matsumuro, T.; Watanabe, T.; Mitani, T.; Shinohara, N.

    2015-02-01

    The temperature dependence of microwave absorption was investigated for Ni1-yO particles over the frequency range 2.0-13.5 GHz and temperature range 25-1000 °C. Using a coaxial transmission line method with a network analyzer, both the real and imaginary parts of the relative permittivity (ε‧r and ε″r, respectively) and permeability (μ‧r and μ″r, respectively) were measured; finding that both are largely dependent on the temperature at all frequencies. Furthermore, permeability loss factors related to shape effects were observed at high frequencies, indicating an increase in the microwave-absorption properties. A modified form of Mie's theory was applied to discuss these effects, wherein a spherical model demonstrating a close fit to the shape effect data suggests a more complex microwave-absorption behavior at increased temperature.

  10. The effects of maintaining temperature in annealing heat treatment for an FSWed 6061-T6 Al alloy.

    PubMed

    Lee, Seung-Jun; Han, Min-Su; Kim, Seong-Jong

    2013-08-01

    The technological development of all kinds of lightweight transportation devices including vehicles, aircraft, ships, etc. has progressed markedly with the demand for energy saving and environmental protection. Aluminum alloy is in the spotlight as it is a suitable environmentally friendly material. However, deformation is a major problem during the welding process because aluminum alloy has a large thermal expansion coefficient. In addition, it is known that its corrosion resistance is excellent; nevertheless, in practice, considerable corrosion is generated and this is a major problem. To solve this problem, the friction stir welding (FSW) technology is applied extensively at various industrial fields as a new welding technique. This method involves a process in which materials are joined by frictional heat and physical force. Therefore, we evaluated improvements in mechanical properties and corrosion resistance through annealing heat treatment after FSW. The electrochemical experiment did not show a significant difference. However, the microstructure observation showed defectless, fine crystal particles, indicating excellent properties at 200-225°C.

  11. The effects of maintaining temperature in annealing heat treatment for an FSWed 6061-T6 Al alloy.

    PubMed

    Lee, Seung-Jun; Han, Min-Su; Kim, Seong-Jong

    2013-08-01

    The technological development of all kinds of lightweight transportation devices including vehicles, aircraft, ships, etc. has progressed markedly with the demand for energy saving and environmental protection. Aluminum alloy is in the spotlight as it is a suitable environmentally friendly material. However, deformation is a major problem during the welding process because aluminum alloy has a large thermal expansion coefficient. In addition, it is known that its corrosion resistance is excellent; nevertheless, in practice, considerable corrosion is generated and this is a major problem. To solve this problem, the friction stir welding (FSW) technology is applied extensively at various industrial fields as a new welding technique. This method involves a process in which materials are joined by frictional heat and physical force. Therefore, we evaluated improvements in mechanical properties and corrosion resistance through annealing heat treatment after FSW. The electrochemical experiment did not show a significant difference. However, the microstructure observation showed defectless, fine crystal particles, indicating excellent properties at 200-225°C. PMID:23920178

  12. Photoelectrochemical, impedance and optical data for self Sn-diffusion doped Fe2O3 photoanodes fabricated at high temperature by one and two-step annealing methods

    PubMed Central

    Shinde, Pravin S.; Annamalai, Alagappan; Kim, Ju Hun; Choi, Sun Hee; Lee, Jae Sung; Jang, Jum Suk

    2015-01-01

    The optical, morphological and photoelectrochemical (PEC) properties of transition metal oxide semiconductors are important to understand their influence on water oxidation performance. Herein, we provide experimental evidences for a better understanding of the factors that dictate the interactions of Sn-diffusion doping on the PEC properties of Fe2O3 photoanodes fabricated at high temperature by one- and two-step annealing methods. The synthesis, characterization methods and other experimental details are provided. Limited previous information on the PEC and electrochemical impedance spectroscopic studies has been published. This data article contains Supplementary data, figures and methods related to the research article by Shinde et al. (2015) [1]. Here, we provide a further set of the obtained experimental data results. PMID:26693514

  13. Temperature dependent photoluminescence from lead sulfide nanosheets and nanocubes.

    PubMed

    Kim, Jungdong; Kim, Seung Gi; Oh, Eunsoon; Kim, Sang Hyuk; Choi, Won Jun

    2016-01-29

    We studied temperature dependent photoluminescence (PL) spectra in the mid-infrared range from lead sulfide (PbS) nanosheets with an average thickness of 25 nm and nanocubes grown by solvothermal and hydrothermal methods. Distinct bandedge PL emission was observed in the whole temperature range between 10 and 300 K, indicating the high optical quality of these nanostructures. The PL peak of the nanosheets was found at 0.326 eV at 10 K, about 40 meV higher than that of bulk PbS due to the quantum confinement effect, whereas no confinement effect was observed for the nanocubes. We also demonstrate that the absorption edges of the nanocubes and nanosheets in the transmission spectra agree very well with their fundamental bandgap.

  14. Simulations of the temperature dependence of amide I vibration.

    PubMed

    Kaminský, Jakub; Bouř, Petr; Kubelka, Jan

    2011-01-13

    For spectroscopic studies of peptide and protein thermal denaturation it is important to single out the contribution of the solvent to the spectral changes from those originated in the molecular structure. To obtain insights into the origin and size of the temperature solvent effects on the amide I spectra, combined molecular dynamics and density functional simulations were performed with the model N-methylacetamide molecule (NMA). The computations well reproduced frequency and intensity changes previously observed in aqueous NMA solutions. An empirical correction of vacuum frequencies in single NMA molecule based on the electrostatic potential of the water molecules provided superior results to a direct density functional average obtained for a limited number of solute-solvent clusters. The results thus confirm that the all-atom quantum and molecular mechanics approach captures the overall influence of the temperature dependent solvent properties on the amide I spectra and can improve the accuracy and reliability of molecular structural studies.

  15. Temperature-dependent potential in cluster-decay process

    NASA Astrophysics Data System (ADS)

    Gharaei, R.; Zanganeh, V.

    2016-08-01

    Role of the thermal effects of the parent nucleus in the Coulomb barrier and the half-life of 28 cluster-decays is systematically analyzed within the framework of the proximity formalism, namely proximity potential 2010. The WKB approximation is used to determine the penetration probability of the emitted cluster. It is shown that the height and width of the Coulomb barrier in the temperature-dependent proximity potential are less than its temperature-independent version. Moreover, this investigation reveals that the calculated values of half-life for selected cluster-decays are in better agreement with the experimental data when the mentioned effects are imposed on the proximity approach. A discussion is also presented about the predictions of the present thermal approach for cluster-decay half-lives of the super-heavy-elements.

  16. Temperature dependence of bulk viscosity in water using acoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Holmes, M. J.; Parker, N. G.; Povey, M. J. W.

    2011-01-01

    Despite its fundamental role in the dynamics of compressible fluids, bulk viscosity has received little experimental attention and there remains a paucity of measured data. Acoustic spectroscopy provides a robust and accurate approach to measuring this parameter. Working from the Navier-Stokes model of a compressible fluid one can show that the bulk viscosity makes a significant and measurable contribution to the frequency-squared acoustic attenuation. Here we employ this methodology to determine the bulk viscosity of Millipore water over a temperature range of 7 to 50°C. The measured attenuation spectra are consistent with the theoretical predictions, while the bulk viscosity of water is found to be approximately three times larger than its shear counterpart, reinforcing its significance in acoustic propagation. Moreover, our results demonstrate that this technique can be readily and generally applied to fluids to accurately determine their temperature dependent bulk viscosities.

  17. Localized subcritical convective cells in temperature-dependent viscosity fluids

    NASA Astrophysics Data System (ADS)

    Solomatov, V. S.

    2012-06-01

    Numerical simulations of infinite Prandtl number convection in the stagnant lid regime of temperature-dependent viscosity convection demonstrate the existence of spatially localized, stable convective cells below the critical Rayleigh number (subcritical convection). These solutions are in stark contrast to the usual, supercritical, convective planforms, where convective cells form in the entire layer. The isolated cell has a shape of an axisymmetric dome with an upwelling at the center and thus appears as a very weak plume. Formation of these structures requires subcritical conditions and a localized initial temperature perturbation but does not require any spatial heterogeneity in the material properties or the heat flux. When several localized plumes form, they tend to attract to each other and form stable clusters. This type of subcritical convection may play a role in the formation and longevity of localized features on planetary bodies, including the crustal dichotomy and Tharsis region on Mars and the asymmetric pattern of volcanism on Mercury.

  18. On the temperature dependence of oceanic export efficiency

    NASA Astrophysics Data System (ADS)

    Cael, B. B.; Follows, Michael J.

    2016-05-01

    Quantifying the fraction of primary production exported from the euphotic layer (termed the export efficiency ef) is a complicated matter. Studies have suggested empirical relationships with temperature which offer attractive potential for parameterization. Here we develop what is arguably the simplest mechanistic model relating the two, using established thermodynamic dependencies for primary production and respiration. It results in a single-parameter curve that constrains the envelope of possible efficiencies, capturing the upper bounds of several ef-T data sets. The approach provides a useful theoretical constraint on this relationship and extracts the variability in ef due to temperature but does not idealize out the remaining variability which evinces the substantial complexity of the system in question.

  19. Temperature dependencies of Henry's law constants for different plant sesquiterpenes.

    PubMed

    Copolovici, Lucian; Niinemets, Ülo

    2015-11-01

    Sesquiterpenes are plant-produced hydrocarbons with important ecological functions in plant-to-plant and plant-to-insect communication, but due to their high reactivity they can also play a significant role in atmospheric chemistry. So far, there is little information of gas/liquid phase partition coefficients (Henry's law constants) and their temperature dependencies for sesquiterpenes, but this information is needed for quantitative simulation of the release of sesquiterpenes from plants and modeling atmospheric reactions in different phases. In this study, we estimated Henry's law constants (Hpc) and their temperature responses for 12 key plant sesquiterpenes with varying structure (aliphatic, mono-, bi- and tricyclic sesquiterpenes). At 25 °C, Henry's law constants varied 1.4-fold among different sesquiterpenes, and the values were within the range previously observed for monocyclic monoterpenes. Hpc of sesquiterpenes exhibited a high rate of increase, on average ca. 1.5-fold with a 10 °C increase in temperature (Q10). The values of Q10 varied 1.2-fold among different sesquiterpenes. Overall, these data demonstrate moderately high variation in Hpc values and Hpc temperature responses among different sesquiterpenes. We argue that these variations can importantly alter the emission kinetics of sesquiterpenes from plants. PMID:26291755

  20. Temperature and moisture dependence of dielectric constant for silica aerogels

    SciTech Connect

    Hrubesh, L.H., LLNL

    1997-03-01

    The dielectric constants of silica aerogels are among the lowest measured for any solid material. The silica aerogels also exhibit low thermal expansion and are thermally stable to temperatures exceeding 500{degrees}C. However, due to the open porosity and large surface areas for aerogels, their dielectric constants are strongly affected by moisture and temperature. This paper presents data for the dielectric constants of silica aerogels as a function of moisture content at 25{degrees}C, and as a function of temperature, for temperatures in the range from 25{degrees}C to 450{degrees}C. Dielectric constant data are also given for silica aerogels that are heat treated in dry nitrogen at 500{degrees}C, then cooled to 25{degrees}C for measurements in dry air. All measurements are made on bulk aerogel spheres at 22GHz microwave frequency, using a cavity perturbation method. The results of the dependence found here for bulk materials can be inferred to apply also to thin films of silica aerogels having similar nano-structures and densities.