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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. Microstructural dependence of annealing temperature in magnetron-sputtered Al-Si-Cu films

    NASA Astrophysics Data System (ADS)

    Liang, Ming-Kaan; Ling, Yong-Chien

    1993-09-01

    The effect of sputtering temperature, sputtering bias, and annealing temperature upon the sheet resistance, WO3 formation at the Al-Si-Cu/Ti-W interface, and diffraction intensity of the Al2Cu precipitates of magnetron-sputtered Al-Si-Cu films were investigated. Statistical methods and microcharacterization techniques were applied to study these effects. Statistical analysis verifies the effect of annealing temperature on the measured sheet resistance. Annealing temperature alone is the dominant factor upon the WO3 formation at the Al-Si-Cu/Ti-W interface and the Al2Cu (211) plane diffraction intensity. Annealed samples are of higher sheet resistance. Increase in sheet resistance is ascribed to the formation of interfacial WO3. Reduced electromigration is related to the formation of Al2Cu precipitates. Secondary ion mass spectrometry (SIMS) analysis of the as-deposited sample depicts the presence of an excess amount of oxygen atoms at the surface and the Al-Si-Cu/Ti-W and Ti-W/Ti interfaces. Rutherford backscattering spectrometry and SIMS analyses reveal the outdiffusion of W from the Ti-W layer toward the Al-Si-Cu layer, the presence of Si nodules at the Al-Si-Cu/Ti-W interface, and the formation of Ti silicides at the Ti/Si interface. These phenomena are confirmed by transmission electron microscopy, energy dispersive x-ray analysis, and scanning electron microscopy analyses. It is concluded that interfacial oxygen, which reacts with W to form WO3 upon annealing, warrants further reduction to yield films of better sheet resistance.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    Due to local field enhancement and subwavelength confinements, nano-plasmonics provide numerous novel applications. Simultaneously, as an efficient nanoscale heat generator from inherent absorption, thermo-plasmonics is emerging as an important branch. However, although significant temperature increase is involved in applications, detailed characterization of metal permittivity at different temperatures and corresponding thermo-derivative are lacking. In this work, we extract the permittivity of gold from 300K to the annealing temperature of 570K. By comparing annealed and unannealed films, more than one-order difference in thermo-derivative of permittivity is revealed, resulting in unexpectedly large variation of plasmonic properties. Our result is valuable not only for characterizing extensively used unannealed nanoparticles, but also for designing future thermo-nano-plasmonic systems.

  6. 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.

  7. The annealing temperature dependences of microstructures and magnetic properties in electro-chemical deposited CoNiFe thin films

    NASA Astrophysics Data System (ADS)

    Suharyadi, Edi; Riyanto, Agus; Abraha, Kamsul

    2016-04-01

    CoNiFe thin films with various compositions had been successfully fabricated using electro-chemical deposition method. The crystal structure of Co65Ni15Fe20, Co62Ni15Fe23, and Co55Ni15Fe30 thin films was fcc, bcc-fcc mix, and bcc, respectively. The difference crystal structure results the difference in magnetic properties. The saturation magnetic flux density (Bs) of Co65Ni15Fe20, Co62Ni15Fe23, and Co55Ni15Fe30 thin films was 1.89 T, 1.93 T, and 2.05 T, respectively. An optimal annealing temperature was determined for controlling the microstructure and magnetic properties of CoNiFe thin films. Depending on annealing temperature, the ratio of bcc and fcc structure varied without changing the film composition. By annealing at temperature of T ≥ 350°C, the intensity ratio of X-ray diffraction peaks for bcc(110) to fcc(111) increased. The increase of phase ratio of bcc(110) to fcc(111) caused the increase of Bs, from 1.89 T to 1.95 T. Coercivity (Hc) also increased after annealing, from 2.6 Oe to 18.6 Oe for fcc phase thin films, from 2.0 Oe to 12.0 Oe for fcc-bcc mix phase thin films, and 7.8 Oe to 8 Oe for bcc phase thin films. The changing crystal structures during annealing process indicated that the thermal treatment at high temperature cause the changing crystallinity and atomic displacement. The TEM bright-field images with corresponding selected-area electron diffraction (SAED) patterns showed that there are strongly effects of thermal annealing on the size of fcc and bcc phase crystalline grain as described by size of individual spot and discontinuous rings. The size of crystalline grains increased by thermal annealing. The evolution of bcc and fcc structures of CoNiFe during annealing is though to be responsible for the change of magnetic properties.

  8. Dependence of the interlayer coupling on anneal temperature in Ni-Fe/Cu evaporated multilayers

    NASA Astrophysics Data System (ADS)

    Borchers, J. A.; Gehring, P. M.; Majkrzak, C. F.; Zeltser, A. M.; Smith, N.; Ankner, J. F.

    1997-04-01

    Resistivity and magnetization studies of [Ni83Fe17(27 Å)|Cu(37 Å)]10 multilayers, grown by electron-beam evaporation, reveal that the magnetoresistance (ΔR/R) increases from <0.3% to 4.4% following a heat treatment at 325 °C. Polarized neutron reflectivity measurements on annealed samples show that the interlayer coupling changes from ferromagnetic to antiferromagnetic, confirming the conclusions of the bulk studies. Data for the 300 and 325 °C annealed samples in small fields show a magnetic peak at half-order that is absent for the as-deposited and 275 °C annealed multilayers. Some of the Ni-Fe spins in the annealed multilayers are thus ordered in large (>100 μm) in-plane domains aligned antiparallel across the Cu layers. An increase in the magnetic scattering at low angles indicates that some of the remaining Ni-Fe moments are randomly oriented from one layer to the next.

  9. 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.

  10. 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.

  11. Effects of thermal annealing on photoluminescence spectra in π-conjugated polymer film: evidence for dual emission by temperature dependent measurements

    NASA Astrophysics Data System (ADS)

    Wang, R. Z.; Yang, X.; Wang, Y. C.; Sheng, C.-X.; Chen, Q.

    2014-09-01

    Various spectroscopy techniques such as absorption, photoluminescence and photoinduced absorption (PIA) spectroscopy, were used to study the photophysics in poly [2-methoxy-5-(20-ethyl-hexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) films, which were dropped cast on glass substrates using its toluene solution and being annealed at various temperatures. With the analysis of temperature dependence PL intensities, we conclude that PL emission around 680 nm at low temperature is due to intertain excimers instead of intrachain excitons for 450 K annealed film. On the other hand, this relative intensity difference is much smaller in both unannealed and 500 K annealed films, in which the morphology is amorphous and microcrystalline, respectively. We conclude that the interchain photoexcitations play crucial roles in the photophysics of MEH-PPV films. The further measurements on PIA spectrum of MEH-PPV films suggest that the interchain photoexciation is also important for the generation of triplet excitons.

  12. Temperature dependent interfacial and electrical characteristics during atomic layer deposition and annealing of HfO2 films in p-GaAs metal-oxide-semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Chen, Liu; Yuming, Zhang; Yimen, Zhang; Hongliang, Lü; Bin, Lu

    2015-12-01

    We have investigated the temperature dependent interfacial and electrical characteristics of p-GaAs metal-oxide-semiconductor capacitors during atomic layer deposition (ALD) and annealing of HfO2 using the tetrakis (ethylmethyl) amino hafnium precursor. The leakage current decreases with the increase of the ALD temperature and the lowest current is obtained at 300 °C as a result of the Frenkel-Poole conduction induced leakage current being greatly weakened by the reduction of interfacial oxides at the higher temperature. Post deposition annealing (PDA) at 500 °C after ALD at 300 °C leads to the lowest leakage current compared with other annealing temperatures. A pronounced reduction in As oxides during PDA at 500 °C has been observed using X-ray photoelectron spectroscopy at the interface resulting in a proportional increase in Ga2O3. The increment of Ga2O3 after PDA depends on the amount of residual As oxides after ALD. Thus, the ALD temperature plays an important role in determining the high-k/GaAs interface condition. Meanwhile, an optimum PDA temperature is essential for obtaining good dielectric properties. Project supported by the Advance Research Project of China (No. 5130803XXXX) and the National Natural Science Foundation of China (No. 61176070).

  13. 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.

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

    PubMed

    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. PMID:26957171

  15. 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.

  16. Temperature-dependent phase separation during annealing of Ge2Sb2Te5 thin films in vacuum

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Pan, Jisheng; Fang, Lina Wei-Wei; Yeo, Yee-Chia; Foo, Yong Lim; Zhao, Rong; Shi, Luping; Tok, Eng Soon

    2012-06-01

    Thermal stability of 100 nm Ge2Sb2Te5 thin film during annealing from room temperature to 240 °C inside a UHV chamber was studied in situ by X-ray photoelectron spectroscopy (XPS) and ex situ by X-ray diffraction (XRD) and atomic force microscopy (AFM). Ge species are found to diffuse preferentially to the surface when GST film is annealed from 25 °C to 100 °C. This process is accompanied by a change of phase whereby the amorphous film completely becomes face-center-cubic (FCC) phase at 100 °C. From 100 °C to 200 °C, both Sb and Te species are observed to diffuse more to the surface. The FCC phase is partially changed into hexagonal-close-pack (HCP) phase at 200 °C. At 220 °C, FCC phase is completely transformed into HCP phase. Loss of Sb and Te are also detected from the surface and this is attributed to desorption due to their high vapor pressures. At 240 °C, Sb and Te species are found to have desorbed completely from the surface, and leave behind Ge-rich 3D droplets on the surface. The separation of Ge2Sb2Te5 into Sb,Te-rich phase and Ge-rich phase is thus the main mechanism to account for the failure of Ge2Sb2Te5-based phase change memory devices under thermal stress.

  17. Analytic modeling of temperature dependence of 2D carrier mobility in as-grown and annealed GaInNAs/GaAs quantum well structures

    NASA Astrophysics Data System (ADS)

    Donmez, O.; Sarcan, F.; Lisesivdin, S. B.; Vaughan, M. P.; Erol, A.; Gunes, M.; Arikan, M. C.; Puustinen, J.; Guina, M.

    2014-12-01

    Temperature and nitrogen dependence of 2D carrier mobility in as-grown and annealed Ga1-xInxNyAs1-y/GaAs quantum well (QW) structures (x = 0.32 y = 0, 0.009, and 0.012) are investigated. An analytical model that accounts for the most prominent scattering mechanisms is used to explain the characteristic of temperature dependence of the carrier mobility. An expression for alloy scattering-limited mobility in N-related alloys is developed to explain the behavior of hole mobility for N-containing p-type samples. Analytical modeling of temperature dependence of the electron mobility indicates that N-related alloy scattering and interface roughness scattering are the dominant mechanism at the entire temperature range of interest. The temperature insensitivity of the electron mobility is explained in terms of the overriding effect of N-related alloy scattering and high 2D electron density. A deviation between theoretical and experimental electron mobility at low temperatures is observed not to have any dependency on N concentration. We, therefore, suggest that CNM interaction parameter of the band anti-crossing (BAC) model must be defined as temperature dependent in order to explain the observed low temperature characteristics of electron mobility. The hole mobility is mainly restricted by interface roughness and alloy scatterings at temperatures lower than 100 K, whilst high temperature hole mobility is drastically affected from optical phonon scattering. Moreover, the hole mobility at high temperatures exhibits an N-independent characteristic and hole density starts to increase at temperatures above 70 K, which is explained using the concept of parallel conduction. Extraction of the hole density in each transport channel (QW and barrier) by using a simple parallel conduction extraction method (SPCEM) shows that, in p-type samples, low temperature hole mobility takes place in quantum well, while as temperature increases barrier channel also contribute to the hole

  18. Effect of Intercritical Annealing Temperature on Martensite and Bainite Start Temperatures After Partial Austenitization

    NASA Astrophysics Data System (ADS)

    Erişir, Ersoy; Bilir, Oğuz Gürkan

    2016-01-01

    The microstructure evolution of dual-phase steel during partial austenitization was investigated for different intercritical annealing temperatures between Ac1 and Ac3 temperatures. Partial austenitization may result in different austenite volume fraction, chemical composition, and grain size of austenite depending on the intercritical annealing temperature. This study examines the effect of intercritical annealing temperature on M s and B s temperatures for dual-phase steels. M s and B s were measured experimentally for different intercritical annealing temperatures by using dilatometry and were compared with calculated values from empirical formulas. The grain sizes of the final microstructures were also quantitatively analyzed. It was shown that M s depends on the intercritical annealing temperature and austenite grain size. It was concluded that this double effect is attributed to the intercritical annealing temperature, which is responsible for both austenite chemical composition and grain size.

  19. Temperature dependent formation of ZnO and Zn2SiO4 nanoparticles by ion implantation and thermal annealing

    NASA Astrophysics Data System (ADS)

    Pandey, B.; Weathers, D. L.

    2014-08-01

    ZnO and Zn2SiO4 nanoparticles have been synthesized by dual beam implantation of 45 keV ZnO- molecular ions and 15 keV O- ions into Si (100) substrates at room temperature to fluences of 1 × 1017 and 2 × 1017 ions/cm2, respectively. Implanted samples were annealed at different temperatures in a mixture of Ar and H2 for 1 h. Rutherford backscattering spectrometry (RBS) was used to confirm the implanted ion fluences. The diffusion of Zn and O ions due to annealing was studied by using X-ray photoelectron spectroscopy (XPS). It was observed that at 700 °C annealing temperature, oxygen diffused into the substrate whereas Zn diffused in both directions; at 900 °C, oxygen diffused more into the substrate but the Zn diffused outward toward the surface. X-ray diffraction (XRD) was used to investigate the phase formation and particle sizes. At 700 °C annealing temperature, ZnO phase with an average nanoparticle size of ∼17.5 nm was observed whereas at 900 °C annealing temperature, Zn2SiO4 phase with an average nanoparticle size of ∼19 nm was observed.

  20. Annealing temperature and O2 partial pressure dependence of T(sub c) in HgBa2CuO(4+delta)

    NASA Technical Reports Server (NTRS)

    Xiong, Q.; Cao, Y.; Chen, F.; Xue, Y. Y.; Chu, C. W.

    1994-01-01

    Samples of HgBa2CuO(4+delta) (Hg-1201) were annealed under various conditions. After carefully controlling annealing time, annealing temperature (T(sub a)) and O2 partial pressure (P(sub 0)), we were able to find the reversible annealing conditions for Hg-1201. Under 1 atm O2 at 260 C less than or equal to T(sub a) less than or equal to 400 C, the obtained T(sub c) is nearly the same (approximately 97 K). However, it decreases quickly with T(sub a) greater than 300 C in high vacuum (P(sub 0) approximately 10(exp -8) atm), and reaches zero at T(sub a) = 400 C. On the other hand, T(sub c) decreases with the decrease of T(sub a) in high-pressure O2 (approximately 500 atm) and reaches approximately 20 K at about 240 C. In the entire annealing region, the oxygen surplus varies significantly from 0.03 to 0.4, and a wide range of T(sub c) variation (0 goes to 97 K goes to 20 K) was obtained with anion doping alone.

  1. High temperature annealing of ion irradiated tungsten

    DOE PAGESBeta

    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

  2. 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.

  3. Effect of annealing on the temperature dependence of inelastic tunneling contributions vis-à-vis tunneling magnetoresistance and barrier parameters in CoFe/MgO/NiFe magnetic tunnel junctions

    SciTech Connect

    Bhusan Singh, Braj; Chaudhary, Sujeet

    2014-02-28

    The effect of annealing on the changes in the inelastic tunneling contributions in tunneling conductance of ion beam sputtered CoFe/MgO/NiFe magnetic tunnel junctions (MTJs) is investigated. The inelastic contributions are evaluated using hopping conduction model of Glazman and Matveev in the temperature range of 25–300 K. The hopping through number of series of localized states present in the barrier due to structural defects increases from 9 (in as deposited MTJ) to 18 after annealing (at 200 °C/1 h); although no changes in the interface roughness of CoFe-MgO and MgO-NiFe interfaces are observed as revealed by the x-ray reflectance studies on planar MTJs. The bias dependence of tunneling magnetoresistance (TMR) at 25 K is found to get improved after annealing as revealed by the value V{sub 1/2} (the bias value at which the TMR reaches to half of its value at nearly zero bias); which is 78 mV (in MTJ annealed at 200 °C/1 h) 2.5 times the value of 33 mV (in as deposited MTJ). At 25 K the inelastic tunneling spectra revealed the presence of zero bias anomaly and magnon excitations in the range of 10–15 mV. While the barrier height exhibited a strong temperature dependence with nearly 100% increase from the value at 300 K to 25 K, the temperature dependence of TMR becomes steep after annealing.

  4. 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.

  5. Annealing temperature and thickness dependence of magnetic properties in epitaxial L1{sub 0}-Mn{sub 1.4}Ga films

    SciTech Connect

    Zheng, Y. H. Lu, H.; Teo, K. L.; Han, G. C.

    2014-01-28

    Mn{sub 1.4}Ga films with high perpendicular magnetic anisotropy and high crystalline quality were grown on MgO substrates with Cr buffer layer using molecular beam epitaxy. The crystalline structure and the surface morphology of the films have been systematically investigated as functions of in-situ annealing temperature (T{sub a}) and film thickness. It is found that the magnetic properties can be largely tuned by adjusting T{sub a}. As T{sub a} increases, both saturation magnetization (M{sub s}) and uniaxial perpendicular magnetic anisotropy constant (K{sub u}) increase to the maximum values of 612 emu/cc and 18 Merg/cc at 300 °C, respectively, and then decrease. The morphology also changes with T{sub a}, showing a minimum roughness of 2.2 Å at T{sub a} = 450 °C. On the other hand, as the thickness increases, M{sub s} and K{sub u} increase while coercivity decreases, which indicates there is a magnetic dead layer with a thickness of about 1.5 nm at the interfaces. The detailed examination on the surface morphology of the films with various thicknesses shows a complicated film growth process, which can be understood from the relaxation mechanism of the interfacial strain.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Iucolano, Ferdinando; Greco, Giuseppe; Roccaforte, Fabrizio

    2013-11-01

    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 ρC, which was explained by a thermionic field emission mechanism, an increasing trend is observed in the contacts formed at 850 °C. In this case, ρC exhibits a "metal-like" behavior, i.e., describable by a T1.8 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.

  8. 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.

  9. Experimental evidence regarding the pressure dependence of fission track annealing in apatite

    NASA Astrophysics Data System (ADS)

    Schmidt, J. S.; Lelarge, M. L. M. V.; Conceicao, R. V.; Balzaretti, N. M.

    2014-03-01

    The main purposes of fission track thermochronology are unravelling the thermal histories of sedimentary basins, determining uplift and denudation rates, identifying the structural evolution of orogenic belts, determining sedimentary provenance, and dating volcanic rocks. The effect of temperature on fission tracks is well known and is used to determine the thermal history; however, the effect of pressure on the stability of tracks is still under debate. The present work aims to understand the role of pressure on the annealing kinetics of apatite fission tracks. The samples of Durango apatite used in our experiments were chosen for their international recognition as a calibration standard for geological dating. Neutron irradiation of the samples, after total annealing of their spontaneous tracks, produced induced tracks with homogeneous densities and lengths. The effect of pressure associated with temperature on fission track annealing was verified by experimental procedures using a hydraulic press of 1000 t with a toroidal chamber profile. The experiments consisted of a combination of applying 2 and 4 GPa with 20,150,190,235, and 290 °C for 1 and 10 h. The annealing rate was analysed by measuring the lengths of the fission tracks after each experiment using optical microscopy. The results demonstrate that the annealing of apatite fission tracks has a pressure dependence for samples subjected to 2 and 4 GPa. However, when extrapolated to pressures of ⩽150 MPa, compatible with the normal geological context in which apatite fission track methodology is broadly used, this dependence becomes insignificant compared to the temperature effect.

  10. Effect of Annealing Temperature on the Structural and Optical Properties of Zn1-xMnxO

    NASA Astrophysics Data System (ADS)

    Rashid, A. R. Abd; Menon, P. S.; Shaari, S.

    2010-10-01

    Mn doped ZnO films with different annealing temperatures were synthesized by sol gel method using a spin coating technique. The annealing temperature was varied from 500° C, 550° C, and 700° C. The atomic force microscopy images show the surface morphologies change greatly with an increase in annealing temperature and it also depends on the type of substrate used. The XRD analysis show the films exhibiting hexagonal wurtzite structure with increasing crystalline size at higher temperatures. The optical properties were characterized using UV-Vis where the transmittance decreases due to ionization at higher temperatures which affect the material band gap.

  11. Effect of annealing temperature on titania nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  12. 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.

  13. Temperature effects on the mechanical properties of annealed and HERF 304L stainless steel.

    SciTech Connect

    Antoun, Bonnie R.

    2004-11-01

    The effect of temperature on the tensile properties of annealed 304L stainless steel and HERF 304L stainless steel forgings was determined by completing experiments over the moderate range of -40 F to 160 F. Temperature effects were more significant in the annealed material than the HERF material. The tensile yield strength of the annealed material at -40 F averaged twenty two percent above the room temperature value and at 160 F averaged thirteen percent below. The tensile yield strength for the three different geometry HERF forgings at -40 F and 160 F changed less than ten percent from room temperature. The ultimate tensile strength was more temperature dependent than the yield strength. The annealed material averaged thirty six percent above and fourteen percent below the room temperature ultimate strength at -40 F and 160 F, respectively. The HERF forgings exhibited similar, slightly lower changes in ultimate strength with temperature. For completeness and illustrative purposes, the stress-strain curves are included for each of the tensile experiments conducted. The results of this study prompted a continuation study to determine tensile property changes of welded 304L stainless steel material with temperature, documented separately.

  14. 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.

  15. Temperature-dependent minority carrier lifetime of crystalline silicon wafers passivated by high quality amorphous silicon oxide

    NASA Astrophysics Data System (ADS)

    Inaba, Masahiro; Todoroki, Soichiro; Nakada, Kazuyoshi; Miyajima, Shinsuke

    2016-04-01

    We investigated the effects of annealing on the temperature-dependent minority carrier lifetime of a crystalline silicon wafer passivated by hydrogenated amorphous silicon oxide. The annealing significantly affects the lifetime and its temperature dependence. Our device simulations clearly indicate that valence band offset significantly affects the temperature dependence. We also found a slight increase in the interface defect density after annealing.

  16. Influence of post-annealing temperature on properties of ZnO:Li thin films

    NASA Astrophysics Data System (ADS)

    Chen, L. L.; He, H. P.; Ye, Z. Z.; Zeng, Y. J.; Lu, J. G.; Zhao, B. H.; Zhu, L. P.

    2006-03-01

    Li-doped ZnO thin films were prepared on glass substrates by DC reactive magnetron sputtering. The influence of post-annealing temperature on the electrical, structural, and optical properties of the films was investigated. A conversion from p-type conduction to n-type in a range of temperature was confirmed by Hall measurement. The optimal p-type conduction is achieved at the annealing temperature of 500 °C with a resistivity of 57 Ω cm, carrier concentration of 1.07 × 10 17 cm -3 and Hall mobility of 1.03 cm 2 V -1 s -1. From the temperature-dependent PL analysis, the energy level of Li Zn acceptor was determined to be ˜140 meV above the valence band.

  17. 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.

  18. Low temperature annealing of cold-drawn pearlitic steel wire

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Bech, J. I.; Hansen, N.

    2015-08-01

    Cold-drawn pearlitic steel wires are nanostructured and the flow stress at room temperature can reach values above 6 GPa. A typical characteristic of the nanostructured metals, is the low ductility and thermal stability. In order to optimize both the processing and application of the wires, the thermal behaviour is of interest. This has been studied by annealing the wires for 1h at temperatures from ambient temperature to 300 °C (573 K). It is expected that a raising temperature may lead to structural changes and a reduction in strength. The change in strength is however not expected to be large. For this reason we have applied a very precise technique to measure the tensile properties of the wires from a strain of 10-4 to the maximum strain of about 1-2%. The structural changes have also been followed to estimate and relate strength changes to changes in structural parameters and morphology.

  19. 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.

  20. 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.

  1. Visible Photoluminescence of Non-Stoichiometric Silicon Nitride Films: The Effect of Annealing Temperature and Atmosphere

    NASA Astrophysics Data System (ADS)

    Vlasukova, L. A.; Komarov, F. F.; Parkhomenko, I. N.; Milchanin, O. V.; Makhavikou, M. A.; Mudryi, A. V.; Żuk, J.; Kopychiński, P.; Togambayeva, A. K.

    2015-07-01

    The radiative properties of non-stoichiometric silicon nitride SiNx fi lms produced by plasma-enhanced chemical vapor deposition were studied. Intense room-temperature photoluminescence (PL) in the visible region was recorded after annealing for both Si-rich (x = 1.13) and N-rich (x = 1.5) silicon nitride fi lms. The position of the PL band maximum depended signifi cantly on the fi lm composition. The PL band maxima for Si-rich and N-rich SiNx fi lms were detected in the red (660 nm) and blue (450 nm) spectral regions, respectively. The effect of the annealing atmosphere on PL of the SiNx fi lms was studied. It was shown that the PL intensity depended not only on the annealing temperature but also on the annealing atmosphere. The observed features of the non-stoichiometric SiNx PL spectra were explained in terms of defect states in the SiNx band gap.

  2. 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+.

  3. 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.

  4. 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.

  5. Growth of Ge/Si(100) Nanostructures by Radio-Frequency Magnetron Sputtering: the Role of Annealing Temperature

    NASA Astrophysics Data System (ADS)

    Alireza, Samavati; K. Ghoshal, S.; Othaman, Z.

    2012-04-01

    Surface morphologies of Ge islands deposited on Si(100) substrates are characterized and their optical properties determined. Samples are prepared by rf magnetron sputtering in a high-vacuum chamber and are annealed at 600°C, 700°C and 800°C for 2 min at nitrogen ambient pressure. Atomic force microscopy, field emission scanning electron microscopy, visible photoluminescence (PL) and energy dispersive x-ray spectroscopy are employed. The results for the annealing temperature-dependent sample morphology and the optical properties are presented. The density, size and roughness are found to be strongly influenced by the annealing temperature. A red shift of ~0.29 eV in the PL peak is observed with increasing annealing temperature.

  6. 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.

  7. 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.

  8. 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.

  9. Effect of Intercritical Annealing Temperature on Phase Transformations in Medium Carbon Dual Phase Steels

    NASA Astrophysics Data System (ADS)

    Erişir, Ersoy; Bilir, Oğuz Gürkan

    2014-03-01

    This paper presents a study concerning phase transformations during quenching of a medium carbon dual phase steel using thermodynamic equilibrium calculations and dilatometry. Medium carbon steel was subjected to the intermediate quenching to produce a fine grained ferrite/martensite dual phase steel. 4 samples quenched after intercritical annealing at 725, 730, 740, and 750 °C. Martensite-start and bainite-start temperatures were calculated from dilatometric curves using plastodilotemeter. Experimental findings are supported by calculated phase diagrams and equilibrium phase compositions using ThermoCalc® and calculations from different empirical formulas. It is concluded that martensite-start temperature depend on chemical composition and grain size of austenite.

  10. Dependence of buried CoSi{sub 2} resistivity on ion implantation and annealing conditions

    SciTech Connect

    Namavar, F.; Kalkhoran, N.M.; Manke, J.M.; Luo, L.; McGinn, J.T.

    1992-04-01

    We have investigated the dependence of electrical and material properties of buried CoSi{sub 2} layers on Co+ implantation and annealing conditions. The results indicated that the electrical resistivity and crystalline quality of the implanted buried CoSi{sub 2} layers depend strongly on the implantation temperature. CoSi{sub 2} layers with the lowest resistivity and best crystalline quality ({chi}{sub min} as low as 3.6%) were obtained from samples implanted at 300{degrees}C--400{degrees}C. Implantation at higher temperatures (e.g., 580{degrees}C) produced cobalt disilicide layers with significantly higher electrical resistivity and a {chi}{sub min} of about 10.7%.

  11. 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.

  12. Surface Morphology Transformation Under High-Temperature Annealing of Ge Layers Deposited on Si(100).

    PubMed

    Shklyaev, A A; Latyshev, A V

    2016-12-01

    We study the surface morphology and chemical composition of SiGe layers after their formation under high-temperature annealing at 800-1100 °C of 30-150 nm Ge layers deposited on Si(100) at 400-500 °C. It is found that the annealing leads to the appearance of the SiGe layers of two types, i.e., porous and continuous. The continuous layers have a smoothened surface morphology and a high concentration of threading dislocations. The porous and continuous layers can coexist. Their formation conditions and the ratio between their areas on the surface depend on the thickness of deposited Ge layers, as well as on the temperature and the annealing time. The data obtained suggest that the porous SiGe layers are formed due to melting of the strained Ge layers and their solidification in the conditions of SiGe dewetting on Si. The porous and dislocation-rich SiGe layers may have properties interesting for applications. PMID:27541814

  13. Room-temperature annealing of Si implantation damage in InP

    SciTech Connect

    Akano, U.G.; Mitchell, I.V. . Dept. of Physics); Shepherd, F.R. )

    1991-11-11

    Spontaneous recovery at 295 K of Si implant damage in InP is reported. InP(Zn) and InP(S) wafers of (100) orientation have been implanted at room temperature with 600 keV Si{sup +} ions to doses ranging from 3.6{times}10{sup 11} to 2{times}10{sup 14} cm{sup {minus}2}. Room-temperature annealing of the resultant damage has been monitored by the Rutherford backscattering/channeling technique. For Si doses {le}4{times}10{sup 13} cm{sup {minus}2}, up to 70% of the initial damage (displaced atoms) annealed out over a period of {approx}85 days. The degree of recovery was found to depend on the initial level of damage. Recovery is characterized by at least two time constants {ital t}{sub 1}{lt}5 days and a longer {ital t}{sub 2}{approx}100 days. Anneal rates observed between 295 and 375 K are consistent with an activation energy of 1.2 eV, suggesting that the migration of implant-induced vacancies is associated with the reordering of the InP lattice.

  14. 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

  15. 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.

  16. Effect of temperature annealing on capacitive and structural properties of hydrous ruthenium oxides

    NASA Astrophysics Data System (ADS)

    Fang, Wei-Chuan; Huang, Jin-Hua; Chen, Li-Chyong; Su, Yuh-Long Oliver; Chen, Kuei-Hsien

    The structure-property relationships of hydrous ruthenium oxides, fabricated by electro deposition on Ti foil, were investigated with different annealing conditions. The annealing temperature was found to play an important role in affecting the electrochemical performance of the annealed hydrous ruthenium oxides. The results indicate that annealing hydrous ruthenium oxide at its crystallization threshold temperature, ∼200 °C, may help to create suitable nanostructure in the oxide that supports the establishment of interpenetrating percolation paths for balanced electron and proton conduction, thereby improving the capacitive response of the oxide dramatically. This finding is useful for fabrication of electrodes with enhanced electrochemical performance for application in microsupercapacitor.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Effect of annealing temperature on magnetic phase transition in Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Jafari, A.; Farjami Shayesteh, S.; Salouti, M.; Boustani, K.

    2015-04-01

    Fe3O4 (magnetite) nanoparticles (NPs) were synthesized using a co-precipitation method, and then annealed at various temperatures between 50 and 850 °C for 1 h in air. After annealing, the NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometer (VSM). The FTIR and XRD results indicated that Fe3O4 NPs were converted to γ-Fe2O3 (maghemite) by annealing at 250 °C for 1 h and then to α-Fe2O3 (hematite) on annealing in the range of 550-650 °C. The average crystallite size of the NPs estimated by the Debye-Scherrer equation increased from 6.6 to 37.6 nm by increasing annealing temperature from 50 to 850 °C. According to VSM results, the magnetite NPs were superparamagnetic and converted to the maghemite with superparamagnetic phase by annealing up to 550 °C. A phase transition from soft to hard ferromagnetic was occurred at annealing temperature 650 and 850 °C, respectively °C. This phase transition was attributed to the conversion of magnetite to hematite. The VSM analysis confirmed the XRD and FTIR results. The saturation magnetization (Ms) of Fe3O4 NPs was increased from 41.69 to 53.61 emu/g by increasing annealing temperature from 50 to 550 °C, and then decreased intensively to 0.49 emu/g after annealing at 850 °C. By increasing annealing temperature from 50 to 550, the crystallite size of NPs was increased from 6.6 to 12.7 and the coercive force (Hc) was reached to 4.20 Oe after annealing at 550 °C and then intensively increased to 1459.02 Oe for any further increasing of particle size up to 850 °C.

  2. 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.

  3. Germanium nanoislands grown by radio frequency magnetron sputtering: Annealing time dependent surface morphology and photoluminescence

    NASA Astrophysics Data System (ADS)

    Alireza, Samavati; Othaman, Z.; K. Ghoshal, S.; J. Amjad, R.

    2013-09-01

    Structural and optical properties of ~ 20 nm Ge nanoislands grown on Si(100) by radio frequency (rf) magnetron sputtering under varying annealing conditions are reported. Rapid thermal annealing at a temperature of 600°C for 30 s, 90 s, and 120 s are performed to examine the influence of annealing time on the surface morphology and photoluminescence properties. X-ray diffraction spectra reveal prominent Ge and GeO2 peaks highly sensitive to the annealing time. Atomic force microscope micrographs of the as-grown sample show pyramidal nanoislands with relatively high-density 1011 cm-2)). The nanoislands become dome-shaped upon annealing through a coarsening process mediated by Oswald ripening. The room temperature photoluminescence peaks for both as-grown 3.29 eV) and annealed 3.19 eV) samples consist of high intensity and broad emission, attributed to the effect of quantum confinement. The red shift (~0.10 eV) of the emission peak is attributed to the change in the size of the Ge nanoislands caused by annealing. Our easy fabrication method may contribute to the development of Ge nanostructure-based optoelectronics.

  4. Effect of low and high temperature anneal on process-induced damage of gate oxide

    SciTech Connect

    King, J.C.; Hu, C. . Dept. of Electrical Engineering and Computer Sciences)

    1994-11-01

    The authors have investigated the ability of high and low temperature anneals to repair the gate oxide damage due to simulated electrical stress caused by wafer charging resulting from plasma etching, etc. Even 800 C anneal cannot restore the stability in interface trap generation. Even 900 C anneal cannot repair the deteriorated charge-to-breakdown and oxide charge trapping. As a small consolation, the ineffectiveness of anneal in repairing the process-induced damage allows them to monitor the damages even at the end of the fabrication process.

  5. 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.

  6. Ion implantation doping and high temperature annealing of GaN

    SciTech Connect

    Zolper, J.C.; Crawford, M.H.; Howard, A.J. |

    1995-12-31

    The III-V nitride-containing semiconductors InN, GaN, and AIN and their ternary alloys are the focus of extensive research for application to visible light emitters and as the basis for high temperature electronics. Recent advances in ion implantation doping of GaN and studies of the effect of rapid thermal annealing up to 1100{degrees}C are making new device structures possible. Both p- and n-type implantation doping of GaN has been achieved using Mg co-implanted with P for p-type and Si-implantation for n-type. Electrical activation was achieved by rapid thermal anneals in excess of 1000{degrees}C. Atomic force microscopy studies of the surface of GaN after a series of anneals from 750 to 1100{degrees}C shows that the surface morphology gets smoother following anneals in Ar or N{sub 2}. The photoluminescence of the annealed samples also shows enhanced bandedge emission for both annealing ambients. For the deep level emission near 2.2 eV, the sample annealed in N{sub 2} shows slightly reduced emission while the sample annealed in Ar shows increased emission. These annealing results suggest a combination of defect interactions occur during the high temperature processing.

  7. 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.

  8. 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.

  9. Influence of annealing temperature on photoluminescence properties and optical constants of N-doped ZnO thin films grown on muscovite mica substrates

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Leem, Jae-Young

    2015-11-01

    A sol-gel spin-coating method was used to synthesize N-doped ZnO (NZO) thin films on muscovite mica substrates; the films were then annealed at 200, 300, 400, and 500 °C. The effects of the annealing temperature on their photoluminescence properties and optical constants were investigated. All the films had strong UV emissions in their photoluminescence spectra, but the green emissions at ~2.4 eV were observed only for the annealed films. The average transmittance of all the films was about 80% in the visible range and the absorption edges in the UV range at 375 nm depended strongly on the annealing temperature. The optical band gap of the films decreased gradually as the annealing temperature was increased up to 400 °C, and the Urbach energy decreased significantly as the annealing temperature increased. Finally, the various optical constants, the dielectric constant, and the optical conductivity were measured for the un-annealed film and the film annealed at 500 °C.

  10. 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

  11. Effects of Solution Annealing Temperature on the Galvanic Corrosion Behavior of the Super Duplex Stainless Steels

    NASA Astrophysics Data System (ADS)

    Lee, Jun-Seob; Jeon, Soon-Hyeok; Park, Yong-Soo

    2013-02-01

    This study investigated the active dissolution of super duplex stainless steel (SDSS) at various solution annealing temperatures. The active dissolutions of the α-phase and γ-phase were compared, and the effects of the surface area ratio on the active dissolutions of both phases were investigated. There were two peaks in the active-passive transition region in the potentiodynamic test in the modified green-death solution. The two peaks changed as the solution annealing temperature was increased from 1050 to 1150 °C. The solution annealing temperature difference affected the critical anodic current densities. This provides useful information for determining the appropriate solution annealing temperature in the modified green-death solution for SDSS.

  12. Laser Annealing to Form High-Temperature Phase of FeS2

    NASA Astrophysics Data System (ADS)

    Umehara, Mitsutaro; Takeda, Yasuhiko; Azuma, Hirozumi; Motohiro, Tomoyoshi

    2012-02-01

    We fabricated single-phase pyrite thin films of FeS2 by laser annealing of multi-phase FeS2 films. Sputter-deposited FeS films followed by sulfurization in sulfur vapor at high temperatures were mainly composed of the high-temperature phase (pyrite) but contained a small amount of the low-temperature phase (marcasite) that likely grew when the samples were naturally cooled after the sulfurization. We applied the rapid cooling feature of laser annealing to preventing the marcasite phase formation. No trace of marcasite phase was observed in Raman spectra and X-ray diffraction patterns of the laser-annealed samples. We analyzed temporal evolution of the sample temperature during the laser-annealing processes to confirm that the laser heating induced phase change of the small amount of marcasite to pyrite and the rapid cooling prevented marcasite regrowth.

  13. The influence of the annealing temperature on deuterium retention in self-damaged tungsten

    NASA Astrophysics Data System (ADS)

    Založnik, Anže; Markelj, Sabina; Schwarz-Selinger, Thomas; Ciupiński, Łukasz; Grzonka, Justyna; Vavpetič, Primož; Pelicon, Primož

    2016-02-01

    The influence of the annealing temperature on deuterium retention was studied for self-ion damaged tungsten in the range from 600-1200 K. Samples were damaged by 20 MeV W ions at room temperature to the peak damage level of 0.5 dpa. Samples were then annealed at the desired temperature for 1 h and exposed to deuterium atom beam with the flux of 2.6× {10}19 {{D}}/{{{m}}}2 {{s}} for 144 h to populate the remaining defects. An unannealed sample was also used as a reference. Nuclear reaction analysis technique was used for deuterium depth profile analysis and thermal desorption was performed on the same samples to measure the amount of total retained D. Scanning transmission electron microscopy was used for the calculation of dislocation densities in the samples. After annealing at 1200 K approximately 66% of those initial defects which retain deuterium were annealed.

  14. Electrochromic performance, wettability and optical study of copper manganese oxide thin films: Effect of annealing temperature

    NASA Astrophysics Data System (ADS)

    Falahatgar, S. S.; Ghodsi, F. E.; Tepehan, F. Z.; Tepehan, G. G.; Turhan, İ.

    2014-01-01

    In the present work, the nanostructured copper manganese oxide (CMO) thin films were prepared from acetate based sol-gel precursors and deposited on glass and indium tin oxide (ITO) substrates by dip-coating technique. The films were annealed at 300, 400 and 500 °C in ambient atmosphere. The effects of annealing temperature on structural, morphological, wettability, electrochromic and optical properties of CMO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), water contact angle measurement (WCA), cyclic voltammetry (CV) measurements and ultraviolet-visible (UV-vis) spectrophotometery. The presence of mixed oxide phases comprising of copper manganese oxide (CuMn2O4) and manganese oxide at different annealing temperature was confirmed by XRD patterns. The results showed that the Mn3O4 phase has been changed to Mn2O3 when the annealing temperature is increased from 300 to 500 °C. The FESEM images indicated that the granular surface morphology was sensitive to annealing temperature. EDX studies indicated that the thin films contained O, Mn and Cu species. Wettability studies showed that the water contact angle of the nanostructured CMO thin films coated on glass substrates was influenced by the variation of annealing temperature and the surface nature of thin films was changed from hydrophilic to hydrophobic. The results of CVs measurement indicated that the anodic and cathodic charge density and capacitance of all CMO samples decreased with increasing scan rate in potential range of -1-1 eV. Also, the annealed CMO thin film at 500 °C showed better electrochromic performance with respect to other samples at lower scan rate. The thickness, refractive index, extinction coefficient and optical band gap of thin films coated on glass substrates were calculated from reflectance and transmittance spectra using an iterative numerical method. The optical band gap of

  15. 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).

  16. 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.

  17. High-temperature annealing of optical centers in type-I diamond

    SciTech Connect

    Collins, Alan T.; Connor, Alex; Ly, C.-H.; Shareef, Abdulla; Spear, Paul M.

    2005-04-15

    Diamonds previously subjected to radiation damage have been annealed at temperatures up to 1750 deg. C at ambient pressure, and at 2300 deg. C using a stabilizing pressure of 5 GPa. The results have been compared with those from similar measurements using natural brown diamonds. The investigation has led to an improved understanding of the commercial process for enhancing the color of brown diamonds by high-pressure, high-temperature (HPHT) annealing. The study has confirmed that the H4 center is less stable than the H3 center, and shown that the destruction of the H4 center in irradiated type-IaB diamonds coincides with the formation of a number of optical centers found to occur naturally in brown diamonds. In type-IaA diamonds the annealing out of the H1b absorption coincides with the production of H2 centers. Annealing measurements on brown diamonds indicate that the plastic deformation, associated with the brown color, occurred at a late stage in the diamonds' history. Optical centers, such as H3 and (N-V){sup -}, that are produced in brown diamonds by HPHT annealing, are destroyed by this process in irradiated dislocation-free diamonds. Formation of these centers during the HPHT annealing of brown diamonds occurs as a result of the release of vacancies from the dislocations, and the present results therefore indicate that the production of these centers is a dynamic process with the generation and annealing in competition.

  18. Tailoring the magnetic properties and magnetorheological behavior of spinel nanocrystalline cobalt ferrite by varying annealing temperature.

    PubMed

    Sedlacik, Michal; Pavlinek, Vladimir; Peer, Petra; Filip, Petr

    2014-05-14

    Magnetic nanoparticles of spinel nanocrystalline cobalt ferrite were synthesized via the sol-gel method and subsequent annealing. The influence of the annealing temperature on the structure, magnetic properties, and magnetorheological effect was investigated. The finite crystallite size of the particles, determined by X-ray diffraction and the particle size observed via transmission electron microscopy, increased with the annealing temperature. The magnetic properties observed via a vibrating sample magnetometer showed that an increase in the annealing temperature leads to the increase in the magnetization saturation and, in contrast, a decrease in the coercivity. The effect of annealing on the magnetic properties of ferrite particles has been explained by the recrystallization process at high temperatures. This resulted in grain size growth and a decrease in an imposed stress relating to defects in the crystal lattice structure of the nanoparticles. The magnetorheological characteristics of suspensions of ferrite particles in silicone oil were measured using a rotational rheometer equipped with a magnetic field generator in both steady shear and small-strain oscillatory regimes. The magnetorheological performance expressed as a relative increase in the magnetoviscosity appeared to be significantly higher for suspensions of particles annealed at 1000 °C. PMID:24668306

  19. 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.

  20. Low-temperature illumination and annealing of ultrahigh quality quantum wells

    NASA Astrophysics Data System (ADS)

    Samani, M.; Rossokhaty, A. V.; Sajadi, E.; Lüscher, S.; Folk, J. A.; Watson, J. D.; Gardner, G. C.; Manfra, M. J.

    2014-09-01

    The effects of low-temperature illumination and annealing on fractional quantum Hall (FQH) characteristics of a GaAs/AlGaAs quantum well are investigated. Illumination alone, below 1 K, decreases the density of the two-dimensional electron gas (2DEG) electrons by more than an order of magnitude and resets the sample to a repeatable initial state. Subsequent thermal annealing at a few Kelvin restores the original density and dramatically improves FQH characteristics. A reliable illumination and annealing recipe is developed that yields an energy gap of 600 mK for the 5/2 state.

  1. Surface Superstructure of Carbon Nanotubes on Highly Oriented Pyrolytic Graphite Annealed at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    An, Bai; Fukuyama, Seiji; Yokogawa, Kiyoshi; Yoshimura, Masamichi

    1998-06-01

    Carbon nanotubes deposited on highly oriented pyrolytic graphite (HOPG) are annealed in ultra high vacuum. The effect of annealing temperature on the surface morphology of the carbon nanotubes on HOPG is examined by scanning tunneling microscopy. The ring-like surface superstructure of (\\sqrt {3}× \\sqrt {3})R30° of graphite is found on the carbon nanotubes annealed above 1593 K. The tips of the carbon nanotubes are destroyed and the stacking misarrangement between the upper and the lower walls of the tube join with HOPG resulting in the superstructure.

  2. The evolution of microstructure and photoluminescence of SiCN films with annealing temperature

    SciTech Connect

    Du Xiwen; Fu Yang; Sun Jing; Yao Pei

    2006-05-01

    Silicon carbonitride (SiCN) films were deposited by radio-frequency magnetron sputtering and then annealed at different temperatures from 1100 to 1300 deg. C in hydrogen atmosphere. The as-deposited films and films annealed at 1100 deg. C did not show photoluminescence (PL), whereas strong PL peaks appeared at 355 and 469 nm after annealing at 1200 and 1300 deg. C. X-ray diffraction, transmission electron microscope, and Fourier transform infrared spectrometer results show that the enhancement of PL properties is due to the change of microstructure and composition.

  3. 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.

  4. 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.

  5. Enhancement of saturation magnetization in Cr-ion implanted silicon by high temperature annealing

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Zhang, Wenyong; Chen, Jihong; Zhou, Zhongpo; Ai, Zhiwei; Guo, Liping; Liu, Congxiao; Du, Honglin

    2011-08-01

    Magnetic properties and microstructure of Cr-implanted Si have been investigated by alternating gradient magnetometer (AGM), superconducting quantum interference device (SQUID) magnetometer, and transmission electron microscopy (TEM). p-Type (1 0 0) Si wafers were implanted at 200 keV at room temperature with a dosage of 1 × 10 16 cm -2 Cr ions and then annealed at 600-900 °C for 5 min. The effect of annealing on the structure and magnetic properties of Cr-implanted Si is studied. The as-implanted sample shows a square M-H loop at low temperature. Magnetic signal becomes weaker after short time annealing of the as-implanted sample at 600 °C, 700 °C, and 800 °C. However, the 900 °C annealed sample exhibits large saturation magnetization at room temperature. TEM images reveal that the implanting process caused amorphization of Si, while annealing at 900 °C led to partial recovery of the crystal. The enhancement of saturation magnetization can be explained by the redistribution and accumulation of Cr atoms in the vacancy-rich region of Si during annealing.

  6. The effects of annealing temperature on the photoluminescence from silicon nitride multilayer structures

    NASA Astrophysics Data System (ADS)

    Scardera, G.; Puzzer, T.; Perez-Wurfl, I.; Conibeer, G.

    2008-07-01

    The room temperature photoluminescence from silicon nitride multilayer structures, grown by plasma enhanced chemical vapour deposition, is monitored for different annealing temperatures and is correlated to structural and molecular changes in the film. Use of various annealing temperatures from 600 °C to 1150 °C results in films which vary from being completely amorphous to an amorphous matrix containing silicon nanocrystals, and finally to a fully crystallized composite containing silicon, α-Si 3N 4 and β-Si 3N 4 nanocrystals. Coupled with the observed trends seen with grazing incidence X-ray diffraction, transmission electron microscopy, and infra-red absorbance with annealing temperature, the photoluminescence from silicon nanocrystals embedded in amorphous silicon nitride is attributed to the presence of the nanocrystals in the film and not to transitions between band tails of the remaining amorphous matrix.

  7. Effect of Long Term, High Temperature Annealing on the Strength of Beta''-Alumina Ceramics

    NASA Astrophysics Data System (ADS)

    Rasmussen, James R.; Williams, Roger M.; Kisor, Adam K.

    2003-01-01

    It has been recently reported that subjecting beta''-alumina ceramics to a long term, high temperature anneal for the purpose of reducing the residual sodium aluminate content within the ceramic results in an apparent increase in the strength of the ceramic as well. In order to examine this hypothesis, a carefully controlled experiment was conducted. Ten tubes were cut into 100 rings 1.5 mm long. A third of the rings (randomly selected) were broken in diametral ring fracture tests, while the remaining rings were packaged and shipped to Jet Propulsion Laboratory (JPL) where half of them were annealed, and the other half were unpacked and stored under appropriate dry conditions to act a shipping and handling control group. Once the annealing was completed, both groups of rings were repackaged and returned to Advanced Modular Power Systems (AMPS) and broken in diametral ring tests. The annealed group had the lowest strength as indicated by the Weibull characteristic strengths. Weibull characteristic strengths for the unannealed, control, and annealed groups were 376 MPa, 326 MPa, and 294 MPa, respectively. The Weibull moduli of the unannealed and annealed groups were nominally the same at 9.0 and 8.6, respectively. That for the handling control group was lower at 6.8. The lower strength of the annealed ceramics is consistent with earlier work showing a decrease in ceramic strength with increasing grain size.

  8. Effects of Annealing Temperature on Structural and Optical Properties of ZnO Thin Films

    NASA Astrophysics Data System (ADS)

    Xu, Jian-Ping; Shi, Shao-Bo; Li, Lan; Zhang, Xiao-Song; Wang, Ya-Xin; Chen, Xi-Ming

    2010-04-01

    The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si (100) substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700°C. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial oxygen (Oi), interstitial zinc (Zni) and zinc vacancy (V-Zn), which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.

  9. Ultraviolet stimulated emission from high-temperature-annealed MgO microcrystals at room temperature

    NASA Astrophysics Data System (ADS)

    Soma, Haruka; Uenaka, Yuki; Asahara, Akifumi; Suemoto, Tohru; Uchino, Takashi

    2015-01-01

    Research on semiconductor nanowires underlies the development of the miniaturization of laser devices with low cost and low energy consumption. In general, nanowire lasers are made of direct band gap semiconductors, e.g., GaN, ZnO and CdS, and their band-edge emissions are used to achieve optically pumped laser emission. In addition to the existing class of nanowire lasers, we here show that air-annealed micrometer-sized MgO cubic crystals with well-defined facets exhibit room-temperature stimulated emission at 394 nm under pulsed laser pumping at ˜350 nm. Surface midgap states are assumed to be responsible for the excitation and emission processes. The present findings will not only provide opportunities for the development of miniaturized lasers composed of insulating oxides, but will also open up functionality in various families of cubic crystalline materials.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Effects of Annealing Temperature on Thermomechanical Properties of Cu-Al-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Canbay, C. Aksu; Karagoz, Z.

    2013-07-01

    The effects of the annealing temperature on structural properties and the phase transformation of a Cu-14.1Al-3.9Ni (mass %) shape memory alloy (SMA) have been investigated. The annealing process was carried out at temperatures in the range of to . The structural changes of the as-quenched and annealed samples were studied by optical microscope and X-ray diffraction measurements. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The activation energy and thermodynamic parameters of the samples were determined. It was found that the heat treatment has an effect on the characteristic transformation temperatures and on thermodynamic parameters such as enthalpy, entropy, and activation energy. The crystallite size of the as-quenched and annealed samples were determined. Vickers hardness measurements of the as-quenched and annealed samples were also carried out. It is evaluated that the transformation parameters of a CuAlNi SMA can be controlled by heat treatment.

  15. 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.

  16. Temperature-dependent Luttinger surfaces.

    PubMed

    Ito, T; Chainani, A; Haruna, T; Kanai, K; Yokoya, T; Shin, S; Kato, R

    2005-12-01

    The Luttinger surface of an organic metal (TTF-TCNQ), possessing charge order and spin-charge separated band dispersions, is investigated using temperature-dependent angle-resolved photoemission spectroscopy. The Luttinger surface topology, obtained from momentum distribution curves, changes from quasi-2D (dimensional) to quasi-1D with temperature. The high temperature quasi-2D surface exhibits 4kF charge-density-wave (CDW) superstructure in the TCNQ derived holon band, in the absence of 2kF order. Decreasing temperature results in quasi-1D nested 2kF CDW order in the TCNQ spinon band and in the TTF surface. The results establish the link in momentum space between charge order and spin-charge separation in a Luttinger liquid. PMID:16384402

  17. 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.

  18. 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

  19. 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.

  20. Size dependent magnetization and high-vacuum annealing enhanced ferromagnetism in Zn(1-x)Co(x)O nanowires.

    PubMed

    Jian, Wen-Bin; Chen, I-Jan; Liao, Tai-Ching; Ou, Yi-Ching; Nien, Cheng-Hsun; Wu, Zhong-Yi; Chen, Fu-Rong; Kai, Ji-Jung; Lin, Juhn-Jong

    2008-01-01

    Diameter controllable ZnO nanowires have been fabricated by thermal evaporation (vapor transport) with various sizes of gold nanoparticles as catalysts. Diluted magnetic semiconductor (DMS) Zn(1-x)Co(x)O nanowires were then made by high energy Co ion implantation. The as-implanted and the argon-annealed Zn(1-x)Co(x)O nanowires displayed weak ferromagnetism while the high-vacuum annealed nanowires exhibited strong ferromagnetic ordering at room temperature. Size dependent behavior has been observed in the magnetic field and temperature dependences of magnetization. The shrinkage of the nanowire diameter reduced the spontaneous magnetization as well as the hysteresis loops. Field cooled and zero-field cooled magnetization and coercivity measurements were performed between 2 and 300 K to study the evolution of magnetism from the weak to the strong ferromagnetic states. In particular, superparamagnetic features were observed and shown to be intrinsic characteristics of the DMS Zn(1-x)Co(x)O nanowires. The room-temperature spontaneous magnetization of individual Zn(1-x)Co(x)O nanowires was also established by using magnetic force microscope measurements. PMID:18468061

  1. Near interface oxide degradation in high temperature annealed Si/SiO{sub 2}/Si structures

    SciTech Connect

    Devine, R.A.B.; Mathiot, D.; Warren, W.L.; Fleetwood, D.M.

    1993-12-31

    Degradation of 430 nm thick SiO{sub 2} layers in Si/SiO{sub 2}/Si structures which results from high temperature annealing (1320 C) has been studied using electron spin resonance, infra-red and refractive index measurements. Large numbers of oxygen vacancies are found in a region {le}100 nm from each Si/SiO{sub 2} interface. Two types of paramagnetic defects are observed following {gamma} or x-irradiation or hole injection. The 1106 cm{sup {minus}1} infra-red absorption associated with O interstitials in the Si substrate is found to increase with annealing time. The infra-red and spin resonance observations can be explained qualitatively and quantitatively in terms of a model in which oxygen atoms are gettered from the oxide into the under or overlying Si, the driving force being the increased O solubility limit associated with the anneal temperature.

  2. The influence of annealing temperature on the strength of TRISO coated particles

    NASA Astrophysics Data System (ADS)

    van Rooyen, I. J.; Neethling, J. H.; van Rooyen, P. M.

    2010-07-01

    The integrity of the Pebble Bed Modular Reactor (PBMR) fuel, and specifically the SiC layer system of the Tristructural Isotropic (TRISO) coated particle (CP), namely inner pyrolytic carbon, silicon carbide and outer pyrolytic carbon (I-PyC-SiC-O-PyC), determines the containment of fission products. The PBMR fuel consists of TRISO coated particles (CPs) embedded in a graphite matrix. One of the characterization techniques investigated by PBMR is the determination of strength of CPs. It is a well known metallurgical fact that temperature, amongst many other parameters, may influence the strength of a material. A recently developed method for measuring the strength of the TRISO coated particles was used and is briefly described in this article. The advantages of this method are demonstrated by the comparison of strength measurements of five experimental PBMR CP batches as a function of annealing temperature. Significant modification of strength after annealing was measured with increased temperature within the range 1000-2100 °C. The interesting feature of decreasing standard deviation of the strength with increasing temperature will also be discussed with a possible explanation. A significant difference in coated particle strength is also demonstrated for two CP batches with layer thickness on the extremities of the SiC layer thickness specification. The effect of long duration annealing on these strength values will also be demonstrated by comparing results from 1 h to 100 h annealing periods of coated particles at a temperature of 1600 °C.

  3. Temperature dependence of FMR and magnetization in nanocrystalline zinc ferrite thin films

    NASA Astrophysics Data System (ADS)

    Sahu, B. N.; Doshi, Akash S.; Prabhu, R.; Venkataramani, N.; Prasad, Shiva; Krishnan, R.

    2016-05-01

    Single phase nano-crystalline zinc ferrite thin films were deposited by RF-magnetron sputtering on quartz substrate at room temperature (RT) in pure Argon environment and annealed (in air) at different temperatures. Temperature dependence of magnetization was studied on these films using both VSM and by observing FMR (in X band). Value of exchange stiffness constant (D) was obtained by fitting Bloch's law to the low temperature magnetization data. The value of D decreased monotonously with the annealing temperature (TA) of the samples. A film annealed at TA = 523 K, exhibited the highest magnetization value. The FMR line width of the films decreased with increase in measurement temperature. At RT (˜293 K), the lowest value of line width (ΔH) was 15 kA/m and 13 kA/m in parallel and perpendicular configuration respectively for the sample annealed at TA = 623 K.

  4. Effects of Co layer thickness and annealing temperature on the magnetic properties of inverted [Pt/Co] multilayers

    SciTech Connect

    Lee, Tae Young; Chan Won, Young; Su Son, Dong; Lee, Seong-Rae; Ho Lim, Sang

    2013-11-07

    The effects of Co layer thickness and annealing temperature on the perpendicular magnetic anisotropy (PMA) properties of inverted [Pt (0.2 nm)/Co (t{sub Co})]{sub 6} multilayers (where t{sub Co} indicates the thickness of the Co layer) have been investigated. The cross-sectional microstructure, as observed from the high-resolution transmission electron microscope images, shows a clear layered structure with atomically flat interfaces both in the as-deposited state as well as after annealing, indicating the interface effects for PMA. The effective PMA energy density (K{sub eff}) increases significantly with an increase in t{sub Co} from 0.2 to 0.28 nm and then becomes almost saturated with further increases in t{sub Co}, followed by a slight reduction at the highest Co thickness, t{sub Co} = 0.6 nm. In order to explain the t{sub Co} dependence on K{sub eff}, the intrinsic PMA energy density (K{sub i}) is calculated by additionally measuring a similar set of results for the saturation magnetization. The K{sub i} value increases nearly linearly with the increase in t{sub Co} from 0.2 to 0.5 nm, followed by saturation at a higher t{sub Co} value of 0.6 nm. Owing to a close relationship between K{sub i} and the quality of the interfaces, these results indicate a similar t{sub Co} dependence on the quality of the interfaces. This is further supported from the magnetic measurements of the samples annealed at the highest temperature of 500 °C, where a second phase is formed, which show a similar t{sub Co} dependence on the amount of the second phase. The K{sub i} value is nearly independent of the annealing temperature at t{sub Co} ≤ 0.4 nm, above which a substantial reduction is observed, when the annealing temperature exceeds 500 °C.

  5. Effect of annealing temperature on morphological, structural and optical properties of nanostructured CuO thin film

    NASA Astrophysics Data System (ADS)

    Akgul, Unal; Yildiz, Koksal; Atici, Yusuf

    2016-04-01

    CuO thin film was grown on a glass substrate by reactive radio frequency (rf) magnetron sputtering. The deposited film was annealed in air at various temperatures for 2h. The SEM images showed that the grain size increased with rising annealing temperature. The EDX and XRD results revealed that the chemical composition and phase of the polycrystalline film were not affected by the annealing conditions. The optical band gap increased from 2.244eV to 2.261eV and then decreased from 2.261eV to 2.145eV by the effect of annealing temperature.

  6. 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.

  7. 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.

  8. Effect of post-annealing temperature on structural and optical properties of ZnO thin films grown on mica substrates using sol-gel spin-coating

    NASA Astrophysics Data System (ADS)

    Kim, Younggyu; Leem, Jae-Young

    2015-09-01

    ZnO thin films were grown on flexible muscovite mica substrates using sol-gel spin-coating. The structural and optical properties of the sol-gel-derived ZnO thin films annealed at temperatures between 300 - 600 °C were investigated. The surface morphology of the ZnO thin films was found to depend slightly on the annealing temperature. In the photoluminescence spectra, the position of the near-band-edge (NBE) peak was shifted towards a lower energy by the post-annealing process, and the full width at half maximum (FWHM) values of the NBE peaks for the annealed ZnO thin films were significantly lower than those for the as-grown film. Defect-related deep-level peaks exhibiting green and red emissions were observed only for the annealed ZnO thin films. The Urbach energy and optical band gap of the films decreased with an increase in annealing temperatures up to 500 °C.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Post-growth annealing of Bridgman-grown CdZnTe and CdMnTe crystals for room-temperature nuclear radiation detectors

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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, so 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 the conditions in local regions, such as composition and structure, as well as on the annealing conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

  15. 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

  16. In Situ Observation of High Temperature Creep Behavior During Annealing of Steel

    NASA Astrophysics Data System (ADS)

    Zhang, X. F.; Terasaki, H.; Komizo, Y.; Murakami, Y.; Yasuda, K.

    2012-12-01

    Previous studies on creep suggested a close relationship between polycrystal grain size, substructure, and creep rate. At present, however, our understanding of the influence of polycrystal grain size, substructure, and thermal stress on creep deformation behavior seems rather insufficient, especially as there is a general lack of in situ data on structural changes during creep. In this study, the effects of thermal stress, austenite grain size, and cooling rate on slip deformations in C-Mn-Al steel during annealing were investigated systematically on the basis of in situ observations using high temperature laser scanning confocal microscopy. Finally, a kinetics model based on thermal expansion anisotropy and temperature difference was developed to explain these interesting experimental results. The in situ investigation of slip deformation during annealing greatly contributes to the understanding of high temperature creep behavior.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Surface Temperature of Protoplanetary Disks Probed by Annealing Experiments Reflecting Spitzer Observations

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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 (ΦBn,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 IF-VF-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 Ni2Si 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 Ni2Si/4H-SiC Schottky contacts.

  7. 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

  8. 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.

  9. Annealing temperature effect on microstructure, magnetic and microwave properties of Fe-based amorphous alloy powders

    NASA Astrophysics Data System (ADS)

    He, Jinghua; Wang, Wei; Wang, Aimin; Guan, Jianguo

    2012-09-01

    Fe74Ni3Si13Cr6W4 amorphous alloy powders were annealed at different temperature (T) for 1.5 h to fabricate the corresponding amorphous and nanocrystalline powders. The influences of T on the crystalline structure, morphology, magnetic and microwave electromagnetic properties of the resultant samples were investigated via X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and vector network analyzer. The results show that the powder samples obtained at T of 650 °C or more are composed of lots of ultra-fine α-Fe(Si) grains embedded in an amorphous matrix. When T increases from 350 to 750 °C, the saturated magnetization and coercivity of the as-annealed powder samples both increase monotonously whereas the relative real permittivity shows a minimal value and the relative real permeability shows a maximal value at T of 650 °C. Thus the powder samples annealed at 650 °C show optimal reflection loss under -10 dB in the whole C-band. These results here suggest that the annealing heat treatment of Fe-based amorphous alloy is an effective approach to fabricate high performance microwave absorber with reasonable permittivity and large permeability simultaneously via adjusting T.

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

    DOE PAGESBeta

    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

  11. 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.

  12. Reliability implications of defects in high temperature annealed Si/SiO{sub 2}/Si structures

    SciTech Connect

    Warren, W.L.; Fleetwood, D.M.; Shaneyfelt, M.R.; Winokur, P.S.; Devine, R.A.B.; Mathiot, D.

    1994-08-01

    High-temperature post-oxidation annealing of poly-Si/SiO{sub 2}/Si structures such as metal-oxide-semiconductor capacitors and metal-oxide-semiconductor field effect transistors is known to result in enhanced radiation sensitivity, increased 1/f noise, and low field breakdown. The authors have studied the origins of these effects from a spectroscopic standpoint using electron paramagnetic resonance (EPR) and atomic force microscopy. One result of high temperature annealing is the generation of three types of paramagnetic defect centers, two of which are associated with the oxide close to the Si/SiO{sub 2} interface (oxygen-vacancy centers) and the third with the bulk Si substrate (oxygen-related donors). In all three cases, the origin of the defects may be attributed to out-diffusion of O from the SiO{sub 2} network into the Si substrate with associated reduction of the oxide. The authors present a straightforward model for the interfacial region which assumes the driving force for O out-diffusion is the chemical potential difference of the O in the two phases (SiO{sub 2} and the Si substrate). Experimental evidence is provided to show that enhanced hole trapping and interface-trap and border-trap generation in irradiated high-temperature annealed Si/SiO{sub 2}/Si systems are all related either directly, or indirectly, to the presence of oxygen vacancies.

  13. 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.

  14. 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.

  15. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  17. 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.

  18. Effects of annealing temperature on shape transformation and optical properties of germanium quantum dots

    NASA Astrophysics Data System (ADS)

    Alireza, Samavati; Othaman, Z.; K. Ghoshal, S.; K. Mustafa, M.

    2015-02-01

    The influences of thermal annealing on the structural and optical features of radio frequency (rf) magnetron sputtered self-assembled Ge quantum dots (QDs) on Si (100) are investigated. Preferentially oriented structures of Ge along the (220) and (111) directions together with peak shift and reduced strain (4.9% to 2.7%) due to post-annealing at 650 °C are discerned from x-ray differaction (XRD) measurement. Atomic force microscopy (AFM) images for both pre-annealed and post-annealed (650 °C) samples reveal pyramidal-shaped QDs (density ˜ 0.26× 1011 cm-2) and dome-shape morphologies with relatively high density ˜ 0.92 × 1011 cm-2, respectively. This shape transformation is attributed to the mechanism of inter-diffusion of Si in Ge interfacial intermixing and strain non-uniformity. The annealing temperature assisted QDs structural evolution is explained using the theory of nucleation and growth kinetics where free energy minimization plays a pivotal role. The observed red-shift ˜ 0.05 eV in addition to the narrowing of the photoluminescence peaks results from thermal annealing, and is related to the effect of quantum confinement. Furthermore, the appearance of a blue-violet emission peak is ascribed to the recombination of the localized electrons in the Ge-QDs/SiO2 or GeOx and holes in the ground state of Ge dots. Raman spectra of both samples exhibit an intense Ge-Ge optical phonon mode which shifts towards higher frequency compared with those of the bulk counterpart. An experimental Raman profile is fitted to the models of phonon confinement and size distribution combined with phonon confinement to estimate the mean dot sizes. A correlation between thermal annealing and modifications of the structural and optical behavior of Ge QDs is established. Tunable growth of Ge QDs with superior properties suitable for optoelectronic applications is demonstrated. Project supported by Ibnu Sina Institute for Fundamental Science Study, Universiti Teknologi Malaysia

  19. 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

  20. 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.

  1. Twinned Si nanowires grown by high temperature annealing of Au/Si system in vacuum

    NASA Astrophysics Data System (ADS)

    Ruffino, F.; Torrisi, V.; Grimaldi, M. G.

    2015-09-01

    Periodically twinned Si nanowires were fabricated on Si surface by high-temperature annealing, in vacuum, of deposited colloidal Au nanoparticles. While performing the annealing process in a gas carrier with trace amounts of oxygen almost-cylindrical silica nanowires are obtained thanks to the stabilizing effect of the oxygen, faceted nanowires are obtained in vacuum condition. In this last case, nanowires with diameter in the 70-150 nm range and length of some microns are obtained. They present an arrangement of periodically twinned segments with a rather uniform thickness along the entire growth length. A minimum surface energy and strain energy argument is used to explain the formation of periodic twins in the Si nanowires. The thickness of the periodic twinned segments is found to be linearly proportional to the nanowire diameter, and a constant volume model is used to explain the relation. By the fit of the experimental data, in particular, an estimation of the twin energy formation is obtained.

  2. 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.

  3. Effect of Annealing Temperature on Structural and Optical Parameters of Sol-Gel Routed Molybdenum Oxide Thin Film

    NASA Astrophysics Data System (ADS)

    Arasu, P. Adal; Williams, R. Victor

    2015-05-01

    The influence of annealing temperature on structural and optical properties of sol-gel routed spin-coated molybdenum tri oxide (MoO3) thin films are studied. The higher annealing temperatures improve the crystalline nature of the film. The X-ray diffraction (XRD) study reveals the formation of α-orthorhombic phase at higher annealing temperature and amorphous nature at lower annealing temperature. The optical bandgap of molybdenum tri oxide (MoO3) film is found to be 3.3-3.8 eV, and the refractive index of the film is found to be 2.2-2.9. The dispersion curve of the refractive index shows that an abnormal dispersion in the absorption region and normal dispersion in the transparent region are observed. The optical polarizability, optical conductivity, dielectric constant, volume and surface energy loss parameters are evaluated.

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

    SciTech Connect

    Robertson, J.P.; Rowcliffe, A.F.; Grossbeck, M.L.; Ioka, Ikuo; Jitsukawa, Shiro

    1996-12-31

    A single heat of solution annealed 316 ss was irradiated to 7 and 18 dpa at 60, 200, 330, and 400 C. Tensile properties were studied vs dose and temperature. Large changes in yield strength, deformation mode, strain to necking (STN), and strain hardening capacity were seen. Magnitude of the changes are dependent on both irradiation temperature and neutron dose. Irradiation can more than triple the yield strength and decrease STN to <0.5% under certain conditions. A maximum increase in yield strength and a minimum in STN occur after irradiation at 330 C but failure mode remains ductile.

  5. 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.

  6. Effect of Annealing Temperature on the Performance of SnO2 Thin Film Transistors Prepared by Spray Pyrolysis.

    PubMed

    Zhang, XinAn; Zhai, JunXia; Yu, XianKun; Zhu, RuiJuan; Zhang, WeiFeng

    2015-08-01

    We fabricated SnO2 thin film transistors on thermally oxidized p-type silicon substrates by low-cost spray pyrolysis. The effect of annealing temperatures on electrical characteristics of SnO2 thin film transistors were investigated. Thermal annealing at higher temperatures induced a negative shift of the threshold voltage (VT) and an increase in the saturation mobility. It was found that the device annealed at 450 °C exhibited a good electrical performance with the field-effect mobility of 0.19 cm2/Vs, the threshold voltage of 2.5 V, and the on/off current ratio of 10(3). PMID:26369222

  7. 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.

  8. Structural, Morphological, and Electron Transport Studies of Annealing Dependent In2O3 Dye-Sensitized Solar Cell

    PubMed Central

    Mahalingam, S.; Abdullah, H.; Shaari, S.; Muchtar, A.; Asshari, I.

    2015-01-01

    Indium oxide (In2O3) thin films annealed at various annealing temperatures were prepared by using spin-coating method for dye-sensitized solar cells (DSSCs). The objective of this research is to enhance the photovoltaic conversion efficiency in In2O3 thin films by finding the optimum annealing temperature and also to study the reason for high and low performance in the annealed In2O3 thin films. The structural and morphological characteristics of In2O3 thin films were studied via XRD patterns, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM), EDX sampling, and transmission electron microscopy (TEM). The annealing treatment modified the nanostructures of the In2O3 thin films viewed through FESEM images. The In2O3-450°C-based DSSC exhibited better photovoltaic performance than the other annealed thin films of 1.54%. The electron properties were studied by electrochemical impedance spectroscopy (EIS) unit. The In2O3-450°C thin films provide larger diffusion rate, low recombination effect, and longer electron lifetime, thus enhancing the performance of DSSC. PMID:26146652

  9. Structural, Morphological, and Electron Transport Studies of Annealing Dependent In2O3 Dye-Sensitized Solar Cell.

    PubMed

    Mahalingam, S; Abdullah, H; Shaari, S; Muchtar, A; Asshari, I

    2015-01-01

    Indium oxide (In2O3) thin films annealed at various annealing temperatures were prepared by using spin-coating method for dye-sensitized solar cells (DSSCs). The objective of this research is to enhance the photovoltaic conversion efficiency in In2O3 thin films by finding the optimum annealing temperature and also to study the reason for high and low performance in the annealed In2O3 thin films. The structural and morphological characteristics of In2O3 thin films were studied via XRD patterns, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM), EDX sampling, and transmission electron microscopy (TEM). The annealing treatment modified the nanostructures of the In2O3 thin films viewed through FESEM images. The In2O3-450 °C-based DSSC exhibited better photovoltaic performance than the other annealed thin films of 1.54%. The electron properties were studied by electrochemical impedance spectroscopy (EIS) unit. The In2O3-450 °C thin films provide larger diffusion rate, low recombination effect, and longer electron lifetime, thus enhancing the performance of DSSC. PMID:26146652

  10. Crystallization, metastable phases, and demixing in a hafnia-titania nanolaminate annealed at high temperature

    SciTech Connect

    Cisneros-Morales, Massiel Cristina; Rubin Aita, Carolyn

    2010-09-15

    Nanolaminate films with a nominal 5 nm HfO{sub 2}-4 nm TiO{sub 2} bilayer architecture are sputter deposited on unheated fused silica and Au-coated glass substrates. Films on fused silica are postdeposition annealed from 573 to 1273 K and characterized by x-ray diffraction, scanning electron microscopy, Raman microscopy, and UV-visible-near IR spectrophotometry. The films show weak but progressive crystallization into orthorhombic (o) HfTiO{sub 4} when annealed up to 973 K. o-HfTiO{sub 4} is expected to form under bulk thermodynamic equilibrium conditions in the case of complete mixing of the bilayer components. Annealing above 973 K produces a crystallization sequence that is not predicted by bulk thermodynamics, ultimately involving o-HfTiO{sub 4} demixing to form monoclinic HfO{sub 2} doped with Ti and rutile TiO{sub 2} doped with Hf. These phases have a higher atomic density than o-HfTiO{sub 4} and segregate into discrete mesoscopic features. The authors propose that o-HfTiO{sub 4} demixing into higher density phases is a mechanism for thermal stress relief at high temperature. Demixing results in a major loss of optical transparency in the visible and ultraviolet spectral regions.

  11. Production of native donors in ZnO by annealing at high temperature in Zn vapor

    NASA Astrophysics Data System (ADS)

    Halliburton, L. E.; Giles, N. C.; Garces, N. Y.; Luo, Ming; Xu, Chunchuan; Bai, Lihai; Boatner, L. A.

    2005-10-01

    Zinc oxide crystals grown by the seeded chemical vapor transport method have been annealed in zinc vapor at 1100 °C for 30 min. These thermochemical reduction treatments produce a deep red coloration in the crystals and increase their n-type electrical conductivity. Electron paramagnetic resonance (EPR), optical absorption, and Hall measurements were used to monitor changes in the crystals. After an anneal, an intense optical absorption band is present that extends from the band edge out to approximately 550 nm, and the EPR signal near g =1.96 (due to shallow donors and/or conduction-band electrons), the free-carrier absorption, and the Hall electron concentration are all larger. Hydrogen was not present during these anneals, thus leaving oxygen vacancies and zinc interstitials as candidates for the added donors. Neutral oxygen vacancies are produced at high temperature by the additive-coloration mechanism, and are responsible for the broad near-edge absorption band. The observed increase in the number of free carriers is a result of either (1) the formation of zinc interstitials or (2) having the ground state of the neutral oxygen vacancy near the conduction band.

  12. 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.

  13. Temperature-dependent Structural Relaxation in As40Se60 Glass

    SciTech Connect

    R Golovchak; A Kozdras; O Shpotyuk; C Gorecki; A Kovalskkiy; H Jain

    2011-12-31

    The origin of structural relaxation in As{sub 40}Se{sub 60} glass at different annealing temperatures is studied by differential scanning calorimetry (DSC) and in situ extended X-ray absorption fine structure (EXAFS) methods. Strong physical aging effect, expressed through the increase of endothermic peak area in the vicinity of Tg, is recorded by DSC technique at the annealing temperatures T{sub a} > 90 C. EXAFS data show that the observed structural relaxation is not associated with significant changes in the short-range order of this glass. An explanation is proposed for this relaxation behavior assuming temperature-dependent constraints.

  14. 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 .

  15. 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.

  16. Effect of annealing temperature on the contact properties of Ni/V/4H-SiC structure

    SciTech Connect

    Dai, Chong-Chong; Zhou, Tian-Yu; University of Chinese Academy of Sciences, Beijing 100049 ; Liu, Xue-Chao Zhuo, Shi-Yi; Kong, Hai-Kuan; Yang, Jian-Hua; Shi, Er-Wei

    2014-04-15

    A sandwich structure of Ni/V/4H-SiC was prepared and annealed at different temperatures from 650 °C to 1050 °C. The electrical properties and microstructures were characterized by transmission line method, X-ray diffraction, Raman spectroscopy and transmission electron microscopy. A low specific contact resistance of 3.3 × 10{sup -5} Ω·cm{sup 2} was obtained when the Ni/V contact was annealed at 1050 °C for 2 min. It was found that the silicide changed from Ni{sub 3}Si to Ni{sub 2}Si with increasing annealing temperature, while the vanadium compounds appeared at 950 °C and their concentration increased at higher annealing temperature. A schematic diagram was proposed to explain the ohmic contact mechanism of Ni/V/4H-SiC structure.

  17. The effect of annealing temperature on the stability of gallium tin zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc; McCall, Briana; Alston, Robert; Collis, Ward; Iyer, Shanthi

    2015-10-01

    With the growing need for large area display technology and the push for a faster and cheaper alternative to the current amorphous indium gallium zinc oxide (a-IGZO) as the active channel layer for pixel-driven thin film transistors (TFTs) display applications, gallium tin zinc oxide (GSZO) has shown to be a promising candidate due to the similar electronic configuration of Sn4+ and In3+. In this work TFTs of GSZO sputtered films with only a few atomic % of Ga and Sn have been fabricated. A systematic and detailed comparison has been made of the properties of the GSZO films annealed at two temperatures: 140 °C and 450 °C. The electrical and optical stabilities of the respective devices have been studied to gain more insight into the degradation mechanism and are correlated with the initial TFT performance prior to the application of stress. Post deposition annealing at 450 °C of the films in air was found to lead to a higher atomic concentration of Sn4+ in these films and a superior quality of the film, as attested by the higher film density and less surface and interface roughness in comparison to the lower annealed temperature device. These result in significantly reduced shallow and deep interface traps with improved performance of the device exhibiting VON of -3.5 V, ION/IOFF of 108, field-effect mobility (μFE) of 4.46 cm2 V-1s-1, and sub-threshold swing of 0.38 V dec-1. The device is stable under both electrical and optical bias for wavelengths of 550 nm and above. Thus, this work demonstrates GSZO-based TFTs as a promising viable option to the IGZO TFTs by further tailoring the film composition and relevant processing temperatures.

  18. 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.

  19. Sample temperature profile during the excimer laser annealing of silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Caninenberg, M.; Verheyen, E.; Kiesler, D.; Stoib, B.; Brandt, M. S.; Benson, N.; Schmechel, R.

    2015-11-01

    Based on the heat diffusion equation we describe the temperature profile of a silicon nanoparticle thin film on silicon during excimer laser annealing using COMSOL Multiphysics. For this purpose system specific material parameters are determined such as the silicon nanoparticle melting point at 1683 K, the surface reflectivity at 248 nm of 20% and the nanoparticle thermal conductivity between 0.3 and 1.2 W/m K. To validate our model, the simulation results are compared to experimental data obtained by Raman spectroscopy, SEM microscopy and electrochemical capacitance-voltage measurements (ECV). The experimental data are in good agreement with our theoretical findings and support the validity of the model.

  20. Damage annealing in low temperature Fe/Mn implanted ZnO

    NASA Astrophysics Data System (ADS)

    Gunnlaugsson, H. P.; Bharuth-Ram, K.; Johnston, K.; Langouche, G.; Mantovan, R.; Mølholt, T. E.; Naidoo, D.; Ólafsson, O.; Weyer, G.

    2015-04-01

    57Fe Emission Mössbauer spectra obtained after low fluence (<1012 cm -2) implantation of 57Mn ( T 1/2= 1.5 min.) into ZnO single crystal held at temperatures below room temperature (RT) are presented. The spectra can be analysed in terms of four components due to Fe 2+ and Fe 3+ on Zn sites, interstitial Fe and Fe in damage regions (Fe D ). The Fe D component is found to be indistinguishable from similar component observed in emission Mössbauer spectra of higher fluence (˜1015 cm -2)57Fe/ 57Co implanted ZnO and 57Fe implanted ZnO, demonstrating that the nature of the damage regions in the two types of experiments is similar. The defect component observed in the low temperature regime was found to anneal below RT.

  1. Damage formation and annealing at low temperatures in ion implanted ZnO

    SciTech Connect

    Lorenz, K.; Alves, E.; Wendler, E.; Bilani, O.; Wesch, W.; Hayes, M.

    2005-11-07

    N, Ar, and Er ions were implanted into ZnO at 15 K within a large fluence range. The Rutherford backscattering technique in the channeling mode was used to study in situ the damage built-up in the Zn sublattice at 15 K. Several stages in the damage formation were observed. From the linear increase of the damage for low implantation fluences, an upper limit of the Zn displacement energy of 65 eV could be estimated for [0001] oriented ZnO. Annealing measurements below room temperature show a significant recovery of the lattice starting at temperatures between 80 and 130 K for a sample implanted with low Er fluence. Samples with higher damage levels do not reveal any damage recovery up to room temperature, pointing to the formation of stable defect complexes.

  2. Fabrication of highly L10-ordered FePt thin films by low-temperature rapid thermal annealing

    NASA Astrophysics Data System (ADS)

    Mizuguchi, M.; Sakurada, T.; Tashiro, T. Y.; Sato, K.; Konno, T. J.; Takanashi, K.

    2013-09-01

    Highly L10-ordered FePt thin films with a strong (001) texture were successfully fabricated on amorphous substrates simply by co-sputtering and rapid thermal annealing at a low temperature of 400 °C. The morphology of FePt thin films depended strongly on the heating rate, changing from a continuous structure with an atomically flat surface to an island-like structure. The change of the morphology resulted in a drastic increase of coercivity, indicating that the magnetization process could be controlled by the heating condition. This fabrication method of ordered FePt thin films is favorable in view of the compatibility for a practical device fabrication process.

  3. 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.

  4. Hydrogen termination of CVD diamond films by high-temperature annealing at atmospheric pressure.

    PubMed

    Seshan, V; Ullien, D; Castellanos-Gomez, A; Sachdeva, S; Murthy, D H K; Savenije, T J; Ahmad, H A; Nunney, T S; Janssens, S D; Haenen, K; Nesládek, M; van der Zant, H S J; Sudhölter, E J R; de Smet, L C P M

    2013-06-21

    A high-temperature procedure to hydrogenate diamond films using molecular hydrogen at atmospheric pressure was explored. Undoped and doped chemical vapour deposited (CVD) polycrystalline diamond films were treated according to our annealing method using a H2 gas flow down to ~50 ml∕min (STP) at ~850 °C. The films were extensively evaluated by surface wettability, electron affinity, elemental composition, photoconductivity, and redox studies. In addition, electrografting experiments were performed. The surface characteristics as well as the optoelectronic and redox properties of the annealed films were found to be very similar to hydrogen plasma-treated films. Moreover, the presented method is compatible with atmospheric pressure and provides a low-cost solution to hydrogenate CVD diamond, which makes it interesting for industrial applications. The plausible mechanism for the hydrogen termination of CVD diamond films is based on the formation of surface carbon dangling bonds and carbon-carbon unsaturated bonds at the applied tempera-ture, which react with molecular hydrogen to produce a hydrogen-terminated surface. PMID:23802976

  5. Hydrogen termination of CVD diamond films by high-temperature annealing at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Seshan, V.; Ullien, D.; Castellanos-Gomez, A.; Sachdeva, S.; Murthy, D. H. K.; Savenije, T. J.; Ahmad, H. A.; Nunney, T. S.; Janssens, S. D.; Haenen, K.; Nesládek, M.; van der Zant, H. S. J.; Sudhölter, E. J. R.; de Smet, L. C. P. M.

    2013-06-01

    A high-temperature procedure to hydrogenate diamond films using molecular hydrogen at atmospheric pressure was explored. Undoped and doped chemical vapour deposited (CVD) polycrystalline diamond films were treated according to our annealing method using a H2 gas flow down to ˜50 ml/min (STP) at ˜850 °C. The films were extensively evaluated by surface wettability, electron affinity, elemental composition, photoconductivity, and redox studies. In addition, electrografting experiments were performed. The surface characteristics as well as the optoelectronic and redox properties of the annealed films were found to be very similar to hydrogen plasma-treated films. Moreover, the presented method is compatible with atmospheric pressure and provides a low-cost solution to hydrogenate CVD diamond, which makes it interesting for industrial applications. The plausible mechanism for the hydrogen termination of CVD diamond films is based on the formation of surface carbon dangling bonds and carbon-carbon unsaturated bonds at the applied tempera-ture, which react with molecular hydrogen to produce a hydrogen-terminated surface.

  6. 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.

  7. Effect of Annealing Temperature on the Corrosion Resistance of Electroless Ni-B-Mo Coatings

    NASA Astrophysics Data System (ADS)

    Serin, Ihsan Gökhan; Göksenli, Ali; Yüksel, Behiye; Yildiz, Rasid Ahmed

    2015-08-01

    The Ni-B-Mo coating on steel by electroless plating and the evaluation of the morphology and corrosion performance after applying heat treatments at different temperatures for 1 h were investigated in this study. The 25-μm-thick coating was uniform and adhesion between the substrate and the coating was good. The coating consisted of an amorphous-like structure in their as-plated condition, and after annealing at 400 °C for 1 h, crystallized nickel, nickel borides, and molybdenum carbide were formed. Immersion tests in 10% HCl solution and potentiodynamic polarization measurements in 3.5% NaCl aqueous solution were applied to investigate corrosion resistance. The corrosion performance of heat-treated coatings was compared with steel and the as-plated coating. By increasing the annealing temperature, corrosion potential shifted toward a noble direction, corrosion current density decreased and the weight loss of specimens decreased, demonstrating an increase in corrosion resistance. Best corrosion performance was achieved by the coating heat treated at 550 °C.

  8. Influence of annealing temperature on structural and optical properties of nanocrystalline Platinum octaethylporphyrin (PtOEP) thin films

    NASA Astrophysics Data System (ADS)

    Abuelwafa, A. A.; El-Denglawey, A.; Dongol, M.; El-Nahass, M. M.; Soga, T.

    2015-11-01

    Thermal evaporation technique was used to prepare the Platinum octaethylporphyrin (PtOEP) thin films at room temperature. The deposited films were studied before and after thermal annealing at 373 and 473 K for 3 h under vacuum (10-3 Pa). The film structure, surface morphologies and molecular structure were investigated as a function of annealing temperature by X-ray Diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM) and Fourier-transform infrared techniques (FT-IR) respectively. The results confirmed that the as-deposited and annealed films have nanostructural features. Optical constants of the as-deposited and annealed films have been obtained in the wavelength range 200-1100 nm by using spectrophotometric measurements. Analysis of the spectra of absorption coefficient showed indirect allowed transition and optical energy gap found to decrease with increase in annealing temperature. The dispersion of refractive index at the normal dispersion (λ > 600 nm) was discussed in terms of single oscillator model of Wemple-Didomenico. Based on generalized Miller's rule the third order non-linear susceptibility, χ(3) and nonlinear refractive index, n2 were estimated and studied at lower photon energy and showing lower value for the annealed film.

  9. Temperature dependence of thermopower in molecular junctions

    NASA Astrophysics Data System (ADS)

    Kim, Youngsang; Lenert, Andrej; Meyhofer, Edgar; Reddy, Pramod

    2016-07-01

    The thermoelectric properties of molecular junctions are of considerable interest due to their promise for efficient energy conversion. While the dependence of thermoelectric properties of junctions on molecular structure has been recently studied, their temperature dependence remains unexplored. Using a custom built variable temperature scanning tunneling microscope, we measured the thermopower and electrical conductance of individual benzenedithiol junctions over a range of temperatures (100 K-300 K). We find that while the electrical conductance is independent of temperature, the thermopower increases linearly with temperature, confirming the predictions of the Landauer theory.

  10. Effects of annealed temperature on the properties of TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Avesh

    2016-05-01

    In this work, the structural, morphological and electrical properties of TiO2 thin films are studied. The phase transformation of TiO2 from anatase to rutile is occurred at a certain temperature. This transformation increases defects concentration onthe surface of the film which acts as trapping sites for carriers, thereby affecting the Fermi level of TiO2 film.Quantitative estimation of Fermi level shifting is measured in terms of work function measurement using scanning Kelvin probe measurement. Work function of TiO2 was found to decrease with increasing annealed temperature indicating shifting of Fermi level towards conduction band. Position of Fermi level plays an important role in phase transformation and electronic properties of TiO2.

  11. 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.

  12. 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.

  13. Temperature dependence of resistive switching behaviors in resistive random access memory based on graphene oxide film

    NASA Astrophysics Data System (ADS)

    Yi, Mingdong; Cao, Yong; Ling, Haifeng; Du, Zhuzhu; Wang, Laiyuan; Yang, Tao; Fan, Quli; Xie, Linghai; Huang, Wei

    2014-05-01

    We reported resistive switching behaviors in the resistive random access memory (RRAM) devices based on the different annealing temperatures of graphene oxide (GO) film as active layers. It was found that the resistive switching characteristics of an indium tin oxide (ITO)/GO/Ag structure have a strong dependence on the annealing temperature of GO film. When the annealing temperature of the GO film was 20 °C, the devices showed typical write-once-read-many-times (WORM) type memory behaviors, which have good memory performance with a higher ON/OFF current ratio (˜104), the higher the high resistance state (HRS)/low resistance state (LRS) ratio (˜105) and stable retention characteristics (>103 s) under lower programming voltage (-1 V and -0.5 V). With the increasing annealing temperature of GO film, the resistive switching behavior of RRAM devices gradually weakened and eventually disappeared. This phenomenon could be understood by the different energy level distributions of the charge traps in GO film, and the different charge injection ability from the Ag electrode to GO film, which is caused by the different annealing temperatures of the GO film.

  14. Temperature dependence of resistive switching behaviors in resistive random access memory based on graphene oxide film.

    PubMed

    Yi, Mingdong; Cao, Yong; Ling, Haifeng; Du, Zhuzhu; Wang, Laiyuan; Yang, Tao; Fan, Quli; Xie, Linghai; Huang, Wei

    2014-05-01

    We reported resistive switching behaviors in the resistive random access memory (RRAM) devices based on the different annealing temperatures of graphene oxide (GO) film as active layers. It was found that the resistive switching characteristics of an indium tin oxide (ITO)/GO/Ag structure have a strong dependence on the annealing temperature of GO film. When the annealing temperature of the GO film was 20 °C, the devices showed typical write-once-read-many-times (WORM) type memory behaviors, which have good memory performance with a higher ON/OFF current ratio (∼10(4)), the higher the high resistance state (HRS)/low resistance state (LRS) ratio (∼10(5)) and stable retention characteristics (>10(3) s) under lower programming voltage (-1 V and -0.5 V). With the increasing annealing temperature of GO film, the resistive switching behavior of RRAM devices gradually weakened and eventually disappeared. This phenomenon could be understood by the different energy level distributions of the charge traps in GO film, and the different charge injection ability from the Ag electrode to GO film, which is caused by the different annealing temperatures of the GO film. PMID:24739543

  15. 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.

  16. 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

  17. Temperature dependent localized surface plasmon resonance properties of supported gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, Ranjit; Ranjan, Pranay

    2016-05-01

    The well known localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) supported on a dielectric substrate depends on the particle shape, size and type of dielectric material. The particle size and shape mainly vary with the method of preparation and the parameters involved there in. In this report, we show preparation of AuNPs supported on quartz substrate by direct current sputtering followed by thermal annealing at an optimized temperature of 400 °C. The samples were characterized using optical absorption spectra, scanning electron microscopy (SEM) and the energy dispersive x-ray spectrum. The LSPR position could be tuned by varying annealing temperature. The LSPR was found to be blue shifted up to 10 nm with annealing temperature varying from 400 °C to 800 °C. The change in LSPR was ascribed to the morphology of AuNPs over quartz.

  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. 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.

  20. Effect of high-temperature annealing for single-Ni-layer gate in AlGaN/GaN high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Nanjo, Takuma; Imai, Akifumi; Kurahashi, Kenichiro; Matsuda, Takashi; Suita, Muneyoshi; Yagyu, Eiji

    2016-05-01

    AlGaN/GaN high-electron-mobility transistors (HEMTs) with Schottky gate contacts are strong candidates for high-power applications with high-frequency operation. The existence of interfacial traps between Schottky gate contacts and an AlGaN surface is one of the issues causing relatively high gate leakage current in these HEMTs. High-temperature gate annealing, which reduces the density of traps owing to the interfacial reaction between Schottky gate contacts and an AlGaN surface, was investigated using a single-Ni-layer gate structure to prevent the alloying of conventional stacked metal layers such as Ni/Au and Pt/Au. As a result, a strong gate annealing temperature dependence of Schottky characteristics was observed and this dependence also caused drain current collapse. In addition, it was confirmed that 700 °C is the optimal gate annealing temperature for improving both the Schottky characteristics and drain current collapse. These results are attributed to the change in the density of interfacial trap states.

  1. Ultrahigh-temperature microwave annealing of Al{sup +}- and P{sup +}-implanted 4H-SiC

    SciTech Connect

    Sundaresan, Siddarth G.; Rao, Mulpuri V.; Tian, Yong-lai; Ridgway, Mark C.; Schreifels, John A.; Kopanski, Joseph J.

    2007-04-01

    In this work, an ultrafast solid-state microwave annealing has been performed, in the temperature range of 1700-2120 degree sign C on Al{sup +}- and P{sup +}-implanted 4H-SiC. The solid-state microwave system used in this study is capable of raising the SiC sample temperatures to extremely high values, at heating rates of {approx}600 degree sign C/s. The samples were annealed for 5-60 s in a pure nitrogen ambient. Atomic force microscopy performed on the annealed samples indicated a smooth surface with a rms roughness of 1.4 nm for 5x5 {mu}m{sup 2} scans even for microwave annealing at 2050 degree sign C for 30 s. Auger sputter profiling revealed a <7 nm thick surface layer composed primarily of silicon, oxygen, and nitrogen for the samples annealed in N{sub 2}, at annealing temperatures up to 2100 degree sign C. X-ray photoelectron spectroscopy revealed that this surface layer is mainly composed of silicon oxide and silicon nitride. Secondary ion mass spectrometry depth profiling confirmed almost no dopant in diffusion after microwave annealing at 2100 degree sign C for 15 s. However, a sublimation of {approx}100 nm of the surface SiC layer was observed for 15 s annealing at 2100 degree sign C. Rutherford backscattering spectra revealed a lattice damage-free SiC material after microwave annealing at 2050 degree sign C for 15 s, with scattering yields near the virgin SiC material. Van der Pauw-Hall measurements have revealed sheet resistance values as low as 2.4 k{omega}/{open_square} for Al{sup +}-implanted material annealed at 2100 degree sign C for 15 s and 14 {omega}/{open_square} for the P{sup +}-implanted material annealed at 1950 degree sign C for 30 s. The highest electron and hole mobilities measured in this work were 100 and 6.8 cm{sup 2}/V s, respectively, for the P{sup +}- and Al{sup +}-implanted materials.

  2. 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

  3. Suppression of phase coarsening in immiscible, co-continuous polymer blends under high temperature quiescent annealing.

    PubMed

    Liu, Xi-Qiang; Li, Ruo-Han; Bao, Rui-Ying; Jiang, Wen-Rou; Yang, Wei; Xie, Bang-Hu; Yang, Ming-Bo

    2014-05-28

    The properties of polymer blends greatly depend on the morphologies formed during processing, and the thermodynamic non-equilibrium nature of most polymer blends makes it important to maintain the morphology stability to ensure the performance stability of structural materials. Herein, the phase coarsening of co-continuous, immiscible polyamide 6 (PA6)-acrylonitrile-butadiene-styrene (ABS) blends in the melt state was studied and the effect of introduction of nano-silica particles on the stability of the phase morphology was examined. It was found that the PA6-ABS (50/50 w) blend maintained the co-continuous morphology but coarsened severely upon annealing at 230 °C. The coarsening process could be divided into two stages: a fast coarsening process at the initial stage of annealing and a second coarsening process with a relatively slow coarsening rate later. The reduction of the coarsening rate can be explained from the reduction of the global curvature of the interface. With the introduction of nano-silica, the composites also showed two stages of coarsening. However, the coarsening rate was significantly decreased and the phase morphology was stabilized. Rheological measurements indicated that a particle network structure was formed when the concentration of nano-silica particles was beyond 2 wt%. The particle network inhibited the movement of molecular chains and thus suppressed the coarsening process. PMID:24663286

  4. Dependence of the electronic transport on the microstructure in annealed Bi thin films

    NASA Astrophysics Data System (ADS)

    Bui, Thanh; Raskin, Jean-Pierre; Malet, Loic; Godet, Stephane; Rodrigues Martins, Frederico; Faniel, Sebastien; Gonze, Xavier; Cabosart, Damien; Hackens, Benoit

    2013-03-01

    Bi thin films, with a thickness ranging from 10 to 100 nm, are deposited by electron-beam evaporation on a thermally oxidized Si(100) substrate. The deposition parameters are optimized in order to maximize the grain size of the polycrystalline films. The evolution of the crystal orientation is examined as a function of the deposition and annealing parameters, by electron back scattering diffraction. Low temperature (21 mK - 150 K) magnetoresistance measurements (up to 15 T) on polycrystalline films reveal weak anti-localization, superimposed by the classical magnetoresistance. The analysis of the weak anti-localization allows us to extract quantum transport parameters, such as the phase coherence and the spin orbit coupling time. From the evolution of the broad magnetoresistance background, we infer the evolution of electronic transport parameters: the mobility, the charge carrier concentration and the mean free path. Magneto-transport and ab initio calculations are combined in order to investigate on the controversial existence of the semimetal-semiconductor transition.

  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. High-temperature measurement with Brillouin optical time domain analysis of an annealed fused-silica single-mode fiber.

    PubMed

    Bao, Yi; Chen, Genda

    2016-07-15

    The effect of annealing is experimentally studied for a fused silica, fully distributed fiber optic sensor based on the pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA). Within a heating rate of 4.3°C/min and 30.6°C/min, and a sustained peak temperature for 120 and 240 min, annealing extended the sensor's upper operation temperature from 800°C to 1000°C and reduced the sensor's measurement variability over a temperature range of 22°C to 1000°C with a maximum Brillouin frequency variation of 1%. The annealed sensor had a linearly decreasing Brillouin frequency sensitivity from 1.349×10-3  GHz/°C at 22°C to 0.419×10-3  GHz/°C at 1000°C. The time required to achieve a stable annealing effect decayed exponentially with annealing temperature. PMID:27420489

  7. 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

  8. 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.

  9. Temperature Dependence of Factors Controlling Isoprene Emissions

    NASA Technical Reports Server (NTRS)

    Duncan, Bryan N.; Yoshida, Yasuko; Damon, Megan R.; Douglass, Anne R.; Witte, Jacquelyn C.

    2009-01-01

    We investigated the relationship of variability in the formaldehyde (HCHO) columns measured by the Aura Ozone Monitoring Instrument (OMI) to isoprene emissions in the southeastern United States for 2005-2007. The data show that the inferred, regional-average isoprene emissions varied by about 22% during summer and are well correlated with temperature, which is known to influence emissions. Part of the correlation with temperature is likely associated with other causal factors that are temperature-dependent. We show that the variations in HCHO are convolved with the temperature dependence of surface ozone, which influences isoprene emissions, and the dependence of the HCHO column to mixed layer height as OMI's sensitivity to HCHO increases with altitude. Furthermore, we show that while there is an association of drought with the variation in HCHO, drought in the southeastern U.S. is convolved with temperature.

  10. 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.

  11. 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.

  12. 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.

  13. Time-dependent annealing and deposition on substrates with repulsive interactions

    NASA Astrophysics Data System (ADS)

    Venables, J. A.; Degraffenreid, J.; Kay, D.; Yang, P.

    2006-08-01

    In models of nucleation and growth of crystals on surfaces, it is often assumed that the energy surface of the substrate is flat, that diffusion is isotropic, and that capture numbers can be calculated in the diffusion-controlled limit. We lift these restrictions and formulate the general time-dependent problem in a two-dimensional (2D) potential field. We utilize the master equation discretization (MED) method to solve the 2D time-dependent diffusion field of adparticles on general nonuniform (rectangular grid) substrates, and compare it against competing algorithms, including the fast Fourier transform (FFT) and hybrid-FFT methods previously introduced, for periodic boundary conditions. The physical context is set by the importance of repulsive interactions in the nucleation and growth of many nanostructures, e.g., metal nanoclusters, hut clusters, and nanowires. The programs, realized in MATLAB®6.5 , are used to obtain quantitative capture numbers, aspect and direct impingement ratios, and other island growth quantities in the presence of potential fields, when particular surface processes are included. The case of no corner rounding is studied in detail. Strongly anisotropic potentials favor wire growth, which can be considerably influenced by alternate deposition and annealing, and the location of neighboring islands. Physical examples are given based on Ge/Si(001) material parameters. Essentially similar programs, differing only in outputs, are used to visualize the diffusion field and to produce realistic movies of crystal growth. Examples given here are linear deterministic calculations, but the framework allows for inclusion of nonlinear and statistical effects for particular applications.

  14. Distribution functions for internal interface energy as a characteristic of submicrocrystalline copper structure evolution under low-temperature annealing

    NASA Astrophysics Data System (ADS)

    Kuznetsov, P.; Rakhmatulina, T.; Koznikov, A.; Belyaeva, I.

    2015-10-01

    Submicrocrystalline structure of 99.99% pure copper produced by equal channel angular pressing was under investigation. After deformation the samples were subjected to low-temperature annealing. Grain and subgrain structure was studied by scanning tunnel microscopy. Internal interface energy was estimated using the method based on measurement of dihedral angles (ψ) of the boundary grooves formed by electrochemical etching. Analysis of the differential and cumulative distribution functions for relative grain boundary energy enabled to qualitatively evaluate energy redistribution between the boundaries of different types and internal bulk crystallites and to study evolution of submicrocrystalline structure under low-temperature annealing.

  15. 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...

  16. E. coli survival in waters: temperature dependence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowing the survival rates of water-borne Escherichia coli is important for evaluating microbial contamination and in making appropriate management decisions. E. coli survival rates are dependent on temperature; this dependency is routinely expressed using an analog of the Q10 model. This suggestion...

  17. 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.

  18. 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.

  19. Transformation of Ba-Al-Si precursors to celsian by high-temperature oxidation and annealing

    NASA Astrophysics Data System (ADS)

    Schmutzler, Hans J.; Sandhage, Kenneth H.

    1995-02-01

    Celsian (monoclinic BaO · A12O3 · 2SiO2) is being considered as a matrix material for ceramic composites used in high-temperature structural applications. The present article describes the synthesis of celsian by the oxidation and annealing of solid, malleable, metallic Ba-Al-Si precursors. The phase and microstructural evolution after various stages of oxidation at 300 °C to 1260 °C in pure oxygen at 1 atm pressure have been examined by X-ray diffraction (XRD) and electron microprobe analyses (EPMA). Barium peroxide, BaO2, formed rapidly during oxidation at 300 °C, with aluminum and silicon remaining largely as unoxidized particles in a BaO2 matrix. Between 300 °C and 500 °C, barium orthosilicate, Ba2Si04, formed by a solid-state reaction between barium peroxide and unoxidized silicon. Further exposure to temperatures between 500 °C and 1200 °C resulted in the oxidation of aluminum and of residual silicon. The oxidized silicon reacted with the barium orthosilicate matrix to yield higher silica-containing barium silicates that, in turn, reacted with alumina or mullite to form metastable hexacelsian (hexagonal BaO-A12O3 · 2SiO2). Celsian was then obtained by further exposure to peak temperatures ≤1260°C.

  20. Influences of annealing temperature on microstructure and properties for TiO2 films deposited by DC magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Shang, Jie-Ting; Chen, Chih-Ming; Cheng, Ta-Chih; Lee, Ying-Chieh

    2015-12-01

    Titanium dioxide films were deposited at 100 °C of substrate temperature with a DC magnetron sputtering system. The crystalline structures, morphological features, and photocatalytic activity of the TiO2 films were systematically studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and ultraviolet spectrophotometry. To obtain the crystalline structure of TiO2 film at a low annealing temperature, high-level DC power (600 W) was applied. The effect of the annealing treatments on the microstructure of the TiO2 films was investigated. The results indicated that the annealing process at 200 °C clearly caused the formation of a nanocrystalline anatase phase that directly affected photocatalytic activity. The dye removal efficiency of the nanostructured anatase attained 53 and 31% for UV and visible light radiation, respectively.

  1. 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.

  2. 454-Pyrosequencing Analysis of Bacterial Communities from Autotrophic Nitrogen Removal Bioreactors Utilizing Universal Primers: Effect of Annealing Temperature

    PubMed Central

    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. PMID:26421306

  3. Catalyst-free growth of ZnO nanowires on ITO seed layer/glass by thermal evaporation method: Effects of ITO seed layer laser annealing temperature

    NASA Astrophysics Data System (ADS)

    Alsultany, Forat H.; Hassan, Z.; Ahmed, Naser M.

    2016-04-01

    Novel catalyst-free growth of ZnO nanowires (ZnO-NWs) on ITO seeds/glass substrate by thermal evaporation method, and effects of continuous wave CO2 laser thermal annealed seed layer on the morphology and properties of ZnO-NWs growth were investigated. The effects of sputtered ITO seed layer laser annealing temperature on the morphological, structural, and optical properties of ZnO-NWs was systematically investigated at temperatures 250, 350, and 450 °C, respectively. The surface morphology and structure of the seeds and the products of ZnO-NWs were characterized in detail by using field emission scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Optical properties were further examined through photoluminescence, and UV-Vis spectrophotometer. A growth mechanism was proposed on the basis of obtained results. The results showed that the nanowires were strongly dependent on the seed layer annealing temperatures, which played an important role in nucleation and dissimilar growth of the nanowires with varying sizes and geometric shapes.

  4. 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.

  5. Temperature dependence of sapphire fiber Raman scattering

    DOE PAGESBeta

    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.

  6. Enhanced Optical Properties of Chemical Vapor Deposited Single Crystal Diamond by Low-Pressure/High-Temperature Annealing

    SciTech Connect

    Meng, Y.; Yan, C; Lai, Y; Krasnicki, S; Shu, H; Yu, T; Liang, Q; Mao, H; Hemley, R

    2008-01-01

    Single crystal diamond produced by chemical vapor deposition (CVD) at very high growth rates (up to 150 em/h) has been successfully annealed without graphitization at temperatures up to 2200 C and pressures <300 torr. Crystals were annealed in a hydrogen environment by using microwave plasma techniques for periods of time ranging from a fraction of minute to a few hours. This low-pressure/high-temperature (LPHT) annealing enhances the optical properties of this high-growth rate CVD single crystal diamond. Significant decreases are observed in UV, visible, and infrared absorption and photoluminescence spectra. The decrease in optical absorption after the LPHT annealing arises from the changes in defect structure associated with hydrogen incorporation during CVD growth. There is a decrease in sharp line spectral features indicating a reduction in nitrogen-vacancy-hydrogen (NVH-) defects. These measurements indicate an increase in relative concentration of nitrogen-vacancy (NV) centers in nitrogen-containing LPHT-annealed diamond as compared with as-grown CVD material. The large overall changes in optical properties and the specific types of alterations in defect structure induced by this facile LPHT processing of high-growth rate single-crystal CVD diamond will be useful in the creation of diamond for a variety of scientific and technological applications.

  7. Scaling temperature dependent rheology of magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Sherman, Stephen G.; Powell, Louise A.; Becnel, Andrew C.; Wereley, Norman M.

    2015-05-01

    Magnetorheological (MR) fluids are suspensions of micron-scale magnetizable particles suspended in a carrier fluid. When field is applied, MR fluids develop a field controllable yield stress and a field independent post-yield viscosity. However, this viscosity has substantial temperature dependence, varying by up to an order of magnitude over the operating temperature range of MR fluid devices. We apply non-Brownian suspension theory to explain this result and find that the majority of this effect should be caused by the temperature dependent behavior of the carrier fluid. Thus, if two fluids share the same carrier fluid, then their fluid properties should scale in temperature similarly. This result is first validated by measuring viscosity across temperature for custom model fluids designed to conform to theory, showing temperature scaling within 5% for both the MR fluids and their carrier fluid. Then, on a series of related commercially available fluids with unknown additive content, we show that the MR fluids exhibit common scaling to within 4%. We also investigate the effects of magnetic hysteresis and find that it induces a negligible increase in yield stress and no measurable change in viscosity. We conclude that our non-dimensional analysis enables the temperature dependence of novel MR fluids to be characterized with fewer experiments.

  8. Influence of annealing temperature on electronic and dielectric properties of ZrO{sub 2} thin films on Si

    SciTech Connect

    Uthanna, S.; Kondaiah, P.; Madhavi, V.; Rao, G. Mohan

    2012-06-25

    Zirconium oxide (ZrO{sub 2}) films were deposited on (100) silicon substrates by DC reactive magnetron sputtering of zirconium target at an oxygen partial pressure of 6 Multiplication-Sign 10{sup -2} Pa. The as-deposited films were annealed in air for 1 hour at different temperatures in the range 773 - 1173 K. The influence of annealing temperature on the structural properties of ZrO{sub 2} films and the electrical properties like Capacitance-Voltage and Current-Voltage of the capacitors of the type Al/ZrO{sub 2}/p-Si were studied. The capacitance and dielectric constant of the capacitors were found to increase with increase in annealing temperature from 773 to 973 K, however, with further increase in annealing temperature to 1173 K they were found to decrease. In addition, the leakage current density was decreased from 1 Multiplication-Sign 10{sup -6} to 4 Multiplication-Sign 10{sup -7} A/cm{sup 2} at 1V gate bias voltage and the electrical conduction mechanism was dominated by Schottky emission for all the films in lower electric fields.

  9. 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.

  10. Temperature dependence of standard model CP violation.

    PubMed

    Brauner, Tomáš; Taanila, Olli; Tranberg, Anders; Vuorinen, Aleksi

    2012-01-27

    We analyze the temperature dependence of CP violation effects in the standard model by determining the effective action of its bosonic fields, obtained after integrating out the fermions from the theory and performing a covariant gradient expansion. We find nonvanishing CP violating terms starting at the sixth order of the expansion, albeit only in the C-odd-P-even sector, with coefficients that depend on quark masses, Cabibbo-Kobayashi-Maskawa matrix elements, temperature and the magnitude of the Higgs field. The CP violating effects are observed to decrease rapidly with temperature, which has important implications for the generation of a matter-antimatter asymmetry in the early Universe. Our results suggest that the cold electroweak baryogenesis scenario may be viable within the standard model, provided the electroweak transition temperature is at most of order 1 GeV. PMID:22400822

  11. 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.

  12. 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

  13. Effect of high temperature annealing on ion-irradiation induced magnetization in FeRh thin films

    NASA Astrophysics Data System (ADS)

    Tohki, A.; Aikoh, K.; Iwase, A.; Yoneda, K.; Kosugi, S.; Kume, K.; Batchuluun, T.; Ishigami, R.; Matsui, T.

    2012-04-01

    Low temperature ferromagnetic FeRh with B2-type crystal structure was successfully synthesized by annealing of the excessively irradiated FeRh thin film samples having nonmagnetic A1-type crystal structure. The B2 phase transformed from the A1 phase by this process contained some amount of lattice defects, such as anti-site defects and vacancies, which made the magnetic spins of the sample aligned. These results imply that the combination of the process of the ion-beam irradiation and annealing of the film samples makes the magnetic state systematically controlled.

  14. Low-temperature post-deposition annealing investigation for 3D charge trap flash memory by Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Huo, Zongliang; Jin, Lei; Han, Yulong; Li, Xinkai; Ye, Tianchun; Liu, Ming

    2015-01-01

    The influence of post-deposition annealing (PDA) temperature condition on charge distribution behavior of HfO2 thin films was systematically investigated by various-temperature Kelvin probe force microscopy technology. Contact potential difference profiles demonstrated that charge storage capability shrinks with decreasing annealing temperature from 1,000 to 500 °C and lower. Compared to 1,000 °C PDA, it was found that 500 °C PDA causes deeper effective trap energy level, suppresses lateral charge spreading, and improves the retention characteristics. It is concluded that low-temperature PDA can be adopted in 3D HfO2-based charge trap flash memory to improve the thermal treatment compatibility of the bottom peripheral logic and upper memory arrays.

  15. Temperature dependence of fluid transport in nanopores

    NASA Astrophysics Data System (ADS)

    Xu, Baoxing; Wang, Binglei; Park, Taehyo; Qiao, Yu; Zhou, Qulan; Chen, Xi

    2012-05-01

    Understanding the temperature-dependent nanofluidic transport behavior is critical for developing thermomechanical nanodevices. By using non-equilibrium molecular dynamics simulations, the thermally responsive transport resistance of liquids in model carbon nanotubes is explored as a function of the nanopore size, the transport rate, and the liquid properties. Both the effective shear stress and the nominal viscosity decrease with the increase of temperature, and the temperature effect is coupled with other non-thermal factors. The molecular-level mechanisms are revealed through the study of the radial density profile and hydrogen bonding of confined liquid molecules. The findings are verified qualitatively with an experiment on nanoporous carbon.

  16. Mixed field peronnel dosimetry: Part 1, High temperature peak characteristics of the reader-annealed TLD-600

    SciTech Connect

    Liu, J.C. ); Sims, C.S. )

    1991-02-01

    The high temperature peaks (TL peaks 6--7) of TLD-600 are known to have higher responses to high LET radiation than to low LET radiation. These high temperature peak characteristics were studied for the automatic reader-annealed Harshaw albedo neutron TLD. The high temperature peaks response is linear for neutrons over the dose equivalent range tested (0.05--3 mSv of a {sup 252}Cf source moderated by a 15 cm radius polyethylene sphere), but is supralinear above 20 mSv of {sup 137}Cs photons. The peaks ratio (peaks 6--7/peaks 3--5) of TLD-600 is 0.15 for neutrons of any incident energy, 0.01 for {sup 137}Cs gammas, and 0.02 for M-150 x-rays. Based on the high temperature peak characteristics, a mixed field neutron-photon personnel dosimetry methodology using a single TLD-600 element was developed. The dosimetric method was evaluated in mixed {sup 238}PuBe + {sup 137}Cs fields with four neutron-gamma dose equivalent ratios, and the neutron, photon and total dose equivalent estimations are better than 20% except in one case. However, it was found that the neutron and photon dose equivalent estimations are sensitive to the neutron and photon peaks ratios, depending on the neutron-photon dose equivalent ratio and the neutron source in the mixed field. Therefore, a successful use of this method requires knowledge of the photon and neutron energies in the mixed field. 13 refs., 6 figs., 2 tabs.

  17. Temperature dependence of BCF plastic scintillation detectors

    NASA Astrophysics Data System (ADS)

    Wootton, Landon; Beddar, Sam

    2013-05-01

    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.

  18. 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.

  19. 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}.

  20. 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.

  1. Effect of annealing temperature on microstructure, hardness and adhesion properties of TiSi xN y superhard coatings

    NASA Astrophysics Data System (ADS)

    Lu, Y. H.; Wang, J. P.; Tao, S. L.; Zhou, Z. F.

    2011-05-01

    A series of TiSi xN y superhard coatings with different Si contents were prepared on M42 steel substrates using two Ti and two Si targets by reactive magnetron sputtering at 500 °C. These samples were subsequently vacuum-annealed at 500, 600, 700, 800 and 900 °C, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), microindenter, Rockwell hardness tester and scratch tester were applied to investigate the microstructure, phase configuration, hardness and adhesion properties of as-deposited and annealed samples. The results indicated that there were two bonds, TiN and Si 3N 4, in all presently deposited TiSi xN y thin films, that structure was nanocomposite of nanocrystalline (nc-) TiN embedded into amorphous Si 3N 4 matrices. Annealing treatment below 900 °C played a little role in microstructure and hardness of the coatings although it greatly affected those of steel substrates. The film-substrate adhesion strength was slightly increased, followed by an abrupt decrease with increasing annealing temperature. Its value got to the maximum at 600 °C. Annealing had little effect on the friction coefficient with its value varying in the range of 0.39-0.40.

  2. 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.

  3. 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.

  4. 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

  5. Simultaneous Measurement of Temperature Dependent Thermophysical Properties

    NASA Astrophysics Data System (ADS)

    Czél, Balázs; Gróf, Gyula; Kiss, László

    2011-11-01

    A new evaluation method for a transient measurement of thermophysical properties is presented in this paper. The aim of the research was to couple a new automatic evaluation procedure to the BICOND thermophysical property measurement method to enhance the simultaneous determination of the temperature dependent thermal conductivity and volumetric heat capacity. The thermophysical properties of two different polymers were measured and compared with the literature data and with the measurement results that were done by well-known, traditional methods. The BICOND method involves a step-down cooling, recording the temperature histories of the inner and the outer surfaces of a hollow cylindrical sample and the thermophysical properties are evaluated from the solution of the corresponding inverse heat conduction using a genetic algorithm-based method (BIGEN) developed by the authors. The BIGEN is able to find the material properties with any kind of temperature dependency, that is illustrated through the measurement results of poly(tetrafluoroethylene) (PTFE) and polyamide (PA) samples.

  6. 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.

  7. Effect of post oxidation annealing in nitric oxide on interface properties of 4H-SiC/SiO2 after high temperature oxidation

    NASA Astrophysics Data System (ADS)

    Yanyue, Li; Xiaochuan, Deng; Yunfeng, Liu; Yanli, Zhao; Chengzhan, Li; Xixi, Chen; Bo, Zhang

    2015-09-01

    The interface properties of 4H-SiC metal-oxide-semiconductor (MOS) capacitors with post-oxidation annealing (POA) in nitric oxide (NO) ambient after high temperature (1300 °C) oxidation have been investigated using capacitance-voltage (C-V) measurements. The experimental results show that the interface states density (Dit) can be obviously decreased by the POA in NO ambient (NO-POA) and further reduced with increasing POA temperature and time. In the meantime significant reduction of the interface states density and oxidation time can be achieved at the higher thermal oxidation temperature, which results in the better oxide MOS characteristics and lower production costs. The dependence of Dit on POA temperature and time has been also discussed in detail. Project supported by the National Natural Science Foundation of China (No. 61234006) and the State Grid of China (No. sgri-wd-71-14-003).

  8. Influence of Step Annealing Temperature on the Microstructure and Pitting Corrosion Resistance of SDSS UNS S32760 Welds

    NASA Astrophysics Data System (ADS)

    Yousefieh, M.; Shamanian, M.; Saatchi, A.

    2011-12-01

    In the present work, the influence of step annealing heat treatment on the microstructure and pitting corrosion resistance of super duplex stainless steel UNS S32760 welds have been investigated. The pitting corrosion resistance in chloride solution was evaluated by potentiostatic measurements. The results showed that step annealing treatments in the temperature ranging from 550 to 1000 °C resulted in a precipitation of sigma phase and Cr2N along the ferrite/austenite and ferrite/ferrite boundaries. At this temperature range, the metastable pits mainly nucleated around the precipitates formed in the grain boundary and ferrite phase. Above 1050 °C, the microstructure contains only austenite and ferrite phases. At this condition, the critical pitting temperature of samples successfully arrived to the highest value obtained in this study.

  9. 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.

  10. 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.

  11. 300 W XeCl excimer laser annealing and sequential lateral solidification in low temperature poly silicon technology

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Kahlert, Hans-Juergen; Fechner, Burkhard; Rebhan, Ulrich; Osmanow, Rustem

    2003-05-01

    Industrial production of low temperature p-Si back plates for LCDs by high power excimer laser annealing was introduced several years ago. Regarding the economy of the process, one of the major advantages of excimer laser annealing is the opportunity to make use of low cost glass substrates due to the low temperature of the annealing process. The Lambda Physik high power excimer laser series are operated with the MicroLas 370 mm line beam optics, integrated by Japan Steel Works into industrial systems. The MicroLas line beam optics for conventional excimer laser annealing (ELA) process converts the raw laser beam profile into a stable and homogeneous rectangular illumination field with high aspect ratio. The excimer laser light source, the LAMBDA STEEL 1000, delivers stabilized pulse energies up to 1 Joule at repetition rates up to 300Hz. The crystallization using excimer lasers allows to produce films with electron mobility of 100-150 cm2/Vsec with the Line beam technique. The new SLS-method, which is currently under industrial investigation, even allows to obtain electron mobility between 200-400 cm2/Vsec.

  12. Dose and doping dependence of damage annealing in Fe MeV implanted InP

    SciTech Connect

    Carnera, A.; Fraboni, B.; Gasparotto, A. |; Priolo, F. |; Camporese, A.; Rossetto, G.; Frigeri, C.; Cassa, A.

    1996-12-31

    High energy (2 MeV) ion implantation of Fe in InP has been investigated by means of Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM) and secondary ions mass spectrometry (SIMS). The implanted doses ranged between 5 {times} 10{sup 13} and 5 {times} 10{sup 14} at/cm{sup 2}. Annealing in the 650--800 C range was performed and the primary as well as secondary damage evolution has been studied. The correlations between defect structure and Fe redistribution properties have been carefully analyzed. The results show the role of the primary defect structure in determining the annealing properties, both for damage recovery and Fe redistribution. The latter is also influenced by the doping of the substrate.

  13. Investigation of thermal annealing by gamma irradiation at room temperature in LiNbO3 crystals

    NASA Astrophysics Data System (ADS)

    Bajor, Andrzej L.; Kaczmarek, Slawomir M.; Pracka, Izabella; Swirkowicz, Marek; Wronska, Teresa

    2001-08-01

    An interesting phenomenon of thermal annealing in gamma irradiated undoped, and photorefractive Cu- and Fe-doped, Z- oriented LiNbO3 crystal has been observed. Prior and after each gamma irradiation the crystals were thermally annealed in the air at 800 degrees C for a couple of hours. Optical homogeneity was investigated on the entire area of LiNbO3 wafers by measuring distributions of birefringence, the principal azimuth, transmission, and parameters associated with birefringence dispersion, and also by measurements of additional absorption in a few wafers' points. It has been rather unexpectedly observed that the classical thermal annealing can lead to a decease in optical homogeneity in the majority of cases. It is attributed to generation of an internal electric field by the pyroelectric effect, and to the electrooptic effect involved thereafter. On the other hand, the secondary electrons generated by gamma irradiation are believed to increase the optical homogeneity by increasing the crystal's conductivity and dissipating this field. A uniform temperature heating across the wafer generated by this irradiation is also a helpful factor in this gamma- annealing. It has been found that this effect at room temperature by this irradiation is also a helpful factor in this gamma-annealing. It has been found that this effect at room temperature is small for gamma irradiation of 105 Gy, while increasing the doses to 106 Gy and 107 Gy can profile in a considerable reduction of the optical inhomogeneity. A certain influence of Cu-doping on this effect has also been observed.

  14. 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

  15. Temperature dependent phonon properties of thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Hellman, Olle; Broido, David; Fultz, Brent

    2015-03-01

    We present recent developments using the temperature dependent effective potential technique (TDEP) to model thermoelectric materials. We use ab initio molecular dynamics to generate an effective Hamiltonian that reproduce neutron scattering spectra, thermal conductivity, phonon self energies, and heat capacities. Results are presented for (among others) SnSe, Bi2Te3, and Cu2Se proving the necessity of careful modelling of finite temperature properties for strongly anharmonic materials. Supported by the Swedish Research Council (VR) Project Number 637-2013-7296.

  16. 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

  17. 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.

  18. 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.

  19. Temperature-dependent reflectivity of silicon carbide

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1992-01-01

    The spectral reflectivity of a commercial silicon carbide (SiC) ceramic surface was measured at wavelengths from 2.5 to 14.5 microns and at temperatures ranging from 358 to 520 K using a NASA-developed multiwavelength pyrometer. The SiC surface reflectivity was low at the short wavelengths, decreasing to almost zero at 10 microns, then increasing rapidly to a maximum at approximately 12.5 microns, and decreasing gradually thereafter. The reflectivity maximum increased in magnitude with increasing surface temperature. The wavelength and temperature dependence can be explained in terms of the classical dispersion theory of crystals and the Lorentz electron theory. Electronic transitions between the donor state and the conduction band states were responsible for the dispersion. The concentration of the donor state in SiC was determined to be approximately 4 x 10 exp 18 and its ionization energy was determined to be approximately 71 meV.

  20. Effect of oxygen partial pressure and anneal temperature on BaTiO3 thin film crystal structure

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Sun, De-gui; Fu, Xiuhua; Liu, Dong-mei; Pan, Yong-gang; Yang, Fei

    2015-08-01

    BaTiO3 film is deposited on single crystal MgO substrate with pulsed laser deposition, and its crystal structure and surface roughness are characterized by X-ray diffraction instrument and atomic force microscope. BaTiO3 film crystal quality is analyzed under three different oxygen partial pressure and three different annealing temperatures. The result shows that when the oxygen partial pressure is 15Pa, crystal surface (001) and (002) diffraction peak of BaTiO3 thin films have higher intensity. It indicated that the film has a good c-axis orientation. When the annealing temperature is 800°C, the intensity of diffraction peak is the maximum, and peak shape is sharper. BaTiO3 crystal film is obtained with highly preferred orientation, and film density is improved. Thus the film has less surface roughness and good crystalline state.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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.

  3. 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.

  4. Annealing prion protein amyloid fibrils at high temperature results in extension of a proteinase K-resistant core.

    PubMed

    Bocharova, Olga V; Makarava, Natallia; Breydo, Leonid; Anderson, Maighdlin; Salnikov, Vadim V; Baskakov, Ilia V

    2006-01-27

    Amyloids are highly ordered, rigid beta-sheet-rich structures that appear to have minimal dynamic flexibility in individual polypeptide chains. Here, we demonstrate that substantial conformational rearrangements occur within mature amyloid fibrils produced from full-length mammalian prion protein. The rearrangement results in a substantial extension of a proteinase K-resistant core and is accompanied by an increase in the beta-sheet-rich conformation. The conformational rearrangement was induced in the presence of low concentrations of Triton X-100 either by brief exposure to 80 degrees C or, with less efficacy, by prolonged incubation at 37 degrees C at pH 7.5 and is referred to here as "annealing." Upon annealing, amyloid fibrils acquired a proteinase K-resistant core identical to that found in bovine spongiform encephalopathy-specific scrapie-associated prion protein. Annealing was also observed when amyloid fibrils were exposed to high temperatures in the absence of detergent but in the presence of brain homogenate. These findings suggest that the amyloid fibrils exist in two conformationally distinct states that are separated by a high energy barrier and that yet unknown cellular cofactors may facilitate transition of the fibrils into thermodynamically more stable state. Our studies provide new insight into the complex behavior of prion polymerization and highlight the annealing process, a previously unknown step in the evolution of amyloid structures. PMID:16314415

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    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 × 1019 cm-3).

  7. 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.

  8. 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.

  9. Effect of rapid thermal annealing temperature on the dispersion of Si nanocrystals in SiO2 matrix

    NASA Astrophysics Data System (ADS)

    Saxena, Nupur; Kumar, Pragati; Gupta, Vinay

    2015-05-01

    Effect of rapid thermal annealing temperature on the dispersion of silicon nanocrystals (Si-NC's) embedded in SiO2 matrix grown by atom beam sputtering (ABS) method is reported. The dispersion of Si NCs in SiO2 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.

  10. 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.

  11. 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.

  12. Correlation between Pd metal thickness and thermally stable perpendicular magnetic anisotropy features in [Co/Pd]n multilayers at annealing temperatures up to 500 °C

    NASA Astrophysics Data System (ADS)

    An, Gwang Guk; Lee, Ja Bin; Yang, Seung Mo; Kim, Jae Hong; Chung, Woo Seong; Yoon, Kap Soo; Hong, Jin Pyo

    2015-02-01

    We examine highly stable perpendicular magnetic anisotropy (PMA) features of [Co/Pd]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.

  13. Effect of annealing temperature on the electrical, structural and surface morphological properties of Ru/Ti Schottky contacts on n-type InP

    NASA Astrophysics Data System (ADS)

    Munikrishna Reddy, Y.; Padmasuvarna, R.; Lakshmi Narasappa, T.; Sreehith, P.; Padma, R.; Dasaradha Rao, L.; Rajagopal Reddy, V.

    2015-10-01

    The effects of annealing temperature on the electrical, structural and surface morphological properties of Ru/Ti/n-InP Schottky diode have been investigated. Calculations showed that the Schottky barrier height (SBH) and ideality factor n of the as-deposited Ru/Ti/n-InP Schottky diode are 0.82 eV (I-V)/1.00 eV (C-V) and 1.19, respectively. However, it is observed that the SBH of Ru/Ti/n-InP Schottky diode decreases upon annealing at 200 °C, 300 °C and 400 °C. Cheung's and Norde method are also employed to calculate the SBH, ideality factor and series resistance of the Ru/Ti/n-InP Schottky diode as a function of annealing temperature. Experimental results reveal that the SBH and series resistance of the Ru/Ti/n-InP Schottky diode decreases upon annealing temperatures. The energy distribution of interface state density (Nss) is determined for the Ru/Ti/n-InP Schottky diode at different annealing temperatures. The X-ray diffraction studies revealed that the formation of phosphide phases at the Ru/Ti/n-InP interface may be the cause for the decrease of SBH upon annealing temperature. The AFM results indicated that there is no significant degradation in the surface morphology of the Ru/Ti Schottky contacts at elevated annealing temperatures.

  14. 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

  15. Modelling of fission gas release from irradiated UO2 fuel under high-temperature annealing conditions

    NASA Astrophysics Data System (ADS)

    Veshchunov, M. S.; Shestak, V. E.

    2012-11-01

    The new model for the vacancy field evolution in grains during annealing of irradiated fuel was developed and implemented in the MFPR code. The model simulates time and spatial variation of the vacancy concentration in the presence of extended vacancy sources (grain boundaries and dislocations) and sinks (growing intragranular bubbles). Being combined with the models for dislocation creep and for bubbles biased migration in the vacancy gradient, the new model self-consistently describes the processes of gas release and microstructure evolution observed in the annealing tests.

  16. 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.

  17. Temperature dependent spin structures in Hexaferrite crystal

    NASA Astrophysics Data System (ADS)

    Chao, Y. C.; Lin, J. G.; Chun, S. H.; Kim, K. H.

    2016-01-01

    In this work, the Hexaferrite Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) is studied due to its interesting characteristics of long-wavelength spin structure. Ferromagnetic resonance (FMR) is used to probe the magnetic states of BSZFO single crystal and its temperature dependence behavior is analyzed by decomposing the multiple lines of FMR spectra into various phases. Distinguished phase transition is observed at 110 K for one line, which is assigned to the ferro(ferri)-magnetic transition from non-collinear to collinear spin state.

  18. 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

  19. Influence of annealing temperatures on corrosion resistance of magnesium thin film-coated electro-galvanized steel

    NASA Astrophysics Data System (ADS)

    Lee, Myeong-Hoon; Kim, Yeon-Won; Lee, Seul-Gee; Kang, Jae-Wook; Park, Jun-Mu; Moon, Kyung-Man; Kim, Yun-Hae

    2015-03-01

    To improve the corrosion resistance of an electro-galvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at 250-330°C. The zinc-magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at 270-290°C showed better corrosion resistance than others. In X-ray diffraction analysis, ZnMg2 was detected throughout the temperature range, whereas Mg2Zn11 and FeZn13 were detected only in the film annealed at 310°C. The depth composition profile showed that the compositions of Mg at 270-290°C are evenly and deeply distributed in the film surface layer. These results demonstrate that 270-290°C is a proper temperature range to produce a layer of MgZn2 intermetallic compound to act as a homogenous passive layer.

  20. 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.

  1. Effect of annealing temperature and layer thickness on the opto-electrical properties of transparent conducting Zn/SnO2/Zn multilayer thin films

    NASA Astrophysics Data System (ADS)

    Kim, Sung Jae; Anwar, M. S.; Kim, Eun Ji; Cho, Hyeon Ji; Song, Tae Kwon; Koo, Bon Heun; Ko, Hang Joo

    2016-01-01

    Highly transparent Zn/SnO2/Zn conducting multilayer films are prepared on quartz glass substrates by using RF sputtering. The deposited films were annealed at various temperatures for thermal diffusion. The influences of annealing temperature, annealing time and the zinc thickness on the structural, electrical and optical properties of the multilayer films were studied. X-ray diffraction results showed that all p-type conducting films possessed polycrystalline SnO2 with a tetragonal rutile structure. Hall measurements indicates that annealing at 450 °C for 2 h was the optimum annealing parameters for p-type Zn (5 nm)/SnO2 (300 nm)/Zn (5 nm) multilayer films with a hole concentration and resistivity of 9.80 × 1016 cm-3 and 352 Ω·cm, respectively. The average transmission of the p-type Zn/SnO2/Zn multilayer films was above 87% in the visible range.

  2. 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.

  3. 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.

  4. 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.

  5. Absorption edge and the refractive index dispersion of carbon-nickel composite films at different annealing temperatures

    NASA Astrophysics Data System (ADS)

    Dalouji, Vali; Elahi, Seyed Mohammad; Solaymani, Shahram; Ghaderi, Atefeh

    2016-04-01

    In this paper, the optical properties of carbon-nickel films annealed at different temperatures 300, 500, 800 and 1000 ° C, with a special emphasis on the absorption edge, were investigated. The optical transmittance spectra in the wavelength range 300-1000nm were used to compute the absorption coefficient. The optical dispersion parameters were calculated according to Wemple and DiDomenico (WDD) single-oscillator model. Photoluminescence (PL) measurements of carbon-nickel films exhibit two main peaks at about 2.5 and 3.3eV which correspond to the fundamental indirect and direct gap, respectively. The field emission scanning electron microscopy (FESEM) showed that the absorption edge in the films was controlled by the nanoparticle size. The films annealed at 500 ° C have minimum indirect optical band gap and maximum disorder.

  6. 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.

  7. Enhanced TiC/SiC Ohmic contacts by ECR hydrogen plasma pretreatment and low-temperature post-annealing

    NASA Astrophysics Data System (ADS)

    Liu, Bingbing; Qin, Fuwen; Wang, Dejun

    2015-11-01

    We proposed an electronic cyclotron resonance (ECR) microwave hydrogen plasma pretreatment (HPT) for moderately doped (1 × 1018 cm-3) SiC surfaces and formed ideal TiC/SiC Ohmic contacts with significantly low contact resistivity (1.5 × 10-5 Ω cm2) after low-temperature annealing (600 °C). This is achieved by reducing barrier height at TiC/SiC interface because of the release of pinned Fermi level by surface flattening and SiC surface states reduction after HPT, as well as the generation of donor-type carbon vacancies, which reduced the depletion-layer width for electron tunneling after annealing. Interface band structures were analyzed to elucidate the mechanism of Ohmic contact formations.

  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. 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

  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. Temperature Dependent Kinetics DNA Charge Transport

    NASA Astrophysics Data System (ADS)

    Wohlgamuth, Chris; McWilliams, Marc; Slinker, Jason

    2012-10-01

    Charge transport (CT) through DNA has been extensively studied, and yet the mechanism of this process is still not yet fully understood. Besides the benefits of understanding charge transport through this fundamental molecule, further understanding of this process will elucidate the biological implications of DNA CT and advance sensing technology. Therefore, we have investigated the temperature dependence of DNA CT by measuring the electrochemistry of DNA monolayers modified with a redox-active probe. By using multiplexed electrodes on silicon chips, we compare square wave voltammetry of distinct DNA sequences under identical experimental conditions. We vary the probe length within the well matched DNA duplex in order to investigate distance dependent kinetics. This length dependent study is a necessary step to understanding the dominant mechanism behind DNA CT. Using a model put forth by O'Dea and Osteryoung and applying a nonlinear least squares analysis we are able to determine the charge transfer rates (k), transfer coefficients (α), and the total surface concentration (&*circ;) of the DNA monolayer. Arrhenius like behavior is observed for the multiple probe locations, and the results are viewed in light of and compared to the prominent charge transport mechanisms.

  13. The influence of annealing temperature on the interface and photovoltaic properties of CdS/CdSe quantum dots sensitized ZnO nanorods solar cells.

    PubMed

    Qiu, Xiaofeng; Chen, Ling; Gong, Haibo; Zhu, Min; Han, Jun; Zi, Min; Yang, Xiaopeng; Ji, Changjian; Cao, Bingqiang

    2014-09-15

    Arrays of ZnO/CdS/CdSe core/shell nanocables with different annealing temperatures have been investigated for CdS/CdSe quantum dots sensitized solar cells (QDSSCs). CdS/CdSe quantum dots were synthesized on the surface of ZnO nanorods that serve as the scaffold via a simple ion-exchange approach. The uniform microstructure was verified by scanning electron microscope and transmission electron microscope. UV-Visible absorption spectrum and Raman spectroscopy analysis indicated noticeable influence of annealing temperature on the interface structural and optical properties of the CdS/CdSe layers. Particularly, the relationship between annealing temperatures and photovoltaic performance of the corresponding QDSSCs was investigated employing photovoltaic conversion, quantum efficiency and electrochemical impedance spectra. It is demonstrated that higher cell efficiency can be obtained by optimizing the annealing temperature through extending the photoresponse range and improving QD layer crystal quality. PMID:24998074

  14. SEM and XRD Characterization of ZnO Nanostructured Thin Films Prepared by Sol-Gel Method with Various Annealing Temperatures

    NASA Astrophysics Data System (ADS)

    Amizam, S.; Abdullah, N.; Rafaie, H. A.; Rusop, M.

    2010-03-01

    ZnO thin films were fabricated by the sol-gel method using Zn(CH3COO)2.2H2O (zinc acetate) as starting material. A homogenous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and ethanolamine. Deposition of ZnO solution on Si substrate was performed by spin-coating technique and annealed at various temperatures from 200° C to 600° C. The surface morphologies and structural properties of the obtained product were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM analysis showed that the surface boundaries of ZnO thin films were decreased with the increasing of annealing temperature. X-ray analysis showed that the crystallinity of ZnO thin films increased with increasing annealing temperature. The effect of annealing temperature of ZnO thin films was studied.

  15. 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

  16. 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.

  17. Temperature-Dependent Photoluminescence of Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Jadhav, S. T.; Rajoba, S. J.; Patil, S. A.; Han, S. H.; Jadhav, L. D.

    2016-01-01

    Graphene oxide thin films have been deposited by spray pyrolysis using graphene oxide powder prepared by modified Hummers method. These thin films were characterized by different physico-chemical techniques. The x-ray diffraction studies revealed the structural properties of GO (graphene oxide) while the Raman spectrum showed the presence of D and G and two-dimensional bands. The D/G intensity ratio for spray-deposited GO film is 1.10. The x-ray photoelectron spectroscopy showed 67% and 33% atomic percentages of carbon and oxygen, respectively. The ratio of O1s/C1s was found to be 0.49. The temperature-dependent photoluminescence of GO thin film and GO solution showed a blue emission.

  18. 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.

    1972-01-01

    To study 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 .25-in.-thick mill annealed Ti-6Al-4V alloy plate. 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 in a dehumidified high purity argon environment. Limited correlative experiments were carried out in distilled water, dehumidified oxygen and hydrogen, and in vacuum. The results indicate that the rate of fatigue crack growth is essentially independent of test temperature in this alloy, and is affected by residual moisture in very small concentrations. Companion fractographic examinations suggest that the mechanims for fatigue crack growth in the various environments are essentially the same.

  19. Effects of low temperature anneals on the photovoltage in Si nanocrystals

    NASA Astrophysics Data System (ADS)

    Korotchenkov, O.; Podolian, A.; Kuryliuk, V.; Romanyuk, B.; Melnik, V.; Khatsevich, I.

    2012-03-01

    We report on the time decays of surface photovoltage (SPV) and SPV spectra for Si nanocrystals (nc-Si) embedded into a SiO2 matrix. After precipitation at 1150 °C anneal in Ar the SPV increases by a factor of ≈30 compared with the value observed in an oxidized Si substrate. An increase in the signal is accompanied by longer time decays in the SPV transients (roughly from tens to hundreds of microseconds). The separation of photoexcited electrons and holes at the nc-Si/SiO2 interface is expected to play a major role in increasing the SPV signal. We emphasize that annealing of nc-Si at 450 °C in either N2 + O2 or H2 results in a remarkable increase (up to 10-fold) in photoluminescence intensity, which is accompanied by a concomitant decrease in the SPV signal and modification of the SPV decay transients. Anneal in N2 + O2 ambient slightly accelerates the SPV decay, whereas anneal in H2 dramatically speeds it up. Employment of Fourier transform infrared absorption and x-ray photoelectron spectroscopy techniques allows us to gain insight about the nature of chemical bonds into the oxidized matrix. A hypothesis is suggested that the observed effects are attributable to different passivating abilities of H2 and N2 + O2 ambients. A simple model, which takes into account the capture of photoexcited carriers at the nc-Si/SiO2 interface and the varying passivation ability of the interface traps, is capable of explaining the observed changes in the SPV transients, even quantitatively. The results may be of interest for studying the passivation of dangling bonds at the nc-Si/SiO2 interface by SPV techniques and can be used in advancing the development of silicon based photovoltaic materials with high efficiency.

  20. 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

  1. Characterization of ZnO thin film grown on c-plane substrates by MO-CVD: Effect of substrate annealing temperature, vicinal-cut angle and miscut direction

    NASA Astrophysics Data System (ADS)

    Boukadhaba, M. A.; Fouzri, A.; Sallet, V.; Hassani, S. S.; Amiri, G.; Lusson, A.; Oumezzine, M.

    2015-09-01

    The annealing effects of c-plane sapphire (α-Al2O3) substrate with a nominally vicinal-cut angle α (α < 0.1°, α = 0.25° toward the m-plane (1 0 1 bar 0) and α = 0.25° toward the a-plane (1 1 2 bar 0)) on the quality of epitaxial ZnO films grown by metal organic chemical vapor deposition (MO-CVD) were studied. The atomic steps formed on sapphire substrate surface by annealing at high temperature were analyzed by atomic force microscopy (AFM). The annealing and the miscut direction of sapphire substrate on the microstructural and optical properties for ZnO films were examined by high resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence spectroscopy (PL). Experimental results indicate that the film quality is strongly affected by annealing treatment and miscut direction of the sapphire substrate. X-ray diffraction study revealed that all films exhibit a wurtzite phase and have a c-axis orientation. ZnO films deposited on sapphire substrate (α < 0.1° and α = 0.25° toward the m-plane (1 0 1 bar 0), annealed substrate at 1100 °C), exhibit a low quantity of defects and a quite good vertical and lateral alignment compared to other disorientation plane (α = 0.25° toward the a-plane (1 1 2 bar 0), annealed substrate at 1100 °C). The Lattice parameters a and c slightly decreases for ZnO layer deposited on annealed sapphire substrate with increase the annealing substrate temperature for all samples. AFM image show significant differences between morphologies of samples depending on annealing treatment and miscut direction of substrates but no significant differences on surface roughness have been found. Sapphire annealing at 1100 °C with a nominally vicinal-cut angle α = 0.25° toward the m-plane (1 0 1 bar 0), provides the best optical quality of ZnO film.

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

    PubMed Central

    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, 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. PMID:26843063

  3. Investigations on opto-electronical properties of DC reactive magnetron sputtered zinc aluminum oxide thin films annealed at different temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, B. Rajesh; Rao, T. Subba

    2013-01-01

    In the present study transparent conducting zinc aluminum oxide (ZAO) thin films were prepared by DC reactive magnetron sputtering technique. The films were deposited on glass substrates at 200 °C and annealed from 200 °C to 500 °C. XRD patterns of ZAO films shows (0 0 2) diffraction peak of hexagonal wurtzite, meaning that the films have c-axis orientation perpendicular to the substrate. Crystallite size was calculated from X-ray diffraction (XRD) spectra using the Scherrer formula. The surface morphology of the films was observed by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The electrical conductivity increases with increase of annealing temperature. The activation energies of conduction were obtained from an Arrhenius equation. The best characteristics of ZAO films have been obtained for the films annealed at 400 °C with an average transmittance of 88% and a minimum resistivity of 2.2 × 10-4 Ω cm. The optical band gap, optical constants, and electron concentrations of ZAO films are obtained from UV-vis-IR spectrophotometer data.

  4. 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, 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. PMID:26843063

  5. 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

  6. 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.

  7. Effect of annealing temperature on optical and electrical properties of ZrO2-SnO2 based nanocomposite thin films

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Transparent nanocomposite ZrO2-SnO2 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 ZrO2 and SnO2 and orthorhombic ZrSnO4. 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 ZrO2-SnO2 films can be used in many applications and in optoelectronic devices.

  8. Effect of annealing temperature on the surface morphology and electrical properties of aluminum doped zinc oxide thin films prepared by sol-gel spin-coating method

    SciTech Connect

    Mamat, M. H.; Hashim, H.; Rusop, M.

    2008-05-20

    Aluminum doped zinc oxide thin films were prepared through sol gel and spin coating technique from zinc acetate dihydrate and aluminum nitrate nanohydrate in alcoholic solution. The electrical properties and surface morphology study are investigated for the thin films annealed at 350{approx}500 deg. C. Zinc oxide thin films deposited on glass and silicon substrates were characterized using electron microscopy (SEM) and current-voltage (I-V) measurement scanning for surface morphology and electrical properties study respectively. The SEM investigation shows that zinc oxide thin films are denser at higher annealing temperature. The result indicates electrical properties of aluminum doped zinc oxide thin films are improved with annealing temperatures. The resistivity of aluminum doped zinc oxide thin films are decreased with annealing temperature up to 500 deg. C.

  9. Corrosion inhibition of stainless steel type AISI 304 by Mn coating and subsequent annealing with flow of nitrogen at different temperatures

    NASA Astrophysics Data System (ADS)

    Grayeli-Korpi, Ali-Reza; Savaloni, Hadi; Habibi, Maryam

    2013-07-01

    This work reports the enhancement of stainless steel corrosion resistance coated with Mn and post-annealed with flow of nitrogen at different annealing temperatures. Crystallographic variation of the samples by annealing temperature is studied by X-ray diffraction (XRD) while their surface morphology and surface roughness was obtained by means of atomic force microscope (AFM) and scanning electron microscope (SEM) analyses before and after corrosion test respectively. Elemental analysis of samples after corrosion test was investigated by energy dispersive spectroscope (EDS) analysis. The corrosion behaviour of the samples was evaluated by potentiodynamic polarization test in 0.6 M NaCl solution. A critical annealing temperature is found at which the highest corrosion resistance can be achieved. Correlation between corrosion resistance, structural and surface morphology results is obtained.

  10. 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

  11. Hot Plate Annealing at a Low Temperature of a Thin Ferroelectric P(VDF-TrFE) Film with an Improved Crystalline Structure for Sensors and Actuators

    PubMed Central

    Mahdi, Rahman Ismael; Gan, W.C.; Abd. Majid, W. H.

    2014-01-01

    Ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer 70/30 thin films are prepared by spin coating. The crystalline structure of these films is investigated by varying the annealing temperature from the ferroelectric phase to the paraelectric phase. A hot plate was used to produce a direct and an efficient annealing effect on the thin film. The dielectric, ferroelectric and pyroelectric properties of the P(VDF-TrFE) thin films are measured as a function of different annealing temperatures (80 to 140 °C). It was found that an annealing temperature of 100 °C (slightly above the Curie temperature, Tc) has induced a highly crystalline β phase with a rod-like crystal structure, as examined by X-ray. Such a crystal structure yields a high remanent polarization, Pr = 94 mC/m2, and pyroelectric constant, p = 24 μC/m2K. A higher annealing temperature exhibits an elongated needle-like crystal domain, resulting in a decrease in the crystalline structure and the functional electrical properties. This study revealed that highly crystalline P(VDF-TrFE) thin films could be induced at 100 °C by annealing the thin film with a simple and cheap method. PMID:25317763

  12. 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.

  13. 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.

  14. Study of electric susceptibility, electrical resistivity and energy loss functions of carbon-nickel composite films at different annealing temperatures

    NASA Astrophysics Data System (ADS)

    Dalouji, V.; Elahi, S. M.; Saadi Alecasir, M.

    2015-11-01

    In this work, the optical and electrical properties of carbon-nickel films annealed at different temperatures (300-1000 °C) were investigated. The obtained data of the refractive index n using the Swanepoel’s method can be analyzed to obtain the high-frequency dielectric constant which describes the free carriers and the lattice vibration modes of dispersion. The lattice dielectric constant ɛL and the plasma frequency ωp at 500 °C have maximum values 4.95 and 40.02 × 106 Hz, respectively. The free carrier electric susceptibility measurements in wavelength range (300-1000 nm) are discussed according to the Spitzer-Fan model. It is shown that the electric susceptibility at 500 °C has maximum value and with increasing wavelength it increases. It is also shown that the waste of electrical energy as heat at 500 °C has maximum value and with increasing wavelength it increases. It is found that energy loss by the free charge carriers when traversing the bulk and surface of films at 800 °C has a minimum value and it is approximately constant with wavelength. It is shown that optical properties were consistent with electrical properties of films annealed at different temperatures in temperature range (15-500 K).

  15. Reinforcement of CVD grown multi-walled carbon nanotubes by high temperature annealing

    NASA Astrophysics Data System (ADS)

    Elumeeva, K. V.; Kuznetsov, V. L.; Ischenko, A. V.; Smajda, R.; Spina, M.; Forró, L.; Magrez, A.

    2013-11-01

    We report on the increase of the Young's modulus (E) of chemical vapor deposition (CVD) grown multi-walled carbon nanotubes (MWNTs) upon high temperature heat treatment. The post heat-treatment at 2200-2800°C in a controlled atmosphere results in a considerable improvement of the microstructure, chemical stability and electro-physical properties of the nanotubes. The Young's modulus of MWNTs of different diameters was measured by the deflection of a single tube suspended across the hole of silicon nitride membrane and loaded by an atomic force microscope tip. Contrary to previous reports, a strong increase of E was feasible due to the improved growth conditions of pristine carbon nanotubes and to the improved heat treatment conditions. However, the elastic modulus of CVD grown MWNTs still shows strong diameter dependence resulting from the remaining structural inhomogeneities in large diameter nanotubes.

  16. Influence of high temperature annealing on the structure, hardness and tribological properties of diamond-like carbon and TiAlSiCN nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Xie, Z. W.; Wang, L. P.; Wang, X. F.; Huang, L.; Lu, Y.; Yan, J. C.

    2011-11-01

    Diamond-like carbon (DLC) and TiAlSiCN nanocomposite coatings were synthesized and annealed at different temperatures in a vacuum environment. The microstructure, hardness and tribological properties of as-deposited and annealed DLC-TiAlSiCN nanocomposite coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, nano-indentation and friction tests. The TEM results reveal that the as-deposited DLC-TiAlSiCN coating has a unique nanocomposite structure consisting of TiCN nanocrystals embedded in an amorphous matrix consisting of a-Si3N4, a-SiC, a-CN and DLC, and the structure changed little after annealing at 800 °C. However, XPS and Raman results show that an obvious graphitization of the DLC phase occurred during the annealing process and it worsened with annealing temperature. Because of the graphitization, the hardness of the DLC-TiAlSiCN coating after annealing at 800 °C decreased from 45 to 36 GPa. In addition, the DLC-TiAlSiCN coating after annealing at 800 °C has a similar friction coefficient to the as-deposited coating.

  17. 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).

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Structural investigations of Al5Co2(2 1 ¯ 0 ) and (100) surfaces: Influence of bonding strength and annealing temperature on surface terminations

    NASA Astrophysics Data System (ADS)

    Meier, M.; Ledieu, J.; De Weerd, M.-C.; Fournée, V.; Gaudry, É.

    2016-02-01

    Structural investigations of the (2 1 ¯0 ) and (100) surfaces of Al5Co2 using experimental ultrahigh vacuum techniques and ab initio computational methods are presented in this work. Both surfaces are identified and show bulk terminations where only specific atoms remain. These atoms can be seen as truncated parts of chemically bonded atomic motifs which have been identified in the bulk in a previous work [M. Meier et al., Phys. Rev. B 91, 085414 (2015), 10.1103/PhysRevB.91.085414]. Whereas the (2 1 ¯0 ) surface presents a single termination, the structure of the (100) topmost layers is found to be highly dependent on the preparation conditions, especially on the annealing temperature. This behavior, also observed for the (001) surface studied previously, can be partly explained when considering the bonding strength of the truncated motif parts with the subsurface.

  6. Cdk1 targets Srs2 to complete synthesis-dependent strand annealing and to promote recombinational repair.

    PubMed

    Saponaro, Marco; Callahan, Devon; Zheng, Xiuzhong; Krejci, Lumir; Haber, James E; Klein, Hannah L; Liberi, Giordano

    2010-02-01

    Cdk1 kinase phosphorylates budding yeast Srs2, a member of UvrD protein family, displays both DNA translocation and DNA unwinding activities in vitro. Srs2 prevents homologous recombination by dismantling Rad51 filaments and is also required for double-strand break (DSB) repair. Here we examine the biological significance of Cdk1-dependent phosphorylation of Srs2, using mutants that constitutively express the phosphorylated or unphosphorylated protein isoforms. We found that Cdk1 targets Srs2 to repair DSB and, in particular, to complete synthesis-dependent strand annealing, likely controlling the disassembly of a D-loop intermediate. Cdk1-dependent phosphorylation controls turnover of Srs2 at the invading strand; and, in absence of this modification, the turnover of Rad51 is not affected. Further analysis of the recombination phenotypes of the srs2 phospho-mutants showed that Srs2 phosphorylation is not required for the removal of toxic Rad51 nucleofilaments, although it is essential for cell survival, when DNA breaks are channeled into homologous recombinational repair. Cdk1-targeted Srs2 displays a PCNA-independent role and appears to have an attenuated ability to inhibit recombination. Finally, the recombination defects of unphosphorylatable Srs2 are primarily due to unscheduled accumulation of the Srs2 protein in a sumoylated form. Thus, the Srs2 anti-recombination function in removing toxic Rad51 filaments is genetically separable from its role in promoting recombinational repair, which depends exclusively on Cdk1-dependent phosphorylation. We suggest that Cdk1 kinase counteracts unscheduled sumoylation of Srs2 and targets Srs2 to dismantle specific DNA structures, such as the D-loops, in a helicase-dependent manner during homologous recombinational repair. PMID:20195513

  7. 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.

  8. 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.

  9. Phase separation in SiGe nanocrystals embedded in SiO{sub 2} matrix during high temperature annealing

    SciTech Connect

    Mogaddam, N. A. P.; Turan, R.; Alagoz, A. S.; Yerci, S.; Foss, S.; Finstad, T. G.

    2008-12-15

    SiGe nanocrystals have been formed in SiO{sub 2} matrix by cosputtering Si, Ge, and SiO{sub 2} independently on Si substrate. Effects of the annealing time and temperature on structural and compositional properties are studied by transmission electron microscopy, x-ray diffraction (XRD), and Raman spectroscopy measurements. It is observed that Ge-rich Si{sub (1-x)}Ge{sub x} nanocrystals do not hold their compositional uniformity when annealed at high temperatures for enough long time. A segregation process leading to separation of Ge and Si atoms from each other takes place. This process has been evidenced by a double peak formation in the XRD and Raman spectra. We attributed this phase separation to the differences in atomic size, surface energy, and surface diffusion disparity between Si and Ge atoms leading to the formation of nonhomogenous structure consist of a Si-rich SiGe core covered by a Ge-rich SiGe shell. This experimental observation is consistent with the result of reported theoretical and simulation methods.

  10. Dependence on the dielectric model and pH in a synthetic helical peptide studied by Monte Carlo simulated annealing.

    PubMed

    Okamoto, Y

    1994-04-01

    Monte Carlo simulated annealing is applied to the tertiary structure prediction of a 17-residue synthetic peptide, which is known by experiment to exhibit high helical content at low pH. Two dielectric models are considered: sigmoidal distance-dependent dielectric function and a constant dielectric function (epsilon = 2). Starting from completely random initial conformations, our simulations for both dielectric models at low pH gave many helical conformations. The obtained low-energy conformations are compared with the nuclear Overhauser effect spectroscopy cross-peak data for both main chain and side chains, and it is shown that the results for the sigmoidal dielectric function are in remarkable agreement with the experimental data. The results predict the existence of two disjoint helices around residues 5-9 and 11-16, while nmr experiments imply significant alpha-helix content between residues 5 and 14. Simulations with high pH, on the other hand, hardly gave a helical conformation, which is also in accord with the experiment. These findings indicate that when side chains are charged, electrostatic interactions due to these changes play a major role in the helix stability. Our results are compared with the previous 500 ps molecular dynamics simulations of the same peptide. It is argued that simulated annealing is superior to molecular dynamics in two respects: (1) direct folding of alpha-helix from completely random initial conformations is possible for the former, whereas only unfolding of an alpha-helix can be studied by the latter; (2) while both methods predict high helix content for low pH, the results for high pH agree with experiment (low helix content) only for the former method. PMID:8186363

  11. Effect of different annealing temperatures on the optical properties of Y3(Al,Ga)5O12:Tb thin films grown by PLD

    NASA Astrophysics Data System (ADS)

    Yousif, A.; Swart, H. C.; Ntwaeaborwa, O. M.

    2014-04-01

    Y3(Al,Ga)5O12:Tb thin films have been prepared on SiO2/Si (1 0 0) substrates by using pulsed laser deposition. The deposited films were annealed in air at 800 °C, 900 °C and 1000 °C. Atomic force microscopy, X-ray diffraction, photoluminescence, X-ray photoelectron spectroscopy and Nano-scanning Auger electron microprobe (NanoSAM) techniques have been applied to characterize these films. The results were compared with those of previously investigated Y3(Al,Ga)5O12:Tb thin films on Si (100) without an oxide (SiO2) layer. No change in photoluminescence (PL) excitation bands as a result of post-annealing was observed. Enhancement of PL intensities was observed as a function of annealing temperatures which was attributed to the improvement in crystallization of the films with an increase in annealing temperature. Annealing caused stress in the films and aggravated cracking occurred. Diffusion occurred, leading to phase changes and changes in stoichiometry. There were regions with enriched Si after annealing at higher temperatures.

  12. 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.

  13. Effects of Growth Temperature and Postgrowth Annealing on Inhomogeneous Luminescence Characteristics of Green-Emitting InGaN Films

    NASA Astrophysics Data System (ADS)

    Masui, Hisashi; Melo, Thiago; Sonoda, Junichi; Weisbuch, Claude; Nakamura, Shuji; Denbaars, Steven P.

    2010-01-01

    Microscopic photoluminescence was applied to investigate μm-order inhomogeneity of InGaN alloys. Samples had InGaN/GaN multiple-quantum-well structures grown on sapphire substrates at various temperatures, and luminescence was adjusted to be green. Luminescence morphologies of dendritic appearance were observed on as-grown samples. Bright spots luminescing at long wavelengths (green to amber) were formed at high growth temperatures. After annealing at 1000°C, the bright spots disappeared and the dendritic morphology turned into a granular morphology. Because of these μm-order inhomogeneities, it has been suggested that small-scale characterization (sub- μm or smaller) requires special attention in order not to miss effects of μm-order inhomogeneity in InGaN alloys.

  14. 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

  15. 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.

  16. 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

  17. 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

  18. Temperature Dependence of Photosynthesis in Cotton

    PubMed Central

    Downton, Joy; Slatyer, R. O.

    1972-01-01

    Cotton plants (Gossypium hirsutum L., var. Deltapine Smooth Leaf) were grown under controlled environmental conditions over a range of day/night temperatures from 20/15 to 40/35 C. Their photosynthetic characteristics were then measured over a comparable temperature range. Net photosynthesis tended stongly to be greatest, and intracellular resistance to CO2 transport to be lowest, when the measurement temperature corresponded to the daytime growth temperature, suggesting pronounced acclimation of the plants to the growth temperature. The preferred growth temperature was close to the 25/20 C regime, since net photosynthesis of these plants, regardless of measurement temperature, was higher and intracellular resistance lower, than in plants from any other regime. Ribulose diphosphate carboxylase activity per unit leaf area was highest in plants grown at 25/20 C, but did not show pronounced changes with growth temperature. Glycolate oxidase activity decreased and NADH-malate dehydrogenase activity tended to increase with increasing growth temperature. In contrast, changes in carbonic anhydrase activity with growth temperature showed a general similarity to changes in photosynthetic rate. This may suggest that the “chemical resistance” component of the intracellular resistance bears a relationship to the amount of carbonic anhydrase in the leaf. PMID:16658208

  19. 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

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

    PubMed

    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

  1. 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.

  2. 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.

  3. Temperature Dependence Of Single-Event Effects

    NASA Technical Reports Server (NTRS)

    Coss, James R.; Nichols, Donald K.; Smith, Lawrence S.; Huebner, Mark A.; Soli, George A.

    1990-01-01

    Report describes experimental study of effects of temperature on vulnerability of integrated-circuit memories and other electronic logic devices to single-event effects - spurious bit flips or latch-up in logic state caused by impacts of energetic ions. Involved analysis of data on 14 different device types. In most cases examined, vulnerability to these effects increased or remain constant with temperature.

  4. 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}).

  5. Influence of the temperature and duration of the annealing on the lattice structure and growth of the Mg-Al spinel layer

    NASA Astrophysics Data System (ADS)

    Zhang, Hailiang; Zhang, Mingfu; Han, Jiecai; Ying, Guobing; Guo, Huaixin; Xu, Chenghai; Shen, Haitao; Song, Ningning

    2011-03-01

    In this paper, MgO film is successfully grown on polycrystalline and monocrystalline alumina substrates using sol-gel method, and polycrystalline and monocrystalline Mg-Al spinels are fabricated by solid state reaction, respectively. The influence of annealing temperature and time on the lattice structure and growth of the formed Mg-Al spinel layer has been investigated. It is indicated that the annealing temperature and time on the as-synthesized polycrystalline Mg-Al spinel has more significant influence than that of single crystal Mg-Al spinel. The thickness of the Mg-Al spinel layer increases with the annealing temperature, both for polycrystalline and for monocrystalline alumina substrates. And the significantly intercrystalline diffusion of Mg 2+ ions and Al 3+ ions results in a quicker growth velocity of the Mg-Al spinel layer than that of intracrystalline diffusion.

  6. 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.

  7. 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

  8. Room-temperature annealing of vacancy-type defect in high-purity n-type Si

    SciTech Connect

    Bleka, J. H.; Monakhov, E. V.; Svensson, B. G.; Avset, B. S.

    2007-12-15

    Electron-irradiated p{sup +}-n{sup -}-n{sup +} diodes produced from low-doped high-purity Si wafers were found, by deep-level transient spectroscopy (DLTS), to have a prominent defect, labeled E4, with an energy level 0.37 eV below the conduction-band edge and a concentration of {approx}(1/4) relative to the divacancy. The samples were kept at room temperature, and the E4 concentration was seen to reduce to half during five weeks. Annealing data revealed a similar peak E5 overlapping that of the single-negatively charged divacancy and showing a one-to-one proportionality with E4. E4 and E5 arise most likely from a vacancy-type defect and a tentative assignment to a planar tetravacancy is put forward.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Temperature dependence of free excitons in GaN

    NASA Astrophysics Data System (ADS)

    Reynolds, D. C.; Hoelscher, J.; Litton, C. W.; Collins, T. C.

    2002-11-01

    The excitons involved in this study are the longitudinal and the Gamma5 and Gamma6 free excitons, as well as the donor bound exciton (D0),X. The temperature dependence of the energy positions of the Gamma5, Gamma6, and (D0),X excitons are well accounted for by the Varshni equation (Y. P. Varshni, Physica (Amsterdam) 34, 149 (1967)). In the same temperature range, the energy positions of the longitudinal excitons depart from the predictions of the Varshni equation. The separation between the longitudinal- and transverse-mode free excitons has been previously reported. One component of this separation is the polarizability, which has a temperature dependence. The longitudinal exciton therefore has a band-gap temperature dependence, predicted by the Varshni equation, as well as an additional dependence due to polarizability. This temperature dependence has been accounted for by the Varshni equation, plus an additional linear and a quadratic temperature dependent term.

  15. The effect of annealing temperatures to prepare ZnO seeds layer on ZnO nanorods array/TiO2 nanoparticles photoanode

    NASA Astrophysics Data System (ADS)

    Chou, Hsueh-Tao; Hsu, Ho-Chun

    2016-02-01

    In this study, we have fabricated a ZnO nanorods array/TiO2 nanoparticles thin-film as a photoanode, and also investigated the annealing effect at various temperatures (as grown, 250 °C, 350 °C, 450 °C and 550 °C) on ZnO seeds layer. The material properties of ZnO nanorods array were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and ultraviolet visible spectroscopy. Besides, the performances of solar cells were evaluated using a source meter (Keithley 2400), which included open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (F.F.) and power conversion efficiency (η%) at one sun (A.M. 1.5G, 100 mW/cm2). The electrochemical properties of the cells were analyzed by electrochemical impedance spectroscopy (EIS). From the EIS results, the cell performances were affected by annealing temperature, especially the fill-factor, at an annealing temperature of 550 °C due to the annealing treatment can enhance the connection between the interfaces of ZnO seeds/TCO, improving the electron lifetime, reducing the electron recombination loss. Finally, the sample annealing at 550 °C has the highest fill-factor of 44, power conversion efficiency of 0.19%, the highest Rct2 of 162.8 Ω and long electron lifetime of 7.25 ms.

  16. 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.

  17. Evidence for Temperature-Dependent Electron Band Dispersion in Pentacene

    SciTech Connect

    Koch,N.; Vollmer, A.; Salzmann, I.; Nickel, B.; Weiss, H.; Rabe, J.

    2006-01-01

    Evidence for temperature-dependent electron band dispersion in a pentacene thin film polymorph on graphite is provided by angle- and energy-dependent ultraviolet photoelectron spectroscopy. The bands derived from the highest occupied molecular orbital exhibit dispersion of {approx}190 meV at room temperature, and {approx}240 meV at 120 K. Intermolecular electronic coupling in pentacene thin films is thus confirmed to be dependent on temperature and possibly crystal structure, as suggested by additional infrared absorption measurements.

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

    DOE PAGESBeta

    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

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Temperature dependence of diffusion properties of soft sticky dipole water

    NASA Astrophysics Data System (ADS)

    Tan, Ming-Liang; Brooks, Bernard R.; Ichiye, Toshiko

    2006-04-01

    The isobaric diffusivities for the soft sticky dipole water model between 230 and 330 K were studied in molecular dynamics simulations using Ewald summations for the long-range interactions. This simple single-point, angularly dependent model with parameters optimized at room temperature reproduces the experimental diffusion rates over a wide range of temperatures better than multi-point models. Its ability to reproduce the unusual temperature dependence of the diffusivities of supercooled water indicates the tetrahedral nature of water is important. Moreover, comparisons with other models indicate more tetrahedral potentials correlate with increasing the so-called Angell critical temperature and decreasing power of the temperature dependence.

  6. 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.

  7. 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.

  8. Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature

    NASA Astrophysics Data System (ADS)

    Aleksandrov, Yuriy; Fowley, Ciarán; Kowalska, Ewa; Sluka, Volker; Yıldırım, Oǧuz; Lindner, Jürgen; Ocker, Berthold; Fassbender, Jürgen; Deac, Alina M.

    2016-06-01

    We report the effect of annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. Angular resolved ferromagnetic resonance measurement results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, Ki, is maximized at an annealing temperature 225∘C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliqueness may be advantageous for specific applications such as spin-transfer oscillators.

  9. 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).

  10. 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.

  11. Configuration, Dimension and Density Control of 3-D Gold Nanostructures on Various Type-B GaAs Surfaces by the Systematic Variation of Annealing Temperature, Annealing Duration and Deposition Amount

    NASA Astrophysics Data System (ADS)

    Lee, Daewoo; Sui, Mao; Li, Ming-Yu; Pandey, Puran; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

    2015-09-01

    Metallic nanoparticles have received extensive research attention due to their potential to be utilized in catalytic, electronic and optical applications. Tunable feature of quantum effect related to the configuration, dimension as well as the density of nanoparticles makes them appropriate building blocks for their applications at the nano-scale. In this paper, we systematically investigate the fabrication of self-assembled Au nanoparticles on high-index type-B GaAs (n11), where n is 9, 8, 4, and 2. By means of varying annealing temperature, Au deposition amount and annealing duration, the evolution of Au nanoparticles in terms of the average height, lateral diameter and average density is systematically studied. We observe that the variation of annealing temperature leads to an abrupt configuration evolution from the wiggly Au nanostructures to the round-dome shaped nanoparticles due to the limited and/or enhanced surface diffusion at various temperatures. Meanwhile, the variation of deposition amount leads to a wide range of dimensions of Au nanoparticles as a result of the size increase and the corresponding density decrease. Furthermore, based on the annealing duration control, the size of Au nanoparticles tends to be gradually increased owing to the Ostwald-ripening. Meanwhile, the effect of surface index on the size and density is also witnessed. The results are systematically analyzed by using the atomic force microscope images, energy-dispersive X-ray spectroscopy spectra and maps, Fourier filter transforms power spectra, cross-sectional line-profiles and size and density plots.

  12. Temperature dependent terahertz properties of energetic materials

    NASA Astrophysics Data System (ADS)

    Azad, Abul K.; Whitley, Von H.; Brown, Kathryn E.; Ahmed, Towfiq; Sorensen, Christian J.; Moore, David S.

    2016-04-01

    Reliable detection of energetic materials is still a formidable challenge which requires further investigation. The remote standoff detection of explosives using molecular fingerprints in the terahertz spectral range has been an evolving research area for the past two decades. Despite many efforts, identification of a particular explosive remains difficult as the spectral fingerprints often shift due to the working conditions of the sample such as temperature, crystal orientation, presence of binders, etc. In this work, we investigate the vibrational spectrum of energetic materials including RDX, PETN, AN, and 1,3-DNB diluted in a low loss PTFE host medium using terahertz time domain spectroscopy (THz-TDS) at cryogenic temperatures. The measured absorptions of these materials show spectral shifts of their characteristic peaks while changing their operating temperature from 300 to 7.5 K. We have developed a theoretical model based on first principles methods, which is able to predict most of the measured modes in 1, 3-DNB between 0.3 to 2.50 THz. These findings may further improve the security screening of explosives.

  13. Nanomechanical Characterization of Temperature-Dependent Mechanical Properties of Ion-Irradiated Zirconium with Consideration of Microstructure and Surface Damage

    NASA Astrophysics Data System (ADS)

    Marsh, Jonathan; Zhang, Yang; Verma, Devendra; Biswas, Sudipta; Haque, Aman; Tomar, Vikas

    2015-12-01

    Zirconium alloys for nuclear applications with different microstructures were produced by manufacturing processes such as chipping, rolling and annealing. The two Zr samples, rolled and rolled-annealed were subjected to different levels of irradiation, 1 keV and 100 eV, to study the effect of irradiation dosages. The effect of microstructure and irradiation on the mechanical properties (reduced modulus, hardness, indentation yield strength) was analyzed with nanoindentation experiments, which were carried out in the temperature range of 25°C to 450°C to investigate temperature dependence. An indentation size effect analysis was performed and the mechanical properties were also corrected for the oxidation effects at high temperatures. The irradiation-induced hardness was observed, with rolled samples exhibiting higher increase compared to rolled and annealed samples. The relevant material parameters of the Anand viscoplastic model were determined for Zr samples containing different level of irradiation to account for viscoplasticity at high temperatures. The effect of the microstructure and irradiation on the stress-strain curve along with the influence of temperature on the mechanisms of irradiation creep such as formation of vacancies and interstitials is presented. The yield strength of irradiated samples was found to be higher than the unirradiated samples which also showed a decreasing trend with the temperature.

  14. Temperature dependence of LRE-HRE-TM thin films

    NASA Astrophysics Data System (ADS)

    Li, Zuoyi; Cheng, Xiaomin; Lin, Gengqi; Li, Zhen; Huang, Zhixin; Jin, Fang; Wang, Xianran; Yang, Xiaofei

    2003-04-01

    Temperature dependence of the properties of RE-TM thin films is very important for MO recording. In this paper, we studied the temperature dependence of the magnetic and magneto-optical properties of the amorphous LRE-HRE-TM single layer thin films and LRE-HRE-TM/HRE-TM couple-bilayered thin films. For LRE-HRE-TM single layer thin films, the temperature dependence of the magnetization was investigated by using the mean field theory. The experimental and theoretical results matched very well. With the LRE substitution in HRE-TM thin film, the compensation temperature Tcomp decreased and the curie temperature Tc remained unchanged. Kerr rotation angle became larger and the saturation magnetization Ms at room temperature increased. For LRE-HRE-TM/HRE-TM couple-bilayered thin films, comparisons of the temperature dependences of the coercivities and Kerr rotation angles were made between isolated sublayers and couple-bilayered thin film.

  15. Temperature dependence of amino acid hydrophobicities

    PubMed Central

    Wolfenden, Richard; Lewis, Charles A.; Yuan, Yang; Carter, Charles W.

    2015-01-01

    The hydrophobicities of the 20 common amino acids are reflected in their tendencies to appear in interior positions in globular proteins and in deeply buried positions of membrane proteins. To determine whether these relationships might also have been valid in the warm surroundings where life may have originated, we examined the effect of temperature on the hydrophobicities of the amino acids as measured by the equilibrium constants for transfer of their side-chains from neutral solution to cyclohexane (Kw>c). The hydrophobicities of most amino acids were found to increase with increasing temperature. Because that effect is more pronounced for the more polar amino acids, the numerical range of Kw>c values decreases with increasing temperature. There are also modest changes in the ordering of the more polar amino acids. However, those changes are such that they would have tended to minimize the otherwise disruptive effects of a changing thermal environment on the evolution of protein structure. Earlier, the genetic code was found to be organized in such a way that—with a single exception (threonine)—the side-chain dichotomy polar/nonpolar matches the nucleic acid base dichotomy purine/pyrimidine at the second position of each coding triplet at 25 °C. That dichotomy is preserved at 100 °C. The accessible surface areas of amino acid side-chains in folded proteins are moderately correlated with hydrophobicity, but when free energies of vapor-to-cyclohexane transfer (corresponding to size) are taken into consideration, a closer relationship becomes apparent. PMID:26034278

  16. Effect of high temperature swaging and annealing on the mechanical properties and thermal conductivity of W-Y2O3

    NASA Astrophysics Data System (ADS)

    Xie, Z. M.; Liu, R.; Miao, S.; Zhang, T.; Wang, X. P.; Fang, Q. F.; Liu, C. S.; Luo, G. N.

    2015-09-01

    The mechanical properties and thermal conductivity of W-1.0 wt%Y2O3 (WY10) alloys prepared by spark plasma sintering (SPS) as well as ordinary sintering followed by swaging and annealing treatment, respectively, were investigated. The grains in the swaged WY10 are of round-bar shape with average diameter and length of 4.6 and 26.7 μm, respectively, which keep stable even after being annealed for 1 h at 1300 °C. The ductile-brittle transition temperature (DBTT) of swaged and annealed WY10 is about 200 °C, much lower than that of WY10 prepared by SPS method (∼500 °C). Annealing significantly improves thermal conductivity from 146 to 198 W/m K at room temperature. In addition, the total elongation is raised by 5.7 times than that of the unannealed one. The results indicate that the strength, ductility and thermal conductivity can be greatly improved by swaging and subsequent annealing.

  17. Temperature dependencies of hydrogen-induced blistering of thin film multilayers

    SciTech Connect

    Kuznetsov, A. S.; Gleeson, M. A.; Bijkerk, F.

    2014-05-07

    We report on the influence of sample temperature on the development of hydrogen-induced blisters in Mo/Si thin-film multilayers. In general, the areal number density of blisters decreases with increasing exposure temperature, whereas individual blister size increases with exposure temperatures up to ∼200 °C but decreases thereafter. Comparison as a function of sample temperature is made between exposures to a flux containing both hydrogen ions and neutrals and one containing only neutrals. In the case of the neutral-only flux, blistering is observed for exposure temperatures ≥90 °C. The inclusion of ions promotes blister formation at <90 °C, while retarding their growth at higher temperatures. In general, ion-induced effects become less evident with increasing exposure temperature. At 200 °C, the main effect discernable is reduced blister size as compared with the equivalent neutral-only exposure. The temperature during exposure is a much stronger determinant of the blistering outcome than either pre- or post-annealing of the sample. The trends observed for neutral-only exposures are attributed to competing effects of defect density thermal equilibration and H-atom induced modification of the Si layers. Energetic ions modify the blistering via (temperature dependent) enhancement of H-mobility and re-crystallization of amorphous Si.

  18. Temperature dependence of particle-particle interactions in electrorheological fluids

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Foulc, J.-N.

    2000-04-01

    We report on the temperature dependence of particle-particle interactions in electrorheological (ER) fluids for the temperature range 20-100 °C. The attraction force between polyamide spheres immersed in silicone oil is measured as a function of temperature. The force-temperature characteristic shows a broad maximum around 40 °C, corresponding to an increase of about 30% compared to the force measured at room temperature. In view of these results we proposed that the temperature dependence of the shear stress in ER fluids is directly related to the variation of the local particle-particle attraction forces. Data are discussed in light of models which were proposed in the literature to describe particle-particle interactions. At high electric fields "conduction models" could explain the observed temperature dependence through the variations of the oil breakdown field with temperature. However, limitations of such models are also clearly evidenced by data obtained at low electric fields.

  19. 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

  20. Effects of the Annealing Temperature and CdCl2 Treatment on the Photovoltaic Properties of the CdS/CdTe Solar Cell

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Hyung; textscLee, Ho-Yeol; Park, Yong-Kwan; Shin, Sung-Ho; Park, Kwang-Ja

    1998-06-01

    Effects of the annealing temperature and CdCl2 treatment of CdTe films prepared by vacuum evaporation on structural properties of the CdTe films and photovoltaic properties of thin film CdS/CdTe solar cells were investigated. The crystal structure of as-deposited CdTe films was zincblende type with preferential orientation of the (111) plane parallel to the substrate. The preferential orientation of the (111) plane in CdTe films decreased, and the grain size of CdTe films increased with the increase of the annealing temperature and the CdCl2 treatment. As increasing annealing temperature, the conversion efficiency of the CdS/CdTe solar cells without and with CdCl2 was increased due to increasing grain size and improving crystalline of CdTe films. However, the efficiency of cells annealed at the temperature of higher than 500°C for cells without CdCl2 treatment and 450°C for cells with CdCl2 treatment was reduced because of increasing reverse saturation current density and series resistance.

  1. 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

  2. Influence of annealing temperature on microstructure and optical properties of sol-gel derived tungsten oxide films

    NASA Astrophysics Data System (ADS)

    Sun, Xilian; Cao, Hongtao; Liu, Zhimin; Li, Jianzhong

    2009-07-01

    Tungsten oxide (WO 3) thin films have been extensively studied for their interesting physical properties and a variety of potential applications in electrochromic devices. In order to explore the possibility of using these in electrochromic devices, a preliminary and thorough study of the optical properties of the host materials is an important step. Based on this, the influence of annealing temperature on the structural, surface morphological, optical and electrochromic properties has been investigated in the present work. The host material, WO 3 films, has been prepared from an ethanolic acetylated peroxotungstic acid sol containing 5 wt.% oxalic acid dehydrate (OAD) by sol-gel technique. The monoclinic structure and textured nature change of the films with the temperature increasing have been investigated by X-ray diffraction analysis. The surface morphology evolution of the films has been characterized by SEM. The shift in absorption edge towards the higher wavelength region observed from optical studies may be due to the electron scattering effects and the optical band filling effect that reveals the crystallization of the film. The amorphous film shows better optical modulation (Δ T = 76.9% at λ = 610 nm), fast color-bleach kinetics ( tc ˜ 4 s and tb ˜ 9 s) and good reversibility ( Qb/ Qc = 90%), thereby rendering it suitable for smart window applications.

  3. Modelling temperature and concentration dependent solid/liquid interfacial energies

    NASA Astrophysics Data System (ADS)

    Lippmann, Stephanie; Jung, In-Ho; Paliwal, Manas; Rettenmayr, Markus

    2016-01-01

    Models for the prediction of the solid/liquid interfacial energy in pure substances and binary alloys, respectively, are reviewed and extended regarding the temperature and concentration dependence of the required thermodynamic entities. A CALPHAD-type thermodynamic database is used to introduce temperature and concentration dependent melting enthalpies and entropies for multicomponent alloys in the temperature range between liquidus and solidus. Several suitable models are extended and employed to calculate the temperature and concentration dependent interfacial energy for Al-FCC with their respective liquids and compared with experimental data.

  4. 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.

  5. 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.

  6. 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.

  7. Temperature-dependent elastic properties of Ti1-xAlxN alloys

    NASA Astrophysics Data System (ADS)

    Shulumba, Nina; Hellman, Olle; Rogström, Lina; Raza, Zamaan; Tasnádi, Ferenc; Abrikosov, Igor A.; Odén, Magnus

    2015-12-01

    Ti1-xAlxN 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: C11 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 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

  9. Temperature and pressure dependence of CO2 extinction coefficients.

    NASA Technical Reports Server (NTRS)

    Demore, W. B.; Patapoff, M.

    1972-01-01

    Results are presented of CO2 extinction coefficient measurements that were performed under conditions of temperature and pressure different from those used by previous investigators. The results show that, whereas pressure effects are generally negligible, temperature dependence is strong enough to invalidate the use of room temperature data for the Mars atmosphere.

  10. 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.

  11. 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.

  12. Unusual temperature dependence of elastic constants of an ambient-temperature discotic nematic liquid crystal.

    PubMed

    Venkata Sai, D; Mirri, G; Kouwer, P H J; Sahoo, R; Musevic, I; Dhara, Surajit

    2016-03-01

    We report the first experimental studies on the temperature dependence of viscoelastic properties of a room temperature discotic nematic liquid crystal. The splay elastic constant is greater than the bend elastic constant and both show unusual temperature and order parameter dependence. The rotational viscosity is remarkably larger than conventional calamitic liquid crystals. We provide a simple physical explanation based on the columnar short-range order to account for the the unusual temperature dependence of the elastic constants. PMID:26883494

  13. Influence of annealing temperature of ZnO film as the electron transport layer on the performance of polymer solar cells

    NASA Astrophysics Data System (ADS)

    Li, Yong-fu; Zhang, Ya-guang; Liu, Jun-liang; Wang, Qing-pu

    2015-07-01

    The surface morphology of ZnO films at different annealing temperatures and the performance of polymer solar cells (PSCs) with ZnO as the electron transport layer are studied. The low temperature sol-gel processed ZnO film has smoother surface than that in higher temperature, which results in the best photovoltaic performance with a power conversion efficiency ( PCE) of 3.66% for P3HT:PC61BM based solar cell. With increasing annealing temperature, the photovoltaic performance first deceases and then increases. It could be ascribed to the synergy effects of interface area, the conductivity and surface energy of ZnO film and series resistance of devices.

  14. Numerical investigation of temperature field Induced by dual wavelength lasers in sub-microsecond laser annealing technology for insulated gate bipolar transistor

    NASA Astrophysics Data System (ADS)

    Cui, GuoDong; Ma, Mingying; Wang, Fan; Sun, Gang; Lan, Yanping; Xu, Wen

    2015-07-01

    To enhance the performance of the Insulated Gate Bipolar Transistor (IGBT), sub-microsecond laser annealing (LA) is propitious to achieve maximal dopant activation with minimal diffusion. In this work, two different lasers are used as annealing resource: a continuous 808 nm laser with larger spot is applied to preheat the wafer and another sub-microsecond pulsed 527 nm laser is responsible to activate the dopant. To optimize the system's performance, a physical model is presented to predict the thermal effect of two laser fields interacting on wafer. Using the Finite-Element method (FEM), we numerically investigate the temperature field induced by lasers in detail. The process window corresponding to the lasers is also acquired which can satisfy the requirements of the IGBT's annealing.

  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. 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).

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Conversion of Y3(Al,Ga)5O12:Tb3+ to Y2Si2O7:Tb3+ thin film by annealing at higher temperatures

    NASA Astrophysics Data System (ADS)

    Yousif, A.; Swart, H. C.; Ntwaeaborwa, O. M.; Coetsee, E.

    2013-04-01

    Y3(Al,Ga)5O12:Tb thin films were grown on Si(1 0 0) substrates in an Ar working atmosphere by using the pulsed laser deposition (PLD) technique. The Y3(Al,Ga)5O12:Tb target was ablation deposited onto a Si(1 0 0) substrate using a 266 nm Nd:YAG laser. The influence of post deposition annealing temperature (1073 K to 1473 K) on the excitation and the emission bands, and the crystal structure of the thin film were monitored. X-ray diffraction (XRD) and photoelectron spectroscopy (XPS) depth profiles of the thin films indicate that there were annealing induced changes in the crystal structure and chemical composition causing changes in the excitation bands. These changes (structure and composition) are attributed to interdiffusion of atomic species between the substrate and the Y3(Al,Ga)5O12:Tb3+ thin film. The XRD and XPS data confirm that after annealing, Y3(Al,Ga)5O12:Tb3+ was converted to Y2Si2O7:Tb3+. A change in the relative ratios of the excitation band intensities was measured. Atomic force microscopy (AFM) showed that topographical changes also occurred during the annealing process. Thermoluminescence (TL) glow curves of the Y3(Al,Ga)5O12:Tb3+ thin films before and after annealing, indicated the presence of different types of traps resulting from the change on the structure of the thin films.

  2. Influence of air annealing temperature and time on the optical properties of Yb:YAG single crystal grown by HDS method

    NASA Astrophysics Data System (ADS)

    Nie, Ying; Liu, Yang; Zhao, Yequan; Zhang, Mingfu

    2015-08-01

    8 at.% Yb:YAG plate single crystal with the dimension of 170 mm × 150 mm × 30 mm was grown in vacuum by Horizontal Directional Solidification method. Aimed at blue-green color centers, annealing treatments of 15 mm × 15 mm × 1 mm samples from 900 °C to 1400 °C for 5 h and at 900 °C from 5 h to 40 h in air were conducted. The absorption spectra, emission spectra, fluorescence lifetime and X-ray photoelectron spectroscopy of samples under different annealing conditions were measured at room temperature, respectively. Annealing at above 1000 °C for 5 h or at 900 °C for 40 h made the blue-green color centers disappear and the samples turned to transparent. Absorption coefficients decreased in the 300 nm-800 nm wavelength range, emission intensities increased and emission bands broadened around 486 nm and 1029 nm with increasing temperature up to 1200 °C, then varied inversely. These values decreased or increased monotonically with increasing annealing time at 900 °C. The maximal increases of fluorescence lifetime were 62.3% and 64.7%, respectively. The calculated emission cross section of 1200 °C for 5 h was up to 4.4 × 10-20 cm2. In X-ray photoelectron spectroscopy, the concentrations of oxygen vacancies reduced from 1.28% down to absence by annealing. These experiments show that color centers are detrimental to the optical properties of HDS-Yb:YAG laser crystal and optimal annealing treatments should be conducted.

  3. Temperature Dependence of the Free Excitons in GaN

    NASA Astrophysics Data System (ADS)

    Reynolds, D. C.; Collins, T. C.

    2002-03-01

    We are presenting the temperature dependence of the photoluminescence (PL) of the free excitons and donor bound exciton ( D^circ ,X) in GaN. The excitons involved are the longitudinal, the Γ5 and the Γ6 excitons as well as D^circ ,X. The temperature dependence of the energy positions of Γ_5, Γ_6, and D^circ ,X are well mapped out using the Varshni equation in a temperature range of 0 -- 60 K. In this temperature range, the energy positions of the longitudinal excitons depart from the predictions of the Varshni equation used for the other excitons. If more than one columnar structural direction is present, then in PL, more than one longitudinal mode might be observed. The sample being investigated shows two longitudinal modes. The energy separation between the longitudinal and transverse modes has been reported by Hopfield and Thomas. One component in the separation is the polarizability, which has some temperature dependence. The longitudinal exciton then has a band gap temperature dependence, which is predicted by the Varshni equation and an additional temperature dependence due to the polarizability. We have used the Varshni equation plus a linear and quadratic temperature dependence term to map the energy positions of the longitudinal excitons.

  4. 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

  5. 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.

  6. 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.

  7. Temperature dependence of the emissivity of platinum in the IR.

    PubMed

    Deemyad, Shanti; Silvera, Isaac F

    2008-08-01

    The accuracy of temperature determination by fitting the spectral irradiance to a Planck curve depends on knowledge of the emissivity at all temperatures and pressures of interest within a spectral region. Here, the emissivity of platinum is measured in the near infrared as a function of temperature. In the wavelength range of study and the temperature range of 650-1100 K, we find the emissivity to be independent of temperature to within experimental error. This result should lead to improved accuracy of temperature measurement by optical pyrometry where platinum is used as a thermal emitter. PMID:19044386

  8. 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.

  9. 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.

  10. Effect of temperature of annealing on optical, structural and electrochromic properties of sol-gel dip coated molybdenum oxide films

    NASA Astrophysics Data System (ADS)

    Dhanasankar, M.; Purushothaman, K. K.; Muralidharan, G.

    2011-01-01

    The sol-gel dip-coating method is used for the preparation of MoO 3 thin films. The 6 layered MoO 3 films were prepared and annealed at various temperatures in the range of 200-350 °C. The band gap value for MoO 3 films were calculated from optical absorption measurements and it is in the range of 3.55-3.73 eV. XRD spectrum reveals (0 2 0) is the major diffraction plane for the films prepared above 250 °C, which reveals the formation of MoO 3 in α-orthorhombic phase. The films prepared at 200 °C and 250 °C exhibits amorphous nature. The FTIR spectrum confirms the presence of Mo-O-Mo and Mo dbnd O bonds. Nanorods were observed in the SEM images in the case of MoO 3 films prepared above 250 °C. The films prepared at 250 °C exhibit maximum anodic diffusion coefficient of 9.61 × 10 -11 cm 2/s. The same film exhibits the change in optical transmission of 58.4% at 630 nm with the optical density of 0.80.

  11. 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.

  12. 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.

  13. 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).

  14. Temperature dependence of the HNO3 UV absorption cross sections

    NASA Technical Reports Server (NTRS)

    Burkholder, James B.; Talukdar, Ranajit K.; Ravishankara, A. R.; Solomon, Susan

    1993-01-01

    The temperature dependence of the HNO3 absorption cross sections between 240 and 360 K over the wavelength range 195 to 350 nm has been measured using a diode array spectrometer. Absorption cross sections were determined using both (1) absolute pressure measurements at 298 K and (2) a dual absorption cell arrangement in which the absorption spectrum at various temperatures is measured relative to the room temperature absorption spectrum. The HNO3 absorption spectrum showed a temperature dependence which is weak at short wavelengths but stronger at longer wavelengths which are important for photolysis in the lower stratosphere. The 298 K absorption cross sections were found to be larger than the values currently recommended for atmospheric modeling (DeMore et al., 1992). Our absorption cross section data are critically compared with the previous measurements of both room temperature and temperature-dependent absorption cross sections. Temperature-dependent absorption cross sections of HNO3 are recommended for use in atmospheric modeling. These temperature dependent HNO3 absorption cross sections were used in a two-dimensional dynamical-photochemical model to demonstrate the effects of the revised absorption cross sections on loss rate of HNO3 and the abundance of NO2 in the stratosphere.

  15. 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.

  16. Role of substrate and annealing temperature on the structure of ZnO and AlxZn1-xO thin films for solar cell applications

    NASA Astrophysics Data System (ADS)

    Nambala, Fred Joe; Nel, Jacqueline M.; Machatine, Augusto G. J.; Mwakikunga, Bonex W.; Njoroge, Eric G.; Maabong, Kelebogile; Das, Arran G. M.; Diale, Mmantsae

    2016-01-01

    This paper reports on the deposition of pure and 5 at% Al doped ZnO (AZO) prepared by sol-gel and applied to the substrates by spin-coating, and the role of annealing temperature on the crystallinity of these layers. It is found that both ZnO and AZO are largely amorphous when coated on glass compared to n-Si(111), as substrates. On both substrates, X-ray diffraction (XRD) shows that the crystallinity improves as annealing temperature is raised from 200 to 600 °C with better crystallinity on Si substrates. The thickness of the films on substrates was determined as 120 nm by Rutherford backscattering spectroscopy (RBS). Specular ultra-violet visible (UV-vis) gives the direct transition optical band gaps (Eg) for AZO as-deposited films are 2.60 and 3.35 eV while that of 600 °C annealed films are 3.00 and 3.60 eV. The Eg calculated from diffuse reflectance spectroscopy (DRS) UV-vis are more diverse in ZnO- and AZO-Si than the ZnO- and AZO-glass samples, although in both sets the Eg tend to converge after annealing 600 °C. The Raman spectra of samples show multiphonon processes of higher order from the AZO and substrates. It is found that residual stresses are related to E2 Raman mode.

  17. Rapid thermal annealing of InAs/GaAs quantum dots with a low-temperature-grown InGaP cap layer

    SciTech Connect

    Jiang, W.H.; Thompson, D.A.; Hul'ko, O.; Robinson, B.J.; Mascher, P.

    2006-05-15

    A single layer of self-assembled InAs quantum dots was grown on a GaAs (001) substrate by gas source molecular-beam epitaxy. The quantum dots were overgrown with 65 nm GaAs, 25 nm InGaP, and a 10 nm GaAs etch-stop layer. This was either uncapped or capped with 100 nm of low-temperature (LT)-grown, lattice-matched InGaP (LT-InGaP) or with a SiO{sub 2} layer or Al{sub 2}O{sub 3} layer. Photoluminescence (PL) measurements were made on samples before and after rapid thermal annealing at 550-900 deg.C and for 15-120 s at 650 deg.C. Samples capped with LT-InGaP showed a significant blueshift of the PL peak wavelength for anneals above 575 deg.C. By comparison, for the SiO{sub 2}-capped and uncapped samples, the net blueshift only becomes significant for anneals >700 deg.C, while an Al{sub 2}O{sub 3} cap actually reduces the blueshift and suppresses the intermixing. It appears that the best conditions for spatially controlling the quantum dot intermixing occur with annealing at low temperatures (600-650 deg.C)

  18. 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.

  19. 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.

  20. Titanium Oxide Adhesion Layer for High Temperature Annealed Si/Si3N4/TiO x /Pt/LiCoO2 Battery Structures

    NASA Astrophysics Data System (ADS)

    Vieira, E. M. F.; Ribeiro, J. F.; Sousa, R.; Silva, M. M.; Dupont, L.; Gonçalves, L. M.

    2016-02-01

    This work describes the influence of a high annealing temperature of about 700°C on the Si(substrate)/Si3N4/TiO x /Pt/LiCoO2 multilayer system for the fabrication of all-solid-state lithium ion thin film microbatteries. Such micro-batteries typically utilize lithium cobalt oxide (LiCoO2) as cathode material with a platinum (Pt) current collector. Silicon nitride (Si3N4) is used to act as a barrier against Li diffusion into the substrate. For a good adherence between Si3N4 and Pt, commonly titanium (Ti) is used as intermediate layer. However, to achieve crystalline LiCoO2 the multilayer system has to be annealed at high temperature. This post-treatment initiates Ti diffusion into the Pt-collector and an oxidation to TiO x , leading to volume expansion and adhesion failures. To solve this adhesion problem, we introduce titanium oxide (TiO x ) as an adhesion layer, avoiding the diffusion during the annealing process. LiCoO2, Pt and Si3N4 layers were deposited by magnetron sputtering and the TiO x layer by thermal oxidation of Ti layers deposited by e-beam technique. As-deposited and annealed multilayer systems using various TiO x layer thicknesses were studied by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS). The results revealed that an annealing process at temperature of 700°C leads to different interactions of Ti atoms between the layers, for various TiO x layer thicknesses (25-45 nm).

  1. 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.

  2. 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.

  3. Temperature and size-dependent Hamaker constants for metal nanoparticles.

    PubMed

    Jiang, K; Pinchuk, P

    2016-08-26

    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. PMID:27454147

  4. 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.

  5. 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

  6. 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

  7. 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].

  8. Temperature dependence of electronic transport property in ferroelectric polymer films

    NASA Astrophysics Data System (ADS)

    Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Zou, Y. H.; Wang, X. D.; Sun, S.; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-10-01

    The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir-Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel-Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. ION AND TEMPERATURE DEPENDENCE OF ELECTRICAL CONDUCTANCE FOR NATURAL WATERS

    EPA Science Inventory

    Four empirical equations describing the temperature dependence of electrical conductance of aqueous solutions are compared for the case of single electrolytes. The best method uses a modified Walden product where the log of the ratio between the conductances at two temperatures i...

  14. 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.

  15. 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…

  16. 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.

  17. Temperature dependence of ethanol depression in mice: dose response.

    PubMed

    Finn, D A; Syapin, P J; Bejanian, M; Jones, B L; Alkana, R L

    1994-04-01

    Manipulation of body temperature during intoxication significantly alters brain sensitivity to ethanol. The current study tested the generality of this effect within the hypnotic dose range. Drug naive, male C57BL/6J mice were injected with 3.2, 3.6, or 4.0 g/kg ethanol (20% w/v) and were exposed to 1 of 7 designated temperatures from 13 degrees to 34 degrees C to manipulate body temperature during intoxication. Rectal temperature at return of righting reflex (RORR) was significantly, positively correlated with loss of righting reflex (LORR) duration and significantly, negatively correlated with blood ethanol concentration (BEC) at RORR at all three doses. These results indicate that increasing body temperature during intoxication increased ethanol sensitivity in C57 mice at all three doses tested and demonstrate the generality of temperature dependence across hypnotic doses in these animals. Interestingly, the LORR duration was dose-dependent at each ambient temperature, but the degree of body temperature change and the BEC at RORR were not dose-dependent. Overall, these results emphasize the importance of body temperature as a variable in ethanol research. PMID:8048742

  18. 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.

  19. Matching properties, and voltage and temperature dependence of MOS capacitors

    NASA Astrophysics Data System (ADS)

    McCreary, J. L.

    1981-12-01

    A technique for designing MOS capacitor arrays is discussed, which includes a method of calculating capacitance ratio errors and subsequent total yield. Data illustrating the sensitivity of the ratio matching to capacitor layout, structures, and technology are presented, and measured voltage coefficients of MOS capacitors as function of surface concentration are compared with the calculated coefficients. It is demonstrated that the temperature dependence of space charge capacitance, thermal expansion, and temperature dependence of the dielectric constant are the major components of the temperature coefficient of capacitance. It is also shown that to a first-order, heavily doped polysilicon accumulates and depletes similar to crystalline silicon.

  20. Low temperature annealed amorphous indium gallium zinc oxide (a-IGZO) as a pH sensitive layer for applications in field effect based sensors

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Kumar, Jitendra; Panda, Siddhartha

    2015-06-01

    The use of a-IGZO instead of the conventional high-k dielectrics as a pH sensitive layer could lead to the simplification of fabrication steps of field effect based devices. In this work, the pH sensitivities of a-IGZO films directly deposited over a SiO2/Si surface were studied utilizing electrolyte-insulator-semiconductor (EIS) structures. Annealing of the films was found to affect the sensitivity of the devices and the device with the film annealed at 400 oC in N2 ambience showed the better sensitivity, which reduced with further increase in the annealing temperature to 500 oC. The increased pH sensitivity with the film annealed at 400 oC in N2 gas was attributed to the enhanced lattice oxygen ions (based on the XPS data) and improved C-V characteristics, while the decrease in sensitivity at an increased annealing temperature of 500 oC was attributed to defects in the films as well as the induced traps at the IGZO/SiO2 interface based on the stretched accumulation and the peak in the inversion region of C-V curves. This study could help to develop a sensor where the material (a-IGZO here) used as the active layer in a thin film transistors (TFTs) possibly could also be used as the pH sensitive layer without affecting the TFT characteristics, and thus obviating the need of high-K dielectrics for sensitivity enhancement.

  1. 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.

  2. 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.

  3. 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}.

  4. 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.

  5. 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.

  6. 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.

  7. Extended temperature dependence of elastic constants in cubic crystals.

    PubMed

    Telichko, A V; Sorokin, B P

    2015-08-01

    To extend the theory of the temperature dependence of the elastic constants in cubic crystals beyond the second- and third-order elastic constants, the fourth-order elastic constants, as well as the non-linearity in the thermal expansion temperature dependence, have been taken into account. Theoretical results were represented as temperature functions of the effective elastic constants and compared with experimental data for a number of cubic crystals, such as alkali metal halides, and elements gold and silver. The relations obtained give a more accurate description of the experimental temperature dependences of second-order elastic constants for a number of cubic crystals, including deviations from linear behavior. A good agreement between theoretical estimates and experimental data has been observed. PMID:25819879

  8. 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.

  9. 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.

  10. Effect of annealing temperature on the microstructure and mechanical properties of an as-rolled Mg-9wt.%Li-3wt.%Al-1wt.%Zn alloy sheet

    NASA Astrophysics Data System (ADS)

    Lin, Meng-Chang; Lin, Shang-Qiu; Uan, Jun-Yen

    2014-09-01

    This study investigated the effect of annealing temperature on the mechanical properties of an as-rolled Mg-9.26wt.%Li-3.03wt.%Al-1.10wt.%Zn (LAZ931) alloy sheet. The dual-phase (α + β) LAZ931 alloy plate of 3 mm in thickness were rolled (67% reduction) and then annealed at temperatures at 100°C-350°C. The alloy's ductility showed a sharp concave downward tendency as a function of annealing temperature. The elongation of the LAZ931 alloy sheet increased with annealing temperature up to 150°C, followed by a sharp decrease of the alloy's ductility as the annealing temperature higher than 150°C. The specimen exhibited an extremely low elongation (only ˜0.5%) at annealing temperature around 300°C. Formation of brittle AlLi particles on boundary resulted in Li depletion zone near by grain boundary, transforming the Li depletion zone into α (hcp) layer. The combined effects including brittle AlLi particles on boundary and the hcp α layer on boundary resulted in the brittlement of the high-temperature-annealing sample.

  11. Impact of the H 2 anneal on the structural and optical properties of thin and thick Ge layers on Si; Low temperature surface passivation of Ge by Si

    NASA Astrophysics Data System (ADS)

    Hartmann, J. M.; Abbadie, A.; Barnes, J. P.; Fédéli, J. M.; Billon, T.; Vivien, L.

    2010-02-01

    Using a low temperature/high temperature strategy, we have grown thin (0.27 μm) and thick (2.45 μm) Ge layers on Si(0 0 1) substrates that we have submitted to various constant temperature (750 °C) or cyclic (750 °C/890 °C) H 2 anneals, the objective being to identify those yielding the smoothest surfaces, the lowest threading dislocations densities (TDDs) and the highest near infra-red optical absorptions. The best trade-off for thin layers was 750 °C, 60 min H 2 anneals. Using longer duration 750 °C anneals and especially 750 °C/890 °C cyclic anneals indeed yielded rougher surfaces and vastly degraded optical absorption (deleterious formation of GeSi alloys). By contrast, short 750 °C/890 °C thermal cyclings yielded the best metrics in thick Ge layers (while being at the same time the best in terms of throughput): root mean square surface roughness around 0.8 nm, TDD around 10 7 cm -2, slightly tensily-strained layers (which a plus for optical absorption as the absorption edge is shifted to higher wavelengths), a limited penetration of Si into Ge (and thus absorption coefficients at 1.3 and 1.55 μm almost equal to those of as-grown layers), etc. We have also described the low temperature (450 °C/525 °C) process that we have developed to passivate Ge surfaces thanks to SiH 4 prior to gate stack deposition. Si layer thickness should be below 20 Å in order to have conformal deposition. A transition of the growth front to 3 dimensions has indeed been evidenced for 20 Å and higher.

  12. Temperature dependence of optical properties of GaAs

    NASA Technical Reports Server (NTRS)

    Yao, Huade; Snyder, Paul G.; Woollam, John A.

    1991-01-01

    The effect of temperature on the optical properties of GaAs was investigated using spectroscopic ellipsometry measurements, between room temperature and about 610 C in increments of 50 C, of pseudodielectric functions and related optical constants of GaAs. A quantitative analysis of the pseudodielectric function spectrum was carried out using a harmonic-oscillator approximation (HOA) to fit the measured dielectric functions. Good fits were obtained with this model, which provides a convenient means of reproducing the GaAs dielectric function at any temperature, by using the temperature-dependent oscillator parameters. The HOA analysis also provides information about band-gap variation with temperature. Using the measured optical constants at a number of fixed temperatures, an algorithm was developed for computing the dielectric function spectrum at an arbitrary temperature in the range 22-610 C.

  13. Formation of donor centers upon the annealing of silicon light-emitting structures implanted with oxygen ions

    SciTech Connect

    Sobolev, N. A. Danilov, D. V.; Aleksandrov, O. V.; Loshachenko, A. S.; Sakharov, V. I.; Serenkov, I. T.; Shek, E. I.; Trapeznikova, I. N.

    2015-03-15

    It is found that the implantation of silicon with oxygen ions and subsequent annealing at high temperatures are accompanied by the formation of electrically active donor centers and by the p-n conversion of the conductivity of silicon. The concentration and spatial distribution of these centers depend on the annealing temperature. The results are accounted for by the interaction of oxygen atoms with intrinsic point defects formed upon the annealing of implantation damages.

  14. Temperature dependent Raman scattering in YCrO{sub 3}

    SciTech Connect

    Mall, A. K. Sharma, Y.; Mukherjee, S.; Garg, A.; Gupta, R.

    2014-04-24

    High quality polycrystalline YCrO{sub 3} samples were synthesized using solid-state-reaction method. The samples were subsequently characterized using X-ray diffraction and magnetometry. Further, temperature dependent Raman spectroscopy over a spectral range from 100 to 800 cm{sup −1} was used to examine the variation of phonons as a function of temperature from 90 to 300 K. In the low temperature ferroelectric phase of YCrO{sub 3}, the observed phonon spectra showed softening of some Raman modes below the magnetic ordering temperature (T{sub N} ∼ 142K), suggesting a coupling between the spin and phonon degrees of freedom.

  15. 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.

  16. Epitaxy of Orthorhombic BaSi2 with Preferential In-Plane Crystal Orientation on Si(001): Effects of Vicinal Substrate and Annealing Temperature

    NASA Astrophysics Data System (ADS)

    Toh, Katsuaki; Hara, Kosuke O.; Usami, Noritaka; Saito, Noriyuki; Yoshizawa, Noriko; Toko, Kaoru; Suemasu, Takashi

    2012-09-01

    We attempted to grow orthorhombic BaSi2 epitaxial films having preferential in-plane crystallographic orientation on both exact and vicinal Si(001) substrates with a miscut angle of 2° toward Si[bar 110] by reactive deposition epitaxy (RDE) and subsequent molecular beam epitaxy (MBE). On the vicinal Si(001) substrate, the initial BaSi2 nuclei formed by RDE tended to grow unidirectionally with the [010] direction parallel to Si[110] when the annealing temperature of the Si substrate before the growth was increased from 830 to 1000 °C. Transmission electron microscopy showed that the grain size of the BaSi2 films grown by MBE increased up to approximately 9 µm on the vicinal Si(001) substrate when the substrate annealing temperature was 1000 °C. This is the largest grain size ever obtained for BaSi2. Even in the case of the exact Si(001) substrate, the MBE-grown BaSi2 grains preferentially grew with the [010] direction along Si[110] when the annealing temperature was 1000 °C.

  17. 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.

  18. Universal temperature-dependent normalized optoacoustic response of blood

    NASA Astrophysics Data System (ADS)

    Petrova, Elena V.; Liopo, Anton; Oraevsky, Alexander A.; Ermilov, Sergey A.

    2015-03-01

    We found and interpreted the universal temperature-dependent optoacoustic (photoacoustic) response (ThOR) in blood; the normalized ThOR is invariant with respect to hematocrit at the hemoglobin's isosbestic point. The unique compartmentalization of hemoglobin, the primary optical absorber at 805 nm, inside red blood cells (RBCs) explains the effect. We studied the temperature dependence of Gruneisen parameter in blood and aqueous solutions of hemoglobin and for the first time experimentally observed transition through the zero optoacoustic response at temperature T0, which was proved to be consistent for various blood samples. On the other hand, the hemoglobin solutions demonstrated linear concentration function of the temperature T0. When this function was extrapolated to the average hemoglobin concentration inside erythrocytes, the temperature T0 was found equivalent to that measured in whole and diluted blood. The obtained universal curve of blood ThOR was validated in both transparent and light scattering media. The discovered universal optoacoustic temperature dependent blood response provides foundation for future development of non-invasive in vivo temperature monitoring in vascularized tissues and blood vessels.

  19. 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.

  20. 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.

  1. 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.

  2. Temperature dependence of damage coefficient in electron irradiated solar cells

    NASA Technical Reports Server (NTRS)

    Faith, T. J.

    1973-01-01

    Measurements of light-generated current vs cell temperature on electron-irradiated n/p silicon solar cells show the temperature coefficient of this current to increase with increasing fluence for both 10-ohm and 20-ohm cells. A relationship between minority-carrier diffusion length and light-generated current was derived by combining measurements of these two parameters: vs fluence at room temperature, and vs cell temperature in cells irradiated to a fluence of 1 x 10 to the 15th power e/sq cm. This relationship was used, together with the light-generated current data, to calculate the temperature dependence of the diffusion-length damage coefficient. The results show a strong decrease in the damage coefficient with increasing temperature in the range experienced by solar panels in synchronous earth orbit.

  3. Temperature Dependent Constitutive Modeling for Magnesium Alloy Sheet

    NASA Astrophysics Data System (ADS)

    Lee, Jong K.; Lee, June K.; Kim, Hyung S.; Kim, Heon Y.

    2010-06-01

    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° 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.

  4. 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.

  5. 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.

  6. A framework for elucidating the temperature dependence of fitness.

    PubMed

    Amarasekare, Priyanga; Savage, Van

    2012-02-01

    Climate warming is predicted to cause large-scale extinctions, particularly of ectothermic species. A striking difference between tropical and temperate ectotherms is that tropical species experience a mean habitat temperature that is closer to the temperature at which fitness is maximized (T(opt)) and an upper temperature limit for survival (T(max)) that is closer to T(opt) than do temperate species. Thus, even a small increase in environmental temperature could put tropical ectotherms at high risk of extinction, whereas temperate ectotherms have a wider temperature cushion. Although this pattern is widely observed, the mechanisms that produce it are not well understood. Here we develop a mathematical framework to partition the temperature response of fitness into its components (fecundity, mortality, and development) and test model predictions with data for insects. We find that fitness declines at high temperatures because the temperature responses of fecundity and mortality act in opposite ways: fecundity decreases with temperature when temperatures exceed the optimal range, whereas mortality continues to increase. The proximity of T(opt) to T(max) depends on how the temperature response of development mediates the interaction between fecundity and mortality. When development is highly temperature sensitive, mortality exceeds reproduction only after fecundity has started to decline with temperature, which causes fitness to decline rapidly to zero when temperatures exceed T(opt). The model correctly predicts empirically observed fitness-temperature relationships in insects from different latitudes. It also suggests explanations for the widely reported phenological shifts in many ectotherms and the latitudinal differences in fitness responses. PMID:22218308

  7. 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

  8. Temperature dependence of coherent oscillations in Josephson phase qubits.

    PubMed

    Lisenfeld, J; Lukashenko, A; Ansmann, M; Martinis, J M; Ustinov, A V

    2007-10-26

    We experimentally investigate the temperature dependence of Rabi oscillations and Ramsey fringes in superconducting phase qubits. In a wide range of temperatures, we find that both the decay time and the amplitude of these coherent oscillations remain nearly unaffected by thermal fluctuations. In the two-level limit, coherent qubit response rapidly vanishes as soon as the energy of thermal fluctuations k(B)T becomes larger than the energy level spacing variant Planck's over h omega of the qubit. In contrast, a sample of much shorter coherence times displayed semiclassical oscillations very similar to Rabi oscillation, but showing a qualitatively different temperature dependence. Our observations shed new light on the origin of decoherence in superconducting qubits. The experimental data suggest that, without degrading already achieved coherence times, phase qubits can be operated at temperatures much higher than those reported till now. PMID:17995313

  9. Ionisation of C60: is it temperature dependent?

    NASA Astrophysics Data System (ADS)

    Baba, M. Sai; Narasimhan, T. S. Lakshmi; Balasubramanian, R.; Mathews, C. K.

    1994-01-01

    In a recent paper, Drewello [T. Drewello, W. Kratschmer, M. Fieber-Erdmann and A. Ding, Int. J. Mass Spectrom. Ion Processes, 124 (1993) R1] reported a temperature dependent ionisation cross section for the formation of C2+60 in their photoionisation dynamic studies on C60 using synchrotron radiation. To check this, the ratio of ion intensities of C2+60 to that of C60 was determined as a function of temperature of C60 samples using a Knudsen effusion mass spectrometer. Our results indicate the absence of any temperature dependence of cross section for the formation of C2+60 in the temperature range of measurement (600-800 K) using electron impact ionisation.

  10. 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.

  11. 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.

  12. Temperature dependence of temporal resolution in an insect nervous system.

    PubMed

    Franz, A; Ronacher, B

    2002-05-01

    The vast majority of animals are poikilotherms, and thus face the problem that the temperature of their nervous systems rather smoothly follows the temperature changes imposed by their environment. Since basic properties of nerve cells, e.g., the time constants of ion channels, strongly depend on temperature, a temperature shift likely affects the processing of the temporal structure of sensory stimuli. This can be critical in acoustic communication systems in which time patterns of signals are decisive for recognition by the receiver. We investigated the temperature dependence of the responses of locust auditory receptors and interneurons by varying the temperature of the experimental animals during intracellular recordings. The resolution of fast amplitude modulations of acoustic signals was determined in a gap detection paradigm. In auditory receptors and local (second order) interneurons, temporal resolution was improved at higher temperatures. This gain could be attributed to a higher precision of spike timing. In a third-order neuron, a rise in temperature affected the interactions of inhibition and excitation in a complex manner, also resulting in a better resolution of gaps in the millisecond range. PMID:12012097

  13. 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

  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. Temperature dependence of self-broadened halfwidths of CO2

    NASA Technical Reports Server (NTRS)

    Suarez, Carlos B.; Valero, Francisco P. J.

    1990-01-01

    The temperature dependence of self-broadened halfwidths of CO2 was studied in the temperature range 165-300 K for the band at 4978/cm. Assuming a power-law of the form gamma(T) = delta(T0)(T0/T)-exp n, the exponent has been determined for J = 6-32. An average value of n = 0.745 + or - 7 percent has been found.

  17. 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.

  18. Models for predicting temperature dependence of material properties of aluminum

    NASA Astrophysics Data System (ADS)

    Marla, Deepak; Bhandarkar, Upendra V.; Joshi, Suhas S.

    2014-03-01

    A number of processes such as laser ablation, laser welding, electric discharge machining, etc involve high temperatures. Most of the processes involve temperatures much higher than the target melting and normal boiling point. Such large variation in target temperature causes a significant variation in its material properties. Due to the unavailability of experimental data on material properties at elevated temperatures, usually the data at lower temperatures is often erroneously extrapolated during modelling of these processes. Therefore, this paper attempts to evaluate the variation in material properties with temperature using some general and empirical theories, along with the available experimental data for aluminum. The evaluated properties of Al using the proposed models show a significant variation with temperature. Between room temperature and near-critical temperature (0.9Tc), surface reflectivity of Al varies from more than 90% to less than 50%, absorption coefficient decreases by a factor of 7, thermal conductivity decreases by a factor of 5, density decreases by a factor of 4, specific heat and latent heat of vapourization vary by a factor between 1.5 and 2. Applying these temperature-dependent material properties for modelling laser ablation suggest that optical properties have a greater influence on the process than thermophysical properties. The numerical predictions of the phase explosion threshold in laser ablation are within 5% of the experimental values.

  19. Periodically pulsed wet annealing approach for low-temperature processable amorphous InGaZnO thin film transistors with high electrical performance and ultrathin thickness.

    PubMed

    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 cm(2) V(-1) s(-1); Ion/Ioff ratio ≈ 10(8); 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

  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. 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).

  2. Temperature dependence of myosin-II tail fragment assembly.

    PubMed

    McMahon, Peggy M; Hostetter, Daniel R; Rice, Sarah E

    2008-01-01

    Dictyostelium myosin-II bipolar thick filament (BTF) assembly is heavily dependent on ionic strength and temperature and is reversible by the phosphorylation of just three threonines. Truncated tail fragments of Dictyostelium myosin-II are commonly used as models for BTF assembly, as they self-assemble into regular paracrystals that recapitulate the ionic strength and phosphorylation dependence of full-length Dictyostelium myosin-II BTF assembly. Here we show that Dictyostelium myosin-II tail fragment assembly is highly temperature dependent, similar to full-length Dictyostelium myosin-II. Assembly of paracrystals was far more robust at 4 degrees C than at higher temperatures. Pre-assembled paracrystals disassembled completely when shifted to 37 degrees C, indicating that assembly does not greatly improve the thermostability of these tail fragments. The melting temperatures of individual Dictyostelium myosin-II tail coiled-coils under both low and high ionic strength conditions that prohibit paracrystal assembly are extremely low, 21 degrees C and 28 degrees C, respectively. These data are consistent with reversible thermal denaturation of the coiled-coil as the most likely explanation for assembly incompetence under either very low ionic strength or high temperature conditions. Assembled paracrystals of a structurally similar fragment of nonmuscle myosin-IIA were far more thermodynamically stable than their Dictyostelium counterparts at the temperatures examined here. PMID:18784979

  3. Temperature dependence of electrical resistivity measurements: A useful infiltration tracer?

    NASA Astrophysics Data System (ADS)

    Pidlisecky, A.; Knight, R.

    2008-12-01

    As part of an ongoing monitoring project, three resistivity probes were installed to a depth of 2m below a seasonal infiltration pond on the central coast of California. The probes were instrumented with 35 resistivity electrodes and 5 temperature loggers. They were designed to monitor the change in bulk resistivity beneath the pond during infiltration. The pond was filled in January 2008 and resistivity measurements were made on each probe every hour for a period of 4 months. In addition to changes in bulk resistivity, we observed diurnal fluctuations in the apparent resistivity signal due to the temperature dependence of in-situ resistivity. By processing the resistivity data, using a band pass filter, we can recover a time-depth section of pseudo- temperature data. We refer to these data as pseudo-temperature because they can be treated as a surrogate for temperature in terms of phase but not amplitude. These pseudo-temperature sections can be used as a tracer to calculate 1D infiltration rates. When compared with in-situ temperature loggers, we see good agreement. Moreover, we note that the resistivity fluctuations correspond to temperature variations that are less than one degree Celsius. The use of the temperature dependence of measured resistivity is a promising field technique. The pseudo-temperature data may prove more robust than using traditional temperature probes given that the larger sampling volume of the resistivity measurement will limit the influence local flow path perturbations caused by probe installation. Future research will involve extending this approach to 2D tomography in hopes of providing us with a technique for obtaining spatially exhaustive estimates of near-surface infiltration rates.

  4. 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

  5. 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.

  6. Temperature Dependent Fluorescence Lifetime Measurements in a Phosphor

    NASA Astrophysics Data System (ADS)

    Nettles, Charles J.; Smith, R. Seth; Heath, Jonathan J.

    2012-03-01

    This poster will describe an undergraduate senior research project involving fluorescence lifetime measurements in a LaSO4:Eu phosphor compound. Specifically, this project seeks to determine the temperature dependence of the lifetime. The temperature of the phosphor will be varied using a heater block with temperature control. The phosphor will be excited with the 337 nm output of a Nitrogen Laser. An Oriel Monochromator will be used to disperse the fluorescence, and the lifetime for a particular wavelength will be determined from a photomultiplier tube signal. At the time of the presentation, this project will be nearing completion; and I will discuss my progress, successes, and challenges.

  7. 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).

  8. Temperature dependence of atomic-scale stick-slip friction.

    PubMed

    Jansen, Lars; Hölscher, Hendrik; Fuchs, Harald; Schirmeisen, André

    2010-06-25

    We report experiments of atomic stick-slip friction on graphite as an explicit function of surface temperature between 100 and 300 K under ultrahigh vacuum conditions. A statistical analysis of the individual stick-slip events as a function of the velocity reveals an agreement with the thermally activated Prandtl-Tomlinson model at all temperatures. Taking into account an explicit temperature-dependence of the attempt frequency all data points collapse onto one single master curve. PMID:20867399

  9. 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.

  10. 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.

  11. The effect of different annealing temperatures on the structure and luminescence properties of Y2O3:Bi3+ thin films fabricated by spin coating

    NASA Astrophysics Data System (ADS)

    Yousif, A.; Jafer, R. M.; Som, S.; Duvenhage, M. M.; Coetsee, E.; Swart, H. C.

    2016-03-01

    This paper reports on the structural, morphology and optical properties of Y2-xO3:Bix=0.005 micro-and nanophosphors synthesized via the spin coating method. The influence of different annealing temperatures (900-1200 °C) on the morphology, crystal structure and the photoluminescence (PL) properties of the synthesized films were studied in detail. The crystal structure of the films was investigated with X-ray diffraction. The presence of the three major diffraction peaks with Miller indexes (2 1 1), (2 2 2) and (4 0 0) indicated that the Y2-xO3:Bix=0.005 thin films were well-crystallized at 900 °C, 1000 °C, 1100 °C and 1200 °C. Additionally, extra diffraction peaks were observed for the sample that was annealed at 1200 °C. Those extra peaks were due to the formation of the Y2Si2O7 phase owing to the annealing induced changes in the crystal structure and chemical composition of the Y2-xO3:Bix=0.005 thin film. This may also be attributed to inter diffusion of atomic species between the Si substrate and the Y2-xO3:Bix=0.005 thin film at the high annealing temperature. Due to structure-sensitive properties of the Bi3+ ions, a blue shift of the centre PL emission band from 495 nm to 410 nm was clearly observed and explained in detail. The time-of-flight secondary ion mass spectroscopy results show the Si diffusion from the Si substrate, whereas, the scanning electron microscopy and the atomic force microscopy were used for the morphology analysis.

  12. Dependence of the optimum parameters of femtosecond laser annealing of lead zirconate titanate films on their thickness

    NASA Astrophysics Data System (ADS)

    Elshin, A. S.; Abdullaev, D. A.; Mishina, E. D.

    2016-06-01

    The optimum parameters of laser annealing (crystallization) induced by repetitive pulses with a pulse duration of 100 fs and a wavelength of 800 nm, which falls in the transparency region of the film and, simultaneously, in the absorption region of the substrate, have been investigated experimentally as a function of the thickness of the ferroelectric film. It has been shown that, with an increase in the thickness of the ferroelectric film by 100 nm (in the range from 300 to 600 nm), the required power density of the laser beam increases, on the average, by 0.1 MW/cm2. The optimum exposure time of the laser beam with the desired power increases nonlinearly with an increase in the thickness of the film.

  13. 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. PMID:25683178

  14. Mechanisms of interaction of YBa2Cu3O y with water vapor at low-temperature annealing

    NASA Astrophysics Data System (ADS)

    Bobylev, I. B.; Zyuzeva, N. A.

    2016-02-01

    Abstract—The interaction of YBa2Cu3O y (123) with water vapor at temperatures T ≤ 150° has been studied. It has been shown that, with an increase in temperature, the mechanism of its interaction with water changes. Near room temperature, the main process is hydrolytic decomposition. At T ~ 100°C, the absorption of water is significantly reduced, because the role of hydrolysis becomes less important and water penetrates the structure weakly and is incorporated into oxygen vacancies mainly in the form of OH--groups, which leads to the transition of YBa2Cu3O y from the tetragonal to orthorhombic phase. With an increase in temperature to 150°C, the absorption of water increases again. In this case, the main mechanism is the penetration of water to the 123 structure, which leads to splitting of Cu-O chains and a phase transition from the 123 to pseudo-124 structure. The role of different mechanisms of interaction with water essentially depends on the oxygen content in the 123 structure. At a low oxygen index ( y = 6.3), the role of hydrolysis is more important, and, at y ≥ 6.5, the incorporation of water into the structure prevails. It has been revealed that, at T = 150°C, after absorption of water, YBa2Cu3O6.96 becomes a proton conductor.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Temperature-dependent absorption cross-sections of perfluorotributylamine

    NASA Astrophysics Data System (ADS)

    Godin, Paul J.; Cabaj, Alex; Conway, Stephanie; Hong, Angela C.; Le Bris, Karine; Mabury, Scott A.; Strong, Kimberly

    2016-05-01

    Cross-sections of perfluorotributylamine (PFTBA) were derived from Fourier transform spectroscopy at 570-3400 cm-1 with a resolution of 0.1 cm-1 over a temperature range of 298-344 K. These results were compared to theoretical density functional theory (DFT) calculations and to previous measurements of PFTBA made at room temperature. DFT calculations were performed using the B3LYP method and the 6-311G(d,p) basis set. We find good agreement between our experimentally derived results, DFT calculations, and previously published data. No significant temperature dependence in the PFTBA cross-sections was observed for the temperature range studied. We calculate an average integrated band strength of 7.81 × 10-16 cm/molecule for PFTBA over the spectral range studied. Radiative efficiencies (RE) and global warming potentials (GWP) for PFTBA were also derived. The calculated radiative efficiencies show no dependence on temperature and agree with prior publications. We find an average RE of 0.77 Wm-2 ppbv-1 and a range of GWP from 6874 to 7571 depending on the lifetime used. Our findings are consistent with previous studies and increase our confidence in the value of the GWP of PFTBA.

  2. Temperature dependence of protein folding kinetics in living cells

    PubMed Central

    Guo, Minghao; Xu, Yangfan; Gruebele, Martin

    2012-01-01

    We measure the stability and folding rate of a mutant of the enzyme phosphoglycerate kinase (PGK) inside bone tissue cells as a function of temperature from 38 to 48 °C. To facilitate measurement in individual living cells, we developed a rapid laser temperature stepping method capable of measuring complete thermal melts and kinetic traces in about two min. We find that this method yields improved thermal melts compared to heating a sample chamber or microscope stage. By comparing results for six cells with in vitro data, we show that the protein is stabilized by about 6 kJ/mole in the cytoplasm, but the temperature dependence of folding kinetics is similar to in vitro. The main difference is a slightly steeper temperature dependence of the folding rate in some cells that can be rationalized in terms of temperature-dependent crowding, local viscosity, or hydrophobicity. The observed rate coefficients can be fitted within measurement uncertainty by an effective two-state model, even though PGK folds by a multistate mechanism. We validate the effective two-state model with a three-state free energy landscape of PGK to illustrate that the effective fitting parameters can represent a more complex underlying free energy landscape. PMID:22665776

  3. Surface-morphology evolution during growth-interrupt in situ annealing on GaAs(110) epitaxial layers

    SciTech Connect

    Yoshita, Masahiro; Akiyama, Hidefumi; Pfeiffer, Loren N.; West, Ken W.

    2007-05-15

    Temperature and surface-coverage dependence of the evolution of surface morphology during growth-interrupt in situ annealing on GaAs epitaxial layers grown on the singular (110) cleaved edges by the cleaved-edge overgrowth method with molecular-beam epitaxy has been studied by means of atomic force microscopy. Annealing at substrate temperatures below 630 degree sign C produced atomically flat surfaces with characteristic islands or pits, depending on the surface coverage. The atomic flatness of the surfaces is enhanced with increasing annealing temperature owing to the enhanced adatom migration. At a higher annealing temperature of about 650 degree sign C, however, 2-monolayer-deep triangular pits with well-defined step edges due to Ga-atom desorption from the crystal appeared in the atomically flat surface. The growth-interrupt annealing temperature optimal for the formation of atomically flat GaAs(110) surfaces is therefore about 630 degree sign C.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Temperature dependence of APD-based PET scanners

    SciTech Connect

    Keereman, Vincent; Van Holen, Roel; Vandenberghe, Stefaan; Vanhove, Christian

    2013-09-15

    Purpose: Solid state detectors such as avalanche photodiodes (APDs) are increasingly being used in PET detectors. One of the disadvantages of APDs is the strong decrease of their gain factor with increasing ambient temperature. The light yield of most scintillation crystals also decreases when ambient temperature is increased. Both effects lead to considerable temperature dependence of the performance of APD-based PET scanners. In this paper, the authors propose a model for this dependence and the performance of the LabPET8 APD-based small animal PET scanner is evaluated at different temperatures.Methods: The model proposes that the effect of increasing temperature on the energy histogram of an APD-based PET scanner is a compression of the histogram along the energy axis. The energy histogram of the LabPET system was acquired at 21 °C and 25 °C to verify the validity of this model. Using the proposed model, the effect of temperature on system sensitivity was simulated for different detector temperature coefficients and temperatures. Subsequently, the effect of short term and long term temperature changes on the peak sensitivity of the LabPET system was measured. The axial sensitivity profile was measured at 21 °C and 24 °C following the NEMA NU 4-2008 standard. System spatial resolution was also evaluated. Furthermore, scatter fraction, count losses and random coincidences were evaluated at different temperatures. Image quality was also investigated.Results: As predicted by the model, the photopeak energy at 25 °C is lower than at 21 °C with a shift of approximately 6% per °C. Simulations showed that this results in an approximately linear decrease of sensitivity when temperature is increased from 21 °C to 24 °C and energy thresholds are constant. Experimental evaluation of the peak sensitivity at different temperatures showed a strong linear correlation for short term (2.32 kcps/MBq/°C = 12%/°C, R = −0.95) and long term (1.92 kcps/MBq/°C = 10%/

  9. Finite element simulation of temperature dependent free surface flows

    NASA Technical Reports Server (NTRS)

    Engelman, M. S.; Sani, R. L.

    1985-01-01

    The method of Engelman and Sani (1984) for a finite-element simulation of incompressible surface flows with a free and/or moving fluid interface, such as encountered in crystal growth and coating and polymer technology, is extended to temperature-dependent flows, including the effect of temperature-dependent surface tension. The basic algorithm of Saito and Scriven (1981) and Ruschak (1980) has been generalized and implemented in a robust and versatile finite-element code that can be employed with relative ease for the simulation of free-surface problems in complex geometries. As a result, the costly dependence on the Newton-Raphson algorithm has been eliminated by replacing it with a quasi-Newton iterative method, which nearly retains the superior convergence properties of the Newton-Raphson method.

  10. Intensity-dependent response to temperature in hydra clones.

    PubMed

    Kaliszewicz, Anita

    2015-01-01

    The intensity of environmental factors differs in natural habitats and could shape the response of an animal that is able to assess a factor's gradient. However, intensity-dependent response to environmental factors has been only occasionally reported in animals. In laboratory experiments, I studied changes in sexual induction in response to a series of temperature decreases in different clones of Hydra oligactis. The percentage of sexually-induced clone-mates was related to the temperature gradient intensity. This intensity-dependent response was observed independently of the H. oligactis clone and gender. The magnitude of the response differed significantly between the clones originated from the distinct sites. The possible significance of the intensity-dependent response in the Hydra clones is discussed in evolutionary terms. PMID:25660699

  11. 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.

  12. Temperature Dependence of Carbon Isotope Fractionation in CAM Plants.

    PubMed

    Deleens, E; Treichel, I; O'leary, M H

    1985-09-01

    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 degrees C nights, 23 degrees C days), the isotope fractionation for both plants is -4 per thousand (that is, malate is enriched in (13)C relative to the atmosphere). For K. daigremontiana, the isotope fractionation decreases with increasing temperature, becoming approximately 0 per thousand at 27 degrees C/33 degrees 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

  13. Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

    2016-01-01

    Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature (T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

  14. Temperature dependence of resonance Raman spectra of carotenoids

    NASA Astrophysics Data System (ADS)

    Andreeva, A.; Apostolova, I.; Velitchkova, M.

    2011-04-01

    To understand the mechanism of the photoprotective and antioxidative functions of carotenoids, it is essential to have a profound knowledge of their excited electronic and vibronic states. In the present study we investigate the most powerful antioxidants: β-carotene and lutein by means of resonance Raman spectroscopy. The aim was to study in detail their Raman spectra in solution at room temperature and their changes as a function of temperature. To measure the spectra in their natural environment pyridine has been used as a solvent. It has been chosen because of its polarizability ( n = 1.5092) which is close to that of membrane lipids and proteins. The temperature dependence of the most intensive ν1 band in the range from 77 K to 295 K at 514.5 nm excitation has been obtained. It was found that in pyridine the C dbnd C stretching frequency, its intensity, line shape, and line width are very sensitive to the temperature (the sensitivity being different for the two studied carotenoids). The observed linear temperature dependence of the C dbnd C stretching frequency is explained by a mechanism involving changes of the vibronic coupling and the extent of π-electron delocalization. The different behavior of the temperature-induced broadening of the ν1 band and its intensity for the two studied carotenoids can be associated with the different nature of their solid matrices: glassy for β-carotene and crystalline-like for lutein, owing to their different chemical structures.

  15. Temperature-dependent Infrared Optical Constants of Olivine and Enstatite

    NASA Astrophysics Data System (ADS)

    Zeidler, S.; Mutschke, H.; Posch, Th.

    2015-01-01

    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.

  16. Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

    2016-06-01

    Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature ( T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

  17. New application of temperature-dependent modelling of high temperature superconductors: Quench propagation and pulse magnetization

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Matsuda, Koichi; Coombs, T. A.

    2012-08-01

    We present temperature-dependent modeling of high-temperature superconductors (HTS) to understand HTS electromagnetic phenomena where temperature fluctuation plays a nontrivial role. Thermal physics is introduced into the well-developed H-formulation model, and the effect of temperature-dependent parameters is considered. Based on the model, we perform extensive studies on two important HTS applications: quench propagation and pulse magnetization. A micrometer-scale quench model of HTS coil is developed, which can be used to estimate minimum quench energy and normal zone propagation velocity inside the coil. In addition, we study the influence of inhomogeneity of HTS bulk during pulse magnetization. We demonstrate how the inhomogeneous distribution of critical current inside the bulk results in varying degrees of heat dissipation and uniformity of final trapped field. The temperature-dependent model is proven to be a powerful tool to study the thermally coupled electromagnetic phenomena of HTS.

  18. Correlation between stoichiometry and surface structure of the polar MgAl2O4(100) surface as a function of annealing temperature.

    PubMed

    Jensen, Thomas N; Rasmussen, Morten K; Knudsen, Jan; Vlad, Alina; Volkov, Sergey; Lundgren, Edvin; Stierle, Andreas; Lauritsen, Jeppe V

    2015-02-28

    The correlation between surface structure, stoichiometry and atomic occupancy of the polar MgAl2O4(100) surface has been studied with an interplay of noncontact atomic force microscopy, X-ray photoelectron spectroscopy and surface X-ray diffraction under ultrahigh vacuum conditions. The Al/Mg ratio is found to significantly increase as the surface is sputtered and annealed in oxygen at intermediate temperatures ranging from 1073-1273 K. The Al excess is explained by the observed surface structure, where the formation of nanometer-sized pits and elongated patches with Al terminated step edges contribute to stabilizing the structure by compensating surface polarity. Surface X-ray diffraction reveals a reduced occupancy in the top two surface layers for both Mg, Al, and O and, moreover, vacancies are preferably located in octahedral sites, indicating that Al and Mg ions interchange sites. The excess of Al and high concentration of octahedral vacancies, very interestingly, indicates that the top few surface layers of the MgAl2O4(100) adopts a surface structure similar to that of a spinel-like transition Al2O3 film. However, after annealing at a high temperature of 1473 K, the Al/Mg ratio restores to its initial value, the occupancy of all elements increases, and the surface transforms into a well-defined structure with large flat terraces and straight step edges, indicating a restoration of the surface stoichiometry. It is proposed that the tetrahedral vacancies at these high temperatures are filled by Mg from the bulk, due to the increased mobility at high annealing temperatures. PMID:25626848

  19. 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

  20. [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