Science.gov

Sample records for annealing time effect

  1. Effects of ambient humidity on the optimum annealing time of mixed-halide Perovskite solar cells.

    PubMed

    Cronin, Harry M; Jayawardena, K D G Imalka; Stoeva, Zlatka; Shkunov, Maxim; Silva, S Ravi P

    2017-03-17

    Mixed halide Perovskite solar cells (PSCs) are commonly produced by depositing PbCl2 and CH3NH3I from a common solvent followed by thermal annealing, which in an up-scaled manufacturing process is likely to take place under ambient conditions. However, it has been reported that, similar to the effects of thermal annealing, ambient humidity also affects the crystallisation behaviour and subsequent growth of the Perovskite films. This implies that both of these factors must be accounted for in solar cell production. In this work, we report for the first time the correlation between the annealing time, relative humidity (RH) and device performance for inverted, mixed halide CH3NH3PbI(3-x)Cl x PSCs with active area ≈1 cm(2). We find a trade-off between ambient humidity and the required annealing time to produce efficient solar cells, with low humidities needing longer annealing times and vice-versa. At around 20% RH, device performance weakly depends on annealing time, but at higher (30%-40% RH) or lower (0%-15% RH) humidities it is very sensitive. Processing in humid environments is shown to lead to the growth of both larger Perovskite grains and larger voids; similar to the effect of thermal annealing, which also leads to grain growth. Therefore, samples which are annealed for too long under high humidity show loss of performance due to low open circuit voltage caused by an increased number of shunt paths. Based on these results it is clear that humidity and annealing time are closely interrelated and both are important factors affecting the performance of PSCs. The findings of this work open a route for reduced annealing times to be employed by control of humidity; critical in roll-to-roll manufacture where low manufacturing time is preferred for cost reductions.

  2. Effects of ambient humidity on the optimum annealing time of mixed-halide Perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Cronin, Harry M.; Imalka Jayawardena, K. D. G.; Stoeva, Zlatka; Shkunov, Maxim; Silva, S. Ravi P.

    2017-03-01

    Mixed halide Perovskite solar cells (PSCs) are commonly produced by depositing PbCl2 and CH3NH3I from a common solvent followed by thermal annealing, which in an up-scaled manufacturing process is likely to take place under ambient conditions. However, it has been reported that, similar to the effects of thermal annealing, ambient humidity also affects the crystallisation behaviour and subsequent growth of the Perovskite films. This implies that both of these factors must be accounted for in solar cell production. In this work, we report for the first time the correlation between the annealing time, relative humidity (RH) and device performance for inverted, mixed halide CH3NH3PbI(3‑x)Cl x PSCs with active area ≈1 cm2. We find a trade-off between ambient humidity and the required annealing time to produce efficient solar cells, with low humidities needing longer annealing times and vice-versa. At around 20% RH, device performance weakly depends on annealing time, but at higher (30%–40% RH) or lower (0%–15% RH) humidities it is very sensitive. Processing in humid environments is shown to lead to the growth of both larger Perovskite grains and larger voids; similar to the effect of thermal annealing, which also leads to grain growth. Therefore, samples which are annealed for too long under high humidity show loss of performance due to low open circuit voltage caused by an increased number of shunt paths. Based on these results it is clear that humidity and annealing time are closely interrelated and both are important factors affecting the performance of PSCs. The findings of this work open a route for reduced annealing times to be employed by control of humidity; critical in roll-to-roll manufacture where low manufacturing time is preferred for cost reductions.

  3. Effects of annealing time on the structure, morphology, and stress of gold-chromium bilayer film

    NASA Astrophysics Data System (ADS)

    Zhang, Hong; Jin, Yun-Xia; Wang, Hu; Kong, Fang-Yu; Huang, Hao-Peng; Cui, Yun

    2016-10-01

    In this work, a 200-nm-thick gold film with a 10-nm-thick chromium layer used as an adhesive layer is fabricated on fused silica by the electron beam evaporation method. The effects of annealing time at 300 °C on the structure, morphology and stress of the film are studied. We find that chromium could diffuse to the surface of the film by formatting a solid solution with gold during annealing. Meanwhile, chromium is oxidized on the surface and diffused downward along the grain grooves in the gold film. The various operant mechanisms that change the residual stresses of gold films for different annealing times are discussed. Project supported by the National Natural Science Foundation of China (Grant No. 61405225).

  4. Study of growth time and post annealing effect on the performance of ZnO nanorods ultraviolet photodetector

    NASA Astrophysics Data System (ADS)

    Shasti, M.; Dariani, R. S.

    2017-02-01

    In this paper, Zinc Oxide nanorods with different thicknesses are grown on a glass substrate by a hydrothermal method to fabricate an ultraviolet photodetector. The sample is post annealed in an argon environment as an annealing process can have a positive effect on the photodetector performance. The morphology, crystalline structure, and optical properties of ZnO nanorods (NRs) are investigated by SEM, XRD, UV-Visible spectrometer, and PL spectra. The goal of this study is to investigate the effect of both growth time and post annealing on enhancement of photoresponse of the ZnO NR photodetector. Measurements indicate that the sample with higher thickness exhibits a higher photocurrent and photoresponsivity. Also, with post annealing, an increase in photocurrent and photoresponsivity is observed due to decreasing defect levels.

  5. Tritium release from neutron irradiated beryllium: Kinetics, long-time annealing and effect or crack formation

    SciTech Connect

    Scaffidi-Argentina, F.; Werle, H.

    1995-09-01

    Since beryllium is considered as one of the best neutron multiplier materials in the blanket of the next generation fusion reactors, several studies have been started to evaluate its behaviour under irradiation during both operating and accidental conditions. Based on safety considerations, tritium produced in beryllium during neutron irradiation represents one important issue, therefore it is necessary to investigate tritium transport processes by using a comprehensive mathematical model and comparing its predictions with well characterized experimental tests. Because of the difficulties in extrapolating the short-time tritium release tests to a longer time scale, also long-time annealing experiments with beryllium samples from the SIBELIUS irradiation. have been carried out at the Forschungszentrum Karlsruhe. Samples were annealed up to 12 months at temperatures up to 650{degrees}C. The inventory after annealing was determined by heating the samples up to 1050{degrees}C with a He+0.1 vo1% H{sub 2} purge gas. Furthermore, in order to investigate the likely effects of cracks formation eventually causing a faster tritium release from beryllium, the behaviour of samples irradiated at low temperature (40-50{degrees}C) but up to very high fast neutron fluences (0.8-3.9{center_dot}10{sup 22} cm{sup -2}, E{sub n}{ge}1 MeV) in the BR2 reactor has been investigated. Tritium was released by heating the beryllium samples up to 1050{degrees}C and purging them with He+0.1 vo1% H{sub 2}. Tritium release from high-irradiated beryllium samples showed a much faster kinetics than from the low-irradiated ones, probably because of crack formation caused by thermal stresses in the brittle material and/or by helium bubbles migration. The obtained experimental data have been compared with predictions of the code ANFIBE with the goal to better understand the physical mechanisms governing tritium behaviour in beryllium and to assess the prediction capabilities of the code.

  6. Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of ultrathin block copolymer films.

    PubMed

    Huang, Changchun; Wen, Gangyao; Li, Jingdan; Wu, Tao; Wang, Lina; Xue, Feifei; Li, Hongfei; Shi, Tongfei

    2016-09-15

    Effects of copolymer composition, film thickness, and solvent vapor annealing time on dewetting of spin-coated polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films (<20nm thick) were mainly investigated by atomic force microscopy. Surface chemical analysis of the ultrathin films annealed for different times were performed using X-ray photoelectron spectroscopy and contact angle measurement. With the annealing of acetone vapor, dewetting of the films with different thicknesses occur via the spinodal dewetting and the nucleation and growth mechanisms, respectively. The PS-b-PMMA films rupture into droplets which first coalesce into large ones to reduce the surface free energy. Then the large droplets rupture into small ones to increase the contact area between PMMA blocks and acetone molecules resulting from ultimate migration of PMMA blocks to droplet surface, which is a novel dewetting process observed in spin-coated films for the first time.

  7. Effect of Annealing Temperature and Time on Microstructure and Mechanical Properties of Multilayered Steel Composite Sheets

    NASA Astrophysics Data System (ADS)

    Cao, R.; Yu, X.; Feng, Z.; Ojima, M.; Inoue, J.; Koseki, T.

    2016-12-01

    Multilayered composite steels consisting of alternating layers of martensitic phase and austenitic phase exhibit an excellent combination of strength and elongation compared with conventional advanced high-strength steels. The deformation processes underlying these properties are of considerable interest. In this article, microstructure, grain size, and phase are characterized by scanning electron microscopy (SEM) and electron backscattering diffraction. The hardness of each layer is analyzed by a microindentation hardness testing system. Finally, the deformation and failure processes in multilayered steel are investigated by in-situ SEM. The hardness results indicate that various hardening modes occur in the soft austenitic layer and the hard martensitic layer. In- situ SEM results combined with microstructure analysis and hardness results reveal that annealing temperature and annealing time have a significant impact on final microstructure, fracture behavior, strength, hardness, and ductility.

  8. Enthalpy relaxation and annealing effect in polystyrene.

    PubMed

    Sakatsuji, Waki; Konishi, Takashi; Miyamoto, Yoshihisa

    2013-07-01

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

  9. Effect of Annealing Time Process on the pH Sensitivity of Spin-coated TiO2/ ZnO Bilayer Film

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    This paper presents an investigation on titanium dioxide (TiO2) and zinc oxide (ZnO) bilayer film, which is used as sensing membrane for extended-gate field effect transistor (EGFET) for pH sensing application. TiO2/ZnO thin films were deposited using sol-gel spin coating method on indium tin oxide (ITO) substrates. After the deposition, the bilayer films were annealed at constant temperatures which is 400 °C for 15, 30, 40 and 60 minutes. The sensitivity of the TiO2 thin film towards pH buffer solution was measured by dipping the sensing membrane in pH4, pH7 and pH10 buffer solution. By varying the annealing time, we found that the TiO2/ZnO thin film annealed at 400°C for 15 minutes gave the highest sensitivity compared to other annealing conditions, with the value of 64.87 mV/pH.

  10. The effect of vacuum annealing on corrosion resistance of titanium

    SciTech Connect

    Chikanov, V.N.; Peshkov, V.V.; Kireev, L.S.

    1994-09-01

    The effect of annealing on the corrosion resistance of OT4-1 sheet titanium in 25% HCl under various air pressures and self-evacuating conditions has been investigated. From the kinetic corrosion curves it follows that the least corrosion resistance of titanium is observed after vacuum annealing. Even low residual air pressure in a chamber improves corrosion resistance. The corrosion resistance of titanium decreases with vacuum-annealing time.

  11. TiO2 photoanode sensitized with nanocrystalline Bi2S3: the effect of sensitization time and annealing on its photovoltaic performance

    NASA Astrophysics Data System (ADS)

    Kulkarni, Anil N.; Rajendra Prasad, M. B.; Pathan, Habib M.; Patil, Rajendra S.

    2016-04-01

    This work deals with the sensitization of the porous TiO2 films of thickness about 4 µm deposited on fluorine-doped tin oxide with nanocrystalline Bi2S3 for photovoltaic application. The sensitization was achieved for four different sensitization times employing chemical solution deposition with bismuth nitrate and sodium thiosulphate as precursors for Bi3+ and S2-, respectively. The unsensitized and sensitized photoelectrodes were characterized using X-ray diffractometry, scanning electron microscopy and diffused reflectance spectroscopy. XRD patterns show the signatures of both anatase TiO2 and orthorhombic Bi2S3 in the sensitized photoanodes. However, crystallinity of Bi2S3 increased with increase in sensitization time from 10 to 40 min. The temporal effect of sensitization and annealing on the photovoltaic performance of the solar cells fabricated using four different photoelectrodes was studied using the photocurrent density versus photovoltage curves. Annealing apparently improved the photovoltaic performance of photoanodes. The best performance was obtained for cell fabricated using annealed TiO2/Bi2S3 photoanode after 30 min sensitization time showing V oc ~ 0.37 mV, J sc ~ 0.52 mA/cm2, FF ~ 68 and 0.43 %.

  12. Effect of the implantation dose and annealing time on the luminescence properties of (113) defects in silicon implanted by oxygen ions

    NASA Astrophysics Data System (ADS)

    Sobolev, N. A.; Kalyadin, A. E.; Aruev, P. N.; Zabrodskii, V. V.; Shek, E. I.; Shtel'makh, K. F.; Karabeshkin, K. V.

    2016-12-01

    The photoluminescence properties of (113) defects formed in a silicon structure after the implantation by oxygen ions with an energy of 350 keV and doses of 1.7 × 1013-1.7 × 1015 cm-2 and the subsequent annealing at a temperature of 700°C for 0.5-2.0 h in a chlorine-containing atmosphere have been investigated. Regardless of the implantation dose and annealing time, the photoluminescence spectra are dominated by the line at a wavelength of 1.37 μm, which is attributed to a (113) defect. The dependences of the line intensity on the implantation dose and annealing time are characterized by curves with maxima. As the measurement temperature increases in the range from 64 to 120 K, the line intensity decreases monotonically.

  13. Reduction of Annealing Times for Energy Conservation in Aluminum

    SciTech Connect

    Anthony D. Rollett; Hasso Weiland; Mohammed Alvi; Abhijit Brahme

    2005-08-31

    Carnegie Mellon University was teamed with the Alcoa Technical Center with support from the US Dept. of Energy (Office of Industrial Technology) and the Pennsylvania Technology Investment Authority (PTIA) to make processing of aluminum less costly and more energy efficient. Researchers in the Department of Materials Science and Engineering have investigated how annealing processes in the early stages of aluminum processing affect the structure and properties of the material. Annealing at high temperatures consumes significant amounts of time and energy. By making detailed measurements of the crystallography and morphology of internal structural changes they have generated new information that will provide a scientific basis for shortening processing times and consuming less energy during annealing.

  14. Annealing effects on optical properties of natural alexandrite

    NASA Astrophysics Data System (ADS)

    Fernandes Scalvi, Rosa M.; Li, Máximo Siu; Scalvi, Luis V. A.

    2003-11-01

    Natural alexandrite (BeAl2O4:Cr3+) crystals are investigated as regards the effects of annealing on their optical properties. Optical absorption spectra are measured from the ultraviolet (190 nm) to the near infrared (900 nm), for a sample subjected to consecutive annealing processes, where time and temperature are varied. Besides this, luminescence spectra are simultaneously obtained for this sample, excited with a Kr+ laser source, tuned on an ultraviolet multi-line mode (337.5, 350.7 and 356.4 nm). We observe from absorption as well as from emission data that annealing mainly influences the distribution of Cr3+ and Fe3+ ions, located on sites of a mirror plane (Cs symmetry), which are responsible for the optical properties of alexandrite. The results obtained lead to the conclusion that annealing induces a modification of the population of Cr3+ on Cs sites as well as on sites located on an inversion plane (Ci). Annealing could improve the optical properties of this material, as regards its application as a tunable laser.

  15. Effect of High-Temperature Annealing on the Microstructure and Hardness of White Pig Iron

    NASA Astrophysics Data System (ADS)

    Afanas'ev, V. K.; Shcherbedinskii, G. V.; Kol'ba, A. V.; Sochnev, A. V.

    2003-03-01

    The effect of high-temperature annealing of different duration on the microstructure of alloy-free cast iron subjected to thermocycling in the molten state is studied. The variation of the hardness of the obtained white cast iron (without graphite segregations) and of the microhardness of pearlite is determined as a function of the annealing time and the cooling conditions. The influence of the modes of high-temperature annealing on the volume fraction of eutectic cementite is analyzed.

  16. Effect of annealing history on free volume in thermoplastics

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; St.clair, T. L.

    1986-01-01

    Two different types of thermoplastic glassy polymers have been investigated for the effects of thermal annealing on their free volumes. It has been observed that free volumes in glassy polymers decrease asymptotically to a steady level after about four thermal anneals lasting for 24 hours at a temperature about 50 C below their glass transition temperatures. These results indicate that composites incorporating properly annealed thermoplastic matrices may not experience any additional internal stresses due to subsequent thermal excursions experienced while in service.

  17. Annealing Effects of Parylene-Caulked Polydimethylsiloxane as a Substrate of Electrodes

    PubMed Central

    Jeong, Jinmo; Chou, Namsun; Lee, Gihyun; Kim, Sohee

    2016-01-01

    This paper investigates the effects of annealing of the electrodes based on parylene-caulked polydimethylsiloxane (pc-PDMS) in terms of mechanical strength and long-term electrical property. Previously, the electrodes based on pc-PDMS showed a better ability to withstand in vivo environments because of the low water absorption and beneficial mechanical properties of the substrate, compared to native PDMS. Moreover, annealing is expected to even strengthen the mechanical strength and lower the water absorption of the pc-PDMS substrate. To characterize the mechanical strength and water absorption of the annealed pc-PDMS, tensile tests were carried out and infrared (IR) spectra were measured using Fourier transform infrared spectroscopy over a month. The results showed that annealed pc-PDMS had higher mechanical strength and lower water absorption than non-annealed pc-PDMS. Then, electrochemical impedance spectroscopy was measured to evaluate the electrical stability of the electrodes based on annealed pc-PDMS in phosphate-buffered saline solution at 36.5 °C. The impedance magnitude of the electrodes on annealed pc-PDMS was twice higher than that of the electrodes on non-annealed pc-PDMS in the initial days, but the impedance magnitude of the electrodes based on two different substrates converged to a similar value after eight months, indicating that the annealing effects disappear after a certain period of time in a physiological environment. PMID:27999346

  18. Facile synthesis of calcium borate nanoparticles and the annealing effect on their structure and size.

    PubMed

    Erfani, Maryam; Saion, Elias; Soltani, Nayereh; Hashim, Mansor; Abdullah, Wan Saffiey B Wan; Navasery, Manizheh

    2012-11-08

    Calcium borate nanoparticles have been synthesized by a thermal treatment method via facile co-precipitation. Differences of annealing temperature and annealing time and their effects on crystal structure, particle size, size distribution and thermal stability of nanoparticles were investigated. The formation of calcium borate compound was characterized by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and Thermogravimetry (TGA). The XRD patterns revealed that the co-precipitated samples annealed at 700 °C for 3 h annealing time formed an amorphous structure and the transformation into a crystalline structure only occurred after 5 h annealing time. It was found that the samples annealed at 900 °C are mostly metaborate (CaB(2)O(4)) nanoparticles and tetraborate (CaB(4)O(7)) nanoparticles only observed at 970 °C, which was confirmed by FTIR. The TEM images indicated that with increasing the annealing time and temperature, the average particle size increases. TGA analysis confirmed the thermal stability of the annealed samples at higher temperatures.

  19. Facile Synthesis of Calcium Borate Nanoparticles and the Annealing Effect on Their Structure and Size

    PubMed Central

    Erfani, Maryam; Saion, Elias; Soltani, Nayereh; Hashim, Mansor; Wan Abdullah, Wan Saffiey B.; Navasery, Manizheh

    2012-01-01

    Calcium borate nanoparticles have been synthesized by a thermal treatment method via facile co-precipitation. Differences of annealing temperature and annealing time and their effects on crystal structure, particle size, size distribution and thermal stability of nanoparticles were investigated. The formation of calcium borate compound was characterized by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and Thermogravimetry (TGA). The XRD patterns revealed that the co-precipitated samples annealed at 700 °C for 3 h annealing time formed an amorphous structure and the transformation into a crystalline structure only occurred after 5 h annealing time. It was found that the samples annealed at 900 °C are mostly metaborate (CaB2O4) nanoparticles and tetraborate (CaB4O7) nanoparticles only observed at 970 °C, which was confirmed by FTIR. The TEM images indicated that with increasing the annealing time and temperature, the average particle size increases. TGA analysis confirmed the thermal stability of the annealed samples at higher temperatures. PMID:23203073

  20. Effect of thermal annealing on the surface properties of electrospun polymer fibers.

    PubMed

    Chen, Jiun-Tai; Chen, Wan-Ling; Fan, Ping-Wen; Yao, I-Chun

    2014-02-01

    Electrospun polymer fibers are gaining importance because of their unique properties and applications in areas such as drug delivery, catalysis, or tissue engineering. Most studies to control the morphology and properties of electrospun polymer fibers focus on changing the electrospinning conditions. The effects of post-treatment processes on the morphology and properties of electrospun polymer fibers, however, are little studied. Here, the effect of thermal annealing on the surface properties of electrospun polymer fibers is investigated. Poly(methyl methacrylate) and polystyrene fibers are fist prepared by electrospinning, followed by thermal annealing processes. Upon thermal annealing, the surface roughness of the electrospun polymer fibers decreases. The driving force of the smoothing process is the minimization of the interfacial energy between polymer fibers and air. The water contact angles of the annealed polymer fibers also decrease with the annealing time.

  1. Heavy Tails in the Distribution of Time to Solution for Classical and Quantum Annealing*

    NASA Astrophysics Data System (ADS)

    Steiger, Damian S.; Rønnow, Troels F.; Troyer, Matthias

    2015-12-01

    For many optimization algorithms the time to solution depends not only on the problem size but also on the specific problem instance and may vary by many orders of magnitude. It is then necessary to investigate the full distribution and especially its tail. Here, we analyze the distributions of annealing times for simulated annealing and simulated quantum annealing (by path integral quantum Monte Carlo simulation) for random Ising spin glass instances. We find power-law distributions with very heavy tails, corresponding to extremely hard instances, but far broader distributions—and thus worse performance for hard instances—for simulated quantum annealing than for simulated annealing. Fast, nonadiabatic, annealing schedules can improve the performance of simulated quantum annealing for very hard instances by many orders of magnitude.

  2. Heavy Tails in the Distribution of Time to Solution for Classical and Quantum Annealing.

    PubMed

    Steiger, Damian S; Rønnow, Troels F; Troyer, Matthias

    2015-12-04

    For many optimization algorithms the time to solution depends not only on the problem size but also on the specific problem instance and may vary by many orders of magnitude. It is then necessary to investigate the full distribution and especially its tail. Here, we analyze the distributions of annealing times for simulated annealing and simulated quantum annealing (by path integral quantum Monte Carlo simulation) for random Ising spin glass instances. We find power-law distributions with very heavy tails, corresponding to extremely hard instances, but far broader distributions-and thus worse performance for hard instances-for simulated quantum annealing than for simulated annealing. Fast, nonadiabatic, annealing schedules can improve the performance of simulated quantum annealing for very hard instances by many orders of magnitude.

  3. Annealing effects on microstrain of cobalt oxide nanoparticles

    SciTech Connect

    Deotale, Anjali Jain Nandedkar, R. V.; Sinha, A. K.; Singh, M. N.; Upadhyay, Anuj

    2014-04-24

    Cobalt oxide nanoparticles in different phases have been synthesized using ash supported method. The effect of isochronal annealing on micro-strain of cobalt oxide nanoparticles has been studied. The lattice strain contribution to the x-ray diffraction line broadening in the nanoparticles was analyzed using Williamson Hall (W-H) plot. It is observed that micro-strain was released at higher annealing temperature.

  4. Annealing effects on the migration of ion-implanted cadmium in glassy carbon

    NASA Astrophysics Data System (ADS)

    Hlatshwayo, T. T.; Sebitla, L. D.; Njoroge, E. G.; Mlambo, M.; Malherbe, J. B.

    2017-03-01

    The migration behaviour of cadmium (Cd) implanted into glassy carbon and the effects of annealing on radiation damage introduced by ion implantation were investigated. The glassy carbon substrates were implanted with Cd at a dose of 2 × 1016 ions/cm2 and energy of 360 keV. The implantation was performed at room temperature (RT), 430 °C and 600 °C. The RT implanted samples were isochronally annealed in vacuum at 350, 500 and 600 °C for 1 h and isothermally annealed at 350 °C up to 4 h. The as-implanted and annealed samples were characterized by Raman spectroscopy and Rutherford backscattering spectrometry (RBS). Raman results revealed that implantation at room temperature amorphized the glassy carbon structure while high temperature implantations resulted in slightly less radiation damage. Isochronal annealing of the RT implanted samples resulted in some recrystallization as a function of increasing temperature. The original glassy carbon structure was not achieved at the highest annealing temperature of 600 °C. Diffusion of Cd in glassy carbon was already taking place during implantation at 430 °C. This diffusion of Cd was accompanied by significant loss from the surface during implantation at 600 °C. Isochronal annealing of the room temperature implanted samples at 350 °C for 1 h caused Cd to diffuse towards the bulk while isothermal annealing at 500 and 600 °C resulted in the migration of implanted Cd toward the surface accompanied by a loss of Cd from the surface. Isothermal annealing at 350 °C for 1 h caused Cd to diffuse towards the bulk while for annealing time >1 h Cd diffused towards the surface. These results were interpreted in terms of trapping and de-trapping of implanted Cd by radiation damage.

  5. Effect of zinc addition and vacuum annealing time on the properties of spin-coated low-cost transparent conducting 1 at% Ga-ZnO thin films.

    PubMed

    Srivastava, Amit Kumar; Kumar, Jitendra

    2013-12-01

    Pure and 1 at% gallium (Ga)-doped zinc oxide (ZnO) thin films have been prepared with a low-cost spin coating technique on quartz substrates and annealed at 500 °C in vacuum ∼10(-3) mbar to create anion vacancies and generate charge carriers for photovoltaic application. Also, 0.5-1.5 at% extra zinc species were added in the precursor sol to investigate changes in film growth, morphology, optical absorption, electrical properties and photoluminescence. It is shown that 1 at% Ga-ZnO thin films with 0.5 at% extra zinc content after vacuum annealing for 60 min correspond to wurtzite-type hexagonal structure with (0001) preferred orientation, electrical resistivity of ∼9 × 10(-3) Ω cm and optical transparency of ∼65-90% in the visible range. Evidence has been advanced for the presence of defect levels within bandgap such as zinc vacancy (VZn), zinc interstitial (Zni), oxygen vacancy (Vo) and oxygen interstitial (Oi). Further, variation in ZnO optical bandgap occurring with Ga doping and insertion of additional zinc species has been explained by invoking two competing phenomena, namely bandgap widening and renormalization, usually observed in semiconductors with increasing carrier concentration.

  6. Effect of zinc addition and vacuum annealing time on the properties of spin-coated low-cost transparent conducting 1 at% Ga–ZnO thin films

    PubMed Central

    Srivastava, Amit Kumar; Kumar, Jitendra

    2013-01-01

    Pure and 1 at% gallium (Ga)-doped zinc oxide (ZnO) thin films have been prepared with a low-cost spin coating technique on quartz substrates and annealed at 500 °C in vacuum ∼10−3 mbar to create anion vacancies and generate charge carriers for photovoltaic application. Also, 0.5–1.5 at% extra zinc species were added in the precursor sol to investigate changes in film growth, morphology, optical absorption, electrical properties and photoluminescence. It is shown that 1 at% Ga–ZnO thin films with 0.5 at% extra zinc content after vacuum annealing for 60 min correspond to wurtzite-type hexagonal structure with (0001) preferred orientation, electrical resistivity of ∼9 × 10−3 Ω cm and optical transparency of ∼65–90% in the visible range. Evidence has been advanced for the presence of defect levels within bandgap such as zinc vacancy (VZn), zinc interstitial (Zni), oxygen vacancy (Vo) and oxygen interstitial (Oi). Further, variation in ZnO optical bandgap occurring with Ga doping and insertion of additional zinc species has been explained by invoking two competing phenomena, namely bandgap widening and renormalization, usually observed in semiconductors with increasing carrier concentration. PMID:27877622

  7. Effect of zinc addition and vacuum annealing time on the properties of spin-coated low-cost transparent conducting 1 at% Ga-ZnO thin films

    NASA Astrophysics Data System (ADS)

    Srivastava, Amit Kumar; Kumar, Jitendra

    2013-12-01

    Pure and 1 at% gallium (Ga)-doped zinc oxide (ZnO) thin films have been prepared with a low-cost spin coating technique on quartz substrates and annealed at 500 °C in vacuum ˜10-3 mbar to create anion vacancies and generate charge carriers for photovoltaic application. Also, 0.5-1.5 at% extra zinc species were added in the precursor sol to investigate changes in film growth, morphology, optical absorption, electrical properties and photoluminescence. It is shown that 1 at% Ga-ZnO thin films with 0.5 at% extra zinc content after vacuum annealing for 60 min correspond to wurtzite-type hexagonal structure with (0001) preferred orientation, electrical resistivity of ˜9 × 10-3 Ω cm and optical transparency of ˜65-90% in the visible range. Evidence has been advanced for the presence of defect levels within bandgap such as zinc vacancy (VZn), zinc interstitial (Zni), oxygen vacancy (Vo) and oxygen interstitial (Oi). Further, variation in ZnO optical bandgap occurring with Ga doping and insertion of additional zinc species has been explained by invoking two competing phenomena, namely bandgap widening and renormalization, usually observed in semiconductors with increasing carrier concentration.

  8. Thermally annealed silicon nitride films: Electrical characteristics and radiation effects

    SciTech Connect

    Stein, H.J.

    1985-03-15

    Electrical characteristics, including retention under /sup 60/Co ..gamma..-ray irradiation of MNOS (metal-nitride-oxide-semiconductor) structures with LPCVD (low-pressure chemical-vapor-deposited) silicon nitride have been investigated. Capacitance-voltage techniques were used to measure injected, retained, and equilibrium charge. Current-voltage techniques were used to measure voltage and temperature dependence of charge transport. Measurements were made on MNOS with the following nitride annealing histories: (1) as-deposited at 750 /sup 0/C, (2) 950 /sup 0/C in N/sub 2/, and (3) 950 /sup 0/C in N/sub 2/ followed by 900 /sup 0/C in H/sub 2/. Internal IR reflection techniques were used to measure chemically bonded hydrogen in the nitride films. Annealing at 950 /sup 0/C in N/sub 2/ (1) decreased the concentration of hydrogen, (2), decreased equilibrium positive charge, and (3) increased low- and high-field transport. Partial restoration of the as-deposited characteristics was achieved by subsequent annealing in H/sub 2/ at 900 /sup 0/C. Charge loss (retention) under /sup 60/Co ..gamma..-ray irradiation is essentially independent of high-temperature annealing whereas degradation is observed for net negative charge retention measured in the absence of ionizing radiation. Effects of annealing on MNOS structures and models to explain the results are discussed.

  9. Thermally annealed silicon nitride films: Electrical characteristics and radiation effects

    NASA Astrophysics Data System (ADS)

    Stein, Herman J.

    1985-03-01

    Electrical characteristics, including retention under 60Co γ-ray irradiation of MNOS (metal-nitride-oxide-semiconductor) structures with LPCVD (low-pressure chemical-vapor-deposited) silicon nitride have been investigated. Capacitance-voltage techniques were used to measure injected, retained, and equilibrium charge. Current-voltage techniques were used to measure voltage and temperature dependence of charge transport. Measurements were made on MNOS with the following nitride annealing histories: (1) as-deposited at 750 °C, (2) 950 °C in N2, and (3) 950 °C in N2 followed by 900 °C in H2. Internal IR reflection techniques were used to measure chemically bonded hydrogen in the nitride films. Annealing at 950 °C in N2 (1) decreased the concentration of hydrogen, (2), decreased equilibrium positive charge, and (3) increased low- and high-field transport. Partial restoration of the as-deposited characteristics was achieved by subsequent annealing in H2 at 900 °C. Charge loss (retention) under 60Co γ-ray irradiation is essentially independent of high-temperature annealing whereas degradation is observed for net negative charge retention measured in the absence of ionizing radiation. Effects of annealing on MNOS structures and models to explain the results are discussed.

  10. The Effect of Solution Annealing on Alloy 22 Weld Properties

    SciTech Connect

    El-Dasher, B S; Torres, S G

    2005-11-08

    The effect of solution annealing temperature on the microstructure and observed corrosion attack mode in Alloy 22 welds was assessed. Specimens were examined in the as-welded state as well as solution annealed for 20 minutes at temperatures ranging from 1075 C to 1300 C. The microstructures of the specimens were first mapped using electron backscatter diffraction to determine the grain structure evolution due to solution annealing. Full recrystallization of the fusion zone was only observed in the 1200 C and 1300 C specimens, although the 1300 C specimen showed abnormal grain growth. As-welded, 1121 C and 1200 C specimens were also subjected to electrochemical testing in a 6 molal NaCl + 0.9 molal KNO{sub 3} environment to initiate crevice corrosion. Examination of the specimen surfaces after corrosion testing showed that in the as-welded specimen, corrosion was present in both the weld dendrites as well as around the secondary phases. However, the specimen solution annealed at 1121 C showed corrosion only at secondary phases and the specimen annealed at 1200 C showed pitting corrosion only in a handful of grains.

  11. Annealing time dependence of the physical, electrical and pH response characteristics of spin coated TiO2 thin films

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Titanium dioxide (TiO2) thin film was deposited on indium tin oxide (ITO) substrate and used as sensing membrane of EGFET pH sensor. The thin film was fabricated using sol- gel spin coating method. All samples were annealed at 400 °C but the annealing time was varied. This is done to study the effects of annealing time on physical and electrical properties of titanium dioxide thin film. The sensitivity of each sample towards H+ ion was measured and result shows that sample annealed for 45 minutes has the highest sensitivity (52.6 mV/pH). It is found that increasing annealing duration will increase the pH sensitivity but a limit will be reached at certain point. Longer annealing processes done beyond this point will results in lower pH sensitivity.

  12. Magnetoimpedance effect in current annealed Co-based amorphous wires

    NASA Astrophysics Data System (ADS)

    Ghanaatshoar, M.; Tehranchi, M. M.; Mohseni, S. M.; Parhizkari, M.; Roozmeh, S. E.; Jazayeri Gharehbagh, A.

    2006-09-01

    Current-annealing of Co68.15Fe4.35Si12.5B15 amorphous wires has been studied at various vacuum orders. Structure-sensitive properties such as the electrical resistance during Joule heating treatment have been monitored to investigate the structural changes. Different driving currents have been flowed through the samples at different vacuums between 6×10-2 and 6×10-5 mbar. Regarding the giant magnetoimpedance (GMI) effect, annealing at different vacuums but with the same current can lead to various responses.

  13. Investigation of solvent annealing time dependence on morphology formation in polystyrene-block-polylactide thin films

    NASA Astrophysics Data System (ADS)

    Gnabasik, Ryan; Nelson, Gunnar; Baruth, Andrew

    2015-03-01

    Solvent vapor annealing exposes a block polymer film to the vapors of one or more solvents, swelling the film. This process increases polymer mobility and can direct a self-assembly process by tuning the surface energy. Despite its efficacy to produce well-ordered, periodic nanostructures, no standardized production scheme exists. This is primarily due to a lack of understanding the intricate role multiple, incommensurate parameters play. By analogy to thermal annealing of elemental solids, the time a thin film spends in an equilibrium solvent concentration is one factor that will dictate the degree of ordering. To elucidate, optimized annealing conditions for perpendicular cylinder forming polystyrene-block-polylactide exist at solvent concentrations just below the order-disorder transition, where the kinetic and thermal processes required for recrystallization and crystal growth are optimally fast (similar to thermal annealing). By use of a purpose-built, climate-controlled solvent annealing chamber, we map out the annealing time dependence for non-optimized solvent concentrations. Namely, at lower solvent concentrations, where mobility is limited, longer times are required for large lateral correlation lengths. In situ spectral reflectance monitors solvent concentration, regulated viaa mass-flow controlled solvent inlet, offering precision control over annealing. Atomic force microscopy, in conjunction with O2 plasma etching, provides 3-dimensional imaging of the nanoscale morphology. This work was funded by NASA Nebraska Space Grant.

  14. 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.

  15. Electrochemical capacitance of iron oxide nanotube (Fe-NT): effect of annealing atmospheres.

    PubMed

    Sarma, Biplab; Jurovitzki, Abraham L; Ray, Rupashree S; Smith, York R; Mohanty, Swomitra K; Misra, Mano

    2015-07-03

    The effect of annealing atmosphere on the supercapacitance behavior of iron oxide nanotube (Fe-NT) electrodes has been explored and reported here. Iron oxide nanotubes were synthesized on a pure iron substrate through an electrochemical anodization process in an ethylene glycol solution containing 3% H2O and 0.5 wt.% NH4F. Subsequently, the annealing of the nanotubes was carried out at 500 °C for 2 h in various gas atmospheres such as air, oxygen (O2), nitrogen (N2), and argon (Ar). The morphology and crystal phases evolved after the annealing processes were examined via field emission scanning electron microscopy, x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy. The electrochemical capacitance properties of the annealed Fe-NT electrodes were evaluated by conducting cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy tests in the Li2SO4 electrolyte. Based on these experiments, it was found that the capacitance of the Fe-NT electrodes annealed in air and O2 atmospheres shows mixed behavior comprising both the electric double layer and pseudocapacitance. However, annealing in N2 and Ar environments resulted in well-defined redox peaks in the CV profiles of the Fe-NT electrodes, which are therefore attributed to the relatively higher pseudonature of the capacitance in these electrodes. Based on the galvanostatic charge-discharge studies, the specific capacitance achieved in the Fe-NT electrode after annealing in Ar was about 300 mF cm(-2), which was about twice the value obtained for N2-annealed Fe-NTs and three times higher than those annealed in air and O2. The experiments also demonstrated excellent cycle stability for the Fe-NT electrodes with 83%-85% capacitance retention, even after many charge-discharge cycles, irrespective of the gas atmospheres used during annealing. The increase in the specific capacitance was discussed in terms of increased oxygen vacancies as a result of the

  16. Effect of dopants on annealing performance of silicon solar cells

    NASA Technical Reports Server (NTRS)

    Scott-Monck, J. A.; Anspaugh, B. E.

    1979-01-01

    The optimum annealing parameters of time and temperature for producing cell output recovery were established. Devices made from gallium doped and boron doped silicon were investigated. The cells ranged in resistivity from 0.1 to 20 ohm-cm and in thickness from 50 to 250 micrometers. The observations can be explained in a qualitative manner by postulating a pair of competing mechanisms to account for the low temperature reverse annealing seen in most boron and gallium doped silicon solar cells. Still another mechanism dominates at higher temperatures (350 C and greater) to complete this model. One of the mechanisms, defined as B, allows migrators to couple with radiation induced recombination sites thus increasing or enhancing their capture cross sections. This would tend to reduce minority carrier diffusion length. The new recombination complex is postulated to be thermally stable up to temperatures of approximately 350 C.

  17. Effect of post-deposition annealing on the growth and properties of cubic SnS films

    NASA Astrophysics Data System (ADS)

    Chalapathi, U.; Poornaprakash, B.; Park, Si-Hyun

    2017-03-01

    We report a detailed investigation of the effect of post-deposition annealing on the growth and physical properties of chemically grown cubic SnS films. Chemically deposited cubic SnS films were subjected to annealing in a graphite box with loaded elemental sulfur under N2 at 150-350 °C for 10, 30, and 60 min in order to understand the grain growth and morphology of the films. Films annealed at 150-250 °C for 10 min showed improved grain size and a more uniform grain morphology. Films annealed at 150-250 °C for 30 and 60 min showed a decrease in the grain size and non-uniform grain morphology for the cubic SnS phase. Films annealed at 300 and 350 °C for 10 min revealed the formation of minor secondary phase SnS2, and the grain morphology changed from round shape to flake-like. Longer annealing at 300 and 350 °C improved the extent of the SnS2 phase, and it was found to be the dominant phase after annealing at 350 °C for 60 min. The direct optical band gap of SnS films is 1.75-1.67 eV, depending on the annealing temperature and time. The films exhibited p-type electrical conductivity. The films annealed at 250 °C for 10 min showed a higher hole mobility of 77.7 cm2V-1s-1. Thus, lower annealing temperatures and shorter annealing times are favorable conditions to produce high-quality cubic SnS films.

  18. Forecasting nonlinear chaotic time series with function expression method based on an improved genetic-simulated annealing algorithm.

    PubMed

    Wang, Jun; Zhou, Bi-hua; Zhou, Shu-dao; Sheng, Zheng

    2015-01-01

    The paper proposes a novel function expression method to forecast chaotic time series, using an improved genetic-simulated annealing (IGSA) algorithm to establish the optimum function expression that describes the behavior of time series. In order to deal with the weakness associated with the genetic algorithm, the proposed algorithm incorporates the simulated annealing operation which has the strong local search ability into the genetic algorithm to enhance the performance of optimization; besides, the fitness function and genetic operators are also improved. Finally, the method is applied to the chaotic time series of Quadratic and Rossler maps for validation. The effect of noise in the chaotic time series is also studied numerically. The numerical results verify that the method can forecast chaotic time series with high precision and effectiveness, and the forecasting precision with certain noise is also satisfactory. It can be concluded that the IGSA algorithm is energy-efficient and superior.

  19. Interrogating the Effects of Radiation Damage Annealing on Helium Diffusion Kinetics in Apatite

    NASA Astrophysics Data System (ADS)

    Willett, C. D.; Fox, M.; Shuster, D. L.

    2015-12-01

    Apatite (U-Th)/He thermochronology is commonly used to study landscape evolution and potential links between climate, erosion and tectonics. The technique relies on a quantitative understanding of (i) helium diffusion kinetics in apatite, (ii) an evolving 4He concentration, (iii) accumulating damage to the crystal lattice caused by radioactive decay[1], and (iv) the thermal annealing of such damage[2],[3], which are each functions of both time and temperature. Uncertainty in existing models of helium diffusion kinetics has resulted in conflicting conclusions, especially in settings involving burial heating through geologic time. The effects of alpha recoil damage annealing are currently assumed to follow the kinetics of fission track annealing (e.g., reference [3]), although this assumption is difficult to fully validate. Here, we present results of modeling exercises and a suite of experiments designed to interrogate the effects of damage annealing on He diffusivity in apatite that are independent of empirical calibrations of fission track annealing. We use the existing experimental results for Durango apatite[2] to develop and calibrate a new function that predicts the effects of annealing temperature and duration on measured diffusivity. We also present a suite of experiments conducted on apatite from Sierra Nevada, CA granite to establish whether apatites with different chemical compositions have the same behavior as Durango apatite. Crystals were heated under vacuum to temperatures between 250 and 500°C for 1, 10, or 100 hours. The samples were then irradiated with ~220 MeV protons to produce spallogenic 3He, the diffusant then used in step-heating diffusion experiments. We compare the results of these experiments and model calibrations to existing models. Citations: [1]Shuster, D., Flowers R., and Farley K., (2006), EPSL 249(3-4), 148-161; [2]Shuster, D. and Farley, K., (2009), GCA 73 (1), 6183-6196; [3]Flowers, R., Ketcham, R., Shuster, D. and Farley, K

  20. Effect of Post-HALT Annealing on Leakage Currents in Solid Tantalum Capacitors

    NASA Technical Reports Server (NTRS)

    Teverovsky, Alexander

    2010-01-01

    Degradation of leakage currents is often observed during life testing of tantalum capacitors and is sometimes attributed to the field-induced crystallization in amorphous anodic tantalum pentoxide dielectrics. However, degradation of leakage currents and the possibility of annealing of degraded capacitors have not been investigated yet. In this work the effect of annealing after highly accelerated life testing (HALT) on leakage currents in various types of solid tantalum capacitors was analyzed. Variations of leakage currents with time during annealing at temperatures from 125 oC to 180 oC, thermally stimulated depolarization (TSD) currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. Annealing resulted in a gradual decrease of leakage currents and restored their initial values. Repeat HALT after annealing resulted in reproducible degradation of leakage currents. The observed results are explained based on ionic charge instability (drift/diffusion of oxygen vacancies) in the tantalum pentoxide dielectrics using a modified Schottky conduction mechanism.

  1. Linear and nonlinear optical response of bismuth and antimony implanted fused silica: annealing effects

    NASA Astrophysics Data System (ADS)

    Pan, Z.; Morgan, S. H.; Henderson, D. O.; Park, S. Y.; Weeks, R. A.; Magruder, R. H.; Zuhr, R. A.

    1995-10-01

    We report the linear and nonlinear optical response of bismuth and antimony implanted fused silica with doses of 6 × 10 16 ions/cm 2. The nonlinear refractive index, n2, was measured using a Z-scan technique with a mode locked Ti:sapphire laser operating in 140 fs pulse duration at 770 nm wavelength. It is found that the nonlinear refractive index n2 of as-implanted samples is large, in the order of 10 -10 cm 2/W and the n2 value of Bi as-implanted sample is about 2.4 times lager than that of Sb as-implanted sample. The large n2 response is attributed to the presence of nanosized metal particles in the implanted layer observed by transmission electron microscopy. We also report the changes of linear and nonlinear optical response when implanted samples were subsequently annealed at temperatures from 500 to 1000 C in argon and oxygen atmospheres. The annealing effect on optical properties is found to be strongly dependent on the annealing atmospheres. Our results indicate that annealing treatment in O 2 affects the local environment of the implanted metal ions and hence the linear and nonlinear optical properties of the metal-dielectric composite. We suggest that a new phase of metal-oxygen-silicate was formed during annealing in O 2 atmosphere.

  2. Annealing effects on electrical behavior of gold nanoparticle film: Conversion of ohmic to non-ohmic conductivity

    NASA Astrophysics Data System (ADS)

    Ebrahimpour, Zeinab; Mansour, Nastaran

    2017-02-01

    This paper reports on the electrical behavior of self-assembled gold nanoparticle films before and after high-temperature annealing in ambient environment. These films are made by depositing gold nanoparticles from a colloidal solution on glass substrates using centrifuge deposition technique. The current-voltage (I-V) characteristics of these films exhibits ohmic and non-ohmic properties for un-annealed and annealed films respectively. As the annealing time duration increases, the onset of non-ohmic behavior occurs at higher voltages. To understand the underlying mechanisms for the observed electrical conduction behavior in these films and how electrical conduction is effected by film morphology and structural properties before and after annealing, systematic comparative studies based on scanning electron microscopy (SEM), UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) have been performed. The morphology of the films shows that the assembled gold nanoparticles are distributed on the substrate in a random way before annealing. After 2 h annealing gold nanoparticles exhibit a higher filling fraction when examined by SEM, which means that they coalesce, upon annealing, with respect to un-annealed films. The UV-vis absorption spectra of the films show that there is a red-shift and broadening in the absorption band for the annealed films. The observed phenomenon is related to the plasmon near-field coupling effect and suggests that the nanoparticle ensembles interspacing has decreased. The structural and crystallinity of the films exhibit amorphous structure before annealing and pure crystalline phases with a preferential growth direction along the (111) plane after annealing. The XPS analysis further suggests the existence of the stable thin oxide layer in the phase of Au2O3 in the annealed films. The I-V characteristics have been described by Simmons' model for tunnel transport through metal-insulator-metal (MIM) junctions. The Fowler

  3. An Effect of Annealing on Shielding Properties of Shungite

    NASA Astrophysics Data System (ADS)

    Belousova, E. S.; Mahmoud, M. Sh.; Lynkou, L. M.

    2013-05-01

    Annealing of shungite is studied in oxidizing conditions in a chamber with NH4Cl, and in vacuum at 900 °C for 2h. Frequency dependencies of transmission and reflection coefficients of annealed shungite are measured in the frequency range of 8-12 GHz. The minimum reflection at 8-10 GHz was shown for shungite annealed in the oxidizing atmosphere.

  4. Variation of the viscosity of molten potassium niobate with annealing time

    NASA Astrophysics Data System (ADS)

    Hong, Xinguo; Chen, Yufeng

    1996-07-01

    Using the double-wire torsion pendulum method, we have measured the viscosity of a potassium niobate molten system with excess K 2O from 50 to 56 mol% at temperatures up to 1190°C in air. Both the viscosity and its activation energy show strong time dependence. While the values for viscosity increase for melts with 50 and 51 mol% K 2O, which are annealed at 1150°C in air, the viscosity, however, of the melt with more than 2 mol% excess K 2O shows a completely different time dependence, i.e. drastic decrease with annealing time. A similar striking reversed variation of temperature-dependent viscosity with annealing time is observed when the K 2O content in the melt is up to 52 mol%. These anomalous variations in viscosity give clear evidence why the KNbO 3 single crystal should be grown from mother melts with excess K 2O above 51 mol%, and after being annealed for a long time. This result also confirms that the double-wire torsion pendulum method is a useful tool to study the time-dependent viscosity of melts at high temperature in air.

  5. Time evolution of sigma 3 annealing twins in secondary recrystallized nickel.

    PubMed

    Booth, M; Randle, V; Owen, G

    2005-02-01

    Samples of commercially pure nickel have been annealed in air at 0.68T(m) (900 degrees C) for 1, 2 and 3 h in order to study the relationship between the grain growth characteristics and grain boundary misorientation, particularly annealing twins (Sigma 3). Orientation mapping by electron backscatter diffraction was used to obtain the experimental data. Anomalous grain growth was observed in commercially pure nickel after each of the anneals. The main findings are as follows. The texture was mainly {100}<001> and {112}<111> and it was more pronounced in coarse-grained areas than in fine-grained areas. The length fraction of Sigma 3s (annealing twins) increased with annealing time and therefore with the level of anomalous grain growth. Two to three twins per grain were sited in coarse-grained regions whereas less than one twin per grain was sited in fine-grained regions. It is suggested that the nucleation and growth of twinning is mechanistically linked to anomalous grain growth.

  6. Annealing effect on Sb2S3-TiO2 nanostructures for solar cell applications

    PubMed Central

    2013-01-01

    Nanostructures composited of vertical rutile TiO2 nanorod arrays and Sb2S3 nanoparticles were prepared on an F:SnO2 conductive glass by hydrothermal method and successive ionic layer adsorption and reaction method at low temperature. Sb2S3-sensitized TiO2 nanorod solar cells were assembled using the Sb2S3-TiO2 nanostructure as the photoanode and a polysulfide solution as an electrolyte. Annealing effects on the optical and photovoltaic properties of Sb2S3-TiO2 nanostructure were studied systematically. As the annealing temperatures increased, a regular red shift of the bandgap of Sb2S3 nanoparticles was observed, where the bandgap decreased from 2.25 to 1.73 eV. At the same time, the photovoltaic conversion efficiency for the nanostructured solar cells increased from 0.46% up to 1.47% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by the annealing treatment. PMID:23421351

  7. Asymptotics in Time, Temperature and Size for Optimization by Simulated Annealing: Theory, Practice and Applications

    DTIC Science & Technology

    1990-01-19

    and studying the growth of this bound as the tem- perature approaches zero asymptotically. Simulated annealing with a time varying temperature gives...rise to a time inhomogeneous Markov chain. This Markov chain is difficult to analyze and study due to the time-inhomogeneity. We have been able to...problem. Moreover, we can study the growth of this bound as the temperature approaches zero or skewness becomes arbitrarily large; thereby, providing

  8. INVESTIGATING ANNEALING EFFECT ON OPTICAL PROPERTIES OF Cd0.8Zn0.2S THIN FILMS

    NASA Astrophysics Data System (ADS)

    Azizi, Somayeh; Dizaji, Hamid Rezagholipour; Ehsani, Mohammad Hossein; Mirmahalle, Seyed Feyzolah Ghavami

    2014-08-01

    Cd0.8Zn0.2S thin films deposited on glass substrates by thermal evaporation method were annealed at different temperatures for the first time in order to investigate annealing effect on optical properties. The compositional, structural of nanoparticles precursor synthesized using microwave irradiation method and optical properties of the films were studied using energy dispersive X-ray (EDX), X-ray diffraction, transmission electron microscopy (TEM), and UV-visible spectrophotometer techniques. The annealed films were found to have hexagonal Wurtzite structure with strong preferential orientation along the (002) diffraction peak. Important optical parameters such as extinction coefficient and refractive index revealed the effect of heat treatment on the deposited thin layers. A reduction in the band gap energy from 2.41 eV to 2.29 eV was observed for the annealed samples.

  9. Effect of annealing at different time intervals on the structure, morphology and luminescent properties of MgAl2O4:0.3% In3+ nanophosphor prepared by citrate sol-gel method

    NASA Astrophysics Data System (ADS)

    Melato, L. T.; Motaung, T. E.; Ntwaeaborwa, O. M.; Motloung, S. V.

    2017-04-01

    Indium-doped magnesium aluminate (MgAl2O4:03% In3+) spinel powders were prepared by citrate sol-gel method. The effect of annealing period (AP) at a fixed annealing temperature (800 °C) and dopant concentration (0.3% In3+) on the structure, particle morphology and photoluminescent properties of the powders were investigated. The X-ray powder diffraction (XRD) results showed that the crystalline quality and crystallite sizes of the powders were influenced by the AP. Doping with 0.3% In3+ did not influence the major crystal structure of the MgAl2O4 (host) material. The scanning electron microscope (SEM) image suggested that the AP influences the particle morphology of the nanophosphor. Transmission electron microscopy (TEM) image suggested that the crystallites sizes were in the region of 10 nm. The Photoluminescence (PL) results showed that the violet emission at 388 nm and green emission at 560 nm both originated from the host material and there was no evidence of any emission from the dopant (In3+). Increasing the AP up to 2 h lead to luminescence enhancement, while further increase in AP lead to luminescence quenching. The Commision Internationale de l'Eclairage (CIE) co-ordinates results showed that the emission colour of all samples was in the blue region and it was not tuned by varying the AP.

  10. Effects of gamma-irradiation and air annealing on Yb-doped Y3Al5O12 single crystal.

    PubMed

    Zeng, Xionghui; Xu, Xiaodong; Wang, Xiaodan; Zhao, Zhiwei; Zhao, Guangjun; Xu, Jun

    2008-03-01

    The effects of gamma-irradiation on the air-annealed 10at.% Yb:Y(3)Al(5)O(12) (YAG) and air annealing on the gamma-irradiated 10at.% Yb:YAG have been studied by the difference absorption spectra before and after treatment. The gamma-irradiation and air annealing led to opposite changes of the absorption properties of the Yb:YAG crystal. After air annealing, the gamma-irradiation induced centers were totally removed and the concentration of Fe(3+) and Yb(3+) were lightly increased. For the first time, the gamma-irradiation induced valence changes between Yb(3+) and Yb(2+) ions in Yb:YAG crystals have been observed.

  11. [Effects of different annealing conditions on the photoluminescence of nanoporous alumina film].

    PubMed

    Xie, Ning; Ma, Kai-Di; Shen, Yi-Fan; Wang, Qian

    2013-12-01

    effects of different annealing conditions on the photoluminescence of nanoporous alumina film are reasonably explained.

  12. Theory of quantum annealing of an Ising spin glass.

    PubMed

    Santoro, Giuseppe E; Martonák, Roman; Tosatti, Erio; Car, Roberto

    2002-03-29

    Probing the lowest energy configuration of a complex system by quantum annealing was recently found to be more effective than its classical, thermal counterpart. By comparing classical and quantum Monte Carlo annealing protocols on the two-dimensional random Ising model (a prototype spin glass), we confirm the superiority of quantum annealing relative to classical annealing. We also propose a theory of quantum annealing based on a cascade of Landau-Zener tunneling events. For both classical and quantum annealing, the residual energy after annealing is inversely proportional to a power of the logarithm of the annealing time, but the quantum case has a larger power that makes it faster.

  13. The effect of size on the strength of FCC metals at elevated temperatures: annealed copper.

    PubMed

    Wheeler, Jeffrey M; Kirchlechner, Christoph; Micha, Jean-Sébastien; Michler, Johann; Kiener, Daniel

    2016-12-01

    As the length scale of sample dimensions is reduced to the micron and sub-micron scales, the strength of various materials has been observed to increase with decreasing size, a fact commonly referred to as the 'sample size effect'. In this work, the influence of temperature on the sample size effect in copper is investigated using in situ microcompression testing at 25, 200 and 400 °C in the SEM on vacuum-annealed copper structures, and the resulting deformed structures were analysed using X-ray μLaue diffraction and scanning electron microscopy. For pillars with sizes between 0.4 and 4 μm, the size effect was measured to be constant with temperature, within the measurement precision, up to half of the melting point of copper. It is expected that the size effect will remain constant with temperature until diffusion-controlled dislocation motion becomes significant at higher temperatures and/or lower strain rates. Furthermore, the annealing treatment of the copper micropillars produced structures which yielded at stresses three times greater than their un-annealed, FIB-machined counterparts.

  14. Effect of annealing on the laser induced damage of polished and CO2 laser-processed fused silica surfaces

    NASA Astrophysics Data System (ADS)

    Doualle, T.; Gallais, L.; Cormont, P.; Donval, T.; Lamaignère, L.; Rullier, J. L.

    2016-06-01

    We investigate the effect of different heat treatments on the laser-induced damage probabilities of fused silica samples. Isothermal annealing in a furnace is applied, with different temperatures in the range 700-1100 °C and 12 h annealing time, to super-polished fused silica samples. The surface flatness and laser damage probabilities at 3 ns, 351 nm are measured before and after the different annealing procedures. We have found a significant improvement of the initial laser damage probabilities of the silica surface after annealing at 1050 °C for 12 h. A similar study has been conducted on CO2 laser-processed sites on the surface of the samples. Before and after annealing, we have studied the morphology of the sites, the evolution of residual stress, and the laser-induced damage threshold measured at 351 nm, 3 ns. In this case, we observe that the laser damage resistance of the laser created craters can reach the damage level of the bare fused silica surface after the annealing process, with a complete stress relieve. The obtained results are then compared to the case of local annealing process by CO2 laser irradiation during 1 s, and we found similar improvements in both cases. The different results obtained in the study are compared to numerical simulations made with a thermo-mechanical model based on finite-element method that allows the simulation of the isothermal or the local annealing process, the evolution of stress and fictive temperature. The simulation results were found to be very consistent with experimental observations for the stresses evolution after annealing and estimation of the heat affected area during laser-processing based on the density dependence with fictive temperature. Following this work, the temperature for local annealing should reach 1330-1470 °C for an optimized reduction of damage probability and be below the threshold for material removal, whereas furnace annealing should be kept below the annealing point to avoid sample

  15. The effect of size on the strength of FCC metals at elevated temperatures: annealed copper

    PubMed Central

    Wheeler, Jeffrey M.; Kirchlechner, Christoph; Micha, Jean-Sébastien; Michler, Johann; Kiener, Daniel

    2016-01-01

    Abstract As the length scale of sample dimensions is reduced to the micron and sub-micron scales, the strength of various materials has been observed to increase with decreasing size, a fact commonly referred to as the ‘sample size effect’. In this work, the influence of temperature on the sample size effect in copper is investigated using in situ microcompression testing at 25, 200 and 400 °C in the SEM on vacuum-annealed copper structures, and the resulting deformed structures were analysed using X-ray μLaue diffraction and scanning electron microscopy. For pillars with sizes between 0.4 and 4 μm, the size effect was measured to be constant with temperature, within the measurement precision, up to half of the melting point of copper. It is expected that the size effect will remain constant with temperature until diffusion-controlled dislocation motion becomes significant at higher temperatures and/or lower strain rates. Furthermore, the annealing treatment of the copper micropillars produced structures which yielded at stresses three times greater than their un-annealed, FIB-machined counterparts. PMID:28003795

  16. 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.

  17. Effect of thermal annealing on properties of polycrystalline ZnO thin films

    NASA Astrophysics Data System (ADS)

    Gritsenko, L. V.; Abdullin, Kh. A.; Gabdullin, M. T.; Kalkozova, Zh. K.; Kumekov, S. E.; Mukash, Zh. O.; Sazonov, A. Yu.; Terukov, E. I.

    2017-01-01

    Electrical properties (density, carriers mobility, resistivity), optical absorption and photoluminescence spectra of ZnO, grown by MOCVD and hydrothermal methods, have been investigated depending on the annealing and treatment modes in a hydrogen plasma. It has been shown that the electrical and photoluminescent (PL) properties of ZnO are strongly dependent on gas atmosphere during annealing. The annealing in oxygen atmosphere causes a sharp drop of carrier mobility and films conductivity due to the absorption of oxygen on grain boundaries. The process of ZnO electrical properties recovery by the thermal annealing in inert atmosphere (nitrogen), in oil (2×10-2 mbar) and oil-free (1×10-5 mbar) vacuum has been investigated. The hydrogen plasma treatment influence on the intensity of near-band-gap emission (NBE) has been studied. The effect of annealing and subsequent plasma treatment on PL intensity depends on the gas atmosphere of preliminary thermal annealing.

  18. Effect of annealing on the magnetic tunnel junction with Co/Pt perpendicular anisotropy ferromagnetic multilayers

    NASA Astrophysics Data System (ADS)

    Wang, Yi.; Wang, W. X.; Wei, H. X.; Zhang, B. S.; Zhan, W. S.; Han, X. F.

    2010-05-01

    Perpendicular magnetic tunnel junctions (pMTJs) with tunneling magnetoresistance (TMR) as high as 14.7% at room temperature were fabricated. The continuous film and pMTJs with Co/Pt multilayer magnetic electrodes and AlOx tunnel barrier were annealed at different temperatures and the effect of annealing on their properties was investigated. The hysteresis loops and X-ray reflectivity measurement show that the interdiffusion of Co and Pt atoms is slight when annealed below 523 K. However, the patterned magnetic tunnel junction gets TMR ratio from 12.3% to the maximum value of 14.7% after annealing at 483 K for 1 h.

  19. Uniform annealing effect of electron irradiation on ferromagnetic GaMnAs thin films

    NASA Astrophysics Data System (ADS)

    Luo, Jia; Xiang, Gang; Gu, Gangxu; Zhang, Xi; Wang, Hailong; Zhao, Jianhua

    2017-01-01

    For more than a decade, researchers have been searching for means to improve the Curie temperature of ferromagnetic GaMnAs samples, among which post-growth annealing in furnace has been treated as the most important one. In this work, we demonstrate that the Curie temperature can be improved by electron irradiation for the first time. Different doses of electron irradiation (1 × 1014, 1 × 1015 and 1 × 1016 electrons/cm2) at 1.7 MeV were applied, the enhancement of magnetic and electrical properties of ferromagnetic GaMnAs films was experimentally confirmed by HR-XRD, SQUID and Magneto-transport measurements. Further SIMS characterizations and analyses reveal that electron irradiation causes bi-directional out-diffusion and redistribution of compensating Mn interstitials towards both the upper surface and the lower interface, a newly found uniform effect clearly different from that of conventional post-growth annealing. The technique of electron irradiation annealing may provide an alternative way to improve the properties of electronic and magnetic compounds such as GaMnAs films.

  20. Effects of different annealing atmospheres on the properties of cadmium sulfide thin films

    SciTech Connect

    Yücel, E.; Kahraman, S.; Güder, H.S.

    2015-08-15

    Graphical abstract: The effects of different annealing atmospheres (air and sulfur) on the structural, morphological and optical properties of CdS thin films were studied at three different pH values. - Highlights: • Compactness and smoothness of the films were enhanced after sulfur annealing. • Micro-strain values of some films were improved after sulfur annealing. • Dislocation density values of some films were improved after sulfur annealing. • Band gap values of the films were improved after sulfur annealing. - Abstract: Cadmium sulfide (CdS) thin films were prepared on glass substrates by using chemical bath deposition (CBD) technique. The effects of different annealing atmospheres (air and sulfur) on the structural, morphological and optical properties of CdS thin films were studied at three different pH values. Compactness and smoothness of the films (especially for pH 10.5 and 11) enhanced after sulfur annealing. pH value of the precursor solution remarkably affected the roughness, uniformity and particle sizes of the films. Based on the analysis of X-ray diffraction (XRD) patterns of the films, micro-strain and dislocation density values of the sulfur-annealed films (pH 10.5 and 11) were found to be lower than those of air-annealed films. Air-annealed films (pH 10.5, 11 and 11.5) exhibited higher transmittance than sulfur-annealed films in the wavelength region of 550–800 nm. Optical band gap values of the films were found between 2.31 eV and 2.36 eV.

  1. 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

  2. Effect of Annealing on the Thermoluminescence Properties of ZnO Nanophosphor

    NASA Astrophysics Data System (ADS)

    Kalita, J. M.; Wary, G.

    2017-02-01

    We report the effect of annealing on the thermoluminescence (TL) properties of zinc oxide (ZnO) nanophosphor. The sample was synthesised by a wet chemical process. The characterisation report shows that the size of the grains is within 123.0 nm-160.5 nm. TL measured at 2 K/s from a fresh un-annealed sample irradiated to 60 mGy shows a composite glow curve containing three peaks at 353.2 K, 429.1 K, and 455.3 K. On the other hand, samples annealed at 473 K and 573 K followed by irradiation to 60 mGy do not give TL. However, annealing at 673 K and 773 K followed by irradiation to the same dose produces a glow curve comprising two overlapping peaks at 352.3 K and 370.6 K. In the TL emission spectrum of un-annealed sample, two emission peaks were found in green ( 523 nm) and orange ( 620 nm) regions whereas in annealed samples, only a peak was found in the orange region ( 618 nm). Kinetic analysis shows that the activation energy corresponding to TL peaks at 353.2 K, 429.1 K, and 455.3 K of the un-annealed sample are 0.64 eV, 0.80 eV, and 1.20 eV whereas that of the peaks at 352.3 K and 370.6 K of 673 K and 773 K annealed samples are 0.64 eV and 0.70 eV, respectively. All peaks of un-annealed and annealed samples, except the one at 429.1 K of the un-annealed sample, follow first-order kinetics whereas the peak at 429.1 K follows second-order kinetics. Considering the kinetic and spectral features, an energy band model for ZnO nanophosphor has been proposed.

  3. The effects of annealing on mechanical, chemical, and physical properties and structural stability of Parylene C.

    PubMed

    von Metzen, Rene Patrick; Stieglitz, Thomas

    2013-10-01

    Parylene C is one of the established encapsulation polymers for chronic implants. We investigated the influence of annealing Parylene C on its mechanical properties, chemical structure, and on the stability of Parylene C - platinum - Parylene C sandwich structures as a model of flexible neural interfaces in 0.9 % saline solution. Films of Parylene C were annealed at 200 °C, 300 °C, 350 °C, and 400 °C in nitrogen atmosphere. Temperatures of 350 °C and higher as well as annealing in air destroyed the Parylene C layers; films annealed at lower temperatures showed identical infrared spectra. Higher anneal temperatures produced increased values of elongation at break, tensile and yield strength, and yield strain while at the same time Young's modulus was shown to decrease. Crystallinity increased with annealing temperature. The structural stability of sandwich structures benefitted remarkably from annealing. Sandwich structures annealed at 300 °C maintained their structural integrity during 320 days in saline solution at 37 °C and the insulation capability stayed consistently high.

  4. Effect of Annealing Treatment on Mechanical Properties of Nanocrystalline α-iron: an Atomistic Study

    PubMed Central

    Tong, Xuhang; Zhang, Hao; Li, D. Y.

    2015-01-01

    Claims are often found in the literature that metallic materials can be nanocrystallized by severe plastic deformation (SPD). However, SPD does not generate a well-defined nanocrystalline (NC) material, which can be achieved by subsequent annealing/recovery treatment. In this study, molecular dynamics (MD) simulation is employed to study the effect of annealing on structure and mechanical properties of cyclic deformed NC α-iron, which simulates SPD-processed α-iron. It is demonstrated that grain boundaries in the deformed NC α-iron evolve to a more equilibrium state during annealing, eliminating or minimizing the residual stress. The annealing treatment increases the system's strength by reducing dislocation emission sources, and improves material ductility through strengthening grain boundaries' resistance to intergranular cracks. The results indicate that the annealing treatment is an essential process for obtaining a well-defined NC structure with superior mechanical properties. PMID:25675978

  5. Effect of Annealing on the Properties of Vanadium Pentoxide Films Prepared by Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Liu, Yaqiang; Du, Xuelian; Liu, Xueqin

    2014-03-01

    The vanadium pentoxide (V2O5) films were obtained by using sol-gel procedure and then were annealed at different temperature in air. The effect of different annealing temperatures on the composition, the microstructure, the surface morphology and the optical properties of the films were characterized by methods such as by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and spectral transmittance. The results revealed that the film annealed at 150°C has amorphous structure and dense with a smooth surface and the films annealed at 300°C and 450°C have a polycrystalline V2O5 structure with preferred growth orientation along (001) planes, the c-axis and perpendicular to the silicon substrate surface. From the spectral transmittance we determined the absorption edge using the Tauc plot. The results indicated that optical bandgap of V2O5 thin films decreased with annealing temperature.

  6. Effect of Annealing Treatment on Mechanical Properties of Nanocrystalline α-iron: an Atomistic Study

    NASA Astrophysics Data System (ADS)

    Tong, Xuhang; Zhang, Hao; Li, D. Y.

    2015-02-01

    Claims are often found in the literature that metallic materials can be nanocrystallized by severe plastic deformation (SPD). However, SPD does not generate a well-defined nanocrystalline (NC) material, which can be achieved by subsequent annealing/recovery treatment. In this study, molecular dynamics (MD) simulation is employed to study the effect of annealing on structure and mechanical properties of cyclic deformed NC α-iron, which simulates SPD-processed α-iron. It is demonstrated that grain boundaries in the deformed NC α-iron evolve to a more equilibrium state during annealing, eliminating or minimizing the residual stress. The annealing treatment increases the system's strength by reducing dislocation emission sources, and improves material ductility through strengthening grain boundaries' resistance to intergranular cracks. The results indicate that the annealing treatment is an essential process for obtaining a well-defined NC structure with superior mechanical properties.

  7. Effect of annealing treatment on mechanical properties of nanocrystalline α-iron: an atomistic study.

    PubMed

    Tong, Xuhang; Zhang, Hao; Li, D Y

    2015-02-13

    Claims are often found in the literature that metallic materials can be nanocrystallized by severe plastic deformation (SPD). However, SPD does not generate a well-defined nanocrystalline (NC) material, which can be achieved by subsequent annealing/recovery treatment. In this study, molecular dynamics (MD) simulation is employed to study the effect of annealing on structure and mechanical properties of cyclic deformed NC α-iron, which simulates SPD-processed α-iron. It is demonstrated that grain boundaries in the deformed NC α-iron evolve to a more equilibrium state during annealing, eliminating or minimizing the residual stress. The annealing treatment increases the system's strength by reducing dislocation emission sources, and improves material ductility through strengthening grain boundaries' resistance to intergranular cracks. The results indicate that the annealing treatment is an essential process for obtaining a well-defined NC structure with superior mechanical properties.

  8. Real-time shape evolution of nanoimprinted polymer structures during thermal annealing.

    PubMed

    Jones, Ronald L; Hu, Tengjiao; Soles, Christopher L; Lin, Eric K; Reano, Ronald M; Pang, Stella W; Casa, Diego M

    2006-08-01

    The real-time shape evolution of nanoimprinted polymer patterns is measured as a function of annealing time and temperature using critical dimension small-angle X-ray scattering (CD-SAXS). Periodicity, line width, line height, and sidewall angle are reported with nanometer resolution for parallel line/space patterns in poly(methyl methacrylate) (PMMA) both below and above the bulk glass transition temperature (T(G)). Heating these patterns below T(G) does not produce significant thermal expansion, at least to within the resolution of the measurement. However, above T(G) the fast rate of loss in pattern size at early times transitions to a reduced rate in longer time regimes. The time-dependent rate of polymer flow from the pattern into the underlying layer, termed pattern "melting", is consistent with a model of elastic recovery from stresses induced by the molding process.

  9. Effect of Pre-annealing on Sintering of Stainless Steel Fiber Felt

    NASA Astrophysics Data System (ADS)

    Tang, H. P.; Ma, J.; Wang, J. Z.; Li, C. L.

    2017-01-01

    Stainless steel fiber felt is a class of unique porous metal materials. This study investigates the effect of pre-annealing on the sintering of stainless steel fiber felt through quantitative characterization of sintered joints based on synchrotron radiation experiments. The sintered joint size was found to follow a marked normal distribution in fiber felt samples sintered with and without pre-annealing. However, pre-annealing prior to sintering led to a significant reduction in the total number of sintered joints as well as a reduction in the percentage of large sintered joints. Consequently, fiber felt samples sintered with pre-annealing achieved less than half the tensile strength of those sintered without pre-annealing. Delamination through fracture of sintered joints was pronounced in fiber felt samples sintered with pre-annealing, while failure occurred mainly through fracture of individual fibers in those sintered without pre-annealing. It was concluded that sintering without pre-annealing is necessary for the fabrication of high-strength fiber felt products and the reasons are briefly discussed.

  10. Effects of annealing on the coercivity of Sm(Co,Fe,Cu,Zr)z ribbons and its temperature dependence

    NASA Astrophysics Data System (ADS)

    Rong, Chuan-bing; Zhang, Hong-wei; Chen, Ren-jie; Shen, Bao-gen; He, Shu-li; Liu, J. Ping

    2006-02-01

    Sm(CobalFe0.1CuxZr0.03)7 (x = 0.0-0.25) ribbons have been prepared by melt spinning. The effects of annealing parameters on coercivity and its temperature dependence have been studied systematically. It is found that the melt-spinning technique remarkably improves the magnetic properties and simplifies the annealing process. The high-performance precipitation-hardened magnets can be obtained by only short-time ageing and slow cooling from 850 to 400 °C, without the standard solid solution. More interestingly, the temperature coefficient of coercivity of the ribbons can be tuned through adjustments of the processing parameters.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  12. Effect of irradiation and thermal annealing on quartz materials luminescence

    NASA Astrophysics Data System (ADS)

    Korovkin, M. V.; Ananyeva, L. G.

    2017-01-01

    X-ray and gamma-quanta irradiation of radiation-resistant quartz materials including natural and synthetic quartz crystals and high-purity quartzite causes the luminescence in the ultraviolet range (365 nm), thermally stimulated luminescence and radiofrequency electromagnetic emission. Preliminary radiation and thermal annealing improves luminescence properties of quartz materials.

  13. Handling time-expensive global optimization problems through the surrogate-enhanced evolutionary annealing-simplex algorithm

    NASA Astrophysics Data System (ADS)

    Tsoukalas, Ioannis; Kossieris, Panagiotis; Efstratiadis, Andreas; Makropoulos, Christos

    2015-04-01

    In water resources optimization problems, the calculation of the objective function usually presumes to first run a simulation model and then evaluate its outputs. In several cases, however, long simulation times may pose significant barriers to the optimization procedure. Often, to obtain a solution within a reasonable time, the user has to substantially restrict the allowable number of function evaluations, thus terminating the search much earlier than required by the problem's complexity. A promising novel strategy to address these shortcomings is the use of surrogate modelling techniques within global optimization algorithms. Here we introduce the Surrogate-Enhanced Evolutionary Annealing-Simplex (SE-EAS) algorithm that couples the strengths of surrogate modelling with the effectiveness and efficiency of the EAS method. The algorithm combines three different optimization approaches (evolutionary search, simulated annealing and the downhill simplex search scheme), in which key decisions are partially guided by numerical approximations of the objective function. The performance of the proposed algorithm is benchmarked against other surrogate-assisted algorithms, in both theoretical and practical applications (i.e. test functions and hydrological calibration problems, respectively), within a limited budget of trials (from 100 to 1000). Results reveal the significant potential of using SE-EAS in challenging optimization problems, involving time-consuming simulations.

  14. Annealing of paramagnetic centres in electron- and ion-irradiated yttria-stabilized zirconia: effect of yttria content

    SciTech Connect

    Costantini, Jean-Marc; Beuneu, Francois; Weber, William J

    2014-01-01

    We have studied the effect of the yttria content on the recovery of paramagnetic centres in electron-irradiated yttria-stabilized zirconia (ZrO2: Y3+). Single crystals with 9.5 mol% or 18 mol% Y2O3 were irradiated with electrons of 1.0, 1.5, 2.0 and 2.5 MeV. Paramagnetic centre thermal annealing was studied by X-band EPR spectroscopy. Hole-centres are found to be annealed more quickly, or at a lower temperature, for 18 mol% than for 9.5 mol% Y2O3. At long annealing times, a non-zero asymptotic behaviour is observed in the isothermal annealing curves of hole-centres and F+-type centres between 300 and 500 K. The normalized asymptotic concentration of both defects has a maximum value of about 0.5 for annealing temperatures near 375 K, below the onset of the (isochronal) recovery stage, regardless of the yttria content. Such an uncommon behaviour is analyzed on the basis of either kinetic rate equations of charge transfer or equilibria between point defects with different charge states.

  15. Distributional behavior of diffusion coefficients obtained by single trajectories in annealed transit time model

    NASA Astrophysics Data System (ADS)

    Akimoto, Takuma; Yamamoto, Eiji

    2016-12-01

    Local diffusion coefficients in disordered systems such as spin glass systems and living cells are highly heterogeneous and may change over time. Such a time-dependent and spatially heterogeneous environment results in irreproducibility of single-particle-tracking measurements. Irreproducibility of time-averaged observables has been theoretically studied in the context of weak ergodicity breaking in stochastic processes. Here, we provide rigorous descriptions of equilibrium and non-equilibrium diffusion processes for the annealed transit time model, which is a heterogeneous diffusion model in living cells. We give analytical solutions for the mean square displacement (MSD) and the relative standard deviation of the time-averaged MSD for equilibrium and non-equilibrium situations. We find that the time-averaged MSD grows linearly with time and that the time-averaged diffusion coefficients are intrinsically random (irreproducible) even in the long-time measurements in non-equilibrium situations. Furthermore, the distribution of the time-averaged diffusion coefficients converges to a universal distribution in the sense that it does not depend on initial conditions. Our findings pave the way for a theoretical understanding of distributional behavior of the time-averaged diffusion coefficients in disordered systems.

  16. Effect of annealing atmospheres on cobalt ferrite nono-particles and their applications

    NASA Astrophysics Data System (ADS)

    Kumar, V.; Pant, R. P.; Jain, V. K.; Yadav, M. S.

    2008-12-01

    Cobalt ferrite nano-particles have been synthesized by co-precipitation and annealed in air and in an inert atmosphere. Change in the physical properties has been analyzed by various analytical techniques like XRD, TEM, VSM, etc. A significant change in the physical properties like structural, particle shape, size, magnetization and microwave absorption has been observed. The effect of annealing on other properties like Curie temperature, electrical conductivity is also investigated. Particles unannealed and annealed in air and in an inert atmosphere are studied for electromagnetic wave interference. Tables 3, Figs 3, Refs 18.

  17. Time-resolved photoluminescence studies of annealed 1.3-μm GaInNAsSb quantum wells

    PubMed Central

    2014-01-01

    Time-resolved photoluminescence (PL) was applied to study the dynamics of carrier recombination in GaInNAsSb quantum wells (QWs) emitting near 1.3 μm and annealed at various temperatures. It was observed that the annealing temperature has a strong influence on the PL decay time, and hence, it influences the optical quality of GaInNAsSb QWs. At low temperatures, the PL decay time exhibits energy dependence (i.e., the decay times change for different energies of emitted photons), which can be explained by the presence of localized states. This energy dependence of PL decay times was fitted by a phenomenological formula, and the average value of E0, which describes the energy distribution of localized states, was extracted from this fit and found to be smallest (E0 = 6 meV) for the QW annealed at 700°C. In addition, the value of PL decay time at the peak energy was compared for all samples. The longest PL decay time (600 ps) was observed for the sample annealed at 700°C. It means that based on the PL dynamics, the optimal annealing temperature for this QW is approximately 700°C. PMID:24533740

  18. Effect of annealing on Raman spectra of monolayer graphene samples gradually disordered by ion irradiation

    NASA Astrophysics Data System (ADS)

    Zion, E.; Butenko, A.; Kaganovskii, Yu.; Richter, V.; Wolfson, L.; Sharoni, A.; Kogan, E.; Kaveh, M.; Shlimak, I.

    2017-03-01

    Raman scattering spectra (RS) of two series of monolayer graphene samples irradiated with various doses of C + and Xe + ions were measured after annealing in a high vacuum and in forming gas (95%Ar + 5%H2). It is shown that annealing below 500 °C leads to a significant decrease in both the D-line, associated with defects, and the 2D-line, associated with the intact lattice structure. This can be explained by annealing-induced enhanced doping. Further annealing in a vacuum up to 1000 °C leads to a significant increase in the 2D-line together with a continuous decrease in the D-line. This gives evidence for the partial removal of the defects and restoration of the damaged lattice. Annealing in forming gas is less effective in this sense. A blue shift of all lines is observed after annealing. It is shown that below 500 °C, unintentional doping is the main origin of the shift. At higher annealing temperatures, the blue shift is mainly due to lattice strain arising because of mismatch between the thermal expansion coefficients of graphene and the substrate. Inhomogeneous distribution of stress and doping across the samples lead to the correlated variation of the height and peak position of RS lines.

  19. Annealing effect in structural and electrical properties of sputtered Mo thin film

    NASA Astrophysics Data System (ADS)

    Chelvanathan, P.; Zakaria, Z.; Yusoff, Y.; Akhtaruzzaman, M.; Alam, M. M.; Alghoul, M. A.; Sopian, K.; Amin, N.

    2015-04-01

    In this study, the effects of vacuum annealing on the structural and electrical properties of DC-sputtered molybdenum (Mo) thin films have been investigated. Mo thin films were deposited by DC sputtering and subsequently subjected to vacuum annealing in a tube furnace from 350 to 500 °C. Films that were deposited with different temperatures showed good adhesion with soda lime glass substrate after "tape testing". X-ray diffraction (XRD) spectra have indicated existence of (1 1 0) and (2 1 1) orientations. However, I(1 1 0)/I(2 1 1) peak intensity ratio decreased for all vacuum annealed Mo films compared to as-sputtered films indicating change of preferential orientation. This suggests vacuum annealing can be employed to tailor the Mo thin film atomic packing density of the plane parallel to the substrate. SEM images of surface morphology clearly show compact and dense triangular like grains for as-sputtered film, while annealed films at 350 °C, 400 °C and 450 °C indicate rice-like grains. Stony grains with less uniformity were detected for films annealed for 500 °C. Meanwhile, electrical resistivity is insensitive to the vacuum annealing condition as all films showed more or less same resistivity in the range of 3 × 10-5-6 × 10-5 Ω cm.

  20. 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.

  1. Annealing effect on structural and optical properties of chemical bath deposited MnS thin film

    NASA Astrophysics Data System (ADS)

    Ulutas, Cemal; Gumus, Cebrail

    2016-03-01

    MnS thin film was prepared by the chemical bath deposition (CBD) method on commercial microscope glass substrate deposited at 30 °C. The as-deposited film was given thermal annealing treatment in air atmosphere at various temperatures (150, 300 and 450 °C) for 1 h. The MnS thin film was characterized by using X-ray diffraction (XRD), UV-vis spectrophotometer and Hall effect measurement system. The effect of annealing temperature on the structural, electrical and optical properties such as optical constants of refractive index (n) and energy band gap (Eg) of the film was determined. XRD measurements reveal that the film is crystallized in the wurtzite phase and changed to tetragonal Mn3O4 phase after being annealed at 300 °C. The energy band gap of film decreased from 3.69 eV to 3.21 eV based on the annealing temperature.

  2. Annealing Effects on Creep and Rupture of Polycrystalline Alumina-Based Fibers

    NASA Technical Reports Server (NTRS)

    Goldsby, J. C.; Yun, H. M.; Morscher, G. N.; DiCarlo, J. A.

    1998-01-01

    Continuous-length polycrystalline aluminum-oxide-based fibers are being considered as reinforcements for advanced high-temperature composite materials. For these fine-grained fibers, basic issues arise concerning grain growth and microstructural instability during composite fabrication and the resulting effects on the fiber's thermo-mechanical properties. To examine these issues, commercially available Nextel 610 (alumina) and Altex (alumina-silica) fibers were annealed at 1100 and 1300 C for up to 100 hr in air. Changes in fiber microstructure, fiber tensile creep, stress rupture, and bend stress relaxation (BSR) that occurred with annealing were then determined. BSR tests were also used to compare as-received and annealed fibers to other polycrystalline oxide fibers. Annealing was shown to have a significant effect, particularly on the Altex fiber, and caused it to have increased creep resistance.

  3. Effect of annealing and pressure on microstructure of cornstarches with different amylose/amylopectin ratios.

    PubMed

    Liu, Hongsheng; Yu, Long; Simon, George; Zhang, Xiaoqing; Dean, Katherine; Chen, Ling

    2009-02-17

    This work focuses on the effect of annealing and pressure on microstructures of starch, in particular the crystal structure and crystallinity to further explore the mechanisms of annealing and pressure treatment. Cornstarches with different amylose/amylopectin ratios were used as model materials. Since the samples covered both A-type (high amylopectin starch: waxy and maize) and B-type (high amylose starch: G50 and G80) crystals, the results can be used to clarify some previous confusion. The effect of annealing and pressure on the crystallinity and double helices were investigated by X-ray diffraction (XRD) and (13)C CP/MAS NMR spectroscopy. The crystal form of various starches remained unchanged after annealing and pressure treatment. XRD detection showed that the relative crystallinity (RC) of high amylopectin starches was increased slightly after annealing, while the RC of high amylose-rich starches remained unchanged. NMR measurement supported the XRD results. The increase can be explained by the chain relaxation. XRD results also indicated that some of the fixed region in crystallinity was susceptible to outside forces. The effect of annealing and pressure on starch gelatinization temperature and enthalpy are used to explore the mechanisms.

  4. Radiation and annealing effects on integrated bipolar Operational Amplifier

    NASA Astrophysics Data System (ADS)

    Assaf, J.

    2017-02-01

    Integrated bipolar Operational Amplifier (op-amp) type μA 741 was irradiated with neutrons and gamma rays. The radiation on gain factors, slew rate, and power supply current have been evaluated. The experimental results show a decrease of these parameter values after exposing to the radiation. The advantage of the increase of the voltage power supplies and the thermal annealing treatment on the damaged parameters was also explored. The relationship among different frequency response parameters is also studied leading to an analytical formula for the above degraded parameters.

  5. Annealing Effect of PbS Quantum Dot Solar Cells

    SciTech Connect

    Gao, J.; Jeong, S.; Semonin, O. E.; Ellingson, R. J.; Nozik, A. J.; Beard, M. C.

    2011-01-01

    We recently reported an NREL certified {approx}3% efficient device with structure of ITO/ZnO/PbS QD/Au. The device is remarkably stable in air without encapsulation for more than 1000 hours. Therefore, in this study we focus on devices with structure of ITO/ZnO/PbS QD/metal fabricated in air. By annealing PbS QD film at low temperature up to 140C, the solar cell efficiency can be achieved to more than 4%.

  6. Post-annealing effects on ZnS thin films grown by using the CBD method

    NASA Astrophysics Data System (ADS)

    Ahn, Heejin; Um, Youngho

    2015-09-01

    Herein, the structural, morphological, and optical properties of zinc sulfide (ZnS) thin films deposited via the chemical bath deposition method are reported. These films were deposited on soda-lime glass (SLG) substrates by using ZnSO4, thiourea, and 25% ammonia at 90 °C. The effect of changing the annealing temperature from 100 °C to 300 °C on the properties of the ZnS thin films was investigated. X-ray diffraction (XRD) patterns showed that the ZnS thin film annealed at 100 °C had an amorphous structure; however, as the annealing temperature was increased, the crystalline quality of the thin film was enhanced. Moreover, transmission measurements showed that the optical transmittance was about 80% for wavelengths above 500 nm. The band gap energy (E g ) value of the film annealed at 300 °C was decreased to about 3.82 eV.

  7. In situ analysis of post-annealing effect on Sn-doped indium oxide films

    NASA Astrophysics Data System (ADS)

    Lim, Hojoon; Yang, Hyeok-Jun; Kim, Ji Woong; Bae, Jong-Seung; Kim, Jin-Woo; Jeong, Beomgyun; Crumlin, Ethan; Park, Sungkyun; Mun, Bongjin Simon

    2016-11-01

    Oxygen post-annealing effects on tin (Sn) doped indium oxide (ITO) film are investigated with various analytical tools as a function of temperature, including in situ XRD, ambient pressure XPS (AP-XPS), and Hall measurement. As the annealing temperature increases up to 200 °C under the oxygen pressure of 100 mTorr, the in situ XRD shows the evidence of crystallization of the film while the AP-XPS reveals the formation of oxygen vacancy and Sn4+ states on surface. In addition, the mobility of ITO thin film is increased as the post-annealing temperature increases, supporting the results of both in situ XRD and AP-XPS. The results of angle-resolved XPS reveal that the degree of Sn segregation changes little after post-annealing procedure.

  8. Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites

    NASA Astrophysics Data System (ADS)

    Wu, Shen; Sun, Aizhi; Zhai, Fuqiang; Wang, Jin; Zhang, Qian; Xu, Wenhuan; Logan, Philip; Volinsky, Alex A.

    2012-03-01

    This paper focuses on novel iron-based soft magnetic composites synthesis utilizing high thermal stability silicone resin to coat iron powder. The effect of an annealing treatment on the magnetic properties of synthesized magnets was investigated. The coated silicone insulating layer was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Silicone uniformly coated the powder surface, resulting in a reduction of the imaginary part of the permeability, thereby increasing the electrical resistivity and the operating frequency of the synthesized magnets. The annealing treatment increased the initial permeability, the maximum permeability, and the magnetic induction, and decreased the coercivity. Annealing at 580 °C increased the maximum permeability by 72.5%. The result of annealing at 580 °C shows that the ferromagnetic resonance frequency increased from 2 kHz for conventional epoxy resin coated samples to 80 kHz for the silicone resin insulated composites.

  9. The Effect of Grain Size and Dislocation Density on the Tensile Properties of Ni-SiCNP Composites During Annealing

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Huang, Hefei; Thorogood, Gordon James; Jiang, Li; Ye, Xiangxi; Li, Zhijun; Zhou, Xingtai

    2016-03-01

    The grain size refinement, enhancement of mechanical properties, and static recrystallization behavior of metallic nickel-silicon carbide nano-particle (Ni-3wt.%SiCNP) composites, milled for times ranging from 8 to 48 h have been examined. One set of Ni-SiCNP composite samples were annealed at 300 °C for 250 h, while the other set of samples were maintained at room temperature for control purposes (reference). The electron backscatter diffraction results indicate that the grain size of the annealed Ni-SiCNP composite was refined due to grain restructuring during static recrystallization. The x-ray diffraction results indicate that low-temperature annealing effectively reduced the density of dislocations; this can be explained by the dislocation pile-up model. Additionally, the tensile tests indicated that the annealed Ni-SiCNP composite had a significant increase in strength due to an increase of the Hall-Petch strengthening effect with a slight increase in the total elongation. The decrease of dislocation pile-up in the grain interiors and the increase in grain boundary sliding are assumed to be the main mechanisms at play. The relationship between the microstructural evolution and the variation of tensile properties is examined in this study.

  10. Annealing effects on electrical properties of pure and tin-doped indium oxide thin films.

    PubMed

    Kato, Kazuhiro; Omoto, Hideo; Yonekura, Masaaki

    2012-12-01

    The annealing effects on the properties of ITO and pure In2O3 thin films have been investigated. The thin films were deposited with various O2 flow ratios to total gas flow by pulsed dc magnetron sputtering. The post-deposition annealing of the thin films was carried out for 30 minutes at various temperatures ranging up to 500 degrees C in air. It was found through the comparison of the carrier density of ITO and In2O3 thin films that the carrier electrons of the ITO thin films came from both of the dopant Sn and oxygen vacancies under the annealing less than 400 degrees C. Therefore, the ITO thin films deposited with lower O2 flow ratio exhibited higher carrier density due to many oxygen vacancies; in consequence, they exhibited lower resistivity at the annealing up to 400 degrees C. On the other hand, the carrier density of ITO thin films was almost identical regardless of O2 flow ratio when they were annealed at 500 degrees C. This fact indicates that most carrier electrons of the ITO thin films were brought by the dopant Sn at the annealing temperature of 500 degrees C. However, the ITO thin films deposited with lower O2 flow ratio exhibited higher Hall mobility; as a result, they showed lower resistivity at the annealing of 500 degrees C. Atomic force microscope, X-ray diffraction and X-ray reflectivity measurements revealed that the ITO thin films deposited with lowe O2 flow ratio exhibited dense structure even after they were annealed at 500 degrees C. Hence, the carrier electrons of the dense ITO thin films deposited with low O2 flow ratio can conduct better, as a result, the ITO thin films exhibited high Hall mobility and low resistivity.

  11. Large Barkhausen effect and Matteucci effect in cold-drawn and torsion annealed amorphous magnetostrictive wires

    SciTech Connect

    Kawamura, H.; Mohri, K.; Yamasaki, J.; Ogasawara, I. )

    1988-07-01

    Amorphous magnetostrictive wires fabricated by super-rapid quenching in water exhibit a remarkably stable Barkhausen effect and Matteucci effect in the as-prepared state. The Matteucci effect in as-prepared wire is under 1 mV. When the wire is drawn or made shorter than 70 mm, the Barkhausen effect vanishes. In this work, the amorphous magnetostrictive wire was cold drawn and then annealed under torsional stress; the wires obtained had a large Matteucci effect, as well as a large Barkhausen effect even when as short as 25 mm. These wires were used as devices for pulse generation. Their magnetic properties are studied.

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

    PubMed

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

    2010-09-22

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

  13. Effect of Metallic Au Seed Layer Annealing on the Properties of Electrodeposited ZnO Nanorods.

    PubMed

    Park, Youngbin; Nam, Giwoong; Kim, Byunggu; Leem, Jae-Young

    2015-11-01

    This study focuses on the effect of annealing the Au seed layer (ASL) on the structural and optical properties of electrodeposited ZnO nanorods. ZnO nanorods were fabricated in a three-step approach. In the first step, ASLs were deposited using an ion sputter technique. In the second step, layers were annealed in air at various temperatures ranging from 400 degrees C to 600 degrees C. Finally, ZnO nanorods were grown using an electrodeposition method. The field-emission scanning electron microscopy analysis showed that better aligned ZnO nanorods are fabricated on the annealed ASL compared with non-annealed ASL The X-ray diffraction analysis showed a notable improvement in directional growth along the (002) crystallographic plane when ZnO nanorods were grown on the annealed ASL. The photoluminescence analysis showed that the UV emission peak of ZnO nanorods on the annealed ASL at 400 degrees C was blue-shifted and increased.

  14. Influence of annealing effects on polyaniline for good microstructural modification

    PubMed Central

    Begum, A. Nishara; Dhachanamoorthi, N.; saravanan, M.E. Raja; Jayamurugan, P.; Manoharan, D.; Ponnuswamy, V.

    2013-01-01

    H2SO4 doped polyaniline (PANI) has synthesized by chemical oxidation method. The prepared Polyaniline were annealed at 150 °C, 200 °C and 250 °C for 30 min in vacuum. Crystal size, percentage of crystallinity, total percentage of crystallinity properties of untreated and heat treated PANI samples were studied by using X-ray diffraction pattern. The molecular structure of untreated and heat treated samples were examined by using Fourier transform infrared spectrophotometer. UV study shows π–π* transition of untreated and heat treated of polyaniline were found at 328 and 636 nm. The peak at 636 nm reveals the extension of conjugated polymer. Thermal properties of untreated and heat treated PANI sample measured by using thermo gravimetric analysis and differential scanning calorimetric spectroscopy. PMID:23378673

  15. Combined current-modulation annealing induced enhancement of giant magnetoimpedance effect of Co-rich amorphous microwires

    NASA Astrophysics Data System (ADS)

    Liu, Jingshun; Qin, Faxiang; Chen, Dongming; Shen, Hongxian; Wang, Huan; Xing, Dawei; Phan, Manh-Huong; Sun, Jianfei

    2014-05-01

    We report on a combined current-modulation annealing (CCMA) method, which integrates the optimized pulsed current (PC) and DC annealing techniques, for improving the giant magnetoimpedance (GMI) effect and its field sensitivity of Co-rich amorphous microwires. Relative to an as-prepared Co68.2Fe4.3B15Si12.5 wire, CCMA is shown to remarkably improve the GMI response of the wire. At 10 MHz, the maximum GMI ratio and its field sensitivity of the as-prepared wire were, respectively, increased by 3.5 and 2.28 times when subjected to CCMA. CCMA increased atomic order orientation and circumferential permeability of the wire by the co-action of high-density pulsed magnetic field energy and thermal activation energy at a PC annealing stage, as well as the formation of uniform circular magnetic domains by a stable DC magnetic field at a DC annealing stage. The magnetic moment can overcome eddy-current damping or nail-sticked action in rotational magnetization, giving rise to a double-peak feature and wider working field range (up to ±2 Oe) at relatively higher frequency (f ≥ 1 MHz).

  16. Combined current-modulation annealing induced enhancement of giant magnetoimpedance effect of Co-rich amorphous microwires

    SciTech Connect

    Liu, Jingshun E-mail: faxiang.qin@gmail.com; Qin, Faxiang E-mail: faxiang.qin@gmail.com; Chen, Dongming; Shen, Hongxian; Wang, Huan; Xing, Dawei; Sun, Jianfei; Phan, Manh-Huong

    2014-05-07

    We report on a combined current-modulation annealing (CCMA) method, which integrates the optimized pulsed current (PC) and DC annealing techniques, for improving the giant magnetoimpedance (GMI) effect and its field sensitivity of Co-rich amorphous microwires. Relative to an as-prepared Co{sub 68.2}Fe{sub 4.3}B{sub 15}Si{sub 12.5} wire, CCMA is shown to remarkably improve the GMI response of the wire. At 10 MHz, the maximum GMI ratio and its field sensitivity of the as-prepared wire were, respectively, increased by 3.5 and 2.28 times when subjected to CCMA. CCMA increased atomic order orientation and circumferential permeability of the wire by the co-action of high-density pulsed magnetic field energy and thermal activation energy at a PC annealing stage, as well as the formation of uniform circular magnetic domains by a stable DC magnetic field at a DC annealing stage. The magnetic moment can overcome eddy-current damping or nail-sticked action in rotational magnetization, giving rise to a double-peak feature and wider working field range (up to ±2 Oe) at relatively higher frequency (f ≥ 1 MHz)

  17. Effect of annealing temperature on properties of RF sputtered Cu(In,Ga)Se2 thin films

    NASA Astrophysics Data System (ADS)

    Yu, Zhou; Yan, Chuanpeng; Yan, Yong; Zhang, Yanxia; Huang, Tao; Huang, Wen; Li, Shasha; Liu, Lian; Zhang, Yong; Zhao, Yong

    2012-09-01

    Cu(In,Ga)Se2 (CIGSe) thin films were prepared by radio frequency (RF) magnetron sputtering at room temperature, following vacuum annealing at different temperatures. We have investigated the effect of annealing temperature (150-550 °C) on the phase transformation process of the CIGSe films. The as-deposited precursor films show a near stoichiometry composition and amorphous structure. Composition loss of the films mainly occur in the annealing temperature range of 150-300 °C. Comparing with samples annealed at 300 °C, films annealed at 350 °C or higher temperatures exhibit almost similar composition and polycrystalline chalcopyrite structure. Crystal quality of the films improves with increasing annealing temperature. Reflectance spectra of the annealed films show interference fringe pattern. The calculated refractive indexes of the films are in the range of 2.4-2.5.

  18. Influence of multi-deposition multi-annealing on time-dependent dielectric breakdown characteristics of PMOS with high-k/metal gate last process

    NASA Astrophysics Data System (ADS)

    Wang, Yan-Rong; Yang, Hong; Xu, Hao; Wang, Xiao-Lei; Luo, Wei-Chun; Qi, Lu-Wei; Zhang, Shu-Xiang; Wang, Wen-Wu; Yan, Jiang; Zhu, Hui-Long; Zhao, Chao; Chen, Da-Peng; Ye, Tian-Chun

    2015-11-01

    A multi-deposition multi-annealing technique (MDMA) is introduced into the process of high-k/metal gate MOSFET for the gate last process to effectively reduce the gate leakage and improve the device’s performance. In this paper, we systematically investigate the electrical parameters and the time-dependent dielectric breakdown (TDDB) characteristics of positive channel metal oxide semiconductor (PMOS) under different MDMA process conditions, including the deposition/annealing (D&A) cycles, the D&A time, and the total annealing time. The results show that the increases of the number of D&A cycles (from 1 to 2) and D&A time (from 15 s to 30 s) can contribute to the results that the gate leakage current decreases by about one order of magnitude and that the time to fail (TTF) at 63.2% increases by about several times. However, too many D&A cycles (such as 4 cycles) make the equivalent oxide thickness (EOT) increase by about 1 Å and the TTF of PMOS worsen. Moreover, different D&A times and numbers of D&A cycles induce different breakdown mechanisms. Project supported by the National High Technology Research and Development Program of China (Grant No. SS2015AA010601) and the National Natural Science Foundation of China (Grant Nos. 61176091 and 61306129).

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

    NASA Astrophysics Data System (ADS)

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

    1982-12-01

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

  20. Influence of Annealing Time and Thermo-Mechanical Cycling on Constrained Recovery Properties of a Cold-Worked NiTi Wire

    NASA Astrophysics Data System (ADS)

    Yan, Xiaojun; Ge, Yuli; Van Humbeeck, Jan

    2017-02-01

    In this work, the influence of parameters such as annealing time, pre-strain and thermo-mechanical cycling on recovery stresses of NiTi wires has been investigated by using a dynamic mechanical analyzer. The results show that the maximum recovery stress decreases with increasing annealing time and increases with increasing pre-strain except for 60-min annealed sample with 4% pre-strain, which has a higher recovery stress than 45-min annealed sample with the same pre-strain. The recovery stresses drastically increase during the first two thermo-mechanical cycles for all samples, regardless of annealing time. The observed changes of recovery stress could be attributed to different transformation temperatures and mechanical properties induced by different annealing times and/or thermo-mechanical cycling.

  1. Effects of stress annealing in nitrogen on the effective contact-potential difference, charges, and traps at the Si/SiO2 interface of metal-oxide-semiconductor devices

    NASA Astrophysics Data System (ADS)

    Przewlocki, Henryk M.; Massoud, Hisham Z.

    2002-08-01

    In this article, we report the results of a study of the effects of high-temperature stress annealing in nitrogen on the electrical properties of metal/oxide/semiconductor devices. In this study, we have experimentally characterized the dependence of the reduced effective contact-potential difference, the effective oxide charge (Neff), and the midgap interface trap density (Dit) on the annealing conditions in nitrogen. We have correlated such properties with the dependence of the index of refraction and oxide stress on the annealing conditions and oxide thickness in a companion article. We consider the contributions of the thermal-relaxation and nitrogen-incorporation processes in determining changes in the electrical properties with annealing time. This model description is consistent with other annealing studies carried out in argon where only the thermal-relaxation process is present.

  2. Effect of annealing process on the phase formation in poly(vinylidene fluoride) thin films

    SciTech Connect

    Abdullah, Ibtisam Yahya; Yahaya, Muhammad; Jumali, Mohd Hafizuddin Haji; Shanshool, Haider Mohammed

    2014-09-03

    This work reports the initial study on the effect of annealing process on the crystalline phase of poly(vinylidene fluoride) (PVDF) thin film. PVDF powder was dissolved in N,N-dimethylformamide before spin-coated onto a glass substrate to form a film. The films were annealed at 30°C, 90°C and 110°C for 5 hrs. The crystalline phase of the powder PVDF as received was investigated by using XRD and FTIR techniques. Moreover, the crystalline phases of thin films after annealing were investigated by using the same techniques. XRD analysis showed that in powder form PVDF exists in α-phase. Each annealed PVDF thin films exhibited identical formation of three-phases material namely γ (as major phase) while α and β phases as the minor phases. The FTIR analysis showed that the powder form of PVDF exists in α and β phases. FTIR measurement further confirmed the XRD results implying that the annealing process has no significant effect on the phase formation in PVDF films.

  3. Effect of annealing on ESR characteristics of zirconia nanopowders with different impurity compositions

    NASA Astrophysics Data System (ADS)

    Bykov, I. P.; Brik, A. B.; Bagmut, N. N.; Kalinichenko, A. M.; Bevz, V. V.; Vereshchak, V. G.; Yastrabik, L.

    2009-06-01

    An ESR study is performed for four groups of zirconia nanopowder samples: nominally pure ZrO2 powders (first group), zirconia samples with Y2O3 and Sc2O3 impurities (second group), samples with different amounts of Cr2O3 (third group), and samples containing both Y2O3 and Cr2O3 (fourth group). The effect of annealing on ESR signals due to Zr3+ ions (sample groups 1 and 2) and Cr5+ ions (groups 3 and 4) is studied. It is established that, although the Zr3+ and Cr5+ ions have similar ESP characteristics, the annealing exerts different effects on ESR signals of these ions. Annealing in the temperature range 200-900°C leads to a monotonic increase in the amount of Zr3+ ions. Interestingly, the annealing temperature at which Zr3+ ions begin to generate ESR signals is different for samples with different impurity compositions. Unlike the Zr3+ ions, the annealing curves of the ESR signals due to the Cr5+ ions pass through an extremum at T = 500-600°C.

  4. Effects of annealing on antiwear and antibacteria behaviors of TaN-Cu nanocomposite thin films

    SciTech Connect

    Hsieh, J. H.; Cheng, M. K.; Chang, Y. K.; Li, C.; Chang, C. L.; Liu, P. C.

    2008-07-15

    TaN-Cu nanocomposite films were deposited by reactive cosputtering on Si and tool steel substrates. The films were then annealed using rapid thermal annealing (RTA) at 400 deg. C for 2, 4, and 8 min, respectively, to induce the nucleation and growth of Cu particles in TaN matrix and on film surface. Field emission scanning electron microscopy was applied to characterize Cu nanoparticles emerged on the surface of TaN-Cu thin films. The effects of annealing on the antiwear and antibacterial properties of these films were studied. The results reveal that annealing by RTA can cause Cu nanoparticles to form on the TaN surface. Consequently, the tribological behaviors, as well as the antibacterial behavior may vary depending on particle size, particle distribution, and total exposed Cu amount. For the samples with large Cu particles, the reduction of averaged friction and wear rate is obvious. Apparently, it is due to the smeared Cu particles adhered onto the wear tracks. This Cu layer may act as a solid lubricant. From the antibacterial testing results, it is found that both Cu particle size and total exposed Cu amount are critical in making short-term antibacterial effect. Overall, all the annealed TaN-Cu samples can reach >99% antibacterial efficiency in 24 h, with respect to uncoated Si substrate.

  5. Annealing Effects on Structure and Optical Properties of Diamond-Like Carbon Films Containing Silver.

    PubMed

    Meškinis, Šarūnas; Čiegis, Arvydas; Vasiliauskas, Andrius; Šlapikas, Kęstutis; Gudaitis, Rimantas; Yaremchuk, Iryna; Fitio, Volodymyr; Bobitski, Yaroslav; Tamulevičius, Sigitas

    2016-12-01

    In the present study, diamond-like carbon films with embedded Ag nanoparticles (DLC:Ag) were deposited by reactive magnetron sputtering. Structure of the films was investigated by Raman scattering spectroscopy. Atomic force microscopy was used to define thickness of DLC:Ag films as well as to study the surface morphology and size distribution of Ag nanoparticles. Optical absorbance and reflectance spectra of the films were studied in the 180-1100-nm range. Air annealing effects on structure and optical properties of the DLC:Ag were investigated. Annealing temperatures were varied in the 180-400 °C range. Changes of size and shape of the Ag nanoclusters took place due to agglomeration. It was found that air annealing of DLC:Ag films can result in graphitization following destruction of the DLC matrix. Additional activation of surface-enhanced Raman scattering (SERS) effect in DLC:Ag films can be achieved by properly selecting annealing conditions. Annealing resulted in blueshift as well as significant narrowing of the plasmonic absorbance and reflectance peaks. Moreover, quadrupole surface plasmon resonance peaks appeared. Modeling of absorption spectra of the nanoclusters depending on the shape and surrounding media has been carried out.

  6. Annealing effects on polycrystalline GaN using nitrogen and ammonia ambients

    NASA Astrophysics Data System (ADS)

    Ariff, A.; Zainal, N.; Hassan, Z.

    2016-09-01

    This paper describes effects of using post-annealing treatment in different conditions on the properties of polycrystalline GaN layer grown on m-plane sapphire substrate by electron beam (e-beam) evaporator. Without annealing, GaN surface was found to have a low RMS roughness with agglomeration of GaN grains in a specific direction and the sample consisted of gallium oxide (Ga2O3) material. When the post-annealing treatment was carried out in N2 ambient at 650 °C, initial re-crystallization of the GaN grains was observed while the evidence of Ga2O3 almost disappeared. As the NH3 annealing was conducted at 950 °C, more effect of re-crystallization occurred but with less grains coalescence. Three dominant XRD peaks of GaN in (10 1 bar 0) , (0002) and (10 1 bar 1) orientations were evident. Near band edge (NBE) related emission in GaN was also observed. The significant improvement was attributed to simultaneous recrystallization and effective reduction of N deficiency density. The post-annealing in a mixture of N2 and NH3 ambient at 950 °C was also conducted, but has limited the effectiveness of the N atoms to incorporate on the GaN layer due to 'clouding' effect by the inert N2 gas. Further increase in the annealing temperature at 980 °C and 1100 °C, respectively caused severe deteriorations of the structural and optical properties of the GaN layer. Overall, this work demonstrated initial potential in improving polycrystalline GaN material in simple and inexpensive manner.

  7. Effects of stress annealing in nitrogen on the index of refraction of silicon dioxide layers in metal-oxide-semiconductor devices

    NASA Astrophysics Data System (ADS)

    Massoud, Hisham Z.; Przewlocki, Henryk M.

    2002-08-01

    In this article, we report the results of a study of the effects of high-temperature stress annealing in nitrogen on the index of refraction of SiO2 layers in metal/oxide/semiconductor (MOS) devices. In this study, we have experimentally characterized the dependence of mechanical stress in the Si-SiO2 system on the oxidation and annealing conditions and correlated such properties with the dependence of the index of refraction on processing conditions and oxide thickness. We consider the contributions of the thermal-relaxation and nitrogen-incorporation processes in determining changes in the index of refraction with annealing time. This description is consistent with other annealing studies carried out in argon where only the thermal-relaxation process is present. Correlations of these experimental observations with the electrical properties of the same MOS devices are presented in a companion article.

  8. Photo-annealing effect of gamma-irradiated erbium-doped fibre by femtosecond pulsed laser

    NASA Astrophysics Data System (ADS)

    Hsiung Chang, Sheng; Liu, Ren-Young; Lin, Chu-En; Chou, Fong-In; Tai, Chao-Yi; Chen, Chii-Chang

    2013-12-01

    In this work, a photo-annealing effect of gamma-irradiated erbium-doped glass fibre is investigated. Two commercial erbium-doped fibres (EDFs) with different doping concentrations were sealed inside a chamber with a cobalt-60 gamma source for 6 h to give an accumulated dose of 3.18 kGy. A tunable femtosecond pulsed laser with a repetition rate of 80 MHz was then used to pump EDF to generate 1550 nm fluorescence and green up-conversion emission, resulting in the annealing effect of the gamma-irradiated EDF. The fluorescence power of gamma-irradiated EDF with a moderate level of doping was almost returned to the initial state by photo-annealing, unlike that of a heavily doped EDF. This finding may facilitate the development of anti-irradiated superfluorescence fibre source for space navigation.

  9. The Effect of Hydrogen Annealing on the Impurity Content of Alumina-Forming Alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    2000-01-01

    Previously, the effect of hydrogen annealing on increasing the adhesion of Al2O3 scales had been related to the effective desulfurization that occurred during this process. The simultaneous reduction of other impurities has now been re-examined for up to 20 impurity elements in the case of five different alloys (NiCrAl, FeCrAl, PWA 1480, Rene'142, and Rene'N5). Hydrogen annealing produced measurable reductions in elemental concentration for B, C, Na, Mg, P, K, Sr, or Sn in varying degrees for at least one and up to three of these alloys. No single element was reduced by hydrogen annealing for all the alloys except sulfur. In many cases spalling occurred at low levels of these other impurities, while in other cases the scales were adherent at high levels of the impurities. No impurity besides sulfur was strongly correlated with adhesion.

  10. Thermal annealing effects on ultra-violet luminescence properties of Gd doped AlN

    SciTech Connect

    Kita, Takashi; Ishizu, Yuta; Tsuji, Kazuma; Harada, Yukihiro; Chigi, Yoshitaka; Nishimoto, Tetsuro; Tanaka, Hiroyuki; Kobayashi, Mikihiro; Ishihara, Tsuguo; Izumi, Hirokazu

    2015-04-28

    We studied energy transfer from AlN to doped Gd{sup 3+} ions as a function of the post-thermal annealing temperature. Gd-doped AlN thin films were deposited on fused-silica substrates using a reactive radio-frequency magnetron sputtering technique. The film is a c-axis oriented polycrystal. The intra-orbital electron transition in Gd{sup 3+} showed an atomically sharp luminescence at 3.9 eV (318 nm). The photoluminescence (PL) excitation spectrum exhibited a resonant peak, indicating efficient energy transfer from the host AlN crystal to Gd{sup 3+} ions. The PL intensity increases approximately ten times by thermal annealing. The PL decay lifetime becomes long with annealing, and mid-gap luminescence relating to the crystal defects in AlN was also found to be reduced by annealing. These results suggest that energy dissipation of excited carriers in AlN was suppressed by annealing, and the efficiency of energy transfer into Gd{sup 3+} was improved.

  11. The annealing effect on structure, magnetoresistance and magnetic properties of Co/Bi/Co thin films

    NASA Astrophysics Data System (ADS)

    Vorobiov, S. I.; Shutylieva, O. V.; Pazukha, I. M.; Chornous, A. M.

    2016-06-01

    Co/Bi/Co thin films were prepared by alternately sputtering at substrate temperature 460K. Their structure, magnetoresistance and magnetic properties were studied using transmission electron microscopy (TEM), software-hardware complex with current-in-plane geometries, and vibrating sample magnetometer (VSM). The trilayer systems have been investigated as functions of the Bi layer thickness and temperature. The film structure in both as-deposited and annealed at 680K states is a granulated structure which consists of a Co magnetic matrix with embedded Bi granules. The film structure after annealing at 900K depends on Bi concentrations and changes from the fcc-Co+amorphous Bi to a fcc-Co+tetragonal phase of Bi2O3 of around 17 at.%. Magnetoresistance has demonstrated independence from annealing processes in the temperature range from 300 to 680K. Besides, the oscillation dependence of magnetoresistance with Bi thickness has been observed. The saturation and remanent magnetization are reduced with the increase of Bi thickness and increase with increasing the annealing temperature; the coercivity slightly depends on Bi thickness in as-deposited state and increases more than 10 times at t_{Bi}=30 nm after annealing at 680K.

  12. The Effect of Annealing on the Elastic Modulus of Orthodontic Wires

    NASA Astrophysics Data System (ADS)

    Higginbottom, Kyle

    Introduction: Nickel Titanium orthodontic wires are currently used in orthodontic treatment due to their heat activated properties and their delivery of constant force. The objective of this study was to determine the effect of annealing on the elastic modulus of Nickel Titanium, Stainless Steel and Beta-titanium (TMA) wires. Different points along the wire were tested in order to determine how far from the annealed ends the elastic modulus of the wires was affected. Methods: Eighty (80) orthodontic wires consisting of 4 equal groups (SS/TMA/Classic NitinolRTM/Super Elastic NitinolRTM) were used as the specimens for this study. All wires were measured and marked at 5mm measurements, and cut into 33.00mm sections. The wires were heated with a butane torch until the first 13.00mm of the wires were red hot. Load deflection tests using an InstronRTM universal testing machine were run at 5mm distances from the end of the wire that had been annealed. The change in elastic modulus was then determined. Results: There was a significant difference (F = 533.001, p = 0.0005) in the change in elastic modulus for the four distances. There was also a significant difference (F = 57.571, p = 0.0005) in the change in elastic modulus for the four wire types. There was a significant interaction (F = 19.601, p = 0.005) between wire type and distance, however this interaction negated the differences between the wires. Conclusion: 1) There are significant differences in the changes in elastic modulus between the areas of the wires within the annealed section and those areas 5mm and 10mm away from the annealed section. The change in elastic modulus within the annealed section was significantly greater at 8 mm than it was at 13mm, and this was significantly greater than 18mm and 23mm (5mm and 10mm beyond the annealed section). However, there was no statistical difference in the change in elastic modulus between 5mm and 10mm away from the annealed section (18mm and 23mm respectively). 2

  13. Effect of Thermal Annealing in Ammonia on the Properties of InGaN Nanowires with Different Indium Concentrations

    SciTech Connect

    Hahn, Cristopher; Cordones, Amy; Andrews, Sean; Gao, Hanwei; Fu, Anthony; Leone, Stephen; Yang, Peidong

    2012-10-02

    The utility of an annealing procedure in ammonia ambient is investigated for improving the optical characteristics of InxGa1?xN nanowires (0.07 ≤ x ≤ 0.42) grown on c-Al2O3 using a halide chemical vapor deposition method. Morphological studies using scanning electron microscopy confirm that the nanowire morphology is retained after annealing in ammonia at temperatures up to 800 ?C. However, significant indium etching and composition inhomogeneities are observed for higher indium composition nanowires (x = 0.28, 0.42), as measured by energy-dispersive X-ray spectroscopy and Z-contrast scanning transmission electron microscopy. Structural analyses, using X-ray diffraction and high-resolution transmission electron microscopy, indicate that this is a result of the greater thermal instability of higher indium composition nanowires. The effect of these structural changes on the optical quality of InGaN nanowires is examined using steady-state and time-resolved photoluminescence measurements. Annealing in ammonia enhances the integrated photoluminescence intensity of InxGa1?xN nanowires by up to a factor of 4.11 ? 0.03 (for x = 0.42) by increasing the rate of radiative recombination. Fitting of photoluminescence decay curves to a Kohlrausch stretched exponential indicates that this increase is directly related to a larger distribution of recombination rates from composition inhomogeneities caused by annealing. The results demonstrate the role of thermal instability on the improved optical properties of InGaN nanowires annealed in ammonia.

  14. Experimental signature of programmable quantum annealing.

    PubMed

    Boixo, Sergio; Albash, Tameem; Spedalieri, Federico M; Chancellor, Nicholas; Lidar, Daniel A

    2013-01-01

    Quantum annealing is a general strategy for solving difficult optimization problems with the aid of quantum adiabatic evolution. Both analytical and numerical evidence suggests that under idealized, closed system conditions, quantum annealing can outperform classical thermalization-based algorithms such as simulated annealing. Current engineered quantum annealing devices have a decoherence timescale which is orders of magnitude shorter than the adiabatic evolution time. Do they effectively perform classical thermalization when coupled to a decohering thermal environment? Here we present an experimental signature which is consistent with quantum annealing, and at the same time inconsistent with classical thermalization. Our experiment uses groups of eight superconducting flux qubits with programmable spin-spin couplings, embedded on a commercially available chip with >100 functional qubits. This suggests that programmable quantum devices, scalable with current superconducting technology, implement quantum annealing with a surprising robustness against noise and imperfections.

  15. High-fluence Ga-implanted silicon—The effect of annealing and cover layers

    SciTech Connect

    Fiedler, J. Heera, V.; Hübner, R.; Voelskow, M.; Germer, S.; Schmidt, B.; Skorupa, W.

    2014-07-14

    The influence of SiO{sub 2} and SiN{sub x} cover layers on the dopant distribution as well as microstructure of high fluence Ga implanted Si after thermal processing is investigated. The annealing temperature determines the layer microstructure and the cover layers influence the obtained Ga profile. Rapid thermal annealing at temperatures up to 750 °C leads to a polycrystalline layer structure containing amorphous Ga-rich precipitates. Already after a short 20 ms flash lamp annealing, a Ga-rich interface layer is observed for implantation through the cover layers. This effect can partly be suppressed by annealing temperatures of at least 900 °C. However, in this case, Ga accumulates in larger, cone-like precipitates without disturbing the surrounding Si lattice parameters. Such a Ga-rich crystalline Si phase does not exist in the equilibrium phase diagram according to which the Ga solubility in Si is less than 0.1 at. %. The Ga-rich areas are capped with SiO{sub x} grown during annealing which only can be avoided by the usage of SiN{sub x} cover layers.

  16. Isothermal anneal effect on microcrack density around leucite particles in dental porcelain.

    PubMed

    Mackert, J R; Rueggeberg, F A; Lockwood, P E; Evans, A L; Thompson, W O

    1994-06-01

    Because of the large differential in thermal expansion coefficient between leucite and the surrounding glass matrix, microcracks form around the leucite crystallites during the manufacture of dental porcelain frits. These microcracks decouple leucite from the surrounding glass matrix and affect the bulk thermal expansion of the porcelain frit (Binns, 1983). The purpose of this study was to determine if the microcrack density in a dental porcelain decreased as a result of isothermal heat treatment. Ten specimens of a commercial dental porcelain that had previously exhibited an increase in thermal expansion as a function of isothermal heat treatment were prepared and divided into two groups. The experimental group was heated to 750 degrees C and held for 16 minutes at that temperature. The control group received no anneal. The mean microcrack densities were determined by quantitative stereology to be 575 cm2/cm3 +/- 75 cm2/cm3 (mean +/- SEM) for the control group (no anneal) and 231 cm2/cm3 +/- 25 cm2/cm3 for the experimental group (16-minute anneal at 750 degrees C). The specimens annealed at 750 degrees C had a significantly lower microcrack density (p < 0.001) than those that received no anneal. A model was developed to estimate the effect of microcracking on thermal expansion of the porcelain, and a 6% increase in the coefficient of thermal expansion of the porcelain was predicted from this model as a result of this decrease in microcrack density.

  17. Effect of external electric field on morphology of copper phthalocyanine-fullerene blended films during annealing

    NASA Astrophysics Data System (ADS)

    Parhi, Anukul Prasad; Iyer, S. Sundar Kumar

    2016-03-01

    The thin-film morphology and segregated phases of constituents in blends of organic semiconductors play an important role in determining the performance of devices fabricated with these constituents. In this study, we explored the effect of an external electric field applied during annealing on the morphology and phase of blended films of two popular organic semiconductors, copper pthalocyanine (CuPc) and buckminsterfullerene (C60). Films of different blend ratios annealed at various temperatures in both the presence and absence of an electric field were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. The characteristics of annealed pristine CuPc films were also included for comparison. The observed changes in the properties of the blended films following the annealing, including the abrupt phase segregation of the blended constituents in the films, are discussed. The polarizability of the molecules was calculated using density functional theory (DFT) to explain the interaction, stacking, and segregation of the molecules in the blend. The results showed that application of an electric field during annealing of the blended films is an additional control parameter that can help tune the properties of the blended film. [Figure not available: see fulltext.

  18. Effect of Post Deposition Annealing Treatments on Properties of AZO Thin Films for Schottky Diode Applications.

    PubMed

    Singh, Shaivalini; Park, Si-Hyun

    2016-01-01

    High-quality aluminum (Al) doped ZnO (AZO) thin films were deposited on silicon substrates by RF sputtering at room temperature. The deposited films were annealed from the temperatures 350 °C to 650 °C in pure nitrogen (N₂) ambient. The effects of annealing on the microstructural, optical and electrical properties of the AZO films were investigated. A detailed analysis by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Four Probe and Hall measurements was performed to study the properties of these AZO thin films. It was observed that all of the as-deposited and annealed AZO films have homogenous surfaces and hexagonal wurtzite structures with good crystalline quality. The study also suggested that there was an intermediate post annealing temperature (450 °C) at which the deposited ZnO film exhibit best surface characteristics. Pd/AZO Schottky devices were fabricated with 450 °C annealed AZO thin films and the parameters of Schottky devices were extracted from I-V characteristics. These results indicated that the Pd/AZO films were very much suitable for various optoelectronics applications particularly for metal semiconductor metal based UV detector application.

  19. Investigation of annealing temperature effect on magnetron sputtered cadmium sulfide thin film properties

    NASA Astrophysics Data System (ADS)

    Akbarnejad, E.; Ghorannevis, Z.; Abbasi, F.; Ghoranneviss, M.

    2016-12-01

    Cadmium sulfide (CdS) thin films are deposited on the fluorine doped tin oxide coated glass substrate using the radio frequency magnetron sputtering setup. The effects of annealing in air on the structural, morphological, and optical properties of CdS thin film are studied. Optimal annealing temperature is investigated by annealing the CdS thin film at different annealing temperatures of 300, 400, and 500 °C. Thin films of CdS are characterized by X-ray diffractometer analysis, field emission scanning electron microscopy, atomic force microscopy, UV-Vis-NIR spectrophotometer and four point probe. The as-grown CdS films are found to be polycrystalline in nature with a mixture of cubic and hexagonal phases. By increasing the annealing temperature to 500 °C, CdS film showed cubic phase, indicating the phase transition of CdS. It is found from physical characterizations that the heat treatment in air increased the mean grain size, the transmission, and the surface roughness of the CdS thin film, which are desired to the application in solar cells as a window layer material.

  20. Effects of rapid thermal annealing conditions on GaInNAs band gap blueshift and photoluminescence intensity

    SciTech Connect

    Liverini, V.; Rutz, A.; Keller, U.; Schoen, S.

    2006-06-01

    We have studied the effects of various conditions of rapid thermal annealing (RTA) on 10 nm GaInNAs/GaAs single quantum wells (SQWs) with fixed indium concentration and increasing nitrogen content to obtain photoluminescence (PL) in the telecom wavelength regime of 1.3 and 1.5 {mu}m. Specifically, we analyzed the results of annealing for a fixed short time but at different temperatures and for longer times at a fixed temperature. In all experiments, InGaAs SQWs with the same In concentration were used as references. For both RTA conditions, the well-known blueshift of the band gap energy and the PL intensity improvement show trends that reveal that these are unrelated effects. At high RTA temperatures the PL efficiency reaches a maximum and then drops independently of N content. On the contrary, the blueshift experiences a rapid increase up to 700 deg. C (strong blueshift regime) and it saturates above this temperature (weak blueshift regime). Both these blueshift regimes are related to the nitrogen content in the SQWs but in different ways. In the strong blueshift regime, we could obtain activation energy for the blueshift process in the range of 1.25 eV, which increases with N content. Analysis with high-resolution x-ray diffraction (HRXRD) shows that the blueshift experienced in this regime is not due to a stoichiometric change in the QW. In the weak blueshift regime, the blueshift, which is only partly due to In outdiffusion, saturates more slowly the higher the N content. Annealing at the same temperature (600 deg. C) for a longer time shows that the blueshift saturates earlier than the PL intensity and that samples with higher nitrogen experience a larger blueshift. Only a small In outdiffusion for annealing at high temperatures (>650 deg. C) and long duration was observed. However, this modest stoichiometric change does not explain the large blueshift experienced by the GaInNAs SQWs. We conclude that the mechanism responsible for the drastic blueshift after

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

    PubMed

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

    2014-06-01

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

  2. The effect of thermal annealing on pentacene thin film transistor with micro contact printing.

    PubMed

    Shin, Hong-Sik; Yun, Ho-Jin; Baek, Kyu-Ha; Ham, Yong-Hyun; Park, Kun-Sik; Kim, Dong-Pyo; Lee, Ga-Won; Lee, Hi-Deok; Lee, Kijun; Do, Lee-Mi

    2012-07-01

    We used micro contact printing (micro-CP) to fabricate inverted coplanar pentacene thin film transistors (TFTs) with 1-microm channels. The patterning of micro-scale source/drain electrodes without etch process was successfully achieved using Polydimethylsiloxane (PDMS) elastomer stamp. We used the Ag nano particle ink as an electrode material, and the sheet resistance and surface roughness of the Ag electrodes were effectively reduced with the 2-step thermal annealing on a hotplate, which improved the mobility, the on-off ratio, and the subthreshold slope (SS) of the pentacene TFTs. In addition, the device annealing on a hotplate in a N2 atmosphere for 30 sec can enhance the off-current and the mobility properties of OTFTs without damaging the pentacene thin films and increase the adhesion between pentacene and dielectric layer (SiO2), which was investigated with the pentacene films phase change of the XRD spectrum after device annealing.

  3. Effect of annealing atmosphere on phase formation and electrical characteristics of bismuth ferrite thin films

    SciTech Connect

    Simoes, A.Z.; Riccardi, C.S.; Dos Santos, M.L.; Garcia, F. Gonzalez; Longo, E.; Varela, J.A.

    2009-08-05

    Bismuth ferrite thin films were deposited on Pt/Ti/SiO{sub 2}/Si substrates by a soft chemical method and spin-coating technique. The effect of annealing atmosphere (air, N{sub 2} and O{sub 2}) on the structure and electrical properties of the films are reported. X-ray diffraction analysis reveals that the film annealed in air atmosphere is a single-phase perovskite structure. The films annealed in air showed better crystallinity and the presence of a single BFO phase leading to lower leakage current density and superior ferroelectric hysteresis loops at room temperature. In this way, we reveal that BFO film crystallized in air atmosphere by the soft chemical method can be useful for practical applications, including nonvolatile digital memories, spintronics and data-storage media.

  4. Effect of annealing on the electrical properties of thallium-doped PbTe single crystals

    SciTech Connect

    Ahmedova, G. A. Abdinova, G. J.; Abdinov, J. Sh.

    2011-02-15

    It is found that electrical parameters of PbTe single crystals, the character of the dependences of these parameters on temperature and Tl impurity concentration, and the conductivity type (signs of {alpha} and R) are governed to a great extent by the temperature of preliminary annealing. The cause of this effect is that the concentration of doubly charged vacancies in the tellurium sublattice increases with an increase in the annealing temperature, as a result of which the formation of electrically neutral or singly charged complexes of impurity-vacancy type becomes more likely.

  5. Effect of post-annealing on the plasma etching of graphene-coated-copper.

    PubMed

    Hui, L S; Whiteway, E; Hilke, M; Turak, A

    2014-01-01

    High temperature deposition of graphene on Cu by chemical vapor deposition can be used to produce high quality films. However, these films tend to have a non-equilibrium structure, with relatively low graphene adhesion. In this study, samples of graphene grown on copper foils by high temperature CVD were post-deposition annealed at temperatures well below the critical temperature of Cu. Resistance to etching under plasma was examined to assess the mechanical robustness of the graphene on the Cu surface, analyzed using optical and Raman microscopies. We found a correlation between the post-annealing time and etching time for the complete removal of graphene from Cu. Etching rates, minimum etch times, and surface appearance were observed to vary depending on the etching plasma (air, oxygen or nitrogen). Oxygen plasmas were found to be the least aggressive, emphasizing the improved adhesion with post-annealing treatments. Our results imply that the etching of graphene on Cu, and hence the adhesion of graphene, can be controlled by proper annealing and choice of plasma gas.

  6. Effects of a modular two-step ozone-water and annealing process on silicon carbide graphene

    SciTech Connect

    Webb, Matthew J. Lundstedt, Anna; Grennberg, Helena; Polley, Craig; Niu, Yuran; Zakharov, Alexei A.; Balasubramanian, Thiagarajan; Dirscherl, Kai; Burwell, Gregory; Guy, Owen J.; Palmgren, Pål; Yakimova, Rositsa

    2014-08-25

    By combining ozone and water, the effect of exposing epitaxial graphene on silicon carbide to an aggressive wet-chemical process has been evaluated after high temperature annealing in ultra high vacuum. The decomposition of ozone in water produces a number of oxidizing species, however, despite long exposure times to the aqueous-ozone environment, no graphene oxide was observed after the two-step process. The systems were comprehensively characterized before and after processing using Raman spectroscopy, core level photoemission spectroscopy, and angle resolved photoemission spectroscopy together with low energy electron diffraction, low energy electron microscopy, and atomic force microscopy. In spite of the chemical potential of the aqueous-ozone reaction environment, the graphene domains were largely unaffected raising the prospect of employing such simple chemical and annealing protocols to clean or prepare epitaxial graphene surfaces.

  7. Photo annealing effect on p-doped inverted organic solar cell

    SciTech Connect

    Lafalce, Evan; Toglia, Patrick; Lewis, Jason E.; Jiang, Xiaomei

    2014-06-28

    We report the transient positive photo annealing effect in which over 600% boost of power conversion efficiency was observed in inverted organic photovoltaic devices (OPV) made from P3HT/PCBM by spray method, after 2 hrs of constant solar AM 1.5 irradiation at low temperature. This is opposite to usual photodegradation of OPV, and cannot be explained by thermal activation alone since the mere temperature effect could only account for 30% of the enhancement. We have investigated the temperature dependence, cell geometry, oxygen influence, and conclude that, for p-doped active layer at room temperature, the predominant mechanism is photo-desorption of O{sub 2}, which eliminates electron traps and reduces space charge screening. As temperature decreases, thermal activation and deep trap-state filling start to show noticeable effect on the enhancement of photocurrent at intermediate low temperature (T = 125 K). At very low temperature, the dominant mechanism for photo annealing is trap-filling, which significantly reduces recombination between free and trapped carriers. At all temperature, photo annealing effect depends on illumination direction from cathode or anode. We also explained the large fluctuation of photocurrent by the capture/reemit of trapped electrons from shallow electron traps of O{sub 2}{sup -} generated by photo-doping. Our study has demonstrated the dynamic process of photo-doping and photo-desorption, and shown that photo annealing in vacuum can be an efficient method to improve OPV device efficiency.

  8. Photo annealing effect on p-doped inverted organic solar cell

    NASA Astrophysics Data System (ADS)

    Lafalce, Evan; Toglia, Patrick; Lewis, Jason E.; Jiang, Xiaomei

    2014-06-01

    We report the transient positive photo annealing effect in which over 600% boost of power conversion efficiency was observed in inverted organic photovoltaic devices (OPV) made from P3HT/PCBM by spray method, after 2 hrs of constant solar AM 1.5 irradiation at low temperature. This is opposite to usual photodegradation of OPV, and cannot be explained by thermal activation alone since the mere temperature effect could only account for 30% of the enhancement. We have investigated the temperature dependence, cell geometry, oxygen influence, and conclude that, for p-doped active layer at room temperature, the predominant mechanism is photo-desorption of O2, which eliminates electron traps and reduces space charge screening. As temperature decreases, thermal activation and deep trap-state filling start to show noticeable effect on the enhancement of photocurrent at intermediate low temperature (T = 125 K). At very low temperature, the dominant mechanism for photo annealing is trap-filling, which significantly reduces recombination between free and trapped carriers. At all temperature, photo annealing effect depends on illumination direction from cathode or anode. We also explained the large fluctuation of photocurrent by the capture/reemit of trapped electrons from shallow electron traps of O2- generated by photo-doping. Our study has demonstrated the dynamic process of photo-doping and photo-desorption, and shown that photo annealing in vacuum can be an efficient method to improve OPV device efficiency.

  9. Effect of thermal annealing on the thermoluminescent properties of nano-calcium fluoride and its dose-response characteristics.

    PubMed

    Mundupuzhakal, J K; Biswas, R H; Chauhan, S; Varma, V; Acharya, Y B; Chakrabarty, B S

    2015-12-01

    Nano-CaF2, prepared by the co-precipitation method, was annealed under different annealing conditions to improve its thermoluminescence (TL) characteristics. Different annealing parameters, such as temperature (400-700°C), duration (1-4 h) and environment (vacuum and air), were explored. The effect on TL sensitivity, peak position (Tm) and full-width at half-maximum (FWHM) with respect to the different annealing conditions are discussed as they are the measure of crystallinity of the material. Annealing temperature of 500°C with annealing duration of two and a half hours in vacuum provided the highest luminescence response (i.e. maximum sensitivity, minimum peak temperature and FWHM). Wide detectable dose range (5 mGy to 2 kGy), absence of thermal quenching and sufficient activation energy (1.04 eV) of this phosphor make it suitable for dosimetric applications.

  10. CrCuAgN PVD nanocomposite coatings: Effects of annealing on coating morphology and nanostructure

    NASA Astrophysics Data System (ADS)

    Liu, Xingguang; Iamvasant, Chanon; Liu, Chang; Matthews, Allan; Leyland, Adrian

    2017-01-01

    CrCuAgN PVD nanocomposite coatings were produced using pulsed DC unbalanced magnetron sputtering. This investigation focuses on the effects of post-coat annealing on the surface morphology, phase composition and nanostructure of such coatings. In coatings with nitrogen contents up to 16 at.%, chromium exists as metallic Cr with N in supersaturated solid solution, even after 300 °C and 500 °C post-coat annealing. Annealing at 300 °C did not obviously change the phase composition of both nitrogen-free and nitrogen-containing coatings; however, 500 °C annealing resulted in significant transformation of the nitrogen-containing coatings. The formation of Ag aggregates relates to the (Cu + Ag)/Cr atomic ratio (threshold around 0.2), whereas the formation of Cu aggregates relates to the (Cu + Ag + N)/Cr atomic ratio (threshold around 0.5). The primary annealing-induced changes were reduced solubility of Cu, Ag and N in Cr, and the composition altering from a mixed ultra-fine nanocrystalline and partly amorphous phase constitution to a coarser, but still largely nanocrystalline structure. It was also found that, with sufficient Cu content (>12 at.%), annealing at a moderately high temperature (e.g. 500 °C) leads to transportation of both Cu and Ag (even at relatively low concentrations of Ag, ≤3 at.%) from inside the coating to the coating surface, which resulted in significant reductions in friction coefficient, by over 50% compared to that of the substrate (from 0.31 to 0.14 with a hemispherical diamond indenter, and from 0.83 to 0.40 with an alumina ball counterface, respectively). Results indicate that the addition of both Cu and Ag (in appropriate concentrations) to nitrogen-containing chromium is a viable strategy for the development of 'self-replenishing' silver-containing thin film architectures for temperature-dependent solid lubrication requirements or antimicrobial coating applications.

  11. The Effect of Thermal Annealing on Charge Transport in Organolead Halide Perovskite Microplate Field-Effect Transistors.

    PubMed

    Li, Dehui; Cheng, Hung-Chieh; Wang, Yiliu; Zhao, Zipeng; Wang, Gongming; Wu, Hao; He, Qiyuan; Huang, Yu; Duan, Xiangfeng

    2017-01-01

    Transformation of unipolar n-type semiconductor behavior to ambipolar and finally to unipolar p-type behavior in CH3 NH3 PbI3 microplate field-effect transistors by thermal annealing is reported. The photoluminescence spectra essentially maintain the same features before and after the thermal annealing process, demonstrating that the charge transport measurement provides a sensitive way to probe low-concentration defects in perovskite materials.

  12. Effect of annealing on proton irradiated AlGaN/GaN based micro-Hall sensors

    SciTech Connect

    Abderrahmane, A.; Takahashi, H.; Tashiro, T.; Ko, P. J.; Okada, H.; Sandhu, A.; Sato, S.; Ohshima, T.

    2014-02-20

    The effect of annealing at 673 K on irradiated micro-Hall sensors irradiated with protons at 380keV and fluences of 10{sup 14}, 10{sup 15} and 10{sup 16} protons/cm{sup 2} is reported. Cathodoluminescence measurements were carried out at room temperature before and after annealing and showed improvement in the band edge band emission of the GaN layer. After annealing a sensor irradiated by 10{sup 15} protons/cm{sup 2} the device became operational with improvements in its magnetic sensitivity. All irradiated sensors showed improvement in their electrical characteristics after annealing.

  13. Effect of Annealing Treatment on Erosion-Corrosion of Zr-Based Bulk Metallic Glass in Saline-Sand Slurry

    NASA Astrophysics Data System (ADS)

    Ji, Xiulin; Shan, Yiping; Chen, Yueyue; Wang, Hui

    2016-06-01

    Bulk metallic glass (BMG) may be a good candidate to solve the erosion-corrosion (E-C) problems of marine pumps in sand-containing seawater. Since annealing treatment is an effective way to improve plasticity of BMGs, the effect of annealing treatment on E-C wear of Zr-based BMG in saline-sand slurry was investigated. All of the annealed BMG samples were crystallized and the quantity of (Zr, Cu) phase increased but that of Al4Cu9 phase decreased with the increase of annealing temperature from 360 to 480 °C. Accordingly, annealing treatment enhances plasticity of the as-cast BMG at the cost of hardness and corrosion resistance. Moreover, 480 °C annealed BMG sample possesses the highest hardness and the lowest corrosion current density in all of the annealed BMG samples. Using a slurry pot erosion tester, the E-C wear of the as-cast and annealed BMG samples was studied under different impingement angles, impact velocities, and concentrations in saline-sand slurry. With the improvement of plasticity, 480 °C annealed BMG sample exhibits the best E-C wear resistance under high impingement angle, high impact velocity, and high sand concentration.

  14. Application of a model for treatment of time dependent effects on irradiation of microelectronic devices

    SciTech Connect

    Brown, D.B.; Jenkins, W.C. ); Johnston, A.H. )

    1989-12-01

    A simple model for interpreting and extrapolating time dependent effects is tested by fitting to published and previously unpublished experimental data. The goal is to evaluate the applicability of such a model to hardness assurance testing in cases where defect growth and annealing processes (time dependent effects) are significant. Data is presented indicating hole annealing times varying by more than six orders of magnitude. The implications of the large variation in hole annealing times for hardness assurance testing are explored.

  15. Annealing of Co-Cr dental alloy: effects on nanostructure and Rockwell hardness

    PubMed Central

    Soylu, Elif Hilal; İde, Semra; Kılıç, Selim; Sipahi, Cumhur; Pişkin, Bulent; Gökçe, Hasan Suat

    2013-01-01

    PURPOSE The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring 4 × 2 × 2 mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of <.05 were accepted as statistically significant. RESULTS The general nanostructures of the samples were composed of small spherical entities stacked atop one another in dendritic form. All groups also displayed different hardness values depending on the manufacturing technique. The annealing procedure and environment directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness (48.16 ± 3.02 HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness (27.40 ± 3.98 HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 Å). CONCLUSION After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic

  16. Effects of neutron irradiation and subsequent annealing on the optical characteristics of sapphire

    NASA Astrophysics Data System (ADS)

    Zhang, M. F.; Zhang, H. L.; Han, J. C.; Guo, H. X.; Xu, C. H.; Ying, G. B.; Shen, H. T.; Song, N. N.

    2011-02-01

    In this paper, the effect of neutron irradiation on sapphire single crystal with fast neutron of 1.0×10 18 and 1.0×10 19 neutrons/cm 2 has been investigated along with the effect of annealing temperature. It is found that the colorless transparent sapphire single crystals were turned yellow after 10 MeV fast neutron irradiation at room temperature. There are peaks at 206, 230, 258, 305, 358 and 452 nm after neutron irradiation. And the intensity of optical absorption bands decrease with wavelength and annealing temperature. A new absorption peak at 452 nm was found after isothermal annealing at 400 °C for 10 min, which was ascribed to F 2+ color center. Because of the recombination of interstitial ions and vacancies, color centers were almost removed after annealing at 1000 °C. The TL peaks were found to shift to higher temperature after neutron irradiation. And a higher fluence of the neutron irradiation would result in deep traps revealed as the new TL peaks at 176 and 227 °C.

  17. Effect of annealing atmosphere on the thermal coarsening of nanoporous gold films

    NASA Astrophysics Data System (ADS)

    Chen, A. Y.; Shi, S. S.; Liu, F.; Wang, Y.; Li, X.; Gu, J. F.; Xie, X. F.

    2015-11-01

    The coarsening of nanoporous gold (NPG) is significantly influenced by surface adsorbates at elevated temperature. In this paper, the effect of annealing atmosphere on the thermal growth of the porous structure was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. The NPG films were annealed in oxidative (air), inert (Ar) and reductive (CO) atmospheres at 100-600 °C for 2 h, respectively. The experimental results indicate that the NPG films show the best stability in the reductive atmosphere and the worst thermal properties in oxidative air. The NPG films annealed in air exhibit a significant pore growth at 200 °C and lose the porous structure at 300 °C, while those annealed in CO gas at 600 °C still remain the porous network. The thermal-induced coarsening of NPG films in air can be attributed to the desorption of O2 from the NPG surface above 200 °C. In contrast, the stabilization of the NPG films in CO gas originates from the strong binding of CO with Au atoms to form a complex adsorption layer, which effectively inhibits the surface diffusion of Au atoms.

  18. 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.

  19. Neutron irradiation and post annealing effect on sapphire by positron annihilation.

    PubMed

    Han, Jie-cai; Zhang, Hai-liang; Zhang, Ming-fu; Wang, Bao-yi; Li, Zhuo-xin; Xu, Cheng-hai; Guo, Huai-xin

    2010-09-01

    Sapphire single crystals grown by an improved Kyropoulos-like method are irradiated by fast neutron flux. The irradiated doses of neutron are 10(18) and 10(19)n/cm(2). The infrared transmission spectra of sapphire were studied before and after irradiation. The irradiated samples were annealed at 200, 400, 600, 800 and 1000 degrees C for 10min in ambient atmosphere. Positron annihilation studies have been carried out before and after neutron irradiation. The experimentally measured positron lifetime in the pristine specimen is 143ps. There were aluminum vacancies produced in sapphire crystals after neutron irradiation. The positron lifetime increased with the dose of neutron flux. A longer value tau(2) was found after annealing at 600 degrees C, which indicated vacancies were aggregated with each other. The second long-time component tau(2) has been found to increase with the annealing temperature. There was almost no change in peak position of the CDB spectra after neutron irradiation and isothermal annealing. The chemical environment of core in sapphire did not change greatly after neutron irradiation.

  20. The effect of annealing on the recovery of irradiated Ni and Fe wires by detection of magnetic property changes

    SciTech Connect

    Shong, W.J.; Stubbins, J.F.

    1995-12-31

    Neutron irradiated Ni and Fe wires with doses ranging from 6.8 {times} 10{sup 17} to 3.6 {times} 10{sup 19} n/cm{sup 2} (E > 1 MeV) at 288 C were annealed isothermally and isochronally. Magnetic coercivity was measured to monitor the recovery process. Iron displayed significant changes while the coercivity of Ni decreased monotonically with increasing annealing temperature. Microhardness was also performed on unirradiated wires following annealing. Hardness was found to show a similar trend to coercivity. The annealing behavior of the Fe and Ni wires and the similarity between coercivity and hardness responses to annealing are interpreted in terms of internal stress relief and clustering of point defects. This investigation indicates that magnetic detection can be a useful nondestructive method for monitoring radiation damage and recovery in nuclear pressure vessel steel.

  1. Tellurium precipitates in (Cd,Mn)Te:V crystals: Effects of annealing

    SciTech Connect

    Kochanowska,D.; Mycielski, A.; Witkowska-Baran, M.; Szadkowski, A.; Witkowska, B.; Kaliszek, W.; Cui, Y.; James, R. B.

    2008-10-19

    We suggest that (Cd,Mn)Te is a suitable material for fabricating gamma- and X-ray detectors. Our investigations, reported here, are focused on producing high-quality (Cd,Mn)Te crystals with high resistivity (10{sup 9} {Omega}-cm) by the Bridgman method. As-grown, undoped (Cd,Mn)Te crystals are typically p-type, signifying that they contain excess Cd vacancies (acting as acceptors), accumulated during growth. Doping with vanadium atoms, which function as compensating centers, results in a semi-insulating material (Cd,Mn)Te:V. Properly annealing the platelets in cadmium vapors at uniform temperature reduces the number of cadmium vacancies, and lowers the level of the vanadium doping required for compensation. We found that annealing in cadmium vapors not only decreases the concentration of the native cadmium vacancies but also improves the crystal's quality. Infrared observations of the interior of the samples show that annealing in a temperature gradient perpendicular to the platelet has an additional effect, viz., the tellurium precipitates migrate towards the side where the temperature is higher. We demonstrate, with IR pictures of monocrystalline (Cd,Mn)Te:V platelets cut parallel to the (111) crystal planes, the influence on tellurium inclusions and precipitates of various conditions of annealing in cadmium vapors.

  2. Effect of thermal annealing on the spectroscopic parameters of Er3+-doped sodium silicate glass

    NASA Astrophysics Data System (ADS)

    de Morais, Rodrigo F.; Serqueira, Elias Oliveira; Dantas, Noelio Oliveira

    2013-10-01

    This paper presents the optical characteristics of Er3+ ions in sodium silicate glass (SiO2-Na2O), synthesized by the fusion method and later annealed for 0, 30, 60 and 90 min. Thermograms, X-ray diffraction, optical absorption, luminescence spectroscopy measurements were performed in order to determine the thermal and structural of the samples and the radiative characteristics of Er3+ ions under influence of thermal annealing of the samples. Differential thermal analysis provided evidence of a phase change in the system. This phase change was confirmed by X-ray diffraction, which showed the formation and growth of Na2SiO3 crystals for the annealed samples. These crystals affect the neighborhood (from second vicinity) of Er3+ ions. These effects were noted by the J-O parameters (Ω2 and Ω4), which were calculated from the optical absorption spectra. Judd-Ofelt calculations also confirmed that heat treatment induced structural rearrangement of the samples that was dependent on Er2O3 concentration. This resulted in changes in the optical and physical properties of the samples, including stimulated emission cross section and rigidity. Analysis of the spectroscopy parameters after of thermal annealing indicate samples are potential materials for in optical device applications.

  3. Effects of thermal annealing and reirradiation on toughness of reactor pressure vessel steels

    SciTech Connect

    Nanstad, R.K.; Iskander, S.K.; Sokolov, M.A.

    1997-02-01

    One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPV) is to thermally anneal them to restore the toughness properties that have been degraded by neutron irradiation. This paper summarizes recent experimental results from work performed at the Oak Ridge National Laboratory (ORNL) to study the annealing response, or {open_quotes}recovery,{close_quotes} of several irradiated RPV steels; it also includes recent results from both ORNL and the Russian Research Center-Kurchatov Institute (RRC-KI) on a cooperative program of irradiation, annealing and reirradiation of both U.S. and Russian RPV steels. The cooperative program was conducted under the auspices of Working Group 3, U.S./Russia Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS). The materials investigated are an RPV plate and various submerged-arc welds, with tensile, Charpy impact toughness, and fracture toughness results variously determined. Experimental results are compared with applicable prediction guidelines, while observed differences in annealing responses and reirradiation rates are discussed.

  4. 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.

  5. The effect of final annealing after β-quenching on the corrosion resistance of Zircaloy-4 in lithiated water with 0.04 M LiOH

    NASA Astrophysics Data System (ADS)

    Yao, M. Y.; Shen, Y. F.; Li, Q.; Peng, J. C.; Zhou, B. X.; Zhang, J. L.

    2013-04-01

    To further understand the effect of heat treatments on the corrosion resistance of Zircaloy-4, some specimens were treated by β-quenching at 1020 °C for 20 min and then annealing at 480-600 °C for 2-200 h. The specimens were corroded in lithiated water with 0.04 M LiOH at 360 °C/18.6 MPa. The microstructures of the specimens and the oxide films were observed by TEM and SEM. The results show that the β-quenched specimen with the cooling rate of 100 °C/s behaves the best corrosion resistance. After annealing at 480-600 °C, the corrosion resistance gets worse with increasing annealing temperature. The annealing time has little effect on the corrosion resistance for the specimens annealed at 480 and 540 °C after β-quenching. However, the corrosion resistance of the specimens annealed at 600 °C becomes worse with the increase of annealing time. The grain size of the oxide on the specimen with high Fe and Cr concentrations in α-Zr is coarser than that on the specimen with low Fe and Cr concentrations in α-Zr, and the pores and cracks are fewer in the oxide film on the former specimen than those on the latter specimen. This indicates that a suitable increase in Fe and Cr concentrations in α-Zr matrix is beneficial to retarding the microstructural evolution of oxide, thereby improving the corrosion resistance.

  6. 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

  7. Effect of Crystal Orientation on Self-Assembly Nanocones Formed on Tungsten Surface Induced by Helium Ion Irradiation and Annealing

    PubMed Central

    Huang, Shilin; Ran, Guang; Lei, Penghui; Wu, Shenghua; Chen, Nanjun; Li, Ning

    2016-01-01

    The self-assembly nanocone structures on the surface of polycrystalline tungsten were created by He+ ion irradiation and then annealing, and the resulting topography and morphology were characterized using atomic force microscopy and scanning electron microscopy. The cross-sectional samples of the self-assembly nanocones were prepared using an in situ–focused ion beam and then observed using transmission electron microscopy. The self-assembly nanocones were induced by the combined effect of He+ ion irradiation, the annealing process and the chromium impurity. The distribution characteristics, density and morphology of the nanocones exhibited a distinct difference relating to the crystal orientations. The highest density of the nanocones was observed on the grain surface with a (1 1 1) orientation, with the opposite for that with a (0 0 1) orientation and a medium value on the (1 0 1)-oriented grain. The size of the self-assembly nanocones increased with increasing the annealing time which met a power-law relationship. Irradiation-induced defects acted as the nucleation locations of the protrusions which attracted the migration of the tiny amount of chromium atoms. Under the action of temperature, the protrusions finally evolved into the nanocones. PMID:28335337

  8. Study on the effect of Cd-diffusion annealing on the electrical properties of CdZnTe

    NASA Astrophysics Data System (ADS)

    Wanwan, Li; Zechun, Cao; Bin, Zhang; Feng, Zhan; Hongtao, Liu; Wenbin, Sang; Jiahua, Min; Kang, Sun

    2006-06-01

    In order to meet the requirements for the device design of radiation detectors, CdZnTe (or Cd 1-xZn xTe) crystals grown by Vertical Bridgman Method often need subsequent annealing to increase their resistivity. The nature of this treatment is a diffusion process. Thus, it is meaningful to relate the change of resistivity to the diffusion parameters. A model correlating resistivity and conduction type of CdZnTe with the main diffusion parameter—diffusion coefficient—is put forward in this paper. Combining the model with the analysis of our experimental data, DCd=1.464×10 -10, 1.085×10 -11 and 4.167×10 -13 cm 2/s are the values of Cd self-diffusion coefficient in Cd 0.9Zn 0.1Te at 1073, 973 and 873 K, respectively. The data coincide closely with the Cd self-diffusion coefficient in CdTe provided by different authors [E.D. Jones, N.M. Stewart, Self-diffusion of cadmium in cadmium telluride, J. Crystal Growth 84 (1987) 289-294; P.M. Borsenberger, D.A. Stevenson, J. Phys. Chem. Solids 29 (1968) 1277; R.C. Whelan, D. Shaw, in: D.G. Thomas (Ed.), II -VI Semiconductor Compounds, Benjamin, New York, 1967, p. 451]. With the data, the effects of annealing time on the change of resistivity and conduction type for Cd 0.9Zn 0.1Te wafers, which are annealed in saturated Cd vapor at 1073, 973 and 873 K, were simulated, and good consistency was found. This work suggests an alternative way to obtain the diffusion coefficient in semiconductor materials and also enables ones to analyze the diffusion process quantitatively and predict the annealing results.

  9. The Effect of Hydrogen Annealing and Sulfur Content on the Oxidation Resistance of PWA 1480

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1997-01-01

    For many decades the dramatic effect of trace amounts of reactive elements on alumina and chromia scale adhesion has been recognized and widely studied. Although various theories have been used to account for such behavior, the connection between scale adhesion and sulfur segregation was initially reported by Smeggil et al. This study found strong surface segregation of sulfur from very low levels in the bulk which could then be curtailed by the addition of reactive elements. It was assumed that the reactive elements, which are strong sulfide formers, acted by getting sulfur in the bulk thus precluding sulfur segregation and weakening of the oxide-metal bond. Subsequent studies confirmed that adhesion could be produced by reducing the sulfur impurity level, without reactive elements. The understanding of this phenomenon has been applied to modern single crystal superalloys, where the addition of Y, although very effective, is problematic. Also problematic is definition of the level of sulfur that is acceptable and below which no further adhesion benefit is reached. Published works have indicated a broad transition defined by various materials and oxidation tests. The present study describes the oxidation behavior of one superalloy (PWA 1480) as a function of various sulfur contents produced by hydrogen annealing for various temperatures, times, and sample thicknesses. The purpose is to define more precisely a criterion for adhesion based on total sulfur reservoir and segregation potential.

  10. Enhanced memory characteristics in organic ferroelectric field-effect transistors through thermal annealing

    SciTech Connect

    Sugano, Ryo; Tashiro, Tomoya; Sekine, Tomohito; Fukuda, Kenjiro; Kumaki, Daisuke; Tokito, Shizuo

    2015-11-15

    We report on the memory characteristics of organic ferroelectric field-effect transistors (FeFETs) using spin-coated poly(vinylidene difluoride/trifluoroethylene) (P(VDF/TrFE)) as a gate insulating layer. By thermal annealing the P(VDF/TrFE) layer at temperatures above its melting point, we could significantly improve the on/off current ratio to over 10{sup 4}. Considerable changes in the surface morphology and x-ray diffraction patterns were also observed in the P(VDF/TrFE) layer as a result of the annealing process. The enhanced memory effect is attributed to large polarization effects caused by rearranged ferroelectric polymer chains and improved crystallinity in the organic semiconductor layer of the FeFET devices.

  11. Effect of Cold Work and Partial Annealing on Thermomechanical Behaviour of Ti-50.5at%Ni

    NASA Astrophysics Data System (ADS)

    Mahmud, Abdus Samad; Wu, Zhigang; Yang, Hong; Liu, Yinong

    2017-03-01

    This study investigated the effect of cold work and partial annealing on the thermal and mechanical behaviour of NiTi. It is well understood that the thermomechanical properties of near-equiatomic NiTi are highly dependent on the microstructure, and hence the history of thermomechanical treatments has undergone through. It has been generally accepted that a sufficiently high cold work is necessary prior to annealing but detailed knowledge of the influence of the level of prior cold work on annealing is unclear. This study determined the threshold effective levels of cold work required for annealing and demonstrated that the thermal and mechanical properties of Ti-50.5at%Ni are sensitive to the level of cold work as well as temperature of partial annealing.

  12. Size Dependence of Oxygen-Annealing Effects on Superconductivity of Fe1+yTe1-xSx

    NASA Astrophysics Data System (ADS)

    Yamazaki, Teruo; Sakurai, Tatsuya; Yaguchi, Hiroshi

    2016-11-01

    For the Fe-based superconductor Fe1+yTe1-xSx, superconductivity is induced by annealing treatment in oxygen atmosphere, whereas as-grown samples do not show superconductivity. We investigated the sample-size dependence of O2-annealing effects in Fe1.01Te0.91S0.09. The annealing conditions were fixed to 1 atm, 200 °C, and 2 h. We carried out magnetic susceptibility and specific heat measurements in order to evaluate the superconducting volume fraction. We found that Fe1+yTe1-xSx has an optimal size for the induction of bulk superconductivity by O2 annealing. Our results indicate that O2 annealing is probably effective near the surface of samples over a length of a few tens of micro meters.

  13. Annealing effects on the structural and magnetic properties of off-stoichiometric Fe-Mn-Ga ferromagnetic shape memory alloys

    DOE PAGES

    Chen, Yan; Bei, Hongbin; Dela Cruz, Clarina R; ...

    2016-05-07

    Annealing plays an important role in modifying structures and properties of ferromagnetic shape memory alloys (FSMAs). The annealing effect on the structures and magnetic properties of off-stoichiometric Fe45Mn26Ga29 FSMA has been investigated at different elevated temperatures. Rietveld refinements of neutron diffraction patterns display that the formation of the γ phase in Fe45Mn26Ga29 annealed at 1073 K increases the martensitic transformation temperature and reduces the thermal hysteresis in comparison to the homogenized sample. The phase segregation of a Fe-rich cubic phase and a Ga-rich cubic phase occurs at the annealing temperature of 773 K. The atomic occupancies of the alloys aremore » determined thanks to the neutron's capability of differentiating transition metals. The annealing effects at different temperatures introduce a different magnetic characteristic that is associated with distinctive structural changes in the crystal.« less

  14. Effect of Thermal Annealing on the Electrical Conductivity of Copper-Tin Polymer Composites.

    PubMed

    Yang, Qing; Beers, Megan Hoarfrost; Mehta, Vishrut; Gao, Ting; Parkinson, Dilworth

    2017-01-11

    Polyvinylidene fluoride (PVDF) copolymer conductive composites containing 40 vol % copper (Cu) and tin (Sn) fillers are prepared by injection molding. Postmolding thermal annealing is found to increase the electrical conductivity of the composites by an order of magnitude. The volume ratio between Cu and Sn is found to have a significant effect on filler distribution but a weaker effect on electrical conductivity compared to the annealing conditions. Synchrotron X-ray tomography is used to visualize and quantitatively analyze the morphology and distribution of the filler particles, indicating that higher conductivity can be attributed to better dispersion of the low-melting-point Sn filler, which provides better interparticle contact in the Cu network.

  15. Effect of annealing over optoelectronic properties of graphene based transparent electrodes

    NASA Astrophysics Data System (ADS)

    Yadav, Shriniwas; Kaur, Inderpreet

    2016-04-01

    Graphene, an atom-thick two dimensional graphitic material have led various fundamental breakthroughs in the field of science and technology. Due to their exceptional optical, physical and electrical properties, graphene based transparent electrodes have shown several applications in organic light emitting diodes, solar cells and thin film transistors. Here, we are presenting effect of annealing over optoelectronic properties of graphene based transparent electrodes. Graphene based transparent electrodes have been prepared by wet chemical approach over glass substrates. After fabrication, these electrodes tested for optical transmittance in visible region. Sheet resistance was measured using four probe method. Effect of thermal annealing at 200 °C was studied over optical and electrical performance of these electrodes. Optoelectronic performance was judged from ratio of direct current conductivity to optical conductivity (σdc/σopt) as a figure of merit for transparent conductors. The fabricated electrodes display good optical and electrical properties. Such electrodes can be alternatives for doped metal oxide based transparent electrodes.

  16. Effects of pre-annealing on the uni- and bi-axial stretching behavior of poly(ethylene naphthalate) films

    SciTech Connect

    Abe, T. Takarada, W. Kikutani, T.

    2014-05-15

    Effect of pre-annealing on stress and birefringence behavior of poly(ethylene naphthalate) (PEN) films during stretching and relaxation processes was investigated. Amorphous and non-oriented PEN films were pre-annealed under the conditions of different temperatures and periods. The pre-annealed films were stretched uniaxially or equi-biaxially and then relaxed at fixed length. It was found that pre-annealing did not cause any notable change for the initial behavior of refractive indices variation, whereas the behaviors after necking were significantly affected. Through the comparison between in-plane and out-of-plane birefringence and the analysis of wide-angle x-ray diffraction patterns of drawn films of both stretching modes, it was confirmed that the orientation of naphthalene ring in the film plane was enhanced by pre-annealing.

  17. On the Stressing of Annealed NITINOL: The Electrical Resistance and Calorimetric Effects

    DTIC Science & Technology

    1987-04-01

    Security Classification) On the Stressing of Annealed NITINOL : The Electrical Resistance and Calorimetric Effects 12 PERSONAL AUTHOR(S) Goldstein, David...COSATI CODES 18 SUBJECT TERMS (Continue on reverse if necessary and identify by blck numbher) FIELD GROUP SUB-GROUP NITINOL 06 Shape Memory Alloy 13 o i...calorimetry curves of NITINOL during its phase transformation are substantial. The generation of a peak occurs in the resistance curve, and an additional

  18. Effect of annealing on the structural, morphological and photoluminescence properties of ZnO thin films prepared by spin coating.

    PubMed

    Kumar, Vinod; Kumar, Vijay; Som, S; Yousif, A; Singh, Neetu; Ntwaeaborwa, O M; Kapoor, Avinashi; Swart, H C

    2014-08-15

    Zinc oxide (ZnO) thin films were deposited on silicon substrates by a sol-gel method using the spin coating technique. The ZnO films were annealed at 700°C in an oxygen environment using different annealing times ranging from 1 to 4 h. It was observed that all the annealed films exhibited a hexagonal wurtzite structure. The particle size increased from 65 to 160 nm with the increase in annealing time, while the roughness of the films increased from 2.3 to 10.6 nm with the increase in the annealing time. Si diffusion from the substrate into the ZnO layer occurred during the annealing process. It is likely that the Si and O2 influenced the emission of the ZnO by reducing the amount of Zn defects and the creation of new oxygen related defects during annealing in the O2 atmosphere. The emission intensity was found to be dependent on the reflectance of the thin films.

  19. Effects of Post-Deposition Annealing on the Properties of Calcium Manganese Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Ferrone, Natalie; Chaudhry, Adeel; Hart, Cacie; Lawson, Bridget; Houston, David; Neubauer, Samuel; Johnson, Anthony; Schaefer, David; Kolagani, Rajeswari

    We will present our results on the effects of post-deposition annealing on the structural and electrical properties of CaMnO3-d thin films grown by Pulsed Laser deposition. The thin films are epitaxially grown on (100) LaAlO3 which has larger in-plane lattice parameters than that of bulk CaMnO3, which leads to bi-axial tensile strain in the thin films. Results from our laboratory show that bi-axial tensile strain leads to low resistivity in thinner films, the resistivity increasing with increasing thickness. These results are suggestive of a coupling between strain and oxygen stoichiometry in the thin films. We have investigated the effects of post-deposition annealing in various gas ambients towards the goal of understanding the effects of relaxation and oxygen stoichiometric changes. We will present a comparison of the structural and electrical properties of as-grown and post-annealed films over a range of thicknesses. Support from Towson University Office of Undergraduate Research, Fisher Endowment Grant & Undergraduate Research Grant from the Fisher College of Science & Mathematics, Seed Funding Grant from the School of Emerging technologies, & NSF Grant ECCS 112856.

  20. Effects of annealing on structure and composition of LSMO thin films

    NASA Astrophysics Data System (ADS)

    Xie, Haipeng; Huang, Han; Cao, Ningtong; Zhou, Conghua; Niu, Dongmei; Gao, Yongli

    2015-11-01

    The effects of annealing on structure and composition of LSMO thin films grown by the means of DC magnetron sputtering have been investigated with the assistance of X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoemission spectroscopy (XPS). The first LSMO-related diffraction peak (A) appears on the sample prepared at 1023 K and shifts toward low-angle direction at higher temperature. A new diffraction peak (B) related to LaMnOx is observed on the sample prepared at 1073 K that becomes stronger with increasing annealing temperature. AFM images display the corresponding morphology evolutions. XPS results reveal that LaMnOx is formed due to strontium segregation on the LSMO surface at a temperature higher than 1023 K. Meanwhile, we find that a new ingredient appears from 973 to 1023 K and disappears from 1073 K to 1123 K, which is predicted to exist as semiconductor or insulator on the surface.

  1. Annealing effect of double dip coated ZnAl2O4 thin films

    NASA Astrophysics Data System (ADS)

    Chandramohan, R.; Dhanasekaran, V.; Sundaram, K.; Mahalingam, T.

    2013-02-01

    Thin films of ZnAl2O4 were prepared by dip technique involving chemical solutions. Investigations on the effect of post heat treatment on the structural, optical properties of ZnAl2O4 thin films were studied and reported. Xray diffraction patterns revealed that the thin films are polycrystalline cubic structure of ZnAl2O4. The microstructural properties of ZnAl2O4 thin films were calculated and crystallite size tends to increase with increase of annealing temperatures. The texture coefficients have been evaluated and found to be greater than unity revealing high texturing of the architecture of the film. The optical band gap values were found to be in the range of 3.48 - 3.62 eV. The n and k were found to decrease with increase of post annealing temperature. The SEM revealed the uniform distribution of spherical grains.

  2. Effects of oxygen-reducing atmosphere annealing on LaMnO3 epitaxial thin films

    SciTech Connect

    Choi, W. S.; Marton, Zsolt; Jang, S. Y.; Moon, S. J.; Jeon, B. C.; Shin, J. H.; Seo, Sung Seok A; Noh, Tae Won; Myung-Whun, Kim; Lee, Ho Nyung; Lee, Y. S.

    2009-01-01

    We investigated the effects of annealing on LaMnO{sub 3} epitaxial thin films grown by pulsed laser deposition (PLD) and propose an efficient method of characterizing their stoichiometry. Structural, magnetic and optical properties coherently indicate non-stoichiometric ferromagnetic and semiconducting phases for as-grown LaMnO{sub 3} films. By annealing in an oxygen-reducing atmosphere, we recovered the antiferromagnetic and insulating phases of bulk-like stoichiometric LaMnO{sub 3}. We show that non-destructive optical spectroscopy at room temperature is one of the most convenient tools for identifying the phases of LaMnO{sub 3} films. Our results serve as a prerequisite for studying LaMnO{sub 3} based heterostructures grown by PLD.

  3. Effect of annealing treatment on electroluminescence from GaN/Si nanoheterostructure array.

    PubMed

    Han, Chang Bao; He, Chuan; Meng, Xiao Bo; Wan, Ya Rui; Tian, Yong Tao; Zhang, Ying Jiu; Li, Xin Jian

    2012-02-27

    A GaN/Si nanoheterostructure array was prepared by growing GaN nanostructures on silicon nanoporous pillar array (Si-NPA). Based on as-grown and annealed GaN/Si-NPA, two light-emitting diodes (LEDs) were fabricated. It was found that after the annealing treatment, both the turn-on voltage and the leakage current density of the nanoheterostructure varied greatly, together with the electroluminescence (EL) changed from a yellow band to a near infrared band. The EL variation was attributed to the radiative transition being transformed from a defect-related recombination in GaN to an interfacial recombination of GaN/Si-NPA. Ours might have provided an effective approach for fabricating GaN/Si-based LEDs with different emission wavelengths.

  4. Effect of acetylation, oxidation and annealing on physicochemical properties of bean starch.

    PubMed

    Simsek, Senay; Ovando-Martínez, Maribel; Whitney, Kristin; Bello-Pérez, Luis A

    2012-10-15

    Black and Pinto bean starches were physically and chemically modified to investigate the effect of modification on digestibility and physicochemical properties of bean starch. The impact of acetylation, oxidation (ozonation) and annealing on the chemical composition, syneresis, swelling volume, pasting, thermal properties and digestibility of starches was evaluated. The physicochemical and estimated glycemic index (eGI) of the Black and Pinto bean starches treated with ozone were not significantly (P>0.05) different than that of their respective control starches. Annealed starches had improved thermal and pasting properties compared to native starches. Acetylated starches presented reduced syneresis, good pasting properties and lower eGI. Also, all modified starches had increased levels of resistant starch (RS). Therefore, the digestibility and physicochemical properties of bean starch were affected by the type of modification but there were no significant (P>0.05) differences between the Black and Pinto bean starches.

  5. Effect of initial-annealing on the microstructure of C-SiC/Cu composite coatings

    NASA Astrophysics Data System (ADS)

    Ren, D.; Du, J. F.; Xiao, T.; Yang, B.; Liu, B.; Lin, L. W.

    2013-07-01

    A copper layer as "binder" was added between C-SiC coating and the stainless steel substrate, before C-SiC coatings were prepared by using ion beam mixing and followed initial-annealing in vacuum. The surface microstructures scanned by atomic force microscopy (AFM) showed the increase or rupture of argon bubbles with the increasing temperature, which showed that initial-annealing could effectively eliminate residual gas in the coatings. The profile microstructure images obtained by scanning electron microscope (SEM) demonstrated that the interfaces of not only between C-SiC films but also between the coatings and the substrates transformed from clear to obscure, which implied the interdiffusion and stress release near these interfaces due to initial-annealing. Further depth profile analyses of major element including Cu, Si and Fe measured by secondary ion mass spectrometry (SIMS) also confirmed the interdiffusion, which could effectively enhance the adhesion strength of the coatings to the substrates by forming a wider extended transition layer.

  6. 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.

  7. Effects of molybdenum doping and thermal annealing on the physical properties of amorphous In–Zn–O films

    SciTech Connect

    Liu, Shiu-Jen; Wu, Kuei-Ching; Peng, Kun-Cheng

    2015-06-15

    Highlights: • The effects of Mo doping and thermal annealing on a-IZO films were studied. • The carrier mobility of Mo-doped a-IZO films was enhanced by thermal annealing. • The optical bandgap of a-IZO films was unaffected by Mo doping. • Ferromagnetism was observed in Mo-doped a-IZO films after annealing. - Abstract: Amorphous In–Zn–O (a-IZO) films doped with Mo were prepared on glass substrates by using magnetron co-sputtering technique. The Mo concentration was controlled by varying the sputtering power applied on the Mo target. The effects of Mo doping and thermal annealing on the electrical, optical and magnetic properties of the a-IZO films were studied. The electrical properties of a-IZO films were found to be strongly affected by Mo doping and thermal annealing. The optical transmission near the absorption edge of a-IZO films is enhanced by Mo doping due to the decrease in reflection. The optical bandgap estimated to be 3.2 eV of a-IZO films is unaffected by Mo doping and thermal annealing. Moreover, some of Mo-doped films exhibit room-temperature ferromagnetism after annealing.

  8. Effect of thermal annealing on structural and optical properties of In2S3 thin films

    NASA Astrophysics Data System (ADS)

    Choudhary, Sonu

    2015-08-01

    There is a highly need of an alternate of toxic materials CdS for solar cell applications and indium sulfide is found the most suitable candidate to replace CdS due to its non-toxic and environmental friendly nature. In this paper, the effect of thermal annealing on the structural and optical properties of indium sulfide (In2S3) thin films is undertaken. The indium sulfide thin films of 121 nm were deposited on glass substrates employing thermal evaporation method. The films were subjected to the X-ray diffractometer and UV-Vis spectrophotometer respectively for structural and optical analysis. The XRD pattern show that the as-deposited thin film was amorphous in nature and crystallinity is found to be varied with annealing temperature. The optical analysis reveals that the optical band gap is varied with annealing. The optical parameters like absorption coefficient, extinction coefficient and refractive index were calculated. The results are in good agreement with available literature.

  9. Annealing effect on thermodynamic and physical properties of mesoporous silicon: A simulation and nitrogen sorption study

    NASA Astrophysics Data System (ADS)

    Kumar, Pushpendra; Huber, Patrick

    2016-04-01

    Discovery of porous silicon formation in silicon substrate in 1956 while electro-polishing crystalline Si in hydrofluoric acid (HF), has triggered large scale investigations of porous silicon formation and their changes in physical and chemical properties with thermal and chemical treatment. A nitrogen sorption study is used to investigate the effect of thermal annealing on electrochemically etched mesoporous silicon (PS). The PS was thermally annealed from 200˚C to 800˚C for 1 hr in the presence of air. It was shown that the pore diameter and porosity of PS vary with annealing temperature. The experimentally obtained adsorption / desorption isotherms show hysteresis typical for capillary condensation in porous materials. A simulation study based on Saam and Cole model was performed and compared with experimentally observed sorption isotherms to study the physics behind of hysteresis formation. We discuss the shape of the hysteresis loops in the framework of the morphology of the layers. The different behavior of adsorption and desorption of nitrogen in PS with pore diameter was discussed in terms of concave menisci formation inside the pore space, which was shown to related with the induced pressure in varying the pore diameter from 7.2 nm to 3.4 nm.

  10. Effects of thermal annealing on photoluminescence of Si+/C+ implanted SiO2 films

    NASA Astrophysics Data System (ADS)

    Chen, Yin-Yu; Chao, Der-Sheng; Tsai, Hsu-Sheng; Liang, Jenq-Horng

    2016-04-01

    The mechanisms of photoluminescence (PL) originating from Si+/C+ implanted SiO2 are still unclear and need to be clarified. Thus, the purpose of this study is to thoroughly investigate the effects of ion implantation and post-annealing temperature on microstructures and PL characteristics of the Si+/C+ implanted SiO2 films. A comparative analysis was also conducted to clarify the different optical properties between the Si+ and Si+/C+ implanted SiO2 films. In this study, thermally-grown SiO2 films on Si substrates were used as the matrix materials. The Si+ ions and C+ ions were separately implanted into the SiO2 films at room temperature. After ion implantation, the post-annealing treatments were carried out using the furnace annealing (FA) method at various temperatures (600-1100 °C) for 1 h in a N2 ambient. The PL characteristics of the implanted SiO2 films were analyzed using a fluorescence spectrophotometer. The results revealed that the distinct PL peaks were observed at approximately 310, 450 and 650 nm in the Si+-implanted SiO2 films, which can be attributed to the defects, the so-called oxygen deficiency centers (ODCs) and non-bridging oxygen hole centers (NBOHCs), in the materials. In contrast to the Si+ ion implantation, the SiO2 films which were sequentially implanted with Si+ and C+ ions and annealed at 1100 °C can emit white light corresponding to the PL peaks located at around 420, 520 and 720 nm, those can be assigned to the Si-C bonding, C-C graphite-like structure (sp2), and Si nanocrystals, respectively. Moreover, a correlation between the optical properties, microstructures, and bonding configurations of the Si+/C+ implanted SiO2 films was also established in this study.

  11. Effect of δ-ferrite evolution and high-temperature annealing on mechanical properties of 11Cr3W3Co ferritic/martensitic steel

    NASA Astrophysics Data System (ADS)

    Shang, Zhongxia; Shen, Yinzhong; Ji, Bo; Zhang, Lanting

    2016-03-01

    An 11Cr3W3Co ferritic/martensitic steel was annealed at 1100 °C for different time to gradually dissolve δ-ferrite, and then conducted tensile, hardness, and short-term creep tests in combination with microstructural characterization to study the effect of δ-ferrite on the mechanical properties of high-Cr ferritic/martensitic steels. The amount of δ-ferrite gradually decreased to a minimum value with increasing annealing time up to 10 h, and then tended to an ascending tendency when annealed for 15 and 20 h. Accordingly the tensile strength at 300 and 650 °C, and Vickers hardness of the steel had an increase and a decrease tendency when δ-ferrite amount decreased down to its minimum value and increased again, respectively. The short-term creep property at 210 MPa at 650 °C of the steel exhibited a serious degradation as annealing time gradually increased to 15 h. The morphology and orientation of δ-ferrite grains seriously affected the short-term creep property of the steel. δ-ferrite with a continuously bamboo-like shape parallel to loading direction effectively improved the short-term creep property of the steel at high temperature, while δ-ferrite with a granular or block shape seriously damaged the short-term creep property of the steel. These findings have also been discussed.

  12. Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

    1994-01-01

    This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content, and is related to the classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is described by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

  13. Effects of Hydrogen Annealing, Sulfur Segregation and Diffusion on the Cyclic Oxidation Resistance of Superalloys: a Review

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

    1994-01-01

    This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content and related to classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is governed by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

  14. Effect of annealing on exchange stiffness of ultrathin CoFeB film with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Sato, Noriyuki; White, Robert M.; Wang, Shan X.

    2016-04-01

    The effect of annealing on the exchange stiffness of ultrathin CoFeB films with perpendicular magnetic anisotropy was investigated through the observation of magnetic domain structures by magneto-optic Kerr-effect microscopy. A significant reduction of the exchange stiffness after an annealing process was observed, which is in striking contrast to a previous report that studied thick CoFeB films with in-plane magnetic anisotropy. Our results suggest that interdiffusion of non-magnetic atoms from the adjacent layer into CoFeB layer reduces the exchange stiffness, which explains the difference between the annealing effect on ultrathin and the thick CoFeB films. Thus, it is critical to prevent annealing-induced interdiffusion in order to suppress undesired sub-volume switching that degrades thermal stability of a free-layer in spin-transfer torque magnetic random access memory.

  15. Quantum simulated annealing

    NASA Astrophysics Data System (ADS)

    Boixo, Sergio; Somma, Rolando; Barnum, Howard

    2008-03-01

    We develop a quantum algorithm to solve combinatorial optimization problems through quantum simulation of a classical annealing process. Our algorithm combines techniques from quantum walks and quantum phase estimation, and can be viewed as the quantum analogue of the discrete-time Markov Chain Monte Carlo implementation of classical simulated annealing.

  16. 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.

  17. Study on effect of annealing conditions on structural, magnetic and superconducting properties of MgB{sub 2} bulk samples

    SciTech Connect

    Phaneendra, Konduru Asokan, K. Kanjilal, D.; Awana, V. P. S.; Sastry, S. Sreehari

    2014-04-24

    Effect of annealing conditions on structural, magnetic and superconducting properties of Magnesium Diboride (MgB{sub 2}) bulk superconductor samples prepared by solid state route method are compared. The samples are made by taking Magnesium and Boron powders in stoichiometric ratio, grounded well and pelletized at pressure of about 10Tonnes. These pellets are annealed in both Argon and vacuum environment separately up to 800°c for two hours. Both the samples show clear superconducting transition at Tc ∼ 38 k. This is further conformed by AC/DC magnetization (M-T), Resistivity [ρ (T, H)] measurements under magnetic field up to 14 Tesla as well. Rietveld refinement of X-ray diffraction of both samples conformed the MgB{sub 2} phase formation with P6/mmm space group symmetry. Scanning Electron Microscopy images of the surface revile more agglomeration of grains in case of Argon annealed samples. This result in more critical current density (J{sub c}) of Argon annealed samples than vacuum annealed one calculated from Bean's critical state model. This high Jc is explained in terms of more inter grain connectivity for Argon annealed sample than vacuum annealed sample.

  18. Effect of recrystallization annealing on the inelastic properties of TiNi alloy under bending

    NASA Astrophysics Data System (ADS)

    Grishkov, V. N.; Lotkov, A. I.; Baturin, A. A.; Cherniavsky, A. G.; Timkin, V. N.; Zhapova, D. Yu.

    2016-11-01

    The data reported here show that recrystallization annealing at 973 K transforms the initial nanocrystalline structure of Ti49.1Ni50.9 (at %) into a microcrystalline structure with an average grain size of ≤11.4 µm and changes the sequence of martensite transformations from B2→R→B19' to B2→B19'. Also dependences of the superelasticity effect (SE), shape memory effect (SME), summary reversible inelastic strain (SIS = SE + SME), and plastic strain on total strain for the alloy exposed to bending in isothermal (295 K) loading-unloading cycles with post-unloading heating are presented.

  19. Annealing of gold nanostructures sputtered on glass substrate

    NASA Astrophysics Data System (ADS)

    Švorčík, V.; Siegel, J.; Šutta, P.; Mistrík, J.; Janíček, P.; Worsch, P.; Kolská, Z.

    2011-03-01

    The effects of annealing at 300 °C on gold nanostructures sputtered onto glass substrate were studied using XRD, SAXSees, the Van der Pauw method and ellipsometry. As-sputtered and annealed samples exhibit a different dependence of the gold lattice parameter on the sputtering time. With increasing sputtering time the average thickness of the layer and the size of gold crystallites increased. Another rapid enlargement of the crystallites is observed after annealing. The volume resistivity decreases rapidly with the increasing sputtering time for both, as-deposited and annealed structures. With increasing sputtering time initially discontinuous gold coverage changes gradually in a continuous one. Electrically continuous gold coverage on the as-sputtered and annealed samples exhibits the same concentration of free charge carriers and Hall mobility. Optical constants of as-deposited and annealed gold films determined by ellipsometry support resistivity measurements and clearly manifest the presence of plasmons in discontinuous films.

  20. Effect of NO annealing on charge traps in oxide insulator and transition layer for 4H-SiC metal-oxide-semiconductor devices

    NASA Astrophysics Data System (ADS)

    Jia, Yifan; Lv, Hongliang; Niu, Yingxi; Li, Ling; Song, Qingwen; Tang, Xiaoyan; Li, Chengzhan; Zhao, Yanli; Xiao, Li; Wang, Liangyong; Tang, Guangming; Zhang, Yimen; Zhang, Yuming

    2016-09-01

    The effect of nitric oxide (NO) annealing on charge traps in the oxide insulator and transition layer in n-type 4H-SiC metal-oxide-semiconductor (MOS) devices has been investigated using the time-dependent bias stress (TDBS), capacitance-voltage (C-V), and secondary ion mass spectroscopy (SIMS). It is revealed that two main categories of charge traps, near interface oxide traps (Nniot) and oxide traps (Not), have different responses to the TDBS and C-V characteristics in NO-annealed and Ar-annealed samples. The Nniot are mainly responsible for the hysteresis occurring in the bidirectional C-V characteristics, which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor. However, Not is mainly responsible for the TDBS induced C-V shifts. Electrons tunneling into the Not are hardly released quickly when suffering TDBS, resulting in the problem of the threshold voltage stability. Compared with the Ar-annealed sample, Nniot can be significantly suppressed by the NO annealing, but there is little improvement of Not. SIMS results demonstrate that the Nniot are distributed within the transition layer, which correlated with the existence of the excess silicon. During the NO annealing process, the excess Si atoms incorporate into nitrogen in the transition layer, allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot. Project supported by the National Natural Science Foundation of China (Grant Nos. 61404098 and 61274079), the Doctoral Fund of Ministry of Education of China (Grant No. 20130203120017), the National Key Basic Research Program of China (Grant No. 2015CB759600), the National Grid Science & Technology Project, China (Grant No. SGRI-WD-71-14-018), and the Key Specific Project in the National Science & Technology Program, China (Grant Nos. 2013ZX02305002-002 and 2015CB759600).

  1. Effect of annealing on structural and optical properties of Ni(1-x)MnxO nanostructures thin films

    NASA Astrophysics Data System (ADS)

    Khodair, Ziad T.; Kamil, Asaad A.; Abdalaah, Yamamah K.

    2016-12-01

    Nanostructured Nickel-Manganese oxide (Ni(1-x)MnxO) thin films, where (x=0%, 2%, 4%, 6% and 8%) have been prepared by a simple and inexpensive chemical spray pyrolysis technique (CSP) on glass substrates at a temperature of (400 °C) and thickness of about (300 nm). The effect of annealing on structural properties has been investigated. The structural properties of these films have been studied using X-ray diffraction. The X-ray results showed that all films before and after annealing are polycrystalline in nature with cubic structure and preferred orientation along (111) plane. The average crystallite size (Dav) was calculated using Scherrer formula for Nickel-Manganese oxide (Ni(1-x)MnxO) thin films before and after annealing and it is found that the (Dav) increases as the Mn-concentration increases and increases after annealing too, and the (Dav) values after annealing were in the range of (11.260-19.943) nm. The Structural parameters including (Lattice Constant (a○), Dislocation Density (δ), Number of Crystal Per Unite area (No) and Texture coeffecient (Tc) were also calculated. AFM results showed the average grain size estimated from the AFM granularity report confirms the XRD results. The optical properties of the films prepared before and after annealing were studied by recording the transmittance and absorbance spectrum in the range of (300-900) nm, the results showed that the absorbance increases with increasing the percentage of doping and it is also found that the energy band gap for the allowed direct transition decreass with increasing the percentage of doping for all films prepared before and after annealing and the values were in the range of (3.59-3.53 eV) before annealing and increased to the range of (3.64-3.57 eV) after annealing.

  2. Annealing effects of tantalum films on Si and SiO2/Si substrates in various vacuums

    NASA Astrophysics Data System (ADS)

    Liu, Ling; Wang, Yue; Gong, Hao

    2001-07-01

    The annealing effects of 550 nm thick β-Ta films sputtered on Si and SiO2 substrates have been investigated under various vacuum conditions. Phase transformation from the tetragonal β-Ta into body-centered-cubic α-Ta of much higher conductivity occurred at annealing temperatures lower than 500 °C and 80% of β-Ta transformed into α-Ta after annealing at 600 °C for Ta on a Si substrate. For Ta on a SiO2 substrate, no phase transformation was observed at 500 °C annealing, and only 20% of β-Ta transformed into α-Ta at 600 °C. Oxygen diffusion into the Ta film at the interface of Ta/SiO2 could hinder β-Ta to α-Ta transformation. Both Ta on Si and Ta on SiO2 samples have smooth surfaces after annealing in 2×10-5 Torr. After annealing in a vacuum lower than 2×10-4 Torr, surface oxidation of the Ta thin films was detected. The increase of oxygen content in the Ta films caused higher compressive stress, and resulted in the film peeling in a serpentine pattern during annealing at 500 °C in 2×10-2 Torr for Ta on a SiO2 substrate. The Ta films cracked and detached from the SiO2 substrate after being annealed at 750 °C in 2×10-2 Torr. In contrast, no crack was found in Ta on Si, probably because of the relief of film stress due to more β-Ta being transformed into α-Ta during annealing. The residual oxygen and moisture in low vacuum may build up stress in Ta thin films during thermal processes, which can cause major reliability problems in electronic and other applications.

  3. Annealing effects in plated-wire memory elements. I - Interdiffusion of copper and Permalloy.

    NASA Technical Reports Server (NTRS)

    Knudson, C. I.; Kench, J. R.

    1971-01-01

    Results of investigations using X-ray diffraction and electron-beam microprobe techniques have shown that copper and Permalloy platings interdiffuse at low temperatures when plated-wire memory elements are annealed for times as short as 50 hr. Measurable interdiffusion between Permalloy platings and gold substrates does not occur in similar conditions. Both magnetic and compositional changes during aging are found to occur by a thermally activated process with activation energies around 38 kcal/mol. It is shown, however, that copper-diffusion and magnetic-dispersion changes during aging are merely concurrent processes, neither being the other's cause.

  4. 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.

  5. Effect of continuous induction annealing on the microstructure and mechanical properties of copper-clad aluminum flat bars

    NASA Astrophysics Data System (ADS)

    Liu, Xin-hua; Jiang, Yan-bin; Zhang, Hong-jie; Xie, Jian-xin

    2016-12-01

    Copper-clad aluminum (CCA) flat bars produced by the continuous casting-rolling process were subjected to continuous induction heating annealing (CIHA), and the effects of induction heating temperature and holding time on the microstructure, interface, and mechanical properties of the flat bars were investigated. The results showed that complete recrystallization of the copper sheath occurred under CIHA at 460°C for 5 s, 480°C for 3 s, or 500°C for 1 s and that the average grain size in the copper sheath was approximately 10.0 μm. In the case of specimens subjected to CIHA at 460-500°C for longer than 1 s, complete recrystallization occurred in the aluminum core. In the case of CIHA at 460-500°C for 1-5 s, a continuous interfacial layer with a thickness of 2.5-5.5 μm formed and the thickness mainly increased with increasing annealing temperature. After CIHA, the interfacial layer consisted primarily of a Cu9Al4 layer and a CuAl2 layer; the average interface shear strength of the CCA flat bars treated by CIHA at 460-500°C for 1-5 s was 45-52 MPa. After full softening annealing, the hardness values of the copper sheath and the aluminum core were HV 65 and HV 24, respectively, and the hardness along the cross section of the CCA flat bar was uniform.

  6. Effect of air annealing on structural and magnetic properties of Ni/NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Nadeem, K.; Ullah, Asmat; Mushtaq, M.; Kamran, M.; Hussain, S. S.; Mumtaz, M.

    2016-11-01

    We reported systematic study on structural and magnetic properties of nickel/nickel oxide (Ni/NiO) nanoparticles annealed under air atmosphere at different temperatures in the range 400-800 °C. The XRD spectra revealed two phases such as Ni and NiO. The average crystallite size increases with increasing annealing temperature. A phase diagram was developed between two phases versus annealing temperature using XRD analysis. At lower annealing temperatures, Ni phase is dominant which does not easily undergo oxidation to form NiO. The NiO phase increases with increasing annealing temperature. FTIR spectroscopy revealed an increase in the NiO phase content at higher annealing temperature, which is in agreement with the XRD analysis. SEM images showed that nanoparticles are well separated at lower annealing temperatures but get agglomerated at higher annealing temperatures. The ferromagnetic (FM) Ni phase content and saturation magnetization (Ms) showed nearly the same trend with increasing annealing temperature. The nanoparticles annealed at 500 °C and 800 °C revealed highest and lowest Ms values, respectively, which is in accordance with the XRD phase diagram. Coercivity showed an overall decreasing trend with increasing annealing temperature due to decreased concentration of FM Ni phase and increasing average crystallite size. All these measurements indicate that the structural and magnetic properties of Ni/NiO nanoparticles are strongly influenced by the annealing temperature.

  7. Formation of n-type pyrite films from electrodeposited iron sulphides: effect of annealing temperature

    SciTech Connect

    Gomes, A.; Ares, J.R.; Ferrer, I.J.; Silva Pereira, M.I. da; Sanchez, C

    2003-06-19

    The n-type polycrystalline pyrite films were obtained by annealing mackinawite electrodeposited on metallic titanium substrates in sulphur atmosphere in the temperature range 523-773 K. The detailed structural and morphological characterisation of the films shows that an increase of crystallite size and a porosity decrease was achieved by increasing the sulphuration temperature. The measurement of thermoelectric effect indicates that pyrite films present n-type conduction, which is attributed to the diffusion of Ti atoms from the substrate. The Seebeck coefficient varies from -54 to -24 {mu}V/K, depending on pyrite grain size.

  8. Annealing effect on Cu2S thin films prepared by chemical bath deposition

    NASA Astrophysics Data System (ADS)

    More, Pawan; Dhanayat, Swapnali; Gattu, Ketan; Mahajan, Sandeep; Upadhye, Deepak; Sharma, Ramphal

    2016-05-01

    In present work Cu2S thin film fabricated on glass substrate by simple, cost effective chemical bath deposition method subsequently it annealed at 150°c.These films were studied for their structural, optical and electrical properties using X-ray diffraction, UV-vis spectrophotometer and I-V system. The results show successful synthesis of Cu2S thin films and improvement in crystalline nature of the thin film which resulted in reduced bad gap and resistance of the film. Thus these thinfilms prove to be a promising candidate for solar cell application.

  9. Effect of irradiation parameters on defect aggregation during thermal annealing of LiF irradiated with swift ions and electrons

    SciTech Connect

    Schwartz, K.; Neumann, R.; Trautmann, C.; Volkov, A. E.; Sorokin, M. V.

    2010-10-01

    Absorption spectroscopy were performed to study the effects of thermal annealing on the aggregation of color centers in LiF crystals irradiated with different ions between carbon and uranium of megaelectron volt-gigaelectron volt energy. The beam parameters such as energy, energy loss, and fluence have a pronounced influence on the initial defect composition and concentration as well as their evolution upon thermal annealing. A distinct phenomenon was observed, viz., the enhancement of F{sub n} centers for annealing temperatures between 500 and 700 K, followed by Li colloid formation above 700 K. The phenomenon requires specific irradiation conditions whereas the formation of Mg colloids from Mg impurities occurs in all irradiated crystals. The mechanisms of annealing and colloid formation are discussed.

  10. Effects of annealing on the structure and magnetic properties of Fe27Co23Pb50 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, R. L.; Tang, S. L.; Shi, Y. G.; Fei, X. L.; Nie, B.; Du, Y. W.

    2008-04-01

    Ferromagnetic-nonmagnetic heterogeneous Fe27Co23Pb50 ternary metal nanowire arrays were successfully fabricated by alternating current electrodeposition into anodic alumina oxide (AAO) template. The effects of the different annealing temperatures (100, 200, 300, 400, 500, 600°C) on the structure and magnetic properties have been discussed. X-ray diffraction observations indicated that FeCo and Pb phases coexist for the as-deposited and annealed samples. Magnetic measurements indicate that the nanowire arrays have high perpendicular magnetic anisotropy with their easy axis parallel to the nanowire arrays. The coercivity and remanence ratio increases as the annealing temperature rises, reaches their maximum at 400°C, and then decreases as the annealing temperature rises further. The mechanism of the magnetic properties and magnetic variety should be attributed to the special structure of the nanowires/AAO.

  11. Neutron, gamma ray and post-irradiation thermal annealing effects on power semiconductor switches

    NASA Technical Reports Server (NTRS)

    Schwarze, G. E.; Frasca, A. J.

    1991-01-01

    The effects of neutron and gamma rays on the electrical and switching characteristics of power semiconductor switches must be known and understood by the designer of the power conditioning, control, and transmission subsystem of space nuclear power systems. The SP-100 radiation requirements at 25 m from the nuclear source are a neutron fluence of 10(exp 13) n/sq cm and a gamma dose of 0.5 Mrads. Experimental data showing the effects of neutrons and gamma rays on the performance characteristics of power-type NPN Bipolar Junction Transistors (BJTs), Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), and Static Induction Transistors (SITs) are presented. These three types of devices were tested at radiation levels which met or exceeded the SP-100 requirements. For the SP-100 radiation requirements, the BJTs were found to be most sensitive to neutrons, the MOSFETs were most sensitive to gamma rays, and the SITs were only slightly sensitive to neutrons. Post-irradiation thermal anneals at 300 K and up to 425 K were done on these devices and the effectiveness of these anneals are also discussed.

  12. 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.

  13. Real-Time observation of PS-PDMS block copolymer self-assembly under solvent vapor annealing

    NASA Astrophysics Data System (ADS)

    Bai, Wubin; Yager, Kevin; Ross, Caroline

    2015-03-01

    Solvent annealing provides a convenient way to produce microphase separation in films of block copolymers, but the morphology transition of the film during the solvent absorption, equilibrium solvent-BCP concentration and solvent desorption process are not well known. An in situ study of solvent annealing of polystyrene-block-polydimethylsiloxane (PS-PDMS, 16 kg/mol, fPDMS = 30%, period 17 nm) diblock copolymer was carried by synchrotron grazing-incidence small-angle X-ray scattering (GISAXS). The swollen film morphology was found to be strongly dependent on swelling ratio. A transition from the disordered state to a highly ordered state which contained multiple layers of in-plane cylinders was observed at a swelling ratio around 1.45 from samples with 100nm to 1000nm as-cast thickness. The rate of solvent absorption was found to be less important to the dried morphology, while the time of equilibrium solvent-BCP concentration stage was found to influence the orientation of self-assembled microdomains and the drying rate was found to affect the degree of structure deformation. The implications of the results to pattern generation for block copolymer directed self-assembly will be discussed. Semiconductor Research Corporation, National Science Foundation.

  14. The effect of annealing ambient on the characteristics of an indium-gallium-zinc oxide thin film transistor.

    PubMed

    Park, Soyeon; Bang, Seokhwan; Lee, Seungjun; Park, Joohyun; Ko, Youngbin; Jeon, Hyeongtag

    2011-07-01

    In this study, the effects of different annealing conditions (air, O2, N2, vacuum) on the chemical and electrical characteristics of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFT) were investigated. The contact resistance and interface properties between the IGZO film and the gate dielectric improved after an annealing treatment. However, the chemical bonds in the IGZO bulk changed under various annealing atmospheres, which, in turn, altered the characteristics of the TFTs. The TFTs annealed in vacuum and N2 ambients exhibited undesired switching properties due to the high carrier concentration (>10(17) cm(-3)) of the IGZO active layer. In contrast, the IGZO TFTs annealed in air and oxygen ambients displayed clear transfer characteristics due to an adequately adjusted carrier concentration in the operating range of the TFT. Such an optimal carrier concentration arose through the stabilization of unstable chemical bonds in the IGZO film. With regard to device performance, the TFTs annealed in O2 and air exhibited saturation mobility values of 8.29 and 7.54 cm2/Vs, on-off ratios of 7.34 x 10(8) and 3.95 x 10(8), and subthreshold swing (SS) values of 0.23 and 0.19 V/decade, respectively. Therefore, proper annealing ambients contributed to internal modifications in the IGZO structure and led to an enhancement in the oxidation state of the metal. As a result, defects such as oxygen vacancies were eliminated. Oxygen annealing is thus effective for controlling the carrier concentration of the active layer, decreasing electron traps, and enhancing TFT performance.

  15. Effect of solvent annealing on the tensile deformation mechanism of a colloidal crystalline polymeric latex film.

    PubMed

    Zhang, Jianqi; Yi, Zhiyong; Wang, Qiao; Liu, Zhenyu; Perlich, Jan; Gehrke, Rainer; Men, Yongfeng

    2011-10-04

    The influence of solvent annealing on microscopic deformational behavior of a styrene/n-butyl acrylate copolymer latex film subjected to uniaxial tensile deformation was studied by small-angle X-ray scattering. It was demonstrated that the microscopic deformation mechanism of the latex films transformed from a nonaffine deformation behavior to an affine deformation behavior after solvent annealing. This was attributed to the interdiffusion of polymeric chains between adjacent swollen latex particles in the film. It turns out that solvent annealing is much more efficient than thermal annealing due to a much slow evaporation process after solvent annealing.

  16. Irradiate-anneal screening of total dose effects in semiconductor devices. [radiation hardening of spacecraft components of Mariner spacecraft

    NASA Technical Reports Server (NTRS)

    Stanley, A. G.; Price, W. E.

    1976-01-01

    An extensive investigation of irradiate-anneal (IRAN) screening against total dose radiation effects was carried out as part of a program to harden the Mariner Jupiter/Saturn 1977 (MJS'77) spacecraft to survive the Jupiter radiation belts. The method consists of irradiating semiconductor devices with Cobalt-60 to a suitable total dose under representative bias conditions and of separating the parts in the undesired tail of the distribution from the bulk of the parts by means of a predetermined acceptance limit. The acceptable devices are then restored close to their preirradiation condition by annealing them at an elevated temperature. IRAN was used when lot screen methods were impracticable due to lack of time, and when members of a lot showed a diversity of radiation response. The feasibility of the technique was determined by testing of a number of types of linear bipolar integrated circuits, analog switches, n-channel JFETS and bipolar transistors. Based on the results of these experiments a number of device types were selected for IRAN of flight parts in the MJS'77 spacecraft systems. The part types, screening doses, acceptance criteria, number of parts tested and rejected as well as the program steps are detailed.

  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. Effect of annealing on structural and magnetic properties of Al substituted nanocrystalline Fe-Si-Co alloy powders

    NASA Astrophysics Data System (ADS)

    Shyni, P. C.; Alagarsamy, Perumal

    2016-11-01

    We report effects of annealing and substitution of Al on structural and magnetic properties of nanocrystalline Fe80-xAlxCo5Si15 (x=0-10) alloy powders prepared by mechanical alloying process using a planetary ball mill technique. All the as-milled powders exhibit non-equilibrium solid solution of α-Fe (Si,Co,Al). While the average size of crystals decreases, the lattice constant and dislocation density increase with increasing Al content. On the other hand, the annealing at elevated temperatures increases the size of the crystals and decreases the dislocation density. In addition, the substitution of Al in FeAlCoSi alloy powders controls growth of the crystals during annealing. As a result, coercivity (HC) of the annealed powders decreases considerably. However, the variation in HC is dominated by the dislocation density. Fe70Al10Co5Si15 powder annealed at 900 °C exhibits improved magnetic properties (HC~14 Oe and moderate magnetization of 160 emu/g) due to optimum nanocrystalline microstructure with fine nanocrystals (~18 nm) and reduced dislocation density. Systematic correlations observed between structural and magnetic properties for Fe80-xAlxCo5Si15 powders reveal a promising approach to control the growth of the crystals in the annealed nanocrystalline alloys and to improve the magnetic properties of mechanically alloyed Fe-Si based nanocrystalline alloys by adding suitable substituting elements.

  19. Effect of annealing environments on self-organized TiO2 nanotubes for efficient photocatalytic applications.

    PubMed

    Hyam, Rajeshkumar Shankar; Lee, Jongseok; Cho, Eunju; Khim, Jeehyeong; Lee, Haigun

    2012-12-01

    In the present study, amorphous titanium dioxide (TiO2) nanotubes were synthesized by one-step anodization technique and subsequently annealed in different environments to investigate the effect of annealing atmospheres on the formation of different crystalline phases. X-ray Diffraction (XRD) patterns clearly showed the presence of anatase TiO2 phase with various crystallite sizes. The samples annealed in oxygen and air atmospheres at 500 degrees C showed a dominant anatase phase and a small amount of rutile phase, on the other hand, the samples annealed in nitrogen and argon atmospheres and in a vacuum at 500 degrees C contained the anatase phase only. XPS analysis of the samples showed a broadening in the binding energy curves with respect to variation in annealing atmosphere, confirming the variation in surface defects, which in turn affect photocatalytic degradation. The vacuum-annealed sample showed superior photocatalytic degradation efficiency as it had relatively higher pseudo-first order rate constants (k) of 0.009/min.

  20. Remarkable changes in interface O vacancy and metal-oxide bonds in amorphous indium-gallium-zinc-oxide thin-film transistors by long time annealing at 250 °C

    SciTech Connect

    Chowdhury, Md Delwar Hossain; Um, Jae Gwang; Jang, Jin

    2014-12-08

    We have studied the effect of long time post-fabrication annealing on negative bias illumination stress (NBIS) of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Annealing for 100 h at 250 °C increased the field effect mobility from 14.7 cm{sup 2}/V s to 17.9 cm{sup 2}/V s and reduced the NBIS instability remarkably. Using X-ray photoelectron spectroscopy, the oxygen vacancy and OH were found to exist at the interfaces of a-IGZO with top and bottom SiO{sub 2}. Long time annealing helps to decrease the vacancy concentration and increase the metal-oxygen bonds at the interfaces; this leads to increase in the free carrier concentrations in a-IGZO and field-effect mobility. X-ray reflectivity measurement indicated the increment of a-IGZO film density of 5.63 g cm{sup −3} to 5.83 g cm{sup −3} (3.4% increase) by 100 h annealing at 250 °C. The increase in film density reveals the decrease of O vacancy concentration and reduction of weak metal-oxygen bonds in a-IGZO, which substantially helps to improve the NBIS stability.

  1. Effects of thermal annealing on the radiation produced electron paramagnetic resonance spectra of bovine and equine tooth enamel: Fossil and modern

    NASA Astrophysics Data System (ADS)

    Weeks, Robert A.; Bogard, James S.; Elam, J. Michael; Weinand, Daniel C.; Kramer, Andrew

    2003-06-01

    The concentration of stable radiation-induced paramagnetic states in fossil teeth can be used as a measure of sample age. Temperature excursions >100 °C, however, can cause the paramagnetic state clock to differ from the actual postmortem time. We have heated irradiated enamel from both fossilized bovid and modern equine (MEQ) teeth for 30 min in 50 °C increments from 100 to 300 °C, measuring the electron paramagnetic resonance (EPR) spectrum after each anneal, to investigate such effects. Samples were irradiated again after the last anneal, with doses of 300-1200 Gy from 60Co photons, and measured. Two unirradiated MEQ samples were also annealed for 30 min at 300 °C, one in an evacuated EPR tube and the other in a tube open to the atmosphere, and subsequently irradiated. The data showed that hyperfine components attributed to the alanine radical were not detected in the irradiated MEQ sample until after the anneals. The spectrum of the MEQ sample heated in air and then irradiated was similar to that of the heat treated fossil sample. We conclude that the hyperfine components are due to sample heating to temperatures/times >100 °C/30 min and that similarities between fossil and MEQ spectra after the 300 °C/30 min MEQ anneal are also due to sample heating. We conclude that the presence of the hyperfine components in spectra of fossil tooth enamel indicate that such thermal events occurred either at the time of death, or during the postmortem history.

  2. Effect of post-pattern annealing on the grain structure and reliability of Al-based interconnects

    SciTech Connect

    Kang, S.H.; Kim, C.; Morris, J.W. Jr. |; Genin, F.Y.

    1996-06-01

    The possibility is addressed of improving the electromigration resistance of Al and Al{endash}Cu thin-film conductors with {open_quote}{open_quote}quasi-bamboo{close_quote}{close_quote} structures by post-pattern anneals that decrease the maximum polygranular segment length. Pure Al, Al{endash}2Cu, and Al{endash}2Cu{endash}1Si lines were patterned and annealed at temperatures high enough to stimulate grain growth. Appropriate anneals led to predominantly bamboo structures with short polygranular segments. These grain structures had a high median time to failure with a relatively low deviation of the time to failure. Metallographic analyses showed that polygranular segment length was a dominant factor in determining the failure site. Post-pattern annealing promotes a preferential shortening of the relatively long polygranular segments that cause early failures. However, even after annealing, failure occurred at the longest residual polygranular segments, even when these were significantly shorter than the {open_quote}{open_quote}Blech length{close_quote}{close_quote} under the test conditions. Statistical analysis of the failure of alloy lines revealed a simple exponential relation between the failure time and the longest polygranular segment length within a line, which is functionally identical to that previously found for lines tested in the as-patterned condition.

  3. Post annealing effect on the electrical properties of top-gate SWNT network transistors.

    PubMed

    Kim, Un Jeong; Suh, D Y; Min, S C; Park, Wanjun

    2011-07-01

    High performance top-gate single walled carbon nanotube network transistors are fabricated with aluminum oxide (Al2O3) layer as a gate dielectric by atomic layer deposition. It exhibits large on/off ratio (>10(4)) due to selective growth of semiconducting tubes by the plasma enhanced chemical vapor deposition. I-V characteristics show p-type or n-type depending on the deposition temperature. We investigate the type dependent characteristics for the carrier polarities with the post annealing effect on the top-gate SWNT network transistors. The dramatic change in the polarity of the top-gate SWNT network transistors, from n-type to p-type due to conversion of I-V characteristics is observed by post-annealing at 350 degrees C for 30 minutes under vacuum. Our observation suggests that competition between electron transfer from the Al2O3 layers to the SWNT surface and electron capture by oxygen molecules adsorbed on the tube walls seems to be the key point for the V(th) change as a function of Al2O3 deposition temperature.

  4. Infrared spectroscopy of water clusters isolated in methane matrices: Effects of isotope substitution and annealing

    NASA Astrophysics Data System (ADS)

    Yamakawa, Koichiro; Ehara, Namika; Ozawa, Nozomi; Arakawa, Ichiro

    2016-07-01

    Using infrared-active solvents of CH4 and CD4 for matrix isolation, we measured infrared spectra of H2O and D2O clusters at 7 K. The solute-concentration dependence of the spectrum of H2O clusters in a CH4 matrix was investigated and was used for the peak assignment. Annealing procedures were found to promote the size growth of water clusters in methane matrices for all the combinations of (H2O, CH4), (H2O, CD4), (D2O, CH4), and (D2O, CD4). We also monitored the ν3 absorption due to methane to find the annealing-induced structural change only of solid CH4. The matrix effects on the vibrations of the clusters are discussed on the basis of "Tc plots", where their frequencies are plotted as a function of the square root of the matrix critical temperature, Tc. The obtained plots assure the validity of the assignment of the cluster peaks.

  5. Effects of annealing pressure and Ar+ sputtering cleaning on Al-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Wang, Jiwei; Mei, Yong; Lu, Xuemei; Fan, Xiaoxing; Kang, Dawei; Xu, Panfeng; Tan, Tianya

    2016-11-01

    Post-treatments of Al-doped ZnO films fabricated by sol-gel method were studied in condition of annealing in air, vacuum and protective ambient, as well as the follow-up Ar+ sputtering cleaning. The effect of annealing pressure on resistivity of AZO films was investigated from 105 to 10-4 Pa, where the resistivity decreased four orders of magnitude as the pressure decreased and approached to its minimum at 10 Pa. It was observed that the main decreasing of resistivity occurred in a very narrow range of middle vacuum (between 100 and 10 Pa) and high vacuum was dispensable. The XRD and XPS characterizations demonstrated that the radical increasing of oxygen vacancy, Zn interstitial and substitution of Al3+ for Zn2+ under middle vacuum were responsible for the significant enhancement of conductivity. The follow-up Ar+ sputtering cleaning can further decrease the resistivity through removing the chemisorbed oxygen on film surface and grain boundaries, meanwhile fulfil the surface texture process, and thus improve both electrical and optical performances for applications.

  6. High-temperature annealing effects on multiwalled carbon nanotubes: electronic structure, field emission and magnetic behaviors.

    PubMed

    Ray, Sekhar Chandra; Pao, Chih-Wen; Tsai, Huang-Ming; Chen, Huang-Chin; Chen, Yu-Shin; Wu, Shang-Lun; Ling, Dah-Chin; Lin, I-Nan; Pong, Way-Faung; Gupta, Sanju; Giorcelli, Mauro; Bianco, Stefano; Musso, Simone; Tagliaferro, Alberto

    2009-12-01

    This work elucidates the effects of high-temperature annealing on the microscopic and electronic structure of multiwalled carbon nanotubes (MWCNTs) using high-resolution transmission electron microscopy, micro-Raman spectroscopy, X-ray diffraction, X-ray absorption near-edge structure (XANES) and valence-band photoemission spectroscopy (VBPES), respectively. The field emission and magnetization behaviors are also presented. The results of annealing are as follows: (1) MWCNTs tend to align in the form of small fringes along their length, promote graphitization and be stable in air, (2) XANES indicates an enhancement in oxygen content on the sample, implying that it can be adopted for sensing and storing oxygen gas, (3) the electron field emission current density (J) is enhanced and the turn-on electric field (E(TOE)) reduced, suggesting potential use in field emission displays and as electron sources in microwave tube amplifiers and (4) as-grown MWCNTs with embedded iron nanoparticles exhibits significantly higher coercivity approximately 750 Oe than its bulk counterpart (Fe(bulk) approximately 0.9 Oe), suggesting its potential use as low-dimensional high-density magnetic recording media.

  7. Synthesis Mechanism and Strengthening Effects of Laminated NiAl by Reaction Annealing

    NASA Astrophysics Data System (ADS)

    Du, Yan; Fan, Guohua; Wang, Qingwei; Geng, Lin

    2017-01-01

    N iA l with a laminated microstructure has been fabricated by reaction annealing of Ni-Al system at 1473 K (1200 °C). The laminated NiAl shows heterogeneity of chemical gradient and bimodal grain size distribution. The objective of this study is to investigate the synthesis mechanism and the strengthening effect of this laminated NiAl, therefore to promote further application of NiAl as a high-temperature structural material. Heat treatments at 1473 K (1200 °C) and subsequent characterization were utilized to study the synthesis mechanism. It shows that in original Al regions NiAl nuclei precipitate from Al(Ni) liquid phase and form fine-grained NiAl layers, whereas in original Ni regions NiAl nuclei precipitate from Ni(Al) saturated solution through diffusion and form coarse-grained NiAl layers. Moreover, heterogeneity of chemical gradient is generated through diffusion during annealing. The mechanical properties of laminated NiAl have also been studied via nanoindentation method. It shows that both chemical gradient and bimodal grain size distribution could strengthen the laminated NiAl.

  8. Effects of low temperature periodic annealing on the deep-level defects in 200 keV proton irradiated AlGaAs-GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Li, S. S.; Chiu, T. T.; Loo, R. Y.

    1981-01-01

    The GaAs solar cell has shown good potential for space applications. However, degradation in performance occurred when the cells were irradiated by high energy electrons and protons in the space environment. The considered investigation is concerned with the effect of periodic thermal annealing on the deep-level defects induced by the 200 keV protons in the AlGaAs-GaAs solar cells. Protons at a fluence of 10 to the 11th P/sq cm were used in the irradiation cycle, while annealing temperatures of 200 C (for 24 hours), 300 C (six hours), and 400 C (six hours) were employed. The most likely candidate for the E(c) -0.71 eV electron trap observed in the 200 keV proton irradiated samples may be due to GaAs antisite, while the observed E(v) +0.18 eV hole trap has been attributed to the gallium vacancy related defect. The obtained results show that periodic annealing in the considered case does not offer any advantages over the one time annealing process.

  9. Effect of thermal annealing on the microstructures and photocatalytic performance of silver orthophosphate: The synergistic mechanism of Ag vacancies and metallic Ag

    NASA Astrophysics Data System (ADS)

    Yan, Tingjiang; Guan, Wenfei; Xiao, Ying; Tian, Jun; Qiao, Zheng; Zhai, Huishan; Li, Wenjuan; You, Jinmao

    2017-01-01

    In this work, a simple thermal annealing route has been developed to improve the photocatalytic performance of silver orthophosphate (Ag3PO4) photocatalyst toward organic pollutants degradation under visible light irradiation. The experimental results indicated that thermal treatment of Ag3PO4 led to an obvious lattice shift towards right and significantly narrowed band gap energies due to the formation of Ag vacancies and metallic Ag during Ag3PO4 decomposition. These structural variations notably affected the photocatalytic performance of Ag3PO4 photocatalysts. The activity of the annealed samples was found to be significantly enhanced toward the degradation of MO dye. The highest activity was observed over the sample annealed at 400 °C, which exceeded that of pristine Ag3PO4 by a factor of about 21 times. By means of photoluminescence spectroscopy and photoelectrochemical measurements, we propose that the enormous enhancement in activity was mainly attributed to the efficient separation of photogenerated electrons and holes driven by the synergistic effect of Ag vacancies and metallic Ag. The strong interaction between annealed particles also inhibited the dissolution of Ag+ from Ag3PO4 into aqueous solution, contributing to an improved photocatalytic stability. The strategy presented here provides an ideal platform for the design of other highly efficient and stable Ag-based photocatalysts for broad applications in the field of photocatalysis.

  10. 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.

  11. A hydrogen curing effect on surface plasmon resonance fiber optic hydrogen sensors using an annealed Au/Ta₂O₅/Pd multi-layers film.

    PubMed

    Hosoki, Ai; Nishiyama, Michiko; Igawa, Hirotaka; Seki, Atsushi; Watanabe, Kazuhiro

    2014-07-28

    In this paper, a response time of the surface plasmon resonance fiber optic hydrogen sensor has successfully improved with keeping sensor sensitivity high by means of hydrogen curing (immersing) process of annealed Au/Ta2O5/ Pd multi-layers film. The hydrogen curing effect on the response time and sensitivity has been experimentally revealed by changing the annealing temperatures of 400, 600, 800°C and through observing the optical loss change in the H2 curing process. When the 25-nm Au/60-nm Ta2O5/10-nm Pd multi-layers film annealed at 600°C is cured with 4% H2/N2 mixture, it is found that a lot of nano-sized cracks were produced on the Pd surface. After H2 curing process, the response time is improved to be 8 s, which is two times faster than previous reported one in the case of the 25-nm Au/60-nm Ta2O5/3-nm Pd multi-layers film with keeping the sensor sensitivity of 0.27 dB for 4% hydrogen adding. Discussions most likely responsible for this effect are given by introducing the α-β transition Pd structure in the H2 curing process.

  12. Effect of Nano-Particle Addition on Grain Structure Evolution of Friction Stir-Processed Al 6061 During Postweld Annealing

    NASA Astrophysics Data System (ADS)

    Guo, Junfeng; Lee, Bing Yang; Du, Zhenglin; Bi, Guijun; Tan, Ming Jen; Wei, Jun

    2016-08-01

    The fabrication of nano-composites is challenging because uniform dispersion of nano-sized reinforcements in metallic substrate is difficult to achieve using powder metallurgy or liquid processing methods. In the present study, Al-based nano-composites reinforced with Al2O3 particles have been successfully fabricated using friction stir processing. The effects of nano-Al2O3 particle addition on grain structure evolution of friction stir-processed Al matrix during post-weld annealing were investigated. It was revealed that the pinning effect of Al2O3 particles retarded grain growth and completely prevented abnormal grain growth during postweld annealing at 470°C. However, abnormal grain growth can still occur when the composite material was annealed at 530°C. The mechanism involved in the grain structure evolution and the effect of nano-sized particle addition on the mechanical properties were discussed therein.

  13. Effect of antireflection coating on the crystallization of amorphous silicon films by flash lamp annealing

    NASA Astrophysics Data System (ADS)

    Sonoda, Yuki; Ohdaira, Keisuke

    2017-04-01

    We succeed in decreasing the fluence of a flash-lamp pulse required for the crystallization of electron-beam (EB)-evaporated amorphous silicon (a-Si) films using silicon nitride (SiN x ) antireflection films. The antireflection effect of SiN x is confirmed not only when SiN x is placed on the surface of a-Si or flash lamp annealing (FLA) is performed from the film side, but also when SiN x is inserted between glass and a-Si and a flash pulse is supplied from the glass side. We also quantitatively confirm, by calculating flash-lamp pulse energies actually reaching a-Si films using reflectance spectra, that the reduction in the fluence of a flash-lamp pulse for the crystallization of a-Si films is due to the antireflection effect of SiN x .

  14. Annealing effect on the dielectric response of novel polymer/nano-quasicrystalline composites

    NASA Astrophysics Data System (ADS)

    Venkatesh, Ch.; Rao, V. V.

    2013-06-01

    In the earlier paper (Ch. Venkatesh et al. Solid State Comm., 2010), a dielectric percolation has been reported in composites of nano-quasicrystalline (nQc) Al-Cu-Fe (filler) and polyvinylidene fluoride (PVDF) (matrix). Though a high value of dielectric constant is observed near to the percolation threshold, these composites show higher dielectric loss values at lower frequencies. An effect of annealing has been investigated on the same composites which lead to decrement in dielectric loss values appreciably. The low dielectric loss values have been attributed due to the formation of thick grain boundaries in polymer matrix which completely surrounds the nQc cluster that weakens the effective tunneling of charge carriers near the filler-polymer interfacial region. Finally, a dielectric constant of 500 with tanδ<1 at 1 KHz is observed which may make the composite useful for low loss capacitive applications.

  15. Effect of annealing on the thermal properties of poly (lactic acid)/starch blends.

    PubMed

    Lv, Shanshan; Gu, Jiyou; Cao, Jun; Tan, Haiyan; Zhang, Yanhua

    2015-03-01

    A comparative study of the thermal behavior of PLA/starch blends annealed at different temperatures has been conducted. Annealing was found to be beneficial to weaken and even eliminate the enthalpy relaxation near Tg. The degree of crystallinity was evaluated by means of DSC, and the results showed that the crystallinity of the samples increased as the annealing temperatures were increased. It was observed that, during the annealing process, the disorder α (α') crystal modification tended to transform into the order α crystal modification. All of the PLA/starch blends showed a double melting behavior. With the increase of annealing temperatures, the lower Tm1 increased, while the Tm2 showed no evident change. The XRD patterns also showed that annealing was beneficial to the samples to form higher crystallinity. The TGA results indicated that the annealed samples did not show any higher thermal stability than the virgin samples. The activation energy calculated by the Flynn-Wall-Ozawa method at lower conversion degrees confirmed that the annealing slightly slowed the degradation. The activation energy did not show any dependence on the conversion degree, which indicated that there existed a complex degradation process of the PLA/starch blends. The average activation energy did not show obvious differences, indicating that the annealing treatment had little influence on the degradation activation energy.

  16. 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.

  17. Post-annealing effects on the surface structure and carrier lifetime of evaporated BaSi2 films

    NASA Astrophysics Data System (ADS)

    Hara, Kosuke O.; Thi Trinh, Cham; Kurokawa, Yasuyoshi; Arimoto, Keisuke; Yamanaka, Junji; Nakagawa, Kiyokazu; Usami, Noritaka

    2017-04-01

    To improve the surface quality for photovoltaic applications, we have investigated the effects of post-annealing on the surface structure and carrier lifetime of evaporated BaSi2 films. Structural characterizations by Raman spectroscopy and X-ray diffraction analysis show that there is an optimum post-annealing duration for fabricating a homogeneous film up to around the surface. By detailed surface analysis by X-ray photoelectron spectroscopy, the existence of a surface oxidation layer consisting of BaCO3 and barium silicate is revealed, and the thickness of the oxidation layer is found to be smallest for the optimum post-annealing duration. These surface structural changes are discussed from a thermodynamic viewpoint. Carrier lifetime is also investigated by the microwave-detected photoconductivity decay method, which shows that the structural change around the surface by post-annealing has negligible effects on carrier lifetime, possibly because the silicate layer covers the BaSi2 surface irrespective of post-annealing duration.

  18. Annealing effects on the structural and magnetic properties of off-stoichiometric Fe-Mn-Ga ferromagnetic shape memory alloys

    SciTech Connect

    Chen, Yan; Bei, Hongbin; Dela Cruz, Clarina R; Wang, Yandong; An, Ke

    2016-05-07

    Annealing plays an important role in modifying structures and properties of ferromagnetic shape memory alloys (FSMAs). The annealing effect on the structures and magnetic properties of off-stoichiometric Fe45Mn26Ga29 FSMA has been investigated at different elevated temperatures. Rietveld refinements of neutron diffraction patterns display that the formation of the γ phase in Fe45Mn26Ga29 annealed at 1073 K increases the martensitic transformation temperature and reduces the thermal hysteresis in comparison to the homogenized sample. The phase segregation of a Fe-rich cubic phase and a Ga-rich cubic phase occurs at the annealing temperature of 773 K. The atomic occupancies of the alloys are determined thanks to the neutron's capability of differentiating transition metals. The annealing effects at different temperatures introduce a different magnetic characteristic that is associated with distinctive structural changes in the crystal.

  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 annealing conditions on the perpendicular magnetic anisotropy of Ta/CoFeB/MgO multilayers

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Hao, Liang; Cao, Jiangwei

    2016-04-01

    Films with a structure of Ta (5 nm)/Co20Fe60B20 (0.8-1.5 nm)/MgO (1 nm)/Ta (1 nm) were deposited on Corning glass substrates by magnetron sputtering. The as-deposited films with CoFeB layer thickness from 0.8 to 1.3 nm show perpendicular magnetic anisotropy (PMA). After annealing at a proper temperature, the PMA of the films can be enhanced remarkably. A maximum effective anisotropy field of up to 9 kOe was obtained for 1.0- and 1.1-nm-thick CoFeB layers annealed at an optimum temperature of 300 °C. A 4-kOe magnetic field was applied during annealing to study its effect on the PMA of the CoFeB layers. The results confirmed that applying a perpendicular magnetic field during annealing did not improve the maximum PMA of the films, but it did enhance the PMA of the thinner films at a lower annealing temperature.

  1. Effects of annealing on the microstructures and photoactivity of fluorinated N-doped TiO2.

    PubMed

    Liu, Shengwei; Yu, Jiaguo; Wang, Wenguang

    2010-10-14

    We investigated the effects of annealing in air on fluorinated N-doped TiO(2) (F/N-TiO(2)) photocatalysts prepared by hydrothermal process. The textural properties (specific surface areas) and surface properties (surface defect density, surface [triple bond]Ti-F density) were significantly modified upon annealing. In contrast, due to the shielding effect of surface fluorination, the phase transformation from anatase to rutile as well as removal of N-dopants during annealing was greatly inhibited. The evolution of the chemical nature of doped nitrogen species upon annealing in air was investigated and correlated with the generation and annihilation of oxygen deficiency. The defect density dominated the visible-light absorption and production of active ˙OH. The textural properties and the surface characteristics were crucial for UV-light photocatalytic performance, while the visible-light photocatalytic activity was mainly associated with the defect density. The 300 °C-annealed F/N-TiO(2) sample showed considerable photocatalytic activity under both UV and visible-light irradiation.

  2. Giant stress-impedance effect in amorphous and current annealed Fe 73.5Cu 1Nb 3Si 13.5B 9 wires

    NASA Astrophysics Data System (ADS)

    Han, Wei; Li, Deren; Lu, Zhichao; Zhou, Shaoxiong; Zhang, Honghao

    2002-02-01

    The giant stress-impedance (GSI) effect in Fe 73.5Cu 1Nb 3Si 13.5B 9 wires is measured to investigate the influence of Joule heating and pulse current annealing as well as tensile stress applied during the annealing process on it. The results show that the GSI effect changes drastically with annealing techniques and the maximum stress-impedance ratio of 80% is obtained at 5.5 MHz under applied tensile stress of 20 MPa.

  3. Effects of annealing conditions on the dielectric properties of solution-processed Al2O3 layers for indium-zinc-tin-oxide thin-film transistors.

    PubMed

    Kim, Yong-Hoon; Kim, Kwang-Ho; Park, Sung Kyu

    2013-11-01

    In this paper, the effects of annealing conditions on the dielectric properties of solution-processed aluminum oxide (Al2O3) layers for indium-zinc-tin-oxide (IZTO) thin-film transistors (TFTs) have been investigated. The dielectric properties of Al2O3 layers such as leakage current density and dielectric strength were largely affected by their annealing conditions. In particular, oxygen partial pressure in rapid thermal annealing, and the temperature profile of hot plate annealing had profound effects on the dielectric properties. From a refractive index analysis, the enhanced dielectric properties of Al2O3 gate dielectrics can be attributed to higher film density depending on the annealing conditions. With the low-temperature-annealed Al2O3 gate dielectric at 350 degrees C, solution-processed IZTO TFTs with a field-effect mobility of approximately 2.2 cm2/Vs were successfully fabricated.

  4. Effects of thermal annealing on the structural and optical properties of carbon-implanted SiO2.

    PubMed

    Poudel, P R; Paramo, J A; Poudel, P P; Diercks, D R; Strzhemechny, Y M; Rout, B; McDaniel, F D

    2012-03-01

    Amorphous carbon (a-C) nanoclusters were synthesized by the implantation of carbon ions (C-) into thermally grown silicon dioxide film (-500 nm thick) on a Si (100) wafer and processed by high temperature thermal annealing. The carbon ions were implanted with an energy of 70 keV at a fluence of 5 x 10(17) atoms/cm2. The implanted samples were annealed at 1100 degrees C for different time periods in a gas mixture of 96% Ar+4% H2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and High Resolution Transmission Electron Microscopy (HRTEM) were used to study the structural properties of both the as-implanted and annealed samples. HRTEM reveals the formation of nanostructures in the annealed samples. The Raman spectroscopy also confirms the formation of carbon nano-clusters in the samples annealed for 10 min, 30 min, 60 min and 90 min. No Raman features originating from the carbon-clusters are observed for the sample annealed further to 120 min, indicating a complete loss of implanted carbon from the SiO2 layer. The loss of the implanted carbon in the 120 min annealed sample from the SiO2 layer was also observed in the XPS depth profile measurements. Room temperature photoluminescence (PL) spectroscopy revealed visible emissions from the samples pointing to carbon ion induced defects as the origin of a broad 2.0-2.4 eV band, and the intrinsic defects in SiO2 as the possible origin of the -2.9 eV bands. In low temperature photoluminescence spectra, two sharp and intense photoluminescence lines at -3.31 eV and -3.34 eV appear for the samples annealed for 90 min and 120 min, whereas no such bands are observed in the samples annealed for 10 min, 30 min, and 60 min. The Si nano-clusters forming at the Si-SiO2 interface could be the origin of these intense peaks.

  5. Effect of thermal annealing Super Yellow emissive layer on efficiency of OLEDs

    NASA Astrophysics Data System (ADS)

    Burns, Samantha; MacLeod, Jennifer; Trang Do, Thu; Sonar, Prashant; Yambem, Soniya D.

    2017-01-01

    Thermal annealing of the emissive layer of an organic light emitting diode (OLED) is a common practice for solution processable emissive layers and reported annealing temperatures varies across a wide range of temperatures. We have investigated the influence of thermal annealing of the emissive layer at different temperatures on the performance of OLEDs. Solution processed polymer Super Yellow emissive layers were annealed at different temperatures and their performances were compared against OLEDs with a non-annealed emissive layer. We found a significant difference in the efficiency of OLEDs with different annealing temperatures. The external quantum efficiency (EQE) reached a maximum of 4.09% with the emissive layer annealed at 50 °C. The EQE dropped by ~35% (to 2.72%) for OLEDs with the emissive layers annealed at 200 °C. The observed performances of OLEDs were found to be closely related to thermal properties of polymer Super Yellow. The results reported here provide an important guideline for processing emissive layers and are significant for OLED and other organic electronics research communities.

  6. Effect of thermal annealing Super Yellow emissive layer on efficiency of OLEDs

    PubMed Central

    Burns, Samantha; MacLeod, Jennifer; Trang Do, Thu; Sonar, Prashant; Yambem, Soniya D.

    2017-01-01

    Thermal annealing of the emissive layer of an organic light emitting diode (OLED) is a common practice for solution processable emissive layers and reported annealing temperatures varies across a wide range of temperatures. We have investigated the influence of thermal annealing of the emissive layer at different temperatures on the performance of OLEDs. Solution processed polymer Super Yellow emissive layers were annealed at different temperatures and their performances were compared against OLEDs with a non-annealed emissive layer. We found a significant difference in the efficiency of OLEDs with different annealing temperatures. The external quantum efficiency (EQE) reached a maximum of 4.09% with the emissive layer annealed at 50 °C. The EQE dropped by ~35% (to 2.72%) for OLEDs with the emissive layers annealed at 200 °C. The observed performances of OLEDs were found to be closely related to thermal properties of polymer Super Yellow. The results reported here provide an important guideline for processing emissive layers and are significant for OLED and other organic electronics research communities. PMID:28106082

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

    PubMed

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

    2005-11-16

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

  8. Microstructure and Texture Evolution in a Yttrium-Containing ZM31 Alloy: Effect of Pre- and Post-deformation Annealing

    NASA Astrophysics Data System (ADS)

    Tahreen, N.; Zhang, D. F.; Pan, F. S.; Jiang, X. Q.; Li, D. Y.; Chen, D. L.

    2016-12-01

    Microstructure and texture evolution of as-extruded ZM31 magnesium alloys with different amounts of yttrium (Y) during pre- and post-deformation annealing were examined with special attention given to the effect of Y on recrystallization. It was observed that the extruded ZM31 alloys exhibited a basal texture with the basal planes parallel to the extrusion direction (ED). The compression of the extruded alloys in the ED to a strain amount of 10 pct resulted in c-axes of hcp unit cells rotating toward the anti-compression direction due to the occurrence of extension twinning. Annealing of the extruded alloys altered the microstructure and texture, and the subsequent compression after annealing showed a relatively weak texture and a lower degree of twinning. A reverse procedure of pre-compression and subsequent annealing was found to further weaken the texture with a more scattered distribution of orientations and to lead to the vanishing of the original basal texture. With increasing Y content, both the extent of extension twinning during compression and the fraction of recrystallization during annealing decreased due to the role of Y present in the substitutional solid solution and in the second-phase particles, leading to a significant increase in the compressive yield strength.

  9. The Effect of Thermal Annealing on Structural-phase Changes in the Ni-Ti Alloy Implanted with Krypton Ions

    NASA Astrophysics Data System (ADS)

    Poltavtseva, V. P.; Kislitsin, S. B.; Ghyngazov, S. A.

    2016-06-01

    The influence of thermal annealing within the temperature range 100-300°C on the structural-phase state of a Ni-Ti alloy with shape memory effect (SME) implanted with 84Kr ions at the energies E = 280 keV and 1.75 MeV/nucl and the fluences within 5·1012-1·1020 ion/m2 is investigated. For the samples modified by 84Kr ions at E = 1.75 MeV/nucl up to the fluences 1·1020 and 5·1012 ion/m2, the formation of a martensitic NiTi phase with the B19 ' structure, responsible for the SME, is revealed at the annealing temperatures 100 and 300°C, respectively, in the near-surface region corresponding to the outrange area. This is accompanied by the formation of nanosized NiTi particles in the R-phase. As the implantation fluence increases, the probability of their formation decreases. It is shown that annealing of the implanted structures can increase the strength of the Ni-Ti alloy. The degree of hardening is determined by the value of annealing temperature, and an increase in strength is primarily due to ordering of the radiation-induced defect structures (phases). A correlation between the onset temperature of a forward martensitic transition and the structural-phase state of the thermally annealed Ni-Ti alloy is established.

  10. Effect of annealing treatments on photoluminescence and charge storage mechanism in silicon-rich SiNx:H films

    PubMed Central

    2011-01-01

    In this study, a wide range of a-SiNx:H films with an excess of silicon (20 to 50%) were prepared with an electron-cyclotron resonance plasma-enhanced chemical vapor deposition system under the flows of NH3 and SiH4. The silicon-rich a-SiNx:H films (SRSN) were sandwiched between a bottom thermal SiO2 and a top Si3N4 layer, and subsequently annealed within the temperature range of 500-1100°C in N2 to study the effect of annealing temperature on light-emitting and charge storage properties. A strong visible photoluminescence (PL) at room temperature has been observed for the as-deposited SRSN films as well as for films annealed up to 1100°C. The possible origins of the PL are briefly discussed. The authors have succeeded in the formation of amorphous Si quantum dots with an average size of about 3 to 3.6 nm by varying excess amount of Si and annealing temperature. Electrical properties have been investigated on Al/Si3N4/SRSN/SiO2/Si structures by capacitance-voltage and conductance-voltage analysis techniques. A significant memory window of 4.45 V was obtained at a low operating voltage of ± 8 V for the sample containing 25% excess silicon and annealed at 1000°C, indicating its utility in low-power memory devices. PMID:21711712

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

    NASA Astrophysics Data System (ADS)

    Cho, Shinho

    2015-10-01

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

  12. Optical transitions and point defects in F:SnO2 films: Effect of annealing

    NASA Astrophysics Data System (ADS)

    El Akkad, Fikry; Paulose, Tressia A. P.

    2014-03-01

    FTO films were deposited on borosilicate glass using chemical spray pyrolysis at 450 °C then subjected to post deposition annealing in air at 500, 550 and 600 °C. The films are characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), optical and electrical measurements. They are found to have the Rutile structure with strong orientation along the (1 1 0) and (2 0 0) planes and with grain size varying with annealing temperature in the range 20-100 nm. Electron concentration and oxygen vacancy concentration in the range (2.61-7.07) × 1020 cm-3 and (1.49-2.41) × 1022 cm-3 were determined using Hall and XPS measurements respectively. The analysis of optical absorption spectra revealed the presence of three direct optical transitions of energies E1 = 3.78 ± 0.07 eV, E2 = 4.39 ± 0.07 eV and E3 = 4.81 ± 0.08 eV. Taking into account the Moss-Burstein and the Urbach tailing effects, E2 was identified as being due to a direct optical transition across the Γ3v+-Γ1c+ gap. The mean value of the width of this gap is determined to be 3.86 ± 0.14 eV. The two other energies E1 and E3 are assigned to electronic transitions originating from the lower valence bands Γ5v- and Γ1v+ respectively to a defect level at Ec -0.61 ± 0.02 eV attributed to the second ionization state of the oxygen vacancy. On the other hand, the analysis of the Hall mobility results on the basis of current theories provides evidence that fluorine is at the origin of a double donor which, according to XPS measurements, must contain FSn bonds. This double donor, suggested to be the complex center [F-Sn-F]++, dominates the electrical properties of as-deposited films and creates isolated substitutional fluorine FO at higher annealing temperatures possibly by thermal dissociation.

  13. Effect of annealing on VmHn complexes in hydrogen ion irradiated Fe and Fe-0.3%Cu alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Jin, Shuoxue; Lu, Eryang; Wang, Baoyi; Zheng, Yongnan; Yuan, Daqing; Cao, Xingzhong

    2015-04-01

    The effect of annealing on VmHn complexes and Cu precipitate behaviours in hydrogen ion irradiated Fe and Fe-0.3%Cu alloys was investigated by positron annihilation spectroscopy using a slow positron beam. The results of S parameters indicated that the room temperature irradiation was benefit for the formation of the VmHn complex compared to the elevated temperature irradiation. The S-W results confirmed the formation of Cu precipitates in Fe-0.3%Cu even at the irradiation dose of 0.1 dpa. The formation of the evident S value peaks in the damage region after annealing treatment suggested that the VmHn complexes were broken and a larger of hydrogen atoms were escaping. The residual vacancy defects would migrate towards both the surface region and the opposite direction with the increasing annealing temperature.

  14. Tin selenide synthesized by a chemical route: the effect of the annealing conditions in the obtained phase

    NASA Astrophysics Data System (ADS)

    Bernardes-Silva, Ana Cláudia; Mesquita, A. F.; de Moura Neto, E.; Porto, A. O.; de Lima, G. M.; Ardisson, J. D.; Lameiras, F. S.

    2005-09-01

    The effects of different annealing conditions over the tin selenide obtained from a chemical route are presented in this work. The tin selenide was annealed at 300 and 600 °C under hydrogen, nitrogen and argon atmospheres. The materials were characterized by X-ray diffraction and 119Sn Mössbauer spectroscopy. In the 'as synthetized' material a considerably amount of tin oxide (57%) was detected by Mössbauer spectroscopy. After thermal annealing the amount of these oxides varied according to the temperature and atmosphere used. At 600 °C/hydrogen the smallest amount of tin oxide was obtained (20%). These oxides were formed during the synthetic procedure through the hydrolysis of tin chloride used as reagent.

  15. Effect of rapid thermal annealing on InP1-xBix grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Wu, X. Y.; Wang, K.; Pan, W. W.; Wang, P.; Li, Y. Y.; Song, Y. X.; Gu, Y.; Yue, L.; Xu, H.; Zhang, Z. P.; Cui, J.; Gong, Q.; Wang, S. M.

    2015-09-01

    The effect of post-growth rapid thermal annealing on structural and optical properties of InP1-xBix thin films was investigated. InPBi shows good thermal stability up to 500 °C and a modest improvement in photoluminescence (PL) intensity with an unchanged PL spectral feature. Bismuth outdiffusion from InPBi and strain relaxation are observed at about 600 °C. The InPBi sample annealed at 800 °C shows an unexpected PL spectrum with different energy transitions.

  16. Effects of rapid thermal annealing on the optical properties of strain-free quantum ring solar cells.

    PubMed

    Wu, Jiang; Wang, Zhiming M; Dorogan, Vitaliy G; Li, Shibin; Lee, Jihoon; Mazur, Yuriy I; Kim, Eun Soo; Salamo, Gregory J

    2013-01-02

    Strain-free GaAs/Al0.33Ga0.67As quantum rings are fabricated by droplet epitaxy. Both photoresponse and photoluminescence spectra confirm optical transitions in quantum rings, suggesting that droplet epitaxial nanomaterials are applicable to intermediate band solar cells. The effects of post-growth annealing on the quantum ring solar cells are investigated, and the optical properties of the solar cells with and without thermal treatment are characterized by photoluminescence technique. Rapid thermal annealing treatment has resulted in the significant improvement of material quality, which can be served as a standard process for quantum structure solar cells grown by droplet epitaxy.

  17. The Effect of Annealing at 1500 C on Migration and Release of Ion Implanted Silver in CVD Silicon Carbide

    SciTech Connect

    HJ MacLean; RG Ballinger; LE Kolaya; SA Simonson; N Lewis; M Hanson

    2004-10-07

    The transport of silver in CVD {beta}-SiC has been studied using ion implantation. Silver ions were implanted in {beta}-SiC using the ATLAS accelerator facility at the Argonne National Laboratory. Ion beams with energies of 93 and 161 MeV were used to achieve deposition with peak concentrations at depths of approximately 9 and 13 {micro}m, respectively. As-implanted samples were then annealed at 1500 C for 210 or 480 hours. XPS, SEM, TEM, STEM, and optical methods were used to analyze the material before and after annealing. Silver concentration profiles were determined using XPS before and after annealing. STEM and SEM equipped with quantitative chemical analysis capability were used to more fully characterize the location and morphology of the silver before and after annealing. The results show that, within the uncertainty of measurement techniques, there is no silver migration, via either inter- or intragrannular paths, for the times and temperature studied. Additionally, the silver was observed to phase separate within the SiC after annealing. The irradiation damage from the implantation process resulted in a three-layer morphology in the as-implanted condition: (1) a layer of unaltered SiC, followed by (2) a layer of crystallized SiC, followed by (3) an amorphized layer which contained essentially all of the implanted silver. After annealing the layer structure changed. Layer 1 was unaltered. The grains in layer 2 recrystallized to form an epitaxial (columnar) layer. Layer 3 recrystallized to form a fine grain equiaxed layer. The results of this work do not support the long held assumption that silver release from CVD SiC, used for gas-reactor coated particle fuel, is dominated by grain boundary diffusion.

  18. Annealing effect for SnS thin films prepared by high-vacuum evaporation

    SciTech Connect

    Revathi, Naidu Bereznev, Sergei; Loorits, Mihkel; Raudoja, Jaan; Lehner, Julia; Gurevits, Jelena; Traksmaa, Rainer; Mikli, Valdek; Mellikov, Enn; Volobujeva, Olga

    2014-11-01

    Thin films of SnS are deposited onto molybdenum-coated soda lime glass substrates using the high-vacuum evaporation technique at a substrate temperature of 300 °C. The as-deposited SnS layers are then annealed in three different media: (1) H{sub 2}S, (2) argon, and (3) vacuum, for different periods and temperatures to study the changes in the microstructural properties of the layers and to prepare single-phase SnS photoabsorber films. It is found that annealing the layers in H{sub 2}S at 400 °C changes the stoichiometry of the as-deposited SnS films and leads to the formation of a dominant SnS{sub 2} phase. Annealing in an argon atmosphere for 1 h, however, causes no deviations in the composition of the SnS films, though the surface morphology of the annealed SnS layers changes significantly as a result of a 2 h annealing process. The crystalline structure, surface morphology, and photosensitivity of the as-deposited SnS films improves significantly as the result of annealing in vacuum, and the vacuum-annealed films are found to exhibit promising properties for fabricating complete solar cells based on these single-phase SnS photoabsorber layers.

  19. Annealing effects on the ferromagnetic resonance linewidths of sputter-deposited Fe{sub 100−x}Co{sub x}(001) thin films (x < 11)

    SciTech Connect

    Kusaoka, A.; Kimura, J.; Takahashi, Y. Inaba, N.; Kirino, F.; Ohtake, M.; Futamoto, M.

    2015-05-07

    Effects of post-growth annealing on the magnetic damping of 3d transition alloy thin films were investigated. Fe{sub 100−x}Co{sub x} (x < 11 at. %) thin films were epitaxially deposited on GaAs(001) substrates by rf magnetron sputtering, and some of them were annealed without exposing to atmosphere. Electrical measurement showed that in-plane resistivity was smaller in the annealed films than in the as-deposited ones, indicating that the annealing mitigates crystalline imperfections and leads to reduced electron scattering rates. Magnetic damping was evaluated by the peak widths of ferromagnetic resonance (FMR) spectra obtained by a conventional Q-band spectrometer. Comparison of as-deposited and annealed specimens showed that the damping was decreased by annealing. Combined with the electrical and FMR measurements, these observations are consistent with the theoretical predictions that crystalline imperfections strongly influence the magnetic damping, both in intrinsic and extrinsic origins.

  20. Effects of annealing in N2 ambient on traps and persistent conduction in hydrothermally grown ZnO

    NASA Astrophysics Data System (ADS)

    Fang, Z.-Q.; Claflin, B.; Look, D. C.

    2008-04-01

    Thermally stimulated current (TSC) spectroscopy and temperature-dependent dark current (DC) measurements have been applied to study traps and photoinduced persistent surface conduction in two hydrothermally grown bulk ZnO samples, as-grown, and annealed at 600°C in N2 ambient for 30min, respectively. The as-grown sample had a room-temperature (RT) resistivity of 1.6×103Ωcm, mobility of 2.1×102cm2/Vs, and carrier concentration of 1.8×1013cm-3, while the annealed sample was highly resistive, with RT resistivity of 3.6×106Ωcm, mobility of 4.4cm2/Vs, and carrier concentration of 3.9×1011cm-3. The as-grown sample showed strong conduction at low temperatures, which has been shown to be due to near-surface carriers in other studies. The annealed sample did not demonstrate this phenomenon. The dominant trap in the as-grown sample had an activation energy of 0.16eV, was strongest near the surface, and is possibly related to VZn. In the annealed sample, however, the dominant trap had an activation energy of 0.22eV, was of bulk nature, and is tentatively assigned to LiZn. After several routine TSC measurements, the DC for the as-grown sample increased by more than one order of magnitude at low temperatures (T<180K), while for the annealed sample, the DC increased by a factor of 2 at high temperatures (T>200K). These effects are generated by the TSC trap-filling illumination and can persist for many days under vacuum. At RT, the DC in the annealed sample returns to its equilibrium state if the sample is vented to air.

  1. Post-deposition annealing effect on RF-sputtered TiO2 thin-film properties for photonic applications

    NASA Astrophysics Data System (ADS)

    Hadjoub, Ilhem; Touam, Tahar; Chelouche, Azeddine; Atoui, Mohamed; Solard, Jeanne; Chakaroun, Mahmoud; Fischer, Alexis; Boudrioua, Azzedine; Peng, Lung-Han

    2016-02-01

    Titanium dioxide (TiO2) thin films were grown on glass substrates at room temperature using RF magnetron sputtering technique. Effect of the post-annealing for 1 h at 400-600 °C on the structural, morphological, optical and waveguide properties was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectrophotometry and m-lines spectroscopy (MLS). XRD studies show that as-grown and post-annealed TiO2 films exhibit (101) XRD peak corresponding to the anatase phase of TiO2. Higher annealing temperatures result in a significant increase in crystallinity. The grain size values were calculated and found to be about 15-37 nm. From the analyses made on the SEM micrographs and AFM images, it was revealed that the morphology and surface roughness of the thin films were influenced by the heat treatment temperature. The UV-visible spectroscopy analyses show that as-grown TiO2 films were transparent in the visible region with an average transmittance of more than 75 % and the transmittance decreases slightly with an increase in annealing temperature. Annealed TiO2 films also exhibit an increase in the values of direct optical band gap. MLS measurements at 633-nm wavelength put into evidence that TiO2 planar waveguides demonstrate a well-guided fundamental mode for both transverse electric and transverse magnetic polarized light. Moreover, the refractive index was found to increase with temperature and to approach to the anatase TiO2 single-crystal value for the TiO2 film annealed at 600 °C.

  2. Improved cost-effectiveness of the block co-polymer anneal process for DSA

    NASA Astrophysics Data System (ADS)

    Pathangi, Hari; Stokhof, Maarten; Knaepen, Werner; Vaid, Varun; Mallik, Arindam; Chan, Boon Teik; Vandenbroeck, Nadia; Maes, Jan Willem; Gronheid, Roel

    2016-04-01

    This manuscript first presents a cost model to compare the cost of ownership of DSA and SAQP for a typical front end of line (FEoL) line patterning exercise. Then, we proceed to a feasibility study of using a vertical furnace to batch anneal the block co-polymer for DSA applications. We show that the defect performance of such a batch anneal process is comparable to the process of record anneal methods. This helps in increasing the cost benefit for DSA compared to the conventional multiple patterning approaches.

  3. Effect of Annealing Twins on Electromigration in Ag-8Au-3Pd Bonding Wires

    NASA Astrophysics Data System (ADS)

    Chuang, Tung-Han; Wang, Hsi-Ching; Chuang, Chien-Hsun; Lee, Jun-Der; Tsai, Hsing-Hua

    2013-03-01

    An innovative Ag-8Au-3Pd bonding wire with a high twin density has been produced. The grain size of this annealing-twinned wire changes moderately during electrical stressing, unlike that of the conventional grained wire, which increases drastically and even leads to a bamboo structure. In addition, the durability against electromigration of the annealing-twinned Ag-8Au-3Pd alloy wire is higher than that of the conventional grained wire. This higher durability can be ascribed to the surface reconstruction of a stepwise morphology and slow grain growth resulting from the abundance of annealing twins in this wire.

  4. The Effect of Hydrogen Annealing on the Oxidation Resistance of Four EPM Single Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Barrett, Charles A.; Garlick, Ralph G.

    2001-01-01

    Four single crystal EPM (enabling propulsion materials) developmental airfoil superalloys were hydrogen annealed at 1300 C for up to 100 hours to remove sulfur and improve oxidation resistance. Although the 1100 and 1150 C cyclic oxidation resistance was remarkably improved by annealing for 24 or 100 hours, the behavior was still considerably inferior to that of commercially available single crystal superalloys, especially those that are either Y-doped or hydrogen annealed. Excessive degradation in the developmental alloys appeared to be correlated with low Cr contents and, to a lesser extent, high Co and Re contents.

  5. Effect of annealing on the martensitic transformation and magnetocaloric effect in Ni44.1Mn44.2Sn11.7 ribbons

    NASA Astrophysics Data System (ADS)

    Xuan, H. C.; Xie, K. X.; Wang, D. H.; Han, Z. D.; Zhang, C. L.; Gu, B. X.; Du, Y. W.

    2008-06-01

    The Ni44.1Mn44.2Sn11.7 ribbons were prepared by melt spinning. A single-phase austenite with L21 structure was confirmed in the melt-spun ribbons at room temperature. After the heat treatment, the martensitic transformation temperature increases obviously in the annealed ribbons. This method may be an effective way to tune the characteristic temperatures in the ferromagnetic shape memory alloys. Giant magnetic entropy changes are observed in the annealed ribbons. The peak values at 10kOe are 32.1 and 20.1J /kgK, for the ribbons annealed at 1123 and 1173K, respectively.

  6. 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.

  7. Effects of annealing on properties of Al2O3 monolayer film at 355 nm

    NASA Astrophysics Data System (ADS)

    Tu, Feifei; Wang, Hu; Xing, Huanbin; Zheng, Ruxi; Zhang, Weili; Yi, Kui

    2015-07-01

    Al2O3 monolayer films were deposited on fused silica substrate and K9 glass substrate by electron-beam deposition. Annealing as a general post-treatment was used to enhance the quality of the Al2O3 coatings. The optical properties of the films were analyzed from the transmission spectra of the samples. The composition of the samples before and after annealing were measured by X-ray photoelectron spectroscopy (XPS). According to the analysis of the results, it can be found that the oxidation degree of the coatings increases after annealing in O2 inside coating chamber. The laser-induced damage thresholds of the Al2O3 films can be increased after the annealing process. Finally, the damage morphologies of the Al2O3 coatings were analyzed.

  8. 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.

  9. Effect of aging and annealing on perpendicular magnetic anisotropy of ultra-thin CoPt films

    NASA Astrophysics Data System (ADS)

    Hara, R.; Hayakawa, K.; Ebata, K.; Sugita, R.

    2016-05-01

    The effect of aging and annealing on the magnetic properties of ultra-thin CoPt films with a Ru underlayer was investigated. For the 3 nm thick CoPt film aged in the air, the decrease of the saturation magnetic moment ms, the drastic increase of the perpendicular coercivity Hc⊥ and the perpendicular anisotropy were observed. This is because the surface layer of the CoPt film was oxidized and the bottom layer with high perpendicular anisotropy due to lattice distortion remained. For the annealed 3 nm thick CoPt film with a Pt protective layer, rising the annealing temperature Ta led to the decrease of ms, the decrease after increase of Hc⊥, and the decrease of the perpendicular squareness ratio S⊥ at Ta of 400 ∘C. The origins of effect of annealing were considered to be the grain boundary diffusion and the bulk diffusion of Ru and Pt into the CoPt film, and relaxation of the lattice distortion.

  10. Correlation of annealing time with crystal structure, composition, and electronic properties of CH3NH3PbI3-xClx mixed-halide perovskite films.

    PubMed

    Ralaiarisoa, Maryline; Busby, Yan; Frisch, Johannes; Salzmann, Ingo; Pireaux, Jean-Jacques; Koch, Norbert

    2016-12-21

    Using 3D imaging with time-of-flight secondary ion mass spectrometry (ToF-SIMS) complemented by grazing-incidence X-ray diffraction (GIXRD), we spatially resolve changes in both the composition and structure of CH3NH3I3-xClx perovskite films on conducting polymer substrates at different annealing stages, in particular, before and after complete perovskite crystallization. The early stage of annealing is characterized by phase separation throughout the entire film into domains with perovskite and domains with a dominating chloride-rich phase. After sufficiently long annealing, one single perovskite phase of homogeneous composition on the (lateral) micrometer scale is observed, along with pronounced film texture. This composition evolution is accompanied by diffusion of chloride from the perovskite layer towards the conducting polymer substrate, and even accumulation there. Photoelectron spectroscopy analysis further shows that perovskite films become increasingly n-type with annealing time and upon full conversion, which correlates with the change of film composition. Our results accentuate the importance of chloride for the formation of crystalline and textured films, which are crucial for enhancing the PV performance of perovskite-based solar cells.

  11. The Effect of Annealing Above Glass Transition Temperature on the Optical Properties of Se85Te10Bi5 Thin Films

    NASA Astrophysics Data System (ADS)

    Atyia, H. E.; Farid, A. S.

    2016-01-01

    Se85Te10Bi5 films have been deposited using the thermal evaporation technique. Films with different thicknesses in the thickness range 590.2-273.9 nm were annealed at different annealing temperatures above the glass transition temperature for 120 min. The structure of the annealed films was checked by x-ray diffraction analysis, which indicated a polycrystalline nature for all annealed films, and that the degree of crystallinity increased with increasing annealing temperature. From the reflectance ( R) and transmittance ( T) measurements, the values of the optical absorption coefficient ( α) for the annealed films were estimated to be in the wavelength range of 500-2500 nm. Analysis of the absorption coefficient data reveals allowed indirect transitions and the values of optical band gap ( E g). The values of ( E g) were found to be obeying the Tauc's relation and decreasing with increasing annealing temperature. This behavior is discussed as due to thermal disordering with the structural changes upon annealing. Optical parameters such as lattice and the infinite frequency dielectric constant as ( ɛ L and ɛ ∞), plasma frequency ( ω p), carrier concentration to the effective mass ratio ( N/m*), single- oscillator and dispersion energies ( E o and E d) were found. The dependence of the optical parameters on the annealing temperature was studied and discussed.

  12. Effect of solvent annealing on heterojunction polymer solar cells based on P3HT/PCBM.

    PubMed

    Park, Hanok; Ambade, Rohan B; Lee, Soo-Hyoung

    2013-12-01

    Heterojunction (HJ) structure has the advantages of high charge collection and transport efficiency, but it also has the disadvantage of low charge collection, due to limited p-n interfaces, compared with bulkheterojunction (BHJ) structure. In order to overcome this disadvantage of HJ, we fabricated HJ solar cells with large p-n interfaces, based on poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butylric acid methyl ester (PC61 BM), treated by a solvent annealing (SA) process under atmospheric condition, which is a simple and low-cost process. The SA process induced a P3HT-PC61 BM interdiffusion layer between the P3HT and PC61 BM layers, by a diffusion of each component, and resulted in an increase of p-n interface areas. These results were confirmed by X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The performance of a HJ device fabricated with a SA process achieved a 30% higher power conversion efficiency (PCE) value (approximately 3.3%), than that without a SA process. Interestingly, the HJ SA device showed higher long-term stability, than that without a SA process.

  13. 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.

  14. In Situ Monitoring of the Thermal-Annealing Effect in a Monolayer of MoS2

    NASA Astrophysics Data System (ADS)

    Su, Liqin; Yu, Yifei; Cao, Linyou; Zhang, Yong

    2017-03-01

    We perform in situ two-cycle thermal-annealing studies for a transferred CVD-grown monolayer MoS2 on a SiO2/Si substrate, using spatially resolved micro-Raman and photoluminescence spectroscopy. The evolution in film morphology and film-substrate bonding is continuously monitored by Raman spectroscopy. After the thermal cycling and being annealed at 305 °C twice, the film morphology and film-substrate bonding are significantly modified, which together with the removal of polymer residues causes major changes in the strain and doping distribution over the film, and thus the optical properties. Before annealing, the strain associated with ripples in the transferred film dominates the spatial distributions of the photoluminescence peak position and intensity over the film; after annealing, the variation in film-substrate bonding, affecting both strain and doping, becomes the leading factor. This work reveals that the film-substrate bonding, and thus the strain and doping, is nonstationary under thermal stress, which is important for understanding the substrate effects on the optical and transport properties of the 2D material and their impact on device applications.

  15. Effects of Annealing Ambient on the Characteristics of LaAlO3 Films Grown by Atomic Layer Deposition.

    PubMed

    Zhao, Lu; Liu, Hong-Xia; Wang, Xing; Fei, Chen-Xi; Feng, Xing-Yao; Wang, Yong-Te

    2017-12-01

    We investigated the effects of different annealing ambients on the physical and electrical properties of LaAlO3 films grown by atomic layer deposition. Post-grown rapid thermal annealing (RTA) was carried out at 600 °C for 1 min in vacuum, N2, and O2, respectively. It was found that the chemical bonding states at the interfacial layers (ILs) between LaAlO3 films and Si substrate were affected by the different annealing ambients. The formation of IL was enhanced during the RTA process, resulting in the decrease of accumulation capacitance, especially in O2 ambient. Furthermore, based on the capacitance-voltage characteristics of LaAlO3/Si MIS capacitors, positive V FB shifting tendency could be observed, indicating the decrease of positive oxide charges. Meanwhile, both trapped charge density and interface trap density showed decreased trends after annealing treatments. In addition, RTA process in various gaseous ambients can reduce the gate leakage current due to the enhancement of valence band offset and the reduction of defects in the LaAlO3/Si structure in varying degrees.

  16. Effects of Annealing Ambient on the Characteristics of LaAlO3 Films Grown by Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Lu; Liu, Hong-xia; Wang, Xing; Fei, Chen-xi; Feng, Xing-yao; Wang, Yong-te

    2017-02-01

    We investigated the effects of different annealing ambients on the physical and electrical properties of LaAlO3 films grown by atomic layer deposition. Post-grown rapid thermal annealing (RTA) was carried out at 600 °C for 1 min in vacuum, N2, and O2, respectively. It was found that the chemical bonding states at the interfacial layers (ILs) between LaAlO3 films and Si substrate were affected by the different annealing ambients. The formation of IL was enhanced during the RTA process, resulting in the decrease of accumulation capacitance, especially in O2 ambient. Furthermore, based on the capacitance-voltage characteristics of LaAlO3/Si MIS capacitors, positive V FB shifting tendency could be observed, indicating the decrease of positive oxide charges. Meanwhile, both trapped charge density and interface trap density showed decreased trends after annealing treatments. In addition, RTA process in various gaseous ambients can reduce the gate leakage current due to the enhancement of valence band offset and the reduction of defects in the LaAlO3/Si structure in varying degrees.

  17. Effect of Solution Annealing on Susceptibility to Intercrystalline Corrosion of Stainless Steel with 20% Cr and 8% Ni

    NASA Astrophysics Data System (ADS)

    Taiwade, R. V.; Patil, A. P.; Patre, S. J.; Dayal, R. K.

    2013-06-01

    In general, as-received (AR) austenitic stainless steels (ASSs) contain complex carbide precipitates due to manufacturing operations, subsequent annealing treatment, or due to the fabrication processes such as welding. The presence of pre-existing carbides leads to cumulative sensitization and make the steel susceptible to intercrystalline corrosion (ICC)/intergranular corrosion (IGC) which causes premature failure during service. Solution annealing (SA) is one of the ways to deal with such situations. In this present investigation, the AR (hot rolled and mill annealed) chromium-nickel (Cr-Ni) ASS is compared with SA Cr-Ni ASS. The extent of ICC/IGC was evaluated qualitatively and quantitatively by various electrochemical tests including ASTM standard A-262 Practice A and Practice E, double loop electrochemical potentiokinetic reactivation and electrochemical impedance spectroscopy. The degree of sensitization for hot rolled mill annealed AR condition is found to be substantially higher (51.55%) than that of SA condition (26.9%) for thermally aged samples (at 700 °C). The chemical composition across the grain boundary was measured using electron probe micro-analyzer for both (AR and SA) conditions and confirms that the pre-sensitization effect was completely removed after SA treatment.

  18. Effect of Variants of Thermomechanical Working and Annealing Treatment on Titanium Alloy Ti6Al4V Closed Die Forgings

    NASA Astrophysics Data System (ADS)

    Gupta, R. K.; Kumar, V. Anil; Kumar, P. Ram

    2016-06-01

    Performance of titanium alloy Ti6Al4V pressure vessels made of closed die forged domes of route `B' (multiple step forged and mill annealed) is reported to be better than route `A' (single/two step forged and mill annealed). Analysis revealed that forgings processed through route `B' have uniformity in microstructure and yield strength at various locations within the forging, as compared to that of route `A.' It is attributed to in-process recrystallization (dynamic as well as static) of route `B' forgings as compared to limited recrystallization of route `A' forgings. Further, post-forging recrystallization annealing (RA) effect is found to be more significant for route `A' forgings in achieving uniform microstructure and mechanical properties, since route `B' forgings have already undergone similar phenomenon during the thermomechanical working process itself. Considering prime importance of yield strength, statistical scatter in yield strength values within the forgings have been evaluated for forgings of both the routes. Standard deviation in the yield strength of route `B' forgings was lower (<10 MPa) as compared to route `A' (>15 MPa), which later became lower (~10 MPa) after RA with a minor decrease in yield strength. The present work discusses these variants of thermomechanical processing along with annealing to achieve better uniformity in properties and microstructure.

  19. Effects of annealing, acid and alcoholic beverages on Fe1+yTe0.6Se0.4

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Taen, T.; Tsuchiya, Y.; Shi, Z. X.; Tamegai, T.

    2013-01-01

    We have systematically investigated and compared different methods to induce superconductivity in the iron chalcogenide Fe1+yTe0.6Se0.4, including annealing in a vacuum, N2, O2 and I2 atmospheres and immersing samples into acid and alcoholic beverages. Vacuum and N2 annealing are proved to be ineffective in inducing superconductivity in a Fe1+yTe0.6Se0.4 single crystal. Annealing in O2 and I2 and immersion in acid and alcoholic beverages can induce superconductivity by oxidizing the excess Fe in the sample. Superconductivity in O2 annealed samples is of a bulk nature, while I2, acid and alcoholic beverages can only induce superconductivity near the surface. By comparing the different effects of O2, I2, acid and alcoholic beverages we propose a scenario to explain how the superconductivity is induced in the non-superconducting as-grown Fe1+yTe0.6Se0.4.

  20. Effect of in situ annealing on structure and optical properties of ZnTe nanoparticles produced by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Orii, Takaaki; Hirasawa, Makoto; Seto, Takafumi

    2007-04-01

    An improvement in morphology, crystallinity, and optical property of ZnTe nanoparticles produced by pulsed laser ablation (PLA) was achieved by in situ annealing. ZnTe nanoparticles produced in argon gas ambience by PLA were annealed in the gas flow at a temperatures Ta ranging from 300 °C to 800 °C and size-selected by a differential mobility analyzer. The bimodal size distribution of the ZnTe nanoparticles changed to unimodal at Ta = 600 °C. In this condition, the shape of the monodispersed ZnTe nanoparticles, classified into around 20 nm, became uniformly spherical and their crystallinity estimated by x-ray diffraction was extremely improved. These improvements by the in situ annealing were examined for ZnTe nanoparticles produced from off-stoichiometric target. Although the optical property of ZnTe nanoparticles produced from a zinc rich target was improved, those produced from a tellurium rich target could not be improved. It was found that the effect of in situ annealing on optical properties of ZnTe nanoparticles was dependent upon its content.

  1. Heterogeneous patterns on block copolymer thin film via solvent annealing: Effect on protein adsorption

    NASA Astrophysics Data System (ADS)

    Shen, Lei; Zhu, Jintao; Liang, Haojun

    2015-03-01

    Heterogeneous patterns consisting of nanometer-scaled hydrophobic/hydrophilic domains were generated by self-assembly of poly(styrene)-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) block copolymer thin film. The effect of the heterogeneity of the polymer film surface on the nonspecific adsorption of the protein human plasma fibrinogen (FBN, 5.0 × 5.0 × 47.5 nm3) was investigated. The kinetics of the FBN adsorption varies from a single-component Langmuir model on homogeneous hydrophilic PHEMA to a two-stage spreading relaxation model on homogeneous hydrophobic PS surface. On a heterogeneous PS-b-PHEMA surface with majority PS part, the initial FBN adsorption rate remains the same as that on the homogeneous PS surface. However, hydrophilic PHEMA microdomains on the heterogeneous surface slow down the second spreading stage of the FBN adsorption process, leading to a surface excess of adsorbed FBN molecules less than the presumed one simply calculated as adsorption onto multiple domains. Importantly, when the PS-b-PHEMA surface is annealed to form minority domelike PS domains (diameter: ˜50-100 nm) surrounded by a majority PHEMA matrix, such surface morphology proves to be strongly protein-repulsive. These interesting findings can be attributed to the enhancement of the spread FBN molecule in a mobile state by the heterogeneity of polymer film surface before irreversible adsorption occurs.

  2. Effect of composition and annealing on electrodeposited CoxPt1-X nanowires

    NASA Astrophysics Data System (ADS)

    Khatri, Manvendra Singh; Agarwal, Shivani; Hsu, Jen-Hwa; Chien, Chia-Hua; Chen, Cheng-Lung; Chen, Yang-Yuan

    2016-05-01

    Highly ordered CoxPt1-x (x ≤ 0.82) magnetic nanowire arrays of 60 nm diameter have been fabricated successfully by electrodeposition process into the pores of anodic aluminum oxide (AAO) templates. Electrodeposition process has been used as it is one of the simplest and most inexpensive, easily controlled method for the synthesis of nanowires.It was found that deposition potential is a key factor to control the composition and thus the magnetic properties of the nanowires. The as-deposited CoxPt1-x nanowires were characterized by XRD to have fcc structure with preferred orientation of (111) or (001) along the nanowire. Co-rich nanowires exhibit ferromagnetic behavior in contrast to near superparamagnetic response of the Pt-rich nanowires. Upon annealing the effects of crystallization cause the decrease of anisotropy along the wire axis for Co82Pt18 nanowires due to the increase of magnetocrystalline anisotropy perpendicular to the wire axis. In the next phase of our work segmented CoPtP/Pt multilayers nanowires will be deposited within the AAO template. Such multilayers nanowires are expected to have the high anisotropy due to the formation of ordered Co-Pt alloy phase at the interface.

  3. Annealing effect on the magnetic properties of evaporated CoCr thin films

    NASA Astrophysics Data System (ADS)

    Kharmouche, Ahmed; Djouada, Intissar; Schmerber, Guy

    2013-08-01

    Series of CoxCr1-x thin films have been evaporated under vacuum onto monocrystalline silicon substrate, x being atomic percent of cobalt. The thickness ranges from 17 to 220 nm, values measured by Rutherford backscattering spectrometry. The samples have been annealed under vacuum for one hour at 700 °C. The as deposited films show a hexagonal close packed (hcp) structure while the annealed films show both hexagonal close packed and face centered cubic (fcc) structures. While the as deposited films are under a compressive stress, the annealed films, on the contrary, are under a tensile stress. The hysteresis loops present the same features for the as deposited and annealed films concerning the in-plane and out-of-plane anisotropies. Nevertheless, the coercive field is strongly improved for the annealed films. Moreover, these latter films present very high values of the squareness. A squareness value up to 0.96 has been measured. All these results and others are analyzed and discussed.

  4. Annealing effects and DLTS study on NPN silicon bipolar junction transistors irradiated by heavy ions

    NASA Astrophysics Data System (ADS)

    Liu, Chaoming; Li, Xingji; Yang, Jianqun; Rui, Erming

    2014-01-01

    Isochronal anneal sequences have been carried out on 3DG112 silicon NPN bipolar junction transistors (BJTs) irradiated with 20 MeV bromine (Br) heavy ions. The Gummel curve is utilized to characterize the annealing behavior of defects in both the emitter-base depletion region and the neutral base. We find that the base current (IB) decreases with the increasing annealing temperature, while the collector current (IC) remains invariable. The current gain varies slightly, when the annealing temperature (TA) is lower than 400 K, while varies rapidly at TA<450 K, and the current gain of the 3DG112 BJT annealing at 700 K almost restore to that of the pre-radiation transistor. Deep level transient spectroscopy (DLTS) data is used to assign the relative magnitude of each of the important defects. Based on the in situ electrical measurement and DLTS spectra, it is clear that the V2(-/0)+V-P traps are the main contribution to the degradation of current gain after the 20 MeV Br ions irradiation. The V2(-/0)+V-P peak has many of the characteristics expected for the current gain degradation.

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

    PubMed

    Yang, Lei; Zhang, Miao; Shi, Shiwei; Lv, Jianguo; Song, Xueping; He, Gang; Sun, Zhaoqi

    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.

  6. Effects of vacuum annealing treatment on microstructures and residual stress of AlSi10Mg parts produced by selective laser melting process

    NASA Astrophysics Data System (ADS)

    Chen, Tian; Wang, Linzhi; Tan, Sheng

    2016-07-01

    Selective laser melting (SLM)-fabricated AlSi10Mg parts were heat-treated under vacuum to eliminate the residual stress. Microstructure evolutions and tensile properties of the SLM-fabricated parts before and after vacuum annealing treatment were studied. The results show that the crystalline structure of SLM-fabricated AlSi10Mg part was not modified after the vacuum annealing treatment. Additionally, the grain refinement had occurred after the vacuum annealing treatment. Moreover, with increasing of the vacuum annealing time, the second phase increased and transformed to spheroidization and coarsening. The SLM-produced parts after vacuum annealing at 300∘C for 2 h had the maximum ultimate tensile strength (UTS), yield strength (YS) and elongation, while the elastic modulus decreased significantly. In addition, the tensile residual stress was found in the as-fabricated AlSi10Mg samples by the microindentation method.

  7. Effects of annealing on the ripple texture and mechanical properties of suspended bilayer graphene

    NASA Astrophysics Data System (ADS)

    Annamalai, M.; Mathew, S.; Jamali, M.; Zhan, D.; Palaniapan, M.

    2013-04-01

    Periodic ripples of amplitude ˜15 nm were formed in suspended bilayer graphene after nanoindentation with incremental forces up to 600 nN. The structure was annealed at ˜620 K in high vacuum and the corresponding modifications in the mechanical properties and surface morphology were investigated. The pre-tension of the pristine sample was found to be 1.46 N m-1 and after annealing it was reduced to 0.72 N m-1. The nanometre-sized ripples induced by mechanical excitation were found to be flattened after annealing. Tailoring surface corrugations in bilayer graphene through nanoindentation and thermal engineering of these ripples thus provides an innovative fabrication route for flexible electronic devices and strain sensors.

  8. Thermal annealing effects on non-peripheral octahexylphthalocyanine doped polymer bulk heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    De Romeo Banoukepa, Gilles; Masuda, Tetsuya; Fujii, Akihiko; Shimizu, Yo; Ozaki, Masanori

    2014-01-01

    We investigated the thermal annealing temperature dependence of the photovoltaic properties of organic thin film solar cells based on a bulk heterojunction of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM) doped with the soluble phthalocyanine derivative 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2). The photocurrent density was increased by 45% and the power conversion efficiency was improved to 3.9% by annealing at 130 °C. The annealing temperature dependence of the photovoltaic properties is discussed by considering the result of X-ray diffraction and photoluminescence measurements.

  9. Annealing effect and photovoltaic properties of nano-ZnS/textured p-Si heterojunction

    PubMed Central

    2013-01-01

    The preparation and characterization of heterojunction solar cell with ZnS nanocrystals synthesized by chemical bath deposition method were studied in this work. The ZnS nanocrystals were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Lower reflectance spectra were found as the annealing temperature of ZnS film increased on the textured p-Si substrate. It was found that the power conversion efficiency (PCE) of the AZO/ZnS/textured p-Si heterojunction solar cell with an annealing temperature of 250°C was η = 3.66%. PMID:24206942

  10. Plasmonic analog of microstrip transmission line and effect of thermal annealing on its propagation loss.

    PubMed

    Chen, Yiting; Wang, Jing; Chen, Xi; Yan, Min; Qiu, Min

    2013-01-28

    We fabricated a plasmonic analog of the microwave microstrip transmission line and measured its propagation loss before and after thermal annealing. It is found that its propagation loss at 980 nm wavelength can be reduced by more than 50%, from 0.45 to 0.20 dB/μm, after thermal annealing at 300 °C. The reduction in loss can be attributed to the improved gold surface condition and probably also to the change in the metal's inner structure. Less evident loss reduction is noticed at 1550 nm, which is owing to extremely small portion of the modal electric field located in the metal regions at this wavelength.

  11. Surface enhanced Raman scattering of aged graphene: Effects of annealing in vacuum

    SciTech Connect

    Wang Yingying; Li Aizhi; Qu Shiliang; Ni Zhenhua; Zafar, Zainab; Qiu Teng; Zhang Yan; Ni Zhonghua; Yu Ting; Shen Zexiang

    2011-12-05

    In this paper, we report a simple method to recover the surface enhanced Raman scattering activity of aged graphene. The Raman signals of Rhodamine molecules absorbed on aged graphene are dramatically increased after vacuum annealing and comparable to those on fresh graphene. Atomic force microscopy measurements indicate that residues on aged graphene surface can efficiently be removed by vacuum annealing, which makes target molecule closely contact with graphene. We also find that the hole doping in graphene will facilitate charge transfer between graphene and molecule. These results confirm the strong Raman enhancement of target molecule absorbed on graphene is due to the charge transfer mechanism.

  12. Substrate heating and emitter dopant effects in laser-annealed solar cells

    NASA Astrophysics Data System (ADS)

    Young, R. T.; Wood, R. F.; Christie, W. H.; Jellison, G. E., Jr.

    1981-08-01

    Experimental evidence is presented to demonstrate that substrate heating during pulsed-laser annealing (PLA) of ion-implanted silicon can significantly improve the electrical properties of the laser-recrystallized region, due to regrowth velocity reduction. Use of the optimum PLA condition shows qualitative agreement with theoretical predictions in that (1) the open-circuit voltage and fill factor of ion-implanted, laser-annealed solar cells are improved by the increase of emitter dopant concentrations, while (2) the short-circuit current remains fairly constant.

  13. Effect of α-damage on fission-track annealing in zircon

    USGS Publications Warehouse

    Kasuya, Masao; Naeser, Charles W.

    1988-01-01

    The thermal stability of confined fission-track lengths in four zircon samples having different spontaneous track densities (i.e., different amounts of ??-damage) has been studied by one-hour isochronal annealing experiments. The thermal stability of spontaneous track lengths is independent of initial spontaneous track density. The thermal stability of induced track lengths in pre-annealed zircon, however, is significantly higher than that of spontaneous track lengths. The results indicate that the presence of ??-damage lowers the thermal stability of fission-tracks in zircon.

  14. The effect of α-damage on fission-track annealing in zircon

    USGS Publications Warehouse

    Kasuya, M.; Naeser, C.W.

    1988-01-01

    The thermal stability of confined fission-track lengths in four zircon samples having different spontaneous track densities (i.e. different amounts of ??-damage) has been studied by one hour isochronal annealing experiments. The thermal stability of spontaneous track lengths is independent of initial spontaneous track density. The thermal stability of induced track lengths in pre-annealed zircon, however, is significantly higher than that of spontaneous track lengths. The results indicate that the presence of ??-damage lowers the thermal stability of fission-tracks in zircon. ?? 1988.

  15. Effect of Annealing on the Electrical Resistivity and Strengthening of Low-Alloy Alloys of the Al - Zr - Si System

    NASA Astrophysics Data System (ADS)

    Alabin, A. N.; Belov, N. A.; Korotkova, N. O.; Samoshinal, M. E.

    2017-01-01

    The effect of annealing at up to 550°C on the electrical resistivity ρ and HB hardness of low-alloy alloys of the Al - Zr - Si system containing up to 0.3% Zr and 0.3% Si is studied. The Thermo-Calc software is used to analyze the phase composition of the system. The computed and experimental data are used to determine the lower and upper limits for heating of cast preforms from Al - Zr alloys (shaped castings and ingots). It is shown that heating below 400°C and above 450°C is not expedient, because it increases the duration of the annealing in the former case and lowers the hardening effect due to coarsening of the Zr-containing particles in the latter case.

  16. Effect of thermal annealing on the emission properties of heterostructures containing a quantum-confined GaAsSb layer

    SciTech Connect

    Dikareva, N. V. Vikhrova, O. V.; Zvonkov, B. N.; Malekhonova, N. V.; Nekorkin, S. M.; Pirogov, A. V.; Pavlov, D. A.

    2015-01-15

    Heterostructures containing single GaAsSb/GaAs quantum wells and bilayer GaAsSb/InGaAs quantum wells are produced by metal-organic vapor-phase epitaxy at atmospheric pressure. The growth temperature of the quantum-confined layers is 500–570°C. The structural quality of the samples and the quality of heterointerfaces of the quantum wells are studied by the high-resolution transmission electron microscopy of cross sections. The emission properties of the heterostructures are studied by photoluminescence measurements. The structures are subjected to thermal annealing under conditions chosen in accordance with the temperature and time of growth of the upper cladding p-InGaP layer during the formation of GaAs/InGaP laser structures with an active region containing quantum-confined GaAsSb layers. It is found that such heat treatment can have a profound effect on the emission properties of the active region, only if a bilayer GaAsSb/InGaAs quantum well is formed.

  17. 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

  18. Simulated annealing model of acupuncture

    NASA Astrophysics Data System (ADS)

    Shang, Charles; Szu, Harold

    2015-05-01

    The growth control singularity model suggests that acupuncture points (acupoints) originate from organizers in embryogenesis. Organizers are singular points in growth control. Acupuncture can cause perturbation of a system with effects similar to simulated annealing. In clinical trial, the goal of a treatment is to relieve certain disorder which corresponds to reaching certain local optimum in simulated annealing. The self-organizing effect of the system is limited and related to the person's general health and age. Perturbation at acupoints can lead a stronger local excitation (analogous to higher annealing temperature) compared to perturbation at non-singular points (placebo control points). Such difference diminishes as the number of perturbed points increases due to the wider distribution of the limited self-organizing activity. This model explains the following facts from systematic reviews of acupuncture trials: 1. Properly chosen single acupoint treatment for certain disorder can lead to highly repeatable efficacy above placebo 2. When multiple acupoints are used, the result can be highly repeatable if the patients are relatively healthy and young but are usually mixed if the patients are old, frail and have multiple disorders at the same time as the number of local optima or comorbidities increases. 3. As number of acupoints used increases, the efficacy difference between sham and real acupuncture often diminishes. It predicted that the efficacy of acupuncture is negatively correlated to the disease chronicity, severity and patient's age. This is the first biological - physical model of acupuncture which can predict and guide clinical acupuncture research.

  19. Hydrophilic CdSe thin films by low cost spray pyrolysis technique and annealing effects

    NASA Astrophysics Data System (ADS)

    Logu, T.; Sankarasubramanian, K.; Soundarrajan, P.; Sethuraman, K.

    2015-03-01

    Cadmium selenide (CdSe) thin films were deposited on glass substrates at 200°C by homemade chemical spray pyrolysis technique. The as-deposited films were annealed in air atmosphere for 3 hrs, at two different temperatures (350 and 450°C). The as-deposited film has been observed to possess uniform surface with crystalline sphalerite cubic structure and optical band gap of E g = 2.4 eV. It is worth noting that after annealing, metastable cubic sphalerite phase transforms into stable well crystalline hexagonal wurtzite phase. The optical band gap was found to decrease from 2.4 eV to 1.75 eV. The average surface roughness is 1.5 nm for the as-deposited film which rises to 4.2 nm after annealing the film in air atmosphere. The contact angle was found to vary from 94° ± 1° to 81° ± 1° with annealing temperature. In addition, from Wenzel's relation it is concluded that CdSe thin film is hydrophilic in nature. [Figure not available: see fulltext.

  20. Annealing Effects on the Surface Plasmon of MgO Implanted with Gold

    NASA Technical Reports Server (NTRS)

    Ueda, A.; Mu, R.; Tung, Y. -S.; Henderson, D. O.; White, C. W.; Zuhr, R. A.; Zhu, Jane G.; Wang, P. W.

    1997-01-01

    Gold ion implantation was carried out with the energy of 1.1 MeV into (100) oriented MgO single crystal. Implanted doses are 1, 3, 6, 10 x 10(exp 16) ions/sq cm. The gold irradiation results in the formation of gold ion implanted layer with a thickness of 0.2 microns and defect formation. In order to form gold colloids from the as-implanted samples, we annealed the gold implanted MgO samples in three kinds of atmospheres: (1)Ar only, (2)H2 and Ar, and (3)O2 and Ar. The annealing over 1200 C enhanced the gold colloid formation which shows surface plasmon resonance band of gold. The surface plasmon bands of samples annealed in three kinds of atmospheres were found to be at 535 nm (Ar only), 524 nm(H2+Ar), and 560 nm (02+Ar), The band positions of surface plasmon can be reversibly changed by an additional annealing.

  1. Effects of NIR annealing on the characteristics of al-doped ZnO thin films prepared by RF sputtering.

    PubMed

    Jun, Min-Chul; Koh, Jung-Hyuk

    2012-06-06

    Aluminum-doped zinc oxide (AZO) thin films have been deposited on glass substrates by employing radio frequency (RF) sputtering method for transparent conducting oxide applications. For the RF sputtering process, a ZnO:Al2O3 (2 wt.%) target was employed. In this paper, the effects of near infrared ray (NIR) annealing technique on the structural, optical, and electrical properties of the AZO thin films have been researched. Experimental results showed that NIR annealing affected the microstructure, electrical resistance, and optical transmittance of the AZO thin films. X-ray diffraction analysis revealed that all films have a hexagonal wurtzite crystal structure with the preferentially c-axis oriented normal to the substrate surface. Optical transmittance spectra of the AZO thin films exhibited transmittance higher than about 80% within the visible wavelength region, and the optical direct bandgap (Eg) of the AZO films was increased with increasing the NIR energy efficiency.

  2. Effect of annealing on the surface and band gap alignment of CdZnS thin films

    NASA Astrophysics Data System (ADS)

    Kumar, T. Prem; Saravanakumar, S.; Sankaranarayanan, K.

    2011-01-01

    Effects of the annealing temperature on structural, optical and surface properties of chemically deposited cadmium zinc sulfide (CdZnS) films were investigated. X-ray diffraction (XRD) results showed that the grown CdZnS thin films formed were polycrystalline with hexagonal structure. Atomic force microscopy (AFM) studies showed that the surface roughness of the CdZnS thin films was about 60-400 nm. Grain sizes of the CdZnS thin films varied between 70 and 300 nm as a function of annealing temperature. The root mean square surface roughness of the selected area, particular point, average roughness profile, topographical area of roughness were measured using the reported AFM software. The band gaps of CdZnS thin films were determined from absorbance measurements in the visible range as 300 nm and 1100 nm, respectively, using Tauc theory.

  3. Hydrophobic switching nature of methylcellulose ultra-thin films: thickness and annealing effects.

    PubMed

    Innis-Samson, Vallerie Ann; Sakurai, Kenji

    2011-11-02

    We have studied the thermosensitive property of methylcellulose (MC) thin films supported on Si substrate by static sessile drop contact angle measurements, and their surface properties and thin film structure by x-ray reflectivity (XRR) and atomic force microscopy (AFM) techniques. From the static sessile drop contact angle measurements, the MC thin films showed the characteristic hydrophilic-to-hydrophobic transition at ∼70 °C, which is the lower critical solution temperature of the bulk solution volume phase separation transition. For films with thickness d ≤ R(g), the onset of such a transition is affected by the film thickness while very thick films, d ≫ R(g), yielded higher contact angles. Annealing the MC thin films with thicknesses ∼200 Å (near the radius of gyration, R(g), of the polymer) below the bulk glass transition temperature (T(g) ∼ 195 ° C) would not change the hydrophobic switch nature of the film but annealing 'at' and above the bulk T(g) would change its surface property. From surface topography images by AFM, there were no significant changes in either the roughness or the film texture before and after annealing. With XRR data, we were able to determine that such changes in the surface properties are highly correlated to the film thickness changes after the annealing process. This study, we believe, is the first to examine the thermal annealing affects on the thermal response function of a thermoresponsive polymer and is important for researching how to tailor the hydrophobic switching property of MC thin films for future sensing applications.

  4. Hydrophobic switching nature of methylcellulose ultra-thin films: thickness and annealing effects

    NASA Astrophysics Data System (ADS)

    Innis-Samson, Vallerie Ann; Sakurai, Kenji

    2011-11-01

    We have studied the thermosensitive property of methylcellulose (MC) thin films supported on Si substrate by static sessile drop contact angle measurements, and their surface properties and thin film structure by x-ray reflectivity (XRR) and atomic force microscopy (AFM) techniques. From the static sessile drop contact angle measurements, the MC thin films showed the characteristic hydrophilic-to-hydrophobic transition at ˜70 °C, which is the lower critical solution temperature of the bulk solution volume phase separation transition. For films with thickness d ≤ Rg, the onset of such a transition is affected by the film thickness while very thick films, d ≫ Rg, yielded higher contact angles. Annealing the MC thin films with thicknesses ˜200 Å (near the radius of gyration, Rg, of the polymer) below the bulk glass transition temperature (Tg ˜ 195 ° C) would not change the hydrophobic switch nature of the film but annealing ‘at’ and above the bulk Tg would change its surface property. From surface topography images by AFM, there were no significant changes in either the roughness or the film texture before and after annealing. With XRR data, we were able to determine that such changes in the surface properties are highly correlated to the film thickness changes after the annealing process. This study, we believe, is the first to examine the thermal annealing affects on the thermal response function of a thermoresponsive polymer and is important for researching how to tailor the hydrophobic switching property of MC thin films for future sensing applications.

  5. Effect of moderate magnetic annealing on the microstructure, quasi-static and viscoelastic mechanical behavior of a structural epoxy

    SciTech Connect

    Tehrani, Mehran; Al-Haik, Marwan; Garmestani, Hamid; Li, Dongsheng

    2012-01-01

    In this study the effect of moderate magnetic fields on the microstructure of a structural epoxy system was investigated. The changes in the microstructure have been quantitatively investigated using wide angle x-ray diffraction (WAXD) and pole figure analysis. The mechanical properties (modulus, hardness and strain rate sensitivity parameter) of the epoxy system annealed in the magnetic field were probed with the aid of instrumented nanoindentation and the results are compared to the reference epoxy sample. To further examine the creep response of the magnetically annealed and reference samples, short 45 min duration creep tests were carried out. An equivalent to the macro scale creep compliance was calculated using the aforementioned nano-creep data. Using the continuous complex compliance (CCC) analysis, the phase lag angle, tan (δ), between the displacement and applied force in an oscillatory nanoindentation test was measured for both neat and magnetically annealed systems through which the effect of low magnetic fields on the viscoelastic properties of the epoxy was invoked. The comparison of the creep strain rate sensitivity parameter , A/d(0), from short term(80 ), creep tests and the creep compliance J(t) from the long term(2700 s) creep tests with the tan(δ) suggests that former parameter is a more useful comparative creep parameter than the creep compliance. The results of this investigation reveal that under low magnetic fields both the quasi-static and viscoelastic mechanical properties of the epoxy have been improved.

  6. 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.

  7. Melt crystallization/dewetting of ultrathin PEO films via carbon dioxide annealing: the effects of polymer adsorbed layers.

    PubMed

    Asada, Mitsunori; Jiang, Naisheng; Sendogdular, Levent; Sokolov, Jonathan; Endoh, Maya K; Koga, Tadanori; Fukuto, Masafumi; Yang, Lin; Akgun, Bulent; Dimitriou, Michael; Satija, Sushil

    2014-09-14

    The effects of CO2 annealing on the melting and subsequent melt crystallization processes of spin-cast poly(ethylene oxide) (PEO) ultrathin films (20-100 nm in thickness) prepared on Si substrates were investigated. By using in situ neutron reflectivity, we found that all the PEO thin films show melting at a pressure as low as P = 2.9 MPa and at T = 48 °C which is below the bulk melting temperature (Tm). The films were then subjected to quick depressurization to atmospheric pressure, resulting in the non-equilibrium swollen state, and the melt crystallization (and/or dewetting) process was carried out in air via subsequent annealing at given temperatures below Tm. Detailed structural characterization using grazing incidence X-ray diffraction, atomic force microscopy, and polarized optical microscopy revealed two unique aspects of the CO2-treated PEO films: (i) a flat-on lamellar orientation, where the molecular chains stand normal to the film surface, is formed within the entire film regardless of the original film thickness and the annealing temperature; and (ii) the dewetting kinetics for the 20 nm thick film is much slower than that for the thicker films. The key to these phenomena is the formation of irreversibly adsorbed layers on the substrates during the CO2 annealing: the limited plasticization effect of CO2 at the polymer-substrate interface promotes polymer adsorption rather than melting. Here we explain the mechanisms of the melt crystallization and dewetting processes where the adsorbed layers play vital roles.

  8. 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.

  9. Effect of thermal annealing on structural and optical properties of In{sub 2}S{sub 3} thin films

    SciTech Connect

    Choudhary, Sonu

    2015-08-28

    There is a highly need of an alternate of toxic materials CdS for solar cell applications and indium sulfide is found the most suitable candidate to replace CdS due to its non-toxic and environmental friendly nature. In this paper, the effect of thermal annealing on the structural and optical properties of indium sulfide (In{sub 2}S{sub 3}) thin films is undertaken. The indium sulfide thin films of 121 nm were deposited on glass substrates employing thermal evaporation method. The films were subjected to the X-ray diffractometer and UV-Vis spectrophotometer respectively for structural and optical analysis. The XRD pattern show that the as-deposited thin film was amorphous in nature and crystallinity is found to be varied with annealing temperature. The optical analysis reveals that the optical band gap is varied with annealing. The optical parameters like absorption coefficient, extinction coefficient and refractive index were calculated. The results are in good agreement with available literature.

  10. Effect of annealing on the properties of nanocrystalline CuInSSe thin films deposited by spray pyrolysis

    SciTech Connect

    Shrotriya, Vipin Rajaram, P.

    2015-08-28

    The effect of annealing CuInSSe thin films, which were grown on glass substrates using the spray pyrolysis technique from spray solutions having S/Se ionic ratio 0.6, were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical transmission measurements. The CuInSSe films were co-deposited from an aqueous solution containing CuCl{sub 2}, InCl{sub 3}, thiourea and SeO{sub 2}. EDC was used as a complexing agent and films were deposited at the constant temperature 300°C. Post annealing (at 350°C) was used to improve the structural, morphological and optical properties of CuInSSe thin films. From the results, it is found that the films are single phase, p-type in conductivity having the chalcopyrite structure. From the Scherrer formula the average size of the films was found to be in the range (15-28) nm. Optical studies show that the optical band gap value increases slightly from 1.35 eV to 1.37 eV with annealing for films grown from spray solutions having S/Se ionic ratio 0.6.

  11. 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.

  12. 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

  13. Annealing effects on recombinative activity of nickel at direct silicon bonded interface

    SciTech Connect

    Kojima, Takuto Ohshita, Yoshio; Yamaguchi, Masafumi

    2015-09-15

    By performing capacitance transient analyses, the recombination activity at a (110)/(100) direct silicon bonded (DSB) interface contaminated with nickel diffused at different temperatures, as a model of grain boundaries in multicrystalline silicon, was studied. The trap level depth from the valence band, trap density of states, and hole capture cross section peaked at an annealing temperature of 300 °C. At temperatures ⩾400 °C, the hole capture cross section increased with temperature, but the density of states remained unchanged. Further, synchrotron-based X-ray analyses, microprobe X-ray fluorescence (μ-XRF), and X-ray absorption near edge structure (XANES) analyses were performed. The analysis results indicated that the chemical phase after the sample was annealed at 200 °C was a mixture of NiO and NiSi{sub 2}.

  14. The effect of annealing on the structural and magnetic properties of Ni-ferrite nanocrystals

    SciTech Connect

    Ojha, Chaturbhuj Chauhan, S. S.; Shrivastava, A. K.; Verma, A. K.

    2015-06-24

    Magnetic nanoparticles NiFe{sub 2}O{sub 4} were prepared by chemical co-precipitation technique using the chlorides of Ni, Fe (III) and oleic acid. The precursors were annealed at different temperature 500, 700, and 900 °C. The XRD of samples show the presence of inverse cubic spinel structure. Grain size was determined using Scherrer formula and SEM technique. The Particle size, Lattice parameter and X-ray density were also estimated from X-ray diffraction data. The particles size was found to vary from 17nm to 37 nm and largely depends on the annealing temperature. Magnetization measurements have also carried out using VSM and it was found that saturation magnetization (Ms), Remanance (Mr) and coercivity (H{sub c}) of nano ferrite materials are lower compared to bulk materials.

  15. Annealing effects on recombinative activity of nickel at direct silicon bonded interface

    NASA Astrophysics Data System (ADS)

    Kojima, Takuto; Ohshita, Yoshio; Yamaguchi, Masafumi

    2015-09-01

    By performing capacitance transient analyses, the recombination activity at a (110)/(100) direct silicon bonded (DSB) interface contaminated with nickel diffused at different temperatures, as a model of grain boundaries in multicrystalline silicon, was studied. The trap level depth from the valence band, trap density of states, and hole capture cross section peaked at an annealing temperature of 300 °C. At temperatures ⩾400 °C, the hole capture cross section increased with temperature, but the density of states remained unchanged. Further, synchrotron-based X-ray analyses, microprobe X-ray fluorescence (μ-XRF), and X-ray absorption near edge structure (XANES) analyses were performed. The analysis results indicated that the chemical phase after the sample was annealed at 200 °C was a mixture of NiO and NiSi2.

  16. Post-annealing effects on EPR response of irradiated nano-structure hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Dowlatshah, F.; Ziaie, F.; Hajiloo, N.; Amraie, R.; Fathollahi, H.

    2012-12-01

    In this work, the nano-structure hydroxyapatite was synthesized via the hydrolysis method. The produced powders were thermally treatment at different temperatures from 400 to 1200°C. The morphological and chemical analyses were carried out using the Fourier transmission infrared spectroscopy, transmission electron microscopy, and X-ray diffraction system. Then, the samples were irradiated at different absorbed doses from 1 to 80 kGy using 60Co γ -ray. Electron paramagnetic resonance (EPR) responses of the samples were measured at room temperature in air. Subsequently, the variations of EPR signal intensities were constructed as the peak-to-peak signal amplitude and results were compared with those of non-annealed samples. The results show that the EPR responses of non-annealed samples are higher rather than other samples and also are saturated at higher doses in comparison with the others.

  17. The effect of magnetic annealing on the magnetostriction for Sm-Dy-Fe rod alloys

    NASA Astrophysics Data System (ADS)

    Wang, Bowen; Wang, Zhihua; Weng, Ling; Huang, Wenmei; Sun, Ying; Cui, Baozhi

    2013-05-01

    The Sm0.86Dy0.14Fex (x = 1.85-2.05) magnetostrictive alloys have been prepared with arc-melting and then cast into a copper mold with a diameter of 8 mm. It is found that the magnetostriction (λ// - λ⊥) increases from -900 × 10-6 for untreated rod alloys to -1200 × 10-6 for magnetically annealed rod alloys at the magnetic field of 640 kA/m. In the magnetic annealing temperature range of 483-643 K, the magnetostriction value exhibits a peak at 543 K. The variation of magnetostriction and magnetization with magnetic fields has been determined and the mechanism of domains' movements has been discussed. This result is very important to improve the magnetostrictive property of Sm-Dy-Fe rod alloys.

  18. Restorative effect of oxygen annealing on device performance in HfIZO thin-film transistors

    NASA Astrophysics Data System (ADS)

    Ha, Tae-Jun

    2015-03-01

    Metal-oxide based thin-film transistors (oxide-TFTs) are very promising for use in next generation electronics such as transparent displays requiring high switching and driving performance. In this study, we demonstrate an optimized process to secure excellent device performance with a favorable shift of the threshold voltage toward 0V in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs by using post-treatment with oxygen annealing. This enhancement results from the improved interfacial characteristics between gate dielectric and semiconductor layers due to the reduction in the density of interfacial states related to oxygen vacancies afforded by oxygen annealing. The device statistics confirm the improvement in the device-to-device and run-to-run uniformity. We also report on the photo-induced stability in such oxide-TFTs against long-term UV irradiation, which is significant for transparent displays.

  19. Effects of Voltage-Bias Annealing on Metastable Defect Populations in CIGS and CZTSe Solar Cells

    SciTech Connect

    Harvey, Steven P.; Johnston, Steve; Teeter, Glenn

    2016-11-21

    We report on voltage-bias annealing (VBA) experiments performed on CIGS and CZTSe solar cells. In these experiments, completed devices were annealed at moderate temperatures and subsequently quenched with continuously applied voltage bias. These treatments resulted in substantial reversible changes in device characteristics. Photovoltaic (PV) conversion efficiency of the CIGS device varied from below 3% to above 15%, with corresponding changes in CIGS hole density from ~1014 cm-3 to ~1017 cm-3. In the CZTSe device, open-circuit voltage varied from 289 meV to 446 meV, caused by an approximately factor of fifty change in the CZTSe hole density. We interpret these findings in terms of reversible changes to the metastable point-defect populations that control key properties in these materials. Implications for optimization of PV materials and connections to long-term stability of PV devices are discussed.

  20. Restorative effect of oxygen annealing on device performance in HfIZO thin-film transistors

    SciTech Connect

    Ha, Tae-Jun

    2015-03-15

    Metal-oxide based thin-film transistors (oxide-TFTs) are very promising for use in next generation electronics such as transparent displays requiring high switching and driving performance. In this study, we demonstrate an optimized process to secure excellent device performance with a favorable shift of the threshold voltage toward 0V in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs by using post-treatment with oxygen annealing. This enhancement results from the improved interfacial characteristics between gate dielectric and semiconductor layers due to the reduction in the density of interfacial states related to oxygen vacancies afforded by oxygen annealing. The device statistics confirm the improvement in the device-to-device and run-to-run uniformity. We also report on the photo-induced stability in such oxide-TFTs against long-term UV irradiation, which is significant for transparent displays.

  1. The effect of annealing on vacuum-evaporated copper selenide and indium telluride thin films

    SciTech Connect

    Peranantham, P.; Jeyachandran, Y.L.; Viswanathan, C.; Praveena, N.N.; Chitra, P.C.; Mangalaraj, D. . E-mail: dmraj800@yahoo.com; Narayandass, Sa. K.

    2007-08-15

    Copper selenide and indium telluride thin films were prepared by a vacuum evaporation technique. The as-deposited films were annealed in a vacuum at different temperatures and the influence on composition, structure and optical properties of copper selenide and indium telluride films was investigated using energy dispersive X-ray analysis, X-ray diffraction, scanning electron microscopy and optical transmission measurements. From the compositional analysis, the as-deposited copper selenide and indium telluride films which were annealed at 473 and 523 K, respectively, were found to possess the nearly stoichiometric composition of CuSe and InTe phases. However, the films annealed at 673 K showed the composition of Cu{sub 2}Se and In{sub 4}Te{sub 3} phases. The structural parameters such as, particle size and strain were determined using X-ray diffractograms of the films. Optical transmittance measurements indicated the existence of direct and indirect transitions in copper selenide films and an indirect allowed transition in indium telluride films.

  2. Effect of annealing copper phthalocyanine on the performance of interdigitated bulk-heterojunction organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Wang, N. N.; Yu, J. S.; Yuan, Z. L.; Jiang, Y. D.

    2012-05-01

    Organic photovoltaic (OPV) cells with improved efficiency using thermal annealing-induced nanostructured copper phthalocyanine as a donor layer were fabricated. A power conversion efficiency of 1.47% in the OPV cell with interdigitated CuPc/C60 bulk heterojunction has been obtained under AM 1.5 solar illumination at an intensity of 100 mW/cm2, which is higher than 0.63% of CuPc/C60 planar cell. Through varying the annealing temperature of CuPc films, the influence of interface morphology and crystallinity of CuPc films on the performance of OPV cells was systematically studied. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and spectrophotometry were used to characterize the CuPc films. The results showed that at an optimal annealing temperature, the crystalline nature and vertical orientation of nanostructured CuPc have been modified, which can facilitate the separation of interfacial electron-hole pairs and charge carrier transport to electrodes.

  3. Annealing effects on the characteristics of AuCl3-doped graphene

    NASA Astrophysics Data System (ADS)

    Hee Shin, Dong; Min Kim, Jong; Wook Jang, Chan; Hwan Kim, Ju; Kim, Sung; Choi, Suk-Ho

    2013-02-01

    Single-layer graphene sheets grown on Cu foils by chemical vapor deposition were transferred on 300 nm SiO2/n-type Si wafers and subsequently doped with 10 mM AuCl3 solution. The doped graphene sheets were annealed at various temperatures (TA) under vacuum below 10-3 Torr for 10 min and characterized by atomic force microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and 4-probe van der Pauw method. The XPS studies show that the compositions of Cl and Au3+ ions in doped graphene sheets increase slightly by annealing at 50 °C, but by further increase of TA above 50 °C, they monotonically decrease and become almost negligible at TA = 500 °C. These XPS results are consistent with the corresponding TA-dependent behaviors of the Raman scattering and the sheet resistance, implying that the doping efficiency is maximized at TA = 50 °C and the Cl and Au3+ ions play a major role in the doping/dedoping processes that are very reversible, different from the case of carbon nanotubes. These results suggest that the annealing temperature is a crucial factor to determine the structural and electrical properties of AuCl3-doped graphene. Possible mechanisms are discussed to explain the doping/dedoping processes of graphene sheets.

  4. Effect of flash lamp annealing on electrical activation in boron-implanted polycrystalline Si thin films

    SciTech Connect

    Do, Woori; Jin, Won-Beom; Choi, Jungwan; Bae, Seung-Muk; Kim, Hyoung-June; Kim, Byung-Kuk; Park, Seungho; Hwang, Jin-Ha

    2014-10-15

    Highlights: • Intensified visible light irradiation was generated via a high-powered Xe arc lamp. • The disordered Si atomic structure absorbs the intensified visible light. • The rapid heating activates electrically boron-implanted Si thin films. • Flash lamp heating is applicable to low temperature polycrystalline Si thin films. - Abstract: Boron-implanted polycrystalline Si thin films on glass substrates were subjected to a short duration (1 ms) of intense visible light irradiation generated via a high-powered Xe arc lamp. The disordered Si atomic structure absorbs the intense visible light resulting from flash lamp annealing. The subsequent rapid heating results in the electrical activation of boron-implanted Si thin films, which is empirically observed using Hall measurements. The electrical activation is verified by the observed increase in the crystalline component of the Si structures resulting in higher transmittance. The feasibility of flash lamp annealing has also been demonstrated via a theoretical thermal prediction, indicating that the flash lamp annealing is applicable to low-temperature polycrystalline Si thin films.

  5. The quenching effects of hot band annealing on grain-oriented electrical steel

    NASA Astrophysics Data System (ADS)

    Tsai, Ming-Chin; Hwang, Yie-Shing

    2010-09-01

    The grain-oriented electrical steels are widely used in transformers, which demand low iron loss and high induction of core materials. In order to obtain good magnetic properties, a series of rolling, annealing and coating processes are carried out. Hot band annealing, which influences the ductility for cold rolling and the development of AlN inhibitors, is one of the most important processes. This study investigated the phases and different kinds of precipitations in microstructures of annealed hot band by means of the optical and electronic microscopies. On the other hand, a Themo-Calc software and the solubility product equations of AlN are used to calculate the phase diagram of Fe-Si-C alloy and the amount of AlN at high temperature. Microstructures including ferrite, cementite, pearlite and martensite were observed. The size and shape of precipitates, i.e. GP Zone, TiN, AlN, MnS, oxide and carbide, were identified. The relationship between the amount of nano-scale AlN and magnetic properties indicated that the suitable cooling method resulted in lower iron loss and higher magnetic induction. The result could help to realize the following microstructure evolution and mechanism of inhibitors in grain-oriented electrical steel.

  6. Effect of annealing treatment on the structural and optical properties of AZO samples

    NASA Astrophysics Data System (ADS)

    Prepelita, P.; Craciun, V.; Garoi, F.; Staicu, A.

    2015-10-01

    AZO (2% Al doped ZnO) thin films, with thicknesses of 30 nm (AZO30), 50 nm (AZO50) and 400 nm (AZO400), deposited onto glass substrate by RF magnetron sputtering were subjected to annealing at a temperature of 700 K for a period of 90 min in air. As-deposited AZO30 and AZO50 samples were almost amorphous, with very small grains. After annealing, a crystallization process from amorphous to crystalline phase occurred. X-ray diffraction and scanning electron microscopy analyses showed a polycrystalline structure and a preferred orientation of the crystallites for the obtained thin films. Atomic force microscopy measurements indicated roughness values of 0.7 nm for AZO30, 1.4 nm for AZO50 and 18 nm for AZO400 annealed samples. Optical transmittance investigations of the layers in the 0.2-1.2 μm wavelength range showed a high transmission in the visible and near infrared range, as well as values between 3.36 and 3.45 eV for the optical bandgap. The present simple processing route is useful for device applications of transparent conductive oxides.

  7. Effect of Hot Band Annealing on Forming Limit Diagrams of Ultra-Pure Ferritic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Shu, Jun; Bi, Hongyun; Li, Xin; Xu, Zhou

    2014-03-01

    In order to better understand the texture evolution, coincidence site lattice (CSL) and forming limit diagrams (FLDs) of ferritic stainless steels with and without hot band annealing, the texture evolution and CSL of ferritic stainless steels with 15% Cr content were studied by using x-ray diffraction and electron back-scattered diffraction technique. The strain hardening exponent n value, the strength coefficient K value, and Plastic strain ratio r value are the key parameters for the FLD. It was found out that the FLDo of plane strain condition and the stretchability were mainly influenced by their n value and K value, respectively. The higher n value and K value, better was the stretchability of investigated steels. The intensity of the γ-fiber dominated by {111} <112> was improved significantly in the cold rolled and annealed sheets because of a hot band annealing treatment and the sharp increase of Σ13b CSL boundaries. The increase of the formability is attributed to the significantly increase of the r value.

  8. 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.

  9. 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.

  10. Microwave anneal effect on magnetic properties of Ni 0.6Zn 0.4Fe 2O 4 nano-particles prepared by conventional hydrothermal method

    NASA Astrophysics Data System (ADS)

    Wang, Zhongzhu; Xie, Yanyu; Wang, Peihong; Ma, Yongqing; Jin, Shaowei; Liu, Xiansong

    2011-12-01

    Ni0.6Zn0.4Fe2O4 ferrite nano-particles with a crystallite size of about 20 nm were prepared by the conventional hydrothermal method, followed by annealing in a microwave oven for 7.5-15 min. The microstructure and magnetic properties of the samples were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and vibrating sample magnetometry. The microwave annealing process has slight effect on the morphology and size of Ni0.6Zn0.4Fe2O4 ferrite nano-particles. However it reduces the lattice parameter and enhances the densification of the particles, and then greatly increases the saturation magnetization (50-56 emu/g) and coercive force of the samples as compared to the non-annealing condition. The microwave annealing process is an effective way to rapidly synthesize high performance ferrite nano-particle.

  11. Effect of annealing on electronic carrier transport properties of gamma-irradiated AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Yadav, Anupama; Schwarz, Casey; Shatkhin, Max; Wang, Luther; Flitsiyan, Elena; Chernyak, Leonid; Liu, Lu; Hwang, Ya; Ren, Fan; Pearton, Stephen; Department of Physics, University of Central Florida Collaboration; Department of Chemical Engineering, University of Florida Collaboration; Department of Materials Science; Engineering, University of Florida Collaboration

    2014-03-01

    AlGaN/GaN High Electron Mobility Transistors were irradiated with 60Co gamma-ray doses from 100Gy to 1000Gy, in order to analyze the effects of irradiation on the devices' transport properties. Temperature dependent Electron Beam Induced Current (EBIC) measurements, conducted on the devices before and after exposure to gamma-irradiation, allowed for the obtaining of activation energy related to radiation-induced defects due to nitrogen vacancies. Later, the devices were annealed at 200o C for 25 minutes. All the measurements were performed again to study the effect of annealing on the gamma-irradiated devices. Annealing of gamma-irradiated transistors shows that partial recovery of device performance is possible at this temperature. DC current-voltage measurements were also conducted on the transistors to assess the impact of gamma-irradiation and annealing on transfer, gate and drain characteristics.

  12. Effect of thermal annealing on the kinetics of rehydroxylation of Eu3+:La2O3 nanocrystals.

    PubMed

    Méndez, Maria; Cesteros, Yolanda; Marsal, Lluís Francesc; Giguère, Alexandre; Drouin, Dominique; Salagre, Pilar; Formentín, Pilar; Pallarès, Josep; Aguiló, Magdalena; Díaz, Francesc; Carvajal, Joan Josep

    2012-06-04

    Europium-doped lanthanum oxide (5 mol % Eu(3+):La(2)O(3)) was prepared by calcining europium-doped lanthanum hydroxide (5 mol % Eu(3+):La(OH)(3)) previously synthesized by a simple hydrothermal method. Interestingly, we observed different emission Eu(3+) signatures depending on the phase of the host (lanthanum oxide or hydroxide) by cathodoluminescence. Taking into account that lanthanum oxide easily rehydroxylates in air, for the first time, we report the use of cathodoluminiscence as a novel characterization technique to follow the lanthanum oxide rehydroxylation reaction versus time according to different annealing procedures. Additionally, differential thermal-thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques were used to identify the phases formed from the Eu(3+):La(OH)(3) depending on temperature and to study the evolution of La(2)O(3) to La(OH)(3) versus time. The results showed that the higher the temperature and the longer the annealing time, the higher the resistance to rehydroxylation of the Eu(3+):La(2)O(3) sample.

  13. Effect of intermediate annealing on the microstructure and mechanical property of ZK60 magnesium alloy produced by twin roll casting and hot rolling

    SciTech Connect

    Chen, Hongmei; Zang, Qianhao; Yu, Hui; Zhang, Jing; Jin, Yunxue

    2015-08-15

    Twin roll cast (designated as TRC in short) ZK60 magnesium alloy strip with 3.5 mm thickness was used in this paper. The TRC ZK60 strip was multi-pass rolled at different temperatures, intermediate annealing heat treatment was performed when the thickness of the strip changed from 3.5 mm to 1 mm, and then continued to be rolled until the thickness reached to 0.5 mm. The effect of intermediate annealing during rolling process on microstructure, texture and room temperature mechanical properties of TRC ZK60 strip was studied by using OM, TEM, XRD and electronic universal testing machine. The introduction of intermediate annealing can contribute to recrystallization in the ZK60 sheet which was greatly deformed, and help to reduce the stress concentration generated in the rolling process. Microstructure uniformity and mechanical properties of the ZK60 alloy sheet were also improved; in particular, the room temperature elongation was greatly improved. When the TRC ZK60 strip was rolled at 300 °C and 350 °C, the room temperature elongation of the rolled sheet with 0.5 mm thickness which was intermediate annealed during the rolling process was increased by 95% and 72% than that of no intermediate annealing, respectively. - Highlights: • Intermediate annealing was introduced during hot rolling process of twin roll cast ZK60 alloy. • Intermediate annealing can contribute to recrystallization and reduce the stress concentration in the deformed ZK60 sheet. • Microstructure uniformity and mechanical properties of the ZK60 sheet were improved, in particular, the room temperature elongation. • The elongation of the rolled ZK60 sheet after intermediate annealed was increased by 95% and 72% than that of no intermediate annealing.

  14. 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.

  15. Effects of uniaxial pressure and annealing on the resistivity of Ba(Fe1-xCox)2As2

    NASA Astrophysics Data System (ADS)

    Liang, T.; Nakajima, M.; Kihou, K.; Tomioka, Y.; Ito, T.; Lee, C. H.; Kito, H.; Iyo, A.; Eisaki, H.; Kakeshita, T.; Uchida, S.

    2011-05-01

    Single crystals of underdoped Ba(Fe1-xCox)2As2 were detwinned by applying uniaxial pressure. The anisotropic in-plane resistivity was measured using the Montgomery method without releasing pressure. The resistivity along the a-axis shows metallic behavior down to 5 K, while the resistivity along the b-axis shows an insulator-like behavior in some temperature range. Annealing the sample radically reduces the residual resistivity for x=0, and at the same time the anisotropy becomes much smaller at low temperatures.

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

    PubMed

    Hang, Da-Ren; Islam, Sk Emdadul; Sharma, Krishna Hari; Kuo, Shiao-Wei; Zhang, Cheng-Zu; Wang, Jun-Jie

    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.

  17. Combined effect of non-equilibrium solidification and thermal annealing on microstructure evolution and hardness behavior of AZ91 magnesium alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Z. Z.; Yang, W.; Chen, S. H.; Yu, H.; Xu, Z. F.

    2014-06-01

    Non-equilibrium solidification of commercial AZ91 magnesium alloy was performed by copper mold spray-casting technique and the thermal stability property of as-formed meta-stable microstructure was investigated by subsequent annealing at different temperatures and times. Remarkable grain refinement appears with increasing cooling rate during solidification process, which is accompanied by a visible cellular/dendrite transition for the grain morphology of primary phase. Moreover, the non-equilibrium solidified alloy exhibits obvious precipitation hardening effect upon annealing at 200 °C, and the precipitation mode of β-Mg17Al12 phase changes from discontinuous to continuous with extending isothermal time from 4 h to 16 h, which generates an increase of resultant micro-hardness value. After solid solution treatment at the elevated temperature of 420 °C, the volume fraction of β-Mg17Al12 phase decreases and a notable grain growth phenomenon occurs, which give rise to a reduction of hardness in comparison with that of as-quenched alloy.

  18. Effect of annealing atmosphere on photoluminescence and gas sensing of solution-combustion-synthesized Al, Pd co-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Yan; Liu, Min; Lv, Tan; Wang, Qiong; Zou, Yun-ling; Lian, Xiao-xue; Liu, Hong-peng

    2015-11-01

    Al, Pd co-doped ZnO nanoparticles (NPs) synthesized using a solution combustion method and subsequent annealing process under various atmospheres, including air, nitrogen, and hydrogen, were characterized using x-ray diffraction, energy-dispersive x-ray spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The gas-sensing properties of the sensors based on the NPs were also examined. The results indicated that the Al, Pd co-doped ZnO NPs, with an average crystallite size of 10 nm, exhibited enhanced gas-sensing performance compared with that of pure ZnO and Al-doped ZnO. The response of the Al, Pd co-doped ZnO NPs annealed in N2 to ethanol (49.22) was nearly 5.7 times higher than that to acetone (8.61) and approximately 20 - 27 times higher than that to benzene (2.38), carbon monoxide (2.23), and methane (1.78), which demonstrates their excellent selectivity to ethanol versus other gases. This high ethanol response can be attributed to the combined effects of the small size, Schottky barrier, lattice defects, and catalysis. [Figure not available: see fulltext.

  19. Effects of rapid thermal annealing on the structural and local atomic properties of ZnO: Ge nanocomposite thin films

    SciTech Connect

    Ceylan, Abdullah Ozcan, Sadan; Rumaiz, Abdul K.; Caliskan, Deniz; Ozbay, Ekmel; Woicik, J. C.

    2015-03-14

    We have investigated the structural and local atomic properties of Ge nanocrystals (Ge-ncs) embedded ZnO (ZnO: Ge) thin films. The films were deposited by sequential sputtering of ZnO and Ge thin film layers on z-cut quartz substrates followed by an ex-situ rapid thermal annealing (RTA) at 600 °C for 30, 60, and 90 s under forming gas atmosphere. Effects of RTA time on the evolution of Ge-ncs were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), hard x-ray photoelectron spectroscopy (HAXPES), and extended x-ray absorption fine structure (EXAFS). XRD patterns have clearly shown that fcc diamond phase Ge-ncs of sizes ranging between 18 and 27 nm are formed upon RTA and no Ge-oxide peak has been detected. However, cross-section SEM images have clearly revealed that after RTA process, Ge layers form varying size nanoclusters composed of Ge-ncs regions. EXAFS performed at the Ge K-edge to probe the local atomic structure of the Ge-ncs has revealed that as prepared ZnO:Ge possesses Ge-oxide but subsequent RTA leads to crystalline Ge structure without the oxide layer. In order to study the occupied electronic structure, HAXPES has been utilized. The peak separation between the Zn 2p and Ge 3d shows no significant change due to RTA. This implies little change in the valence band offset due to RTA.

  20. Temperature dependence of GMR and effect of annealing on electrodeposited Co-Ag granular films

    NASA Astrophysics Data System (ADS)

    Garcia-Torres, Jose; Vallés, Elisa; Gómez, Elvira

    2010-10-01

    The magnetoresistance of Co-Ag granular films composed of superparamagnetic and ferromagnetic particles was studied at different temperatures. The increase in the GMR values while decreasing temperature down to 20 K was quantified. The non-saturating behaviour of the MR( H) curves was retained even at the lowest measurement temperature, which was mainly attributed to the dipolar interaction among the superparamagnetic particles. The influence of the annealing conditions on the magnetoresistance was also studied. In all conditions, a decrease in the GMR values was measured being attributed to an increase in the particle size.

  1. Effect of the Solution Annealing and Chemical Passivation Followed by Aging on the Corrosion of Shell Mold Cast CF8 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kim, Kuk-Jin; Ju, Heongkyu; Moon, Young-Dae; Hong, Jun Ho; Pak, Sung Joon

    2016-10-01

    The effects of solution annealing and passivation of shell mold cast CF8 stainless steels on Elbow pipe fittings with 2-month room temperature aging have been studied using a corrosion technique. The resistance of corrosion increased with 2-month room temperature aging combined with solid solution annealing and chemical passivation. The mode of corrosion was deeply related to the δ-ferrite content, permeability, and passivation. The corrosion probability decreased as both the δ-ferrite content and the permeability decreased. Therefore, it is considered that δ-ferrite content and passive film of Cr2O3 play an important role in corrosion resistance of CF8 Elbow pipe fittings due to the long-term aging with solid solution annealing and chemical passivation. This result shows that the corrosion resistance of CF8 fittings can be enhanced by the solid solution annealing and chemical passivation. Decreased ferrite phases and permeability improve IGC resistance in CF8 steel.

  2. Effects of Annealing Process on the Formability of Friction Stir Welded Al-Li Alloy 2195 Plates

    NASA Technical Reports Server (NTRS)

    Chen, Po-Shou; Bradford, Vann; Russell, Carolyn

    2011-01-01

    Large rocket cryogenic tank domes have typically been fabricated using Al-Cu based alloys like Al-Cu alloy 2219. The use of aluminum-lithium based alloys for rocket fuel tank domes can reduce weight because aluminum-lithium alloys have lower density and higher strength than Al-Cu alloy 2219. However, Al-Li alloys have rarely been used to fabricate rocket fuel tank domes because of the inherent low formability characteristic that make them susceptible to cracking during the forming operations. The ability to form metal by stretch forming or spin forming without excessive thinning or necking depends on the strain hardening exponent "n". The stain hardening exponent is a measure of how rapidly a metal becomes stronger and harder. A high strain hardening exponent is beneficial to a material's ability to uniformly distribute the imposed strain. Marshall Space Flight Center has developed a novel annealing process that can achieve a work hardening exponent on the order of 0.27 to 0.29, which is approximately 50% higher than what is typically obtained for Al-Li alloys using the conventional method. The strain hardening exponent of the Al-Li alloy plates or blanks heat treated using the conventional method is typically on the order of 0.17 to 0.19. The effects of this novel annealing process on the formability of friction stir welded Al-Li alloy blanks are being studied at Marshall Space Flight Center. The formability ratings will be generated using the strain hardening exponent, strain rate sensitivity and forming range. The effects of forming temperature on the formability will also be studied. The objective of this work is to study the deformation behavior of the friction stir welded Al-Li alloy 2195 blank and determine the formability enhancement by the new annealing process.

  3. Isochronal annealing effects on local structure, crystalline fraction, and undamaged region size of radiation damage in Ga-stabilized δ-Pu

    SciTech Connect

    Olive, D. T.; Booth, C. H.; Wang, D. L.; Bauer, E. D.; Pugmire, A. L.; Freibert, F. J.; McCall, S. K.; Wall, M. A.; Allen, P. G.

    2016-07-19

    The effects on the local structure due to self-irradiation damage of Ga stabilized δ-Pu stored at cryogenic temperatures have been examined using extended x-ray absorption fine structure (EXAFS) experiments. Extensive damage, seen as a loss of local order, was evident after 72 days of storage below 15 K. The effect was observed from both the Pu and the Ga sites, although less pronounced around Ga. Isochronal annealing was performed on this sample to study the annealing processes that occur between cryogenic and room temperature storage conditions, where damage is mostly reversed. Damage fractions at various points along the annealing curve have been determined using an amplitude-ratio method, a standard EXAFS fitting, and a spherical crystallite model, and provide information complementary to the previous electrical resistivity- and susceptibility-based isochronal annealing studies. The use of a spherical crystallite model accounts for the changes in EXAFS spectra using just two parameters, namely, the crystalline fraction and the particle radius. Altogether, these results are discussed in terms of changes to the local structure around Ga and Pu throughout the annealing process and highlight the unusual role of Ga in the behavior of the lowest temperature anneals.

  4. Isochronal annealing effects on local structure, crystalline fraction, and undamaged region size of radiation damage in Ga-stabilized δ-Pu

    DOE PAGES

    Olive, D. T.; Booth, C. H.; Wang, D. L.; ...

    2016-07-19

    The effects on the local structure due to self-irradiation damage of Ga stabilized δ-Pu stored at cryogenic temperatures have been examined using extended x-ray absorption fine structure (EXAFS) experiments. Extensive damage, seen as a loss of local order, was evident after 72 days of storage below 15 K. The effect was observed from both the Pu and the Ga sites, although less pronounced around Ga. Isochronal annealing was performed on this sample to study the annealing processes that occur between cryogenic and room temperature storage conditions, where damage is mostly reversed. Damage fractions at various points along the annealing curvemore » have been determined using an amplitude-ratio method, a standard EXAFS fitting, and a spherical crystallite model, and provide information complementary to the previous electrical resistivity- and susceptibility-based isochronal annealing studies. The use of a spherical crystallite model accounts for the changes in EXAFS spectra using just two parameters, namely, the crystalline fraction and the particle radius. Altogether, these results are discussed in terms of changes to the local structure around Ga and Pu throughout the annealing process and highlight the unusual role of Ga in the behavior of the lowest temperature anneals.« less

  5. Effects of thermal annealing of W/SiO2 multilayer Bragg reflectors on resonance characteristics of film bulk acoustic resonator devices with cobalt electrodes

    NASA Astrophysics Data System (ADS)

    Yim, Munhyuk; Kim, Dong-Hyun; Chai, Dongkyu; Yoon, Giwan

    2004-05-01

    In this article, we present the thermal annealing effects of the W/SiO2 multilayer reflectors in ZnO-based film bulk acoustic resonator (FBAR) devices with cobalt (Co) electrodes in comparison with those with aluminum (Al) electrodes. Various thermal annealing conditions have been implemented on the W/SiO2 multilayer reflectors formed on p-type (100) silicon substrates. The resonance characteristics could be significantly improved due to the thermal annealing and were observed to depend strongly on the annealing conditions applied to the reflectors. Particularly, the FBAR devices with the W/SiO2 multilayer reflectors annealed at 400 °C/30 min have shown superior resonance characteristics in terms of return loss and quality factor. In addition, the use of Co electrodes has resulted in the further improvement of the resonance characteristics as compared with the Al electrodes. As a result, the combined use of both the thermal annealing and Co electrodes seems very useful to more effectively improve the resonance characteristics of the FBAR devices with the W/SiO2 multilayer reflectors. .

  6. Effect of substrate temperature and post-annealing on the properties of CIGS thin films deposited using e-beam evaporation

    NASA Astrophysics Data System (ADS)

    Chen, Jieyi; Shen, Honglie; Zhai, Zihao; Li, Jinze; Wang, Wei; Shang, Huirong; Li, Yufang

    2016-12-01

    Cu(InGa)Se2 (CIGS) thin films were prepared using e-beam evaporation on a soda-lime glass substrate. The effect of substrate temperature and the difference between substrate temperature and post-annealing on the properties of the CIGS thin films and solar cells were studied. X-ray diffraction (XRD) and Raman spectroscopy, energy-dispersive spectroscopy, scanning electron microscopy, UV-Vis-NIR and the Hall effect were used to characterize the structural properties, composition, morphology, optical properties and electrical properties of the as-prepared CIGS thin films, respectively. The results demonstrated that the photoelectric properties of CIGS thin films prepared at a substrate temperature of 300 °C were optimal, with an efficiency of 7.1%. As the substrate temperature increased to over 300 °C, element gallium tended to evaporate from the substrate, which resulted in the variation of the Cu/(In  +  Ga) and Ga/(In  +  Ga) ratios of the films. The post-annealing process with in situ annealing temperatures of 300 °C and 400 °C was also studied. The results indicated that the post-annealing process, unlike the process of direct deposition at certain substrate temperatures, was able to avoid the element loss. At 300 °C in situ post-annealing temperature, there formed a ‘polygon grains’ Cu2-x Se phase, which disappeared when the in situ post-annealing temperature rose to 400 °C. The XRD patterns revealed that the post-annealing process made the element diffusion in films more uniform. The post-treated sample with an in situ post-annealing temperature at 400 °C, as a result, showed the highest efficiency of 9.0%, accompanied by the highest open-circuit voltage, short circuit current and fill factor.

  7. Thermal Annealing Effect on Poly(3-hexylthiophene): Fullerene:Copper-Phthalocyanine Ternary Photoactive Layer

    PubMed Central

    Derouiche, H.; Mohamed, A. B.

    2013-01-01

    We have fabricated poly(3-hexylthiophene) (P3HT)/copper phthalocyanine (CuPc)/fullerene (C60) ternary blend films. This photoactive layer is sandwiched between an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT/PSS) photoanode and a bathocuproine (BCP)/aluminium photocathode. The thin films have been characterized by atomic force microscope (AFM) and ultraviolet/visible spectroscopy in order to study the influence of P3HT doping on the morphological and optical properties of the photoactive layer. We have also compared the I-V characteristics of three different organic solar cells: ITO/PEDOT:PSS/CuPc0.5:C600.5/BCP/Al and ITO/PEDOT:PSS/P3HT0.3:CuPc0.3:C600.4/BCP/Al with and without annealing. Both structures show good photovoltaic behaviour. Indeed, the incorporation of P3HT into CuPc:C60 thin film improves all the photovoltaic characteristics. We have also seen that thermal annealing significantly improves the optical absorption ability and stabilizes the organic solar cells making it more robust to chemical degradation. PMID:23766722

  8. Effect of thermal annealing treatment with titanium chelate on buffer layer in inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyong; Wang, Ning; Fu, Yan

    2016-12-01

    The solution processable electron extraction layer (EEL) is crucial for polymer solar cells (PSCs). Here, we investigated titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as an EEL and fabricated inverted PSCs with a blend of poly(3-hexylthiophene) (P3HT) and indene-C60 bisadduct (ICBA) acting as the photoactive layer, with a structure of ITO/TIPD/P3HT:ICBA/MoO3/Ag. After thermal annealing treatment at 150 °C for 15 min, the PSC performances increased from 3.85% to 6.84% and they achieve stable power conversion efficiency (PCE), with a similar PCE compared with TiO2 as an EEL by the vacuum evaporated method. Fourier transform infrared spectroscopy (FTIR) and ultraviolet photoelectron spectroscopy (UPS) confirmed that the TIPD decomposed and formed the Tidbnd O bond, and the energy level of the lowest unoccupied molecular orbital and the highest occupied molecular orbital increased. The space charge limited current (SCLC) measurements further confirmed the improvement in electron collection and the transport ability using TIPD as the EEL and thermal annealing.

  9. Thermal annealing effect on poly(3-hexylthiophene): fullerene:copper-phthalocyanine ternary photoactive layer.

    PubMed

    Derouiche, H; Mohamed, A B

    2013-01-01

    We have fabricated poly(3-hexylthiophene) (P3HT)/copper phthalocyanine (CuPc)/fullerene (C60) ternary blend films. This photoactive layer is sandwiched between an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT/PSS) photoanode and a bathocuproine (BCP)/aluminium photocathode. The thin films have been characterized by atomic force microscope (AFM) and ultraviolet/visible spectroscopy in order to study the influence of P3HT doping on the morphological and optical properties of the photoactive layer. We have also compared the I-V characteristics of three different organic solar cells: ITO/PEDOT:PSS/CuPc₀.₅:C60₀.₅/BCP/Al and ITO/PEDOT:PSS/P3HT₀.₃:CuPc₀.₃:C60₀.₄/BCP/Al with and without annealing. Both structures show good photovoltaic behaviour. Indeed, the incorporation of P3HT into CuPc:C60 thin film improves all the photovoltaic characteristics. We have also seen that thermal annealing significantly improves the optical absorption ability and stabilizes the organic solar cells making it more robust to chemical degradation.

  10. Optimization of silver nanowire-based transparent electrodes: effects of density, size and thermal annealing

    NASA Astrophysics Data System (ADS)

    Lagrange, M.; Langley, D. P.; Giusti, G.; Jiménez, C.; Bréchet, Y.; Bellet, D.

    2015-10-01

    Silver nanowire (AgNW) networks are efficient as flexible transparent electrodes, and are cheaper to fabricate than ITO (Indium Tin Oxide). Hence they are a serious competitor as an alternative to ITO in many applications such as solar cells, OLEDs, transparent heaters. Electrical and optical properties of AgNW networks deposited on glass are investigated in this study and an efficient method to optimize them is proposed. This paper relates network density, nanowire dimensions and thermal annealing directly to the physical properties of the nanowire networksusing original physical models. A fair agreement is found between experimental data and the proposed models. Moreover thermal stability of the nanowires is a key issue in thermal optimization of such networks and needs to be studied. In this work the impact of these four parameters on the networks physical properties are thoroughly investigated via in situ measurements and modelling, such a method being also applicable to other metallic nanowire networks. We demonstrate that this approach enables the optimization of both optical and electrical properties through modification of the junction resistance by thermal annealing, and a suitable choice of nanowire dimensions and network density. This work reports excellent optical and electrical properties of electrodes fabricated from AgNW networks with a transmittance T = 89.2% (at 550 nm) and a sheet resistance of Rs = 2.9 Ω □-1, leading to the highest reported figure of merit.

  11. Annealing effect on the property of ultraviolet and green emissions of ZnO thin films

    NASA Astrophysics Data System (ADS)

    Kang, Hong Seong; Kang, Jeong Seok; Kim, Jae Won; Lee, Sang Yeol

    2004-02-01

    The mechanism of ultraviolet (UV) and green emission of ZnO thin films deposited on (001) sapphire substrates by pulsed laser deposition was investigated by using postannealing treatment at various annealing temperatures after deposition. Structural, electrical, and optical properties of ZnO films have been also observed. As the postannealing temperature increased, the intensity of UV (380 nm) peak and the carrier concentration were decreased while the intensity of the visible (about 490-530 nm) peak and the resistivity were increased. The role of oxygen in ZnO thin film during the annealing process was important to the change of optical properties. The mechanism of the luminescence suggested that UV luminescence of ZnO thin film was related to the transition from near band edge to valence band, and green luminescence of ZnO thin film was caused by the transition from deep donor level to valence band due to oxygen vacancies. The activation energy derived by using the variation of green emission intensity was 1.19 eV.

  12. Optimization of silver nanowire-based transparent electrodes: effects of density, size and thermal annealing.

    PubMed

    Lagrange, M; Langley, D P; Giusti, G; Jiménez, C; Bréchet, Y; Bellet, D

    2015-11-07

    Silver nanowire (AgNW) networks are efficient as flexible transparent electrodes, and are cheaper to fabricate than ITO (Indium Tin Oxide). Hence they are a serious competitor as an alternative to ITO in many applications such as solar cells, OLEDs, transparent heaters. Electrical and optical properties of AgNW networks deposited on glass are investigated in this study and an efficient method to optimize them is proposed. This paper relates network density, nanowire dimensions and thermal annealing directly to the physical properties of the nanowire networksusing original physical models. A fair agreement is found between experimental data and the proposed models. Moreover thermal stability of the nanowires is a key issue in thermal optimization of such networks and needs to be studied. In this work the impact of these four parameters on the networks physical properties are thoroughly investigated via in situ measurements and modelling, such a method being also applicable to other metallic nanowire networks. We demonstrate that this approach enables the optimization of both optical and electrical properties through modification of the junction resistance by thermal annealing, and a suitable choice of nanowire dimensions and network density. This work reports excellent optical and electrical properties of electrodes fabricated from AgNW networks with a transmittance T = 89.2% (at 550 nm) and a sheet resistance of Rs = 2.9 Ω □(-1), leading to the highest reported figure of merit.

  13. Sequential annealing gradient Gamma-Knife radiosurgery optimization

    NASA Astrophysics Data System (ADS)

    Ove, Roger; Popple, Richard

    2003-07-01

    Simulated annealing and gradient methods are commonly employed for inverse planning of radiotherapy delivery schemes. Annealing is effective in finding an approximation of the global solution, suffering from slow late convergence and in some cases poor dose homogeneity. Gradient methods converge well but not necessarily to the global minimum. We explored simulated annealing followed by gradient optimization to improve on either method alone, using radiosurgery as the model system. Simulated annealing and gradient inverse planning programs using the same objective function were adapted for radiosurgical optimization. The objective function chosen is a least-squares dose-matching function, with differential weighting of tissues. A simple test target allowing local minima in the objective function was evaluated. Two hundred trials using the gradient method were done. The gradient method approximated the global solution only 12% of the time, commonly finding a local minimum. The annealing-gradient technique converged to the global minimum in 78 out of 80 trials, more efficiently than annealing alone. Dose homogeneity was improved. In conclusion, sequential annealing-gradient optimization can improve on either method alone. The technique may be extensible to radiotherapy inverse planning in general, with benefit expected for problems characterized by slow gradient method convergence and local minima.

  14. Effects of process variables in decarburization annealing of Fe-3%Si-0.3%C steel sheet on textures and magnetic properties

    NASA Astrophysics Data System (ADS)

    Park, Se Min; Koo, Yang Mo; Shim, Byoung Yul; Lee, Dong Nyung

    2017-01-01

    In Fe-3%Si-0.3%C steel sheet, a relatively strong <100>//ND texture can evolve in the surface layer through the α→γ→α phase transformation in relatively low vacuum (4 Pa) for an annealing time of 10 min and at a cooling rate of 20 K/s. Oxidation of the steel sheet surface prevents the evolution of the <100>//ND texture. However, vacuum-annealing under a vacuum pressure of 1.3×10-3 Pa causes decarburization of the steel sheet, which suppresses oxidation of the steel sheet surface, and subsequent annealing in wet hydrogen of 363 K in dew points causes a columnar grain structure with the <100>//ND texture. After the two-step-annealing (the vacuum annealing under a vacuum pressure of 1.3×10-3 Pa and subsequent decarburizing annealing in wet hydrogen of 363 K in dew points), the decarburized steel sheet exhibits good soft magnetic properties in NO with 3%Si, W15/50 (core loss at 1.5T and 50 Hz) = 2.47 W/kg and B50 (magnetic flux density at 5000 A/m) = 1.71 T.

  15. Effect of surface energy and seed layer annealing temperature on ZnO seed layer formation and ZnO nanowire growth

    NASA Astrophysics Data System (ADS)

    Park, Ji-Sub; Mahmud, Imtiaz; Shin, Han Jae; Park, Min-Kyu; Ranjkesh, Amid; Lee, Do Kyung; Kim, Hak-Rin

    2016-01-01

    We discuss the effects of surface energy and seed layer annealing temperature (Tannealing) on seed layer growth and hydrothermally-grown zinc oxide (ZnO) nanowires (NWs). In this work, by varying the ultraviolet ozone (UVO) treatment times on a silicon surface, the surface energy conditions for the seed layer formation changed and the seed layer was annealed under different Tannealing conditions. Under a lower surface energy condition of the substrate, with increasing Tannealing, the coverage density and the average thickness of the seed layer increased, but island-like growth was observed. This case was inevitably accompanied by an increase in surface roughness, which resulted in agglomerated low density growth of ZnO NWs. After sufficient UVO treatment, hydroxyl groups on the silicon surface activated the ZnO seed layer formation in the chemical reaction and increased the bonding energy between the active nucleation sites of the seed layer and the substrate surface. This ensured higher coverage density of the seed layer with lower surface roughness under the same Tannealing condition, thereby providing the ZnO NW growth with an enhanced density and aspect ratio as well as good crystallinity.

  16. Effect of Annealing on Mechanical Properties and Formability of Cold Rolled Thin Sheets of Fe-P P/M Alloys

    NASA Astrophysics Data System (ADS)

    Trivedi, Shefali; Ravi Kumar, D.; Aravindan, S.

    2016-10-01

    Phosphorus in steel is known to increase strength and hardness and decrease ductility. Higher phosphorus content (more than 0.05%), however, promotes brittle behavior due to segregation of Fe3P along the grain boundaries which makes further mechanical working of these alloys difficult. In this work, thin sheets of Fe-P alloys (with phosphorus in range of 0.1-0.35%) have been developed through processing by powder metallurgy followed by hot rolling and cold rolling. The effect of phosphorus content and annealing parameters (temperature and time) on microstructure, mechanical properties, formability in biaxial stretching and fracture behavior of the cold rolled and annealed sheets has been studied. A comparison has also been made between the properties of the sheets made through P/M route and the conventional cast route with similar phosphorus content. It has been shown that thin sheets of Fe-P alloys with phosphorous up to 0.35% possessing a good combination of strength and formability can be produced through rolling of billets of these alloys made through powder metallurgy technique without the problem of segregation.

  17. Effect of fuel rate and annealing process of LiFePO{sub 4} cathode material for Li-ion batteries synthesized by flame spray pyrolysis method

    SciTech Connect

    Halim, Abdul; Setyawan, Heru; Machmudah, Siti; Nurtono, Tantular; Winardi, Sugeng

    2014-02-24

    In this study the effect of fuel rate and annealing on particle formation of LiFePO{sub 4} as battery cathode using flame spray pyrolysis method was investigated numerically and experimentally. Numerical study was done using ANSYS FLUENT program. In experimentally, LiFePO{sub 4} was synthesized from inorganic aqueous solution followed by annealing. LPG was used as fuel and air was used as oxidizer and carrier gas. Annealing process attempted in inert atmosphere at 700°C for 240 min. Numerical result showed that the increase of fuel rate caused the increase of flame temperature. Microscopic observation using Scanning Electron Microscopy (SEM) revealed that all particles have sphere and polydisperse. Increasing fuel rate caused decreasing particle size and increasing particles crystallinity. This phenomenon attributed to the flame temperature. However, all produced particles still have more amorphous phase. Therefore, annealing needed to increase particles crystallinity. Fourier Transform Infrared (FTIR) analysis showed that all particles have PO4 function group. Increasing fuel rate led to the increase of infrared spectrum absorption corresponding to the increase of particles crystallinity. This result indicated that phosphate group vibrated easily in crystalline phase. From Electrochemical Impedance Spectroscopy (EIS) analysis, annealing can cause the increase of Li{sup +} diffusivity. The diffusivity coefficient of without and with annealing particles were 6.84399×10{sup −10} and 8.59888×10{sup −10} cm{sup 2} s{sup −1}, 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. Effect of annealing on cation distribution and magnetic properties of nano sized Mn0.34Co0.66Fe2O4 microwave ferrites

    NASA Astrophysics Data System (ADS)

    Datt, Gopal; Abhyankar, A. C.

    2016-05-01

    Microwave spinel ferrites are ubiquitous in systems that receive, send, and manipulate electromagnetic signals across very high frequency to quasi-optical frequency bands. This paper elaborates the effects of annealing on structural and magnetic properties of the Mn0.34Co0.66Fe2O4 ferrite nano-particles, synthesised by solvothermal method. The Rietveld refinement of XRD data reveals that nanoparticles are crystallized in spinel structure with Fd-3m space group and on annealing the Mn2+ ions migrates from tetrahedral to octahedral site. The FESEM microstructures reveal that grain size increase from 30 nm to 200 nm on annealing and morphology of the particles changes from spherical to rhombohedral. The magnetic data analysis shows that on annealing the magnetization improves significantly from Ms = 59.23 emu/g to Ms = 86.80 emu/g. Magnetocrystalline anisotropy and coercivity increased significantly on annealing. The change in magnetic properties on annealing is strongly correlated to redistribution of Mn2+ cations on different sites.

  20. Air annealing effects on the optical properties of ZnO SnO2 thin films deposited by a filtered vacuum arc deposition system

    NASA Astrophysics Data System (ADS)

    Çetinörgü, E.; Goldsmith, S.; Boxman, R. L.

    2006-03-01

    ZnO-SnO2 transparent and conducting thin films were deposited on microscope glass substrates by a filtered vacuum arc deposition (FVAD) system. The cathode was prepared with 50%:50% atomic concentration of Zn:Sn. The films were annealed in air at 500 °C for 1 h. Structural and compositional analyses were obtained using XRD and XPS diagnostics. X-ray diffraction analysis indicated that as-deposited and air-annealed thin ZnO-SnO2 films were amorphous. The atomic ratio of Zn to Sn in the film obtained using the 50%:50% cathode as determined by XPS analysis was ~2.7:1 in the bulk film. The optical properties were determined from normal incidence transmission measurements. Film transmission in the visible was 70% to 90%, affected by interference effects. Annealed films did not show higher transmission in the VIS compared to as-deposited films. Assuming that the interband electron transition is direct, the optical band gap was found to be in the range 3.34-3.61 eV for both as-deposited and annealed films. However, the average Eg for annealed films was 3.6 eV, larger by 0.2 eV than that of as-deposited. The refractive index n increased while the extinction index k decreased significantly with annealing.

  1. Effects of Annealing Treatment Prior to Cold Rolling on Delayed Fracture Properties in Ferrite-Austenite Duplex Lightweight Steels

    NASA Astrophysics Data System (ADS)

    Sohn, Seok Su; Song, Hyejin; Kim, Jung Gi; Kwak, Jai-Hyun; Kim, Hyoung Seop; Lee, Sunghak

    2016-02-01

    Tensile properties of recently developed automotive high-strength steels containing about 10 wt pct of Mn and Al are superior to other conventional steels, but the active commercialization has been postponed because they are often subjected to cracking during formation or to the delayed fracture after formation. Here, the delayed fracture behavior of a ferrite-austenite duplex lightweight steel whose microstructure was modified by a batch annealing treatment at 1023 K (750 °C) prior to cold rolling was examined by HCl immersion tests of cup specimens, and was compared with that of an unmodified steel. After the batch annealing, band structures were almost decomposed as strong textures of {100}<011> α-fibers and {111}<112> γ-fibers were considerably dissolved, while ferrite grains were refined. The steel cup specimen having this modified microstructure was not cracked when immersed in an HCl solution for 18 days, whereas the specimen having unmodified microstructure underwent the delayed fracture within 1 day. This time delayed fracture was more critically affected by difference in deformation characteristics such as martensitic transformation and deformation inhomogeneity induced from concentration of residual stress or plastic strain, rather than the difference in initial microstructures. The present work gives a promise for automotive applications requiring excellent mechanical and delayed fracture properties as well as reduced specific weight.

  2. 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.

  3. Annealing effect on physical properties of evaporated molybdenum oxide thin films for ethanol sensing

    NASA Astrophysics Data System (ADS)

    Touihri, S.; Arfaoui, A.; Tarchouna, Y.; Labidi, A.; Amlouk, M.; Bernede, J. C.

    2017-02-01

    This paper deals with some physical investigations on molybdenum oxide thin films growing on glass substrates by the thermal evaporation method. These films have been subjected to an annealing process under vacuum, air and oxygen at various temperatures 673, 723 and 773 K. First, the physical properties of these layers were analyzed by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM) and optical measurements. These techniques have been used to investigate the oxygen index in MoOx properties during the heat treatment. Second, from the reflectance and transmittance optical measurements, it was found that the direct band gap energy value increased from 3.16 to 3.90 eV. Finally, the heat treatments reveal that the oxygen index varies in such molybdenum oxides showing noticeably sensitivity toward ethanol gas.

  4. Effective 3D protein structure prediction with local adjustment genetic-annealing algorithm.

    PubMed

    Zhang, Xiao-Long; Lin, Xiao-Li

    2010-09-01

    The protein folding problem consists of predicting protein tertiary structure from a given amino acid sequence by minimizing the energy function. The protein folding structure prediction is computationally challenging and has been shown to be NP-hard problem when the 3D off-lattice AB model is employed. In this paper, the local adjustment genetic-annealing (LAGA) algorithm was used to search the ground state of 3D offlattice AB model for protein folding structure. The algorithm included an improved crossover strategy and an improved mutation strategy, where a local adjustment strategy was also used to enhance the searching ability. The experiments were carried out with the Fibonacci sequences. The experimental results demonstrate that the LAGA algorithm appears to have better performance and accuracy compared to the previous methods.

  5. The Effects of Thermal Annealing on ZnO Thin Films Produced by Spin-Coating Method on Quartz Substrates

    NASA Astrophysics Data System (ADS)

    Ertek, Özlem; Okur, İbrahim

    2015-07-01

    In this work, zinc oxide (ZnO) thin films on quartz substrates were fabricated using the spin-coating method. Thermal annealings from to have been performed in increments and for two annealing durations (0.5 h and 8 h). X-ray diffraction (XRD) spectra, scanning electron microscopy micrographs, and UV-Vis absorption spectra of all the samples have been elucidated from mechanical and optical points of view. It has been observed that for all annealing temperatures, the crystal phase has been obtained. After annealings, a new crystal phase related to (willemite) has also been appeared in XRD spectra. This phase remained stable up to annealing together with the ZnO crystal phase. It has been found that the nano/micro rod diameters of the ZnO crystals reach to a maximum at the annealing for both annealing durations. For annealings, ZnO nanorods appeared to be split into two homogeneous nanorods of length of and of width of (350 nm) which was not the case for all other annealing temperatures. After annealings, ZnO nano/micro rods started to disappear and formed homogeneous ZnO thin films.

  6. Ultraclean suspended monolayer graphene achieved by in situ current annealing

    NASA Astrophysics Data System (ADS)

    Wang, Haidong; Zhang, Xing; Takamatsu, Hiroshi

    2017-01-01

    Ultraclean graphene is essential for studying its intrinsic transport properties or fabricating high-performance electronic devices. Unfortunately, the contamination on graphene is unavoidable after microelectromechanical system processing. Here, we report an in situ current-annealing method for achieving ultraclean suspended monolayer graphene. The charge mobility of cleaned graphene reached a surprising 3.8 × 105 cm2 V-1 s-1, one of the highest values ever reported. For the first time, the process of current annealing was recorded under a high-resolution electron scanning microscope. It was demonstrated that temperature was the only dominant factor of the current-annealing process. Meanwhile, the mobility of suspended graphene was found to be highly sensitive to structural defects. The mobility decreased by a factor of over 100 after ion irradiation on graphene. The results revealed the underlying mechanism of current annealing on graphene and provided an effective means of preparing ultraclean graphene membranes.

  7. Oxygen annealing effects on optical properties of ZnO and TiO nanocluster thin film

    NASA Astrophysics Data System (ADS)

    Souza, Ryan; Che, Hui; Tian, Yufeng; Qiang, You; Rodriguez, Rene; Lau, Lisa; Turner, Paul; Tenne, Dmitri

    2009-05-01

    Thin films of zinc oxide (ZnO) and titanium oxides (TiO) were deposited on Si (100) substrate by third generation nanocluster source. Post deposition Oxygen Annealing (OA) effects were evaluated by X-Ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL). As deposited, diameter of ZnO nanoclusters ˜24 nm and ZnO OA nanoclusters ˜30 nm. As deposited TiO clusters ˜10 nm in diameter, and TiO OA cluster ˜20 nm. XRD shows increased crystal quality and improved ZnO c-axis crystal growth. XRD shows improved stoichiometric TiO2 clusters and preferred anatase phase. Intensity of ZnO PL spectrum has temperature dependence from 10K to 300K. ZnO OA produces red-shifted PL peak, and there are no below-bandgap PL peaks. TiO has room temperature PL with UV peak ˜388 nm and visible peak ˜426 nm. ZnO OA nanoclusters show narrower, red shifted peak by ˜0.07eV compared to as deposited ZnO nanoclusters. This indicates increased average grain size and improved size homogeneity after annealing. This is confirmed by Raman spectra showing blue-shifted and narrower peak of the A1 (LO) phonon peak in ZnO OA sample. DOE-EPSCoR (DE-FG02-04ER46142) DOE-BES (DE-FG02-07ER46386).

  8. Modeling the effects of ion dose and crystallographic symmetry on the morphological evolution of embedded precipitates under thermal annealing

    NASA Astrophysics Data System (ADS)

    Li, Kun-Dar

    2014-10-01

    Thermal annealing is one of the most common techniques to synthesize embedded precipitates by ion implantation process. In this study, an anisotropic phase field model is presented to investigate the effects of ion dose and crystallographic symmetry on the morphological formation and evolution of embedded precipitates during post-implantation thermal annealing process. This theoretical model provides an efficient numerical approach to understand the phenomenon of faceted precipitates formation by ion implantation. As a theoretical analysis, the interfacial energy and diffusion kinetics play prominent roles in the mechanism of atomic diffusion for the precipitates formation. With a low ion dose, faceted precipitates are developed by virtue of the anisotropic interfacial energy. As an increase of ion dose, connected precipitates with crystallographic characters on the edge are appeared. For a high ion dose, labyrinth-like nanostructures of precipitates are produced and the characteristic morphology of crystallographic symmetry becomes faint. These simulation results for the morphological evolutions of embedded precipitates by ion implantation are corresponded with many experimental observations in the literatures. The quantitative analyses of the simulations are also well described the consequence of precipitates formation under different conditions.

  9. In situ optical characterizations of the annealing effects upon SnO2:F films by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Yuan, Guangzhong; Wang, Kangkai; Li, Ming; Gao, Qian; Liu, Yong; Jia, Shaohui; Song, Chenlu; Han, Gaorong

    2016-10-01

    In situ study of the annealing effects, up to 600 °C, upon the optical performance of SnO2:F films have been successfully conducted with spectroscopic ellipsometry. The thickness and optical parameters were obtained by the regression of the measured ellipsometry parameters using a five-layer model. The results show that the re-densification of the SnO2:F layers occurs at above 200 °C, resulting in an irreversible thickness reducing from about 326 nm to about 321 nm. The refractive index of the SnO2:F layer increases with temperature and decreases in the cooling period. The in situ temperature dependence of the average refractive index has a good agreement with the sheet resistance measurement results, not only verifying the annealing process deteriorates the low-emissivity performance, but also demonstrates that spectroscopic ellipsometry method is a suitable optical characterization technique to adjust the on-line coating process of float glass.

  10. Optical properties of planar waveguides on ZnWO₄ formed by carbon and helium ion implantation and effects of annealing.

    PubMed

    Zhao, Jin-Hua; Liu, Tao; Guo, Sha-Sha; Guan, Jing; Wang, Xue-Lin

    2010-08-30

    We report on the optical properties of ZnWO(4) planar waveguides created by ion implantation, and the effect annealing has on these structures. Planar optical waveguides in ZnWO(4) crystals are fabricated by 5.0 MeV carbon ion implantation with a fluence of 1 × 10(15) ions/cm(2) or 500 keV helium ion implantation with the a fluence of 1 × 10(16) ions/cm(2). The thermal stability was investigated by 60 minute annealing cycles at different temperatures ranging from 260°C to 550°C in air. The guided modes were measured by a model 2010 prism coupler at wavelengths of 633 nm and 1539 nm. The reflectivity calculation method (RCM) was applied to simulate the refractive index profile in these waveguides. The near-field light intensity profiles were measured using the end-face coupling method. The absorption spectra show that the implantation processes have almost no influence on the visible band absorption.

  11. Controllable nitrogen doping in as deposited TiO{sub 2} film and its effect on post deposition annealing

    SciTech Connect

    Deng, Shaoren; Devloo-Casier, Kilian; Devulder, Wouter; Dendooven, Jolien; Deduytsche, Davy; Detavernier, Christophe; Lenaerts, Silvia; Martens, Johan A.; Van den Berghe, Sven

    2014-01-15

    In order to narrow the band gap of TiO{sub 2}, nitrogen doping by combining thermal atomic layer deposition (TALD) of TiO{sub 2} and plasma enhanced atomic layer deposition (PEALD) of TiN has been implemented. By altering the ratio between TALD TiO{sub 2} and PEALD TiN, the as synthesized TiO{sub x}N{sub y} films showed different band gaps (from 1.91 eV to 3.14 eV). In situ x-ray diffraction characterization showed that the crystallization behavior of these films changed after nitrogen doping. After annealing in helium, nitrogen doped TiO{sub 2} films crystallized into rutile phase while for the samples annealed in air a preferential growth of the anatase TiO{sub 2} along (001) orientation was observed. Photocatalytic tests of the degradation of stearic acid were done to evaluate the effect of N doping on the photocatalytic activity.

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

    SciTech Connect

    Uthirakumar, Periyayya; Hong, Chang-Hee

    2009-11-15

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

  13. 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.

  14. Real-time solution measurement of RAD51- and RecA-mediated strand assimilation without background annealing.

    PubMed

    Budke, Brian; Chan, Yuen-Ling; Bishop, Douglas K; Connell, Philip P

    2013-07-01

    RAD51 is the central strand exchange recombinase in somatic homologous recombination, providing genomic stability and promoting resistance to DNA damage. An important tool for mechanistic studies of RAD51 is the D-loop or strand assimilation assay, which measures the ability of RAD51-coated single-stranded DNA (ssDNA) to search for, invade and exchange ssDNA strands with a homologous duplex DNA target. As cancer cells generally overexpress RAD51, the D-loop assay has also emerged as an important tool in oncologic drug design programs for targeting RAD51. Previous studies have adapted the traditional gel-based D-loop assay by using fluorescence-based substrates, which in principle allow for use in high-throughput screening platforms. However, these existing D-loop methods depend on linear oligonucleotide DNA duplex targets, and these substrates enable recombinase-independent ssDNA annealing that can obscure the recombinase-dependent strand assimilation signal. This compelled us to fundamentally re-design this assay, using a fluorescent target substrate that consists of a covalently closed linear double-hairpin dsDNA. This new microplate-based method represents a fast, inexpensive and non-radioactive alternative to existing D-loop assays. It provides accurate kinetic analysis of strand assimilation in high-throughput and performs well with human RAD51 and Escherichia coli RecA protein. This advance will aid in both mechanistic studies of homologous recombination and drug screening programs.

  15. Effects of MgO buffer annealing on optical and electrical quality of P-MBE grown ZnO films on c-sapphire

    NASA Astrophysics Data System (ADS)

    Setiawan, A.; Yao, T.

    2016-04-01

    Zinc oxide (ZnO) has been attracting much attention because of its potential applications in photonic and optoelectronic devices. In this present study, we investigated the effect of MgO buffer annealing on the optical and electrical quality of P-MBE grown ZnO films on c-sapphire with MgO buffer layer. The optical quality was observed by low-temperature PL (photoluminescence) measurement in the near band edge emission region measured at 10K and at 77K. The emission line located at 3.368eV dominates the spectrum in both samples (ZnO with and without MgO buffer annealing) at 10K and 77K. This emission can be divided into two peaks, 3.367eV and 3.363eV and assigned as I2 (ionized donor bound excitons emission) and I4 (Hydrogen donor related emission), respectively. The relative intensity of these donor bound exactions to free exaction emission of the sample without MgO buffer annealing is greater than that of the sample with MgO buffer annealing. Comparison of the PL spectra of ZnO with and without annealing revealed that the intensity of free exciton emission from the sample with MgO buffer annealing is twice of that from the sample without annealing. We also found that the intensity of deep-level broad emission is reduced by about 1/3 by MgO-buffer annealing. Hence, the decrease of deep level emission intensity and the increase of free exciton emission intensity by annealing of MgO buffer corresponds to the reduction of defects of the ZnO film. The PL properties also suggest that there are fewer nonradiative recombination centers in ZnO layers with MgO buffer annealing than those in ZnO layers grown without MgO buffer annealing. The electrical quality was measured by room temperature Hall measurements. We found that the samples have a background n-type carrier concentration. The ZnO samples with MgO buffer annealing has a carrier concentration of 1.17×1017 cm-3 and Hall mobility of 120 cm2/V.s, while the ZnO sample without MgO buffer annealing has a carrier

  16. 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.

  17. Growth of different phases and morphological features of MnS thin films by chemical bath deposition: Effect of deposition parameters and annealing

    NASA Astrophysics Data System (ADS)

    Hannachi, Amira; Maghraoui-Meherzi, Hager

    2017-03-01

    Manganese sulfide thin films have been deposited on glass slides by chemical bath deposition (CBD) method. The effects of preparative parameters such as deposition time, bath temperature, concentration of precursors, multi-layer deposition, different source of manganese, different complexing agent and thermal annealing on structural and morphological film properties have been investigated. The prepared thin films have been characterized using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It exhibit the metastable forms of MnS, the hexagonal γ-MnS wurtzite phase with preferential orientation in the (002) plane or the cubic β-MnS zinc blende with preferential orientation in the (200) plane. Microstructural studies revealed the formation of MnS crystals with different morphologies, such as hexagons, spheres, cubes or flowers like.

  18. Experimental tests of irradiation-anneal-reirradiation effects on mechanical properties of RPV plate and weld materials

    SciTech Connect

    Hawthorne, J.R.

    1996-01-01

    The Charpy-V (C{sub V}) notch ductility and tension test properties of three reactor pressure vessel (RPV) steel materials were determined for the 288{degree}C (550{degree}F) irradiated (I), 288{degree}C (550{degree}F) irradiated + 454{degree}C (850{degree}F)-168 h postirradiation annealed (IA), and 288{degree}C (550{degree}F) reirradiated (IAR) conditions. Total fluences of the I condition and the IAR condition were, respectively, 3.33 {times} 10{sup 19} n/cm{sup 2} and 4.18 {times} 10{sup 19} n/cm{sup 2}, E > 1 MeV. The irradiation portion of the IAR condition represents an incremental fluence increase of 1. 05 {times} 10{sup 19} n/cm{sup 2}, E > 1 MeV, over the I-condition fluence. The materials (specimens) were supplied by the Yankee Atomic Electric Company and represented high and low nickel content plates and a high nickel, high copper content weld deposit prototypical of the Yankee-Rowe reactor vessel. The promise of the IAR method for extending the fluence tolerance of radiation-sensitive steels and welds is clearly shown by the results. The annealing treatment produced full C{sub V} upper shelf recovery and full or nearly full recovery in the C{sub V} 41 J (30 ft-lb) transition temperature. The C{sub V} transition temperature increases produced by the reirradiation exposure were 22% to 43% of the increase produced by the first cycle irradiation exposure. A somewhat greater radiation embrittlement sensitivity and a somewhat greater reirradiation embrittlement sensitivity was exhibited by the low nickel content plate than the high nickel content plate. Its high phosphorus content is believed to be responsible. The IAR-condition properties of the surface vs. interior regions of the low nickel content plate are also compared.

  19. [Effects of annealing temperature on the structure and optical properties of ZnMgO films prepared by atom layer deposition].

    PubMed

    Sun, Dong-Xiao; Li, Jin-Hua; Fang, Xuan; Chen, Xin-Ying; Fang, Fang; Chu, Xue-Ying; Wei, Zhi-Peng; Wang, Xiao-Hua

    2014-07-01

    In the present paper, we report the research on the effects of annealing temperature on the crystal quality and optical properties of ZnMgO films deposited by atom layer deposition(ALD). ZnMgO films were prepared on quartz substrates by ALD and then some of the samples were treated in air ambient at different annealing temperature. The effects of annealing temperature on the crystal quality and optical properties of ZnMgO films were characterized by X-ray diffraction (XRD), photoluminescence (PL) and ultraviolet-visible (UV-Vis) absorption spectra. The XRD results showed that the crystal quality of ZnMgO films was significantly improved when the annealing temperature was 600 degrees C, meanwhile the intensity of(100) diffraction peak was the strongest. Combination of PL and UV-Vis absorption measurements showed that it can strongly promote the Mg content increasing in ZnMgO films and increase the band gap of films. So the results illustrate that suitable annealing temperature can effectively improve the crystal quality and optical properties of ZnMgO films.

  20. Asymmetric magnetoimpedance effect in CoFeSiB amorphous ribbons by combination of field and current annealing for sensor applications

    NASA Astrophysics Data System (ADS)

    Hajiali, Mohammadreza; Mohseni, S. Majid; Roozmeh, S. Ehsan; Moradi, Mehrdad

    2016-08-01

    The roles of applied magnetic field during the current annealing of Co68.15Fe4.35Si12.5B15 soft magnetic amorphous ribbons are studied. Samples heat treated by Joule heating effect in open air and simultaneously in the present of longitudinal external magnetic field showed asymmetric magnetoimpedance (AMI) behavior. The AMI profile can be related to the exchange bias interaction between the soft magnetic amorphous material and a harder magnetic crystalline phase formed on the surface of the ribbon. This effect stems from thermal effect, the transverse Oe field generated from the annealing current which is thickness dependent and the longitudinal external field. The single peak AMI with the field sensitivity of 101%/Oe for DC annealing current is achieved. Our results could address a simple way to achieve the AMI response toward developing high sensitive magnetic field sensors.

  1. Effect of annealing temperature of Bi1.5Zn1.0Nb1.5O7 gate insulator on performance of ZnO based thin film transistors

    NASA Astrophysics Data System (ADS)

    Wei, Ye; Wei, Ren; Peng, Shi; Zhuangde, Jiang

    2016-07-01

    The bottom-gate structure ZnO based thin film transistors (ZnO-TFTs) using Bi1.5Zn1.0Nb1.5O7 (BZN) thin films as gate insulator were fabricated on Pt/SiO2/Si substrate by radio frequency magnetic sputtering. We investigated the effect of annealing temperature at 300, 400, and 500 °C on the performance of BZN thin films and ZnO-TFTs. XRD measurement confirmed that BZN thin films were amorphous in nature. BZN thin films annealed at 400 °C obtain the high capacitance density of 249 nF/cm2, high dielectric constant of 71, and low leakage current density of 10-7 A/cm2 on/off current ratio and field effect mobility of ZnO-TFTs annealed at 400 °C are approximately one order of magnitude and two times, respectively higher than that of ZnO-TFTs annealed at 300 °C. When the annealing temperature is 400 °C, the electrical performance of ZnO-TFTs is enhanced remarkably. Devices obtain a low sub-threshold swing of 470 mV/dec and surface states density of 3.21 × 1012cm-2. Project supported by the National Natural Science Foundation of China (Nos. 51332003, 51202184), the International Science & Technology Cooperation Program of China (Nos. 2010DFB13640, 2011DFA51880), and the “111 Project” of China (No. B14040).

  2. Thermal Conductivity Changes in Titanium-Graphene Composite upon Annealing

    NASA Astrophysics Data System (ADS)

    Jagannadham, Kasichainula

    2016-02-01

    Ti-graphene composite films were prepared on polished Ti substrates by deposition of graphene platelets from suspension followed by deposition of Ti by magnetron sputtering. The films were annealed at different temperatures up to 1073 K (800 °C) and different time periods in argon atmosphere. The annealed films were characterized by X-ray diffraction for phase identification, scanning electron microscopy for microstructure, energy-dispersive spectrometry for chemical analysis, atomic force microscopy for surface roughness, and transient thermoreflectance for thermal conductivity and interface thermal conductance. The results showed that the interface between the composite film and Ti substrate remained continuous with the absence of voids. Oxygen concentration in the composite films has increased for higher temperature and time of annealing. TiO2 and TiC phases are formed only in the film annealed at 1073 K (800 °C). The thermal conductivity of the composite film decreased with increasing oxygen concentration. The effective thermal conductance of the film annealed at 1073 K (800 °C) was significantly lower. The interface thermal conductance between the composite film and the Ti substrate is also reduced for higher oxygen concentration. Formation of microscopic TiO2 phase bound by interface boundaries and oxygen incorporation is considered responsible for the lower thermal conductance of the Ti-graphene composite annealed at 1073 K (800 °C).

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

    PubMed

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

    2009-03-01

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

  4. Determination of effects of deposition and anneal properties for tetranitratotitanium deposited TiO2 dielectrics

    NASA Astrophysics Data System (ADS)

    Kim, Hyeon-Seag; Campbell, S. A.; Gilmer, D. C.; Kaushik, V.; Conner, J.; Prabhu, L.; Anderson, A.

    1999-03-01

    Carbon and hydrogen free tetranitratotitanium was synthesized, which is believed to thermally decomposed primarily as: Ti(NO3)4→TiO2+4NO2+O2. The by-products of the thermal decomposition of tetranitratotitanium, which include NO2 and O2, may possibly provide a robust ultrathin tunnel interfacial layer. Due to the hydrogen free nature of thermolysis, N2O may form an oxynitride layer which has been shown to produce thermal oxynitrides with higher quality than NH3-based nitride oxides. Unlike titanium tetrakis isopropoxide (TTIP) deposited films, the interface state density more closely follows the "U" shape characteristic of conventional thermal SiO2/Si interfaces. The integrated interface state density is considerably less for the film annealed at higher temperature, which should produce considerably higher inversion layer mobilities. This improvement of the interface, compared to TTIP deposited films, is believed to be due to the elimination of water vapor from the deposition ambient.

  5. The effect of laser annealing of thin W(100) films on positron transmission reemission properties

    SciTech Connect

    Jacobsen, F.M.; Charlton, M.; Chevallier, J.; Deutch, B.I.; Laricchia, G.; Poulsen, M.R. )

    1990-01-01

    Results on {ital e}{sup +} transmission reemission properties are presented for three single-crystal W(100) films of thicknesses 1000, 2000, and 3100 A for incident {ital e}{sup +} energies of 1.4--16 keV. The films were first cleaned with a 10-s laser pulse, then annealed in O{sub 2} (10{sup {minus}6} Torr), and finally heated in a vacuum (10{sup {minus}9} Torr). Thereafter the films showed good reemission properties. The maximum transmitted yields of slow {ital e}{sup +} were 38% (1000 A), 27% (2000 A), and 17% (3100 A) at incident {ital e}{sup +} energies of 4, 5.2, and 7.2 keV, respectively. The energy distributions of the reemitted {ital e}{sup +} were characterized by a full width half maximum of 0.15--0.2 eV located at 2.8 eV containing 60%--70% of the {ital e}{sup +} superimposed onto a nearly uniform distribution covering the energy interval 0--2.8 eV.

  6. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    SciTech Connect

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.; Yang, Mengjin; Kovarik, Libor; Holesinger, Terry G.; Al-Jassim, Mowafak; Zhu, Kai; Zhou, Weilie; Berry, Joseph J.

    2016-07-08

    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapor results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 °C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 °C in ±25 °C steps (150-200 °C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.

  7. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    SciTech Connect

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.; Yang, Mengjin; Kovarik, Libor; Holesinger, Terry G.; Al-Jassim, Mowafak; Zhu, Kai; Zhou, Weilie; Berry, Joseph J.

    2016-07-08

    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapor results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 degrees C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 degrees C in +/-25 degrees C steps (150-200 degrees C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.

  8. Effect of thermal annealing in vacuum and in air on nanograin sizes in hard and superhard coatings Zr-Ti-Si-N.

    PubMed

    Pogrebnjak, A D; Shpak, A P; Beresnev, V M; Kolesnikov, D A; Kunitskii, Yu A; Sobol, O V; Uglov, V V; Komarov, F F; Shypylenko, A P; Makhmudov, N A; Demyanenko, A A; Baidak, V S; Grudnitskii, V V

    2012-12-01

    Zr-Ti-Si-N coating had high thermal stability of phase composition and remained structure state under thermal annealing temperatures reached 1180 degrees C in vacuum and 830 degrees C in air. Effect of isochronous annealing on phase composition, structure, and stress state of Zr-Ti-Si-N-ion-plasma deposited coatings (nanocomposite coatings) was reported. Below 1000 degrees C annealing temperature in vacuum, changing of phase composition is determined by appearing of siliconitride crystallites (beta-Si3N4) with hexagonal crystalline lattice and by formation of ZrO2 oxide crystallites. Formation of the latter did not result in decay of solid solution (Zr, Ti)N but increased in it a specific content of Ti-component. Vacuum annealing increased sizes of solid solution nanocrystallites from (12 to 15) in as-deposited coatings to 25 nm after annealing temperature reached 1180 degrees C. One could also find macro- and microrelaxations, which were accompanied by formation of deformation defects, which values reached 15.5 vol.%. Under 530 degrees C annealing in vacuum or in air, nanocomposite coating hardness increased. When Ti and Si concentration increased and three phases nc-ZrN, (Zr, Ti)N-nc, and alpha-Si3N4 were formed, average hardness increased to 40.8 +/- 4 GPa. Annealing to 500 degrees C increased hardness and demonstrated lower spread in values H = 48 +/- 6 GPa and E = (456 +/- 78) GPa. Zr-Ti-Si-N coatings has high wear resistance and low friction coefficient in comparison at a temperature of 500 degrees C possess with coatings TiN, Ti-Si-N.

  9. 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.

  10. Nanocrystalline Cs{sub x}WO{sub 3} particles: Effects of N{sub 2} annealing on microstructure and near-infrared shielding characteristics

    SciTech Connect

    Liu, Jing-Xiao; Shi, Fei; Dong, Xiao-Li; Xu, Qiang; Yin, Shu; Sato, Tsugio

    2013-10-15

    In order to further improve the near-infrared shielding properties of cesium tungsten bronze (Cs{sub x}WO{sub 3}) for solar filter applications, Cs{sub x}WO{sub 3} particles were prepared by solvothermal reaction method and the effects of nitrogen annealing on the microstructure and near-infrared shielding properties of Cs{sub x}WO{sub 3} were investigated. The obtained Cs{sub x}WO{sub 3} samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and spectrophotometer. The results indicate that nanosheet-like Cs{sub x}WO{sub 3} particles with hexagonal structure began to transform into nanorods after annealed at temperature higher than 600 °C. The near-infrared shielding properties of Cs{sub x}WO{sub 3} particles could be further improved by N{sub 2} annealing at 500–700 °C. Particularly, the 500 °C-annealed Cs{sub x}WO{sub 3} samples in the N{sub 2} atmosphere showed best near-infrared shielding properties. It was suggested that the excellent near-infrared shielding ability of the 500 °C-annealed Cs{sub x}WO{sub 3} samples is correlated with its minimum O/W atomic ratio and most oxygen vacancies. Highlights: • N{sub 2} annealing could further improve the near-infrared (NIR) shielding of Cs{sub x}WO{sub 3}. • Effects of N{sub 2} annealing on microstructure and NIR shielding of Cs{sub x}WO{sub 3} were studied. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} exhibited minimum O/W ratio and most oxygen vacancies. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} particles exhibited best NIR shielding properties.

  11. Effects of Pre-tempering on Intercritical Annealing in Fe-2Mn-0.3C Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Qing; Miyamoto, Goro; Yang, Zhi-Gang; Zhang, Chi; Furuhara, Tadashi

    2014-11-01

    As-quenched martensite was pre-tempered at 623 K and 923 K (350 °C and 650 °C), and then it reverted to austenite by intercritical annealing at 998 K (725 °C) in a Fe-2Mn-0.3C alloy. Pre-tempering at 623 K (350 °C) accelerates austenite formation, while pre-tempering at 923 K (650 °C) significantly retards it. It is proposed that austenite nucleation is accelerated by increasing the number density and particle size of cementite during tempering, whereas austenite growth is retarded by Mn enrichment in cementite during tempering at high temperature, leading to opposite effects of pre-tempering on reversion kinetics.

  12. Effect of self-ion irradiation on the microstructural changes of alloy EK-181 in annealed and severely deformed conditions

    NASA Astrophysics Data System (ADS)

    Aydogan, E.; Chen, T.; Gigax, J. G.; Chen, D.; Wang, X.; Dzhumaev, P. S.; Emelyanova, O. V.; Ganchenkova, M. G.; Kalin, B. A.; Leontiva-Smirnova, M.; Valiev, R. Z.; Enikeev, N. A.; Abramova, M. M.; Wu, Y.; Lo, W. Y.; Yang, Y.; Short, M.; Maloy, S. A.; Garner, F. A.; Shao, L.

    2017-04-01

    EK-181 is a low-activation ferritic/martensitic steel that is an attractive candidate for in-core component materials for both fast reactors and fusion reactors. To assess the effect of microstructural engineering on radiation response, two variants of EK-181 were studied: one in an annealed condition and the other subject to severe plastic deformation. These specimens were irradiated with 3.5 MeV Fe self-ions up to 400 peak displacements per atom (dpa) at temperatures ranging from 400 °C to 500 °C. The deformation did not suppress swelling over the whole irradiated region. Instead, deformed samples showed higher swelling in the near-surface region. Void swelling was found to be correlated with grain boundary instability. Significant grain growth occurred when steady-state void growth started.

  13. Band alignment of TiO{sub 2}/FTO interface determined by X-ray photoelectron spectroscopy: Effect of annealing

    SciTech Connect

    Fan, Haibo E-mail: liusz@snnu.edu.cn; Yang, Zhou; Ren, Xianpei; Gao, Fei; Yin, Mingli; Liu, Shengzhong E-mail: liusz@snnu.edu.cn

    2016-01-15

    The energy band alignment between pulsed-laser-deposited TiO{sub 2} and FTO was firstly characterized using high-resolution X-ray photoelectron spectroscopy. A valence band offset (VBO) of 0.61 eV and a conduction band offset (CBO) of 0.29 eV were obtained across the TiO{sub 2}/FTO heterointerface. With annealing process, the VBO and CBO across the heterointerface were found to be -0.16 eV and 1.06 eV, respectively, with the alignment transforming from type-I to type-II. The difference in the band alignment is believed to be dominated by the core level down-shift of the FTO substrate, which is a result of the oxidation of Sn. Current-voltage test has verified that the band alignment has a significant effect on the current transport of the heterojunction.

  14. GenAnneal: Genetically modified Simulated Annealing

    NASA Astrophysics Data System (ADS)

    Tsoulos, Ioannis G.; Lagaris, Isaac E.

    2006-05-01

    A modification of the standard Simulated Annealing (SA) algorithm is presented for finding the global minimum of a continuous multidimensional, multimodal function. We report results of computational experiments with a set of test functions and we compare to methods of similar structure. The accompanying software accepts objective functions coded both in Fortran 77 and C++. Program summaryTitle of program:GenAnneal Catalogue identifier:ADXI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXI_v1_0 Program available from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: The tool is designed to be portable in all systems running the GNU C++ compiler Installation: University of Ioannina, Greece on Linux based machines Programming language used:GNU-C++, GNU-C, GNU Fortran 77 Memory required to execute with typical data: 200 KB No. of bits in a word: 32 No. of processors used: 1 Has the code been vectorized or parallelized?: No No. of bytes in distributed program, including test data, etc.:84 885 No. of lines in distributed program, including test data, etc.:14 896 Distribution format: tar.gz Nature of physical problem: A multitude of problems in science and engineering are often reduced to minimizing a function of many variables. There are instances that a local optimum does not correspond to the desired physical solution and hence the search for a better solution is required. Local optimization techniques are frequently trapped in local minima. Global optimization is hence the appropriate tool. For example, solving a non-linear system of equations via optimization, employing a "least squares" type of objective, one may encounter many local minima that do not correspond to solutions (i.e. they are far from zero). Typical running time: Depending on the objective function. Method of solution: We modified the process of step selection that the traditional Simulated

  15. 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.

  16. Molecular beam epitaxy and properties of GaAsBi/GaAs quantum wells grown by molecular beam epitaxy: effect of thermal annealing.

    PubMed

    Makhloufi, Hajer; Boonpeng, Poonyasiri; Mazzucato, Simone; Nicolai, Julien; Arnoult, Alexandre; Hungria, Teresa; Lacoste, Guy; Gatel, Christophe; Ponchet, Anne; Carrère, Hélène; Marie, Xavier; Fontaine, Chantal

    2014-03-17

    We have grown GaAsBi quantum wells by molecular beam epitaxy. We have studied the properties of a 7% Bi GaAsBi quantum well and their variation with thermal annealing. High-resolution X-ray diffraction, secondary ion mass spectrometry, and transmission electron microscopy have been employed to get some insight into its structural properties. Stationary and time-resolved photoluminescence shows that the quantum well emission, peaking at 1.23 μm at room temperature, can be improved by a rapid annealing at 650°C, while the use of a higher annealing temperature leads to emission degradation and blue-shifting due to the activation of non-radiative centers and bismuth diffusion from the quantum well.

  17. Semantic search via concept annealing

    NASA Astrophysics Data System (ADS)

    Dunkelberger, Kirk A.

    2007-04-01

    Annealing, in metallurgy and materials science, is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. We define concept annealing as a lexical, syntactic, and semantic expansion capability (the removal of defects and the internal stresses that cause term- and phrase-based search failure) coupled with a directed contraction capability (semantically-related terms, queries, and concepts nucleate and grow to replace those originally deformed by internal stresses). These two capabilities are tied together in a control loop mediated by the information retrieval precision and recall metrics coupled with intuition provided by the operator. The specific representations developed have been targeted at facilitating highly efficient and effective semantic indexing and searching. This new generation of Find capability enables additional processing (i.e. all-source tracking, relationship extraction, and total system resource management) at rates, precisions, and accuracies previously considered infeasible. In a recent experiment, an order magnitude reduction in time to actionable intelligence and nearly three orderss magnitude reduction in false alarm rate was achieved.

  18. Effect of annealing on the microwave characteristics of carbon nanotubes and the nanocomposite materials based on them

    NASA Astrophysics Data System (ADS)

    Usanov, D. A.; Skripal', A. V.; Romanov, A. V.

    2014-06-01

    Transmission and reflection spectra of electromagnetic microwave radiation are used to determine the complex permittivity of the composite materials consisting of a dielectric matrix and multiwalled carbon nanotubes subjected to high-temperature annealing in an inert atmosphere. The dependence of the electrical conductivity of multiwalled carbon nanotubes on the annealing temperature in an inert atmosphere is shown to be nonmonotonic.

  19. Effect of annealing treatment on the photocatalytic activity of TiO2 thin films deposited by dc reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Arias, L. M. Franco; Arias Duran, A.; Cardona, D.; Camps, E.; Gómez, M. E.; Zambrano, G.

    2015-07-01

    Titanium dioxide (TiO2) thin films have been deposited by DC reactive magnetron sputtering on silicon and quartz substrates with different Ar/O2 ratios in the gas mixture. Substrate temperature was kept constant at 400 °C during the deposition process, and the TiO2 thin films were later annealed at 700 °C for 3 h. The effect of the Ar/O2 ratio in the gas flow and the annealing treatment on the phase composition, deposition rate, crystallinity, surface morphology and the resulting photocatalytic properties were investigated. For photocatalytic measurements, the variation of the concentration of the methylene blue (MB) dye under UV irradiation was followed by a change in the intensity of the characteristic MB band in the UV- Vis transmittance spectra. We report here that the as-grown TiO2 films showed only the anatase phase, whereas after annealing, the samples exhibited both the anatase and rutile phases in proportions that varied with the Ar/O2 ratio in the mixture of gases used during growth. In particular, the annealed TiO2 thin film deposited at a 50/50 ratio of Ar/O2, composed of both anatase (80%) and rutile phases (20%), exhibited the highest photocatalytic activity (30% of MB degradation) compared with the samples without annealing and composed of only the anatase phase.

  20. 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.

  1. Annealing effect on the structural and optical properties of Cr/α-Cr2O3 monodispersed particles based solar absorbers

    NASA Astrophysics Data System (ADS)

    Khamlich, S.; McCrindle, R.; Nuru, Z. Y.; Cingo, N.; Maaza, M.

    2013-01-01

    A cost-effective and environmentally friendly green chemical method, the so-called aqueous chemical growth (ACG) method, was used to deposit chromium/alpha-chromium(III) oxide, Cr/α-Cr2O3, monodispersed particles, for solar absorbers applications. The deposited particles were annealed at various temperatures in a hydrogen atmosphere for 2 h to study the annealing temperature dependence of the structural, chemical and optical properties of the particles grown on tantalum substrates. The deposited Cr/α-Cr2O3 was characterized by X-ray diffraction (XRD), attenuated total reflection (ATR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and diffuse reflectance UV-vis-NIR spectroscopy. The XRD and ATR analysis indicated that by increasing annealing temperature, the particles crystallinity was improved and Ta2O5 was formed around 600 °C, due to the fast oxygen diffusion from the deposited α-Cr2O3 toward the tantalum substrate. The optical measurements show that samples annealed at 400 and 500 °C exhibit the targeted high absorbing optical characteristics of "Black chrome", while those annealed below 400 °C and above 500 °C show a significant low absorptivity and high emissivity.

  2. Effects of drying, heating, annealing, and roasting on carbonate skeletal material, with geochemical and diagenetic implications

    NASA Astrophysics Data System (ADS)

    Gaffey, Susan J.; Kolak, Jonathan J.; Bronnimann, Charles E.

    1991-06-01

    Carbonate skeletons subjected to drying, heating, annealing, or roasting at elevated temperatures as part of routine sample preparation for chemical analyses or geochemical experiments differ significantly from skeletal materials as they occur in nature. Heating of skeletal samples can degrade organic material, expel H 2O and OH -, reduce the concentration of some trace elements, and change the mineralogy and texture of the material. Thermal degradation of organics and expulsion of water in inclusions, which can occur at temperatures of 100-105°C, cause fracturing and pitting of skeletal samples; areas of pitting reflect original concentrations of volatile phases within the skeleton. Coralline aragonites are partially or completely altered to calcite at temperatures of 150°C or higher; the degree of alteration varies with temperature and duration of heating, and genus of the coral. High Mg calcites (HMCs) tend to form calcian dolomite and multiple HMCs of lower Mg content on heating, but the rate of alteration is related to the taxonomic group rather than the Mg content; echinoids alter very rapidly (dolomite detectable by X-ray diffraction formed in Clypeaster heated for 6 h at 200°C), while the coralline red alga Neogoniolithon showed no alteration after heating at 400°C for 23 h. Mineralogical alteration of coralline aragonites and echinoid HMCs is positively correlated with water loss. Skeletal carbonates comprise a very diverse and heterogeneous suite of materials, and their diversity and heterogeneity are reflected in their responses to heating. Variations in rate and degree of alteration on heating, in many cases between different subsamples of material produced by the same organism, make it difficult to obtain a consistent product from heat treatment. Many workers have used high temperature experiments to model diagenetic processes, and the results of this study have implications for diagenetic alteration as well as for laboratory analyses and

  3. 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

  4. Rietveld analysis of the effect of annealing atmosphere on phase evolution of nanocrystalline TiO2 powders.

    PubMed

    Salari, M; Rezaee, M; Chidembo, A T; Konstantinov, K; Liu, H K

    2012-06-01

    The structural evolution of nanocrystalline TiO2 was studied by X-ray diffraction (XRD) and the Rietveld refinement method (RRM). TiO2 powders were prepared by the sol-gel technique. Post annealing of as-synthesized powders in the temperature range from 500 degrees C to 800 degrees C under air and argon atmospheres led to the formation of TiO2 nanoparticles with mean crystallite size in the range of 37-165 nm, based on the Rietveld refinement results. It was found that the phase structure, composition, and crystallite size of the resulting particles were dependent on not only the annealing temperature, but also the annealing atmosphere. Rietveld refinement of the XRD data showed that annealing the powders under argon atmosphere promoted the polymorphic phase transformation from anatase to rutile. Field emission scanning electron microscopy (FESEM) was employed to investigate the morphology and size of the annealed powders.

  5. Effect of annealing on the properties of Sb doped ZnO thin films prepared by spray pyrolysis technique

    SciTech Connect

    Kumar, N. Sadananda; Bangera, Kasturi V.; Shivakumar, G. K.

    2014-01-28

    Sb doped ZnO thin films have been deposited on glass substrate at 450°C using spray pyrolysis technique. The X-ray diffraction studies revealed that the as deposited films are polycrystalline in nature with (100) preferred orientation. Whereas the films annealed at 450° C for 6h show a preferential orientation along (101) direction. Crystallites size varies from 15.7 nm to 34.95 nm with annealing duration. The Scanning electron microscopic analysis shows the plane and smooth surface of the films. The optical properties of annealed films have shown a variation in the band gap between 3.37 eV and 3.19 eV. Transparency of as grown and annealed films decreases from 78 % to 65% respectively in the visible region. The electrical conductivity of the as grown film shows an increase in the electrical conductivity by one order of magnitude with increase in the annealing duration.

  6. Effects of post-deposition vacuum annealing on film characteristics of p-type Cu2O and its impact on thin film transistor characteristics

    NASA Astrophysics Data System (ADS)

    Han, Sanggil; Niang, Kham M.; Rughoobur, Girish; Flewitt, Andrew J.

    2016-10-01

    Annealing of cuprous oxide (Cu2O) thin films in vacuum without phase conversion for subsequent inclusion as the channel layer in p-type thin film transistors (TFTs) has been demonstrated. This is based on a systematic study of vacuum annealing effects on the sputtered p-type Cu2O as well as the performance of TFTs on the basis of the crystallographic, optical, and electrical characteristics. It was previously believed that high-temperature annealing of Cu2O thin films would lead to phase conversion. In this work, it was observed that an increase in vacuum annealing temperature leads to an improvement in film crystallinity and a reduction in band tail states based on the X-ray diffraction patterns and a reduction in the Urbach tail, respectively. This gave rise to a considerable increase in the Hall mobility from 0.14 cm2/V.s of an as-deposited film to 28 cm2/V.s. It was also observed that intrinsic carrier density reduces significantly from 1.8 × 1016 to 1.7 × 1013 cm-3 as annealing temperature increases. It was found that the TFT performance enhanced significantly, resulting from the improvement in the film quality of the Cu2O active layer: enhancement in the field-effect mobility and the on/off current ratio, and a reduction in the off-state current. Finally, the bottom-gate staggered p-type TFTs using Cu2O annealed at 700 °C showed a field-effect mobility of ˜0.9 cm2/V.s and an on/off current ratio of ˜3.4 × 102.

  7. Thermal effect on the optical and morphological properties of TiO2 thin films obtained by annealing a Ti metal layer

    NASA Astrophysics Data System (ADS)

    Butt, M. A.; Fomchenkov, S. A.

    2017-01-01

    Titanium metal layers of different thicknesses were deposited on optical glass, quartz and ceramic at 50 °C and 150 °C substrate temperatures with the help of magnetron deposition. The metal layers were converted into a rutile phase of TiO2 at different annealing temperatures. The effect of thermal annealing on the morphology and the refractive index of the thin film was investigated. The film's quality and roughness were found to depend on the substrate's temperature during metal film deposition and on the annealing temperature. The TiO2 thin films obtained on ceramic and glass substrates were seem to show less surface roughness at low substrate temperature as compared to the quartz substrate.

  8. Effects of annealing on electrical performance of multilayer MoS2 transistors with atomic layer deposited HfO2 gate dielectric

    NASA Astrophysics Data System (ADS)

    Wen, Ming; Xu, Jingping; Liu, Lu; Lai, Pui-To; Tang, Wing-Man

    2016-09-01

    Atomic layer deposited HfO2 annealed in different ambients (N2, O2, and NH3) is used to replace SiO2 as a gate dielectric for fabricating back-gated multilayer MoS2 transistors. Excellent electrical properties such as a mobility of 15.1 cm2/(V·s), an on/off ratio exceeding 107, and a hysteresis of 0.133 V are achieved for samples annealed in NH3 at 400 °C for 10 min. This is caused by the NH3 annealing passivation effects that reduce defective states in the HfO2 dielectric and the interface. The capacitance equivalent thickness is only 7.85 nm, which is quite small for a back-gated MoS2 transistor and is conducive to the scaling down of the device.

  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. Thermal annealing effect of on optical constants of vacuum evaporated Se 75S 25-xCd x chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Khan, Shamshad A.; Lal, J. K.; Al-Ghamdi, A. A.

    2010-07-01

    Chalcogenide glasses are interesting materials due to their infrared transmitting properties and photo induced effects exhibited by them. Thin films with thickness of 3000 Å of the glasses Se 75S 25-xCd x with x=6, 8 and 10 at% prepared by melt quench technique were evaporated by thermal evaporation onto glass substrates under a vacuum of 10 -6 Torr. The optical constants (absorption coefficient, refractive index and extinction coefficient) of as-prepared and annealed films have been studied as a function of photon energy in the wave length region 400-1000 nm. Analysis of the optical absorption data shows that the rule of non-direct transitions predominates. It has been found that the absorption coefficient and optical band gap increase with increasing annealing temperatures. The refractive index ( n) and the extinction coefficient ( k) were observed to decrease with increasing annealing temperature.

  11. Study on the effect of heat-annealing and irradiation on spectroscopic properties of Bi:alpha-BaB2O4 single crystal.

    PubMed

    Xu, Jun; Zhao, Hengyu; Su, Liangbi; Yu, Jun; Zhou, Peng; Tang, Huili; Zheng, Lihe; Li, Hongjun

    2010-02-15

    The absorption, excitation, and ultrabroadband near-infrared luminescence spectra of Bismuth were investigated in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4)(alpha-BBO) single crystals, respectively. Energy-level diagrams of the near-infrared luminescent centers were fixed. The electronic transition energies of near-infrared active centers are basically consistent with the multiplets of free Bi(+) ions. The minor difference of the energy-level diagrams of Bi(+) ions in H(2)-annealed and gamma-irradiated Bi:alpha-BaB(2)O(4) crystals can be ascribed to the difference of the local lattice environments. The involved physical and chemical processes were discussed. The effect of Ar-, air-annealing and electron-irradiation on Bi:alpha-BaB(2)O(4) crystal were also investigated.

  12. EFFECT OF PRE-ANNEALING TEMPERATURE ON THE GROWTH OF ALIGNED α-Fe2O3 NANOWIRES VIA A TWO-STEP THERMAL OXIDATION

    NASA Astrophysics Data System (ADS)

    Rashid, Norhana Mohamed; Kishi, Naoki; Soga, Tetsuo

    2016-03-01

    Pre-annealing as part of a two-step thermal oxidation process has a significant effect on the growth of hematite (α-Fe2O3) nanowires on Fe foil. High-density aligned nanowires were obtained on iron foils pre-annealed at 300∘C under a dry air flow for 30min. The X-ray diffraction (XRD) patterns indicate that the nanowires are transformed from the small α-Fe2O3 grains and uniquely grow in the (110) direction. The formation of a high-density of small grains by pre-annealing improved the alignment and density of the α-Fe2O3 nanowires.

  13. Effect of post-growth rapid thermal annealing on bilayer InAs/GaAs quantum dot heterostructure grown with very thin spacer thickness

    SciTech Connect

    Sengupta, S.; Halder, N.; Chakrabarti, S.

    2010-11-15

    We have investigated the effect of post-growth rapid thermal annealing on self-assembled InAs/GaAs bilayer quantum dot samples having very thin barrier thickness (7.5-8.5 nm). In/Ga interdiffusion in the samples due to annealing is presumed to be controlled by the vertical strain coupling from the seed dots in bilayer heterostructure. Strain coupling from embedded seed QD layer maintains a strain relaxed state in active top islands of the bilayer quantum dot sample grown with comparatively thick spacer layer (8.5 nm). This results in minimum In/Ga interdiffusion. However controlled interdiffusion across the interface between dots and GaAs barrier, noticeably enhances the emission efficiency in such bilayer quantum dot heterostructure on annealing up to 700 {sup o}C.

  14. 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.

  15. The effect of millisecond flash lamp annealing on electrical and structural properties of ZnO:Al/Si structures

    NASA Astrophysics Data System (ADS)

    Lindberg, P. F.; Lipp Bregolin, F.; Wiesenhütter, K.; Wiesenhütter, U.; Riise, H. N.; Vines, L.; Prucnal, S.; Skorupa, W.; Svensson, B. G.; Monakhov, E. V.

    2016-05-01

    The effect of millisecond flash lamp annealing (FLA) on aluminum doped ZnO (AZO) films and their interface with Si have been studied. The AZO films were deposited by magnetron sputtering on Si (100) substrates. The electrical and structural properties of the film and AZO/Si structures were characterized by current-voltage, capacitance-voltage, and deep level transient spectroscopy measurements, X-ray diffraction, and secondary ion mass spectrometry. The resistivity of the AZO film is reduced to a close to state-of-the-art value of 2 × 10-4 Ω cm after FLA for 3 ms with an average energy density of 29 J/cm2. In addition, most of the interfacial defects energy levels are simultaneously annealed out, except for one persisting shallow level, tentatively assigned to the vacancy-oxygen complex in Si, which was not affected by FLA. Subsequent to the FLA, the samples were treated in N2 or forming gas (FG) (N2/H2, 90/10%mole) ambient at 200-500 °C. The latter samples maintained the low resistivity achieved after the FLA, but not the former ones. The interfacial defect level persisting after the FLA is removed by the FG treatment, concurrently as another level emerges at ˜0.18 eV below the conduction band. The electrical data of the AZO films are discussed in term of point defects controlling the resistivity, and it is argued that the FLA promotes formation of electrically neutral clusters of Zink vacancies (VZn's) rather than passivating/compensating complexes between the Al donors and VZn's.

  16. Effects of hydrogen, oxygen, and argon annealing on the electrical properties of ZnO and ZnO devices studied by current-voltage, deep level transient spectroscopy, and Laplace DLTS

    NASA Astrophysics Data System (ADS)

    Mtangi, W.; Auret, F. D.; Meyer, W. E.; Legodi, M. J.; Janse van Rensburg, P. J.; Coelho, S. M. M.; Diale, M.; Nel, J. M.

    2012-05-01

    Effects of annealing ZnO in hydrogen, oxygen, and argon have been investigated using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS) measurements. Current-voltage (IV) measurements indicate a decrease in zero-bias barrier height for all the annealed samples. Conventional DLTS measurements reveal the presence of three prominent peaks in the un-annealed and annealed samples. A new peak with an activation enthalpy of 0.60 eV has been observed in the H2 annealed samples, while an estimated energy level of 0.67 eV has been observed in Ar annealed samples. O2 annealing does not introduce new peaks but causes a decrease in the concentration of the E3 peak and an increase in concentration of the E1 peak. The concentrations of all the intrinsic defects have decreased after H2 and Ar annealing; with Ar annealing giving peaks with the lowest concentrations. The E2 peak anneals out after annealing ZnO in Ar and H2 at 300 °C. From the annealing behaviour of E3, we have attributed to transition metal ion related defects, while E4 has been explained as a defect, whose formation favours oxygen deficient conditions. Laplace DLTS has successfully been employed to resolve the closely spaced energy levels in the E4 peak, splitting it into three peaks with energy levels, 0.68 eV, 0.58 eV, and 0.50 eV below the minimum of the conduction band for the Ar annealed sample.

  17. Effects of thickness and annealing condition on magnetic properties and thermal stabilities of Ta/Nd/NdFeB/Nd/Ta sandwiched films

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Feng; Zhang, Min-Gang; Zhang, Ke-Wei; Zhang, Hai-Jie; Xu, Xiao-Hong; Chai, Yue-Sheng

    2016-11-01

    Ta/Nd/NdFeB/Nd/Ta sandwiched films are deposited by magnetron sputtering on Si (100) substrates, and subsequently annealed in vacuum at different temperatures for different time. It is found that both the thickness of NdFeB and Nd layer and the annealing condition can affect the magnetic properties of Ta/Nd/NdFeB/Nd/Ta films. Interestingly, the thickness and annealing temperature show the relevant behaviors that can affect the magnetic properties of the film. The high coercivity of 24.1 kOe (1 Oe = 79.5775 A/m) and remanence ratio (remanent magnetization/saturation magnetization) of 0.94 can be obtained in a Ta/Nd(250 nm)/NdFeB(600 nm)/Nd(250 nm)/Ta film annealed for 3 min at 1023 K. In addition, the thermal stability of the film is also linked to the thickness of NdFeB and Nd layer and the annealing temperature as well. The excellent thermal stability can be achieved in a Ta/Nd(250 nm)/NdFeB(600 nm)/Nd(250 nm)/Ta film annealed at 1023 K. Program supported by the National Natural Science Foundation of China (Grant No. 51305290), the Higher Education Technical Innovation Project of Shanxi Province, China (Grant No. 2013133), the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals of Shanxi Province, China (Grant No. 2015003), and the Program for the Key Team of Scientific and Technological Innovation of Shanxi Province, China (Grant No. 2013131009).

  18. The annealing influence onto the electrical and magnetic behavior of magnetoresistive/insulator system

    NASA Astrophysics Data System (ADS)

    Ahmed, A. M.; Mohamed, Abd El-Mo'ez A.; Mohamed, H. F.; Diab, A. K.; Mohamed, Aml M.; Mazen, A. E. A.

    2016-09-01

    This investigation is mainly concerned with the effect of annealing temperature (600, 700, 800, and 900 °C) in air for (La0.7Ba0.3MnO3)1-x/(NiO)x with x = 0 and x = 0.10 samples. It was shown that the annealing temperature does not affect the structure and parameters of rhombohedral lattice of the samples. However, it is observed that the annealing treatment has a notable effect on the electrical resistivity and the metal-semiconductor transition temperature Tms. Temperature dependent magnetization measurements showed a decrease in Curie temperature TC with annealing temperature. In the same time, annealing process decreases the magnetoresistance of La0.7Ba0.3MnO3, in contrast to (La0.7Ba0.3MnO3)0.9/(NiO)0.1 composite.

  19. Effect of Annealing Temperature on Microstructure and Mechanical Properties of Hot Swaged cp-Ti Produced by Investment Casting

    NASA Astrophysics Data System (ADS)

    Ibrahim, Khaled M.; Mhaede, Mansour; Wagner, Lothar

    2012-01-01

    The purpose of this study is to evaluate the influence of hot swaging (SW) and annealing treatment on microstructure and mechanical properties of commercially pure titanium (grade 4) produced by investment casting. During SW at 700 °C, the diameter of the cast titanium bars was reduced from 25 to 8.5 mm in 14 steps. After SW, material was annealed for 1 h at 500, 700, or 870 °C. The as-cast samples showed a typical microstructure consisting of a variety of α-morphologies, while the hot swaged samples exhibited a kinked lamellar microstructure. Annealing at 500 °C did not significantly change this microstructure, while annealing at both 700 and 870 °C led to recrystallization and formation of equiaxed microstructures. The cast bars exhibited a typical hard α-layer in near-surface regions with maximum depth and maximum hardness of 720 μm and 660 HV0.5, respectively. Due to SW, the tensile strength of the as-cast material drastically increased from 605 to 895 MPa. Annealing at 500 °C decreased this tensile strength slightly from 895 to 865 MPa while annealing at 700 °C led to a further pronounced drop in tensile strength from 865 to 710 MPa. No additional decrease in tensile strength was observed by increasing the annealing temperature from 700 to 870 °C. The tensile ductility of the as-cast and hot swaged samples was approximately the same in the range of 0.05 to 0.11, while the annealed samples showed values in the range of 0.25 to 0.53. In addition, the as-cast and hot swaged samples revealed a brittle cleavage fracture surfaces. However, the annealed samples showed a transgranular ductile fracture with formation of dimples.

  20. Effect of oxygen annealing on the multiferroic properties of Ca{sup 2+} doped BiFeO{sub 3} nanoceramics

    SciTech Connect

    Tirupathi, Patri; Mandal, Satish Kumar; Chandra, Amreesh

    2014-12-28

    The high leakage current in divalent ion doped BiFeO{sub 3} systems is limiting their large scale application. It is clearly shown that the methodology of oxygen annealing will prove to be an effective procedure for suppressing the detrimental consequences that originate from the oxygen vacancies. The samples annealed under oxygen also show different particle morphologies and packing density that can help in tuning the relevant physical properties, viz., magnetic, ferroelectric, and magnetoelectric. The difference in magnetic behaviour in samples annealed in air and oxygen can be explained in terms of the modification in the Fe-O-Fe bonds, domain wall pinning centres, and crystal anisotropy. Another important observation is the stabilization of a dielectric anomaly near the magnetic transition temperature. This observation can make this multiferroic system very interesting for application in sensors where the change in the magnetic parameters can be observed by monitoring the electrical parameters. Detailed analysis of the dielectric and impedance curves indicate towards the presence of non-Debye type processes in samples obtained by annealing in air or oxygen. From the calculated activation energy values, the vacancy related relaxation mechanism is predominant in air annealed samples, while the oxygen annealed samples show the presence of two type of relaxation processes, viz., electron hopping mechanism stabilizes at low temperature while, at higher temperatures, the process associated with the diffusion of doubly ionized oxygen ions predominates. The ac-conductivity data suggests that the correlated barrier tunnelling mechanism, where single electron or two electrons hopping through neighbouring lattice sites leads to ac-conduction.

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

    PubMed

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

    2004-04-28

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

  2. The kinetics of swelling in block copolymer thin films during ``solvo-microwave'' and solvo-thermal annealing: The effect of vapour pressure

    NASA Astrophysics Data System (ADS)

    Mokarian-Tabari, Parvanrh; Collins, Timothy; Cummins, Cian; Delgado Simão, Claudia; Sotomayor, Clivia; Morris, Michael A.

    2015-03-01

    Long annealing time associated with high chi block copolymers is a major disadvantage for their integration in industrial applications. Microwave-assisted microphase separation appears to offer considerable benefits in reducing annealing times for BCPs. However, despite the promise of this technique, little is known about the mechanism of how microwave irradiation might sponsor the molecular motion that accompanies microphase separation. In our earlier work we carried out an in situ temperature measurement during ``solvo-microwave'' annealing of poly(styrene-b-lactic acid) (PS- b-PLA) in presence of THF and also in the conventional oven. Comparing the results indicated that vapour pressure of THF might have a major role to achieve fast self- assembly (60 seconds) in PS- b-PLA film. Here, we study the kinetics of swelling by monitoring the pressure through in situ pressure experiments during ``solvo-microwave'' and solvo-thermal annealing. The preliminary data suggest that the rate at which the THF pressure increases is the key factor. This suggests that kinetics, i.e., the rate of film swelling and diffusion, affects the order and the coherence length of the pattern. We estimated the defect density in the patterns by our recently developed defect analysis software.

  3. Effects of Rapid Thermal Annealing and Different Oxidants on the Properties of LaxAlyO Nanolaminate Films Deposited by Atomic Layer Deposition.

    PubMed

    Fei, Chenxi; Liu, Hongxia; Wang, Xing; Zhao, Lu; Zhao, Dongdong; Feng, Xingyao

    2017-12-01

    A comparative study of different sequences of two metal precursors [trimethylaluminum (TMA) and Tris(isopropylcyclopentadienyl) lanthanum (La((i)PrCp)3)] for atomic layer deposition (ALD) lanthanum aluminum oxide (LaxAlyO) films is carried out. The percentage compositions of C and N impurity of LaxAlyO films were investigated using in situ X-ray photoelectron spectroscopy (XPS). The effects of different oxidants on the physical and chemical properties and electrical characteristics of LaxAlyO films are studied before and after annealing. Preliminary testing results indicate that the impurity level of LaxAlyO films grown with different oxidants can be well controlled before and after annealing. Analysis indicates the rapid thermal annealing (RTA) and kinds of oxidants have significant effects on the equivalent oxide thickness (EOT), dielectric constant, electrical properties, and stability of LaxAlyO films. Additionally, the change of chemical bond types of rapid thermal annealing effects on the properties of LaxAlyO films are grown with different oxidants also investigated by XPS.

  4. Classical Simulated Annealing Using Quantum Analogues

    NASA Astrophysics Data System (ADS)

    La Cour, Brian R.; Troupe, James E.; Mark, Hans M.

    2016-08-01

    In this paper we consider the use of certain classical analogues to quantum tunneling behavior to improve the performance of simulated annealing on a discrete spin system of the general Ising form. Specifically, we consider the use of multiple simultaneous spin flips at each annealing step as an analogue to quantum spin coherence as well as modifications of the Boltzmann acceptance probability to mimic quantum tunneling. We find that the use of multiple spin flips can indeed be advantageous under certain annealing schedules, but only for long anneal times.

  5. Laser annealing of silicon surface defects for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Sun, Zeming; Gupta, Mool C.

    2016-10-01

    High power lasers are increasingly used for low cost fabrication of solar cell devices. High power laser processes generate crystal defects, which lower the cell efficiency. This study examines the effect of low power laser annealing for the removal of high power laser induced surface defects. The laser annealing behavior is demonstrated by the significant decrease of photoluminescence generated from dislocation-induced defects and the increase of band-to-band emission. This annealing effect is further confirmed by the X-ray diffraction peak reversal. The dislocation density is quantified by observing etch pits under the scanning electron microscope (SEM). For as-melted samples, the dislocation density is decreased to as low as 1.01 × 106 cm- 2 after laser annealing, resulting in an excellent surface carrier lifetime of 920 μs that is comparable to the value of 1240 μs for the silicon starting wafer. For severely defective samples, the dislocation density is decreased by 4 times and the surface carrier lifetime is increased by 5 times after laser annealing.

  6. Thermal Quantum Annealing on the D-Wave device

    NASA Astrophysics Data System (ADS)

    Mishra, Anurag; Vinci, Walter; Albash, Tameem; Warburton, Paul; Lidar, Daniel

    2014-03-01

    We report on new experimental results supporting previous work concluding that the D-Wave processor implements quantum annealing. We introduce techniques adopted to the D-Wave programmable annealer to correct for systematic fabrication and control errors. Correcting for systematic errors allows us to explore the behavior of the annealer at low energy scales, which were previously inaccessible. We describe the behavior of the annealer as we investigate the effect of thermal noise on the programmed Ising Hamiltonian. Thermal noise becomes dominant when we scale down the overall energy of the final-time Ising Hamiltonian, or increase the total annealing time. We found three qualitatively different thermal noise regimes; a high energy scale where ground state statistics dominates, a moderate noise regime regime where low lying excited states contribute, and a high thermal noise regime where the system dynamics are dominated by thermalization effects. The qualitative results are robust to increasing the size (number of qubits) of the benchmark Hamiltonian. We additionally investigated auto-correlations in the final state statistics.

  7. Effect of particle size and annealing on spin and phonon behavior in TbMnO3

    NASA Astrophysics Data System (ADS)

    Das, Raja; Jaiswal, Adhish; Adyanthaya, Suguna; Poddar, Pankaj

    2011-03-01

    Interest has grown to study TbMnO3 as it was recently reported to show a gigantic magnetoelectric effect. Here, we report the synthesis and detailed magnetic and Raman spectroscopy study on TbMnO3 particles of size ˜25 nm and 2-3 μm, respectively. The incommensurate-commensurate (lock-in) transition, usually observed at 27 K for bulk phase of TbMnO3 was not observed in susceptibility versus T curve but was seen at 30 K in the coercivity versus T curve in ˜25 nm particles. This transition, which is due to the spin modulation length scale, gets weakened in nanosize due to the increased intrinsic lattice strain observed in 2-3 μm particles, due to the effect of increased particle size. The increased value of magnetization in the 2-3 μm sample was attributed to double exchange interactions between Mn+3 and Mn+4 spins. The role of annealing related effects on the fate of the Néel temperature for TbMnO3 was investigated. Raman spectroscopy indicated a decrease in the lattice distortion for ˜25 nm particles.

  8. Effect of annealing on Cu precipitates in H ion irradiated Fe-0.6%Cu studied by positron annihilation

    NASA Astrophysics Data System (ADS)

    Jin, Shuoxue; Zhang, Peng; Lu, Eryang; Wang, Baoyi; Yuan, Daqing; Wei, Long; Cao, Xingzhong

    2016-10-01

    Fe-0.6%Cu alloy was irradiated with H ions to 0.1 dpa, and then annealed for 30 min from 150 °C to 500 °C. We focused the evolution of Cu precipitates in irradiated Fe-0.6%Cu alloy after the isochronal annealing from the perspective of positron annihilation. The ΔW parameters after thermal annealing (400 °C and 500 °C) were much larger than that induced by 0.1 dpa H irradiation. Annealing could promote the aggregation of the Cu-vacancy complexes, and form the Cu cluster-vacancies complexes. When the vacancy-like defects recovered around 500 °C, it meant the formation and growing of the defect-free Cu precipitates.

  9. Structural characterization of Peruvian carrot (Arracacia xanthorrhiza) starch and the effect of annealing on its semicrystalline structure.

    PubMed

    Rocha, Thais S; Cunha, Verena A G; Jane, Jay-Lin; Franco, Celia M L

    2011-04-27

    Structural characteristics of native and annealed Peruvian carrot (Arracacia xanthorrhiza) starches were determined and compared to those of cassava and potato starches. Peruvian carrot starch presented round and irregular shaped granules, low amylose content and B-type X-ray pattern. Amylopectin of this starch contained a large proportion of long (DP > 37) and short (DP 6-12) branched chains. These last ones may contribute to its low gelatinization temperature. After annealing, the gelatinization temperatures of all starches increased, but the ΔH and the crystallinity increased only in Peruvian carrot and potato starches. The annealing process promoted a higher exposure of Peruvian carrot amylose molecules, which were more quickly attacked by enzymes, whereas amylopectin molecules became more resistant to hydrolysis. Peruvian carrot starch had structural characteristics that differed from those of cassava and potato starches. Annealing affected the semicrystalline structure of this starch, enhancing its crystallinity, mainly due to a better interaction between amylopectin chains.

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

    SciTech Connect

    Dai, Chong-Chong; Zhou, Tian-Yu; 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.

  11. Effect of annealing on the interfacial Dzyaloshinskii-Moriya interaction in Ta/CoFeB/MgO trilayers

    NASA Astrophysics Data System (ADS)

    Khan, R. A.; Shepley, P. M.; Hrabec, A.; Wells, A. W. J.; Ocker, B.; Marrows, C. H.; Moore, T. A.

    2016-09-01

    The interfacial Dzyaloshinskii-Moriya interaction (DMI) has been shown to stabilize homochiral Néel-type domain walls in thin films with perpendicular magnetic anisotropy, and as a result, permit them to be propagated by a spin Hall torque. In this study, we demonstrate that in Ta/Co20Fe60B20/MgO, the DMI may be influenced by annealing. We find that the DMI peaks at D = 0.057 ± 0.003 mJ/m2 at an annealing temperature of 230 °C. DMI fields were measured using a purely field-driven creep regime domain expansion technique. The DMI field and the anisotropy field follow a similar trend as a function of annealing temperature. We infer that the behavior of the DMI and the anisotropy are related to interfacial crystal ordering and B expulsion out of the CoFeB layer as the annealing temperature is increased.

  12. Rapid thermal annealing effects on the electrical and structural properties of Ru/V/n-InP Schottky barrier diode

    NASA Astrophysics Data System (ADS)

    Padma, R.; Shanthi Latha, K.; Rajagopal Reddy, V.; Choi, Chel-Jong

    2015-07-01

    A Ru/V/n-InP Schottky barrier diode (SBD) is fabricated and investigated its electrical and structural properties as a function of annealing temperature. Measurements showed that the barrier height (BH) of the as-deposited Ru/V/n-InP SBD is found to be 0.83 eV (I-V) and 1.03 eV (C-V). Experimental results indicate that the SBD with high BH and low ideality factors (0.87 eV (I-V), 1.20 eV (C-V), and 1.12) can be achieved after annealing at 400 °C for 1 min in N2 atmosphere. Further, it is observed that the BH slightly decreases to 0.85 eV (I-V) and 1.09 eV (C-V) upon annealing at 500 °C. The BH, ideality factor and series resistance are also determined by Cheung's functions and Norde method. Further, the energy distribution of interface state density of Ru/V/n-InP SBD is calculated from the forward bias I-V characteristics as a function of annealing temperature. It is found that the interface state density decreases upon annealing at 400 °C and then slightly increases after annealing at 500 °C. The AES and XRD results revealed that the formation of indium phases at the Ru/V/n-InP interface could be the reason for the increase of BH upon annealing at 400 °C. The formation of phosphide phases at the interface may be the cause for the decrease of BH after annealing at 500 °C. The overall surface morphology of Ru/V Schottky contacts is considerably smooth at elevated temperatures.

  13. Effect of annealing temperature on structural and electrical properties of high-κ YbTixOy gate dielectrics for InGaZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Pan, Tung-Ming; Chen, Fa-Hsyang; Hung, Meng-Ning

    2015-01-01

    This paper describes the effect of annealing temperature on the structural properties and electrical characteristics of high-κ YbTixOy gate dielectrics for indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs). X-ray diffraction, x-ray photoelectron spectroscopy and atomic force microscopy were used to study the structural, chemical and morphological features, respectively, of these dielectric films annealed at 200, 300 and 400 °C. The YbTixOy IGZO TFT that had been annealed at 400 °C exhibited better electrical characteristics, such as a small threshold voltage of 0.53 V, a large field-effect mobility of 19.1 cm2 V-1 s-1, a high Ion/Ioff ratio of 2.8 × 107, and a low subthreshold swing of 176 mV dec.-1, relative to those of the systems that had been subjected to other annealing conditions. This result suggests that YbTixOy dielectric possesses a higher dielectric constant as well as lower oxygen vacancies (or defects) in the film. In addition, the instability of YbTixOy IGZO TFT was studied under positive gate-bias stress and negative gate-bias stress conditions.

  14. Effects of post annealing on structural, electrical and optical properties of ZnO:Al thin films prepared by RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Ma, Jianhua; Liang, Yan; Yao, Niangjuan; Zhu, Xiaojing; Jiang, Jinchun; Chu, Junhao

    2013-12-01

    Al doped ZnO (ZnO:Al, AZO) thin films were deposited on ordinary soda-lime glass (SLG) substrates by RF magnetron sputtering. Effects of post annealing (300~600 °C for 2~30 min in air and N2, respectively) were studied. All the films were wurtzite structure with highly c-axis preferential orientation. Their electrical properties were relatively stable at the post annealing temperature of 300 °C. As the temperature further increasing, post annealing in air leaded to drastic degradation in the electrical properties, while that in N2 had relatively small influence. Diffusion of alkali ions from SLG substrates was deduced to be one of the influence factors for electrical properties. The spectra measurements showed that the post annealing mainly affected the transmittance in the near-infrared and infrared (NIR-IR) range and the optical band gap (Eg). The variation of Eg was attributed to the Burstein-Moss (BM) shift modulated by many-body effects.

  15. Effect of thermal annealing on the structural and optical properties of tris-(8-hydroxyquinoline)aluminum(III) (Alq3 ) films.

    PubMed

    Cuba, M; Muralidharan, G

    2015-05-01

    Tris-(8-hydroxyquionoline)aluminum (Alq3 ) was synthesized and coated on to a glass substrate using the dip coating method. The structural and optical properties of the Alq3 film after thermal annealing from 50°C to 300°C in 50° steps was studied. The films have been prepared with 2 to 16 layers (42-324 nm). The thickness and thermal annealing of Alq3 films were optimized for maximum luminescence yield. The Fourier transform infrared spectrum confirms the formation of quinoline with absorption in the region 700 - 500/cm. Partial sublimation and decomposition of quinoline ion was observed with the Alq3 films annealed at 300°C. The X-ray diffraction pattern of the Alq3 film annealed at 50°C to 150°C reveals the amorphous nature of the films. The Alq3 film annealed above 150°C were crystalline nature. Film annealed at 150°C exhibits a photoluminescence intensity maximum at 512 nm when excited at 390 nm. The Alq3 thin film deposited with 10 layers (220 nm) at 150°C exhibited maximum luminescence yield.

  16. The effects of annealing on the microstructure and mechanical properties of Fe28Ni18Mn33Al21

    DOE PAGES

    Meng, Fanling; Qiu, Jingwen; Baker, Ian; ...

    2015-08-20

    In this paper, As-cast Fe28Ni18Mn33Al21, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation.more » Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.« less

  17. Activation of Al2O3 passivation layers on silicon by microwave annealing

    NASA Astrophysics Data System (ADS)

    Ziegler, Johannes; Otto, Martin; Sprafke, Alexander N.; Wehrspohn, Ralf B.

    2013-11-01

    Thin aluminum oxide layers deposited on silicon by thermal atomic layer deposition can be used to reduce the electronic recombination losses by passivating the silicon surfaces. To activate the full passivation ability of such layers, a post-deposition annealing step at moderate temperatures (≈400 ∘C, duration≈30 min) is required. Such an annealing step is commonly done in an oven in air, nitrogen, or forming gas atmosphere. In this work, we investigate the ability to reduce the duration of the annealing step by heating the silicon wafer with a microwave source. The annealing time is significantly reduced to durations below 1 min while achieving effective minority carrier lifetimes similar or higher to that of conventionally oven-annealed samples.

  18. Annealing effect of fluorine-doped SnO2/WO3 core-shell inverse opal nanoarchitecture for photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Cho, Seo Yoon; Kang, Soon Hyung; Yun, Gun; Balamurugan, Maheswari; Ahn, Kwang-Soon

    2017-01-01

    Fluorine-doped SnO2 inverse opal (FTO IO) was developed on a polystyrene bead template with a size of 350 nm (± 20 nm) by using the sol-gel-assisted spin-coating method. The resulting FTO IO film exhibited a pore diameter of 270 nm (± 5 nm), and a WO3 layer was electrodeposited with a constant charge of 400 mC/cm2, followed by a high-temperature annealing process (400, 475, and 550 °C) to increase the crystallinity of the IO films. The annealing temperature affected the morphology and the overall resistance of the thin film, thus significantly affecting the photoelectrochemical performance. In particular, the FTO/WO3 IO film annealed at 475 °C exhibited a photocurrent density of 2.9 mA/cm2 at 1.23 V versus normal hydrogen electrode, showing more than a three times higher photocurrent density in comparison with the other samples (550 °C), which is attributed to the large surface area and low resistance for the charge transport. Therefore, the annealing temperature significantly affects the morphological and the photoelectrochemical features of the FTO/WO3 IO films.

  19. Effect of annealing temperature on the microstructure and tensile properties of a bimodal nano/micro grained 1020 carbon steel prepared by aluminothermic reaction casting

    NASA Astrophysics Data System (ADS)

    La, Peiqing; Guo, Xin; Wang, Hongding; Shi, Ting; Zhen, Xiaojuan; Wei, Fuan; Lu, Xuefeng

    2016-03-01

    Bulk 1020 carbon steel was prepared by aluminothermic reaction casting. After casting, isothermal aging treatments at different temperatures are performed for different periods up to 8 h. Microstructure characterization was performed using many methods, including optical microscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that the steel consisted of a nanocrystalline- ferrite matrix and a microcrystalline pearlite phase with a laminar structure. The average grain sizes of the ferrite were 23, 24, 28, and 37 nm for the cast steel and for samples annealed at 600, 800, and 1000 °C, respectively. As the annealing temperature increased, the volume fraction of the pearlite initially increased and then decreased, while the laminar spacing of pearlite increased from 240 to 900 nm. When annealed at 1000 °C, a spherical black micron pearlite particle was formed. The tensile and yield strength dramatically decreased, and the elongation varied slightly with the annealing temperature. A ductile phase was achieved by extending the holding time.

  20. Porphyrin assemblies through the air/water interface: effect of hydrogen bond, thermal annealing, and amplification of supramolecular chirality.

    PubMed

    Rong, Yunlong; Chen, Penglei; Wang, Dongjun; Liu, Minghua

    2012-04-17

    Molecular assemblies of two achiral porphyrins with different substituents, 5-(4-methoxycarbonylphenyl)-10,15,20-triphenyl-21H,23H-porphine (TPPCOOMe) and 5-(4-carboxyphenyl)-10,15,20-triphenyl-21H,23H-porphine (TPPCOOH), have been fabricated by the Langmuir-Blodgett (LB) technique. It is disclosed that although only slight differences exist in the molecular skeleton of these two compounds, their interfacial assemblies display distinct chiroptical properties. It is found that weak circular dichroism (CD) signals are observed from the TPPCOOH assemblies, while in the case of the TPPCOOMe assemblies, only negligible CD signals could be detected. Interestingly, after the assemblies are subjected to a thermal annealing treatment, TPPCOOH assemblies show a distinct amplification of CD signals, while those of TPPCOOMe do not. An explanation in terms of the effect of substituents on the spreading properties of the compounds and the effect of intermolecular hydrogen bonds on the cooperative stacking of the building blocks is proposed to explain these new findings. The investigation suggests that in the present porphyrin systems, besides a nice spreading property, the cooperative interaction of various noncovalent interactions, including hydrogen bonding, π-π stacking, and hydrophobic interactions, is essentially required for the occurrence of symmetry breaking at the air/water interface.

  1. Linear response theory for annealing of radiation damage in semiconductor devices

    NASA Technical Reports Server (NTRS)

    Litovchenko, Vitaly

    1988-01-01

    A theoretical study of the radiation/annealing response of MOS ICs is described. Although many experiments have been performed in this field, no comprehensive theory dealing with radiation/annealing response has been proposed. Many attempts have been made to apply linear response theory, but no theoretical foundation has been presented. The linear response theory outlined here is capable of describing a broad area of radiation/annealing response phenomena in MOS ICs, in particular, both simultaneous irradiation and annealing, as well as short- and long-term annealing, including the case when annealing is nearing completion. For the first time, a simple procedure is devised to determine the response function from experimental radiation/annealing data. In addition, this procedure enables us to study the effect of variable temperature and dose rate, effects which are of interest in spaceflight. In the past, the shift in threshold potential due to radiation/annealing has usually been assumed to depend on one variable: the time lapse between an impulse dose and the time of observation. While such a suggestion of uniformity in time is certainly true for a broad range of radiation annealing phenomena, it may not hold for some ranges of the variables of interest (temperature, dose rate, etc.). A response function is projected which is dependent on two variables: the time of observation and the time of the impulse dose. This dependence on two variables allows us to extend the theory to the treatment of a variable dose rate. Finally, the linear theory is generalized to the case in which the response is nonlinear with impulse dose, but is proportional to some impulse function of dose. A method to determine both the impulse and response functions is presented.

  2. Effect of thermal annealing on the optical properties and residual stress of TiO2 films produced by ion-assisted deposition.

    PubMed

    Lee, Cheng-Chung; Chen, Hsi-Chao; Jaing, Cheng-Chung

    2005-05-20

    The effects of thermal annealing of titanium oxide films deposited by ion-beam assistance at annealing temperatures from 100 degrees C to 300 degrees C on the residual stress and optical properties of the films was investigated. The refractive indices and extinction coefficients increased gradually as the temperature was increased from 100 degrees C to 200 degrees C and then declined gradually as the temperature was increased further from 200 degrees C to 300 degrees C. The film lost oxygen and slowly generated lower suboxides as the annealing temperature was reduced below 200 degrees C, as determined by x-ray photoelectron spectroscopy (XPS). As the annealing temperature increased above 200 degrees C, the lower suboxides began to capture oxygen and form stable oxides. XPS measurements were made to verify both the binding energy associated with the Ti 2p line and the variation of the O 1s line. A Twyman-Green interferometer was employed for phase-shift interferometry to study the residual stress. The residual stress declined as the temperature was reduced from 100 degrees C to 200 degrees C because the lower suboxides reduced the stress in the film. Above 200 degrees C, the film began to capture oxygen, so the residual stress rose. At 300 degrees C, the film was no longer amorphous as the anatase was observed by x-ray diffraction.

  3. 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.

  4. Investigation of the annealing effects on the structural and optoelectronic properties of RF-sputtered ZnO films studied by the Drude-Lorentz model

    NASA Astrophysics Data System (ADS)

    García-Méndez, Manuel; Bedoya-Calle, Álvaro; Segura, Ricardo Rangel; Coello, Víctor

    2015-09-01

    Zinc oxide films were deposited on glass substrates by RF reactive magnetron sputtering and post-annealed in vacuum at 100, 200, and 300 ºC. Structural and optical properties of films were obtained using X-ray diffraction and UV-visible spectroscopy. Optical parameters were extracted from transmittance curves using the single-oscillator Drude-Lorentz model. The evolution of the optical and structural properties of films with the annealing process was investigated. The films crystallized into the hexagonal würzite lattice structure, with preferential growth along the c-axis [0002]. The results indicate that the crystalline quality of films improved with annealing, whereas transparency was reduced from 90 to 80 % at 300 ºC. With post-annealing, the absorption edge shifted to the red, while the optical band gap decreased from to eV because of the Burstein-Moss effect. Calculated values of plasma frequency, fall within the IR range and decrease with temperature, from rad/s () to rad/s ().

  5. Post annealing effects on structural, optical and electrical properties of CuSbS2 thin films fabricated by combinatorial thermal evaporation technique

    NASA Astrophysics Data System (ADS)

    Hussain, Arshad; Ahmed, R.; Ali, N.; Butt, Faheem K.; Shaari, A.; Shamsuri, W. N. Wan; Khenata, R.; Prakash, Deo; Verma, K. D.

    2016-01-01

    Copper antimony sulfide (CuSbS2) thin films were fabricated by combinatorial thermal evaporation technique on well cleaned glass substrates. The deposited thin films were annealed in argon gas atmosphere for 1 h at temperature range of 150-350 °C. The effect of annealing temperature on structural, morphological, optical and electrical properties was studied using the different characterization techniques. The XRD analysis confirmed the crystallinity of the obtained samples with CuSbS2 phase in chalcostibite structure. Optical properties of the deposited samples showed good response in the visible and NIR region, envisaging the potential of CuSbS2 as an efficient solar cell material. The optical band gap of CuSbS2 thin films was measured to be 1.5 eV. A decrease (12.5-1.43 KΩ-cm) was observed for the resistivity of samples with the increase in annealing temperature. The plot of sheet resistance with annealing temperature confirmed the uniformity of samples. These thin films were found as a sustainable substitute material for the absorber layer in conventional thin film solar cell system, because of the abundance and low cost of its constituent elements. This study opens new avenue of research for scalable synthesis of CuSbS2 thin films for solar cell and photovoltaic applications.

  6. Effect of annealing in a various oxygen atmosphere on structural, optical, electrical and gas sensing properties of MoxOy thin films

    NASA Astrophysics Data System (ADS)

    Arfaoui, A.; Ouni, B.; Touihri, S.; Mhamdi, A.; Labidi, A.; Manoubi, T.

    2015-07-01

    Molybdenum oxide thin films were thermally evaporated on a glass substrate and monitored by an annealing process in a variable oxygen atmosphere. The effects of post annealing condition on the microstructural, morphological, optical and electrical properties were investigated using X-ray diffraction, Raman spectroscopy, atomic force microscope, spectroscopic ellipsometry and impedance spectroscopy. As-deposited amorphous films crystallized into tetragonal metastable phase of Mo5O14 on annealing at 500 °C in vacuum and air. This structure transformed to stable orthorhombic of MoO3 with annealing in oxygen environment. The optical parameters such as the refractive index, extinction coefficient, optical band gap energy and the Urbach energy were calculated from Cauchy formalism. Ellipsometric measurements reveal that the samples present optical gap located between 3.24 and 3.90 eV when the atmosphere becomes rich on oxygen. The variation of the conductivity in terms of the temperature shows an electrical behavior with oxygen environment. Finally, it has been found that MoO3 thin films had high sensitivity to ethanol, which made them as a good candidate for the ethanol sensor.

  7. Luminescence properties of europium ions-doped yttrium silicate (Y2SiO5:Eu3+) nanocrystalline phosphors: effect of Eu3+ ion concentration and thermal annealing.

    PubMed

    Ko, Yeong Hwan; Lee, Soo Hyun; Yu, Jae Su

    2013-05-01

    The trivalent europium ions-doped yttrium silicate (Y2SiO5:Eu3+) nanocrystalline phosphors were synthesized via a sol-gel method, followed by post thermal annealing. The effects of thermal annealing temperature and doping concentration on the structural and luminescent properties of Y2SiO5:Eu3+ nanocrystalline phosphors were systematically investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence measurements. The nanocrystalline phosphors with a high crystallinity were obtained at an annealing temperature of 1300 degrees C. The luminescent spectra were affected strongly by the Eu3+ ion concentration and annealing temperature. The Eu3+ ion concentration was optimized at 5 mol%, exhibiting excellent red emission (-612 nm) corresponding to the 5D0 --> 7F2 transition of Eu3+ ions at the excitation wavelengths of 262 and 396 nm. For the optimized Y2SiO5:Eu3+ nanocrystalline phosphors, the lifetimes were also estimated from the decay curves under the ultraviolet excitations.

  8. Effect of RF power and annealing on chemical bonding and morphology of a-CN{sub x} thin films as humidity sensor

    SciTech Connect

    Aziz, N. F. H; Hussain, N. S. Mohamed; Awang, R.; Ritikos, R.; Kamal, S. A. A.

    2013-11-27

    Amorphous carbon nitride (a-CN{sub x}) thin films were deposited using radio frequency plasma enhanced chemical vapor deposition (rf-PECVD) technique. A set of a-CN{sub x} thin films were prepared using pure methane (CH{sub 4}) gas diluted with nitrogen (N{sub 2}) gas. The rf power was varied at 50, 60, 70, 80, 90 and 100 W. These films were then annealed at 400 °C in a quartz tube furnace in argon (Ar) gas. The effects of rf power and thermal annealing on the chemical bonding and morphology of these samples were studied. Surface profilometer was used to measure film thickness. Fourier transform infra-red spectroscopy (FTIR) and Field emission scanning electron microscopy (FESEM) measurements were used to determine their chemical bonding and morphology respectively. The deposition rate of the films increased constantly with increasing rf power up to 80W, before decreasing with further increase in rf power. Fourier transform infra-red spectroscopy (FTIR) studies showed a systematic change in the spectra and revealed three main peaks included C-N, C=N, C=C and C≡N triple bond. C=N and C≡N bonds decreased with increased C-N bonds after thermal annealing process. The FESEM images showed that the structure is porous for as-deposited and covered by granule-like grain structure after thermal annealing process was done. The resistance of the a-CN{sub x} thin film changed from 23.765 kΩ to 5.845 kΩ in the relative humidity range of 5 to 92 % and the film shows a good response and repeatability as a humidity sensing materials. This work showed that rf power and thermal annealing has significant effects on the chemical bonding and surface morphology of the a-CN{sub x} films and but yield films which are potential candidate as humidity sensor device.

  9. Simple and fast annealing synthesis of titanium dioxide nanostructures and morphology transformation during annealing processes.

    PubMed

    Park, Jongbok; Ryu, Yeontack; Kim, Hansoo; Yu, Choongho

    2009-03-11

    Wire- and belt-like single-crystalline titanium dioxide nanostructures were synthesized by using a simple thermal annealing method, which has often been avoided for the synthesis of metal oxide nanostructures from high melting point metals such as Ti. The synthesis method requires neither high reaction temperature nor complicated reaction processes, and can be used for producing dense nanomaterials with relatively short reaction time at temperatures much lower than the melting point of titanium and titanium dioxide. Key synthesis factors including the choice of eutectic catalyst, growth temperature, and annealing time were systematically investigated. The synthesis reaction was promoted by a copper eutectic catalyst, producing long nanostructures with short reaction times. For example, it was observed that only 30 min of annealing time at 850 degrees C was enough to produce densely grown approximately 10 microm long nanowires with diameters of approximately 100 nm, and longer reaction time brought about morphology changes from wires to belts as well as producing longer nanostructures up to approximately 30 microm. The nanostructures have the crystalline rutile structure along the [Formula: see text] growth direction. Finally, our simple and effective method for the synthesis of TiO2 nanostructures could be utilized for growing other metal oxide nanowires from high melting temperature metals.

  10. Effect of synthesis methods with different annealing temperatures on micro structure, cations distribution and magnetic properties of nano-nickel ferrite

    NASA Astrophysics Data System (ADS)

    El-Sayed, Karimat; Mohamed, Mohamed Bakr; Hamdy, Sh.; Ata-Allah, S. S.

    2017-02-01

    Nano-crystalline NiFe2O4 was synthesized by citrate and sol-gel methods at different annealing temperatures and the results were compared with a bulk sample prepared by ceramic method. The effect of methods of preparation and different annealing temperatures on the crystallize size, strain, bond lengths, bond angles, cations distribution and degree of inversions were investigated by X-ray powder diffraction, high resolution transmission electron microscope, Mössbauer effect spectrometer and vibrating sample magnetometer. The cations distributions were determined at both octahedral and tetrahedral sites using both Mössbauer effect spectroscopy and a modified Bertaut method using Rietveld method. The Mössbauer effect spectra showed a regular decrease in the hyperfine field with decreasing particle size. Saturation magnetization and coercivity are found to be affected by the particle size and the cations distribution.

  11. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Effects of concentration and annealing on the performance of regioregular poly(3-hexylthiophene) field-effect transistors

    NASA Astrophysics Data System (ADS)

    Tian, Xue-Yan; Xu, Zheng; Zhao, Su-Ling; Zhang, Fu-Jun; Yuan, Guang-Cai; Xu, Xu-Rong

    2009-08-01

    This paper investigates the effects of concentration on the crystalline structure, the morphology, and the charge carrier mobility of regioregular poly(3-hexylthiophene) (RR-P3HT) field-effect transistors (FETs). The RR-P3HT FETs with RR-P3HT as an active layer with different concentrations of RR-P3HT solution from 0.5 wt% to 2 wt% are prepared. The results indicate that the performance of RR-P3HT FETs improves drastically with the increase of RR-P3HT weight percentages in chloroform solution due to the formation of more microcrystalline lamellae and bigger nanoscale islands. It finds that the field-effect mobility of RR-P3HT FET with 2 wt% can reach 5.78 × 10-3 cm2/Vs which is higher by a factor of 13 than that with 0.5 wt%. Further, an appropriate thermal annealing is adopted to improve the performance of RR-P3HT FETs. The field-effect mobility of RR-P3HT FETs increases drastically to 0.09 cm2/Vs by thermal annealing at 150 °C, and the value of on/off current ratio can reach 104.

  12. Effects of high magnetic field assisted annealing on structure and optical, electric properties of electrodeposited ZnO films

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Li, Guojian; Wu, Chun; Sui, Xudong; Du, Jiaojiao; Wang, Qiang

    2017-01-01

    Electrodeposited ZnO films have been annealed at 300 °C for 2 h under 12 T high magnetic field (HMF) with the directions of parallel and perpendicular to the films, respectively. The structural, optical and electric properties were characterized by scanning electron microscopy, X-ray diffraction, photoluminescence (PL) spectra, X-ray photoemission spectroscopy (XPS) and Seebeck coefficient/electrical resistance measuring system. The results show that HMF has a significant effect on the growth of ZnO films along c-axis and leads to hexagonal platelets of ZnO growing parallel to the direction of HMF. Furthermore, the hexagonal platelets become bulky platelets with an obvious trendy rotating their c-axis parallel to the substrate. The PL spectra of all the films exhibits the UV and blue emission, moreover, the blue emission plays the main role. The resistivity of ZnO films increases with the increase of measure temperature, which shows a typical degenerate semiconductor characteristic. HMF reduces significantly the intensity of whole emission peaks and the resistivity of ZnO films. These may be attribute to the significant changes of the structure and morphology of ZnO films, leading to various amounts of the defects in the ZnO crystal.

  13. Transversal Kerr effect of In1- x Mn x As layers prepared by ion implantation followed by pulsed laser annealing

    NASA Astrophysics Data System (ADS)

    Gan'shina, Elena; Golik, Leonard; Kun'kova, Zoya; Bykov, Igor; Novikov, Andrey; Rukovishnikov, Alexander; Yuan, Ye; Zykov, Georgy; Böttger, Roman; Zhou, Shengqiang

    2016-07-01

    In1- x Mn x As (x = 6.9%) layers prepared by ion implantation and subsequent pulsed laser annealing have been studied using the magnetooptical transversal Kerr effect (TKE) and spectral ellipsometry. Ellipsometry data reveal the good crystal quality of the layers. The samples show ferromagnetic behaviour below 77 K. Near the absorption edge of the parent InAs semiconductor, large TKE values are observed. In the energy regions of the transitions in the Γ and L critical points of the InAs Brillouin zone, there are several clearly defined structures in the low-temperature TKE spectra. We have calculated the spectral dependences of the diagonal and nondiagonal components of the permittivity tensor (PT), as well as the spectrum of magnetic circular dichroism (MCD) for our samples. A number of extrema in the obtained MCD and PT spectra are close to the energies of transitions in the critical points of the parent semiconductor band structure, which confirms the intrinsic ferromagnetism of the Mn-doped InAs layers.

  14. Effect of rapid thermal annealing on the noise properties of InAs/GaAs quantum dot structures

    SciTech Connect

    Arpatzanis, N.; Tsormpatzoglou, A.; Dimitriadis, C. A.; Song, J. D.; Choi, W. J.; Lee, J. I.; Charitidis, C.

    2007-09-01

    Self-assembled InAs quantum dots (QDs) were grown by molecular beam epitaxy (MBE) on n{sup +}-GaAs substrates, capped between 0.4 {mu}m thick n-type GaAs layers with electron concentration of 1x10{sup 16} cm{sup -3}. The effect of rapid thermal annealing at 700 deg. C for 60 s on the noise properties of the structure has been investigated using Au/n-GaAs Schottky diodes as test devices. In the reference sample without containing QDs, the noise spectra show a generation-recombination (g-r) noise behavior due to a discrete energy level located about 0.51 eV below the conduction band edge. This trap is ascribed to the M4 (or EL3) trap in GaAs MBE layers, related to a chemical impurity-native defect complex. In the structure with embedded QDs, the observed g-r noise spectra are due to a midgap trap level ascribed to the EL2 trap in GaAs, which is related to the InAs QDs dissolution due to the thermal treatment.

  15. Effect of rapid thermal annealing on the noise properties of InAs /GaAs quantum dot structures

    NASA Astrophysics Data System (ADS)

    Arpatzanis, N.; Tsormpatzoglou, A.; Dimitriadis, C. A.; Song, J. D.; Choi, W. J.; Lee, J. I.; Charitidis, C.

    2007-09-01

    Self-assembled InAs quantum dots (QDs) were grown by molecular beam epitaxy (MBE) on n+-GaAs substrates, capped between 0.4μm thick n-type GaAs layers with electron concentration of 1×1016cm-3. The effect of rapid thermal annealing at 700°C for 60s on the noise properties of the structure has been investigated using Au /n-GaAs Schottky diodes as test devices. In the reference sample without containing QDs, the noise spectra show a generation-recombination (g-r) noise behavior due to a discrete energy level located about 0.51eV below the conduction band edge. This trap is ascribed to the M4 (or EL3) trap in GaAs MBE layers, related to a chemical impurity-native defect complex. In the structure with embedded QDs, the observed g-r noise spectra are due to a midgap trap level ascribed to the EL2 trap in GaAs, which is related to the InAs QDs dissolution due to the thermal treatment.

  16. Microstructure evolution during helium irradiation and post-irradiation annealing in a nanostructured reduced activation steel

    NASA Astrophysics Data System (ADS)

    Liu, W. B.; Ji, Y. Z.; Tan, P. K.; Zhang, C.; He, C. H.; Yang, Z. G.

    2016-10-01

    Severe plastic deformation, intense single-beam He-ion irradiation and post-irradiation annealing were performed on a nanostructured reduced activation ferritic/martensitic (RAFM) steel to investigate the effect of grain boundaries (GBs) on its microstructure evolution during these processes. A surface layer with a depth-dependent nanocrystalline (NC) microstructure was prepared in the RAFM steel using surface mechanical attrition treatment (SMAT). Microstructure evolution after helium (He) irradiation (24.8 dpa) at room temperature and after post-irradiation annealing was investigated using Transmission Electron Microscopy (TEM). Experimental observation shows that GBs play an important role during both the irradiation and the post-irradiation annealing process. He bubbles are preferentially trapped at GBs/interfaces during irradiation and cavities with large sizes are also preferentially trapped at GBs/interfaces during post-irradiation annealing, but void denuded zones (VDZs) near GBs could not be unambiguously observed. Compared with cavities at GBs and within larger grains, cavities with smaller size and higher density are found in smaller grains. The average size of cavities increases rapidly with the increase of time during post-irradiation annealing at 823 K. Cavities with a large size are observed just after annealing for 5 min, although many of the cavities with small sizes also exist after annealing for 240 min. The potential mechanism of cavity growth behavior during post-irradiation annealing is also discussed.

  17. Annealing studies of boron implanted emitters for n-silicon solar cells

    NASA Astrophysics Data System (ADS)

    Liang, Peng; Han, Peide; Yujie, Fan; Xing, Yupeng

    2014-03-01

    Effects of annealing on the properties of B-implanted Si for n-type solar cells were investigated by comparing rapid thermal annealing (RTA) and furnace annealing (FA) conditions. Profiles of boron and residual damage were theoretically simulated by technology computer aided design based on boron diffusion kinetics mechanism of transient enhanced diffusion. Compared with the rapid thermally annealed samples, the furnace annealed one showed the lowest remnant damage spectra obtained by channeling Rutherford backscattering spectrometry. Furthermore, the electrical properties of boron implanted samples were characterized by Hall and QSSPC technique, revealing a trend that increasing annealing thermal budget would result in higher active carrier density and lower emitter saturation current density. Finally, passivated emitter solar cells were fabricated to verify the influence of annealing conditions on the performances at device level. The champion cell with efficiency of 18.85% received FA for 20 min, whereas those with lower thermal budgets exhibited significantly lower performance. From diode parameters obtained by fitting dark I-V curves and short wavelength responses of internal quantum efficiency spectrum, it was found that B-implanted samples required an annealing temperature of at least 1000 °C together with a sufficiently long time. Rather low thermal budget such as RTA for dozens of seconds was far enough to realize full activation of boron and removal of implantation damage.

  18. Optimization Via Open System Quantum Annealing

    DTIC Science & Technology

    2016-01-07

    mapping between the Ising spin glass partition function and circuit model decision problems, discovered in a previous ARO Quantum Algorithms funded...of tunneling in providing quantum annealing speedup over classical algorithms • Characterized the effects of classical hardness on the performance...15 Annual APS March meeting, Tutorial on Quantum Annealing 12/14 Quantum Sensing, Metrology, and Algorithms Workshop, Northrop Grumman, Los

  19. The microstructural evolution of ultrananocrystalline diamond films due to P ion implantation process—the annealing effect

    SciTech Connect

    Lin, Sheng-Chang; Yeh, Chien-Jui; Leou, Keh-Chyang; Kurian, Joji; Lin, I.-Nan; Dong, Chung-Li; Niu, Huan

    2014-11-14

    The microstructural evolution of UNCD films which are P-ion implanted and annealed at 600 °C (or 800 °C) is systematically investigated. The difference of interaction that the UNCD content undergoes along the trajectory of the incident P-ions is reflected in the alteration of the granular structure. In regions where the P-ions reside, the “interacting zone,” which is found at about 300 nm beneath the surface of the films, coalescence of diamond grains occurs inducing nano-graphitic clusters. The annealing at 600 °C (or 800 °C) heals the defects and, in some cases, forms interconnected graphitic filaments that result in the decrease in surface resistance. However, the annealing at 600 °C (800 °C) induces marked UNCD-to-Si layers interaction. This interaction due to the annealing processes hinders the electron transport across the interface and degrades the electron field emission properties of the UNCD films. These microstructural evolution processes very well account for the phenomenon elaborating that, in spite of enhanced conductivity of the UNCD films along the film's surface due to the P-ion implantation and annealing processes, the electron field emission properties for these UNCD films do not improve.

  20. Annealing effects and DLTS study on PNP silicon bipolar junction transistors irradiated by 20 MeV Br ions

    NASA Astrophysics Data System (ADS)

    Liu, Chaoming; Li, Xingji; Yang, Jianqun; Bollmann, Joachim

    2014-01-01

    Isochronal anneal sequences have been carried out on 3CG130 silicon PNP bipolar junction transistors (BJTs) irradiated with 20 MeV bromine (Br) heavy ions. The Gummel curve was utilized to characterize the annealing behavior of defects in both the emitter-base depletion region and the neutral base. The results show that the base current (IB) decreases with the increasing annealing temperature, while the collector current (IC) keeps invariably. The current gain varies slightly, when the annealing temperature (TA) is lower than 500 K, while varies rapidly at TA>550 K, and the current gain of the 3CG130 BJT annealing at 700 K almost restore to that of the pre-radiation transistor. The deep level transient spectroscopy (DLTS) data was used to assign the relative magnitude of each of the important defects. Based on the in situ electrical measurement and DLTS spectra, it is clear that the V2(+/0) trap is the main contribution to the degradation of current gain after the 20 MeV Br ions irradiation. The V2(+/0) peak has many characteristics expected for the current gain degradation.

  1. Effect of multiple strain-anneal cycles on the 1000 C creep behaviour of gamma/gamma prime-alpha

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Buzek, B. C.; Wirth, G.

    1986-01-01

    Various multiple strain-anneal cycles (1000 C) were imposed on specimens of the directionally solidified eutectic (DSE) alloy gamma/gamma prime-alpha to identify thermomechanical processing methods (TMP) which would improve the creep behavior. Specimens of the Ni-32.3Mo-6.3Al wt pct alloy were grown with a modified Bridgeman technique. Some of the cylindrical specimens were alternately heat-treated at 900 C, then strained, or heat-treated only, while other specimens were annealed at 900 C after swaging and then worked at ambient temperature. The specimens were all examined microstructurally using transmission electron microscopy, some before and after being exposed to constant-load compression tests at 1000 C. The creep strain increased for all TMP specimens for strain rates of at least 2 millionths per sec. Strain rates of about 2 ten millionths per sec were only improved with strain annealing with 13 percent work at ambient temperature. A slight improvement, compared to as-grown materials, was observed in the 1000 C creep behavior of materials annealed at 900 C. Strain-annealing was found to introduce three-dimensional dislocation networks into the gamma-prime matrix.

  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. Effects of post-deposition annealing on the structure and magnetization of PLD grown yttrium iron garnet films

    NASA Astrophysics Data System (ADS)

    Kumar, Ravinder; Hossain, Z.; Budhani, R. C.

    2017-03-01

    We report on the recrystallization of 200 nm thick as-grown Yttrium Iron Garnet ( Y 3.4 Fe 4.6 O 12 ) films on the (111) face of gadolinium gallium garnet single crystals by post-deposition annealing. Epitaxial conversion of the as-grown microcrystalline yttrium iron garnet films was seen after annealing at 800 °C for more than 30 min both in ambient oxygen and in air. The as-grown oxygen annealed samples at 800 °C for 60 min crystallize epitaxially and show excellent figure-of-merit for saturation magnetization (MS = 3.3 μB/f.u., comparable to the bulk value) and coercivity (HC ˜ 1.1 Oe). The ambient air annealing at 800 °C with a very slow rate of cooling (2 °C/min) results in a double layer structure with a thicker unstrained epitaxial top layer having the MS and HC of 2.9 μB/f.u. and 0.12 Oe, respectively. The symmetric and asymmetric reciprocal space maps of both the samples reveal a locking of the in-plane lattice of the film to the in-plane lattice of the substrate, indicating a pseudomorphic growth. The residual stress calculated by the sin 2 ψ technique is compressive in nature. The lower layer in the air annealed sample is highly strained, whereas the top layer has negligible compressive stress.

  4. 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.

  5. 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.

  6. 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.

  7. Spectroscopic ellipsometry study of the effect of illumination and thermal annealing on the optical constants of thin Ge-As-S films

    NASA Astrophysics Data System (ADS)

    Pamukchieva, V.; Szekeres, A.; Arsova, D.

    2011-02-01

    The effects of illumination and post-illumination thermal annealing on the optical properties of chalcogenide thin (~150 nm) films were studied by spectroscopic ellipsometry. The films were thermally evaporated from Ge30.8As5.7S63.5 and Ge32As5S63 glasses. They were exposed to illumination with an HBO 500 lamp and to subsequent thermal annealing at a temperature of 350 °C. Ellipsometric measurements in the spectral range 300-820 nm were carried out after each technological step. From the ellipsometric data analysis the optical constants (n, k, ɛ), optical band gap energy Eog and film thickness have been determined, while the oscillator energies E0 and Ed have been estimated applying the single-oscillator approximation theory. In the ɛ2 spectra three peaks, denoted by E1, E2 and E3, have appeared, which are attributed to interband transitions. By illumination, the values of the complex refractive index (\\tilde n = n - {\\rm{i}}k), dielectric function (\\skew3\\tilde \\varepsilon = \\varepsilon _1 - {\\rm{i}}\\varepsilon _{\\rm{2}} ) and dispersion energy Ed decrease, whereas the band gap energy (Eog) and the oscillator energy (E0) values increase. All these are accompanied by a ~12-13% enhancement of film thickness. Thermal annealing leads to a further increase of the energetic parameters values, but causes a ~14-15% decrease of film thickness in comparison to that of illuminated films. The E1 and E2 peaks diminish on illumination and post-illumination annealing, whereas the magnitude of the E3 peak decreases on illumination and increases by annealing, approaching its initial value for the as-deposited state.

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

    SciTech Connect

    Kumar, Narendra; Kumar, Jitendra; Panda, Siddhartha

    2015-06-15

    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 SiO{sub 2}/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 {sup o}C in N{sub 2} ambience showed the better sensitivity, which reduced with further increase in the annealing temperature to 500 {sup o}C. The increased pH sensitivity with the film annealed at 400 {sup o}C in N{sub 2} 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 {sup o}C was attributed to defects in the films as well as the induced traps at the IGZO/SiO{sub 2} 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.

  9. Effect of post-deposition annealing on the growth of Cu2ZnSnSe4 thin films for a solar cell absorber layer

    NASA Astrophysics Data System (ADS)

    Babu, G. Suresh; Kishore Kumar, Y. B.; Uday Bhaskar, P.; Sundara Raja, V.

    2008-08-01

    The effect of substrate temperature and post-deposition annealing on the growth and properties of Cu2ZnSnSe4 thin films, a potential candidate for a solar cell absorber layer, is investigated. The substrate temperature (Ts) is chosen to be in the range 523-673 K and the annealing temperature (Tpa) is kept at 723 K. Powder x-ray diffraction (XRD) patterns of as-deposited films revealed that the films deposited at Ts = 523 K and 573 K contain Cu2-xSe as a secondary phase. Single phase, polycrystalline Cu2ZnSnSe4 films are obtained at Ts = 623 K and films deposited at Ts = 673 K have ZnSe as a secondary phase along with Cu2ZnSnSe4. Direct band gap of as-deposited CZTSe films is found to lie between 1.40 eV and 1.65 eV depending on Ts. XRD patterns of post-deposition annealed films revealed that the films deposited at Ts = 523-623 K are single phase CZTSe and films deposited at Ts = 673 K still contain ZnSe secondary phase. CZTSe films are found to exhibit kesterite structure with the lattice parameters a = 0.568 nm and c = 1.136 nm. Optical absorption studies of post-deposition annealed films show that there is a slight increase in the band gap on annealing, due to decrease in the Cu content. Electrical resistivity of the films is found to lie in the range 0.02-2.6 Ω cm depending on Ts.

  10. Investigation of the impact of annealing on global molecular mobility in glasses: optimization for stabilization of amorphous pharmaceuticals.

    PubMed

    Luthra, Suman A; Hodge, Ian M; Pikal, Michael J

    2008-09-01

    The purpose of this research was to investigate the effect of annealing on the molecular mobility in lyophilized glasses using differential scanning calorimetry (DSC) and isothermal microcalorimetry (IMC) techniques. A second objective that emerged was a systematic study of the unusual pre-T(g) thermal events that were observed during DSC warming scans after annealing. Aspartame lyophilized with three different excipients; sucrose, trehalose and poly vinyl pyrrolidone (PVP) was studied. The aim of this work was to quantify the decrease in mobility in amorphous lyophilized aspartame formulations upon systematic postlyophilization annealing. DSC scans of aspartame:sucrose formulation (T(g) = 73 degrees C) showed the presence of a pre-T(g) endotherm which disappeared upon annealing. Aspartame:trehalose (T(g) = 112 degrees C) and aspartame:PVP (T(g) = 100 degrees C) showed a broad exotherm before T(g) and annealing caused appearance of endothermic peaks before T(g). This work also employed IMC to measure the global molecular mobility represented by structural relaxation time (tau(beta)) in both un-annealed and annealed formulations. The effect of annealing on the enthalpy relaxation of lyophilized glasses, as measured by DSC and IMC, was consistent with the behavior predicted using the Tool-Narayanaswamy-Moynihan (TNM) phenomenology (Luthra et al., 2007, in press). The results show that the systems annealed at T(g) -15 degrees C to T(g) -20 degrees C have the lowest molecular mobility.

  11. Annealing effect on the electrical properties and composition of a NiCrAl thin film resistor

    NASA Astrophysics Data System (ADS)

    Chuang, Nai-Chuan; Lin, Jyi-Tsong; Chen, Huey-Ru

    2015-12-01

    The composition of NiCrAl thin film resistors, under different annealing conditions in a N2 atmosphere, was investigated. The Auger electron spectrum (AES) has been used in studying the composition of NiCrAl thin films. The concentration ratio of Cr to Ni decreases when the annealing temperature increases. The electrical properties of a NiCrAl thin film resistor are affected by the concentrations of Cr and Ni, which lead to a higher temperature coefficient of resistance (TCR) and a lower sheet resistivity. The TCR of a NiCrAl thin film resistor is -5 ppm/°C at a 250 °C annealing temperature.

  12. Effects of annealing conditions on optical and electrical characteristics of titanium dioxide films deposited by electron beam evaporation

    NASA Astrophysics Data System (ADS)

    Mikhelashvili, V.; Eisenstein, G.

    2001-03-01

    We report measured evolutions of the optical band gap, refractive index, and relative dielectric constant of TiO2 film obtained by electron beam gun evaporation and annealed in an oxygen environment. A negative shift of the flat band voltage with increasing annealing temperatures, for any film thickness, is observed. A dramatic reduction of the leakage current by about four orders of magnitude to 5×10-6 A/cm2 (at 1 MV/cm) after 700 °C and 60 min annealing is found for films thinner than 15 nm. An equivalent SiO2 thickness of the order of 3-3.5 nm is demonstrated. An approach is presented to establish that at different ranges of applied voltage the hopping, space charge limited current, and Fowler-Nordheim are the basic mechanisms of carrier transport into the TiO2 film.

  13. Effects of Annealing Temperature on Properties of Ti-Ga–Doped ZnO Films Deposited on Flexible Substrates

    PubMed Central

    Chen, Tao-Hsing; Chen, Ting-You

    2015-01-01

    An investigation is performed into the optical, electrical, and microstructural properties of Ti-Ga–doped ZnO films deposited on polyimide (PI) flexible substrates and then annealed at temperatures of 300 °C, 400 °C, and 450 °C, respectively. The X-ray diffraction (XRD) analysis results show that all of the films have a strong (002) Ga doped ZnO (GZO) preferential orientation. As the annealing temperature is increased to 400 °C, the optical transmittance increases and the electrical resistivity decreases. However, as the temperature is further increased to 450 °C, the transmittance reduces and the resistivity increases due to a carbonization of the PI substrate. Finally, the crystallinity of the ZnO film improves with an increasing annealing temperature only up to 400 °C and is accompanied by a smaller crystallite size and a lower surface roughness.

  14. Effect of thermal annealing on the properties of transparent conductive In–Ga–Zn oxide thin films

    SciTech Connect

    Li, Ling; Fan, Lina; Li, Yanhuai; Song, Zhongxiao; Ma, Fei E-mail: chlliu@mail.xjtu.edu.cn; Liu, Chunliang E-mail: chlliu@mail.xjtu.edu.cn

    2014-03-15

    Amorphous In–Ga–Zn oxide (IGZO) thin films were prepared using radio frequency magnetron sputtering at room temperature. Upon thermal annealing at temperatures even up to 500 °C, the amorphous characteristics were still maintained, but the electronic properties could be considerably enhanced. This could be ascribed to the increased optical band gap and the increased oxygen vacancies, as corroborated by the microstructure characterizations. In addition, the surface became smoother upon thermal annealing, guaranteeing good interface contact between electrode and a-IGZO. The optical transmittance at 400–800 nm exceeded 90% for all samples. All in all, thermal annealing at appropriate temperatures is expected to improve the performances of relevant a-IGZO thin film transistors.

  15. Quantum coherence phenomenon in disordered Bi2SeTe2 topological single crystal: effect of annealing.

    PubMed

    Amaladass, E P; Devidas, T R; Sharma, Shilpam; Mani, Awadhesh

    2017-05-04

    We report a comparative magnetotransport study on pristine and annealed Bi2SeTe2 single crystals. The pristine sample shows a metallic trend from 300 to 180 K, and an insulating behavior for T  <  180 K, whereas the annealed sample exhibits an insulating nature in the entire 4.2-300 K temperature range. Magnetoresistance (MR) of pristine and annealed samples reveals contrasting behaviour as a function of temperature (T) and magnetic field (B). At 4.2 K, the pristine sample shows weak antilocalization (WAL) behavior at low fields and transforms to weak localization (WL) behavior (negative MR) for B  >  2.5 T. Further, the quantum MR behaviours seen at low temperature gradually transform to classical B (2) dependent upon increasing the temperatures. In contrast, the annealed sample shows a WAL at small field superimposed on a parabolic feature for B  >  ±4 T at low temperatures (T  <  20 K). It shows a linear MR at intermediate temperatures (40 K  <  T  <  100 K) and a parabolic MR at temperatures T  >  100 K. Hall measurements on both samples exhibit a nonlinear behavior at 4.2 K pointing to the existence of two types of carriers with different mobility. The annealed sample also shows a drastic decrease in mobility by one order of magnitude and a reduction in Ioffe-Regel parameter (k F l) by a factor of ~3. Disorder-induced localization of bulk carriers and its coexistence with localization-immune surface carriers at low T leads to WAL and WL. MR observed in the annealed sample can be attributed to the presence of both quantum-classical contribution and has been analysed using the Hikami-Larkin-Nagaoka (HLN) equation.

  16. Effects of vacuum annealing and oxygen ion beam bombarding on the electrical and optical properties of ITO films deposited by E-beam evaporation

    NASA Astrophysics Data System (ADS)

    Pan, Yongqiang; Hang, Lingxia

    2012-10-01

    Tin doped indium oxide (ITO) transparent conductive thin films with composition of 10 wt% SnO2 and 89.8 wt% In2O3 have been deposited by electron beam evaporation technique on K9 glass substrates at room temperature. The post annealing processes are done in vacuum with different annealing temperature at 100, 200, 300 and 350 ° for 1 hour, respectively. The oxygen ion energy is 800 eV; oxygen ion beam bombarding time is 10,20,30,40 and 50min, respectively. The results show that conductivity of ITO thin films are improved by increasing annealing temperature. The resistivity of the ITO thin films decrease from 5.2×10-3Ω •cm at room temperature to 1.3×10-3Ω •cm(350 °C). The transmittance values of all samples in the visible range have been increased. As the oxygen ion beam bombarding time increases the resistivity reduce from 5.2×10-3Ω •cm to 9×10-4Ω •cm, the transmittance value improve from 66% to 82% at 550nm. Finally, the vacuum annealing and oxygen ion beam bombarding are done simultaneously, at temperature of 350 °C for 1 hours, ion bombardment time for 40 min. The resistivity of obtained ITO thin film is 7×10-4Ω •cm. The maximum transmittance value is above 89% in the visible wavelength region.

  17. Understanding the microwave annealing of silicon

    NASA Astrophysics Data System (ADS)

    Fu, Chaochao; Wang, Yan; Xu, Peng; Yue, Lei; Sun, Feng; Zhang, David Wei; Zhang, Shi-Li; Luo, Jun; Zhao, Chao; Wu, Dongping

    2017-03-01

    Though microwave annealing appears to be very appealing due to its unique features, lacking an in-depth understanding and accurate model hinder its application in semiconductor processing. In this paper, the physics-based model and accurate calculation for the microwave annealing of silicon are presented. Both thermal effects, including ohmic conduction loss and dielectric polarization loss, and non-thermal effects are thoroughly analyzed. We designed unique experiments to verify the mechanism and extract relevant parameters. We also explicitly illustrate the dynamic interaction processes of the microwave annealing of silicon. This work provides an in-depth understanding that can expedite the application of microwave annealing in semiconductor processing and open the door to implementing microwave annealing for future research and applications.

  18. Effect of post deposition annealing on the structure, morphology, optical and electrical properties of CuInGaSe2 thin films

    NASA Astrophysics Data System (ADS)

    Pugalenthi, A. S.; Balasundaraprabhu, R.; Prasanna, S.; Habibuddin, S.; Muthukumarasamy, N.; Mohan Rao, G.; Kannan, M. D.

    2016-12-01

    Polycrystalline copper indium gallium diselenide (CIGS) thin film is a favourable candidate for solar cell applications. In the present work the effect of post-deposition annealing on the structure, surface morphology, optical and electrical properties are discussed. Initially, gallium rich CIG thin films were deposited by RF magnetron sputtering followed by an indium rich CIG layer and subjected to selenization to realize CIGS stoichiometry. X-ray diffraction (XRD) results revealed the polycrystalline nature of the films with chalcopyrite structure having preferential orientation along <112> direction normal to the substrate. Optical properties of CIGS thin films were studied using UV-vis spectrophotometry and the band gap of CIGS was found to be around 1.15 eV. Hall Effect studies carried out on the CIGS thin films showed a linear dependence of conductivity with post deposition annealing. The elemental composition of the films was quantified using X-ray photoelectron spectroscopy (XPS) and the results are discussed.

  19. Effect of double annealing on the critical parameters of highly textured YBa{sub 2}Cu{sub 3}O{sub 6.9}

    SciTech Connect

    Bobylev, I. B. Gerasimov, E. G.; Zyuzeva, N. A.

    2012-09-15

    The effect of low-temperature treatment (200 Degree-Sign C) and subsequent annealing at 930 Degree-Sign C on the critical parameters of highly textured YBa{sub 2}Cu{sub 3}O{sub 6.9} is studied. The structural defects that are formed during the low-temperature decomposition of this compound into phases with different oxygen contents and during interaction with atmospheric moisture are shown to deteriorate the superconducting properties. After annealing at T = 930 Degree-Sign C and subsequent oxidation, superconductivity is restored and the formed defects are partly retained and serve as effective pinning centers, including the case of high magnetic fields. The stresses induced by the low-temperature treatment lead to primary recrystallization at T = 930 Degree-Sign C, which results in the disappearance of texture and an isotropic state of the material in high fields.

  20. Experimental quantum annealing: case study involving the graph isomorphism problem

    PubMed Central

    Zick, Kenneth M.; Shehab, Omar; French, Matthew

    2015-01-01

    Quantum annealing is a proposed combinatorial optimization technique meant to exploit quantum mechanical effects such as tunneling and entanglement. Real-world quantum annealing-based solvers require a combination of annealing and classical pre- and post-processing; at this early stage, little is known about how to partition and optimize the processing. This article presents an experimental case study of quantum annealing and some of the factors involved in real-world solvers, using a 504-qubit D-Wave Two machine and the graph isomorphism problem. To illustrate the role of classical pre-processing, a compact Hamiltonian is presented that enables a reduced Ising model for each problem instance. On random N-vertex graphs, the median number of variables is reduced from N2 to fewer than N log2 N and solvable graph sizes increase from N = 5 to N = 13. Additionally, error correction via classical post-processing majority voting is evaluated. While the solution times are not competitive with classical approaches to graph isomorphism, the enhanced solver ultimately classified correctly every problem that was mapped to the processor and demonstrated clear advantages over the baseline approach. The results shed some light on the nature of real-world quantum annealing and the associated hybrid classical-quantum solvers. PMID:26053973

  1. DOE`s annealing prototype demonstration projects

    SciTech Connect

    Warren, J.; Nakos, J.; Rochau, G.

    1997-02-01

    One of the challenges U.S. utilities face in addressing technical issues associated with the aging of nuclear power plants is the long-term effect of plant operation on reactor pressure vessels (RPVs). As a nuclear plant operates, its RPV is exposed to neutrons. For certain plants, this neutron exposure can cause embrittlement of some of the RPV welds which can shorten the useful life of the RPV. This RPV embrittlement issue has the potential to affect the continued operation of a number of operating U.S. pressurized water reactor (PWR) plants. However, RPV material properties affected by long-term irradiation are recoverable through a thermal annealing treatment of the RPV. Although a dozen Russian-designed RPVs and several U.S. military vessels have been successfully annealed, U.S. utilities have stated that a successful annealing demonstration of a U.S. RPV is a prerequisite for annealing a licensed U.S. nuclear power plant. In May 1995, the Department of Energy`s Sandia National Laboratories awarded two cost-shared contracts to evaluate the feasibility of annealing U.S. licensed plants by conducting an anneal of an installed RPV using two different heating technologies. The contracts were awarded to the American Society of Mechanical Engineers (ASME) Center for Research and Technology Development (CRTD) and MPR Associates (MPR). The ASME team completed its annealing prototype demonstration in July 1996, using an indirect gas furnace at the uncompleted Public Service of Indiana`s Marble Hill nuclear power plant. The MPR team`s annealing prototype demonstration was scheduled to be completed in early 1997, using a direct heat electrical furnace at the uncompleted Consumers Power Company`s nuclear power plant at Midland, Michigan. This paper describes the Department`s annealing prototype demonstration goals and objectives; the tasks, deliverables, and results to date for each annealing prototype demonstration; and the remaining annealing technology challenges.

  2. Dopant rearrangement and superconductivity in Bi(2)Sr(2-x)La(x)CuO(6) thin films under annealing.

    PubMed

    Cancellieri, C; Lin, P H; Ariosa, D; Pavuna, D

    2007-06-20

    By combining x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and AC susceptibility measurements we investigate the evolution of structural and superconducting properties of La-doped Bi-2201 thin films grown by pulsed laser deposition (PLD) under different annealing conditions. We find that the main effect of oxygen annealing is to improve the crystal coherence by enabling La cation migration to the Sr sites. This activates the desired hole doping. Short-time Ar annealing removes the interstitial oxygen between the BiO layers, fine adjusting the effective hole doping. The superconducting critical temperature is consequently enhanced. However, longer annealings result in phase separation and segregation of the homologous compound Bi-1201. We attribute this effect to the loss of Bi during the annealing.

  3. Tuning of the surface plasmon resonance in TiO{sub 2}/Au thin films grown by magnetron sputtering: The effect of thermal annealing

    SciTech Connect

    Torrell, M.; Kabir, R.; Cunha, L.; Vasilevskiy, M. I.; Vaz, F.; Cavaleiro, A.; Alves, E.; Barradas, N. P.

    2011-04-01

    Nanocomposites consisting of a dielectric matrix, such as TiO{sub 2}, with embedded noble metal nanoparticles (NPs) possess specific optical properties due to the surface plasmon resonance (SPR) effect, interesting for several applications. The aim of this work is to demonstrate that these properties are sensitive to the nanostructure of magnetron-sputtered TiO{sub 2}/Au thin films, which can be tuned by annealing. We study the role of the shape and size distribution of the NPs, as well as the influence of the crystallinity and phase composition of the host matrix on the optical response of the films. All these characteristics can be modified by vacuum annealing treatments of the deposited films. A theoretical interpretation and modeling of the experimental results obtained is presented. The model involves a modified Maxwell-Garnett approach for the effective dielectric function of the composite (describing the SPR effect) and the transfer matrix formalism for multilayer optics. Input data are based on the experimental information obtained from the detailed structural characterization of the films. It is shown that the annealing treatments can be used for controlling the optical properties of the composite films, making them attractive for decorative coatings.

  4. The effect of magnetic field annealing on the texture of 2nd recrystallization for a deformed Fe-3.2% Si steel sheet

    NASA Astrophysics Data System (ADS)

    Kim, Byung Geol; Part, Su Dong; Kim, Shang Shu

    2004-12-01

    The effects of deformation on 2nd recrystallization behavior with or without magnetic field for a 1st recrystallized electrical steel sheet have been investigated. Annealing temperatures (800, 1000 °C) and cold-rolling rates (50, 70 %) were experimental parameters. A magnetic field of 5 T using a superconducting magnet at a heating rate of 15 °C/min was applied in a direction parallel to the rolling direction. The intensity of α-fiber was increased due to the deformation and, in particular, the formation of {100}<110> component was tremendous. Considerable formation of {001}<100> component was also found. At 800 °C, α-fiber was developed rapidly due to deformation, and η-fiber was also formed in the components {100}<100> and {110}<100> The effect of magnetic field annealing was more significant at 800 °C, while the effect at 1000 °C was negligible. These results are discussed in a phenomenological context considering the atomic fluctuation and magnetic induction depending on annealing temperature and magnetic field.

  5. Effects of quenching, irradiation, and annealing processes on the radiation hardness of silica fiber cladding materials (I)

    NASA Astrophysics Data System (ADS)

    Wen, Jianxiang; Gong, Renxiang; Xiao, Zhongyin; Luo, Wenyun; Wu, Wenkai; Luo, Yanhua; Peng, Gang-ding; Pang, Fufei; Chen, Zhenyi; Wang, Tingyun

    2016-07-01

    Silica optical fiber cladding materials were experimentally treated by a series of processes. The treatments involved quenching, irradiation, followed by annealing and subsequent re-irradiation, and they were conducted in order to improve the radiation hardness. The microstructural properties of the treated materials were subsequently investigated. Following the treatment of the optical fiber cladding materials, the results from the electron spin resonance (ESR) analysis demonstrated that there was a significant decrease in the radiation-induced defect structures. The ESR signals became significantly weaker when the samples were annealed at 1000 °C in combination with re-irradiation. In addition, the microstructure changes within the silica optical fiber cladding material were also analyzed using Raman spectroscopy. The experimental results demonstrate that the Sisbnd Osbnd Si bending vibrations at ω3 = 800-820 cm-1 and ω4 = 1000-1200 cm-1 (with longitudinal optical (LO) and transverse optical (TO) splitting bands) were relatively unaffected by the quenching, irradiation, and annealing treatments. In particular, the annealing process resulted in the disappearance of the defect centers; however, the LO and TO modes at the ω3 and ω4 bands were relatively unchanged. With the additional support of the ESR test results, we can conclude that the combined treatment processes can significantly enhance the radiation hardness properties of the optical fiber cladding materials.

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

    PubMed

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

    2014-06-01

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

  7. Effect of annealing on structural and electrical properties of ZnO and In2S3:Al thin layers

    NASA Astrophysics Data System (ADS)

    Jebbari, N.; Ajili, M.; Guasch, C.; Kamoun, N.; Bennaceur, R.

    2010-11-01

    Thin films of ZnO and In2S3:Al are deposited on Pyrex substrates by spray technique. Structural and electrical properties of ZnO and β-In2S3:Al compounds were studied using X Ray Diffraction (XRD), (MEB) and the Vander Pauw method before and after annealing. The X-rays revealed that, ZnO and In2S3:Al were well crystallized respectively in the hexagonal and cubic structure. The main orientations of ZnO were (101), (100) and (110). The (101) direction is the preferentially one. The annealing favors the preferential peak crystallization with a reduction of the grains size and the thickness layer. The β-In2S3 contain Aluminum inclusion by introducing the ratio x= [Al3+]/[In3+] in sprayed solution. X-ray diffraction spectra of In2-xAlxS3 thin layer, realized for the value of z equal to 20%, show well-defined peaks of (311), (400), (511), and (440) principal orientations corresponding to cubic structure of β-In2S3. For In2S3:Al, we note that the annealing increase the intensity of all peaks with an increase of the grains size and the thickness layer. Besides, thanks to the determination of the resistance from which we calculated resistivity, we note that the annealing increase conductivity of β-In2S3:Al and decrease it for ZnO.

  8. Effects of concentration and thermal annealing on the optical activation of Er implanted into GaN layers

    NASA Astrophysics Data System (ADS)

    Sathish, N.; Pathak, A. P.; Devaraju, G.; Trave, E.; Mazzoldi, P.; Dhamodaran, S.; Kulkarni, V. N.

    2012-07-01

    The wide band gap semiconductor, GaN, has emerged as an important host for rare earth-electroluminescence. The annealing behaviour and lattice site location of Er implanted into GaN were studied with the Rutherford Backscattering Spectrometry (RBS)/channelling and photoluminescence (PL) techniques. Also Er site dependence on the annealing temperature and implantation dose has been studied in detail. The optical properties of the Er-doped GaN system, evidencing their dependence on the parameters adopted during the synthesis procedure (Er implantation dose, annealing temperature) have been discussed. RBS/channelling measurements suggested that mostly Er occupy substitutional site and depends on the Er concentration. The main result is the activation of a typical Er giving rise to PL emission in the 1450-1650 nm range, related to radiative 4 I 13/2→4 I 15/2 transitions. Depending on the Er dose, we observe a specific behaviour linked to variation of the annealing temperature that strongly determines PL emission band. We observed a PL spectral shape with the main peak located at 1542 nm and shoulder peak at 1558 nm (and full width at half maximum (FWHM) of 33 nm) with a series of weaker PL structures at 1519, 1572 and 1591 nm, due to the Stark sub-level splitting.

  9. 454-Pyrosequencing Analysis of Bacterial Communities from Autotrophic Nitrogen Removal Bioreactors Utilizing Universal Primers: Effect of Annealing Temperature.

    PubMed

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

    2015-01-01

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

  10. Effect of high temperature annealing on the thermoelectric properties of GaP doped SiGe

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W.; Wood, Charles; Draper, Susan

    1987-01-01

    Silicon-germanium alloys doped with GaP are used for thermoelectric energy conversion in the temperature range 300-1000 C. The conversion efficiency depends on Z = S-squared/rho lambda, a material's parameter (the figure of merit), where S is the Seebeck coefficient, rho is the electrical resistivity and lambda is the thermal conductivity. The annealing of several samples in the temperature range of 1100-1300 C resulted in the power factor P (= S-squared/rho) increasing with increased annealing temperature. This increase in P was due to a decrease in rho which was not completely offset by a drop in S-squared suggesting that other changes besides that in the carrier concentration took place. SEM and EDX analysis of the samples indicated the formation of a Ga-P-Ge rich phase as a result of the annealing. It is speculated that this phase is associated with the improved properties. Several reasons which could account for the improvement in the power factor of annealed GaP doped SiGe are given.

  11. 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}.

  12. Effect of annealing on the sub-bandgap, defects and trapping states of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Wahyuono, Ruri Agung; Hermann-Westendorf, Felix; Dellith, Andrea; Schmidt, Christa; Dellith, Jan; Plentz, Jonathan; Schulz, Martin; Presselt, Martin; Seyring, Martin; Rettenmeyer, Markus; Dietzek, Benjamin

    2017-02-01

    Annealing treatment was applied to different mesoporous ZnO nanostructures prepared by wet chemical synthesis, i.e. nanoflowers (NFs), spherical aggregates (SPs), and nanorods (NRs). The sub-bandgap, defect properties as well as the trapping state characteristics after annealing were characterized spectroscopically, including ultrasensitive photothermal deflection spectroscopy (PDS), photoluminescence and photo-electrochemical methods. The comprehensive experimental analysis reveals that annealing alters both the bandgap and the sub-bandgap. The defect concentration and the density of surface traps in the ZnO nanostructures are suppressed upon annealing as deduced from photoluminescence and open-circuit voltage decay analysis. The photo-electrochemical investigations reveal that the surface traps dominate the near conduction band edge of ZnO and, hence, lead to high recombination rates when used in DSSCs. The density of bulk traps in ZnO SPs is higher than that in ZnO NFs and ZnO NRs and promote lower recombination loss between photoinjected electrons with the electrolyte-oxidized species on the surface. The highest power conversion efficiency of ZnO NFs-, ZnO SPs-, and ZnO NRs-based DSSC obtained in our system is 2.0, 4.5, and 1.8%, respectively.

  13. Role of deposition and annealing of the top gate dielectric in a-IGZO TFT-based dual-gate ion-sensitive field-effect transistors

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Sutradhar, Moitri; Kumar, Jitendra; Panda, Siddhartha

    2017-03-01

    The deposition of the top gate dielectric in thin film transistor (TFT)-based dual-gate ion-sensitive field-effect transistors (DG ISFETs) is critical, and expected not to affect the bottom gate TFT characteristics, while providing a higher pH sensitive surface and efficient capacitive coupling between the gates. Amorphous Ta2O5, in addition to having good sensing properties, possesses a high dielectric constant of ∼25 making it well suited as the top gate dielectric in a DG ISFET by providing higher capacitive coupling (ratio of C top/C bottom) leading to higher amplification. To avoid damage of the a-IGZO channel reported to be caused by plasma exposure, deposition of Ta2O5 by e-beam evaporation followed by annealing was investigated in this work to obtain sensitivity over the Nernst limit. The deteriorated bottom gate TFT characteristics, indicated by an increase in the channel conductance, confirmed that plasma exposure is not the sole contributor to the changes. Oxygen vacancies at the Ta2O5/a-IGZO interface, which emerged during processing, increased the channel conductivity, became filled by optimum annealing in oxygen at 400 °C for 1 h, which was confirmed by an x-ray photoelectron spectroscopy depth profiling analysis. The obtained pH sensitivity of the TFT-based DG ISFET was 402 mV pH‑1, which is about 6.8 times the Nernst limit (59 mV pH‑1). The concept of capacitive coupling was also demonstrated by simulating an a-IGZO-based DG TFT structure. Here, the exposure of the top gate dielectric to the electrolyte without applying any top gate bias led to changes in the measured threshold voltage of the bottom gate TFT, and this obviated the requirement of a reference electrode needed in conventional ISFETs and other reported DG ISFETs. These devices, with high sensitivities and requiring low volumes (∼2 μl) of analyte solution, could be potential candidates for utilization as chemical sensors and biosensors.

  14. Comparative study of the performance of quantum annealing and simulated annealing.

    PubMed

    Nishimori, Hidetoshi; Tsuda, Junichi; Knysh, Sergey

    2015-01-01

    Relations of simulated annealing and quantum annealing are studied by a mapping from the transition matrix of classical Markovian dynamics of the Ising model to a quantum Hamiltonian and vice versa. It is shown that these two operators, the transition matrix and the Hamiltonian, share the eigenvalue spectrum. Thus, if simulated annealing with slow temperature change does not encounter a difficulty caused by an exponentially long relaxation time at a first-order phase transition, the same is true for the corresponding process of quantum annealing in the adiabatic limit. One of the important differences between the classical-to-quantum mapping and the converse quantum-to-classical mapping is that the Markovian dynamics of a short-range Ising model is mapped to a short-range quantum system, but the converse mapping from a short-range quantum system to a classical one results in long-range interactions. This leads to a difference in efficiencies that simulated annealing can be efficiently simulated by quantum annealing but the converse is not necessarily true. We conclude that quantum annealing is easier to implement and is more flexible than simulated annealing. We also point out that the present mapping can be extended to accommodate explicit time dependence of temperature, which is used to justify the quantum-mechanical analysis of simulated annealing by Somma, Batista, and Ortiz. Additionally, an alternative method to solve the nonequilibrium dynamics of the one-dimensional Ising model is provided through the classical-to-quantum mapping.

  15. Crystal growth and annealing method and apparatus

    DOEpatents

    Gianoulakis, Steven E.; Sparrow, Robert

    2001-01-01

    A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing. An embodiment of the present invention comprises a secondary heater incorporated into a conventional crystal growth and annealing apparatus. The secondary heater supplies heat to minimize the temperature gradients in the crystal during the annealing process. The secondary heater can mount near the bottom of the crucible to effectively maintain appropriate temperature gradients.

  16. Annealing effect on the magnetic induced austenite transformation in polycrystalline freestanding Ni-Co-Mn-In films produced by co-sputtering

    SciTech Connect

    Crouïgneau, G.; Porcar, L.; Pairis, S.; Mossang, E.; Eyraud, E.; Bourgault, D.; Courtois, P.

    2015-01-21

    Ni-Co-Mn-In freestanding films, with a magneto-structural transformation at room temperature were successfully produced by co-sputtering and post-annealing methods leading to film composition mastering. For a post-annealing temperature of 700 °C, the phase transformation occurs slightly above room temperature, with a twisted martensitic microstructure phase observed at 300 K by Field Emission Scanning Electron Microscopy. Magnetization measurements on a polycrystalline film showed a phase transformation from a weakly magnetic martensite to a magnetic austenite phase. Moreover, an inverse magnetocaloric effect with an entropy variation of 4 J/kg K under 5 T was also measured. A simple magneto-actuation experiment based on the magnetic induced austenite transformation was also successfully completed. The possibility to insert such films in microsystems is clearly demonstrated in this work.

  17. Effective reduction of interfacial traps in Al2O3/GaAs (001) gate stacks using surface engineering and thermal annealing

    NASA Astrophysics Data System (ADS)

    Chang, Y. C.; Merckling, C.; Penaud, J.; Lu, C. Y.; Wang, W.-E.; Dekoster, J.; Meuris, M.; Caymax, M.; Heyns, M.; Kwo, J.; Hong, M.

    2010-09-01

    To effectively passivate the technologically important GaAs (001) surfaces, in situ deposition of Al2O3 was carried out with molecular beam epitaxy. The impacts of initial GaAs surface reconstruction and post-deposition annealing have been systematically investigated. The corresponding interfacial state density (Dit) were derived by applying the conductance method at 25 and 150 °C on both p-type and n-type GaAs metal-oxide-semiconductor capacitors to establish the Dit spectra in proximity of the critical midgap region. We show that significant reduction of Dit near the midgap is achieved by applying an optimized thermal annealing on samples grown on a Ga-rich (4×6) reconstructed surface.

  18. Effect of the sample annealing temperature and sample crystallographic orientation on the charge kinetics of MgO single crystals subjected to keV electron irradiation.

    PubMed

    Boughariou, A; Damamme, G; Kallel, A

    2015-04-01

    This paper focuses on the effect of sample annealing temperature and crystallographic orientation on the secondary electron yield of MgO during charging by a defocused electron beam irradiation. The experimental results show that there are two regimes during the charging process that are better identified by plotting the logarithm of the secondary electron emission yield, lnσ, as function of the total trapped charge in the material QT. The impact of the annealing temperature and crystallographic orientation on the evolution of lnσ is presented here. The slope of the asymptotic regime of the curve lnσ as function of QT, expressed in cm(2) per trapped charge, is probably linked to the elementary cross section of electron-hole recombination, σhole, which controls the trapping evolution in the reach of the stationary flow regime.

  19. Modernizing quantum annealing using local searches

    NASA Astrophysics Data System (ADS)

    Chancellor, Nicholas

    2017-02-01

    I describe how real quantum annealers may be used to perform local (in state space) searches around specified states, rather than the global searches traditionally implemented in the quantum annealing algorithm (QAA). Such protocols will have numerous advantages over simple quantum annealing. By using such searches the effect of problem mis-specification can be reduced, as only energy differences between the searched states will be relevant. The QAA is an analogue of simulated annealing, a classical numerical technique which has now been superseded. Hence, I explore two strategies to use an annealer in a way which takes advantage of modern classical optimization algorithms. Specifically, I show how sequential calls to quantum annealers can be used to construct analogues of population annealing and parallel tempering which use quantum searches as subroutines. The techniques given here can be applied not only to optimization, but also to sampling. I examine the feasibility of these protocols on real devices and note that implementing such protocols should require minimal if any change to the current design of the flux qubit-based annealers by D-Wave Systems Inc. I further provide proof-of-principle numerical experiments based on quantum Monte Carlo that demonstrate simple examples of the discussed techniques.

  20. 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.

  1. Effects of Annealing, Thermomigration, and Electromigration on the Intermetallic Compounds Growth Kinetics of Cu/Sn-2.5Ag Microbump.

    PubMed

    Kim, Seung-Hyun; Park, Gyu-Tae; Park, Jong-Jin; Park, Young-Bae

    2015-11-01

    The effects of annealing, thermomigration (TM), and electromigration (EM) on the intermetallic com- pound (IMC) growth kinetics of Cu/Sn-2.5Ag microbumps were investigated using in-situ scanning electron microscopy at 120-165 degrees C with a current density of 1.5 x 10(5) A/cm2. The IMC growth kinetics was controlled by a diffusion-dominant mechanism and a chemical-reaction-dominant mechanism with annealing and current-stressing conditions, respectively. Before all of the Sn was fully transformed into IMCs, the activation energies of the Cu3Sn IMCs were 0.54 eV, 0.50 eV, and 0.40 eV for annealing, TM, and EM, respectively, which is closely related to the acceleration effect of the interfacial reaction by electron wind force under current stressing. After all of the Sn was fully transformed into IMCs by reacting with Cu, the Cu3Sn IMC growth rates of the three structures became similar due to the reduced and similar diffusion rates inside the IMCs with and without current stressing.

  2. SiO{sub 2}/SiC structures annealed in D{sub 2}{sup 18}O: Compositional and electrical effects

    SciTech Connect

    Pitthan, E. Corrêa, S. A.; Soares, G. V.; Boudinov, H. I.; Stedile, F. C.

    2014-03-17

    Effects of water vapor annealing on SiO{sub 2}/4H-SiC structures formed following different routes were investigated using water isotopically enriched in {sup 18}O and {sup 2}H (D). Isotopic exchange between oxygen from the water vapor and oxygen from SiO{sub 2} films deposited on 4H-SiC was observed in the whole depth of the films, differently from the behavior of SiO{sub 2} films thermally grown on 4H-SiC. The highest amount of D was obtained in the sample with the highest negative fixed charge concentration, suggesting that the D incorporation occurs in defects in the structure that exist prior to the annealing. As a consequence of the water annealing, a significant reduction in the negative effective charge in metal-oxide-semiconductor capacitors and the removal of the SiO{sub 2}/SiC interfacial region was observed, attributed to the reduction of the amount of SiO{sub x}C{sub y} compounds in the interfacial region.

  3. Combined effects of transition metal (Ni and Rh) substitution and annealing/quenching on the physical properties of CaFe2As2

    SciTech Connect

    Ran, S; Bud'ko, S L; Straszheim, W E; Canfield, P C

    2014-08-01

    We performed systematic studies of the combined effects of annealing/quenching temperature (TA/Q) and T=Ni, Rh substitution (x) on the physical properties of Ca(Fe1-xTx)2As2. We constructed two-dimensional, TA/Q-x phase diagrams for the low-temperature states for both substitutions to map out the relations between ground states and compared them with that of Co substitution. Ni substitution, which brings one more extra electron per substituted atom and suppresses the c-lattice parameter at roughly the same rate as Co substitution, leads to a similar parameter range of antiferromagnetic/orthorhombic phase space in the TA/Q-x space as that found for Co substitution, but the parameter range for superconductivity has been shrunk (roughly by a factor of 2). This result is similar to what is found when Co- and Ni-substituted BaFe2As2 are compared. On the other hand, Rh substitution, which brings the same amount of extra electrons as does Co substitution, but suppresses the c-lattice parameter more rapidly, has a different phase diagram. The collapsed tetragonal phase exists much more pervasively, to the exclusion of the normal, paramagnetic, tetragonal phase. The range of antiferromagnetic/orthorhombic phase space is noticeably reduced, and the superconducting region is substantially suppressed, essentially truncated by the collapsed tetragonal phase. In addition, we found that whereas for Co substitution there was no difference between phase diagrams for samples annealed for 1 or 7 days, for Ni and Rh substitutions a second, reversible effect of annealing was revealed by 7-day anneals.

  4. Effect of annealing InGaP/InAlGaP laser structure at 950°C on laser characteristics

    NASA Astrophysics Data System (ADS)

    Al-Jabr, Ahmad A.; Mishra, Pawan; Majid, Mohammed A.; Ng, Tien Khee; Ooi, Boon S.

    2016-07-01

    We achieved considerable laser diode (LD) improvement after annealing InGaP/InAlGaP laser structure at 950°C for a total annealing time of 2 min. The photoluminescence intensity is increased by 10 folds and full-wave at half-maximum is reduced from ˜30 to 20 nm. The measured LDs exhibited significantly reduced threshold current (Ith), from 2 to 1.5 A for a 1-mm long LD, improved internal efficiency (ηi), from 63% to 68%, and increased internal losses αi, from 14.3 to 18.6 cm-1. Our work suggests that the use of strain-induced quantum well intermixing is a viable solution for high-efficiency AlGaInP devices at shorter wavelengths. The advent of laser-based solid-state lighting (SSL) and visible-light communications (VLC) highlighted the importance of the current findings, which are aimed at improving color quality and photodetector received power in SSL and VLC, respectively, via annealed red LDs.

  5. Rapid thermal annealing effect on the spatial resistivity distribution of AZO thin films deposited by pulsed-direct-current sputtering for solar cells applications

    NASA Astrophysics Data System (ADS)

    Ayachi, Boubakeur; Aviles, Thomas; Vilcot, Jean-Pierre; Sion, Cathy

    2016-03-01

    Room temperature deposited aluminium-doped zinc oxide thin films on glass substrate, using pulsed-DC magnetron sputtering, have shown high optical transmittance and low electrical resistivity with high uniformity of its spatial distribution after they were exposed to a rapid thermal annealing process at 400 °C under N2H2 atmosphere. It is particularly interesting to note that such an annealing process of AZO thin films for only 30 s was sufficient, on one hand to improve their optical transmittance from 73% to 86%, on the other hand to both decrease their resistivity from 1.7 × 10-3 Ω cm to 5.1 × 10-4 Ω cm and achieve the highest uniformity spatial distribution. To understand the mechanisms behind such improvements of the optoelectronic properties, electrical, optical, structural and morphological changes as a function of annealing time have been investigated by using hall measurement, UV-visible spectrometry, X-ray diffraction and scanning electron microscope imaging, respectively.

  6. Effects of post-deposition annealing ambient on band alignment of RF magnetron-sputtered Y2O3 film on gallium nitride

    PubMed Central

    2013-01-01

    The effects of different post-deposition annealing ambients (oxygen, argon, forming gas (95% N2 + 5% H2), and nitrogen) on radio frequency magnetron-sputtered yttrium oxide (Y2O3) films on n-type gallium nitride (GaN) substrate were studied in this work. X-ray photoelectron spectroscopy was utilized to extract the bandgap of Y2O3 and interfacial layer as well as establishing the energy band alignment of Y2O3/interfacial layer/GaN structure. Three different structures of energy band alignment were obtained, and the change of band alignment influenced leakage current density-electrical breakdown field characteristics of the samples subjected to different post-deposition annealing ambients. Of these investigated samples, ability of the sample annealed in O2 ambient to withstand the highest electric breakdown field (approximately 6.6 MV/cm) at 10−6 A/cm2 was related to the largest conduction band offset of interfacial layer/GaN (3.77 eV) and barrier height (3.72 eV). PMID:23360596

  7. Structures and properties of La- and Sm-doped BaTiO3 sputtered films: Post-annealing and dopant effects

    NASA Astrophysics Data System (ADS)

    Wu, C. H.; Chu, J. P.; Chang, W. Z.; John, V. S.; Wang, S. F.; Lin, C. H.

    2008-01-01

    200-nm-thick La- and Sm-doped BaTiO3 thin films with A /B ratio of unity fabricated by magnetron sputtering on the Pt /Ti/SiO2/Si substrate have been characterized. The effects of post-annealing and the amount of dopant on structure and electrical properties were studied. X-ray diffraction studies reveal that the films annealed at 750°C show tetragonal BaTiO3 crystal structure without any detectable second phase formation. X-ray photoelectron spectroscopy results confirm that La substitutes the A site and Sm is in the B site in lightly doped films. La2O3 or Sm2O3 is present in the BaTiO3 structure when the dopant content is more than 1.4at.% La or 1.0% Sm. The permittivity increases with increasing annealing temperature up to 750°C due to the coarse grains and better crystallinity. The leakage current property is found to vary with the type of dopant.

  8. Postprocessing annealing effects on direct current and microwave performance of AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Lee, Jaesun; Liu, Dongmin; Kim, Hyeongnam; Lu, Wu

    2004-09-01

    The effects of postprocessing annealing on direct current, radio frequency small signal, and power performances of AlGaN /GaN high electron mobility transistors with a gate-length of 0.2μm were investigated. The postannealing technique can improve the device performance, especially, after 10min postannealing at 400°C, the gate-to-drain breakdown voltage of devices exhibits remarkable improvement from 25 to 187V. The maximum extrinsic transconductance increases from 223 to 233mS/mm at a drain bias of 10V after 10min annealing at 400°C. The maximum drain current at a gate bias of 1V increases from 823 to 956mA/mm. After annealing, the values of the unity current gain cut-off frequency and the maximum oscillation frequency increases from 24 and 80GHz to 55 and 150GHz, respectively. The output power and gain at 10GHz were improved from 16.4dBm and 11.4dB to 25.9dBm and 19dB, respectively.

  9. Analysis of improved photovoltaic properties of pentacene/C60 organic solar cells: Effects of exciton blocking layer thickness and thermal annealing

    SciTech Connect

    Yoo, Seunghyup; Potscavage, William J.; Domercq, Benoit; Han, Sung-Ho; Li, Tai-De; Jones, Simon C.; Szoszkiewicz, Robert; Levi, Dean; Riedo, Elisa; Marder, Seth R.; Kippelen, Bernard

    2007-10-01

    We report on the photovoltaic properties of organic solar cells based on pentacene and C60 thin films with a focus on their spectral responses and the effect of thermal annealing. Spectra of external quantum efficiency (EQE) are measured and analyzed with a one-dimensional exciton diffusion model dependent upon the complex optical functions of pentacene films, which are measured by spectroscopic ellipsometry. An improvement in EQE is observed when the thickness of the bathocuproine (BCP) layer is decreased from 12 nm to 6 nm. Detailed analysis of the EQE spectra indicates that large exciton diffusion lengths in the pentacene films are responsible for the overall high EQE values near wavelengths of 668 nm. Analysis also shows that improvement in the EQE of devices with the thinner BCP layer can be attributed to a net gain in optical field distribution and improvement in carrier collection efficiency. An improvement in open-circuit voltage (VOC) is also achieved through a thermal annealing process, leading to a net increase in power conversion efficiency. Integration of the EQE spectrum with an AM1.5 G spectrum yields a predicted power conversion efficiency of 1.8 ± 0.2%. The increase in VOC is attributed to a significant reduction in the diode reverse saturation current upon annealing.

  10. Effect of Si and Mn Interactions on the Spheroidization and Coarsening Behavior of Cementite During Annealing in Severe Cold-Drawn Pearlitic Steel

    NASA Astrophysics Data System (ADS)

    Tu, Yiyou; Huang, Linghui; Wang, Xiaohui; Zhou, Xuefeng; Fang, Feng; Jiang, Jianqing

    2016-01-01

    The effects of Si and Mn interactions on the spheroidization and coarsening behavior of cementite during annealing in severe cold-drawn pearlitic steel were studied. Spheroidization of cementite particles annealed at 873 K (600 °C) in heavily cold-drawn pearlitic steel was obviously retarded by higher Si contents. The coarsening kinetics of cementite particles in heavily cold-drawn and annealed pearlite obeyed a power-law relationship. The values of ECD increase steadily according to a temporal dependence of n S87B (0.21 ± 0.02) for S87B and n S87BM (0.23 ± 0.06) for S87BM. The n values lie between 0.20 and 0.25, indicating that cementite particles coarsening occurs through a combination of dislocation diffusion ( n = 0.20) controlled and grain boundary diffusion ( n = 0.25) controlled coarsening mechanisms. Higher Si content in S87BM led to more pronounced partitioning of Mn than that in S87B, resulting in more significant suppression of alloying elements and lower coarsening rate constant K on the cementite particles coarsening behavior.

  11. Effect of air-annealing on the morphological, microstructural and optical properties of CdSe NCs grown into porous anodic alumina template

    NASA Astrophysics Data System (ADS)

    Laatar, F.; Hassen, M.; Smida, A.; Riahi, R.; Bel Haj Mohamed, N.; Ezzaouia, H.

    2015-07-01

    In this work, cadmium selenide nanocrystals (CdSe NCs) were embedded into porous anodic alumina (PAA) template by simple immersion in aqueous solution containing L-cysteine (Cys) functionalized CdSe NCs and water. The prepared samples were heat treated at different temperatures between 150 and 300 °C during 30 min under air. The effect of thermal treatment under air on the CdSe NCs/PAA has been shown from morphological, microstructural and optical studies. Several characterization techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) spectroscopy were used to investigate the surface morphology and microstructural properties of CdSe nanoparticles on the PAA template as function of air-annealing temperature. XRD study shows the transformation phase of deposited CdSe nanoparticles on the PAA template from cubic structure to hexagonal structure at 300 °C. The morphology of CdSe nanorods array which are into the PAA surface were exhibited by AFM scan. Optical properties of CdSe NCs into PAA have been studied at different air-annealing temperatures using optical absorption and photoluminescence (PL) spectroscopy. The results showed that the crystal quality was significantly improved with the annealing temperature increase, bringing about an enhancement in PL and a decrease in optical band gap from 2.44 to 2.2 eV exhibiting a red shift.

  12. 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.

  13. Effects of post-deposition annealing ambient on band alignment of RF magnetron-sputtered Y2O3 film on gallium nitride.

    PubMed

    Quah, Hock Jin; Cheong, Kuan Yew

    2013-01-29

    The effects of different post-deposition annealing ambients (oxygen, argon, forming gas (95% N2 + 5% H2), and nitrogen) on radio frequency magnetron-sputtered yttrium oxide (Y2O3) films on n-type gallium nitride (GaN) substrate were studied in this work. X-ray photoelectron spectroscopy was utilized to extract the bandgap of Y2O3 and interfacial layer as well as establishing the energy band alignment of Y2O3/interfacial layer/GaN structure. Three different structures of energy band alignment were obtained, and the change of band alignment influenced leakage current density-electrical breakdown field characteristics of the samples subjected to different post-deposition annealing ambients. Of these investigated samples, ability of the sample annealed in O2 ambient to withstand the highest electric breakdown field (approximately 6.6 MV/cm) at 10-6 A/cm2 was related to the largest conduction band offset of interfacial layer/GaN (3.77 eV) and barrier height (3.72 eV).

  14. Effect of post-deposition implantation and annealing on the properties of PECVD deposited silicon nitride films

    SciTech Connect

    Shams, Q.A.

    1988-01-01

    Recently it has been shown that memory-quality silicon nitride can be deposited using plasma enhanced chemical vapor deposition (PECVD). Nitrogen implantation and post-deposition annealing resulted in improved memory properties of MNOS devices. The primary objective of the work described here is the continuation of the above work. Silicon nitride films were deposited using argon as the carrier gas and evaluated in terms of memory performance as the charge-trapping layer in the metal-nitride-oxide-silicon (MNOS) capacitor structure. The bonding structure of PECVD silicon nitride was modified by annealing in different ambients at temperatures higher than the deposition temperature. Post-deposition ion implantation was used to introduce argon into the films in an attempt to influence the transfer, trapping, and emission of charge during write/erase exercising of the MNOS devices. Results show that the memory performance of PECVD silicon nitride is sensitive to the deposition parameters and post-deposition processing.

  15. Annealing effects on the microstructure and coercive field of two ferritic-martensitic Eurofer steels: A comparative study

    NASA Astrophysics Data System (ADS)

    Oliveira, V. B.; Sandim, M. J. R.; Stamopoulos, D.; Renzetti, R. A.; Santos, A. D.; Sandim, H. R. Z.

    2013-04-01

    Reduced-activation ferritic-martensitic steels are promising candidates for structural applications in future nuclear fusion power plants. Oxide dispersion strengthened ODS-Eurofer and Eurofer 97 steels were cold rolled to 80% reduction in thickness and annealed in vacuum for 1 h from 200 to 1350 °C to evaluate both their thermal stability and magnetic behavior. The microstructural changes were followed by magnetic measurements, in particular the corresponding variation of the coercive field (Hc), as a function of both annealing and tempering treatments. Results show that Y2O3 nanoparticles strongly affect the mechanical properties of ODS-Eurofer steel but leave their magnetic properties fairly unchanged when compared with Eurofer-97 steel.

  16. Effects of nickel ions implantation and subsequent thermal annealing on structural and magnetic properties of titanium dioxide

    NASA Astrophysics Data System (ADS)

    Vakhitov, I. R.; Lyadov, N. M.; Valeev, V. F.; Nuzhdin, V. I.; Tagirov, L. R.; Khaibullin, R. I.

    2014-12-01

    Wide bandgap semiconducting rutile (TiO2) doped with 3d-elements is a promising material for spintronic applications. In our work a composite material of TiO2:Ni has been formed by using implantation of Ni+ ions into single-crystalline (100)- and (001)- plates of TiO2. Sub-micron magnetic layers of TiO2 containing nickel dopant have been obtained at high implantation fluence of 1×1017 ion/cm2. A part of the implanted samples was then annealed in vacuum at different temperatures Tann = 450-1200 K for 30 min. The influence of the implantation fluence, crystalline orientation, as well as subsequent annealing on the structural and magnetic properties of the nickel-implanted TiO2 have been investigated by using X-ray photoelectron spectroscopy, scanning electron microscopy and coil magnetometry techniques.

  17. Effect of annealing on structural and optical properties of sol-gel prepared Cd doped ZnO thin films

    SciTech Connect

    Sahoo, Guruprasad Jain, Mahaveer K.; Meher, S. R.

    2015-06-24

    Zn{sub 1-x}Cd{sub x}O thin films have been prepared by sol-gel spin coating method. Structural analysis shows that the Cd substitution into the wutrzite ZnO lattice is achieved up to about 20 mol %. The optical band gap is found to decrease with the increase in Cd content. Increase in the annealing temperature up to a certain critical temperature leads to band gap narrowing because of the proper substitution of Zn by Cd and thereafter the band gap increases due to Cd re-evaporation from the lattice sites. This critical temperature lowers down with the increase in Cd doping concentration. The resistivity decreases with the increase in Cd content and increases with the increase in annealing temperature.

  18. Local microscopic properties and annealing effect of Rb0.85Fe1.9Se2 single crystals

    NASA Astrophysics Data System (ADS)

    Szymański, K.; Olszewski, W.; Satuła, D.; Matwiejczyk, A.; Gawryluk, D. J.; Krztoń-Maziopa, A.; Puźniak, R.; Wiśniewski, A.

    2017-04-01

    Investigation of mesoscopically phase-separated Rb0.85Fe1.9Se2 single crystals has been performed and two iron sites: nonmagnetic and magnetic ones, were observed by Mössbauer spectroscopy. The softening of the nonmagnetic one, having clearly more soft dynamics, was found to be gained further by the annealing of the single crystals at phase separation temperature, T p, leading to the reduction of size of initially separated domains and their more homogenous distribution in the tetragonal matrix of the studied sample. The magnetic Fe sites of Rb0.85Fe1.9Se2 show strong magnetic texture, indicating the perpendicular to the ab-plane orientation of the iron magnetic moments. It was found that the annealing at T p causes a systematic decrease of the isomer shift of the doublet by 0.02(1) mm s‑1.

  19. Effect of annealing treatment on soft magnetic properties of Fe-6.5 wt% Si wide ribbons

    NASA Astrophysics Data System (ADS)

    Roy, R. K.; Panda, A. K.; Ghosh, M.; Mitra, A.; Ghosh, R. N.

    2009-09-01

    The 25 mm wide ribbons of Fe-6.5 wt% Si alloy have been developed by melt spinning technique, showing sufficient ductility and white silver appearance. Two magnetic transitions take place at 676 and 760 °C due to the formation of B2 ordered phase and A2 disordered paramagnetic phase, respectively. The saturation magnetization of the ribbon is 17.5 kG under the applied field of 12 kG. The as-cast ribbons consist of disordered A2 structure with a low volume of B2 phases while the annealed microstructure comprises a dispersion of B2 domains in the disordered A2 matrix. The alloy shows the enhancement of the soft magnetic properties with a reduction in coercivity from 150 A/m in the as-cast state to 45 A/m in the annealed condition at 850 °C.

  20. Effect of annealing atmosphere on the structure and luminescence of Sn-implanted SiO{sub 2} layers

    SciTech Connect

    Lopes, J.M.J.; Zawislak, F.C.; Fichtner, P.F.P.; Lovey, F.C.; Condo, A.M.

    2005-01-10

    Sn nanoclusters are synthesized in 180 nm SiO{sub 2} layers after ion implantation and heat treatment. Annealings in N{sub 2} ambient at high temperatures (T{>=}700 deg. C) lead to the formation of Sn nanoclusters of different sizes in metallic and in oxidized phases. High-resolution transmission electron microscopy (TEM) analyses revealed that the formed larger nanoparticles are composed by a Sn metallic core and a SnO{sub x} shell. The corresponding blue-violet photoluminescence (PL) presents low intensity. However, for heat treatments in vacuum, the PL intensity is increased by a factor of 5 and the TEM data show a homogeneous size distribution of Sn nanoclusters. The low intensity of PL for the N{sub 2} annealed samples is associated with Sn oxidation.