Tuning the properties of tin oxide thin films for device fabrications

NASA Astrophysics Data System (ADS)

Sudha, A.; Sharma, S. L.; Gupta, A. N.; Sharma, S. D.

2017-11-01

Tin oxide thin films were deposited on well cleaned glass substrates by thermal evaporation in vacuum and were annealed at 500 ∘C in the open atmosphere inside a furnace for 90 min for promoting the sensitivity of the films. The X-ray diffraction studies revealed that the as-deposited films were amorphous in nature and the annealed films showed appreciable crystalline behavior. The annealed thin films were then irradiated using 60Co gamma source. The radiation induced changes were then studied by X-ray diffraction, scanning electron microscopy, UV-vis spectroscopy and I- V characterization. The remarkable increase in the average grain size, the decrement in the energy band gap and resistivity due to the gamma irradiations up to a certain dose and the reversal of these properties at higher doses are the important observations. The large changes in the conductivity and energy band gap of the annealed thin films due to gamma irradiation make these films quite important device material for the fabrication of gamma sensors and dosimeters.

ROLE OF THE NETWORK FORMER IN SEMICONDUCTING OXIDE GLASSES.

DTIC Science & Technology

SEMICONDUCTOR DEVICES, * GLASS ), (*ELECTRICAL NETWORKS, GLASS ), ELECTRICAL PROPERTIES, SEEBECK EFFECT, BORATES, PHOSPHATES, ELECTRICAL RESISTANCE, X RAY DIFFRACTION, ANNEALING, OXIDATION, OXIDES, ELECTRODES, VANADIUM

X-ray absorption fine structure and x-ray diffraction studies of crystallographic grains in nanocrystalline FePd:Cu thin films

NASA Astrophysics Data System (ADS)

Krupinski, M.; Perzanowski, M.; Polit, A.; Zabila, Y.; Zarzycki, A.; Dobrowolska, A.; Marszalek, M.

2011-03-01

FePd alloys have recently attracted considerable attention as candidates for ultrahigh density magnetic storage media. In this paper we investigate FePd thin alloy film with a copper admixture composed of nanometer-sized grains. [Fe(0.9 nm)/Pd(1.1 nm)/Cu(d nm)]×5 multilayers were prepared by thermal deposition at room temperature in UHV conditions on Si(100) substrates covered by 100 nm SiO2. The thickness of the copper layer has been changed from 0 to 0.4 nm. After deposition, the multilayers were rapidly annealed at 600 °C in a nitrogen atmosphere, which resulted in the creation of the FePd:Cu alloy. The structure of alloy films obtained this way was determined by x-ray diffraction (XRD), glancing angle x-ray diffraction, and x-ray absorption fine structure (EXAFS). The measurements clearly showed that the L10 FePd:Cu nanocrystalline phase has been formed during the annealing process for all investigated copper compositions. This paper concentrates on the crystallographic grain features of FePd:Cu alloys and illustrates that the EXAFS technique, supported by XRD measurements, can help to extend the information about grain size and grain shape of poorly crystallized materials. We show that, using an appropriate model of the FePd:Cu grains, the comparison of EXAFS and XRD results gives a reasonable agreement.

Effect of Annealing Temperature on Structural and Optical Properties of Sol-Gel-Derived ZnO Thin Films

NASA Astrophysics Data System (ADS)

Arif, Mohd.; Sanger, Amit; Vilarinho, Paula M.; Singh, Arun

2018-04-01

Nanocrystalline ZnO thin films were deposited on glass substrate via sol-gel dip-coating technique then annealed at 300°C, 400°C, and 500°C for 1 h. Their optical, structural, and morphological properties were studied using ultraviolet-visible (UV-Vis) spectrophotometry, x-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). XRD diffraction revealed that the crystalline nature of the thin films increased with increasing annealing temperature. The c-axis orientation improved, and the grain size increased, as indicated by increased intensity of the (002) plane peak at 2θ = 34.42° corresponding to hexagonal ZnO crystal. The average crystallite size of the thin films ranged from 13 nm to 23 nm. Increasing the annealing temperature resulted in larger crystallite size and higher crystallinity with increased surface roughness. The grain size according to SEM analysis was in good agreement with the x-ray diffraction data. The optical bandgap of the thin films narrowed with increasing annealing temperature, lying in the range of 3.14 eV to 3.02 eV. The transmission of the thin films was as high as 94% within the visible region. The thickness of the thin films was 400 nm, as measured by ellipsometry, after annealing at the different temperatures of 300°C, 400°C, and 500°C.

Thermoluminescence, ESR and x-ray diffraction studies of CaSO4 : Dy phosphor subjected to post preparation high temperature thermal treatment

NASA Astrophysics Data System (ADS)

Bakshi, A. K.; Patwe, S. J.; Bhide, M. K.; Sanyal, B.; Natarajan, V.; Tyagi, A. K.; Kher, R. K.

2008-01-01

Thermoluminescence (TL), electron spin resonance (ESR) and x ray diffraction studies of CaSO4 : Dy phosphor subjected to post preparation high temperature treatment were carried out. Analysis of the TL glow curve indicated that the dosimetric glow peak at 240 °C reduces, whereas the low temperature satellite peak increases with the increase in the annealing temperature in the range 650-1000 °C. The influence of the annealing atmosphere on the TL glow curve structure was also observed. Reduction of the photoluminescence intensity of the annealed phosphor indicated that the environment of Dy3+ ions might have undergone some change due to high temperature treatment. Reduction in the ESR signal intensity corresponding to O_{3}^{-} and SO_{3}^{-} radicals was observed initially with the increase in the annealing temperaure; subsequently their intensity increased with temperature. Signals due to the SO_{4}^{-} radical vanished, when the phosphor was annealed beyond 800 °C. A signal corresponding to SH2- radicals was also observed in the ESR spectra for samples subjected to annealing in the temperature regime 800-1000 °C. XRD of the in situ annealed phosphor showed a change in the unit cell parameters. An endothermic peak at 860 °C in the DTA spectrum was observed.

X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

NASA Astrophysics Data System (ADS)

Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

2018-05-01

In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration ( Q a) and the activation energy of microstrain relaxation ( Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

NASA Astrophysics Data System (ADS)

Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

2018-04-01

In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration (Q a) and the activation energy of microstrain relaxation (Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

In Situ XRD Studies of the Process Dynamics During Annealing in Cold-Rolled Copper

NASA Astrophysics Data System (ADS)

Dey, Santu; Gayathri, N.; Bhattacharya, M.; Mukherjee, P.

2016-12-01

The dynamics of the release of stored energy during annealing along two different crystallographic planes, i.e., {111} and {220}, in deformed copper have been investigated using in situ X-ray diffraction measurements at 458 K and 473 K (185 °C and 200 °C). The study has been carried out on 50 and 80 pct cold-rolled Cu sheets. The microstructures of the rolled samples have been characterized using optical microscopy and electron backscattered diffraction measurements. The microstructural parameters were evaluated from the X-ray diffractogram using the Scherrer equation and the modified Rietveld method. The stored energy along different planes was determined using the modified Stibitz formula from the X-ray peak broadening, and the bulk stored energy was evaluated using differential scanning calorimetry. The process dynamics of recovery and recrystallization as observed through the release of stored energy have been modeled as the second-order and first-order processes, respectively.

In situ defect annealing of swift heavy ion irradiated CeO 2 and ThO 2 using synchrotron X-ray diffraction and a hydrothermal diamond anvil cell

DOE PAGES

Palomares, Raul I.; Tracy, Cameron L.; Zhang, Fuxiang; ...

2015-04-16

Hydrothermal diamond anvil cells (HDACs) provide facile means for coupling synchrotron Xray techniques with pressure up to 10 GPa and temperature up to 1300 K. This manuscript reports on an application of the HDAC as an ambient-pressure sample environment for performing in situ defect annealing and thermal expansion studies of swift heavy ion irradiated CeO 2 and ThO 2 using synchrotron X-ray diffraction. The advantages of the in situ HDAC technique over conventional annealing methods include: rapid temperature ramping and quench times, high-resolution measurement capability, simultaneous annealing of multiple samples, and prolonged temperature- and apparatus stability at high temperatures. Isochronalmore » annealing between 300 K and 1100 K revealed 2-stage and 1-stage defect recovery processes for irradiated CeO 2 and ThO 2, respectively; indicating that the morphology of the defects produced by swift heavy ion irradiation of these two materials differs significantly. These results suggest that electronic configuration plays a major role in both the radiation-induced defect production and high temperature defect recovery mechanisms of CeO 2 and ThO 2.« less

Impacts of excimer laser annealing on Ge epilayer on Si

NASA Astrophysics Data System (ADS)

Huang, Zhiwei; Mao, Yichen; Yi, Xiaohui; Lin, Guangyang; Li, Cheng; Chen, Songyan; Huang, Wei; Wang, Jianyuan

2017-02-01

The impacts of excimer laser annealing on the crystallinity of Ge epilayers on Si substrate grown by low- and high-temperature two-step approach in an ultra-high vacuum chemical vapor deposition system were investigated. The samples were treated by excimer laser annealing (ELA) at various laser power densities with the temperature above the melting point of Ge, while below that of Si, resulting in effective reduction of point defects and dislocations in the Ge layer with smooth surface. The full-width at half-maximum (FWHM) of X-ray diffraction patterns of the low-temperature Ge epilayer decreases with the increase in laser power density, indicating the crystalline improvement and negligible effect of Ge-Si intermixing during ELA processes. The short laser pulse time and large cooling rate cause quick melting and recrystallization of Ge epilayer on Si in the non-thermal equilibrium process, rendering tensile strain in Ge epilayer as calculated quantitatively with thermal mismatch between Si and Ge. The FWHM of X-ray diffraction patterns is significantly reduced for the two-step grown samples after treated by a combination of ELA and conventional furnace thermal annealing, indicating that the crystalline of Ge epilayer is improved more effectively with pre- annealing by excimer laser.

Long annealing effect on spin Seebeck devices fabricated using Ce x Y3- x Fe5O12 deposited by metal-organic decomposition

NASA Astrophysics Data System (ADS)

Ono, Tatsuyoshi; Hirata, Satoshi; Amemiya, Yoshiteru; Tabei, Tetsuo; Yokoyama, Shin

2018-04-01

The effects of Ce content and annealing temperature on the electromotive force produced by spin Seebeck devices fabricated using Ce x Y3- x Fe5O12 deposited by metal-organic decomposition was investigated. The Ce content was first varied (x = 0,1,2,3) for a fixed annealing condition of 3 h at 900 °C. It was found that increasing the Ce content led to a decrease in electromotive force, which meant that x = 0 was the optimum Ce content. Next, the effect of annealing temperature was investigated for a Ce1Y2Fe5O12 film for an annealing time of 14 h. The highest electromotive force of 24.0 µV/50 °C was obtained for a sample annealed for 14 h at 800 °C, although the X-ray diffraction peaks were weaker than those for a sample annealed for 14 h at 950 °C.

Effect of cadmium incorporation on the properties of zinc oxide thin films

NASA Astrophysics Data System (ADS)

Bharath, S. P.; Bangera, Kasturi V.; Shivakumar, G. K.

2018-02-01

Cd x Zn1- x O (0 ≤ x ≤ 0.20) thin films are deposited on soda lime glass substrates using spray pyrolysis technique. To check the thermal stability, Cd x Zn1- x O thin films are subjected to annealing. Both the as-deposited and annealed Cd x Zn1- x O thin films are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDAX) to check the structural, surface morphological and compositional properties, respectively. XRD analysis reveals that the both as-deposited and annealed Cd x Zn1- x O thin films are (002) oriented with wurtzite structure. SEM studies confirm that as-deposited, as well as annealed Cd x Zn1- x O thin films are free from pinholes and cracks. Compositional analysis shows the deficiency in Cd content after annealing. Optical properties evaluated from UV-Vis spectroscopy shows red shift in the band gap for Cd x Zn1- x O thin films. Electrical property measured using two probe method shows a decrease in the resistance after Cd incorporation. The results indicate that cadmium can be successfully incorporated in zinc oxide thin films to achieve structural changes in the properties of films.

Impact of grain size and structural changes on magnetic, dielectric, electrical, impedance and modulus spectroscopic characteristics of CoFe2O4 nanoparticles synthesized by honey mediated sol-gel combustion method

NASA Astrophysics Data System (ADS)

Singh Yadav, Raghvendra; Kuřitka, Ivo; Vilcakova, Jarmila; Havlica, Jaromir; Masilko, Jiri; Kalina, Lukas; Tkacz, Jakub; Švec, Jiří; Enev, Vojtěch; Hajdúchová, Miroslava

2017-12-01

In this work CoFe2O4 spinel ferrite nanoparticles were synthesized by honey mediated sol-gel combustion method and further annealed at higher temperature 500 °C, 700 °C, 900 °C and 1100 °C. The synthesized spinel ferrite nanoparticles is investigated by x-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), field emission scanning electron microscopy, x-ray photoelectron spectroscopy and vibrating sample magnetometer. The x-ray diffraction study reveals face-centered cubic spinel cobalt ferrite crystal phase formation. The crystallite size and lattice parameter are increased with annealing temperature. Raman and Fourier transform infrared spectra also confirm spinel ferrite crystal structure of synthesized nanoparticles. The existence of cation at octahedral and tetrahedral site in cobalt ferrite nanoparticles is confirmed by x-ray photoelectron spectroscopy. Magnetic measurement shows increased saturation magnetization 74.4 emu g-1 at higher annealing temperature 1100 °C, high coercivity 1347.3 Oe at lower annealing temperature 500 °C, and high remanent magnetization 32.3 emu g-1 at 900 °C annealing temperature. The magnetic properties of synthesized ferrite nanoparticles can be tuned by adjusting sizes through annealing temperature. Furthermore, the dielectric constant and ac conductivity shows variation with frequency (1-107 Hz), grain size and cation redistribution. The modulus spectroscopy study reveals the role of bulk grain and grain boundary towards the resistance and capacitance. The cole-cole plots in modulus formalism also well support the electrical response of nanoparticles originated from both grain and grain boundaries. The dielectric, electrical, magnetic, impedance and modulus spectroscopic characteristics of synthesized CoFe2O4 spinel ferrite nanoparticles demonstrate the applicability of these nanoparticles for magnetic recording, memory devices and for microwave applications.

Electron spectroscopy imaging and surface defect configuration of zinc oxide nanostructures under different annealing ambient

NASA Astrophysics Data System (ADS)

Ann, Ling Chuo; Mahmud, Shahrom; Bakhori, Siti Khadijah Mohd

2013-01-01

In this study, electron spectroscopy imaging was used to visualize the elemental distribution of zinc oxide nanopowder. Surface modification in zinc oxide was done through annealing treatment and type of surface defect was also inferred from the electron spectroscopy imaging investigation. The micrographs revealed the non-stoichiometric distribution of the elements in the unannealed samples. Annealing the samples in nitrogen and oxygen ambient at 700 °C would alter the density of the elements in the samples as a result of removal or absorption of oxygen. The electrical measurement showed that nitrogen annealing treatment improved surface electrical conductivity, whereas oxygen treatment showed an adverse effect. Observed change in the photoluminescence green emission suggested that oxygen vacancies play a significant role as surface defects. Structural investigation carried out through X-ray diffraction revealed the polycrystalline nature of both zinc oxide samples with hexagonal phase whereby annealing process increased the crystallinity of both zinc oxide specimens. Due to the different morphologies of the two types of zinc oxide nanopowders, X-ray diffraction results showed different stress levels in their structures and the annealing treatment give significant effect to the structural stress. Electron spectroscopy imaging was a useful technique to identify the elemental distribution as well as oxygen defect in zinc oxide nanopowder.

Phase transformation from cubic ZnS to hexagonal ZnO by thermal annealing

NASA Astrophysics Data System (ADS)

Mahmood, K.; Asghar, M.; Amin, N.; Ali, Adnan

2015-03-01

We have investigated the mechanism of phase transformation from ZnS to hexagonal ZnO by high-temperature thermal annealing. The ZnS thin films were grown on Si (001) substrate by thermal evaporation system using ZnS powder as source material. The grown films were annealed at different temperatures and characterized by X-ray diffraction (XRD), photoluminescence (PL), four-point probe, scanning electron microscope (SEM) and energy dispersive X-ray diffraction (EDX). The results demonstrated that as-deposited ZnS film has mixed phases but high-temperature annealing leads to transition from ZnS to ZnO. The observed result can be explained as a two-step process: (1) high-energy O atoms replaced S atoms in lattice during annealing process, and (2) S atoms diffused into substrate and/or diffused out of the sample. The dissociation energy of ZnS calculated from the Arrhenius plot of 1000/T versus log (resistivity) was found to be 3.1 eV. PL spectra of as-grown sample exhibits a characteristic green emission at 2.4 eV of ZnS but annealed samples consist of band-to-band and defect emission of ZnO at 3.29 eV and 2.5 eV respectively. SEM and EDX measurements were additionally performed to strengthen the argument.

Impact of laser anneal on NiPt silicide texture and chemical composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feautrier, C.; Ozcan, A. S.; Lavoie, C.

We have combined synchrotron X-ray pole figure measurements and transmission electron microscopy (TEM) nano-beam diffraction to study the impact of millisecond laser anneal on the texture and microstructure of NiPt silicide thin films. The powerful use of nano-beam diffraction in plan-view geometry allows here for both a mapping of grain orientation and intra-grain measurements even if these crystalline grains become very small. With this unique combination of local and large-scale probes, we find that silicide formation on n and p doped substrates using laser annealing results in smaller grains compared with the films processed using standard rapid thermal annealing. Themore » laser annealed samples also result in grains that are more epitaxially oriented with respect to the Si substrate. For n-type substrate, the film is dominated by (020) and (013) oriented fibers with significant levels of intra-grain bending (transrotation) observed in both types of grains. For p-type substrates, mostly epitaxially aligned grains are detected. TEM coupled with energy-dispersive X-ray analysis was also used to study the elemental distribution in the silicide samples. Here, we confirm that laser anneal leads to a larger accumulation of platinum at the silicide-substrate interface and modifies the distribution of dopants throughout the film.« less

Impact of laser anneal on NiPt silicide texture and chemical composition

NASA Astrophysics Data System (ADS)

Feautrier, C.; Ozcan, A. S.; Lavoie, C.; Valery, A.; Beneyton, R.; Borowiak, C.; Clément, L.; Pofelski, A.; Salem, B.

2017-06-01

We have combined synchrotron X-ray pole figure measurements and transmission electron microscopy (TEM) nano-beam diffraction to study the impact of millisecond laser anneal on the texture and microstructure of NiPt silicide thin films. The powerful use of nano-beam diffraction in plan-view geometry allows here for both a mapping of grain orientation and intra-grain measurements even if these crystalline grains become very small. With this unique combination of local and large-scale probes, we find that silicide formation on n and p doped substrates using laser annealing results in smaller grains compared with the films processed using standard rapid thermal annealing. The laser annealed samples also result in grains that are more epitaxially oriented with respect to the Si substrate. For n-type substrate, the film is dominated by (020) and (013) oriented fibers with significant levels of intra-grain bending (transrotation) observed in both types of grains. For p-type substrates, mostly epitaxially aligned grains are detected. TEM coupled with energy-dispersive X-ray analysis was also used to study the elemental distribution in the silicide samples. Here, we confirm that laser anneal leads to a larger accumulation of platinum at the silicide-substrate interface and modifies the distribution of dopants throughout the film.

Effect of annealing on structural and luminescence properties of Eu3+ doped NaYF4 phosphor

NASA Astrophysics Data System (ADS)

Pathak, Trilok K.; Kumar, Ashwini; Swart, H. C.; Kroon, R. E.

2018-04-01

Eu3+ doped NaYF4 phosphors have been synthesized by the combustion method. The effect of annealing on the structural, morphological and luminescence properties has been investigated. X-ray diffraction analysis revealed that the Eu3+ doped NaYF4 phosphors consisted of mixed phases: α-phase and β-phase which were affected by the annealing of the phosphor. The surface morphology showed a significant change with annealing in the Eu3+ doped NaYF4 phosphors. The elemental mapping and energy dispersive X-ray spectroscopy spectra proved the formation of the desired materials. The photoluminescence spectra illustrated the optical properties of Eu3+ in the as-prepared and annealed Eu3+ doped NaYF4 phosphors. The intensity of the peaks 5D0 → 7F2 and 5D0 → 7F1 varied in as-prepared and annealed samples. The lifetime of the Eu3+ luminescence at 615 nm was also weakly affected by the Eu3+ doping and annealing temperature.

A laboratory based system for laue micro x-ray diffraction.

PubMed

Lynch, P A; Stevenson, A W; Liang, D; Parry, D; Wilkins, S; Tamura, N

2007-02-01

A laboratory diffraction system capable of illuminating individual grains in a polycrystalline matrix is described. Using a microfocus x-ray source equipped with a tungsten anode and prefigured monocapillary optic, a micro-x-ray diffraction system with a 10 microm beam was developed. The beam profile generated by the ellipsoidal capillary was determined using the "knife edge" approach. Measurement of the capillary performance, indicated a beam divergence of 14 mrad and a useable energy bandpass from 5.5 to 19 keV. Utilizing the polychromatic nature of the incident x-ray beam and application of the Laue indexing software package X-Ray Micro-Diffraction Analysis Software, the orientation and deviatoric strain of single grains in a polycrystalline material can be studied. To highlight the system potential the grain orientation and strain distribution of individual grains in a polycrystalline magnesium alloy (Mg 0.2 wt % Nd) was mapped before and after tensile loading. A basal (0002) orientation was identified in the as-rolled annealed alloy; after tensile loading some grains were observed to undergo an orientation change of 30 degrees with respect to (0002). The applied uniaxial load was measured as an increase in the deviatoric tensile strain parallel to the load axis.

Impact of magnetic fields on the morphology of hybrid perovskite films for solar cells

NASA Astrophysics Data System (ADS)

Corpus-Mendoza, Asiel N.; Moreno-Romero, Paola M.; Hu, Hailin

2018-05-01

The impact of magnetic fields on the morphology of hybrid perovskite films is assessed via scanning electron microscopy and X-ray diffraction. Small-grain non-uniform perovskite films are obtained when a large magnetic flux density is applied to the sample during reaction of PbI2 and methylammonium iodide (chloride). Similarly, X-ray diffraction reveals a change of preferential crystalline planes when large magnetic fields are applied. Furthermore, we experimentally demonstrate that the quality of the perovskite film is affected by the magnetic field induced by the magnetic stirring system of the hot plate where the samples are annealed. As a consequence, optimization of the perovskite layer varies with magnetic field and annealing temperature. Finally, we prove that uncontrolled magnetic fields on the environment of preparation can severely influence the reproducibility of results.

Post-growth annealing of germanium-tin alloys using pulsed excimer laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lanxiang; Wang, Wei; Zhou, Qian

2015-07-14

We investigate the impact of pulsed excimer laser anneal on fully strained germanium-tin alloys (Ge{sub 1−x}Sn{sub x}) epitaxially grown on Ge substrate by molecular beam epitaxy. Using atomic force microscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, the morphological and compositional evolution of Ge{sub 1−x}Sn{sub x} with Sn content up to 17% after annealing using various conditions is studied. Ge{sub 0.83}Sn{sub 0.17} samples annealed at 80 mJ/cm{sup 2} or 150 mJ/cm{sup 2} have no observable changes with respect to the as-grown sample. However, Ge{sub 0.83}Sn{sub 0.17} samples annealed at 250 mJ/cm{sup 2} or 300 mJ/cm{sup 2} have Sn-richmore » islands on the surface, which is due to Sn segregation in the compressively strained epitaxial film. For Ge{sub 0.89}Sn{sub 0.11}, significant Sn redistribution occurs only when annealed at 300 mJ/cm{sup 2}, indicating that it has better thermal stability than Ge{sub 0.83}Sn{sub 0.17}. A mechanism is proposed to explain the formation of Sn-rich islands and Sn-depleted regions.« less

Optical and Structural Characterization of ZnO/TiO2 Bilayer Thin Films Grown by Sol-Gel Spin Coating

NASA Astrophysics Data System (ADS)

Gareso, P. L.; Musfitasari; Juarlin, Eko

2018-03-01

Structural and optical properties of ZnO/TiO2 bilayers thin films have been investigated using x-ray diffraction (X-RD), scanning electron microscopy (SEM), and optical transmittance UV-Vis measurements. ZnO thin films were prepared by dissolving zinc acetate dehydrated into a solvent of ethanol and then added triethanolamin. In the case of TiO2 layers, tetraisoproxide was dissolved into ethanol and then added an acetate acid. The layer of ZnO was deposited first followed by TiO2 layer on a glass substrate using a spin coating technique. The ZnO/TiO2 bilayers were annealed at various temperatures from 300°C until 600°C for 60 minutes. The X-ray diffraction results show that there was an enhancement of the x-ray spectra as annealed temperature increased to 600°C in comparison to the samples that were annealed at 300°C. Based on the optical measurement of UV-Vis, the band gap energy of ZnO/TiO2 bilayer is around 3.2 eV at temperature of 300°C. This value is similar to the band gap energy of ZnO. SEM results show that there is no cluster in the surface of ZnO/TiO2 bilayer.

Some physical properties of naturally irradiated fluorite

USGS Publications Warehouse

Berman, Robert

1955-01-01

Five samples of purple fluorite found in association with radioactive, materials, and a synthetic colorless control sample were studied and compared.  Before and after heating, observations were made on specific gravity, index of refraction, unit-cell size, breadth of X-ray diffraction lines, and fluorescence.  The purple samples became colorless on heating above 175° C.  During the process, observations were made on color, thermoluminescence, and differential thermal analysis curves.  There were strong correlations between the various physical properties, and it was found possible to arrange the samples in order of increasing difference in their physical properties from the control sample. This order apparently represents increasing structural damage by radiation; if so, it correlates with decreasing specific gravity, increasing index of refraction, broadening of X-ray lines, and increasingly strong exothermic reactions on annealing. The differences between the samples in index of refraction and X-ray pattern are largely eliminated on annealing.  Annealing begins at 1750 C; thermoluminescence at lower temperatures is due to electrons escaping from the metastable potential traps, not the destruction of those traps which takes place on annealing.

Microstructural evolution and grain growth kinetics of GZ31 magnesium alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roostaei, M., E-mail: miladroustaei68@ut.ac.ir

2016-08-15

Grain growth behavior of Mg–3Gd–1Zn (GZ31) magnesium alloy was studied in a wide range of annealing time and temperature to clarify the kinetics of grain growth, microstructural evolution and related metallurgical phenomena. This material exhibited typical normal grain growth mode under annealing conditions with annealing temperature of lower than 300 °C and soaking time of lower than 240 min. However, the abnormality in grain growth was also evident at annealing temperature of 400 °C and 500 °C. The dependence of abnormal grain growth (AGG) at mentioned annealing temperatures upon microstructural features such as dispersed precipitates, which were rich in Znmore » and Gd, was investigated by optical micrographs, X-ray diffraction patterns, scanning electron microscopy images, and energy dispersive X-ray analysis spectra. The bimodality in grain-size distribution histograms also signified the occurrence of AGG. Based on the experimental data on grain growth obtained by annealing treatments, the grain growth exponent and the activation energy were also figured out.« less

Sb-related defects in Sb-doped ZnO thin film grown by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Luo, Caiqin; Ho, Lok-Ping; Azad, Fahad; Anwand, Wolfgang; Butterling, Maik; Wagner, Andreas; Kuznetsov, Andrej; Zhu, Hai; Su, Shichen; Ling, Francis Chi-Chung

2018-04-01

Sb-doped ZnO films were fabricated on c-plane sapphire using the pulsed laser deposition method and characterized by Hall effect measurement, X-ray photoelectron spectroscopy, X-ray diffraction, photoluminescence, and positron annihilation spectroscopy. Systematic studies on the growth conditions with different Sb composition, oxygen pressure, and post-growth annealing were conducted. If the Sb doping concentration is lower than the threshold ˜8 × 1020 cm-3, the as-grown films grown with an appropriate oxygen pressure could be n˜4 × 1020 cm-3. The shallow donor was attributed to the SbZn related defect. Annealing these samples led to the formation of the SbZn-2VZn shallow acceptor which subsequently compensated for the free carrier. For samples with Sb concentration exceeding the threshold, the yielded as-grown samples were highly resistive. X-ray diffraction results showed that the Sb dopant occupied the O site rather than the Zn site as the Sb doping exceeded the threshold, whereas the SbO related deep acceptor was responsible for the high resistivity of the samples.

Influence of Annealing on the Depth Microstructure of the Shot Peened Duplex Stainless Steel at Elevated Temperature

NASA Astrophysics Data System (ADS)

Feng, Qiang; She, Jia; Xiang, Yong; Wu, Xianyun; Wang, Chengxi; Jiang, Chuanhai

The depth profiles of residual stresses and lattice parameters in the surface layers of shot peened duplex stainless steel at elevated temperature were investigated utilizing X-ray diffraction analysis. At each deformation depth, residual stress distributions in both ferrite and austenite were studied by X-ray diffraction stress analysis which is performed on the basis of the sin2ψ method and the lattice parameters were explored by Rietveld method. The results reveal that difference changes of depth residual compressive stress profiles between ferrite and austenite under the same annealing condition are resulted from the diverse coefficient of thermal expansion, dislocation density, etc. for different phases in duplex stainless steel. The relaxations of depth residual stresses in austenite are more obvious than those in ferrite. The lattice parameters decrease in the surface layer with the extending of annealing time, however, they increase along the depth after annealing for 16min. The change of the depth lattice parameters can be ascribed to both thermal expansion and the relaxation of residual stress. The different changes of microstructure at elevated temperature between ferrite and austenite are discussed.

Post-Annealing Effects on Surface Morphological, Electrical and Optical Properties of Nanostructured Cr-Doped CdO Thin Films

NASA Astrophysics Data System (ADS)

Hymavathi, B.; Rajesh Kumar, B.; Subba Rao, T.

2018-01-01

Nanostructured Cr-doped CdO thin films were deposited on glass substrates by reactive direct current magnetron sputtering and post-annealed in vacuum from 200°C to 500°C. X-ray diffraction studies confirmed that the films exhibit cubic nature with preferential orientation along the (111) plane. The crystallite size, lattice parameters, unit cell volume and strain in the films were determined from x-ray diffraction analysis. The surface morphology of the films has been characterized by field emission scanning electron microscopy and atomic force microscopy. The electrical properties of the Cr-doped CdO thin films were measured by using a four-probe method and Hall effect system. The lowest electrical resistivity of 2.20 × 10-4 Ω cm and a maximum optical transmittance of 88% have been obtained for the thin films annealed at 500°C. The optical band gap of the films decreased from 2.77 eV to 2.65 eV with the increase of annealing temperature. The optical constants, packing density and porosity of Cr-doped CdO thin films were also evaluated from the transmittance spectra.

Magnetic analysis of a melt-spun Fe-dilute Cu60Ag35Fe5 alloy

NASA Astrophysics Data System (ADS)

Kondo, Shin-ichiro; Kaneko, Kazuhiro; Morimura, Takao; Nakashima, Hiromichi; Kobayashi, Shin-Taro; Michioka, Chishiro; Yoshimura, Kazuyoshi

2015-04-01

The magnetic properties of a melt-spun Fe-dilute Cu60Ag35Fe5 alloy are examined by X-ray diffraction, magnetic measurements, and transmission electron microscopy (TEM). The X-ray diffraction patterns show that the as-spun and annealed (773 K×36 ks) samples contain Cu and Ag phases and no Fe phases; thus, most Fe atoms are dispersed as clusters. Magnetic measurements indicate that the as-spun and annealed samples exhibit superparamagnetic behavior at 300 K, whereas ferromagnetic and superparamagnetic behaviors coexist at 4.2 K. The magnetic moments of small clusters at 300 K are determined by the nonlinear least squares method as 5148 and 4671 μB for as-spun and annealed samples, respectively, whereas those at 300 K are experimentally determined as 3500 and 3200 μB. This decrease in magnetic moments may imply the formation of anti-ferromagnetic coupling by annealing. TEM observation of the melt-spun sample suggests that there are three regions with different compositions: Cu-rich, Ag-rich, and Fe-rich with no precipitation in the matrix. In addition, these regions have obscure interfaces. The magnetic clusters are attributed to the Fe-rich regions.

Ferromagnetic Mn-Implanted GaP: Microstructures vs Magnetic Properties.

PubMed

Yuan, Ye; Hübner, René; Liu, Fang; Sawicki, Maciej; Gordan, Ovidiu; Salvan, G; Zahn, D R T; Banerjee, D; Baehtz, Carsten; Helm, Manfred; Zhou, Shengqiang

2016-02-17

Ferromagnetic GaMnP layers were prepared by ion implantation and pulsed laser annealing (PLA). We present a systematic investigation on the evolution of microstructure and magnetic properties depending on the pulsed laser annealing energy. The sample microstructure was analyzed by high-resolution X-ray diffraction (HR-XRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), ultraviolet Raman spectroscopy (UV-RS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of X-ray Pendellösung fringes around GaP (004) and RBS channeling prove the epitaxial structure of the GaMnP layer annealed at the optimized laser energy density (0.40 J/cm(2)). However, a forbidden TO vibrational mode of GaP appears and increases with annealing energy, suggesting the formation of defective domains inside the layer. These domains mainly appear in the sample surface region and extend to almost the whole layer with increasing annealing energy. The reduction of the Curie temperature (TC) and of the uniaxial magnetic anisotropy gradually happens when more defects and the domains appear as increasing the annealing energy density. This fact univocally points to the decisive role of the PLA parameters on the resulting magnetic characteristics in the processed layers, which eventually determine the magnetic (or spintronics) figure of merit.

Application of valence-to-core X-ray emission spectroscopy for identification and estimation of amount of carbon covalently bonded to chromium in amorphous Cr-C coatings prepared by magnetron sputtering

NASA Astrophysics Data System (ADS)

Safonov, V. A.; Habazaki, H.; Glatzel, P.; Fishgoit, L. A.; Drozhzhin, O. A.; Lafuerza, S.; Safonova, O. V.

2018-01-01

Cr-C coatings containing different amount of carbon ranging from ∼5 to 50 at.% were prepared by the direct current (DC) magnetron sputtering on a polished substrate of polycrystalline silicon. The thickness of the samples was about 400 nm. We characterized the composition and the structure of the as-received coatings and those annealed at 500 °C by X-ray diffraction (XRD), Energy dispersion X-ray spectroscopy (EDX) and valence-to-core X-ray emission spectroscopy (vtc-XES) methods As follows from XRD measurements, the samples with the carbon content above 35 at.% do not demonstrate any sign of the long-range order and annealing at 500 °C does not change their crystallinity. The vtc-XES curves of the as-prepared and annealed samples can be fitted as a superposition of corresponding spectra of chromium metal and chromium carbide (Cr3C2) phases. After the annealing, the content of carbides in the samples (and, correspondingly, the content of covalently bonded carbon) somewhat increases. This suggests that the as-received coatings contain a certain amount of carbon that is not covalently bonded to chromium (most likely, elemental carbon) and their annealing at 500 °C transforms this carbon into the additional (of the order of 2-5 at.%) amount of chromium carbide compounds. It deserves mentioning that for Cr-C coatings prepared by the electrochemical deposition from Cr(III) electrolytes containing organic compounds we have not observed changes in the vtc-X-ray emission spectra after similar annealing. This suggests that electrochemical deposition method in contrast to magnetron sputtering technique even at low temperatures favors the formation of only covalently bonded carbon.

Structural analysis of aluminium substituted nickel ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Singh, H. S.; Sangwa, Neha

2018-05-01

Aluminium substituted nickel ferrite nanoparticles were synthesized by High Energy Ball milling (HEBM) of the mixture of α-NiO, α-Al2O3 and α-Fe2O3 followed by annealing at 1000˚C. X-ray diffraction (XRD) and Energy dispersive spectroscopy analysis (EDS) characterization was done for Aluminium substituted nickel ferrite. The structural analysis reveals the formation of the single phase compound. The average grain size was estimated by X-ray diffraction technique ranges from 30 to 10 nm with the increasing concentration of Aluminium. EDS spectra conforms the homogeneous mixing and purity of ferrite.

Comparative study of structural and magnetic properties of nano-crystalline Li 0.5Fe 2.5O 4 prepared by various methods

NASA Astrophysics Data System (ADS)

Verma, Vivek; Pandey, Vibhav; Singh, Sukhveer; Aloysius, R. P.; Annapoorni, S.; Kotanala, R. K.

2009-08-01

Lithium ferrite has been considered as one of the highly strategic magnetic material. Nano-crystalline Li 0.5Fe 2.5O 4 was prepared by four different techniques and characterized by X-ray diffraction, vibrating sample magnetometer (VSM), transmission electron microscope (TEM) and Fourier transform infrareds (FTIR). The effect of annealing temperature (700, 900 and 1050 °C) on microstructure has been correlated to the magnetic properties. From X-ray diffraction patterns, it is confirmed that the pure phase of lithium ferrite began to form at 900 °C annealing. The particle size of as-prepared lithium ferrite was observed around 40, 31, 22 and 93 nm prepared by flash combustion, sol-gel, citrate precursor and standard ceramic technique, respectively. Lithium ferrite prepared by citrate precursor method shows a maximum saturation magnetization 67.6 emu/g at 5 KOe.

Structural Properties Characterized by the Film Thickness and Annealing Temperature for La2O3 Films Grown by Atomic Layer Deposition.

PubMed

Wang, Xing; Liu, Hongxia; Zhao, Lu; Fei, Chenxi; Feng, Xingyao; Chen, Shupeng; Wang, Yongte

2017-12-01

La 2 O 3 films were grown on Si substrates by atomic layer deposition technique with different thickness. Crystallization characteristics of the La 2 O 3 films were analyzed by grazing incidence X-ray diffraction after post-deposition rapid thermal annealing treatments at several annealing temperatures. It was found that the crystallization behaviors of the La 2 O 3 films are affected by the film thickness and annealing temperatures as a relationship with the diffusion of Si substrate. Compared with the amorphous La 2 O 3 films, the crystallized films were observed to be more unstable due to the hygroscopicity of La 2 O 3 . Besides, the impacts of crystallization characteristics on the bandgap and refractive index of the La 2 O 3 films were also investigated by X-ray photoelectron spectroscopy and spectroscopic ellipsometry, respectively.

Oxidized Mn:Ge magnetic semiconductor: Observation of anomalous Hall effect and large magnetoresistance

NASA Astrophysics Data System (ADS)

Duc Dung, Dang; Choi, Jiyoun; Feng, Wuwei; Cao Khang, Nguyen; Cho, Sunglae

2018-03-01

We report on the structural and magneto-transport properties of the as-grown and oxidized Mn:Ge magnetic semiconductors. Based on X-ray diffraction and X-ray photoelectron spectroscopy results, the samples annealed at 650 and 700 °C became fully oxidized and the chemical binding energies of Mn was found to be Mn3O4. Thus, the system became Mn3O4 clusters embedded in Ge1-yOy. The as-grown sample showed positive linear Hall effect and negligible negative magnetoresistance (MR), which trend remained for the sample annealed up to 550 °C. Interestingly, for the samples annealed at above 650 °C, we observed the anomalous Hall effect around 45 K and the giant positive MR, which are respectively 59.2% and 78.5% at 7 kOe annealed at 650 °C and 700 °C.

Evidence of room temperature ferromagnetism in argon/oxygen annealed TiO2 thin films deposited by electron beam evaporation technique

NASA Astrophysics Data System (ADS)

Mohanty, P.; Kabiraj, D.; Mandal, R. K.; Kulriya, P. K.; Sinha, A. S. K.; Rath, Chandana

2014-04-01

TiO2 thin films deposited by electron beam evaporation technique annealed in either O2 or Ar atmosphere showed ferromagnetism at room temperature. The pristine amorphous film demonstrates anatase phase after annealing under Ar/O2 atmosphere. While the pristine film shows a super-paramagnetic behavior, both O2 and Ar annealed films display hysteresis at 300 K. X-ray photo emission spectroscopy (XPS), Raman spectroscopy, Rutherford's backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) were used to refute the possible role of impurities/contaminants in magnetic properties of the films. The saturation magnetization of the O2 annealed film is found to be higher than the Ar annealed one. It is revealed from shifting of O 1s and Ti 2p core level spectra as well as from the enhancement of high binding energy component of O 1s spectra that the higher magnetic moment is associated with higher oxygen vacancies. In addition, O2 annealed film demonstrates better crystallinity, uniform deposition and smoother surface than that of the Ar annealed one from glancing angle X-ray diffraction (GAXRD) and atomic force microscopy (AFM). We conclude that although ferromagnetism is due to oxygen vacancies, the higher magnetization in O2 annealed film could be due to crystallinity, which has been observed earlier in Co doped TiO2 film deposited by pulsed laser deposition (Mohanty et al., 2012 [10]).

Structure and giant magnetoresistance of granular Co-Cu nanolayers prepared by cross-beam pulsed laser deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jesche, A.; Stoecker, H.; Levin, A. A.

2010-01-15

A series of Co{sub x}Cu{sub 100-x} (x=0, 40-75, 100) layers with thicknesses between 13 and 55 nm were prepared on silicon substrates using cross-beam pulsed laser deposition. Wide-angle x-ray diffraction (WAXRD), transmission electron microscopy (TEM), and electrical transport measurements revealed a structure consisting of decomposed cobalt and copper grains with grain sizes of about 10 nm. The influence of cobalt content and layer thickness on the grain size is discussed. Electron diffraction indicates the presence of an intermetallic Co-Cu phase of Cu{sub 3}Au structure type. Thermal treatment at temperatures between 525 and 750 K results in the progressive decomposition ofmore » Co and Cu, with an increase of the grain sizes up to about 100 nm. This is tunable by controlling the temperature and duration of the anneal, and is directly observable in WAXRD patterns and TEM images. A careful analysis of grain size and the coherence length of the radiation used allows for an accurate interpretation of the x-ray diffraction patterns, by taking into account coherent and noncoherent scattering. The alloy films show a giant magnetoresistance of 1%-2.3% with the maximum obtained after annealing at around 725 K.« less

Glass-derived superconducting ceramics with zero resistance at 107 K in the Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) system

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Farrell, D. E.

1989-01-01

A melt of composition Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) was fast quenched to form a glass. This was subsequently air annealed and the influence of annealing time and temperature on the formation of various crystalline phases was investigated. X-ray powder diffraction indicate that none of the resulting samples were single phase. However, for an annealing temperature of 840 C, the volume fraction of the high Tc phase (isostructural with Bi2Sr2Ca2Cu3O10) increased with annealing time. A specimen annealed at this temperature for 243 h followed by slow cooling showed a sharp transition and Tc (R = 0) = 107.2 K.

Effect of reducing atmosphere on the magnetism of Zn(1-x)Co(x)O (0≤x≤0.10) nanoparticles.

PubMed

Naeem, M; Hasanain, S K; Kobayashi, M; Ishida, Y; Fujimori, A; Buzby, Scott; Shah, S Ismat

2006-05-28

We report the crystal structure and magnetic properties of Zn(1-x)Co(x)O (0≤x≤0.10) nanoparticles synthesized by heating metal acetates in organic solvent. The nanoparticles were crystallized in the wurtzite ZnO structure after annealing in air and in a forming gas (Ar95% + H5%). The x-ray diffraction and x-ray photoemission spectroscopy (XPS) data for different Co content show clear evidence for the Co(2+) ions in tetrahedral symmetry, indicating the substitution of Co(2+) in the ZnO lattice. However, samples with x = 0.08 and higher cobalt content also indicate the presence of Co metal clusters. Only those samples annealed in the reducing atmosphere of the forming gas, that showed the presence of oxygen vacancies, exhibited ferromagnetism at room temperature. The air annealed samples remained non-magnetic down to 77 K. The essential ingredient in achieving room temperature ferromagnetism in these Zn(1-x)Co(x)O nanoparticles was found to be the presence of additional carriers generated by the presence of the oxygen vacancies.

Stress relaxation in pre-stressed aluminum core–shell particles: X-ray diffraction study, modeling, and improved reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle L.

Stress relaxation in aluminum micron-scale particles covered by alumina shell after pre-stressing by thermal treatment and storage was measured using X-ray diffraction with synchrotron radiation. Pre-stressing was produced by annealing Al particles at 573K followed by fast cooling. While averaged dilatational strain in Al core was negligible for untreated particles, it was measured at 4.40×10 -5 and 2.85×10 -5 after 2 and 48 days of storage. Consistently, such a treatment leads to increase in flame propagation speed for Al+CuO mixture by 37% and 25%, respectively. Analytical model for creep in alumna shell and stress relaxation in Al core-alumina shellmore » structure is developed and activation energy and pre-exponential multiplier are estimated. The effect of storage temperature and annealing temperature on the kinetics of stress relaxation was evaluated theoretically. These results provide estimates for optimizing Al reactivity with the holding time at annealing temperature and allowable time for storage of Al particles for various environmental temperatures.« less

Stress relaxation in pre-stressed aluminum core–shell particles: X-ray diffraction study, modeling, and improved reactivity

DOE PAGES

Levitas, Valery I.; McCollum, Jena; Pantoya, Michelle L.; ...

2016-05-30

Stress relaxation in aluminum micron-scale particles covered by alumina shell after pre-stressing by thermal treatment and storage was measured using X-ray diffraction with synchrotron radiation. Pre-stressing was produced by annealing Al particles at 573K followed by fast cooling. While averaged dilatational strain in Al core was negligible for untreated particles, it was measured at 4.40×10 -5 and 2.85×10 -5 after 2 and 48 days of storage. Consistently, such a treatment leads to increase in flame propagation speed for Al+CuO mixture by 37% and 25%, respectively. Analytical model for creep in alumna shell and stress relaxation in Al core-alumina shellmore » structure is developed and activation energy and pre-exponential multiplier are estimated. The effect of storage temperature and annealing temperature on the kinetics of stress relaxation was evaluated theoretically. These results provide estimates for optimizing Al reactivity with the holding time at annealing temperature and allowable time for storage of Al particles for various environmental temperatures.« less

International Conference (4th) on Nanostructured Materials Held in Stockholm, Sweden on 14-19 June 1998. Special Volume - Part A. Volume 12, Numbers 1-4, 1999

DTIC Science & Technology

1998-06-19

correlation was found between the X - ray grain size and the TEM grain size. Table 2 contains the hardness and density data for the nanocrystalline 5083...temperature with a Neophot hardness tester and a load of 0.2 N. RESULTS AND DISCUSSION X - ray diffraction and transmission electron microscopy combined with...For Single- Wall Carbon Nanotubes by Raman Scattering Technique Microstructure Change in Co46AI19035 Granular Thin Films by Annealing X - Ray

Diffuse x-ray scattering and transmission electron microscopy study of defects in antimony-implanted silicon

NASA Astrophysics Data System (ADS)

Takamura, Y.; Marshall, A. F.; Mehta, A.; Arthur, J.; Griffin, P. B.; Plummer, J. D.; Patel, J. R.

2004-04-01

Ion implantation followed by laser annealing has been used to create supersaturated and electrically active concentrations of antimony in silicon. Upon subsequent thermal annealing, however, these metastable dopants deactivate towards the equilibrium solubility limit. In this work, the formation of inactive antimony structures has been studied with grazing incidence diffuse x-ray scattering, and transmission electron microscopy, and the results are correlated to previous high-resolution x-ray diffraction data. We find that at a concentration of 6.0×1020 cm-3, small, incoherent clusters of radius 3-4 Å form during annealing at 900 °C. At a higher concentration of 2.2×1021 cm-3, deactivation at 600 °C occurs through the formation of small, antimony aggregates and antimony precipitates. The size of these precipitates from diffuse x-ray scattering is roughly 15 Å in radius for anneal times from 15 to 180 seconds. This value is consistent with the features observed in high-resolution and mass contrast transmission electron microscopy images. The coherent nature of the aggregates and precipitates causes the expansion of the surrounding silicon matrix as the deactivation progresses. In addition, the sensitivity of the diffuse x-ray scattering technique has allowed us to detect the presence of small clusters of radius ˜2 Å in unprocessed Czochralski silicon wafers. These defects are not observed in floating zone silicon wafers, and are tentatively attributed to thermal donors.

Current-voltage characteristics of n-AlMgZnO/p-GaN junction diodes

NASA Astrophysics Data System (ADS)

Hsueh, Kuang-Po; Cheng, Po-Wei; Cheng, Yi-Chang; Sheu, Jinn-Kong; Yeh, Yu-Hsiang; Chiu, Hsien-Chin; Wang, Hsiang-Chun

2013-03-01

This study investigates the temperature dependence of the current-voltage (I-V) characteristics of Al-doped MgxZn1-xO/p-GaN junction diodes. Specifically, this study reports the deposition of n-type Al-doped MgxZn1-xO (AMZO) films on p-GaN using a radio-frequency (RF) magnetron sputtering system followed by annealing at 700, 800, 900, and 1000 °C in a nitrogen ambient for 60 seconds, respectively. The AMZO/GaN films were thereafter analyzed using Hall measurement and the x-ray diffraction (XRD) patterns. The XRD results show that the diffraction angles of the annealed AMZO films remain the same as that of GaN without shifting. The n-AMZO/p-GaN diode with 900 °C annealing had the lowest leakage current in forward and reverse bias. However, the leakage current of the diodes did not change significantly with an increase in annealing temperatures. These findings show that the n-AMZO/p-GaN junction diode is feasible for GaN-based heterojunction bipolar transistors (HBTs) and UV light-emitting diodes (LEDs).

Influence of synthesis conditions on the crystal structure of the powder formed in the “HfO2 - CeO2/Ce2O3” system

NASA Astrophysics Data System (ADS)

Popov, V. V.; Menushenkov, A. P.; Khubbutdinov, R. M.; Yastrebtsev, A. A.; Svetogorov, R. D.; Zubavichus, Ya V.; Trigub, A. L.; Sharapov, A. S.; Pisarev, A. A.; Kurilkin, V. V.; Tsarenko, N. A.; Arzhatkina, L. A.

2017-12-01

Influence of synthesis conditions (type of atmosphere: reduction or oxidation, annealing temperature) on the chemical composition and structure of the compounds formed in the “HfO2 - CeO2/Ce2O3” system has been investigated by X-ray absorption fine structure spectroscopy combined with Raman spectroscopy, X-ray diffraction and thermogravimetric analysis. It was revealed that isothermal annealing of precursor at temperatures less than 1000°C in air leads to formation of Ce0.5Hf0.5O2 powders with cubic fluorite-type structure (space group Fm-3m). Further increase of annealing temperatures above 1000°C causes decomposition of formed crystal structure into two phases: cubic and monoclinic. Annealing in reduction hydrogen atmosphere causes formation of Ce4+ 2x Ce3+ 2-2x Hf2O7+x compounds with intermediate oxidation state of cerium, where value of x depends on the reducing conditions and treatment parameters. Annealing in vacuum at 1400°C strongly reduces the content of Ce4+ in a powder samples and leads to formation of pyrochlore structure (space group Fd-3m) with predominant +3 oxidation state of cerium.

Nanocrystalline Cs{sub x}WO{sub 3} particles: Effects of N{sub 2} annealing on microstructure and near-infrared shielding characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jing-Xiao, E-mail: drliu-shi@dlpu.edu.cn; Institute of Multidisciplinary Research for Advanced Material, Tohoku University, Sendai, 980-8577,Japan; Shi, Fei

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 propertiesmore » 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.« less

Electron-spectroscopy and -diffraction study of the conductivity of CVD diamond ( 0 0 1 )2×1 surface

NASA Astrophysics Data System (ADS)

Kono, S.; Takano, T.; Shimomura, M.; Goto, T.; Sato, K.; Abukawa, T.; Tachiki, M.; Kawarada, H.

2003-04-01

A chemical vapor deposition as-grown diamond (0 0 1) single-domain 2 × 1 surface was studied by electron-spectroscopy and electron-diffraction in ultrahigh vacuum (UHV). In order to change the surface conductivity (SC) of the diamond in UHV, three annealing stages were used; without annealing, annealing at 300 °C and annealing at 550 °C. From low energy electron diffraction and X-ray photoelectron spectroscopic (XPS) studies, an existence of SC was suggested for the first two stages of annealing and an absence of SC was suggested for the last stage of annealing. Changes in C KVV Auger electron spectroscopic spectra, C KVV Auger electron diffraction (AED) patterns and C 1s XPS peak positions were noticed between the annealing stages at 300 and 550 °C. These changes are interpreted as such that the state of hydrogen involvement in a subsurface of diamond (0 0 1)2 × 1 changes as SC changes. In particular, the presence of local disorder in diamond configuration in SC subsurface is pointed out from C KVV AED. From C 1s XPS peak shifts, a lower bound for the Fermi-level for SC layers from the valence band top is presented to be ˜0.5 eV.

Composition and annealing effects on superconductivity in sintered and arc-melted Fe1+εTe0.5Se0.5

NASA Astrophysics Data System (ADS)

Foreman, M. M.; Ponti, G.; Mozaffari, S.; Markert, J. T.

2018-03-01

We present the results of x-ray diffraction, electrical resistivity, and ac magnetic susceptibility measurements on specimens of the “11”-structure superconductor Fe1+εTe0.50Se0.50 (0 ≤ ε ≤ 0.15). Samples were initially either sintered in sealed quartz tubes or melted in a zirconium-gettered arc furnace. Sintered samples were fired two to three times at temperatures of 425°C, 600°C, or 675°C, while arc-melted samples were studied both asmelted and after annealing at 650°C. X-ray diffraction data show a predominant PbO-type tetragonal phase, with a secondary hexagonal NiAs-type phase; for sintered specimens annealed at 600°C, the secondary phase decreases as ε increases over the range 0 ≤ ε ≤ 0.10, with the composition Fe1.10Te0.5Se0.5 exhibiting x-ray phase purity. A higher annealing temperature of 675°C provided such tetragonal phase purity at the composition Fe1.05Te0.5Se0.5. The resistive superconducting transition temperature Tc was nearly independent of the iron concentration 1+ε, suggesting a single superconducting phase, while the magnetic screening fraction varied greatly with concentration and conditions, peaking at ɛ = 0.07, indicating that the amount of superconducting phase is strongly dependent on conditions. We propose that the behaviour can also be viewed in terms of an electron-doped, chalcogen-deficient stoichiometry.

Determination of the solubility of tin indium oxide using in situ and ex x-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonzalez, G. B.; Mason, T. O.; Okasinski, J. S.

A novel approach to determine the thermodynamic solubility of tin in indium oxide via the exsolution from tin overdoped nano-ITO powders is presented. High-energy, in situ and ex situ synchrotron X-ray diffraction was utilized to study the solubility limit at temperatures ranging from 900 C to 1375 C. The tin exsolution from overdoped nanopowders and the formation of In{sub 4}Sn{sub 3}O{sub 12} were observed in situ during the first 4-48 h of high-temperature treatment. Samples annealed between 900 C and 1175 C were also studied ex situ with heat treatments for up to 2060 h. Structural results obtained from Rietveldmore » analysis include compositional phase analysis, atomic positions, and lattice parameters. The tin solubility in In{sub 2}O{sub 3} was determined using the phase analysis compositions from X-ray diffraction and the elemental compositions obtained from X-ray fluorescence. Experimental complications that can lead to incorrect tin solubility values in the literature are discussed.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajachidambaram, Jaana Saranya; Sanghavi, Shail P.; Nachimuthu, Ponnusamy

Amorphous zinc tin oxide (ZTO) was investigated to determine the effect of deposition and post annealing conditions on film structure, composition, surface contamination, and thin film transistor (TFT) device performance. X-ray diffraction results indicated that the ZTO films remain amorphous even after annealing to 600 °C. We found that the bulk Zn:Sn ratio of the sputter deposited films were slightly tin rich compared to the composition of the ceramic sputter target, and there was a significant depletion of zinc at the surface. X-ray photoelectron spectroscopy also indicated that residual surface contamination depended strongly on the sample post-annealing conditions where water,more » carbonate and hydroxyl species were absorbed to the surface. Electrical characterization of ZTO films, using TFT test structures, indicated that mobilities as high as 17 cm2/Vs could be obtained for depletion mode devices.« less

Post Deformation Annealing Behaviour of Mg-Al-Sn Alloys

NASA Astrophysics Data System (ADS)

Kabir, Abu Syed Humaun; Su, Jing; Sanjari, Mehdi; Jung, In-Ho; Yue, Stephen

In this study, effects of dynamically formed precipitates on the microstructure and texture evolutions were investigated after the post deformation annealing for various times. Two ternary alloys of Mg, Al and Sn were designed, produced and deformed at 300°C at a strain rate of 0.01s-1 to form different amounts of strain induced precipitates during deformation. Subsequent annealing at deformation temperature was performed for up to 4 hours. Microstructures and precipitation were investigated by optical and scanning electron microscopes and macro and micro-texture were measured by X-ray diffraction (XRD) and Electron Back-Scattered Diffraction (EBSD) techniques, respectively. It was found that certain amount of strain induced precipitates was necessary to prevent grain growth for a certain time during annealing by grain boundary pinning effect. Also, texture randomization was possible with the presence of precipitates after certain time of annealing.

Effect of Ag doping and annealing on thermoelectric properties of PbTe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bala, Manju, E-mail: Manjubala474@gmail.com; Tripathi, T. S.; Avasthi, D. K.

2015-06-24

The present study reveals that annealing Ag doped PbTe thin films enhance thermoelectric properties. Phase formation was identified by using X-ray diffraction measurement. Annealing increases the crystallinity of both undoped and Ag doped PbTe. Electrical resistivity and thermoelectric power measurements are done using four probe and bridge method respectively. The increase in thermoelectric power of Ag doped PbTe is 29 % in comparison to undoped PbTe and it further increases to 34 % after annealing at 250{sup o} C for 1 hour whereas thermoelectric power increases by 14 % on annealing undoped PbTe thin films at same temperature.

Evolution of microstructure and residual stress during annealing of austenitic and ferritic steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wawszczak, R.; Baczmański, A., E-mail: Andrzej.Baczmanski@fis.agh.edu.pl; Marciszko, M.

2016-02-15

In this work the recovery and recrystallization processes occurring in ferritic and austenitic steels were studied. To determine the evolution of residual stresses during material annealing the nonlinear sin{sup 2}ψ diffraction method was used and an important relaxation of the macrostresses as well as the microstresses was found in the cold rolled samples subjected to heat treatment. Such relaxation occurs at the beginning of recovery, when any changes of microstructure cannot be detected using other experimental techniques. Stress evolution in the annealed steel samples was correlated with the progress of recovery process, which significantly depends on the value of stackingmore » fault energy. - Highlights: • X-ray diffraction was used to determine the first order and second order stresses. • Diffraction data were analyzed using scale transition elastoplastic models model. • Stress relaxation in annealed ferritic and austenitic steels was correlated with evolution of microstructure. • Influence of stacking fault energy on thermally induced processes was discussed.« less

In-situ XRD vs ex-situ vacuum annealing of tantalum oxynitride thin films: Assessments on the structural evolution

NASA Astrophysics Data System (ADS)

Cunha, L.; Apreutesei, M.; Moura, C.; Alves, E.; Barradas, N. P.; Cristea, D.

2018-04-01

The purpose of this work is to discuss the main structural characteristics of a group of tantalum oxynitride (TaNxOy) thin films, with different compositions, prepared by magnetron sputtering, and to interpret and compare the structural changes, by X-ray diffraction (XRD), when the samples are vacuum annealed under two different conditions: i) annealing, followed by ex-situ XRD: one sample of each deposition run was annealed at a different temperature, until a maximum of 800 °C, and the XRD patterns were obtained, at room temperature, after each annealing process; ii) annealing with in-situ XRD: the diffraction patterns are obtained, at certain temperatures, during the annealing process, using always the same sample. In-situ XRD annealing could be an interesting process to perform annealing, and analysing the evolution of the structure with the temperature, when compared to the classical process. A higher structural stability was observed in some of the samples, particularly on those with highest oxygen content, but also on the sample with non-metal (O + N) to metal (Ta) ratio around 0.5.

Self-aligned Ni-P ohmic contact scheme for silicon solar cells by electroless deposition

NASA Astrophysics Data System (ADS)

Lee, Eun Kyung; Lim, Dong Chan; Lee, Kyu Hwan; Lim, Jae-Hong

2012-08-01

We report a Ni-P metallization scheme for low resistance ohmic contacts to n-type Si for silicon solar cells. As-deposited Ni-P contacts to n-type Si showed a specific contact resistance of 6.42 × 10-4 Ω·cm2. The specific contact resistance decreased with increasing thermal annealing temperature. When the Ni-P contact was annealed at 600°C for 30 min in ambient air, the specific contact resistance was greatly decreased, to 6.37 × 10-5Ω·cm2. The improved ohmic property was attributed to the decrease in the work function due to the formation of Ni-silicides from Ni in-diffusion during the thermal annealing process. Effects of the annealing process on the electrical and crystal properties of the contacts were investigated by means of various resistivity measurements (circular transmission line method (c-TLM), 4-point probe), glancing angle x-ray diffraction (GAXRD), and x-ray photoelectron spectroscopy (XPS).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srivastava, Himanshu; Ganguli, Tapas; Deb, S. K.

Growth of CuO nanowires by annealing method has been studied in-situ by grazing incidence Energy Dispersive X-ray Diffraction (EDXRD) technique on Indus-2. It was observed that Cu slowly oxidized to Cu{sub 2}O and finally to CuO. The data was taken as a function of time at two annealing temperatures 500 Degree-Sign C where nanowires form and 300 Degree-Sign C where nanowires don't form. We found that the strain in the CuO layer may be a principal factor for the spontaneous growth of nanowires in annealing method.

Growth and Surface Modification of LaFeO3 Thin Films Induced By Reductive Annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flynn, Brendan T.; Zhang, Hongliang; Shutthanandan, V.

2015-03-01

The electronic and ionic conductivity of perovskite oxides has enabled their use in diverse applications such as automotive exhaust catalysts, solid oxide fuel cell cathodes, and visible light photocatalysts. The redox chemistry at the surface of perovskite oxides is largely dependent on the oxidation state of the metal cations as well as the oxide surface stoichiometry. In this study, LaFeO3 (LFO) thin films grown on yttria-stabilized zirconia (YSZ) was characterized using both bulk and surface sensitive techniques. A combination of in situ reflection high energy electron diffraction (RHEED), x-ray diffraction (XRD), transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS)more » demonstrated that the film is highly oriented and stoichiometric. The film was annealed in an ultra-high vacuum chamber to simulate reducing conditions and studied by angle-resolved x-ray photoelectron spectroscopy (XPS). Iron was found to exist as Fe(0), Fe(II), and Fe(III) depending on the annealing conditions and the depth within the film. A decrease in the concentration of surface oxygen species was correlated with iron reduction. These results should help guide and enhance the design of perovskite materials for catalysts.« less

XRD analysis of undoped and Fe doped TiO{sub 2} nanoparticles by Williamson Hall method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bharti, Bandna; Barman, P. B.; Kumar, Rajesh, E-mail: rajesh.kumar@juit.ac.in

2015-08-28

Undoped and Fe doped titanium dioxide (TiO{sub 2}) nanoparticles were synthesized by sol-gel method at room temperature. The synthesized samples were annealed at 500°C. For structural analysis, the prepared samples were characterized by X-ray diffraction (XRD). The crystallite size of TiO{sub 2} and Fe doped TiO{sub 2} nanoparticles were calculated by Scherer’s formula, and was found to be 15 nm and 11 nm, respectively. Reduction in crystallite size of TiO{sub 2} with Fe doping was observed. The anatase phase of Fe-doped TiO{sub 2} nanoparticles was also confirmed by X-ray diffraction. By using Williamson-Hall method, lattice strain and crystallite size weremore » also calculated. Williamson–Hall plot indicates the presence of compressive strain for TiO{sub 2} and tensile strain for Fe-TiO{sub 2} nanoparticles annealed at 500°C.« less

Thermal annealing of natural, radiation-damaged pyrochlore

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zietlow, Peter; Beirau, Tobias; Mihailova, Boriana

Abstract Radiation damage in minerals is caused by the α-decay of incorporated radionuclides, such as U and Th and their decay products. The effect of thermal annealing (400–1000 K) on radiation-damaged pyrochlores has been investigated by Raman scattering, X-ray powder diffraction (XRD), and combined differential scanning calorimetry/thermogravimetry (DSC/TG). The analysis of three natural radiation-damaged pyrochlore samples from Miass/Russia [6.4 wt% Th, 23.1·10

Unusual Thermal Stability of High-Entropy Alloy Amorphous Structure

DTIC Science & Technology

2012-06-20

incident angle X - ray diffractometer (GIAXRD, RIGAKU D/MAX2500) with Cu Kα radiation and at the incident angle of 1°. The surface morphology and...microanalyzer (EPMA, JEOL JAX-8800). The crystallographic structures of as-deposited and annealed metallic films were characterized utilizing a glancing ...field image and selected-area- diffraction (SAD) patterns of (a) 800 °C-, (b) 850 °C- and (c) 900 °C-annealed alloy thin films, respectively. Both

Imaging local electric fields produced upon synchrotron X-ray exposure

DOE PAGES

Dettmar, Christopher M.; Newman, Justin A.; Toth, Scott J.; ...

2014-12-31

Electron–hole separation following hard X-ray absorption during diffraction analysis of soft materials under cryogenic conditions produces substantial local electric fields visualizable by second harmonic generation (SHG) microscopy. Monte Carlo simulations of X-ray photoelectron trajectories suggest the formation of substantial local electric fields in the regions adjacent to those exposed to X-rays, indicating a possible electric-field–induced SHG (EFISH) mechanism for generating the observed signal. In studies of amorphous vitreous solvents, analysis of the SHG spatial profiles following X-ray microbeam exposure was consistent with an EFISH mechanism. Within protein crystals, exposure to 12-keV (1.033-Å) X-rays resulted in increased SHG in the regionmore » extending ~3 μm beyond the borders of the X-ray beam. Moderate X-ray exposures typical of those used for crystal centering by raster scanning through an X-ray beam were sufficient to produce static electric fields easily detectable by SHG. The X-ray–induced SHG activity was observed with no measurable loss for longer than 2 wk while maintained under cryogenic conditions, but disappeared if annealed to room temperature for a few seconds. In conclusion, these results provide direct experimental observables capable of validating simulations of X-ray–induced damage within soft materials. Additionally, X-ray–induced local fields may potentially impact diffraction resolution through localized piezoelectric distortions of the lattice.« less

Fabrication of VO2 thin film by rapid thermal annealing in oxygen atmosphere and its metal—insulator phase transition properties

NASA Astrophysics Data System (ADS)

Liang, Ji-Ran; Wu, Mai-Jun; Hu, Ming; Liu, Jian; Zhu, Nai-Wei; Xia, Xiao-Xu; Chen, Hong-Da

2014-07-01

Vanadium dioxide thin films have been fabricated through sputtering vanadium thin films and rapid thermal annealing in oxygen. The microstructure and the metal—insulator transition properties of the vanadium dioxide thin films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and a spectrometer. It is found that the preferred orientation of the vanadium dioxide changes from (1¯11) to (011) with increasing thickness of the vanadium thin film after rapid thermal annealing. The vanadium dioxide thin films exhibit an obvious metal—insulator transition with increasing temperature, and the phase transition temperature decreases as the film thickness increases. The transition shows hysteretic behaviors, and the hysteresis width decreases as the film thickness increases due to the higher concentration carriers resulted from the uncompleted lattice. The fabrication of vanadium dioxide thin films with higher concentration carriers will facilitate the nature study of the metal—insulator transition.

The effect of cerium oxide argon-annealed coatings on the high temperature oxidation of a FeCrAl alloy

NASA Astrophysics Data System (ADS)

Nguyen, C. T.; Buscail, H.; Cueff, R.; Issartel, C.; Riffard, F.; Perrier, S.; Poble, O.

2009-09-01

Ceria coatings were applied in order to improve the adherence of alumina scales developed on a model Fe-20Cr-5Al alloy during oxidation at high temperature. These coatings were performed by argon annealing of a ceria sol-gel coating at temperatures ranging between 600 and 1000 °C. The influence of these coatings on the alloy oxidation behaviour was studied at 1100 °C. In situ X-ray diffraction (XRD) was performed to characterize the coating crystallographic nature after annealing and during the oxidation process. The alumina scale morphologies were studied by means of scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). The present work shows that the alumina scale morphology observed on cerium sol-gel coated alloy was very convoluted. On the cerium sol-gel coated alloy, argon annealing results in an increase of the oxidation rate in air, at 1100 °C. The 600 °C argon annealing temperature results in a good alumina scale adherence under thermal cycling conditions at 1100 °C.

Effect of template post-annealing on Y(Dy)BaCuO nucleation on CeO2 buffered metallic tapes

NASA Astrophysics Data System (ADS)

Hu, Xuefeng; Zhong, Yun; Zhong, Huaxiao; Fan, Feng; Sang, Lina; Li, Mengyao; Fang, Qiang; Zheng, Jiahui; Song, Haoyu; Lu, Yuming; Liu, Zhiyong; Bai, Chuanyi; Guo, Yanqun; Cai, Chuanbing

2017-08-01

Substrate engineering is very significant in the synthesis of the high-temperature superconductor (HTS) coated conductor. Here we design and synthesize several distinct and stable Cerium oxide (CeO2) surface reconstructions which are used to grow epitaxial films of the HTS YBa2Cu3O7-δ (YBCO). To identify the influence of annealing and post-annealing surroundings on the nature of nucleation centers, including Ar/5%H2, humid Ar/5%H2 and O2 in high temperature annealing process, we study the well-controlled structure, surface morphology, crystal constants and surface redox processes of the ceria buffers by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and field-emission scanning electronic microscopy (FE-SEM), respectively. The ceria film post-annealed under humid Ar/5%H2 gas shows the best buffer layer properties. Furthermore, the film absorbs more oxygen ions, which appears to contribute to oxygenation of superconductor film. The film is well-suited for ceria model studies as well as a perfect substitute for CeO2 bulk material.

Formation of nanostructures in Eu3+ doped glass-ceramics: an XAS study.

PubMed

Pellicer-Porres, J; Segura, A; Martínez-Criado, G; Rodríguez-Mendoza, U R; Lavín, V

2013-01-16

We describe the results of x-ray absorption experiments carried out to deduce structural and chemical information in Eu(3+) doped, transparent, oxyfluoride glass and nanostructured glass-ceramic samples. The spectra were measured at the Pb and Eu-L(III) edges. The Eu environment in the glass samples is observed to be similar to that of EuF(3). Complementary x-ray diffraction experiments show that thermal annealing creates β-PbF(2) type nanocrystals. X-ray absorption indicates that Eu ions act as seeds in the nanocrystal formation. There is evidence of interstitial fluorine atoms around Eu ions as well as Eu dimers. X-ray absorption at the Pb-L(III) edge shows that after the thermal treatment most lead atoms form a PbO amorphous phase and that only 10% of the lead atoms remain available to form β-PbF(2) type nanocrystals. Both x-ray diffraction and absorption point to a high Eu content in the nanocrystals. Our study suggests new approaches to the oxyfluoride glass-ceramic synthesis in order to further improve their properties.

Crystalline silicon growth in nickel/a-silicon bilayer

NASA Astrophysics Data System (ADS)

Mohiddon, Md Ahamad; Naidu, K. Lakshun; Dalba, G.; Rocca, F.; Krishna, M. Ghanashyam

2013-02-01

The effect of substrate temperature on amorphous Silicon crystallization, mediated by metal impurity is reported. Bilayers of Ni(200nm)/Si(400nm) are deposited on fused silica substrate by electron beam evaporator at 200 and 500 °C. Raman mapping shows that, 2 to 5 micron size crystalline silicon clusters are distributed over the entire surface of the sample. X-ray diffraction and X-ray absorption spectroscopy studies demonstrate silicon crystallizes over the metal silicide seeds and grow with the annealing temperature.

Correlation of x-ray diffraction and Mössbauer effect measurements with magnetic properties of heat-treated Cu80Co15Fe5 ribbons

NASA Astrophysics Data System (ADS)

Harris, V. G.; Rubinstein, M.; Das, B. N.; Koon, N. C.

1994-05-01

X-ray diffraction (XRD) and Mössbauer Effect (ME) measurements were performed on heat-treated Cu80Co15Fe5 melt-spun ribbons in an attempt to understand the trends in magnetic properties with heat treatment. ME measurements indicate that the majority of Fe atoms (86%) occupy sites in ferromagnetic FCC CoFe clusters after the initial quench. A heat treatment at 900 °C acts to complete the chemical separation of Fe from the Cu matrix. The presence of Co in the Cu matrix, even after high temperature anneals, provides a paramagnetic component that prohibits saturation even at high fields.

Ni(3)Si(Al)/a-SiO(x) core-shell nanoparticles: characterization, shell formation, and stability.

PubMed

Pigozzi, G; Mukherji, D; Gilles, R; Barbier, B; Kostorz, G

2006-08-28

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni(3)Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni(3)Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiO(x)). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

Controlled nucleation and growth of CdS nanoparticles in a polymer matrix.

PubMed

Di Luccio, Tiziana; Laera, Anna Maria; Tapfer, Leander; Kempter, Susanne; Kraus, Robert; Nickel, Bert

2006-06-29

In-situ synchrotron X-ray diffraction (XRD) was used to monitor the thermal decomposition (thermolysis) of Cd thiolates precursors embedded in a polymer matrix and the nucleation of CdS nanoparticles. A thiolate precursor/polymer solid foil was heated to 300 degrees C in the X-ray diffraction setup of beamline W1.1 at Hasylab, and the diffraction curves were each recorded at 10 degrees C. At temperatures above 240 degrees C, the precursor decomposition is complete and CdS nanoparticles grow within the polymer matrix forming a nanocomposite with interesting optical properties. The nanoparticle structural properties (size and crystal structure) depend on the annealing temperature. Transmission electron microscopy (TEM) and photoluminescence (PL) analyses were used to characterize the nanoparticles. A possible mechanism driving the structural transformation of the precursor is inferred from the diffraction features arising at the different temperatures.

Investigation of (Ti-Zr-Hf-V-Nb)N Multicomponent Nanostructured Coatings before and after Thermal Annealing by Nuclear Physics Methods of Analysis

NASA Astrophysics Data System (ADS)

Pogrebnjak, A. D.; Beresnev, V. M.; Bondar', A. V.; Kaverin, M. V.; Ponomarev, A. G.

2013-10-01

(Ti-Zr-Hf-V-Nb)N multicomponent nanostructured coatings with thickness of 1.0-1.4 μm synthesized by the method of cathode arc-vapor deposition at temperatures of 250-300°С are investigated by various mutually complementary methods of elemental structural analysis using slow positron beams (SPB), proton microbeam based particle-induced x-ray emission (μ-PIXE), energy-dispersive x-ray spectroscopy (EDS) and scanning electron microscopy (SEM) analyses based on electron micro- and nanobeams, x-ray diffraction (XRD) method of phase structural analysis, and the "a-sin2φ" method of measuring a stressed-strained state (x-ray tensometry). The elemental composition, microstructure, residual stress in nanograins, profiles of defect and atom distributions with depth and over the coating surface in 3D-representation are studied for these coatings, and their phase composition, severely strained state, and composition of coatings before and after annealing at Tann = 600°С for annealing time τ = 30 min are investigated. It is demonstrated that the oxidation resistance of the examined coatings can be significantly increased by high-temperature annealing that leads to the formation of elastic severely strained compression state of the coating. Redistribution of elements and defects, their segregation near the interface boundaries and around grains and subgrains in the process of thermostimulated diffusion, and termination of spinodal segregation without considerable change of the average nanograin size are revealed.

Neutron and hard X-ray diffraction studies of the isothermal transformation kinetics in the research reactor fuel candidate U–8 wt%Mo

PubMed Central

Säubert, Steffen; Jungwirth, Rainer; Zweifel, Tobias; Hofmann, Michael; Hoelzel, Markus; Petry, Winfried

2016-01-01

Exposing uranium–molybdenum alloys (UMo) retained in the γ phase to elevated temperatures leads to transformation reactions during which the γ-UMo phase decomposes into the thermal equilibrium phases, i.e. U2Mo and α-U. Since α-U is not suitable for a nuclear fuel exposed to high burn-up, it is necessary to retain the γ-UMo phase during the production process of the fuel elements for modern high-performance research reactors. The present work deals with the isothermal transformation kinetics in U–8 wt%Mo alloys for temperatures between 673 and 798 K and annealing durations of up to 48 h. Annealed samples were examined at room temperature using either X-ray or neutron diffraction to determine the phase composition after thermal treatment, and in situ annealing studies disclosed the onset of phase decomposition. While for temperatures of 698 and 673 K the start of decomposition is delayed, for higher temperatures the first signs of transformation are already observable within 3 h of annealing. The typical C-shaped curves in a time–temperature–transformation (TTT) diagram for both the start and the end of phase decomposition could be determined in the observed temperature regime. Therefore, a revised TTT diagram for U–8 wt%Mo between 673 and 798 K and annealing durations of up to 48 h is proposed. PMID:27275139

Applied Crystallography - Proceedings of the XVth Conference

NASA Astrophysics Data System (ADS)

Morawiec, H.; Ströż, D.

1993-06-01

The Table of Contents for the full book PDF is as follows: * Foreword * The International Centre for Diffraction Data and Its Future Developments * The Rietveld Method - A Historical Perspective * Real Structure in Quantitative Powder Diffraction Phase Analysis * Neutron Focusing Optics in Applied Crystallography * The Crystal Structures of Oxygen Deficient Rare Earth Oxides * Short-Range Order in Layer-Structured Ba1-xSrxBi2Nb2O9 Ferroelectrics * Radial Distribution Function as a Tool of Structural Studies on Noncrystalline Materials * Determination of Radial Distribution Function (RDF) of Electrodeposited Cu-Cd Alloys After Annealing * Spheres Packing as a Factor Describing the Local Environment and Structure Stability * X-Ray Stress Measurement of Samples Combined with Diffraction Line Analysis * Phase Stability and Martensitic Transformation in Cu-Zn and Cu-Zn-Al Single Crystals * Order, Defects, Precipitates and the Martensitic Transformation in β Cu-Zn-Al * Effect of γ Precipitates on the Martensitic Transformation in Cu-Zn-Al Alloys * Phase Transitions and Shape Memory Effect in a Thermomechanically Treated NiTi Alloy * Structure of Martensite and Bainite in CuAlMn Alloys * Glass-Ceramics * Mechanism of Texture Formation at the Rolling of Low Stacking Fault Energy Metals and Alloys * Shear Texture of Zinc and the Conditions of Its Occuring * The Development of Texture of ZnAlMg Sheets Depending on Deformation Geometry * Texture Stability of the D.S. NiAlMoCrTi Alloy After Heat Treatment * X-Ray Diffraction Method for Controlling of Texture Evolution in Layers * Texture and Lattice Imperfections Study of Some Low Alloyed Copper Alloys * Selected Examples of the Calculation of the Orientation Distribution Function for Low Crystal and Sample Symmetries * Automatical X-Ray Quantitative Phase Analysis * Application of a PC Computer for Crystallographic Calculations * Electron Diffraction Analysis using a Personal Computer * CA.R.INE Crystallography Version 2.1-1992 * PC-MINREF: The Computer Program Package for Neutron Refinement of Incommensurate Multiphase Crystal and Magnetic Structures on IBM PC Computers * Possibilities of Deflections from Stoichiometry Investigation for Phases of b1-b37 Structure by X-Ray Method * A Computer Program: “Measurement of Elastic Constants of Phases in Nontextured Polycrystalline Materials by X-Ray Method” * Crystallite Sizes and Lattice Strains of Hydrogenatid Tungsten Carbid Powder * The Bragg-Case Images of Dislocations at Different Absorption * Extended X-Ray Bremsstrahlung Isochromat of Molybdenum * Size Distribution Determination of Heterogeneity Regions in Electrodeposited Metals by Saxs Method * The Possibility of the Application of the CH2I2 - Paraffin Oil Mixture as a Masking Liquid for Metal/Carrier Systems in Saxs Investigations * Investigation on Mechanical Alloying and Amorphisation Processes by the Rietveld Method * Growth of β' Phase Single Crystals of Sn-Sb Alloy * Effect of Oxygen Agglomeration on Structure of Annealed Cz-Si Single Crystal * X-Ray Investigation of Non-Uniform Stress Fields * Problem of Polytype Structures Series for Martensitic Phases of Metals and Alloys * Structure of Strain-Induced Martensite in β-CuZnAl Alloy * The Effect of Heat Treatment on the Phase Transitions in NiTiCo Shape Memory Alloy * 9R → 18R Phase Transformation in Cu-13Zn-8Al Alloy * Effect of Austenite Thermal Instability on Characteristics of Martensitic Transformation in Fe-Ni Alloys * Vacuum Annealing Study of Thin Ti Layers on High Carbon Steel Substrates * Vacuum Annealing Study of Thin Ta Layers on High Carbon Steel Substrates * Investigation of Speed of Ionic Sputtering of NiTi Alloys in Sea 02 Auger Spectrometer * Effect of Precipitation Hardening on Thermal Stability of Austenite in Fe-Ni Alloys * Structure of 18Cr-25Ni-Nb L Steel After Two Years Operation in Catalytic Tubes * Influence of Magnetic Field on Mechanical Barkhausen Effect Stress Dependence in Steel * Precipitation Structure in High Strength Aluminium Alloys * Morphology of Laser Treated Al-Zn and Al-Fe Alloys * Structure of Rapidly Solidified AlFe and AlFeNi Ribbons After Continuous Heating * X-Ray Diffractometric Investigations of Anatase—Rutile Titanium Dioxide Forms Transformation in the Presence of Some Additives * Investigations on Phase Transformation of Coprecipitated Iron-Magnesium Hydroxides * Determination of the Crystallinity of Polymer Blends by X-Ray Diffraction Method * XPD Study of the Selected Magnesium Compounds with the Expected Pharmacological Activity * Supermolecular Structure of the Nylon 6.10 Crystallized from the Melt and Its Changes During Heating * The Analysis of Substructural Parameters of PZT-Type Ferroelectric Ceramics

Unambiguous determination of H-atom positions: comparing results from neutron and high-resolution X-ray crystallography.

PubMed

Gardberg, Anna S; Del Castillo, Alexis Rae; Weiss, Kevin L; Meilleur, Flora; Blakeley, Matthew P; Myles, Dean A A

2010-05-01

The locations of H atoms in biological structures can be difficult to determine using X-ray diffraction methods. Neutron diffraction offers a relatively greater scattering magnitude from H and D atoms. Here, 1.65 A resolution neutron diffraction studies of fully perdeuterated and selectively CH(3)-protonated perdeuterated crystals of Pyrococcus furiosus rubredoxin (D-rubredoxin and HD-rubredoxin, respectively) at room temperature (RT) are described, as well as 1.1 A resolution X-ray diffraction studies of the same protein at both RT and 100 K. The two techniques are quantitatively compared in terms of their power to directly provide atomic positions for D atoms and analyze the role played by atomic thermal motion by computing the sigma level at the D-atom coordinate in simulated-annealing composite D-OMIT maps. It is shown that 1.65 A resolution RT neutron data for perdeuterated rubredoxin are approximately 8 times more likely overall to provide high-confidence positions for D atoms than 1.1 A resolution X-ray data at 100 K or RT. At or above the 1.0sigma level, the joint X-ray/neutron (XN) structures define 342/378 (90%) and 291/365 (80%) of the D-atom positions for D-rubredoxin and HD-rubredoxin, respectively. The X-ray-only 1.1 A resolution 100 K structures determine only 19/388 (5%) and 8/388 (2%) of the D-atom positions above the 1.0sigma level for D-rubredoxin and HD-rubredoxin, respectively. Furthermore, the improved model obtained from joint XN refinement yielded improved electron-density maps, permitting the location of more D atoms than electron-density maps from models refined against X-ray data only.

Effect of annealing on structural, optical and electrical properties of SILAR synthesized CuO thin film

NASA Astrophysics Data System (ADS)

Das, M. R.; Mukherjee, A.; Mitra, P.

2017-05-01

Nano crystalline CuO thin films were synthesize on glass substrate using SILAR technique. The structural, optical and electrical properties of the films were carried out for as deposited as well as for films post annealed in the temperature range 300 - 500° C. The X-ray diffraction pattern shows all the films are polycrystalline in nature with monoclinic phase. The crystallite size increase and lattice strain decreases with increase of annealing temperature indicating high quality of the films for annealed films. The value of band gap decreases with increases of annealing temperature of the film. The effect of annealing temperature on ionic conductivity and activation energy to electrical conduction process are discussed.

Room temperature synthesis of Cu₂O nanospheres: optical properties and thermal behavior.

PubMed

Nunes, Daniela; Santos, Lídia; Duarte, Paulo; Pimentel, Ana; Pinto, Joana V; Barquinha, Pedro; Carvalho, Patrícia A; Fortunato, Elvira; Martins, Rodrigo

2015-02-01

The present work reports a simple and easy wet chemistry synthesis of cuprous oxide (Cu2O) nanospheres at room temperature without surfactants and using different precursors. Structural characterization was carried out by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy coupled with focused ion beam and energy-dispersive X-ray spectroscopy. The optical band gaps were determined from diffuse reflectance spectroscopy. The photoluminescence behavior of the as-synthesized nanospheres showed significant differences depending on the precursors used. The Cu2O nanospheres were constituted by aggregates of nanocrystals, in which an on/off emission behavior of each individual nanocrystal was identified during transmission electron microscopy observations. The thermal behavior of the Cu2O nanospheres was investigated with in situ X-ray diffraction and differential scanning calorimetry experiments. Remarkable structural differences were observed for the nanospheres annealed in air, which turned into hollow spherical structures surrounded by outsized nanocrystals.

Effect of in situ annealing on the structural and electrical properties and infrared photodetection of III-Sb on GaAs using interfacial misfit array

NASA Astrophysics Data System (ADS)

Jia, Bo Wen; Tan, Kian Hua; Loke, Wan Khai; Wicaksono, Satrio; Yoon, Soon Fatt

2018-01-01

This work presents the effects of in situ thermal annealing under antimony overpressure on the structural, electrical, and optical properties of III-Sb (GaSb and InSb) grown on (100) GaAs using an interfacial misfit array to accommodate the lattice mismatch. Both the sample growth and the in situ thermal annealing were carried out in the in the molecular beam epitaxy system, and the temperature of the as-grown sample was increased to exceed its growth temperature during the annealing. X-ray diffraction demonstrates nearly fully relaxed as-grown and annealed III-Sb layers. The optimal annealing temperatures and durations are for 590 °C, 5 min for GaSb and 420 °C, 15 min for InSb, respectively. In situ annealing decreased the surface roughness of the III-Sb layers. X-ray reciprocal space mapping and transmission electron microscopy observation showed stable interfacial misfit arrays, and no interfacial diffusion occurred in the annealed III-Sb layers. A Hall measurement of unintentionally doped III-Sb layers showed greater carrier mobility and a lower carrier concentration in the annealed samples at both 77 and 300 K. In situ annealing improved the photoresponsivity of GaSb and InSb photoconductors grown on GaAs in the near- and mid-infrared ranges, respectively.

Structural Properties and Sensing Performance of CeYxOy Sensing Films for Electrolyte-Insulator-Semiconductor pH Sensors.

PubMed

Pan, Tung-Ming; Wang, Chih-Wei; Chen, Ching-Yi

2017-06-07

In this study we developed CeY x O y sensing membranes displaying super-Nernstian pH-sensitivity for use in electrolyte-insulator-semiconductor (EIS) pH sensors. We examined the effect of thermal annealing on the structural properties and sensing characteristics of the CeY x O y sensing membranes deposited through reactive co-sputtering onto Si substrates. X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy revealed the structural, morphological, and chemical features, respectively, of the CeY x O y films after their annealing at 600-900 °C. Among the tested systems, the CeY x O y EIS device prepared with annealing at 800 °C exhibited the highest sensitivity (78.15 mV/pH), the lowest hysteresis voltage (1.4 mV), and the lowest drift rate (0.85 mV/h). Presumably, these annealing conditions optimized the stoichiometry of (CeY)O 2 in the film and its surface roughness while suppressing silicate formation at the CeY x O y -Si interface. We attribute the super-Nernstian pH-sensitivity to the incorporation of Y ions in the Ce framework, thereby decreasing the oxidation state Ce (Ce 4+  → Ce 3+ ) and resulting in less than one electron transferred per proton in the redox reaction.

Morphology and structural development of reduced anatase-TiO{sub 2} by pure Ti powder upon annealing and nitridation: Synthesis of TiO{sub x} and TiO{sub x}N{sub y} powders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolokang, A.S., E-mail: Sylvester.Bolokang@transnet.net; DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria 0001; Transnet Engineering, Product Development, Private Bag X 528, Kilnerpark 0127

2015-02-15

It is well known that nitriding of titanium is suitable for surface coating of biomaterials and in other applications such as anti-reflective coating, while oxygen-rich titanium oxynitride has been applied in thin film resistors and photocatalysis. Thus in this work anatase was reduced with pure titanium powder during annealing in argon. This was done to avoid any metallic contamination and unwanted residual metal doping. As a result, interesting and different types of particle morphology were synthesized when the pre-milled elemental anatase and titanium powders were mixed. The formation of metastable face centred cubic and monoclinic titanium monoxide was detected bymore » the X-ray diffraction technique. The phases were confirmed by energy dispersive X-ray spectroscopy analysis. Raman analysis revealed weak intensity peaks for samples annealed in argon as compared to those annealed under nitrogen. - Graphical abstract: Display Omitted - Highlights: • Reaction of TiO{sub 2} and Ti induced metastable FCC and monoclinic TiO{sub x}. • Compositions of mixed powder were prepared from the unmilled and pre-milled powders. • Nitridation of TiO{sub x} yielded TiO{sub x}N{sub y} phase. • Mixed morphology was observed on all three powder samples.« less

Effects of surface morphology of ZnO seed layers on growth of ZnO nanostructures prepared by hydrothermal method and annealing.

PubMed

Yim, Kwang Gug; Kim, Min Su; Leem, Jae-Young

2013-05-01

ZnO nanostructures were grown on Si (111) substrates by a hydrothermal method. Prior to growing the ZnO nanostructures, ZnO seed layers with different post-heat temperatures were prepared by a spin-coating process. Then, the ZnO nanostructures were annealed at 500 degrees C for 20 min under an Ar atmosphere. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out at room temperature (RT) to investigate the structural and optical properties of the as-grown and annealed ZnO nanostructures. The surface morphologies of the seed layers changed from a smooth surface to a mountain chain-like structure as the post-heating temperatures increased. The as-grown and annealed ZnO nanostructures exhibited a strong (002) diffraction peak. Compared to the as-grown ZnO nanostructures, the annealed ZnO nanostructures exhibited significantly strong enhancement in the PL intensity ratio by almost a factor of 2.

Role of Ga particulates on the structure and optical properties of Y3(Al,Ga)5O12:Tb thin films prepared by PLD

NASA Astrophysics Data System (ADS)

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

2018-04-01

Y3(Al,Ga)5O12:Tb thin films (70 nm) have been prepared by pulsed laser deposition on a Si (100) substrate at the substrate temperature of 300 °C. The effect of annealing time on the structural, morphological and luminescence properties of Y3(Al,Ga)5O12:Tb thin films at 800 °C were studied. The crystal structure of the samples was studied by X- ray diffraction (XRD) and showed shifts in the peak positions to lower diffraction angles for the annealed film compared to the XRD peak positions of the commercial Y3(Al,Ga)5O12:Tb powder. A new excitation band different from the original Y3(Al,Ga)5O12:Tb powder was also observed for the annealed films. The shift in the XRD pattern and the new excitation band for the annealed film suggested that the films were enriched with Ga after annealing.

Thermal effects on the structural properties of tungsten oxide nanoparticles

NASA Astrophysics Data System (ADS)

Yang, Tsung-Yeh; Wu, Chung-Yi; Tsai, Meng-Hung; Lin, Hong-Ming; Tsai, Wen-Li; Hwu, Yeukuang

2004-06-01

Tungsten oxide nanoparticles are prepared by evaporating and oxidizing the tungsten boat in helium and oxygen atmosphere and then quenched to the liquid nitrogen temperature. The as-prepared tungsten oxide nanoparticles are porous-free with uniform size. The morphology and particle size distribution of the as-prepared and after sinter treatments tungsten oxide nanoparticles are revealed by TEM and AFM. The long-range order of these nanoparticles can be examined by X-ray diffraction technique. The as-prepared nanoparticles exhibit a mixture structure of monoclinic and hexagonal crystals. Preliminary X-ray diffraction results indicate that the hexagonal structure is transformed to monoclinic structure after annealing to above 600°C. In order to better distinguish the structural properties of the tungsten oxide (WO3- x) nanoparticles before and after annealing, the X-ray absorption spectrum technique is utilized; thus, the detailed local atomic arrangement of oxygen and/or tungsten can be determined. According to the XAS result, the shape of the W L3-edge undergoes no considerable changes. This infers that structural transformation of tungsten oxide nanoparticle may be caused by the migration of oxygen after sintering. From the O K-edge of absorption spectrum, it suggests that a mixture phase structure is obtained when sintered below 300°C. And this result indicates that heat treatment to approximately 600°C produces a stable structure of a monoclinic crystal of WO3.

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

PubMed

Ji, Liang-Wen; Hsiao, Yu-Jen; Tang, I-Tseng; Meen, Teen-Hang; Liu, Chien-Hung; Tsai, Jenn-Kai; Wu, Tien-Chuan; Wu, Yue-Sian

2013-11-09

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%.

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

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

NASA Astrophysics Data System (ADS)

Ji, Liang-Wen; Hsiao, Yu-Jen; Tang, I.-Tseng; Meen, Teen-Hang; Liu, Chien-Hung; Tsai, Jenn-Kai; Wu, Tien-Chuan; Wu, Yue-Sian

2013-11-01

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%.

Formation of TiO2 nanorings due to rapid thermal annealing of swift heavy ion irradiated films.

PubMed

Thakurdesai, Madhavi; Sulania, I; Narsale, A M; Kanjilal, D; Bhattacharyya, Varsha

2008-09-01

Amorphous thin films of TiO2 deposited by Pulsed Laser Deposition (PLD) method are irradiated by Swift Heavy Ion (SHI) beam. The irradiated films are subsequently annealed by Rapid Thermal Annealing (RTA) method. Atomic Force Microscopy (AFM) study reveals formation of nano-rings on the surface after RTA processing. Phase change is identified by Glancing Angle X-ray Diffraction (GAXRD) and Raman spectroscopy. Optical characterisation is carried out by UV-VIS absorption spectroscopy. Though no shift of absorption edge is observed after irradiation, RTA processing does show redshift.

In situ X-ray measurements of MOVPE growth of InxGa1-xN single quantum wells

NASA Astrophysics Data System (ADS)

Ju, Guangxu; Fuchi, Shingo; Tabuchi, Masao; Takeda, Yoshikazu

2013-05-01

GaN/InxGa1-xN/GaN single quantum wells (SQWs) have been grown on c-plane GaN/sapphire substrates using MOVPE system. PL (photoluminescence) and AFM (atomic force microscope) measurements demonstrate good quality of after-growth thermal-annealed SQWs. In situ XRD (X-ray diffraction), XRR (X-ray reflectivity), and X-ray CTR (crystal truncation rod) scattering measurements were successfully conducted on the SQWs under the NH3+N2 ambient at 1103 K. The analysis results of the XRR and the X-ray CTR spectra at 1103 K and at 300 K on the same sample matched well. It demonstrated that In0.09Ga0.91N SQW structure with several ML (monolayer) InGaN thicknesses was successfully investigated using the XRR and CTR scattering measurements at 1103 K.

Improved memory characteristics by NH3-nitrided GdO as charge storage layer for nonvolatile memory applications

NASA Astrophysics Data System (ADS)

Liu, L.; Xu, J. P.; Ji, F.; Chen, J. X.; Lai, P. T.

2012-07-01

Charge-trapping memory capacitor with nitrided gadolinium oxide (GdO) as charge storage layer (CSL) is fabricated, and the influence of post-deposition annealing in NH3 on its memory characteristics is investigated. Transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction are used to analyze the cross-section and interface quality, composition, and crystallinity of the stack gate dielectric, respectively. It is found that nitrogen incorporation can improve the memory window and achieve a good trade-off among the memory properties due to NH3-annealing-induced reasonable distribution profile of a large quantity of deep-level bulk traps created in the nitrided GdO film and reduction of shallow traps near the CSL/SiO2 interface.

Characterization of pulsed laser deposition grown V2O3 converted VO2

NASA Astrophysics Data System (ADS)

Majid, Suhail; Shukla, D. K.; Rahman, F.; Gautam, Kamini; Sathe, V. G.; Choudhary, R. J.; Phase, D. M.

2016-10-01

Controllable tuning of Metal-insulator transition in VxOy thin film has been a field of extensive research. However controlled synthesis of desired Vanadium oxide phase is a challenging task. We have successfully achieved VO2 phase on Silicon substrate after post deposition annealing treatment to the PLD grown as deposited V2O3 thin films. The annealed thin film was characterized by x-ray diffraction (XRD), resistivity, Raman spectroscopy, X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) measurements. XRD confirms the crystalline nature and growth of VO2 phase in thin film. The characteristic MIT was observed from resistivity measurements and transition temperature appeared at lower value around 336 K, compared to bulk VO2. The structural transition accompanied with MIT from lower temperature monoclinic phase to higher temperature Rutile phase became evident from temperature dependent Raman measurements. Chemical state of vanadium was examined using XAS and XPS measurements which confirm the presence of +4 oxidation state of vanadium in thin film.

Room temperature magnetization in Co-doped anatase phase of TiO2

NASA Astrophysics Data System (ADS)

Karimipour, Masoud; Mageto, Maxwel Joel; Etefagh, Reyhaneh; Azhir, Elahe; Mwamburi, Mghendi; Topalian, Zareh

2013-01-01

CoxTi1-xO2 films were deposited by spray pyrolysis technique on Si(1 0 0) substrates at 475 °C. A hydro-alcoholic solution containing titanium (iv) isopropoxide and Co(NO3)2 with various Co doping levels from x = 0-0.015 in solution was used as spray solution. Grazing incident angle of X-ray diffraction illustrates that the CoxTi1-xO2 films are single phase and polycrystal with mixed orientations. Study of surface morphology of the films by atomic force microscope reveals that the annealing atmosphere does not significantly affect the grain size and the microstructure of the films. This study provides further insight into the importance of annealing atmosphere on magnetization of the films. Room temperature magneto-optical Kerr measurement was employed in polar mode. A hysteresis loop and a paramagnetic behavior have been recorded for samples annealed in H2 ambient gas and air, respectively. Chemical composition analysis by X-ray photo-electron spectroscopy showed that Co atoms are bounded to oxygen and no metallic clusters are present. Moreover, it indicates the formation of high spin Co2+ for the sample x = 0.008 annealed in H2 ambient gas. The origin of magnetization can be attributed to the contribution of oxygen vacancies in the spin polarization of the structure.

Structural and morphological study of ZrO2 thin films

NASA Astrophysics Data System (ADS)

Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

2018-05-01

In this paper we discuss the fabrication of transparent thin films of Zirconium Oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Further these fabricated films were characterized for different annealing temperatures and withdrawal speed. X-ray diffraction is used to study the structural properties of deposited thin films and it reveals the change in crystallographic properties with the change in annealing temperature. Thickness of thin films is estimated by using scanning electron microscope.

Ultrasonic determination of recrystallization

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1986-01-01

Ultrasonic attenuation was measured for cold worked Nickel 200 samples annealed at increasing temperatures. Localized dislocation density variations, crystalline order and colume percent of recrystallized phase were determined over the anneal temperature range using transmission electron microscopy, X-ray diffraction, and metallurgy. The exponent of the frequency dependence of the attenuation was found to be a key variable relating ultrasonic attenuation to the thermal kinetics of the recrystallization process. Identification of this key variable allows for the ultrasonic determination of onset, degree, and completion of recrystallization.

Effect of Annealing Temperature and Oxygen Flow in the Properties of Ion Beam Sputtered SnO-₂x Thin Films.

PubMed

Wang, Chun-Min; Huang, Chun-Chieh; Kuo, Jui-Chao; Sahu, Dipti Ranjan; Huang, Jow-Lay

2015-08-14

Tin oxide (SnO 2-x ) thin films were prepared under various flow ratios of O₂/(O₂ + Ar) on unheated glass substrate using the ion beam sputtering (IBS) deposition technique. This work studied the effects of the flow ratio of O₂/(O₂ + Ar), chamber pressures and post-annealing treatment on the physical properties of SnO₂ thin films. It was found that annealing affects the crystal quality of the films as seen from both X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. In addition, the surface RMS roughness was measured with atomic force microscopy (AFM). Auger electron spectroscopy (AES) analysis was used to obtain the changes of elemental distribution between tin and oxygen atomic concentration. The electrical property is discussed with attention to the structure factor.

Cation ordering/disordering kinetics in Ba3CoNb2O9: An in situ study using synchrotron x-ray powder diffraction

NASA Astrophysics Data System (ADS)

Mallinson, P. M.; Claridge, J. B.; Rosseinsky, M. J.; Ibberson, R. M.; Wright, J. P.; Fitch, A. N.; Price, T.; Iddles, D. M.

2007-11-01

In situ synchrotron x-ray powder diffraction has been used to study the kinetics of cation ordering and disordering in the microwave dielectric electroceramic Ba3CoNb2O9 with a time resolution of 15s. The method enables the order/disorder temperature (To /d) in this material of 1430°C to be directly observed. The changes in the rate and degree of cation ordering and in the growth of ordered domains between samples ordered from standard precursor material and then subsequently reordered following an annealing period above To /d show that small changes in precursor order state and phase assemblage strongly influence the final domain size.

Hard X-ray irradiation of cosmic silicate analogs: structural evolution and astrophysical implications

NASA Astrophysics Data System (ADS)

Gavilan, L.; Jäger, C.; Simionovici, A.; Lemaire, J. L.; Sabri, T.; Foy, E.; Yagoubi, S.; Henning, T.; Salomon, D.; Martinez-Criado, G.

2016-03-01

Context. Protoplanetary disks, interstellar clouds, and active galactic nuclei contain X-ray-dominated regions. X-rays interact with the dust and gas present in such environments. While a few laboratory X-ray irradiation experiments have been performed on ices, X-ray irradiation experiments on bare cosmic dust analogs have been scarce up to now. Aims: Our goal is to study the effects of hard X-rays on cosmic dust analogs via in situ X-ray diffraction. By using a hard X-ray synchrotron nanobeam, we seek to simulate cumulative X-ray exposure on dust grains during their lifetime in these astrophysical environments and provide an upper limit on the effect of hard X-rays on dust grain structure. Methods: We prepared enstatite (MgSiO3) nanograins, which are analogs to cosmic silicates, via the melting-quenching technique. These amorphous grains were then annealed to obtain polycrystalline grains. These were characterized via scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) before irradiation. Powder samples were prepared in X-ray transparent substrates and were irradiated with hard X-rays nanobeams (29.4 keV) provided by beamline ID16B of the European Synchrotron Radiation Facility (Grenoble). X-ray diffraction images were recorded in transmission mode, and the ensuing diffractograms were analyzed as a function of the total X-ray exposure time. Results: We detected the amorphization of polycrystalline silicates embedded in an organic matrix after an accumulated X-ray exposure of 6.4 × 1027 eV cm-2. Pure crystalline silicate grains (without resin) do not exhibit amorphization. None of the amorphous silicate samples (pure and embedded in resin) underwent crystallization. We analyze the evolution of the polycrystalline sample embedded in an organic matrix as a function of X-ray exposure. Conclusions: Loss of diffraction peak intensity, peak broadening, and the disappearance of discrete spots and arcs reveal the amorphization of the resin embedded (originally polycrystalline) silicate sample. We explore the astrophysical implications of this laboratory result as an upper limit to the effect of X-rays on the structure of cosmic silicates.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuz'micheva, G. M., E-mail: galkuz@mitht.ru; Zaharko, O.; Tyunina, E. A.

Langatate crystals of the general composition La{sub 3}(Ga{sub 0.5}Ta{sub 0.5})Ga{sub 5}O{sub 14}, grown by the Czochralski method, have been investigated by neutron diffraction (single crystals) and X-ray diffraction (ground single crystals). The crystals were grown in an atmosphere of 99% Ar + 1% O{sub 2} in the Y54{sup o} direction (rotation by 54{sup o} with respect to the y axis), without subsequent annealing (orange crystal) or with vacuum annealing (colorless crystal). It is established that colorless crystals have a higher gallium content and, therefore, a larger number of oxygen vacancies in comparison with colored crystals; this is a possible reasonmore » for their lower microhardness.« less

Preparation of mesoporous carbon nitride structure by the dealloying of Ni/a-CN nanocomposite films

NASA Astrophysics Data System (ADS)

Zhou, Han; Shen, Yongqing; Huang, Jie; Liao, Bin; Wu, Xianying; Zhang, Xu

2018-05-01

The preparation of mesoporous carbon nitride (p-CN) structure by the selective dealloying process of Ni/a-CN nanocomposite films is investigated. The composition and structure of the Ni/a-CN nanocomposite films and porous carbon nitride (p-CN) films are determined by scan electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Phase separated structure including nickel carbide phase and the surrounding amorphous carbon nitride (a-CN) matrix are detected for the as-deposited films. Though the bulk diffusion is introduced in the film during the annealing process, the grain sizes for the post-annealed films are around 10 nm and change little comparing with the ones of the as-deposited films, which is associated with the thermostability of the CN surrounding in the film. The p-CN skeleton with its pore size around 12.5 nm is formed by etching the post-annealed films, indicative of the stability of the phase separated structure during the annealing process.

Effect of heat treatment on surface hydrophilicity-retaining ability of titanium dioxide nanotubes

NASA Astrophysics Data System (ADS)

Sun, Yu; Sun, Shupei; Liao, Xiaoming; Wen, Jiang; Yin, Guangfu; Pu, Ximing; Yao, Yadong; Huang, Zhongbing

2018-05-01

The aim of this study is to investigate the effect of different annealing temperature and atmosphere on the surface wettability retaining properties of titania nanotubes (TNs) fabricated by anodization. The TNs morphology, crystal phase composition and surface elemental composition and water contact angle (WCA) were investigated by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and contact angle instrument, respectively. After the samples annealed at 200 °C, 450 °C, 850 °C have been stored in air for 28 days, the WCAs increase to 31.7°, 21.1° and 110.5°, respectively. The results indicate that crystal phase composition of TNs plays an important role in surface wettability. Compared with the WCA (21.1°) of the samples annealed in air after 28 days, the WCA of samples annealed in oxygen-deficient atmosphere is lower, suggesting the contribution of oxygen vacancy in the enhanced hydrophilicity-retaining ability. Our study demonstrates that the surface hydrophilicity-retaining ability of TNs is related to the ordered nanotubular structure, crystal structure, the amount of surface hydroxyl group and oxygen vacancy defects.

Paramagnetism of cobalt-doped ZnO nanoparticles obtained by microwave solvothermal synthesis.

PubMed

Wojnarowicz, Jacek; Kusnieruk, Sylwia; Chudoba, Tadeusz; Gierlotka, Stanislaw; Lojkowski, Witold; Knoff, Wojciech; Lukasiewicz, Malgorzata I; Witkowski, Bartlomiej S; Wolska, Anna; Klepka, Marcin T; Story, Tomasz; Godlewski, Marek

2015-01-01

Zinc oxide nanopowders doped with 1-15 mol % cobalt were produced by the microwave solvothermal synthesis (MSS) technique. The obtained nanoparticles were annealed at 800 °C in nitrogen (99.999%) and in synthetic air. The material nanostructure was investigated by means of the following techniques: X-ray diffraction (XRD), helium pycnometry density, specific surface area (SSA), inductively coupled plasma optical emission spectrometry (ICP-OES), extended X-ray absorption fine structure (EXAFS) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and with magnetometry using superconducting quantum interference device (SQUID). Irrespective of the Co content, nanoparticles in their initial state present a similar morphology. They are composed of loosely agglomerated spherical particles with wurtzite-type crystal structure with crystallites of a mean size of 30 nm. Annealing to temperatures of up to 800 °C induced the growth of crystallites up to a maximum of 2 μm in diameter. For samples annealed in high purity nitrogen, the precipitation of metallic α-Co was detected for a Co content of 5 mol % or more. For samples annealed in synthetic air, no change of phase structure was detected, except for precipitation of Co3O4 for a Co content of 15 mol %. The results of the magentometry investigation indicated that all as-synthesized samples displayed paramagnetic properties with a contribution of anti-ferromagnetic coupling of Co-Co pairs. After annealing in synthetic air, the samples remained paramagnetic and samples annealed under nitrogen flow showed a magnetic response under the influences of a magnetic field, likely related to the precipitation of metallic Co in nanoparticles.

Local configurations and atomic intermixing in as-quenched and annealed Fe1-xCrx and Fe1-xMox ribbons

NASA Astrophysics Data System (ADS)

Stanciu, A. E.; Greculeasa, S. G.; Bartha, C.; Schinteie, G.; Palade, P.; Kuncser, A.; Leca, A.; Filoti, G.; Birsan, A.; Crisan, O.; Kuncser, V.

2018-04-01

Local atomic configuration, phase composition and atomic intermixing in Fe-rich Fe1-xCrx and Fe1-xMox ribbons (x = 0.05, 0.10, 0.15), of potential interest for high-temperature applications and nuclear devices, are investigated in this study in relation to specific processing and annealing routes. The Fe-based thin ribbons have been prepared by induction melting, followed by melt spinning and further annealed in He at temperatures up to 1250 °C. The complex structural, compositional and atomic configuration characterisation has been performed by means of X-ray diffraction (XRD), transmission Mössbauer spectroscopy and differential scanning calorimetry (TG-DSC). The XRD analysis indicates the formation of the desired solid solutions with body-centred cubic (bcc) structure in the as-quenched state. The Mössbauer spectroscopy results have been analysed in terms of the two-shell model. The distribution of Cr/Mo atoms in the first two coordination spheres is not homogeneous, especially after annealing, as supported by the short-range order parameters. In addition, high-temperature annealing treatments give rise to oxidation of Fe (to haematite, maghemite and magnetite) at the surface of the ribbons. Fe1-xCrx alloys are structurally more stable than the Mo counterpart under annealing at 700 °C. Annealing at 1250 °C in He enhances drastically the Cr clustering around Fe nuclei.

Photocatalytic properties of h-WO3 nanoparticles obtained by annealing and h-WO3 nanorods prepared by hydrothermal method

NASA Astrophysics Data System (ADS)

Boyadjiev, Stefan I.; Nagy-Kovács, Teodóra; Lukács, István; Szilágyi, Imre M.

2016-03-01

In the present study, two different methods for preparing hexagonal WO3 (h-WO3) photocatalysts were used - controlled thermal decomposition and hydrothermal synthesis. WO3 nanoparticles with hexagonal structure were obtained by annealing (NH4)xWO3-y at 500 °C in air. WO3 nanorods were prepared by a hydrothermal method using sodium tungstate Na2WO4, HCl, (COOH)2 and NaSO4 precursors at 200 °C. The formation, morphology, structure and composition of the as-prepared nanoparticles and nanorods were studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX). The photocatalytic activity of the h-WO3 nanoparticles and nanorods was studied by decomposing methyl orange in aqueous solution under UV light irradiation.

[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.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abe, T., E-mail: kikutani.t.aa@m.titech.ac.jp; Takarada, W., E-mail: kikutani.t.aa@m.titech.ac.jp; Kikutani, T., E-mail: kikutani.t.aa@m.titech.ac.jp

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, itmore » was confirmed that the orientation of naphthalene ring in the film plane was enhanced by pre-annealing.« less

Effect of annealing process on the heterostructure CuO/Cu2O as a highly efficient photocathode for photoelectrochemical water reduction

NASA Astrophysics Data System (ADS)

Du, Fan; Chen, Qing-Yun; Wang, Yun-Hai

2017-05-01

CuO/Cu2O photocathodes were successfully prepared via simply annealing the electrodeposited Cu2O on fluoride doped tin oxide (FTO) substrate. They were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscope (TEM), UV-vis absorption spectra and X-ray photoelectron spectroscopy (XPS). The results showed that the heterojunction of CuO/Cu2O was formed during the annealing process and presented the nature of p-type semiconductor. The photocurrent density and photoelectrochemical (PEC) stability of the p-type heterostructure CuO/Cu2O photocathode was improved greatly compared with the pure Cu2O, which was greatly affected by annealing time and temperature. The highest photo current density of -0.451 mA/cm2 and highest stability was obtained via annealing at 650 °C for 15 min (at -0.3 V vs. Ag/AgCl), which gave a remarkable improvement than the as-deposited Cu2O (-0.08 mA/cm2). This suggested that the CuO/Cu2O heterojunction facilitated the electron-hole pair separation and improved the photocathode's current and stability.

Investigation of the annealing temperature effect on structural, morphology, dielectric and magnetic properties of BiFeO3 nanoparticles

NASA Astrophysics Data System (ADS)

Ranjbar, M.; Ghazi, M. E.; Izadifard, M.

2018-06-01

In this paper we have investigated the annealing temperature effect on the structure, morphology, dielectric and magnetic properties of sol-gel synthesized multiferroic BiFeO3 nanoparticles. X-ray diffraction spectroscopy revealed that all the samples have rhombohedrally distorted perovskite structure and the most pure BFO phase is obtained on the sample annealed at 800 °C. Field emission scanning electron microscopy (FESEM) revealed that increasing annealing temperature would increase the particle size. Decrease in dielectric constant was also observed by increasing annealing temperature. Vibrating sample method (VSM) analysis confirmed that samples annealed at 500-700 °C with particle size below the BFO's spiral spin structure length, have well saturated M-H curve and show ferromagnetic behavior.

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.

Mechanical properties of amorphous and devitrified Ni-Zr alloy thin films: A cyclic nanoindentation study

NASA Astrophysics Data System (ADS)

Bhattacharya, Debarati; Chatterjee, Arnomitra; Jana, Swapan

2018-04-01

Thin films of Ni-Zr glassy alloy were deposited at room temperature by magnetron co-sputtering. The alloy films were vacuum annealed in steps of 200°C from room temperature up to 800 °C, where devitrification finally occurred. Mechanical properties of the films were measured after each thermal anneal, through (cyclic) nanoindentation technique. The hardness values were observed to steadily increase with annealing temperature, as the alloy films underwent an amorphous to crystalline transformation. Grazing incidence X-ray diffraction measurements were performed on the as-deposited and annealed films both before and after nanoindentation. The resistance to plastic deformation was strongly linked to the (nano)structure of the material.

Connected Au network in annealed Ni/Au thin films on p-GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, S. P.; Jang, H. W.; Noh, D. Y.

2007-11-12

We report the formation of a connected Au network in annealed Ni/Au thin films on p-GaN, which was studied by scanning electron microscopy, transmission electron microscopy, and synchrotron x-ray diffraction. As the Ni was oxidized into NiO upon annealing at 530 deg. C in air, the Au layer was transformed to an interconnected network with an increased thickness. During annealing, Ni atoms diffuse out onto the Au through defects to form NiO, while Au atoms replace the Ni positions. The Au network grows downward until it reaches the p-GaN substrate, and NiO columns fill the space between the Au network.

Electroless Nickel Deposition for Front Side Metallization of Silicon Solar Cells

PubMed Central

Hsieh, Shu Huei; Hsieh, Jhong Min; Chen, Wen Jauh; Chuang, Chia Chih

2017-01-01

In this work, nickel thin films were deposited on texture silicon by electroless plated deposition. The electroless-deposited Ni layers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and sheet resistance measurement. The results indicate that the dominant phase was Ni2Si and NiSi in samples annealed at 300–800 °C. Sheet resistance values were found to correlate well with the surface morphology obtained by SEM and the results of XRD diffraction. The Cu/Ni contact system was used to fabricate solar cells by using two different activating baths. The open circuit voltage (Voc) of the Cu/Ni samples, before and after annealing, was measured under air mass (AM) 1.5 conditions to determine solar cell properties. The results show that open circuit voltage of a solar cell can be enhanced when the activation solution incorporated hydrofluoric acid (HF). This is mainly attributed to the native silicon oxide layer that can be decreased and/or removed by HF with the corresponding reduction of series resistance. PMID:28805724

Surfactant Mediated Growth of Co on MgO(111)

NASA Astrophysics Data System (ADS)

Johnson-Steigelman, H. Trevor; Parihar, Somendra S.; Lyman, Paul F.

2010-03-01

Monolayer films of Co were deposited using an electrostatic electron-beam evaporator on single-crystal MgO(111)- √3 x√3 R 30^o substrates held at room temperature, with subsequent annealing of temperatures 400 C to 800 C. These films were characterized using low-energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and x-ray diffraction (XRD). After short anneals of 400 C, AFM, LEED, and XPS suggest that islanding has occurred at the surface. XPS and XRD indicate the presence of elemental Co. 1-2 ML films of Ag were examined as a potential surfactant to aid in the growth of smooth Co films. Despite the fact that Ag itself formed islands, it was found that the presence of Ag did have a surfactant effect upon the thin-film growth of Co on Ag/MgO(111)- √3 x√3 R 30^o. Co islands were still present, but much more smooth than islands formed without Ag. XPS and AFM suggest strongly that Ag floated to the top of these samples at temperatures above 400 ^oC.

Effect of annealing conditions on the microstructure and magnetic properties of sintered Nd-Fe-B magnets as seen by magnetic small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Périgo, Élio A.; Titov, Ivan; Weber, Raoul; Mettus, Denis; Peral, Inma; Vallcorba, Oriol; Honecker, Dirk; Feoktystov, Artem; Michels, Andreas

2018-03-01

We have investigated the effect of the annealing conditions (heating rate and temperature) on the magnetic microstructure of sintered Nd-Fe-B magnets by means of magnetometry, scanning electron microscopy, high-energy synchrotron x-ray diffraction, and small-angle neutron scattering (SANS). While the temperature treatment has a strong effect on the coercivity (reduction by about 50% on annealing), the associated changes in the microstructure do surprisingly not show up (or at best only very weakly) in the neutron-scattering signal, which probes a mesoscopic real-space length scale ranging between about 1–300 nm. On the other hand, the x-ray data reveal microstructural changes in the Nd-rich phases, presumably due to modifications in grain-boundary regions. Moreover, we observe an unusual diamond-shaped angular anisotropy in the SANS cross section, which strongly points towards the existence of texture in the nuclear microstructure.

Annealing of aromatic polyimide precursors

NASA Technical Reports Server (NTRS)

Wakelyn, N. T.

1975-01-01

A study has been made of the thermal behavior of polyimide precursors: an isomeric pair of crystals of the complex formed by p-phenylenediamine with the separated isomers of the di-isopropyl ester of pyromellitic acid. Specimens of this material were isothermally annealed in the temperature range 120 C to 170 C for periods of time up to 1 week. Although this temperature range is well below that customarily used for imidizations, the working hypothesis was that it would be more likely that a polymer embodying at least part of the precursor structure could be formed if the molecular motion was minimized to that actually required for the formation of the imide linkage. The progress of the annealing was followed by: infrared spectroscopy, differential thermal analysis, powder X-ray diffraction, and thermal gravimetric analysis. Single crystal X-ray analysis of the meta monomer yields a structure of chains of alternating acid and base and suggests that this monomer is amenable to polymerization with a minimum of geometrical disruption.

Formation of (Ti,Al)N/Ti{sub 2}AlN multilayers after annealing of TiN/TiAl(N) multilayers deposited by ion beam sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolique, V.; Jaouen, M.; Cabioc'h, T.

2008-04-15

By using ion beam sputtering, TiN/TiAl(N) multilayers of various modulation wavelengths ({lambda}=8, 13, and 32 nm) were deposited onto silicon substrates at room temperature. After annealing at 600 deg. C in vacuum, one obtains for {lambda}=13 nm a (Ti,Al)N/Ti{sub 2}AlN multilayer as it is evidenced from x-ray diffraction, high resolution transmission electron microscopy, and energy filtered electron imaging experiments. X-ray photoelectron spectroscopy (XPS) experiments show that the as-deposited TiAl sublayers contain a noticeable amount of nitrogen atoms which mean concentration varies with the period {lambda}. They also evidenced the diffusion of aluminum into TiN sublayers after annealing. Deduced from thesemore » observations, we propose a model to explain why this solid-state phase transformation depends on the period {lambda} of the multilayer.« less

Influence of Thermal Annealing Treatment on Bipolar Switching Properties of Vanadium Oxide Thin-Film Resistance Random-Access Memory Devices

NASA Astrophysics Data System (ADS)

Chen, Kai-Huang; Cheng, Chien-Min; Kao, Ming-Cheng; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Wu, Sean; Su, Feng-Yi

2017-04-01

The bipolar switching properties and electrical conduction mechanism of vanadium oxide thin-film resistive random-access memory (RRAM) devices obtained using a rapid thermal annealing (RTA) process have been investigated in high-resistive status/low-resistive status (HRS/LRS) and are discussed herein. In addition, the resistance switching properties and quality improvement of the vanadium oxide thin-film RRAM devices were measured by x-ray diffraction (XRD) analysis, x-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and current-voltage ( I- V) measurements. The activation energy of the hopping conduction mechanism in the devices was investigated based on Arrhenius plots in HRS and LRS. The hopping conduction distance and activation energy barrier were obtained as 12 nm and 45 meV, respectively. The thermal annealing process is recognized as a candidate method for fabrication of thin-film RRAM devices, being compatible with integrated circuit technology for nonvolatile memory devices.

Formation of CaB6 in the thermal decomposition of the hydrogen storage material Ca(BH4)2.

PubMed

Sahle, Christoph J; Sternemann, Christian; Giacobbe, Carlotta; Yan, Yigang; Weis, Christopher; Harder, Manuel; Forov, Yury; Spiekermann, Georg; Tolan, Metin; Krisch, Michael; Remhof, Arndt

2016-07-20

Using a combination of high resolution X-ray powder diffraction and X-ray Raman scattering spectroscopy at the B K- and Ca L2,3-edges, we analyzed the reaction products of Ca(BH4)2 after annealing at 350 °C and 400 °C under vacuum conditions. We observed the formation of nanocrystalline/amorphous CaB6 mainly and found only small contributions from amorphous B for annealing times larger than 2 h. For short annealing times of 0.5 h at 400 °C we observed neither CaB12H12 nor CaB6. The results indicate a reaction pathway in which Ca(BH4)2 decomposes to B and CaH2 and finally reacts to form CaB6. These findings confirm the potential of using Ca(BH4)2 as a hydrogen storage medium and imply the desired cycling capabilities for achieving high-density hydrogen storage materials.

Characteristics of layered tin disulfide deposited by atomic layer deposition with H2S annealing

NASA Astrophysics Data System (ADS)

Lee, Seungjin; Shin, Seokyoon; Ham, Giyul; Lee, Juhyun; Choi, Hyeongsu; Park, Hyunwoo; Jeon, Hyeongtag

2017-04-01

Tin disulfide (SnS2) has attracted much attention as a two-dimensional (2D) material. A high-quality, low-temperature process for producing 2D materials is required for future electronic devices. Here, we investigate tin disulfide (SnS2) layers deposited via atomic layer deposition (ALD) using tetrakis(dimethylamino)tin (TDMASn) as a Sn precursor and H2S gas as a sulfur source at low temperature (150° C). The crystallinity of SnS2 was improved by H2S gas annealing. We carried out H2S gas annealing at various conditions (250° C, 300° C, 350° C, and using a three-step method). Angle-resolved X-ray photoelectron spectroscopy (ARXPS) results revealed the valence state corresponding to Sn4+ and S2- in the SnS2 annealed with H2S gas. The SnS2 annealed with H2S gas had a hexagonal structure, as measured via X-ray diffraction (XRD) and the clearly out-of-plane (A1g) mode in Raman spectroscopy. The crystallinity of SnS2 was improved after H2S annealing and was confirmed using the XRD full-width at half-maximum (FWHM). In addition, high-resolution transmission electron microscopy (HR-TEM) images indicated a clear layered structure.

The Evolution of Fabricated Gold Thin Films to Nano-Micro Particles Under Thermal Annealing Process

NASA Astrophysics Data System (ADS)

Hajivaliei, Mahdi; Nazari, Saeed

2016-06-01

Gold (Au) thin films with thickness of 35nm were prepared by electron beam deposition onto flat glass substrates under high vacuum (5.3×10-3Pa) condition and they were annealed in the range of 573-873 K for 1 and 2h in atmospheric pressure. The influence of the annealing temperature on the evolution of Au thin film to nano-micro particles was studied. Moreover, the basic properties of the films, namely morphological, structural and optical were investigated. The X-ray diffraction (XRD) analysis revealed that the Au thin films were cubic structure phase with lattice parameter around a=4.0786Å. The most preferential orientation is along (111) planes for all Au films. The lattice parameter and grain size in the films were calculated by X-ray patterns and correlated with annealing temperatures. The obtained results of ultraviolet-visible spectrometry (UV-Vis) indicate that with increasing annealing temperature, the surface plasmon resonance peak of gold nanocrystallite will disappear which implies the size of particles are grown. Field-emission scanning electron microscopy (FE-SEM) results show that the prepared gold thin films have been converted to nano-micro gold particles in different annealing temperatures. These results lead to controlling the size of produced nanocrystallite.

Self-organized TiO2 nanotube arrays in the photocatalytic degradation of methylene blue under UV light irradiation

NASA Astrophysics Data System (ADS)

Chung, Eun Hyuk; Baek, Seong Rim; Yu, Seong Mi; Kim, Jong Pil; Hong, Tae Eun; Kim, Hyun Gyu; Bae, Jong-Seong; Jeong, Euh Duck; Khan, F. Nawaz; Jung, Ok-sang

2015-04-01

Nanostructured titanium dioxide (NTiO2) is known to possess efficient photocatalytic activity and to have diverse applications in many fields due to its chemical stability, high surface area/volume ratio, high transmittance, and high refractive index in the visible and the near-ultraviolet regions. These facts prompted us to develop TiO2 nanotube (TiO2 NT) arrays through electrochemical anodic oxidation involving different electrolytes comprised of phosphoric acid — hydrofluoric acid aqueous systems by varying the voltage and the time. The annealing temperature of the nanotubes, TiO2 NTs, were varied to modify the surface morphology and were characterized by using X-ray diffraction and scanning electron microscopy. Scanning electron microscopy and X-ray diffraction results showed that the samples had uniform morphologies and good crystalline structures of the anatase phase at lower annealing temperatures and of the rutile phase at higher annealing temperatures. A secondary-ion mass-spectrometry analysis was used to investigate the surface atoms and to conduct a depth profile analysis of the TiO2 NTs. The efficiency of the photocatalytic activity of the TiO2 NT arrays in degrading methylene blue (MB) was investigated under UV-Vis light irradiation. The maximum photocatalytic activity was achieved for the samples with lower annealing temperatures due to their being in the anatase phase and having a higher surface area and a smaller crystal size, which play important roles in the degradation of organic pollutants.

Epitaxial growth of a mono-crystalline metastable AuIn layer at the Au/InP(001) interface

NASA Astrophysics Data System (ADS)

Renda, M.; Morita, K.

1990-01-01

Thermal annealing of a gold layer deposited on the InP(001)-p(2×4) surface has been studied in-situ by means of LEED, AES and RBS techniques and by post analysis of RBS-channeling and glancing incidence X-ray diffraction. A clean LEED pattern of p(2×2) spots was observed for the specimen annealed for 10 min at 300°C. The composition ratio of Au/In in the epitaxial compound layer was found to be 49/51 by RBS and several at% of P was also detected by post sputter-AES analysis. It was also found that the epitaxial layer shows a clear channeling dip for an incident ion beam which is aligned along the <001> axis of InP substrate. The glancing incidence X-ray diffraction analysis indicates diffraction peaks from the pseudo-orthorombic phase of AuIn. From these experimental results, it is concluded that the epitaxial Au-compound layer is a mono-crystalline metastable phase of AuIn, of which every three atomic rows of Au or In in the [110] direction would be situated on every four atomic rows in the [010] direction of the In(001) face of the InP crystal.

Hydrogen incorporation induced the octahedral symmetry variation in VO2 films

NASA Astrophysics Data System (ADS)

Lee, Dooyong; Kim, Hyegyeong; Kim, Ji Woong; Lee, Ik Jae; Kim, Yooseok; Yun, Hyung-Joong; Lee, Jouhahn; Park, Sungkyun

2017-02-01

This study examined the microscopic aspects of macroscopic physical property variations of hydrogen annealed VO2 films, deposited on Al2O3(0001) substrates by RF magnetron sputtering. The temperature-dependent electrical resistivity showed that the as-grown film exhibited a metal-insulator-transition (MIT) at 55.20 °C and 49.26 °C during heating and cooling, respectively. On the other hand, no MIT was observed for the film annealed under a hydrogen environment. Spectroscopic measurements during the in-situ hydrogenation process showed that hydrogen annealing (∼0.3 mbar, up to 300 °C) promoted the V3+ state above 100 °C. Raman spectroscopy and X-ray diffraction confirmed that the as-grown film changed from a monoclinic to rutile structure during hydrogen annealing. In addition, the shift of the (020) diffraction peak position of the hydrogen-annealed film to a lower angle compare to that of the known rutile VO2 film was attributed to the expansion of the unit cell. In addition, local structure analysis showed that an increase in octahedral symmetry after hydrogen annealing is one of the main explanations for the metallic characteristics of the hydrogen-annealed film.

Effect of Aluminum Addition on the Evolution of Microstructure, Crystallographic Texture and Mechanical Properties of Single Phase Hexagonal Close Packed Mg-Li Alloys

NASA Astrophysics Data System (ADS)

Bhagat Singh, P.; Sabat, R. K.; Kumaran, S.; Suwas, S.

2018-02-01

In the present investigation, an effort has been made to understand the effect of aluminum addition to α Mg-Li alloys. The corresponding composition Mg-4Li- xAl ( x = 0, 2, 4 and 6 wt.%) alloys have been prepared by stir casting route under an argon environment. Extrusion was carried out at 300 °C with the extrusion ratio of 15:1. Significant grain refinement was observed after extrusion. X-ray diffraction-based investigation of the cast and extruded alloys showed the presence of intermetallic compounds such as Mg17Al12 and AlLi in the Al-rich alloys namely, Mg-4Li- xAl ( x = 4 and 6 wt.%). These precipitates were also present in the extruded plus annealed samples, indicating the stability of the precipitates at high temperature. The bulk x-ray texture measurement revealed a crystallographic texture where the c-axis of the h.c.p crystals was perpendicular to the extrusion direction (ED) for extruded sample. A texture transition was observed on annealing. The c-axis was oriented parallel to the ED. Mechanical properties of the cast, extruded and extruded plus annealed material illustrate that the addition of Al led to enhancement in hardness, yield strength and ultimate tensile strength.

Annealing induced reorientation of crystallites in Sn doped ZnO films

NASA Astrophysics Data System (ADS)

Ravichandran, K.; Vasanthi, M.; Thirumurugan, K.; Sakthivel, B.; Karthika, K.

2014-11-01

Tin doped ZnO thin films were prepared by employing a simplified spray pyrolysis technique using a perfume atomizer and subsequently annealed under different temperatures from 350 °C to 500 °C in steps of 50 °C. The structural, optical, electrical, photoluminescence and surface morphological properties of the as-deposited films were studied and compared with that of the annealed films. The X-ray diffraction studies showed that as-deposited film exhibits preferential orientation along the (0 0 2) plane and it changes in favour of (1 0 0) plane after annealing. The increase in crystallite size due to annealing is explained on the basis of Ostwald ripening effect. It is found that the optical transmittance and band gap increases with increase in annealing temperature. A slight decrease in resistivity caused by annealing is discussed in correlation with annealing induced defect modifications and surface morphology.

Structural analysis of as-deposited and annealed low-temperature gallium arsenide

NASA Astrophysics Data System (ADS)

Matyi, R. J.; Melloch, M. R.; Woodall, J. M.

1993-04-01

The structure of GaAs grown at low substrate temperatures (LT-GaAs) by molecular beam epitaxy has been studied using high resolution X-ray diffraction methods. Double crystal rocking curves from the as-deposited LT-GaAs show well defined interference fringes, indicating a high level of structural perfection. Triple crystal diffraction analysis of the as-deposited sample showed significantly less diffuse scattering near the LT-GaAs 004 reciprocal lattice point compared with the substrate 004 reciprocal lattice point, suggesting that despite the incorporation of approximately 1% excess arsenic, the epitaxial layer had superior crystalline perfection than did the GaAs substrate. Triple crystal scans of annealed LT-GaAs showed an increase in the integrated diffuse intensity by approximately a factor of three as the anneal temperature was increased from 700 to 900°C. Analogous to the effects of SiO2 precipitates in annealed Czochralski silicon, the diffuse intensity is attributed to distortions in the epitaxial LT-GaAs lattice by arsenic precipitates.

Irradiation induced formation of VN in CrN thin films

NASA Astrophysics Data System (ADS)

Novaković, M.; Popović, M.; Zhang, K.; Mitrić, M.; Bibić, N.

2015-09-01

Reactively sputtered CrN layer, deposited on Si(1 0 0) wafer, was implanted at room temperature with 80-keV V+ ions to the fluence of 2 × 1017 ions/cm2. After implantation the sample was annealed in a vacuum, for 2 h at 700 °C. The microstructure and chemical composition of CrN films was investigated using Rutherford backscattering spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and cross-sectional transmission electron microscopy (conventional and high-resolution), together with fast Fourier transformation analyses. It was found that vanadium atoms are distributed in the sub-surface region of CrN layer, with the maximum concentration at ∼20 nm. After annealing the formation of VN nanoparticles was observed. The nanoparticles are spherical shaped with a size of 8-20 nm in diameter.

Twin-induced phase transition from β-Ga2O3 to α-Ga2O3 in Ga2O3 thin films

NASA Astrophysics Data System (ADS)

Choi, Byeongdae; Allabergenov, Bunyod; Lyu, Hong-Kun; Lee, Seong Eui

2018-06-01

We deposited a 300-nm-thick Ga2O3 thin film on an amorphous SiO2/Si substrate via pulsed laser deposition. X-ray diffraction patterns revealed the formation of β-Ga2O3 phase at a substrate temperature of 700 °C. X-ray photoelectron spectra indicated that the degree of oxidation increased after annealing at 700 °C. Further annealings at higher temperatures led to a transition of the β-Ga2O3 phase to the α-Ga2O3 phase; this transition was caused by the twin structure formed during the crystallinity improvement process. In addition, we discuss the mechanism of the transition from the β phase to the α phase in the β-Ga2O3 thin films.

Structural and photoluminescence study of bulk SrZnO2

NASA Astrophysics Data System (ADS)

Manju, Jain, Megha; Kumar, Ravi; Kumar, Shalendra; Thakur, Anup; Vij, Ankush

2018-05-01

In present work, we report synthesis, X-ray diffraction study and photoluminescence of SrZnO2. The SrZnO2 phosphors were prepared through high energy ball milling process and subsequent annealing. The annealing at various temperatures helped in emergence of single phased SrZnO2 phosphors. The texture coefficient of prominent planes was found to be growing with annealing temperature. At an excitation wavelength of 325 nm, the photoluminescence spectrum is spanning from yellow to IR region. As SrZnO2 is wide band gap phosphor, so the observed emission is believed to be due to oxygen vacancies or cation interstitial defects.

Removal of Micrometer Size Morphological Defects and Enhancement of Ultraviolet Emission by Thermal Treatment of Ga-Doped ZnO Nanostructures

PubMed Central

Manzoor, Umair; Kim, Do K.; Islam, Mohammad; Bhatti, Arshad S.

2014-01-01

Mixed morphologies of Ga-doped Zinc Oxide (ZnO) nanostructures are synthesized by vapor transport method. Systematic scanning electron microscope (SEM) studies of different morphologies, after periodic heat treatments, gives direct evidence of sublimation. SEM micrographs give direct evidence that morphological defects of nanostructures can be removed by annealing. Ultra Violet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with each subsequent heat treatment. X-Ray diffraction (XRD) results suggest that crystal quality improved by annealing and phase separation may occur at high temperatures. PMID:24489725

Removal of micrometer size morphological defects and enhancement of ultraviolet emission by thermal treatment of Ga-doped ZnO nanostructures.

PubMed

Manzoor, Umair; Kim, Do K; Islam, Mohammad; Bhatti, Arshad S

2014-01-01

Mixed morphologies of Ga-doped Zinc Oxide (ZnO) nanostructures are synthesized by vapor transport method. Systematic scanning electron microscope (SEM) studies of different morphologies, after periodic heat treatments, gives direct evidence of sublimation. SEM micrographs give direct evidence that morphological defects of nanostructures can be removed by annealing. Ultra Violet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with each subsequent heat treatment. X-Ray diffraction (XRD) results suggest that crystal quality improved by annealing and phase separation may occur at high temperatures.

Coherent diffractive imaging of solid state reactions in zinc oxide crystals

NASA Astrophysics Data System (ADS)

Leake, Steven J.; Harder, Ross; Robinson, Ian K.

2011-11-01

We investigated the doping of zinc oxide (ZnO) microcrystals with iron and nickel via in situ coherent x-ray diffractive imaging (CXDI) in vacuum. Evaporated thin metal films were deposited onto the ZnO microcrystals. A single crystal was selected and tracked through annealing cycles. A solid state reaction was observed in both iron and nickel experiments using CXDI. A combination of the shrink wrap and guided hybrid-input-output phasing methods were applied to retrieve the electron density. The resolution was 33 nm (half order) determined via the phase retrieval transfer function. The resulting images are nevertheless sensitive to sub-angstrom displacements. The exterior of the microcrystal was found to degrade dramatically. The annealing of ZnO microcrystals coated with metal thin films proved an unsuitable doping method. In addition the observed defect structure of one crystal was attributed to the presence of an array of defects and was found to change upon annealing.

Order-disorder-reorder process in thermally treated dolomite samples: a combined powder and single-crystal X-ray diffraction study

NASA Astrophysics Data System (ADS)

Zucchini, A.; Comodi, P.; Katerinopoulou, A.; Balic-Zunic, T.; McCammon, C.; Frondini, F.

2012-04-01

A combined powder and single-crystal X-ray diffraction analysis of dolomite [CaMg(CO3)2] heated to 1,200°C at 3 GPa was made to study the order-disorder-reorder process. The order/disorder transition is inferred to start below 1,100°C, and complete disorder is attained at approximately 1,200°C. Twinned crystals characterized by high internal order were found in samples annealed over 1,100°C, and their fraction was found to increase with temperature. Evidences of twinning domains combined with probable remaining disordered portions of the structure imply that reordering processes occur during the quench. Twin domains are hereby proposed as a witness to thermally induced intra-layer-type cation disordering.

Role of annealing duration on the microstructure and electrochemical performance of β-V2O5 thin films

NASA Astrophysics Data System (ADS)

Jeyalakshmi, K.; Muralidharan, G.

2014-03-01

Vanadium pentoxide thin films have been prepared by sol-gel spin coating method. The eight-layered films coated on fluorine-doped tin oxide substrate and glass substrate were subjected to different durations of annealing under a constant annealing temperature of 300 °C from 30 to 120 min. The X-ray diffraction spectrum reveals crystallinity along (2 0 0) direction. The SEM images of these films show the variation in the surface morphology with increase in annealing duration. The supercapacitor behaviour has been studied using cyclic voltammetry technique and electrochemical impedance spectroscopy. The film annealed for 60 min exhibits a maximum specific capacitance of 346 F/g at a scan rate of 5 mV/s with a charge transfer resistance of 172 Ω.

Homogenization of CZ Si wafers by Tabula Rasa annealing

NASA Astrophysics Data System (ADS)

Meduňa, M.; Caha, O.; Kuběna, J.; Kuběna, A.; Buršík, J.

2009-12-01

The precipitation of interstitial oxygen in Czochralski grown silicon has been investigated by infrared absorption spectroscopy, chemical etching, transmission electron microscopy and X-ray diffraction after application of homogenization annealing process called Tabula Rasa. The influence of this homogenization step consisting in short time annealing at high temperature has been observed for various temperatures and times. The experimental results involving the interstitial oxygen decay in Si wafers and absorption spectra of SiOx precipitates during precipitation annealing at 1000∘ C were compared with other techniques for various Tabula Rasa temperatures. The differences in oxygen precipitation, precipitate morphology and evolution of point defects in samples with and without Tabula Rasa applied is evident from all used experimental techniques. The results qualitatively correlate with prediction of homogenization annealing process based on classical nucleation theory.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rittman, Dylan R.; Turner, Katlyn M.; Park, Sulgiye

Strain engineering is a promising method for next-generation materials processing techniques. Here, we use mechanical milling and annealing followed by compression in diamond anvil cell to tailor the intrinsic and extrinsic strain in pyrochlore, Dy 2Ti 2O 7 and Dy 2Zr 2O 7. Raman spectroscopy, X-ray pair distribution function analysis, and X-ray diffraction were used to characterize atomic order over short-, medium-, and long-range spatial scales, respectively, under ambient conditions. Raman spectroscopy and X-ray diffraction were further employed to interrogate the material in situ at high pressure. High-pressure behavior is found to depend on the species and concentration of defectsmore » in the sample at ambient conditions. Overall, we show that defects can be engineered to lower the phase transformation onset pressure by ~50% in the ordered pyrochlore Dy 2Ti 2O 7, and lower the phase transformation completion pressure by ~20% in the disordered pyrochlore Dy 2Zr 2O 7. Lastly, these improvements are achieved without significantly sacrificing mechanical integrity, as characterized by bulk modulus.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rittman, Dylan R.; Turner, Katlyn M.; Park, Sulgiye

Strain engineering is a promising method for next-generation materials processing techniques. Here, we use mechanical milling and annealing followed by compression in diamond anvil cell to tailor the intrinsic and extrinsic strain in pyrochlore, Dy 2Ti 2O 7 and Dy 2Zr 2O 7. Raman spectroscopy, X-ray pair distribution function analysis, and X-ray diffraction were used to characterize atomic order over short-, medium-, and long-range spatial scales, respectively, under ambient conditions. Raman spectroscopy and X-ray diffraction were further employed to interrogate the material in situ at high pressure. High-pressure behavior is found to depend on the species and concentration of defectsmore » in the sample at ambient conditions. Overall, we show that defects can be engineered to lower the phase transformation onset pressure by ~50% in the ordered pyrochlore Dy 2Zr 2O 7, and lower the phase transformation completion pressure by ~20% in the disordered pyrochlore Dy 2Zr 2O 7. These improvements are achieved without significantly sacrificing mechanical integrity, as characterized by bulk modulus.« less

Effect of annealing and In content on the properties of electron beam evaporated ZnO films

NASA Astrophysics Data System (ADS)

Mohamed, S. H.; Ali, H. M.; Mohamed, H. A.; Salem, A. M.

2005-08-01

The effect of both annealing and In content on the properties of ZnO films prepared by electron beam evaporation were investigated. The evaporation was carried out at room temperature from bulk samples prepared by sintering technique. X-ray diffraction showed that the structure of ZnO-In{2}O{3} films depends on both the In content and annealing temperature. Amorphous, highly transparent and relatively low resistive films which can be suitable for the usage as transparent electrode of organic light-emitting diode were obtained upon annealing at 300 circC. Partially crystalline, highly transparent and highly resistive films which can be used in piezoelectric applications were obtained upon annealing at 500 circC. For each composition the refractive index has no monotonic variation upon increasing annealing temperature.

Formation of a Polycrystalline Silicon Thin Film by Using Blue Laser Diode Annealing

NASA Astrophysics Data System (ADS)

Choi, Young-Hwan; Ryu, Han-Youl

2018-04-01

We report the crystallization of an amorphous silicon thin film deposited on a SiO2/Si wafer using an annealing process with a high-power blue laser diode (LD). The laser annealing process was performed using a continuous-wave blue LD of 450 nm in wavelength with varying laser output power in a nitrogen atmosphere. The crystallinity of the annealed poly-silicon films was investigated using ellipsometry, electron microscope observation, X-ray diffraction, and Raman spectroscopy. Polysilicon grains with > 100-nm diameter were observed to be formed after the blue LD annealing. The crystal quality was found to be improved as the laser power was increased up to 4 W. The demonstrated blue LD annealing is expected to provide a low-cost and versatile solution for lowtemperature poly-silicon processes.

Structure refinement for tantalum nitrides nanocrystals with various morphologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Lianyun; School of Science, Beijing Jiaotong University, 3 Shang Yuan Cun, Haidian District, Beijing 100044; Huang, Kai

2012-07-15

Graphical abstract: Tantalum nitrides nanocrystals with various phases and morphologies for the first time have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. Highlights: ► The spherical TaN, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. ► The crystal structures of different tantalum nitrides were determined by Rietveld refinement on the X-ray diffraction data and the examinations of electron microcopies. ► The specific surface area of the tantalum nitrides powders was around 10 m{supmore » 2} g{sup −1}. ► Tantalum nitrides powders could be suitable for capacitor with high specific capacitance. -- Abstract: Tantalum nitrides (TaN{sub x}) nanocrystals with different phase and morphology have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. The crystal structures of tantalum nitrides were determined by Rietveld refinement based on the X-ray diffraction data. The morphologies of various tantalum nitrides nanocrystals in high quality were analyzed through the electron microcopies examinations. The spherical TaN nanoparticles, cuboidal TaN{sub 0.83} and TaN{sub 0.5} nanocrystals have been selectively prepared at different annealing temperatures. In addition, the specific surface areas of the tantalum nitrides nanocrystals measured by BET method were around 9.87–11.64 m{sup 2} g{sup −1}, indicating that such nano-sized tantalum nitrides could be suitable for capacitor with high specific capacitance.« less

Tm-doped TiO2 and Tm2Ti2O7 pyrochlore nanoparticles: enhancing the photocatalytic activity of rutile with a pyrochlore phase.

PubMed

De Los Santos, Desiré M; Navas, Javier; Aguilar, Teresa; Sánchez-Coronilla, Antonio; Fernández-Lorenzo, Concha; Alcántara, Rodrigo; Piñero, Jose Carlos; Blanco, Ginesa; Martín-Calleja, Joaquín

2015-01-01

Tm-doped TiO2 nanoparticles were synthesized using a water-controlled hydrolysis reaction. Analysis was performed in order to determine the influence of the dopant concentration and annealing temperature on the phase, crystallinity, and electronic and optical properties of the resulting material. Various characterization techniques were utilized such as X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. For the samples annealed at 773 and 973 K, anatase phase TiO2 was obtained, predominantly internally doped with Tm(3+). ICP-AES showed that a doping concentration of up to 5.8 atom % was obtained without reducing the crystallinity of the samples. The presence of Tm(3+) was confirmed by X-ray photoelectron spectroscopy and UV-vis spectroscopy: the incorporation of Tm(3+) was confirmed by the generation of new absorption bands that could be assigned to Tm(3+) transitions. Furthermore, when the samples were annealed at 1173 K, a pyrochlore phase (Tm2Ti2O7) mixed with TiO2 was obtained with a predominant rutile phase. The photodegradation of methylene blue showed that this pyrochlore phase enhanced the photocatalytic activity of the rutile phase.

The effect of cyclic heat treatment on the physicochemical properties of bio hydroxyapatite from bovine bone.

PubMed

Londoño-Restrepo, S M; Jeronimo-Cruz, R; Rubio-Rosas, E; Rodriguez-García, M E

2018-05-02

This paper focus on physicochemical changes in bio-hydroxyapatite (BIO-HAp) from bovine femur obtained by calcination at high temperatures: 520-620 (each 20 °C) at 7.4 °C/min and from 700 to 1100 °C (each 100 °C) at three heating rates: 7.4, 9.9, and 11.1 °C/min. BIO-HAp samples were obtained using a multi-step process: cleaning, milling, hydrothermal process, calcination in an air atmosphere, and cooling in furnace air. Inductively Couple Plasma (ICP) showed that the presence of Mg, K, S, Ba, Zn, and Na, is not affected by the annealing temperature and heating rate. While Scanning Electron Microscopy (SEM) images showed the continuous growth of the HAp crystals during the calcination process due to the coalescence phenomenon, and the Full Width at the Half Maximum for the X-ray patterns for temperatures up to 700 is affected by the annealing temperature and the heating rate. Through X-ray diffraction, thermal, and calorimetric analysis (TGA-DSC), a partial dehydroxylation of hydroxyapatite was found in samples calcined up to 900 °C for the three heating rates. Also, Ca/P molar ratio decreased for samples calcined up to 900 °C as a result of the dehydroxylation process. NaCaPO 4 , CaCO 3 , Ca 3 (PO 4 ) 2 , MgO, and Ca(H 2 PO 4 ) 2 are some phases identified by X-ray diffraction; some of them are part of the bone and others were formed during the calcination process as a function of annealing temperature and heating rate, as it is the case for MgO.

Effect of processing parameters on the characteristics of high-Tc superconductor YBa2Cu3Oy

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1988-01-01

SEM, thermogravimetric analysis, powder X-ray diffraction,and measurements of electrical resistivity and magnetic susceptibility, are presently used to characterize the influence of sintering temperature, sintering and annealing atmospheres, and quench-rate on the properties of the YBa2Cu3Oy superconducting oxide. It is established that annealing in oxygen, together with slow cooling rates, are required for preparation of high-Tc superconductors with sharp transitions; rapid quenching from high temperature does not yield good superconductors, due to low oxygen content.

Ultrasonic attenuation measurements determine onset, degree, and completion of recrystallization

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1988-01-01

Ultrasonic attenuation was measured for cold worked Nickel 200 samples annealed at increasing temperatures. Localized dislocation density variations, crystalline order and volume percent of recrystallized phase were determined over the anneal temperature range using transmission electron microscopy, X-ray diffraction, and metallurgy. The exponent of the frequency dependence of the attenuation was found to be a key variable relating ultrasonic attenuation to the thermal kinetics of the recrystallization process. Identification of this key variable allows for the ultrasonic determination of onset, degree, and completion of recrystallization.

Li-ion transport in all-solid-state lithium batteries with LiCoO 2 using NASICON-type glass ceramic electrolytes

NASA Astrophysics Data System (ADS)

Xie, J.; Imanishi, N.; Zhang, T.; Hirano, A.; Takeda, Y.; Yamamoto, O.

LiCoO 2 thin films were deposited on the NASICON-type glass ceramics, Li 1+ x+ yAl xTi 2- xSi yP 3- yO 12, by radio frequency (RF) magnetron sputtering and were annealed at different temperatures. The as-deposited and the annealed LiCoO 2 thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). It was found that the films exhibited a (1 0 4) preferred orientation after annealing and Co 3O 4 was observed by annealing over 500 °C due to the reaction between the LiCoO 2 and the glass ceramics. The effect of annealing temperature on the interfacial resistance of glass ceramics/LiCoO 2 and Li-ion transport in the bulk LiCoO 2 thin film was investigated by galvanostatic cycling, cyclic voltammetry (CV), potentiostatic intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) with the Li/PEO/glass ceramics/LiCoO 2 cell. The cell performance was limited by the Li-ion diffusion resistance in Ohara/LiCoO 2 interface as well as in bulk LiCoO 2.

Effect of In Situ Annealing Treatment on the Mobility and Morphology of TIPS-Pentacene-Based Organic Field-Effect Transistors.

PubMed

Yang, Fuqiang; Wang, Xiaolin; Fan, Huidong; Tang, Ying; Yang, Jianjun; Yu, Junsheng

2017-08-23

In this work, organic field-effect transistors (OFETs) with a bottom gate top contact structure were fabricated by using a spray-coating method, and the influence of in situ annealing treatment on the OFET performance was investigated. Compared to the conventional post-annealing method, the field-effect mobility of OFET with 60 °C in situ annealing treatment was enhanced nearly four times from 0.056 to 0.191 cm 2 /Vs. The surface morphologies and the crystallization of TIPS-pentacene films were characterized by optical microscope, atomic force microscope, and X-ray diffraction. We found that the increased mobility was mainly attributed to the improved crystallization and highly ordered TIPS-pentacene molecules.

Effect of In Situ Annealing Treatment on the Mobility and Morphology of TIPS-Pentacene-Based Organic Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Yang, Fuqiang; Wang, Xiaolin; Fan, Huidong; Tang, Ying; Yang, Jianjun; Yu, Junsheng

2017-08-01

In this work, organic field-effect transistors (OFETs) with a bottom gate top contact structure were fabricated by using a spray-coating method, and the influence of in situ annealing treatment on the OFET performance was investigated. Compared to the conventional post-annealing method, the field-effect mobility of OFET with 60 °C in situ annealing treatment was enhanced nearly four times from 0.056 to 0.191 cm2/Vs. The surface morphologies and the crystallization of TIPS-pentacene films were characterized by optical microscope, atomic force microscope, and X-ray diffraction. We found that the increased mobility was mainly attributed to the improved crystallization and highly ordered TIPS-pentacene molecules.

In Situ Ramp Anneal X-ray Diffraction Study of Atomic Layer Deposited Ultrathin TaN and Ta 1-x Al x N y Films for Cu Diffusion Barrier Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Consiglio, S.; Dey, S.; Yu, K.

2016-01-01

Ultrathin TaN and Ta 1-xAl xN y films with x = 0.21 to 0.88 were deposited by atomic layer deposition (ALD) and evaluated for Cu diffusion barrier effectiveness compared to physical vapor deposition (PVD) grown TaN. Cu diffusion barrier effectiveness was investigated using in-situ ramp anneal synchrotron X-ray diffraction (XRD) on Cu/1.8 nm barrier/Si stacks. A Kissinger-like analysis was used to assess the kinetics of Cu 3Si formation and determine the effective activation energy (E a) for Cu silicidation. Compared to the stack with a PVD TaN barrier, the stacks with the ALD films exhibited a higher crystallization temperature (Tmore » c) for Cu silicidation. The Ea values of Cu 3Si formation for stacks with the ALD films were close to the reported value for grain boundary diffusion of Cu whereas the Ea of Cu 3Si formation for the stack with PVD TaN is closer to the reported value for lattice diffusion. For 3 nm films, grazing incidence in-plane XRD showed evidence of nanocrystallites in an amorphous matrix with broad peaks corresponding to high density cubic phase for the ALD grown films and lower density hexagonal phase for the PVD grown film further elucidating the difference in initial failure mechanisms due to differences in barrier crystallinity and associated phase.« less

Structural and Mössbauer characterization of the ball milled Fe x(Cr 2O 3) 1- x system

NASA Astrophysics Data System (ADS)

Biondo, Valdecir; de Medeiros, Suzana Nóbrega; Paesano, Andrea, Jr.; Ghivelder, Luis; Hallouche, Bachir; da Cunha, João Batista Marimon

2009-08-01

The Fe x(Cr 2O 3) 1- x system, with 0.10 ≤ X ≤ 0.80, was mechanically processed for 24 h in a high-energy ball-mill. In order to examine the possible formation of iron-chromium oxides and alloys, the milled samples were, later, thermally annealed in inert (argon) and reducing (hydrogen) atmospheres. The as-milled and annealed products were characterized by X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy and magnetization. The as-milled samples showed the formation of an Fe 1+ YCr 2- YO 4- δ nanostructured and disordered spinel phase, the α 1-Fe(Cr) and α 2-Cr(Fe) solid solutions and the presence of non-exhausted precursors. For the samples annealed in inert atmosphere, the chromite (FeCr 2O 4) formation and the recrystallization of the precursors were verified. The hydrogen treated samples revealed the reduction of the spinel phase, with the phase separation of the chromia phase and retention of the Fe-Cr solid solutions. All the samples, either as-milled or annealed, presented the magnetization versus applied field curves typical for superparamagnetic systems.

Crystal structure and high-temperature properties of the Ruddlesden–Popper phases Sr{sub 3−x}Y{sub x}(Fe{sub 1.25}Ni{sub 0.75})O{sub 7−δ} (0≤x≤0.75)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samain, Louise; Amshoff, Philipp; Biendicho, Jordi J.

2015-07-15

Ruddlesden–Popper n=2 member phases Sr{sub 3−x}Y{sub x}Fe{sub 1.25}Ni{sub 0.75}O{sub 7−δ}, 0≤x≤0.75, have been investigated by X-ray and neutron powder diffraction, thermogravimetry and Mössbauer spectroscopy. Both samples as-prepared at 1300 °C under N{sub 2}(g) flow and samples subsequently air-annealed at 900 °C were studied. The as-prepared x=0.75 phase is highly oxygen deficient with δ=1, the O1 atom site being vacant, and the Fe{sup 3+}/Ni{sup 2+} ions having a square pyramidal coordination. For as-prepared phases with lower x values, the Mössbauer spectral data are in good agreement with the presence of both 5- and 4-coordinated Fe{sup 3+} ions, implying in addition amore » partial occupancy of the O3 atom sites that form the basal plane of the square pyramid. The air-annealed x=0.75 sample has a δ value of 0.61(1) and the structure has Fe/Ni ions in both square pyramids and octahedra. Mössbauer spectroscopy shows the phase to contain only Fe{sup 3+}, implying that all Ni is present as Ni{sup 3+}. Air-annealed phases with lower x values are found to contain both Fe{sup 3+} and Fe{sup 4+}. For both the as-prepared and the air-annealed samples, the Y{sup 3+} cations are found to be mainly located in the perovskite block. The high-temperature thermal expansion of as-prepared and air-annealed x=0.75 phases were investigated by high-temperature X-ray diffraction and dilatometry and the linear thermal expansion coefficient determined to be 14.4 ppm K{sup −1}. Electrical conductivity measurements showed that the air-annealed samples have higher conductivity than the as-prepared ones. - Highlights: • Ruddlesden–Popper, n=2, Sr{sub 3−x}Y{sub x}Fe{sub 1.25}Ni{sub 0.75}O{sub 7−δ}, 0≤x≤0.75, have been synthesised. • The crystal structures of the phases have been determined. • Sr{sub 2.25}Y{sub 0.75}Fe{sub 1.25}Ni{sub 0.75}O{sub 6}, made in N{sub 2}(g) has Fe{sup 3+}/Ni{sup 2+} in square pyramides. • Sr{sub 2.25}Y{sub 0.75}Fe{sub 1.25}Ni{sub 0.75}O{sub 6.4}, made in air has Fe{sup 3+}/Ni{sup 3+} in square pyramides and octahedra. • Air annealed samples have higher electrical conductivity than N{sub 2}(g) annealed.« less

Some studies on TiO2 films deposited by sol-gel technique

NASA Astrophysics Data System (ADS)

Narasimha Rao, K.; Vishwas, M.; Kumar Sharma, Sudhir; Arjuna Gowda, K. V.

2008-08-01

TiO2 films are extensively used in various applications including optical multi-layers, sensors, photo catalysis, environmental purification, and solar cells etc. These are prepared by both vacuum and non-vacuum methods. In this paper, we present the results on TiO2 thin films prepared by a sol-gel spin coating process in non-aqueous solvent. Titanium isopropoxide is used as TiO2 precursor. The films were annealed at different temperatures up to 3000 C for 5 hours in air. The influence of the various deposition parameters like spinning speed, spinning time and annealing temperature on the thickness of the TiO2 films has been studied. The variation of film thickness with time in ambient atmosphere was also studied. The optical, structural and morphological characteristics were investigated by optical transmittance-reflectance measurements, X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The refractive index and extinction coefficient of the films were determined by envelope technique and spectroscopic ellipsometry. TiO2 films exhibited high transparency (92%) in the visible region with a refractive index of 2.04 at 650 nm. The extinction coefficient was found to be negligibly small. The X-ray diffraction analysis showed that the TiO2 film deposited on glass substrate changes from amorphous to crystalline (anatase) phase with annealing temperature above 2500 C. SEM results show that the deposited films are uniform and crack free.

Pair distribution function analysis of sulfide glassy electrolytes for all-solid-state batteries: Understanding the improvement of ionic conductivity under annealing condition.

PubMed

Shiotani, Shinya; Ohara, Koji; Tsukasaki, Hirofumi; Mori, Shigeo; Kanno, Ryoji

2017-08-01

In general, the ionic conductivity of sulfide glasses decreases with their crystallization, although it increases for a few sulphide glasses owing to the crystallization of a highly conductive new phase (e.g., Li 7 P 3 S 11 : 70Li 2 S-30P 2 S 5 ). We found that the ionic conductivity of 75Li 2 S-25P 2 S 5 sulfide glass, which consists of glassy and crystalline phases, is improved by optimizing the conditions of the heat treatment, i.e., annealing. A different mechanism of high ionic conductivity from the conventional mechanism is expected in the glassy phase. Here, we report the glassy structure of 75Li 2 S-25P 2 S 5 immediately before the crystallization by using the differential pair distribution function (d-PDF) analysis of high-energy X-ray diffraction. Even though the ionic conductivity increases during the optimum annealing, the d-PDF analysis indicated that the glassy structure undergoes no structural change in the sulfide glass-ceramic electrolyte at a crystallinity of 33.1%. We observed the formation of a nanocrystalline phase in the X-ray and electron diffraction patterns before the crystallization, which means that Bragg peaks were deformed. Thus, the ionic conductivity in the mixture of glassy and crystalline phases is improved by the coexistence of the nanocrystalline phase.

Annealing effect on thermal conductivity and microhardness of carbon nanotube containing Se80Te16Cu4 glassy composites

NASA Astrophysics Data System (ADS)

Upadhyay, A. N.; Tiwari, R. S.; Singh, Kedar

2018-02-01

This study deals with the effect of thermal annealing on structural/microstructural, thermal and mechanical behavior of pristine Se80Te16Cu4 and carbon nanotubes (CNTs) containing Se80Te16Cu4 glassy composites. Pristine Se80Te16Cu4, 3 and 5 wt%CNTs-Se80Te16Cu4 glassy composites are annealed in the vicinity of glass transition temperature to onset crystallization temperature (340-380 K). X-ray diffraction (XRD) pattern revealed formation of polycrystalline phases of hexagonal CuSe and trigonal selenium. The indexed d-values in XRD patterns are in well conformity with the d-values obtained after the indexing of the ring pattern of selected area electron diffraction pattern of TEM images. The SEM investigation exhibited that the grain size of the CNTs containing Se80Te16Cu4 glassy composites increased with increasing annealing temperature and decreased at further higher annealing temperature. Thermal conductivity, microhardness exhibited a substantial increase with increasing annealing temperature of 340-360 K and slightly decreases for 380 K. The variation of thermal conductivity and microhardness can be explained by cross-linking formation and voids reduction.

A novel technique based on a plasma focus device for nano-porous gallium nitride formation on P-type silicon

NASA Astrophysics Data System (ADS)

Sharifi Malvajerdi, S.; Salar Elahi, A.; Habibi, M.

2017-04-01

A new deposition formation was observed with a Mather-type Plasma Focus Device (MPFD). MPFD was unitized to fabricate porous Gallium Nitride (GaN) on p-type Silicon (Si) substrate with a (100) crystal orientation for the first time in a deposition process. GaN was deposited on Si with 4 and 7 shots. The samples were subjected to a 3 phase annealing procedure. First, the semiconductors were annealed in the PFD with nitrogen plasma shots after their deposition. Second, a thermal chemical vapor deposition annealed the samples for 1 h at 1050 °C by nitrogen gas at a pressure of 1 Pa. Finally, an electric furnace annealed the samples for 1 h at 1150 °C with continuous flow of nitrogen. Porous GaN structures were observed by Field emission scanning electron microscopy and atomic force microscopy. Furthermore, X-Ray diffraction analysis was carried out to determine the crystallinity of GaN after the samples were annealed. Energy-Dispersive X-Ray Spectroscopy indicated the amount of gallium, nitrogen, and oxygen due to the self-oxidation of the samples. Photoluminescence spectroscopy revealed emissions at 2.94 eV and 3.39 eV, which shows that hexagonal wurtzite crystal structures were formed.

Crystallized InBiS3 thin films with enhanced optoelectronic properties

NASA Astrophysics Data System (ADS)

Ali, N.; Hussain, Arshad; Ahmed, R.; Omar, M. Firdaus Bin; Sultan, M.; Fu, Yong Qing

2018-04-01

In this paper, a one-step thermal evaporation approach was used for fabrication of indium bismuth sulphide thin films, and the synergetic effects of co-evaporation of two sources (indium granules and Bi2S3 powders) were investigated using different characterization techniques. X-ray diffraction (XRD) analysis confirmed the crystalline orthorhombic structure for the post-annealed samples. Surface roughness and crystal size of the obtained film samples were increased with increasing annealing temperatures. Analysis using X-ray photoelectron spectroscopy showed the formation of the InBiS3 structure for the obtained films, which is also confirmed by the XRD results. The optical absorption coefficient value of the annealed samples was found to be in the order of 105 cm-1 in the visible region of the solar spectrum. The optical band gap energy and electrical resistivity of the fabricated samples were observed to decrease (from 2.2 to 1.3 eV, and from 0.3 to 0.01 Ω-cm, respectively) with increasing annealing temperatures (from 200 to 350 °C), indicating the suitability of the prepared InBiS3 thin films for solar cell applications.

Characteristics of OMVPE grown GaAsBi QW lasers and impact of post-growth thermal annealing

NASA Astrophysics Data System (ADS)

Kim, Honghyuk; Guan, Yingxin; Babcock, Susan E.; Kuech, Thomas F.; Mawst, Luke J.

2018-03-01

Laser diodes employing a strain-compensated GaAs1-xBix/GaAs1-yPy single quantum well (SQW) active region were grown by organometallic vapor phase epitaxy (OMVPE). High resolution x-ray diffraction, room temperature photoluminescence, and real-time optical reflectance measurements during the OMVPE growth were used to find the optimum process window for the growth of the active region material. Systematic post-growth in situ thermal anneals of various lengths were carried out in order to investigate the impacts of thermal annealing on the laser device performance characteristics. While the lowest threshold current density was achieved after the thermal annealing for 30 min at 630 °C, a gradual decrease in the external differential quantum efficiency was observed as the annealing time increases. It was observed that the temperature sensitivities of the threshold current density increase while those of lasing wavelength and slope efficiency remain nearly constant with increasing annealing time. Z-contrast scanning transmission electron microscopic) analysis revealed inhomogeneous Bi distribution within the QW active region.

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.

Modification of carbon composites by nanoceramic compounds

NASA Astrophysics Data System (ADS)

Stoch, A.; Jastrzebski, W.; Długoń, E.; Stoch, G. J.; Błażewicz, S.; Adamczyk, A.; Tatarzyńska, K.

2005-06-01

Carbon-carbon composites (C/C) exhibit excellent high-temperature mechanical properties but their air oxidation limits their use at temperatures above 500 °C to inert atmosphere. Variety of coatings has been used to protect C/C composites from oxidation. In this work C/C composite substrates were covered with ceramic multilayer coats by electrophoretic deposition from ceramic sols such as silica sol, alumina sol and silica-lumina sol. Sol particles were of nano-sized dimensions. Deposited coats were annealed at 900-1500 °C. Oxidation tests at 600 °C reveal that the best protection of C/C composite against oxidation gives the multilayer coat formed by three or four electrophoretic depositions. The phase composition in the final annealed layers was analyzed by Infrared spectroscopy (FTIR) and by X-ray diffraction analysis (XRD). Morphology and chemical composition was observed using Scanning electron microscopy (SEM) with energy dispersive X-ray microanalysis (EDS).

Effect of Heat Treatment on Microstructure and Magnetostrictive Property of Melt-Spun Fe85Ga15 Ribbons

NASA Astrophysics Data System (ADS)

Liu, Hao; Wang, Haiou; Cao, Mengxiong; Tan, Weishi; Shi, Yangguang; Chen, Yu; Huang, Yuying

2013-09-01

In order to study the microstructure of Fe-Ga alloy, Fe85Ga15 ribbons prepared with different wheel velocity were studied by high resolution X-ray diffraction (HRXRD) and extend X-ray absorption fine structure (EXAFS). HRXRD patterns showed that only disordered A2 phase was observed in as-cast Fe85Ga15 alloy. A modified-DO3 phase was detected in all of the melt spun samples. The HRXRD associated with EXAFS results indicated that Ga atoms were located as second-nearest neighbor along [100] orientation. A little DO3 phase was found in ribbons annealed at 1000°C under 0.06 MPa Ar atmosphere. The result of magnetostriction measurement revealed that in the ribbon prepared with higher wheel velocity, more modified-DO3 phase will enhance the magnetostriction. DO3 phase in the annealed sample will deteriorate the magnetostrictive properties of Fe-Ga ribbons.

GePb Alloy Growth Using Layer Inversion Method

NASA Astrophysics Data System (ADS)

Alahmad, Hakimah; Mosleh, Aboozar; Alher, Murtadha; Banihashemian, Seyedeh Fahimeh; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Du, Wei; Li, Bauhoa; Yu, Shui-Qing; Naseem, Hameed A.

2018-04-01

Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material.

GePb Alloy Growth Using Layer Inversion Method

NASA Astrophysics Data System (ADS)

Alahmad, Hakimah; Mosleh, Aboozar; Alher, Murtadha; Banihashemian, Seyedeh Fahimeh; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Du, Wei; Li, Bauhoa; Yu, Shui-Qing; Naseem, Hameed A.

2018-07-01

Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material.

P-type ZnO:N Films Prepared by Thermal Oxidation of Zn3N2

NASA Astrophysics Data System (ADS)

Zhang, Bin; Li, Min; Wang, Jian-Zhong; Shi, Li-Qun

2013-02-01

We prepare p-type ZnO:N films by annealing Zn3N2 films in oxygen over a range of temperatures. The prepared films are characterized by various techniques, such as Rutherford backscattering spectroscopy, x-ray diffraction, x-ray photoemission spectroscopy, the Hall effect and photoluminescence spectra. The results show that the Zn3N2 films start to transform to ZnO at 300°C and the N content decreases with an increase in annealing temperature. N has two local chemical states: zinc oxynitride (ZnO1-xNx) and substitutional NO in O-rich local environments (α -NO). The conduction type changes from n-type to p-type upon oxidation at 400-600°C, indicating that N is an effective acceptor in the ZnO film. The photoluminescence spectra show the UV emission and defect-related emissions of ZnO:N films. The mechanism and efficiency of p-type doping are briefly discussed.

Texture measurement of shaped material by impulse acoustic microscopy

PubMed

Eyraud; Nadal; Gondard

2000-03-01

All the microstructural parameters involved in metallurgical processes are difficult to determine directly on a shaped material. The aim of this paper is to use an impulse line-focus acoustic microscope (LFAM) as a non-destructive alternative to X-ray diffraction for measuring texture of slightly anisotropic materials. We apply it to characterize the rolling and annealing texture for tantalum sheets.

Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite.

PubMed

Holopainen, Jani; Santala, Eero; Heikkilä, Mikko; Ritala, Mikko

2014-12-01

Calcium carbonate (CaCO3) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO3 fibers with average diameters from 140 to 290 nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO3 layer by spin or dip coating Ca(NO3)2/PVP precursor solution on the CaCO3 fibers followed by annealing of the gel formed inside the fiber layer. The CaCO3 fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings. Copyright © 2014 Elsevier B.V. All rights reserved.

Ni3Si(Al)/a-SiOx core shell nanoparticles: characterization, shell formation, and stability

NASA Astrophysics Data System (ADS)

Pigozzi, G.; Mukherji, D.; Gilles, R.; Barbier, B.; Kostorz, G.

2006-08-01

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni3Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni3Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiOx). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

The annealing investigation on morphology and photoluminescence properties of In2O3 1-D nanostructures in resistive evaporation mechanism

NASA Astrophysics Data System (ADS)

Shariati, Mohsen; Ghafouri, Vahid

2014-02-01

Synthesis of In2O3 nanostructures grown on Si substrate by the resistive evaporation of metallic indium granules followed by dry oxidation process has been articulated. To prepare nucleation growth sites, selected samples pre-annealed around indium melting point in free-oxygen atmosphere and then to fabricate 1-D nanostructures, they annealed in a horizontal thermal furnace in presence of argon and oxygen. For comparison, one sample, the same origin as initially pre-annealed samples, was excluded in pre-annealing process but presented in annealing step. Characterization of the products with FESEM revealed that the pre-annealed obtained nanostructures are mostly nanorod and nanowire with different morphologies. For the comparative sample, no 1-D structures achieved. X-ray diffraction (XRD) patterns for pre-annealed samples indicated that they are crystalline and the comparative one is polycrystalline. Photoluminescence (PL) measurements carried out at room temperature revealed that emission band shifted to shorter wavelength from pre-annealed samples to comparative one.

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.

Enhanced exchange bias in MnN/CoFe bilayers after high-temperature annealing

NASA Astrophysics Data System (ADS)

Dunz, M.; Schmalhorst, J.; Meinert, M.

2018-05-01

We report an exchange bias of more than 2700 Oe at room temperature in MnN/CoFe bilayers after high-temperature annealing. We studied the dependence of exchange bias on the annealing temperature for different MnN thicknesses in detail and found that samples with tMnN > 32nm show an increase of exchange bias for annealing temperatures higher than TA = 400 °C. Maximum exchange bias values exceeding 2000 Oe with reasonably small coercive fields around 600 Oe are achieved for tMnN = 42, 48 nm. The median blocking temperature of those systems is determined to be 180 °C after initial annealing at TA = 525 °C. X-ray diffraction measurements and Auger depth profiling show that the large increase of exchange bias after high-temperature annealing is accompanied by strong nitrogen diffusion into the Ta buffer layer of the stacks.

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.

Evolution of microstructure and surface topography of gold thin films under thermal annealing

NASA Astrophysics Data System (ADS)

Dash, P.; Rath, H.; Dash, B. N.; Mallick, P.; Basu, T.; Som, T.; Singh, U. P.; Mishra, N. C.

2012-07-01

In the present study, we probe into evolution of microstructure and surface morphology of gold thin films of 10 to 50 nm thickness deposited on Si (100) substrate by thermal evaporation method. These films were annealed at 250°C under vacuum. The as-deposited and annealed films were characterized by glancing angle X-Ray diffraction (GAXRD) and atomic force microscopy (AFM), techniques. XRD indicated improvement of crystallinity up to 2 hours of annealing and degradation of the same thereafter. In agreement with XRD result, the grain size distribution histogram obtained from AFM indicated grain growth with annealing time up to 2 hours and saturation or decrease of grain size thereafter. The observed result is explained by the occurrence of two competing phenomena like roughening induced grain growth and smoothening induced inhibition of grain growth with increasing annealing time.

Investigation on Structural and Optical Properties of Copper Telluride Thin Films with Different Annealing Temperature

NASA Astrophysics Data System (ADS)

Nishanthini, R.; Muthu Menaka, M.; Pandi, P.; Bahavan Palani, P.; Neyvasagam, K.

The copper telluride (Cu2Te) thin film of thickness 240nm was coated on a microscopic glass substrate by thermal evaporation technique. The prepared films were annealed at 150∘C and 250∘C for 1h. The annealing effect on Cu2Te thin films was examined with different characterization methods like X-ray Diffraction Spectroscopy (XRD), Scanning Electron Microscopy (SEM), Ultra Violet-Visible Spectroscopy (UV-VIS) and Photoluminescence (PL) Spectroscopy. The peak intensities of XRD spectra were increased while increasing annealing temperature from 150∘C to 250∘C. The improved crystallinity of the thin films was revealed. However, the prepared films are exposed complex structure with better compatibility. Moreover, the shift in band gap energy towards higher energies (blue shift) with increasing annealing temperature is observed from the optical studies.

Effect of stress, strain and optical properties in vacuum and normal annealed ZnO thin films using RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Kumar, B. Santhosh; Purvaja, K.; Harinee, N.; Venkateswaran, C.

2018-05-01

Zinc oxide thin films have been deposited on quartz substrate using RF magnetron sputtering. The deposited films were subjected to different annealing atmosphere at a fixed temperature of 500 °C for 5h. The X-ray diffraction (XRD) patterns reveals the shift in the peak of both normal annealed and vacuum annealed thin films when compared to as-deposited ZnO film. The crystallite size, intrinsic stress and other parameters were calculated from XRD data. The surface morphology of the obtained films were studied using Atomic force microscopy (AFM). From Uv-Visible spectroscopy, the peak at 374 nm of all the films is characteristics of ZnO. The structural, thermal stability and optical properties of the annealed ZnO films are discussed in detail.

Microstructure and magnetic behavior of Cu-Co-Si ternary alloy synthesized by mechanical alloying and isothermal annealing

NASA Astrophysics Data System (ADS)

Chabri, Sumit; Bera, S.; Mondal, B. N.; Basumallick, A.; Chattopadhyay, P. P.

2017-03-01

Microstructure and magnetic behavior of nanocrystalline 50Cu-40Co-10Si (at%) alloy prepared by mechanical alloying and subsequent isothermal annealing in the temperature range of 450-650 °C have been studied. Phase evolution during mechanical alloying and isothermal annealing is characterized by X-ray diffraction (XRD), differential thermal analyzer (DTA), high resolution transmission electron microscopy (HRTEM) and magnetic measurement. Addition of Si has been found to facilitate the metastable alloying of Co in Cu resulting into the formation of single phase solid solution having average grain size of 9 nm after ball milling for 50 h duration. Annealing of the ball milled alloy improves the magnetic properties significantly and best combination of magnetic properties has been obtained after annealing at 550 °C for 1 h duration.

Enhancement of the barrier performance in organic/inorganic multilayer thin-film structures by annealing of the parylene layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Namsu, E-mail: nkim@keti.re.kr; Components and Materials Physics Research Center, #68 Yatop-dong, Korea Electronics Technology Institute, Bundang-gu, 463-816; Graham, Samuel

2014-10-15

Highlights: • High performance thin-film barrier structure for encapsulation was fabricated. • By annealing parylene in encapsulation structure, the barrier performance was improved. • The effective water vapor transmission rate is 7.2 ± 3.0 × 10{sup −6} g/m{sup 2}/day. - Abstract: A multilayered barrier structure was fabricated by chemical vapor deposition of parylene and subsequent plasma-enhanced chemical vapor deposition of SiO{sub x} or SiN{sub x}. The barrier performance against water vapor ingress was significantly improved by annealing the parylene layer before the deposition of either SiO{sub x} or SiN{sub x}. The mechanism of this enhancement was investigated using atomic forcemore » microscopy, Raman spectroscopy, and X-ray diffraction. The surface roughness of the parylene before the deposition of either SiO{sub x} or SiN{sub x} was found to correlate closely with the barrier performance of the multilayered structures. In addition, removing absorbed water vapor in the film by annealing results in a lower water vapor transmission rate in the transient region and a longer lag time. Annealing the parylene leads to a large decrease in the effective water vapor transmission rate, which reaches 7.2 ± 3.0 × 10{sup −6} g/m{sup 2}/day.« less

Control of interface reactions in SIC/TI composites

NASA Technical Reports Server (NTRS)

Houska, C. R.; Rao, V.

1982-01-01

The reaction between a 0.5 to 1.0 Al film and a thick Ti substrate to form TiAl3 occurs very rapidly on heating to 635 C and causes the Al to be confined to the surface region. After heating to 900 C Ti3Al is formed with little release of Al into alpha Ti. Further annealing at 900 C eventually causes the Ti3Al phase to decompose and a substantial amount of Al is released into alpha Ti. The interdiffusion coefficient for Al in alpha Ti at 900 C increases by less than one order of magnitude as Al is varied from 0 to 20 at %. These data were obtained from the (101) X-ray diffraction intensity band using polycrystalline samples. Improvements in the analysis of X-ray diffraction data for the determination of composition profiles are discussed.

Ferromagnetism in sphalerite and wurtzite CdS nanostructures

PubMed Central

2013-01-01

Room-temperature ferromagnetism is observed in undoped sphalerite and wurtzite CdS nanostructures which are synthesized by hydrothermal methods. Scanning electron microscopy and transmission electron microscopy results indicate that the sphalerite CdS samples show a spherical-like shape and the wurtzite CdS ones show a flower-like shape, both of which are aggregated by lots of smaller particles. The impurity of the samples has been ruled out by the results of X-ray diffraction, selected-area electron diffraction, and X-ray photoelectron spectroscopy. Magnetization measurements indicate that all the samples exhibit room-temperature ferromagnetism and the saturation magnetization decreases with the increased crystal sizes, revealing that the observed ferromagnetism is defect-related, which is also confirmed by the post-annealing processes. This finding in CdS should be the focus of future electronic and spintronic devices. PMID:23294671

Thermal, spectroscopic and structural characterization of isostructural phase transition in 4-hydroxybenzaldehyde

NASA Astrophysics Data System (ADS)

Panicker, Lata

2018-05-01

Polycrystalline samples of 4-hydroxybenzaldehyde (4-HOBAL) were investigated using differential scanning calorimeter (DSC), Raman spectroscopy and X-ray powder diffraction. The DSC data indicated that 4-HOBAL on heating undergoes a polymorphic transformation from polymorph I to polymorph II. The polymorph II formed remains metastable at ambient condition and transforms to polymorph I when annealed at ambient temperature for more than seven days. The structural information of polymorphs I and II obtained using its X-ray powder diffraction patterns indicated that 4-HOBAL undergoes an isostructural phase transition from polymorph I (monoclinic, P21/c) to polymorph II (monoclinic, P21/c). Raman data suggest that this structural change is associated with some change in its molecular interactions. Thus, in 4-HOBAL the polymorphic phase transformation (II to I) even though energetically favoured is kinetically hindered.

Investigation of ZrO x /ZrC-ZrN/Zr thin-film structural evolution and their degradation using X-ray diffraction and Raman spectrometry

NASA Astrophysics Data System (ADS)

Usmani, B.; Vijay, V.; Chhibber, R.; Dixit, A.

2016-11-01

The thin-film structures of DC/FR magnetron-sputtered ZrO x /ZrC-ZrN/Zr tandem solar-selective coatings are investigated using X-ray diffraction and room-temperature Raman spectroscopic measurements. These studies suggest that the major contribution is coming from h-ZrN0.28, c-ZrC, h-Zr3C2 crystallographic phases in ZrN-ZrC absorber layer, in conjunction with mixed ZrO x crystallographic phases. The change in structure for thermally annealed samples has been examined and observed that cubic and hexagonal ZrO x phase converted partially into tetragonal and monoclinic ZrO x phases, whereas hexagonal and cubic ZrN phases, from absorber layer, have not been observed for these thermally treated samples in air. These studies suggest that thermal treatment may lead to the loss of ZrN phase in absorber, degrading the thermal response for the desired wavelength range in open ambient conditions in contrast to vacuum conditions.

Room temperature ferromagnetism and luminescent behavior of Ni doped ZnO nanoparticles prepared by coprecipitation method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arora, Deepawali; Mahajan, Aman; Kaur, Parvinder

2016-05-23

The samples of Zn{sub 1-x}Ni{sub x}O (x= 0.00 and 0.05) were prepared using coprecipitation method and annealed at different temperatures. The effect of Ni ion substitution on the structural and optical properties has been studied using X-ray Diffraction, UV-Visible, Photoluminescence and Magnetic measurements. XRD measurements demonstrate that all the prepared samples are wurtzite polycrystalline single phase in nature, ruling out the presence of any secondary phase formation. Ultraviolet visible measurements showed a decrease in band gap with the increase in annealing temperature and doping concentration. The PL data shows the red shift in all the samples and luminescence quenching withmore » Ni doping. Compared to undoped ZnO, Ni doped ZnO showed room temperature ferromagnetism.« less

Tunability of morphological properties of Nd-doped TiO2 thin films

NASA Astrophysics Data System (ADS)

Rehan, Imran; Sultana, Sabiha; Khan, Nauman; Qamar, Zahid; Rehan, Kamran

2016-11-01

In this work, an endeavor is made toward structural assessment and morphological variation of titanium dioxide (TiO2) thin films when doped with neodymium (Nd). The electron beam deposition technique was employed to fabricate Nd-based TiO2 thin films on n-Type Si substrates. Nd concentration was varied from 0.0 to 2.0 atomic percent (at.%) under identical growth environments. The films were deposited in an oxygen-deficient environment to cause the growth of rutile phases. Energy dispersive x-ray spectroscopy confirmed the presence and variation of Nd dopant in TiO2. X-ray diffraction analysis showed the transformation of amorphous structures of the as-grown samples to anatase polycrystalline after annealing at 500 °C, while atomic force microscopy exposed linearity in grain density in as-grown samples with doping until 1 at.%. Raman spectrums of as-grown and annealed samples revealed the growth of the anatase phase in the annealed samples. Based on these results it can be proposed that Nd doping has pronounced effects on the structural characteristics of TiO2 thin films.

Fabrication and characterization of silicon quantum dots in Si-rich silicon carbide films.

PubMed

Chang, Geng-Rong; Ma, Fei; Ma, Dayan; Xu, Kewei

2011-12-01

Amorphous Si-rich silicon carbide films were prepared by magnetron co-sputtering and subsequently annealed at 900-1100 degrees C. After annealing at 1100 degrees C, this configuration of silicon quantum dots embedded in amorphous silicon carbide formed. X-ray photoelectron spectroscopy was used to study the chemical modulation of the films. The formation and orientation of silicon quantum dots were characterized by glancing angle X-ray diffraction, which shows that the ratio of silicon and carbon significantly influences the species of quantum dots. High-resolution transmission electron microscopy investigations directly demonstrated that the formation of silicon quantum dots is heavily dependent on the annealing temperatures and the ratio of silicon and carbide. Only the temperature of about 1100 degrees C is enough for the formation of high-density and small-size silicon quantum dots due to phase separation and thermal crystallization. Deconvolution of the first order Raman spectra shows the existence of a lower frequency peak in the range 500-505 cm(-1) corresponding to silicon quantum dots with different atom ratio of silicon and carbon.

Scalable high-mobility MoS2 thin films fabricated by an atmospheric pressure chemical vapor deposition process at ambient temperature

NASA Astrophysics Data System (ADS)

Huang, Chung-Che; Al-Saab, Feras; Wang, Yudong; Ou, Jun-Yu; Walker, John C.; Wang, Shuncai; Gholipour, Behrad; Simpson, Robert E.; Hewak, Daniel W.

2014-10-01

Nano-scale MoS2 thin films are successfully deposited on a variety of substrates by atmospheric pressure chemical vapor deposition (APCVD) at ambient temperature, followed by a two-step annealing process. These annealed MoS2 thin films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-VIS-NIR spectrometry, photoluminescence (PL) and Hall Effect measurement. Key optical and electronic properties of APCVD grown MoS2 thin films are determined. This APCVD process is scalable and can be easily incorporated with conventional lithography as the deposition is taking place at room temperature. We also find that the substrate material plays a significant role in the crystalline structure formation during the annealing process and single crystalline MoS2 thin films can be achieved by using both c-plane ZnO and c-plane sapphire substrates. These APCVD grown nano-scale MoS2 thin films show great promise for nanoelectronic and optoelectronic applications.

The effect of annealing on structural, optical and electrical properties of ZnS/porous silicon composites

NASA Astrophysics Data System (ADS)

Wang, Cai-Feng; Li, Qing-Shan; Hu, Bo; Li, Wei-Bing

2009-06-01

ZnS films were prepared by pulsed laser deposition (PLD) on porous silicon (PS) substrates. This paper investigates the effect of annealing temperature on the structural, morphological, optical and electrical properties of ZnS/PS composites by x-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) and I-V characteristics. It is found that the ZnS films deposited on PS substrates were grown in preferred orientation along β-ZnS (111) direction, and the intensity of diffraction peak increases with increasing annealing temperature, which is attributed to the grain growth and the enhancement of crystallinity of ZnS films. The smooth and uniform surface of the as-prepared ZnS/PS composite becomes rougher through annealing treatment, which is related to grain growth at the higher annealing temperature. With the increase of annealing temperature, the intensity of self-activated luminescence of ZnS increases, while the luminescence intensity of PS decreases, and a new green emission located around 550 nm appeared in the PL spectra of ZnS/PS composites which is ascribed to the defect-center luminescence of ZnS. The I-V characteristics of ZnS/PS heterojunctions exhibited rectifying behavior, and the forward current increases with increasing annealing temperature.

Thin Films

NASA Astrophysics Data System (ADS)

Khorshidi, Zahra; Bahari, Ali; Gholipur, Reza

2014-11-01

Effect of annealing temperature on the characteristics of sol-gel-driven Ta ax La(1- a) x O y thin film spin-coated on Si substrate as a high- k gate dielectric was studied. Ta ax La(1- a) x O y thin films with different amounts of a were prepared (as-prepared samples). X-ray diffraction measurements of the as-prepared samples indicated that Ta0.3 x La0.7 x Oy film had an amorphous structure. Therefore, Ta0.3 x La0.7 x O y film was chosen to continue the present studies. The morphology of Ta0.3 x La0.7 x O y films was studied using scanning electron microscopy and atomic force microscopy techniques. The obtained results showed that the size of grain boundaries on Ta0.3 x La0.7 x O y film surfaces was increased with increasing annealing temperature. Electrical and optical characterizations of the as-prepared and annealed films were investigated as a function of annealing temperature using capacitance-voltage ( C- V) and current density-voltage ( J- V) measurements and the Tauc method. The obtained results demonstrated that Ta0.3 x La0.7 x O y films had high dielectric constant (≈27), wide band gap (≈4.5 eV), and low leakage current density (≈10-6 A/cm2 at 1 V).

Effect of annealing temperature and copper mole ratio on the morphology, structure and magnetic properties of Mg0.5-xCuxZn0.5Fe2O4 nanoparticles prepared by the modified Pechini method

NASA Astrophysics Data System (ADS)

Loghman-Estarki, M. R.; Torkian, S.; Rastabi, R. Amini; Ghasemi, A.

2017-11-01

In this study, magnesium copper zinc ferrite (MCZ) nanoparticles were synthesized by the modified Pechini method. In this approach, the magnesium nitrate, copper nitrate, zinc nitrate, iron nitrate, citric acid and diethylene glycol (instead of ethylene glycol in conventional Pechini method) were used as a source of Mg2+, Cu2+, Zn2+, complex and stabilizer and solvent agent, respectively. The effect of annealing temperature and copper mole ratio on the morphology, structural and magnetic properties of Mg0.5xCuxZn0.5Fe2O4 (x = 0-0.5) nanoparticles were investigated. Various characterization methods, including X-ray diffraction (XRD), field emission scanning electron microscope (FeSEM), energy-dispersive spectroscopy (EDS), X-ray mapping, Fourier transforms infrared spectroscopy (FTIR), adsorption-desorption isotherm and vibrating sample magnetometer (VSM) were used to study the phase, microstructure, particle size, elemental distribution, functional group determination, porosity and magnetic properties of nanoparticles, respectively. The results showed that cubic spinel phase with various morphologies such as semi-spherical, sheet-like shapes was obtained by the modified Pechini method. Furthermore, the nanoparticles with the x value of 0.2, annealed at 700 °C have the highest saturation magnetization (Ms = 56.5 emu/g) among the other synthesized MCZ ferrite nanoparticles.

Influence of annealing temperature on structural and optical properties of Lu{sub 2}O{sub 3}:Eu{sup 3+}, Tb{sup 3+} transparent films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morales-Ramírez, Ángel de Jesús; García-Murillo, Antonieta, E-mail: angarciam@ipn.mx; Carrillo-Romo, Felipe de Jesús

2015-10-15

Highlights: • Lu{sub 2}O{sub 3}:Eu{sup 3+}, Tb{sup 3+} films were synthesized by sol–gel and by dip-coating technique. • Effects of annealing treatment on structural and optical properties were studied. • Optogeometrical characteristics of synthesized films were analyzed. • X-ray diffraction results showed that Lu{sub 2}O{sub 3}:Eu{sup 3+}, Tb{sup 3+} crystallizes at 700 °C. • High reddish emission on transparent films with at least 1 μm thick was observed. - Abstract: High-optical quality Lu{sub 2}O{sub 3}:Eu{sup 3+} 5 mol%, X Tb{sup 3+} (X = 0–0.04 mol%) thin films were prepared by the sol–gel process and dip-coating technique. The procedure was asmore » follows: lutetium, europium and terbium nitrates were used as precursors, and ethanol as a solvent. Etylenglycol (EG) was added as a sol stabilizer, and the pH was adjusted by acetic acid. After 10 dipping-cycles, followed by an annealing process (600–900 °C) for 1 h, transparent, smooth and crack-free films (ra = 8–9 nm) were formed. The X-ray diffraction (XRD) results showed crystallized films into the cubic structure at 800 °C. The ellipsometry results showed that the thickness of the films varied from 1 to 1.4 μm at 1000 and 600 °C, respectively. Finally, the films presented a typical Eu{sup 3+} red emission at 611 nm ({sup 5}D{sub 0} → {sup 7}F{sub 2}); furthermore, the effect of the Tb{sup 3+} content showed that the highest emission intensity corresponded to the lower Tb{sup 3+} content.« less

Fabrication of three-dimensional crystalline silicon-on-carbon nanotube nanocomposite anode by sputtering and laser annealing for high-performance lithium-ion battery

NASA Astrophysics Data System (ADS)

Kim, Ilwhan; Hyun, Seungmin; Nam, Seunghoon; Lee, Hoo-Jeong; Kang, Chiwon

2018-05-01

In this study, we fabricate a three-dimensional (3D) crystalline Si (c-Si)/carbon nanotube (CNT) nanocomposite anode by sputtering Si on 3D CNTs followed by laser annealing for Si crystallization — a simple, cost-effective route — for advanced Li-ion battery (LIB) applications. We use scanning electron microscopy, X-ray diffraction spectroscopy, and Raman spectroscopy to analyze the samples annealed at different laser energy densities. As a result, we confirm that laser annealing enables Si crystallization without damaging the CNTs. We assemble half-type coin cells for the battery performance test: the 3D c-Si/CNT anode sample demonstrates a specific capacity superior to that of its control counterpart; the cyclic stability is also enhanced significantly.

Effect of thermal annealing on structure and optical band gap of amorphous Se{sub 72}Te{sub 25}Sb{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dwivedi, D. K., E-mail: dwivedidkphys@rediffmail.com; Pathak, H. P., E-mail: dwivedidkphys@rediffmail.com; Shukla, Nitesh

2014-04-24

Thin films of a−Se{sub 72}Te{sub 25}Sb{sub 3} were prepared by vacuum evaporation technique in a base pressure of 10{sup −6} Torr on to well cleaned glass substrate. a−Se{sub 72}Te{sub 25}Sb{sub 3} thin films were annealed at different temperatures below their crystallization temperatures for 2h. The structural analysis of the films has been investigated using X-ray diffraction technique. The optical band gap of as prepared and annealed films as a function of photon energy in the wavelength range 400–1100 nm has been studied. It has been found that the optical band gap decreases with increasing annealing temperatures in the present system.

Thermodynamics of post-growth annealing of cadmium zinc telluride nuclear radiation detectors

NASA Astrophysics Data System (ADS)

Adams, Aaron Lee

Nuclear Radiation Detectors are used for detecting, tracking, and identifying radioactive materials which emit high-energy gamma and X-rays. The use of Cadmium Zinc Telluride (CdZnTe) detectors is particularly attractive because of the detector's ability to operate at room temperature and measure the energy spectra of gamma-ray sources with a high resolution, typically less than 1% at 662 keV. While CdZnTe detectors are acceptable imperfections in the crystals limit their full market potential. One of the major imperfections are Tellurium inclusions generated during the crystal growth process by the retrograde solubility of Tellurium and Tellurium-rich melt trapped at the growth interface. Tellurium inclusions trap charge carriers generated by gamma and X-ray photons and thus reduce the portion of generated charge carriers that reach the electrodes for collection and conversion into a readable signal which is representative of the ionizing radiation's energy and intensity. One approach in resolving this problem is post-growth annealing which has the potential of removing the Tellurium inclusions and associated impurities. The goal of this project is to use experimental techniques to study the thermodynamics of Tellurium inclusion migration in post-growth annealing of CdZnTe nuclear detectors with the temperature gradient zone migration (TGZM) technique. Systematic experiments will be carried out to provide adequate thermodynamic data that will inform the engineering community of the optimum annealing parameters. Additionally, multivariable correlations that involve the Tellurium diffusion coefficient, annealing parameters, and CdZnTe properties will be analyzed. The experimental approach will involve systematic annealing experiments (in Cd vapor overpressure) on different sizes of CdZnTe crystals at varying temperature gradients ranging from 0 to 60°C/mm (used to migrate the Tellurium inclusion to one side of the crystal), and at annealing temperatures ranging from 500 to 800°C. The characterization techniques that will be used to quantify the effects of the post-growth annealing experiments include: 1) 3D infrared transmission microscopy to measure the size, distribution, and concentration of Tellurium inclusions; 2) current-voltage measurements to determine the effect of post-growth annealing on the resistivity of CdZnTe crystals; and 3) X-ray diffraction topography, available at the National Synchrotron Light Source (NSLS) facilities at Brookhaven National Laboratory (BNL), to measure the correlation between device performance and annealing conditions

Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

DOE PAGES

Wang, H.; Kirkham, M. J.; Watkins, T. R.; ...

2016-02-17

N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubicmore » symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.« less

Annealing effects on electron-beam evaporated Al 2O 3 films

NASA Astrophysics Data System (ADS)

Shuzhen, Shang; Lei, Chen; Haihong, Hou; Kui, Yi; Zhengxiu, Fan; Jianda, Shao

2005-04-01

The effects of post-deposited annealing on structure and optical properties of electron-beam evaporated Al 2O 3 single layers were investigated. The films were annealed in air for 1.5 h at different temperatures from 250 to 400 °C. The optical constants and cut-off wavelength were deduced. Microstructure of the samples was characterized by X-ray diffraction (XRD). Profile and surface roughness measurement instrument was used to determine the rms surface roughness. It was found that the cut-off wavelength shifted to short wavelength as the annealing temperature increased and the total optical loss decreased. The film structure remained amorphous even after annealing at 400 °C temperature and the samples annealed at higher temperature had the higher rms surface roughness. The decreasing total optical loss with annealing temperature was attributed to the reduction of absorption owing to oxidation of the film by annealing. Guidance to reduce the optical loss of excimer laser mirrors was given.

New diamond cell for single-crystal x-ray diffraction

NASA Astrophysics Data System (ADS)

Boehler, Reinhard

2006-11-01

A new design for a high-precision diamond cell is described. Two kinematically mounted steel disks are elastically deflected to generate pressure. This principle provides higher precision in the diamond anvil alignment than most sliding piston-cylinder or guide-pin devices at significantly lower cost. With this new diamond cell conical diamond anvils with an x-ray aperture of 85° were successfully tested to over 50GPa using helium as a pressure medium. Anvil thickness of less than 1.4mm provides high x-ray transmission and low background, a significant improvement compared to beryllium or diamond-disk backing plates. Because the diamond anvils are supported by tungsten carbide seats, samples and pressure media can be annealed by external or laser heating to provide hydrostatic pressure conditions.

Interfacial characterization and electrical properties of Ni–GaSb contacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Kun-Lin, E-mail: kllin@narlabs.org.tw; Chen, Szu-Hung, E-mail: shchen168@narlabs.org.tw

2014-10-06

The microstructural characterization of Ni–GaSb junctions in samples annealed at 300 °C, 350 °C, and 400 °C in a N{sub 2} atmosphere was elucidated using transmission electron microscopy in conjunction with energy-dispersive spectrometry, nanobeam electron diffraction, and grazing-incident X-ray diffraction. Only the NiSb(Ga) phase is formed at the interface of Ni/GaSb when the annealing temperature is below 350 °C. However, three phases—NiSb, Ni{sub 2}Ga{sub 3}, and NiSb(Ga)—are formed simultaneously at the interface between Ni/GaSb when the annealing temperature is increased to 400 °C, which causes a significant increase in the sheet resistance of the Ni–GaSb alloy. These results indicate that the annealing temperature of themore » Ni/GaSb structure should be maintained below 350 °C for the formation of low-resistance metal Ni/GaSb contacts in GaSb-based p-type metal-oxide-semiconductor field-effect transistors.« less

Ultra-soft magnetic properties and correlated phase analysis by {sup 57}Fe Mössbauer spectroscopy of Fe{sub 74}Cu{sub 0.8}Nb{sub 2.7}Si{sub 15.5}B{sub 7} alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manjura Hoque, S.; Liba, S. I.; Akhter, Shireen

2016-02-15

A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe{sub 74}Cu{sub 0.8}Nb{sub 2.7}Si{sub 15.5}B{sub 7} was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark fieldmore » (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications.« less

Ultra-soft magnetic properties and correlated phase analysis by 57Fe Mössbauer spectroscopy of Fe74Cu0.8Nb2.7Si15.5B7 alloy

NASA Astrophysics Data System (ADS)

Manjura Hoque, S.; Liba, S. I.; Anirban, A.; Choudhury, Shamima; Akhter, Shireen

2016-02-01

A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe74Cu0.8Nb2.7Si15.5B7 was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark field (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications.

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.

Influence of annealing on mechanical properties of TiNi (55.8 mass % of Ni) wire made for medical purposes

NASA Astrophysics Data System (ADS)

Kaplan, M. A.; Nasakina, E. O.; Sevostyanov, M. A.; Sergienko, K. V.; Baikin, A. S.; Konushkin, S. V.; Kolmakov, A. G.; Smirnov, M. A.; Izvin, A. V.; Ustinova, Yu N.

2018-04-01

Mechanical properties of titanium nickelide processed with various heat treatments are investigated. Fractographic, microstructural and X-ray diffraction analysis’ were carried out as well as strength and plasticity measurements. It is shown that titanium nickelide (55.8 mass % of Ni) wires treated by two annealing stages, which consist of heating up to 300°C on the first stage and 450°C on the second, with 4 hours and 15 minutes long exposures on each stage respectively, conducted in an air environment, possess the best strength while saving good elasticity figures.

Synthesis and microstructural studies of annealed Cu(2)O/Cu(x)S bilayer as transparent electrode material for photovoltaic and energy storage devices.

PubMed

Taleatu, B A; Arbab, E A A; Omotoso, E; Mola, G T

2014-10-01

Cu2 O thin film and a transparent bilayer have been fabricated by electrodeposition method. The growths were obtained in potentiostatic mode with gradual degradation of anodic current. X-ray diffraction (XRD) study showed that the bilayer is polycrystalline and it possesses mixture of different crystallite phases of copper oxides. Surface morphology of the films was investigated by scanning electron microscopy (SEM). The SEM images revealed that the films were uniformly distributed and the starting material (Cu2 O) had cubical structure. Grains agglomeration and crystallinity were enhanced by annealing. Optical studies indicated that all the samples have direct allowed transition. Energy band gap of the bilayer film was reduced by annealing treatment thus corroborating quantum confinement upshot. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

Existence of Fe{sup 4+} ions in Co{sub 2.25}Fe{sub 0.75}O{sub 4} spinel ferrite confirmed from SXRD and XANES spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panda, Manas Ranjan, E-mail: manasranjan056@gmail.com; Bhowmik, R. N.; Sinha, A. K.

2015-06-24

The Co{sub 2.25}Fe{sub 0.75}O{sub 4} ferrite composition has been prepared by chemical co-precipitation route. The as-prepared sample after annealing at 900°C in air formed single phase cubic spinel structure. Synchrotron X-ray diffraction and X-ray absorption near edge structure (XANES) measurements were used to study charge states of the cations in octahedral and tetrahedral sites of the cubic spinel structure. Raman spectra indicated normal cubic spinel structure. XANES data suggested the existence of Fe{sup 4+} ions in the spinel structure.

Structures having enhanced biaxial texture

DOEpatents

Goyal, Amit; Budai, John D.; Kroeger, Donald M.; Norton, David P.; Specht, Eliot D.; Christen, David K.

1999-01-01

A biaxially textured alloy article includes a rolled and annealed biaxially textured base metal substrate characterized by an x-ray diffraction phi scan peak of no more than 20.degree. FWHM; and a biaxially textured layer of an alloy or another material on a surface thereof. The article further includes at least one of an electromagnetic device or an electro-optical device epitaxially joined to the alloy.

Investigation of phase transition properties of ZrO2 thin films

NASA Astrophysics Data System (ADS)

Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

2018-05-01

This paper presents the synthesis of transparent thin films of zirconium oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Synthesized films were characterized for different annealing time and withdrawal speed. Change in crystallographic properties of thin films was investigated by using X-ray diffraction. Surface morphology of transparent thin films was estimated by using scanning electron microscope.

Mg(1 + x)Ir(1 - x) (x = 0, 0.037 and 0.054), a binary intermetallic compound with a new orthorhombic structure type determined from powder and single-crystal X-ray diffraction.

PubMed

Cerný, Radovan; Renaudin, Guillaume; Favre-Nicolin, Vincent; Hlukhyy, Viktor; Pöttgen, Rainer

2004-06-01

The new binary compound Mg(1 + x)Ir(1 - x) (x = 0-0.054) was prepared by melting the elements in the Mg:Ir ratio 2:3 in a sealed tantalum tube under an argon atmosphere in an induction furnace (single crystals) or by annealing cold-pressed pellets of the starting composition Mg:Ir 1:1 in an autoclave under an argon atmosphere (powder sample). The structure was independently solved from high-resolution synchrotron powder and single-crystal X-ray data: Pearson symbol oC304, space group Cmca, lattice parameters from synchrotron powder data a = 18.46948 (6), b = 16.17450 (5), c = 16.82131 (5) A. Mg(1 + x)Ir(1 - x) is a topologically close-packed phase, containing 13 Ir and 12 Mg atoms in the asymmetric unit, and has a narrow homogeneity range. Nearly all the atoms have Frank-Kasper-related coordination polyhedra, with the exception of two Ir atoms, and this compound contains the shortest Ir-Ir distances ever observed. The solution of a rather complex crystal structure from powder diffraction, which was fully confirmed by the single-crystal method, shows the power of powder diffraction in combination with the high-resolution data and the global optimization method.

Strain engineered pyrochlore at high pressure

DOE PAGES

Rittman, Dylan R.; Turner, Katlyn M.; Park, Sulgiye; ...

2017-05-22

Strain engineering is a promising method for next-generation materials processing techniques. Here, we use mechanical milling and annealing followed by compression in diamond anvil cell to tailor the intrinsic and extrinsic strain in pyrochlore, Dy 2Ti 2O 7 and Dy 2Zr 2O 7. Raman spectroscopy, X-ray pair distribution function analysis, and X-ray diffraction were used to characterize atomic order over short-, medium-, and long-range spatial scales, respectively, under ambient conditions. Raman spectroscopy and X-ray diffraction were further employed to interrogate the material in situ at high pressure. High-pressure behavior is found to depend on the species and concentration of defectsmore » in the sample at ambient conditions. Overall, we show that defects can be engineered to lower the phase transformation onset pressure by ~50% in the ordered pyrochlore Dy 2Ti 2O 7, and lower the phase transformation completion pressure by ~20% in the disordered pyrochlore Dy 2Zr 2O 7. Lastly, these improvements are achieved without significantly sacrificing mechanical integrity, as characterized by bulk modulus.« less

Crystallization dynamics and interface stability of strontium titanate thin films on silicon.

PubMed

Hanzig, Florian; Hanzig, Juliane; Mehner, Erik; Richter, Carsten; Veselý, Jozef; Stöcker, Hartmut; Abendroth, Barbara; Motylenko, Mykhaylo; Klemm, Volker; Novikov, Dmitri; Meyer, Dirk C

2015-04-01

Different physical vapor deposition methods have been used to fabricate strontium titanate thin films. Within the binary phase diagram of SrO and TiO 2 the stoichiometry ranges from Ti rich to Sr rich, respectively. The crystallization of these amorphous SrTiO 3 layers is investigated by in situ grazing-incidence X-ray diffraction using synchrotron radiation. The crystallization dynamics and evolution of the lattice constants as well as crystallite sizes of the SrTiO 3 layers were determined for temperatures up to 1223 K under atmospheric conditions applying different heating rates. At approximately 473 K, crystallization of perovskite-type SrTiO 3 is initiated for Sr-rich electron beam evaporated layers, whereas Sr-depleted sputter-deposited thin films crystallize at 739 K. During annealing, a significant diffusion of Si from the substrate into the SrTiO 3 layers occurs in the case of Sr-rich composition. This leads to the formation of secondary silicate phases which are observed by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy.

High Ms Fe16N2 thin film with Ag under layer on GaAs substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allard Jr, Lawrence Frederick

2016-01-01

(001) textured Fe16N2 thin film with Ag under layer is successfully grown on GaAs substrate using a facing target sputtering (FTS) system. After post annealing, chemically ordered Fe16N2 phase is formed and detected by X-ray diffraction (XRD). High saturation magnetization (Ms) is measured by a vibrating sample magnetometer (VSM). In comparison with Fe16N2 with Ag under layer on MgO substrate and Fe16N2 with Fe under layer on GaAs substrate, the current layer structure shows a higher Ms value, with a magnetically softer feature in contrast to the above cases. In addition, X-ray photoelectron spectroscopy (XPS) is performed to characterize themore » binding energy of N atoms. To verify the role of strain that the FeN layer experiences in the above three structures, Grazing Incidence X-ray Diffraction (GIXRD) is conducted to reveal a large in-plane lattice constant due to the in-plane biaxial tensile strain. INTRODUCTION« less

Crystallization behavior of amorphous indium-gallium-zinc-oxide films and its effects on thin-film transistor performance

NASA Astrophysics Data System (ADS)

Suko, Ayaka; Jia, JunJun; Nakamura, Shin-ichi; Kawashima, Emi; Utsuno, Futoshi; Yano, Koki; Shigesato, Yuzo

2016-03-01

Amorphous indium-gallium-zinc oxide (a-IGZO) films were deposited by DC magnetron sputtering and post-annealed in air at 300-1000 °C for 1 h to investigate the crystallization behavior in detail. X-ray diffraction, electron beam diffraction, and high-resolution electron microscopy revealed that the IGZO films showed an amorphous structure after post-annealing at 300 °C. At 600 °C, the films started to crystallize from the surface with c-axis preferred orientation. At 700-1000 °C, the films totally crystallized into polycrystalline structures, wherein the grains showed c-axis preferred orientation close to the surface and random orientation inside the films. The current-gate voltage (Id-Vg) characteristics of the IGZO thin-film transistor (TFT) showed that the threshold voltage (Vth) and subthreshold swing decreased markedly after the post-annealing at 300 °C. The TFT using the totally crystallized films also showed the decrease in Vth, whereas the field-effect mobility decreased considerably.

Grain growth mechanism and magnetic properties in L10-FePt thin films

NASA Astrophysics Data System (ADS)

Li, W.; Chen, L.

2017-08-01

This paper focuses on the grain growth mechanisms and magnetic properties of FePt thin films during an annealing process. The grain size and grain orientation distribution have been quantitatively investigated by electron backscatter diffraction (EBSD), and the grain growth kinetics of thin films were described by the phenomenological kinetic grain growth model. The results show that the grain growth exponent and activation energy of the FePt thin films were 4.26 and 136 kJ/mol respectively, indicating that the grain growth mechanism is mainly controlled by the stochastic jumping of atoms crossing the grain boundaries. X-ray diffraction (XRD) results show that disorder-order transformation was concurrent with grain growth during the annealing process, slowing down the velocity of grain growth. The hysteresis loops reveal that the out-of-plane coercivity and squareness is enhanced with increasing annealing temperature and this can be attributed to the improvement of L10-ordered phase volume fraction and texture intensity.

Growth and surface modification of LaFeO3 thin films induced by reductive annealing

NASA Astrophysics Data System (ADS)

Flynn, Brendan T.; Zhang, Kelvin H. L.; Shutthanandan, Vaithiyalingam; Varga, Tamas; Colby, Robert J.; Oleksak, Richard P.; Manandhar, Sandeep; Engelhard, Mark H.; Chambers, Scott A.; Henderson, Michael A.; Herman, Gregory S.; Thevuthasan, Suntharampillai

2015-03-01

The mixed electronic and ionic conductivity of perovskite oxides has enabled their use in diverse applications such as automotive exhaust catalysts, solid oxide fuel cell cathodes, and visible light photocatalysts. The redox chemistry at the surface of perovskite oxides is largely dependent on the oxidation state of the metal cations as well as the oxide surface stoichiometry. In this study, LaFeO3 (LFO) thin films grown on yttria-stabilized zirconia (YSZ) was characterized using both bulk and surface sensitive techniques. A combination of in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) demonstrated that the film is primarily textured in the [1 0 0] direction and is stoichiometric. High-resolution transmission electron microscopy measurements show regions that are dominated by [1 0 0] oriented LFO grains that are oriented with respect to the substrates lattice. However, selected regions of the film show multiple domains of grains that are not [1 0 0] oriented. The film was annealed in an ultra-high vacuum chamber to simulate reducing conditions and studied by angle-resolved X-ray photoelectron spectroscopy (XPS). Iron was found to exist as Fe(0), Fe(II), and Fe(III) depending on the annealing conditions and the depth within the film. A decrease in the concentration of surface oxygen species was correlated with iron reduction. These results should help guide and enhance the design of LFO materials for catalytic applications.

Strong emission in Yb3+/Er3+ co-doped phosphate glass ceramics

NASA Astrophysics Data System (ADS)

Liu, Yanling; Song, Feng; Jia, Guozhi; Zhang, Yanbang; Tang, Yi

Yb3+/Er3+ co-doped phosphate glass and glass ceramics were prepared by high-temperature melting method. The X-ray diffraction, transmission electron micrographs, up-conversion and infrared emissions, photothermal conversion properties of the samples have been measured. The results showed the annealing time had a great impact on the microstructure and luminous performance of the phosphate glass. At the beginning of annealing, the metaphosphate crystals were firstly dissolved out. The metaphosphate crystals gradually turned into the orthophosphate with the increasing of annealing time. The emission intensity of the sample was obviously improved after the precursor glass was annealed. The up-conversion and infrared emissions of the sample annealed at 600 °C for 24 h, reached the maximum intensity. Compared with the photothermal properties of glass, the lower photothermal conversion efficiency of the glass ceramics testified the strong emission.

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

Transparent nanocomposite ZrO2-SnO2 thin films were prepared by sol-gel dip-coating technique. Films were annealed at 500°C, 800°C and 1200°C respectively. X-ray diffraction(XRD) spectra showed a mixture of three phases: tetragonal ZrO2 and SnO2 and orthorhombic ZrSnO4. The grain size of all the three phases' increased with annealing temperature. An average transmittance greater than 85%(in UV-Visible region) is observed for all the films. The band gap for the films decreased from 4.79 eV to 4.62 eV with increase in annealing temperature from 500 to 1200 °C. The electrical resistivity increased with increase in annealing temperature. Such composite ZrO2-SnO2 films can be used in many applications and in optoelectronic devices.

Synthesis and annealing study of RF sputtered ZnO thin film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Shushant Kumar, E-mail: singhshushant86@gmail.com; Sharma, Himanshu; Singhal, R.

2016-05-23

In this paper, we have investigated the annealing effect on optical and structural properties of ZnO thin films, synthesized by RF magnetron sputtering. ZnO thin films were deposited on glass and silicon substrates simultaneously at a substrate temperature of 300 °C using Argon gas in sputtering chamber. Thickness of as deposited ZnO thin film was found to be ~155 nm, calculated by Rutherford backscattering spectroscopy (RBS). These films were annealed at 400 °C and 500 °C temperature in the continuous flow of oxygen gas for 1 hour in tube furnace. X-ray diffraction analysis confirmed the formation of hexagonal wurtzite structuremore » of ZnO thin film along the c-axis (002) orientation. Transmittance of thin films was increased with increasing the annealing temperature estimated by UV-visible transmission spectroscopy. Quality and texture of the thin films were improved with annealing temperature, estimated by Raman spectroscopy.« less

Correlation between ferromagnetism and defects in MgO nanocrystals studied by positron annihilation

NASA Astrophysics Data System (ADS)

Wang, D. D.; Chen, Z. Q.; Li, C. Y.; Li, X. F.; Cao, C. Y.; Tang, Z.

2012-07-01

High purity MgO nanopowders were pressed into pellets and annealed in air from 100 to 1400 °C. Variation of the microstructures was investigated by X-ray diffraction and positron annihilation spectroscopy. Annealing induces an increase in the MgO grain size from 27 to 60 nm with temperature increasing up to 1400 °C. Positron annihilation measurements reveal vacancy defects including Mg vacancies, vacancy clusters, microvoids and large pores in the grain boundary region. Rapid recovery of Mg monovacancies and vacancy clusters was observed after annealing above 1200 °C. Room temperature ferromagnetism was observed for MgO nanocrystals annealed at 100, 700, and 1000 °C. However, after 1400 °C annealing, MgO nanocrystals turn into diamagnetic. Our results suggest that the room temperature ferromagnetism in MgO nanocrystals might originate from the interfacial defects.

Self-Supported Copper Oxide Electrocatalyst for Water Oxidation at Low Overpotential and Confirmation of Its Robustness by Cu K-edge X-ray Absorption Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xiang; Cui, Shengsheng; Sun, Zijun

Developing efficient water oxidation catalysts made of earth-abundant elements is a demanding challenge that should be met to fulfill the promise of water splitting for clean energy. Herein we report an annealing approach to synthesize binder-free, self-supported heterogeneous copper oxide (CuO) on conductive electrodes for oxygen evolution reaction (OER), producing electrodes with excellent electrocatalytic properties such as high efficiency, low overpotential, and good stability. The catalysts were grown in situ on fluorine-doped tin oxide (FTO) by electrodeposition from a simple Cu(II) salt solution, followed by annealing at a high temperature. Under optimal conditions, the CuO-based OER catalyst shows an onsetmore » potential of <0.58 V (vs Ag/AgCl) in 1.0 M KOH at pH 13.6. From the Tafel plot, the required overpotentials for current densities of 0.1 and 1.0 mA/cm2 are only 360 and 430 mV, respectively. The structure and the presence of a CuO motif in the catalyst have been identified by high-energy X-ray diffraction (HE-XRD), Cu K-edge X-ray absorption (XAS) spectra including X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS). To the best of our knowledge, this represents the best catalytic activity for CuO-based OER catalysts to date.« less

Au-free ohmic Ti/Al/TiN contacts to UID n-GaN fabricated by sputter deposition

NASA Astrophysics Data System (ADS)

Garbe, V.; Weise, J.; Motylenko, M.; Münchgesang, W.; Schmid, A.; Rafaja, D.; Abendroth, B.; Meyer, D. C.

2017-02-01

The fabrication and characterization of an Au-free Ti/Al/TiN (20/100/100 nm) contact stack to unintentionally doped n-GaN with TiN serving as the diffusion barrier is presented. Sputter deposition and lift-off in combination with post deposition annealing at 850 °C are used for contact formation. After annealing, contact shows ohmic behavior to n-GaN and a specific contact resistivity of 1.60 × 10-3 Ω cm2. To understand the contact formation on the microscopic scale, the contact was characterized by current-voltage measurements, linear transmission line method, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show the formation of Ti-N bonds at the GaN/Ti interface in the as-deposited stack. Annealing leads to diffusion of Ti, Al, Ga, and N, and the remaining metallic Ti is fully consumed by the formation of the intermetallic tetragonal Al3Ti phase. Native oxide from the GaN surface is trapped during annealing and accumulated in the Al interlayer. The TiN capping layer, however, was chemically stable during annealing. It prevented oxidation of the Ti/Al contact bilayer successfully and thus proved to be a well suitable diffusion barrier with ideal compatibility to the Ti/Al contact metallization.

Effect of non-vacuum thermal annealing on high indium content InGaN films deposited by pulsed laser deposition.

PubMed

Wang, Tzu-Yu; Ou, Sin-Liang; Shen, Kun-Ching; Wuu, Dong-Sing

2013-03-25

InGaN films with 33% and 60% indium contents were deposited by pulsed laser deposition (PLD) at a low growth temperature of 300 °C. The films were then annealed at 500-800 °C in the non-vacuum furnace for 15 min with an addition of N(2) atmosphere. X-ray diffraction results indicate that the indium contents in these two films were raised to 41% and 63%, respectively, after annealing in furnace. In(2)O(3) phase was formed on InGaN surface during the annealing process, which can be clearly observed by the measurements of auger electron spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. Due to the obstruction of indium out-diffusion by forming In(2)O(3) on surface, it leads to the efficient increment in indium content of InGaN layer. In addition, the surface roughness was greatly improved by removing In(2)O(3) with the etching treatment in HCl solution. Micro-photoluminescence measurement was performed to analyze the emission property of InGaN layer. For the as-grown InGaN with 33% indium content, the emission wavelength was gradually shifted from 552 to 618 nm with increasing the annealing temperature to 800 °C. It reveals the InGaN films have high potential in optoelectronic applications.

Synthesis and characterization of lanthanum doped zinc oxide nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Vinod; Sonia,; Suman,

La doped ZnO (Zn{sub 1-x}La{sub x}O, x = 0, 3, 6 and 9) were prepared via chemical co-precipitation method using Zinc Acetate, Lanthanum Acetate and Sodium Hydroxide at 50°C. Hydrate nanoparticles were annealed in air at 300°C for 3 hours. The synthesized samples have been characterized by powder X-ray diffraction and UV–Visible spectrophotometer. The XRD measurement revealsthat the prepared nanoparticles have different microstructure without changing a hexagonal wurtzite structure. The result shows the change in nanoparticles size with the increment of lanthanum concentration for lower concentration for x = 0 to 6 and decreases at x = 9.

Lattice modification in KTiOPO4 by hydrogen and helium sequentially implantation in submicrometer depth

NASA Astrophysics Data System (ADS)

Ma, Changdong; Lu, Fei; Xu, Bo; Fan, Ranran

2016-05-01

We investigated lattice modification and its physical mechanism in H and He co-implanted, z-cut potassium titanyl phosphate (KTiOPO4). The samples were implanted with 110 keV H and 190 keV He, both to a fluence of 4 × 1016 cm-2, at room temperature. Rutherford backscattering/channeling, high-resolution x-ray diffraction, and transmission electron microscopy were used to examine the implantation-induced structural changes and strain. Experimental and simulated x-ray diffraction results show that the strain in the implanted KTiOPO4 crystal is caused by interstitial atoms. The strain and stress are anisotropic and depend on the crystal's orientation. Transmission electron microscopy studies indicate that ion implantation produces many dislocations in the as-implanted samples. Annealing can induce ion aggregation to form nanobubbles, but plastic deformation and ion out-diffusion prevent the KTiOPO4 surface from blistering.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Changdong; Department of Radiation Oncology, Qilu Hospital, Shandong University, Jinan, Shandong 250012; Lu, Fei, E-mail: lufei@sdu.edu.cn

We investigated lattice modification and its physical mechanism in H and He co-implanted, z-cut potassium titanyl phosphate (KTiOPO{sub 4}). The samples were implanted with 110 keV H and 190 keV He, both to a fluence of 4 × 10{sup 16 }cm{sup −2}, at room temperature. Rutherford backscattering/channeling, high-resolution x-ray diffraction, and transmission electron microscopy were used to examine the implantation-induced structural changes and strain. Experimental and simulated x-ray diffraction results show that the strain in the implanted KTiOPO{sub 4} crystal is caused by interstitial atoms. The strain and stress are anisotropic and depend on the crystal's orientation. Transmission electron microscopy studies indicate that ion implantationmore » produces many dislocations in the as-implanted samples. Annealing can induce ion aggregation to form nanobubbles, but plastic deformation and ion out-diffusion prevent the KTiOPO{sub 4} surface from blistering.« less

A comparative study of heterostructured CuO/CuWO4 nanowires and thin films

NASA Astrophysics Data System (ADS)

Polyakov, Boris; Kuzmin, Alexei; Vlassov, Sergei; Butanovs, Edgars; Zideluns, Janis; Butikova, Jelena; Kalendarev, Robert; Zubkins, Martins

2017-12-01

A comparative study of heterostructured CuO/CuWO4 core/shell nanowires and double-layer thin films was performed through X-ray diffraction, confocal micro-Raman spectroscopy and electron (SEM and TEM) microscopies. The heterostructures were produced using a two-step process, starting from a deposition of amorphous WO3 layer on top of CuO nanowires and thin films by reactive DC magnetron sputtering and followed by annealing at 650 °C in air. The second step induced a solid-state reaction between CuO and WO3 oxides through a thermal diffusion process, revealed by SEM-EDX analysis. Morphology evolution of core/shell nanowires and double-layer thin films upon heating was studied by electron (SEM and TEM) microscopies. A formation of CuWO4 phase was confirmed by X-ray diffraction and confocal micro-Raman spectroscopy.

Positron annihilation and X-ray diffraction studies on tin oxide thin films

NASA Astrophysics Data System (ADS)

Prabakar, K.; Abhaya, S.; Krishnan, R.; Kalavathi, S.; Dash, S.; Jayapandian, J.; Amarendra, G.

2009-04-01

Positron annihilation spectroscopy along with glancing incidence X-ray diffraction have been used to investigate tin oxide thin films grown on Si by pulsed laser deposition. The films were prepared at room temperature and at 670 K under oxygen partial pressure. As-grown samples are amorphous and are found to contain large concentration of open volume sites (vacancy defects). Post-deposition annealing of as-grown samples at 970 K is found to drastically reduce the number of open volume sites and the film becomes crystalline. However, film grown under elevated temperature and under partial pressure of oxygen is found to exhibit a lower S-parameter, indicating lower defect concentration. Based on the analysis of experimental positron annihilation results, the defect-sensitive S-parameter and the overlayer thickness of tin oxide thin films are deduced. S- W correlation plots exhibit distinct positron trapping defect states in three samples.

Influence of annealing on X-ray radiation sensing properties of TiO2 thin film

NASA Astrophysics Data System (ADS)

Sarma, M. P.; Kalita, J. M.; Wary, G.

2018-03-01

A recent study shows that the titanium dioxide (TiO2) thin film synthesised by a chemical bath deposition technique is a very useful material for the X-ray radiation sensor. In this work, we reported the influence of annealing on the X-ray radiation detection sensitivity of the TiO2 film. The films were annealed at 333 K, 363 K, 393 K, 473 K, and 573 K for 1 hour. Structural analyses showed that the microstrain and dislocation density decreased whereas the average crystallite size increased with annealing. The band gap of the films also decreased from 3.26 eV to 3.10 eV after annealing. The I-V characteristics record under the dark condition and under the X-ray irradiation showed that the conductivity increased with annealing. The influence of annealing on the detection sensitivity was negligible if the bias voltage applied across the films was low (within 0.2 V‒1.0 V). At higher bias voltage (>1.0 V), the contribution of electrons excited by X-ray became less significant which affected the detection sensitivity.

Thermodynamics of a phase transition of silicon nanoparticles at the annealing and carbonization of porous silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagornov, Yu. S., E-mail: Nagornov.Yuri@gmail.com

2015-12-15

The formation of SiC nanocrystals of the cubic modification in the process of high-temperature carbonization of porous silicon has been analyzed. A thermodynamic model has been proposed to describe the experimental data obtained by atomic-force microscopy, Raman scattering, spectral analysis, Auger spectroscopy, and X-ray diffraction spectroscopy. It has been shown that the surface energy of silicon nanoparticles and quantum filaments is released in the process of annealing and carbonization. The Monte Carlo simulation has shown that the released energy makes it possible to overcome the nucleation barrier and to form SiC nanocrystals. The processes of laser annealing and electron irradiationmore » of carbonized porous silicon have been analyzed.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simoes, A.Z., E-mail: alezipo@yahoo.com; Riccardi, C.S.; Dos Santos, M.L.

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 themore » soft chemical method can be useful for practical applications, including nonvolatile digital memories, spintronics and data-storage media.« less

Annealing induced effect on the physical properties of ion-beam sputtered 0.5 Ba(Zr0.2Ti0.8)O3 - 0.5 (Ba0.7Ca0.3)TiO3-δ ferroelectric thin films

NASA Astrophysics Data System (ADS)

Oliveira, M. J. S.; Silva, J. P. B.; Veltruská, Kateřina; Matolín, V.; Sekhar, K. C.; Moreira, J. Agostinho; Pereira, M.; Gomes, M. J. M.

2018-06-01

This work reports thermal annealing induced effect on the structural, optical, chemical and ferroelectric properties of ion-beam sputtered lead-free ferroelectric 0.5 Ba(Zr0.2Ti0.8)O3 - 0.5 (Ba0.7Ca0.3)TiO3-δ (0.5BZT-0.5BCT) thin films. X-ray diffraction studies reveal that the tetragonality increases with the annealing temperature (Ta), while photoluminescence and X-ray photoelectron spectroscopy studies confirm that this effect is associated with the annihilation of the oxygen vacancies as well as changes in the Ba2+ coordination. The films annealed at 750 °C show a remarkable remnant polarization of Pr = 45.0 μC/cm2, with a coercive field of 32 kV/cm. The temperature dependence of the spontaneous polarization of the 0.5BZT-0.5BCT film reveals a mean field behavior of the polarization and the fatigue study reveals that Pr only decreases 3% after passing 109 cycles. Therefore the high remnant polarization and its high Pr stability make these films as promising candidates for memory applications.

Solid-to-solid phase transformations of nanostructured selenium-tin thin films induced by thermal annealing in oxygen atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serra, A.; Rossi, M.; Buccolieri, A.

2014-06-19

The structural and morphological evolution of nanostructured thin films obtained from thermal evaporation of polycrystalline Sn-Se starting charge as a function of the subsequent annealing temperature in an oxygen flow has been analysed. High-resolution transmission electron microscopy, small area electron diffraction, digital image processing, x-ray diffraction and Raman spectroscopy have been employed in order to investigate the structure and the morphology of the obtained films. The results evidenced, in the temperature range from RT to 500°C, the transition of the material from a homogeneous mixture of SnSe and SnSe{sub 2} nanocrystals, towards a homogeneous mixture of SnO{sub 2} and SeO{submore » 2} nanocrystals, with an intermediate stage in which only SnSe{sub 2} nanocrystals are present.« less

Phase change studies in Se85In15-xZnx chalcogenide thin films

NASA Astrophysics Data System (ADS)

Srivastava, Archana; Tiwari, S. N.; Alvi, M. A.; Khan, Shamshad A.

2018-03-01

This research work describes the phase change studies in Se85In15-xZnx thin films at various annealing temperatures. Glassy samples of Se85In15-xZnx were synthesized by the melt quenching method and thin films of thickness 400 nm were prepared by the vacuum evaporation technique on a glass/Si wafer substrate. The glass transition temperature (Tg) and the on-set crystallization temperature (Tc) of the prepared alloys were evaluated by non-isothermal differential scanning calorimetry studies. Thin films were annealed at three temperatures 330 K, 340 K, and 350 K (which are in between Tg and Tc of the synthesized samples) in a vacuum furnace for 2 h. High resolution X-ray diffraction studies demonstrate that the as-prepared films are amorphous in nature whereas the annealed films are of crystalline/polycrystalline in nature. Field emission scanning electron microscopy studies of thin films (as-deposited and crystallized) confirm the phase transformation in Se85In15-xZnx thin films. Optical band gaps were calculated from the Tauc's extrapolation procedure and were found to be enhanced with the Zn concentration and decrease with the increasing annealing temperature. Various optical parameters were evaluated for as-prepared and annealed Se85In15-xZnx thin films. The changes in optical parameters with annealing temperature were described on the basis of structural relaxation as well as changes in defect states and density of localized states during amorphous to crystalline phase transformation in Se85In15-xZnx thin films.

Structural and spectroscopic analysis of ex-situ annealed RF sputtered aluminium doped zinc oxide thin films

NASA Astrophysics Data System (ADS)

Otieno, Francis; Airo, Mildred; Erasmus, Rudolph M.; Billing, David G.; Quandt, Alexander; Wamwangi, Daniel

2017-08-01

Aluminium doped zinc oxide thin films are prepared by Radio Frequency magnetron sputtering in pure argon atmosphere at 100 W. The structural results reveal good film adhesion on a silicon substrate (001). The thin films were then subjected to heat treatment in a furnace under ambient air. The structural, morphological, and optical properties of the thin films as a function of deposition time and annealing temperatures have been investigated using Grazing incidence X-Ray Diffraction (GIXRD), Atomic Force Microscopy, and Scanning Electronic Microscopy. The photoluminescence properties of the annealed films showed significant changes in the optical properties attributed to mid gap defects. Annealing increases the crystallite size and the roughness of the film. The crystallinity of the films also improved as evident from the Raman and XRD studies.

Effect of annealing on optical properties and structure of the vanadium dioxide thin films

NASA Astrophysics Data System (ADS)

Zhu, Huiqun; Li, Yi; Li, Yuming; Huang, Yize; Tong, Guoxiang; Fang, Baoying; Zheng, Qiuxin; Li, Liu; Shen, Yujian

2012-10-01

VO2 thin films were prepared on soda-lime glass substrates by DC magnetron sputtering at room temperature using vanadium target and post annealing in air. X-ray diffraction and FTIR spectroscopy analyses showed that the films obtained at the optimized parameters have high VO2 (011) orientation. Both low temperature deposition and post annealing method were beneficial to grow the nano-films with pure VO2 phase-structure and composition. Metalinsulator transition properties of the VO2 films in terms of infrared transmittance, transmittance variation and film thickness were investigated under varying annealing temperature. Results showed that infrared transmittance variation and transition temperature of the nano-films were significantly improved and reduced respectively. Therefore, this study was able to develop practical low-cost preparation methods for high-performance intelligent energy-saving thin films.

Probing the thermal stability and the decomposition mechanism of a magnesium-fullerene polymer via X-ray Raman spectroscopy, X-ray diffraction and molecular dynamics simulations.

PubMed

Aramini, Matteo; Niskanen, Johannes; Cavallari, Chiara; Pontiroli, Daniele; Musazay, Abdurrahman; Krisch, Michael; Hakala, Mikko; Huotari, Simo

2016-02-21

We report the microscopic view of the thermal structural stability of the magnesium intercalated fullerene polymer Mg2C60. With the application of X-ray Raman spectroscopy and X-ray diffraction, we study in detail the decomposition pathways of the polymer system upon annealing at temperatures between 300 and 700 °C. We show that there are at least two energy scales involved in the decomposition reaction. Intermolecular carbon bonds, which are responsible for the formation of a 2D fullerene polymer, are broken with a relatively modest thermal energy, while the long-range order of the original polymer remains intact. With an increased thermal energy, the crystal structure in turn is found to undergo a transition to a novel intercalated cubic phase that is stable up to the highest temperature studied here. The local structure surrounding magnesium ions gets severely modified close to, possibly at, the phase transition. We used density functional theory based calculations to study the thermodynamic and kinetic aspects of the collapse of the fullerene network, and to explain the intermediate steps as well as the reaction pathways in the break-up of this peculiar C60 intermolecular bonding architecture.

Preparation of γ-LiV2O5 from polyoxovanadate cluster Li7[V15O36(CO3)] as a high-performance cathode material and its reaction mechanism revealed by operando XAFS

NASA Astrophysics Data System (ADS)

Wang, Heng; Isobe, Jin; Shimizu, Takeshi; Matsumura, Daiju; Ina, Toshiaki; Yoshikawa, Hirofumi

2017-08-01

γ-phase LiV2O5, which shows superior electrochemical performance as cathode material in Li-ion batteries, was prepared by annealing the polyoxovanadate cluster Li7 [V15O36(CO3)]. The reaction mechanism was studied using operando X-ray absorption fine structure (XAFS), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS) analyses. The X-ray absorption near edge structure (XANES) and XPS results reveal that γ-LiV2O5 undergoes two-electron redox reaction per V2O5 pyramid unit, resulting in a large reversible capacity of 260 Ah/kg. The extended X-ray absorption fine structure (EXAFS) and PXRD analyses also suggest that the V-V distance slightly increases, due to the reduction of V5+ to V4+ during Li ion intercalation as the material structure is maintained. As a result, γ-LixV2O5 shows highly reversible electrochemical reaction with x = 0.1-1.9.

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

X-Ray Nanoscopy of a Bulk Heterojunction

NASA Astrophysics Data System (ADS)

Patil, Nilesh; Torbjørn, Eirik; Skjønsfjell, Bakken; Van den Brande, Niko; Chavez Panduro, Elvia Anabela; Claessens, Raf; Guizar-Sicairos, Manuel; Van Mele, Bruno; Breiby, Dag Werner

2016-07-01

Optimizing the morphology of bulk heterojunctions is known to significantly improve the photovoltaic performance of organic solar cells, but available quantitative imaging techniques are few and have severe limitations. We demonstrate X-ray ptychographic coherent diffractive imaging applied to all-organic blends. Specifically, the phase-separated morphology in bulk heterojunction photoactive layers for organic solar cells, prepared from a 50:50 blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) and thermally treated for different annealing times is imaged to high resolution. Moreover, using a fast-scanning calorimetry chip setup, the nano-morphological changes caused by repeated thermal annealing applied to the same sample could be monitored. X-ray ptychography resolves to better than 100 nm the phase-segregated domains of electron donor and electron acceptor materials over a large field of view within the active layers. The quantitative phase contrast images further allow us to estimate the local volume fraction of PCBM across the photovoltaically active layers. The volume fraction gradient for different regions provides insight on the PCBM diffusion across the depletion zone surrounding PCBM aggregates. Phase contrast X-ray microscopy is under rapid development, and the results presented here are promising for future studies of organic-organic blends, also under in situ conditions, e.g., for monitoring the structural stability during UV-Vis irradiation.

X-Ray Nanoscopy of a Bulk Heterojunction.

PubMed

Patil, Nilesh; Skjønsfjell, Eirik Torbjørn Bakken; Van den Brande, Niko; Chavez Panduro, Elvia Anabela; Claessens, Raf; Guizar-Sicairos, Manuel; Van Mele, Bruno; Breiby, Dag Werner

2016-01-01

Optimizing the morphology of bulk heterojunctions is known to significantly improve the photovoltaic performance of organic solar cells, but available quantitative imaging techniques are few and have severe limitations. We demonstrate X-ray ptychographic coherent diffractive imaging applied to all-organic blends. Specifically, the phase-separated morphology in bulk heterojunction photoactive layers for organic solar cells, prepared from a 50:50 blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) and thermally treated for different annealing times is imaged to high resolution. Moreover, using a fast-scanning calorimetry chip setup, the nano-morphological changes caused by repeated thermal annealing applied to the same sample could be monitored. X-ray ptychography resolves to better than 100 nm the phase-segregated domains of electron donor and electron acceptor materials over a large field of view within the active layers. The quantitative phase contrast images further allow us to estimate the local volume fraction of PCBM across the photovoltaically active layers. The volume fraction gradient for different regions provides insight on the PCBM diffusion across the depletion zone surrounding PCBM aggregates. Phase contrast X-ray microscopy is under rapid development, and the results presented here are promising for future studies of organic-organic blends, also under in situ conditions, e.g., for monitoring the structural stability during UV-Vis irradiation.

Effects of high temperature and film thicknesses on the texture evolution in Ag thin films

NASA Astrophysics Data System (ADS)

Eshaghi, F.; Zolanvari, A.

2017-04-01

In situ high-temperature X-ray diffraction techniques were used to study the effect of high temperatures (up to 600°C) on the texture evolution in silver thin films. Ag thin films with different thicknesses of 40, 80, 120 and 160nm were sputtered on the Si(100) substrates at room temperature. Then, microstructure of thin films was determined using X-ray diffraction. To investigate the influence of temperature on the texture development in the Ag thin films with different thicknesses, (111), (200) and (220) pole figures were evaluated and orientation distribution functions were calculated. Minimizing the total energy of the system which is affected by competition between surface and elastic strain energy was a key factor in the as-deposited and post annealed thin films. Since sputtering depositions was performed at room temperature and at the same thermodynamic conditions, the competition growth caused the formation of the {122} < uvw \\rangle weak fiber texture in as-deposited Ag thin films. It was significantly observed that the post annealed Ag thin films showed {111} < uvw \\rangle orientations as their preferred orientations, but their preferred fiber texture varied with the thickness of thin films. Increasing thin film thickness from 40nm to 160nm led to decreasing the intensity of the {111} < uvw \\rangle fiber texture.

Annealing Temperature Dependent Structural and Optical Properties of RF Sputtered ZnO Thin Films.

PubMed

Sharma, Shashikant; Varma, Tarun; Asokan, K; Periasamy, C; Boolchandani, Dharmendar

2017-01-01

This work investigates the effect of annealing temperature on structural and optical properties of ZnO thin films grown over Si 100 and glass substrates using RF sputtering technique. Annealing temperature has been varied from 300 °C to 600 °C in steps of 100, and different microstructural parameters such as grain size, dislocation density, lattice constant, stress and strain have been evaluated. The structural and surface morphological characterization has been done using X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). XRD analysis reveals that the peak intensity of 002 crystallographic orientation increases with increased annealing temperature. Optical characterization of deposited films have been done using UV-Vis-NIR spectroscopy and photoluminescence spectrometer. An increase in optical bandgap of deposited ZnO thin films with increasing annealing temperature has been observed. The average optical transmittance was found to be more than 85% for all deposited films. Photoluminiscense spectra (PL) suggest that the crystalline quality of deposited film has increased at higher annealing temperature.

Defects versus grain size effects on the ferromagnetism of ZrO2 nanocrystals clarified by positron annihilation

NASA Astrophysics Data System (ADS)

Wang, D. D.; Qi, N.; Jiang, M.; Chen, Z. Q.

2013-01-01

Undoped ZrO2 nanocrystals were annealed in open air from 100 °C to 1300 °C. X-ray diffraction and transmission electron microscope were used to study the structure change and grain growth. Both the methods reveal that the ZrO2 grain size has very slight increase after annealing up to 900 °C. Positron annihilation measurements reveal a high concentration of vacancy defects which most probably exist in the grain boundary region. Thermal annealing above 500 °C causes recovery of these defects, and after annealing at 1200 °C, most of them are removed. Room temperature ferromagnetism is observed for the sample annealed at 100 °C and 500 °C. The magnetization becomes very weak after the nanocrystals are annealed at 700 °C, and it almost disappears at 1000 °C. It is clear that the intrinsic ferromagnetism in our ZrO2 nanocrystals is mostly related with the interfacial defects instead of grain size effects.

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

PubMed

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

2013-05-15

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

Thermal annealing effect on the Mg-doped AlGaN/GaN superlattice

NASA Astrophysics Data System (ADS)

Wang, Baozhu; An, Shengbiao; Wen, Huanming; Wu, Ruihong; Wang, Xiaojun; Wang, Xiaoliang

2009-11-01

Mg-doped AlGaN/GaN superlattice has been grown by metalorganic chemical vapor deposition (MOCVD). Rapid thermal annealing (RTA) treament are carryied out on the samples under nitrogen as protect gas. Hall, photoluminescence (PL), high resolution x-ray diffraction (HRXRD) and atomic-force microscopy (AFM) are used to characterize the electrical, optical and structural properties of the as-grown and annealed samples, respectively. After annealing, the Hall results indicate more Mg acceptors are activated, which leads to higher hole concentration and lower p-type resistivity. The PL intensity of Mg related defect band shows a strong decrease after annealing. The annealing of the superlattice degrade the interface quality of the AlGaN/GaN from the HRXRD results. Many nanometer-grains can be observed on the surface of AlGaN/GaN superlattice from the AFM image. This maybe related with the decomposing of GaN or the separating of Mg from the AlGaN/GaN superlattice.

Design and characterization of biofunctional magnetic porous silicon flakes.

PubMed

Muñoz Noval, A; García, R; Ruiz Casas, D; Losada Bayo, D; Sánchez Vaquero, V; Torres Costa, V; Martín Palma, R J; García, M A; García Ruiz, J P; Serrano Olmedo, J J; Muñoz Negrete, J F; del Pozo Guerrero, F; Manso Silván, M

2013-04-01

Magnetic porous silicon flakes (MPSF) were obtained from mesoporous silicon layers formed by multi-step anodization and subsequent composite formation with Fe oxide nanoparticles by thermal annealing. The magnetic nanoparticles adhered to the surface and penetrated inside the pores. Their structure evolved as a result of the annealing treatments derived from X-ray diffraction and X-ray absorption analyses. Moreover, by tailoring the magnetic load, the dynamic and hydrodynamic properties of the particles were controlled, as observed by the pressure displayed against a sensor probe. Preliminary functionality experiments were performed using an eye model, seeking potential use of MPSF as reinforcement for restored detached retina. It was observed that optimal flake immobilization is obtained when the MPSF reach values of magnetic saturation >10(-4)Am(2)g(-1). Furthermore, the MPSF were demonstrated to be preliminarily biocompatible in vitro. Moreover, New Zealand rabbit in vivo models demonstrated their short-term histocompatibility and their magnetic functionality as retina pressure actuators. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Fast solid-phase synthesis of large-area few-layer 1T'-MoTe2 films

NASA Astrophysics Data System (ADS)

Xie, Sheng; Chen, Lin; Zhang, Tian-Bao; Nie, Xin-Ran; Zhu, Hao; Ding, Shi-Jin; Sun, Qing-Qing; Zhang, David Wei

2017-06-01

In this study, we report on a novel approach to produce ∼12 nm thick few-layer monoclinic 1T'-MoTe2 films. The deposition method comprised sputtering of Mo, molecular beam epitaxy of Te, and rapid thermal processing to effect tellurization of the Mo into 1T'-MoTe2. The heating rate and annealing time are the critical factors. 30 °C s-1 heating rate and 2 min annealing at 470 °C were adopted in this work. X-ray photoelectron spectroscopy confirmed the formation of stoichiometric 1T'-MoTe2 films, while X-ray diffraction confirmed the monoclinic polymorph. Raman spectroscopy confirmed spatial uniformity over the sample size of 1 cm × 1.5 cm. Our fast synthesis approach to realize high-quality 1T'-MoTe2 paves the way towards the large-scale application of 1T'-MoTe2 in high-performance nanoelectronics and optoelectronics.

Annealing Induced Re-crystallization in CH3NH3PbI3−xClx for High Performance Perovskite Solar Cells

PubMed Central

Yang, Yingguo; Feng, Shanglei; Li, Meng; Xu, Weidong; Yin, Guangzhi; Wang, Zhaokui; Sun, Baoquan; Gao, Xingyu

2017-01-01

Using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as hole conductor, a series of inverted planar CH3NH3PbI3−xClx perovskite solar cells (PSCs) were fabricated based on perovskite annealed by an improved time-temperature dependent (TTD) procedure in a flowing nitrogen atmosphere for different time. Only after an optimum annealing time, an optimized power conversion efficiency of 14.36% could be achieved. To understand their performance dependence on annealing time, an in situ real-time synchrotron-based grazing incidence X-ray diffraction (GIXRD) was used to monitor a step-by-step gradual structure transformation from distinct mainly organic-inorganic hybrid materials into highly ordered CH3NH3PbI3 crystal during annealing. However, a re-crystallization process of perovskite crystal was observed for the first time during such an annealing procedure, which helps to enhance the perovskite crystallization and preferential orientations. The present GIXRD findings could well explain the drops of the open circuit voltage (Voc) and the fill factor (FF) during the ramping of temperature as well as the optimized power conversion efficiency achieved after an optimum annealing time. Thus, the present study not only illustrates clearly the decisive roles of post-annealing in the formation of solution-processed perovskite to better understand its formation mechanism, but also demonstrates the crucial dependences of device performance on the perovskite microstructure in PSCs. PMID:28429762

Interfacial reactions of nano-structured Cu-doped indium oxide/indium tin oxide ohmic contacts to p-GaN.

PubMed

Yoon, Young Joon; Chae, S W; Kim, B K; Park, Min Joo; Kwak, Joon Seop

2010-05-01

Interfacial microstructure and elemental diffusion of Cu-doped indium oxide (CIO)/indium tin oxide (ITO) ohmic contacts to p-type GaN for light-emitting diodes (LEDs) were investigated using cross-sectional transmission electron microscopy (XTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction. The CIO/ITO contacts gave specific contact resistances of approximately 10(-4) omegacm2 and transmittance greater than 95% at a wavelength of 405 nm when annealed at 630 degrees C for 1 min in air. After annealing at 630 degrees C, multi-component oxides composed of Ga2O3-In2O3, Ga2O3-CuO, and In2O3-CuO formed at the interface between p-GaN and ITO. Formation of multi-component oxides reduced the barrier height between p-GaN and ITO due to their higher work functions than that of ITO, and caused Ga in the GaN to diffuse into the CIO/ITO layer, followed by generation of acceptor-like Ga vacancies near the GaN surface, which lowered contact resistivity of the CIO/ITO contacts to p-GaN after the annealing.

Preparation of nitrogen-doped graphene/activated carbon composite papers to enhance energy storage in supercapacitors

NASA Astrophysics Data System (ADS)

Li, Yong-feng; Liu, Yan-zhen; Liang, Yu; Guo, Xiao-hui; Chen, Cheng-meng

2017-09-01

This report presents a facile and effective method to synthesize freestanding nitrogen-doped reduced graphene oxide (rGO)/activated carbon (AC) composite papers for supercapacitors by a method combining vacuum filtration with post-annealing in NH3 atmosphere. The effect of activated carbon contents on the microstructure and capacitive behavior of the resulting composite papers before and after the annealing was investigated by X-ray diffraction, scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy. Results show that the composite paper with a 30% activated carbon loading has a high nitrogen content of 14.6 at% and superior capacitive performance (308 F/g, 1 A/g) to the other composite papers with various activated carbon loadings. Nitrogen was doped and GO reduced during the annealing. The rGO nanosheets acted as a framework, and the AC particles served as spacers to avoid agglomeration of graphene sheets. The high capacitance of the composite paper is ascribed to the electric double-layer behavior and the reversible redox reactions of the nitrogen and oxygen groups. The entire process is simple, environmental friendly and easily scalable for mass production.

The influence of an MgO nanolayer on the planar Hall effect in NiFe films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Minghua, E-mail: mhli@ustb.edu.cn; Department of Electrical Engineering, University of California, Los Angeles, California 90095; Zhao, Zhiduo

2015-03-28

The Planar Hall Effect (PHE) in NiFe films was studied using MgO as the buffer and capping layer to reduce the shunt effect. The thermal annealing was found to be effective in increasing the sensitivity. The sensitivity of the magnetic field reached as high as 865 V/AT in a MgO (3 nm)/NiFe (5 nm)/MgO(3 nm)/Ta(3 nm) structure after annealing at 500 °C for 2 h, which is close to the sensitivity of semiconductor Hall Effect (HE) sensors. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were used to study the sample. The results show that the top crystallization of MgO and NiFemore » (111) texture were improved by proper annealing. The smooth and clear bottom MgO/NiFe and top NiFe/MgO interface is evident from our data. In addition, the shunt current of Ta was decreased. These combined factors facilitate the improvement of the sensitivity of the magnetic field.« less

Misfit strain of oxygen precipitates in Czochralski silicon studied with energy-dispersive X-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gröschel, A., E-mail: alexander.groeschel@fau.de; Will, J.; Bergmann, C.

Annealed Czochralski Silicon wafers containing SiO{sub x} precipitates have been studied by high energy X-ray diffraction in a defocused Laue setup using a laboratory tungsten tube. The energy dispersive evaluation of the diffracted Bragg intensity of the 220 reflection within the framework of the statistical dynamical theory yields the static Debye-Waller factor E of the crystal, which gives access to the strain induced by the SiO{sub x} precipitates. The results are correlated with precipitate densities and sizes determined from transmission electron microscopy measurements of equivalent wafers. This allows for the determination of the constrained linear misfit ε between precipitate andmore » crystal lattice. For samples with octahedral precipitates the values ranging from ε = 0.39 (+0.28/−0.12) to ε = 0.48 (+0.34/−0.16) indicate that self-interstitials emitted into the matrix during precipitate growth contribute to the lattice strain. In this case, the expected value calculated from literature values is ε = 0.26 ± 0.05. Further, the precise evaluation of Pendellösung oscillations in the diffracted Bragg intensity of as-grown wafers reveals a thermal Debye-Waller parameter for the 220 reflection B{sup 220}(293 K) of 0.5582 ± 0.0039 Å{sup 2} for a structure factor based on spherically symmetric scattering contributions.« less

Effect of thermal annealing on structure and optical band gap of Se{sub 66}Te{sub 25}In{sub 9} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dwivedi, D. K.; Pathak, H. P.; Shukla, Nitesh

2015-05-15

Thin films of a-Se{sub 66}Te{sub 25}In{sub 9} have been deposited onto a chemically cleaned glass substrate by thermal evaporation technique under vacuum. Glassy nature of the films has been ascertained by X-ray diffraction pattern. The analysis of absorption spectra, measured at normal incidence, in the spectral range 400-1100 nm has been used for the optical characterization of thin films under investigation. The effect of thermal annealing on structure and optical band gap (E{sub g}) of a-Se{sub 66}Te{sub 25}In{sub 9} have been studied.

Radio frequency surface resistance of Tl-Ba-Ca-Cu-O films on metal and single-crystal substrates

NASA Astrophysics Data System (ADS)

Arendt, P. N.; Reeves, G. A.; Elliott, N. E.; Cooke, D. W.; Gray, E. R.; Houlton, R. J.; Brown, D. R.

1990-01-01

Films of Tl-Ba-Ca-Cu were dc magnetron sputtered from a single multielement target. The films were deposited onto substrates of: (1) magnesium oxide, (2) a silver based alloy (Consil 995), (3) a nickel based alloy (Haynes 230), and (4) buffer layers of barium fluoride or copper oxide on Consil. To form superconducting phases, post-deposition anneals were made on these films using an alumina crucible with an over pressure of thallium and flowing oxygen. After annealing, the film phases were determined using x-ray diffraction. The film surface resistances (Rs) were measured at 22 GHz in a TE011 cavity.

Materials physics of half-metallic magnetic oxide films by pulsed laser deposition: Controlling the crystal structure and near-surface properties of strontium iron molybdenum oxide and chromium oxide films

NASA Astrophysics Data System (ADS)

Jalili, Helia

The idea of half-metallic ferromagnets was first introduced by de Groot et al. in 1983 based on their calculations. The density of state at the Fermi level for half-metallic ferromagnet is completely polarized, meaning that only one of the spin up or spin down channel exists and has metallic behaviour while the other spin channel behaves as a semiconductor or insulator. This unusual electronic structure can be seen in different materials including Sr2FeMoO6, CrO2 and Mn-based Heusler alloys. The high spin polarization degree of the half-metallic ferromagnets makes them a perfect candidate to be used as a spin-injector/detector in spin-based electronics device (spintronics). However, the degree of spin polarization of these materials, particularly in the multilayered structure spintronic devices, strongly depends on the surface/interface quality and the presence of defects, which was the subject of the present study. Pulsed laser deposition (PLD) has been used to grow two examples of the half-metallic ferromagnets, namely, Sr2FeMoO6 and CrO2. The effects of the growth conditions (deposition temperature, gas pressure, laser power, target-to-substrate distance, post-annealing) and of the substrate lattice mismatch and thickness evolution have been studied. By optimizing the growth conditions, nanocrystalline Sr2FeMoO6 films have been grown on a Si(100) substrate for the first time. This single-phase Sr 2FeMoO6 film was obtained at a temperature as low as 600°C, and it exhibits a high saturation magnetic moment of 3.4 muB per formula unit at 77 K. By using glancing-incidence X-ray diffraction with different incident beam angles, the crystal structure of the film was sampled as a function of depth. Despite the lack of good lattice matching with the Si substrate, a preferential orientation of the nanocrystals in the film was observed for the as-grown Sr2FeMoO6 films thicker than 60 nm. Furthermore, effects of the deposition temperature on the epitaxial growth of the Sr2FeMoO6 films on MgO(001) have been studied by means of high-resolution X-ray diffraction. The film grown at 800°C was post-annealed in oxygen, producing epitaxial films of SrMoO4 on top of the Sr2FeMoO6 film. The corresponding magnetization data showed that the post-annealing treatment lowered the saturation magnetic moment from 3.4 muB per formula unit (or /f.u.) for the as-grown Sr2FeMoO6 film to 1.4 muB/f.u. after annealing. X-ray photoemission measurements as a function of sputtering time further revealed the presence of SrMoO4 on both the as-grown and annealed films, and their corresponding depth profiles indicated a thicker SrMoO 4 overlayer on the annealed film. The intensity ratios of the 3d features of Mo4+, Mo5+, and Mo6+ for Sr 2FeMoO6 remained unchanged with sputtering depth (after 160 s of sputtering), supporting the conclusion that the observed secondary phase (SrMoO4) was formed predominantly on the surface and not in the sub-grain boundaries of the as-grown Sr2FeMoO6 film. The epitaxial growth evolution of Sr2FeMoO6 films of different thickness on substrates of MgO(001), SrTiO3(100) and LaAlO3(100) have also been studied. For each thickness, surface morphology, grain size, film epitaxy, and crystal quality were determined by atomic force microscopy and X-ray diffraction (o-2theta scan and reciprocal space mapping). For thicker films (˜120 nm), high resolution X-ray diffraction studies revealed that SrMoO4 and other parasitic phases tend to forms on SrTiO3 and LaAlO3 substrates, but not on those grown on MgO substrates. As a second part of the project, single-phase CrO2 nanostructured thin films have been grown for the first time directly on MgO(001) by PLD from a metallic Cr target in an O2 environment. X-ray diffraction shows that these films are strained and consist of CrO2 crystallites with two possible epitaxial relationships to the substrate: either CrO 2(110) or CrO2(200) is parallel to MgO(001). X-ray photoemission further confirms that the films are primarily CrO2 covered with a thin CrO3 overlayer, and indicates its complete synthesis without any residual metallic Cr.

Synthesis and magnetic properties of Zr doped ZnO Nanoparticles.

PubMed

Zhang, Jing; Gao, Daqiang; Yang, Guijin; Zhang, Jinlin; Shi, Zhenhua; Zhang, Zhaohui; Zhu, Zhonghua; Xue, Desheng

2011-11-10

Zr doped ZnO nanoparticles are prepared by the sol-gel method with post-annealing. X-ray diffraction results show that all samples are the typical hexagonal wurtzite structure without any other new phase, as well as the Zr atoms have successfully entered into the ZnO lattices instead of forming other lattices. Magnetic measurements indicate that all the doping samples show room temperature ferromagnetism and the pure ZnO is paramagneism. The results of Raman and X-ray photoelectron spectroscopy indicate that there are a lot of oxygen vacancies in the samples by doping element of Zr. It is considered that the observed ferromagnetism is related to the doping induced oxygen vacancies.

Growth of high quality yttrium iron garnet films using standard pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Zaki, Aliaa M.; Blythe, Harry J.; Heald, Steve M.; Fox, A. Mark; Gehring, Gillian A.

2018-05-01

Thin films with properties comparable to bulk single crystals were grown by pulsed laser deposition using a substrate temperature of only 500 °C. This was achieved by a careful choice of both the oxygen pressure in the deposition chamber and the temperature of the air anneal. The best films were grown on gadolinium gallium garnet substrates but we also report data for films grown on the diamagnetic substrate yttrium aluminium garnet. The films were analysed using X-ray diffraction, near edge X-ray absorption and magnetometry. Our best films had a magnetisation of 143 emu/cm3 and a coercive field of ∼1 Oe.

Effects of annealing on arrays of Ge nanocolumns formed by glancing angle deposition

NASA Astrophysics Data System (ADS)

Khare, C.; Gerlach, J. W.; Höche, T.; Fuhrmann, B.; Leipner, H. S.; Rauschenbach, B.

2012-10-01

Post-deposition thermal annealing of glancing angle deposited Ge nanocolumn arrays was carried out in a continuous Ar-flow at temperatures ranging from TA = 300 to 800 °C for different annealing durations. Morphological alterations and the recrystallization process induced by the thermal annealing treatment were investigated for the Ge nanocolumns deposited on planar and pre-patterned Si substrates. From X-ray diffraction (XRD) measurements, the films annealed at TA ≥ 500 °C were found to be polycrystalline. On planar Si substrates, at TA = 600 °C nanocolumns exhibited strong coarsening and merging, while a complete disintegration of the nanocolumns was detected at TA = 700 °C. The morphology of nanostructures deposited on pre-patterned substrates differs substantially, where the merging or column-disintegration effect was absent at elevated annealing temperatures. The two-arm-chevron nanostructures grown on pre-patterned substrates retained their complex shape and morphology, after extended annealing intervals. Investigations by transmission electron microscopy revealed nanocrystalline domains of the order of 5-30 nm (in diameter) present within the chevron structures after the annealing treatment.

Effect of wheel speed and annealing temperature on microstructure and texture evolution of Ni{sub 45}Mn{sub 36.6}In{sub 13.4}Co{sub 5} ribbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Yan, E-mail: yanfeng@nwpu.edu.cn

Ni{sub 45}Mn{sub 36.6}In{sub 13.4}Co{sub 5} magnetic shape memory alloy was successfully produced as preferentially textured ribbon by melting spinning with different wheel speed. X-ray diffraction (XRD) and electron back scatter diffraction (EBSD) were used to study structure and texture evolution of these melt-spun ribbons. The thickness of melt-spun ribbon is 42 μm, 65 μm and 30 μm depending on wheel speed of 1 0 m/s, 15 m/s and 20 m/s, respectively. Density of α fiber texture (〈100〉//ND) vary with wheel speed changes, and is most intensive in the ribbon with wheel speed of 15 m/s. Grains of the ribbons growmore » after being annealed at 873 K, 973 K, 1073 K and 1173 K, recrystallization was not observed in ribbons after being annealed at 873 K but occurred in ribbons after being annealed at higher temperatures. The α fiber texture becomes weaker to some extent after annealing at different temperatures, due to new recrystallization texture formed at the process of annealing. - Highlights: •Sectional part of shape memory ribbon is firstly investigated by EBSD method. •Thickness and texture of ribbons vary with wheel speed. •Annealing temperature affect texture and microstructure evolution greatly. •Recrystallization textures were observed in ribbons after being annealed.« less

Microstructural investigation of nickel silicide thin films and the silicide-silicon interface using transmission electron microscopy.

PubMed

Bhaskaran, M; Sriram, S; Mitchell, D R G; Short, K T; Holland, A S; Mitchell, A

2009-01-01

This article discusses the results of transmission electron microscopy (TEM)-based investigation of nickel silicide (NiSi) thin films grown on silicon. Nickel silicide is currently used as the CMOS technology standard for local interconnects and in electrical contacts. Films were characterized with a range of TEM-based techniques along with glancing angle X-ray diffraction. The nickel silicide thin films were formed by vacuum annealing thin films of nickel (50 nm) deposited on (100) silicon. The cross-sectional samples indicated a final silicide thickness of about 110 nm. This investigation studied and reports on three aspects of the thermally formed thin films: the uniformity in composition of the film using jump ratio maps; the nature of the interface using high resolution imaging; and the crystalline orientation of the thin films using selected-area electron diffraction (SAED). The analysis highlighted uniform composition in the thin films, which was also substantiated by spectroscopy techniques; an interface exhibiting the desired abrupt transition from silicide to silicon; and desired and preferential crystalline orientation corresponding to stoichiometric NiSi, supported by glancing angle X-ray diffraction results.

Synthesis And Characterization Of Reduced Size Ferrite Reinforced Polymer Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borah, Subasit; Bhattacharyya, Nidhi S.

2008-04-24

Small sized Co{sub 1-x}Ni{sub x}Fe{sub 2}O{sub 4} ferrite particles are synthesized by chemical route. The precursor materials are annealed at 400, 600 and 800 C. The crystallographic structure and phases of the samples are characterized by X-ray diffraction (XRD). The annealed ferrite samples crystallized into cubic spinel structure. Transmission Electron Microscopy (TEM) micrographs show that the average particle size of the samples are <20 nm. Particulate magneto-polymer composite materials are fabricated by reinforcing low density polyethylene (LDPE) matrix with the ferrite samples. The B-H loop study conducted at 10 kHz on the toroid shaped composite samples shows reduction in magneticmore » losses with decrease in size of the filler sample. Magnetic losses are detrimental for applications of ferrite at high powers. The reduction in magnetic loss shows a possible application of Co-Ni ferrites at high microwave power levels.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ovcharov, A. V.; Karateev, I. A.; Mikhutkin, A. A.

The surface microstructure of Ni–W alloy tapes, which are used as substrates to form films of high-temperature superconductors and photovoltaic devices, has been studied. Several samples of a Ni{sub 95}W{sub 5} tape (Evico) annealed under different conditions were analyzed using scanning electron microscopy, energy-dispersive X-ray microanalysis, electron diffraction, and electron energy-loss spectroscopy. NiWO{sub 4} precipitates are found on the surface of annealed samples. The growth of precipitates at a temperature of 950°C is accompanied by the formation of pores on the surface or under an oxide film. Depressions with a wedge-shaped profile are found at the grain boundaries. Annealing inmore » a reducing atmosphere using a specially prepared chamber allows one to form a surface free of nickel tungstate precipitates.« less

Comparison of as-grown and annealed GaN/InGaN : Mg samples

NASA Astrophysics Data System (ADS)

Deng, Qingwen; Wang, Xiaoliang; Xiao, Hongling; Wang, Cuimei; Yin, Haibo; Chen, Hong; Lin, Defeng; Jiang, Lijuan; Feng, Chun; Li, Jinmin; Wang, Zhanguo; Hou, Xun

2011-08-01

Mg-doped InGaN was grown on unintentionally doped GaN layer, and Mg and defect behaviours in both GaN and InGaN : Mg were investigated through photoluminescence measurement at 7 K. Mg acceptor was found in unintentionally doped GaN after thermal annealing in N2 ambient, and Mg activation energy was estimated to be 200 meV and 110 meV for GaN and InGaN, respectively. Particularly, the ultraviolet band (3.0-3.2 eV) in the GaN layer was infrequently observed in the unannealed sample but quenched in the annealed sample; this band may be associated with oxygen-substituted nitrogen defects. Moreover, the measurement errors of photoluminescence and x-ray diffraction originated from strain were taken into account.

Through-silicon via-induced strain distribution in silicon interposer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vianne, B., E-mail: benjamin.vianne@st.com; STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles; Richard, M.-I.

2015-04-06

Strain in silicon induced by Through-Silicon Via (TSV) integration is of particular interest in the frame of the integration of active devices in silicon interposer. Nano-focused X-ray beam diffraction experiments were conducted using synchrotron radiation to investigate the thermally induced strain field in silicon around copper filled TSVs. Measurements were performed on thinned samples at room temperature and during in situ annealing at 400 °C. In order to correlate the 2D strain maps with finite elements analysis, an analytical model was developed, which takes into account beam absorption in the sample for a given diffraction geometry. The strain field along themore » [335] direction is found to be in the 10{sup −5} range at room temperature and around 10{sup −4} at 400 °C. Simulations support the expected plastification in some regions of the TSV during the annealing step.« less

On a Fast and Accurate In Situ Measuring Strategy for Recrystallization Kinetics and Its Application to an Al-Fe-Si Alloy

NASA Astrophysics Data System (ADS)

Kühbach, Markus; Brüggemann, Thiemo; Molodov, Konstantin D.; Gottstein, Günter

2015-03-01

In the current study, we detail a novel in situ X-ray diffraction-based bulk measurement technique, which allows for the continuous tracking of primary recrystallization kinetics. The approach is based on measuring the diffracted intensity that is correlated with the evolution of the volume fraction of particular texture components during annealing of a sample within a texture goniometer. The method is applied in an experimental study on a cold-rolled industrial Al-Fe-Si alloy. For comparison purposes, the macrotexture and the hardness evolution were monitored ex situ along isothermal and nonisothermal annealing. These measurements were then contrasted to the in situ obtained growth kinetics of recrystallizing grains in beta-fiber deformation and cube orientation. The results showed clearly that this method can be reliably utilized for the characterization of recrystallization kinetics in an industrial context.

Thermal annealing induced structural and optical properties of Se{sub 72}Te{sub 25}In{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pathak, H. P.; Dwivedi, D. K., E-mail: todkdwivedi@gmail.com; Shukla, Nitesh

2016-05-06

Thin films of a- Se{sub 72}Te{sub 25}In{sub 3} were prepared by vacuum evaporation technique in a base pressure of 10{sup -6} Torr on to well cleaned glass substrate. a-Se{sub 72}Te{sub 25}In{sub 3} thin films were annealed at different temperatures below their crystallization temperatures for 2h. The structural analysis of the films has been investigated using X-ray diffraction technique. The optical absorption spectra of these films were measured in the wavelength range 400-1100 nm in order to derive the absorption coefficient of these films. The optical band gap of as prepared and annealed films as a function of photon energy hasmore » been studied. It has been found that the optical band gap decreases with increasing annealing temperatures in the present system.« less

Effects of Annealing Temperature on Properties of Ti-Ga-Doped ZnO Films Deposited on Flexible Substrates.

PubMed

Chen, Tao-Hsing; Chen, Ting-You

2015-11-03

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.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Effect of Annealing Conditions on Properties of Sol-Gel Derived Al-Doped ZnO Thin Films

NASA Astrophysics Data System (ADS)

Gao, Mei-Zhen; Zhang, Feng; Liu, Jing; Sun, Hui-Na

2009-08-01

Transparent conductive Al-doped ZnO (AZO) thin films are prepared on normal glass substrates by the sol-gel spin coating method. The effects of drying conditions, annealing temperature and cooling rate on the structural, electrical and optical properties of AZO films are investigated by x-ray diffraction, scanning electron microscopy, the four-point probe method and UV-VIS spectrophotometry, respectively. The deposited films show a hexagonal wurtzite structure and high preferential c-axis orientation. As the drying temperature increases from 100°C to 300°C the resistivity of AZO films decreases dramatically. In contrast to the annealed films cooled in a furnace and in air, the resistivity of the annealed film which is cooled at -15°C is greatly reduced. Increasing the cooling rate dramatically increases the electrical conductivity of AZO films.

Magnetostructural transitions and magnetocaloric effects in Ni50Mn35In14.25B0.75 ribbons

NASA Astrophysics Data System (ADS)

Pandey, Sudip; Quetz, Abdiel; Ibarra-Gaytan, P. J.; Sánchez-Valdés, C. F.; Aryal, Anil; Dubenko, Igor; Sanchez Llamazares, Jose Luis; Stadler, Shane; Ali, Naushad

2018-05-01

The structural, thermal, and magnetic behaviors, as well as the martensitic phase transformation and related magnetocaloric response of Ni50Mn35In14.25B0.75 annealed ribbons have been investigated using room-temperature X-ray diffraction (XRD), differential scanning calorimetry (DSC), and magnetization measurements. Ni50Mn35In14.25B0.75 annealed ribbons show a sharper change in magnetization at the martensitic transition, resulting in larger magnetic entropy changes in comparison to bulk Ni50Mn35In14.25B0.75. A drastic shift in the martensitic transformation temperature (TM) of 70 K to higher temperature was observed for the annealed ribbons relative to that of the bulk (TM = 240 K). The results obtained for magnetic, thermal, structural, and magnetocaloric properties of annealed ribbons have been compared to those of the corresponding bulk alloys.

Superconductivity in sputtered CuMO6S8

NASA Technical Reports Server (NTRS)

Alterovitz, S.; Woollam, J. A.; Kammerdiner, L.; Luo, H. L.; Martin, C.

1977-01-01

Samples were prepared by melting the metals, followed by annealing to various temperatures. The result was a structurally weak material. Sputtered films on sapphire substrates were prepared and studied. The substrates give the films mechanical strength and permit easy attachment of electrical leads. Materials were characterized by X-ray diffraction, electron microscopy, electrical resistance vs. temperature, and critical current measurements. Some of the results on CuMo6S8 are presented.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiangkai; Yang, Xuyue, E-mail: yangxuyue@csu.edu.cn; Institute for Materials Microstructure, Central South University, Changsha 410083

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 themore » 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.« less

Characterization of nanocrystalline ZnO:Al films by sol-gel spin coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gareso, P. L., E-mail: pgareso@gmail.com; Rauf, N., E-mail: pgareso@gmail.com; Juarlin, E., E-mail: pgareso@gmail.com

2014-09-25

Nanocrystalline ZnO films doped with aluminium by sol-gel spin coating method have been investigated using optical transmittance UV-Vis and X-ray diffraction (X-RD) measurements. ZnO films were prepared using zinc acetate dehydrate (Zn(CH{sub 3}COO){sub 2}@@‡2H{sub 2}O), ethanol, and diethanolamine (DEA) as a starting material, solvent, and stabilizer, respectively. For doped films, AlCl{sub 3} was added to the mixture. The ZnO:Al films were deposited on a transparent conductive oxide (TCO) substrate using spin coating technique at room temperature with a rate of 3000 rpm in 30 sec. The deposited films were annealed at various temperatures from 400°C to 600°C during 60 minutes.more » The transmittance UV-Vis measurement results showed that after annealing at 400°C, the energy band gap profile of nanocrystalline ZnO:Al film was a blue shift. This indicated that the band gap of ZnO:Al increased after annealing due to the increase of crystalline size. As the annealing temperature increased the bandgap energy was a constant. In addition to this, there was a small oscillation occurring after annealing compared to the as–grown samples. In the case of X-RD measurements, the crystalinity of the films were amorphous before annealing, and after annealing the crystalinity became enhance. Also, X-RD results showed that structure of nanocrystalline ZnO:Al films were hexagonal polycrystalline with lattice parameters are a = 3.290 Å and c = 5.2531 Å.« less

Effect of Co2+ and Y3+ ions insertion on the microstructure development and magnetic properties of Ni0.5Zn0.5Fe2O4 powders synthesized using Co-precipitation method

NASA Astrophysics Data System (ADS)

Rashad, M. M.; Rayan, D. A.; Turky, A. O.; Hessien, M. M.

2015-01-01

Nanocrystalline Ni0.5Zn0.5-xCoxFe2-zYzO4 powders (x=0-0.3 and z from 0 to 0.3) have been synthesized via a facile co-precipitation technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) are utilized in order to study the effect of variation of cobalt and yttrium substitutions and its impact on crystalline size, lattice parameter, X-ray density, microstructure and magnetic properties of the formed powders. X-ray diffraction data indicated that, after doping, all samples consisted of the main spinel phase for the formed precursors precipitated at pH 10 annealed at 1000 oC for 2 h. The lattice parameter and the unit cell were decreased linearly with increasing Co content whereas they were increased with increasing the Y incorporation. Additionally, the porosity was increased with increasing Co concentration while it was decreased with increasing the Y insertion. The mean ionic radii and hopping and bond lengths was decreased with the value of Co2+ and they were increased with the value of Y3+ ion as well as both of Y3+ and Co2+ ions. The microstructures of the produced powders were found to be cubic like structure. The addition of Y3+ ion suppressed the grain size whereas addition of Co2+ ion enhanced the grain growth availably. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Co and Y concentrations incorporation up to x=0.3. Meanwhile, the formed powders exhibited superparamagnetic characteristics. A high saturation magnetization (77.0 emu/g) was achieved for Ni0.5Zn0.2Co0.3Fe2O4 sample annealed at 1000 oC for 2 h.

Thermal-induced structural and optical investigations of Agsbnd ZnO nanocomposite thin films

NASA Astrophysics Data System (ADS)

Singh, S. K.; Singhal, R.

2018-07-01

In the present paper, we have successfully synthesized Agsbnd ZnO nanocomposite thin films by RF-magnetron sputtering technique at room temperature. Systematic investigations of thermal-induced structural and optical modifications in Agsbnd ZnO thin films have been observed and described. The Agsbnd ZnO thin films were annealed at three different temperatures of 300 °C, 400 °C and 500 °C in vacuum to prevent the oxidation of Ag. The presence and formation of Ag nanoparticles were estimated by transmission electron microscopy. X-ray diffraction analysis revealed the structural information about the crystalline quality of ZnO. The crystallinity as well as the crystallite size of the films have been found to be improved with annealing temperatures. The estimated crystallite size was ∼15.8 nm for as-deposited film and 19.0 nm for the film at a higher temperature. The chemical composition and structural analysis of as-deposited film were carried out by X-ray photoelectron spectroscopy. A very sharp absorption band appeared at ∼540 nm for Ag NPs that is associated with the surface plasmon resonance band of Ag. A noticeable red shift of about ∼12 nm has been recorded for films annealed at 500 °C. Atomic force microscopy has been utilized to examine the surface morphology of the as-deposited and annealed films. The grain size was found to be increase with increasing annealing temperature, while no significant changes were observed in the roughness of Agsbnd ZnO thin films. Raman spectroscopy revealed lattice defects and disordering in the films after the thermal annealing.

Sequentially evaporated thin Y-Ba-Co-O superconducting films on microwave substrates

NASA Technical Reports Server (NTRS)

Valco, G. J.; Rohrer, N. J.; Warner, J. D.; Bhasin, K. B.

1989-01-01

The development of high T sub c superconducting thin films on various microwave substrates is of major interest in space electronic systems. Thin films of YBa2Cu3O(7-Delta) were formed on SrTiO3, MgO, ZrO2 coated Al2O3, and LaAlO3 substrates by multi-layer sequential evaporation and subsequent annealing in oxygen. The technique allows controlled deposition of Cu, BaF2 and Y layers, as well as the ZrO buffer layers, to achieve reproducibility for microwave circuit fabrication. The three layer structure of Cu/BaF2/Y is repeated a minimum of four times. The films were annealed in an ambient of oxygen bubbled through water at temperatures between 850 C and 900 C followed by slow cooling (-2 C/minute) to 450 C, a low temperature anneal, and slow cooling to room temperature. Annealing times ranged from 15 minutes to 5 hrs. at high temperature and 0 to 6 hr. at 450 C. Silver contacts for four probe electrical measurements were formed by evaporation followed with an anneal at 500 C. The films were characterized by resistance-temperature measurements, energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning electron microscopy. Critical transition temperatures ranged from 30 K to 87 K as a function of the substrate, composition of the film, thicknesses of the layers, and annealing conditions. Microwave ring resonator circuits were also patterned on these MgO and LaAlO3 substrates.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mogaddam, N. A. P.; Turan, R.; Alagoz, A. S.

2008-12-15

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

Ultrathin IBAD MgO films for epitaxial growth on amorphous substrates and sub-50 nm membranes

DOE PAGES

Wang, Siming; Antonakos, C.; Bordel, C.; ...

2016-11-07

Here, a fabrication process has been developed for high energy ion beam assisted deposition (IBAD) biaxial texturing of ultrathin (~1 nm) MgO films, using a high ion-to-atom ratio and post-deposition annealing instead of a homoepitaxial MgO layer. These films serve as the seed layer for epitaxial growth of materials on amorphous substrates such as electron/X-ray transparent membranes or nanocalorimetry devices. Stress measurements and atomic force microscopy of the MgO films reveal decreased stress and surface roughness, while X-ray diffraction of epitaxial overlayers demonstrates the improved crystal quality of films grown epitaxially on IBAD MgO. The process simplifies the synthesis ofmore » IBAD MgO, fundamentally solves the “wrinkle” issue induced by the homoepitaxial layer on sub-50 nm membranes, and enables studies of epitaxial materials in electron/X-ray transmission and nanocalorimetry.« less

Annealing induced atomic rearrangements on (Ga,In) (N,As) probed by hard X-ray photoelectron spectroscopy and X-ray absorption fine structure.

PubMed

Ishikawa, Fumitaro; Higashi, Kotaro; Fuyuno, Satoshi; Morifuji, Masato; Kondow, Masahiko; Trampert, Achim

2018-04-13

We study the effects of annealing on (Ga 0.64 ,In 0.36 ) (N 0.045 ,As 0.955 ) using hard X-ray photoelectron spectroscopy and X-ray absorption fine structure measurements. We observed surface oxidation and termination of the N-As bond defects caused by the annealing process. Specifically, we observed a characteristic chemical shift towards lower binding energies in the photoelectron spectra related to In. This phenomenon appears to be caused by the atomic arrangement, which produces increased In-N bond configurations within the matrix, as indicated by the X-ray absorption fine structure measurements. The reduction in the binding energies of group-III In, which occurs concomitantly with the atomic rearrangements of the matrix, causes the differences in the electronic properties of the system before and after annealing.

Synthesis of stable TiO2 nanotubes: effect of hydrothermal treatment, acid washing and annealing temperature.

PubMed

López Zavala, Miguel Ángel; Lozano Morales, Samuel Alejandro; Ávila-Santos, Manuel

2017-11-01

Effect of hydrothermal treatment, acid washing and annealing temperature on the structure and morphology of TiO 2 nanotubes during the formation process was assessed. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy analysis were conducted to describe the formation and characterization of the structure and morphology of nanotubes. Hydrothermal treatment of TiO 2 precursor nanoparticles and acid washing are fundamental to form and define the nanotubes structure. Hydrothermal treatment causes a change in the crystallinity of the precursor nanoparticles from anatase phase to a monoclinic phase, which characterizes the TiO 2 nanosheets structure. The acid washing promotes the formation of high purity nanotubes due to Na + is exchanged from the titanate structure to the hydrochloric acid (HCl) solution. The annealing temperature affects the dimensions, structure and the morphology of the nanotubes. Annealing temperatures in the range of 400 °C and 600 °C are optimum to maintain a highly stable tubular morphology of nanotubes. Additionally, nanotubes conserve the physicochemical properties of the precursor Degussa P25 nanoparticles. Temperatures greater than 600 °C alter the morphology of nanotubes from tubular to an irregular structure of nanoparticles, which are bigger than those of the precursor material, i.e., the crystallinity turn from anatase phase to rutile phase inducing the collapse of the nanotubes.

Effect of negative bias on the composition and structure of the tungsten oxide thin films deposited by magnetron sputtering

NASA Astrophysics Data System (ADS)

Wang, Meihan; Lei, Hao; Wen, Jiaxing; Long, Haibo; Sawada, Yutaka; Hoshi, Yoichi; Uchida, Takayuki; Hou, Zhaoxia

2015-12-01

Tungsten oxide thin films were deposited at room temperature under different negative bias voltages (Vb, 0 to -500 V) by DC reactive magnetron sputtering, and then the as-deposited films were annealed at 500 °C in air atmosphere. The crystal structure, surface morphology, chemical composition and transmittance of the tungsten oxide thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometer. The XRD analysis reveals that the tungsten oxide films deposited at different negative bias voltages present a partly crystallized amorphous structure. All the films transfer from amorphous to crystalline (monoclinic + hexagonal) after annealing 3 h at 500 °C. Furthermore, the crystallized tungsten oxide films show different preferred orientation. The morphology of the tungsten oxide films deposited at different negative bias voltages is consisted of fine nanoscale grains. The grains grow up and conjunct with each other after annealing. The tungsten oxide films deposited at higher negative bias voltages after annealing show non-uniform special morphology. Substoichiometric tungsten oxide films were formed as evidenced by XPS spectra of W4f and O1s. As a result, semi-transparent films were obtained in the visible range for all films deposited at different negative bias voltages.

Effects of anodizing conditions and annealing temperature on the morphology and crystalline structure of anodic oxide layers grown on iron

NASA Astrophysics Data System (ADS)

Pawlik, Anna; Hnida, Katarzyna; Socha, Robert P.; Wiercigroch, Ewelina; Małek, Kamilla; Sulka, Grzegorz D.

2017-12-01

Anodic iron oxide layers were formed by anodization of the iron foil in an ethylene glycol-based electrolyte containing 0.2 M NH4F and 0.5 M H2O at 40 V for 1 h. The anodizing conditions such as electrolyte composition and applied potential were optimized. In order to examine the influence of electrolyte stirring and applied magnetic field, the anodic samples were prepared under the dynamic and static conditions in the presence or absence of magnetic field. It was shown that ordered iron oxide nanopore arrays could be obtained at lower anodizing temperatures (10 and 20 °C) at the static conditions without the magnetic field or at the dynamic conditions with the applied magnetic field. Since the as-prepared anodic layers are amorphous in nature, the samples were annealed in air at different temperatures (200-500 °C) for a fixed duration of time (1 h). The morphology and crystal phases developed after anodization and subsequent annealing were characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The results proved that the annealing process transforms the amorphous layer into magnetite and hematite phases. In addition, the heat treatment results in a substantial decrease in the fluorine content and increase in the oxygen content.

Structure and high temperature oxidation of mechanical alloyed Fe-Al coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aryanto, Didik, E-mail: Didik-phys@yahoo.co.id, E-mail: didi027@lipi.go.id; Sudiro, Toto; Wismogroho, Agus S.

2016-04-19

The structure and high temperature oxidation resistance of Fe-Al coating on low carbon steel were investigated. The Fe-Al coating was deposited on the surface of low carbon steel using a mechanical alloying method. The coating was then annealed at 600°C for 2 hour in a vacuum of 5 Pa. The cyclic-oxidation tests of low carbon steel, Fe-Al coatings with and without annealing were performed at 600°C for up to 60h in air. The structure of oxidized samples was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy X-ray spectroscopy (EDS). The results show that the Fe-Al coatingsmore » exhibit high oxidation resistance compared to the uncoated steel. After 60 h exposure, the uncoated steel formed mainly Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} layers with the total thickness of around 75.93 µm. Fe-Al coating without annealing formed a thin oxide layer, probably (Fe,Al){sub 2}O{sub 3}. Meanwhile, for annealed sample, EDX analysis observed the formation of two Fe-Al layers with difference in elements concentration. The obtained results suggest that the deposition of Fe-Al coating on low carbon steel can improve the oxidation resistance of low carbon steel.« less

Quantitative x-ray diffraction analysis of bimodal damage distributions in Tm implanted Al0.15Ga0.85N

NASA Astrophysics Data System (ADS)

Magalhães, S.; Fialho, M.; Peres, M.; Lorenz, K.; Alves, E.

2016-04-01

In this work radial symmetric x-ray diffraction scans of Al0.15Ga0.85N thin films implanted with Tm ions were measured to determine the lattice deformation and crystal quality as functions of depth. The alloys were implanted with 300 keV Tm with 10° off-set to the sample normal to avoid channelling, with fluences varying between 1013 Tm cm-2 and 5  ×  1015 Tm cm-2. Simulations of the radial 2θ-ω scans were performed under the frame of the dynamical theory of x-ray diffraction assuming Gaussian distributions of the lattice strain induced by implantation defects. The structure factor of the individual layers is multiplied by a static Debye-Waller factor in order to take into account the effect of lattice disorder due to implantation. For higher fluences two asymmetric Gaussians are required to describe well the experimental diffractograms, although a single asymmetric Gaussian profile for the deformation is found in the sample implanted with 1013 Tm cm-2. After thermal treatment at 1200 °C, the crystal quality partially recovers as seen in a reduction of the amplitude of the deformation maximum as well as the total thickness of the deformed layer. Furthermore, no evidence of changes with respect to the virgin crystal mosaicity is found after implantation and annealing.

Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study.

PubMed

Pimentel, Ana; Ferreira, Sofia Henriques; Nunes, Daniela; Calmeiro, Tomas; Martins, Rodrigo; Fortunato, Elvira

2016-04-20

The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C.

Microwave Synthesized ZnO Nanorod Arrays for UV Sensors: A Seed Layer Annealing Temperature Study

PubMed Central

Pimentel, Ana; Ferreira, Sofia Henriques; Nunes, Daniela; Calmeiro, Tomas; Martins, Rodrigo; Fortunato, Elvira

2016-01-01

The present work reports the influence of zinc oxide (ZnO) seed layer annealing temperature on structural, optical and electrical properties of ZnO nanorod arrays, synthesized by hydrothermal method assisted by microwave radiation, to be used as UV sensors. The ZnO seed layer was produced using the spin-coating method and several annealing temperatures, ranging from 100 to 500 °C, have been tested. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectrophotometry measurements have been used to investigate the structure, morphology, and optical properties variations of the produced ZnO nanorod arrays regarding the seed layer annealing temperatures employed. After the growth of ZnO nanorod arrays, the whole structure was tested as UV sensors, showing an increase in the sensitivity with the increase of seed layer annealing temperature. The UV sensor response of ZnO nanorod arrays produced with the seed layer annealed temperature of 500 °C was 50 times superior to the ones produced with a seed layer annealed at 100 °C. PMID:28773423

Understanding the effect of annealing temperature on crystalline structure, morphology, and photocatalytic activity of silver-loaded TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Viet, Pham Van; Phuong Trang, Duong Dao; Phat, Bui Dai; Hieu, Le Van; Thi, Cao Minh

2018-05-01

In this study, we classified the effect of the annealing temperature on silver-loaded TiO2 nanotubes (Ag/TNTs). X-ray diffraction results demonstrate that TNTs have a tendency of phase transformation owing to silver nanoparticles (Ag NPs). The Brunauer-Emmett-Teller method indicates that Ag/TNTs is a mesopore material and the surface area of Ag/TNTs decreases when the annealing temperature increases. This research concluded that the TNT structure begins to break at high annealing temperatures (>400 °C) and is completely broken at 500 °C. The average diameter of the Ag NPs in Ag/TNTs increases linearly with the annealing temperature. In addition, this study clearly explained the oxidation state transformation of Ag in Ag/TNTs under the impact of the annealing temperature, therein, the Ag0 state is transferred completely to Ag+ at 400 °C, and some Ag+ is oxidized to form Ag2+. The Ag/TNTs and Ag/TNTs annealed at 300 °C provided the good methylene blue photodegradation ability for 150 min under sunlight condition.

Investigation of the Thermal Stability of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) Materials Proposed for Inert Matrix Fuel Applications.

PubMed

Hayes, John R; Grosvenor, Andrew P; Saoudi, Mouna

2016-02-01

Inert matrix fuels (IMF) consist of transuranic elements (i.e., Pu, Am, Np, Cm) embedded in a neutron transparent (inert) matrix and can be used to "burn up" (transmute) these elements in current or Generation IV nuclear reactors. Yttria-stabilized zirconia has been extensively studied for IMF applications, but the low thermal conductivity of this material limits its usefulness. Other elements can be used to stabilize the cubic zirconia structure, and the thermal conductivity of the fuel can be increased through the use of a lighter stabilizing element. To this end, a series of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials has been synthesized via a co-precipitation reaction and characterized by multiple techniques (Nd was used as a surrogate for Am). The long-range and local structures of these materials were studied using powder X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy. Additionally, the stability of these materials over a range of temperatures has been studied by annealing the materials at 1100 and 1400 °C. It was shown that the Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials maintained a single cubic phase upon annealing at high temperatures only when both Nd and Sc were present with y ≥ 0.10 and x + y > 0.15.

Crystallization Kinetics in Fluorochloroziroconate Glass-Ceramics

NASA Astrophysics Data System (ADS)

Alvarez, Carlos J.

Annealing fluorochlorozirconate (FCZ) glasses nucleates BaCl2 nanocrystals in the glass matrix, resulting in a nanocomposite glass-ceramic that has optical properties suitable for use as a medical X-ray imaging plate. Understanding the way in which the BaCl¬2 nanocrystal nucleation, growth and phase transformation processes proceed is critical to controlling the optical behavior. However, there is a very limited amount of information about the formation, morphology, and distribution of the nanocrystalline particles in FCZ glass-ceramics. In this thesis, the correlation between the microstructure and the crystallization kinetics of FCZ glass-ceramics, are studied in detail. In situ X-ray diffraction and transmission electron microscopy annealing experiments are used to analyze the crystal structure, size and distribution of BaCl 2 nanocrystals in FCZ glass-ceramics as a function of annealing rate and temperature. Microstructural analysis of the early stages on nucleation identified the formation of both BaCl2 and BaF2 nanocrystals. Annealing FCZ glass-ceramics above 280°C can cause the formation of additional glass matrix phase crystals, their microstructure and the annealing parameters required for their growth are identified. As the crystalline phases grow directly from the glass, small variations in processing of the glass can have a profound influence on the crystallization process. The information obtained from these experiments improves the understanding of the nucleation, growth and phase transformation process of the BaCl¬2 nanocrystals and additional crystalline phases that form in FCZ glass-ceramics, and may help expedite the implementation of FCZ glass-ceramics as next-generation X-ray detectors. Lastly, as these glass-ceramics may one day be commercialized, an investigation into their degradation in different environmental conditions was also performed. The effects of direct contact with water or prolonged exposure to humid environments on the microstructure and the optical properties for FCZ glasses and glass-ceramics was explored.

Combinatorial investigation of Fe–B thin-film nanocomposites

PubMed Central

Brunken, Hayo; Grochla, Dario; Savan, Alan; Kieschnick, Michael; Meijer, Jan D; Ludwig, Alfred

2011-01-01

Combinatorial magnetron sputter deposition from elemental targets was used to create Fe–B composition spread type thin film materials libraries on thermally oxidized 4-in. Si wafers. The materials libraries consisting of wedge-type multilayer thin films were annealed at 500 or 700 °C to transform the multilayers into multiphase alloys. The libraries were characterized by nuclear reaction analysis, Rutherford backscattering, nanoindentation, vibrating sample magnetometry, x-ray diffraction (XRD) and transmission electron microscopy (TEM). Young's modulus and hardness values were related to the annealing parameters, structure and composition of the films. The magnetic properties of the films were improved by annealing in a H2 atmosphere, showing a more than tenfold decrease in the coercive field values in comparison to those of the vacuum-annealed films. The hardness values increased from 8 to 18 GPa when the annealing temperature was increased from 500 to 700 °C. The appearance of Fe2B phases, as revealed by XRD and TEM, had a significant effect on the mechanical properties of the films. PMID:27877435

Effect of annealing on structure, morphology and optoelectronic properties of nanocrystalline CuO thin films

NASA Astrophysics Data System (ADS)

Jundale, D. M.; Pawar, S. G.; Patil, S. L.; Chougule, M. A.; Godse, P. R.; Patil, V. B.

2011-10-01

The nanocrystalline CuO thin films were prepared on glass substrates by the sol-gel method. The structural, morphological, electrical and optical properties of CuO thin films, submitted to an annealing treatment in the 400-700 °C ranges are studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Four Probe Technique and UV-visible spectroscopic. XRD measurements show that all the films are crystallized in the monoclinic phase and present a random orientation. Four prominent peaks, corresponding to the (110) phase (2θ≈32.70°), (002) phase (2θ≈35.70°), (111) phase (2θ≈38.76°) and (202) phase (2θ≈49.06°) appear on the diffractograms. The crystallite size increases with increasing annealing temperature. These modifications influence the microstructure, electrical and optical properties. The optical band gap energy decreases with increasing annealing temperature. These mean that the optical quality of CuO films is improved by annealing.

Electrical properties of Mg doped ZnO nanostructure annealed at different temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, R., E-mail: ruziana12@gmail.com; Mamat, M. H., E-mail: hafiz-030@yahoo.com; Rusop, M., E-mail: nanouitm@gmail.com

In this work, ZincOxide (ZnO) nanostructures doped with Mg were successfully grown on the glass substrate. Magnesium (Mg) metal element was added in the ZnO host which acts as a doping agent. Different temperature in range of 250°C to 500°C was used in order to investigate the effect of annealing temperature of ZnO thin films. Field Emission Scanning Electron Microscopy (FESEM) was used to investigate the physical characteristic of ZnO thin films. FESEM results have revealed that ZnO nanorods were grown vertically aligned. The structural properties were determined by using X-Ray Diffraction (XRD) analysis. XRD results showed Mg doped ZnOmore » thin have highest crystalinnity at 500°C annealing temperature. The electrical properties were investigating by using Current-Voltage (I-V) measurement. I-V measurement showed the electrical properties were varied at different annealing temperature. The annealing temperature at 500°C has the highest electrical conductance properties.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulutas, Cemal, E-mail: cemalulutas@hakkari.edu.tr; Gumus, Cebrail

2016-03-25

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 (E{sub g}) of the film was determined. XRD measurements reveal that the film is crystallized inmore » the wurtzite phase and changed to tetragonal Mn{sub 3}O{sub 4} 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.« less

Response of Gd 2 Ti 2 O 7 and La 2 Ti 2 O 7 to swift-heavy ion irradiation and annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Sulgiye; Lang, Maik; Tracy, Cameron L.

2015-07-01

Swift heavy ion (2 GeV 181Ta) irradiation-induced amorphization and temperature-induced recrystallization of cubic pyrochlore Gd2Ti2O7 (Fd3¯m) are compared with the response of a compositionally-similar material with a monoclinic-layered perovskite-type structure, La2Ti2O7 (P21). The averaged electronic energy loss, dE/dx, was 37 keV/nm and 35 keV/nm in Gd2Ti2O7 and La2Ti2O7, respectively. Systematic analysis of the structural modifications was completed using transmission electron microscopy, synchrotron X-ray diffraction, Raman spectroscopy, and small-angle X-ray scattering. Increasing ion-induced amorphization with increasing ion fluence was evident in the X-ray diffraction patterns of both compositions by a reduction in the intensity of the diffraction maxima concurrent with themore » growth in intensity of a broad diffuse scattering halo. Transmission electron microscopy analysis showed complete amorphization within ion tracks (diameter: ~10 nm) for the perovskite-type material; whereas a concentric, core–shell morphology was evident in the ion tracks of the pyrochlore, with an outer shell of disordered yet still crystalline material with the fluorite structure surrounding an amorphous track core (diameter: ~9 nm). The radiation response of both titanate oxides with the same stoichiometry can be understood in terms of differences in their structures and compositions. While the radiation damage susceptibility of pyrochlore A2B2O7 materials decreases as a function of the cation radius ratio rA/rB, the current study correlates this behavior with the stability field of monoclinic structures, where rLa/rTi > rGd/rTi. Isochronal annealing experiments of the irradiated materials showed complete recrystallization of La2Ti2O7 at 775 °C and of Gd2Ti2O7 at 850 °C. The annealing behavior is discussed in terms of enhanced damage recovery in La2Ti2O7, compared to the pyrochlore compounds Gd2Ti2O7. The difference in the recrystallization behavior may be related to structural constraints, i.e., reconstructing a low symmetry versus a high symmetry phase.« less

Fabrication of Planar Heterojunction Perovskite Solar Cells by Controlled Low-Pressure Vapor Annealing.

PubMed

Li, Yanbo; Cooper, Jason K; Buonsanti, Raffaella; Giannini, Cinzia; Liu, Yi; Toma, Francesca M; Sharp, Ian D

2015-02-05

A new method for achieving high efficiency planar CH3NH3I3-xClx perovskite photovoltaics, based on a low pressure, reduced temperature vapor annealing is demonstrated. Heterojunction devices based on this hybrid halide perovskite exhibit a top PCE of 16.8%, reduced J-V hysteresis, and highly repeatable performance without need for a mesoporous or nanocrystalline metal oxide layer. Our findings demonstrate that large hysteresis is not an inherent feature of planar heterojunctions, and that efficient charge extraction can be achieved with uniform halide perovskite materials with desired composition. X-ray diffraction, valence band spectroscopy, and transient absorption measurements of these thin films reveal that structural modifications induced by chlorine clearly dominate over chemical and electronic doping effects, without affecting the Fermi level or photocarrier lifetime in the material.

Structural and electrical properties of ferroelectric Na{sub 0.5} (Bi{sub 1-x}Pr{sub x} ){sub 0.5}TiO{sub 3} (x=0.00 and 0.10) ceramics synthesized by Sol-Gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shalini, K.; Muneeswaran, M.; Giridharan, N. V., E-mail: giri@nitt.edu

2016-05-23

Ferroelectric Na{sub 0.5}(Bi{sub 1-x}Pr{sub x}){sub 0.5}TiO{sub 3} (x=0.00, 0.10) ceramics have been synthesized through sol-gel method. The phase formation has been confirmed by X-ray diffraction analysis of ceramics annealed at 800°C. The relaxation mechanism is observed from variation of dielectric constant with respect to temperature and frequency. Substitution of Pr reduces vacancies and defects identified from leakage current measurements. Further, the polarization Vs electric field (P-E) measurements have been performed at room temperature.

Structure and magnetic properties of Sm1-xZrx Fe10Si2 (x=0.2-0.6) alloys

NASA Astrophysics Data System (ADS)

Gjoka, M.; Sarafidis, C.; Psycharis, V.; Devlin, E.; Niarchos, D.; Hadjipanayis, G.

2017-10-01

Structure and magnetic properties of Sm1-xZrxFe10Si2 (0.1 ≤ x ≤ 0.6) alloys have been characterized using X-ray diffraction, thermomagnetic analysis and Mössbauer spectroscopy. The formation of the tetragonal ThMn12 -type structure was been observed in all alloys, without further annealing. The Curie temperature decreases linearly with Zr substitution from 322 °C for x=0.1 to 395 °C for x=0.6. Mössbauer spectroscopy showed the iron hyperfine field values decrease with increasing Zr content, and also confirmed changes to the magnetic anisotropy with increasing Zr content observed by XRD on oriented samples.

Diffraction leveraged modulation of X-ray pulses using MEMS-based X-ray optics

DOEpatents

Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore

2016-08-09

A method and apparatus are provided for implementing Bragg-diffraction leveraged modulation of X-ray pulses using MicroElectroMechanical systems (MEMS) based diffractive optics. An oscillating crystalline MEMS device generates a controllable time-window for diffraction of the incident X-ray radiation. The Bragg-diffraction leveraged modulation of X-ray pulses includes isolating a particular pulse, spatially separating individual pulses, and spreading a single pulse from an X-ray pulse-train.

Cadmium sulfide rod-bundle structures decorated with nanoparticles from an inorganic/organic composite

NASA Astrophysics Data System (ADS)

Pan, Jun; Xi, Baojuan; Li, Jingfa; Yan, Yan; Li, Qianwen; Qian, Yitai

2011-08-01

We report a new morphology of wurzite cadmium sulfide with nanoparticles decorated on rod-bundle structures, which were synthesized via calcinations of an inorganic/organic composite at 400 °C in air. The composite was hydrothermally synthesized at 180 °C using thioglycolic acid (TGA) and cadmium acetate as starting materials. The structure, composition, and morphology of the prepared material were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, FT-IR spectrometry, photoluminescence spectrometry, and UV-visible spectrometry. Results indicated that the composite could be defined as CdS 0.65/Cd-TGA0.35. X-ray diffraction revealed that the annealed product is CdS with wurtizite phase. The diameter of the rod is about 150-400 nm and the length from the top to the bottom of the decorated nanoparticle is about 100 nm. The composite showed high intensity of photoluminescence with similar peak position, compared to that of wurtzite CdS, because of the structure defects.

Layer dependence of the superconducting transition temperature of HgBa2Can-1 CunO2 n+2+ δ

NASA Astrophysics Data System (ADS)

Scott, B. A.; Suard, E. Y.; Tsuei, C. C.; Mitzi, D. B.; McGuire, T. R.; Chen, B.-H.; Walker, D.

1994-09-01

High-pressure methods have been used to synthesize multiphase compositions in the Hg12{ n-1} n homologous series. The phase assemblages were examined by optical, electron diffraction and X-ray diffraction techniques, and their stoichiometries verified by electron microprobe. Transport and magnetic susceptibility measurements were combined with the results of the phase analysis to establish superconducting transition temperatures for both as-prepared and O 2- or Ar-annealed materials. It was found that the transition temperature peaks at Tc = 134 K for n = 3 and then decreases abruptly for n>4, reaching Tc<90 K for n⪖7.

Band-gap modulation via gallium substitution in cerium doped gadolinium aluminum garnet using a mixed fuel combustion approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tyagi, Mohit; Pitale, Shreyas S.; Ghosh, Manoranjan

2014-04-24

Cerium doped Gadolinium garnets (Gd{sub 3}Al{sub x}Ga{sub 5−x}O{sub 12} where 0≤x≤5) are synthesized via combustion synthesis using mixture of urea and glycine fuels. A 4h Post annealing at 1400 oC is found to be necessary for pure phase formation. Lattice spacing variation as a result of partial or total Ga substitution at Al site was mapped by X-ray diffraction. Photoluminescence emission of Ce shifts as a consequence of Ga substitution and therefore suggests a local re-adjustment of crystal field around activator site.

Synthesis of embedded titanium dioxide nanoparticles by oxygen ion implantation in titanium films

NASA Astrophysics Data System (ADS)

Rukade, Deepti. A.; Desai, C. A.; Kulkarni, Nilesh; Tribedi, L. C.; Bhattacharyya, Varsha

2013-02-01

Thin films of titanium of 100nm thickness are deposited on fused silica substrates. These films are implanted by oxygen ions with implantation energy of 60keV obtained from ECR based highly charged ion accelerator. The implanted films are later annealed in a tube furnace to establish nanophase formation. The post implanted annealed films are characterized by UV-Visible Spectroscopy and Glancing Angle X-ray Diffraction technique (GAXRD). The phase formed and particle size is determined by GAXRD. Nanoparticle formation is confirmed by the UV-VIS spectroscopic analysis that shows quantum size effects in the form of a blue shift in the band-gap energy of titanium-oxide.

Effect of annealing temperature on titania nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manikandan, K., E-mail: sanjaymani367@gmail.com; Arumugam, S., E-mail: sanjaymani367@gmail.com; Chandrasekaran, G.

2014-04-24

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

Physical metallurgy of metastable Bcc lanthanide-magnesium alloys for R = La, Gd, and Dy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herchenroeder, J.W.; Manfrinetti, P.; Gschneidner, K.A. Jr.

1989-09-01

Bcc La-Mg, Gd-Mg, and Dy-Mg alloys have been prepared by an ice water/acetone quench from liquid melts. Single-phase alloys could be retained in a window around the eutectoid composition: 13 to 22 at. pct Mg, 23.6 to 29 at. pct Mg, and 27 to 29 at. pct Mg for La, Gd, and Dy alloys, respectively. At the center of the windows, x-ray diffraction peaks are extremely sharp as in equilibrium bcc structures; however, as alloy composition is moved away from the eutectoid, line broadening is observed. Reversion of the bcc phase to the equilibrium microstructure for R-Mg alloys (R =more » La, Gd, or Dy) has been characterized by differential thermal analysis (DTA) or differential scanning calorimetry (DSC) and isothermal annealing. La-Mg alloys revert directly to {alpha}La (dhcp) + LaMg at about 350{degrees}C when heated at 10{degrees}C/min. In contrast, the Gd and Dy alloys revert by a two-step process: first, a transition to an intermediate distorted hcp phase between 300{degrees}C and 400{degrees}C, and, second, the relaxation of this phase to {alpha}R (hcp) + RMg at about 490{degrees}C when heated at 10{degrees}C/min. Isothermal annealing and high temperature x-ray diffraction confirm the nature of these reactions.« less

The effects of different heat treatment annealing on structural properties of LaFe11.5Si1.5 compound

NASA Astrophysics Data System (ADS)

Norizan, Yang Nurhidayah Asnida; Din, Muhammad Faiz Md; Zamri, Wan Fathul Hakim W.; Hashim, Fakroul Ridzuan; Jusoh, Mohd Taufik; Rahman, Mohd Rashid Abdul

2018-02-01

The cubic NaZn13-type LaFe13-xSix based compounds have been studied systematically and has become one of the most interesting systems for exploring large MCE. Its magnetic properties are strongly doping dependent and provides many of advantage compare to other as magnetic materials for magnetic refrigerator application. In other to produce high quality of cubic NaZn13-type structure, the structural properties of LaFe11.5Si1.5 compounds annealed at different temperature have been investigated. The LaFe11.5Si1.5 compounds was prepared by arc melting and annealed at two different heat treatment which are 1323 K for 14 days and 1523 K for 4 hour. The powder X-ray diffraction (XRD) shows that a short time and high temperature annealing process has benefits for the formation of the NaZn13-type phase compared to a long time and low temperature annealing process. This is shown by the weight fraction of cubic NaZn13- type structure increases from 80% for low temperature annealing to 83% for high temperature annealing. At the same time, high temperature annealing increase the main structure and decrease the impurity (α-Fe and LaFeSi). Furthermore, it can be clearly seen in the Rietveld refinement results that the lattice parameter is increase at the high temperature annealing because of more cubic NaZn13 is formed at higher temperature.

Effect of pressure-assisted thermal annealing on the optical properties of ZnO thin films.

PubMed

Berger, Danielle; Kubaski, Evaldo Toniolo; Sequinel, Thiago; da Silva, Renata Martins; Tebcherani, Sergio Mazurek; Varela, José Arana

2013-01-01

ZnO thin films were prepared by the polymeric precursor method. The films were deposited on silicon substrates using the spin-coating technique, and were annealed at 330 °C for 32 h under pressure-assisted thermal annealing and under ambient pressure. Their structural and optical properties were characterized, and the phases formed were identified by X-ray diffraction. No secondary phase was detected. The ZnO thin films were also characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, photoluminescence and ultraviolet emission intensity measurements. The effect of pressure on these thin films modifies the active defects that cause the recombination of deep level states located inside the band gap that emit yellow-green (575 nm) and orange (645 nm) photoluminescence. Copyright © 2012 John Wiley & Sons, Ltd.

KF addition to Cu2SnS3 thin films prepared by sulfurization process

NASA Astrophysics Data System (ADS)

Nakashima, Mitsuki; Fujimoto, Junya; Yamaguchi, Toshiyuki; Sasano, Junji; Izaki, Masanobu

2017-04-01

Cu2SnS3 thin films were fabricated by sulfurization with KF addition and applied to photovoltaic devices. Two methods, two-stage annealing and the use of four-layer precursors, were employed, and the quantity of NaF and KF and the annealing temperature were changed. By electron probe microanalysis (EPMA), the Cu/Sn mole ratio was found to range from 0.81 to 1.51. The X-ray diffraction (XRD) patterns and Raman spectra indicated that the fabricated thin films had a monoclinic Cu2SnS3 structure. The Cu2SnS3 thin films fabricated by two-stage annealing had a close-packed structure and a pinhole-free surface morphology. The best solar cell in this study showed V oc of 293 mV, which surpassed the previously reported value.

Synthesis, characterization and antistructure modeling of Ni nano ferrite

NASA Astrophysics Data System (ADS)

Kane, S. N.; Raghuvanshi, S.; Satalkar, M.; Reddy, V. R.; Deshpande, U. P.; Tatarchuk, T. R.; Mazaleyrat, F.

2018-05-01

We report the role played by cation distribution in determining magnetic properties by comparing dry gel, thermally annealed Ni ferrite prepared by sol-gel auto-combustion technique. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Mössbauer spectroscopy were used to characterize the samples. Both XRD and Mössbauer measurements validate the formation of spinel phase with grain diameter 39.13-45.53 nm. First time antistructural modeling for Ni ferrite is reported to get information on active surface centers. Decrease of Debye temperature θD in annealed sample shows enhancement of lattice vibrations. With thermal annealing experimental and Néel magnetic moment (nBe, nBN) increases, suggesting migration of Ni2+ from B to A site with concurrent migration of Fe3+ from A to B site (non-equilibrium cationic distribution), affecting magnetic properties.

Fabrication, characterization and annealing of polymer-fullerene bulk heterojunction organic solar cells

NASA Astrophysics Data System (ADS)

Sharma, Trupti; Singhal, R.; Vishnoi, R.; Biswas, S. K.

2017-05-01

The structural and optical properties of bulk heterojunction (BHJ) organic solar cell devices have been studied before and after heat treatment. The BHJ structure is fabricated by making the blend of Poly [3-hexylthiophene] (P3HT) and Phenyl C61 butyric acid methyl ester (PCBM) for active layer. After the heat treatment at 140 °C temperature, the device is characterized by X-ray diffraction (XRD) measurement, Raman spectroscopy and UV-visible absorption spectroscopy. The reduced intensity of XRD peak corresponding to (100) plane and decreased crystallite size was observed after annealing. The Raman peak intensity corresponding to C=C stretching mode and optical absorption peak intensity is also found to be reduced after the heat treatment to the device. The diminished intensitiesafter annealing may be due to diffusion of Al into active layer.

Cryptomelane-type manganese oxide (KMn8O16) nanorods cathode materials synthesized by a rheological phase for lithium ion batteries

NASA Astrophysics Data System (ADS)

Zheng, Hao; Wang, Ting; Zhao, Rongfei; Chen, Jinsong; Li, Lin

2018-01-01

Cryotolerance-type manganese oxide (KMn8O16) nanorods were prepared for the first time by a rheological phase reaction method. The KMn8O16 samples were characterized by X-ray diffraction, scanning electron microscopy, the effects of different annealed temperatures on the morphologies and electrochemical properties of the final products were systematically investigated. The result that the annealed samples exhibit the superior electrochemical performances compared to the unannealed sample. The KMn8O16 nanorods annealed at 400 °C show the highest reversible discharge capacity (147.9 mAh/g even after 80 cycles) at current density of 50 mA/g and the best cycling stability. These results indicate that the KMn8O16 nanorods could be a promising cathode material for lithium ion batteries.

Epitaxial growth of iridate pyrochlore Nd 2Ir 2O 7 films

DOE PAGES

Gallagher, J. C.; Esser, B. D.; Morrow, R.; ...

2016-02-29

Epitaxial films of the pyrochlore Nd 2Ir 2O 7 have been grown on (111)-oriented yttria-stabilized zirconia (YSZ) substrates by off-axis sputtering followed by post-growth annealing. X-ray diffraction (XRD) results demonstrate phase-pure epitaxial growth of the pyrochlore films on YSZ. Scanning transmission electron microscopy (STEM) investigation of an Nd 2Ir 2O 7 film with a short post-annealing provides insight into the mechanism for crystallization of Nd 2Ir 2O 7 during the post-annealing process. STEM images reveal clear pyrochlore ordering of Nd and Ir in the films. As a result, the epitaxial relationship between the YSZ and Nd 2Ir 2O 7 ismore » observed clearly while some interfacial regions show a thin region with polycrystalline Ir nanocrystals.« less

Preparation and Characterization of Niobium Doped Lead-Telluride Glass Ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sathish, M.; Eraiah, B.; Anavekar, R. V.

2011-07-15

Niobium-lead-telluride glass ceramics of composition xNb{sub 2}O{sub 5}-(20-x) pbO-80TeO{sub 2}(where x = 0.1 mol% to 0.5 mol%) were prepared by using conventional melt quenching method. The prepared glass samples were initially amorphous in nature after annealed at 400 deg. c all samples were crystallized. This was confined by X-ray diffraction and scanning electron microscopy. The particle size of these glass ceramics have been calculated by using Debye-Scherer formula and the particle size is in the order of 15 nm to 60 nm. The scanning electron microscopy (SEM) photograph shows the presence of needle-like crystals in these samples.

Structural analysis of emerging ferrite: Doped nickel zinc ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Rajinder; Kumar, Hitanshu; Singh, Ragini Raj

2015-08-28

Ni{sub 0.6-x}Zn{sub 0.4}Co{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.033, 0.264) nanoparticles were synthesized by sol-gel method and annealed at 900°C. Structural properties of all prepared samples were examined with X-ray diffraction (XRD). The partial formation of hematite (α-Fe{sub 2}O{sub 3}) secondary phase with spinel phase cubic structure of undoped and cobalt doped nickel zinc ferrite was found by XRD peaks. The variation in crystallite size and other structural parameters with cobalt doping has been calculated for most prominent peak (113) of XRD and has been explained on the basis of cations ionic radii difference.

Structural and electrical characterization of annealed Si1-xCx/SiC thin film prepared by magnetron sputtering

NASA Astrophysics Data System (ADS)

Huang, Shi-Hua; Liu, Jian

2014-05-01

Si-rich Si1—xCx /SiC multilayer thin films are prepared using magnetron sputtering, subsequently followed by thermal annealing in the range of 800-1200 °C. The influences of annealing temperature (Ta) on the formation of Si and/or SiC nanocrystals (NCs) and on the electrical characteristics of the multilayer film are investigated by using a variety of analytical techniques, including X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectrometry (FT-IR), current—voltage (I—V) technique, and capacitance-voltage (C—V) technique. XRD and Raman analyses indicate that Si NCs begin to form in samples for Ta >= 800 °C. At annealing temperatures of 1000 °C or higher, the formation of Si NCs is accompanied by the formation of SiC NCs. With the increase in the annealing temperature, the shift of FT-IR Si—C bond absorption spectra toward a higher wave number along with the change of band shape can be explained by a Si—C transitional phase between the loss of substitutional carbon and the formation of SiC precipitates and a precursor for the growth of SiC crystalline. The C—V and I—V results indicate that the interface quality of Si1—xCx/SiC multilayer film is improved significantly and the leakage current is reduced rapidly for Ta >= 1000 °C, which can be ascribed to the formation of Si and SiC NCs.

Band-gap modulation via gallium substitution in cerium doped gadolinium aluminum garnet using a mixed fuel combustion approach

NASA Astrophysics Data System (ADS)

Tyagi, Mohit; Pitale, Shreyas S.; Ghosh, Manoranjan; Shinde, Seema

2014-04-01

Cerium doped Gadolinium garnets (Gd3AlxGa5-xO12 where 0≤x≤5) are synthesized via combustion synthesis using mixture of urea and glycine fuels. A 4h Post annealing at 1400 oC is found to be necessary for pure phase formation. Lattice spacing variation as a result of partial or total Ga substitution at Al site was mapped by X-ray diffraction. Photoluminescence emission of Ce shifts as a consequence of Ga substitution and therefore suggests a local re-adjustment of crystal field around activator site.

Lanthanum aluminum oxide thin-film dielectrics from aqueous solution.

PubMed

Plassmeyer, Paul N; Archila, Kevin; Wager, John F; Page, Catherine J

2015-01-28

Amorphous LaAlO3 dielectric thin films were fabricated via solution processing from inorganic nitrate precursors. Precursor solutions contained soluble oligomeric metal-hydroxyl and/or -oxo species as evidenced by dynamic light scattering (DLS) and Raman spectroscopy. Thin-film formation was characterized as a function of annealing temperature using Fourier transform infrared (FTIR), X-ray diffraction (XRD), X-ray reflectivity (XRR), scanning electron microscopy (SEM), and an array of electrical measurements. Annealing temperatures ≥500 °C result in thin films with low leakage-current densities (∼1 × 10(-8) A·cm(-2)) and dielectric constants ranging from 11.0 to 11.5. When incorporated as the gate dielectric layer in a-IGZO thin-film transistors (TFTs), LaAlO3 thin films annealed at 600 °C in air yielded TFTs with relatively low average mobilities (∼4.5 cm(2)·V(-1)·s(-1)) and high turn-on voltages (∼26 V). Interestingly, reannealing the LaAlO3 in 5%H2/95%N2 at 300 °C before deposition of a-IGZO channel layers resulted in TFTs with increased average mobilities (11.1 cm(2)·V(-1)·s(-1)) and lower turn-on voltages (∼6 V).

Effects of crystallization and dopant concentration on the emission behavior of TiO2:Eu nanophosphors

PubMed Central

2012-01-01

Uniform, spherical-shaped TiO2:Eu nanoparticles with different doping concentrations have been synthesized through controlled hydrolysis of titanium tetrabutoxide under appropriate pH and temperature in the presence of EuCl3·6H2O. Through air annealing at 500°C for 2 h, the amorphous, as-grown nanoparticles could be converted to a pure anatase phase. The morphology, structural, and optical properties of the annealed nanostructures were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy [EDS], and UV-Visible diffuse reflectance spectroscopy techniques. Optoelectronic behaviors of the nanostructures were studied using micro-Raman and photoluminescence [PL] spectroscopies at room temperature. EDS results confirmed a systematic increase of Eu content in the as-prepared samples with the increase of nominal europium content in the reaction solution. With the increasing dopant concentration, crystallinity and crystallite size of the titania particles decreased gradually. Incorporation of europium in the titania particles induced a structural deformation and a blueshift of their absorption edge. While the room-temperature PL emission of the as-grown samples is dominated by the 5D0 - 7Fj transition of Eu+3 ions, the emission intensity reduced drastically after thermal annealing due to outwards segregation of dopant ions. PMID:22214494

High-Efficiency Small Molecule-Based Bulk-Heterojunction Solar Cells Enhanced by Additive Annealing.

PubMed

Li, Lisheng; Xiao, Liangang; Qin, Hongmei; Gao, Ke; Peng, Junbiao; Cao, Yong; Liu, Feng; Russell, Thomas P; Peng, Xiaobin

2015-09-30

Solvent additive processing is important in optimizing an active layer's morphology and thus improving the performance of organic solar cells (OSCs). In this study, we find that how 1,8-diiodooctane (DIO) additive is removed plays a critical role in determining the film morphology of the bulk heterojunction OSCs in inverted structure based on a porphyrin small molecule. Different from the cases reported for polymer-based OSCs in conventional structures, the inverted OSCs upon the quick removal of the additive either by quick vacuuming or methanol washing exhibit poorer performance. In contrast, the devices after keeping the active layers in ambient pressure with additive dwelling for about 1 h (namely, additive annealing) show an enhanced power conversion efficiency up to 7.78% with a large short circuit current of 19.25 mA/cm(2), which are among the best in small molecule-based solar cells. The detailed morphology analyses using UV-vis absorption spectroscopy, grazing incidence X-ray diffraction, resonant soft X-ray scattering, and atomic force microscopy demonstrate that the active layer shows smaller-sized phase separation but improved structure order upon additive annealing. On the contrary, the quick removal of the additive either by quick vacuuming or methanol washing keeps the active layers in an earlier stage of large scaled phase separation.

Study of annealing effect on the growth of ZnO nanorods on ZnO seed layers

NASA Astrophysics Data System (ADS)

Sannakashappanavar, Basavaraj S.; Pattanashetti, Nandini A.; Byrareddy, C. R.; Yadav, Aniruddh Bahadur

2018-04-01

A zinc oxide (ZnO) seed layer was deposited on the SiO2/Si substrate by RF sputtering. To study the effect of annealing, the seed layers were classified into annealed and unannealed thin films. Annealing of the seed layers was carried at 450°C. Surface morphology of the seed layers were studied by Atomic force microscopy. ZnO nanorods were then grown on both the types of seed layer by hydrothermal method. The morphology and the structural properties of the nanorods were characterized by X-ray diffraction and Scanning electron microscopy. The effect of seed layer annealing on the growth and orientation of the ZnO nanorods were clearly examined on comparing with the nanorods grown on unannealed seed layer. The nanorods grown on annealed seed layers were found to be well aligned and oriented. Further, the I-V characteristic study was carried out on these aligned nanorods. The results supports positively for the future work to further enhance the properties of developed nanorods for their wide applications in electronic and optoelectronic devices.

Enhancement of optical transmittance and electrical resistivity of post-annealed ITO thin films RF sputtered on Si

NASA Astrophysics Data System (ADS)

Ali, Ahmad Hadi; Hassan, Zainuriah; Shuhaimi, Ahmad

2018-06-01

This paper reports on the enhancement of optical transmittance and electrical resistivity of indium tin oxide (ITO) transparent conductive oxides (TCO) deposited by radio frequency (RF) sputtering on Si substrate. Post-annealing was conducted on the samples at temperature ranges of 500-700 °C. From X-ray diffraction analysis (XRD), ITO (2 2 2) peak was observed after post-annealing indicating crystallization phase of the films. From UV-vis measurements, the ITO thin film shows highest transmittance of more than 90% at post-annealing temperature of 700 °C as compared to the as-deposited thin films. From atomic force microscope (AFM), the surface roughness becomes smoother after post-annealing as compared to the as-deposited. The lowest electrical resistivity for ITO sample is 6.68 × 10-4 Ω cm after post-annealed at 700 °C that are contributed by high carrier concentration and mobility. The improved structural and surface morphological characteristics helps in increasing the optical transmittance and reducing the electrical resistivity of the ITO thin films.

FAST TRACK COMMUNICATION: Directional annealing-induced texture in melt-spun (Sm12Co88)99Nb1 alloy

NASA Astrophysics Data System (ADS)

Jayaraman, T. V.; Rogge, P.; Shield, J. E.

2010-07-01

Developing texture in nanocrystalline permanent magnet alloys is of significant importance. Directional annealing is shown to produce texture in the permanent magnet alloy (Sm12Co88)99Nb1. Melt spinning produced isotropic grain structures of the hard magnetic metastable SmCo7 phase, with grain sizes of ~300 nm. Conventional annealing of melt-spun (Sm12Co88)99Nb1 alloy produced Sm2Co17 phase with random crystallographic orientation. Directional annealing of melt-spun (Sm12Co88)99Nb1 alloy, with appropriate combinations of annealing temperature and translational velocity, produced Sm2Co17 phase with (0 0 0 6) in-plane texture, as determined by x-ray diffraction analysis and magnetic measurements. The magnetization results show out-of-plane remanence higher than the in-plane remanence resulting in the degree of 'magnetic' texture in the order of 25-40%. Coercivity values above 2 kOe were maintained. The texture development via directional annealing while minimizing exposure to elevated temperatures provides a new route to anisotropic high-energy permanent magnets.

Thermal engineering of FAPbI3 perovskite material via radiative thermal annealing and in situ XRD

PubMed Central

Pool, Vanessa L.; Dou, Benjia; Van Campen, Douglas G.; Klein-Stockert, Talysa R.; Barnes, Frank S.; Shaheen, Sean E.; Ahmad, Md I.; van Hest, Maikel F. A. M.; Toney, Michael F.

2017-01-01

Lead halide perovskites have emerged as successful optoelectronic materials with high photovoltaic power conversion efficiencies and low material cost. However, substantial challenges remain in the scalability, stability and fundamental understanding of the materials. Here we present the application of radiative thermal annealing, an easily scalable processing method for synthesizing formamidinium lead iodide (FAPbI3) perovskite solar absorbers. Devices fabricated from films formed via radiative thermal annealing have equivalent efficiencies to those annealed using a conventional hotplate. By coupling results from in situ X-ray diffraction using a radiative thermal annealing system with device performances, we mapped the processing phase space of FAPbI3 and corresponding device efficiencies. Our map of processing-structure-performance space suggests the commonly used FAPbI3 annealing time, 10 min at 170 °C, can be significantly reduced to 40 s at 170 °C without affecting the photovoltaic performance. The Johnson-Mehl-Avrami model was used to determine the activation energy for decomposition of FAPbI3 into PbI2. PMID:28094249

Effect of Annealing Treatments on the Microstructure, Mechanical Properties and Corrosion Behavior of Direct Metal Laser Sintered Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Xu, Yangzi; Lu, Yuan; Sundberg, Kristin L.; Liang, Jianyu; Sisson, Richard D.

2017-05-01

An experimental investigation on the effects of post-annealing treatments on the microstructure, mechanical properties and corrosion behavior of direct metal laser sintered Ti-6Al-4V alloys has been conducted. The microstructure and phase evolution as affected by annealing treatment temperature were examined through scanning electron microscopy and x-ray diffraction. The tensile properties and Vickers hardness were measured and compared to the commercial Grade 5 Ti-6Al-4V alloy. Corrosion behavior of the parts was analyzed electrochemically in simulated body fluid at 37 °C. It was found out that the as-printed parts mainly composed of non-equilibrium α' phase. Annealing treatment allowed the transformation from α' to α phase and the development of β phase. The tensile test results indicated that post-annealing treatment could improve the ductility and decrease the strength. The as-printed Ti-6Al-4V part exhibits inferior corrosion resistance compared to the commercial alloy, and post-annealing treatment can reduce its susceptibility to corrosion by reducing the two-phase interface area.

Effect of thermal annealing on the structure and magnetism of Fe-doped ZnO nanocrystals synthesized by solid state reaction

NASA Astrophysics Data System (ADS)

Wang, Dong; Chen, Z. Q.; Wang, D. D.; Gong, J.; Cao, C. Y.; Tang, Z.; Huang, L. R.

2010-11-01

High purity Fe 2O 3/ZnO nanocomposites were annealed in air at different temperatures between 100 and 1200 °C to get Fe-doped ZnO nanocrystals. The structure and grain size of the Fe 2O 3/ZnO nanocomposites were investigated by X-ray diffraction 2θ scans. Annealing induces an increase of the grain size from 25 to 195 nm and appearance of franklinite phase of ZnFe 2O 4. Positron annihilation measurements reveal large number of vacancy defects in the interface region of the Fe 2O 3/ZnO nanocomposites, and they are gradually recovered with increasing annealing temperature. After annealing at temperatures higher than 1000 °C, the number of vacancies decreases to the lower detection limit of positrons. Room temperature ferromagnetism can be observed in Fe-doped ZnO nanocrystals using physical properties measurement system. The ferromagnetism remains after annealing up to 1000 °C, suggesting that it is not related with the interfacial defects.

Thermal engineering of FAPbI 3 perovskite material via radiative thermal annealing and in situ XRD

DOE PAGES

Pool, Vanessa L.; Dou, Benjia; Van Campen, Douglas G.; ...

2017-01-17

Lead halide perovskites have emerged as successful optoelectronic materials with high photovoltaic power conversion efficiencies and low material cost. However, substantial challenges remain in the scalability, stability and fundamental understanding of the materials. Here we present the application of radiative thermal annealing, an easily scalable processing method for synthesizing formamidinium lead iodide (FAPbI 3) perovskite solar absorbers. Devices fabricated from films formed via radiative thermal annealing have equivalent efficiencies to those annealed using a conventional hotplate. By coupling results from in situ X-ray diffraction using a radiative thermal annealing system with device performances, we mapped the processing phase space ofmore » FAPbI 3 and corresponding device efficiencies. Our map of processing-structure-performance space suggests the commonly used FAPbI 3 annealing time, 10 min at 170 degrees C, can be significantly reduced to 40 s at 170 degrees C without affecting the photovoltaic performance. Lastly, the Johnson-Mehl-Avrami model was used to determine the activation energy for decomposition of FAPbI 3 into PbI 2.« less

CdO thin films based on the annealing temperature differences prepared by sol-gel method and their heterojunction devices

NASA Astrophysics Data System (ADS)

Soylu, M.; Yazici, T.

2017-12-01

Undoped CdO films were prepared on glass substrate and p-type silicon wafer using sol-gel spin coating method. The structural and optical properties of the films were investigated as a function of the annealing temperature. X-ray diffraction (XRD) patterns reveal that the films are formed from CdO with cubic crystal structure and (1 1 1) preferred orientation. It is seen that good crystallinity is due to the high annealing temperature. The surface morphology of the CdO films was found to be depending on the annealing temperature, showing cauliflower like structure. Optical band gaps for annealing temperature of 250 °C and 450 °C were found to be 2.49 eV and 2.27 eV, respectively, showing a decrease with raising temperature. Optics parameters such as extinction coefficient, refractive index, and surface-volume energy loss were determined with spectrophotometric analysis as a function of annealing temperature. CdO/p-Si heterojunction structure showed weak rectifying behavior. The diode parameters were found to be depending on annealing temperature. The results are encouraging to get better conjunction with CdO thin film component at optimize annealing temperature.

Influence of Annealing Duration on the Growth of V2O5 Nanorods Synthesized by Spray Pyrolysis Technique

NASA Astrophysics Data System (ADS)

Abd-Alghafour, N. M.; Ahmed, Naser M.; Hassan, Z.; Abubakar, D.; Bououdina, M.

2016-06-01

This paper deals with the investigation of annealing effects on the structural, morphological and optical properties of V2O5 nanorods (NRs) grown on the glass substrates by using chemical spray pyrolysis technique. The as-prepared samples were annealed at 500∘ for 40, 60 and 120 min in a quartz tube furnace. The high resolution X-ray diffraction (XRD) analysis revealed V2O5 NRs with preferred orientation along (001) plane. The crystallite size of the V2O5 NRs was increased by increasing the annealing duration. The morphological observations using field emission scanning electron microscope (FESEM) displayed NRs structures whose diameter and length were found to increase with increase of the annealing duration. The transmission electron microscopy (TEM) analysis confirmed the orthorhombic structures of the NRs. The AFM measurements indicated an increase of the average surface roughness by increasing the annealing time. The Raman spectroscopy revealed V-O-V phonon mode in the NRs annealed for 120 min. The optical bandgap was found in the range 2.6-2.58eV and observed to decrease with various duration annealed.

Temperature dependent surface and spectral modifications of nano V2O5 films

NASA Astrophysics Data System (ADS)

Manthrammel, M. Aslam; Fatehmulla, A.; Al-Dhafiri, A. M.; Alshammari, A. S.; Khan, Aslam

2017-03-01

Nanocrystalline V2O5 films have been deposited on glass substrates at 300°C substrate temperature using thermal evaporation technique and were subjected to thermal annealing at different temperatures 350, 400, and 550°C. X-ray diffraction (XRD) spectra exhibit sharper and broader characteristic peaks respectively indicating the rearrangement of nanocrystallite phases with annealing temperatures. Other phases of vanadium oxides started emerging with the rise in annealing temperature and the sample converted completely to VO2 (B) phase at 550°C annealing. FESEM images showed an increase in crystallite size with 350 and 400°C annealing temperatures followed by a decrease in crystallite size for the sample annealed at 550°C. Transmission spectra showed an initial redshift of the fundamental band edge with 350 and 400°C while a blue shift for the sample annealed at 550°C, which was in agreement with XRD and SEM results. The films exhibited smart window properties as well as nanorod growth at specific annealing temperatures. Apart from showing the PL and defect related peaks, PL studies also supported the observations made in the transmission spectra.

Effect of annealing on Curie temperature and phase transition in La{sub 0.55}Sr{sub 0.08}Mn{sub 0.37}O{sub 3} epitaxial films grown on SrTiO{sub 3} (100) substrates by reactive radio frequency magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ichinose, T.

2016-08-15

Mn-poor LaSrMnO{sub 3} (LSMO) epitaxial films were grown on SrTiO{sub 3} (100) substrates by radio frequency magnetron sputtering in an argon and oxygen gas mix, and then the samples were annealed in air at various temperatures (T{sub a}). 2 theta-chi X-ray diffraction mapping, nano-beam diffraction analysis through transmission electron microscopy, and electron back scatter diffraction through scanning electron microscopy revealed that the crystal symmetry of the LSMO films changed from monoclinic/orthorhombic to rhombohedral on annealing in air. Curie temperature (T{sub C}) of the LSMO films was found to increase with increasing T{sub a}, and become higher than the room temperaturemore » at T{sub a} ≥ 861 °C, indicating that the cause of these changes was the filling of oxygen and the transition of the crystal symmetry into rhombohedral. - Highlights: •Mn-poor LSMO changed from monoclinic/orthorhombic to rhombohedral by oxygen supply. •Mn-poor LSMO was increased T{sub C} by changed crystal symmetry, and it showed T{sub C} above RT. •Annealed in air effectively supplied O{sub 2} more than O{sub 2} gas during sputtering •EBSD is useful to evaluate crystal symmetry of complex oxide film from the substrate.« less

Sintering behavior of spin-coated FePt and FePtAu nanoparticles

NASA Astrophysics Data System (ADS)

Kang, Shishou; Jia, Zhiyong; Zoto, I.; Reed, D.; Nikles, David E.; Harrell, J. W.; Thompson, Gregory; Mankey, Gary; Krishnamurthy, Vemuru V.; Porcar, L.

2006-04-01

FePt and [FePt]95Au5 nanoparticles with an average size of about 4 nm were chemically synthesized and spin coated onto silicon substrates. Samples were subsequently thermally annealed at temperatures ranging from 250 to 500 °C for 30 min. Three-dimensional structural characterization was carried out with small-angle neutron scattering (SANS) and small-angle x-ray diffraction (SAXRD) measurements. For both FePt and [FePt]95Au5 particles before annealing, SANS measurements gave an in-plane coherence length parameter a=7.3 nm, while SAXRD measurements gave a perpendicular coherence length parameter c=12.0 nm. The ratio of c/a is about 1.64, indicating the as-made particle array has a hexagonal close-packed superstructure. For both FePt and FePtAu nanoparticles, the diffraction peaks shifted to higher angles and broadened with increasing annealing temperature. This effect corresponds to a shrinking of the nanoparticle array, followed by agglomeration and sintering of the nanoparticles, resulting in the eventual loss of positional order with increasing annealing temperature. The effect is more pronounced for FePtAu than for FePt. Dynamic coercivity measurements show that the FePtAu nanoparticles have both higher intrinsic coercivity and higher switching volume at the same annealing temperature. These results are consistent with previous studies that show that additive Au both lowers the chemical ordering temperature and promotes sintering.

Behavior of Sn atoms in GeSn thin films during thermal annealing: Ex-situ and in-situ observations

NASA Astrophysics Data System (ADS)

Takase, Ryohei; Ishimaru, Manabu; Uchida, Noriyuki; Maeda, Tatsuro; Sato, Kazuhisa; Lieten, Ruben R.; Locquet, Jean-Pierre

2016-12-01

Thermally induced crystallization processes for amorphous GeSn thin films with Sn concentrations beyond the solubility limit of the bulk crystal Ge-Sn binary system have been examined by X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, and (scanning) transmission electron microscopy. We paid special attention to the behavior of Sn before and after recrystallization. In the as-deposited specimens, Sn atoms were homogeneously distributed in an amorphous matrix. Prior to crystallization, an amorphous-to-amorphous phase transformation associated with the rearrangement of Sn atoms was observed during heat treatment; this transformation is reversible with respect to temperature. Remarkable recrystallization occurred at temperatures above 400 °C, and Sn atoms were ejected from the crystallized GeSn matrix. The segregation of Sn became more pronounced with increasing annealing temperature, and the ejected Sn existed as a liquid phase. It was found that the molten Sn remains as a supercooled liquid below the eutectic temperature of the Ge-Sn binary system during the cooling process, and finally, β-Sn precipitates were formed at ambient temperature.

P-type single-crystalline ZnO films obtained by (N,O) dual implantation through dynamic annealing process

NASA Astrophysics Data System (ADS)

Zhang, Zhiyuan; Huang, Jingyun; Chen, Shanshan; Pan, Xinhua; Chen, Lingxiang; Ye, Zhizhen

2016-12-01

Single-crystalline ZnO films were grown on a-plane sapphire substrates by plasma-assisted molecular beam epitaxy technique. The films have been implanted with fixed fluence of 120 keV N and 130 keV O ions at 460 °C. Hall measurements show that the dually-implanted single-crystalline ZnO films exhibit p-type characteristics with hole concentration in the range of 2.1 × 1018-1.1 × 1019 cm-3, hole mobilities between 1.6 and 1.9 cm2 V-1 s-1, and resistivities in the range of 0.353-1.555 Ω cm. The ZnO films exhibit (002) (c-plane) orientation as identified by the X-ray diffraction pattern. It is confirmed that N ions were effectively implanted by SIMS results. Raman spectra, polarized Raman spectra, and X-ray photoelectron spectroscopy results reflect that the concentration of oxygen vacancies is reduced, which is attributed to O ion implantation. It is concluded that N and O implantation and dynamic annealing play a critical role in forming p-type single-crystalline ZnO films.

Synthesis and characterization of (3-Aminopropyl)trimethoxy-silane (APTMS) functionalized Gd2O3:Eu(3+) red phosphor with enhanced quantum yield.

PubMed

Jain, Akhil; Hirata, G A; Farías, M H; Castillón, F F

2016-02-12

We report the surface modification of nanocrystalline Gd2O3:Eu(3+) phosphor by (3-Aminopropyl)trimethoxysilane (APTMS). The nanoparticles were first coated with silica using the Stöber process, and then annealed at 650 °C for 2 h. Afterwards, APTMS was functionalized onto the silica layer to obtain Gd2O3:Eu(3+) nanoparticles bearing amine groups on the surface. The effect of silica coating, and the subsequent annealing process on the crystallization of the nanophosphor were analyzed by x-ray diffraction (XRD). High-resolution transmission electron microscopy (HR-TEM) confirmed the presence of a silica layer of ∼45 nm thickness. X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of silica and the amine groups. Photoluminescence (PL) analysis demonstrated an increased emission after functionalization of nanoparticles. Absolute quantum yield (QY) measurements revealed an 18% enhancement in QY in functionalized nanoparticles compared with unmodified nanoparticles, which is of great importance for their biomedical applications.

Synthesis and characterization of (3-Aminopropyl)trimethoxy-silane (APTMS) functionalized Gd2O3:Eu3+ red phosphor with enhanced quantum yield

NASA Astrophysics Data System (ADS)

Jain, Akhil; Hirata, G. A.; Farías, M. H.; Castillón, F. F.

2016-02-01

We report the surface modification of nanocrystalline Gd2O3:Eu3+ phosphor by (3-Aminopropyl)trimethoxysilane (APTMS). The nanoparticles were first coated with silica using the Stöber process, and then annealed at 650 °C for 2 h. Afterwards, APTMS was functionalized onto the silica layer to obtain Gd2O3:Eu3+ nanoparticles bearing amine groups on the surface. The effect of silica coating, and the subsequent annealing process on the crystallization of the nanophosphor were analyzed by x-ray diffraction (XRD). High-resolution transmission electron microscopy (HR-TEM) confirmed the presence of a silica layer of ∼45 nm thickness. X-ray photoelectron (XPS) and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of silica and the amine groups. Photoluminescence (PL) analysis demonstrated an increased emission after functionalization of nanoparticles. Absolute quantum yield (QY) measurements revealed an 18% enhancement in QY in functionalized nanoparticles compared with unmodified nanoparticles, which is of great importance for their biomedical applications.

On the Discontinuity of Polycrystalline Silicon Thin Films Realized by Aluminum-Induced Crystallization of PECVD-Deposited Amorphous Si

NASA Astrophysics Data System (ADS)

Pan, Qingtao; Wang, Tao; Yan, Hui; Zhang, Ming; Mai, Yaohua

2017-04-01

Crystallization of glass/Aluminum (50, 100, 200 nm) /hydrogenated amorphous silicon (a-Si:H) (50, 100, 200 nm) samples by Aluminum-induced crystallization (AIC) is investigated in this article. After annealing and wet etching, we found that the continuity of the polycrystalline silicon (poly-Si) thin films was strongly dependent on the double layer thicknesses. Increasing the a-Si:H/Al layer thickness ratio would improve the film microcosmic continuity. However, too thick Si layer might cause convex or peeling off during annealing. Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) are introduced to analyze the process of the peeling off. When the thickness ratio of a-Si:H/Al layer is around 1 to 1.5 and a-Si:H layer is less than 200 nm, the poly-Si film has a good continuity. Hall measurements are introduced to determine the electrical properties. Raman spectroscopy and X-ray diffraction (XRD) results show that the poly-Si film is completely crystallized and has a preferential (111) orientation.

Thickness and annealing effects on thermally evaporated InZnO thin films for gas sensors and blue, green and yellow emissive optical devices

NASA Astrophysics Data System (ADS)

Sugumaran, Sathish; Jamlos, Mohd Faizal; Ahmad, Mohd Noor; Bellan, Chandar Shekar; Sivaraj, Manoj

2016-08-01

Indium zinc oxide (InZnO) thin films with thicknesses of 100 nm and 200 nm were deposited on glass plate by thermal evaporation technique. Fourier transform infrared spectra showed a strong metal-oxide bond. X-ray diffraction patterns revealed amorphous nature for as-deposited film whereas polycrystalline structure for annealed films. Scanning electron microscope images showed a uniform distribution of spherical shape grains. Grain size was found to be higher for 200 nm film than 100 nm film. The presence of elements (In, Zn and O) was confirmed from energy dispersive X-ray analysis. Photoluminescence study of 200 nm film showed a blue, blue-green and blue-yellow emission whereas 100 nm film showed a broad green and green-yellow emissions. Both 100 nm and 200 nm films showed good oxygen sensitivity from room temperature to 400 °C. The observed optical and sensor results indicated that the prepared InZnO films are highly potential for room temperature gas sensor and blue, green and yellow emissive opto-electronic devices.

Synthesis of high-oxidation Y-Ba-Cu-O phases in superoxygenated thin films

NASA Astrophysics Data System (ADS)

Zhang, H.; Gauquelin, N.; McMahon, C.; Hawthorn, D. G.; Botton, G. A.; Wei, J. Y. T.

2018-03-01

It is known that solid-state reaction in high-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large surface-to-volume ratio, are more reactive thermodynamically. Epitaxial thin films of YBa2Cu3O7 -δ grown by pulsed laser deposition are annealed at up to 700 atm O2 and 900 ∘C , in conjunction with Cu enrichment by solid-state diffusion. The films show the clear formation of Y2Ba4Cu7O15 -δ and Y2Ba4Cu8O16 as well as regions of YBa2Cu5O9 -δ and YBa2Cu6O10 -δ phases, according to scanning transmission electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Similarly annealed YBa2Cu3O7 -δ powders show no phase conversion. Our results demonstrate a route of synthesis towards discovering more complex phases of cuprates and other superconducting oxides.

Surface microstructures and corrosion resistance of Ni-Ti-Nb shape memory thin films

NASA Astrophysics Data System (ADS)

Li, Kun; Li, Yan; Huang, Xu; Gibson, Des; Zheng, Yang; Liu, Jiao; Sun, Lu; Fu, Yong Qing

2017-08-01

Ni-Ti-Nb and Ni-Ti shape memory thin films were sputter-deposited onto silicon substrates and annealed at 600 °C for crystallization. X-ray diffraction (XRD) measurements indicated that all of the annealed Ni-Ti-Nb films were composed of crystalline Ni-Ti (Nb) and Nb-rich grains. X-ray photoelectron spectroscopy (XPS) tests showed that the surfaces of Ni-Ti-Nb films were covered with Ti oxides, NiO and Nb2O5. The corrosion resistance of the Ni-Ti-Nb films in 3.5 wt.% NaCl solution was investigated using electrochemical tests such as open-circuit potential (OCP) and potentio-dynamic polarization tests. Ni-Ti-Nb films showed higher OCPs, higher corrosion potentials (Ecorr) and lower corrosion current densities (icorr) than the binary Ni-Ti film, which indicated a better corrosion resistance. The reason may be that Nb additions modified the passive layer on the film surface. The OCPs of Ni-Ti-Nb films increased with further Nb additions, whereas no apparent difference of Ecorr and icorr was found among the Ni-Ti-Nb films.

Microstress, strain, band gap tuning and photocatalytic properties of thermally annealed and Cu-doped ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Prasad, Neena; V. M. M, Saipavitra; Swaminathan, Hariharan; Thangaraj, Pandiyarajan; Ramalinga Viswanathan, Mangalaraja; Balasubramanian, Karthikeyan

2016-06-01

ZnO nanoparticles and Cu-doped ZnO nanoparticles were prepared by co-precipitation method. Also, a part of the pure ZnO nanoparticles were annealed at 750 °C for 3, 6, and 9 h. X-ray diffraction studies were carried out and the lattice parameters, unit cell volume, interplanar spacing, and Young's modulus were calculated for all the samples, and also the crystallite size was found using the Scherrer method. X-ray peak broadening analysis was used to estimate the crystallite sizes and the strain using the Williamson-Hall (W-H) method and the size-strain plot (SSP) method. Stress and the energy density were calculated using the W-H method assuming different models such as uniform deformation model, uniform strain deformation model, uniform deformation energy density model, and the SSP method. Optical absorption properties of the samples were understood from their UV-visible spectra. Photocatalytic activities of ZnO and 5 % Cu-doped ZnO were observed by the degradation of methylene blue dye in aqueous medium under the irradiation of 20-W compact fluorescent lamp for an hour.

Annealing induced low coercivity, nanocrystalline Co-Fe-Si thin films exhibiting inverse cosine angular variation

NASA Astrophysics Data System (ADS)

Hysen, T.; Al-Harthi, Salim; Al-Omari, I. A.; Geetha, P.; Lisha, R.; Ramanujan, R. V.; Sakthikumar, D.; Anantharaman, M. R.

2013-09-01

Co-Fe-Si based films exhibit high magnetic moments and are highly sought after for applications like soft under layers in perpendicular recording media to magneto-electro-mechanical sensor applications. In this work the effect of annealing on structural, morphological and magnetic properties of Co-Fe-Si thin films was investigated. Compositional analysis using X-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a native oxide surface layer consisting of oxides of Co, Fe and Si on the surface. The morphology of the as deposited films shows mound like structures conforming to the Volmer-Weber growth model. Nanocrystallisation of amorphous films upon annealing was observed by glancing angle X-ray diffraction and transmission electron microscopy. The evolution of magnetic properties with annealing is explained using the Herzer model. Vibrating sample magnetometry measurements carried out at various angles from 0° to 90° to the applied magnetic field were employed to study the angular variation of coercivity. The angular variation fits the modified Kondorsky model. Interestingly, the coercivity evolution with annealing deduced from magneto-optical Kerr effect studies indicates a reverse trend compared to magetisation observed in the bulk. This can be attributed to a domain wall pinning at native oxide layer on the surface of thin films. The evolution of surface magnetic properties is correlated with morphology evolution probed using atomic force microscopy. The morphology as well as the presence of the native oxide layer dictates the surface magnetic properties and this is corroborated by the apparent difference in the bulk and surface magnetic properties.

Effect of cobalt doping on the phase transformation of TiO2 nanoparticles.

PubMed

Barakat, M A; Hayes, G; Shah, S Ismat

2005-05-01

Co-doped TiO2 nanoparticles containing 0.0085, 0.017, 0.0255, 0.034, and 0.085 mol % Co(III) ion dopant were synthesized via sol-gel and dip-coating techniques. The effects of metal ion doping on the transformation of anatase to the rutile phase have been investigated. Several analytical tools, such as X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray analysis (EDAX) were used to investigate the nanoparticle structure, size distribution, and composition. Results obtained revealed that the rutile to anatase concentration ratio increases with increase of the cobalt dopant concentration and annealing temperature. The typical composition of Co-doped TiO2 was Ti(1-x)Co(x)O2, where x values ranged from 0.0085 to 0.085. The activation energy for the phase transformation from anatase to rutile was measured to be 229, 222, 211, and 195 kJ/mole for 0.0085, 0.017, 0.0255, and 0.034 mol % Co in TiO2, respectively.

Growth and luminescent properties of Yb:YAG and Ca co-doped Yb:YAG ultrafast scintillation crystals

NASA Astrophysics Data System (ADS)

Zhu, Maodong; Qi, Hongji; Pan, Mingyan; Hou, Qing; Jiang, Benxue; Jin, Yaxue; Han, Hetong; Song, Zhaohui; Zhang, Hui

2018-05-01

In this work, Yb-doped Y3Al5O12 [yttrium aluminum garnet (YAG)] crystals and Ca co-doped Yb:YAG crystals were grown by the Czochralski (CZ) method. The chemical formulas of the two crystals are (Yb0.1Y0.9)3Al5O12 and (Ca0.001Yb0.1Y0.899)3Al5O12, respectively. The structural, optical and luminescent properties of the Yb:YAG and Ca, Yb:YAG crystals were investigated by X-ray rocking curve, X-ray diffraction, Raman spectra, UV-Visble-NIR absorption spectra and X-ray fluorescence. X-ray fluorescence spectrum with two emission peaks at 330 nm and 490 nm were observed in the two kinds of crystals, which would increase slightly after the annealing. Comparing to the Yb:YAG crystal, Ca co-doped Yb:YAG crystal behaved the better luminescent intensity without changing the crystal structure and vibrational modes. This indicates that by doping Ca2+ in Yb:YAG crystal may be an appropriate way to enhance the luminescent property of the scintillation crystal.

Phase formation and texture of thin nickel germanides on Ge(001) and Ge(111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Schutter, B., E-mail: deschutter.bob@ugent.be; Detavernier, C.; Van Stiphout, K.

2016-04-07

We studied the solid-phase reaction between a thin Ni film and a single crystal Ge(001) or Ge(111) substrate during a ramp anneal. The phase formation sequence was determined using in situ X-ray diffraction and in situ Rutherford backscattering spectrometry (RBS), while the nature and the texture of the phases were studied using X-ray pole figures and transmission electron microscopy. The phase sequence is characterized by the formation of a single transient phase before NiGe forms as the final and stable phase. X-ray pole figures were used to unambiguously identify the transient phase as the ϵ-phase, a non-stoichiometric Ni-rich germanide withmore » a hexagonal crystal structure that can exist for Ge concentrations between 34% and 48% and which forms with a different epitaxial texture on both substrate orientations. The complementary information gained from both RBS and X-ray pole figure measurements revealed a simultaneous growth of both the ϵ-phase and NiGe over a small temperature window on both substrate orientations.« less

Low-Temperature Ozone Exposure Technique to Modulate the Stoichiometry of WO(x) Nanorods and Optimize the Electrochromic Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, F.; Li, C. P.; Chen, G.

A low-temperature ozone exposure technique was employed for the post-treatment of WO{sub x} nanorod thin films fabricated from hot-wire chemical vapor deposition (HWCVD) and ultrasonic spray deposition (USD) techniques. The resulting films were characterized with x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UV-vis-NIR spectroscopy and x-ray photoelectron spectroscopy (XPS). The stoichiometry and surface crystallinity of the WO{sub x} thin films were subsequently modulated upon ozone exposure and thermal annealing without particle growth. The electrochromic performance was studied in a LiClO{sub 4}-propylene carbonate electrolyte, and the results suggest that the low-temperature ozone exposure technique is superior to the traditionalmore » high-temperature thermal annealing (employed to more fully oxidize the WO{sub x}). The optical modulation at 670 nm was improved from 35% for the as-deposited film to 57% for the film after ozone exposure at 150 C. The coloration efficiency was improved and the switching speed to the darkened state was significantly accelerated from 18.0 s for the as-deposited film to 11.8 s for the film after the ozone exposure. The process opens an avenue for low-temperature and cost-effective manufacturing of electrochromic films, especially on flexible polymer substrates.« less

Bacteria Adherence Properties of Nitrogen-Doped TiO2 Coatings by Plasma Surface Alloying Technique

NASA Astrophysics Data System (ADS)

Wang, Hefeng; Tang, Bin; Li, Xiuyan; Fan, Ailan

Titanium nitride coatings on 316L stainless steel (S. S) were obtained by plasma surface alloying technique. Nitrogen-doped titanium dioxide (TiO2-xNx) was synthesized by oxidative annealing the resulted TiNx coatings in air. The reference TiO2 samples were also prepared by oxidation of sputtered Ti coatings. The as-prepared coatings were characterized by X-ray diffraction, glow discharge optical emission spectrometer (GDOES), scanning electron microscopy, X-ray hotoelectron spectroscopy and UV-Vis spectrophotometry, respectively. The bacteria adherence property of the TiO2-xNx coatings on stainless steel on the oral bacteria Streptococcus Mutans was investigated and compared with that of stainless steel by fluorescence microscopy. The mechanism of the bacteria adherence was discussed. The results show that the TiO2-xNx coatings are composed of anatase crystalline structure. SEM measurement indicates a rough surface morphology with three-dimensional homogenous protuberances after annealing treatment. Optical properties reveal an extended tailing of the absorption edge toward the visible region due to nitrogen presence. The band gap of the N-doped sample is reduced from 2.29 eV to 1.90 eV compared with the pure TiO2 one. Because of the different roughness and microstructure, the TiO2-xNx coatings inhibit the bacteria adherence.

Meta-stable magnetic transitions and its field dependence in Co2.75Fe0.25O4 ferrite

NASA Astrophysics Data System (ADS)

Aswathi M., C.; Bhowmik, R. N.

2018-04-01

The Co2.75Fe0.25O4 ferrite has been prepared by chemical co-precipitation route. The as-prepared sample has been annealed at 500° C. X-ray diffraction pattern indicated cubic spinel structure in the sample. The sample showed ferrimagnetic nature with magnetic irreversibility and hysteresis loop. Magnetization data revealed high anisotropic nature and at least two prominent meta-stable magnetic transitions below the highest measurement temperature 350 K.

Telluride Misfit Layer Compounds: [(PbTe) 1.17 ] m (TiTe 2 ) n

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Daniel B.; Beekman, Matt; Disch, Sabrina

Telluride misfit layer compounds are reported for the first time. These compounds were synthesized using a novel approach of structurally designing a precursor that would form the desired product upon low-temperature annealing, which allows the synthesis of kinetically stable products that do not appear on the equilibrium phase diagram. Four new compounds of the [(PbTe)1.17]m(TiTe2)n family are reported, and their structures were examined by a variety of X-ray diffraction techniques.

Magnetic anisotropy and order parameter in nanostructured CoPt particles

NASA Astrophysics Data System (ADS)

Komogortsev, S. V.; Iskhakov, R. S.; Zimin, A. A.; Filatov, E. Yu.; Korenev, S. V.; Shubin, Yu. V.; Chizhik, N. A.; Yurkin, G. Yu.; Eremin, E. V.

2013-10-01

The correlation of magnetic anisotropy energy with order parameter in the crystallites of CoPt nanostructured particles prepared by thermal decomposition and further annealing has been studied by investigation of the approach magnetization to saturation curves and x-ray powder diffraction pattern profiles. It is shown that magnetic anisotropy energy value in partially ordered CoPt crystallite could be described as an intermediate case between two extremes, corresponding to either single or several c-domains of L10 phase in crystallite.

The effect of Al intermediate layer on thermal resistance of EB-PVD yttria-stabilized zirconia coatings on titanium substrate

NASA Astrophysics Data System (ADS)

Panin, Alexey; Panin, Victor; Kazachenok, Marina; Shugurov, Artur; Sinyakova, Elena; Martynov, Sergey; Rusyaev, Andrey; Kasterov, Artur

2017-12-01

The yttria-stabilized zirconia coatings sprayed on titanium substrates by the electron beam physical vapor deposition were subjected to thermal annealing in air at 1000°C for 1, 30 and 60 min. The delamination and fracture of the coatings are studied by the scanning electron microscopy and X-ray diffraction. It is shown that a magnetron sputtered Al interlayer between the coating and the substrate considerably improves the thermal resistance of ceramic coatings.

CO2-laser ablation of Bi-Sr-Ca-Cu oxide by millisecond pulse lengths

NASA Astrophysics Data System (ADS)

Meskoob, M.; Honda, T.; Safari, A.; Wachtman, J. B.; Danforth, S.; Wilkens, B. J.

1990-03-01

We have achieved ablation of Bi-Sr-Ca-Cu oxide from single targets of superconducting pellets by CO2-laser pulses of l ms length to grow superconducting thin films. Upon annealing, the 6000-Å thin films have a Tc (onset) of 90 K and zero resistance at 78 K. X-ray diffraction patterns indicate the growth of single-phase thin films. This technique allows growth of uniform single-phase superconducting thin films of lateral area greater than 1 cm2.

Telluride Misfit Layer Compounds: [(PbTe) 1.17 ] m (TiTe 2 ) n

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Daniel B.; Beekman, Matt; Disch, Sabrina

2014-04-09

Telluride misfit layer compounds are reported for the first time. These compounds were synthesized using a novel approach of structurally designing a precursor that would form the desired product upon low-temperature annealing, which allows the synthesis of kinetically stable products that do not appear on the equilibrium phase diagram. Four new compounds of the [(PbTe)1.17]m(TiTe2)n family are reported, and their structures were examined by a variety of X-ray diffraction techniques.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jana, S.; Devaraj, A.; Kovarik, L.

Transformation kinetics of metastable body-centered cubic γ-UMo phase in U-10 wt.percent Mo alloy during annealing at sub-eutectoid temperatures of 500C and 400C has been determined as a function of time using detailed microstructural characterization by scanning electron microscopy, X-ray diffraction analysis, scanning transmission electron microscopy, and atom probe tomography. Based on the results, we found that the phase transformation is initiated by cellular transformation at both the temperatures, which results in formation of a lamellar microstructure along prior γ-UMo grain boundaries.

Applying Thienyl Side Chains and Different π-Bridge to Aromatic Side-Chain Substituted Indacenodithiophene-Based Small Molecule Donors for High-Performance Organic Solar Cells.

PubMed

Wang, Jin-Liang; Liu, Kai-Kai; Liu, Sha; Liu, Feng; Wu, Hong-Bin; Cao, Yong; Russell, Thomas P

2017-06-14

A pair of linear tetrafluorinated small molecular donors, named as ThIDTTh4F and ThIDTSe4F, which are with tetrathienyl-substituted IDT as electron-rich central core, electron-deficient difluorobenzothiadiazole as acceptor units, and donor end-capping groups, but having differences in the π-bridge (thiophene and selenophene), were successfully synthesized and evaluated as donor materials in organic solar cells. Such π-bridge and core units in these small molecules play a decisive role in the formation of the nanoscale separation of the blend films, which were systematically investigated through absorption spectra, grazing incidence X-ray diffraction pattern, transmission electron microscopy images, resonant soft X-ray scattering profiles, and charge mobility measurement. The ThIDTSe4F (with selenophene π-bridge)-based device exhibited superior performance than devices based on ThIDTh4F (with thiophene π-bridge) after post annealing treatment owing to optimized film morphology and improved charge transport. Power conversion efficiency of 7.31% and fill factor of ∼0.70 were obtained by using a blend of ThIDTSe4F and PC 71 BM with thermal annealing and solvent vapor annealing treatments, which is the highest PCE from aromatic side-chain substituted IDT-based small molecular solar cells. The scope of this study is to reveal the structure-property relationship of the aromatic side-chain substituted IDT-based donor materials as a function of π-bridge and the post annealing conditions.

Modeling of Interface and Internal Disorder Applied to XRD Analysis of Ag-Based Nano-Multilayers.

PubMed

Ariosa, Daniel; Cancellieri, Claudia; Araullo-Peters, Vicente; Chiodi, Mirco; Klyatskina, Elizaveta; Janczak-Rusch, Jolanta; Jeurgens, Lars P H

2018-06-20

Multilayered structures are a promising route to tailor electronic, magnetic, optical, and/or mechanical properties and durability of functional materials. Sputter deposition at room temperature, being an out-of-equilibrium process, introduces structural defects and confers to these nanosystems an intrinsic thermodynamical instability. As-deposited materials exhibit a large amount of internal atomic displacements within each constituent block as well as severe interface roughness between different layers. To access and characterize the internal multilayer disorder and its thermal evolution, X-ray diffraction investigation and analysis are performed systematically at differently grown Ag-Ge/aluminum nitride (AlN) multilayers (co-deposited, sequentially deposited with and without radio frequency (RF) bias) samples and after high-temperature annealing treatment. We report here on model calculations based on a kinematic formalism describing the displacement disorder both within the multilayer blocks and at the interfaces to reproduce the experimental X-ray diffraction intensities. Mixing and displacements at the interface are found to be considerably reduced after thermal treatment for co- and sequentially deposited Ag-Ge/AlN samples. The application of a RF bias during the deposition causes the highest interface mixing and introduces random intercalates in the AlN layers. X-ray analysis is contrasted to transmission electron microscopy pictures to validate the approach.

Evolution of Nano-structured Quasicrystals from Amorphous alloys

NASA Astrophysics Data System (ADS)

Xing, L. Q.; Kelton, K. F.

2002-03-01

Ta shows a significant effect on the precipitation of quasicrystals in (Zr_1-xTa_x)_64Cu_18Ni_8Al_10 amorphous alloys. The amorphous alloy made without Ta forms precipitates of tetragonal Zr_2Cu primary phases upon annealing. The addition of a small amount of Ta ( ~ 3 at%) to the alloy initiates the precipitation of primary icosahedral quasicrystal phases. Moreover, as the Ta concentration increases, the size of the precipitates decreases dramatically. To study the effect of Ta in this alloy system and to understand the mechanism for the precipitation of nano-structured quasicrystals, we have investigated the crystallization characteristics of the alloys made with different Ta concentration using DSC, checked the structures of the annealed samples with TEM and X-ray diffraction, and analyzed the kinetics of the crystallization processes. The kinetic parameter and the measured crystal size distribution will be compared with theoretical predictions from conventional nucleation and growth model and from a new model for nucleation that couples the long-range diffusion flux with the interfacial attachment processes.

Carbon- and oxygen-free Cu(InGa)(SSe)₂ solar cell with a 4.63% conversion efficiency by electrostatic spray deposition.

PubMed

Yoon, Hyun; Na, Seung Heon; Choi, Jae Young; Kim, Min Woo; Kim, Hayong; An, Hee Sang; Min, Byoung Koun; Ahn, SeJin; Yun, Jae Ho; Gwak, Jihye; Yoon, KyungHoon; Kolekar, Sanjay S; van Hest, Maikel F A M; Al-Deyab, Salem S; Swihart, Mark T; Yoon, Sam S

2014-06-11

We have demonstrated the first example of carbon- and oxygen-free Cu(In,Ga)(SSe)2 (CIGSSe) absorber layers prepared by electrospraying a CuInGa (CIG) precursor followed by annealing, sulfurization, and selenization at elevated temperature. X-ray diffraction and scanning electron microscopy showed that the amorphous as-deposited (CIG) precursor film was converted into polycrystalline CIGSSe with a flat-grained morphology after post-treatment. The optimal post-treatment temperature was 300 °C for annealing and 500 °C for both sulfurization and selenization, with a ramp rate of 5 °C/min. The carbon impurities in the precursor film were removed by air annealing, and oxide that was formed during annealing was removed by sulfurization. The fabricated CIGSSe solar cell showed a conversion efficiency of 4.63% for a 0.44 cm(2) area, with Voc = 0.4 V, Jsc = 21 mA/cm(2), and FF = 0.53.

Effect of annealing on structural, electrical and optical properties of p-quaterphenyl thin films

NASA Astrophysics Data System (ADS)

Darwish, A. A. A.

2017-05-01

Thin films of p-quaterphenyl are deposited by an evaporation technique. IR spectra confirm that the thermal evaporation method is a decent one to acquire p-quaterphenyl films without dissociation. The X-ray diffraction studies demonstrate that the as-deposited and annealed films are polycrystalline with monoclinic structure. The electrical conductivity shows an activated behavior and indicating that p-quaterphenyl behaves as an organic semiconductor. The value of activation energy decreases by annealing, which explains due to the adjustment in the crystallite size. Optical properties of p-quaterphenyl films were performed to determine some optical constants. Dispersion of the refractive index is described utilizing the Wemple-DiDomenico model. In addition, the third order nonlinear susceptibility and the nonlinear refractive index are calculated. The analysis of the absorption coefficient for the as-deposited film showed an allowed direct optical band gap with a value of 2.35 eV, which decreased by annealing to 2.05 eV.

Effect of annealing on the structural and optical properties of TiO2 powder prepared by sol-gel route

NASA Astrophysics Data System (ADS)

Halder, Nilanjan; Misra, Kamakhya Prakash

2016-05-01

Using titanium isopropoxide as the precursor, Titanium dioxide (TiO2) powder was synthesized via sol-gel method, a promising low temperature route for preparing nanosized metal oxide semiconductors with good homogeneity at low cost. The as-prepared nano powder was thermally treated in air at 550, 650, 750, 900 and 1100°C for 1hr after drying at room temperature and used for further characterization. X-ray diffraction measurements showed that the annealing treatment has a strong impact on the crystal phase of TiO2 samples. The crystallite size as calculated from Debye Scherer formula lies in the range 29-69 nm and is found to increase with increase in annealing temperature. Photoluminescence studies exhibit an improvement in the optical efficiency of the samples with post synthesis heat treatment. Annealing at temperature above 900°C results in a degradation of the structural and optical quality of the TiO2 nano powder samples.

Influence of growth flux solvent on anneal-tuning of ground states in CaFe2As2

NASA Astrophysics Data System (ADS)

Roncaioli, Connor; Drye, Tyler; Saha, Shanta R.; Paglione, Johnpierre

2018-04-01

The effects of anneal-tuning of single-crystalline samples of CaFe2As2 synthesized via a molten Sn-flux method are investigated using x-ray diffraction, chemical composition, electrical transport, and magnetic susceptibility measurements in order to understand the role of growth conditions on the resultant phase diagram. Previous studies of CaFe2As2 crystals synthesized using a self-flux (FeAs) method revealed an ability to tune the structural and magnetic properties of this system by control of post-synthesis annealing conditions, resulting in an ambient pressure phase diagram that spans from tetragonal/orthorhombic antiferromagnetism to the collapsed tetragonal phase of this system. In this work, we compare previous results to those obtained on crystals synthesized via Sn flux, finding similar tunability in both self- and Sn-flux cases, but less sensitivity to annealing temperatures in the latter case, resulting in a temperature-shifted phase diagram.

Fabrication of PbFe12O19 nanoparticles and study of their structural, magnetic and dielectric properties

NASA Astrophysics Data System (ADS)

Mousavi Ghahfarokhi, S. E.; Rostami, Z. A.; Kazeminezhad, I.

2016-02-01

In this study, M-type Lead hexaferrite (PbFe12O19) nanoparticles were prepared by a sol-gel method and the prepared powders were annealed at 700-1000 °C for 1, 1.5, 2, 2.5 and 3 h. The Lead hexaferrite powders were characterized using thermogravimetry-differential thermal analysis, X-ray diffraction, scanning electron microscopy, LCR meter, vibrating sample magnetometer, and Fourier transforms infrared spectroscopy. The size of the nanoparticles was increased with the annealing temparature. The results reveal that the best annealing temperature and annealing time for preparing PbFe12O19 nanoparticles at 800 °C and 3 h are obtained. The infrared spectra measured in range of 4000-400 cm-1 exhibit stretching modes of metal ions in tetrahedral site at 580-550 cm-1 and octahedral site at 470-430 cm-1. The variation in ac conductivity (σac) with frequency shows that the electrical conductivity in these ferrites is mainly attributed to the electron hopping mechanism.

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.

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

PubMed

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

2014-05-14

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

Accumulative Roll Bonding and Post-Deformation Annealing of Cu-Al-Mn Shape Memory Alloy

NASA Astrophysics Data System (ADS)

Moghaddam, Ahmad Ostovari; Ketabchi, Mostafa; Afrasiabi, Yaser

2014-12-01

Accumulative roll bonding is a severe plastic deformation process used for Cu-Al-Mn shape memory alloy. The main purpose of this study is to investigate the possibility of grain refinement of Cu-9.5Al-8.2Mn (in wt.%) shape memory alloy using accumulative roll bonding and post-deformation annealing. The alloy was successfully subjected to 5 passes of accumulative roll bonding at 600 °C. The microstructure, properties as well as post-deformation annealing of this alloy were investigated by optical microscopy, scanning electron microscopy, x-ray diffraction, differential scanning calorimeter, and bend and tensile testing. The results showed that after 5 passes of ARB at 600 °C, specimens possessed α + β microstructure with the refined grains, but martensite phases and consequently shape memory effect completely disappeared. Post-deformation annealing was carried out at 700 °C, and the martensite phase with the smallest grain size (less than 40 μm) was obtained after 150 s of annealing at 700 °C. It was found that after 5 passes of ARB and post-deformation annealing, the stability of SME during thermal cycling improved. Also, tensile properties of alloys significantly improved after post-deformation annealing.

Controlled tuning of thin film deposition of IrO{sub 2} on Si using pulsed laser ablation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koshy, Abraham M., E-mail: abraham@ug.iisc.in; Bhat, Shwetha G., E-mail: shwethabhat@physics.iisc.ernet.in; Kumar, P. S. Anil, E-mail: anil@physics.iisc.ernet.in

2016-05-06

We have successfully grown a stable phase of polycrystalline IrO{sub 2} on Si (100) substrate. We have found that the phase of IrO{sub 2} can be controllably tuned to obtain either Ir or IrO{sub 2} using pulsed laser ablation technique. O{sub 2} conditions during the deposition influences the phase directly and drastically whereas annealing conditions do not show any variation in the phase of thin film. X-ray diffraction and X-ray photoemission experiments confirm both Ir and IrO{sub 2} can be successively grown on Si using IrO{sub 2} target. Also, the morphology is found to be influenced by the O{sub 2}more » conditions.« less

Low-moment ferrimagnetic phase of the Heusler compound Cr2CoAl

NASA Astrophysics Data System (ADS)

Jamer, Michelle E.; Marshall, Luke G.; Sterbinsky, George E.; Lewis, Laura H.; Heiman, Don

2015-11-01

Synthesizing half-metallic fully compensated ferrimagnets that form in the inverse Heusler phase could lead to superior spintronic devices. These materials would have high spin polarization at room temperature with very little fringing magnetic fields. Previous theoretical studies indicated that Cr2CoAl should form in a stable inverse Heusler lattice due to its low activation energy. Here, stoichiometric Cr2CoAl samples were arc-melted and annealed at varying temperatures, followed by studies of their structural and magnetic properties. High-resolution synchrotron X-ray diffraction revealed a chemically ordered Heusler phase in addition to CoAl and Cr phases. Soft X-ray magnetic circular dichroism revealed that the Cr and Co magnetic moments are antiferromagnetically oriented leading to the observed low magnetic moment in Cr2CoAl.

Magnetic and electronic properties of SrMnO3 thin films

NASA Astrophysics Data System (ADS)

Mandal, Arup Kumar; Panchal, Gyanendra; Choudhary, R. J.; Phase, D. M.

2018-05-01

Single phase hexagonal bulk SrMnO3 (SMO) was prepared by solid state route and it was used for depositing thin films by pulsed laser deposition (PLD) technique on single crystalline (100) oriented SrTiO3 (STO) substrate. X-ray diffraction shows that the thin film is deposited in cubic SrMnO3 phase. From X-ray absorption at the Mn L edge we observed the mixed valency of Mn (Mn3+& Mn4+) due to strain induced by the lattice mismatching between SMO and STO. Due to this mixed valency of Mn ion in SMO film, the ferromagnetic nature is observed at lower temperature because of double exchange. After post annealing with very low oxygen partial pressure, magnetic and electronic property of SMO films are effectively modified.

Role of precursor crystal structure on electrochemical performance of carbide-derived carbon electrodes

NASA Astrophysics Data System (ADS)

Palazzo, Benjamin; Norris, Zach; Taylor, Greg; Yu, Lei; Lofland, Samuel; Hettinger, Jeffrey

2015-03-01

Binary carbides with hexagonal and cubic crystal structures have been synthesized by reactive magnetron sputtering of vanadium and other transition metals in acetylene or methane gas mixed with argon. The binary carbides are converted to carbide-derived carbon (CDC) films using chlorine gas in a post-deposition process in an external vacuum reaction furnace. Residual chlorine has been removed using an annealing step in a hydrogen atmosphere. The CDC materials have been characterized by x-ray diffraction, x-ray fluorescence, and scanning electron microscopy. The performance of the CDC materials in electrochemical device applications has been measured with the hexagonal phase precursor demonstrating a significantly higher specific capacitance in comparison to that of the cubic phase. We report these results and pore-size distributions of these and similar materials.

Low temperature InP /Si wafer bonding using boride treated surface

NASA Astrophysics Data System (ADS)

Huang, Hui; Ren, Xiaomin; Wang, Wenjuan; Song, Hailan; Wang, Qi; Cai, Shiwei; Huang, Yongqing

2007-04-01

An approach for InP /Si wafer bonding based on boride-solution treatment was presented. The bonding energy is higher than the InP fracture energy by annealing at 280°C. An In0.53Ga0.47As/InP multiple-quantum-well (MQW) structure grown on InP was transferred onto Si substrate via the bonding process. X-ray diffraction and photoluminescence reveal that crystal quality of the bonded MQW was preserved. A thin B2O3-POx-SiO2 oxide layer of about 28nm thick at the bonding interface was detected. X-ray photoelectron spectroscopy and Raman analyses indicate that the formation of oxygen bridging bonds by boride treatment is responsible for the strong fusion obtained at such low temperature.

Strain relaxation in single crystal SrTiO3 grown on Si (001) by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Choi, Miri; Posadas, Agham; Dargis, Rytis; Shih, Chih-Kang; Demkov, Alexander A.; Triyoso, Dina H.; David Theodore, N.; Dubourdieu, Catherine; Bruley, John; Jordan-Sweet, Jean

2012-03-01

An epitaxial layer of SrTiO3 grown directly on Si may be used as a pseudo-substrate for the integration of perovskite oxides onto silicon. When SrTiO3 is initially grown on Si (001), it is nominally compressively strained. However, by subsequent annealing in oxygen at elevated temperature, an SiOx interlayer can be formed which alters the strain state of SrTiO3. We report a study of strain relaxation in SrTiO3 films grown on Si by molecular beam epitaxy as a function of annealing time and oxygen partial pressure. Using a combination of x-ray diffraction, reflection high energy electron diffraction, and transmission electron microscopy, we describe the process of interfacial oxidation and strain relaxation of SrTiO3 on Si (001). Understanding the process of strain relaxation of SrTiO3 on silicon will be useful for controlling the SrTiO3 lattice constant for lattice matching with functional oxide overlayers.

Structural and morphological study on ZnO:Al thin films grown using DC magnetron sputtering

NASA Astrophysics Data System (ADS)

Astuti, B.; Sugianto; Mahmudah, S. N.; Zannah, R.; Putra, N. M. D.; Marwoto, P.; Aryanto, D.; Wibowo, E.

2018-03-01

ZnO doped Al (ZnO:Al ) thin film was deposited on corning glass substrate using DC magnetron sputtering method. Depositon process of the ZnO:Al thin films was kept constant at plasma power, deposition temperature and deposition time are 40 watt, 400°C and 2 hours, respectivelly. Furthermore, for annealing process has been done on the variation of oxygen pressure are 0, 50, and 100 mTorr. X-ray diffraction (XRD), and SEM was used to characterize ZnO:Al thin film was obtained. Based on XRD characterization results of the ZnO:Al thin film shows that deposited thin film has a hexagonal structure with the dominant diffraction peak at according to the orientation of the (002) plane and (101). Finally, the crystal structure of the ZnO:Al thin films that improves with an increasing the oxygen pressure at annealing process up to 100 mTorr and its revealed by narrow FWHM value and also with dense crystal structure.

Analysis of structural and optical properties of annealed fullerene thin films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.; Gadallah, A.-S.; Atta Khedr, M.; Afify, H. A.

2015-08-01

Fullerene thin films were thermally deposited onto different substrates. The films annealed at 523 K for 10 h. X-ray diffraction technique was used to examine the structure of the films. The morphology of films was examined by field emission scanning electron microscopy. Fourier transform infrared spectra were recorded in wavenumber range 400-2000 cm-1. The optical characteristics were analyzed using UV- Vis-NIR spectrophotometric measurements in the spectral range 200-2500 nm. The refractive index and extinction coefficient were determined. Some dispersion parameters were calculated such as single oscillator energy, dispersion energy, dielectric constant at high frequency and lattice dielectric constant. As well as, the nonlinear optical susceptibility χ(3) and nonlinear refractive index n2 were determined.

Crystallographic and magnetic structure of HAVAR under high-pressure using diamond anvil cell (DAC)

NASA Astrophysics Data System (ADS)

Halevy, Itzhak; Haroush, Shlomo; Eisen, Yosef; Silberman, Ido; Moreno, Dany; Hen, Amir; Winterrose, Mike L.; Ghose, Sanjit; Chen, Zhiqiang

2010-04-01

Annealed (H1) and cold-rolled (H2) HAVAR has been studied using high-pressure synchrotron X-ray diffraction. A structural phase transformation was discovered at ˜13 GPa at ambient temperature, transforming from m - 3 m (S.G. 225) to P 63/m m c (S.G. 194) symmetry. The transition was not reversible on pressure release. The low-pressure cubic phase was found to be more compressible than the high-pressure hexagonal phase. Conventional Mössbauer and NFS shows that the HAVAR is not magnetic at room temperature and no splitting is observed. The SQUID indicates a huge difference in the temperature dependence of the magnetic susceptibility between the cold Rolled HAVAR compared to the annealed HAVAR.

Impact of additional sulphur on structure, morphology and optical properties of SnS thin films by thermal evaporation

NASA Astrophysics Data System (ADS)

Banotra, Arun; Padha, Naresh; Kumar, Shiv; Kapoor, Ashok K.

2018-05-01

Thin films of SnS have been obtained from Sn and S powders which were mixed up using ball mill technique with and without evaporating additional sulphur prior to annealing at 523K. The obtained samples were taken for structural, optical, chemical and morphological studies. The X-ray diffraction reveals the formation of SnS phase on annealing in vacuum having S/Sn ratio of 0.67 obtained from EDAX. This deficit in `S' is removed by supplementing additional `S' of 200nm prior to annealing which results in the S/Sn ratio of 1.01. The optical transmission recorded from spectrophotometer used to study different optical parameters. Morphological results corroborate well with the XRD, EDAX and optical study. The obtained stoichiometric films were also tested for Ag/p-SnS Schottky diodes on In coated glass substrates using current voltage measurements.

New Insights into Shape Memory Alloy Bimorph Actuators Formed by Electron Beam Evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Hao; Nykypanchuk, Dmytro

In order to create shape memory alloy (SMA) bimorph microactuators with high-precision features, a novel fabrication process combined with electron beam (E-beam) evaporation, lift-off resist and isotropic XeF2 dry etching method was developed. To examine the effect of E-beam deposition and annealing process on nitinol (NiTi) characteristics, the NiTi thin film samples with different deposition rate and overflow conditions during annealing process were investigated. With the characterizations using scanning electron microscope and x-ray diffraction, the results indicated that low E-beam deposition rate and argon employed annealing process could benefit the formation of NiTi crystalline structure. In addition, SMA bimorph microactuatorsmore » with high-precision features as small as 5 microns were successfully fabricated. Furthermore, the thermomechanical performance was experimentally verified and compared with finite element analysis simulation results.« less

Effect of dopent on the structural and optical properties of ZnS thin film as a buffer layer in solar cell application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vashistha, Indu B., E-mail: indu-139@yahoo.com; Sharma, S. K.; Sharma, Mahesh C.

2015-08-28

In order to find the suitable alternative of toxic CdS buffer layer, deposition of pure ZnS and doped with Al by chemical bath deposition method have been reported. Further as grown pure and doped thin films have been annealed at 150°C. The structural and surface morphological properties have been characterized by X-Ray diffraction (XRD) and Atomic Force Microscope (AFM).The XRD analysis shows that annealed thin film has been polycrystalline in nature with sphalerite cubic crystal structure and AFM images indicate increment in grain size as well as growth of crystals after annealing. Optical measurement data give band gap of 3.5more » eV which is ideal band gap for buffer layer for solar cell suggesting that the obtained ZnS buffer layer is suitable in a low-cost solar cell.« less

Structural and magnetic properties of new uniaxial nanocrystalline Pr5Co19 compound

NASA Astrophysics Data System (ADS)

Bouzidi, W.; Mliki, N.; Bessais, L.

2017-11-01

Highly-coercive nanocrystalline Pr5Co19 powders have been synthesized by mechanical milling for the first time. The structural properties are studied by X-ray diffraction and refined with Rietveld method. This analysis revealed that whatever annealing temperature, samples crystallize in the rhombohedral (3R) of Ce5Co19-type structure (space group R 3 bar m). The magnetization curve as a function of temperature shows a magnetic transition state at the Curie temperature TC = 690 K. The optimum hard magnetic properties have been obtained for Pr5Co19 milled for 5 h and annealed at 1048 K for 30 min. These alloys exhibit a coercivity of 15 kOe at room temperature. This high coercivity is attributed to the high uniaxial magnetocrystalline anisotropy, nanoscale grain size, and to the homogeneous nanostructure developed by mechanical milling process and subsequent annealing.

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.

Ambipolar SnOx thin-film transistors achieved at high sputtering power

NASA Astrophysics Data System (ADS)

Li, Yunpeng; Yang, Jia; Qu, Yunxiu; Zhang, Jiawei; Zhou, Li; Yang, Zaixing; Lin, Zhaojun; Wang, Qingpu; Song, Aimin; Xin, Qian

2018-04-01

SnO is the only oxide semiconductor to date that has exhibited ambipolar behavior in thin-film transistors (TFTs). In this work, ambipolar behavior was observed in SnOx TFTs fabricated at a high sputtering power of 200 W and post-annealed at 150-250 °C in ambient air. X-ray-diffraction patterns showed polycrystallisation of SnO and Sn in the annealed SnOx films. Scanning-electron-microscopy images revealed that microgrooves appeared after the films were annealed. Clusters subsequently segregated along the microgrooves, and our experiments suggest that they were most likely Sn clusters. Atomic force microscopy images indicate an abrupt increase in film roughness due to the cluster segregations. An important implication of this work is that excess Sn in the film, which has generally been thought to be detrimental to the film quality, may promote the ambipolar conduction when it is segregated from the film to enhance the stoichiometric balance.

Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yerci, S.; Serincan, U.; Dogan, I.

2006-10-01

Silicon nanocrystals, average sizes ranging between 3 and 7 nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800 deg. C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. Whilemore » the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix.« less

Dislocation density evolution in the process of high-temperature treatment and creep of EK-181 steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vershinina, Tatyana, E-mail: vershinina@bsu.edu.ru

2017-03-15

X-ray diffraction has been used to study the dislocation structure in ferrite-martensite high-chromium steel EK-181 in the states after heat treatment and high-temperature creep. The influence of heat treatment and stress on evolution of lath martensite structure was investigated by and electron back-scattered diffraction. The effect of nitrogen content on the total dislocation density, fraction of edge and screw dislocation segments are analyzed. - Highlights: •Fraction of edge dislocation in quenched state depends on nitrogen concentration. •Nitrogen affects the character of dislocation structure evolution during annealing. •Edge dislocations fraction influences on dislocation density after aging and creep.

Micro X-ray diffraction analysis of thin films using grazing-exit conditions.

PubMed

Noma, T; Iida, A

1998-05-01

An X-ray diffraction technique using a hard X-ray microbeam for thin-film analysis has been developed. To optimize the spatial resolution and the surface sensitivity, the X-ray microbeam strikes the sample surface at a large glancing angle while the diffracted X-ray signal is detected with a small (grazing) exit angle. Kirkpatrick-Baez optics developed at the Photon Factory were used, in combination with a multilayer monochromator, for focusing X-rays. The focused beam size was about 10 x 10 micro m. X-ray diffraction patterns of Pd, Pt and their layered structure were measured. Using a small exit angle, the signal-to-background ratio was improved due to a shallow escape depth. Under the grazing-exit condition, the refraction effect of diffracted X-rays was observed, indicating the possibility of surface sensitivity.

Positron annihilation study of the interfacial defects in ZnO nanocrystals: Correlation with ferromagnetism

NASA Astrophysics Data System (ADS)

Wang, Dong; Chen, Z. Q.; Wang, D. D.; Qi, N.; Gong, J.; Cao, C. Y.; Tang, Z.

2010-01-01

High purity ZnO nanopowders were pressed into pellets and annealed in air between 100 and 1200 °C. The crystal quality and grain size of the ZnO nanocrystals were investigated by x-ray diffraction 2θ scans. Annealing induces an increase in the grain size from 25 to 165 nm with temperature increasing from 400 to 1200 °C. Scanning electron microscopy and high-resolution transmission electron microscopy observations also confirm the grain growth during annealing. Positron annihilation measurements reveal vacancy defects including Zn vacancies, vacancy clusters, and voids in the grain boundary region. The voids show an easy recovery after annealing at 100-700 °C. However, Zn vacancies and vacancy clusters observed by positrons remain unchanged after annealing at temperatures below 500 °C and begin to recover at higher temperatures. After annealing at temperatures higher than 1000 °C, no positron trapping by the interfacial defects can be observed. Raman spectroscopy studies confirm the recovery of lattice disorder after annealing. Hysteresis loops are observed for the 100 and 400 °C annealed samples, which indicate ferromagnetism in ZnO nanocrystals. However, the ferromagnetism disappears after annealing above 700 °C, suggesting that it might originate from the surface defects such as Zn vacancies.

Room-temperature H2S Gas Sensor Based on Au-doped ZnFe2O4 Yolk-shell Microspheres.

PubMed

Yan, Yin; Nizamidin, Patima; Turdi, Gulmira; Kari, Nuerguli; Yimit, Abliz

2017-01-01

Room-temperature type H 2 S sensing devices that use Au-doped ZnFe 2 O 4 yolk-shell microspheres as the active material have been fabricated using a solvothermal method as well as subsequent annealing and a chemical etching process. The samples are characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the doping of Au does not change the spinel structure of the products, which were yolk-shell microspheres, while the particle size varied with the Au doping concentration. Also, the as-fabricated sensor device exhibited excellent selectivity toward H 2 S gas at the room temperature; the gas-sensing property of 2 wt% Au-doped ZnFe 2 O 4 microspheres was the best. The Au-doped ZnFe 2 O 4 yolk-shell microspheres can be promising as a sensing material for H 2 S gas detecting at room temperature.

The microstructural changes of Ge2Sb2Te5 thin film during crystallization process

NASA Astrophysics Data System (ADS)

Xu, Jingbo; Qi, Chao; Chen, Limin; Zheng, Long; Xie, Qiyun

2018-05-01

Phase change memory is known as the most promising candidate for the next generation nonvolatile memory technology. In this paper, the microstructural changes of Ge2Sb2Te5 film, which is the most common choice of phase change memory material, has been carefully studied by the combination of several characterization techniques. The combination of resistance measurements, X-ray diffraction, Raman spectroscopy and X-ray reflectivity allows us to simultaneously extract the characteristics of microstructural changes during crystallization process. The existence of surface/interface Ge2Sb2Te5 layer has been proposed here based on X-ray reflectivity measurements. Although the total film thickness decreases, as a result of the phase transition from amorphous to metastable crystalline cubic and then to the stable hexagonal phase, the surface/interface thickness increases after crystallization. Moreover, the increase of average grain size, density and surface roughness has been confirmed during thermal annealing process.

Thermal annealing and transient electronic excitations induced interfacial and magnetic effects on Pt/Co/Pt trilayer

NASA Astrophysics Data System (ADS)

Sehdev, Neeru; Medwal, Rohit; Malik, Rakesh; Kandasami, Asokan; Kanjilal, Dinakar; Annapoorni, S.

2018-04-01

Present study investigates the importance of thermal annealing and transient electronic excitations (using 100 MeV oxygen ions) in assisting the interfacial atomic diffusion, alloy composition, and magnetic switching field distributions in Pt/Co/Pt stacked trilayer. X-ray diffraction analysis reveals that thermal annealing results in the formation of the face centered tetragonal L1°CoPt phase. The Rutherford back scattering spectra shows a trilayer structure for as-deposited and as-irradiated films. Interlayer mixing on the thermally annealed films further improves by electronic excitations produced by high energy ion irradiation. Magnetically hard face centered tetragonal CoPt alloy retains its hard phase after ion irradiation and reveals an enhancement in the structural ordering and magnetic stability. Enhancement in the homogeneity of alloy composition and its correlation with the magnetic switching field is evident from this study. A detailed investigation of the contributing parameters shows that the magnetic switching behaviour varies with the type of thermal annealing, transient electronic excitations of ion beams and combination of these processes.

Dense nanocrystalline yttrium iron garnet films formed at room temperature by aerosol deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Scooter D., E-mail: scooter.johnson@nrl.navy.mil; Glaser, Evan R.; Cheng, Shu-Fan

Highlights: • We deposit yttrium iron garnet films at room temperature using aerosol deposition. • Films are 96% of theoretical density for yttrium iron garnet. • We report magnetic and structural properties post-deposition and post-annealing. • Low-temperature annealing decreases the FMR linewidth. • We discuss features of the FMR spectra at each anneal temperature. - Abstract: We have employed aerosol deposition to form polycrystalline yttrium iron garnet (YIG) films on sapphire at room temperature that are 90–96% dense. We characterize the structural and dynamic magnetic properties of the dense films using scanning electron microscopy, X-ray diffraction, and ferromagnetic resonance techniques.more » We find that the as-deposited films are pure single-phase YIG formed of compact polycrystallites ∼20 nm in size. The ferromagnetic resonance mode occurs at 2829 G with a linewidth of 308 G. We perform a series of successive anneals up to 1000 °C on a film to explore heat treatment on the ferromagnetic resonance linewidth. We find the narrowest linewidth of 98 G occurs after a 750 °C anneal.« less

Mechanical and structural characterizations of gamma- and alpha-alumina nanofibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vahtrus, Mikk; Umalas, Madis; Polyakov, Boris

2015-09-15

We investigate the applicability of alumina nanofibers as a potential reinforcement material in ceramic matrix compounds by comparing the mechanical properties of individual nanofibers before and after annealing at 1400 °C. Mechanical testing is performed inside a scanning electron microscope (SEM), which enables observation in real time of the deformation and fracture of the fibers under loading, thereby providing a close-up inspection of the freshly fractured area in vacuum. Improvement of both the Young's modulus and the breaking strength for annealed nanofibers is demonstrated. Mechanical testing is supplemented with the structural characterization of the fibers before and after annealing usingmore » SEM, transmission electron microscopy and X-ray diffraction methods. - Highlights: • Mechanical properties of individual alumina nanofibers were measured using in situ SEM cantilevered beam bending technique. • Improvement of mechanical properties of the alumina fibers after annealing at 1400 °C is demonstrated. • Formation of branched structures is demonstrated and their mechanical properties are studied. • XRD and electron microscopy were used for structural characterization of untreated and annealed nanofibers.« less

The role of annealing temperature and bio template (egg white) on the structural, morphological and magnetic properties of manganese substituted MFe2O4 (M=Zn, Cu, Ni, Co) nanoparticles

NASA Astrophysics Data System (ADS)

Ranjith Kumar, E.; Jayaprakash, R.; Kumar, Sanjay

2014-02-01

Manganese substituted ferrites (ZnFe2O4, CuFe2O4, NiFe2O4 and CoFe2O4) have been prepared in the bio template medium by using a simple evaporation method. The annealing temperature plays an important position on changing particle size and morphology of the mixed ferrite nanoparticles were found out by X-ray diffraction, transmission electron microscopy and scanning electron microscopy methods. The role of manganese substitution in the mixed ferrite nanoparticles were also analyzed for different annealing temperature. The substitution of Mn also creates a vital change in magnetic properties which is studied by using vibrating sample magnetometer (VSM). These spinel ferrites are decomposed to α-Fe2O3 after annealing above 550 °C in air. However, α-Fe2O3 phase was slowly vanished after ferrites annealing above 900 °C. The effect of this secondary phase on the structural change and magnetic properties of the mixed ferrite nanoparticles is discussed.

Photoluminescence and compositional-structural properties of ion-beam sputter deposited Er-doped TiO2-xNx films: Their potential as a temperature sensor

NASA Astrophysics Data System (ADS)

Scoca, D.; Morales, M.; Merlo, R.; Alvarez, F.; Zanatta, A. R.

2015-05-01

Er-doped TiO2-xNx films were grown by Ar+ ion-beam sputtering a Ti + Er target under different N2 + O2 high-purity atmospheres. The compositional-structural properties of the samples were investigated after thermal annealing the films up to 1000 °C under a flow of oxygen. Sample characterization included x-ray photoelectron spectroscopy, grazing incidence x-ray diffraction, Raman scattering, and photoluminescence experiments. According to the experimental data, both composition and atomic structure of the samples were very sensitive to the growth conditions and annealing temperature. In the as-deposited form, the N-rich TiO2-xNx films presented TiN crystallites and no photoluminescence. As the thermal treatments proceed, the films were transformed into TiO2 and Er3+-related light emission were observed in the visible and near-infrared ranges at room-temperature. Whereas the development of TiO2 occurred due to the insertion-diffusion of oxygen in the films, light emission originated because of optical bandgap widening and/or structural-chemical variations in the vicinity of the Er3+ ions. Finally, the photoluminescence results in the visible range suggested the potential of the present samples in producing an optically based temperature sensor in the ˜150-500 K range.

Structural, optical and photovoltaic properties of P3HT and Mn-doped CdS quantum dots based bulk hetrojunction hybrid layers

NASA Astrophysics Data System (ADS)

Jabeen, Uzma; Adhikari, Tham; Pathak, Dinesh; Shah, Syed Mujtaba; Nunzi, Jean-Michel

2018-04-01

Cadmium sulphide (CdS) and Mn-doped CdS nanocrystals were synthesized by co-precipitation method. The nanocrystals were characterized by Fluorescence, Fourier Transformed Infra-red Spectrometer (FTIR), UV-Visible, X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), Field Emission Scanning Electron Microscope (FESEM), and High Resolution Transmission Electron Microscope (HRTEM). A considerable blue shift of absorption band with respect to the cadmium sulphide was observed by the Mn concentration (0.5 M) in the doped sample with decreasing the size of nanocrystals. Other reason for this may be Mn doping. Subsequently the band gap was altered from 2.11 to 2.21 eV due to quantum confinement effect. Scanning electron microscope supplemented with EDAX was operated to find grain size and chemical composition of the synthesized nanomaterials. The PL spectrum of Mn-doped CdS nanocrystals displays three PL bands the first one, within the range of 500 nm and the second band at 537 nm, and the third one around 713 nm is labelled red band emission due to attributed to a 4T1→6A1 transition within the 3d shell of divalent manganese. XRD analysis showed that the material was in cubic crystalline state. A comparative study of surfaces of un-doped and metal doped CdS nanocrystals were investigated using X-ray Photoelectron Spectroscopy (XPS). The synthesized nanomaterial in combination with polymer, poly (3-hexyl thiophene) was operated in the construction of photovoltaic cells. The photovoltaic devices with CdS nanocrystals exhibited power conversion efficiency of 0.34% without annealing and 0.38% with annealing. However, the power conversion efficiency was enhanced by a factor of 0.35 without annealing and 0.42 with annealing with corporation of Mn impurity in CdS lattice. Atomic Force Microscopy was employed for morphology and packing behavior of blend of nanocrystals with organic polymer.

Large enhancement of X-ray excited luminescence in Ga-doped ZnO nanorod arrays by hydrogen annealing

NASA Astrophysics Data System (ADS)

Li, Qianli; Liu, Xiaoliln; Gu, Mu; Li, Fengrui; Zhang, Juannan; Wu, Qiang; Huang, Shiming; Liu, Si

2018-03-01

Highly c-axis oriented and densely packed ZnO:Ga nanorod arrays were fabricated on ZnO-seeded substrates by hydrothermal method, and the effect of hydrogen annealing on their morphology, structure and luminescence properties was investigated in detail. Under ultraviolet or X-ray excitation, an intense ultraviolet luminescence appeared in the hydrogen-annealed samples owing to the formation of a shallow hydrogen donor state, which can sharply activate the reconbination radiation. The luminescence intensity increased with the annealing temperature, and then decreased at a higher temperature due to the dissociation of the hydrogen ion. The optimum concentration and time of hydrogen annealing were acquired simultaneously. It is expected that the ZnO:Ga nanorod array is a promising candidate for application in ultrafast and high-spatial-resolution X-ray imaging detector.

High coercivity Gd-substituted Ba hexaferrites, prepared by chemical coprecipitation

NASA Astrophysics Data System (ADS)

Litsardakis, G.; Manolakis, I.; Serletis, C.; Efthimiadis, K. G.

2008-04-01

A series of Gd-substituted Ba hexaferrites with nominal formula (Ba1-xGdx)Oṡ5.25 Fe2O3 (x=0-0.30) were prepared by the chemical coprecipitation method from nitrate precursors and heating at T =800-1200°C for 2h. The samples have been examined by x-ray diffraction, vibrating-sample magnetometer, and scanning electron microscopy methods. Gd substituted samples form single phase materials with the M-type hexaferrite structure at all heating temperatures, in the range of x ⩽0.10-0.20. The saturation magnetization (at 1.8T) varies slightly with x in most cases and, for x =0.05-0.10, it increases up to 66.7Am2/kg, exceeding the value of the unsubstituted hexaferrite. A strong enhancement of the coercivity is observed for all substituted samples, with maximum values Hc=457kA/m for the single-phase x =0.10 sample annealed at 1000°C and Hc=477kA/m for the x =0.25 sample annealed at 1100°C which contains Fe2O3 and GdFeO3 impurities. As the variation of coercivity with either substitution rate (x ) or annealing temperature is not monotonic, three different factors may account for the high coercivities that are obtained: (a) an inhibition of grain growth due to the presence of Gd, (b) a possible inherent effect on magnetocrystalline anisotropy, especially for single phase samples, and (c) a microstructural effect of secondary phases.

In-situ studies of Fe2B phase formation in MgB2 wires and tapes by means of high-energy x-ray diffraction

NASA Astrophysics Data System (ADS)

Grivel, J. C.; Andersen, N. H.; Pinholt, R.; Ková, P.; Husek, I.; Hässler, W.; Herrmann, M.; Perner, O.; Rodig, C.; Homeyer, J.

2006-06-01

The phase transformations occurring in the ceramic core of Fe-sheathed MgB2 wires and tapes prepared by in-situ reaction of Mg and B precursor powders, have been studied by means of high-energy x-ray diffraction. In particular, the time evolution of the Fe2B phase, forming at the interface between the sheath and the ceramic, was studied at different sintering temperatures. The reactivity of the sheath towards Fe2B formation is strongly dependent on powder pre-treatment. In wires produced with commercial Mg and B powders without additional mechanical activation, the Fe2B phase starts forming around 650°C. In contrast, in tapes produced from a mixture of Mg and B powders subjected to high-energy ball milling, the interfacial Fe2B layer forms readily at 600°C. The increase of Fe2B volume fraction is linear to first approximation, showing that the interfacial layer does not act as a diffusion barrier against further reaction between the sheath and the ceramic core. If the ceramic core is converted to MgB2 at a temperature, which is low enough to avoid Fe2B formation, the interface is stable during further annealing at temperatures up to 700°C at least. However, too high annealing temperatures (T > 800°C), would result in formation of Fe2B, probably following the partial decomposition of MgB2.

Investigating the Effect of Pyridine Vapor Treatment on Perovskite Solar Cells - Oral Presentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ong, Alison J.

2015-08-25

Perovskite photovoltaics have recently come to prominence as a viable alternative to crystalline silicon based solar cells. In an effort to create consistent and high-quality films, we studied the effect of various annealing conditions as well as the effect of pyridine vapor treatment on mixed halide methylammonium lead perovskite films. Of six conditions tested, we found that annealing at 100 degree Celsius for 90 minutes followed by 120 degree Celsius for 15 minutes resulted in the purest perovskite. Perovskite films made using that condition were treated with pyridine for various amounts of time, and the effects on perovskite microstructure weremore » studied using x-ray diffraction, UV-Vis spectroscopy, and time-resolved photoluminescence lifetime analysis (TRPL). A previous study found that pyridine vapor caused perovskite films to have higher photoluminescence intensity and become more homogenous. In this study we found that the effects of pyridine are more complex: while films appeared to become more homogenous, a decrease in bulkphotoluminescence lifetime was observed. In addition, the perovskite bandgap appeared to decrease with increased pyridine treatment time. Finally, X-ray diffraction showed that pyridine vapor treatment increased the perovskite (110) peak intensity but also often gave rise to new unidentified peaks, suggesting the formation of a foreign species. It was observed that the intensity of this unknown species had an inverse correlation with the increase in perovskite peak intensity, and also seemed to be correlated with the decrease in TRPL lifetime.« less

Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope

PubMed Central

Shen, Haoting; Bendersky, Leonid A.; Young, Kwo; Nei, Jean

2015-01-01

The microstructure of an annealed alloy with a Zr8Ni21 composition was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of three phases, Zr8Ni21, Zr2Ni7, and Zr7Ni10, was confirmed by SEM/X-ray energy dispersive spectroscopy compositional mapping and TEM electron diffraction. Distribution of the phases and their morphology can be linked to a multi-phase structure formed by a sequence of reactions: (1) L → Zr2Ni7 + L’; (2) peritectic Zr2Ni7 + L’ → Zr2Ni7 + Zr8Ni21 + L”; (3) eutectic L” → Zr8Ni21 + Zr7Ni10. The effect of annealing at 960 °C, which was intended to convert a cast structure into a single-phase Zr8Ni21 structure, was only moderate and the resulting alloy was still multi-phased. TEM and crystallographic analysis of the Zr2Ni7 phase show a high density of planar (001) defects that were explained as low-energy boundaries between rotational variants and stacking faults. The crystallographic features arise from the pseudo-hexagonal structure of Zr2Ni7. This highly defective Zr2Ni7 phase was identified as the source of the broad X-ray diffraction peaks at around 38.4° and 44.6° when a Cu-K was used as the radiation source. PMID:28793460

Investigating the Effect of Pyridine Vapor Treatment on Perovskite Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ong, Alison

2015-08-20

Perovskite photovoltaics have recently come to prominence as a viable alternative to crystalline silicon based solar cells. In an effort to create consistent and high-quality films, we studied the effect of various annealing conditions as well as the effect of pyridine vapor treatment on mixed halide methylammonium lead perovskite films. Of six conditions tested, we found that annealing at 100°C for 90 minutes followed by 120°C for 15 minutes resulted in the purest perovskite. Perovskite films made using that condition were treated with pyridine for various amounts of time, and the effects on perovskite microstructure were studied using x-ray diffraction,more » UV-Vis spectroscopy, and time-resolved photoluminescence lifetime analysis (TRPL). A previous study found that pyridine vapor caused perovskite films to have higher photoluminescence intensity and become more homogenous. In this study we found that the effects of pyridine are more complex: while films appeared to become more homogenous, a decrease in bulk photoluminescence lifetime was observed. In addition, the perovskite bandgap appeared to decrease with increased pyridine treatment time. Finally, X-ray diffraction showed that pyridine vapor treatment increased the perovskite (110) peak intensity but also often gave rise to new unidentified peaks, suggesting the formation of a foreign species. It was observed that the intensity of this unknown species had an inverse correlation with the increase in perovskite peak intensity, and also seemed to be correlated with the decrease in TRPL lifetime.« less

Observation of glassy state relaxation during annealing of frozen sugar solutions by X-ray computed tomography.

PubMed

Nakagawa, Kyuya; Tamiya, Shinri; Do, Gabsoo; Kono, Shinji; Ochiai, Takaaki

2018-06-01

Glassy phase formation in a frozen product determines various properties of the freeze-dried products. When an aqueous solution is subjected to freezing, a glassy phase forms as a consequence of freeze-concentration. During post-freezing annealing, the relaxation of the glassy phase and the ripening of ice crystals (i.e. Ostwald ripening) spontaneously occur, where the kinetics are controlled by the annealing and glass transition temperatures. This study was motivated to observe the progress of glassy state relaxation separate from ice coarsening during annealing. X-ray computed tomography (CT) was used to observe a frozen and post-freezing annealed solutions by using monochromatized X-ray from the synchrotron radiation. CT images were successfully obtained, and the frozen matrix were analyzed based on the gray level values that were equivalent to the linear X-ray attenuation coefficients of the observed matters. The CT images obtained from rapidly frozen sucrose and dextrin solutions with different concentrations gave clear linear relationships between the linear X-ray attenuation coefficients values and the solute concentrations. It was confirmed that the glassy state relaxation progressed as increasing annealing time, and this trend was larger in the order of the glass transition temperature of the maximally freeze-concentrated phase. The sucrose-water system required nearly 20 h of annealing time at -5 °C for the completion of the glassy phase relaxation, whereas dextrin-water systems required much longer periods because of their higher glass transition temperatures. The trends of ice coarsening, however, did not perfectly correspond to the trends of the relaxation, suggesting that the glassy phase relaxation and Ostwald ripening would jointly control the ice crystal growth/ripening kinetics, and the dominant mechanism differed by the annealing stage. Copyright © 2018 Elsevier B.V. All rights reserved.

Mesoscale Science with High Energy X-ray Diffraction Microscopy at the Advanced Photon Source

NASA Astrophysics Data System (ADS)

Suter, Robert

2014-03-01

Spatially resolved diffraction of monochromatic high energy (> 50 keV) x-rays is used to map microstructural quantities inside of bulk polycrystalline materials. The non-destructive nature of High Energy Diffraction Microscopy (HEDM) measurements allows tracking of responses as samples undergo thermo-mechanical or other treatments. Volumes of the order of a cubic millimeter are probed with micron scale spatial resolution. Data sets allow direct comparisons to computational models of responses that frequently involve long-ranged, multi-grain interactions; such direct comparisons have only become possible with the development of HEDM and other high energy x-ray methods. Near-field measurements map the crystallographic orientation field within and between grains using a computational reconstruction method that simulates the experimental geometry and matches orientations in micron sized volume elements to experimental data containing projected grain images in large numbers of Bragg peaks. Far-field measurements yield elastic strain tensors through indexing schemes that sort observed diffraction peaks into sets associated with individual crystals and detect small radial motions in large numbers of such peaks. Combined measurements, facilitated by a new end station hutch at Advanced Photon Source beamline 1-ID, are mutually beneficial and result in accelerated data reduction. Further, absorption tomography yields density contrast that locates secondary phases, void clusters, and cracks, and tracks sample shape during deformation. A collaboration led by the Air Force Research Laboratory and including the Advanced Photon Source, Lawrence Livermore National Laboratory, Carnegie Mellon University, Petra-III, and Cornell University and CHESS is developing software and hardware for combined measurements. Examples of these capabilities include tracking of grain boundary migrations during thermal annealing, tensile deformation of zirconium, and combined measurements of nickel superalloys and a titanium alloy under tensile forces. Work supported by NSF grant DMR-1105173

Broadening and shifting of Bragg reflections of nanoscale-microtwinned LT-Ni3Sn2

NASA Astrophysics Data System (ADS)

Leineweber, Andreas; Krumeich, Frank

2013-12-01

The effect of nanoscale microtwinning of long-range ordered domains in LT-Ni3Sn2 on its diffraction behaviour was studied by X-ray powder diffraction and electron microscopy. LT-Ni3Sn2 exhibits a Ni2In/NiAs-type structure with a superstructure breaking the symmetry relative to the hexagonal high-temperature (HT) to the orthorhombic low-temperature (LT) phase, implying three different twin-domain orientations. The microstructure was generated by annealing HT-Ni3Sn2 considerably below the order-disorder transition temperature, establishing the LT phase avoiding too much domain coarsening. High-resolution electron microscopy reveals domain sizes of 100-200 Å compatible with the Scherrer broadening of the superstructure reflections recorded by X-ray diffraction. Whereas the orthorhombic symmetry of the LT phase leads in powder-diffraction patterns from coarse-domain size material to splitting of the fundamental reflections, this splitting does not occur for the LT-Ni3Sn2 with nanoscale domains. Instead, a (pseudo)hexagonal indexing is possible giving hexagonal lattice parameters, which are, however, incompatible with the positions of the superstructure reflections. This can be attributed to interference between X-rays scattered by the differently oriented, truly orthorhombic domains leading to merging of the fundamental reflections. These show pronounced anisotropic microstrain-like broadening, where the integral breadths ? on the reciprocal d-spacing scale of a series of higher order reflection increase in a non-linear fashion with upward curvature with the reciprocal d-spacings ? of these reflections. Such a type of unusual microstrain broadening appears to be typical for microstructures which are inhomogeneous on the nanoscale, and in which the structural inhomogeneities lead to small phase shifts of the scattered radiation from different locations (e.g. domains).

New class of single-source precursors for the synthesis of main group-transition metal oxides: heterobimetallic Pb-Mn beta-diketonates.

PubMed

Zhang, Haitao; Yang, Jen-Hsien; Shpanchenko, Roman V; Abakumov, Artem M; Hadermann, Joke; Clérac, Rodolphe; Dikarev, Evgeny V

2009-09-07

Heterometallic lead-manganese beta-diketonates have been isolated in pure form by several synthetic methods that include solid-state and solution techniques. Two compounds with different Pb/Mn ratios, PbMn(2)(hfac)(6) (1) and PbMn(hfac)(4) (2) (hfac = hexafluoroacetylacetonate), can be obtained in quantitative yield by using different starting materials. Single crystal X-ray investigation revealed that the solid-state structure of 1 contains trinuclear molecules in which lead metal center is sandwiched between two [Mn(hfac)(3)] units, while 2 consists of infinite chains of alternating [Pb(hfac)(2)] and [Mn(hfac)(2)] fragments. The heterometallic structures are held together by strong Lewis acid-base interactions between metal atoms and diketonate ligands acting in chelating-bridging fashion. Spectroscopic investigation confirmed the retention of heterometallic structures in solutions of non-coordinating solvents as well as upon sublimation-deposition procedure. Thermal decomposition of heterometallic diketonates has been systematically investigated in a wide range of temperatures and annealing times. For the first time, it has been shown that thermal decomposition of heterometallic diketonates results in mixed-metal oxides, while both the structure of precursors and the thermolysis conditions have a significant influence on the nature of the resulting oxides. Five different Pb-Mn oxides have been detected by X-ray powder diffraction when studying the decomposition of 1 and 2 in the temperature range 500-800 degrees C. The phase that has been previously reported as "Pb(0.43)MnO(2.18)" was synthesized in the pure form by decomposition of 1, and crystallographically characterized. The orthorhombic unit cell parameters of this oxide, obtained by electron diffraction technique, have been subsequently refined using X-ray powder diffraction data. Besides that, a previously unknown lead-manganese oxide has been obtained at low temperature decomposition and short annealing times. The parameters of its monoclinically distorted unit cell have been determined. The EDX analysis revealed that this compound has a Pb/Mn ratio close to 1:4 and contains no appreciable amount of fluorine.

Thermally induced phase transformation in multi-phase iron oxide nanoparticles on vacuum annealing

NASA Astrophysics Data System (ADS)

Anupama, A. V.; Keune, W.; Sahoo, B.

2017-10-01

The evolution of magnetic phases in multi-phase iron oxide nanoparticles, synthesized via the transferred arc plasma induced gas phase condensation method, was investigated by X-ray diffraction, vibrating sample magnetometry and 57Fe Mössbauer spectroscopy. The particles are proposed to be consisting of three different iron oxide phases: α-Fe2O3, γ-Fe2O3 and Fe3O4. These nanoparticles were exposed to high temperature (∼935 K) under vacuum (10-3 mbar He pressure), and the thermally induced phase transformations were investigated. The Rietveld refinement of the X-ray diffraction data corroborates the least-squares fitting of the transmission Mössbauer spectra in confirming the presence of Fe3O4, γ-Fe2O3 and α-Fe2O3 phases before the thermal treatment, while only Fe3O4 and α-Fe2O3 phases exist after thermal treatment. On thermal annealing in vacuum, conversion from γ-Fe2O3 to Fe3O4 and α-Fe2O3 was observed. Interestingly, we have observed a phase transformation occurring in the temperature range ∼498 K-538 K, which is strikingly lower than the phase transformation temperature of γ-Fe2O3 to α-Fe2O3 (573-623 K) in air. Combining the results of Rietveld refinement of X-ray diffraction patterns and Mössbauer spectroscopy, we have attributed this phase transformation to the phase conversion of a metastable "defected and strained" d-Fe3O4 phase, present in the as-prepared sample, to the α-Fe2O3 phase. Stabilization of the phases by controlling the phase transformations during the use of different iron-oxide nanoparticles is the key factor to select them for a particular application. Our investigation provides insight into the effect of temperature and chemical nature of the environment, which are the primary factors governing the phase stability, suitability and longevity of the iron oxide nanomaterials prepared by the gas-phase condensation method for various applications.

Stabilization of high Tc phase in bismuth cuprate superconductor by lead doping

NASA Technical Reports Server (NTRS)

Gupta, Ram. P.; Pachauri, J. P.; Khokle, W. S.; Nagpal, K. C.; Date, S. K.

1991-01-01

It has been widely ascertained that doping of lead in Bi-Sr-Ca-Cu-O systems promotes the growth of high T sub c (110 K) phase, improves critical current density, and lowers processing temperature. A systematic study was undertaken to determine optimum lead content and processing conditions to achieve these properties. A large number of samples with cationic compositions of Bi(2-x)Pb(x)Sr2Ca2Cu3 (x = 0.2 to 2.0) were prepared by conventional solid state reaction technique. Samples of all compositions were annealed together at a temperature and characterized through resistance temperature (R-T) measurements and x ray diffraction to determine the zero resistance temperature, T sub c(0) and to identify presence of phases, respectively. The annealing temperature was varied between 790 and 880 C to optimize processing parameters. Results are given. In brief, an optimum process is reported along with composition of leaded bismuth cuprate superconductor which yields nearly a high T sub c single phase with highly stable superconducting properties.

Stabilization of high T(sub c) phase in bismuth cuprate superconductor by lead doping

NASA Technical Reports Server (NTRS)

Gupta, Ram. P.; Pachauri, J. P.; Khokle, W. S.; Nagpal, K. C.; Date, S. K.

1990-01-01

It has widely been ascertained that doping of lead in Bi:Sr:Ca:Cu:O systems promotes the growth of high T(sub c) (110 K) phase, improves critical current density, and lowers processing temperature. A systematic investigation is undertaken to determine optimum lead content and processing conditions to achieve these. A large number of samples with cationic compositions of Bi(2-x)Pb(x)Sr2Ca2Cu3 (x = 0.2 to 2.0) were prepared by conventional solid state reaction technique. Samples of all compositions were annealed together at a temperature and characterized through resistance-temperature (R-T) measurements and x ray diffraction (XRD) to determine the zero resistance temperature, T(sub c)(0) and to identify presence of phases, respectively. The annealing temperature was varied between 790 C to optimize processing parameters. Results are given. In brief, an optimum process is reported along with composition of leaded bismuth cuprate superconductor which yields nearly a high T(sub c) single phase with highly stable superconducting properties.

Cubic phase stabilization in nanoparticles of hafnia-zirconia oxides: Particle-size and annealing environment effects

NASA Astrophysics Data System (ADS)

Lu, Chih-Hsin; Raitano, Joan M.; Khalid, Syed; Zhang, Lihua; Chan, Siu-Wai

2008-06-01

Amorphous hafnia (HfO2-y), zirconia (ZrO2-y), and hafnia-zirconia (xHfO2-y-(1-x)(ZrO2-y)) nanoparticles were prepared by combining aqueous solutions of hexamethylenetetramine (HMT) with hafnium dichloride oxide (HfOCl2ṡ8H2O), zirconium dichloride oxide (ZrOCl2ṡ8H2O), or a mixture of these two salts at room temperature. For pure hafnia, transmission electron microscopy showed that the lower cation concentration (0.01M) resulted in the precipitation of smaller amorphous nanoparticles relative to higher concentrations (0.015M-0.04M). Consequently, the lower concentration preparation route coupled with a reducing environment (H2:N2=9:91) during annealing at temperatures between 650 and 850°C allowed for nanoparticles with a cubic structure to be prepared as determined by x-ray diffraction. The structurally cubic hafnia nanoparticles were 6nm or less in diameter and equiaxed. Using the same method (0.01M total metal cation concentration and reducing environment during annealing), nanoparticles of cubic structure were prepared across the entire hafnia-zirconia compositional spectrum, with a critical particle size for the cubic structure of about 6nm. Nanoparticles of tetragonal and monoclinic structure were prepared by increasing the annealing temperature and/or using a less reducing environment. The unique role of HMT in sample preparation is discussed as well.

Epitaxial growth of hexagonal boron nitride monolayers by a three-step boration-oxidation-nitration process

NASA Astrophysics Data System (ADS)

Müller, Frank; Hüfner, Stefan; Sachdev, Hermann; Gsell, Stefan; Schreck, Matthias

2010-08-01

The formation of well-ordered monolayers of hexagonal boron nitride on the surface of a Rh/YSZ/Si(111) multilayer substrate via a three-step boration-oxidation-nitration process was investigated by x-ray photoelectron spectroscopy (XPS), x-ray photoelectron diffraction (XPD) and low-energy electron diffraction (LEED). The chemical vapor deposition (CVD) of trimethylborate B(OCH3)3 results in a selective decomposition of the precursor, leading to a dilute distribution of boron within the interstitials of the Rh lattice. After oxidation, the layer of a boron oxygen species of about 1 nm thickness can be transformed into a hexagonal monolayer of BN by annealing in NH3 atmosphere. The results of the present study clearly show that the formation of BN monolayers is also possible when boron and nitrogen are provided successively from separate sources. This procedure represents an alternative routine for the preparation of well-ordered BN monolayers, which benefits from a strong reduction of hazardous potential and economic costs compared to the use of borazine as the current standard precursor.

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

PubMed Central

2013-01-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration. PMID:23680100

Non-convergent ordering and displacive phase transition in pigeonite: in situ HT XRD study

NASA Astrophysics Data System (ADS)

Cámara, F.; Carpenter, M. A.; Domeneghetti, M. C.; Tazzoli, V.

A natural Ca-rich pigeonite (En47Fs43Wo10), free of augite exsolution products, was studied by in situ high-temperature single-crystal X-ray diffraction. The sample, monoclinic P21/c (a=9.719(7) Å, b=8.947(9) Å, c=5.251(3) Å, β=108.49(5), V=433.0(6) Å3), was annealed up to 1000 °C to induce a phase transition from P21/c to C2/c symmetry. Complete single-crystal X-ray diffraction data collections were carried out in situ at 650, 750, 850 and 950 °C after the crystal had reached equilibrium for the Fe-Mg intracrystalline exchange reaction at each temperature. The variation, with increasing temperature, of lattice parameters, of intensity of hkl reflections with h + k=2n + 1 (which vanish at high temperature) and of some geometrical parameters from structure refinement, showed that the displacive phase transition P21/cC2/c was continuous in character. This contrasts with the first-order character for the HT phase transition in pigeonite containing significantly less calcium.

Itinerant Antiferromagnetism in FeMnP 0.8Si 0.2

DOE PAGES

Sales, Brian C.; Susner, Michael A.; Conner, Benjamin S.; ...

2015-09-25

Compounds based on the Fe 2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a noncentrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. We report the growth and characterization of millimeter-sized single crystals of FeMnP 0.8Si 0.2 with the Fe 2P structure. Single-crystal x-ray diffraction, magnetization, resistivity, and Hall and heat capacity data are reported. The crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. Themore » room-temperature resistivity is close to the Ioffe-Regel limit for a metal. Single-crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism were not changed after high-temperature anneals and a rapid quench to room temperature« less

Large exchange bias effect in NiFe2O4/CoO nanocomposites

NASA Astrophysics Data System (ADS)

Mohan, Rajendra; Prasad Ghosh, Mritunjoy; Mukherjee, Samrat

2018-03-01

In this work, we report the exchange bias effect of NiFe2O4/CoO nanocomposites, synthesized via chemical co-precipitation method. Four samples of different particle size ranging from 4 nm to 31 nm were prepared with the annealing temperature varying from 200 °C to 800 °C. X-ray diffraction analysis of all the samples confirmed the presence of cubic spinel phase of Nickel ferrite along with CoO phase without trace of any impurity. Sizes of the particles were studied from transmission electron micrographs and were found to be in agreement with those estimated from x-ray diffraction. Field cooled (FC) hysteresis loops at 5 K revealed an exchange bias (HE) of 2.2 kOe for the sample heated at 200 °C which decreased with the increase of particle size. Exchange bias expectedly vanished at 300 K due to high thermal energy (kBT) and low effective surface anisotropy. M-T curves revealed a blocking temperature of 135 K for the sample with smaller particle size.

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Kwon, Yiseul; Choe, Youngson

2013-05-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration.

Ultrathin Cr added Ru film as a seedless Cu diffusion barrier for advanced Cu interconnects

NASA Astrophysics Data System (ADS)

Hsu, Kuo-Chung; Perng, Dung-Ching; Yeh, Jia-Bin; Wang, Yi-Chun

2012-07-01

A 5 nm thick Cr added Ru film has been extensively investigated as a seedless Cu diffusion barrier. High-resolution transmission electron microscopy micrograph, X-ray diffraction (XRD) pattern and Fourier transform-electron diffraction pattern reveal that a Cr contained Ru (RuCr) film has a glassy microstructure and is an amorphous-like film. XRD patterns and sheet resistance data show that the RuCr film is stable up to 650 °C, which is approximately a 200 °C improvement in thermal stability as compared to that of the pure Ru film. X-ray photoelectron spectroscopy depth profiles show that the RuCr film can successfully block Cu diffusion, even after a 30-min 650 °C annealing. The leakage current of the Cu/5 nm RuCr/porous SiOCH/Si stacked structure is about two orders of magnitude lower than that of a pristine Ru sample for electric field below 1 MV/cm. The RuCr film can be a promising Cu diffusion barrier for advanced Cu metallization.

Interdiffusion in nanometer-scale multilayers investigated by in situ low-angle x-ray diffraction

NASA Astrophysics Data System (ADS)

Wang, Wei-Hua; Bai, Hai Yang; Zhang, Ming; Zhao, J. H.; Zhang, X. Y.; Wang, W. K.

1999-04-01

An in situ low-angle x-ray diffraction technique is used to investigate interdiffusion phenomena in various metal-metal and metal-amorphous Si nanometer-scale compositionally modulated multilayers (ML's). The temperature-dependent interdiffusivities are obtained by accurately monitoring the decay of the first-order modulation peak as a function of annealing time. Activation enthalpies and preexponential factors for the interdiffusion in the Fe-Ti, Ag-Bi, Fe-Mo, Mo-Si, Ni-Si, Nb-Si, and Ag-Si ML's are determined. Activation enthalpies and preexponential factors for the interdiffusion in the ML's are very small compared with that in amorphous alloys and crystalline solids. The relation between the atomic-size difference and interdiffusion in the ML's are investigated. The observed interdiffusion characteristics are compared with that in amorphous alloys and crystalline α-Zr, α-Ti, and Si. The experimental results suggest that a collective atomic-jumping mechanism govern the interdiffusion in the ML's, the collective proposal involving 8-15 atoms moving between extended nonequilibrium defects by thermal activation. The role of the interdiffusion in the solid-state reaction in the ML's is also discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hongfen, E-mail: wanghongfen11@163.com; Wang, Zhiqi; Chen, Shougang

Molybdenum carbides with surfactants as carbon sources were prepared using the carbothermal reduction of the appropriate precursors (molybdenum oxides deposited on surfactant micelles) at 1023 K under hydrogen gas. The carburized products were characterized using scanning electron microscopy (SEM), X-ray diffraction and BET surface area measurements. From the SEM images, hollow microspherical and rod-like molybdenum carbides were observed. X-ray diffraction patterns showed that the annealing time of carburization had a large effect on the conversion of molybdenum oxides to molybdenum carbides. And BET surface area measurements indicated that the difference of carbon sources brought a big difference in specific surfacemore » areas of molybdenum carbides. - Graphical abstract: Molybdenum carbides having hollow microspherical and hollow rod-like morphologies that are different from the conventional monodipersed platelet-like morphologies. Highlights: Black-Right-Pointing-Pointer Molybdenum carbides were prepared using surfactants as carbon sources. Black-Right-Pointing-Pointer The kinds of surfactants affected the morphologies of molybdenum carbides. Black-Right-Pointing-Pointer The time of heat preservation at 1023 K affected the carburization process. Black-Right-Pointing-Pointer Molybdenum carbides with hollow structures had larger specific surface areas.« less

Bonding temperature dependence of GaInAsP/InP laser diode grown on hydrophilically directly bonded InP/Si substrate

NASA Astrophysics Data System (ADS)

Aikawa, Masaki; Onuki, Yuya; Hayasaka, Natsuki; Nishiyama, Tetsuo; Kamada, Naoki; Han, Xu; Kallarasan Periyanayagam, Gandhi; Uchida, Kazuki; Sugiyama, Hirokazu; Shimomura, Kazuhiko

2018-02-01

The bonding-temperature-dependent lasing characteristics of 1.5 a µm GaInAsP laser diode (LD) grown on a directly bonded InP/Si substrate were successfully obtained. We have fabricated the InP/Si substrate using a direct hydrophilic wafer bonding technique at bonding temperatures of 350, 400, and 450 °C, and deposited GaInAsP/InP double heterostructure layers on this InP/Si substrate. The surface conditions, X-ray diffraction (XRD) analysis, photoluminescence (PL) spectra, and electrical characteristics after the growth were compared at these bonding temperatures. No significant differences were confirmed in X-ray diffraction analysis and PL spectra at these bonding temperatures. We realized the room-temperature lasing of the GaInAsP LD on the InP/Si substrate bonded at 350 and 400 °C. The threshold current densities were 4.65 kA/cm2 at 350 °C and 4.38 kA/cm2 at 400 °C. The electrical resistance was found to increase with annealing temperature.

Effect of continuous annealing temperature on microstructure and properties of ferritic rolled interstitial-free steel

NASA Astrophysics Data System (ADS)

Qiu, Chen-yang; Li, Lang; Hao, Lei-lei; Wang, Jian-gong; Zhou, Xun; Kang, Yong-lin

2018-05-01

In this report, the microstructure, mechanical properties, and textures of warm rolled interstitial-free steel annealed at four different temperatures (730, 760, 790, and 820°C) were studied. The overall structural features of specimens were investigated by optical microscopy, and the textures were measured by X-ray diffraction (XRD). Nano-sized precipitates were then observed by a transmission electron microscope (TEM) on carbon extraction replicas. According to the results, with increased annealing temperatures, the ferrite grains grew; in addition, the sizes of Ti4C2S2 and TiC precipitates also increased. Additionally, the sizes of TiN and TiS precipitates slightly changed. When the annealing temperature increased from 730 to 820°C, the yield strength (YS) and the ultimate tensile strength (UTS) showed a decreasing trend. Meanwhile, elongation and the strain harden exponent (n value) increased to 49.6% and 0.34, respectively. By comparing textures annealed at different temperatures, the intensity of {111} texture annealed at 820°C was the largest, while the difference between the intensity of {111}<110> and {111}<112> was the smallest when the annealing temperature was 820°C. Therefore, the plastic strain ratio (r value) annealed at 820°C was the highest.

X-ray diffraction from shock-loaded polycrystals.

PubMed

Swift, Damian C

2008-01-01

X-ray diffraction was demonstrated from shock-compressed polycrystalline metals on nanosecond time scales. Laser ablation was used to induce shock waves in polycrystalline foils of Be, 25-125 microm thick. A second laser pulse was used to generate a plasma x-ray source by irradiation of a Ti foil. The x-ray source was collimated to produce a beam of controllable diameter, which was directed at the Be sample. X-rays were diffracted from the sample, and detected using films and x-ray streak cameras. The diffraction angle was observed to change with shock pressure. The diffraction angles were consistent with the uniaxial (elastic) and isotropic (plastic) compressions expected for the loading conditions used. Polycrystalline diffraction will be used to measure the response of the crystal lattice to high shock pressures and through phase changes.

Structural and magnetic properties of pure and Ca-doped LaCoO3 nanopowders obtained by a sol-gel route.

PubMed

Armelao, Lidia; Barreca, Davide; Bottaro, Gregorio; Maragno, Cinzia; Tondello, Eugenio; Caneschi, Andrea; Sangregorio, Claudio; Gialanella, Stefano

2006-04-01

Pure and Ca-doped LaCoO3 nanopowders were prepared by a non-alkoxidic sol-gel route using cobalt(II) acetate, lanthanum(III) nitrate and calcium(II) acetate as oxide precursors. The structural evolution and magnetic properties of the samples were studied as a function of thermal treatments in air up to 1273 K. In particular, the microstructure and composition of the systems were analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Both pure and calcium-doped samples annealing at 973 K resulted in the formation of cubic LaCoO3 (average crystallite size <30 nm). This phase was fully retained in the calcium-doped materials even after annealing at higher temperatures, whereas a transition to the rhomboedral polymorph was detected in the pure samples at 1073 K. The magnetic behavior of the nanopowders was investigated as a function of temperature and applied field using both dynamic and static susceptibility measurements. Pure lanthanum cobaltite samples underwent a transition to an ordered state at 88 K, and their magnetic properties changed as a function of thermal treatments. As concerns calcium-doped samples, they ordered ferromagnetically at 171 and 185 K depending on the annealing temperature and displayed open hysteresis loops with coercive fields as large as 1.75 T at low temperatures.

Formation of nickel germanides from Ni layers with thickness below 10 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jablonka, Lukas; Kubart, Tomas; Primetzhofer, Daniel

2017-03-01

The authors have studied the reaction between a Ge (100) substrate and thin layers of Ni ranging from 2 to 10 nm in thickness. The formation of metal-rich Ni5Ge3Ni5Ge3 was found to precede that of the monogermanide NiGe by means of real-time in situ x-ray diffraction during ramp-annealing and ex situ x-ray pole figure analyses for phase identification. The observed sequential growth of Ni5Ge3Ni5Ge3 and NiGe with such thin Ni layers is different from the previously reported simultaneous growth with thicker Ni layers. The phase transformation from Ni5Ge3Ni5Ge3 to NiGe was found to be nucleation-controlled for Ni thicknesses <5 nm<5more » nm, which is well supported by thermodynamic considerations. Specifically, the temperature for the NiGe formation increased with decreasing Ni (rather Ni5Ge3Ni5Ge3) thickness below 5 nm. In combination with sheet resistance measurement and microscopic surface inspection of samples annealed with a standard rapid thermal processing, the temperature range for achieving morphologically stable NiGe layers was identified for this standard annealing process. As expected, it was found to be strongly dependent on the initial Ni thickness« less

Synthesis and Characterization of SiO2@Y2MoO6:Eu3+ Core-Shell Structured Spherical Phosphors by Sol-Gel Process.

PubMed

Li, G Z; Liu, F H; Chu, Z S; Wu, D M; Yang, L B; Li, J L; Wang, M N; Wang, Z L

2016-04-01

SiO2@Y2MoO6:Eu3+ core-shell phosphors were prepared by the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Y2MoO6:Eu3+ core-shell phosphors. The XRD results demonstrated that the Y2MoO6:Eu3+ layers on the SiO2 spheres crystallized after being annealed at 700 °C and the crystallinity increased with raising the annealing temperature. The obtained core-shell phosphors have spherical shape with narrow size distribution (average size ca. 640 nm), non-agglomeration, and smooth surface. The thickness of the Y2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (70 nm for four deposition cycles). The Eul+ shows a strong PL emission (dominated by 5D0-7F2 red emission at 614 nm) under the excitation of 347 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

Zirconolites from Sri Lanka, South Africa and Brazil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ewing, R.C.; Haaker, R.F.; Headley, T.J.

1981-01-01

Zirconolites, CaZrTi/sub 2/O/sub 7/, from Sri Lanka and Pala Bora, South Africa, and a calzirtite, CaZr/sub 3/TiO/sub 9/, from Jacupiranga, Brazil, were examined using the electron microprobe, x-ray diffraction (annealing study), transmission electron microscopy, scanning electron microscopy and optical microscopy. The x-ray data indicate that all three zirconolites are metamict. Both Sri Lanka zirconolites are amorphous to the limits of resolution of the electron microscope (approx. 10 A). The Pala Bora zirconolite is largely amorphous but contains isolated domains (50 to 200 A) of crystalline material which may be the result of post-metamict recrystallization and alteration. The only other significantmore » evidence for chemical alteration was the lower ThO/sub 2/ concentration (1 to 2 weight percent) and slightly lower analytic totals for the rims of the Sri Lanka zirconolites. Upon annealing at 1130/sup 0/C for 5 hours, all three zirconolites recrystallized as microcrystalline aggregates. Refined unit cell parameters and volumes are consistent with published data for synthetic zirconolites. Both Sri Lanka zirconolites contain microvoids, spherical in shape, and 200 Angstroms to 2 microns in size. This porosity may be the result of helium accumulation arising from the decay of U and Th. The calzirtite was highly crystalline, exhibited no porosity, and was unchanged by the annealing treatment.« less

Interfacial Reaction During High Energy Ball Milling Dispersion of Carbon Nanotubes into Ti6Al4V

NASA Astrophysics Data System (ADS)

Adegbenjo, A. O.; Olubambi, P. A.; Potgieter, J. H.; Nsiah-Baafi, E.; Shongwe, M. B.

2017-12-01

The unique thermal and mechanical properties of carbon nanotubes (CNTs) have made them choice reinforcements for metal matrix composites (MMCs). However, there still remains a critical challenge in achieving homogeneous dispersion of CNTs in metallic matrices. Although high energy ball milling (HEBM) has been reported as an effective method of dispersing CNTs into metal matrices, a careful selection of the milling parameters is important not to compromise the structural integrity of CNTs which may cause interfacial reactions with the matrix. In this study, multi-walled carbon nanotubes (MWCNTs) were purified by annealing in argon and vacuum atmospheres at 1000 and 1800 °C, respectively, for 5 h to remove possible metallic catalyst impurities. Subsequently, 1, 2 and 3 wt.% MWCNTs were dispersed by adapted HEBM into Ti6Al4V alloy metal matrix. Raman spectroscopy (RS), x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectrometry and transmission electron microscopy techniques were used to characterize the as-received and annealed MWCNTs, as well as the admixed MWCNT/Ti6Al4V nanocomposite powders. The experimental results showed that vacuum annealing successfully eliminated retained nickel (Ni) catalysts from MWCNTs, while the adapted HEBM method achieved a relative homogeneous dispersion of MWCNTs into the Ti6Al4V matrix and helped to control interfacial reactions between defective MWCNTs and the metal matrix.

Miscibility of amorphous ZrO2-Al2O3 binary alloy

NASA Astrophysics Data System (ADS)

Zhao, C.; Richard, O.; Bender, H.; Caymax, M.; De Gendt, S.; Heyns, M.; Young, E.; Roebben, G.; Van Der Biest, O.; Haukka, S.

2002-04-01

Miscibility is a key factor for maintaining the homogeneity of the amorphous structure in a ZrO2-Al2O3 binary alloy high-k dielectric layer. In the present work, a ZrO2/Al2O3 laminate thin layer has been prepared by atomic layer chemical vapor deposition on a Si (100) wafer. This layer, with artificially induced inhomogeneity (lamination), enables one to study the change in homogeneity of the amorphous phase in the ZrO2/Al2O3 system during annealing. High temperature grazing incidence x-ray diffraction (HT-XRD) was used to investigate the change in intensity of the constructive interference peak of the x-ray beams which are reflected from the interfaces of ZrO2/Al2O3 laminae. The HT-XRD spectra show that the intensity of the peak decreases with an increase in the anneal temperature, and at 800 °C, the peak disappears. The same samples were annealed by a rapid thermal process (RTP) at temperatures between 700 and 1000 °C for 60 s. Room temperature XRD of the RTP annealed samples shows a similar decrease in peak intensity. Transmission electronic microscope images confirm that the laminate structure is destroyed by RTP anneals and, just below the crystallization onset temperature, a homogeneous amorphous ZrAlxOy phase forms. The results demonstrate that the two artificially separated phases, ZrO2 and Al2O3 laminae, tend to mix into a homogeneous amorphous phase before crystallization. This observation indicates that the thermal stability of ZrO2-Al2O3 amorphous phase is suitable for high-k applications.

Thermal-induced SPR tuning of Ag-ZnO nanocomposite thin film for plasmonic applications

NASA Astrophysics Data System (ADS)

Singh, S. K.; Singhal, R.

2018-05-01

The formation of silver (Ag) nanoparticles in a ZnO matrix were successfully synthesized by RF-magnetron sputtering at room temperature. As prepared Ag-ZnO nanocomposite (NCs) thin films were annealed in vacuum at three different temperatures of 300 °C, 400 °C and 500 °C, respectively. The structural modifications for as-deposited and annealed films were estimated by X-ray diffraction and TEM techniques. The crystalline behavior preferably along the c-axis of the hexagonal wurtzite structure was observed in as-deposited Ag-ZnO film and improved significantly with increasing the annealing temperature. The crystallite size of as-deposited film was measured to be 13.6 nm, and increases up to 28.5 nm at higher temperatures. The chemical composition and surface structure of the as-deposited films were estimated by X-ray photoelectron spectroscopy. The presence of Ag nanoparticles with average size of 8.2 ± 0.2 nm, was confirmed by transmission electron microscopy. The strong surface plasmon resonance (SPR) band was observed at the wavelength of ∼565 nm for as-deposited film and a remarkable red shift of ∼22 nm was recorded after the annealing treatment as confirmed by UV-visible spectroscopy. Atomic force microscopy confirmed the grain growth from 60.38 nm to 79.42 nm for as-deposited and higher temperature annealed film respectively, with no significant change in the surface roughness. Thermal induced modifications such as disordering and lattice defects in Ag-ZnO NCs thin films were carried out by Raman spectroscopy. High quality Ag-ZnO NCs thin films with minimum strain and tunable optical properties could be useful in various plasmonic applications.

Influence of annealing temperature on physical properties and photocatalytic ability of g-C3N4 nanosheets synthesized through urea polymerization in Ar atmosphere

NASA Astrophysics Data System (ADS)

Mai Oanh, Le Thi; Hang, Lam Thi; Lai, Ngoc Diep; Phuong, Nguyen Thi; Thang, Dao Viet; Hung, Nguyen Manh; Danh Bich, Do; Minh, Nguyen Van

2018-03-01

The influences of annealing temperature on structure, morphology, vibration, optical properties and photocatalytic ability of g-C3N4 nanosheets synthesized from urea in Ar atmosphere were investigated in detail by using x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), UV-vis absorption, and photoluminescence (PL). It was found that the preparation temperature had a great effect on structure and physical properties of g-C3N4. As the processing temperature increased from 450 °C to 650 °C, the interlayer stacking distance of g-C3N4 decreased from 3.281 Å to 3.217 Å and the lattice parameter a decreased from 5.010 Å to 4.934 Å. This indicated a denser packing fashion of g-C3N4 at high annealing temperature. Moreover, the FTIR spectra and SEM images revealed a large fraction of small polymer segments containing only a few heptazine units as annealing temperature increased. BET result indicated an increasing specific surface area as preparation temperature increased. UV-vis absorption spectra showed a decrease of the band gap energy with increasing calcination temperature which agrees well with the measured PL spectra. It was demonstrated that samples annealed at 550 °C exhibited the strongest photocatalytic activity. A decomposition of 80% and 100% of rhodamine B was obtained within respectively 1 h and 2 h under Xenon lamp irradiation. Photocatalytic result could be adequately explained based on evidences of specific surface area, average pore volume and pore size, and recombination rate of photoinduced electron-hole pairs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, Congfei; Liang, Xiaojuan, E-mail: lxj6126@126

The titanate, is a material of interest for various energy applications, including photovoltaics, catalysts, and high-rate energy storage devices. Herein, its related materials, CuO/CaTi{sub 4}O{sub 9} [CCTO] thin films, were successfully fabricated on SrTiO{sub 3} (100) substrates by RF magnetron sputtering assisted with subsequent oxygen annealing. This obtained CCTO thin films were then systemically studied by X-ray powder diffraction (XRD), atomic force microscopy (AFM), scan electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). It was found that CuO and CaTi{sub 4}O{sub 9} (001) particles were closely accumulated together on the surface of the substrate inmore » the annealing process after comparing with that of the as-prepared thin film, which was verified by SEM and AFM results. Furthermore, we investigated the third-order nonlinear optical (NLO) properties of the as-prepared and annealed CCTO thin film by means of the Z-scan technique using 650 nm femtosecond laser pulse. Post-deposition oxygen annealing was found to modify the morphological characteristics of the films, resulting in enhancing their NLO properties. The observation of NLO performance of annealed CCTO thin film indicates that RF magnetron sputtering is a feasible method for the fabrication of optical thin films, which can be expanded to fabricate other NLO materials from the corresponding dispersions. Naturally, we concluded that the CCTO thin film occupy a better NLO property, and thus enlarge its application in nonlinear optics. - Highlights: • The CCTO thin film was prepared using the RF magnetron sputtering and oxygen annealing. • The film was prepared on the SrTiO{sub 3}(100) substrates with a Ca{sub 2}CuO{sub 3} target. • The oxygen annealing was found can effectively enhance the film quality and NLO property. • The film was characterized using XPS, SEM, AFM, TEM, XRD and Z-scan techniques.« less

Defect reduction in MBE-grown AlN by multicycle rapid thermal annealing

NASA Astrophysics Data System (ADS)

Greenlee, Jordan D.; Gunning, Brendan; Feigelson, Boris N.; Anderson, Travis J.; Koehler, Andrew D.; Hobart, Karl D.; Kub, Francis J.; Doolittle, W. Alan

2016-01-01

Multicycle rapid thermal annealing (MRTA) is shown to reduce the defect density of molecular beam epitaxially grown AlN films. No damage to the AlN surface occurred after performing the MRTA process at 1520°C. However, the individual grain structure was altered, with the emergence of step edges. This change in grain structure and diffusion of AlN resulted in an improvement in the crystalline structure. The Raman E2 linewidth decreased, confirming an improvement in crystal quality. The optical band edge of the AlN maintained the expected value of 6.2 eV throughout MRTA annealing, and the band edge sharpened after MRTA annealing at increased temperatures, providing further evidence of crystalline improvement. X-ray diffraction shows a substantial improvement in the (002) and (102) rocking curve FWHM for both the 1400 and 1520°C MRTA annealing conditions compared to the as-grown films, indicating that the screw and edge type dislocation densities decreased. Overall, the MRTA post-growth annealing of AlN lowers defect density, and thus will be a key step to improving optoelectronic and power electronic devices. [Figure not available: see fulltext.

Room temperature photoluminescence properties of ZnO nanorods grown by hydrothermal reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iwan, S., E-mail: iwan-sugihartono@unj.ac.id; Prodi Ilmu Material, Departemen Fisika, FMIPA, Universitas Indonesia, Kampus UI Depok; Fauzia, Vivi

Zinc oxide (ZnO) nanorods were fabricated by a hydrothermal reaction on silicon (Si) substrate at 95 °C for 6 hours. The ZnO seed layer was fabricated by depositing ZnO thin films on Si substrates by ultrasonic spray pyrolisis (USP). The annealing effects on crystal structure and optical properties of ZnO nanorods were investigated. The post-annealing treatment was performed at 800 °C with different environments. The annealed of ZnO nanorods were characterized by X-ray diffraction (XRD) and photoluminescence (PL) in order to analyze crystal structure and optical properties, respectively. The results show the orientations of [002], [101], [102], and [103] diffractionmore » peaks were observed and hexagonal wurtzite structure of ZnO nanorods were vertically grown on Si substrates. The room temperature PL spectra show ultra-violet (UV) and visible emissions. The annealed of ZnO nanorods in vacuum condition (3.8 × 10{sup −3} Torr) has dominant UV emission. Meanwhile, non-annealed of ZnO nanorods has dominant visible emission. It was expected that the annealed of ZnO in vacuum condition suppresses the existence of native defects in ZnO nanorods.« less

Single-pulse x-ray diffraction using polycapillary optics for in situ dynamic diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maddox, B. R., E-mail: maddox3@llnl.gov; Akin, M. C., E-mail: akin1@llnl.gov; Teruya, A.

2016-08-15

Diagnostic use of single-pulse x-ray diffraction (XRD) at pulsed power facilities can be challenging due to factors such as the high flux and brightness requirements for diffraction and the geometric constraints of experimental platforms. By necessity, the x-ray source is usually positioned very close, within a few inches of the sample. On dynamic compression platforms, this puts the x-ray source in the debris field. We coupled x-ray polycapillary optics to a single-shot needle-and-washer x-ray diode source using a laser-based alignment scheme to obtain high-quality x-ray diffraction using a single 16 ns x-ray pulse with the source >1 m from themore » sample. The system was tested on a Mo sample in reflection geometry using 17 keV x-rays from a Mo anode. We also identified an anode conditioning effect that increased the x-ray intensity by 180%. Quantitative measurements of the x-ray focal spot produced by the polycapillary yielded a total x-ray flux on the sample of 3.3 ± 0.5 × 10{sup 7} molybdenum Kα photons.« less

The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Cios, G.; Tokarski, T.; Żywczak, A.; Dziurka, R.; Stępień, M.; Gondek, Ł.; Marciszko, M.; Pawłowski, B.; Wieczerzak, K.; Bała, P.

2017-10-01

This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (-60 °C) in order to obtain a different volume fraction of strain-induced martensite (up to 70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (α' → γ). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted—strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov-Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.

Effect of annealing temperature on the properties of copper oxide films prepared by dip coating technique

NASA Astrophysics Data System (ADS)

Raship, N. A.; Sahdan, M. Z.; Adriyanto, F.; Nurfazliana, M. F.; Bakri, A. S.

2017-01-01

Copper oxide films were grown on silicon substrates by sol-gel dip coating method. In order to study the effects of annealing temperature on the properties of copper oxide films, the temperature was varied from 200 °C to 450 °C. In the process of dip coating, the substrate is withdrawn from the precursor solution with uniform velocity to obtain a uniform coating before undergoing an annealing process to make the copper oxide film polycrystalline. The physical properties of the copper oxide films were measured by an X-ray diffraction (XRD), a field emission scanning electron microscope (FESEM), an atomic force microscopy (AFM) and a four point probe instrument. From the XRD results, we found that pure cuprite (Cu2O) phase can be obtained by annealing the films annealed at 200 °C. Films annealed at 300 °C had a combination phase which consists of tenorite (CuO) and cuprite (Cu2O) phase while pure tenorite (CuO) phase can be obtained at 450 °C annealing temperature. The surface microstructure showed that the grains size is increased whereas the surface roughness is increased and then decreases by increasing in annealing temperature. The films showed that the resistivity decreased with increasing annealing temperature. Consequently, it was observed that annealing temperature has strong effects on the structural, morphological and electrical properties of copper oxide films.

X-Ray Diffraction Apparatus

NASA Technical Reports Server (NTRS)

Blake, David F. (Inventor); Bryson, Charles (Inventor); Freund, Friedmann (Inventor)

1996-01-01

An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample is introduced. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.

CdTe1-x S x (x  ⩽  0.05) thin films synthesized by aqueous solution deposition and annealing

NASA Astrophysics Data System (ADS)

Pruzan, Dennis S.; Hahn, Carina E.; Misra, Sudhajit; Scarpulla, Michael A.

2017-11-01

While CdS thin films are commonly deposited from aqueous solutions, CdTe thin films are extremely difficult to deposit directly from aqueous solution. In this work, we report on polycrystalline CdTe1-x S x thin films synthesized via deposition from aqueous precursor solutions followed by annealing treatments and on their physical properties. The deposition method uses spin-coating of alternating Cd2+ and Te2- aqueous solutions and rinse steps to allow formation of the films but to shear off excess reactants and poorly-bonded solids. Films are then annealed in the presence of CdCl2 as is commonly done for CdTe photovoltaic absorber layers deposited by any means. Scanning electron microscopy (SEM) reveals low void fractions and grain sizes up to 4 µm and x-ray diffraction (XRD) shows that the films are primarily cubic CdTe1-x S x (x  ⩽  0.05) with random crystallographic orientation. Optical transmission yields bandgap absorption consistent with a CdTe1-x S x dilute alloy and low-temperature photoluminescence (PL) consists of an emission band centered at 1.35 eV consistent with donor-acceptor pair (DAP) transitions in CdTe1-x S x . Together, the crystalline quality and PL yield from films produced by this method represent an important step towards electroless, ligand-free solution processed CdTe and related alloy thin films suitable for optoelectronic device applications such as thin film heterojunction or nanodipole-based photovoltaics.

Defect-mediated room temperature ferromagnetism in vanadium dioxide thin films

NASA Astrophysics Data System (ADS)

Yang, Tsung-Han; Nori, Sudhakar; Zhou, Honghui; Narayan, Jagdish

2009-09-01

High quality epitaxial undoped vanadium oxide (VO2) thin films on c-plane sapphire (0001) substrate have been grown using pulsed laser deposition technique. The as-grown films exhibited excellent structural and transport properties without requiring further annealing treatments for these oxygen-deficient oxide films. The epitaxial growth has been achieved via domain matching epitaxy, where matching of integral multiples of planes occurs across the film-substrate interface. The magnetic properties of vanadium oxide (VO2) films investigated at different temperatures in the range of 10-360 K showed significant magnetic hysteresis as well as saturation of the magnetic moment. The origin of ferromagnetic properties with an estimated Curie temperature above 500 K is discussed in the absence of magnetic impurities in VO2 thin films as determined by x-ray photoelectron spectroscopy, x-ray diffraction, and transmission electron microscopy.

Effect of content silver and heat treatment temperature on morphological, optical, and electrical properties of ITO films by sol-gel technique

NASA Astrophysics Data System (ADS)

Mirzaee, Majid; Dolati, Abolghasem

2014-09-01

Silver-doped indium tin oxide thin films were synthesized using sol-gel dip-coating technique. The influence of different silver-dopant contents and annealing temperature on the electrical, optical, structural, and morphological properties of the films were characterized by means of four-point probe, UV-Vis spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscope (XPS). XRD analysis confirmed the formation of cubic bixbyte structure of In2O3 with silver nanoparticles annealed at 350 °C. XPS analysis showed that divalent tin transformed to tetravalent tin through oxidization, and silver nanoparticles embedded into ITO matrix covered with silver oxide shell, resulting in high quality nanocomposite thin films. The embedment of polyvinylpyrrolidone inhibited the growth of silver nanoparticles and ITO annealed at 350 °C. Delafossite structure of tin-doped AgInO2 was found at higher annealing temperatures. XRD analysis and FESEM micrographs showed that the optimum temperature to prevent the formation of AgInO2 is 350 °C. The embedment of silver particles (5-10 nm) from reduction of silver ion in ITO thin films improved the electrical conductivity and optical transmittance of ITO nanolayers. The lowest stable sheet resistance of 1,952 Ω/Sq for a 321 nm thick and an average optical transmittance of 91.8 % in the visible region with a band gap of 3.43 eV were achieved for silver-doping content of 0.04 M.

Solid state characterization and crystal structure from X-ray powder diffraction of two polymorphic forms of ranitidine base.

PubMed

de Armas, Héctor Novoa; Peeters, Oswald M; Blaton, Norbert; Van Gyseghem, Elke; Martens, Johan; Van Haele, Gerrit; Van Den Mooter, Guy

2009-01-01

Ranitidine hydrochloride (RAN-HCl), a known anti-ulcer drug, is the product of reaction between HCl and ranitidine base (RAN-B). RAN-HCl has been extensively studied; however this is not the case of the RAN-B. The solid state characterization of RAN-B polymorphs has been carried out using different analytical techniques (microscopy, thermal analysis, Fourier transform infrared spectrometry in the attenuated total reflection mode, (13)C-CPMAS-NMR spectroscopy and X-ray powder diffraction). The crystal structures of RAN-B form I and form II have been determined using conventional X-ray powder diffraction in combination with simulated annealing and whole profile pattern matching, and refined using rigid-body Rietveld refinement. RAN-B form I is a monoclinic polymorph with cell parameters: a = 7.317(2), b = 9.021(2), c = 25.098(6) A, beta = 95.690(1) degrees and space group P2(1)/c. The form II is orthorhombic: a = 31.252(4), b = 13.052(2), c = 8.0892(11) A with space group Pbca. In RAN-B polymorphs, the nitro group is involved in a strong intramolecular hydrogen bond responsible for the existence of a Z configuration in the enamine portion of the molecules. A tail to tail packing motif can be denoted via intermolecular hydrogen bonds. The crystal structures of RAN-B forms are compared to those of RAN-HCl polymorphs. RAN-B polymorphs are monotropic polymorphic pairs. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

Copper-Zinc-Tin-Sulfur Thin Film Using Spin-Coating Technology

PubMed Central

Yeh, Min-Yen; Lei, Po-Hsun; Lin, Shao-Hsein; Yang, Chyi-Da

2016-01-01

Cu2ZnSnS4 (CZTS) thin films were deposited on glass substrates by using spin-coating and an annealing process, which can improve the crystallinity and morphology of the thin films. The grain size, optical gap, and atomic contents of copper (Cu), zinc (Zn), tin (Sn), and sulfur (S) in a CZTS thin film absorber relate to the concentrations of aqueous precursor solutions containing copper chloride (CuCl2), zinc chloride (ZnCl2), tin chloride (SnCl2), and thiourea (SC(NH2)2), whereas the electrical properties of CZTS thin films depend on the annealing temperature and the atomic content ratios of Cu/(Zn + Sn) and Zn/Sn. All of the CZTS films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), Raman spectroscopy, and Hall measurements. Furthermore, CZTS thin film was deposited on an n-type silicon substrate by using spin-coating to form an Mo/p-CZTS/n-Si/Al heterostructured solar cell. The p-CZTS/n-Si heterostructured solar cell showed a conversion efficiency of 1.13% with Voc = 520 mV, Jsc = 3.28 mA/cm2, and fill-factor (FF) = 66%. PMID:28773647

Iron-based soft magnetic composites with Mn-Zn ferrite nanoparticles coating obtained by sol-gel method

NASA Astrophysics Data System (ADS)

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

2012-11-01

This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn-Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20 nm, were obtained via the sol-gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn-Zn ferrites. Mn-Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn-Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10 kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn-Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400 °C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability.

Optimisation of growth of epitaxial Tl 2Ba 2Ca 1Cu 2O 8 superconducting thin films for electronic device applications

NASA Astrophysics Data System (ADS)

Michael, Peter C.; Johansson, L.-G.; Bengtsson, L.; Claeson, T.; Ivanov, Z. G.; Olsson, E.; Berastegui, P.; Stepantsov, E.

1994-12-01

Epitaxial thin films of Tl 2Ba 2Ca 1Cu 2O 8 (Tl-2212) superconductor have been grown on single crystal (100) lanthanum aluminate (LaAlO 3) substrates by a two stage process: laser ablation of a BaCaCuO (0212) sintered target and post-deposition anneal ex-situ in a thallium environment. The films are c-axis oriented with in-plane epitaxy as determined by x-ray diffraction (XRD θ-2θ and φ-scans). Superconducting transition temperatures as high as 105.5K have been obtained both from four-probe resistance and a.c. magnetic susceptibility measurements. Film morphology and chemical composition have been assessed by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). Sensitivity of the precursor film to environmental exposure has proven to be a determining factor in the reproducibility of film growth characteristics. The effect of oxygen partial pressure and substrate temperature used in the precursor film synthesis, as well as the thallium annealing temperature and duration, on the growth of Tl-2212 thin films is reported.

Synthesis of Poly-Silicon Thin Films on Glass Substrate Using Laser Initiated Metal Induced Crystallization of Amorphous Silicon for Space Power Application

NASA Technical Reports Server (NTRS)

Abu-Safe, Husam H.; Naseem, Hameed A.; Brown, William D.

2007-01-01

Poly-silicon thin films on glass substrates are synthesized using laser initiated metal induced crystallization of hydrogenated amorphous silicon films. These films can be used to fabricate solar cells on low cost glass and flexible substrates. The process starts by depositing 200 nm amorphous silicon films on the glass substrates. Following this, 200 nm of sputtered aluminum films were deposited on top of the silicon layers. The samples are irradiated with an argon ion cw laser beam for annealing. Laser power densities ranging from 4 to 9 W/cm2 were used in the annealing process. Each area on the sample is irradiated for a different exposure time. Optical microscopy was used to examine any cracks in the films and loss of adhesion to the substrates. X-Ray diffraction patterns from the initial results indicated the crystallization in the films. Scanning electron microscopy shows dendritic growth. The composition analysis of the crystallized films was conducted using Energy Dispersive x-ray Spectroscopy. The results of poly-silicon films synthesis on space qualified flexible substrates such as Kapton are also presented.

Structural, thermal, optical, and photoacoustic study of nanocrystalline Bi{sub 2}Te{sub 3} produced by mechanical alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Souza, S. M.; Triches, D. M.; Poffo, C. M.

2011-01-01

Nanocrystalline Bi{sub 2}Te{sub 3} was produced by mechanical alloying and its properties were investigated by differential scanning calorimetry (DSC) x-ray diffraction (XRD), Raman spectroscopy (RS), and photoacoustic spectroscopy (PAS). Combining the XRD and RS results, the volume fraction of the interfacial component in as-milled and annealed samples was estimated. The PAS results suggest that the contribution of the interfacial component to the thermal diffusivity of nanostructured Bi{sub 2}Te{sub 3} is very significant.

The thermal stability of the carbon-palladium films for hydrogen sensor applications

NASA Astrophysics Data System (ADS)

Rymarczyk, Joanna; Czerwosz, ElŻbieta; Diduszko, Ryszard; Kozłowski, Mirosław

2017-08-01

The thermal stability of two types of C-Pd films prepared in PVD process were studied. These films are composed of Pd nanograins embedded in a multiphase carbonaceous matrix. These films were distinguished by Pd content. These films were annealed in a range of temperatures 50÷1000°C. The structural, topographical and molecular changes were studied by scanning electron microscopy (SEM), infrared spectroscopy (FTIR) and X-ray diffraction (XRD) methods. The results show that investigated films are thermally stable up to 200°C.

Existence of a stable intermixing phase for monolayer Ge on Si(001)

NASA Astrophysics Data System (ADS)

Yeom, H. W.; Sasaki, M.; Suzuki, S.; Sato, S.; Hosoi, S.; Iwabuchi, M.; Higashiyama, K.; Fukutani, H.; Nakamura, M.; Abukawa, T.; Kono, S.

1997-06-01

A monolayer adsorption of Ge on a single-domain Si(001)2 × 1 surface has been investigated by X-ray excited Auger electron diffraction (AED) and scanning tunneling microscopy. Contrary to the common belief, a significant intermixing of Ge down to at least the fourth layer is identified. This intermixing is found to progress to a stable interface alloy phase that develops fully for annealing at 500-600°C. A possible reason for the alloy phase is discussed to be an elastic interaction from the Si(001) surface.

Preparation of tungsten oxide

DOEpatents

Bulian, Christopher J [Yankton, SD; Dye, Robert C [Los Alamos, NM; Son, Steven F [Los Alamos, NM; Jorgensen, Betty S [Jemez Springs, NM; Perry, W Lee [Jemez Springs, NM

2009-09-22

Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.

Preparation of AgInSe2 thin films grown by vacuum evaporation method

NASA Astrophysics Data System (ADS)

Matsuo, H.; Yoshino, K.; Ikari, T.

2006-09-01

Polycrystalline AgInSe2 thin films were successfully grown on glass substrates by an evaporation method. The starting materials were stoichiometrically mixed Ag2Se and In2Se3 powders. X-ray diffraction revealed that the sample annealed at 600 °C consisted of AgInSe2 single phase, with (112) orientation and a large grain size. The lattice constant (a axis) was close to JCPDS values. From optical transmittance and reflectance measurements, the bandgap energy was estimated to be 1.17 eV.

Damage mechanisms of MoN/SiN multilayer optics for next-generation pulsed XUV light sources.

PubMed

Sobierajski, R; Bruijn, S; Khorsand, A R; Louis, E; van de Kruijs, R W E; Burian, T; Chalupsky, J; Cihelka, J; Gleeson, A; Grzonka, J; Gullikson, E M; Hajkova, V; Hau-Riege, S; Juha, L; Jurek, M; Klinger, D; Krzywinski, J; London, R; Pelka, J B; Płociński, T; Rasiński, M; Tiedtke, K; Toleikis, S; Vysin, L; Wabnitz, H; Bijkerk, F

2011-01-03

We investigated the damage mechanism of MoN/SiN multilayer XUV optics under two extreme conditions: thermal annealing and irradiation with single shot intense XUV pulses from the free-electron laser facility in Hamburg - FLASH. The damage was studied "post-mortem" by means of X-ray diffraction, interference-polarizing optical microscopy, atomic force microscopy, and scanning transmission electron microscopy. Although the timescale of the damage processes and the damage threshold temperatures were different (in the case of annealing it was the dissociation temperature of Mo2N and in the case of XUV irradiation it was the melting temperature of MoN) the main damage mechanism is very similar: molecular dissociation and the formation of N2, leading to bubbles inside the multilayer structure.

Performance improvement of GaN-based metal-semiconductor-metal photodiodes grown on Si(111) substrate by thermal cycle annealing process

NASA Astrophysics Data System (ADS)

Lin, Jyun-Hao; Huang, Shyh-Jer; Su, Yan-Kuin

2014-01-01

A simple thermal cycle annealing (TCA) process was used to improve the quality of GaN grown on a Si substrate. The X-ray diffraction (XRD) and etch pit density (EPD) results revealed that using more process cycles, the defect density cannot be further reduced. However, the performance of GaN-based metal-semiconductor-metal (MSM) photodiodes (PDs) prepared on Si substrates showed significant improvement. With a two-cycle TCA process, it is found that the dark current of the device was only 1.46 × 10-11 A, and the photo-to-dark-current contrast ratio was about 1.33 × 105 at 5 V. Also, the UV/visible rejection ratios can reach as high as 1077.

Synthesis Of Noble Metal Nanoparticle Composite Glasses Using Low Energy Ion Beam Mixing

NASA Astrophysics Data System (ADS)

Varma, Ranjana S.; Kothari, D. C.; Mahadkar, A. G.; Kulkarni, N. A.; Kanjilal, D.; Kumar, P.

2010-12-01

Carbon coated thin films of Cu or Au on fused silica glasses have been irradiated using 100 keV Ar+ ions at different fluences ranging from 1×1013 to 1×1016 ion/cm2. In this article, we explore a route to form noble metal nanoparticles in amorphous glass matrices without post irradiation annealing using low energy ion beam mixing where nuclear energy loss process is dominant. Optical and structural properties were studied using UV-Vis-NIR absorbance spectroscopy and Glancing angle X-ray Diffraction (GXRD). Results showed that Cu and Au nanoparticles are formed at higher fluence of 1×1016 ion/cm2 used in this work without annealing. The diameters of metal nanoparticles obtained from UV-Vis NIR and GXRD are in agreement.

Flower-like Rh/Cu superhydrophobic coating via electrodeposition and its self-cleaning property

NASA Astrophysics Data System (ADS)

Zhao, N.; Lu, S. X.; Xu, W. G.; Cheng, X. L.

2017-01-01

Rh/Cu superhydrophobic coatings with textured flower-like dual micro-nano structures were fabricated on copper substrates via electrodesposition of Rh followed by annealing treatment. The scanning electron microscopy and X-ray diffraction pattern were conducted to analyse the morphology and chemical composition of the coating surfaces, respectively. The water drops exhibited a water contact angle of 168±1° and a sliding angle of 0±1° on the coating surfaces which were obtained by etching in concentrated hydrochloric acid and nitric acid, electrodeposited at -1.0 V for 30 min and annealing in an oven at 180°C for 60 min. The prepared superhydrophobic coatings showed excellent water repellence and self-cleaning property due to its extremely high water contact angle.

Real-time X-ray Diffraction: Applications to Materials Characterization

NASA Technical Reports Server (NTRS)

Rosemeier, R. G.

1984-01-01

With the high speed growth of materials it becomes necessary to develop measuring systems which also have the capabilities of characterizing these materials at high speeds. One of the conventional techniques of characterizing materials was X-ray diffraction. Film, which is the oldest method of recording the X-ray diffraction phenomenon, is not quite adequate in most circumstances to record fast changing events. Even though conventional proportional counters and scintillation counters can provide the speed necessary to record these changing events, they lack the ability to provide image information which may be important in some types of experiment or production arrangements. A selected number of novel applications of using X-ray diffraction to characterize materials in real-time are discussed. Also, device characteristics of some X-ray intensifiers useful in instantaneous X-ray diffraction applications briefly presented. Real-time X-ray diffraction experiments with the incorporation of image X-ray intensification add a new dimension in the characterization of materials. The uses of real-time image intensification in laboratory and production arrangements are quite unlimited and their application depends more upon the ingenuity of the scientist or engineer.

Radiation damage free ghost diffraction with atomic resolution

DOE PAGES

Li, Zheng; Medvedev, Nikita; Chapman, Henry N.; ...

2017-12-21

The x-ray free electron lasers can enable diffractive structural determination of protein nanocrystals and single molecules that are too small and radiation-sensitive for conventional x-ray diffraction. However the electronic form factor may be modified during the ultrashort x-ray pulse due to photoionization and electron cascade caused by the intense x-ray pulse. For general x-ray imaging techniques, the minimization of the effects of radiation damage is of major concern to ensure reliable reconstruction of molecular structure. Here in this paper, we show that radiation damage free diffraction can be achieved with atomic spatial resolution by using x-ray parametric down-conversion and ghostmore » diffraction with entangled photons of x-ray and optical frequencies. We show that the formation of the diffraction patterns satisfies a condition analogous to the Bragg equation, with a resolution that can be as fine as the crystal lattice length scale of several Ångstrom. Since the samples are illuminated by low energy optical photons, they can be free of radiation damage.« less

Radiation damage free ghost diffraction with atomic resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zheng; Medvedev, Nikita; Chapman, Henry N.

The x-ray free electron lasers can enable diffractive structural determination of protein nanocrystals and single molecules that are too small and radiation-sensitive for conventional x-ray diffraction. However the electronic form factor may be modified during the ultrashort x-ray pulse due to photoionization and electron cascade caused by the intense x-ray pulse. For general x-ray imaging techniques, the minimization of the effects of radiation damage is of major concern to ensure reliable reconstruction of molecular structure. Here in this paper, we show that radiation damage free diffraction can be achieved with atomic spatial resolution by using x-ray parametric down-conversion and ghostmore » diffraction with entangled photons of x-ray and optical frequencies. We show that the formation of the diffraction patterns satisfies a condition analogous to the Bragg equation, with a resolution that can be as fine as the crystal lattice length scale of several Ångstrom. Since the samples are illuminated by low energy optical photons, they can be free of radiation damage.« less

Synchrotron Radiation X-ray Diffraction Techniques Applied to Insect Flight Muscle.

PubMed

Iwamoto, Hiroyuki

2018-06-13

X-ray fiber diffraction is a powerful tool used for investigating the molecular structure of muscle and its dynamics during contraction. This technique has been successfully applied not only to skeletal and cardiac muscles of vertebrates but also to insect flight muscle. Generally, insect flight muscle has a highly ordered structure and is often capable of high-frequency oscillations. The X-ray diffraction studies on muscle have been accelerated by the advent of 3rd-generation synchrotron radiation facilities, which can generate brilliant and highly oriented X-ray beams. This review focuses on some of the novel experiments done on insect flight muscle by using synchrotron radiation X-rays. These include diffraction recordings from single myofibrils within a flight muscle fiber by using X-ray microbeams and high-speed diffraction recordings from the flight muscle during the wing-beat of live insects. These experiments have provided information about the molecular structure and dynamic function of flight muscle in unprecedented detail. Future directions of X-ray diffraction studies on muscle are also discussed.

Texture and structure contribution to low-temperature plasticity enhancement of Mg-Al-Zn-Mn Alloy MA2-1hp after ECAP and annealing

NASA Astrophysics Data System (ADS)

Serebryany, V. N.; D'yakonov, G. S.; Kopylov, V. I.; Salishchev, G. A.; Dobatkin, S. V.

2013-05-01

Equal channel angular pressing (ECAP) in magnesium alloys due to severe plastic shear deformations provides both grain refinement and the slope of the initial basal texture at 40°-50° to the pressing direction. These changes in microstructure and texture contribute to the improvement of low-temperature plasticity of the alloys. Quantitative texture X-ray diffraction analysis and diffraction of backscattered electrons are used to study the main textural and structural factors responsible for enhanced low-temperature plasticity based on the example of magnesium alloy MA2-1hp of the Mg-Al-Zn-Mn system. The possible mechanisms of deformation that lead to this positive effect are discussed.

A facile thermal decomposition route to synthesise CoFe2O4 nanostructures

NASA Astrophysics Data System (ADS)

Kalpanadevi, K.; Sinduja, C. R.; Manimekalai, R.

2014-01-01

The synthesis of CoFe2O4 nanoparticles has been achieved by a simple thermal decomposition method from an inorganic precursor, cobalt ferrous cinnamate hydrazinate (CoFe2(cin)3(N2H4)3) which was obtained by a novel precipitation method from the corresponding metal salts, cinnamic acid and hydrazine hydrate. The precursor was characterized by hydrazine and metal analyses, infrared spectral analysis and thermo gravimetric analysis. Under appropriate annealing, CoFe2(cin)3(N2H4)3 yielded CoFe2O4 nanoparticles, which were characterized for their size and structure using X-Ray diffraction (XRD), high resolution transmission electron microscopic (HRTEM), selected area electron diffraction (SAED) and scanning electron microscopic (SEM) techniques.

X-ray absorption spectroscopy study of annealing process on Sr1-xLaxCuO2 electron-doped cuprate thin films

NASA Astrophysics Data System (ADS)

Galdi, A.; Orgiani, P.; Sacco, C.; Gobaut, B.; Torelli, P.; Aruta, C.; Brookes, N. B.; Minola, M.; Harter, J. W.; Shen, K. M.; Schlom, D. G.; Maritato, L.

2018-03-01

The superconducting properties of Sr1-xLaxCuO2 thin films are strongly affected by sample preparation procedures, including the annealing step, which are not always well controlled. We have studied the evolution of Cu L2,3 and O K edge x-ray absorption spectra (XAS) of Sr1-xLaxCuO2 thin films as a function of reducing annealing, both qualitatively and quantitatively. By using linearly polarized radiation, we are able to identify the signatures of the presence of apical oxygen in the as-grown sample and its gradual removal as a function of duration of 350 °C Ar annealing performed on the same sample. Even though the as-grown sample appears to be hole doped, we cannot identify the signature of the Zhang-Rice singlet in the O K XAS, and it is extremely unlikely that the interstitial excess oxygen can give rise to a superconducting or even a metallic ground state. XAS and x-ray linear dichroism analyses are, therefore, shown to be valuable tools to improving the control over the annealing process of electron doped superconductors.

Synthesis and surface characterization of alumina-silica-zirconia nanocomposite ceramic fibres on aluminium at room temperature

NASA Astrophysics Data System (ADS)

Mubarak Ali, M.; Raj, V.

2010-04-01

Alumina-silica-zirconia nanocomposite (ASZNC) ceramic fibres were synthesized by conventional anodization route. Scanning Electron Microscopy (SEM), Atomic Force microscopy (AFM), X-Ray Diffraction (XRD) and Energy Dispersive X-Ray spectroscopy (EDAX) were used to characterize the morphology and crystalloid structure of ASZNC fibres. Current density (DC) is one of the important parameters to get the alumina-silica-zirconia nanocomposite (ASZNC) ceramic fibres by this route. Annealing of the films exhibited a drastic change in the properties due to improved crystallinity. The root mean square roughness of the sample observed from atomic force microscopic analysis is about 71.5 nm which is comparable to the average grain size of the coatings which is about 72 nm obtained from X-Ray diffraction. The results indicate that, the ASZNC fibres are arranged well in the nanostructure. The thickness of the coating increased with the anodizing time, but the coatings turned rougher and more porous. At the initial stage the growth of ceramic coating increases inwards to the metal substrate and outwards to the coating surface simultaneously. Subsequently, it mainly grows towards the metal substrate and the density of the ceramic coating increases gradually, which results in the decrease of the total thickness as anodizing time increases. This new approach of preparing ASZNC ceramic fibres may be important in applications ranging from gas sensors to various engineering materials.

Thermal annealing evolution to physical properties of ZnS thin films as buffer layer for solar cell applications

NASA Astrophysics Data System (ADS)

Kaushalya; Patel, S. L.; Purohit, A.; Chander, S.; Dhaka, M. S.

2018-07-01

The conventional CdS window layer in solar cells is found to be hazardous for the environment due to toxic nature of the cadmium. Therefore, in order to seek an alternative, a study on effect of post-annealing treatment on physical properties of e-beam evaporated ZnS thin films has been carried out where films of thickness 150 nm were deposited on glass and indium tin oxide (ITO) substrates. The post annealing treatment was performed in air atmosphere within the temperature range from 100 °C to 500 °C. X-ray diffraction analysis reveals that the films on glass substrate are found to be amorphous at low temperature annealing (≤300 °C) while have α-ZnS hexagonal phase (wurtzite structure) at higher annealing. The patterns also show that the possibility of oxidation is increased significantly at temperature 500 °C which leads to decrease in direct band gap from 3.28 eV to 3.18 eV except films annealed at 300 °C (i.e. 3.39 eV). The maximum transmittance is found about 95% as a result of Doppler blue shift while electrical analysis indicated almost ohmic behavior between current and voltage and surface roughness is increased with post-annealing treatment.

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. Copyright © 2014 John Wiley & Sons, Ltd.

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.

Enhanced reactivity of nanoscale iron particles through a vacuum annealing process

NASA Astrophysics Data System (ADS)

Riba, Olga; Barnes, Robert J.; Scott, Thomas B.; Gardner, Murray N.; Jackman, Simon A.; Thompson, Ian P.

2011-10-01

A reactivity study was undertaken to compare and assess the rate of dechlorination of chlorinated aliphatic hydrocarbons (CAHs) by annealed and non-annealed nanoscale iron particles. The current study aims to resolve the uncertainties in recently published work studying the effect of the annealing process on the reduction capability of nanoscale Fe particles. Comparison of the normalized rate constants (m2/h/L) obtained for dechlorination reactions of trichloroethene (TCE) and cis-1,2-dichloroethene (cis-1,2-DCE) indicated that annealing nanoscale Fe particles increases their reactivity 30-fold. An electron transfer reaction mechanism for both types of nanoscale particles was found to be responsible for CAH dechlorination, rather than a reduction reaction by activated H2 on the particle surface (i.e., hydrogenation, hydrogenolysis). Surface analysis of the particulate material using X-ray diffraction (XRD) and transmission electron microscopy (TEM) together with surface area measurement by Brunauer, Emmett, Teller (BET) indicate that the vacuum annealing process decreases the surface area and increases crystallinity. BET surface area analysis recorded a decrease in nanoscale Fe particle surface area from 19.0 to 4.8 m2/g and crystallite dimensions inside the particle increased from 8.7 to 18.2 nm as a result of annealing.

The role of nickel addition and annealing temperature on ion storage performance of nanostructured nickel ferrite thin films

NASA Astrophysics Data System (ADS)

Bazhan, Z.; Ghodsi, F. E.; Mazloom, J.

2016-10-01

The sol-gel spin-coated nickel ferrite (NF), NiFe2O4, thin films were synthesised and the effect of annealing temperature and compositional ratio on different properties of samples were investigated. Electrochemical performance of the films was measured in the presence of KOH and LiClO4/PC electrolyte. Generally, addition of nickel increases the current density. The NF thin films with molar ratio of 0.5 and annealed at 400 °C have the highest charge density value and the highest capacitance in both electrolytes. Annealing temperature had significant effect on electrochemical properties of NF thin films and the diffusion coefficient enhanced by increasing the annealing temperature. X-ray diffraction patterns of prepared samples showed the rhombohedral structure, hematite phase (α-Fe2O3), of iron oxide sample and the presence of inverse spinel structure confirms the formation of NF. Field emission scanning electron microscopy images revealed that the morphology of films changes from larvae shape to granular structure by nickel incorporation and the grain size increased by raising the annealing temperature. The absorption edge of the hematite shift to higher wavelength by annealing and nickel incorporation and band gap narrowing has been occurred.

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

PubMed Central

2014-01-01

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

Electrical and structural properties of (Pd/Au) Schottky contact to as grown and rapid thermally annealed GaN grown by MBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nirwal, Varun Singh, E-mail: varun.nirwal30@gmail.com; Singh, Joginder; Gautam, Khyati

2016-05-06

We studied effect of thermally annealed GaN surface on the electrical and structural properties of (Pd/Au) Schottky contact to Ga-polar GaN grown by molecular beam epitaxy on Si substrate. Current voltage (I-V) measurement was used to study electrical properties while X-ray diffraction (XRD) measurement was used to study structural properties. The Schottky barrier height calculated using I-V characteristics was 0.59 eV for (Pd/Au) Schottky contact on as grown GaN, which increased to 0.73 eV for the Schottky contact fabricated on 700 °C annealed GaN film. The reverse bias leakage current at -1 V was also significantly reduced from 6.42×10{sup −5} Amore » to 7.31×10{sup −7} A after annealing. The value of series resistance (Rs) was extracted from Cheung method and the value of R{sub s} decreased from 373 Ω to 172 Ω after annealing. XRD results revealed the formation of gallide phases at the interface of (Pd/Au) and GaN for annealed sample, which could be the reason for improvement in the electrical properties of Schottky contact after annealing.« less

Combining experiment and optical simulation in coherent X-ray nanobeam characterization of Si/SiGe semiconductor heterostructures

DOE PAGES

Tilka, J. A.; Park, J.; Ahn, Y.; ...

2016-07-06

Here, the highly coherent and tightly focused x-ray beams produced by hard x-ray light sources enable the nanoscale characterization of the structure of electronic materials but are accompanied by significant challenges in the interpretation of diffraction and scattering patterns. X-ray nanobeams exhibit optical coherence combined with a large angular divergence introduced by the x-ray focusing optics. The scattering of nanofocused x-ray beams from intricate semiconductor heterostructures produces a complex distribution of scattered intensity. We report here an extension of coherent xray optical simulations of convergent x-ray beam diffraction patterns to arbitrary x-ray incident angles to allow the nanobeam diffraction patternsmore » of complex heterostructures to be simulated faithfully. These methods are used to extract the misorientation of lattice planes and the strain of individual layers from synchrotron x-ray nanobeam diffraction patterns of Si/SiGe heterostructures relevant to applications in quantum electronic devices. The systematic interpretation of nanobeam diffraction patterns from semiconductor heterostructures presents a new opportunity in characterizing and ultimately designing electronic materials.« less

Polycrystalline La1-xSrxMnO3 films on silicon: Influence of post-Deposition annealing on structural, (Magneto-)Optical, and (Magneto-)Electrical properties

NASA Astrophysics Data System (ADS)

Thoma, Patrick; Monecke, Manuel; Buja, Oana-Maria; Solonenko, Dmytro; Dudric, Roxana; Ciubotariu, Oana-Tereza; Albrecht, Manfred; Deac, Iosif G.; Tetean, Romulus; Zahn, Dietrich R. T.; Salvan, Georgeta

2018-01-01

The integration of La1-xSrxMnO3 (LSMO) thin film technology into established industrial silicon processes is regarded as challenging due to lattice mismatch, thermal expansion, and chemical reactions at the interface of LSMO and silicon. In this work, we investigated the physical properties of thin La0.73Sr0.27MnO3 films deposited by magnetron sputtering on silicon without a lattice matching buffer layer. The influence of a post-deposition annealing treatment on the structural, (magneto-)optical, and (magneto-)electrical properties was investigated by a variety of techniques. Using Rutherford backscattering spectroscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction we could show that the thin films exhibit a polycrystalline, rhombohedral structure after a post-deposition annealing of at least 700 °C. The dielectric tensor in the spectral range from 1.7 eV to 5 eV determined from spectroscopic ellipsometry in combination with magneto-optical Kerr effect spectroscopy was found to be comparable to that of lattice matched films on single crystal substrates reported in literature [1]. The values of the metal-isolator transition temperature and temperature-dependent resistivities also reflect a high degree of crystalline quality of the thermally treated films.

Phase diagram of the relaxor ferroelectric (1- x )Pb(Mg 1/3Nb 2/3)O 3+ x PbTiO 3 revisited: a neutron powder diffraction study of the relaxor skin effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phelan, D.; Rodriguez, E. E.; Gao, J.

2014-11-17

We revisit the phase diagram of the relaxor ferroelectric PMN- xPT using neutron powder diffraction to test suggestions that residual oxygen vacancies and/or strain affect the ground state crystal structure. Powdered samples of PMN- xPT were prepared with nominal compositions of x = 0:10, 0.20, 0.30, and 0.40 and divided into two identical sets, one of which was annealed in air to relieve grinding-induced strain and to promote an ideal oxygen stoichiometry. For a given composition and temperature the same structural phase is observed for each specimen. However, the distortions in all of the annealed samples are smaller than thosemore » in the as-grown samples. Further, the diffraction patterns for x = 0:10, 0.20, and 0.30 are best refined using the monoclinic Cm space group. By comparing our neutron diffraction results to those obtained on single crystals having similar compositions, we conclude that the relaxor skin effect in PMN- xPT vanishes on the Ti-rich side of the morphotropic phase boundary.« less

Fabrication and testing of a newly designed slit system for depth-resolved X-ray diffraction measurements

DOE PAGES

Sinsheimer, John; Bouet, Nathalie; Ghose, Sanjit; ...

2016-10-06

A new system of slits called `spiderweb slits' have been developed for depth-resolved powder or polycrystalline X-ray diffraction measurements. The slits act on diffracted X-rays to select a particular gauge volume of sample, while absorbing diffracted X-rays from outside of this volume. Although the slit geometry is to some extent similar to that of previously developed conical slits or spiral slits, this new design has advantages over the previous ones in use for complex heterogeneous materials and in situ and operando diffraction measurements. For example, the slits can measure a majority of any diffraction cone for any polycrystalline material, overmore » a continuous range of diffraction angles, and work for X-ray energies of tens to hundreds of kiloelectronvolts. In addition, the design is generated and optimized using ray-tracing simulations, and fabricated through laser micromachining. The first prototype was successfully tested at the X17A beamline at the National Synchrotron Light Source, and shows similar performance to simulations, demonstrating gauge volume selection for standard powders, for all diffraction peaks over angles of 2–10°. A similar, but improved, design will be implemented at the X-ray Powder Diffraction beamline at the National Synchrotron Light Source II.« less

Magnetic and structural properties of rapidly quenched Nd-Fe-Co-Ge-B alloys

NASA Astrophysics Data System (ADS)

Beitollahi, A.; Gholamipour, R.; Marghusian, V. K.; Andreev, S. V.; Bogatkin, A. N.; Duragin, S. S.; Kozlov, A. N.; Kudrevatykh, N. V.; Bogdanov, S. G.; Pirogov, A. N.

2006-12-01

We have studied the structure and magnetic properties of some rapidly quenched and subsequently annealed alloys prepared by centrifugal method with a composition (in wt %) Nd(29.5), Co(6), B(1.1), Ge (x), Fe(balance) with x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0 (wt %) for Ge. Based on X-ray diffraction (XRD), elastic neutron diffraction, and small-angle neutron scattering (SANS), the formation of partially crystallized main hard magnetic 2:14:1 (Φ) phase in the amorphous matrix was detected for all as-spun samples. The size of the clusters formed for the sample with 1 wt % Ge determined based on SANS profiles was about 10 nm. It was shown that the addition of Ge shifts the maximum crystallization peak of the main 2:14:1 phase to higher temperatures. The variation of the magnitudes of different magnetic parameters such as i H c and M s versus Ge concentration for as-spun samples can be possibly related to the different rate of crystallization of the 2:14:1 phase formed. Further, for the samples doped with 0.8 and 1.0 wt % Ge and annealed at 760°C for 5 min the formation of some extra phases such as Nd5Ge3, NdFe2, NdB4, as well as α-Fe was detected by XRD. The magnetic measurements carried out using a vibrating-sample magnetometer (VSM) for these samples also supported the XRD data obtained. While the highest values of coercivity i H c = 772 kA/m were obtained for the annealed samples without Ge, the highest value of σr = 69 emu/g was also obtained for the samples substituted with 0.8 wt % Ge without an appreciable reduction in i H c.

Dynamical scattering in coherent hard x-ray nanobeam Bragg diffraction

NASA Astrophysics Data System (ADS)

Pateras, A.; Park, J.; Ahn, Y.; Tilka, J. A.; Holt, M. V.; Kim, H.; Mawst, L. J.; Evans, P. G.

2018-06-01

Unique intensity features arising from dynamical diffraction arise in coherent x-ray nanobeam diffraction patterns of crystals having thicknesses larger than the x-ray extinction depth or exhibiting combinations of nanoscale and mesoscale features. We demonstrate that dynamical scattering effects can be accurately predicted using an optical model combined with the Darwin theory of dynamical x-ray diffraction. The model includes the highly divergent coherent x-ray nanobeams produced by Fresnel zone plate focusing optics and accounts for primary extinction, multiple scattering, and absorption. The simulation accurately reproduces the dynamical scattering features of experimental diffraction patterns acquired from a GaAs/AlGaAs epitaxial heterostructure on a GaAs (001) substrate.

Complete p-type activation in vertical-gradient freeze GaAs co-implanted with gallium and carbon

NASA Astrophysics Data System (ADS)

Horng, S. T.; Goorsky, M. S.

1996-03-01

High-resolution triple-axis x-ray diffractometry and Hall-effect measurements were used to characterize damage evolution and electrical activation in gallium arsenide co-implanted with gallium and carbon ions. Complete p-type activation of GaAs co-implanted with 5×1014 Ga cm-2 and 5×1014 C cm-2 was achieved after rapid thermal annealing at 1100 °C for 10 s. X-ray diffuse scattering was found to increase after rapid thermal annealing at 600-900 °C due to the aggregation of implantation-induced point defects. In this annealing range, there was ˜10%-72% activation. After annealing at higher annealing temperatures, the diffuse scattered intensity decreased drastically; samples that had been annealed at 1000 °C (80% activated) and 1100 °C (˜100% activated) exhibited reciprocal space maps that were indicative of high crystallinity. The hole mobility was about 60 cm2/V s for all samples annealed at 800 °C and above, indicating that the crystal perfection influences dopant activation more strongly than it influences mobility. Since the high-temperature annealing simultaneously increases dopant activation and reduces x-ray diffuse scattering, we conclude that point defect complexes which form at lower annealing temperatures are responsible for both the diffuse scatter and the reduced activation.

Single-source-precursor synthesis of hafnium-containing ultrahigh-temperature ceramic nanocomposites (UHTC-NCs).

PubMed

Yuan, Jia; Hapis, Stefania; Breitzke, Hergen; Xu, Yeping; Fasel, Claudia; Kleebe, Hans-Joachim; Buntkowsky, Gerd; Riedel, Ralf; Ionescu, Emanuel

2014-10-06

Amorphous SiHfBCN ceramics were prepared from a commercial polysilazane (HTT 1800, AZ-EM), which was modified upon reactions with Hf(NEt2)4 and BH3·SMe2, and subsequently cross-linked and pyrolyzed. The prepared materials were investigated with respect to their chemical and phase composition, by means of spectroscopy techniques (Fourier transform infrared (FTIR), Raman, magic-angle spinning nuclear magnetic resonance (MAS NMR)), as well as X-ray diffraction (XRD) and transmission electron microscopy (TEM). Annealing experiments of the SiHfBCN samples in an inert gas atmosphere (Ar, N2) at temperatures in the range of 1300-1700 °C showed the conversion of the amorphous materials into nanostructured UHTC-NCs. Depending on the annealing atmosphere, HfC/HfB2/SiC (annealing in argon) and HfN/Si3N4/SiBCN (annealing in nitrogen) nanocomposites were obtained. The results emphasize that the conversion of the single-phase SiHfBCN into UHTC-NCs is thermodynamically controlled, thus allowing for a knowledge-based preparative path toward nanostructured ultrahigh-temperature stable materials with adjusted compositions.

Effect of annealing on the structural and optical properties of TiO{sub 2} powder prepared by sol-gel route

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halder, Nilanjan; Misra, Kamakhya Prakash

2016-05-06

Using titanium isopropoxide as the precursor, Titanium dioxide (TiO{sub 2}) powder was synthesized via sol-gel method, a promising low temperature route for preparing nanosized metal oxide semiconductors with good homogeneity at low cost. The as-prepared nano powder was thermally treated in air at 550, 650, 750, 900 and 1100°C for 1hr after drying at room temperature and used for further characterization. X-ray diffraction measurements showed that the annealing treatment has a strong impact on the crystal phase of TiO{sub 2} samples. The crystallite size as calculated from Debye Scherer formula lies in the range 29-69 nm and is found to increasemore » with increase in annealing temperature. Photoluminescence studies exhibit an improvement in the optical efficiency of the samples with post synthesis heat treatment. Annealing at temperature above 900°C results in a degradation of the structural and optical quality of the TiO{sub 2} nano powder samples.« less

Effect of annealing atmosphere on properties of Cu2ZnSn(S,Se)4 thin films

NASA Astrophysics Data System (ADS)

Xue, Yuming; Yu, Bingbing; Li, Wei; Feng, Shaojun; Wang, Yukun; Huang, Shengming; Zhang, Chao; Qiao, Zaixiang

2017-12-01

Earth-abundant Cu2ZnSn(S,Se)4(CZTSSe) thin film photovoltaic absorber layers were fabricated by co-evaporated Cu, ZnS, SnS and Se sources in a vacuum chamber followed by annealing at tubular furnace for 30 min at 550 °C. In this paper, we investigated the metal elements with stoichiometric ratio film to study the effect of annealing conditions of Se, SnS + Se, S and SnS + S atmosphere on the structure, surface morphological, optical and electrical properties of Cu2ZnSn(S,Se)4 thin films respectively. These films were characterized by Inductively Coupled Plasma-Mass Spectrometer, scanning electron microscopy, X-ray diffraction to investigate the composition, morphological and crystal structural properties. The grain size of samples were found to increase after annealing. XRD patterns confirmed the formation of pure polycrystalline CZTSSe thin films at S atmosphere, the optical band gaps are 1.02, 1.05, 1.23, 1.35 eV for Se, SnS + Se, SnS + S and S atmosphere respectively.

Post-annealing effect on optical absorbance of hydrothermally grown zinc oxide nanorods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohar, Rahmat Setiawan; Djuhana, Dede; Imawan, Cuk

In this study, the optical absorbance of zinc oxide (ZnO) nanorods was investigated. The ZnO thin film were deposited on indium tin oxide (ITO) layers using ultrasonic spray pyrolysis (USP) method and then grown by hydrothermal method. In order to improve the optical absorbance, the ZnO nanorods were then post-annealed for one hour at three different of temperatures, namely 250, 400, and 500 °C. The X-ray diffraction (XRD) spectra and FESEM images show that the ZnO nanorods have the hexagonal wurtzite crystal structure and the increasing of post-annealing temperature resulted in the increasing of crystallite size from 38.2 nm to 48.4 nm.more » The UV-vis spectra shows that all samples of ZnO nanorods exhibited the identical sharp absorption edge at 390 nm indicating that all samples have the same bandgap. The post-annealing process seemed to decrease the optical absorbance in the region of 300-550 nm and increase the optical absorbance in the region of 550-700 nm..« less

Characterization of Cu2ZnSnS4 thin films prepared by photo-chemical deposition

NASA Astrophysics Data System (ADS)

Moriya, Katsuhiko; Watabe, Jyunichi; Tanaka, Kunihiko; Uchiki, Hisao

2006-09-01

Cu2ZnSnS4 (CZTS) thin films were prepared by post-annealing films of metal sulfides of Cu2S, ZnS and SnS2 precursors deposited on soda-lime glass substrates by photo-chemical deposition (PCD) from aqueous solution containing CuSO4, ZnSO4, SnSO4 and Na2S2O3. In this study, sulfurization was employed to prepare high quality CZTS thin films. Deposited films of metal sulfides were annealed in a furnace in an atmosphere of N2 or N2+H2S(5%) at the temperature of 300°, 400° or 500 °C. The sulfured films showed X-ray diffraction peaks from (112), (220), and (312) planes of CZTS and the peaks became sharp by an increase in the sulfurization temperature. CZTS thin film annealed in atmosphere of N2 was S-poor. After annealing atmosphere was changed from N2 into N2+H2S(5%), the decrease of a composi- tional ratio of sulfur could be suppressed.

Reverse-transformation austenite structure control with micro/nanometer size

NASA Astrophysics Data System (ADS)

Wu, Hui-bin; Niu, Gang; Wu, Feng-juan; Tang, Di

2017-05-01

To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure, the influences of cold deformation and annealing parameters on the microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. The samples were first cold-rolled, and then samples deformed to different extents were annealed at different temperatures. The microstructure evolutions were analyzed by optical microscopy, scanning electron microscopy (SEM), magnetic measurements, and X-ray diffraction (XRD); the mechanical properties are also determined by tensile tests. The results showed that the fraction of stain-induced martensite was approximately 72% in the 90% cold-rolled steel. The micro/nanometric microstructure was obtained after reversion annealing at 820-870°C for 60 s. Nearly 100% reversed austenite was obtained in samples annealed at 850°C, where grains with a diameter ≤ 500 nm accounted for 30% and those with a diameter > 0.5 μm accounted for 70%. The micro/nanometer-grain steel exhibited not only a high strength level (approximately 959 MPa) but also a desirable elongation of approximately 45%.

Investigation of Nd xY 0.25-xZr 0.75O 1.88 inert matrix fuel materials made by a co-precipitation synthetic route

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, John R.; Grosvenor, Andrew P.

Yttria-stabilized zirconia (YSZ) is a material that we are considering in our inert matrix fuel nuclear reactors, but a complete characterization of these materials is required for them to be licensed for use. A series of NdxY0.25–xZr0.75O1.88 materials have been synthesized using a co-precipitation method, and the thermal stability of these materials has been studied by annealing them at 1400 and 1500 °C. (Nd was used as surrogate for Am.) The long-range and local structures of the materials were characterized via powder X-ray diffraction, scanning electron microscopy, wavelength dispersive spectroscopy, and X-ray absorption spectroscopy at the Zr K- and Ymore » K-edges. These results were compared with the previous characterization of Nd-YSZ materials synthesized using a ceramic method. Moreover, the results indicated that the ordering in the local metal–oxygen polyhedral remains relatively unaffected by the synthetic method, but there was increased long-range disorder in the materials prepared by the co-precipitation method. Further, it was found that the materials produced by the co-precipitation method were unexpectedly unstable when annealed at high temperature. This study highlights the importance of determining the effect of synthetic method on material properties and demonstrates how the co-precipitation route could be used to produce inert matrix fuels.« less

Coherent x-ray diffraction imaging with nanofocused illumination.

PubMed

Schroer, C G; Boye, P; Feldkamp, J M; Patommel, J; Schropp, A; Schwab, A; Stephan, S; Burghammer, M; Schöder, S; Riekel, C

2008-08-29

Coherent x-ray diffraction imaging is an x-ray microscopy technique with the potential of reaching spatial resolutions well beyond the diffraction limits of x-ray microscopes based on optics. However, the available coherent dose at modern x-ray sources is limited, setting practical bounds on the spatial resolution of the technique. By focusing the available coherent flux onto the sample, the spatial resolution can be improved for radiation-hard specimens. A small gold particle (size <100 nm) was illuminated with a hard x-ray nanobeam (E=15.25 keV, beam dimensions approximately 100 x 100 nm2) and is reconstructed from its coherent diffraction pattern. A resolution of about 5 nm is achieved in 600 s exposure time.

Rapid Sintering of Li₂O-Nb₂O₅-TiO₂ Solid Solution by Air Pressure Control and Clarification of Its Mechanism.

PubMed

Nakano, Hiromi; Kamimoto, Konatsu; Yamamoto, Takahisa; Furuta, Yoshio

2018-06-11

We first successfully synthesized Li 1+ x − y Nb 1− x −3 y Ti x +4 y O₃ (LNT) solid solutions (0.13 ≤ x ≤ 0.18, 0 ≤ y ≤ 0.06) rapidly at 1373 K for one hour under 0.35 MPa by the controlling of air pressure using an air-pressure control atmosphere furnace. The composition is a formation area of a superstructure for LNT, in which the periodical intergrowth layer was formed in the matrix, and where it can be controlled by Ti content. Therefore, the sintering time depended on Ti content, and annealing was repeated for over 24 h until a homogeneous structure was formed using a conventional electric furnace. We clarified the mechanism of the rapid sintering using various microscale to nanoscale characterization techniques: X-ray diffraction, a scanning electron microscope, a transmission electron microscope (TEM), a Cs-corrected scanning TEM equipped with electron energy-loss spectroscopy, and X-ray absorption fine structure spectroscopy.

DynAMITe: a prototype large area CMOS APS for breast cancer diagnosis using x-ray diffraction measurements

NASA Astrophysics Data System (ADS)

Konstantinidis, A.; Anaxagoras, T.; Esposito, M.; Allinson, N.; Speller, R.

2012-03-01

X-ray diffraction studies are used to identify specific materials. Several laboratory-based x-ray diffraction studies were made for breast cancer diagnosis. Ideally a large area, low noise, linear and wide dynamic range digital x-ray detector is required to perform x-ray diffraction measurements. Recently, digital detectors based on Complementary Metal-Oxide- Semiconductor (CMOS) Active Pixel Sensor (APS) technology have been used in x-ray diffraction studies. Two APS detectors, namely Vanilla and Large Area Sensor (LAS), were developed by the Multidimensional Integrated Intelligent Imaging (MI-3) consortium to cover a range of scientific applications including x-ray diffraction. The MI-3 Plus consortium developed a novel large area APS, named as Dynamically Adjustable Medical Imaging Technology (DynAMITe), to combine the key characteristics of Vanilla and LAS with a number of extra features. The active area (12.8 × 13.1 cm2) of DynaMITe offers the ability of angle dispersive x-ray diffraction (ADXRD). The current study demonstrates the feasibility of using DynaMITe for breast cancer diagnosis by identifying six breast-equivalent plastics. Further work will be done to optimize the system in order to perform ADXRD for identification of suspicious areas of breast tissue following a conventional mammogram taken with the same sensor.

Fast synthesis of La-substituted apatite by the dry mechanochemical method and analysis of its structure

NASA Astrophysics Data System (ADS)

Bulina, Natalia V.; Chaikina, Marina V.; Prosanov, Igor Yu.; Dudina, Dina V.; Solovyov, Leonid A.

2017-08-01

Compared to pure apatite, La-substituted apatites have improved thermal, mechanical and biological characteristics. In this article, a fast synthesis of La-substituted apatites by a dry mechanochemical method is presented. Structural studies by X-ray diffraction and Fourier transform infrared spectroscopy indicated the formation of a single-phase nanosized product after 30 min of high-energy ball milling of the reaction mixtures. The dry mechanochemical method is technologically attractive for the preparation of La-substituted apatites, as it allows reducing the processing time down to half an hour and does not require prolonged high-temperature annealing normally used in the synthesis practice of the substituted apatite. As the mechanochemically synthesized samples are nanosized, it is difficult to determine the details of their crystal structure by the Rietveld refinement method. Therefore, a series of the mechanochemically synthesized samples with different concentrations of lanthanum were annealed at 1000°C for 5 h. It was found that the annealed powders are microcrystalline La-substituted apatites Ca10-xLax(PO4)6Ox(OH)2-x, where 0 ≤ x ≤2. In their structure, the Ca2+ ions are replaced by the La3+ ions localized near the Ca2 sites, and the OH- groups are replaced by the O2- ions in the hexagonal channels.

TiO 2 nanotube arrays for photocatalysis: Effects of crystallinity, local order, and electronic structure

DOE PAGES

Liu, Jing; Hosseinpour, Pegah M.; Luo, Si; ...

2014-11-19

To furnish insight into correlations of electronic and local structure and photoactivity, arrays of short and long TiO₂ nanotubes were synthesized by electrochemical anodization of Ti foil, followed by thermal treatment in O₂ (oxidizing), Ar (inert), and H₂ (reducing) environments. The physical and electronic structures of these nanotubes were probed with x-ray diffraction, scanning electron microscopy, and synchrotron-based x-ray absorption spectroscopy, and correlated with their photocatalytic properties. The photocatalytic activity of the nanotubes was evaluated by monitoring the degradation of methyl orange under UV-VIS light irradiation. Results show that upon annealing at 350 °C all as-anodized amorphous TiO₂ nanotube samplesmore » partially transform to the anatase structure, with variations in the degree of crystallinity and in the concentration of local defects near the nanotubes' surface (~5 nm) depending on the annealing conditions. Degradation of methyl orange was not detectable for the as-anodized TiO₂ nanotubes regardless of their length. The annealed long nanotubes demonstrated detectable catalytic activity, which was more significant with the H₂-annealed nanotubes than with the Ar- and O₂-annealed nanotube samples. This enhanced photocatalytic response of the H₂-annealed long nanotubes relative to the other samples is positively correlated with the presence of a larger concentration of lattice defects (such as Ti 3+ and anticipated oxygen vacancies) and a slightly lower degree of crystallinity near the nanotube surface. These physical and electronic structural attributes impact the efficacy of visible light absorption; moreover, the increased concentration of surface defects is postulated to promote the generation of hydroxyl radicals and thus accelerate the photodegradation of the methyl orange. The information obtained from this study provides unique insight into the role of the near-surface electronic and defect structure, crystal structure, and the local chemical environment on the photocatalytic activity and may be employed for tailoring the materials' properties for photocatalysis and other energy-related applications.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jing; Hosseinpour, Pegah M.; Lewis, Laura H., E-mail: lhlewis@neu.edu

To furnish insight into correlations of electronic and local structure and photoactivity, arrays of short and long TiO{sub 2} nanotubes were synthesized by electrochemical anodization of Ti foil, followed by thermal treatment in O{sub 2} (oxidizing), Ar (inert), and H{sub 2} (reducing) environments. The physical and electronic structures of these nanotubes were probed with x-ray diffraction, scanning electron microscopy, and synchrotron-based x-ray absorption spectroscopy, and correlated with their photocatalytic properties. The photocatalytic activity of the nanotubes was evaluated by monitoring the degradation of methyl orange under UV-VIS light irradiation. Results show that upon annealing at 350 °C all as-anodized amorphous TiO{submore » 2} nanotube samples partially transform to the anatase structure, with variations in the degree of crystallinity and in the concentration of local defects near the nanotubes' surface (∼5 nm) depending on the annealing conditions. Degradation of methyl orange was not detectable for the as-anodized TiO{sub 2} nanotubes regardless of their length. However, the annealed long nanotubes demonstrated detectable catalytic activity, which was more significant with the H{sub 2}-annealed nanotubes than with the Ar- and O{sub 2}-annealed nanotube samples. This enhanced photocatalytic response of the H{sub 2}-annealed long nanotubes relative to the other samples is positively correlated with the presence of a larger concentration of lattice defects (such as Ti{sup 3+} and anticipated oxygen vacancies) and a slightly lower degree of crystallinity near the nanotube surface. These physical and electronic structural attributes impact the efficacy of visible light absorption; moreover, the increased concentration of surface defects is postulated to promote the generation of hydroxyl radicals and thus accelerate the photodegradation of the methyl orange. The information obtained from this study provides unique insight into the role of the near-surface electronic and defect structure, crystal structure, and the local chemical environment on the photocatalytic activity and may be employed for tailoring the materials' properties for photocatalysis and other energy-related applications.« less

Physico-mechanical and morphological features of zirconia substituted hydroxyapatite nano crystals

PubMed Central

Mansour, S. F.; El-dek, S. I.; Ahmed, M. K.

2017-01-01

Zirconia doped Hydroxyapatite (HAP) nanocrystals [Ca10(PO4)6−x(ZrO2)x(OH)2]; (0 ≤ x ≤ 1 step 0.2) were synthesized using simple low cost facile method. The crystalline phases were examined by X-ray diffraction (XRD). The crystallinity percentage decreased with increasing zirconia content for the as-synthesized samples. The existence of zirconia as secondary phase on the grain boundaries; as observed from scanning electron micrographs (FESEM); resulted in negative values of microstrain. The crystallite size was computed and the results showed that it increased with increasing annealing temperature. Thermo-gravimetric analysis (TGA) assured the thermal stability of the nano crystals over the temperature from room up to 1200 °C depending on the zirconia content. The corrosion rate was found to decrease around 25 times with increasing zirconia content from x = 0.0 to 1.0. Microhardness displayed both compositional and temperature dependence. For the sample (x = 0.6), annealed at 1200 °C, the former increased up to 1.2 times its original value (x = 0.0). PMID:28256557

Amorphization reaction in thin films of elemental Cu and Y

NASA Astrophysics Data System (ADS)

Johnson, R. W.; Ahn, C. C.; Ratner, E. R.

1989-10-01

Compositionally modulated thin films of Cu and Y were prepared in an ultrahigh-vacuum dc ion-beam deposition chamber. The amorphization reaction was monitored by in situ x-ray-diffraction measurements. Growth of amorphous Cu1-xYx is observed at room temperature with the initial formation of a Cu-rich amorphous phase. Further annealing in the presence of unreacted Y leads to Y enrichment of the amorphous phase. Growth of crystalline CuY is observed for T=469 K. Transmission-electron-microscopy measurements provide real-space imaging of the amorphous interlayer and growth morphology. Models are developed, incorporating metastable interfacial and bulk free-energy diagrams, for the early stage of the amorphization reaction.

Effects of deposition temperature on the electrical properties of Ti/SiC Schottky barrier diodes

NASA Astrophysics Data System (ADS)

Oder, Tom N.; Kundeti, Krishna C.; Borucki, Nicholas; Isukapati, Sundar B.

2017-12-01

Ti Schottky contacts were deposited on n-type 4H-SiC at different temperatures ranging from 28 oC to 900 oC using a magnetron sputtering deposition system to fabricate Schottky barrier diodes. Post deposition annealing at 500 oC for up to 60 hours in vacuum was carried to further improve the contact properties. Optimum barrier height of 1.13 eV and ideality factor of 1.04 was obtained in contacts deposited at 200 oC and annealed for 60 hours. Under a reverse voltage bias of 400 V, the average leakage current on these set of diodes was 6.6 x 10-8 A. Based on the x-ray diffraction analysis, TiC, Ti5Si3 and Ti3SiC2 were formed at the Ti/SiC interface. These results could be beneficial to improving the performance of 4H-SiC Schottky diodes for high power and high temperature applications.

Resolution enhancement in coherent x-ray diffraction imaging by overcoming instrumental noise.

PubMed

Kim, Chan; Kim, Yoonhee; Song, Changyong; Kim, Sang Soo; Kim, Sunam; Kang, Hyon Chol; Hwu, Yeukuang; Tsuei, Ku-Ding; Liang, Keng San; Noh, Do Young

2014-11-17

We report that reference objects, strong scatterers neighboring weak phase objects, enhance the phase retrieval and spatial resolution in coherent x-ray diffraction imaging (CDI). A CDI experiment with Au nano-particles exhibited that the reference objects amplified the signal-to-noise ratio in the diffraction intensity at large diffraction angles, which significantly enhanced the image resolution. The interference between the diffracted x-ray from reference objects and a specimen also improved the retrieval of the phase of the diffraction signal. The enhancement was applied to image NiO nano-particles and a mitochondrion and confirmed in a simulation with a bacteria phantom. We expect that the proposed method will be of great help in imaging weakly scattering soft matters using coherent x-ray sources including x-ray free electron lasers.

Oxygen vacancy induced room temperature ferromagnetism in (In1-xNix)2O3 thin films

NASA Astrophysics Data System (ADS)

Chakraborty, Deepannita; Kaleemulla, S.; Kuppan, M.; Rao, N. Madhusudhana; Krishnamoorthi, C.; Omkaram, I.; Reddy, D. Sreekantha; Rao, G. Venugopal

2018-05-01

Nickel doped indium oxide thin films (In1-xNix)2O3 at x = 0.00, 0.03, 0.05 and 0.07 were deposited onto glass substrates by electron beam evaporation technique. The deposited thin films were subjected to annealing in air at 250 °C, 350 °C and 450 °C for 2 h using high temperature furnace. A set of films were vacuum annealed at 450 °C to study the role of oxygen on magnetic properties of the (In1-xNix)2O3 thin films. The thin films were subjected to different characterization techniques to study their structural, chemical, surface, optical and magnetic properties. All the synthesized air annealed and vacuum annealed films exhibit body centered cubic structure without any secondary phases. No significant change in the diffraction peak position, either to lower or higher diffraction angles has been observed. The band gap of the films decreased from 3.73 eV to 3.63 eV with increase of annealing temperature from 250 °C to 450 °C, in the presence of air. From a slight decrease in strength of magnetization to a complete disappearance of hysteresis loop has been observed in pure In2O3 thin films with increasing the annealing temperature from 250 °C to 450 °C, in the presence of air. The (In1-xNix)2O3 thin films annealed under vacuum follow a trend of enhancement in the strength of magnetization to increase in temperature from 250 °C to 450 °C. The hysteresis loop does not disappear at 450 °C in (In1-xNix)2O3 thin films, as observed in the case of pure In2O3 thin films.

Cyclic electrical conductivity in BaTiO3-PbTiO3-V2O5 glass-ceramic nanocomposite

NASA Astrophysics Data System (ADS)

Bahgat, A. A.; Heikal, Sh.; Mahdy, Iman A.; Abd-Rabo, A. S.; Abdel Ghany, A.

2014-08-01

In this present work a glass of the composition 22.5 BaTiO3+7.5 PbTiO3+70 V2O5 was prepared by applying the conventional melt quashing technique. Isothermal annealing of the glass was applied at 732 K following differential scanning calorimetric analysis. The annealing was performed during different time intervals in the range of 0.25-24.0 h. X-ray diffraction and transmission electron microscopy were used to identify different phases as well as particle size precipitated during the annealing process. Nanocomposite glass-ceramic precipitation was recognized with nonperiodic cyclic particle sizes as a function of the annealing period. DC electrical conductivity, on the other hand, was conducted in the temperature range from 300 to 625 K. Electrical conductivity enhancement of the order 3×103 times after 2.5 h of annealing was observed. Nonperiodic cyclic DC electrical conductivity behavior was also observed and which was encountered in a reverse manner with particle size development. Furthermore, the analysis of the electrical conduction mechanism predicts that both adiabatic and nonadiabatic small polaron hopping trend may describe the experimental data depending on the particle size.

Effect of annealing on the optical properties of amorphous Se79Te10Sb4Bi7 thin films

NASA Astrophysics Data System (ADS)

Nyakotyo, H.; Sathiaraj, T. S.; Muchuweni, E.

2017-07-01

Thin films of Se79Te10Sb4Bi7, were prepared by Electron beam deposition technique. The structure of the as-prepared and annealed films has been studied by X-ray diffraction and the surface morphology by the scanning electron microscope (SEM). These studies show that there is a gradual change in structure and the formation of some polycrystalline structures in the amorphous phases is observed when the Se79Te10Sb4Bi7 film is annealed in the temperature range of 333-393 K. The optical transmission of these films has been studied as a function of photon wavelength in the range 300-2500 nm. It has been found that the optical band gap Egopt decreased with increasing annealing temperature in the range 333-393 K. The Urbach energy (Eu), optical conductivity (σopt), imaginary (εi), and real (εr) parts of the complex dielectric constant (ε) and lattice dielectric constant (εL) were also determined. The changes noticed in optical parameters with increasing annealing temperature were explained on the basis of structural relaxation as well as change in defect states and density of localized states due to amorphous-crystalline transformation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shipra, Fnu; Idrobo Tapia, Juan Carlos; Sefat, Athena Safa

This study provides an account of the bulk preparation of TlBa 2Ca 2Cu 3O 9-δ (Tl-1223) superconductor at ambient pressure, and the Tc features under thermal-annealing conditions. The ‘as-prepared’ Tl-1223 (Tc =106 K) presents a significantly higher T c = 125 K after annealing the polycrystalline material in either flowing Ar+4% H 2, or N 2 gases. In order to understand the fundamental reasons for a particular Tc, we refined the average bulk structures using powder X-ray diffraction data. Although Ar+4%H2 annealed Tl- 1223 shows an increased ‘c’ lattice parameter, it shrinks by 0.03% (approximately unchanged) upon N2 anneal. Duemore » to such indeterminate conclusions on the average structural changes, local structures were investigated at using aberration-corrected scanning-transmission electron microscopy technique. Similar compositional changes in the atomic arrangements of both annealed-samples of Tl-1223 were detected in which the plane containing Ca atomic layer gives a non-uniform contrast, due to substitution of some heavier Tl. In this report, extensive bulk properties are summarized through temperature-dependent resistivity, and shielding and Meissner fractions of magnetic susceptibility results; the bulk and local structures are investigated to correlate to properties.« less

The lateral In2O3 nanowires and pyramid networks manipulation by controlled substrate surface energy in annealing evolution

NASA Astrophysics Data System (ADS)

Shariati, Mohsen; Darjani, Mojtaba

2016-02-01

The continuous laterally aligned growth of In2O3 nanocrystal networks extended with nanowire and pyramid connections under annealing influence has been reported. These nanostructures have been grown on Si substrate by using oxygen-assisted annealing process through PVD growth technique. The formation of In2O3 nanocrystals has been achieved by the successive growth of critical self-nucleated condensation in three orientations. The preferred direction was the route between two pyramids especially in the smallest surface energy. The effects of substrate temperature in annealing process on the morphological properties of the as-grown nanostructures were investigated. The annealing technique showed that by controlling the surface energy, the morphology of structures was changed from unregulated array to defined nanostructures; especially nanowires 50 nm in width. The obtained nanostructures also were investigated by the (transmission electron microscopy) TEM, Raman spectrum and the (X-ray diffraction) XRD patterns. They indicated that the self-assembled In2O3 nanocrystal networks have been fabricated by the vapor-solid (VS) growth mechanism. The growth mechanism process was prompted to attribute the relationship among the kinetics parameters, surface diffusion and morphology of nanostructures.

High frequency permeability of Fe-Cu-Nb-Si-B nanocrystalline flakes with the distribution of shape anisotropy fields

NASA Astrophysics Data System (ADS)

Luo, Xing; Wu, Yanhui; Han, Mangui; Deng, Longjiang

2018-04-01

Fe-Cu-Nb-Si-B flakes with multiphase nanostructures have been obtained by annealing the amorphous ribbon and subsequently ball milled for 30 h. The crystal structures have been examined by X-ray diffraction pattern and Mössbauer spectrum. The results show that the particles annealed at 900 °C are made up of amorphous ferromagnetic phase, α-Fe3Si ferromagnetic phase and Fe2B phase, and the average hyperfine magnetic field (HBhf) of particles is 24.02 T. Meanwhile, the relationships between the structure and the high frequency permeability have been studied. Compared with particles annealed at 600 °C, particles annealed at 900 °C exhibit higher saturation magnetization, which is evidenced by the larger HBhf. Also, three magnetic loss peaks in a permeability spectrum have been observed for the particles annealed at 900 °C. The natural resonance frequencies are calculated, which are in good agreement with the experimental resonance peaks. The origin of the multiple magnetic loss peaks can be explained from the perspective of the distribution of shape anisotropy fields which is caused by multiple phase structure.