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1

Dielectric spectroscopy studies of ZnO single crystal  

NASA Astrophysics Data System (ADS)

Dielectric relaxation and charge transport induced by electron hopping in ZnO single crystal are measured by using a novocontrol broadband dielectric spectrometer. Typical Debye-like dielectric relaxation originating from electronic hopping between electronic traps and conductive band in surface Schottky barrier region is observed for ZnO single crystal-Au electrode system. However, after insulation of ZnO single crystal by heat treatment in rich oxygen atmosphere, dielectric relaxation and alternating current conductance are observed simultaneously in the dielectric spectra, implying that dielectric relaxation and charge transport can be induced simultaneously by electronic hopping at high temperature in an ordered system. The intrinsic correlation between local dielectric relaxation and long range charge transport offers us a new method to explore complicated dielectrics.

Cheng, Peng-Fei; Li, Sheng-Tao; Wang, Hui

2013-10-01

2

Hydrogen-mediated ferromagnetism in ZnO single crystals  

NASA Astrophysics Data System (ADS)

We investigated the magnetic properties of hydrogen-plasma-treated ZnO single crystals by using superconducting quantum interferometer device magnetometry. In agreement with the expected hydrogen penetration depth, we found that ferromagnetic behavior is present in the first 20 nm of the H-treated surface of ZnO with magnetization at saturation up to 6 emu g-1 at 300 K and a Curie temperature of Tcgsim400 K. In the ferromagnetic samples, a hydrogen concentration of a few atomic per cent in the first 20 nm of the surface layer was determined by nuclear reaction analysis. The saturation magnetization of H-treated ZnO increases with the concentration of hydrogen.

Khalid, M.; Esquinazi, P.; Spemann, D.; Anwand, W.; Brauer, G.

2011-06-01

3

Growth and characterization of large-diameter, lithium-free ZnO single crystals  

NASA Astrophysics Data System (ADS)

Large-diameter, lithium-free ZnO single-crystal substrates of high crystalline quality will enable development and commercialization of high-performance ZnO-based semiconductor devices, such as UV and visible light emitting diodes (LEDs), UV laser diodes and solar-blind UV detectors for variety of applications. We have recently developed a novel crystal growth technique for producing lithium-free ZnO single crystal boules of 1 inch in diameter. We also fabricated ZnO single crystal wafers in sizes up to 1 inch in diameter. Chemical purity, crystalline defects, and electrical resistivity of ZnO single crystals were analyzed. Results from crystal growth and material characterization are presented and discussed. Our research results suggest that the novel crystal growth technique is a viable production technique for producing ZnO single crystals and substrates for semiconductor device applications.

Wang, Shaoping; Kopec, Aneta; Timmerman, Andrew G.

2012-02-01

4

Nitrogen doping of single crystal ZnO  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) is a wide band gap semiconductor with a range of potential optical, electronic, and mechanical applications. The lack of control over defects, in particular reliable p-type doping, is a problem that needs to be overcome. Nitrogen is a promising acceptor dopant. We incorporated nitrogen-hydrogen (N-H) complexes in ZnO during chemical vapor transport (CVT) growth, using ammonia as an ambient. Using commercial ZnO as a seed, we obtained bulk single-crystal growth. The N-H bond-stretching mode gives rise to an infrared (IR) absorption peak at 3150.6 cm-1 at liquid helium temperatures. Isotopic substitutions result in the expected frequency shifts, providing an unambiguous identification of these complexes. The N-H complexes are stable up to ˜700 C. Annealing in oxygen appears to enhance the dissociation of the N-H bond, an observation that could prove useful in achieving reliable p-type conductivity.

McCluskey, M. D.; Jokela, S. J.; Tarun, M. C.

2010-03-01

5

Bio-inspired synthesis of ZnO polyhedral single crystals under eggshell membrane direction  

NASA Astrophysics Data System (ADS)

A simple and versatile technique was developed to prepare hierarchical ZnO single crystals by introducing eggshell membrane (ESM) to a bio-inspired approach. Based on the control of nucleation and gestation, ZnO nanocrystallites could grow at three dimensions into polyhedral single crystals through a surface sol-gel process followed by a calcination treatment. Different from traditional wet chemical techniques, our synthetic process depends more on the restrictive or directing functions of the ESM biomacromolecules. The hierarchical ZnO nanostructures doped with polyhedral single crystallites could be desirable for catalysts, photoelectrochemical devices, especially solar cells.

Su, Huilan; Song, Fang; Dong, Qun; Li, Tuoqi; Zhang, Xin; Zhang, Di

2011-07-01

6

Characterization of bulk ZnO single crystal grown by a CVT method  

NASA Astrophysics Data System (ADS)

Hall effect, photoluminescence spectroscopy (PL), mass spectroscopy and X-ray diffraction have been used to study bulk ZnO single crystal grown by a closed seeded chemical vapor transport method. Enhancement of n-type electrical conduction and increase of nitrogen concentration are observed of the ZnO samples after high temperature annealing. The results suggest that vacancy is dominant native defect in the ZnO material. These phenomena are explained by a generation of shallow donor defect and suppression of deep level defects in ZnO after the annealing.

Wei, Xuecheng; Zhao, Youwen; Dong, Zhiyuan; Li, Jinmin

2008-03-01

7

Surface chemistry and surface electronic properties of ZnO single crystals and nanorods  

SciTech Connect

The surface chemistry of ZnO single crystals of (0001) and (1010) orientations and ZnO nanorods was studied using x-ray and ultraviolet photoelectron spectroscopies. Air drying and UV-ozone preparations were studied in particular as chemical treatments that could be applied to poly(3-hexylthiophene) (P3HT)-ZnO solar cells to enhance performance. The UV-ozone treatment showed negligible effect by photoelectron spectroscopy on the ZnO single crystal surfaces, but brought about electronic shifts consistent with increased upward band bending by {approx}0.25 eV on the ZnO nanorod surface. Modest interface dipoles of {approx}0.15 and {approx}0.25 eV were measured between P3HT and the (1010) and (0001) single crystal orientations, respectively, with the dipole moment pointing from ZnO to the P3HT layer. The sol-gel films showed evidence of forming a small interface dipole in the opposite direction, which illustrates the difference in surface chemistry between the solution-grown ZnO and the ZnO single crystals.

Uhlrich, J. J.; Olson, D. C.; Hsu, J. W. P.; Kuech, T. F. [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706 (United States); Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706 (United States)

2009-03-15

8

Encapsulation of nanoparticles into single-crystal ZnO nanorods and microrods  

PubMed Central

Summary One-dimensional single crystal incorporating functional nanoparticles of other materials could be an interesting platform for various applications. We studied the encapsulation of nanoparticles into single-crystal ZnO nanorods by exploiting the crystal growth of ZnO in aqueous solution. Two types of nanodiamonds with mean diameters of 10 nm and 40 nm, respectively, and polymer nanobeads with size of 200 nm have been used to study the encapsulation process. It was found that by regrowing these ZnO nanorods with nanoparticles attached to their surfaces, a full encapsulation of nanoparticles into nanorods can be achieved. We demonstrate that our low-temperature aqueous solution growth of ZnO nanorods do not affect or cause degradation of the nanoparticles of either inorganic or organic materials. This new growth method opens the way to a plethora of applications combining the properties of single crystal host and encapsulated nanoparticles. We perform micro-photoluminescence measurement on a single ZnO nanorod containing luminescent nanodiamonds and the spectrum has a different shape from that of naked nanodiamonds, revealing the cavity effect of ZnO nanorod.

Notarianni, Marco; Rintoul, Llew; Motta, Nunzio

2014-01-01

9

Growth of the 2-in-size bulk ZnO single crystals by the hydrothermal method  

Microsoft Academic Search

The hydrothermal method combined with a platinum inner container was applied to grow zinc oxide (ZnO) single crystals. High-purity and transparent single crystals with a large size of 50×50×15mm3 were successfully grown. The higher crystallinity of the hydrothermally grown ZnO crystal compared with the commercial ZnO substrate grown by the chemical vapor transport method was confirmed by X-ray diffraction. The

Eriko Ohshima; Hiraku Ogino; Ikuo Niikura; Katsumi Maeda; Mitsuru Sato; Masumi Ito; Tsuguo Fukuda

2004-01-01

10

Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes  

SciTech Connect

The photoelectrochemical stability and surface-alteration characteristics of both doped and undoped n-type ZnO single-crystal photoanode electrodes have been investigated. The single-crystal ZnO photoanode properties were analyzed using current-voltage measurements plus spectral and time-dependent quantum-yield methods. These measurements revealed the presence of a distinct anodic peak and an accompanying cathodic surface degradation process at negative potentials. The features of this peak were found to depend on time as well as the NaOH concentration in the electrolyte, but they were independent of the presence of electrode illumination. Current measurements performed at the peak indicate that charging and discharging effects are apparently taking place at the semiconductor/electrolyte interface. This result is consistent with the significant reactive degradation that takes place on the ZnO single crystal photoanode surface and that ultimately leads to the reduction of the ZnO surface to Zn metal. The resulting Zn-metal reaction products create unusual, dendrite-like, surface alteration structural features that were analyzed using x-ray diffraction, energy-dispersive analysis, and scanning electron microscopy. The ZnO doping methods employed here are also shown to be an effective way of increasing the n-type character of the crystals. Higher doping levels result in smaller depletion widths and lower quantum yields, since the minority carrier diffusion lengths are very short in these materials.

Paulauskas, Irene E. [University of Tennessee, Knoxville (UTK); Jellison Jr, Gerald Earle [ORNL; Boatner, Lynn A [ORNL; Brown, G. M. [Oak Ridge National Laboratory (ORNL)

2011-01-01

11

Hydrothermal growth of single crystal ZnO nanorods on surface-modified graphite  

NASA Astrophysics Data System (ADS)

ZnO nanostructures were hydrothermally grown at 90°C on bare and surface-modified graphite. Thermodynamically active sites along the grain boundaries on the graphite surface initiated scattered nucleation of ZnO, leading to the formation of a bunched structure. The uniformity of nucleation and the size distribution of nanorods were controlled by modifying the graphite surface with a seed layer. The seed layer was created on the graphite rod by coating it with ethanolic solution of zinc acetate followed by baking at 300°C. The preformed particles on this layer acted as nucleation center for subsequent growth of ZnO nanorods. The resulting ZnO nanorods were vertically well-aligned single crystals, exhibiting strong band edge luminescence.

Sahoo, Trilochan; Jang, Lee-Woon; Jeon, Dae-Woo; Yu, Yeon-Tae; Lee, In-Hwan

2013-11-01

12

Ultraviolet Lasing from ZnO Single Crystal at Room Temperature  

NASA Astrophysics Data System (ADS)

We experimentally studied ultraviolet photoluminescence (PL) from ZnO (0001) single crystal at room temperature. The PL spectra taken from the sample edge show spectral width narrowing; lifetime shortening (100 ps) and super linear intensity increase with pumping power, while the PL spectra taken from the sample surface only show broad spontaneous emission with a much longer lifetime (>5 ns). These findings suggest that stimulated emission and lasing were only achieved at edges of the ZnO single crystal. Scanning-electron-microscopic images show a smooth sample surface morphology and a rougher morphology at the single crystal edge. Electron-hole plasma enhancement of gain may be attributed to the lasing effect observed from the sample edge.

Xiang, Wang-Hua; Zhang, Gui-Zhong; Sun, Yi; Wang, Gang; John., Ketterson B.

2003-02-01

13

Native deep level defects in ZnO single crystal grown by CVT method  

NASA Astrophysics Data System (ADS)

Hall effect, photoluminescence (PL), infrared absorption, deep level transient spectroscopy (DLTS), and Raman scattering have been used to study property and defects of ZnO single crystal grown by a chemical vapor transport method (CVT). As-grown ZnO is N type with free electron density of 1016-1017cm-3. It has a slight increase after 900°C annealing in oxygen ambient. The DLTS measurement revealed four deep level defects with energy at 0.30eV, 0.50eV, 0.68eV and 0.90eV in the as-grown ZnO sample, respectively. After the high temperature annealing, only the 0.5eV defect survive and has a concentration increase. PL results of the as-grown and annealed ZnO indicate that the well-known green emission disappear after the annealing. The result suggests a correlation between the 0.68eV defect and the green PL peak. Results of P-doped ZnO were also compared with the undoped ZnO sample. The nature of the defects and their influence on the material property have been discussed.

Zhao, Youwen; Zhang, Fan; Zhang, Rui; Dong, Zhiyuan; Wei, Xuecheng; Zeng, Yiping; Li, Jinmin

2008-03-01

14

Photoluminescence and positron annihilation spectroscopic investigation on a H+ irradiated ZnO single crystal  

NASA Astrophysics Data System (ADS)

Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6 MeV H+ ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378 eV (10 K). The irradiation creates an intense and narrow emission at 3.368 eV (10 K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368 eV emission indicate its origin as a ‘hydrogen at oxygen vacancy’ type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (164 ± 1 ps) and irradiated crystal (175 ± 1 ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ˜4 × 1017 cm-3 (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ˜175 ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed.

Sarkar, A.; Chakrabarti, Mahuya; Sanyal, D.; Bhowmick, D.; Dechoudhury, S.; Chakrabarti, A.; Rakshit, Tamita; Ray, S. K.

2012-08-01

15

Photoluminescence and positron annihilation spectroscopic investigation on a H(+) irradiated ZnO single crystal.  

PubMed

Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6 MeV H(+) ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378 eV (10 K). The irradiation creates an intense and narrow emission at 3.368 eV (10 K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368 eV emission indicate its origin as a 'hydrogen at oxygen vacancy' type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (164 ± 1 ps) and irradiated crystal (175 ± 1 ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ?4 × 10(17) cm(-3) (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ?175 ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed. PMID:22790024

Sarkar, A; Chakrabarti, Mahuya; Sanyal, D; Bhowmick, D; Dechoudhury, S; Chakrabarti, A; Rakshit, Tamita; Ray, S K

2012-08-15

16

Neutron monochromators of BeO, MgO and ZnO single crystals  

NASA Astrophysics Data System (ADS)

The monochromatic features of BeO, MgO and ZnO single crystals are discussed in terms of orientation, mosaic spread, and thickness within the wavelength band from 0.05 up to 0.5 nm. A computer program MONO, written in “FORTRAN”, has been developed to carry out the required calculations. Calculation shows that a 5 mm thick MgO single crystal cut along its (2 0 0) plane having mosaic spread of 0.5° FWHM has the optimum parameters when it is used as a neutron monochromator. Moreover, at wavelengths shorter than 0.24 nm the reflected monochromatic neutrons are almost free from the higher order ones. The same features are seen with BeO (0 0 2) with less reflectivity than that of the former. Also, ZnO cut along its (0 0 2) plane is preferred over the others only at wavelengths longer than 0.20 nm. When the selected monochromatic wavelength is longer than 0.24 nm, the neutron intensities of higher orders from a thermal reactor flux are higher than those of the first-order one. For a cold reactor flux, the first order of BeO and MgO single crystals is free from the higher orders up to 0.4 nm, and ZnO at wavelengths up to 0.5 nm.

Adib, M.; Habib, N.; Bashter, I. I.; Morcos, H. N.; El-Mesiry, M. S.; Mansy, M. S.

2014-05-01

17

Molecular adsorption on ZnO(1010) single-crystal surfaces: morphology and charge transfer.  

PubMed

While ZnO has excellent electrical properties, it has not been widely used for dye-sensitized solar cells, in part because ZnO is chemically less stable than widely used TiO(2). The functional groups typically used for surface passivation and for attaching dye molecules either bind weakly or etch the ZnO surface. We have compared the formation of molecular layers from alkane molecules with terminal carboxylic acid, alcohol, amine, phosphonic acid, or thiol functional groups on single-crystal zinc oxide (1010) surfaces. Atomic force microscopy (AFM) images show that alkyl carboxylic acids etch the surface whereas alkyl amine and alkyl alcohols bind only weakly on the ZnO(1010) surface. Phosphonic acid-terminated molecules were found to bind to the surface in a heterogeneous manner, forming clusters of molecules. Alkanethiols were found to bind to the surface, forming highly uniform monolayers with some etching detected after long immersion times in an alkanethiol solution. Monolayers of hexadecylphosphonic acid and octadecanethiol were further analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. AFM scratching shows that thiols were bound strongly to the ZnO surface, suggesting the formation of strong Zn-S covalent bonds. Surprisingly, the tridentate phosphonic acids adhered much more weakly than the monodentate thiol. The influence of organic grafting on the charge transfer to ZnO was studied by time-resolved surface photovoltage measurements and electrochemical impedance measurements. Our results show that the grafting of thiols to ZnO leads to robust surfaces and reduces the surface band bending due to midgap surface states. PMID:22680252

Chen, Jixin; Ruther, Rose E; Tan, Yizheng; Bishop, Lee M; Hamers, Robert J

2012-07-17

18

Coloration of single crystal ZnO with ultraviolet laser irradiation  

NASA Astrophysics Data System (ADS)

Many dielectric crystals color in the visible region of the spectrum when exposed to intense ultraviolet light such as excimer laser irradiation. In the alkali and alkaline earth halides, the decay of self-trapped excitons produces strongly absorbing defects. We were recently surprised to see single crystal ZnO darken dramatically during exposure to 193-nm ArF excimer laser radiation. ZnO is a wide bandgap (3.44 eV) semiconductor of significant technological interest. The increase in absorption is very broadband, extending from the bandgap into the infrared, and appears nearly black or grey. We present convincing evidence that this color is due to metallic zinc nanoparticles residing on the surface of the irradiated region. As expected, the laser fluence has considerable impact on the size, number, and spatial distribution of these nanoparticles. We propose a model for production of metallic nanoparticles on the surface.

Khan, Enamul; Langford, S. C.; Dickinson, J. T.

2009-03-01

19

Electrical Properties of ZnO Thin Films and Single Crystals  

NASA Astrophysics Data System (ADS)

We have investigated the electrical properties of ZnO single crystals and thin films. Low resistive ohmic contacts were realized by annealing thermally evaporated Ti-Au contacts at 400°C in vacuum. Hall effect measurements provided information about dominant scattering mechanisms in the single crystals and the epitaxial thin films. Dominant donor levels were found in an energy range from 37 meV to 350 meV below the conduction band for the different samples. Schottky contacts of good quality (j(-5V) = 4 × 10-5 A/cm2, n = 1.3) were produced on thin films after etching with HNO3. Deep level transient spectroscopy yielded the activation energy of deep traps for single crystals of 300 meV and 540 meV and for the thin films of 300 meV, respectively.

Grundmann, M.; von Wenckstern, H.; Pickenhain, R.; Weinhold, S.; Chengnui, B.; Breitenstein, O.

20

Growth of high-quality ZnO single crystals by seeded CVT using the newly designed ampoule  

NASA Astrophysics Data System (ADS)

The high-quality ZnO single crystals were grown by seeded chemical vapor transport (CVT) in a newly designed ampoule using carbon as a transport agent. The well-faceted crystal of about 5×5×5 mm 3 can be grown reproducibly. Secondary ion mass spectroscopy (SIMS) analysis, X-ray rocking curve (XRC) and photoluminescence (PL) measurements demonstrate that the grown single crystal is of high purity and high crystallinity.

Hong, Sang-Hwui; Mikami, Makoto; Mimura, Kouji; Uchikoshi, Masahito; Yasuo, Akihiko; Abe, Seishi; Masumoto, Katashi; Isshiki, Minoru

2009-07-01

21

Impedance analysis of secondary phases in a Co-implanted ZnO single crystal.  

PubMed

Co ions with 100 keV energy with a fluence of 1 × 10(15) cm(-2) are implanted into ZnO(0001) single crystals at 300 °C under vacuum. The resulting Co-implanted ZnO single crystals and the subsequent 750 °C and 900 °C annealed samples are analysed with respect to their structural, optical, electronic, magnetic and ac electrical properties. Photoluminescence and X-ray photoelectron spectroscopy results indicate the signatures of the Co(2+) state and its substitution at the tetrahedrally coordinated Zn-sites. X-ray diffraction and X-ray photoelectron spectroscopy identify the presence of the ZnCo2O4 and Co3O4 phases in the 900 °C annealed sample. By comparing the resistance response of the identified phases towards different magnetic environments, the impedance spectroscopy results successfully identify two magnetic phases (ZnCo2O4 and Co3O4) and a paramagnetic (CoZn) phase for the 750 °C and 900 °C annealed samples, implying the extrinsic nature of room temperature ferromagnetism. The observed ferromagnetism in each sample is not of single origin, instead the mutual effects of the secondary phases embedded in the paramagnetic host matrix are in competition with each other. PMID:24963819

Younas, M; Zou, L L; Nadeem, M; Naeem-Ur-Rehman; Su, S C; Wang, Z L; Anwand, W; Wagner, A; Hao, J H; Leung, C W; Lortz, R; Ling, F C C

2014-07-01

22

Structure and stability of N-H complexes in single-crystal ZnO  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) is semiconductor with a wide band gap of 3.4 eV. It continues to gain more attention not only for its versatile use in industry but also its potential for further application in electronics, optics, spintronics, and transparent circuits. Many of these applications require p-type ZnO. Nitrogen substituting for oxygen is a possible acceptor for such applications. In this paper, we report a study of nitrogen-hydrogen (N-H) complexes grown into single-crystal ZnO, using seeded chemical vapor transport in an ammonia ambient. An infrared (IR) absorption peak arising from N-H complexes was observed at 3150.6 cm-1 at liquid-helium temperatures. The assignment of this peak was confirmed by nitrogen and hydrogen isotope substitution. Polarized IR spectroscopy shows that the N-H dipole is oriented at an angle ~114° to the c axis, in agreement with previous first-principles calculations. To probe the stability of the N-H complexes, samples were annealed in air, oxygen, and argon. Samples annealed in oxygen at 725 °C showed a significant increase in resistivity, due to outdiffusion of hydrogen and compensation by nitrogen acceptors.

Jokela, S. J.; McCluskey, M. D.

2010-06-01

23

Electrical and photoluminescence properties of carbon implanted ZnO bulk single crystals  

NASA Astrophysics Data System (ADS)

Carbon-ions, which are expected as an amphoteric impurity, are implanted into ZnO bulk single crystals with a fluence of 1.5 × 10 15 cm -2. The carbon-ion implanted ZnO shows the n-type conductivity and the resistivity varies from 6 × 10 4 ? cm (for unimplanted samples) to 3 × 10 -2 ? cm (for 800 °C-annealed ones). The Rutherford backscattering (RBS) studies show the existence of the displaced zinc atoms. In photoluminescence (PL) measurements, the broad emission at 2.34 eV observed in un-implanted and as-implanted samples is related to oxygen vacancy and zinc interstitial. After annealing, the weak PL-emission related to carbon donor is observed at 3.06 eV, indicating that the donor level lies at ˜310 meV below the conduction band. The carbon-ion implanted ZnO layer with the low resistivity achieved in the present study suggests the possibility of transparent conductive oxide.

Matsumoto, K.; Kuriyama, K.; Kushida, K.

2009-05-01

24

Fabrication and characterization of a ZnO X-ray sensor using a high-resistivity ZnO single crystal grown by the hydrothermal method  

NASA Astrophysics Data System (ADS)

We investigated the X-ray detection capability of a fabricated Pt/ZnO diode using a high-resistivity ZnO single crystal grown by the hydrothermal method. The X-ray sensor consists of a Pt electrode on the Zn-face, an Au/Ti electrode on the O-face and a (0 0 0 1) ZnO substrate with high resistivity. The fabricated X-ray sensor showed ohmic-like characteristics in the measurement of current-applied voltage characteristics. We attributed these ohmic characteristics to degradation of the surface quality of the ZnO substrate caused by handling damage that occurred when carrying out a series of electrical and optical ZnO characterizations. The fabricated X-ray sensor at a bias of 20 V responded to X-rays in current-mode measurement. The sensor current increased linearly with X-ray tube current at 60 keV, and the results showed that sensitivity was approximately 1.5 ?C/Gy. We demonstrated that a ZnO single crystal has potential for the development of an X-ray detector.

Endo, Haruyuki; Chiba, Tetsuya; Meguro, Kazuyuki; Takahashi, Kyo; Fujisawa, Mitsuru; Sugimura, Shigeaki; Narita, Shinya; Kashiwaba, Yasube; Sato, Eiichi

2011-02-01

25

Coherent scattering of exciton polaritons and acoustic phonons in a ZnO single crystal  

NASA Astrophysics Data System (ADS)

The light reflection oscillations resulting from the coherent scattering of polariton states and propagating coherent acoustic phonons (CAPs) in a ZnO single crystal are studied by using a two-color femtosecond pump-probe technique. The oscillation frequency manifested in the photoinduced reflectance shows a nonlinear dependence on the probe-beam wave vector owing to the variation of the refractive index near the band gap. The oscillation amplitude is affected by the refractive index modulation derived from the CAP-detuning polariton states. The larger oscillation for shorter probe-beam wavelengths is consistent with the stronger scattering between the CAP and excitonlike polariton states closer to the band gap.

Liu, Wenhui; Xie, Wei; Guo, Wenping; Xu, Dan; Hu, Tao; Ma, Tianping; Yuan, Haochen; Wu, Yizheng; Zhao, Haibin; Shen, Xuechu; Chen, Zhanghai

2014-05-01

26

The effect of flash lamp annealing on Fe implanted ZnO single crystals  

SciTech Connect

The effect of flash lamp annealing applied to ZnO single crystals implanted with 3.6 at. % Fe has been studied. For intermediate light power, the implantation-induced surface defects could be annealed without creation of secondary phases within the implanted region. At the same annealing temperatures, however, ion-beam-induced open volume defects start to increase in size. Recrystallization is initiated for the highest light power applied, i.e., the ion-beam-induced lattice disorder reflected by the minimum channeling yield of Rutherford backscattering spectroscopy decreases from 76% to 46% and the open volume defects are annealed. At the same time, the Fe{sup 3+} fraction increases at the cost of the Fe{sup 2+} states. Weak ferromagnetic properties that are mainly associated with nanoparticles are induced.

Potzger, K.; Anwand, W.; Reuther, H.; Zhou, Shengqiang; Talut, G.; Brauer, G.; Skorupa, W.; Fassbender, J. [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, P.O. Box 510119, 01314 Dresden (Germany)

2007-02-01

27

Glycine adsorption and photo-reaction over ZnO(000?) single crystal  

NASA Astrophysics Data System (ADS)

The adsorption and reaction of the amino acid glycine (NH2CH2COOH) are studied experimentally on the polar single crystal surface of zinc oxide, ZnO(000?), by X-ray photoelectron spectroscopy (XPS) under UV light in presence and absence of molecular O2. Deposition at 350 K mainly resulted in a largely deprotonated monolayer (NH2CH2COO?(a) + OH(s); where O is surface oxygen, (a) is for adsorbed and (s) is for surface species) identified by its XPS C1s binding energy at 289.3 eV (COO), 286.7 eV (CH2) and XPS O1s at 531.8 eV (COO). A decrease in the signals of all functional groups of the adsorbed glycine (monitored by their C1s, O1s, and N1s lines) is seen upon UV excitation in the absence and presence of O2 pressures up to 5 × 10? 6 mbar. The photoreaction cross sections extracted from the decrease in the C1s peaks were found to be = 2.6 × 10? 18 (COO(a)) and 1.4 × 10? 18(CH2) cm2. The photoactivity of the ZnO(000?) surface under UHV-conditions is found to be comparable to that seen in direct photolysis of amino acids in solution.

Gao, Y. K.; Traeger, F.; Wöll, C.; Idriss, H.

2014-06-01

28

Analysis of strained surface layers of ZnO single crystals after irradiation with intense femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

Structural modifications of ZnO single crystals that were created by the irradiation with femtosecond laser pulses at fluences far above the ablation threshold were investigated with micro-Raman spectroscopy. After light-matter interaction on the femtosecond time scale, rapid cooling and the pronounced thermal expansion anisotropy of ZnO are likely to cause residual strains of up to 1.8% and also result in the formation of surface cracks. This process relaxes the strain only partially and a strained surface layer remains. Our findings demonstrate the significant role of thermoelastic effects for the irradiation of solids with intense femtosecond laser pulses.

Schneider, Andreas; Wolverson, Daniel; Sebald, Kathrin; Hodges, Chris; Kuball, Martin; Voss, Tobias

2013-05-01

29

Analysis of strained surface layers of ZnO single crystals after irradiation with intense femtosecond laser pulses  

SciTech Connect

Structural modifications of ZnO single crystals that were created by the irradiation with femtosecond laser pulses at fluences far above the ablation threshold were investigated with micro-Raman spectroscopy. After light-matter interaction on the femtosecond time scale, rapid cooling and the pronounced thermal expansion anisotropy of ZnO are likely to cause residual strains of up to 1.8% and also result in the formation of surface cracks. This process relaxes the strain only partially and a strained surface layer remains. Our findings demonstrate the significant role of thermoelastic effects for the irradiation of solids with intense femtosecond laser pulses.

Schneider, Andreas; Sebald, Kathrin; Voss, Tobias [Semiconductor Optics, Institute of Solid State Physics, University of Bremen, D-28359 Bremen (Germany)] [Semiconductor Optics, Institute of Solid State Physics, University of Bremen, D-28359 Bremen (Germany); Wolverson, Daniel [Nanoscience Group, Department of Physics, University of Bath, BA2 7AY Bath (United Kingdom)] [Nanoscience Group, Department of Physics, University of Bath, BA2 7AY Bath (United Kingdom); Hodges, Chris; Kuball, Martin [Center for Device Thermography and Reliability (CDTR), H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)] [Center for Device Thermography and Reliability (CDTR), H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)

2013-05-27

30

Giant coercivity in ferromagnetic Co doped ZnO single crystal thin film  

NASA Astrophysics Data System (ADS)

The origin of ferromagnetism in ZnO doped with transition metal impurities has been discussed extensively and appeared to be a highly controversial and challenging topic in today's solid state physics. Magnetism observed in this system is generally weak and soft. We have grown Co:ZnO up to 30 at% Co in single crystal thin film form on c-plane sapphire. A composition dependent coercivity is observed in this system which reaches peak value at 25 at% Co, the values are 860 Oe and 1149 Oe with applied field along parallel and perpendicular to the film substrate interface respectively. This giant coercivity might pave the way to exploit this material as a magnetic semiconductor with novel logic functionalities. The findings are explained based on defect band itinerant ferromagnetism and its partial interaction with localized d electrons of Co through charge transfer. Besides large coercivity, an increase in the band gap with Co concentration has also been observed along with blue emission peak with long tail confirming the formation of extended point defect levels in the host lattice band gap.

Loukya, B.; Negi, D. S.; Dileep, K.; Kumar, N.; Ghatak, Jay; Datta, R.

2013-11-01

31

Optical and Magnetic Resonance Studies of Na-Diffused ZnO Bulk Single Crystals  

NASA Astrophysics Data System (ADS)

Photoluminescence (PL) and optically-detected magnetic resonance (ODMR) at 24 GHz were performed on bulk ZnO crystals after diffusion of Na impurities that were explored as an alternate doping source for p-type conductivity. PL at 2K revealed strong bandedge excitonic recombination at 3.361 eV and a broad ``orange'' PL band at 2.17 eV with FWHM of ˜0.5 eV. This ``orange'' emission is very similar to that reported previouslyfootnotetextD. Zwingel and F. Gartner, Solid State Commun. 14, 45 (1974). from thermoluminescence measurements of intentionally Na-doped bulk ZnO and, thus, strongly suggests the incorporation and activation of the Na-diffused impurities. ODMR performed on this ``orange'' PL revealed two signals. The first was a sharp feature with g-value of ˜1.96 and is a well-known ``fingerprint'' of shallow donors in ZnO. The second signal consisted of a pair of lines with an intensity ratio of ˜3:1 and with g-tensors (g,g˜2.008-2.029) very similar to ESR signals attributed previouslyfootnotetextIbid. to holes bound to Na impurities located at the axial and non-axial Zn host lattice sites in Na-doped ZnO. Thus, the ``orange'' PL can be tentatively assigned to radiative recombination between residual shallow donors and deep Na-related hole traps.

Glaser, E. R.; Garces, N. Y.; Parmar, N. S.; Lynn, K. G.

2013-03-01

32

Rutherford backscattering and nuclear reaction analyses of hydrogen ion-implanted ZnO bulk single crystals  

NASA Astrophysics Data System (ADS)

The origins of low resistivity in H ion-implanted ZnO bulk single crystals are studied by Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA) photoluminescence (PL), and Van der Pauw methods. The H-ion implantation (peak concentration: 1.45 × 1020 cm-3) into ZnO is performed using a 500 keV implanter. The resistivity decreases from 2.5 × 103 ? cm for unimplanted ZnO to 6.5 ? cm for as-implanted one. RBS measurements show that Zn interstitial as a shallow donor is not recognized in as-implanted samples. From photoluminescence measurements, the broad green band emission is observed in as-implanted samples. NRA measurements for as-implanted ZnO suggest the existence of the oxygen interstitial. The origins of the low resistivity in the as-implanted sample are attributed to both the H interstitial as a shallow donor and complex donor between H and disordered O. The activation energy of H related donors estimated from the temperature dependence of carrier concentration is 29 meV.

Kaida, T.; Kamioka, K.; Ida, T.; Kuriyama, K.; Kushida, K.; Kinomura, A.

2014-08-01

33

Single-crystal ZnO nanorods fabricated with different end morphologies  

NASA Astrophysics Data System (ADS)

In this study, highly crystallized ZnO nanorods produced with hexagonal prism-like, tower-like and tip-like ends were successfully synthesized from the starting raw material of Zn3N2 powder. The experimental results indicate that the different morphologies of the ends of nanorods depend on the concentration of NH3 in the hydrothermal process. Furthermore, the size of the nanorods is significantly influenced by the synthesis temperature. Nanorods of a small diameter (about 10 nm), for example, can be produced at low temperatures. A possible growth mechanism is proposed for the formation of nanorods that exhibit different end morphologies.

Wei, Mingdeng; Qi, Zhi-mei; Ichihara, Masaki; Honma, Itaru; Zhou, Haoshen

2007-03-01

34

Effects of ultrathin layers on the growth of vertically aligned wurtzite ZnO nanostructures on perovskite single-crystal substrates  

NASA Astrophysics Data System (ADS)

In this study, ZnO nanostructures were grown on various ultra-thin layers coated (1 0 0)-oriented SrTiO3 (STO) single-crystal substrates using thermal evaporation of metallic zinc at 600 °C. This study used the ZnO seed layer and/or metal catalyst layer to grow high-density ZnO nanostructures on STO substrates. X-ray diffraction and scanning electron microscopy (SEM) measurements showed that the use of Au and Ag catalysts is crucial in producing ZnO nanostructures with a preferential c-axis direction. The as-grown ZnO nanostructures had a hexagonal facet. Among various STO substrates (Au/STO, Ag/STO, ZnO/STO, Au/ZnO/STO, and Ag/ZnO/STO), the ZnO nanostructures grown on the Au/STO substrate had the highest degree of vertical alignment, and the intensity ratio of the UV to visible emission band reached 55. Conversely, the ZnO nanostructures grown on the ZnO seed layer-coated STO substrate were more randomly oriented, and the intensity ratio of the UV to visible emission band was only 9.5. The cathodoluminescence (CL) results showed that higher vertically aligned ZnO nanostructures have lower-density crystal defects. The current-voltage measurements supported the structural analysis.

Liang, Yuan-Chang; Hu, Chia-Yen; Zhong, Hua

2012-11-01

35

Evaluation of Melt-Grown, ZnO Single Crystals for Use as Alpha-Particle Detectors  

SciTech Connect

As part of an ongoing investigation of the scintillation properties of zinc-oxide-based scintillators, several melt-grown, ZnO single crystals have been characterized using -particle excitation, infrared reflectance, and room temperature photoluminescence. The crystals, grown by Cermet, Inc. using a pressurized melt growth process, were doped with Group 1 elements (Li), Group 2 elements (Mg), Group 3 elements (Ga, In) and Lanthanides (Gd, Er, Tm). The goals of these studies are to better understand the scintillation mechanisms associated with various members of the ZnO scintillator family and to then use this knowledge to improve the radiation detection capabilities of ZnO-based scintillators. One application for which ZnO is particularly well suited as a scintillator is as the associated particle detector in a deuterium-tritium (D-T) neutron generator. Application requirements include the exclusion of organic materials, outstanding timing resolution, and high radiation resistance. ZnO(Ga) and ZnO(In) have demonstrated fast (sub-nanosecond) decay times with relatively low light yields, and ZnO(Ga) has been used in a powder form as the associated particle detector for a D-T neutron generator. Four promising candidate materials, ZnO, ZnO:Ga, ZnO:In,Li, and ZnO:Er,Li, were identified in this study. These four samples demonstrated sub-nanosecond decay times and alpha particle excited luminescence comparable to BC-400 fast plastic scintillator. The ZnO:Mg,Ga, ZnO:Gd, and ZnO:Li samples demonstrated appreciable slow (microsecond) decay components that would be incompatible with high-counting-rate applications.

Neal, John S [ORNL; Giles, N. C. [West Virginia University; Yang, Xiaocheng [West Virginia University; Wall, R. Andrew [Wake Forest University, Winston-Salem, NC; Ucer, Burak [Wake Forest University, Winston-Salem, NC; Williams, Richard T. [Wake Forest University, Winston-Salem, NC; Wisniewski, Dariusz J [ORNL; Boatner, Lynn A [ORNL; Rengarajan, Varatharajan [ORNL; Nause, Jeff E [ORNL; Nemeth, Bell [Cermet, Inc., Atlanta

2008-01-01

36

Growth of ZnO single crystal thin films on c-plane (0 0 0 1) sapphire by plasma enhanced molecular beam epitaxy  

Microsoft Academic Search

ZnO single crystal thin films were grown by plasma enhanced molecular beam epitaxy on (0 0 0 1) sapphire. The growth modes of ZnO epilayers were investigated by reflection high-energy electron diffraction. A transition from two-dimensional nucleation to three-dimensional nucleation is found at the initial growth stage. Optical properties of the films, studied by photoluminescence spectroscopy, exhibit a dominant bound

Yefan Chen; D. M. Bagnall; Ziqiang Zhu; Takashi Sekiuchi; Ki-tae Park; Kenji Hiraga; Takafumi Yao; S. Koyama; M. Y. Shen; T. Goto

1997-01-01

37

Study of the local environment diversity between Co and Mn-doped ZnO single crystal film by multilayer growth technique  

Microsoft Academic Search

We investigated the room temperature ferromagnetism and their local coordination environment of Co and Mn doped in ZnO single crystal films. Both films show room temperature ferromagnetism and the saturated magnetization of the Mn-doped ZnO film is stronger than that of the Co-doped films. From the analysis on the local structures of Zn, Co, and Mn, we verify that the

J. C. A. Huang; H. S. Hsu; J. H. Sun; S. L. Chiu; C. H. Lee; Y. F. Liao; H. Chou

2008-01-01

38

Hydrogen released from bulk ZnO single crystals investigated by time-of-flight electron-stimulated desorption  

SciTech Connect

Electron beam (e-beam) irradiation effects on ZnO single crystals have been investigated by using time-of-flight electron-stimulated desorption (TOF-ESD). The samples were irradiated by using a continuous 0.5 or 1.5 keV e-beam, while the TOF-ESD spectra were taken by using a pulsed 0.5 keV e-beam. For both the O-terminated and Zn-terminated surfaces, the major desorption is H{sup +} desorption. The main trend of H{sup +} desorption intensity and evolution as a function of irradiation time is similar for both faces. The H{sup +} peak is much higher after 1.5 keV irradiation than after 0.5 keV irradiation. The intensity of the H{sup +} peak decreases exponentially as a function of irradiation time and partially recovers after the irradiation is stopped. These observations suggest that the main contribution of the H{sup +} desorption is hydrogen released from the dissociation of H-related defects and complexes in the bulk region of the ZnO by e-beam irradiation. This finding can be used to explain the reported ultraviolet degradation of ZnO single crystals under electron irradiation observed by cathodoluminescence. The surfaces play a lesser role for the H{sup +} desorption, as there are differences of the decreasing rate between the two faces and additionally the intensity of the H{sup +} peak for both the unclean O-face and Zn-facesis smaller than that for clean faces. While the H{sup +} desorption is mainly dominated by the bulk region, O{sup +} desorption is more influenced by the surfaces. There are two kinds of O{sup +} desorbed from ZnO having 13.0 {mu}s TOF and 14.2 {mu}s TOF. The O{sup +} desorption depends on the surface polarity, the surface conditions and the energy used for irradiation.

Dierre, Benjamin; Sekiguchi, Takashi [Advanced Electronic Materials Center, National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0003 (Japan); Yuan, Xiaoli [Advanced Electronic Materials Center, National Institute for Materials Science (NIMS), Tsukuba 305-0044 (Japan); Ueda, Kazuyuki [Nano High-Tech Research Center, Graduate School of Engineering, Toyota Technological Institute, Nagoya 468-8511 (Japan)

2010-11-15

39

Formation of isolated Zn vacancies in ZnO single crystals by absorption of ultraviolet radiation: a combined study using positron annihilation, photoluminescence, and mass spectroscopy.  

PubMed

Positron annihilation spectra reveal isolated zinc vacancy (V(Zn)) creation in single-crystal ZnO exposed to 193-nm radiation at 100 mJ/cm(2) fluence. The appearance of a photoluminescence excitation peak at 3.18 eV in irradiated ZnO is attributed to an electronic transition from the V(Zn) acceptor level at ~100 meV to the conduction band. The observed V(Zn) density profile and hyperthermal Zn(+) ion emission support zinc vacancy-interstitial Frenkel pair creation by exciting a wide 6.34 eV Zn-O antibonding state at 193-nm photon-a novel photoelectronic process for controlled V(Zn) creation in ZnO. PMID:23863026

Khan, Enamul H; Weber, Marc H; McCluskey, Matthew D

2013-07-01

40

Emission characteristics of electrically- and optically-pumped single ZnO micro-spherical crystal  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nano/microstructures have been attractive as the building blocks for the efficient opto-electronic devices in the ultraviolet (UV) region. We have succeeded in growing the ZnO micro/nanosphere by a simple laser ablation in the air, and therefore we have obtained UV lasing from the sphere under optical pumping. Recently, large size of several 10 micrometer ZnO microspheres were grown using Nd:YAG laser without Q-switching, and ZnO microsphere/p-GaN heterojunction were fabricated to obtain the electroluminescence (EL) from the microsphere by electrical pumping. Room-temperature EL in near-UV region with peak wavelength of 400 nm is observed under forward bias.

Nakamura, D.; Shimogaki, T.; Tetsuyama, N.; Fusazaki, K.; Mizokami, Y.; Higashihata, M.; Ikenoue, H.; Okada, T.

2014-03-01

41

ZnO dense nanowire array on a film structure in a single crystal domain texture for optical and photoelectrochemical applications  

NASA Astrophysics Data System (ADS)

A single crystal domain texture quality (a unique in-plane and out-of-plane crystalline orientation over a large area) ZnO nanostructure of a dense nanowire array on a thick film has been homogeneously synthesized on a-plane sapphire substrates over large areas through a one-step chemical vapor deposition (CVD) process. The growth mechanism is clarified: a single crystal [0\\bar {2}1] oriented ZnAl2O4 buffer layer was formed at the ZnO film and the a-plane sapphire substrate interface via a diffusion reaction process during the CVD process, providing improved epitaxial conditions that enable the synthesis of the high crystalline quality ZnO nanowire array on a film structure. The high optoelectronic quality of the ZnO nanowire array on a film sample is evidenced by the free exitonic emissions in the low-temperature photoluminescence spectroscopy. A carrier density of ˜1017 cm-3 with an n-type conductivity of the ZnO nanowire array on a film sample is obtained by electrochemical impedance analysis. Finally, the ZnO nanowire array on a film sample is demonstrated to be an ideal template for a further synthesis of a single crystal quality ZnO-ZnGa2O4 core-shell nanowire array on a film structure. The fabricated ZnO-ZnGa2O4 sample revealed an enhanced anticorrosive ability and photoelectrochemical performance when used as a photoanode in a photoelectrochemical water splitting application.

Zhong, Miao; Sato, Yukio; Kurniawan, Mario; Apostoluk, Aleksandra; Masenelli, Bruno; Maeda, Etsuo; Ikuhara, Yuichi; Delaunay, Jean-Jacques

2012-12-01

42

ZnO dense nanowire array on a film structure in a single crystal domain texture for optical and photoelectrochemical applications.  

PubMed

A single crystal domain texture quality (a unique in-plane and out-of-plane crystalline orientation over a large area) ZnO nanostructure of a dense nanowire array on a thick film has been homogeneously synthesized on a-plane sapphire substrates over large areas through a one-step chemical vapor deposition (CVD) process. The growth mechanism is clarified: a single crystal [02(-)1] oriented ZnAl(2)O(4) buffer layer was formed at the ZnO film and the a-plane sapphire substrate interface via a diffusion reaction process during the CVD process, providing improved epitaxial conditions that enable the synthesis of the high crystalline quality ZnO nanowire array on a film structure. The high optoelectronic quality of the ZnO nanowire array on a film sample is evidenced by the free exitonic emissions in the low-temperature photoluminescence spectroscopy. A carrier density of ~10(17) cm(-3) with an n-type conductivity of the ZnO nanowire array on a film sample is obtained by electrochemical impedance analysis. Finally, the ZnO nanowire array on a film sample is demonstrated to be an ideal template for a further synthesis of a single crystal quality ZnO-ZnGa(2)O(4) core-shell nanowire array on a film structure. The fabricated ZnO-ZnGa(2)O(4) sample revealed an enhanced anticorrosive ability and photoelectrochemical performance when used as a photoanode in a photoelectrochemical water splitting application. PMID:23150203

Zhong, Miao; Sato, Yukio; Kurniawan, Mario; Apostoluk, Aleksandra; Masenelli, Bruno; Maeda, Etsuo; Ikuhara, Yuichi; Delaunay, Jean-Jacques

2012-12-14

43

Application of ZnO Single Crystal Rods as Anti-Reflective Material for PV Cells  

Microsoft Academic Search

In this study, ZnO nanorods for antireflection coatings application to the silicon solar cells were epitaxially grown over the Si substrate using both thermal evaporation method and wet chemical method and their characteristics were investigated. A precursor for the thermal evaporation method was prepared by impregnating zinc acetate over the activated carbon at three different loading amounts: 10, 20, and

No-Kuk Park; Yong Sul Kim; Jun Hyuk Chang; Do Hyeong Kim; Si Ok Ryu; Tae Jin Lee; Heun Duk Kim; Won Gun Lee

2012-01-01

44

Nitrogen and hydrogen in bulk single-crystal ZnO  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) is a wide band gap II-VI semiconductor with optical, electronic, and mechanical applications. Nitrogen is a promising acceptor dopant. Nitrogen-hydrogen (N-H) complexes were introduced into ZnO during chemical vapor transport (CVT) growth, using ammonia as a doping source. The N-H bond-stretching mode gives rise to an infrared (IR) absorption peak at 3151 cm -1 at liquid-helium temperatures. Along with passivating acceptors, hydrogen also acts as a shallow donor. In the previous work, we observed an IR peak at 3326 cm -1 that corresponds to a hydrogen donor. It is possible that this donor is actually a Ca-OH complex.

Jokela, S. J.; Tarun, M. C.; McCluskey, M. D.

2009-12-01

45

Characteristics of intermediate state related to anti-Stokes luminescence of ZnO single crystals  

NASA Astrophysics Data System (ADS)

Anti-Stokes luminescence from ZnO is supposed to be a two-step two-photon absorption process with an intermediate state. The intermediate state is assumed to be a localized state with two different excited and relaxed states. One of the localized states is believed to be the well-known 2.4 eV green luminescence; the other is difficult to observe experimentally. We found an interesting 2.25 eV deep luminescence from ZnO, which has been shown to relate to anti-Stokes luminescence. The 2.25 eV yellow luminescence was observable only below the band gap excitation and through a time-resolved observation after the excitation light was turned off. The intermediate states were found to be a photo-excited donor-acceptor pair and its lattice relaxation state. The characteristics and the role of the intermediate state of ZnO related to the anti-Stokes luminescence are discussed.

Fujii, Katsushi; Goto, Takenari; Yao, Takafumi

2014-06-01

46

Toward an understanding of intermediate- and short-range defects in ZnO single crystals. A combined experimental and theoretical study.  

PubMed

A joint use of experimental and theoretical techniques allows us to understand the key role of intermediate- and short-range defects in the structural and electronic properties of ZnO single crystals obtained by means of both conventional hydrothermal and microwave-hydrothermal synthesis methods. X-ray diffraction, Raman spectra, photoluminescence, scanning electronic and transmission electron microscopies were used to characterize the thermal properties, crystalline and optical features of the obtained nano and microwires ZnO structures. In addition, these properties were further investigated by means of two periodic models, crystalline and disordered ZnO wurtzite structure, and first principles calculations based on density functional theory at the B3LYP level. The theoretical results indicate that the key factor controlling the electronic behavior can be associated with a symmetry breaking process, creating localized electronic levels above the valence band. PMID:18652436

Lima, R C; Macario, L R; Espinosa, J W M; Longo, V M; Erlo, R; Marana, N L; Sambrano, J R; dos Santos, M L; Moura, A P; Pizani, P S; Andrés, J; Longo, E; Varela, J A

2008-09-25

47

Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices  

NASA Astrophysics Data System (ADS)

The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6 × 1020 cm-3) into ZnO is performed using a multiple-step energy. The high resistivity of ?103 ? cm in un-implanted samples remarkably decreased to ?10-2 ? cm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000 °C annealed ZnO.

Kamioka, K.; Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Kinomura, A.

2014-08-01

48

Raman scattering and photoluminescence of As ion-implanted ZnO single crystal  

NASA Astrophysics Data System (ADS)

We have converted the surface of undoped ZnO bulk into the As-doped p-ZnO layer by means of the As ion implantation method. After postimplantation annealing, the As-related properties were investigated by using Raman scattering and photoluminescence (PL) experiments. The Raman spectrum shows that the E2high peak obtained from the As-doped p-ZnO shifted toward the higher energy side of 0.55 cm-1 in comparison with that of the undoped ZnO bulk. This result is related to the stress increment of the sample surface due to the As implantation. After the As-implanted p-ZnO annealed at 800 °C, the PL spectroscopy reveals the neutral acceptor bound exciton emission (A?,X) at 3.3589 eV. This emission shows a tendency to quench the intensity and extend the emission linewidth with increasing temperatures. Also, two As-related peaks associating with recombination emissions between free electrons and acceptor holes were observed at 3.3159 and 3.2364 eV. In addition, the I-V characteristic curves of the p-n homojunction fabricated with the As ion implantation method clearly have shown the behavior of the diode.

Jeong, T. S.; Han, M. S.; Youn, C. J.; Park, Y. S.

2004-07-01

49

Evaluation of Carbon Interstitial in C-ion Implanted ZnO Bulk Single Crystals by a Nuclear Reaction Analysis Study: An Origin of Low Resistivity  

SciTech Connect

Nuclear reaction analysis (NRA) of carbon-implanted ZnO bulk single crystals (carbon concentration: 1.5x10{sup 20} cm{sup -3}), in conjunction with the channeling technique, using the {sup 12}C(d,p){sup 13}C and {sup 16}O(d,p){sup 17}O reactions shows the presence of the interstitial carbon (C{sub i}) and the occupancy of substitute sites of oxygen atoms. These results suggest that the variation in resistivity from the order of 10{sup 4} {Omega}cm(for un-implanted samples) to that of 10 {Omega}cm (for as-implanted ones) is attributed to the C{sub i} and/or its complex defects, which would act as a shallow donor in ZnO.

Izawa, Y.; Matsumoto, K.; Oga, T.; Kuriyama, K. [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kushida, K. [Department of Arts and Sciences, Osaka Kyoiku University, Kashiwara, Osaka 582-8582 (Japan); Kinomura, A. [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

2011-12-23

50

Electronic structure of N3 DYE molecules on the ZnO single crystal and epitaxial film surfaces  

NASA Astrophysics Data System (ADS)

Most dye-sensitized solar cells use TiO2 nanoparticle films as the electrode, but ZnO offers an interesting alternative. We have used direct and inverse photoemission to measure the occupied and unoccupied electronic states, and their alignment with the band edges of the substrate, of N3 dye adsorbed on ZnO(0001), ZnO(11-2), epitaxial ZnO a-plane film surfaces, and ZnO nanopillars. As the unoccupied states of ZnO are of sp-character and of relatively low cross section, the LUMO of the dye is easily observed. Samples were prepared and passivated with a pivalate layer in UHV, then sensitized in air in a solution of N3 dye in acetonitrile. As opposed to the case of the TiO2(110) surface, STM measurements indicate that the pivalic acid does. From UPS, the N3 HOMO is found at ˜0.8 eV above the ZnO valence band edge, and the LUMO is found ˜1.5 eV above the conduction band edge for the epifilm. Differences in dye adsorption and orbital alignment for these different ZnO surfaces will be discussed.

Theisen, Jean-Patrick; Bersch, Eric; Rangan, Sylvie; Lu, Yicheng; Bartynski, Robert

2008-03-01

51

Simultaneous measurement of absorbance and quantum yields for photocurrent generation at dye-sensitized single-crystal ZnO electrodes.  

PubMed

It is often assumed that the photoresponse or incident photon-to-current conversion efficiency (IPCE) spectrum of a sensitized semiconductor electrode is directly correlated with the amount of sensitizing species present on the semiconductor surface. In reality, the various forms of adsorbed species, such as dye aggregates or dye molecules bound to different adsorption sites, such as terrace edges, can have significantly different electron injection yields and carrier recombination rates. To provide information about the amounts of the various adsorbed dye species and their effectiveness as sensitizers, we report the simultaneous acquisition of IPCE and attenuated total reflectance (ATR) UV-vis spectra for a thiacyanine dye bound to a single-crystal oxide semiconductor electrode surface. ZnO single crystals were fashioned into internal-reflection elements to act both as a waveguide for the internally reflected probe beam for UV-vis spectra and as the substrate for dye sensitization using dyes with distinct spectral signatures for monomers and aggregates. Strong agreement was observed between the quantum efficiency and ATR UV-vis spectra, suggesting that, under the conditions employed, both monomers and aggregates of the dye studied generate photocurrent with the same efficiency. PMID:24090190

Rowley, John G; Parkinson, B A

2013-11-12

52

Characterization of Mn and Fe diffusion into ZnO Films and single crystals for diluted magnetic semiconductor applications  

Microsoft Academic Search

There is growing interesting in the use of transition metal (TM) doped ZnO films as a diluted magnetic semiconductor for room temperature spintronics applications. Various methods of doping have been investigated including ion implantation and co-deposition during the growth process. In essentially all approaches, doping either accompanies, or is followed by, an annealing step intended to achieve a uniform distribution

R. Gateau; D. H. Hill; R. A. Bartynski; P. Wu; Y. Lu

2006-01-01

53

Semipolar Single-Crystal ZnO Films Deposited by Low-Temperature Aqueous Solution Phase Epitaxy on GaN Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

Low-temperature aqueous solution deposition has been used for the first time to produce epitaxial ZnO layers on the semipolar (10\\bar{1}\\bar{1}) surface of bulk GaN substrates and LEDs. Although the ZnO films have single in-plane and out-of-plane orientations, which are nominally the same as those of the (10\\bar{1}\\bar{1}) GaN substrate, the ZnO lattice is observed to be slightly tilted with respect to that of the substrate. A (10\\bar{1}\\bar{1}) light-emitting diode using an epitaxial ZnO film as a transparent current-spreading layer achieved a high external quantum efficiency of 48%.

Richardson, Jacob J.; Koslow, Ingrid; Pan, Chih-Chien; Zhao, Yuji; Ha, Jun-Seok; DenBaars, Steven P.

2011-12-01

54

Physical vapor transport crystal growth of ZnO  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) has a wide band gap, high stability and a high thermal operating range that makes it a suitable material as a semiconductor for fabricating light emitting diodes (LEDs) and laser diodes, photodiodes, power diodes and other semiconductor devices. Recently, a new crystal growth for producing ZnO crystal boules was developed, which was physical vapor transport (PVT), at temperatures exceeding 1500 °C under a certain system pressure. ZnO crystal wafers in sizes up to 50 mm in diameter were produced. The conditions of ZnO crystal growth, growth rate and the quality of ZnO crystal were analyzed. Results from crystal growth and material characterization are presented and discussed. Our research results suggest that the novel crystal growth technique is a viable production technique for producing ZnO crystals and substrates for semiconductor device applications.

Yang, Liu; Jianping, Ma; Fuli, Liu; Yuan, Zang; Yantao, Liu

2014-03-01

55

Single Crystals  

NASA Astrophysics Data System (ADS)

We have prepared single crystals of type-VIII clathrate Ba8Ga15.9- x In x Sn30.1 for x ? 0.60 by the Sn-flux method. As x is increased from 0 to 0.60, the lattice parameter increases by 0.2%, which is consistent with the larger covalent diameter for In than for Ga. The Seebeck coefficient ?, electrical resistivity ?, and thermal conductivity ? were measured in the temperature range from 300 K to 600 K. For all samples, ? is negative, indicating the dominant charge carriers are electrons. With increasing x from 0 to 0.20, ? and decrease by 50% and 30%, respectively. As a result, the lattice thermal conductivity at 300 K decreases from 0.58 W/Km to 0.41 W/Km, which is ascribed to enhancement of rattling of the guest atoms. It is found that the maximum of the dimensionless figure of merit ZT reaches 1.05 at 540 K for x = 0.20.

Chen, Yuexing; Du, Baoli; Kajisa, Kousuke; Takabatake, Toshiro

2014-06-01

56

Induced growth of high quality ZnO thin films by crystallized amorphous ZnO  

NASA Astrophysics Data System (ADS)

This paper reports the induced growth of high quality ZnO thin film by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by solid-state pyrolytic reaction, then by taking crystallized amorphous ZnO as seeds (buffer layer), ZnO thin films have been grown in diethyene glycol solution of zinc acetate at 80°C. X-ray Diffraction curve indicates that the films were preferentially oriented [001] out-of-plane direction of the ZnO. Atomic force microscopy and scanning electron microscopy were used to evaluate the surface morphology of the ZnO thin film. Photoluminescence spectrum exhibits a strong ultraviolet emission while the visible emission is very weak. The results indicate that high quality ZnO thin film was obtained.

Wang, Zhi-Jun; Song, Li-Jun; Li, Shou-Chun; Lu, You-Ming; Tian, Yun-Xia; Liu, Jia-Yi; Wang, Lian-Yuan

2006-11-01

57

Epitaxial Growth and Properties of Cobalt-doped ZnO on ?-Al?O? Single-Crystal Substrates  

SciTech Connect

Co-doped ZnO (CoxZn?-xO) is of potential interest for spintronics due to the prediction of room-temperature ferromagnetism. We have grown epitaxial CoxZn?-xO films on Al?O?(012) substrates by metalorganic chemical vapor deposition using a liquid precursor delivery system. High concentrations of Co (x < 0.35) can be uniformly incorporated into the film without phase segregation. Co is found to be in the ?² oxidation state, independent of x. This material can be grown n type by the deliberate incorporation of oxygen vacancies, but not by inclusion of ~1 at. % Al. Semiconducting films remain ferromagnetic up to 350 K. In contrast films without oxygen vacancies are insulating and nonmagnetic, suggesting that exchange interaction is mediated by itinerant carriers. The saturation and remanent magnetization on a per Co basis was very small (< 0.1 ?B/Co), even in the best films. The dependence of saturation magnetization, as measured by optical magnetic circular dichroism, on magnetic field and temperature, agrees with the theoretical Brillouin function, demonstrating that the majority of the Co(II) ions behave as magnetically isolated S = 3/2 spins.

Tuan, Allan C.; Bryan, John D.; Pakhomov, Alexandre; Shutthanandan, V.; Thevuthasan, Suntharampillai; McCready, David E.; Gaspar, Dan J.; Engelhard, Mark H.; Rogers, J. W.; Krishnan, Kannan M.; Gamelin, Daniel R.; Chambers, Scott A.

2004-08-30

58

Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal  

NASA Astrophysics Data System (ADS)

We report ultraviolet (UV) whispering-gallery-mode (WGM) lasing in a zinc oxide (ZnO) micro/nanosphere crystal fabricated by simply ablating a ZnO sintered target, which was much more productive method without any time-consuming crystal-growth process. The lasing spectral mode spacing was controlled by changing the diameters, and single-mode lasing was realized from a ZnO nanosphere. Experimental results were in good agreement with predictions from WGM theories. Since the ZnO sphere can operate as an active WGM refractometric sensor for small molecules in UV region, high sensitivity enhanced by high quality factor, refractive index, and wavelength dispersion can be expected.

Okazaki, Kota; Shimogaki, Tetsuya; Fusazaki, Koshi; Higashihata, Mitsuhiro; Nakamura, Daisuke; Koshizaki, Naoto; Okada, Tatsuo

2012-11-01

59

Elasticity and piezoelectricity of zinc oxide crystals, single layers, and possible single-walled nanotubes  

NASA Astrophysics Data System (ADS)

The elasticity and piezoelectricity of zinc oxide (ZnO) crystals and single layers are investigated from the first-principles calculations. It is found that a ZnO thin film less than three Zn-O layers prefers a planar graphitelike structure to the wurtzite structure. ZnO single layers are much more flexible than graphite single layers in the elasticity and stronger than boron nitride single layers in the piezoelectricity. Single-walled ZnO nanotubes (SWZONTs) can exist in principle because of their negative binding energy. The piezoelectricity of SWZONTs depends on their chirality. For most ZnO nanotubes except the zigzag type, twists around the tube axis will induce axial polarizations. A possible scheme is proposed to achieve the SWZONTs from the solid-vapor phase process with carbon nanotubes as templates.

Tu, Z. C.; Hu, X.

2006-07-01

60

Next-generation hydrothermal ZnO crystals  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) crystals were grown by the hydrothermal method under significantly improved conditions. Careful adjustment of critical growth conditions led the way towards ZnO crystals with extremely low (<10 14 cm -3) lithium and potassium content. Photoluminescence reveals the low defect levels. The as-grown (0 0 0 1) surface exposes steps of 0.52 nm in height. High growth rates above 0.4 mm per day while observing narrow values for the X-ray rocking curve, FWHM from (0 0 2) reflection below 20 arcsec, and the growth of highly transparent, apparently colorless ZnO crystals are reported. Cautious co-doping with indium and lithium yields high-quality crystals.

Ehrentraut, Dirk; Maeda, Katsumi; Kano, Masataka; Fujii, Katsushi; Fukuda, Tsuguo

2011-04-01

61

Positive temperature coefficient of resistance of single ZnO nanorods  

NASA Astrophysics Data System (ADS)

ZnO nanorods were synthesized by a simple aqueous solution method. Crystal structures and morphology studies show that the ZnO nanorods are single crystalline with the growth direction aligned with the c axis of ZnO. An Au-ZnO nanorod-Au (metal-semiconductor-metal, MSM) device using the synthesized nanorod was fabricated. An electronic model with two back-to-back Schottky diodes in series with a nanorod was used to describe the electrical transport of the MSM device. A positive temperature coefficient of resistance is observed on a single ZnO nanorod from 383 to 473 K. A simple model has been proposed to explain such an abnormal behavior including the effect of the interface states and the adsorption-desorption of the water/oxygen molecules on the surface of the nanorod.

He, Guan-nan; Huang, Bo; Shen, Hui

2011-02-01

62

Positive temperature coefficient of resistance of single ZnO nanorods.  

PubMed

ZnO nanorods were synthesized by a simple aqueous solution method. Crystal structures and morphology studies show that the ZnO nanorods are single crystalline with the growth direction aligned with the c axis of ZnO. An Au-ZnO nanorod-Au (metal-semiconductor-metal, MSM) device using the synthesized nanorod was fabricated. An electronic model with two back-to-back Schottky diodes in series with a nanorod was used to describe the electrical transport of the MSM device. A positive temperature coefficient of resistance is observed on a single ZnO nanorod from 383 to 473 K. A simple model has been proposed to explain such an abnormal behavior including the effect of the interface states and the adsorption-desorption of the water/oxygen molecules on the surface of the nanorod. PMID:21212482

He, Guan-nan; Huang, Bo; Shen, Hui

2011-02-11

63

Single Crystal Membranes  

NASA Technical Reports Server (NTRS)

Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

Stormont, R. W.; Morrison, A.

1974-01-01

64

Single Crystal Diamond Films.  

National Technical Information Service (NTIS)

Diamond films are important for radiation tolerant devices. However, fabrication of single crystal films has proven to be much more difficult than polycrystalline deposits. A novel deposition process is proposed which can be used to deposit diamond on a s...

S. N. Bunker R. Sahagian

1993-01-01

65

Chemically assisted vapour transport for bulk ZnO crystal growth  

NASA Astrophysics Data System (ADS)

A chemically assisted vapour phase transport (CVT) method is proposed for the growth of bulk ZnO crystals. Thermodynamic computations have confirmed the possibility of using CO as a sublimation activator for enhancing the sublimation rate of the feed material in a large range of pressures (10 -3 to 1 atm) and temperatures (800-1200 °C). Growth runs in a specific and patented design yielded single ZnO crystals up to 46 mm in diameter and 8 mm in thickness, with growth rates up to 400 ?m/h. These values are compatible with an industrial production rate. N type ZnO crystals ( ?=182 cm 2/(V s) and n=7 10 15 cm -3) obtained by this CVT method (Chemical Vapour Transport) present a high level of purity (10-30 times better than hydrothermal ZnO crystals), which may be an advantage for obtaining p-type doped layers ([Li] and [Al] <10 +15 cm -3). Structural (HR-XRD), defect density (EPD), electrical (Hall measurements) and optical (photoluminescence) properties are presented.

Santailler, Jean-Louis; Audoin, Claire; Chichignoud, Guy; Obrecht, Rémy; Kaouache, Belkhiri; Marotel, Pascal; Pelenc, Denis; Brochen, Stéphane; Merlin, Jérémy; Bisotto, Isabelle; Granier, Carole; Feuillet, Guy; Levy, François

2010-11-01

66

SINGLE CRYSTAL NEUTRON DIFFRACTION.  

SciTech Connect

Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

KOETZLE,T.F.

2001-03-13

67

Growth and characterization of undoped ZnO films for single crystal based device use by radical source molecular beam epitaxy (RS-MBE)  

Microsoft Academic Search

The integrated use of (112?0)a-plane sapphire substrates and high temperature growth with low temperature buffer layers have led to high quality undoped ZnO epitaxial films with mobilities as high as 120cm2V?1s?1 and residual carrier concentrations as low as 7.6×1016cm?3. Pole figure measurements reveal that a-plane sapphire substrates are effective for the elimination of 30° rotation domains, which usually appear using

K. Nakahara; H. Takasu; P. Fons; K. Iwata; A. Yamada; K. Matsubara; R. Hunger; S. Niki

2001-01-01

68

Polarized Raman scattering of single ZnO nanorod  

NASA Astrophysics Data System (ADS)

Polarized Raman scattering measurement on single wurtzite c-plane (001) ZnO nanorod grown by hydrothermal method has been performed at room temperature. The polarization dependence of the intensity of the Raman scattering for the phonon modes A1(TO), E1(TO), and E2high in the ZnO nanorod are obtained. The deviations of polarization-dependent Raman spectroscopy from the prediction of Raman selection rules are observed, which can be attributed to the structure defects in the ZnO nanorod as confirmed by the comparison of the transmission electron microscopy, photoluminescence spectra as well as the polarization dependent Raman signal of the annealed and unannealed ZnO nanorod. The Raman tensor elements of A1(TO) and E1(TO) phonon modes normalized to that of the E2high phonon mode are |a/d|=0.32±0.01, |b/d|=0.49±0.02, and |c/d|=0.23±0.01 for the unannealed ZnO nanorod, and |a/d|=0.33±0.01, |b/d|=0.45±0.01, and |c/d|=0.20±0.01 for the annealed ZnO nanorod, which shows strong anisotropy compared to that of bulk ZnO epilayer.

Yu, J. L.; Lai, Y. F.; Wang, Y. Z.; Cheng, S. Y.; Chen, Y. H.

2014-01-01

69

Hydrothermal synthesis, characterizations and photoluminescence study of single crystalline hexagonal ZnO nanorods with three dimensional flowerlike microstructures  

NASA Astrophysics Data System (ADS)

A simple, low-cost, and environmentally benign hydrothermal approach has been successfully developed to synthesize uniform, large-scale well-crystallized ZnO nanorods with different aspect ratios that were united together to form three dimensional (3D) flowerlike structures. The method involved direct growth of ZnO 3D microstructures using aqueous solution of Zn(CH3COO)2 as the precursor and NaOH to adjust the pH of resultant solution. Surfactants or templates were not used during the entire synthetic process. Moreover, the morphology evolution of the ZnO nanorods with reaction time suggests a recrystallization–dissolution–growth mechanism that continuously takes place for prolonged interval of time. The XRD pattern of the as-grown ZnO nanorods and relevant analyses confirm the well crystallized hexagonal structure of the ZnO microstructures and no evidence of any other impurity phases. SEM observations reveal that the ZnO product grew in the form of nanorods that were united together to form 3D flowerlike morphology. The high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) shows that the ZnO nanorods were single crystalline and grew along the c-axis of the crystal plane. PL measurements of the as-synthesized nanorods exhibit excellent excitation features and strong band-edge UV luminescence even at room temperature. The uniform single crystalline, defect free, and high aspect ratio nanorods may find promising applications in optoelectronics and photo-catalysts. The growth habit of ZnO crystal is also illustrated. This method is suitable for large-scale production of ZnO microstructures and could be extended for syntheses of other metal oxides.

Kale, Rohidas B.; Hsu, Yung-Jung; Lin, Yi-Feng; Lu, Shih-Yuan

2014-05-01

70

Strain Sensors Based on Single High-Quality Zno Microwires  

NASA Astrophysics Data System (ADS)

Using single ZnO microwires, two strain sensors were fabricated. The sensor I made by a two-ends-bonded ZnO microwire was applied a tensile strain, demonstrating a strain-induced increase in the resistance. The coupled piezoresistance and piezoelectric effects were used to expain the phenomenon. The one-end-bonded ZnO microwire based sensor II was deflected at the free end, showing a linear relationship between the resistance and the bending degree, which is suggested to be associated with the piezoresistance effect. The work exhibits that the ZnO microwires are promising building blocks that can be integrated into the MEMS as a strain sensor for measuring tiny displacement.

Liu, Zhiwei; Yan, Xiaoqin; Zhang, Yue

2012-08-01

71

Cathodoluminescence Study of ZnO Wafers Cut from Hydrothermal Crystals.  

National Technical Information Service (NTIS)

ZnO is a wide bandgap semiconductor with very promising expectation for UV optoelectronics. The existence of large crystals should allow homoepitaxial growth of ZnO films for advanced optoelectronic devices. However, the ZnO substrates are not yet mature....

A. Rodriguez J. Jimenez J. Mass M. Avella T. Rodriguez

2008-01-01

72

ZnO nanorod-smectic liquid crystal composites: Role of ZnO particle size, shape, and concentration on liquid crystal order and current-voltage properties  

NASA Astrophysics Data System (ADS)

This paper investigates how changing the ZnO nanorod size and concentration in a smectic liquid crystal affect the order of the liquid crystal and the current-voltage (I-V) curves in these ZnO nanorods - octylcyanobiphenyl (8CB) liquid crystal nanocomposites. 7 × 5 × 5 and 18 × 7 × 7 nm3 nanorods show an improvement in the alignment of the liquid crystal with increasing weight percentage of ZnO nanoparticles, up to a concentration of approximately 35% wt., similar to our previous results on ZnO nanoparticles with 8CB. The resulting I-V curves are comparable to those obtained in other organic materials used for photovoltaic applications. The I-V response of these nanorod-liquid crystal nanocomposite represents an order of magnitude improvement over what was obtained with spherical nanoparticles.

Branch, J.; Thompson, R.; Taylor, J. W.; Salamanca-Riba, L.; Martínez-Miranda, L. J.

2014-04-01

73

Unambiguous identification of the role of a single Cu atom in the ZnO structured green band.  

PubMed

High quality and purity single crystal ZnO samples doped with single isotopes of (63)Cu and (65)Cu, with equal concentrations of both these isotopes, and with natural Cu using a wet chemical atomic substitution reaction and anneal were studied using low temperature optical spectroscopy. Our data on the zero phonon line of the structured green band in ZnO confirm unambiguously the involvement of a single Cu atom in this defect emission. These data allow us to confirm the main features of the assignment proposed by Dingle in 1969 and to comment further on the defect structure. PMID:22575904

Byrne, D; Herklotz, F; Henry, M O; McGlynn, E

2012-05-30

74

Controlled growth of vertically aligned ZnO nanowires with different crystal orientation of the ZnO seed layer.  

PubMed

A novel synthesis and growth method achieving vertically aligned zinc oxide (ZnO) nanowires on a silicon dioxide (SiO(2)) coated silicon (Si) substrate is demonstrated. The growth direction of the ZnO nanowires is determined by the crystal structure of the ZnO seed layer, which is formed by the oxidation of a DC-sputtered Zn film. The [002] crystal direction of the seed layer is dominant under optimized thickness of the Zn film and thermal treatment. Vertically aligned ZnO nanowires on SiO(2) coated Si substrate are realized from the appropriately thick oxidized Zn seed layer by a vapor-solid growth mechanism by catalyst-free thermal chemical vapor deposition (CVD). These experimental results raise the possibility of using the nanowires as functional blocks for high-density integration systems and/or photonic applications. PMID:21825796

Cha, S N; Song, B G; Jang, J E; Jung, J E; Han, I T; Ha, J H; Hong, J P; Kang, D J; Kim, J M

2008-06-11

75

Formation of single crystalline ZnO nanotubes without catalysts and templates  

SciTech Connect

Oxide and nitride nanotubes have gained attention for their large surface areas, wide energy band gaps, and hydrophilic natures for various innovative applications. These nanotubes were either grown by templates or multistep processes with uncontrollable crystallinity. Here the authors show that single crystal ZnO nanotubes can be directly grown on planar substrates without using catalysts and templates. These results are guided by the theory of nucleation and the vapor-solid crystal growth mechanism, which is applicable for transforming other nanowires or nanorods into nanotubular structures.

Ivanov, Ilia N [ORNL; Geohegan, David B [ORNL

2007-01-01

76

Paramagnetism and antiferromagnetic interactions in single-phase Fe-implanted ZnO  

NASA Astrophysics Data System (ADS)

As the intrinsic origin of the high-temperature ferromagnetism often observed in wide-gap dilute magnetic semiconductors becomes increasingly debated, there is a growing need for comprehensive studies on the single-phase region of the phase diagram of these materials. Here we report on the magnetic and structural properties of Fe-doped ZnO prepared by ion implantation of ZnO single crystals. A detailed structural characterization shows that the Fe impurities substitute for Zn in ZnO in a wurtzite Zn1-xFexO phase which is coherent with the ZnO host. In addition, the density of beam-induced defects is progressively decreased by thermal annealing up to 900?° C, from highly disordered after implantation to highly crystalline upon subsequent annealing. Based on a detailed analysis of the magnetometry data, we demonstrate that isolated Fe impurities occupying Zn-substitutional sites behave as localized paramagnetic moments down to 2 K, irrespective of the Fe concentration and the density of beam-induced defects. With increasing local concentration of Zn-substitutional Fe, strong nearest-cation-neighbor antiferromagnetic interactions favor the antiparallel alignment of the Fe moments.

Pereira, L. M. C.; Wahl, U.; Correia, J. G.; Van Bael, M. J.; Temst, K.; Vantomme, A.; Araújo, J. P.

2013-10-01

77

Bioengineering single crystal growth.  

PubMed

Biomineralization is a "bottom-up" synthesis process that results in the formation of inorganic/organic nanocomposites with unrivaled control over structure, superior mechanical properties, adaptive response, and the capability of self-repair. While de novo design of such highly optimized materials may still be out of reach, engineering of the biosynthetic machinery may offer an alternative route to design advanced materials. Herein, we present an approach using micro-contact-printed lectins for patterning sea urchin embryo primary mesenchyme cells (PMCs) in vitro. We demonstrate not only that PMCs cultured on these substrates show attachment to wheat germ agglutinin and concanavalin A patterns but, more importantly, that the deposition and elongation of calcite spicules occurs cooperatively by multiple cells and in alignment with the printed pattern. This allows us to control the placement and orientation of smooth, cylindrical calcite single crystals where the crystallographic c-direction is parallel to the cylinder axis and the underlying line pattern. PMID:21265521

Wu, Ching-Hsuan; Park, Alexander; Joester, Derk

2011-02-16

78

Homo-buffer layer effects and single crystalline ZnO hetero-epitaxy on c-plane sapphire by a conventional RF magnetron sputtering  

Microsoft Academic Search

In this article, it is shown that high quality single crystalline ZnO films could be successfully grown on c-plane sapphire by a conventional RF magnetron sputtering. High-resolution X-ray diffractometry, transmission electron microscopy (TEM), scanning electron microscopy, and low-temperature photoluminescence investigations clearly confirmed that the ZnO films grown on Al2O3(0001) at substrate temperatures above 650°C were high quality single crystal, showing

Sang-Hun Jeong; Il-Soo Kim; Sang-Sub Kim; Jae-Keun Kim; Byung-Teak Lee

2004-01-01

79

Deep-level emission in ZnO nanowires and bulk crystals: Excitation-intensity dependence versus crystalline quality  

NASA Astrophysics Data System (ADS)

The excitation-intensity dependence of the excitonic near-band-edge emission (NBE) and deep-level related emission (DLE) bands in ZnO nanowires and bulk crystals is studied, which show distinctly different power laws. The behavior can be well explained with a rate-equation model taking into account deep donor and acceptor levels with certain capture cross sections for electrons from the conduction band and different radiative lifetimes. In addition, a further crucial ingredient of this model is the background n-type doping concentration inherent in almost all ZnO single crystals. The interplay of the deep defects and the background free-electron concentration in the conduction band at room temperature reproduces the experimental results well over a wide range of excitation intensities (almost five orders of magnitude). The results demonstrate that for many ZnO bulk samples and nanostructures, the relative intensity R = INBE/IDLE can be adjusted over a wide range by varying the excitation intensity, thus, showing that R should not be taken as an indicator for the crystalline quality of ZnO samples unless absolute photoluminescence intensities under calibrated excitation conditions are compared. On the other hand, the results establish an all-optical technique to determine the relative doping levels in different ZnO samples by measuring the excitation-intensity dependence of the UV and visible luminescence bands.

Hou, Dongchao; Voss, Tobias; Ronning, Carsten; Menzel, Andreas; Zacharias, Margit

2014-06-01

80

Irradiation effects in CaF2: ZnO nanostructed crystals  

NASA Astrophysics Data System (ADS)

Effects of ?, X, and UV radiation were studied in CaF2: ZnO single crystals in which ZnO was embedded as nanoparticles. Absorption measurements of these crystals showed a steep increase below 250nm and a weak absorption peak at about 310nm. After prolonged ? irradiation, additional absorption bands were recorded at 395 and 595nm. The irradiated samples showed during heating several thermoluminescence (TL) peaks. Samples which had been exposed to ?-irradiation at RT and subsequently illuminated at LNT with 390nm light showed during re-heating to RT several TL peaks that are attributed to a process of photo-transferred TL (PTTL). Main photoluminescence (PL) emission bands were recorded at 320 and 340nm with excitation maxima near 250 and 300nm. These emission bands were also observed during X-irradiation as well as additional emission bands near 355 and 400nm. In pre-irradiated samples, a 320nm luminescence band could also be excited by 395nm light and is attributed to a process of photostimulation. The stimulation maxima of the OSL and PTTL in the 390nm region are apparently due to the observed absorption band at 395nm induced by the ?-irradiation. The fact that some of the same emission bands appeared in the XL, PL, TL and OSL of this crystal indicates that the same luminescence centers are involved in these emissions.

Kristianpoller, N.; Chen, Wei; Chen, Reuven; Liu, Yinchu

2010-11-01

81

Growth of single crystal diamond  

Microsoft Academic Search

The subject of the research presented in this dissertation is the growth of single crystal diamond by microwave plasma chemical vapor deposition (CVD). Both heteroepitaxial and homoepitaxial growth methods have been examined, with emphasis on producing large diamond crystals of high structural and chemical perfection. By heteroepitaxy, epitaxial growth on a foreign substrate, diamond was grown on (001) Ir thin-film

Murari Regmi

2007-01-01

82

Preparation of vertically aligned ZnO crystal rods in aqueous solution at external electric field  

NASA Astrophysics Data System (ADS)

In this study, an external electric field was used to facilitate the growth of vertically aligned ZnO crystal rods on the surface of indium tin oxide (ITO) glass substrates in an aqueous solution. We used Zn(NO3) and C6H12N4 as precursor and reagent. We found that the external electric field generated by DC potential of 5 kV between two electrodes that were placed outside the bottle could facilitate the growth of homogeneous, high density and vertically aligned ZnO crystal rods. Position of the substrate during the growth of crystal was found to be important to obtain well aligned crystal. The crystals that were grown near the negative electrode had the best properties. Photoluminescence measurement at room temperature revealed sharp peaks at around 360 and 380 nm and a broad peak around 420 nm that indicated good properties of ZnO crystals grown with external electric field.

Prijamboedi, B.; Maryanti, E.; Haryati, T.

2014-05-01

83

Single Crystal Silicon Instrument Mirrors  

NASA Technical Reports Server (NTRS)

The goals for the fabrication of single crystal silicon instrument mirrors include the following: 1) Develop a process for fabricating lightweight mirrors from single crystal silicon (SCS); 2) Modest lightweighting: 3X to 4X less than equivalent solid mirror; 3) High surface quality, better than lambda/40 RMS @ 633nm; 4) Significantly less expensive than current technology; and 5) Negligible distortion when cooled to cryogenic temperatures.

Bly, Vince

2007-01-01

84

Optical nonlinear investigations on morphology controlled growth of ZnO crystals  

NASA Astrophysics Data System (ADS)

We report a methodical study about the third order optical nonlinearity of anisotropic growth of ZnO crystals embedded in polymeric matrices and nanowires on the glass substrate with the use of pre-existing textured ZnO, ZnS and TiO2 seeds using a Z-scan method with Nd:YAG laser (532 nm, 7 ns, 10 Hz). The studies show that the optical nonlinearity of ZnO crystals is highly dependent on the structural geometry and the correlation of semiconductor. Our study offers better insights into the third-order nonlinear optical characteristics of ZnO crystals and reveals great potential for applications in nonlinear photonic devices.

Thankappan, Aparna; Linslal, C. L.; Divya, S.; Sabitha, P. V.; Thomas, Sheenu; Nampoori, V. P. N.

2014-12-01

85

Room temperature solution synthesis of monodispersed single-crystalline ZnO nanorods and derived hierarchical nanostructures.  

PubMed

In this work, we report a room temperature wet-chemical approach to synthesize highly regulated, monodispersed ZnO nanorods and derived hierarchical nanostructures. In particular, ZnO has been prepared into single-crystalline conical or prismatic nanorods, and various hierarchical structures such as hexagonally branched, reversed umbrella-type, and cactus-like ZnO nanostructures comprising individual c-oriented nanorods. Depending on the synthetic conditions used, the diameter of nanorods can be controlled with a size down to 10-30 nm, while the aspect ratio can be controlled up to 50-100. Various preparative parameters, such as initial reactant concentrations, solvents, ligands, surfactants, precursor salts, and reaction time, have been systematically examined. Due to slow reactions at room temperature, excellent crystallinity and high morphological yield (100% in most cases) have been achieved via tuning the synthetic parameters. Our photoluminescence and UV measurements also confirm the attained crystal perfection and size uniformity. PMID:15969417

Liu, Bin; Zeng, Hua Chun

2004-05-11

86

Aqueous synthesis of single-crystalline ZnO prisms on graphite substrates  

NASA Astrophysics Data System (ADS)

Morphological change from ZnO films to ZnO prisms is achieved by an electrochemical deposition method on a graphite substrate at the low temperature of 70 °C. The ZnO prisms, which are prism-shaped ZnO rods with a wide diameter, have hexagonal well-defined crystallographic facets. The ZnO prism is 1.4 ?m in diameter and 1.3 ?m in length. Transmission electron microscopy and electron diffraction patterns indicate that the ZnO prisms have a single-crystalline wurtzite structure with c-axis orientation. Additionally, cathodoluminescence shows that the annealed ZnO prisms in nitrogen gas emit a significant level of near-band-edge ultraviolet light.

Hamada, Takahiro; Fujii, Eiji; Chu, Dewei; Kato, Kazumi; Masuda, Yoshitake

2011-01-01

87

Aligned single crystal boron nanowires  

Microsoft Academic Search

The well aligned boron nanowires (BNWs) with single crystalline structure were successfully prepared by using nanochannel-Al2O3 as a substrate and a chemical vapor deposition process. The diameter and length of BNWs were around of 40 nm and several micrometers, respectively. The formation of single crystal BNWs has been conceptually interpreted.

Q. Yang; J Sha; J Xu; Y. J Ji; X. Y Ma; J. J Niu; H. Q Hua; D. R Yang

2003-01-01

88

Growth of periodic ZnO nano-crystals on buffer layer patterned by interference laser irradiation  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nano-crystal is great interest for optoelectronic applications in particular ultraviolet (UV) region such as UV-LEDs, UV-lasers, etc. For the practical optoelectronic applications based on the ZnO nanocrystals, control of nanowire growth direction, shape, density, and position are essentially required. In our study, we introduced a ZnO buffer layer and interference laser irradiation to control the growth position of ZnO nanocrystals. In this presentation, structural and morphological characteristics of periodic ZnO nano-crystals synthesized by the nanoparticle-assisted pulsed laser deposition will be discussed.

Nakamura, D.; Shimogaki, T.; Okazaki, K.; Higashihata, M.; Nakata, Y.; Okada, T.

2013-03-01

89

Growth of Single- and Bilayer ZnO on Au(111) and Interaction with Copper  

SciTech Connect

The stoichiometric single- and bi-layer ZnO(0001) have been prepared by reactive deposition of Zn on Au(111) and studied in detail with X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory calculations. Both single- and bi-layer ZnO(0001) adopt a planar, graphite-like structure similar to freestanding ZnO(0001) due to the weak van der Waals interactions dominating their adhesion with the Au(111) substrate. At higher temperature, the single-layer ZnO(0001) converts gradually to bi-layer ZnO(0001) due to the twice stronger interaction between two ZnO layers than the interfacial adhesion of ZnO with Au substrate. It is found that Cu atoms on the surface of bi-layer ZnO(0001) are mobile with a diffusion barrier of 0.31 eV, and likely to agglomerate and form nanosized particles at low coverages; while Cu atoms tend to penetrate a single layer of ZnO(0001) with a barrier of 0.10 eV, resulting in a Cu free surface.

Deng, Xingyi; Yao, Kun; Sun, Keju; Li, Wei-Xue; Lee, Junseok; Matranga, Christopher

2013-05-30

90

A simple method for systematically controlling ZnO crystal size and growth orientation  

SciTech Connect

We present a simple, easy and reproducible method to systematically control the dimension and shape evolution of zinc oxide (ZnO) as thin film on glass substrate by chemical bath deposition (CBD). The only varying factor to control crystal transformation is the molar ratio of Cd{sup 2+}/Zn{sup 2+}, R{sub m}, in the initial chemical solution. With the increase of R{sub m}, ZnO crystals transformed from long-and-slim hexagonal rods to fat-and-short hexagonal pyramids, and then to twinning hexagonal dots as observed by scanning electron microscopy (SEM). Film crystallinity was characterized by X-ray diffraction (XRD). Chemical component analysis by energy dispersive spectroscopy (EDS) showed that most cadmium was present in the residual solution instead of the developed film and the precipitate at the bottom of beaker. The mechanism of the cadmium effect, with different initial concentrations, on ZnO crystal transformation was tentatively addressed. We believe that cadmium influences the chelate ligands adsorption onto (0001-bar) plane of ZnO crystals, alters the crystal growth orientation, and thus directs the transformation of the size and shape of ZnO crystals.

Zhang Rong [Department of Paper and Chemical Engineering, Miami University, Oxford, OH 45056 (United States); Kerr, Lei L. [Department of Paper and Chemical Engineering, Miami University, Oxford, OH 45056 (United States)], E-mail: kerrll@muohio.edu

2007-03-15

91

Development of single crystal membranes  

NASA Technical Reports Server (NTRS)

The design and construction of a high pressure crystal growth chamber was accomplished which would allow the growth of crystals under inert gas pressures of 2 MN/sq m (300 psi). A novel crystal growth technique called EFG was used to grow tubes and rods of the hollandite compounds, BaMgTi7O16, K2MgTi7O16, and tubes of sodium beta-alumina, sodium magnesium-alumina, and potassium beta-alumina. Rods and tubes grown are characterized using metallographic and X-ray diffraction techniques. The hollandite compounds are found to be two or three-phase, composed of coarse grained orientated crystallites. Single crystal c-axis tubes of sodium beta-alumina were grown from melts containing excess sodium oxide. Additional experiments demonstrated that crystals of magnesia doped beta-alumina and potassium beta-alumina also can be achieved by this EFG technique.

Stormont, R. W.; Cocks, F. H.

1972-01-01

92

Surface-assisted unidirectional orientation of ZnO nanorods hybridized with nematic liquid crystals.  

PubMed

Inorganic semiconductor nanorods are regarded as the primary components of optical and electrical nanoscale devices. In this paper, we demonstrate the unidirectional alignment of monolayered and dispersed ZnO nanorods on a rubbed polyimide alignment layer, which was achieved by a conventional liquid crystal alignment technique. The outermost surfaces of the ZnO nanorods (average diameter 7 nm; length 50 nm) were modified by polymerization initiator moieties, and nematic liquid crystalline (LC) methacrylate polymers were grown by atom transfer radical polymerization. By regulating the densities of the polymerization initiator moieties, we successfully hybridized LC-polymer-grafted ZnO nanorods and small nematic LC molecules. The LC-polymer-modified ZnO nanorods were hierarchically aligned on the substrate via cooperative molecular interactions among the liquid crystal mesogens, which induced molecular orientation on the rubbed polyimide alignment layer. PMID:24299205

Kubo, Shoichi; Taguchi, Rei; Hadano, Shingo; Narita, Mamiko; Watanabe, Osamu; Iyoda, Tomokazu; Nakagawa, Masaru

2014-01-22

93

Single Crystal Surfaces  

NASA Astrophysics Data System (ADS)

The present work studies (0001) Al2O3 and (111) Al2MgO4 wetting with pure molten Al by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) under Ar at PO2 10-15 Pa. Al pure liquid wets a smooth and chemically homogeneous surface of an inert solid, the wetting driving force ( t, T) can be readily studied when surface solid roughness increases in the system. Both crystals planes (0001) Al2O3 and (111) Al2MgO4 have crystallographic surfaces with identical O-2 crystalline positions however considering Mg2+ content in Al2MgO4 structure may influence a reactive mode. Kinetic models results under similar experimental conditions show that Al wetting on (0001) Al2O3 is less reactive than (111) Al2MgO4, however at >1273 K (1000 °C) (0001) Al2O3 transformation occurs and a transition of wetting improves. The (111) Al2MgO4 and Al system promotes interface formations that slow its wetting process.

Aguilar-Santillan, Joaquin

2014-06-01

94

Adsorption on Single Crystal Planes.  

National Technical Information Service (NTIS)

A working instrument has been developed and tested for measuring work functions of perfect single crystal planes. The longstanding high work function value (6.0 eV) for emission from the (110) plane of tungsten was investigated using the new FN plus energ...

R. D. Young H. E. Clark

1967-01-01

95

[Microanalysis study of Co-doped ZnO DMS crystal by SEM and XREDS].  

PubMed

In the present paper,with CoCl2 x 6H2O used as precursor, Co-doped ZnO diluted magnetic semiconductor (DMS) crystals were synthesized by hydrothermal method with KOH as mineralizer. The morphology, and the relative content and distribution uniformity of the surface and inner Co element of synthesized crystals were investigated by scanning electron microscope (SEM) and X-ray energy dispersive spectrometry (XREDS), respectively. It was found that Co-doped ZnO crystals with different morphology were yielded, while the bigger crystals showed polar growth charactertistics, and the Co content in the crystal depended on its morphology. The exposed face also changed with crystal morphology. There was more Co in bigger crystals than in smaller ones. Moreover, more Co located in +c (10 11)compared to +c (10 10) exposed face, especially for cone crystals. In addition, it was observed that there was a little amount of cobalt oxide cluster in inner crystal,and the distribution of Co content was relative uniform in both the surface and inner part of the crystal. Cobalt oxide cluster may have effect on the magnetic properties of Co-doped ZnO diulted magnetic semiconductor since Co2+ possesses magnetic property. PMID:19385257

Qiu, Man-De; Yao, Zi-Hua; Wei, Zhi-Ren; Zhai, Yong-Qing; Tian, Shuai; Zhang, Shuang

2009-01-01

96

Melt growth of ZnO bulk crystals in Ir crucibles  

NASA Astrophysics Data System (ADS)

The growth of ZnO bulk crystals from the melt is difficult due to the high melting point of the material ( Tm = 1975 °C), requiring the use of Ir crucibles, and its thermal decomposition upon heating. A thermodynamic analysis shows that the oxygen partial pressure in the surrounding vapour phase should be as low as possible during the heating cycle at lower temperatures in order to avoid the oxidation of Ir to IrO 2. Approaching the ZnO melting point, however, higher oxygen pressure is required for suppressing the ZnO decomposition, while IrO 2 decomposes in the elements. The required increasing oxygen supply with increasing temperature can be accomplished by the addition of CO 2 to the gas atmosphere. Experimental results prove the correctness of these results. In a Bridgman-like process ZnO boules are obtained that consist of a few large grains with cm dimensions.

Jacobs, Klaus; Schulz, Detlev; Klimm, Detlef; Ganschow, Steffen

2010-03-01

97

Sample Preparation and Photoluminescence of ZnO Particles Embedded in Thin Alkali Halide Crystals  

NASA Astrophysics Data System (ADS)

We have prepared samples of ZnO particles embedded in thin alkali halide crystals by a melt growth method and have measured photoluminescence spectra at various temperatures. In the spectra measured at 8.5 K, free exciton (FE) and bound exciton (BE) emission lines are clearly recognized, while the well-known green band is hardly observed. The FE line appears at temperatures between 8.5 K and 300 K. The widths of both lines are very sharp and almost equal to that of ZnO epitaxial layers grown by a molecular beam epitaxy method. These results strongly suggest that high-quality ZnO particles can be well embedded in thin alkali halide crystals.

Harada, Yoshiyuki; Kondo, Hisao; Ichimura, Nobuko; Hashimoto, Satoshi

1999-11-01

98

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis

1992-01-01

99

Fatigue in Single Crystal Nickel Superalloys.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

D. P. DeLuca C. Annis

1993-01-01

100

ZnO crystal growth on microelectrode by electrochemical deposition method  

NASA Astrophysics Data System (ADS)

Zinc Oxide crystals were grown by constant potential electrochemical deposition method on the substrate with the Pt working electrode which consists of Pt film with large area and ?m-sized line and space structured area. In case of depositions with cathodic potential of -0.3V, ZnO crystal is not observed on the micro electrode, but observed on the electrode with large area (0.2 cm2). By using electrolyte with higher pH, ZnO crystal grows on both areas. In case of lower pH, ZnO crystal does not grow on either. From these results, the pH range for growth of ZnO on the microelectrode seems to be higher than that on the electrode with large area. And, it is expected that the pH just on the surface of ?m-sized electrode is lower than that in the bulk of electrolyte. Based on these results, it can be concluded that control of the pH in vicinity of the surface is very important to ECD method for micro- and nano-scaled devices.

Kondo, Y.; Ashida, A.; Nouzu, N.; Fujimura, N.

2011-10-01

101

Single Crystals (M = Fe, Co)  

NASA Astrophysics Data System (ADS)

FeGa3 and related compounds have been subjects of recent investigation for their interesting thermoelectric, electronic, and magnetic behaviors. Here, single crystals of FeGa3- y Ge y were grown by the self-flux technique with effective y = 0, 0.09(1), 0.11(1), and 0.17(1) in order to investigate the evolution of the diamagnetic semiconducting compound FeGa3 into a ferromagnetic metal, which occurs through the electron doping and band structure modifications that result from substitution of Ge for Ga. Heat capacity and magnetization measurements reveal non-Fermi liquid behavior in the vicinity of the transition from a paramagnetic to ferromagnetic ground state, suggesting the presence of a ferromagnetic quantum critical point (FMQCP). We also present the first results of hole doping in this system by the growth of FeGa3- y Zn y single crystals, and electron- and hole doping of the related compound CoGa3 by CoGa3- y Ge y and CoGa3- y Zn y crystal growths, aiming to search for further routes to band structure and charge carrier tuning, thermoelectric optimization, and quantum criticality in this family of compounds. The ability to tune the charge carrier type warrants further investigation of the MGa3 system's thermoelectric properties above room temperature.

Cabrera-Baez, M.; Magnavita, E. Thizay; Ribeiro, Raquel A.; Avila, Marcos A.

2014-06-01

102

Photocatalytic studies of crystal violet dye using mn doped and PVP capped ZnO nanoparticles.  

PubMed

Mn (0.5%, 1%, 1.5% and 2%) doped and undoped ZnO nanoparticles (NPs) capped with PVP (1.0%) were successfully synthesized via co-precipitation approach using zinc acetate, sodium hydroxide and manganese acetate as precursors. Structural analysis was performed by XRD confirming phase purity and crystalline wurtzite structure. TEM results show average particle size 15-20 nm and 22-25 nm for Mn (1%) and Mn (2%) doped ZnO NPs respectively. Manganese (Mn) doping has led to reduction in band gap which facilitate the absorption of radiation in visible region. The Photocatalytic activity of undoped and Mn (0.5%,1%,1.5% and 2%) doped NPs was analyzed via degradation of crystal violet (CV) dye. The crystal violet decomposition rate of undoped and Mn doped NPs were studied under UV-visible region. It is observed from degradation studies that the doping has a pronounced effect on the photocatalytic activity of ZnO NPs. Kinetic studies shows that photo degradation of CV follow a pseudo first-order kinetic law. Experiments for reusability of Mn (1%) doped with PVP (1%) capped ZnO were also performed to determine the stability of as prepared sample. It shows an increase in catalytic activity of NPs by small amount when exposed to UV irradiation for 3 h. Photoluminescence and UV-Visible absorption spectroscopy studies were also performed for studying the effect of UV irradiation on the surface of ZnO NPs. PMID:24734685

Mittal, Manish; Sharma, Manoj; Pandey, O P

2014-04-01

103

Optical injection probing of single ZnO tetrapod lasers  

SciTech Connect

The properties of zinc oxide (ZnO) nanotetrapod lasers are characterized by a novel ultrafast two-color pump/stimulated emission probe technique. Single legs of tetrapod species are isolated by a microscope objective, pumped by 267 nm pulses, and subjected to a time-delayed 400 nm optical injection pulse, which permits investigation of the ultrafast carrier dynamics in the nanosize materials. With the optical injection pulse included, a large increase in the stimulated emission at 400 nm occurs, which partially depletes the carriers at this wavelength and competes with the normal 390 nm lasing. At the 390 nm lasing wavelengths, the optical injection causes a decrease in the stimulated emission due to the energetic redistribution of the excited carrier depletion, which occurs considerably within the time scale of the subpicosecond duration of the injection pulse. The effects of the optical injection on the spectral gain are employed to probe the lasing dynamics, which shows that the full width at half maximum of the lasing time is 3 ps.

Szarko, Jodi M.; Song, Jae Kyu; Blackledge, Charles Wesley; Swart, Ingmar; Leone, Stephen R.; Li, Shihong; Zhao, Yiping

2004-11-23

104

Energy harvesting from millimetric ZnO single wire piezo-generators  

NASA Astrophysics Data System (ADS)

This work reports on investigations into the possibility of harvesting energy from the piezoelectric response of millimetric ZnO rods to movement. SEM & PL studies of hydrothermally grown ZnO rods revealed sizes ranging from 1 - 3 mm x 100 - 400 microns and suggested that each was a wurtzite monocrystal. Studies of current & voltage responses as a function of time during bending with a probe arm gave responses coherent with those reported elsewhere in the literature for ZnO nanowires or micro-rod single wire generators. The larger scale of these rods provided some advantages over such nano- and microstructures in terms of contacting ease, signal level & robustness.

Rogers, D. J.; Carroll, C.; Bove, P.; Sandana, V. E.; Goubert, L.; Largeteau, A.; Teherani, F. Hosseini; Demazeau, G.; McClintock, R.; Drouhin, H.-J.; Razeghi, M.

2012-02-01

105

Tunable magnetic and transport properties of single crystalline (Co, Ga)-codoped ZnO films  

SciTech Connect

A series of metallic (Co, Ga)-codoped ZnO single crystalline films have been grown by molecular beam epitaxy. All of the films exhibit metallic conducting behavior and high free carrier concentrations. Besides room temperature ferromagnetism, the anomalous Hall effect due to spin-orbit interaction was also found. Both the saturation magnetization and anomalous Hall effect can be tuned by the carrier concentration or conductivity, revealing that the ferromagnetism is carrier mediated in (Co, Ga)-codoped ZnO films. Our experimental observations are consistent with the recent theoretical description of carrier mediated magnetism in Co doped ZnO.

Lu Zhonglin [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Department of Physics, Southeast University, Nanjing 211189 (China); Institute of Innovations and Advanced Studies (IIAS), National Cheng Kung University, Tainan 701, Taiwan (China); Hsu, H.-S. [Department of Applied Physics, National Ping Tung University of Education, Ping Tung 900, Taiwan (China); Tzeng Yonhua [Institute of Innovations and Advanced Studies (IIAS), National Cheng Kung University, Tainan 701, Taiwan (China); Department of Electrical Engineering, Institute of Microelectronics, National Cheng Kung University, Tainan 701, Taiwan (China); Zhang Fengming; Du Youwei [Department of Physics, Nanjing University, Nanjing 210093 (China); Huang, Jung-Chun-Andrew [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Innovations and Advanced Studies (IIAS), National Cheng Kung University, Tainan 701, Taiwan (China)

2009-08-10

106

Ultraviolet microphotoluminescence resonance and lasing action in a single ZnO micro-tetrapod  

NASA Astrophysics Data System (ADS)

ZnO micro-tetrapod microstructures were fabricated by a vapor phase transport method. Under the excitation of 325 nm continuous wave He-Cd laser, the microphotoluminescence spectrum from a single ZnO micro-tetrapod presented a two-band structure with a series of optical resonance modes; a possible optical resonance loop formed in two adjacent legs of the tetrapod was suggested, and the two-band spectrum structure was attributed to the exciton-exciton scattering process. The lasing emission was obtained from single ZnO micro-tetrapod under intense excitation of 355 nm nanosecond pulsed laser. The lasing spectrum shows clear mode structure with the lasing quality factor of 1300 and the lasing threshold of 150 kW/cm2. The microphotoluminescence resonance and lasing results indicate that ZnO tetrapod can serve as a high-Q ultraviolet microcavity laser.

Dai, J.; Xu, C. X.; Zhu, G. Y.; Lin, Y.; Shi, Z. L.

2014-06-01

107

Materialization of single multicomposite nanowire: entrapment of ZnO nanoparticles in polyaniline nanowire  

PubMed Central

We present materialization of single multicomposite nanowire (SMNW)-entrapped ZnO nanoparticles (NPs) via an electrochemical growth method, which is a newly developed fabrication method to grow a single nanowire between a pair of pre-patterned electrodes. Entrapment of ZnO NPs was controlled via different conditions of SMNW fabrication such as an applied potential and mixture ratio of NPs and aniline solution. The controlled concentration of ZnO NP results in changes in the physical properties of the SMNWs, as shown in transmission electron microscopy images. Furthermore, the electrical conductivity and elasticity of SMNWs show improvement over those of pure polyaniline nanowire. The new nano-multicomposite material showed synergistic effects on mechanical and electrical properties, with logarithmical change and saturation increasing ZnO NP concentration.

2011-01-01

108

Improved acetone sensing properties of ZnO hollow nanofibers by single capillary electrospinning  

Microsoft Academic Search

Solid and hollow ZnO nanofibers were fabricated through a facile single capillary electrospinning. The samples have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). A comparative acetone sensing study between the two samples were also performed. The results indicate that the ZnO hollow nanofibers show improved response

Shaohong Wei; Meihua Zhou; Weiping Du

109

Antimicrobial mechanism based on H2O2 generation at oxygen vacancies in ZnO crystals.  

PubMed

The production of H2O2 has been taken for a crucial reason for antimicrobial activity of ZnO without light irradiation. However, how the H2O2 generates in ZnO suspension is not clear. In the present work, the comparatively detections on three kinds of ZnO, tetrapod-like ZnO whiskers (t-ZnO), nanosized ZnO particles (n-ZnO), and microsized ZnO particles (m-ZnO), showed that the antimicrobial activity of ZnO was correlated with its production of H2O2. Oxygen vacancy (V(O)) in the surface layer of ZnO crystals determined by XPS indicated that it was quite probably involved in the production of H2O2. To validate the role of V(O), the concentration of VO in t-ZnO was adjusted by heat-treatment under the atmospheres of H2, vacuum, and O2, respectively, and the H2O2 production and antimicrobial effect were detected. Consistently, the t-ZnO treated in H2, which possessed the most V(O) in its crystal, produced the most H2O2 and displayed the best antimicrobial activity. These results provide the basis for developing a more detailed mechanism for H2O2 generation catalyzed by ZnO and for taking greater advantage of this type of antimicrobial agent. PMID:23570415

Xu, Xiaoling; Chen, Dan; Yi, Zhigang; Jiang, Man; Wang, Li; Zhou, Zuowan; Fan, Ximei; Wang, Yong; Hui, David

2013-05-01

110

Synthesis and optical property of nanostructured ZnO crystals by nanoparticle-assisted pulsed laser deposition  

NASA Astrophysics Data System (ADS)

ZnO crystals have attracted a great attention for next generation nanodevices because it has a superior crystalline quality, a better electrical/optical quality, a freedom to choose substrate and a large surface area to volume ratio. We have been succeeded in growing nano-structured ZnO crystals by nanoparticle-assisted pulsed-laser deposition without using any catalyst. Not only vertically aligned ZnO nanowires but also horizontally aligned ZnO nanowires have been successfully grown on the annealed c-plane and a-plane sapphire substrates, respectively. Besides, Depending on the PLD growth conditions and the composition of the target, ZnO nanowalls with thickness of tens of nanometers and dimension of several micrometers were synthesized. The room temperature photoluminescence spectrum of such a ZnO nanowall exhibited a strong intrinsic UV emission and a week defect-related visible emission. Synthesized ZnO nanowires were applied to a heterojunction light-emitting diode and an UV photo-sensor. In addition, it was found that the ZnO nanowalls showed stable field emission properties with low threshold field and a big field enhancement factor. Furthermore, layer-structured ZnO nanowires were fabricated by NAPLD using a multi-target changer system.

Nakamura, D.; Okada, T.; Sakai, K.

2010-07-01

111

Homoepitaxial ZnO Film Growth  

NASA Technical Reports Server (NTRS)

ZnO films have high potential for many applications, such as surface acoustic wave filters, UV detectors, and light emitting devices due to its structural, electrical, and optical properties. High quality epitaxial films are required for these applications. The Al2O3 substrate is commonly used for ZnO heteroepitaxial growth. Recently, high quality ZnO single crystals are available for grow homoepitaxial films. Epitaxial ZnO films were grown on the two polar surfaces (O-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. As a comparison, films were also deposited on (0001) Al2O3 substrates. It was found that the two polar ZnO surfaces have different photoluminescence (PL) spectrum, surface structure and morphology, which strongly influence the epitaxial film growth. The morphology and structure of homoepitaxial films grown on the ZnO substrates were different from heteroepitaxial films grown on the Al2O3. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite surface. The measurements of PL, low-angle incident x-ray diffraction, and atomic force microscopy of ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth.

Zhu, Shen; Su, C-H; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; McCarty, P.; George, M. A.; Rose, M. Franklin (Technical Monitor)

2000-01-01

112

On the correlation of crystal defects and band gap properties of ZnO nanobelts  

NASA Astrophysics Data System (ADS)

We report here investigations of crystal and electronic structure of as-synthesized and annealed ZnO nanobelts by an in-situ high-resolution transmission electron microscope equipped with a scanning tunneling microscopy probe. The in-situ band gap measurements of individual ZnO nanobelts were carried out in scanning tunneling spectroscopy mode using the differential conductance d I/d V- V data. The band gap value of the as-synthesized ZnO nanobelts was calculated to be ˜2.98 eV, while this property for the annealed nanobelts (˜3.21 eV) was close to the band gap value for bulk ZnO materials (˜3.37 eV). The difference in the band gap value of the as-synthesized ZnO nanobelts and annealed ones was attributed to the planar defects (e.g. stacking faults and twins). These defects can alter the electronic structure by producing localized resonant states that result in band gap reduction.

Asthana, A.; Momeni, K.; Prasad, A.; Yap, Y. K.; Yassar, R. S.

2011-12-01

113

Structural and Optical Characterization of ZnO Single Crystalline Nanobamboos  

NASA Astrophysics Data System (ADS)

ZnO nanobamboos and nanowires with diameters of 10-30 nm and lengths of 2-4 ?m have been prepared by laser ablation in vacuum with precisely controlled pressure, growth and post-annealing temperature. XRD results show the annealed sample is hexagonal ZnO. Low-magnified TEM observation reveals the annealed sample includes ZnO nanobamboos and nanowires. High resolution TEM image and electron diffraction pattern confirm that the structure of ZnO nanobamboo is regular stacking of Zn and O layers with high crystal quality. The growth direction is determined as along [001] direction (c axis). TEM observations confirm that the formation of bamboo-shape ZnO is due to the stacking fault and cleavage. The bundle of those stacking faults seems to be the origin of the black contrast at the nodes. The uniformity of chemical composition for the nanobamboos is identified by EDS profiles. A strong-narrow UV band centred at 390 nm and a weak-broad green band centred at 515 nm are observed at room temperature in the PL spectrum recorded from the annealed ZnO nanobamboos and nanowires.

Miao, Lei; Tanemura, Sakae; Hayashi, Yasuhiko; Tanemura, Masaki; Wang, Rongping; Toh, Shoichi; Kaneko, Kaneko

114

Vapor-Deposited Single-Crystal Germanium  

Microsoft Academic Search

Germanium layers have been formed on single-crystal Ge substrates by the thermal decomposition of GeI2. The single-crystal nature of the layers has been established by x-ray and electron diffraction examination and by electrical measurements. The deposition process is described briefly. The crystal growth rate varies with crystal direction, and under certain conditions Ge whiskers appear. The layers as deposited are

Ralph P. Ruth; John C. Marinace; W. C. Dunlap

1960-01-01

115

Performance of Single Crystal Niobium Cavities  

Microsoft Academic Search

We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other

Peter Kneisel; Gianluigi Ciovati; Waldemar Singer; Xenia Singer; Detlef Reschke; A. Brinkmann

2008-01-01

116

Nanoindentation of gold single crystals  

NASA Astrophysics Data System (ADS)

Nanoindentation is an increasingly used tool to investigate the mechanical properties of very small volumes of material. Gold single crystals were chosen as a model system for surface modification studies, because of the electrochemical advantages and the simple structure of the material. Experiments on these samples displayed a spectrum of residual deformation, with measured hardness values on the same surface differing by over a factor of two. The yield point also exhibited considerable variation, but the depth of penetration was independent of this elastic-plastic transition. The onset of plastic deformation in these tests is observed at stress levels on the order of the theoretical yield strength. There are a limited number of defects in a single crystal specimen of gold, especially on the length scale required to influence nearly every indentation experiment. A test matrix was designed to change the concentrations of possible defects in a sample (dislocations, vacancies, and structural features), by altering some of the surface preparation parameters. The results of these experiments were extremely consistent. Observed trends within the matrix, combined with the observations of reduced hardness and earlier plasticity when compared to the preliminary testing, indicate a decline in the structural continuity of the sample. This is surprising considering the extensive material removal and thermal history of some of these surfaces. There is no indication of a cause for the dramatic inconsistencies in mechanical properties observed in preliminary testing, but a consistent surface enables the study of intentional modifications. Changes in contact area that were undetectable in preliminary results now demonstrate predictable shifts in hardness values. The deposition of a single monolayer of gold oxide raised the average load at yield by a factor of three and increased the hardness by over 26%. Attributing this change to the oxide is corroborated by the reduction of hardness when the oxide is stripped. Similar behavior is observed when a lead monolayer is deposited and tested ex-situ. It is surprising that layers <0.5 nm in thickness would have such a dramatic influence on indentation tests at least 35 nm deep. This indicates that no surface layer can be ignored at this scale. These experiments demonstrate that there is still much to be learned about nanoscale deformation mechanisms.

McCann, Martha Mary

117

Dislocation Distribution in Deformed Copper Single Crystals.  

National Technical Information Service (NTIS)

Observations of dislocation distribution in copper single crystals oriented for single glide and deformed at low temperatures are described. In stage I the dislocation population consists mainly of bundles of long edge dislocations belonging to the primar...

Z. S. Basinski

1964-01-01

118

Confinement stabilises single crystal vaterite rods.  

PubMed

Single-crystals of vaterite, the least-stable anhydrous polymorph of CaCO3, are rare in biogenic and synthetic systems. We here describe the synthesis of high aspect ratio single crystal vaterite rods under additive-free conditions by precipitating CaCO3 within the cylindrical pores of track-etch membranes. PMID:24676457

Schenk, Anna S; Albarracin, Eduardo J; Kim, Yi-Yeoun; Ihli, Johannes; Meldrum, Fiona C

2014-04-01

119

Single crystal growth of actinide compounds  

Microsoft Academic Search

During recent years, the importance of solid state actinide research has been increasingly recognized. Further progress in actinide solid state physics depends on the availability of pure and perfect single crystals. Actinide compounds have large magnetic anisotropy with anisotropy fields of 8 × 107 A.m-1 or higher. Investigation of the mechanism responsible for such unique behaviour requires large single crystals

J. C. Spirlet; W. Müller; J. van Audenhove

1985-01-01

120

Ames Lab 101: Single Crystal Growth  

SciTech Connect

Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

Schlagel, Deborah

2013-09-27

121

Ames Lab 101: Single Crystal Growth  

ScienceCinema

Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

Schlagel, Deborah

2014-06-04

122

Electrical and optical properties of ZnO bulk crystals with and without lithium grown by the hydrothermal technique  

NASA Astrophysics Data System (ADS)

Lithium is usually added into the solution to improve ZnO hydrothermal growth; however, lithium doping affects the properties of the resulting crystals. Optical and electrical properties of hydrothermal ZnO bulk crystals without lithium, have been studied by photoluminescence and Hall-effect measurements. High quality ZnO crystals without lithium were grown in H2O/D2O and in NH3-H2O solutions. The crystals grown from H2O/D2O are conductive with resistivities of 0.6-0.7 ?cm and mobilities of ~ 100 cm2/Vs, while lithium doped ZnO crystals typically have resistivities of ~ 103?-cm and mobilities of ~ 200 cm2/Vs, but can be varied from dozens to 1010 ?-cm depending on lithium concentration. Lithium-free but nitrogen doped crystals grown in NH3-H2O solution have resistivities of 1×100 ?-cm and sometimes show p-type conduction; the resistivity increases to ~ 1×108 ?-cm after annealing at 600° C in air. Lithium and nitrogen co-doped ZnO crystals have resistivities of 108-1012 ?-cm and are semi-insulating after annealling. Electronic irradiation also increases the ZnO resistivity. For lithium-doped samples, a 3.357 eV peak can be seen in the photoluminescence spectra. This is close to the donor-exciton peaks in indium-doped ZnO where 3.3586 eV and 3.357 eV were found on the C+ and C- faces, respectively. More studies are needed to identify lithium-related complexes (defects).

Wang, Buguo; Claflin, Bruce; Callahan, Michael; Fang, Z.-.; Look, David

2014-03-01

123

Photoresponse from single upright-standing ZnO nanorods explored by photoconductive AFM  

PubMed Central

Summary Background: ZnO nanostructures are promising candidates for the development of novel electronic devices due to their unique electrical and optical properties. Here, photoconductive atomic force microscopy (PC-AFM) has been applied to investigate transient photoconductivity and photocurrent spectra of upright-standing ZnO nanorods (NRs). With a view to evaluate the electronic properties of the NRs and to get information on recombination kinetics, we have also performed time-resolved photoluminescence measurements macroscopically. Results: Persistent photoconductivity from single ZnO NRs was observed for about 1800 s and was studied with the help of photocurrent spectroscopy, which was recorded locally. The photocurrent spectra recorded from single ZnO NRs revealed that the minimum photon energy sufficient for photocurrent excitation is 3.1 eV. This value is at least 100 meV lower than the band-gap energy determined from the photoluminescence experiments. Conclusion: The obtained results suggest that the photoresponse in ZnO NRs under ambient conditions originates preferentially from photoexcitation of charge carriers localized at defect states and dominates over the oxygen photodesorption mechanism. Our findings are in agreement with previous theoretical predictions based on density functional theory calculations as well as with earlier experiments carried out at variable oxygen pressure.

Beinik, Igor; Kratzer, Markus; Wachauer, Astrid; Wang, Lin; Piryatinski, Yuri P; Brauer, Gerhard; Chen, Xin Yi; Hsu, Yuk Fan; Djurisic, Aleksandra B

2013-01-01

124

The sensitivity of gas sensor based on single ZnO nanowire modulated by helium ion radiation  

NASA Astrophysics Data System (ADS)

In this letter, we present a gas sensor using a single ZnO nanowire as a sensing unit. This ZnO nanowire-based sensor has quick and high sensitive response to H2S in air at room temperature. It has also been found that the gas sensitivity of the ZnO nanowires could be modulated and enhanced by He+ implantation at an appropriate dose. A possible explanation is given based on the modulation model of the depletion layer.

Liao, L.; Lu, H. B.; Li, J. C.; Liu, C.; Fu, D. J.; Liu, Y. L.

2007-10-01

125

Hall effect analysis of bulk ZnO comparing different crystal growth techniques  

NASA Astrophysics Data System (ADS)

The relaxation time approximation was used to interpret Hall effect data from n-type ZnO bulk samples grown using the high-pressure melt, seeded-chemical-vapor transport, and hydrothermal techniques. These samples represent a range of free-carrier concentrations due to different amounts of donors and compensating acceptors. Treatment of intrinsic mechanisms includes polar-optical phonon scattering using an effective Tpo=750 K, piezoelectric potential scattering using P?=0.25, and deformation potential scattering using E1=3.8 eV. Intrinsic mobilities from 60 to 400 K for electrons and for holes in ZnO are predicted. For extrinsic behaviors, ionized and neutral impurities are included. Donor ionization energies for dilute concentrations were determined. Shallow group III donors (Al, Ga) are responsible for the free carriers in the high-pressure melt and seeded-chemical-vapor transport crystals. The hydrothermally grown sample is closely compensated and exhibits hopping conduction below 200 K. Free carriers in the hydrothermal ZnO crystal are generated by thermal activation of deep nickel donors with the Ni2+/3+ level at about 270 meV below the conduction band.

Yang, Xiaocheng; Giles, N. C.

2009-03-01

126

Single crystal research — Crystal quality control — Industrial production  

Microsoft Academic Search

A summary is given of the tasks involved in improving crystal quality, their interrelations and the organizational framework\\u000a required for completing them. The possibilities inherent in single crystal research for the development of industrial products\\u000a are demonstrated.

R. Voszka

1985-01-01

127

Seeded Single Crystal Silicon Carbide Growth and Resulting Crystals.  

National Technical Information Service (NTIS)

A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system and in the absence of a solid silicon carbide source, by reducing the separation between a silicon carbide seed crystal and a seed holder u...

D. P. Malta H. M. Hobgood J. R. Jenny M. Brady S. G. Mueller

2005-01-01

128

Photo-response of a nanopore device with a single embedded ZnO nanoparticle  

NASA Astrophysics Data System (ADS)

The photo-response of a ZnO nanoparticle embedded in a nanopore made on a silicon nitride membrane is investigated. The ZnO nanoparticle is manipulated onto the nanopore and sandwiched between aluminum contact electrodes from both the top and bottom. The asymmetric device structure facilitates current-voltage rectification that enables photovoltaic capacity. Under illumination, the device shows open-circuit voltage as well as short-circuit current. The fill factor is found to increase at low temperatures and reaches 48.6% at 100 K. The nanopore structure and the manipulation technique provide a solid platform for exploring the electrical properties of single nanoparticles.

Nguyen, Linh-Nam; Lin, Ming-Chou; Chen, Horng-Shyang; Lan, Yann-Wen; Wu, Cen-Shawn; Chang-Liao, Kuei-Shu; Chen, Chii-Dong

2012-04-01

129

Nano-X-ray absorption spectroscopy of single Co-implanted ZnO nanowires.  

PubMed

We report on the local structure of single Co-implanted ZnO nanowires studied using a hard X-ray nanoprobe. X-ray fluorescence maps show uniform Zn and Co distributions along the wire within the length scale of the beam size. The X-ray fluorescence data allow the estimation of the Co content within the nanowire. Polarization dependent X-ray absorption near edge structure shows no structural disorder induced neither in the radial nor axial directions of the implanted nanowires after subsequent annealing. Co2+ ions occupy Zn sites into the wurtzite ZnO lattice. Extended X-ray absorption fine structure data reveal high structural order in the host lattice without distortion in their interatomic distances, confirming the recovery of the radiation damaged ZnO structure through thermal annealing. PMID:22007972

Segura-Ruiz, J; Martínez-Criado, G; Chu, M H; Geburt, S; Ronning, C

2011-12-14

130

Single Crystal Sapphire Optical Fiber Sensor Instrumentation  

SciTech Connect

The goal of this 30 month program is to develop reliable accurate temperature sensors based on single crystal sapphire materials that can withstand the temperatures and corrosive agents present within the gasifier environment. The research for this reporting period has been segregated into two parallel paths--corrosion resistance measurements for single crystal sapphire fibers and investigation of single crystal sapphire sensor configurations. The ultimate goal of this phase one segment is to design, develop and demonstrate on a laboratory scale a suitable temperature measurement device that can be field tested in phase two of the program.

Anbo Wang; Russell May; Gary R. Pickrell

2000-10-28

131

Defects in ZnO thin films grown on ScAlMgO4 substrates probed by a monoenergetic positron beam  

Microsoft Academic Search

Zinc oxide (ZnO) thin films grown on ScAlMgO4 substrates were characterized by means of positron annihilation. We measured Doppler broadening spectra of annihilation radiation and photoluminescence spectra for the ZnO films deposited by laser molecular-beam epitaxy and single-crystal ZnO. Although the lifetime of positrons in single-crystal ZnO was close to the lifetime of positrons annihilated from the free state, the

A. Uedono; T. Koida; A. Tsukazaki; M. Kawasaki; Z. Q. Chen; Sf. Chichibu; H. Koinuma

2003-01-01

132

Research Advances: Mass Spectrometric Monitoring of Animal Feed for BSE Spread; Ancient Oceans Had Less Oxygen; A Model for the Formation of Piezoelectric Single-Crystal Nanorings and Nanobows  

NASA Astrophysics Data System (ADS)

Recent work by Zhong L. Wang and William Hughes at Georgia Tech demonstrates that ZnO nanorods and nanobows formed by bending single crystal, PSD ZnO nanobelts exclusively supports the electrostatic polar charge model as the dominant bending mechanism.

King, Angela G.

2004-09-01

133

Color Centers in Cesium Halide Single Crystals  

Microsoft Academic Search

Color centers have been investigated in the CsCl-type alkali halides. Cesium chloride, bromide, and iodide single crystals were grown from the melt and CsCl crystals also from solution. Coloration was produced by 130-kv x rays, 3.0-Mev electrons, and by electrolysis. In CsI coloration resulted from electrolysis only. The absorption of uncolored and colored crystals has been measured from 0.175 to

Peter Avakian; A. Smakula

1960-01-01

134

Neutron irradiation effects on YBCO single crystals.  

National Technical Information Service (NTIS)

Fast neutron irradiation of YBCO single crystals has proved to result in significant increases of magnetization hysteresis and consequently an enhancement of critical current densities. In addition, shifts of the irreversibility line have been observed. B...

F. M. Sauerzopf H. P. Wiesinger H. W. Weber G. W. Crabtree

1991-01-01

135

Molybdenum-Reinforced Aluminum Oxide Single Crystals.  

National Technical Information Service (NTIS)

Molybdenum wire-reinforced aluminum oxide single crystals have been fabricated by the heat exchanger method of seeded unidirectional solidification. No interfacial reaction products were observed and cathodoluminescent evaluation indicated a good diffusio...

J. W. McCauley F. Schmid D. J. Viechnicki

1979-01-01

136

Investigation of Growth of Electromagnetic Single Crystals.  

National Technical Information Service (NTIS)

Research was carried out on the growth of single crystals of plain and doped sapphire, ruby, spinel, yttrium oxide, magnesium titanate, yttrium iron garnet, beryl, cerium molybdate, lanthanum molybdate, sodium ferrite, and high melting fluorides. The meth...

C. M. Cobb J. A. Adamski E. B. Wallis

1964-01-01

137

Imaging Single ZnO Vertical Nanowire Laser Cavities using UV-Laser Scanning Confocal Microscopy  

Microsoft Academic Search

We report the fabrication and optical characterization of individual ZnO vertical nanowire laser cavities. Dilute nanowire arrays with interwire spacing>10 ?m were produced by a modified chemical vapor transport (CVT) method yielding an ideal platform for single nanowire imaging and spectroscopy. Lasing characteristics of a single vertical nanowire are presented, as well as high-resolution photoluminescence imaging by UV-laser scanning confocal

D. J. Gargas; M. E. Toimil-Molares; P. Yang

2008-01-01

138

Optical properties of electrochemically deposited ZnO thin films on colloidal crystal film of SiO2 microspheres.  

PubMed

The optical properties of electrochemically deposited ZnO thin films on colloidal crystal film of SiO2 microspheres structures were studied. Colloidal crystal film of SiO2 microspheres were self-assembled by evaporation using SiO2 in solution at a constant 0.1 wt%. ZnO in thin films was then electrochemically deposited on to colloidal crystal film of SiO2 microspheres. During electrochemical deposition, the content of Zn(NO3)2 x 6H2O in solution was 5 wt%, and the process's conditions were varied between of 2-4 V and 30-120 s at room temperature, with subsequent heat-treatment between 200 and 400 degrees C. A smooth surface and uniform thickness of 1.8 microm were obtained at 3 V for 90 s. The highest PL peak intensity was obtained in the ZnO thin film heat-treated at 400 degrees C. The double layered ZnO/SiO2 colloidal crystals showed clearly better emission properties than the SiO2/ZnO and ZnO structures. PMID:22630036

Oh, Yong Taeg; Choi, Bum Ho; Shin, Dong Chan

2012-02-01

139

Characterizations of Ohmic and Schottky-behaving contacts of a single ZnO nanowire  

NASA Astrophysics Data System (ADS)

Current-voltage and Kelvin probe force microscopy (KPFM) measurements were performed on single ZnO nanowires. Measurements are shown to be strongly correlated with the contact behavior, either Ohmic or diode-like. The ZnO nanowires were obtained by metallo-organic chemical vapor deposition (MOCVD) and contacted using electronic-beam lithography. Depending on the contact geometry, good quality Ohmic contacts (linear I-V behavior) or non-linear (diode-like) contacts were obtained. Current-voltage and KPFM measurements on both types of contacted ZnO nanowires were performed in order to investigate their behavior. A clear correlation could be established between the I-V curve, the electrical potential profile along the device and the nanowire geometry. Some arguments supporting this behavior are given based on technological issues and on depletion region extension. This work will help to better understand the electrical behavior of Ohmic contacts on single ZnO nanowires, for future applications in nanoscale field-effect transistors and nano-photodetectors.

Bercu, Bogdan; Geng, Wei; Simonetti, Olivier; Kostcheev, Sergei; Sartel, Corinne; Sallet, Vincent; Lérondel, Gilles; Molinari, Michaël; Giraudet, Louis; Couteau, Christophe

2013-10-01

140

Mechanistic study for heterogeneous product growth in topochemical single-crystal-to-single-crystal transformation  

Microsoft Academic Search

Kinetic evaluation for the solid-state reaction of 1,4-dithiin\\/anthracene mixed single crystal proved the mechanism of the anisotropic heterogeneous propagation during the single-crystal-to-single-crystal transformation. The number of hydrogen bonds in the reactive molecule is directly correlated with the activation energy for the reaction––the ‘chain’ character of solid-state propagation being triggered by the breaking of the C–H?O hydrogen bonds.

Jae Hong Kim; Jae Yun Jaung; Sung Hoon Jeong

2003-01-01

141

Linear analytical theory of a transformation from a single crystal A to another single crystal B  

Microsoft Academic Search

An isothermal phase transformation from a single crystal A to another single crystal B is theoretically investigated along preferred lines (Rosiwal's lines). It is supposed that the nuclei of the B-phase are Poisson distributed within the single crystal A. From these nuclei the B-grains grow instantaneously, equioriented, and in the form of cuboids with three different growth ratesvx,vy andvz. If

G. E. W. Schulze; H.-P. Wilbert

1987-01-01

142

ZnO field-effect transistors prepared by aqueous solution-growth ZnO crystal thin film  

NASA Astrophysics Data System (ADS)

A ZnO thin-film transistor (TFT) with a channel layer formed via aqueous solution-growth at low temperature is demonstrated. This ZnO thin-film semiconductor has a well-controlled crystalline form, exhibiting n-channel, enhancement-mode behavior with a channel mobility as large as 0.56 cm2 V-1 s-1. Low-cost, superior transistor characteristics and low-temperature processing makes ZnO TFT attractive for flexible electronics on temperature sensitive substrates.

Li, Chensha; Li, Yuning; Wu, Yiliang; Ong, Beng S.; Loutfy, Rafik O.

2007-10-01

143

Transition metal complexes with oligopeptides: single crystals and crystal structures.  

PubMed

The coordination chemistry of short chain peptides with transition metals is described in terms of the available crystal structures. Despite their high interest as synthetic models for metalloproteins and as building blocks for molecular materials based on the tuneable properties of oligopeptides, single crystal X-ray diffraction studies are scarce. A perusal of the most relevant results in this field allows us to define the main characteristics of oligopeptide-metal interactions, the fundamental problems for the crystallization of these complexes, and some hints to identify future promising approaches to advance the development of metallopeptide chemistry. PMID:24874062

Lillo, Vanesa; Galán-Mascarós, José Ramón

2014-07-14

144

Zinc self-diffusion, electrical properties, and defect structure of undoped, single crystal zinc oxide  

NASA Astrophysics Data System (ADS)

Zinc self-diffusion was measured in single crystal zinc oxide using nonradioactive 70Zn as the tracer isotope and secondary ion mass spectrometry for data collection. Crystal mass was closely monitored to measure ZnO evaporation. Diffusion coefficients were isotropic with an activation energy of 372 kJ/mol. Zinc self-diffusion is most likely controlled by a vacancy mechanism. Electrical property measurements exhibit a plateau in conductivity at intermediate pO2 with an increase in reducing atmospheres. An analysis of the defect structure is presented that indicates that oxygen vacancies are probably the intrinsic ionic defects responsible for n-type conductivity in reducing atmospheres.

Tomlins, Gregory W.; Routbort, Jules L.; Mason, Thomas O.

2000-01-01

145

Performance of Single Crystal Niobium Cavities  

SciTech Connect

We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other cavities of the scaled "Low Loss" (LL) shape (two) and "High Gradient" (HG) shape (one) resonated at 2.3 GHz and were fabricated from "as received" single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing most cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.

Kneisel, Peter; Ciovati, Gianluigi; Singer, Waldemar; Singer, Xenia; Reschke, Detlef; Brinkmann, A.

2008-07-01

146

Enhancement of photoluminescence from ZnO film by single wall carbon nanotubes.  

PubMed

Optical emissions from ZnO films were enhanced by a formation of hybrid structures with single wall carbon-nanotubes (SWCNTs). The SWCNTs were characterized by the presence of the associated fibers and islands together with many carbon nanotube structures and their average height was about < or = 40 nm from atomic force microscope and scanning electron microscope measurements. The intensities of photoluminescence on ZnO films with SWCNTs were increased up to about 30 and 60% in the region of 3.3 eV (near band edge) and 2.3 eV (deep-level) bands, respectively. It was considered that the enhancement of optical emissions from ZnO might be resulted from the effects of an excitation light scattering by SWCNTs and a surface plasmon resonance between bandgap of ZnO and SWCNTs. The surface plasmon resonance mode in the ultra-violet regions is smaller than the deep-level region relatively. This result showed that the commercial ZnO/carbon nanotubes have a feasibility of application to optoelectronic device. PMID:22121675

Suh, Jooyoung; Song, Hooyoung; Kim, Eun Kyu

2011-07-01

147

Oxygen incorporation in rubrene single crystals.  

PubMed

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed. PMID:24786311

Mastrogiovanni, Daniel D T; Mayer, Jeff; Wan, Alan S; Vishnyakov, Aleksey; Neimark, Alexander V; Podzorov, Vitaly; Feldman, Leonard C; Garfunkel, Eric

2014-01-01

148

Oxygen Incorporation in Rubrene Single Crystals  

NASA Astrophysics Data System (ADS)

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed.

Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

2014-05-01

149

Neutron detection with single crystal organic scintillators  

SciTech Connect

Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10-diphenylanthracene and diphenylacetylene.

Zaitseva, N; Newby, J; Hamel, S; Carman, L; Faust, M; Lordi, V; Cherepy, N; Stoeffl, W; Payne, S

2009-07-15

150

Oxygen Incorporation in Rubrene Single Crystals  

PubMed Central

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed.

Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

2014-01-01

151

Low temperature synthesis of single crystalline ZnO nanorods by oblique angle deposition  

Microsoft Academic Search

The authors report the growth of single crystalline ZnO nanorods by direct current magnetron sputtering in the oblique angle deposition configuration near room temperature. These isolated nanorods have a diameter of ?40 nm, an inter-rod spacing of ?20 nm, and a height of ?100 nm. The nanorods show a (002) orientation along the rod-axis which is normal to the substrate. The low temperature

Ranganath Teki; Thomas C. Parker; Huafang Li; Nikhil Koratkar; Toh-Ming Lu; Sabrina Lee

2008-01-01

152

??-SnSb single crystals obtained by the method of inclined front crystallization  

Microsoft Academic Search

?? phase plates of single crystals of SnSb alloy were obtained by using a modification of the horizontal Bridgman method. It was ascertained that during crystallization the single crystals grow in the upper layer of the charge. It was found that the thickness of the single crystal (single crystal layer) and also its relative antimony content, depend on the growth

W. Bogdanowicz; Z. Bojarski

1995-01-01

153

Single-Crystal-to-Single-Crystal Transformations in One Dimensional Ag-Eu Helical System  

SciTech Connect

Single-crystal-to-single-crystal transformation of 1-D 4d-4f coordination polymers have been investigated for the first time. It displays high selectivity for Mg2+ and can be used as magnesium ion-selective luminescent probe. More importantly, we observed the transformation of meso-helical chain to rac-helical chain as a function of temperature.

Cai, Yue-Peng; Zhout, Xiu-Xia; Zhout, Zheng-Yuan; Zhu, Shi-Zheng; Thallapally, Praveen K.; Liu, Jun

2009-07-06

154

Self-diffusion in naphthalene single crystals  

Microsoft Academic Search

Studies of self-diffusion in pure single crystals of naphthalene have been carried out by a sectioning method, using a 14C labelled tracer. The effects of impurity content and pre-annealing upon the diffusion process “were examined. Diffusion coefficients are low compared to those found for other solid systems. In the best available crystals self-diffusion can be described by an equation D

J. N. Sherwood; D. J. White

1967-01-01

155

Single crystals of metal solid solutions  

NASA Technical Reports Server (NTRS)

The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project.

Miller, J. F.; Austin, A. E.; Richard, N.; Griesenauer, N. M.; Moak, D. P.; Mehrabian, M. R.; Gelles, S. H.

1974-01-01

156

Czochralski single crystal growth, modeling, and characterization of ilmenite  

Microsoft Academic Search

Ilmenite is a wide band gap material, and could be used for electronic applications. Since ilmenite is stoichiometric at its melting point, the single crystals are grown using Czochralski crystal growth method. Earlier research in ilmenite uses ceramic material, and smaller size single crystals. In this research large size single crystals of ilmenite are grown. To grow large size single

Jayakumar Muthusami

1998-01-01

157

Analysis of Indium Diffusion Profiles Based on the Fermi-Level Effect in Single-Crystal Zinc Oxide  

NASA Astrophysics Data System (ADS)

The diffusion of indium in single-crystal ZnO was studied by an ion implantation technique (accelerating voltage of 170 keV and dose of 1× 1016 cm-2) in the temperature range between 750 and 850 °C. The indium profiles have a characteristic tail with a constant concentration region due to the Fermi-level effect on the diffusion. The simulated profiles of indium diffusion in ZnO fitted well with the experimentally determined profiles. We propose a possible models for indium diffusion based on an interstitialcy mechanism or a vacancy mechanism.

Nakagawa, Tsubasa; Matsumoto, Kenji; Sakaguchi, Isao; Uematsu, Masashi; Haneda, Hajime; Ohashi, Naoki

2008-10-01

158

Morphology investigation of hydrothermally prepared ZnO micro-crystals influenced by Cu{sup 2+} ions  

SciTech Connect

Micrometer-sized ZnO with various shapes have been synthesized by a hydrothermal route with Zn(Ac){sub 2}/NH{sub 3}.H{sub 2}O in the presence of copper ions. Powder X-ray diffraction and scanning electron microscopy were utilized to characterize the composition and structure of the samples, respectively. As-synthesized, the ultrasonic pretreatment, pH value, reaction time and hydrothermal temperature played important roles in crystal structure tailoring. Novel nut-like ZnO crystal with improved crystal quality was obtained with initial Zn{sup 2+}/Cu{sup 2+} ratio of 10, at reaction temperature of 100 {sup o}C, with initial pH of 7.0 and in a reaction time of 4 h, with ultrasonic pretreatment. Time-dependent experiments show that transfer of the Cu ions plays a crucial role as it causes the difference in crystal growth velocity.

Jin, Dalai, E-mail: jindl@zstu.edu.cn [Center of Materials Engineering, Zhejiang Sci-Tech University, Xiasha University Town, No. 2 Street, Hangzhou 310018 (China)] [Center of Materials Engineering, Zhejiang Sci-Tech University, Xiasha University Town, No. 2 Street, Hangzhou 310018 (China); Yue, Linhai, E-mail: zjchem_yue@126.com [Chemistry Department of Zhejiang University, 310027 (China)] [Chemistry Department of Zhejiang University, 310027 (China); Zheng, Yifan [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China)] [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China)

2010-04-15

159

Systematic study of hydrothermal crystallization of zinc oxide (ZnO) nano-sized powders with superior UV attenuation  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) powders were synthesized by the hydrothermal method at 160-280 °C for 6-24 h, under 90-930 psi pressure, from concentrated precursors without stirring. The precursors were formed by mixing aqueous solutions of zinc acetate, chloride, sulfate, or nitrate with KOH (aq) under either controlled or rapid precipitation conditions. The precursor quantities were chosen to yield zinc concentration of 0.3-4.0 m, KOH concentration of 0.6-8.0 m, and pH between 4 and 14 after precipitation had been completed. Several of the synthesized powders exhibited equiaxed morphology, low aggregation levels, narrow crystallite size distributions in the range 60-200 nm, and excellent dispersability. Some of the ZnO powders consisted of nano-sized equiaxed crystallites mixed with large, mostly elongated crystals, 0.5-4.0 ?m in size. Based on this systematic study encompassing a wide range of synthesis conditions, temperature-controlled growth rate and Ostwald ripening were found to dominate the hydrothermal crystallization of ZnO powders. Comparison with several commercially available ZnO powders revealed superior purity, particle size distributions, defect structure, and ultimately the UV attenuation, in selected powders synthesized hydrothermally. Results of this study enable the use of hydrothermally made ZnO powders in sunscreens or other UV absorption applications and make their hydrothermal production commercially feasible.

Suchanek, Wojciech L.

2009-12-01

160

Single-Crystal Springs For Accelerometers  

NASA Technical Reports Server (NTRS)

Thermal noise reduced, enabling use of smaller proof masses. Spring-and-mass accelerometers in which springs made of single-crystal material being developed. In spring-and-mass accelerometer, proof mass attached to one end of spring, and acceleration of object at other end of spring measured in terms of deflection of spring, provided frequency spectrum of acceleration lies well below resonant frequency of spring-and-proof-mass system. Use of single-crystal spring materials instead of such polycrystalline spring materials as ordinary metals makes possible to construct highly sensitive accelerometers (including seismometers) with small proof masses.

Vanzandt, Thomas R.; Kaiser, William J.; Kenny, Thomas W.

1995-01-01

161

Inkjet printing of single-crystal films  

NASA Astrophysics Data System (ADS)

The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. `Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4cm2V-1s-1. This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.

Minemawari, Hiromi; Yamada, Toshikazu; Matsui, Hiroyuki; Tsutsumi, Jun'ya; Haas, Simon; Chiba, Ryosuke; Kumai, Reiji; Hasegawa, Tatsuo

2011-07-01

162

Charge transport in single crystal organic semiconductors  

NASA Astrophysics Data System (ADS)

Organic electronics have engendered substantial interest in printable, flexible and large-area applications thanks to their low fabrication cost per unit area, chemical versatility and solution processability. Nevertheless, fundamental understanding of device physics and charge transport in organic semiconductors lag somewhat behind, partially due to ubiquitous defects and impurities in technologically useful organic thin films, formed either by vacuum deposition or solution process. In this context, single-crystalline organic semiconductors, or organic single crystals, have therefore provided the ideal system for transport studies. Organic single crystals are characterized by their high chemical purity and outstanding structural perfection, leading to significantly improved electrical properties compared with their thin-film counterparts. Importantly, the surfaces of the crystals are molecularly flat, an ideal condition for building field-effect transistors (FETs). Progress in organic single crystal FETs (SC-FETs) is tremendous during the past decade. Large mobilities ~ 1 - 10 cm2V-1s-1 have been achieved in several crystals, allowing a wide range of electrical, optical, mechanical, structural, and theoretical studies. Several challenges still remain, however, which are the motivation of this thesis. The first challenge is to delineate the crystal structure/electrical property relationship for development of high-performance organic semiconductors. This thesis demonstrates a full spectrum of studies spanning from chemical synthesis, single crystal structure determination, quantum-chemical calculation, SC-OFET fabrication, electrical measurement, photoelectron spectroscopy characterization and extensive device optimization in a series of new rubrene derivatives, motivated by the fact that rubrene is a benchmark semiconductor with record hole mobility ~ 20 cm2V-1s-1. With successful preservation of beneficial pi-stacking structures, these rubrene derivatives form high-quality single crystals and exhibit large ambipolar mobilities. Nevertheless, a gap remains between the theory-predicted properties and this preliminary result, which itself is another fundamental challenge. This is further addressed by appropriate device optimization, and in particular, contact engineering approach to improve the charge injection efficiencies. The outcome is not only the achievement of new record ambipolar mobilities in one of the derivatives, namely, 4.8 cm2V-1s-1 for holes and 4.2 cm2V-1s-1 for electrons, but also provides a comprehensive and rational pathway towards the realization of high-performance organic semiconductors. Efforts to achieve high mobility in other organic single crystals are also presented. The second challenge is tuning the transition of electronic ground states, i.e., semiconducting, metallic and superconducting, in organic single crystals. Despite an active research area since four decades ago, we aim to employ the electrostatic approach instead of chemical doping for reversible and systematic control of charge densities within the same crystal. The key material in this study is the high-capacitance electrolyte, such as ionic liquids (ILs), whose specific capacitance reaches ~ ?F/cm2, thus allowing accumulation of charge carrier above 1013 cm-2 when novel transport phenomena, such as insulator-metal transition and superconductivity, are likely to occur. This thesis addresses the electrical characterization, device physics and transport physics in electrolyte-gated single crystals, in the device architecture known as the electrical double layer transistor (EDLT). A detailed characterization scheme is first demonstrated for accurate determination of several key parameters, e.g., carrier mobility and charge density, in organic EDLTs. Further studies, combining both experiments and theories, are devoted to understanding the unusual charge density dependent channel conductivity and gate-to-channel capacitance behaviors. In addition, Hall effect and temperature-dependent measurements are employed for more in-depth unders

Xie, Wei

163

Photoluminescence properties of highly dispersed ZnO quantum dots in polyvinylpyrrolidone nanotubes prepared by a single capillary electrospinning  

NASA Astrophysics Data System (ADS)

Highly dispersed ZnO quantum dots (QDs) in polyvinylpyrrolidone (PVP) nanotubes have been prepared by a single capillary electrospinning. The structure and optical properties characterizations were performed by x-ray diffraction, scanning and transmission electron microscopy, absorption, photoluminescence, and resonant Raman spectra. In the composites, PVP molecules passivate the surface defects of ZnO QDs and prevent the aggregations of ZnO QDs. As a result, the composites exhibit narrower band edge emissions and less laser thermal effects. Blueshifted band gap, enlarged exciton energy, and less exciton-longitudinal optical (LO) phonon interaction due to the quantum confinement effect have also been observed.

Li, X. H.; Shao, C. L.; Liu, Y. C.; Chu, X. Y.; Wang, C. H.; Zhang, B. X.

2008-09-01

164

CVD-diamond single-crystal growth  

NASA Astrophysics Data System (ADS)

The synthesis of diamond volume crystals is of particular interest due to the material's outstanding physical and mechanical properties. Various techniques are pursued by numerous research groups. In hot-filament CVD (HF-CVD) we found a new process parameter window where the growth of single diamond volume crystals can be stabilized. These parameters are far beyond growth conditions for HF-CVD diamond coating processes. Extremely low methane content in the feed gas along with high substrate temperatures allows single diamond nuclei of a certain minimum size to grow stable. Crystals up to 100 ?m in diameter were successfully synthesized on ultrasonic pretreated substrates. They were characterized by SEM and Raman spectroscopy. A model for the observed exclusive growth of sufficiently large nuclei is presented. Based on well accepted diamond growth models, an advanced growth theory for the different morphologies and diamond qualities at the {1 0 0} and {1 1 1} faces of the crystals is postulated. The results give bases on which growing processes can be optimized and upscaled in order to evaluate the applicability of the method for single-crystal diamond growth.

Schwarz, S.; Rottmair, C.; Hirmke, J.; Rosiwal, S.; Singer, R. F.

2004-11-01

165

Imaging Single ZnO Vertical Nanowire Laser Cavities using UV-Laser Scanning Confocal Microscopy  

SciTech Connect

We report the fabrication and optical characterization of individual ZnO vertical nanowire laser cavities. Dilute nanowire arrays with interwire spacing>10 ?m were produced by a modified chemical vapor transport (CVT) method yielding an ideal platform for single nanowire imaging and spectroscopy. Lasing characteristics of a single vertical nanowire are presented, as well as high-resolution photoluminescence imaging by UV-laser scanning confocal microscopy. In addition, three-dimensional (3D) mapping of the photoluminescence emission performed in both planar and vertical dimensions demonstrates height-selective imaging useful for vertical nanowires and heteronanostructures emerging in the field of optoelectronics and nanophotonics.

Gargas, D.J.; Toimil-Molares, M.E.; Yang, P.

2008-11-17

166

Scientific Review: The Single Crystal Diffractometer RESI  

Microsoft Academic Search

The single crystal diffractometer RESI (REciprocal Space Investigator) provides powerful techniques for structure research using thermal neutrons. With its unique setup of a kappa-goniometer and a neutron sensitive imaging plate, it is very well-suited for recording Bragg data, in particular, on samples with large unit cells, incommensurate structures, phase transitions, or dense patterns of reflections (quasicrystals). It is also designed

Björn Pedersen; Friedrich Frey; Wolfgang Scherer

2007-01-01

167

Multiphonon relaxation in YVO4 single crystals  

Microsoft Academic Search

Multiphonon relaxation rates were measured for 13 different energy levels of various rare-earth ions in YVO4 single crystals at 77 K. Dependence of the multiphonon relaxation rate on the energy gap that separates each emitting multiplet from the one lying just below it was investigated over the range from 980 to 5200 cm-1. A significant change in gap dependence was

F. S. Ermeneux; C. Goutaudier; R. Moncorgé; Y. Sun; R. L. Cone; E. Zannoni; E. Cavalli; M. Bettinelli

2000-01-01

168

Growth and Properties of Hydorxyapatite Single Crystals.  

National Technical Information Service (NTIS)

Four methods were attempted for the growth of large single crystals of hydroxyapatite: hydrothermal synthesis, growth in gels under hydrothermal conditions, growth in aqueous solution at 100C, and growth under conditions where the pH is controlled by the ...

J. F. Kirn H. Leidheiser

1967-01-01

169

Fracture in single crystal NiTi  

Microsoft Academic Search

This paper presents an investigation of the pseudoelastic transformation of two crystallographic orientations of a single crystal NiTi shape memory alloy (SMA). Both uniaxial tension and notched tension samples are considered with the tensile axes along the [100] and [111] directions. The phase transformation is observed using optical techniques in situ. For the uniaxial tension samples, martensite plates and Lüders-band

A. Creuziger; L. J. Bartol; K. Gall; W. C. Crone

2008-01-01

170

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

We have explored the terminal ballistic performance of single crystal tungsten as a kinetic energy penetrator. Scientific speculation as to the anticipated penetration performance and nature of the interaction between such a kinetic energy penetrator and semi-infinite and spaced metallic targets has led us to perform laboratory scale experiments and metallographic examinations of post-impact penetrator materials. The single tungsten crystals were ground into kinetic energy penetrators with the [l angle]111[r angle] and [l angle]100[r angle] crystal direction being coincident with the axis of symmetry of the penetrators. The crystals were electro-polished to their final diameter. We, compared the terminal performance at current ordnance speeds of [l angle]111[r angle] single crystal tungsten to 90W-10 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against a spaced steel (triple) target at sixty-five degrees obliquity. We also compared the terminal performance of [l angle]100[r angle] and [l angle]111[r angle] single crystal tungsten with 90W-10 and 98W02 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against monolithic 4340 alloy steel (HRC = 36) at normal impact. We radiographed the penetrators during the interactions with the targets, we recovered portions of the penetrators after the ballistic experiments, and we conducted metallographic examinations of penetrator remnants. From the radiographic records and the metallographic examinations, we drew conclusions pertaining to insights into the terminal interactions of the penetrators with the targets and suggestions as to improved compositions of the cemented tungsten penetrators.

Cline, C.F.; Gogolewski, R.P.

1992-05-01

171

Single crystal tungsten kinetic energy penetrators  

SciTech Connect

We have explored the terminal ballistic performance of single crystal tungsten as a kinetic energy penetrator. Scientific speculation as to the anticipated penetration performance and nature of the interaction between such a kinetic energy penetrator and semi-infinite and spaced metallic targets has led us to perform laboratory scale experiments and metallographic examinations of post-impact penetrator materials. The single tungsten crystals were ground into kinetic energy penetrators with the {l_angle}111{r_angle} and {l_angle}100{r_angle} crystal direction being coincident with the axis of symmetry of the penetrators. The crystals were electro-polished to their final diameter. We, compared the terminal performance at current ordnance speeds of {l_angle}111{r_angle} single crystal tungsten to 90W-10 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against a spaced steel (triple) target at sixty-five degrees obliquity. We also compared the terminal performance of {l_angle}100{r_angle} and {l_angle}111{r_angle} single crystal tungsten with 90W-10 and 98W02 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against monolithic 4340 alloy steel (HRC = 36) at normal impact. We radiographed the penetrators during the interactions with the targets, we recovered portions of the penetrators after the ballistic experiments, and we conducted metallographic examinations of penetrator remnants. From the radiographic records and the metallographic examinations, we drew conclusions pertaining to insights into the terminal interactions of the penetrators with the targets and suggestions as to improved compositions of the cemented tungsten penetrators.

Cline, C.F.; Gogolewski, R.P.

1992-05-01

172

Diluted magnetism in Mn-doped SrZnO2 single crystals  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic properties of Mn- and Cu-substituted SrZnO2 single crystals (SrZn1-xMnxO2 and SrZn1-xCuxO2). We observed signatures of weak ferromagnetism as a sharp increase of magnetic susceptibility below 5 K even in the low-percentage (x = 0.01) of Mn-substituted single crystals. Magnetic susceptibility data measured parallel or perpendicular to the ab-plane yield anisotropic behavior with Curie-Weiss temperature of about -320 K and -410 K, respectively, suggesting the presence of strong antiferromagnetic couplings among Mn at high temperatures, similar to the Mn-doped ZnO and Fe-doped BaTiO3. In contrast, the SrZn0.99Cu0.01O2 crystal shows paramagnetic behavior down to 2 K.

Rahman, M. R.; Koteswararao, B.; Huang, S. H.; Hoon Kim, Kee; Chou, F. C.

2013-09-01

173

Size-dependent elastic properties of single-walled ZnO nanotubes: A first-principles study  

SciTech Connect

By means of first-principles calculations, we have investigated a size dependence of elastic modulus in single-walled ZnO nanotubes with armchair and zigzag forms. It is found that for these tubes the Young's modulus is increased dramatically with the increased diameters and inversely proportional to the Zn-O bond length. Further, the amount of charge transfer, calculated by the Bader analysis, is introduced to elucidate the strength of bonding between Zn and O atoms in these tubes.

Wen Yuhua; Zhang Yang; Wu Shunqing; Zhu Zizhong [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China)

2011-04-15

174

Photoluminescence of C60 Single Crystals  

NASA Astrophysics Data System (ADS)

The photoluminescence (PL) spectra of C60 single crystals grown under double temperature gradient (DTG) and single temperature gradient (STG) techniques were investigated at room temperature. The results show that the PL emission intensity increases first and then decreases with increasing illuminated power density for the C60 single crystals grown by both DTG and STG techniques. Furthermore, one main peak with a shoulder peak can be clearly distinguished at low illumination, while only one main peak without the shoulder peak can be seen at high illumination. The main peak undergoes a continuous blue shift and broadening with the increase of illuminated power density. The difference of PL emission energy at the same illumination density of DTG and STG samples may correlated with the degree of both the orientational disorder of C60 molecule and lattice perfectness. The Laue diffraction patterns show that the DTG sample has stronger strains and poorer crystalline quality than the STG sample.

Li, Chaorong; Wang, Gang; Zhang, Jiaming; Mai, Zhenhong; Zhao, Tienan; Xu, Lu; Xie, Sishen

1995-05-01

175

Neutron Scattering Study of Single Crystal PZT  

NASA Astrophysics Data System (ADS)

Single crystal specimens of the technologically important ferroelectric material Pb(Zr1-xTix)O3, or PZT, have only recently been grown for the first time at Simon Fraser University. We have characterized the transition temperatures, thermal expansion, and crystal structure of a PZT single crystal between 10 K and 670 K using neutron scattering methods. This crystal, which has a composition (x˜0.46) that lies close to the morphotropic phase boundary (MPB), exhibits a surprisingly large thermal expansion (˜ 10-3 1/K) that changes sign near 545 K, and a rhombohedral crystal structure at 30 K. In addition we observe an enormous relief of extinction beginning around 650 K, which was observed through the temperature dependence of the (200) Bragg peak. Neutron inelastic measurements are planned as are measurements under an applied electric field. This work was supported by the U. S. Office of Naval Research (Grant No. N00014-1-06-0166). All neutron measurements were performed at the NIST Center for Neutron Research.

Phelan, Daniel; Gehring, Peter; Ye, Zuo-Guang; Long, Xifa

2010-03-01

176

ZnO and ZnO:Mn crystals obtained with the chemical vapour transport method  

NASA Astrophysics Data System (ADS)

Successful growth of the ZnO and ZnO:Mn crystals by the CVT method and their characterisation are reported. The source material was synthesized at 650 ° C from oxygen and zinc vapours and subsequently - baked (as a powder) to achieve stoichiometry. Crystal growth (at 1100 ° C, with the rate 1-2 mm/day) proceeded in graphite-covered quartz ampoules containing pure (6N) hydrogen or nitrogen or chlorine and a little of water vapour and carbon. The crystals, both as-grown and annealed in pure oxygen, were characterised by the measurements of: transmission spectra in energy gap and far infrared regions, photoluminescence and reflectivity spectra, electrical transport properties and EDXRF - the energy dispersive X-ray fluorescence (for Mn content determination). In the surface region - the impurities and the Mn content were studied by the secondary ion mass spectroscopy (SIMS). Manganese and native defects (VO) were investigated by electron paramagnetic resonance (EPR) and Raman spectroscopy. Results of the measurements are presented and discussed.

Mycielski, A.; Szadkowski, A.; Kowalczyk, L.; Witkowska, B.; Kaliszek, W.; Chwalisz, B.; Wysmoek, A.; Stpniewski, R.; Baranowski, J. M.; Potemski, M.; Witowski, A. M.; Jakiea, R.; Barcz, A.; Aleshkevych, P.; Jouanne, M.; Szuszkiewicz, W.; Suchocki, A.; Usakowska, E.; Kamiska, E.; Dobrowolski, W.

2004-03-01

177

Polar phonons in SO 2 single crystal  

NASA Astrophysics Data System (ADS)

The Raman spectrum of a single SO 2 crystal in various polarization geometries has been measured at 20 K and discussed in terms of LO and TO components of polar crystal modes. Lattice phonons have been assigned on the basis of their behaviour with polarization. Lattice dynamical calculations on both the internal and lattice phonons are in good agreement with experimental data. Using gas-phase transition dipole moments and a dipole—dipole intermolecular potential the angular dispersion of fundamental vibrons has been calculated. For lattice phonons, a combination of atom—atom and electrostatic potential reproduces not only the phonon frequencies but, for polar phonons, also their LO—TO splitting.

Tafi, A.; Procacci, P.; Castellucci, E.; Salvi, P. R.

1991-03-01

178

THERMAL STRESS ANALYSIS OF TETRAGONAL SINGLE CRYSTAL DURING GROWTH PROCESS : PMO SINGLE CRYSTAL  

Microsoft Academic Search

A three-dimensional finite element computer code was developed to deal with thermal stress analyses of tetragonal single crystals during the growth. They have the crystal anisotropy, so three-dimensional analysis is required for calculation of the thermal stress, even though they have axisymmetrical shapes. A tensor transformation technique was used to obtain the components of elastic constant matrix and thermal strain

N. Miyazaki; Y. Matsuura; D. Imahase

179

Lightweight optical mirrors formed in single crystal substrate  

NASA Technical Reports Server (NTRS)

This invention is directed to a process for manufacturing a lightweight mirror from a single crystal material, such as single crystal silicon. As a near perfect single crystal material, single crystal silicon has much lower internal stress than a conventional material. This means much less distortion of the optical surface during the light weighting process. After being ground and polished, a single crystal silicon mirror is light weighted by removing material from the back side using ultrasonic machining. After the light weighting process, the single crystal silicon mirror may be used as-is or further figured by conventional polishing or ion milling, depending on the application and the operating wavelength.

Bly, Vincent T. (Inventor)

2006-01-01

180

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

The objective of the study is to establish the effects of processing semiconducting, solid solution, single crystals in a microgravity environment on the metallurgical, compositional, electrical, and optical characteristics of the crystals. The alloy system being investigated is the solid solution semiconductor Hg(1-x)Cd(x)Te, with x-values appropriate for infrared detector applications in the 8 to 14 mm wavelength region. Both melt and Te-solvent growth are being performed. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. The ground-based portion of the investigation also includes the evaluation of the relative effectiveness of stabilizing techniques, such as applied magnetic fields, for suppressing convective flow during the melt growth of the crystals.

Lehoczky, Sandor L.; Szofran, Frank R.; Gillies, Donald C.; Watring, Dale A.

1999-01-01

181

SSME single crystal turbine blade dynamics  

NASA Technical Reports Server (NTRS)

A study was performed to determine the dynamic characteristics of the Space Shuttle main engine high pressure fuel turbopump (HPFTP) blades made of single crystal (SC) material. The first and second stage drive turbine blades of HPFTP were examined. The nonrotating natural frequencies were determined experimentally and analytically. The experimental results of the SC second stage blade were used to verify the analytical procedures. The analytical study examined the SC first stage blade natural frequencies with respect to crystal orientation at typical operating conditions. The SC blade dynamic response was predicted to be less than the directionally solidified blade. Crystal axis orientation optimization indicated the third mode interference will exist in any SC orientation.

Moss, Larry A.; Smith, Todd E.

1987-01-01

182

The Creep of Single Crystals of Aluminum  

NASA Technical Reports Server (NTRS)

The creep of single crystals of high-purity aluminum was investigated in the range of temperatures from room temperature to 400 F and at resolved-shear-stress levels of 200, 300, and 400 psi. The tests were designed in an attempt to produce data regarding the relation between the rate of strain and the mechanism of deformation. The creep data are analyzed in terms of shear strain rate and the results are discussed with regard to existing creep theories. Stress-strain curves were determined for the crystals in tinsel and constant-load-rate tests in the same temperature range to supplement the study of plastic deformation by creep with information regarding the part played by crystal orientation, differences in strain markings, and other variables in plastic deformation.

Johnson, R D; Shober, F R; Schwope, A D

1953-01-01

183

Optical properties of some borate single crystals  

NASA Astrophysics Data System (ADS)

This paper describes efforts taken in Institute of Applied Physics and Institute of Electronic Materials Technology to obtain several single crystals from borate family, namely, CsLiB6)10, Ca4GdO(BO3)3, Li2B4O7, (beta) -BaB2O4, and Yal3(BO3)4, pure and doped with several ions. The main goal of this investigation was to develop technology of these new nonlinear optical materials to create possibility of their applications in higher harmonics generators and self- frequency doubling lasers. Depending on such properties of crystallized borate materials as incongruent melting or high temperature phase transitions, Czochralski technique or high temperature solution growth technique were used. The main aspects of crystallization of these materials as well as their optical properties are discussed.

Majchrowski, Andrzej; Lukasiewicz, Tadeusz; Mierczyk, Zygmunt; Malinowski, Michal

2001-08-01

184

Crack growth in single-crystal silicon  

NASA Technical Reports Server (NTRS)

Crack growth in single-crystal silicon at room temperature in air was evaluated by double torsion (DT) load-relaxation method and monitored by acoustic emission (AE) technique. Both DT and AE methods indicated lack of subcritical crack growth in silicon. At the critical stress intensity factor, the crack front was found to be jumping several times in a 'mirror' region and then followed by fast crack growth in a 'hackle' region. Hackle marks were found to be associated with plastic deformation at the tip of the fast moving crack. No dislocation etch pits were found in the 'mirror' region, in which crack growth may result from interatomic bonds broken at the crack tip under stress without any plastic deformation. Acoustic emission appears to be spontaneously generated from both interatomic bonds broken and dislocation generation at the moving crack tip during the crack growth in single-crystal silicon.

Chen, C. P.; Leipold, M. H.

1986-01-01

185

Bridgman growth of paratellurite single crystals  

Microsoft Academic Search

The growth of paratellurite single crystals by the vertical-gradient freezing technique is reported for the first time. Boules of 120mm long and 25mm in diameter were obtained under a temperature gradient of 10°Ccm?1 and translation rates lower than 0.6mmh?1. The spatial distribution of defects along the growth axis reveals a continuous evolution of the free convective fluid-flow regime as growth

P. Veber; J. Mangin; P. Strimer; P. Delarue; C. Josse; L. Saviot

2004-01-01

186

Crack Growth in Single-Crystal Silicon  

NASA Technical Reports Server (NTRS)

Report describes experiments on crack growth in single-crystal silicon at room temperature in air. Crack growth in (111) cleavage plane of wafers, 50 by 100 by 0.76 mm in dimension, cut from Czochralski singlecrystal silicon studied by double-torsion load-relaxation method and by acoustic-emission measurements. Scanning electron microscopy and X-ray topography also employed. Results aid in design and fabrication of silicon photovoltaic and microelectronic devices.

Chen, C. P.; Leipold, M. H.

1986-01-01

187

Q-1 of forsterite single crystals  

Microsoft Academic Search

Internal friction (Q-1) experiments have been performed on synthetic forsterite single crystals in order to investigate the role of temperature, frequency and dislocation density on the Q-1 factor. Data have been obtained for both deformed and undeformed specimens over a frequency range from 10 to 10-4 Hz at 15, 1000, 1200 and 1400°C. Measurements were done using a torsional pendulum

Y. Gueguen; M. Darot; P. Mazot; J. Woirgard

1989-01-01

188

Single crystal cylinder transducers for sonar applications  

NASA Astrophysics Data System (ADS)

A segmented cylinder transducer constructed of single crystal lead magnesium niobate-lead titanate (PMN-PT) has been under development at NUWC and EDO Corporation for several years. The purpose of this development was to provide an extremely compact, high power broadband source. By virtue of their extraordinary material properties, ferroelectric single crystals are the ideal transduction material for developing such compact broadband systems. This presentation shall review the evolution of the transducer design as well as present the results of a successful in-water test conducted at NUWC in October of 2003. It shall be shown that design changes intended to eliminate spurious modes limiting the transducer bandwidth first observed in 2002 were successful, resulting in a transducer with a clean frequency response and an effective coupling factor of 0.85. The measured transducer admittance was in nearly exact agreement with theoretical predictions. The NUWC in-water tests demonstrated that the single crystal cylinder achieved an admittance bandwidth (based on the Stansfield criterion) of over 100%, while the tuned power factor was 0.8 or more over 2.5 octaves of frequency. Additionally, the transducer produced 12 dB higher source levels than a similarly sized PZT transducer. [Work sponsored by DARPA.

Robinson, Harold; Stevens, Gerald; Buffman, Martin; Powers, James

2005-04-01

189

Single crystal diffraction by synchrotron radiation  

SciTech Connect

The tunability and access to short wavelengths in combination with high intensity and the low divergence of the x-ray radiation produced by synchrotron storage rings opens up new and challenging fields for single crystal diffraction. These areas include microcrystal diffraction, studies of time-dependent phenomena, element selective diffraction, studies of materials under extreme conditions, solution of the crystallographic phase problem either by the use of the wavelength dependency of the anomalous scattering or by direct experimental determination of the phases. Single crystal diffraction from proteins and macromolecules using photographic film as a detection medium has already reached considerable maturity, but high-precision data collections using diffractometers at storage rings are still not routine because of the severe requirements for beam stability over extended periods of time. Development work at institutions such as the National Synchrotron Light Source, The Photon Factory, SSRL, CHESS, Hasylab and Daresbury, however, suggest that synchrotron single-crystal diffraction will become an essential part of the research at the synchrotron storage rings in the near future. 9 refs., 2 figs.

Kvick, A.

1988-01-01

190

Selective Area Growth of Well-Ordered ZnO Nanowire Arrays with Controllable Polarity.  

PubMed

Controlling the polarity of ZnO nanowires in addition to the uniformity of their structural morphology in terms of position, vertical alignment, length, diameter, and period is still a technological and fundamental challenge for real-world device integration. In order to tackle this issue, we specifically combine the selective area growth on prepatterned polar c-plane ZnO single crystals using electron-beam lithography, with the chemical bath deposition. The formation of ZnO nanowires with a highly controlled structural morphology and a high optical quality is demonstrated over large surface areas on both polar c-plane ZnO single crystals. Importantly, the polarity of ZnO nanowires can be switched from O- to Zn-polar, depending on the polarity of prepatterned ZnO single crystals. This indicates that no fundamental limitations prevent ZnO nanowires from being O- or Zn-polar. In contrast to their catalyst-free growth by vapor-phase deposition techniques, the possibility to control the polarity of ZnO nanowires grown in solution is remarkable, further showing the strong interest in the chemical bath deposition and hydrothermal techniques. The single O- and Zn-polar ZnO nanowires additionally exhibit distinctive cathodoluminescence spectra. To a broader extent, these findings open the way to the ultimate fabrication of well-organized heterostructures made from ZnO nanowires, which can act as building blocks in a large number of electronic, optoelectronic, and photovoltaic devices. PMID:24720628

Consonni, Vincent; Sarigiannidou, Eirini; Appert, Estelle; Bocheux, Amandine; Guillemin, Sophie; Donatini, Fabrice; Robin, Ivan-Christophe; Kioseoglou, Joseph; Robaut, Florence

2014-05-27

191

Fatigue In Single Crystal Nickel Superalloys Technical Progress Report.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis

1992-01-01

192

Fatigue In Single Crystal Nickel Superalloys Technical Progress Report.  

National Technical Information Service (NTIS)

This program investigates the seemingly unusual behavior of single crystal airfoil materials. The fatigue initiation processes in single crystal (SC) materials are significantly more complicated and involved than fatigue initiation and subsequent behavior...

C. Annis D. P. DeLuca

1993-01-01

193

Single Crystal Niobium RF Cavity of the TESLA Shape.  

National Technical Information Service (NTIS)

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without gra...

P. Kneisel W. Singer X. Singer

2007-01-01

194

Unidirectional seeded single crystal growth from solution of benzophenone  

Microsoft Academic Search

A novel crystal growth method has been established for the growth of single crystal with selective orientation at room temperature. Using volatile solvent, the saturated solution containing the material to be crystallized was taken in an ampoule and allowed to crystallize by slow solvent evaporation assisted with a ring heater. The orientation of the growing crystal was imposed by means

K. Sankaranarayanan; P. Ramasamy

2005-01-01

195

Manipulation and assembly of ZnO nanowires with single holographic optical tweezers system.  

PubMed

ZnO nanowires, characterized with high melting points, are hard to assemble together with laser fusion. In order to build micro-nano structures with ZnO nanowires, a polymer film with a low melting point and high optical transparency is introduced as a substrate for ZnO nanowires to be deposited. A holographic optical tweezers system is used not only to manipulate ZnO nanowires, but also to melt the polymer film for the fixation of ZnO nanowires. By this method, micro-nano structures composed of ZnO nanowires are produced, which can be utilized as subwavelength optical waveguides. PMID:24514119

Li, Jing; Du, Gang

2014-01-20

196

Single crystal x-ray diffraction: optical and micro hardness studies on chalcone derivative single crystal  

NASA Astrophysics Data System (ADS)

1-(4-methylphenyl)-3-(4- N, N dimethyl amino phenyl)-2-propen-1-one, a chalcone derivative nonlinear optical material has been synthesized by standard method. FT-IR and NMR spectral studies have been performed to confirm the molecular structure of the synthesized compound. The single crystals up to a dimension of 13 x 9 x 3 mm3 were grown by slow evaporation method. The grown crystals were transparent in the entire visible region and absorbs in the UV-region. The refractive index has been measured using a He-Ne laser. The grown crystals have been subjected to single crystal X-ray diffraction studies to determine the crystal structure and hence the cell parameters of the crystal. From this study it is found that this compound crystallizes in orthorhombic system with a space group P212121 and corresponding lattice parameters are, a = 7.3610(13) Å, b = 11.651(2) Å, c = 17.6490(17) Å. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for Photonic application. The micro hardness test on these crystals were carried out and the load dependence hardness was observed

Crasta, Vincent; Ravindrachary, V.; Bhajantri, R. F.; Naveen, S.; Shridar, M. A.; Shashidhara Prasad, J.

2005-08-01

197

?'-SnSb single crystals obtained by the method of inclined front crystallization  

NASA Astrophysics Data System (ADS)

?' phase plates of single crystals of SnSb alloy were obtained by using a modification of the horizontal Bridgman method. It was ascertained that during crystallization the single crystals grow in the upper layer of the charge. It was found that the thickness of the single crystal (single crystal layer) and also its relative antimony content, depend on the growth rate and on the angle of inclination of the crystallization front relative to the growth direction. A model proposed for the crystallization process permits the description of these relations obtained. This method for obtaining single crystals, the inclined front crystallization (IFC) method, offers new possibilities for control of chemical composition of plate single crystals of intermetallic phases, by varying the angle of inclination of the crystallization front.

Bogdanowicz, W.; Bojarski, Z.

1995-02-01

198

Single phase formation of Co-implanted ZnO thin films by swift heavy ion irradiation: Optical studies  

SciTech Connect

Low temperature photoluminescence and optical absorption studies on 200 MeV Ag{sup +15} ion irradiated Co-implanted ZnO thin films were studied. The Co clusters present in as implanted samples were observed to be dissolved using 200 MeV Ag{sup +15} ion irradiation with a fluence of 1x10{sup 12} ions/cm{sup 2}. The photoluminescence spectrum of pure ZnO thin film was characterized by the I{sub 4} peak due to the neutral donor bound excitons and the broad green emission. The Co-doped ZnO films show three sharp levels and two shoulders corresponding to 3t{sub 2g} and 2e{sub g} levels of crystal field splitted Co d orbitals, respectively. The ultraviolet-visible absorption spectroscopy also shows the systematic variation of band gap after 200 MeV Ag{sup +15} ion irradiation.

Kumar, Ravi; Singh, Fouran; Angadi, Basavaraj; Choi, Ji-Won; Choi, Won-Kook; Jeong, Kwangho; Song, Jong-Han; Khan, M. Wasi; Srivastava, J. P.; Kumar, Ajay; Tandon, R. P. [Materials Science Division, Inter-University Accelerator Centre, P.O. Box 10502, Aruna Asaf Ali Marg, New Delhi 110067 (India); Thin Films Materials Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of); Institute of Physics and Applied Physics, Yonsei University, Shincheon-dong 134, Seoul 120-749 (Korea, Republic of); Advanced Analysis Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650 (Korea, Republic of); Department of Physics, Aligarh Muslim University, Aligarh 202002 (India); Department of Physics and Astrophysics, Delhi University, Delhi 110007 (India)

2006-12-01

199

Large electrostrictive actuation of barium titanate single crystals  

Microsoft Academic Search

An experimental investigation of the electromechanical behavior of single crystals of the ferroelectric perovskite barium titanate is presented. An experimental setup has been designed to investigate large strain actuation in single crystal ferroelectrics subjected to combined electrical and mechanical loading. Experiments have been performed on initially single domain crystals of barium titanate with (100) and (001) orientation at compressive stresses

E. Burcsu; G. Ravichandran; K. Bhattacharya

2004-01-01

200

Dye sensitization of single crystal semiconductor electrodes.  

PubMed

Even though investigations of dye-sensitized nanocrystalline semiconductors in solar cells has dominated research on dye-sensitized semiconductors over the past two decades, single crystal electrodes represent far simpler model systems for studying the sensitization process with a continuing train of studies dating back more than 40 years. Even today single crystal surfaces prove to be more controlled experimental models for the study of dye-sensitized semiconductors than the nanocrystalline substrates. This Account analyzes the scientific advances in the model sensitized single crystal systems that preceded the introduction of nanocrystalline semiconductor electrodes. It then follows the single crystal research to the present, illustrating both their striking simplicity of use and clarity of interpretation relative to nanocrystalline electrodes. Researchers have employed many electrochemical, photochemical, and scanning probe techniques for studying monolayer quantities of sensitizing dyes at specific crystallographic faces of different semiconductors. These methods include photochronocoulometry, electronic spectroscopy, and flash photolysis of dyes at potential-controlled semiconductor electrodes and the use of total internal reflection methods. In addition, we describe the preparation of surfaces of single crystal SnS(2) and TiO(2) electrodes to serve as reproducible model systems for charge separation at dye-sensitized solar cells. This process involves cleaving the SnS(2) electrodes and a photoelectrochemical surface treatment for TiO(2) that produces clean surfaces for sensitization (as verified by AFM) resulting in near unity yields for electron transfer from the molecular excited dyes into the conduction band. In recent experiments with ruthenium complexes at TiO(2) and with carboxylated cyanine dyes, we demonstrate the promise of this simple model for understanding dye-sensitized solar cells. In each of these systems, we can observe and analyze the complex photochemistry in a quantitative manner. Molecules of the well-known N3 ruthenium complex attach to four different crystallographic faces of anatase and rutile TiO(2) at different rates and to a different extent. With carboxylated cyanine dye sensitizers on these surfaces, molecular aggregation on the surface is a function of molecular structure and crystallographic face. In contrast with the N3 sensitizer these organic dyes undergo a photoinduced dimerization and desorption reaction when hydroquinone regenerators are present. With both classes of sensitizers, we demonstrate a new photochronocoulometric technique that quantifies the amount of attached dye on the electrode surface. We have completed initial experiments examining quantum dot sensitization of TiO(2) crystals, which could eventually lead to sensitizers with higher stability and absorption coefficients. Although these single crystal electrode models show promise for providing insights and predictive value in understanding the sensitization process, more sophisticated models will be needed to fully understand the charge transfer from the localized electronic states of the sensitizer to the extended states of the semiconductor. PMID:19924998

Spitler, Mark T; Parkinson, B A

2009-12-21

201

Polycrystalline ZnO and Mn-doped ZnO nanorod arrays with variable dopant content via a template based synthesis from Zn(II) and Mn(II) Schiff base type single source molecular precursors  

NASA Astrophysics Data System (ADS)

The synthesis and full characterisation of pure and Mn-doped polycrystalline zinc oxide nanorods with tailored dopant content are obtained via a single source molecular precursor approach using two Schiff base type coordination compounds is reported. The infiltration of precursor solutions into the cylindrical pores of a polycarbonate template and their thermal conversion into a ceramic green body followed by dissolution of the template gives the desired ZnO and Mn-doped ZnO nanomaterial as compact rods. The ZnO nanorods have a mean diameter between 170 and 180 nm or 60-70 nm, depending on the template pore size employed, comprising a length of 5-6 ?m. These nanorods are composed of individual sub-5 nm ZnO nanocrystals. Exact doping of these hierarchically structured ZnO nanorods was achieved by introducing Mn(II) into the ZnO host lattice with the precursor complex Diaquo-bis[2-(meth-oxyimino)-propanoato]manganese, which allows to tailor the exact Mn(II) doping content of the ZnO rods. Investigation of the Mn-doped ZnO samples by XRD, TEM, XPS, PL and EPR, reveals that manganese occurs exclusively in its oxidation state + II and is distributed within the volume as well as on the surface of the ZnO host.

Pashchanka, Mikhail; Hoffmann, Rudolf C.; Burghaus, Olaf; Corzilius, Björn; Cherkashinin, Gennady; Schneider, Jörg J.

2011-01-01

202

Inelastic deformation in shocked sapphire single crystals  

NASA Astrophysics Data System (ADS)

To gain insight into orientation-dependent inelastic deformation of shocked sapphire (?-Al2O3) single crystals, resolved shear stresses, applicable for various dislocation slip and twinning systems, were determined for shock compression along different crystal orientations. Results from our anisotropic wave propagation analysis provide an explanation for why the measured elastic limit of shocked r-cut sapphire is lower, compared to c-cut and a-cut sapphire: Shock wave compression of r-cut sapphire favors activation of basal slip and basal twinning. In contrast, shock wave compression of c-cut and a-cut sapphire favors rhombohedral twinning and prismatic slip, respectively. Also, basal slip and/or basal twinning may be important for understanding why r-cut sapphire shocked beyond the elastic limit loses optical transparency gradually, when compared to c-cut and a-cut sapphire.

Fuller, H. D.; Winey, J. M.; Gupta, Y. M.

2013-06-01

203

Substrate Preparations in Epitaxial ZnO Film Growth  

NASA Technical Reports Server (NTRS)

Epitaxial ZnO films were grown on the two polar surfaces (O-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. Annealing-temperature dependence of ZnO substrates was studied. ZnO films grown on sapphire substrates have also been investigated for comparison purposes and the annealing temperature of A1203 substrates is 1000 C. Substrates and films were characterized using photoluminescence (PL) spectrum, x-ray diffraction, atomic force microscope, energy dispersive spectrum, and electric transport measurements. It has been found that the ZnO film properties were different when films were grown on the two polarity surfaces of ZnO substrates and the A1203 substrates. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite surface. The measurements of homoepitaxial ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth.

Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; George, M. A.

2000-01-01

204

Oriented single-crystal-to-single-crystal phase transition with dramatic changes in the dimensions of crystals.  

PubMed

We report here a new polymorph of cocrystal CuQ2-TCNQ that shows an oriented single-crystal-to-single-crystal phase transition along its a-axis at ambient conditions. Upon mechanical stimulation, it converts into another polymorph accompanied by almost doubling its length and halving its thickness. Our crystallographic studies indicate the dramatic changes in crystal dimensions resulted from the prominent changes of molecular stacking patterns. A reasonable mechanism for the phenomenon was proposed on the basis of the structural, microscopic, and thermal analysis. PMID:24372005

Liu, Guangfeng; Liu, Jie; Liu, Yang; Tao, Xutang

2014-01-15

205

Single crystal to single crystal polymerization of a columnar assembled diacetylene macrocycle  

NASA Astrophysics Data System (ADS)

Organic tubular materials have attracted lots of attentions for their potential applications as nanoscale fluidic transport systems, specific ion sensors, molecular sieves and confined molecular reaction containers. While conjugated polymers, due to delocalized Pi electrons, exhibit interesting solar cells and sensors applications. In this thesis, we developed a conjugated polymer which combines the attributes of conjugated polymers with tubular materials, which should have great potential to work as a sensing material. We reproduced and scaled-up the synthesis of a polymerizable macrocycle 1 that contains two rigidly separated diacetylene units. We found that, through hydrogen bonding, 1 can assemble into columnar crystals and can be polymerized under a single crystal to single crystal transformation process to afford porous polydiacetylene (PDA) crystals. We studied the assembly of the macrocycles 1 under different conditions to give three different crystalline forms and micro-phase crystals, and also investigated their subsequent polymerizations. The macrocycle assembly and polymerized materials were characterized by a variety of technique. Since the gas adsorption measurement exhibited PDA crystals still retained its porosity and the polymer should have ability to uptake suitable guest molecules, therefore the absorption of iodine for PDA crystals was investigated as well.

Xu, Weiwei

206

Roflumilast - A reversible single-crystal to single-crystal phase transition at 50 °C  

NASA Astrophysics Data System (ADS)

Roflumilast is a selective phosphodiesterase type 4 inhibitor and is marketed under the brand names Daxas®, Daliresp® and Libertec®. A phase transition of the drug substance roflumilast was observed at 50 °C. The low temperature form, the high temperature form and the phase transition were characterised by differential scanning calorimetry, variable temperature powder X-ray diffraction and single crystal X-ray diffraction, Raman spectroscopy and solid state NMR spectroscopy. The phase transition of roflumilast at 50 °C is completely reversible, the high temperature form cannot be stabilised by quench cooling and the phase transition does not influence the quality of the active pharmaceutical ingredient (API) and the drug product. It was observed to be a single crystal to single crystal phase transition.

Viertelhaus, Martin; Holst, Hans Christof; Volz, Jürgen; Hummel, Rolf-Peter

2013-01-01

207

Metallisation of single crystal diamond radiation detectors  

NASA Astrophysics Data System (ADS)

Properties such as a large band gap, high thermal conductivity and resistance to radiation damage make diamond an extremely attractive candidate for detectors in next generation particle physics experiments. This paper presents our technique for metallisation of a single crystal diamond grown by chemical vapour deposition (CVD) for use as a radiation detector, suitable for operation in places such as the Large Hadron Collider. The front and back side of the diamond are metalised with aluminium and gold on top of titanium respectively, after which the diamond is mounted and read out via a charge sensitive preamplifier. The device is found to collect charge at an efficiency of 97%.

Ong, Lucas; Ganesan, Kumaravelu; Alves, Andrew; Barberio, Elisabetta

2012-10-01

208

Fabrication of single-crystal diamond microcomponents  

SciTech Connect

We have combined a technique for the lift-off of thin diamond films from a bulk diamond with a technique for engraving diamond with a focused excimer laser to produce free-standing single-crystal diamond microstructures. One microcomponent that has been produced is a 12 tooth gear [similar to]400 [mu]m in diameter and [similar to]13 [mu]m thick. Other microstructures have also been demonstrated, showing the versatility of this method. This process should be applicable to producing diamond microcomponents down to spatial dimensions (width and thickness) of a few micrometers.

Hunn, J.D.; Withrow, S.P.; White, C.W.; Clausing, R.E.; Heatherly, L. (Oak Ridge National Laboratory, Bldg 5500 MS-6376, Oak Ridge, Tennessee 37831-6376 (United States)); Christensen, C.P. (Potomac Photonics, Lanham, Maryland 20705 (United States))

1994-12-12

209

High power single crystal piezoelectric transformer  

US Patent & Trademark Office Database

A piezoelectric transformer includes a single crystal relaxor ferroelectric element poled along a [0 11] direction and selected from the group consisting of PZN-PT, PMN-PZT, PZN-PT and PMN-PT. The element has two opposed surfaces substantially perpendicular to the [0 11] direction with an input electrode and an output electrode positioned on one surface. The output electrode is isolated from electrical communication with the input electrode. A ground electrode is positioned on the second, opposed surface. Input electrical energy results in piezoelectric change in the element that is mechanically coupled through the element to generate piezoelectric output energy.

2013-03-12

210

Conduction mechanism of single-crystal alumina  

NASA Technical Reports Server (NTRS)

The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

1992-01-01

211

Phase transition in sarcosine phosphite single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of sarcosine phosphite (SarcH3PO3) have been grown. The amino acid sarcosine is an isomer of the protein amino acid alanine. Both amino acids are described by the same chemical formula but have different structures; or, more specifically, in contrast to the alanine molecule, the sarcosine molecule has a symmetric structure. It has been found that the sarcosine phosphite compound undergoes a structural phase transition at a temperature of approximately 200 K. This result has demonstrated that compounds of achiral amino acids are more susceptible to structural phase transitions.

Lemanov, V. V.; Popov, S. N.; Pankova, G. A.

2011-06-01

212

Electrochemical Sc 2O 3 single crystal growth  

Microsoft Academic Search

Scandium oxide single crystals were successfully grown electrochemically by applying the Sc3+ ion-conducting Sc2(MoO4)3 solid electrolyte at 1223K. The single crystal growth can be regulated by the electrolysis condition, and the crystal size can be intentionally controlled by adjusting the electrolysis period. Although the single crystal growth of such refractory oxides as Sc2O3 is considerably difficult by the conventional thermal

Toshiyuki Masui; Young Woon Kim; Nobuhito Imanaka; Gin-ya Adachi

2004-01-01

213

Growth of Oxalic Acid Single Crystals from Solution: Solvent Effects on Crystal Habit  

Microsoft Academic Search

Single crystals of oxalic acid dihydrate are difficult to grow from pure water solution, but good single crystals of the material may be obtained by growth from mixtures of acetone and water. The solvent markedly affects the crystal habit. Crystals grown in mixtures of acetone and water develop the prismatic habit, while those grown in water alone develop the tabular

John L. Torgesen; John Strassburger

1964-01-01

214

Single-crystal fiber optics: a review  

NASA Astrophysics Data System (ADS)

Single-crystal (SC) fiber optics have been grown for many years for use as passive fibers for the delivery of IR laser radiation and as active fibers useful as minirod lasers. Most of the early work on SC fiber optics involved the growth of unclad sapphire fibers for the transmission of Er:YAG laser radiation at 2.94 ?m. More recently there has been a renewed interest in rare-earth (RE) doped oxide crystal fibers for use as high power fiber lasers. By analogy with RE doped-bulk laser crystals it is expected that pure YAG and other crystalline SC fibers should be capable of transmitting extremely high laser energies. SC oxide fibers have some distinct advantages over conventional glass fibers including higher thermal conductivity and low stimulated Brillouin scattering (SBS) gain coefficients. The latter can limit the ultimate power output of glass fiber lasers. To date most of the investigators have used the technique of Laser Heated Pedestal Growth (LHPG) to grow unclad SC fibers with diameters ranging from 30 to 350 ?m and in lengths as long as 5 m. The loss for SC sapphire fibers at 2.94 ?m has been measured as low as 0.3 dB/m. In this review we discuss the technique of LHPG, the various SC fiber optics that have been grown for both active and passive applications, and methods that may be used to clad the fibers.

Harrington, James A.

2014-02-01

215

Fabrication of crystals from single metal atoms  

PubMed Central

Metal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15?Å in diameter, within 1?h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium–osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms.

Barry, Nicolas P. E.; Pitto-Barry, Anais; Sanchez, Ana M.; Dove, Andrew P.; Procter, Richard J.; Soldevila-Barreda, Joan J.; Kirby, Nigel; Hands-Portman, Ian; Smith, Corinne J.; O'Reilly, Rachel K.; Beanland, Richard; Sadler, Peter J.

2014-01-01

216

Thermodynamic forces in single crystals with dislocations  

NASA Astrophysics Data System (ADS)

A simple model for the evolution of macroscopic dislocation regions in a single crystal is presented. This model relies on maximal dissipation principle within Kröner's geometric description of the dislocated crystal. Mathematical methods and tools from shape optimization theory provide equilibrium relations at the dislocation front, similarly to previous work achieved on damage modelling (J Comput Phys 33(16):5010-5044, 2011). The deformation state variable is the incompatible strain as related to the dislocation density tensor by a relation involving the Ricci curvature of the crystal underlying elastic metric. The time evolution of the model variables follows from a novel interpretation of the Einstein-Hilbert flow in terms of dislocation microstructure energy. This flow is interpreted as the dissipation of non-conservative dislocations, due to the climb mechanism, modelled by an average effect of mesoscopic dislocations moving normal to their glide planes by adding or removing points defects. The model equations are a fourth-order tensor parabolic equation involving the operator "incompatibility," here appearing as a tensorial counterpart of the scalar Laplacian. This work encompasses and generalizes results previously announced (C R Acad Sci Paris Ser I 349:923-927, 2011), with in addition a series of physical interpretations to give a meaning to the newly introduced concepts.

Van Goethem, Nicolas

2014-06-01

217

Fabrication of crystals from single metal atoms.  

PubMed

Metal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15?Å in diameter, within 1?h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium-osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms. PMID:24861089

Barry, Nicolas P E; Pitto-Barry, Anaïs; Sanchez, Ana M; Dove, Andrew P; Procter, Richard J; Soldevila-Barreda, Joan J; Kirby, Nigel; Hands-Portman, Ian; Smith, Corinne J; O'Reilly, Rachel K; Beanland, Richard; Sadler, Peter J

2014-01-01

218

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation  

NASA Astrophysics Data System (ADS)

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation were constructed with ohmic and Schottky contact characteristics. Localized UV irradiation at the third leg of the tetrapod was monitored by measuring the sensor's current response. Measurements of I-V performances and time-resolved current were conducted. The results demonstrate that localized UV irradiation can be detected in real time as electrical transport properties can be modulated by localized UV irradiation, and the higher the UV light power density gets, the larger the current response becomes, which is observed to be completely repeatable and reversible. Additionally, Schottky-contact type sensors clearly show a greater current response than ohmic-contact-type sensors, which further proved that Schottky-contact-type sensors are a better choice for detection in an irradiation environment. Two possible explanations are given for the phenomenon, including an electron transfer effect and a surface/interface effect on the band structure. The as-constructed sensors exhibit different sensitivities towards irradiation with various power densities, indicating that ZnO nanotetrapod-based sensors can be a promising candidate for detection in many areas including electron irradiation detection, ultraviolet irradiation monitoring, strain sensing, and complicated microenvironment observations such as biological cell inspection.

Wang, Wenhua; Qi, Junjie; Wang, Qinyu; Huang, Yunhua; Liao, Qingliang; Zhang, Yue

2013-06-01

219

Growth and field-emission properties of single-crystalline conic ZnO nanotubes  

NASA Astrophysics Data System (ADS)

Single-crystalline conic ZnO nanotubes were synthesized on Si(001) without catalysts by thermal chemical vapour deposition at 475 °C. The nanotubes grown along the ZnO [0001] direction are sharp open-ended tips consisting of planar defects revealed by transmission electron microscopy and scanning electron microscopy. The nanotubes were formed by self-assembly of numerous six-radiated branches of hexagram nanosheets. The diameters and the wall thicknesses of the nanotubes are in the ranges 30-100 and 15-30 nm, respectively. The lengths and areal densities of the nanotubes are around 0.5 µm and 1-9 × 108 cm-2, respectively. Field-emission measurements on the conic nanotubes show a low turn-on field of 3.5 V µm-1 at 10 µA cm-2. The field-emission properties related to the nanotube density and geometry and the nonlinearity in the Fowler-Nordheim (FN) plot at lower field region are discussed.

Wang, Ruey-Chi; Liu, Chuan-Pu; Huang, Jow-Lay; Chen, Shu-Jen

2006-02-01

220

Constitutive modeling for single crystal superalloys  

NASA Technical Reports Server (NTRS)

The inelastic response of single crystal gamma/gamma prime superalloys is quite different from the behavior of polycrystalline nickel base superalloys. Upto a critical temperature the yield stress of single crystal alloys is a function of the material orientation relative to the direction of the applied stress and the material exhibits significant tension/compression asymmetry. This behavior is primarily due to slip on the octahedral slip system. Above the critical temperature there is a sharp drop in the yield stress, cube slip becomes more predominant and the tension/compression asymmetry is reduced. Similar orientation and tension/compression asymmetry is observed in creep and secondary creep above the critical temperature is inferred to occur by octahedral slip. There are two exceptions to this behavior. First, loading near the (111) orientation exhibits cube slip at all temperatures, and; second, loading near the (001) orientation produces only octahedral slip at all temperatures. The constitutive model is based on separating the total global strain into elastic and inelastic components. This model is developed and briefly discussed.

Stouffer, D. C.; Jayaraman, N.; Sheh, M.; Alden, D.

1986-01-01

221

Crystal synthesis and effects of epitaxial perovskite manganite underlayer conditions on characteristics of ZnO nanostructured heterostructures.  

PubMed

This study presents the synthesis of high-density aligned wurtzite ZnO nanostructures using thermal evaporation on perovskite (La,Sr)MnO3(LSMO) epitaxy to form a heterostructure without the assistance of metallic catalysis. LSMO epitaxial films are RF-sputtered with various crystal qualities to examine the correlation between the interface and electrical characteristics of the heterostructures. The ZnO nanostructures-LSMO epitaxial heterostructures show electrical rectifying behavior without inserting an ultrathin insulating layer at the hetero-interface. Misfit strain, intrinsic strain, and crystal defects are major factors in causing a phase separation in the as-prepared manganite LSMO epitaxial films. The coexistence of a charge-ordered insulating domain and a ferromagnetic metallic domain causes inhomogeneous electrical contact at the ZnO-LSMO heterointerfaces, further deteriorating the junction characteristics. A high-temperature annealing procedure and moderate LSMO epitaxy film thickness are required for the construction of an efficient ZnO nanostructures-LSMO epitaxy junction. PMID:23392563

Liang, Yuan-Chang; Hu, Chia-Yen; Zhong, Hua; Wang, Jyh-Liang

2013-03-21

222

Liquid Crystal-ZnO Nanoparticle Potential Photovoltaics: Role of LC Order and ZnO Particle Size and Concentration  

NASA Astrophysics Data System (ADS)

We investigate the role order plays in the transfer of charges in ZnO nanoparticle - 8CB liquid crystal system for photovoltaic applications as well as the role the nominally 5x7nm^2 ZnO nanoparticles play in improving that order. Our results for the 5nm nanoparticles show an improvement in the alignment of the liquid crystal with increasing weight percentage of ZnO nanoparticles, up to a concentration of 30% wt for the 5nm particles accompanied by an increase by three orders of magnitude in the current generated.ootnotetextL. J. Mart'inez-Miranda, Kaitlin M. Traister, Iriselies Mel'endez-Rodr'iguez, and Lourdes Salamanca-Riba, Appl. Phys. Letts, 97, in press (2010). Our results for the 5 x 7 nm^2 sample show that the current is larger than the current obtained for the 5 nm samples. The photocurrent can be expressed as the conductivity as a function dependent in the order in the sample times the portion of the electric field that is absorbed and transformed into the current.

Martinez-Miranda, Luz J.; Branch, Janelle; Thompson, Robert; Taylor, Jefferson W.; Salamanca-Riba, Lourdes

2011-03-01

223

ZnO nanodisk based UV detectors with printed electrodes.  

PubMed

The fabrication of highly functional materials for practical devices requires a deep understanding of the association between morphological and structural properties and applications. A controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks, nanorings, and nanoroses using a mixed solution of zinc sulfate (ZnSO4) and hexamethylenetetramine (HMTA) without the need of catalysts, substrates, or templates at low temperature (75 °C) is introduced. Metal-semiconductor-metal (MSM) ultraviolet (UV) detectors were fabricated based on individual and multiple single-crystal zinc oxide (ZnO) hexagonal nanodisks. High quality single crystal individual nanodisk devices were fabricated with inkjet-printed silver electrodes. The detectors fabricated show record photoresponsivity (3300 A/W) and external quantum efficiency (1.2 × 10(4)), which we attribute to the absence of grain boundaries in the single crystal ZnO nanodisk and the polarity of its exposed surface. PMID:24611747

Alenezi, Mohammad R; Alshammari, Abdullah S; Alzanki, Talal H; Jarowski, Peter; Henley, Simon John; Silva, S Ravi P

2014-04-01

224

Structural analysis of vertically-aligned single crystalline ZnO nanorods grown on different seed layers with chemical solution deposition.  

PubMed

We report the structural properties of the vertically-oriented ZnO nanorods fabricated on various ZnO seed layers with chemical solution deposition (CSD) technique. The ZnO nanorods were prepared using an aqueous solution with Zinc nitrate (Zn(NO3)2 x 6H2O, Aldrich) and hexamethylenetetramine (HMT, Aldrich) in a convection oven. A-plane sapphire substrates with a deposited ZnO thin film were placed upside down in a quartz holder to avoid any micro-crystalline contamination. Especially, our hydro-thermal syntheses are automatically processed on precision pump drive systems (Masterflex) to accurately control the pH of the aqueous solution. The [002] crystal orientation of the ZnO seed layer was observed by the X-ray diffraction pattern. Structural features of ZnO nanorods were systematically analyzed by scanning electron microscopy and tunneling electron microscopy, together with selective area electron diffraction patterns. Experimental observations clearly demonstrated the dependence of the growth direction of the ZnO nanorods on the crystal structures of the ZnO seed layers. PMID:22966704

Ko, Wonbae; Lee, Sang Hyo; Lee, Jun Seok; Hong, Jin Pyo

2012-07-01

225

Pulse shape discrimination with new single crystal organic scintillators  

Microsoft Academic Search

Pulse shape discrimination in organic single crystal and liquid scintillators provides a means of identifying fission energy neutrons with high specificity. We present the results of a broad survey of over one hundred single crystal organic scintillators produced from low-temperature solution growth technique. Each crystal was evaluated for light yield and pulse shape discrimination performance. The pulse shape dependence on

Jason Newby; Natalia Zaitseva; Stephen Payne; Nerine Cherepy; Leslie Carman; Giulia Hull

2009-01-01

226

Growth of strontium tartrate tetrahydrate single crystals in silica gels  

Microsoft Academic Search

Growth of single crystals of strontium tartrate tetrahydrate by controlled diffusion in silica gels has been narrated. In the field of material science, there is always a keen and competitive race to grow perfect single crystals with sufficient purity and perfection. Successful attempts to larger as well as more perfect crystals of SrTr are described in this paper and thus

A. R. Patel; S. K. Arora

1976-01-01

227

Single crystal alumina for dental implants and bone screws.  

PubMed

When ground to a suitable form, flexural strength of single crystal alumina (Al2O3) decreases to as low as one third the strength of the intact crystal. This flexural strength decrease is, however, recovered by chemical etching at a high temperature to eliminate surface defects caused by grinding. By using this strength recovery treatment, various types of single crystal implants with fine structure were able to be designed. Four kinds of single crystal bone screws and single crystal dental implants of screw and anchor type were designed. Flexural strength and impact strength of the implants were measured. PMID:7349666

Kawahara, H; Hirabayashi, M; Shikita, T

1980-09-01

228

Zinc self-diffusion, electrical properties, and defect structure of undoped, single crystal zinc oxide  

SciTech Connect

Zinc self-diffusion was measured in single crystal zinc oxide using nonradioactive {sup 70}Zn as the tracer isotope and secondary ion mass spectrometry for data collection. Crystal mass was closely monitored to measure ZnO evaporation. Diffusion coefficients were isotropic with an activation energy of 372 kJ/mol. Zinc self-diffusion is most likely controlled by a vacancy mechanism. Electrical property measurements exhibit a plateau in conductivity at intermediate pO{sub 2} with an increase in reducing atmospheres. An analysis of the defect structure is presented that indicates that oxygen vacancies are probably the intrinsic ionic defects responsible for n-type conductivity in reducing atmospheres. (c) 2000 American Institute of Physics.

Tomlins, Gregory W. [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Routbort, Jules L. [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Energy Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Mason, Thomas O. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)] [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

2000-01-01

229

Co doped ZnO(0001)Zn by diffusion method and its magnetic properties  

Microsoft Academic Search

The diffusion behaviors of Co clusters on clean ZnO(0001)-Zn single crystal surface and their magnetic properties are studied. Co clusters are deposited on the clean ZnO(0001)-Zn surface at room temperature and then undergone ultrahigh vacuum annealing until fully reconstructed. The replacement of Zn2+ by Co2+ is confirmed by scanning tunneling microscopy and x-ray photoelectron spectroscopy. The Co doped ZnO shows

W. G. Xie; F. Y. Xie; X. L. Yu; K. Xue; J. B. Xu; J. Chen; R. Zhang

2009-01-01

230

Solar cell structure incorporating a novel single crystal silicon material  

DOEpatents

A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

Pankove, Jacques I. (Princeton, NJ); Wu, Chung P. (Trenton, NJ)

1983-01-01

231

Mode Gruneisen Parameters for Single Crystal Al2O3.  

National Technical Information Service (NTIS)

Single crystal Al2O3 (sapphire or corundum), crystallizes in the trigonal lattice, point group 3m. Its thermodynamic properties have been extensively investigated over the last years. As the pressure derivatives of its elastic moduli have recently become ...

D. Gerlich

1969-01-01

232

Hydrogen Annealing Of Single-Crystal Superalloys  

NASA Technical Reports Server (NTRS)

Annealing at temperature equal to or greater than 2,200 degrees F in atmosphere of hydrogen found to increase ability of single-crystal superalloys to resist oxidation when subsequently exposed to oxidizing atmospheres at temperatures almost as high. Supperalloys in question are principal constituents of hot-stage airfoils (blades) in aircraft and ground-based turbine engines; also used in other high-temperature applications like chemical-processing plants, coal-gasification plants, petrochemical refineries, and boilers. Hydrogen anneal provides resistance to oxidation without decreasing fatigue strength and without need for coating or reactive sulfur-gettering constituents. In comparison with coating, hydrogen annealing costs less. Benefits extend to stainless steels, nickel/chromium, and nickel-base alloys, subject to same scale-adhesion and oxidation-resistance considerations, except that scale is chromia instead of alumina.

Smialek, James L.; Schaeffer, John C.; Murphy, Wendy

1995-01-01

233

Magnetoplasticity and diffusion in silicon single crystals  

SciTech Connect

The effect of static magnetic fields on the dynamics of surface dislocation segments, as well as the diffusion mobility of a dopant in silicon single crystals, has been analyzed. It has been experimentally found that the preliminary treatment of p-type silicon plates (the dopant is boron with a concentration of 10{sup 16} cm{sup -3}) in the static magnetic field (B = 1 T, a treatment time of 30 min) leads to an increase in the mobility of surface dislocation segments. The characteristic times of observed changes (about 80 h) and the threshold dopant concentration (10{sub 15} cm{sup -3}) below which the magneto-optical effect in silicon is not fixed have been determined. It has been found that diffusion processes in dislocation-free silicon are magnetically sensitive: the phosphorus diffusion depth in p-type silicon that is preliminarily aged in the static magnetic field increases (by approximately 20%) compared to the reference samples.

Skvortsov, A. A., E-mail: SkvortsovAA2009@yandex.ru; Karizin, A. V. [Moscow State Technical University 'MAMI' (Russian Federation)

2012-01-15

234

Constitutive modeling for single crystal superalloys  

NASA Technical Reports Server (NTRS)

A crystallographic approach to constitutive modeling of single crystal superalloys is discussed. The approach is based on identifying the active slip planes and slip directions. The shear stresses are computed on each of the slip planes from applied stress components. The slip rate is then computed on each slip system and the microscopic inelastic strain rates are the sum of the slip in the individual slip systems. The constitutive model was implemented in a finite element code using twenty noted isoparametric solid elements. Constants were determined for octahedral and cube slip systems. These constants were then used to predict tension-compression asymmetry and fatigue loops. Other data was used to model the tensile and creep response.

Stouffer, Donald C.; Dame, L. Thomas; Jayaraman, N.

1985-01-01

235

Structural and optical properties of ZnO thin films by rf magnetron sputtering with rapid thermal annealing  

SciTech Connect

Epitaxial ZnO thin films were grown on c-plane sapphire substrates by rf magnetron sputtering at room temperature followed by a rapid thermal annealing process. We found that crystallinity of the films was strongly affected by the partial oxygen pressure during deposition. Both x-ray diffraction and transmission electron microscopy studies revealed that the ZnO films grow epitaxially predominantly with aligned ZnO domains. An unresolved excitonic resonance was observed in the optical absorption spectrum. Nevertheless, refractive index and absorption edge of the ZnO films are similar to that of single crystal ZnO.

Suvorova, N. A.; Usov, I. O.; Stan, L.; DePaula, R. F.; Dattelbaum, A. M.; Jia, Q. X. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Suvorova, A. A. [Centre for Microscopy, Characterization and Analysis, University of Western Australia, Crawley, 6009 Western Australia (Australia)

2008-04-07

236

TOPICAL REVIEW: Organic field-effect transistors using single crystals  

Microsoft Academic Search

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of

Tatsuo Hasegawa; Jun Takeya

2009-01-01

237

Effect of Thermal Annealing on the Characteristics of Phosphorus-Implanted ZnO Crystals  

NASA Astrophysics Data System (ADS)

A P-doped ZnO surface layer on undoped ZnO wafers was prepared by phosphorus (P) ion implantation. Hall effect measurement revealed p-type conduction in such layers annealed at 800°C. This indicates that acceptor levels are present in P-doped ZnO, even though the ZnO is still n-type. Micro-Raman scattering in -z(xy)z geometry was conducted on P-implanted ZnO. The E {2/high} mode shift observed toward the high-energy region was related to compressive stress as a result of P-ion implantation. This compressive stress led to the appearance of an A 1(LO) peak, which is an inactive mode. This A 1(LO) peak relaxed during thermal annealing in ambient oxygen at temperatures higher than 700°C. The P2p3/2 peak observed at 135.6 eV by x-ray photoelectron spectroscopy is associated with chemical bond formation leading to 2(P2O5) molecules. This indicates that implanted P ions substituted Zn sites in the ZnO layer. In photoluminescence spectroscopy, the P-related peaks observed at energies ranging between 3.1 and 3.5 eV originated from (A0, X) emission, because of PZn-2VZn complexes acting as shallow acceptors. The acceptor level was observed to be 126.9 meV above the valence band edge. Observation of this P-related emission indicates that ion implantation results in acceptor levels in the P-doped ZnO layer. This suggests that the P2O5 bonds are responsible for the p-type activity of P-implanted ZnO.

Jeong, T. S.; Yu, J. H.; Mo, H. S.; Kim, T. S.; Lim, K. Y.; Youn, C. J.; Hong, K. J.; Kim, H. S.

2014-04-01

238

Effect of Thermal Annealing on the Characteristics of Phosphorus-Implanted ZnO Crystals  

NASA Astrophysics Data System (ADS)

A P-doped ZnO surface layer on undoped ZnO wafers was prepared by phosphorus (P) ion implantation. Hall effect measurement revealed p-type conduction in such layers annealed at 800°C. This indicates that acceptor levels are present in P-doped ZnO, even though the ZnO is still n-type. Micro-Raman scattering in - z( xy) z geometry was conducted on P-implanted ZnO. The E {2/high} mode shift observed toward the high-energy region was related to compressive stress as a result of P-ion implantation. This compressive stress led to the appearance of an A 1(LO) peak, which is an inactive mode. This A 1(LO) peak relaxed during thermal annealing in ambient oxygen at temperatures higher than 700°C. The P2p3/2 peak observed at 135.6 eV by x-ray photoelectron spectroscopy is associated with chemical bond formation leading to 2(P2O5) molecules. This indicates that implanted P ions substituted Zn sites in the ZnO layer. In photoluminescence spectroscopy, the P-related peaks observed at energies ranging between 3.1 and 3.5 eV originated from (A0, X) emission, because of PZn-2VZn complexes acting as shallow acceptors. The acceptor level was observed to be 126.9 meV above the valence band edge. Observation of this P-related emission indicates that ion implantation results in acceptor levels in the P-doped ZnO layer. This suggests that the P2O5 bonds are responsible for the p-type activity of P-implanted ZnO.

Jeong, T. S.; Yu, J. H.; Mo, H. S.; Kim, T. S.; Lim, K. Y.; Youn, C. J.; Hong, K. J.; Kim, H. S.

2014-07-01

239

Ultratough CVD single crystal diamond and three dimensional growth thereof  

DOEpatents

The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

Hemley, Russell J. (Washington, DC) [Washington, DC; Mao, Ho-kwang (Washington, DC) [Washington, DC; Yan, Chih-shiue (Washington, DC) [Washington, DC

2009-09-29

240

Characterization of the single and double films consisting of Al, Sc-co-doped ZnO\\/Al-doped ZnO and Al-doped ZnO\\/Al, Sc-co-doped ZnO  

Microsoft Academic Search

Single and double films consisting of Al, Sc-co-doped ZnO (denoted as S) and Al-doped ZnO (denoted as A) layers were deposited on the Super Twisted Nematic (STN) glass by dc-sputtering on the pure aluminum (99.999%) or Al-0.8 wt.% Sc eutectic alloy target (99.999%) combined with rf-sputtering on the pure zinc oxide (99.99%). The thickness of each layer in the double film

Kun-Cheng Peng; Jing-Chie Lin; C. A. Tseng; Sheng-Long Lee

2008-01-01

241

Formation of curved micrometer-sized single crystals.  

PubMed

Crystals in nature often demonstrate curved morphologies rather than classical faceted surfaces. Inspired by biogenic curved single crystals, we demonstrate that gold single crystals exhibiting curved surfaces can be grown with no need of any fabrication steps. These single crystals grow from the confined volume of a droplet of a eutectic composition melt that forms via the dewetting of nanometric thin films. We can control their curvature by controlling the environment in which the process is carried out, including several parameters, such as the contact angle and the curvature of the drops, by changing the surface tension of the liquid drop during crystal growth. Here we present an energetic model that explains this phenomenon and predicts why and under what conditions crystals will be forced to grow with the curvature of the microdroplet even though the energetic state of a curved single crystal is very high. PMID:24694217

Koifman Khristosov, Maria; Kabalah-Amitai, Lee; Burghammer, Manfred; Katsman, Alex; Pokroy, Boaz

2014-05-27

242

Investigation of single crystal silicates for blue tunable lasers  

NASA Astrophysics Data System (ADS)

The single crystal growth of rare earth silicates was investigated for the purpose of tunable laser hosts. Silicates of the type R2SiO5, where R = La, Gd, Y, Lu, were prepared from stoichiometric melts and doped with Ce(3+) activators. Seed crystals were obtained from crystallized melt sections or by growth on an iridium wire. These seeds were utilized in standard Czochralski type growth to obtain larger single crystals. Cathodoluminescence experiments on both powders and single crystals showed wavelength shifts with different rare earth ions. The Gd, Y, and mixed crystals of Gd-Y silicates gave good bright emission with Ce(3+). The emission is broad band and covers the wavelength range of 370 to 525 nm. The peak emission can be centered near 450 to 460 nm by other compositions. Larger single crystals for laser hosts are under development.

Belt, R. F.; Catalano, J. A.

1986-01-01

243

Reversible single-crystal-to-single-crystal photochemical formation and thermal cleavage of a cyclobutane ring.  

PubMed

A [2+2] cycloaddition reaction has been observed in a number of solids. The cyclobutane ring in a photodimerized material can be cleaved into olefins by UV light and heat. The high thermal stability of the metal-organic salt K2SDC (H2SDC = 4,4'-stilbenedicarboxylic acid) has been successfully utilized to investigate the reversible cleavage of a cyclobutane ring. The two polymorphs of K2SDC undergo reversible cyclobutane formation by UV light and cleavage by heat in cycles. Of these, one polymorph retains its single-crystal nature during the reversible processes. Polymorphs are known to show different physical properties and chemical reactivities. This work reveals that the retention of single-crystal nature is strongly associated with the packing of molecules, which is controlled by kinetics and thermodynamics. The photoemissive nature of the products makes this as a promising material for photoswitches and optical data storage devices. PMID:24459072

Kole, Goutam Kumar; Kojima, Tatsuhiro; Kawano, Masaki; Vittal, Jagadese J

2014-02-17

244

Growth of benzophenone single crystals from solution: A novel approach with 100% solute - crystal conversion efficiency  

Microsoft Academic Search

An unidirectional 60mm diameter benzophenone single crystal was successfully grown by utilizing a novel crystal growth method at room temperature. <110> oriented single crystal ingots were grown out of xylene as solvent and by fixing a seed at the bottom of the ampoule. The obtained benzophenone ingots with the sizes of 10mm, 25mm and 60mm diameter evident that ease in

K. Sankaranarayanan; P. Ramasamy

2006-01-01

245

Growth of Homoepitaxial ZnO Semiconducting Films  

NASA Technical Reports Server (NTRS)

As a high temperature semiconductor, ZnO has been used for many applications such as wave-guide, solar cells, and surface acoustic wave devices. Since the ZnO material has an energy gap of 3.3 eV at room temperature and an excitonic binding energy (60 meV) that is possible to make excitonic lasering at room temperature a recent surge of interest is to synthesize ZnO films for electro-optical devices. These applications require films with a smooth surface, good crystal quality, and low defect density. Homoepitaxial films have been studied in terms of morphology, crystal structure, and electrical and optical properties. ZnO single crystals are grown by the hydrothermal method. Substrates are mechanically polished and annealed in air for four hours before deposited films. The annealing temperature-dependence of ZnO substrates is studied. Films are synthesized by the off-axis reactive sputtering deposition. The films have very smooth surface with a roughness crystal substrate. The film quality is determined by measuring the film resistivity, the Hall mobility, carrier densities and the energy band gap. The properties of ZnO films grown of (0001) ZnO and (0001) sapphire substrates will be also compared and discussed in the presentation.

Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Harris, M. T.; George, Michael A.; McCarty, P.

1999-01-01

246

Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals  

DOEpatents

A method of fabricating bulk YBa.sub.2 Cu.sub.3 O.sub.x where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa.sub.2 Cu.sub.3 O.sub.x are heated in the presence of a Nd.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y seed crystal to a temperature sufficient to form a liquid phase in the YBa.sub.2 Cu.sub.3 O.sub.x while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa.sub.2 Cu.sub.3 O.sub.x material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material.

Todt, Volker (Lemont, IL); Miller, Dean J. (Darien, IL); Shi, Donglu (Oak Park, OH); Sengupta, Suvankar (Columbus, OH)

1998-01-01

247

Amorphouslike Density of Gap States in Single-Crystal Pentacene  

Microsoft Academic Search

We show that optical and electrical measurements on pentacene single crystals can be used to extract the density of states in the highest occupied molecular orbital lowest unoccupied molecular orbital band gap. It is found that these highly purified crystals possess band tails broader than those typically observed in inorganic amorphous solids. Results on field-effect transistors fabricated from similar crystals

Arthur Ramirez; David Lang; Xiaoliu Chi; Theo Siegrist; Mike Sergent

2004-01-01

248

Structural, optical and electrical properties of ZnO films grown on c-plane sapphire and (1 0 0) ?-LiAlO 2 by pulse laser deposition  

Microsoft Academic Search

ZnO thin films were grown on single-crystal ?-LiAlO2 (LAO) and sapphire (0001) substrate by pulsed laser deposition (PLD). The structural, optical and electrical properties of ZnO films were investigated. The results show that LAO is more suitable for fabricating ZnO films than sapphire substrate and the highest-quality ZnO film was attained on LAO at the substrate temperature of 550°C. However,

Jun Zou; Shengming Zhou; Changtai Xia; Yin Hang; Jun Xu; Shulin Gu; Rong Zhang

2005-01-01

249

Microscale Laser Peen Forming of Single Crystal  

SciTech Connect

As the result of quickly increased requirement in many industrial products resulting from microtechnology, laser thermal microforming and microsurface treatment [microscale laser shock peening (?LSP)] have been well studied. By combining the beneficial effects of these two processes with a controlled bending deformation, microscale laser peen forming (?LPF) attracts more attention recently since it not only improves the fatigue life of the material but also shapes microscale metallic parts at the same time. In the present study, ?LSP of single crystal aluminum was presented to study anisotropic material response. Local plastic deformation was characterized by lattice rotation measured through electron backscatter diffraction. Residual stress distributions of both sides of a peened sample, characterized by x-ray microdiffraction, were compared with the results obtained from finite element method simulation. ?LPF anisotropic behavior was investigated in three effective slip systems via both the anisotropic slip line theory and numerical method. Also, the work hardening effect resulted from self-hardening, and latent hardening was analyzed through comparing the results with and without considering hardening.

Wang,Y.; Fan, Y.; Kysar, J.; Vukelic, S.; Yao, Y.

2008-01-01

250

Q-1 of forsterite single crystals  

NASA Astrophysics Data System (ADS)

Internal friction ( Q-1) experiments have been performed on synthetic forsterite single crystals in order to investigate the role of temperature, frequency and dislocation density on the Q-1 factor. Data have been obtained for both deformed and undeformed specimens over a frequency range from 10 to 10 -4 Hz at 15, 1000, 1200 and 1400°C. Measurements were done using a torsional pendulum operating in forced oscillations on specimens with dimensions of 20 mm × 5 mm × 1 mm. Samples were maintained in vacuum. Stress amplitudes were 0.1 MPa and strains 10 -6-10 -5. Pre-deformation experiments were creep tests performed at 1600°C and 20 MPa. The amount of strain was 10 -2. Dislocation microstructures were investigated by transmission electron microscopy. At room temperature, undeformed samples show low attenuation with no frequency dependence. At high temperature (1400°C), Q-1 increases up to 5 × 10 -2 for very low frequencies (10 -4 Hz). Deformed specimens show the same trend but there is a more pronounced increase in Q-1 with both frequency and temperature ( Q-1 = 2 × 10 -1, 10 -4 Hz at 1400°C). This high-temperature attenuation is the result of dislocation processes which are probably non-linear in the strain range explored by the present experiments ( ? > 10 -6). Non-linearity appears to be the best explanation for the disagreement between high Q-1 data reported in laboratory and low Q 1 data reported for the upper mantle.

Gueguen, Y.; Darot, M.; Mazot, P.; Woirgard, J.

1989-06-01

251

Preparation and morphology of pyramidal MFI single-crystal segments.  

PubMed

Single-crystal segments of tetra-n-propylammonium-templated Silicalite-1 and ZSM-5 were prepared by postsynthetic treatment of twinned MFI prisms. Microwave irradiation of the parent crystallites in alkaline solution containing hydrogen peroxide, followed by ultrasound treatment, led to disintegration of the zeolite prisms. The resulting wedge-shaped crystal segments proved to be single crystals of excellent crystallinity as shown by optical and X-ray investigations. The hydroxyl ions, compensating the positive charges of the tetrapropylammonium cations, were located by single-crystal structure refinement in template-containing Silicalite-1 and ZSM-5 but absent from the calcined samples. PMID:17988115

Schmidt, Wolfgang; Wilczok, Ursula; Weidenthaler, Claudia; Medenbach, Olaf; Goddard, Richard; Buth, Gernot; Cepak, Alexander

2007-12-01

252

Fabrication of polypyrrole nano-arrays in lysozyme single crystals  

NASA Astrophysics Data System (ADS)

A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals.A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals. Electronic supplementary information (ESI) available: Optical microscopy, SEM, TEM images, FTIR spectra and tables, conductivity plot. Experimental methods. See DOI: 10.1039/c2nr32413j

England, Matt W.; Lambert, Elizabeth M.; Li, Mei; Turyanska, Lyudmila; Patil, Avinash J.; Mann, Stephen

2012-10-01

253

Shear localization in dynamic deformation of copper single crystals  

Microsoft Academic Search

Dynamic deformation of copper single crystals, especially of fatigued copper single crystals with different orientations, was conducted on a split-Hopkinson pressure bar apparatus. The strain rates were in the range 2 - 9 × 103 s-1. After dynamic deformation, the adiabatic shear bands (ASBs) were examined in a light microscope and SEM. The width and spacing of ASBs formed under

S. X. Li; R. Q. Yang; J. W. Li; Z. F. Zhang

2006-01-01

254

Coefficients of thermal expansion for single crystal piezoelectric fiber composites  

Microsoft Academic Search

Piezoelectric fiber composites were developed to overcome drawbacks of typical monolithic piezoceramic (PZT) actuators. Although piezoelectric fiber composites had many improvements over the monolithic PZT, there are still improvements. Thus, the single crystal piezoelectric fiber composite actuator is proposed. Single crystal piezoelectric materials such as PMN-PT have larger piezoelectric strain constants, higher bandwidth and higher energy density than polycrystalline counterparts.

Jae-Sang Park; Ji-Hwan Kim

2007-01-01

255

Field Emission from Tungsten and Thoriated Tungsten Single Crystals  

Microsoft Academic Search

A reproducible time sequence of different pattern types has been found to appear in electron projector images of field emission from tungsten single crystals when the crystals are kept at temperatures above 1100°K. These pattern types, some of which have been observed before and attributed to migrations of surface tungsten atoms, can best be explained (with a single possible exception)

J. H. Daniel

1942-01-01

256

A Multivariant model for single crystal shape memory alloy behavior  

Microsoft Academic Search

A general 3-D multivariant model based on thermodynamics and micromechanics for single crystal shape memory alloy (SMA) behavior is presented. This model is based on the habit plane and transformation directions for the variants of martensite in a given material. From this information, the single crystal behavior of the material to temperature and mechanical loads is derived using the concept

Miinshiou Huang; L. C. Brinson

1998-01-01

257

Growth and Structure of Single-Crystal Films.  

National Technical Information Service (NTIS)

This research project was concerned with basic research on the growth and structure of single-crystal films of metals obtained by evaporation in ultra-high vaccum onto two types of substrates: mica and metal single-crystal films. The films were prepared i...

E. Grunbaum

1968-01-01

258

Preparation Techniques for Growth of Single Crystals of Nonmetallic Materials.  

National Technical Information Service (NTIS)

The report describes two techniques for growth of highpurity single crystals of nonmetallic materials using r-f induction-heating equipment in a frequency range of 5 to 100 Mc. One technique used for single-crystal growth was the Verneuil method using an ...

E. M. Clausen J. W. Rutter

1964-01-01

259

A Single Crystal Niobium RF Cavity of the TESLA Shape  

Microsoft Academic Search

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material

W. Singer; X. Singer; P. Kneisel

2007-01-01

260

A Quick Method for Determining the Density of Single Crystals.  

ERIC Educational Resources Information Center

Shows how the Archimedes method is used to determine the density of a single crystal of ammonium oxalate monohydrate. Also shows how to calculate the density of other chemicals when they are available as single crystals. Experimental procedures and materials needed are included. (JN)

Roman, Pascual; Gutierrez-Zorrilla, Juan M.

1985-01-01

261

Thermally induced single crystal to single crystal transformation leading to polymorphism  

NASA Astrophysics Data System (ADS)

The robust complex [La(1,10-phen)2(NO3)3] (1,10-phen = 1,10-phenanthroline) exhibits thermally induced single crystal to single crystal transformation from one polymorphic phase to another. The complex crystallizes in monoclinic C2/c space group with C2 molecular symmetry at 293 K while at 100 K it shows P21/c space group with C1 molecular symmetry. Supramolecular investigation shows that at 100 K the complex forms 2D achiral sheets whereas at 293 K forms two different homochiral 2D sheets. Low temperature DSC analysis indicates that this structural transformation occurs at 246 K and also this transformation is reversible in nature. We have shown that thermally induced coherent movement of ligands changes the molecular symmetry of the complex and leads to polymorphism. Photoluminescence property of complex has been studied in both solid state and in methanolic solution at room temperature. The effect of the presence low-lying LUMO orbital of ?-character in the complex is elucidated by theoretical calculation using DFT method.

Saha, Rajat; Biswas, Susobhan; Dey, Sanjoy Kumar; Sen, Arijit; Roy, Madhusudan; Steele, Ian M.; Dey, Kamalendu; Ghosh, Ashutosh; Kumar, Sanjay

2014-09-01

262

Thermally induced single crystal to single crystal transformation leading to polymorphism.  

PubMed

The robust complex [La(1,10-phen)2(NO3)3] (1,10-phen=1,10-phenanthroline) exhibits thermally induced single crystal to single crystal transformation from one polymorphic phase to another. The complex crystallizes in monoclinic C2/c space group with C2 molecular symmetry at 293K while at 100K it shows P21/c space group with C1 molecular symmetry. Supramolecular investigation shows that at 100K the complex forms 2D achiral sheets whereas at 293K forms two different homochiral 2D sheets. Low temperature DSC analysis indicates that this structural transformation occurs at 246K and also this transformation is reversible in nature. We have shown that thermally induced coherent movement of ligands changes the molecular symmetry of the complex and leads to polymorphism. Photoluminescence property of complex has been studied in both solid state and in methanolic solution at room temperature. The effect of the presence low-lying LUMO orbital of ?-character in the complex is elucidated by theoretical calculation using DFT method. PMID:24813281

Saha, Rajat; Biswas, Susobhan; Dey, Sanjoy Kumar; Sen, Arijit; Roy, Madhusudan; Steele, Ian M; Dey, Kamalendu; Ghosh, Ashutosh; Kumar, Sanjay

2014-09-15

263

Structural and spectroscopic studies on calcium succinate single crystals  

NASA Astrophysics Data System (ADS)

Calcium succinate crystals have been grown by gel aided solution growth technique. The structure of the crystal is solved by single crystal XRD analysis. The Crystal structure of the title compound is triclinic having space group P(1) Powder XRD studies confirmed the good crystalline nature of the sample. The different functional groups and their assigned vibrations are discussed by FT-IR and FT Raman spectroscopic studies.

Binitha, M. P.; Pradyumnan, P. P.

2014-04-01

264

Magnetic field controlled FZ single crystal growth of intermetallic compounds  

Microsoft Academic Search

Intermetallic rare-earth-transition-metal compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of bulk single crystals is very often unsuccessful due to an unfavorable solid–liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds.

R. Hermann; G. Behr; G. Gerbeth; J. Priede; H.-J. Uhlemann; F. Fischer; L. Schultz

2005-01-01

265

Role of curvature elasticity in sectorization and ripple formation during melt crystallization of polymer single crystals  

NASA Astrophysics Data System (ADS)

The present article focuses on theoretical elucidation of possible effect of mechanical deformation on spatio-temporal emergence of unusual polymer morphology subjected to quiescent isothermal crystallization conditions. The present theory developed is based on a phase field model consisted of non-conserved time dependent Ginzburg-Landau equation having an asymmetric double well potential in the crystal order parameter signifying metastability for crystallization, coupled with the chain tilt angle involving curvature elasticity and strain recovery potentials. Under quiescent crystallization conditions, the curvature elasticity term is needed to discern the emergence of sectorized single crystals. Upon coupling with the strain recovery potential, the numerical calculation captures ripple formation running across the long lamellar growth front, which may be attributed to lamellar buckling caused by the volume shrinkage. Of particular interest is that these simulated topologies of the single crystals are in good accord with the growth character of syndiotactic polypropylene single crystals observed experimentally by us during isothermal crystallization from the melt.

Mehta, Rujul; Keawwattana, Wirunya; Guenthner, Andrew L.; Kyu, Thein

2004-06-01

266

Single-element ultrasonic probe using PZN-PT single crystal  

Microsoft Academic Search

In order to improve the sensitivity and the bandwidth of an ultrasonic probe, the single-element probe using single crystals of the solid solution Pb(Zn1\\/3Nb2\\/3)O3- PbTiO3 (PZN-PT) has been investigated. Single crystals of PZN-PT with 9 mol% PbTiO3 (PZN-PT 91\\/9) single crystals were grown by the self flux method using PbO-based flux. It was confirmed that the single crystal of good

Shiroh Saitoh; Tsuyoshi Kobayashi; Senji Shimanuki; Yohachi Yamashita

1997-01-01

267

Optical and Mechanical Characteristics of PETN Single Crystal  

NASA Astrophysics Data System (ADS)

Pentaerythritol tetranitrate (PETN) is an extensively used crystalline high explosive. A good understanding of the laser- induced chemical decomposition and growth to detonation of PETN is important. This work on PETN single crystals focused primarily on its mechanical and optical properties under laser pulse interaction. Laser pulse (E<2 J, ?= 150 ps, &=tilde; 1.06 ?m) was focused on the single crystal surface to focal point size 80 .. 800 ?m. The goal of this work was to study the early stages of laser-induced explosion decomposition. Crystal response to the laser radiation was determined by the luminescence and conductivity of crystals. Explosion decomposition of PETN single crystals failed to occur within the studied range of initiation energies. Experiments measured the threshold of the optical breakdown for PETN and determined energies when its mechanical destruction begins. Analysis of experiments allowed a new scheme to be proposed for experiments when the laser radiation energy is injected inside the crystal.

Gromov, V. T.

2005-07-01

268

Investigation of single crystal silicates for blue tunable lasers  

NASA Astrophysics Data System (ADS)

The single crystal growth of rare earth silicates was investigated for the purpose of tunable laser hosts. Silicates of the type R2Si05, where R = La, Gd, Y, were prepared from stoichiometric melts and doped with Ce3+ activators. Seed crystals were obtained from crystallized melt sections or by growth on an iridium wire. Cathodoluminescence experiments on both powders and single crystals showed wavelength shifts with different rare earth ions. The Gd, Y, and mixed crystals of Gd-Y silicates gave good bright emission with Ce3+. The emission is broad band and covers the wavelength range of 370 to 525 micron. The peak emission can be centered near 450 to 460 micron by other compositions. Larger single crystals for laser hosts are under development.

Belt, R. F.; Catalano, J. A.

1986-06-01

269

Development of a thermal stress analysis system for anisotropic single crystal growth  

Microsoft Academic Search

We developed a thermal stress analysis system for anisotropic single crystal growth. The analysis system takes account of crystal anisotropy in elastic constants and thermal expansion coefficients and can deal with the thermal stress analyses of five kinds of single crystals, that is, cubic crystal, trigonal crystal, monoclinic crystal, tetragonal crystal and orthorhombic crystal. After calculating thermal stress, we can

N. Miyazaki

2002-01-01

270

Off-axis sputter deposition of ZnO films on c-sapphire substrates with buffer layers prepared via nitrogen-mediated crystallization  

NASA Astrophysics Data System (ADS)

High-quality epitaxial ZnO films on c-plane sapphire substrates have been obtained by utilizing off-axis sputtering configuration together with buffer layers prepared via nitrogen mediated crystallization (NMC). The role of NMC buffer layers is to provide high density of nucleation site and thus to reduce the strain energy caused by the large lattice mismatch (18%) between ZnO and sapphire. The NMC buffer layers allow two dimensional (2D) growth of subsequently grown ZnO films, being particularly enhanced by employing off-axis sputtering configuration, in which the substrate is positioned out of the high-energy particles such as negative oxygen ions originating from the targets. As a result, ZnO films with smooth surfaces (root-mean-square roughness: 0.76 nm) and high electron mobility of 88 cm2/V?sec are fabricated. Photoluminescence spectra of the ZnO films show strong near-band-edge emission, and the intensity of the orange-red defect emission significantly decreases with increasing the horizontal distance between the target and the substrate. From these results, we conclude that off-axis sputtering together with NMC buffer layers is a promising method for obtaining high quality epitaxial ZnO films.

Itagaki, N.; Matsushima, K.; Yamashita, D.; Seo, H.; Koga, K.; Shiratani, M.

2014-03-01

271

Study of single crystals of metal solid solutions  

NASA Technical Reports Server (NTRS)

The growth of single crystals of relatively high melting point metals such as silver, copper, gold, and their alloys was investigated. The purpose was to develop background information necessary to support a space flight experiment and to generate ground based data for comparison. The ground based data, when compared to the data from space grown crystals, are intended to identify any effects which zero-gravity might have on the basic process of single crystal growth of these metals. The ultimate purposes of the complete investigation are to: (1) determine specific metals and alloys to be investigated; (2) grow single metal crystals in a terrestrial laboratory; (3) determine crystal characteristics, properties, and growth parameters that will be effected by zero-gravity; (4) evaluate terrestrially grown crystals; (5) grow single metal crystals in a space laboratory such as Skylab; (6) evaluate the space grown crystals; (7) compare for zero-gravity effects of crystal characteristics, properties, and parameters; and (8) make a recommendation as to production of these crystals as a routine space manufacturing proceses.

Doty, J. P.; Reising, J. A.

1973-01-01

272

PAC Studies of Implanted 111Ag in Single-Crystalline ZnO  

NASA Astrophysics Data System (ADS)

The local environment of implanted 111Ag ( t 1/2 = 7.45 d) in single-crystalline [0001] ZnO was evaluated by means of the perturbed angular correlation (PAC) technique. Following the 60 keV low dose (1 × 1013 cm-2) 111Ag implantation, the PAC measurements were performed for the as-implanted state and following 30 min air annealing steps, at temperatures ranging from 200 to 1050°C. The results revealed that 42% of the probes are located at defect-free SZn sites ( ? Q ˜ 32 MHz, ? = 0) in the as-implanted state and that this fraction did not significantly change with annealing. Moreover, a progressive lattice recovery in the near vicinity of the probes was observed. Different EFGs assigned to point defects were furthermore measured and a general modification of their parameters occurred after 600°C. The 900°C annealing induced the loss of 30% of the 111Ag atoms, 7% of which were located in regions of high defects concentration.

Rita, E.; Correia, J. G.; Wahl, U.; Alves, E.; Lopes, A. M. L.; Soares, J. C.

2004-11-01

273

Green emission in carbon doped ZnO films  

NASA Astrophysics Data System (ADS)

The emission behavior of C-doped ZnO films, which were prepared by implantation of carbon into ZnO films, is investigated. Orange/red emission is observed for the films with the thickness of 60-100 nm. However, the film with thickness of 200 nm shows strong green emission. Further investigations by annealing bulk ZnO single crystals under different environments, i.e. Ar, Zn or C vapor, indicated that the complex defects based on Zn interstitials are responsible for the strong green emission. The existence of complex defects was confirmed by electron spin resonance (ESR) and low temperature photoluminescence (PL) measurement.

Tseng, L. T.; Yi, J. B.; Zhang, X. Y.; Xing, G. Z.; Fan, H. M.; Herng, T. S.; Luo, X.; Ionescu, M.; Ding, J.; Li, S.

2014-06-01

274

Unexpected optical response of single ZnO nanowires probed using controllable electrical contacts.  

PubMed

Relying on combined electron-beam lithography and lift-off methods Au/Ti bilayer electrical contacts were attached to individual ZnO nanowires (NWs) that were grown by a vapor phase deposition method. Reliable Schottky-type as well as ohmic contacts were obtained depending on whether or not an ion milling process was used. The response of the ZnO NWs to ultraviolet light was found to be sensitive to the type of contacts. The intrinsic electronic properties of the ZnO NWs were studied in a field-effect transistor configuration. The transfer characteristics, including gate threshold voltage, hysteresis and operational mode, were demonstrated to unexpectedly respond to visible light. The origin of this effect could be accounted for by the presence of point defects in the ZnO NWs. PMID:21399828

Zeng, Y J; Menghini, M; Li, D Y; Lin, S S; Ye, Z Z; Hadermann, J; Moorkens, T; Seo, J W; Locquet, J-P; Van Haesendonck, C

2011-04-21

275

Hg-1212 and Hg-1223 single crystals: Synthesis and characterisation  

NASA Astrophysics Data System (ADS)

Single crystals of HgBa 2CaCu 2O 6+? (Hg-1212) and HgBa 2Ca 2Cu 3O 8+? (Hg-1223) were grown from the melt at an argon pressure of 10 kbar. Electron microscopy, as well as single crystal X-ray diffraction studies show that the crystals are well ordered. The EDS analysis indicates the presence of a minor amount of other cations replacing Hg, Ba and Ca in the structure. Refined fractional coordinates and thermal parameters are given for a crystal of Hg-1223 type. Magnetic and resistive measurements show a Tc of 133 K for the Hg-1223 phase.

Gatt, R.; Olsson, E.; Morawski, A.; Lada, T.; Paszewin, A.; Bryntse, I.; Grishin, A. M.; Eeltsev, Yu.; Berastegui, P.; Johansson, L.-G.

1997-02-01

276

Growth of Sb-Bi gradient single crystals  

SciTech Connect

The growth conditions and structural quality of Sb-Bi gradient single crystals with Bi content from 2 to 18 at %, grown by the Czochralski method with solid phase feed, are investigated. Bi distribution in the crystals along their pulling direction are studied by electron probe microanalysis and the change in the interplanar spacing is analyzed by double-crystal X-ray diffraction. It is established that the pulling rate and feed mass affect the Bi distribution in Sb-Bi single crystals.

Kozhemyakin, G. N., E-mail: genakozhemyakin@mail.ru; Lutskiy, D. V. [Dal Eastern Ukraine National University (Ukraine); Rom, M. A.; Mateychenko, P. V. [National Academy of Sciences of Ukraine, Institute for Single Crystals (Ukraine)

2008-12-15

277

Method for harvesting single crystals from a peritectic melt  

DOEpatents

A method of preparing single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid. 2 figs.

Todt, V.R.; Sengupta, S.; Shi, D.

1996-08-27

278

Flexible piezoresistive strain sensor based on single Sb-doped ZnO nanobelts  

Microsoft Academic Search

Using a two-end bonded Sb-doped ZnO nanobelt on a flexible polystyrene substrate, the decrease of the resistance with increasing compressed strains in the nanobelt has been observed, which is suggested to be attributed to the piezoresistance effect. The longitudinal piezoresistance coefficient of the Sb-doped ZnO nanobelt is about 350. On the basis of this finding, we made a flexible piezoresistive

Ya Yang; Wen Guo; Junjie Qi; Yue Zhang

2010-01-01

279

Hard polarized photon emission in single crystals by high energy electrons for planar crystal orientations  

Microsoft Academic Search

The radiation emission spectra of polarized photons emitted from charged particle in single crystals are obtained in the semiclassical theory in Baier-Katkov-Strakhovenko approximation for planar crystal orientation. Optimal crystal orientations for producing unpolarized and polarized photon beams are also found.

S. M. Darbinyan; N. L. Ter-Isaakyan

2002-01-01

280

Hard polarized photon emission in single crystals by high energy electrons for planar crystal orientations  

Microsoft Academic Search

The radiation emission spectra of polarized photons emitted from charged particle in single crystals are obtained in the semiclassical theory in Baier–Katkov–Strakhovenko approximation for planar crystal orientation. Optimal crystal orientations for producing unpolarized and polarized photon beams are also found.

S. M. Darbinyan; N. L. Ter-Isaakyan

2002-01-01

281

Stability of Detached Grown Germanium Single Crystals  

NASA Technical Reports Server (NTRS)

Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years especially, under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 microns, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 microns. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be discussed in detail.

Schweizer, M.; Volz, M. P.; Cobb, S. D.; Motakef, S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

2002-01-01

282

ZnO thin film deposition using colliding plasma plumes and single plasma plume: Structural and optical properties  

NASA Astrophysics Data System (ADS)

We report the comparative study on synthesis of thin films of ZnO on glass substrates using IR laser ablated colliding plasma plumes and conventional pulsed laser deposition using 355 nm in oxygen ambient. The optical properties of deposited films are characterized using optical transmission in the UV-visible range of spectrum and photoluminescence measurements. X-ray diffraction and atomic force microscopy are used to investigate the surface morphology of synthesized ZnO films. The films synthesized using colliding plumes created with 1064 nm are non-polar a-plane ZnO with transmission in UV-visible (300-800 nm) region ˜60% compared to polycrystalline thin film deposited using single plume which has chunk deposition and poor optical response. However, deposition with 355 nm single plume shows polar c-axis oriented thin film with average roughness (˜thickness) of ˜86 nm (˜850 nm) compared to ˜2 nm (˜3 ?m) for 1064 nm colliding plumes. These observed differences in the quality and properties of thin films are attributed to the flux of mono-energetic plasma species with almost uniform kinetic energy and higher thermal velocity reaching the substrate from interaction/stagnation zone of colliding plasma plumes.

Gupta, Shyam L.; Thareja, Raj K.

2013-12-01

283

Nanointegration of ZnO with Si and SiC  

NASA Astrophysics Data System (ADS)

The study is dedicated to some aspects of the controlled heteroepitaxial growth of nanoscaled ZnO structures and an investigation of their general and dimension mediated properties. ZnO nanostructures were synthesized by optimized MOCVD process via two growth approaches: (i) catalyst free self-organized growth of ZnO on Si substrates and (ii) ZnO heteroepitaxy on p-type hexagonal 4H-SiC substrates. The SiC substrate was prepared by sublimation epitaxy and served as a template for the ZnO epitaxial growth. The epitaxial growth of n-ZnO on p-SiC resulted in a regular matrix of well-faceted hexagonally shaped ZnO single crystals. The achievement of ZnO integration with Si encompasses controlled growth of vertically oriented nanosized ZnO pillars. The grown structures were characterized by transmission electron microscopy and microphotoluminescence. Low concentration of native defects due to a stoichiometry balance, advanced optical emission, (excitonic type near-band-edge emission and negligible defect related luminescence) and continuous interfaces (epitaxial relationship ZnO [0 0 0 1] /SiC [0 0 0 1] ) are evidenced. The ZnO nanopillars were further probed as field emitters: the grown structures exhibits advanced field emission properties, which are explained in term of dimensionality and spatial uniformity of the nanopillars. The present results contribute to understanding and resolving growth and device related issues of ZnO as a functional nanostructured material.

Khranovskyy, V.; Tsiaoussis, I.; Larsson, L. A.; Holtz, P. O.; Yakimova, Rositza

2009-12-01

284

A Single Crystal Niobium RF Cavity of the TESLA Shape  

NASA Astrophysics Data System (ADS)

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material without destruction of the single crystal. A prototype single crystal single cell cavity was build. An accelerating gradient of 37.5 MV/m was reached after approximately 110 ?m of Buffered Chemical Polishing (BCP) and in situ baking at 120°C for 6 hrs with a quality factor exceeding 2×1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

Singer, W.; Singer, X.; Kneisel, P.

2007-08-01

285

Growth of Solid Solution Single Crystals.  

National Technical Information Service (NTIS)

The bulk growth of HgCdTe crystals by modified Bridgman techniques and by quenching anneal recrystallization yields deficient material. The primary complication for growth arises from a pronounced tendency for constitutional supercooling caused by the cha...

A. F. Witt

1981-01-01

286

Barium iodide single-crystal scintillator detectors  

SciTech Connect

We find that the high-Z crystal Barium Iodide is readily growable by the Bridgman growth technique and is less prone to crack compared to Lanthanum Halides. We have grown Barium Iodide crystals: undoped, doped with Ce{sup 3+}, and doped with Eu{sup 2+}. Radioluminescence spectra and time-resolved decay were measured. BaI{sub 2}(Eu) exhibits luminescence from both Eu{sup 2+} at 420 nm ({approx}450 ns decay), and a broad band at 550 nm ({approx}3 {micro}s decay) that we assign to a trapped exciton. The 550 nm luminescence decreases relative to the Eu{sup 2+} luminescence when the Barium Iodide is zone refined prior to crystal growth. We also describe the performance of BaI{sub 2}(Eu) crystals in experimental scintillator detectors.

Cherepy, N

2007-07-30

287

The Growth of Large Single Crystals.  

ERIC Educational Resources Information Center

Presented is an experiment which demonstrates principles of experimental design, solubility, and crystal growth and structure. Materials, procedures and results are discussed. Suggestions for adapting this activity to the high school laboratory are provided. (CW)

Baer, Carl D.

1990-01-01

288

Single-drop optimization of protein crystallization.  

PubMed

A completely new crystal-growth device has been developed that permits charting a course across the phase diagram to produce crystalline samples optimized for diffraction experiments. The utility of the device is demonstrated for the production of crystals for the traditional X-ray diffraction data-collection experiment, of microcrystals optimal for data-collection experiments at a modern microbeam insertion-device synchrotron beamline and of nanocrystals required for data collection on an X-ray laser beamline. PMID:22869140

Meyer, Arne; Dierks, Karsten; Hilterhaus, Dierk; Klupsch, Thomas; Mühlig, Peter; Kleesiek, Jens; Schöpflin, Robert; Einspahr, Howard; Hilgenfeld, Rolf; Betzel, Christian

2012-08-01

289

Epitaxial electrodeposition of freestanding large area single crystal substrates  

SciTech Connect

The authors report on a method for producing freestanding single crystal metal films over large areas using electrodeposition and selective etching. The method can be turned into an inexpensive continuous process for making long ribbons or a large area of single crystal films. Results from a 5x5 mm{sup 2} Ni single crystal film using electron backscattering pattern pole figures and x-ray diffraction demonstrate that the quality of material produced is equivalent to the initial substrate without annealing or polishing.

Shin, Jae Wook; Standley, Adam; Chason, Eric [Brown University, Box D, Providence, Rhode Island 02912 (United States)

2007-06-25

290

Raman study of TiO 2 role in SiO 2–Al 2O 3–MgO–TiO 2–ZnO glass crystallization  

Microsoft Academic Search

Tough glass-ceramic material of special mechanical properties with nanosize crystal phases formed by appropriately controlled crystallization was studied by Raman spectroscopy. It was obtained by TiO2 activated crystallization of Mg–aluminosilicate glass of SiO2–Al2O3–MgO–TiO2–ZnO composition. Crystallization was preceded by a change in the TiO2 structural position and state, which is manifested by a changed color of glass from yellow into blue

Krešimir Furi?; Leszek Stoch; Jan Dutkiewicz

2005-01-01

291

A study of crystal growth by solution technique. [triglycine sulfate single crystals  

NASA Technical Reports Server (NTRS)

The advantages and mechanisms of crystal growth from solution are discussed as well as the effects of impurity adsorption on the kinetics of crystal growth. Uncertainities regarding crystal growth in a low gravity environment are examined. Single crystals of triglycine sulfate were grown using a low temperature solution technique. Small components were assembled and fabricated for future space flights. A space processing experiment proposal accepted by NASA for the Spacelab-3 mission is included.

Lal, R. B.

1979-01-01

292

Crystal growth and characterization of La 3Ga 5SiO 14 single crystals  

Microsoft Academic Search

An almost colorless La3Ga5SiO14 (LGS) single crystal with 26 mm in diameter and 25 mm in length was grown by the Czochralski technique. The coloration of the crystal depends on the growth atmosphere. The cutoff wavelength of the colorless LGS crystal is shorter than an annealed crystal and the piezoelectric properties of the former are nearly equal to those of

Zengmei Wang; Duorong Yuan; Lihu Pan; Peilin Zhang; Xiufeng Cheng; Minglei Zhao; Zhengfa Li; Xiulan Duan; Zhenxiang Chen; Shiyi Guo; Dong Xu; Mengkai Lv

2003-01-01

293

Single crystal Processing and magnetic properties of gadolinium nickel  

SciTech Connect

GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd{sub 2}O{sub 3} W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

Shreve, Andrew John [Ames Laboratory

2012-11-02

294

Performance of Large grain and Single Crystal Niobium Cavities  

Microsoft Academic Search

We have fabricated and tested several single and one multi-cell cavity made from large grain niobium of four different ingots. Two cavities at a frequency of ~ 2.2 GHz were made from single crystal sheets. Large grain material was used for four single cell cavities of the HG â and OC shapes, a 7-cell cavity of the HG â shape

Peter Kneisel; Gianluigi Ciovati; Jacek Sekutowicz

2006-01-01

295

Nitrogen doping in bulk and epitaxial ZnO  

NASA Astrophysics Data System (ADS)

We report on the characterization of bulk and epitaxial ZnO films doped by nitrogen. The ZnO thin films were grown on GaN templates and on ZnO single crystals by vapor phase deposition using Zn and NO2/N2O as precursors. Nitrogen was introduced in the epitaxial films by a mixture of ammonia in the total N2 flow and by ion implantation into the bulk crystals. The optical properties were investigated by steady state and time resolved photoluminescence (PL). We observed a well structured donor-acceptor-pair (DAP) band with a zero phonon line (ZPL) at 3.235 eV. Time resolved PL measurements allowed to conclude on the compensation. Diffusion of Ga from the GaN templates into the ZnO layers was detected by SIMS.

Zeuner, A.; Alves, H.; Sann, J.; Kriegseis, W.; Neumann, C.; Hofmann, D. M.; Meyer, B. K.; Hoffmann, A.; Haboeck, U.; Straßburg, M.; Kaschner, A.

2004-03-01

296

Growth and characterization of ammonium acid phthalate single crystals  

NASA Astrophysics Data System (ADS)

Ammonium acid phthalate (AAP) has been synthesized and single crystals were grown by slow evaporation solution growth technique. The unit cell parameters were confirmed by single crystal X-ray diffraction analysis and it belongs to orthorhombic system with the space group of Pcab. The high resolution X-ray diffraction studies revealed the crystalline perfection of the grown crystal. The various functional groups of AAP were identified by FT-IR and Raman spectral analyses. Thermal stability of the grown crystals was studied by TGA/DTA. The optical properties of the grown crystals were analyzed by UV-Vis-NIR and photoluminescence spectral studies. The mechanical property of the grown crystal was studied by Vickers microhardness measurement. The growth features of AAP were analyzed by chemical etching.

Arunkumar, A.; Ramasamy, P.

2013-04-01

297

Twisted Single Crystals of Meta-Aromatic Polyamides  

NASA Astrophysics Data System (ADS)

The morphology of single crystals of the aromatic polyamide poly(metaphenylene isophthalamide) (MPDI or Nomex) was studied by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The single crystals of MPDI were slowly grown from 0.1 weight percent solution. MPDI forms elongated crystals which aggregate together to form highly regular twisted helical bundles. The repeat periods of the helices typically range from 240 nm to 1000 nm and the bundle diameters vary from 36 nm to 120 nm. The angle between the edge of the crystal and the bundle axis varies from 40 to 65 degrees. The regular twisting evidently arises from a bending moment induced by the triclinic symmetry of the MPDI unit cell and the lamellar geometry of the chain-folded single crystal.

Lawrence, D. P.; Martin, D. C.

1996-03-01

298

Growing intermetallic single crystals using in situ decanting  

SciTech Connect

High temperature metallic solution growth is one of the most successful and versatile methods for single crystal growth, and is particularly suited for exploratory synthesis. The method commonly utilizes a centrifuge at room temperature and is very successful for the synthesis of single crystal phases that can be decanted from the liquid below the melting point of the silica ampoule. In this paper, we demonstrate the extension of this method that enables single crystal growth and flux decanting inside the furnace at temperatures above 1200°C. This not only extends the number of available metallic solvents that can be used in exploratory crystal growth but also can be particularly well suited for crystals that have a rather narrow exposed solidification surface in the equilibrium alloy phase diagram.

Petrovic, Cedomir; Canfield, Paul; Mellen, Jonathan

2012-05-16

299

On the growth of calcium tartrate tetrahydrate single crystals  

Microsoft Academic Search

Calcium tartrate single crystals were grown using silica gel as the growth medium. Calcium formate mixed with formic acid\\u000a was taken as the supernatant solution. It was observed that the nucleation density was reduced and the size of the crystals\\u000a was improved to a large extent compared to the conventional way of growing calcium tartrate crystals with calcium chloride.\\u000a The

X. Sahaya Shajan; C. Mahadevan

2004-01-01

300

Large Single Crystal growth of Bi2212 superconducting oxide  

Microsoft Academic Search

A floating zone method was used to study the effects of the growth velocity and starting composition of the feed rod on the crystal growth behaviour of Bi-2212 superconducting materials. It shows that a necessary condition for large single crystal growth is that the solid-liquid interface of a rod maintains a planar interface during crystal growth. The planar solid-liquid interface

Genda Gu; Gangyong Xu; John Tranquada

2006-01-01

301

Phase transitions in potassium ammonium dihydrogen phosphate single crystals  

Microsoft Academic Search

An apparatus for growing single crystals from aqueous solution by the slow evaporation method was constructed. Mixed crystals of K1-x(NH 4)xH2PO4 (KADP) with (NH4)H 2PO4 (ADP) fractions of 0.021 and 0.12 were successfully grown. Their composition was determined by means of the x-ray powder diffraction method. This analysis also suggests that those crystals are a mixture of two phases even

Marek Bromberek

2008-01-01

302

Morphology and orientational disorder of C 70 single crystals  

Microsoft Academic Search

C70 single crystals, free from solvent contamination, were grown via vapor phase transport technique. The (0001) face of the C70 crystal was imaged with Atomic Force Microscopy (AFM) under ambient atmosphere. Low-resolution images of a freshly prepared crystal revealed well-ordered faceted regions with multiple terraces extending over a region of several hundred square nanometers. The terraced structure in the images

L. Jiang; J. Li; L. A. Nagahara; N. Kino; K. Kitazawa; T. Iyoda; K. Hashimoto; A. Fujishima

1995-01-01

303

Zone refining and single crystal growth of cuprous oxide  

Microsoft Academic Search

A method of purification and single crystal growth of cuprous oxide by an R. F. induction heating float zone technique was developed. Ingots of 5\\/1 inches diameter and 6 inches long, with three to six columnar crystals extending the entire length of the rod, were prepared. After etching, these rods can be viewed as red by transmitted visible light. The

ANAND SWAROOP KAKAR

1978-01-01

304

Investigation of Single Crystal Silicates for Blue Tunable Lasers.  

National Technical Information Service (NTIS)

The single crystal growth of rare earth silicates was investigated for the purpose of tunable laser host. Silicates of the type R2SiO5, where R + La, Gd, Y were prepared from stoichiometric melts and doped with Ce+3 activator. Seed crystals were obtained ...

R. F. Belt J. A. Catalano

1986-01-01

305

Single crystal orientation effects in shock initiation of PETN explosive  

SciTech Connect

Over the past nine years in Los Alamos we have studied shock initiation of detonation in single crystals of PETN explosive. We have demonstrated the effects of point defects and crystal orientation on shock sensitivity. Here we report recent work on orientation effects and anomalous detonation in <110> orientation at 4 GPa. 5 refs.

Dick, J.J.

1988-01-01

306

Investigation of Single Crystal Silicates for Blue Tunable Lasers.  

National Technical Information Service (NTIS)

The single crystal growth of rare earth silicates was investigated for the purpose of tunable laser hosts. Silicates of the type R2SiO5, where R = La, Gd, Y, Lu, were prepared from stoichiometric melts and doped with Ce(3+) activators. Seed crystals were ...

R. F. Belt J. A. Catalano

1986-01-01

307

RESEARCH NOTES: Directional electric breakdown of KCl single crystals  

Microsoft Academic Search

Controversy exists about whether the discharge channel existing after breakdown in alkali halide crystals marks the path of the electronic instability or results from secondary processes. A fast electro-optical shutter has been used to observe the pre-breakdown light emission from KCl single crystals, and it has been found that the discharge channel does lie in the path of the electronic

R. Cooper; C. T. Elliott

1968-01-01

308

Frequency dependent electro-optic property of SBN single crystal  

NASA Astrophysics Data System (ADS)

In electro-optic (EO) modulator devices ferroelectric crystals of strontium barium niobate (SBN) are attractive due to exceptional high EO coefficients and low half wave voltage. SBN single crystals grown by laser heated pedestal growth are investigated to explore frequency dependent EO property at low frequency and near resonant frequency range. The mechanism of its frequency dependence is discussed briefly.

Huang, Chuanyong; Fu, John; Liu, Hongbo; Liu, Yuexin; Gu, Man; Bhalla, Amar S.; Guo, Ruyan

2005-09-01

309

Heterogeneous deformation resulting from stress gradients in calcite single crystals  

Microsoft Academic Search

The stress gradient calculated from an isotropic elastic approximation does not directly reflect the distribution of permanent deformation in a crystal of the same shape under the same conditions. However, with additional crystallographic constraints, it serves to predict locations where twinning and slip are first activated in a stressed crystal. In this study, thick-walled hollow cylinders were cored from single

Annemarie Meike

1988-01-01

310

Bismuth and aluminum-substituted YIG single-crystal films on modified gadolinium gallium garnet single-crystal substrates  

Microsoft Academic Search

Bismuth- and aluminum-substituted yttrium iron garnet single-crystal films with the nominal composition of Y1.5Bi1.5Fe4.2Al0.8O12 (Bi,Al:YIG) were prepared by spin coating a gel on the (111) plane of (GdCa)3(GaMgZn)5O12 single-crystal garnet plates. Crystallinity of the films varies with temperature and time of heat treatment in air after gel coating. Single-crystal films were obtained at Ta=650 °C for 4 h. The onset

Koji Matsumoto; Satoshi Sasaki; Yasunori Yamanobe; Kazuhiro Yamaguchi; Toshitaka Fujii; Yousuke Asahara

1991-01-01

311

Constitutive Modelling of Single Crystal and Directionally Solidified Superalloys.  

National Technical Information Service (NTIS)

The trend towards improved engine efficiency and durability places increasing demands on materials that operate in the hot section of the gas turbine engine. These demands are being met by new coatings and materials such as single crystal and directionall...

E. H. Jordan K. P. Walker

1986-01-01

312

Single Crystal Growth of Potassium Lithium Niobate for SAW Applications.  

National Technical Information Service (NTIS)

We have successfully demonstrated the growth of good quality, crack-free medium size KLN single crystals using the Czochralski method, with dielectric and piezoelectric properties comparable or superior to the best known bronze composition SBN. However, w...

R. R. Neurgaonkar

1983-01-01

313

Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals  

DOEpatents

A method of fabricating bulk YBa{sub 2}Cu{sub 3}O{sub x} where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa{sub 2}Cu{sub 3}O{sub x} are heated in the presence of a Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y} seed crystal to a temperature sufficient to form a liquid phase in the YBa{sub 2}Cu{sub 3}O{sub x} while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa{sub 2}Cu{sub 3}O{sub x} material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material. 7 figs.

Todt, V.; Miller, D.J.; Shi, D.; Sengupta, S.

1998-07-07

314

Measurement of single crystal surface parameters  

NASA Technical Reports Server (NTRS)

The sticking coefficient and thermal desorption spectra of Cs from the (110) plane of W was investigated. A sticking coefficient of unity for the monolayer region was measured for T 250 K. Several distinct binding states were observed in the thermal desorption spectrum. Work function and electron reflection measurements were made on the (110) and (100) crystal faces of Mo. Both LEED and Auger were used to determine the orientation and cleanliness of the crystal surfaces. The work function values obtained for the (110) and (100) planes of Mo were 4.92 and 4.18 eV respectively.

Swanson, L. W.; Bell, A. E.; Strayer, R. W.

1972-01-01

315

Piezoelectric properties of tetragonal single-domain Mn-doped NBT-6 %BT single crystals  

NASA Astrophysics Data System (ADS)

We report a study of properties of Mn-doped NBT-6 %BT single crystals. We show that tetragonal single-domain states can be stabilized by poling along a [001] direction. For carefully prepared crystals, the piezoelectric coefficient d_{33} can reach 570 pC/N. When poled along non-polar directions, the crystals exhibit ferroelectric domain structures consistent with tetragonal micron-sized domains, as revealed by optical observation and Raman spectroscopy. The multidomain crystals have lower d_{33} values, 225 and 130 pC/N for [011] and [111]-oriented crystals, respectively. This trend is commented on from a domain-engineering perspective.

Guennou, Mael; Savinov, Maxim; Drahokoupil, Jan; Luo, Haosu; Hlinka, Jirka

2013-11-01

316

Deuteron NMR in Formic and Acetic Acid Single Crystals  

Microsoft Academic Search

The deuteron quadrupole coupling constants and asymmetry factors in single crystals of DCOOH and HCOOD are found to be 161± 2 kHz, &eegr;=0.040± 0.025 and 165.1± 2.7 kHz, &eegr;=0.125± 0.030, respectively. These are compared with free molecule and single crystal results of others on the formate group. In addition, attention is called to influence of the X-fragment electronegativity upon the

Guy J. Adriaenssens; John L. Bjorkstam

1972-01-01

317

Shear localization in dynamic deformation of copper single crystals  

Microsoft Academic Search

Dynamic deformation of copper single crystals, especially of fatigued copper single crystals with different orientations, was conducted on a split-Hopkinson pressure bar apparatus. The strain rates were in the range 2???9?×?10?s. After dynamic deformation, the adiabatic shear bands (ASBs) were examined in a light microscope and SEM. The width and spacing of ASBs formed under different strain rates in a

S. X. Li; R. Q. Yang; J. W. Li; Z. F. Zhang

2006-01-01

318

Preparation of Large Area Single-Crystal Cuprous Oxide  

Microsoft Academic Search

Large area single crystals of Cu2O were grown by the process of high temperature annealing. Cu2O was prepared in finely polycrystalline form by the complete oxidation of Cu plate in air at temperatures of 1020°C to 1050°C. Subsequent annealing of the polycrystalline plates at higher temperatures allowed secondary recrystallization to occur. Single-crystal grains having surface areas larger than 1 in.2

Robert S. Toth; Rein Kilkson; Dan Trivich

1960-01-01

319

Electrochemical In 2O 3 single crystal growth  

Microsoft Academic Search

An In2O3 single crystal was successfully grown electrochemically applying the In3+ ion conducting In2(MoO4)3 solid electrolyte. In the In2(MoO4)3 solid electrolyte, only In3+ ion species can migrate in the molybdate solid, and by the DC electrolysis, the In3+ ion species continuously supplied and deposited on the cathodic surface of the electrolyte. Since the single crystal growth can be regulated by

Nobuhito Imanaka; Toshiyuki Masui; Young Woon Kim; Gin-ya Adachi

2004-01-01

320

Bulk GaN single-crystals growth  

Microsoft Academic Search

Gallium nitride powder was prepared from gallium and ammonia at temperatures of 1000–1200°C. Parameters of the crystallographic lattice as well as photoluminescence and Raman spectra were determined for the obtained powder. As a result of GaN powder sublimation, GaN single crystals of 3×2×0.2mm were received, at temperatures 1200–1250°C. Single crystals of gallium nitride were also synthesised in a reaction of

Grzegorz Kamler; Janusz Zachara; S?awomir Podsiad?o; Leszek Adamowicz; Wojciech G?bicki

2000-01-01

321

Inhomogeneities in single crystals of cuprate oxide superconductors  

NASA Technical Reports Server (NTRS)

The next stage in the evolution of experimental research on the high temperature superconductors will require high quality single crystals and epitaxially grown crystalline films. However, inhomogeneities and other defects are not uncommon in single crystals of cuprate oxide superconductors, so a corollary requirement will be a reliable method for judging the quality of these materials. The application of magnetically modulated resistance methods in this task is briefly described and illustrated.

Moorjani, K.; Bohandy, J.; Kim, B. F.; Adrian, F. J.

1991-01-01

322

Single Crystal Growth of Photorefractive Sillenites.  

National Technical Information Service (NTIS)

The compounds, crystallized in the cubic form similar to sillenite structure, occur in a number of isomorphs. The well-known representatives of this family are bismuth germanium (BGO) and bismuth silicon oxides (BSo), both of which can be grown from their...

V. V. Volkov Y. F. Kargin V. M. Skorikov

1992-01-01

323

Poly(vinylidene fluoride) single crystals  

Microsoft Academic Search

Information about the structure and properties of bulk poly (vinylidence fluoride) PVF2 has been previously obtained in this laboratory from X-ray diffraction [1], NMR spectra [1], and dielectric constant measurements [2, 3]. Depending on sample preparation, one finds two different types of orthorhomic unit cells (Table 1). Type II appears in samples crystallized from the melt either isothermally or at

K. Sakaoku; A. Peterlin

1967-01-01

324

Effect of solution concentration on the functional properties of ZnO nanostructures: Role of Hexamethylenetetramine  

NASA Astrophysics Data System (ADS)

In this research, ZnO nanorods have been successfully synthesized via wet chemical method. XRD results revealed the single phase nature with the wurtzite structure of the as prepared ZnO nanorods. By only varying the concentration of Hexamethylenetetramine (HMT) in the solution, morphology of ZnO changed from hexagonal facet nanorods to pencil like nanorods and size of nanorods also changed. The band gap of as-synthesized ZnO nanorods was found to increase with increasing the concentration of HMT in the solution. The narrow full-width at half-maximum (FWHM) of the UV emission of PL spectra indicated that the grown ZnO nanorods have high crystal quality and is well matched with the obtained XRD results. These results revealed that the concentration of Hexamethylenetetramine plays a vital role to control the properties of ZnO nanorods.

Heo, Si Nae; Park, Keun Young; Seo, Yong Jun; Ahmed, Faheem; Anwar, M. S.; Koo, Bon Heun

2013-05-01

325

Vortex structure in superconducting iron pnictide single crystals  

NASA Astrophysics Data System (ADS)

The vortex structure in the iron pnictide single crystals Ba1- x K x Fe2As2 and Sr1- x K x Fe2As2 of the 122 type and SmFeAsO1- x F x of the 1111 type has been investigated using the decoration method. In all of the crystals under investigation, no regular vortex lattice has been revealed in the magnetic field range up to 200 Oe. The disordered vortex structure is discussed in view of the vortex pinning in single crystals.

Vinnikov, L. Ya.; Artemova, T. M.; Veshchunov, I. S.; Zhigadlo, N. D.; Karpinski, J.; Popovich, P.; Sun, D. L.; Lin, C. T.; Boris, A. V.

2009-10-01

326

CeSi 2? ? single crystals: growth features and properties  

Microsoft Academic Search

Single crystals of CeSix (x=1.79–1.85) with an orthorhombic structure have been grown by floating zone methods both with RF induction and optical heating at feed rod compositions CeSiy (y=1.76–1.89). High-perfection single crystals were achieved for a narrow composition interval y=1.81–1.82. A slight axial segregation of Si in the crystal and 2nd phase inclusions of Si (y>1.82) and of CeSi (y<1.80),

D. Souptel; G. Behr; W. Löser; A. Teresiak; S. Drotziger; C. Pfleiderer

2004-01-01

327

Optical and photoelectrochemical study of WTe2 single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of Tungsten Ditelluride (WTe2) having a layered structure grown by chemical vapor transport method using iodine as the transporting agent are studied here. The optical response of these crystals has been obtained by UV-Vis-NIR spectroscopy at room temperature. Results of optical spectra have been analyzed on the basis of three dimensional models. Photoelectrochemical (PEC) characterization of WTe 2 single crystals have been carried out. Photo response measurements were obtained at different intensities of light source to illuminate the photoanode. The effect of intensity in the efficiency of PEC solar cell has been studied. The implications of the results have been discussed.

Desai, P. F.; Patel, D. D.; Bhavsar, D. N.; Jani, A. R.

2013-06-01

328

Flexible piezoresistive strain sensor based on single Sb-doped ZnO nanobelts  

NASA Astrophysics Data System (ADS)

Using a two-end bonded Sb-doped ZnO nanobelt on a flexible polystyrene substrate, the decrease of the resistance with increasing compressed strains in the nanobelt has been observed, which is suggested to be attributed to the piezoresistance effect. The longitudinal piezoresistance coefficient of the Sb-doped ZnO nanobelt is about 350. On the basis of this finding, we made a flexible piezoresistive strain sensor in a signature pen, which can be used to detect the corresponding compressed strains when the characters are recorded.

Yang, Ya; Guo, Wen; Qi, Junjie; Zhang, Yue

2010-11-01

329

Growth and properties of benzil doped benzimidazole (BMZ) single crystals  

SciTech Connect

In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.

Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Sukumar, M. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Vasudevan, V. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India) [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Shakir, Mohd. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India); Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India)] [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Bhagavannarayana, G. [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)] [Crystal Growth and Crystallography Section, National Physical Laboratory, Krishnan Marg, New Delhi 110 012 (India)

2010-09-15

330

Vapor crystal growth studies of single crystals of mercuric iodide (3-IML-1)  

NASA Technical Reports Server (NTRS)

A single crystal of mercuric iodide (HgI2) will be grown during the International Microgravity Lab. (IML-1) mission. The crystal growth process takes place by sublimation of HgI2 from an aggregate of purified material, transport of the molecules in the vapor from the source to the crystal, and condensation on the crystal surface. The objectives of the experiment are as follow: to grow a high quality crystal of HgI2 of sufficient size so that its properties can be extensively analyzed; and to study the vapor transport process, specifically the rate of diffusion transport at greatly reduced gravity where convection is minimized.

Vandenberg, Lodewijk

1992-01-01

331

Shock Driven Twinning in Tantalum Single Crystals  

SciTech Connect

Recovery based observations of high pressure material behavior generated under high explosively driven flyer based loading conditions are reported. Two shock pressures, 25, and 55 GPa and four orientations {l_brace}(100), (110), (111), (123){r_brace} were considered. Recovered material was characterized using electron backscatter diffraction along with a limited amount of transmission electron microscopy to assess the occurrence of twinning under each test condition. Material recovered from 25 GPa had a very small fraction of twinning for the (100), (110), and (111) oriented crystals while a more noticeable fraction of the (123) oriented crystal was twinned. Material recovered from 55 GPa showed little twinning for (100) orientation slightly more for the (111) orientation and a large area fraction for the (123) orientation. The EBSD and TEM observations of the underlying deformation substructure are rationalized by comparing with previous static and dynamic results.

McNaney, J M; HSUING, L M; Barton, N R; Kumar, M

2009-07-20

332

Raman spectra of deuteriated taurine single crystals  

NASA Astrophysics Data System (ADS)

The polarized Raman spectra of partially deuteriated taurine [(ND 3+) 0.65(NH 3+) 0.35(CH 2) 2SO 3-] crystals from x( zz) x and x( zy) x scattering geometries of the A g and B g irreducible representations of the factor group C 2h are reported. The temperature-dependent Raman spectra of partially deuteriated taurine do not reveal any evidence of the structural phase transition undergone by normal taurine at about 250 K, but an anomaly observed in the 180 cm -1 band at ˜120 K implies a different dynamic for this band (which is involved in a pressure-induced phase transition) in the deuteriated crystal.

Souza, J. M. de; Lima, R. J. C.; Freire, P. T. C.; Sasaki, J. M.; Melo, F. E. A.; Filho, J. Mendes; Jones, Derry W.

2005-05-01

333

Elastic Moduli, Pressure Derivatives, and Temperature Derivatives of Single-Crystal Olivine and Single-Crystal Forsterite  

Microsoft Academic Search

Ultrasonic wave velocities in single-crystal forsteritc (F) and single-crystal olivine (0) have been measured as a function of pressure and of temperature near ambient conditions. Shear and longitudinal velocities were measured in eighteen independent modes, so that each of the nine elastic constants could be calculated by at least two independent equations. The adiabatic stiffness constants c{j (in Mb), their

Mineo Kumazawa; Orson L. Anderson

1969-01-01

334

Extending the contact regimes to single-crystal indentations  

NASA Astrophysics Data System (ADS)

This article provides a fresh look into the concept of the contact regimes in mechanistic analyses of indentation experiments performed in single crystals. In this context, spherical microindentation experiments in fcc metals are examined through detailed continuum crystal plasticity finite element simulations in order to provide meaning to the onset of fully-plastic and elasto-plastic contact regimes, which are well-known to rule the behavior of polycrystals exhibiting isotropic uniaxial stress-strain curves. Attention is then given to evaluate the applicability of Tabor's hardness relation in ruling fully-plastic single-crystal spherical indentations as well as the extraction of the uniaxial plastic flow properties from a series of microindentation tests performed at different penetrations. A discussion is finally provided on the applicability of self-similarity assumptions to the analysis of single-crystal fully-plastic indentations.

Alcalá, Jorge; Esqué-de los Ojos, Daniel

2011-07-01

335

Light scattering by single ice crystals of cirrus clouds  

NASA Astrophysics Data System (ADS)

In situ measurements of angular scattering intensities (ASIs) related to single ice crystals of cirrus clouds were obtained for the first time with the airborne Polar Nephelometer instrument. These observations were performed in the southern mid-latitudes during the INCA project. The analysis of the data shows that the well marked peaks of the ASIs are undoubtedly attributed to quasi-specular reflections from crystal facets and the refracted rays passed through the ice crystals. Emphasizing that it is not enough to know the shape of the crystal, but also the internal structure is of great importance. Ray tracing simulations reproduce most of the observed ASIs features. The model of surface roughness, which assumes the Weibull statistics, enables to reproduce the quasi-specular external reflection from crystal facets. It follows from the retrievals that the surface of the crystals was deeply rough and the amount of the internal inclusions (air bubbles) was quite high.

Shcherbakov, Valery; Gayet, Jean-François; Jourdan, Olivier; Ström, Johan; Minikin, Andreas

2006-08-01

336

SINGLE CRYSTAL NIOBIUM TUBES FOR PARTICLE COLLIDERS ACCELERATOR CAVITIES  

SciTech Connect

The objective of this research project is to produce single crystal niobium (Nb) tubes for use as particle accelerator cavities for the Fermi laboratory’s International Linear Collider project. Single crystal Nb tubes may have superior performance compared to a polycrystalline tubes because the absence of grain boundaries may permit the use of higher accelerating voltages. In addition, Nb tubes that are subjected to the high temperature, high vacuum crystallization process are very pure and well annealed. Any impurity with a significantly higher vapor pressure than Nb should be decreased by the relatively long exposure at high temperature to the high vacuum environment. After application of the single crystal process, the surfaces of the Nb tubes are bright and shiny, and the tube resembles an electro polished Nb tube. For these reasons, there is interest in single crystal Nb tubes and in a process that will produce single crystal tubes. To convert a polycrystalline niobium tube into a single crystal, the tube is heated to within a few hundred ?C of the melting temperature of niobium, which is 2477 ?C. RF heating is used to rapidly heat the tube in a narrow zone and after reaching the operating temperature, the hot zone is slowly passed along the length of the tube. For crystallization tests with Nb tubes, the traverse rate was in the range of 1-10 cm per hour. All the crystallization tests in this study were performed in a water-cooled, stainless steel chamber under a vacuum of 5 x10-6 torr or better. In earliest tests of the single crystal growth process, the Nb tubes had an OD of 1.9 cm and a wall thickness of 0.15 mm. With these relatively small Nb tubes, the single crystal process was always successful in producing single crystal tubes. In these early tests, the operating temperature was normally maintained at 2200 ?C, and the traverse rate was 5 cm per hour. In the next test series, the Nb tube size was increased to 3.8 cm OD and the wall thickness was increased 0.18 mm and eventually to 0.21 mm. Again, with these larger tubes, single crystal tubes were usually produced by the crystallization process. The power supply was generally operated at full output during these tests, and the traverse rate was 5 cm per hour. In a few tests, the traverse rate was increased to 10 cm per hour, and at the faster traverse rate, single crystal growth was not achieved. In these tests with a faster traverse rate, it was thought that the tube was not heated to a high enough temperature to achieve single crystal growth. In the next series of tests, the tube OD was unchanged at 3.8 cm and the wall thickness was increased to 0.30 mm. The increased wall thickness made it difficult to reach an operating temperature above 2,000 ?C, and although the single crystal process caused a large increase in the crystal grains, no single crystal tubes were produced. It was assumed that the operating temperature in these tests was not high enough to achieve single crystal growth. In FY 2012, a larger power supply was purchased and installed. With the new power supply, temperatures above the melting point of Nb were easily obtained regardless of the tube thickness. A series of crystallization tests was initiated to determine if indeed the operating temperature of the previous tests was too low to achieve single crystal growth. For these tests, the Nb tube OD remained at 3.8 cm and the wall thickness was 0.30 mm. The first test had an operating temperature of 2,000 ?C. and the operating temperature was increased by 50 ?C increments for each successive test. The final test was very near the Nb melting temperature, and indeed, the Nb tube eventually melted in the center of the tube. These tests showed that higher temperatures did yield larger grain sizes if the traverse rate was held constant at 5 cm per hour, but no single crystal tubes were produced even at the highest operating temperature. In addition, slowing the traverse rate to as low as 1 cm per hour did not yield a single crystal tube regardless of operating temperature. At this time, it

MURPHY, JAMES E [University of Nevada, Reno] [University of Nevada, Reno

2013-02-28

337

Precise Magnetic Torque Measurements on Single Crystals of Iron  

Microsoft Academic Search

A rugged balance of sufficiently high sensitivity and a rotating magnet capable of producing a field of over 3000 oersteds are used to make magnetic torque curves. The equations for the torque curve of a single crystal disk of any orientation whatsoever are derived on the assumption that the magnetic anisotropy is adequately described by a single constant. Furthermore, a

L. P. Tarasov; F. Bitter

1937-01-01

338

Optical and Mechanical Characteristics of PETN Single Crystal  

Microsoft Academic Search

Pentaerythritol tetranitrate (PETN) is an extensively used crystalline high explosive. A good understanding of the laser- induced chemical decomposition and growth to detonation of PETN is important. This work on PETN single crystals focused primarily on its mechanical and optical properties under laser pulse interaction. Laser pulse (E<2 J, tau= 150 ps, &=tilde; 1.06 mum) was focused on the single

V. T. Gromov

2005-01-01

339

Study on production and current-voltage characteristics of ZnO nano-thin films deposited by DC magnetron sputtering  

Microsoft Academic Search

We deposited ZnO thin Alms on single-crystal p-type Silicon substrates by direct current (DC) magnetron sputtering method. The ZnO thin films deposited at room temperature by DC magnetron sputtering were annealed, when powers were 60, 90 and 120W, and temperature were 400, 500, 600 and 700 degC respectively. Analyzed microstructure of the ZnO thin films by X-ray diffraction (XRD).Observed Cross-sectional

Xiaofeng Zhao; Dianzhong Wen

2008-01-01

340

Solution-processed, Self-organized Organic Single Crystal Arrays with Controlled Crystal Orientation  

PubMed Central

A facile solution process for the fabrication of organic single crystal semiconductor devices which meets the demand for low-cost and large-area fabrication of high performance electronic devices is demonstrated. In this paper, we develop a bottom-up method which enables direct formation of organic semiconductor single crystals at selected locations with desired orientations. Here oriented growth of one-dimensional organic crystals is achieved by using self-assembly of organic molecules as the driving force to align these crystals in patterned regions. Based upon the self-organized organic single crystals, we fabricate organic field effect transistor arrays which exhibit an average field-effect mobility of 1.1?cm2V?1s?1. This method can be carried out under ambient atmosphere at room temperature, thus particularly promising for production of future plastic electronics.

Kumatani, Akichika; Liu, Chuan; Li, Yun; Darmawan, Peter; Takimiya, Kazuo; Minari, Takeo; Tsukagoshi, Kazuhito

2012-01-01

341

Organic single crystal transistor characteristics of single-crystal phase pentacene grown by ionic liquid-assisted vacuum deposition  

NASA Astrophysics Data System (ADS)

Organic transistor characteristics of single-crystal phase pentacene were investigated. Ionic liquids (ILs) were used as not only a gate dielectric material in the transistors but also a crystallization solvent in vacuum deposition of pentacene. The crystal sizes reached 200 ?m and their surface exhibits a molecularly step-and-terrace structure. There was no sign of IL molecules inside the crystal, and the impurity level of 6,13-pentacenequinone was also reduced. The average value of the field-effect mobility was not so inferior to those for the conventional pentacene single crystals, and the highest value exceeded 5 cm2/Vs, with the on/off current ratio of 104.

Takeyama, Yoko; Ono, Shimpei; Matsumoto, Yuji

2012-08-01

342

Stress-induced single-polarization single-transverse mode photonic crystal fiber with low nonlinearity  

Microsoft Academic Search

We report on the design of a single-polarization single-transverse mode large mode area photonic crystal fiber. By including index-matched stress applying elements in the photonic cladding an ultra-broadband single polarization window is obtained while a large mode field area of ~700 mum is maintained. Based on that design, an Yb-doped double-clad photonic crystal fiber is realized that combines low nonlinearity

T. Schreiber; F. Röser; O. Schmidt; J. Limpert; R. Iliew; F. Lederer; A. Petersson; C. Jacobsen; K. P. Hansen; J. Broeng; A. Tünnermann

2005-01-01

343

Method of making macrocrystalline or single crystal semiconductor material  

NASA Technical Reports Server (NTRS)

A macrocrystalline or single crystal semiconductive material is formed from a primary substrate including a single crystal or several very large crystals of a relatively low melting material. This primary substrate is deposited on a base such as steel or ceramic, and it may be formed from such metals as zinc, cadmium, germanium, aluminum, tin, lead, copper, brass, magnesium silicide, or magnesium stannide. These materials generally have a melting point below about 1000 C and form on the base crystals the size of fingernails or greater. The primary substrate has an epitaxial relationship with a subsequently applied layer of material, and because of this epitaxial relationship, the material deposited on the primary substrate will have essentially the same crystal size as the crystals in the primary substrate. If required, successive layers are formed, each of a material which has an epitaxial relationship with the previously deposited layer, until a layer is formed which has an epitaxial relationship with the semiconductive material. This layer is referred to as the epitaxial substrate, and its crystals serve as sites for the growth of large crystals of semiconductive material. The primary substrate is passivated to remove or otherwise convert it into a stable or nonreactive state prior to deposition of the seconductive material.

Shlichta, P. J. (inventor); Holliday, R. J. (inventor)

1986-01-01

344

Optical and structural properties of chalcone NLO single crystals  

NASA Astrophysics Data System (ADS)

Organic compound (E)-1-(4-methoxyphenyl)-3-(2,3,5-trichlorophenyl)prop-2-en-1-one [MPTCPP] with molecular formula C 16H 11Cl 3O 2 was synthesized using Claisen-Schmidt condensation reaction method. 1H NMR spectra was recorded to identify the various functional groups present in the compound and confirm the chemical structure. The single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum study reveals that the crystal is transparent in the entire visible region and the absorption is observed at 364 nm. The Kurtz powder second harmonic generation (SHG) test shows that the MPTCPP is NLO active and its SHG efficiency is three times that of urea. Single crystal XRD study shows that the compound crystallizes in the monoclinic system with a space group Cc. The corresponding lattice parameters of the crystal are a = 28.215(5) Å, b = 3.9740(4) Å, c = 16.178(3) Å and V = 1503.0(4) Å 3. The micro hardness test was carried out and the work hardening coefficient value ( n) of the crystal was found to be 1.48. This indicates that the crystal is hard and is suitable for device application. The thermal study reveals that the thermal stability of the crystal is good.

Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Manjunath, H. R.; Karegouda, Prakash; Crasta, Vincent; Sridhar, M. A.

2011-11-01

345

''6-Degrees of Freedom'' Single Crystal Plasticity Experiments  

SciTech Connect

A deformation experiment has been developed specifically for the purpose of validation of dislocation dynamics simulations of plastic flow up to strains on the order of 1% [1]. The experiment has been designed so that a compressive uniaxial stress field is essentially super imposed on the test sample, and the crystal is free to deform with 3 orthogonal translation directions, and 3 rotation/tilt axes of freedom and has been given the name ''6-degrees of freedom'' (6DOF) experiment. The rotation, tilt and translation of the crystal are monitored by 5 laser displacement gages and 3 extensometers. Experiments are being performed on high purity Mo single crystals orientated for ''single slip''. All of the experiments are performed in pairs, with one test sample having highly polished surfaces for optical light and AFM slip-trace analyses, and the other having 4 strain gage rosettes mounted on the sides for measurement of the bi-axial surface strains during testing. All of the experimental data is used together to determine the slip activity of the orientated single crystal during deformation. Experimental results on high-purity Mo single crystals are presented. The results of these experiments show that slip behavior is in substantial deviation from the expected ''Schmid'' behavior. These experimental results bring into question some of the fundamental assumptions used in both the construction of crystal plasticity constitutive relationships and rules for dislocation mobility use in 3-D dislocation dynamics simulations.

Lassila, D H; Florando, J N; LeBlanc, M M; Arsenlis, T; Rhee, M

2003-05-21

346

Double-crystal x-ray diffractometry of single crystals with microdefects  

Microsoft Academic Search

The known method of the `integral' diffuse scattering has been generalized in the Bragg case of x-ray diffraction for crystals, which contain large microdefects commensurable with the extinction length. In the framework of the developed statistical dynamical theory, relatively simple analytical expressions have been derived for coherent and diffuse components of reflectivity of single crystals with randomly distributed microdefects. To

V. B. Molodkin; S. I. Olikhovskii; E. N. Kislovskii; V. P. Krivitsky; E. G. Len; E. V. Pervak; G. E. Ice; B. C. Larson

2001-01-01

347

Synthesis and synchrotron light-induced luminescence of ZnO nanostructures: nanowires, nanoneedles, nanoflowers, and tubular whiskers.  

PubMed

ZnO nanostructures, including single-crystal nanowires, nanoneedles, nanoflowers, and tubular whiskers, have been fabricated at a modestly low temperature of 550 degrees C via the oxidation of metallic Zn powder without a metal catalyst. Specific ZnO nanostructures can be obtained at a specific temperature zone in the furnace depending on the temperature and the pressure of oxygen. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) studies show that ZnO nanostructures thus prepared are single crystals with a wurtzite structure. X-ray excited optical luminescence (XEOL) from the ZnO nanostructures show noticeable morphology-dependent luminescence. Specifically, ZnO nanowires of around 15 nm in diameter emit the strongest green light. The morphology of these nanostructures, their XEOL, and the implication of the results will be discussed. PMID:16851331

Sun, X H; Lam, S; Sham, T K; Heigl, F; Jürgensen, A; Wong, N B

2005-03-01

348

Enhancing the Mechanical Properties of Single-Crystal CVD Diamond  

SciTech Connect

Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

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

2009-01-01

349

Single-atom switching in photonic crystals  

NASA Astrophysics Data System (ADS)

We describe the role of first non-Markovian corrections to resonance fluorescence in photonic crystals, using a perturbative expansion of the Heisenberg equations of motion in powers of the atom-field reservoir coupling strength. Non-Markovian effects arise from the rapid variation of the photonic density of states with frequency. Our method recaptures the physics of the photon-atom bound state in the presence of a full photonic band gap. For the anisotropic three-dimensional photonic band gap, it predicts remarkable features in the resonance fluorescence, such as atomic population inversion and switching behavior in a two-level atom for moderate values of the applied laser field. The magnitude of the switching effect depends sensitively on the external laser intensity and its detuning frequency from the atomic transition. The robustness of this effect against nonradiative decay and dephasing mechanisms is also investigated.

Florescu, Marian; John, Sajeev

2001-09-01

350

Growth of solid solution single crystals  

NASA Technical Reports Server (NTRS)

Based on the thermophysical properties of Hg sub 1-x Cd sub x Te alloys, the reasons are discussed for the failure of conventional Bridgman-Stockbarger growth methods to produce high quality homogeneous crystals in the presence of Earth's gravity. The deleterious effects are considered which arise from the dependence of the thermophysical properties on temperature and composition and from the large amount of heat carried by the fused silica ampules. An improved growth method, developed to optimize heat flow conditions, is described and experimental results are presented. The problems associated with growth in a gravitational environment are discussed. The anticipated advantages of growth in microgravity are given and the implications of the requirements for spaceflight experiments are summarized.

Lehoczky, S. L.; Szofran, F. R.

1987-01-01

351

Highly enhanced acetone sensing performances of porous and single crystalline ZnO nanosheets: high percentage of exposed (100) facets working together with surface modification with Pd nanoparticles.  

PubMed

Porous and single crystalline ZnO nanosheets, which were synthesized by annealing hydrozincite Zn(5)(CO(3))(2)(OH)(6) nanoplates produced with a water/ethylene glycol solvothermal method, are used as building blocks to construct functional Pd-ZnO nanoarchitectures together with Pd nanoparticles based on a self-assembly approach. Chemical sensing performances of the ZnO nanosheets were investigated carefully before and after their surface modification with Pd nanoparticles. It was found that the chemical sensors made with porous ZnO nanosheets exhibit high selectivity and quick response for detecting acetone, because of the 2D ZnO nanocrystals exposed in (100) facets at high percentage. The performances of the acetone sensors can be further improved dramatically, after the surfaces of ZnO nanosheets are modified with Pd nanoparticles. Novel acetone sensors with enhanced response, selectivity and stability have been fabricated successfully by using nanoarchitectures consisting of ZnO nanosheets and Pd nanoparticles. PMID:22853192

Xiao, Yuanhua; Lu, Lingzhen; Zhang, Aiqin; Zhang, Yonghui; Sun, Li; Huo, Lei; Li, Feng

2012-08-01

352

Single-crystal structure of a covalent organic framework.  

PubMed

The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 °C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m(2)/g and a methane total uptake of 15.0 wt % (176 cm(3)/cm(3)) at 25 °C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry. PMID:24143961

Zhang, Yue-Biao; Su, Jie; Furukawa, Hiroyasu; Yun, Yifeng; Gándara, Felipe; Duong, Adam; Zou, Xiaodong; Yaghi, Omar M

2013-11-01

353

Method for harvesting rare earth barium copper oxide single crystals  

DOEpatents

A method of preparing high temperature superconductor single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid. 2 figs.

Todt, V.R.; Sengupta, S.; Shi, D.

1996-04-02

354

Single crystal growth of potassium lithium niobate for SAW applications  

NASA Astrophysics Data System (ADS)

The growth of good quality, crack free medium size KLN single crystals using the Czochralski method, with dielectric and piezoelectric properties comparable or superior to the best known bronze composition SBN was demontrated. However, large ( 1 cm diameter) KLN crystals suitable for SAE Surface Acoustic Waves characterization without considerable cracking were not grown. Therefore, in pursuit of alternative bronze compositions with the potential for large crystal growth, work was initiated or, the growth and characterization of PBN and the stuffed bronze BSKNN. Initial characterization work shows both of these materials to be very promising for future SAW device development, and good quality single crystals of BSKNN with 1 cm square cross-section already were successfully grown. The physical properties of PBN and BSKNN also make them of interest for other piezoelectric, electro-optic, and nonlinear optic applications in addition to SAW devices.

Neurgaonkar, R. R.

1982-10-01

355

Isotropic behavior of an anisotropic material: single crystal silicon  

NASA Astrophysics Data System (ADS)

Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si components and will provide subsecond thermal equilibrium and sub-micron creep.

McCarter, Douglas R.; Paquin, Roger A.

2013-09-01

356

Dispersion of optical activity of magnesium sulfite hexahydrate single crystals  

NASA Astrophysics Data System (ADS)

The magnesium sulfite hexahydrate (MgSO3.6H2O) crystals are unique because they are the only representative (with sodium periodate) of the crystallographic class C3 (without a center of symmetry). The crystal symmetry suggests presence of nonlinearity, piezo- and pyro-electric properties and gyrotropy as well. Single crystals of MgSO3.6H2O (pure and doped with Ni, Co and Zn) for the time being are grown only by the original method developed in the Laboratory for Crystal growth at the Faculty of Physics in Sofia University. The first results of optical activity of pure MgSO3.6H2O and Zn doped MgSO3.6H2O crystals are described and analyzed in a wide spectral range. The optical activity manifests itself in the direction (0001) as a rotation of the polarization plane.

Dimov, T.; Bunzarov, Zh; Iliev, I.; Petkova, P.; Tzoukrovski, Y.

2010-11-01

357

Indium and nitrogen doping of GaSb single crystals  

NASA Astrophysics Data System (ADS)

GaSb single crystals doped with nitrogen and indium were grown using the Czochralski method without encapsulant in a flowing atmosphere of hydrogen and were studied for etch pit density (EPD) and Hall mobility. It has been found that the dopants had no influence on the average EPD in the GaSb crystals. However, EPD profiles of undoped and In-doped GaSb showed a decrease along the growth direction (from the beginning to the end of the crystals), while the EPD profile of N-doped crystals showed a sharp increase. This behaviour of N-doped crystals can be explained by the development of stresses near the solidification interface, as a result of nitrogen volatilization during growth.

Št?pánek, Bed?ich; Šesták'ová, V?ra

1992-09-01

358

Acquisition of Single Crystal Growth and Characterization Equipment  

Microsoft Academic Search

Final Report for DOE Grant No. DE-FG02-04ER46178 'Acquisition of Single Crystal Growth and Characterization Equipment'. There is growing concern in the condensed matter community that the need for quality crystal growth and materials preparation laboratories is not being met in the United States. It has been suggested that there are too many researchers performing measurements on too few materials. As

M. Brian Maple; Diego A. Zocco

2008-01-01

359

Single Crystal Neutron Diffraction Study of Potassium Cyanide  

Microsoft Academic Search

Neutron diffraction measurements were made on single crystals of KCN to obtain information about the disorder of the CN? ions in the cubic phase. The crystals were obtained by pulling from the melt by a modified Czochralski method. Data were collected on two four-circle diffractometers at room temperature and at 180°K, just above the cubic-orthorhombic phase transition. Structure factors were

D. L. Price; J. M. Rowe; J. J. Rush; E. Prince; D. G. Hinks; S. Susman

1972-01-01

360

Irradiation effects on sodium sulphanilate dihydrate single crystals  

NASA Astrophysics Data System (ADS)

The induced damage in single crystals of Sodium sulphanilate dihydrate (SSDH) irradiated at IUAC, New Delhi with 15 MV Pelletron accelerator with 100 MeV Ag 7+ and 70 MeV Li 3+ ions has been studied by optical measurements, mechanical hardness measurements, Electrical and ERDA measurements. Optical absorption measurements increase with the increase in fluence. The mechanical hardness of the crystal decreases on irradiation. The dielectric constant of SSDH increases on irradiation.

Mythili, P.; Kanagasekaran, T.; Khan, S. A.; Kulriya, P. K.; Kanjilal, D.; Gopalakrishnan, R.

2008-04-01

361

Infrared Optical Properties of Single Crystals of Tellurium  

Microsoft Academic Search

The fundamental optical absorption and photoconductivity of single crystals of tellurium has been investigated. Tellurium crystals exhibit dichroism in the infrared, i.e., the absorption constant depends on the polarization of the incident radiation. At 300°K for radiation polarized perpendicular to the C axis the absorption edge, located by means of an arbitrary criterion, is at 3.82 microns (0.324 ev); for

Joseph J. Loferski

1954-01-01

362

Doubling microsecond single pulses in a KTP crystal  

SciTech Connect

The 90{sup 0} phase-matching SHG is performed for microsecond single pulses from a Nd{sup 3+}:YAP laser in a KTP crystal with the 29% conversion efficiency. The 90{sup 0} phase-matching temperature is 54{sup 0}C. The crystal surface damage threshold measured without and with an antireflection coating was 107{+-}11 and 40{+-}4 J cm{sup -2}, respectively. (nonlinear optical phenomena)

Abrosimov, S A; Kochiev, D G [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Maklakova, N Yu; Semenenko, V N [Institute of Mineralogy and Petrography, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

2001-07-31

363

Solution hardening and softening of Nb-Zr single crystals  

Microsoft Academic Search

Single crystals of Nb-Zr solid-solution alloys containing 0.05–2 wt% Zr have been tested in compression at temperatures in the range 4 to 373 K. Stress-strain curves were obtained, and differential tests were made to measure both the strain-rate sensitivity and the thermal stress over the same temperature range. The mechanical data were supplemented by optical microscopy of the crystal surfaces

W. J. Botta; J. W. Christian; G. Taylor

1988-01-01

364

Semiconductor parameters of Bi 2Te 3 single crystal  

Microsoft Academic Search

Single crystals of Bi2Te3 were prepared by a modified Bridgman method. The as-prepared Bi2Te3 was investigated by X-ray diffraction (XRD). Anisotropic phenomena in the layered Bi2Te3 crystal was investigated. The measurements showed that the electrical conductivity, Hall mobility and Seebeck coefficient (TEP) have anisotropic nature. From these measurements type of conduction and several physical parameters such as diffusion coefficients, diffusion

M. M. Nassary; H. T. Shaban; M. S. El-Sadek

2009-01-01

365

Microstructural instability in coated single crystal superalloys  

Microsoft Academic Search

Specimens of CMSX-4 and CMSX-10 alloys have been platinum aluminised to give a single phase (Ni,Pt)Al coating and a two phase PtAl2–(Ni,Pt)Al coating, respectively. Specimens of the coated alloys were exposed in an oxidising environment for 188, 350 and 750h at a temperature of 1100°C. Specimens were then sectioned, polished and examined using scanning electron microscopy (SEM), energy dispersive X-ray

M. Reid; M. J. Pomeroy; J. S. Robinson

2004-01-01

366

High Resolution Technique and Instrument for Measuring Lattice Parameters in Single Crystals.  

National Technical Information Service (NTIS)

A method of measuring the lattice parameter in an unknown single crystal by comparing its diffraction angle to a standard single crystal, on a double-crystal diffractometer is disclosed. The method comprises several steps including mounting the unknown an...

M. Fatemi

1990-01-01

367

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

The solidification of a solid solution semiconductor, having a wide separation between liquidus and serious has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; mercury cadmium telluride with 80.0 mole percent of HgTe and 84.8 mole percent respectively. These alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed of residual acceleration effects. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system by a previously processed sample, the sample was not received until May 1998, and the preliminary analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. Early results are indicating that the sample may not accomplish the desired objectives. As with the USMP-2 mission, the results of the ground based experiments were compared with the crystal grown in orbit under microgravity conditions. On the earth, it has been demonstrated that the application of the magnetic field leads to a significant reduction in fluid flow, with improved homogeneity of composition. The field strength required to suppress flow increases with diameter of the material. The 8 mm diameter sample used here was less than the upper diameter limit for a ST magnet. The configuration for USMP-4 was changed so that the material was seeded and other processing techniques were also modified. It was decided to examine the effects of a strong magnetic field under the modified configuration and parameters. A further change from USMP-2 was that a different composition of material was grown, namely with 0.152 mole fraction of cadmium telluride rather than the 0.200 of the USMP-2 experiment. The objective was to grow highly homogeneous, low defect density material of a composition at which the conduction band and the valence band of the material impinge against each other. As indicated, the furnace was contaminated during the mission. As a result of solid debris remaining in the furnace bore, the cartridge in this experiment, denoted as SL1-417, was significantly bent during the insertion phase. During translation the cartridge scraped against the plate which isolates the hot and cold zones of the furnace. Thermocouples indicated that a thermal assymetry resulted. The scraping in the slow translation or crystal growth part of the processing was not smooth and it is probable that the jitter was sufficient to give rise to convection in the melt. Early measurements of composition from the surface of the sample have shown that the composition varies in an oscillatory manner.

Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.; Watring, D. A.

1999-01-01

368

Skylab experiments on semiconductors and alkali halides. [single crystal growth  

NASA Technical Reports Server (NTRS)

The space processing experiments performed during the Skylab missions included one on single crystal growth of germanium selenide and telluride, one on pure and doped germanium crystals, two on pure and doped indium antimonide, one on gallium-indium-antimony systems, and one on a sodium chloride-sodium fluoride eutectic. In each experiment, three ampoules of sample were processed in the multipurpose electric furnace within the Skylab Materials Processing Facility. All were successful in varying degrees and gave important information about crystal growth removed from the effects of earth surface gravity.

Lundquist, C. A.

1974-01-01

369

Lithium niobate single-crystal and photo-functional device  

DOEpatents

Provided are lithium niobate single-crystal that requires a low voltage of not larger than 10 kV/nm for its ferroelectric polarization inversion and of which the polarization can be periodically inverted with accuracy even at such a low voltage, and a photo-functional device comprising the crystal. The crystal has a molar fraction of Li.sub.2 O/(Nb.sub.2 O.sub.5 +Li.sub.2 O) of falling between 0.49 and 0.52. The photo-functional device can convert a laser ray being incident thereon.

Gopalan, Venkatraman (State College, PA); Mitchell, Terrence E. (Los Alamos, NM); Kitamura, Kenji (Tsukuba, JP); Furukawa, Yasunori (Tsukuba, JP)

2001-01-01

370

Growth and luminescence properties of GaSb single crystals  

NASA Astrophysics Data System (ADS)

The growth of undoped GaSb single-crystals by the horizontal Bridgman method is analyzed. Photoluminescence measurements are used to determine the usefulness of this method for the production of device quality substrate material. The observed efficient quenching of bound exciton recombination by crystal inhomogeneities and residual stress demonstrated the high crystal quality of the Bridgman grown material. Antisite defect formation is also considered and the following are observed: formation of antimonium vacancies during the solidification process and defect migration causing the formation of double acceptor antisite defect.

Lewandowski, W.; Gajewska, M.; Pastuszka, B.; Bugajski, M.

371

Nucleation kinetics, growth and studies of ?-alanine single crystals  

NASA Astrophysics Data System (ADS)

Solubility and metastable zone width for the re-crystallized salt of ?-alanine was determined. Induction period measurement for the selected supersaturation ratios at room temperature (31 °C) was carried out for supersaturated aqueous solutions of ?-alanine and it is noticed that induction period decreases with increase of supersaturation ratio. The nucleation parameters such as Gibbs free energy change, radius and number of molecules of the critical nucleus, interfacial tension and the nucleation rate have been evaluated by classical nucleation theory. Single crystals of ?-alanine were grown using the optimized nucleation parameters by solution method and grown crystals have been subjected to various studies like XRD studies, FTIR, optical, thermal and SHG studies.

Shanthi, D.; Selvarajan, P.; HemaDurga, K. K.; Lincy Mary Ponmani, S.

2013-06-01

372

Single-crystal growth, crystal and electronic structure of NaCoO 2  

Microsoft Academic Search

Single crystals of NaCoO2 have been successfully synthesized for the first time by a flux method at 1323K. A single-crystal X-ray diffraction study confirmed the trigonal R3?m space group and the lattice parameters a=2.8897(15)A?, c=15.609(3)A?. The crystal structure has been refined to the conventional values R=1.9% and wR=2.1% for 309 independent observed reflections. The electron density distribution of NaCoO2 has

Yasuhiko Takahashi; Yoshito Gotoh; Junji Akimoto

2003-01-01

373

Crystal growth and electrical properties of lead indium niobate–lead titanate binary single crystal  

Microsoft Academic Search

The largest Pb(In1\\/2Nb1\\/2)O3–PbTiO3(PIN-PT) binary system single crystal (about 20mmx10mm×5mm,4.5g) near the morphotropic phase boundary composition with well-developed (100) planes was grown by the flux method using PbO–PbF2–B2O3 flux. The PIN-PT(72\\/28) single crystal was found by simultaneous microdifferential thermal analysis and thermogravimetric analysis to show a peritectic melting at 1283°C with a partial decomposition of the perovskite crystal into a pyrochlore

N. Yasuda; H Ohwa; M Kume; K Hayashi; Y Hosono; Y Yamashita

2001-01-01

374

The Load Capability of Piezoelectric Single Crystal Actuators  

NASA Technical Reports Server (NTRS)

Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

2007-01-01

375

The Load Capability of Piezoelectric Single Crystal Actuators  

NASA Technical Reports Server (NTRS)

Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

2006-01-01

376

Improved growth technology of large MgO single crystals  

NASA Astrophysics Data System (ADS)

An improved growth technology (the arc-fusion method) has been successfully employed to grow large magnesium oxide (MgO) single crystals with an average size of 4-6 cm. Three adjustable graphite electrodes with different electric currents ( I>I>I) are applied, which technology is different from the conventional technology (using a uniform current). In addition, a proper control for the efficient use of different currents reduces the number of bubbles in the growth system, which allows us to obtain optically transparent high-purity MgO single crystals. Our present work shows that control of the temperature-gradient field in the whole process is the key to growing high-purity and large MgO single crystals.

Zhang, Xu; Xue, Dongfeng; Wang, Jiyang; Feng, Xiqi

2006-07-01

377

Elastic constants of single crystal Hastelloy X at elevated temperatures  

SciTech Connect

An acoustic time of flight technique is described in detail for measuring the elastic constants of cubic single crystals that allows for the constants to be determined at elevated temperature. Although the overall technique is not new, various aspects of the present work may prove extremely useful to others interested in finding these values, especially for aerospace materials applications. Elastic constants were determined for the nickel based alloy, Hastelloy X from room temperature to 1,000 C. Accurate elastic constants were needed as part of an effort to predict both polycrystal mechanical properties and the nature of grain induced heterogeneous mechanical response. The increased accuracy of the acoustically determined constants resulted in up to a 15% change in the predicted stresses in individual grains. These results indicate that the use of elastic single crystal constants of pure nickel as an approximation for the constants of gas turbine single crystal alloys, which is often done today, is inaccurate.

Canistraro, H.A. [Univ. of Hartford, CT (United States). Dept. of Mechanical and Audio Engineering Technology; Jordan, E.H.; Shi Shixiang [Univ. of Connecticut, Storrs, CT (United States); Favrow, L.H.; Reed, F.A. [United Technologies Research Center, East Hartford, CT (United States)

1998-07-01

378

Spin and charge transport study in single crystal organic semiconductors  

NASA Astrophysics Data System (ADS)

Spin transport studies in amorphous rubrene films have shown exciting and promising results [1]. A large spin diffusion length in these amorphous films has increased the motivation to perform spin transport study in high purity single crystal rubrene. This will provide the fundamental understanding on the spin transport behavior in OS; not influenced by defects or traps. We will present work on small channel single crystal rubrene FET device with magnetic electrodes. For example, our preliminary studies have show mobility for FET with Co electrode to be 0.014cm^2/V-s. A study on the spin and charge transport properties in single crystals of OS with magnetic electrodes is being done and the results will be reported. The influence of gate voltage and applied magnetic field on the transport properties will be discussed. [1] J.H. Shim et al., PRL 100, 226603 (2008)

Raman, Karthik V.; Mulder, Carlijn L.; Baldo, Marc A.; Moodera, Jagadeesh S.

2009-03-01

379

Solution-phase growth of organic single-crystal arrays  

NASA Astrophysics Data System (ADS)

We have successfully developed a method for directly forming organic single-crystal thin films at designated locations on a substrate by solution-phase growth. An original micropattern, in which small rectangular regions were connected to a large rectangular region, was designed. The small regions and the large region were used as nucleation control regions (NCRs) and a growth control region (GCR), respectively. The key to success was to vary local supersaturation of a solution droplet by making a large difference in solvent evaporation between a NCR and a GCR. We found that the NCR played a very important role in forming a single nucleus and in investigating the possibility of control of the crystal orientation. By using the developed micropattern and controlling the solvent vapor pressure during growth, we fabricated single-crystal arrays of a stable organic semiconductor, 3,9-bis(4-ethylphenyl)-peri-xanthenoxanthene (C2Ph-PXX).

Goto, Osamu; Tomiya, Shigetaka; Murakami, Yosuke; Shinozaki, Akira; Toda, Akira; Kasahara, Jiro; Hobara, Daisuke

2012-10-01

380

Synthesis and properties of erbium oxide single crystals  

SciTech Connect

Erbium oxide (Er{sub 2}O{sub 3}, erbia) is a highly stable cubic rare earth oxide with a high melting point of 2,430 C. Because of this, it may have potential applications where high temperature stability and corrosion resistance are required. However, relatively little is known about the properties of this oxide ceramic. The authors have employed a xenon optical floating zone unit with a temperature capability of 3,000 C to grow high quality single crystals of erbia. The conditions for single crystal growth of erbia have been established. The mechanical properties of erbia single crystals have been initially examined using microhardness indentation as a function of temperature.

Petrovic, J.J.; Romero, R.S.; Mendoza, D.; Kukla, A.M.; Hoover, R.C.; McClellan, K.J.

1999-04-01

381

Single Crystal Synthesis and STM Studies of High Temperature Superconductors  

NASA Technical Reports Server (NTRS)

This is a final report for the work initiated in September of 1994 under the grant NAG8-1085 - NASA/OMU, on the fabrication of bulk and single crystal synthesis, specific heat measuring and STM studies of high temperature superconductors. Efforts were made to fabricate bulk and single crystals of mercury based superconducting material. A systematic thermal analysis on the precursors for the corresponding oxides and carbonates were carried out to synthesized bulk samples. Bulk material was used as seed in an attempt to grow single crystals by a two-step self flux process. On the other hand bulk samples were characterized by x-ray diffraction, electrical resistivity and magnetic susceptibility, We studied the specific heat behavior in the range from 80 to 300 K. Some preliminary attempts were made to study the atomic morphology of our samples. As part of our efforts we built an ac susceptibility apparatus for measuring the transition temperature of our sintered samples.

Barrientos, Alfonso

1997-01-01

382

Galvanic deposition of nanocrystalline ZnO thin films from a ZnO Zn(OH)2 mixed phase precursor on pSi substrate  

Microsoft Academic Search

A galvanic technique for the deposition of ZnO thin films is reported. The depositions were carried out on p-type single-crystal silicon substrates at room temperature, from a solution of ZnSO4, where the Zn rod acted as a sacrificing anode and p-Si was the cathode. The deposition of ZnO by this method is pH sensitive, and a pH between 4 and

N. Mukherjee; P. Bhattacharyya; M. Banerjee; A. Mondal; Robert T. T. Gettens; P. K. Ghosh; H. Saha

2006-01-01

383

Magnetothermal properties of single crystal dysprosium  

NASA Astrophysics Data System (ADS)

The magnetocaloric properties (the adiabatic temperature change) of the high purity single crystalline dysprosium have been measured directly over the temperature range from 78 to 220 K in magnetic fields from 0 to 14 kOe applied along the easy magnetization direction (a-axis). These results are in good to excellent agreement, except for two regions (105 to 127 K, and 179 to 182 K), with the previous magnetocaloric effect data reported on lower purity dysprosium samples. The magnetic phase diagram of Dy has been refined based on the results of these measurements and two new high magnetic field phases have been identified. .

Chernyshov, A. S.; Tishin, A. M.; Gschneidner, K. A.; Pecharsky, A. O.; Pecharsky, V. K.; Lograsso, T. A.

2002-05-01

384

Contact properties and surface reaction kinetics of single ZnO nanowire devices fabricated by dielectrophoresis  

NASA Astrophysics Data System (ADS)

This work describes the development of ZnO nanowire (NW) devices for ultraviolet detection and cost-effective gas sensing. A dielectrophoresis (DEP) flow cell fabricated for the integration of NWs on different substrates is presented. The system includes the possibility to set characteristic parameters such as alternating current (AC) frequency, amplitude or flow speed in order to control NW trapping on specific sites defined by micro-gapped electrodes. The electrical characteristics of the rectifying metal/NW contact fabricated by DEP are investigated in darkness and under direct illumination of the metal-NW interface through the ZnO NW. A significant downshift of the turn-on voltage is observed in the current-voltage characteristics during the illumination with photon energies higher than the ZnO bandgap. The reduction is attributed to a barrier height lowering induced by interface charge emission. The effects of AC bias on the thermal drift of the DC average current in NW devices are also discussed. Finally, the reaction kinetics of ethanol and water vapors on the NW surface are compared through the analysis of the DC current under direct exposure to gas flows. Device responses to more complex compound mixtures such as coffee or mint are also monitored over time, showing different performance in both cases.

Pau, J. L.; García Núñez, C.; García Marín, A.; Guerrero, C.; Rodríguez, P.; Borromeo, S.; Piqueras, J.

2014-03-01

385

Crystal growth of alkali metal ion doped potassium niobate fiber single crystals  

NASA Astrophysics Data System (ADS)

Alkali metal (Na, Rb or Cs) ion doped KNbO 3 fiber single crystals are grown using an original pulling down method, to improve their composition change during a crystal growth, by means of co-doping of small ionic size Na and large ionic size Rb or Cs into KNbO 3. In spite of the co-doping, single crystals can be grown with orthorhombic single-phase at room temperature, as well as pure KNbO 3. Their electric properties, such as impedance, are changed depending on the doping ions. Na and Rb co-doped KNbO 3 is promising Pb free ferroelectric and piezoelectric crystals.

Kimura, H.; Tanahashi, R.; Zhao, H. Y.; Maiwa, K.; Cheng, Z. X.; Wang, X. L.

2010-05-01

386

Evaluation of zinc self-diffusion at the interface between homoepitaxial ZnO thin films and (0001) ZnO substrates  

NASA Astrophysics Data System (ADS)

Isotopic ZnO thin films were deposited on the c-plane of ZnO single crystals by pulsed laser deposition. The isotopic abundance of Zn in the films was determined with a secondary ion mass spectrometry before and after the films was diffusion annealed. The diffusion profiles across the film/substrate interface behaved smooth features. The zinc diffusion coefficient (DZn) was obtained by analyzing the slope of the profile in the annealed sample. The temperature dependence of DZn was determined to be DZn(cm2/s)=8.0×104exp(-417[kJ/mol])/RT, where R and T are gas constant and temperature. The zinc ion diffusion coefficients were of the same order as that in a ZnO single crystal. A comparison of the experimental and theoretical values indicated that the zinc ions diffused in the thin film and the single crystal through a vacancy mechanism.

Watanabe, Ken; Matsumoto, Kenji; Adachi, Yutaka; Ohgaki, Takeshi; Nakagawa, Tsubasa; Ohashi, Naoki; Haneda, Hajime; Sakaguchi, Isao

2012-10-01

387

Copper underpotential deposition on Ru quasi-single-crystal films  

Microsoft Academic Search

Ru quasi-single-crystal electrodes, prepared by resistive heating of Ru deposited on Pt single-crystal surfaces in a nitrogen atmosphere, have been used to study copper underpotential deposition (Cu-UPD), Bulk and surface Cu stripping experiments were performed on the low-index Ru\\/Pt(100), Ru\\/Pt(110) and Ru\\/Pt(111) quasi-crystalline film electrodes and also stepped Ru\\/Pt(S)[n(100)×(111)] and Ru\\/Pt(S)[4(111)×(100)] electrodes vicinal to the (100) and (111) planes respectively.

Nicky Bogolowski; Sharon Huxter; Abd-El-Aziz A. Abd-El-Latif; Gary A. Attard; Helmut Baltruschat

2010-01-01

388

Cryogenic motion performances of a piezoelectric single crystal micromotor  

NASA Astrophysics Data System (ADS)

This study investigates the cryogenic performances of a millimeter-size piezoelectric ultrasonic linear micromotor. The piezoelectric vibrator of the micromotor is made of Pb(In1/2Nb1/2)O3 -Pb(Mg1/3Nb2/3)-PbTiO3 single crystal and operated in first-bending wobbling mode. Experiments show that the piezoelectric single crystal micromotor works effectively even at extremely low temperature of -175 °C, although its resonance peaks vary with temperature significantly. This work confirms the feasibility of cryogenic operation of the piezo-micromotor, which is meaningful for aerospace or superconducting microwave application.

Li, Xiaotian; Wu, Yuting; Chen, Zhijiang; Wei, Xiaoyong; Luo, Haosu; Dong, Shuxiang

2014-04-01

389

Apparatus And Method For Producing Single Crystal Metallic Objects  

SciTech Connect

A mold is provided for enabling casting of single crystal metallic articles including a part-defining cavity, a sorter passage positioned vertically beneath and in fluid communication with the part-defining cavity, and a seed cavity positioned vertically beneath and in fluid communication with the sorter passage. The sorter passage includes a shape suitable for encouraging a single crystal structure in solidifying molten metal. Additionally, a portion of the mold between the sorter passage and the part-defining cavity includes a notch for facilitating breakage of a cast article proximate the notch during thermal stress build-up, so as to prevent mold breakage or the inclusion of part defects.

Huang, Shyh-Chin (Latham, NY); Gigliotti, Jr., Michael Francis X. (Scotia, NY); Rutkowski, Stephen Francis (Duanesburg, NY); Petterson, Roger John (Fultonville, NY); Svec, Paul Steven (Scotia, NY)

2006-03-14

390

Shock wave compression of single-crystal forsterite  

Microsoft Academic Search

Hugoniot equation of state measurements have been performed on pure synthetic single-crystal forsterite (Mg2SiO4) in the pressure range 70-160 GPa (0.7-1.6 Mbar). These and earlier data for polycrystalline forsterite are compared with theoretical Hugoniots for the assemblages 2MgO (rocksalt) +SiO2 (stishovite) and MgO (rocksalt) +MgSiO3 (perovskite). The densities attained by single-crystal forsterite at pressures in excess of 120 GPa are

Ian Jackson; Thomas J. Ahrens

1979-01-01

391

Synthesis of Large Single Crystals of LaMnPO  

NASA Astrophysics Data System (ADS)

The compound LaMnPO is isostructural with LaFeAsO, a recently discovered high-temperature superconductor, but optical spectroscopy and transport measurements of this compound have been heretofore limited by small crystal size. Accordingly, crystal syntheses from Sn, Pb and molten salt fluxes (including NaCl/KCl, LiCl/NaCl, KCl, CaCl2, BaCl2/CaCl2 and KCl/CaCl2) were investigated. Fluorine doping was explored; concentrations less than 30 at.% (nominal) had no effect on crystal size; concentrations greater than 40 at.% (nominal) did not yield crystals. Once growth parameters were optimized, the crystals grew in a flat rectangular shape with black luster; their composition was verified with powder and single crystal x-ray diffraction. Successful growths yielded crystals with dimensions up to 3.2 mm by 1 mm by 10 ?m, a significant improvement upon previously reported growths in the literature. These large crystals enabled our group to perform a wide range of experiments that were previously restricted to polycrystalline materials. It may be feasible to extend these methods to the synthesis of similar compounds.

Smith, Greg; Simonson, Jack; Marques, Carlos; Leyva, Victor; Aronson, Meigan

2011-03-01

392

Structural, spectral and mechanical studies of bimetallic crystal: cadmium manganese thiocyanate single crystals  

NASA Astrophysics Data System (ADS)

A nonlinear optical bimetallic thiocyanate complex crystal, cadmium manganese thiocyanate (CMTC) has been successfully synthesized. The growth of single crystals of cadmium manganese thiocyanate has been accomplished from aqueous solution using slow evaporation method. The presence of manganese and cadmium in the synthesized material was confirmed through energy dispersive spectrum (EDS) analysis. Structural analysis was carried out using powder X-ray diffractometer (PXRD) and crystalline perfection of the grown crystals was ascertained by high-resolution X-ray diffraction (HRXRD) analysis. Fourier transform infrared (FTIR) spectrum was taken to confirm the functional groups. The transmittance spectrum of the crystal in the UV-visible region has been recorded and the cutoff wavelength has been determined. The dielectric measurements for the crystals were performed for various frequencies and temperatures. The mechanical properties were evaluated by Vickers microhardness testing, which reveals hardness and stiffness constant of the crystals.

Manikandan, M.; Vijaya Prasath, G.; Bhagavannarayan, G.; Vijayan, N.; Mahalingam, T.; Ravi, G.

2012-09-01

393

Crystal growth and spectral studies of nonlinear optical ?-glycine single crystal grown from phosphoric acid  

NASA Astrophysics Data System (ADS)

Single crystals of the organic nonlinear material ?-glycine have been grown in the presence of phosphoric acid by slow-evaporation method. The crystal structure is confirmed by X-ray powder diffraction method. The thermal stability and decomposition of the sample have been studied by thermal analysis. The result shows that the transition temperature, i.e. transition from ?- to ?-glycine is enhanced from 165 °C to 191 °C. The modes of vibrations of different molecular groups present in glycine have been identified by spectral analyses. The transmittance spectrum of ?-glycine crystal shows that the lower UV cut-off wavelength lies at 230 nm. Second harmonic generation (SHG) conversion efficiency has been estimated as 125 mV and the output power by the crystal was 1.3 times that of potassium dihydrogen phosphate (KDP) crystal. The dielectric and microhardness measurements have been carried out on the ?-glycine crystal.

Parimaladevi, R.; Sekar, C.

2010-09-01

394

Growth of Solid Solution Single Crystals  

NASA Technical Reports Server (NTRS)

The solidification of a solid solution semiconductor, having a wide separation between liquidus and solidus has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; with 80.0 mole percent of HgTe and 84.8 mole percent of HgTe respectively, the remainder being cadmium telluride. Such alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed correlating composition variations to measured residual acceleration. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system, analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. The results indicate that the sample did accomplish the desired objectives.

Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.

2001-01-01

395

Structural and optical properties of a new chalcone single crystal  

NASA Astrophysics Data System (ADS)

A new nonlinear optical material 1-(4-methylthiophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one with molecular formula C17H16O2S was synthesized by using the Claisen-Schmidt condensation reaction method. The Various functional groups present in the compound were identified using recorded FT-IR spectrum. The crystal growth parameters have been studied using solubility test and acetone is found to be a very good solvent for the crystal growth at an ambient temperature. The transparent high quality single crystals up to a size of 26×2×2 mm3 were grown using the slow evaporation solution growth technique. UV-visible study was carried out and the spectrum reveals that the crystal is transparent in the entire visible region and absorptive in the UV region. The refractive index is determined using Brewster's angle method. The optical energy band gap of the material is measured using Tauc's plot and the direct method. The single crystal XRD of MMPP crystal shows the following cell parameters: a=5.9626(2) Å, b=15.3022(6) Å, c=16.0385(7) Å, ?=?=?=90°, volume=1463.37(10) Å3 with a space group of Pna21. The compound MMPP exhibits optical nonlinearity (NLO) and its second order NLO efficiency is 3.15 times to that of urea. The effect of functional groups OCH3 and SCH3 on the non-linearity as well as the structural property of the compound has been discussed. The crystal is thermally stable. High NLO efficiency, good thermal stability, good transparency and ability to grow as a high quality single crystal make this material very attractive for opto-electronic applications.

Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Poojary, Boja

2012-09-01

396

Dipole field guided orientated attachment of nanocrystals to twin-brush ZnO mesocrystals.  

PubMed

Mesocrystals of ZnO were synthesized hydrothermally by using gum arabic as a structure-directing agent. Their hierarchical structure has a unique twin-brush form consisting of vertically aligned nanorods in a single-crystal-like porous form. The formation mechanism of the twin-brush ZnO was investigated by quenching a series of samples at different times and examining them by TEM, SEM, and XRD. The alignment of ZnO crystal units can be modulated by adding simple salts such as KCl to change the units from nanorods to nanoplates. This can be explained by screening the dipolar force of the polar crystal. Local cathodoluminescence of twin-brush ZnO was used to follow the local structure changes. PMID:23080346

Liu, Ming-Han; Tseng, Yao-Hung; Greer, Heather F; Zhou, Wuzong; Mou, Chung-Yuan

2012-12-01

397

perovskite: a single-crystal X-ray diffraction study  

NASA Astrophysics Data System (ADS)

Magnesium silicate perovskite is the predominant phase in the Earth's lower mantle, and it is well known that incorporation of iron has a strong effect on its crystal structure and physical properties. To constrain the crystal chemistry of (Mg, Fe)SiO3 perovskite more accurately, we synthesized single crystals of Mg0.946(17)Fe0.056(12)Si0.997(16)O3 perovskite at 26 GPa and 2,073 K using a multianvil press and investigated its crystal structure, oxidation state and iron-site occupancy using single-crystal X-ray diffraction and energy-domain Synchrotron Mössbauer Source spectroscopy. Single-crystal refinements indicate that all iron (Fe2+ and Fe3+) substitutes on the A-site only, where based on Mössbauer spectroscopy. Charge balance likely occurs through a small number of cation vacancies on either the A- or the B-site. The octahedral tilt angle ( ?) calculated for our sample from the refined atomic coordinates is 20.3°, which is 2° higher than the value calculated from the unit-cell parameters ( a = 4.7877 Å, b = 4.9480 Å, c = 6.915 Å) which assumes undistorted octahedra. A compilation of all available single-crystal data (atomic coordinates) for (Mg, Fe)(Si, Al)O3 perovskite from the literature shows a smooth increase of ? with composition that is independent of the nature of cation substitution (e.g., or substitution mechanism), contrary to previous observations based on unit-cell parameter calculations.

Sinmyo, Ryosuke; Bykova, Elena; McCammon, Catherine; Kupenko, Ilya; Potapkin, Vasily; Dubrovinsky, Leonid

2014-06-01

398

Long single ZnO nanowire for logic and memory circuits: NOT, NAND, NOR gate, and SRAM.  

PubMed

We demonstrate logic and static random access memory (SRAM) circuits using a 100 ?m long and 100 nm thin single ZnO nanowire (NW), which acts as a channel of field-effect transistors (FETs) with Al2O3 dielectrics. NW FETs are thus arrayed in one dimension to consist of NOT, NAND, and NOR gate logic, and SRAM circuits. Two respective top-gate NW FETs with Au and indium-tin-oxide (ITO) were connected to form an inverter, the basic NOT gate component, since the former gate leads to an enhanced mode FET while the latter to depletion mode due to their work function difference. Our inverters showed a high voltage gain of 22 under a 5 V operational voltage, resulting in successful operation of all other devices. We thus conclude that our long single NW approach is quite promising to extend the field of nano-electronics. PMID:23584636

Lee, Young Tack; Ali Raza, Syed Raza; Jeon, Pyo Jin; Ha, Ryong; Choi, Heon-Jin; Im, Seongil

2013-05-21

399

Investigations into the impact of various substrates and ZnO ultra thin seed layers prepared by atomic layer deposition on growth of ZnO nanowire array.  

PubMed

The impact of various substrates and zinc oxide (ZnO) ultra thin seed layers prepared by atomic layer deposition on the geometric morphology of subsequent ZnO nanowire arrays (NWs) fabricated by the hydrothermal method was investigated. The investigated substrates included B-doped ZnO films, indium tin oxide films, single crystal silicon (111), and glass sheets. Scanning electron microscopy and X-ray diffraction measurements revealed that the geometry and aligment of the NWs were controlled by surface topography of the substrates and thickness of the ZnO seed layers, respectively. According to atomic force microscopy data, we suggest that the substrate, fluctuate amplitude and fluctuate frequency of roughness on ZnO seed layers have a great impact on the alignment of the resulting NWs, whereas the influence of the seed layers' texture was negligible. PMID:22759838

Ding, Jn; Liu, Yb; Tan, Cb; Yuan, Ny

2012-01-01

400

Investigations into the impact of various substrates and ZnO ultra thin seed layers prepared by atomic layer deposition on growth of ZnO nanowire array  

NASA Astrophysics Data System (ADS)

The impact of various substrates and zinc oxide (ZnO) ultra thin seed layers prepared by atomic layer deposition on the geometric morphology of subsequent ZnO nanowire arrays (NWs) fabricated by the hydrothermal method was investigated. The investigated substrates included B-doped ZnO films, indium tin oxide films, single crystal silicon (111), and glass sheets. Scanning electron microscopy and X-ray diffraction measurements revealed that the geometry and aligment of the NWs were controlled by surface topography of the substrates and thickness of the ZnO seed layers, respectively. According to atomic force microscopy data, we suggest that the substrate, fluctuate amplitude and fluctuate frequency of roughness on ZnO seed layers have a great impact on the alignment of the resulting NWs, whereas the influence of the seed layers' texture was negligible.

Ding, JN; Liu, YB; Tan, CB; Yuan, NY

2012-07-01

401

Magnetic Resonance Studies of Oxygen and Zinc-Vacancy Native Defects in Bulk ZnO Crystals  

Microsoft Academic Search

ZnO is currently attracting increasing attention as a key material for a wide variety of electronic and optoelectronic applications. Optical, electrical, and magnetic properties of ZnO are believed to be strongly influenced by native defects. However, unambiguous experimental evidence confirming the formation of these defects in as-grown ZnO as well as evaluations of defect densities is currently sparse. In this

Irina Buyanova

2010-01-01

402

Tunable Single-Polarization Single-Mode Photonic Crystal Fiber Based on Liquid Infiltrating  

Microsoft Academic Search

We proposed and demonstrated a tunable single-po- larization single-mode photonic crystal fiber (SPSM-PCF) based on selectively infiltrating liquid into air holes of high birefringence photonic crystal fiber (HB-PCF). A full-vector finite-element method (FEM) is used to analyze the SPSM operation range and its tunable characteristics. The starting wavelength of the SPSM operation range can be widely tuned from 2014 to

Xibao Zheng; Yan-Ge Liu; Zhi Wang; Tingting Han; Boyin Tai

2011-01-01

403

Single Gap Transflective Liquid Crystal Display with Dual Orientation of Liquid Crystal  

Microsoft Academic Search

We propose a single-cell-gap transflective liquid crystal display (LCD) with dual orientation of LC at an initial state. Owing to hybrid alignment in the reflective region, the effective cell retardation value becomes half of that in the transmissive region where the LCs are homogenously aligned. Consequently, a transflective display driven by a vertical or fringe electric field with a single

Young Jin Lim; Je Hoon Song; Yong Bae Kim; Seung Hee Lee

2004-01-01

404

Long single ZnO nanowire for logic and memory circuits: NOT, NAND, NOR gate, and SRAM  

NASA Astrophysics Data System (ADS)

We demonstrate logic and static random access memory (SRAM) circuits using a 100 ?m long and 100 nm thin single ZnO nanowire (NW), which acts as a channel of field-effect transistors (FETs) with Al2O3 dielectrics. NW FETs are thus arrayed in one dimension to consist of NOT, NAND, and NOR gate logic, and SRAM circuits. Two respective top-gate NW FETs with Au and indium-tin-oxide (ITO) were connected to form an inverter, the basic NOT gate component, since the former gate leads to an enhanced mode FET while the latter to depletion mode due to their work function difference. Our inverters showed a high voltage gain of 22 under a 5 V operational voltage, resulting in successful operation of all other devices. We thus conclude that our long single NW approach is quite promising to extend the field of nano-electronics.We demonstrate logic and static random access memory (SRAM) circuits using a 100 ?m long and 100 nm thin single ZnO nanowire (NW), which acts as a channel of field-effect transistors (FETs) with Al2O3 dielectrics. NW FETs are thus arrayed in one dimension to consist of NOT, NAND, and NOR gate logic, and SRAM circuits. Two respective top-gate NW FETs with Au and indium-tin-oxide (ITO) were connected to form an inverter, the basic NOT gate component, since the former gate leads to an enhanced mode FET while the latter to depletion mode due to their work function difference. Our inverters showed a high voltage gain of 22 under a 5 V operational voltage, resulting in successful operation of all other devices. We thus conclude that our long single NW approach is quite promising to extend the field of nano-electronics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01015e

Lee, Young Tack; Ali Raza, Syed Raza; Jeon, Pyo Jin; Ha, Ryong; Choi, Heon-Jin; Im, Seongil

2013-05-01

405

Relaxor-PT Single crystals: Observations and Developments  

PubMed Central

Relaxor-PT based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZNT) and Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) attracted lot of attentions in last decade due to their ultra high electromechanical coupling factors and piezoelectric coefficients. However, owing to a strongly curved morphotropic phase boundary (MPB), the usage temperature of these perovskite single crystals is limited by TRT - the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature TC. Furthermore, the low mechanical quality factors and coercive fields of these crystals, usually being on the order of ~70 and 2–3kV/cm, respectively, restrict their usage in high power applications. Thus, it is desirable to have high performance crystals with high temperature usage range and high power characteristics. In this survey, different binary and ternary crystal systems were explored, with respect to their temperature usage range, general trends of dielectric and piezoelectric properties of relaxor-PT crystal systems were discussed related to their TC/TRT. In addition, two approaches were proposed to improve mechanical Q values, including acceptor dopant strategy, analogous to “hard” polycrystalline ceramics, and anisotropic domain engineering configurations.

Zhang, Shujun; Shrout, Thomas R.

2011-01-01

406

Growth of Rare Earth-Cobalt Single Crystals  

NASA Astrophysics Data System (ADS)

The next generation of permanent magnet materials appears to be of the rare earth-cobalt type having the general formula R2(Co1-xFex)17. Research on these and related materials requires single crystals for evaluation of fundamental parameters. Two of these, Y2Co17 and Ho2Co17, are the subject of this paper. They are both congruently melting but due to their chemical reactivity and low surface tension are difficult to grow as single crystals. A unique crystal growth method based on thermal-imaging was used and will be briefly described. This technique requires no crucible for Czochralski growth and can operate with any desired atmosphere. Single crystals of both materials have been grown. These crystals are of sufficient size (8 by 30 mm.) for essentially all magnetic measurements. Problems related to their growth are discussed and the growth parameters are given. Results of their evaluation are also presented. They include x-ray, electron microprobe and mass spectrographic evaluation of crystalline perfection and purity.

Field, William G.; Sampson, John L.

1973-01-01

407

Single-point diamond turning of DAST crystals  

NASA Astrophysics Data System (ADS)

Organic nonlinear optical crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate (DAST) can be used for new optical devices such as high frequency electro-optical sampling wavelength conversion, submillimeter wave generation, and terahertz-wave generation. The crystal is soft, brittle and hygroscopic so that it is very difficult to get optical surfaces by using conventional optical polishing process. This paper deals with single-point diamond turning for getting optical surfaces on DAST crystals. Three typical planes on DAST crystals were finished by single-point diamond turning. The quality of single-point diamond turned surface depends upon the crystallographic plane, cutting direction, cutting speed, depth of cut, feed rate, rake angle, nose radius of diamond tool, tool clearance angle, tool wear, lubricant and its supplying method. The turned surface was measured with a Nomarski interference microscope, atomic force microscope, and a three-dimensional optical profiler. By optimizing the machining conditions, 0.33 nm rms surface roughness and 8.7 nm p-v flatness in 1 mm square were obtained on a b-plane of DAST crystal.

Namba, Yoshiharu; Tsukahara, Masahiro; Fushiki, Atsuya; Suizu, Koji; Ito, Hiromasa

2004-01-01

408

Green "planting" nanostructured single crystal silver  

PubMed Central

Design and fabrication of noble metal nanocrystals have attracted much attention due to their wide applications in catalysis, optical detection and biomedicine. However, it still remains a challenge to scale-up the production in a high-quality, low-cost and eco-friendly way. Here we show that single crystalline silver nanobelts grow abundantly on the surface of biomass-derived monolithic activated carbon (MAC), using [Ag(NH3)2]NO3 aqueous solution only. By varying the [Ag(NH3)2]NO3 concentration, silver nanoplates or nanoflowers can also be selectively obtained. The silver growth was illustrated using a galvanic-cell mechanism. The lowering of cell potential via using [Ag(NH3)2]+ precursor, together with the AgCl crystalline seed initiation, and the releasing of OH? in the reaction process, create a stable environment for the self-compensatory growth of silver nanocrystals. Our work revealed the great versatility of a new type of template-directed galvanic-cell reaction for the controlled growth of noble metal nanocrystals.

Zhao, Hong; Wang, Fei; Ning, Yuesheng; Zhao, Binyuan; Yin, Fujun; Lai, Yijian; Zheng, Junwei; Hu, Xiaobin; Fan, Tongxiang; Tang, Jianguo; Zhang, Di; Hu, Keao

2013-01-01

409

Nanowire coupling to photonic crystal nanocavities for single photon sources  

Microsoft Academic Search

We demonstrate highly efficient evanescent coupling via a silica loop-nanowire, to ultra-small (0.5 (lambda\\/n)3 ), InAs\\/InP quantum dot photonic crystal cavities, specifically designed for single photon source applications. This coupling technique enables the tuning of both the Q-factor and the wavelength of the cavity mode independently, which is highly relevant for single photon source applications. First, this allows for the

Christian Grillet; Christelle Monat; Cameron L. Smith; Benjamin J. Eggleton; David J. Moss; Simon Frédérick; Dan Dalacu; Philip J. Poole; Jean Lapointe; Geof Aers; Robin L. Williams

2007-01-01

410

Single-photon frequency conversion in nonlinear crystals  

NASA Astrophysics Data System (ADS)

Frequency conversion of single photons in a nonlinear crystal is theoretically discussed. Losses and noise are included within a Heisenberg-Langevin formalism for the propagating photon field. We calculate the first- and second-order correlation functions of the frequency-converted light when the input is a train of single-photon pulses. This model allows one to identify the requirements on the nonlinear device so that it can be integrated in a quantum network.

Blum, Susanne; Olivares-Rentería, G. A.; Ottaviani, Carlo; Becher, Christoph; Morigi, Giovanna

2013-11-01

411

Single Zno Nanowire-Based Biofet Sensors for Ultrasensitive, Label-Free and Real-Time Detection of Uric Acid  

NASA Astrophysics Data System (ADS)

Qualitative and quantitative detection of biological and chemical species is crucial in many areas, ranging from clinical diagnosis to homeland security. Due to the advantages of ultrahigh sensitivity, label-free, fast readout and easy fabrication over the traditional detection systems, semiconductor nanowire based electronic devices have emerged as a potential platform. In this paper, we fabricated a single ZnO nanowire-based bioFET sensor for the detection of low and high concentration uric acid solution at the same time. The addition of uric acid with the concentrations from 1 pM to 0.5 mM resulted in the electrical conductance changes of up to 227 nS, and the response time turns out to be in the order of millisecond. The ZnO NW biosensor could easily detect as low as 1 pM of the uric acid with 14.7 nS of conductance increase, which implied that the sensitivity of the biosensor can be below the 1pM concentration.

Lin, Pei; Liu, Xi; Yan, Xiaoqin; Kang, Zhuo; Lei, Yang; Zhao, Yanguang

2012-08-01

412

Polymer single crystal membrane from liquid/liquid interface  

NASA Astrophysics Data System (ADS)

Vesicles, mimicking the structure of cell membrane at the molecular scale, are small membrane-enclosed sacks that can store or transport substances. The weak mechanical properties and the nature of environment-sensitivity of the current available vesicles: liposomes, polymersomes, colloidsomes limit their applications as an excellent candidate for targeting delivery of drugs/genes in biomedical engineering and treatment. Recently, we developed an emulsion-based method to grow curved polymer single crystals. Varying the polymer concentration and/or the emulsification conditions (such as surfactant concentration, water-oil volume ratio), curved crystals with different sizes and different openness could be obtained. This growing process was attributed to polymer crystal growth along the liquid/liquid interface. In addition, the liquid/liquid interfacial crystal growth is promising for synthesis of enclosed hollow sphere.

Wang, Wenda; Li, Christopher

2013-03-01

413

Sodium sulfate heptahydrate I: The growth of single crystals  

NASA Astrophysics Data System (ADS)

Sodium sulfate is one of the most damaging salts for porous building materials. In our quest to increase the durability of civil structures and cultural heritage we need to understand its crystallization behavior. In this paper we investigate the cooling-induced growth of the metastable heptahydrate crystal phase by combining nuclear magnetic resonance, for non-destructive measurement of the concentration, with time-lapse microscopy, to visualize the crystal growth. The growth rate is found to be controlled by interface attachment kinetics. The kinetic growth parameter Gk ranges from 0.001 to 0.007 mm/s for single crystals in a temperature range of 4.8-13 °C.

Derluyn, Hannelore; Saidov, Tamerlan A.; Espinosa-Marzal, Rosa M.; Pel, Leo; Scherer, George W.

2011-08-01

414

Growth of KDP single crystal blocks in defined crystallographic direction  

NASA Astrophysics Data System (ADS)

It has been shown that sectorial and zonary unhomogeneities of the crystal together with changing temperature conditions in the course of its growth are among the main causes of appearance of the structure defectiveness and property unhomogeneities in the volume of crystals grown. The method of rapid growing in the defined crystallographic direction [101] of the large-size KDP and DKDP single crystallites on the plain seed has been developed, which are applicable for production of wide aperture frequency multipliers of laser emission into the second/third harmonics (type II). Usage of such a method of growing allows to increase the coefficient of use of crystal material (KDP up to 40% and DKDP up to 70%) at production of nonlinear laser elements. High quality of the crystals grown has been confirmed by the results of investigation of structural perfection, optical homogeneity and bulk laser damage resistance threshold.

Salo, V. I.; Voronov, A. P.; Tkachenko, V. F.; Babenko, G. N.; Makoveev, A. V.

2011-12-01

415

Strain incompatibility and residual strains in ferroelectric single crystals  

PubMed Central

Residual strains in ferroelectrics are known to adversely affect the material properties by aggravating crack growth and fatigue degradation. The primary cause for residual strains is strain incompatibility between different microstructural entities. For example, it was shown in polycrystalline ferroelectrics that residual strains are caused due to incompatibility between the electric-field-induced strains in grains with different crystallographic orientations. However, similar characterization of cause-effect in multidomain ferroelectric single crystals is lacking. In this article, we report on the development of plastic residual strains in [111]-oriented domain engineered BaTiO3 single crystals. These internal strains are created due to strain incompatibility across 90° domain walls between the differently oriented domains. The average residual strains over a large crystal volume measured by in situ neutron diffraction is comparable to previous X-ray measurements of localized strains near domain boundaries, but are an order of magnitude lower than electric-field-induced residual strains in polycrystalline ferroelectrics.

Pramanick, A.; Jones, J. L.; Tutuncu, G.; Ghosh, D.; Stoica, A. D.; An, K.

2012-01-01

416

Room Temperature Single-Photon Source: Single-Dye Molecule Fluorescence in Liquid Crystal Host  

SciTech Connect

OAK-(B204)We report on new approaches toward an implementation of an efficient, room temperature, deterministically polarized, single-photon source (SPS) on demand-a key hardware element for quantum information and quantum communication. Operation of a room temperature SPS is demonstrated via photon antibunching in the fluorescence from single terrylene-dye molecules embedded in a cholesteric liquid crystal host. Using oxygen-depleted liquid crystal hosts, dye-bleaching was avoided over the course of more than 1 h of continuous 532-nm excitation. Liquid crystal hosts (including liquid crystal oligomers/polymers) permit further increase of the efficiency of the source: (1) by aligning the dye molecules along a direction preferable for the maximum excitation efficiency; (2) by tuning a one-dimensional (1-D) photonic-band-gap microcavity of planar-aligned cholesteric (chiral nematic) liquid crystal layer to the dye fluorescence band.

Lukishova, S.G.; Schmid, A.W.; McNamara, A.J.; Boyd, R.W.; Stroud, C.R.Jr.

2003-12-31

417

Isotopic Mixing in OO'-Dideuterosuccinic Acid Single Crystals  

Microsoft Academic Search

Extensive isotopic mixing in partially deuterated succinic acid single crystals brought about by moderate doses of ionizing radiation point to a radiochemical reaction occurring with very large G value and thus to a free radical chain reaction. The isotopic mixing is evident in the ESR spectrum of the free radicals produced in low concentration and also, remarkably, in the IR

L. G. Ericson; D. R. Cutten

1969-01-01

418

A Study of Single Crystal Fatigue Failure Criteria  

NASA Technical Reports Server (NTRS)

This paper presents the results of a study whose objective was to study the applicability of different failure equations in modeling low cycle fatigue (LCF) test data for single crystal test specimens. A total of four failure criteria were considered in this study. One of the failure equations was developed by Pratt & Whitney and is based on normal and shear strains on the primary crystallographic slip planes of the single crystal material. Other failure equations considered are based on isotropic criteria. Because these failure equations were originally developed for isotropic materials such as structural steel, they were modified to be applicable to the single crystal slip systems of the LCF specimen material. By observing how closely the various equations were able to reduce the scatter in the LCF test data, the applicability of those equations in modeling the LCF test data was assessed. It is desired to subsequently use the failure equation with the highest correlation in the development of a new single crystal failure criterion for the Alternative Turbopump Development (ATD) for the space shuttle main engine (SSME) High Pressure Fuel Turbopump (HPFTP).

Sayyah, Tarek; Swanson, Gregory R.; Schonberg, William P.

2000-01-01

419

Single Crystals of CeMg3 (TEXUS 7) ESA.  

National Technical Information Service (NTIS)

On Earth, the growth of single crystals of the compound CeMg3 using the vertical Bridgman technique is impeded by the sedimentation of the denser component, cerium, which leads to the formation of the CeMg phase at the bottom of the crucible. By operating...

J. Pierre J. Baruchel M. Schlenker E. Siaud

1991-01-01

420

Low-Cost Single-Crystal Turbine Blades. Volume 2.  

National Technical Information Service (NTIS)

The overall objectives of Project 3 were to develop the exothermic casting process to produce uncooled single-crystal (SC) HP turbine blades in MAR-M 247 and higher strength derivative alloys and to validate the materials process and components through ex...

T. E. Strangman R. E. Dennis B. R. Heath

1984-01-01

421

Low-Cost Single-Crystal Turbine Blades, Volume 1.  

National Technical Information Service (NTIS)

The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be...

T. E. Strangman B. Heath M. Fujii

1983-01-01

422

Anisotropy of Nickel-Base Superalloy Single Crystals.  

National Technical Information Service (NTIS)

The influence of orientation on the tensile and stress rupture behavior of 52 Mar-M247 single crystals was studied. Tensile tests were performed at temperatures between 23 and 1093 C; stress rupture behavior was examined between 760 and 1038 C. The mechan...

R. A. Mackay R. L. Dreshfield R. D. Maier

1980-01-01

423

Neutron spectrometers based on single crystal CVD diamond  

Microsoft Academic Search

A new grade of single crystal CVD diamond has been developed that possesses unprecendented electrical properties [1]. The carrier lifetime in this new material is reported to be > 2 microseconds, a 1000 fold improvement over existing grades of CVD diamond. This could lead to a new generation of electrical devices based on diamond, including radiation sensors. Over the past

Gregory Schmid; Jeffrey Koch; Michael Moran; Richard Lerche; Nobuhiko Izumi; Hye-Sook Park; Thomas Phillips; Robert Turner

2003-01-01

424

Reliability analysis of single crystal NiAl turbine blades  

NASA Technical Reports Server (NTRS)

As part of a co-operative agreement with General Electric Aircraft Engines (GEAE), NASA LeRC is modifying and validating the Ceramic Analysis and Reliability Evaluation of Structures algorithm for use in design of components made of high strength NiAl based intermetallic materials. NiAl single crystal alloys are being actively investigated by GEAE as a replacement for Ni-based single crystal superalloys for use in high pressure turbine blades and vanes. The driving force for this research lies in the numerous property advantages offered by NiAl alloys over their superalloy counterparts. These include a reduction of density by as much as a third without significantly sacrificing strength, higher melting point, greater thermal conductivity, better oxidation resistance, and a better response to thermal barrier coatings. The current drawback to high strength NiAl single crystals is their limited ductility. Consequently, significant efforts including the work agreement with GEAE are underway to develop testing and design methodologies for these materials. The approach to validation and component analysis involves the following steps: determination of the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; measurement of the failure strength envelope of the material; coding of statistically based reliability models; verification of the code and model; and modeling of turbine blades and vanes for rig testing.

Salem, Jonathan; Noebe, Ronald; Wheeler, Donald R.; Holland, Fred; Palko, Joseph; Duffy, Stephen; Wright, P. Kennard

1995-01-01

425

Electrolytic Growth and Preparations of Transition Metal Compound Single Crystals.  

National Technical Information Service (NTIS)

Single crystals of NbSe2, and WSe2 were grown by a chemical transport technique. The conductivity of NbSe2 which is metallic, varies from 5.5 ohm-cm at 300K to 28 ohm-cm at 100K. It has a superconducting transition temperature at 7K. WSe2 is a p-type semi...

A. Wold

1967-01-01

426

The Growth of Berlinite (AlPO4) Single Crystals.  

National Technical Information Service (NTIS)

Single crystals of the berlinite mineral phase of anhydrous aluminum orthophosphate have been grown for possible surface acoustic wave applications. The desired piezoelectric form of AlPO4 is the alpha-phase which is stable from 130 to 580 C. A seeded hyd...

L. E. Drafall R. F. Belt

1980-01-01

427

Elastic constants of single crystal Hastelloy X at elevated temperatures  

Microsoft Academic Search

An acoustic time of flight technique is described in detail for measuring the elastic constants of cubic single crystals that allows for the constants to be determined at elevated temperature. Although the overall technique is not new, various aspects of the present work may prove extremely useful to others interested in finding these values, especially for aerospace materials applications. Elastic

Howard A. Canistraro; Eric H. Jordan; Shi Shixiang; Leroy H. Favrow; Francis A. Reed

1998-01-01

428

Some Debye temperatures from single-crystal elastic constant data  

USGS Publications Warehouse

The mean velocity of sound has been calculated for 14 crystalline solids by using the best recent values of their single-crystal elastic stiffness constants. These mean sound velocities have been used to obtain the elastic Debye temperatures ??De for these materials. Models of the three wave velocity surfaces for calcite are illustrated. ?? 1966 The American Institute of Physics.

Robie, R. A.; Edwards, J. L.

1966-01-01

429

Creep, plasticity, and fatigue of single crystal superalloy  

Microsoft Academic Search

Single crystal components in gas turbine engines are subject to such extreme temperatures and stresses that life prediction becomes highly inaccurate resulting in components that can only be shown to meet their requirements through experience. Reliable life prediction methodologies are required both for design and life management. In order to address this issue we have developed a thermo-viscoplastic constitutive model

Alexander Staroselsky; Brice N. Cassenti

2011-01-01

430

Single Sideband Quartz Crystal Units for VHF Applications (Metal Enclosures).  

National Technical Information Service (NTIS)

The purpose of this contract is to design, develop and fabricate 4 MHz single sideband quartz crystal units for operation on the fundamental frequency at antiresonance into a load capacitance of 32pf. Improved reliability and frequency-time stability are ...

G. E. Ritter

1966-01-01

431

Ambipolar Electric Double Layer Transistors Using Organic Single Crystals  

Microsoft Academic Search

Among organic devices, ambipolar transistors are very unique device, in which both electrons and holes are equally mobile and we are able to observe light emission through the recombination of them. Progress in the applications of such light-emitting transistors (LETs) based on organic single crystals has provided possibilities in developing organic laser. However, in these LETs, the current density is

Taishi Takenobu; Di Wen; Hidekazu Shimotani; Shimpei Ono; Yoshihiro Iwasa

2011-01-01

432

Ambipolar organic single-crystal transistors based on ion gels.  

PubMed

Ambipolar electric double-layer transistors (EDLTs) using organic single crystals and ion-gel electrolytes are successfully created by optimising the fabrication of gel films. The p- and n-type EDLTs enable us to investigate the HOMO-LUMO gap energy of semiconductors, offering a new method with which to measure it. PMID:22729886

Yomogida, Yohei; Pu, Jiang; Shimotani, Hidekazu; Ono, Shimpei; Hotta, Shu; Iwasa, Yoshihiro; Takenobu, Taishi

2012-08-22

433

MAGNETIZATION IN SINGLE CRYSTALS OF SOME RARE-EARTH ORTHOFERRITES  

Microsoft Academic Search

Single crystals of the rare-earth orthoferrites (MFeOâ) have been ; prepared and their magnetic properties measured from room temperature to 1.3 deg ; K for M = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. (L.T.W.);

R. M. Bozorth; Vivian Kramer; J. P. Remeika

1958-01-01

434

Microwave Resonance Relations in Anisotropic Single Crystal Ferrites  

Microsoft Academic Search

The ferromagnetic resonance relations in magnetically anisotropic single crystal ferrites are reexamined. Detailed analyses are presented for spherical specimens. Generalized nomograms are shown which relate the resonance frequency to static field H, anisotropy parameter K\\/M, and the static field orientation. The nature of the susceptibility tensor is discussed. Below magnetic saturation, multidomain structure is expected. Under these conditions, with H

Joseph Artman

1956-01-01

435

TOPICAL REVIEW: Organic field-effect transistors using single crystals  

NASA Astrophysics Data System (ADS)

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm2 Vs-1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

Hasegawa, Tatsuo; Takeya, Jun

2009-04-01

436

Unified constitutive model for single crystal deformation behavior with applications  

NASA Technical Reports Server (NTRS)

Single crystal materials are being used in gas turbine airfoils and are candidates for other hot section components because of their increased temperature capabilities and resistance to thermal fatigue. Development of a constitutive model which assesses the inelastic behavior of these materials has been studied in 2 NASA programs: Life Prediction and Constitutive Models for Engine Hot Section Anisotropic Materials and Biaxial Constitutive Equation Development for Single Crystals. The model has been fit to a large body of constitutive data for single crystal PWA 1480 material. The model uses a unified approach for computing total inelastic strains (creep plus plasticity) on crystallographic slip systems reproducing observed directional and strain rate effects as a natural consequence of the summed slip system quantities. The model includes several of the effects that have been reported to influence deformation in single crystal materials, such as shear stress, latent hardening, and cross slip. The model is operational in a commercial Finite Element code and is being installed in a Boundary Element Method code.

Walker, K. P.; Meyer, T. G.; Jordan, E. H.

1988-01-01

437

Vapor Phase Growth of Stannic Oxide Single Crystals.  

National Technical Information Service (NTIS)

Single crystals of stannic oxide, SnO2, of higher purity and with higher Hall mobility than any previously reported have been grown from the vapor using the reaction SnC14 + 2H2 + 02 = SnO2 + 4HCl at 1250C and 10 Torr. The stannic chloride is obtained fro...

C. G. Fanstad A. Linz R. H. Rediker

1969-01-01

438

A Technique for producing Regular Patterns on Single Crystals  

Microsoft Academic Search

TO examine the deformation of single crystals, it is often necessary to have regularly spaced marks or a grid on the surface of the specimen. In particular, the analysis of plastic strains is carried out by investigating the distortion of the grid using the intersections of the lines as reference points. There are several methods for producing a grid, but

G. B. Craig

1963-01-01

439

Dielectric properties of lithium niobate single crystals doped with gadolinium  

NASA Astrophysics Data System (ADS)

In this paper dielectric properties of LiNbO3:Gd single crystals at temperatures ~ 290-490 K at narrow frequency range (0.5-106 Hz) are presented. The influence of growth conditions was also investigated. The anomalies on dielectric plots depend on the development of the micro- and nano-domain structure.

Palatnikov, M. N.; Sidorov, N. V.; Sandler, V. A.; Bormanis, K.; Smeltere, I.

2013-12-01

440

Single-crystal elasticity of hydrous mantle minerals  

Microsoft Academic Search

Elastic properties of minerals are crucial in modeling the velocity structure of Earth's interior, and can be strongly affected by hydration. Measurements on the elasticity of hydrous minerals are essential to help identify hydrogen-rich regions, and understand the behavior of hydrogen in the Earth's deep interior. In this thesis, I used Brillouin scattering to measure the single-crystal elasticity of some

Zhu Mao

2009-01-01

441

Tribological Properties of Sintered Polycrystalline and Single Crystal Silicon Carbide.  

National Technical Information Service (NTIS)

Tribological studies and X-ray photoelectron spectroscopy analyses were conducted with sintered polycrystalline and single crystal silicon carbide surfaces in sliding contact with iron at various temperatures to 1500 C in a vacuum of 30 nPa. The results i...

D. H. Buckley K. Miyoshi M. inivasan

1982-01-01

442

Mechanical Effects of Electron Irradiation in Iron Single Crystals.  

National Technical Information Service (NTIS)

Electron irradiation (2 MeV, up to 6 x 10 exp 18 e/cm exp 2 ) decreased the yield stress of iron single crystals in the temperature range from 4.2 to 80 exp 0 K. The softening effect was highly dependent on the tensile axis orientation. The temperature an...

M. Meshii A. Sato

1976-01-01

443

Growth and Characterization of Disodium Hydrogen Orthophosphate (DSHP) Single Crystals  

Microsoft Academic Search

Nonlinear optical materials are expected to be active elements for optical communication and optoelectronics. Because of their higher nonlinearity, these materials show the second order nonlinear optical effects. Among the nonlinear phenomena frequency doubling, frequency mixing, and electro-optic modulation are important in the field of optical image storage and optical communications. In the present work, disodium hydrogen orthophosphate single crystals

N. J. John; P. Selvarajan; S. Benita Jeba Silviya; C. K. Mahadevan

2007-01-01

444

Transient Oxidation of Single Crystal NiAl+Zr.  

National Technical Information Service (NTIS)

The 800 C oxidation of oriented single crystals of Zr doped beta-NiAl was studied using transmission electron microscopy. The oxide phases and metal-oxide orientation relationships were determined to characterize the transient stages of oxidation prior to...

J. K. Doychak

1983-01-01

445

Growth of large single crystals of MgO  

SciTech Connect

The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market for this material. Specifically, the demand for MgO crystals in large sizes and quantities is presently increasing due to existing and developing applications that include: (a) MgO substrates for the formation of electro-optic thin films and devices, (b) epitaxial substrates for high-temperature thin-film superconducting devices MgO optical components - including high-temperature windows, lenses, and prisms, and (d) specialty MgO crucibles and evaporation sources for thin-film production. In the course of CRADA ORNL92-0091,