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Sample records for bafe2as2 single-crystal thin

  1. H+ irradiation effect in Co-doped BaFe2As2 single crystals

    International Nuclear Information System (INIS)

    Nakajima, Y.; Tsuchiya, Y.; Taen, T.; Tamegai, T.; Kitamura, H.; Murakami, T.

    2011-01-01

    The effect of H + irradiation on the suppression of Tc in Co-doped BaFe 2 As 2 . H + irradiation introduces nonmagnetic scattering centers. Critical Scattering rate is much higher than that expected in s±-pairing scenario. We report the suppression of the critical temperature T c in single crystalline Ba(Fe 1-x Co x ) 2 As 2 at under-, optimal-, and over-doping levels by 3 MeV proton irradiation. T c decreases and residual resistivity increases monotonically with increasing the dose. The low-temperature resistivity does not show the upturn in contrast with the α-particle irradiated NdFeAs(O,F), which suggests that proton irradiation introduces nonmagnetic scattering centers. Critical scattering rates for all samples obtained by three different ways are much higher than that expected in s±-pairing scenario based on inter-band scattering due to antiferro-magnetic spin fluctuations.

  2. Terahertz conductivity measurement of FeSe0.5Te0.5 and Co-doped BaFe2As2 thin films

    International Nuclear Information System (INIS)

    Nakamura, D.; Akiike, T.; Takahashi, H.; Nabeshima, F.; Imai, Y.; Maeda, A.; Katase, T.; Hiramatsu, H.; Hosono, H.; Komiya, S.; Tsukada, I.

    2011-01-01

    We investigated the THz conductivity of FeSe 0.5 Te 0.5 and Ba (Fe 2-x Co x )As 2 thin films. We estimated the superconducting gap energy values. We found anomolous conductivity spectrum in the antiferromagnetic phase. The terahertz (THz) conductivity of FeSe 0.5 Te 0.5 ('11'-type) and Co-doped BaFe 2 As 2 ('122'-type) thin films are investigated. For '11'-type, the frequency dependence of the complex conductivity can be understood as that of BCS-type superconductor near the superconducting gap energy, and we estimated the superconducting gap energy to be 0.6 meV. For '122'-type, we estimated the superconducting gap energy to be 2.8 meV, which is considered to be the superconducting gap opened at the electron-type Fermi surface near the M point.

  3. Transport properties and pinning analysis for Co-doped BaFe2As2 thin films on metal tapes

    Science.gov (United States)

    Xu, Zhongtang; Yuan, Pusheng; Fan, Fan; Chen, Yimin; Ma, Yanwei

    2018-05-01

    We report on the transport properties and pinning analysis of BaFe1.84Co0.16As2 (Ba122:Co) thin films on metal tapes by pulsed laser deposition. The thin films exhibit a large in-plane misorientation of 5.6°, close to that of the buffer layer SrTiO3 (5.9°). Activation energy U 0(H) analysis reveals a power law relationship with field, having three different exponents at different field regions, indicative of variation from single-vortex pinning to a collective flux creep regime. The Ba122:Co coated conductors present {{T}{{c}}}{{onset}} = 20.2 K and {{T}{{c}}}{{zero}} = 19.0 K along with a self-field J c of 1.14 MA cm‑2 and an in-field J c as high as 0.98 and 0.86 MA cm‑2 up to 9 T at 4.2 K for both major crystallographic directions of the applied field, promising for high field applications. Pinning force analysis indicates a significant enhancement compared with similar Ba122:Co coated conductors. By using the anisotropic scaling approach, intrinsic pinning associated with coupling between superconducting blocks can be identified as the pinning source in the vicinity of H//ab, while for H//c random point defects are likely to play a role but correlated defects start to be active at high temperatures.

  4. Anomalous magneto-elastic and charge doping effects in thallium-doped BaFe2As2

    Science.gov (United States)

    Sefat, Athena S.; Li, Li; Cao, Huibo B.; McGuire, Michael A.; Sales, Brian; Custelcean, Radu; Parker, David S.

    2016-01-01

    Within the BaFe2As2 crystal lattice, we partially substitute thallium for barium and report the effects of interlayer coupling in Ba1-xTlxFe2As2 crystals. We demonstrate the unusual effects of magneto-elastic coupling and charge doping in this iron-arsenide material, whereby Néel temperature rises with small x, and then falls with additional x. Specifically, we find that Néel and structural transitions in BaFe2As2 (TN = Ts = 133 K) increase for x = 0.05 (TN = 138 K, Ts = 140 K) from magnetization, heat capacity, resistivity, and neutron diffraction measurements. Evidence from single crystal X-ray diffraction and first principles calculations attributes the stronger magnetism in x = 0.05 to magneto-elastic coupling related to the shorter intraplanar Fe-Fe bond distance. With further thallium substitution, the transition temperatures decrease for x = 0.09 (TN = Ts = 131 K), and this is due to charge doping. We illustrate that small changes related to 3d transition-metal state can have profound effects on magnetism. PMID:26867821

  5. Critical current densities and flux creep rate in Co-doped BaFe2As2 with columnar defects introduced by heavy-Ion irradiation

    International Nuclear Information System (INIS)

    Nakajima, Y.; Tsuchiya, Y.; Taen, T.; Yagyuda, H.; Tamegai, T.; Okayasu, S.; Sasase, M.; Kitamura, H.; Murakami, T.

    2010-01-01

    We report the formation of columnar defects in Co-doped BaFe 2 As 2 single crystals with different heavy-ion irradiations. The formation of columnar defects by 200 MeV Au ion irradiation is confirmed by transmission electron microscopy and their density is about 40% of the irradiation dose. Magneto-optical imaging and bulk magnetization measurements reveal that the critical current density J c is enhanced in the 200 MeV Au and 800 MeV Xe ion irradiated samples while J c is unchanged in the 200 MeV Ni ion irradiated sample. We also find that vortex creep rates are strongly suppressed by the columnar defects. We compare the effect of heavy-ion irradiation into Co-doped BaFe 2 As 2 and cuprate superconductors.

  6. High-Temperature Superconductivity in Doped BaFe2As2

    International Nuclear Information System (INIS)

    Martin, Marianne

    2011-01-01

    This thesis provides a detailed look on the synthesis, structural features and physical properties of iron arsenides. Especially the properties of BaFe 2 As 2 and the solid solutions (Ba 1-x K x )Fe 2 As 2 , (Ba 1-x Sr x )Fe 2 As 2 and BaFe 2 (As 1-x P x ) 2 which were all synthesized by solid state reactions by heating mixtures of the elements, were intensively investigated.

  7. Accurate projected augmented wave datasets for BaFe2As2

    International Nuclear Information System (INIS)

    Cao Chao; Wu Yuing; Hamdan, Rashid; Wang, Yunpeng; Cheng Haiping

    2010-01-01

    By carefully choosing parameters and including more semi-core orbitals as valence electrons, we have constructed a high-quality projected augmented wave dataset that yields results comparable to existing full-potential linearized augmented plane-wave calculations. The dataset was then applied to BaFe 2 As 2 to study the effects of different levels of structure optimization, as well as different choices of exchange-correlation functionals. It was found that the local density approximation exchange-correlation functional fails to find the correct spin-density-wave anti-ferromagnetic (SDW-AFM) ground state under full optimization, while the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional obtains the correct state but significantly overestimates the magnetism. The electronic structure of the SDW-AFM state is not very sensitive to structure optimizations with the PBE exchange-correlation functional because the positions of the As atoms are preserved under optimizations. We further investigated the Ba atom diffusion process on the BaFe 2 As 2 surface using the nudged elastic bands method. The Ba atom was found to be stable above the center of the squares formed by the surface As atoms, and a diffusion barrier of 1.2 eV was found. Our simulated scanning tunneling microscopy image suggests an ordered surface Ba atom structure, in agreement with Massee et al (2009 Phys. Rev. B 80 140507; van Heumen E et al 2010 arXiv:1009.3493v1).

  8. Structural feature controlling superconductivity in compressed BaFe2As2

    International Nuclear Information System (INIS)

    Yang, Wenge; Jia, Feng-Jiang; Tang, Ling-Yun; Tao, Qian; Xu, Zhu-An; Chen, Xiao-Jia

    2014-01-01

    Superconductivity can be induced with the application of pressure but it disappears eventually upon heavy compression in the iron-based parent compound BaFe 2 As 2 . Structural evolution with pressure is used to understand this behavior. By performing synchrotron X-ray powder diffraction measurements with diamond anvil cells up to 26.1 GPa, we find an anomalous behavior of the lattice parameter with a S shape along the a axis but a monotonic decrease in the c-axis lattice parameter with increasing pressure. The close relationship between the axial ratio c/a and the superconducting transition temperature T c is established for this parent compound. The c/a ratio is suggested to be a measure of the spin fluctuation strength. The reduction of T c with the further increase of pressure is a result of the pressure-driven weakness of the spin-fluctuation strength in this material

  9. Longitudinal Spin Excitations and Magnetic Anisotropy in Antiferromagnetically Ordered BaFe_{2}As_{2}

    Directory of Open Access Journals (Sweden)

    Chong Wang

    2013-12-01

    Full Text Available We report on a spin-polarized inelastic neutron-scattering study of spin waves in the antiferromagnetically ordered state of BaFe_{2}As_{2}. Three distinct excitation components are identified, with spins fluctuating along the c axis, perpendicular to the ordering direction in the ab plane and parallel to the ordering direction. While the first two “transverse” components can be described by a linear spin-wave theory with magnetic anisotropy and interlayer coupling, the third “longitudinal” component is generically incompatible with the local-moment picture. It points toward a contribution of itinerant electrons to the magnetism that is already in the parent compound of this family of Fe-based superconductors.

  10. Electronic structure of BaFe2As2 as obtained from DFT/ASW first-principles calculations

    KAUST Repository

    Schwingenschlö gl, Udo; Di Paola, Cono

    2010-01-01

    We use ab-initio calculations based on the augmented spherical wave method within density functional theory to study the magnetic ordering and Fermi surface of BaFe2As2, the parent compound of the hole-doped iron pnictide superconductors (K,Ba)Fe2As

  11. Defect free single crystal thin layer

    KAUST Repository

    Elafandy, Rami Tarek Mahmoud

    2016-01-28

    A gallium nitride film can be a dislocation free single crystal, which can be prepared by irradiating a surface of a substrate and contacting the surface with an etching solution that can selectively etch at dislocations.

  12. Defect free single crystal thin layer

    KAUST Repository

    Elafandy, Rami Tarek Mahmoud; Ooi, Boon S.

    2016-01-01

    A gallium nitride film can be a dislocation free single crystal, which can be prepared by irradiating a surface of a substrate and contacting the surface with an etching solution that can selectively etch at dislocations.

  13. Doping dependence of magnetic and transport properties in single crystalline Co-doped BaFe2As2

    International Nuclear Information System (INIS)

    Nakajima, Yasuyuki; Taen, Toshihiro; Tamegai, Tsuyoshi

    2010-01-01

    We report the doping dependence of transport and magnetic properties in Co-doped BaFe 2 As 2 . With increasing Co concentration x, structural and magnetic transitions are suppressed and superconductivity emerges in the range of 0.3 c at low temperatures and low fields obtained from bulk magnetization is reasonably large and the doping dependence shows a maximum at x∼0.07 similar to T c . The values of J c at low temperatures reach about 1x10 6 A/cm 2 around the optimally doped region, which is potentially attractive for technological applications.

  14. Pressure dependence of effective Coulomb interaction parameters in BaFe2As2 by first-principle calculation

    Science.gov (United States)

    Aghajani, M.; Hadipour, H.; Akhavan, M.

    2018-05-01

    Pressure dependence of the onsite Coulomb interactions of the BaFe2As2 has been studied by employing the constrained random phase approximation within first-principle calculations. Analyzing total and projected density of states, a pseudogap is found for dxy band at the energy roughly 0.25 eV higher than the Fermi level. Also, by applying pressure the spectral weight of the dxy orbital vanishes while other orbitals remain metallic. The different screening channels, as discussed in four different models, affect significantly on the Hubbard U while the Hund J remains almost unchanged. The average onsite bare and partially and fully screened Coulomb interactions increase with different rates upon compression. These different rates can be explained by competition between the electronic screening and reduction of bond lengths.

  15. Electronic structure of BaFe2As2 as obtained from DFT/ASW first-principles calculations

    KAUST Repository

    Schwingenschlögl, Udo

    2010-07-02

    We use ab-initio calculations based on the augmented spherical wave method within density functional theory to study the magnetic ordering and Fermi surface of BaFe2As2, the parent compound of the hole-doped iron pnictide superconductors (K,Ba)Fe2As2, for the tetragonal I4/mmm as well as the orthorhombic Fmmm structure. In comparison to full potential linear augmented plane wave calculations, we obtain significantly smaller magnetic energies. This finding is remarkable, since the augmented spherical wave method, in general, is known for a most reliable description of magnetism. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Tetragonal To Collapsed Tetragonal Phase Transition In BaFe2As2 and CaFe2As2

    International Nuclear Information System (INIS)

    Mittal, R.; Mishra, S. K.; Chaplot, S. L.; Ovsyannikov, S. V.; Trots, D. M.; Dubrovinsky, L.; Greenberg, E.; Su, Y.; Brueckel, Th.; Matsuishi, S.; Hosono, H.; Garbarino, G.

    2010-01-01

    Superconductivity in MFe 2 As 2 (M = Ba, Ca) compounds appears either at a critical doping level at ambient pressure or in the parent compound itself by application of pressure above a critical value. We report high pressure powder x-ray diffractions studies for these compounds at 300 K up to about 56 GPa using membrane diamond anvil cells. The measurements for BaFe 2 As 2 show a new tetragonal to collapsed tetragonal phase transition at about 22 GPa that remains stable upto 56 GPa. CaFe 2 As 2 is already known to transform to collapsed phase at 1.7 GPa at 300 K. Our measurements on CaFe 2 As 2 do not show any post collapsed phase transition on increase of pressure 50 GPa at 300 K. It is important to note that the transition in both compounds occurs when they are compressed to almost the same value of the unit cell volume and attain similar c t /a t ratios. We present a detailed analysis of the pressure dependence and structure phase transitions as well as equation of state in these important FeAs compounds that should be useful in the context of possible superconductivity in the collapsed phase.

  17. Photon emission by electrons and positrons traversing thin single crystal

    International Nuclear Information System (INIS)

    Ol'chak, A.S.

    1984-01-01

    Radiation emission by planar channeled particles (electrons, positrons) in a thin single crystal of thickness L is considered. It is shown that for L approximately πb/THETAsub(L) (b is the lattice constant, THETA sub(L) the Lindhard angle) besides the main spontaneous channeling maxima there exist auxiliary interference maxima, the positions of all the maxima depending on L. The dependence of the radiation spectral intensity on crystal thickness is discussed

  18. Microstructure and transport properties of [0 0 1]-tilt bicrystal grain boundaries in iron pnictide superconductor, cobalt-doped BaFe2As2

    International Nuclear Information System (INIS)

    Hiramatsu, Hidenori; Katase, Takayoshi; Ishimaru, Yoshihiro; Tsukamoto, Akira; Kamiya, Toshio; Tanabe, Keiichi; Hosono, Hideo

    2012-01-01

    Relationships between microstructure and transport properties of bicrystal grain boundary (BGB) junctions were studied in cobalt-doped BaFe 2 As 2 (BaFe 2 As 2 :Co) epitaxial films grown on [0 0 1]-tilt bicrystal substrates of MgO and (La, Sr)(Al, Ta)O 3 with misorientation angles θ GB = 3–45°. The θ GB of BaFe 2 As 2 :Co BGBs were exactly transferred from those of the bicrystal substrates. No segregation of impurities was detected at the BGB junction interfaces, and the chemical compositions of the BGBs were uniform and the same as those in the bulk film regions. A transition from a strongly-coupled GB behavior to a weak-link behavior was observed in current density–voltage characteristics under self-field around θ GB ∼ 9°. The critical current density decreased from (1.2–1.6) × 10 6 A/cm 2 of the intragrain transport to (0.7–1.1) × 10 5 A/cm 2 of θ GB = 45° because supercurrent becomes more governed by Josephson current with increasing θ GB .

  19. Uniaxial-strain mechanical detwinning of CaFe2As2 and BaFe2As2 crystals: Optical and transport study

    International Nuclear Information System (INIS)

    Tanatar, M.A.; Blomberg, E.C.; Kreyssig, A.; Kim, M.G.; Ni, N.; Thaler, A.; Bud'ko, S.L.; Canfield, P.C.; Goldman, A.I.; Mazin, I.I.; Prozorov, R.

    2010-01-01

    The parent compounds of iron-arsenide superconductors, AFe 2 As 2 (A=Ca, Sr, Ba), undergo a tetragonal to orthorhombic structural transition at a temperature T TO in the range 135-205 K depending on the alkaline-earth element. Below T TO the free standing crystals split into equally populated structural domains, which mask intrinsic, in-plane, anisotropic properties of the materials. Here we demonstrate a way of mechanically detwinning CaFe 2 As 2 and BaFe 2 As 2 . The detwinning is nearly complete, as demonstrated by polarized light imaging and synchrotron x-ray measurements, and reversible, with twin pattern restored after strain release. Electrical resistivity measurements in the twinned and detwinned states show that resistivity, ρ, decreases along the orthorhombic a o axis but increases along the orthorhombic b o axis in both compounds. Immediately below T TO the ratio ρ bo /ρ ao = 1.2 and 1.5 for Ca and Ba compounds, respectively. Contrary to CaFe 2 As 2 , BaFe 2 As 2 reveals an anisotropy in the nominally tetragonal phase, suggesting that either fluctuations play a larger role above T TO in BaFe 2 As 2 than in CaFe 2 As 2 or that there is a higher temperature crossover or phase transition.

  20. Tuning the magnetism of the top-layer FeAs on BaFe2As2 (001): First-principles study

    Science.gov (United States)

    Zhang, Bing-Jing; Liu, Kai; Lu, Zhong-Yi

    2018-04-01

    Magnetism may play an important role in inducing the superconductivity in iron-based superconductors. As a prototypical system, the surface of BaFe2As2 provides a good platform for studying related magnetic properties. We have designed systematic first-principles calculations to clarify the surface magnetism of BaFe2As2 (001), which previously has received little attention in comparison with surface structures and electronic states. We find that the surface environment has an important influence on the magnetic properties of the top-layer FeAs. For As-terminated surfaces, the magnetic ground state of the top-layer FeAs is in the staggered dimer antiferromagnetic (AFM) order, distinct from that of the bulk, while for Ba-terminated surfaces the collinear (single-stripe) AFM order is the most stable, the same as that in the bulk. When a certain coverage of Ba or K atoms is deposited onto the As-terminated surface, the calculated energy differences among different AFM orders for the top-layer FeAs on BaFe2As2 (001) can be much reduced, indicating enhanced spin fluctuations. To compare our results with available scanning tunneling microscopy (STM) measurements, we have simulated the STM images of several structural/magnetic terminations. Astonishingly, when the top-layer FeAs is in the staggered dimer AFM order, a stripe pattern appears in the simulated STM image even when the surface Ba atoms adopt a √{2 }×√{2 } structure, while a √{2 }×√{2 } square pattern comes out for the 1 ×1 full As termination. Our results suggest: (i) the magnetic state at the BaFe2As2 (001) surface can be quite different from that in the bulk; (ii) the magnetic properties of the top-layer FeAs can be tuned effectively by surface doping, which may likely induce superconductivity at the surface layer; (iii) both the surface termination and the AFM order in the top-layer FeAs can affect the STM image of BaFe2As2 (001), which needs to be taken into account when identifying the surface termination.

  1. Critical current densities and vortex dynamics in FeTexSe1-x single crystals

    International Nuclear Information System (INIS)

    Taen, T.; Tsuchiya, Y.; Nakajima, Y.; Tamegai, T.

    2010-01-01

    The critical current density and the normalized relaxation rate are reported in FeTe 0.59 Se 0.41 single crystal. Critical current density is of order of 10 5 A/cm 2 , which is comparable to that in Co-doped BaFe 2 As 2 . In low temperature and low field region, the vortex dynamics of this system is well defined by the collective creep theory, which is quite similar to Co-doped BaFe 2 As 2 reported before. We also discuss the origin of the anomaly in the field dependence of the relaxation rate.

  2. Comprehensive study of out-of-plane transport properties in BaFe2As2 : Three-dimensional electronic state and effect of chemical substitution

    Science.gov (United States)

    Nakajima, M.; Nagafuchi, M.; Tajima, S.

    2018-03-01

    We investigated the out-of-plane transport properties of parent and chemically substituted BaFe2As2 for various types of substitution. Based on the studies of the Hall coefficient and chemical-substitution effect, we have clarified the origin for the unusual temperature dependence of out-of-plane resistivity ρc(T ) in the high-temperature paramagnetic-tetragonal phase. Electron (hole) carriers have an incoherent (coherent) character, which is responsible for nonmetallic (metallic) ρc(T ) . Although the electron and hole contributions are almost comparable, a slightly larger contribution comes from electrons at high temperatures but from holes at low temperatures, resulting in a maximum in ρc(T ) . In the low-temperature antiferromagnetic-orthorhombic phase, the major effect of substitution is to increase the residual-resistivity component, as in the case for the in-plane transport. In particular, Co atoms substituted for Fe give rise to strong scattering with large ac anisotropy. We found that K substitution induces a nonmetallic behavior in ρc(T ) at low temperatures, which is likely due to a weakly localized nature along the c -axis direction.

  3. Single-Crystal Mesoporous ZnO Thin Films Composed of Nanowalls

    KAUST Repository

    Wang, Xudong; Ding, Yong; Li, Zhou; Song, Jinhui; Wang, Zhong Lin

    2009-01-01

    This paper presents a controlled, large scale fabrication of mesoporous ZnO thin films. The entire ZnO mesoporous film is one piece of a single crystal, while high porosity made of nanowalls is present. The growth mechanism was proposed

  4. Perovskite single crystals and thin films for optoelectronic devices (Conference Presentation)

    Science.gov (United States)

    Li, Gang; Han, Qifeng; Yang, Yang; Bae, Sang-Hoon; Sun, Pengyu

    2016-09-01

    Hybrid organolead trihalide perovskite (OTP) solar cells have developed as a promising candidate in photovoltaics due to their excellent properties including a direct bandgap, strong absorption coefficient, long carrier lifetime, and high mobility. Most recently, formamidinium (NH2CH=NH2+ or FA) lead iodide (FAPbI3) has attracted significant attention due to several advantages: (1) the larger organic FA cation can replace the MA cation and form a more symmetric crystal structure, (2) the smaller bandgap of FAPbI3 allows for near infrared (NIR) absorption, and (3) FAPbI3 has an elevated decomposition temperature and thus potential to improve stability. Single crystals provide an excellent model system to study the intrinsic electrical and optical properties of these materials due to their high purity, which is particularly important to understand the limits of these materials. In this work, we report the growth of large ( 5 millimeter size) single crystal FAPbI3 using a novel liquid based crystallization method. The single crystal FAPbI3 demonstrated a δ-phase to α-phase transition with a color change from yellow to black when heated to 185°C within approximately two minutes. The crystal structures of the two phases were identified and the PL emission peak of the α-phase FAPbI3 (820 nm) shows clear red-shift compared to the FAPbI3 thin film (805 nm). The FAPbI3 single crystal shows a long carrier lifetime of 484 ns, a high carrier mobility of 4.4 cm2·V-1·s-1, and even more interestingly a conductivity of 1.1 × 10-7(ohm·cm)-1, which is approximately one order of magnitude higher than that of the MAPbI3 single crystal. Finally, high performance photoconductivity type photodetectors were successfully demonstrated using the single crystal FAPbI3.

  5. Thin Single Crystal Silicon Solar Cells on Ceramic Substrates: November 2009 - November 2010

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A.; Ravi, K. V.

    2011-06-01

    In this program we have been developing a technology for fabricating thin (< 50 micrometres) single crystal silicon wafers on foreign substrates. We reverse the conventional approach of depositing or forming silicon on foreign substrates by depositing or forming thick (200 to 400 micrometres) ceramic materials on high quality single crystal silicon films ~ 50 micrometres thick. Our key innovation is the fabrication of thin, refractory, and self-adhering 'handling layers or substrates' on thin epitaxial silicon films in-situ, from powder precursors obtained from low cost raw materials. This 'handling layer' has sufficient strength for device and module processing and fabrication. Successful production of full sized (125 mm X 125 mm) silicon on ceramic wafers with 50 micrometre thick single crystal silicon has been achieved and device process flow developed for solar cell fabrication. Impurity transfer from the ceramic to the silicon during the elevated temperature consolidation process has resulted in very low minority carrier lifetimes and resulting low cell efficiencies. Detailed analysis of minority carrier lifetime, metals analysis and device characterization have been done. A full sized solar cell efficiency of 8% has been demonstrated.

  6. Single-Crystal Mesoporous ZnO Thin Films Composed of Nanowalls

    KAUST Repository

    Wang, Xudong

    2009-02-05

    This paper presents a controlled, large scale fabrication of mesoporous ZnO thin films. The entire ZnO mesoporous film is one piece of a single crystal, while high porosity made of nanowalls is present. The growth mechanism was proposed in comparison with the growth of ZnO nanowires. The ZnO mesoporous film was successfully applied as a gas sensor. The fabrication and growth analysis of the mesoporous ZnO thin film gi ve general guidance for the controlled growth of nanostructures. It also pro vides a unique structure with a superhigh surface-to-volume ratio for surface-related applications. © 2009 American Chemical Society.

  7. Epitaxial TiN(001) wetting layer for growth of thin single-crystal Cu(001)

    Energy Technology Data Exchange (ETDEWEB)

    Chawla, J. S.; Zhang, X. Y.; Gall, D. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2011-08-15

    Single-crystal Cu(001) layers, 4-1400 nm thick, were deposited on MgO(001) with and without a 2.5-nm-thick TiN(001) buffer layer. X-ray diffraction and reflection indicate that the TiN(001) surface suppresses Cu-dewetting, yielding a 4 x lower defect density and a 9 x smaller surface roughness than if grown on MgO(001) at 25 deg. C. In situ and low temperature electron transport measurements indicate that ultra-thin (4 nm) Cu(001) remains continuous and exhibits partial specular scattering at the Cu-vacuum boundary with a Fuchs-Sondheimer specularity parameter p = 0.6 {+-} 0.2, suggesting that the use of epitaxial wetting layers is a promising approach to create low-resistivity single-crystal Cu nanoelectronic interconnects.

  8. Fabrication of high-quality single-crystal Cu thin films using radio-frequency sputtering.

    Science.gov (United States)

    Lee, Seunghun; Kim, Ji Young; Lee, Tae-Woo; Kim, Won-Kyung; Kim, Bum-Su; Park, Ji Hun; Bae, Jong-Seong; Cho, Yong Chan; Kim, Jungdae; Oh, Min-Wook; Hwang, Cheol Seong; Jeong, Se-Young

    2014-08-29

    Copper (Cu) thin films have been widely used as electrodes and interconnection wires in integrated electronic circuits, and more recently as substrates for the synthesis of graphene. However, the ultra-high vacuum processes required for high-quality Cu film fabrication, such as molecular beam epitaxy (MBE), restricts mass production with low cost. In this work, we demonstrated high-quality Cu thin films using a single-crystal Cu target and radio-frequency (RF) sputtering technique; the resulting film quality was comparable to that produced using MBE, even under unfavorable conditions for pure Cu film growth. The Cu thin film was epitaxially grown on an Al2O3 (sapphire) (0001) substrate, and had high crystalline orientation along the (111) direction. Despite the 10(-3) Pa vacuum conditions, the resulting thin film was oxygen free due to the high chemical stability of the sputtered specimen from a single-crystal target; moreover, the deposited film had >5× higher adhesion force than that produced using a polycrystalline target. This fabrication method enabled Cu films to be obtained using a simple, manufacturing-friendly process on a large-area substrate, making our findings relevant for industrial applications.

  9. Thin films of metal oxides on metal single crystals: Structure and growth by scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Galloway, H.C.

    1995-12-01

    Detailed studies of the growth and structure of thin films of metal oxides grown on metal single crystal surfaces using Scanning Tunneling Microscopy (STM) are presented. The oxide overlayer systems studied are iron oxide and titanium oxide on the Pt(III) surface. The complexity of the metal oxides and large lattice mismatches often lead to surface structures with large unit cells. These are particularly suited to a local real space technique such as scanning tunneling microscopy. In particular, the symmetry that is directly observed with the STM elucidates the relationship of the oxide overlayers to the substrate as well as distinguishing, the structures of different oxides

  10. Comparative study of broadband electrodynamic properties of single-crystal and thin-film strontium titanate

    International Nuclear Information System (INIS)

    Findikoglu, A. T.; Jia, Q. X.; Kwon, C.; Reagor, D. W.; Kaduchak, G.; Rasmussen, K. Oe.; Bishop, A. R.

    1999-01-01

    We have used a coplanar waveguide structure to study broadband electrodynamic properties of single-crystal and thin-film strontium titanate. We have incorporated both time- and frequency-domain measurements to determine small-signal effective refractive index and loss tangent as functions of frequency (up to 4 GHz), dc bias (up to 10 6 V/m), and cryogenic temperature (17 and 60 K). The large-signal impulse response of the devices and the associated phenomenological nonlinear wave equation illustrate how dissipation and nonlinearity combine to produce the overall response in the large-signal regime. (c) 1999 American Institute of Physics

  11. Giant coercivity in ferromagnetic Co doped ZnO single crystal thin film

    International Nuclear Information System (INIS)

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

    2013-01-01

    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. - Highlights: • Co doped ZnO ferromagnetic single crystal thin film. • Giant coercivity in Co:ZnO thin film which may help to turn this material into application. • Cathodoluminescence (CL) data showing increase in band gap with Co concentrations. • A theoretical proposal is made to explain the observed giant coercivity

  12. Measurement of positron reemission from thin single-crystal W(100) films

    International Nuclear Information System (INIS)

    Chen, D.M.; Lynn, K.G.; Pareja, R.; Nielsen, B.

    1985-01-01

    Epitaxial thin single-crystal (100) tungsten films 1000, 2500, and 5000 A thick have been fabricated by high-vacuum electron-beam evaporation. These films were subsequently used as thin-film moderators for the study of the positron-transmission-reemission process with a variable-energy (0--80 keV) monoenergetic positron beam in an ultrahigh-vacuum system. The films were shown to be routinely cleanable by heating first in oxygen (10 -6 Torr) and then in vacuum (10 -9 Torr). Transmission and back reemission of slow positrons from these surfaces was observed. The positron work function, phi/sub +/ has been determined to be approx. =3.0 eV ( +- 0.3 eV). The transmission slow positrons were emitted in a narrow cone with a full width at half maximum of approx. =30 0 consistent with the angular distribution of back-reemission positrons. The reemitted yields as a function of incident positron energy were found to be very different between forward reemission and back reemission. The maximum forward-reemission yields were 18% for 1000-A-thick W film and 12% for 2500-A-thick W film at 5 and 10 keV optimum incident positron energies, respectively. These results show that one can use thin single-crystal tungsten films as positron moderators or remoderators

  13. X-ray beam monitor made by thin-film CVD single-crystal diamond.

    Science.gov (United States)

    Marinelli, Marco; Milani, E; Prestopino, G; Verona, C; Verona-Rinati, G; Angelone, M; Pillon, M; Kachkanov, V; Tartoni, N; Benetti, M; Cannatà, D; Di Pietrantonio, F

    2012-11-01

    A novel beam position monitor, operated at zero bias voltage, based on high-quality chemical-vapor-deposition single-crystal Schottky diamond for use under intense synchrotron X-ray beams was fabricated and tested. The total thickness of the diamond thin-film beam monitor is about 60 µm. The diamond beam monitor was inserted in the B16 beamline of the Diamond Light Source synchrotron in Harwell (UK). The device was characterized under monochromatic high-flux X-ray beams from 6 to 20 keV and a micro-focused 10 keV beam with a spot size of approximately 2 µm × 3 µm square. Time response, linearity and position sensitivity were investigated. Device response uniformity was measured by a raster scan of the diamond surface with the micro-focused beam. Transmissivity and spectral responsivity versus beam energy were also measured, showing excellent performance of the new thin-film single-crystal diamond beam monitor.

  14. Ultra-thin distributed Bragg reflectors via stacked single-crystal silicon nanomembranes

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Minkyu; Seo, Jung-Hun; Lee, Jaeseong; Mi, Hongyi; Kim, Munho; Ma, Zhenqiang, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Zhao, Deyin; Zhou, Weidong [Nanophotonics Lab, Department of Electrical Engineering, University of Texas at Arlington, Arlington, Texas 76019 (United States); Yin, Xin; Wang, Xudong [Department of Material Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2015-05-04

    In this paper, we report ultra-thin distributed Bragg reflectors (DBRs) via stacked single-crystal silicon (Si) nanomembranes (NMs). Mesh hole-free single-crystal Si NMs were released from a Si-on-insulator substrate and transferred to quartz and Si substrates. Thermal oxidation was applied to the transferred Si NM to form high-quality SiO{sub 2} and thus a Si/SiO{sub 2} pair with uniform and precisely controlled thicknesses. The Si/SiO{sub 2} layers, as smooth as epitaxial grown layers, minimize scattering loss at the interface and in between the layers. As a result, a reflection of 99.8% at the wavelength range from 1350 nm to 1650 nm can be measured from a 2.5-pair DBR on a quartz substrate and 3-pair DBR on a Si substrate with thickness of 0.87 μm and 1.14 μm, respectively. The high reflection, ultra-thin DBRs developed here, which can be applied to almost any devices and materials, holds potential for application in high performance optoelectronic devices and photonics applications.

  15. Quasi van der Waals epitaxy of copper thin film on single-crystal graphene monolayer buffer

    Science.gov (United States)

    Lu, Zonghuan; Sun, Xin; Washington, Morris A.; Lu, Toh-Ming

    2018-03-01

    Quasi van der Waals epitaxial growth of face-centered cubic Cu (~100 nm) thin films on single-crystal monolayer graphene is demonstrated using thermal evaporation at an elevated substrate temperature of 250 °C. The single-crystal graphene was transferred to amorphous (glass) and crystalline (quartz) SiO2 substrates for epitaxy study. Raman analysis showed that the thermal evaporation method had minimal damage to the graphene lattice during the Cu deposition. X-ray diffraction and electron backscatter diffraction analyses revealed that both Cu films are single-crystal with (1 1 1) out-of-plane orientation and in-plane Σ3 twin domains of 60° rotation. The crystallinity of the SiO2 substrates has a negligible effect on the Cu crystal orientation during the epitaxial growth, implying the strong screening effect of graphene. We also demonstrate the epitaxial growth of polycrystalline Cu on a commercial polycrystalline monolayer graphene consisting of two orientation domains offset 30° to each other. It confirms that the crystal orientation of the epitaxial Cu film follows that of graphene, i.e. the Cu film consists of two orientation domains offset 30° to each other when deposited on polycrystalline graphene. Finally, on the contrary to the report in the literature, we show that the direct current and radio frequency flip sputtering method causes significant damage to the graphene lattice during the Cu deposition process, and therefore neither is a suitable method for Cu epitaxial growth on graphene.

  16. Epitaxial Growth of Permalloy Thin Films on MgO Single-Crystal Substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Matsubara, Katsuki; Futamoto, Masaaki; Kirino, Fumiyoshi

    2011-01-01

    Permalloy (Py: Ni - 20 at. % Fe) thin films were prepared on MgO single-crystal substrates of (100), (110), and (111) orientations by molecular beam epitaxy. Py crystals consisting of fcc(100) and hcp(112-bar 0) orientations epitaxially nucleate on MgO(100) substrates. With increasing the substrate temperature, the volume ratio of fcc(100) to hcp(112-bar 0) crystal increases. The metastable hcp(112-bar 0) structure transforms into more stable fcc(110) structure with increasing the film thickness. Py(110) fcc single-crystal films are obtained on MgO(110) substrates, whereas Py films epitaxially grow on MgO(111) substrates with two types of fcc(111) variants whose orientations are rotated around the film normal by 180 deg. each other. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of these fcc-Py films agree within ±0.4% with the values of bulk fcc-Py crystal, suggesting that the strains in the films are very small. High-resolution transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the films around the Py/MgO(100) and the Py/MgO(110) interfaces to reduce the lattice mismatches. The magnetic properties are considered to be reflecting the magnetocrystalline anisotropies of bulk fcc-Py and/or metastable hcp-Py crystals and the shape anisotropy caused by the surface undulations.

  17. Epitaxial Growth of Permalloy Thin Films on MgO Single-Crystal Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru; Tanaka, Takahiro; Matsubara, Katsuki; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2011-07-06

    Permalloy (Py: Ni - 20 at. % Fe) thin films were prepared on MgO single-crystal substrates of (100), (110), and (111) orientations by molecular beam epitaxy. Py crystals consisting of fcc(100) and hcp(112-bar 0) orientations epitaxially nucleate on MgO(100) substrates. With increasing the substrate temperature, the volume ratio of fcc(100) to hcp(112-bar 0) crystal increases. The metastable hcp(112-bar 0) structure transforms into more stable fcc(110) structure with increasing the film thickness. Py(110){sub fcc} single-crystal films are obtained on MgO(110) substrates, whereas Py films epitaxially grow on MgO(111) substrates with two types of fcc(111) variants whose orientations are rotated around the film normal by 180 deg. each other. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of these fcc-Py films agree within {+-}0.4% with the values of bulk fcc-Py crystal, suggesting that the strains in the films are very small. High-resolution transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the films around the Py/MgO(100) and the Py/MgO(110) interfaces to reduce the lattice mismatches. The magnetic properties are considered to be reflecting the magnetocrystalline anisotropies of bulk fcc-Py and/or metastable hcp-Py crystals and the shape anisotropy caused by the surface undulations.

  18. Polarized Raman scattering study of PSN single crystals and epitaxial thin films

    Directory of Open Access Journals (Sweden)

    J. Pokorný

    2015-06-01

    Full Text Available This paper describes a detailed analysis of the dependence of Raman scattering intensity on the polarization of the incident and inelastically scattered light in PbSc0.5Nb0.5O3 (PSN single crystals and epitaxially compressed thin films grown on (100-oriented MgO substrates. It is found that there are significant differences between the properties of the crystals and films, and that these differences can be attributed to the anticipated structural differences between these two forms of the same material. In particular, the scattering characteristics of the oxygen octahedra breathing mode near 810 cm-1 indicate a ferroelectric state for the crystals and a relaxor state for the films, which is consistent with the dielectric behaviors of these materials.

  19. Formation of SmFe5(0001) ordered alloy thin films on Cu(111) single-crystal underlayers

    International Nuclear Information System (INIS)

    Yabuhara, Osamu; Ohtake, Mitsuru; Nukaga, Yuri; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    SmFe 5 (0001) single-crystal thin films are prepared by molecular beam epitaxy employing Cu(111) single-crystal underlayers on MgO(111) substrates. The Cu atoms diffuse into the Sm-Fe layer and substitute the Fe sites in SmFe 5 structure forming an alloy compound of Sm(Fe,Cu) 5 . The Sm(Fe,Cu) 5 film is more Cu enriched with increasing the substrate temperature. The Cu underlayer plays an important role in assisting the formation of the ordered phase.

  20. Formation of SmFe{sub 5}(0001) ordered alloy thin films on Cu(111) single-crystal underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Yabuhara, Osamu; Ohtake, Mitsuru; Nukaga, Yuri; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: yabuhara@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2010-01-01

    SmFe{sub 5}(0001) single-crystal thin films are prepared by molecular beam epitaxy employing Cu(111) single-crystal underlayers on MgO(111) substrates. The Cu atoms diffuse into the Sm-Fe layer and substitute the Fe sites in SmFe{sub 5} structure forming an alloy compound of Sm(Fe,Cu){sub 5}. The Sm(Fe,Cu){sub 5} film is more Cu enriched with increasing the substrate temperature. The Cu underlayer plays an important role in assisting the formation of the ordered phase.

  1. Positron reemission: measurement of thin single crystal W(100) films to be used as transmission moderator or re-moderators

    International Nuclear Information System (INIS)

    Chen, D.M.; Lynn, K.G.; Pareja, R.; Nielsen, B.

    1984-11-01

    It has been shown that one can produce thin single crystal W films capable of reemitting positrons at a sufficiently high fraction to be used either as a moderator or as a re-moderator. Both the impurities and the defects could be removed by the appropriate cleaning and annealing procedures, and narrow beam emission could be attained when the films were cleaned. This technique would also be a good method for characterizing defect concentration at interfaces or in thin films

  2. A coupled atomistics and discrete dislocation plasticity simulation of nanoindentation into single crystal thin films

    International Nuclear Information System (INIS)

    Miller, Ronald E.; Shilkrot, L.E.; Curtin, William A.

    2004-01-01

    The phenomenon of 2D nanoindentation of circular 'Brinell' indenter into a single crystal metal thin film bonded to a rigid substrate is investigated. The simulation method is the coupled atomistics and discrete dislocation (CADD) model recently developed by the authors. The CADD model couples a continuum region containing any number of discrete dislocations to an atomistic region, and permits accurate, automatic detection and passing of dislocations between the atomistic and continuum regions. The CADD model allows for a detailed study of nanoindentation to large penetration depths (up to 60 A here) using only a small region of atoms just underneath the indenter where dislocation nucleation, cross-slip, and annihilation occur. Indentation of a model hexagonal aluminum crystal shows: (i) the onset of homogeneous dislocation nucleation at points away from the points of maximum resolved shear stress; (ii) size-dependence of the material hardness, (iii) the role of dislocation dissociation on deformation; (iv) reverse plasticity, including nucleation of dislocations on unloading and annihilation; (v) permanent deformation, including surface uplift, after full unloading; (vi) the effects of film thickness on the load-displacement response; and (vii) the differences between displacement and force controlled loading. This application demonstrates the power of the CADD method in capturing both long-range dislocation plasticity and short-range atomistic phenomena. The use of CADD permits for a clear study of the physical and mechanical influence of both complex plastic flow and non-continuum atomistic-level processes on the macroscopic response of material under indentation loading

  3. Scalable Fabrication of Integrated Nanophotonic Circuits on Arrays of Thin Single Crystal Diamond Membrane Windows.

    Science.gov (United States)

    Piracha, Afaq H; Rath, Patrik; Ganesan, Kumaravelu; Kühn, Stefan; Pernice, Wolfram H P; Prawer, Steven

    2016-05-11

    Diamond has emerged as a promising platform for nanophotonic, optical, and quantum technologies. High-quality, single crystalline substrates of acceptable size are a prerequisite to meet the demanding requirements on low-level impurities and low absorption loss when targeting large photonic circuits. Here, we describe a scalable fabrication method for single crystal diamond membrane windows that achieves three major goals with one fabrication method: providing high quality diamond, as confirmed by Raman spectroscopy; achieving homogeneously thin membranes, enabled by ion implantation; and providing compatibility with established planar fabrication via lithography and vertical etching. On such suspended diamond membranes we demonstrate a suite of photonic components as building blocks for nanophotonic circuits. Monolithic grating couplers are used to efficiently couple light between photonic circuits and optical fibers. In waveguide coupled optical ring resonators, we find loaded quality factors up to 66 000 at a wavelength of 1560 nm, corresponding to propagation loss below 7.2 dB/cm. Our approach holds promise for the scalable implementation of future diamond quantum photonic technologies and all-diamond photonic metrology tools.

  4. Epitaxial growth of thin single-crystals and their quality study by Rutherford scattering in channeling conditions

    International Nuclear Information System (INIS)

    Kirsch, Robert.

    1975-01-01

    Some aspects of thin crystalline layers are reminded: vacuum deposition, epitaxial growth, annealing and interdiffusion ion channeling and scattering of 1-2MeV helium ions are used to study the crystalline quality, the annealing effects and in some cases the interdiffusion in epitaxial multilayers of silver, copper gold and nickel. Thin single-crystals of gold and nickel oriented (III) plan parallel to the surface were obtained by successive epitaxial growth from muscovite mica clivages. The mounting techniques of single crystalline, self-supporting, 300 to 1200 Angstroems thick, gold and nickel targets of 3mm diameter are described. The gold single-crystals have dislocation densities of 10 8 cm -2 and the various epitaxial layers are obtained without twinning [fr

  5. Manufacture of Bi-cuprate thin films on MgO single crystal substrates by chemical solution deposition

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Bertelsen, Christian Vinther; Andersen, Niels Hessel

    2014-01-01

    Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors dissolved in xylene. Pyrolysis takes place between 200°C and 450°C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c...

  6. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  7. Precipitation of thin-film organic single crystals by a novel crystal growth method using electrospray and ionic liquid film

    Science.gov (United States)

    Ueda, Hiroyuki; Takeuchi, Keita; Kikuchi, Akihiko

    2018-04-01

    We report an organic single crystal growth technique, which uses a nonvolatile liquid thin film as a crystal growth field and supplies fine droplets containing solute from the surface of the liquid thin film uniformly and continuously by electrospray deposition. Here, we investigated the relationships between the solute concentration of the supplied solution and the morphology and size of precipitated crystals for four types of fluorescent organic low molecule material [tris(8-hydroxyquinoline)aluminum (Alq3), 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), N,N‧-bis(3-methylphenyl)-N,N‧-diphenylbenzidine (TPD), and N,N-bis(naphthalene-1-yl)-N,N-diphenyl-benzidine (NPB)] using an ionic liquid as the nonvolatile liquid. As the concentration of the supplied solution decreased, the morphology of precipitated crystals changed from dendritic or leaf shape to platelike one. At the solution concentration of 0.1 mg/ml, relatively large platelike single crystals with a diagonal length of over 100 µm were obtained for all types of material. In the experiment using ionic liquid and dioctyl sebacate as nonvolatile liquids, it was confirmed that there is a clear positive correlation between the maximum volume of the precipitated single crystal and the solubility of solute under the same solution supply conditions.

  8. Antiphase inversion domains in lithium cobaltite thin films deposited on single-crystal sapphire substrates

    International Nuclear Information System (INIS)

    Zheng, S.J.; Fisher, C.A.J.; Hitosugi, T.; Kumatani, A.; Shiraki, S.; Ikuhara, Y.H.; Kuwabara, A.; Moriwake, H.; Oki, H.; Ikuhara, Y.

    2013-01-01

    Antiphase inversion domains in LiCoO 2 thin films prepared by pulsed laser deposition on sapphire single-crystal substrates are analyzed using a combination of (scanning) transmission electron microscopy and first-principles calculations. Domains form epitaxially on the substrates with orientation relationships of [112 ¯ 0] LiCoO 2 (0001) LiCoO 2 //[11 ¯ 00] α-Al 2 O 3 (0001) α-Al 2 O 3 and [1 ¯ 1 ¯ 20] LiCoO 2 (0001) LiCoO 2 //[11 ¯ 00] α-Al 2 O 3 (0001) α-Al 2 O 3 . In addition, substrate/film interfaces with the above orientation relationships always have the same stacking sequence of Al–O–Co–O–Li–O. This is confirmed to be the most energetically stable stacking arrangement according to first-principles calculations. Individual domains form as a result of steps one (0 0 0 1) O–Al–O spacing in height on the otherwise flat substrate surface. Because the orientation of adjacent (0 0 0 1) AlO 6 octahedra in Al 2 O 3 are rotated by 180°, while LiO 6 and CoO 6 octahedra in LiCoO 2 are all aligned in the same direction, substrate steps produce LiCoO 2 domains rotated 180° relative to their neighbors. The similar size of oxygen octahedra in the two materials also means that the step height is close to the layer spacing in LiCoO 2 , so that (0 0 0 1) Li and Co layers of adjacent domains are shifted by one layer relative to each other at each domain boundary, aligning Li layers with Co layers across the boundary. The combination of these two effects generates antiphase inversion domains. The domain boundaries effectively sever Li-ion diffusion pathways in the (0 0 0 1) planes between domains and thus are expected to have a detrimental effect on Li-ion conductivity

  9. single crystals

    Indian Academy of Sciences (India)

    2018-05-18

    May 18, 2018 ... Abstract. 4-Nitrobenzoic acid (4-NBA) single crystals were studied for their linear and nonlinear optical ... studies on the proper growth, linear and nonlinear optical ..... between the optic axes and optic sign of the biaxial crystal.

  10. Photoinduced Optical Spectroscopy of La2CuO4+x Single Crystals and C60 Thin Films

    International Nuclear Information System (INIS)

    Bazhenov, A.V.; Gorbunov, A.V.; Timofeev, V.B.

    1995-01-01

    The evolution of both vibration and electronic spectra of insulating La 2 CuO 4+x single crystals upon charge-transfer gap photoexcitation has been studied by means of photoinduced reflection spectroscopy. Interaction of self-localized hole with some of the A g , B 2g (B 3g ), B 3u optical phonons has been observed. Formation of self-localized hole state and its multiparticle complexes is supposed. Photoinduced absorption in C 60 thin films has been found to differ essentially from that in cuprates

  11. Structural characterization of metastable hcp-Ni thin films epitaxially grown on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni(1120) epitaxial thin films with hcp structure were prepared on Au(100) single-crystal underlayers at 100 deg. C by ultra high vacuum molecular beam epitaxy. The detailed film structure is studied by in situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy. The hcp-Ni film consists of two types of variants whose c-axes are rotated around the film normal by 90 deg. each other. An atomically sharp boundary is recognized between the film and the underlayer, where misfit dislocations are introduced. Presence of such dislocations seems to relieve the strain caused by the lattice mismatch between the film and the underlayer.

  12. Highly polarized single-c-domain single-crystal Pb(Mn,Nb)O(3)-PZT thin films.

    Science.gov (United States)

    Wasa, Kiyotaka; Adachi, Hideaki; Nishida, Ken; Yamamoto, Takashi; Matsushima, Tomoaki; Kanno, Isaku; Kotera, Hidetoshi

    2012-01-01

    In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ξPb(Mn,Nb)O3-(1 - ξ)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 μC/cm(2), small relative dielectric constants, ε* = 100 to 150, high Curie temperature, Tc = ~600 °C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ξ = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS. © 2012 IEEE

  13. Advances in Single-Crystal Fibers and Thin Rods Grown by Laser Heated Pedestal Growth

    Directory of Open Access Journals (Sweden)

    Gisele Maxwell

    2017-01-01

    Full Text Available Single-crystal fibers are an intermediate between laser crystals and doped glass fibers. They have the advantages of both guiding laser light and matching the efficiencies found in bulk crystals, which is making them ideal candidates for high-power laser and fiber laser applications. This work focuses on the growth of a flexible fiber with a core of dopant (Er, Nd, Yb, etc. and a polycrystalline clad of yttrium aluminum garnet (YAG that will exhibit good wave guiding properties. Direct growth or a combination of growth and cladding experiments are described. Scattering loss measurements at visible wavelengths, along with dopant profile characterization with damage threshold results, are also presented. For single-pass amplification, a single-pass linear gain of 7.4 was obtained for 29 nJ pulses of 5 ns duration at 1 MHz repetition rate. We also obtained a laser efficiency of over 58% in a diode-pumped configuration. These results confirm the potential for single-crystal fibers to overcome the limitations of the glass fibers commonly used in fiber lasers, making them prime candidates for high-power compact fiber lasers and amplifiers.

  14. Effect of annealing ambient on anisotropic retraction of film edges during solid-state dewetting of thin single crystal films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Gye Hyun; Thompson, Carl V., E-mail: cthomp@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Ma, Wen [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Yildiz, Bilge [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 01239 (United States)

    2016-08-21

    During solid-state dewetting of thin single crystal films, film edges retract at a rate that is strongly dependent on their crystallographic orientations. Edges with kinetically stable in-plane orientations remain straight as they retract, while those with other in-plane orientations develop in-plane facets as they retract. Kinetically stable edges have retraction rates that are lower than edges with other orientations and thus determine the shape of the natural holes that form during solid-state dewetting. In this paper, measurements of the retraction rates of kinetically stable edges for single crystal (110) and (100) Ni films on MgO are presented. Relative retraction rates of kinetically stable edges with different crystallographic orientations are observed to change under different annealing conditions, and this accordingly changes the initial shapes of growing holes. The surfaces of (110) and (100) films were also characterized using low energy electron diffraction, and different surface reconstructions were observed under different ambient conditions. The observed surface structures were found to correlate with the observed changes in the relative retraction rates of the kinetically stable edges.

  15. Epitaxial growth of fcc-CoxNi100-x thin films on MgO(110) single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Nukaga, Yuri; Sato, Yoichi; Futamoto, Masaaki; Kirino, Fumiyoshi

    2009-01-01

    Co x Ni 100-x (x=100, 80, 20, 0 at. %) epitaxial thin films were prepared on MgO(110) single-crystal substrates heated at 300 deg. C by ultrahigh vacuum molecular beam epitaxy. The growth mechanism is discussed based on lattice strain and crystallographic defects. CoNi(110) single-crystal films with a fcc structure are obtained for all compositions. Co x Ni 100-x film growth follows the Volmer-Weber mode. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the Co x Ni 100-x films are in agreement within ±0.5% with the values of the respective bulk Co x Ni 100-x crystals, suggesting that the strain in the film is very small. High-resolution cross-sectional transmission microscopy shows that an atomically sharp boundary is formed between a Co(110) fcc film and a MgO(110) substrate, where periodical misfit dislocations are preferentially introduced in the film at the Co/MgO interface. The presence of such periodical misfit dislocations relieves the strain caused by the lattice mismatch between the film and the substrate.

  16. Comparison of Ab initio low-energy models for LaFePO, LaFeAsO, BaFe2As2, LiFeAs, FeSe, and FeTe. Electron correlation and covalency

    International Nuclear Information System (INIS)

    Miyake, Takashi; Nakamura, Kazuma; Arita, Ryotaro; Imada, Masatoshi

    2010-01-01

    Effective low-energy Hamiltonians for several different families of iron-based superconductors are compared after deriving them from the downfolding scheme based on first-principles calculations. Systematic dependences of the derived model parameters on the families are elucidated, many of which are understood from the systematic variation of the covalency between Fe-3d and pnictogen-/chalcogen-p orbitals. First, LaFePO, LaFeAsO (1111), BaFe 2 As 2 (122), LiFeAs (111), FeSe, and FeTe (11) have overall similar band structures near the Fermi level, where the total widths of 10-fold Fe-3d bands are mostly around 4.5 eV. However, the derived effective models of the 10-fold Fe-3d bands (d model) for FeSe and FeTe have substantially larger effective onsite Coulomb interactions U - 4.2 and 3.4 eV, respectively, after the screening by electrons on other bands and after averaging over orbitals, as compared to ∼2.5 eV for LaFeAsO. The difference is similar in the effective models containing p orbitals of As, Se or Te (dp or dpp model), where U ranges from ∼4 eV for the 1111 family to ∼7 eV for the 11 family. The exchange interaction J has a similar tendency. The family dependence of models indicates a wide variation ranging from weak correlation regime (LaFePO) to substantially strong correlation regime (FeSe). The origin of the larger effective interaction in the 11 family is ascribed to smaller spread of the Wannier orbitals generating larger bare interaction, and to fewer screening channels by the other bands. This variation is primarily derived from the distance h between the pnictogen/chalcogen position and the Fe layer: The longer h for the 11 family generates more ionic character of the bonding between iron and anion atoms, while the shorter h for the 1111 family leads to more covalent-bonding character, the larger spread of the Wannier orbitals, and more efficient screening by the anion p orbitals. The screened interaction of the d model is strongly orbital dependent, which is also understood from the Wannier spread. The dp and dpp models show much weaker orbital dependence. The larger h also explains why the 10-fold 3d bands for the 11 family are more entangled with the smearing of the 'pseudogap' structure above the Fermi level seen in the 1111 family. While the family-dependent semimetallic splitting of the bands primarily consists of d yz /d zx and d x2-y2 orbitals, the size of the pseudogap structure is controlled by the hybridization between these orbitals and d xy /d 3z2-r2 : A large hybridization in the 1111 family generates a large 'band-insulating'-like pseudogap (hybridization gap), whereas a large h in the 11 family weakens them, resulting in a 'half-filled' like bands of orbitals. This may enhance strong correlation effects in analogy with Mott physics and causes the orbital selective crossover in the three orbitals. On the other hand, the geometrical frustration t'/t, inferred from the ratio of the next-nearest transfer t' to the nearest one t of the d model is relatively larger for the 1111 family than the 11 one. The models comprehensively derived here may serve as a firm starting basis of understanding both common and diverse properties of the iron-based superconductors including magnetism and superconductivity. (author)

  17. Microstructure and magnetic properties of FeCo epitaxial thin films grown on MgO single-crystal substrates

    International Nuclear Information System (INIS)

    Shikada, Kouhei; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2009-01-01

    FeCo epitaxial films were prepared on MgO(100), MgO(110), and MgO(111) substrates by ultrahigh vacuum molecular beam epitaxy. FeCo thin films with (100), (211), and (110) planes parallel to the substrate surface grow on respective MgO substrates. FeCo/MgO interface structures are studied by high-resolution cross-sectional transmission electron microscopy and the epitaxial growth mechanism is discussed. Atomically sharp boundaries are recognized between the FeCo thin films and the MgO substrates where misfit dislocations are introduced in the FeCo thin films presumably to decrease the lattice misfits. Misfit dislocations are observed approximately every 9 and 1.4 nm in FeCo thin film at the FeCo/MgO(100) and the FeCo/MgO(110) interfaces, respectively. X-ray diffraction analysis indicates that the lattice spacing measured parallel to the single-crystal substrate surfaces are in agreement within 0.1% with those of the respective bulk values of Fe 50 Co 50 alloy crystal, showing that the FeCo film strain is very small. The magnetic anisotropies of these epitaxial films basically reflect the magnetocrystalline anisotropy of bulk FeCo alloy crystal

  18. Velocities of dislocation groups in very thin neutron-irradiated copper single crystals measured by slip line cinematography

    Energy Technology Data Exchange (ETDEWEB)

    Potthoff, H.H. (Technische Univ. Braunschweig (Germany, F.R.). Inst. fuer Metallphysik und Nukleare Festkoerperphysik)

    1983-05-16

    Slip line development on very thin flat single crystals of neutron-irradiated Cu (thickness down to only 15 to 20 ..mu..m, orientation for single glide, yield region, room temperature) is recorded by high-speed cinematography during tensile deformation. In such very thin crystals glide dislocations on the slip plane must be arranged in a rather simple way. Drops in tensile load occuring during initiation of single slip lines at the Lueders band front indicate that in the beginning of a slip line development dislocation groups traverse the whole glide plane in very short times. Evaluating the data measured for the slip line growth v/sub s/ >= 10 cm/s is found for screw dislocations and v/sub e/ >= v/sub s/ for edge dislocations. For later stages on thin crystals and for all stages on thick crystals (>= several 100 ..mu..m) slip line development is much slower and slip line show many cross slip events which then appear to control the mean velocity of the dislocations.

  19. Velocities of dislocation groups in very thin neutron-irradiated copper single crystals measured by slip line cinematography

    International Nuclear Information System (INIS)

    Potthoff, H.H.

    1983-01-01

    Slip line development on very thin flat single crystals of neutron-irradiated Cu (thickness down to only 15 to 20 μm, orientation for single glide, yield region, room temperature) is recorded by high-speed cinematography during tensile deformation. In such very thin crystals glide dislocations on the slip plane must be arranged in a rather simple way. Drops in tensile load occuring during initiation of single slip lines at the Lueders band front indicate that in the beginning of a slip line development dislocation groups traverse the whole glide plane in very short times. Evaluating the data measured for the slip line growth v/sub s/ >= 10 cm/s is found for screw dislocations and v/sub e/ >= v/sub s/ for edge dislocations. For later stages on thin crystals and for all stages on thick crystals (>= several 100 μm) slip line development is much slower and slip line show many cross slip events which then appear to control the mean velocity of the dislocations. (author)

  20. Periodic domain inversion in x-cut single-crystal lithium niobate thin film

    Energy Technology Data Exchange (ETDEWEB)

    Mackwitz, P., E-mail: peterm@mail.upb.de; Rüsing, M.; Berth, G.; Zrenner, A. [Department Physik, Universität Paderborn, 33095 Paderborn (Germany); Center for Optoelectronics and Photonics Paderborn, 33095 Paderborn (Germany); Widhalm, A.; Müller, K. [Department Physik, Universität Paderborn, 33095 Paderborn (Germany)

    2016-04-11

    We report the fabrication of periodically poled domain patterns in x-cut lithium niobate thin-film. Here, thin films on insulator have drawn particular attention due to their intrinsic waveguiding properties offering high mode confinement and smaller devices compared to in-diffused waveguides in bulk material. In contrast to z-cut thin film lithium niobate, the x-cut geometry does not require back electrodes for poling. Further, the x-cut geometry grants direct access to the largest nonlinear and electro-optical tensor element, which overall promises smaller devices. The domain inversion was realized via electric field poling utilizing deposited aluminum top electrodes on a stack of LN thin film/SiO{sub 2} layer/Bulk LN, which were patterned by optical lithography. The periodic domain inversion was verified by non-invasive confocal second harmonic microscopy. Our results show domain patterns in accordance to the electrode mask layout. The second harmonic signatures can be interpreted in terms of spatially, overlapping domain filaments which start their growth on the +z side.

  1. Catalyst growth of single crystal aligned ZnO nanorods on ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Dongxu; Andreazza, Caroline; Andreazza, Pascal [Centre de Recherche sur la Matiere Divisee, CNRS-Universite d' Orleans, 1b rue de la Ferollerie, 45071 Orleans cedex 2 (France)

    2005-02-01

    One dimensional ZnO nanorods were successfully fabricated on Si substrates via a simple physical vapor-phase transport method at 950 C. A ZnO shell covered Au/Zn alloy is assumed as the nucleation site, then ZnO nanorods grow following a vapor-solid (VS) process. In order to guide the nanorod growth a c-axis oriented ZnO thin film and Au catalyst were first deposited on Si (100) surface. SEM images show nanorods grown on this substrate are vertical to the substrate surface. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Electrical properties of single crystal Yttrium Iron Garnet ultra-thin films at high temperatures

    OpenAIRE

    Thiery, Nicolas; Naletov, Vladimir V.; Vila, Laurent; Marty, Alain; Brenac, Ariel; Jacquot, Jean-François; de Loubens, Grégoire; Viret, Michel; Anane, Abdelmadjid; Cros, Vincent; Youssef, Jamal Ben; Demidov, Vladislav E.; Demokritov, Sergej O.; Klein, Olivier

    2017-01-01

    We report a study on the electrical properties of 19 nm thick Yttrium Iron Garnet (YIG) films grown by liquid phase epitaxy. The electrical conductivity and Hall coefficient are measured in the high temperature range [300,400]~K using a Van der Pauw four-point probe technique. We find that the electrical resistivity decreases exponentially with increasing temperature following an activated behavior corresponding to a band-gap of $E_g\\approx 2$ eV, indicating that epitaxial YIG ultra-thin film...

  3. Upper critical field and superconducting anisotropy of BaFe2-xRuxAs2 (x=0.48 and 0.75) single crystals

    International Nuclear Information System (INIS)

    Jo, Youn Jung; Eom, Man Jin; Kim, Jun Sung; Kang, W.

    2014-01-01

    The upper critical field (H c 2 ) was determined by applying a magnetic field along the ab plane and c axis for two single crystals of BaFe 2-x Ru x As 2 (x=0.48 and 0.75). The anisotropy of the H c 2 (0), γ(0)=H c 2 ab (0)/H c 2 c (0), was ∼1.6 for x=0.48 and ∼2.3 for x=0.75. The angle-dependent resistance measured below T c allowed perfect scaling features based on anisotropic Ginzburg-Landau theory, leading to consistent anisotropy values. Because only one fitting parameter γ is used in the scaling for each temperature, the validity of the γ value was compared with that determined from γ=H c 2 ab /H c 2 c . The γ obtained at a temperature close to Tc was 3.0 and decreased to 2.0 at low temperatures. Comparing to the anisotropy determined for electron- or hole-doped BaFe 2 As 2 using the same method, the present results point to consistent anisotropy in Ru-doped BaFe 2 As 2 with other electron- or hole-doped BaFe 2 As 2 .

  4. Coupling of carbon monoxide molecules over oxygen-defected UO2(111) single crystal and thin film surfaces.

    Science.gov (United States)

    Senanayake, S D; Waterhouse, G I N; Idriss, H; Madey, Theodore E

    2005-11-22

    While coupling reactions of carbon-containing compounds are numerous in organometallic chemistry, they are very rare on well-defined solid surfaces. In this work we show that the reductive coupling of two molecules of carbon monoxide to C2 compounds (acetylene and ethylene) could be achieved on oxygen-defected UO2(111) single crystal and thin film surfaces. This result allows in situ electron spectroscopic investigation of a typical organometallic reaction such as carbon coupling and extends it to heterogeneous catalysis and solids. By using high-resolution photoelectron spectroscopy (HRXPS) it was possible to track the changes in surface states of the U and O atoms as well as identify the intermediate of the reaction. Upon CO adsorption U cations in low oxidation states are oxidized to U4+ ions; this was accompanied by an increase of the O-to-U surface ratios. The HRXPS C 1s lines show the presence of adsorbed species assigned to diolate species (-OCH=CHO-) that are most likely the reaction intermediate in the coupling of two CO molecules to acetylene and ethylene.

  5. Coupling of Carbon Monoxide Molecules over Oxygen Defected UO2 (111) Single Crystal and Thin Film Surfaces

    International Nuclear Information System (INIS)

    Senanayake, S.; Waterhouse, G.; Idriss, H.; Madey, T.

    2005-01-01

    While coupling reactions of carbon-containing compounds are numerous in organometallic chemistry, they are very rare on well-defined solid surfaces. In this work we show that the reductive coupling of two molecules of carbon monoxide to C 2 compounds (acetylene and ethylene) could be achieved on oxygen-defected UO 2 (111) single crystal and thin film surfaces. This result allows in situ electron spectroscopic investigation of a typical organometallic reaction such as carbon coupling and extends it to heterogeneous catalysis and solids. By using high-resolution photoelectron spectroscopy (HRXPS) it was possible to track the changes in surface states of the U and O atoms as well as identify the intermediate of the reaction. Upon CO adsorption U cations in low oxidation states are oxidized to U 4+ ions; this was accompanied by an increase of the O-to-U surface ratios. The HRXPS C 1s lines show the presence of adsorbed species assigned to diolate species (-OCH=CHO-) that are most likely the reaction intermediate in the coupling of two CO molecules to acetylene and ethylene

  6. Microstructure of Co(112-bar 0) epitaxial thin films, grown on MgO(100) single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Nukaga, Yuri; Ohtake, Mitsuru; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: nukaga@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2010-01-01

    Co(112-bar 0) epitaxial thin films with hcp structure were prepared on MgO(100) single-crystal substrates heated at 300 {sup 0}C by ultra high vacuum molecular beam epitaxy. The microstructure is investigated by employing X-ray diffraction and high-resolution transmission electron microscopy. The film consists of two types of domains whose c-axes are rotated around the film normal by 90{sup 0} each other. Stacking faults are observed for the film along the Co[0001] direction. An atomically sharp boundary is recognized between the film and the substrate, where some misfit dislocations are introduced in the film at the Co/MgO interface. Dislocations are also observed in the film up to 15 nm thickness from the interface. Presence of such stacking faults and misfit dislocations seem to relieve the strain caused by the lattice mismatch between the film and the substrate. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the film are in agreement within 0.5% and 0.1%, respectively, with those of the bulk hcp-Co crystal, suggesting the strain in the film is very small.

  7. Microstructure of Co(112-bar 0) epitaxial thin films, grown on MgO(100) single-crystal substrates

    International Nuclear Information System (INIS)

    Nukaga, Yuri; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Co(112-bar 0) epitaxial thin films with hcp structure were prepared on MgO(100) single-crystal substrates heated at 300 0 C by ultra high vacuum molecular beam epitaxy. The microstructure is investigated by employing X-ray diffraction and high-resolution transmission electron microscopy. The film consists of two types of domains whose c-axes are rotated around the film normal by 90 0 each other. Stacking faults are observed for the film along the Co[0001] direction. An atomically sharp boundary is recognized between the film and the substrate, where some misfit dislocations are introduced in the film at the Co/MgO interface. Dislocations are also observed in the film up to 15 nm thickness from the interface. Presence of such stacking faults and misfit dislocations seem to relieve the strain caused by the lattice mismatch between the film and the substrate. X-ray diffraction analysis indicates that the out-of-plane and the in-plane lattice spacings of the film are in agreement within 0.5% and 0.1%, respectively, with those of the bulk hcp-Co crystal, suggesting the strain in the film is very small.

  8. A 350 mK, 9 T scanning tunneling microscope for the study of superconducting thin films on insulating substrates and single crystals.

    Science.gov (United States)

    Kamlapure, Anand; Saraswat, Garima; Ganguli, Somesh Chandra; Bagwe, Vivas; Raychaudhuri, Pratap; Pai, Subash P

    2013-12-01

    We report the construction and performance of a low temperature, high field scanning tunneling microscope (STM) operating down to 350 mK and in magnetic fields up to 9 T, with thin film deposition and in situ single crystal cleaving capabilities. The main focus lies on the simple design of STM head and a sample holder design that allows us to get spectroscopic data on superconducting thin films grown in situ on insulating substrates. Other design details on sample transport, sample preparation chamber, and vibration isolation schemes are also described. We demonstrate the capability of our instrument through the atomic resolution imaging and spectroscopy on NbSe2 single crystal and spectroscopic maps obtained on homogeneously disordered NbN thin film.

  9. Spectroelectrochemical study of the adsorption of acetate anions at gold single crystal and thin-film electrodes

    International Nuclear Information System (INIS)

    Berna, Antonio; Delgado, Jose Manuel; Orts, Jose Manuel; Rodes, Antonio; Feliu, Juan Miguel

    2008-01-01

    Acetate adsorption at gold electrodes is studied in perchloric acid solutions by cyclic voltammetry and in-situ infrared spectroscopy. External reflection measurements, performed with gold single crystal electrodes, are combined with Surface Enhanced Infrared Reflection Absorption Spectroscopy experiments under attenuated total reflection conditions (ATR-SEIRAS) carried out with sputtered gold thin-film electrodes. Theoretical harmonic IR frequencies of acetate species adsorbed with different geometries on Au clusters with (1 1 1), (1 0 0) and (1 1 0) orientations have been obtained from B3LYP/LANL2DZ, 6-31 + G* calculations. The theoretical and experimental results confirm that, irrespective of the surface crystallographic orientation, bonding of acetate to the surface involves the two oxygen atoms of the carboxylate group, with the OCO plane perpendicular to the metal surface. DFT calculations reveal also that the total charge of the metal cluster-acetate supermolecule has small effect on the vibrational frequencies of adsorbed acetate species. Both the external and the internal reflection measurements show the co-adsorption of acetate and perchlorate anions. Step-scan measurements carried out with the gold thin-film electrodes have allowed the monitoring of the time-dependent behaviour of perchlorate, acetate and water bands in potential step experiments. Acetate adsorption under those conditions is shown to involve perchlorate desorption and to follow a Langmuir-type kinetics. The step-scan spectra also show the rise and decay of transient water structures with parallel time-dependent shifts of the background intensity in the infrared spectra

  10. Preparation and characterization of Bi2Sr2CaCu2O8+δ thin films on MgO single crystal substrates by chemical solution deposition

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Kepa, Katarzyna; Hlásek, T.

    2013-01-01

    Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors. Pyrolysis takes place between 200°C and 450°C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c-axis oriented Bi2Sr2Ca...

  11. Optical characterization of epitaxial single crystal CdTe thin films on Al{sub 2}O{sub 3} (0001) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, S.M.; Devenyi, G.A., E-mail: devenyga@mcmaster.ca; Jarvis, V.M.; Meinander, K.; Haapamaki, C.M.; Kuyanov, P.; Gerber, M.; LaPierre, R.R.; Preston, J.S.

    2014-11-03

    The optoelectronic properties of single crystal CdTe thin films were investigated by photoluminescence spectroscopy, photoreflectance spectroscopy and variable angle spectroscopic ellipsometry. The room temperature bandgap was measured to be 1.51 eV and was consistent between spectroscopic measurements and previously reported values. Breadth of bandgap emission was consistent with high quality material. Low temperature photoluminescence spectra indicated a dominant emission consistent with bound excitons. Emissions corresponding to self-compensation defects, doping and contaminants were not found. Variable angle spectroscopic ellipsometry measurements over the near-UV to infrared range demonstrated sharp resonance peaks. All spectroscopic measurements indicate high quality thin film material of comparable or better quality than bulk CdTe. - Highlights: • High quality epitaxial CdTe thin films were grown. • Two dimensional X-ray diffraction characterization confirmed single crystal material. • Photoluminescence indicated low defect density when compared to bulk single crystals. • Optical characterization indicated the presence of room temperature excitons.

  12. High-Performance Flexible Thin-Film Transistors Based on Single-Crystal-like Silicon Epitaxially Grown on Metal Tape by Roll-to-Roll Continuous Deposition Process.

    Science.gov (United States)

    Gao, Ying; Asadirad, Mojtaba; Yao, Yao; Dutta, Pavel; Galstyan, Eduard; Shervin, Shahab; Lee, Keon-Hwa; Pouladi, Sara; Sun, Sicong; Li, Yongkuan; Rathi, Monika; Ryou, Jae-Hyun; Selvamanickam, Venkat

    2016-11-02

    Single-crystal-like silicon (Si) thin films on bendable and scalable substrates via direct deposition are a promising material platform for high-performance and cost-effective devices of flexible electronics. However, due to the thick and unintentionally highly doped semiconductor layer, the operation of transistors has been hampered. We report the first demonstration of high-performance flexible thin-film transistors (TFTs) using single-crystal-like Si thin films with a field-effect mobility of ∼200 cm 2 /V·s and saturation current, I/l W > 50 μA/μm, which are orders-of-magnitude higher than the device characteristics of conventional flexible TFTs. The Si thin films with a (001) plane grown on a metal tape by a "seed and epitaxy" technique show nearly single-crystalline properties characterized by X-ray diffraction, Raman spectroscopy, reflection high-energy electron diffraction, and transmission electron microscopy. The realization of flexible and high-performance Si TFTs can establish a new pathway for extended applications of flexible electronics such as amplification and digital circuits, more than currently dominant display switches.

  13. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011){sub B3} single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Higuchi, Jumpei; Yabuhara, Osamu [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011){sub B3} single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar]{sub bcc} || GaAs(011)[011-bar]{sub B3}. The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{l_brace}011{r_brace} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011){sub B3} substrates.

  14. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011)B3 single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Higuchi, Jumpei; Yabuhara, Osamu; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011) B3 single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar] bcc || GaAs(011)[011-bar] B3 . The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{011} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011) B3 substrates.

  15. Fast neutron induced flux pinning in Tl-based high-Tc single crystals and thin films, highly textured tapes and melt-textured bulk 123-superconductors

    International Nuclear Information System (INIS)

    Brandstaetter, G.; Samadi Hosseinalli, G.; Kern, C.; Sauerzopf, F.M.; Schulz, G.W.; Straif, W.; Yang, X.; Weber, H.W.; Hu, Q.Y.

    1999-01-01

    Various compounds (TI-2223, TI-1223, TI-2212) as well as material forms (single crystals, thin films, ceramics, tapes) of TI-based high temperature superconductors were investigated by magnetic and transport techniques. TI-2223 has a very 'low lying' irreversibility line (H parallel e) and negligible critical current densities J c at 77 K. However, the irreversibility line shifts to higher fields and temperatures and J c is strongly enhanced, even at 77 K, after fast neutron irradiation. In contrast, the related TI-1223 compound has a much steeper irreversibility line (H parallel c) similar to that of Y-123. J c is significant up to 77 K, even in the unirradiated state, and can be largely improved by neutron irradiation. Transport measurements made on TI-1223 tapes still show much lower critical current densities. TI-2212 and Tl-2223 thin films have J c 's at 77 K, which are comparable to those of TI-1223 single crystals. Transport measurements on highly textured Bi-2223 tapes as well as flux profile measurements on Nd-123 bulk superconductors confirm the beneficial effects of neutron induced defects (collision cascades) for flux pinning. (author)

  16. Breakthrough to Non-Vacuum Deposition of Single-Crystal, Ultra-Thin, Homogeneous Nanoparticle Layers: A Better Alternative to Chemical Bath Deposition and Atomic Layer Deposition

    Directory of Open Access Journals (Sweden)

    Yu-Kuang Liao

    2017-04-01

    Full Text Available Most thin-film techniques require a multiple vacuum process, and cannot produce high-coverage continuous thin films with the thickness of a few nanometers on rough surfaces. We present a new ”paradigm shift” non-vacuum process to deposit high-quality, ultra-thin, single-crystal layers of coalesced sulfide nanoparticles (NPs with controllable thickness down to a few nanometers, based on thermal decomposition. This provides high-coverage, homogeneous thickness, and large-area deposition over a rough surface, with little material loss or liquid chemical waste, and deposition rates of 10 nm/min. This technique can potentially replace conventional thin-film deposition methods, such as atomic layer deposition (ALD and chemical bath deposition (CBD as used by the Cu(In,GaSe2 (CIGS thin-film solar cell industry for decades. We demonstrate 32% improvement of CIGS thin-film solar cell efficiency in comparison to reference devices prepared by conventional CBD deposition method by depositing the ZnS NPs buffer layer using the new process. The new ZnS NPs layer allows reduction of an intrinsic ZnO layer, which can lead to severe shunt leakage in case of a CBD buffer layer. This leads to a 65% relative efficiency increase.

  17. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 {sup 0}C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc{sub r}eases in the film. The Ni film prepared at 100 {sup 0}C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  18. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 0 C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc r eases in the film. The Ni film prepared at 100 0 C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  19. Characterization of single crystal uranium-oxide thin films grown via reactive-gas magnetron sputtering on yttria-stabilized zirconia and sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Strehle, Melissa M.; Heuser, Brent J., E-mail: bheuser@illinois.edu; Elbakhshwan, Mohamed S.; Han Xiaochun; Gennardo, David J.; Pappas, Harrison K.; Ju, Hyunsu

    2012-06-30

    The microstructure and valence states of three single crystal thin film systems, UO{sub 2} on (11{sup Macron }02) r-plane sapphire, UO{sub 2} on (001) yttria-stabilized zirconia, and U{sub 3}O{sub 8} on (11{sup Macron }02) r-plane sapphire, grown via reactive-gas magnetron sputtering are analyzed primarily with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). XRD analysis indicates the growth of single crystal domains with varying degrees of mosaicity. XPS and UPS analyses yield U-4f, U-5f, O-1s, and O-2p electron binding energies consistent with reported bulk values. A change from p-type to n-type semiconductor behavior induced by preferential sputtering of oxygen during depth profile analysis was observed with both XPS and UPS. Trivalent cation impurities (Nd and Al) in UO{sub 2} lower the Fermi level, shifting the XPS spectral weight. This observation is consistent with hole-doping of a Mott-Hubbard insulator. The uranium oxide-(11{sup Macron }02) sapphire system is unstable with respect to Al interdiffusion across the film-substrate interface at elevated temperature. - Highlights: Black-Right-Pointing-Pointer Single crystal uranium-oxides grown on sapphire and yttria-stabilized zirconia. Black-Right-Pointing-Pointer Anion and cation valence states studied by photoelectron emission spectroscopy. Black-Right-Pointing-Pointer Trivalent Nd and Al impurities lower the Fermi level. Black-Right-Pointing-Pointer Uranium-oxide films on sapphire found to be unstable with respect to Al interdiffusion.

  20. Single-crystal-like GdNdO{sub x} thin films on silicon substrates by magnetron sputtering and high-temperature annealing for crystal seed layer application

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ziwei; Xiao, Lei; Liang, Renrong, E-mail: wang-j@tsinghua.edu.cn, E-mail: liangrr@tsinghua.edu.cn; Shen, Shanshan; Xu, Jun; Wang, Jing, E-mail: wang-j@tsinghua.edu.cn, E-mail: liangrr@tsinghua.edu.cn [Tsinghua National Laboratory for Information Science and Technology, Institute of Microelectronics, Tsinghua University, Beijing 100084 (China)

    2016-06-15

    Single-crystal-like rare earth oxide thin films on silicon (Si) substrates were fabricated by magnetron sputtering and high-temperature annealing processes. A 30-nm-thick high-quality GdNdO{sub x} (GNO) film was deposited using a high-temperature sputtering process at 500°C. A Gd{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} mixture was used as the sputtering target, in which the proportions of Gd{sub 2}O{sub 3} and Nd{sub 2}O{sub 3} were controlled to make the GNO’s lattice parameter match that of the Si substrate. To further improve the quality of the GNO film, a post-deposition annealing process was performed at a temperature of 1000°C. The GNO films exhibited a strong preferred orientation on the Si substrate. In addition, an Al/GNO/Si capacitor was fabricated to evaluate the dielectric constant and leakage current of the GNO films. It was determined that the single-crystal-like GNO films on the Si substrates have potential for use as an insulator layer for semiconductor-on-insulator and semiconductor/insulator multilayer applications.

  1. Single-crystal-like GdNdOx thin films on silicon substrates by magnetron sputtering and high-temperature annealing for crystal seed layer application

    Directory of Open Access Journals (Sweden)

    Ziwei Wang

    2016-06-01

    Full Text Available Single-crystal-like rare earth oxide thin films on silicon (Si substrates were fabricated by magnetron sputtering and high-temperature annealing processes. A 30-nm-thick high-quality GdNdOx (GNO film was deposited using a high-temperature sputtering process at 500°C. A Gd2O3 and Nd2O3 mixture was used as the sputtering target, in which the proportions of Gd2O3 and Nd2O3 were controlled to make the GNO’s lattice parameter match that of the Si substrate. To further improve the quality of the GNO film, a post-deposition annealing process was performed at a temperature of 1000°C. The GNO films exhibited a strong preferred orientation on the Si substrate. In addition, an Al/GNO/Si capacitor was fabricated to evaluate the dielectric constant and leakage current of the GNO films. It was determined that the single-crystal-like GNO films on the Si substrates have potential for use as an insulator layer for semiconductor-on-insulator and semiconductor/insulator multilayer applications.

  2. Surface texture of single-crystal silicon oxidized under a thin V{sub 2}O{sub 5} layer

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, S. E., E-mail: nikitin@mail.ioffe.ru; Verbitskiy, V. N.; Nashchekin, A. V.; Trapeznikova, I. N.; Bobyl, A. V.; Terukova, E. E. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2017-01-15

    The process of surface texturing of single-crystal silicon oxidized under a V{sub 2}O{sub 5} layer is studied. Intense silicon oxidation at the Si–V{sub 2}O{sub 5} interface begins at a temperature of 903 K which is 200 K below than upon silicon thermal oxidation in an oxygen atmosphere. A silicon dioxide layer 30–50 nm thick with SiO{sub 2} inclusions in silicon depth up to 400 nm is formed at the V{sub 2}O{sub 5}–Si interface. The diffusion coefficient of atomic oxygen through the silicon-dioxide layer at 903 K is determined (D ≥ 2 × 10{sup –15} cm{sup 2} s{sup –1}). A model of low-temperature silicon oxidation, based on atomic oxygen diffusion from V{sub 2}O{sub 5} through the SiO{sub 2} layer to silicon, and SiO{sub x} precipitate formation in silicon is proposed. After removing the V{sub 2}O{sub 5} and silicon-dioxide layers, texture is formed on the silicon surface, which intensely scatters light in the wavelength range of 300–550 nm and is important in the texturing of the front and rear surfaces of solar cells.

  3. Transverse anisotropic magnetoresistance effects in pseudo-single-crystal γ′-Fe4N thin films

    Directory of Open Access Journals (Sweden)

    Kazuki Kabara

    2016-05-01

    Full Text Available Transverse anisotropic magnetoresistance (AMR effects, for which magnetization is rotated in an orthogonal plane to the current direction, were investigated at various temperatures, in order to clarify the structural transformation from a cubic to a tetragonal symmetry in a pseudo-single-crystal Fe4N film, which is predicted from the usual in-plane AMR measurements by the theory taking into account the spin-orbit interaction and crystal field splitting of 3d bands. According to a phenomenological theory of AMR, which derives only from the crystal symmetry, a cos 2θ component ( C 2 tr exists in transverse AMR curves for a tetragonal system but does not for a cubic system. In the Fe4N film, the C 2 tr shows a positive small value (0.12% from 300 K to 50 K. However, the C 2 t r increases to negative value below 50 K and reaches to -2% at 5 K. The drastic increasing of the C 2 tr demonstrates the structural transformation from a cubic to a tetragonal symmetry below 50 K in the Fe4N film. In addition, the out-of-plane and in-plane lattice constants (c and a were precisely determined with X-ray diffraction at room temperature using the Nelson-Riely function. As a result, the positive small C 2 t r above 50 K is attributed to a slightly distorted Fe4N lattice (c/a = 1.002.

  4. Preparation and structural characterization of FeCo epitaxial thin films on insulating single-crystal substrates

    International Nuclear Information System (INIS)

    Nishiyama, Tsutomu; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    FeCo epitaxial films were prepared on MgO(111), SrTiO 3 (111), and Al 2 O 3 (0001) single-crystal substrates by ultrahigh vacuum molecular beam epitaxy. The effects of insulating substrate material on the film growth process and the structures were investigated. FeCo(110) bcc films grow on MgO substrates with two type domains, Nishiyama-Wassermann (NW) and Kurdjumov-Sachs (KS) relationships. On the contrary, FeCo films grown on SrTiO 3 and Al 2 O 3 substrates include FeCo(111) bcc crystal in addition to the FeCo(110) bcc crystals with NW and KS relationships. The FeCo(111) bcc crystal consists of two type domains whose orientations are rotated around the film normal by 180 deg. each other. The out-of-plane and the in-plane lattice spacings of FeCo(110) bcc and FeCo(111) bcc crystals formed on the insulating substrates are in agreement with those of the bulk Fe 50 Co 50 (at. %) crystal with small errors ranging between +0.2% and +0.4%, showing that the strains in the epitaxial films are very small.

  5. Scanning tunneling spectroscopic studies of superconducting NbN single crystal thin films at 4.2 K

    International Nuclear Information System (INIS)

    Kashiwaya, S.; Koyanagi, M.; Matsuda, M.; Shoji, A.; Shibata, H.

    1991-01-01

    This paper reports on a Low Temperature Scanning Tunneling Microscope (LTSTM) constructed to study the microscopic properties of superconductors. It has atomic resolution from room temperature to 4.2 K. Conductance spectra obtained between a Pt tip and a NbN thin film agreed well with theoretical curves based on the BCS theory

  6. Deposition of thin layer (monoatomic layer) of barium on gold single crystal surfaces and studies of its oxidation employing X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Ahmad, H.; Ahmad, R.; Khalid, M.; Alvi, R.A.

    2007-01-01

    Due to the high reactivity of barium with oxygen, some oxygen diffuse into the bulk to form bulk oxide and it is very difficult to differentiate the oxide over layer and the bulk oxide. To study the oxidation of barium surface layer, a thin layer (monolayer) of barium is developed over gold single crystal surface. Gold is selected as support because it is one of the least reactive metal in transition metal group and have very low probability of reaction with oxygen at room temperature (300K). Nitrous oxide (N/sub 2/O) was used as oxidant. Thin layer of barium was deposited on Au(100) surface. The barium coverage on gold surface was calculated that varied from 0.4 to 1.4 monolayer (ML). Photoelectron spectra for O(ls), N(ls), Ba (3d), and Au (4f) have been recorded on X-ray photoelectron spectrometer at different binding energy region specific for each element. The decomposition of nitrous oxide has been observed in all cases. It has found that nitrogen is evolved in the gaseous state and oxygen is adsorbed/chemisorbed on barium over layer. (author)

  7. Surface study and thickness control of thin Al2O3 film on Cu-9%Al(111) single crystal

    International Nuclear Information System (INIS)

    Yamauchi, Yasuhiro; Yoshitake, Michiko; Song Weijie

    2004-01-01

    We were successful in growing a uniform flat Al 2 O 3 film on the Cu-9%Al(111) surface using the improved cleaning process, low ion energy and short time sputtering. The growth of ultra-thin film of Al 2 O 3 on Cu-9%Al was investigated using Auger electron spectroscopy (AES) and a scanning electron microscope (SEM). The Al 2 O 3 film whose maximum thickness was about 4.0 nm grew uniformly on the Cu-9%Al surface. The Al and O KLL Auger peaks of Al 2 O 3 film shifted toward low kinetic energy, and the shifts were related to Schottky barrier formation and band bending at the Al 2 O 3 /Cu-9%Al interface. The thickness of Al 2 O 3 film on the Cu-9%Al surface was controlled by the oxygen exposure

  8. Optical properties of Pb2 -based aggregated phases in CsBr Thin film and single crystal matrices

    Science.gov (United States)

    Nikl, M.; Nitsch, K.; Mihokova, E.; Polak, K.; Fabeni, P.; Pazzi, G. P.; Gurioli, M.; Phani, R.; Santucci, S.; Scacco, A.; Somma, F.

    Emission characteristics of CsPbBr3 and Cs4PbBr6 aggregates in CsBr bulk and thin film matrices are reported. The emission of the former aggregated phase is peaking about 520-560 nm. It shows small Stokes shift (50 meV) related to narrow free exciton emission line of sub-nanosecond decay times. Quantum size effect was evidenced for the aggregates of 6-7 nm in diameter. The Cs4PbBr6 aggregates show emission peak at 375 nm and overall emission characteristics are similar to those of KBr: Pb, which is explained by very close local arrangement of emission centres-(PbBr6)4- octahedra-in both structures.

  9. Epitaxial growth of bcc-FexCo100-x thin films on MgO(1 1 0) single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Nishiyama, Tsutomu; Shikada, Kouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

    2010-01-01

    Fe x Co 100-x (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe x Co 100-x film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe x Co 100-x crystals with very small errors less than ±0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe 50 Co 50 /MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

  10. Epitaxial growth of bcc-Fe{sub x}Co{sub 100-x} thin films on MgO(1 1 0) single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Nishiyama, Tsutomu; Shikada, Kouhei [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2010-07-15

    Fe{sub x}Co{sub 100-x} (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe{sub x}Co{sub 100-x} film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe{sub x}Co{sub 100-x} crystals with very small errors less than +-0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe{sub 50}Co{sub 50}/MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.

  11. Hall coefficients and optical properties of La/sub 2-//sub x/Sr/sub x/CuO4 single-crystal thin films

    International Nuclear Information System (INIS)

    Suzuki, M.

    1989-01-01

    The low-field Hall coefficient R/sub H/, optical reflectance and transmittance of the La/sub 2-//sub x/Sr/sub x/CuO 4 system with various Sr concentrations from x = 0 to 0.36 are systematically studied using single-crystal thin films epitaxially grown on (100) face SrTiO 3 substrates with the c axis normal to the film surface. For the x range measured, R/sub H/ is positive and decreases more rapidly than that expected from the Sr concentration but more slowly than reported earlier for polycrystalline specimens, indicating anisotropy of R/sub H/. Furthermore, the x dependence indicates deviation from that expected from a simple band model. Within the superconducting composition range, R/sub H/ exhibits characteristic temperature dependence. The optical reflectance spectrum changes from that of a semiconductor at x = 0 to a typical metallic one characterized by the Drude model for x>0.1, indicating the development of itinerant holes in the Cu-O planes. In the optical transmission spectra, an anomalous absorption band is seen in addition to the fundamental absorption corresponding to an energy gap of about 2 eV. This band, which develops with Sr doping, implies an enhancement of the density of states near the Fermi level. Taking these observations into account, the normal-state transport properties are explained with a qualitative consistence

  12. Electrically Anisotropic Layered Perovskite Single Crystal

    KAUST Repository

    Li, Ting-You

    2016-04-01

    Organic-inorganic hybrid perovskites (OIHPs), which are promising materials for electronic and optoelectronic applications (1-10), have made into layered organic-inorganic hybrid perovskites (LOIHPs). These LOIHPs have been applied to thin-film transistors, solar cells and tunable wavelength phosphors (11-18). It is known that devices fabricated with single crystal exhibit the superior performance, which makes the growth of large-sized single crystals critical for future device applications (19-23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating the potentials in mass production. After that, we reveal anisotropic electrical and optoelectronic properties which proved the carrier propagating along inorganic framework. The carrier mobility of in-inorganic-plane (in-plane) devices shows the average value of 45 cm2 V–1 s–1 which is about 100 times greater than the record of LOIHP devices (15), showing the importance of single crystal in device application. Moreover, the LOIHP single crystals show its ultra-short carrier lifetime of 42.7 ps and photoluminescence quantum efficiency (PLQE) of 25.4 %. We expect this report to be a start of LOIHPs for advanced applications in which the anisotropic properties are needed (24-25), and meets the demand of high-speed applications and fast-response applications.

  13. High-resolution, hard x-ray photoemission investigation of BaFe2As2: Moderate influence of the surface and evidence for a low degree of Fe 3d-As 4p hybridization of electronic states near the Fermi energy

    NARCIS (Netherlands)

    de Jong, S.; Huang, Y.; Huisman, R.; Massee, F.; Thirupathaiah, R.; Gorgoi, M.; Schaefers, F.; Follath, F.; Goedkoop, J.B.; Golden, M.S.

    2009-01-01

    Photoemission data taken with hard x-ray radiation on cleaved single crystals of the barium parent compound of the MFe2As2 pnictide high-temperature superconductor family are presented. Making use of the increased bulk sensitivity upon hard x-ray excitation, and comparing the results to data taken

  14. Inkjet printing of single-crystal films.

    Science.gov (United States)

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

    2011-07-13

    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 (C(8)-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4 cm(2) V(-1) s(-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.

  15. Magnetization of correlated electron systems. MnSi thin films, CrB2 single crystals and two-dimensional electron systems in MgZnO/ZnO

    International Nuclear Information System (INIS)

    Brasse, Matthias

    2014-01-01

    Torque magnetometry at low temperature is performed to investigate the magnetic properties of MnSi thin films, of a CrB 2 single crystal and of a two-dimensional electron system (2DESs) formed at the interface of MgZnO/ZnO. The magnetic anisotropy and phase diagram of MnSi as well as information on the electronic structure of CrB 2 are obtained. The MgZnO/ZnO 2DESs exhibits the de Haas-van Alphen effect and non-equilibrium currents which are analyzed in order to determine ground state properties and excited states, respectively.

  16. Epitaxial single-crystal thin films of MnxTi1-xO2-δ grown on (rutile)TiO2 substrates with pulsed laser deposition: Experiment and theory

    Energy Technology Data Exchange (ETDEWEB)

    Ilton, Eugene S.; Droubay, Timothy C.; Chaka, Anne M.; Kovarik, Libor; Varga, Tamas; Arey, Bruce W.; Kerisit, Sebastien N.

    2015-02-01

    Epitaxial rutile-structured single-crystal MnxTi1-xO2-δ films were synthesized on rutile- (110) and -(001) substrates using pulsed laser deposition. The films were characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and aberration-corrected transmission electron microscopy (ACTEM). Under the present conditions, 400oC and PO2 = 20 mTorr, single crystal epitaxial thin films were grown for x = 0.13, where x is the nominal average mole fraction of Mn. In fact, arbitrarily thick films could be grown with near invariant Mn/Ti concentration profiles from the substrate/film interface to the film surface. In contrast, at x = 0.25, Mn became enriched towards the surface and a secondary nano-scale phase formed which appeared to maintain the basic rutile structure but with enhanced z-contrast in the tunnels, or tetrahedral interstitial sites. Ab initio thermodynamic calculations provided quantitative estimates for the destabilizing effect of expanding the β-MnO2 lattice parameters to those of TiO2-rutile, the stabilizing effect of diluting Mn with increasing Ti concentration, and competing reaction pathways.

  17. Effect of holes on the room temperature tensile behaviors of thin wall specimens with (210) side surface of Ni-base single crystal superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Z.J.; Liu, T.; Pu, S. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenyang 110016 (China); Xu, H. [Materials Fatigue and Fracture Division, Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenyang 110016 (China); Wang, L., E-mail: wangli@imr.ac.cn [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenyang 110016 (China); Lou, L.H. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, No. 72, Wenhua Road, Shenyang 110016 (China)

    2015-10-25

    Tensile properties of Ni-base single crystal superalloy plate specimens with and without a hole at room temperature were studied in the present paper. During the testing process, an ARAMIS system based on the digital image correlation technique and in-situ scanning electron microscopy were employed to in-situ observe the strain distribution and slip traces development on the sample surfaces. It was demonstrated that the yield stress was decreased with the appearance of a hole due to the stress concentration. The results were analyzed based on the stress and strain states of specimens and the slip traces development observed on specimen surfaces. - Graphical abstract: The strain distribution for samples without and with a hole, respectively. - Highlights: • Tensile tests of plate specimens without and with a hole were performed. • Surface strain fields were in-situ observed by ARAMIS system. • Slip traces development on sample surfaces was in-situ observed by SEM. • The hole deteriorated both the tensile strength and elongation of the samples. • Tensile strength of specimens without and with a hole was discussed respectively.

  18. A multistep single-crystal-to-single-crystal bromodiacetylene dimerization

    Science.gov (United States)

    Hoheisel, Tobias N.; Schrettl, Stephen; Marty, Roman; Todorova, Tanya K.; Corminboeuf, Clémence; Sienkiewicz, Andrzej; Scopelliti, Rosario; Schweizer, W. Bernd; Frauenrath, Holger

    2013-04-01

    Packing constraints and precise placement of functional groups are the reason that organic molecules in the crystalline state often display unusual physical or chemical properties not observed in solution. Here we report a single-crystal-to-single-crystal dimerization of a bromodiacetylene that involves unusually large atom displacements as well as the cleavage and formation of several bonds. Density functional theory computations support a mechanism in which the dimerization is initiated by a [2 + 1] photocycloaddition favoured by the nature of carbon-carbon short contacts in the crystal structure. The reaction proceeded up to the theoretical degree of conversion without loss of crystallinity, and it was also performed on a preparative scale with good yield. Moreover, it represents the first synthetic pathway to (E)-1,2-dibromo-1,2-diethynylethenes, which could serve as synthetic intermediates for the preparation of molecular carbon scaffolds. Our findings both extend the scope of single-crystal-to-single-crystal reactions and highlight their potential as a synthetic tool for complex transformations.

  19. Synthesis of highly conductive thin-walled Al-doped ZnO single-crystal microtubes by a solid state method

    Science.gov (United States)

    Hu, Shuopeng; Wang, Yue; Wang, Qiang; Xing, Cheng; Yan, Yinzhou; Jiang, Yijian

    2018-06-01

    ZnO has attracted considerable attention in fundamental studies and practical applications for the past decade due to its outstanding performance in gas sensing, photocatalytic degradation, light harvesting, UV-light emitting/lasing, etc. The large-sized thin-walled ZnO (TW-ZnO) microtube with stable and rich VZn-related acceptors grown by optical vapor supersaturated precipitation (OVSP) is a novel multifunctional optoelectronic material. Unfortunately, the OVSP cannot achieve doping due to the vapor growth process. To obtain doped TW-ZnO microtubes, a solid state method is introduced in this work to achieve thin-walled Al-doping ZnO (TW-ZnO:Al) microtubes with high electrical conductivity. The morphology and microstructures of ZnO:Al microtubes are similar to undoped ones. The Al3+ ions are confirmed to substitute Zn2+ sites and Zn(0/-1) vacancies in the lattice of ZnO by EDS, XRD, Raman and temperature-dependent photoluminescence analyses. The Al dopant acting as a donor level offers massive free electrons to increase the carrier concentrations. The resistivity of the ZnO:Al microtube is reduced down to ∼10-3 Ω·cm, which is one order of magnitude lower than that of the undoped microtube. The present work provides a simple way to achieve doped ZnO tubular components for potential device applications in optoelectronics.

  20. Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals

    International Nuclear Information System (INIS)

    Lu Xin; Park, W K; Greene, L H; Yuan, H Q; Chen, G F; Luo, G L; Wang, N L; Sefat, A S; McGuire, M A; Jin, R; Sales, B C; Mandrus, D; Gillett, J; Sebastian, Suchitra E

    2010-01-01

    Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe 2 As 2 (A = Ba, Sr) family ('Fe-122'). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba 0.6 K 0.4 )Fe 2 As 2 and Ba(Fe 0.9 Co 0.1 ) 2 As 2 , and the other with a V 2/3 background conductance universally observed, extending even up to 100 meV for Sr 0.6 Na 0.4 Fe 2 As 2 and Sr(Fe 0.9 Co 0.1 ) 2 As 2 . The latter is also observed in point-contact junctions on the nonsuperconducting parent compound BaFe 2 As 2 and superconducting (Ba 0.6 K 0.4 )Fe 2 As 2 crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba 0.6 K 0.4 Fe 2 As 2 , double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder-Tinkham-Klapwijk model, the data show a gap size of ∼ 3.0-4.0 meV with 2Δ 0 /k B T c ∼ 2.0-2.6, consistent with the smaller gap size reported for the LnFeAsO family ('Fe-1111'). For the Ba(Fe 0.9 Co 0.1 ) 2 As 2 , the G(V) curves typically display a zero-bias conductance peak.

  1. Patterning of Perovskite Single Crystals

    KAUST Repository

    Corzo, Daniel

    2017-06-12

    As the internet-of-things hardware integration continues to develop and the requirements for electronics keep diversifying and expanding, the necessity for specialized properties other than the classical semiconductor performance becomes apparent. The success of emerging semiconductor materials depends on the manufacturability and cost as much as on the properties and performance they offer. Solution-based semiconductors are an emerging concept that offers the advantage of being compatible with large-scale manufacturing techniques and have the potential to yield high-quality electronic devices at a lower cost than currently available solutions. In this work, patterns of high-quality MAPbBr3 perovskite single crystals in specific locations are achieved through the modification of the substrate properties and solvent engineering. The fabrication of the substrates involved modifying the surface adhesion forces through functionalization with self-assembled monolayers and patterning them by photolithography processes. Spin coating and blade coating were used to deposit the perovskite solution on the modified silicon substrates. While single crystal perovskites were obtained with the modification of substrates alone, solvent engineering helped with improving the Marangoni flows in the deposited droplets by increasing the contact angle and lowering the evaporation rate, therefore controlling and improving the shape of the grown perovskite crystals. The methodology is extended to other types of perovskites such as the transparent MAPbCl3 and the lead-free MABi2I9, demonstrating the adaptability of the process. Adapting the process to electrode arrays opened up the path towards the fabrication of optoelectronic devices including photodetectors and field-effect transistors, for which the first iterations are demonstrated. Overall, manufacturing and integration techniques permitting the fabrication of single crystalline devices, such as the method in this thesis work, are

  2. Organic field-effect transistors using single crystals

    International Nuclear Information System (INIS)

    Hasegawa, Tatsuo; Takeya, Jun

    2009-01-01

    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 cm 2 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. (topical review)

  3. Organic field-effect transistors using single crystals

    Directory of Open Access Journals (Sweden)

    Tatsuo Hasegawa and Jun Takeya

    2009-01-01

    Full Text Available 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.

  4. Electrically Anisotropic Layered Perovskite Single Crystal

    KAUST Repository

    Li, Ting-You

    2016-01-01

    -23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating

  5. Confinement stabilises single crystal vaterite rods.

    OpenAIRE

    Schenk, AS; Albarracin, EJ; Kim, YY; Ihli, J; Meldrum, FC

    2014-01-01

    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.

  6. Relaxor-PT Single Crystal Piezoelectric Sensors

    Directory of Open Access Journals (Sweden)

    Xiaoning Jiang

    2014-07-01

    Full Text Available Relaxor-PbTiO3 piezoelectric single crystals have been widely used in a broad range of electromechanical devices, including piezoelectric sensors, actuators, and transducers. This paper reviews the unique properties of these single crystals for piezoelectric sensors. Design, fabrication and characterization of various relaxor-PT single crystal piezoelectric sensors and their applications are presented and compared with their piezoelectric ceramic counterparts. Newly applicable fields and future trends of relaxor-PT sensors are also suggested in this review paper.

  7. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei

    2017-04-01

    With the soaring advancement of organolead halide perovskite solar cells rising from a power conversion efficiency of merely 3% to more than 22% shortly in five years, researchers’ interests on this big material family have been greatly spurred. So far, both in-depth studies on the fundamental properties of organolead halide perovskites and their extended applications such as photodetectors, light emitting diodes, and lasing have been intensively reported. The great successes have been ascribed to various superior properties of organolead halide hybrid perovskites such as long carrier lifetimes, high carrier mobility, and solution-processable high quality thin films, as will be discussed in Chapter 1. Notably, most of these studies have been limited to their polycrystalline thin films. Single crystals, as a counter form of polycrystals, have no grain boundaries and higher crystallinity, and thus less defects. These characteristics gift single crystals with superior optical, electrical, and mechanical properties, which will be discussed in Chapter 2. For example, organolead halide perovskite single crystals have been reported with much longer carrier lifetimes and higher carrier mobilities, which are especially intriguing for optoelectronic applications. Besides their superior optoelectronic properties, organolead halide perovskites have shown large composition versatility, especially their organic components, which can be controlled to effectively adjust their crystal structures and further fundamental properties. Single crystals are an ideal platform for such composition-structure-property study since a uniform structure with homogeneous compositions and without distraction from grain boundaries as well as excess defects can provide unambiguously information of material properties. As a major part of work of this dissertation, explorative work on the composition-structure-property study of organic-cation-alloyed organolead halide perovskites using their single

  8. Oriented hydroxyapatite single crystals produced by the electrodeposition method

    Energy Technology Data Exchange (ETDEWEB)

    Santos, E.A. dos, E-mail: euler@ufs.br [INSA - Groupe Ingenierie des Surfaces, 24, Bld de la Victoire, 67084 Strasbourg (France); IPCMS - Departement de Surfaces et Interfaces, 23, rue du Loess, BP 43, 67034 Strasbourg (France); Moldovan, M.S. [INSA - Groupe Ingenierie des Surfaces, 24, Bld de la Victoire, 67084 Strasbourg (France); IPCMS - Departement de Surfaces et Interfaces, 23, rue du Loess, BP 43, 67034 Strasbourg (France); Jacomine, L. [INSA - Groupe Ingenierie des Surfaces, 24, Bld de la Victoire, 67084 Strasbourg (France); Mateescu, M. [IS2M - Equipe Interaction Surface-Matiere Vivant, 15, rue Jean Starcky, BP 2488, 68057 Mulhouse (France); Werckmann, J. [IPCMS - Departement de Surfaces et Interfaces, 23, rue du Loess, BP 43, 67034 Strasbourg (France); Anselme, K. [IS2M - Equipe Interaction Surface-Matiere Vivant, 15, rue Jean Starcky, BP 2488, 68057 Mulhouse (France); Mille, P.; Pelletier, H. [INSA - Groupe Ingenierie des Surfaces, 24, Bld de la Victoire, 67084 Strasbourg (France)

    2010-05-25

    We propose here the use of cathodic electrodeposition as tool to fabricate implant coatings consisting in nano/micro single crystals of hydroxyapatite (HA), preferentially orientated along the c-axis. Coating characterization is the base of this work, where we discuss the mechanisms related to the deposition of oriented hydroxyapatite thin films. It is shown that when deposited on titanium alloys, the HA coating is constituted by two distinct regions with different morphologies: at a distance of few microns from the substrate, large HA single crystals are oriented along the c-axis and appear to grow up from a base material, consisting in an amorphous HA. This organized system has a great importance for cell investigation once the variables involved in the cell/surface interaction are reduced. The use of such systems could give a new insight on the effect of particular HA orientation on the osteoblast cells.

  9. Raman analysis of gold on WSe2 single crystal film

    International Nuclear Information System (INIS)

    Mukherjee, Bablu; Sun Leong, Wei; Li, Yida; Thong, John T L; Gong, Hao; Sun, Linfeng; Xiang Shen, Ze; Simsek, Ergun

    2015-01-01

    Synthesis and characterization of high-quality single-crystal tungsten diselenide (WSe 2 ) films on a highly insulating substrate is presented. We demonstrate for the first time that the presence of gold (Au) nanoparticles in the basal plane of a WSe 2 film can enhance its Raman scattering intensity. The experimentally observed enhancement ratio in the Raman signal correlates well with the simulated electric field intensity using both three-dimensional electromagnetic software and theoretical calculation considering layered medium coupled-dipole approximation (LM-CDA). This work serves as a guideline for the use of Au nanoparticles on WSe 2 single-crystal thin films for surface enhanced Raman scattering (SERS) applications in the future. (paper)

  10. Preparation of TiC single crystals

    International Nuclear Information System (INIS)

    Scheerer, B.; Fink, J.; Reichardt, W.

    1975-07-01

    TiC single crystals were prepared by vertical zone melting for measurements of the phonon dispersion by inelastic neutron scattering. The influence of the starting material and of the growing conditions on the growth of the crystal were studied. The crystals were characterized by chemical methods, EMX and neutron diffraction. It was possible to grow single crystals with a volume of up to 0.6 cm 3 and mosaic spread of less then 0.4 0 . (orig.) [de

  11. AFM studies on heavy ion irradiated YBCO single crystals

    International Nuclear Information System (INIS)

    Lakhani, Archana; Marhas, M.K.; Saravanan, P.; Ganesan, V.; Srinivasan, R.; Kanjilal, D.; Mehta, G.K.; Elizabeth, Suja; Bhat, H.L.

    2000-01-01

    Atomic Force Microscopy (AFM) is extensively used to characterise the surface morphology of high energy ion irradiated single crystals of high temperature superconductor - YBCO. Our earlier systematic studies on thin films of YBCO under high energy and heavy ion irradiation shows clear evidence of ion induced sputtering or erosion, even though the effect is more on the grain boundaries. These earlier results were supported by electrical resistance measurements. In order to understand more clearly, the nature of surface modification at these high energies, AFM studies were carried out on single crystals of YBCO. Single crystals were chosen in order to see the effect on crystallites alone without interference from grain boundaries. 200 MeV gold ions were used for investigation using the facilities available at Nuclear Science Centre, New Delhi. The type of ion and the range of energies were chosen to meet the threshold for electronically mediated defect production. The results are in conformity with our earlier studies and will be described in detail in the context of electronic energy loss mediated sputtering or erosion. (author)

  12. Thermopower, electrical and Hall conductivity of undoped and doped iron disilicide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Heinrich, A; Behr, G; Griessmann, H; Teichert, S; Lange, H

    1997-07-01

    The electrical transport properties of {beta}-FeSi{sub 2} single crystals have been investigated in dependence on the purity of the source material and on doping with 3d transition metals. The transport properties included are electrical conductivity, Hall conductivity and thermopower mainly in the temperature range from 4K to 300K. The single crystals have been prepared by chemical transport reaction in a closed system with iodine as transport agent. In undoped single crystals prepared with 5N Fe both electrical conductivity and thermopower depend on the composition within the homogeneity range of {beta}-FeSi{sub 2} which is explained by different intrinsic defects at the Si-rich and Fe-rich phase boundaries. In both undoped and doped single crystals impurity band conduction is observed at low temperatures but above 100K extrinsic behavior determined by shallow impurity states. The thermopower shows between 100K and 200K a significant phonon drag contribution which depends on intrinsic defects and additional doping. The Hall resistivity is considered mainly with respect to an anomalous contribution found in p-type and n-type single crystals and thin films. In addition doped single crystals show at temperatures below about 130K an hysteresis of the Hall voltage. These results make former mobility data uncertain. Comparison will be made between the transport properties of single crystals and polycrystalline material.

  13. Mechanical and optical nanodevices in single-crystal quartz

    Science.gov (United States)

    Sohn, Young-Ik; Miller, Rachel; Venkataraman, Vivek; Lončar, Marko

    2017-12-01

    Single-crystal α-quartz, one of the most widely used piezoelectric materials, has enabled a wide range of timing applications. Owing to the fact that an integrated thin-film based quartz platform is not available, most of these applications rely on macroscopic, bulk crystal-based devices. Here, we show that the Faraday cage angled-etching technique can be used to realize nanoscale electromechanical and photonic devices in quartz. Using this approach, we demonstrate quartz nanomechanical cantilevers and ring resonators featuring Qs of 4900 and 8900, respectively.

  14. Friction stir welding of single crystal aluminium

    DEFF Research Database (Denmark)

    Fonda, Richard Warren; Wert, John A.; Reynolds, A.P.

    2007-01-01

    Friction stir welds were prepared in different orientations in an aluminium single crystal. The welds were quenched to preserve the microstructure surrounding the tool and then electron backscattered diffraction was used to reveal the generation of grain boundaries and the evolution...... of crystallographic texture around the tool in each weld. The extent of both dynamic recrystallisation and conventional recrystallisation varied considerably as a function of weld orientation. As the base plate begins to interact with the deformation field surrounding the tool, regions of the single crystal rotate...

  15. Universal doping evolution of the superconducting gap anisotropy in single crystals of electron-doped Ba(Fe1‑x Rh x )2As2 from London penetration depth measurements

    Science.gov (United States)

    Kim, Hyunsoo; Tanatar, M. A.; Martin, C.; Blomberg, E. C.; Ni, Ni; Bud’ko, S. L.; Canfield, P. C.; Prozorov, R.

    2018-06-01

    Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4d-electron doped Ba(Fe1‑x Rh x )2As2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth . Single crystals with doping levels representative of an underdoped regime x  =  0.039 ( K), close to optimal doping x  =  0.057 ( K) and overdoped x  =  0.079 ( K) and x  =  0.131( K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n, by fitting the data to the power-law, . The exponent n varies non-monotonically with x, increasing to a maximum n  =  2.5 for x  =  0.079 and rapidly decreasing towards overdoped compositions to 1.6 for x  =  0.131. This behavior is qualitatively similar to the doping evolution of the superconducting gap anisotropy in other iron pnictides, including hole-doped (Ba,K)Fe2As2 and 3d-electron-doped Ba(Fe,Co)2As2 superconductors, finding a full gap near optimal doping and strong anisotropy toward the ends of the superconducting dome in the T-x phase diagram. The normalized superfluid density in an optimally Rh-doped sample is almost identical to the temperature-dependence in the optimally doped Ba(Fe,Co)2As2 samples. Our study supports the universal superconducting gap variation with doping and pairing at least in iron based superconductors of the BaFe2As2 family.

  16. Lattice effects in YVO3 single crystal

    NARCIS (Netherlands)

    Marquina, C; Sikora, M; Ibarra, MR; Nugroho, AA; Palstra, TTM

    In this paper we report on the lattice effects in the Mott insulator yttrium orthovanadate (YVO3). Linear thermal expansion and magnetostriction experiments have been performed on a single crystal, in the temperature range from 5 K to room temperature. The YVO3 orders antiferromagnetically at T-N =

  17. Antiferromagnetism in chromium alloy single crystals

    DEFF Research Database (Denmark)

    Bjerrum Møller, Hans; Trego, A.L.; Mackintosh, A.R.

    1965-01-01

    The antiferromagnetism of single crystals of dilute alloys of V, Mn and Re in Cr has been studied at 95°K and 300°K by neutron diffraction. The addition of V causes the diffraction peaks to decrease in intensity and move away from (100), while Mn and Re cause them to increase and approach (100) s...

  18. Neutron forward diffraction by single crystal prisms

    Indian Academy of Sciences (India)

    We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater sensitivity to ...

  19. Properties of single crystal beta''-aluminas

    International Nuclear Information System (INIS)

    Bates, J.B.; Brown, G.M.; Kaneda, T.; Brundage, W.E.; Wang, J.C.; Engstrom, H.

    1979-01-01

    Large single crystals of sodium beta''-alumina were grown by slow evaporation of Na 2 O at 1690 0 C from a mixture of Na 2 CO 3 , MgO, and Al 2 O 3 . Polarized Raman measurements were made on the Na β'' single crystals and on single crystals of Li, K, Rb, and Ag β'' prepared by ion exchange of Na β''. The low frequency Raman spectra of Na, K, Rb, and Ag β'' contained four or more bands due to vibrations of the mobile cations. These results were analyzed by assuming the spectra to be due to the normal modes of a defect cluster consisting of a cation vacancy surrounded by three cations. From model calculations, the Raman band of Na β'' at 33 cm -1 is assigned to the attempt mode for diffusion of Na + ions. The structure of a Ag β'' single crystal was investigated by neutron diffraction, and 20% of the Ag + ion sites were found to be vacant

  20. Method for manufacturing a single crystal nanowire

    NARCIS (Netherlands)

    van den Berg, Albert; Bomer, Johan G.; Carlen, Edwin; Chen, S.; Kraaijenhagen, Roderik Adriaan; Pinedo, Herbert Michael

    2013-01-01

    A method for manufacturing a single crystal nano-structure is provided comprising the steps of providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing

  1. Method for manufacturing a single crystal nanowire

    NARCIS (Netherlands)

    van den Berg, Albert; Bomer, Johan G.; Carlen, Edwin; Chen, S.; Kraaijenhagen, R.A.; Pinedo, Herbert Michael

    2010-01-01

    A method for manufacturing a single crystal nano-structure is provided comprising the steps of providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing

  2. Gallium arsenide single crystal solar cell structure and method of making

    Science.gov (United States)

    Stirn, Richard J. (Inventor)

    1983-01-01

    A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

  3. Types of defect ordering in undoped and lanthanum-doped Bi2201 single crystals

    International Nuclear Information System (INIS)

    Martovitsky, V. P.

    2006-01-01

    Undoped and lanthanum-doped Bi2201 single crystals having a perfect average structure have been comparatively studied by x-ray diffraction. The undoped Bi2201 single crystals exhibit very narrow satellite reflections; their half-width is five to six times smaller than that of Bi2212 single crystals grown by the same technique. This narrowness indicates three-dimensional defect ordering in the former crystals. The lanthanumdoped Bi2201 single crystals with x = 0.7 and T c = 8-10 K exhibit very broad satellite reflections consisting of two systems (modulations) misoriented with respect to each other. The modulation-vector components of these two modulations are found to be q 1 = 0.237b* + 0.277c* and q 2 = 0.238b* + 0.037c*. The single crystals having a perfect average structure and a homogeneous average distribution of doping lanthanum consist of 70-to 80-A-thick layers that alternate along the c axis and have two different types of modulated superlattice. The crystals having a less perfect average structure also consist of alternating layers, but they have different lanthanum concentrations. The low value of T c in the undoped Bi2201 single crystals (9.5 K) correlates with three-dimensional defect ordering in them, and an increase in T c to 33 K upon lanthanum doping can be related to a thin-layer structure of these crystals and to partial substitution of lanthanum for the bismuth positions

  4. Single-Crystal Diamond Nanobeam Waveguide Optomechanics

    Science.gov (United States)

    Khanaliloo, Behzad; Jayakumar, Harishankar; Hryciw, Aaron C.; Lake, David P.; Kaviani, Hamidreza; Barclay, Paul E.

    2015-10-01

    Single-crystal diamond optomechanical devices have the potential to enable fundamental studies and technologies coupling mechanical vibrations to both light and electronic quantum systems. Here, we demonstrate a single-crystal diamond optomechanical system and show that it allows excitation of diamond mechanical resonances into self-oscillations with amplitude >200 nm . The resulting internal stress field is predicted to allow driving of electron spin transitions of diamond nitrogen-vacancy centers. The mechanical resonances have a quality factor >7 ×105 and can be tuned via nonlinear frequency renormalization, while the optomechanical interface has a 150 nm bandwidth and 9.5 fm /√{Hz } sensitivity. In combination, these features make this system a promising platform for interfacing light, nanomechanics, and electron spins.

  5. Single-Crystal Diamond Nanobeam Waveguide Optomechanics

    Directory of Open Access Journals (Sweden)

    Behzad Khanaliloo

    2015-12-01

    Full Text Available Single-crystal diamond optomechanical devices have the potential to enable fundamental studies and technologies coupling mechanical vibrations to both light and electronic quantum systems. Here, we demonstrate a single-crystal diamond optomechanical system and show that it allows excitation of diamond mechanical resonances into self-oscillations with amplitude >200  nm. The resulting internal stress field is predicted to allow driving of electron spin transitions of diamond nitrogen-vacancy centers. The mechanical resonances have a quality factor >7×10^{5} and can be tuned via nonlinear frequency renormalization, while the optomechanical interface has a 150 nm bandwidth and 9.5  fm/sqrt[Hz] sensitivity. In combination, these features make this system a promising platform for interfacing light, nanomechanics, and electron spins.

  6. Single Crystals Grown Under Unconstrained Conditions

    Science.gov (United States)

    Sunagawa, Ichiro

    Based on detailed investigations on morphology (evolution and variation in external forms), surface microtopography of crystal faces (spirals and etch figures), internal morphology (growth sectors, growth banding and associated impurity partitioning) and perfection (dislocations and other lattice defects) in single crystals, we can deduce how and by what mechanism the crystal grew and experienced fluctuation in growth parameters through its growth and post-growth history under unconstrained condition. The information is useful not only in finding appropriate way to growing highly perfect and homogeneous single crystals, but also in deciphering letters sent from the depth of the Earth and the Space. It is also useful in discriminating synthetic from natural gemstones. In this chapter, available methods to obtain molecular information are briefly summarized, and actual examples to demonstrate the importance of this type of investigations are selected from both natural minerals (diamond, quartz, hematite, corundum, beryl, phlogopite) and synthetic crystals (SiC, diamond, corundum, beryl).

  7. Bloch walls in a nickel single crystal

    International Nuclear Information System (INIS)

    Peters, J.; Treimer, W.

    2001-01-01

    We present a consistent theory for the dependence of the magnetic structure in bulk samples on external static magnetic fields and corresponding experimental results. We applied the theory of micromagnetism to this crystal and calculated the Bloch wall thickness as a function of external magnetic fields. The theoretical results agree well with the experimental data, so that the Bloch wall thickness of a 71 deg. nickel single crystal was definitely determined with some hundred of nanometer

  8. Single crystal spectrometer FOX at KENS

    International Nuclear Information System (INIS)

    Takahashi, M.

    2001-01-01

    Single crystal spectrometer FOX installed at H1 thermal neutron line on KENS has been renewed recently for the measurement of very weak scattering. We have installed a multidetector system of 36 linearly placed 3 He detectors with collimators instead of former four-circle diffractometer and scintillator detectors. Though the system is quite simple, a large two-dimensional reciprocal space is observed effectively with high S/N rate on new FOX. (author)

  9. Isotopically pure single crystal epitaxial diamond films and their preparation

    International Nuclear Information System (INIS)

    Banholzer, W.F.; Anthony, T.R.; Williams, D.M.

    1992-01-01

    The present invention is directed to the production of single crystal diamond consisting of isotopically pure carbon-12 or carbon-13. In the present invention, isotopically pure single crystal diamond is grown on a single crystal substrate directly from isotopically pure carbon-12 or carbon-13. One method for forming isotopically pure single crystal diamond comprises the steps of placing in a reaction chamber a single substrate heated to an elevated diamond forming temperature. Another method for forming isotopically pure single crystal diamond comprises diffusing isotopically pure carbon-12 or carbon-13 through a metallic catalyst under high pressure to a region containing a single crystal substrate to form an isotopically pure single crystal diamond layer on said single crystal substrate

  10. Radiation effects in corundum single crystals

    International Nuclear Information System (INIS)

    Gevorkyan, V.A.; Harutunyan, V.V.; Hakhverdyan, E.A.

    2005-01-01

    On the basis of new experimental results and analysis of publications it is shown that in the lattice of corundum crystals the high-energy particles create stable structural defects due to knocking out of atoms from normal sites of the anionic sublattice; this leads to the formation of F and F '+ centers as well as to other complex [Al i '+ F] type color centers. The essence of 'radiation memory' effect in corundum single crystals is that the high-energy particles irradiation, annealing at high temperatures and additional irradiation by X-rays result in the restoration of some spectral bands of the optical absorption in the range 200-650 nm

  11. Single Crystal Filters for Neutron Spectrometry

    International Nuclear Information System (INIS)

    Habib, N.

    2008-01-01

    A study of neutron transmission properties trough a large single crystals specimens of Si, Ge, Pb, Bi and sapphire at 300 K and 80 K have been made for a wide range of neutron energies. The effectiveness of such filters is given by the ratio of the total cross-section of unwanted epithermal neutrons to that the desired thermal neutron beam and by the optimum choice of the crystal orientation, its mosaic spread, thickness and temperature.Our study indicates that sapphire is significantly more effective than the others for a wide range of neutron energies

  12. Pressure-driven phase transitions in TiOCl and the family (Ca, Sr, Ba)Fe2As2

    International Nuclear Information System (INIS)

    Zhang YuZhong; Opahle, Ingo; Jeschke, Harald O; ValentI, Roser

    2010-01-01

    Motivated by recent experimental measurements on pressure-driven phase transitions in Mott insulators as well as the new iron pnictide superconductors, we show that first principles Car-Parrinello molecular dynamics calculations are a powerful method to describe the microscopic origin of such transitions. We present results for (i) the pressure-induced insulator to metal phase transition in the prototypical Mott insulator TiOCl as well as (ii) the pressure-induced structural and magnetic phase transitions in the family of correlated metals AFe 2 As 2 (A = Ca, Sr, Ba). Comparison of our predictions with existing experimental results yields very good agreement.

  13. The new single crystal diffractometer SC3

    International Nuclear Information System (INIS)

    Schefer, J.; Koch, M.; Keller, P.; Fischer, S.; Thut, R.

    1996-01-01

    Single crystal diffraction is a powerful method for the determination of precise structure parameters, superlattices, stress. Neutron single crystal diffraction gives additionally to X-rays information on magnetic structures, both commensurate and incommensurate, hydrogen positions, hydrogen bonding behavior and accurate bondlengths, e.g. important in cuprates. The method is therefore especially powerful if combined with X-ray diffraction results. The new instrument at SINQ has been designed for inorganic materials and is positioned at a thermal beam tube, pointing on a water scatterer. This scatterer is presently operating with H 2 O at ambient temperature, but a change to another medium at different temperature is possible. The instrument will be equipped with three area detectors, moving at fixed difference in 2Θ. each detector may be individually moved around a vertical circle (tilting angle γ), allowing to use not only 4-circle geometry in the temperature range from 1.5 to 380 K, but also any equipment from a dilution refrigerator (7 mK) to a heavy magnet. A high temperature furnace for 4-circle geometry is foreseen as a future option. (author) 6 figs., 1 tab., 7 refs

  14. The new single crystal diffractometer SC3

    Energy Technology Data Exchange (ETDEWEB)

    Schefer, J; Koch, M; Keller, P; Fischer, S; Thut, R [Lab. for Neutron Scattering ETH Zurich, Zurich (Switzerland) and Paul Scherrer Institute, Villigen (Switzerland)

    1996-11-01

    Single crystal diffraction is a powerful method for the determination of precise structure parameters, superlattices, stress. Neutron single crystal diffraction gives additionally to X-rays information on magnetic structures, both commensurate and incommensurate, hydrogen positions, hydrogen bonding behavior and accurate bondlengths, e.g. important in cuprates. The method is therefore especially powerful if combined with X-ray diffraction results. The new instrument at SINQ has been designed for inorganic materials and is positioned at a thermal beam tube, pointing on a water scatterer. This scatterer is presently operating with H{sub 2}O at ambient temperature, but a change to another medium at different temperature is possible. The instrument will be equipped with three area detectors, moving at fixed difference in 2{Theta}. each detector may be individually moved around a vertical circle (tilting angle {gamma}), allowing to use not only 4-circle geometry in the temperature range from 1.5 to 380 K, but also any equipment from a dilution refrigerator (7 mK) to a heavy magnet. A high temperature furnace for 4-circle geometry is foreseen as a future option. (author) 6 figs., 1 tab., 7 refs.

  15. Thermal shock cracking of GSO single crystal

    International Nuclear Information System (INIS)

    Miyazaki, Noriyuki; Yamamoto, Kazunari; Tamura, Takaharu; Kurashige, Kazuhisa; Ishibashi, Hiroyuki; Susa, Kenzo

    1998-01-01

    The quantitative estimation of the failure stress of a gadolinium orthosilicate (Gd 2 SiO 5 , hereafter abbreviated as GSO) single crystal due to thermal shock was investigated. A cylindrical test specimen was heated in a silicone oil bath, then subjected to thermal shock by pouring room temperature silicone oil. Cracking occurred during cooling. The heat conduction analysis was performed to obtain temperature distribution in a GSO single crystal at cracking, using the surface temperatures measured in the thermal shock cracking test. Then the thermal stress was calculated using temperature profile of the test specimen obtained from the heat conduction analysis. It is found from the results of the thermal stress analysis and the observation of the cracking in test specimens that the thermal shock cracking occurs in a cleavage plane due to the stress normal to the plane. Three-point bending tests were also performed to examine the relationship between the critical stress for thermal shock cracking and the three-point bending strength obtained from small-sized test specimens. (author)

  16. Press forging of single crystal calcium fluoride

    International Nuclear Information System (INIS)

    Turk, R.R.

    1975-01-01

    Single crystals of high-purity calcium fluoride have been deformed uniaxially in an attempt to improve strength and resistance to cleavage, without impairing infrared transmission. Order of magnitude increases in strength, such as those found in forged KCl, have not been attained, but fine-grained polycrystalling material has been produced which is resistant to crystalline cleavage. Deformation rates of 10 -2 min -1 , reductions of 10 to 73 percent in height, and deformation temperatures of 550 to 1000 0 C have been used. Flexural strengths over 13,000 psi and grain sizes down to 5 μm have been obtained. Reduction of residual stress through heat treatment has been studied, and resultant techniques applied before, during, and after deformation. No increase in infrared absorption has been noted at the CO laser wavelength of 5.3 μm

  17. Colour centre-free perovskite single crystals

    International Nuclear Information System (INIS)

    Petit, Pierre-Olivier; Petit, Johan; Goldner, Philippe; Viana, Bruno

    2009-01-01

    Yb 3+ :YAlO 3 (YAP) and Yb 3+ :GdAlO 3 (GAP) are interesting 1 μm high-power laser media thanks to their very good thermo-mechanical properties. However, as-grown perovskite single crystals exhibit colour centres. Parasitic thermal load generated by these centres is deleterious for high-power laser action and can lead to crystal damages. Moreover these defects decrease Yb 3+ lifetime. They are related to trapped holes on the oxygen network. In the present work, several schemes to remove colour centres are presented. Attention is focused on cerium codoping, thermal annealing under reducing atmosphere and growth of non-stoechiometric compounds.

  18. Electronic structure of single crystal C60

    International Nuclear Information System (INIS)

    Wu, J.; Shen, Z.X.; Dessau, D.S.; Cao, R.; Marshall, D.S.; Pianetta, P.; Lindau, I.; Yang, X.; Terry, J.; King, D.M.; Wells, B.O.; Elloway, D.; Wendt, H.R.; Brown, C.A.; Hunziker, H.; Vries, M.S. de

    1992-01-01

    We report angle-resolved photoemission data from single crystals of C 60 cleaved in UHV. Unlike the other forms of pure carbon, the valence band spectrum of C 60 consists of many sharp features that can be essentially accounted for by the quantum chemical calculations describing individual molecules. This suggests that the electronic structure of solid C 60 is mainly determined by the bonding interactions within the individual molecules. We also observe remarkable intensity modulations of the photoemission features as a function of photon energy, suggesting strong final state effects. Finally, we address the issue of the band width of the HOMO state of C 60 . We assert that the width of the photoemission peak of C 60 does not reflect the intrinsic band width because it is broadened by the non 0-0 transitions via the Franck-Condon principle. Our view point provides a possible reconciliation between these photoemission data and those measured by other techniques. (orig.)

  19. Photoluminescent properties of single crystal diamond microneedles

    Science.gov (United States)

    Malykhin, Sergey A.; Ismagilov, Rinat R.; Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Fedotov, Pavel V.; Ermakova, Anna; Siyushev, Petr; Katamadze, Konstantin G.; Jelezko, Fedor; Rakovich, Yury P.; Obraztsov, Alexander N.

    2018-01-01

    Single crystal needle-like diamonds shaped as rectangular pyramids were produced by combination of chemical vapor deposition and selective oxidation with dimensions and geometrical characteristics depending on the deposition process parameters. Photoluminescence spectra and their dependencies on wavelength of excitation radiation reveal presence of nitrogen- and silicon-vacancy color centers in the diamond crystallites. Photoluminescence spectra, intensity mapping, and fluorescence lifetime imaging microscopy indicate that silicon-vacancy centers are concentrated at the crystallites apex while nitrogen-vacancy centers are distributed over the whole crystallite. Dependence of the photoluminescence on excitation radiation intensity demonstrates saturation and allows estimation of the color centers density. The combination of structural parameters, geometry and photoluminescent characteristics are prospective for advantageous applications of these diamond crystallites in quantum information processing and optical sensing.

  20. Hydrogen Annealing Of Single-Crystal Superalloys

    Science.gov (United States)

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

    1995-01-01

    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.

  1. Chlorination of irradiated polyethylene single crystals

    International Nuclear Information System (INIS)

    Grimm, H.J.

    1978-01-01

    The chlorination of electron beam-irradiation polyethylene (PE) single crystals was studied for a range of irradiation doses, temperatures, and chlorine interaction times. The results presented show that PE chlorination was quite extensive, even in unirradiated PE single crystals at 25 0 C in the dark. Electron Spin Resonance (ESR, EPR) was used in this study in order to determine the alkyl radical concentration, decay constant, and diffusivity for (unchlorinated) specimens. An alkyl radical diffusivity D/sub a/ = 1.6 x 10 -17 cm 2 /sec at 25 0 C was estimated from ESR data and alkyl radical migration as one-dimensional unsteady-state diffusion process. In irradiated PE, chlorination occurred mainly via chain reactions which were initiated by the irradiation-produced free radicals. Chlorine content values were determined by X-ray Energy Spectroscopy (XES). It was found that the magnitude of the chlorine uptake increased with increasing dose, and decreased with decreasing temperature at constant dose. Otherwise the observed PE chlorination phenomena was quite similar for all of the doses and temperatures studied here, consisting of a two step mechanism: a fast uptake which occurred between time tCl 2 = 0 - 5 minutes and a slower, approximately first-order rate of uptake which occurred between times tCl 2 = 5 - 120 minutes. Chlorination was essentially complete by time tCl 2 = 120 minutes. The rapid uptake probably occurred in the amorphous surface zones where Cl 2 is relatively high and the second, slower step was probably attributable to Cl 2 diffusion into the crystalline regions and subsequent chlorination there. Inasmuch as the PE density decreases with increasing dose (for 1-600 Mrad), Cl 2 diffusivity was enhanced, resulting in higher chlorine uptake values at higher doses

  2. Solar cell structure incorporating a novel single crystal silicon material

    Science.gov (United States)

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    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.

  3. Production and several properties of single crystal austenitic stainless steels

    International Nuclear Information System (INIS)

    Okamoto, Kazutaka; Yoshinari, Akira; Kaneda, Junya; Aono, Yasuhisa; Kato, Takahiko

    1998-01-01

    The single crystal austenitic stainless steels Type 316L and 304L were grown in order to improve the resistance to stress corrosion cracking (SCC) using a unidirectional solidification method which can provide the large size single crystals. The mechanical properties and the chemical properties were examined. The orientation and temperature dependence of tensile properties of the single crystals were measured. The yield stress of the single crystal steels are lower than those of the conventional polycrystal steels because of the grain boundary strength cannot be expected in the single crystal steels. The tensile properties of the single crystal austenitic stainless steel Type 316L depend strongly on the orientation. The tensile strength in orientation are about 200 MPa higher than those in the and orientations. The microstructure of the single crystal consists of a mixture of the continuous γ-austenitic single crystal matrix and the δ-ferrite phase so that the effects of the γ/δ boundaries on the chemical properties were studied. The effects of the δ-ferrite phases and the γ/δ boundaries on the resistance to SCC were examined by the creviced bent beam test (CBB test). No crack is observed in all the CBB test specimens of the single crystals, even at the γ/δ boundaries. The behavior of the radiation induced segregation (RIS) at the γ/δ boundaries in the single crystal austenitic stainless steel Type 316L was evaluated by the electron irradiation test in the high voltage electron microscope (HVEM). The depletion of oversized solute chromium at the γ/δ boundary in the single crystal austenitic stainless steel Type 316L is remarkably lower than that at the grain boundary in the polycrystalline-type 316L. (author)

  4. High quality single crystal Ge nano-membranes for opto-electronic integrated circuitry

    International Nuclear Information System (INIS)

    Shah, V. A.; Gammon, P. M.; Rhead, S. D.; Halpin, J. E.; Trushkevych, O.; Wilson, N. R.; Myronov, M.; Edwards, R. S.; Patchett, D. H.; Allred, P. S.; Prest, M. J.; Whall, T. E.; Parker, E. H. C.; Leadley, D. R.; Chávez-Ángel, E.; Shchepetov, A.; Prunnila, M.; Kachkanov, V.; Dolbnya, I. P.; Reparaz, J. S.

    2014-01-01

    A thin, flat, and single crystal germanium membrane would be an ideal platform on which to mount sensors or integrate photonic and electronic devices, using standard silicon processing technology. We present a fabrication technique compatible with integrated-circuit wafer scale processing to produce membranes of thickness between 60 nm and 800 nm, with large areas of up to 3.5 mm 2 . We show how the optical properties change with thickness, including appearance of Fabry-Pérot type interference in thin membranes. The membranes have low Q-factors, which allow the platforms to counteract distortion during agitation and movement. Finally, we report on the physical characteristics showing sub-nm roughness and a homogenous strain profile throughout the freestanding layer, making the single crystal Ge membrane an excellent platform for further epitaxial growth or deposition of materials

  5. High quality single crystal Ge nano-membranes for opto-electronic integrated circuitry

    Energy Technology Data Exchange (ETDEWEB)

    Shah, V. A., E-mail: vishal.shah@warwick.ac.uk; Gammon, P. M. [Department of Engineering, The University of Warwick, Coventry CV4 7AL (United Kingdom); Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Rhead, S. D.; Halpin, J. E.; Trushkevych, O.; Wilson, N. R.; Myronov, M.; Edwards, R. S.; Patchett, D. H.; Allred, P. S.; Prest, M. J.; Whall, T. E.; Parker, E. H. C.; Leadley, D. R. [Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Chávez-Ángel, E. [ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); Department of Physics, UAB, 08193 Bellaterra (Barcelona) (Spain); Shchepetov, A.; Prunnila, M. [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Espoo (Finland); Kachkanov, V.; Dolbnya, I. P. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Reparaz, J. S. [ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); and others

    2014-04-14

    A thin, flat, and single crystal germanium membrane would be an ideal platform on which to mount sensors or integrate photonic and electronic devices, using standard silicon processing technology. We present a fabrication technique compatible with integrated-circuit wafer scale processing to produce membranes of thickness between 60 nm and 800 nm, with large areas of up to 3.5 mm{sup 2}. We show how the optical properties change with thickness, including appearance of Fabry-Pérot type interference in thin membranes. The membranes have low Q-factors, which allow the platforms to counteract distortion during agitation and movement. Finally, we report on the physical characteristics showing sub-nm roughness and a homogenous strain profile throughout the freestanding layer, making the single crystal Ge membrane an excellent platform for further epitaxial growth or deposition of materials.

  6. Transistor properties of exfoliated single crystals of 2 H -Mo (Se1-xT ex ) 2(0 ≤x ≤1 )

    Science.gov (United States)

    Uesugi, Eri; Miao, Xiao; Ota, Hiromi; Goto, Hidenori; Kubozono, Yoshihiro

    2017-06-01

    Field-effect transistors (FETs) were fabricated using exfoliated single crystals of Mo (Se1-xT ex) 2 with an x range of 0 to 1, and the transistor properties fully investigated at 295 K in four-terminal measurement mode. The chemical composition and crystal structure of exfoliated single crystals were identified by energy-dispersive x-ray spectroscopy (EDX), single-crystal x-ray diffraction, and Raman scattering, suggesting the 2 H - structure in all Mo (Se1-xT ex) 2 . The lattice constants of a and c increase monotonically with increasing x , indicating the substitution of Se by Te. When x 0.4 . In contrast, the polarity of a thick single-crystal Mo (Se1-xT ex) 2 FET did not change despite an increase in x . The change of polarity in a thin single-crystal FET was well explained by the variation of electronic structure. The absence of such change in the thick single-crystal FET can be reasonably interpreted based on the large bulk conduction due to naturally accumulated electrons. The μ value in the thin single-crystal FET showed a parabolic variation, with a minimum μ at around x =0.4 , which probably originates from the disorder of the single crystal caused by the partial replacement of Se by Te, i.e., a disorder that may be due to ionic size difference of Se and Te.

  7. Thermomechanical fatigue in single crystal superalloys

    Directory of Open Access Journals (Sweden)

    Moverare Johan J.

    2014-01-01

    Full Text Available Thermomechanical fatigue (TMF is a mechanism of deformation which is growing in importance due to the efficiency of modern cooling systems and the manner in which turbines and associated turbomachinery are now being operated. Unfortunately, at the present time, relatively little research has been carried out particularly on TMF of single crystal (SX superalloys, probably because the testing is significantly more challenging than the more standard creep and low cycle fatigue (LCF cases; the scarcity and relative expense of the material are additional factors. In this paper, the authors summarise their experiences on the TMF testing of SX superalloys, built up over several years. Emphasis is placed upon describing: (i the nature of the testing method, the challenges involved in ensuring that an given testing methodology is representative of engine conditions (ii the behaviour of a typical Re-containing second generation alloy such as CMSX-4, and its differing performance in out-of-phase/in-phase loading and crystallographic orientation and (iii the differences in behaviour displayed by the Re-containing alloys and new Re-free variants such as STAL15. It is demonstrated that the Re-containing superalloys are prone to different degradation mechanisms involving for example microtwinning, TCP precipitation and recrystallisation. The performance of STAL15 is not too inferior to alloys such as CMSX-4, suggesting that creep resistance itself does not correlate strongly with resistance to TMF. The implications for alloy design efforts are discussed.

  8. Cyclic deformation of Nb single crystals

    International Nuclear Information System (INIS)

    Guiu, F.; Anglada, M.

    1982-01-01

    The temperature and strain-rate dependence of the cyclic flow stress of Nb single crystals with two different axial orientations has been studied at temperatures between 175 and 350 K. This dependence is found to be independent of the crystal orientation when the internal stresses are taken into account, and the results are discussed in terms of the theory of thermally activated dislocation glide. A transition temperature can be identified at about 250 K which separates two regions with different thermally activated deformation behaviour. Above this transition temperature the strain rate can be described by a stress power law, and the activation energy can be represented by a logarithmic function of the stress, as in Escaig's model of screw dislocation mobility. In the temperature range 170 to 250 K the results are also in agreement with the more recent model proposed by Seeger. The large experimental errors inherent in the values of activation enthalpy at low stresses are emphasized and taken into account in the discussion of the results. It is suggested that either impurity-kink interactions or the flexibility of the screw dislocations are responsible for the trend towards the high values of activation enthalpy measured at the low stresses. (author)

  9. Irradiation creep in zirconium single crystals

    International Nuclear Information System (INIS)

    MacEwen, S.R.; Fidleris, V.

    1976-07-01

    Two identical single crystals of crystal bar zirconium have been creep tested in reactor. Both specimens were preirradiated at low stress to a dose of about 4 x 10 23 n/m 2 (E > 1 MeV), and were then loaded to 25 MPa. The first specimen was loaded with reactor at full power, the second during a shutdown. The loading strain for both crystals was more than an order of magnitude smaller than that observed when an identical unirradiated crystal was loaded to the same stress. Both crystals exhibited periods of primary creep, after which their creep rates reached nearly constant values when the reactor was at power. During shutdowns the creep rates decreased rapidly with time. Electron microscopy revealed that the irradiation damage consisted of prismatic dislocation loops, approximately 13.5 nm in diameter. Cleared channels, identified as lying on (1010) planes, were also observed. The results are discussed in terms of the current theories for flux enhanced creep in the light of the microstructures observed. (author)

  10. Spall response of single-crystal copper

    Science.gov (United States)

    Turley, W. D.; Fensin, S. J.; Hixson, R. S.; Jones, D. R.; La Lone, B. M.; Stevens, G. D.; Thomas, S. A.; Veeser, L. R.

    2018-02-01

    We performed a series of systematic spall experiments on single-crystal copper in an effort to determine and isolate the effects of crystal orientation, peak stress, and unloading strain rate on the tensile spall strength. Strain rates ranging from 0.62 to 2.2 × 106 s-1 and peak shock stresses in the 5-14 GPa range, with one additional experiment near 50 GPa, were explored as part of this work. Gun-driven impactors, called flyer plates, generated flat top shocks followed by spall. This work highlights the effect of crystal anisotropy on the spall strength by showing that the spall strength decreases in the following order: [100], [110], and [111]. Over the range of stresses and strain rates explored, the spall strength of [100] copper depends strongly on both the strain rate and shock stress. Except at the very highest shock stress, the results for the [100] orientation show linear relationships between the spall strength and both the applied compressive stress and the strain rate. In addition, hydrodynamic computer code simulations of the spall experiments were performed to calculate the relationship between the strain rate near the spall plane in the target and the rate of free surface velocity release during the pullback. As expected, strain rates at the spall plane are much higher than the strain rates estimated from the free surface velocity release rate. We have begun soft recovery experiments and molecular dynamics calculations to understand the unusual recompression observed in the spall signature for [100] crystals.

  11. Magnetoresistance in terbium and holmium single crystals

    International Nuclear Information System (INIS)

    Singh, R.L.; Jericho, M.H.; Geldart, D.J.W.

    1976-01-01

    The longitudinal magnetoresistance of single crystals of terbium and holmium metals in their low-temperature ferromagnetic phase has been investigated in magnetic fields up to 80 kOe. Typical magnetoresistance isotherms exhibit a minimum which increases in depth and moves to higher fields as the temperature increases. The magnetoresistance around 1 0 K, where inelastic scattering is negligible, has been interpreted as the sum of a negative contribution due to changes in the domain structure and a positive contribution due to normal magnetoresistance. At higher temperatures, a phenomenological approach has been developed to extract the inelastic phonon and spin-wave components from the total measured magnetoresistance. In the temperature range 4--20 0 K (approximately), the phonon resistivity varies as T 3 . 7 for all samples. Approximate upper and lower bounds have been placed on the spin-wave resistivity which is also found to be described by a simple power law in this temperature range. The implications of this result for theoretical treatments of spin-wave resistivity due to s-f exchange interactions are considered. It is concluded that the role played by the magnon energy gap is far less transparent than previously suggested

  12. Thermal and fast neutron dosimetry using artificial single crystal diamond detectors

    International Nuclear Information System (INIS)

    Angelone, M.; Pillon, M.; Prestopino, G.; Marinelli, Marco; Milani, E.; Verona, C.; Verona-Rinati, G.; Aielli, G.; Cardarelli, R.; Santonico, R.; Bedogni, R.; Esposito, A.

    2011-01-01

    In this work we propose the artificial Single Crystal Diamond (SCD) detector covered with a thin layer (0.5 μm/4 μm) of 6 LiF as a simultaneous thermal and fast neutron fluence monitor. Some interesting properties of the diamond response versus the neutron energy are evidenced thanks to Monte Carlo simulation using the MCNPX code which allows to propose the diamond detector also as an ambient dose equivalent (H∗(10)) monitor (REM counter).

  13. Atomic Structure Control of Silica Thin Films on Pt(111)

    KAUST Repository

    Crampton, Andrew S; Ridge, Claron J.; Rö tzer, Marian David; Zwaschka, Gregor; Braun, Thomas; D'Elia, Valerio; Basset, Jean-Marie; Schweinberger, Florian Frank; Gü nther, Sebastian; Heiz, Ueli

    2015-01-01

    Metal oxide thin films grown on metal single crystals are commonly used to model heterogeneous catalyst supports. The structure and properties of thin silicon dioxide films grown on metal single crystals have only recently been thoroughly

  14. Azeotropic binary solvent mixtures for preparation of organic single crystals

    NARCIS (Netherlands)

    Li, X.; Kjellander, B.K.C.; Anthony, J.E.; Bastiaansen, C.W.M.; Broer, D.J.; Gelinck, G.H.

    2009-01-01

    Here, a new approach is introduced to prepare large single crystals of π-conjugated organic molecules from solution. Utilizing the concept of azeotropism, single crystals of tri-isopropylsilylethynyl pentacene (TIPS-PEN) with dimensions up to millimeters are facilely self-assembled from homogeneous

  15. Azeotropic binary solvent mixtures for preparation of organic single crystals

    NARCIS (Netherlands)

    Li, X.; Kjellander, B.K.C.; Anthony, J.E.; Bastiaansen, C.W.M.; Broer, D.J.; Gelinck, G.H.

    2009-01-01

    Here, a new approach is introduced to prepare large single crystals of p-conjugated organic molecules from solution. Utilizing the concept of azeotropism, single crystals of tri-isopropylsilylethynyl pentacene (TIPS-PEN) with dimensions up to millimeters are facilely self-assembled from homogeneous

  16. Excitonic polaritons of zinc diarsenide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Syrbu, N.N., E-mail: sirbunn@yahoo.com [Technical University of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of); Stamov, I.G. [T.G. Shevchenko State University of Pridnestrovie, Tiraspol, Republic of Moldova (Moldova, Republic of); Zalamai, V.V. [Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of); Dorogan, A. [Technical University of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of)

    2017-02-01

    Excitonic polaritons of ZnAs{sub 2} single crystals had been investigated. Parameters of singlet excitons with Г{sub 2}¯(z) symmetry and orthoexcitons 2Г{sub 1}¯(y)+Г{sub 2}¯(x) had been determined. Spectral dependencies of ordinary and extraordinary dispersion of refractive index had been calculated using interferential reflection and transmittance spectra. It was shown, that A excitonic series were due to hole (V{sub 1}) and electron (C{sub 1}) bands. The values of effective masses of electrons (m{sub c}{sup *}=0.10 m{sub 0}) and holes (m{sub v1}{sup *}=0.89 m{sub 0}) had been estimated. It was revealed that the hole mass m{sub v1}{sup *} changes from 1.03 m{sub 0} to 0.55 m{sub 0} at temperature increasing from 10 K up to 230 K and that the electron mass m{sub c}{sup *} does not depend on temperature. The integral absorption A (eV cm{sup −1}) of the states n=1, 2 and 3 of Г{sub 2}¯(z) excitons depends on the A{sub n}≈n{sup −3} equality, which it is characteristic for S-type excitonic functions. Temperature dependences of the integral absorption of ground states for Г{sub 2}¯(z) and Г{sub 2}¯(Ñ…) excitons differ. The ground states of B and C excitons formed by V{sub 3} – C{sub 1} and V{sub 4} – C{sub 1} bands and its parameters had been determined.

  17. Measurement of lattice parameters of single crystals and thin layers

    Czech Academy of Sciences Publication Activity Database

    Drahokoupil, Jan; Veřtát, P.; Richterová, Kristina; Laufek, František

    2014-01-01

    Roč. 21, č. 2 (2014), s. 97-97 ISSN 1211-5894. [Struktura 2014 : kolokvium Krystalografické společnosti. 09.06.2014-12.06.2014, Kutná Hora] Institutional support: RVO:68378271 Keywords : XRD * lattice parameters Subject RIV: BM - Solid Matter Physics ; Magnetism http://www. xray .cz/ms/bul2014-2/wednesday1.pdf

  18. Ge-Au eutectic bonding of Ge (100) single crystals

    International Nuclear Information System (INIS)

    Knowlton, W.B.; Beeman, J.W.; Emes, J.H.; Loretto, D.; Itoh, K.M.; Haller, E.E.

    1993-01-01

    The author present preliminary results on the eutectic bonding between two (100) Ge single crystal surfaces using thin films of Au ranging from 900 angstrom/surface to 300 angstrom/surface and Pd (10% the thickness of Au). Following bonding, plan view optical microscopy (OM) of the cleaved interface of samples with Au thicknesses ≤ 500 angstrom/surface show a eutectic morphology more conducive to phonon transmission through the bond interface. High resolution transmission electron microscopy (HRTEM) cross sectional interface studies of a 300 angstrom/surface Au sample show epitaxial growth of Ge. In sections of the bond, lattice continuity of the Ge is apparent through the interface. TEM studies also reveal heteroepitaxial growth of Au with a Au-Ge lattice mismatch of less than 2%. Eutectic bonds with 200 angstrom/surface Au have been attained with characterization pending. An optical polishing technique for Ge has been optimized to insure intimate contact between the Ge surfaces prior to bonding. Interferometry analysis of the optically polished Ge surface shows that surface height fluctuations lie within ±150 angstrom across an interval of lmm. Characterization of phonon transmission through the interface is discussed with respect to low temperature detection of ballistic phonons

  19. Understanding surface structure and chemistry of single crystal lanthanum aluminate

    KAUST Repository

    Pramana, Stevin S.

    2017-03-02

    The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

  20. Ion implantation of CdTe single crystals

    International Nuclear Information System (INIS)

    Wiecek, Tomasz; Popovich, Volodymir; Bester, Mariusz; Kuzma, Marian

    2017-01-01

    Ion implantation is a technique which is widely used in industry for unique modification of metal surface for medical applications. In semiconductor silicon technology ion implantation is also widely used for thin layer electronic or optoelectronic devices production. For other semiconductor materials this technique is still at an early stage. In this paper based on literature data we present the main features of the implantation of CdTe single crystals as well as some of the major problems which are likely to occur when dealing with them. The most unexpected feature is the high resistance of these crystals against the amorphization caused by ion implantation even at high doses (10"1"7 1/cm"2). The second property is the disposal of defects much deeper in the sample then it follows from the modeling calculations. The outline of principles of the ion implantation is included in the paper. The data based on RBS measurements and modeling results obtained by using SRIM software were taken into account.

  1. Reshock and release response of aluminum single crystal

    International Nuclear Information System (INIS)

    Huang, H.; Asay, J. R.

    2007-01-01

    Reshock and release experiments were performed on single crystal aluminum along three orientations and on polycrystalline 1050 aluminum with 50 μm grain size at shock stresses of 13 and 21 GPa to investigate the mechanisms for previously observed quasielastic recompression behavior. Particle velocity profiles obtained during reshocking both single crystals and polycrystalline aluminum from initial shock stresses of 13-21 GPa show similar quasielastic recompression behavior. Quasielastic release response is also observed in all single crystals, but the magnitude of the effect is crystal orientation dependent, with [111] and [110] exhibiting more ideal elastic-plastic release for unloading from the shocked state than for the [100] orientation and polycrystalline aluminum. The quasielastic response of 1050 aluminum is intermediate to that of the [100] and [111] orientations. Comparison of the wave profiles obtained for both unloading and reloading of single crystals and polycrystalline 1050 aluminum from shocked states suggests that the observed quasielastic response of polycrystalline aluminum results from the averaging response of single crystals for shock propagation along different orientations, and that the response of 1050 aluminum with large grain boundaries is not significantly different from the results obtained on single crystal aluminum. The yield strength of the single crystals and 1050 aluminum is found to increase with shock stress, which is consistent with previous results [H. Huang and I. R. Asay, J. Appl. Phys. 98, 033524 (2005)

  2. Ultra-large single crystals by abnormal grain growth.

    Science.gov (United States)

    Kusama, Tomoe; Omori, Toshihiro; Saito, Takashi; Kise, Sumio; Tanaka, Toyonobu; Araki, Yoshikazu; Kainuma, Ryosuke

    2017-08-25

    Producing a single crystal is expensive because of low mass productivity. Therefore, many metallic materials are being used in polycrystalline form, even though material properties are superior in a single crystal. Here we show that an extraordinarily large Cu-Al-Mn single crystal can be obtained by abnormal grain growth (AGG) induced by simple heat treatment with high mass productivity. In AGG, the sub-boundary energy introduced by cyclic heat treatment (CHT) is dominant in the driving pressure, and the grain boundary migration rate is accelerated by repeating the low-temperature CHT due to the increase of the sub-boundary energy. With such treatment, fabrication of single crystal bars 70 cm in length is achieved. This result ensures that the range of applications of shape memory alloys will spread beyond small-sized devices to large-scale components and may enable new applications of single crystals in other metallic and ceramics materials having similar microstructural features.Growing large single crystals cheaply and reliably for structural applications remains challenging. Here, the authors combine accelerated abnormal grain growth and cyclic heat treatments to grow a superelastic shape memory alloy single crystal to 70 cm.

  3. Single-crystal growth of ceria-based materials

    International Nuclear Information System (INIS)

    Ulbrich, Gregor

    2015-01-01

    In this work it could be shown that Skull-Melting is a suitable method for growing ceria single crystals. Twenty different ceria-based single crystals could be manufactured. It was possible to dope ceria single crystals with Gd, Sm, Y, Zr, Ti, Ta, and Pr in different concentrations. Also co-doping with the named metals was realized. However, there remain some problems for growing ceria-based single crystals by Skull-Melting. As ignition metal zirconium was used because no ceria-based material works well. For that reason all single crystals show small zirconium contamination. Another problem is the formation of oxygen by the heat-induced reduction of ceria during the melting process. Because of that the skull of sintered material is often destroyed by gas pressure. This problem had to be solved individually for every single crystal. The obtained single crystals were characterized using different methods. To ensure the single crystal character the y were examined by Laue diffraction. All manufactured crystals are single crystals. Also powder diffraction patterns of the milled and oxidized samples were measured. For the determination of symmetry and metric the structural parameters were analyzed by the Rietveld method. All synthesized materials crystallize in space group Fm-3m known from calcium fluoride. The cubic lattice parameter a was determined for all crystals. In the case of series with different cerium and zirconium concentrations a linear correlation between cerium content and cubic lattice parameter was detected. The elemental composition was determined by WDX. All crystals show a homogeneous elemental distribution. The oxygen content was calculated because the WDX method isn't useful for determination.

  4. Spherical Nb single crystals containerlessly grown by electrostatic levitation

    International Nuclear Information System (INIS)

    Sung, Y.S.; Takeya, H.; Hirata, K.; Togano, K.

    2003-01-01

    Spherical Nb (T m =2750 K) single crystals were grown via containerless electrostatic levitation (ESL). Samples became spherical at melting in levitation and undercooled typically 300-450 K prior to nucleation. As-processed samples were still spherical without any macroscopic shape change by solidification showing a uniform dendritic surface morphology. Crystallographic {111} planes exposed in equilateral triangular shapes on the surface by preferential macroetching and spotty back-reflection Laue patterns confirm the single crystal nature of the ESL-processed Nb samples. No hysteresis in magnetization between zero field and field cooling also implies a clean defect-free condition of the spherical Nb single crystals

  5. Electroerosion impulse effect on W single crystal structure

    International Nuclear Information System (INIS)

    Aleshina, S.A.; Khvostikova, V.D.; Zolotykh, B.N.; Marchuk, A.I.

    1977-01-01

    The mechanism has been studied of brittle failure of single crystal tungsten on planes of crystallographic orientations [100], [110]; [111] in the process of electro-erosion machining by pulses of energies ranging from 1200 to 5000 μJ and of duration of 1 μs. It is shown that the electro-erosion machining of single crystal tungsten is characterized by the formation of a defect layer with a grid of microcracks which lie at a depth of approximately 80 μm. The appearance and the distribution of cracks on the surface of single crystals depends on the crystallogrpahic orientation

  6. Dielectric and baric characteristics of TlS single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Mustafaeva, S.N., E-mail: solmust@gmail.com [Institute of Physics, ANAS, G. Javid prosp. 33, Az 1143 Baku (Azerbaijan); Asadov, M.M. [Institute of Chemical Problems, ANAS, G. Javid prosp. 29, Az 1143 Baku (Azerbaijan); Ismailov, A.A. [Institute of Physics, ANAS, G. Javid prosp. 33, Az 1143 Baku (Azerbaijan)

    2014-11-15

    The investigation of the frequency dependences of the dielectric coefficients and ac-conductivity of the TlS single crystals made it possible to elucidate the nature of dielectric loss and the charge transfer mechanism. Moreover, we evaluated the density and energy spread of localized states near the Fermi level, the average hopping time and the average hopping length. It was shown that the dc-conductivity of the TlS single crystals can be controlled by varying the hydrostatic pressure. This has opened up possibilities for using TlS single crystals as active elements of pressure detectors.

  7. Growth of Ga2O3 single crystal

    OpenAIRE

    龍見, 雅美; 小池, 裕之; 市木, 伸明; Tatsumi, Masami; Koike, Hiroyuki; Ichiki, Nobuaki

    2010-01-01

    Single crystals of β-Ga2O3 for substrates of GaN LED were grown by Floating Zone(FZ) method. The transparent single crystals of 5-6 mm in diameter were reproducibly obtained by applying necking procedure and the preferential growth direction was . Many cracks were induced along the cleavage plane of (100) in slicing process, which is related to thermal stress and the growth direction. However, this preliminary growth experiments suggested that β-Ga2O3 single crystal is promising as a substrat...

  8. Wrinkle-Free Single-Crystal Graphene Wafer Grown on Strain-Engineered Substrates.

    Science.gov (United States)

    Deng, Bing; Pang, Zhenqian; Chen, Shulin; Li, Xin; Meng, Caixia; Li, Jiayu; Liu, Mengxi; Wu, Juanxia; Qi, Yue; Dang, Wenhui; Yang, Hao; Zhang, Yanfeng; Zhang, Jin; Kang, Ning; Xu, Hongqi; Fu, Qiang; Qiu, Xiaohui; Gao, Peng; Wei, Yujie; Liu, Zhongfan; Peng, Hailin

    2017-12-26

    Wrinkles are ubiquitous for graphene films grown on various substrates by chemical vapor deposition at high temperature due to the strain induced by thermal mismatch between the graphene and substrates, which greatly degrades the extraordinary properties of graphene. Here we show that the wrinkle formation of graphene grown on Cu substrates is strongly dependent on the crystallographic orientations. Wrinkle-free single-crystal graphene was grown on a wafer-scale twin-boundary-free single-crystal Cu(111) thin film fabricated on sapphire substrate through strain engineering. The wrinkle-free feature of graphene originated from the relatively small thermal expansion of the Cu(111) thin film substrate and the relatively strong interfacial coupling between Cu(111) and graphene, based on the strain analyses as well as molecular dynamics simulations. Moreover, we demonstrated the transfer of an ultraflat graphene film onto target substrates from the reusable single-crystal Cu(111)/sapphire growth substrate. The wrinkle-free graphene shows enhanced electrical mobility compared to graphene with wrinkles.

  9. Evaluation of undoped ZnS single crystal materials for x-ray imaging applications

    Science.gov (United States)

    Saleh, Muad; Lynn, Kelvin G.; McCloy, John S.

    2017-05-01

    ZnS-based materials have a long history of use as x-ray luminescent materials. ZnS was one of the first discovered scintillators and is reported to have one of the highest scintillator efficiencies. The use of ZnS for high energy luminescence has been thus far limited to thin powder screens, such as ZnS:Ag which is used for detecting alpha radiation, due to opacity to its scintillation light, primarily due to scattering. ZnS in bulk form (chemical vapor deposited, powder processed, and single crystal) has high transmission and low scattering compared to powder screens. In this paper, the performance of single crystalline ZnS is evaluated for low energy x-ray (PLE) of several undoped ZnS single crystals is compared to their Radioluminescence (RL) spectra. It was found that the ZnS emission wavelength varies on the excitation source energy.

  10. Solution-printed organic semiconductor blends exhibiting transport properties on par with single crystals.

    Science.gov (United States)

    Niazi, Muhammad R; Li, Ruipeng; Qiang Li, Er; Kirmani, Ahmad R; Abdelsamie, Maged; Wang, Qingxiao; Pan, Wenyang; Payne, Marcia M; Anthony, John E; Smilgies, Detlef-M; Thoroddsen, Sigurdur T; Giannelis, Emmanuel P; Amassian, Aram

    2015-11-23

    Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm(2) V(-1) s(-1), low threshold voltages oforganic semiconductor films with transport properties and other figures of merit on par with their single-crystal counterparts.

  11. Crystallinity of the epitaxial heterojunction of C60 on single crystal pentacene

    Science.gov (United States)

    Tsuruta, Ryohei; Mizuno, Yuta; Hosokai, Takuya; Koganezawa, Tomoyuki; Ishii, Hisao; Nakayama, Yasuo

    2017-06-01

    The structure of pn heterojunctions is an important subject in the field of organic semiconductor devices. In this work, the crystallinity of an epitaxial pn heterojunction of C60 on single crystal pentacene is investigated by non-contact mode atomic force microscopy and high-resolution grazing incidence x-ray diffraction. Analysis shows that the C60 molecules assemble into grains consisting of single crystallites on the pentacene single crystal surface. The in-plane mean crystallite size exceeds 0.1 μm, which is at least five time larger than the size of crystallites deposited onto polycrystalline pentacene thin films grown on SiO2. The results indicate that improvement in the crystal quality of the underlying molecular substrate leads to drastic promotion of the crystallinity at the organic semiconductor heterojunction.

  12. Investigations of morphological changes during annealing of polyethylene single crystals

    NARCIS (Netherlands)

    Tian, M.; Loos, J.

    2001-01-01

    The morphological evolution of isolated individual single crystals deposited on solid substrates was investigated during annealing experiments using in situ and ex situ atomic force microscopy techniques. The crystal morphology changed during annealing at temperatures slightly above the original

  13. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei

    2017-01-01

    Despite their outstanding charge transport characteristics, organolead halide perovskite single crystals grown by hitherto reported crystallization methods are not suitable for most optoelectronic devices due to their small aspect ratios

  14. High-quality single crystals for neutron experiments

    Indian Academy of Sciences (India)

    studies and our collaborative research projects with other UK and international groups will be discussed. Keywords. Crystal growth; floating zone method; neutron scattering. ... of single crystals of new materials is a highly competitive business.

  15. Single crystal magnetisation of UFe10Mo2

    International Nuclear Information System (INIS)

    Estrela, P.; Godinho, M.; Spirlet, J.C.

    1997-01-01

    Magnetisation measurements have been performed for different directions on aligned UFe 10 Mo 2 single crystals. The results confirm a basal plane anisotropy and suggest an important magnetic contribution from the uranium sublattice. (orig.)

  16. Distributed Feedback Laser Based on Single Crystal Perovskite

    Science.gov (United States)

    Sun, Shang; Xiao, Shumin; Song, Qinghai

    2017-06-01

    We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

  17. Growth and characterization of nonlinear optical single crystals: bis ...

    Indian Academy of Sciences (India)

    Administrator

    molecules have received great attention for NLO applica- tions. However ... Figure 3. Single crystals of bis(cyclohexylammonium) terephthalate (crystal a) and cyclohexylammo- .... from ground state to higher energy states.17 Optical window ...

  18. Prospects for the synthesis of large single-crystal diamonds

    International Nuclear Information System (INIS)

    Khmelnitskiy, R A

    2015-01-01

    The unique properties of diamond have stimulated the study of and search for its applications in many fields, including optics, optoelectronics, electronics, biology, and electrochemistry. Whereas chemical vapor deposition allows the growth of polycrystalline diamond plates more than 200 mm in diameter, most current diamond application technologies require large-size (25 mm and more) single-crystal diamond substrates or films suitable for the photolithography process. This is quite a challenge, because the largest diamond crystals currently available are 10 mm or less in size. This review examines three promising approaches to fabricating large-size diamond single crystals: growing large-size single crystals, the deposition of heteroepitaxial diamond films on single-crystal substrates, and the preparation of composite diamond substrates. (reviews of topical problems)

  19. How far could energy transport within a single crystal

    Science.gov (United States)

    Zhang, Yifan; Che, Yanke; Zhao, Jincai; Steve, Granick

    Efficient transport of excitation energy over long distance is a vital process in light-harvesting systems and molecular electronics. The energy transfer distance is largely restricted by the probability decay of the exciton when hopping within a single crystal. Here, we fabricated an organic single crystal within which the energy could transfer more than 100 μm, a distance only limited by its crystal size. Our system could be regarded as a ``Sprint relay game'' performing on different surface of tracks. Photoinduced ``athletes'' (excitons) triggered intermolecular ``domino'' reaction to propagate energy for a long distance. In addition, athletes with the same ability runs much farther on smooth ideal track (single crystal assembled from merely van der Waals interaction) than bumpy mud track (crystal assembled from combination of pi-stacking, hydrogen bond and van der Waals interactions). Our finding presents new physics on enhancing energy transfer length within a single crystal. Current Affiliation: Institute for Basic Science, South Korea.

  20. Nanomechanical resonant structures in single-crystal diamond

    OpenAIRE

    Burek, Michael J.; Ramos, Daniel; Patel, Parth; Frank, Ian W.; Lončar, Marko

    2013-01-01

    With its host of outstanding material properties, single-crystal diamond is an attractive material for nanomechanical systems. Here, the mechanical resonance characteristics of freestanding, single-crystal diamond nanobeams fabricated by an angled-etching methodology are reported. Resonance frequencies displayed evidence of significant compressive stress in doubly clamped diamond nanobeams, while cantilever resonance modes followed the expected inverse-length-squared trend. Q-factors on the o...

  1. Czochralski method of growing single crystals. State-of-art

    International Nuclear Information System (INIS)

    Bukowski, A.; Zabierowski, P.

    1999-01-01

    Modern Czochralski method of single crystal growing has been described. The example of Czochralski process is given. The advantages that caused the rapid progress of the method have been presented. The method limitations that motivated the further research and new solutions are also presented. As the example two different ways of the technique development has been described: silicon single crystals growth in the magnetic field; continuous liquid feed of silicon crystals growth. (author)

  2. LASER PROCESSING ON SINGLE CRYSTALS BY UV PULSE LASER

    OpenAIRE

    龍見, 雅美; 佐々木, 徹; 高山, 恭宜

    2009-01-01

    Laser processing by using UV pulsed laser was carried out on single crystal such as sapphire and diamond in order to understand the fundamental laser processing on single crystal. The absorption edges of diamond and sapphire are longer and shorter than the wave length of UV laser, respectively. The processed regions by laser with near threshold power of processing show quite different state in each crystal.

  3. Development of n- and p-type Doped Perovskite Single Crystals Using Solid-State Single Crystal Growth (SSCG) Technique

    Science.gov (United States)

    2017-10-09

    for AGG should be minimal. For this purpose, the seeds for AGG may also be provided externally. This process is called the solid-state single...bonding process . Figure 31 shows (a) the growth of one large single crystal from one small single crystal seed as well as (b) the growth of one...one bi-crystal seed : One large bi-crystal can be grown from one small bi-crystal by SSCG process . Fig. 32. Diffusion bonding process for

  4. Single Crystal Synthesis and STM Studies of High Temperature Superconductors

    Science.gov (United States)

    Barrientos, Alfonso

    1997-01-01

    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.

  5. Mesoporous Zeolite Single Crystals for Catalytic Hydrocarbon Conversion

    DEFF Research Database (Denmark)

    Schmidt, I.; Christensen, Claus H.; Kustova, Marina

    2005-01-01

    Recently, mesoporous zeolite single crystals were discovered. They constitute a novel family of materials that features a combined micropore and mesopore architecture within each individual crystal. Here, we briefly summarize recent catalytic results from cracking and isomerization of alkalies......, alkylation of aromatics and present new results on isomerization of aromatics. Specifically, the shape-selective isomerization of meta-xylenc into para-xylene and ortho-xylene is studied. In all these reactions, rnesoporous zeolite single crystals prove to be unique catalysts since they provide easy...... transport to and from active sites and at the same time maintain the shape-selectivity required. Thus, all these results support the idea that the beneficial effect of the mesopores system in the mesoporous zeolite single crystals call be solely attributed to enhanced mass transport....

  6. Mechanical properties of hydroxyapatite single crystals from nanoindentation data

    Science.gov (United States)

    Zamiri, A.; De, S.

    2011-01-01

    In this paper we compute elasto-plastic properties of hydroxyapatite single crystals from nanindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young’s modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals. PMID:21262492

  7. Light emission from organic single crystals operated by electrolyte doping

    Science.gov (United States)

    Matsuki, Keiichiro; Sakanoue, Tomo; Yomogida, Yohei; Hotta, Shu; Takenobu, Taishi

    2018-03-01

    Light-emitting devices based on electrolytes, such as light-emitting electrochemical cells (LECs) and electric double-layer transistors (EDLTs), are solution-processable devices with a very simple structure. Therefore, it is necessary to apply this device structure into highly fluorescent organic materials for future printed applications. However, owing to compatibility problems between electrolytes and organic crystals, electrolyte-based single-crystal light-emitting devices have not yet been demonstrated. Here, we report on light-emitting devices based on organic single crystals and electrolytes. As the fluorescent materials, α,ω-bis(biphenylyl)terthiophene (BP3T) and 5,6,11,12-tetraphenylnaphthacene (rubrene) single crystals were selected. Using ionic liquids as electrolytes, we observed clear light emission from BP3T LECs and rubrene EDLTs.

  8. Metal Halide Perovskite Single Crystals: From Growth Process to Application

    Directory of Open Access Journals (Sweden)

    Shuigen Li

    2018-05-01

    Full Text Available As a strong competitor in the field of optoelectronic applications, organic-inorganic metal hybrid perovskites have been paid much attention because of their superior characteristics, which include broad absorption from visible to near-infrared region, tunable optical and electronic properties, high charge mobility, long exciton diffusion length and carrier recombination lifetime, etc. It is noted that perovskite single crystals show remarkably low trap-state densities and long carrier diffusion lengths, which are even comparable with the best photovoltaic-quality silicon, and thus are expected to provide better optoelectronic performance. This paper reviews the recent development of crystal growth in single-, mixed-organic-cation and fully inorganic halide perovskite single crystals, in particular the solution approach. Furthermore, the application of metal hybrid perovskite single crystals and future perspectives are also highlighted.

  9. Principles of crystallization, and methods of single crystal growth

    International Nuclear Information System (INIS)

    Chacra, T.

    2010-01-01

    Most of single crystals (monocrystals), have distinguished optical, electrical, or magnetic properties, which make from single crystals, key elements in most of technical modern devices, as they may be used as lenses, Prisms, or grating sin optical devises, or Filters in X-Ray and spectrographic devices, or conductors and semiconductors in electronic, and computer industries. Furthermore, Single crystals are used in transducer devices. Moreover, they are indispensable elements in Laser and Maser emission technology.Crystal Growth Technology (CGT), has started, and developed in the international Universities and scientific institutions, aiming at some of single crystals, which may have significant properties and industrial applications, that can attract the attention of international crystal growth centers, to adopt the industrial production and marketing of such crystals. Unfortunately, Arab universities generally, and Syrian universities specifically, do not give even the minimum interest, to this field of Science.The purpose of this work is to attract the attention of Crystallographers, Physicists and Chemists in the Arab universities and research centers to the importance of crystal growth, and to work on, in the first stage to establish simple, uncomplicated laboratories for the growth of single crystal. Such laboratories can be supplied with equipment, which are partly available or can be manufactured in the local market. Many references (Articles, Papers, Diagrams, etc..) has been studied, to conclude the most important theoretical principles of Phase transitions,especially of crystallization. The conclusions of this study, are summarized in three Principles; Thermodynamic-, Morphologic-, and Kinetic-Principles. The study is completed by a brief description of the main single crystal growth methods with sketches, of equipment used in each method, which can be considered as primary designs for the equipment, of a new crystal growth laboratory. (author)

  10. Photoluminescence properties of boron doped InSe single crystals

    International Nuclear Information System (INIS)

    Ertap, H.; Bacıoğlu, A.; Karabulut, M.

    2015-01-01

    Undoped and boron doped InSe single crystals were grown by Bridgman–Stockbarger technique. The PL properties of undoped, 0.1% and 0.5% boron doped InSe single crystals have been investigated at different temperatures. PL measurements revealed four emission bands labeled as A, B, C and D in all the single crystals studied. These emission bands were associated with the radiative recombination of direct free excitons (n=1), impurity-band transitions, donor–acceptor recombinations and structural defect related band (impurity atoms, defects, defect complexes, impurity-vacancy complex etc.), respectively. The direct free exciton (A) bands of undoped, 0.1% and 0.5% boron doped InSe single crystals were observed at 1.337 eV, 1.335 eV and 1.330 eV in the PL spectra measured at 12 K, respectively. Energy positions and PL intensities of the emission bands varied with boron addition. The FWHM of direct free exciton band increases while the FWHM of the D emission band decreases with boron doping. Band gap energies of undoped and boron doped InSe single crystals were calculated from the PL measurements. It was found that the band gap energies of InSe single crystals decreased with increasing boron content. - Highlights: • PL spectra of InSe crystals have been studied as a function of temperature. • Four emission bands were observed in the PL spectra at low temperatures. • PL intensity and position of free exciton band vary with doping and temperature. • Temperature dependences of the bands observed in the PL spectra were analyzed

  11. Hydrothermal growth of PbSO4 (Anglesite) single crystal

    International Nuclear Information System (INIS)

    Kikuta, Ko-ichi; Yoneta, Yasuhito; Yogo, Toshinobu; Hirano, Shin-ichi

    1994-01-01

    Hydrothermal growth of single crystals of PbSO 4 , which is known as a natural mineral called anglesite, was investigated. Lead nitrate and nitric acid solutions were found to be useful for the growth of angle-site on the basis of the experimental results on the dissolution behavior. Relatively large euhedral single crystals bound by {210} and {101} planes were successfully grown in 1.5 mol/kg Pb(NO 3 ) 2 at 400degC and 100 MPa. Optical characterization revealed that the grown anglesite crystals can be useful for scintillators material. (author)

  12. Observation of plastic deformation in freestanding single crystal Au nanowires

    International Nuclear Information System (INIS)

    Lee, Dongyun; Zhao Manhong; Wei Xiaoding; Chen Xi; Jun, Seong C.; Hone, James; Herbert, Erik G.; Oliver, Warren C.; Kysar, Jeffrey W.

    2006-01-01

    Freestanding single crystal nanowires of gold were fabricated from a single grain of pure gold leaf by standard lithographic techniques, with center section of 7 μm in length, 250 nm in width, and 100 nm in thickness. The ends remained anchored to a silicon substrate. The specimens were deflected via nanoindenter until plastic deformation was achieved. Nonlocalized and localized plastic deformations were observed. The resulting force-displacement curves were simulated using continuum single crystal plasticity. A set of material parameters which closely reproduce the experimental results suggests that the initial critical resolved shear stress was as high as 135 MPa

  13. Welding and joining of single crystals of BCC refractory metals

    International Nuclear Information System (INIS)

    Hiraoka, Yutaka; Fujii, Tadayuki

    1989-01-01

    Welding and joining is one of key technologies for the wider utilizations of a material. In the present work, the applicability of welding and joining for a single crystal of BCC refractory metal was investigated. Electron-beam welding and tungsten-inert-gas welding by a melt-run technique, and high-temperature brazing by using brazing metals such as Mo-40%Ru alloy, vanadium or platinum were conducted for molybdenum single crystal which had been prepared by means of secondary recrystallization. 12 refs.,12 figs., 2 tabs. (Author)

  14. Cryogenic motion performances of a piezoelectric single crystal micromotor

    Science.gov (United States)

    Li, Xiaotian; Wu, Yuting; Chen, Zhijiang; Wei, Xiaoyong; Luo, Haosu; Dong, Shuxiang

    2014-04-01

    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.

  15. Iron single crystal growth from a lithium-rich melt

    Science.gov (United States)

    Fix, M.; Schumann, H.; Jantz, S. G.; Breitner, F. A.; Leineweber, A.; Jesche, A.

    2018-03-01

    α -Fe single crystals of rhombic dodecahedral habit were grown from a Li84N12Fe∼3 melt. Crystals of several millimeter along a side form at temperatures around T ≈ 800 ° C. Upon further cooling the growth competes with the formation of Fe-doped Li3N. The b.c.c. structure and good sample quality of α -Fe single crystals were confirmed by X-ray and electron diffraction as well as magnetization measurements and chemical analysis. A nitrogen concentration of 90 ppm was detected by means of carrier gas hot extraction. Scanning electron microscopy did not reveal any sign of iron nitride precipitates.

  16. Regularities of recrystallization in rolled Zr single crystals

    International Nuclear Information System (INIS)

    Isaenkova, M; Perlovich, Yu; Fesenko, V; Krymskaya, O; Krapivka, N; Thu, S S

    2015-01-01

    Experiments by rolled single crystals give a more visible conception of the operating mechanisms of plastic deformation and the following recrystallization, than experiments by polycrystals. Studies by usage of X-ray diffraction methods were conducted by Zr single crystals. It was revealed, that regions of the α-Zr matrix, deformed mainly by twinning, are characterized with decreased tendency to recrystallization. Orientations of recrystallized α-Zr grains correspond to “slopes” of maxima in the rolling texture, where the level of crystalline lattice distortion is maximal and the number of recrystallization nuclei is most of all. (paper)

  17. Growth and surface topography of WSe_2 single crystal

    International Nuclear Information System (INIS)

    Dixit, Vijay; Vyas, Chirag; Pataniya, Pratik; Jani, Mihir; Pathak, Vishal; Patel, Abhishek; Pathak, V. M.; Patel, K. D.; Solanki, G. K.

    2016-01-01

    Tungsten Di-Selenide belongs to the family of TMDCs showing their potential applications in the fields of Optoelectronics and PEC solar cells. Here in the present investigation single crystals of WSe_2 were grown by Direct Vapour Transport Technique in a dual zone furnace having temperature difference of 50 K between the two zones. These single crystals were characterized by EDAX which confirms the stiochiometry of the grown crystals. Surface topography of the crystal was studied by optical micrograph showing the left handed spirals on the surface of WSe_2 crystals. Single crystalline nature of the crystals was confirmed by SAED.

  18. Preparation of single-crystal copper ferrite nanorods and nanodisks

    International Nuclear Information System (INIS)

    Du Jimin; Liu Zhimin; Wu Weize; Li Zhonghao; Han Buxing; Huang Ying

    2005-01-01

    This article, for the first time, reports the preparation of single-crystal copper ferrite nanorods and nanodisks. Using amorphous copper ferrite nanoparticles synthesized by reverse micelle as reaction precursor, single-crystal copper ferrite nanorods were synthesized via hydrothermal method in the presence of surfactant polyethylene glycol (PEG), however, copper ferrite nanodisks were prepared through the same procedures except the surfactant PEG. The resulting nanomaterials have been characterized by powder X-ray diffraction (XRD), selected electron area diffraction (SEAD), and transmission electron microscopy (TEM). The bulk composition of the samples was determined by means of X-ray photoelectron spectroscopy (XPS)

  19. Deformation twinning in zinc-aluminium single crystals after slip

    International Nuclear Information System (INIS)

    Lukac, P.; Kral, F.; Trojanova, Z.; Kral, R.

    1993-01-01

    Deformation twinning in Zn-Al single crystals deformed by slip in the basal system is examined. The influence of temperature and the content of aluminium in zinc on the twinning stress is investigated in the temperature range from 198 to 373 K. It is shown that the twinning stress rises with increasing temperature and increases with the concentration of Al atoms. (orig.)

  20. Structural science using single crystal and pulse neutron scattering

    International Nuclear Information System (INIS)

    Noda, Yukio; Kimura, Hiroyuki; Watanabe, Masashi; Ishikawa, Yoshihisa; Tamura, Itaru; Arai, Masatoshi; Takahashi, Miwako; Ohshima, Ken-ichi; Abe, Hiroshi; Kamiyama, Takashi

    2008-01-01

    The application to single crystal neutron structural analysis is overviewed. Special attention is paid to the pulse neutron method, which will be available soon under J-PARC project in Japan. New proposal and preliminary experiment using Sirius at KENS are described. (author)

  1. Annealing behavior of solution grown polyethylene single crystals

    NARCIS (Netherlands)

    Loos, J.; Tian, M.

    2006-01-01

    The morphology evolution of solution grown polyethylene single crystals has been studied upon annealing below their melting temperature by using atomic force microscopy (AFM). AFM investigations have been performed ex situ, which means AFM investigations at room temperature after the annealing

  2. Corelli: Efficient single crystal diffraction with elastic discrimination

    Indian Academy of Sciences (India)

    Here, we discuss the potential of the cross-correlation technique for efficient measurement of single crystal diffuse scattering with energy discrimination, as will be implemented in a novel instrument, Corelli. Utilizing full experiment simulations, we show that this technique readily leads up to a fifty-fold gain in efficiency, ...

  3. Magnetic structure of URhSi single crystal

    Czech Academy of Sciences Publication Activity Database

    Prokeš, K.; Andreev, Alexander V.; Honda, F.; Sechovský, V.

    2003-01-01

    Roč. 261, - (2003), s. 131-138 ISSN 0304-8853 R&D Projects: GA ČR GA202/02/0739 Institutional research plan: CEZ:AV0Z1010914 Keywords : URhSi single crystal * magnetization * neutron diffraction * magnetic structure determination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.910, year: 2003

  4. Bulk study of a DyNiAl single crystal

    Czech Academy of Sciences Publication Activity Database

    Prchal, J.; Andreev, Alexander V.; Javorský, P.; Honda, F.; Jurek, Karel

    272-276, - (2004), e419-e420 ISSN 0304-8853 R&D Projects: GA ČR GA106/02/0943 Keywords : rare-earth * DyNiAl * magnetic anisotropy * single crystal Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.031, year: 2004

  5. Lattice effects in HoVo(3) single crystal

    NARCIS (Netherlands)

    Sikora, M.; Marquina, C.; Ibarra, M. R.; Nugroho, A. A.; Palstra, T. T. M.

    We report the study of lattice effects in the Mott insulator HoVO3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO3 reveals gradual orbital ordering (OO) below T-OO = 200K and orders antiferromagnetically at T-N =

  6. Synthesis and room temperature single crystal EPR studies of a ...

    Indian Academy of Sciences (India)

    Unknown

    Hamiltonian parameters calculated from single crystal rotations are: g ... studies on two nickel complexes with SalX ligands (X = NH, NCH3) have shown the ..... here the positive sign is required for a shell that is less than half-filled and the ...

  7. Growth features of ammonium hydrogen d-tartrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Ammonium hydrogen d-tartrate (d-AHT) single crystals were grown in silica gel. The growth fea- ... solution (specific gravity, 1⋅04 g/cc) with d-tartaric acid solution having ... resulting in the production of crystal nuclei. The interface.

  8. Attenuation of thermal neutrons by an imperfect single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Naguib, K.; Adib, M. [National Research Centre, Cairo (Egypt). Reactor and Neutron Physics Dept.

    1996-06-14

    A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3-40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range. (author).

  9. Attenuation of thermal neutrons by an imperfect single crystal

    Science.gov (United States)

    Naguib, K.; Adib, M.

    1996-06-01

    A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3 - 40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range.

  10. Chromium and molybdenum diffusion in tungsten single crystals

    International Nuclear Information System (INIS)

    Klotsman, S.M.; Koloskov, V.M.; Osetrov, S.V.; Polikarpova, I.P.; Tatarinova, G.N.; Timofeev, A.N.

    1989-01-01

    Consideration is given to results of measuring temperature dependences of diffusion coefficients of homovalent impurities of chromium and molybdenum in tungsten single crystals. It is concluded that the difference of activation energies of selfdiffusion and impurity diffusion in the system 'tungsten-homovalent impurity' is conditioned by interaction of screened potentials of impurity and vacancy with Lazarus-Le Claire model

  11. Dynamic Actuation of Single-Crystal Diamond Nanobeams

    OpenAIRE

    Sohn, Young-Ik; Burek, Michael J.; Kara, Vural; Kearns, Ryan; Lončar, Marko

    2014-01-01

    We show the dielectrophoretic actuation of single-crystal diamond nanomechanical devices. Gradient radio-frequency electromagnetic forces are used to achieve actuation of both cantilever and doubly clamped beam structures, with operation frequencies ranging from a few MHz to ~50MHz. Frequency tuning and parametric actuation are also studied.

  12. High definition TV projection via single crystal faceplate technology

    Science.gov (United States)

    Kindl, H. J.; St. John, Thomas

    1993-03-01

    Single crystal phosphor faceplates are epitaxial phosphors grown on crystalline substrates with the advantages of high light output, resolution, and extended operational life. Single crystal phosphor faceplate industrial technology in the United States is capable of providing a faceplate appropriate to the projection industry of up to four (4) inches in diameter. Projection systems incorporating cathode ray tubes utilizing single crystal phosphor faceplates will produce 1500 lumens of white light with 1000 lines of resolution, non-interlaced. This 1500 lumen projection system will meet all of the currently specified luminance and resolution requirements of Visual Display systems for flight simulators. Significant logistic advantages accrue from the introduction of single crystal phosphor faceplate CRT's. Specifically, the full performance life of a CRT is expected to increase by a factor of five (5); ie, from 2000 to 10,000 hours of operation. There will be attendant reductions in maintenance time, spare CRT requirements, system down time, etc. The increased brightness of the projection system will allow use of lower gain, lower cost simulator screen material. Further, picture performance characteristics will be more balanced across the full simulator.

  13. On the growth of calcium tartrate tetrahydrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Calcium tartrate single crystals were grown using silica gel as the growth medium. Calcium for- mate mixed with formic acid was taken as the supernatant solution. It was observed that the nucleation den- sity was reduced and the size of the crystals was improved to a large extent compared to the conventional way.

  14. Lattice location of helium in uranium dioxide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Garrido, F.; Nowicki, L. E-mail: lech.nowicki@fuw.edu.pl; Sattonnay, G.; Sauvage, T.; Thome, L

    2004-06-01

    Lattice location of {sup 3}He atoms implanted into UO{sub 2} single crystals was performed by means of the channeling technique combined with nuclear reaction analysis (NRA) and Rutherford backscattering spectrometry (RBS). The {sup 3}He(d,p){sup 4}He reaction was used. The experimental angular scans show that helium atoms occupy octahedral interstitial positions.

  15. Multiscale modelling of single crystal superalloys for gas turbine blades

    NARCIS (Netherlands)

    Tinga, T.

    2009-01-01

    Gas turbines are extensively used for power generation and for the propulsion of aircraft and vessels. Their most severely loaded parts, the turbine rotor blades, are manufactured from single crystal nickel-base superalloys. The superior high temperature behaviour of these materials is attributed to

  16. Discrete dislocation plasticity modeling of short cracks in single crystals

    NARCIS (Netherlands)

    Deshpande, VS; Needleman, A; Van der Giessen, E

    2003-01-01

    The mode-I crack growth behavior of geometrically similar edge-cracked single crystal specimens of varying size subject to both monotonic and cyclic axial loading is analyzed using discrete dislocation dynamics. Plastic deformation is modeled through the motion of edge dislocations in an elastic

  17. Double minimum creep of single crystal Ni-base superalloys

    Czech Academy of Sciences Publication Activity Database

    WU, X.; Wollgramm, P.; Somsen, C.; Dlouhý, Antonín; Kostka, A.; Eggeler, G.

    2016-01-01

    Roč. 112, JUN (2016), s. 242-260 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA14-22834S Institutional support: RVO:68081723 Keywords : Single crystal Ni-base superalloys * Primary creep * Transmission electron microscopy * Dislocations * Stacking faults Subject RIV: JG - Metallurgy Impact factor: 5.301, year: 2016

  18. Detection of anomalies in NLO sulphamic acid single crystals by ...

    Indian Academy of Sciences (India)

    The ultrasonic pulse echo overlap technique (PEO) has been used to measure the ... acid single crystals in the range of 300–400 K. This study evaluated all the elastic stiff- .... tic constants C11, C22, C33, C44, C55 and C66 have direct rela-.

  19. METHOD FOR MANUFACTURING A SINGLE CRYSTAL NANO-WIRE

    NARCIS (Netherlands)

    Van Den Berg, Albert; Bomer, Johan; Carlen Edwin, Thomas; Chen, Songyue; Kraaijenhagen Roderik, Adriaan; Pinedo Herbert, Michael

    2012-01-01

    A method for manufacturing a single crystal nano-structure includes providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing parts of the stress layer to

  20. METHOD FOR MANUFACTURING A SINGLE CRYSTAL NANO-WIRE.

    NARCIS (Netherlands)

    Van Den Berg, Albert; Bomer, Johan; Carlen Edwin, Thomas; Chen, Songyue; Kraaijenhagen Roderik, Adriaan; Pinedo Herbert, Michael

    2011-01-01

    A method for manufacturing a single crystal nano-structure is provided comprising the steps of providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing

  1. Electronic transport properties of single crystal thallium-2201 superconductors

    International Nuclear Information System (INIS)

    Yandrofski, R.M.

    1992-01-01

    Four-probe resistance measurements on single crystals of the calcium-free thallium-based superconducting Tl 2 Ba 2 CuO 6+σ phase (Tl-2201) were performed in magnetic fields up to 12 Telsa. Single crystals of sizes were grown by a self-flux technique and were characterized by single crystal X-ray diffraction and X-ray Dispersive Analysis. Field measurements were taken at dc and at low frequencies using a lock-in technique. Techniques were developed to oxygen-anneal the as-grown single crystals to generate single crystal samples of the same Tl-2201 phase with varying transition interaction effect against appropriate composite general alternatives are developed for the standard two-way layout with a single observation per cell. Nonparametric aligned-rank test procedures are introduced. One of the new procedures is shown to be equivalent to a slight modification of the previously studied Latin square procedures when the factors have the same number of levels. The equal in distribution technique is used to show that any statistic based on the joint ranks should not be used to test the hypotheses of interest. The tests based on aligning with the averages do not depend on the nuisance main effects, while those based on aligning with the median do depend on the nuisance main effects. The relative power performance of the competing tests are examined via Monte Carlo simulation. Power studies conducted on the 5 x 5, 5 x 6, and 5 x 9 two-way layouts with one observation per cell show that the new procedures based on a comparison of all possible pairs of rank-profiles perform quite well for two types of product interaction, a general class of interaction effects proposed by Martin, and several sets of specific interaction effects. Approximate critical values for some of the proposed procedures are explored in the special case when the main effect parameters for one factor are known

  2. Twinning processes in Cu-Al-Ni martensite single crystals investigated by neutron single crystal diffraction method

    International Nuclear Information System (INIS)

    Molnar, P.; Sittner, P.; Novak, V.; Lukas, P.

    2008-01-01

    A neutron single crystal diffraction method for inspecting the quality of martensite single crystals is introduced. True interface-free martensite single crystals are indispensable for, e.g. measurement of elastic constants of phases by ultrasonic techniques. The neutron diffraction method was used to detect and distinguish the presence of individual lattice correspondence variants of the 2H orthorhombic martensite phase in Cu-Al-Ni as well as to follow the activity of twinning processes during the deformation test on the martensite variant single crystals. When preparing the martensite single variant prism-shaped crystals by compression deformation method, typically a small fraction of second unwanted martensitic variant (compound twin) remains in the prism samples. Due to the very low stress (∼1 MPa) for the compound twinning in many shape memory alloys, it is quite difficult not only to deplete the martensite prisms of all internal interfaces but mainly to keep them in the martensite single variant state for a long time needed for further investigations

  3. Twinning processes in Cu-Al-Ni martensite single crystals investigated by neutron single crystal diffraction method

    Czech Academy of Sciences Publication Activity Database

    Molnar, P.; Šittner, P.; Novák, V.; Lukáš, Petr

    2008-01-01

    Roč. 481, Sp.Iss.SI (2008), s. 513-517 ISSN 0921-5093 R&D Projects: GA AV ČR IAA100480704 Institutional research plan: CEZ:AV0Z10480505 Keywords : Cu-Al-Ni * single crystals * neutron diffraction Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.806, year: 2008

  4. van der Waals epitaxy of SnS film on single crystal graphene buffer layer on amorphous SiO2/Si

    Science.gov (United States)

    Xiang, Yu; Yang, Yunbo; Guo, Fawen; Sun, Xin; Lu, Zonghuan; Mohanty, Dibyajyoti; Bhat, Ishwara; Washington, Morris; Lu, Toh-Ming; Wang, Gwo-Ching

    2018-03-01

    Conventional hetero-epitaxial films are typically grown on lattice and symmetry matched single crystal substrates. We demonstrated the epitaxial growth of orthorhombic SnS film (∼500 nm thick) on single crystal, monolayer graphene that was transferred on the amorphous SiO2/Si substrate. Using X-ray pole figure analysis we examined the structure, quality and epitaxy relationship of the SnS film grown on the single crystal graphene and compared it with the SnS film grown on commercial polycrystalline graphene. We showed that the SnS films grown on both single crystal and polycrystalline graphene have two sets of orientation domains. However, the crystallinity and grain size of the SnS film improve when grown on the single crystal graphene. Reflection high-energy electron diffraction measurements show that the near surface texture has more phases as compared with that of the entire film. The surface texture of a film will influence the growth and quality of film grown on top of it as well as the interface formed. Our result offers an alternative approach to grow a hetero-epitaxial film on an amorphous substrate through a single crystal graphene buffer layer. This strategy of growing high quality epitaxial thin film has potential applications in optoelectronics.

  5. Aluminum-rich mesoporous MFI - type zeolite single crystals

    DEFF Research Database (Denmark)

    Kustova, Marina; Kustov, Arkadii; Christensen, Christina Hviid

    2005-01-01

    Zeolitcs are crystalline materials, which are widely used as solid acid catalysts and supports in many industrial processes. Recently, mesoporous MFI-type zeolite single crystals were synthesized by use of carbon particles as a mesopore template and sodium aluminate as the aluminum Source....... With this technique, only zeolites with relatively low Al contents were reported (Si/Al ratio about 100). In this work, the preparation of aluminum-rich mesoporous MFI-type zeolite single crystals (Si/Al similar to 16-50) using aluminum isopropoxide as the aluminum Source is reported for the first time. All samples...... are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature programmed desorption (NH3-TPD), and N-2 adsorption measurements. The obtained zeolites combine the high crystallinity and the characteristic micropores of zeolites with an intracrystalline mesopore system...

  6. Resistivity distribution of silicon single crystals using codoping

    Science.gov (United States)

    Wang, Jong Hoe

    2005-07-01

    Numerous studies including continuous Czochralski method and double crucible technique have been reported on the control of macroscopic axial resistivity distribution in bulk crystal growth. The simple codoping method for improving the productivity of silicon single-crystal growth by controlling axial specific resistivity distribution was proposed by Wang [Jpn. J. Appl. Phys. 43 (2004) 4079]. Wang [J. Crystal Growth 275 (2005) e73] demonstrated using numerical analysis and by experimental results that the axial specific resistivity distribution can be modified in melt growth of silicon crystals and relatively uniform profile is possible by B-P codoping method. In this work, the basic characteristic of 8 in silicon single crystal grown using codoping method is studied and whether proposed method has advantage for the silicon crystal growth is discussed.

  7. Young's Modulus of Single-Crystal Fullerene C Nanotubes

    Directory of Open Access Journals (Sweden)

    Tokushi Kizuka

    2012-01-01

    Full Text Available We performed bending tests on single-crystal nanotubes composed of fullerene C70 molecules by in situ transmission electron microscopy with measurements of loading forces by an optical deflection method. The nanotubes with the outer diameters of 270–470 nm were bent using simple-beam and cantilever-beam loading by the piezomanipulation of silicon nanotips. Young's modulus of the nanotubes increased from 61 GPa to 110 GPa as the outer diameter decreased from 470 nm to 270 nm. Young's modulus was estimated to be 66% of that of single-crystal C60 nanotubes of the same outer diameter.

  8. Ordered macro-microporous metal-organic framework single crystals

    Science.gov (United States)

    Shen, Kui; Zhang, Lei; Chen, Xiaodong; Liu, Lingmei; Zhang, Daliang; Han, Yu; Chen, Junying; Long, Jilan; Luque, Rafael; Li, Yingwei; Chen, Banglin

    2018-01-01

    We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional–ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent–induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

  9. Heterogeneous Monolithic Integration of Single-Crystal Organic Materials.

    Science.gov (United States)

    Park, Kyung Sun; Baek, Jangmi; Park, Yoonkyung; Lee, Lynn; Hyon, Jinho; Koo Lee, Yong-Eun; Shrestha, Nabeen K; Kang, Youngjong; Sung, Myung Mo

    2017-02-01

    Manufacturing high-performance organic electronic circuits requires the effective heterogeneous integration of different nanoscale organic materials with uniform morphology and high crystallinity in a desired arrangement. In particular, the development of high-performance organic electronic and optoelectronic devices relies on high-quality single crystals that show optimal intrinsic charge-transport properties and electrical performance. Moreover, the heterogeneous integration of organic materials on a single substrate in a monolithic way is highly demanded for the production of fundamental organic electronic components as well as complex integrated circuits. Many of the various methods that have been designed to pattern multiple heterogeneous organic materials on a substrate and the heterogeneous integration of organic single crystals with their crystal growth are described here. Critical issues that have been encountered in the development of high-performance organic integrated electronics are also addressed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Ordered macro-microporous metal-organic framework single crystals

    KAUST Repository

    Shen, Kui

    2018-01-16

    We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional-ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent-induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

  11. Scintillation activity in an unirradiated single crystal of 3-hydroxyxanthine

    International Nuclear Information System (INIS)

    Cooke, D.W.; Jahan, M.S.; Alexander, C. Jr.

    1976-01-01

    A method of growing single crystals (approximately 4mm long) of 3-hydroxyxanthine is described. Observed scintillations occurring in an unirradiated single crystal of this potent oncogen as the temperature is lowered from 300 to 90 K are shown. It was found that these scintillations occur upon heating or cooling and do not diminish in activity as the number of heating and cooling cycles increase. It was found that a short duration u.v. exposure would terminate the scintillation activity and various attempts (such as annealing and pressure changes) to rejuvenate them were unsuccessful. With these observations in mind speculation is made concerning the mechanisms associated with the production of purine N-oxide derivatives. (U.K.)

  12. Ordered macro-microporous metal-organic framework single crystals

    KAUST Repository

    Shen, Kui; Zhang, Lei; Chen, Xiaodong; Liu, Lingmei; Zhang, Daliang; Han, Yu; Chen, Junying; Long, Jilan; Luque, Rafael; Li, Yingwei; Chen, Banglin

    2018-01-01

    We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional-ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent-induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

  13. Spall behaviour of single crystal aluminium at three principal orientations

    Science.gov (United States)

    Owen, G. D.; Chapman, D. J.; Whiteman, G.; Stirk, S. M.; Millett, J. C. F.; Johnson, S.

    2017-10-01

    A series of plate impact experiments have been conducted to study the spall strength of the three principal crystallographic orientations of single crystal aluminium ([100], [110] and, [111]) and ultra-pure polycrystalline aluminium. The samples have been shock loaded at two impact stresses (4 GPa and 10 GPa). Significant differences have been observed in the elastic behaviour, the pullback velocities, and the general shape of the wave profiles, which can be accounted for by considerations of the microscale homogeneity, the dislocation density, and the absence of grain boundaries in the single crystal materials. The data have shown that there is a consistent order of spall strength measured for the four sample materials. The [111] orientation has the largest spall strength and elastic limit, followed closely by [110], [100], and then the polycrystalline material. This order is consistent with both quasi-static data and geometrical consideration of Schmid factors.

  14. Anisotropic Thermoelectric Devices Made from Single-Crystal Semimetal Microwires in Glass Coating

    Science.gov (United States)

    Konopko, L. A.; Nikolaeva, A. A.; Kobylianskaya, A. K.; Huber, T. E.

    2018-06-01

    Thermoelectric heat conversion based on the Seebeck and Peltier effects generated at the junction between two materials of type- n and type- p is well known. Here, we present a demonstration of an unconventional thermoelectric energy conversion that is based on a single element made of an anisotropic material. In such materials, a heat flow generates a transverse thermoelectric electric field lying across the heat flow. Potentially, in applications involving miniature devices, the anisotropic thermoelectric (AT) effect has the advantage over traditional thermoelectrics that it simplifies the thermoelectric generator architecture. This is because the generator can be made of a single thermoelectric material without the complexity of a series of contacts forming a pile. A feature of anisotropic thermoelectrics is that the thermoelectric voltage is proportional to the element length and inversely proportional to the effective thickness. The AT effect has been demonstrated with artificial anisotropic thin film consisting of layers of alternating thermoelectric type, but there has been no demonstration of this effect in a long single-crystal. Electronic transport measurements have shown that the semimetal bismuth is highly anisotropic. We have prepared an experimental sample consisting of a 10-m-long glass-insulated single-crystal tin-doped bismuth microwire ( d = 4 μm). Crucial for this experiment is the ability to grow the microwire as a single-crystal using a technique of recrystallization with laser heating and under a strong electric field. The sample was wound as a spiral, bonded to a copper disk, and used in various experiments. The sensitivity of the sample to heat flow is as high as 10-2 V/W with a time constant τ of about 0.5 s.

  15. Anisotropic Thermoelectric Devices Made from Single-Crystal Semimetal Microwires in Glass Coating

    Science.gov (United States)

    Konopko, L. A.; Nikolaeva, A. A.; Kobylianskaya, A. K.; Huber, T. E.

    2018-04-01

    Thermoelectric heat conversion based on the Seebeck and Peltier effects generated at the junction between two materials of type-n and type-p is well known. Here, we present a demonstration of an unconventional thermoelectric energy conversion that is based on a single element made of an anisotropic material. In such materials, a heat flow generates a transverse thermoelectric electric field lying across the heat flow. Potentially, in applications involving miniature devices, the anisotropic thermoelectric (AT) effect has the advantage over traditional thermoelectrics that it simplifies the thermoelectric generator architecture. This is because the generator can be made of a single thermoelectric material without the complexity of a series of contacts forming a pile. A feature of anisotropic thermoelectrics is that the thermoelectric voltage is proportional to the element length and inversely proportional to the effective thickness. The AT effect has been demonstrated with artificial anisotropic thin film consisting of layers of alternating thermoelectric type, but there has been no demonstration of this effect in a long single-crystal. Electronic transport measurements have shown that the semimetal bismuth is highly anisotropic. We have prepared an experimental sample consisting of a 10-m-long glass-insulated single-crystal tin-doped bismuth microwire (d = 4 μm). Crucial for this experiment is the ability to grow the microwire as a single-crystal using a technique of recrystallization with laser heating and under a strong electric field. The sample was wound as a spiral, bonded to a copper disk, and used in various experiments. The sensitivity of the sample to heat flow is as high as 10-2 V/W with a time constant τ of about 0.5 s.

  16. Low temperature deformation mechanisms in LiF single crystals

    International Nuclear Information System (INIS)

    Fotedar, H.L.; Stroebe, T.G.

    1976-01-01

    An analysis of the deformation behavior of high purity LiF single crystals is given using yielding and work hardening data and thermally activated deformation parameters obtained in the temperature range 77-423 0 K. It is found that while the Fleischer mechanism is apparently valid experimentally over the thermally activated temperature range, vacancies produced in large numbers at 77 0 K could also play a role in determining the critical resolved shear stress at that temperature

  17. Trapezoidal diffraction grating beam splitters in single crystal diamond

    Science.gov (United States)

    Kiss, Marcell; Graziosi, Teodoro; Quack, Niels

    2018-02-01

    Single Crystal Diamond has been recognized as a prime material for optical components in high power applications due to low absorption and high thermal conductivity. However, diamond microstructuring remains challenging. Here, we report on the fabrication and characterization of optical diffraction gratings exhibiting a symmetric trapezoidal profile etched into a single crystal diamond substrate. The optimized grating geometry diffracts the transmitted optical power into precisely defined proportions, performing as an effective beam splitter. We fabricate our gratings in commercially available single crystal CVD diamond plates (2.6mm x 2.6mm x 0.3mm). Using a sputter deposited hard mask and patterning by contact lithography, the diamond is etched in an inductively coupled oxygen plasma with zero platen power. The etch process effectively reveals the characteristic {111} diamond crystal planes, creating a precisely defined angled (54.7°) profile. SEM and AFM measurements of the fabricated gratings evidence the trapezoidal shape with a pitch of 3.82μm, depth of 170 nm and duty cycle of 35.5%. Optical characterization is performed in transmission using a 650nm laser source perpendicular to the sample. The recorded transmitted optical power as function of detector rotation angle shows a distribution of 21.1% in the 0th order and 23.6% in each +/-1st order (16.1% reflected, 16.6% in higher orders). To our knowledge, this is the first demonstration of diffraction gratings with trapezoidal profile in single crystal diamond. The fabrication process will enable beam splitter gratings of custom defined optical power distribution profiles, while antireflection coatings can increase the efficiency.

  18. Ion implantation induced blistering of rutile single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Bing-Xi [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Jiao, Yang [College of Physics and Electronics, Shandong Normal University, Jinan, Shandong 250100 (China); Guan, Jing [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Wang, Lei [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (China)

    2015-07-01

    The rutile single crystals were implanted by 200 keV He{sup +} ions with a series fluence and annealed at different temperatures to investigate the blistering behavior. The Rutherford backscattering spectrometry, optical microscope and X-ray diffraction were employed to characterize the implantation induced lattice damage and blistering. It was found that the blistering on rutile surface region can be realized by He{sup +} ion implantation with appropriate fluence and the following thermal annealing.

  19. Single-crystal diffraction instrument TriCS at SINQ

    Science.gov (United States)

    Schefer, J.; Könnecke, M.; Murasik, A.; Czopnik, A.; Strässle, Th; Keller, P.; Schlumpf, N.

    2000-03-01

    The single-crystal diffractometer TriCS at the Swiss Continuous Spallation Source (SINQ) is presently in the commissioning phase. A two-dimensional wire detector produced by EMBL was delivered in March 1999. The instrument is presently tested with a single detector. First measurements on magnetic structures have been performed. The instrument is remotely controlled using JAVA-based software and a UNIX DEC-α host computer.

  20. The Taylor relation in compression deformed Ge single crystals

    International Nuclear Information System (INIS)

    Nyilas, K; Ungar, T; Dupas, C; Martin, J L; Kruml, T

    2010-01-01

    Ge single crystals are deformed in compression at 850K and the same strain rate to various extents of strains. In each sample, the internal stress is measured through stress reduction tests and the dislocation densities by X-ray measurements. Data about these two parameters follow fairly well the Taylor-Saada relation, provided a correction term is added. It probably corresponds to dislocations which are seen by X-rays, though they do not contribute to crystal hardening.

  1. Three-dimensional charge transport in organic semiconductor single crystals.

    Science.gov (United States)

    He, Tao; Zhang, Xiying; Jia, Jiong; Li, Yexin; Tao, Xutang

    2012-04-24

    Three-dimensional charge transport anisotropy in organic semiconductor single crystals - both plates and rods (above and below, respectively, in the figure) - is measured in well-performing organic field-effect transistors for the first time. The results provide an excellent model for molecular design and device preparation that leads to good performance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A macroscopic model for magnetic shape-memory single crystals

    Czech Academy of Sciences Publication Activity Database

    Bessoud, A. L.; Kružík, Martin; Stefanelli, U.

    2013-01-01

    Roč. 64, č. 2 (2013), s. 343-359 ISSN 0044-2275 R&D Projects: GA AV ČR IAA100750802; GA ČR GAP201/10/0357 Institutional support: RVO:67985556 Keywords : magnetostriction * evolution Subject RIV: BA - General Mathematics Impact factor: 1.214, year: 2013 http://library.utia.cas.cz/separaty/2012/MTR/kruzik-a macroscopic model for magnetic shape- memory single crystals.pdf

  3. The early stages of oxidation of magnesium single crystal surfaces

    International Nuclear Information System (INIS)

    Hayden, B.E.; Schweizer, E.; Koetz, R.; Bradshaw, A.M.

    1981-01-01

    The early stages of oxidation of Mg(001) and Mg(100) single crystal surfaces at 300 K have been investigated by LEED, ELS, work function and ellipsometric measurements. A sharp decrease in work function on both surfaces during the first 12 L exposure indicates the incorporation of oxygen in the earliest stages of the interaction. The incorporated oxygen on Mg(001) gives rise to a broadening of the integral order LEED spots for an exposure 3 L. (orig.)

  4. Application of GRID to Foreign Atom Localization in Single Crystals.

    Science.gov (United States)

    Karmann, A; Wesch, W; Weber, B; Börner, H G; Jentschel, M

    2000-01-01

    The application of GRID (Gamma Ray Induced Doppler broadening) spectroscopy to the localization of foreign atoms in single crystals is demonstrated on erbium in YAP. By the investigation of the Doppler broadened secondary γ line for two crystalline directions, the Er was determined to be localized on the Y site. Conditions for the nuclear parameters of the impurity atoms used for the application of GRID spectroscopy are discussed.

  5. Preparation and characterization of single-crystal multiferroic nanofiber composites

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Zhaohui; Xiao, Zhen; Yin, Simin; Mai, Jiangquan; Liu, Zhenya; Xu, Gang; Li, Xiang; Shen, Ge [State Key Lab of Silicon Materials, Department of Material Science and Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027 (China); Han, Gaorong, E-mail: hgr@zju.edu.cn [State Key Lab of Silicon Materials, Department of Material Science and Engineering, Cyrus Tang Center for Sensor Materials and Applications, Zhejiang University, Hangzhou 310027 (China)

    2013-03-05

    Graphical abstract: One-dimensional single-crystal multiferroic composites composed of PbTiO{sub 3} nanofiber-CoFe{sub 2}O{sub 4} nanodot have been prepared for the first time by a facile in situ solid state sintering method. The composites demonstrate ferroelectricity and ferromagnetism as well as strong coupling between them. Highlights: ► 1D single-crystal multiferroic PTO-CFO was prepared via in situ solid state sintering method. ► A simple epitaxial growth relation has been found between the PTO–CFO composites. ► The composites reveal ferroelectricity and ferromagnetism as well as coupling between them. -- Abstract: One-dimensional single-crystal multiferroic composites consisting of PbTiO{sub 3} (PTO) nanofiber-CoFe{sub 2}O{sub 4} (CFO) nanodot were prepared using an in situ solid state sintering method, where pre-perovskite PTO nanofibers and CFO nanodots were used as precursors. Structural analyses by using transmission electron microscopy, scanning electron microscopy and X-ray diffraction determined a epitaxial growth relation between the PTO nanofiber and the CFO nanodot. Ferromagnetism and ferroelectricity of the nanofiber composites were investigated by using vibarting sample magnetometer (VSM) and piezoresponse force microscopy (PFM)

  6. Parasitic neutron bragg reflections from large imperfect single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Naguib, K.; Adib, M

    1998-12-01

    A formula is given which allows to calculate the contribution of the total Bragg scattering from different (hkl) planes to the neutron transmission through a large imperfect single crystals. The formula takes into account the crystal structure type, its mosaic spread value, the plane along which the crystal surface is cut along and its orientation with respect to the neutron beam direction. A computer program ISCANF-1 was developed to calculate the total parasitic scattering cross-section from different (hkl) planes as well as the nuclear and diffuse scattering cross-sections. The ISCANF-1 program was applied to calculate the neutron attenuation through Cu and Zn single crystals, each of them cut along (002) planes. The calculated values of the neutron transmission through Cu and Zn crystals were compared with the measured ones in the wavelength range 0.21-0.47 nm and 0.04-0.52 nm respectively. The measured and calculated values were found to be in reasonable agreement within the statistical accuracy. The computer program ISCANF-1 was also applied to investigate the effect of parasitic Bragg scattering on the neutron filtering characteristics of both Zn and Cu single crystals as a function of their physical parameters.

  7. Parasitic neutron bragg reflections from large imperfect single crystals

    International Nuclear Information System (INIS)

    Naguib, K.; Adib, M.

    1998-01-01

    A formula is given which allows to calculate the contribution of the total Bragg scattering from different (hkl) planes to the neutron transmission through a large imperfect single crystals. The formula takes into account the crystal structure type, its mosaic spread value, the plane along which the crystal surface is cut along and its orientation with respect to the neutron beam direction. A computer program ISCANF-1 was developed to calculate the total parasitic scattering cross-section from different (hkl) planes as well as the nuclear and diffuse scattering cross-sections. The ISCANF-1 program was applied to calculate the neutron attenuation through Cu and Zn single crystals, each of them cut along (002) planes. The calculated values of the neutron transmission through Cu and Zn crystals were compared with the measured ones in the wavelength range 0.21-0.47 nm and 0.04-0.52 nm respectively. The measured and calculated values were found to be in reasonable agreement within the statistical accuracy. The computer program ISCANF-1 was also applied to investigate the effect of parasitic Bragg scattering on the neutron filtering characteristics of both Zn and Cu single crystals as a function of their physical parameters

  8. Neutron transmission measurements of zinc and lead single crystals

    International Nuclear Information System (INIS)

    Adib, M.; Abdel-Kawy, A.

    1988-01-01

    Neutron transmission measurements of zinc and lead single crystals have been carried out in a neutron wavelength band from 0.03 to 0.55 nm at different orientations of the crystal with regard to the beam direction. The measurements were performed using both time-of-flight and fixed-angle scattering spectrometers installed in front of the ET-RR-1 reactor horizontal channels. It was found that the position of the observed dips in the neutron transmission measurements corresponded to the reflections from the (h k l) planes of the hexagonal zinc single crystal which was cut along the (0 0 2) plane, while in the case of lead, the single crystal was cut perpendicular to the (3 1 1) plane. The reflectivity from the (0 0 2) plane of zinc was determined using both transmission and reflection methods. The maximum reflectivity was found to be 55% when the zinc crystal was orientated at 45 0 to the beam direction. The wavelength spread of the observed reflectivity curve was found to be in agreement with the calculated one, taking into consideration the spectrometer's resolution and the crystal mosaic spread. (author)

  9. Clean Transfer of Large Graphene Single Crystals for High-Intactness Suspended Membranes and Liquid Cells.

    Science.gov (United States)

    Zhang, Jincan; Lin, Li; Sun, Luzhao; Huang, Yucheng; Koh, Ai Leen; Dang, Wenhui; Yin, Jianbo; Wang, Mingzhan; Tan, Congwei; Li, Tianran; Tan, Zhenjun; Liu, Zhongfan; Peng, Hailin

    2017-07-01

    The atomically thin 2D nature of suspended graphene membranes holds promising in numerous technological applications. In particular, the outstanding transparency to electron beam endows graphene membranes great potential as a candidate for specimen support of transmission electron microscopy (TEM). However, major hurdles remain to be addressed to acquire an ultraclean, high-intactness, and defect-free suspended graphene membrane. Here, a polymer-free clean transfer of sub-centimeter-sized graphene single crystals onto TEM grids to fabricate large-area and high-quality suspended graphene membranes has been achieved. Through the control of interfacial force during the transfer, the intactness of large-area graphene membranes can be as high as 95%, prominently larger than reported values in previous works. Graphene liquid cells are readily prepared by π-π stacking two clean single-crystal graphene TEM grids, in which atomic-scale resolution imaging and temporal evolution of colloid Au nanoparticles are recorded. This facile and scalable production of clean and high-quality suspended graphene membrane is promising toward their wide applications for electron and optical microscopy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Stress-induced martensitic transformation and ferroelastic deformation adjacent microhardness indents in tetragonal zirconia single crystals

    International Nuclear Information System (INIS)

    Chien, F.R.; Ubic, F.J.; Prakash, V.; Heuer, A.H.

    1998-01-01

    The stress-induced tetragonal to monoclinic (t → m) martensitic transformation, stress-induced ferroelastic domain switching, and dislocation slip were induced by Vickers microindentation at elevated temperatures in polydomain single crystals of 3 mol%-Y 2 O 3 -stabilized tetragonal ZrO 2 single crystals (3Y-TZS). Chemical etching revealed traces along t directions adjacent to indentations, and Raman spectroscopy and TEM have shown that these traces are caused by products of the martensitic transformation, i.e. the monoclinic product phase forms primarily as thin, long plates with a habit plane approximately on (bar 301) m . This habit plane and the associated shear strain arising from the transformation, visible in TEM micrographs at the intersection of crystallographically equivalent martensite plates, were successfully predicted using the observed lattice correspondence and the phenomenological invariant plane strain theory of martensitic transformations. The extent of the martensitic transformation increased with increasing temperature from room temperature up to 300 C, but then decreased at higher temperatures. Ferroelastic deformation of tetragonal ZrO 2 has been observed at all temperatures up to 1,000 C. At the highest temperature, only ferroelastic domain switching and dislocation slip occurred during indentation-induced deformation

  11. Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering

    KAUST Repository

    Shi, Dong

    2016-04-15

    We report the crystal structure and hole-transport mechanism in spiro-OMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene], the dominant hole-transporting material in perovskite and solid-state dye-sensitized solar cells. Despite spiro-OMeTAD’s paramount role in such devices, its crystal structure was unknown because of highly disordered solution-processed films; the hole-transport pathways remained ill-defined and the charge carrier mobilities were low, posing a major bottleneck for advancing cell efficiencies. We devised an antisolvent crystallization strategy to grow single crystals of spiro-OMeTAD, which allowed us to experimentally elucidate its molecular packing and transport properties. Electronic structure calculations enabled us to map spiro-OMeTAD’s intermolecular charge-hopping pathways. Promisingly, single-crystal mobilities were found to exceed their thin-film counterparts by three orders of magnitude. Our findings underscore mesoscale ordering as a key strategy to achieving breakthroughs in hole-transport material engineering of solar cells.

  12. Photoluminescence and lasing properties of MAPbBr3 single crystals grown from solution

    Science.gov (United States)

    Aryal, Sandip; Lafalce, Evan; Zhang, Chuang; Zhai, Yaxin; Vardeny, Z. Valy

    Recent studies of solution-grown single crystals of inorganic-organic hybrid lead-trihalide perovskites have suggested that surface traps may play a significant role in their photophysics. We study electron-hole recombination in single crystal MAPbBr3 through such trap states using cw photoluminescence (PL) and ps transient photoinduced absorption (PA) spectroscopies. By varying the depth of the collecting optics we examined the contributions from surface and bulk radiative recombination. We found a surface dominated PL band at the band-edge that is similar to that observed from polycrystalline thin films, as well as a weaker red-shifted emission band that originates from the bulk crystal. The two PL bands are distinguished in their temperature, excitation intensity and polarization dependencies, as well as their ps dynamics. Additionally, amplified spontaneous emission and crystal-related cavity lasing modes were observed in the same spectral range as the PL band assigned to the surface recombination. This work was funded by AFOSR through MURI Grant RA 9550-14-1-0037.

  13. Solution-printed organic semiconductor blends exhibiting transport properties on par with single crystals

    KAUST Repository

    Niazi, Muhammad Rizwan; Li, Ruipeng; Li, Erqiang; Kirmani, Ahmad R.; Abdelsamie, Maged; Wang, Qingxiao; Pan, Wenyang; Payne, Marcia M.; Anthony, John E.; Smilgies, Detlef-M.; Thoroddsen, Sigurdur T; Giannelis, Emmanuel P.; Amassian, Aram

    2015-01-01

    Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm2 V−1 s−1, low threshold voltages of<1 V and low subthreshold swings <0.5 V dec−1). Our findings demonstrate that careful control over phase separation and crystallization can yield solution-printed polycrystalline organic semiconductor films with transport properties and other figures of merit on par with their single-crystal counterparts.

  14. Temperature dependent evolution of wrinkled single-crystal silicon ribbons on shape memory polymers.

    Science.gov (United States)

    Wang, Yu; Yu, Kai; Qi, H Jerry; Xiao, Jianliang

    2017-10-25

    Shape memory polymers (SMPs) can remember two or more distinct shapes, and thus can have a lot of potential applications. This paper presents combined experimental and theoretical studies on the wrinkling of single-crystal Si ribbons on SMPs and the temperature dependent evolution. Using the shape memory effect of heat responsive SMPs, this study provides a method to build wavy forms of single-crystal silicon thin films on top of SMP substrates. Silicon ribbons obtained from a Si-on-insulator (SOI) wafer are released and transferred onto the surface of programmed SMPs. Then such bilayer systems are recovered at different temperatures, yielding well-defined, wavy profiles of Si ribbons. The wavy profiles are shown to evolve with time, and the evolution behavior strongly depends on the recovery temperature. At relatively low recovery temperatures, both wrinkle wavelength and amplitude increase with time as evolution progresses. Finite element analysis (FEA) accounting for the thermomechanical behavior of SMPs is conducted to study the wrinkling of Si ribbons on SMPs, which shows good agreement with experiment. Merging of wrinkles is observed in FEA, which could explain the increase of wrinkle wavelength observed in the experiment. This study can have important implications for smart stretchable electronics, wrinkling mechanics, stimuli-responsive surface engineering, and advanced manufacturing.

  15. Solution-printed organic semiconductor blends exhibiting transport properties on par with single crystals

    KAUST Repository

    Niazi, Muhammad Rizwan

    2015-11-23

    Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm2 V−1 s−1, low threshold voltages of<1 V and low subthreshold swings <0.5 V dec−1). Our findings demonstrate that careful control over phase separation and crystallization can yield solution-printed polycrystalline organic semiconductor films with transport properties and other figures of merit on par with their single-crystal counterparts.

  16. Paramagnetic Spin Correlations in CaFe2As2 Single Crystals

    International Nuclear Information System (INIS)

    Omar Diallo, Souleymane; Pratt, Daniel; Fernandes, Rafael; Tian, Wei; Zarestky, J.L.; Lumsden, Mark D.; Perring, T.G.; Broholm, C.; Ni, Ni; Budko, S.L.; Canfield, Paul; Li, Haifeng; Vaknin, D.; Kreyssig, A.; Goldman, A.I.; Mcqueeney, R.J.

    2010-01-01

    Magnetic correlations in the paramagnetic phase of CaFe2As2(TN=172 K) have been examined by means of inelastic neutron scattering from 180 K ( 1.05TN) up to 300 K (1.8TN). Despite the first-order nature of the magnetic ordering, strong but short-ranged antiferromagnetic (AFM) correlations are clearly observed. These correlations, which consist of quasielastic scattering centered at the wave vector QAFM of the low-temperature AFM structure, are observed up to the highest measured temperature of 300 K and at high energy transfer ( >60 meV). The L dependence of the scattering implies rather weak interlayer coupling in the tetragonal c direction corresponding to nearly two-dimensional fluctuations in the (ab) plane. The spin correlation lengths within the Fe layer are found to be anisotropic, consistent with underlying fluctuations of the AFM stripe structure. Similar to the cobalt-doped superconducting BaFe2As2 compounds, these experimental features can be adequately reproduced by a scattering model that describes short-ranged and anisotropic spin correlations with overdamped dynamics.

  17. X-ray dosimetry of TlGaSe2 single crystals

    International Nuclear Information System (INIS)

    Kerimova, E.M.; Mustafaeva, S.N.; Mamedbeili, S.D.; Jabarov, J.N.; Iskenderova, P.M.; Kazimov, S.B.

    2002-01-01

    TlGaSe 2 compound belongs to group of layered semiconductors of A 3 B 3 C 2 6 -type. Photoelectric and optical properties of TlGaSe 2 single crystals were investigated in detail. Influence of gamma-, electron and neutron radiation on photoelectric properties of TlGaSe 2 single crystals is investigated too. The present work deals with experimental results relative to X-ray dosimetric characteristics of TlGaSe 2 crystals at 300 K. X-ray conductivity and X-ray dosimetric characteristic measurements are carried out in low load resistance regime. The source of X-ray radiation is the installation of X-ray diffraction analysis (URS-55a) with the BCV-2(Cu). Intensity of X-ray radiation (E) is regulated by measurement with current variation in tube at each given value of X-ray radiation dose E (R/min) are measured by crystal dosimeter DRGZ-02. X-ray conductivity coefficients K σ characterising X-ray sensitivity of investigated crystals are determined as the relative change of conductivity under X-ray radiation a per dose. There have been determined values of characteristic coefficients of TlGaSe 2 single crystal X-ray conductivity at different values of accelerating voltage (V a ) on the tube and corresponding doses of X-ray radiation. Analysis of obtained data showed that X-ray conductivity coefficients K σ in studied crystals are regularly decreased (from 0.276 to 0.033) as with the rise of dose (E=0.75-78.0 R/min) as with the increase of values of V a on X-ray tube (V a =254-50 keV). One of the possible reasons of observed regularities is that X-ray conductivity in investigated crystals, especially at comparatively low V a is due predominantly to radiation of thin layer of crystal. In this case with the rise of radiation intensity there have been started to prevail the mechanism of surface quadratic recombination which leads to observed decrease of X-ray conductivity. With the rise of accelerating potential 'effective hardness' is increased, as a result of which there

  18. Evaluation of single crystal coefficients from mechanical and x-ray elastic constants of the polycrystal

    International Nuclear Information System (INIS)

    Hauk, V.; Kockelmann, H.

    1979-01-01

    Methods of calculation are developed for determination of single crystal elastic compliance or stiffness constants of cubic and hexagonal materials from mechanical and X-ray elastic constants of polycrystals. The calculations are applied to pure, cubic iron and hexagonal WC. There are no single crystal constants in the literature for WC, because no single crystals suitable for measurement are available. (orig.) [de

  19. Magnetic order of Nd5Pb3 single crystals

    Science.gov (United States)

    Yan, J.-Q.; Ochi, M.; Cao, H. B.; Saparov, B.; Cheng, J.-G.; Uwatoko, Y.; Arita, R.; Sales, B. C.; Mandrus, D. G.

    2018-04-01

    We report millimeter-sized Nd5Pb3 single crystals grown out of a Nd-Co flux. We experimentally study the magnetic order of Nd5Pb3 single crystals by measuring the anisotropic magnetic properties, electrical resistivity under high pressure up to 8 GPa, specific heat, and neutron single crystal diffraction. Two successive magnetic orders are observed at T N1  =  44 K and T N2  =  8 K. The magnetic cells can be described with a propagation vector k=(0.5, 0, 0) . Cooling below T N1, Nd1 and Nd3 order forming ferromagnetic stripes along the b-axis, and the ferromagnetic stripes are coupled antiferromagnetically along the a-axis for the k=(0.5, 0, 0) magnetic domain. Cooling below T N2, Nd2 orders antiferromagnetically to nearby Nd3 ions. All ordered moments align along the crystallographic c-axis. The magnetic order at T N1 is accompanied by a quick drop of electrical resistivity upon cooling and a lambda-type anomaly in the temperature dependence of specific heat. At T N2, no anomaly was observed in electrical resistivity but there is a weak feature in specific heat. The resistivity measurements under hydrostatic pressures up to 8 GPa suggest a possible phase transition around 6 GPa. Our first-principles band structure calculations show that Nd5Pb3 has the same electronic structure as does Y5Si3 which has been reported to be a one-dimensional electride with anionic electrons that do not belong to any atom. Our study suggests that R 5Pb3 (R  =  rare earth) can be a materials playground for the study of magnetic electrides. This deserves further study after experimental confirmation of the presence of anionic electrons.

  20. Infrared absorption in PbTe single crystals

    International Nuclear Information System (INIS)

    Kudykina, T.A.

    1982-01-01

    A group-theoretical analysis is conducted to select rules for optical transitions between bands in PbTe single crystals. It is shown that transitions between valence bands which are near a forbidden band are also forbidden. The extra absorption observed in p-PbTe and p-Pbsub(1-x)Snsub(x)Te in the region between the self-absorption edge and the free-carrier absorption edge is probably connected with transitions between one of valence bands and the p-state of the impurity

  1. Characteristics of trapped electrons and electron traps in single crystals

    International Nuclear Information System (INIS)

    Budzinski, E.E.; Potter, W.R.; Potienko, G.; Box, H.C.

    1979-01-01

    Two additional carbohydrates are reported whose crystal structures trap electrons intermolecularly in single crystals x irradiated at low temperature, namely sucrose and rhamnose. Five carbohydrate and polyhydroxy compounds are now known which exhibit this phenomenon. The following characteristics of the phenomenon were investigated: (1) the hyperfine couplings of the electron with protons of the polarized hydroxy groups forming the trap; (2) the distances between these protons and the trapped electron; (3) the spin density of the electron at the protons and (4) the relative stabilities of the electron trapped in various crystal structures

  2. Pyroelectric effect in tryglicyne sulphate single crystals - Differential measurement method

    Science.gov (United States)

    Trybus, M.

    2018-06-01

    A simple mathematical model of the pyroelectric phenomenon was used to explain the electric response of the TGS (triglycine sulphate) samples in the linear heating process in ferroelectric and paraelectric phases. Experimental verification of mathematical model was realized. TGS single crystals were grown and four electrode samples were fabricated. Differential measurements of the pyroelectric response of two different regions of the samples were performed and the results were compared with data obtained from the model. Experimental results are in good agreement with model calculations.

  3. The sublimation kinetics of GeSe single crystals

    Science.gov (United States)

    Irene, E. A.; Wiedemeier, H.

    1975-01-01

    The sublimation kinetics of (001) oriented GeSe single crystal platelets was studied by high-temperature mass spectroscopy, quantitative vacuum microbalance techniques, and hot stage optical microscopy. For a mean experimental temperature of 563 K, the activation enthalpy and entropy are found to equal 32.3 kcal/mole and 19.1 eu, respectively. The vaporization coefficient is less than unity for the range of test temperatures, and decreases with increasing temperature. The combined experimental data are correlated by means of a multistep surface adsorption mechanism.

  4. EPR studies of gamma-irradiated taurine single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Bulut, A. E-mail: abulut@samsun.omu.edu.tr; Karabulut, B.; Tapramaz, R.; Koeksal, F

    2000-04-01

    An EPR study of gamma-irradiated taurine [C{sub 2}H{sub 7}NO{sub 3}S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of {sup 32}SO{sup -}{sub 2} and {sup 33}SO{sup -}{sub 2} radicals. The hyperfine values of {sup 33}SO{sup -}{sub 2} radical were used to obtain O-S-O bond angle for both sites.

  5. Acquisition of Single Crystal Growth and Characterization Equipment. Final report

    International Nuclear Information System (INIS)

    Maple, M. Brian; Zocco, Diego A.

    2008-01-01

    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 a result, many user facilities are not being used optimally. The number of proficient crystal growers is too small. In addition, insufficient attention is being paid to the enterprise of finding new and interesting materials, which is the driving force behind much of condensed matter research and, ultimately, technology. While a detailed assessment of this situation is clearly needed, enough evidence of a problem already exists to compel a general consensus that the situation must be addressed promptly. This final report describes the work carried out during the last four years in our group, in which a state-of-the-art single crystal growth and characterization facility was established for the study of novel oxides and intermetallic compounds of rare earth, actinide and transition metal elements. Research emphasis is on the physics of superconducting (SC), magnetic, heavy fermion (HF), non-Fermi liquid (NFL) and other types of strongly correlated electron phenomena in bulk single crystals. Properties of these materials are being studied as a function of concentration of chemical constituents, temperature, pressure, and magnetic field, which provide information about the electronic, lattice, and magnetic excitations at the root of various strongly correlated electron phenomena. Most importantly, the facility makes possible the investigation of material properties that can only be achieved in high quality bulk single crystals, including magnetic and transport phenomena, studies of the effects of disorder, properties in the clean limit, and spectroscopic and scattering

  6. EPR studies of gamma-irradiated taurine single crystals

    International Nuclear Information System (INIS)

    Bulut, A.; Karabulut, B.; Tapramaz, R.; Koeksal, F.

    2000-01-01

    An EPR study of gamma-irradiated taurine [C 2 H 7 NO 3 S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32 SO - 2 and 33 SO - 2 radicals. The hyperfine values of 33 SO - 2 radical were used to obtain O-S-O bond angle for both sites

  7. Lattice effects in HoVo3 single crystal

    International Nuclear Information System (INIS)

    Sikora, M.; Marquina, C.; Ibarra, M.R.; Nugroho, A.A.; Palstra, T.T.M.

    2007-01-01

    We report the study of lattice effects in the Mott insulator HoVO 3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO 3 reveals gradual orbital ordering (OO) below T OO =200 K and orders antiferromagnetically at T N =113 K. A first-order structural phase transition takes place at T S ∼38 K, which is probably accompanied by change of the OO type and hence the type of antiferromagnetic spin ordering

  8. Radiation defects produced by neutron irradiation in germanium single crystals

    International Nuclear Information System (INIS)

    Fukuoka, Noboru; Honda, Makoto; Atobe, Kozo; Yamaji, Hiromichi; Ide, Mutsutoshi; Okada, Moritami.

    1992-01-01

    The nature of defects produced in germanium single crystals by neutron irradiation at 25 K was studied by measuring the electrical resistivity. It was found that two levels located at E c -0.06 eV and E c -0.13 eV were introduced in an arsenic-doped sample. Electron traps at E c -0.10eV were observed in an indium-doped sample. The change in electrical resistivity during irradiation was also studied. (author)

  9. Single crystal NMR studies of high temperature superconductors

    International Nuclear Information System (INIS)

    Pennington, C.H.; Durand, D.J.; Zax, D.B.; Slichter, C.P.; Rice, J.P.; Bukowski, E.D.; Ginsberg, D.M.

    1989-01-01

    The authors report Cu NMR studies in the normal state of a single crystal of the T/sub c/ = 90 K superconductor YBa 2 Cu 3 O/sub 7/minus/δ/. The authors have measured the magnetic shift tensor, the electric field gradient tensor, the nuclear spin-lattice relaxation rate tensor, and the time dependence and functional form of the transverse decay. From these data they obtain information about the charge state and magnetic state of the Cu atoms, and the existence and size of the electronic exchange coupling between spins of adjacent Cu atoms. 18 refs., 3 figs., 2 tabs

  10. Crystal structure and magnetic susceptibility of UOSe single crystals

    International Nuclear Information System (INIS)

    Kaczorowski, D.; Muenster Univ.; Poettgen, R.; Jeitschko, W.; Gajek, Z.; Zygmunt, A.

    1993-01-01

    The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T N =100±2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author)

  11. Crystal structure and magnetic susceptibility of UOSe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kaczorowski, D. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Poettgen, R.; Jeitschko, W. (Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Gajek, Z.; Zygmunt, A. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research)

    1993-01-01

    The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T[sub N]=100[+-]2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author).

  12. Nonstoichiometry and conductivity anisotropy of lead germanate single crystals

    International Nuclear Information System (INIS)

    Jermakov, O.S.; Duda, V.M.

    2010-01-01

    The conductivity of lead germanate single crystals with the stoichiometric composition, PbO deficiency, and PbO excess has been measured. A reduction of the PbO fraction in the initial blend leads to a considerable increase of the conductivity, because the fraction of lead ions which change their valency from Pb 2+ to Pb 3+ grows. The relative arrangement of lead ions, which are able to change their valency and trap holes, can be responsible for a significant anisotropy of conductivity.

  13. Laser induced single-crystal transition in polycrystalline silicon

    International Nuclear Information System (INIS)

    Vitali, G.; Bertolotti, M.; Foti, G.; Rimini, E.

    1978-01-01

    Transition to single crystal of polycrystalline Si material underlying a Si crystal substrate of 100 orientation was obtained via laser irradiation. The changes in the structure were analyzed by reflection high energy electron diffraction and by channeling effect technique using 2.0 MeV He Rutherford scattering. The power density required to induce the transition in a 4500 A thick polycrystalline layer is about 70 MW/cm 2 (50ns). The corresponding amorphous to single transition has a threshold of about 45 MW/cm 2 . (orig.) 891 HPOE [de

  14. Magnetic anisotropy of YNi2B2C single crystals

    International Nuclear Information System (INIS)

    Baran, M.; Gladczuk, L.; Gorecka, J.; Szymczak, H.; Szymczak, R.; Drzazga, Z.; Winiarska, H.

    1994-01-01

    Reversible and irreversible magnetization processes in YNi 2 B 2 C single crystal have been measured and analysed in terms of existing theories. Performed measurements suggest that anisotropy of the effective mass in YNi 2 B 2 C superconductor is rather small and similar to that observed in conventional superconductors. Effect of hydrostatic pressure on T c is shown to be typical of low-temperature superconductors. It is suggested that the layered structure of YNi 2 B 2 C has some effect on the irreversible magnetization processes observed in this superconductor. ((orig.))

  15. Elastic Properties of Ho0.5Er0.5 Single Crystal

    DEFF Research Database (Denmark)

    Spichkin, Yu.I.; Bohr, Jakob; Tishin, A.M.

    1996-01-01

    The results of an investigation of the Young's modulus E and the interval friction Q-1 of a Ho0.5Er0.5 single crystal in the basal plane in the temperature range 4.2-400 K are reported. The measurements were carried out by the method of flexural autovibrations of a thin sample with sound frequency...... (3 kHz). The Young's modulus at 4.2 K was measured to be 154 GPa. From the obtained data the magnetic part of the Young's modulus and the Debye temperature theta-D=375 K were calculated. The anomalies on the Young's modulus and the interval friction temperature dependencies corresponding to magnetic...

  16. Electrical resistivity anisotropy of osmium single crystals in the range 4,2 to 300 K

    International Nuclear Information System (INIS)

    Volkenshtejn, N.V.; Dyakina, V.P.; Dyakin, V.V.; Startsev, V.E.; Cherepanov, V.I.; Azhazha, V.M.; Kovtun, G.P.; Elenskij, V.A.; AN Ukrainskoj SSR, Kharkov. Fiziko-Tekhnicheskij Inst.)

    1981-01-01

    Electrical resistivity and size effect anisotropies of pure osmium single crystals with rhosub(273.2/rhosub(4.2)2600 were investigated in the temperature range 4.2 to 300 K. It is found that the electrical resistivity anisotropy (αT)=rhosub( )/rhosub( ) is less than unit and has a maximum at T approximately 50 K; the size effect anisotropy (rho1)sub( )/(rho1)sub( ) is 0.39+-0.07 at T=4.2 K; at liquid helium temperature, the dependence of thin samples is controlled by the scattering of conduction electrons by the surface of the sample. The results are discussed for the specific shape of the Fermi surface geometry of osmium with an account for the scattering processes of conduction electrons by phonons and by surface of the sample

  17. Irradiation damage in aluminium single crystals produced by 50-keV aluminium and copper ions

    DEFF Research Database (Denmark)

    Henriksen, L.; Johansen, A.; Koch, J.

    1968-01-01

    Aluminium single crystals, thin enough to be examined by electron microscopy, have been irradiated with 50-keV aluminium and copper ions. The irradiation fluxes were in the range 1011–1014 cm−2 s−1 and the doses were from 6 × 1012 to 6 × 1014 cm−2. Irradiation along either a or a direction produces...... rows of dislocation loops all lying parallel to one particular direction. If the aluminium target is quenched from 600 °C and annealed at room temperature prior to irradiation with aluminium ions, the rows of loops are suppressed. The amount of damage observed is considerably less than would...

  18. A PMMA coated PMN–PT single crystal resonator for sensing chemical agents

    International Nuclear Information System (INIS)

    Frank, Michael; Kassegne, Sam; Moon, Kee S

    2010-01-01

    A highly sensitive lead magnesium niobate–lead titanate (PMN–PT) single crystal resonator coated with a thin film of polymethylmethacrylate (PMMA) useful for detecting chemical agents such as acetone, methanol, and isopropyl alcohol is presented. Swelling of the cured PMMA polymer layer in the presence of acetone, methanol, and isopropyl alcohol vapors is sensed as a mass change transduced to an electrical signal by the PMN–PT thickness shear mode sensor. Frequency change in the PMN–PT sensor is demonstrated to vary according to the concentration of the chemical vapor present within the sensing chamber. For acetone, the results indicate a frequency change more than 6000 times greater than that which would be expected from a quartz crystal microbalance coated with PMMA. This study is the first of its kind to demonstrate vapor loading of adsorbed chemical agents onto a polymer coated PMN–PT resonator

  19. Stacking fault tetrahedron induced plasticity in copper single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liang, E-mail: lz592@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Lu, Cheng, E-mail: chenglu@uow.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Tieu, Kiet; Su, Lihong; Zhao, Xing [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Pei, Linqing [Department of Mechanical Engineering, Chongqing University, Chongqing 400044 (China)

    2017-01-05

    Stacking fault tetrahedron (SFT) is the most common type of vacancy clustered defects in fcc metals and alloys, and can play an important role in the mechanical properties of metallic materials. In this study, molecular dynamics (MD) simulations were carried out to investigate the incipience of plasticity and the underlying atomic mechanisms in copper single crystals with SFT. Different deformation mechanisms of SFT were reported due to the crystal orientations and loading directions (compression and tension). The results showed that the incipient plasticity in crystals with SFT resulted from the heterogeneous dislocation nucleation from SFT, so the stress required for plastic deformation was less than that needed for perfect single crystals. Three crystal orientations ([1 0 0], [1 1 0] and [1 1 1]) were specified in this study because they can represent most of the typical deformation mechanisms of SFT. MD simulations revealed that the structural transformation of SFT was frequent under the applied loading; a metastable SFT structure and the collapse of SFT were usually observed. The structural transformation resulted in a different reduction of yield stress in compression and tension, and also caused a decreased or reversed compression/tension asymmetry. Compressive stress can result in the unfaulting of Frank loop in some crystal orientations. According to the elastic theory of dislocation, the process of unfaulting was closely related to the size of the dislocation loop and the stacking fault energy.

  20. Mesoscale martensitic transformation in single crystals of topological defects

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiao; Martínez-González, José A.; Hernández-Ortiz, Juan P.; Ramírez-Hernández, Abelardo; Zhou, Ye; Sadati, Monirosadat; Zhang, Rui; Nealey, Paul F.; de Pablo, Juan J.

    2017-09-05

    Liquid crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of doubletwisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with considerable precision by relying on chemically nano-patterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of meso-crystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local re-organization of the crystalline array, without diffusion of the double twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the sub-micron regime, is found to be martensitic in nature, with the diffusion-less feature associated to the collective behavior of the double twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal-nucleation and the controlled growth of soft matter.

  1. Large single-crystal diamond substrates for ionizing radiation detection

    Energy Technology Data Exchange (ETDEWEB)

    Girolami, Marco; Bellucci, Alessandro; Calvani, Paolo; Trucchi, Daniele M. [Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR), Sede Secondaria di Montelibretti, Monterotondo Stazione, Roma (Italy)

    2016-10-15

    The need for large active volume detectors for ionizing radiations and particles, with both large area and thickness, is becoming more and more compelling in a wide range of applications, spanning from X-ray dosimetry to neutron spectroscopy. Recently, 8.0 x 8.0 mm{sup 2} wide and 1.2 mm thick single-crystal diamond plates have been put on the market, representing a first step to the fabrication of large area monolithic diamond detectors with optimized charge transport properties, obtainable up to now only with smaller samples. The more-than-double thickness, if compared to standard plates (typically 500 μm thick), demonstrated to be effective in improving the detector response to highly penetrating ionizing radiations, such as γ-rays. Here we report on the first measurements performed on large active volume single-crystal diamond plates, both in the dark and under irradiation with optical wavelengths (190-1100 nm), X-rays, and radioactive γ-emitting sources ({sup 57}Co and {sup 22}Na). (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Chiral multichromic single crystals for optical devices (LDRD 99406).

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Richard Alan; Felix, Ana M. (University of New Mexico, Albuquerque, NM)

    2006-12-01

    This report summarizes our findings during the study of a novel system that yields multi-colored materials as products. This system is quite unusual as it leads to multi-chromic behavior in single crystals, where one would expect that only a single color would exist. We have speculated that these novel solids might play a role in materials applications such as non-linear optics, liquid crystal displays, piezoelectric devices, and other similar applications. The system examined consisted of a main-group alkyl compound (a p block element such as gallium or aluminum) complexed with various organic di-imines. The di-imines had substituents of two types--either alkyl or aromatic groups attached to the nitrogen atoms. We observed that single crystals, characterized by X-ray crystallography, were obtained in most cases. Our research during January-July, 2006, was geared towards understanding the factors leading to the multi-chromic nature of the complexes. The main possibilities put forth initially considered (a) the chiral nature of the main group metal, (b) possible reduction of the metal to a lower-valent, radical state, (c) the nature of the ligand(s) attached to the main group metal, and (d) possible degradation products of the ligand leading to highly-colored products. The work carried out indicates that the most likely explanation considered involves degradation of the aromatic ligands (a combination of (c) and (d)), as the experiments performed can clearly rule out (a) and (b).

  3. Plastic deformation of Ni3Nb single crystals

    International Nuclear Information System (INIS)

    Hagihara, Kouji; Nakano, Takayoshi; Umakoshi, Yukichi

    1999-01-01

    Temperature dependence of yield stress and operative slip system in Ni 3 Nb single crystals with the D0 a structure was investigated in comparison with that in an analogous L1 2 structure. Compression tests were performed at temperatures between 20 C and 1,200 C for specimens with loading axes perpendicular to (110), (331) and (270). (010)[100] slip was operative for three orientations, while (010)[001] slip for (331) and [211] twin for (270) orientations were observed, depending on deformation temperature. The critical resolved shear stress (CRSS) for the (010)[100] slip anomaly increased with increasing temperature showing a maximum peak between 400 C and 800 C depending on crystal orientation. The CRSS showed orientation dependence and no significant strain rate dependence in the temperature range for anomalous strengthening. The [100] dislocations with a screw character were aligned on the straight when the anomalous strengthening occurred. The anomalous strengthening mechanism for (010)[100] slip in Ni 3 Nb single crystals is discussed on the basis of a cross slip model which has been widely accepted for some L1 2 -type compounds

  4. Strength anomaly in B2 FeAl single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimi, K.; Hanada, S.; Yoo, M.H. [Oak Ridge National Lab., TN (United States); Matsumoto, N. [Tohoku Univ. (Japan). Graduate School

    1994-12-31

    Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.

  5. Anisotropy of Single-Crystal Silicon in Nanometric Cutting.

    Science.gov (United States)

    Wang, Zhiguo; Chen, Jiaxuan; Wang, Guilian; Bai, Qingshun; Liang, Yingchun

    2017-12-01

    The anisotropy exhibited by single-crystal silicon in nanometric cutting is very significant. In order to profoundly understand the effect of crystal anisotropy on cutting behaviors, a large-scale molecular dynamics model was conducted to simulate the nanometric cutting of single-crystal silicon in the (100)[0-10], (100)[0-1-1], (110)[-110], (110)[00-1], (111)[-101], and (111)[-12-1] crystal directions in this study. The simulation results show the variations of different degrees in chip, subsurface damage, cutting force, and friction coefficient with changes in crystal plane and crystal direction. Shear deformation is the formation mechanism of subsurface damage, and the direction and complexity it forms are the primary causes that result in the anisotropy of subsurface damage. Structurally, chips could be classified into completely amorphous ones and incompletely amorphous ones containing a few crystallites. The formation mechanism of the former is high-pressure phase transformation, while the latter is obtained under the combined action of high-pressure phase transformation and cleavage. Based on an analysis of the material removal mode, it can be found that compared with the other crystal direction on the same crystal plane, the (100)[0-10], (110)[-110], and (111)[-101] directions are more suitable for ductile cutting.

  6. Free-standing nanomechanical and nanophotonic structures in single-crystal diamond

    Science.gov (United States)

    Burek, Michael John

    Realizing complex three-dimensional structures in a range of material systems is critical to a variety of emerging nanotechnologies. This is particularly true of nanomechanical and nanophotonic systems, both relying on free-standing small-scale components. In the case of nanomechanics, necessary mechanical degrees of freedom require physically isolated structures, such as suspended beams, cantilevers, and membranes. For nanophotonics, elements like waveguides and photonic crystal cavities rely on light confinement provided by total internal reflection or distributed Bragg reflection, both of which require refractive index contrast between the device and surrounding medium (often air). Such suspended nanostructures are typically fabricated in a heterolayer structure, comprising of device (top) and sacrificial (middle) layers supported by a substrate (bottom), using standard surface nanomachining techniques. A selective, isotropic etch is then used to remove the sacrificial layer, resulting in free-standing devices. While high-quality, crystalline, thin film heterolayer structures are readily available for silicon (as silicon-on-insulator (SOI)) or III-V semiconductors (i.e. GaAs/AlGaAs), there remains an extensive list of materials with attractive electro-optic, piezoelectric, quantum optical, and other properties for which high quality single-crystal thin film heterolayer structures are not available. These include complex metal oxides like lithium niobate (LiNbO3), silicon-based compounds such as silicon carbide (SiC), III-V nitrides including gallium nitride (GaN), and inert single-crystals such as diamond. Diamond is especially attractive for a variety of nanoscale technologies due to its exceptional physical and chemical properties, including high mechanical hardness, stiffness, and thermal conductivity. Optically, it is transparent over a wide wavelength range (from 220 nm to the far infrared), has a high refractive index (n ~ 2.4), and is host to a vast

  7. The fabrication and characterization of organic light-emitting diodes using transparent single-crystal Si membranes

    International Nuclear Information System (INIS)

    Lee, Su-Hwan; Kim, Dal-Ho; Kim, Ji-Heon; Lee, Gon-Sub; Park, Jea-Gun; Takeo, Katoh

    2009-01-01

    For applications such as solar cells and displays, transparent single-crystal Si membranes were fabricated on a silicon-on-insulator (SOI) wafer. The SOI wafer included a buried layer of SiO 2 and Si 3 N 4 as an etch-stop layer. The etch-stop layer enabled fabrication of transparent single-crystal Si membranes with various thicknesses, and the thinning technology is described. For membranes with thicknesses of 18, 72 and 5000 nm, the respective optical transparent were 96.9%, 93.7% and 9% for R (red, λ = 660 nm), 96.9%, 91.4% and 1% for G (green, λ = 525 nm), and 97.0%, 93.2% and 0% for B (blue, λ = 470 nm). Organic light-emitting diodes (OLEDs) were then fabricated on transparent single-crystal Si membranes with various top Si thicknesses. OLEDs fabricated on 18, 72 and 5000 nm thick membranes and operated at 6 V demonstrated a luminance of 1350, 443 and 27 cd m -2 at the current densities of 148, 131 and 1.5 mA cm -2 , respectively.

  8. Strength and deformation of shocked diamond single crystals: Orientation dependence

    Science.gov (United States)

    Lang, J. M.; Winey, J. M.; Gupta, Y. M.

    2018-03-01

    Understanding and quantifying the strength or elastic limit of diamond single crystals is of considerable scientific and technological importance, and has been a subject of long standing theoretical and experimental interest. To examine the effect of crystalline anisotropy on strength and deformation of shocked diamond single crystals, plate impact experiments were conducted to measure wave profiles at various elastic impact stresses up to ˜120 GPa along [110] and [111] crystal orientations. Using laser interferometry, particle velocity histories and shock velocities in the diamond samples were measured and were compared with similar measurements published previously for shock compression along the [100] direction. Wave profiles for all three orientations showed large elastic wave amplitudes followed by time-dependent inelastic deformation. From the measured wave profiles, the elastic limits were determined under well characterized uniaxial strain loading conditions. The measured elastic wave amplitudes for the [110] and [111] orientations were lower for higher elastic impact stress (stress attained for an elastic diamond response), consistent with the result reported previously for [100] diamond. The maximum resolved shear stress (MRSS) on the {111}⟨110⟩ slip systems was determined for each orientation, revealing significant orientation dependence. The MRSS values for the [100] and [110] orientations (˜33 GPa) are 25%-30% of theoretical estimates; the MRSS value for the [111] orientation is significantly lower (˜23 GPa). Our results demonstrate that the MRSS depends strongly on the stress component normal to the {111} planes or the resolved normal stress (RNS), suggesting that the RNS plays a key role in inhibiting the onset of inelastic deformation. Lower elastic wave amplitudes at higher peak stress and the effect of the RNS are inconsistent with typical dislocation slip mechanisms of inelastic deformation, suggesting instead an inelastic response

  9. Polarised IR-microscope spectra of guanidinium hydrogensulphate single crystal.

    Science.gov (United States)

    Drozd, M; Baran, J

    2006-07-01

    Polarised IR-microscope spectra of C(NH(2))(3)*HSO(4) small single crystal samples were measured at room temperature. The spectra are discussed on the basis of oriented gas model approximation and group theory. The stretching nuOH vibration of the hydrogen bond with the Ocdots, three dots, centeredO distance of 2.603A gives characteristic broad AB-type absorption in the IR spectra. The changes of intensity of the AB bands in function of polariser angle are described. Detailed assignments for bands derived from stretching and bending modes of sulphate anions and guanidinium cations were performed. The observed intensities of these bands in polarised infrared spectra were correlated with theoretical calculation of directional cosines of selected transition dipole moments for investigated crystal. The vibrational studies seem to be helpful in understanding of physical and chemical properties of described compound and also in design of new complexes with exactly defined behaviors.

  10. Polarized IR-microscope spectra of guanidinium hydrogenselenate single crystal.

    Science.gov (United States)

    Drozd, M; Baran, J

    2005-10-01

    The polarized IR-microscope spectra of C(NH2)3.HSeO4 small single crystal samples were measured at room temperature. The spectra are discussed with the framework of oriented gas model approximation and group theory. The stretching nuOH vibration of the hydrogen bond with the O...O distance of 2.616 A gives characteristic broad AB-type absorption in the IR spectra. The changes of intensity of the AB bands in function of polarizer angle are described. Detailed assignment for bands derived from stretching and bending modes of selenate anions and guanidinium cations were performed. The observed intensities of these bands in polarized infrared spectra were correlated with theoretical calculation of directional cosines of selected transition dipole moments for investigated crystal. The vibrational studies seem to be helpful in understanding of physical and chemical properties of described compound and also in design of new complexes with exactly defined behaviors.

  11. Mesoporous zeolite and zeotype single crystals synthesized in fluoride media

    DEFF Research Database (Denmark)

    Egeblad, Kresten; Kustova, Marina; Klitgaard, Søren Kegnæs

    2007-01-01

    We report the synthesis and characterization of a series of new mesoporous zeolite and zeotype materials made available by combining new and improved procedures for directly introducing carbon into reaction mixtures with the fluoride route for conventional zeolite synthesis. The mesoporous...... materials were all prepared by hydrothermal crystallization of gels adsorbed on carbon matrices which were subsequently removed by combustion. The procedures presented here resulted in mesoporous zeolite and zeotypes materials with MFI, MEL, BEA, AFI and CHA framework structures. All samples were...... characterized by XRPD, SEM, TEM and N-2 physisorption measurements. For the zeolite materials it A as found that mesoporous MFI and MEL structured single crystals could indeed be crystallized from fluoride media using an improved carbon-templating approach. More importantly, it was found that mesoporous BEA...

  12. Twinning structures in near-stoichiometric lithium niobate single crystals

    International Nuclear Information System (INIS)

    Yao, Shuhua; Chen, Yanfeng

    2010-01-01

    A near-stoichiometric lithium niobate single crystal has been grown by the Czochralski method in a hanging double crucible with a continuous powder supply system. Twins were found at one of the three characteristic growth ridges of the as-grown crystal. The twin structure was observed and analyzed by transmission synchrotron topography. The image shifts ΔX and ΔY in the transmission synchrotron topograph were calculated for the 3 anti 2 anti 12 and 0 anti 222 reflections based on results from high-resolution X-ray diffractometry. It is confirmed that one of the {01 anti 1 anti 2} m planes is the composition face of the twin and matrix crystals. The formation mechanism of these twins is discussed. (orig.)

  13. Giant negative photoresistance of ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Barzola-Quiquia, Jose; Esquinazi, Pablo [Division of Superconductivity and Magnetism, University of Leipzig (Germany); Heluani, Silvia [Laboratorio de Fisica del Solido, FCEyT, Universidad Nacional de Tucuman, 4000 S. M. de Tucuman (Argentina); Villafuerte, Manuel [Dept. de Fisica, FCEyT, Universidad Nacional de Tucuman (Argentina); CONICET, Tucuman (Argentina); Poeppl, Andreas [Division of Magnetic Resonance of Complex Quantum Solids, University of Leipzig, D-04103 Leipzig (Germany)

    2011-07-01

    ZnO is a wide band gap semiconductor exhibiting the largest charge-carrier mobility among oxides. ZnO is a material with potential applications for short-wavelength optoelectronic devices, as a blue light emitting diodes and in spintronics. In this contribution we have measured the temperature dependence (30 K < T < 300 K) of the electrical resistance of ZnO single crystals prepared by hydrothermal method in darkness and under the influence of light in the ultraviolet range. The resistance decreases several orders of magnitude at temperatures T < 200 K after illumination. Electron paramagnetic resonance studies under illumination reveal that the excitation of Li acceptor impurities is the origin for the giant negative photoresistance effect. Permanent photoresistance effect is also observed, which remains many hours after leaving the crystal in darkness.

  14. Neutron transmission and reflection at a copper single crystal

    International Nuclear Information System (INIS)

    Adib, M.; Maayouf, R.M.A.; Abdel-Kawy, A.; Fayek, M.; Habib, N.; Wahba, M.

    1991-01-01

    Neutron transmission and reflection at a copper single crystal cut along the (111) plane were studied with the fixed-scattering-angle spectrometer installed at the ET-RR-1 reactor. The transmission was measured for neutron wavelengths between 0.15 and 0.46 nm and various orientations of the (111) plane with respect to the incident beam. When used as a neutron band pass filter, the crystal is optimally oriented when the neutron beam is incident parallel to the [111] direction. The reflectivity was measured for the (111) plane at 45deg with respect to the incident beam. The results were found to be in reasonable agreement with a value predicted for the reflected intensity at an imperfect crystal with finite absorption. (orig.) [de

  15. IPNS time-of-flight single crystal diffractometer

    International Nuclear Information System (INIS)

    Schultz, A.J.; Teller, R.G.; Williams, J.M.

    1983-01-01

    The single crystal diffractometer (SCD) at the Argonne Intense Pulsed Neutron Source (IPNS) utilizes the time-of-flight (TOF) Laue technique to provide a three-dimensional sampling of reciprocal space during each pulse. The instrument contains a unique neutron position-sensitive 6 Li-glass scintillation detector with an active area of 30 x 30 cm. The three-dimensional nature of the data is very useful for fast, efficient measurement of Bragg intensities and for the studies of superlattice and diffuse scattering. The instrument was designed to achieve a resolution of 2% or better (R = δQ/Q) with 2 THETA > 60 0 and lambda > 0.7A

  16. Thermal conductivity of niobium single crystals in a magnetic field

    International Nuclear Information System (INIS)

    Gladun, C.; Vinzelberg, H.

    1980-01-01

    The thermal conductivity in longitudinal magnetic fields up to 5 T and in the temperature range 3.5 to 15 K is measured in two high purity niobium single crystals having residual resistivity ratios of 22700 and 19200 and orientations of the rod axis [110] and [100]. The investigations show that by means of the longitudinal magnetic field the thermal conductivity may decrease only to a limiting value. In the crystal directions [110] and [100] for the ratio of the thermal conductivity in zero field and the thermal conductivity in the saturation field the temperature-independent factors 1.92 and 1.27, respectively, are determined. With the aid of these factors the thermal conductivity in the normal state is evaluated from the measured values of thermal conductivity below Tsub(c) in the magnetic field. The different conduction and scattering mechanisms are discussed. (author)

  17. Superconductivity in SrNi2P2 single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Park, Tuscon [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory

    2009-01-01

    Heat capacity, magnetic susceptibility, and resistivity of SrNi{sub 2}P{sub 2} single crystals are presented, illustrating the structural transition at 325 K, and bulk superconductivity at 1.4 K. The magnitude of {Tc}, fits to the heat capacity data, the small upper critical field H{sub c2} = 390 Oe, and {kappa} = 2.1 suggests a conventional fully gapped superconductor. With applied pressure we find that superconductivity persists into the so-called 'collapsed tetragonal' phase, although the transition temperature is monotonically suppressed with increasing pressure. This argues that reduced dimensionality can be a mechanism for increasing the transition temperatures of layered NiP, as well as layered FeAs and NiAs, superconductors.

  18. Preparation of high purity yttrium single crystals by electrotransport

    International Nuclear Information System (INIS)

    Volkov, V.T.; Nikiforova, T.V.; Ionov, A.M.; Pustovit, A.N.; Sikharulidse, G.G.

    1981-01-01

    The possibility of obtaining yttrium crystals of high purity by the method of solid state electrotransport (SSE) was investigated in the present work. The behaviour of low contents of iron, aluminium, silicon, tantalum, copper, silver and vanadium as metallic impurities was studied using mass spectrometry. It is shown that all the impurities investigated, except copper, migrate to the anode. During electrotransfer a purification with respect to these impurities by a factor of 4 - 6 is obtained. It is proposed that the diffusion coefficients of the metallic impurities investigated are anomalously high and that the behaviour of the impurities during SSE in adapters necessitates further investigation. By using a three-stage process with intermediate removal of the anode end yttrium single crystals with a resistance ratio rho 293 /rhosub(4.2)=570 were produced. (Auth.)

  19. Microscopic single-crystal refractometry as a function of wavelength

    International Nuclear Information System (INIS)

    DeLoach, L.D.

    1994-01-01

    The refractive indices of crystal fragments 50--200 μm in size can be measured for light wavelengths between 365 and 1100 nm with a spindle-stage refractometer. Established methods from optical crystallograpy are used to orient a crystal on the microscope spindle stage and then to match its refractive index to an immersion fluid. The refractive index of the fluid for the wavelength of light and matching temperature is determined by comparison of a reference crystal on a second spindle axis with the fluid under the match conditions. Investigations of new nonlinear-optical crystals admirably demonstrate the advantages of measuring the refractive index to ± 0.0004 in small single crystals

  20. Induced defects in neutron irradiated GaN single crystals

    International Nuclear Information System (INIS)

    Park, I. W.; Koh, E. K.; Kim, Y. M.; Choh, S. H.; Park, S. S.; Kim, B. G.; Sohn, J. M.

    2005-01-01

    The local structure of defects in undoped, Si-doped, and neutron irradiated free standing GaN bulk crystals, grown by hydride vapor phase epitaxy, has been investigated by employing Raman scattering and cathodoluminescence. The GaN samples were irradiated to a dose of 2 x 10 17 neutrons in an atomic reactor at Korea Atomic Energy Research Institute. There was no appreciable change in the Raman spectra for undoped GaN samples before and after neutron irradiation. However, a forbidden transition, A 1 (TO) mode, appeared for a neutron irradiated Si-doped GaN crystal. Cathodoluminescence spectrum for the neutron irradiated Si-doped GaN crystal became much more broadened than that for the unirradiated one. The experimental results reveal the generation of defects with locally deformed structure in the wurtzite Si-doped GaN single crystal

  1. Quantum nernst effect in a bismuth single crystal

    International Nuclear Information System (INIS)

    Matsuo, M.; Endo, A.; Hatano, N.; Nakamura, H.; Shirasaki, R.; Sugihara, K.

    2009-07-01

    We calculate the phonon-drag contribution to the transverse (Nernst) thermoelectric power S yx in a bismuth single crystal subjected to a quantizing magnetic field. The calculated heights of the Nernst peaks originating from the hole Landau levels and their temperature dependence reproduce the right order of magnitude for those of the pronounced magneto-oscillations recently reported by Behnia et al. A striking experimental finding that S yx is much larger than the longitudinal (Seebeck) thermoelectric power S xx can be naturally explained as the effect of the phonon drag, combined with the well-known relation between the longitudinal and the Hall resistivity ρ xx >> |ρ yx | in a semi-metal bismuth. The calculation that includes the contribution of both holes and electrons suggests that some of the hitherto unexplained minor peaks located roughly at the fractional filling of the hole Landau levels are attributable to the electron Landau levels. (author)

  2. Shock compression experiments on Lithium Deuteride single crystals.

    Energy Technology Data Exchange (ETDEWEB)

    Knudson, Marcus D.; Desjarlais, Michael Paul; Lemke, Raymond W.

    2014-10-01

    S hock compression exper iments in the few hundred GPa (multi - Mabr) regime were performed on Lithium Deuteride (LiD) single crystals . This study utilized the high velocity flyer plate capability of the Sandia Z Machine to perform impact experiments at flyer plate velocities in the range of 17 - 32 km/s. Measurements included pressure, density, and temperature between %7E200 - 600 GPa along the Principal Hugoniot - the locus of end states achievable through compression by large amplitude shock waves - as well as pressure and density of re - shock states up to %7E900 GPa . The experimental measurements are compared with recent density functional theory calculations as well as a new tabular equation of state developed at Los Alamos National Labs.

  3. Optical properties of Sulfur doped InP single crystals

    Science.gov (United States)

    El-Nahass, M. M.; Youssef, S. B.; Ali, H. A. M.

    2014-05-01

    Optical properties of InP:S single crystals were investigated using spectrophotometric measurements in the spectral range of 200-2500 nm. The absorption coefficient and refractive index were calculated. It was found that InP:S crystals exhibit allowed and forbidden direct transitions with energy gaps of 1.578 and 1.528 eV, respectively. Analysis of the refractive index in the normal dispersion region was discussed in terms of the single oscillator model. Some optical dispersion parameters namely: the dispersion energy (Ed), single oscillator energy (Eo), high frequency dielectric constant (ɛ∞), and lattice dielectric constant (ɛL) were determined. The volume and the surface energy loss functions (VELF & SELF) were estimated. Also, the real and imaginary parts of the complex conductivity were calculated.

  4. White beam synchrotron fractography of molybdenum and niobium single crystals

    International Nuclear Information System (INIS)

    Bilello, J.C.; Hmelo, A.B.

    1983-01-01

    It has been demonstrated that a White Beam Synchrotron reflection technique can be used to characterize the fracture surface of Mo and Nb single crystals. This technique when used in conjunction with Berg-Barrett (or in the future monochromatic synchrotron topography) gives detailed information which correlates the internal defect structure to the cleavage surface morphology. In particular, synchrotron fractography has revealed the full extent of the plastic zone associated with a precursor crack, has clearly identified the nature of the initial crack where more than one precursor could have existed, and give detailed information on the extent of twinning and microtwinning. In comparison with other fractography methods for such semi-brittle metals the White Beam Synchrotron method not only achieves rapid data collection, but also provides internal defect structure correlation non-destructively. (author)

  5. Trapped electrons in irradiated single crystals of polyhydroxy compounds

    International Nuclear Information System (INIS)

    Box, H.C.; Budzinski, E.E.; Freund, H.G.; Potter, W.R.

    1979-01-01

    The intermolecular trapping of electrons has been observed in single crystals of dulcitol and L(+) arabinose x-irradiated at 4.2 0 K. Attribution of a major component of the ESR absorption to trapped electrons is based upon the character of the hyperfine pattern, which arises from multiple anisotropic hyperfine interactions with exchangeable protons, and on the g value of the absorption, which is always less than the free spin value. The removal of the trapped electron absorption upon irradiation with visible light has also been demonstrated. In these experiments all of the electrons are trapped in identical sites. This circumstance provides some important advantages in the study of the factors affecting the stabilization of charge in an environment of polarizable molecules

  6. Growth of single-crystal YAG fiber optics.

    Science.gov (United States)

    Nie, Craig D; Bera, Subhabrata; Harrington, James A

    2016-07-11

    Single-crystal YAG (Y3Al5O12) fibers have been grown by the laser heated pedestal growth technique with losses as low as 0.3 dB/m at 1.06 μm. These YAG fibers are as long as about 60 cm with diameters around 330 μm. The early fibers were grown from unoriented YAG seed fibers and these fibers exhibited facet steps or ridges on the surface of the fiber. However, recently we have grown fibers using an oriented seed to grow step-free fibers. Scattering losses made on the fibers indicate that the scattering losses are equal to about 30% of the total loss.

  7. Platinum single crystal electrodes for the electrocatalysis of methane oxidation

    Directory of Open Access Journals (Sweden)

    Mayara Munaretto

    2011-03-01

    Full Text Available The main objective of this paper is to characterize the voltammetric profiles of platinum single crystals of low Miller indexes Pt(100 and Pt(110 and study their catalytic activities on the oxidation of methane. In this way, it was developed a metallic surface modified by presence of other metal oxide, which presents catalytic activity for this reaction. It is well known that the electrooxidation of methane (CH4 leads mainly to the formation of CO2 and H2O, however, the oxidation can also lead to the formation of CO, a reaction intermediate that has strong interaction with metal surfaces, such as platinum. This molecule tends to accumulate on the platinum surface and to passive it, due to the self-poisoning, decreasing its catalytic activity. Therefore, the main aim of this work was the development of a platinum electrode modified by deposition of titanium oxide, which presented electrocatalytic properties for the oxidation of methane.

  8. Phonon interactions with methyl radicals in single crystals

    Directory of Open Access Journals (Sweden)

    James W. Wells

    2017-04-01

    Full Text Available The high temperature ESR spectra’s anomalous appearance at very low temperatures for the methyl radical created in single crystals is explained by magnetic dipole interactions with neighboring protons. These protons acting via phonon vibrations induce resonant oscillations with the methyl group to establish a very temperature sensitive ‘‘relaxation’’ mode that allows the higher energy ‘‘E’’ state electrons with spin 12 to ‘‘decay’’ into ‘‘A’’ spin 12 states. Because of the amplitude amplification with temperature, the ‘‘E’’ state population is depleted and the ‘‘A’’ state population augmented to produce the high temperature ESR spectrum. This phenomenon is found to be valid for all but the very highest barriers to methyl group tunneling. In support, a time dependent spin population study shows this temperature evolution in the state populations under this perturbation.

  9. Neutron transmission and reflection at a copper single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Adib, M.; Maayouf, R.M.A.; Abdel-Kawy, A.; Fayek, M.; Habib, N. (Atomic Energy Establishment, Cairo (Egypt). Reactor and Neutron Physics Dept.); Wahba, M. (Ain Shams Univ., Cairo (Egypt). Dept. of Engineering Physics and Mathematics)

    1991-06-01

    Neutron transmission and reflection at a copper single crystal cut along the (111) plane were studied with the fixed-scattering-angle spectrometer installed at the ET-RR-1 reactor. The transmission was measured for neutron wavelengths between 0.15 and 0.46 nm and various orientations of the (111) plane with respect to the incident beam. When used as a neutron band pass filter, the crystal is optimally oriented when the neutron beam is incident parallel to the (111) direction. The reflectivity was measured for the (111) plane at 45deg with respect to the incident beam. The results were found to be in reasonable agreement with a value predicted for the reflected intensity at an imperfect crystal with finite absorption. (orig.).

  10. Neutron transmission of single-crystal sapphire filters

    International Nuclear Information System (INIS)

    Adib, M.; Kilany, M.; Habib, N.; Fathallah, M.

    2005-01-01

    An additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for single-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula fits and experimental data. We discuss the use of sapphire single crystal as a thermal neutron filter in terms of the optimum crystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons. (author)

  11. Neutron Transmission of Single-crystal Sapphire Filters

    Science.gov (United States)

    Adib, M.; Kilany, M.; Habib, N.; Fathallah, M.

    2005-05-01

    An additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for single-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula and experimental data. We discuss the use of sapphire single crystal as a thermal neutron filter in terms of the optimum cystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons.

  12. Neutron transmission of single-crystal sapphire filters

    International Nuclear Information System (INIS)

    Adib, M.; Kilany, M.; Habib, N.; Fathallah, M.

    2004-01-01

    A simple additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for mono-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula fits and experimental data. We discuss the use of sapphire single-crystal as a thermal neutron filter in terms of the optimum crystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons

  13. Angular correlation of annihilation photons in ice single crystals

    DEFF Research Database (Denmark)

    Mogensen, O. E.; Kvajic, G.; Eldrup, Morten Mostgaard

    1971-01-01

    -lattice vectors g⃗ on the direction perpendicular to the slits and the sample surface. The relative area of the central plus the side peaks was (15.2 ± 0.4)% for all curves. All the peaks are interpreted as due to parapositronium annihilation. The side peaks are explained as evidence for the positronium center......Linear-slit angular-correlation curves were obtained at - 148 °C for the [0001], [10¯10], and [11¯20] directions in single crystals of ice. Besides the narrow central peak, pronounced narrow side peaks were also observed. They occurred at angles θ=2πℏgz/mc, where gz is the projection of reciprocal...

  14. Effect of neutron irradiation on single crystal V3Si

    International Nuclear Information System (INIS)

    Viswanathan, R.; Caton, R.; Cox, D.E.; Guha, A.; Sarachik, M.P.; Smith, F.W.; Testardi, L.R.

    1977-01-01

    We We have investigated the effect of successive neutron irradiation up to a fluence of approximately 2 x 10 19 n/cm 2 , by measurements of heat capacity, susceptibility, resistivity, acoustic velocity and neutron diffraction in a single crystal V 3 Si. We find that for low level doses (phi t greater than or equal to 3.5 x 10 18 n/cm 2 ) (a) the structural transformation is very sensitive, whereas the suerconducting transition temperature, T/sub c/, is hardly affected, and (b) except for low temperature heat capacity, most of the other measurements show very little change. For the highest fluence of 2 x 10 19 n/cm 2 used to date, the T/sub c/ dropped to 7.5 K with large changes in the linear heat capacity coefficient, magnetic susceptibility and sound velocity. These results are discussed briefly in this paper

  15. Neutron radiation damage in NbO single crystals

    International Nuclear Information System (INIS)

    Onozuka, T.; Koiwa, M.; Ishikawa, Y.; Yamaguchi, S.; Hirabayashi, M.

    1977-01-01

    The effect of neutron irradiation and subsequent recovery has been studied for Nb0 single crystals of a defective NaCl structure containing 25% vacancies of niobium and oxygen. A very large increase (about 1%) in the lattice constant is observed after irradiation of 1.5 x 10 19 and 1 x 10 20 nvt (> 1 MeV). From the intensity measurements of x-ray and neutron diffraction, it is revealed that the knock-on atoms fill preferentially their respective vacant sites; Nb atoms occupy Nb-vacancies, and 0 atoms occupy 0-vacancies with nearly the same probabilities; 0.53 for 1.5 x 10 19 nvt. The mean threshold energy for displacement is estimated to be about 3 eV. (author)

  16. Diffusion of Ti in α-Zr single crystals

    International Nuclear Information System (INIS)

    Hood, G.M.; Zou, H.; Schultz, R.J.; Jackman, J.A.

    1994-11-01

    Ti diffusion coefficients (D) have been measured in nominally pure αZr single crystals (773-1124 K) in directions both parallel (D pa ) and perpendicular (D pe , few data) to the c-axis: tracer techniques and secondary ion mass spectrometry were used to determine the diffusion profiles. The results show a temperature dependence which suggests two regions of diffusion behaviour. Above 1035 K, region I, diffusion conforms to the expectations of intrinsic behaviour with normal Arrhenius law constants: D pa = 1.7 x 10 -3 exp(-2.93 ± 0.08 eV/kΤ) m 2 /s. Below 1035 K, region II, D's are enhanced with respect to an extrapolation of region I behaviour. The region II data are associated with extrinsic effects. (author). 13 refs., 1 tab., 3 figs

  17. Fishtail effect in twinned and detwinned YBCO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boudissa, M. [Universite Ferhat Abbas, Faculte des Sciences de l' Ingenieur, Setif (Algeria); Halimi, R. [Universite Mentouri, Unite de Recherche de Physique des Materiaux, Constantine (Algeria); Frikach, K.; Senoussi, S. [Universite Paris-Sud, Laboratoire de Physique des Solides, Orsay (France)

    2006-09-15

    We have studied the magnetization hysteresis loops of a twinned and detwinned single crystals in a temperature range between 4.2 and 100 K and a magnetic field (H) range between 0 and 6 T. We carried out relaxation measurements on the samples at different temperatures and magnetic fields. We investigated the twin pinning as a function of temperature (T) and the fishtail anomaly in the critical current density of the two samples. We tried in this study to confirm or infirm the different models which explain the fishtail effect by confronting them to our experimental results We found that the collective creep theory is consistent with the results of our experiment in the field region where the magnetization is at its minimum. This field marks a crossover between the small and large bundle pinning regimes. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Fishtail effect in twinned and detwinned YBCO single crystals

    International Nuclear Information System (INIS)

    Boudissa, M.; Halimi, R.; Frikach, K.; Senoussi, S.

    2006-01-01

    We have studied the magnetization hysteresis loops of a twinned and detwinned single crystals in a temperature range between 4.2 and 100 K and a magnetic field (H) range between 0 and 6 T. We carried out relaxation measurements on the samples at different temperatures and magnetic fields. We investigated the twin pinning as a function of temperature (T) and the fishtail anomaly in the critical current density of the two samples. We tried in this study to confirm or infirm the different models which explain the fishtail effect by confronting them to our experimental results We found that the collective creep theory is consistent with the results of our experiment in the field region where the magnetization is at its minimum. This field marks a crossover between the small and large bundle pinning regimes. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Optical absorption in gel grown cadmium tartrate single crystals

    International Nuclear Information System (INIS)

    Arora, S K; Kothari, A J; Patel, R G; Chauha, K M; Chudasama, B N

    2006-01-01

    Single crystals of cadmium tartrate pentahydrate (CTP) have been grown by the famous gel technique. The slow and controlled reaction between Cd 2+ and (C 4 H 4 O 6 ) 2- ions in silica hydrogel results in formation of the insoluble product, CdC 4 H 4 O 6 .5H 2 O. Optical absorption spectra have been recorded in the range 200 to 2500 nm. Fundamental absorption edge for electronic transition has been analyzed. The direct allowed transition is found to be present in the region of relatively higher photon energy. Analysis of the segments of α 1/2 versus hν graph has been made to separate individual contribution of phonons. The phonons involved in the indirect transition are found to correspond to 335 and 420 cm -1 . Scattering of charge carriers in the lattice is found due to acoustic phonons

  20. Radiation damage mechanisms in single crystals of creatine monohydrate

    International Nuclear Information System (INIS)

    Wells, J.W.; Ko, C.

    1978-01-01

    ENDOR spectroscopy is utilized to define the temperature dependent sequence of molecular fragmentation processes occuring in x-irradiated single crystals of creatine monohydrate. Two conformations of the primary reduction product =OOC--C(H 2 ) --N(CH) 3 --C(NH 2 ) 2 + are found to undergo a series of subtle changes before deamination. The resultant radical -OOC--CH 2 then induces hydrogen abstraction to form a final room temperature product - OOC--CH--N(CH 3 ) --C(NH 2 ) + . An unknown initial oxidation species is found to decarboxylate forming the radical H 2 C--N(CH 3 ) --C(NH 2 ) 2 + which, although similar to the deamination product, exists at room temperature. The stability of this species is attributed to a delocalization of spin indicated by calculation and measurement

  1. Temperature and fluence effects in lead implanted cobalt single crystals

    International Nuclear Information System (INIS)

    Johansen, A.; Sarholt-Kristensen, L.; Johnson, E.; Steenstrup, S.; Chernysh, V.S.

    1988-01-01

    The channeled sputtering yields of the hcp and fcc phases of cobalt depend on the crystal structure and the radiation induced damage. Earlier irradiations of cobalt with argon ions channeled in the hcp direction give sputtering yields higher than expected in the temperature range 100-350deg C. This effect was attributed to a combination of radiation induced damage and a possible implantation induced hcp --> fcc phase transition. Sputtering yields for cobalt single crystals irradiated with 150 keV Pb + ions along the direction of the hcp phase and the direction of the fcc phase have been measured using the weightloss method. The radiation damage and the amount of lead retained in the implanted surface has been investigated by 'in situ' RBS/channeling analysis. Measured partial sputtering yields of lead ≅ 1 atom/ion indicate preferential sputtering of lead atoms. (orig.)

  2. X-ray conductivity of ZnSe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Degoda, V. Ya., E-mail: degoda@univ.kiev.ua; Podust, G. P. [Taras Shevchenko Kyiv National University, Physics Department (Ukraine)

    2016-05-15

    The experimental I–V and current–illuminance characteristics of the X-ray conductivity and X-ray luminescence of zinc-selenide single crystals feature a nonlinear shape. The performed theoretical analysis of the kinetics of the X-ray conductivity shows that even with the presence of shallow and deep traps for free charge carriers in a semiconductor sample, the integral characteristics of the X-ray conductivity (the current–illuminance and I–V dependences) should be linear. It is possible to assume that the nonlinearity experimentally obtained in the I–V and current–illuminance characteristics can be caused by features of the generation of free charge carriers upon X-ray irradiation, i.e., the generation of hundreds of thousands of free charge carriers of opposite sign in a local region with a diameter of <1 μm and Coulomb interaction between the free charge carriers of opposite signs.

  3. Temperature dependence of magnetoresistance in copper single crystals

    Science.gov (United States)

    Bian, Q.; Niewczas, M.

    2018-03-01

    Transverse magnetoresistance of copper single crystals has been measured in the orientation of open-orbit from 2 K to 20 K for fields up to 9 T. The experimental Kohler's plots display deviation between individual curves below 16 K and overlap in the range of 16 K-20 K. The violation of the Kohler's rule below 16 K indicates that the magnetotransport can not be described by the classical theory of electron transport on spherical Fermi surface with a single relaxation time. A theoretical model incorporating two energy bands, spherical and cylindrical, with different relaxation times has been developed to describe the magnetoresistance data. The calculations show that the electron-phonon scattering rates at belly and neck regions of the Fermi surface have different temperature dependencies, and in general, they do not follow T3 law. The ratio of the relaxation times in belly and neck regions decreases parabolically with temperature as A - CT2 , with A and C being constants.

  4. The characterization of tungsten disulfide single crystals doped with gold

    International Nuclear Information System (INIS)

    Dumcenco, D.O.; Huang, Y.S.; Tiong, K.K.; Liang, C.H.; Chen, C.H.

    2007-01-01

    Single crystals of WS 2 doped with gold (WS 2 :Au) have been grown by the chemical vapour transport method using iodine as a transporting agent. Hall measurements indicate that the samples are p-type in nature. The doping effect of the materials are characterized by conductivity, surface photovoltage and piezo reflectance measurements. The higher conductivity respect to that of the undoped one suggests that more charge carriers are available for conduction in the doped compound. The surface photovoltage spectrum reveals an impurity level located below the A exciton. The direct band-edge excitonic transition energies for WS 2 :Au show redshifts and the broadening parameters of the excitonic transition features increase due to impurity scattering. (authors)

  5. Comprehensive studies on irradiated single-crystal diamond sensors

    Energy Technology Data Exchange (ETDEWEB)

    Stegler, Martin [DESY, Zeuthen (Germany)

    2015-07-01

    Single-crystal diamond sensors are used as part of the Beam and Radiation Instrumentation and Luminosity (BRIL) projects of the CMS experiment. Due to an upgrade of the Fast Beam Conditions Monitor (BCM1F) these diamond sensors are exchanged and the irradiated ones are now used for comprehensive studies. Current over voltage (IV), current over time (CT) and charge collection efficiency (CCE) measurements were performed for a better understanding of the radiation damage incurred during operation and to compensate in the future. The effect of illumination with various light sources on the charge collection efficiency was investigated and led to interesting results. Intensity and wavelength of the light were varied for deeper insight of polarization effects.

  6. Photoinduced surface voltage mapping study for large perovskite single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaojing; Liu, Yucheng; Gao, Fei; Yang, Zhou [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Laboratory for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi' an 710062 (China); Liu, Shengzhong, E-mail: liusz@snnu.edu.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Laboratory for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi' an 710062 (China); Dalian Institute of Chemical Physics, iChEM, Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian 116023 (China)

    2016-05-02

    Using a series of illumination sources, including white light (tungsten-halogen lamp), 445-nm, 532-nm, 635-nm, and 730-nm lasers, the surface photovoltage (SPV) images were mapped for centimeter-sized CH{sub 3}NH{sub 3}PbX{sub 3} (X = Cl, Br, I) perovskite single crystals using Kelvin probe force microscopy. The significant SPV signals were observed to be wavelength-dependent. We attribute the appreciable SPV to the built-in electric field in the space charge region. This study shines light into the understanding of photoinduced charge generation and separation processes at nanoscale to help advance the development of perovskite solar cells, optoelectronics, laser, photodetector, and light-emitting diode (LED).

  7. Isothermal equation of state of a lithium fluoride single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.Y.

    1975-01-01

    An isothermal equation of state of a LiF single crystal was determined from length change measurements of the specimen as a function of hydrostatic pressure up to approximately 7 kbars at 28 to 41/sup 0/C. The length change was measured with an accuracy of approximately 500 A by using a Fabry Perot type He--Ne laser interferometer for a 1-m long specimen at temperatures constant to less than 0.002/sup 0/C. Several two- and three-parameter equations of state were used in analyzing the measured pressure-volume data. The computer fit for each equation of state determines not only the value of its parameters but also the standard deviations associated with them and one dependent variable, either pressure or volume. With the parameters determined, the equations of state are extrapolated to approximately 5 megabars in order to see discrepancies. Using the Born model of ionic solids, two equations of state were derived both from a power law potential and from an exponential form for the repulsive energy of alkali metal halides and used to fit the pressure-volume data of a LiF single crystal. They are also extrapolated to approximately 5 megabars. The Birch's two-parameter equation and the Grover, Getting, and Kennedy equation are indistinguishable from the two equations of state derived from the Born model for pressures approximately equal to or less than 800 kbars within +-20 kbars. The above four equations of state also fit closely the Pagannone and Drickamer static compression data, the Christian shock wave data, and the Kormer et al. shock wave data. The isothermal bulk modulus and its first pressure derivative at atmospheric pressure and 28.83/sup 0/C are 664.5 +- 0.5 kbars and 5.40 +- 0.18, respectively, in close agreement with those values ultrasonically measured by R. A. Miller and C. S. Smith. (auth)

  8. A discrete dislocation–transformation model for austenitic single crystals

    International Nuclear Information System (INIS)

    Shi, J; Turteltaub, S; Remmers, J J C; Van der Giessen, E

    2008-01-01

    A discrete model for analyzing the interaction between plastic flow and martensitic phase transformations is developed. The model is intended for simulating the microstructure evolution in a single crystal of austenite that transforms non-homogeneously into martensite. The plastic flow in the untransformed austenite is simulated using a plane-strain discrete dislocation model. The phase transformation is modeled via the nucleation and growth of discrete martensitic regions embedded in the austenitic single crystal. At each instant during loading, the coupled elasto-plasto-transformation problem is solved using the superposition of analytical solutions for the discrete dislocations and discrete transformation regions embedded in an infinite homogeneous medium and the numerical solution of a complementary problem used to enforce the actual boundary conditions and the heterogeneities in the medium. In order to describe the nucleation and growth of martensitic regions, a nucleation criterion and a kinetic law suitable for discrete regions are specified. The constitutive rules used in discrete dislocation simulations are supplemented with additional evolution rules to account for the phase transformation. To illustrate the basic features of the model, simulations of specimens under plane-strain uniaxial extension and contraction are analyzed. The simulations indicate that plastic flow reduces the average stress at which transformation begins, but it also reduces the transformation rate when compared with benchmark simulations without plasticity. Furthermore, due to local stress fluctuations caused by dislocations, martensitic systems can be activated even though transformation would not appear to be favorable based on the average stress. Conversely, the simulations indicate that the plastic hardening behavior is influenced by the reduction in the effective austenitic grain size due to the evolution of transformation. During cyclic simulations, the coupled plasticity

  9. Third order nonlinear optical properties of a paratellurite single crystal

    Science.gov (United States)

    Duclère, J.-R.; Hayakawa, T.; Roginskii, E. M.; Smirnov, M. B.; Mirgorodsky, A.; Couderc, V.; Masson, O.; Colas, M.; Noguera, O.; Rodriguez, V.; Thomas, P.

    2018-05-01

    The (a,b) plane angular dependence of the third-order nonlinear optical susceptibility, χ(3) , of a c-cut paratellurite (α-TeO2) single crystal was quantitatively evaluated here by the Z-scan technique, using a Ti:sapphire femtosecond laser operated at 800 nm. In particular, the mean value Re( ⟨χ(3)⟩a,b )(α-TeO2) of the optical tensor has been extracted from such experiments via a direct comparison with the data collected for a fused silica reference glass plate. A R e (⟨χ(3)⟩(a,b )(α-TeO2)):R e (χ(3))(SiO2 glass) ratio roughly equal to 49.1 is found, and our result compares thus very favourably with the unique experimental value (a ratio of ˜50) reported by Kim et al. [J. Am. Ceram. Soc. 76, 2486 (1993)] for a pure TeO2 glass. In addition, it is shown that the angular dependence of the phase modulation within the (a,b) plane can be fully understood in the light of the strong dextro-rotatory power known for TeO2 materials. Taking into account the optical activity, some analytical model serving to estimate the diagonal and non-diagonal components of the third order nonlinear susceptibility tensor has been thus developed. Finally, Re( χxxxx(3) ) and Re( χxxyy(3) ) values of 95.1 ×10-22 m 2/V2 and 42.0 ×10-22 m2/V2 , respectively, are then deduced for a paratellurite single crystal, considering fused silica as a reference.

  10. Single crystal diamond detectors grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    Tuve, C.; Angelone, M.; Bellini, V.; Balducci, A.; Donato, M.G.; Faggio, G.; Marinelli, M.; Messina, G.; Milani, E.; Morgada, M.E.; Pillon, M.; Potenza, R.; Pucella, G.; Russo, G.; Santangelo, S.; Scoccia, M.; Sutera, C.; Tucciarone, A.; Verona-Rinati, G.

    2007-01-01

    The detection properties of heteropitaxial (polycrystalline, pCVD) and homoepitaxial (single crystal, scCVD) diamond films grown by microwave chemical vapor deposition (CVD) in the Laboratories of Roma 'Tor Vergata' University are reported. The pCVD diamond detectors were tested with α-particles from different sources and 12 C ions produced by 15MV Tandem accelerator at Southern National Laboratories (LNS) in Catania (Italy). pCVDs were also used to monitor 14MeV neutrons produced by the D-T plasma at Joint European Torus (JET), Culham, U.K. The limit of pCVDs is the poor energy resolution. To overcome this problem, we developed scCVD diamonds using the same reactor parameters that optimized pCVD diamonds. scCVD were grown on a low cost (100) HPHT single crystal substrate. A detector 110μm thick was tested under α-particles and under 14MeV neutron irradiation. The charge collection efficiency spectrum measured under irradiation with a triple α-particle source shows three clearly resolved peaks, with an energy resolution of about 1.1%. The measured spectra under neutron irradiation show a well separated C(n,α 0 ) 9 Be12 reaction peak with an energy spread of 0.5MeV for 14.8MeV neutrons and 0.3MeV for 14.1MeV neutrons, which are fully compatible with the energy spread of the incident neutron beams

  11. Low propagation loss in a one-port SAW resonator fabricated on single-crystal diamond for super-high-frequency applications.

    Science.gov (United States)

    Fujii, Satoshi; Odawara, Tatsuya; Yamada, Haruya; Omori, Tatsuya; Hashimoto, Ken-Ya; Torii, Hironori; Umezawa, Hitoshi; Shikata, Shinichi

    2013-05-01

    Diamond has the highest known SAW phase velocity, sufficient for applications in the gigahertz range. However, although numerous studies have demonstrated SAW devices on polycrystalline diamond thin films, all have had much larger propagation loss than single-crystal materials such as LiNbO3. Hence, in this study, we fabricated and characterized one-port SAW resonators on single-crystal diamond substrates synthesized using a high-pressure and high-temperature method to identify and minimize sources of propagation loss. A series of one-port resonators were fabricated with the interdigital transducer/ AlN/diamond structure and their characteristics were measured. The device with the best performance exhibited a resonance frequency f of 5.3 GHz, and the equivalent circuit model gave a quality factor Q of 5509. Thus, a large fQ product of approximately 2.9 × 10(13) was obtained, and the propagation loss was found to be only 0.006 dB/wavelength. These excellent properties are attributed mainly to the reduction of scattering loss in a substrate using a single-crystal diamond, which originated from the grain boundary of diamond and the surface roughness of the AlN thin film and the diamond substrate. These results show that single-crystal diamond SAW resonators have great potential for use in low-noise super-high-frequency oscillators.

  12. Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates.

    Science.gov (United States)

    Chadwick, F Mark; McKay, Alasdair I; Martinez-Martinez, Antonio J; Rees, Nicholas H; Krämer, Tobias; Macgregor, Stuart A; Weller, Andrew S

    2017-08-01

    Single-crystal to single-crystal solid/gas reactivity and catalysis starting from the precursor sigma-alkane complex [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(η 2 η 2 -NBA)][BAr F 4 ] (NBA = norbornane; Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ) is reported. By adding ethene, propene and 1-butene to this precursor in solid/gas reactions the resulting alkene complexes [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(alkene) x ][BAr F 4 ] are formed. The ethene ( x = 2) complex, [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(ethene) 2 ][BAr F 4 ]-Oct , has been characterized in the solid-state (single-crystal X-ray diffraction) and by solution and solid-state NMR spectroscopy. Rapid, low temperature recrystallization using solution methods results in a different crystalline modification, [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(ethene) 2 ][BAr F 4 ]-Hex , that has a hexagonal microporous structure ( P 6 3 22). The propene complex ( x = 1) [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(propene)][BAr F 4 ] is characterized as having a π-bound alkene with a supporting γ-agostic Rh···H 3 C interaction at low temperature by single-crystal X-ray diffraction, variable temperature solution and solid-state NMR spectroscopy, as well as periodic density functional theory (DFT) calculations. A fluxional process occurs in both the solid-state and solution that is proposed to proceed via a tautomeric allyl-hydride. Gas/solid catalytic isomerization of d 3 -propene, H 2 C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111

  13. Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride

    Science.gov (United States)

    2015-08-01

    ARL-RP-0528 ● AUG 2015 US Army Research Laboratory Sample Size Induced Brittle-to- Ductile Transition of Single-Crystal Aluminum...originator. ARL-RP-0528 ● AUG 2015 US Army Research Laboratory Sample Size Induced Brittle-to- Ductile Transition of Single-Crystal...Sample Size Induced Brittle-to- Ductile Transition of Single-Crystal Aluminum Nitride 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  14. Cryogenic Fluid Transfer Components Using Single Crystal Piezoelectric Actuators, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Cryogenic fluid transfer components using single crystal piezoelectric actuators are proposed to enable low thermal mass, minimal heat leak, low power consumption...

  15. Advanced Electroactive Single Crystal and Polymer Actuator Concepts for Passive Optics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes large stroke and high precision piezoelectric single crystal and electroactive polymer actuator concepts?HYBrid Actuation System (HYBAS)...

  16. Cryogenic Fluid Transfer Components Using Single Crystal Piezoelectric Actuators, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Cryogenic fluid transfer components using single crystal piezoelectric actuators are proposed to enable low thermal mass, minimal heat leak, low power consumption...

  17. Growth of single crystals of BaFe12O19 by solid state crystal growth

    International Nuclear Information System (INIS)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-01-01

    Single crystals of BaFe 12 O 19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe 12 O 19 are buried in BaFe 12 O 19 +1 wt% BaCO 3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe 12 O 19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe 12 O 19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth. - Highlights: • Single crystals of BaFe 12 O 19 are grown by solid state crystal growth. • A single crystal up to ∼130 μm thick (c-axis direction) grows on the seed crystal. • The single crystal and surrounding ceramic matrix have similar composition. • Micro-Raman scattering shows the single crystal has the BaFe 12 O 19 structure.

  18. Nanomechanical investigation of ion implanted single crystals - Challenges, possibilities and pitfall traps related to nanoindentation

    Science.gov (United States)

    Kurpaska, Lukasz

    2017-10-01

    Nanoindentation technique have developed considerably over last thirty years. Nowadays, commercially available systems offer very precise measurement in nano- and microscale, environmental noise cancelling (or at least noise suppressing), in situ high temperature indentation in controlled atmosphere and vacuum conditions and different additional options, among them dedicated indentation is one of the most popular. Due to its high precision, and ability to measure mechanical properties from very small depths (tens of nm), this technique become quite popular in the nuclear society. It is known that ion implantation (to some extent) can simulate the influence of neutron flux. However, depth of the material damage is very limited resulting in creation of thin layer of modified material over unmodified bulk. Therefore, only very precise technique, offering possibility to control depth of the measurement can be used to study functional properties of the material. For this reason, nanoindentation technique seems to be a perfect tool to investigate mechanical properties of ion implanted specimens. However, conducting correct nanomechanical experiment and extracting valuable mechanical parameters is not an easy task. In this paper a discussion about the nanoindentation tests performed on ion irradiated YSZ single crystal is presented. The goal of this paper is to discuss possible traps when studying mechanical properties of such materials and thin coatings.

  19. Observation of the Josephson effect on Ba-122 iron pnictide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hasan, Noor; Schmidt, Stefan; Doering, Sebastian; Tympel, Volker; Schmidl, Frank; Seidel, Paul [Friedrich-Schiller- Universitaet Jena, Institut fuer Festkoerperphysik, Helmholtzweg 5, 07743 Jena (Germany); Wolf, Thomas [Karlsruhe Institute of Technology, Institut fuer Festkoerperphysik, Hermann-von- Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2015-07-01

    Since the discovery of the first Fe-based superconductors in 2006, extensive effort has been directed characterizing and modeling the novel properties of these exotic materials. Therefore Josephson junction offer ways to investigate the fundamental properties of iron pnictides. We use Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} single crystals, prepared by a self-flux method, with an optimal Co concentration of 0.065 (critical temperature T{sub c}=23.5 K). We realize Josephson junctions along the c-axis. To prepare them a newly developed surface polishing as well as standard thin film technologies are used. The artificial barrier consists of thin sputtered layers of various materials, normal conductors as well as insulators. A thermally evaporated double layer film of Pb and In was used as the counter electrode. For the characterization of the Josephson effect we will present temperature dependent I-V characteristics as well as I{sub c} R{sub n} - T dependencies and measurements under microwave radiation, including. Additionally results from tunneling and Andreev spectroscopy i.e temperature dependent dI/dV - V spectra are shown.

  20. Structure of cleaved (001) USb2 single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shao-ping [Los Alamos National Laboratory; Hawley, Marilyn [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Stockum, Phil B [STANFORD UNIV.; Manoharan, Hari C [STANFORD UNIV

    2009-01-01

    We have achieved what we believe to be the first atomic resolution STM images for a uranium compound taken at room temperature. The a, b, and c lattice parameters in the images confirm that the USb{sub 2} crystals cleave on the (001) basal plane as expected. The a and b dimensions were equal, with the atoms arranged in a cubic pattern. Our calculations indicate a symmetric cut between Sb planes to be the most favorable cleavage plane and U atoms to be responsible for most of the DOS measured by STM. Some strange features observed in the STM will be discussed in conjunction with ab initio calculations. The purpose of this work is to demonstrate the power of scanning tunneling microscopy (STM) techniques combined with a theoretical underpinning to determine the surface atomic structure and properties of actinide materials, such as the quasi 2-dimensional uranium dipnictide USb{sub 2} single crystal, thereby contributing to the understanding of their surface structural and electronic properties. The members of this interesting UX{sub 2} (X=P, As, Sb, Bi) series of compounds display dual localized and itinerant 5f electron behavior within the same compound due to the hybridization of the 5f orbitals with the conduction band. With the exception of UO{sub 2}, which has to be studied at elevated temperature to generate enough carriers for STM imaging, STM techniques have not been applied successfully to the characterization of the surface atomic structure of any other single crystal actinide compound, to the best of our knowledge. However, STM has been used to a limited extent for the study of some cerium compounds. STM probes electronic properties at the atomic level and can directly provide information about the local density of filled and empty states (LDOS) states simultaneously. A STM topograph provides the local atomic arrangement and spacing of the atoms on the surface, local defect structures (e.g. steps, vacancies, and kink sites) and the presence of contaminants

  1. Growth and characterisation of lead iodide single crystals

    International Nuclear Information System (INIS)

    Tonn, Justus

    2012-01-01

    The work in hand deals with the growth and characterisation of lead iodide (PbI 2 ) single crystals. PbI 2 is regarded as a promising candidate for low-noise X- and gamma ray detection at room temperature. Its benefits if compared to conventional materials like HgI 2 , CdTe, Si, or GaAs lie in a band gap energy of 2.32 eV, an excellent ability to absorb radiation, and a high electrical resistivity. For an application of PbI 2 as detector material the growth and characterisation of crystals with high chemical and structural quality is extremely challenging. In light of this, the effectiveness of zone purification of the PbI 2 used for crystal growth was confirmed by spectroscopic analysis. Furthermore, technological aspects during processing of purified PbI 2 were investigated. With the help of thermal analysis, a correlation was found between the degree of exposing the source material to oxygen from the air and the structural quality of the resulting crystals. A hydrogen treatment was applied to PbI 2 as an effective method for the removal of oxidic pollutions, which resulted in a significant reduction of structural defects like polytypic growth and stress-induced cracking. The growth of PbI 2 single crystals was, among others, carried out by the Bridgman-Stockbarger method. In this context, much effort was put on the investigation of influences resulting from the design and preparation of ampoules. For the first time, crystal growth of PbI 2 was also carried out by the Czochralski method. If compared to the Bridgman-Stockbarger method, the Czochralski technique allowed a significantly faster growth of nearly crack-free crystals with a reproducible predetermination of crystallographic orientation. By an optimised sample preparation of PbI 2 , surface orientations perpendicular to the usually cleaved (0001) plane were realised. It is now possible to determine the material properties along directions which were so far not accessible. Thus, for example, the ratio of

  2. Frictional properties of single crystals HMX, RDX and PETN explosives

    International Nuclear Information System (INIS)

    Wu, Y.Q.; Huang, F.L.

    2010-01-01

    The frictional properties of single crystals of cyclotetramethylene tetranitramine (HMX), cyclotrimethylene trinitramine (RDX) and pentaerythritol tetranitrate (PETN) secondary explosives are examined using a sensitive friction machine. The explosive crystals used for the measurements are at least 3.5 mm wide. The friction coefficients between crystals of the same explosive (i.e., HMX on HMX, etc.), crystals of different explosives (i.e., HMX on RDX, etc.), and each explosive and a well-polished gauge steel surface are determined. The frictional surfaces are also studied under an environmental scanning electron microscope (ESEM) to analyze surface microstructural changes under increasing loading forces. The friction coefficients vary considerably with increasing normal loading forces and are particularly sensitive to slider shapes, crystal roughness and the mechanical properties of both the slider and the sample. With increasing loading forces, most friction experiments show surface damage, consisting of grooves, debris, and nano-particles, on both the slider and sample. In some cases, a strong evidence of a localized molten state is found in the central region of the friction track. Possible mechanisms that affect the friction coefficient are discussed based on microscopic observations.

  3. Buckling of Single-Crystal Silicon Nanolines under Indentation

    Directory of Open Access Journals (Sweden)

    Min K. Kang

    2008-01-01

    Full Text Available Atomic force microscope-(AFM- based indentation tests were performed to examine mechanical properties of parallel single-crystal silicon nanolines (SiNLs of sub-100-nm line width, fabricated by a process combining electron-beam lithography and anisotropic wet etching. The SiNLs have straight and nearly atomically flat sidewalls, and the cross section is almost perfectly rectangular with uniform width and height along the longitudinal direction. The measured load-displacement curves from the indentation tests show an instability with large displacement bursts at a critical load ranging from 480 μN to 700 μN. This phenomenon is attributed to a transition of the buckling mode of the SiNLs under indentation. Using a set of finite element models with postbuckling analyses, we analyze the indentation-induced buckling modes and investigate the effects of tip location, contact friction, and substrate deformation on the critical load of mode transition. The results demonstrate a unique approach for the study of nanomaterials and patterned nanostructures via a combination of experiments and modeling.

  4. Plastic deformation of cubic zirconia single crystals at 1400 C

    International Nuclear Information System (INIS)

    Baufeld, B.; Baither, D.; Bartsch, M.; Messerschmidt, U.

    1998-01-01

    Cubic zirconia single crystals stabilized with 11 mol% yttria were deformed in air at 1400 C and around 1200 C at different strain rates along [1 anti 12] and [100] compression directions. The strain rate sensitivity of the flow stress was determined by strain rate cycling and stress relaxation tests. The microstructure of the deformed specimens was investigated by transmission high-voltage electron microscopy, including contrast extinction analysis for determining the Burgers vectors as well as stereo pairs and wide-angle tilting experiments to find the active slip planes. At deformation along [1 anti 12], the primary and secondary slip planes are of {100} type. Previous experiments had shown that the dislocations move easily on these planes in an athermal way. During deformation along [100], mainly dislocations on {100} planes are activated, which move in a viscous way by the aid of thermal activation. The discussion of the different deformation behaviours during deformation along [1 anti 12] and [100] is based on the different dynamic properties of dislocations and the fact that recovery is an essential feature of the deformation of cubic zirconia at 1400 C. The results on the shape of the deformation curve and the strain rate sensitivity of the flow stress are partly at variance with those of previous authors. (orig.)

  5. Thermal neutron scattering kernels for sapphire and silicon single crystals

    International Nuclear Information System (INIS)

    Cantargi, F.; Granada, J.R.; Mayer, R.E.

    2015-01-01

    Highlights: • Thermal cross section libraries for sapphire and silicon single crystals were generated. • Debye model was used to represent the vibrational frequency spectra to feed the NJOY code. • Sapphire total cross section was measured at Centro Atómico Bariloche. • Cross section libraries were validated with experimental data available. - Abstract: Sapphire and silicon are materials usually employed as filters in facilities with thermal neutron beams. Due to the lack of the corresponding thermal cross section libraries for those materials, necessary in calculations performed in order to optimize beams for specific applications, here we present the generation of new thermal neutron scattering kernels for those materials. The Debye model was used in both cases to represent the vibrational frequency spectra required to feed the NJOY nuclear data processing system in order to produce the corresponding libraries in ENDF and ACE format. These libraries were validated with available experimental data, some from the literature and others obtained at the pulsed neutron source at Centro Atómico Bariloche

  6. The neutron transmission of single crystal MgO filters

    International Nuclear Information System (INIS)

    Carpenter, J.M.; Hilleke, R.O.

    1989-01-01

    We have measured and analyzed the wavelength dependence of the transmission probability of a beam of neutrons passing through a single crystal MgO filter at 77 K. The 12.7 cm filter transmits 70% or more of the incident beam at wavelengths greater than about 1.8 A. At shorter wavelengths the transmission probability drops sharply, with 50% transmission occurring at about 1.2 A, and 1% transmission for the range 0.1-0.4 A. We have determined that cooling the filter to 77 K improves the transmission of >1 A neutrons, while further cooling to 25 K shows little additional improvement, and no improvement for short wavelengths. We have identified the wavelengths of the sharp dips in the transmission found in this region caused by Bragg scattering in MgO. We also show how these peaks may be used to calibrate the wavelength scale of time-of-flight measurements taken on instruments using similar filters. (orig.)

  7. Polymorphic transitions in single crystals: A new molecular dynamics method

    Energy Technology Data Exchange (ETDEWEB)

    Parrinello, M.; Rahman, A.

    1981-12-01

    A new Lagrangian formulation is introduced. It can be used to make molecular dynamics (MD) calculations on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamical equations given by this Lagrangian. This new MD technique is well suited to the study of structural transformations in solids under external stress and at finite temperature. As an example of the use of this technique we show how a single crystal of Ni behaves under uniform uniaxial compressive and tensile loads. This work confirms some of the results of static (i.e., zero temperature) calculations reported in the literature. We also show that some results regarding the stress-strain relation obtained by static calculations are invalid at finite temperature. We find that, under compressive loading, our model of Ni shows a bifurcation in its stress-strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. It is suggested that such a transformation could perhaps be observed experimentally under extreme conditions of shock.

  8. The CCP14 for single crystal and powder diffraction

    International Nuclear Information System (INIS)

    Cranswick, L.M.D.

    1999-01-01

    Full text: The Collaborative Computation Project Number 14 for Single Crystal and Powder Diffraction (CCP14) is continuing in its objective to provide freely available software and resources for the powder diffraction and crystallographic community. Using the Internet and World Wide Web, we are presently compiling software and web resources, creating tutorials and help files. It also endeavours to encourage and provide resources to assist program authors with developing their software. The CCP14 presently has its web-site at and a mirror at (at CSIRO, Melbourne, Australia). Auto web-mirroring is being implemented to allow users to obtain software and access to resources in a more time effective manner. For people in countries isolated from the Internet, the CCP14 on CD-ROM can be snail mailed on request. This is in the form of a Virtual World Wide Web/Virtual Internet; in the same vein as the existing Crystallographic Nexus CD-ROM. Copyright (1999) Australian X-ray Analytical Association Inc

  9. Analysis of ripple formation in single crystal spot welds

    Energy Technology Data Exchange (ETDEWEB)

    Rappaz, M. [Ecole Polytechnique Federale de Lausanne (Switzerland). Lab de Metallurgie Physique; Corrigan, D.; Boatner, L.A. [Oak Ridge National Lab., TN (United States). Solid State Div.

    1997-10-01

    Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 {micro}m) and spacing (typically {approximately} 60 {micro}m) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f{sub 0} given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v{sub s}/f{sub 0}, where v{sub s} is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

  10. High temperature microhardness of ZrB2 single crystals

    International Nuclear Information System (INIS)

    Yi Xuan; Chen Chunhua; Otani, Shigeki

    2002-01-01

    Vickers microhardness of (0001), (101-bar 0) and (112-bar 0) planes of ZrB 2 single crystal prepared by the floating zone method has been investigated at various temperatures and loading times. As the temperature increases from 25 deg. C to 1000 deg. C, hardness drops from ∼20.9 GN m -2 of all planes to ∼7.85 GN m -2 for (0001) plane and ∼4.91 GN m -2 for (101-bar 0) and (112-bar 0) planes. The hardness of (101-bar 0) and (112-bar 0) planes exhibits almost same tendency and is always lower than that of (0001) plane by about 35%. The thermal softening coefficients of all three planes strongly depends on the temperature range with clear inflections at 400 deg. C and 700 deg. C. The loading time dependence of hardness is used to calculate the activation energy for creep. In addition, a relationship was found that shows the variation of hardness with temperature to be proportional to the variation with the loading time in a specific temperature range. (rapid communication)

  11. DEVELOPMENT OF PROTECTIVE COATINGS FOR SINGLE CRYSTAL TURBINE BLADES

    Energy Technology Data Exchange (ETDEWEB)

    Amarendra K. Rai

    2006-12-04

    Turbine blades in coal derived syngas systems are subject to oxidation and corrosion due to high steam temperature and pressure. Thermal barrier coatings (TBCs) are developed to address these problems. The emphasis is on prime-reliant design and a better coating architecture, having high temperature and corrosion resistance properties for turbine blades. In Phase I, UES Inc. proposed to develop, characterize and optimize a prime reliant TBC system, having smooth and defect-free NiCoCrAlY bond layer and a defect free oxide sublayer, using a filtered arc technology. Phase I work demonstrated the deposition of highly dense, smooth and defect free NiCoCrAlY bond coat on a single crystal CMSX-4 substrate and the deposition of alpha-alumina and yttrium aluminum garnet (YAG) sublayer on top of the bond coat. Isothermal and cyclic oxidation test and pre- and post-characterization of these layers, in Phase I work, (with and without top TBC layer of commercial EB PVD YSZ) revealed significant performance enhancement.

  12. Defect sensitive etching of hexagonal boron nitride single crystals

    Science.gov (United States)

    Edgar, J. H.; Liu, S.; Hoffman, T.; Zhang, Yichao; Twigg, M. E.; Bassim, Nabil D.; Liang, Shenglong; Khan, Neelam

    2017-12-01

    Defect sensitive etching (DSE) was developed to estimate the density of non-basal plane dislocations in hexagonal boron nitride (hBN) single crystals. The crystals employed in this study were precipitated by slowly cooling (2-4 °C/h) a nickel-chromium flux saturated with hBN from 1500 °C under 1 bar of flowing nitrogen. On the (0001) planes, hexagonal-shaped etch pits were formed by etching the crystals in a eutectic mixture of NaOH and KOH between 450 °C and 525 °C for 1-2 min. There were three types of pits: pointed bottom, flat bottom, and mixed shape pits. Cross-sectional transmission electron microscopy revealed that the pointed bottom etch pits examined were associated with threading dislocations. All of these dislocations had an a-type burgers vector (i.e., they were edge dislocations, since the line direction is perpendicular to the [ 2 11 ¯ 0 ]-type direction). The pit widths were much wider than the pit depths as measured by atomic force microscopy, indicating the lateral etch rate was much faster than the vertical etch rate. From an Arrhenius plot of the log of the etch rate versus the inverse temperature, the activation energy was approximately 60 kJ/mol. This work demonstrates that DSE is an effective method for locating threading dislocations in hBN and estimating their densities.

  13. Pyroelectric properties of phosphoric acid-doped TGS single crystals

    International Nuclear Information System (INIS)

    Saxena, Aparna; Fahim, M; Gupta, Vinay; Sreenivas, K

    2003-01-01

    Pyroelectric properties of phosphoric acid (H 3 PO 4 )-doped triglycine sulfate (TGSP) single crystals grown from solutions containing 0.1-0.5 mol of H 3 PO 4 have been studied. Incorporation of H 3 PO 4 into the crystal lattice is found to induce an internal bias field (E b ) and is observed through the presence of a sustained polarization and pyroelectricity beyond the transition temperature. The internal bias field has been estimated theoretically by fitting the experimentally measured data on temperature dependence of the pyroelectric coefficient (λ), dielectric constant (ε') and polarization (P). A high E b value in the range 9 x 10 3 -15.5 x 10 4 V m -1 is obtained for crystals grown with 0.1-0.5 mol of H 3 PO 4 in the solution, and a specific concentration of 0.2-0.25 mol of H 3 PO 4 in the solution during crystal growth is found to be optimum for a high figure of merit for detectivity, F d = 428 μC m -2 K -1

  14. Pyroelectric properties of phosphoric acid-doped TGS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, Aparna; Fahim, M; Gupta, Vinay; Sreenivas, K [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2003-12-21

    Pyroelectric properties of phosphoric acid (H{sub 3}PO{sub 4})-doped triglycine sulfate (TGSP) single crystals grown from solutions containing 0.1-0.5 mol of H{sub 3}PO{sub 4} have been studied. Incorporation of H{sub 3}PO{sub 4} into the crystal lattice is found to induce an internal bias field (E{sub b}) and is observed through the presence of a sustained polarization and pyroelectricity beyond the transition temperature. The internal bias field has been estimated theoretically by fitting the experimentally measured data on temperature dependence of the pyroelectric coefficient ({lambda}), dielectric constant ({epsilon}') and polarization (P). A high E{sub b} value in the range 9 x 10{sup 3}-15.5 x 10{sup 4} V m{sup -1} is obtained for crystals grown with 0.1-0.5 mol of H{sub 3}PO{sub 4} in the solution, and a specific concentration of 0.2-0.25 mol of H{sub 3}PO{sub 4} in the solution during crystal growth is found to be optimum for a high figure of merit for detectivity, F{sub d} = 428 {mu}C m{sup -2} K{sup -1}.

  15. Thermal diffusion boron doping of single-crystal natural diamond

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Wu, Henry; Morgan, Dane [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Blanchard, James P. [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Zhou, Weidong [Department of Electrical Engineering, NanoFAB Center, University of Texas at Arlington, Arlington, Texas 76019 (United States); Gong, Shaoqin [Department of Biomedical Engineering and Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2016-05-28

    With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

  16. Electron irradiation effect on single crystal of niobium

    International Nuclear Information System (INIS)

    Otero, M.P.; Lucki, G.

    1984-01-01

    The effect of electron irradiation (900 KeV) on gliding dislocations of single crystal Nb with its tensile axe in the [941] orientation was observed for the in-situ deformation in a high voltage electron microscope (HVEM) at Argonne National Laboratory. The experimental was carried out by the 1 hour-electron irradiation with no stress applied. Straight dislocations actuating as sinks for the electron produced defects became helicoidal as the irradiation proceeded. Frenkel pairs were created in Nb for electron energies > = 650 KeV and, as the single vacancies do not undergo long-range migration in Nb at temperatures much below 620 K, the defects that are entrapped by the dislocations are self-interstitials produced by electron displacement. Applying the stress it was possible to observe that modified dislocations did not glide while the dislocations not affected by the irradiation are visibly in movement. This important result explains the neutron and electron-irradiation induced work-hardening effect for Nb that was previously observed. (Author) [pt

  17. Thermal diffusion boron doping of single-crystal natural diamond

    International Nuclear Information System (INIS)

    Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang; Wu, Henry; Morgan, Dane; Blanchard, James P.; Zhou, Weidong; Gong, Shaoqin

    2016-01-01

    With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

  18. Reduction of precursor decay anomaly in single crystal lithium fluoride

    Science.gov (United States)

    Sano, Yukio

    2000-08-01

    The purpose of this study is to reveal that the precursor decay anomaly in single crystal lithium fluoride is reduced by Sano's decay curve [Y. Sano, J. Appl. Phys. 85, 7616 (1999)], which is much smaller in slope than Asay's decay curve [J. R. Asay, G. R. Fowles, G. E. Duvall, M. H. Miles, and R. F. Tinder, J. Appl. Phys. 43, 2132 (1972)]. To this end, strain, particle, velocity, and stress in a precursor and near the leading edge of the follower changing with time along Sano's decay curve are first analyzed quantitatively. The analysis verified the existence of degenerate contraction waves I and II and a subrarefaction wave R', and the decay process [Y. Sano, J. Appl. Phys. 77, 3746 (1995)] caused in sequence by evolving followers C, I, II, R', Rb. Next, inequalities relating decay rates qualitatively to plastic strain rates at the leading edge of the follower, which are derived using the properties of the followers, are incorporated into the analysis. Calculation results showed that the plastic strain rates were reduced by low decay rates. This indicates that the precursor decay anomaly might be greatly reduced by Sano's decay curve.

  19. Simulations of surface stress effects in nanoscale single crystals

    Science.gov (United States)

    Zadin, V.; Veske, M.; Vigonski, S.; Jansson, V.; Muszinsky, J.; Parviainen, S.; Aabloo, A.; Djurabekova, F.

    2018-04-01

    Onset of vacuum arcing near a metal surface is often associated with nanoscale asperities, which may dynamically appear due to different processes ongoing in the surface and subsurface layers in the presence of high electric fields. Thermally activated processes, as well as plastic deformation caused by tensile stress due to an applied electric field, are usually not accessible by atomistic simulations because of the long time needed for these processes to occur. On the other hand, finite element methods, able to describe the process of plastic deformations in materials at realistic stresses, do not include surface properties. The latter are particularly important for the problems where the surface plays crucial role in the studied process, as for instance, in the case of plastic deformations at a nanovoid. In the current study by means of molecular dynamics (MD) and finite element simulations we analyse the stress distribution in single crystal copper containing a nanovoid buried deep under the surface. We have developed a methodology to incorporate the surface effects into the solid mechanics framework by utilizing elastic properties of crystals, pre-calculated using MD simulations. The method leads to computationally efficient stress calculations and can be easily implemented in commercially available finite element software, making it an attractive analysis tool.

  20. Implanted strontium titanate single crystals for energy storage applications

    Energy Technology Data Exchange (ETDEWEB)

    Stoeber, Max; Cherkouk, Charaf; Walter, Juliane; Strohmeyer, Ralph; Leisegang, Tilmann; Meyer, Dirk Carl [TU Bergakademie, Freiberg (Germany); Schelter, Matthias; Zosel, Jens [Kurt Schwabe Institute, Meinsberg (Germany); Prucnal, Slawomir [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (Germany)

    2016-07-01

    A rapid increase of the demand on efficient energy storage solutions requires new approaches beyond the Li-ion technology. In particular, metal-air batteries as well as solid-state fuel cells offer a great potential for high-energy-density storage devices. Since the efficiency of such devices is significantly limited by the activation of both the oxygen reduction reaction (ORR) and the ionic and electronic conductivities, an adequate porosity as well as a controlled doping are required. The ion implantation is a key technology to achieve this goal. In this work, p- and n-doped strontium titanate (SrTiO{sub 3}) single crystals were used as oxidic materials. The oxygen exchange kinetics as well as the structural changes of the SrTiO{sub 3} crystal surface induced by the ion implantation were investigated. On one hand, the depth profile of dopant concentration and dopant valence state were determined using sputtered X-ray photoelectron spectroscopy (XPS). On the other hand, the overall oxygen exchange kinetic of the implanted SrTiO{sub 3} crystal was quantitatively described by means of coulometric titration using Zirox system (ZIROX GmbH, Germany). Furthermore, the surface morphology of the samples was investigated using atomic force microscopy (AFM).

  1. A discrete dislocation dynamics model of creeping single crystals

    Science.gov (United States)

    Rajaguru, M.; Keralavarma, S. M.

    2018-04-01

    Failure by creep is a design limiting issue for metallic materials used in several high temperature applications. Current theoretical models of creep are phenomenological with little connection to the underlying microscopic mechanisms. In this paper, a bottom-up simulation framework based on the discrete dislocation dynamics method is presented for dislocation creep aided by the diffusion of vacancies, known to be the rate controlling mechanism at high temperature and stress levels. The time evolution of the creep strain and the dislocation microstructure in a periodic unit cell of a nominally infinite single crystal is simulated using the kinetic Monte Carlo method, together with approximate constitutive laws formulated for the rates of thermal activation of dislocations over local pinning obstacles. The deformation of the crystal due to dislocation glide between individual thermal activation events is simulated using a standard dislocation dynamics algorithm, extended to account for constant stress periodic boundary conditions. Steady state creep conditions are obtained in the simulations with the predicted creep rates as a function of stress and temperature in good agreement with experimentally reported values. Arrhenius scaling of the creep rates as a function of temperature and power-law scaling with the applied stress are also reproduced, with the values of the power-law exponents in the high stress regime in good agreement with experiments.

  2. Optical properties of tungsten disulfide single crystals doped with gold

    International Nuclear Information System (INIS)

    Dumcenco, D.O.; Hsu, H.P.; Huang, Y.S.; Liang, C.H.; Tiong, K.K.; Du, C.H.

    2008-01-01

    Single crystals of WS 2 doped with gold have been grown by the chemical vapour transport method using iodine as a transporting agent. X-ray diffraction (XRD) pattern analysis revealed presence of mixed three-layer rhombohedral (3R) and two-layer hexagonal (2H) polytypes for the doped crystals while the undoped one shows only 2H form. Hall measurements indicate that the samples are p-type in nature. The doping effects of the materials are characterized by surface photovoltage (SPV), photoconductivity (PC) and piezoreflectance (PzR) measurements. Room temperature SPV and PC spectra reveal a feature located at ∼60 meV below the A exciton and has been tentatively assigned to be an impurity level caused by Au dopant. Excitonic transition energies of the A, B, d and C excitons detected in PzR spectra show red shift due to the presence of a small amount of Au and the broadening parameters of the excitonic transition features increase due to impurity scattering. The values of the parameters that describe the electron (exciton)-phonon interaction of excitonic transitions of A-B are about two times larger than that of d-C excitonic pairs. The possible assignments of the different origins of A-B and d-C excitonic pairs have been discussed

  3. Ion beam synthesis of buried single crystal erbium silicide

    International Nuclear Information System (INIS)

    Golanski, A.; Feenstra, R.; Galloway, M.D.; Park, J.L.; Pennycook, S.J.; Harmon, H.E.; White, C.W.

    1990-01-01

    High doses (10 16 --10 17 /cm 2 ) of 170 keV Er + were implanted into single-crystal left-angle 111 right-angle Si at implantation temperatures between 350 degree C and 520 degree C. Annealing at 800 degree C in vacuum following the implant, the growth and coalescence of ErSi 2 precipitates leads to a buried single crystalline ErSi 2 layer. This has been studied using Rutherford backscattering/channeling, X-ray diffraction, cross-sectional TEM and resistance versus temperature measurements. Samples implanted at 520 degree C using an Er dose of 7 x 10 16 /cm 2 and thermally annealed were subsequently used as seeds for the mesoepitaxial growth of the buried layer during a second implantation and annealing process. Growth occurs meso-epitaxially along both interfaces through beam induced, defect mediated mobility of Er atoms. The crystalline quality of the ErSi 2 layer strongly depends on the temperature during the second implantation. 12 refs., 4 figs

  4. Polymorphic transitions in single crystals: A new molecular dynamics method

    International Nuclear Information System (INIS)

    Parrinello, M.; Rahman, A.

    1981-01-01

    A new Lagrangian formulation is introduced. It can be used to make molecular dynamics (MD) calculations on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamical equations given by this Lagrangian. This new MD technique is well suited to the study of structural transformations in solids under external stress and at finite temperature. As an example of the use of this technique we show how a single crystal of Ni behaves under uniform uniaxial compressive and tensile loads. This work confirms some of the results of static (i.e., zero temperature) calculations reported in the literature. We also show that some results regarding the stress-strain relation obtained by static calculations are invalid at finite temperature. We find that, under compressive loading, our model of Ni shows a bifurcation in its stress-strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. It is suggested that such a transformation could perhaps be observed experimentally under extreme conditions of shock

  5. Growth of single crystals from solutions using semi-permeable membranes

    Science.gov (United States)

    Varkey, A. J.; Okeke, C. E.

    1983-05-01

    A technique suitable for growth of single crystals from solutions using semi-preamble membranes is described. Using this technique single crystals of copper sulphate, potassium bromide and ammonium dihydrogen phosphate have been successfully grown. Advantages of this technique over other methods are discussed.

  6. Probing the crossover in CO desorption from single crystal to nanoparticulate Ru model catalysts

    DEFF Research Database (Denmark)

    Murphy, Shane; Strebel, Christian Ejersbo; Vendelbo, Søren Bastholm

    2011-01-01

    Crossover in CO desorption behavior and nanoscale structure probed with STM from ruthenium single crystals to PVD and mass-selected nanoparticles.......Crossover in CO desorption behavior and nanoscale structure probed with STM from ruthenium single crystals to PVD and mass-selected nanoparticles....

  7. A review on solar cells from Si-single crystals to porous materials and quantum dots.

    Science.gov (United States)

    Badawy, Waheed A

    2015-03-01

    Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12-16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper-indium-selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. The third generation solar cells are based on nano-crystals and nano-porous materials. An advanced photovoltaic cell, originally developed for satellites with solar conversion efficiency of 37.3%, based on concentration of the solar spectrum up to 400 suns was developed. It is based on extremely thin concentration cells. New sensitizer or semiconductor systems are necessary to broaden the photo-response in solar spectrum. Hybrids of solar and conventional devices may provide an interim benefit in seeking economically valuable devices. New quantum dot solar cells based on CdSe-TiO2 architecture have been developed.

  8. A review on solar cells from Si-single crystals to porous materials and quantum dots

    Directory of Open Access Journals (Sweden)

    Waheed A. Badawy

    2015-03-01

    Full Text Available Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12–16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper–indium–selenide and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. The third generation solar cells are based on nano-crystals and nano-porous materials. An advanced photovoltaic cell, originally developed for satellites with solar conversion efficiency of 37.3%, based on concentration of the solar spectrum up to 400 suns was developed. It is based on extremely thin concentration cells. New sensitizer or semiconductor systems are necessary to broaden the photo-response in solar spectrum. Hybrids of solar and conventional devices may provide an interim benefit in seeking economically valuable devices. New quantum dot solar cells based on CdSe–TiO2 architecture have been developed.

  9. Effect of grain boundary on the field-effect mobility of microrod single crystal organic transistors.

    Science.gov (United States)

    Kim, Jaekyun; Kang, Jingu; Cho, Sangho; Yoo, Byungwook; Kim, Yong-Hoon; Park, Sung Kyu

    2014-11-01

    High-performance microrod single crystal organic transistors based on a p-type 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) semiconductor are fabricated and the effects of grain boundaries on the carrier transport have been investigated. The spin-coating of C8-BTBT and subsequent solvent vapor annealing process enabled the formation of organic single crystals with high aspect ratio in the range of 10 - 20. It was found that the organic field-effect transistors (OFETs) based on these single crystals yield a field-effect mobility and an on/off current ratio of 8.04 cm2/Vs and > 10(5), respectively. However, single crystal OFETs with a kink, in which two single crystals are fused together, exhibited a noticeable drop of field-effect mobility, and we claim that this phenomenon results from the carrier scattering at the grain boundary.

  10. Growth of single crystals of BaFe12O19 by solid state crystal growth

    Science.gov (United States)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-10-01

    Single crystals of BaFe12O19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe12O19 are buried in BaFe12O19+1 wt% BaCO3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe12O19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe12O19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth.

  11. Tensile properties of electron-beam-welded single crystals of molybdenum

    International Nuclear Information System (INIS)

    Hiraoka, Yutaka; Okada, Masatoshi; Irie, Hirosada; Fujii, Tadayuki.

    1987-01-01

    The purpose of this study is to investigate the macro- and microstructures and the tensile properties of electron-beam-welded single crystals of molybdenum. The single-crystal sheets were prepared by means of secondary recrystallization. The welding was carried out by a melt-run technique. The weld metal had the same crystallographic orientation as the base metal, and no grain boundary was observed. However, many large weld pores were formed mostly along the weld bond. The strength and ductility of the welded joints of single crystals were almost the same as those of the base metal (''annealed'' single crystals). It is concluded that the joint efficiency of molybdenum single crystals at room temperature or above was excellent and nearly 100 %. (author)

  12. Single-Crystal Sapphire Optical Fiber Sensor Instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Pickrell, Gary [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Scott, Brian [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Wang, Anbo [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Yu, Zhihao [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States)

    2013-12-31

    This report summarizes technical progress on the program “Single-Crystal Sapphire Optical Fiber Sensor Instrumentation,” funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. This project was completed in three phases, each with a separate focus. Phase I of the program, from October 1999 to April 2002, was devoted to development of sensing schema for use in high temperature, harsh environments. Different sensing designs were proposed and tested in the laboratory. Phase II of the program, from April 2002 to April 2009, focused on bringing the sensor technologies, which had already been successfully demonstrated in the laboratory, to a level where the sensors could be deployed in harsh industrial environments and eventually become commercially viable through a series of field tests. Also, a new sensing scheme was developed and tested with numerous advantages over all previous ones in Phase II. Phase III of the program, September 2009 to December 2013, focused on development of the new sensing scheme for field testing in conjunction with materials engineering of the improved sensor packaging lifetimes. In Phase I, three different sensing principles were studied: sapphire air-gap extrinsic Fabry-Perot sensors; intensity-based polarimetric sensors; and broadband polarimetric sensors. Black body radiation tests and corrosion tests were also performed in this phase. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. At the beginning of Phase II, in June 2004, the BPDI sensor was tested at the Wabash River coal gasifier

  13. Radiation-electromagnetic effect in germanium single crystals

    International Nuclear Information System (INIS)

    Kikoin, I.K.; Kikoin, L.I.; Lazarev, S.D.

    1980-01-01

    An experimental study was made of the radiation-electromagnetic effect in germanium single crystals when excess carriers were generated by bombardment with α particles, protons, or x rays in magnetic fields up to 8 kOe. The source of α particles and protons was a cyclotron and x rays were provided by a tube with a copper anode. The radiation-electromagnetic emf increased linearly on increase in the magnetic field and was directly proportional to the flux of charged particles at low values of the flux, reaching saturation at high values of the flux (approx.5 x 10 11 particles .cm -2 .sec -1 ). In the energy range 4--40 MeV the emf was practically independent of the α-particle energy. The sign of the emf was reversed when samples with a ground front surface were irradiated. Measurements of the photoelectromagnetic and Hall effects in the α-particle-irradiated samples showed that a p-n junction was produced by these particles and its presence should be allowed for in investigations of the radiation-electromagnetic effect. The measured even radiation-electromagnetic emf increased quadratically on increase in the magnetic field. An investigation was made of the barrier radiation-voltaic effect (when the emf was measured between the irradiated and unirradiated surfaces). Special masks were used to produce a set of consecutive p-n junctions in germanium crystals irradiated with α particles. A study of the photovoltaic and photoelectromagnetic effects in such samples showed that the method could be used to increase the efficiency of devices utilizing the photoelectromagnetic effect

  14. Crystal plasticity study of single crystal tungsten by indentation tests

    International Nuclear Information System (INIS)

    Yao, Weizhi

    2012-01-01

    Owing to its favorable material properties, tungsten (W) has been studied as a plasma-facing material in fusion reactors. Experiments on W heating in plasma sources and electron beam facilities have shown an intense micro-crack formation at the heated surface and sub-surface. The cracks go deep inside the irradiated sample, and often large distorted areas caused by local plastic deformation are present around the cracks. To interpret the crack-induced microscopic damage evolution process in W, one needs firstly to understand its plasticity on a single grain level, which is referred to as crystal plasticity. In this thesis, the crystal plasticity of single crystal tungsten (SCW) has been studied by spherical and Berkovich indentation tests and the finite element method with a crystal plasticity model. Appropriate values of the material parameters included in the crystal plasticity model are determined by fitting measured load-displacement curves and pile-up profiles with simulated counterparts for spherical indentation. The numerical simulations reveal excellent agreement with experiment. While the load-displacement curves and the deduced indentation hardness exhibit little sensitivity to the indented plane at small indentation depths, the orientation of slip directions within the crystals governs the development of deformation hillocks at the surface. It is found that several factors like friction, indentation depth, active slip systems, misoriented crystal orientation, misoriented sample surface and azimuthal orientation of the indenter can affect the indentation behavior of SCW. The Berkovich indentation test was also used to study the crystal plasticity of SCW after deuterium irradiation. The critical load (pop-in load) for triggering plastic deformation under the indenter is found to depend on the crystallographic orientation. The pop-in loads decrease dramatically after deuterium plasma irradiation for all three investigated crystallographic planes.

  15. Single-crystal elastic constants of natural ettringite

    KAUST Repository

    Speziale, Sergio

    2008-07-01

    The single-crystal elastic constants of natural ettringite were determined by Brillouin spectroscopy at ambient conditions. The six non-zero elastic constants of this trigonal mineral are: C11 = 35.1 ± 0.1 GPa, C12 = 21.9 ±0.1 GPa, C13 = 20.0 ± 0.5 GPa, C14 = 0.6 ± 0.2 GPa, C33 = 55 ± 1 GPa, C44 = 11.0 ± 0.2 GPa. The Hill average of the aggregate bulk, shear modulus and the polycrystal Young\\'s modulus and Poisson\\'s ratio are 27.3 ± 0.9 GPa, 9.5 ± 0.8 GPa, 25 ± 2 GPa and 0.34 ± 0.02 respectively. The longitudinal and shear elastic anisotropy are C33/C11 = 0.64 ± 0.01 and C66/C44 =0.60 ± 0.01. The elastic anisotropy in ettringite is connected to its crystallographic structure. Stiff chains of [Al(OH)6]3- octahedra alternating with triplets of Ca2+ in eight-fold coordination run parallel to the c-axis leading to higher stiffness along this direction. The determination of the elastic stiffness tensor can help in the prediction of the early age properties of cement paste when ettringite crystals precipitate and in the modeling of both internal and external sulfate attack when secondary ettringite formation leads to expansion of concrete. © 2008 Elsevier Ltd. All rights reserved.

  16. Single-crystal elastic constants of natural ettringite

    KAUST Repository

    Speziale, Sergio; Jiang, Fuming; Mao, Zhu; Monteiro, Paulo J.M.; Wenk, Hans-Rudolf; Duffy, Thomas S.; Schilling, Frank R.

    2008-01-01

    The single-crystal elastic constants of natural ettringite were determined by Brillouin spectroscopy at ambient conditions. The six non-zero elastic constants of this trigonal mineral are: C11 = 35.1 ± 0.1 GPa, C12 = 21.9 ±0.1 GPa, C13 = 20.0 ± 0.5 GPa, C14 = 0.6 ± 0.2 GPa, C33 = 55 ± 1 GPa, C44 = 11.0 ± 0.2 GPa. The Hill average of the aggregate bulk, shear modulus and the polycrystal Young's modulus and Poisson's ratio are 27.3 ± 0.9 GPa, 9.5 ± 0.8 GPa, 25 ± 2 GPa and 0.34 ± 0.02 respectively. The longitudinal and shear elastic anisotropy are C33/C11 = 0.64 ± 0.01 and C66/C44 =0.60 ± 0.01. The elastic anisotropy in ettringite is connected to its crystallographic structure. Stiff chains of [Al(OH)6]3- octahedra alternating with triplets of Ca2+ in eight-fold coordination run parallel to the c-axis leading to higher stiffness along this direction. The determination of the elastic stiffness tensor can help in the prediction of the early age properties of cement paste when ettringite crystals precipitate and in the modeling of both internal and external sulfate attack when secondary ettringite formation leads to expansion of concrete. © 2008 Elsevier Ltd. All rights reserved.

  17. Charged-particle spectroscopy in organic semiconducting single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ciavatti, A.; Basiricò, L.; Fraboni, B. [Department of Physics and Astronomy, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna (Italy); Sellin, P. J. [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Fraleoni-Morgera, A. [ELETTRA-Sincrotrone Trieste, Strada Statale 14, Km 163.5, Basovizza, Trieste (Italy); Department of Engineering and Architecture, University of Trieste, V. Valerio 10, 34100 Trieste (Italy); CNR-Nano S3 Institute, Via Campi 213/A, 41125 Modena (Italy)

    2016-04-11

    The use of organic materials as radiation detectors has grown, due to the easy processability in liquid phase at room temperature and the possibility to cover large areas by means of low cost deposition techniques. Direct charged-particle detectors based on solution-grown Organic Semiconducting Single Crystals (OSSCs) are shown to be capable to detect charged particles in pulse mode, with very good peak discrimination. The direct charged-particle detection in OSSCs has been assessed both in the planar and in the vertical axes, and a digital pulse processing algorithm has been used to perform pulse height spectroscopy and to study the charge collection efficiency as a function of the applied bias voltage. Taking advantage of the charge spectroscopy and the good peak discrimination of pulse height spectra, an Hecht-like behavior of OSSCs radiation detectors is demonstrated. It has been possible to estimate the mobility-lifetime value in organic materials, a fundamental parameter for the characterization of radiation detectors, whose results are equal to μτ{sub coplanar} = (5 .5 ± 0.6 ) × 10{sup −6} cm{sup 2}/V and μτ{sub sandwich} = (1 .9 ± 0.2 ) × 10{sup −6} cm{sup 2}/V, values comparable to those of polycrystalline inorganic detectors. Moreover, alpha particles Time-of-Flight experiments have been carried out to estimate the drift mobility value. The results reported here indicate how charged-particle detectors based on OSSCs possess a great potential as low-cost, large area, solid-state direct detectors operating at room temperature. More interestingly, the good detection efficiency and peak discrimination observed for charged-particle detection in organic materials (hydrogen-rich molecules) are encouraging for their further exploitation in the detection of thermal and high-energy neutrons.

  18. Mechanical properties of low temperature proton irradiated single crystal copper

    International Nuclear Information System (INIS)

    Schildcrout, M.

    1975-01-01

    Single crystal copper samples, of varying degrees of cold work, were irradiated near either liquid helium or liquid nitrogen temperature by 10.1-MeV protons. The internal friction and dynamic Young's modulus were observed as a function of either temperature or integrated proton flux. The primary effect of irradiation was to produce dislocation pinning. The initial pinning rate was found to be very sensitive to cold work. During irradiation it was found that heavily cold worked samples (25 percent compression) exhibited, almost exclusively, exponential pinning given by Y = e/sup --lambda phi/. This is attributed to the immobilization, rather than shortening, of loop lengths and is characterized by the pinning constant lambda. Exponential pinning was also found, to a smaller degree, in less heavily cold worked samples. Cold work appears to reduce the ''effective volume'' within which the defect clusters produced by irradiation, can immobilize dislocation segments. The bulk effect was observed after dislocation pinning was completed. Expressed in terms of the fractional change in Young's modulus per unit concentration of irradiation induced defects, it was measured at liquid helium temperature to be --18.5 +- 3. An anelastic process occurring near 10 0 K for low kHz frequencies and due to stress-induced ordering of point defects produced by irradiation has also been studied. The peak height per unit fluence was found to decrease with increasing cold work. The peak was not observed in samples compressed 25 percent. For the most carefully handled sample the activation energy was (1.28 +- 0.05) x 10 -2 eV, the attempt frequency was 10/sup 11.6 +- .8/ s -1 , the shape factor was 0.20, and the half width of the peak was 11 percent larger than the theoretical value calculated from the Debye equation for a single relaxation process

  19. Ferrite Nanoparticles, Films, Single Crystals, and Metamaterials: High Frequency Applications

    International Nuclear Information System (INIS)

    Harris, V.

    2006-01-01

    Ferrite materials have long played an important role in power conditioning, conversion, and generation across a wide spectrum of frequencies (up to ten decades). They remain the preferred magnetic materials, having suitably low losses, for most applications above 1 MHz, and are the only viable materials for nonreciprocal magnetic microwave and millimeter-wave devices (including tunable filters, isolators, phase shifters, and circulators). Recently, novel processing techniques have led to a resurgence of research interest in the design and processing of ferrite materials as nanoparticles, films, single crystals, and metamaterials. These latest developments have set the stage for their use in emerging technologies that include cancer remediation therapies such as magnetohyperthermia, magnetic targeted drug delivery, and magneto-rheological fluids, as well as enhanced magnetic resonance imaging. With reduced dimensionality of nanoparticles and films, and the inherent nonequilibrium nature of many processing schemes, changes in local chemistry and structure have profound effects on the functional properties and performance of ferrites. In this lecture, we will explore these effects upon the fundamental magnetic and electronic properties of ferrites. Density functional theory will be applied to predict the properties of these ferrites, with synchrotron radiation techniques used to elucidate the chemical and structural short-range order. This approach will be extended to study the atomic design of ferrites by alternating target laser-ablation deposition. Recently, this approach has been shown to produce ferrites that offer attractive properties not found in conventionally grown ferrites. We will explore the latest research developments involving ferrites as related to microwave and millimeter-wave applications and the attempt to integrate these materials with semiconductor materials platforms

  20. Carbon monoxide MgO from dispersed solids to single crystals: a review and new advances

    Science.gov (United States)

    Spoto, G.; Gribov, E. N.; Ricchiardi, G.; Damin, A.; Scarano, D.; Bordiga, S.; Lamberti, C.; Zecchina, A.

    2004-10-01

    In this review we describe 30 years of research on the surface properties of magnesium oxide, considered as the model prototype oxide of cubic structure. The surface properties of single crystals, thin films and powdered samples (sintered at progressive higher temperatures) are considered and compared, with the aim of demonstrating that the gap between “believed perfect” single crystal surfaces, typical of “pure” Surface Science, and high surface area samples, typical of Catalysis Science, can be progressively reduced. The surface features considered in this review are the structural (morphological), optical, absorptive and reactive properties. As the carbon monoxide molecule is able to probe the surface properties of both anions and cations, it can give a complete information of the surface structure of MgO samples. For this reason the adsorption and spectroscopy of this molecule is preferentially considered in this review. Particular emphasis is given in reviewing results obtained by high resolution transmission microscopy and in situ IR spectroscopy of adsorbed species (in both reflection and transmission modes), but also UV-Vis diffuse reflectance, photoluminescence, TDS, EPR, electron based techniques are mentioned. Reviewed experimental results are also commented in view of the important theoretical literature available on this topic and are complemented by new transmission IR data concerning CO adsorbed, down to 60 K, on powdered MgO samples with increasing surface area. These innovative experiments allow us to perform, on powdered samples, the adsorption experiments typical of single crystals (or films) Surface Science, with an increase of the S/N of the vibrational features higher than two order of magnitude. As far the new results (never published before) are concerned, we report IR spectra of CO dosed at 60 K on polycrystalline MgO samples with different surface area obtained by Mg(OH) 2 decomposition and progressive sintering at high temperature

  1. Quality improvement of CdZnTe single crystal by ultrasound processing

    Science.gov (United States)

    Lisiansky, M.; Berner, A.; Korchnoy, V.

    2017-06-01

    Intrinsic defects and contaminations removal from the undoped p-type Cd0.96Zn0.04Te single crystals has been achieved by the ultrasound vibration processing at the room temperature. Surface analysis based on Auger Electron Spectroscopy, Energy Dispersive Spectroscopy, and Scanning Electron Spectroscopy shows a significant reconstruction of the crystal surface after processing, namely, the appearance of numerous "volcano craters" and triangle-shaped defects with a typical size of 0.2-5.0 μm. Elemental analysis of these defects shows that they are Te inclusions emerged on the surface. The regular crystal surface outside the defects also displays a considerable enrichment by Te. Distinct presence of copper is found in both the thin surface layer and in the defects emerged on the surface. The surface reconstruction is associated with a remarkable change in the bulk material properties, electrical (an increase in the resistivity by a factor of ∼6) and optical (an IR transmittance increase). A post-polishing following the ultrasound processing makes the CdZnTe material more stable and reliable for a wide range of device applications.

  2. Reliability of Single Crystal Silver Nanowire-Based Systems: Stress Assisted Instabilities.

    Science.gov (United States)

    Ramachandramoorthy, Rajaprakash; Wang, Yanming; Aghaei, Amin; Richter, Gunther; Cai, Wei; Espinosa, Horacio D

    2017-05-23

    Time-dependent mechanical characterization of nanowires is critical to understand their long-term reliability in applications, such as flexible-electronics and touch screens. It is also of great importance to develop a theoretical framework for experimentation and analysis on the mechanics of nanowires under time-dependent loading conditions, such as stress-relaxation and fatigue. Here, we combine in situ scanning electron microscope (SEM)/transmission electron microscope (TEM) tests with atomistic and phase-field simulations to understand the deformation mechanisms of single crystal silver nanowires held under constant strain. We observe that the nanowires initially undergo stress-relaxation, where the stress reduces with time and saturates after some time period. The stress-relaxation process occurs due to the formation of few dislocations and stacking faults. Remarkably, after a few hours the nanowires rupture suddenly. The reason for this abrupt failure of the nanowire was identified as stress-assisted diffusion, using phase-field simulations. Under a large applied strain, diffusion leads to the amplification of nanowire surface perturbation at long wavelengths and the nanowire fails at the stress-concentrated thin cross-sectional regions. An analytical analysis on the competition between the elastic energy and the surface energy predicts a longer time to failure for thicker nanowires than thinner ones, consistent with our experimental observations. The measured time to failure of nanowires under cyclic loading conditions can also be explained in terms of this mechanism.

  3. Advanced Fabrication of Single-Crystal Diamond Membranes for Quantum Technologies

    Directory of Open Access Journals (Sweden)

    Michel Challier

    2018-03-01

    Full Text Available Many promising applications of single crystal diamond and its color centers as sensor platform and in photonics require free-standing membranes with a thickness ranging from several micrometers to the few 100 nm range. In this work, we present an approach to conveniently fabricate such thin membranes with up to about one millimeter in size. We use commercially available diamond plates (thickness 50 μ m in an inductively coupled reactive ion etching process which is based on argon, oxygen and SF 6 . We thus avoid using toxic, corrosive feed gases and add an alternative to previously presented recipes involving chlorine-based etching steps. Our membranes are smooth (RMS roughness <1 nm and show moderate thickness variation (central part: <1 μ m over ≈200 × 200 μ m 2 . Due to an improved etch mask geometry, our membranes stay reliably attached to the diamond plate in our chlorine-based as well as SF 6 -based processes. Our results thus open the route towards higher reliability in diamond device fabrication and up-scaling.

  4. The nature of γ-hydride in crept zirconium single crystals

    International Nuclear Information System (INIS)

    Akhtar, A.

    1977-01-01

    Single crystals prepared from crystal bar zirconium have been subjected to uniaxial tensile-creep under a vacuum of 10 -4 Pa for 160 h. Transmission electron microscopy of crept crystals has revealed the presence of thin fct γ-zirconium hydride platelets lying parallel to (1100) planes and elongated along the [1120]sub(α) direction. The platelets maintain the following lattice relationship with the hcp (α) matrix: [1120]sub(α)//[110]sub(γ), (0001)sub(α)//(001)sub(γ). This relationship is different from that obtained for needle γ-hydride generally observed in quenched samples. Lattice misfit calculations indicate that the platelets have a large positive misfit normal to the plane of the disc and a small misfit in the plane of the disc, which remains parallel to (1010)sub(α). Displacement fringe contrast is observed inside the platelets under conditions consistent with the lattice misfit. It is proposed that the nucleation of these precipitates occurs at stacking faults in the presence of applied stress. (Auth.)

  5. Crystal growth and scintillation properties of Pr-doped SrI2 single crystals

    Science.gov (United States)

    Yokota, Yuui; Ito, Tomoki; Yoshino, Masao; Yamaji, Akihiro; Ohashi, Yuji; Kurosawa, Shunsuke; Kamada, Kei; Yoshikawa, Akira

    2018-04-01

    Pr-doped SrI2 (Pr:SrI2) single crystals with various Pr concentrations were grown by the halide-micro-pulling-down (H-μ-PD) method, and the scintillation properties were investigated. Pr1%:SrI2 single crystal with high transparency could be grown by the H-μ-PD method while Pr2, 3 and 5%:SrI2 single crystals included some cracks and opaque parts. In the photoluminescence spectrum of the Pr1%:SrI2 single crystal, an emission peak originated from the Pr3+ ion was observed around 435 nm while the radioluminescence spectra showed an emission peak around 535 nm for the undoped SrI2 and Pr:SrI2 single crystals. Light yields of Pr1, 2, 3 and 5%:SrI2 single crystals under γ-ray irradiation were 7700, 8700, 7200 and 6700 photons/MeV, respectively. Decay times of Pr1 and 2%:SrI2 single crystals under γ-ray irradiation were 55.9 and 35.0 ns of the fast decay component, and 435 and 408 ns of the slow decay component, respectively.

  6. Photoelectron diffraction studies of small adsorbates on single crystal surfaces

    International Nuclear Information System (INIS)

    Pascal, Mathieu

    2002-01-01

    The structural determination of small molecules adsorbed on single crystal surfaces has been investigated using scanned energy mode photoelectron diffraction (PhD). The experimental PhD data were compared to theoretical models using a simulation program based on multiple scattering calculations. Three adsorption systems have been examined on Ag(110), Cu(110) and Cu(111) crystals. The structure of the (2x1)-O adsorption phase on Ag(110) revealed that the O atoms occupied the long bridge site and are almost co-planar with the top layer of Ag atoms. The best agreement between multiple scattering theory and experiment has been obtained for a missing-row (or equivalently an 'added- row') reconstruction. Alternative buckled-row and unreconstructed surface models can be excluded. The adsorption of the benzoate species on Cu(110) has been found to occur via the carboxylate group. The molecules occupy short bridge sites with the O atoms being slightly displaced from atop sites and are aligned along the close-packed azimuth. The tilt of the molecule with respect to the surface and the degree to which the surface is relaxed have also been investigated. The adsorption of methyl on Cu(111) was studied using either azomethane or methyl iodide to prepare the surface layers. At saturation coverage the preferred adsorption site is the fcc threefold hollow site, whereas at half saturation coverage ∼ 30 % of the methyl species occupy the hop threefold hollow sites. Best agreement between theory and experiment corresponded to a methyl group adsorbed with C 3v symmetry. The height of the C above the surface in a pure methyl layer was 1.66 ± 0.02 A, but was reduced to 1.62 ± 0.02 A in the presence of co-adsorbed iodine, suggesting that iodine increases the strength of adsorption. Iodine was also found to occupy the fee threefold hollow sites with a Cu-l bondlength of 2.61 ± 0.02 A. (author)

  7. Compression of Single-Crystal Orthopyroxene to 60GPa

    Science.gov (United States)

    Finkelstein, G. J.; Dera, P. K.; Holl, C. M.; Dorfman, S. M.; Duffy, T. S.

    2010-12-01

    Orthopyroxene ((Mg,Fe)SiO3) is one of the dominant phases in Earth’s upper mantle - it makes up ~20% of the upper mantle by volume. At high pressures and temperatures, this phase undergoes several well-characterized phase transitions. However, when compressed at low temperature and high-pressure, orthopyroxene is predicted to exhibit metastable behavior(1). Previous researchers have found orthoenstatite (Mg endmember of orthopyroxene) persists up to ~10 GPa, and diffraction(2-3), Raman(4), and elasticity(5) experiments suggest a phase transition above this pressure to an as-yet unidentified structure. While earlier diffraction data has surprisingly only been evaluated for structural information to ~9 GPa(2), changes in high-pressure Raman spectra to ~70 GPa indicate that several more high-pressure phase transitions in orthopyroxene are likely, including at least one change in Si-coordination(6). We have recently conducted exploratory experiments to further elucidate the high-pressure behavior of orthopyroxene. Compressing a single crystal of Fe-rich orthopyroxene (Fe0.66Mg0.24Ca0.05SiO3) using a diamond anvil cell, we observe phase transitions at ~10, 14, and 30 GPa, with the new phases having monoclinic, orthorhombic, and orthorhombic symmetries, respectively. While the first two transitions do not show a significant change in volume, the phase transition at ~30 GPa shows a large decrease in volume, which is consistent with a change in Si coordination number to mixed 4- and 6-fold coordination. References: [1] S. Jahn, American Mineralogist 93, 528-532 (2008). [2] R. J. Angel, J. M. Jackson, American Mineralogist 87, 558-561 (2002). [3] R. J. Angel, D. A. Hugh-Jones, Journal of Geophysical Research-Solid Earth 99, 19,777-19,783 (1994). [4] G. Serghiou, Journal of Raman Spectroscopy 34, 587-590 (2003). [5] J. Kung et al., Physics of the Earth and Planetary Interiors 147, 27-44 (2004). [6] G. Serghiou, A. Chopelas, R. Boehler, Journal of Physics: Condensed Matter

  8. Study of dopamine reactivity on platinum single crystal electrode surfaces

    International Nuclear Information System (INIS)

    Chumillas, Sara; Figueiredo, Marta C.; Climent, Víctor; Feliu, Juan M.

    2013-01-01

    Dopamine is the biological molecule responsible, among other functions, of the heart beat and blood pressure regulation. Its loss, in the human body, can result in serious diseases such as Parkinson's, schizophrenia or depression. Structurally, this molecule belongs to the group of catecholamines, together with epinephrine (adrenaline) and norepinephrine (noradrenaline). The hydroquinone moiety of the molecule can be easily oxidized to quinone, rendering the electrochemical methods a convenient approach for the development of dopamine biosensors. The reactivity of similar aromatic molecules, such as catechol and hydroquinone, at well-ordered platinum surfaces, has recently been investigated in our group. In this paper, we extend these studies to the structurally related molecule dopamine. The study has been performed in neutral pH, since this is closer to the natural conditions for these molecules in biological media. Cyclic voltammetry and in situ infra-red spectroscopy have been combined to extract information about the behavior of this molecule on well-defined platinum surfaces. Dopamine appears to be electrochemically active and reveals interesting adsorption phenomena at low potentials (0.15–0.25 V vs RHE), sensitive to the single crystal orientation. The adsorption of dopamine on these surfaces is very strong, taking place at much lower potentials than the electron transfer from solution species. Specifically, the voltammetry of Pt(1 1 1) and Pt(1 0 0) in dopamine solutions shows an oxidation peak at potentials close to the onset of hydrogen evolution, which is related to the desorption of hydrogen and the adsorption of dopamine. On the other hand, adsorption on Pt(1 1 0) is irreversible and the surface appears totally blocked. Spectroscopic results indicate that dopamine is adsorbed flat on the surface. At potentials higher than 0.6 V vs RHE the three basal planes show a common redox process. The initial formation of the quinone moiety is followed by a

  9. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

    Science.gov (United States)

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

    2011-12-23

    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Annealing effect on superconductivity of La2CuO4 single crystals

    International Nuclear Information System (INIS)

    Tanaka, I.; Takahashi, H.; Kojima, H.

    1992-01-01

    This paper reports that La 2 CuO 4 single crystals grown at an oxygen pressure of 0.2 MPa by TSFZ method are superconducting below 32 K, and show a semiconducting behavior in nonsuperconducting state. The single crystals of La 2 CuO 4 are changed from superconductors to semiconductors by annealing in argon, and are returned to superconductors by annealing at ambient pressure of oxygen. Therefore, superconductivity of the La 2 CuO 4 single crystals is due to excess oxygen

  11. Annealing effect on superconductivity of La2CuO4 single crystals

    International Nuclear Information System (INIS)

    Tanaka, L.; Takahashi, H.; Kojima, H.

    1992-01-01

    La 2 CuO 4 single crystals grown at an oxygen pressure of 0.2 MPa by TSFZ method are superconducting below 32 K, and show a semiconducting behavior in nonsuperconducting state. The single crystals of La 2 CuO 4 are changed from superconductors to semiconductors by annealing in argon, and are returned to superconductors by annealing at ambient pressure of oxygen. Therefore, superconductivity of the La 2 CuO 4 single crystals is due to excess oxygen. (orig.)

  12. Experimental study and numerical simulation of the plastic deformation of zirconium single crystals

    International Nuclear Information System (INIS)

    Lebon, C.

    2011-01-01

    There is only few experimental data in the literature on the zirconium single crystals and no constitutive laws for this single crystal material are provided. The goal of this work is then to create an experimental database like the Critical Resolved Shear Stress (CRSS) for the prismatic slip, the strain-hardening, the activation of the prismatic glide system and the activation volumes. We determine theses parameters from image correlation method. Then, we develop a new multi-scale approach using dislocations dynamics concept and finite element computations. Finally, a first single crystal constitutive law for the zirconium is proposed and a good agreement with the experimental data is obtained. (author) [fr

  13. Growth and microtopographic study of CuInSe{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Sanjaysinh M.; Chaki, Sunil, E-mail: sunilchaki@yahoo.co.in; Deshpande, M. P. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat - 388120 (India); Tailor, J. P. [Applied Physics Department, S.V.N.I.T., Surat, Gujarat - 395007 (India)

    2016-05-23

    The CuInSe{sub 2} single crystals were grown by chemical vapour transport (CVT) technique using iodine as transporting agent. The elemental composition of the as-grown CuInSe{sub 2} single crystals was determined by energy dispersive analysis of X-ray (EDAX). The unit cell crystal structure and lattice parameters were determined by X-ray diffraction (XRD) technique. The surface microtopographic study of the as-grown CuInSe{sub 2} single crystals surfaces were done to study the defects, growth mechanism, etc. of the CVT grown crystals.

  14. Regio-Regular Oligo and Poly(3-hexyl thiophene): Precise Structural Markers from the Vibrational Spectra of Oligomer Single Crystals.

    KAUST Repository

    Brambilla, Luigi; Tommasini, Matteo; Botiz, Ioan; Rahimi, Khosrow; Agumba, John O.; Stingelin, Natalie; Zerbi, Giuseppe

    2014-01-01

    , namely, amorphous, semicrystalline, polycrystalline and single crystal. We have based our analysis on the spectra of the (3HT)8 single crystal (whose structure has been determined by selected area electron diffraction) taken as reference

  15. Direct Observation of Halide Migration and its Effect on the Photoluminescence of Methylammonium Lead Bromide Perovskite Single Crystals.

    Science.gov (United States)

    Luo, Yanqi; Khoram, Parisa; Brittman, Sarah; Zhu, Zhuoying; Lai, Barry; Ong, Shyue Ping; Garnett, Erik C; Fenning, David P

    2017-11-01

    Optoelectronic devices based on hybrid perovskites have demonstrated outstanding performance within a few years of intense study. However, commercialization of these devices requires barriers to their development to be overcome, such as their chemical instability under operating conditions. To investigate this instability and its consequences, the electric field applied to single crystals of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) is varied, and changes are mapped in both their elemental composition and photoluminescence. Synchrotron-based nanoprobe X-ray fluorescence (nano-XRF) with 250 nm resolution reveals quasi-reversible field-assisted halide migration, with corresponding changes in photoluminescence. It is observed that higher local bromide concentration is correlated to superior optoelectronic performance in CH 3 NH 3 PbBr 3 . A lower limit on the electromigration rate is calculated from these experiments and the motion is interpreted as vacancy-mediated migration based on nudged elastic band density functional theory (DFT) simulations. The XRF mapping data provide direct evidence of field-assisted ionic migration in a model hybrid-perovskite thin single crystal, while the link with photoluminescence proves that the halide stoichiometry plays a key role in the optoelectronic properties of the perovskite. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Anisotropic magnetoresistance and anomalous Nernst effect in exchange biased permalloy/(1 0 0) NiO single-crystal

    Energy Technology Data Exchange (ETDEWEB)

    Holanda, J., E-mail: joseholanda@df.ufpe.br; Maior, D.S.; Azevedo, A.; Rezende, S.M.

    2017-06-15

    Highlights: • We have investigated the anisotropic magnetoresistance (AMR) and the anomalous Nernst effect (ANE) in an exchange-biased bilayer Py/(100) NiO single-Crystal. • The shift of the hysteresis loop, measured with the different techniques, yield approximately the same value of H{sub EB}. • In spite of the measurement techniques be based in different physical phenomena, our results confirm the robustness of the exchange anisotropy at the Py/NiO interface. • The strength of the anomalous Nernst effect for the exchange-biased permalloy film is compared to values measured in non biased films. - Abstract: We have investigated the anisotropic magnetoresistance (AMR) and the anomalous Nernst effect (ANE) in an exchange-biased bilayer consisting of a thin film of permalloy deposited on a single crystal antiferromagnetic NiO (1 0 0). The exchange bias field (H{sub EB}) value was obtained by means of AMR, ANE and magnetization hysteresis measurements. The shift of the hysteresis loop, measured with the three different techniques, yield approximately the same value of H{sub EB.} In spite of the measurement techniques be based in different physical phenomena, our results confirm the robustness of the exchange anisotropy at the Py/NiO interface. The strength of the anomalous Nernst effect for the exchange-biased permalloy film is compared to values measured in non biased films.

  17. Growth of single - crystals of Pb1-x Snx Te by vapor phase transport with the formation of a liquid/solid growth interface

    International Nuclear Information System (INIS)

    An, C.Y.; Bandeira, I.N.

    1985-01-01

    Due to segregation effects single-crystals of Pb 1-x Sn x Te growth by Bridgman techniques have an inhomogeneous composition profile. A vapor phase transport growth process has been developed in order to reduce convective flows. This is due to the very thin melt layer in front of the crystal, that makes convective flows small and solute mixing in the melt very low. By this process single-crystals with 60mm length by 15 mm diameter and a high degree of homogeneity have been grown. A process for determination of the exact composition profile by measurements of the crystal density, for isomorphous alloys of the type A 1-x B x , is also shown. (Author) [pt

  18. Single Crystal Piezomotor for Large Stroke, High Precision and Cryogenic Actuations, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes a novel single crystal piezomotor for large stroke, high precision, and cryogenic actuations with capability of position set-hold with...

  19. The tensile effect on crack formation in single crystal silicon irradiated by intense pulsed ion beam

    Science.gov (United States)

    Liang, Guoying; Shen, Jie; Zhang, Jie; Zhong, Haowen; Cui, Xiaojun; Yan, Sha; Zhang, Xiaofu; Yu, Xiao; Le, Xiaoyun

    2017-10-01

    Improving antifatigue performance of silicon substrate is very important for the development of semiconductor industry. The cracking behavior of silicon under intense pulsed ion beam irradiation was studied by numerical simulation in order to understand the mechanism of induced surface peeling observed by experimental means. Using molecular dynamics simulation based on Stillinger Weber potential, tensile effect on crack growth and propagation in single crystal silicon was investigated. Simulation results reveal that stress-strain curves of single crystal silicon at a constant strain rate can be divided into three stages, which are not similar to metal stress-strain curves; different tensile load velocities induce difference of single silicon crack formation speed; the layered stress results in crack formation in single crystal silicon. It is concluded that the crack growth and propagation is more sensitive to strain rate, tensile load velocity, stress distribution in single crystal silicon.

  20. Mechanism of the superior mechanical strength of nanometer-sized metal single crystals revealed

    KAUST Repository

    Afify, N. D.; Salem, H. G.; Yavari, A.; El Sayed, Tamer S.

    2013-01-01

    Clear understanding of the superior mechanical strength of nanometer-sized metal single crystals is required to derive advanced mechanical components retaining such superiority. Although high quality studies have been reported on nano

  1. Electrolytic coloration and spectral properties of hydroxyl-doped potassium chloride single crystals

    International Nuclear Information System (INIS)

    Gu Hongen; Wu Yanru

    2011-01-01

    Hydroxyl-doped potassium chloride single crystals are colored electrolytically at various temperatures and voltages using a pointed cathode and a flat anode. Characteristic OH - spectral band is observed in the absorption spectrum of uncolored single crystal. Characteristic O - , OH - , U, V 2 , V 3 , O 2- -V a + , F, R 2 and M spectral bands are observed simultaneously in absorption spectra of colored single crystals. Current-time curve for electrolytic coloration of hydroxyl-doped potassium chloride single crystal and its relationship with electrolytic coloration process are given. Production and conversion of color centers are explained. - Highlights: → Expanded the traditional electrolysis method. → Hydroxyl-doped potassium chloride crystals were colored electrolytically for the first time. → Useful V, F and F-aggregate color centers were produced in colored crystals. → V color centers were produced directly and F and F-aggregate color centers indirectly.

  2. Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering

    KAUST Repository

    Shi, Dong; Qin, X.; Li, Yuan; He, Yao; Zhong, Cheng; Pan, Jun; Dong, H.; Xu, Wei; Li, T.; Hu, W.; Bredas, Jean-Luc; Bakr, Osman

    2016-01-01

    bottleneck for advancing cell efficiencies. We devised an antisolvent crystallization strategy to grow single crystals of spiro-OMeTAD, which allowed us to experimentally elucidate its molecular packing and transport properties. Electronic structure

  3. Mechanism of the superior mechanical strength of nanometer-sized metal single crystals revealed

    KAUST Repository

    Afify, N. D.

    2013-10-01

    Clear understanding of the superior mechanical strength of nanometer-sized metal single crystals is required to derive advanced mechanical components retaining such superiority. Although high quality studies have been reported on nano-crystalline metals, the superiority of small single crystals has neither been fundamentally explained nor quantified to this date. Here we present a molecular dynamics study of aluminum single crystals in the size range from 4.1 nm to 40.5 nm. We show that the ultimate mechanical strength deteriorates exponentially as the single crystal size increases. The small crystals superiority is explained by their ability to continuously form vacancies and to recover them. © 2013 Published by Elsevier B.V.

  4. Twinning behavior in the Ti-5at.% Al single crystals during cyclic loading along [0001

    International Nuclear Information System (INIS)

    Xiao Lin

    2005-01-01

    Cyclic deformation behavior of Ti-5at.% Al single crystals subjected to pull-push cyclic load along [0001] crystallographic orientation was studied. A higher cyclic stress response was displayed in the Ti-5Al single crystal oriented for [0001] than that oriented for single prism slip. Optical microscopy and transmission electron microscopy examinations show that twinning is a dominant plastic deformation mode in the single crystals during cycling. Trace analysis of prepolished surfaces was used to identify the twin systems primarily responsible for deformation. The major twin type observed was {101-bar 2}, {112-bar 2}, {101-bar 1} and {112-bar 1}. slip was observed in the neighboring region of twins in the fatigued specimens. The activation of multiple twinning systems contributed to the higher cyclic saturation stress in Ti-5Al single crystals oriented for [0001

  5. Ultrafast carrier dynamics in pentacene, functionalized pentacene, tetracene, and rubrene single crystals

    NARCIS (Netherlands)

    Ostroverkhova, O; Cooke, DG; Hegmann, FA; Anthony, JE; Podzorov, [No Value; Gershenson, ME; Jurchescu, OD; Palstra, TTM

    2006-01-01

    We measure the transient photoconductivity in pentacene, functionalized pentacene, tetracene, and rubrene single crystals using optical pump-terahertz probe techniques. In all of the samples studied, we observe subpicosecond charge photogeneration and a peak photoconductive response that increases

  6. Growth, structural, optical and surface analysis of piperazinium tartrate: A NLO single crystal

    Science.gov (United States)

    Gupta, Apurva; Raseel Rahman M., K.; Nair, Lekha

    2018-05-01

    Single crystal of piperazinium tartrate (PPZT) was grown by the slow evaporation solution growth technique at room temperature. Crystallinity of grown crystal was examined by powder X-ray diffraction. High transparency and wide band gap were observed in the UV-Visible spectroscopic studies. Intense and broad emissions were observed in the blue region, as that is indicated by photoluminescence spectroscopy. The quality of the grown PPZT single crystals were analyzed by the etching studies using the water as the etchant.

  7. Modeling Nonlinear Elastic-plastic Behavior of RDX Single Crystals During Indentation

    Science.gov (United States)

    2012-01-01

    single crystals has also been probed using shock experiments (6, 12) and molecular dynamics simulations (12–14). RDX undergoes a polymorphic phase...Patterson, J.; Dreger, Z.; Gupta, Y. Shock-wave Induced Phase Transition in RDX Single Crystals. J. Phys. Chem. B 2007, 111, 10897–10904. 17. Bedrov, D...and Volume Compression of β - HMX and RDX . In Proc. Int. Symp. High Dynamic Pressures; Commissariat a l’Energie Atomique: Paris, 1978; pp 3–8. 24

  8. Welding and Weldability of Directionally Solidified Single Crystal Nickel-Base Superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Vitek, J M; David, S A; Reed, R W; Burke, M A; Fitzgerald, T J

    1997-09-01

    Nickel-base superalloys are used extensively in high-temperature service applications, and in particular, in components of turbine engines. To improve high-temperature creep properties, these alloys are often used in the directionally-solidified or single-crystal form. The objective of this CRADA project was to investigate the weldability of both experimental and commercial nickel-base superalloys in polycrystalline, directionally-solidified, and single-crystal forms.

  9. Reversible Single-Crystal-to-Single-Crystal Structural Transformation in a Mixed-Ligand 2D Layered Metal-Organic Framework: Structural Characterization and Sorption Study

    Directory of Open Access Journals (Sweden)

    Chih-Chieh Wang

    2017-12-01

    Full Text Available A 3D supramolecular network, [Cd(bipy(C4O4(H2O2]·3H2O (1 (bipy = 4,4′-bipyridine and C4O42− = dianion of H2C4O4, constructed by mixed-ligand two-dimensional (2D metal-organic frameworks (MOFs has been reported and structurally determined by the single-crystal X-ray diffraction method and characterized by other physicochemical methods. In 1, the C4O42− and bipy both act as bridging ligands connecting the Cd(II ions to form a 2D layered MOF, which are then extended to a 3D supramolecular network via the mutually parallel and interpenetrating arrangements among the 2D-layered MOFs. Compound 1 shows a two-step dehydration process with weight losses of 11.0% and 7.3%, corresponding to the weight-loss of three guest and two coordinated water molecules, respectively, and exhibits an interesting reversible single-crystal-to-single-crystal (SCSC structural transformation upon de-hydration and re-hydration for guest water molecules. The SCSC structural transformation have been demonstrated and monitored by single-crystal and X-ray powder diffraction, and thermogravimetic analysis studies.

  10. Effect of indium and antimony doping in SnS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chaki, Sunil H., E-mail: sunilchaki@yahoo.co.in; Chaudhary, Mahesh D.; Deshpande, M.P.

    2015-03-15

    Highlights: • Single crystals growth of pure SnS, indium doped SnS and antimony doped SnS by direct vapour transport (DVT) technique. • Doping of In and Sb occurred in SnS single crystals by cation replacement. • The replacement mechanism ascertained by EDAX, XRD and substantiated by Raman spectra analysis. • Dopants concentration affects the optical energy bandgap. • Doping influences electrical transport properties. - Abstract: Single crystals of pure SnS, indium (In) doped SnS and antimony (Sb) doped SnS were grown by direct vapour transport (DVT) technique. Two doping concentrations of 5% and 15% each were employed for both In and Sb dopants. Thus in total five samples were studied viz., pure SnS (S1), 5% In doped SnS (S2), 15% In doped SnS (S3), 5% Sb doped SnS (S4) and 15% Sb doped SnS (S5). The grown single crystal samples were characterized by evaluating their surface microstructure, stoichiometric composition, crystal structure, Raman spectroscopy, optical and electrical transport properties using appropriate techniques. The d.c. electrical resistivity and thermoelectric power variations with temperature showed semiconducting and p-type nature of the as-grown single crystal samples. The room temperature Hall Effect measurements further substantiated the semiconducting and p-type nature of the as-grown single crystal samples. The obtained results are deliberated in detail.

  11. Unidirectional growth and characterization of L-arginine monohydrochloride monohydrate single crystals

    International Nuclear Information System (INIS)

    Sangeetha, K.; Babu, R. Ramesh; Bhagavannarayana, G.; Ramamurthi, K.

    2011-01-01

    Highlights: → L-Arginine monohydrochloride monohydrate (LAHCl) single crystal was grown successfully by unidirectional solution growth method for the first time. → High crystalline perfection was observed for UDS grown crystal compared to CS grown crystal. → The optical transparency and mechanical stability are high for UDS grown LAHCl single crystal. → Optical birefringence measurement on this material. → The piezoelectric resonance frequencies observation - first time observation on this material. - Abstract: L-Arginine monohydrochloride monohydrate (LAHCl) single crystals were grown successfully by conventional and unidirectional solution growth methods. The crystalline perfection of grown crystals was analyzed by high-resolution X-ray diffraction. The linear optical transmittance, mechanical stability of conventional and unidirectional grown LAHCl single crystals were analyzed and compared along (0 0 1) plane. The refractive index and birefringence of LAHCl single crystals were also measured using He-Ne laser source. From the dielectric studies, piezoelectric resonance frequencies were observed in kHz frequency range for both conventional and unidirectional grown LAHCl single crystals along (0 0 1) plane.

  12. Growth and characterization of air annealing Mn-doped YAG:Ce single crystal for LED

    International Nuclear Information System (INIS)

    Xiang, Weidong; Zhong, Jiasong; Zhao, Yinsheng; Zhao, Binyu; Liang, Xiaojuan; Dong, Yongjun; Zhang, Zhimin; Chen, Zhaoping; Liu, Bingfeng

    2012-01-01

    Highlights: ► The YAG:Ce,Mn single crystal was well synthesized by the Czochralski (CZ) method. ► The emission intensity of the sample has been influenced after annealing. ► Annealed in the air at 1200 °C was the most optimal annealing condition. ► The single crystal could be used in the white light LED which emitted by blue light. - Abstract: The growth of Mn-doped YAG:Ce (yttrium aluminum garnet doped cerium) single crystal by the Czochralski (CZ) method and the characterization of its spectroscopy and color-electric parameters are presented. The absorption spectra indicate that the crystal absorbed highly in the 300–500 nm wavelength range. The emission spectrum of the crystal consists of a peak around 538 nm when excited by 460 nm blue light, which prove the YAG:Ce,Mn single crystal could be used in the white light emitting doides (LED). The different charges of Mn ions have different luminescence properties, and the air annealing process for the single crystal would change the concentration of Mn ions with different charges, which could influence the emission intensity of the single crystal.

  13. Critical current, pinning and resistive state of superconducting single-crystal niobium with different types of defect structure

    International Nuclear Information System (INIS)

    Sokolenko, V.I.; Starodubov, Ya.D.

    2005-01-01

    Critical current pinning and resistive state of single crystal niobium of texture orientation are studied for different structural states obtained by rolling at 20 K by 42% and polishing the surface layers. It is found that the heterogeneous structures typical of the strained sample even after its thinning down to approx 10% display a lower current-carrying capability due to an increase of the thermomagnetic instability within the fragmented structure sections in the near-surface layers. For a homogeneous defect structure of the sample core with the density of equilibrium distributed dislocations of 1.3 centre dot 10 11 cm -2 , a correlation between the normal current density and the critical current density in the resistive state is found, in agreement with the concepts of flux creep due to the scatter of local values of J c

  14. Effect of amaranth dye on the growth and properties of conventional and SR method grown KAP single crystals

    Science.gov (United States)

    Babu Rao, G.; P., Rajesh; Ramasamy, P.

    2018-04-01

    The 0.1 mol% amaranth added KAP single crystals were grown from aqueous solutions by both slow evaporation solution technique and Sankaranarayanan-Ramasamy method. The single crystal having dimension of 45 mm length and 12 mm diameter was grown with growth rate of 1.5 mm/day using SR method. 87 % transmittance is obtained for SR method grown amaranth added KAP single crystal. The high intense luminescence at 661 nm is obtained from amaranth added conventional and SR method grown KAP single crystal. The amaranth added KAP single crystal possesses good mechanical and laser damage threshold stability.

  15. UV detectors based on epitaxial diamond films grown on single-crystal diamond substrates by vapor-phase synthesis

    International Nuclear Information System (INIS)

    Sharonov, G.V.; Petrov, S.A.; Bol'shakov, A.P.; Ral'chenko, V.G.; Kazyuchits, N.M.

    2010-01-01

    The prospects for use of CVD-technology for epitaxial growth of single-crystal diamond films of instrumental quality in UHF plasma for the production of optoelectronic devices are discussed. A technology for processing diamond single crystals that provides a perfect surface crystal structure with roughness less than 0,5 nm was developed. It was demonstrated that selective UV detectors based on synthetic single-crystal diamond substrates coated with single-crystal films can be produced. A criterion for selecting clean and structurally perfect single crystals of synthetic diamond was developed for the epitaxial growth technology. (authors)

  16. Hopping conduction in gamma-irradiated InSe and InSe:Sn single crystals

    International Nuclear Information System (INIS)

    MUSTAFAEVA, S.N.; ISMAILOV, A.A.; ASADOV, M.M.

    2010-01-01

    Full text : The semiconductive InSe layer compound is characterized by a strong covalent bond inside the layers and a weak Van der Waals bonding between them. It was shown that across the layers of InSe single crystals at low temperatures (T ≤ 200 K) at direct current (dc) hopping conduction through localized states near the Fermi level takes place. The results of dc-conductivity of gamma-irradiated p-InSe and n-InSe : Sn layer single crystals have been presented in this work. ρ-InSe single crystal specimens grown by the Bridgman method were used in the experiments. Plates of the crystals under study were obtained by cleaving along the layers of single crystal ingots. The single-crystal InSe samples for electric measurements had the form of planar capacitors normal to the C axis of the crystals, with silver-paste electrodes. The thickness of the InSe samples was 300 mkm. Co 60 serves as the source of irradiation with energy of gamma-quantum equal to 1.3 MeV. The electric properties of non-irradiated and gamma-irradiated InSe crystals were measured under the same conditions. It is revealed that InSe and InSe : Sn (0.2 and 0.4 mole percent Sn) single crystals exhibit a variable range hopping conduction along a normal to their natural layers at temperatures T≤200 K in a dc electric field. From experimental data the parameters of localized states of p-InSe and n-InSe : Sn were calculated before and after gamma-irradiation. It is revealed that gamma-irradiation of p-InSe and n-InSe : Sn (0.2 and 0.4 mole percent Sn) single crystals leads to significant change of localized states parameters. After gamma-irradiation the density of states near the Fermi level increased, but their energy spread and the average jump distance decreased. The concentrations of radiated defects were estimated in p-InSe (5.18*10 1 7 sm - 3) and n-InSe : Sn (2.5*10 1 7 - 2.7*10 1 8 sm - 3) single crystals. The present results demonstrate that gamma-irradiation offers the possibility of tuning

  17. Single crystal and optical ceramic multicomponent garnet scintillators: A comparative study

    International Nuclear Information System (INIS)

    Wu, Yuntao; Luo, Zhaohua; Jiang, Haochuan; Meng, Fang; Koschan, Merry; Melcher, Charles L.

    2015-01-01

    Multicomponent garnet materials can be made in optical ceramic as well as single crystal form due to their cubic crystal structure. In this work, high-quality Gd 3 Ga 3 Al 2 O 12 :0.2 at% Ce (GGAG:Ce) single crystal and (Gd,Lu) 3 Ga 3 Al 2 O 12 :1 at% Ce (GLuGAG:Ce) optical ceramics were fabricated by the Czochralski method and a combination of hot isostatic pressing (HIPing) and annealing treatment, respectively. Under optical and X-ray excitation, the GLuGAG:Ce optical ceramic exhibits a broad Ce 3+ transition emission centered at 550 nm, while the emission peak of the GGAG:Ce single crystal is centered at 540 nm. A self-absorption effect in GLuGAG:Ce optical ceramic results in this red-shift of the Ce 3+ emission peak compared to that in the GGAG:Ce single crystal. The light yield under 662 keV γ-ray excitation was 45,000±2500 photons/MeV and 48,200±2410 photons/MeV for the GGAG:Ce single crystal and GLuGAG:Ce optical ceramic, respectively. An energy resolution of 7.1% for 662 keV γ-rays was achieved in the GLuGAG:Ce optical ceramic with a Hamamatsu R6231 PMT, which is superior to the value of 7.6% for a GGAG:Ce single crystal. Scintillation decay time measurements under 137 Cs irradiation show two exponential decay components of 58 ns (47%) and 504 ns (53%) for the GGAG:Ce single crystal, and 84 ns (76%) and 148 ns (24%) for the GLuGAG:Ce optical ceramic. The afterglow level after X-ray cutoff in the GLuGAG:Ce optical ceramic is at least one order of magnitude lower than in the GGAG:Ce single crystal. - Highlights: • GGAG:Ce single crystal and GLuGAG:Ce optical ceramics were fabricated. • The light yield of both ceramic and crystal G(Lu)GAG:Ce reached the level of 45,000 photons/MeV. • GLuGAG:Ce optical ceramic showed a better energy resolution of 7.1% for 662 keV. • GLuGAG:Ce ceramics exhibited lower afterglow level than that of GGAG:Ce single crystals. • The possible optimization strategies for multicomponent aluminate garnets are discussed

  18. Determination of temperature-dependent thermal conductivity of a BaSnO{sub 3−δ} single crystal by using the 3ω method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyung Joon; Kim, Tai Hoon; Lee, Woong-Jhae; Chai, Yisheng; Kim, Jae Wook; Jwa, Yeon Jae; Chung, Sukhwan; Kim, Seon Joong; Sohn, Egon [Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Lee, Seung Min [Hanbeam Corporation Ltd, Iui-dong 906-5, Yeongtong-gu, Suwon-si, Gyeonggi-do (Korea, Republic of); Choi, Ki-Young [Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Kim, Kee Hoon, E-mail: khkim@phya.snu.ac.kr [Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-06-01

    Highlights: • This is the first report about thermal conductivity of BaSnO{sub 3−δ} single crystals. • We report the successful κ measurement of the crystals by employing the 3ω method. • The BaSnO{sub 3−δ} single crystal can be a good perovskite substrate with high κ. • We found that phonons mainly contribute to the heat transport in BaSnO{sub 3−δ}. - Abstract: The single crystal of the electron doped BaSnO{sub 3−δ} system has been recently found to have high electrical mobility (up to 320 cm{sup 2} V{sup −1} s{sup −1}) at room temperature and excellent oxygen stability. Although thermal conductivity (κ) of the BaSnO{sub 3−δ} single crystal is an important physical quantity, the κ measurement by the conventional DC method has been difficult due to the limited crystal size. Herein, we report the first measurement of κ by using the 3ω method from ∼20 to 300 K in the oxygen deficient BaSnO{sub 3−δ} single crystal with carrier concentration of ∼10{sup 18} cm{sup −3}. We found that κ is proportional to T{sup −1} above 50 K, indicating that phonons mainly contribute to the heat transport. Moreover, the electronic contribution is determined as ∼4% of the measured κ from the Wiedemann–Franz law. The κ value is 0.132 W cm{sup −1} K{sup −1} at room temperature and is increased progressively at lower temperatures, becoming overall larger than that of the SrTiO{sub 3} single crystal. Our results thus point out that BaSnO{sub 3−δ} can be a good substrate for growing transparent electronic thin films with the perovskite structure.

  19. Anisotropic surface hole-transport property of triphenylamine-derivative single crystal prepared by solution method

    Energy Technology Data Exchange (ETDEWEB)

    Umeda, Minoru, E-mail: mumeda@vos.nagaokaut.ac.jp [Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Katagiri, Mitsuhiko; Shironita, Sayoko [Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Nagayama, Norio [Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Ricoh Company, Ltd., Nishisawada, Numazu, Shizuoka 410-0007 (Japan)

    2016-12-01

    Highlights: • A hole transport molecule was investigated based on its electrochemical redox characteristics. • The solubility and supersolubility curves of the molecule were measured in order to prepare a large crystal. • The polarization micrograph and XRD results revealed that a single crystal was obtained. • An anisotropic surface conduction, in which the long-axis direction exceeds that of the amorphous layer, was observed. • The anisotropic surface conduction was well explained by the molecular stacked structure. - Abstract: This paper reports the anisotropic hole transport at the triphenylamine-derivative single crystal surface prepared by a solution method. Triphenylamine derivatives are commonly used in a hole-transport material for organic photoconductors of laser-beam printers, in which the materials are used as an amorphous form. For developing organic photovoltaics using the photoconductor’s technology, preparation of a single crystal seems to be a specific way by realizing the high mobility of an organic semiconductor. In this study, a single crystal of 4-(2,2-diphenylethenyl)-N,N-bis(4-methylphenyl)-benzenamine (TPA) was prepared and its anisotropic hole-transport property measured. First, the hole-transport property of the TPA was investigated based on its chemical structure and electrochemical redox characteristics. Next, a large-scale single crystal formation at a high rate was developed by employing a solution method based on its solubility and supersolubility curves. The grown TPA was found to be a single crystal based on the polarization micrograph observation and crystallographic analysis. For the TPA single crystal, an anisotropic surface conduction was found, which was well explained by its molecular stack structure. The measured current in the long-axis direction is one order of magnitude greater than that of amorphous TPA.

  20. Synthesis and photocatalytic activity of mesoporous – (001) facets TiO_2 single crystals

    International Nuclear Information System (INIS)

    Dong, Yeshuo; Fei, Xuening; Zhou, Yongzhu

    2017-01-01

    Highlights: • The (001) facets of TiO_2 single crystals with mesoporous structure. • The (010) and (100) facets of TiO_2 single crystals were covered by the flower – shaped TiO_2 crystals. • This special structure could promote charge separation and provide more active sites, which will lead to a substantial increase in photocatalytic activity. - Abstract: In this work, the mesoporous – (001) facets TiO_2 single crystals have been successfully synthesized through a two-step solvothermal route without any template. Their structure and morphology were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy and energy dispersive X-ray spectrometer (EDX). Based on the different characteristics and atomic arrangements on each facet of anatase TiO_2 single crystals, we synthesized these mesoporous – (001) facets TiO_2 single crystals by controlling the interaction characteristics of hydrofluoric acid (HF) and isopropanol (i-PrOH) on the crystal facets. It can been seen that the (001) facets of these as-synthesized TiO_2 single crystals have a clear mesoporous structure through the SEM images and BET methods. Moreover, the other four facets were covered by the flower – shaped TiO_2 crystals with the generation of the mesoporous – (001) facets. This special and interesting morphology could promote charge separation and provide more active sites, which will lead to a substantial increase in photocatalytic activity. Moreover, it is more intuitive to reflect that the different crystal facets possess the different properties due to their atomic arrangement. Besides, according to the different synthetic routes, we proposed and discussed a plausible synthesis mechanism of these mesoporous – (001) facets TiO_2 single crystals.

  1. Synthesis and ultrastructure of plate-like apatite single crystals as a model for tooth enamel

    International Nuclear Information System (INIS)

    Zhuang, Zhi; Yoshimura, Hideyuki; Aizawa, Mamoru

    2013-01-01

    Hydroxyapatite (HAp) is an inorganic constituent compound of human bones and teeth, with superior biocompatibility and bioactivity characteristics. Its crystal structure is hexagonal, characterized by a(b)- and c-planes. In vertebrate long bones, HAp crystals have a c-axis orientation, while in tooth enamel, they have an a(b)-axis orientation. Many methods can be used to synthesize c-axis oriented HAp single crystals; however, to the best of our knowledge, there have been no reports on a synthesis method for a(b)-axis oriented HAp single crystals. In this study, we successfully synthesized plate-like HAp crystals at the air–liquid interface of a starting solution via an enzyme reaction of urea with urease. Crystal phase analysis and ultrastructure observations were carried out, and the results indicated that the particles were single crystals, with almost the same a(b)-axis orientation as tooth enamel. It is hoped that by utilizing their unique surface charge and atomic arrangement, the resulting particles can be used as a high-performance biomaterial, capable of adsorbing bio-related substances and a model for tooth enamel. - Highlights: ► Synthesis of plate-like hydroxyapatite crystals at air–liquid interface ► Ultrastructural analysis of plate-like hydroxyapatite crystals ► Plate-like hydroxyapatite single crystals with a high a(b)-axis orientation ► Plate-like hydroxyapatite single crystals as a model for tooth enamel

  2. BiI{sub 3} single crystal for room-temperature gamma ray detectors

    Energy Technology Data Exchange (ETDEWEB)

    Saito, T., E-mail: saito.tatsuya125@canon.co.jp [Frontier Research Center, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo 146-8501 (Japan); Iwasaki, T. [Frontier Research Center, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo 146-8501 (Japan); Kurosawa, S.; Yoshikawa, A. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Den, T. [Frontier Research Center, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo 146-8501 (Japan)

    2016-01-11

    BiI{sub 3} single crystals were grown by the physical vapor transport method. The repeated sublimation of the starting material reduced impurities in the BiI{sub 3} single crystal to sub-ppm levels. The detector was fabricated by depositing Au electrodes on both surfaces of the 100-μm-thick BiI{sub 3} single crystal platelet. The resistivity of the BiI{sub 3} single crystal was increased by post-annealing in an iodine atmosphere (ρ=1.6×10{sup 11} Ω cm). Pulse height spectroscopy measurements showed clear peaks in the energy spectrum of alpha particles or gamma rays. It was estimated that the mobility-lifetime product was μ{sub e}τ{sub e}=3.4–8.5×10{sup −6} cm{sup 2}/V and the electron–hole pair creation energy was 5.8 eV. Our results show that BiI{sub 3} single crystals are promising candidates for detectors used in radiographic imaging or gamma ray spectroscopy.

  3. Atomic structures and mechanical properties of single-crystal GaN nanotubes

    International Nuclear Information System (INIS)

    Xu, B.; Lu, A.J.; Pan, B.C.; Yu, Q.X.

    2005-01-01

    An approach is proposed to theoretically construct a realistic single-crystal GaN nanotube at atomic scale. The generated atomic structures of the single-crystal GaN nanotubes match the structural aspects from experiment very well. Our energetic calculations show that a single-crystal GaN nanotube with [100]-oriented lateral facets is more stable than that with [110]-oriented lateral facets, when they have around the same wall thickness. For a specified orientation of the lateral facets on the single-crystal GaN nanotubes, the energetic stabilities of the tubes obey a P rule, in which P is the ratio of the number of four-coordinated atoms to the number of three-coordinated atoms. Furthermore, the Young's modulus of the considered GaN nanotubes decrease with increasing the ratio of the number of bulk atoms to the number of surface atoms in each type of tube. Our calculations and analysis demonstrate that the surface effect of a single-crystal nanotube enhances its Young's modulus significantly

  4. High Performance Relaxor-Based Ferroelectric Single Crystals for Ultrasonic Transducer Applications

    Directory of Open Access Journals (Sweden)

    Yan Chen

    2014-07-01

    Full Text Available Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3O3-PbTiO3 (PMN-PT have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60% near the morphotropic phase boundary (MPB. Ternary Pb(In1/2Nb1/2O3-Pb(Mg1/3Nb2/3O3-PbTiO3 (PIN-PMN-PT single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed.

  5. Synthesis and ultrastructure of plate-like apatite single crystals as a model for tooth enamel

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Zhi, E-mail: zhuang@meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Yoshimura, Hideyuki, E-mail: hyoshi@isc.meiji.ac.jp [Department of Physics, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Aizawa, Mamoru, E-mail: mamorua@isc.meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan)

    2013-07-01

    Hydroxyapatite (HAp) is an inorganic constituent compound of human bones and teeth, with superior biocompatibility and bioactivity characteristics. Its crystal structure is hexagonal, characterized by a(b)- and c-planes. In vertebrate long bones, HAp crystals have a c-axis orientation, while in tooth enamel, they have an a(b)-axis orientation. Many methods can be used to synthesize c-axis oriented HAp single crystals; however, to the best of our knowledge, there have been no reports on a synthesis method for a(b)-axis oriented HAp single crystals. In this study, we successfully synthesized plate-like HAp crystals at the air–liquid interface of a starting solution via an enzyme reaction of urea with urease. Crystal phase analysis and ultrastructure observations were carried out, and the results indicated that the particles were single crystals, with almost the same a(b)-axis orientation as tooth enamel. It is hoped that by utilizing their unique surface charge and atomic arrangement, the resulting particles can be used as a high-performance biomaterial, capable of adsorbing bio-related substances and a model for tooth enamel. - Highlights: ► Synthesis of plate-like hydroxyapatite crystals at air–liquid interface ► Ultrastructural analysis of plate-like hydroxyapatite crystals ► Plate-like hydroxyapatite single crystals with a high a(b)-axis orientation ► Plate-like hydroxyapatite single crystals as a model for tooth enamel.

  6. Structure of single-chain single crystals of isotactic polystyrene and their radiation resistance

    International Nuclear Information System (INIS)

    Bu Haishan; Cao Jie; Xu Shengyong; Zhang Ze

    1997-01-01

    The structure of the single-chain single crystals of isotactic polystyrene (i-PS) was investigated by electron diffraction (ED) and high resolution electron microscopy (HREM). The nano-scale single-chain single crystals were found to be very stable to electron irradiation. According to the unit cell of i-PS crystals, the reflection rings in ED pattern and the lattice fringes in HREM images could be indexed, but the lower-index diffractions were not found. It is proposed that the single-chain single crystals are very small, thus secondary electrons may be allowed to escape and radiation damage is highly reduced, and that there are less lower-index lattice planes in the single-chain single crystals to provide sufficient diffraction intensity for recording. HREM images can be achieved at room temperature in the case of single-chain single crystals because of its stability to electron irradiation, therefore, this might be a novel experimental approach to the study of crystal structure of macromolecules

  7. Optical properties of GaS:Ho3+ and GaS:Tm3+ single crystals

    International Nuclear Information System (INIS)

    Jin, Moon-Seog; Kim, Chang-Dae; Kim, Wha-Tek

    2004-01-01

    GaS:Ho 3+ and GaS:Tm 3+ single crystals were grown by using the chemical transport reaction method. We measured the optical absorption, the infra-red absorption, and the photoluminescence spectra of the single crystals. The direct and the indirect energy band gaps of the single crystals at 13 K were identified. Infra-red absorption peaks at 6 K appeared in the single crystals. Broad emission bands at 6 K were observed at 464 nm and 580 nm for GaS:Ho 3+ and 462 nm and 581 nm for GaS:Tm 3+ . These broad emission bands were identified as originating from donor-acceptor pair recombinations. Sharp emission peak groups were observed near 435 nm, 495 nm, and 660 nm for GaS:Ho 3+ and near 672 nm for GaS:Tm 3+ . These sharp emission peak groups were identified as being due to the electron transitions between the energy levels of Ho 3+ and Tm 3+ . Especially, white photoluminescence was obtained in the GaS:Ho 3+ single crystal.

  8. Angular and magnetic field dependences of critical current in irradiated YBaCuO single crystals

    International Nuclear Information System (INIS)

    Petrusenko, Yu.

    2010-01-01

    The investigation of mechanisms responsible for the current-carrying capability of irradiated high-temperature superconductors (HTSC) was realized. For the purpose, experiments were made to investigate the effect of point defects generated by high-energy electron irradiation on the critical temperature and the critical current in high-Tc superconducting single crystals YBa 2 Cu 3 O 7-x . The transport current density measured in HTSC single crystals YBa 2 Cu 3 O 7-x by the dc-method was found to exceed 80000 A/cm 2 . The experiments have demonstrated a more than 30-fold increase in the critical current density in single crystals irradiated with 2.5 MeV electrons to a dose of 3·10 18 el/cm 2 . Detailed studies were made into the anisotropy of critical current and the dependence of critical current on the external magnetic field strength in irradiated single crystals. A high efficiency of point defects as centers of magnetic vortex pinning in HTSC single crystals was first demonstrated.

  9. Strengthening mechanisms of Fe nanoparticles for single crystal Cu–Fe alloy

    International Nuclear Information System (INIS)

    Shi, Guodong; Chen, Xiaohua; Jiang, Han; Wang, Zidong; Tang, Hao; Fan, Yongquan

    2015-01-01

    A single crystal Cu–Fe alloy with finely dispersed precipitate Fe nanoparticles was fabricated in this study. The interface relationship of iron nanoparticle and copper matrix was analyzed with a high-resolution transmission electron microscope (HRTEM), and the effect of Fe nanoparticles on mechanical properties of single crystal Cu–Fe alloy was discussed. Results show that, the finely dispersed Fe nanoparticles can be obtained under the directional solidification condition, with the size of 5–50 nm and the coherent interface between the iron nanoparticle and the copper matrix. Single crystal Cu–Fe alloy possesses improved tensile strength of 194.64 MPa, and total elongation of 44.72%, respectively, at room temperature, in contrast to pure Cu sample. Nanoparticles which have coherent interface with matrix can improve the dislocation motion state. Some dislocations can slip through the nanoparticle along the coherent interface and some dislocations can enter into the nanoparticles. Thus to improve the tensile strength of single crystal Cu–Fe alloy without sacrificing the ductility simultaneously. Based on the above analyses, strengthening mechanisms of Fe nanoparticles for single crystal Cu–Fe alloy was described

  10. Growth and characterization of isotopically enriched 70Ge and 74Ge single crystals

    International Nuclear Information System (INIS)

    Itoh, K.

    1992-10-01

    Isotopically enriched 70 Ge and 74 Ge single crystals were successfully gown by a newly developed vertical Bridgman method. The system allows us to reliably grow high purity Ge single crystals of approximately 1 cm 3 volume. To our knowledge, we have grown the first 70 Ge single crystal. The electrically active chemical impurity concentration for both crystals was found to be ∼2 x cm -3 which is two order of magnitude better that of 74 Ge crystals previously grown by two different groups. Isotopic enrichment of the 70 Ge and the 74 Ge crystals is 96.3% and 96.8%, respectively. The residual chemical impurities present in both crystals were identified as phosphorus, copper, aluminum, and indium. A wide variety of experiments which take advantage of the isotopic purity of our crystals are discussed

  11. Investigations on the nucleation kinetics of γ-glycine single crystal

    International Nuclear Information System (INIS)

    Yogambal, C.; Rajan Babu, D.; Ezhil Vizhi, R.

    2014-01-01

    Single crystals of γ-glycine were grown by slow evaporation technique. The crystalline system was confirmed by single crystal X-ray diffraction analysis. The optical absorption study has shown that the grown crystal possesses lower cut-off wavelength. Solubility and metastable zone width were estimated for different temperatures. The induction period of title compound was determined by varying the temperature and concentration. Nucleation parameters such as Gibbs volume free energy change (ΔG v ), interfacial tension (γ), critical free energy change of the nucleus (ΔG ⁎ ), nucleation rate (J), number of molecules in the critical nucleus (i ⁎ ) have been calculated for the aqueous solution grown γ-glycine single crystals. The second harmonic generation (SHG) of γ-glycine was confirmed by Q-switched Nd:YAG laser technique

  12. Dielectric Losses and Charge Transfer in Antimony-Doped TlGaS2 Single Crystal

    Science.gov (United States)

    Asadov, S. M.; Mustafaeva, S. N.

    2018-03-01

    Effect of semimetallic antimony (0.5 mol % Sb) on the dielectric properties and ac-conductivity of TlGaS2-based single crystals grown by the Bridgman-Stockbarger method has been studied. The experimental results on the frequency dispersion of dielectric coefficients and the conductivity of TlGa0.995Sb0.005S2 single crystals allowed the revealing of the dielectric loss nature, the charge transfer mechanism, and the estimation of the parameters of the states localized in the energy gap. The antimony-doping of the TlGaS2 single crystal leads to an increase in the density of states near the Fermi level and a decrease in the average time and average distance of hopes.

  13. Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

    KAUST Repository

    Shi, Dong

    2015-01-29

    The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3(MA = CH3NH3 +; X = Br- or I- ) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics.We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

  14. Extension of an anisotropic creep model to general high temperature deformation of a single crystal superalloy

    International Nuclear Information System (INIS)

    Pan, L.M.; Ghosh, R.N.; McLean, M.

    1993-01-01

    A physics based model has been developed that accounts for the principal features of anisotropic creep deformation of single crystal superalloys. The present paper extends this model to simulate other types of high temperature deformation under strain controlled test conditions, such as stress relaxation and tension tests at constant strain rate in single crystals subject to axial loading along an arbitrary crystal direction. The approach is applied to the SRR99 single crystal superalloy where a model parameter database is available, determined via analysis of a database of constant stress creep curves. A software package has been generated to simulate the deformation behaviour under complex stress-strain conditions taking into account anisotropic elasticity. (orig.)

  15. High-quality single crystal growth and magnetic property of Mn4Ta2O9

    Science.gov (United States)

    Cao, Yiming; Xu, Kun; Yang, Ya; Yang, Wangfan; Zhang, Yuanlei; Kang, Yanru; He, Xijia; Zheng, Anmin; Liu, Mian; Wei, Shengxian; Li, Zhe; Cao, Shixun

    2018-06-01

    A large-size single crystal of Mn4Ta2O9 with ∼3.5 mm in diameter and ∼65 mm in length was successfully grown for the first time by a newly designed one-step method based on the optical floating zone technique. Both the clear Laue spots and sharp XRD Bragg reflections suggest the high quality of the single crystal. In Mn4Ta2O9 single crystal, an antiferromagnetic phase transition was observed below Néel temperature 102 K along c axis, which is similar to the isostructural compound Mn4Nb2O9, but differs from the isostructural Co4Nb2O9. Relative dielectric constant at 30 kOe suggests that no magnetoelectric coupling exists in Mn4Ta2O9.

  16. Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

    KAUST Repository

    Shi, Dong; Adinolfi, Valerio; Comin, Riccardo; Yuan, Mingjian; Alarousu, Erkki; Buin, Andrei K.; Chen, Yin; Hoogland, Sjoerd H.; Rothenberger, Alexander; Katsiev, Khabiboulakh; Losovyj, Yaroslav B.; Zhang, Xin; Dowben, Peter A.; Mohammed, Omar F.; Sargent, E. H.; Bakr, Osman

    2015-01-01

    The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3(MA = CH3NH3 +; X = Br- or I- ) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics.We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

  17. Measurements on very small single crystals of NdFeB using a vibrating reed magnetometer

    International Nuclear Information System (INIS)

    Richter, H.J.; Hempel, K.A.; Verhoef, R.

    1988-01-01

    Nd 2 Fe 14 B single crystals with magnetic moments ranging from 1.6 x 10 -8 Acm 2 to 9.5 x 10 -7 Acm 2 are measured using the ultra high sensitivity vibrating reed magnetometer. The hysteresis loops are compared to those of BaFe 12 O 19 single crystals. It turns out that the magnetization reversal of the Nd 2 Fe 14 B samples is similar to that of BaFe 12 O 19 single crystals if the ferrite samples are considerably bigger in size. This does not hold for bigger Nd 2 Fe 14 B particles where stronger domain wall pinning is observed. For very small grains of Nd 2 Fe 14 B there is still evidence of domain wall processes while for BaFe 12 O 19 grains of the same size true single domain behaviour can be observed

  18. Luminescence and scintillation properties of YAG:Ce single crystal and optical ceramics

    CERN Document Server

    Mihóková, E; Mareš, J A; Beitlerová, A; Vedda, A; Nejezchleb, K; Blažek, K; D’Ambrosio, C

    2007-01-01

    We use various techniques to study optical and scintillation properties of Ce-doped yttrium aluminum garnet, Y3Al5O12 (YAG:Ce), in the form of a high-quality industrial single crystal. This was compared to optical ceramics prepared from YAG:Ce nanopowders. We present experimental data in the areas of optical absorption, radioluminescence, scintillation decay, photoelectron yield, thermally stimulated luminescence and radiation-induced absorption. The results point to an interesting feature—the absence of antisite (YAl, i.e. Y at the Al site) defects in optical ceramics. The scintillation decay of the ceramics is faster than that of the single crystal, but its photoelectron yield (measured with 1 μs integration time) is about 30–40% lower. Apart from the photoelectron yield value the YAG:Ce optical ceramic is fully comparable to a high quality industrial YAG:Ce single crystal and can become a competitive scintillator material.

  19. Non-destructive local determination of doping additions and main components in single crystals

    International Nuclear Information System (INIS)

    Ehksperiandova, L.P.; Blank, A.B.; Kukhtina, N.N.; Afanasiadi, L.I.

    1994-01-01

    Procedures for local non-destructive determination of elements in optical and scintillation single crystals are developed. They are applied for determination of the main components (in cadmium tungstate) and doping additions (tellurium in zinc selenide, europium in gadolinium silicate). The metrological characteristics of the developed micro-analysis methods are estimated. Segregation of the main components and doping additions in the objects under consideration are investigated. Tellurium is found to be distributed uniformly on the cross-sections of bulk zinc selenide single crystals. The segregation of europium along gadolinium silicate ingots is almost absent. On the cross-section surface of cadmium tungstate single crystals the microregions are found characterized by the prevailing contents of cadmium or tungsten

  20. Alloying effects of refractory elements in the dislocation of Ni-based single crystal superalloys

    Directory of Open Access Journals (Sweden)

    Shiyu Ma

    2016-12-01

    Full Text Available The alloying effects of W, Cr and Re in the [100] (010 edge dislocation cores (EDC of Ni-based single crystal superalloys are investigated using first-principles based on the density functional theory (DFT. The binding energy, Mulliken orbital population, density of states, charge density and radial distribution functions are discussed, respectively. It is clearly demonstrated that the addition of refractory elements improves the stability of the EDC systems. In addition, they can form tougher bonds with their nearest neighbour (NN Ni atoms, which enhance the mechanical properties of the Ni-based single crystal superalloys. Through comparative analysis, Cr-doped system has lower binding energy, and Cr atom has evident effect to improve the systemic stability. However, Re atom has the stronger alloying effect in Ni-based single crystal superalloys, much more effectively hindering dislocation motion than W and Cr atoms.

  1. Blue luminescence in Tm3+-doped KGd(WO4)2 single crystals

    International Nuclear Information System (INIS)

    Gueell, F.; Mateos, X.; Gavalda, Jna.; Sole, R.; Aguilo, M.; Diaz, F.; Massons, J.

    2004-01-01

    Up-conversion blue emissions of trivalent thulium ions in monoclinic KGd(WO 4 ) 2 single crystals at 454 and 479 nm are reported for a single pump laser source at 688 nm. We grew thulium-doped KGd(WO 4 ) 2 single crystals at several concentrations from 0.1% to 10%. We recorded a polarized optical absorption spectrum for the 3 F 2 + 3 F 3 energy levels of thulium at room temperature and low temperature (6 K). From the low temperature emission spectra we determined the splitting of the 3 H 6 ground state. The blue emissions are characterized as a function of the dopant concentration and temperature from 10 K to room temperature. To our knowledge, this is the first time that sequential two-photon excitation process (STEP) generated blue emissions in thulium-doped single crystals with a single excitation wavelength

  2. Oriented growing and anisotropy of emission properties of lanthanum hexaboride single crystals

    International Nuclear Information System (INIS)

    Lazorenko, V.I.; Lotsko, D.V.; Platonov, V.F.; Kovalev, A.V.; Galasun, A.P.; Matvienko, A.A.; Klinkov, A.E.

    1987-01-01

    Single crystals of lanthanum hexaboride with preset crystallographic orientation are grown by the method of crucible-free zone melting. It is shown that oriented growing of single crystals of the given compound is possible only when using seed crystals of the required orientation because no predominant orientation of the LaB 6 growth is found in case of spontaneous crystallization. Orientation of spontaneously growing LaB 6 crystals does not depend on their growth rate, degree of the melt diffusion annealing, purity of the inital powder. Anisotropy of the electronic work function for single crystal lanthanum hexaboride is confirmed. Its value grows as (100)<(110)<(111). Conditions of the preliminary thermovacuum purification of the surface are shown to affect the measured work function

  3. Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities

    Science.gov (United States)

    Gnäupel-Herold, Thomas; Myneni, Ganapati Rao; Ricker, Richard E.

    2007-08-01

    This work investigates properties of large grained, high purity niobium with respect to the forming of superconducting radio frequency (SRF) cavities from such large grained sheets. The yield stresses were examined using tensile specimens that were essentially single crystals in orientations evenly distributed in the standard projection triangle. No distinct yield anisotropy was found, however, vacuum annealing increased the yield strength by a factor 2…3. The deep drawing forming operation of the half cells raises the issues of elastic shape changes after the release of the forming tool (springback) and residual stresses, both of which are indicated to be negligible. This is a consequence of the low yield stress (sheet metal forming). However, the significant anisotropy of the transversal plastic strains after uniaxial deformation points to potentially critical thickness variations for large grained / single crystal half cells, thus raising the issue of controlling grain orientation or using single crystal sheet material.

  4. Controlled growth of filamentary crystals and fabrication of single-crystal whisker probes

    International Nuclear Information System (INIS)

    Givargizov, E. I.

    2006-01-01

    The growth of filamentary crystals (whiskers) on a single-crystal substrate through the vapour-liquid-solid mechanism is described. The possibility of fabricating oriented systems of whiskers on the basis of this mechanism of crystal growth is noted. A phenomenon that is important for nanotechnology is noted: the existence of a critical diameter of whiskers, below which they are not formed. The phenomenon of radial periodic instability, which is characteristic of nanowhiskers, is described and the ways of its elimination are shown. The possibility of transforming whiskers into single-crystal tips and the growth of crystalline diamond particles at their apices are noted as important for practice. Possible applications of systems of whiskers and tips are described briefly. Particular attention is paid to the latest direction in whisker technology-fabrication of single-crystal whisker probes for atomic force microscopy

  5. The relationship between elastic constants and structure of shock waves in a zinc single crystal

    Science.gov (United States)

    Krivosheina, M. N.; Kobenko, S. V.; Tuch, E. V.

    2017-12-01

    The paper provides a 3D finite element simulation of shock-loaded anisotropic single crystals on the example of a Zn plate under impact using a mathematical model, which allows for anisotropy in hydrostatic stress and wave velocities in elastic and plastic ranges. The simulation results agree with experimental data, showing the absence of shock wave splitting into an elastic precursor and a plastic wave in Zn single crystals impacted in the [0001] direction. It is assumed that the absence of an elastic precursor under impact loading of a zinc single crystal along the [0001] direction is determined by the anomalously large ratio of the c/a-axes and close values of the propagation velocities of longitudinal and bulk elastic waves. It is shown that an increase in only one elastic constant along the [0001] direction results in shock wave splitting into an elastic precursor and a shock wave of "plastic" compression.

  6. Elastic neutron diffraction study of transforming and non-transforming single crystal ZrV2

    International Nuclear Information System (INIS)

    Bostock, J.; Wong, M.; MacVicar, M.L.A.; Levinson, M.

    1980-01-01

    The mosaic spread of single crystal ZrV 2 is unusually narrow, approx. 1' from room temperature to 130K. For non-transforming perfect single crystal the mosaic gradually increases to approx. 1.86' at 4.2K; for transforming, twinned single crystal the room temperature mosaic is maintained to 110K, then increases to 2.76' at 94K when the crystal transforms to a mixed cubic (30%) and rhombohedral state (70%). The onset of the electronic instability (approx. 100K) is accompanied by an increase in diffuse scattering background which, for the twinned crystal, peaks at the structural transformation. The electronic instability coupled to the localized lattice stress appears to be the driving mechanism for the transformation

  7. Ferroelectric lead magnesium niobate-lead titanate single crystals for ultrasonic hydrophone applications

    International Nuclear Information System (INIS)

    Lau, S.T.; Lam, K.H.; Chan, H.L.W.; Choy, C.L.; Luo, H.S.; Yin, Q.R.; Yin, Z.W.

    2004-01-01

    Ferroelectric lead magnesium niobate-lead titanate (PMN-PT) single crystals with a composition around the rhombohedral-tetragonal morphotropic phase boundary (65 mol% of PMN) were used to fabricate single-element needle-type hydrophones for measuring the spatial and temporal characteristics of medical ultrasonic transducers. PMN-PT single crystal was grown by a modified Bridgman method. Discs (0.5 mm thick) with normal along the direction were cut and then poled by a dc field in the thickness direction. The single crystal has a high relative permittivity (ε r ∼4000) making it appropriate for small area hydrophone applications. Single-element needle-type hydrophones with this material as the sensing element have been fabricated and characterized. The hydrophones have flat frequency response and good receiving sensitivity over certain frequency range in the megahertz region

  8. The use of single-crystal iron frames in transient field measurements

    International Nuclear Information System (INIS)

    Zalm, P.C.; Laan, J. van der; Middelkoop, G. van

    1979-01-01

    Single-crystal Fe frames have been investigated for use as a ferromagnetic backing in transient magnetic field experiments. For this purpose the surface magnetization as a function of applied magnetic field has been determined with the magneto-optical Kerr effect. The frames, which have two sides parallel to the crystal axis, can be fully magnetized at low external fields such that fringing fields are negligibly small. These single-crystal Fe backings have been used in several transient magnetic field experiments. Comparison of the measured precession angles with previous results, obtained in polycrystalline Fe foils at high external magnetic fields, shows that the single-crystal backings are satisfactory. After extended periods of heavy-ion bombardment the crystals exhibited no radiation damage effects. The absence of fringing fields leads to a reduction of a factor of four in the measuring time for transient field experiments. (Auth.)

  9. Controlling Chain Conformations of High-k Fluoropolymer Dielectrics to Enhance Charge Mobilities in Rubrene Single-Crystal Field-Effect Transistors.

    Science.gov (United States)

    Adhikari, Jwala M; Gadinski, Matthew R; Li, Qi; Sun, Kaige G; Reyes-Martinez, Marcos A; Iagodkine, Elissei; Briseno, Alejandro L; Jackson, Thomas N; Wang, Qing; Gomez, Enrique D

    2016-12-01

    A novel photopatternable high-k fluoropolymer, poly(vinylidene fluoride-bromotrifluoroethylene) P(VDF-BTFE), with a dielectric constant (k) between 8 and 11 is demonstrated in thin-film transistors. Crosslinking P(VDF-BTFE) reduces energetic disorder at the dielectric-semiconductor interface by controlling the chain conformations of P(VDF-BTFE), thereby leading to approximately a threefold enhancement in the charge mobility of rubrene single-crystal field-effect transistors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. The first pseudo-ternary thiocyanate containing two alkali metals. Synthesis and single-crystal structure of LiK{sub 2}[SCN]{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Reckeweg, Olaf; DiSalvo, Francis J. [Cornell Univ., Ithaca, NY (United States). Baker Lab.

    2016-04-01

    A procedure was empirically developed to prepare the compound LiK{sub 2}[SCN]{sub 3}, which forms colorless, transparent, very fragile, and extremely hygroscopic thin rectangular plates. Its unique crystal structure was determined by single-crystal X-ray diffraction. LiK{sub 2}[SCN]{sub 3} adopts the orthorhombic space group Pna2{sub 1} (no. 33, Z = 4) with the cell parameters a = 1209.32(9), b = 950.85(9), and c = 849.95(6) pm.

  11. Polarized Raman scattering study of PSN single crystals and epitaxial thin films

    Czech Academy of Sciences Publication Activity Database

    Pokorný, Jan; Rafalovskyi, Iegor; Gregora, Ivan; Borodavka, Fedir; Savinov, Maxim; Drahokoupil, Jan; Tyunina, Marina; Kocourek, Tomáš; Jelínek, Miroslav; Bing, Y.; Ye, Z. -G.; Hlinka, Jiří

    2015-01-01

    Roč. 5, č. 2 (2015), "1550013-1"-"1550013-6" ISSN 2010-135X R&D Projects: GA ČR GA15-04121S; GA ČR GA15-15123S Institutional support: RVO:68378271 Keywords : PSN * relaxors * ferroelectrics * complex perovskites * Raman scattering Subject RIV: BM - Solid Matter Physics ; Magnetism

  12. Electronic Coupling Dependence of Ultrafast Interfacial Electron Transfer on Nanocrystalline Thin Films and Single Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Lian, Tianquan

    2014-04-22

    The long-term goal of the proposed research is to understand electron transfer dynamics in nanoparticle/liquid interface. This knowledge is essential to many semiconductor nanoparticle based devices, including photocatalytic waste degradation and dye sensitized solar cells.

  13. Study of structural and optical properties of YAG and Nd:YAG single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kostić, S. [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, Zemun, Belgrade (Serbia); Lazarević, Z.Ž., E-mail: lzorica@yahoo.com [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, Zemun, Belgrade (Serbia); Radojević, V. [Faculty of Technology and Metallurgy, University of Belgrade, Belgrade (Serbia); Milutinović, A.; Romčević, M.; Romčević, N.Ž. [Institute of Physics, University of Belgrade, P.O. Box 68, Pregrevica 118, Zemun, Belgrade (Serbia); Valčić, A. [Faculty of Technology and Metallurgy, University of Belgrade, Belgrade (Serbia)

    2015-03-15

    Highlights: • Transparent YAG and pale pink Nd:YAG single crystals were produced by the Czochralski technique. • Growth mechanisms and shape of the liquid/solid interface and incorporation of Nd{sup 3+} were studied. • The structure of the crystals was investigated by X-ray diffraction, Raman and IR spectroscopy. • The 15 Raman and 17 IR modes were observed. • The obtained YAG and Nd:YAG single crystals were without core and of good optical quality. - Abstract: Yttrium aluminum garnet (YAG, Y{sub 3}Al{sub 5}O{sub 12}) and yttrium aluminum garnet doped with neodymium (Nd:YAG) single crystals were grown by the Czochralski technique. The critical diameter and the critical rate of rotation were calculated. Suitable polishing and etching solutions were determined. As a result of our experiments, the transparent YAG and pale pink Nd:YAG single crystals were produced. The obtained crystals were studied by X-ray diffraction, Raman and IR spectroscopy. The crystal structure was confirmed by XRD. The 15 Raman and 17 IR modes were observed. The Raman and IR spectroscopy results are in accordance with X-ray diffraction analysis. The obtained YAG and Nd:YAG single crystals were without core and of good optical quality. The absence of a core was confirmed by viewing polished crystal slices. Also, it is important to emphasize that the obtained Nd:YAG single crystal has a concentration of 0.8 wt.% Nd{sup 3+} that is characteristic for laser materials.

  14. Ultraviolet laser-induced voltages in LaSrAlO4 single crystal

    International Nuclear Information System (INIS)

    Zhi-Qing, Lü; Kun, Zhao; Song-Qing, Zhao; Hui, Zhao; Qing-Li, Zhou

    2009-01-01

    Laser-induced ultrafast photovoltaic effect is observed in LaSrAlO 4 single crystal at ambient temperature without any applied bias. An open-circuit photovoltage is obtained when the wafer is irradiated by a 248-nm-KrF laser pulse of 20 ns duration. The response time and full width at half maximum of the photovoltage pulse are 6 ns and 19 ns, respectively, indicating that LaSrAlO 4 single crystal has potential application in ultraviolet detector. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  15. Hierarchical zeolites: progress on synthesis and characterization of mesoporous zeolite single crystal catalysts

    DEFF Research Database (Denmark)

    Kustova, Marina; Egeblad, Kresten; Christensen, Claus H.

    2007-01-01

    Recently, a new family of crystalline zeolitic materials was reported, the so-called mesoporous zeolite single crystals featuring individual zeolite single crystals with an additional noncrystalline mesopore system interconnected with the usual micropore system of the zeolite, resulting...... measurements. Additionally, the results of diffusion of n-hexadecane in conventional and mesoporous zeolites are presented. Isomerization and cracking of n-hexadecane was chosen as model test reaction for these materials. All results support that mesoporous zeolites are superior catalysts due to improved mass...... transport. Importantly, the mesoporous zeolites show significant improved resistance to poisoning by carbon formation....

  16. Influence of submelting on formation of single crystals of nickel alloy with cellular-dendritic structure

    International Nuclear Information System (INIS)

    Pankin, G.N.; Esin, V.O.; Ponomarev, V.V.

    1996-01-01

    A study was made into specific features of cellular - dendritic structure formation in single crystals of nickel base alloy ZhS26 which had been crystallized following the pattern of solid solution. The single crystals in growing were subjected to periodic partial remelting to suppress the transition of cellular structure into a cellular - dendritic one during directional solidification. The results obtained showed the possibility to stabilize cellular growth of solid solution by way of inversion of interphase surface motion in the process of directional crystallization. 4 refs.; 5 figs

  17. Method for single crystal growth of photovoltaic perovskite material and devices

    Science.gov (United States)

    Huang, Jinsong; Dong, Qingfeng

    2017-11-07

    Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container, also including at least one small perovskite single crystal, and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows, in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate. For example, a top portion of the substrate external to the solution may be cooled.

  18. Optical power limiting and transmitting properties of cadmium iodide single crystals: Temperature dependence

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.a [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)] [Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)] [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

    2009-09-14

    Optical limiting properties of the single crystals of cadmium iodide are investigated using ns laser pulses. It is found that the transmissions in the crystals increase with increasing temperature. However, they limit the transmissions at high input powers. The limiting power is found to be higher at higher temperature. From the measured transmission data, the photon absorption coefficients are estimated. The temperature dependence of the coefficients shows a decrease in magnitude with increasing temperature. This might be due to the temperature-dependent bandgap shift of the material. The results demonstrate that the cadmium iodide single crystals are promising materials for applications in optical power limiting devices.

  19. Optical power limiting and transmitting properties of cadmium iodide single crystals: Temperature dependence

    International Nuclear Information System (INIS)

    Miah, M. Idrish

    2009-01-01

    Optical limiting properties of the single crystals of cadmium iodide are investigated using ns laser pulses. It is found that the transmissions in the crystals increase with increasing temperature. However, they limit the transmissions at high input powers. The limiting power is found to be higher at higher temperature. From the measured transmission data, the photon absorption coefficients are estimated. The temperature dependence of the coefficients shows a decrease in magnitude with increasing temperature. This might be due to the temperature-dependent bandgap shift of the material. The results demonstrate that the cadmium iodide single crystals are promising materials for applications in optical power limiting devices.

  20. Anisotropy effect of crater formation on single crystal silicon surface under intense pulsed ion beam irradiation

    Science.gov (United States)

    Shen, Jie; Yu, Xiao; Zhang, Jie; Zhong, Haowen; Cui, Xiaojun; Liang, Guoying; Yu, Xiang; Huang, Wanying; Shahid, Ijaz; Zhang, Xiaofu; Yan, Sha; Le, Xiaoyun

    2018-04-01

    Due to the induced extremely fast thermal and dynamic process, Intense Pulsed Ion Beam (IPIB) is widely applied in material processing, which can bring enhanced material performance and surface craters as well. To investigate the craters' formation mechanism, a specific model was built with Finite Element Methods (FEM) to simulate the thermal field on irradiated single crystal silicon. The direct evidence for the existence of the simulated 6-fold rotational symmetric thermal distribution was provided by electron microscope images obtained on single crystal silicon. The correlation of the experiment and simulation is of great importance to understand the interaction between IPIB and materials.

  1. Cavity Pull Rod: Device to Promote Single Crystal Growth from the Melt

    Science.gov (United States)

    Goldsby, Jon (Inventor)

    2017-01-01

    A pull rod for use in producing a single crystal from a molten alloy is provided that includes an elongated rod having a first end and a second end, a first cavity defined at the first end and a second cavity defined at the first end and in communication with the first cavity. The first cavity receives the molten alloy and the second cavity vents a gas from the molten alloy to thereby template a single crystal when the pull rod is dipped into and extracted from the molten alloy.

  2. Absorption measurement s in InSe single crystal under an applied electric field

    International Nuclear Information System (INIS)

    Ates, A.; Guerbulak, B.; Guer, E.; Yildirim, T.; Yildirim, M.

    2002-01-01

    InSe single crystal was grown by Bridgman-Stockberger method. Electric field effect on the absorption measurements have been investigated as a function of temperature in InSe single crystal. The absorption edge shifted towards longer wavelengths and decreased of intensity in absorption spectra under an electric field. Using absorption measurements, Urbach energy was calculated under an electric field. Applied electric field caused a increasing in the Urbach energy. At 10 K and 320 K, the first exciton energies were calculated as 1.350 and 1.311 eV for zero voltage and 1.334 and 1.301 eV for electric field respectively

  3. Advanced x-ray stress analysis method for a single crystal using different diffraction plane families

    International Nuclear Information System (INIS)

    Imafuku, Muneyuki; Suzuki, Hiroshi; Sueyoshi, Kazuyuki; Akita, Koichi; Ohya, Shin-ichi

    2008-01-01

    Generalized formula of the x-ray stress analysis for a single crystal with unknown stress-free lattice parameter was proposed. This method enables us to evaluate the plane stress states with any combination of diffraction planes. We can choose and combine the appropriate x-ray sources and diffraction plane families, depending on the sample orientation and the apparatus, whenever diffraction condition is satisfied. The analysis of plane stress distributions in an iron single crystal was demonstrated combining with the diffraction data for Fe{211} and Fe{310} plane families

  4. About some practical aspects of X-ray diffraction : From single crystal to powders

    Energy Technology Data Exchange (ETDEWEB)

    Giacovazzo, C [Bari Univ. (Italy). Dip. Geomineralogico

    1996-09-01

    An ideal polycrystalline material or power is an ensemble of a very large number of randomly oriented crystallites. It is shown the effect that this random orientation has on the diffraction of a specimen assumed to contain only one reciprocal lattice node. The most remarkable difference with the single-crystal case is that now must think of scattering vectors not as lying on discrete nodes of reciprocal lattice vectors, the distances from the single-crystal reciprocal lattice nodes to the origin of reciprocal space.

  5. Surface relief grating formation on a single crystal of 4-(dimethylamino)azobenzene

    International Nuclear Information System (INIS)

    Nakano, Hideyuki; Tanino, Takahiro; Shirota, Yasuhiko

    2005-01-01

    Surface relief grating (SRG) formation on an organic single crystal by irradiation with two coherent laser beams has been demonstrated by using 4-(dimethylamino)azobenzene (DAAB). It was found that the SRG formation was greatly depending upon both the coordination of the crystal and the polarization of the writing beams. The dependence of the polarization of writing beams on the SRG formation using the single crystal was found to be quite different from that reported for amorphous polymers and photochromic amorphous molecular materials, suggesting that the mechanism of the SRG formation on the organic crystal is somewhat different from that on amorphous materials

  6. Influence of gamma radiation and impurity atoms on the photoconductivity of GeS single crystals

    International Nuclear Information System (INIS)

    Madatov, R.S.; Alekperov, A.S.

    2013-01-01

    Wide opportunities for using of layered semiconductors, particularly in optoelectronics have generated considerable interest to them. Recently it was created the unique device from GeS for the storage of solar energy. The investigated GeS 1 -xNd x S single crystals were grown by the Bridgman method. The samples were irradiated by gamma-quanta and was conducted to install 60Co at room temperature. Irradiation of p-GeS 1 -xNd x S single crystals by small doses of gamma rays increases the photoconductivity on 40%

  7. About some practical aspects of X-ray diffraction : From single crystal to powders

    International Nuclear Information System (INIS)

    Giacovazzo, C.

    1996-01-01

    An ideal polycrystalline material or power is an ensemble of a very large number of randomly oriented crystallites. It is shown the effect that this random orientation has on the diffraction of a specimen assumed to contain only one reciprocal lattice node. The most remarkable difference with the single-crystal case is that now must think of scattering vectors not as lying on discrete nodes of reciprocal lattice vectors, the distances from the single-crystal reciprocal lattice nodes to the origin of reciprocal space

  8. A study on the growth of compound semiconductor single crystal by TOM technique

    International Nuclear Information System (INIS)

    Kim, H.C.; Kwon, S.I.; Chung, M.K.; Chang, J.S.

    1981-01-01

    This paper describes the merit of the HgI 2 single crystals obtained by solution growth, 2- and 3-region temperature growth, and temperature oscillation growth for soft γ-ray detectors which can be operated at room temperature. Special efforts are put on the design, construction, and operation of the TOM (Temperature Oscillation Method) single crystal growing furnace. Experimental results show that HgI 2 detectors fabricated by vapour phase growth method usually exhibit sufficient enough detector characteristics for soft γ-ray spectrometry. However, further investigation should be carried out to eliminate detector deterioration due to polarization effect. (author)

  9. Growth of binary solid solution single crystals and calculation of melt surface displacement velocity

    International Nuclear Information System (INIS)

    Agamaliyev, Z.A.; Tahirov, V.I.; Hasanov, Z.Y.; Quliyev, A.F.

    2007-01-01

    A binary solid solution single crystal growth method has been worked out. Cylinder feeding alloy with complex content distribution and truncated cone crucible are used. Second component distribution coefficient is more than unit. Content distribution along grown crystal is found by solving continuity equation. After reaching dynamic equilibrium state second component concentration in grown crystal is saturated the value of which is less than the average ona in the feeding alloy. Using the method Ge-Si perfect single crystals has been grown. Calculation method of melt surface displacement velocity has been offered as well

  10. Morphology of growth of Bi2Sr2CaCu2O8 single crystals

    Science.gov (United States)

    Indenbom, M. V.; van der Beek, C. J.; Berseth, V.; Wolf, Th.; Berger, H.; Benoit, W.

    1996-12-01

    A good correlation of twins on the basal surface of flux-grown Bi2Sr2CaCu2Ox (BSCCO) single crystals with surface. growth steps is observed, the b-axis being perpendicular to the steps and, thus, parallel to the growth direction. It is found that mono-twin BSCCO single crystals produced by the travelling solvent floating zone method also grow preferentially along b, i.e. nearly perpendicularly to the boule axis, contrary to the common belief. This new understanding of the morphology of growth explains the nature of major defects in these crystals, which considerably change their measured superconducting properties, in a different way.

  11. Cross-section of single-crystal materials used as thermal neutron filters

    International Nuclear Information System (INIS)

    Adib, M.

    2005-01-01

    Transmission properties of several single crystal materials important for neutron scattering instrumentation are presented. A computer codes are developed which permit the calculation of thermal diffuse and Bragg-scattering cross-sections of silicon., and sapphire as a function of material's constants, temperature and neutron energy, E, in the range 0.1 MeV .A discussion of the use of their single-crystal as a thermal neutron filter in terms of the optimum crystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons is given

  12. Design considerations for a Space Shuttle Main Engine turbine blade made of single crystal material

    Science.gov (United States)

    Abdul-Aziz, A.; August, R.; Nagpal, V.

    1993-01-01

    Nonlinear finite-element structural analyses were performed on the first stage high-pressure fuel turbopump blade of the Space Shuttle Main Engine. The analyses examined the structural response and the dynamic characteristics at typical operating conditions. Single crystal material PWA-1480 was considered for the analyses. Structural response and the blade natural frequencies with respect to the crystal orientation were investigated. The analyses were conducted based on typical test stand engine cycle. Influence of combined thermal, aerodynamic, and centrifugal loadings was considered. Results obtained showed that the single crystal secondary orientation effects on the maximum principal stresses are not highly significant.

  13. Crystal growth and characterization of a semiorganic nonlinear optical single crystal of gamma glycine

    International Nuclear Information System (INIS)

    Prakash, J. Thomas Joseph; Kumararaman, S.

    2008-01-01

    Gamma glycine has been successfully synthesized by taking glycine and potassium chloride and single crystals have been grown by solvent evaporation method for the first time. The grown single crystals have been analyzed with XRD, Fourier transform infrared (FTIR), and thermo gravimetric and differential thermal analyses (TG/DTA) measurements. Its mechanical behavior has been assessed by Vickers microhardness measurements. Its nonlinear optical property has been tested by Kurtz powder technique. Its optical behavior was examined by UV-vis., and found that the crystal is transparent in the region between 240 and 1200 nm. Hence, it may be very much useful for the second harmonic generation (SHG) applications

  14. Method of growing yttrium aluminate and/or lanthanide single crystals with perovskite structure

    International Nuclear Information System (INIS)

    Kvapil, Jiri; Perner, B.; Kvapil, Josef; Blazek, K.

    1989-01-01

    Single crystals of yttrium aluminate and/or lanthanide with perovskite structure are grown from melt in a vacuum at a pressure of gas residues of max. 0.01 Pa. The melt contains 1±0.05 gram-ions of aluminium per gram-ion of yttrium and/or lanthanides. The single crystals are then heated in a vacuum (0.01 Pa) at temperatures of 1,450 to 1,800 degC for 2 to 3 hours. (B.S.)

  15. Method of Promoting Single Crystal Growth During Melt Growth of Semiconductors

    Science.gov (United States)

    Su, Ching-Hua (Inventor)

    2013-01-01

    The method of the invention promotes single crystal growth during fabrication of melt growth semiconductors. A growth ampoule and its tip have a semiconductor source material placed therein. The growth ampoule is placed in a first thermal environment that raises the temperature of the semiconductor source material to its liquidus temperature. The growth ampoule is then transitioned to a second thermal environment that causes the semiconductor source material in the growth ampoule's tip to attain a temperature that is below the semiconductor source material's solidus temperature. The growth ampoule so-transitioned is then mechanically perturbed to induce single crystal growth at the growth ampoule's tip.

  16. Synthesis and Single Crystal Structures of Substituted-1,3-Selenazol-2-amines

    Directory of Open Access Journals (Sweden)

    Guoxiong Hua

    2016-12-01

    Full Text Available The synthesis and X-ray single crystal structures of a series of new 4-substituted-1,3-selenazol-2-amines is reported. The efficient preparation of these compounds was carried out by two-component cyclization of the selenoureas with equimolar amounts of α-haloketones. The selenoureas were obtained from the reaction of Woollins’ reagent with cyanamides, followed by hydrolysis with water. All new compounds have been characterized by IR spectroscopy, multi-NMR (1H, 13C, 77Se spectroscopy, accurate mass measurement and single crystal X-ray structure analysis.

  17. Particularities of the recombination electron emission of single crystals of tungsten and niobium

    International Nuclear Information System (INIS)

    Mashtakova, V.A.; Shishkin, B.B.

    1984-01-01

    The volt-ampere characteristics (vac) of vacuum diodes with metal single cr ystal electrodes are measured. Studied were: crystallographic plane (100) of a tungsten single crystal and (110) face of a niobium single crystal. Anomalies o n the initial portions of the vac of diodes with niobium ((110) face) electrodes are discovered. Anomalies appear at cathode temperatures t exceeding characteri stic thermoionic temperatures thetasub(the). The ''steps'' on the vac at t >thetasub(the) for tungsten are considered as voltage jumps. The ''steps'' on th e vac for niobium are considered as diode current jumps due to fluctuation processes resulting in the formation of small amount of slow electrons

  18. Synthesis and single crystal X-ray analysis of two griseofulvin metabolites

    DEFF Research Database (Denmark)

    Rønnest, Mads Holger; Harris, Pernille; Gotfredsen, Charlotte Held

    2010-01-01

    The two phenols, 6-O-desmethyl griseofulvin and 4-O-desmethyl griseofulvin are metabolites of the antifungal drug griseofulvin. Herein, we present an improved synthesis of the 6-phenol derivative, and an unequivocal proof of both structures by single-crystal X-ray analysis.......The two phenols, 6-O-desmethyl griseofulvin and 4-O-desmethyl griseofulvin are metabolites of the antifungal drug griseofulvin. Herein, we present an improved synthesis of the 6-phenol derivative, and an unequivocal proof of both structures by single-crystal X-ray analysis....

  19. In-situ TEM study of dislocation patterning during deformation in single crystal aluminum

    International Nuclear Information System (INIS)

    Landau, P; Shneck, R Z; Makov, G; Venkert, A

    2010-01-01

    The evolution of dislocation patterns in single crystal aluminum was examined using transmission electron microscopy (TEM). In-situ tensile tests of single crystals were carried out in a manner that activated double slip. Cross slip of dislocations, which is prominent in all stages of work hardening, plays an important role in dislocation motion and microstructural evolution. In spite of the limitations of in-situ straining to represent bulk phenomena, due to surface effects and the thickness of the samples, it is shown that experiments on prestrained samples can represent the early stages of deformation. Transition between stage I and stage II of work hardening and evolution during stage III were observed.

  20. Orientation dependence of the thermal fatigue of nickel alloy single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dul' nev, R A; Svetlov, I L; Bychkov, N G; Rybina, T V; Sukhanov, N N

    1988-11-01

    The orientation dependence of the thermal stability and the thermal fatigue fracture characteristics of single crystals of MAR-M200 nickel alloy are investigated experimentally using X-ray diffraction analysis and optical and scanning electron microscopy. It is found that specimens with the 111-line orientation have the highest thermal stability and fatigue strength. Under similar test conditions, the thermal fatigue life of single crystals is shown to be a factor of 1.5-2 higher than that of the directionally solidified and equiaxed alloys. 6 references.

  1. Growth and characterization of nonlinear optical single crystal: Nicotinic L-tartaric

    Energy Technology Data Exchange (ETDEWEB)

    Sheelarani, V.; Shanthi, J., E-mail: shanthinelson@gmail.com [Department of Physics, Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore-641043 (India)

    2015-06-24

    Nonlinear optical single crystals were grown from Nicotinic and L-Tartaric acid by slow evaporation technique at room temperature. Structure of the grown crystal was confirmed by single crystal X-ray diffraction studies, The crystallinity of the Nicotinic L-Tartaric (NLT) crystals was confirmed from the powder XRD pattern. The transparent range and cut off wavelength of the grown crystal was studied by the UV–Vis spectroscopic analysis.The thermal stability of the crystal was studied by TG-DTA. The second harmonic generation (SHG) efficiency of NLT was confirmed by Kurtz Perry technique.

  2. Growth and characterization of air annealing Tb-doped YAG:Ce single crystal for white-light-emitting diode

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Maogao [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Xiang, Weidong, E-mail: xiangweidong001@126.com [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Liang, Xiaojuan [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China); Zhong, Jiasong; Chen, Daqin [College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Huang, Jun; Gu, Guorui; Yang, Cheng; Xiang, Run [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035 (China)

    2015-08-05

    Highlights: • We report preparation of transparent Ce,Tb:YAG single crystal by Czochralski method. • The effect of annealing on Ce,Tb:YAG single crystal had been investigated. • The Ce,Tb:YAG single crystal after annealing exhibited better optical performance. • The Ce,Tb:YAG single crystal could be used as an ideal candidate for WLED. - Abstract: We report the preparation of transparent Ce and Tb co-doped Y{sub 3}Al{sub 5}O{sub 12} single crystal by the Czochralski method. The characterization of the resulting single crystal was accomplished by using X-ray powder diffractometer, scanning electron microscopy and energy dispersive X-ray spectroscopy. Absorption peak of the single crystal at about 460 nm has been obtained from ultraviolet–visible absorption spectrometer and their intensity is changed with different annealing condition. Its optical properties also have been investigated using fluorescence spectrometer. What’s more, its photoelectric parameters were studied by LED fast spectrometer. The constructed single crystal based white-light-emitting diode exhibits a high luminous efficiency of 140.89 lm/W, and a correlated color temperature of 4176 K as well as a color rendering index of 56.7, which reveal the prominent feasibility of the present single crystal material in white-light-emitting diode application.

  3. Growth and characterization of air annealing Tb-doped YAG:Ce single crystal for white-light-emitting diode

    International Nuclear Information System (INIS)

    Gong, Maogao; Xiang, Weidong; Liang, Xiaojuan; Zhong, Jiasong; Chen, Daqin; Huang, Jun; Gu, Guorui; Yang, Cheng; Xiang, Run

    2015-01-01

    Highlights: • We report preparation of transparent Ce,Tb:YAG single crystal by Czochralski method. • The effect of annealing on Ce,Tb:YAG single crystal had been investigated. • The Ce,Tb:YAG single crystal after annealing exhibited better optical performance. • The Ce,Tb:YAG single crystal could be used as an ideal candidate for WLED. - Abstract: We report the preparation of transparent Ce and Tb co-doped Y 3 Al 5 O 12 single crystal by the Czochralski method. The characterization of the resulting single crystal was accomplished by using X-ray powder diffractometer, scanning electron microscopy and energy dispersive X-ray spectroscopy. Absorption peak of the single crystal at about 460 nm has been obtained from ultraviolet–visible absorption spectrometer and their intensity is changed with different annealing condition. Its optical properties also have been investigated using fluorescence spectrometer. What’s more, its photoelectric parameters were studied by LED fast spectrometer. The constructed single crystal based white-light-emitting diode exhibits a high luminous efficiency of 140.89 lm/W, and a correlated color temperature of 4176 K as well as a color rendering index of 56.7, which reveal the prominent feasibility of the present single crystal material in white-light-emitting diode application

  4. High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

    Science.gov (United States)

    Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah; Scarpulla, Michael A.

    2018-05-01

    Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 1016 and 1020 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 1017 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 1017/cm3 range is observed for samples quenched at 200-300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 1016 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 1018 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

  5. Magnetic properties of a hydrogenation-extracted UCoSn single crystal

    Czech Academy of Sciences Publication Activity Database

    Kolomiets, A.; Andreev, Alexander V.; Havela, L.

    2009-01-01

    Roč. 471, 1-2 (2009), s. 21-23 ISSN 0925-8388 R&D Projects: GA MŠk OC 144 Institutional research plan: CEZ:AV0Z10100520 Keywords : uranium intermetallics * single crystal * ferromagnetism * hydrides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.135, year: 2009

  6. Inside Perovskites: Quantum Luminescence from Bulk Cs4PbBr6 Single Crystals

    KAUST Repository

    de Bastiani, Michele; Dursun, Ibrahim; Zhang, Yuhai; Alshankiti, Buthainah; Miao, Xiaohe; Yin, Jun; Yengel, Emre; Alarousu, Erkki; Turedi, Bekir; Almutlaq, Jawaher; Saidaminov, Makhsud I.; Mitra, Somak; Gereige, Issam; Alsaggaf, Ahmed; Zhu, Yihan; Han, Yu; Roqan, Iman S.; Bredas, Jean-Luc; Mohammed, Omar F.; Bakr, Osman

    2017-01-01

    the chemistry and structure of these materials, without revealing the origins of their optical behaviour, which is contradictory to the well-studied APbX3 perovskites. In this work, we synthesize single crystals of Cs4PbBr6 0D-PRS, and investigated the origins

  7. Structural defect generation in indium antimonide single crystals during electro-erosion cutting

    International Nuclear Information System (INIS)

    Kravetskij, M.Yu.; Matsas, E.P.; Skorokhod, M.Ya.; Fomin, A.V.; Khromyak, K.Ya.

    1990-01-01

    Using X-ray topography structural defects generating during electro-erosion cutting of InSb single crystals are studied. It is shown that dislocations, are introduced into so cut dislocation-free ingot plates, nucleation centers being located on their surfaces. It is detected that foreign phase inclusions in InSb are efficient sources of dislocations during cutting

  8. Stress induced martensitic transformations in tension/torsion of CuAlNi single crystal tube

    Czech Academy of Sciences Publication Activity Database

    Šittner, Petr; Hashimoto, K.; Kato, M.; Tokuda, M.

    2003-01-01

    Roč. 48, - (2003), s. 1153-1159 ISSN 1359-6462 R&D Projects: GA AV ČR IAA1048107 Institutional research plan: CEZ:AV0Z1010914 Keywords : shape memory alloys(SMAs) * martensitic phase transformation * single crystal tube * tension test * torsion Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.633, year: 2003

  9. Quasi-static crack tip fields in rate-sensitive FCC single crystals

    Indian Academy of Sciences (India)

    In this work, the effects of loading rate, material rate sensitivity and constraint level on quasi-static crack tip fields in a FCC single crystal are studied. ... Global General Motors R&D, India Science Lab, GM Technical Centre (India), Bangalore 560 066, India; Department of Mechanical Engineering, Indian Institute of Science, ...

  10. Stages in the Recovery of Deformed Single Crystals of Iron Studied by Position Annihilation Techniques

    NARCIS (Netherlands)

    Lee, Jong-Lam; Waber, James T.; Park, Yong-Ki; Hosson, J.T.M. De

    Isochronal as well as isothermal measurements have been made on high purity single crystals of iron which had been cold rolled about 10% prior to annealing. Two steps were isolated corresponding first to the annihilation of screw dislocations and then to the elimination of edge dislocations at

  11. Bulk single crystal ternary substrates for a thermophotovoltaic energy conversion system

    Science.gov (United States)

    Charache, Greg W.; Baldasaro, Paul F.; Nichols, Greg J.

    1998-01-01

    A thermophotovoltaic energy conversion device and a method for making the device. The device includes a substrate formed from a bulk single crystal material having a bandgap (E.sub.g) of 0.4 eVternary or quaternary III-V semiconductor active layers.

  12. Lattice and Molecular Vibrations in Single Crystal I2 at 77 K by Inelastic Neutron Scattering

    DEFF Research Database (Denmark)

    Smith, H. G.; Nielsen, Mourits; Clark, C. B.

    1975-01-01

    Phonon dispersion curves of single crystal iodine at 77 K have been measured by one-phonon coherent inelastic neutron scattering techniques. The data are analysed in terms of two Buckingham-six intermolecular potentials; one to represent the shortest intermolecular interaction (3.5 Å) and the other...

  13. Ellipsometric studies of ErMnO3 single crystals

    DEFF Research Database (Denmark)

    Babonas, G.-J.; Grivel, Jean-Claude; Reza, A.

    2007-01-01

    Ellipsometric studies of ErMnO3 single crystals have been carried out in the spectral range of 1-5 eV by means of photometric ellipsometers. Experimental ellipsometric data were analysed in the uniaxial crystal model. For the first time, the components of dielectric function of ErMnO3 were...

  14. Anisotropic charge transport in large single crystals of π-conjugated organic molecules.

    Science.gov (United States)

    Hourani, Wael; Rahimi, Khosrow; Botiz, Ioan; Koch, Felix Peter Vinzenz; Reiter, Günter; Lienerth, Peter; Heiser, Thomas; Bubendorff, Jean-Luc; Simon, Laurent

    2014-05-07

    The electronic properties of organic semiconductors depend strongly on the nature of the molecules, their conjugation and conformation, their mutual distance and the orientation between adjacent molecules. Variations of intramolecular distances and conformation disturb the conjugation and perturb the delocalization of charges. As a result, the mobility considerably decreases compared to that of a covalently well-organized crystal. Here, we present electrical characterization of large single crystals made of the regioregular octamer of 3-hexyl-thiophene (3HT)8 using a conductive-atomic force microscope (C-AFM) in air. We find a large anisotropy in the conduction with charge mobility values depending on the crystallographic orientation of the single crystal. The smaller conduction is in the direction of π-π stacking (along the long axis of the single crystal) with a mobility value in the order of 10(-3) cm(2) V(-1) s(-1), and the larger one is along the molecular axis (in the direction normal to the single crystal surface) with a mobility value in the order of 0.5 cm(2) V(-1) s(-1). The measured current-voltage (I-V) curves showed that along the molecular axis, the current followed an exponential dependence corresponding to an injection mode. In the π-π stacking direction, the current exhibits a space charge limited current (SCLC) behavior, which allows us to estimate the charge carrier mobility.

  15. Variation of low temperature internal friction of microplastic deformation of high purity molybdenum single crystals

    International Nuclear Information System (INIS)

    Pal-Val, P.P.; Kaufmann, H.J.

    1984-01-01

    Amplitude and temperature spectra of ultrasound absorption in weakly deformed high purity molybdenum single crystals of different orientations were measured. The results were discussed in terms of parameter changes related to quasiparticle or dislocation oscillations, respectively, dislocation point defect interactions as well as defect generation at microplastic deformation. (author)

  16. High-temperature and low-stress creep anisotropy of single-crystal superalloys

    Czech Academy of Sciences Publication Activity Database

    Jacome, L. A.; Nortershauser, P.; Heyer, J. K.; Lahni, A.; Frenzel, J.; Dlouhý, Antonín; Somsen, C.; Eggeler, G.

    2013-01-01

    Roč. 61, č. 8 (2013), s. 2926-2943 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA202/09/2073 Institutional support: RVO:68081723 Keywords : superalloy single crystals * creep anisotropy * rafting * dislocations * deformation mechanisms Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.940, year: 2013

  17. Hydroxylamine electrochemistry at low-index single-crystal platinum electrodes in acidic media

    NARCIS (Netherlands)

    Rosca, V.; Beltramo, G.L.; Koper, M.T.M.

    2004-01-01

    The electrochemistry of hydroxylamine at low-index single-crystal platinum electrodes in acidic media has been studied by voltammetry and in-situ FTIRRAS. Hydroxylamine (HAM) reactivity at platinum is largely controlled by interaction of the other components of the solution or products of the HAM

  18. High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization

    KAUST Repository

    Saidaminov, Makhsud I.; Abdelhady, Ahmed L.; Banavoth, Murali; Alarousu, Erkki; Burlakov, Victor M.; Peng, Wei; Dursun, Ibrahim; Wang, Lingfei; He, Yao; Maculan, Giacomo; Goriely, Alain; Wu, Tao; Mohammed, Omar F.; Bakr, Osman

    2015-01-01

    Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3+, X=Br− or I−) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process

  19. Organometallic halide perovskite single crystals having low deffect density and methods of preparation thereof

    KAUST Repository

    Bakr, Osman; Shi, Dong

    2016-01-01

    The present disclosure presents a method of making a single crystal organometallic halide perovskites, with the formula: AMX3, wherein A is an organic cation, M is selected from the group consisting of: Pb, Sn, Cu, Ni, Co, Fe, Mn, Pd, Cd, Ge, and Eu

  20. Self-templated synthesis of single-crystal and single-domain ferroelectric nanoplates

    KAUST Repository

    Chao, Chunying; Ren, Zhaohui; Zhu, Yihan; Xiao, Zhen; Liu, Zhenya; Xú , Gang; Mai, Jiangquan; Li, Xiang; Shen, Ge; Han, Gaorong

    2012-01-01

    Free-standing single-crystal PbTiO 3 nanoplates (see picture) were synthesized by a facile hydrothermal method. A "self-templated" crystal growth is presumed to lead to the formation of the PbTiO 3 nanoplates, which have ferroelectric single