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Sample records for thin epitaxial fe

  1. 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

  2. Carbon dioxide and water adsorption on highly epitaxial Delafossite CuFeO2 thin film

    Science.gov (United States)

    Rojas, S.; Joshi, T.; Borisov, P.; Sarabia, M.; Lederman, D.; Cabrera, A. L.

    2015-03-01

    Thermal programmed desorption (TPD) of CO2 and H2O from a 200 nm thick CuFeO2 Delafossite surface was performed in a standard UHV chamber, The CuFeO2 thin film grown using Pulsed Laser Deposition (PLD) over an Al2O3 (0001) substrate with controlled O2 atmosphere resulted with highly epitaxial crystal structure. The adsorption/desorption of CO2 and H2O process was also monitored with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Our results revealed that carbon dioxide interacts with CuFeO2 forming Fe carbonates compounds on its surface. Hydroxides were also formed on the surface due to water presence. Using TPD data, Arrhenius plots for CO2 and water desorption were done and activation energy for desorption was obtained. Funds FONDECyT 1130372; Thanks to P. Ferrari.

  3. Dielectric dynamics of epitaxial BiFeO3 thin films

    Directory of Open Access Journals (Sweden)

    Peng Ren

    2012-06-01

    Full Text Available We report the detailed study on the low temperature dielectric dynamics of the epitaxial BiFeO3 thin films grown on Nb-doped SrTiO3 substrate. The results indicate that the contributions from the thin film dominate the dielectric response, although it comes from both the thin film and the electrode interface. Furthermore, the origins of the low temperature dielectric anomalies are investigated with electric circuit fittings. A possible phase transition at 210 K is revealed from analysis with dielectric loss tangent. The dielectric constants obtained from the constant phase elements (CPEs are more than 400 even at low temperatures. Finally, the physical significances of the CPE model are discussed.

  4. The preparation of Zn-ferrite epitaxial thin film from epitaxial Fe3O4:ZnO multilayers by ion beam sputtering deposition

    International Nuclear Information System (INIS)

    Su, Hui-Chia; Dai, Jeng-Yi; Liao, Yen-Fa; Wu, Yu-Han; Huang, J.C.A.; Lee, Chih-Hao

    2010-01-01

    A new method to grow a well-ordered epitaxial ZnFe 2 O 4 thin film on Al 2 O 3 (0001) substrate is described in this work. The samples were made by annealing the ZnO/Fe 3 O 4 multilayer which was grown with low energy ion beam sputtering deposition. Both the Fe 3 O 4 and ZnO layers were found grown epitaxially at low temperature and an epitaxial ZnFe 2 O 4 thin film was formed after annealing at 1000 o C. X-ray diffraction shows the ZnFe 2 O 4 film is grown with an orientation of ZnFe 2 O 4 (111)//Al 2 O 3 (0001) and ZnFe 2 O 4 (1-10)//Al 2 O 3 (11-20). X-ray absorption spectroscopy studies show that Zn 2+ atoms replace the tetrahedral Fe 2+ atoms in Fe 3 O 4 during the annealing. The magnetic properties measured by vibrating sample magnetometer show that the saturation magnetization of ZnFe 2 O 4 grown from ZnO/Fe 3 O 4 multilayer reaches the bulk value after the annealing process.

  5. Depth resolved lattice-charge coupling in epitaxial BiFeO3 thin film

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    Lee, Hyeon Jun; Lee, Sung Su; Kwak, Jeong Hun; Kim, Young-Min; Jeong, Hu Young; Borisevich, Albina Y.; Lee, Su Yong; Noh, Do Young; Kwon, Owoong; Kim, Yunseok; Jo, Ji Young

    2016-12-01

    For epitaxial films, a critical thickness (tc) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the tc in BiFeO3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO3/SrRuO3/SrTiO3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO3 film was resolved into a strained layer with an extremely low piezoelectric coefficient of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical coupling.

  6. Thin film growth of CaFe2As2 by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Hatano, T; Fujimoto, R; Nakamura, I; Mori, Y; Ikuta, H; Kawaguchi, T; Harada, S; Ujihara, T

    2016-01-01

    Film growth of CaFe 2 As 2 was realized by molecular beam epitaxy on six different substrates that have a wide variation in the lattice mismatch to the target compound. By carefully adjusting the Ca-to-Fe flux ratio, we obtained single-phase thin films for most of the substrates. Interestingly, an expansion of the CaFe 2 As 2 lattice to the out-of-plane direction was observed for all films, even when an opposite strain was expected. A detailed microstructure observation of the thin film grown on MgO by transmission electron microscope revealed that it consists of cube-on-cube and 45°-rotated domains. The latter domains were compressively strained in plane, which caused a stretching along the c-axis direction. Because the domains were well connected across the boundary with no appreciable discontinuity, we think that the out-of-plane expansion in the 45°-rotated domains exerted a tensile stress on the other domains, resulting in the unexpectedly large c-axis lattice parameter, despite the apparently opposite lattice mismatch. (paper)

  7. Topotactic Metal-Insulator Transition in Epitaxial SrFeOx Thin Films.

    Science.gov (United States)

    Khare, Amit; Shin, Dongwon; Yoo, Tae Sup; Kim, Minu; Kang, Tae Dong; Lee, Jaekwang; Roh, Seulki; Jung, In-Ho; Hwang, Jungseek; Kim, Sung Wng; Noh, Tae Won; Ohta, Hiromichi; Choi, Woo Seok

    2017-10-01

    Topotactic phase transformation enables structural transition without losing the crystalline symmetry of the parental phase and provides an effective platform for elucidating the redox reaction and oxygen diffusion within transition metal oxides. In addition, it enables tuning of the emergent physical properties of complex oxides, through strong interaction between the lattice and electronic degrees of freedom. In this communication, the electronic structure evolution of SrFeO x epitaxial thin films is identified in real-time, during the progress of reversible topotactic phase transformation. Using real-time optical spectroscopy, the phase transition between the two structurally distinct phases (i.e., brownmillerite and perovskite) is quantitatively monitored, and a pressure-temperature phase diagram of the topotactic transformation is constructed for the first time. The transformation at relatively low temperatures is attributed to a markedly small difference in Gibbs free energy compared to the known similar class of materials to date. This study highlights the phase stability and reversibility of SrFeO x thin films, which is highly relevant for energy and environmental applications exploiting the redox reactions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Thin epitaxial silicon detectors

    International Nuclear Information System (INIS)

    Stab, L.

    1989-01-01

    Manufacturing procedures of thin epitaxial surface barriers will be given. Some improvements have been obtained: larger areas, lower leakage currents and better resolutions. New planar epitaxial dE/dX detectors, made in a collaboration work with ENERTEC-INTERTECHNIQUE, and a new application of these thin planar diodes to EXAFS measurements, made in a collaboration work with LURE (CNRS,CEA,MEN) will also be reported

  9. Magnetic and magnetoelastic properties of epitaxial SmFe{sub 2} thin film

    Energy Technology Data Exchange (ETDEWEB)

    Fuente, C de la; Arnaudas, J I; Ciria, M; Del Moral, A [Departamento de Magnetismo de Solidos and Departamento de Fisica de la Materia Condensada, Instituto de Ciencia de los Materiales de Aragon and Universidad de Zaragoza, 50071, Zaragoza (Spain); Dufour, C; Dumesnil, K, E-mail: cesar@unizar.e [Laboratoire de Metallurgie Physique et de Science des Materiaux, Universite Henry Poincare, Nancy 1, BP 239, 54506 (France)

    2010-02-03

    We report on magnetic and magnetoelastic measurements for a 5000 A (110) SmFe{sub 2} thin film, which was successfully analyzed by means of a point charge model for describing the effect of the epitaxial growth in this kind of system. Some of the main conclusions of the Moessbauer and magnetoelastic results and the new magnetization results up to 5 T allow us to get a full description of the crystal electric field, exchange, and magnetoelastic behavior in this compound. So, new single-ion parameters are obtained for the crystal field interaction of samarium ions, A{sub 4}(r{sup 4}) = +755 K/ion and A{sub 6}(r{sup 6}) = -180 K/ion, and new single-ion magnetoelastic coupling B{sup gamma}{sup ,2}approx =-200 MPa and B{sup epsilon}{sup ,2}approx =800 MPa, which represent the tetragonal and the in-plane shear deformations, respectively. Moreover, the new thermal behavior of the samarium magnetic moment, the exchange coupling parameter, and the magnetocrystalline anisotropy of the iron sublattice are obtained too. From these, the softening of the spin reorientation transition with respect to the bulk case could be accounted for.

  10. Study of electronic structure and magnetic properties of epitaxial Co{sub 2}FeAl Heusler Alloy Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Soni, S. [Department of Pure & Applied Physics, University of Kota, Kota 324007 (India); Dalela, S., E-mail: sdphysics@rediffmail.com [Department of Pure & Applied Physics, University of Kota, Kota 324007 (India); Sharma, S.S. [Department of Physics, Govt. Women Engineering College, Ajmer (India); Liu, E.K.; Wang, W.H.; Wu, G.H. [State Key Laboratory for Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Kumar, M. [Department of Physics, Malviya National Institute of Technology, Jaipur-302017 (India); Garg, K.B. [Department of Physics, University of Rajasthan, Jaipur-302004 (India)

    2016-07-25

    This work reports the magnetic and electronic characterization of plane magnetized buried Heusler Co{sub 2}FeAl nano thin films of different thickness by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements. . The spectra on both Fe- and Co L{sub 2,3} edges show a pronounced magnetic dichroic signal in remanence, corresponding to a ferromagnetically-aligned moments on Fe and Co atoms conditioning the peculiar characteristics of the Co{sub 2}FeAl Heusler compound (a half-metallic ferromagnet). The detailed knowledge of the related magnetic and electronic properties of these samples over a wide range of thickness of films are indispensable for achieving a higher tunnel magnetoresistance ratio, and thus for spintronics device applications. - Highlights: • Electronic structure and Magnetic Properties of Epitaxial Co{sub 2}FeAl Heusler Films. • X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). • Fe- and Co L{sub 2,3} edges show a pronounced magnetic dichroic signal in remanence. • Calculated Orbital, Spin and total magnetic moments of Fe and Co for 30 nm Co{sub 2}FeAl thin film. • The total magnetic moment of Fe at L{sub 2,3} edges increases with the thickness of the Co2FeAl films.

  11. Epitaxial thin films

    Science.gov (United States)

    Hunt, Andrew Tye; Deshpande, Girish; Lin, Wen-Yi; Jan, Tzyy-Jiuan

    2006-04-25

    Epitatial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal gain boundary/interface microstructure. Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed by high-quality, dense, gas-tight, pinhole free sub-micro scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

  12. Antiphase boundaries induced exchange coupling in epitaxial Fe3O4 thin films

    International Nuclear Information System (INIS)

    Arora, S.K.; Sofin, R.G.S.; Nolan, A.; Shvets, I.V.

    2005-01-01

    We have observed an exchange bias effect on field cooling of epitaxial magnetite, Fe 3 O 4 , films on MgO (1 0 0) substrates. We attribute this effect to the presence of antiphase boundaries (APBs). Magnitude of the exchange bias field (H e ) strongly depends on the thermo-magnetic history of the sample. The strength of the H e was found to increase with an increase in film thickness and is attributed to the strain driven redistribution of atoms in the vicinity of APBs leading to enhanced antiferromagnetic exchange interactions

  13. Magnetoelectric and multiferroic properties of variously oriented epitaxial BiFeO3-CoFe2O4 nanostructured thin films

    Science.gov (United States)

    Yan, Li; Wang, Zhiguang; Xing, Zengping; Li, Jiefang; Viehland, D.

    2010-03-01

    We report the ferroelectric, ferromagnetic, and magnetoelectric (ME) properties of self-assembled epitaxial BiFeO3-CoFe2O4 (BFO-CFO) nanostructure composite thin films deposited on (001), (110), and (111) SrTiO3 (STO) single crystal substrates. These various properties are shown to depend on orientation. The maximum values of the relative dielectric constant, saturation polarization, longitudinal piezoelectric coefficient, saturation magnetization, and ME coefficient at room temperature were 143, 86 μm/cm2, 50 pm/V, 400 emu/cc, and 20 mV/cm Oe, respectively.

  14. Direct measurement of magnetoelectric exchange in self-assembled epitaxial BiFeO3-CoFe2O4 nanocomposite thin films

    Science.gov (United States)

    Yan, Li; Xing, Zengping; Wang, Zhiguang; Wang, Tao; Lei, Guangyin; Li, Jiefang; Viehland, D.

    2009-05-01

    We report the direct measurement of a magnetoelectric (ME) exchange between magnetostrictive CoFe2O4 nanopillars in a piezoelectric BiFeO3 matrix for single-layer nanocomposite epitaxial thin films grown on (001) SrTiO3 substrates with SrRuO3 bottom electrodes. The ME coefficient was measured by a magnetic cantilever method and had a maximum value of ˜20 mV/cm Oe. The films possessed saturation polarization (60 μC/cm2) and magnetization (410 emu/cc) properties equivalent to bulk values, with typical hysteresis loops.

  15. Interfacial-strain-induced structural and polarization evolutions in epitaxial multiferroic BiFeO3 (001) thin films.

    Science.gov (United States)

    Guo, Haizhong; Zhao, Ruiqiang; Jin, Kui-Juan; Gu, Lin; Xiao, Dongdong; Yang, Zhenzhong; Li, Xiaolong; Wang, Le; He, Xu; Gu, Junxing; Wan, Qian; Wang, Can; Lu, Huibin; Ge, Chen; He, Meng; Yang, Guozhen

    2015-02-04

    Varying the film thickness is a precise route to tune the interfacial strain to manipulate the properties of the multiferroic materials. Here, to explore the effects of the interfacial strain on the properties of the multiferroic BiFeO3 films, we investigated thickness-dependent structural and polarization evolutions of the BiFeO3 films. The epitaxial growth with an atomic stacking sequence of BiO/TiO2 at the interface was confirmed by scanning transmission electron microscopy. Combining X-ray diffraction experiments and first-principles calculations, a thickness-dependent structural evolution was observed from a fully strained tetragonality to a partially relaxed one without any structural phase transition or rotated twins. The tetragonality (c/a) of the BiFeO3 films increases as the film thickness decreases, while the polarization is in contrast with this trend, and the size effect including the depolarization field plays a crucial role in this contradiction in thinner films. These findings offer an alternative strategy to manipulate structural and polarization properties by tuning the interfacial strain in epitaxial multiferroic thin films.

  16. Microstructure and Magnetic Properties of Fe and Fe-alloy Thin Films Epitaxially Grown on MgO(100) Substrates

    International Nuclear Information System (INIS)

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

    2011-01-01

    Fe, Fe 50 Co 50 , and Fe 80 Ni 20 (at. %) single-crystal films with the (100) bcc plane parallel to the substrate surface were prepared on MgO(100) single-crystals heated at 300 0 C by ultra high vacuum molecular beam epitaxy. The film growth mechanism, the film structure, and the magnetic properties were investigated. In-situ reflection high energy electron diffraction and X-ray diffraction analyses indicate that the strains in the films are very small though there are fairly large mismatches of -3.7∼-4.3% at the film/substrate interface. Cross-sectional high-resolution transmission electron microscopy shows that misfit dislocations are introduced in the film at the interface. Dislocations are also observed in the film up to around 10∼20 nm distance from the interface. The presence of such dislocation relieves the strain caused by the lattice mismatch. The in-plane magnetization properties of these films reflect the magnetocrystalline anisotropies of respective bulk Fe, Fe 50 Co 50 , and Fe 80 Ni 20 crystals.

  17. Magneto-transport and thermoelectric properties of epitaxial FeSb{sub 2} thin film on MgO substrate

    Energy Technology Data Exchange (ETDEWEB)

    Duong, Anh Tuan; Rhim, S. H., E-mail: sonny@ulsan.ac.kr; Shin, Yooleemi; Nguyen, Van Quang; Cho, Sunglae, E-mail: slcho@ulsan.ac.kr [Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 680-749 (Korea, Republic of)

    2015-01-19

    We report magneto-transport and thermoelectric properties of FeSb{sub 2} thin film epitaxially grown on the MgO substrate using molecular beam epitaxy. The film exhibits compressive strain of 1.74% owing to large lattice mismatch, whose physical consequences are nontrivial. Magnetic phase has been changed from diamagnetic in bulk, as evidenced by anomalous Hall effect (AHE) and negative magneto-resistance (MR). The FeSb{sub 2} film is semiconducting without any metallic transition unlike the bulk counterpart. In particular, hysteresis in MR with distinct feature of AHE is evident with coercive field of 500 and 110 Oe for T = 20 and 50 K, respectively. Furthermore, from the Seebeck coefficients and temperature dependence of the resistivity, it is evident that the film is semiconducting with small band gap: 3.76 meV for T < 40 K and 13.48 meV for T > 40 K, respectively, where maximum thermoelectric power factor of 12 μV/cm·K at T = 50 K.

  18. Epitaxy, thin films and superlattices

    International Nuclear Information System (INIS)

    Jagd Christensen, Morten

    1997-05-01

    This report is the result of structural investigations of 3d transition metal superlattices consisting of Fe/V, Cr/Mn, V/Mn and Fe/Mn, and a structural and magnetic study of a series of Ho/Pr alloys. The work includes preparation and characterization of substrates as well as growth of thin films and Fe/V superlattices by molecular beam epitaxy, including in-situ characterization by reflection high energy electron diffraction and Auger electron spectroscopy. Structural characterization has been done by x-ray diffraction and neutron diffraction. The x-ray diffraction experiments have been performed on the rotating copper anode at Risoe, and at synchrotron facilities in Hamburg and Brookhaven, and the neutron scattering was done at the Danish research reactor DR3 at Risoe. In addition to longitudinal scans, giving information about the structural parameters in the modulation direction, non-specular scans were also performed. This type of scans gives information about in-plane orientation and lattice parameters. From the analysis, structural information is obtained about lattice parameters, epitaxial strain, coherence lengths and crystallographic orientation for the superlattice systems, except Fe/Mn superlattices, which could not be modelled. For the Ho/Pr alloys, x-ray magnetic scattering was performed, and the crystal and magnetic structure was investigated. (au)

  19. Epitaxy, thin films and superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Jagd Christensen, Morten

    1997-05-01

    This report is the result of structural investigations of 3d transition metal superlattices consisting of Fe/V, Cr/Mn, V/Mn and Fe/Mn, and a structural and magnetic study of a series of Ho/Pr alloys. The work includes preparation and characterization of substrates as well as growth of thin films and Fe/V superlattices by molecular beam epitaxy, including in-situ characterization by reflection high energy electron diffraction and Auger electron spectroscopy. Structural characterization has been done by x-ray diffraction and neutron diffraction. The x-ray diffraction experiments have been performed on the rotating copper anode at Risoe, and at synchrotron facilities in Hamburg and Brookhaven, and the neutron scattering was done at the Danish research reactor DR3 at Risoe. In addition to longitudinal scans, giving information about the structural parameters in the modulation direction, non-specular scans were also performed. This type of scans gives information about in-plane orientation and lattice parameters. From the analysis, structural information is obtained about lattice parameters, epitaxial strain, coherence lengths and crystallographic orientation for the superlattice systems, except Fe/Mn superlattices, which could not be modelled. For the Ho/Pr alloys, x-ray magnetic scattering was performed, and the crystal and magnetic structure was investigated. (au) 14 tabs.; 58 ills., 96 refs.

  20. Effect of epitaxial strain and lattice mismatch on magnetic and transport behaviors in metamagnetic FeRh thin films

    Directory of Open Access Journals (Sweden)

    Yali Xie

    2017-05-01

    Full Text Available We grew 80 nm FeRh films on different single crystals with various lattice constants. FeRh films on SrTiO3 (STO and MgO substrates exhibit an epitaxial growth of 45° in-plane structure rotation. In contrast, FeRh on LaAlO3 (LAO displays a mixed epitaxial growth of both 45° in-plane structure rotation and cube-on-cube relationships. Due to the different epitaxial growth strains and lattice mismatch values, the critical temperature for the magnetic phase transition of FeRh can be changed between 405 and 360 K. In addition, the external magnetic field can shift this critical temperature to low temperature in different rates for FeRh films grown on different substrates. The magnetoresistance appears a maximum value at different temperatures between 320 and 380 K for FeRh films grown on different substrates.

  1. Effect of epitaxial strain and lattice mismatch on magnetic and transport behaviors in metamagnetic FeRh thin films

    Science.gov (United States)

    Xie, Yali; Zhan, Qingfeng; Shang, Tian; Yang, Huali; Wang, Baomin; Tang, Jin; Li, Run-Wei

    2017-05-01

    We grew 80 nm FeRh films on different single crystals with various lattice constants. FeRh films on SrTiO3 (STO) and MgO substrates exhibit an epitaxial growth of 45° in-plane structure rotation. In contrast, FeRh on LaAlO3 (LAO) displays a mixed epitaxial growth of both 45° in-plane structure rotation and cube-on-cube relationships. Due to the different epitaxial growth strains and lattice mismatch values, the critical temperature for the magnetic phase transition of FeRh can be changed between 405 and 360 K. In addition, the external magnetic field can shift this critical temperature to low temperature in different rates for FeRh films grown on different substrates. The magnetoresistance appears a maximum value at different temperatures between 320 and 380 K for FeRh films grown on different substrates.

  2. Epitaxial integration of CoFe2O4 thin films on Si (001) surfaces using TiN buffer layers

    Science.gov (United States)

    Prieto, Pilar; Marco, José F.; Prieto, José E.; Ruiz-Gomez, Sandra; Perez, Lucas; del Real, Rafael P.; Vázquez, Manuel; de la Figuera, Juan

    2018-04-01

    Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe2, or ceramic, CoFe2O4, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFe2O4 [100]/TiN [100]/Si [100]. Mössbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in-plane anisotropy depends on the lattice mismatch between CoFe2O4 and TiN, which is larger for CoFe2O4 thin films grown on the reactive sputtering process with ceramic targets.

  3. Interplay of uniaxial and cubic anisotropy in epitaxial Fe thin films on MgO (001 substrate

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    Srijani Mallik

    2014-09-01

    Full Text Available Epitaxial Fe thin films were grown on annealed MgO(001 substrates at oblique incidence by DC magnetron sputtering. Due to the oblique growth configuration, uniaxial anisotropy was found to be superimposed on the expected four-fold cubic anisotropy. A detailed study of in-plane magnetic hysteresis for Fe on MgO thin films has been performed by Magneto Optic Kerr Effect (MOKE magnetometer. Both single step and double step loops have been observed depending on the angle between the applied field and easy axis i.e. along ⟨100⟩ direction. Domain images during magnetization reversal were captured by Kerr microscope. Domain images clearly evidence two successive and separate 90° domain wall (DW nucleation and motion along cubic easy cum uniaxial easy axis and cubic easy cum uniaxial hard axis, respectively. However, along cubic hard axis two 180° domain wall motion dominate the magnetization reversal process. In spite of having four-fold anisotropy it is essential to explain magnetization reversal mechanism in 0°< ϕ < 90° span as uniaxial anisotropy plays a major role in this system. Also it is shown that substrate rotation can suppress the effect of uniaxial anisotropy superimposed on four-fold anisotropy.

  4. Magnetic surface domain imaging of uncapped epitaxial FeRh(001 thin films across the temperature-induced metamagnetic transition

    Directory of Open Access Journals (Sweden)

    Xianzhong Zhou

    2016-01-01

    Full Text Available The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001 thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001 surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different thermal expansion coefficients of MgO and FeRh.

  5. Oxygen vacancy induced structural evolution of SrFeO3 -x epitaxial thin film from brownmillerite to perovskite

    Science.gov (United States)

    Roh, Seulki; Lee, Seokbae; Lee, Myounghoon; Seo, Yu-Seong; Khare, Amit; Yoo, Taesup; Woo, Sungmin; Choi, Woo Seok; Hwang, Jungseek; Glamazda, A.; Choi, K.-Y.

    2018-02-01

    We investigated SrFeO3 -x thin films on a SrTiO3 (001) substrate prepared via pulsed laser epitaxy using an optical spectroscopy technique. The oxygen vacancy level (x ) was controlled by post-annealing processes at different oxygen partial pressures. We achieved a brownmillerite (BM) structure at x =0.5 and observed the evolution of the crystal structure from BM into perovskite (PV) as the oxygen concentration increased. We observed the evolution of infrared-active phonons with respect to the oxygen concentration, which was closely related to the structural evolution observed via x-ray diffraction. We identified the phonons using the shell-model calculation. Furthermore, we studied temperature-dependent behaviors of the phonon modes of three representative samples: PV and two BMs (BMoop and BMip) with different orientations of the oxygen vacancy channel. In the BMoop sample, we observed a phonon mode, which exhibited an unusual redshift with decreasing temperature; this behavior may have been due to the apical oxygen instability in the FeO6 octahedron. Our results provide important information regarding the ionic conduction mechanism in SrFeO3 -x material systems.

  6. Superconducting spin valves based on epitaxial Fe/V-hybrid thin film heterostructures

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    Nowak, Gregor

    2010-12-10

    This study presents a systematic investigation of the SSV effect in FM/SC/FM and FM/N/FM/SC heterostructures. Before investigating the actual SSV effect, we first pre-analyzed structural, magnetic and superconducting properties of the Fe/V system. In these preliminary studies we demonstrated, that epitaxial Fe/V heterostructures of superior crystalline quality can be grown by DC sputter deposition. With a Fe/V interface thickness of only one monolayer, the chemical separation of the Fe and V layers is extremely sharp. Moreover, the magnetic investigation showed that from thicknesses of two Fe(001) monolayers on the Fe layers in the superlattice possess a magnetic moment. Furthermore, we demonstrated the interlayer exchange coupling as oscillatory function of the V interlayer thickness. The investigations of the superconducting parameters of the Fe/V system revealed a non-monotonic T{sub S} vs. d{sub Fe} dependence in sample series (1). This observation proves the presence of the FM/SC proximity effect. The studies of various heterostructures of the design AFM/FM/SC/FM revealed a strong counteracting influence on the SSV effect, the stray field effect. The sample containing Fe{sub 25}V{sub 75} alloy layers, has the highest ratio of Cooper pair coherence length and superconductor thickness (ξ{sub S})/(d{sub S}), and its superconducting transition temperature is comparable to the sample with Fe{sub 35}V{sub 65} alloy layers. Nevertheless, the SSV effect in sample Fe{sub 25}V{sub 75} with alloy layers is much smaller than in sample with Fe{sub 35}V{sub 65} alloy layers. For a high-performance superconducting spin valve based on a FM1/SC/FM2 heterostructure at least four parameters have to be optimized simultaneously. 1. The magnetic domain size in FM1 and FM2 has to be as large as possible in order to reduce the stray field effect resulting from magnetization components in the FM domain walls perpendicular to the SC layer. 2. When using ferromagnetic alloys as

  7. 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.

  8. Comparative study of water and carbon dioxide adsorption on CuFeO2 and CuFe1-xGaxO2 highly epitaxial thin films

    Science.gov (United States)

    Rojas, S.; Joshi, T.; Borisov, P.; Lederman, D.; Cabrera, A. L.

    Thermal programmed desorption (TPD) of CO2 and H2O from a 200 nm thick CuFeO2 and 52 nm thick CuFe1-xGaxO2 delafossite surfaces was performed in a Ultra-high vacuum (UHV) chamber. The thin films with epitaxial quality were grown by Pulsed Laser Deposition (PLD) on Al2O3 (0001) substrates . The adsorption / desorption of CO2 and H2O process was also monitored with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Our results revealed that carbon dioxide is preferentially chemisorbed by CuFe1-xGaxO2 over water and we observed the opposite behavior with regard to chemisorption of CO2 and H2O over CuFeO2. Hydroxyls and metal carbonates were formed on the surface due to the chemisorption of H2O and CO2. Arrhenius plots for CO2 and H2O desorption were done and activation energy for desorption were obtained. Supported by FONDECyT 1130372.

  9. Temperature dependences of ferroelectricity and resistive switching behavior of epitaxial BiFeO3 thin films

    Science.gov (United States)

    Lu, Zeng-Xing; Song, Xiao; Zhao, Li-Na; Li, Zhong-Wen; Lin, Yuan-Bin; Zeng, Min; Zhang, Zhang; Lu, Xu-Bing; Wu, Su-Juan; Gao, Xing-Sen; Yan, Zhi-Bo; Liu, Jun-Ming

    2015-10-01

    We investigate the resistive switching and ferroelectric polarization properties of high-quality epitaxial BiFeO3 thin films in various temperature ranges. The room temperature current-voltage (I-V) curve exhibits a well-established polarization-modulated memristor behavior. At low temperatures (originates from the dielectric relaxation effects, accompanied with a current hump due to the polarization reversal displacement current. While at relative higher temperatures (> 253 K), the I-V behaviors are governed by both space-charge-limited conduction (SCLC) and Ohmic behavior. The polarization reversal is able to trigger the conduction switching from Ohmic to SCLC behavior, leading to the observed ferroelectric resistive switching. At a temperature of > 298 K, there occurs a new resistive switching hysteresis at high bias voltages, which may be related to defect-mediated effects. Project supported by the National Natural Science Foundation of China (Grant Nos. 51272078 and 51332007), the State Key Program for Basic Research of China (Grant No 2015CB921202), the Guangdong Provincial Universities and Colleges Pearl River Scholar Funded Scheme, China (2014), the International Science & Technology Cooperation Platform Program of Guangzhou, China (Grant No. 2014J4500016), and the Program for Changjiang Scholars and Innovative Research Team in University of China (Grant No. IRT1243).

  10. Mechanisms of exchange bias with multiferroic BiFeO3 epitaxial thin films

    OpenAIRE

    Bea, H.; Bibes, M.; Ott, F.; Dupe, B.; Zhu, X. -H.; Petit, S.; Fusil, S.; Deranlot, C.; Bouzehouane, K.; Barthelemy, A.

    2007-01-01

    We have combined neutron scattering and piezoresponse force microscopy to study the relation between the exchange bias observed in CoFeB/BiFeO3 heterostructures and the multiferroic domain structure of the BiFeO3 films. We show that the exchange field scales with the inverse of the ferroelectric and antiferromagnetic domain size, as expected from Malozemoff's model of exchange bias extended to multiferroics. Accordingly, polarized neutron reflectometry reveals the presence of uncompensated sp...

  11. Correlation of High Magnetoelectric Coupling with Oxygen Vacancy Superstructure in Epitaxial Multiferroic BaTiO3-BiFeO3 Composite Thin Films

    OpenAIRE

    Lorenz, Michael; Wagner, Gerald; Lazenka, Vera; Schwinkendorf, Peter; Bonholzer, Michael; Van Bael, Margriet J.; Vantomme, Andr?; Temst, Kristiaan; Oeckler, Oliver; Grundmann, Marius

    2016-01-01

    Epitaxial multiferroic BaTiO3-BiFeO3 composite thin films exhibit a correlation between the magnetoelectric (ME) voltage coefficient αME and the oxygen partial pressure during growth. The ME coefficient αME reaches high values up to 43 V/(cm·Oe) at 300 K and at 0.25 mbar oxygen growth pressure. The temperature dependence of αME of the composite films is opposite that of recently-reported BaTiO3-BiFeO3 superlattices, indicating that strain-mediated ME coupling alone cannot explain its origin. ...

  12. In situ Polarized Neutron Reflectometry: Epitaxial Thin-Film Growth of Fe on Cu(001) by dc Magnetron Sputtering

    Science.gov (United States)

    Kreuzpaintner, Wolfgang; Wiedemann, Birgit; Stahn, Jochen; Moulin, Jean-François; Mayr, Sina; Mairoser, Thomas; Schmehl, Andreas; Herrnberger, Alexander; Korelis, Panagiotis; Haese, Martin; Ye, Jingfan; Pomm, Matthias; Böni, Peter; Mannhart, Jochen

    2017-05-01

    The stepwise growth of epitaxial Fe on Cu (001 )/Si (001 ) , investigated by in situ polarized neutron reflectometry is presented. A sputter deposition system was integrated into the neutron reflectometer AMOR at the Swiss neutron spallation source SINQ, which enables the analysis of the microstructure and magnetic moments during all deposition steps of the Fe layer. We report on the progressive evolution of the accessible parameters describing the microstructure and the magnetic properties of the Fe film, which reproduce known features and extend our knowledge on the behavior of ultrathin iron films.

  13. Structural and superconducting properties of epitaxial Fe{sub 1+y}Se{sub 1-x}Te{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Stefan; Yuan, Feifei; Grinenko, Vadim; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Sala, Alberto; Putti, Marina [Dipartimento di Fisica, Universita di Genova (Italy)

    2015-07-01

    The iron based superconductor Fe(Se,Te) is in the center of much ongoing research. The reason for this is on the one hand its simple crystal structure, that consists only of stacked Fe(Se,Te) layers so that structural and superconducting properties can be connected more easily, on the other hand FeSe itself shows a high sensibility for strain and changes in stoichiometry and can have potentially very high critical temperatures under hydrostatic pressure or in monolayers. We investigate epitaxial thin films of Fe{sub 1+y}Se{sub 1-x}Te{sub x} grown by pulsed laser deposition on different single crystalline substrates. A high crystalline quality and a superconducting transition of up to about 20 K can be achieved using optimized deposition parameters. The influence of growth conditions, Te-doping, film thickness and post growth oxygen treatment on the structural and superconducting properties on these films will be presented in detail.

  14. Magnetic domain configuration of (111-oriented LaFeO3 epitaxial thin films

    Directory of Open Access Journals (Sweden)

    I. Hallsteinsen

    2017-08-01

    Full Text Available In antiferromagnetic spintronics control of the domains and corresponding spin axis orientation is crucial for devices. Here we investigate the antiferromagnetic axis in (111-oriented LaFeO3/SrTiO3, which is coupled to structural twin domains. The structural domains have either the orthorhombic a- or b-axis along the in-plane ⟨11¯0⟩ cubic directions of the substrate, and the corresponding magnetic domains have the antiferromagnetic axis in the sample plane. Six degenerate antiferromagnetic axes are found corresponding to the ⟨11¯0⟩ and ⟨112¯⟩ in-plane directions. This is in contrast to the biaxial anisotropy in (001-oriented films and reflects how crystal orientation can be used to control magnetic anisotropy in antiferromagnets.

  15. Ferroelectric domains and phase transition of sol-gel processed epitaxial Sm-doped BiFeO3 (001 thin films

    Directory of Open Access Journals (Sweden)

    Zhen Zhou

    2018-03-01

    Full Text Available BiFeO3, a room-temperature multiferroic material, has recently been increasingly applied as a potential lead-free piezoelectric material due to its large piezoelectricity achieved by doping. In this work, 12% Sm-doped BiFeO3 epitaxial thin films were fabricated on Nb-doped SrTiO3 (001 single crystal substrates via sol-gel method. The epitaxy was verified by reciprocal space mapping (RSM and transmission electron microscope (TEM. The TEM results indicated the coexistence of R3c and Pbam phases in the film. The domains and piezoelectric properties from room temperature to 200 °C were characterized by piezoresponse force microscopy (PFM. Domains became active from 110 °C to 170 °C, and domain configurations changed obviously. A partially fading piezoresponse indicated the emergence of antiferroelectric Pbam. The in-situ domain analysis suggested that the phase transition was accompanied by domain wall motion. Switching spectroscopy PFM (SS-PFM was further conducted to investigate the piezoresponse during the phase transition. Anomalous responses were found in both ON and OFF states at 170 °C, and the film exhibits typical antiferroelectric behavior at 200 °C, implying that the completion of phase transition and structure turned to the Pbam phase. This work revealed the origin of the high piezoresponse of Sm-doped BiFeO3 thin films at the morphotropic phase boundary (MPB.

  16. Structural and magnetic properties of epitaxial delafossite CuFeO{sub 2} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Toyanath; Senty, Tess R.; Trappen, Robbyn; Zhou, Jinling; Borisov, Pavel; Holcomb, Mikel B.; Bristow, Alan D.; Lederman, David [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Chen, Song; Song, Xueyan [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6070 (United States); Ferrari, Piero; Cabrera, Alejandro L. [Pontificia Universidad Catolica, Instituto de Física, Santiago (Chile)

    2015-01-07

    Growth of pure phase delafossite CuFeO{sub 2} thin films on Al{sub 2}O{sub 3} (00.1) substrates by pulsed laser deposition was systematically investigated as a function of growth temperature and oxygen pressure. X-ray diffraction, transmission electron microscopy, Raman scattering, and x-ray absorption spectroscopy confirmed the existence of the delafossite phase. Infrared reflectivity spectra determined a band edge at 1.15 eV, in agreement with the bulk delafossite data. Magnetization measurements on CuFeO{sub 2} films demonstrated a phase transition at T{sub C} ≈ 15 ± 1 K, which agrees with the first antiferromagnetic transition at 14 K in the bulk CuFeO{sub 2}. Low temperature magnetic phase is best described by commensurate, weak ferromagnetic spin ordering along the c-axis.

  17. Structural and magnetic anisotropy in the epitaxial FeV2O4 (110 spinel thin films

    Directory of Open Access Journals (Sweden)

    Xiaolan Shi

    2015-11-01

    Full Text Available The epitaxial 200-nm-thick FeV2O4(110 films on (110-oriented SrTiO3, LaAlO3 and MgAl2O4 substrates were fabricated for the first time by pulsed laser deposition, and the structural, magnetic, and magnetoresistance anisotropy were investigated systematically. All the films are monoclinic, whereas its bulk is cubic. Compared to FeV2O4 single crystals, films on SrTiO3 and MgAl2O4 are strongly compressively strained in [001] direction, while slightly tensily strained along normal [110] and in-plane [ 1 1 ¯ 0 ] directions. In contrast, films on LaAlO3 are only slightly distorted from cubic. The magnetic hard axis is in direction, while the easier axis is along normal [110] direction for films on SrTiO3 and MgAl2O4, and in-plane [ 1 1 ¯ 0 ] direction for films on LaAlO3. Magnetoresistance anisotropy follows the magnetization. The magnetic anisotropy is dominated by the magnetocrystalline energy, and tuned by the magneto-elastic coupling.

  18. Revealing the flexoelectricity in the mixed-phase regions of epitaxial BiFeO3 thin films

    Science.gov (United States)

    Cheng, Cheng-En; Liu, Heng-Jui; Dinelli, Franco; Chen, Yi-Chun; Chang, Chen-Shiung; Chien, Forest Shih-Sen; Chu, Ying-Hao

    2015-01-01

    Understanding the elastic response on the nanoscale phase boundaries of multiferroics is an essential issue in order to explain their exotic behaviour. Mixed-phase BiFeO3 films, epitaxially grown on LaAlO3 (001) substrates, have been investigated by means of scanning probe microscopy to characterize the elastic and piezoelectric responses in the mixed-phase region of rhombohedral-like monoclinic (MI) and tilted tetragonal-like monoclinic (MII,tilt) phases. Ultrasonic force microscopy reveal that the regions with low/high stiffness values topologically coincide with the MI/MII,tilt phases. X-ray diffraction strain analysis confirms that the MI phase is more compliant than the MII,tilt one. Significantly, the correlation between elastic modulation and piezoresponse across the mixed-phase regions manifests that the flexoelectric effect results in the enhancement of the piezoresponse at the phase boundaries and in the MI regions. This accounts for the giant electromechanical effect in strained mixed-phase BiFeO3 films.

  19. Structural and magnetic anisotropy in the epitaxial FeV2O4 (110) spinel thin films

    Science.gov (United States)

    Shi, Xiaolan; Wang, Yuhang; Zhao, Kehan; Liu, Na; Sun, Gaofeng; Zhang, Liuwan

    2015-11-01

    The epitaxial 200-nm-thick FeV2O4(110) films on (110)-oriented SrTiO3, LaAlO3 and MgAl2O4 substrates were fabricated for the first time by pulsed laser deposition, and the structural, magnetic, and magnetoresistance anisotropy were investigated systematically. All the films are monoclinic, whereas its bulk is cubic. Compared to FeV2O4 single crystals, films on SrTiO3 and MgAl2O4 are strongly compressively strained in [001] direction, while slightly tensily strained along normal [110] and in-plane [ 1 1 ¯ 0 ] directions. In contrast, films on LaAlO3 are only slightly distorted from cubic. The magnetic hard axis is in direction, while the easier axis is along normal [110] direction for films on SrTiO3 and MgAl2O4, and in-plane [ 1 1 ¯ 0 ] direction for films on LaAlO3. Magnetoresistance anisotropy follows the magnetization. The magnetic anisotropy is dominated by the magnetocrystalline energy, and tuned by the magneto-elastic coupling.

  20. Electronic structure of Fe1.08Te bulk crystals and epitaxial FeTe thin films on Bi2Te3

    Science.gov (United States)

    Arnold, Fabian; Warmuth, Jonas; Michiardi, Matteo; Fikáček, Jan; Bianchi, Marco; Hu, Jin; Mao, Zhiqiang; Miwa, Jill; Singh, Udai Raj; Bremholm, Martin; Wiesendanger, Roland; Honolka, Jan; Wehling, Tim; Wiebe, Jens; Hofmann, Philip

    2018-02-01

    The electronic structure of thin films of FeTe grown on Bi2Te3 is investigated using angle-resolved photoemission spectroscopy, scanning tunneling microscopy and first principles calculations. As a comparison, data from cleaved bulk Fe1.08Te taken under the same experimental conditions is also presented. Due to the substrate and thin film symmetry, FeTe thin films grow on Bi2Te3 in three domains, rotated by 0°, 120°, and 240°. This results in a superposition of photoemission intensity from the domains, complicating the analysis. However, by combining bulk and thin film data, it is possible to partly disentangle the contributions from three domains. We find a close similarity between thin film and bulk electronic structure and an overall good agreement with first principles calculations, assuming a p-doping shift of 65 meV for the bulk and a renormalization factor of around two. By tracking the change of substrate electronic structure upon film growth, we find indications of an electron transfer from the FeTe film to the substrate. No significant change of the film’s electronic structure or doping is observed when alkali atoms are dosed onto the surface. This is ascribed to the film’s high density of states at the Fermi energy. This behavior is also supported by the ab initio calculations.

  1. Correlation of High Magnetoelectric Coupling with Oxygen Vacancy Superstructure in Epitaxial Multiferroic BaTiO₃-BiFeO₃ Composite Thin Films.

    Science.gov (United States)

    Lorenz, Michael; Wagner, Gerald; Lazenka, Vera; Schwinkendorf, Peter; Bonholzer, Michael; Van Bael, Margriet J; Vantomme, André; Temst, Kristiaan; Oeckler, Oliver; Grundmann, Marius

    2016-01-13

    Epitaxial multiferroic BaTiO₃-BiFeO₃ composite thin films exhibit a correlation between the magnetoelectric (ME) voltage coefficient α ME and the oxygen partial pressure during growth. The ME coefficient α ME reaches high values up to 43 V/(cm·Oe) at 300 K and at 0.25 mbar oxygen growth pressure. The temperature dependence of α ME of the composite films is opposite that of recently-reported BaTiO₃-BiFeO₃ superlattices, indicating that strain-mediated ME coupling alone cannot explain its origin. Probably, charge-mediated ME coupling may play a role in the composite films. Furthermore, the chemically-homogeneous composite films show an oxygen vacancy superstructure, which arises from vacancy ordering on the {111} planes of the pseudocubic BaTiO₃-type structure. This work contributes to the understanding of magnetoelectric coupling as a complex and sensitive interplay of chemical, structural and geometrical issues of the BaTiO₃-BiFeO₃ composite system and, thus, paves the way to practical exploitation of magnetoelectric composites.

  2. Correlation of High Magnetoelectric Coupling with Oxygen Vacancy Superstructure in Epitaxial Multiferroic BaTiO3-BiFeO3 Composite Thin Films

    Directory of Open Access Journals (Sweden)

    Michael Lorenz

    2016-01-01

    Full Text Available Epitaxial multiferroic BaTiO3-BiFeO3 composite thin films exhibit a correlation between the magnetoelectric (ME voltage coefficient αME and the oxygen partial pressure during growth. The ME coefficient αME reaches high values up to 43 V/(cm·Oe at 300 K and at 0.25 mbar oxygen growth pressure. The temperature dependence of αME of the composite films is opposite that of recently-reported BaTiO3-BiFeO3 superlattices, indicating that strain-mediated ME coupling alone cannot explain its origin. Probably, charge-mediated ME coupling may play a role in the composite films. Furthermore, the chemically-homogeneous composite films show an oxygen vacancy superstructure, which arises from vacancy ordering on the {111} planes of the pseudocubic BaTiO3-type structure. This work contributes to the understanding of magnetoelectric coupling as a complex and sensitive interplay of chemical, structural and geometrical issues of the BaTiO3-BiFeO3 composite system and, thus, paves the way to practical exploitation of magnetoelectric composites.

  3. Correlation of High Magnetoelectric Coupling with Oxygen Vacancy Superstructure in Epitaxial Multiferroic BaTiO3-BiFeO3 Composite Thin Films

    Science.gov (United States)

    Lorenz, Michael; Wagner, Gerald; Lazenka, Vera; Schwinkendorf, Peter; Bonholzer, Michael; Van Bael, Margriet J.; Vantomme, André; Temst, Kristiaan; Oeckler, Oliver; Grundmann, Marius

    2016-01-01

    Epitaxial multiferroic BaTiO3-BiFeO3 composite thin films exhibit a correlation between the magnetoelectric (ME) voltage coefficient αME and the oxygen partial pressure during growth. The ME coefficient αME reaches high values up to 43 V/(cm·Oe) at 300 K and at 0.25 mbar oxygen growth pressure. The temperature dependence of αME of the composite films is opposite that of recently-reported BaTiO3-BiFeO3 superlattices, indicating that strain-mediated ME coupling alone cannot explain its origin. Probably, charge-mediated ME coupling may play a role in the composite films. Furthermore, the chemically-homogeneous composite films show an oxygen vacancy superstructure, which arises from vacancy ordering on the {111} planes of the pseudocubic BaTiO3-type structure. This work contributes to the understanding of magnetoelectric coupling as a complex and sensitive interplay of chemical, structural and geometrical issues of the BaTiO3-BiFeO3 composite system and, thus, paves the way to practical exploitation of magnetoelectric composites. PMID:28787843

  4. Reorientation of magnetic anisotropy in epitaxial cobalt ferrite thin films

    NARCIS (Netherlands)

    Lisfi, A.; Williams, C.M.; Nguyen, L.T.; Lodder, J.C.; Coleman, A.; Corcoran, H.; Johnson, A.; Chang, P.; Abhishek Kumar, A.K.; Kumar, A.; Morgan, W.

    2007-01-01

    Spin reorientation has been observed in CoFe2O4 thin single crystalline films epitaxially grown on (100) MgO substrate upon varying the film thickness. The critical thickness for such a spin-reorientation transition was estimated to be 300 nm. The reorientation is driven by a structural transition

  5. Structural features of epitaxial NiFe2O4 thin films grown on different substrates by direct liquid injection chemical vapor deposition

    Science.gov (United States)

    Datta, R.; Loukya, B.; Li, N.; Gupta, A.

    2012-04-01

    NiFe2O4 (NFO) thin films are grown on four different substrates, i.e., Lead Zinc Niobate-Lead Titanate (PZN-PT), Lead Magnesium Niobate-Lead Titanate (PMN-PT), MgAl2O4 (MAO) and SrTiO3 (STO), by a direct liquid injection chemical vapor deposition technique (DLI-CVD) under optimum growth conditions where relatively high growth rate (˜20 nm/min), smooth surface morphology and high saturation magnetization values in the range of 260-290 emu/ cm3 are obtained. The NFO films with correct stoichiometry (Ni:Fe=1:2) grow epitaxially on all four substrates, as confirmed by energy dispersive X-ray spectroscopy, transmission electron microscopy and x-ray diffraction. While the films on PMN-PT and PZN-PT substrates are partially strained, essentially complete strain relaxation occurs for films grown on MAO and STO. The formations of threading dislocations along with dark diffused contrast areas related to antiphase domains having a different cation ordering are observed on all four substrates. These crystal defects are correlated with lattice mismatch between the film and substrate and result in changes in magnetic properties of the films. Atomic resolution HAADF imaging and EDX line profiles show formation of a sharp interface between the film and the substrate with no inter-diffusion of Pb or other elements across the interface. Antiphase domains are observed to originate at the film-substrate interface.

  6. Structure and magnetism of nanocrystalline and epitaxial (Mn,Zn,Fe)3O4 thin films

    Energy Technology Data Exchange (ETDEWEB)

    Alaan, U. S. [Univ. of California, Berkeley, CA (United States); Wong, F. J. [Univ. of California, Berkeley, CA (United States); Grutter, A. J. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Iwata-Harms, J. M. [Univ. of California, Berkeley, CA (United States); Mehta, V. V. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Arenholz, E. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Suzuki, Y. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2012-02-21

    We study nanocrystalline (NC) textured Mn0.5Zn0.6Fe1.9O4 (MZFO) films, grown at room temperature on both isostructural and non-isostructural substrates, that show magnetization values significantly suppressed from epitaxial MZFO films. X-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements indicate larger ratios of Fe3+ to Fe2+ ions on the tetrahedral sites in the NC films compared to the epitaxialfilms. The magnetization loops of the NC films are shifted by 200-400 Oe at low temperatures. No such effect is observed in the epitaxialfilms. In conclusion, we hypothesize that the presence of a more structurally disordered, possibly magnetically frustrated, matrix exchange biases the crystalline regions.

  7. On the Relationship of Magnetocrystalline Anisotropy and Stoichiometry in Epitaxial L1{sub 0} CoPt(001) and FePt(001) Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Barmak, K

    2004-08-10

    Two series of epitaxial CoPt and FePt films, with nominal thicknesses of 42 or 50 nm, were prepared by sputtering onto single crystal MgO(001) substrates in order to investigate the chemical ordering and the resultant magnetic properties as a function of alloy composition. In the first series, the film composition was kept constant, while the substrate temperature was increased from 144 to 704 C. In the second series the substrate temperature was kept constant at 704 C for CoPt and 620 C for FePt, while the alloy stoichiometry was varied in the nominalrange of 40-60 at% Co(Fe). Film compositions and thicknesses were measured via Rutherford backscattering spectrometry. The lattice and long-range order parameter for the L1{sub 0} phase were obtained for both sets of films using x-ray diffraction. The room-temperature magnetocrystalline anisotropy constants were determined for a subset of the films using torque magnetometry. The order parameter was found to increase with increasing temperature, with ordering occurring more readily in FePt when compared with CoPt. A perpendicular anisotropy developed in CoPt for substrate temperatures above 534 C and in FePt above 321 C. The structure and width of the magnetic domains in CoPt and FePt, as seen by magnetic force microscopy, also demonstrated an increase in magnetic anisotropy with increasing temperature. For the films deposited at the highest temperatures (704 C for CoPt and 620 C for FePt), the order parameter reached a maximum near the equiatomic composition, whereas the magnetocrystalline anisotropy increased as the concentration of Co or Fe was increased from below to slightly above the equiatomic composition. It is concluded that non-stoichiometric L1{sub 0} CoPt and FePt, with a slight excess of Co or Fe, are preferable for applications requiring the highest anisotropies.

  8. Josephson junction in cobalt-doped BaFe2As2 epitaxial thin films on (La,Sr)(Al,Ta)O3 bicrystal substrates

    Science.gov (United States)

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

    2010-04-01

    Josephson junctions were fabricated in epitaxial films of cobalt-doped BaFe2As2 on [001]-tilt (La,Sr)(Al,Ta)O3 bicrystal substrates. 10-μm-wide microbridges spanning a 30°-tilted bicrystal grain boundary (BGB bridge) exhibited resistively-shunted-junction (RSJ)-like current-voltage characteristics up to 17 K, and the critical current was suppressed remarkably by a magnetic field. Microbridges without a BGB did not show the RSJ-like behavior, and their critical current densities were 20 times larger than those of BGB bridges, confirming BGB bridges display a Josephson effect originating from weakly-linked BGB.

  9. Magnetic property tuning of epitaxial spinel ferrite thin films by strain and composition modulation

    Science.gov (United States)

    Kang, Young-Min; Lee, Seung Han; Kim, Tae Cheol; Jeong, Jaeeun; Yang, Daejin; Han, Kyu-Sung; Kim, Dong Hun

    2017-10-01

    Epitaxial spinel ferrite CoFe2O4 and NiFe2O4 thin films and bilayers of NiFe2O4 and CoFe2O4 have been grown by pulsed laser deposition on (001)-oriented SrTiO3 and MgO substrates. Both the single layer thin films showed epitaxial growth on MgO substrates with out-of-plane magnetic easy axis, originating from the out-of-plane compressive strain and negative magnetostriction constant. However, films on SrTiO3 substrates exhibited a magnetic easy axis along the in-plane. Magnetic hysteresis loops showed intermediate shape between magnetically hard CoFe2O4 and magnetically soft NiFe2O4 without two-step switching. Interdiffusion between spinel phases was suppressed using a blocking layer of MgO.

  10. Epitaxial oxide thin films by pulsed laser deposition: Retrospect and ...

    Indian Academy of Sciences (India)

    Epitaxial thin films of high c cuprates, metallic, ferroelectric, ferromagnetic, dielectric oxides, super conduc tor-metal-superconductor Josephson junctions and oxide superlattices have been made by PLD. In this article, an overview of preparation, characterization and properties of epitaxial oxide films and their applications ...

  11. Oxygen pressure-tuned epitaxy and magnetic properties of magnetite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Junran [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Liu, Wenqing [York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, Department of Electronics, The University of York, YO10 3DD (United Kingdom); Zhang, Minhao; Zhang, Xiaoqian; Niu, Wei; Gao, Ming [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Wang, Xuefeng, E-mail: xfwang@nju.edu.cn [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Du, Jun [School of Physics, Nanjing University, Nanjing 210093 (China); Zhang, Rong [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu, Yongbing, E-mail: ybxu@nju.edu.cn [Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, Department of Electronics, The University of York, YO10 3DD (United Kingdom)

    2017-06-15

    Highlights: • Quasi-2D Fe{sub 3}O{sub 4} films were obtained by PLD. • RHEED under different oxygen pressure were observed. • Influence of oxygen pressure on Fe{sub 3}O{sub 4} films were investigated. • Epitaxy and magnetic properties were tuned by oxygen pressure. • The ratio of Fe{sup 2+}/Fe{sup 3+} fitted by XPS is the tuned factor of M{sub s}. - Abstract: Quasi-two-dimensional magnetite epitaxial thin films have been synthesized by pulsed laser deposition technique at various oxygen pressures. The saturation magnetizations of the magnetite films were found to decrease from 425 emu/cm{sup 3}, which is close to the bulk value, to 175 emu/cm{sup 3} as the growth atmospheres varying from high vacuum (∼1 × 10{sup −8} mbar) to oxygen pressure of 1 × 10{sup −3} mbar. The ratio of the Fe{sup 3+} to Fe{sup 2+} increases from 2 to 2.7 as oxygen pressure increasing shown by XPS fitting, which weakens the net magnetic moment generated by Fe{sup 2+} at octahedral sites as the spins of the Fe{sup 3+} ions at octahedral and tetrahedral sites are aligned in antiparallel. The results offer direct experimental evidence of the influence to the Fe{sup 3+}/Fe{sup 2+} ratio and the magnetic moment in magnetite epitaxy films by oxygen pressure, which is significant for spintronic applications.

  12. Epitaxial growth of Fe/BaTiO3 heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Brivio, S., E-mail: m.gooley@elsevier.com [LNESS, Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, 22100, Como (Italy); Rinaldi, C.; Petti, D.; Bertacco, R. [LNESS, Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, 22100, Como (Italy); Sanchez, F. [Institut de Ciencia de Materials de Barcelona, Consejo Superior de Investigaciones Cientificas, Campus Universitat Autonoma de Barcelona, Bellaterra 08193, Catalunya (Spain)

    2011-06-30

    The realization of epitaxial heterostructures involving ferroelectric (FE) and ferromagnetic (FM) materials is one of the possible routes towards the realization of devices exploiting sizable magnetoelectric effects. In this paper we demonstrate the epitaxial growth of Fe on BaTiO{sub 3}(001) as this system represents a prototypical example of interface between well known FE and FM materials with bcc and perovskite structure respectively, both with Curie temperature well above 300 K. Fe grows on BaTiO{sub 3} with 45 deg. rotation of its cubic lattice with respect to that of the substrate in order to reduce the lattice mismatch. Negligible interdiffusion of Ba and Ti cations or Fe atoms is found by X-ray photoemission spectroscopy, while a sizable Fe oxidation occurs within an interfacial layer with thicknesses thinner than 3 nm.

  13. Experimental and theoretical investigation of electronic structure of SrFeO3-xFx epitaxial thin films prepared via topotactic reaction

    Science.gov (United States)

    Katayama, Tsukasa; Chikamatsu, Akira; Kamisaka, Hideyuki; Kumigashira, Hiroshi; Hasegawa, Tetsuya

    2016-02-01

    We investigated the electronic structure of perovskite SrFeO3-xFx (0.6 ≤ x ≤ 1) films by optical absorption, photoemission, and X-ray absorption spectroscopies, as well as density functional theory (DFT)-based calculations. The optical bandgap expanded with x, yielding a wider direct bandgap for the SrFeO2F film than for the LaFeO3 film. The DFT calculations suggested that the majority of FeO4F2 octahedra in the SrFeO2F film had cis configurations and that the enlarged bandgap mainly originated from bond bending in the O-Fe-O chains. We experimentally observed the valence and conduction bands of the SrFeO2F film, and found them to be qualitatively consistent with the results of DFT-based calculations.

  14. Electrical properties of epitaxially grown VOx thin films

    NARCIS (Netherlands)

    Rata, A.D.; Chezan, A.R; Presura, C.N.; Hibma, T

    2003-01-01

    High quality VOx thin films on MgO(100) substrates were prepared and studied from the structural and electronic point of view. Epitaxial growth was confirmed by RHEED and XRD techniques. The oxygen content of VOx thin films as a function of oxygen flux was determined using RBS. The upper and lower

  15. Structure and Magnetism of Nanocrystalline and Epitaxial (Mn,Zn,Fe)3O4

    Science.gov (United States)

    2012-01-01

    excitation. In particular, photomagnetism has been observed in a few spinel structure materials,2,3 including doped spinel structure ferrites and... ferrite films have been identified to exhibit photomagnetic effects at room temperature.7,8 Because optical sensitivity of spinel ferrites can be...and epitaxial (Mn,Zn,Fe)3O4 (MZFO) spinel thin films with their magnetic properties. X-ray diffraction (XRD) studies indicate that room temperature

  16. Giant flexoelectric effect in ferroelectric epitaxial thin films.

    Science.gov (United States)

    Lee, D; Yoon, A; Jang, S Y; Yoon, J-G; Chung, J-S; Kim, M; Scott, J F; Noh, T W

    2011-07-29

    We report on nanoscale strain gradients in ferroelectric HoMnO(3) epitaxial thin films, resulting in a giant flexoelectric effect. Using grazing-incidence in-plane x-ray diffraction, we measured strain gradients in the films, which were 6 or 7 orders of magnitude larger than typical values reported for bulk oxides. The combination of transmission electron microscopy, electrical measurements, and electrostatic calculations showed that flexoelectricity provides a means of tuning the physical properties of ferroelectric epitaxial thin films, such as domain configurations and hysteresis curves. © 2011 American Physical Society

  17. Joining Chemical Pressure and Epitaxial Strain to Yield Y-doped BiFeO3 Thin Films with High Dielectric Response

    Science.gov (United States)

    Scarisoreanu, N. D.; Craciun, F.; Birjega, R.; Ion, V.; Teodorescu, V. S.; Ghica, C.; Negrea, R.; Dinescu, M.

    2016-05-01

    BiFeO3 is one of the most promising multiferroic materials but undergoes two major drawbacks: low dielectric susceptibility and high dielectric loss. Here we report high in-plane dielectric permittivity (ε’ ∼2500) and low dielectric loss (tan δ priced target.

  18. Removable polytetrafluoroethylene template based epitaxy of ferroelectric copolymer thin films

    Science.gov (United States)

    Xia, Wei; Chen, Qiusong; Zhang, Jian; Wang, Hui; Cheng, Qian; Jiang, Yulong; Zhu, Guodong

    2018-04-01

    In recent years ferroelectric polymers have shown their great potentials in organic and flexible electronics. To meet the requirements of high-performance and low energy consumption of novel electronic devices and systems, structural and electrical properties of ferroelectric polymer thin films are expected to be further optimized. One possible way is to realize epitaxial growth of ferroelectric thin films via removable high-ordered polytetrafluoroethylene (PTFE) templates. Here two key parameters in epitaxy process, annealing temperature and applied pressure, are systematically studied and thus optimized through structural and electrical measurements of ferroelectric copolymer thin films. Experimental results indicate that controlled epitaxial growth is realized via suitable combination of both parameters. Annealing temperature above the melting point of ferroelectric copolymer films is required, and simultaneously moderate pressure (around 2.0 MPa here) should be applied. Over-low pressure (around 1.0 MPa here) usually results in the failure of epitaxy process, while over-high pressure (around 3.0 MPa here) often results in residual of PTFE templates on ferroelectric thin films.

  19. Strain-induced properties of epitaxial VOx thin films

    NARCIS (Netherlands)

    Rata, AD; Hibma, T

    We have grown VOx thin films on different substrates in order to investigate the influence of epitaxial strain on the transport properties. We found that the electric conductivity is much larger for films grown under compressive strain on SrTiO3 substrates, as compared to bulk material and VOx films

  20. Liquid phase epitaxial growth of heterostructured hierarchical MOF thin films

    KAUST Repository

    Chernikova, Valeriya

    2017-05-10

    Precise control of epitaxial growth of MOF-on-MOF thin films, for ordered hierarchical tbo-type structures is demonstrated. The heterostructured MOF thin film was fabricated by successful sequential deposition of layers from two different MOFs. The 2-periodic layers, edge-transitive 4,4-square lattices regarded as supermolecular building layers, were commendably cross-linked using a combination of inorganic/organic and organic pillars.

  1. Epitaxial growth of zinc oxide thin films on silicon

    International Nuclear Information System (INIS)

    Jin Chunming; Narayan, Roger; Tiwari, Ashutosh; Zhou Honghui; Kvit, Alex; Narayan, Jagdish

    2005-01-01

    Epitaxial zinc oxide thin films were grown on Si(111) using aluminum nitride and magnesium oxide/titanium nitride buffer layers. The resultant films were examined using transmission electron microscopy, X-ray diffraction, electrical conductivity, and photoluminescence spectroscopy. The following epitaxial relationships were observed in the ZnO/AlN/Si(111) heterostructure: ZnO[0001] parallel AlN[0001] parallel Si[111] along the growth direction, and ZnO[21-bar 1-bar 0] parallel AlN[21-bar 1-bar 0] parallel Si[011-bar] along the in-plane direction. Domain-matching epitaxial growth of TiN on Si(111) substrate allows successful epitaxial growth of MgO and ZnO layers in a ZnO/MgO/TiN/Si(111) heterostructure. The epitaxial relationships observed for this heterostructure were ZnO[0001] parallel MgO/TiN/Si[111] along the growth direction and ZnO[21-bar 1-bar 0] parallel MgO/TiN/Si[011-bar] along in-plane direction. The resultant ZnO films demonstrate excellent electrical and optical properties. ZnO thin films exhibit extremely bright ultraviolet luminescence with relatively weak green-band emission

  2. From epitaxial growth of ferrite thin films to spin-polarized tunnelling

    International Nuclear Information System (INIS)

    Moussy, Jean-Baptiste

    2013-01-01

    This paper presents a review of the research which is focused on ferrite thin films for spintronics. First, I will describe the potential of ferrite layers for the generation of spin-polarized currents. In the second step, the structural and chemical properties of epitaxial thin films and ferrite-based tunnel junctions will be presented. Particular attention will be given to ferrite systems grown by oxygen-assisted molecular beam epitaxy. The analysis of the structure and chemistry close to the interfaces, a key-point for understanding the spin-polarized tunnelling measurements, will be detailed. In the third part, the magnetic and magneto-transport properties of magnetite (Fe 3 O 4 ) thin films as a function of structural defects such as the antiphase boundaries will be explained. The spin-polarization measurements (spin-resolved photoemission, tunnel magnetoresistance) on this oxide predicted to be half-metallic will be discussed. Fourth, the potential of magnetic tunnel barriers, such as CoFe 2 O 4 , NiFe 2 O 4 or MnFe 2 O 4 , whose insulating behaviour and the high Curie temperatures make it exciting candidates for spin filtering at room temperature will be described. Spin-polarized tunnelling experiments, involving either Meservey–Tedrow or tunnel magnetoresistance measurements, will reveal significant spin-polarizations of the tunnelling current at low temperatures but also at room temperatures. Finally, I will mention a few perspectives with ferrite-based heterostructures. (topical review)

  3. Deposition and characterisation of epitaxial oxide thin films for SOFCs

    KAUST Repository

    Santiso, José

    2010-10-24

    This paper reviews the recent advances in the use of thin films, mostly epitaxial, for fundamental studies of materials for solid oxide fuel cell (SOFC) applications. These studies include the influence of film microstructure, crystal orientation and strain in oxide ionic conducting materials used as electrolytes, such as fluorites, and in mixed ionic and electronic conducting materials used as electrodes, typically oxides with perovskite or perovskite-related layered structures. The recent effort towards the enhancement of the electrochemical performance of SOFC materials through the deposition of artificial film heterostructures is also presented. These thin films have been engineered at a nanoscale level, such as the case of epitaxial multilayers or nanocomposite cermet materials. The recent progress in the implementation of thin films in SOFC devices is also reported. © 2010 Springer-Verlag.

  4. Magnetism of FePt Thin Films

    Science.gov (United States)

    Alqhtany, Norah H.

    Materials with large magnetic anisotropy have received significant attention from the scientific community due to its advantages in technological applications. Equiatomic FePt has been identified as such a material which could possibly be a potential candidate for ultra- high density magnetic recording and other applications like permanent magnets. FePt thin films exhibit ordered L10 texture with high magnetocrystalline anisotropy and high saturation magnetization which seem lucrative for technological applications. This thesis presents an investigation of structural and magnetic properties of granular and epitaxial FePt films with L10 phase prepared by DC sputtering on different substrates (SrTiO3 and glass). X-ray Diffraction (XRD), Atomic Force Microscopy/Magnetic Force Microscopy (AFM/MFM) and Vibrating Sample Magnetometer (VSM) were employed in characterization process. The measurements obtained from these equipment were significant in establishing the relationship between the microstructure and the magnetic properties of these films. The symmetry and magnitude of magnetic anisotropy has also been analyzed and discussed in detail.

  5. Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.

    Science.gov (United States)

    Asaba, Tomoya; Wang, Yongjie; Li, Gang; Xiang, Ziji; Tinsman, Colin; Chen, Lu; Zhou, Shangnan; Zhao, Songrui; Laleyan, David; Li, Yi; Mi, Zetian; Li, Lu

    2018-04-25

    In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe 2 ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe 2 thin films with a high precision rotation stage, we map the upper critical field H c2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field H c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H c2 in Ising superconductors.

  6. Tailoring of magnetic properties of ultrathin epitaxial Fe films by Dy doping

    Directory of Open Access Journals (Sweden)

    A. A. Baker

    2015-07-01

    Full Text Available We report on the controlled modification of relaxation parameters and magnetic moments of epitaxial Fe thin films through Dy doping. Ferromagnetic resonance measurements show that an increase of Dy doping from 0.1% to 5% gives a tripling in Gilbert damping, and more importantly a strongly enhanced anisotropic damping that can be qualitatively understood through the slow-relaxing impurity model. X-ray magnetic circular dichroism measurements show a pronounced suppression of the orbital moment of the Fe with Dy doping, leading to an almost threefold drop in the orbital to spin moment ratio, ml/ms. Doping with Dy can therefore be used to control both dynamic and static properties of thin ferromagnetic films for improved performance in spintronics device applications, mediated through the antiferromagnetic interaction of the 4f and 3d states.

  7. Tailoring of magnetic properties of ultrathin epitaxial Fe films by Dy doping

    Energy Technology Data Exchange (ETDEWEB)

    Baker, A. A. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU (United Kingdom); Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE (United Kingdom); Figueroa, A. I.; Laan, G. van der [Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE (United Kingdom); Hesjedal, T. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU (United Kingdom)

    2015-07-15

    We report on the controlled modification of relaxation parameters and magnetic moments of epitaxial Fe thin films through Dy doping. Ferromagnetic resonance measurements show that an increase of Dy doping from 0.1% to 5% gives a tripling in Gilbert damping, and more importantly a strongly enhanced anisotropic damping that can be qualitatively understood through the slow-relaxing impurity model. X-ray magnetic circular dichroism measurements show a pronounced suppression of the orbital moment of the Fe with Dy doping, leading to an almost threefold drop in the orbital to spin moment ratio, m{sub l}/m{sub s}. Doping with Dy can therefore be used to control both dynamic and static properties of thin ferromagnetic films for improved performance in spintronics device applications, mediated through the antiferromagnetic interaction of the 4f and 3d states.

  8. Structure and magnetism of single-phase epitaxial gamma '-Fe4N

    NARCIS (Netherlands)

    Costa-Kramer, JL; Borsa, DM; Garcia-Martin, JM; Martin-Gonzalez, MS; Boerma, DO; Briones, F

    Single phase epitaxial pure gamma(')-Fe4N films are grown on MgO (001) by molecular beam epitaxy of iron in the presence of nitrogen obtained from a radio frequency atomic source. The epitaxial, single phase nature of the films is revealed by x-ray diffraction and by the local magnetic environment

  9. Squid measurement of the Verwey transition on epitaxial (1 0 0) magnetite thin films

    International Nuclear Information System (INIS)

    Dediu, V.; Arisi, E.; Bergenti, I.; Riminucci, A.; Solzi, M.; Pernechele, C.; Natali, M.

    2007-01-01

    We report results on epitaxial magnetite (Fe 3 O 4 ) thin films grown by electron beam ablation on (1 0 0) MgAl 2 O 4 substrates. At 120 K magnetite undergoes a structural and electronic transition, the so-called Verwey transition, at which magnetic and conducting properties of the material change. We observed the Verwey transition on epitaxial films with a thickness of 50 nm by comparing zero-field cooling (ZFC) and field cooling (FC) curves measured with a superconducting quantum interference device (SQUID) magnetometer. Observation of the Verwey transition by SQUID measurements in the films is sign of their high crystalline quality. Room temperature ferromagnetism has also been found by magneto-optical Kerr rotation (MOKE) and confirmed by SQUID measurements, with a hysteresis loop showing a coercive field of hundreds of Oe

  10. Directed Self-Assembly of Epitaxial CoFe2O4-BiFeO3 Multiferroic Nanocomposites

    Science.gov (United States)

    2012-04-09

    REPORT Directed Self-Assembly of Epitaxial CoFe 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: CoFe2O4 (CFO)? BiFeO3 (BFO) nanocomposites are an intriguing...Prescribed by ANSI Std. Z39.18 - CoFe2O4- BiFeO3 Multiferroic Nanocomposites Directed Self-Assembly of Epitaxial CoFe Report Title ABSTRACT CoFe2O4...CFO)? BiFeO3 (BFO) nanocomposites are an intriguing option for future memory and logic technologies due to the magnetoelectric properties of the system

  11. Controlled growth of epitaxial BiFeO3 films using self-assembled BiFeO3-CoFe2O4 multiferroic heterostructures as a template

    Science.gov (United States)

    Li, Yanxi; Yang, Yaodong; Yao, Jianjun; Viswan, Ravindranath; Wang, Zhiguang; Li, Jiefang; Viehland, D.

    2012-07-01

    The growth mechanism of a BiFeO3 layer deposited on self assembled (0.65) BiFeO3-(0.35) CoFe2O4 (BFO-CFO) composite thin films was studied. Epitaxial and self-assembled BFO-CFO thin films were deposited on SrTiO3 (111) substrates by pulsed laser deposition and were subsequently used as a seed layer for the deposition of an additional BFO layer. x-ray line scans showed the heterostructures were highly epitaxial. Cross-sectional scanning electron microscopy and focused ion beam images revealed the top BFO layer grew preferentially from BFO nanopillars in the BFO-CFO thin films, thus, demonstrating controlled growth. The multiferroic properties of this new nanostructure were then studied.

  12. Single-domain epitaxial silicene on diboride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Fleurence, A., E-mail: antoine@jaist.ac.jp; Friedlein, R.; Aoyagi, K.; Yamada-Takamura, Y. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Gill, T. G. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Sadowski, J. T. [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Copel, M.; Tromp, R. M. [IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Hirjibehedin, C. F. [London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Department of Physics and Astronomy, UCL, London WC1E 6BT (United Kingdom)

    2016-04-11

    Epitaxial silicene, which forms spontaneously on ZrB{sub 2}(0001) thin films grown on Si(111) wafers, has a periodic stripe domain structure. By adsorbing additional Si atoms on this surface, we find that the domain boundaries vanish, and a single-domain silicene sheet can be prepared without altering its buckled honeycomb structure. The amount of Si required to induce this change suggests that the domain boundaries are made of a local distortion of the silicene honeycomb lattice. The realization of a single domain sheet with structural and electronic properties close to those of the original striped state demonstrates the high structural flexibility of silicene.

  13. Role of spinel substrate in the morphology of BiFeO3-CoFe2O4 epitaxial nanocomposite films

    Science.gov (United States)

    Stern, Ilan; He, Jibao; Zhou, Xiaolan; Silwal, Punam; Miao, Ludi; Vargas, Jose Marcelo; Spinu, Leonard; Kim, Dae Ho

    2011-08-01

    Epitaxial thin films of BiFeO3-CoFe2O4 composite were grown on spinel MgAl2O4 substrates with a (001) orientation. The composite formed an intriguing nanogrid structure where perovskite BiFeO3 forms linear mounds embedded in a matrix of spinel CoFe2O4. The structure makes a stark distinction with similar composite films on (001) perovskite SrTiO3 substrates where CoFe2O4 forms nanopillars surrounded by a BiFeO3 matrix. This result shows the interface between the film and the substrate that plays a determining role during the formation of the composite.

  14. Study of strain-modulated effects on CoFe2O4 epitaxial films

    Science.gov (United States)

    Chen, Yi-Chun; Liou, Yi-De; Wu, Kun-Hong; Wang, Chih-Kuo; Chu, Ying-Hao

    Due to the improvement of thin film growth technique, epitaxial films directly grown on flexible substrates became possible recently. These kinds of flexible systems not only have the advantage of easy integration for device applications, but also provide a template to purify strain effects for physical mechanism study. Here, we investigate the evolution of the spinel CoFe2O4 (CFO) epitaxial film on a muscovite substrate with variable curvatures. CFO possesses superior magnetic properties with high Curie temperature and large magnetostrictive anisotropy. The CFO film on muscovite is (111) oriented, corresponding to a magnetic hard-axis along the out-of-plane direction. Under the in-plane asymmetric strain, based on the frequency shift of Raman A1g phonon, the unit cell volume of CFO increases with the tensile strain while decreases with the compressive strain. The tunable volume ratio is about 0.7 %. The A1g and T2g phonon evolutions also show the Co/Fe cation migration temperature decreases both under tensile and compressive strain with the degradation up to 40 K. Moreover, when out-of-plane magnetic field is applied, the magnetostriction constant increases with the compressive strain, which implies the tunable orientation of magnetic easy axis in this flexible system.

  15. The influence of Fe doping on the surface topography of GaN epitaxial material

    International Nuclear Information System (INIS)

    Cui Lei; Yin Haibo; Jiang Lijuan; Wang Quan; Feng Chun; Xiao Hongling; Wang Cuimei; Wang Xiaoliang; Gong Jiamin; Zhang Bo; Li Baiquan; Wang Zhanguo

    2015-01-01

    Fe doping is an effective method to obtain high resistivity GaN epitaxial material. But in some cases, Fe doping could result in serious deterioration of the GaN material surface topography, which will affect the electrical properties of two dimensional electron gas (2DEG) in HEMT device. In this paper, the influence of Fe doping on the surface topography of GaN epitaxial material is studied. The results of experiments indicate that the surface topography of Fe-doped GaN epitaxial material can be effectively improved and the resistivity could be increased after increasing the growth rate of GaN materials. The GaN material with good surface topography can be manufactured when the Fe doping concentration is 9 × 10 19 cm −3 . High resistivity GaN epitaxial material which is 1 × 10 9 Ω·cm is achieved. (paper)

  16. Chemically stabilized epitaxial wurtzite-BN thin film

    Science.gov (United States)

    Vishal, Badri; Singh, Rajendra; Chaturvedi, Abhishek; Sharma, Ankit; Sreedhara, M. B.; Sahu, Rajib; Bhat, Usha; Ramamurty, Upadrasta; Datta, Ranjan

    2018-03-01

    We report on the chemically stabilized epitaxial w-BN thin film grown on c-plane sapphire by pulsed laser deposition under slow kinetic condition. Traces of no other allotropes such as cubic (c) or hexagonal (h) BN phases are present. Sapphire substrate plays a significant role in stabilizing the metastable w-BN from h-BN target under unusual PLD growth condition involving low temperature and pressure and is explained based on density functional theory calculation. The hardness and the elastic modulus of the w-BN film are 37 & 339 GPa, respectively measured by indentation along direction. The results are extremely promising in advancing the microelectronic and mechanical tooling industry.

  17. Resistance switching in epitaxial SrCoOx thin films

    Science.gov (United States)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-08-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO2.5) and conducting perovskite (SrCoO3-δ) depending on the oxygen content. The current-voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoOx thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO2.5.

  18. Resistance switching in epitaxial SrCoOx thin films

    International Nuclear Information System (INIS)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-01-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO 3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO 2.5 ) and conducting perovskite (SrCoO 3−δ ) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO x thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO 2.5

  19. Flexoelectric control of defect formation in ferroelectric epitaxial thin films.

    Science.gov (United States)

    Lee, Daesu; Jeon, Byung Chul; Yoon, Aram; Shin, Yeong Jae; Lee, Myang Hwan; Song, Tae Kwon; Bu, Sang Don; Kim, Miyoung; Chung, Jin-Seok; Yoon, Jong-Gul; Noh, Tae Won

    2014-08-06

    Flexoelectric control of defect formation and associated electronic function is demonstrated in ferroelectric BiFeO3 thin films. An intriguing, so far never demonstrated, effect of internal electric field (Eint ) on defect formation is explored by a means of flexoelectricity. Our study provides novel insight into defect engineering, as well as allows a pathway to design defect configuration and associated electronic function. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. High magnetic field properties of Fe-pnictide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, Fritz

    2015-11-20

    The recent discovery of high-temperature superconductivity in Fe-based materials triggered worldwide efforts to investigate their fundamental properties. Despite a lot of similarities to cuprates and MgB{sub 2}, important differences like near isotropic behaviour in contrast to cuprates and the peculiar pairing symmetry of the order parameter (OP) have been reported. The OP symmetry of Fe-based superconductors (FBS) was theoretically predicted to be of so-called s± state prior to various experimental works. Still, most of the experimental results favour the s± scenario; however, definitive evidence has not yet been reported. Although no clear understanding of the superconducting mechanisms yet exists, potential applications such as high-field magnets and Josephson devices have been explored. Indeed, a lot of reports about FBS tapes, wires, and even SQUIDs have been published to this date. In this thesis, the feasibility of high-field magnet applications of FBS is addressed by studying their transport properties, involving doped BaFe{sub 2}As{sub 2} (Ba-122) and LnFeAs(O,F) [Ln=Sm and Nd]. Particularly, it is important to study physical properties in a sample form (i.e. thin films) that is close to the conditions found in applications. However, the realisation of epitaxial FBS thin films is not an easy undertaking. Recent success in growing epitaxial FBS thin films opens a new avenue to delve into transport critical current measurements. The information obtained through this research will be useful for exploring high-field magnet applications. This thesis consists of 7 chapters: Chapter 1 describes the motivation of this study, the basic background of superconductivity, and a brief summary of the thin film growth of FBS. Chapter 2 describes experimental methods employed in this study. Chapter 3 reports on the fabrication of Co-doped Ba-122 thin films on various substrates. Particular emphasis lies on the discovery of fluoride substrates to be beneficial for

  1. Epitaxial ternary nitride thin films prepared by a chemical solution method

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Hongmei [Los Alamos National Laboratory; Feldmann, David M [Los Alamos National Laboratory; Wang, Haiyan [TEXAS A& M; Bi, Zhenxing [TEXAS A& M

    2008-01-01

    It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.

  2. Metal-insulator transition in epitaxial vanadium sesquioxide thin films

    Science.gov (United States)

    Allimi, Bamidele S.

    Of all the transition metal oxides which exhibit metal-insulator transitions (MIT), one of the most extensively studied in recent years is the vanadium sesquioxide (V2O3), both from experimental and theoretical point of view. At a transition temperature of about 160 K at an ambient pressure of 1 atm, pure V2O3 transforms from a rhombohedral paramagnetic metallic (PM) to a monoclinic antiferromagnetic insulating (AFI) phase upon cooling, with a jump in the resistivity of about seven orders of magnitude. Experimental studies have focused more on bulk V2O3 and recently there have been significant interest in thin film fabrication of this material due to potential applications as thermal sensors, current limiters, Positive Temperature Coefficient (PTC) thermistors, and optical switches. This study addresses the deposition, characterization, and properties of high-quality epitaxial V2O3 thin films grown on a-, c-Al2O3 and c-LiTaO 3 substrates by a straightforward method of pulsed laser deposition (PLD). Various characterization techniques including X-ray diffraction, atomic force microscopy, scanning electron microscopy, and X-ray photoemission spectroscopy were used to examine the structural, crystallographic, and surface properties, while four point probe resistivity measurements were used to examine the electrical properties of the films. V2O3 thin films of different thicknesses ranging from 10-450 nm were deposited on c-Al 2O3 and c-LiTaO3 substrates by PLD to understand also the role of epitaxial strains. Resistivity measurements showed that depending on the thicknesses of films, different electrical transitions were exhibited by the samples. While some of the samples displayed the expected metal-insulator transition typical of bulk V2O3, some showed insulating behavior only and others exhibited metallic characteristics only over the whole temperature range. For example, for films on c-LiTaO3 with increasing film thickness, first an insulator-insulator, then a

  3. Magnetic and magneto-optical properties of FeRh thin films

    International Nuclear Information System (INIS)

    Inoue, Sho; Nam, Nguyen T.; Phuoc, Nguyen N.; Cao Jiangwei; Yu Ko, Hnin Yu; Suzuki, Takao

    2008-01-01

    The magnetic and magneto-optical properties of FeRh thin films epitaxially deposited onto MgO(1 0 0) substrates by RF sputter-deposition system have been investigated in conjunction with the structure. An intriguing virgin effect has been found in the M-T curves of the as-deposited FeRh thin films, which is presumably interpreted in term of a change in structural phase when heating. Also, a (negative) maximum peak of Kerr rotation at around 3.8 eV has been observed when FeRh thin films are in ferromagnetic state. The polar Kerr rotation angle is found to increase at temperatures above 100 deg. C, which corresponds to the antiferromagnet (AF)-ferromagnet (FM) transition of FeRh thin films

  4. Epitaxial growth of highly-crystalline spinel ferrite thin films on perovskite substrates for all-oxide devices.

    Science.gov (United States)

    Moyer, Jarrett A; Gao, Ran; Schiffer, Peter; Martin, Lane W

    2015-06-01

    The potential growth modes for epitaxial growth of Fe3O4 on SrTiO3 (001) are investigated through control of the energetics of the pulsed-laser deposition growth process (via substrate temperature and laser fluence). We find that Fe3O4 grows epitaxially in three distinct growth modes: 2D-like, island, and 3D-to-2D, the last of which is characterized by films that begin growth in an island growth mode before progressing to a 2D growth mode. Films grown in the 2D-like and 3D-to-2D growth modes are atomically flat and partially strained, while films grown in the island growth mode are terminated in islands and fully relaxed. We find that the optimal structural, transport, and magnetic properties are obtained for films grown on the 2D-like/3D-to-2D growth regime boundary. The viability for including such thin films in perovskite-based all-oxide devices is demonstrated by growing a Fe3O4/La0.7Sr0.3MnO3 spin valve epitaxially on SrTiO3.

  5. Magnetoresistance at artificial interfaces in epitaxial ferromagnetic thin films

    International Nuclear Information System (INIS)

    Fontcuberta, J.; Bibes, M.; Martinez, B.; Trtik, V.; Ferrater, C.; Sanchez, F.; Varela, M.

    2000-01-01

    Epitaxial La 2/3 Sr 1/3 MnO 3 and SrRuO 3 thin films have been grown by laser ablation on single-crystalline SrTiO 3 substrates. Prior to manganite or ruthenate deposition tracks have been patterned on the SrTiO 3 substrate by using an appropriately focused laser beam. In the experiments here reported linear tracks have been formed. The magnetotransport properties of the films, particularly the magnetoresistance, along paths parallel and perpendicular to the track have been extensively investigated and compared to similar data recorded on films grown on bicrystalline STO substrates. Whereas in LSMO a significant low-field tunnel magnetoresistance develops across the artificial interface, in SRO this tunnel contribution is absent. However, a significant high-field magnetoresistance is observed for both metallic and ferromagnetic systems. The results are analysed and discussed within the framework of the current understanding of double exchange and itinerant ferromagnets. Magnetoresistance data for various configurations of the track array are presented

  6. Temperature dependence of resistance in epitaxial Fe/MgO/Fe magnetic tunnel junctions

    Science.gov (United States)

    Ma, Q. L.; Wang, S. G.; Zhang, J.; Wang, Yan; Ward, R. C. C.; Wang, C.; Kohn, A.; Zhang, X.-G.; Han, X. F.

    2009-08-01

    The temperature dependence of resistance in parallel (P) and antiparallel (AP) configurations (RP,AP) has been investigated in epitaxial Fe/MgO/Fe junctions with varying MgO barrier thicknesses tMgO. RAP exhibits a substantial decrease with increasing temperature for samples with tMgO ranging from 3.0 to 1.5 nm. In contrast, RP is approximately temperature independent when tMgO=3.0 nm and increases with temperature when tMgO=2.1 and 1.5 nm. Possible origins of this temperature dependence of resistance, which include taking into account a spin independent term and consideration of spin-flip scattering, are discussed. We attribute the temperature dependence of RP,AP to the misalignment of magnetic moments in the electrodes due to thermal excitations and its effect on the spin dependent tunneling.

  7. 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.

  8. Pillar shape modulation in epitaxial BiFeO3–CoFe2O4 vertical nanocomposite films

    OpenAIRE

    Dong Hun Kim; Nicolas M. Aimon; C. A. Ross

    2014-01-01

    Self-assembled epitaxial CoFe2O4-BiFeO3 nanocomposite films, in which pillars of CoFe2O4 grow within a single crystal BiFeO3 matrix, show both ferrimagnetism and ferroelectricity. The pillars typically have a uniform cross-section, but here two methods are demonstrated to produce a width modulation during growth by pulsed laser deposition. This was achieved by growing a blocking layer of BiFeO3 to produce layers of separated pillars or pillars with constrictions, or by changing the temperatur...

  9. Epitaxial thin film growth and properties of unconventional oxide superconductors. Cuprates and cobaltates

    International Nuclear Information System (INIS)

    Krockenberger, Y.

    2006-01-01

    The discovery of high-temperature superconductors has strongly driven the development of suited thin film fabrication methods of complex oxides. One way is the adaptation of molecular beam epitaxy (MBE) for the growth of oxide materials. Another approach is the use of pulsed laser deposition (PLD) which has the advantage of good stoichiometry transfer from target to the substrate. Both techniques are used within this thesis. Epitaxial thin films of new materials are of course needed for future applications. In addition, the controlled synthesis of thin film matter which can be formed far away from thermal equilibrium allows for the investigation of fundamental physical materials properties. (orig.)

  10. Epitaxial thin film growth and properties of unconventional oxide superconductors. Cuprates and cobaltates

    Energy Technology Data Exchange (ETDEWEB)

    Krockenberger, Y.

    2006-07-01

    The discovery of high-temperature superconductors has strongly driven the development of suited thin film fabrication methods of complex oxides. One way is the adaptation of molecular beam epitaxy (MBE) for the growth of oxide materials. Another approach is the use of pulsed laser deposition (PLD) which has the advantage of good stoichiometry transfer from target to the substrate. Both techniques are used within this thesis. Epitaxial thin films of new materials are of course needed for future applications. In addition, the controlled synthesis of thin film matter which can be formed far away from thermal equilibrium allows for the investigation of fundamental physical materials properties. (orig.)

  11. Deposition of epitaxial BiFeO3/CoFe2O4 nanocomposites on (001) SrTiO3 by combinatorial pulsed laser deposition

    Science.gov (United States)

    Aimon, Nicolas M.; Hun Kim, Dong; Kyoon Choi, Hong; Ross, C. A.

    2012-02-01

    BiFeO3/CoFe2O4 (BFO/CFO) nanocomposites were grown on SrTiO3 by pulsed laser deposition using a combinatorial method in which Bi1.2FeO3 and CoFe2O4 targets are alternately ablated. The films had the same vertically nanostructured morphology as thin films prepared by ablation of a single target, consisting of epitaxial CoFe2O4 pillars in a BiFeO3 matrix. In a series of samples synthesized with a compositional spread, the out-of-plane magnetic anisotropy and the out-of-plane compressive strain of the CoFe2O4 pillars increased with decreasing volume fraction, and the anisotropy agreed with the value predicted from the strain state and magnetoelastic coefficients of CoFe2O4. These results show the dominant effect of magnetoelastic anisotropy in determining the magnetic hysteresis of the nanocomposite.

  12. Magnetic properties of hexagonal YbFeO3 thin film

    Science.gov (United States)

    Sinha, Kishan; Zhang, Xin; Wang, Xiao; Liu, Yaohua; Cheng, Xuemei; N'diaye, Alpha; Dowben, Peter; Xu, Xiaoshan

    We have synthesized epitaxial single crystal thin films of multiferroic hexagonal YbFeO3 (0001) on YSZ (111) substrates using Pulsed Laser Deposition. In-plane XRD and RHEED study confirms the existence of six-fold symmetry in YbFeO3 thin films, consistent with the proposed hexagonal structure. The epitaxial orientation is found to be h-YbFeO3\\ (100)||YSZ(11-2). We have studied magnetic properties of h-YbFeO3/YSZ thin films using SQUID, neutron diffraction and X-ray Circular Magnetic Dichroism (XMCD). SQUID study of h-YbFeO3/YSZ thin films show emergence of out-of-plane magnetic moment at 140 K, possibly due to spin canting resulting from Dzyaloshinskii-Moriya interaction. This ferromagnetic transition is consistent with our temperature dependent neutron diffraction study where appearance of the forbidden (purely magnetic) (101) peak marks a magnetic transition around 150 K while the intensity of the nuclear (144) peak remains unaltered. In addition, SQUID and XMCD studies at low temperatures clearly indicate that Yb3+ ions carry a much lower magnetic moment than the previously reported values. This research used CORELLI beamline at SNS, ORNL. The project was supported by the NSF, DMR under Award DMR-1454618.

  13. Thin-film GaAs epitaxial life-off solar cells for space applications

    NARCIS (Netherlands)

    Schermer, J.J.; Mulder, P.; Bauhuis, G.J.; Larsen, P.K.; Oomen, G.; Bongers, E.

    2005-01-01

    In the present work the space compatibility of thin-film GaAs solar cells is studied. These cells are separated from their GaAs substrate by the epitaxial lift-off (ELO) technique and mounted behind a CMG cover glass which at the same time serves as a stable carrier for the thin film cells. In the

  14. Electron holography study of remanence states in exchange-biased MnPd/Fe bilayers grown epitaxially on MgO(001).

    Science.gov (United States)

    Jeong, Jong Seok; Akase, Zentaro; Shindo, Daisuke; Zhan, Qing-Feng; Krishnan, Kannan M

    2011-01-01

    We investigated magnetic remanence states of epitaxially grown, exchange-biased MnPd/Fe bilayers by electron holography emphasizing the crystallographic orientations of the layers. Thin-foil transmission electron microscopy (TEM) specimens were carefully prepared along both hard and easy axes of the Fe layer. The ex situ magnetization-reversal process was carried out using the TEM specimens, and magnetic flux densities of the ultra-thin Fe layers were evaluated at different remanence states. We show that a spin configuration in the TEM specimens is determined by the competition between an exchange coupling at the MnPd/Fe bilayer interface, shape anisotropy of TEM specimens and intrinsic magnetocrystalline anisotropy of Fe.

  15. Local conductivity and the role of vacancies around twin walls of (001)-BiFeO3 thin films

    NARCIS (Netherlands)

    Farokhipoor, S.; Noheda, Beatriz

    2012-01-01

    BiFeO3 thin films epitaxially grown on SrRuO3-buffered (001)-oriented SrTiO3 substrates show orthogonal bundles of twin domains, each of which contains parallel and periodic 71 degrees domain walls. A smaller amount of 109 degrees domain walls are also present at the boundaries between two adjacent

  16. van der Waals epitaxial ZnTe thin film on single-crystalline graphene

    Science.gov (United States)

    Sun, Xin; Chen, Zhizhong; Wang, Yiping; Lu, Zonghuan; Shi, Jian; Washington, Morris; Lu, Toh-Ming

    2018-01-01

    Graphene template has long been promoted as a promising host to support van der Waals flexible electronics. However, van der Waals epitaxial growth of conventional semiconductors in planar thin film form on transferred graphene sheets is challenging because the nucleation rate of film species on graphene is significantly low due to the passive surface of graphene. In this work, we demonstrate the epitaxy of zinc-blende ZnTe thin film on single-crystalline graphene supported by an amorphous glass substrate. Given the amorphous nature and no obvious remote epitaxy effect of the glass substrate, this study clearly proves the van der Waals epitaxy of a 3D semiconductor thin film on graphene. X-ray pole figure analysis reveals the existence of two ZnTe epitaxial orientational domains on graphene, a strong X-ray intensity observed from the ZnTe [ 1 ¯ 1 ¯ 2] ǁ graphene [10] orientation domain, and a weaker intensity from the ZnTe [ 1 ¯ 1 ¯ 2] ǁ graphene [11] orientation domain. Furthermore, this study systematically investigates the optoelectronic properties of this epitaxial ZnTe film on graphene using temperature-dependent Raman spectroscopy, steady-state and time-resolved photoluminescence spectroscopy, and fabrication and characterization of a ZnTe-graphene photodetector. The research suggests an effective approach towards graphene-templated flexible electronics.

  17. Growth of epitaxial thin films by pulsed laser ablation

    International Nuclear Information System (INIS)

    Lowndes, D.H.

    1992-01-01

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs

  18. Giant Faraday rotation in Bi(x)Ce(3-x)Fe5O12 epitaxial garnet films.

    Science.gov (United States)

    Chandra Sekhar, M; Singh, Mahi R; Basu, Shantanu; Pinnepalli, Sai

    2012-04-23

    Thin films of Bi(x)Ce(3-x)Fe(5)O(12) with x = 0.7 and 0.8 compositions were prepared by using pulsed laser deposition. We investigated the effects of processing parameters used to fabricate these films by measuring various physical properties such as X-ray diffraction, transmittance, magnetization and Faraday rotation. In this study, we propose a phase diagram which provides a suitable window for the deposition of Bi(x)Ce(3-x)Fe(5)O(12) epitaxial films. We have also observed a giant Faraday rotation of 1-1.10 degree/µm in our optimized films. The measured Faraday rotation value is 1.6 and 50 times larger than that of CeYIG and YIG respectively. A theoretical model has been proposed for Faraday rotation based on density matrix method and an excellent agreement between experiment and theory is found. © 2012 Optical Society of America

  19. 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.

  20. NiFe epitaxial films with hcp and fcc structures prepared on bcc-Cr underlayers

    International Nuclear Information System (INIS)

    Higuchi, Jumpei; Ohtake, Mitsuru; Sato, Yoichi; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    NiFe epitaxial films are prepared on Cr(211) bcc and Cr(100) bcc underlayers grown hetero-epitaxially on MgO single-crystal substrates by ultra-high vacuum rf magnetron sputtering. The film growth behavior and the crystallographic properties are studied by reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-NiFe(11-bar 00) and hcp-NiFe(112-bar 0) crystals respectively nucleate on Cr(211) bcc and Cr(100) bcc underlayers, where the hcp-NiFe crystals are stabilized through hetero-epitaxial growth. The hcp-NiFe(11-bar 00) crystal is a single-crystal with the c-axis parallel to the substrate surface, whereas the hcp-NiFe(112-bar 0) crystal is a bi-crystal with the respective c-axes lying in plane and perpendicular each other. With increasing the film thickness, the hcp structure in the NiFe films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) close packed plane. The resulting films consist of hcp and fcc crystals.

  1. Microstructure of epitaxial YBa2Cu3O7-x thin films grown on LaAlO3 (001)

    International Nuclear Information System (INIS)

    Hsieh, Y.; Siegal, M.P.; Hull, R.; Phillips, J.M.

    1990-01-01

    We report a microstructural investigation of the epitaxial growth of YBa 2 Cu 3 O 7-x (YBCO) thin films on LaAlO 3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c (axis normal to the surface and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35--200 nm thick. In 35 nm YBCO films annealed at 850 degree C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a-epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy

  2. Stress induced magnetic anisotropy of CoFe2O4 thin films using pulsed laser deposition

    NARCIS (Netherlands)

    Pham Duc Thang, P.D.T.; Rijnders, Augustinus J.H.M.; Blank, David H.A.

    2007-01-01

    Cobalt ferrite (CoFe2O4) thin films (E70 nm) were epitaxially grown on TiO2-terminated (0 0 1) SrTiO3 substrates by pulsed laser deposition (PLD). Films with very smooth surface, which follow the terrace of the substrate, were obtained at temperatures below 600 1C. The magnetic properties of CoFe2O4

  3. Crystalline CoFeB/graphite interfaces for carbon spintronics fabricated by solid phase epitaxy

    NARCIS (Netherlands)

    Wong, P.K.J.; van Geijn, Elmer; van Geijn, E.; Zhang, W.; Starikov, A.A.; Tran, T. Lan Ahn; Sanderink, Johannes G.M.; Siekman, Martin Herman; Brocks, Gerardus H.L.A.; Kelly, Paul J.; van der Wiel, Wilfred Gerard; de Jong, Machiel Pieter

    2013-01-01

    Structurally ordered interfaces between ferromagnetic electrodes and graphene or graphite are of great interest for carbon spintronics, since they allow spin-filtering due to k-vector conservation. By solid phase epitaxy of amorphous/nanocrystalline CoFeB at elevated temperatures, the feasibility of

  4. Magnetisation reversal of epitaxial films of γ'-Fe4N on Cu(1 0 0)

    International Nuclear Information System (INIS)

    Ecija, D.; Jimenez, E.; Camarero, J.; Gallego, J.M.; Vogel, J.; Mikuszeit, N.; Sacristan, N.; Miranda, R.

    2007-01-01

    Epitaxial single-phase γ'-Fe 4 N(1 0 0) thin films have been grown on Cu(1 0 0). The growth mode and structure have been studied from the early stages up to 50 nm thick films by means of in situ scanning tunnelling microscopy, low-energy electron diffraction and Auger electron spectroscopy. The nitride films are single crystals with sharp interfaces with the substrate, atomically flat and grown layer by layer. The magnetic properties have been studied ex situ by high-resolution vectorial Kerr magnetometry. The films are ferromagnetic at room temperature. The magnetisation lies within the plane of the film. The hysteresis loops are non-consistent with a simple cubic symmetry. Two easy axes, close to the directions, but at ∼81 o from each other, are found. The angular dependence of the vector hysteresis loops reveals different magnetisation reversal behaviours around the two hard-axes directions and around the two easy-axes directions. The origin of these features is discussed

  5. Tunable magnetotransport in Fe/hBN/graphene/hBN/Pt(Fe) epitaxial multilayers

    Science.gov (United States)

    Magnus Ukpong, Aniekan

    2018-03-01

    Theoretical and computational analysis of the magnetotransport properties and spin-transfer torque field-induced switching of magnetization density in vertically-stacked multilayers is presented. Using epitaxially-capped free layers of Pt and Fe, atom-resolved magnetic moments and spin-transfer torques are computed at finite bias. The calculations are performed within linear response approximation to the spin-density reformulation of the van der Waals density functional theory. Dynamical spin excitations are computed as a function of a spin-transfer torque induced magnetic field along the magnetic easy axis, and the corresponding spin polarization perpendicular to the easy axis is obtained. Bias-dependent giant anisotropic magnetoresistance of up to 3200% is obtained in the nonmagnetic-metal-capped Fe/hBN/graphene/hBN/Pt multilayer architecture. Since this specific heterostructure is not yet fabricated and characterized, the predicted high performance has not been demonstrated experimentally. Nevertheless, similar calculations performed on the Fe/hBN/Co stack show that the tunneling magnetoresistance obtained at the Fermi-level is in excellent agreement with results of recent magnetotransport measurements on magnetic tunnel junctions that contain the monolayer hBN tunnel region. The magnitude of the spin-transfer torque is found to increase as the tunneling spin current increases, and this activates the magnetization switching process due to increased charge accumulation. This mechanism causes substantial spin backflow, which manifests as rapid undulations in the bias-dependent tunneling spin currents. The implication of these findings on the design of nanoscale spintronic devices with spin-transfer torque tunable magnetization density is discussed. Insights derived from this study are expected to enhance the prospects for developing and integrating artificially assembled van der Waals multilayer heterostructures as the preferred material platform for efficient

  6. Physicochemical analysis of Bi2Te3 - (Fe, Eu) - Bi2Te3 junctions grown by molecular beam epitaxy method

    Science.gov (United States)

    Balin, K.; Rapacz, R.; Weis, M.; Szade, J.

    2017-05-01

    Topological insulators (TI) are a class of materials gaining in importance due to their unique spin/electronic properties, which may allow for the generation of quasiparticles and electronic states which are not accessible in classical condensed-matter systems. Not surprisingly, TI are considered as promising materials for multiple applications in next generation electronic or spintronic devices, as well as for applications in energy conversion, such as thermo-electrics. In this study, we examined the practical challenges associated with the formation of a well-defined junction between a model 3D topological insulator, Bi2Te3, and a metal, Fe or Eu, from which spin injection could potentially be realized. The properties of multilayer systems grown by molecular beam epitaxy (MBE), with Fe or Eu thin films sandwiched between two Bi2Te3 layers, were studied in-situ using electron diffraction and photoelectron spectroscopy. Their magnetic properties were measured using a SQUID magnetometer, while the in-depth chemical structure was assessed using secondary ion mass spectroscopy. An examination of impact of Bi2Te3 structure on chemical stability of the junction area has been realized. For Fe, we found that despite room temperature growth, a reaction between the Fe film and Bi2Te3 takes place, leading to the formation of FeTe and also the precipitation of metallic Bi. For the Eu tri-layer, a reaction also occurs, but the Te chemical state remains intact.

  7. Carrier dynamics and gain spectra at room-temperature in epitaxial ZNO thin films

    DEFF Research Database (Denmark)

    Yu, Ping; Hvam, Jørn Märcher; Wong, K. S.

    1999-01-01

    Carrier dynamics of epitaxial ZnO thin film was investigated using a frequency up-conversion tehcnique. At lower carrier densities, the decay time of free exciton recombination was measured to be 24 ps. Rapid decay times of a few picoseconds were observed at higher carrier densities, which show a...

  8. Determination of the Young's modulus of pulsed laser deposited epitaxial PZT thin films

    NARCIS (Netherlands)

    Nazeer, H.; Nguyen, Duc Minh; Woldering, L.A.; Abelmann, Leon; Rijnders, Augustinus J.H.M.; Elwenspoek, Michael Curt

    2011-01-01

    We determined the Young’s modulus of pulsed laser deposited epitaxially grown PbZr0.52Ti0.48O3 (PZT) thin films on microcantilevers by measuring the difference in cantilever resonance frequency before and after deposition. By carefully optimizing the accuracy of this technique, we were able to show

  9. Skyrmions and Novel Spin Textures in FeGe Thin Films and Artificial B20 Heterostructures

    Science.gov (United States)

    Ahmed, Adam Saied

    Skyrmions are magnetic spin textures that have a non-zero topological winding number associated with them. They have attracted much interest recently since they can be as small as 1 nm and could be the next generation of magnetic memory and logic. First, we grow epitaxial films of FeGe by molecular beam epitaxy and characterized the skyrmion properties. This had led us to image skyrmions in real-space with Lorentz transmission electron microscopy for the first time in the United States. Next, from an extensive series of thin and thick films, we have experimentally shown the existence of a magnetic surface state in FeGe and, consequently, any skyrmion material for the first time. Complementary theoretical calculations supported the existence of chiral bobbers--a surface state only predicted in 2015. Next, we fabricated for the first time a new class of skyrmion materials: B20 superlattices. These novel heterostructures of [FeGe/MnGe/CrGe] have now opened the door for tunable skyrmion systems with both Dresselhaus and Rashba Dzyaloshinskii-Moriya interactions. Additionally, we perform resonant soft x-ray scattering to image magnetic spin textures in reciprocal space for FeGe thin films in transmission. We have accomplished the removal of substrate and left an isolated single-crystal FeGe film. Lastly, SrO is grown on graphene as a crystalline, atomically smooth, and pinhole free tunnel barrier for spin injection.

  10. van der Waals epitaxy of CdS thin films on single-crystalline graphene

    Science.gov (United States)

    Sun, Xin; Lu, Zonghuan; Xie, Weiyu; Wang, Yiping; Shi, Jian; Zhang, Shengbai; Washington, Morris A.; Lu, Toh-Ming

    2017-04-01

    van der Waals epitaxy (vdWE) of three-dimensional CdS thin films on both single-crystalline graphene/Cu(111)/spinel(111) and single-crystalline graphene/SiO2/Si substrates is achieved via thermal evaporation. X-ray and electron backscatter diffraction pole figures reveal that the CdS films are a Wurtzite structure with a weak epitaxy on graphene and accompanied with a fiber texture background. The epitaxial alignment between CdS and graphene is observed to be an unusual non-parallel epitaxial relationship with a 30° rotation between the unit vectors of CdS and graphene. A geometrical model based on the minimization of superlattice area mismatch is employed to calculate possible interface lattice arrangement. It is found that the 30° rotation between CdS and graphene is indeed the most probable interface epitaxial lattice alignment. The vdWE of CdS on graphene, transferrable to arbitrary substrates, may represent a step forward for the growth of quality CdS thin films on arbitrary substrates through a graphene buffer.

  11. Vapor phase epitaxial growth of FeS sub 2 pyrite and evaluation of the carrier collection in liquid-junction solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Ennaoui, A.; Schlichthoerl, G.; Fiechter, S.; Tributsch, H. (Hahn-Meitner-Inst., Abt. Solare Energetik und Materialforschung, Berlin (Germany))

    1992-01-01

    Photoactive epitaxial layers of FeS{sub 2} were grown using bromine as a transport agent and a simple closed ampoule technique. The substrates used were (100)-oriented slices of natural pyrite 1 mm thick. A vapor-liquid-solid (VLS) growth mechanism was elucidated by means of optical microscopy. Macrosteps, terrace surfaces and protuberances are often accompanied with the presence of liquid FeBr{sub 3} droplets. In the absence of a liquid phase growth hillocks are found. Localized photovoltaic response for the evaluation of carrier collection using a scanning laser spot system has been used to effectively locate and characterize non-uniformities present in the epitaxial thin films. (orig.).

  12. Epitaxial patterning of nanometer-thick Y3Fe5O12 films with low magnetic damping.

    Science.gov (United States)

    Li, Shaozhen; Zhang, Wei; Ding, Junjia; Pearson, John E; Novosad, Valentine; Hoffmann, Axel

    2016-01-07

    Magnetic insulators such as yttrium iron garnet, Y3Fe5O12, with extremely low magnetic damping have opened the door for low power spin-orbitronics due to their low energy dissipation and efficient spin current generation and transmission. We demonstrate here reliable and efficient epitaxial growth and nanopatterning of Y3Fe5O12 thin-film based nanostructures on insulating Gd3Ga5O12 substrates. In particular, our fabrication process is compatible with conventional sputtering and lift-off, and does not require aggressive ion milling which may be detrimental to the oxide thin films. Their structural and magnetic properties indicate good qualities, in particular low magnetic damping of both films and patterned structures. The dynamic magnetic properties of the nanostructures are systematically investigated as a function of the lateral dimension. By comparing with ferromagnetic nanowire structures, a distinct edge mode in addition to the main mode is identified by both experiments and simulations, which also exhibit cross-over with the main mode upon varying the width of the wires. The non-linear evolution of dynamic modes over nanostructural dimensions highlights the important role of size confinement to their material properties in magnetic devices where Y3Fe5O12 nanostructures serve as the key functional component.

  13. Pillar shape modulation in epitaxial BiFeO3–CoFe2O4 vertical nanocomposite films

    Directory of Open Access Journals (Sweden)

    Dong Hun Kim

    2014-08-01

    Full Text Available Self-assembled epitaxial CoFe2O4-BiFeO3 nanocomposite films, in which pillars of CoFe2O4 grow within a single crystal BiFeO3 matrix, show both ferrimagnetism and ferroelectricity. The pillars typically have a uniform cross-section, but here two methods are demonstrated to produce a width modulation during growth by pulsed laser deposition. This was achieved by growing a blocking layer of BiFeO3 to produce layers of separated pillars or pillars with constrictions, or by changing the temperature during growth to produce bowling-pin shaped pillars. Modulated nanocomposites showed changes in their magnetic anisotropy compared to nanocomposites with uniform width. The magnetic anisotropy was interpreted as a result of magnetoelastic and shape anisotropies.

  14. Pillar shape modulation in epitaxial BiFeO3-CoFe2O4 vertical nanocomposite films

    Science.gov (United States)

    Kim, Dong Hun; Aimon, Nicolas M.; Ross, C. A.

    2014-08-01

    Self-assembled epitaxial CoFe2O4-BiFeO3 nanocomposite films, in which pillars of CoFe2O4 grow within a single crystal BiFeO3 matrix, show both ferrimagnetism and ferroelectricity. The pillars typically have a uniform cross-section, but here two methods are demonstrated to produce a width modulation during growth by pulsed laser deposition. This was achieved by growing a blocking layer of BiFeO3 to produce layers of separated pillars or pillars with constrictions, or by changing the temperature during growth to produce bowling-pin shaped pillars. Modulated nanocomposites showed changes in their magnetic anisotropy compared to nanocomposites with uniform width. The magnetic anisotropy was interpreted as a result of magnetoelastic and shape anisotropies.

  15. Giant electric field controlled magnetic anisotropy in epitaxial BiFeO3-CoFe2O4 thin film heterostructures on single crystal Pb(Mg1/3Nb2/3)0.7Ti0.3O3 substrate

    Science.gov (United States)

    Wang, Zhiguang; Yang, Yaodong; Viswan, Ravindranath; Li, Jiefang; Viehland, D.

    2011-07-01

    We have deposited self-assembled BiFeO3 (BFO)-CoFe2O4 (CFO) thin films on Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrates and studied the change in magnetic anisotropy under different strain conditions induced by an applied electric field. After electric field poling, we observed (i) giant magnetization change: magnetization of original CFO phase is three times larger than that of strained one and (ii) magnetic force microscopy line profiles that exhibited significant change in the CFO magnetic domain response in accordance to magnetization-field (M-H) loops. Together, these results demonstrate good control of the magnetic properties of CFO via an electric field induced strain.

  16. Self-modulated nanostructures in super-large-period Bi{sub 11}(Fe{sub 5}CoTi{sub 3}){sub 10/9}O{sub 33} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Dechao; Huang, Haoliang; Yun, Yu; Huang, Yan [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zhai, Xiaofang, E-mail: xfzhai@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Hefei Physical Sciences and Technology Center, CAS Hefei Institutes of Physical Sciences, Hefei, Anhui 230031 (China); Ma, Chao [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Fu, Zhengping; Peng, Ranran [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Mao, Xiangyu; Chen, Xiaobing [College of Physics Science and Technology, Yangzhou University, Yangzhou 225002 (China); Brown, Gail [Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio 45433 (United States); and others

    2015-05-25

    Super-large-period Aurivillius thin films with a pseudo-period of ten were grown on (0 0 1) SrTiO{sub 3} substrates using the pulsed laser deposition method. The as-grown films are found to be coherently strained to the substrate and atomically smooth. X-ray diffraction indicates an average periodicity of ten, while analysis with the high resolution scanning transmission electron microscopy reveals a self-modulated nanostructure in which the periodicity changes as the film thickness increases. Finally, we discuss the magnetic and possible ferroelectric properties of the self-modulated large period Aurivillius films at the room temperature.

  17. The origin of local strain in highly epitaxial oxide thin films.

    Science.gov (United States)

    Ma, Chunrui; Liu, Ming; Chen, Chonglin; Lin, Yuan; Li, Yanrong; Horwitz, J S; Jiang, Jiechao; Meletis, E I; Zhang, Qingyu

    2013-10-31

    The ability to control the microstructures and physical properties of hetero-epitaxial functional oxide thin films and artificial structures is a long-sought goal in functional materials research. Normally, only the lattice misfit between the film and the substrate is considered to govern the physical properties of the epitaxial films. In fact, the mismatch of film unit cell arrangement and the Surface-Step-Terrace (SST) dimension of the substrate, named as "SST residual matching", is another key factor that significantly influence the properties of the epitaxial film. The nature of strong local strain induced from both lattice mismatch and the SST residual matching on ferroelectric (Ba,Sr)TiO3 and ferromagnetic (La,Ca)MnO3 thin films are systematically investigated and it is demonstrated that this combined effect has a dramatic impact on the physical properties of highly epitaxial oxide thin films. A giant anomalous magnetoresistance effect (~10(10)) was achieved from the as-designed vicinal surfaces.

  18. High quality atomically thin PtSe2 films grown by molecular beam epitaxy

    Science.gov (United States)

    Yan, Mingzhe; Wang, Eryin; Zhou, Xue; Zhang, Guangqi; Zhang, Hongyun; Zhang, Kenan; Yao, Wei; Lu, Nianpeng; Yang, Shuzhen; Wu, Shilong; Yoshikawa, Tomoki; Miyamoto, Koji; Okuda, Taichi; Wu, Yang; Yu, Pu; Duan, Wenhui; Zhou, Shuyun

    2017-12-01

    Atomically thin PtSe2 films have attracted extensive research interests for potential applications in high-speed electronics, spintronics and photodetectors. Obtaining high quality thin films with large size and controlled thickness is critical. Here we report the first successful epitaxial growth of high quality PtSe2 films by molecular beam epitaxy. Atomically thin films from 1 ML to 22 ML have been grown and characterized by low-energy electron diffraction, Raman spectroscopy and x-ray photoemission spectroscopy. Moreover, a systematic thickness dependent study of the electronic structure is revealed by angle-resolved photoemission spectroscopy (ARPES), and helical spin texture is revealed by spin-ARPES. Our work provides new opportunities for growing large size single crystalline films to investigate the physical properties and potential applications of PtSe2.

  19. Directed self-assembly of epitaxial CoFe2O(4)-BiFeO3 multiferroic nanocomposites.

    Science.gov (United States)

    Comes, Ryan; Liu, Hongxue; Khokhlov, Mikhail; Kasica, Richard; Lu, Jiwei; Wolf, Stuart A

    2012-05-09

    CoFe(2)O(4) (CFO)-BiFeO(3) (BFO) nanocomposites are an intriguing option for future memory and logic technologies due to the magnetoelectric properties of the system. However, these nanocomposites form with CFO pillars randomly located within a BFO matrix, making implementation in devices difficult. To overcome this, we present a technique to produce patterned nanocomposites through self-assembly. CFO islands are patterned on Nb-doped SrTiO(3) to direct the self-assembly of epitaxial CFO-BFO nanocomposites, producing square arrays of CFO pillars.

  20. Metallic atomically-thin layered silicon epitaxially grown on silicene/ZrB2

    Science.gov (United States)

    Gill, Tobias G.; Fleurence, Antoine; Warner, Ben; Prüser, Henning; Friedlein, Rainer; Sadowski, Jerzy T.; Hirjibehedin, Cyrus F.; Yamada-Takamura, Yukiko

    2017-06-01

    Using low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM), we observe a new two-dimensional (2D) silicon crystal that is formed by depositing additional Si atoms onto spontaneously-formed epitaxial silicene on a ZrB2 thin film. From scanning tunnelling spectroscopy (STS) studies, we find that this atomically-thin layered silicon has distinctly different electronic properties. Angle resolved photoelectron spectroscopy (ARPES) reveals that, in sharp contrast to epitaxial silicene, the layered silicon exhibits significantly enhanced density of states at the Fermi level resulting from newly formed metallic bands. The 2D growth of this material could allow for direct contacting to the silicene surface and demonstrates the dramatic changes in electronic structure that can occur by the addition of even a single monolayer amount of material in 2D systems.

  1. Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Tanmoy, E-mail: pramanik.tanmoy@utexas.edu; Roy, Anupam, E-mail: anupam@austin.utexas.edu; Dey, Rik, E-mail: rikdey@utexas.edu; Rai, Amritesh; Guchhait, Samaresh; Movva, Hema C.P.; Hsieh, Cheng-Chih; Banerjee, Sanjay K.

    2017-09-01

    Highlights: • Perpendicular magnetic anisotropy in epitaxial Cr{sub 2}Te{sub 3} has been investigated. • Presence of a relatively strong second order anisotropy contribution is observed. • Magnetization reversal is explained quantitatively using a 1D defect model. • Relative roles of nucleation and pinning in magnetization reversal are discussed. • Domain structures and switching process are visualized by micromagnetic simulation. - Abstract: We investigate magnetic anisotropy and magnetization reversal mechanism in chromium telluride thin films grown by molecular beam epitaxy. We report existence of strong perpendicular magnetic anisotropy in these thin films, along with a relatively strong second order anisotropy contribution. The angular variation of the switching field observed from the magnetoresistance measurement is explained quantitatively using a one-dimensional defect model. The model reveals the relative roles of nucleation and pinning in the magnetization reversal, depending on the applied field orientation. Micromagnetic simulations are performed to visualize the domain structure and switching process.

  2. Quasi-epitaxial barium hexaferrite thin films prepared by a topotactic reactive diffusion process

    Science.gov (United States)

    Meng, Siqin; Yue, Zhenxing; Zhang, Xiaozhi; Li, Longtu

    2014-01-01

    Quasi-epitaxial barium hexaferrite thin films (BaM) with crystallographic c-axis parallel to film normal were prepared through a topotactic reactive diffusion process using two-step solution deposition on c-plane sapphire. The two-step spin coating process involves preparing an epitaxial hematite film, coating the film with barium precursor solution and thermal annealing. The crystal orientation and magnetic anisotropy of BaM thin films were investigated by X-ray diffraction analysis, SEM observation and magnetic measurements. Hysteresis loops showed good magnetic anisotropy and high remanence ratio (RR) Mr/Ms = 0.97. The films fabricated by two-step spin coating process displayed wider rocking curve width but better magnetic anisotropy than one-step spin coating. The possible mechanism of this discrepancy is discussed in this paper.

  3. Quasi-epitaxial barium hexaferrite thin films prepared by a topotactic reactive diffusion process

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Siqin; Yue, Zhenxing, E-mail: yuezhx@tsinghua.edu.cn; Zhang, Xiaozhi; Li, Longtu

    2014-01-30

    Quasi-epitaxial barium hexaferrite thin films (BaM) with crystallographic c-axis parallel to film normal were prepared through a topotactic reactive diffusion process using two-step solution deposition on c-plane sapphire. The two-step spin coating process involves preparing an epitaxial hematite film, coating the film with barium precursor solution and thermal annealing. The crystal orientation and magnetic anisotropy of BaM thin films were investigated by X-ray diffraction analysis, SEM observation and magnetic measurements. Hysteresis loops showed good magnetic anisotropy and high remanence ratio (RR) Mr/Ms = 0.97. The films fabricated by two-step spin coating process displayed wider rocking curve width but better magnetic anisotropy than one-step spin coating. The possible mechanism of this discrepancy is discussed in this paper.

  4. Single orientation graphene synthesized on iridium thin films grown by molecular beam epitaxy

    OpenAIRE

    Dangwal Pandey, A.; Krausert, Konstantin; Franz, D.; Grånäs, E.; Shayduk, R.; Müller, P.; Keller, Thomas F.; Noei, H.; Vonk, V.; Stierle, A.

    2016-01-01

    Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated system atically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force mic...

  5. Molecular Beam Epitaxy Growth and Characterization of Thin Layers of Semiconductor Tin

    Science.gov (United States)

    2016-09-01

    Semiconductor Tin by P Folkes, P Taylor, C Rong, B Nichols, H Hier, and M Neupane Approved for public release; distribution...Laboratory Molecular Beam Epitaxy Growth and Characterization of Thin Layers of Semiconductor Tin by P Folkes, P Taylor, C Rong, B Nichols... Semiconductor Tin 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) P Folkes, P Taylor, C Rong, B Nichols, H Hier, and M

  6. Capacitance-voltage measurements in GaAs thin-film epitaxial structures

    Directory of Open Access Journals (Sweden)

    Gorev N. B.

    2009-10-01

    Full Text Available It is shown that capacitance–voltage characteristics that feature steeply dropping regions, in particular those of GaAs thin-film structures, may be measured at moderately small amplitudes of the measuring ac voltage (of the order of 100 mV at the expense of taking measurements at two different amplitudes. This conclusion is confirmed by the results of numerical calculation of the apparent capacitance of GaAs epitaxial structures.

  7. Domain structure and magnetotransport in epitaxial colossal magnetoresistance thin films

    OpenAIRE

    Suzuki, Yuri; Wu, Yan; Yu, Jun; Rüdiger, Ulrich; Kent, Andrew D.; Nath, Tapan K.; Eom, Chang-Beom

    2000-01-01

    Our studies of compressively strained La0.7 Sr0.3 MnO7 (LSMO) thin films reveal the importance of domain structure and strain effects in the magnetization reversal and magnetotransport. Normal and grazing incidence x-ray diffraction indicate that the compressive strain on these LSMO thin films on (100) LaAlO3 is not completely relaxed up to thicknesses on the order of 1000 Å. The effect of the compressive strain is evident in the shape of the magnetization loops and the magnetotransport measu...

  8. Probing the bulk ionic conductivity by thin film hetero-epitaxial engineering

    KAUST Repository

    Pergolesi, Daniele

    2015-02-01

    Highly textured thin films with small grain boundary regions can be used as model systems to directly measure the bulk conductivity of oxygen ion conducting oxides. Ionic conducting thin films and epitaxial heterostructures are also widely used to probe the effect of strain on the oxygen ion migration in oxide materials. For the purpose of these investigations a good lattice matching between the film and the substrate is required to promote the ordered film growth. Moreover, the substrate should be a good electrical insulator at high temperature to allow a reliable electrical characterization of the deposited film. Here we report the fabrication of an epitaxial heterostructure made with a double buffer layer of BaZrO3 and SrTiO3 grown on MgO substrates that fulfills both requirements. Based on such template platform, highly ordered (001) epitaxially oriented thin films of 15% Sm-doped CeO2 and 8 mol% Y2O3 stabilized ZrO2 are grown. Bulk conductivities as well as activation energies are measured for both materials, confirming the success of the approach. The reported insulating template platform promises potential application also for the electrical characterization of other novel electrolyte materials that still need a thorough understanding of their ionic conductivity.

  9. Selectable spontaneous polarization direction and magnetic anisotropy in BiFeO3-CoFe2O4 epitaxial nanostructures.

    Science.gov (United States)

    Dix, Nico; Muralidharan, Rajaram; Rebled, Jose-Manuel; Estradé, Sonia; Peiró, Francesca; Varela, Manuel; Fontcuberta, Josep; Sánchez, Florencio

    2010-08-24

    We demonstrate that epitaxial strain engineering is an efficient method to manipulate the ferromagnetic and ferroelectric properties in BiFeO(3)-CoFe(2)O(4) columnar nanocomposites. On one hand, the magnetic anisotropy of CoFe(2)O(4) is totally tunable from parallel to perpendicular controlling the CoFe(2)O(4) strain with proper combinations of substrate and ferroelectric phase. On the other hand, the selection of the used substrate allows the growth of the rhombohedral bulk phase of BiFeO(3) or the metastable nearly tetragonal one, which implies a rotation of the ferroelectric polar axis from [111] to close to the [001] direction. Remarkably, epitaxy is preserved and interfaces are semicoherent even when lattice mismatch is above 10%. The broad range of sustainable mismatch suggests new opportunities to assemble epitaxial nanostructures combining highly dissimilar materials with distinct functionalities.

  10. 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.

  11. MFM study of NdFeB and NdFeB/Fe/NdFeB thin films

    International Nuclear Information System (INIS)

    Gouteff, P.C.; Folks, L.; Street, R.

    1998-01-01

    Domain structures of NdFeB thin films, ranging in thickness between 1500 and 29 nm, have been studied qualitatively by magnetic force microscopy (MFM). Samples were prepared using a range of sputtering conditions resulting in differences in properties such as texture, coercivity and magnetic saturation. MFM images of all the films showed extensive interaction domain structures, similar to those observed in nanocrystalline bulk NdFeB. An exchange-coupled NdFeB/Fe/NdFeB trilayer with layer thicknesses 18 nm/15 nm/18 nm, respectively, was also examined using MFM. (orig.)

  12. Magnetism and deformation of epitaxial Pd and Rh thin films

    Czech Academy of Sciences Publication Activity Database

    Káňa, Tomáš; Hüger, E.; Legut, D.; Čák, M.; Šob, Mojmír

    2016-01-01

    Roč. 93, č. 13 (2016), č. článku Art. number 134422. ISSN 2469-9950 R&D Projects: GA MŠk(CZ) LQ1601; GA ČR(CZ) GA16-24711S Institutional support: RVO:68081723 Keywords : ab initio calculations * magnetism * palladium * rhodium * thin films * deformation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  13. Reversal of lattice, electronic structure, and magnetism in epitaxial SrCoOx thin films

    Science.gov (United States)

    Jeen, H.; Choi, W. S.; Lee, J. H.; Cooper, V. R.; Lee, H. N.; Seo, S. S. A.; Rabe, K. M.

    2014-03-01

    SrCoOx (x = 2.5 - 3.0, SCO) is an ideal material to study the role of oxygen content for electronic structure and magnetism, since SCO has two distinct topotactic phases: the antiferromagnetic insulating brownmillerite SrCoO2.5 and the ferromagnetic metallic perovskite SrCoO3. In this presentation, we report direct observation of a reversible lattice and electronic structure evolution in SrCoOx epitaxial thin films as well as different magnetic and electronic ground states between the topotactic phases.[2] By magnetization measurements, optical absorption, and transport measurements drastically different electronic and magnetic ground states are found in the epitaxially grown SrCoO2.5 and SrCoO3 thin films by pulsed laser epitaxy. First-principles calculations confirm substantial, which originate from the modification in the Co valence states and crystallographic structures. By real-time spectroscopic ellipsometry, the two electronically and magnetically different phases can be reversibly changed by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides. The work was supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

  14. Magnetic Properties of Fe(001) Thin Films on GaAs(001) Deposited by RF Magnetron Sputtering

    International Nuclear Information System (INIS)

    Ikeya, Hirokazu; Takahashi, Yutaka; Inaba, Nobuyuki; Kirino, Fumiyoshi; Ohtake, Mitsuru; Futamoto, Masaaki

    2011-01-01

    Fe thin films, down to 6 nm thick, were prepared on GaAs(001) substrates by RF magnetron sputtering. The x-ray diffraction (XRD) analyses show that the epitaxial thin films of Fe(001) were grown with cube-on-cube orientation on GaAs(001). Magnetic properties were investigated by vibrating sample magnetometry (VSM) and ferromagnetic resonance (FMR) spectroscopy. The magnetization curves obtained by applying in-plane magnetic fields indicate that easy (hard) direction is along [100] ([110]) and the saturation magnetization is close to the bulk values. The in-plane magnetic anisotropy measured by FMR shows four-fold symmetry, as expected for bcc Fe. We did not observe the in-plane uniaxial magnetic anisotropy reported on the MBE-grown Fe films on GaAs substrates.

  15. Tuning piezoelectric properties through epitaxy of La2Ti2O7 and related thin films.

    Science.gov (United States)

    Kaspar, Tiffany C; Hong, Seungbum; Bowden, Mark E; Varga, Tamas; Yan, Pengfei; Wang, Chongmin; Spurgeon, Steven R; Comes, Ryan B; Ramuhalli, Pradeep; Henager, Charles H

    2018-02-14

    Current piezoelectric sensors and actuators are limited to operating temperatures less than ~200 °C due to the low Curie temperature of the piezoelectric material. Strengthening the piezoelectric coupling of high-temperature piezoelectric materials, such as La 2 Ti 2 O 7 (LTO), would allow sensors to operate across a broad temperature range. The crystalline orientation and piezoelectric coupling direction of LTO thin films can be controlled by epitaxial matching to SrTiO 3 (001), SrTiO 3 (110), and rutile TiO 2 (110) substrates via pulsed laser deposition. The structure and phase purity of the films are investigated by x-ray diffraction and scanning transmission electron microscopy. Piezoresponse force microscopy is used to measure the in-plane and out-of-plane piezoelectric coupling in the films. The strength of the out-of-plane piezoelectric coupling can be increased when the piezoelectric direction is rotated partially out-of-plane via epitaxy. The strongest out-of-plane coupling is observed for LTO/STO(001). Deposition on TiO 2 (110) results in epitaxial La 2/3 TiO 3 , an orthorhombic perovskite of interest as a microwave dielectric material and an ion conductor. La 2/3 TiO 3 can be difficult to stabilize in bulk form, and epitaxial stabilization on TiO 2 (110) is a promising route to realize La 2/3 TiO 3 for both fundamental studies and device applications. Overall, these results confirm that control of the crystalline orientation of epitaxial LTO-based materials can govern the resulting functional properties.

  16. Heterojunction Effect in Weak Epitaxy Growth Thin Films Investigated by Kelvin Probe Force Microscopy

    International Nuclear Information System (INIS)

    Hai-Chao, Huang; Hai-Bo, Wang; Dong-Hang, Yan

    2010-01-01

    We investigate the heterojunction effect between para-sexiphenyl (p-6P) and copper phthalocyanine (CuPc) using Kelvin probe force microscopy. CuPc films are grown on the inducing layer p-6P by a weak epitaxy growth technique. The surface potential images of Kelvin probe force microscopy indicate the band bending in CuPc, which reduces grain boundary barriers and lead to the accumulation of holes in the CuPc layer. The electrical potential distribution on the surface of heterojunction films shows negligible grain boundary barriers in the CuPc layers. The relation between band bending and grain boundary barrier in the weak epitaxy growth thin films is revealed. (condensed matter: structure, mechanical and thermal properties)

  17. The liquid phase epitaxy method for the construction of oriented ZIF-8 thin films with controlled growth on functionalized surfaces

    KAUST Repository

    Shekhah, Osama

    2013-01-01

    Highly-oriented ZIF-8 thin films with controllable thickness were grown on an -OH-functionalized Au substrate using the liquid phase epitaxy method at room temperature, as evidenced by SEM and PXRD. The adsorption-desorption properties of the resulting ZIF-8 thin film were investigated for various VOCs using the QCM technique. © The Royal Society of Chemistry 2013.

  18. The enhanced photocurrent of epitaxial BiFeO{sub 3} film at 130 °C

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuxi; Xu, Wenting; Xu, Xijun; Wang, Yaojin [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Yuan, Guoliang, E-mail: yuanguoliang@njust.edu.cn [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Wang, Yiping [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Liu, Zhiguo [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2016-01-28

    The short-circuit photocurrent (I{sub SC}) that can be reversed by polarization switch enhances with temperature increasing to 130 °C in the epitaxial BiFeO{sub 3} thin film on SrTiO{sub 3} substrate. The La{sub 2/3}Sr{sub 1/3}MnO{sub 3}/BiFeO{sub 3}/indium tin oxide (In{sub 2}O{sub 3}:SnO{sub 2} = 9:1) junction shows the current rectifying characteristic and the photovoltaic effect at 20–130 °C. Importantly, the I{sub SC} can be reversed by the polarization switch in this temperature range. More charge carriers are activated and the density of free electrons enhances with the increase in the temperature, which results in the decrease in the depletion layer width. As a result, the open-circuit voltage decreases 50% and the I{sub SC} increases from 180 nA to 404 nA with the increase in the temperature from 20 °C to 130 °C. This suggests that the corresponding sensors and devices can be used at a relatively high temperature.

  19. Optical observation of different conformational isomers in rubrene ultra-thin molecular films on epitaxial graphene

    Energy Technology Data Exchange (ETDEWEB)

    Udhardt, Christian; Forker, Roman; Gruenewald, Marco [Friedrich Schiller University, Institute of Solid State Physics, Helmholtzweg 5, 07743 Jena (Germany); Watanabe, Yu; Yamada, Takashi; Ueba, Takahiro; Munakata, Toshiaki [Osaka University, Graduate School of Science, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Fritz, Torsten, E-mail: torsten.fritz@uni-jena.de [Friedrich Schiller University, Institute of Solid State Physics, Helmholtzweg 5, 07743 Jena (Germany); Osaka University, Graduate School of Science, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)

    2016-01-01

    Optical differential reflectance spectroscopy in combination with low-energy electron diffraction and scanning tunneling microscopy is used to investigate (ultra-)thin rubrene films grown on epitaxial graphene. The optical absorption behavior is compared to thin films on graphite(0001), muscovite mica(0001), and amorphous glass. All the optical spectra can be explained by the presence of two different spectral components, namely a high-energy and a low-energy component. We assign these two optical species to two different conformations of the rubrene molecule. - Highlights: • Optical properties of ultra-thin rubrene films on various substrates obtained • Two molecular species which differ in their optical absorption were identified. • Different molecular conformations contribute to the optical absorption behavior.

  20. Catalytic Activity Enhancement for Oxygen Reduction on Epitaxial Perovskite Thin Films for Solid-Oxide Fuel Cells

    KAUST Repository

    la O', Gerardo Jose

    2010-06-22

    Figure Presented The active ingredient: La0.8Sr 0.2CoO3-δ (LSC) epitaxial thin films are prepared on (001 )-oriented yttria-stabilized zirconia (YSZ) single crystals with a gadolinium-doped ceria (GDC) buffer layer (see picture). The LSC epitaxial films exhibit better oxygen reduction kinetics than bulk LSC. The enhanced activity is attributed in part to higher oxygen nonstoichiometry. © 2010 Wiley-VCH Verlag GmbH & Co. KCaA, Weinheim.

  1. Molecular beam epitaxy growth of [CrGe/MnGe/FeGe] superlattices: Toward artificial B20 skyrmion materials with tunable interactions

    Science.gov (United States)

    Ahmed, Adam S.; Esser, Bryan D.; Rowland, James; McComb, David W.; Kawakami, Roland K.

    2017-06-01

    Skyrmions are localized magnetic spin textures whose stability has been shown theoretically to depend on material parameters including bulk Dresselhaus spin orbit coupling (SOC), interfacial Rashba SOC, and magnetic anisotropy. Here, we establish the growth of a new class of artificial skyrmion materials, namely B20 superlattices, where these parameters could be systematically tuned. Specifically, we report the successful growth of B20 superlattices comprised of single crystal thin films of FeGe, MnGe, and CrGe on Si(1 1 1) substrates. Thin films and superlattices are grown by molecular beam epitaxy and are characterized through a combination of reflection high energy electron diffraction, X-ray diffraction, and cross-sectional scanning transmission electron microscopy (STEM). X-ray energy dispersive spectroscopy (XEDS) distinguishes layers by elemental mapping and indicates good interface quality with relatively low levels of intermixing in the [CrGe/MnGe/FeGe] superlattice. This demonstration of epitaxial, single-crystalline B20 superlattices is a significant advance toward tunable skyrmion systems for fundamental scientific studies and applications in magnetic storage and logic.

  2. Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu1 - x Fe x O3 - δ Thin Films

    Science.gov (United States)

    Dash, Umasankar; Acharya, Susant Kumar; Lee, Bo Wha; Jung, Chang Uk

    2017-03-01

    Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu1 - x Fe x O3 - δ epitaxial thin films ( x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu1 - x Fe x O3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR ( 36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies ( δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr1 - x La x )(Ru1 - x Fe x )O3. These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu1 - x Fe x O3 - δ thin films.

  3. Flexoelectricity induced increase of critical thickness in epitaxial ferroelectric thin films

    International Nuclear Information System (INIS)

    Zhou Hao; Hong Jiawang; Zhang Yihui; Li Faxin; Pei Yongmao; Fang Daining

    2012-01-01

    Flexoelectricity describes the coupling between polarization and strain/stress gradients in insulating crystals. In this paper, using the Landau-Ginsburg-Devonshire phenomenological approach, we found that flexoelectricity could increase the theoretical critical thickness in epitaxial BaTiO 3 thin films, below which the switchable spontaneous polarization vanishes. This increase is remarkable in tensile films while trivial in compressive films due to the electrostriction caused decrease of potential barrier, which can be easily destroyed by the flexoelectricity, between the ferroelectric state and the paraelectric state in tensile films. In addition, the films are still in a uni-polar state even below the critical thickness due to the flexoelectric effect.

  4. Irradiation induced improvement in crystallinity of epitaxially grown Ag thin films on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Takahiro, Katsumi; Nagata, Shinji; Yamaguchi, Sadae [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

    1997-03-01

    We report the improvement in crystallinity of epitaxially grown Ag films on Si(100) substrates with ion irradiation. The irradiation of 0.5 MeV Si ions to 2x10{sup 16}/cm{sup 2} at 200degC, for example, reduces the channeling minimum yield from 60% to 6% at Ag surface. The improvement originates from the decrease of mosaic spread in the Ag thin film. In our experiments, ion energy, ion species and irradiation temperature have been varied. The better crystallinity is obtained as the higher concentration of defect is generated. The mechanism involved in the irradiation induced improvement is discussed. (author)

  5. Laser energy tuning of carrier effective mass and thermopower in epitaxial oxide thin films

    KAUST Repository

    Abutaha, Anas I.

    2012-04-18

    The effect of the laser fluence on high temperature thermoelectric properties of the La doped SrTiO3 (SLTO) thin films epitaxially grown on LaAlO3 〈100〉 substrates by pulsed laser deposition is clarified. It is shown that oxygen vacancies that influence the effective mass of carriers in SLTO films can be tuned by varying the laser energy. The highest power factor of 0.433 W K−1 m−1 has been achieved at 636 K for a filmdeposited using the highest laser fluence of 7 J cm−2 pulse−1.

  6. Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaopu, E-mail: xl6ba@virginia.edu; Ma, Chung T.; Poon, S. Joseph, E-mail: sjp9x@virginia.edu [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Lu, Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Devaraj, Arun [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Spurgeon, Steven R.; Comes, Ryan B. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)

    2016-01-04

    Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switching using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.

  7. Epitaxial growth of barium titanate thin films on germanium via atomic layer deposition

    Science.gov (United States)

    Lin, Edward L.; Posadas, Agham B.; Wu, Hsin Wei; Smith, David J.; Demkov, Alexander A.; Ekerdt, John G.

    2017-10-01

    Barium titanate BaTiO3 (BTO) thin films were epitaxially grown at 225 °C on 2 × 1-reconstructed Ge(001) surfaces via atomic layer deposition (ALD). Approximately 2 nm of BTO film was grown directly on Ge(001) as an amorphous film. Electron diffraction confirmed the epitaxy of the BTO films after post-deposition annealing at 650 °C. Additional BTO layers grown on the crystalline BTO/Ge(001) film were crystalline as-deposited. X-ray diffraction indicated that the epitaxial BTO films had a c-axis out-of-plane orientation, and the abrupt BTO/Ge interface was preserved with no sign of any interfacial germanium oxide. Scanning transmission electron microscopy provided evidence of Ba atoms occupying the troughs of the dimer rows of the 2 × 1-reconstructed Ge(001) surface, as well as preservation of the 2 × 1-reconstructed Ge(001) surface. This study presents a low-temperature process to fabricate BTO/Ge heterostructures.

  8. Epitaxial Ni-Mn-Ga-Co thin films on PMN-PT substrates for multicaloric applications

    Energy Technology Data Exchange (ETDEWEB)

    Schleicher, B., E-mail: b.schleicher@ifw-dresden.de; Niemann, R.; Schultz, L.; Fähler, S. [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany); TU Dresden, Institute for Solid State Physics, D-01062 Dresden (Germany); Diestel, A.; Hühne, R. [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany)

    2015-08-07

    Multicaloric stacks consisting of a magnetocaloric film on a piezoelectric substrate promise improved caloric properties as the transition temperature can be controlled by both magnetic and electric fields. We present epitaxially grown magnetocaloric Ni-Mn-Ga-Co thin films on ferroelectric Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.72}Ti{sub 0.28}O{sub 3} substrates. Structure and microstructure of two samples, being in the austenitic and martensitic state at room temperature, are investigated by X-ray diffraction in two- and four-circle geometry and by atomic force microscopy. In addition, high temperature magnetometry was performed on the latter sample. The combination of these methods allows separating the influence of epitaxial growth and martensitic transformation. A preferential alignment of twin boundaries is observed already in the as-deposited state, which indicates the presence of prestress, without applying an electric field to the substrate. A temperature-magnetic field phase diagram is presented, which demonstrates the inverse magnetocaloric effect of the epitaxial Ni-Mn-Ga-Co film.

  9. Silicon thin film growth by low temperature liquid phase epitaxy for photovoltaic applications

    International Nuclear Information System (INIS)

    Abdo, F.

    2007-03-01

    In this thesis is presented an economic, clean and innovating way to carry out silicon substrate in thin layer for photovoltaic applications. It is based on layer growth by low temperature liquid phase epitaxy on silicon substrates embrittled by ion implantation. The aim of this work is to find experimental conditions to decrease the epitaxy temperature (≤800 C instead of 1050 C) while conserving a relatively high growth velocity. An innovating method has been implemented; it consists to use two different baths: the first one Al-Sn-Si allows to de-oxidize the silicon substrate surface without using hydrogen and the second one containing Sn-Si allows the growth of a thick layer of silicon. Uniform layers of a thickness of 15μm have been obtained after three hours of growth. Thermodynamic studies exploiting the phase diagrams of ternary or quaternary mixtures have been carried out to reach high growth velocity. Tin and copper based alloys have been chosen, tin for lowering the temperature and copper for increasing the silicon solubility. Layers of 30 μm have been obtained after two hours of growth. It has been shown too that this epitaxy step could be compatible with the technology of ion implantation embrittlement. (O.M.)

  10. Induced ferromagnetism and magnetoelectric coupling in ion-beam synthesized BiFeO3-CoFe2O4 nanocomposite thin films

    Science.gov (United States)

    Modarresi, H.; Lazenka, V.; Menéndez, E.; Lorenz, M.; Bisht, M.; Volodin, A.; Van Haesendonck, C.; Grundmann, M.; Van Bael, M. J.; Temst, K.; Vantomme, A.

    2016-08-01

    Ferrimagnetic CoFe2O4 (cobalt ferrite) is formed within an epitaxial BiFeO3 (bismuth ferrite) thin film matrix by Co channeled ion implantation and subsequent annealing. The presence of nanoscale CoFe2O4 crystals in the matrix is confirmed by x-ray diffraction using synchrotron radiation. The significantly increased magnetic moment and the low-temperature coercive field of the composite system evidence the formation of ferrimagnetic cobalt ferrite and its nanoscale character, respectively. The results demonstrate that ion beam synthesis is an appropriate method to controllably transform a planar system into a granular one, increasing the interface area between cobalt ferrite and bismuth ferrite. The ferroelectric nature of the BiFeO3-CoFe2O4 composite is confirmed by several scanning probe microscopy techniques. At room temperature, the composite exhibits a magnetoelectric voltage coefficient of α ME  =  17.5 V (cm · Oe)-1, while a single-phase BiFeO3 thin film shows a α ME value of 4.2 V (cm · Oe)-1. The high magnetoelectric voltage coefficient is interpreted to be the result of the interfacial interaction between the ferrimagnetic CoFe2O4 nanocrystallites and the multiferroic BiFeO3 matrix.

  11. Strain dependent microstructural modifications of BiCrO{sub 3} epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kannan, Vijayanandhini, E-mail: kvnandhini@gmail.com [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); CNRS, University of Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Arredondo, Miryam; Johann, Florian; Hesse, Dietrich [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); Labrugere, Christine [CNRS, University of Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); CeCaMA, University of Bordeaux, ICMCB, F-33600 Pessac (France); Maglione, Mario [CNRS, University of Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Vrejoiu, Ionela [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany)

    2013-10-31

    Strain-dependent microstructural modifications were observed in epitaxial BiCrO{sub 3} (BCO) thin films fabricated on single crystalline substrates, utilizing pulsed laser deposition. The following conditions were employed to modify the epitaxial-strain: (i) in-plane tensile strain, BCO{sub STO} [BCO grown on buffered SrTiO{sub 3} (001)] and in-plane compressive strain, BCO{sub NGO} [BCO grown on buffered NdGaO{sub 3} (110)] and (ii) varying BCO film thickness. A combination of techniques like X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (TEM) was used to analyse the epitaxial growth quality and the microstructure of BCO. Our studies revealed that in the case of BCO{sub STO}, a coherent interface with homogeneous orthorhombic phase is obtained only for BCO film with thicknesses, d < 50 nm. All the BCO{sub STO} films with d ≥ 50 nm were found to be strain-relaxed with an orthorhombic phase showing 1/2 <100> and 1/4 <101> satellite reflections, the latter oriented at 45° from orthorhombic diffraction spots. High angle annular dark field scanning TEM of these films strongly suggested that the satellite reflections, 1/2 <100> and 1/4 <101>, originate from the atomic stacking sequence changes (or “modulated structure”) as reported for polytypes, without altering the chemical composition. The unaltered stoichiometry was confirmed by estimating both valency of Bi and Cr cations by surface and in-depth XPS analysis as well as the stoichiometric ratio (1 Bi:1 Cr) using scanning TEM–energy dispersive X-ray analysis. In contrast, compressively strained BCO{sub NGO} films exhibited monoclinic symmetry without any structural modulations or interfacial defects, up to d ∼ 200 nm. Our results indicate that both the substrate-induced in-plane epitaxial strain and the BCO film thickness are the crucial parameters to stabilise a homogeneous BCO phase in an epitaxially grown film. - Highlights: • Phase pure

  12. Ferroelectric domain structures of epitaxial CaBi2Nb2O9 thin films on single crystalline Nb doped (1 0 0) SrTiO3 substrates

    Science.gov (United States)

    Ahn, Yoonho; Seo, Jeong Dae; Son, Jong Yeog

    2015-07-01

    Epitaxial CaBi2Nb2O9 (CBNO) thin films were deposited on Nb-doped SrTiO3 substrates. The CBNO thin films as a lead-free ferroelectric material exhibit a good ferroelectric property with the remanent polarization of 10.6 μC/cm2. In the fatigue resistance test, the CBNO thin films have no degradation in polarization up to 1×1012 switching cycles, which is applicable for non-volatile ferroelectric random access memories (FeRAMs). Furthermore, piezoresponse force microscopy study (PFM) reveals that the CBNO thin films have larger ferroelectric domain structures than those of PbTiO3 thin films. From the Landau, Lifshiftz, and Kittel's scaling law, it is inferred that the domain wall energy of CBNO thin films is probably very similar to that of the PbTiO3 thin films.

  13. Structure, magnetism, and interface properties of epitactical thin Fe and FePt films on GaAs(001) substrates; Struktur, Magnetismus und Grenzflaecheneigenschaften epitaktischer duenner Fe- und FePt-Filme auf GaAs(001)-Substraten

    Energy Technology Data Exchange (ETDEWEB)

    Schuster, Ellen Ursula

    2007-12-17

    The research in this thesis is focused on the study of the Fe spin structure and interface magnetism of thin epitaxial Fe layers or epitaxial FePt alloy films with chemical L1{sub 0} order on GaAs(001) surfaces. The main method of investigation was isotope-specific conversion electron Moessbauer spectroscopy (CEMS) combined with the {sup 57}Fe probe-layer technique in the temperature range of 4.2-300 K. The film structure was studied using electron diffraction (RHEED) and X-ray diffraction (XRD). The chemical order parameter S determined by XRD was found to increase with rising growth temperature, T{sub S}, to a maximum value of 0.71, until long range order is destroyed at T{sub S}>350 C by alloying with the substrate. As an important result a linear correlation between short-range order (revealed by the relative spectral area of the L1{sub 0} phase) and long-range order S was observed. The observed perpendicular Fe spin texture, characterized by the mean tilting angle left angle {theta} right angle of the Fe spins (relative to the film normal direction), was found to correlate with the L1{sub 0} phase content and with S. Furthermore, epitaxial Fe(001) films on GaAs(001)-(4 x 6) and on GaAs(001)-LED surfaces were grown successfully. In the initial stage of Fe film growth non-monotonous behavior of the in-plane lattice parameter was observed by RHEED. The magnetic hyperfine field distributions P(B{sub hf}) at the Fe/GaAs interface extracted from CEMS spectra for T{sub S}=-140 C or room temperature (RT) were found to be very similar. The observed large mean hyperfine fields of left angle B{sub hf} right angle {approx}25-27 T at the interface indicate the presence of high average Fe moments of 1.7-1.8 {mu}{sub B}. Nonmagnetic interface layers either can be excluded (Fe/GaAs) or are very thin (0.5 ML,Fe/GaAs-LED). Owing to its island structure an ultrathin (1.9 ML thick) uncoated Fe(001) film on GaAs(001)-(4 x 6) shows superparamagnetism with a blocking temperature of

  14. Strain Induced Magnetism in SrRuO3 Epitaxial Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Grutter, A.; Wong, F.; Arenholz, E.; Liberati, M.; Suzuki, Y.

    2010-01-10

    Epitaxial SrRuO{sub 3} thin films were grown on SrTiO{sub 3}, (LaAlO{sub 3}){sub 0.3}(SrAlO{sub 3}){sub 0.7} and LaAlO{sub 3} substrates inducing different biaxial compressive strains. Coherently strained SrRuO{sub 3} films exhibit enhanced magnetization compared to previously reported bulk and thin film values of 1.1-1.6 {micro}{sub B} per formula unit. A comparison of (001) and (110) SrRuO{sub 3} films on each substrate indicates that films on (110) oriented have consistently higher saturated moments than corresponding (001) films. These observations indicate the importance of lattice distortions in controlling the magnetic ground state in this transitional metal oxide.

  15. Tuning of Transport and Magnetic Properties in Epitaxial LaMnO3+δ Thin Films

    Directory of Open Access Journals (Sweden)

    J. Chen

    2014-01-01

    Full Text Available The effect of compressive strain on the transport and magnetic properties of epitaxial LaMnO3+δ thin films has been investigated. It is found that the transport and magnetic properties of the LaMnO3+δ thin films grown on the LaAlO3 substrates can be tuned by the compressive strain through varying film thickness. And the insulator-metal transition, charge/orbital ordering transition, and paramagnetic-ferromagnetic transition are suppressed by the compressive strain. Consequently, the related electronic and magnetic transition temperatures decrease with an increase in the compressive strain. The present results can be explained by the strain-controlled lattice deformation and the consequent orbital occupation. It indicates that the lattice degree of freedom is crucial for understanding the transport and magnetic properties of the strongly correlated LaMnO3+δ.

  16. Coexistence of Low Damping and Strong Magnetoelastic Coupling in Epitaxial Spinel Ferrite Thin Films.

    Science.gov (United States)

    Emori, Satoru; Gray, Benjamin A; Jeon, Hyung-Min; Peoples, Joseph; Schmitt, Maxwell; Mahalingam, Krishnamurthy; Hill, Madelyn; McConney, Michael E; Gray, Matthew T; Alaan, Urusa S; Bornstein, Alexander C; Shafer, Padraic; N'Diaye, Alpha T; Arenholz, Elke; Haugstad, Greg; Meng, Keng-Yuan; Yang, Fengyuan; Li, Dongyao; Mahat, Sushant; Cahill, David G; Dhagat, Pallavi; Jander, Albrecht; Sun, Nian X; Suzuki, Yuri; Howe, Brandon M

    2017-09-01

    Low-loss magnetization dynamics and strong magnetoelastic coupling are generally mutually exclusive properties due to opposing dependencies on spin-orbit interactions. So far, the lack of low-damping, magnetostrictive ferrite films has hindered the development of power-efficient magnetoelectric and acoustic spintronic devices. Here, magnetically soft epitaxial spinel NiZnAl-ferrite thin films with an unusually low Gilbert damping parameter (ferrite. At the same time, the coherently strained film structure suppresses extrinsic damping, enables soft magnetic behavior, and generates large easy-plane magnetoelastic anisotropy. These findings provide a foundation for a new class of low-loss, magnetoelastic thin film materials that are promising for spin-mechanical devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

    KAUST Repository

    Sarath Kumar, S. R.

    2012-02-01

    The influence of oxygen vacancies on the transport properties of epitaxial thermoelectric (Sr,La)TiO3 thin films is determined using electrical and spectroscopic ellipsometry (SE) measurements. Oxygen vacancy concentration was varied by ex-situ annealing in Ar and Ar/H2. All films exhibited degenerate semiconducting behavior, and electrical conductivity decreased (258–133 S cm−1) with increasing oxygen content. Similar decrease in the Seebeck coefficient is observed and attributed to a decrease in effective mass (7.8–3.2 me ), as determined by SE. Excellent agreement between transport properties deduced from SE and direct electrical measurements suggests that SE is an effective tool for studying oxide thin film thermoelectrics.

  18. Epitaxial thin film growth of LiH using a liquid-Li atomic template

    Energy Technology Data Exchange (ETDEWEB)

    Oguchi, Hiroyuki, E-mail: oguchi@nanosys.mech.tohoku.ac.jp [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan); Micro System Integration Center (muSIC), Tohoku University, Sendai 980-0845 (Japan); Ikeshoji, Tamio; Orimo, Shin-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Ohsawa, Takeo; Shiraki, Susumu; Hitosugi, Taro [Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Kuwano, Hiroki [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan)

    2014-11-24

    We report on the synthesis of lithium hydride (LiH) epitaxial thin films through the hydrogenation of a Li melt, forming abrupt LiH/MgO interface. Experimental and first-principles molecular dynamics studies reveal a comprehensive microscopic picture of the crystallization processes, which sheds light on the fundamental atomistic growth processes that have remained unknown in the vapor-liquid-solid method. We found that the periodic structure that formed, because of the liquid-Li atoms at the film/MgO-substrate interface, serves as an atomic template for the epitaxial growth of LiH crystals. In contrast, films grown on the Al{sub 2}O{sub 3} substrates indicated polycrystalline films with a LiAlO{sub 2} secondary phase. These results and the proposed growth process provide insights into the preparation of other alkaline metal hydride thin films on oxides. Further, our investigations open the way to explore fundamental physics and chemistry of metal hydrides including possible phenomena that emerge at the heterointerfaces of metal hydrides.

  19. Monolithic Mid-Infrared Integrated Photonics Using Silicon-on-Epitaxial Barium Titanate Thin Films.

    Science.gov (United States)

    Jin, Tiening; Li, Leigang; Zhang, Bruce; Lin, Hao-Yu Greg; Wang, Haiyan; Lin, Pao Tai

    2017-07-05

    Broadband mid-infrared (mid-IR) photonic circuits that integrate silicon waveguides and epitaxial barium titanate (BTO) thin films are demonstrated using the complementary metal-oxide-semiconductor process. The epitaxial BTO thin films are grown on lanthanum aluminate (LAO) substrates by the pulsed laser deposition technique, wherein a broad infrared transmittance between λ = 2.5 and 7 μm is observed. The optical waveguiding direction is defined by the high-refractive-index amorphous Si (a-Si) ridge structure developed on the BTO layer. Our waveguides show a sharp fundamental mode over the broad mid-IR spectrum, whereas its optical field distribution between the a-Si and BTO layers can be modified by varying the height of the a-Si ridge. With the advantages of broad mid-IR transparency and the intrinsic electro-optic properties, our monolithic Si on a ferroelectric BTO platform will enable tunable mid-IR microphotonics that are desired for high-speed optical logic gates and chip-scale biochemical sensors.

  20. Epitaxial thin film growth of LiH using a liquid-Li atomic template

    International Nuclear Information System (INIS)

    Oguchi, Hiroyuki; Ikeshoji, Tamio; Orimo, Shin-ichi; Ohsawa, Takeo; Shiraki, Susumu; Hitosugi, Taro; Kuwano, Hiroki

    2014-01-01

    We report on the synthesis of lithium hydride (LiH) epitaxial thin films through the hydrogenation of a Li melt, forming abrupt LiH/MgO interface. Experimental and first-principles molecular dynamics studies reveal a comprehensive microscopic picture of the crystallization processes, which sheds light on the fundamental atomistic growth processes that have remained unknown in the vapor-liquid-solid method. We found that the periodic structure that formed, because of the liquid-Li atoms at the film/MgO-substrate interface, serves as an atomic template for the epitaxial growth of LiH crystals. In contrast, films grown on the Al 2 O 3 substrates indicated polycrystalline films with a LiAlO 2 secondary phase. These results and the proposed growth process provide insights into the preparation of other alkaline metal hydride thin films on oxides. Further, our investigations open the way to explore fundamental physics and chemistry of metal hydrides including possible phenomena that emerge at the heterointerfaces of metal hydrides

  1. Epitaxial growth of Bi ultra-thin films on GaAs by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Plaza, M. [Dpto. Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Abuin, M. [Dpto. Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Unidad Asociada IQFR(CSIC)-UCM, Madrid 28040 (Spain); Mascaraque, A., E-mail: arantzazu.mascaraque@fis.ucm.es [Dpto. Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Unidad Asociada IQFR(CSIC)-UCM, Madrid 28040 (Spain); Gonzalez-Barrio, M.A. [Dpto. Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Unidad Asociada IQFR(CSIC)-UCM, Madrid 28040 (Spain); Perez, L. [Dpto. Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Instituto de Sistemas Optoelectronicos y Microtecnologia, Universidad Politecnica de Madrid, 28040 Madrid (Spain)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Electrodeposition of Bi films on GaAs substrates with different orientations. Black-Right-Pointing-Pointer Ultra thin films - 50 nm - are continuous and smooth. Black-Right-Pointing-Pointer Bi always grows with (0 1 L) orientations. Black-Right-Pointing-Pointer Epitaxial growth onto As terminated surfaces. Black-Right-Pointing-Pointer Proposed model based on structural and chemical considerations. - Abstract: We report on the growth of thin bismuth films on GaAs substrates with different orientations by means of electrochemical deposition. Atomic force microscopy reveals that the films are continuous and exhibit low roughness when they are grown under the appropriate overpotential. {omega}-2{theta} X-ray diffraction scans only show reflections that can be indexed as (0 1 L), meaning that Bi grows onto GaAs only in combinations of the (0 0 1) and (0 1 0) orientations. The matching between the GaAs substrate and the Bi layer has been studied by asymmetric X-ray scans, finding that Bi grows epitaxially on GaAs(1 1 0) and GaAs(1 1 1)B, both As-terminated surfaces. We explain these results by structural and chemical considerations.

  2. Self-regulated growth of LaVO3 thin films by hybrid molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zhang, Hai-Tian; Engel-Herbert, Roman; Dedon, Liv R.; Martin, Lane W.

    2015-01-01

    LaVO 3 thin films were grown on SrTiO 3 (001) by hybrid molecular beam epitaxy. A volatile metalorganic precursor, vanadium oxytriisopropoxide (VTIP), and elemental La were co-supplied in the presence of a molecular oxygen flux. By keeping the La flux fixed and varying the VTIP flux, stoichiometric LaVO 3 films were obtained for a range of cation flux ratios, indicating the presence of a self-regulated growth window. Films grown under stoichiometric conditions were found to have the largest lattice parameter, which decreased monotonically with increasing amounts of excess La or V. Energy dispersive X-ray spectroscopy and Rutherford backscattering measurements were carried out to confirm film compositions. Stoichiometric growth of complex vanadate thin films independent of cation flux ratios expands upon the previously reported self-regulated growth of perovskite titanates using hybrid molecular beam epitaxy, thus demonstrating the general applicability of this growth approach to other complex oxide materials, where a precise control over film stoichiometry is demanded by the application

  3. Tuning the magnetism of epitaxial cobalt oxide thin films by electron beam irradiation

    Science.gov (United States)

    Lan, Q. Q.; Zhang, X. J.; Shen, X.; Yang, H. W.; Zhang, H. R.; Guan, X. X.; Wang, W.; Yao, Y.; Wang, Y. G.; Peng, Y.; Liu, B. G.; Sun, J. R.; Yu, R. C.

    2017-07-01

    Tuning magnetic properties of perovskite thin films is a central topic of recent studies because of its fundamental significance. In this work, we demonstrated the modification of the magnetism of L a0.9C a0.1Co O3 (LCCO) thin films by introducing a stripelike superstructure in a controllable manner using electron beam irradiation (EBI) in a transmission electron microscope. The microstructure, electronic structure, strain change, and origin of magnetism of the LCCO thin films were studied in detail using aberration-corrected scanning transmission electron microscopy, electron energy loss spectroscopy, and ab initio calculations based on density functional theory. The results indicate that the EBI-induced unit cell volume expansion accompanies the formation of oxygen vacancies and leads to the spin state transition of Co ions. The low spin state of C o4 + ions depress the stripelike superstructure, while higher spin states of Co ions with lower valences are conductive to the formation of "dark stripes". Our work clarifies the origin of magnetism of epitaxial LCCO thin films, benefiting a comprehensive understanding of correlated physics in cobalt oxide thin films.

  4. Controllable Photovoltaic Effect of Microarray Derived from Epitaxial Tetragonal BiFeO3Films.

    Science.gov (United States)

    Lu, Zengxing; Li, Peilian; Wan, Jian-Guo; Huang, Zhifeng; Tian, Guo; Pan, Danfeng; Fan, Zhen; Gao, Xingsen; Liu, Jun-Ming

    2017-08-16

    Recently, the ferroelectric photovoltaic (FePV) effect has attracted great interest due to its potential in developing optoelectronic devices such as solar cell and electric-optical sensors. It is important for actual applications to realize a controllable photovoltaic process in ferroelectric-based materials. In this work, we prepared well-ordered microarrays based on epitaxially tetragonal BiFeO 3 (T-BFO) films by the pulsed laser deposition technique. The polarization-dependent photocurrent image was directly observed by a conductive atomic force microscope under ultraviolet illumination. By choosing a suitable buffer electrode layer and controlling the ferroelectric polarization in the T-BFO layer, we realized the manipulation of the photovoltaic process. Moreover, based on the analysis of the band structure, we revealed the mechanism of manipulating the photovoltaic process and attributed it to the competition between two key factors, i.e., the internal electric field caused by energy band alignments at interfaces and the depolarization field induced by the ferroelectric polarization in T-BFO. This work is very meaningful for deeply understanding the photovoltaic process of BiFeO 3 -based devices at the microscale and provides us a feasible avenue for developing data storage or logic switching microdevices based on the FePV effect.

  5. Anisotropic magnetoresistance across Verwey transition in charge ordered Fe3O4 epitaxial films

    KAUST Repository

    Liu, Xiang

    2017-12-26

    The anisotropic magnetoresistance (AMR) near the Verwey temperature (T-V) is investigated in charge ordered Fe3O4 epitaxial films. When the temperature continuously decreases below T-V, the symmetry of AMR in Fe3O4(100) film evolves from twofold to fourfold at a magnetic field of 50 kOe, where the magnetic field is parallel to the film surface, whereas AMR in Fe3O4(111) film maintains twofold symmetry. By analyzing AMR below T-V, it is found that the Verwey transition contains two steps, including a fast charge ordering process and a continuous formation process of trimeron, which is comfirmed by the temperature-dependent Raman spectra. Just below T-V, the twofold AMR in Fe3O4(100) film originates from uniaxial magnetic anisotropy. The fourfold AMR at a lower temperature can be ascribed to the in-plane trimerons. By comparing the AMR in the films with two orientations, it is found that the trimeron shows a smaller resistivity in a parallel magnetic field. The field-dependent AMR results show that the trimeron-sensitive field has a minimum threshold of about 2 kOe.

  6. Structure, site-specific magnetism, and magnetotransport properties of epitaxial D 022 -structure Mn2FexGa thin films

    Science.gov (United States)

    Betto, Davide; Lau, Yong-Chang; Borisov, Kiril; Kummer, Kurt; Brookes, N. B.; Stamenov, Plamen; Coey, J. M. D.; Rode, Karsten

    2017-07-01

    Ferrimagnetic Mn2FexGa (0.26 ≤x ≤1.12 ) thin films have been characterized by x-ray diffraction, magnetometry, x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and Mössbauer spectroscopy with the aim of determining the structure and site-specific magnetism of this tetragonal, D 022 -structure Heusler compound. High-quality epitaxial films with low root-mean-square surface roughness (˜0.6 nm) are grown by magnetron cosputtering. The tetragonal distortion induces strong perpendicular magnetic anisotropy along the c axis with a typical coercive field μ0H ˜0.8 T and an anisotropy field ranging from 6 to 8 T. On increasing the Fe content x , substantial uniaxial anisotropy, Ku≥1.0 MJm -3 , can be maintained over the full x range, while the magnetization of the compound is reduced from 400 to 280 kAm -1 . The total magnetization is almost entirely given by the sum of the spin moments originating from the ferrimagnetic Mn and Fe sublattices, with the latter being coupled ferromagnetically to one of the former. The orbital magnetic moments are practically quenched and have negligible contributions to the magnetization. The films with x =0.73 exhibit an anomalous Hall angle of 2.5 % and a Fermi-level spin polarization above 51 % , as measured by point contact Andreev reflection. The Fe-substituted Mn2Ga films are tunable with a unique combination of high anisotropy, low magnetization, appreciable spin polarization, and low surface roughness, making them strong candidates for thermally stable spin-transfer-torque switching nanomagnets with lateral dimensions down to 10 nm.

  7. Fe{sub 3}Si nanodots epitaxially grown on Si(111) substrates using ultrathin SiO{sub 2} film technique

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Yoshiaki, E-mail: nakamura@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Fukuda, Kenjiro; Amari, Shogo; Ichikawa, Masakazu [Department of Applied Physics, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2011-10-03

    Ultrahigh density (> 10{sup 12} cm{sup -2}) Fe{sub 3}Si nanodots (NDs) are epitaxially grown on Si(111) substrates by codeposition of Fe and Si on the ultrathin SiO{sub 2} films with ultrahigh density nanovoids. We used two kinds of methods for epitaxial growth: molecular beam epitaxy (MBE) and solid phase epitaxy. For MBE, low temperature (< 300 deg. C) growth of the Fe{sub 3}Si NDs is needed to suppress the interdiffusion between Fe atoms deposited on the surfaces and Si atoms in the substrate. These epitaxial NDs exhibited the ferromagnetism at low temperatures, which were expected in terms of the application to the magnetic memory device materials.

  8. Structure and magnetic properties of an epitaxial Fe(110)/MgO(111)/GaN(0001) heterostructure

    Science.gov (United States)

    Khalid, N.; Kim, J.-Y.; Ionescu, A.; Hussain, T.; Oehler, F.; Zhu, T.; Oliver, R. A.; Farrer, I.; Ahmad, R.; Barnes, C. H. W.

    2018-03-01

    We present the structural and magnetic properties of fully epitaxial Fe(110)/MgO(111)/GaN(0001) tunnel barrier structures grown by molecular beam epitaxy. In-situ reflection high-energy electron diffraction and ex-situ X-ray diffraction measurements indicate epitaxial Fe(110) films on top of an epitaxial 2 nm MgO(111) tunnel barrier on GaN(0001). X-ray reflectivity measurements confirm a roughness of approximately 0.3 nm and 0.7 nm for the MgO/GaN and the Fe/MgO interfaces, respectively. Results of in-situ magneto-optical Kerr effect measurements indicate that 1 nm thick Fe film shows signs of in-plane ferromagnetism at room temperature. Vibrating sample magnetometer measurements determine the saturation magnetisation of the 5 nm thick film to be 1660 ± 100 emu/cm3 and show that this system has a predominant uniaxial anisotropy contribution despite the presence of cyclic twinned crystals. We estimate the values of effective uniaxial ( KUeff) and cubic ( K1eff) anisotropy constants to be 11700 ± 170 erg cm-3 and -3300 ± 700 erg cm-3 by fitting the angular dependence of the magnetising energy.

  9. Impact of lattice dynamics on the phase stability of metamagnetic FeRh: Bulk and thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wolloch, M.; Gruner, M. E.; Keune, W.; Mohn, P.; Redinger, J.; Hofer, F.; Suess, D.; Podloucky, R.; Landers, J.; Salamon, S.; Scheibel, F.; Spoddig, D.; Witte, R.; Roldan Cuenya, B.; Gutfleisch, O.; Hu, M. Y.; Zhao, J.; Toellner, T.; Alp, E. E.; Siewert, M.; Entel, P.; Pentcheva, R.; Wende, H.

    2016-11-01

    We present phonon dispersions, element-resolved vibrational density of states (VDOS) and corresponding thermodynamic properties obtained by a combination of density functional theory (DFT) and nuclear resonant inelastic x-ray scattering (NRIXS) across the metamagnetic transition of B2 FeRh in the bulk material and thin epitaxial films. We see distinct differences in the VDOS of the antiferromagnetic (AF) and ferromagnetic (FM) phases, which provide a microscopic proof of strong spin-phonon coupling in FeRh. The FM VDOS exhibits a particular sensitivity to the slight tetragonal distortions present in epitaxial films, which is not encountered in the AF phase. This results in a notable change in lattice entropy, which is important for the comparison between thin film and bulk results. Our calculations confirm the recently reported lattice instability in the AF phase. The imaginary frequencies at the X point depend critically on the Fe magnetic moment and atomic volume. Analyzing these nonvibrational modes leads to the discovery of a stable monoclinic ground-state structure, which is robustly predicted from DFT but not verified in our thin film experiments. Specific heat, entropy, and free energy calculated within the quasiharmonic approximation suggest that the new phase is possibly suppressed because of its relatively smaller lattice entropy. In the bulk phase, lattice vibrations contribute with the same sign and in similar magnitude to the isostructural AF-FM phase transition as excitations of the electronic and magnetic subsystems demonstrating that lattice degrees of freedom need to be included in thermodynamic modeling.

  10. Ferromagnetism and nonmetallic transport of thin-film α-FeSi(2): a stabilized metastable material.

    Science.gov (United States)

    Cao, Guixin; Singh, D J; Zhang, X-G; Samolyuk, German; Qiao, Liang; Parish, Chad; Jin, Ke; Zhang, Yanwen; Guo, Hangwen; Tang, Siwei; Wang, Wenbin; Yi, Jieyu; Cantoni, Claudia; Siemons, Wolter; Payzant, E Andrew; Biegalski, Michael; Ward, T Z; Mandrus, David; Stocks, G M; Gai, Zheng

    2015-04-10

    A metastable phase α-FeSi_{2} was epitaxially stabilized on a silicon substrate using pulsed laser deposition. Nonmetallic and ferromagnetic behaviors are tailored on α-FeSi_{2} (111) thin films, while the bulk material of α-FeSi_{2} is metallic and nonmagnetic. The transport property of the films renders two different conducting states with a strong crossover at 50 K, which is accompanied by the onset of a ferromagnetic transition as well as a substantial magnetoresistance. These experimental results are discussed in terms of the unusual electronic structure of α-FeSi_{2} obtained within density functional calculations and Boltzmann transport calculations with and without strain. Our finding sheds light on achieving ferromagnetic semiconductors through both their structure and doping tailoring, and provides an example of a tailored material with rich functionalities for both basic research and practical applications.

  11. Development of thin pixel detectors on epitaxial silicon for HEP experiments

    International Nuclear Information System (INIS)

    Boscardin, Maurizio; Calvo, Daniela; Giacomini, Gabriele; Wheadon, Richard; Ronchin, Sabina; Zorzi, Nicola

    2013-01-01

    The foreseen luminosity of the new experiments in High Energy Physics will require that the innermost layer of vertex detectors will be able to sustain fluencies up to 10 16 n eq /cm 2 . Moreover, in many experiments there is a demand for the minimization of the material budget of the detectors. Therefore, thin pixel devices fabricated on n-type silicon are a natural choice to fulfill these requirements due to their rad-hard performances and low active volume. We present an R and D activity aimed at developing a new thin hybrid pixel device in the framework of PANDA experiments. The detector of this new device is a p-on-n pixel sensor realized starting from epitaxial silicon wafers and back thinned up to 50–100 μm after process completion. We present the main technological steps and some electrical characterization on the fabricated devices before and after back thinning and after bump bonding to the front-end electronics

  12. Development of thin pixel detectors on epitaxial silicon for HEP experiments

    Energy Technology Data Exchange (ETDEWEB)

    Boscardin, Maurizio, E-mail: boscardi@fbk.eu [FBK, CMM, Via Sommarive 18, I-38123 Povo, Trento (Italy); Calvo, Daniela [INFN and Dipartimento di Fisica, Università di Torino, Via Pietro Giuria, I-10125 Torino (Italy); Giacomini, Gabriele [FBK, CMM, Via Sommarive 18, I-38123 Povo, Trento (Italy); Wheadon, Richard [INFN and Dipartimento di Fisica, Università di Torino, Via Pietro Giuria, I-10125 Torino (Italy); Ronchin, Sabina; Zorzi, Nicola [FBK, CMM, Via Sommarive 18, I-38123 Povo, Trento (Italy)

    2013-08-01

    The foreseen luminosity of the new experiments in High Energy Physics will require that the innermost layer of vertex detectors will be able to sustain fluencies up to 10{sup 16} n{sub eq}/cm{sup 2}. Moreover, in many experiments there is a demand for the minimization of the material budget of the detectors. Therefore, thin pixel devices fabricated on n-type silicon are a natural choice to fulfill these requirements due to their rad-hard performances and low active volume. We present an R and D activity aimed at developing a new thin hybrid pixel device in the framework of PANDA experiments. The detector of this new device is a p-on-n pixel sensor realized starting from epitaxial silicon wafers and back thinned up to 50–100 μm after process completion. We present the main technological steps and some electrical characterization on the fabricated devices before and after back thinning and after bump bonding to the front-end electronics.

  13. Epitaxial growth of BiFeO3 films on TiN under layers by sputtering deposition

    Directory of Open Access Journals (Sweden)

    Yue Wang

    2017-05-01

    Full Text Available BiFeO3/TiN/MgO (001 films have been prepared by magneton sputtering, where TiN serves as a conductive under layer. X-ray diffraction profiles and cross-sectional transmission electron microscopy images reveal that not only (001-epitaxial BiFeO3 films are obtained, but also both tetragonal and rhombohedral phases co-exist in BiFeO3 films. Their crystallographic relationship is shown as following: tetragonal-BiFeO3 (001 [100]//TiN (001 [100]//MgO (001 [100] and rhombohedral-BiFeO3 (001 [100]//TiN (001 [100]//MgO (001 [100]. Besides, an oxidized TiN layer (∼ 20 nm has also been detected between BiFeO3 and TiN layers and its formation may originate from oxygen inter-diffusion from BiFeO3 layer. Despite of the existence of the oxidized TiN layer, it does not affect the epitaxial growth of BiFeO3 films. On the other hand, the coercivity electric field obtained in ferroelectric loop of BiFeO3 is greatly enhanced to 49 MV/cm due to the existence of oxidized TiN layer.

  14. Antidot density dependence of magnetization reversal dynamics in ultrathin epitaxial Fe/GaAs(001)

    International Nuclear Information System (INIS)

    Moore, T A; Wastlbauer, G; Bland, J A C; Cambril, E; Natali, M; Decanini, D; Chen, Y

    2004-01-01

    Easy axis dynamic magneto-optic Kerr effect loops have been measured from ultrathin (2 nm) epitaxial Fe/GaAs(001) films patterned with arrays of 1 μm square antidots of different densities (antidot spacings 10-50 μm). The applied field was sinusoidal with frequency f = 0.01 Hz-2.3 kHz. A study of dynamic coercivity H c * as a function of f reveals an intermediate dynamic regime (20 Hz c * that is suppressed at high antidot density. The dip is attributed to timescale matching of the sweeping applied field with the domain wall propagation in the film. Suppression of the dip is explained by an increase of domain nucleation in the higher antidot density films in the intermediate dynamic regime. (letter to the editor)

  15. Optimization studies of HgSe thin film deposition by electrochemical atomic layer epitaxy (EC-ALE)

    CSIR Research Space (South Africa)

    Venkatasamy, V

    2006-06-01

    Full Text Available Studies of the optimization of HgSe thin film deposition using electrochemical atomic layer epitaxy (EC-ALE) are reported. Cyclic voltammetry was used to obtain approximate deposition potentials for each element. These potentials were then coupled...

  16. Physicochemical analysis of Bi2Te3 – (Fe, Eu – Bi2Te3 junctions grown by molecular beam epitaxy method

    Directory of Open Access Journals (Sweden)

    K. Balin

    2017-05-01

    Full Text Available Topological insulators (TI are a class of materials gaining in importance due to their unique spin/electronic properties, which may allow for the generation of quasiparticles and electronic states which are not accessible in classical condensed-matter systems. Not surprisingly, TI are considered as promising materials for multiple applications in next generation electronic or spintronic devices, as well as for applications in energy conversion, such as thermo-electrics. In this study, we examined the practical challenges associated with the formation of a well-defined junction between a model 3D topological insulator, Bi2Te3, and a metal, Fe or Eu, from which spin injection could potentially be realized. The properties of multilayer systems grown by molecular beam epitaxy (MBE, with Fe or Eu thin films sandwiched between two Bi2Te3 layers, were studied in-situ using electron diffraction and photoelectron spectroscopy. Their magnetic properties were measured using a SQUID magnetometer, while the in-depth chemical structure was assessed using secondary ion mass spectroscopy. An examination of impact of Bi2Te3 structure on chemical stability of the junction area has been realized. For Fe, we found that despite room temperature growth, a reaction between the Fe film and Bi2Te3 takes place, leading to the formation of FeTe and also the precipitation of metallic Bi. For the Eu tri-layer, a reaction also occurs, but the Te chemical state remains intact.

  17. Unit cell determination of epitaxial thin films based on reciprocal space vectors by high-resolution X-ray diffractometry

    OpenAIRE

    Yang, Ping; Liu, Huajun; Chen, Zuhuang; Chen, Lang; Wang, John

    2013-01-01

    A new approach, based on reciprocal space vectors (RSVs), is developed to determine Bravais lattice types and accurate lattice parameters of epitaxial thin films by high-resolution X-ray diffractometry (HR-XRD). The lattice parameters of single crystal substrates are employed as references to correct the systematic experimental errors of RSVs of thin films. The general procedure is summarized, involving correction of RSVs, derivation of raw unit cell, subsequent conversion to the Niggli unit ...

  18. In-situ grazing incidence X-ray diffraction measurements of relaxation in Fe/MgO/Fe epitaxial magnetic tunnel junctions during annealing

    Energy Technology Data Exchange (ETDEWEB)

    Eastwood, D.S. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Ali, M.; Hickey, B.J. [Department of Physics and Astronomy, University of Leeds, Leeds LS2 1JT (United Kingdom); Tanner, B.K., E-mail: b.k.tanner@dur.ac.uk [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)

    2013-12-15

    The relaxation of Fe/MgO/Fe tunnel junctions grown epitaxially on (001) MgO substrates has been measured by in-situ grazing incidence in-plane X-ray diffraction during the thermal annealing cycle. We find that the Fe layers are fully relaxed and that there are no irreversible changes during annealing. The MgO tunnel barrier is initially strained towards the Fe but on annealing, relaxes and expands towards the bulk MgO value. The strain dispersion is reduced in the MgO by about 40% above 480 K post-annealing. There is no significant change in the “twist” mosaic. Our results indicate that the final annealing stage of device fabrication, crucial to attainment of high TMR, induces substantial strain relaxation at the MgO barrier/lower Fe electrode interface. - Highlights: • Lattice relaxation of Fe/MgO/Fe epitaxial magnetic tunnel junctions measured. • In-plane lattice parameter of Fe equal to bulk value; totally relaxed. • MgO barrier initially strained towards the Fe but relaxes on annealing. • Reduction in strain dispersion in the MgO barrier by 40% above about 470 K. • No change in the in-plane “twist” mosaic throughout the annealing cycle.

  19. Single orientation graphene synthesized on iridium thin films grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Dangwal Pandey, A., E-mail: arti.pandey@desy.de; Grånäs, E.; Shayduk, R.; Noei, H.; Vonk, V. [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Krausert, K.; Franz, D.; Müller, P.; Keller, T. F.; Stierle, A., E-mail: andreas.stierle@desy.de [Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg (Germany); Fachbereich Physik, Universität Hamburg, D-22607 Hamburg (Germany)

    2016-08-21

    Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated systematically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Our study reveals (111) oriented iridium films with high crystalline quality and extremely low surface roughness, on which the formation of large-area epitaxial graphene is achieved. The presence of defects, like dislocations, twins, and 30° rotated domains in the iridium films is also discussed. The coverage of graphene was found to be influenced by the presence of 30° rotated domains in the Ir films. Low iridium deposition rates suppress these rotated domains and an almost complete coverage of graphene was obtained. This synthesis route yields inexpensive, air-stable, and large-area graphene with a well-defined orientation, making it accessible to a wider community of researchers for numerous experiments or applications, including those which use destructive analysis techniques or irreversible processes. Moreover, this approach can be used to tune the structural quality of graphene, allowing a systematic study of the influence of defects in various processes like intercalation below graphene.

  20. Thin-film GaN Schottky diodes formed by epitaxial lift-off

    Science.gov (United States)

    Wang, Jingshan; Youtsey, Chris; McCarthy, Robert; Reddy, Rekha; Allen, Noah; Guido, Louis; Xie, Jinqiao; Beam, Edward; Fay, Patrick

    2017-04-01

    The performance of thin-film GaN Schottky diodes fabricated using a large-area epitaxial lift-off (ELO) process is reported in this work. Comparison of the device characteristics before and after lift-off processing reveals that the Schottky barrier height remains unchanged by the liftoff processing and is consistent with expectations based on metal-semiconductor work function differences, with a barrier height of approximately 1 eV obtained for Ni/Au contacts on n- GaN. However, the leakage current in both reverse and low-forward-bias regimes is found to improve significantly after ELO processing. Likewise, the ideality factor of the Schottky diodes also improves after ELO processing, decreasing from n = 1.12-1.18 before ELO to n = 1.04-1.10 after ELO. A possible explanation for the performance improvement obtained for Schottky diodes after substrate removal by ELO processing is the elimination of leakage paths consisting of vertical leakage along threading dislocations coupled with lateral conduction through the underlying n+ buffer layer that is removed in the ELO process. Epitaxial liftoff with GaN may enable significant improvement in device performance and economics for GaN-based electronics and optoelectronics.

  1. In-plane microwave dielectric properties of paraelectric barium strontium titanate thin films with anisotropic epitaxy

    Science.gov (United States)

    Simon, W. K.; Akdogan, E. K.; Safari, A.; Bellotti, J. A.

    2005-08-01

    In-plane dielectric properties of ⟨110⟩ oriented epitaxial (Ba0.60Sr0.40)TiO3 thin films in the thickness range from 25-1200nm have been investigated under the influence of anisotropic epitaxial strains from ⟨100⟩ NdGaO3 substrates. The measured dielectric properties show strong residual strain and in-plane directional dependence. Below 150nm film thickness, there appears to be a phase transition due to the anisotropic nature of the misfit strain relaxation. In-plane relative permittivity is found to vary from as much as 500-150 along [11¯0] and [001] respectively, in 600nm thick films, and from 75 to 500 overall. Tunability was found to vary from as much as 54% to 20% in all films and directions, and in a given film the best tunability is observed along the compressed axis in a mixed strain state, 54% along [11¯0] in the 600nm film for example.

  2. Strain induced room temperature ferromagnetism in epitaxial magnesium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Zhenghe; Kim, Ki Wook [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Nori, Sudhakar; Lee, Yi-Fang; Narayan, Jagdish [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Kumar, D. [Department of Mechanical Engineering, North Carolina A & T State University, Greensboro, North Carolina 27411 (United States); Wu, Fan [Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, New Jersey 08540 (United States); Prater, J. T. [Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States)

    2015-10-28

    We report on the epitaxial growth and room-temperature ferromagnetic properties of MgO thin films deposited on hexagonal c-sapphire substrates by pulsed laser deposition. The epitaxial nature of the films has been confirmed by both θ-2θ and φ-scans of X-ray diffraction pattern. Even though bulk MgO is a nonmagnetic insulator, we have found that the MgO films exhibit ferromagnetism and hysteresis loops yielding a maximum saturation magnetization up to 17 emu/cc and large coercivity, H{sub c} = 1200 Oe. We have also found that the saturation magnetization gets enhanced and that the crystallization degraded with decreased growth temperature, suggesting that the origin of our magnetic coupling could be point defects manifested by the strain in the films. X-ray (θ-2θ) diffraction peak shift and strain analysis clearly support the presence of strain in films resulting from the presence of point defects. Based on careful investigations using secondary ion mass spectrometer and X-ray photoelectron spectroscopy studies, we have ruled out the possibility of the presence of any external magnetic impurities. We discuss the critical role of microstructural characteristics and associated strain on the physical properties of the MgO films and establish a correlation between defects and magnetic properties.

  3. Structural and electrical properties of evaporated Fe thin films

    International Nuclear Information System (INIS)

    Mebarki, M.; Layadi, A.; Guittoum, A.; Benabbas, A.; Ghebouli, B.; Saad, M.; Menni, N.

    2011-01-01

    Series of Fe thin films have been prepared by thermal evaporation onto glass and Si(1 0 0) substrates. The Rutherford backscattering (RBS), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and the four point probe techniques have been used to investigate the structural and electrical properties of these Fe thin films as a function of the substrate, the Fe thickness t in the 76-431 nm range and the deposition rate. The Fe/Si samples have a for all thicknesses, whereas the Fe/glass grows with a strong texture; as t increases (>100 nm), the preferred orientation changes to . The compressive stress in Fe/Si remains constant over the whole thickness range and is greater than the one in Fe/glass which is relieved when t > 100 nm. The grain size D values are between 9.2 and 30 nm. The Fe/glass films are more electrically resistive than the Fe/Si(1 0 0) ones. Diffusion at the grain boundary seems to be the predominant factor in the electrical resistivity ρ values with the reflection coefficient R greater in Fe/glass than in Fe/Si. For the same thickness (100 nm), the decrease of the deposition rate from 4.3 to 0.3 A/s did not affect the texture and the reflection coefficient R but led to an increase in D and a decrease in the strain and in ρ for both Fe/glass and Fe/Si systems. On the other hand, keeping the same deposition rate (0.3 A/s) and increasing the thickness t from 76 to 100 nm induced different changes in the two systems.

  4. Strain-Dependence of the Structure and Ferroic Properties of Epitaxial NiTiO3 Thin Films Grown on Different Substrates

    Directory of Open Access Journals (Sweden)

    Tamas Varga

    2015-01-01

    Full Text Available Polarization-induced weak ferromagnetism has been predicted a few years back in perovskite MTiO3 (M = Fe, Mn, and Ni. We set out to stabilize this metastable perovskite structure by growing NiTiO3 epitaxially on different substrates and to investigate the dependence of polar and magnetic properties on strain. Epitaxial NiTiO3 films were deposited on Al2O3, Fe2O3, and LiNbO3 substrates by pulsed laser deposition and characterized using several techniques. The effect of substrate choice on lattice strain, film structure, and physical properties was investigated. Our structural data from X-ray diffraction and electron microscopy shows that substrate-induced strain has a marked effect on the structure and crystalline quality of the films. Physical property measurements reveal a dependence of the weak ferromagnetism and lattice polarization on strain and highlight our ability to control the ferroic properties in NiTiO3 thin films by the choice of substrate. Our results are also consistent with the theoretical prediction that the ferromagnetism in acentric NiTiO3 is polarization induced. From the substrates studied here, the perovskite substrate LiNbO3 proved to be the most promising one for strong multiferroism.

  5. Extremely smooth YBa 2Cu 3O 7- δ "thin" film grown by liquid phase epitaxy

    Science.gov (United States)

    Hao, Z.; Wu, Y.; Enomoto, Y.; Tanabe, K.; Koshizuka, N.

    2002-02-01

    Extremely smooth single crystal YBa 2Cu 3O 7- δ "thin" films, 1-3 μm thick, have been successfully grown on YBCO-seeded MgO substrates by liquid phase epitaxy. The morphology study on the as-grown samples has revealed a step-flow growth mechanism, with each step height of about 1.1 nm, i.e. the c-axis lattice constant of YBCO. The mean surface roughness in a large 25 μm×25 μm area is ˜0.76 nm, determined by an atomic force microscope. After annealing in pure oxygen, the ˜2 μm thick films exhibit high-quality high- Tc superconductivity with zero resistance transition temperature TC0≈91 K and critical current density JC=4.74×10 4 A/cm 2 (transport measurement with 1 μV/cm criterion) at 77 K.

  6. Flexoelectricity induced increase of critical thickness in epitaxial ferroelectric thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Hao [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Hong Jiawang; Zhang Yihui [Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China); Li Faxin [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Pei Yongmao, E-mail: peiym@pku.edu.cn [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Fang Daining, E-mail: fangdn@pku.edu.cn [State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871 (China); Department of Engineering Mechanics, Tsinghua University, Beijing 100084 (China)

    2012-09-01

    Flexoelectricity describes the coupling between polarization and strain/stress gradients in insulating crystals. In this paper, using the Landau-Ginsburg-Devonshire phenomenological approach, we found that flexoelectricity could increase the theoretical critical thickness in epitaxial BaTiO{sub 3} thin films, below which the switchable spontaneous polarization vanishes. This increase is remarkable in tensile films while trivial in compressive films due to the electrostriction caused decrease of potential barrier, which can be easily destroyed by the flexoelectricity, between the ferroelectric state and the paraelectric state in tensile films. In addition, the films are still in a uni-polar state even below the critical thickness due to the flexoelectric effect.

  7. 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.

  8. Doping site dependent thermoelectric properties of epitaxial strontium titanate thin films

    KAUST Repository

    Abutaha, Anas I.

    2014-01-01

    We demonstrate that the thermoelectric properties of epitaxial strontium titanate (STO) thin films can be improved by additional B-site doping of A-site doped ABO3 type perovskite STO. The additional B-site doping of A-site doped STO results in increased electrical conductivity, but at the expense of Seebeck coefficient. However, doping on both sites of the STO lattice significantly reduces the lattice thermal conductivity of STO by adding more densely and strategically distributed phononic scattering centers that attack wider phonon spectra. The additional B-site doping limits the trade-off relationship between the electrical conductivity and total thermal conductivity of A-site doped STO, leading to an improvement in the room-temperature thermoelectric figure of merit, ZT. The 5% Pr3+ and 20% Nb5+ double-doped STO film exhibits the best ZT of 0.016 at room temperature. This journal is

  9. CeCo5 thin films with perpendicular anisotropy grown by molecular beam epitaxy

    Science.gov (United States)

    Sharma, S.; Hildebrandt, E.; Major, M.; Komissinskiy, P.; Radulov, I.; Alff, L.

    2018-04-01

    Buffer-free, highly textured (0 0 1) oriented CeCo5 thin films showing perpendicular magnetic anisotropy were synthesized on (0 0 1) Al2O3 substrates by molecular beam epitaxy. Ce exists in a mixture of Ce3+ and Ce4+ valence states as shown by X-ray photoelectron spectroscopy. The first anisotropy constant, K1, as measured by torque magnetometry was 0.82 MJ/m3 (8.2 ×106erg /cm3) . A maximum coercivity of 5.16 kOe with a negative temperature coefficient of -0.304%K-1 and a magnetization of 527.30 emu/cm3 was measured perpendicular to the film plane at 5 K. In addition, a large anisotropy of the magnetic moment of 15.5% was observed. These magnetic parameters make CeCo5 a potential candidate material for spintronic and magnetic recording applications.

  10. The effect of a thin silver layer on the critical current of epitaxial YBCO films

    International Nuclear Information System (INIS)

    Polturak, E.; Koren, G.; Cohen, D.; Cohen, D.; Snapiro, I.

    1992-01-01

    We compare measurements of the critical current density of an epitaxial YBCO film with that of an identical film overlaid by a thin silver layer. We find that the presence of the silver lowers Tc of the film by about 1.5 K, which is two orders of magnitude larger than predicted by the theory of the proximity effect for our experimental conditions. In addition, J c of the Ag/YBCO film near Tc is also significantly lower than that of the bare YBCO film. We propose two alternate interpretations of this effect, one in terms of destabilization of the flux distribution in the film and the other making use of the effect of the silver on the Bean-Livingston surface barrier for the initial penetration of flux. The latter seems the more plausible explanation of our results. (orig.)

  11. Resistance switching in epitaxial SrCoO{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk, E-mail: cu-jung@hufs.ac.kr [Department of Physics, Hankuk University of Foreign Studies, Yongin 449-791 (Korea, Republic of); Kim, Yeon Soo; Park, Bae Ho [Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-791 (Korea, Republic of); Jeong, Huiseong; Park, Ji-Yong [Department of Physics and Division of Energy System Research, Ajou University, Suwon 443-749 (Korea, Republic of); Cho, Myung Rae; Park, Yun Daniel [Department of Physics and Astronomy and Center for Subwavelength Optics, Seoul National University, Seoul 151-747 (Korea, Republic of); Choi, Woo Seok [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Dong-Wook [Department of Physics, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Jin, Hyunwoo; Lee, Suyoun [Electronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong [Department of Material Science and Engineering, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-08-11

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO{sub 3} (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO{sub 2.5}) and conducting perovskite (SrCoO{sub 3−δ}) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO{sub x} thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO{sub 2.5}.

  12. High efficiency thin film solar cells grown by molecular beam epitaxy (HEFTY)

    Energy Technology Data Exchange (ETDEWEB)

    Mason, N.B.; Barnham, K.W.J.; Ballard, I.M.; Zhang, J. [Imperial College, London (United Kingdom)

    2006-05-04

    The project sought to show the UK as a world leader in the field of thin film crystalline solar cells. A premise was that the cell design be suitable for large-scale manufacturing and provide a basis for industrial exploitation. The study demonstrated (1) that silicon films grown at temperatures suitable for deposition on glass by Gas Phase Molecular Beam Epitaxy gives better PV cells than does Ultra Low Pressure Chemical Vapor Deposition; (2) a conversion energy of 15 per cent was achieved - the project target was 18 per cent and (3) one of the highest reported conversion efficiencies for a 15 micrometre silicon film was achieved. The study was carried out by BP Solar Limited under contract to the DTI.

  13. Epitaxial growth and electronic structure of oxyhydride SrVO{sub 2}H thin films

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Tsukasa; Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Yamada, Keisuke; Onozuka, Tomoya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Shigematsu, Kei [Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan); Minohara, Makoto; Kumigashira, Hiroshi [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Mikazuki-cho, Hyogo 679-5198 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan)

    2016-08-28

    Oxyhydride SrVO{sub 2}H epitaxial thin films were fabricated on SrTiO{sub 3} substrates via topotactic hydridation of oxide SrVO{sub 3} films using CaH{sub 2}. Structural and composition analyses suggested that the SrVO{sub 2}H film possessed one-dimensionally ordered V-H{sup −}-V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO{sub 2}H film was reversible to SrVO{sub 3} by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V{sup 3+} valence state in the SrVO{sub 2}H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

  14. Interfacial Exchange Coupling Induced Anomalous Anisotropic Magnetoresistance in Epitaxial γ′-Fe 4 N/CoN Bilayers

    KAUST Repository

    Li, Zirun

    2015-02-02

    Anisotropic magnetoresistance (AMR) of the facing-target reactively sputtered epitaxial γ′-Fe4N/CoN bilayers is investigated. The phase shift and rectangular-like AMR appears at low temperatures, which can be ascribed to the interfacial exchange coupling. The phase shift comes from the exchange bias (EB) that makes the magnetization lag behind a small field. When the γ′-Fe4N thickness increases, the rectangular-like AMR appears. The rectangular-like AMR should be from the combined contributions including the EB-induced unidirectional anisotropy, intrinsic AMR of γ′-Fe4N layer and interfacial spin scattering.

  15. Charge ordering in reactive sputtered (1 0 0) and (1 1 1) oriented epitaxial Fe3O4 films

    KAUST Repository

    Mi, Wenbo

    2013-06-01

    Epitaxial Fe3O4 films with (1 0 0) and (1 1 1) orientations fabricated by reactive sputtering present simultaneous magnetic and electrical transitions at 120 and 124 K, respectively. The symmetry decreases from face-centered cubic to monoclinic structure across the Verwey transition. Extra spots with different brightness at different positions appear in selected-area diffraction patterns at 95 K. The extra spots come from the charge ordering of outer-layer electrons of Fe atoms, and should be related to the charge ordering of octahedral B-site Fe atoms. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  16. Epitaxial thin films of Dirac semimetal antiperovskite Cu3PdN

    Science.gov (United States)

    Quintela, C. X.; Campbell, N.; Shao, D. F.; Irwin, J.; Harris, D. T.; Xie, L.; Anderson, T. J.; Reiser, N.; Pan, X. Q.; Tsymbal, E. Y.; Rzchowski, M. S.; Eom, C. B.

    2017-09-01

    The growth and study of materials showing novel topological states of matter is one of the frontiers in condensed matter physics. Among this class of materials, the nitride antiperovskite Cu3PdN has been proposed as a new three-dimensional Dirac semimetal. However, the experimental realization of Cu3PdN and the consequent study of its electronic properties have been hindered due to the difficulty of synthesizing this material. In this study, we report fabrication and both structural and transport characterization of epitaxial Cu3PdN thin films grown on (001)-oriented SrTiO3 substrates by reactive magnetron sputtering and post-annealed in NH3 atmosphere. The structural properties of the films, investigated by x-ray diffraction and scanning transmission electron microscopy, establish single phase Cu3PdN exhibiting cube-on-cube epitaxy (001)[100]Cu3PdN||(001)[100]SrTiO3. Electrical transport measurements of as-grown samples show metallic conduction with a small temperature coefficient of the resistivity of 1.5 × 10-4 K-1 and a positive Hall coefficient. Post-annealing in NH3 results in the reduction of the electrical resistivity accompanied by the Hall coefficient sign reversal. Using a combination of chemical composition analyses and ab initio band structure calculations, we discuss the interplay between nitrogen stoichiometry and magneto-transport results in the framework of the electronic band structure of Cu3PdN. Our successful growth of thin films of antiperovskite Cu3PdN opens the path to further investigate its physical properties and their dependence on dimensionality, strain engineering, and doping.

  17. Epitaxial thin films of Dirac semimetal antiperovskite Cu3PdN

    Directory of Open Access Journals (Sweden)

    C. X. Quintela

    2017-09-01

    Full Text Available The growth and study of materials showing novel topological states of matter is one of the frontiers in condensed matter physics. Among this class of materials, the nitride antiperovskite Cu3PdN has been proposed as a new three-dimensional Dirac semimetal. However, the experimental realization of Cu3PdN and the consequent study of its electronic properties have been hindered due to the difficulty of synthesizing this material. In this study, we report fabrication and both structural and transport characterization of epitaxial Cu3PdN thin films grown on (001-oriented SrTiO3 substrates by reactive magnetron sputtering and post-annealed in NH3 atmosphere. The structural properties of the films, investigated by x-ray diffraction and scanning transmission electron microscopy, establish single phase Cu3PdN exhibiting cube-on-cube epitaxy (001[100]Cu3PdN||(001[100]SrTiO3. Electrical transport measurements of as-grown samples show metallic conduction with a small temperature coefficient of the resistivity of 1.5 × 10−4 K−1 and a positive Hall coefficient. Post-annealing in NH3 results in the reduction of the electrical resistivity accompanied by the Hall coefficient sign reversal. Using a combination of chemical composition analyses and ab initio band structure calculations, we discuss the interplay between nitrogen stoichiometry and magneto-transport results in the framework of the electronic band structure of Cu3PdN. Our successful growth of thin films of antiperovskite Cu3PdN opens the path to further investigate its physical properties and their dependence on dimensionality, strain engineering, and doping.

  18. 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.

  19. Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy

    OpenAIRE

    Kawashima, Kazuhiro; Okamoto, Yuji; Annayev, Orazmuhammet; Toyokura, Nobuo; Takahashi, Ryota; Lippmaa, Mikk; Itaka, Kenji; Suzuki, Yoshikazu; Matsuki, Nobuyuki; Koinuma, Hideomi

    2017-01-01

    Abstract As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic?inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thic...

  20. Oxygen-dependent epitaxial growth of Pt(001) thin films on MgO(001) by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, X.Y., E-mail: qxy2001@swu.edu.cn [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Wang, R.X.; Li, G.Q.; Zhang, T.; Li, L.T.; Wei, M.L.; Meng, X.S. [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Ji, H. [School of Energy Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Zhang, Z.; Chan, C.H.; Dai, J.Y. [Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong (China)

    2017-06-01

    Highlights: • The optimized oxygen ratio for high-quality epitaxial Pt (001) thin films is 15%. • Platinum oxides is formed after the oxygen ratio is more than 30%. • Epitaxial growth of Pt on MgO(001) is cube to cube with Pt(001)//MgO(001). - Abstract: The roles of oxygen gas in crystal orientation, surface morphology and electrical resistivity of Pt thin films grown on MgO(001) substrate by magnetron sputtering are studied. With a well-controlled oxygen ratio (15% oxygen) during sputtering deposition with Ar-O{sub 2} mixture ambient, (001) epitaxial growth of Pt film on MgO substrate is achieved with an epitaxial orientation relationship of (001)Pt//(001)MgO and [100]Pt//[100]MgO. Microstructural and electrical characterizations reveal that the (001) Pt thin films possess very smooth surface and good conductivity. The formation and subsequent decomposition of platinum oxides in the Pt films grown with more than 30% oxygen result in an increase of surface roughness and electrical resistivity. The high-quality Pt(001) film has large potential for integrated electronic device applications.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    Highlights: • LaFeO 3 was grown by molecular beam epitaxy on ZrO 2 :Y 2 O 3 . • The film was highly oriented but not single crystalline. • Angle resolved XPS revealed differences between surface and bulk oxygen. • Annealing the film in vacuum resulted in the sequential reduction of Fe cations. • A greater degree of Fe reduction was found at the surface. - Abstract: The mixed electronic and ionic conductivity of perovskite oxides has enabled their use in diverse applications such as automotive exhaust catalysts, solid oxide fuel cell cathodes, and visible light photocatalysts. The redox chemistry at the surface of perovskite oxides is largely dependent on the oxidation state of the metal cations as well as the oxide surface stoichiometry. In this study, LaFeO 3 (LFO) thin films grown on yttria-stabilized zirconia (YSZ) was characterized using both bulk and surface sensitive techniques. A combination of in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) demonstrated that the film is primarily textured in the [1 0 0] direction and is stoichiometric. High-resolution transmission electron microscopy measurements show regions that are dominated by [1 0 0] oriented LFO grains that are oriented with respect to the substrates lattice. However, selected regions of the film show multiple domains of grains that are not [1 0 0] oriented. The film was annealed in an ultra-high vacuum chamber to simulate reducing conditions and studied by angle-resolved X-ray photoelectron spectroscopy (XPS). Iron was found to exist as Fe(0), Fe(II), and Fe(III) depending on the annealing conditions and the depth within the film. A decrease in the concentration of surface oxygen species was correlated with iron reduction. These results should help guide and enhance the design of LFO materials for catalytic applications

  2. Electronic and optical properties of La-doped S r3I r2O7 epitaxial thin films

    Science.gov (United States)

    Souri, M.; Terzic, J.; Johnson, J. M.; Connell, J. G.; Gruenewald, J. H.; Thompson, J.; Brill, J. W.; Hwang, J.; Cao, G.; Seo, A.

    2018-02-01

    We have investigated structural, transport, and optical properties of tensile strained (Sr1-xL ax ) 3I r2O7 (x =0 , 0.025, 0.05) epitaxial thin films. While high-Tc superconductivity is predicted theoretically in the system, we have observed that all of the samples remain insulating with finite optical gap energies and Mott variable-range hopping characteristics in transport. Cross-sectional scanning transmission electron microscopy indicates that structural defects such as stacking faults appear in this system. The insulating behavior of the La-doped S r3I r2O7 thin films is presumably due to disorder-induced localization and ineffective electron doping of La, which brings to light the intriguing difference between epitaxial thin films and bulk single crystals of the iridates.

  3. Preparation and structure characterization of SmCo5(0001) epitaxial thin films grown on Cu(111) underlayers

    International Nuclear Information System (INIS)

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

    2009-01-01

    SmCo 5 (0001) epitaxial films were prepared on Cu(111) single-crystal underlayers formed on Al 2 O 3 (0001) substrates at 500 deg. C. The nucleation and growth mechanism of (0001)-oriented SmCo 5 crystal on Cu(111) underlayer is investigated and a method to control the nucleation is proposed. The SmCo 5 epitaxial thin film formed directly on Cu underlayer consists of two types of domains whose orientations are rotated around the film normal by 30 deg. each other. By introducing a thin Co seed layer on the Cu underlayer, a SmCo 5 (0001) single-crystal thin film is successfully obtained. Nucleation of SmCo 5 crystal on Cu underlayer seems controllable by varying the interaction between the Cu underlayer and the SmCo 5 layer

  4. Magnetic anisotropy of epitaxial Fe layers grown on Si(0 0 1)

    International Nuclear Information System (INIS)

    Bertoncini, P.; Wetzel, P.; Berling, D.; Mehdaoui, A.; Loegel, B.; Gewinner, G.; Poinsot, R.; Pierron-Bohnes, V.

    2001-01-01

    The magnetic properties of epitaxial iron films up to 80 monolayers (ML) thickness grown on Si(0 0 1) by using a template technique were investigated by means of superconducting quantum interference device and magneto-optic Kerr effect techniques. The thinnest films investigated (∼3 ML) exhibit a composition close to Fe 3 Si with a Curie temperature below room temperature (RT) and strong out-of-plane remanent magnetization that reflects the presence of a dominant second order surface anisotropy term. Thicker films (≥4 ML) are ferromagnetic at RT with remanent magnetization in film-plane and a composition closer to pure Fe with typically 8-10% silicon content. When deposited at normal incidence such films show simple in-plane fourfold anisotropy without uniaxial contribution. The relevant fourth-order effective anisotropy constant K 4 eff was measured versus film thickness and found to change its sign near 18 ML. The origin of this remarkable behavior is investigated by means of a Neel model and mainly traced back to fourth-order surface anisotropy and magneto-elastic effects related to the large biaxial in-plane compressive strain up to 3.5% in the thinnest (≤25 ML) films

  5. General Top-Down Ion Exchange Process for the Growth of Epitaxial Chalcogenide Thin Films and Devices

    KAUST Repository

    Xia, Chuan

    2016-12-30

    We demonstrate a versatile top-down ion exchange process, done at ambient temperature, to form epitaxial chalcogenide films and devices, with nanometer scale thickness control. To demonstrate the versatility of our process we have synthesized (1) epitaxial chalcogenide metallic and semiconducting films and (2) free-standing chalcogenide films and (3) completed in situ formation of atomically sharp heterojunctions by selective ion exchange. Epitaxial NiCo2S4 thin films prepared by our process show 115 times higher mobility than NiCo2S4 pellets (23 vs 0.2 cm(2) V-1 s(-1)) prepared by previous reports. By controlling the ion exchange process time, we made free-standing epitaxial films of NiCo2S4 and transferred them onto different substrates. We also demonstrate in situ formation of atomically sharp, lateral Schottky diodes based on NiCo2O4/NiCo2S4 heterojunction, using a single ion exchange step. Additionally, we show that our approach can be easily extended to other chalcogenide semiconductors. Specifically, we used our process to prepare Cu1.8S thin films with mobility that matches single crystal Cu1.8S (25 cm(2) V-1 s(-1)), which is ca. 28 times higher than the previously reported Cu1.8S thin film mobility (0.58 cm(2) V-1 s(-1)), thus demonstrating the universal nature of our process. This is the first report in which chalcogenide thin films retain the epitaxial nature of the precursor oxide films, an approach that will be useful in many applications.

  6. Fabrication of highly spin-polarized Co2FeAl0.5Si0.5 thin-films

    Directory of Open Access Journals (Sweden)

    M. Vahidi

    2014-04-01

    Full Text Available Ferromagnetic Heusler Co2FeAl0.5Si0.5 epitaxial thin-films have been fabricated in the L21 structure with saturation magnetizations over 1200 emu/cm3. Andreev reflection measurements show that the spin polarization is as high as 80% in samples sputtered on unheated MgO (100 substrates and annealed at high temperatures. However, the spin polarization is considerably smaller in samples deposited on heated substrates.

  7. Mechanisms of stress generation and relaxation during pulsed laser deposition of epitaxial Fe-Pd magnetic shape memory alloy films on MgO

    International Nuclear Information System (INIS)

    Edler, Tobias; Mayr, S G; Buschbeck, Joerg; Mickel, Christine; Faehler, Sebastian

    2008-01-01

    Mechanical stress generation during epitaxial growth of Fe-Pd thin films on MgO from pulsed laser deposition is a key parameter for the suitability in shape memory applications. By employing in situ substrate curvature measurements, we determine the stress states as a function of film thickness and composition. Depending on composition, different stress states are observed during initial film growth, which can be attributed to different misfits. Compressive stress generation by atomic peening is observed in the later stages of growth. Comparison with ex situ x-ray based strain measurements allows integral and local stress to be distinguished and yields heterogeneities of the stress state between coherent and incoherent regions. In combination with cross-sectional TEM measurements the relevant stress relaxation mechanism is identified to be stress-induced martensite formation with (111) twinning

  8. Absence of strain-mediated magnetoelectric coupling at fully epitaxial Fe/BaTiO{sub 3} interface (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Radaelli, G., E-mail: greta.radaelli@gmail.com; Petti, D.; Cantoni, M.; Rinaldi, C.; Bertacco, R. [LNESS Center - Dipartimento di Fisica del Politecnico di Milano, Como 22100 (Italy)

    2014-05-07

    Interfacial MagnetoElectric coupling (MEC) at ferroelectric/ferromagnetic interfaces has recently emerged as a promising route to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO{sub 3} (BTO) system, various MEC mechanisms have been theoretically predicted. Experimentally, it is well established that using BTO single crystal substrates MEC is dominated by strain-mediated mechanisms. In case of ferromagnetic layers epitaxially grown onto BTO films, instead, no direct evidence for MEC has been provided, apart from the results obtained on tunneling junction sandwiching a BTO tunneling barrier. In this paper, MEC at fully epitaxial Fe/BTO interface is investigated by Magneto-Optical Kerr Effect and magnetoresistance measurements on magnetic tunnel junctions fabricated on BTO. We find no evidence for strain-mediated MEC mechanisms in epitaxial systems, likely due to clamping of BTO to the substrate. Our results indicate that pure electronic MEC is the route of choice to be explored for achieving the electrical writing of information in epitaxial ferromagnet-ferroelectric heterostructures.

  9. Absence of strain-mediated magnetoelectric coupling at fully epitaxial Fe/BaTiO3 interface (invited)

    International Nuclear Information System (INIS)

    Radaelli, G.; Petti, D.; Cantoni, M.; Rinaldi, C.; Bertacco, R.

    2014-01-01

    Interfacial MagnetoElectric coupling (MEC) at ferroelectric/ferromagnetic interfaces has recently emerged as a promising route to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO 3 (BTO) system, various MEC mechanisms have been theoretically predicted. Experimentally, it is well established that using BTO single crystal substrates MEC is dominated by strain-mediated mechanisms. In case of ferromagnetic layers epitaxially grown onto BTO films, instead, no direct evidence for MEC has been provided, apart from the results obtained on tunneling junction sandwiching a BTO tunneling barrier. In this paper, MEC at fully epitaxial Fe/BTO interface is investigated by Magneto-Optical Kerr Effect and magnetoresistance measurements on magnetic tunnel junctions fabricated on BTO. We find no evidence for strain-mediated MEC mechanisms in epitaxial systems, likely due to clamping of BTO to the substrate. Our results indicate that pure electronic MEC is the route of choice to be explored for achieving the electrical writing of information in epitaxial ferromagnet-ferroelectric heterostructures

  10. Understanding Strain‐Induced Phase Transformations in BiFeO3 Thin Films

    Science.gov (United States)

    Beekman, Christianne; Schlepütz, Christian M.; Siemons, Wolter; Yang, Yongsoo; Senabulya, Nancy; Clarke, Roy; Chi, Miaofang

    2015-01-01

    Experiments demonstrate that under large epitaxial strain a coexisting striped phase emerges in BiFeO3 thin films, which comprises a tetragonal‐like (T′) and an intermediate S′ polymorph. It exhibits a relatively large piezoelectric response when switching between the coexisting phase and a uniform T′ phase. This strain‐induced phase transformation is investigated through a synergistic combination of first‐principles theory and experiments. The results show that the S′ phase is energetically very close to the T′ phase, but is structurally similar to the bulk rhombohedral (R) phase. By fully characterizing the intermediate S′ polymorph, it is demonstrated that the flat energy landscape resulting in the absence of an energy barrier between the T′ and S′ phases fosters the above‐mentioned reversible phase transformation. This ability to readily transform between the S′ and T′ polymorphs, which have very different octahedral rotation patterns and c/a ratios, is crucial to the enhanced piezoelectricity in strained BiFeO3 films. Additionally, a blueshift in the band gap when moving from R to S′ to T′ is observed. These results emphasize the importance of strain engineering for tuning electromechanical responses or, creating unique energy harvesting photonic structures, in oxide thin film architectures. PMID:27980962

  11. Epitaxial ferromagnetic Fe3Si on GaAs(111)A with atomically smooth surface and interface

    International Nuclear Information System (INIS)

    Liu, Y. C.; Hung, H. Y.; Kwo, J.; Chen, Y. W.; Lin, Y. H.; Cheng, C. K.; Hong, M.; Tseng, S. C.; Hsu, C. H.; Chang, M. T.; Lo, S. C.

    2015-01-01

    Single crystal ferromagnetic Fe 3 Si(111) films were grown epitaxially on GaAs(111)A by molecular beam epitaxy. These hetero-structures possess extremely low surface roughness of 1.3 Å and interfacial roughness of 1.9 Å, measured by in-situ scanning tunneling microscope and X-ray reflectivity analyses, respectively, showing superior film quality, comparing to those attained on GaAs(001) in previous publications. The atomically smooth interface was revealed by the atomic-resolution Z (atomic number)-contrast scanning transmission electron microscopy (STEM) images using the correction of spherical aberration (Cs)-corrected electron probe. Excellent crystallinity and perfect lattice match were both confirmed by high resolution x-ray diffraction. Measurements of magnetic property for the Fe 3 Si/GaAs(111) yielded a saturation moment of 990 emu/cm 3 with a small coercive field ≤1 Oe at room temperature

  12. InGaN-based thin film solar cells: Epitaxy, structural design, and photovoltaic properties

    International Nuclear Information System (INIS)

    Sang, Liwen; Liao, Meiyong; Koide, Yasuo; Sumiya, Masatomo

    2015-01-01

    In x Ga 1−x N, with the tunable direct bandgaps from ultraviolet to near infrared region, offers a promising candidate for the high-efficiency next-generation thin-film photovoltaic applications. Although the adoption of thick InGaN film as the active region is desirable to obtain efficient light absorption and carrier collection compared to InGaN/GaN quantum wells structure, the understanding on the effect from structural design is still unclear due to the poor-quality InGaN films with thickness and difficulty of p-type doping. In this paper, we comprehensively investigate the effects from film epitaxy, doping, and device structural design on the performances of the InGaN-based solar cells. The high-quality InGaN thick film is obtained on AlN/sapphire template, and p-In 0.08 Ga 0.92 N is achieved with a high hole concentration of more than 10 18  cm −3 . The dependence of the photovoltaic performances on different structures, such as active regions and p-type regions is analyzed with respect to the carrier transport mechanism in the dark and under illumination. The strategy of improving the p-i interface by using a super-thin AlN interlayer is provided, which successfully enhances the performance of the solar cells

  13. InGaN-based thin film solar cells: Epitaxy, structural design, and photovoltaic properties

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Liwen, E-mail: SANG.Liwen@nims.go.jp [International Center for Material Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); JST-PRESTO, The Japan Science and Technology Agency, Tokyo 102-0076 (Japan); Liao, Meiyong; Koide, Yasuo [Wide Bandgap Materials Group, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Sumiya, Masatomo [Wide Bandgap Materials Group, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); JST-ALCA, The Japan Science and Technology Agency, Tokyo 102-0076 (Japan)

    2015-03-14

    In{sub x}Ga{sub 1−x}N, with the tunable direct bandgaps from ultraviolet to near infrared region, offers a promising candidate for the high-efficiency next-generation thin-film photovoltaic applications. Although the adoption of thick InGaN film as the active region is desirable to obtain efficient light absorption and carrier collection compared to InGaN/GaN quantum wells structure, the understanding on the effect from structural design is still unclear due to the poor-quality InGaN films with thickness and difficulty of p-type doping. In this paper, we comprehensively investigate the effects from film epitaxy, doping, and device structural design on the performances of the InGaN-based solar cells. The high-quality InGaN thick film is obtained on AlN/sapphire template, and p-In{sub 0.08}Ga{sub 0.92}N is achieved with a high hole concentration of more than 10{sup 18 }cm{sup −3}. The dependence of the photovoltaic performances on different structures, such as active regions and p-type regions is analyzed with respect to the carrier transport mechanism in the dark and under illumination. The strategy of improving the p-i interface by using a super-thin AlN interlayer is provided, which successfully enhances the performance of the solar cells.

  14. Persistent semi-metal-like nature of epitaxial perovskite CaIrO3 thin films

    International Nuclear Information System (INIS)

    Biswas, Abhijit; Jeong, Yoon Hee

    2015-01-01

    Strong spin-orbit coupled 5d transition metal based ABO 3 oxides, especially iridates, allow tuning parameters in the phase diagram and may demonstrate important functionalities, for example, by means of strain effects and symmetry-breaking, because of the interplay between the Coulomb interactions and strong spin-orbit coupling. Here, we have epitaxially stabilized high quality thin films of perovskite (Pv) CaIrO 3 . Film on the best lattice-matched substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile or compressive strain on the film by altering the underlying lattice-mismatched substrates still maintains semi-metallicity with minute modification of the effective correlation as tensile (compressive) strain results in tiny increases (decreases) of the electronic bandwidth. In addition, magnetoresistance remains positive with a quadratic field dependence. This persistent semi-metal-like nature of Pv-CaIrO 3 thin films with minute changes in the effective correlation by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide physics

  15. Spin-dependent transport in epitaxial Fe wires on GaAs(110); Spinabhaengiger Transport in epitaktischen Fe-Leiterbahnen auf GaAs(110)

    Energy Technology Data Exchange (ETDEWEB)

    Hassel, Christoph

    2009-08-11

    In the present thesis, the spin dependent transport in epitaxial Fe wires as well as in perpendicularly magnetized multilayer wires is investigated. The main focus is on the investigation of quantum transport phenomena, the domain wall resistance as well as the current induced domain wall motion. Epitaxial Fe wires are prepared from epitaxial Fe films by means of electron beam lithography. Because of the intrinsic magnetic anisotropy, it is possible to prepare wires with a remanent transversal magnetization. Magnetic force microscopy is used to image the magnetic state of single wires. The magnetization reversal behaviour of these wires is investigated in detail using magnetoresistance measurements. These measurements are dominated by effects of the anisotropic magnetoresistance and can be explained by micromagnetic calculations. For the first time, quantum transport phenomena in epitaxial Fe wires are studied by magnetoresistance measurements for temperatures down to 20 mK. These measurements clearly indicate that, independent of the wire width and orientation, no contribution due to weak electron localization can be observed. The results are quantitatively explained within the framework of enhanced electron-electron interactions. Furthermore, by reducing the wire width the onset of the transition from two-dimensional to one-dimensional behaviour is found. To determine the domain wall resistance, a different number of domain walls is created in various structures, whereby the epitaxial samples allow to investigate different domain wall structures. First, a technique based on the stray field of a magnetic force microscope tip is presented. Furthermore, the influence of the shape anisotropy on the coercive field of single wires is used. Contributions to the observed resistance change due to the anisotropic magnetoresistance are calculated using micromagnetic simulations. A positive intrinsic relative resistance increase of 0.2% within the domain wall is found at

  16. Epitaxial growth of BaTiO3 thin films by plasma-enhanced metalorganic chemical vapor deposition

    Science.gov (United States)

    Chern, C. S.; Zhao, J.; Luo, L.; Lu, P.; Li, Y. Q.; Norris, P.; Kear, B.; Cosandey, F.; Maggiore, C. J.; Gallois, B.; Wilkens, B. J.

    1992-03-01

    High-quality BaTiO3 thin films have been epitaxially grown on (001) LaAlO3 and (001) NdGaO3 substrates by plasma-enhanced metalorganic chemical vapor deposition at a substrate temperature of 680 °C. X-ray diffraction θ-2θ, ω, and φ scan results all indicate that single-crystalline BaTiO3 thin films were epitaxially grown on the substrates with orientation perpendicular to the substrates. The high degree of epitaxial crystallinity is further confirmed by Rutherford backscattering spectrometry which gives a minimum yield of 7.5% and 11% for films deposited on LaAlO3 and NdGaO3, respectively. Cross-section high-resolution electron microscopy images also showed that the layer epitaxy of BaTiO3 was characterized by an atomically abrupt film/substrate interface. Scanning electron micrographs showed that these films had very smooth surface morphologies.

  17. Electric-field effects on magnetism of Fe/NCZF/PZT composite thin film

    Science.gov (United States)

    Mudinepalli, Venkata Ramana; Chang, Po-Chun; Hsu, Chuan-Che; Lo, Fang-Yuh; Chang, Huang-Wei; Lin, Wen-Chin

    2017-06-01

    Electric field control of magnetism has many potential applications in magnetic memory storage, sensors and spintronics. Epitaxial heterostructure involving ferroelectric (FE), ferromagnetic (FM) materials is one of the possible routes towards the realization of devices exploiting sizable magnetoelectric effects. In this study, we prepared multiferroic composite ferromagnet/ferrite/ferroelectric thin films on SrTiO3(1 1 1) substrate by electron beam evaporation and pulsed laser deposition. This system represents a prototypical example of interface between body-centered-cubic Fe, spinel NCZF (Ni0.25Cu0.05Zn0.7Fe1.96O3.96) and perovskite PZT (PbZr0.52Ti0.48O3), respectively. Magnetoelectric effects measured as a function of bias voltage on these heterostructures have been investigated via magneto-optical Kerr effect (MOKE). The magnetic coercivity (Hc) considerably decreased as a voltage was applied. The Hc values exhibited the similar variation whether the applied voltage was positive or negative and the reversibility was demonstrated. The strain coupling-mediated magnetoelectric effect and local heating effect are supposed to be the possible origins of Hc variation.

  18. High energy storage responses in all-oxide epitaxial relaxor ferroelectric thin films with the coexistence of relaxor and antiferroelectric-like behaviors

    NARCIS (Netherlands)

    Nguyen, Chi T.Q.; Nguyen, Duc Minh; Vu, H.T.; Houwman, Evert Pieter; Vu, Hung N.; Rijnders, A.J.H.M.

    2017-01-01

    Relaxor ferroelectric Pb0.9La0.1(Zr0.52Ti0.48)O3 (PLZT) thin films have been epitaxially grown via pulsed laser deposition on SrRuO3/SrTiO3 single crystal with different orientations. The high recoverable energy-storage density and energy-storage efficiency in the epitaxial PLZT thin films are

  19. Study of thin nuclear detectors, using passivation and ion implantation technologies and epitaxial silicon. Applications to heavy ions and synchrotron radiation

    International Nuclear Information System (INIS)

    Lavergne-Gosselin, L.

    1989-01-01

    Thin nuclear detectors using epitaxial silicon technology are described. The following manufacturing procedures are presented: the planar technology, which consists in the passivation of the surface for the background noise minimization and in ion implantation to obtain a PN junction; and the epitaxial silicon electrochemical machining, to obtain thin monocrystalline films. The detector's characterization is performed by means of alpha particles and x-rays, and their energy resolution is given. The results show that a suitable Z discrimination is obtained [fr

  20. Epitaxial Heusler superlattice Co2MnAl /Fe2MnAl with perpendicular magnetic anisotropy and termination-dependent half-metallicity

    Science.gov (United States)

    Brown-Heft, Tobias L.; Logan, John A.; McFadden, Anthony P.; Guillemard, Charles; Le Fèvre, Patrick; Bertran, François; Andrieu, Stéphane; Palmstrøm, Chris J.

    2018-03-01

    Single-crystal Heusler atomic-scale superlattices that have been predicted to exhibit perpendicular magnetic anisotropy and half-metallicity have been successfully grown by molecular beam epitaxy. Superlattices consisting of full-Heusler Co2MnAl and Fe2MnAl with one- to three-unit-cell periodicity were grown on GaAs (001), MgO (001), and Cr (001)/MgO (001). Electron-energy-loss spectroscopy maps confirmed clearly segregated epitaxial Heusler layers with high cobalt or high iron concentrations for samples grown near room temperature on GaAs (001). Superlattice structures grown with an excess of aluminum had significantly lower thin-film shape anisotropy and resulted in an out-of-plane spin reorientation transition at temperatures below 200 K for samples grown on GaAs (001). Synchrotron-based spin-resolved photoemission spectroscopy found that the superlattice structure improves the Fermi-level spin polarization near the X point in the bulk Brillouin zone. Stoichiometric Co2MnAl terminated superlattice grown on MgO (001) had a spin polarization of 95%, while a pure Co2MnAl film had a spin polarization of only 65%.

  1. Microstructure of Co/X (X=Cu,Ag,Au) epitaxial thin films grown on Al2O3(0001) substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Akita, Yuta; Futamoto, Masaaki; Kirino, Fumiyoshi

    2007-01-01

    Epitaxial thin films of Co/X (X=Cu,Ag,Au) were prepared on Al 2 O 3 (0001) substrates at substrate temperatures of 100 and 300 degree sign C by UHV molecular beam epitaxy. A complicated microstructure was realized for the epitaxial thin films. In-situ reflection high-energy electron diffraction observation has shown that X atoms of the buffer layer segregated to the surface during Co layer deposition, and it yielded a unique epitaxial granular structure. The structure consists of small Co grains buried in the X buffer layer, where both the magnetic small Co grains and the nonmagnetic X layer are epitaxially grown on the single crystal substrate. The structure varied depending on the X element and the substrate temperature. The crystal structure of Co grains is influenced by the buffer layer material and determined to be hcp and fcc structures for the buffer layer materials of Au and Cu, respectively

  2. Epitaxial Lift-Off of Centimeter-Scaled Spinel Ferrite Oxide Thin Films for Flexible Electronics.

    Science.gov (United States)

    Shen, Lvkang; Wu, Liang; Sheng, Quan; Ma, Chunrui; Zhang, Yong; Lu, Lu; Ma, Ji; Ma, Jing; Bian, Jihong; Yang, Yaodong; Chen, Aiping; Lu, Xiaoli; Liu, Ming; Wang, Hong; Jia, Chun-Lin

    2017-09-01

    Mechanical flexibility of electronic devices has attracted much attention from research due to the great demand in practical applications and rich commercial value. Integration of functional oxide materials in flexible polymer materials has proven an effective way to achieve flexibility of functional electronic devices. However, the chemical and mechanical incompatibilities at the interfaces of dissimilar materials make it still a big challenge to synthesize high-quality single-crystalline oxide thin film directly on flexible polymer substrates. This study reports an improved method that is employed to successfully transfer a centimeter-scaled single-crystalline LiFe 5 O 8 thin film on polyimide substrate. Structural characterizations show that the transferred films have essentially no difference in comparison with the as-grown films with respect to the microstructure. In particular, the transferred LiFe 5 O 8 films exhibit excellent magnetic properties under various mechanical bending statuses and show excellent fatigue properties during the bending cycle tests. These results demonstrate that the improved transfer method provides an effective way to compose single-crystalline functional oxide thin films onto flexible substrates for applications in flexible and wearable electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Tensile strain induced changes in the optical spectra of SrTiO.sub.3./sub. epitaxial thin films

    Czech Academy of Sciences Publication Activity Database

    Dejneka, Alexandr; Tyunina, M.; Narkilahti, J.; Levoska, J.; Chvostová, Dagmar; Jastrabík, Lubomír; Trepakov, Vladimír

    2010-01-01

    Roč. 52, č. 10 (2010), 2082-2089 ISSN 1063-7834 R&D Projects: GA ČR GA202/08/1009; GA AV ČR KAN301370701; GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : SrTiO 3 epitaxial thin films * effect of biaxial tensile strains on optical spectra Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.727, year: 2010

  4. Mn doping effect on structure and magnetism of epitaxial (FePt)1-xMnx films

    International Nuclear Information System (INIS)

    Huang, J.C.A.; Chang, Y.C.; Yu, C.C.; Yao, Y.D.; Hu, Y.M.; Fu, C.M.

    2003-01-01

    We study the structure and perpendicular magnetism of molecular beam epitaxy grown (FePt) 1-x Mn x films with doping concentration x=0, 1%, 2%, 3%, 4%, and 5%. The (FePt) 1-x Mn x films were made by multilayers growth of [Fe/Pt/Mn]xN at 100 deg. C and annealed at 600 deg. C. X-ray diffraction scans indicate that relatively better L1 0 ordered structure for low Mn doping (x 3%. The perpendicular magnetic anisotropy effect of the (FePt) 1-x Mn x films tends to decrease with the increase of Mn doping for x>1%. However, the x=1% doped films possess slightly better perpendicular magnetic anisotropy effect than the zero doped film. The perpendicular magnetic anisotropy constant are of about 1.3x10 7 and 1.6x10 7 erg/cm 3 for x=0% and x=1%, respectively

  5. Magnetoelastic coupling in TbFe2 (110) thin films

    International Nuclear Information System (INIS)

    Ciria, M.; Arnaudas, J.I.; Dufour, C.; Oderno, V.; Dumesnil, K.; del Moral, A.

    1997-01-01

    We have determined the rhombohedral magnetoelastic stress of a Laves phase TbFe 2 (110) single-crystal film, grown by molecular-beam epitaxy. The film thickness was 1300 Angstrom. The magnetoelastic stress was directly measured by using a low-temperature cantilever capacitive method, between 300 and 10 K. The isotherms clearly display the coercive field but, unlike bulk alloy behavior, do not saturate even at the maximum field of 12 T. The determined rhombohedral magnetoelastic parameter of the film is B ε,2 =-0.43 GPa, at 0 K and 12 T, which is 0.67 times the value for bulk TbFe 2 . B ε,2 follows a power m 3 of the reduced magnetization m, indicating a single-ion volume origin for the rhombohedral magnetoelastic stress of this film. Measurements performed in a 300 Angstrom TbFe 2 (110) film deposited onto a YFe 2 buffer show that the coercive field is drastically lowered and that the magnetoelastic distortion is negligible. copyright 1997 American Institute of Physics

  6. Finite-size effects in the nuclear magnetic resonance of epitaxial palladium thin films

    Science.gov (United States)

    MacFarlane, W. A.; Parolin, T. J.; Larkin, T. I.; Richter, G.; Chow, K. H.; Hossain, M. D.; Kiefl, R. F.; Levy, C. D. P.; Morris, G. D.; Ofer, O.; Pearson, M. R.; Saadaoui, H.; Song, Q.; Wang, D.

    2013-10-01

    We have measured the NMR of 8Li+ implanted in a set of thin epitaxial films of Pd. We find a large, negative, strongly temperature-dependent Knight shift K consistent with previous measurements on polycrystalline films. The temperature dependence of the shift exhibits a characteristic deviation from the susceptibility χ(T). In particular, at low temperature, K(T) continues to follow a simple Curie-Weiss dependence. This result provides important insight into the origin of the low-temperature behavior of χ(T) in strongly paramagnetic metals. In addition, we find the room temperature shift depends on film thickness, with changes on the order of 20% between films 100 nm and 30 nm thick. We also observe a surface-related resonance in both Au-capped and uncapped films with a small positive shift. These features bear a striking similarity to the Pt NMR line shapes in much smaller Pt particles. However, they seem to originate, not from adsorbed species, but rather in confinement effects on the highly exhange-enhanced Pd d band.

  7. Epitaxial growth and properties of YBaCuO thin films

    International Nuclear Information System (INIS)

    Geerk, J.; Linker, G.; Meyer, O.

    1989-08-01

    The growth quality of YBaCuO thin films deposited by sputtering on different substrates (Al 2 O 3 , MgO, SrTiO 3 , Zr(Y)O 2 ) has been studied by X-ray diffraction and channeling experiments as a function of the deposition temperature. Besides the substrate orientation, the substrate temperature is the parameter determining whether films grow in c-, a-, (110) or mixed directions. Epitaxial growth correlates with high critical current values in the films of up to 5.5x10 6 A/cm 2 at 77 K. Ultrathin films with thicknesses down to 2 nm were grown revealing three-dimensional superconducting behaviour. Films on (100) SrTiO 3 of 9 nm thickness and below are partially strained indicating commensurate growth. From the analysis of the surface disorder 1 displaced Ba atom per Ba 2 Y row was obtained indicating that the disordered layer thickness is about 0.6 nm. Tunnel junctions fabricated on these films reveal gap-like structures near ±16 mV and ±30 mV. (orig.) [de

  8. Characterization of thin irradiated epitaxial silicon sensors for the CMS phase II pixel upgrade

    CERN Document Server

    Centis Vignali, Matteo; Eichhorn, Thomas; Garutti, Erika; Junkes, Alexandra; Steinbrueck, Georg

    2015-01-01

    The high-luminosity upgrade fo the large hadron collider foreseen for 2023 resulted in the decision to replace the tracker system of the CMS experiment. The innermost layer of the new pixel detector will experience fluences in the order of $\\phi_{eq} \\approx 10^{16}$~cm$^{-2}$ and a dose of $\\approx 5$~MGy after an integrated luminosity of 3000~fb$^{-1}$. Several materials and designs are under investigation in order to build a detector that can withstand such high fluences. Thin planar silicon sensors are good canditates to achieve this goal since the degradation of the signal produced by traversing particles is less severe than for thicker devices. A study has been carried out in order to characterize highly irradiated planar epitaxial silicon sensors with an active thickness of 100~$\\mu$m. The investigation includes pad diodes and strip detectors irradiated up to a fluence of $\\phi_{eq} = 1.3 \\times 10^{16}$~cm$^{-2}$. The electrical properties of diodes have bee...

  9. Electronic structure of fully epitaxial Co2TiSn thin films

    Energy Technology Data Exchange (ETDEWEB)

    Meinert, Markus; Schmalhorst, Jan; Wulfmeier, Hendrik; Reiss, Gunter; Arenholz, Elke; Graf, Tanja; Felser, Claudia

    2010-10-28

    In this article we report on the properties of thin films of the full Heusler compound Co{sub 2}TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures above 600 C. The films are well ordered in the L2{sub 1} structure, and the Curie temperature exceeds slightly the bulk value. They show a significant, isotropic magnetoresistance and the resistivity becomes strongly anomalous in the paramagnetic state. The films are weakly ferrimagnetic, with nearly 1 {mu}{sub B} on the Co atoms, and a small antiparallel Ti moment, in agreement with theoretical expectations. From comparison of x-ray absorption spectra on the Co L{sub 3,2} edges, including circular and linear magnetic dichroism, with ab initio calculations of the x-ray absorption and circular dichroism spectra we infer that the electronic structure of Co{sub 2}TiSn has essentially non-localized character. Spectral features that have not been explained in detail before, are explained here in terms of the final state band structure.

  10. Oxygen flux influence on the morphological, structural and optical properties of Zn1-xMgxO thin films grown by plasma-assisted molecular beam epitaxy

    International Nuclear Information System (INIS)

    Su, S.C.; Lu, Y.M.; Zhang, Z.Z.; Li, B.H.; Shen, D.Z.; Yao, B.; Zhang, J.Y.; Zhao, D.X.; Fan, X.W.

    2008-01-01

    The Zn 1-x Mg x O thin films were grown on Al 2 O 3 substrate with various O 2 flow rates by plasma-assisted molecular beam epitaxy (P-MBE). The growth conditions were optimized by the characterizations of morphology, structural and optical properties. The Mg content of the Zn 1-x Mg x O thin film increases monotonously with decreasing the oxygen flux. X-ray diffractometer (XRD) measurements show that all the thin films are preferred (0 0 2) orientated. By transmittance and absorption measurements, it was found that the band gap of the film decreases gradually with increasing oxygen flow rate. The surface morphology dependent on the oxygen flow rate was also studied by field emission scanning electron microscopy (FE-SEM). The surface roughness became significant with increasing oxygen flow rate, and the nanostructures were formed at the larger flow rate. The relationship between the morphology and the oxygen flow rate of Zn 1-x Mg x O films was discussed

  11. Microstructure of epitaxial SrRuO 3 thin films on MgO substrates

    Science.gov (United States)

    Ai, Wan Yong; Zhu, Jun; Zhang, Ying; Li, Yan Rong; Liu, Xing Zhao; Wei, Xian Hua; Li, Jin Long; Zheng, Liang; Qin, Wen Feng; Liang, Zhu

    2006-09-01

    SrRuO 3 thin films have been grown on singular (1 0 0) MgO substrates using pulsed laser deposition (PLD) in 30 Pa oxygen ambient and at a temperature of 400-700 °C. Ex situ reflection high-energy electron diffraction (RHEED) as well as X-ray diffraction (XRD) θ/2 θ scan indicated that the films deposited above 650 °C were well crystallized though they had a rough surface as shown by atom force microscopy (AFM). XRD Φ scans revealed that these films were composed of all three different types of orientation domains, which was further confirmed by the RHEED patterns. The heteroepitaxial relationship between SrRuO 3 and MgO was found to be [1 1 0] SRO//[1 0 0] MgO and 45°-rotated cube-on-cube [0 0 1] SRO//[1 0 0] MgO. These domain structures and surface morphology are similar to that of ever-reported SrRuO 3 thin films deposited on the (0 0 1) LaAlO 3 substrates, and different from those deposited on (0 0 1) SrTiO 3 substrates that have an atomically flat surface and are composed of only the [1 1 0]-type domains. The reason for this difference was ascribed to the effect of lattice mismatch across the film/substrate interface. The room temperature resistivity of SrRuO 3 films fabricated at 700 °C was 300 μΩ cm. Therefore, epitaxial SrRuO 3 films on MgO substrate could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.

  12. Optical properties of aluminum nitride thin films grown by direct-current magnetron sputtering close to epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Stolz, A. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Soltani, A., E-mail: ali.soltani@iemn.univ-lille1.fr [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Abdallah, B. [Department of Materials Physics, Atomic Energy Commission of Syria, Damascus, P.O. Box 6091 (Syrian Arab Republic); Charrier, J. [Fonctions Optiques pour les Technologies de l' informatiON (FOTON), UMR CNRS 6082, 6, rue de Kerampont CS 80518, 22305 Lannion Cedex (France); Deresmes, D. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France); Jouan, P.-Y.; Djouadi, M.A. [Institut des Matériaux Jean Rouxel – IMN, UMR CNRS 6502, 2, rue de la Houssinère BP 32229, 44322 Nantes (France); Dogheche, E.; De Jaeger, J.-C. [Institut d' Electronique de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, PRES Lille, Université Nord de France, Avenue Poincaré, 59652 Villeneuve d' Ascq Cedex (France)

    2013-05-01

    Low-temperature Aluminum Nitride (AlN) thin films with a thickness of 3 μm were deposited by Direct-Current magnetron sputtering on sapphire substrate. They present optical properties similar to those of epitaxially grown films. Different characterization methods such as X-Ray Diffraction, Transmission Electron Microscopy and Atomic Force Microscopy were used to determine the structural properties of the films such as its roughness and crystallinity. Newton interferometer was used for stress measurement of the films. Non-destructive prism-coupling technique was used to determine refractive index and thickness homogeneity by a mapping on the whole sample area. Results show that AlN films grown on AlGaN layer have a high crystallinity close to epitaxial films, associated to a low intrinsic stress for low thickness. These results highlight that it is possible to grow thick sample with microstructure and optical properties close to epitaxy, even on a large surface. - Highlights: ► Aluminum Nitride sputtering technique with a low temperature growth process ► Epitaxial quality of two microns sputtered Aluminum Nitride film ► Optics as a non-destructive accurate tool for acoustic wave investigation.

  13. Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu1 - x Fe x O3 - δ Thin Films.

    Science.gov (United States)

    Dash, Umasankar; Acharya, Susant Kumar; Lee, Bo Wha; Jung, Chang Uk

    2017-12-01

    Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu 1 - x Fe x O 3 - δ epitaxial thin films (x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu 1 - x Fe x O 3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR (~36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies (δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr 1 - x La x )(Ru 1 - x Fe x )O 3 . These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu 1 - x Fe x O 3 - δ thin films.

  14. Influence of anisotropic strain relaxation on the magnetoresistance properties of epitaxial Fe3O4 (110) films

    Science.gov (United States)

    Sofin, R. G. S.; Wu, Han-Chun; Ramos, R.; Arora, S. K.; Shvets, I. V.

    2015-11-01

    We studied Fe3O4 (110) films grown epitaxially on MgO (110) substrates using oxygen plasma assisted molecular beam epitaxy. The films with thickness of 30-200 nm showed anisotropic in-plane partial strain relaxation. Magneto resistance (MR) measurements with current and magnetic field along ⟨001⟩ direction showed higher MR compared to ⟨1 ¯ 10 ⟩ direction. Maximum value of MR was measured at Verwey transition temperature for both directions. We explain the observed anisotropy in the MR on the basis of the effects of anisotropic misfit strain, and the difference between the density of antiferromagnetically coupled antiphase boundaries formed along ⟨001⟩ and ⟨1 ¯ 10 ⟩ crystallographic directions, suggesting the dependence of spin polarisation on the anisotropic strain relaxation along the said crystallographic directions.

  15. Fe-doped semi-insulating GaN with solid Fe source grown on (110) Si substrates by NH3 molecular beam epitaxy

    Science.gov (United States)

    Noh, Young Kyun; Lee, Sang Tae; Kim, Moon Deock; Oh, Jae Eung

    2017-02-01

    Iron doped GaN layers were grown on (110) Si substrates by ammonia molecular beam epitaxy (MBE) using solid elemental iron as a source. Specular films with concentrations up to 1×1020 cm-3, as determined by secondary ion mass spectroscopy, were grown, unlike a limited incorporation of Fe into GaN by metal-rich rf plasma MBE. The Fe concentration in the film showed an exponential dependence on the inverse of source temperature with an activation energy of 3.4 eV, which agrees well to the reported value for the sublimation of Fe. A 1.5 μm thick GaN film with a sheet resistance of 1 GΩ/sq. was obtained by compensating unintentional residual donors with a small Fe concentration of 1×1017 cm-3. X-ray diffraction rocking curves indicated high crystalline quality, very similar to an undoped film, showing that the Fe incorporation required to obtain the semi-insulating film properties did not affect the structural properties of the film. The low-temperature PL spectra of highly resistive and semi-insulating Fe:GaN in the range of 1017 1018 cm-3 show dominant exciton emissions and enhanced donor-acceptor-pair (DAP) emissions, implying that Fe ions contribute to the DAP transition between donor levels and Fe-related acceptor levels, possibly compensating the residual donors to achieve the semi-insulating electrical properties.

  16. Gilbert damping constant of FePd alloy thin films estimated by broadband ferromagnetic resonance

    Directory of Open Access Journals (Sweden)

    Kawai T.

    2014-07-01

    Full Text Available Magnetic relaxation of FePd alloy epitaxial thin films with very flat surfaces prepared on MgO(001 substrate are measured by in-plane broadband ferromagnetic resonance (FMR. Magnetic relaxation is investigated as Δω for FMR absorption peak by frequency sweep measurements. ΔH is calculated by using the measured Δω. Gilbert damping constant, α, is estimated by employing a straight line fitting of the resonant frequency dependence of ΔH. The α value for an FePd film deposited at 200 ˚C, which shows disordered A1 structure, is 0.010 and ΔH0, which is frequency independent part of ΔH, is 10 Oe. The α value for a film annealed at 400 ˚C, which shows partially L10 ordered structure (S=0.32, is 0.013, which is slightly larger than that for the disorder A1 structure film. However, ΔH0 for the annealed film is 85 Oe, which is much larger than that for the film with disordered structure. The results show that the magnetic relaxation of the 400 ˚C annealed film is mainly dominated by ΔH0, which is related with magnetic in-homogeneity caused by the appearance of perpendicular anisotropy of partially ordered phase.

  17. Uniaxial stress influence on electrical conductivity of thin epitaxial lanthanum-strontium manganite films

    Energy Technology Data Exchange (ETDEWEB)

    Stankevič, V., E-mail: wstan@pfi.lt [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius Gediminas Technical University, Sauletekio 11, Vilnius (Lithuania); Šimkevičius, Č.; Balevičius, S.; Žurauskienė, N. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius Gediminas Technical University, Sauletekio 11, Vilnius (Lithuania); Cimmperman, P. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Abrutis, A. [Vilnius University, Dept. of General and Inorganic Chemistry, Naugarduko 24, Vilnius (Lithuania); Plaušinaitienė, V. [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A.Gostauto 11, Vilnius (Lithuania); Vilnius University, Dept. of General and Inorganic Chemistry, Naugarduko 24, Vilnius (Lithuania)

    2013-07-01

    This is a study of the influence of external uniaxial mechanical strains on the transport properties of thin epitaxial La{sub 0.83}Sr{sub 0.17}MnO{sub 3} (LSMO) films. Our measurements were carried out using standard isosceles triangle-shaped cantilever. Films which were tensed in-plane or compressed or were subjected to both tension and compression strains were grown onto SrTiO{sub 3} (STO), LaAlO{sub 3} (LAO) and (001) NdGaO{sub 3} (NGO) substrates, respectively. It was found that for thin films (less than 100 nm), the uniaxial compression of such films which were initially tensed in-plane (grown onto STO substrates) produces a decrease of their resistance, whereas the compression of initially compressed films (on LAO substrates) produces an increase of the films' resistance. The same results were obtained for LSMO films grown onto (001) NGO substrates when they were compressed along the [010] and [100] directions, respectively. For thicker films (more than 100 nm), the resistance behavior after uniaxial compression was found to be identical to that produced by hydrostatic compression, namely, the resistance decreases irrespective of the substrate. These experiments also reveal an increase of resistance and a shift of metal–insulator transition temperature T{sub m} to lower temperatures corresponding to a decrease of the film thickness. The occurrence of this effect is also independent of the kind of substrate used. Thus it was concluded that the influence of film thickness on its resistance as well as on the behavior of such films while under external uniaxial compression cannot be explained fully by only the presence of residual stress in these films. A possible reason is that the inhomogeneous distribution of the mechanical stresses in the films can lead to the appearance of two conductivity phases, each having a different mechanism. The results which were obtained when these films were subjected to hydrostatic compression were also explained by this

  18. Effects of Interfaces on the Structure and Novel Physical Properties in Epitaxial Multiferroic BiFeO3 Ultrathin Films

    Directory of Open Access Journals (Sweden)

    Chuanwei Huang

    2014-07-01

    Full Text Available In functional oxide films, different electrical/mechanical boundaries near film surfaces induce rich phase diagrams and exotic phenomena. In this paper, we review some key points which underpin structure, phase transition and related properties in BiFeO3 ultrathin films. Compared with the bulk counterparts, we survey the recent results of epitaxial BiFeO3 ultrathin films to illustrate how the atomic structure and phase are markedly influenced by the interface between the film and the substrate, and to emphasize the roles of misfit strain and depolarization field on determining the domain patterns, phase transformation and associated physical properties of BiFeO3 ultrathin films, such as polarization, piezoelectricity, and magnetism. One of the obvious consequences of the misfit strain on BiFeO3 ultrathin films is the emergence of a sequence of phase transition from tetragonal to mixed tetragonal & rhombohedral, the rhombohedral, mixed rhombohedral & orthorhombic, and finally orthorhombic phases. Other striking features of this system are the stable domain patterns and the crossover of 71° and 109° domains with different electrical boundary conditions on the film surface, which can be controlled and manipulated through the depolarization field. The external field-sensitive enhancements of properties for BiFeO3 ultrathin films, including the polarization, magnetism and morphotropic phase boundary-relevant piezoelectric response, offer us deeper insights into the investigations of the emergent properties and phenomena of epitaxial ultrathin films under various mechanical/electrical constraints. Finally, we briefly summarize the recent progress and list open questions for future study on BiFeO3 ultrathin films.

  19. EuO and Gd-doped EuO thin films. Epitaxial growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Sutarto, Ronny

    2009-07-06

    this respect the quality of many of the doped EuO samples used in the past bulk studies. The focus of this thesis is on the preparation and the properties of high-quality single-crystalline EuO and Gd-doped EuO thin films. The so-called Eu-distillation-assisted molecular beam epitaxy (MBE) has been employed to achieve full control of the stoichiometry. The films have been epitaxially grown on yttria-stabilized cubic zirconia (YSZ) (001) substrates. By a systematic variation of the oxygen deposition rates, we have been able to observe sustained oscillations in the intensity of the reflection high-electron energy diffraction (RHEED) pattern during growth. We thus have demonstrated that layer-by-layer growth has been achieved for the first time. We also have confirmed that YSZ indeed supplies oxygen during the initial stages of growth, yet the EuO stoichiometry can still be well maintained. In the case of Gd-doped EuO films, the presence of Gd even helps to stabilize the layer-by-layer growth mode. It is important to achieve this growth mode, since it enables the preparation of films with very smooth and at surfaces. This in turn facilitates the capping of the films with a thin Al overlayer in order to protect the films against degradation under ambient conditions. More important, the smoothness of the lm will enable the preparation of high quality device structures. By using ex-situ soft x-ray absorption spectroscopy (XAS) at the Eu and Gd M{sub 4,5} edges, we have confirmed that the films are completely free from Eu{sup 3+} contaminants, and we were able to determine reliably the actual Gd concentration. This actual Gd concentration could in fact significantly deviate from the nominal Gd/Eu evaporation ratio. From magnetization and susceptibility measurements, we found the Curie temperature to increase smoothly as a function of doping from 69 K up to a maximum of 125 K, all with a saturation moment of 7 {mu}B. A threshold behavior was not observed for Gd concentrations

  20. EuO and Gd-doped EuO thin films. Epitaxial growth and properties

    International Nuclear Information System (INIS)

    Sutarto, Ronny

    2009-01-01

    quality of many of the doped EuO samples used in the past bulk studies. The focus of this thesis is on the preparation and the properties of high-quality single-crystalline EuO and Gd-doped EuO thin films. The so-called Eu-distillation-assisted molecular beam epitaxy (MBE) has been employed to achieve full control of the stoichiometry. The films have been epitaxially grown on yttria-stabilized cubic zirconia (YSZ) (001) substrates. By a systematic variation of the oxygen deposition rates, we have been able to observe sustained oscillations in the intensity of the reflection high-electron energy diffraction (RHEED) pattern during growth. We thus have demonstrated that layer-by-layer growth has been achieved for the first time. We also have confirmed that YSZ indeed supplies oxygen during the initial stages of growth, yet the EuO stoichiometry can still be well maintained. In the case of Gd-doped EuO films, the presence of Gd even helps to stabilize the layer-by-layer growth mode. It is important to achieve this growth mode, since it enables the preparation of films with very smooth and at surfaces. This in turn facilitates the capping of the films with a thin Al overlayer in order to protect the films against degradation under ambient conditions. More important, the smoothness of the lm will enable the preparation of high quality device structures. By using ex-situ soft x-ray absorption spectroscopy (XAS) at the Eu and Gd M 4,5 edges, we have confirmed that the films are completely free from Eu 3+ contaminants, and we were able to determine reliably the actual Gd concentration. This actual Gd concentration could in fact significantly deviate from the nominal Gd/Eu evaporation ratio. From magnetization and susceptibility measurements, we found the Curie temperature to increase smoothly as a function of doping from 69 K up to a maximum of 125 K, all with a saturation moment of 7 μB. A threshold behavior was not observed for Gd concentrations as low as 0.2 %. Analysis of the

  1. Epitaxial growth of YBa2Cu3O7-δ thin films on LiNbO3 substrates

    International Nuclear Information System (INIS)

    Lee, S.G.; Koren, G.; Gupta, A.; Segmuller, A.; Chi, C.C.

    1989-01-01

    In situ epitaxial growth of YBa 2 Cu 3 O 7-δ thin films on Y-cut LiNbO 3 substrates using a standard laser ablation technique is reported. Resistance of the films shows a normal metallic behavior and a very sharp ( c (R=0) of 92 K. High critical current density of J c (77 K)=2x10 5 A/cm 2 is observed, which is in accordance with epitaxial growth. Film orientation observed from x-ray diffraction spectra indicates that the c axis is normal to the substrate plane and the a axis is at 45 degree to the [11.0] direction of the hexagonal lattice of the substrate with two domains in mirror image to the (110) plane

  2. Resistivity Effects of Cation Ordering in Highly-Doped La2-xSrxCu4 Epitaxial Thin Films

    Science.gov (United States)

    Burquest, Franklin; Marmol, Rodrigo; Cox, Nicholas; Nelson-Cheeseman, Brittany

    Highly-doped La2-xSrxCuO4 (LSCO) films (0.5 causes internal polar electrostatic forces, which have been shown to cause stretching of the apical oxygen bond in analogous epitaxial nickelate films. Thin film samples are grown concurrently to minimize extraneous effects on film structure and properties. Atomic force microscopy and x-ray reflectivity demonstrate that the films are single crystalline, epitaxial, and smooth. X-ray diffraction is used to measure the c-axis of the films as a function of doping and dopant cation ordering. Electrical transport data of the ordered samples is compared with transport data of conventional disordered cation samples. Preliminary data indicates significant differences in resistivity at both 300K and 10K between the cation-ordered and cation-disordered samples. This work indicates that dopant cation ordering within the layered cuprates could significantly modify the conduction mechanisms at play in these materials.

  3. Magnetic properties of Fe0.4Mn0.6/Co2FeAl bilayers grown on GaAs by molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Meng, K. K.; Nie, S. H.; Yu, X. Z.; Wang, S. L.; Zhao, J. H.; Yan, W. S.

    2011-01-01

    Polycrystalline Fe 0.4 Mn 0.6 layers with the different thickness are deposited on 4-nm-thick single-crystalline Co 2 FeAl layers, which are grown on GaAs (001) substrates at room temperature by molecular-beam epitaxy. Both the exchange bias and the in-plane magnetic anisotropies of the bilayers are strongly dependent on the thickness of the Fe 0.4 Mn 0.6 layer. The former is described using a granular level model. A modified Stoner-Wohlfarth model is used to explain the in-plane magnetic anisotropies observed at 5 K, while one possible reason for the magnetic anisotropies measured at 300 K is the complex interfacial magnetic properties proved by x-ray magnetic circular dichroism measurements.

  4. Determination of the Fe magnetic anisotropies and the CoO frozen spins in epitaxial CoO/Fe/Ag(001)

    Energy Technology Data Exchange (ETDEWEB)

    Meng, J. Li, Y.; Park, J. S.; Jenkins, C. A.; Arenholz, E.; Scholl, A.; Tan, A.; Son, H.; Zhao, H. W.; Hwang, Chanyong; Qiu, Z. Q.

    2011-04-28

    CoO/Fe/Ag(001) films were grown epitaxially and studied by X-ray Magnetic Circular Dichroism (XMCD) and X-ray Magnetic Linear Dichroism (XMLD). After field cooling along the Fe[100] axis to 80 K, exchange bias, uniaxial anisotropy, and 4-fold anisotropy of the films were determined by hysteresis loop and XMCD measurements by rotating the Fe magnetization within the film plane. The CoO frozen spins were determined by XMLD measurement as a function of CoO thickness.We find that among the exchange bias, uniaxial anisotropy, and 4-fold anisotropy, only the uniaxial magnetic anisotropy follows thickness dependence of the CoO frozen spins.

  5. Ultra-smooth epitaxial Ge grown on Si(001) utilizing a thin C-doped Ge buffer layer

    KAUST Repository

    Mantey, J.

    2013-01-01

    Here, we present work on epitaxial Ge films grown on a thin buffer layer of C doped Ge (Ge:C). The growth rate of Ge:C is found to slow over time and is thus unsuitable for thick (>20 nm) layers. We demonstrate Ge films from 10 nm to >150 nm are possible by growing pure Ge on a thin Ge:C buffer. It is shown that this stack yields exceedingly low roughness levels (comparable to bulk Si wafers) and contains fewer defects and higher Hall mobility compared to traditional heteroepitaxial Ge. The addition of C at the interface helps reduce strain by its smaller atomic radius and its ability to pin defects within the thin buffer layer that do not thread to the top Ge layer. © 2013 AIP Publishing LLC.

  6. Spin configurations and negative coercivity in epitaxially grown DyFe{sub 2}/YFe{sub 2} superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Gordeev, S. N.; Beaujour, J.-M. L.; Bowden, G. J.; de Groot, P. A. J.; Rainford, B. D.; Ward, R. C. C.; Wells, M. R.

    2001-06-01

    Molecular beam epitaxial methods have been used to grow single crystal Laves phase DyFe{sub 2}/YFe{sub 2} superlattice samples with a (110) growth direction. In particular, the magnetic properties of the YFe{sub 2} dominated multilayer samples [wDyFe{sub 2}/4wYFe{sub 2}]{times}N with w=20, 30, 40, 45, 50, and 55 Aa are presented and discussed. In principle, the multilayer films should possess similar magnetic properties because they are all nominally Dy{sub 0.2}Y{sub 0.8}Fe{sub 2}. However, it is shown that their magnetic properties depend strongly on the thickness of the DyFe{sub 2} layers w. Those films with w{ge}45Aa possess negative coercivities, while those with w{le}40Aa are positive. It is argued that this behavior can be understood in terms of a strong increase of the intrinsic coercivity of the DyFe{sub 2}/YFe{sub 2} superlattice, taken as a whole, as w is reduced. For w{le}40Aa almost none of the DyFe{sub 2} moments can be flipped over in the available field range (12 T). {copyright} 2001 American Institute of Physics.

  7. Epitaxial yttria-stabilized zirconia on (1 -1 0 2) sapphire for YBa2Cu3O(7-delta) thin films

    Science.gov (United States)

    Wu, X. D.; Muenchausen, R. E.; Nogar, N. S.; Pique, A.; Edwards, R.

    1991-01-01

    Epitaxial yttria-stabilized zirconia (YSZ) films were deposited on (1 -1 0 2) sapphire by pulsed laser deposition. The films are formed in a cubic phase with the a axis normal to the substrate surface. Ion beam channeling measurements show that the YSZ films are highly crystalline with a channeling minimum yield of 8 percent. The epitaxial relationship between the film and substrate is further confirmed by a cross-section TEM study. Epitaxial YBa2Cu3O(7-delta) thin films deposited on YSZ/sapphire have Tc and Jc of up to 89 K and 10 to the 6th A/sq cm at 77 K, respectively.

  8. Self-regulation of Bi/(Bi+Fe) ratio in metalorganic chemical vapor deposition of BiFeO3 thin films

    Science.gov (United States)

    Fujisawa, Hironori; Yoshimura, Nao; Nakashima, Seiji; Shimizu, Masaru

    2017-10-01

    Metalorganic chemical vapor deposition (MOCVD) is one of the suitable techniques for practical applications of BiFeO3 films. To develop the potential of MOCVD as a device fabrication process, we investigated the relationship between the film and gas compositions, and the growth under highly oxidizing conditions using O2 and O3 gases. In the growth of epitaxial BiFeO3 thin films on SrRuO3-covered 4° vicinal SrTiO3(001) at 620 °C, the self-regulation of the film composition was achieved for Bi and Fe precursor supply ratios between 62.1 to 78.5% under O2 and 56.1 to 73.2% under 5 wt % O3-mixed O2 atmospheres. The leakage was very sensitive to the precursor supply ratio and oxidizing gas. 150-nm-thick MOCVD-BiFeO3 films grown using O2+O3 gas showed the minimum leakage current density of 2.3 × 10-7 A/cm2 at +1 V. The highly oxidizing growth conditions using O3 can suppress the leakage while precise composition control is required.

  9. Development of buffer layer structure for epitaxial growth of (100)/(001)Pb(Zr,Ti)O3-based thin film on (111)Si wafer

    Science.gov (United States)

    Hayasaka, Takeshi; Yoshida, Shinya; Tanaka, Shuji

    2017-07-01

    This paper reports on the development of a novel buffer layer structure, (100)SrRuO3/(100)LaNiO3/(111)Pt/(111)CeO2, for the epitaxial growth of a (100)/(001)-oriented Pb(Zr,Ti)O3 (PZT)-based thin film on a (111)Si wafer. (111)Pt and (111)CeO2 were epitaxially grown on (111)Si straightforwardly. Then, the crystal orientation was forcibly changed from (111) to (100) at the LaNiO3 layer owing to its strong (100)-self-orientation property, which enabled the cube-on-cube epitaxial growth of the subsequent (100)SrRuO3 layer and preferentially (100)/(001)-oriented PZT-based thin film. The PZT-based epitaxial thin films were comprehensively characterized in terms of the crystallinity, in-plane epitaxial relationships, piezoelectricity, and so forth. This buffer layer structure for the epitaxial growth of PZT can be applied to piezoelectric micro-electro-mechanical systems (MEMS) vibrating ring gyroscopes.

  10. Influence of the V/III ratio in the gas phase on thin epitaxial AlN layers grown on (0001) sapphire by high temperature hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Claudel, A., E-mail: arnaud.claudel@grenoble-inp.org [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Fellmann, V. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Gélard, I. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Coudurier, N. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Sauvage, D. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Balaji, M. [ACERDE, 354 Voie Magellan — Alpespace, 73800 Ste Hélène du Lac (France); Science et Ingénierie des Matériaux et des Procédés, Grenoble INP-CNRS-UJF, BP 75, 38402 Saint Martin d' Hères (France); Crystal Growth Center, Anna University, Chennai 600025 (India); and others

    2014-12-31

    Thin (0001) epitaxial aluminum nitride (AlN) layers were grown on c-plane sapphire using high temperature hydride vapor phase epitaxy. The experimental set-up consists of a vertical cold-wall quartz reactor working at low pressure in which the reactions take place on a susceptor heated by induction. The reactants used are ammonia and aluminum chlorides in situ formed via hydrogen chloride reaction with high purity aluminum pellets. As-grown AlN layers have been characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, transmission electron microscopy, photoluminescence and Raman spectroscopies. The influence of the V/III ratio in the gas phase, from 1.5 to 15, on growth rate, surface morphology, roughness and crystalline quality is investigated in order to increase the quality of thin epitaxial AlN layers grown at high temperature. Typical growth rates of around 0.45 μm/h were obtained for such thin epitaxial AlN layers. The growth rate was unaffected by the V/III ratio. An optimum for roughness, crystalline quality and optical properties seems to exist at V/III = 7.5. As a matter of fact, for a V/III ratio of 7.5, best root mean square roughness and crystalline quality — measured on 0002 symmetric reflection — as low as 6.9 nm and 898 arcsec were obtained, respectively. - Highlights: • Growth of thin epitaxial AlN layers by high temperature hydride vapor phase epitaxy • Influence of V/III ratio on growth rate, morphology and crystalline quality • The effect of surface morphology on strain state and crystal quality is established.

  11. Electronic structure of Cr doped Fe3O4 thin films by X-ray absorption near-edge structure spectroscopy

    Science.gov (United States)

    Chen, Chi-Liang; Dong, Chung-Li; Asokan, Kandasami; Chern, G.; Chang, C. L.

    2018-04-01

    Present study reports the electronic structures of Cr doped Fe3O4 (Fe3-xCrxO4 (0 ≤ x ≤ 3) grown on MgO (100) substrates in the form of thin films fabricated by a plasma-oxygen assisted Molecular Beam Epitaxy (MBE). X-ray absorption near-edge structure (XANES) spectra at Cr & Fe L-, and O K-edges were used to understand the electronic structure: changes in the bonding nature, valence states, and site occupancies. Cr doping in Fe3O4 results in the change of charge transfer, crystal structure, and selective occupation of ions in octahedral and tetrahedral sites. Such change modifies the electrical and magnetic properties due to the covalency of Cr ions. The physical and chemical properties of ferrites are strongly dependent on the lattice site, ion size of dopant, and magnetic nature present at different structural symmetry of the spinel structure.

  12. Band gap tuning of epitaxial SrTiO{sub 3-δ}/Si(001) thin films through strain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Cottier, Ryan J.; Steinle, Nathan A.; Currie, Daniel A.; Theodoropoulou, Nikoleta, E-mail: ntheo@txstate.edu [Physics Department, Texas State University, San Marcos, Texas 78666 (United States)

    2015-11-30

    We investigate the effect of strain and oxygen vacancies (V{sub O}) on the crystal and optical properties of oxygen deficient, ultra-thin (4–30 nm) films of SrTiO{sub 3-δ} (STO) grown heteroepitaxially on p-Si(001) substrates by molecular beam epitaxy. We demonstrate that STO band gap tuning can be achieved through strain engineering and show that the energy shift of the direct energy gap transition of SrTiO{sub 3-δ}/Si films has a quantifiable dimensional and doping dependence that correlates well with the changes in crystal structure.

  13. Improving stability of photoluminescence of ZnSe thin films grown by molecular beam epitaxy by incorporating Cl dopant

    International Nuclear Information System (INIS)

    Wang, J. S.; Shen, J. L.; Chen, W. J.; Tsai, Y. H.; Wang, H. H.; Yang, C. S.; Chen, R. H.; Tsai, C. D.

    2011-01-01

    This investigation studies the effect of chlorine (Cl) dopant in ZnSe thin films that were grown by molecular beam epitaxy on their photoluminescence (PL) and the stability thereof. Free excitonic emission was observed at room-temperature in the Cl-doped sample. Photon irradiation with a wavelength of 404 nm and a power density of 9.1 W/cm 2 has a much stronger effect on PL degradation than does thermal heating to a temperature of 150 deg. C. Additionally, this study shows that the generation of nonradiative centers by both photon irradiation and thermal heating can be greatly inhibited by incorporating Cl dopant.

  14. Nanoscale Phase Separation in Fe3O4(111) Films on Sapphire(0001) and Phase Stability of Fe3O4(001) Films on MgO(001) Grown by Oxygen-Plasma-Assisted Molecular Beam Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Toney, Michael F

    2003-06-25

    We report a phase instability in oxygen-plasma-assisted molecular beam epitaxy of Fe{sub 3}O{sub 4} films on sapphire (0001) substrates. Under a wide range of growth conditions, Fe{sub 3}O{sub 4} (111) films phase separate, on a nanometer length scale, into Fe{sub 3}O{sub 4}, Fe0 and metallic Fe, which is attributed to formation of the thermodynamically unstable phase Fe0 in the initial stages of (111) growth. In contrast, Fe{sub 3}O{sub 4} (001) films, grown simultaneously on MgO(001) substrates, do not exhibit this phase instability. We specify growth conditions for which single-phase, epitaxial Fe{sub 3}O{sub 4} (111) films can be grown by plasma-assisted molecular beam epitaxy or by reactive evaporation of Fe in molecular oxygen. Film orientation and phase separation strongly influence magnetic properties. Single-phase Fe{sub 3}O{sub 4} (111) films are much more difficult to magnetize than Fe{sub 3}O{sub 4} (001) films and phase separation makes the films even more difficult to magnetize.

  15. Advanced fabrication method for the preparation of MOF thin films: Liquid-phase epitaxy approach meets spin coating method.

    KAUST Repository

    Chernikova, Valeriya

    2016-07-14

    Here we report a new and advanced method for the fabrication of highly oriented/polycrystalline metal-organic framework (MOF) thin films. Building on the attractive features of the liquid-phase epitaxy (LPE) approach, a facile spin coating method was implemented to generate MOF thin films in a high-throughput fashion. Advantageously, this approach offers a great prospective to cost-effectively construct thin-films with a significantly shortened preparation time and a lessened chemicals and solvents consumption, as compared to the conventional LPE-process. Certainly, this new spin-coating approach has been implemented successfully to construct various MOF thin films, ranging in thickness from a few micrometers down to the nanometer scale, spanning 2-D and 3-D benchmark MOF materials including Cu2(bdc)2•xH2O, Zn2(bdc)2•xH2O, HKUST-1 and ZIF-8. This method was appraised and proved effective on a variety of substrates comprising functionalized gold, silicon, glass, porous stainless steel and aluminum oxide. The facile, high-throughput and cost-effective nature of this approach, coupled with the successful thin film growth and substrate versatility, represents the next generation of methods for MOF thin film fabrication. Thereby paving the way for these unique MOF materials to address a wide range of challenges in the areas of sensing devices and membrane technology.

  16. Fabrication of Multiferroic Co-Substituted BiFeO3 Epitaxial Films on SrTiO3 (100 Substrates by Radio Frequency Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Yasuo Ando

    2011-06-01

    Full Text Available The 10 at.% Co-substituted BiFeO3 films (of thickness 50 nm were successfully prepared by radio frequency (r.f. magnetron sputtering on SrTiO3 (100 substrates with epitaxial relationships of [001](001Co-BiFeO3//[001](001SrTiO3. In this study, a single phase Co-substituted BiFeO3 epitaxial film was fabricated by r.f. magnetron sputtering. Sputtering conditions such as Ar, O2 gas pressure, annealing temperature, annealing atmosphere, and sputtering power were systematically changed. It was observed that a low Ar gas pressure and low sputtering power is necessary to suppress the formation of the secondary phases of BiOx. The Co-substituted BiFeO3 films were crystalized with post-annealing at 600 °C in air. The process window for single phase films is narrower than that for pure BiFeO3 epitaxial films. By substituting Fe with Co in BiFeO3, the magnetization at room temperature increased to 20 emu/cm3. This result suggests that Co-substituted BiFeO3 films can be used in spin-filter devices.

  17. Interfacial electronic transport phenomena in single crystalline Fe-MgO-Fe thin barrier junctions

    Energy Technology Data Exchange (ETDEWEB)

    Gangineni, R. B., E-mail: rameshg.phy@pondiuni.edu.in [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R. V. Nagar, Kalapet, Pondicherry 605 014 (India); SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Bellouard, C., E-mail: christine.bellouard@ijl.nancy-universite.fr; Duluard, A. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Negulescu, B. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); UFR de Sciences et Techniques, Matériaux, microélectronique, acoustique, nanotechnologies (GREMAN), University François Rabelais, Parc de Grandmont, 37200 Tours (France); Baraduc, C.; Gaudin, G. [SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Tiusan, C., E-mail: coriolan.tiusan@phys.utcluj.ro [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Department of Physics and Chemistry, Center of Superconductivity, Spintronics and Surface Science, Technical University of Cluj Napoca, Str. Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania)

    2014-05-05

    Spin filtering effects in nano-pillars of Fe-MgO-Fe single crystalline magnetic tunnel junctions are explored with two different sample architectures and thin MgO barriers (thickness: 3–8 monolayers). The two architectures, with different growth and annealing conditions of the bottom electrode, allow tuning the quality of the bottom Fe/MgO interface. As a result, an interfacial resonance states (IRS) is observed or not depending on this interface quality. The IRS contribution, observed by spin polarized tunnel spectroscopy, is analyzed as a function of the MgO barrier thickness. Our experimental findings agree with theoretical predictions concerning the symmetry of the low energy (0.2 eV) interfacial resonance states: a mixture of Δ{sub 1}-like and Δ{sub 5}-like symmetries.

  18. Ferroelectric size effects in multiferroic BiFeO3 thin films

    NARCIS (Netherlands)

    Chu, Y.H.; Zhao, T.; Cruz, M.P.; Zhan, Q.; Yang, P.L.; Martin, L.W.; Huijben, Mark; Yang, C.H.; Zavaliche, F.; Zheng, H.; Ramesh, R.

    2007-01-01

    Ferroelectric size effects in multiferroic BiFeO3 have been studied using a host of complementary measurements. The structure of such epitaxial films has been investigated using atomic force microscopy, transmission electron microscopy, and x-ray diffraction. The crystal structure of the films has

  19. Influence of Fe content on the structural and optical properties of ZnFeS thin films

    International Nuclear Information System (INIS)

    Feng, Q.J.; Shen, D.Z.; Zhang, J.Y.; Lu, Y.M.; Liu, Y.C.; Fan, X.W.

    2006-01-01

    ZnFeS thin films have been grown on c-plane sapphire substrate using low-pressure metalorganic chemical vapor deposition (LP-MOCVD) equipment. The X-ray diffraction (XRD) patterns indicated that the diffraction peaks positions of ZnFeS thin films shifts gradually towards the lower angle side due to substitution of Zn by Fe atoms in the crystal lattice with increasing Fe content. When gas flow rates of Fe (CO) 5 varied from 1 to 6 ml min -1 , crystalline phase of the ZnFeS thin film changed from the hexagonal to cubic structure. And when gas flow rates of Fe (CO) 5 was less than 6 ml min -1 , ZnFeS single-crystal structure was obtained. From the measurements of optical absorption spectrum, the energy gaps of the samples were evidently narrowed with increasing Fe component. The electronic states of ZnFeS were investigated by X-ray photoelectron spectroscopy (XPS). It was found that the S 2p shifted towards higher binding energies side due to the larger bond strength of Fe-S than that of Zn-S, but the Fe incorporated into the ZnS lattice did not affect the Zn 2p core levels

  20. Growth of epitaxial Pt thin films on (0 0 1) SrTiO{sub 3} by rf magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Kahsay, A. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Polo, M.C., E-mail: mcpolo@ub.edu [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Ferrater, C.; Ventura, J. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain); Rebled, J.M. [Departament d’Electrònica, Universitat de Barcelona Institut de Nanociència i Nanotecnologia IN 2UB, 08028 Barcelona (Spain); Varela, M. [Departament de Física Aplicada i Òptica, Universitat de Barcelona, 08028 Barcelona (Spain)

    2014-07-01

    The growth of platinum thin film by rf magnetron sputtering on SrTiO{sub 3}(0 0 1) substrates for oxide based devices was investigated. Platinum films grown at temperatures higher than 750 °C were epitaxial ([1 0 0]Pt(0 0 1)//[1 0 0]STO(0 0 1)), whereas at lower temperatures Pt(1 1 1) films were obtained. The surface morphology of the Pt films showed a strong dependence on the deposition temperature as was revealed by atomic force microscopy (AFM). At elevated temperatures there is a three-dimensional (3D) growth of rectangular atomically flat islands with deep boundaries between them. On the other hand, at low deposition temperatures, a two-dimensional (2D) layered growth was observed. The transition from 2D to 3D growth modes was observed that occurs for temperatures around 450 °C. The obtained epitaxial thin films also formed an atomically sharp interface with the SrTiO{sub 3}(0 0 1) substrate as confirmed by HRTEM.

  1. Photoconductivity of transparent perovskite oxide semiconductors BaSnO3 and SrTiO3 epitaxial thin films

    Science.gov (United States)

    Park, Jisung; Kim, Useong; Char, Kookrin; Institute of Applied Physics, Department of Physics; Astronomy, Seoul National University, Seoul Team

    We have measured the photoconductivity (PC) of epitaxial thin films of transparent semiconductor BaSnO3 (BSO) and SrTiO3 (STO) at room temperature. The epitaxial thin films of BSO and STO were grown by pulsed laser ablation technique on the MgO substrates to exclude any conductance from the substrate owing to its large bandgap (~7.8 eV). Despite the same crystalline structure and similar band gap sizes (~3.2 eV), the PC of BSO behaved very differently. The slowly varying component in the PC of BSO is much larger than that of STO; the PC of BSO increased slowly, reached higher magnitude after the same duration of illumination, and persisted longer than many hours after the light was turned off, whereas the PC of STO showed little persistent conductivity. The spectral responses of the PC of BSO and STO showed their highest peaks below 400 nm when measured by a UV monochromator system, suggesting that the electron-hole pair generation is the main mechanism of the PC for both materials. The higher mobility of BSO should be partially responsible for the higher PC. The large persistent PC of BSO seems related to the dislocations that trap electrons easily.

  2. Ordered misfit dislocations in epitaxial Gd doped CeO2 thin films deposited on (001)YSZ single crystal substrates

    Science.gov (United States)

    Petrișor, T.; Meledin, A.; Boulle, A.; Moș, R. B.; Gabor, M. S.; Ciontea, L.; Petrișor, T.

    2018-03-01

    Misfit dislocations are ubiquitous in thin film systems, and their presence can profoundly affect the chemical and physical properties of materials. In the present paper, we investigate the misfit dislocation array present at the interface of a Gd doped CeO2 thin film epitaxially grown on a (001) yttria stabilized zirconia (YSZ) single crystal substrate. Because of the large misfit strain (-4.9%), the growth takes place by domain-matching epitaxy with the formation of geometrical misfit dislocations. Transmission electron microscopy (TEM) observations, combined with geometrical phase analysis and strain field calculations (in the case of elastic isotropy), reveal that the misfit dislocations are of purely edge type with Burgers vector b = ½[110] and with the dislocations lines parallel to the [1-10] direction. X-ray diffraction, combined with Monte Carlo simulations, allow to quantify the statistical properties of the dislocations ensemble. It is found that the dislocations are distributed according to a Gamma distribution with a mean dislocation spacing of 7.4 nm and with a spacing ranging from 3.5 to 12 nm, in excellent agreement with TEM observations and with the values expected from the relaxation of the misfit strain.

  3. Molecular beam epitaxy of germanium nanoclusters and indium gallium nitride thin films

    Science.gov (United States)

    Liu, Bing

    Molecular beam epitaxy (MBE) is an important method of growth of thin crystalline films. In this thesis, I study MBE of Ge on Si(100) substrates and InGaN on silicon and sapphire substrates. Formation and evolution of three-dimensional Ge/Si(100) islands of diameters between 10 to 150 nm are first investigated. Three types of Ge clusters are identified ex situ by atomic force microscopy. These are (i) pyramidal islands with four {105} facets, (ii) dome-type islands with steeper facets of {113}, and (iii) very large and strain relaxed "superdome" islands of {112}, {125} and {215} facets. The island size, shape, and spatial distributions are examined as functions of major growth parameters such as substrate temperature, Ge beam flux, and time of annealing. The growth of Ge on Si(100) is divided into different regimes according to the total coverage. In the low and moderate coverage (10 monolayers) regime, formation of pyramidal islands is a kinetically favored process. These pyramids can evolve into larger dome type islands by several kinetic pathways including coarsening and coalescence. By appropriate low temperature annealing, an ensemble of pyramids can reach a local equilibrium state where the islands can have a narrow size distribution and a locally ordered spatial distribution. This can be useful for growth of self-assembled quantum dot devices. At higher coverages, very large superdome-type islands could form and grow at the expense of the nearby small pyramids and domes. However, the superdome island formation can also be suppressed by using high Ge beam fluxes. The mechanisms of the evolution of the Ge islands and the transition of one type of islands to another type of islands in each growth regime are discussed. After I obtain an overall understanding of the growth and evolution of Ge nanoclusters on flat Si(100) surfaces, lateral alignment of Ge/Si(100) islands is explored using pre-patterned Si(100) substrates as the growth templates. The patterns are

  4. Atomic layer epitaxy of hematite on indium tin oxide for application in solar energy conversion

    Science.gov (United States)

    Martinson, Alex B.; Riha, Shannon; Guo, Peijun; Emery, Jonathan D.

    2016-07-12

    A method to provide an article of manufacture of iron oxide on indium tin oxide for solar energy conversion. An atomic layer epitaxy method is used to deposit an uncommon bixbytite-phase iron (III) oxide (.beta.-Fe.sub.2O.sub.3) which is deposited at low temperatures to provide 99% phase pure .beta.-Fe.sub.2O.sub.3 thin films on indium tin oxide. Subsequent annealing produces pure .alpha.-Fe.sub.2O.sub.3 with well-defined epitaxy via a topotactic transition. These highly crystalline films in the ultra thin film limit enable high efficiency photoelectrochemical chemical water splitting.

  5. High Temperature Magnetic Properties of Indirect Exchange Spring FePt/M(Cu,C/Fe Trilayer Thin Films

    Directory of Open Access Journals (Sweden)

    Anabil Gayen

    2013-01-01

    Full Text Available We report the investigation of temperature dependent magnetic properties of FePt and FePt(30/M(Cu,C/Fe(5 trilayer thin films prepared by using magnetron sputtering technique at ambient temperature and postannealed at different temperatures. L10 ordering, hard magnetic properties, and thermal stability of FePt films are improved with increasing postannealing temperature. In FePt/M/Fe trilayer, the formation of interlayer exchange coupling between magnetic layers depends on interlayer materials and interface morphology. In FePt/C/Fe trilayer, when the C interlayer thickness was about 0.5 nm, a strong interlayer exchange coupling between hard and soft layers was achieved, and saturation magnetization was enhanced considerably after using interlayer exchange coupling with Fe. In addition, incoherent magnetization reversal process observed in FePt/Fe films changes into coherent switching process in FePt/C/Fe films giving rise to a single hysteresis loop. High temperature magnetic studies up to 573 K reveal that the effective reduction in the coercivity decreases largely from 34 Oe/K for FePt/Fe film to 13 Oe/K for FePt/C(0.5/Fe film demonstrating that the interlayer exchange coupling seems to be a promising approach to improve the stability of hard magnetic properties at high temperatures, which is suitable for high-performance magnets and thermally assisted magnetic recording media.

  6. Epitaxial Piezoelectric Pb(Zr0.2Ti0.8O3 Thin Films on Silicon for Energy Harvesting Devices

    Directory of Open Access Journals (Sweden)

    A. Sambri

    2012-01-01

    Full Text Available We report on the properties of ferroelectric Pb(Zr0.2Ti0.8O3 (PZT thin films grown epitaxially on (001 silicon and on the performance of such heterostructures for microfabricated piezoelectric energy harvesters. In the first part of the paper, we investigate the epitaxial stacks through transmission electron microscopy and piezoelectric force microscopy studies to characterize in detail their crystalline structure. In the second part of the paper, we present the electrical characteristics of piezoelectric cantilevers based on these epitaxial PZT films. The performance of such cantilevers as vibration energy transducers is compared with other piezoelectric harvesters and indicates the potential of the epitaxial approach in the field of energy harvesting devices.

  7. Focused-ion-beam induced damage in thin films of complex oxide BiFeO3

    Directory of Open Access Journals (Sweden)

    W. Siemons

    2014-02-01

    Full Text Available An unexpected, strong deterioration of crystal quality is observed in epitaxial perovskite BiFeO3 films in which microscale features have been patterned by focused-ion-beam (FIB milling. Specifically, synchrotron x-ray microdiffraction shows that the damaged region extends to tens of μm, but does not result in measureable changes to morphology or stoichiometry. Therefore, this change would go undetected with standard laboratory equipment, but can significantly influence local material properties and must be taken into account when using a FIB to manufacture nanostructures. The damage is significantly reduced when a thin metallic layer is present on top of the film during the milling process, clearly indicating that the reduced crystallinity is caused by ion beam induced charging.

  8. CdFe2O4 thin films for the detection of benzene vapors

    Science.gov (United States)

    Nagarajan, V.; Thayumanavan, A.

    2018-02-01

    Spinel cadmium ferrite thin films were prepared using spray pyrolysis technique. The structural analysis of synthesized CdFe2O4 thin films shows the spinel structure, which exhibits polycrystalline nature. Morphological study confirms that the crystallites of CdFe2O4 thin film have island-like nature. The size of the crystallite is recorded to be around 13.0-37 nm. Energy-dispersion spectroscopy confirms the presence of oxygen, iron and cadmium in cadmium ferrites film. The prepared CdFe2O4 thin film is extremely sensitive towards toxic benzene vapor molecules at ambient temperature. The resistance of synthesized CdFe2O4 thin film decreases considerably when this material is exposed to benzene vapor molecules. The selectivity, stability, recovery time, sensitivity and response time of CdFe2O4 thin film towards benzene vapor molecules were explored in the present study.

  9. Research Update: Van-der-Waals epitaxy of layered chalcogenide Sb2Te3 thin films grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Isom Hilmi

    2017-05-01

    Full Text Available An attempt to deposit a high quality epitaxial thin film of a two-dimensionally bonded (layered chalcogenide material with van-der-Waals (vdW epitaxy is of strong interest for non-volatile memory application. In this paper, the epitaxial growth of an exemplary layered chalcogenide material, i.e., stoichiometric Sb2Te3 thin films, is reported. The films were produced on unreconstructed highly lattice-mismatched Si(111 substrates by pulsed laser deposition (PLD. The films were grown by vdW epitaxy in a two-dimensional mode. X-ray diffraction measurements and transmission electron microscopy revealed that the films possess a trigonal Sb2Te3 structure. The single atomic Sb/Te termination layer on the Si surface was formed initializing the thin film growth. This work demonstrates a straightforward method to deposit vdW-epitaxial layered chalcogenides and, at the same time, opens up the feasibility to fabricate chalcogenide vdW heterostructures by PLD.

  10. Epitaxial effects in thin films of high-Tc cuprates with the K2NiF4 structure

    Science.gov (United States)

    Naito, Michio; Sato, Hisashi; Tsukada, Akio; Yamamoto, Hideki

    2018-03-01

    La2-xSrxCuO4 (LSCO) and La2-xBaxCuO4 (LBCO) have been recognized as the archetype materials of "hole-doped" high-Tc superconductors. Their crystal structures are relatively simple with a small number of constituent cation elements. In addition, the doping level can be varied by the chemical substitution over a wide range enough to obtain the full spectrum of doping-dependent electronic and magnetic properties. These attractive features have dedicated many researchers to thin-film growth of LSCO and LBCO. The critical temperature (Tc) of LSCO and LBCO is sensitive to strain as manifested by a positive pressure coefficient of Tc in bulk samples. In general, films are strained if they are grown on lattice-mismatched substrates (epitaxial strain). Early attempts (before 1997) at the growth of LSCO and LBCO films resulted in depressed Tc below 30 K as they were grown on a commonly used SrTiO3 substrate (in-plane lattice parameter asub = 3.905 Å): the in-plane lattice parameters of LSCO and LBCO are ≤3.80 Å, and hence tensile epitaxial strain is introduced. The situation was changed by the use of LaSrAlO4 substrates with a slightly shorter in-plane lattice constant (asub = 3.756 Å). On LaSrAlO4 substrates, the Tc reaches 45 K in La1.85Sr0.15CuO4, 47 K in La1.85Ba0.15CuO4, and 56 K in ozone-oxidized La2CuO4+δ films, substantially higher than the Tc's of the bulk compounds. The Tc increase in La1.85Sr0.15CuO4 films on LaSrAlO4 and decrease on SrTiO3 are semi-quantitatively in accord with the phenomenological estimations based on the anisotropic strain coefficients of Tc (dTc/dεi). In this review article, we describe the growth and properties of films of cuprates having the K2NiF4 structure, mainly focusing on the increase/decrease of Tc by epitaxial strain and quasi-stable phase formation by epitaxial stabilization. We further extract the structural and/or physical parameters controlling Tc toward microscopic understanding of the variation of Tc by epitaxial strain.

  11. Fabrication of highly spin-polarized Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} thin-films

    Energy Technology Data Exchange (ETDEWEB)

    Vahidi, M.; Zhang, S. K.; Yu, L.; Huang, M.; Newman, N., E-mail: Nathan.Newman@asu.edu [School of Materials, Arizona State University, Tempe, Arizona 85287-8706 (United States); Gifford, J. A.; Chen, T. Y. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Krishnamurthy, S.; Yu, Z. G. [SRI International, 301-64, Menlo Park, California 94025 (United States); Youngbull, C. [The Biodesign Institute, Arizona State University, Tempe, Arizona 85287 (United States)

    2014-04-01

    Ferromagnetic Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} epitaxial thin-films have been fabricated in the L2{sub 1} structure with saturation magnetizations over 1200 emu/cm{sup 3}. Andreev reflection measurements show that the spin polarization is as high as 80% in samples sputtered on unheated MgO (100) substrates and annealed at high temperatures. However, the spin polarization is considerably smaller in samples deposited on heated substrates.

  12. Flexoelectric effect in the reversal of self-polarization and associated changes in the electronic functional properties of BiFeO(3) thin films.

    Science.gov (United States)

    Jeon, Byung Chul; Lee, Daesu; Lee, Myang Hwan; Yang, Sang Mo; Chae, Seung Chul; Song, Tae Kwon; Bu, Sang Don; Chung, Jin-Seok; Yoon, Jong-Gul; Noh, Tae Won

    2013-10-18

    Flexoelectricity can play an important role in the reversal of the self-polarization direction in epitaxial BiFeO3 thin films. The flexoelectric and interfacial effects compete with each other to determine the self-polarization state. In Region I, the self-polarization is downward because the interfacial effect is more dominant than the flexoelectric effect. In Region II, the self-polarization is upward, because the flexoelectric effect becomes more dominant than the interfacial effect. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Formation of Fe2SiO4 thin films on Si substrates and influence of substrate to its thermoelectric transport properties

    Science.gov (United States)

    Choi, Jeongyong; Nguyen, Van Quang; Duong, Van Thiet; Shin, Yooleemi; Duong, Anh Tuan; Cho, Sunglae

    2018-03-01

    Fe2SiO4 thin films have been grown on n-type, p-type and semi-insulating Si(100) substrates by molecular beam epitaxy. When Fe-O thin films were deposited on Si(100) substrate at 300 °C, the film reacted with Si, resulting in a Fe2SiO4 film because of the high reactivity between Fe and Si. The electrical resistance and Seebeck coefficient of Fe2SiO4 thin films grown were different in different doping states. On n-type and p-type Si(100), the electrical resistance decreased suddenly and increased again at 350 and 250 K, respectively, while on semi-insulating Si(100), it exhibited typical semiconducting resistance behavior. We observed similar crossovers at 350 and 250 K in temperature dependent Seebeck coefficients on n-type and p-type Si(100), respectively. These results suggest that the measured electrical and thermoelectric properties originate from Si substrate.

  14. Electric field effect on epitaxial YBa2Cu3O7-x thin films

    NARCIS (Netherlands)

    Joosse, K.; Joosse, K.; Boguslavskij, Yu.M.; Boguslavskij, Y.M.; Gerritsma, G.J.; Rogalla, Horst

    1994-01-01

    By applying a strong electric field perpendicular to the surface of an ultrathin, highly uniform epitaxial YBa2Cu3O7¿x film, the critical current was depressed and enhanced over 20% at temperatures close to Tc, and 5% at lower temperatures. Careful analysis of the electric field dependent I-V

  15. Formation of HgSe thin films using electrochemical atomic Layer epitaxy

    CSIR Research Space (South Africa)

    Mathe, MK

    2005-09-01

    Full Text Available The growth of HgSe using electrochemical atomic-layer epitaxy (EC-ALE) is reported. EC-ALE is the electrochemical analog of ALE, where electrochemical surface-limited reactions referred to as underpotential deposits, generally result...

  16. Tuning piezoelectric properties through epitaxy of La2Ti2O7 and related thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Hong, Seungbum; Bowden, Mark E.; Varga, Tamas; Yan, Pengfei; Wang, Chongmin; Spurgeon, Steven R.; Comes, Ryan B.; Ramuhalli, Pradeep; Henager, Charles H.

    2018-02-14

    Current piezoelectric sensors and actuators are limited to operating temperatures less than ~200°C due to the low Curie temperature of the piezoelectric material. High temperature piezoelectric materials such as La2Ti2O7 (LTO) would facilitate the development of high-temperature sensors if the piezoelectric coupling coefficient could be maximized. We have deposited epitaxial LTO films on SrTiO3(001), SrTiO3(110), and rutile TiO2(110) substrates by pulsed laser deposition, and show that the crystalline orientation of the LTO film, and thus its piezoelectric coupling direction, can be controlled by epitaxial matching to the substrate. The structure and phase purity of the films were investigated by x-ray diffraction and scanning transmission electron microscopy. To characterize the piezoelectric properties, piezoresponse force microscopy was used to measure the in-plane and out-of-plane piezoelectric coupling in the films. We find that the strength of the out-of-plane piezoelectric coupling can be increased when the piezoelectric crystalline direction is rotated partially out-of-plane via epitaxy. The strongest out-of-plane coupling is observed for LTO/STO(001). Deposition on TiO2(110) results in epitaxial La2/3TiO3, an orthorhombic perovskite of interest as a microwave dielectric material. La2/3TiO3 can be difficult to stabilize in bulk form, and epitaxial deposition has not been previously reported. These results confirm that control of the crystalline orientation of LTO-based materials can increase the out-of-plane strength of its piezoelectric coupling, which can be exploited in piezoelectric devices.

  17. Interlayer exchange coupling, crystalline and magnetic structure in Fe/CsCl-FeSi multilayers grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Dekoster, J.; Degroote, S.; Meersschaut, J.; Moons, R.; Vantomme, A. [K.U. Leuven, Instituut voor Kern- en Stralingsfysica (Belgium); Bottyan, L.; Deak, L.; Szilagyi, E.; Nagy, D.L. [KFKI Research Institute for Particle and Nuclear Physics (Hungary); Baron, A.Q.R. [European Synchrotron Radiation Facility (France); Langouche, G. [K.U. Leuven, Instituut voor Kern- en Stralingsfysica (Belgium)

    1999-09-15

    Crystalline and magnetic structure as well as the interlayer exchange coupling in MBE grown Fe/FeSi multilayers are investigated. From conversion electron Moessbauer spectroscopy and ion beam channeling measurements the spacer FeSi material is found to be stabilized in a crystalline metastable metallic FeSi phase with the CsCl structure. Strong non-oscillatory interlayer exchange coupling is identified with magnetometry and synchrotron Moessbauer reflectometry. From the fits of the time spectrum and the resonant {phi}-{phi} scans a model for the sublayer magnetization of the multilayer is deduced.

  18. Epitaxial Growth of MOF Thin Film for Modifying the Dielectric Layer in Organic Field-Effect Transistors.

    Science.gov (United States)

    Gu, Zhi-Gang; Chen, Shan-Ci; Fu, Wen-Qiang; Zheng, Qingdong; Zhang, Jian

    2017-03-01

    Metal-organic framework (MOF) thin films are important in the application of sensors and devices. However, the application of MOF thin films in organic field effect transistors (OFETs) is still a challenge to date. Here, we first use the MOF thin film prepared by a liquid-phase epitaxial (LPE) approach (also called SURMOFs) to modify the SiO 2 dielectric layer in the OFETs. After the semiconductive polymer of PTB7-Th (poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene-co-3-fluorothieno[3,4-b]thiophene-2-carboxylate]) was coated on MOF/SiO 2 and two electrodes on the semiconducting film were deposited sequentially, MOF-based OFETs were fabricated successfully. By controlling the LPE cycles of SURMOF HKUST-1 (also named Cu 3 (BTC) 2 , BTC = 1,3,5-benzenetricarboxylate), the performance of the HKUST-1/SiO 2 -based OFETs showed high charge mobility and low threshold voltage. This first report on the application of MOF thin film in OFETs will offer an effective approach for designing a new kind of materials for the OFET application.

  19. P-type ZnO thin films prepared by plasma molecular beam epitaxy using radical NO

    Energy Technology Data Exchange (ETDEWEB)

    Liang, H.W.; Lu, Y.M.; Shen, D.Z.; Liu, Y.C.; Yan, J.F.; Li, B.H.; Zhang, Z.Z.; Zhang, J.Y.; Fan, X.W. [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16-Dongnanhu Road, Changchun 130033 (China); Shan, C.X. [Department of Physics, Chinese University of Hong Kong, Shatin, Hong Kong (China)

    2005-05-01

    N-doped p-type ZnO thin films were grown by plasma molecular beam epitaxy (P-MBE) on c-plane sapphire (Al{sub 2}O{sub 3}) using radical NO as oxygen source and nitrogen dopant. The reproducible ZnO thin films have maximum net hole concentration (N{sub A}-N{sub D}) of 1.2 x 10{sup 18} cm{sup -3} and minimum resistivity of 9.36 {omega} cm. The influence of N incorporation on the quality of the ZnO thin films was studied using X-ray diffraction and absorption spectra. The photoluminescence spectra at 77 K of p-type ZnO thin films are dominated by the emission from donor-acceptor pair recombination. The formation mechanism of p-type ZnO is explained by the optical emission spectra of radical N{sub 2} and radical NO. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Orientation-dependent physical properties of layered perovskite La1.3Sr1.7Mn2O7 epitaxial thin films

    Science.gov (United States)

    Niu, Li-Wei; Guo, Bing; Chen, Chang-Le; Luo, Bing-Cheng; Dong, Xiang-Lei; Jin, Ke-Xin

    2017-04-01

    In this paper, the resistivity and magnetization of orientation-engineered layered perovskite La1.3Sr1.7Mn2O7 epitaxial thin films have been investigated. Epitaxial thin films were deposited on single-crystalline LaAlO3 (LAO) (001), (110) and (111) substrates by pulse laser deposition (PLD) technique. It is found that only the (100)-oriented thin film performs insulator behavior, whereas the (110) and (111)-oriented thin films exhibit obvious metal-insulator transition at 70 K and between 85 and 120 K, respectively. Moreover, the same spin freezing temperature and different spin-glass-like transition temperatures have been observed in various oriented films. The observed experimental results were discussed according to the electron-transport mechanism and spin dynamics.

  1. Bulk Single Crystal-Like Structural and Magnetic Characteristics of Epitaxial Spinel Ferrite Thin Films with Elimination of Antiphase Boundaries.

    Science.gov (United States)

    Singh, Amit V; Khodadadi, Behrouz; Mohammadi, Jamileh Beik; Keshavarz, Sahar; Mewes, Tim; Negi, Devendra Singh; Datta, Ranjan; Galazka, Zbigniew; Uecker, Reinhard; Gupta, Arunava

    2017-08-01

    Spinel ferrite NiFe 2 O 4 thin films have been grown on three isostructural substrates, MgAl 2 O 4 , MgGa 2 O 4 , and CoGa 2 O 4 using pulsed laser deposition. These substrates have lattice mismatches of 3.1%, 0.8%, and 0.2%, respectively, with NiFe 2 O 4 . As expected, the films grown on MgAl 2 O 4 substrate show the presence of the antiphase boundary defects. However, no antiphase boundaries (APBs) are observed for films grown on near-lattice-matched substrates MgGa 2 O 4 and CoGa 2 O 4 . This demonstrates that by using isostructural and lattice-matched substrates, the formation of APBs can be avoided in NiFe 2 O 4 thin films. Consequently, static and dynamic magnetic properties comparable with the bulk can be realized. Initial results indicate similar improvements in film quality and magnetic properties due to the elimination of APBs in other members of the spinel ferrite family, such as Fe 3 O 4 and CoFe 2 O 4 , which have similar crystallographic structure and lattice constants as NiFe 2 O 4 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Enhanced piezoelectric properties of (110)-oriented PbZr1−xTixO3 epitaxial thin films on silicon substrates at shifted morphotropic phase boundary

    NARCIS (Netherlands)

    Wan, X.; Houwman, Evert Pieter; Steenwelle, Ruud Johannes Antonius; van Schaijk, R.; Nguyen, Duc Minh; Dekkers, Jan M.; Rijnders, Augustinus J.H.M.

    2014-01-01

    Piezoelectrical, ferroelectrical, and structural properties of epitaxial pseudocubic (110)pc oriented 500 nm thick PbZr1−xTixO3 thin films, prepared by pulsed laser deposition on (001) silicon substrates, were measured as a function of composition. The dependence of the measurement data on the Ti

  3. Magnetization process in FePd thin films

    International Nuclear Information System (INIS)

    Klein, O.; Samson, Y.; Marty, A.; Guillous, S.; Viret, M.; Fermon, C.; Alloul, H.

    2001-01-01

    A custom made magnetic force microscope is used to study the magnetization process in thin films of FePd throughout the entire hysteresis loop. The 40 nm thick sample has a strong perpendicular anisotropy, which leads to a maze of 80 nm wide stripes of opposite polarity in the remanent state. The growth of M, when H increases, happens through an unwinding of the reversed domain along their axis. Together with the length recession, the reversed domain width also contracts with increasing field. The later effect is estimated by comparison of our images with magneto-optical Kerr measurements. A large disorder in the propagation process of the domain walls is observed. It is also found that the bubble configuration near the saturation field is unstable. [copyright] 2001 American Institute of Physics

  4. Reactively sputtered epitaxial γ′-Fe4N films: Surface morphology, microstructure, magnetic and electrical transport properties

    KAUST Repository

    Mi, Wenbo

    2013-10-01

    Epitaxial γ′-Fe4N films with (1 0 0) and (1 1 0) orientations have been fabricated by reactive sputtering; these films were characterized by X-ray θ-2θ and φ scans, pole figures and high-resolution transmission electron microscopy. The film surface is very smooth as the film is less than 58 nm thick. The films exhibit soft ferromagnetism, and the saturation magnetization decreases with an increase in temperature, following Bloch\\'s spin wave theory. The films also exhibit a metallic conductance mechanism. Below 30 K, magnetoresistance (MR) is positive and increases linearly with the applied field in the high-field range. In the low-field range, MR increases abruptly. Above 30 K, MR is negative, and its value increases linearly with the applied field.

  5. Strain-mediated magnetic and transport properties of epitaxial LuxFe3-xO4 films

    Science.gov (United States)

    Wang, P.; Jin, C.; Zheng, D. X.; Bai, H. L.

    2015-10-01

    Strain mediated structure, magnetic, and transport properties of spinel ferrites were investigated by growing epitaxial LuxFe3-xO4 (LFO, 0 ≤ x ≤ 0.26 ) films on SrTiO3 and MgO substrates with in-plane compressive and tensile strains, respectively. The lattice parameter of LFO films decreases on SrTiO3 substrates, while increases on MgO substrates with the increasing Lu content. The LFO films on SrTiO3 substrates exhibit larger saturation magnetization and smaller exchange bias and coercive field. Phase shift of anisotropic magnetoresistance is also observed in the LFO films on SrTiO3 substrates. In addition, the nonmagnetic Lu3+ ions in spinel ferrites enhance the spin canting, which further increases the exchange bias and coercive field and strengthens the four-fold symmetry of anisotropic magnetoresistance and the two-fold symmetry of planar Hall effect.

  6. Heterogeneous Two-Phase Pillars in Epitaxial NiFe 2 O 4 -LaFeO 3 Nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan B. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Department of Physics, Auburn University, Auburn AL 36849 USA; Perea, Daniel E. [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99352 USA; Spurgeon, Steven R. [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA

    2017-07-10

    Self-assembled epitaxial oxide nanocomposites have been explored for a wide range of applications, including multiferroic and magnetoelectric properties, plasmonics, and catalysis. These so-called “vertically aligned nanocomposites” form spontaneously during the deposition process when segregation into two phases is energetically favorable as compared to a solid solution. However, there has been surprisingly little work understanding the driving forces that govern the synthesis of these materials, which can include point defect energetics, surface diffusion, and interfacial energies. To explore these factors, La-Ni-Fe-O films have been synthesized by molecular beam epitaxy and it is shown that these phase segregate into spinel-perovskite nanocomposites. Using complementary scanning transmission electron microscopy and atom-probe tomography, the elemental composition of each phase is examined and found that Ni ions are exclusively found in the spinel phase. From correlative analysis, a model for the relative favorability of the Ni2+ and Ni3+ valences under the growth conditions is developed. It is shown that multidimensional characterization techniques provide previously unobserved insight into the growth process and complex driving forces for phase segregation.

  7. Producing ZnFe{sub 2}O{sub 4} thin films from ZnO/FeO multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Salcedo Rodríguez, Karen L., E-mail: klsalcedor@fisica.unlp.edu.ar [IFLP y Departamento Física, Facultad de Ciencias Exactas, Universidad Nacional de la Plata-CCT La Plata CONICET, C.C. 67, CP 1900 La Plata (Argentina); Hoffmann, Martin [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Institute for Physics, Martin Luther University Halle-Wittenberg, Von-Seckendorff-Platz 1, 06120 Halle (Saale) (Germany); Golmar, Federico [CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country (Spain); I.N.T.I.-CONICET and ECyT-UNSAM, San Martín, Bs. As. (Argentina); Pasquevich, Gustavo [IFLP y Departamento Física, Facultad de Ciencias Exactas, Universidad Nacional de la Plata-CCT La Plata CONICET, C.C. 67, CP 1900 La Plata (Argentina); Departamento de Ciencias Básicas, Facultad de Ingeniería, Universidad Nacional de La Plata, CP 1900 La Plata (Argentina); Werner, Peter [Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Saale) (Germany); Hergert, Wolfram [Institute for Physics, Martin Luther University Halle-Wittenberg, Von-Seckendorff-Platz 1, 06120 Halle (Saale) (Germany); Rodríguez Torres, Claudia E. [IFLP y Departamento Física, Facultad de Ciencias Exactas, Universidad Nacional de la Plata-CCT La Plata CONICET, C.C. 67, CP 1900 La Plata (Argentina)

    2017-01-30

    Highlights: • Zinc ferrite thin film was obtained from a FeO/ZnO multilayers process. • Two scenarios were proposed to explain structural changes on the thin film. • Cation inversion on surface of the sample as the cause of magnetic contributions. - Abstract: The present work investigates the structural and magnetic properties of ZnFe{sub 2}O{sub 4} thin films obtained from ZnO/FeO multilayers deposited on MgO substrate by DC reactive sputtering. We show that this method is good to grow efficiently ordered ZnFe{sub 2}O{sub 4} films. The quality of the thin films is ensured by TEM measurements, which showed a well ordered film of ZnFe{sub 2}O{sub 4}. The magnetic properties of these thin films present still minimal differences when compared to bulk ZnFe{sub 2}O{sub 4} powders. They exhibit a ferromagnetic-like behavior at low temperatures, whereas ZnFe{sub 2}O{sub 4} is expected to be antiferromagnetic. We found that the magnetic signal originated from the film surface, where cation inversion was visible from grazing incidence X-ray fluorescence measurements. The inversion of Fe ions with Zn ions caused a magnetic spin glass state, which created then the ferromagnetic-like behavior differently to bulk ZnFe{sub 2}O{sub 4}. These facts point to possible routes in order to improve the growing process of ZnFe{sub 2}O{sub 4} via ZnO/FeO multilayers.

  8. Epitaxial layers of 2122 BCSCO superconductor thin films having single crystalline structure

    Science.gov (United States)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal K. (Inventor); Solayappan, Narayanan (Inventor)

    1995-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  9. 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.

  10. 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.

  11. Structural and magnetic phase transitions in chromium nitride thin films grown by rf nitrogen plasma molecular beam epitaxy

    Science.gov (United States)

    Alam, Khan; Disseler, Steven M.; Ratcliff, William D.; Borchers, Julie A.; Ponce-Pérez, Rodrigo; Cocoletzi, Gregorio H.; Takeuchi, Noboru; Foley, Andrew; Richard, Andrea; Ingram, David C.; Smith, Arthur R.

    2017-09-01

    A magnetostructural phase transition is investigated in single-crystal chromium nitride (CrN) thin films grown by rf plasma molecular beam epitaxy on MgO(001) substrates. While still within the vacuum environment following molecular beam epitaxy growth, in situ low-temperature scanning tunneling microscopy, and in situ variable low-temperature reflection high-energy electron diffraction are applied, revealing an atomically smooth and metallic CrN(001) surface, and an in-plane structural transition from 1 ×1 (primitive CrN unit cell) to √{2 }×√{2 }-R 45∘ with a transition temperature of (278 ±3 ) K, respectively. Ex situ temperature-dependent measurements using neutron diffraction are also performed, looking at the structural peaks and likewise revealing a first-order structural transition along the [111] out-of-plane direction, with transition temperatures of (268 ± 3) K. Turning to the magnetic peaks, neutron diffraction confirms a clear magnetic transition from paramagnetic at room temperature to antiferromagnetic at low temperatures with a sharp, first-order phase transition and a Néel temperature of (270 ±2 ) K or (280 ±2 ) K for two different films. In addition to the experimental measurements of structural and magnetic ordering, we also discuss results from first-principles theoretical calculations which explore various possible magnetostructural models.

  12. Nanoscale Control of Exchange Bias with BiFeO3 Thin Films

    NARCIS (Netherlands)

    Martin, Lane W.; Chu, Ying-Hao; Holcomb, Mikel B.; Huijben, Mark; Yu, Pu; Han, Shu-Jen; Lee, Donkoun; Wang, Shan X.; Ramesh, R.

    2008-01-01

    We demonstrate a direct correlation between the domain structure of multiferroic BiFeO3 thin films and exchange bias of Co0.9Fe0.1/BiFeO3 heterostructures. Two distinct types of interactions − an enhancement of the coercive field (exchange enhancement) and an enhancement of the coercive field

  13. Perpendicular Magnetic Anisotropy and Spin Glass-like Behavior in Molecular Beam Epitaxy Grown Chromium Telluride Thin Films.

    Science.gov (United States)

    Roy, Anupam; Guchhait, Samaresh; Dey, Rik; Pramanik, Tanmoy; Hsieh, Cheng-Chih; Rai, Amritesh; Banerjee, Sanjay K

    2015-04-28

    Reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), vibrating sample magnetometry, and other physical property measurements are used to investigate the structure, morphology, magnetic, and magnetotransport properties of (001)-oriented Cr2Te3 thin films grown on Al2O3(0001) and Si(111)-(7×7) surfaces by molecular beam epitaxy. Streaky RHEED patterns indicate flat smooth film growth on both substrates. STM studies show the hexagonal arrangements of surface atoms. Determination of the lattice parameter from the atomically resolved STM image is consistent with the bulk crystal structures. Magnetic measurements show the film is ferromagnetic, having a Curie temperature of about 180 K, and a spin glass-like behavior was observed below 35 K. Magnetotransport measurements show the metallic nature of the film with a perpendicular magnetic anisotropy along the c-axis.

  14. Upper-critical fields of YBa2Cu3O7-δ epitaxial thin films with variable oxygen deficiency δ

    International Nuclear Information System (INIS)

    Jones, E.C.; Christen, D.K.; Thompson, J.R.; Ossandon, J.G.; Feenstra, R.; Phillips, J.M.; Siegal, M.P.

    1994-01-01

    Fluctuation analysis in the limit of high magnetic fields was performed on three epitaxial thin films of YBa 2 Cu 3 O 7-δ for various oxygen deficiencies δ c2 (T) slope of -1.7 T/K for H parallel c, consistent with previous observations of transport and magnetic properties. Moreover, the 3D scaling showed better convergence than the 2D scaling, which gave relatively low values of H c2 . In contrast, the transitions were not adequately described by either scaling for T c off the 90-K plateau; it is speculated that this is due to an extrinsic broadening of the transitions, possibly due to the lack of a complete percolation path of the ortho-I phase (δ=0)

  15. Strain effect in epitaxial VO2 thin films grown on sapphire substrates using SnO2 buffer layers

    Science.gov (United States)

    Kim, Heungsoo; Bingham, Nicholas S.; Charipar, Nicholas A.; Piqué, Alberto

    2017-10-01

    Epitaxial VO2/SnO2 thin film heterostructures were deposited on m-cut sapphire substrates via pulsed laser deposition. By adjusting SnO2 (150 nm) growth conditions, we are able to control the interfacial strain between the VO2 film and SnO2 buffer layer such that the semiconductor-to-metal transition temperature (TC) of VO2 films can be tuned without diminishing the magnitude of the transition. It is shown that in-plane tensile strain and out-of-plane compressive strain of the VO2 film leads to a decrease of Tc. Interestingly, VO2 films on SnO2 buffer layers exhibit a structural phase transition from tetragonal-like VO2 to tetragonal-VO2 during the semiconductor-to-metal transition. These results suggest that the strain generated by SnO2 buffer provides an effective way for tuning the TC of VO2 films.

  16. Epitaxial growth of high temperature superconductors by cathodic sputtering I: thin films of YBaCuO

    International Nuclear Information System (INIS)

    Navacerrada, M.A.; Sefrioui, Z.; Arias, D.; Varela, M.; Loos, G.; Leon, C.; Lucia, M.L.; Santamaria, J.; Sanchez-Quesada, F.

    1998-01-01

    High quality c-oriented YBa 2 Cu 3 O 7 -x thin films have been grown on SrTiO 3 (100)substrates by high pressure sputtering in pure oxygen atmosphere. Low angle X-ray diffraction and atomic force microscopy were performed on films less than 250 angstrom thick showing a plenitude better than one unit cell. Moreover, the structural characterization by means of X ray φ scans showed that growth is epitaxial. The critical temperature has been measured by different ways and was always in the range 89.5-90.5K. the resistance transition is sharper than 1K and the mutual inductance response always shows magnetic losses peaks narrower than 0.3K. Critical current densities are in excess of 10''''6 angstrom/cm''''2 at 77K. (Author) 8 refs

  17. Epitaxial growth of CdTe thin film on cube-textured Ni by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Gaire, C.; Rao, S.; Riley, M.; Chen, L.; Goyal, A.; Lee, S.; Bhat, I.; Lu, T.-M.; Wang, G.-C.

    2012-01-01

    Single crystal-like CdTe thin film has been grown by metalorganic chemical vapor deposition on cube-textured Ni(100) substrate. Using X-ray pole figure measurements we observed the epitaxial relationship of {111} CdTe //{001} Ni with [11 ¯ 0] CdTe //[010] Ni and [112 ¯ ] CdTe //[100] Ni . The 12 diffraction peaks in the (111) pole figure of CdTe film and their relative positions with respect to the four peak positions in the (111) pole figure of Ni substrate are consistent with four equivalent orientational domains of CdTe with three to four superlattice match of about 1.6% in the [11 ¯ 0] direction of CdTe and the [010] direction of Ni. The electron backscattered diffraction images show that the CdTe domains are 30° oriented from each other. These high structural quality films may find applications in low cost optoelectronic devices.

  18. Structure and chemistry of epitaxial ceria thin films on yttria-stabilized zirconia substrates, studied by high resolution electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, Robert, E-mail: bobsinc@stanford.edu [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Lee, Sang Chul, E-mail: sclee99@stanford.edu [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Shi, Yezhou; Chueh, William C. [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States)

    2017-05-15

    We have applied aberration-corrected transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy (EELS) to study the structure and chemistry of epitaxial ceria thin films, grown by pulsed laser deposition onto (001) yttria-stabilized zirconia (YSZ) substrates. There are few observable defects apart from the expected mismatch interfacial dislocations and so the films would be expected to have good potential for applications. Under high electron beam dose rate (above about 6000 e{sup -}/Å{sup 2}s) domains of an ordered structure appear and these are interpreted as being created by oxygen vacancy ordering. The ordered structure does not appear at lower lose rates (ca. 2600 e{sup -}/Å{sup 2}s) and can be removed by imaging under 1 mbar oxygen gas in an environmental TEM. EELS confirms that there is both oxygen deficiency and the associated increase in Ce{sup 3+} versus Ce{sup 4+} cations in the ordered domains. In situ high resolution TEM recordings show the formation of the ordered domains as well as atomic migration along the ceria thin film (001) surface. - Highlights: • The local structure and chemistry of ceria can be studied by TEM combined with EELS. • At lower electron, there are no observable changes in the ceria thin films. • At higher dose rates, an ordered phase is created due to oxygen vacancy ordering. • In situ HRTEM shows the oxygen vacancy ordering and the movement of surface atoms.

  19. Epitaxial Stabilization of the Perovskite Phase in (Sr(1-x)Ba(x))MnO3 Thin Films.

    Science.gov (United States)

    Langenberg, Eric; Guzmán, Roger; Maurel, Laura; Martínez de Baños, Lourdes; Morellón, Luis; Ibarra, M Ricardo; Herrero-Martín, Javier; Blasco, Javier; Magén, César; Algarabel, Pedro A; Pardo, José A

    2015-11-04

    A novel mechanism of ferroelectricity driven by off-centering magnetic Mn(4+) ions was proposed in (Sr1-xBax)MnO3, in its ideal perovskite phase, which yields enormous expectations in the search for strong magnetoelectric materials. Still, the desired perovskite phase has never been stabilized in thin films due to its extremely metastable character. Here, we report on a thorough study of the perovskite phase stabilization of (Sr1-xBax)MnO3 thin films, 0.2 ≤ x ≤ 0.5, grown by pulsed laser deposition onto (001)-oriented perovskite substrates. X-ray diffraction measurements and scanning transmission electron microscopy reveal that, under appropriate deposition conditions, the perovskite phase is fully stabilized over the nonferroelectric hexagonal phase, despite the latter being increasingly favored on increasing Ba-content. Moreover, we have managed to grow epitaxial coherent cube-on-cube (Sr1-xBax)MnO3 films upon strains ranging from 0% to 4%. Our results become a milestone in further studying perovskite (Sr1-xBax)MnO3 thin films and pave the way for tailoring ferroic and magnetoelectric properties either by strain engineering or Ba-doping.

  20. Evidence of non-Dzyaloshinskii–Moriya ferromagnetism in epitaxial BiFeO3 films

    NARCIS (Netherlands)

    Prokhorov, V.G.; Kaminsky, G.G.; Kim, J.M.; Eom, T.W.; Park, J.S.; Lee, Y.P.; Svetchnikov, V.L.; Levtchenko, G.G.; Nikolaenko, Y.M.; Khokhlov, V.A.

    2011-01-01

    X-ray diffraction analysis and high-resolution electron microscopy of BiFeO3 films prepared by dc magnetron sputtering on single-crystal LaAlO3 (001) substrates reveal that the films have a highly c-oriented orthorhombic crystalline structure. The magnetic properties of the BiFeO3 films are typical

  1. Epitaxial growth of indium oxyfluoride thin films by reactive pulsed laser deposition: Structural change induced by fluorine insertion into vacancy sites in bixbyite structure

    International Nuclear Information System (INIS)

    Okazaki, Sohei; Hirose, Yasushi; Nakao, Shoichiro; Yang, Chang; Harayama, Isao; Sekiba, Daiichiro; Hasegawa, Tetsuya

    2014-01-01

    InO x F y thin films were epitaxially grown on Y-stabilized ZrO 2 (111) substrates by reactive pulsed laser deposition. By changing the substrate temperature (T S ), we were able to control the fluorine content of the film. Phase-pure epitaxial thin films with bixbyite-like ordering in the anion-site occupancy were obtained at high T S (≥ 240 °C), where fluorine was inserted into the vacancy sites in the bixbyite lattice up to y / (x + y) ∼ 0.3. By decreasing T S , y / (x + y) increased and the bixbyite-like ordering disappeared; simultaneously, fluorine-rich and fluorine-poor subphases emerged. The films grown at T S ≤ 150 °C were amorphous and exhibited higher optical absorbance and electrical resistivity than the epitaxial films. - Highlights: • InO x F y epitaxial thin films with high fluorine concentration were grown on Y:ZrO 2 . • Anion composition and structural, optical and transport properties were studied. • Fluorine is topotactically inserted into the oxygen vacancy sites in bixbyite cell. • Bixbyite-like ordering of the anion site occupancy was conserved in y / (x + y) ≤ ∼ 0.3

  2. Epitaxial growth of indium oxyfluoride thin films by reactive pulsed laser deposition: Structural change induced by fluorine insertion into vacancy sites in bixbyite structure

    Energy Technology Data Exchange (ETDEWEB)

    Okazaki, Sohei [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Hirose, Yasushi, E-mail: hirose@chem.s.u-tokyo.ac.jp [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Yang, Chang [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Harayama, Isao; Sekiba, Daiichiro [Tandem Accelerator Complex, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8577 (Japan); Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2014-05-30

    InO{sub x}F{sub y} thin films were epitaxially grown on Y-stabilized ZrO{sub 2} (111) substrates by reactive pulsed laser deposition. By changing the substrate temperature (T{sub S}), we were able to control the fluorine content of the film. Phase-pure epitaxial thin films with bixbyite-like ordering in the anion-site occupancy were obtained at high T{sub S} (≥ 240 °C), where fluorine was inserted into the vacancy sites in the bixbyite lattice up to y / (x + y) ∼ 0.3. By decreasing T{sub S}, y / (x + y) increased and the bixbyite-like ordering disappeared; simultaneously, fluorine-rich and fluorine-poor subphases emerged. The films grown at T{sub S} ≤ 150 °C were amorphous and exhibited higher optical absorbance and electrical resistivity than the epitaxial films. - Highlights: • InO{sub x}F{sub y} epitaxial thin films with high fluorine concentration were grown on Y:ZrO{sub 2}. • Anion composition and structural, optical and transport properties were studied. • Fluorine is topotactically inserted into the oxygen vacancy sites in bixbyite cell. • Bixbyite-like ordering of the anion site occupancy was conserved in y / (x + y) ≤ ∼ 0.3.

  3. Epitaxial YBa2Cu3O7-x nanocomposite thin films from colloidal solutions

    Science.gov (United States)

    Cayado, P.; De Keukeleere, K.; Garzón, A.; Perez-Mirabet, L.; Meledin, A.; De Roo, J.; Vallés, F.; Mundet, B.; Rijckaert, H.; Pollefeyt, G.; Coll, M.; Ricart, S.; Palau, A.; Gázquez, J.; Ros, J.; Van Tendeloo, G.; Van Driessche, I.; Puig, T.; Obradors, X.

    2015-12-01

    A methodology of general validity to prepare epitaxial nanocomposite films based on the use of colloidal solutions containing different crystalline preformed oxide nanoparticles (ex situ nanocomposites) is reported. The trifluoroacetate (TFA) metal-organic chemical solution deposition route is used with alcoholic solvents to grow epitaxial YBa2Cu3O7 (YBCO) films. For this reason stabilizing oxide nanoparticles in polar solvents is a challenging goal. We have used scalable nanoparticle synthetic methodologies such as thermal and microwave-assisted solvothermal techniques to prepare CeO2 and ZrO2 nanoparticles. We show that stable and homogeneous colloidal solutions with these nanoparticles can be reached using benzyl alcohol, triethyleneglycol, nonanoic acid, trifluoroacetic acid or decanoic acid as protecting ligands, thereby allowing subsequent mixing with alcoholic TFA solutions. An elaborate YBCO film growth analysis of these nanocomposites allows the identification of the different relevant growth phenomena, e.g. nanoparticles pushing towards the film surface, nanoparticle reactivity, coarsening and nanoparticle accumulation at the substrate interface. Upon mitigation of these effects, YBCO nanocomposite films with high self-field critical currents (J c ˜ 3-4 MA cm-2 at 77 K) were reached, indicating no current limitation effects associated with epitaxy perturbation, while smoothed magnetic field dependences of the critical currents at high magnetic fields and decreased effective anisotropic pinning behavior confirm the effectiveness of the novel developed approach to enhance vortex pinning. In conclusion, a novel low cost solution-derived route to high current nanocomposite superconducting films and coated conductors has been developed with very promising features.

  4. Epitaxial growth of atomically flat gadolinia-doped ceria thin films by pulsed laser deposition

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Pryds, Nini; Schou, Jørgen

    2011-01-01

    Epitaxial growth of Ce0.8Gd0.2O2(CGO) films on (001) TiO2-terminated SrTiO3 substrates by pulsed laser deposition was investigated using in situ reflective high energy electron diffraction. The initial film growth shows a Stransky–Krastanov growth mode. However, this three-dimensional island...... formation is replaced by a two-dimensional island nucleation during further deposition, which results in atomically smooth CGO films. The obtained high-quality CGO films may be attractive for the electrolyte of solid-oxide fuel cells operating at low temperature....

  5. Magnetic Properties of FeNi-Based Thin Film Materials with Different Additives

    Directory of Open Access Journals (Sweden)

    Cai Liang

    2014-07-01

    Full Text Available This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B.

  6. Magnetic properties of FeNi-based thin film materials with different additives

    KAUST Repository

    Liang, C.

    2014-07-04

    This paper presents a study of FeNi-based thin film materials deposited with Mo, Al and B using a co-sputtering process. The existence of soft magnetic properties in combination with strong magneto-mechanical coupling makes these materials attractive for sensor applications. Our findings show that FeNi deposited with Mo or Al yields magnetically soft materials and that depositing with B further increases the softness. The out-of-plane magnetic anisotropy of FeNi thin films is reduced by depositing with Al and completely removed by depositing with B. The effect of depositing with Mo is dependent on the Mo concentration. The coercivity of FeNiMo and FeNiAl is reduced to less than a half of that of FeNi, and a value as low as 40 A/m is obtained for FeNiB. The surfaces of the obtained FeNiMo, FeNiAl and FeNiB thin films reveal very different morphologies. The surface of FeNiMo shows nano-cracks, while the FeNiAl films show large clusters and fewer nano-cracks. When FeNi is deposited with B, a very smooth morphology is obtained. The crystal structure of FeNiMo strongly depends on the depositant concentration and changes into an amorphous structure at a higher Mo level. FeNiAl thin films remain polycrystalline, even at a very high concentration of Al, and FeNiB films are amorphous, even at a very low concentration of B. 2014 by the authors.

  7. Fe-doping in hydride vapor-phase epitaxy for semi-insulating gallium nitride

    Science.gov (United States)

    Richter, E.; Gridneva, E.; Weyers, M.; Tränkle, G.

    2016-12-01

    Fe-doping of GaN layers of 3 in. in diameter and a thickness of 1 mm in a vertical AIX-HVPE reactor is studied. Ferrocen was used as Fe source. It is shown that a sufficient uniformity of growth conditions, a high purity of undoped GaN layers, and a moderate Fe incorporation of 2×1018 cm-3 allow for growth of semi-insulating GaN layers with a sufficiently high specific resistivity even at elevated temperature. This makes the material suitable as substrate for electronic power devices at high power or in harsh ambient.

  8. Epitaxial growth of Co(0 0 0 1)hcp/Fe(1 1 0)bcc magnetic bi-layer films on SrTiO3(1 1 1) substrates

    International Nuclear Information System (INIS)

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

    2008-01-01

    Co(0 0 0 1) hcp /Fe(1 1 0) bcc epitaxial magnetic bi-layer films were successfully prepared on SrTiO 3 (1 1 1) substrates. The crystallographic properties of Co/Fe epitaxial magnetic bi-layer films were investigated. Fe(1 1 0) bcc soft magnetic layer grew epitaxially on SrTiO 3 (1 1 1) substrate with two type variants, Nishiyama-Wasserman and Kurdjumov-Sachs relationships. An hcp-Co single-crystal layer is obtained on Ru(0 0 0 1) hcp interlayer, while hcp-Co layer formed on Au(1 1 1) fcc or Ag(1 1 1) fcc interlayer is strained and may involve fcc-Co phase. It has been shown possible to prepare Co/Fe epitaxial magnetic bi-layer films which can be usable for patterned media application

  9. Epitaxial Ba2IrO4 thin-films grown on SrTiO3 substrates by pulsed laser deposition

    OpenAIRE

    Nichols, J.; Korneta, O. B.; Terzic, J.; Cao, G.; Brill, J. W.; Seo, S. S. A.

    2014-01-01

    We have synthesized epitaxial Ba2IrO4 (BIO) thin-films on SrTiO3 (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metalinsulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr2IrO4. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlatio...

  10. Effects of substrate temperature and Cu underlayer thickness on the formation of SmCo5(0001) epitaxial thin films

    International Nuclear Information System (INIS)

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

    2010-01-01

    SmCo 5 (0001) epitaxial thin films were prepared on Cu(111) underlayers heteroepitaxially grown on Al 2 O 3 (0001) single-crystal substrates by molecular beam epitaxy. The effects of substrate temperature and Cu underlayer thickness on the crystallographic properties of SmCo 5 (0001) epitaxial films were investigated. The Cu atoms of underlayer diffuse into the SmCo 5 film and substitute the Co sites in SmCo 5 structure forming an alloy compound of Sm(Co,Cu) 5 . The ordered phase formation is enhanced with increasing the substrate temperature and with increasing the Cu underlayer thickness. The Cu atom diffusion into the SmCo 5 film is assisting the formation of Sm(Co,Cu) 5 ordered phase.

  11. Observation of longitudinal spin-Seebeck effect in cobalt-ferrite epitaxial thin films

    Directory of Open Access Journals (Sweden)

    Tomohiko Niizeki

    2015-05-01

    Full Text Available The longitudinal spin-Seebeck effect (LSSE has been investigated in cobalt ferrite (CFO, an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110 exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. External-magnetic-field (H dependence of the LSSE voltage (VLSSE in the Pt/CFO(110 sample with H ∥ [001] was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with H ∥ [ 1 1 ̄ 0 ] shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of VLSSE has a linear relationship with the temperature difference (ΔT, giving the relatively large VLSSE /ΔT of about 3 μV/K for CFO(110 which was kept even at zero external field.

  12. Solid phase epitaxial growth of high mobility La:BaSnO3 thin films co-doped with interstitial hydrogen

    Science.gov (United States)

    Niedermeier, Christian A.; Rhode, Sneha; Fearn, Sarah; Ide, Keisuke; Moram, Michelle A.; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-04-01

    This work presents the solid phase epitaxial growth of high mobility La:BaSnO3 thin films on SrTiO3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO3 thin films, and a 9%-16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO3 thin films were increased to 3 × 1019 cm-3 and in La:BaSnO3 thin films from 6 × 1019 cm-3 to 1.5 × 1020 cm-3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO3 electron effective mass of 0.27 ± 0.05 m0 and an optical mobility of 26 ± 7 cm2/Vs. As compared to La:BaSnO3 single crystals, the smaller electron mobility in epitaxial thin films grown on SrTiO3 substrates is ascribed to threading dislocations as observed in high resolution transmission electron micrographs.

  13. Microstructure of epitaxial thin films of the ferromagnetic shape memory alloy Ni{sub 2}MnGa

    Energy Technology Data Exchange (ETDEWEB)

    Eichhorn, Tobias

    2011-12-09

    This work is concerned with the preparation and detailed characterization of epitaxial thin films of the Heusler compound Ni{sub 2}MnGa. This multiferroic compound is of both technological and scientific interest due to the outstanding magnetic shape memory (MSM) behavior. Huge magnetic-field-induced strains up to 10 % have been observed for single crystals close to a Ni{sub 2}MnGa composition. The effect is based on a redistribution of crystallographic twin variants of tetragonal or orthorhombic symmetry. Under the driving force of the external magnetic field twin boundaries can move through the crystal, which largely affects the macroscopic shape. The unique combination of large reversible strain, high switching frequency and high work output makes the alloy a promising actuator material. Since the MSM effect results from an intrinsic mechanism, MSM devices possess great potential for implementation in microsystems, e.g. microfluidics. So far significant strains, in response to an external magnetic field, have been observed for bulk single crystals and foams solely. In order to take advantage of the effect in applications concepts for miniaturization are needed. The rather direct approach, based on epitaxial thin films, is explored in the course of this work. This involves sample preparation under optimized deposition parameters and fabrication of freestanding single-crystalline films. Different methods to achieve freestanding microstructures such as bridges and cantilevers are presented. The complex crystal structure is extensively studied by means of X-ray diffraction. Thus, the different crystallographic twin variants that are of great importance for the MSM effect are identified. In combination with microscopy the twinning architecture for films of different crystallographic orientation is clarified. Intrinsic blocking effects in samples of (100) orientation are explained on basis of the variant configuration. In contrast, a promising twinning microstructure

  14. Nanoscale monoclinic domains in epitaxial SrRuO3 thin films deposited by pulsed laser deposition

    Science.gov (United States)

    Ghica, C.; Negrea, R. F.; Nistor, L. C.; Chirila, C. F.; Pintilie, L.

    2014-07-01

    In this paper, we analyze the structural distortions observed by transmission electron microscopy in thin epitaxial SrRuO3 layers used as bottom electrodes in multiferroic coatings onto SrTiO3 substrates for future multiferroic devices. Regardless of the nature and architecture of the multilayer oxides deposited on the top of the SrRuO3 thin films, selected area electron diffraction patterns systematically revealed the presence of faint diffraction spots appearing in forbidden positions for the SrRuO3 orthorhombic structure. High-resolution transmission electron microscopy (HRTEM) combined with Geometric Phase Analysis (GPA) evidenced the origin of these forbidden diffraction spots in the presence of structurally disordered nanometric domains in the SrRuO3 bottom layers, resulting from a strain-driven phase transformation. The local high compressive strain (-4% ÷ -5%) measured by GPA in the HRTEM images induces a local orthorhombic to monoclinic phase transition by a cooperative rotation of the RuO6 octahedra. A further confirmation of the origin of the forbidden diffraction spots comes from the simulated diffraction patterns obtained from a monoclinic disordered SrRuO3 structure.

  15. Surface analysis of topmost layer of epitaxial layered oxide thin film: Application to delafossite oxide for oxygen evolution reaction

    Science.gov (United States)

    Toyoda, Kenji; Adachi, Hideaki; Miyata, Nobuhiro; Hinogami, Reiko; Orikasa, Yuki; Uchimoto, Yoshiharu

    2018-02-01

    Delafossite oxides (ABO2) have a layered structure with alternating layers of A and B elements, the topmost layer of which appears to determine their performance, such as the oxygen evolution reaction (OER) activity. In this study, we investigated the topmost layer of single-domain (0 0 1)-oriented AgCoO2 epitaxial thin film for potential use as an OER catalyst. The thin film was confirmed to possess OER activity at a level comparable to the catalyst in powder form. Atomic scattering spectroscopy revealed the topmost layer to be composed of CoO6 octahedra. In situ X-ray absorption spectroscopy showed that the oxidation of Co at the surface did not change under different potentials, which suggests that there is no valence fluctuation of Co in the stable CoO6 octahedral structure. However, the oxidation number of Co at the surface was lower than that in the bulk. Our density functional theoretical calculations also showed the Co atoms at the surface to have a slightly higher electron occupancy than those in the bulk, and suggests that the unoccupied t2g states of Co at the surface have an influence on OER activity.

  16. Persistent semi-metal-like nature of epitaxial perovskite CaIrO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Abhijit; Jeong, Yoon Hee, E-mail: yhj@postech.ac.kr [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)

    2015-05-21

    Strong spin-orbit coupled 5d transition metal based ABO{sub 3} oxides, especially iridates, allow tuning parameters in the phase diagram and may demonstrate important functionalities, for example, by means of strain effects and symmetry-breaking, because of the interplay between the Coulomb interactions and strong spin-orbit coupling. Here, we have epitaxially stabilized high quality thin films of perovskite (Pv) CaIrO{sub 3}. Film on the best lattice-matched substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile or compressive strain on the film by altering the underlying lattice-mismatched substrates still maintains semi-metallicity with minute modification of the effective correlation as tensile (compressive) strain results in tiny increases (decreases) of the electronic bandwidth. In addition, magnetoresistance remains positive with a quadratic field dependence. This persistent semi-metal-like nature of Pv-CaIrO{sub 3} thin films with minute changes in the effective correlation by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide physics.

  17. Single-Crystal Thin Films of Cesium Lead Bromide Perovskite Epitaxially Grown on Metal Oxide Perovskite (SrTiO3).

    Science.gov (United States)

    Chen, Jie; Morrow, Darien J; Fu, Yongping; Zheng, Weihao; Zhao, Yuzhou; Dang, Lianna; Stolt, Matthew J; Kohler, Daniel D; Wang, Xiaoxia; Czech, Kyle J; Hautzinger, Matthew P; Shen, Shaohua; Guo, Liejin; Pan, Anlian; Wright, John C; Jin, Song

    2017-09-27

    High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr 3 ) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO 3 (100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcoming the limitation of island-forming Volmer-Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr 3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity (10 4 cm s -1 ), and low defect density of 10 12 cm -3 , which are comparable to those of CsPbBr 3 single crystals. This work suggests a general approach using oxide perovskites as substrates for heteroepitaxial growth of halide perovskites. The high-quality halide perovskite SCTFs epitaxially integrated with multifunctional oxide perovskites could open up opportunities for a variety of high-performance optoelectronics devices.

  18. Heterointerface design and strain tuning in epitaxial BiFeO3:CoFe2O4 nanocomposite films

    Science.gov (United States)

    Zhang, Wenrui; Fan, Meng; Li, Leigang; Chen, Aiping; Su, Qing; Jia, Quanxi; MacManus-Driscoll, Judith L.; Wang, Haiyan

    2015-11-01

    The ability to control the morphology of heterointerfaces with coupled functionalities is fascinating from both fundamental and technological perspectives. Here, using BiFeO3:CoFe2O4 vertically aligned nanocomposite (VAN) films as a model system, we demonstrate a simple and effective method to modulate the heterointerface and its morphology in nanocomposite films with pulsed laser deposition. By tuning the deposition frequency through thickness during film growth, both vertically straight and gradient heterointerfaces have been achieved. The modulated heterointerface is strongly correlated with strain tuning and interface coupling, and thus modifies the magnetic anisotropy, coercive fields, and ferroelectric switching behavior. This study provides a viable approach for tailoring the interface strain and coupling in VAN and achieving tunable physical properties.

  19. Annealing effects on the ferromagnetic resonance linewidths of sputter-deposited Fe100−xCox(001) thin films (x < 11)

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  20. Anisotropic strain relaxation in (Ba0.6Sr0.4)TiO3 epitaxial thin films

    Science.gov (United States)

    Simon, W. K.; Akdogan, E. K.; Safari, A.

    2005-05-01

    We have studied the evolution of anisotropic epitaxial strains in ⟨110⟩-oriented (Ba0.60Sr0.40)TiO3 paraelectric (m3m) thin films grown on orthorhombic (mm2) ⟨100⟩-oriented NdGaO3 by high-resolution x-ray diffractometry. All the six independent components of the three-dimensional strain tensor were measured in films with 25-1200-nm thickness, from which the principal stresses and strains were obtained. Pole figure analysis indicated that the epitaxial relations are [001]m3m‖[001]mm2 and [1¯10]m3m‖[010]mm2 in the plane of the film, and [110]m3m‖[100]mm2 along the growth direction. The dislocation system responsible for strain relief along [001] has been determined to be ∣b ∣(001)=3/4∣b∣. Strain relief along the [1¯10] direction, on the other hand, has been determined to be due to a coupled mechanism given by ∣b∣(1¯10)=∣b∣ and ∣b∣(1¯10)=√3 /4∣b∣. Critical thicknesses, as determined from nonlinear regression using the Matthews-Blakeslee equation, for misfit dislocation formation along [001] and [1¯10] direction were found to be 5 and 7 nm, respectively. The residual strain energy density was calculated as ˜2.9×106J/m3 at 25 nm, which was found to relax an order of magnitude by 200 nm. At 200 nm, the linear dislocation density along [001] and [1¯10] are ˜6.5×105 and ˜6×105cm-1, respectively. For films thicker than 600 nm, additional strain relief occurred through surface undulations, indicating that this secondary strain-relief mechanism is a volume effect that sets in upon cooling from the growth temperature.

  1. Photoelectrochemical Performance Observed in Mn-Doped BiFeO3 Heterostructured Thin Films

    Directory of Open Access Journals (Sweden)

    Hao-Min Xu

    2016-11-01

    Full Text Available Pure BiFeO3 and heterostructured BiFeO3/BiFe0.95Mn0.05O3 (5% Mn-doped BiFeO3 thin films have been prepared by a chemical deposition method. The band structures and photosensitive properties of these films have been investigated elaborately. Pure BiFeO3 films showed stable and strong response to photo illumination (open circuit potential kept −0.18 V, short circuit photocurrent density was −0.023 mA·cm−2. By Mn doping, the energy band positions shifted, resulting in a smaller band gap of BiFe0.95Mn0.05O3 layer and an internal field being built in the BiFeO3/BiFe0.95Mn0.05O3 interface. BiFeO3/BiFe0.95Mn0.05O3 and BiFe0.95Mn0.05O3 thin films demonstrated poor photo activity compared with pure BiFeO3 films, which can be explained by the fact that Mn doping brought in a large amount of defects in the BiFe0.95Mn0.05O3 layers, causing higher carrier combination and correspondingly suppressing the photo response, and this negative influence was more considerable than the positive effects provided by the band modulation.

  2. Spin lattice relaxation of 8Li in a ferromagnetic EuO epitaxial thin film

    Science.gov (United States)

    Song, Q.; Chow, K. H.; Egilmez, M.; Fan, I.; Hossain, M. D.; Kiefl, R. F.; Kreitzman, S. R.; Levy, C. D. P.; Morris, G. D.; Parolin, T. J.; Pearson, M. R.; Salman, Z.; Saadaoui, H.; Smadella, M.; Wang, D.; Ingle, N. J. C.; MacFarlane, W. A.

    2009-04-01

    We inject a low energy spin polarized Li+8 beam into an epitaxially grown multilayer film consisting of Au(20 nm)/EuO(100 nm)/ LaAlO3, and investigate the nuclear spin relaxation at 3.33 T. The relaxation varies with implantation energy below 28 keV as the fraction of the probe Li8 stopping in each layer changes. We attribute the fast relaxating component to the EuO, while the much slower relaxation has contributions from both the Au and the substrate. However, fast relaxation is still observed at the lowest implantation energy where all the Li8 stops in the Au capping layer. This may be due to a proximity effect from the EuO.

  3. Electron tomography on nanopores embedded in epitaxial GaSb thin films.

    Science.gov (United States)

    Niehle, Michael; Trampert, Achim

    2015-06-01

    This work reports on the morphology of nanopores and their spatial position in group III-Sb based multilayer heterostructures grown by molecular beam epitaxy on Si(001) substrates. By using electron tomography based on dark-field scanning transmission electron microscopy, quantitative information in real space is obtained about individual nanopores unintentionally embedded in GaSb layers. For this purpose adequate needle-shaped samples have to be specifically prepared from the compact material system by focused ion beam. The three-dimensional reconstruction of the probed volume allows the determination of the spatial arrangement of the pores and the analysis of the detailed shape, i.e. the crystallographic facets. Based on these results, the nanopore's geometric shape is discussed with respect to the minimization of surface tension. The formation process can be explained by an agglomeration of vacancies which are generated during the heterostructure growth. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Spin lattice relaxation of {sup 8}Li in a ferromagnetic EuO epitaxial thin film

    Energy Technology Data Exchange (ETDEWEB)

    Song, Q., E-mail: susan@phas.ubc.c [Department of Physics, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Chow, K.H.; Egilmez, M.; Fan, I. [Department of Physics, University of Alberta, Edmonton, AB, T6G 2G7 (Canada); Hossain, M.D. [Department of Physics, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Kiefl, R.F. [Department of Physics, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Canadian Institute of Advanced Research (Canada); Kreitzman, S.R.; Levy, C.D.P.; Morris, G.D. [TRIMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Parolin, T.J. [Chemistry Department, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Pearson, M.R. [TRIMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Salman, Z. [TRIMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Physics Department, Oxford University, Parks Road, Oxford, OX1 3PU (United Kingdom); Saadaoui, H.; Smadella, M.; Wang, D. [Department of Physics, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Ingle, N.J.C. [AMPEL, University of British Columbia, Vancouver (Canada); MacFarlane, W.A. [Chemistry Department, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada)

    2009-04-15

    We inject a low energy spin polarized {sup 8}Li{sup +} beam into an epitaxially grown multilayer film consisting of Au(20 nm)/EuO(100 nm)/LaAlO{sub 3}, and investigate the nuclear spin relaxation at 3.33 T. The relaxation varies with implantation energy below 28 keV as the fraction of the probe {sup 8}Li stopping in each layer changes. We attribute the fast relaxating component to the EuO, while the much slower relaxation has contributions from both the Au and the substrate. However, fast relaxation is still observed at the lowest implantation energy where all the {sup 8}Li stops in the Au capping layer. This may be due to a proximity effect from the EuO.

  5. A study of strain in thin epitaxial films of yttrium silicide on Si(111)

    Science.gov (United States)

    Siegal, Michelle F.; Martínez-Miranda, L. J.; Santiago-Avilés, J. J.; Graham, W. R.; Siegal, M. P.

    1994-02-01

    We present the results of an x-ray diffraction analysis of epitaxial yttrium silicide films grown on Si(111), with thicknesses ranging from 14 to 100 Å. The macroscopic strain along the out-of-plane direction for films containing pits or pinholes follows the trend observed previously in films of thicknesses up to 510 Å. The out-of-plane lattice parameter decreases linearly with film thickness. We show preliminary evidence that pinhole-free films do not follow the above trend, and that strain in these films has the opposite sign than in films with pinholes. Finally, our results also indicate that the mode of growth, coupled to the interfacial thermal properties of the films, affects the observed value for the strain in the films.

  6. A study of strain in thin epitaxial films of yttrium silicide on Si(111)

    International Nuclear Information System (INIS)

    Siegal, M.F.; Martinez-Miranda, L.J.; Santiago-Aviles, J.J.; Graham, W.R.; Siegal, M.P.

    1994-01-01

    We present the results of an x-ray diffraction analysis of epitaxial yttrium silicide films grown on Si(111), with thicknesses ranging from 14 to 100 A. The macroscopic strain along the out-of-plane direction for films containing pits or pinholes follows the trend observed previously in films of thicknesses up to 510 A. The out-of-plane lattice parameter decreases linearly with film thickness. We show preliminary evidence that pinhole-free films do not follow the above trend, and that strain in these films has the opposite sign than in films with pinholes. Finally, our results also indicate that the mode of growth, coupled to the interfacial thermal properties of the films, affects the observed value for the strain in the films

  7. Hydrogen reduction in GaAsN thin films by flow rate modulated chemical beam epitaxy

    International Nuclear Information System (INIS)

    Saito, K.; Nishimura, K.; Suzuki, H.; Ohshita, Y.; Yamaguchi, M.

    2008-01-01

    The amount of residual H in the GaAsN film grown by chemical beam epitaxy (CBE) can be decreased by flow rate modulation growth. Many H atoms in the films grown by CBE exist as N-H or N-H 2 structures. Although a higher growth temperature was required for decreasing the H concentration ([H]), it caused a decrease in the N concentration ([N]). A reduction in [H] while keeping [N] constant was necessary. By providing an intermittent supply of Ga source while continuously supplying As and N sources, [H] effectively decreased in comparison with the [H] value in the film grown at the same temperature by conventional CBE without reducing [N

  8. Magnetocrystalline anisotropy in a (110) (Tb0.27Dy0.73)Fe2 thin-film

    International Nuclear Information System (INIS)

    Fuente, C de la; Arnaudas, J I; Benito, L; Ciria, M; Moral, A del; Dufour, C; Dumesnil, K

    2004-01-01

    Magnetic anisotropy measurements performed in a (110) (Tb 0.27 Dy 0.73 )Fe 2 (Terfenol-D) film epitaxially grown on a sapphire substrate are presented. The magnetic torque curves have been determined by using a vectorial vibrating sample magnetometer, which allows us to measure the angular dependence of magnetization components parallel, M parallel , and perpendicular, M perp , to the applied field up to 2 T. The fourfold symmetry associated with the cubic structure within the (110) plane is clearly observed. The analysis of the experimental torque has been carried out considering magnetocrystalline anisotropy up to sixth order and magnetoelastic energy up to second order; so, the magnetocrystalline anisotropy constants in the (110) plane of the film, K 1 and K 2 , have been obtained. This allows us to determine the direction of the magnetization easy axis for (110) Terfenol-D thin-film: it is [1bar12] at RT, passes through [3bar34] at 140 K and then changes to [1bar20] at 40 K. It was completely impossible to explain the angular dependence of the experimental magnetic torque without including shear and tetragonal magnetoelastic stress parameters, b 2 and b 1 , respectively. This confirms the paramount role of the strain in the determination of the magnetic properties in this kind of Terfenol-D thin film

  9. Effects of Surface Electron Doping and Substrate on the Superconductivity of Epitaxial FeSe Films.

    Science.gov (United States)

    Zhang, W H; Liu, X; Wen, C H P; Peng, R; Tan, S Y; Xie, B P; Zhang, T; Feng, D L

    2016-03-09

    Superconductivity in FeSe is greatly enhanced in films grown on SrTiO3 substrates, although the mechanism behind remains unclear. Recently, surface potassium (K) doping has also proven able to enhance the superconductivity of FeSe. Here, by using scanning tunneling microscopy, we compare the K doping dependence of the superconductivity in FeSe films grown on two substrates: SrTiO3 (001) and graphitized SiC (0001). For thick films (20 unit cells (UC)), the optimized superconducting (SC) gaps are of similar size (∼9 meV) regardless of the substrate. However, when the thickness is reduced to a few UC, the optimized SC gap is increased up to ∼15 meV for films on SrTiO3, whereas it remains unchanged for films on SiC. This clearly indicates that the FeSe/SrTiO3 interface can further enhance the superconductivity, beyond merely doping electrons. Intriguingly, we found that this interface enhancement decays exponentially as the thickness increases, with a decay length of 2.4 UC, which is much shorter than the length scale for relaxation of the lattice strain, pointing to interfacial electron-phonon coupling as the likely origin.

  10. The polarized neutron reflectivity and X-ray reflectivity studies of the magnetic profiles of epitaxial Ni80Fe20/Ru multilayers

    International Nuclear Information System (INIS)

    Su, H.-C.; Peir, J.-J.; Lee, C.-H.; Lin, M.-Z.; Wu, P.-T.; Huang, J.C.A.; Tun Zin

    2005-01-01

    The depth profiles of the epitaxial Ni 80 Fe 20 (1 1 1)/Ru(0 0 0 1) multilayers were studied by polarized neutron reflectivity and X-ray reflectivity. At the Ru thickness that the anti-ferromagnetic coupling was found, the magnetic moments between two Ni 80 Fe 20 interlayers show a biquadratic coupling effect with a double unit cell at low applied fields. A magnetic dead layer of about 0.3 nm was also found at the interface boundaries. The maximal polarization effect applied to the Ru layer is less than 0.03μ B

  11. Misfit strain dependence of ferroelectric and piezoelectric properties of clamped (001) epitaxial Pb(Zr0.52,Ti0.48)O3 thin films

    Science.gov (United States)

    Nguyen, Minh D.; Dekkers, Matthijn; Houwman, Evert; Steenwelle, Ruud; Wan, Xin; Roelofs, Andreas; Schmitz-Kempen, Thorsten; Rijnders, Guus

    2011-12-01

    A study on the effects of the residual strain in Pb(Zr0.52Ti0.48)O3 (PZT) thin films on the ferroelectric and piezoelectric properties is presented. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between SrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations by pulsed laser deposition. Compressive or tensile strain caused by the difference in thermal expansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. All the PZT stacks show ferroelectric and piezoelectric behavior that is consistent with the theoretical model for strained thin films in the ferroelectric r-phase. We conclude that clamped (001) oriented Pb(Zr0.52Ti0.48)O3 thin films strained by the substrate always show rotation of the polarization vector.

  12. Low-temperature liquid-phase epitaxy and optical waveguiding of rare-earth-ion-doped KY(WO4)2 thin layers

    NARCIS (Netherlands)

    Romanyuk, Y.E.; Utke, I.; Ehrentraut, D.; Apostolopoulos, V.; Pollnau, Markus; Garcia-Revilla, S.; Valiente, B.

    2004-01-01

    Crystalline $KY(WO_{4})_{2}$ thin layers doped with different rare-earth ions were grown on b-oriented, undoped $KY(WO_{4})_{2}$ substrates by liquid-phase epitaxy employing a low-temperature flux. The ternary chloride mixture of NaCl, KCl, and CsCl with a melting point of 480°C was used as a

  13. Near-surface effects of transient oxidation and reduction on Nb-doped SrTiO3 epitaxial thin films

    Science.gov (United States)

    Chang, C. F.; Chen, Q. Y.; Wadekar, P. V.; Lozano, O.; Wong, M. S.; Hsieh, W. C.; Lin, W. Y.; Ko, H. H.; Lin, Q. J.; Huang, H. C.; Ho, N. J.; Tu, L. W.; Liao, H. H.; Chinta, P. V.; Chu, W. K.; Seo, H. W.

    2014-03-01

    We studied the effects of transient oxidation and reduction of Nb-doped epitaxial thin films through variations of PAr and PO2. The samples were prepared by co-sputtering of Nb and SrTiO3 on LaAlO3 substrates. The Nb-content were varied from 0-33.7%, as determined by PIXE. Contact resistance, sheet resistance, and optical properties are used to discriminate the effects.

  14. Fabrication of Ag, FeNi, Cu Thin Film for Magnetic Sensor

    International Nuclear Information System (INIS)

    Subarkah; Trimarji Atmono

    2003-01-01

    It has been fabricated a Ag, FeNi, Cu thin film by sputtering method. The thin film material is deposited on the glass substrate heated from 100 o C to 400 o C having dimensions of 2.5 x 1 cm 2 . The sputtering time of Ag, FeNi and Cu materials are 10 minutes respectively operating voltage is 2.5 kV and electrode distance 2.5 cm. The FeNi material is alloy having ratio 70% : 30%, that is the best composition formed by previous observer. On the glass substrate, there are four layers such as: the first is FeNi, second Cu, third FeNi, and the fourth, Ag. During the sputtering process the power was 40 Watts (2 kV, 20 mA). The thin film Ag, FeNi, CuFeNi was varied for variation of sputtering to get the optimum conditions of parameter process. From the sputtering result, it was produced thin films having resistivity R o in range of 5 to 48 Ohm (magnetron operating varied magnetic field). To measure resistance influenced the external magnetic field the thin film yields was put on the external magnetic field included four points probe system. The result showed that there was some changes of the resistances (R o - R)/ R o % between 10 to 14 % with error 7 - 10 %. (author)

  15. On the Novel Biaxial Strain Relaxation Mechanism in Epitaxial Composition Graded La1−xSrxMnO3 Thin Film Synthesized by RF Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Yishu Wang

    2015-11-01

    Full Text Available We report on a novel method to fabricate composition gradient, epitaxial La1−xSrxMnO3 thin films with the objective to alleviate biaxial film strain. In this work, epitaxial, composition gradient La1−xSrxMnO3, and pure LaMnO3 and La0.67Sr0.33MnO3 thin films were deposited by radio frequency (RF magnetron sputtering. The crystalline and epitaxy of all films were first studied by symmetric θ–2θ X-ray diffraction (XRD and low angle XRD experiments. Detailed microstructural characterization across the film thickness was conducted by high-resolution transmission electron microscopy and electron diffraction. Four compositional gradient domains were observed in the La1−xSrxMnO3 film ranging from LaMnO3 rich to La0.67Sr0.33MnO3 at the surface. A continuous reduction in the lattice parameter was observed accompanied by a significant reduction in the out-of-plane strain in the film. Fabrication of the composition gradient La1−xSrxMnO3 thin film was found to be a powerful method to relieve biaxial strain under critical thickness. Besides, the coexistence of domains with a composition variance is opening up various new possibilities of designing new nanoscale structures with unusual cross coupled properties.

  16. Domain Selectivity in BiFeO3 Thin Films by Modified Substrate Termination

    NARCIS (Netherlands)

    Solmaz, Alim; Huijben, Mark; Koster, Gertjan; Egoavil, Ricardo; Gauquelin, Nicolas; Van Tendeloo, Gustaaf; Verbeeck, Jo; Noheda, Beatriz; Rijnders, Guus

    2016-01-01

    Ferroelectric domain formation is an essential feature in ferroelectric thin films. These domains and domain walls can be manipulated depending on the growth conditions. In rhombohedral BiFeO3 thin films, the ordering of the domains and the presence of specific types of domain walls play a crucial

  17. Magnetic properties of epitaxial MnAs thin films on GaAs (001)

    CERN Document Server

    Park, Y S

    2000-01-01

    The magnetic properties of two types of epitaxial MnAs films on GaAs (001) substrates in the thickness range of 20 approx 200 nm were studied. Using longitudinal a magneto-optical Kerr-effect(MOKE) apparatus at lambda=632.8 nm, we determined the Curie temperatures of the 100-nm thick films to be 54.0+-0.5 .deg. C and 63.7+-0.5 .deg. C for type A films and type B films, respectively. The observed Curie temperatures corresponded to increases of 36.8 .deg. C and 33.9 .deg. C per one percent increase in the unit cell volume for type A and B, respectively. The normalized maximum MOKE signal from the type A film exhibited a first-order-like magnetic transition while that of type B underwent a second-order-like transition. These different behaviors between types A and B stem from different residual stresses being exerted on the hexagonal phase. Utilizing a Foner-type vibrating sample magnetometer at room temperature, we examined the thickness dependence of the coercive force and the saturation magnetization of the f...

  18. Photoluminescence study of epitaxially grown ZnSnAs2:Mn thin films

    International Nuclear Information System (INIS)

    Mammadov, E; Haneta, M; Toyota, H; Uchitomi, N

    2011-01-01

    The photoluminescence (PL) properties of heavily Mn-doped ZnSnAs 2 layers epitaxially grown on nearly lattice-matched semi-insulating InP substrates are studied. PL spectra are obtained for samples with Mn concentrations of 5, 12 and 24 mol% relative to the combined concentrations of Zn and Sn. A broad emission band centered at ∼ 1 eV is detected for Mn-doped layers at room temperature. The emission is a intense broad asymmetric line at low temperatures. The line is reconstructed by superposition of two bands with peak energies of ∼ 0.99 and 1.07 eV, similar to those reported for InP. These bands are superimposed onto a 1.14 eV band with well-resolved phonon structure for the layer doped with 12 % Mn. Recombination mechanism involving the split-off band of the ZnSnAs 2 is suggested. Temperature dependence of integrated intensities of the PL bands indicates to thermally activated emission with activation energies somewhat different from those found for InP. Mn substitution at cationic sites increases the concentration of holes which may act as recombination centers. Recombination to the holes bound to Mn ions with the ground state located below the top of the valence band has been proposed as a possible PL mechanism.

  19. Low-temperature technique of thin silicon ion implanted epitaxial detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kordyasz, A.J.; Bednarek, A. [Warsaw University, Heavy Ion Laboratory, Warsaw (Poland); Le Neindre, N.; Bougault, R.; Lopez, O.; Merrer, Y.; Vient, E. [Universite de Caen, LPC, IN2P3-CNRS, ENSICAEN, Caen-Cedex (France); Parlog, M. [Universite de Caen, LPC, IN2P3-CNRS, ENSICAEN, Caen-Cedex (France); ' ' Horia Hulubei' ' National Institute of Physics and Nuclear Engineering (IFIN-HH), Bucharest Magurele (Romania); Casini, G.; Poggi, G.; Bini, M.; Valdre, S.; Scarlini, E.; Pasquali, G.; Pastore, G.; Piantelli, S.; Stefanini, A.; Olmi, A.; Barlini, S. [INFN Firenze, Sesto Fiorentino (Italy); Universita di Firenze, Sesto Fiorentino (Firenze) (Italy); Kowalczyk, M. [Warsaw University, Heavy Ion Laboratory, Warsaw (Poland); University of Warsaw, Institute of Experimental Physics, Warsaw (Poland); Frankland, J.D.; Bonnet, E.; Chbihi, A.; Gruyer, D. [CEA et IN2P3-CNRS, GANIL, Caen-Cedex 05 (France); Borderie, B.; Ademard, G.; Edelbruck, P.; Rivet, M.F.; Salomon, F. [IN2P3-CNRS, Institut de Physique Nucleaire, Orsay-Cedex (France); Boiano, A.; Rosato, E.; Meoli, A.; Ordine, A.; Spadaccini, G.; Tortone, G.; Vigilante, M.; Vanzanella, E. [Universita di Napoli ' ' Federico II' ' , Dipartimento di Scienze Fisiche, Napoli (Italy); INFN, Napoli (Italy); Bruno, M.; Serra, S.; Morelli, L.; Guerzoni, M. [INFN, Bologna (Italy); Universita di Bologna, Bologna (Italy); Alba, R.; Santonocito, D.; Maiolino, C. [INFN, Catania (Italy); Universita di Catania, LNS, Catania (Italy); Cinausero, M.; Gramegna, F.; Marchi, T. [INFN LNL Legnaro, Legnaro (Padova) (Italy); Kozik, T.; Kulig, P.; Twarog, T.; Sosin, Z. [Jagiellonian University, Cracow (Poland); Gasior, K.; Grzeszczuk, A.; Zipper, W. [University of Silesia, Silesian University, Katowice (Poland); Sarnecki, J.; Lipinski, D.; Wodzinska, H.; Brzozowski, A.; Teodorczyk, M.; Gajewski, M.; Zagojski, A.; Krzyzak, K. [Institute of Electronic Materials Technology, Warsaw (Poland); Tarasiuk, K.J. [University of Warsaw, Institute of Experimental Physics, Warsaw (Poland); Khabanowa, Z. [Faculty of Physics, Warsaw University of Technology, Warsaw (Poland); Kordyasz, L. [Warsaw University of Technology, Faculty of Mechatronics, Institute of Mikromechanics and Photonics, Department of Design of Precision Devices, Warsaw (Poland)

    2015-02-01

    A new technique of large-area thin ion implanted silicon detectors has been developed within the R and D performed by the FAZIA Collaboration. The essence of the technique is the application of a low-temperature baking process instead of high-temperature annealing. This thermal treatment is performed after B{sup +} ion implantation and Al evaporation of detector contacts, made by using a single adjusted Al mask. Extremely thin silicon pads can be therefore obtained. The thickness distribution along the X and Y directions was measured for a prototype chip by the energy loss of α-particles from {sup 241}Am (left angle E{sub α} right angle = 5.5 MeV). Preliminary tests on the first thin detector (area ∼ 20 x 20 mm{sup 2}) were performed at the INFN-LNS cyclotron in Catania (Italy) using products emitted in the heavy-ion reaction {sup 84}Kr (E = 35 A MeV) + {sup 112}Sn. The ΔE - E ion identification plot was obtained using a telescope consisting of our thin ΔE detector (21 μm thick) followed by a typical FAZIA 510 μm E detector of the same active area. The charge distribution of measured ions is presented together with a quantitative evaluation of the quality of the Z resolution. The threshold is lower than 2 A MeV depending on the ion charge. (orig.)

  20. Epitaxial growth of highly conductive RuO2 thin films on (100) Si

    International Nuclear Information System (INIS)

    Jia, Q.X.; Song, S.G.; Wu, X.D.; Cho, J.H.; Foltyn, S.R.; Findikoglu, A.T.; Smith, J.L.

    1996-01-01

    Conductive RuO 2 thin films have been heteroepitaxially grown by pulsed laser deposition on Si substrates with yttria-stabilized zirconia (YSZ) buffer layers. The RuO 2 thin films deposited under optimized processing conditions are a-axis oriented normal to the Si substrate surface with a high degree of in-plane alignment with the major axes of the (100) Si substrate. Cross-sectional transmission electron microscopy analysis on the RuO 2 /YSZ/Si multilayer shows an atomically sharp interface between the RuO 2 and the YSZ. Electrical measurements show that the crystalline RuO 2 thin films are metallic over a temperature range from 4.2 to 300 K and are highly conductive with a room-temperature resistivity of 37±2 μΩcm. The residual resistance ratio (R 300K /R 4.2K ) above 5 for our RuO 2 thin films is the highest ever reported for such films on Si substrates. copyright 1996 American Institute of Physics

  1. Planar Hall effect and magnetic anisotropy in epitaxially strained chromium dioxide thin films

    NARCIS (Netherlands)

    Goennenwein, S.T.B.; Keizer, R.S.; Schink, S.W.; Van Dijk, I.; Klapwijk, T.M.; Miao, G.X.; Xiao, G.; Gupta, A.

    2007-01-01

    We have measured the in-plane anisotropic magnetoresistance of 100?nm thick CrO2 thin films at liquid He temperatures. In low magnetic fields H, both the longitudinal and the transverse (planar Hall) resistance show abrupt switches, which characteristically depend on the orientation of H. All the

  2. Liquid phase epitaxy and optical investigation of KYb(WO4)2 thin layers

    NARCIS (Netherlands)

    Romanyuk, Y.E.; Ehrentraut, D.; Aznar, A.; Sole, R.; Aguilo, M.; Gerner, P.; Güdel, H.U.; Pollnau, Markus

    In recent years, Yb3+ has attracted much attention as an activating ion because of its small quantum defect for laser emission from 2F5/2 to 2F7/2 at ~1.03 µm [1], which provides high efficiency and reduced heat generation. Of high practical interest is the thin-disk laser concept [2], which

  3. Characterization of α-Fe-Free Heteroepitaxial NdFe12- x Ti x Thin-Film Materials with a Novel Cubic Laves Fe2Ti Phase

    Science.gov (United States)

    Hadorn, Jason Paul; Hirayama, Yusuke; Ohkubo, Tadakatsu

    2018-01-01

    Thin films with compositions of NdFe12 and NdFe11Ti1 were fabricated on W-buffered MgO(001) substrates of varying roughness. In this study, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the films microstructurally, chemically, and crystallographically. This study revealed successful heteroepitaxial synthesis of the tetragonal NdFe12 and NdFe12- x Ti x phases in the Ti-free and Ti-containing films, respectively, both with surface-normal c-axis orientation. It also revealed the presence of other phases within the magnetic layer. The NdFe12 films contained many α-Fe particles, which preferentially precipitated at locally rough regions of the W-buffer interface. The NdFe11Ti1 film showed the ubiquitous presence of an Fe2Ti phase, which covered most of the buffer thereby preventing the formation of α-Fe. This phase was determined to have a novel Cu2Mg-type cubic Laves ( C15) crystal structure with fourfold interfacial symmetry, good coherency, and a low mismatch with the W-buffer, thus rendering itself as being an ideal interface for the heteroepitaxial synthesis of NdFe12- x Ti x crystals. It is proposed that successful application of a cubic Fe2Ti underlayer on W can contribute to the development of a fabrication strategy for NdFe12 thin films without the presence of soft magnetic α-Fe.

  4. Atomic Structure of Highly Strained BiFeO3 Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Rossell, M.D. [Lawrence Berkeley National Laboratory (LBNL); Erni, R. [Lawrence Berkeley National Laboratory (LBNL); Prange, Micah P [ORNL; Idrobo Tapia, Juan C [ORNL; Luo, Weidong [ORNL; Zeches, R J [University of California, Berkeley; Pantelides, Sokrates T [ORNL; Ramesh, R [Lawrence Berkeley National Laboratory (LBNL)

    2012-01-01

    We determine the atomic structure of the pseudotetragonal T phase and the pseudorhombohedral R phase in highly strained multiferroic BiFeO3 thin films by using a combination of atomic-resolution scanning transmission electron microscopy and electron energy-loss spectroscopy. The coordination of the Fe atoms and their displacement relative to the O and Bi positions are assessed by direct imaging. These observations allow us to interpret the electronic structure data derived from electron energy-loss spectroscopy and provide evidence for the giant spontaneous polarization in strained BiFeO3 thin films.

  5. Damage evolution of ion irradiated defected-fluorite La 2 Zr 2 O 7 epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Gigax, Jonathan G.; Shao, Lin; Bowden, Mark E.; Varga, Tamas; Shutthanandan, Vaithiyalingam; Spurgeon, Steven R.; Yan, Pengfei; Wang, Chongmin; Ramuhalli, Pradeep; Henager, Charles H.

    2017-05-01

    Pyrochlore-structure oxides, A2B2O7, may exhibit remarkable radiation tolerance due to the ease with which they can accommodate disorder by transitioning to a defected fluorite structure. The mechanism of defect formation was explored by evaluating the radiation damage behavior of high quality epitaxial La2Zr2O7 thin films with the defected fluorite structure, irradiated with 1 MeV Zr+ at doses up to 10 displacements per atom (dpa). The level of film damage was evaluated as a function of dose by Rutherford backscattering spectrometry in the channeling geometry (RBS/c) and scanning transmission electron microscopy (STEM). At lower doses, the surface of the La2Zr2O7 film amorphized, and the amorphous fraction as a function of dose fit well to a stimulated amorphization model. As the dose increased, the surface amorphization slowed, and amorphization appeared at the interface. Even at a dose of 10 dpa, the core of the film remained crystalline, despite the prediction of amorphization from the model. To inform future ab initio simulations of La2Zr2O7, the bandgap of a thick La2Zr2O7 film was measured to be indirect at 4.96 eV, with a direct transition at 5.60 eV.

  6. Frequency response improvement of a two-port surface acoustic wave device based on epitaxial AlN thin film

    Science.gov (United States)

    Gao, Junning; Hao, Zhibiao; Luo, Yi; Li, Guoqiang

    2018-01-01

    This paper presents an exploration on improving the frequency response of the symmetrical two-port AlN surface acoustic wave (SAW) device, using epitaxial AlN thin film on (0001) sapphire as the piezoelectric substrate. The devices were fabricated by lift-off processes with Ti/Al composite electrodes as interleaved digital transducers (IDT). The impact of DL and the number of the IDT finger pairs on the frequency response was carefully investigated. The overall properties of the device are found to be greatly improved with DL elongation, indicated by the reduced pass band ripple and increased stop band rejection ratio. The rejection increases by 8.3 dB when DL elongates from 15.5λ to 55.5λ and 4.4 dB further accompanying another 50λ elongation. This is because larger DL repels the stray acoustic energy out of the propagation path and provides a cleaner traveling channel for functional SAW, and at the same time restrains electromagnetic feedthrough. It is also found that proper addition of the IDT finger pairs is beneficial for the device response, indicated by the ripple reduction and the insertion loss drop.

  7. Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by control of growth kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaoran; Cao, Yanwei; Pal, B.; Middey, S.; Kareev, M.; Choi, Y.; Shafer, P.; Haskel, D.; Arenholz, E.; Chakhalian, J.

    2017-12-01

    We report on the selective fabrication of high-quality Sr2IrO4 and SrIrO3 epitaxial thin films from a single polycrystalline Sr2IrO4 target by pulsed laser deposition. Using a combination of x-ray diffraction and photoemission spectroscopy characterizations, we discover that within a relatively narrow range of substrate temperature, the oxygen partial pressure plays a critical role in the cation stoichiometric ratio of the films, and triggers the stabilization of different Ruddlesden-Popper (RP) phases. Resonant x-ray absorption spectroscopy measurements taken at the Ir L edge and the O K edge demonstrate the presence of strong spin-orbit coupling, and reveal the electronic and orbital structures of both compounds. These results suggest that in addition to the conventional thermodynamics consideration, higher members of the Srn+1IrnO3n+1 series can possibly be achieved by kinetic control away from the thermodynamic limit. These findings offer an approach to the synthesis of ultrathin films of the RP series of iridates and can be extended to other complex oxides with layered structure.

  8. Electronic band structure of epitaxial PbTe (111) thin films observed by angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Ye, Zhenyu; Cui, Shengtao; Shu, Tianyu; Ma, Songsong; Liu, Yang; Sun, Zhe; Luo, Jun-Wei; Wu, Huizhen

    2017-04-01

    Using angle-resolved photoemission spectroscopy (ARPES), we studied bulk and surface electronic band structures of narrow-gap semiconductor lead telluride (PbTe) thin films grown by molecular beam epitaxy both perpendicular and parallel to the Γ -L direction. The comparison of ARPES data with the first-principles calculation reveals the details of band structures, orbital characters, spin-orbit splitting energies, and surface states. The photon-energy-dependent spectra show the bulk character. Both the L and Σ valence bands are observed and their energy difference is determined. The spin-orbit splitting energies at L and Γ points are 0.62 eV and 0.88 eV, respectively. The surface states below and close to the valence band maximum are identified. The valence bands are composed of a mixture of Pb 6 s and Te 5 pz orbitals with dominant in-plane even parity, which is attributed to the layered distortion in the vicinity of the PbTe (111) surface. These findings provide insights into PbTe fundamental properties and shall benefit relevant thermoelectric and optoelectronic applications.

  9. Epitaxial growth of CdTe thin film on cube-textured Ni by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gaire, C. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Rao, S. [Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Riley, M. [Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Chen, L. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Goyal, A. [Oak Ridge National Lab, Oak ridge, TN, 37831-6116 (United States); Lee, S. [US Army ARDEC Benet Labs, Watervliet, NY, 12189-4050 (United States); Bhat, I. [Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Lu, T.-M. [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States); Wang, G.-C., E-mail: wangg@rpi.edu [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY, 12180-3590 (United States)

    2012-01-01

    Single crystal-like CdTe thin film has been grown by metalorganic chemical vapor deposition on cube-textured Ni(100) substrate. Using X-ray pole figure measurements we observed the epitaxial relationship of {l_brace}111{r_brace}{sub CdTe}//{l_brace}001{r_brace}{sub Ni} with [11{sup Macron }0]{sub CdTe}//[010]{sub Ni} and [112{sup Macron }] {sub CdTe}//[100]{sub Ni}. The 12 diffraction peaks in the (111) pole figure of CdTe film and their relative positions with respect to the four peak positions in the (111) pole figure of Ni substrate are consistent with four equivalent orientational domains of CdTe with three to four superlattice match of about 1.6% in the [11{sup Macron }0] direction of CdTe and the [010] direction of Ni. The electron backscattered diffraction images show that the CdTe domains are 30 Degree-Sign oriented from each other. These high structural quality films may find applications in low cost optoelectronic devices.

  10. Electro-oxidized epitaxial graphene channel field-effect transistors with single-walled carbon nanotube thin film gate electrode.

    Science.gov (United States)

    Ramesh, Palanisamy; Itkis, Mikhail E; Bekyarova, Elena; Wang, Feihu; Niyogi, Sandip; Chi, Xiaoliu; Berger, Claire; de Heer, Walt; Haddon, Robert C

    2010-10-20

    We report the effect of electrochemical oxidation in nitric acid on the electronic properties of epitaxial graphene (EG) grown on silicon carbide substrates; we demonstrate the availability of an additional reaction channel in EG, which is not present in graphite but which facilitates the introduction of the reaction medium into the graphene galleries during electro-oxidation. The device performance of the chemically processed graphene was studied by patterning the EG wafers with two geometrically identical macroscopic channels; the electro-oxidized channel showed a logarithmic increase of resistance with decreasing temperature, which is ascribed to the scattering of charge carriers in a two-dimensional electronic gas, rather than the presence of an energy gap at the Fermi level. Field-effect transistors were fabricated on the electro-oxidized and pristine graphene channels using single-walled carbon nanotube thin film top gate electrodes, thereby allowing the study of the effect of oxidative chemistry on the transistor performance of EG. The electro-oxidized channel showed higher values for the on-off ratio and the mobility of the graphene field-effect transistor, which we ascribe to the availability of high-quality internal graphene layers after electro-oxidation of the more defective top layers. Thus, the present oxidative process provides a clear contrast with previously demonstrated covalent chemistry in which sp(3) hybridized carbon atoms are introduced into the graphitic transport layer of the lattice by carbon-carbon bond formation, thereby opening an energy gap.

  11. Structural, mechanical and magnetic study on galvanostatic electroplated nanocrystalline NiFeP thin films

    Science.gov (United States)

    Kalaivani, A.; Senguttuvan, G.; Kannan, R.

    2018-03-01

    Nickel based alloys has a huge applications in microelectronics and micro electromechanical systems owing to its superior soft magnetic properties. With the advantages of simplicity, cost-effectiveness and controllable patterning, electroplating processes has been chosen to fabricate thin films in our work. The soft magnetic NiFeP thin film was successfully deposited over the surface of copper plate through galvanostatic electroplating method by applying constant current density of 10 mA cm-2 for a deposition rate for half an hour. The properties of the deposited NiFeP thin films were analyzed by subjecting it into different physio-chemical characterization such as XRD, SEM, EDAX, AFM and VSM. XRD pattern confirms the formation of NiFeP particles and the structural analysis reveals that the NiFeP particles were uniformly deposited over the surface of copper substrate. The surface roughness analysis of the NiFeP films was done using AFM analysis. The magnetic studies and the hardness of the thin film were evaluated from the VSM and hardness test. The NiFeP thin films possess lower coercivity with higher magnetization value of 69. 36 × 10-3 and 431.92 Gauss.

  12. Anomalously high thermoelectric power factor in epitaxial ScN thin films

    International Nuclear Information System (INIS)

    Kerdsongpanya, Sit; Zukauskaite, Agne; Jensen, Jens; Birch, Jens; Lu Jun; Hultman, Lars; Wingqvist, Gunilla; Eklund, Per; Van Nong, Ngo; Pryds, Nini

    2011-01-01

    Thermoelectric properties of ScN thin films grown by reactive magnetron sputtering on Al 2 O 3 (0001) wafers are reported. X-ray diffraction and elastic recoil detection analyses show that the composition of the films is close to stoichiometry with trace amounts (∼1 at. % in total) of C, O, and F. We found that the ScN thin-film exhibits a rather low electrical resistivity of ∼2.94 μΩm, while its Seebeck coefficient is approximately ∼-86 μV/K at 800 K, yielding a power factor of ∼2.5 x 10 -3 W/mK 2 . This value is anomalously high for common transition-metal nitrides.

  13. Anomalously high thermoelectric power factor in epitaxial ScN thin films

    DEFF Research Database (Denmark)

    Kerdsongpanya, Sit; Van Nong, Ngo; Pryds, Nini

    2011-01-01

    found that the ScN thin-film exhibits a rather low electrical resistivity of ∼2.94 μΩm, while its Seebeck coefficient is approximately ∼−86 μV/K at 800 K, yielding a power factor of ∼2.5 × 10−3 W/mK2. This value is anomalously high for common transition-metal nitrides. © 2011 American Institute...

  14. Spectroscopic and microscopic investigation of MBE-grown CdTe (211)B epitaxial thin films on GaAs (211)B substrates

    Science.gov (United States)

    Özden, Selin; Koc, Mumin Mehmet

    2018-03-01

    CdTe epitaxial thin films, for use as a buffer layer for HgCdTe defectors, were grown on GaAs (211)B using the molecular beam epitaxy method. Wet chemical etching (Everson method) was applied to the epitaxial films using various concentrations and application times to quantify the crystal quality and dislocation density. Surface characterization of the epitaxial films was achieved using Atomic force microscopy and Scanning electron microscopy (SEM) before and after each treatment. The Energy Dispersive X-Ray apparatus of SEM was used to characterize the chemical composition. Untreated CdTe films show smooth surface characteristics with root mean square (RMS) roughnesses of 1.18-3.89 nm. The thicknesses of the CdTe layers formed were calculated via FTIR spectrometry and obtained by ex situ spectroscopic ellipsometry. Raman spectra were obtained for various temperatures. Etch pit densities (EPD) were measured, from which it could be seen that EPD changes between 1.7 × 108 and 9.2 × 108 cm-2 depending on the concentration of the Everson etch solution and treatment time. Structure, shape and depth of pits resulting from each etch pit implementation were also evaluated. Pit widths varying between 0.15 and 0.71 µm with heights varying between 2 and 80 nm were observed. RMS roughness was found to vary by anything from 1.56 to 26 nm.

  15. Structural and electrical properties of c-axis epitaxial and polycrystalline Sr sub 3 Bi sub 4 Ti sub 6 O sub 2 sub 1 thin films

    CERN Document Server

    Zhang, S T; Sun, H P; Pan Xiao Qing; Tan, W S; Liu, Z G; Ming, N B

    2003-01-01

    c-axis epitaxial and polycrystalline Sr sub 3 Bi sub 4 Ti sub 6 O sub 2 sub 1 (SBTi) thin films were fabricated on (001)SrTiO sub 3 (STO) single-crystal substrates and Pt/Ti sub 2 /SiO sub 2 /Si substrates respectively, by pulsed laser deposition (PLD). Structures of the films were systematically characterized by x-ray diffraction (XRD), including theta-2 theta-scans, rocking curve scans and phi-scans, atomic force microscopy and transmission electron microscopy (TEM). The epitaxial orientation relation of the SBTi films on STO is established by selected-area electron diffraction and XRD phi-scans to be (001)SBTi || (001)STO, [11-bar 0]SBTi || [010]STO. Cross-sectional high-resolution TEM studies on the epitaxial SBTi film revealed that SBTi is a single-phase material. A special kind of irrational atomic shift along the [001] direction was observed and is discussed in detail. By using an evanescent microwave probe (EMP), the room-temperature dielectric constant of the epitaxial SBTi film was measured to be 21...

  16. Epitaxial Oxide Thin Films Grown by Solid Source Metal-Organic Chemical Vapor Deposition.

    Science.gov (United States)

    Lu, Zihong

    1995-01-01

    The conventional liquid source metal-organic chemical vapor deposition (MOCVD) technique is capable of producing large area, high quality, single crystal semiconductor films. However, the growth of complex oxide films by this method has been hampered by a lack of suitable source materials. While chemists have been actively searching for new source materials, the research work reported here has demonstrated the successful application of solid metal-organic sources (based on tetramethylheptanedionate) to the growth of high quality thin films of binary compound cerium dioxide (CeO_2), and two more complex materials, the ternary compound lithium niobate (LiNbO_3), with two cations, and the quaternary compound strontium barium niobate (SBN), with three cations. The growth of CeO_2 thin films on (1012)Al_2O_3 substrates has been used as a model to study the general growth behavior of oxides. Factors affecting deposition rate, surface morphology, out-of-plane mosaic structure, and film orientation have been carefully investigated. A kinetic model based on gas phase prereaction is proposed to account for the substrate temperature dependence of film orientation found in this system. Atomically smooth, single crystal quality cerium dioxide thin films have been obtained. Superconducting YBCO films sputtered on top of solid source MOCVD grown thin cerium dioxide buffer layers on sapphire have been shown to have physical properties as good as those of YBCO films grown on single crystal MgO substrates. The thin film growth of LiNbO_3 and Sr_{1-x}Ba _{x}Nb_2 O_6 (SBN) was more complex and challenging. Phase purity, transparency, in-plane orientation, and the ferroelectric polarity of LiNbO _3 films grown on sapphire substrates was investigated. The first optical quality, MOCVD grown LiNbO _3 films, having waveguiding losses of less than 2 dB/cm, were prepared. An important aspect of the SBN film growth studies involved finding a suitable single crystal substrate material. Mg

  17. Characterization and Photovoltaic Properties of BiFeO3 Thin Films

    Directory of Open Access Journals (Sweden)

    Yasuhiro Shirahata

    2016-12-01

    Full Text Available Bismuth ferrite (BiFeO3 thin films were prepared by a spin-coating method. Crystal structure and optical properties of the BiFeO3 films were evaluated using X-ray diffraction. The lattice constants, crystallite size, and energy gap of BiFeO3 films depended on the concentration of the BiFeO3 precursor solution. BiFeO3/CH3NH3PbI3 photovoltaic devices were fabricated to investigate photovoltaic properties of BiFeO3. Current density–voltage characteristics of the photovoltaic devices showed rectifying behavior, indicating that BiFeO3 worked as an electron transport layer in CH3NH3PbI3-based photovoltaic devices.

  18. Potentiostatic electrodeposition of Co-Ni-Fe thin films from sulfate medium

    International Nuclear Information System (INIS)

    Hanafi, Ismail; Daud, Abdul Razak; Radiman, Shahidan

    2016-01-01

    The aim of this study was to produce thin films of ternary cobalt-nickel-iron (Co-Ni-Fe) alloy by electrochemical deposition method at different electrodeposition potentials in a sulfate solution (0.15 M CoSO 4 , + 0.2 M NiSO 4 + 0.00 5M FeSO 4 ). The Co-Ni-Fe alloy thin films were electrodeposited on indium-doped tin oxide (ITO) coated on a conducting glass substrate. Voltammetric studies indicated that potential range for successful deposition of Co, Ni and Fe was between -1.10 to -1.30 V (SCE). The energy dispersive X-ray (EDX) analysis indicated that the films exhibited anomalous behavior with Ni content of the films significantly increased, whereas the Co and Fe content decreased as the electrodeposition potentials were made more negative. The field emission scanning electron microscopy (FESEM) study showed that the electrodeposited films were uniform for all applied potential values and larger particles were formed when higher electrodeposition potentials were applied. Investigation by X-ray diffraction (XRD) revealed that the dominant phase in the deposited film was amorphous Co-Ni-Fe. Hysteresis curves of the ternary alloy film obtained from vibrating sample magnetometer prove that the alloy is ferromagnetic. The coercivity mechanism of the Co-Ni-Fe films obeyed Neel’s relation which is thickness dependent. Keywords: applied potential, Co-Ni-Fe thin films, ferromagnetic, Neel’s relation.

  19. Fabrication and high frequency magnetic characterization of FeCoAl ternary thin films

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Yung-Wang [Center for Nanotechnology, Materials Science, and Microsystems, National Tsing Hua University, 101 Kuang-Fu Rd., Sec. 2, Hsinchu 300 (China); Wu, Fan-Bean [Department of Materials Science and Engineering, National United University, 1 Lein-Da, Kung-Ching Li, MiaoLi 360 (China); Li, Shandong [Center for Nanotechnology, Materials Science, and Microsystems, National Tsing Hua University, 101 Kuang-Fu Rd., Sec. 2, Hsinchu 300 (China); Department of Physics, Fujian Normal University, Fuzhou 35007 (China); Kuo, Cheng-Lun [Department of Materials Science and Engineering, National Tsing Hua University, 101 Kuang-Fu Rd., Sec. 2, Hsinchu 300 (China); Duh, Jenq-Gong [Center for Nanotechnology, Materials Science, and Microsystems, National Tsing Hua University, 101 Kuang-Fu Rd., Sec. 2, Hsinchu 300 (China); Department of Materials Science and Engineering, National Tsing Hua University, 101 Kuang-Fu Rd., Sec. 2, Hsinchu 300 (China)

    2007-12-15

    Integration of ferromagnetic materials with electronic components represents a key solution to the enhancement of high frequency characteristics for recent miniaturized communication devices. In this study, Al element was introduced into FeCo binary alloy to form a ternary FeCoAl magnetic thin film by co-sputtering technique followed by annealing in the presence of an external magnetic field. X-ray diffraction results revealed that the FeCoAl films exhibited a solid solution microstructure of FeCo matrix with Al as the solute element. The saturation magnetization (M{sub s}) of FeCoAl thin film still maintained a high value around 1780 emu/cm{sup 3}. It was found that the FeCoAl system possessed a high permeability around 1000 and an uni-axial anisotropic field (H{sub k}) of 50 Oe. In addition, with the incorporation of Al element, the resonance frequency of the FeCoAl film reached 2.1 GHz. Hence, it is suggested that the FeCoAl magnetic thin film is a potential candidate for high frequency devices operated in GHz bands. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. KTa{sub 0.65}Nb{sub 0.35}O{sub 3} thin films epitaxially grown by pulsed laser deposition on metallic and oxide epitaxial electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Bouyasfi, A.; Mouttalie, M. [Sciences Chimiques de Rennes, UMR 6226 CNRS/Universite de Rennes 1/UEB, Campus de Beaulieu, 263 avenue du general Leclerc CS 74205, 35042 Rennes Cedex (France); Laboratoire de Compatibilite Electromagnetique, Maintenance Industrielle et Nanostructures (LCEMINAS), Faculte des Sciences et Techniques, Route d' Imouzzer B.P. 2202 Fes 30000 (Morocco); Demange, V. [Sciences Chimiques de Rennes, UMR 6226 CNRS/Universite de Rennes 1/UEB, Campus de Beaulieu, 263 avenue du general Leclerc CS 74205, 35042 Rennes Cedex (France); Gautier, B.; Grandfond, A. [Institut des Nanotechnologies de Lyon/INSA, 7 Avenue Capelle, 69621 Villeurbanne Cedex (France); Deputier, S.; Ollivier, S. [Sciences Chimiques de Rennes, UMR 6226 CNRS/Universite de Rennes 1/UEB, Campus de Beaulieu, 263 avenue du general Leclerc CS 74205, 35042 Rennes Cedex (France); Hamedi, L' H. [Laboratoire de Compatibilite Electromagnetique, Maintenance Industrielle et Nanostructures (LCEMINAS), Faculte des Sciences et Techniques, Route d' Imouzzer B.P. 2202 Fes 30000 (Morocco); Guilloux-Viry, M., E-mail: maryline.guilloux-viry@univ-rennes1.fr [Sciences Chimiques de Rennes, UMR 6226 CNRS/Universite de Rennes 1/UEB, Campus de Beaulieu, 263 avenue du general Leclerc CS 74205, 35042 Rennes Cedex (France)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Ferroelectric KTa{sub 0.65}Nb{sub 0.35}O{sub 3} thin films grown by pulsed laser deposition. Black-Right-Pointing-Pointer KTa{sub 0.65}Nb{sub 0.35}O{sub 3} epitaxially grown on Pt and LaNiO{sub 3} epitaxial electrodes. Black-Right-Pointing-Pointer Influence of oxide vs. metal electrode on ferroelectric's structural properties. Black-Right-Pointing-Pointer AFM/TUNA mode investigation of KTa{sub 0.65}Nb{sub 0.35}O{sub 3}/Pt heterostructure. Black-Right-Pointing-Pointer Asymmetry of the conduction mechanisms (positive vs. negative applied voltage). - Abstract: Ferroelectric KTa{sub 0.65}Nb{sub 0.35}O{sub 3} (KTN) thin films were grown by pulsed laser deposition on Pt and LaNiO{sub 3} epitaxial electrodes, on (1 0 0) and (1 1 0) SrTiO{sub 3} substrates. The effect of the nature of the electrode on structural and microstructural quality of KTN films was investigated. While epitaxial KTN thin films were successfully obtained on both electrodes, two orientations compete on Pt, whatever the main orientation of Pt is (1 0 0) or (1 1 0). On LaNiO{sub 3} in contrast, pure (1 0 0) and (1 1 0) oriented KTN films were achieved with a high crystalline quality illustrated by narrow {omega}-scans ({Delta}{omega} = 0.56 Degree-Sign and {Delta}{omega} = 0.80 Degree-Sign for (1 0 0) and (1 1 0) KTN, to be compared to 0.048 Degree-Sign and 0.22 Degree-Sign for (1 0 0) and (1 1 0) LaNiO{sub 3}, respectively). Electrical measurements performed in tunneling atomic force microscopy (TUNA mode) on a KTN/Pt heterostructure showed a high asymmetry of the conduction mechanisms when a positive or a negative bias is applied on the sample. In particular leakage currents appear even at very low positive applied voltage. TUNA imaging operated at a moderate negative applied voltage of -3 V shows that some areas corresponding to grain boundaries seem to be more leaky than others.

  1. Tuning of thermally induced first-order semiconductor-to-metal transition in pulsed laser deposited VO2 epitaxial thin films

    Science.gov (United States)

    Behera, Makhes K.; Pradhan, Dhiren K.; Pradhan, Sangram K.; Pradhan, Aswini K.

    2017-12-01

    Vanadium oxide (VO2) thin films have drawn significant research and development interest in recent years because of their intriguing physical origin and wide range of functionalities useful for many potential applications, including infrared imaging, smart windows, and energy and information technologies. However, the growth of highly epitaxial films of VO2, with a sharp and distinct controllable transition, has remained a challenge. Here, we report the structural and electronic properties of high quality and reproducible epitaxial thin films of VO2, grown on c-axis oriented sapphire substrates using pulsed laser deposition at different deposition pressures and temperatures, followed by various annealing schedules. Our results demonstrate that the annealing of epitaxial VO2 films significantly enhances the Semiconductor to Metal Transition (SMT) to that of bulk VO2 transition. The effect of oxygen partial pressure during the growth of VO2 films creates a significant modulation of the SMT from around room temperature to as high as the theoretical value of 68 °C. We obtained a bulk order transition ≥104 while reducing the transition temperature close to 60 °C, which is comparatively less than the theoretical value of 68 °C, demonstrating a clear and drastic improvement in the SMT switching characteristics. The results reported here will open the door to fundamental studies of VO2, along with tuning of the transition temperatures for potential applications for multifunctional devices.

  2. Dielectric and ferroelectric properties of strain-relieved epitaxial lead-free KNN-LT-LS ferroelectric thin films on SrTiO3 substrates

    Science.gov (United States)

    Abazari, M.; Akdoǧan, E. K.; Safari, A.

    2008-05-01

    We report the growth of single-phase (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated ⟨001⟩ oriented SrTiO3 substrates by using pulsed laser deposition. Films grown at 600°C under low laser fluence exhibit a ⟨001⟩ textured columnar grained nanostructure, which coalesce with increasing deposition temperature, leading to a uniform fully epitaxial highly stoichiometric film at 750°C. However, films deposited at lower temperatures exhibit compositional fluctuations as verified by Rutherford backscattering spectroscopy. The epitaxial films of 400-600nm thickness have a room temperature relative permittivity of ˜750 and a loss tangent of ˜6% at 1kHz. The room temperature remnant polarization of the films is 4μC /cm2, while the saturation polarization is 7.1μC/cm2 at 24kV/cm and the coercive field is ˜7.3kV/cm. The results indicate that approximately 50% of the bulk permittivity and 20% of bulk spontaneous polarization can be retained in submicron epitaxial KNN-LT-LS thin film, respectively. The conductivity of the films remains to be a challenge as evidenced by the high loss tangent, leakage currents, and broad hysteresis loops.

  3. Epitaxial Fe{sub 3-x}Ti{sub x}O{sub 4} films from magnetite to ulvöspinel by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Droubay, T.C.; Pearce, C.I.; Ilton, E.S.; Engelhard, M.H.; Engelhard, M.H.; Heald, S.M.; Arenholz, E.; Rosso, K.M.

    2011-07-21

    Epitaxial films along the Fe{sub 3-x}Ti{sub x}O{sub 4} (titanomagnetite) compositional series from pure end-members magnetite (Fe{sub 3}O{sub 4}) to ulvöspinel (Fe{sub 2}TiO{sub 4}) were successfully grown by pulsed laser deposition on MgO(100) substrates. Spectroscopic characterization including high resolution x-ray diffraction, x-ray photoelectron spectroscopy, and synchrotron-based x-ray absorption and magnetic circular dichroism consistently shows that Ti(IV) substitutes for Fe(III) in the inverse spinel lattice with a proportional increase in lattice Fe(II) concentration. No evidence of Ti interstitials, spinodal decomposition, or secondary phases was found in the bulk of the grown films. At the uppermost few nanometers of the Ti-bearing film surfaces, evidence suggests that Fe(II) is susceptible to facile oxidation, and that an associated lower Fe/Ti ratio in this region is consistent with surface compositional incompleteness or alteration to a titanomaghemite-like composition and structure. The surface of these films nonetheless appear to remain highly ordered and commensurate with the underlying structure despite facile oxidation, a surface condition that is found to be reversible to some extent by heating in low oxygen environments.

  4. Buffer-layer enhanced crystal growth of BaB{sub 6} (1 0 0) thin films on MgO (1 0 0) substrates by laser molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Yushi; Yamauchi, Ryosuke; Arai, Hideki; Tan, Geng [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259-J2-46, Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Tsuchimine, Nobuo; Kobayashi, Susumu [Toshima Manufacturing Company Limited, 1414 Shimonomoto, Higashimatsuyama-shi, Saitama 355-0036 (Japan); Saeki, Kazuhiko; Takezawa, Nobutaka [Department of Materials Technology, Industrial Technology Center of Tochigi Prefecture, 367-1 Karinuma, Utsunomiya-shi, Tochigi 321-3224 (Japan); Mitsuhashi, Masahiko; Kaneko, Satoru [Kanagawa Industrial Technology Center, Kanagawa Prefectural Government, 705-1 Shimo-Imaizumi, Ebina, Kanagawa 243-0435 (Japan); Yoshimoto, Mamoru, E-mail: yoshimoto.m.aa@m.titech.ac.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259-J2-46, Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Patent Attorney, Tokyo Institute of Technology, 4259-J2-46, Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan)

    2012-02-01

    Crystalline BaB{sub 6} (1 0 0) thin films can be fabricated on MgO (1 0 0) substrates by inserting a 2-3 nm-thick epitaxial SrB{sub 6} (1 0 0) buffer layer by pulsed laser deposition (PLD) in ultra-high vacuum (i.e., laser molecular beam epitaxy). Reflection high-energy electron diffraction and X-ray diffraction measurements indicated the heteroepitaxial structure of BaB{sub 6} (1 0 0)/SrB{sub 6} (1 0 0)/MgO (1 0 0) with the single domain of the epitaxial relationship. Conversely, BaB{sub 6} thin films without the buffer layer were not epitaxial instead they developed as polycrystalline films with a random in-plane configuration and some impurity phases. As a result, the buffer layer is considered to greatly affect the initial growth of epitaxial BaB{sub 6} thin films; therefore, in this study, buffering effects have been discussed. From the conventional four-probe measurement, it was observed that BaB{sub 6} epitaxial thin films exhibit n-type semiconducting behavior with a resistivity of 2.90 Multiplication-Sign 10{sup -1} {Omega} cm at room temperature.

  5. Topotactic Metal-Insulator Transition in Epitaxial SrFeO x Thin Films

    International Nuclear Information System (INIS)

    Khare, Amit; Shin, Dongwon; Yoo, Tae Sup; Kim, Minu; Kang, Tae Dong

    2017-01-01

    Multivalent transition metal oxides provide fascinating and rich physics related to oxygen stoichiometry. In particular, the adoptability of various valence states of transition metals enables perovskite oxides to display mixed (oxygen) ionic and electronic conduction and catalytic activity useful in many practical applications, including solid-oxide fuel cells (SOFCs), rechargeable batteries, gas sensors, and memristive devices. For proper realization of the ionic conduction and catalytic activity, it is essential to understand the reversible oxidation and reduction process, which is governed by oxygen storage/release steps in oxides. Topotactic phase transformation facilitates the redox process in perovskites with specific oxygen vacancy ordering by largely varying the oxygen concentration of a material without losing the lattice framework. The concentration and diffusion of oxide ions (O 2– ), the valence state of the transition metal cations, and the thermodynamic structural integrity together provide fundamental understanding and ways to explicitly control the redox reaction.[6] In addition, it offers an attractive route for tuning the emergent physical properties of transition metal oxides, via strong coupling between the crystal lattice and electronic structure.

  6. Scanning proximal microscopy study of the thin layers of silicon carbide-aluminum nitride solid solution manufactured by fast sublimation epitaxy

    Directory of Open Access Journals (Sweden)

    Tománek P.

    2013-05-01

    Full Text Available The objective of the study is a growth of SiC/(SiC1−x(AlNx structures by fast sublimation epitaxy of the polycrystalline source of (SiC1−x(AlNx and their characterisation by proximal scanning electron microscopy and atomic force microscopy. For that purpose optimal conditions of sublimation process have been defined. Manufactured structures could be used as substrates for wide-band-gap semiconductor devices on the basis of nitrides, including gallium nitride, aluminum nitride and their alloys, as well as for the production of transistors with high mobility of electrons and also for creation of blue and ultraviolet light emitters (light-emitted diodes and laser diodes. The result of analysis shows that increasing of the growth temperature up to 2300 K allows carry out sublimation epitaxy of thin layers of aluminum nitride and its solid solution.

  7. Epitaxial growth of YBa sub 2 Cu sub 3 O sub 7 minus. delta. thin films on LiNbO sub 3 substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.G.; Koren, G.; Gupta, A.; Segmuller, A.; Chi, C.C. (IBM Thomas J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (US))

    1989-09-18

    {ital In} {ital situ} epitaxial growth of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films on {ital Y}-cut LiNbO{sub 3} substrates using a standard laser ablation technique is reported. Resistance of the films shows a normal metallic behavior and a very sharp ({lt}1 K) superconducting transition with {ital T}{sub {ital c}}({ital R}=0) of 92 K. High critical current density of {ital J}{sub {ital c}}(77 K)=2{times}10{sup 5} A/cm{sup 2} is observed, which is in accordance with epitaxial growth. Film orientation observed from x-ray diffraction spectra indicates that the {ital c} axis is normal to the substrate plane and the {ital a} axis is at 45{degree} to the (11.0) direction of the hexagonal lattice of the substrate with two domains in mirror image to the (110) plane.

  8. Electrically induced insulator to metal transition in epitaxial SmNiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Nikhil, E-mail: nss152@psu.edu; Dasgupta, Sandeepan; Datta, Suman [Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Joshi, Toyanath; Borisov, Pavel; Lederman, David [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

    2014-07-07

    We report on the electrically induced insulator to metal transition (IMT) in SmNiO{sub 3} thin films grown on (001) LaAlO{sub 3} by pulsed laser deposition. The behavior of the resistivity as a function of temperature suggests that the primary transport mechanism in the SmNiO{sub 3} insulating state is dominated by Efros-Shklovskii variable range hopping (ES-VRH). Additionally, the magnetic transition in the insulating state of SmNiO{sub 3} modifies the characteristics of the ES-VRH transport. Systematic DC and pulsed current-voltage measurements indicate that current-induced joule heating is the fundamental mechanism driving the electrically induced IMT in SmNiO{sub 3}. These transport properties are explained in context of the IMT in SmNiO{sub 3} being related to the strong electron-lattice coupling.

  9. Adjusting the electronic properties and gas reactivity of epitaxial graphene by thin surface metallization

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Jens, E-mail: jenser@ifm.liu.se; Puglisi, Donatella; Kang, Yu Hsuan; Yakimova, Rositza; Lloyd Spetz, Anita

    2014-04-15

    Graphene-based chemical gas sensors normally show ultra-high sensitivity to certain gas molecules but at the same time suffer from poor selectivity and slow response and recovery times. Several approaches based on functionalization or modification of the graphene surface have been demonstrated as means to improve these issues, but most such measures result in poor reproducibility. In this study we investigate reproducible graphene surface modifications by sputter deposition of thin nanostructured Au or Pt layers. It is demonstrated that under the right metallization conditions the electronic properties of the surface remain those of graphene, while the surface chemistry is modified to improve sensitivity, selectivity and speed of response to nitrogen dioxide.

  10. Growth, luminescence and magnetic properties of GaN:Er semiconductor thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Dasari, K.; Wu, J.; Huhtinen, H.; Jadwisienczak, W. M.; Palai, R.

    2017-05-01

    We report on the growth, surface, luminescence and magnetic properties of 180 nm thick Er-doped GaN thin films grown by molecular beam epitaxy (MBE) on c-sapphire substrates with no buffer layer and with different Er concentrations. In situ reflection high-energy electron diffraction (RHEED) patterns revealed crystalline and uniform growth of the films. The x-ray diffraction (XRD) pattern showed c-axis-oriented growth. Atomic force microscopy (AFM) analysis showed enhancement of surface morphology and smoothness with increasing Er doping, which could be due to minimization of surface defects because of the gettering effect of the rare earth. Scanning area-dependent surface morphology analysis showed a power law dependence indicating the fractal nature of the surface, which is confirmed by the observation of a non-integer D (fractal dimension) value. X-ray photoluminescence spectroscopy (XPS) revealed the formation of a GaN:Er phase and ruled out the presence of Ga and Er metallic and native oxide phases. The semi-quantitative elemental composition of the films was determined using N 1s, Ga 2p3/2 and Er 4d photoemission lines. The Er concentration was estimated from the x-ray photoelectron spectra and found to be between 3.0 and 9.0 at.% (˜1021 atoms cm-3). Photoluminescence (PL) and cathodoluminescence (CL) studies showed visible emission and concentration quenching of Er3+ ions in agreement with reported results. Excitation of the Er3+ ion might be affected by charge trapping due to Er-doping-induced defect complexes. The magnetic measurements carried out by a superconducting quantum interference device (SQUID) showed a ferromagnetic-paramagnetic phase transition at low temperature, contrary to the reported room temperature ferromagnetism in metalorganic chemical vapor deposition (MOCVD)-grown GaN:Er thick films of 550 nm.

  11. Photocatalytic and magnetic behaviors of BiFeO3 thin films deposited on different substrates

    Science.gov (United States)

    Xu, Hao-Min; Wang, Huan-Chun; Shen, Yang; Lin, Yuan-Hua; Nan, Ce-Wen

    2014-11-01

    Single phase polycrystalline BiFeO3 thin films were grown on three different substrates via chemical solution deposition. Our results indicate that the band gap of as-prepared BiFeO3 films can be tuned (2.02-2.67 eV) by the grain size effects caused by the substrates. These BiFeO3 films show good photocatalytic properties by the degradation of Congo red solution under visible-light irradiation ( λ> 400 nm). Additionally, weak ferromagnetic behaviors can be observed at room temperature in all the films, which should be correlated to the destruction of the incommensurate cycloid spin structure of BiFeO3 phase and the coexistence of Fe3+ and Fe2+ as confirmed by X-ray photoelectron spectroscopy.

  12. Laser MBE-grown CoFeB epitaxial layers on MgO: Surface morphology, crystal structure, and magnetic properties

    Science.gov (United States)

    Kaveev, Andrey K.; Bursian, Viktor E.; Krichevtsov, Boris B.; Mashkov, Konstantin V.; Suturin, Sergey M.; Volkov, Mikhail P.; Tabuchi, Masao; Sokolov, Nikolai S.

    2018-01-01

    Epitaxial layers of CoFeB were grown on MgO by means of laser molecular beam epitaxy using C o40F e40B20 target. The growth was combined with in situ structural characterization by three-dimensional reciprocal space mapping obtained from reflection high energy electron diffraction (RHEED) data. High-temperature single stage growth regime was adopted to fabricate CoFeB layers. As confirmed by the atomic force microscopy, the surface of CoFeB layers consists of closely spaced nanometer sized islands with dimensions dependent on the growth temperature. As shown by RHEED and XRD analysis, the CoFeB layers grown at high-temperature on MgO(001) possess body centered cubic (bcc) crystal structure with the lattice constant a =2.87 Å close to that of the C o75F e25 alloy. It was further shown that following the same high-temperature growth technique the MgO/CoFeB/MgO(001) heterostructures can be fabricated with top and bottom MgO layers of the same crystallographic orientation. The CoFeB layers were also grown on the GaN(0001) substrates using MgO(111) as a buffer layer. In this case, the CoFeB layers crystallize in bcc crystal structure with the (111) axis perpendicular to the substrate surface. The magnetic properties of the CoFeB/MgO (001) heterostructures have been investigated by measuring magnetization curves with a vibrating sample magnetometer as well as by performing magneto-optical Kerr effect (MOKE) and ferromagnetic resonance (FMR) studies. FMR spectra were obtained for the variety of the magnetic field directions and typically consisted of a single relatively narrow resonance line. The magnetization orientations and the resonance conditions were calculated in the framework of a standard magnetic energy minimization procedure involving a single K1 c cubic term for the magnetocrystalline anisotropy. This allows a fairly accurate description of the angular dependences of the resonance fields—both in-plane and out-of-plane. It was shown that CoFeB layers exhibit

  13. The magnetic map of FeMn alloy thin films on Co(001) and Co/FeMn/Co(001) trilayers

    International Nuclear Information System (INIS)

    M'Passi-Mabiala, B.; Meza-Aguilar, S.; Demangeat, C.

    2003-08-01

    Recent x-ray magnetic circular dichroism and magneto-optical Kerr effect performed by Matthes et al (J. Appl. Phys. 93 (2003) 6504) on in situ layered systems of fcc Co and FeMn epitaxially grown onto Cu(001) templates as well as Co/FeMn/Co trilayers display very interesting results. Measurements showed that the magnetic moment on Fe is parallel to the Co magnetization direction whereas, for Mn the XMCD signals are small. In order to explain this behavior ab initio density functional calculations on (Fe 0.5 Mn 0.5 ) n /Co(001) and Co/(Fe 0.5 Mn 0.5 ) n /Co(001) have been performed for n varying from 1 to 3. Within generalized gradient corrections the Fe-Mn interfacial alloy, one monolayer thick on Co(001), with ferromagnetic coupling between Fe and Mn corresponds to the ground state whereas the same Fe-Mn monolayer in Co/FeMn/Co presents a magnetic moment of Mn opposite to that of Fe and Co. For all systems investigated we obtain a ferromagnetic polarization between Fe and Co atoms in agreement with the XMCD results. The behavior of the Mn polarization is more complex: an antiferromagnetic polarization between Mn atoms in nearest neighboring FeMn alloy plane is always obtained. (author)

  14. Visual study of domain structure in the spin reorientation range for (BiTm)3(FeGa)5O15 epitaxial films

    International Nuclear Information System (INIS)

    Belyaeva, A.I.; Antonov, A.V.; Egiazaryan, G.S.; Yur'ev, V.P.

    1980-01-01

    Carried out is visual study of the domain structure of (BiTm) 3 (FeGa) 5 O 12 ferrite-garnet epitaxial film with induced one-axial anisotropy within a wide temperature range of 4.2-400 K. Found is hysteresicless spin-reorientation phase transition, related to anisotropy change (light axis type on the anisotropy of light plane tyre). Intermediade state, connected with this transition, is investigated. It is shown, that double structure within temperature range Tsub(room)>=T>=Tsub(ph.tr) can be considered as thermodynamically equilibrium one

  15. Fabrication of Fe{sub 3}Si/CaF{sub 2} heterostructures ferromagnetic resonant tunneling diode by selected-area molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Sadakuni-Makabe, Kenji; Suzuno, Mitsushi; Harada, Kazunori [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8573 (Japan); Suemasu, Takashi, E-mail: suemasu@bk.tsukuba.ac.jp [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8573 (Japan); Akinaga, Hiro [Nanodevice Innovation Research Center and Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2011-10-03

    We have fabricated 200-nm-diameter ferromagnetic resonant tunneling diodes (FM-RTDs) using CaF{sub 2}/Fe{sub 3}Si heterostructures on Si(111) substrates, by selected-area molecular beam epitaxy (MBE) using electron-beam (EB) lithography. Clear negative differential resistances (NDRs) were observed in the current-voltage (I-V) characteristics at room temperature (RT). The reproducibility of the I-V characteristics was greatly improved, and approximately 40% of the FM-RTDs showed clear NDRs at RT.

  16. Ultra-thin epitaxial films of graphite and hexagonal boron nitride on solid surfaces

    CERN Document Server

    Oshima, C

    1997-01-01

    In this article, we have reviewed the recent progress of the experimental studies on ultra-thin films of graphite and hexagonal boron nitride (h-BN) by using angle-resolved electron spectroscopy together with other techniques. The fundamental properties of these high-quality films are discussed on the basis of the data on dispersion relations of valence electrons, phonon dispersion etc. The interfacial orbital mixing of the pi-state of the monolayer graphite (MG) with the d states of the reactive substrates is the origin for the phonon softening, expansion of the nearest-neighbour C-C distance, modification of the pi-band, low work function, and two-dimensional plasmons with high electron density, etc. In the cases of weak mixing at the interface between the MG and relatively inert substrates, the observed properties of the MG are very close to the bulk ones. In contrast to the case for MG, the interfacial interaction between the h-BN monolayer and the substrate is weak. (author)

  17. Thin films of NdFeB deposited by PLD technique

    International Nuclear Information System (INIS)

    Constantinescu, C.; Scarisoreanu, N.; Moldovan, A.; Dinescu, M.; Petrescu, L.; Epureanu, G.

    2007-01-01

    Neodymium-iron-boron (NdFeB) is a material with important magnetic properties, mostly used in permanent magnet fabrication. Thin layers of NdFeB are needed for miniaturization in electrical engineering, electronics and for high-tech devices. In this paper we applied pulsed lased deposition (PLD) in vacuum for obtaining thin films of NdFeB from stoichiometric targets. The influence of different buffer layers and of the laser parameters (wavelength and fluence) on the NdFeB structures, composition and magnetic properties have been investigated. The obtained structures were characterized by atomic force microscopy (AFM) and optical microscopy. Vibrating sample magnetometry (VSM) has been performed for specific magnetic characterization

  18. Thin films of NdFeB deposited by PLD technique

    Energy Technology Data Exchange (ETDEWEB)

    Constantinescu, C. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania); Scarisoreanu, N. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania); Moldovan, A. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania); Dinescu, M. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO-077125 Magurele, Bucharest (Romania)]. E-mail: dinescum@ifin.nipne.ro; Petrescu, L. [Department of Electrical Engineering, ' Politehnica' University of Bucharest, 313 Spl. Independentei, 060042 Bucharest (Romania); Epureanu, G. [Department of Electrical Engineering, ' Politehnica' University of Bucharest, 313 Spl. Independentei, 060042 Bucharest (Romania)

    2007-07-31

    Neodymium-iron-boron (NdFeB) is a material with important magnetic properties, mostly used in permanent magnet fabrication. Thin layers of NdFeB are needed for miniaturization in electrical engineering, electronics and for high-tech devices. In this paper we applied pulsed lased deposition (PLD) in vacuum for obtaining thin films of NdFeB from stoichiometric targets. The influence of different buffer layers and of the laser parameters (wavelength and fluence) on the NdFeB structures, composition and magnetic properties have been investigated. The obtained structures were characterized by atomic force microscopy (AFM) and optical microscopy. Vibrating sample magnetometry (VSM) has been performed for specific magnetic characterization.

  19. Zn Thin Film Deposition for Fe Layer Shielding Use the Sputtering Technique on Cylindrical Form

    International Nuclear Information System (INIS)

    Yunanto; Tjipto Sujitno, BA; Suprapto; Simbolon, Sahat

    2002-01-01

    Deposition of thin film on Fe substrate use sputtering technique on cylindrical form was carried out. The purpose of this research is to protect Fe due to the corrosion with Zn thin film. Sputtering method was proposed to protect a component of complex form. Substrate has functioned as anode, meanwhile target in cylindrical form as a cathode. Argon ion from anode bombard Zn with enough energy for releasing Zn. Zn atom would scatter and some of then was focused on the anode. For testing Zn atom on Fe by using XRF and corrosion rate with potentiostat. It was found that corrosion rate was decreased from 0.051 mpy to 0.031 mpy on 0.63 % of Fe substrate. (author)

  20. Fabrication and properties of SmFe2-PZT magnetoelectric thin films

    KAUST Repository

    Giouroudi, Ioanna

    2013-05-17

    Magnetoelectric (ME) thin film composites are attracting a continually increasing interest due to their unique features and potential applications in multifunctional microdevices and integrated units such as sensors, actuators and energy harvesting modules. By combining piezoelectric and highly magnetostrictive thin films, the potentialities of these materials increase. In this paper we report the fabrication of SmFe2 and PZT thin films and the investigation of their properties. First of all, a ~ 400 nm thin SmFe film was deposited on top of Si/SiO2 substrate by magnetron sputter deposition. Afterwards, a 140 nm Pt bottom electrode was sputtered on top of the SmFe film forming a bottom electrode. Spin coating was employed for the deposition of the 150 nm thin PZT layer. A PZT solution with 10 %Pb excess was utilized for this fabrication step. Finally, circular Pt top electrodes were sputtered as top electrodes. This paper focuses on the microstructure of the individual films characterized by X-Ray diffractometer (XRD) and scanning electron microscopy (SEM). A piezoelectric evaluation system, aixPES, with TF2000E analyzer component was used for the electric hysteresis measurements of PZT thin films and a vibrating sample magnetometer (VSM) was employed for the magnetic characterization of the SmFe. The developed thin films and the fabricated double layer SmFe-PZT exhibit both good ferromagnetic and piezoelectric responses which predict a promising ME composite structure. The quantitative chemical composition of the samples was confirmed by energy dispersive spectroscopy (EDX). © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  1. Atomic structure of Fe thin-films on Cu(0 0 1) studied with stereoscopic photography

    International Nuclear Information System (INIS)

    Hattori, Azusa N.; Fujikado, M.; Uchida, T.; Okamoto, S.; Fukumoto, K.; Guo, F.Z.; Matsui, F.; Nakatani, K.; Matsushita, T.; Hattori, K.; Daimon, H.

    2004-01-01

    The complex magnetic properties of Fe films epitaxially grown on Cu(0 0 1) have been discussed in relation to their atomic structure. We have studied the Fe films on Cu(0 0 1) by a new direct method for three-dimensional (3D) atomic structure analysis, so-called 'stereoscopic photography'. The forward-focusing peaks in the photoelectron angular distribution pattern excited by the circularly polarized light rotate around the light axis in either clockwise or counterclockwise direction depending on the light helicity. By using a display-type spherical mirror analyzer for this phenomenon, we can obtain stereoscopic photographs of atomic structure. The photographs revealed that the iron structure changes from bcc to fcc and almost bcc structure with increasing iron film thickness

  2. BiFeO 3 thin films: Novel effects

    Indian Academy of Sciences (India)

    In this paper we report synthesis of phase-pure highly resistive magnetoelectric BiFeO3 thin films on Pt/TiO2/SiO2/Si substrate by using pulsed laser deposition technique. For the first time saturated ferroelectric hysteresis loop has been observed. It has confirmed the presence of ferroelectricity in BiFeO3 compound.

  3. Magnetic and Electric Properties of Amorphous Co40Fe40B20 Thin Films

    Directory of Open Access Journals (Sweden)

    Yuan-Tsung Chen

    2012-01-01

    Full Text Available C40Fe40B20 was deposited on a glass substrate to a thickness (tf of between 100 Å and 500 Å. X-ray diffraction patterns (XRD indicate that C40Fe40B20 films are in an amorphous state. The plane-view microstructures and grain size distributions of CoFeB thin films are observed under a high-resolution transmission electron microscope (HRTEM. The thicker CoFeB films have larger grain size distribution than thinner CoFeB films. The saturation magnetization (Ms exhibits a size effect, meaning that Ms increases as tf increases. The magnetic remanence magnetization (Mr of CoFeB thin films are sensitive to thinner CoFeB films, and the refined grain size of thinner CoFeB films can induce ferromagnetic stronger spin exchange-coupling behavior than thicker CoFeB films, resulting in higher remanence. The highest magnetic squareness ratio (Mr/Ms of the CoFeB films occurs at thickness of 100 Å, suggesting the 100 Å of the as-deposited CoFeB film is suitable for magnetic memory application. These results also demonstrate that coercivity (Hc is increased by an increase in the width of the distribution of grain sizes. The electrical resistivity (ρ of such a film is typically higher than normally exceeding 100 μΩ cm, revealing that the amorphous phase dominates. These results are consistent with the XRD results.

  4. Reversal of the lattice structure in SrCoOx epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations

    OpenAIRE

    Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S. S. Ambrose; Cooper, Valentino R.; Rabe, Karin M.; Lee, Ho Nyung

    2013-01-01

    Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoOx (x = 2.5 - 3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases, i.e. the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator tran...

  5. Reversible pyroelectric and photogalvanic current in epitaxial Pb(Zr0.52Ti0.48)O3 thin films

    Science.gov (United States)

    Lee, J.; Esayan, S.; Prohaska, J.; Safari, A.

    1994-01-01

    The pyroelectric and photogalvanic effects have been studied in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films. Photoinduced currents, which were completely reversible by electrical voltage, were observed. The photoinduced currents exhibited transient and steady state components. The transient component, in turn, consisted of two components with fast (<1 s) and slow (˜hours) relaxation times. The mechanisms of the photoinduced currents in PZT films and their possible applications in nondestructive readout ferroelectric memory are discussed.

  6. Multiferroic behavior and impedance spectroscopy of bilayered BiFeO3/CoFe2O4 thin films

    Science.gov (United States)

    Wu, Jiagang; Wang, John

    2009-06-01

    Lead-free bilayered multiferroic thin films consisting of BiFeO3 (BFO) and CoFe2O4 (CFO) layers with different thicknesses were grown on SrRuO3-coated Pt/TiO2/SiO2/Si substrates by radio frequency sputtering. The effects of constituent layer thicknesses on the ferroelectric and magnetic behavior have been studied. The physical behaviors are shown to strongly depend on the thicknesses of the constituent layers. BFO (220 nm)/CFO (30 nm) bilayered thin film demonstrated much improved ferroelectric and ferromagnetic behavior (2Pr=144.2 μC/cm2, 2Ec=778.0 kV/cm, Ms=61.2 emu/cm3, and Hc=200.8 Oe) as compared to those of the single layer BFO thin film. The dielectric behavior and conductivity of BFO (220 nm)/CFO (30 nm) bilayered thin film were investigated as a function of both temperature (in the range of 294-534 K) and frequency (in the range of 10-1-106 Hz), where an activation energy of ˜1.11 eV for dielectric relaxation was demonstrated. From the conductivity behavior, an activation energies of ˜0.98 eV was derived for dc conductivity are, implying that oxygen vacancies are involved in the conduction of the BFO (220 nm)/CFO (30 nm) bilayered film.

  7. Epitaxy physical principles and technical implementation

    CERN Document Server

    Herman, Marian A; Sitter, Helmut

    2004-01-01

    Epitaxy provides readers with a comprehensive treatment of the modern models and modifications of epitaxy, together with the relevant experimental and technological framework. This advanced textbook describes all important aspects of the epitaxial growth processes of solid films on crystalline substrates, including a section on heteroepitaxy. It covers and discusses in details the most important epitaxial growth techniques, which are currently widely used in basic research as well as in manufacturing processes of devices, namely solid-phase epitaxy, liquid-phase epitaxy, vapor-phase epitaxy, including metal-organic vapor-phase epitaxy and molecular-beam epitaxy. Epitaxy’s coverage of science and texhnology thin-film is intended to fill the need for a comprehensive reference and text examining the variety of problems related to the physical foundations and technical implementation of epitaxial crystallization. It is intended for undergraduate students, PhD students, research scientists, lecturers and practic...

  8. Low-field tunnel-type magnetoresistance properties of polycrystalline and epitaxial La sub 0 sub . sub 6 sub 7 Sr sub 0 sub . sub 3 sub 3 MnO sub 3 thin films

    CERN Document Server

    Shim, I B; Choi, S Y

    2000-01-01

    The low-field tunnel-type magnetoresistance (TMB) properties of sol-gel derived polycrystalline and epitaxial La sub 0 sub . sub 6 sub 7 Sr sub 0 sub . sub 3 sub 3 MnO sub 3 (LSMO) thin films were investigated. The polycrystalline thin films were fabricated on Si (100) with a thermally oxidized SiO sub 2 layer while the epitaxial thin films were grown on LaAlO sub 3 (001) single-crystal substrates. The epitaxial thin films displayed both typical intrinsic colossal magnetoresistance (CMR) and abnormal extrinsic tunnel-type magnetoresistance behaviors. Tunnel-type MR ratio as high as 0.4% were observed in the polycrystalline thin films at a field of 120 Oe at room temperature (300 K) whereas the ratios were less than 0.1% for the epitaxial films in the same field range. The low-field tunnel-type MR of polycrystalline LSMO/SiO sub 2 ?Si (100) thin films originated from the behaviors of the grain-boundary properties.

  9. Magnetoresistance anomaly in DyFeCo thin films

    International Nuclear Information System (INIS)

    Wu, J. C.; Wu, C. S.; Wu, Te-ho; Chen, Bing-Mau; Shieh, Han-Ping D.

    2001-01-01

    Microstructured rare-earth - transition-metal DyFeCo films have been investigated using magnetoresistance and extraordinary Hall-effect measurements. The Hall loops reveal variation of coercive fields depending on the linewidth and the composition of the films. The magnetoresistance curves, with changes up to as high as 1.3%, show positive/negative magnetoresistance peaks centered on the coercive fields depending on the linewidth of the films only. The variation of the coercivity can be attributed to the magnetic moment canting between the Dy and FeCo subcomponents and the existence of the diverged magnetization on the edges, and the anomalous magnetoresistance peaks observed are discussed with the existing theories. [copyright] 2001 American Institute of Physics

  10. Development of FeNiMoB thin film materials for microfabricated magnetoelastic sensors

    KAUST Repository

    Liang, Cai

    2012-12-07

    MetglasTM 2826MB foils of 25–30 μm thickness with the composition of Fe40Ni38Mo4B18 have been used for magnetoelastic sensors in various applications over many years. This work is directed at the investigation of ∼3 μm thick iron-nickel-molybdenum-boron (FeNiMoB) thin films that are intended for integrated microsystems. The films are deposited on Si substrate by co-sputtering of iron-nickel (FeNi), molybdenum(Mo), and boron (B) targets. The results show that dopants of Mo and B can significantly change the microstructure and magnetic properties of FeNi materials. When FeNi is doped with only Mo its crystal structure changes from polycrystalline to amorphous with the increase of dopant concentration; the transition point is found at about 10 at. % of Mo content. A significant change in anisotropic magneticproperties of FeNi is also observed as the Modopant level increases. The coercivity of FeNi filmsdoped with Mo decreases to a value less than one third of the value without dopant.Doping the FeNi with B together with Mo considerably decreases the value of coercivity and the out-of-plane magnetic anisotropyproperties, and it also greatly changes the microstructure of the material. In addition, doping B to FeNiMo remarkably reduces the remanence of the material. The filmmaterial that is fabricated using an optimized process is magnetically as soft as amorphous MetglasTM 2826MB with a coercivity of less than 40 Am−1. The findings of this study provide us a better understanding of the effects of the compositions and microstructure of FeNiMoB thin filmmaterials on their magnetic properties.

  11. Conduction through 71 degrees DomainWalls in BiFeO3 Thin Films

    NARCIS (Netherlands)

    Farokhipoor, S.; Noheda, Beatriz

    2011-01-01

    Local conduction at domains and domain walls is investigated in BiFeO3 thin films containing mostly 71 degrees domain walls. Measurements at room temperature reveal conduction through 71 degrees domain walls. Conduction through domains could also be observed at high enough temperatures. It is found

  12. BiFeO3 thin films: Novel effects

    Indian Academy of Sciences (India)

    thin films on Pt/TiO2/SiO2/Si substrate by using pulsed laser deposition technique. For the first time ... conditions used during ablation were as follows: laser energy density incident on the target,. – fluence ∼1.5 J cm2; ... very critical as it is an important deciding factor for oxygen stoichiometry in the films. The deviation from ...

  13. Inhomogeneous nucleation and domain wall motion with Barkhausen avalanches in epitaxial PbZr0.4Ti0.6O3 thin films

    International Nuclear Information System (INIS)

    Yang, Sang Mo; Kim, Hun Ho; Kim, Tae Heon; Kim, Ik Joo; Yoon, Jong Gul

    2012-01-01

    We investigated the ferroelectric (FE) domain nucleation and domain wall motion in epitaxial PbZr 0.4 Ti 0.6 O 3 capacitors by using modified piezoresponse force microscopy with the domain-tracing method. From time-dependent FE domain evolution images, we observed that defect-mediated inhomogeneous nucleation occurred with a stochastic nature. In addition, we found that the number of nuclei N(t) was linearly proportional to log t, where t is the accumulated time of the applied pulse fields. The time-dependence of N(t) suggests a distribution of energy barriers for nucleation, which may determine the stochastic nature of domain nucleation. We also observed that the domain grew with consecutive Barkhausen avalanches and that the growth direction became anisotropic when the domain radius was larger than a critical radius of about 100 nm.

  14. Magnetic domain observation of FeCo thin films fabricated by alternate monoatomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ohtsuki, T., E-mail: ohtsuki@spring8.or.jp; Kotsugi, M.; Ohkochi, T. [Japan Synchrotron Radiation Research Institute (JASRI), 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Kojima, T.; Mizuguchi, M.; Takanashi, K. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2014-01-28

    FeCo thin films are fabricated by alternate monoatomic layer deposition method on a Cu{sub 3}Au buffer layer, which in-plane lattice constant is very close to the predicted value to obtain a large magnetic anisotropy constant. The variation of the in-plane lattice constant during the deposition process is investigated by reflection high-energy electron diffraction. The magnetic domain images are also observed by a photoelectron emission microscope in order to microscopically understand the magnetic structure. As a result, element-specific magnetic domain images show that Fe and Co magnetic moments align parallel. A series of images obtained with various azimuth reveal that the FeCo thin films show fourfold in-plane magnetic anisotropy along 〈110〉 direction, and that the magnetic domain structure is composed only of 90∘ wall.

  15. High-coercivity FePt nanoparticle assemblies embedded in silica thin films

    International Nuclear Information System (INIS)

    Yan, Q; Purkayastha, A; Singh, A P; Li, H; Ramanath, G; Li, A; Ramanujan, R V

    2009-01-01

    The ability to process assemblies using thin film techniques in a scalable fashion would be a key to transmuting the assemblies into manufacturable devices. Here, we embed FePt nanoparticle assemblies into a silica thin film by sol-gel processing. Annealing the thin film composite at 650 deg. C transforms the chemically disordered fcc FePt phase into the fct phase, yielding magnetic coercivity values H c >630 mT. The positional order of the particles is retained due to the protection offered by the silica host. Such films with assemblies of high-coercivity magnetic particles are attractive for realizing new types of ultra-high-density data storage devices and magneto-composites.

  16. X-ray characterization of CdO thin films grown on a-, c-, r- and m-plane sapphire by metalorganic vapour phase-epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zuniga-Perez, J.; Martinez-Tomas, C.; Munoz-Sanjose, V. [Departamento de Fisica Aplicada y Electromagnetismo, Universitat de Valencia, C/Dr. Moliner 50, 46100 Burjassot (Spain)

    2005-02-01

    CdO thin films have been grown on a-plane (11 anti 20), c-plane (0001), r-plane (01 anti 12) and m-plane (10 anti 10) sapphire substrates by metalorganic vapour-phase epitaxy (MOVPE). The effects of different substrate orientations on the structural properties of the films have been analyzed by means of X-ray diffraction, including {theta}-2{theta} scans, pole figures and rocking curves. (111), (001) and (110) orientations are found on a-, r-, and m-sapphire respectively, while films deposited on c-plane exhibit an orientation in which no low-index crystal plane is parallel to the sample surface. The recorded pole figures have allowed determining the epitaxial relationships between films and substrates, as well as the presence or absence of extended defects. The rocking curves indicate that high quality thin films, in terms of tilt and twist, can be obtained on r-, c- and m-plane sapphire, while further improvement is needed over the a-orientation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Effects of strain on the magnetic and transport properties of the epitaxial La0.5Ca0.5MnO3 thin films

    International Nuclear Information System (INIS)

    Zarifi, M.; Kameli, P.; Ehsani, M.H.; Ahmadvand, H.; Salamati, H.

    2016-01-01

    The epitaxial strain can considerably modify the physical properties of thin films compared to the bulk. This paper reports the effects of substrate-induced strain on La 0.5 Ca 0.5 MnO 3 (LCMO) thin films, grown on (100) SrTiO 3 (STO) and LaAlO 3 (LAO) substrates by pulsed laser deposition technique. Transport and magnetic properties were found to be strongly dependent on strain type. It is also shown that compressive (tensile) strain leads to the increase (decrease) in the magnetization of the films. Moreover, it was observed that all LCMO films deposited on both LAO and STO substrates behave as an insulator, but LCMO/LAO thin films with compressive strain have lower resistivity than LCMO/STO thin films with tensile strain. Applying magnetic field to LCMO/STO thin films with thickness of 25 and 50 nm leads to very small change in the resistivity, while the effects of magnetic field on the sample with thickness of 125 nm leads to an insulator–metal transition. For LCMO/LAO thin films, the magnetic field has a strong impact on the resistivity of samples. The results show that the magnetoresistance (MR) is enhanced by increasing film thickness for LCMO/LAO samples, due to the relatively stronger phase separation. For LCMO/STO thin films MR is drastically decreased by reduction of film thickness, which is attributed to the enhancement of the charge–orbital order (CO–O) accompanying the complex spin order (the so-called CE type). The changes of the antiferromagnetic structure from the CE to C type and the enhancement of the CE type could be attributed to the in-plane compressive and tensile strain, respectively. - Highlights: • Epitaxial La 0.5 Ca 0.5 MnO 3 thin films, grown on (100) SrTiO 3 and LaAlO 3 substrates. • The compressive strain leads to the increase in the magnetization of the films. • The tensile strain leads to the decrease in the magnetization of the films. • The magnetoresistance is enhanced by increasing film thickness.

  18. Effect of Ti seed and spacer layers on structure and magnetic properties of FeNi thin films and FeNi-based multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Svalov, A.V., E-mail: andrey.svalov@ehu.es [Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Department of Magnetism and Magnetic Nanomaterials, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Larrañaga, A. [SGIker, Servicios Generales de Investigación, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Kurlyandskaya, G.V. [Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48080 Bilbao (Spain); Department of Magnetism and Magnetic Nanomaterials, Ural Federal University, 620002 Ekaterinburg (Russian Federation)

    2014-10-15

    Highlights: • Fe{sub 19}Ni{sub 81} films and FeNi-based multilayers were prepared by magnetron sputtering. • The samples were deposited onto glass substrates at room temperature. • Ti/FeNi films exhibit good (1 1 1) texture and crystallinity. • The thick Cu seed increases the coercive force of the magnetic layer. • The thin Ti spacer restores the magnetic softness of the Cu/Ti/FeNi multilayers. - Abstract: The microstructure and magnetic properties of sputtered permalloy films and FeNi-based multilayers prepared by magnetron sputtering have been studied. X-ray diffraction measurements indicate that Ti/FeNi films exhibit good (1 1 1) texture and crystallinity. Ti/FeNi bilayers with high crystallographic quality have relatively low resistivity. The Ti seed layer does not influence the magnetic properties of FeNi film in Ti/FeNi bilayers, but the thick Cu seed layer leads to an increase of the coercive force of the magnetic layer. For the FeNi films deposited on thick Cu seed layer, the (0 1 0) and (0 0 2) diffraction peaks of hcp nickel were clearly observed. The thin Ti spacer between Cu and FeNi layers prevents the formation of the nickel phase and restores the magnetic softness of the FeNi layer in the Cu/Ti/FeNi sample. Obtained results can be important for the development of multilayer sensitive elements for giant magnetoimpedance or magnetoresistance detectors.

  19. Rapid thermal annealing of FePt and FePt/Cu thin films

    Energy Technology Data Exchange (ETDEWEB)

    Brombacher, Christoph

    2011-01-10

    Chemically ordered FePt is one of the most promising materials to reach the ultimate limitations in storage density of future magnetic recording devices due to its high uniaxial magnetocrystalline anisotropy and a corrosion resistance superior to rare-earth based magnets. In this study, FePt and FePt/Cu bilayers have been sputter deposited at room temperature onto thermally oxidized silicon wafers, glass substrates and self-assembled arrays of spherical SiO{sub 2} particles with diameters down to 10 nm. Millisecond flash lamp annealing, as well as conventional rapid thermal annealing was employed to induce the phase transformation from the chemically disordered A1 phase into the chemically ordered L1{sub 0} phase. The influence of the annealing temperature, annealing time and the film thickness on the ordering transformation and (001) texture evolution of FePt films with near equiatomic composition was studied. Whereas flash lamp annealed FePt films exhibit a polycrystalline morphology with high chemical L1{sub 0} order, rapid thermal annealing can lead to the formation of chemically ordered FePt films with (001) texture on amorphous SiO{sub 2}/Si substrates. The resultant high perpendicular magnetic anisotropy and large coercivities up to 40 kOe are demonstrated. Simultaneously to the ordering transformation, rapid thermal annealing to temperatures exceeding 600 C leads to a break up of the continuous FePt film into separated islands. This dewetting behavior was utilized to create regular arrays of FePt nanostructures on SiO{sub 2} particle templates with periods down to 50 nm. The addition of Cu improves the (001) texture formation and chemical ordering for annealing temperatures T{sub a} {<=}600 C. In addition, the magnetic anisotropy and the coercivity of the ternary FePtCu alloy can be effectively tailored by adjusting the Cu content. The prospects of FePtCu based exchange spring media, as well as the magnetic properties of FePtCu nanostructures fabricated

  20. REMOVAL OF CU (II AND FE (II IONS THROUGH THIN FILM COMPOSITE (TFC WITH HYBRID MEMBRANE

    Directory of Open Access Journals (Sweden)

    NURUL AIDA SULAIMAN

    2016-07-01

    Full Text Available In recent years, there has been rising concern about environmental issues and specifically about the presence of heavy metal in water. Therefore, the removal of heavy metal ions from wastewater is very important with respect to the ecological health and public health. This paper presents the possibility of removing metal ions by using a hybrid membrane through thin film composite (TFC membrane which represents an integrated polymer complexation method. The hybrid membrane was formulated from blended poly(vinyl alcohol (PVA and chitosan which was cross linked with various concentration of tetraethyl orthosilicate (TEOS such as 1%, 3% w/w and 5%w/w through using sol-gel technique under acidic condition. The hybrid membrane was coated on polysulfone membrane as the porous support. The separation process was conducted on the different heavy metal solutions containing Cu (II and Fe (II ions at various concentrations (50,100,150,200,250 ppm.The properties of the thin film composite (TFC membranes were characterized by using Fourier Transform Infrared (FTIR spectroscopy and hermogravimetric Analysis (TGA. The influence of TEOS concentration and Cu (II and Fe (II ion concentration was investigated with the aim to identify on the removal percentage efficiency of Cu (II and Fe (II ions. Result showed that the fabricated thin film composites with higher concentrations of TEOS were able to remove higher percentage Cu (II and Fe (II from the feed solution.

  1. Effects of strain on the magnetic and transport properties of the epitaxial La0.5Ca0.5MnO3 thin films

    Science.gov (United States)

    Zarifi, M.; Kameli, P.; Ehsani, M. H.; Ahmadvand, H.; Salamati, H.

    2016-12-01

    The epitaxial strain can considerably modify the physical properties of thin films compared to the bulk. This paper reports the effects of substrate-induced strain on La0.5Ca0.5MnO3 (LCMO) thin films, grown on (100) SrTiO3 (STO) and LaAlO3 (LAO) substrates by pulsed laser deposition technique. Transport and magnetic properties were found to be strongly dependent on strain type. It is also shown that compressive (tensile) strain leads to the increase (decrease) in the magnetization of the films. Moreover, it was observed that all LCMO films deposited on both LAO and STO substrates behave as an insulator, but LCMO/LAO thin films with compressive strain have lower resistivity than LCMO/STO thin films with tensile strain. Applying magnetic field to LCMO/STO thin films with thickness of 25 and 50 nm leads to very small change in the resistivity, while the effects of magnetic field on the sample with thickness of 125 nm leads to an insulator-metal transition. For LCMO/LAO thin films, the magnetic field has a strong impact on the resistivity of samples. The results show that the magnetoresistance (MR) is enhanced by increasing film thickness for LCMO/LAO samples, due to the relatively stronger phase separation. For LCMO/STO thin films MR is drastically decreased by reduction of film thickness, which is attributed to the enhancement of the charge-orbital order (CO-O) accompanying the complex spin order (the so-called CE type). The changes of the antiferromagnetic structure from the CE to C type and the enhancement of the CE type could be attributed to the in-plane compressive and tensile strain, respectively.

  2. Room temperature exchange bias in BiFeO3 / Co-Fe bilayers

    OpenAIRE

    Sterwerf, Christian; Meinert, Markus; Arenholz, Elke; Schmalhorst, Jan-Michael; Reiss, Günter

    2015-01-01

    Thin highly epitaxial BiFeO$_3$ films were prepared on SrTiO$_3$ (100) substrates by reactive magnetron co-sputtering. Detailed MOKE measurements on BiFeO$_3$/Co-Fe bilayers were performed to investigate the exchange bias as a function of the films thicknesses and Co-Fe stoichiometries. We found a maximum exchange bias of H$_{\\mathrm{eb}}$=92 Oe and a coercive field of H$_{\\mathrm{c}}$=89 Oe for a 12.5 nm thick BiFeO$_3$ film with a 2 nm thick Co layer. The unidirectional anisotropy is clearl...

  3. Impact of thickness on microscopic and macroscopic properties of Fe-Te-Se superconductor thin films

    Directory of Open Access Journals (Sweden)

    N. Zhang

    2015-04-01

    Full Text Available A series of iron based Fe-Te-Se superconductor thin films depositing on 0.7wt% Nb-doped SrTiO3 at substrate temperatures in the 250°C -450°C range by pulsed laser ablation of a constituents well defined precursor FeTe0.55Se0.55 target sample. We study the possible growth mechanism and its influence on the superconductor properties. Experimental results indicate the superconductive and non-superconductive properties are modulated only by the thickness of the thin films through the temperature range. The films appear as superconductor whenever the thickness is above a critical value ∼30nm and comes to be non-superconductor below this value. Relative ratios of Fe to (Te+Se in the films retained Fe/(Te+Se1 for non-superconductor no matter what the film growth temperature was. The effect of film growth temperature takes only the role of modulating the ratio of Te/Se and improving crystallinity of the systems. According to the experimental results we propose a sandglass film growth mechanism in which the interfacial effect evokes to form a Fe rich area at the interface and Se or Te starts off a consecutive filling up process of chalcogenide elements defect sides, the process is significant before the film thickness reaches at ∼30nm.

  4. 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.

  5. Oxygen-induced immediate onset of the antiferromagnetic stacking in thin Cr films on Fe(001)

    Energy Technology Data Exchange (ETDEWEB)

    Berti, Giulia, E-mail: giulia.berti@polimi.it; Brambilla, Alberto; Calloni, Alberto; Bussetti, Gianlorenzo; Finazzi, Marco; Duò, Lamberto; Ciccacci, Franco [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy)

    2015-04-20

    We investigated the magnetic coupling of ultra-thin Cr films grown at 600 K on a Fe(001)-p(1 × 1)O substrate by means of spin-polarized photoemission spectroscopy. Our findings show that the expected antiferromagnetic stacking of the magnetization in Cr(001) layers occurs right from the first atomic layer at the Cr/Fe interface. This is at variance with all previous observations in similar systems, prepared in oxygen-free conditions, which always reported on a delayed onset of the magnetic oscillations due to the occurrence of significant chemical alloying at the interface, which is substantially absent in our preparation.

  6. Combinatorial magnetron sputtering of AgFeO2 thin films with the delafossite structure

    OpenAIRE

    Mao, Fang; Nyberg, Tomas; Thersleff, Thomas; Andersson, Anna; Jansson, Ulf

    2016-01-01

    The main objective of this study is to demonstrate the strength of the combinatorial approach to rapidly and effectively identify suitable process parameters for the synthesis of AgFeO2 filmswith layered delafossite structure. (00l)- textured delafossite AgFeO2 thin films have been successfully deposited for the first time without post-annealing by magnetron sputtering from elemental silver and iron targets in a reactive Ar-O-2 atmosphere. Gradient filmswith a wide composition range were depo...

  7. Spin-dependent scattering and the spin polarization of a diffusive current in partly disordered L10 epitaxial FePd

    International Nuclear Information System (INIS)

    Seemann, K M; Hickey, M C; Baltz, V; Hickey, B J; Marrows, C H

    2010-01-01

    We report magnetic domain wall (DW) resistance in epitaxial films of FePd. When equal numbers of Fe and Pd atoms are present, this material forms an ordered structure with alternating crystal planes of Fe and Pd. We prepared films enriched with Pd to varying degrees, gradually degrading this structure. As might be expected, this increased the electrical resistivity of the films by introducing extra defects that can scatter electrons. However, unexpectedly, the additional resistance arising from the ∼10 nm thick DWs rose as a proportion of the overall resistivity, roughly doubling when halving the degree of chemical ordering-as determined from x-ray diffraction measurements-within the films. These data can be used to infer a rise in the spin polarization of the current flowing in the layers when extra Pd atoms are introduced. On the other hand, a separate measurement of spin polarization using a superconducting point contact technique that is insensitive to electron scattering revealed no changes as extra Pd was introduced. We conclude that Pd atoms scatter electrons of one spin far more strongly than the other, suggesting a possible means of producing highly spin-polarized currents for use in spintronic devices.

  8. Epitaxial growth of branched {alpha}-Fe{sub 2}O{sub 3}/SnO{sub 2} nano-heterostructures with improved lithium-ion battery performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Weiwei; Cheng, Chuanwei; Jia, Xingtao; Yu, Ting; Fan, Hong Jin [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 (Singapore); Liu, Jinping; Jiang, Jian [Institute of Nanoscience and Nanotechnology, Department of Physics, Huazhong Normal University, Wuhan 430079 (China); Tay, Yee Yan; Hng, Huey Hoon [School of Materials Science and Engineering, Nanyang Technological University, 639798 (Singapore); Zhang, Jixuan; Gong, Hao [Department of Materials Science and Engineering, National University of Singapore, 117576 (Singapore)

    2011-07-08

    We report the synthesis of a novel branched nano-heterostructure composed of SnO{sub 2} nanowire stem and {alpha}-Fe{sub 2}O{sub 3} nanorod branches by combining a vapour transport deposition and a facile hydrothermal method. The epitaxial relationship between the branch and stem is investigated by high resolution transmission electron microscopy (HRTEM). The SnO{sub 2} nanowire is determined to grow along the [101] direction, enclosed by four side surfaces. The results indicate that distinct crystallographic planes of SnO{sub 2} stem can induce different preferential growth directions of secondary nanorod branches, leading to six-fold symmetry rather than four-fold symmetry. Moreover, as a proof-of-concept demonstration of the function, such {alpha}-Fe{sub 2}O{sub 3}/SnO{sub 2} composite material is used as a lithium-ion batteries (LIBs) anode material. Low initial irreversible loss and high reversible capacity are demonstrated, in comparison to both single components. The synergetic effect exerted by SnO{sub 2} and {alpha}-Fe{sub 2}O{sub 3} as well as the unique branched structure are probably responsible for the enhanced performance. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. FY 1997 report on the study on lamination control technology for functional multi-element oxide thin films by complex beam epitaxy (CxBE) process; 1997 nendo chosa hokokusho (sakutaisen epitaxy (CxBE) ho ni yoru kinosei tagenso sankabutsu usumaku no sekiso seigyo gijutsu ni kansuru kenkyu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Complex beam epitaxy (CxBE) process was proposed and demonstrated as new deposition process of multi-element oxide thin films. This process radiates excimer laser onto a metal complex target of ethylenediamine-tetraacetate complex under reduced pressure oxygen atmosphere condition in a reaction vessel to supply raw material onto a heated substrate. This process allowed deposition of YBCO123 phase hetero-epitaxial film onto a single-crystalline SrTiO3 substrate. This process was proved to be promising through study on crystal orientation, composition transcription and surface smoothness of the obtained oxide thin films. In addition, epitaxial ZnO film was also deposited onto a single crystalline Al2O3 substrate by this process. The relation between the obtained film and substrate epitaxy was examined, and photoluminescence of specimens was measured by triple wave of Nd:YAG laser. As a result, it was clarified that the epitaxial ZnO film prepared by this process is useful as laser material. 60 refs., 48 figs., 5 tabs.

  10. Influence of Oxygen Pressure on the Domain Dynamics and Local Electrical Properties of BiFe0.95Mn0.05O3 Thin Films Studied by Piezoresponse Force Microscopy and Conductive Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Kunyu Zhao

    2017-11-01

    Full Text Available In this work, we have studied the microstructures, nanodomains, polarization preservation behaviors, and electrical properties of BiFe0.95Mn0.05O3 (BFMO multiferroic thin films, which have been epitaxially created on the substrates of SrRuO3, SrTiO3, and TiN-buffered (001-oriented Si at different oxygen pressures via piezoresponse force microscopy and conductive atomic force microscopy. We found that the pure phase state, inhomogeneous piezoresponse force microscopy (PFM response, low leakage current with unidirectional diode-like properties, and orientation-dependent polarization reversal properties were found in BFMO thin films deposited at low oxygen pressure. Meanwhile, these films under high oxygen pressures resulted in impurities in the secondary phase in BFMO films, which caused a greater leakage that hindered the polarization preservation capability. Thus, this shows the important impact of the oxygen pressure on modulating the physical effects of BFMO films.

  11. 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.

  12. Structural and dielectric properties of (001) and (111)-oriented BaZr0.2Ti0.8O3 epitaxial thin films

    International Nuclear Information System (INIS)

    Ventura, J.; Fina, I.; Ferrater, C.; Langenberg, E.; Coy, L.E.; Polo, M.C.; Garcia-Cuenca, M.V.; Fabrega, L.; Varela, M.

    2010-01-01

    We have grown and characterized BaZr 0.2 Ti 0.8 O 3 (BZT) epitaxial thin films deposited on (001) and (111)-oriented SrRuO 3 -buffered SrTiO 3 substrates by pulsed laser deposition. Structural and morphological characterizations were performed using X-ray diffractometry and atomic force microscopy, respectively. A cube-on-cube epitaxial relationship was ascertained from the θ-2θ and φ diffractograms in both (001) and (111)-oriented films. The (001)-oriented films showed a smooth granular morphology, whereas the faceted pyramid-like crystallites of the (111)-oriented films led to a rough surface. The dielectric response of BZT at room temperature was measured along the growth direction. The films were found to be ferroelectric, although a well-saturated hysteresis loop was obtained only for the (001)-oriented films. High leakage currents were observed for the (111) orientation, likely associated to charge transport along the boundaries of its crystallites. The remanent polarization, coercive field, dielectric constant, and relative change of dielectric permittivity (tunability) of (111)-oriented BZT were higher than those of (001)-oriented BZT.

  13. Electric-field effects on magnetic properties of molecular beam epitaxially grown thin (Ga,Mn)Sb layers

    Science.gov (United States)

    Chang, H. W.; Akita, S.; Matsukura, F.; Ohno, H.

    2014-09-01

    We report molecular beam epitaxy of a ferromagnetic semiconductor (Ga,Mn)Sb, which is a single crystal without detectable second phases. We report also the details of magnetotransport properties of (Ga,Mn)Sb and the effects of electric fields on them. The difference between the properties observed here and properties of those reported earlier for a ferromagnetic semiconductor (Ga,Mn)As, provides information critical for further understanding of fundamental and device physics of ferromagnetic semiconductors.

  14. Viability of thin wall tube forming of ATF FeCrAl

    Energy Technology Data Exchange (ETDEWEB)

    Maloy, Stuart Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Aydogan, Eda [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Anderoglu, Osman [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lavender, Curt [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Yamamoto, Yukinori [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-16

    Fabrication of thin walled tubing of FeCrAl alloys is critical to its success as a candidate enhanced accident-tolerant fuel cladding material. Alloys that are being investigated are Generation I and Generation II FeCrAl alloys produced at ORNL and an ODS FeCrAl alloy, MA-956 produced by Special Metals. Gen I and Gen II FeCrAl alloys were provided by ORNL and MA-956 was provided by LANL (initially produced by Special Metals). Three tube development efforts were undertaken. ORNL led the FeCrAl Gen I and Gen II alloy development and tube processing studies through drawing tubes at Rhenium Corporation. LANL received alloys from ORNL and led tube processing studies through drawing tubes at Century Tubing. PNNL led the development of tube processing studies on MA-956 through pilger processing working with Sandvik Corporation. A summary of the recent progress on tube development is provided in the following report and a separate ORNL report: ORNL/TM-2015/478, “Development and Quality Assessments of Commercial Heat Production of ATF FeCrAl Tubes”.

  15. Soft magnetic properties and damping parameter of (FeCo-Al alloy thin films

    Directory of Open Access Journals (Sweden)

    Isao Kanada

    2017-05-01

    Full Text Available For high frequency device applications, a systematic study of the soft magnetic properties and magnetization dynamics of (FeCo-Al alloy thin films has been carried out. A low effective damping parameter αeff of 0.002 and a high saturation magnetization of about 1,800 emu/cc are obtained at y=0.2∼0.3 for (Fe1-yCoy98Al2 alloy thin films deposited onto fused silica and MgO(100 at an ambient temperature during deposition. Those films are of the bcc structure with the orientation normal to the film plane. They possess a columnar structure, grown along the film normal. The column width is found to be about 20 nm for y=0.25. It is concluded that the (FeCo-Al thin films with a damping parameter as low as 0.002 and high saturation magnetization of about 1,800 emu/cc have been successfully fabricated, and that they are potential for future high frequency device applications.

  16. Temperature dependent structural and magnetic study of Co-sputtered Fe-Al thin film

    Science.gov (United States)

    Vyas, Anupam; Brajpuriya, Ranjeet

    2017-05-01

    The authors have deposited co-sputtered Fe-Al thin film on a glass substrate. It is the first ever reporting of Fe and Al co-sputtering in an Argon atmosphere under vacuum conditions. The sample was annealed at 200°C, 300°C, 400°C, so as to allow different phase formation in it. To study the structural and magnetic properties of the samples the GIXRD, XRR and MOKE measurements were done. After annealing at 400°C we observed disordered FeAl formation and which after further converted to more ordered phase which is also confirmed from reflectivity measurements. The magnetic measurement shows the magnetic nature of the sample even after annealing at 400°C/5hr.

  17. {sup 57}Fe Moessbauer probe of spin crossover thin films on a bio-membrane

    Energy Technology Data Exchange (ETDEWEB)

    Naik, Anil D.; Garcia, Yann, E-mail: yann.garcia@uclouvain.be [Universite Catholique de Louvain, Institute of Condensed Matter and Nanosciences (Belgium)

    2012-03-15

    An illustrious complex [Fe(ptz){sub 6}](BF{sub 4}){sub 2} (ptz = 1-propyl-tetrazole) (1) which was produced in the form of submicron crystals and thin film on Allium cepa membrane was probed by {sup 57}Fe Mossbauer spectroscopy in order to follow its intrinsic spin crossover. In addition to a weak signal that corresponds to neat SCO compound significant amount of other iron compounds are found that could have morphed from 1 due to specific host-guest interaction on the lipid-bilayer of bio-membrane. Further complimentary information about biogenic role of membrane, was obtained from variable temperature Mossbauer spectroscopy on a {approx}5% enriched [{sup 57}Fe(H{sub 2}O){sub 6}](BF{sub 4}){sub 2} salt on this membrane.

  18. Substrate induced tuning of compressive strain and phonon modes in large area MoS2 and WS2 van der Waals epitaxial thin films

    Science.gov (United States)

    Sahu, Rajib; Radhakrishnan, Dhanya; Vishal, Badri; Negi, Devendra Singh; Sil, Anomitra; Narayana, Chandrabhas; Datta, Ranjan

    2017-07-01

    Large area MoS2 and WS2 van der Waals epitaxial thin films with control over number of layers including monolayer is grown by pulsed laser deposition utilizing slower growth kinetics. The films grown on c-plane sapphire show stiffening of A1g and E12g phonon modes with decreasing number of layers for both MoS2 and WS2. The observed stiffening translate into the compressive strain of 0.52% & 0.53% with accompanying increase in fundamental direct band gap to 1.74 and 1.68 eV for monolayer MoS2 and WS2, respectively. The strain decays with the number of layers. HRTEM imaging directly reveals the nature of atomic registry of van der Waals layers with the substrate and the associated compressive strain. The results demonstrate a practical route to stabilize and engineer strain for this class of material over large area device fabrication.

  19. Optical properties of epitaxial Na0.5Bi0.5TiO3 lead-free piezoelectric thin films: Ellipsometric and theoretical studies

    Science.gov (United States)

    Dorywalski, Krzysztof; Lemée, Nathalie; Andriyevsky, Bohdan; Schmidt-Grund, Rüdiger; Grundmann, Marius; Piasecki, Michał; Bousquet, Marie; Krzyzynski, Tomasz

    2017-11-01

    Ultra-thin Na0.5Bi0.5TiO3 films were epitaxially deposited on (001)SrTiO3 substrate by pulsed laser deposition. From the ellipsometric spectra collected in the photon energy range 2÷8.7 eV, real and imaginary parts of the complex dielectric function were determined. It was found, that the electronic transitions related to the fundamental absorption edge are of indirect type, which is confirmed by ab initio band structure calculations. This finding is in contradiction to previous theoretical studies but in agreement with the most recent experimental works. Based on their determined energies, phonons involved in the band gap transition can be primarily associated with vibrations involving oxygen atoms. Contributions to the VUV absorption spectra come mainly from the electronic transitions from the O 2p valence band levels to Ti 3d conduction band levels and a little to the Bi p levels.

  20. Strain Influence on the Oxygen Electrocatalysis of the (100)-Oriented Epitaxial La 2 NiO 4+δ Thin Films at Elevated Temperatures

    KAUST Repository

    Lee, Dongkyu

    2013-09-19

    Ruddlesden-Popper materials such as La2NiO4+δ (LNO) have high activities for surface oxygen exchange kinetics promising for solid oxide fuel cells and oxygen permeation membranes. Here we report the synthesis of the (100)tetragonal-oriented epitaxial LNO thin films prepared by pulsed laser deposition. The surface oxygen exchange kinetics determined from electrochemical impedance spectroscopy (EIS) were found to increase with decreasing film thickness from 390 to 14 nm. No significant change of the surface chemistry with different film thicknesses was observed using ex situ auger electron spectroscopy (AES). Increasing volumetric strains in the LNO films at elevated temperatures determined from in situ high-resolution X-ray diffraction (HRXRD) were correlated with increasing surface exchange kinetics and decreasing film thickness. Volumetric strains may alter the formation energy of interstitial oxygen and influence on the surface oxygen exchange kinetics of the LNO films. © 2013 American Chemical Society.

  1. Deposition of epitaxial thin films of Nd1.85Ce0.15CuO4-y by laser ablation

    International Nuclear Information System (INIS)

    Gupta, A.; Koren, G.; Tsuei, C.C.; Segmuller, A.; McGuire, T.R.

    1989-01-01

    Thin films of the electron-doped superconductor Nd 1.85 Ce 0.15 CuO 4-y have been deposited on (100) SrTiO 3 substrates at 780 degree C using the laser ablation technique. The deposited films are very smooth and show epitaxial growth with the c axis normal to the substrate. The transport properties of the films are very sensitive to the concentration of oxygen vacancies. Films deposited and cooled in the presence of 150 mTorr O 2 exhibit localization behavior with no evidence of superconductivity down to 5 K. Superconductivity is observed on vacuum annealing the films in situ after deposition. Films with optimum concentration of oxygen vacancies show a superconducting onset temperature of 21 K and T c (R=0) of 20 K, with a critical current density of 2x10 5 A/cm 2 at 5.5 K in zero magnetic field

  2. Reversal of the Lattice Structure in SrCoOx Epitaxial Thin Films Studied by Real-Time Optical Spectroscopy and First-Principles Calculations

    Science.gov (United States)

    Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S. S. Ambrose; Cooper, Valentino R.; Rabe, Karin M.; Lee, Ho Nyung

    2013-08-01

    Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoOx (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.

  3. Reversal of the lattice structure in SrCoO(x) epitaxial thin films studied by real-time optical spectroscopy and first-principles calculations.

    Science.gov (United States)

    Choi, Woo Seok; Jeen, Hyoungjeen; Lee, Jun Hee; Seo, S S Ambrose; Cooper, Valentino R; Rabe, Karin M; Lee, Ho Nyung

    2013-08-30

    Using real-time spectroscopic ellipsometry, we directly observed a reversible lattice and electronic structure evolution in SrCoO(x) (x=2.5-3) epitaxial thin films. Drastically different electronic ground states, which are extremely susceptible to the oxygen content x, are found in the two topotactic phases: i.e., the brownmillerite SrCoO2.5 and the perovskite SrCoO3. First-principles calculations confirmed substantial differences in the electronic structure, including a metal-insulator transition, which originate from the modification in the Co valence states and crystallographic structures. More interestingly, the two phases can be reversibly controlled by changing the ambient pressure at greatly reduced temperatures. Our finding provides an important pathway to understanding the novel oxygen-content-dependent phase transition uniquely found in multivalent transition metal oxides.

  4. Anisotropic Proton and Oxygen Ion Conductivity in Epitaxial Ba2In2O5 Thin Films

    DEFF Research Database (Denmark)

    Fluri, Aline; Gilardi, Elisa; Karlsson, Maths

    2017-01-01

    Solid oxide oxygen ion and proton conductors are a highly important class of materials for renewable energy conversion devices like solid oxide fuel cells. Ba2In2O5 (BIO) exhibits both oxygen ion and proton conduction, in a dry and humid environment, respectively. In a dry environment......, the brownmillerite crystal structure of BIO exhibits an ordered oxygen ion sublattice, which has been speculated to result in anisotropic oxygen ion conduction. The hydrated structure of BIO, however, resembles a perovskite and the protons in it were predicted to be ordered in layers. To complement the significant...... theoretical and experimental efforts recently reported on the potentially anisotropic conductive properties in BIO, we measure here both the proton and oxygen ion conductivity along different crystallographic directions. Using epitaxial thin films with different crystallographic orientations, the charge...

  5. Misfit strain relaxation in (Ba0.60Sr0.40)TiO3 epitaxial thin films on orthorhombic NdGaO3 substrates

    Science.gov (United States)

    Simon, W. K.; Akdogan, E. K.; Safari, A.

    2006-07-01

    Strain relaxation in (Ba0.60Sr0.40)TiO3 (BST) thin films on ⟨110⟩ orthorhombic NdGaO3 substrates is investigated by x-ray diffractometry. Pole figure analysis indicates a [010]BST∥[1¯10]NGO and [001]BST∥[001]NGO in-plane and [100]BST∥[100]NGO out-of-plane epitaxial relationship. The residual strains are relaxed at h ˜200nm, and for h >600nm, films are essentially strain free. Two independent dislocations mechanisms operate to relieve the anisotropic misfit strains along the principal directions. The critical thickness for misfit dislocation formation along [001] and [010] are 11 and 15nm, respectively. Stress analysis indicates deviation from linear elasticity for h <200. The films with 10

  6. Investigation of the magnetic properties of electrodeposited NiFe thin films

    International Nuclear Information System (INIS)

    Bakkaloglu, O. F.; Bedir, M.; Oeztas, M.; Karahan, I. H.

    2002-01-01

    Most magnetic devices used today are based on the magnetic thin film. Rapid and extensive developments in magnetic sensor / actuator and magnetic recording technology place a growing demand on the use of different thin film fabrication techniques for magnetic materials. The electroplating technique is especially interesting due to its low cost, high throughput and high quality of the deposits which are extensively used in the magnetic recording industry to deposit relatively thick permalloy layers. Much recent attention has focused on the electrodeposited NiFe thin films, which exhibit giant magneto resistive behaviour as well as anisotropic magnetoresistance properties. n this study, NiFe thin films were developed by using electrodeposition technique and their crystallinity structures were investigated by using x-ray diffractometer measurements. The magneto resistive properties of the samples were investigated by Wan der Pauw method with a home made electromagnet under the different magnetic fields. The magnetoresistance measurements of the samples were carried out in two configurations; current parallel ( longitudinal ) and perpendicular ( transverse ) to the magnetic field. In the longitudinal configuration giant magnetoresistance was observed while anisotropic magnetoresistance was detected in the other configuration

  7. On the dielectric and optical properties of surface-anchored metal-organic frameworks: A study on epitaxially grown thin films

    Science.gov (United States)

    Redel, Engelbert; Wang, Zhengbang; Walheim, Stefan; Liu, Jinxuan; Gliemann, Hartmut; Wöll, Christof

    2013-08-01

    We determine the optical constants of two highly porous, crystalline metal-organic frameworks (MOFs). Since it is problematic to determine the optical constants for the standard powder modification of these porous solids, we instead use surface-anchored metal-organic frameworks (SURMOFs). These MOF thin films are grown using liquid phase epitaxy (LPE) on modified silicon substrates. The produced SURMOF thin films exhibit good optical properties; these porous coatings are smooth as well as crack-free, they do not scatter visible light, and they have a homogenous interference color over the entire sample. Therefore, spectroscopic ellipsometry (SE) can be used in a straightforward fashion to determine the corresponding SURMOF optical properties. After careful removal of the solvent molecules used in the fabrication process as well as the residual water adsorbed in the voids of this highly porous solid, we determine an optical constant of n = 1.39 at a wavelength of 750 nm for HKUST-1 (stands for Hong Kong University of Science and Technology-1; and was first discovered there) or [Cu3(BTC)2]. After exposing these SURMOF thin films to moisture/EtOH atmosphere, the refractive index (n) increases to n = 1.55-1.6. This dependence of the optical properties on water/EtOH adsorption demonstrates the potential of such SURMOF materials for optical sensing.

  8. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yiqin [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Li, Heqin, E-mail: lhqjs@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zuo, Min; Tao, Lei; Wang, Wei [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zhang, Jing; Tang, Qiong [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009 (China); Bai, Peiwen [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China)

    2016-07-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB. - Highlights: • The same thick Al, SiC and SiC/Al films are deposited on NdFeB by magnetron sputtering. • 510 nm SiC/Al bilayer films can improve the corrosion resistance of the NdFeB evidently. • Al buffer layer improves effectively the surface roughness of the SiC thin film. • SiC/Al bilayer films do not deteriorate the magnetic properties of NdFeB.

  9. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    International Nuclear Information System (INIS)

    Huang, Yiqin; Li, Heqin; Zuo, Min; Tao, Lei; Wang, Wei; Zhang, Jing; Tang, Qiong; Bai, Peiwen

    2016-01-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB. - Highlights: • The same thick Al, SiC and SiC/Al films are deposited on NdFeB by magnetron sputtering. • 510 nm SiC/Al bilayer films can improve the corrosion resistance of the NdFeB evidently. • Al buffer layer improves effectively the surface roughness of the SiC thin film. • SiC/Al bilayer films do not deteriorate the magnetic properties of NdFeB.

  10. Magnetic and microstructural properties of thin NdFeB based films and nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bommer, Lars; Goll, Dagmar [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)

    2010-07-01

    The magnetic and microstructural properties of NdFeB and NdFeB/Fe thin films and nanostructures are presented. Samples with Cr buffer and protection layer (minimum thickness: d=50 nm) have been produced by ion beam sputtering at elevated temperatures (T{sub s}=700 C) using Al{sub 2}O{sub 3} and MgO(001) single crystal substrates. Films deposited on Al{sub 2}O{sub 3} substrates show c-axis growth in out-of-plane direction down to thicknesses of the NdFeB film of d=10 nm with coercivities up to {mu}{sub 0}H{sub c}=1 T. The texture of films deposited on MgO(001) substrates is less pronounced and films below d=20 nm show no hard magnetic behavior. For comparison, films were deposited at room temperature on Al{sub 2}O{sub 3} and MgO(001) followed by post-annealing in Ar atmosphere (T{sub pa}=525-650 C) leading to coercivities as high as {mu}{sub 0}H{sub c}=1.2 T but with isotropic behavior. By TEM images the grain structure of the NdFeB samples is studied. Bilayers of NdFeB (d=50 nm) and Fe (d=0-20 nm) show fully exchange coupled behavior. From the temperature dependence of the coercivity the microstructural parameters of all samples have been determined. Furthermore NdFeB periodical patterns were produced by means of electron beam lithography with dot sizes of 1000 nm and 500 nm, respectively.

  11. Crystallization engineering as a route to epitaxial strain control

    Directory of Open Access Journals (Sweden)

    Andrew R. Akbashev

    2015-10-01

    Full Text Available The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001SrTiO3 and (001LaAlO3 substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001BiFeO3 phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001SrTiO3 results in a coherently strained film, the same films obtained on (001LaAlO3 showed an unstrained, dislocation-rich interface, with an even lower temperature onset of the perovskite phase crystallization than in the case of (001SrTiO3. Our results demonstrate how the strain control in an epitaxial film can be accomplished via its crystallization from the amorphous state.

  12. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    Science.gov (United States)

    Huang, Yiqin; Li, Heqin; Zuo, Min; Tao, Lei; Wang, Wei; Zhang, Jing; Tang, Qiong; Bai, Peiwen

    2016-07-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB.

  13. Growth, structure and magnetic properties of magnetron sputtered FePt thin films

    Energy Technology Data Exchange (ETDEWEB)

    Cantelli, Valentina

    2010-07-01

    The L1{sub 0} FePt phase belongs to the most promising hard ferromagnetic materials for high density recording media. The main challenges for thin FePt films are: (i) to lower the process temperature for the transition from the soft magnetic A1 to the hard magnetic L1{sub 0} phase, (ii) to realize c-axes preferential oriented layers independently from the substrate nature and (iii) to control layer morphology supporting the formation of FePt-L1{sub 0} selforganized isolated nanoislands towards an increase of the signal-to-noise ratio. In this study, dc magnetron sputtered FePt thin films on amorphous substrates were investigated. The work is focused on the correlation between structural and magnetic properties with respect to the influence of deposition parameters like growth mode (cosputtering vs. layer - by - layer) and the variation of the deposition gas (Ar, Xe) or pressure (0.3-3 Pa). In low-pressure Ar discharges, high energetic particle impacts support vacancies formation during layer growth lowering the phase transition temperature to (320{+-}20) C. By reducing the particle kinetic energy in Xe discharges, highly (001) preferential oriented L1{sub 0}-FePt films were obtained on a-SiO{sub 2} after vacuum annealing. L1{sub 0}-FePt nano-island formation was supported by the introduction of an Ag matrix, or by random ballistic aggregation and atomic self shadowing realized by FePt depositions at very high pressure (3 Pa). The high coercivity (1.5 T) of granular, magnetic isotropic FePt layers, deposited in Ar discharges, was measured with SQUID magnetometer hysteresis loops. For non-granular films with (001) preferential orientation the coercivity decreased (0.6 T) together with an enhancement of the out-of- plane anisotropy. Nanoislands show a coercive field close to the values obtained for granular layers but exhibit an in-plane easy axis due to shape anisotropy effects. An extensive study with different synchrotron X-ray scattering techniques, mainly

  14. Effect of TiN-ZrO{sub 2} intermediate layer on the microstructure and magnetic properties of FePt and FePt-SiO{sub 2}-C thin films

    Energy Technology Data Exchange (ETDEWEB)

    Dong, K.F., E-mail: dongkf1981@163.com; Mo, W.Q.; Jin, F.; Song, J.L.

    2017-06-15

    Highlights: • The TiN-ZrO{sub 2} consisted of solid solution of Ti(Zr)ON segregated by amorphous ZrO{sub 2}. • With doping ZrO{sub 2} into TiN layer, grain size of FePt films significantly decreased. • By introducing TiN-ZrO{sub 2}/TiN combined layer, the magnetic properties were improved. - Abstract: The microstructures and magnetic properties of FePt based thin films grown on TiN-ZrO{sub 2} and TiN-ZrO{sub 2}/TiN intermediate layers were systematically investigated. The TiN-ZrO{sub 2} intermediate layer was granular consisting of grains of solid solution of Ti(Zr)ON segregated by amorphous ZrO{sub 2}. It was found with doping ZrO{sub 2} into TiN intermediate layer, grain size of FePt-SiO{sub 2}-C films significantly decreased. Simultaneously, the isolation was obviously improved and grain size distribution became more uniform. However, the magnetic properties of the FePt-SiO{sub 2}-C films grown on TiN-ZrO{sub 2} intermediate layers were slowly deteriorated, which was due to the disturbance of the epitaxial growth of FePt by amorphous ZrO{sub 2} in TiN-ZrO{sub 2} intermediate layer. In order to improve the TiN-ZrO{sub 2} (0 0 2) texture and the crystallinity of TiN-ZrO{sub 2}, TiN-ZrO{sub 2}/TiN combined intermediate layer was introduced. And the magnetic properties were improved, simultaneously, achieving the benefit of grain size reduction. For the FePt 4 nm-SiO{sub 2} 40 vol%-C 20 vol% film grown on TiN/TiN-ZrO{sub 2} 30 vol% combined intermediate layer, well isolated FePt (0 0 1) granular films with coercivity higher than 17.6 kOe and an average size as small as 6.5 nm were achieved.

  15. A study on the electrodeposition of NiFe alloy thin films using chronocoulometry and electrochemical quartz crystal microgravimetry

    CERN Document Server

    Myung, N S

    2001-01-01

    Ni, Fe and NiFe alloy thin films were electrodeposited at a polycrystalline Au surface using a range of electrolytes and potentials. Coulometry and EQCM were used for real-time monitoring of electroplating efficiency of the Ni and Fe. The plating efficiency of NiFe alloy thin films was computed with the aid of ICP spectrometry. In general, plating efficiency increased to a steady value with deposition time. Plating efficiency of Fe was lower than that of Ni at -0.85 and -1.0 V but the efficiency approached to the similar plateau value to that of Ni at more negative potentials. The films with higher content of Fe showed different stripping behavior from the ones with higher content of Ni. Finally, compositional data and real-time plating efficiency are presented for films electrodeposited using a range of electrolytes and potentials.

  16. Structural, mechanical, and magnetic properties of GaFe3N thin films

    International Nuclear Information System (INIS)

    Junaid, Muhammad; Music, Denis; Hans, Marcus; Schneider, Jochen M.; Scholz, Tanja; Dronskowski, Richard; Primetzhofer, Daniel

    2016-01-01

    Using the density-functional theory, the structural, mechanical, and magnetic properties were investigated for different GaFe 3 N configurations: ferromagnetic, ferrimagnetic, paramagnetic, and nonmagnetic. Ferrimagnetic and high-spin ferromagnetic states exhibit the lowest energy and are the competing ground states as the total energy difference is 0.3 meV/atom only. All theoretically predicted values could be fully confirmed by experiments. For this, the authors synthesized phase pure, homogeneous, and continuous GaFe 3 N films by combinatorial reactive direct current magnetron sputtering. Despite the low melting point of gallium, the authors succeeded in the growth of GaFe 3 N films at a temperature of 500 °C. Those thin films exhibit a lattice parameter of 3.794 Å and an elastic modulus of 226 ± 20 GPa. Magnetic susceptibility measurements evidence a magnetic phase transitions at 8.0 ± 0.1 K. The nearly saturated magnetic moment at ±5 T is about 1.6 μB/Fe and is close to the theoretically determined magnetic moment for a ferrimagnetic ordering (1.72 μB/Fe).

  17. AFM, XRD and HRTEM Studies of Annealed FePd Thin Films

    International Nuclear Information System (INIS)

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

    2010-01-01

    Ferromagnetic FePd L1 0 ordered alloys are highly expected as forthcoming high-density recording materials, because they reveal a large perpendicular magnetocrystalline anisotropy. The value of the magnetic anisotropy of FePd alloy strongly depends on the alloy composition, degree of alloy order as well as on the crystallographic grain orientation. In particular, to obtain the perpendicular anisotropy, it is necessary to get the films with (001) texture. One of the successful methods, which allows one to obtain highly ordered alloy, is a subsequent deposition of Fe and Pd layers, followed by an annealing at high temperature. This paper presents the study of the FePd thin alloy film structure changing in the result of high temperature annealing. During the annealing in high vacuum, the measurements of electrical resistance were performed, indicating the regions of different structure evolution. Changes in the crystal structure and surface morphology induced by thermal treatment were investigated by X-ray diffraction, atomic force microscopy, as well as high resolution transmission electron microscopy and then compared with electrical resistivity measurement. The slow thermal annealing of the deposited layers leads to the formation of L1 0 ordered FePd alloy with preferred (111) grain orientation. After the annealing at the highest used temperature, the dewetting process was observed, resulting in a creation of well oriented, regular nanoparticles. (author)

  18. Multilayer Ni/Fe thin films as oxygen evolution catalysts for solar fuel production

    International Nuclear Information System (INIS)

    Biset-Peiró, M; Murcia-López, S; Fàbrega, C; Morante, J R; Andreu, T

    2017-01-01

    The slow kinetics and high overpotential of the oxygen evolution reaction is one of the main limiting factors to achieve the minimum required performances of the so-called photoelectrochemical water splitting systems. An oxygen evolution catalyst (OEC) becomes essential in order to perform this process with higher efficiency. Herein, we report the physical, optical and electrochemical characterization of multilayer Ni/Fe thin films as earth-abundant OEC, to avoid the use of platinum group metals (PGM). Uniform films of thicknesses ranging from 1 to 10 nm were fabricated by sequential and alternate thermal evaporation of Ni and Fe. It was found that the successive deposition allows the fabrication of a Ni terminated surface that does not need activation due to the Fe underlayer. The lowest overpotential achieved for NiFe was 370 mV at 10 mA cm −2 and a Tafel slope of 37 mV dec −1 with 1 nm thickness and 95% transmittance. Finally, NiFe OEC was implemented on top of Mo:BiVO 4 photoanodes which resulted in a reduction of the open circuit potential of 0.2 V and up to five fold increase of the oxidation efficiency at 0.7 V RHE . The results presented facilitate the practical implementation of BiVO 4 photoanodes in tandem configuration for bias free photoassisted water splitting. (paper)

  19. Structural, mechanical, and magnetic properties of GaFe{sub 3}N thin films

    Energy Technology Data Exchange (ETDEWEB)

    Junaid, Muhammad, E-mail: junaid@mch.rwth-aachen.de; Music, Denis, E-mail: music@mch.rwth-aachen.de; Hans, Marcus; Schneider, Jochen M. [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Scholz, Tanja; Dronskowski, Richard [Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Primetzhofer, Daniel [Department of Physics and Astronomy, Uppsala University, Lägerhyddsvägen 1, S-75120 Uppsala (Sweden)

    2016-07-15

    Using the density-functional theory, the structural, mechanical, and magnetic properties were investigated for different GaFe{sub 3}N configurations: ferromagnetic, ferrimagnetic, paramagnetic, and nonmagnetic. Ferrimagnetic and high-spin ferromagnetic states exhibit the lowest energy and are the competing ground states as the total energy difference is 0.3 meV/atom only. All theoretically predicted values could be fully confirmed by experiments. For this, the authors synthesized phase pure, homogeneous, and continuous GaFe{sub 3}N films by combinatorial reactive direct current magnetron sputtering. Despite the low melting point of gallium, the authors succeeded in the growth of GaFe{sub 3}N films at a temperature of 500 °C. Those thin films exhibit a lattice parameter of 3.794 Å and an elastic modulus of 226 ± 20 GPa. Magnetic susceptibility measurements evidence a magnetic phase transitions at 8.0 ± 0.1 K. The nearly saturated magnetic moment at ±5 T is about 1.6 μB/Fe and is close to the theoretically determined magnetic moment for a ferrimagnetic ordering (1.72 μB/Fe).

  20. ARPES study of cesium-coated FeSe thin films on SrTiO3

    Science.gov (United States)

    Phan, G. N.; Nakayama, K.; Kanayama, S.; Kuno, M.; Sugawara, K.; Sato, T.; Takahashi, T.

    2017-07-01

    We have performed in-situ angle-resolved photoemission spectroscopy measurements of cesium(Cs)-deposited FeSe thin films on SrTiO3. We found that Cs deposition enables heavily electron doping into the FeSe layer. In properly doped films, we also revealed the occurrence of superconductivity accompanied by the suppression of electronic nematicity. The present result demonstrates that Cs deposition is an effective way to realize and enhance superconductivity in FeSe.

  1. AES study of the reaction between a thin Fe-film and β-SiC (100) surface

    International Nuclear Information System (INIS)

    Mizokawa, Yusuke; Nakanishi, Shigemitsu; Miyase, Sunao

    1989-01-01

    The solid state reaction between thin Fe-films and β-SiC(100) in UHV has been studied using AES. Even at room temperature, the reaction between the thin Fe-film and SiC occurred and formed Fe-silicide and graphite with a minor product of Fe-carbide (Fe 3 C). The reaction proceeded with an increase of Fe-coverage to some extent. With annealing of 15 A-Fe-film/SiC below 540degC, the Fe-silicide formation was accelerated, but because the amount of available Fe was small, the dissolved carbon atoms were forced to form not the Fe-carbide but the graphite phase. Above 640degC, the Fe-silicide started to decompose and the carbon atoms diffused to the surface and formed surface graphite layers. With annealing at 1080degC, the free-Si segregats at the surface and formed Si-Si bonds, as well as the Si-C bonds consuming the surface graphite phase. (author)

  2. Effect of thickness on the electrical and optical properties of epitaxial (La0.07Ba0.93)SnO3 thin films

    Science.gov (United States)

    Liu, Qinzhuang; Jin, Feng; Dai, Jianming; Li, Bing; Geng, Lei; Liu, Jianjun

    2016-08-01

    Transparent conductive oxide (La0.07Ba0.93)SnO3 (LBSO) thin films with thickness ranged from 220 nm to 11 nm were epitaxially grown on MgO substrate by pulsed laser deposition. The effect of thickness on the structural, transport, and optical properties of LBSO thin films was investigated in detail. With the film thickness decreasing, x-ray diffraction characterizations show that the LBSO (002) diffraction peak has no obvious shift, but the values of the full width at half maximum increase gradually from 0.608° to 1.136° due to the deterioration of crystalline quality of LBSO films. Atomic force microcopy reveals that the root-mean-square surface roughness of LBSO films decreases from 3.93 to 0.268 nm with film thickness decreasing. The lowest resistivity value of 1.181 × 10-4 Ωcm at room temperature was observed in 220 nm thick films, with the highest carrier mobility of 41.06 cm2 V-1 s-1 and carrier concentration of 8.377 × 1020 cm-3. Furthermore, the resistivity increases gradually with the decrease of LBSO film thickness. Temperature dependent resistivity measurements indicate that the metal-semiconductor transition temperature of LBSO thin film changes regularly with the film thickness. The optical band gap of LBSO thin film decreases from 4.58 to 3.55 eV with decreasing the thickness, which was explained by the Burstein-Moss effect.

  3. O and Fe abundance correlations and distributions inferred for the thick and thin disk

    Directory of Open Access Journals (Sweden)

    Caimmi R.

    2015-01-01

    Full Text Available A linear [Fe/H]-[O/H] relation is found for different stellar populations in the Galaxy (halo, thick disk, thin disk from a data sample obtained in a recent investigation (Ramґırez et al. 2013. These correlations support previous results inferred from poorer samples: stars display a “main sequence” expressed as [Fe/H] = a[O/H] + b -+ Δb where the unit slope, a = 1, implies a constant [O/Fe] abundance ratio. Oxygen and iron empirical abundance distributions are then determined for different subsamples, which are well explained by the theoretical predictions of multistage closed-(box+reservoir (MCBR chemical evolution models taking into account the found correlations. The interpretation of these distributions in the framework of MCBR models gives us clues about inflow/outflow rates in these different Galactic regions and their corresponding evolution. Outflow rates for the thick and the thin disks are lower than the halo outflow rate. Besides that, the iron-to-oxygen yield ratio and the primary to not primary contribution ratio for the iron production are obtained from the data, resulting consistent with the SNII progenitor nucleosynthesis and with the iron production from SNIa supernova events.

  4. Growth and Characterization of Magnetoelectric Fe2TeO6 Thin Films

    Science.gov (United States)

    Wang, Junlei; Colon Santana, Juan; Wu, Ning; Dowben, Peter; Binek, Christian

    2013-03-01

    Voltage-controlled spintronics is of vital importance in information technology where power consumption and Joule heating restrict progress through scaling. Motivated by spintronic concepts and specifically by device applications utilizing electrically controlled interface or boundary magnetization (BM) in magnetic thin film heterostructures, we report on growth, structural, magnetic and magnetoelectric (ME) characterization of the antiferromagnet Fe2TeO6. Magnetometry of synthesized Fe2TeO6 powder, in combination with ME susceptibility data reveals 3D Heisenberg criticality in striking similarity to the archetypical ME chromia. X-ray diffraction shows (110) texture of the PLD grown films. Measurements of the magnetic susceptibility of the latter confirm in-plane magnetic anisotropy. X-ray photoemission spectroscopy indicates a Te-O terminated (110) surface. We interpret it in terms of surface reconstruction. Measurements of X-ray magnetic circular dichroism combined with photoemission electron microscopy support the presence of electrically controllable BM in the PLD-grown Fe2TeO6 thin film. We acknowledge financial support by NSF-MRSEC & Nanoelectronics Research Initiative.

  5. Preparation and measurement of hysteresis curve FeCoNi thin film for the application of electromagnet design

    International Nuclear Information System (INIS)

    Yunanto; Tri Mardji Atmono

    2015-01-01

    The preparation and preceiving nature of hysteresis curve of FeCoNi thin film for application in electromagnet design have been done. The aim of the research is to obtain FeCoNi thin film having high saturation and magnetic permeability, that can be used to design the electromagnet for cyclotron. The desired alloy based on this thin film FeCoNi should produce a magnetic field of 2.4 T by low power supply 3 kW. To get the thin film FeCoNi, it was used the material target Co with Ni and Fe as chip put on the surface of Co, to form a mosaic target, bombarded by Ar-ions + . The result of VSM measurement showed a hysteresis curve having saturation of 0.5 T, higher than that of thin film Ni having 0.2 T. The composition which was analyzed by using EDAX showed 17,2 %, 52,78 %, 19,76 %, 10,26 % content of Fe, Co, Ni and O, respectively. (author)

  6. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Jumpei; Oka, Daichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); Hirose, Yasushi, E-mail: hirose@chem.s.u-tokyo.ac.jp; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Harayama, Isao; Sekiba, Daiichiro [University of Tsukuba Tandem Accelerator Complex (UTTAC), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577 (Japan)

    2015-12-07

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO{sub x}N{sub y}) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO{sub x}N{sub y} thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO{sub x}N{sub y} thin films monotonically decreased from the order of 10{sup 5} Ω cm to 10{sup −4} Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO{sub x}N{sub y} phase, which has not yet been reported in Co{sup 2+}/Co{sup 3+} mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO{sub x}N{sub y} phase, on the 10{sup −3} Ω cm order, may have originated from the intermediate spin state of Co{sup 3+} stabilized by the lowered crystal field symmetry of the CoO{sub 6−n}N{sub n} octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO{sub x}N{sub y} films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides.

  7. Strain induced ferromagnetism and large magnetoresistance of epitaxial La1.5Sr0.5CoMnO6 thin films

    Science.gov (United States)

    Krishna Murthy, J.; Jyotsna, G.; N, Nileena; Anil Kumar, P. S.

    2017-08-01

    In this study, the structural, magnetic, and magneto-transport properties of La1.5Sr0.5CoMnO6 (LSCMO) thin films deposited on a SrTiO3 (001) substrate were investigated. A normal θ/2θ x-ray diffraction, rocking curve, ϕ-scan, and reciprocal space mapping data showed that prepared LSCMO thin films are single phase and highly strained with epitaxial nature. Temperature vs. magnetization of LSCMO films exhibits strain-induced ferromagnetic ordering with TC ˜ 165 K. In contrast to the bulk samples, there was no exchange bias and canted type antiferromagnetic and spin glass behavior in films having thickness (t) ≤ 26 nm. Temperature dependent resistivity data were explained using Schnakenberg's model and the polaron hopping conduction process. The slope change in resistivity and magnetoresistance maximum (˜65%) around TC indicates the existence of a weak double exchange mechanism between the mixed valence states of transition metal ions. Suppression of spin dependent scattering with the magnetic field is attributed for the large negative magnetoresistance in LSCMO films.

  8. Growth kinetics of thin oxide layers; oxidation of Fe and Fe-N phases at room temperature

    NARCIS (Netherlands)

    Kooi, Bart J.; Somers, Marcel A.J.; Mittemeijer, Eric J.

    1996-01-01

    The evolution of iron-oxide layers at room temperature on pure polycrystalline α-Fe and on the Fe-N phases γ-Fe[N], γ'-Fe4N1-x and ε-Fe2N1-z was followed in situ with Auger-Electron Spectroscopy. The observed oxidation kinetics of the Fe and Fe-N phases were interpreted using a model considering

  9. Local probing of magnetoelectric coupling and magnetoelastic control of switching in BiFeO3-CoFe2O4 thin-film nanocomposite

    Science.gov (United States)

    Yan, Feng; Chen, Guannan; Lu, Li; Finkel, Peter; Spanier, Jonathan E.

    2013-07-01

    We report on the combination of piezoresponse force microscopy (PFM), magnetic force microscopy, and local ferroelectric switching with magnetic field for the study of a thin-film magnetoelectric (ME) nanocomposite. The collection of PFM under an applied variable magnetic field within a polycrystalline perovskite-spinel BiFeO3-CoFe2O4 (BFO-CFO) 0-3 type thin-film nanocomposite enables quantitative and proximal measurement of magnetoelastic strain-driven ME response. Combination of measurement of the as-grown strain state with local measurements of microstructure and macroscopic magnetization permits local mapping of ME coupling.

  10. Synthesis, structure, and magnetic studies on self-assembled BiFeO3-CoFe2O4 nanocomposite thin films

    Science.gov (United States)

    Muralidharan, R.; Dix, N.; Skumryev, V.; Varela, M.; Sánchez, F.; Fontcuberta, J.

    2008-04-01

    Self-assembled (0.65)BiFeO3-(0.35)CoFe2O4 (BFO-CFO) nanostructures were deposited on SrTiO3 (001) and (111) substrates by pulsed laser deposition at various temperatures from 500to800°C. The crystal phases and the lattice strain for the two different substrate orientations have been determined and compared. The films grow epitaxial on both substrates but separation of the spinel and perovskite crystallites, without parasitic phases, is only obtained for growth temperatures of around 600-650°C. The BFO crystallites are out-of-plane expanded on STO(001), whereas they are almost relaxed on (111). In contrast, CFO crystallites grow out-of-plane compressed on both substrates. The asymmetric behavior of the cell parameters of CFO and BFO is discussed on the basis of the role of the epitaxial stress caused by the substrate and the spinel-perovskite interfacial stress. It is concluded that interfacial stress dominates the elastic properties of CFO crystallites and thus it may play a fundamental on the interface magnetoelectric coupling in these nanocomposites.

  11. The effects of Fe2O3 nanoparticles on MgB2 superconducting thin films

    International Nuclear Information System (INIS)

    Koparan, E.T.; Sidorenko, A.; Yanmaz, E.

    2013-01-01

    Full text: Since the discovery of superconductivity in binary MgB 2 compounds, extensive studies have been carried out because of its excellent properties for technological applications, such as high transition temperature (T c = 39 K), high upper critical field (H c2 ), high critical current density (J c ). Thin films are important for fundamental research as well as technological applications of any functional materials. Technological applications primarily depend on critical current density. The strong field dependence of J c for MgB 2 necessitates an enhancement in flux pinning performance in order to improve values in high magnetic fields. An effective way to improve the flux pinning is to introduce flux pinning centers into MgB 2 through a dopant having size comparable to the coherence length of MgB 2 . In this study, MgB 2 film with a thickness of about 600 nm was deposited on the MgO (100) single crystal substrate using a 'two-step' synthesis technique. Firstly, deposition of boron thin film was carried out by rf magnetron sputtering on MgO substrates and followed by a post deposition annealing at 850 degrees Celsius in magnesium vapour. In order to investigate the effect of Fe 2 O 3 nanoparticles on the structural and magnetic properties of films, MgB 2 films were coated with different concentrations of Fe 2 O 3 nanoparticles by a spin coating process. The effects of different concentrations of ferromagnetic Fe 2 O 3 nanoparticles on superconducting properties of obtained films were carried out by using structural (XRD, SEM, AFM), electrical (R-T) and magnetization (M-H, M-T and AC Susceptibility) measurements. It was calculated that anisotropic coefficient was about γ = 1.2 and coherence length of 5 nm for the uncoated film. As a result of coherence length, the appropriate diameters of Fe 2 O 3 nanoparticles were found to be 10 nm, indicating that these nanoparticles served as the pinning centers. Based on the data obtained from this study, it can be

  12. Formation dynamics of FeN thin films on Cu(100)

    KAUST Repository

    Heryadi, Dodi

    2012-01-01

    To investigate the structural and magnetic properties of thin films of FeN we have performed ab initio molecular dynamics simulations of their formation on Cu(100) substrates. The iron nitride layers exhibit a p4gm(2 × 2) reconstruction and order ferromagnetically in agreement with experiment. We establish the dynamics and time scale of the film formation as a function of the film thickness. The process is split in two phases: formation of almost flat FeN layers and optimization of the distance to the substrate. Our calculated magnetic moments are 1.67 μ B, 2.14 μ B, and 2.21 μ B for one, two, and three monolayers of iron nitride. © 2011 Elsevier B.V. All rights reserved.

  13. Effect of anisotropy on anomalous Hall effect in Tb-Fe thin films

    International Nuclear Information System (INIS)

    Babu, V. Hari; Markandeyulu, G.; Subrahmanyam, A.

    2009-01-01

    The electrical and Hall resistivities of Tb x Fe 100-x thin films in the temperature range 13-300 K were investigated. The sign of Hall resistivity at 300 K is found to change from positive for x=28 film to negative for x=30 film, in accordance with the compensation of Tb and Fe moments. All the films are seen to have planar magnetic anisotropy at 13 K. The temperature coefficients of electrical resistivities of the amorphous films with 19≤x≤51 are seen to be negative. The temperature dependence of Hall resistivity of these films is explained on the basis of random magnetic anisotropy model. The temperature dependences of Hall resistivities of the x=22 and 41 films are seen to exhibit a nonmonotonous behavior due to change in anisotropy from perpendicular to planar. The same behavior is considered for the explanation regarding the probable formation of Berry phase curvature in these films.

  14. Nanostructural origin of semiconductivity and large magnetoresistance in epitaxial NiCo2O4/Al2O3 thin films

    Science.gov (United States)

    Zhen, Congmian; Zhang, XiaoZhe; Wei, Wengang; Guo, Wenzhe; Pant, Ankit; Xu, Xiaoshan; Shen, Jian; Ma, Li; Hou, Denglu

    2018-04-01

    Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the NiCo2O4 (1 1 1)/MgAl2O4 (1 1 1) and the NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, they show metallic and semiconducting electrical transport, respectively. Post-growth annealing decreases the resistivity of NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, but the annealed films are still semiconducting. While the semiconductivity and the large magnetoresistance in NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films cannot be accounted for in terms of non-optimal valence mixing and spinel inversion, the presence of anti-phase boundaries between nano-sized crystallites, generated by the structural mismatch between NiCo2O4 and Al2O3, may explain all the experimental observations in this work. These results reveal nanostructural disorder as being another key factor for controlling the electrical transport of NiCo2O4, with potentially large magnetoresistance for spintronics applications.

  15. The influence of oxygen flow rate on properties of SnO{sub 2} thin films grown epitaxially on c-sapphire by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Y.M. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University (China); Key Laboratory of Green Preparation and Application for Functional Materials, Ministry of Education, Hubei University (China); Faculty of Materials Science & Engineering, Hubei University (China); Jiang, J. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany); Xia, C. [Physical Chemistry Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen (Germany); Kramm, B.; Polity, A. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany); He, Y.B., E-mail: ybhe@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University (China); Key Laboratory of Green Preparation and Application for Functional Materials, Ministry of Education, Hubei University (China); Faculty of Materials Science & Engineering, Hubei University (China); Klar, P.J.; Meyer, B.K. [I. Physics Institute, Justus-Liebig University of Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen (Germany)

    2015-11-02

    Tin dioxide (SnO{sub 2}) thin films were grown on c-plane sapphire substrates by chemical vapor deposition using SnI{sub 2} and O{sub 2} as reactants. The growth experiments were carried out at a fixed substrate temperature of 510 °C and different O{sub 2} flow rates. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–Vis–IR spectrophotometry and Hall-effect measurement were used to characterize the films. All films consisted of pure-phase SnO{sub 2} with a rutile structure and showed an epitaxial relationship with the substrate of SnO{sub 2}(100)||Al{sub 2}O{sub 3}(0001) and SnO{sub 2}[010]||Al{sub 2}O{sub 3}< 11–20 >. The crystalline quality and properties of the films were found to be sensitively dependent on the O{sub 2} flow rate during the film growth. The absolute average transmittance of the SnO{sub 2} films exceeded 85% in the visible and infrared spectral region. The films had optical band-gaps (3.72–3.89 eV) that are in line with the band gap of single-crystal SnO{sub 2}. The carrier concentration and Hall mobility of the films decreased from 3.3 × 10{sup 19} to 9 × 10{sup 17} cm{sup −3} and from 19 to 2 cm{sup 2} V{sup −1} s{sup −1}, respectively, while the resistivity increased from 0.01 to 3 Ω cm with increasing of the O{sub 2} flow rate from 5 to 60 sccm. - Highlights: • SnI{sub 2} (Sn{sup 2+}) was used as tin precursor to prepare tin oxide films by CVD. • Epitaxial SnO{sub 2} (100) films were obtained on c-sapphire with thickness more than 1 μm. • The epitaxial relationship is SnO{sub 2}(100)||Al{sub 2}O{sub 3}(0001) and SnO{sub 2}[010]||Al{sub 2}O{sub 3}< 11–20 >. • B{sub 2g} Raman mode was found to be absent in (100)-orientated SnO{sub 2} films on c-sapphire. • The crystal quality and properties of SnO{sub 2} films depended sensitively on the O{sub 2} flow rate.

  16. Si/Fe flux ratio influence on growth and physical properties of polycrystalline β-FeSi2 thin films on Si(100) surface

    Science.gov (United States)

    Tarasov, I. A.; Visotin, M. A.; Aleksandrovsky, A. S.; Kosyrev, N. N.; Yakovlev, I. A.; Molokeev, M. S.; Lukyanenko, A. V.; Krylov, A. S.; Fedorov, A. S.; Varnakov, S. N.; Ovchinnikov, S. G.

    2017-10-01

    This work investigates the Si/Fe flux ratio (2 and 0.34) influence on the growth of β-FeSi2 polycrystalline thin films on Si(100) substrate at 630 °C. Lattice deformations for the films obtained are confirmed by X-ray diffraction analysis (XRD). The volume unit cell deviation from that of β-FeSi2 single crystal are 1.99% and 1.1% for Si/Fe =2 and Si/Fe =0.34, respectively. Absorption measurements show that the indirect transition ( 0.704 eV) of the Si/Fe =0.34 sample changes to the direct transition with a bandgap value of 0.816 eV for the sample prepared at Si/Fe =2. The absorption spectrum of the Si/Fe =0.34 sample exhibits an additional peak located below the bandgap energy value with the absorption maximum of 0.36 eV. Surface magneto-optic Kerr effect (SMOKE) measurements detect the ferromagnetic behavior of the β-FeSi2 polycrystalline films grown at Si/Fe =0.34 at T=10 K, but no ferromagnetism was observed in the samples grown at Si/Fe =2. Theoretical calculations refute that the cell deformation can cause the emergence of magnetization and argue that the origin of the ferromagnetism, as well as the lower absorption peak, is β-FeSi2 stoichiometry deviations. Raman spectroscopy measurements evidence that the film obtained at Si/Fe flux ratio equal to 0.34 has the better crystallinity than the Si/Fe =2 sample.

  17. Magnetic properties of Fe3O4 thin films grown on different substrates by laser ablation

    International Nuclear Information System (INIS)

    Parames, M.L.; Viskadourakis, Z.; Rogalski, M.S.; Mariano, J.; Popovici, N.; Giapintzakis, J.; Conde, O.

    2007-01-01

    Magnetite thin films have been grown onto (1 0 0)Si (1 0 0)GaAs and (0 0 0 1)Al 2 O 3 , at substrate temperatures varying from 473 to 673 K, by UV pulsed laser ablation of Fe 3 O 4 targets in reactive atmospheres of O 2 and Ar, at working pressure of 8 x 10 -2 Pa. The influence of the substrate on stoichiometry, microstructure and the magnetic properties has been studied by X-ray diffraction (XRD), conversion electron Moessbauer spectroscopy (CEMS) and magnetic measurements. Magnetite crystallites, with stoichiometry varying from Fe 2.95 O 4 to Fe 2.99 O 4 , are randomly oriented for (1 0 0)GaAs and (1 0 0)Si substrates and exhibit (1 1 1) texture if grown onto (0 0 0 1)Al 2 O 3 . Interfacial Fe 3+ diffusion, which is virtually absent for (1 0 0)Si substrates, was found for both (0 0 0 1)Al 2 O 3 and (1 0 0)GaAs, with some deleterious effect on the subsequent microstructure and magnetic behaviour

  18. Influence of the spacer layer on microstructure and magnetic properties of [NdFeB/(NbCu)]xn thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chiriac, H. [National Institute of R and D for Technical Physics, 47 Mangeron Blvd., 700050 Iasi (Romania); Grigoras, M. [National Institute of R and D for Technical Physics, 47 Mangeron Blvd., 700050 Iasi (Romania); Urse, M. [National Institute of R and D for Technical Physics, 47 Mangeron Blvd., 700050 Iasi (Romania)]. E-mail: urse@phys-iasi.ro

    2007-09-15

    Some results concerning the influence of the composition and thickness of NbCu spacer layer on the microstructure and magnetic properties of multilayer [NdFeB/(NbCu)]xn films, in view of their utilization for manufacturing the thin film permanent magnets are presented. A comparison between the microstructure and magnetic properties of NdFeB single layer and [NdFeB/(NbCu)]xn multilayer is also presented. The multilayer [NdFeB/(NbCu)]xn thin films with the thickness of the NdFeB layer of 180nm and the thickness of the NbCu spacer layer of 3nm, exhibit good hard magnetic characteristics such as coercive force H{sub c} of about 1510kA/m and the remanence ratio M{sub r}/M{sub s} of about 0.8.

  19. Influence of the spacer layer on microstructure and magnetic properties of [NdFeB/(NbCu)]xn thin films

    International Nuclear Information System (INIS)

    Chiriac, H.; Grigoras, M.; Urse, M.

    2007-01-01

    Some results concerning the influence of the composition and thickness of NbCu spacer layer on the microstructure and magnetic properties of multilayer [NdFeB/(NbCu)]xn films, in view of their utilization for manufacturing the thin film permanent magnets are presented. A comparison between the microstructure and magnetic properties of NdFeB single layer and [NdFeB/(NbCu)]xn multilayer is also presented. The multilayer [NdFeB/(NbCu)]xn thin films with the thickness of the NdFeB layer of 180nm and the thickness of the NbCu spacer layer of 3nm, exhibit good hard magnetic characteristics such as coercive force H c of about 1510kA/m and the remanence ratio M r /M s of about 0.8

  20. Phase transitions in Fe0.5Co0.5 (110) thin films

    International Nuclear Information System (INIS)

    Ramírez-Dámaso, G.; Castillo-Alvarado, F.L.; Rojas-Hernández, E.

    2016-01-01

    In this paper, we present calculations for two second-order phase transitions in (110) Fe 0.5 Co 0.5 thin films with 11, 15, and 19 monoatomic layers. The lattice and magnetic transitions are based on thermodynamic equilibrium considerations of the magnetic alloy. The procedure proposed by Valenta and Sukiennicki was applied to calculate the composition x(i), the lattice order parameter t(i), and the magnetic order parameter σ(i) as a function of temperature T. We confirmed that both phase transitions, lattice and magnetic, are of the second order, in accordance with experimental results in the literature. The obtained behavior of these parameters indicates their inhomogeneity due to the boundary conditions on the surfaces of the thin film.

  1. Self-assembled thin films of Fe3O4-Ag composite nanoparticles for spintronic applications

    Science.gov (United States)

    Jiang, Chengpeng; Leung, Chi Wah; Pong, Philip W. T.

    2017-10-01

    Controlled self-assembly of multi-component magnetic nanoparticles could lead to nanomaterial-based magnetic devices with novel structures and intriguing properties. Herein, self-assembled thin films of Fe3O4-Ag composite nanoparticles (CNPs) with hetero-dimeric shapes were fabricated using interfacial assembly method. The CNP-assembled thin films were further transferred to patterned silicon substrates followed by vacuum annealing, producing CNP-based magnetoresistive (MR) devices. Due to the presence of intra-particle interfaces and inter-particle barriers, an enhanced MR ratio and a non-linear current-voltage relation were observed in the device. The results of this work can potentially pave the way to the future exploration and development of spintronic devices built from composite nanomaterials.

  2. Growth and crystallographic feature-dependent characterization of spinel zinc ferrite thin films by RF sputtering.

    Science.gov (United States)

    Liang, Yuan-Chang; Hsia, Hao-Yuan

    2013-12-19

    ZnFe2O4 (ZFO) thin films exhibiting varying crystallographic features ((222)-epitaxially, (400)-epitaxially, and randomly oriented films) were grown on various substrates by radio-frequency magnetron sputtering. The type of substrate used profoundly affected the surface topography of the resulting ZFO films. The surface of the ZFO (222) epilayer was dense and exhibited small rectangular surface grains; however, the ZFO (400) epilayer exhibited small grooves. The surface of the randomly oriented ZFO thin film exhibited distinct three-dimensional island-like grains that demonstrated considerable surface roughness. Magnetization-temperature curves revealed that the ZFO thin films exhibited a spin-glass transition temperature of approximately 40 K. The crystallographic orientation of the ZFO thin films strongly affected magnetic anisotropy. The ZFO (222) epitaxy exhibited the strongest magnetic anisotropy, whereas the randomly oriented ZFO thin film exhibited no clear magnetic anisotropy.

  3. Screening effects in ferroelectric resistive switching of BiFeO3 thin films

    Directory of Open Access Journals (Sweden)

    S. Farokhipoor

    2014-05-01

    Full Text Available We investigate ferroelectric resistive switching in BiFeO3 thin films by performing local conductivity measurements. By comparing conduction characteristics at artificially up-polarized domains with those at as-grown down-polarized domains, the change in resistance is attributed to the modification of the electronic barrier height at the interface with the electrodes, upon the reversal of the electrical polarization. We also study the effect of oxygen vacancies on the observed conduction and we propose the existence of a different screening mechanism for up and down polarized domains.

  4. High resolution x-ray scattering studies of strain in epitaxial thin films of yttrium silicide grown on silicon (111)

    International Nuclear Information System (INIS)

    Marthinez-Miranda, L.J.; Santiago-Aviles, J.J.; Siegal, M.P.; Graham, W.R.; Heiney, P.A.

    1990-01-01

    The authors have used high resolution grazing incidence x-ray scattering (GIXS) to study the in- plane and out-of-plane structure of epitaxial YSi 2-x films grown on Si(111), with thicknesses ranging from 85 Angstrom to 510 Angstrom. Their results indicate that the films are strained, and that film strain increases as a function of thickness, with lattice parameters varying from a = 3.846 Angstrom/c = 4.142 Angstrom for the 85 Angstrom film to a = 3.877 Angstrom/c = 4.121 Angstrom for the 510 Angstrom film. The authors correlate these results with an increase in pinhole areal coverage as a function of thickness. In addition, the authors' measurements show no evidence for the existence of ordered silicon vacancies in the films

  5. Effect of thermal annealing on structural properties of GeSn thin films grown by molecular beam epitaxy

    Science.gov (United States)

    Zhang, Z. P.; Song, Y. X.; Li, Y. Y.; Wu, X. Y.; Zhu, Z. Y. S.; Han, Y.; Zhang, L. Y.; Huang, H.; Wang, S. M.

    2017-10-01

    GeSn alloy with 7.68% Sn concentration grown by molecular beam epitaxy has been rapidly annealed at different temperatures from 300°C to 800°C. Surface morphology and roughness annealed below or equal to 500°C for 1 min have no obvious changes, while the strain relaxation rate increasing. When the annealing temperature is above or equal to 600°C, significant changes occur in surface morphology and roughness, and Sn precipitation is observed at 700°C. The structural properties are analyzed by reciprocal space mapping in the symmetric (004) and asymmetric (224) planes by high resolution X-ray diffraction. The lateral correlation length and the mosaic spread are extracted for the epi-layer peaks in the asymmetric (224) diffraction. The most suitable annealing temperature to improve both the GeSn lattice quality and relaxation rate is about 500°C.

  6. High efficiency phototransducers based on a novel vertical epitaxial heterostructure architecture (VEHSA) with thin p/n junctions

    Science.gov (United States)

    York, Mark C. A.; Fafard, Simon

    2017-05-01

    This review outlines a series of developments in the design, modelling and growth of multi-junction laser power converters, including several observations of multi-junction GaAs monolithic vertical epitaxial heterostructure architecture devices with astonishing mono-chromatic optical to electrical conversion efficiencies in the 65-70% range. Experimental data is presented for devices ranging from single up to 20 p/n junctions, generally exhibiting weak dependence on source detuning which serves as evidence for strong photon recycling effects in these devices. Considerations for further design optimizations are discussed in detail, as well as the future direction of this research including the growth of devices with up to 100 subcells.

  7. Metal-semiconductor transition materials. FeS and VO{sub 2} thin films by RF reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Fu Ganhua

    2007-06-15

    In the present work, two MST systems, FeS and VO{sub 2} thin films were investigated. Iron sulfide thin films over a range of composition were prepared by reactive sputtering. The influence of the substrate, sputter power, substrate temperature and stoichiometry on the structure and MST of iron sulfide films was investigated. Iron sulfide films deposited at different temperatures show temperature dependent structure and MST. FeS films on float glass show (110) and (112) orientations when the substrate temperature is 200 and 500 C, respectively. The transition temperature and width of the hysteresis loop determined from the temperature dependent conductivity curves of iron sulfide films decrease with the substrate temperature. Fe and S excess in FeS films both result in the decrease of the transition temperature and width of the hysteresis loop. The vacuum-annealing affects the MST of FeS films significantly. When FeS films were annealed below the deposition temperature, the transition temperature decreases; otherwise increases. The residual stress plays an important role during the annealing process. The higher the residual stress inside the FeS films is, the higher the transition temperature of FeS films. With the increase of the annealing temperature, the residual stress in FeS films is first released and then enhances, which gives rise first to the decrease and then increase of the transition temperature of FeS films. At high substrate temperatures, the residual stress is higher. In addition, the MST of FeS films was influenced by the ambient aging. With the increase of the aging time, the transition temperature first increases and then decreases. FeS films with different thicknesses were prepared. The correlation between the film thickness (grain size) and the MST switching characteristics of FeS films was established. With the decrease of the grain size, the density of grain boundaries increases, causing the increase of the conductivity of the semiconducting

  8. Metal-semiconductor transition materials. FeS and VO2 thin films by RF reactive sputtering

    International Nuclear Information System (INIS)

    Fu, Ganhua

    2007-06-01

    In the present work, two MST systems, FeS and VO 2 thin films were investigated. Iron sulfide thin films over a range of composition were prepared by reactive sputtering. The influence of the substrate, sputter power, substrate temperature and stoichiometry on the structure and MST of iron sulfide films was investigated. Iron sulfide films deposited at different temperatures show temperature dependent structure and MST. FeS films on float glass show (110) and (112) orientations when the substrate temperature is 200 and 500 C, respectively. The transition temperature and width of the hysteresis loop determined from the temperature dependent conductivity curves of iron sulfide films decrease with the substrate temperature. Fe and S excess in FeS films both result in the decrease of the transition temperature and width of the hysteresis loop. The vacuum-annealing affects the MST of FeS films significantly. When FeS films were annealed below the deposition temperature, the transition temperature decreases; otherwise increases. The residual stress plays an important role during the annealing process. The higher the residual stress inside the FeS films is, the higher the transition temperature of FeS films. With the increase of the annealing temperature, the residual stress in FeS films is first released and then enhances, which gives rise first to the decrease and then increase of the transition temperature of FeS films. At high substrate temperatures, the residual stress is higher. In addition, the MST of FeS films was influenced by the ambient aging. With the increase of the aging time, the transition temperature first increases and then decreases. FeS films with different thicknesses were prepared. The correlation between the film thickness (grain size) and the MST switching characteristics of FeS films was established. With the decrease of the grain size, the density of grain boundaries increases, causing the increase of the conductivity of the semiconducting phase

  9. Magnetic state controllable critical temperature in epitaxial Ho/Nb bilayers

    Directory of Open Access Journals (Sweden)

    Yuanzhou Gu

    2014-04-01

    Full Text Available We study the magnetic properties of Ho thin films with different crystallinity (either epitaxial or non-epitaxial and investigate their proximity effects with Nb thin films. Magnetic measurements show that epitaxial Ho has large anisotropy in two different crystal directions in contrast to non-epitaxial Ho. Transport measurements show that the superconducting transition temperature (Tc of Nb thin films can be significantly suppressed at zero field by epitaxial Ho compared with non-epitaxial Ho. We also demonstrate a direct control over Tc by changing the magnetic states of the epitaxial Ho layer, and attribute the strong proximity effects to exchange interaction.

  10. Structural, topographical and magnetic evolution of RF-sputtered Fe-Ni alloy based thin films with thermal annealing

    International Nuclear Information System (INIS)

    Lisha, R; Geetha, P; Anantharaman, M R; Hysen, T; Avasthi, D K; Ramanujan, R V

    2014-01-01

    Metglas 2826 MB having a nominal composition of Fe 40 Ni 38 Mo 4 B 18 is an excellent soft magnetic material and finds application in sensors and memory heads. However, the thin-film forms of Fe 40 Ni 38 Mo 4 B 18 are seldom studied, although they are important in micro-electro-mechanical systems/nano-electro-mechanical systems devices. The stoichiometry of the film plays a vital role in determining the structural and magnetic properties of Fe 40 Ni 38 Mo 4 B 18 thin films: retaining the composition in thin films is a challenge. Thin films of 52 nm thickness were fabricated by RF sputtering technique on silicon substrate from a target of nominal composition of Fe 40 Ni 38 Mo 4 B 18 . The films were annealed at temperatures of 400 °C and 600 °C. The micro-structural studies of films using glancing x-ray diffractometer (GXRD) and transmission electron microscope (TEM) revealed that pristine films are crystalline with (FeNiMo) 23 B 6 phase. Atomic force microscope (AFM) images were subjected to power spectral density analysis to understand the probable surface evolution mechanism during sputtering and annealing. X-ray photoelectron spectroscopy (XPS) was employed to determine the film composition. The sluggish growth of crystallites with annealing is attributed to the presence of molybdenum in the thin film. The observed changes in magnetic properties were correlated with annealing induced structural, compositional and morphological changes. (papers)

  11. Spin injection from epitaxial Heusler alloy thin films into InGaAs/GaAs quantum wells

    DEFF Research Database (Denmark)

    Damsgaard, Christian Danvad

    2006-01-01

    no anisotropy is seen for near stoichiometry thin films on an ordinary GaAs surface. Typically thin films grown on GaAs show lower saturation magnetization than expected from bulk properties. The electrical characterizations have revealed resistivities around ρ = 350μΩcm at 300 K. Generally, the near......, magnetically, and electrically. The crystal structure has been studied by X-ray diffraction techniques. The expected Heusler structure L21 has been observed. Anisotropy of in-plane magnetization in near stoichiometric thin films grown on a 2 × 4 Ga-rich reconstructed GaAs surface has been observed while...... stoichiometric films have a very weak temperature dependence, with resistivity dropping slightly when cooled. A small room temperature anisotropic magneto resistance has been measured to 0.062 %. From transmission line measurements at low current, interface resistance in δ-doped GaAs-ferromagnet is found...

  12. Controlled growth of epitaxial CeO2 thin films with self-organized nanostructure by chemical solution method

    DEFF Research Database (Denmark)

    Yue, Zhao; Grivel, Jean-Claude

    2013-01-01

    a fluorite structure but exhibits an alternative in-plane texture with eight fold symmetry on the surface. According to phase and texture stability studies, these off-stoichiometric phases gradually transform back to fully oxidized CeO2 with a 45° rotated cube texture during storage in ambient air. Moreover......Chemical solution deposition is a versatile technique to grow oxide thin films with self-organized nanostructures. Morphology and crystallographic orientation control of CeO2 thin films grown on technical NiW substrates by a chemical solution deposition method are achieved in this work. Based......, the morphology of the CeO2 thin films is controlled by precisely regulating the film thickness and crystallization temperature. A temperature-induced transition from the commonly observed granular grain to an atomically flat surface is found in the CeO2–NiW constitution. Cross-sectional transmission electron...

  13. Selfsupported epitaxial silicon films

    International Nuclear Information System (INIS)

    Lazarovici, D.; Popescu, A.

    1975-01-01

    The methods of removing the p or p + support of an n-type epitaxial silicon layer using electrochemical etching are described. So far, only n + -n junctions have been processed. The condition of anodic dissolution for some values of the support and layer resistivity are given. By this method very thin single crystal selfsupported targets of convenient areas can be obtained for channeling - blocking experiments

  14. Comparison of Microstructural and Morphological Properties of Electrodeposited Fe-Cu Thin Films with Low and High Fe : Cu Ratio

    Directory of Open Access Journals (Sweden)

    Umut Sarac

    2013-01-01

    Full Text Available Fe-Cu films with low and high Fe : Cu ratio have been produced from the electrolytes with different Fe ion concentrations at a constant deposition potential of −1400 mV versus saturated calomel electrode (SCE by electrodeposition technique onto indium tin oxide (ITO coated conducting glass substrates. It was observed that the variation of Fe ion concentration in the electrolyte had a very strong influence on the compositional, surface morphological, and microstructural properties of the Fe-Cu films. An increase in the Fe ion concentration within the plating bath increased the Fe content, consequently Fe : Cu ratio within the films. The crystallographic structure analysis showed that the Fe-Cu films had a mixture of face-centered cubic (fcc Cu and body centered cubic (bcc α-Fe phases. The average crystallite size decreased with the Fe ion concentration. The film electrodeposited from the electrolyte with low Fe ion concentration exhibited a morphology consisting of dendritic structures. However, the film morphology changed from dendritic structure to cauliflower-like structure at high Fe ion concentration. The surface roughness and grain size were found to decrease significantly with increasing Fe ion concentration in the electrolyte. The significant differences observed in the microstructural and morphological properties caused by the change of Fe ion concentration in the electrolyte were ascribed to the change of Fe : Cu ratio within the films.

  15. Multiferroics properties in BiFeO3/CoFe2O4 heterostructures thin films deposited on (111) SrTiO3

    Science.gov (United States)

    Singh, Gulab; Singh, Manoj K.; Kumar, Aditya; Dussan, S.; Katiyar, Ram S.

    2016-05-01

    The multiferroic properties of BiFeO3-CoFe2O4 (BFO-CFO) heterostructures thin film grown on (111) SrTiO3 (STO) substrates by employing pulsed laser deposition (PLD) method, have been studied.X ray diffraction analysis reveals the presence of BFO and CFO in two separate phases. The heterostructures BFO/CFO/STO(111) thin films show well - shaped hysteresis loop with saturated magnetization and coercive field, which are much larger than pure BFO/STO thin film. The frequency dependent dielectric anomalies in BFO-CFO multilayer are attributed to the interfacial effect across the presence of CFO as a separate phase embedded in BFO matrix.

  16. Band gap and mobility of epitaxial perovskite BaSn1 -xHfxO3 thin films

    Science.gov (United States)

    Shin, Juyeon; Lim, Jinyoung; Ha, Taewoo; Kim, Young Mo; Park, Chulkwon; Yu, Jaejun; Kim, Jae Hoon; Char, Kookrin

    2018-02-01

    A wide band-gap perovskite oxide BaSn O3 is attracting much attention due to its high electron mobility and oxygen stability. On the other hand, BaHf O3 was recently reported to be an effective high-k gate oxide. Here, we investigate the band gap and mobility of solid solutions of BaS n1 -xH fxO3 (x =0 -1 ) (BSHO) as a basis to build advanced perovskite oxide heterostructures. All the films were epitaxially grown on MgO substrates using pulsed laser deposition. Density functional theory calculations confirmed that Hf substitution does not create midgap states while increasing the band gap. From x-ray diffraction and optical transmittance measurements, the lattice constants and the band-gap values are significantly modified by Hf substitution. We also measured the transport properties of n -type La-doped BSHO films [(Ba ,La ) (Sn ,Hf ) O3 ] , investigating the feasibility of modulation doping in the BaSn O3/BSHO heterostructures. The Hall measurement data revealed that, as the Hf content increases, the activation rate of the La dopant decreases and the scattering rate of the electrons sharply increases. These properties of BSHO films may be useful for applications in various heterostructures based on the BaSn O3 system.

  17. 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.

  18. Photoconductivity of transparent perovskite semiconductor BaSnO3 and SrTiO3 epitaxial thin films

    Science.gov (United States)

    Park, Jisung; Kim, Useong; Char, Kookrin

    2016-02-01

    We measured the photoconductivity of transparent semiconductor BaSnO3 and compared it with that of SrTiO3. Epitaxial BaSnO3 and SrTiO3 films were grown on MgO substrates to exclude any contribution to photoconductivity from the substrate due to its large bandgap. In spite of the same perovskite structure and similar bandgap sizes (3.1-3.2 eV), the photoconductive behaviors of the two materials are quite different in terms of their magnitude and time dependence. The photoconductivity of BaSnO3 persists for many hours after removal from light exposure, whereas the photoconductivity of SrTiO3 shows little persistent conductivity. In addition, the photoconductivity of BaSnO3 increases to a value over 25 times higher than that of SrTiO3, after 3 h of illuminations. The spectral photoconductive responses of both BaSnO3 and SrTiO3 show their highest peaks below 400 nm, suggesting that the electron-hole pair generation is the main mechanism of the photoconductivity for the both materials. The large persistent photoconductivity of BaSnO3 seems related with deep level defects with relatively large barriers for charge trapping and detrapping.

  19. Optical, ferroelectric and magnetic properties of multiferroelectric BiFeO3-(K0.5Na0.5)0.4(Sr 0.6Ba0.4)0.8Nb2O6 thin films

    KAUST Repository

    Yao, Yingbang

    2014-02-01

    Multiferroic BiFeO3-(K0.5Na0.5) 0.4(Sr0.6Ba0.4)0.8Nb 2O6 (BFO-KNSBN) trilayer thin films, were epitaxially grown on MgO(0 0 1) and SrTiO3(0 0 1) by using pulsed laser deposition (PLD). Their ferroelectric, magnetic, dielectric and optical properties were investigated. It was found that both ferroelectric polarization and dielectric constant of the films were enhanced by introducing KNSBN as a barrier layer. Meanwhile, ferromagnetism of BFO was maintained. More interestingly, a double hysteresis magnetic loop was observed in the KNSBN-BFO-KNSBN trilayer films, where exchange bias and secondary phase in the BFO layer played crucial roles. Interactions between adjacent layers were revealed by temperature-dependent Raman spectroscopic measurements. © 2013 Elsevier B.V. All rights reserved.

  20. Low-temperature liquid phase epitaxy of rare-earth-ion doped KY(WO4)2 thin layers

    NARCIS (Netherlands)

    Romanyuk, Y.E.; Utke, I.; Ehrentraut, D.; Pollnau, Markus; Garcia-Revilla, S.; Valiente, R.; Kuleshov, N.V.

    2004-01-01

    Rare-earth-ion doped KY(WO4)2 (hereafter KYW) is a promising material for novel solid-state lasers. Low laser threshold, high efficiency, high output powers, and third-order nonlinear effects have stimulated research towards miniaturized thin-film waveguide lasers and amplifiers for future photonic

  1. Liquid-phase epitaxy and optical investigation of stoichiometric KYb(WO4)2 thin layers

    NARCIS (Netherlands)

    Ehrentraut, D.; Aznar, A.; Sole, R.; Aguilo, M.; Gerner, P.; Güdel, H.U.; Pollnau, Markus

    In recent years, Yb3+ has attracted much attention as an activating ion because of its small quantum defect for laser emission from 2F5/2 to 2F7/2 at ~1.03 µm [1], which provides high efficiency and reduced heat generation. Of high practical interest is the thin-disk laser concept [2], which

  2. Synthesis and characterization of Bi{sub 1−x}Nd{sub x}FeO{sub 3} thin films deposited using a high throughput physical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Darby, M.S.B., E-mail: darbymsb@gmail.com [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom); Karpinsky, D.V. [Complexo de Laboratórios Tecnológicos, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Pokorny, J. [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom); Institute of Physics, Academy of Sciences of the Czech Republic, 182 21 Prague (Czech Republic); Guerin, S. [Ilika Technologies Limited, Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton, SO16 7NS (United Kingdom); Kholkin, A.L. [Complexo de Laboratórios Tecnológicos, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Miao, S. [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom); Hayden, B.E. [Ilika Technologies Limited, Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton, SO16 7NS (United Kingdom); Reaney, I.M. [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom)

    2013-03-01

    The high throughput synthesis of BiFeO{sub 3} and rare earth doped BiFeO{sub 3} films using a modified molecular beam epitaxy technique is reported. Optimum conditions for deposition have been established and compositionally graded Bi{sub (1−x)}Nd{sub x}FeO{sub 3} (x = 0.08 to 0.24) thin films have been fabricated on platinised silicon substrate (Si/SiO{sub 2}/TiO{sub 2}/Pt) with the aim of finding the optimum Nd dopant concentrations for enhanced piezoelectric properties. For x < 0.12, the structure and symmetry were identical to that of the R3c BiFeO{sub 3} end member. For x > 0.20, the structure and symmetry were consistent with the NdFeO{sub 3} end member (Pnma). For compositions 0.12 < x < 0.2, a gradual transition from R3c to Pnma was observed via a mixed phase region but no compositional interval could be unambiguously identified in which the intermediate PbZrO{sub 3}-like structure, reported by Karimi et al. (2009) [6], existed as a single phase. Piezoresponse force microscopy remanent hysteresis measurements of the film revealed a statistical increase in the piezoelectric response at x ≈ 0.11 within the R3c region adjacent to the mixed phase field. - Highlights: ► High throughput synthesis and characterization of BiFeO3 and Nd-doped BiFeO3 films ► The piezoelectric properties of compositionally graded bismuth ferrite are studied. ► The structure and phase assemblage of Nd-doped bismuth ferrite have been studied.

  3. Rutherford Backscattering and Channeling Studies of Al and Mg Diffusion in Iron Oxide Thin Films

    International Nuclear Information System (INIS)

    Thevuthasan, Theva; McCready, David E.; Jiang, Weilin; Mcdaniel, Emily P.; Yi, Sang I.; Chambers, Scott A.; J.L. Duggan and I.L. Morgan

    1999-01-01

    Thin films of alpha-Fe2O3(0001) (hermatite) and gamma-Fe2O3 (001) (maghemite) were epitaxially grown on Al2O3(0001) substrates, respectively, using the new molecular beam epitaxy (MBE) system at the Environmental Molecular Sciences Laboratory (EMSL). We have investigated the crystalline quality of these films using Rutherford Backscattering (RBS) and channeling experiments. Minimum yields obtained from aligned and random spectra are 2.7+-0.3% for the alpha-Fe2o3(0001) film and 14.5+-0.6% for the gamma-Fe2O3 (001) film. Al and Mg outdiffusion into the hematite and maghemite films were observed at higher temperatures. Indiffusion of Fe atoms from the film into the substrate was observed for the gamma-Fe2o3(001)/MgO(001) system. In contrast, no Fe indiffusion was observed for the sapphire substrate

  4. Control of Microstructure and Magnetic Properties of FePt Thin Films with TiN-MgO Intermediate Layer.

    Science.gov (United States)

    Dong, Kai-Feng; Jin, Fang; Mo, Wen-Qin; Song, Jun-Lei; Cheng, Wei-Ming

    2018-04-01

    The effects of TiN-MgO intermediate layer on the microstructure and magnetic properties of FePt-SiNx-C films were investigated. With doping MgO into TiN, three components were formed, including titanium dioxide, titanium nitride and titanium oxynitride. This caused the decrease of the surface energy and the increase of the interface energy, and further induced the promotion of island growth of FePt, thus the improvement of the isolation and the decrease of FePt grains. On the other hand, the decrease of surface energy and the forming of some titanium dioxide with doping MgO would accompany the deterioration of epitaxial growth and thus the deterioration of the perpendicular magnetic anisotropy of FePt films in a certain degree. By optimizing the concentration of TiN and MgO, the FePt-SiNx-C films with small grain size of 5.86±1.03 nm and good perpendicular anisotropy would be obtained.

  5. Ab initio calculations and experimental study of piezoelectric YxIn1−xN thin films deposited using reactive magnetron sputter epitaxy

    International Nuclear Information System (INIS)

    Tholander, C.; Birch, J.; Tasnádi, F.; Hultman, L.; Palisaitis, J.; Persson, P.O.Å.; Jensen, J.; Sandström, P.; Alling, B.; Žukauskaitė, A.

    2016-01-01

    By combining theoretical prediction and experimental verification we investigate the piezoelectric properties of yttrium indium nitride (Y x In 1−x N). Ab initio calculations show that the Y x In 1−x N wurtzite phase is lowest in energy among relevant alloy structures for 0≤x≤0.5. Reactive magnetron sputter epitaxy was used to prepare thin films with Y content up to x=0.51. The composition dependence of the lattice parameters observed in the grown films is in agreement with that predicted by the theoretical calculations confirming the possibility to synthesize a wurtzite solid solution. An AlN buffer layer greatly improves the crystalline quality and surface morphology of subsequently grown Y x In 1−x N films. The piezoelectric response in films with x=0.09 and x=0.14 is observed using piezoresponse force microscopy. Theoretical calculations of the piezoelectric properties predict Y x In 1−x N to have comparable piezoelectric properties to Sc x Al 1−x N.

  6. Intrinsic quantum spin Hall and anomalous Hall effects in h-Sb/Bi epitaxial growth on a ferromagnetic MnO2 thin film.

    Science.gov (United States)

    Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

    2016-06-07

    Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.

  7. Correlations between the Hall coefficient and the superconducting transport properties of oxygen-deficient YBa2Cu3O7-δ epitaxial thin films

    International Nuclear Information System (INIS)

    Jones, E.C.; Christen, D.K.; Thompson, J.R.; Feenstra, R.; Zhu, S.; Lowndes, D.H.; Phillips, J.M.; Siegal, M.P.; Budai, J.D.

    1993-01-01

    Strong correlations between the Hall coefficient R H , the transition temperature T c , and the critical current density J c were established in a series of epitaxial YBa 2 Cu 3 O 7-δ thin films as a function of oxygen deficiency δ. Steady increases in R H with δ suggest that deoxygenation reduces the density of states which, according to BCS theory, should lead to corresponding decreases in T c . In contrast, two well-known plateaus occurring at 90 K and 60 K were observed in T c vs δ. Others have ascribed these plateaus to either electronic phenomena or phase separations. We find that in the 90-K plateau, the critical current density J c (δ,H=0) decreases with δ and extrapolates toward zero at the edge of the plateau, while the relative-field dependence of J c (δ,H) and the flux-creep pinning energies are independent of δ. These observations suggest that the phase-separation scenario occurs on the 90-K plateau. However, electronic origins cannot be ruled out at present due to difficulties in determining the equilibrium superconducting properties of oxygen-deficient YBa 2 Cu 3 O 7-δ films

  8. Structural properties of Bi{sub 2−x}Mn{sub x}Se{sub 3} thin films grown via molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Babakiray, Sercan; Johnson, Trent A.; Borisov, Pavel; Holcomb, Mikel B.; Lederman, David, E-mail: david.lederman@mail.wvu.edu [Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Marcus, Matthew A. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Tarafder, Kartick [Department of Physics, BITS-Pilani Hyderabad Campus, Secunderabad, Andhra Pradesh 500078 (India)

    2015-07-28

    The effects of Mn doping on the structural properties of the topological insulator Bi{sub 2}Se{sub 3} in thin film form were studied in samples grown via molecular beam epitaxy. Extended x-ray absorption fine structure measurements, supported by density functional theory calculations, indicate that preferential incorporation occurs substitutionally in Bi sites across the entire film volume. This finding is consistent with x-ray diffraction measurements which show that the out of plane lattice constant expands while the in plane lattice constant contracts as the Mn concentration is increased. X-ray photoelectron spectroscopy indicates that the Mn valency is 2+ and that the Mn bonding is similar to that in MnSe. The expansion along the out of plane direction is most likely due to weakening of the Van der Waals interactions between adjacent Se planes. Transport measurements are consistent with this Mn{sup 2+} substitution of Bi sites if additional structural defects induced by this substitution are taken into account.

  9. Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

    KAUST Repository

    Sarath Kumar, S. R.

    2012-12-03

    A detailed study of the role of oxygen vacancies in determining the effective mass and high temperature (300–1000 K) thermoelectricproperties of La-doped epitaxial SrTiO3 thin films is presented. It is observed that at intermediate temperatures, a transition from degenerate to non-degenerate behavior is observed in the Seebeck coefficient, but not electrical conductivity, which is attributed to heterogeneous oxygen non-stoichiometry. Heikes formula is found to be invalid for the films with oxygen vacancies. By fitting the spectroscopic ellipsometry (SE) data, obtained in the range 300–2100 nm, using a Drude-Lorentz dispersion relation with two Lorentz oscillators, the electrical and optical properties of the films are extracted. Using the excellent agreement between the transport properties extracted from SE modeling and direct electrical measurements, we demonstrate that an increase in concentration of oxygen vacancies results in a simultaneous increase of both carrier concentration and electron effective mass, resulting in a higher power factor.

  10. Epitaxial growth of single-crystalline Ni46Co4Mn37In13 thin film and investigation of its magnetoresistance

    Directory of Open Access Journals (Sweden)

    Chao Jing

    2014-02-01

    Full Text Available Single-crystalline thin film of Ni46Co4Mn37In13 alloy grown on MgO(0 0 1 was prepared by Pulsed Laser Deposition (PLD method. The epitaxial growth process was monitored by in situ Reflection High Energy Electron Diffraction (RHEED. Structure measurements reveal that the single-crystalline Ni46Co4Mn37In13 film could be stabilized on MgO(0 0 1 as a face-centered-cubic (fcc structure. From the evolution of RHEED, it can be deduced from the patterns that Volmer-Weber growth mechanism (3-D dominates at the initial stage. Then, it becomes layer-by-layer growth mechanism (2-D with the increase of the film thickness. Lastly, growth mechanism converts back to 3-D when the film is thick enough. Both electrical resistance and magnetoresistance (MR were measured at various temperatures using Physical Property Measurement System (PPMS. The electrical resistance measurement indicates that the film sample does not have martensitic transformation in the measurement temperature range. However, with the temperature increasing, the film sample exhibits a transition from metallic to semiconductor-like properties. Moreover, a small negative magnetoresistance was observed at different temperature, which can be explained by the spin-dependent scattering of the conduction electrons.

  11. Effects of Nb and Sr doping on crystal structure of epitaxial BaTiO3 thin films on MgO substrates

    International Nuclear Information System (INIS)

    Kim, Yongsam; Chen, Chunhua; Saiki, Atsushi; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

    2002-01-01

    Niobium (Nb) and strontium (Sr) doped barium titanate (BT) films were deposited by radio frequency (RF) magnetron sputtering with Nb and Sr doped BT ceramic targets, respectively. The effect of Nb and Sr doping on the crystal structure of epitaxial BaTiO 3 thin films on MgO substrates was investigated. The crystal structure of the films was examined using the reciprocal space mapping measurement. All the films exhibit a cube-on-cube relation with respect to the substrates. As the amount of doped Sr increased, both of the in-plane and out-of-plane lattice constants of Sr doped BT films slowly approached the BT bulk values. On the other hand, the lattice constants of Nb doped BT films were rapidly coming close to the bulk values. These indicated that the lattices of doped BT films were relaxed as the amount of doped elements increased. In addition, Nb doping had greater influence on the relaxation of the films than Sr doping for the same content of dopant. (author)

  12. Field geometry dependence of magnetotransport in epitaxial La2/3Ca1/3MnO3 thin films

    International Nuclear Information System (INIS)

    Saldarriaga, W.; Baca, E.; Prieto, P.; Moran, O.; Grube, K.; Fuchs, D.; Schneider, R.

    2006-01-01

    In-plane and out-of-plane magnetoresistance measurements on epitaxial ∼200nm thin (001)-oriented films of high oxygen pressure DC-sputtering grown manganite La 2/3 Ca 1/3 MnO 3 were carried out. Single crystal (001)-SrTiO 3 substrates were used. The samples featured a Curie temperature T C ∼260K and a magnetic moment μ(T->0K)∼3μ B per Mn atom. Magnetocrystalline anisotropy with the easy axes lying on film plane was evidenced by recording the in-plane and out-of-plane magnetization loops at temperatures, below T C , in magnetic field strengths up to 5T. Evidence for anisotropic magnetotransport in these films was provided by electric measurements in a wide temperature range up to 6T magnetic field strengths applied both perpendicular and parallel to the film plane. In both applied magnetic field geometries, current and magnetic field were maintained perpendicular to each other. Neither low-field magnetoresistance nor large magnetoresistance hysteresis were observed on these samples, suggesting that the tensile strain imposed by the substrate in the first monolayers has partially been released. In addition, by rotating the sample 360 o around an axis parallel to film plane, in magnetic fields >=2T, a quadratic sinusoidal dependence of the magnetoresistance on the polar angle θ was observed. These results can be consistently interpreted using a generalized version of the theory of anisotropic magnetoresistance in transition-metal ferromagnets

  13. Epitaxial growth and dielectric properties of Bi sub 2 VO sub 5 sub . sub 5 thin films on TiN/Si substrates with SrTiO sub 3 buffer layers

    CERN Document Server

    Lee, H Y; Choi, B C; Jeong, J H; Joseph, M; Tabata, H; Kawai, T

    2000-01-01

    Bi sub 2 VO sub 5 sub . sub 5 (BVO) thin films were epitaxially grown on SrTiO sub 3 /TiN/Si substrates by using pulsed laser ablation. A TiN thin film was prepared at 700 .deg. C as a bottom electrode. The TiN film exhibited a high alpha axis orientation and a very smooth morphology. Before the preparation of the BVO thin film, a crystallized SrTiO sub 3 thin film was deposited as a buffer layer on TiN/Si. The BVO thin film grown at a substrate temperature at 700 .deg. C and an oxygen pressure of 50 mTorr was found to be epitaxial along the c-axis. Also, BVO films were observed to have flat surfaces and the step-flow modes. The dielectric constant of the BVO film on STO/TiN/Si was constant at about 8 approx 4 in the applied frequency range between 10 sup 2 and 10 sup 6 Hz.

  14. Local Structure of the Amorphous Precursor to Ba-Hexaferrite Thin Films: An Anisotropic Octahedral Fe-O Glass Network

    Science.gov (United States)

    Snyder, J. E.; Harris, V. G.; Koon, N. C.; Sui, X.; Kryder, M. H.

    1996-10-01

    Anisotropic local structure has been observed around both the Fe and Ba ions in the amorphous precursor to Ba-hexaferrite thin films, using polarization-dependent extended x-ray-absorption fine structure. This anisotropic local structure, consisting mainly of a network of Fe-O octahedra, determines the orientation of the fast-growing basal planes during crystallization, and thus the directions of the c axes and the resulting magnetic anisotropy.

  15. Influence of target composition and deposition temperature on the domain structure of BiFeO3 thin films

    Directory of Open Access Journals (Sweden)

    Rui Guo

    2012-12-01

    Full Text Available Domain structure of BiFeO3 thin films can be controlled by adjusting the target composition or the substrate temperature during pulsed laser deposition. Decreasing Bi content in the target or increasing substrate temperature changes the domain structure of BiFeO3 from 71° to 109°. We suggest that a combination of interface effect and defect induced internal field causes this evolution.

  16. Uniaxial anisotropy of two-magnon scattering in an ultrathin epitaxial Fe layer on GaAs

    Science.gov (United States)

    Kurebayashi, H.; Skinner, T. D.; Khazen, K.; Olejník, K.; Fang, D.; Ciccarelli, C.; Campion, R. P.; Gallagher, B. L.; Fleet, L.; Hirohata, A.; Ferguson, A. J.

    2013-02-01

    We report an on-chip, electrically detected ferromagnetic resonance study on microbars made from GaAs/Fe(1 nm)/GaAs layers. Our experiments, performed at several different microwave frequencies and static magnetic field directions, enable us to observe a strong in-plane uniaxial anisotropy of the linewidth. We attribute the linewidth anisotropy to the two magnon scattering process, supporting this by calculations of possible linewidth broadening mechanisms. Our findings are useful for designing future high-performance spintronic devices based on nanoscale magnetic structures.

  17. Synthesis and characterization of multilayered BaTiO3/NiFe2O4 thin films

    Directory of Open Access Journals (Sweden)

    Branimir Bajac

    2013-03-01

    Full Text Available Presented research was focused on the fabrication of multiferroic thin film structures, composed of ferrielectric barium titanate perovskite phase and magnetostrictive nickel ferrite spinel phase. The applicability of different, solution based, deposition techniques (film growth from solution, dip coating and spin coating for thefabrication of multilayered BaTiO3 /NiFe2O4 thin films was investigated. It was shown that only spin coating produces films of desired nanostructure, thickness and smooth and crackfree surfaces.

  18. Control of the magnetic properties of LaMnO3 epitaxial thin films grown by Pulsed Laser Deposition

    Science.gov (United States)

    Martinez, Benjamin; Roqueta, Jaume; Pomar, Alberto; Balcells, Lluis; Frontera, Carlos; Konstantinovic, Zorica; Sandiumenge, Felip; Santiso, Jose; Advanced materials characterization Team; Thin films growth Team

    2015-03-01

    LaMnO3 (LMO), the parent compound of colossal magnetoresistance based manganites has gained renewed attention as a building block in heterostructures with unexpected properties. In its bulk phase, stoichiometric LMO is an A-type antiferromagnetic (AFM) insulator (TN = 140K) with orthorhombic structure that easily accommodate an oxygen excess by generating cationic (La or Mn) vacancies. As a result, a fraction of Mn 3+ changes to Mn 4+ leading to a double-exchange mediated ferromagnetic (FM) behavior. In thin films the AFM phase has been elusive up to now and thin films with FM ordering are usually reported. In this work, we have systematically studied the growth process of LaMnO3 thin films by pulsed laser deposition on SrTiO3 (001) substrates under different oxygen partial pressures (PO2) . A close correlation between the structure (explored by XRD) and the magnetic properties (SQUID measurements) of the films with PO2 has been identified. At high PO2 FM behavior is observed. In contrast, at very low PO2, the results obtained for unit cell volume (close to stoichiometric bulk values) and magnetic moment (0.2 μB/Mn) strongly indicate antiferromagnetic ordering. We acknowledge financial support from the Spanish MINECO (MAT2012-33207).

  19. ZnO and ZnSe thin films grown by Atomic Layer Epitaxy in a gas flow system

    Science.gov (United States)

    Godlewski, Marek; Guziewicz, Elzbieta; Kopalko, Krzysztof; Lusalowska, Elzbieta

    2003-03-01

    In the presentation we will briefly review our recent works on thin films of ZnO and ZnSe for possible applications in opto-electronics. Thin films of ZnO were grown by four different methods on either semiconductor substrates or on a glass plates. The latter system was successfully used as a substrate for deposition of amorphous GaN epilayers, using low temperature plasma-assisted MOCVD technique. Properties of ALE-grown ZnO films and of GaN epilayers grown on ZnO buffer layer will be shortly analyzed. Thin films of ZnSe were grown using synthesis from Zn and Se. These films show bright white color light emission. Temperature of the emission and brightness can be optimized by either modifications in a growth procedure or variations in excitation conditions. Nature of white emission and optimization procedures will be described. This work was partly supported by grant no. PBZ-KBN-044/P03/2001 of KBN. The ALE reactor was bought using SEZAM grant of Foundation for Polish Science.

  20. Dynamic magnetization of NiZn ferrite doped FeSiAl thin films fabricated by oblique sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China); Phuoc, Nguyen N. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore); Soh, Wee Tee [Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Ong, C.K. [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 2, Singapore 117411 (Singapore); Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Li, Lezhong [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China)

    2017-06-15

    Highlights: • We prepared NiZn ferrite doped FeSiAl-based thin films using oblique deposition technique. • The magnetic properties of FeSiAl-based thin films were systematically studied. • Two ferromagnetic resonance peaks were observed in the permeability spectra. • The thermal stability of microwave properties of FeSiAl-based films was studied. • The thermal stability of properties we studied was relatively good. - Abstract: In this study, we comprehensively investigate the dynamic magnetic properties of FeSiAl-NiZnFeO thin films prepared by the oblique deposition method via a shorted microstrip perturbation technique. For the films with higher oblique angle and NiZn ferrite doping amount, there are two ferromagnetic resonance peaks observed in the permeability spectra, and both of the two peaks originate from FeSiAl. Furthermore, the magnetic anisotropy field H{sub K} of the ferromagnetic resonance peak at higher frequency is enhanced with increasing doping amount, which is interpreted in terms of the contribution of reinforced stress-induced anisotropy and shape anisotropy brought about by doping elements and oblique sputtering method. In addition, the thermal stability of the ferromagnetic resonance frequency f{sub FMR} of FeSiAl-NiZnFeO films with oblique angles of 35° and 45° with respect to temperature ranging from 300 K to 420 K is deteriorated with increasing ferrite doping amount, which is mainly ascribed to the influence of pair-ordering anisotropy and/or the reduction of the FeSiAl grain size.