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Sample records for molecular beam deposition

  1. Method of deposition by molecular beam epitaxy

    DOEpatents

    Chalmers, S.A.; Killeen, K.P.; Lear, K.L.

    1995-01-10

    A method is described for reproducibly controlling layer thickness and varying layer composition in an MBE deposition process. In particular, the present invention includes epitaxially depositing a plurality of layers of material on a substrate with a plurality of growth cycles whereby the average of the instantaneous growth rates for each growth cycle and from one growth cycle to the next remains substantially constant as a function of time. 9 figures.

  2. Method of deposition by molecular beam epitaxy

    DOEpatents

    Chalmers, Scott A.; Killeen, Kevin P.; Lear, Kevin L.

    1995-01-01

    A method is described for reproducibly controlling layer thickness and varying layer composition in an MBE deposition process. In particular, the present invention includes epitaxially depositing a plurality of layers of material on a substrate with a plurality of growth cycles whereby the average of the instantaneous growth rates for each growth cycle and from one growth cycle to the next remains substantially constant as a function of time.

  3. High mobility n-type organic thin-film transistors deposited at room temperature by supersonic molecular beam deposition

    SciTech Connect

    Chiarella, F. Barra, M.; Ciccullo, F.; Cassinese, A.; Toccoli, T.; Aversa, L.; Tatti, R.; Verucchi, R.

    2014-04-07

    In this paper, we report on the fabrication of N,N′-1H,1H-perfluorobutil dicyanoperylenediimide (PDIF-CN{sub 2}) organic thin-film transistors by Supersonic Molecular Beam Deposition. The devices exhibit mobility up to 0.2 cm{sup 2}/V s even if the substrate is kept at room temperature during the organic film growth, exceeding by three orders of magnitude the electrical performance of those grown at the same temperature by conventional Organic Molecular Beam Deposition. The possibility to get high-mobility n-type transistors avoiding thermal treatments during or after the deposition could significantly extend the number of substrates suitable to the fabrication of flexible high-performance complementary circuits by using this compound.

  4. Ion-beam assisted deposition of thin molybdenum films studied by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Robbemond, Arie; Thijsse, Barend J.

    1997-05-01

    We report results obtained by molecular dynamics simulation of low energy argon-ion assisted growth of thin molybdenum films (≈ 20 Å). The effects of a single ion impact are discussed, but more particularly we consider film growth from a manufacturing viewpoint and examine the properties of the completed films. Results for ion-beam assisted deposition are compared with those for unassisted growth (i.e. physical vapor deposition). Surface orientation, atomic displacements, surface roughness, sputtering, point defects, and the influence of off-normal atom incidence are discussed.

  5. Semiconductor-based heterostructure formation using low energy ion beams: Ion beam deposition (IBD) and combined ion and molecular beam deposition (CIMD)

    SciTech Connect

    Herbots, N.; Hellman, O.C.; Cullen, P.A.; Vancauwenberghe, O.

    1988-09-15

    In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at temperatures lower than those used in thermal processing (less than 500/sup 0/C). Presently, we have applied IBD to the growth of dense (6.4 x 10/sup 22/ atom/cm/sup 3/) silicon dioxide thin films at 400/sup 0/C. Through these experiments we have found several clues to the microscopic processes leading to the formation of thin film phases by low energy ions. Using Monte-Carlo simulations, we have found that low energy collision cascades in silicon have unique features such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of interstitials in covalent materials can be used to athermally generate atomic displacements tha can lead to ordering. These displacements can lead to epitaxial ordering at substrate temperatures below the minimum temperature necessary for molecular beam epitaxy (550/sup 0/C). It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. <850/sup 0/C). A growth model which we derive from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitaxy or compound formation at low temperatures.

  6. Importance of dewetting in organic molecular-beam deposition: Pentacene on gold

    SciTech Connect

    Beernink, G.; Strunskus, T.; Witte, G.; Woell, Ch.

    2004-07-19

    Organic molecular-beam deposition of pentacene on gold substrates has been investigated using a multitechnique approach. The morphology of the organic thin films depends strongly on the substrate temperature. Pronounced dewetting and island formation are observed at room temperature. Whereas pentacene molecules adopt a planar monolayer structure, they continue to grow in an upright orientation in multilayer films as inferred from x-ray absorption spectroscopy and atomic force microscopy. These results are in pronounced contrast to a recent scanning tunneling microscopy (STM) study by Kang and Zhu [Appl. Phys. Lett. 82, 3248 (2003)] and indicate fundamental problems in the interpretation of STM measurements for organic thin films.

  7. Preparation and Characterization of CuInSe2 Thin Films by Molecular-Beam Deposition Method

    NASA Astrophysics Data System (ADS)

    Nishitani, Mikihiko; Negami, Takayuki; Terauchi, Masaharu; Hirao, Takashi

    1992-02-01

    Polycrystalline CuInSe2 films were prepared by coevaporation of the elements under an ultrahigh vacuum by a molecular-beam deposition method. The composition of the film was controlled by changing the In molecular-beam flux intensity while the other elements remained at a constant value. It is shown, at the substrate temperature of 500°C, that there is a critical In molecular-beam flux intensity for the fabrication of stoichiometric films. At the In molecular-beam intensities higher than the critical value, single-phase CuInSe2 films with nearly constant compositions are obtained as a result of the removal effects of excess In. It is shown that the present coevaporation process is suitable for the fabrication of stoichiometric or slightly In-rich composition films. Furthermore, the structural and electrical properties of the films were investigated and discussed in relation to film composition.

  8. Rubidium beam flux dependence of film properties of Ba1 - xRbxBiO3 deposited by molecular-beam epitaxy using distilled ozone

    NASA Astrophysics Data System (ADS)

    Ogihara, M.; Toda, F.; Makita, T.; Abe, H.

    1993-10-01

    We have focused our attention on the dependence of Ba1-xRbxBiO3 (BRBO) film composition ratio and film properties on rubidium-beam-flux intensity. BRBO films were deposited on MgO(100) substrates by molecular-beam epitaxy (MBE) using distilled ozone. Systematic measurements showed that the rubidium content was nearly independent of rubidium-beam-flux intensity in a wide beam-flux range. Therefore, it can be concluded that some degree of self-control of rubidium stoichiometry is actually possible in BRBO film growth by MBE. This study also revealed that the BRBO film properties had strong dependences on rubidium-beam-flux intensity even in the range for self-control of rubudium stoichiometry. Our study also clarified that rubidium-beam flux affects the barium content in the BRBO film.

  9. Transition between wurtzite and zinc-blende GaN: An effect of deposition condition of molecular-beam epitaxy

    SciTech Connect

    Shi, B. M.; Xie, M. H.; Wu, H. S.; Wang, N.; Tong, S. Y.

    2006-10-09

    GaN exists in both wurtzite and zinc-blende phases and the growths of the two on its (0001) or (111) surfaces are achieved by choosing proper deposition conditions of molecular-beam epitaxy (MBE). At low substrate temperatures but high gallium fluxes, metastable zinc-blende GaN films are obtained, whereas at high temperatures and/or using high nitrogen fluxes, equilibrium wurtzite phase GaN epilayers resulted. This dependence of crystal structure on substrate temperature and source flux is not affected by deposition rate. Rather, the initial stage nucleation kinetics plays a primary role in determining the crystallographic structures of epitaxial GaN by MBE.

  10. Electrical performance of phase change memory cells with Ge3Sb2Te6 deposited by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Boschker, Jos E.; Boniardi, Mattia; Redaelli, Andrea; Riechert, Henning; Calarco, Raffaella

    2015-01-01

    Here, we report on the electrical characterization of phase change memory cells containing a Ge3Sb2Te6 (GST) alloy grown in its crystalline form by Molecular Beam Epitaxy (MBE). It is found that the high temperature growth on the amorphous substrate results in a polycrystalline film exhibiting a rough surface with a grain size of approximately 80-150 nm. A detailed electrical characterization has been performed, including I-V characteristic curves, programming curves, set operation performance, crystallization activation at low temperature, and resistance drift, in order to determine the material related parameters. The results indicate very good alignment of the electrical parameters with the current state-of-the-art GST, deposited by physical vapor deposition. Such alignment enables a possible employment of the MBE deposition technique for chalcogenide materials in the phase change memory technology, thus leading to future studies of as-deposited crystalline chalcogenides as integrated in electrical vehicles.

  11. Molecular beam epitaxy deposition of Gd2O3 thin films on SrTiO3 (100) substrate

    NASA Astrophysics Data System (ADS)

    Wang, Jinxing; Hao, Jinghua; Zhang, Yangyang; Wei, Hongmei; Mu, Juyi

    2016-06-01

    Gd2O3 thin films are grown on the SrTiO3 (100) substrate by molecular beam epitaxy (MBE) deposition. X-ray diffraction (XRD) analysis, conventional transmission electron microscopy (TEM) and aberration-corrected scanning transmission electron microscopy (STEM) are performed to investigate the microstructure of deposited thin films. It is found that the as-deposited thin film possesses a very uniform thickness of ∼40 nm and is composed of single cubic phase Gd2O3 grains. STEM and TEM observations reveal that Gd2O3 thin film grows epitaxially on the SrTiO3 (100) substrate with (001)Gd2O3//(100)STO and [110]Gd2O3//[001]STO orientations. Furthermore, the Gd atoms are found to diffuse into the SrTiO3 substrate for a depth of one unit cell and substitute for the Sr atoms near the interface.

  12. Ionized cluster beam deposition

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, A. R.

    1983-01-01

    Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

  13. LaAlO3/Si capacitors: Comparison of different molecular beam deposition conditions and their impact on electrical properties

    NASA Astrophysics Data System (ADS)

    Pelloquin, Sylvain; Saint-Girons, Guillaume; Baboux, Nicolas; Albertini, David; Hourani, Waël; Penuelas, Jose; Grenet, Geneviève; Plossu, Carole; Hollinger, Guy

    2013-01-01

    A study of the structural and electrical properties of amorphous LaAlO3 (LAO)/Si thin films fabricated by molecular beam deposition (MBD) is presented. Two substrate preparation procedures have been explored namely a high temperature substrate preparation technique—leading to a step and terraces surface morphology—and a chemical HF-based surface cleaning. The LAO deposition conditions were improved by introducing atomic plasma-prepared oxygen instead of classical molecular O2 in the chamber. An Au/Ni stack was used as the top electrode for its electrical characteristics. The physico-chemical properties (surface topography, thickness homogeneity, LAO/Si interface quality) and electrical performance (capacitance and current versus voltage and TunA current topography) of the samples were systematically evaluated. Deposition conditions (substrate temperature of 550 °C, oxygen partial pressure settled at 10-6 Torr, and 550 W of power applied to the O2 plasma) and post-depositions treatments were investigated to optimize the dielectric constant (κ) and leakage currents density (JGate at |VGate| = |VFB - 1|). In the best reproducible conditions, we obtained a LAO/Si layer with a dielectric constant of 16, an equivalent oxide thickness of 8.7 Å, and JGate ≈ 10-2A/cm2. This confirms the importance of LaAlO3 as an alternative high-κ for ITRS sub-22 nm technology node.

  14. Controlling field-effect mobility in pentacene-based transistors by supersonic molecular-beam deposition

    SciTech Connect

    Toccoli, T.; Pallaoro, A.; Coppede, N.; Iannotta, S.; De Angelis, F.; Mariucci, L.; Fortunato, G.

    2006-03-27

    We show that pentacene field-effect transistors, fabricated by supersonic molecular beams, have a performance strongly depending on the precursor's kinetic energy (K{sub E}). The major role played by K{sub E} is in achieving highly ordered and flat films. In the range K{sub E}{approx_equal}3.5-6.5 eV, the organic field effect transistor linear mobility increases of a factor {approx}5. The highest value (1.0 cm{sup 2} V{sup -1} s{sup -1}) corresponds to very uniform and flat films (layer-by-layer type growth). The temperature dependence of mobility for films grown at K{sub E}>6 eV recalls that of single crystals (bandlike) and shows an opposite trend for films grown at K{sub E}{<=}5.5 eV.

  15. Experimental cell for molecular beam deposition and magnetic resonance studies of matrix isolated radicals at temperatures below 1 K

    SciTech Connect

    Sheludiakov, S. Ahokas, J.; Vainio, O.; Järvinen, J.; Zvezdov, D.; Vasiliev, S.; Khmelenko, V. V.; Mao, S.; Lee, D. M.

    2014-05-15

    We present the design and performance of an experimental cell constructed for matrix isolation studies of H and D atoms in solid H{sub 2}/D{sub 2} films, which are created by molecular beam deposition at temperatures below 1 K. The sample cell allows sensitive weighing of the films by a quartz microbalance (QM) and their studies by magnetic resonance techniques in a strong magnetic field of 4.6 T. We are able to regulate the deposition rate in the range from 0.01 to 10 molecular layers/s, and measure the thickness with ≈0.2 monolayer resolution. The upper QM electrode serves as a mirror for a 128 GHz Fabry-Perot resonator connected to an electron spin resonance (ESR) spectrometer. H and D atoms were created by RF discharge in situ in the sample cell, and characterized by ESR and electron-nuclear double resonance. From the magnetic resonance measurements we conclude that the films are smooth and provide homogeneous trapping conditions for embedded atoms. The current sample cell design also makes it possible to calibrate the ESR signal and estimate the average and local concentrations of H and D radicals in the film.

  16. High temperature step-flow growth of gallium phosphide by molecular beam epitaxy and metalorganic chemical vapor deposition

    SciTech Connect

    Ratcliff, C.; Grassman, T. J.; Ringel, S. A.; Carlin, J. A.

    2011-10-03

    Post-growth surface morphologies of high-temperature homoepitaxial GaP films grown by molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) have been studied. Smooth, stepped surface morphologies of MBE-grown layers, measured by atomic force microscopy, were found for a wide range of substrate temperatures and P{sub 2}:Ga flux ratios. A MOCVD-based growth study performed under similar conditions to MBE-grown samples shows a nearly identical smooth, step-flow surface morphology, presenting a convergence of growth conditions for the two different methods. The additional understanding of GaP epitaxy gained from this study will impact its use in applications that include GaP-based device technologies, III-V metamorphic buffers, and III-V materials integration with silicon.

  17. Comparison of morphology evolution of Ge(001) homoepitaxial films grown by pulsed laser deposition and molecular-beam epitaxy

    SciTech Connect

    Shin Byungha; Leonard, John P.; McCamy, James W.; Aziz, Michael J.

    2005-10-31

    Using a dual molecular-beam epitaxy (MBE)-pulsed laser deposition (PLD) ultrahigh vacuum chamber, we have conducted the first experiments under identical thermal, background, and surface preparation conditions to compare Ge(001) homoepitaxial growth morphology in PLD and MBE. We find that in PLD with low kinetic energy and in MBE the film morphology evolves in a similar fashion: initially irregularly shaped mounds form, followed by pyramidal mounds with edges of the square-base along the <100> directions; the film roughness and mound separation increase with film thickness. In PLD with high kinetic energy, well-defined pyramidal mounds are not observed and the morphology rather resembles that of an ion-etched Ge(001) surface. The areal feature density is higher for PLD films than for MBE films grown at the same average growth rate and temperature. Furthermore, the dependence upon film thickness of roughness and feature separation differ for PLD and MBE. We attribute these differences to the higher yield of defect generation by energetic species in PLD.

  18. Optical properties of organic films, multilayers and plasmonic metal-organic waveguides fabricated by organic molecular beam deposition

    NASA Astrophysics Data System (ADS)

    Wickremasinghe, Niranjala D.

    In this thesis, the optical properties of tris (8-hydroxyquinoline) aluminum (Alq3) and 3,5,9,10-perylentetracarboxylic dianhydride (PTCDA) organic films, PTCDA/ Alq3 multilayers and plasmonic Alq3 -metal waveguides are investigated. The organic films and heterostructures used for this work were fabricated by organic molecular beam deposition (OMBD). We investigated the quenching of the light emission in Alq3 films grown on a Si substrate as a function of cw laser excitation intensity at varying temperatures from 15 to 300 K. The saturation of the singlet-singlet annihilation coefficient was measured with spectrally-integrated (SI) photoluminescence (PL) using a photodiode. The bimolecular quenching coefficient was further studied with time-resolved (TR) PL as a function of 100 fs pulse fluences. The PL quenching is attributed to the annihilation of trapped excitons at Alq3 nanocrystal grain boundaries. The saturation is explained by the limited density of available trapping states at the grain boundaries. Our interpretation is supported by structural investigations of ultrathin Alq3 films with atomic force microscopy (AFM), scanning electron microscopy (SEM) and by comparing the experimental data with calculations using a coupled rate equation model. The wavelength dispersion of the refractive indices of PTCDA and Alq 3 layers and of PTCDA/Alq3 multilayer waveguides grown on Pyrex substrates was investigated. The m-line technique, an evanescent prism coupling technique, was used to determine the layers' thickness and the in-plane (TE modes) and normal (TM modes) refractive indices. The potential for controlling the refractive index dispersion and anisotropy by tailored organic multilayer waveguides is discussed.

  19. Molecular beam epitaxy and metalorganic chemical vapor deposition growth of epitaxial CdTe on (100) GaAs/Si and (111) GaAs/Si substrates

    NASA Technical Reports Server (NTRS)

    Nouhi, A.; Radhakrishnan, G.; Katz, J.; Koliwad, K.

    1988-01-01

    Epitaxial CdTe has been grown on both (100)GaAs/Si and (111)GaAs/Si substrates. A combination of molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) has been employed for the first time to achieve this growth: the GaAs layers are grown on Si substrates by MBE and the CdTe film is subsequently deposited on GaAs/Si by MOCVD. The grown layers have been characterized by X-ray diffraction, scanning electron microscopy, and photoluminescence.

  20. Electron Beam Ablation and Deposition

    NASA Astrophysics Data System (ADS)

    Kovaleski, S. D.; Gilgenbach, R. M.; Ang, L. K.; Lau, Y. Y.

    1997-11-01

    Ablation of fused silica, titanium nitride, and boron nitride with a channel spark electron beam is being studied. The channel spark is a low energy (15-20kV), high current (1600A) electron beam source developed at KFK(G. Muller and C. Schultheiss, Proc. of Beams `94, Vol. II, p833). This is a pseudospark device which operates in the ion focused regime of electron beam transport. For this reason, a low pressure (10-15mTorr of Ar) background gas is used to provide electron beam focusing. Plume composition and excitation has been studied via optical emission spectroscopy. Ablation has also been imaged photographically. Electron density gradients and densities are being studied through laser deflection. Film deposition experiments are also being performed. Electron transport and energy deposition in metals are being simulated in the ITS-TIGER code(Sandia Report No. SAND 91-1634).

  1. Investigation of ZnO thin films deposited on ferromagnetic metallic buffer layer by molecular beam epitaxy toward realization of ZnO-based magnetic tunneling junctions

    SciTech Connect

    Belmoubarik, M.; Nozaki, T.; Sahashi, M.; Endo, H.

    2013-05-07

    Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co{sub 3}Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 Degree-Sign C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 {Omega} cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co{sub 3}Pt surface oxidation was discussed.

  2. Room temperature photoluminescence from In{sub x}Al{sub (1−x)}N films deposited by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Kong, W. Jiao, W. Y.; Kim, T. H.; Brown, A. S.; Mohanta, A.; Roberts, A. T.; Fournelle, J.; Losurdo, M.; Everitt, H. O.

    2014-09-29

    InAlN films deposited by plasma-assisted molecular beam epitaxy exhibited a lateral composition modulation characterized by 10–12 nm diameter, honeycomb-shaped, columnar domains with Al-rich cores and In-rich boundaries. To ascertain the effect of this microstructure on its optical properties, room temperature absorption and photoluminescence characteristics of In{sub x}Al{sub (1−x)}N were comparatively investigated for indium compositions ranging from x = 0.092 to 0.235, including x = 0.166 lattice matched to GaN. The Stokes shift of the emission was significantly greater than reported for films grown by metalorganic chemical vapor deposition, possibly due to the phase separation in these nanocolumnar domains. The room temperature photoluminescence also provided evidence of carrier transfer from the InAlN film to the GaN template.

  3. Ion beam deposited protective films

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.

    1981-01-01

    Sputter deposition of adherent thin films on complex geometric surfaces by ion beam sources is examined in order to evaluate three different types of protective coatings for die materials. In the first experiment, a 30 cm diameter argon ion source was used to sputter deposit adherent metallic films up to eight microns thick on H-13 steel, and a thermal fatigue test specimen sputter deposited with metallic coatings one micron thick was immersed in liquid aluminum and cooled by water for 15,000 cycles to simulate operational environments. Results show that these materials do protect the steel by reducing thermal fatigue and thereby increasing die lifetime. The second experiment generated diamond-like carbon films using a dual beam ion source system that directed an eight cm argon ion source beam at the substrates. These films are still in the process of being evaluated for crystallinity, hardness and infrared absorption. The third experiment coated a fiber glass beam shield incorporated in the eight-cm diameter mercury ion thruster with molybdenum to ensure proper electrical and thermal properties. The coating maintained its integrity even under acceleration tests.

  4. Silicon Holder For Molecular-Beam Epitaxy

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E.; Grunthaner, Paula J.; Grunthaner, Frank J.

    1993-01-01

    Simple assembly of silicon wafers holds silicon-based charge-coupled device (CCD) during postprocessing in which silicon deposited by molecular-beam epitaxy. Attains temperatures similar to CCD, so hotspots suppressed. Coefficients of thermal expansion of holder and CCD equal, so thermal stresses caused by differential thermal expansion and contraction do not develop. Holder readily fabricated, by standard silicon processing techniques, to accommodate various CCD geometries. Silicon does not contaminate CCD or molecular-beam-epitaxy vacuum chamber.

  5. Electrical performance of phase change memory cells with Ge{sub 3}Sb{sub 2}Te{sub 6} deposited by molecular beam epitaxy

    SciTech Connect

    Boschker, Jos E.; Riechert, Henning; Calarco, Raffaella; Boniardi, Mattia; Redaelli, Andrea

    2015-01-12

    Here, we report on the electrical characterization of phase change memory cells containing a Ge{sub 3}Sb{sub 2}Te{sub 6} (GST) alloy grown in its crystalline form by Molecular Beam Epitaxy (MBE). It is found that the high temperature growth on the amorphous substrate results in a polycrystalline film exhibiting a rough surface with a grain size of approximately 80–150 nm. A detailed electrical characterization has been performed, including I-V characteristic curves, programming curves, set operation performance, crystallization activation at low temperature, and resistance drift, in order to determine the material related parameters. The results indicate very good alignment of the electrical parameters with the current state-of-the-art GST, deposited by physical vapor deposition. Such alignment enables a possible employment of the MBE deposition technique for chalcogenide materials in the phase change memory technology, thus leading to future studies of as-deposited crystalline chalcogenides as integrated in electrical vehicles.

  6. Molecular-beam scattering

    SciTech Connect

    Vernon, M.F.

    1983-07-01

    The molecular-beam technique has been used in three different experimental arrangements to study a wide range of inter-atomic and molecular forces. Chapter 1 reports results of a low-energy (0.2 kcal/mole) elastic-scattering study of the He-Ar pair potential. The purpose of the study was to accurately characterize the shape of the potential in the well region, by scattering slow He atoms produced by expanding a mixture of He in N/sub 2/ from a cooled nozzle. Chapter 2 contains measurements of the vibrational predissociation spectra and product translational energy for clusters of water, benzene, and ammonia. The experiments show that most of the product energy remains in the internal molecular motions. Chapter 3 presents measurements of the reaction Na + HCl ..-->.. NaCl + H at collision energies of 5.38 and 19.4 kcal/mole. This is the first study to resolve both scattering angle and velocity for the reaction of a short lived (16 nsec) electronic excited state. Descriptions are given of computer programs written to analyze molecular-beam expansions to extract information characterizing their velocity distributions, and to calculate accurate laboratory elastic-scattering differential cross sections accounting for the finite apparatus resolution. Experimental results which attempted to determine the efficiency of optically pumping the Li(2/sup 2/P/sub 3/2/) and Na(3/sup 2/P/sub 3/2/) excited states are given. A simple three-level model for predicting the steady-state fraction of atoms in the excited state is included.

  7. Room-temperature ferromagneticlike behavior in Mn-implanted and postannealed InAs layers deposited by molecular beam epitaxy

    SciTech Connect

    Gonzalez-Arrabal, R.; Gonzalez, Y.; Gonzalez, L.; Martin-Gonzalez, M. S.; Munnik, F.

    2009-04-01

    We report on the magnetic and structural properties of Ar- and Mn-implanted InAs epitaxial films grown on GaAs (100) by molecular beam epitaxy and the effect of rapid thermal annealing (RTA) for 30 s at 750 deg. C. Channeling particle induced x-ray emission (PIXE) experiments reveal that after Mn implantation almost all Mn atoms are substitutional in the In site of the InAs lattice, like in a diluted magnetic semiconductor. All of these samples show diamagnetic behavior. However, after RTA treatment the Mn-InAs films exhibit room-temperature magnetism. According to PIXE measurements the Mn atoms are no longer substitutional. When the same set of experiments was performed with Ar as implantation ion, all of the layers present diamagnetism without exception. This indicates that the appearance of room-temperature ferromagneticlike behavior in the Mn-InAs-RTA layer is not related to lattice disorder produced during implantation but to a Mn reaction produced after a short thermal treatment. X-ray diffraction patterns and Rutherford backscattering measurements evidence the segregation of an oxygen-deficient MnO{sub 2} phase (nominally MnO{sub 1.94}) in the Mn-InAs-RTA epitaxial layers which might be the origin of the room-temperature ferromagneticlike response observed.

  8. LaAlO{sub 3}/Si capacitors: Comparison of different molecular beam deposition conditions and their impact on electrical properties

    SciTech Connect

    Pelloquin, Sylvain; Baboux, Nicolas; Albertini, David; Hourani, Waeel; Plossu, Carole; Saint-Girons, Guillaume; Penuelas, Jose; Grenet, Genevieve; Hollinger, Guy

    2013-01-21

    A study of the structural and electrical properties of amorphous LaAlO{sub 3} (LAO)/Si thin films fabricated by molecular beam deposition (MBD) is presented. Two substrate preparation procedures have been explored namely a high temperature substrate preparation technique-leading to a step and terraces surface morphology-and a chemical HF-based surface cleaning. The LAO deposition conditions were improved by introducing atomic plasma-prepared oxygen instead of classical molecular O{sub 2} in the chamber. An Au/Ni stack was used as the top electrode for its electrical characteristics. The physico-chemical properties (surface topography, thickness homogeneity, LAO/Si interface quality) and electrical performance (capacitance and current versus voltage and TunA current topography) of the samples were systematically evaluated. Deposition conditions (substrate temperature of 550 Degree-Sign C, oxygen partial pressure settled at 10{sup -6} Torr, and 550 W of power applied to the O{sub 2} plasma) and post-depositions treatments were investigated to optimize the dielectric constant ({kappa}) and leakage currents density (J{sub Gate} at Double-Vertical-Line V{sub Gate} Double-Vertical-Line = Double-Vertical-Line V{sub FB}- 1 Double-Vertical-Line ). In the best reproducible conditions, we obtained a LAO/Si layer with a dielectric constant of 16, an equivalent oxide thickness of 8.7 A, and J{sub Gate} Almost-Equal-To 10{sup -2}A/cm{sup 2}. This confirms the importance of LaAlO{sub 3} as an alternative high-{kappa} for ITRS sub-22 nm technology node.

  9. Interface characteristics of n-n and p-n Ge/SiC heterojunction diodes formed by molecular beam epitaxy deposition

    SciTech Connect

    Gammon, P. M.; Jennings, M. R.; Davis, M. C.; Roberts, G. J.; Covington, J. A.; Mawby, P. A.; Perez-Tomas, A.; Shah, V. A.; Burrows, S. E.; Wilson, N. R.; Boden, S. A.

    2010-06-15

    In this article, we report on the physical and electrical nature of Ge/SiC heterojunction layers that have been formed by molecular beam epitaxy (MBE) deposition. Using x-ray diffraction, atomic force microscopy, and helium ion microscopy, we perform a thorough analysis of how MBE growth conditions affect the Ge layers. We observe the layers developing from independent islands at thicknesses of 100 nm to flat surfaces at 300 nm. The crystallinity and surface quality of the layer is shown to be affected by the deposition parameters and, using a high temperature deposition and a light dopant species, the layers produced have large polycrystals and hence a low resistance. The p-type and n-type layers, 300 nm thick are formed into Ge/SiC heterojunction mesa diodes and these are characterized electrically. The polycrystalline diodes display near ideal diode characteristics (n<1.05), low on resistance and good reverse characteristics. Current-voltage (I-V) measurements at varying temperature prove that all the layers have two-dimensional fluctuations in the Schottky barrier height (SBH) due to inhomogeneities at the heterojunction interface. Capacitance-voltage analysis and the SBH size extracted from I-V analysis suggest strongly that interface states are present at the surface causing Fermi-level pinning throughout the bands. A simple model is used to quantify the concentration of interface states at the surface.

  10. Strong affinity of hydrogen for the GaN(000-1) surface: Implications for molecular beam epitaxy and metalorganic chemical vapor deposition

    SciTech Connect

    Northrup, J.E.; Neugebauer, J.

    2004-10-18

    The stabilities of clean and hydrogen covered GaN(000-1) surfaces are determined using density functional theory together with a finite temperature thermodynamics approach. Hydrogen has an extremely high affinity for the N-face surface: Even under ultrahigh vacuum conditions as realized in molecular beam epitaxial growth, with a residual hydrogen pressure of 10{sup -12} atm, the hydrogen terminated surface is, for very N-rich conditions, more stable than any clean surface. A transition to a surface covered by a Ga adlayer is predicted to occur as the Ga chemical potential increases. In typical metalorganic chemical vapor deposition conditions the (000-1) surface is predicted to be covered by 0.75 monolayers of hydrogen. The slower growth rate on the (000-1) surface in comparison to the (0001) surface is attributed to low adsorption of N on the H-covered (000-1) surface.

  11. Molecular beam deposition of Dy sub 1 Ba sub 2 Cu sub 3 O sub 7 minus. delta. (001) high-temperature superconductor thin films

    SciTech Connect

    Bae, J.; Seshadri, P.; Choudhary, K.M. )

    1992-03-01

    Epitaxial Dy{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}(001) high-temperature superconductor thin films on LaAlO{sub 3} substrates have been prepared by coevaporation of Dy, BaF{sub 2}, and Cu and postannealing. The vapors in desired ratio were evaporated from effusion cells in a miniature molecular beam deposition system. The films show critical transition temperature ({ital T}{sub {ital c},0}) of 89.5{plus minus}0.5 K. During process development it was found that single phase Dy{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y}(001) thin films can be grown ({ital x}=0 to 0.3). Their electrical properties were useful in calibration of quartz crystal thin film thickness monitor (FTM) for determination of relationships between the actual vapor arrival rate (flux) and FTM reading.

  12. Growth of 3C-SiC( 1 0 0 ) thin films on Si( 1 0 0 ) by the molecular ion beam deposition

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takashi; Kiuchi, Masato; Sugimoto, Satoshi; Goto, Seiichi

    2001-11-01

    Silicon carbide (SiC) thin films were produced on Si(1 0 0) at low growth temperatures of 750-1000°C, using the molecular ion beam deposition (IBD) technique with a precursor of organosilicon ions. The ions extracted at 25 keV were mass selected, and decelerated to 100 eV. The precursor of methylsilicenium ions (SiCH 3+), which has a Si-C bond in the molecular structure, was generated from dimethylsilane (SiH 2(CH 3) 2). The energy distribution of SiCH 3+ ions was measured by a PPM421 plasma process monitor. It was confirmed that the energy distributions were 100±1 eV. The chemical bondings and surface structures of SiC thin films were analyzed by Raman spectroscopy and reflection high-energy electron diffraction (RHEED). In the Raman spectrum, a peak at 796 cm -1 was assigned to transverse optic phonon scattering in 3C-SiC. As a result of the analysis of RHEED patterns, 3C-SiC(1 0 0) were formed on Si(1 0 0) substrates. Using the molecular IBD technique with the precursor of methylsilicenium ions, the formation of SiC thin films is available on Si(1 0 0) at low temperature (750°C).

  13. Delayed Shutters For Dual-Beam Molecular Epitaxy

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J.; Liu, John L.; Hancock, Bruce

    1989-01-01

    System of shutters for dual-molecular-beam epitaxy apparatus delays start of one beam with respect to another. Used in pulsed-beam equipment for deposition of low-dislocation layers of InAs on GaAs substrates, system delays application of arsenic beam with respect to indium beam to assure proper stoichiometric proportions on newly forming InAs surface. Reflectance high-energy electron diffraction (RHEED) instrument used to monitor condition of evolving surface of deposit. RHEED signal used to time pulsing of molecular beams in way that minimizes density of defects and holds lattice constant of InAs to that of GaAs substrate.

  14. Photoelectron photoion molecular beam spectroscopy

    SciTech Connect

    Trevor, D.J.

    1980-12-01

    The use of supersonic molecular beams in photoionization mass spectroscopy and photoelectron spectroscopy to assist in the understanding of photoexcitation in the vacuum ultraviolet is described. Rotational relaxation and condensation due to supersonic expansion were shown to offer new possibilities for molecular photoionization studies. Molecular beam photoionization mass spectroscopy has been extended above 21 eV photon energy by the use of Stanford Synchrotron Radiation Laboratory (SSRL) facilities. Design considerations are discussed that have advanced the state-of-the-art in high resolution vuv photoelectron spectroscopy. To extend gas-phase studies to 160 eV photon energy, a windowless vuv-xuv beam line design is proposed.

  15. Optical and structural properties of microcrystalline GaN on an amorphous substrate prepared by a combination of molecular beam epitaxy and metal–organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Min, Jung-Wook; Hwang, Hyeong-Yong; Kang, Eun-Kyu; Park, Kwangwook; Kim, Ci-Hyun; Lee, Dong-Seon; Jho, Young-Dahl; Bae, Si-Young; Lee, Yong-Tak

    2016-05-01

    Microscale platelet-shaped GaN grains were grown on amorphous substrates by a combined epitaxial growth method of molecular beam epitaxy (MBE) and metal–organic chemical vapor deposition (MOCVD). First, MBE GaN was grown on an amorphous substrate as a pre-orienting layer and its structural properties were investigated. Second, MOCVD grown GaN samples using the different growth techniques of planar and selective area growth (SAG) were comparatively investigated by transmission electron microscopy (TEM), cathodoluminescence (CL), and photoluminescence (PL). In MOCVD planar GaN, strong bound exciton peaks dominated despite the high density of the threading dislocations (TDs). In MOCVD SAG GaN, on the other hand, TDs were clearly reduced with bending, but basal stacking fault (BSF) PL peaks were observed at 3.42 eV. The combined epitaxial method not only provides a deep understanding of the growth behavior but also suggests an alternative approach for the growth of GaN on amorphous substances.

  16. Laser annealing of laser assisted molecular beam deposited ZnO thin films with application to metal-semiconductor-metal photodetectors

    SciTech Connect

    Li Meiya; Anderson, Wayne; Chokshi, Nehal; De Leon, Robert L.; Tompa, Gary

    2006-09-01

    We report on the effect of postdeposition laser annealing of undoped zinc oxide (ZnO) thin films grown by laser assisted molecular beam deposition. Hall-effect measurements show that some undoped ZnO films change from n type with mobility values in the range of 200 cm{sup 2} V{sup -1} s{sup -1} to p-type material with mobility value of 73 cm{sup 2} V{sup -1} s{sup -1}, after laser annealing. The photoconductive behavior was clearly seen on the laser-annealed samples, with values of 0.28 m{omega}{sup -1}. The structural and optical properties of the films were improved with laser annealing as shown by scanning electron microscopy, x-ray photoelectron spectroscopy analysis, and photoluminescence measurement. All of the nonlaser and laser annealed samples showed near-band emission at {approx}3.3 eV. Metal-semiconductor-metal photodetectors were fabricated from the films.

  17. Characterization of high-κ LaLuO3 thin film grown on AlGaN/GaN heterostructure by molecular beam deposition

    NASA Astrophysics Data System (ADS)

    Yang, Shu; Huang, Sen; Chen, Hongwei; Schnee, Michael; Zhao, Qing-Tai; Schubert, Jürgen; Chen, Kevin J.

    2011-10-01

    We report the study of high-dielectric-constant (high-κ) dielectric LaLuO3 (LLO) thin film that is grown on AlGaN/GaN heterostructure by molecular beam deposition (MBD). The physical properties of LLO on AlGaN/GaN heterostrucure have been investigated with atomic force microscopy, x-ray photoelectron spectroscopy, and TEM. It is revealed that the MBD-grown 16 nm-thick LLO film is polycrystalline with a thin (˜2 nm) amorphous transition layer at the LLO/GaN interface. The bandgap of LLO is derived as 5.3 ± 0.04 eV from O1s energy loss spectrum. Capacitance-voltage (C-V) characteristics of a Ni-Au/LLO/III-nitride metal-insulator-semiconductor diode exhibit small frequency dispersion (<2%) and reveal a high effective dielectric constant of ˜28 for the LLO film. The LLO layer is shown to be effective in suppressing the reverse and forward leakage current in the MIS diode. In particular, the MIS diode forward current is reduced by 7 orders of magnitude at a forward bias of 1 V compared to a conventional Ni-Au/III-nitride Schottky diode.

  18. A photoluminescence comparison of CdTe thin films grown by molecular-beam epitaxy, metalorganic chemical vapor deposition, and sputtering in ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Feng, Z. C.; Bevan, M. J.; Krishnaswamy, S. V.; Choyke, W. J.

    1988-09-01

    High perfection CdTe thin films have been grown on (001) InSb and CdTe substrates by molecular-beam epitaxy, metalorganic chemical vapor deposition (MOCVD), and sputtering in ultrahigh vacuum techniques. The quality of the as-grown CdTe films are characterized by 2-K photoluminescence. The spectra show strong and sharp exciton transitions and weak 1.40-1.50-eV defect-related bands. Radiative defect densities of lower than 0.002 are realized. High-resolution spectroscopy shows that the full width at half maximum of the principal bound exciton lines is about 0.1 meV. Such small ρ values and narrow photoluminescence lines have not been previously reported. The largest luminescence efficiency is observed for MOCVD-CdTe films grown on CdTe substrates. A variety of impurities appear to be responsible for the observed radiative transitions in these three kinds of CdTe films. We attempt to assign the observed impurity related lines by a comparison with ``known'' impurities in bulk CdTe spectra given in the literature.

  19. Core and grain boundary sensitivity of tungsten-oxide sensor devices by molecular beam assisted particle deposition

    NASA Astrophysics Data System (ADS)

    Huelser, T. P.; Lorke, A.; Ifeacho, P.; Wiggers, H.; Schulz, C.

    2007-12-01

    In this study, we investigate the synthesis of WO3 and WOx (2.6≥x≤2.8) by adding different concentrations of tungsten hexafluoride (WF6) into a H2/O2/Ar premixed flame within a low-pressure reactor equipped with a particle-mass spectrometer (PMS). The PMS results show that mean particle diameters dp between 5 and 9 nm of the as-synthesized metal-oxides can be obtained by varying the residence time and precursor concentration in the reactor. This result is further validated by N2 adsorption measurements on the particle surface, which yielded a 91 m2/g surface area, corresponding to a spherical particle diameter of 9 nm (Brunauer-Emmett-Teller technique). H2/O2 ratios of 1.6 and 0.63 are selected to influence the stoichiometry of the powders, resulting in blue-colored WOx and white WO3 respectively. X-ray diffraction (XRD) analysis of the as-synthesized materials indicates that the powders are mostly amorphous, and the observed broad reflexes can be attributed to the orthorhombic structure of β-WO3. Thermal annealing at 973 K for 3 h in air resulted in crystalline WO3 comprised of both monoclinic and orthorhombic phases. The transmission electron microscope micrograph analysis shows that the particles exhibit spherical morphology with some degree of agglomeration. Impedance spectroscopy is used for the electrical characterization of tungsten-oxide thin films with a thickness of 50 nm. Furthermore, the temperature-dependent gas-sensing properties of the material deposited on interdigital capacitors are investigated. Sensitivity experiments reveal two contributions to the overall sensitivity, which result from the surface and the core of each particle.

  20. Ion beam sputter deposited diamond like films

    NASA Technical Reports Server (NTRS)

    Banks, B. A.; Rutledge, S. K.

    1982-01-01

    A single argon ion beam source was used to sputter deposit carbon films on fused silica, copper, and tantalum substrates under conditions of sputter deposition alone and sputter deposition combined with simultaneous argon ion bombardment. Simultaneously deposited and ion bombarded carbon films were prepared under conditions of carbon atom removal to arrival ratios of 0, 0.036, and 0.71. Deposition and etch rates were measured for films on fused silica substrates. Resulting characteristics of the deposited films are: electrical resistivity of densities of 2.1 gm/cu cm for sputter deposited films and 2.2 gm/cu cm for simultaneously sputter deposited and Ar ion bombarded films. For films approximately 1700 A thick deposited by either process and at 5550 A wavelength light the reflectance was 0.2, the absorptance was 0.7, the absorption coefficient was 67,000 cm to the -1 and the transmittance was 0.1.

  1. Molecular Models for DSMC Simulations of Metal Vapor Deposition

    SciTech Connect

    Venkattraman, A.; Alexeenko, A. A.

    2011-05-20

    The direct simulation Monte Carlo (DSMC) method is applied here to model the electron-beam (e-beam) physical vapor deposition of copper thin films. A suitable molecular model for copper-copper interactions have been determined based on comparisons with experiments for a 2D slit source. The model for atomic copper vapor is then used in axi-symmetric DSMC simulations for analysis of a typical e-beam metal deposition system with a cup crucible. The dimensional and non-dimensional mass fluxes obtained are compared for two different deposition configurations with non-uniformity as high as 40% predicted from the simulations.

  2. Microfabricated cantilever-based detector for molecular beam experiments

    NASA Astrophysics Data System (ADS)

    Bachels, T.; Schäfer, R.

    1998-11-01

    A low cost detector for particles in molecular beam experiments is presented which can easily be mounted in a molecular beam apparatus. The detector is based on microfabricated cantilevers, which can be employed either as single sensors or as sensor arrays. The single cantilever technique has been used to measure the absolute number of atoms coming out of a pulsed laser vaporization cluster source. The particles are detected by the shift of the thermally excited resonance frequency of the cantilever due to the cluster deposition. We have determined with the single cantilever the ratio of neutral to ionized clusters and we have investigated the cluster generation at different source conditions. In addition to this, a microfabricated cantilever array has been used to measure molecular beam profiles, which opens new possibilities for molecular beam deflection experiments.

  3. Ion beam sputter deposited zinc telluride films

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.

    1986-01-01

    Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter deposition are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq cm resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x 10 to the -6th/ohm cm for 300 angstrom film to 2.56 x 10 to the -1/ohm cm for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

  4. 14th international symposium on molecular beams

    SciTech Connect

    Not Available

    1992-09-01

    This report discusses research being conducted with molecular beams. The general topic areas are as follows: Clusters I; reaction dynamics; atomic and molecular spectroscopy; clusters II; new techniques; photodissociation & dynamics; and surfaces.

  5. 14th international symposium on molecular beams

    SciTech Connect

    Not Available

    1992-01-01

    This report discusses research being conducted with molecular beams. The general topic areas are as follows: Clusters I; reaction dynamics; atomic and molecular spectroscopy; clusters II; new techniques; photodissociation dynamics; and surfaces.

  6. Ion beam sputter deposited zinc telluride films

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.

    1985-01-01

    Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter depoairion are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq. cm. resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x to to the -6/ohm. cm. for 300 angstrom film to 2.56 x 10 to the -1/ohm. cm. for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

  7. Ion beam sputter etching and deposition of fluoropolymers

    NASA Technical Reports Server (NTRS)

    Banks, B. A.; Sovey, J. S.; Miller, T. B.; Crandall, K. S.

    1978-01-01

    Fluoropolymer etching and deposition techniques including thermal evaporation, RF sputtering, plasma polymerization, and ion beam sputtering are reviewed. Etching and deposition mechanisms and material characteristics are discussed. Ion beam sputter etch rates for polytetrafluoroethylene (PTFE) were determined as a function of ion energy, current density and ion beam power density. Peel strengths were measured for epoxy bonds to various ion beam sputtered fluoropolymers. Coefficients of static and dynamic friction were measured for fluoropolymers deposited from ion bombarded PTFE.

  8. Ion beam sputter etching and deposition of fluoropolymers

    NASA Technical Reports Server (NTRS)

    Banks, B. A.; Sovey, J. S.; Miller, T. B.; Crandall, K. S.

    1978-01-01

    Fluoropolymer etching and deposition techniques including thermal evaporation, RF sputtering, plasma polymerization, and ion beam sputtering are reviewed. Etching and deposition mechanism and material characteristics are discussed. Ion beam sputter etch rates for polytetrafluoroethylene (PTFE) were determined as a function of ion energy, current density and ion beam power density. Peel strengths were measured for epoxy bonds to various ion beam sputtered fluoropolymers. Coefficients of static and dynamic friction were measured for fluoropolymers deposited from ion bombarded PTFE.

  9. Investigation on the electrical transport properties of highly (00l)-textured Sb{sub 2}Te{sub 3} films deposited by molecular beam epitaxy

    SciTech Connect

    Zhang, Xiangpeng; Zeng, Zhigang E-mail: zhiyuhu@shu.edu.cn; Shen, Chao; Wang, Zhichong; Lin, Cong; Zhang, Ziqiang; Hu, Zhiyu E-mail: zhiyuhu@shu.edu.cn

    2014-01-14

    Highly (00l)-textured antimony telluride films were fabricated using molecular beam epitaxy (MBE) on Si (111) substrate at 280 °C. X-ray diffraction analysis implying the samples have good crystalline quality, simultaneously, the grain sizes coarsening with increasing thickness. The results of Hall coefficient measurement demonstrated that the carrier concentration and mobility are strongly affected by grain boundaries and microcrystalline internal defects. It was found that the grain boundaries play a primary factor influencing the carrier concentration in thinner film. At room temperature, the results in a maximum mobility value of 305 cm{sup 2}/Vs for 121-nm-thick film, and the electrical conductivity increased from 425.7 S/cm to 1036 S/cm as the thickness varied from 28 nm to 121 nm. In the range of room temperature to 150 °C, the resistivity almost linearly increased with increasing temperature. This may be explained by low concentration of impurities or defects and shallow impurity band. For difference thickness films, temperature coefficients of resistivity are substantially equal, and the values are about 3 ∼ 4 μΩ⋅cm/K.

  10. Dual ion beam assisted deposition of biaxially textured template layers

    DOEpatents

    Groves, James R.; Arendt, Paul N.; Hammond, Robert H.

    2005-05-31

    The present invention is directed towards a process and apparatus for epitaxial deposition of a material, e.g., a layer of MgO, onto a substrate such as a flexible metal substrate, using dual ion beams for the ion beam assisted deposition whereby thick layers can be deposited without degradation of the desired properties by the material. The ability to deposit thicker layers without loss of properties provides a significantly broader deposition window for the process.

  11. An Introduction to the Supersonic Molecular Beam Injection

    NASA Astrophysics Data System (ADS)

    Wang, En-yao

    2001-04-01

    Recently a new fuelling method with supersonic molecular beam injection (MBI) has been developed and used in the tokamaks experiments successfully. It is economical to develop and maintain. The advantages of supersonic MBI compared with the conventional of gas-puffing method are as follows: Deep deposition of fuel, better fuelling efficiency, reduced recycling and pure plasma. Particle and energy confinement can be improved and density limit extended. This review described the Laval nozzle molecular beam and a simple collective model for the injection of a supersonic MBI into the tokamak plasma.

  12. Focused electron beam induced deposition of pure SIO II

    NASA Astrophysics Data System (ADS)

    Perentes, Alexandre; Hoffmann, Patrik; Munnik, Frans

    2007-02-01

    Focused electron beam induced processing (FEBID) equipments are the "all in one" tools for high resolution investigation, and modification of nano-devices. Focused electron beam induced deposition from a gaseous precursor usually results in a nano-composite sub-structured material, in which the interesting material is embedded in an amorphous carbonaceous matrix. Using the Hydrogen free tetraisocyanatosilane Si(NCO) 4 molecule as Si source, we show how a controlled oxygen flux, simultaneously injected with the precursor vapors, causes contaminants to vanish from the FEB deposits obtained and leads to the deposition of pure SiO II. The chemical composition of the FEBID material could be controlled from SiC IINO 3 to SiO II, the latter containing undetectable foreign element contamination. The [O II] / [TICS] ratio needed to obtain SiO II in our FEB deposition equipment is larger than 300. The evolution of the FEBID material chemical composition is presented as function of the [O II] / [TICS] molecular flux ratios. A hypothetical decomposition pathway of this silane under these conditions is discussed based on the different species formed under electron bombardment of TICS. Transmission electron microscopy investigations demonstrated that the deposited oxide is smooth (roughness sub 2nm) and amorphous. Infrared spectroscopy confirmed the low concentration of hydroxyl groups. The Hydrogen content of the deposited oxide, measured by elastic recoil detection analysis, is as low as 1 at%. 193nm wavelength AIMS investigations of 125nm thick SiO II pads (obtained with [O II] / [TICS] = 325) showed an undetectable light absorption.

  13. Molecular beams: our legacy from Otto Stern

    NASA Astrophysics Data System (ADS)

    Ramsey, N. F.

    1988-06-01

    It is an honor to contribute to this celebration of the hundredth anniversary of the birth of Otto Stern, who developed molecular beams to become one of the most nowerful and fruitful physics research methods.

  14. Focused electron beam induced deposition: A perspective

    PubMed Central

    Porrati, Fabrizio; Schwalb, Christian; Winhold, Marcel; Sachser, Roland; Dukic, Maja; Adams, Jonathan; Fantner, Georg

    2012-01-01

    Summary Background: Focused electron beam induced deposition (FEBID) is a direct-writing technique with nanometer resolution, which has received strongly increasing attention within the last decade. In FEBID a precursor previously adsorbed on a substrate surface is dissociated in the focus of an electron beam. After 20 years of continuous development FEBID has reached a stage at which this technique is now particularly attractive for several areas in both, basic and applied research. The present topical review addresses selected examples that highlight this development in the areas of charge-transport regimes in nanogranular metals close to an insulator-to-metal transition, the use of these materials for strain- and magnetic-field sensing, and the prospect of extending FEBID to multicomponent systems, such as binary alloys and intermetallic compounds with cooperative ground states. Results: After a brief introduction to the technique, recent work concerning FEBID of Pt–Si alloys and (hard-magnetic) Co–Pt intermetallic compounds on the nanometer scale is reviewed. The growth process in the presence of two precursors, whose flux is independently controlled, is analyzed within a continuum model of FEBID that employs rate equations. Predictions are made for the tunability of the composition of the Co–Pt system by simply changing the dwell time of the electron beam during the writing process. The charge-transport regimes of nanogranular metals are reviewed next with a focus on recent theoretical advancements in the field. As a case study the transport properties of Pt–C nanogranular FEBID structures are discussed. It is shown that by means of a post-growth electron-irradiation treatment the electronic intergrain-coupling strength can be continuously tuned over a wide range. This provides unique access to the transport properties of this material close to the insulator-to-metal transition. In the last part of the review, recent developments in mechanical strain

  15. Electron beam deposition for nanofabrication: Insights from surface science

    NASA Astrophysics Data System (ADS)

    Wnuk, J. D.; Rosenberg, S. G.; Gorham, J. M.; van Dorp, W. F.; Hagen, C. W.; Fairbrother, D. H.

    2011-02-01

    Electron beam induced deposition (EBID) is a direct-write lithographic technique that utilizes the dissociation of volatile precursors by a focused electron beam in a low vacuum environment to create nanostructures. Notable advantages of EBID over competing lithographic techniques are that it is a single step process that allows three-dimensional free-standing structures to be created, including features with single-nanometer scale dimensions. However, despite the inherent advantages of EBID, scientific and technological issues are impeding its development as an industrial nanofabrication tool. Perhaps the greatest single limitation of EBID is that metal-containing nanostructures deposited from organometallic precursors typically possess unacceptable levels of organic contamination which adversely affects the material's properties. In addition to the issue of purity, there is also a lack of understanding and quantitative information on the fundamental surface reactions and reaction cross-sections that are responsible for EBID. In this prospective, we describe how surface analytical techniques have begun to provide mechanistic and kinetic insights into the molecular level processes associated with EBID. This has been achieved by observing the effect of electron irradiation on nanometer thick films of organometallic precursors adsorbed onto solid substrates at low temperatures (< 200 K) under ultra-high vacuum conditions. Experimental observations include probing changes in surface composition, metal oxidation state, and the evolution of volatile species. Insights into surface reactions associated with purification strategies are also detailed. We also discuss unresolved scientific challenges and opportunities for future EBID research.

  16. Comparison of electrical properties and deep traps in p-Al{sub x}Ga{sub 1-x}N grown by molecular beam epitaxy and metal organic chemical vapor deposition

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Kozhukhova, E. A.; Dabiran, A. M.; Chow, P. P.; Wowchak, A. M.; Lee, In-Hwan; Ju, Jin-Woo; Pearton, S. J.

    2009-10-01

    The electrical properties, admittance spectra, microcathodoluminescence, and deep trap spectra of p-AlGaN films with an Al mole fraction up to 45% grown by both metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were compared. The ionization energy of Mg increases from 0.15 to 0.17 eV in p-GaN to 0.3 eV in 45% Al p-AlGaN. In p-GaN films grown by MBE and MOCVD and in MOCVD grown p-AlGaN, we observed additional acceptors with a concentration an order lower than that of Mg acceptors, with a higher hole capture cross section and an ionization energy close to that of Mg. For some of the MBE grown p-AlGaN, we also detected the presence of additional acceptor centers, but in that case the centers were located near the p-AlGaN layer interface with the semi-insulating AlGaN buffer and showed activation energies considerably lower than those of Mg.

  17. Multi-purpose InGaAsP buried heterostructure laser diodes for uncooled digital, analog, and wireless applications grown by molecular beam epitaxy and metal-organic chemical-vapor deposition

    NASA Astrophysics Data System (ADS)

    Pickrell, G. W.; Zhang, H. L.; Ren, H. W.; Zhang, D.; Xue, Q.; Um, J.; Lin, H. C.; Anselm, K. A.; Makino, T.; Hwang, W. Y.

    2009-02-01

    Using a combination of molecular beam epitaxy (MBE) and metal-organic, chemical-vapor deposition (MOCVD), highperformance, buried-heterostructure, distributed feedback (DFB), laser diodes are being manufactured for multiple, uncooled (-20 to 85 °C and -40 to 95 °C) product lines. MBE is used to grow the active regions and the p-type cladding layers, while MOCVD is used for the Fe-doped blocking layers. Multi-wafer growths are used to reduce device costs. Devices, employing the same basic active region design, have been fabricated operating at wavelengths from 1490 to 1610 nm for applications including coarse wavelength division multiplexing (CWDM) OC-48 digital, analog return path, and 2.2 GHz (3G) wireless code division multiple access (W-CDMA). These devices show good linearity (analog return path and wireless) and high-speed operation (digital). Accelerated lifetime testing of these devices shows excellent reliability with a median lifetime of 17 years at 90 °C.

  18. High-permitivity cerium oxide prepared by molecular beam deposition as gate dielectric and passivation layer and applied to AlGaN/GaN power high electron mobility transistor devices

    NASA Astrophysics Data System (ADS)

    Chiu, Yu Sheng; Liao, Jen Ting; Lin, Yueh Chin; Chien Liu, Shin; Lin, Tai Ming; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

    2016-05-01

    High-κ cerium oxide (CeO2) was applied to AlGaN/GaN high-electron-mobility transistors (HEMTs) as a gate insulator and a passivation layer by molecular beam deposition (MBD) for high-power applications. From capacitance–voltage (C–V) measurement results, the dielectric constant of the CeO2 film was 25.2. The C–V curves showed clear accumulation and depletion behaviors with a small hysteresis (20 mV). Moreover, the interface trap density (D it) was calculated to be 5.5 × 1011 eV‑1 cm‑2 at 150 °C. A CeO2 MOS-HEMT was fabricated and demonstrated a low subthreshold swing (SS) of 87 mV/decade, a high ON/OFF drain current ratio (I ON/I OFF) of 1.14 × 109, and a low gate leakage current density (J leakage) of 2.85 × 10‑9 A cm‑2 with an improved dynamic ON-resistance (R ON), which is about one order of magnitude lower than that of a conventional HEMT.

  19. Patterned electrochemical deposition of copper using an electron beam

    SciTech Connect

    Heijer, Mark den; Shao, Ingrid; Reuter, Mark C.; Ross, Frances M.; Radisic, Alex

    2014-02-01

    We describe a technique for patterning clusters of metal using electrochemical deposition. By operating an electrochemical cell in the transmission electron microscope, we deposit Cu on Au under potentiostatic conditions. For acidified copper sulphate electrolytes, nucleation occurs uniformly over the electrode. However, when chloride ions are added there is a range of applied potentials over which nucleation occurs only in areas irradiated by the electron beam. By scanning the beam we control nucleation to form patterns of deposited copper. We discuss the mechanism for this effect in terms of electron beam-induced reactions with copper chloride, and consider possible applications.

  20. Molecular-beam spectroscopy of interhalogen molecules

    SciTech Connect

    Sherrow, S.A.

    1983-08-01

    A molecular-beam electric-resonance spectrometer employing a supersonic nozzle source has been used to obtain hyperfine spectra of /sup 79/Br/sup 35/Cl. Analyses of these spectra and of microwave spectra published by other authors have yielded new values for the electric dipole moment and for the nuclear quadrupole coupling constants in this molecule. The new constants are significantly different from the currently accepted values. Van der Waals clusters containing chlorine monofluoride have been studied under various expansion conditions by the molecular-beam electric-deflection method. The structural possibilities indicated by the results are discussed, and cluster geometries are proposed.

  1. Molecular beam mass spectrometer development

    NASA Technical Reports Server (NTRS)

    Brock, F. J.; Hueser, J. E.

    1976-01-01

    An analytical model, based on the kinetics theory of a drifting Maxwellian gas is used to determine the nonequilibrium molecular density distribution within a hemispherical shell open aft with its axis parallel to its velocity. The concept of a molecular shield in terrestrial orbit above 200 km is also analyzed using the kinetic theory of a drifting Maxwellian gas. Data are presented for the components of the gas density within the shield due to the free stream atmosphere, outgassing from the shield and enclosed experiments, and atmospheric gas scattered off a shield orbiter system. A description is given of a FORTRAN program for computating the three dimensional transition flow regime past the space shuttle orbiter that employs the Monte Carlo simulation method to model real flow by some thousands of simulated molecules.

  2. MCNPX benchmark of in-beam proton energy deposition

    SciTech Connect

    Corzine, K.; Ferguson, P.; Morgan, G.; Quintana, D.; Waters, L.; Cooper, R.; Liljestrand, R.; Whiteson, A.

    2000-07-01

    The MCNPX code is being used to calculate energy deposition in the accelerator production of tritium (APT) target/blanket system components. To ensure that these components are properly designed, the code must be validated. An energy deposition experiment was designed to aid in the code validation using thermocouple sensors in-beam and thermistor-type sensors in decoupler- and blanketlike regions. This paper focuses on the in-beam thermocouple sensors.

  3. An autoneutralizing neutral molecular beam gun

    SciTech Connect

    Delmore, J.E.; Appelhans, A.D.; Dahl, D.A. )

    1990-01-01

    A high-energy (up to 28 keV) neutral molecular beam gun has been developed and put into routine use that takes advantage of the autoneutralization properties of the sulfur hexafluoride anion for the production of high-energy sulfur hexafluoride neutral molecules. The anions are produced in an electron-capture source, accelerated, and focused in a lens assembly designed to minimize residence time, allowed to drift at their terminal velocity for a suitable distance during which up to 30% auto-eject an electron, and all remaining charged particles are electrostatically skimmed, resulting in a focused neutral beam. Rasterable neutral beams focused to a 5-mm spot size up to 3 m from the source have been produced with beam currents up to 40 pA equivalent. Spot sizes of 1 mm can be produced with intensity levels of a few picoamperes equivalent.

  4. Zeeman-Sisyphus Deceleration of Molecular Beams

    NASA Astrophysics Data System (ADS)

    Fitch, Noah; Tarbutt, Mike

    2016-05-01

    Ultracold molecules are useful for testing fundamental physics and studying strongly-interacting quantum systems. One production method is via direct laser cooling in a magneto-optical trap (MOT). In this endeavor, one major challenge is to produce molecules below the MOT capture velocity. Established molecular beam deceleration techniques are poorly suited because they decelerate only a small fraction of a typical molecular pulse. Direct laser cooling is a natural choice, but is also problematic due to transverse heating and the associated molecule loss. I will present a new technique that we are developing, which we call Zeeman-Sisyphus deceleration and which shows great promise for preparing molecular beams for MOT loading. This technique decelerates molecules using a linear array of permanent magnets, along with lasers that periodically optically pump molecules between weak and strong-field seeking quantum states. Being time-independent, this method is well-suited for temporally extended molecular beams. Simultaneous deceleration and transverse guiding makes this approach attractive as an alternative to direct laser cooling. I will present our development of the Zeeman-Sisyphus decelerator and its application to a molecular MOT of CaF and an ultracold fountain of YbF.

  5. Molecular Beam Epitaxy Growth of Iron Phthalocyanine Nanostructures

    SciTech Connect

    Debnath, A. K.; Samanta, S.; Singh, Ajay; Aswal, D. K.; Gupta, S. K.; Yakhmi, J. V.

    2009-06-29

    FePc films of different thickness have been deposited by molecular beam epitaxy (MBE) as a function of substrate temperature (25-300 deg. C) and deposition rate (0.02-0.07 nm/s). The morphology of a 60 nm alpha-phase film has been tuned from nanobrush (nearly parallel nanorods aligned normal to the substrate plane) to nanoweb (nanowires forming a web-like structure in the plane of the substrate) by changing the deposition rate from 0.02 to 0.07 nm/s. We propose growth mechanisms of nanoweb and nanobrush morphology based on the van der Waals (vdW) epitaxy. For air exposed FePc films I-V hysteresis was observed at 300 K and it is attributed to surface traps created by chemisorbed oxygen.

  6. Calculation of neutral beam deposition accounting for excited states

    SciTech Connect

    Gianakon, T.A.

    1992-09-01

    Large-scale neutral-beam auxillary heating of plasmas has led to new plasma operational regimes which are often dominated by fast ions injected via the absorption of an energetic beam of hydrogen neutrals. An accurate simulation of the slowing down and transport of these fast ions requires an intimate knowledge of the hydrogenic neutral deposition on each flux surface of the plasma. As a refinement to the present generation of transport codes, which base their beam deposition on ground-state reaction rates, a new set of routines, based on the excited states of hydrogen, is presented as mechanism for computing the attenuation and deposition of a beam of energetic neutrals. Additionally, the numerical formulations for the underlying atomic physics for hydrogen impacting on the constiuent plasma species is developed and compiled as a numerical database. Sample results based on this excited state model are compared with the ground-state model for simple plasma configurations.

  7. Deposition of reactively ion beam sputtered silicon nitride coatings

    NASA Technical Reports Server (NTRS)

    Grill, A.

    1982-01-01

    An ion beam source was used to deposit silicon nitride films by reactively sputtering a silicon target with beams of Ar + N2 mixtures. The nitrogen fraction in the sputtering gas was 0.05 to 0.80 at a total pressure of 6 to 2 millionth torr. The ion beam current was 50 mA at 500 V. The composition of the deposited films was investigated by auger electron spectroscopy and the rate of deposition was determined by interferometry. A relatively low rate of deposition of about 2 nm. one-tenth min. was found. AES spectra of films obtained with nitrogen fractions higher than 0.50 were consistent with a silicon to nitrogen ratio corresponding to Si3N4. However the AES spectra also indicated that the sputtered silicon nitride films were contaminated with oxygen and carbon and contained significant amounts of iron, nickel, and chromium, most probably sputtered from the holder of the substrate and target.

  8. Physics with fast molecular-ion beams

    SciTech Connect

    Kanter, E.P.

    1980-01-01

    Fast (MeV) molecular-ion beams provide a unique source of energetic projectile nuclei which are correlated in space and time. The recognition of this property has prompted several recent investigations of various aspects of the interactions of these ions with matter. High-resolution measurements on the fragments resulting from these interactions have already yielded a wealth of new information on such diverse topics as plasma oscillations in solids and stereochemical structures of molecular ions as well as a variety of atomic collision phenomena. The general features of several such experiments will be discussed and recent results will be presented.

  9. Molecular-beam gas-sampling system

    NASA Technical Reports Server (NTRS)

    Young, W. S.; Knuth, E. L.

    1972-01-01

    A molecular beam mass spectrometer system for rocket motor combustion chamber sampling is described. The history of the sampling system is reviewed. The problems associated with rocket motor combustion chamber sampling are reported. Several design equations are presented. The results of the experiments include the effects of cooling water flow rates, the optimum separation gap between the end plate and sampling nozzle, and preliminary data on compositions in a rocket motor combustion chamber.

  10. Direct simulation Monte Carlo modeling of e-beam metal deposition

    SciTech Connect

    Venkattraman, A.; Alexeenko, A. A.

    2010-07-15

    Three-dimensional direct simulation Monte Carlo (DSMC) method is applied here to model the electron-beam physical vapor deposition of copper thin films. Various molecular models for copper-copper interactions have been considered and a suitable molecular model has been determined based on comparisons of dimensional mass fluxes obtained from simulations and previous experiments. The variable hard sphere model that is determined for atomic copper vapor can be used in DSMC simulations for design and analysis of vacuum deposition systems, allowing for accurate prediction of growth rates, uniformity, and microstructure.

  11. A molecular view of vapor deposited glasses

    SciTech Connect

    Singh, Sadanand; Pablo, Juan J. de

    2011-05-21

    Recently, novel organic glassy materials that exhibit remarkable stability have been prepared by vapor deposition. The thermophysical properties of these new ''stable'' glasses are equivalent to those that common glasses would exhibit after aging over periods lasting thousands of years. The origin of such enhanced stability has been elusive; in the absence of detailed models, past studies have discussed the formation of new polyamorphs or that of nanocrystals to explain the observed behavior. In this work, an atomistic molecular model of trehalose, a disaccharide of glucose, is used to examine the properties of vapor-deposited stable glasses. Consistent with experiment, the model predicts the formation of stable glasses having a higher density, a lower enthalpy, and higher onset temperatures than those of the corresponding ''ordinary'' glass formed by quenching the bulk liquid. Simulations reveal that newly formed layers of the growing vapor-deposited film exhibit greater mobility than the remainder of the material, thereby enabling a reorganization of the film as it is grown. They also reveal that ''stable'' glasses exhibit a distinct layered structure in the direction normal to the substrate that is responsible for their unusual properties.

  12. Use of beam deflection to control an electron beam wire deposition process

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M. (Inventor); Hofmeister, William H. (Inventor); Hafley, Robert A. (Inventor)

    2013-01-01

    A method for controlling an electron beam process wherein a wire is melted and deposited on a substrate as a molten pool comprises generating the electron beam with a complex raster pattern, and directing the beam onto an outer surface of the wire to thereby control a location of the wire with respect to the molten pool. Directing the beam selectively heats the outer surface of the wire and maintains the position of the wire with respect to the molten pool. An apparatus for controlling an electron beam process includes a beam gun adapted for generating the electron beam, and a controller adapted for providing the electron beam with a complex raster pattern and for directing the electron beam onto an outer surface of the wire to control a location of the wire with respect to the molten pool.

  13. Silicon nitride films deposited with an electron beam created plasma

    NASA Astrophysics Data System (ADS)

    Bishop, D. C.; Emery, K. A.; Rocca, J. J.; Thompson, L. R.; Zamani, H.; Collins, G. J.

    1984-03-01

    The electron beam assisted chemical vapor deposition (EBCVD) of silicon nitride films using NH3, N2, and SiH4 as the reactant gases is reported. The films have been deposited on aluminum, SiO2, and polysilicon film substrates as well as on crystalline silicon substrates. The range of experimental conditions under which silicon nitrides have been deposited includes substrate temperatures from 50 to 400 C, electron beam currents of 2-40 mA, electron beam energies of 1-5 keV, total ambient pressures of 0.1-0.4 Torr, and NH3/SiH4 mass flow ratios of 1-80. The physical, electrical, and chemical properties of the EBCVD films are discussed.

  14. Hydrogenated amorphous silicon deposited by ion-beam sputtering

    NASA Technical Reports Server (NTRS)

    Lowe, V. E.; Henin, N.; Tu, C.-W.; Tavakolian, H.; Sites, J. R.

    1981-01-01

    Hydrogenated amorphous silicon films 1/2 to 1 micron thick were deposited on metal and glass substrates using ion-beam sputtering techniques. The 800 eV, 2 mA/sq cm beam was a mixture of argon and hydrogen ions. The argon sputtered silicon from a pure (7.6 cm) single crystal wafer, while the hydrogen combined with the sputtered material during the deposition. Hydrogen to argon pressure ratios and substrate temperatures were varied to minimize the defect state density in the amorphous silicon. Characterization was done by electrical resistivity, index of refraction and optical absorption of the films.

  15. Nanopillar growth by focused helium ion-beam-induced deposition.

    PubMed

    Chen, Ping; van Veldhoven, Emile; Sanford, Colin A; Salemink, Huub W M; Maas, Diederik J; Smith, Daryl A; Rack, Philip D; Alkemade, Paul F A

    2010-11-12

    A 25 keV focused helium ion beam has been used to grow PtC nanopillars on a silicon substrate by beam-induced decomposition of a (CH(3))(3)Pt(C(P)CH(3)) precursor gas. The ion beam diameter was about 1 nm. The observed relatively high growth rates suggest that electronic excitation is the dominant mechanism in helium ion-beam-induced deposition. Pillars grown at low beam currents are narrow and have sharp tips. For a constant dose, the pillar height decreases with increasing current, pointing to depletion of precursor molecules at the beam impact site. Furthermore, the diameter increases rapidly and the total pillar volume decreases slowly with increasing current. Monte Carlo simulations have been performed with realistic values for the fundamental deposition processes. The simulation results are in good agreement with experimental observations. In particular, they reproduce the current dependences of the vertical and lateral growth rates and of the volumetric deposition efficiency. Furthermore, the simulations reveal that the vertical pillar growth is due to type-1 secondary electrons and primary ions, while the lateral outgrowth is due to type-2 secondary electrons and scattered ions. PMID:20947951

  16. Superconducting nanowires by electron-beam-induced deposition

    SciTech Connect

    Sengupta, Shamashis; Li, Chuan; Guéron, S.; Bouchiat, H.; Baumier, Cedric; Fortuna, F.; Kasumov, Alik

    2015-01-26

    Superconducting nanowires can be fabricated by decomposition of an organometallic gas using a focused beam of Ga ions. However, physical damage and unintentional doping often result from the exposure to the ion beam, motivating the search for a means to achieve similar structures with a beam of electrons instead of ions. This has so far remained an experimental challenge. We report the fabrication of superconducting tungsten nanowires by electron-beam-induced-deposition, with critical temperature of 2.0 K and critical magnetic field of 3.7 T, and compare them with superconducting wires made with ions. This work is an important development for the template-free realization of nanoscale superconducting devices, without the requirement of an ion beam column.

  17. Superconducting nanowires by electron-beam-induced deposition

    NASA Astrophysics Data System (ADS)

    Sengupta, Shamashis; Li, Chuan; Baumier, Cedric; Kasumov, Alik; Guéron, S.; Bouchiat, H.; Fortuna, F.

    2015-01-01

    Superconducting nanowires can be fabricated by decomposition of an organometallic gas using a focused beam of Ga ions. However, physical damage and unintentional doping often result from the exposure to the ion beam, motivating the search for a means to achieve similar structures with a beam of electrons instead of ions. This has so far remained an experimental challenge. We report the fabrication of superconducting tungsten nanowires by electron-beam-induced-deposition, with critical temperature of 2.0 K and critical magnetic field of 3.7 T, and compare them with superconducting wires made with ions. This work is an important development for the template-free realization of nanoscale superconducting devices, without the requirement of an ion beam column.

  18. Materials issues in molecular beam epitaxy

    SciTech Connect

    Tsao, J.Y.

    1993-12-31

    The technology of crystal growth has advanced enormously during the past two decades; among those advances, the development and refinement of molecular beam epitaxy (MBE) has been among the most important. Crystals grown by MBE are more precisely controlled than those grown by any other method, and today form the basis for many of the most advanced device structures in solid-state physics, electronics and optoelectronics. In addition to its numerous device applications, MBE is also an enormously rich and interesting area of materials science in and of itself. This paper, discusses a few examples of some of these materials issues, organized according to whether they involve bulk, thin films, or surfaces.

  19. Perspective: Oxide molecular-beam epitaxy rocks!

    SciTech Connect

    Schlom, Darrell G.

    2015-06-01

    Molecular-beam epitaxy (MBE) is the “gold standard” synthesis technique for preparing semiconductor heterostructures with high purity, high mobility, and exquisite control of layer thickness at the atomic-layer level. Its use for the growth of multicomponent oxides got off to a rocky start 30 yr ago, but in the ensuing decades, it has become the definitive method for the preparation of oxide heterostructures too, particularly when it is desired to explore their intrinsic properties. Examples illustrating the unparalleled achievements of oxide MBE are given; these motivate its expanding use for exploring the potentially revolutionary states of matter possessed by oxide systems.

  20. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1987-03-01

    Purpose of this research project is two-fold: (1) to elucidate detailed dynamics of simple elementary reactions which are theoretically important and to unravel the mechanism of complex chemical reactions or photo chemical processes which play an important role in many macroscopic processes and (2) to determine the energetics of polyatomic free radicals using microscopic experimental methods. Most of the information is derived from measurement of the product fragment translational energy and angular distributions using unique molecular beam apparati designed for these purposes.

  1. Perspective: Oxide molecular-beam epitaxy rocks!

    NASA Astrophysics Data System (ADS)

    Schlom, Darrell G.

    2015-06-01

    Molecular-beam epitaxy (MBE) is the "gold standard" synthesis technique for preparing semiconductor heterostructures with high purity, high mobility, and exquisite control of layer thickness at the atomic-layer level. Its use for the growth of multicomponent oxides got off to a rocky start 30 yr ago, but in the ensuing decades, it has become the definitive method for the preparation of oxide heterostructures too, particularly when it is desired to explore their intrinsic properties. Examples illustrating the unparalleled achievements of oxide MBE are given; these motivate its expanding use for exploring the potentially revolutionary states of matter possessed by oxide systems.

  2. Applying CLIPS to control of molecular beam epitaxy processing

    NASA Technical Reports Server (NTRS)

    Rabeau, Arthur A.; Bensaoula, Abdelhak; Jamison, Keith D.; Horton, Charles; Ignatiev, Alex; Glover, John R.

    1990-01-01

    A key element of U.S. industrial competitiveness in the 1990's will be the exploitation of advanced technologies which involve low-volume, high-profit manufacturing. The demands of such manufacture limit participation to a few major entities in the U.S. and elsewhere, and offset the lower manufacturing costs of other countries which have, for example, captured much of the consumer electronics market. One such technology is thin-film epitaxy, a technology which encompasses several techniques such as Molecular Beam Epitaxy (MBE), Chemical Beam Epitaxy (CBE), and Vapor-Phase Epitaxy (VPE). Molecular Beam Epitaxy (MBE) is a technology for creating a variety of electronic and electro-optical materials. Compared to standard microelectronic production techniques (including gaseous diffusion, ion implantation, and chemical vapor deposition), MBE is much more exact, though much slower. Although newer than the standard technologies, MBE is the technology of choice for fabrication of ultraprecise materials for cutting-edge microelectronic devices and for research into the properties of new materials.

  3. PHOTOELECTRON SPECTROSCOPY OF SUPERSONIC MOLECULAR BEAMS

    SciTech Connect

    Pollard, J.E.; Trevor, D.J.; Lee, Y.T.; Shirley, D.A.

    1981-06-01

    We report the development of an instrument for gas-phase ultraviolet photoelectron spectroscopy which opens several new areas for study through use of the supersonic molecular beam technique. The key features in which we have sought an improvement on earlier spectrometer designs are (1) the optimization of electron energy resolution and sensitivity, (2) vacuum isolation, and (3) the capability for mass spectrometric analysis. Our principal interests are in the high resolution spectroscopy of small molecules and in studies of weakly bound complexes formed under collisionless conditions. As shown in Fig. 1 the apparatus is essentially a molecular beam chamber with allowance for access by a beam source, an electron energy analyzer, and a quadrupole mass spectrometer. These three plug-in units are equipped with individual differential pumping systems. The photon source is a rare-gas resonance lamp which may be directed toward the molecular beam either 90{sup o} or 54.7{sup o} from the direction of electron collection. Electrons which pass through entrance aperture are transported by a series of electrostatic lenses to a 90{sup o} spherical sector pre-analyzer (R{sub 0} = 3.8 cm) and then on to a 180{sup o} hemispherical analyzer (R{sub 0} = 10.2 cm). The detector consists of a microchannel plate electron multiplier (40 mm diam.) with a resistive-anode position encoder. The function of the pre-analyzer is to improve the signal-to-noise ratio by reducing the background of scattered electrons incident upon the microchannel plate. The electron optical system is designed such that the energy bandpass (FWHN) leaving the pre-analyzer just fills the energy window presented by the multichannel detector. The multichannel capability of this analyzer is very advantageous for working with the rather low number density (< 10{sup 13} cm{sup -3}) of molecular beam samples, since the data collection rate is improved by more than an order of magnitude over single channel operation. To

  4. Electron Beam Freeform Fabrication: A Rapid Metal Deposition Process

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M. B.; Hafley, Robert A.

    2003-01-01

    Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley REsearch Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Thus far, this technique has been demonstrated on aluminum and titanium alloys of interest for aerospace structural applications nickel and ferrous based alloys are also planned. Deposits resulting from 2219 aluminum demonstrations have exhibited a range of grain morphologies depending upon the deposition parameters. These materials ave exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF process is capable of bulk metal deposition at deposition rated in excess of 2500 cubic centimeters per hour (150 cubic inches per our) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

  5. Formation of aluminum films on silicon by ion beam deposition: A comparison with ionized cluster beam deposition

    SciTech Connect

    Zuhr, R.A.; Haynes, T.E.; Galloway, M.D. ); Tanaka, S.; Yamada, A.; Yamada, I. . Ion Beam Engineering Lab.)

    1990-01-01

    The direct ion beam deposition (IBD) technique has been used to study the formation of oriented aluminum films on single crystal silicon substrates. In the IBD process, thin film growth is accomplished by decelerating a magnetically-analyzed ion beam to low energies (10--200 eV) for direct deposition onto the substrate under UHV conditions. The energy of the incident ions can be selected to provide the desired growth conditions, and the mass analysis ensures good beam purity. The aluminum on silicon system is one which has been studied extensively by ionized cluster beam (ICB) deposition. In this work, we have studied the formation of such films by IBD with emphasis on the effects of ion energy, substrate temperature, and surface cleanliness. Oriented films have been grown on Si(111) at temperatures from 40{degree} to 300{degree}C and with ion energies from 30 to 120 eV per ion. Completed films were analyzed by ion scattering, x-ray diffraction, scanning electron microscopy, and optical microscopy. Results achieved for thin films grown by IBD are compared with results for similar films grown by ICB deposition. 15 refs., 3 figs.

  6. Site control technique for quantum dots using electron beam induced deposition

    SciTech Connect

    Iizuka, Kanji; Jung, JaeHun; Yokota, Hiroshi

    2014-05-15

    To develop simple and high throughput sit definition technique for quantum dots (QDs), the electron beam induced deposition (EBID) method was used as desorption guide of phosphorus atoms form InP substrate. As the results one or a few indium (In) droplets (DLs) were created in the carbon grid pattern by thermal annealing at a temperature of 450°C for 10 min in the ultra high vacuum condition. The size of In DLs was larger than QDs, but arsenide DLs by molecular beam in growth chamber emitted wavelength of 1.028μm at 50K by photoluminescence measurement.

  7. Site control technique for quantum dots using electron beam induced deposition

    NASA Astrophysics Data System (ADS)

    Iizuka, Kanji; Jung, JaeHun; Yokota, Hiroshi

    2014-05-01

    To develop simple and high throughput sit definition technique for quantum dots (QDs), the electron beam induced deposition (EBID) method was used as desorption guide of phosphorus atoms form InP substrate. As the results one or a few indium (In) droplets (DLs) were created in the carbon grid pattern by thermal annealing at a temperature of 450°C for 10 min in the ultra high vacuum condition. The size of In DLs was larger than QDs, but arsenide DLs by molecular beam in growth chamber emitted wavelength of 1.028μm at 50K by photoluminescence measurement.

  8. Molecular dynamics and quasidynamics simulations of the annealing of bulk and near-surface interstitials formed in molecular-beam epitaxial Si due to low-energy particle bombardment during deposition

    NASA Technical Reports Server (NTRS)

    Kitabatake, M.; Fons, P.; Greene, J. E.

    1991-01-01

    The relaxation, diffusion, and annihilation of split and hexagonal interstitials resulting from 10 eV Si irradiation of (2x1)-terminated Si(100) are investigated. Molecular dynamics and quasidynamics simulations, utilizing the Tersoff many-body potential are used in the investigation. The interstitials are created in layers two through six, and stable atomic configurations and total potential energies are derived as a function of site symmetry and layer depth. The interstitial Si atoms are allowed to diffuse, and the total potential energy changes are calculated. Lattice configurations along each path, as well as the starting configurations, are relaxed, and minimum energy diffusion paths are derived. The results show that the minimum energy paths are toward the surface and generally involved tetrahedral sites. The calculated interstitial migration activation energies are always less than 1.4 eV and are much lower in the near-surface region than in the bulk.

  9. Electrostatic particle trap for ion beam sputter deposition

    DOEpatents

    Vernon, Stephen P.; Burkhart, Scott C.

    2002-01-01

    A method and apparatus for the interception and trapping of or reflection of charged particulate matter generated in ion beam sputter deposition. The apparatus involves an electrostatic particle trap which generates electrostatic fields in the vicinity of the substrate on which target material is being deposited. The electrostatic particle trap consists of an array of electrode surfaces, each maintained at an electrostatic potential, and with their surfaces parallel or perpendicular to the surface of the substrate. The method involves interception and trapping of or reflection of charged particles achieved by generating electrostatic fields in the vicinity of the substrate, and configuring the fields to force the charged particulate material away from the substrate. The electrostatic charged particle trap enables prevention of charged particles from being deposited on the substrate thereby enabling the deposition of extremely low defect density films, such as required for reflective masks of an extreme ultraviolet lithography (EUVL) system.

  10. Studies of the mechanism of electron beam induced deposition (EBID)

    NASA Astrophysics Data System (ADS)

    Choi, Young Ryong

    The controlled deposition of metals resulting from the passage of an ion beam through an atmosphere of a suitable precursor gas is a well-established procedure for micro scale materials manipulation. While the ion beam technique is rapid and reliable it has the disadvantage that the beam itself can ablate and contaminate the target with Gallium or other materials, and the fact that ion optics are less widely accessible than electron optical columns. We have therefore been investigating the theory and practice of depositing metal using an electron beam and variety of precursor gases. The aim of this work is to develop techniques that can be applied to the repair of the optical, ultra-violet (UV) and extreme ultra-violet (EUV) masks used in high performance photo-lithography. This thesis is concentrated on electron beam induced deposition (EBID) performed in a commercial Scanning Electron Microscope (SEM). For EBID experiments, we have developed a gas injection system for the specimen chamber of a standard SEM which is able to control the pressure and the delivery flow rate of gas for experiment. Studies of factors that control the properties of the deposition---such as the electron-gas interactions, the effects of gas pressure, and the temperature of the substrate---have been made and experiments to determine the fundamental mechanisms of EBID---such as which types of electrons are responsible for the initial interaction event with the precursor---have been carried out and analyzed and systematically studied to determine the optimum conditions for the practical application of the EBID approach. Finally the practical applications of the EBID have been applied to repair of masks.

  11. Beam-Induced Deposition of Thin Metallic Films.

    NASA Astrophysics Data System (ADS)

    Funsten, Herbert Oliver, III

    1990-01-01

    Ion and electron beam induced deposition (BID) of thin (1 μm), conductive films is accomplished by dissociating and removing the nonmetallic components of an adsorbed, metal-based, molecular gas. Current research has focused primarily on room temperature (monolayer adsorption) BID using electrons and slow, heavy ions. This study investigates low temperature (50 to 200 K) BID in which the condensation of the precursor gases (SnCl _4 and (CH_3) _4Sn) maximizes the efficiency of the incident radiation which can create and remove nonmetallic fragments located several monolayers below the film surface. The desired properties of the residual metallic films are produced by using as incident radiation either nuclear (35 keV Ar ^+) or electronic (2 keV electrons, 25 keV H^+, or 50 keV H ^+) energy loss mechanisms. Residual films are analyzed ex situ by Scanning Electron Microscopy (SEM), thickness measurements, resistivity measurements, Rutherford Backscattering Spectroscopy (RBS), and infrared spectroscopy. Low temperature BID film growth models, which are derived from both a computer simulation and a mathematical analysis, closely agree. Both the fragmentation and sputtering cross sections for a particular ion and energy are derived for films created from (CH_3) _4Sn. The fragmentation cross section, which corresponds to film growth, is roughly related to the electronic stopping power by the 1.9 power. The loss of carbon in films which were created from (CH_3) _4Sn is strongly dependent on the nuclear stopping power. Film growth rates for low temperature BID have been found to be 10 times those of room temperature BID.

  12. Molecular contamination study by interaction of a molecular beam with a platinum surface

    NASA Technical Reports Server (NTRS)

    Nuss, H. E.

    1976-01-01

    The capability of molecular beam scattering from a solid surface is analyzed for identification of molecular contamination of the surface. The design and setup of the molecular beam source and the measuring setup for the application of a phase sensitive measuring technique for the determination of the scattered beam intensity are described. The scattering distributions of helium and nitrogen molecular beams interacting with a platinum surface were measured for different amounts of contamination from diffusion pump oil for surface temperatures ranging from 30 to 400 C. The results indicate the scattering of molecular beams from a platinum surface is a very sensitive method for detecting surface contamination.

  13. Twenty years of molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Cho, A. Y.

    1995-05-01

    The term "molecular beam epitaxy" (MBE) was first used in one of our crystal growth papers in 1970, after having conducted extensive surface physics studies in the late 1960's of the interaction of atomic and molecular beams with solid surfaces. The unique feature of MBE is the ability to prepare single crystal layers with atomic dimensional precision. MBE sets the standard for epitaxial growth and has made possible semiconductor structures that could not be fabricated with either naturally existing materials or by other crystal growth techniques. MBE led the crystal growth technologies when it prepared the first semiconductor quantum well and superlattice structures that gave unexpected and exciting electrical and optical properties. For example, the discovery of the fractional quantized Hall effect. It brought experimental quantum physics to the classroom, and practically all major universities throughout the world are now equipped with MBE systems. The fundamental principles demonstrated by the MBE growth of III-V compound semiconductors have also been applied to the growth of group IV, II-VI, metal, and insulating materials. For manufacturing, the most important criteria are uniformity, precise control of the device structure, and reproducibility. MBE has produced more lasers (3 to 5 million per month for compact disc application) than any other crystal growth technique in the world. New directions for MBE are to incorporate in-situ, real-time monitoring capabilities so that complex structures can be precisely "engineered". In the future, as environmental concerns increase, the use of toxic arsine and phosphine may be limited. Successful use of valved cracker cells for solid arsenic and phosphorus has already produced InP based injection lasers.

  14. Hydrogen removal from e-beam deposited alumina thin films by oxygen ion beam

    SciTech Connect

    Das, Arijeet Mukharjee, C. Rajiv, K. Bose, Aniruddha Singh, S. D. Rai, S. K.; Ganguli, Tapas; Joshi, S. C.; Deb, S. K.; Phase, D. M.

    2014-04-24

    Hydrogen interstitials and oxygen vacancies defects create energy levels in the band gap of alumina. This limits the application of alumina as a high-k dielectric. A low thermal budget method for removal of hydrogen from alumina is discussed. It is shown that bombardment of alumina films with low energy oxygen ion beam during electron beam evaporation deposition decreases the hydrogen concentration in the film significantly.

  15. Molecular sputter depth profiling using carbon cluster beams

    PubMed Central

    Winograd, Nicholas

    2010-01-01

    Sputter depth profiling of organic films while maintaining the molecular integrity of the sample has long been deemed impossible because of the accumulation of ion bombardment-induced chemical damage. Only recently, it was found that this problem can be greatly reduced if cluster ion beams are used for sputter erosion. For organic samples, carbon cluster ions appear to be particularly well suited for such a task. Analysis of available data reveals that a projectile appears to be more effective as the number of carbon atoms in the cluster is increased, leaving fullerene ions as the most promising candidates to date. Using a commercially available, highly focused C60q+ cluster ion beam, we demonstrate the versatility of the technique for depth profiling various organic films deposited on a silicon substrate and elucidate the dependence of the results on properties such as projectile ion impact energy and angle, and sample temperature. Moreover, examples are shown where the technique is applied to organic multilayer structures in order to investigate the depth resolution across film-film interfaces. These model experiments allow collection of valuable information on how cluster impact molecular depth profiling works and how to understand and optimize the depth resolution achieved using this technique. PMID:19649771

  16. An investigation of nonuniform dose deposition from an electron beam

    NASA Astrophysics Data System (ADS)

    Lilley, William; Luu, Kieu X.

    1994-08-01

    In a search for an explanation of nonuniform electron-beam dose deposition, the integrated tiger series (ITS) of coupled electron/photon Monte Carlo transport codes was used to calculate energy deposition in the package materials of an application-specific integrated circuit (ASIC) while the thicknesses of some of the materials were varied. The thicknesses of three materials that were in the path of an electron-beam pulse were varied independently so that analysis could determine how the radiation dose measurements using thermoluminescent dosimeters (TLD's) would be affected. The three materials were chosen because they could vary during insertion of the die into the package or during the process of taking dose measurements. The materials were aluminum, HIPEC (a plastic), and silver epoxy. The calculations showed that with very small variations in thickness, the silver epoxy had a large effect on the dose uniformity over the area of the die.

  17. Molecular beam studies of stratospheric photochemistry

    NASA Astrophysics Data System (ADS)

    Moore, Teresa Anne

    1998-12-01

    Photochemistry of chlorine oxide containing species plays a major role in stratospheric ozone depletion. This thesis discusses two photodissociation studies of the key molecules ClONO2 and ClOOCl which were previously thought to only produce Cl-atom (ozone depleting) products at wavelengths relevant to the stratosphere. The development of a molecular beam source of ClOOCl and the photodissociation dynamics of the model system Cl2O are also discussed. In the first chapter, the photochemistry of ClONO2 is examined at 308 nm using the technique of photofragment translational spectroscopy. Two primary decomposition pathways, leading to Cl + NO3 and ClO + NO2, were observed, with a lower limit of 0.33 for the relative yield of ClO. The angular distributions for both channels were anisotropic, indicating that the dissociation occurs within a rotational period. Chapter two revisits the photodissociation dynamics of Cl2O at 248 and 308 nm, on which we had previously reported preliminary findings. At 248 nm, three distinct dissociation pathways leading to Cl + ClO products were resolved. At 308 nm, the angular distribution was slightly more isotropic that previously reported, leaving open the possibility that Cl2O excited at 308 nm lives longer than a rotational period. Chapter three describes the development and optimization of a molecular beam source of ClOOCl. We utilized pulsed laser photolysis of ClA2O to generate ClO radicals, and cooled the cell to promote three body recombination to form ClOOCl. The principal components in the beam were Cl2, Cl2O, and ClOOCl. In the fourth chapter, the photodissociation dynamics of ClOOCl are investigated at 248 and 308 nm. We observed multiple dissociation pathways which produced ClO + ClO and 2Cl + O2 products. The relative Cl:ClO product yields are 1.0:0.13 and 1.0:0.20 for ClOOCl photolysis at 248 and 308 nm, respectively. The upper limit for the relative yield of the ClO + ClO channel was 0.19 at 248 nm and 0.31 at 308 nm

  18. On the Growth of Complex Oxides by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Fong, Dillon

    Functional materials based on complex oxides in thin film form offer new and exciting strategies for meeting many of our outstanding energy challenges through systematic control of layer sequencing, strain, etc. However, the synthesis of such oxide films can be a major challenge even when utilizing reactive molecular-beam epitaxy (MBE), a powerful deposition technique that allows the construction of materials atomic plane by atomic plane. To understand the fundamental physics of oxide growth by reactive MBE, we present in situ surface x-ray diffraction results on the growth of SrTiO3 and SrO-SrTiO3 thin films on (001)-oriented SrTiO3 substrates. For homoepitaxy, we compare sequential deposition (alternating Sr and Ti monolayer doses) with that of co-deposition of Sr and Ti, both in a background of oxygen pressure, and observe drastically different growth pathways due to the presence of a TiO2 double layer. For heteroepitaxial growth of Ruddlesden-Popper SrO-SrTiO3 films, we find that layers rearrange dynamically, resulting in layer sequences distinct from the shutter sequence. In general, the starting surface structure and composition, in combination with local thermodynamic considerations, strongly influence our ability to atomically construct new complex oxides.

  19. Anomalous scaling behavior and surface roughening in molecular thin-film deposition

    SciTech Connect

    Yim, S.; Jones, T. S.

    2006-04-15

    The thin film growth dynamics of a molecular semiconductor, free-base phthalocyanine (H{sub 2}Pc), deposited by organic molecular beam deposition, has been studied by atomic force microscopy (AFM) and height difference correlation function (HDCF) analysis. The measured dynamic scaling components ({alpha}{sub loc}=0.61{+-}0.12, {beta}=1.02{+-}0.08, and 1/z=0.72{+-}0.13) are consistent with rapid surface roughening and anomalous scaling behavior. A detailed analysis of AFM images and simple growth models suggest that this behavior arises from the pronounced upward growth of crystalline H{sub 2}Pc mounds during the initial stages of thin film growth.

  20. Rapid tooling by electron-beam vapor deposition

    SciTech Connect

    Meier, T. C., LLNL

    1998-02-25

    Electron-beam physical vapor deposition (EBPVD) of tooling metal, onto a shaped substrate to produce a replica of the substrate surface, offers the potential for significant cost savings over present methods of injection mold manufacturing. These savings are realized by the high deposition rate and the corresponding short manufacturing times provided by the EBPVD process. However, on route to realizing these gains, there are process technical issues which need to be resolved. Mold surfaces typically contain relatively high aspect ratio details that must be replicated to dimensional tolerances within +/- 2 mils. The deposited mold material must also provide high surface hardness and high fracture toughness. Good quality grain structure can be obtained in deposited Al 10-wt% Cu mold material when the substrate and corresponding deposit are at high process temperature. However, the resulting mold is subject to distortion during cooldown due to differential temperatures and shrinkage rates. Thermally controlled cooldown and the use of crushable substrate materials reduce these distortions, but not to the required levels of tolerance. Deposition of the Al-Cu at lower temperature produces columnar, poorly joined grains which result in a brittle and weakened mold material. When Al 10-wt% Cu metal vapor is deposited across high aspect ratio step features on the substrate surface, a grain growth defect can form in the step-shadowed regions of the deposited material, alongside the step feature. The step coverage defect consists of entrained voids which persist at intermediate deposition temperatures and produce a weakened mold. This final 1997 LDRD report investigates causes of this step coverage defect and offers methods for their control and elimination.

  1. An Optimized Nanoparticle Separator Enabled by Electron Beam Induced Deposition

    SciTech Connect

    Fowlkes, Jason Davidson; Doktycz, Mitchel John; Rack, P. D.

    2010-01-01

    Size based separations technologies will inevitably benefit from advances in nanotechnology. Direct write nanofabrication provides a useful mechanism to deposit/etch nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition (EBID) was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam interaction region (BIR). Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub 50nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects), (2) preserved the fidelity of spacing between nanopillars (which maximizes the size based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing.

  2. An optimized nanoparticle separator enabled by electron beam induced deposition.

    PubMed

    Fowlkes, J D; Doktycz, M J; Rack, P D

    2010-04-23

    Size-based separations technologies will inevitably benefit from advances in nanotechnology. Direct-write nanofabrication provides a useful mechanism for depositing/etching nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam-interaction region. Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub-50 nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular-sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects) and (2) preserved the fidelity of the spacing between nanopillars (which maximizes the size-based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing. PMID:20351412

  3. Magnetron deposition of TCO films using ion beam

    NASA Astrophysics Data System (ADS)

    Asainov, O.; Umnov, S.; Chinin, A.

    2015-11-01

    Thin films of tin oxide (TO) were deposited on the glass substrates at room temperature using reactive magnetron sputtering at various oxygen partial pressures. After the deposition the films were irradiated with argon ions beam. The change of the optical and electrical properties of the films depending on the irradiation time was studied. Films optical properties in the range of 300-1100 nm were investigated by photometry as well as their structural properties were studied using X-ray diffraction. Diffractometric research showed that the films, deposited on a substrate, have a crystal structure, and after argon ions irradiation they become quasi-crystalline (amorphous). It was found that the transmission increases proportionally with the irradiation time, but the surface resistance -disproportionally.

  4. A critical literature review of focused electron beam induced deposition

    NASA Astrophysics Data System (ADS)

    van Dorp, W. F.; Hagen, C. W.

    2008-10-01

    An extensive review is given of the results from literature on electron beam induced deposition. Electron beam induced deposition is a complex process, where many and often mutually dependent factors are involved. The process has been studied by many over many years in many different experimental setups, so it is not surprising that there is a great variety of experimental results. To come to a better understanding of the process, it is important to see to which extent the experimental results are consistent with each other and with the existing model. All results from literature were categorized by sorting the data according to the specific parameter that was varied (current density, acceleration voltage, scan patterns, etc.). Each of these parameters can have an effect on the final deposit properties, such as the physical dimensions, the composition, the morphology, or the conductivity. For each parameter-property combination, the available data are discussed and (as far as possible) interpreted. By combining models for electron scattering in a solid, two different growth regimes, and electron beam induced heating, the majority of the experimental results were explained qualitatively. This indicates that the physical processes are well understood, although quantitatively speaking the models can still be improved. The review makes clear that several major issues remain. One issue encountered when interpreting results from literature is the lack of data. Often, important parameters (such as the local precursor pressure) are not reported, which can complicate interpretation of the results. Another issue is the fact that the cross section for electron induced dissociation is unknown. In a number of cases, a correlation between the vertical growth rate and the secondary electron yield was found, which suggests that the secondary electrons dominate the dissociation rather than the primary electrons. Conclusive evidence for this hypothesis has not been found. Finally

  5. Note: High density pulsed molecular beam for cold ion chemistry

    SciTech Connect

    Kokish, M. G.; Rajagopal, V.; Marler, J. P.; Odom, B. C.

    2014-08-15

    A recent expansion of cold and ultracold molecule applications has led to renewed focus on molecular species preparation under ultrahigh vacuum conditions. Meanwhile, molecular beams have been used to study gas phase chemical reactions for decades. In this paper, we describe an apparatus that uses pulsed molecular beam technology to achieve high local gas densities, leading to faster reaction rates with cold trapped ions. We characterize the beam's spatial profile using the trapped ions themselves. This apparatus could be used for preparation of molecular species by reactions requiring excitation of trapped ion precursors to states with short lifetimes or for obtaining a high reaction rate with minimal increase of background chamber pressure.

  6. A source of translationally cold molecular beams

    NASA Astrophysics Data System (ADS)

    Sarkozy, Laszlo C.

    Currently the fields studying or using molecules with low kinetic energies are experiencing an unprecedented growth. Astronomers and chemists are interested in chemical reactions taking place at temperatures below or around 20 K, spectroscopists could make very precise measurements on slow molecules and molecular physicists could chart the potential energy surfaces more accurately. And the list continues. All of these experiments need slow molecules, with kinetic energies from around 10 cm-1 down to 0. Several designs of cold sources have already been made. The most interesting ones are presented. This work describes the design and the testing of a cold source based on the collisional cooling technique: the molecules of interest are cooled well below their freezing point by a precooled buffer gas. This way condensation is avoided. The source is a copper cell cooled to 4.2 K by an external liquid helium bath. The cell is filled with cold buffer gas (helium). The molecules of choice (ammonia) are injected through a narrow tube in the middle of the cell. The cold molecules leave the cell through a 1 millimeter hole. Two versions of pulsing techniques have been employed: a shutter blade which covers the source hole and opens it only for short moments, and a chopper that modulates the beam further downstream. Both produced pulse lengths around 1 millisecond. The source is tested in an experiment in which the emerging molecules are focused and detected. Time of flight technique is used to measure the kinetic energies. Two detectors have been employed: a microwave cavity to analyze the state of the molecules in the beam, and a mass spectrometer to measure the number density of the particles. The molecules coming out of the source hole are formed into a beam by an electrostatic quadrupole state selector. The quantum mechanical aspects and the elements of electrodynamics involved in the focusing are described. A computer simulation program is presented, which helped

  7. Substrate heating measurements in pulsed ion beam film deposition

    SciTech Connect

    Olson, J.C.; Davis, H.A.; Rej, D.J.; Waganaar, W.J.; Tallant, D.R.; Thompson, M.O.

    1995-05-01

    Diamond-like Carbon (DLC) films have been deposited at Los Alamos National Laboratory by pulsed ion beam ablation of graphite targets. The targets were illuminated by an intense beam of hydrogen, carbon, and oxygen ions at a fluence of 15-45 J/cm{sup 2}. Ion energies were on the order of 350 keV, with beam current rising to 35 kA over a 400 ns ion current pulse. Raman spectra of the deposited films indicate an increasing ratio of sp{sup 3} to sp{sup 2} bonding as the substrate is moved further away from the target and further off the target normal. Using a thin film platinum resistor at varying positions, we have measured the heating of the substrate surface due to the kinetic energy and heat of condensation of the ablated material. This information is used to determine if substrate heating is responsible for the lack of DLC in positions close to the target and near the target normal. Latest data and analysis will be presented.

  8. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Yuan T.

    1991-03-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  9. Molecular beam studies of reaction dynamics

    SciTech Connect

    Lee, Y.T.

    1993-12-01

    The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

  10. Molecular beam surface analysis. 1993 Summary report

    SciTech Connect

    Appelhans, A.D.; Ingram, J.C.; Groenewold, G.S.; Dahl, D.A.; Delmore, J.E.

    1993-09-01

    The Molecular Beam Surface Analysis (MBSA) program is developing both laboratory-based and potentially field-portable chemical analyses systems taking advantage of new surface analysis technology developed at the Idaho National Engineering Laboratory (INEL). The objective is to develop the means to rapidly detect and identify, with high specificity and high sensitivity, nonvolatile and low volatile organics found in Chemical Weapons (CW) and High Explosives (HE) feedstocks, agents, and decomposition products on surfaces of plants, rocks, paint chips, filters, smears of buildings, vehicles, equipment, etc.. Ideally, the method would involve no sample preparation and no waste generation, and would have the potential for being implemented as a field-portable instrument. In contrast to existing analytical methods that rely on sample volatility, MBSA is optimized for nonvolatile and low volatile compounds. This makes it amenable for rapidly screening field samples for CW agent decomposition products and feedstock chemicals and perhaps actual agents. In its final configuration (benchtop size) it could be operated in a non-laboratory environment (such as an office building) requiring no sample preparation chemistry or chemical supplies. It could also be included in a mobile laboratory used in on-site, ore remote site cooperative surveys, or in a standard laboratory, where it would provide fast screening of samples at minimal cost.

  11. ALLIGATOR - An apparatus for ion beam assisted deposition with a broad-beam ion source

    NASA Astrophysics Data System (ADS)

    Wituschek, H.; Barth, M.; Ensinger, W.; Frech, G.; Rück, D. M.; Leible, K. D.; Wolf, G. K.

    1992-04-01

    Ion beam assisted deposition is a versatile technique for preparing thin films and coatings for various applications. Up to now a prototype setup for research purposes has been used in our laboratory. Processing of industrial standard workpieces requires a high current ion source with broad beam and high uniformity for homogeneous bombardment. In this contribution a new apparatus for large area samples will be described. It is named ALLIGATOR (German acronym of facility for ion assisted evaporation on transverse movable or rotary targets). In order to have a wide energy range available two ion sources are used. One delivers a beam energy up to 1.3 keV. The other is suitable for energies from 5 keV up to 40 keV. The ``high-energy'' ion source is a multicusp multiaperture source with 180-mA total current and a beam diameter of 280 mm at the target position.

  12. Orientational anisotropy in simulated vapor-deposited molecular glasses

    SciTech Connect

    Lyubimov, Ivan; Antony, Lucas; Walters, Diane M.; Ediger, M. D.; Rodney, David; Pablo, Juan J. de

    2015-09-07

    Enhanced kinetic stability of vapor-deposited glasses has been established for a variety of glass organic formers. Several recent reports indicate that vapor-deposited glasses can be orientationally anisotropic. In this work, we present results of extensive molecular simulations that mimic a number of features of the experimental vapor deposition process. The simulations are performed on a generic coarse-grained model and an all-atom representation of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), a small organic molecule whose vapor-deposited glasses exhibit considerable orientational anisotropy. The coarse-grained model adopted here is found to reproduce several key aspects reported in experiments. In particular, the molecular orientation of vapor-deposited glasses is observed to depend on substrate temperature during deposition. For a fixed deposition rate, the molecular orientation in the glasses changes from isotropic, at the glass transition temperature, T{sub g}, to slightly normal to the substrate at temperatures just below T{sub g}. Well below T{sub g}, molecular orientation becomes predominantly parallel to the substrate. The all-atom model is used to confirm some of the equilibrium structural features of TPD interfaces that arise above the glass transition temperature. We discuss a mechanism based on distinct orientations observed at equilibrium near the surface of the film, which get trapped within the film during the non-equilibrium process of vapor deposition.

  13. Development of Crystal Al MKIDs by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Naruse, M.; Sekimoto, Y.; Noguchi, T.; Miyachi, A.; Nitta, T.; Uzawa, Y.

    2011-11-01

    We report here the effect of film qualities in superconductors on the properties of Microwave Kinetic Inductance Detectors (MKIDs). The sensitivity of MKIDs between crystal aluminum films and amorphous aluminum films is compared. The good quality and crystallized aluminum films have been prepared by using molecular beam epitaxy. We have confirmed that epitaxial Al(111) films were grown on Si(111) substrates with X-ray diffraction and in-situ reflection high-energy electron diffraction measurements. The amorphous aluminum films on the Si(111) wafers have been deposited by electron beam evaporation. We have measured transmission losses of MKIDs, noise spectrum and relaxation time against optical pulses, changing MKIDs' bath temperature from 0.11 K to 0.55 K in a dilution refrigerator. Despite of the improvement in normal resistivity, the quasiparticle decay time of both films are equivalent and 450 μs at 0.11 K. The electrical noise equivalent power of the both MKIDs are also comparable and around 10^{-17} W/sqrt{Hz}. Fabrication details and performance data of both films are presented.

  14. Creating Ruddlesden-Popper phases by hybrid molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Haislmaier, Ryan C.; Stone, Greg; Alem, Nasim; Engel-Herbert, Roman

    2016-07-01

    The synthesis of a 50 unit cell thick n = 4 Srn+1TinO3n+1 (Sr5Ti4O13) Ruddlesden-Popper (RP) phase film is demonstrated by sequentially depositing SrO and TiO2 layers in an alternating fashion using hybrid molecular beam epitaxy (MBE), where Ti was supplied using titanium tetraisopropoxide (TTIP). A detailed calibration procedure is outlined for determining the shuttering times to deposit SrO and TiO2 layers with precise monolayer doses using in-situ reflection high energy electron diffraction (RHEED) as feedback. Using optimized Sr and TTIP shuttering times, a fully automated growth of the n = 4 RP phase was carried out over a period of >4.5 h. Very stable RHEED intensity oscillations were observed over the entire growth period. The structural characterization by X-ray diffraction and high resolution transmission electron microscopy revealed that a constant periodicity of four SrTiO3 perovskite unit cell blocks separating the double SrO rocksalt layer was maintained throughout the entire film thickness with a very little amount of planar faults oriented perpendicular to the growth front direction. These results illustrate that hybrid MBE is capable of layer-by-layer growth with atomic level precision and excellent flux stability.

  15. BEAM INDUCED ENERGY DEPOSITION IN MUON STORAGE RINGS.

    SciTech Connect

    MOKHOV,N.V.; JOHNSTONE,C.J.; PARKER,B.L.

    2001-06-18

    Beam-induced radiation effects have been simulated for 20 and 50 GeV muon storage rings designed for a Neutrino Factory. It is shown that by appropriately shielding the superconducting magnets, quench stability, acceptable dynamic heat loads, and low residual dose rates can be achieved. Alternatively, if a specially-designed skew focusing magnet without superconducting coils on the magnet's mid-plane is used, then the energy is deposited preferentially in the warm iron yoke or outer cryostat layers and internal shielding may not be required. In addition to the component irradiation analysis, shielding studies have been performed. Calculations of the external radiation were done for both designs but the internal energy deposition calculations for the 20 GeV Study-2 lattice are still in progress.

  16. Beam-induced energy deposition in muon storage rings

    SciTech Connect

    Nikolai V. Mokhov; Carol J. Johnstone; Brett Parker

    2001-06-22

    Beam-induced radiation effects have been simulated for 20 and 50 GeV muon storage rings designed for a Neutrino Factory. It is shown that by appropriately shielding the superconducting magnets, quench stability, acceptable dynamic heat loads, and low residual dose rates can be achieved. Alternatively, if a specially-designed skew focusing magnet without superconducting coils on the magnet's mid-plane is used, then the energy is deposited preferentially in the warm iron yoke or outer cryostat layers and internal shielding may not be required. In addition to the component irradiation analysis, shielding studies have been performed. Calculations of the external radiation were done for both designs but the internal energy deposition calculations for the 20 GeV Study-2 lattice are still in progress.

  17. Epitaxial growth and heterostructure synthesis by ion beam deposition (IBD)

    SciTech Connect

    Herbots, N.; Appleton, B.R.; Noggle, T.S.; Pennycook, S.J.; Zuhr, R.A.; Zehner, D.M.

    1986-01-01

    The synthesis of heterostructures and the possibility of low-temperature epitaxy by direct ion beam deposition at low energies (10 to 200 eV) were investigated both theoretically and experimentally. Monte-Carlo simulations of ion-solid interactions were used to study collision processes during IBD and have led to a qualitative understanding of the physical parameters involved in the deposition process. /sup 30/Si and /sup 74/Ge were deposited on Si(100) and Ge(100) directly from mass- and energy-analyzed ion beams. Ge/Si multilayers with interfaces as sharp as 0.35 nm were formed by IBD at 65 eV. Reactive ion etching with 20 eV /sup 37/Cl was used to clean Si surfaces in-situ at 625 and 870/sup 0/K. IBD epitaxy was then observed between 625 and 870/sup 0/K with ion energies ranging from 10 to 65 eV. /sup 30/Si films on Si(100) grown at 700/sup 0/K exhibited an ion channeling minimum yield of 4.8%. The dopant species in the substrate affected the occurrence of silicon epitaxy below 870/sup 0/K. Cross-section transmission electron microscopy (TEM) showed that dislocation loops were formed within the substrate during heated deposition, at a depth larger than 40 nm below the bombarded region. A uniaxial lattice expansion normal to the surface was measured in IBD crystals by x-ray Bragg reflection profiling and ion channeling. It is concluded that epitaxial layers and heterostructures can be formed at low temperature by IBD.

  18. Properties of boron nitride coating films prepared by the ion beam and vapor deposition method (IVD)

    NASA Astrophysics Data System (ADS)

    Andoh, Y.; Ogata, K.; Suzuki, Y.; Kamijo, E.; Satou, M.; Fujimoto, F.

    The authors have studied coating films of boron nitride prepared by the ion implantation and vapor deposition method (IVD method) and it was found that the films consisted of the cubic, wurzite and hexagonal boron nitride. These films were manufactured by bombardment of nitrogen molecular ion with energy 25-40 keV. In the present work, we prepared films by the nitrogen molecular ions with much lower energy than the previous case. Boron was evaporated by electron beam bombardment on substrates of silicon crystal wafers and nitrogen molecular ions with energy 2-25 keV were simultaneously irradiated. Infrared absorption spectra showed a clear and strong peak due to the boron nitride of cubic structures together with a broad peak of hexagonal one. The hardness of the films was tested. The result showed that the films had 3000-5000 Hv which is much harder than titanium carbide.

  19. Low-temperature beam-induced deposition of thin tin films

    NASA Astrophysics Data System (ADS)

    Funsten, H. O.; Boring, J. W.; Johnson, R. E.; Brown, W. L.

    1992-02-01

    Ion and electron beam-induced deposition (BID) of thin (1-4 μm), conductive films is accomplished by dissociating and removing the nonmetallic components of an adsorbed, metal-based, molecular gas [SnCl4 and (CH3)4Sn]. Previous research has focused primarily on room-temperature (monolayer adsorption) BID using electrons and slow, heavy ions. This study investigates low-temperature (120 K) BID in which the condensation rate of the precursor gas is well controlled. The residual metallic films are produced by using as incident beams either 2-keV electrons, 25-keV H2+, or 50-keV H2+, all of which provide predominantly electronic energy deposition, or 30-keV Ar+, which provides predominantly nuclear energy deposition. Residual films are analyzed ex situ by scanning electron microscopy, mechanical thickness measurements, resistivity measurements, Rutherford backscattering spectroscopy, and infrared spectrometry. A model is developed that considers bulk and surface dissociation mechanisms and sputtering to describe the BID process. The derived cross sections for the formation of a residue from condensed (CH3)4Sn are nonlinearly related to the total deposited energy approximately to the 1.4 power. The lowest electrical resistivity values of the residues (650 μΩ cm) are obtained only by significant loss of carbon, which is strongly dependent on the nuclear stopping power.

  20. Molecular Beam Mass Spectrometry (MBMS) (Revised) (Fact Sheet)

    SciTech Connect

    Not Available

    2011-07-01

    This fact sheet provides information about Molecular Beam Mass Spectrometry (MBMS) capabilities and applications at NREL's National Bioenergy Center. NREL has six MBMS systems that researchers and industry partners can use to understand thermochemical biomass conversion and biomass composition recalcitrance.

  1. Characterization of CrBN films deposited by ion beam assisted deposition

    NASA Astrophysics Data System (ADS)

    Aouadi, S. M.; Namavar, F.; Tobin, E.; Finnegan, N.; Haasch, R. T.; Nilchiani, R.; Turner, J. A.; Rohde, S. L.

    2002-02-01

    This article reports on the growth and analysis of CrBN nanocrystalline materials using an ion beam assisted deposition process. In addition, this article addresses the utilization of spectroscopic ellipsometry for in situ analysis of ternary nitrides. Coatings, with a total thickness of 1.5±0.2 μm, were deposited at low temperatures (<200 °C) on silicon substrates using ion beam assisted deposition. These coatings were characterized postdeposition using x-ray diffraction (XRD), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), visible-light spectroscopic ellipsometry (VIS-SE), infrared spectroscopic ellipsometry (IR-SE), and nanoindentation. The primary phases in the films were investigated using XRD. The surface morphology and nanocrystalline nature of the coatings (grain size of 5-7 nm) were deduced using AFM. The elemental composition and phase composition of the samples were determined from XPS and AES measurements and were subsequently deduced from the analysis of the VIS-SE data, and these correlated well. XPS, AES, and IR-SE revealed the crystal structure of the BN phase in the ternary compounds. The correlation of the results from these various techniques indicates that in situ SE may be a potential technique to control the growth of ternary nitride coatings in the future. The mechanical properties of the coatings were evaluated using nanohardness testing. The hardness and elastic modulus were measured to be 19-22 GPa and 250-270 GPa, respectively.

  2. Atomic and molecular layer deposition for surface modification

    SciTech Connect

    Vähä-Nissi, Mika; Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija; Johansson, Leena-Sisko; Koskinen, Jorma T.; Harlin, Ali

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas–solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin – even non-uniform – atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid. - Graphical abstract: Print quality of a polylactide film surface modified with atomic layer deposition prior to inkjet printing (360 dpi) with an aqueous ink. Number of printed dots illustrated as a function of 0, 5, 15 and 25 deposition cycles of trimethylaluminum and water. - Highlights: • ALD/MLD can be used to adjust surface characteristics of films and fiber materials. • Hydrophobicity after few deposition cycles of Al{sub 2}O{sub 3} due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO{sub 2}. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt.

  3. Energy deposition studies for the LBNE beam absorber

    SciTech Connect

    Rakhno, Igor L.; Mokhov, Nikolai V.; Tropin, Igor S.

    2015-01-29

    Results of detailed Monte Carlo energy deposition studies performed for the LBNE absorber core and the surrounding shielding with the MARS15 code are described. The model of the entire facility, that includes a pion-production target, focusing horns, target chase, decay channel, hadron absorber system – all with corresponding radiation shielding – was developed using the recently implemented ROOT-based geometry option in the MARS15 code. This option provides substantial flexibility and automation when developing complex geometry models. Both normal operation and accidental conditions were studied. Various design options were considered, in particular the following: (i) filling the decay pipe with air or helium; (ii) the absorber mask material and shape; (iii) the beam spoiler material and size. Results of detailed thermal calculations with the ANSYS code helped to select the most viable absorber design options.

  4. Fundamental proximity effects in focused electron beam induced deposition.

    PubMed

    Plank, Harald; Smith, Daryl A; Haber, Thomas; Rack, Philip D; Hofer, Ferdinand

    2012-01-24

    Fundamental proximity effects for electron beam induced deposition processes on nonflat surfaces were studied experimentally and via simulation. Two specific effects were elucidated and exploited to considerably increase the volumetric growth rate of this nanoscale direct write method: (1) increasing the scanning electron pitch to the scale of the lateral electron straggle increased the volumetric growth rate by 250% by enhancing the effective forward scattered, backscattered, and secondary electron coefficients as well as by strong recollection effects of adjacent features; and (2) strategic patterning sequences are introduced to reduce precursor depletion effects which increase volumetric growth rates by more than 90%, demonstrating the strong influence of patterning parameters on the final performance of this powerful direct write technique. PMID:22181556

  5. Fundamental Proximity Effects in Focused electron Beam Induced Deposition

    SciTech Connect

    Plank, Harald; Smith, Daryl; Haber, Thomas; Rack, Philip D; Hofer, Ferdinand

    2012-01-01

    Fundamental proximity effects for electron beam induced deposition processes on nonflat surfaces were studied experimentally and via simulation. Two specific effects were elucidated and exploited to considerably increase the volumetric growth rate of this nanoscale direct write method: (1) increasing the scanning electron pitch to the scale of the lateral electron straggle increased the volumetric growth rate by 250% by enhancing the effective forward scattered, backscattered, and secondary electron coefficients as well as by strong recollection effects of adjacent features; and (2) strategic patterning sequences are introduced to reduce precursor depletion effects which increase volumetric growth rates by more than 90%, demonstrating the strong influence of patterning parameters on the final performance of this powerful direct write technique.

  6. Thickness dependence of resistivity for Cu films deposited by ion beam deposition

    NASA Astrophysics Data System (ADS)

    Lim, J.-W.; Mimura, K.; Isshiki, M.

    2003-07-01

    The thickness dependence of the resistivity for Cu films deposited by ion beam deposition (IBD) was evaluated using Fuchs-Sondheimer (F-S) model for electron surface scattering and Mayadas-Shatzkes (M-S) model for electron grain boundary scattering. For fitting the F-S and M-S models to the experimental data, the approximate equations proposed in both models were discussed and it was confirmed that the experimental resistivity of the Cu films could be described well by a simple form combined of the approximate equations for both models. By means of the simple form in this work, the most reasonable fit to the experimental data could be obtained under the conditions of the surface scattering coefficient p=0 and the reflection coefficient at grain boundary R=0.40.

  7. Dual ion beam deposition of carbon films with diamondlike properties

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.; Swec, D. M.; Angus, J. C.

    1984-01-01

    A single and dual ion beam system was used to generate amorphous carbon films with diamond like properties. A methane/argon mixture at a molar ratio of 0.28 was ionized in the low pressure discharge chamber of a 30-cm-diameter ion source. A second ion source, 8 cm in diameter was used to direct a beam of 600 eV Argon ions on the substrates (fused silica or silicon) while the deposition from the 30-cm ion source was taking place. Nuclear reaction and combustion analysis indicate H/C ratios for the films to be 1.00. This high value of H/C, it is felt, allowed the films to have good transmittance. The films were impervious to reagents which dissolve graphitic and polymeric carbon structures. Although the measured density of the films was approximately 1.8 gm/cu cm, a value lower than diamond, the films exhibited other properties that were relatively close to diamond. These films were compared with diamondlike films generated by sputtering a graphite target.

  8. Synthesis of silicon nitride films by ion beam enhanced deposition

    NASA Astrophysics Data System (ADS)

    Xianghuai, Liu; Bin, Xue; Zhihong, Zheng; Zuyao, Zhou; Shichang, Zou

    1989-03-01

    Silicon nitride films with stoichiometric ratio of Si 3N 4 have been synthesized by concurrent electron beam evaporation of silicon and bombardment with nitrogen ions. The results show that the component ratio of nitrogen to silicon in IBED silicon nitride films can be controlled and predicted by the atomic arrival rate ratio of nitrogen to silicon. IR measurement shows that the characteristic absorption peak of IBED Si 3N 4 is located at a wavenumber of 840 cm -1. The refractive index ranges from 2.2 to 2.6. RBS, AES, TEM, SEM, ED and spreading resistance measurement were used for investigation of the depth profiles of composition and structure of silicon nitride films synthesized by IBED. An intermixed layer is formed at the interface by the knock on effect, and a silicon enriched layer is observed at the surface region of the film. Normally the films were found to be amorphous, but electron diffraction patterns taken from deposited layer showed a certain crystallinity. The silicon nitride films prepared by IBED have dramatically less oxygen content than that formed by non-ion-assisted deposition.

  9. Nanostructured component fabrication by electron beam-physical vapor deposition

    NASA Astrophysics Data System (ADS)

    Singh, Jogender; Wolfe, Douglas E.

    2005-08-01

    Fabrication of cost-effective, nano-grained net-shaped components has brought considerable interest to Department of Defense, National Aeronautics and Space Administration, and Department of Energy. The objective of this paper is to demonstrate the versatility of electron beam-physical vapor deposition (EB-PVD) technology in engineering new nanostructured materials with controlled microstructure and microchemistry in the form of coatings and net-shaped components for many applications including the space, turbine, optical, biomedical, and auto industries. Coatings are often applied on components to extent their performance and life under severe environmental conditions including thermal, corrosion, wear, and oxidation. Performance and properties of the coatings depend upon their composition, microstructure, and deposition condition. Simultaneous co-evaporation of multiple ingots of different compositions in the high energy EB-PVD chamber has brought considerable interest in the architecture of functional graded coatings, nano-laminated coatings, and design of new structural materials that could not be produced economically by conventional methods. In addition, high evaporation and condensate rates allowed fabricating precision net-shaped components with nanograined microstructure for various applications. Using EB-PVD, nano-grained rhenium (Re) coatings and net-shaped components with tailored microstructure and properties were fabricated in the form of tubes, plates, and Re-coated spherical graphite cores. This paper will also present the results of various metallic and ceramic coatings including chromium, titanium carbide (TiC), titanium diboride (TiB2), hafnium nitride (HfN), titanium-boron-carbonitride (TiBCN), and partially yttria stabilized zirconia (YSZ) TBC coatings deposited by EB-PVD for various applications.

  10. Nanoscale electron beam-induced deposition and purification of ruthenium for extreme ultraviolet lithography mask repair

    NASA Astrophysics Data System (ADS)

    Noh, J. H.; Stanford, M. G.; Lewis, B. B.; Fowlkes, J. D.; Plank, H.; Rack, P. D.

    2014-12-01

    One critical area for the adoption of extreme ultraviolet (EUV) lithography is the development of appropriate mask repair strategies. To this end, we have explored focused electron beam-induced deposition of the ruthenium capping or protective layer. Electron beam-induced deposition (EBID) was used to deposit a ruthenium capping/protective film using the liquid bis(ethylcyclopentyldienyl)ruthenium(II) precursor. The carbon to ruthenium atomic ratio in the as-deposited material was estimated to be ~9/1. Subsequent to deposition, we demonstrate an electron stimulated purification process to remove carbon by-products from the deposit. Results indicate that high-fidelity nanoscale ruthenium repairs can be realized.

  11. Large-scale Molecular Dynamics Simulations of Glancing Angle Deposition

    NASA Astrophysics Data System (ADS)

    Hubartt, Bradley; Liu, Xuejing; Amar, Jacques

    2013-03-01

    While a variety of methods have been developed to carry out atomistic simulations of thin-film growth at small deposition angles with respect to the substrate normal, due to the complex morphology as well as the existence of multiple scattering of depositing atoms by the growing thin-film, realistically modeling the deposition process for large deposition angles can be quite challenging. Accordingly, we have developed a computationally efficient method based on the use of a single graphical processing unit (GPU) to carry out molecular dynamics (MD) simulations of the deposition and growth of thin-films via glancing angle deposition. Using this method we have carried out large-scale MD simulations, based on an embedded-atom-method potential, of Cu/Cu(100) growth up to 20 monolayers for deposition angles ranging from 50° to 85° and for both random and fixed azimuthal angles. Our results for the thin-film porosity, roughness, lateral correlation length, and density vs height will be presented and compared with experiments. Results for the dependence of the microstructure, grain-size distribution, surface texture, and defect concentration on deposition angle will also be presented. Supported by NSF DMR-0907399

  12. Molecular Mechanisms of Bone 18F-NaF Deposition

    PubMed Central

    Czernin, Johannes; Satyamurthy, Nagichettiar; Schiepers, Christiaan

    2011-01-01

    There is renewed interest in 18F-NaF bone imaging with PET or PET/CT. The current brief discussion focuses on the molecular mechanisms of 18F-NaF deposition in bone and presents model-based approaches to quantifying bone perfusion and metabolism in the context of preclinical and clinical applications of bone imaging with PET. PMID:21078790

  13. Reactive Collisions in Crossed Molecular Beams

    DOE R&D Accomplishments Database

    Herschbach, D. R.

    1962-02-01

    The distribution of velocity vectors of reaction products is discussed with emphasis on the restrictions imposed by the conservation laws. The recoil velocity that carries the products away from the center of mass shows how the energy of reaction is divided between internal excitation and translation. Similarly, the angular distributions, as viewed from the center of mass, reflect the partitioning of the total angular momentum between angular momenta of individual molecules and orbital angular momentum associated with their relative motion. Crossed-beam studies of several reactions of the type M + RI yields R + MI are described, where M = K, Rb, Cs, and R = CH{sub 3}, C{sub 3}H{sub 5}, etc. The results show that most of the energy of reaction goes into internal excitation of the products and that the angular distribution is quite anisotropic, with most of the MI recoiling backward (and R forward) with respect to the incoming K beam. (auth)

  14. Measuring Incorporation Of Arsenic In Molecular-Beam Expitaxy

    NASA Technical Reports Server (NTRS)

    Lewis, Blair F.; Fernandez, Rouel F.; Madhukar, Anupam; Grunthaner, Frank J.

    1988-01-01

    Changes in surface layers cause oscillations in RHEED measurements. Specular RHEED Beam intensity measured before, during, and after deposition of seven to eight monomolecular layers of gallium during 1.5 seconds. Arsenic pressure was 1.7x10 to the negative seventh power torr (2.3x10 to the negative fifth power Pa) throughout measurements.

  15. Area-selective formation of Si nanocrystals by assisted ion-beam irradiation during dual-ion-beam deposition

    SciTech Connect

    Kim, Jae Kwon; Cha, Kyu Man; Kang, Jung Hyun; Kim, Yong; Yi, Jae-Yel; Chung, Tae Hun; Bark, Hong Jun

    2004-08-30

    We investigate the effect of Ar-ion-beam irradiation during the deposition of SiO{sub x} films by dual-ion-beam deposition system. Ion-beam irradiation effectively increases the oxygen content, x, in SiO{sub x} films indicative of the preferential sputtering of Si phase as compared to SiO{sub 2} phase in SiO{sub x} films. We observe the intense photoluminescence from nonirradiated sample after postdeposition annealing at 1100 deg. C indicating the formation of Si nanocrystals as shown by a cross-sectional transmission electron microscope. However, the increased oxygen content in ion-beam-irradiated sample results in small optical volume of small Si nanocrystals not sufficient for yielding appreciable photoluminescence intensity after postdeposition annealing. The property is utilized for achieving the area-selective formation of Si nanocrytals by inserting a shadow mask in assist ion beam during deposition.

  16. Preparation of high-purity Cu films by non-mass separated ion beam deposition

    NASA Astrophysics Data System (ADS)

    Lim, J.-W.; Mimura, K.; Miyake, K.; Yamashita, M.; Isshiki, M.

    2003-05-01

    Cu films were deposited on Si(1 0 0) substrates by applying a negative substrate bias voltage using non-mass separated ion beam deposition (IBD) method. By the SIMS results with Cs + ion beam, the Cu film deposited at VS=0 V was found to contain more impurities than the Cu film deposited at VS=-50 V. On the other hand, from the SIMS results with O 2+ ion beam, it was found that elements which are easy to be positive ions such as B, Mg, Na, Al, K, Ca and Fe seem to be increased slightly as compared to the those of the Cu film deposited at VS=0 V. As a result, higher-purity Cu film deposited at VS=-50 V could be obtained in comparison with the film deposited at VS=0 V. The purification effect of the Cu film deposited at VS=-50 V was described in details.

  17. Molecular-beam Studies of Primary Photochemical Processes

    DOE R&D Accomplishments Database

    Lee, Y. T.

    1982-12-01

    Application of the method of molecular-beam photofragmentation translational spectroscopy to the investigation of primary photochemical processes of polyatomic molecules is described. Examples will be given to illustrate how information concerning the energetics, dynamics, and mechanism of dissociation processes can be obtained from the precise measurements of angular and velocity distributions of products in an experiment in which a well-defined beam of molecules is crossed with a laser.

  18. A low Earth orbit molecular beam space simulation facility

    NASA Technical Reports Server (NTRS)

    Cross, J. B.

    1984-01-01

    A brief synopsis of the low Earth orbit (LEO) satellite environment is presented including neutral and ionic species. Two ground based atomic and molecular beam instruments are described which are capable of simulating the interaction of spacecraft surfaces with the LEO environment and detecting the results of these interactions. The first detects mass spectrometrically low level fluxes of reactively and nonreactively surface scattered species as a function of scattering angle and velocity while the second ultrahigh velocity (UHV) molecular beam, laser induced fluorescence apparatus is capable of measuring chemiluminescence produced by either gas phase or gas-surface interactions. A number of proposed experiments are described.

  19. Focused electron beam induced deposition as a tool to create electron vortices.

    PubMed

    Béché, A; Winkler, R; Plank, H; Hofer, F; Verbeeck, J

    2016-01-01

    Focused electron beam induced deposition (FEBID) is a microscopic technique that allows geometrically controlled material deposition with very high spatial resolution. This technique was used to create a spiral aperture capable of generating electron vortex beams in a transmission electron microscope (TEM). The vortex was then fully characterized using different TEM techniques, estimating the average orbital angular momentum to be ∼0.8ℏ per electron with almost 60% of the beam ending up in the ℓ=1 state. PMID:26432987

  20. Production of high density molecular beams with wide velocity scanning

    NASA Astrophysics Data System (ADS)

    Sheffield, L. S.; Woo, S. O.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Herschbach, D. R.

    2016-06-01

    We describe modifications of a pulsed rotating supersonic beam source that improve performance, particularly increasing the beam density and sharpening the pulse profiles. As well as providing the familiar virtues of a supersonic molecular beam (high intensity, narrowed velocity distribution, and drastic cooling of rotation and vibration), the rotating source enables scanning the translational velocity over a wide range. Thereby, beams of any atom or molecule available as a gas can be slowed or speeded. Using Xe beams in the slowing mode, we have obtained lab speeds down to about 40 ± 5 m/s with density near 1011 cm-3 and in the speeding mode lab speeds up to about 660 m/s and density near 1014 cm-3. We discuss some congenial applications. Providing low lab speeds can markedly enhance experiments using electric or magnetic fields to deflect, steer, or further slow polar or paramagnetic molecules. The capability to scan molecular speeds facilitates merging velocities with a codirectional partner beam, enabling study of collisions at very low relative kinetic energies, without requiring either beam to be slow.

  1. Electromigration in focused ion beam deposited tungsten single nanowires

    NASA Astrophysics Data System (ADS)

    Mandal, Pabitra; Das, Bipul; Raychaudhuri, A. K.

    As the focused ion beam induced deposited (FIBID) nanowires (NWs) of W, Pt are being used in nanoelectronic technology to connect individual nanodevices, repairing damaged interconnects in integrated circuit (IC), electromigration study in FIBID-NWs has become essential. Briefly, when a thin conductor, like metallic Al, Cu interconnects in an IC chip carry quite high current density ~1012 A/m2, ions or atoms start migrating. Such migration causes void and hillock formation leading to interconnect discontinuity, short circuit and ultimately IC failure. Our electromigration study in single FIBID-NWs of W reveals that failure in NWs of width and thickness ~100 nm occurs typically at 1011 A/m2. Most notably, void and hillock always form in opposite polarity compared to typical metallic NWs. Such distinctly new outcome is explained via electromigration driven by direct force (ionic charge*electric field) opposed to wind force driven migration observed in metallic NWs. As FIBID-NWs are composite in nature, different species (e.g., Ga, W and C) migrate with different degree and direction depending on their oxidation state, leading to redistribution of species across NW length and formation of a Ga rich hillock. S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata-98, India.

  2. Pulsed rotating supersonic source for merged molecular beams

    NASA Astrophysics Data System (ADS)

    Sheffield, L.; Hickey, M. S.; Krasovitskiy, V.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Herschbach, D. R.

    2012-06-01

    We describe a pulsed rotating supersonic beam source, evolved from an ancestral device [M. Gupta and D. Herschbach, J. Phys. Chem. A 105, 1626 (2001)]. The beam emerges from a nozzle near the tip of a hollow rotor which can be spun at high-speed to shift the molecular velocity distribution downward or upward over a wide range. Here we consider mostly the slowing mode. Introducing a pulsed gas inlet system, cryocooling, and a shutter gate eliminated the main handicap of the original device in which continuous gas flow imposed high background pressure. The new version provides intense pulses, of duration 0.1-0.6 ms (depending on rotor speed) and containing ˜1012 molecules at lab speeds as low as 35 m/s and ˜1015 molecules at 400 m/s. Beams of any molecule available as a gas can be slowed (or speeded); e.g., we have produced slow and fast beams of rare gases, O2, Cl2, NO2, NH3, and SF6. For collision experiments, the ability to scan the beam speed by merely adjusting the rotor is especially advantageous when using two merged beams. By closely matching the beam speeds, very low relative collision energies can be attained without making either beam very slow.

  3. Pulsed rotating supersonic source for merged molecular beams

    NASA Astrophysics Data System (ADS)

    Sheffield, Les; Hickey, Mark; Krasovitskiy, Vitaliy; Rathnayaka, Daya; Lyuksyutov, Igor; Herschbach, Dudley

    2012-10-01

    We continue the characterization of a pulsed rotating supersonic beam source. The original device was described by M. Gupta and D. Herschbach, J. Phys. Chem. A 105, 1626 (2001). The beam emerges from a nozzle near the tip of a hollow rotor which can be spun at high-speed to shift the molecular velocity distribution downward or upward over a wide range. Here we consider mostly the slowing mode. Introducing a pulsed gas inlet system, and a shutter gate eliminate the main handicap of the original device in which continuous gas flow imposed high background pressure. The new version provides intense pulses, of duration 0.1--0.6 ms (depending on rotor speed) and containing ˜10^12 molecules at lab speeds as low as 35 m/s and ˜10^15 molecules at 400 m/s. Beams of any molecule available as a gas can be slowed (or speeded); e.g., we have produced slow and fast beams of rare gases, O2, NO2, NH3, and SF6. For collision experiments, the ability to scan the beam speed by merely adjusting the rotor is especially advantageous when using two merged beams. By closely matching the beam speeds, very low relative collision energies can be attained without making either beam very slow.

  4. Metallic impurities in gallium nitride grown by molecular beam epitaxy

    SciTech Connect

    McHugo, S.A.; Krueger, J.; Kisielowski, C.

    1997-04-01

    Transition metals are often encountered in trace amounts in semiconductors. They have been extensively studied in most elemental and compound systems, since they form deep donor and/or acceptor levels which usually degrade the electronic and optical material properties. Only very little is known about transition metals in recent III-V semiconducting materials, such as GaN, AlN and InN. These few studies have been done exclusively on Metal-Organic Chemical Vapor Deposition (MOCVD) or Hybrid Vapor Phase Epitaxy HVPE-grown GaN. Preliminary x-ray fluorescence studies at the Advanced Light Source, beamline 10.3.1, Lawrence Berkeley National Laboratory have revealed that GaN materials grown by Molecular Beam Epitaxy (MBE) have Fe, Ni and Cr as the dominant transition metal contaminants. This finding is commensurate with the extremely high concentrations of hydrogen, carbon and oxygen (up to 10{sup 20} cm{sup {minus}3}) measured by Secondary Ion Mass Spectroscopy (SIMS). Preliminary work using the mapping capabilities of the x-ray fluorescence microprobe revealed the metal impurities were inhomogeneously distributed over the film. Future work of this collaboration will be to find a correlation between the existence of transition metals in MBE films, as revealed by x-ray fluorescence, and Photoluminescence (PL) spectra taken in the infrared region. Also, the authors will make use of the 1 {mu}m spatial resolution of x-ray microprobe to locate the contaminants in relation to structural defects in the GaN films. Because of the large strain caused by the lattice mismatch between the GaN films and the substrates, the films grow in a columnar order with high densities of grain boundaries and dislocations. These structural defects offer preferential sites for metal precipitation or agglomeration which could degrade the optical properties of this material more so than if the impurities were left dissolved in the GaN.

  5. Molecular dynamics simulation of gold cluster growth during sputter deposition

    NASA Astrophysics Data System (ADS)

    Abraham, J. W.; Strunskus, T.; Faupel, F.; Bonitz, M.

    2016-05-01

    We present a molecular dynamics simulation scheme that we apply to study the time evolution of the self-organized growth process of metal cluster assemblies formed by sputter-deposited gold atoms on a planar surface. The simulation model incorporates the characteristics of the plasma-assisted deposition process and allows for an investigation over a wide range of deposition parameters. It is used to obtain data for the cluster properties which can directly be compared with recently published experimental data for gold on polystyrene [M. Schwartzkopf et al., ACS Appl. Mater. Interfaces 7, 13547 (2015)]. While good agreement is found between the two, the simulations additionally provide valuable time-dependent real-space data of the surface morphology, some of whose details are hidden in the reciprocal-space scattering images that were used for the experimental analysis.

  6. Full characterization of an intense pulsed hyperthermal molecular beam

    SciTech Connect

    Watanabe, D.; Che, D.-C.; Fukuyama, T.; Hashinokuchi, M.; Teraoka, Y.; Kasai, T.

    2005-05-15

    A molecular beam technique for generating an intense pulsed hyperthermal molecular beam (pulsed HTMB) was developed. The beam source consists of a pulse valve, a cooling-water bottle that protects the pulse valve from heat transfer of the high temperature nozzle, and a nozzle with a heater. The point was a pulse-valve operation with the high temperature nozzle which was 30-mm long and was made of pyrolytic boron nitride. The pulsed HTMB of HCl was practically generated. The total beam intensity of the pulsed HTMB was measured by a quadrupole mass spectrometer. It was determined that the beam intensity of the pulsed HTMB was two orders of magnitude larger than that obtained in continuous-HTMB conditions. The pulsed HTMB of HCl was fully characterized by means of (2+1) resonance-enhanced multiphoton ionization and ion time-of-flight techniques. We found that the velocity distribution of the pulsed HTMB was well expressed as supersonic molecular beams. At the highest nozzle temperature of 1400 K, the mean translational energy value of HCl molecules was 1.38 eV. The translational energy distribution of the pulsed HTMB covered a range from 0.8 to 1.6 eV. The fraction of higher translational energy molecules greater than 1.0 eV was 80% in the 1400 K nozzle. The rotational state distributions of HCl molecules in the pulsed HTMB were expressed as the Boltzmann distribution. While the rotational temperature decreased by an adiabatic expansion of the beam, the vibrational temperature, which was determined by the ratio of the ground-state population to the excited state one, almost equaled the nozzle temperature.

  7. CNT manipulation: inserting a carbonaceous dielectric layer beneath using electron beam induced deposition.

    PubMed

    Kurrat, Narendra; Vijaykumar, T; Kulkarni, G U

    2011-02-01

    Electron beam induced carbonaceous deposition has been carried out in the presence of water vapor at 0.4 torr pressure amidst residual hydrocarbons present in the SEM chamber. When performed at a CNT location on a Si substrate with low e beam energy (10 kV), the deposition was taking place beneath the CNT. While higher beam energy (25 kV) causing the deposition on the top surface of the CNT, in agreement with the earlier reports. The insertion of dielectric carbonaceous layer beneath the CNT allowed us to measure the I-V data along the length of the nanotube using CAFM. PMID:21456133

  8. Influence of Molecular Shape on Molecular Orientation and Stability of Vapor-Deposited Organic Semiconductors

    NASA Astrophysics Data System (ADS)

    Walters, Diane M.; Johnson, Noah D.; Ediger, M. D.

    Physical vapor deposition is commonly used to prepare active layers in organic electronics. Recently, it has been shown that molecular orientation and packing can be tuned by changing the substrate temperature during deposition, while still producing macroscopically homogeneous films. These amorphous materials can be highly anisotropic when prepared with low substrate temperatures, and they can exhibit exceptional kinetic stability; films retain their favorable packing when heated to high temperatures. Here, we study the influence of molecular shape on molecular orientation and stability. We investigate disc-shaped molecules, such as TCTA and m-MTDATA, nearly spherical molecules, such as Alq3, and linear molecules covering a broad range of aspect ratios, such as p-TTP and BSB-Cz. Disc-shaped molecules have preferential horizontal orientation when deposited at low substrate temperatures, and their orientation can be tuned by changing the substrate temperature. Alq3 forms stable, amorphous films that are optically isotropic when vapor deposited over a broad range of substrate temperatures. This work may guide the choice of material and deposition conditions for vapor-deposited films used in organic electronics and allow for more efficient devices to be fabricated.

  9. (abstract) Optical Scattering and Surface Microroughness of Ion Beam Deposited Au and Pt Thin Films

    NASA Technical Reports Server (NTRS)

    Al-Jumaily, Ghanim A.; Raouf, Nasrat A.; Edlou, Samad M.; Simons, John C.

    1994-01-01

    Thin films of gold and platinum have been deposited onto superpolished fused silica substrates using thermal evaporation, ion assisted deposition (IAD), and ion assisted sputtering. The influence of ion beam flux, thin film material, and deposition rate on the films microroughness have been investigated. Short range surface microroughness of the films has been examined using scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Long range surface microroughness has been characterized using an angle resolved optical scatterometer. Results indicate that ion beam deposited coatings have improved microstructure over thermally evaporated films.

  10. Inert gas jets for growth control in electron beam induced deposition

    SciTech Connect

    Henry, M. R.; Kim, S.; Rykaczewski, K.; Fedorov, A. G.

    2011-06-27

    An inert, precursor free, argon jet is used to control the growth rate of electron beam induced deposition. Adjustment of the jet kinetic energy/inlet temperature can selectively increase surface diffusion to greatly enhance the deposition rate or deplete the surface precursor due to impact-stimulated desorption to minimize the deposition or completely clean the surface. Physical mechanisms for this process are described. While the electron beam is also observed to generate plasma upon interaction with an argon jet, our results indicate that plasma does not substantially contribute to the enhanced deposition rate.

  11. Hybrid inorganic–organic superlattice structures with atomic layer deposition/molecular layer deposition

    SciTech Connect

    Tynell, Tommi; Yamauchi, Hisao; Karppinen, Maarit

    2014-01-15

    A combination of the atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques is successfully employed to fabricate thin films incorporating superlattice structures that consist of single layers of organic molecules between thicker layers of ZnO. Diethyl zinc and water are used as precursors for the deposition of ZnO by ALD, while three different organic precursors are investigated for the MLD part: hydroquinone, 4-aminophenol and 4,4′-oxydianiline. The successful superlattice formation with all the organic precursors is verified through x-ray reflectivity studies. The effects of the interspersed organic layers/superlattice structure on the electrical and thermoelectric properties of ZnO are investigated through resistivity and Seebeck coefficient measurements at room temperature. The results suggest an increase in carrier concentration for small concentrations of organic layers, while higher concentrations seem to lead to rather large reductions in carrier concentration.

  12. Low interfacial trap density and sub-nm equivalent oxide thickness in In0.53Ga0.47As (001) metal-oxide-semiconductor devices using molecular beam deposited HfO2/Al2O3 as gate dielectrics

    NASA Astrophysics Data System (ADS)

    Chu, L. K.; Merckling, C.; Alian, A.; Dekoster, J.; Kwo, J.; Hong, M.; Caymax, M.; Heyns, M.

    2011-07-01

    We investigated the passivation of In0.53Ga0.47As (001) surface by molecular beam epitaxy techniques. After growth of strained In0.53Ga0.47As on InP (001) substrate, HfO2/Al2O3 high-κ oxide stacks have been deposited in-situ after surface reconstruction engineering. Excellent capacitance-voltage characteristics have been demonstrated along with low gate leakage currents. The interfacial density of states (Dit) of the Al2O3/In0.53Ga0.47As interface have been revealed by conductance measurement, indicating a downward Dit profile from the energy close to the valence band (medium 1012 cm-2eV-1) towards that close to the conduction band (1011 cm-2eV-1). The low Dit's are in good agreement with the high Fermi-level movement efficiency of greater than 80%. Moreover, excellent scalability of the HfO2 has been demonstrated as evidenced by the good dependence of capacitance oxide thickness on the HfO2 thickness (dielectric constant of HfO2 ˜20) and the remained low Dit's due to the thin Al2O3 passivation layer. The sample with HfO2 (3.4 nm)/Al2O3 (1.2 nm) as the gate dielectrics has exhibited an equivalent oxide thickness of ˜0.93 nm.

  13. Dual beam optical system for pulsed laser ablation film deposition

    DOEpatents

    Mashburn, D.N.

    1996-09-24

    A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

  14. GaSb molecular beam epitaxial growth on p-InP(001) and passivation with in situ deposited Al{sub 2}O{sub 3} gate oxide

    SciTech Connect

    Merckling, C.; Brammertz, G.; Hoffmann, T. Y.; Caymax, M.; Dekoster, J.; Sun, X.; Alian, A.; Heyns, M.; Afanas'ev, V. V.

    2011-04-01

    The integration of high carrier mobility materials into future CMOS generations is presently being studied in order to increase drive current capability and to decrease power consumption in future generation CMOS devices. If III-V materials are the candidates of choice for n-type channel devices, antimonide-based semiconductors present high hole mobility and could be used for p-type channel devices. In this work we first demonstrate the heteroepitaxy of fully relaxed GaSb epilayers on InP(001) substrates. In a second part, the properties of the Al{sub 2}O{sub 3}/GaSb interface have been studied by in situ deposition of an Al{sub 2}O{sub 3} high-{kappa} gate dielectric. The interface is abrupt without any substantial interfacial layer, and is characterized by high conduction and valence band offsets. Finally, MOS capacitors show well-behaved C-V with relatively low D{sub it} along the bandgap, these results point out an efficient electrical passivation of the Al{sub 2}O{sub 3}/GaSb interface.

  15. Inert gas enhanced laser-assisted purification of platinum electron-beam-induced deposits

    SciTech Connect

    Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; Fowlkes, Jason Davidson; Rack, Philip D.

    2015-06-30

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar–H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some loss of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. Lastly, a sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.

  16. Inert gas enhanced laser-assisted purification of platinum electron-beam-induced deposits

    DOE PAGESBeta

    Stanford, Michael G.; Lewis, Brett B.; Noh, Joo Hyon; Fowlkes, Jason Davidson; Rack, Philip D.

    2015-06-30

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar–H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some lossmore » of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. Lastly, a sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention.« less

  17. Inert Gas Enhanced Laser-Assisted Purification of Platinum Electron-Beam-Induced Deposits.

    PubMed

    Stanford, Michael G; Lewis, Brett B; Noh, Joo Hyon; Fowlkes, Jason D; Rack, Philip D

    2015-09-01

    Electron-beam-induced deposition patterns, with composition of PtC5, were purified using a pulsed laser-induced purification reaction to erode the amorphous carbon matrix and form pure platinum deposits. Enhanced mobility of residual H2O molecules via a localized injection of inert Ar-H2 (4%) is attributed to be the reactive gas species for purification of the deposits. Surface purification of deposits was realized at laser exposure times as low as 0.1 s. The ex situ purification reaction in the deposit interior was shown to be rate-limited by reactive gas diffusion into the deposit, and deposit contraction associated with the purification process caused some loss of shape retention. To circumvent the intrinsic flaws of the ex situ anneal process, in situ deposition and purification techniques were explored that resemble a direct write atomic layer deposition (ALD) process. First, we explored a laser-assisted electron-beam-induced deposition (LAEBID) process augmented with reactive gas that resulted in a 75% carbon reduction compared to standard EBID. A sequential deposition plus purification process was also developed and resulted in deposition of pure platinum deposits with high fidelity and shape retention. PMID:26126173

  18. Space processing applications of ion beam technology. [surface finishing, welding, milling and film deposition

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.

    1977-01-01

    Ion thruster engines for spacecraft propulsion can serve as ion beam sources for potential space processing applications. The advantages of space vacuum environments and the possible gravity effects on thruster ion beam materials operations such as thin film growth, ion milling, and surface texturing were investigated. The direct gravity effect on sputter deposition and vapor deposition processes are discussed as well as techniques for cold and warm welding.

  19. MCNPX benchmark of out-of-beam energy deposition in LiAl

    SciTech Connect

    Corzine, K.; Ferguson, P.; Morgan, G.; Quintana, D.; Waters, L.; Cooper, R.; Liljestrand, R.; Whiteson, A.

    2000-07-01

    The MCNPX code is currently being used to calculate energy deposition in the accelerator production of tritium (APT) target/blanket system components. To ensure that these components are properly designed, the code must be validated. An energy deposition experiment was designed to aid in the code validation using thermocouple sensors in-beam and thermistor-type sensors in decoupler- and blanketlike regions. This paper focuses on the out-of-beam thermistor sensors constructed of LiAl.

  20. Laser controlled deposition of metal microstructures via nondiffracting Bessel beam illumination

    NASA Astrophysics Data System (ADS)

    Drampyan, Rafael; Leonov, Nikita; Vartanyan, Tigran

    2016-04-01

    The technique of the laser controlled deposition of sodium and rubidium deposits on the sapphire substrate is presented. The metals were deposited on the clean sapphire substrate from the vapor phase contained in the evacuated and sealed cell. We use an axicon to produce a non-diffracting Bessel beam out of the beam got from the cw diode laser with 200 mW power at the wavelength of 532 nm. After 30 minutes of the laser-controlled deposition the substrates were examined in the optical microscope. The obtained metal deposits form the sharp-cut circles with the pitch of 10 μm, coincident with the tens of dark rings of the Bessel beam. Reduction of the laser power leads to the build up of the continuous metal film over the whole substrate.

  1. Molecular layer deposition of alucone films using trimethylaluminum and hydroquinone

    SciTech Connect

    Choudhury, Devika; Sarkar, Shaibal K.; Mahuli, Neha

    2015-01-01

    A hybrid organic–inorganic polymer film grown by molecular layer deposition (MLD) is demonstrated here. Sequential exposures of trimethylaluminum [Al(CH{sub 3}){sub 3}] and hydroquinone [C{sub 6}H{sub 4}(OH){sub 2}] are used to deposit the polymeric films, which is a representative of a class of aluminum oxide polymers known as “alucones.” In-situ quartz crystal microbalance (QCM) studies are employed to determine the growth characteristics. An average growth rate of 4.1 Å per cycle at 150 °C is obtained by QCM and subsequently verified with x-ray reflectivity measurements. Surface chemistry during each MLD-half cycle is studied in depth by in-situ Fourier transform infrared (FTIR) vibration spectroscopy. Self limiting nature of the reaction is confirmed from both QCM and FTIR measurements. The conformal nature of the deposit, typical for atomic layer deposition and MLD, is verified with transmission electron microscopy imaging. Secondary ion mass spectroscopy measurements confirm the uniform elemental distribution along the depth of the films.

  2. Pulsed Helium Ion Beam Induced Deposition: A Means to High Growth Rates

    SciTech Connect

    Alkemade, Paul F. A.; Miro, Hozanna; Van Veldhoven, Emile; Maas, Diederick; Smith, Daryl; Rack, P. D.

    2011-01-01

    The sub-nanometer beam of a helium ion microscope was used to study and optimize helium-ion beam induced deposition of PtC nanopillars with the (CH{sub 3}){sub 3}Pt(CPCH{sub 3}) precursor. The beam current, beam dwell time, precursor refresh time, and beam focus have been independently varied. Continuous beam exposure resulted in narrow but short pillars, while pulsed exposure resulted in thinner and higher ones. Furthermore, at short dwell times the deposition efficiency was very high, especially for a defocused beam. Efficiencies were measured up to 20 times the value for continuous exposure conditions. The interpretation of the experimental data was aided by a Monte Carlo simulation of the deposition. The results indicate that two regimes are operational in ion beam induced deposition (IBID). In the first one, the adsorbed precursor molecules originally present in the beam interaction region decompose. After the original precursor layer is consumed, further depletion is averted and growth continues by the supply of molecules via adsorption and surface diffusion. Depletion around the beam impact site can be distinguished from depletion on the flanges of the growing pillars. The Monte Carlo simulations for low precursor surface coverage reproduce measured growth rates, but predict considerably narrower pillars, especially at short dwell times. Both the experiments and the simulations show that the pillar width rapidly increases with increasing beam diameter. Optimal writing strategy, good beam focusing, and rapid beam positioning are needed for efficient and precise fabrication of extended and complex nanostructures by He-IBID.

  3. Friction and Wear of Ion-Beam-Deposited Diamondlike Carbon on Chemical-Vapor-Deposited, Fine-Grain Diamond

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Wu, Richard L. C.; Lanter, William C.

    1996-01-01

    Friction and wear behavior of ion-beam-deposited diamondlike carbon (DLC) films coated on chemical-vapor-deposited (CVD), fine-grain diamond coatings were examined in ultrahigh vacuum, dry nitrogen, and humid air environments. The DLC films were produced by the direct impact of an ion beam (composed of a 3:17 mixture of Ar and CH4) at ion energies of 1500 and 700 eV and an RF power of 99 W. Sliding friction experiments were conducted with hemispherical CVD diamond pins sliding on four different carbon-base coating systems: DLC films on CVD diamond; DLC films on silicon; as-deposited, fine-grain CVD diamond; and carbon-ion-implanted, fine-grain CVD diamond on silicon. Results indicate that in ultrahigh vacuum the ion-beam-deposited DLC films on fine-grain CVD diamond (similar to the ion-implanted CVD diamond) greatly decrease both the friction and wear of fine-grain CVD diamond films and provide solid lubrication. In dry nitrogen and in humid air, ion-beam-deposited DLC films on fine-grain CVD diamond films also had a low steady-state coefficient of friction and a low wear rate. These tribological performance benefits, coupled with a wider range of coating thicknesses, led to longer endurance life and improved wear resistance for the DLC deposited on fine-grain CVD diamond in comparison to the ion-implanted diamond films. Thus, DLC deposited on fine-grain CVD diamond films can be an effective wear-resistant, lubricating coating regardless of environment.

  4. Growth of atomically smooth MgO films on graphene by molecular beam epitaxy

    SciTech Connect

    Wang, W. H.; Han, W.; Pi, K.; McCreary, K. M.; Miao, F.; Bao, W.; Lau, C. N.; Kawakami, R. K.

    2008-11-03

    We investigate the growth of MgO films on graphene by molecular beam epitaxy and find that surface diffusion promotes a rough morphology. To reduce the mobility of surface atoms, the graphene surface is dressed by Ti atoms prior to MgO deposition. With as little as 0.5 ML (monolayer) of Ti, the MgO overlayer becomes atomically smooth. Furthermore, no aggregation of MgO is observed at the edges of the graphene sheet. These results are important for the fabrication of nanoscale electronic and spintronic devices.

  5. Application of ellipsometry to crystal growth by organometallic molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Aspnes, D. E.; Quinn, W. E.; Gregory, S.

    1990-06-01

    We report the first use of ellipsometry as a real-time monitor of III-V semiconductor crystal growth by molecular beam epitaxy, specifically growth of GaAs and AlGaAs from arsine, triethylgallium, and triethylaluminum sources. Our results provide new insight into the oxide desorption process and show a sensitivity of ±0.03 in compositions x>0.2 for 10 Å thickness increments of AlxGa1-xAs during initial deposition on GaAs.

  6. Pulsed Molecular Beams For Growth Of InAs On GaAs

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J.

    1989-01-01

    Pauses for annealing reduce number of defects. Deposition process that includes pulsed molecular beams produces high-quality epitaxial layers of indium arsenide on gallium arsenide substrates. Layers made as much as 30 atoms thick without introducing excessive numbers of dislocations, despite 7.4-percent mismatch between InAs and GaAs crystal lattices. Layers offer superior electrical properties in such devices as optically addressed light modulators, infrared sensors, semiconductor lasers, and high-electron-mobility transistors. Technique applicable to other epitaxial systems in which lattices highly mismatched.

  7. Bismuth nano-droplets for group-V based molecular-beam droplet epitaxy

    NASA Astrophysics Data System (ADS)

    Li, C.; Zeng, Z. Q.; Fan, D. S.; Hirono, Y.; Wu, J.; Morgan, T. A.; Hu, X.; Yu, S. Q.; Wang, Zh. M.; Salamo, G. J.

    2011-12-01

    Self-assembly of bismuth droplets at nanoscale on GaAs(100) surface using molecular beam epitaxy was demonstrated. Fine control of density and size was achieved by varying growth temperature and total bismuth deposition. Droplet density was tuned by roughly 3 orders of magnitude, and the density-temperature dependence was found to be consistent with classical nucleation theory. These results may extend the flexibility of droplet epitaxy by serving as templates for group V based droplet epitaxy, which is in contrast to conventional group III based droplet epitaxy and may encourage nanostructure formation of bismuth-containing materials.

  8. Induced base transistor fabricated by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Chang, C.-Y.; Liu, W. C.; Jame, M. S.; Wang, Y. H.; Luryi, S.

    1986-09-01

    A novel three-terminal hot-electron device, the induced base transistor (IBT), has been fabricated by molecular beam epitaxy. Two-dimensional electron gas induced by the applied collector field in an undoped GaAs quantum well is used as the base of the IBT. The common-base current gain alpha has been achieved as high as 0.96 under a collector bias of 2.5 V and an emitter current of 3 mA.

  9. Resistively Heated SiC Nozzle for Generating Molecular Beams

    NASA Technical Reports Server (NTRS)

    Cagiano, Steven; Abell, Robert; Patrick, Edward; Bendt, Miri; Gundersen, Cynthia

    2007-01-01

    An improved nozzle has been developed to replace nozzles used previously in an apparatus that generates a substantially unidirectional beam of molecules passing through a vacuum at speeds of several kilometers per second. The basic principle of operation of the apparatus is the same for both the previous and the present nozzle designs. The main working part of the nozzle is essentially a cylinder that is closed except that there is an inlet for a pressurized gas and, at one end, the cylinder is closed by a disk that contains a narrow central hole that serves as an outlet. The cylinder is heated to increase the thermal speeds of the gas molecules into the desired high-speed range. Heated, pressurized gas escapes through the outlet into a portion of the vacuum chamber that is separated, by a wall, from the rest of the vacuum chamber. In this portion of the vacuum chamber, the gas undergoes a free jet expansion. Most of the expanded gas is evacuated and thus does not become part of the molecular beam. A small fraction of the expanded beam passes through a narrow central orifice in the wall and thereby becomes a needle- thin molecular beam in the portion of the vacuum on the downstream side of the wall.

  10. Laser Probing of Molecular Beam Epitaxy on SILICON(100) Surface.

    NASA Astrophysics Data System (ADS)

    Smilgys, Russell Victor

    The work presented here investigates the desorption kinetics of Ga and In from films of Ga, In, GaAs, and InAs on Si(100). Films a few monolayers (ML) thick are deposited from molecular beams under ultrahigh vacuum conditions. Laser induced fluorescence (LIF) is used to detect Ga and In in the gas phase. Using the techniques of temperature programmed desorption and isothermal desorption the desorption kinetics of each species are measured. The variation in the kinetic order and rate constant with temperature and coverage reflect the morphology and energetics of the film growth. Individually, Ga, In, and As each interact strongly with Si(100) at low coverages to form a two dimensional film. Above 1 ML for Ga and {1over2 } ML for In three dimensional islands form. For temperatures above 550 K, As coverage saturates at 1 ML. When As is codeposited with either Ga or In, As occupies the interfacial sites bound to Si. Ga and In atoms form three dimensional islands on top of the two dimensional As film. When the As coverage is below 1 ML, Ga and As strongly interact, probably to form a GaAs structure. Under the same conditions no comparable InAs structure is evident. The much larger lattice mismatch between InAs and Si(100) is proposed to explain this difference. The desorption kinetics and dynamics of the interfacial As film are also investigated. To measure As_2 desorption rates and vibrational populations, LIF detection of As_2 is developed. A result is that As_4 dissociates on Si(100) to yield chemisorbed As atoms. During desorption As atoms recombine to yield As_2. The vibrational populations of desorbed As_2 suggest a direct desorption mechanism in which the directionality of the covalent bonding to the substrate strongly influences the dynamics. To expand the detection capabilities to species not readily detected by LIF, a time-of-flight mass spectrometer is built. In the first studies nonresonant multiphoton ionization is used. As_4 is detected using 266 nm

  11. Molecular Orientation in Two Component Vapor-Deposited Glasses: Effect of Substrate Temperature and Molecular Shape

    NASA Astrophysics Data System (ADS)

    Powell, Charles; Jiang, Jing; Walters, Diane; Ediger, Mark

    Vapor-deposited glasses are widely investigated for use in organic electronics including the emitting layers of OLED devices. These materials, while macroscopically homogenous, have anisotropic packing and molecular orientation. By controlling this orientation, outcoupling efficiency can be increased by aligning the transition dipole moment of the light-emitting molecules parallel to the substrate. Light-emitting molecules are typically dispersed in a host matrix, as such, it is imperative to understand molecular orientation in two-component systems. In this study we examine two-component vapor-deposited films and the orientations of the constituent molecules using spectroscopic ellipsometry, UV-vis and IR spectroscopy. The role of temperature, composition and molecular shape as it effects molecular orientation is examined for mixtures of DSA-Ph in Alq3 and in TPD. Deposition temperature relative to the glass transition temperature of the two-component mixture is the primary controlling factor for molecular orientation. In mixtures of DSA-Ph in Alq3, the linear DSA-Ph has a horizontal orientation at low temperatures and slight vertical orientation maximized at 0.96Tg,mixture, analogous to one-component films.

  12. An effusive molecular beam technique for studies of polyatomic gas-surface reactivity and energy transfer

    NASA Astrophysics Data System (ADS)

    Cushing, G. W.; Navin, J. K.; Valadez, L.; Johánek, V.; Harrison, I.

    2011-04-01

    An effusive molecular beam technique is described to measure alkane dissociative sticking coefficients, S(Tg, Ts; ϑ), on metal surfaces for which the impinging gas temperature, Tg, and surface temperature, Ts, can be independently varied, along with the angle of incidence, ϑ, of the impinging gas. Effusive beam experiments with Tg = Ts = T allow for determination of angle-resolved dissociative sticking coefficients, S(T; ϑ), which when averaged over the cos (ϑ)/π angular distribution appropriate to the impinging flux from a thermal ambient gas yield the thermal dissociative sticking coefficient, S(T). Nonequilibrium S(Tg, Ts; ϑ) measurements for which Tg ≠ Ts provide additional opportunities to characterize the transition state and gas-surface energy transfer at reactive energies. A resistively heated effusive molecular beam doser controls the Tg of the impinging gas striking the surface. The flux of molecules striking the surface from the effusive beam is determined from knowledge of the dosing geometry, chamber pressure, and pumping speed. Separate experiments with a calibrated leak serve to fix the chamber pumping speed. Postdosing Auger electron spectroscopy is used to measure the carbon of the alkyl radical reaction product that is deposited on the surface as a result of alkane dissociative sticking. As implemented in a typical ultrahigh vacuum chamber for surface analysis, the technique has provided access to a dynamic range of roughly 6 orders of magnitude in the initial dissociative sticking coefficient for small alkanes on Pt(111).

  13. Ion Beam Induced Surface Modulations from Nano to Pico: Optimizing Deposition During Erosion and Erosion During Deposition.

    SciTech Connect

    MoberlyChan, W J; Schalek, R

    2007-11-08

    Ion beams of sufficient energy to erode a surface can lead to surface modulations that depend on the ion beam, the material surface it impinges, and extrinsic parameters such as temperature and geometric boundary conditions. Focused Ion Beam technology both enables site-specific placement of these modulations and expedites research through fast, high dose and small efficient use of material. The DualBeam (FIB/SEM) enables in situ metrology, with movies observing ripple formation, wave motion, and the influence of line defects. Nanostructures (ripples of >400nm wavelength to dots spaced <40nm) naturally grow from atomically flat surfaces during erosion, however, a steady state size may or may not be achieved as a consequence of numerous controlled parameters: temperature, angle, energy, crystallography. Geometric factors, which can be easily invoked using a FIB, enable a controlled component of deposition (and/or redeposition) to occur during erosion, and conversely allow a component of etching to be incurred during (ion-beam assisted) deposition. High angles of ion beam inclination commonly lead to 'rougher' surfaces, however, the extreme case of 90.0{sup o} etching enables deposition of organized structures 1000 times smaller than the aforementioned, video-recorded nanostructures. Orientation and position of these picostructures (naturally quantized by their atomic spacings) may be controlled by the same parameters as for nanostructures (e.g. ion inclination and imposed boundary conditions, which are flexibly regulated by FIB). Judicious control of angles during FIB-CVD growth stimulates erosion with directionality that produces surface modulations akin to those observed for sputtering. Just as a diamond surface roughens from 1-D ripples to 2-D steps with increasing angle of ion sputtering, so do ripples and steps appear on carbon-grown surfaces with increase in angle of FIB-CVD. Ion beam processing has been a stalwart of the microelectronics industry, is now a

  14. Hydroquinone-ZnO nano-laminate deposited by molecular-atomic layer deposition

    SciTech Connect

    Huang, Jie; Lucero, Antonio T.; Cheng, Lanxia; Kim, Jiyoung; Hwang, Hyeon Jun; Ha, Min-Woo

    2015-03-23

    In this study, we have deposited organic-inorganic hybrid semiconducting hydroquinone (HQ)/zinc oxide (ZnO) superlattices using molecular-atomic layer deposition, which enables accurate control of film thickness, excellent uniformity, and sharp interfaces at a low deposition temperature (150 °C). Self-limiting growth of organic layers is observed for the HQ precursor on ZnO surface. Nano-laminates were prepared by varying the number of HQ to ZnO cycles in order to investigate the physical and electrical effects of different HQ to ZnO ratios. It is indicated that the addition of HQ layer results in enhanced mobility and reduced carrier concentration. The highest Hall mobility of approximately 2.3 cm{sup 2}/V·s and the lowest n-type carrier concentration of approximately 1.0 × 10{sup 18}/cm{sup 3} were achieved with the organic-inorganic superlattice deposited with a ratio of 10 ZnO cycles to 1 HQ cycle. This study offers an approach to tune the electrical transport characteristics of ALD ZnO matrix thin films using an organic dopant. Moreover, with organic embedment, this nano-laminate material may be useful for flexible electronics.

  15. Supercritical fluid molecular spray film deposition and powder formation

    DOEpatents

    Smith, Richard D.

    1986-01-01

    Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. Upon expansion and supersonic interaction with background gases in the low pressure region, any clusters of solvent are broken up and the solvent is vaporized and pumped away. Solute concentration in the solution is varied primarily by varying solution pressure to determine, together with flow rate, the rate of deposition and to control in part whether a film or powder is produced and the granularity of each. Solvent clustering and solute nucleation are controlled by manipulating the rate of expansion of the solution and the pressure of the lower pressure region. Solution and low pressure region temperatures are also controlled.

  16. Influence of ion beam assisted deposition parameters on the growth of MgO and CoFeB

    SciTech Connect

    Ferreira, Ricardo; Freitas, Paulo P.; Petrova, Rumyana; McVitie, Stephen

    2012-04-01

    The effect of the kinetic parameters of an assistance ion beam on the crystallization of ion beam deposited MgO was investigated. It is shown that the crystallization of MgO in the as-deposited state is strongly dependent on the assistance beam parameters. Furthermore, two deposition regimes corresponding to different ranges of the assistance beam energy are found. XRD and TEM studies of CoFeB/MgO/CoFeB with MgO deposited in the two regimes show that CoFeB crystallization is favored when low energy assist beams are used, despite no differences being found in the MgO.

  17. Beam-induced energy deposition issues in the Very Large Hadron Collider

    SciTech Connect

    Nikolai V. Mokhov; Alexandr I. Drozhdin; G. William Foster

    2001-06-26

    Energy deposition issues are extremely important in the Very Large Hadron Collider (VLHC) with huge energy stored in its 20 TeV (Stage-1) and 87.5 TeV (Stage-2) beams. The status of the VLHC design on these topics, and possible solutions of the problems are discussed. Protective measures are determined based on the operational and accidental beam loss limits for the prompt radiation dose at the surface, residual radiation dose, ground water activation, accelerator components radiation damage and quench stability. The beam abort and beam collimation systems are designed to protect accelerator from accidental and operational beam losses, IP region quadrupoles from irradiation by the products of beam-beam collisions, and to reduce the accelerator-induced backgrounds in the detectors.

  18. Electron-stimulated purification of platinum nanostructures grown via focused electron beam induced deposition

    PubMed Central

    Lewis, Brett B; Stanford, Michael G; Fowlkes, Jason D; Lester, Kevin; Plank, Harald

    2015-01-01

    Summary Platinum–carbon nanostructures deposited via electron beam induced deposition from MeCpPt(IV)Me3 are purified during a post-deposition electron exposure treatment in a localized oxygen ambient at room temperature. Time-dependent studies demonstrate that the process occurs from the top–down. Electron beam energy and current studies demonstrate that the process is controlled by a confluence of the electron energy loss and oxygen concentration. Furthermore, the experimental results are modeled as a 2nd order reaction which is dependent on both the electron energy loss density and the oxygen concentration. In addition to purification, the post-deposition electron stimulated oxygen purification process enhances the resolution of the EBID process due to the isotropic carbon removal from the as-deposited materials which produces high-fidelity shape retention. PMID:25977862

  19. Electron-stimulated purification of platinum nanostructures grown via focused electron beam induced deposition

    DOE PAGESBeta

    Lewis, Brett B.; Stanford, Michael G.; Fowlkes, Jason D.; Lester, Kevin; Plank, Harald; Rack, Philip D.

    2015-04-08

    In this paper, platinum–carbon nanostructures deposited via electron beam induced deposition from MeCpPt(IV)Me3 are purified during a post-deposition electron exposure treatment in a localized oxygen ambient at room temperature. Time-dependent studies demonstrate that the process occurs from the top–down. Electron beam energy and current studies demonstrate that the process is controlled by a confluence of the electron energy loss and oxygen concentration. Furthermore, the experimental results are modeled as a 2nd order reaction which is dependent on both the electron energy loss density and the oxygen concentration. Finally, in addition to purification, the post-deposition electron stimulated oxygen purification process enhancesmore » the resolution of the EBID process due to the isotropic carbon removal from the as-deposited materials which produces high-fidelity shape retention.« less

  20. Electron-stimulated purification of platinum nanostructures grown via focused electron beam induced deposition

    SciTech Connect

    Lewis, Brett B.; Stanford, Michael G.; Fowlkes, Jason D.; Lester, Kevin; Plank, Harald; Rack, Philip D.

    2015-04-08

    In this paper, platinum–carbon nanostructures deposited via electron beam induced deposition from MeCpPt(IV)Me3 are purified during a post-deposition electron exposure treatment in a localized oxygen ambient at room temperature. Time-dependent studies demonstrate that the process occurs from the top–down. Electron beam energy and current studies demonstrate that the process is controlled by a confluence of the electron energy loss and oxygen concentration. Furthermore, the experimental results are modeled as a 2nd order reaction which is dependent on both the electron energy loss density and the oxygen concentration. Finally, in addition to purification, the post-deposition electron stimulated oxygen purification process enhances the resolution of the EBID process due to the isotropic carbon removal from the as-deposited materials which produces high-fidelity shape retention.

  1. Molecular Beam Optical Stark Spectroscopy of Magnesium Deuteride

    NASA Astrophysics Data System (ADS)

    Steimle, Timothy; Zhang, Ruohan; Wang, Hailing

    2014-06-01

    Light polar, paramagnetic molecules, such as magnesium hydride, MgH, are attractive for slowing and trapping experiments because these molecules have both non-zero permanent electric dipole, μel, and magnetic dipole, μm moments. The permanent electric dipole moment is particularly relevant to Stark deceleration which depends on the ratio of the Stark shift to molecular mass. Here we report on the Stark effect in the (0,0) A2Π - X 2Σ+ band system of a cold molecular beam sample of magnesium deuteride, MgD. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce an improved set of fine structure parameters for the A2Π(v = 0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, μel,of 2.561(10)D and 1.34(8)D for A2Π(v = 0) and X2Σ+(v=0)states, respectively. This is the first molecular beam study of MgD.

  2. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy.

    PubMed

    Lee, J H; Tung, I C; Chang, S-H; Bhattacharya, A; Fong, D D; Freeland, J W; Hong, Hawoong

    2016-01-01

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques. PMID:26827327

  3. In situ surface/interface x-ray diffractometer for oxide molecular beam epitaxy

    SciTech Connect

    Lee, J. H.; Tung, I. C.; Chang, S. -H.; Bhattacharya, A.; Fong, D. D.; Freeland, J. W.; Hong, Hawoong

    2016-01-01

    In situ studies of oxide molecular beam epitaxy by synchrotron x-ray scattering has been made possible by upgrading an existing UHV/molecular beam epitaxy (MBE) six-circle diffractometer system. For oxide MBE growth, pure ozone delivery to the chamber has been made available, and several new deposition sources have been made available on a new 12 in. CF (ConFlat, a registered trademark of Varian, Inc.) flange. X-ray diffraction has been used as a major probe for film growth and structures for the system. In the original design, electron diffraction was intended for the secondary diagnostics available without the necessity of the x-ray and located at separate positions. Deposition of films was made possible at the two diagnostic positions. And, the aiming of the evaporation sources is fixed to the point between two locations. Ozone can be supplied through two separate nozzles for each location. Also two separate thickness monitors are installed. Additional features of the equipment are also presented together with the data taken during typical oxide film growth to illustrate the depth of information available via in situ x-ray techniques.

  4. Low interfacial trap density and sub-nm equivalent oxide thickness in In{sub 0.53}Ga{sub 0.47}As (001) metal-oxide-semiconductor devices using molecular beam deposited HfO{sub 2}/Al{sub 2}O{sub 3} as gate dielectrics

    SciTech Connect

    Chu, L. K.; Merckling, C.; Dekoster, J.; Caymax, M.; Alian, A.; Heyns, M.; Kwo, J.; Hong, M.

    2011-07-25

    We investigated the passivation of In{sub 0.53}Ga{sub 0.47}As (001) surface by molecular beam epitaxy techniques. After growth of strained In{sub 0.53}Ga{sub 0.47}As on InP (001) substrate, HfO{sub 2}/Al{sub 2}O{sub 3} high-{kappa} oxide stacks have been deposited in-situ after surface reconstruction engineering. Excellent capacitance-voltage characteristics have been demonstrated along with low gate leakage currents. The interfacial density of states (D{sub it}) of the Al{sub 2}O{sub 3}/In{sub 0.53}Ga{sub 0.47}As interface have been revealed by conductance measurement, indicating a downward D{sub it} profile from the energy close to the valence band (medium 10{sup 12} cm{sup -2}eV{sup -1}) towards that close to the conduction band (10{sup 11} cm{sup -2}eV{sup -1}). The low D{sub it}'s are in good agreement with the high Fermi-level movement efficiency of greater than 80%. Moreover, excellent scalability of the HfO{sub 2} has been demonstrated as evidenced by the good dependence of capacitance oxide thickness on the HfO{sub 2} thickness (dielectric constant of HfO{sub 2}{approx}20) and the remained low D{sub it}'s due to the thin Al{sub 2}O{sub 3} passivation layer. The sample with HfO{sub 2} (3.4 nm)/Al{sub 2}O{sub 3} (1.2 nm) as the gate dielectrics has exhibited an equivalent oxide thickness of {approx}0.93 nm.

  5. Dual Ion Assist Beam Deposition of Magnesium Oxide for Coated Conductors

    NASA Astrophysics Data System (ADS)

    Groves, J. R.; Arendt3, P. N.; Holesinger, T. G.; Hammond, R. H.; Foltyn, S. R.; DePaula, R. F.; Stan, L.; Usov, I. O.

    2006-03-01

    Ion Beam Assisted Deposition (IBAD) of Magnesium Oxide (MgO) has been proven to be a viable route for producing template films used to deposit high quality YBCO coated conductors on flexible polycrystalline metal substrates. Here we will discuss improvements in this process using a dual ion assist beam configuration. Dual ion assist beam deposition of MgO reduces the requirements for substrate surface finishing while maintaining comparable film quality (phi scan full-width at half-maximum values between 7 and 8 degrees). Furthermore, this adaptation of the IBAD process eliminates the degradation of MgO texture observed in thick IBAD MgO films deposited on silicon nitride. We have deposited films up to 50 nanometers thick without degradation of in-plane texture. Increasing the MgO thickness increases the chemical stability of the template layer and can eliminate the necessity for subsequent buffer layers or the application of the homoepitaxial MgO layer needed to stabilize the thin, conventional IBAD MgO layer. Initial results of subsequently deposited YBCO on these dual assist ion beam MgO templates are quite promising.

  6. Note: A helical velocity selector for continuous molecular beams

    SciTech Connect

    Szewc, Carola; Collier, James D.; Ulbricht, Hendrik

    2010-10-15

    We report on a modern realization of the classic helical velocity selector for gas phase particle beams. The device operates stably under high vacuum conditions at rotational frequencies limited only by commercial dc motor capabilities. Tuning the rotational frequency allows selective scanning over a broad velocity band. The width of the selected velocity distributions at full-width-half-maximum is as narrow as a few percent of the selected mean velocity and independent of the rotational speed of the selector. The selector generates low vibrational noise amplitudes comparable to mechanically damped state-of-the-art turbo-molecular pumps and is therefore compatible with vibration sensitive experiments like molecule interferometry.

  7. Corrosion properties of aluminium coatings deposited on sintered NdFeB by ion-beam-assisted deposition

    NASA Astrophysics Data System (ADS)

    Mao, Shoudong; Yang, Hengxiu; Li, Jinlong; Huang, Feng; Song, Zhenlun

    2011-04-01

    Pure Al coatings were deposited by direct current (DC) magnetron sputtering to protect sintered NdFeB magnets. The effects of Ar+ ion-beam-assisted deposition (IBAD) on the structure and the corrosion behaviour of Al coatings were investigated. The Al coating prepared by DC magnetron sputtering with IBAD (IBAD-Al-coating) had fewer voids than the coating without IBAD (Al-coating). The corrosion behaviour of the Al-coated NdFeB specimens was investigated by potentiodynamic polarisation, a neutral salt spray (NSS) test, and electrochemical impedance spectroscopy (EIS). The pitting corrosion of the Al coatings always began at the voids of the grain boundaries. Bombardment by the Ar+ ion-beams effectively improved the corrosion resistance of the IBAD-Al-coating.

  8. Mass transport and alloying during InN growth on GaN by molecular-beam epitaxy

    SciTech Connect

    Liu, Y.; Xie, M.H.; Wu, H.S.; Tong, S.Y.

    2006-05-29

    During Stranski-Krastanov (SK) growth of InN on GaN by molecular-beam epitaxy, a mass transport is noted from the two-dimensional wetting layer and/or the surface excess metal adlayers to the SK islands when the excess nitrogen flux is used for deposition. The extent of mass transport depends on the material coverage. For growth under the excess indium flux condition, no such mass transport is observed.

  9. Crystalline lattice phase-conversion on thin boron nitride films deposited on silicon wafers by an ion beam assisted deposition method

    NASA Astrophysics Data System (ADS)

    Yokota, Katsuhiro; Kimura, Hidekazu; Miyashita, Fumiyoshi

    2007-04-01

    Boron nitride (BN) was deposited on (1 0 0) silicon wafers by using an ion beam assisted deposition system comprised of an electron beam evaporator and a Kaufman ion source. The intensities of XRD-peaks on turbostratic-BN and IR-peaks on hexagonal-BN increased with increasing nitrogen ion beam energy, and decreased after reached a maximum value on a BN film deposited at 2 keV. On the other hand, a XRD-peak on (1 0 0) cubic-BN first was measured on a BN film deposited at 3 keV.

  10. Nanoengineering of Ruddlesden-Popper phases using molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Haeni, Jeffrey Hewlett

    Epitaxial films including superlattices of the A n+1BnO3 n+1 Ruddlesden-Popper homologous series with A=Sr and Ba and B=Ti and Ru have been grown by reactive molecular beam epitaxy (MBE) on (LaAlO3)0.3--(SrAl0.5Ta 0.5O3)0.7 (LSAT), SrTiO3, DyScO 3 and Si substrates. The strict composition control necessary for the synthesis of these phases was achieved through the use of reflection high-energy electron diffraction (RHEED) intensity oscillations. The first five members of the Srn+1 TinO3n+1 and the Sr n+1RunO3 n+1 Ruddlesden-Popper homologous series, i.e., Sr 2TiO4, Sr3Ti2O7, Sr 4Ti3O10, Sr5Ti4O13 , and Sr6Ti5O16, and Sr2RuO 4, Sr3Ru2O7, Sr4Ru 3O10, Sr5Ru4O13, and Sr 6Ru5O16, respectively, were grown with layer-by-layer deposition. Dielectric measurements indicate that the dielectric constant tensor coefficient epsilon33 of the Srn +1TinO3n +1 series increases from a minimum of 44 +/- 4 in the n = 1 (Sr2TiO4) film to a maximum of 263 +/- 2 in the n = infinity (SrTiO3) film. XPS measurements on Sr2TiO4/SrTiO3 heterostructures indicate a type II interface between the two materials, with a valence band offset of -0.40 +/- 0.1 eV, and a conduction band offset of -0.2 +/- 0.1 eV. Epitaxial SrTiO3 thin films grown on DyScO3 and LSAT substrates show dramatically different dielectric properties, as measured with interdigitated electrodes. The film on DyScO3 is under biaxial tensile strain and shows significant room temperature tunability and a sharp Curie-Weiss peak at 293 K. Under biaxial compressive strain, the SrTiO 3 exhibits negligible room temperature tunability. Epitaxial SrTiO3/BaTiO3 short period superlattices were grown with nearly atomically-abrupt interfaces that are maintained even after annealing to high temperature. In addition, cross-sectional TEM reveals that all superlattice periods grown are coherently strained to the underlying (001) SrTiO3 and (001) LSAT substrates. Epitaxial SrRuO3 layers were grown on Si (100) on which a thin epitaxial (Ba,Sr)O/SrSi2

  11. Understanding the high pressure properties of molecular solids and molecular surfaces deposited on hetrogeneous substrates

    NASA Technical Reports Server (NTRS)

    Etters, R. D.

    1985-01-01

    Work directed toward understanding the high pressure properties of molecular solids and molecular surfaces deposited on hetrogeneous substrates is reported. The motivation, apart from expanding our basic knowledge about these systems, was to understand and predict the properties of new materials synthesized at high pressure, including pressure induced metallic and superconducting states. As a consequence, information about the states of matter of the Jovian planets and their satellites, which are natural high pressure laboratories was also provided. The work on molecular surfaces and finite two and three dimensional clusters of atoms and molecules was connected with the composition and behavior of planetary atmospheres and on the processes involved in forming surface layers, which is vital to the development of composite materials and microcircuitry.

  12. Single-crystal nanowires grown via electron-beam-induced deposition

    SciTech Connect

    Klein, Kate L; Randolph, Steven J; Fowlkes, Jason Davidson; Allard Jr, Lawrence Frederick; Meyer III, Harry M; Simpson, Michael L; Rack, Philip D

    2008-01-01

    Electron-beam-induced deposition (EBID) is a useful technique for direct-writing of 3-dimensional dielectric, semiconductor, and metallic materials with nanoscale precision and resolution. The EBID process, however, has been limited in many cases because precursor byproducts (typically from organic precursors like W(CO)6) are incorporated into the deposited material resulting in contaminated and amorphous structures. In this manuscript, we have investigated the structure and composition of EBID tungsten nanostructures as-deposited from a tungsten hexafluoride (WF6) precursor. High-resolution transmission electron microscopy, electron diffraction and electron spectroscopy were employed to determine the effects that the electron beam scanning conditions have on the deposit characteristics. The results show that slow, one-dimensional lateral scanning produces textured -tungsten nanowire cores surrounded by an oxide secondary layer, while stationary vertical growth leads to single-crystal [100]-oriented W3O nanowires. Furthermore we correlate how the growth kinetics affect the resultant nanowire structure and composition.

  13. Electron-beam-directed vapor deposition of multifunctional structures for electrochemical storage

    NASA Astrophysics Data System (ADS)

    Queheillalt, Douglas T.; Hass, Derek D.; Wadley, Haydn N. G.

    2002-07-01

    Multifunctional structures are those, which combine load- bearing support in addition to additional functions such as mechanical actuation, distributed power supply or thermal management. Electron beam - directed vapor deposition technology has been used to investigate deposition methodologies for two multifunctional battery concepts: a linear/truss base nickel - metal hydride and a fiber based solid-state Li+ ion multifunctional battery. Porous nickel coatings for the cathodes and porous rare earth metal coatings based on La and Ni or Ti and Zr for the anodes are being investigated for the nickel - metal hydride system; where LiV2O5, LiPON, and Sn3N4 are being investigated for the Li+ ion based system. Electron beam - directed vapor deposition is being used for deposition of all cathode/anode structures to provide an economical method for the development of these novel multifunctional structures.

  14. Origin and control of magnetic exchange coupling in between focused electron beam deposited cobalt nanostructures

    SciTech Connect

    Nikulina, E.; Idigoras, O.; Porro, J. M.; Berger, A.; Vavassori, P.; Chuvilin, A.; Ikerbasque, Basque Foundation for Science, Alameda Urquijo 36-5, 48011 Bilbao

    2013-09-16

    We demonstrate the existence and control of inter-particle magnetic exchange coupling in densely packed nanostructures fabricated by focused electron beam induced deposition. With Xe beam post-processing, we have achieved the controlled reduction and eventual elimination of the parasitic halo-like cobalt deposits formed in the proximity of intended nanostructures, which are the identified source of the magnetic exchange coupling. The elimination of the halo-mediated exchange coupling is demonstrated by magnetic measurements using Kerr microscopy on Co pillar arrays. Electron microscopy studies allowed us to identify the mechanisms underlying this process and to verify the efficiency and opportunities of the described nano-scale fabrication approach.

  15. Optical and scratch resistant properties of diamondlike carbon films deposited with single and dual ion beams

    NASA Technical Reports Server (NTRS)

    Kussmaul, Michael T.; Bogdanski, Michael S.; Banks, Bruce A.; Mirtich, Michael J.

    1993-01-01

    Amorphous diamondlike carbon (DLC) films were deposited using both single and dual ion beam techniques utilizing filament and hollow cathode ion sources. Continuous DLC films up to 3000 A thick were deposited on fused quartz plates. Ion beam process parameters were varied in an effort to create hard, clear films. Total DLC film absorption over visible wavelengths was obtained using a Perkin-Elmer spectrophotometer. An ellipsometer, with an Ar-He laser (wavelength 6328 A) was used to determine index of refraction for the DLC films. Scratch resistance and frictional and adherence properties were determined for select films. Applications for these films range from military to the ophthalmic industries.

  16. Optical and Scratch Resistant Properties of Diamondlike Carbon Films Deposited with Single and Dual Ion Beams

    NASA Technical Reports Server (NTRS)

    Kussmaul, Michael T.; Bogdanski, Michael S.; Banks, Bruce A.; Mirtich, Michael J.

    1993-01-01

    Amorphous diamond-like carbon (DLC) films were deposited using both single and dual ion beam techniques utilizing filament and hollow cathode ion sources. Continuous DLC films up to 3000 A thick were deposited on fused quartz plates. Ion beam process parameters were varied in an effort to create hard, clear films. Total DLC film absorption over visible wavelengths was obtained using a Perkin-Elmer spectrophotometer. An ellipsometer, with an Ar-He laser (wavelength 6328 A) was used to determine index of refraction for the DLC films. Scratch resistance, frictional, and adherence properties were determined for select films. Applications for these films range from military to the ophthalmic industries.

  17. Beam-deposited platinum as versatile catalyst for bottom-up silicon nanowire synthesis

    SciTech Connect

    Hibst, N.; Strehle, S.; Knittel, P.; Kranz, C.; Mizaikoff, B.

    2014-10-13

    The controlled localized bottom-up synthesis of silicon nanowires on arbitrarily shaped surfaces is still a persisting challenge for functional device assembly. In order to address this issue, electron beam and focused ion beam-assisted catalyst deposition have been investigated with respect to platinum expected to form a PtSi alloy catalyst for a subsequent bottom-up nanowire synthesis. The effective implementation of pure platinum nanoparticles or thin films for silicon nanowire growth has been demonstrated recently. Beam-deposited platinum contains significant quantities of amorphous carbon due to the organic precursor and gallium ions for a focused ion beam-based deposition process. Nevertheless, silicon nanowires could be grown on various substrates regardless of the platinum purity. Additionally, p-type doping could be realized with diborane whereas n-type doping suppressed a nanowire growth. The rational utilization of this beam-assisted approach enables us to control the localized synthesis of single silicon nanowires at planar surfaces but succeeded also in single nanowire growth at the three-dimensional apex of an atomic force microscopy tip. Therefore, this catalyst deposition method appears to be a unique extension of current technologies to assemble complex nanowire-based devices.

  18. Hard X-ray multilayer coated astronomical mirrors by e-beam deposition

    NASA Astrophysics Data System (ADS)

    Spiga, Daniele; Pareschi, Giovanni; Grisoni, Gabriele; Valsecchi, Giuseppe

    2004-10-01

    A number of X-ray astronomical missions of near future (Constellation-X, XEUS, Simbol-X) will make use of hard X-rays (10-100 keV) optics with broad-band multilayer coatings. A possible technique under development is based on an extension of the already tested replication of a coated mandrel by e-beam deposition and nickel electroforming already successfully used for the soft (0.1 - 10 keV) X-ray mirrors of the Beppo-SAX, XMM, JET-X/Swift missions. In this case graded multilayers are deposited and replicated from the mandrel replicated instead of a single layer. The roughness reduction in order to improve the coating reflectivity could be achieved by an ion assistance during the e-beam deposition. The e-beam deposition with ion assistance is a technique that allows to reach comparable (if not better) smoothness levels with respect to other methods (e.g. ion sputtering), taking the advantage of a stress mitigation between the layers and of a further improvement in reflectivity due to the low density of the e-beam evaporated Carbon, which is used as bilayer spacer. In this paper we discuss the adopted deposition technique and its implementation: we present topographic (AFM) tests and X-ray reflectivity tests performed on preliminary samples.

  19. Molecular Beam Epitaxy of BaSi2 Films with Grain Size over 4 µm on Si(111)

    NASA Astrophysics Data System (ADS)

    Baba, Masakazu; Nakamura, Kotaro; Du, Weijie; Ajmal Khan, M.; Koike, Shintaro; Toko, Kaoru; Usami, Noritaka; Saito, Noriyuki; Yoshizawa, Noriko; Suemasu, Takashi

    2012-09-01

    100-nm-thick BaSi2 epitaxial films were grown on Si(111) substrates by a two-step growth method including reactive deposition epitaxy (RDE) and molecular beam epitaxy (MBE). The Ba deposition rate and duration were varied from 0.25 to 1.0 nm/min and from 5 to 120 min during RDE, respectively. Plan-view transmission electron micrographs indicated that the grain size in the MBE-grown BaSi2 was significantly dependent on the RDE growth conditions and was varied from approximately 0.2 to more than 4 µm.

  20. Surface modification of biomedical implants using ion-beam-assisted sputter deposition

    NASA Astrophysics Data System (ADS)

    Ektessabi, A. M.

    1997-05-01

    Hydroxy-apatite (Ca 10(PO 4) 6(OH) 2), owing to its good bioaffinity and enhancement of osseo-integration, is a potential material for coating on dental and orthopedic implants. At present, hydroxy-apatite is coated on metal implants by a plasma-spraying method or is used in its bulk form in reconstruction surgery. In this paper, experimental results are given for preparation of hydroxy-apatite thin films on various biomedical implant materials using ion-beam sputter deposition and ion-beam-assisted sputter deposition methods. By using the ion-beam-assisted sputter deposition method, the adhesion of hydroxy-apatite thin films to substrate has improved significantly and increased to a level comparable to Ti and Al oxide thin films. Relative atomic densities of Ca, P, O and H in hydroxy-apatite thin films were obtained using ion-beam analysis methods such as RBS, RE-RBS, ERDA, and PIXE. The relative concentrations of Ca, and P were affected by assisting-beam density, and stoichiometric films were obtained for certain assisting-beam current densities.

  1. Energy deposition of heavy ions in the regime of strong beam-plasma correlations.

    PubMed

    Gericke, D O; Schlanges, M

    2003-03-01

    The energy loss of highly charged ions in dense plasmas is investigated. The applied model includes strong beam-plasma correlation via a quantum T-matrix treatment of the cross sections. Dynamic screening effects are modeled by using a Debye-like potential with a velocity dependent screening length that guarantees the known low and high beam velocity limits. It is shown that this phenomenological model is in good agreement with simulation data up to very high beam-plasma coupling. An analysis of the stopping process shows considerably longer ranges and a less localized energy deposition if strong coupling is treated properly. PMID:12689203

  2. A molecular beam/quadrupole mass spectrometer system with synchronized beam modulation and digital waveform analysis

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Adams, B. R.

    1983-01-01

    A performance evaluation is conducted for a molecular beam/mass spectrometer (MB/MS) system, as applied to a 1-30 torr microwave-discharge flow reactor (MWFR) used in the formation of the methylperoxy radical and a study of its subsequent destruction in the presence or absence of NO(x). The modulated MB/MS system is four-staged and differentially pumped. The results obtained by the MWFR study is illustrative of overall system performance, including digital waveform analysis; significant improvements over previous designs are noted in attainable S/N ratio, detection limit, and accuracy.

  3. Annealing of TiO2 Films Deposited on Si by Irradiating Nitrogen Ion Beams

    SciTech Connect

    Yokota, Katsuhiro; Yano, Yoshinori; Miyashita, Fumiyoshi

    2006-11-13

    Thin TiO2 films were deposited on Si at a temperature of 600 deg. C by an ion beam assisted deposition (IBAD) method. The TiO2 films were annealed for 30 min in Ar at temperatures below 700 deg. C. The as-deposited TiO2 films had high permittivities such 200 {epsilon}o and consisted of crystallites that were not preferentially oriented to the c-axis but had an expanded c-axis. On the annealed TiO2 films, permittivities became lower with increasing annealing temperature, and crystallites were oriented preferentially to the (110) plane.

  4. Vacuum Ultraviolet Radiation Desorption of Molecular Contaminants Deposited on Quartz Crystal Microbalances

    NASA Technical Reports Server (NTRS)

    Albyn, Keith; Burns, Dewitt

    2006-01-01

    Recent quartz crystal microbalance measurements made in the Marshall Space Flight Center, Photo-Deposition Facility, for several materials, recorded a significant loss of deposited contaminants when the deposition surface of the microbalance was illuminated by a deuterium lamp. These measurements differ from observations made by other investigators in which the rate of deposition increased significantly when the deposition surface was illuminated with vacuum ultraviolet radiation. These observations suggest that the accelerated deposition of molecular contaminants on optically sensitive surfaces is dependant upon the contaminant being deposited and must be addressed during the materials selection process by common material screening techniques.

  5. Texture-Induced Anisotropy in an Inconel 718 Alloy Deposited Using Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Tayon, W.; Shenoy, R.; Bird, R.; Hafley, R.; Redding, M.

    2014-01-01

    A test block of Inconel (IN) 718 was fabricated using electron beam freeform fabrication (EBF(sup 3)) to examine how the EBF(sup 3) deposition process affects the microstructure, crystallographic texture, and mechanical properties of IN 718. Tests revealed significant anisotropy in the elastic modulus for the as-deposited IN 718. Subsequent tests were conducted on specimens subjected to a heat treatment designed to decrease the level of anisotropy. Electron backscatter diffraction (EBSD) was used to characterize crystallographic texture in the as-deposited and heat treated conditions. The anisotropy in the as-deposited condition was strongly affected by texture as evidenced by its dependence on orientation relative to the deposition direction. Heat treatment resulted in a significant improvement in modulus of the EBF(sup 3) product to a level nearly equivalent to that for wrought IN 718 with reduced anisotropy; reduction in texture through recrystallization; and production of a more homogeneous microstructure.

  6. Interfacial electrical properties of ion-beam sputter deposited amorphous carbon on silicon

    NASA Technical Reports Server (NTRS)

    Khan, A. A.; Woollam, J. A.; Chung, Y.; Banks, B.

    1983-01-01

    Amorphous, 'diamond-like' carbon films have been deposited on Si substrates, using ion-beam sputtering. The interfacial properties are studied using capacitance and conductance measurements. Data are analyzed using existing theories for interfacial electrical properties. The density of electronic states at the interface, along with corresponding time constants are determined.

  7. A comparison of neon versus helium ion beam induced deposition via Monte Carlo simulations.

    PubMed

    Timilsina, Rajendra; Smith, Daryl A; Rack, Philip D

    2013-03-22

    The ion beam induced nanoscale synthesis of PtCx (where x ∼ 5) using the trimethyl (methylcyclopentadienyl)platinum(IV) (MeCpPt(IV)Me3) precursor is investigated by performing Monte Carlo simulations of helium and neon ions. The helium beam leads to more lateral growth relative to the neon beam because of its larger interaction volume. The lateral growth of the nanopillars is dominated by molecules deposited via secondary electrons in both the simulations. Notably, the helium pillars are dominated by SE-I electrons whereas the neon pillars are dominated by SE-II electrons. Using a low precursor residence time of 70 μs, resulting in an equilibrium coverage of ∼4%, the neon simulation has a lower deposition efficiency (3.5%) compared to that of the helium simulation (6.5%). At larger residence time (10 ms) and consequently larger equilibrium coverage (85%) the deposition efficiencies of helium and neon increased to 49% and 21%, respectively; which is dominated by increased lateral growth rates leading to broader pillars. The nanoscale growth is further studied by varying the ion beam diameter at 10 ms precursor residence time. The study shows that total SE yield decreases with increasing beam diameters for both the ion types. However, helium has the larger SE yield as compared to that of neon in both the low and high precursor residence time, and thus pillars are wider in all the simulations studied. PMID:23449368

  8. Tribological properties of boron nitride synthesized by ion beam deposition

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.; Spalvins, T.

    1985-01-01

    The adhesion and friction behavior of boron nitride films on 440 C bearing stainless steel substrates was examined. The thin films containing the boron nitride were synthesized using an ion beam extracted from a borazine plasma. Sliding friction experiments were conducted with BN in sliding contact with itself and various transition metals. It is indicated that the surfaces of atomically cleaned BN coating film contain a small amount of oxides and carbides, in addition to boron nitride. The coefficients of friction for the BN in contact with metals are related to the relative chemical activity of the metals. The more active the metal, the higher is the coefficient of friction. The adsorption of oxygen on clean metal and BN increases the shear strength of the metal - BN contact and increases the friction. The friction for BN-BN contact is a function of the shear strength of the elastic contacts. Clean BN surfaces exhibit relatively strong interfacial adhesion and high friction. The presence of adsorbates such as adventitious carbon contaminants on the BN surfaces reduces the shear strength of the contact area. In contrast, chemically adsorbed oxygen enhances the shear strength of the BN-BN contact and increases the friction.

  9. Molecular beam-thermal hydrogen desorption from palladium

    SciTech Connect

    Lobo, R. F. M.; Berardo, F. M. V.; Ribeiro, J. H. F.

    2010-04-15

    Among the most efficient techniques for hydrogen desorption monitoring, thermal desorption mass spectrometry is a very sensitive one, but in certain cases can give rise to uptake misleading results due to residual hydrogen partial pressure background variations. In this work one develops a novel thermal desorption variant based on the effusive molecular beam technique that represents a significant improvement in the accurate determination of hydrogen mass absorbed on a solid sample. The enhancement in the signal-to-noise ratio for trace hydrogen is on the order of 20%, and no previous calibration with a chemical standard is required. The kinetic information obtained from the hydrogen desorption mass spectra (at a constant heating rate of 1 deg. C/min) accounts for the consistency of the technique.

  10. Atmospheric processes on ice nanoparticles in molecular beams

    PubMed Central

    Fárník, Michal; Poterya, Viktoriya

    2014-01-01

    This review summarizes some recent experiments with ice nanoparticles (large water clusters) in molecular beams and outlines their atmospheric relevance: (1) Investigation of mixed water–nitric acid particles by means of the electron ionization and sodium doping combined with photoionization revealed the prominent role of HNO3 molecule as the condensation nuclei. (2) The uptake of atmospheric molecules by water ice nanoparticles has been studied, and the pickup cross sections for some molecules exceed significantly the geometrical sizes of the ice nanoparticles. (3) Photodissociation of hydrogen halides on water ice particles has been shown to proceed via excitation of acidically dissociated ion pair and subsequent biradical generation and H3O dissociation. The photodissociation of CF2Cl2 molecules in clusters is also mentioned. Possible atmospheric consequences of all these results are briefly discussed. PMID:24790973

  11. Production and all-optical deceleration of molecular beams

    NASA Astrophysics Data System (ADS)

    Chen, Gary; Jayich, Andrew; Long, Xueping; Ransford, Anthony; Campbell, Wesley

    2015-05-01

    Ultracold molecules open up new opportunities in many areas of study, including many-body physics, quantum chemistry, quantum information, and precision measurements. Current methods cannot easily address the spontaneous decay of molecules into dark states without an amalgam of repump lasers. We present an alternative method to produce cold molecules. A cryogenic buffer gas beam (CBGB) is used to create an intense, slow, cold source of molecules. By using a CBGB for the production, we can quench vibrational modes that cannot be addressed with optical methods. This is then followed by an all-optical scheme using a single ultra-fast laser to decelerate the molecules and a continuous wave laser to cool the species. We have started experiments with strontium monohydride (SrH), but the proposed method should be applicable to a wide range of molecular species.

  12. Crossed-molecular-beams reactive scattering of oxygen atoms

    SciTech Connect

    Baseman, R.J.

    1982-11-01

    The reactions of O(/sup 3/P) with six prototypical unsaturated hydrocarbons, and the reaction of O(/sup 1/D) with HD, have been studied in high-resolution crossed-molecular-beams scattering experiments with mass-spectrometric detection. The observed laboratory-product angular and velocity distributions unambiguously identify parent-daughter ion pairs, distinguish different neutral sources of the same ion, and have been used to identify the primary products of the reactions. The derived center-of-mass product angular and translational energy distributions have been used to elucidate the detailed reaction dynamics. These results demonstrate that O(/sup 3/P)-unsaturated hydrocarbon chemistry is dominated by single bond cleavages, leading to radical products exclusively.

  13. InPBi Single Crystals Grown by Molecular Beam Epitaxy

    PubMed Central

    Wang, K.; Gu, Y.; Zhou, H. F.; Zhang, L. Y.; Kang, C. Z.; Wu, M. J.; Pan, W. W.; Lu, P. F.; Gong, Q.; Wang, S. M.

    2014-01-01

    InPBi was predicted to be the most robust infrared optoelectronic material but also the most difficult to synthesize within In-VBi (V = P, As and Sb) 25 years ago. We report the first successful growth of InPBi single crystals with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InPBi thin films reveal excellent surface, structural and optical qualities making it a promising new III–V compound family member for heterostructures. The Bi concentration is found to be 2.4 ± 0.4% with 94 ± 5% Bi atoms at substitutional sites. Optical absorption indicates a band gap of 1.23 eV at room temperature while photoluminescence shows unexpectedly strong and broad light emission at 1.4–2.7 μm which can't be explained by the existing theory. PMID:24965260

  14. Supersonic Molecular Beam Optical Stark Spectroscopy of MnH.

    NASA Astrophysics Data System (ADS)

    Gengler, Jamie; Ma, Tongmei; Harrison, Jeremy; Steimle, Timothy

    2006-03-01

    The large moment of inertia, large magnetic moment, and possible large permanent electric dipole moment of manganese monohydride, MnH, makes it a prime candidate for ultra-cold molecule production via Stark deceleration and magnetic trapping. Here we report the first molecular beam production of MnH and the analysis of the Stark effect in the (0,0) A^7 π -- X^ 7σ^+ band. The sample was prepared by laser ablation of solid Mn in an H2 supersonic expansion. The low rotational temperature (<50 K) and near natural linewidth resolution (˜50 MHz) facilitated analysis of the ^55Mn (I=5/2) and ^1H (I=1/2) hyperfine structure. A comparison of the derived field-free parameters with those obtained from sub- Doppler optical measurements will be made. Progress on the analysis of the Stark effect will be given. J.R. Bochinski, E.R. Hudson, H.J. Lewandowski, and J. Ye, Phys. Rev. A 70, 043410 (2004). S.Y.T. van de Meerakker, R.T. Jongma, H.L. Bethlem, and G. Meijer, Phys. Rev. A 64, 041401(R) (2001) report the first molecular beam production of MnH and the analysis of T.D. Varberg, J.A. Gray, R.W. Field, and A.J. Merer, J. Mol. Spec. 156, 296-318 (1992). I.E. Gordon, D.R.T. Appadoo, A. Shayesteh, K.A. Walker, and P.F. Bernath, J. Mol. Spec., 229, 145-149 (2005).

  15. A high pressure modulated molecular beam mass spectrometric sampling system

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.; Kohl, F. J.; Fryburg, G. C.; Miller, R. A.

    1977-01-01

    The current state of understanding of free-jet high pressure sampling is critically reviewed and modifications of certain theoretical and empirical considerations are presented. A high pressure, free-jet expansion, modulated molecular beam, mass spectrometric sampling apparatus was constructed and this apparatus is described in detail. Experimental studies have demonstrated that the apparatus can be used to sample high temperature systems at pressures up to one atmosphere. Condensible high temperature gaseous species have been routinely sampled and the mass spectrometric detector has provided direct identification of sampled species. System sensitivity is better than one tenth of a part per million. Experimental results obtained with argon and nitrogen beams are presented and compared to theoretical predictions. These results and the respective comparison are taken to indicate acceptable performance of the sampling apparatus. Results are also given for two groups of experiments related to hot corrosion studies. The formation of gaseous sodium sulfate in doped methane-oxygen flames was characterized and the oxidative vaporization of metals was studied in an atmospheric pressure flowing gas system to which gaseous salt partial pressures were added.

  16. Metal delocalization and surface decoration in direct-write nanolithography by electron beam induced deposition

    SciTech Connect

    Gopal, Vidyut; Stach, Eric A.; Radmilovic, Velimir R.; Mowat, Ian A.

    2004-07-05

    The ability to interconnect different nanostructures is crucial to nanocircuit fabrication efforts. A simple and versatile direct-write nanolithography technique for the fabrication of interconnects is presented. Decomposition of a metalorganic precursor gas by a focused electron beam resulted in the deposition of conductive platinum nanowires. The combination of in situ secondary electron imaging with deposition allows for the simultaneous identification and interconnection of nanoscale components. However, the deposition was not entirely localized to the electron beam raster area, as shown by secondary ion mass spectrometry measurements. The electrical impact of the metallic spread was quantified by measuring the leakage current between closely spaced wires. The origins of the spread and strategies for minimizing it are discussed. These results indicate that, while this direct-write methodology is a convenient one for rapid prototyping of nanocircuits, caution must be used to avoid unwanted decoration of nanostructures by metallic species.

  17. Molecular Beam Epitaxy Growth of GaBi, InBi and InGaBi

    NASA Astrophysics Data System (ADS)

    Keen, B.; Makin, R.; Stampe, P. A.; Kennedy, R. J.; Piper, L. F. J.; McCombe, B.; McConville, C. F.; Durbin, S. M.

    2014-03-01

    Recent interest in bismuth alloys of III-V semiconductors for infrared and far-infrared device applications, specifically GaAsBi and InAsBi, has indicated that further study of the III-Bi family of binary compounds would be of great help in improving the quality of these material systems. While immiscibility issues have so far frustrated the growth of GaBi and AlBi, InBi is less problematic, and we have grown it by molecular beam epitaxy on (001) GaAs substrates. However, regions of varying composition exist across the substrate due to poor wetting of the surface. In an effort to improve film quality we have continued to refine the growth parameters by adjusting substrate temperature, beam flux ratio, and deposition rate. Characterization of these films has been performed by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Additionally, we have explored growth of GaBi and In1-xGaxBi at low Ga mole fractions, and modeled this using molecular dynamics simulations. This work is supported by the Research Foundation of the State University of New York Collaborations Fund.

  18. Optimization of ion-atomic beam source for deposition of GaN ultrathin films

    SciTech Connect

    Mach, Jindřich Kolíbal, Miroslav; Zlámal, Jakub; Voborny, Stanislav; Bartošík, Miroslav; Šikola, Tomáš; Šamořil, Tomáš

    2014-08-15

    We describe the optimization and application of an ion-atomic beam source for ion-beam-assisted deposition of ultrathin films in ultrahigh vacuum. The device combines an effusion cell and electron-impact ion beam source to produce ultra-low energy (20–200 eV) ion beams and thermal atomic beams simultaneously. The source was equipped with a focusing system of electrostatic electrodes increasing the maximum nitrogen ion current density in the beam of a diameter of ≈15 mm by one order of magnitude (j ≈ 1000 nA/cm{sup 2}). Hence, a successful growth of GaN ultrathin films on Si(111) 7 × 7 substrate surfaces at reasonable times and temperatures significantly lower (RT, 300 °C) than in conventional metalorganic chemical vapor deposition technologies (≈1000 °C) was achieved. The chemical composition of these films was characterized in situ by X-ray Photoelectron Spectroscopy and morphology ex situ using Scanning Electron Microscopy. It has been shown that the morphology of GaN layers strongly depends on the relative Ga-N bond concentration in the layers.

  19. Enhanced material purity and resolution via synchronized laser assisted electron beam induced deposition of platinum.

    PubMed

    Roberts, Nicholas A; Fowlkes, Jason D; Magel, Gregory A; Rack, Philip D

    2013-01-01

    We introduce a laser assisted electron beam induced deposition (LAEBID) process which is a nanoscale direct write synthesis method that integrates an electron beam induced deposition process with a synchronized pulsed laser step to induce thermal desorption of reaction by-products. Localized, spatially overlapping electron and photon pulses enable the thermal desorption of the reaction by-product while mitigating issues associated with bulk substrate heating, which can shorten the precursor residence time and distort pattern fidelity due to thermal drift. Current results demonstrate purification of platinum deposits (reduced carbon content by ~50%) with the addition of synchronized laser pulses as well as a significant reduction in deposit resistivity. Measured resistivities from platinum LAEBID structures (4 × 10(3)μΩ cm) are nearly 4 orders of magnitude lower than standard EBID platinum structures (2.2 × 10(7)μΩ cm) from the same precursor and are lower than the lowest reported EBID platinum resistivity with post-deposition annealing (1.4 × 10(4)μΩ cm). Finally the LAEBID process demonstrates improved deposit resolution by ~25% compared to EBID structures under the conditions investigated in this work. PMID:23184056

  20. Cerenkov emission induced by external beam radiation stimulates molecular fluorescence

    SciTech Connect

    Axelsson, Johan; Davis, Scott C.; Gladstone, David J.; Pogue, Brian W.

    2011-07-15

    Purpose: Cerenkov emission is induced when a charged particle moves faster than the speed of light in a given medium. Both x-ray photons and electrons produce optical Cerenkov photons in everyday radiation therapy of tissue; yet, this phenomenon has never been fully documented. This study quantifies the emissions and also demonstrates that the Cerenkov emission can excite a fluorophore, protoporphyrin IX (PpIX), embedded in biological phantoms. Methods: In this study, Cerenkov emission induced by radiation from a clinical linear accelerator is investigated. Biological mimicking phantoms were irradiated with x-ray photons, with energies of 6 or 18 MV, or electrons at energies 6, 9, 12, 15, or 18 MeV. The Cerenkov emission and the induced molecular fluorescence were detected by a camera or a spectrometer equipped with a fiber optic cable. Results: It is shown that both x-ray photons and electrons, at MeV energies, produce optical Cerenkov photons in tissue mimicking media. Furthermore, we demonstrate that the Cerenkov emission can excite a fluorophore, protoporphyrin IX (PpIX), embedded in biological phantoms. Conclusions: The results here indicate that molecular fluorescence monitoring during external beam radiotherapy is possible.

  1. Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy

    PubMed Central

    Baiutti, Federico; Christiani, Georg

    2014-01-01

    Summary In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE) which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2− xSrxNiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control. PMID:24995148

  2. Synthesis of atomically thin hexagonal boron nitride films on nickel foils by molecular beam epitaxy

    SciTech Connect

    Nakhaie, S.; Wofford, J. M.; Schumann, T.; Jahn, U.; Ramsteiner, M.; Hanke, M.; Lopes, J. M. J. Riechert, H.

    2015-05-25

    Hexagonal boron nitride (h-BN) is a layered two-dimensional material with properties that make it promising as a dielectric in various applications. We report the growth of h-BN films on Ni foils from elemental B and N using molecular beam epitaxy. The presence of crystalline h-BN over the entire substrate is confirmed by Raman spectroscopy. Atomic force microscopy is used to examine the morphology and continuity of the synthesized films. A scanning electron microscopy study of films obtained using shorter depositions offers insight into the nucleation and growth behavior of h-BN on the Ni substrate. The morphology of h-BN was found to evolve from dendritic, star-shaped islands to larger, smooth triangular ones with increasing growth temperature.

  3. Intense terahertz emission from molecular beam epitaxy-grown GaAs/GaSb(001)

    SciTech Connect

    Sadia, Cyril P.; Laganapan, Aleena Maria; Agatha Tumanguil, Mae; Estacio, Elmer; Somintac, Armando; Salvador, Arnel; Que, Christopher T.; Yamamoto, Kohji; Tani, Masahiko

    2012-12-15

    Intense terahertz (THz) electromagnetic wave emission was observed in undoped GaAs thin films deposited on (100) n-GaSb substrates via molecular beam epitaxy. GaAs/n-GaSb heterostructures were found to be viable THz sources having signal amplitude 75% that of bulk p-InAs. The GaAs films were grown by interruption method during the growth initiation and using various metamorphic buffer layers. Reciprocal space maps revealed that the GaAs epilayers are tensile relaxed. Defects at the i-GaAs/n-GaSb interface were confirmed by scanning electron microscope images. Band calculations were performed to infer the depletion region and electric field at the i-GaAs/n-GaSb and the air-GaAs interfaces. However, the resulting band calculations were found to be insufficient to explain the THz emission. The enhanced THz emission is currently attributed to a piezoelectric field induced by incoherent strain and defects.

  4. Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

    SciTech Connect

    Fontcuberta i Morral, A.; Colombo, C.; Abstreiter, G.; Arbiol, J.; Morante, J. R.

    2008-02-11

    Molecular beam epitaxy Ga-assisted synthesis of GaAs nanowires is demonstrated. The nucleation and growth are seen to be related to the presence of a SiO{sub 2} layer previously deposited on the GaAs wafer. The interaction of the reactive gallium with the SiO{sub 2} pinholes induces the formation of nanocraters, found to be the key for the nucleation of the nanowires. With SiO{sub 2} thicknesses up to 30 nm, nanocraters reach the underlying substrate, resulting into a preferential growth orientation of the nanowires. Possibly related to the formation of nanocraters, we observe an incubation period of 258 s before the nanowires growth is initiated.

  5. Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy.

    PubMed

    Baiutti, Federico; Christiani, Georg; Logvenov, Gennady

    2014-01-01

    In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE) which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2- x Sr x NiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control. PMID:24995148

  6. Effects of substrate orientation on the growth of InSb nanostructures by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Chou, C. Y.; Torfi, A.; Pei, C.; Wang, W. I.

    2016-05-01

    In this work, the effects of substrate orientation on InSb quantum structure growth by molecular beam epitaxy (MBE) are presented. Motivated by the observation that (411) evolves naturally as a stable facet during MBE crystal growth, comparison studies have been carried out to investigate the effects of the crystal orientation of the underlying GaSb substrate on the growth of InSb by MBE. By depositing InSb on a number of different substrate orientations, namely: (100), (311), (411), and (511), a higher nanostructure density was observed on the (411) surface compared with the other orientations. This result suggests that the (411) orientation presents a superior surface in MBE growth to develop a super-flat GaSb buffer surface, naturally favorable for nanostructure growth.

  7. Growth of high quality AlGaAs by metalorganic molecular beam epitaxy using trimethylamine alane

    NASA Astrophysics Data System (ADS)

    Abernathy, C. R.; Jordan, A. S.; Pearton, S. J.; Hobson, W. S.; Bohling, D. A.; Muhr, G. T.

    1990-06-01

    AlGaAs grown by metalorganic molecular beam epitaxy (MOMBE) has been problematic due to oxygen and carbon contamination, particularly when triethylaluminum (TEAl) has been used as the aluminum source. Consequently, we have investigated trimethylamine alane (TMAAl) as a potential replacement for the conventional metalorganic Al sources. AlGaAs films with excellent structural and optical properties have been grown with this source. Photoluminescence intensities from AlGaAs grown by MOMBE at 500 °C using TMAAl are comparable to those from material grown by metalorganic chemical vapor deposition at 675 °C using triethylaluminum (TMAl). Carbon and oxygen levels in MOMBE-grown AlGaAs are drastically reduced in comparison to similar films grown with TEAl.

  8. Growth regimes during homoepitaxial growth of GaN by ammonia molecular beam epitaxy

    SciTech Connect

    Corrion, A. L.; Wu, F.; Speck, J. S.

    2012-09-01

    c-plane GaN films were grown by ammonia molecular beam epitaxy on metal-organic chemical vapor deposition templates for a wide range of NH{sub 3}:Ga flux ratios and growth temperatures, and the resulting films were characterized using atomic force microscopy, reflection high-energy electron diffraction, and transmission electron microscopy. Three distinct nitrogen-rich growth regimes - unstable layer-by-layer, quasi-stable step flow, and dislocation-mediated pitting - were identified based on the growth mode and film properties. In addition, step flow growth was observed under conditions of gallium droplet accumulation. The results indicate the existence of two regimes for step-flow growth of GaN by ammonia MBE - both gallium-rich and nitrogen-rich. Growth mode instabilities and mound formation were observed and are discussed in the context of a step-edge energy barrier to adatom diffusion over a terrace.

  9. The electron beam deposition of titanium on polyetheretherketone (PEEK) and the resulting enhanced biological properties.

    PubMed

    Han, Cheol-Min; Lee, Eun-Jung; Kim, Hyoun-Ee; Koh, Young-Hag; Kim, Keung N; Ha, Yoon; Kuh, Sung-Uk

    2010-05-01

    The surface of polyetheretherketone (PEEK) was coated with a pure titanium (Ti) layer using an electron beam (e-beam) deposition method in order to enhance its biocompatibility and adhesion to bone tissue. The e-beam deposition method was a low-temperature coating process that formed a dense, uniform and well crystallized Ti layer without deteriorating the characteristics of the PEEK implant. The Ti coating layer strongly adhered to the substrate and remarkably enhanced its wettability. The Ti-coated samples were evaluated in terms of their in vitro cellular behaviors and in vivo osteointegration, and the results were compared to a pure PEEK substrate. The level of proliferation of the cells (MC3T3-E1) was measured using a methoxyphenyl tetrazolium salt (MTS) assay and more than doubled after the Ti coating. The differentiation level of cells was measured using the alkaline phosphatase (ALP) assay and also doubled. Furthermore, the in vivo animal tests showed that the Ti-coated PEEK implants had a much higher bone-in-contact (BIC) ratio than the pure PEEK implants. These in vitro and in vivo results suggested that the e-beam deposited Ti coating significantly improved the potential of PEEK for hard tissue applications. PMID:20153890

  10. Selective atomic layer deposition with electron-beam patterned self-assembled monolayers

    SciTech Connect

    Huang, Jie; Lee, Mingun; Kim, Jiyoung

    2012-01-15

    The authors selectively deposited nanolines of titanium oxide (TiO{sub 2}) through atomic layer deposition (ALD) using an octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) as a nucleation inhibition layer. Electron-beam (e-beam) patterning is used to prepare nanoline patterns in the OTS SAM on SiO{sub 2}/Si substrates suitable for selective ALD. The authors have investigated the effect of an e-beam dose on the pattern width of the selectively deposited TiO{sub 2} lines. A high dose (e.g., 20 nC/cm) causes broadening of the linewidth possibly due to scattering, while a low dose (e.g., 5 nC/cm) results in a low TiO{sub 2} deposition rate because of incomplete exposure of the OTS SAMs. The authors have confirmed that sub-30 nm isolated TiO{sub 2} lines can be achieved by selective ALD combined with OTS patterned by EBL at an accelerating voltage of 2 kV and line dose of 10 nC/cm. This research offers a new approach for patterned gate dielectric layer fabrication, as well as potential applications for nanosensors and solar cells.

  11. Epitaxial composition-graded perovskite films grown by a dual-beam pulsed laser deposition method

    NASA Astrophysics Data System (ADS)

    Sakai, Joe; Autret-Lambert, Cécile; Sauvage, Thierry; Courtois, Blandine; Wolfman, Jérôme; Gervais, François

    2013-10-01

    We prepared SrTiO3 (STO) to Ba0.6Sr0.4TiO3 (BST06) out-of-plane composition-graded films on STO (100) substrates by means of a dual-beam dual-target pulsed laser deposition technique. In the deposition system, a sliding mirror divides one KrF excimer laser beam into two, realizing the dual-beam of controlled intensity ratio. X-ray diffraction reciprocal space mapping has revealed that the graded films deposited under oxygen pressure at or lower than 1×10-3 mbar were coherently strained with the same in-plane lattice parameter as the substrate. Their composition gradient along the growth direction was confirmed by Rutherford backscattering analysis to be uniform. We deposited BST06 top layers of various thickness on epitaxial composition-graded (ECG) buffer layers and examined their coherency and crystallinity. In comparison with the cases of STO homoepitaxial buffer layers, ECG buffer layers achieved better crystallinity of top BST06 layers, suggesting that the crystallinity of a heteroepitaxially-grown film is affected not only by the in-plane lattice matching but also by the out-of-plane lattice continuity with the substrate. ECG films that bridge compositions of substrate and top layer materials can be useful buffer layers for epitaxial growth of lattice-mismatched oxide films.

  12. Effect of molecular weight on the electrophoretic deposition of carbon black nanoparticles in moderately viscous systems.

    PubMed

    Modi, Satyam; Panwar, Artee; Mead, Joey L; Barry, Carol M F

    2013-08-01

    Electrophoretic deposition from viscous media has the potential to produce in-mold assembly of nanoparticles onto three-dimensional parts in high-rate, polymer melt-based processes like injection molding. The effects of the media's molecular weight on deposition behavior were investigated using a model system of carbon black and polystyrene in tetrahydrofuran. Increases in molecular weight reduced the electrophoretic deposition of the carbon black particles due to increases in suspension viscosity and preferential adsorption of the longer polystyrene chains on the carbon black particles. At low deposition times (≤5 s), only carbon black deposited onto the electrodes, but the deposition decreased with increasing molecular weight and the resultant increases in suspension viscosity. For longer deposition times, polystyrene codeposited with the carbon black, with the amount of polystyrene increasing with molecular weight and decreasing with greater charge on the polystyrene molecules. This deposition behavior suggests that use of lower molecular polymers and control of electrical properties will permit electrophoretic deposition of nanoparticles from polymer melts for high-rate, one-step fabrication of nano-optical devices, biochemical sensors, and nanoelectronics. PMID:23848316

  13. Development of Ultra Small Shock Tube for High Energy Molecular Beam Source

    SciTech Connect

    Miyoshi, Nobuya; Nagata, Shuhei; Kinefuchi, Ikuya; Shimizu, Kazuya; Matsumoto, Yoichiro; Takagi, Shu

    2008-12-31

    A molecular beam source exploiting a small shock tube is described for potential generation of high energy beam in a range of 1-5 eV without any undesirable impurities. The performance of a non-diaphragm type shock tube with an inner diameter of 2 mm was evaluated by measuring the acceleration and attenuation process of shock waves. With this shock tube installed in a molecular beam source, we measured the time-of-flight distributions of shock-heated beams, which demonstrated the ability of controlling the beam energy with the initial pressure ratio of the shock tube.

  14. Development of Ultra Small Shock Tube for High Energy Molecular Beam Source

    NASA Astrophysics Data System (ADS)

    Miyoshi, Nobuya; Nagata, Shuhei; Kinefuchi, Ikuya; Shimizu, Kazuya; Takagi, Shu; Matsumoto, Yoichiro

    2008-12-01

    A molecular beam source exploiting a small shock tube is described for potential generation of high energy beam in a range of 1-5 eV without any undesirable impurities. The performance of a non-diaphragm type shock tube with an inner diameter of 2 mm was evaluated by measuring the acceleration and attenuation process of shock waves. With this shock tube installed in a molecular beam source, we measured the time-of-flight distributions of shock-heated beams, which demonstrated the ability of controlling the beam energy with the initial pressure ratio of the shock tube.

  15. Molecular collision studies with Stark-decelerated beams

    NASA Astrophysics Data System (ADS)

    Meijer, Gerard

    2008-03-01

    Molecular scattering behaviour has generally proven difficult to study at low collision energies. We formed a molecular beam of OH radicals with a narrow velocity distribution and a tunable velocity by passing the beam through a Stark decelerator [1]. The transition probabilities for inelastic scattering of the OH radicals with Xe atoms were measured as a function of the collision energy in the range of 50 to 400 wavenumbers. The behaviour of the cross-sections for inelastic scattering near the energetic thresholds was accurately measured, and excellent agreement was obtained with cross-sections derived from coupled- channel calculations on ab initio computed potential energy surfaces [2]. For collision studies at lower energies, the decelerated beams of molecules can be loaded into a variety of traps. In these traps, electric fields are used to keep the molecules confined in a region of space where they can be studied in complete isolation from the (hot) environment. Typically, 10^5 state- selected molecules can be trapped for times up to several seconds at a density of 10^7 mol/cm^3 and at a temperature of several tens of mK [3]. The long interaction time afforded by the trap has been exploited to measure the infrared radiative lifetime of vibrationally excited OH radicals, for instance, as well as to study the far-infrared optical pumping of these polar molecules due to blackbody radiation [4]. As an alternative to these traps, we have demonstrated an electrostatic storage ring for neutral molecules. In its simplest form, a storage ring is a trap in which the molecules - rather than having a minimum potential energy at a single location in space - have a minimum potential energy on a circle. To fully exploit the possibilities offered by a ring structure, it is imperative that the molecules remain in a bunch as they revolve around the ring. This ensures a high density of stored molecules, moreover, this makes it possible to inject multiple - either co-linear or

  16. Growth of textured MgO through e-beam evaporation and inclined substrate deposition

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Lei, C. H.; Ma, B.; Evans, H.; Efstathiadis, H.; Manisha, R.; Massey, M.; Balachandran, U.; Bhattacharya, R.

    2006-08-01

    Long length textured MgO template on Hastelloy C276™ (HC) has been successfully deposited in a reel-to-reel (R2R) electron beam (e-beam) evaporation system by inclined substrate deposition (ISD). High deposition rate up to 10 nm s-1 with exposure length of 7 cm has been realized. The MgO template showed good in-plane texture of 9.5°-11.5° measured from the (002) phi scans. Experimental results reveal that MgO in-plane texture is formed by the preferred growth direction of [11n]\\parallel \\mathrm {substrate} normal and one of the MgO {200} planes rotates to the in-flux direction. A new expression, termed the 'two-thirds relationship', between the inclination angle α and the tilted angle of the (00l) plane from the substrate normal, β, has been summarized. YBa2Cu3O7-δ (YBCO) film deposited by pulsed laser deposition (PLD) on strontium ruthenate (SRO) buffered ISD MgO showed Tc of 91 K with transition width of 1 K. Critical current measurement indicated an Ic of 110 A cm-1 at 77 K in self-field for 0.68 µm YBCO film, corresponding to a Jc of 1.6 MA cm-2.

  17. Functional nickel-based deposits synthesized by focused beam induced processing.

    PubMed

    Córdoba, R; Barcones, B; Roelfsema, E; Verheijen, M A; Mulders, J J L; Trompenaars, P H F; Koopmans, B

    2016-02-12

    Functional nanostructures fabricated by focused electron/ion beam induced processing (FEBIP/FIBIP) open a promising route for applications in nanoelectronics. Such developments rely on the exploration of new advanced materials. We report here the successful fabrication of nickel-based deposits by FEBIP/FIBIP using bis(methyl cyclopentadienyl)nickel as a precursor. In particular, binary compounds such as nickel oxide (NiO) are synthesized by using an in situ two-step process at room temperature. By this method, as-grown Ni deposits transform into homogeneous NiO deposits using focused electron beam irradiation under O2 flux. This procedure is effective in producing highly pure NiO deposits with resistivity of 2000 Ωcm and a polycrystalline structure with face-centred cubic lattice and grains of 5 nm. We demonstrate that systems based on NiO deposits displaying resistance switching and an exchange-bias effect could be grown by FEBIP using optimized parameters. Our results provide a breakthrough towards using these techniques for the fabrication of functional nanodevices. PMID:26759183

  18. Physical properties of nitrogenated amorphous carbon films produced by ion-beam-assisted deposition

    NASA Astrophysics Data System (ADS)

    Rossi, Francois; Andre, Bernard; Veen, A. Van; Mijnarends, P. E.; Schut, H.; Labohm, F.; Delplancke, Marie Paule; Dunlop, Hugh; Anger, Eric

    1994-12-01

    Carbon films with up to 32 at.% N (a-C:N) have been prepared using an ion-beam-assisted magnetron, with an N2(+) beam at energies between 50 and 300 eV. The composition and density of the films vary strongly with the deposition parameters. Electron energy loss spectroscopy shows that these a-C:N films are mostly graphitic with up to 20% C Sp3 bonding. Rutherford backscattering spectroscopy and neutron depth profiling show that the density goes through a maximum as the average deposited energy per unit depth increases. X-ray photoelectron spectroscopy shows that nitrogen is mostly combined with carbon in triple (C(triple bond)N and double (C=N) bonds. Positron annihilation spectroscopy shows that the void concentration in the films goes through a minimum with deposited energy. These results are consistent with a densification induced by the collisions at low deposited energy, and damage-induced graphitization at high deposited energy values.

  19. Functional nickel-based deposits synthesized by focused beam induced processing

    NASA Astrophysics Data System (ADS)

    Córdoba, R.; Barcones, B.; Roelfsema, E.; Verheijen, M. A.; Mulders, J. J. L.; Trompenaars, P. H. F.; Koopmans, B.

    2016-02-01

    Functional nanostructures fabricated by focused electron/ion beam induced processing (FEBIP/FIBIP) open a promising route for applications in nanoelectronics. Such developments rely on the exploration of new advanced materials. We report here the successful fabrication of nickel-based deposits by FEBIP/FIBIP using bis(methyl cyclopentadienyl)nickel as a precursor. In particular, binary compounds such as nickel oxide (NiO) are synthesized by using an in situ two-step process at room temperature. By this method, as-grown Ni deposits transform into homogeneous NiO deposits using focused electron beam irradiation under O2 flux. This procedure is effective in producing highly pure NiO deposits with resistivity of 2000 Ωcm and a polycrystalline structure with face-centred cubic lattice and grains of 5 nm. We demonstrate that systems based on NiO deposits displaying resistance switching and an exchange-bias effect could be grown by FEBIP using optimized parameters. Our results provide a breakthrough towards using these techniques for the fabrication of functional nanodevices.

  20. Ion beam sputter deposition of TiNi shape memory alloy thin films

    NASA Astrophysics Data System (ADS)

    Davies, Sam T.; Tsuchiya, Kazuyoshi

    1999-08-01

    The development of functional or smart materials for integration into microsystem is of increasing interest. An example is the shape memory effect exhibited by certain metal alloys which, in principle, can be exploited in the fabrication of micro-scale manipulators or actuators, thereby providing on-chip micromechanical functionality. We have investigated an ion beam sputter deposition process for the growth of TiNi shape memory alloy thin films and demonstrated the required control to produce equiatomic composition, uniform coverage and atomic layer-by-layer growth rates on engineering surfaces. The process uses argon ions at intermediate energy produced by a Kaufman-type ion source to sputter non-alloyed targets of high purity titanium and nickel. Precise measurements of deposition rates allows compositional control during thin film growth. As the sputtering targets and substrates are remote from the discharge plasma, deposition occurs under good vacuum of approximately 10-6 mtorr thus promoting high quality films. Furthermore, the ion beam energetics allow deposition at relatively low substrate temperatures of < 150 degrees C with as-deposited films exhibiting shape memory properties without post-process high temperature annealing. Thermal imagin is used to monitor changes which are characteristic of the shape memory effect and is indicative of changes in specific heat capacity and thermal conductivity as the TiNi shape memory alloy undergoes martensitic to austenitic phase transformations.

  1. Thermally induced transformations of amorphous carbon nanostructures fabricated by electron beam induced deposition.

    PubMed

    Kulkarni, Dhaval D; Rykaczewski, Konrad; Singamaneni, Srikanth; Kim, Songkil; Fedorov, Andrei G; Tsukruk, Vladimir V

    2011-03-01

    We studied the thermally induced phase transformations of electron-beam-induced deposited (EBID) amorphous carbon nanostructures by correlating the changes in its morphology with internal microstructure by using combined atomic force microscopy (AFM) and high resolution confocal Raman microscopy. These carbon deposits can be used to create heterogeneous junctions in electronic devices commonly known as carbon-metal interconnects. We compared two basic shapes of EBID deposits: dots/pillars with widths from 50 to 600 nm and heights from 50 to 500 nm and lines with variable heights from 10 to 150 nm but having a constant length of 6 μm. We observed that during thermal annealing, the nanoscale amorphous deposits go through multistage transformation including dehydration and stress-relaxation around 150 °C, dehydrogenation within 150-300 °C, followed by graphitization (>350 °C) and formation of nanocrystalline, highly densified graphitic deposits around 450 °C. The later stage of transformation occurs well below commonly observed graphitization for bulk carbon (600-800 °C). It was observed that the shape of the deposits contribute significantly to the phase transformations. We suggested that this difference is controlled by different contributions from interfacial footprints area. Moreover, the rate of graphitization was different for deposits of different shapes with the lines showing a much stronger dependence of its structure on the density than the dots. PMID:21319745

  2. Optimization of ion assist beam deposition of magnesium oxide template films during initial nucleation and growth

    SciTech Connect

    Groves, James R; Matias, Vladimir; Stan, Liliana; De Paula, Raymond F; Hammond, Robert H; Clemens, Bruce M

    2010-01-01

    Recent efforts in investigating the mechanism of ion beam assisted deposition (IBAD) of biaxially textured thin films of magnesium oxide (MgO) template layers have shown that the texture develops suddenly during the initial 2 nm of deposition. To help understand and tune the behavior during this initial stage, we pre-deposited thin layers of MgO with no ion assist prior to IBAD growth of MgO. We found that biaxial texture develops for pre-deposited thicknesses < 2 nm, and that the thinnest layer tested, at 1 nm, resulted in the best qualitative RHEED image, indicative of good biaxial texture development. The texture developed during IBAD growth on the 1.5 nm pre-deposited layer is slightly worse and IBAD growth on the 2 nm pre-deposited layer produces a fiber texture. Application of these layers on an Al{sub 2}O{sub 3} starting surface, which has been shown to impede texture development, improves the overall quality of the IBAD MgO and has some of the characteristics of a biaxially texture RHEED pattern. It is suggested that the use of thin (<2 nm) pre-deposited layers may eliminate the need for bed layers like Si{sub 3}N{sub 4} and Y{sub 2}O{sub 3} that are currently thought to be required for proper biaxial texture development in IBAD MgO.

  3. Room temperature operational single electron transistor fabricated by focused ion beam deposition

    NASA Astrophysics Data System (ADS)

    Karre, P. Santosh Kumar; Bergstrom, Paul L.; Mallick, Govind; Karna, Shashi P.

    2007-07-01

    We present the fabrication and room temperature operation of single electron transistors using 8nm tungsten islands deposited by focused ion beam deposition technique. The tunnel junctions are fabricated using oxidation of tungsten in peracetic acid. Clear Coulomb oscillations, showing charging and discharging of the nanoislands, are seen at room temperature. The device consists of an array of tunnel junctions; the tunnel resistance of individual tunnel junction of the device is calculated to be as high as 25.13GΩ. The effective capacitance of the array of tunnel junctions was found to be 0.499aF, giving a charging energy of 160.6meV.

  4. Growth of cluster assembled ZnO film by nanocluster beam deposition technique

    SciTech Connect

    Halder, Nilanjan

    2015-06-24

    ZnO is considered as one of the most promising material for optoelectronic devices. The present work emphasizes production of cluster assembled ZnO films by a UHV nanocluster beam deposition technique where the nanoclusters were produced in a laser vaporization cluster source. The microstructural and the optical properties of the ZnO nanocluster film deposited were investigated. As the wet chemical processes are not compatible with current solid state methods of device fabrication, therefore alternative UHV technique described in the paper is the need of the hour.

  5. Percolation of gallium dominates the electrical resistance of focused ion beam deposited metals

    SciTech Connect

    Faraby, H.; DiBattista, M.; Bandaru, P. R.

    2014-04-28

    Metal deposition through focused ion beam (FIB) based systems is thought to result in material composed of the primary metal from the metallo-organic precursor in addition to carbon, oxygen, and gallium. We determined, through electrical resistance and chemical composition measurements on a wide range of FIB deposited platinum and tungsten lines, that the gallium ion (Ga{sup +}) concentration in the metal lines plays the dominant role in controlling the electrical resistivity. Effective medium theory, based on McLachlan's formalisms, was used to describe the relationship between the Ga{sup +} concentration and the corresponding resistivity.

  6. Adherence of ion beam sputter deposited metal films on H-13 steel

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.

    1980-01-01

    An electron bombardment argon ion source was used to sputter deposit 17 different metal and metal oxide films ranging in thickness from 1 to 8 micrometers on H-13 steel substrates. The film adherence to the substrate surface was measured using a tensile test apparatus. Comparisons in bond strength were made between ion beam, ion plating, and RF deposited films. A protective coating to prevent heat checking in H-13 steel dies used for aluminum die casting was studied. The results of exposing the coated substrates to temperatures up to 700 degrees are presented.

  7. Low-temperature epitaxy of Si and Ge by direct ion beam deposition

    SciTech Connect

    Zuhr, R.A.; Appleton, B.R.; Herbots, N.; Larson, B.C.; Noggle, T.S.; Pennycook, S.J.

    1987-07-01

    Amorphous, polycrystalline, and epitaxial thin films of Si and Ge have been grown by ion beam deposition (IBD) under ultrahigh-vacuum conditions. IBD involves the direct deposition of ions onto single-crystal substrates from mass- and energy-analyzed beams with energies of 10 to 200 eV. The IBD films were characterized by Rutherford backscattering, ion channeling, cross-section transmission electron microscopy, and x-ray diffraction. The effects of substrate temperature, ion energy, and substrate cleaning were studied. Differences in the formation of epitaxial thin films on p- and n-type Si substrates were observed with n/sup -/ Si showing better epitaxy at low temperatures. Epitaxial overlayers which showed good minimum yields by ion channeling (3%--4%) have been produced at temperatures as low as 375/sup 0/C for Ge on Ge(100) and Si on Si(100).

  8. Low leakage current gate dielectrics prepared by ion beam assisted deposition for organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Chang Su; Jo, Sung Jin; Kim, Jong Bok; Ryu, Seung Yoon; Noh, Joo Hyon; Baik, Hong Koo; Lee, Se Jong; Kim, Youn Sang

    2007-12-01

    This communication reports on the fabrication of low operating voltage pentacene thin-film transistors with high-k gate dielectrics by ion beam assisted deposition (IBAD). These densely packed dielectric layers by IBAD show a much lower level of leakage current than those created by e-beam evaporation. These results, from the fact that those thin films deposited with low adatom mobility, have an open structure, consisting of spherical grains with pores in between, that acts as a significant path for leakage current. By contrast, our results demonstrate the potential to limit this leakage. The field effect mobility, on/off current ratio, and subthreshold slope obtained from pentacene thin-film transistors (TFTs) were 1.14 cm2/V s, 105, and 0.41 V/dec, respectively. Thus, the high-k gate dielectrics obtained by IBAD show promise in realizing low leakage current, low voltage, and high mobility pentacene TFTs.

  9. Size effect of large deformable nanopillar by focused-ion-beam chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tanaka, H.; Shinkai, M.; Shibutani, Y.; Kogo, Y.

    2009-11-01

    Nanoscopic fabrication technique has been achieved by the direct deposition methods using focused-ion-beam chemical vapor deposition (FIB-CVD). The nanopillar fabricated by FIB-CVD consists of an outer amorphous carbon ring and a inner gallium core. We developed the original double-cantilever (DC) bending test using two pillars rigidly connected by the exposure of a focused electron beam in a scanning electron microscope. The obtained deflection curves suggest that nanopillars have the size dependence to the mechanical response. The pillar with the diameter over 180 nm exhibits a wide region of stiffness weakening after linear response and then becomes extremely hardened at a large deflection. Thus, the pillar intrinsically possesses much more flexibility for bending without any fracturing. The accuracy of a DC testing is also discussed by estimating the bending rigidities of nanopillars, comparing to those obtained by resonance frequency tests.

  10. Ion-beam inertial fusion: the requirements posed by target and deposition physics

    SciTech Connect

    Mark, J.W.K.

    1981-10-19

    The demonstration of ICF scientific feasibility requires success in target design, driver development and target fabrication. Since these are interrelated, we present here some results of ion beam target studies and relate them to parameters of interest to ion accelerators. Ion deposition physics have long been a well known subject apart from high beam currents. Recent NRL experiments at up to 250 kA/cm/sup 2/ ions confirm the classical deposition physics now at current densities which are comparable to most ion targets. On the other hand, GSI data at low current density but 1 to 10 MeV/nucleon are continually being accumulated. They have yet to find anomalous results. Relying on target concepts outlined briefly, we report on the energy gain of ion-driven fusion targets as a function of input energy, ion ranges and focal spot radius. We also comment on some consequences of target gain versus driver and reactor requirements.