Samarium Films Research Articles

Adsorption of Carbon Dioxide on Mono-Layer Thick Oxidized Samarium Films on Ni(100).

Studies of adsorption of CO on nanoscopic surfaces are relevant for technological applications in heterogeneous catalysis as well as for sorption of this important greenhouse gas. Presently, adsorption of carbon dioxide on pure and oxidized thin samarium layers near mono-layer thickness on Ni(100) has been investigated by photoelectron spectroscopy and temperature programmed desorption. It is observed that very little CO adsorb on the metallic sample for exposures in the vacuum regime at room temperature. For the oxidized sample, a large enhancement in CO adsorption is observed in the desorption measurements. Indications of carbonate formation on the surface were found by C 1s and O 1s XPS. After annealing of the oxidized samples to 900 K very little CO was found to adsorb. Differences in desorption spectra before and after annealing of the oxidized samples are correlated with changes in XPS intensities, and with changes in sample work function which determines the energy difference between molecular orbitals and substrate Fermi level, and thus the probability of charge transfer between adsorbed molecule and substrate.

Synthesis of thin isotopic samarium targets for elastic cross-section measurements

Various fabrication techniques of thin films of lanthanides are very well known. Two major techniques, electron gun deposition and thermal resistivity method have been employed here to know their validity in using the fabricated thin films of Samarium (Sm) for elastic cross-section measurements. The purity and thickness of these prepared targets have been verified and confirmed by using several advanced techniques. These targets have also been irradiated during one of the recent nuclear physics experiment involving measurement of the quasi-elastic cross-section. Detailed fabrication methods as well as characterization techniques have been reported.

Efek Annealing Temperture Terhadap Sifat Magnetik Dan Struktur Multilapisan Tipis Cobalt-Samarium

<span>Multilayer thin films of cobalt and samarium with the structur of 20[Co (4.2 nm)/Sm (3.8 nm)] <span>have been fabricated using dc magnetron sputtering technique. Crystalline formation due to <span>heat treatment of about 450<span>o<span>C of the sample is responsible for increase of coercivity from <span>300Oe to 3500 Oe. Due to heat treatment (annealing) of the sample caused the value of the <span>magnetization of the sample decreases. This is due to the formation of none magnetic phase in<br /><span>interfacial mixing between the layers as a result of inter-diffusion between the layers. <span>Structural properties of as deposited and annealed samples was studied using transmission <span>electron microscope (TEM). Electron diffraction patterns for as deposited sample exhibit <span>diffused rings for samarium reflection however, for the annealed sample of about 450<span>o<span>C for 30 <span>minutes produces sharp diffraction rings. This indicates that alloys of CoSm in interfacial <span>mixing has a crystalline properties. By modifying the annealing temperature and time one can <span>obtain higher value of coercivity of alloy of CoSm between the layers as one of the<br /><span>requirements for higher density magnetic recording media.</span></span></span></span></span></span></span></span></span></span></span></span><br /></span></span></span></span></span>

Initial stages of the interaction with oxygen of samarium thin films grown on the iridium surface

The interaction of thin (<1 nm) samarium films deposited on a textured iridium ribbon has been investigated by thermal desorption spectrometry. Samarium atoms deposited at T = 300 K desorb in three phases associated with the formation of a submonolayer samarium coverage on iridium, a compound of samarium with iridium, and a multilayer samarium film. The interaction with oxygen leads to the appearance of a new desorption phase, which is associated with the formation of samarium oxide. Oxidation of samarium is observed during exposure in oxygen already at room temperature. An increase in temperature of the iridium ribbon, at which exposure in oxygen occurs, to T = 1100 K leads to the formation of the compound of samarium with iridium. Further, the film of the compound decomposes in the course of interaction with oxygen, and samarium oxide grows on the Ir surface.

Oxidation of a thin samarium film on iridium

Thermal desorption spectroscopy has been used to study the interaction of oxygen with a thin (<1 nm) samarium film deposited onto a textured iridium ribbon. Desorption of Sm atoms from Ir surface takes place from various states (chemisorbed, condensed, from compound with iridium, and oxide). The formation of samarium oxide is observed already at room temperature. As the temperature increases to T = 1100 K, a compound of samarium with iridium is formed at the first stage and then oxygen interacts with Sm atoms from this compound and “slow” (compared to the first process) growth of samarium oxide takes place.

Ferroelectric Properties of Laser Ablated Sm Modified PCT Thin Films

Crystallized thin films of samarium modified lead calcium titanate ceramics with composition; Pb0.66Sm0.08Ca0.24Mn0.02Ti0.98O3 were deposited under different annealing and laser energy conditions. Thin films deposited at these conditions show a surface roughness, coercive field and remnant polarization in the range of 1.9–6.0 nm, 120–220 kV/cm and 4–11.5 μC/cm2, respectively. I-V and C-V measurements were also performed in order to study the electrical behaviour of the films.

Studies on electrophoretic deposition of nanocrystalline SDC electrolyte films

Thin films of nanocrystalline samarium doped ceria (SDC) were electrophoretically deposited on stainless steel substrate using Sm 0.2Ce 0.8O 1 .9 nanopowder prepared by polyvinyl alcohol (PVA) assisted combustion method. The thermal behavior of the combusted powder was studied by thermogravimetric and differential thermal analysis (TG-DTA). Nanocrystallinity and phase purity of the calcinated SDC powder were confirmed from transmission electron microscope (TEM) and X-ray diffraction (XRD). In electrophoretic deposition (EPD), the parameters related to the suspension and deposition process were optimized in acetone. The film formation during deposition was found to be diffusion controlled process. The surface morphology of the deposited films and its cross-section were studied by scanning electron microscope (SEM). The preparation of nanocrystalline SDC electrolyte films from acetone-based suspension by EPD is reported for the first time in this paper.

Thermodesorption of samarium from oxidized tungsten surface

Thermodesorption of samarium (Sm) atoms and samarium oxide (SmO) molecules from samarium films deposited in vacuum onto tungsten substrates covered with thin (<1 nm thick) layers of tungsten oxides has been studied. It is established that samarium reduces tungsten from its oxides. The parameters of Sm and SmO desorption from an oxidized tungsten surface are determined.

Effect of Current Density on Thermodynamic Properties of Nanocrystalline Palladium Capped Samarium Hydride Thin Film Switchable Mirrors

A 55 nm samarium film capped with a 10 nm palladium overlayer switched from a metallic reflecting to a semiconducting, transparent in visible state during ex-situ hydrogen loading via electrochemical means in 1 M KOH electrolytic aqueous solution at room temperature. The switching between metal to semiconductor was accompanied by measurement of transmittance during hydrogen loading/unloading. The effect of current density on switching and thermodynamic properties was studied between dihydride state (FCC phase) and trihydride state (hexagonal phase). From the plateau of partial pressure of hydrogen atx=2.6, enthalpy of formation was calculated at different current densities. The diffusion coefficients and switching kinetics are shown to depend on applied current density.

Effect of Palladium Overlayer on Samarium Hydride Thin Film Switchable Mirror: Electrochemical and Topographical Study

Samarium films with a typical thickness of 55 nm deposited by vacuum evaporation and covered with Pd overlayers with thicknesses of 5, 8, 11, and 15 nm were loaded with hydrogen and deloaded in a 1 M KOH solution galvanostatically at room temperature. Our study showed that palladium overlayer thickness plays the most crucial role in observing the fast transition between an as-deposited metallic state and a semiconducting nearly samarium trihydride state as well as in obtaining a very high optical contrast. The desorption of hydrogen from palladium-capped SmH3-δ films was studied by in situ transmission measurement during the electrochemical loading/unloading of hydrogen. It was shown that palladium cap layer thickness affects the deloading of hydrogen from the hydrided films. The effect of a palladium overlayer on the surface morphology of metallic and hydrogen-desorbed samarium films showed the sequence of nucleation and growth.

Mechanism of the electrochemical deposition of samarium-based coatings

Samarium-based films have been shown to form from aqueous solutions on the surfaces of metallic substrates such as steel or aluminum, and their presence has been reported to decrease substantially the corresponding corrosion rate of the underlying metallic substrate. Based on previous reports on the deposition of oxides or hydroxides of the closely related element cerium, this work demonstrates that samarium films are formed following a similar mechanism, which involves as the fundamental step an increase in interfacial pH resulting from cathodic oxygen-reduction or hydrogen-evolution reactions. With cyclic voltammetry (CV), electrochemical quartz-crystal microbalance (EQCM) measurements, rotating-disk electrode (RDE) tests, and surface characterization techniques, namely, scanning electron microscopy (SEM) and X-ray surface microanalysis (EDX), the postulated mechanism was verified, and the surface morphology of the resulting films was correlated with the nature of the reduction reaction that triggers film formation.

Luminescence from thulium and samarium doped amorphous AlN thin films deposited by RF magnetron sputtering and the effect of thermal activation on luminescence

Thin films of thulium and samarium doped AlN are deposited on silicon (111) substrates at 77 K by rf magnetron sputtering method. 200–400 nm thick films are grown at 100–200 watts RF power and 5–8 mtorr nitrogen, using a metal target of Al with Tm and Sm separately. X-rays diffraction results show that films are amorphous. Cathodoluminescence studies are performed at room temperature and two dominant peaks are observed in Tm at 467 nm from transition and 480 nm from 1 G 4 to the ground state 3 H 6 transition. Other peaks in the visible region are obtained at 650 nm and 685 nm due to and transitions. Peaks in the ultraviolet and infrared region are also obtained at 371 nm, and 802 nm as a result from and transition respectively. Sm gives four peaks at 564 nm, 600 nm, 648 nm and 707 nm as a result of , , and transitions. Films are thermally activated at 1200 K for half an hour in a nitrogen atmosphere. Thermal activation enhances the intensity of luminescence.

Electrochemical study of Pd capped samarium hydride thin film switchable mirror

A 55-nm samarium film capped with a 15-nm palladium overlayer switched from a metallic reflecting to a semiconducting, transparent in visible state during ex-situ hydrogen loading via electrochemical means in 1 M KOH electrolytic aqueous solution at room temperature. The optical transmittance exhibits a hysteresis effects on loading and unloading of hydrogen in SmH x thin film between x = 2 and 3. The hysteresis is discussed in terms of strain (and consequently stress) at the interface between the dihydride and trihydride. The diffusion coefficients and switching kinetics are shown to depend on applied current density. The changes of anodic overpotential with time during applied constant current discharge have been used to determine the electrochemical parameters the exchange current density i 0 and the symmetry factor β.

Palladium capped samarium thin films as potential hydrogen sensors

We show here that a palladium capped samarium film at room temperature can be used as an efficient sensor material for hydrogen detection. As low as 194 ppm of hydrogen gas can be detected without any cross sensitivity problem. Depending upon the partial pressure of hydrogen, response times varying from 6 to 30 s have been obtained. An interesting observation is very fast hydrogen desorption (2 s) at room temperature, thus making the sensing element ready for reuse quickly. No external source is needed with this sensor element.

Electrochemically induced switching in SmHx thin films

Discovery of optical and electrical switching in yttrium and lanthanum hydride thin films in 1996, has triggered large scale investigations of rare earth hydride thin films. Both light and heavy rare earths have been shown to exhibit this so called ‘switchable mirror’ effect. Besides gas phase loading, solid as well as liquid electrolytes have been used as means of hydrogen loading. In this paper, we report on the ability of samarium films to switch between the reflecting and transparent states electrochemically by altering the hydrogen content. Samarium films of typical thickness 55nm deposited by vacuum evaporation and covered with Pd overlayer of thicknesses 5, 8 and 11nm were loaded with hydrogen and deloaded in a 1M KOH solution galvanostatically at room temperature. Our studies have shown that thickness of palladium overlayer plays the most crucial role in observing fast transition between the as deposited metallic and the semiconducting nearly samarium trihydride states as well as to obtain a very high optical contrast. The large reversible change in transparency between di and trihydride states suggests possibilities of use of samarium films as an optical shutter as well as a hydrogen sensor material.

Electrochemical loading of hydrogen in palladium capped samarium thin film: structural, electrical, and optical properties

A 50 nm samarium film capped with a 7 nm palladium overlayer switched from a metallic to semiconducting state during ex-situ hydrogen loading via electrochemical means at room temperature. The transition is accompanied by a change in transmittance measured during hydrogen loading and the associated optical appearance. The monitoring of working electrode (WE) potential, the transmittance and chi potential difference (Δ χ) has been used to identify the phases present during hydrogen loading. Deloading of hydrogen has been studied in open circuit potential condition. Glancing angle X-ray diffraction (GAXRD) studies show that the rhombohedral structure of metallic samarium film ( a 0=8.989 Å) changes to hexagonal structure of the SmH 3− δ film with average lattice parameters of a=3.775 Å and c=6.743 Å. A direct optical band gap of 2.9 eV has been obtained for SmH 3− δ film and 2.0 eV for SmH 2 ± ε film from reflectance and transmittance data. Removal of hydrogen from SmH 3− δ leads to the formation of localized states within the band whose signature is clearly seen in transmittance and Tauc’s plot curves of SmH 2 ± ε film. The Hall coefficient R H measured as a function of hydrogen concentration, changes from a metal-like value −14.23×10 -10 m 3/C to −1001.1×10 −10 m 3/C for SmH 3− δ films. On unloading hydrogen, the value of R H changes to −3.56×10 −10 m 3/C at the dihydride composition.

Separation of spin and orbital magnetizations in a samarium film

The L/ S ratio of samarium has been determined by X-ray magnetic scattering from a thick epitaxial film, via the azimuthal dependence of the scattered intensity. This new method allows a direct determination of L/ S in antiferromagnetic systems where charge scattering is not negligible at the position of the magnetic signal. The Russell–Saunders predictions fall within the accuracy of our results.

Influence of Palladium Overlayer on Switching Behaviour of Samarium Hydride Thin Films

Samarium films capped with a thin palladium overlayer undergo a metal to semiconductor transition during in-situ hydrogen loading (PH2=1.01×105 Pa) at room temperature. The transition is accompanied by a change in optical appearance, i.e. metallic gray samarium films change to golden greenish transparent samarium hydride (SmH3-δ) films. Glancing angle X-ray diffraction (GAXRD) studies show that the rhombohedral structure of metallic samarium films changes to hexagonal structure of the SmH3-δ films with average lattice parameters of a=3.775 Å, c=6.743 Å. A direct optical band gap of 3.0 eV has been obtained for SmH3-δ films from reflectance and transmittance data. The Hall coefficient measured as a function of hydrogen concentration, changes from a metal-like RH value -14.9×10-10 m3/C to -1081.8×10-10 m3/C for SmH3-δ films. On unloading hydrogen, the value of RH changes to -3.85×10-10m3/C at the dihydride composition.

Magnetic structures in a dhcp samarium film

Thick samarium films with a four plane dhcp structure instead of the nine-layer stacking characteristic of the element in bulk form, have been prepared by molecular-beam epitaxy. The magnetic structure of this dhcp phase has been elucidated using both neutron-scattering and resonant x-ray magnetic scattering experiments. The magnetic moments align along the c direction. In a given basal plane, for the hexagonal (h) sites as well as for the cubic (c) sites, the magnetic ordering is the same as in bulk samarium. However, the three-dimensional magnetic ordering is modified compared to the bulk one, since both types of planes (h and c) couple antiferromagnetically along the c axis. Moreover, both sets of sites order nearly simultaneously at about 25 K. Compared to bulk, the magnetic ordering temperature is thus lower for the hexagonal sites and higher for the cubic ones.

Preparation of 4:55:45 samarium doped PZT films by sol-gel technique and their characterization

Thin ferroelectric films of samarium doped PZT (4:55:45) were prepared by sol-gel technique on ITO coated corning 7059 glass. Characterization of these films by X-ray diffraction and scanning electron microscopy shows that the films are formed perovskite tetragonal phase with submicron crystallite size. Charge field hysteresis, dielectric relaxation and pyroelectric studies were carried on these films. It is concluded that these films with their high pyroelectric coefficient ∼45 nC cm −2 K −1 and low dielectric constant ∼230 will find application as pyroelectric sensor elements.