scispace - formally typeset
Search or ask a question

Showing papers on "Pulsed laser deposition published in 2011"


Journal ArticleDOI
TL;DR: In this article, a small amount of secondary phase on a (001) La0.8Sr0.2CoO3−δ (LSC) surface can either significantly activate or passivate the electrode.
Abstract: Surface-decoration of perovskites can strongly affect the oxygen reduction activity, and therefore is a new and promising approach to improve SOFC cathode materials. In this study, we demonstrate that a small amount of secondary phase on a (001) La0.8Sr0.2CoO3−δ (LSC) surface can either significantly activate or passivate the electrode. LSC (001) microelectrodes prepared by pulsed laser deposition on a (001)-oriented yttria-stabilized zirconia (YSZ) substrate were decorated with La-, Co-, and Sr-(hydr)oxides/carbonates. “Sr”-decoration with nanoparticle coverage in the range from 50% to 80% of the LSC surface enhanced the surface exchange coefficient, kq, by an order of magnitude while “La”-decoration and “Co”-decoration led to no change and reduction in kq, respectively. Although the physical origin for the enhancement is not fully understood, results from atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy suggest that the observed kq enhancement for “Sr”-decorated surfaces can be attributed largely to catalytically active interface regions between surface Sr-enriched particles and the LSC surface.

192 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of composition, energetic, and kinetics in the evolution of the microstructure and texture of the TixTa1−xN thin films were studied.
Abstract: The mechanisms controlling the structural and morphological features (texture and microstructure) of ternary transition metal nitride thin films of the TixTa1−xN system, grown by various physical vapor deposition techniques, are reported. Films deposited by pulsed laser deposition, dual cathode magnetron sputtering, and dual ion beam sputtering have been investigated by means of x-ray diffraction in various geometries and scanning electron microscopy. We studied the effects of composition, energetic, and kinetics in the evolution of the microstructure and texture of the films. We obtain films with single and mixed texture as well as films with columnar “zone-T” and globular type morphology. The results have shown that the texture evolution of ternary transition metal nitrides as well as the microstructural features of such films can be well understood in the framework of the kinetic mechanisms proposed for their binary counterparts, thus giving these mechanisms a global application.

181 citations


Journal ArticleDOI
TL;DR: In this paper, a tunable and enhanced low-field magnetoresistance (LFMR) was observed in epitaxial (La 0.7Sr 0.3MnO3)0.5 self-assembled vertically aligned nanocomposite (VAN) thin films, which have been grown on SrTiO3 (001) substrates by pulsed laser deposition (PLD).
Abstract: Tunable and enhanced low-field magnetoresistance (LFMR) is observed in epitaxial (La0.7Sr0.3MnO3)0.5:(ZnO)0.5 (LSMO:ZnO) self-assembled vertically aligned nanocomposite (VAN) thin films, which have been grown on SrTiO3 (001) substrates by pulsed laser deposition (PLD). The enhanced LFMR properties of the VAN films reach values as high as 17.5% at 40 K and 30% at 154 K. They can be attributed to the spin-polarized tunneling across the artificial vertical grain boundaries (GBs) introduced by the secondary ZnO nanocolumns and the enhancement of spin fluctuation depression at the spin-disordered phase boundary regions. More interestingly, the vertical residual strain and the LFMR peak position of the VAN films can be systematically tuned by changing the deposition frequency. The tunability of the physical properties is associated with the vertical phase boundaries that change as a function of the deposition frequency. The results suggest that the tunable artificial vertical GB and spin-disordered phase boundary in the unique VAN system with vertical ferromagnetic-insulating-ferromagnetic (FM-I-FM) structure provides a viable route to manipulate the low-field magnetotransport properties in VAN films with favorable epitaxial quality.

179 citations


Journal ArticleDOI
Lin Sun1, Jun He1, Hui Kong1, Fangyu Yue1, Pingxiong Yang1, Junhao Chu1 
TL;DR: In this article, the results of energy dispersive X-ray spectroscopy (EDX) indicate that these CZTS thin films are Cu-rich and S-poor.

178 citations


Journal ArticleDOI
TL;DR: In this paper, high quality Cu2ZnSnS4 (CZTS) thin films were synthesized by pulsed laser deposition as a function of pulse repetition rate onto the SLG substrates.

159 citations


Journal ArticleDOI
TL;DR: In this article, a micro-solid oxide fuel cell (μ-SOFC) is fabricated on nanoporous anodic aluminum oxide (AAO) templates with a cell structure composed of a 600-nm-thick AAO free-standing membrane embedded on a Si substrate, sputter-deposited Pt electrodes (cathode and anode) and an yttria-stabilized zirconia (YSZ) electrolyte deposited by pulsed laser deposition (PLD).
Abstract: Micro-solid oxide fuel cells (μ-SOFCs) are fabricated on nanoporous anodic aluminum oxide (AAO) templates with a cell structure composed of a 600-nm-thick AAO free-standing membrane embedded on a Si substrate, sputter-deposited Pt electrodes (cathode and anode) and an yttria-stabilized zirconia (YSZ) electrolyte deposited by pulsed laser deposition (PLD). Initially, the open circuit voltages (OCVs) of the AAO-supported μ-SOFCs are in the range of 0.05 V to 0.78 V, which is much lower than the ideal value, depending on the average pore size of the AAO template and the thickness of the YSZ electrolyte. Transmission electron microscopy (TEM) analysis reveals the formation of pinholes in the electrolyte layer that originate from the porous nature of the underlying AAO membrane. In order to clog these pinholes, a 20-nm thick Al2O3 layer is deposited by atomic layer deposition (ALD) on top of the 300-nm thick YSZ layer and another 600-nm thick YSZ layer is deposited after removing the top intermittent Al2O3 layer. Fuel cell devices fabricated in this way manifest OCVs of 1.02 V, and a maximum power density of 350 mW cm−2 at 500 °C.

155 citations


Journal ArticleDOI
TL;DR: In this article, thin titania films on BiFeO3 substrates were grown by pulsed laser deposition to photochemically reduce aqueous silver cations from solution in patterns that mimic the structure of the ferroelectric domains in the substrate.
Abstract: Heterostructures of thin titania films on BiFeO3 substrates were grown by pulsed laser deposition. The heterostructures, when excited by visible light with energies between 2.53 and 2.70 eV, photochemically reduce aqueous silver cations from solution in patterns that mimic the structure of the ferroelectric domains in the substrate. Under the same conditions, titania by itself reduces insignificant amounts of silver. The observations indicate that electrons generated in the substrate are influenced by dipolar fields in the ferroelectric domains and transported through the titania film to reduce silver on the surface.

128 citations


Journal ArticleDOI
TL;DR: An optimal background pressure of oxygen during deposition was found to produce a photoanode structure that both achieves high dye loading and enhanced photoelectrochemical performance.
Abstract: Vertically aligned bundles of Nb2O5 nanocrystals were fabricated by pulsed laser deposition (PLD) and tested as a photoanode material in dye-sensitized solar cells (DSSC). They were characterized using scanning and transmission electron microscopies, optical absorption spectroscopy (UV–vis), and incident-photon-to-current efficiency (IPCE) experiments. The background gas composition and the thickness of the films were varied to determine the influence of those parameters in the photoanode behavior. An optimal background pressure of oxygen during deposition was found to produce a photoanode structure that both achieves high dye loading and enhanced photoelectrochemical performance. For optimal structures, IPCE values up to 40% and APCE values around 90% were obtained with the N3 dye and I3–/I– couple in acetonitrile with open circuit voltage of 0.71 V and 2.41% power conversion efficiency.

121 citations


Journal ArticleDOI
TL;DR: In this article, the effect of deposition time (film thickness) and annealing onto the structural, morphological, compositional and optical properties of CZTS thin films have been investigated.

115 citations


Journal ArticleDOI
TL;DR: In this paper, a single-step fabrication of line patterns using laser-induced chemical vapor deposition (LCVD) was developed using a thin nickel foil in a CH4 and H2 environment.
Abstract: Rapid single-step fabrication of graphene patterns was developed using laser-induced chemical vapor deposition (LCVD). A laser beam irradiates a thin nickel foil in a CH4 and H2 environment to induce a local temperature rise, thereby allowing the direct writing of graphene patterns in precisely controlled positions at room temperature. Line patterns can be achieved with a single scan without pre- or postprocesses. Surprisingly, the growth rate is several thousand times faster than that of general CVD methods. The discovery and development of the LCVD growth process provide a route for the rapid fabrication of graphene patterns for various applications.

115 citations


Journal ArticleDOI
Ling Cao1, Liping Zhu1, Jie Jiang1, Ran Zhao1, Zhizhen Ye1, Buihui Zhao1 
TL;DR: In this article, high transparent and conducting fluorine-doped ZnO (FZO) thin films were deposited on glass substrates by pulsed laser deposition and the structural, electrical, and optical properties of the films were investigated as a function of oxygen pressure ranging from 0.01 to 0.5 Pa.

Journal ArticleDOI
TL;DR: In this article, the existence of spontaneous magnetization in Mn-doped polycrystalline BaTiO3 thin films was shown to be inconsistent with the presence of ferroelectricity.
Abstract: Single-phase perovskite 5 at. % Mn-doped and undoped polycrystalline BaTiO3 thin films have been grown under different oxygen partial pressures by pulsed laser deposition on platinum-coated sapphire substrates. Ferroelectricity is only observed for the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. Compared to undoped BaTiO3, Mn-doped BaTiO3 reveals a low leakage current, increased dielectric loss, and a decreased dielectric constant. Ferromagnetism is seen on Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure and is attributed to the formation of bound magnetic polarons (BMPs). This BMP formation is enhanced by oxygen vacancies. The present work confirms a theoretical work from C. Ederer and N. Spaldin on ferroelectric perovskites [Nature Mat. 3, 849 (2004)] that shows that the existence of ferroelectricity is incompatible with the existence of a spontaneous magnetization in Mn-doped BaTiO3 thin films.

Journal ArticleDOI
TL;DR: In this paper, the existence of spontaneous magnetization in Mn-doped polycrystalline BaTiO3 thin films was shown to be inconsistent with the presence of ferroelectricity.
Abstract: Single-phase perovskite 5 at.% Mn-doped and undoped polycrystalline BaTiO3 thin films have been grown under different oxygen partial pressures by pulsed laser deposition on platinum-coated sapphire substrates. Ferroelectricity is only observed for the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. Compared to undoped BaTiO3, Mn-doped BaTiO3 reveals a low leakage current, increased dielectric loss, and a decreased dielectric constant. Ferromagnetism is seen on Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure and is attributed to the formation of bound magnetic polarons (BMPs). This BMP formation is enhanced by oxygen vacancies. The present work confirms a theoretical work from C. Ederer and N. Spaldin on ferroelectric perovskites [Nature Mat. 3, 849 (2004)] which shows that the existence of ferroelectricity is incompatible with the existence of a spontaneous magnetization in Mn-doped BaTiO3 thin films.

Journal ArticleDOI
TL;DR: In this paper, an overview of the fabrication and properties of high-quality La0.67Sr0.33MnO3 (LSMO) thin films is given.
Abstract: In this paper, an overview of the fabrication and properties of high-quality La0.67Sr0.33MnO3 (LSMO) thin films is given. A high-quality LSMO film combines a smooth surface morphology with a large magnetization and a small residual resistivity, while avoiding precipitates and surface segregation. In the literature, typically only a few of these issues are adressed. We therefore present a thorough characterization of our films, which were grown by pulsed laser deposition. The films were characterized with reflection high energy electron diffraction, atomic force microscopy, x-ray diffraction, magnetization and transport measurements, x-ray photoelectron spectroscopy and scanning transmission electron microscopy. The films have a saturation magnetization of 4.0 µB/Mn, a Curie temperature of 350 K and a residual resistivity of 60 µΩ cm. These results indicate that high-quality films, combining both large magnetization and small residual resistivity, were realized. A comparison between different samples presented in the literature shows that focussing on a single property is insufficient for the optimization of the deposition process. For high-quality films, all properties have to be adressed. For LSMO devices, the thin-film quality is crucial for the device performance. Therefore, this research is important for the application of LSMO in devices.

Journal ArticleDOI
25 Feb 2011-Vacuum
TL;DR: In this paper, a tin-doped cadmium oxide (Sn)-CdO thin film with different Sn concentration was deposited on quartz glass substrates by pulse laser deposition (PLD) at 400°C.

Journal ArticleDOI
TL;DR: In this paper, LaAlO3 epitaxial films with La:Al cation ratios ranging from 09 to 12 were grown on TiO2-terminated SrTiO3 (001) substrates by off-axis pulsed laser deposition.
Abstract: LaAlO3 epitaxial films with La:Al cation ratios ranging from 09 to 12 were grown on TiO2-terminated SrTiO3 (001) substrates by off-axis pulsed laser deposition Although all films are epitaxial, rocking curve and Kiessig fringe oscillation measurements show that the crystallographic quality degrades with increasing La:Al ratio Films with La:Al ratios of 09, 10, and 11 were coherently strained to the substrate However, the out-of-plane lattice parameter increases over this range, revealing a decrease in film tetragonality Although all film surfaces exhibit hydroxylation, the extent of hydroxylation is greater for the La-rich films Rutherford backscattering spectrometry reveals that La from the film diffuses deeply into the SrTiO3 substrate and secondary ion mass spectroscopy shows unambiguous Sr outdiffusion into the films Intermixing, which is generally not investigated in studies of the LaAlO3/SrTiO3 interface, may have important implications for the mechanism of electrical conductivity

Journal ArticleDOI
TL;DR: In this paper, the dependence of the mechanical and optical properties on the film microstructure and chemical composition was investigated by nanoindentation experiments and transmission spectrophotometry.

Journal ArticleDOI
TL;DR: An improved electrode geometry is proposed to study thin ion conducting films by impedance spectroscopy and it is shown that long, thin, and closely spaced electrodes arranged interdigitally allow a separation of grain and grain boundary effects also in very thin films.

Journal ArticleDOI
TL;DR: In this paper, the epitaxial growth of BaTiO"3 films on Si(001) substrate buffered by 5nm-thick SrTiO'3 layer using both MBE and PLD techniques was reported.

Journal ArticleDOI
TL;DR: In this article, temperature-dependent tailoring of acceptor defects in oxygen-rich ZnO thin films, for enhanced p-type conductivity, was reported, which was successfully grown by pulsed laser deposition on silicon substrate at different postdeposition annealing temperatures (500-800 °C).
Abstract: This paper reports the temperature-dependent tailoring of acceptor defects in oxygen rich ZnO thin films, for enhanced p-type conductivity. The oxygen rich p-type ZnO thin films were successfully grown by pulsed laser deposition on silicon substrate at different postdeposition annealing temperatures (500–800 °C). The oxygen rich ZnO powder was synthesized by wet chemical method using zinc acetate dihydrate [Zn(CH3COO)2·2H2O] and potassium hydroxide (KOH) as precursors. The powder was then compressed and sintered to make pellets for pulsed laser deposition system. The x-ray diffraction analysis exhibits an improved crystallinity in thin films annealed at elevated temperatures with a temperature-dependent variation in lattice constants. An analysis of Auger Zn L3M4,5M4,5 peak reveals a consistent decrease in interstitial zinc (Zni) exhibiting its temperature-dependent reversion to zinc lattice sites. Room temperature photoluminescence of the p-type ZnO shows a dominant deep level emission peak at ∼3.12 eV r...

Journal ArticleDOI
TL;DR: In this article, the effects of H2 plasma treatment on structural, electrical, and optical properties of al-doped ZnO (AZO) thin films were investigated on glass substrates by radiofrequency magnetron sputtering at deposition temperatures ranging from room temperature (RT) to 300 °C for transparent electrode applications.
Abstract: article i nfo Al-doped ZnO (AZO) thin films were prepared on glass substrates by radio-frequency magnetron sputtering at deposition temperatures ranging from room temperature (RT) to 300 °C for transparent electrode applications. This study investigates the effects of H2 plasma treatment on structural, electrical, and optical properties of AZO thin films. Plasma treatment was conducted at 300 °C using a plasma-enhanced chemical vapor deposition system for potential large size substrate applications. The crystal structure of plasma treated AZO films did not change considerably, but the surface roughness and surface grain size increased slightly. Improvement in electrical properties was strongly dependent on the deposition temperature. When the depositiontemperaturerangedfrom300 °CtoRT,theresistivityofplasmatreated filmsdecreasedsignificantly by 22.7% to 97.6%, and the optical bandgap broadened by 0.011 to 0.076 eV.

Journal ArticleDOI
TL;DR: In this article, the chemical vapor deposition (CVD) of Cu2ZnSnS4 thin films using diethyldithiocarbamato complexes of copper, zinc and tin was reported.
Abstract: Cu2ZnSnS4 is a potentially important solar cell material. We report for the first time the chemical vapor deposition (CVD) of Cu2ZnSnS4 thin films using diethyldithiocarbamato complexes of copper, zinc and tin.

Journal ArticleDOI
TL;DR: In this paper, the role of temperature on the optical and crystalline properties of polycrystalline zinc oxide (ZnO) thin films by pulsed laser deposition (PLD) on indium tin oxide (ITO) is reported.
Abstract: The growth of polycrystalline zinc oxide (ZnO) thin films by pulsed laser deposition (PLD) on indium tin oxide (ITO) is reported. For the first time the influence of deposition temperature over an extended range (50–650 °C) is investigated on ITO. We describe the role of temperature on the optical and crystalline properties of the deposited films, of 120–250 nm thickness. Additionally, the effect of the background oxygen pressure is reported. Under all of the deposition conditions highly textured c-axis oriented, transparent (>85%) and low roughness (RMS < 10 nm) ZnO films are formed. Growth temperatures ≥450 °C lead to the highest degree of crystallinity and film quality with measured full width half maximum (FWHM) of X-ray diffraction (XRD) peaks as small as 0.14°2θ. XRD measurements of films grown at <350 °C show a shift in the (002) diffraction peak to lower 2θ values, indicating that the deposited films are oxygen deficient. Increasing the oxygen pressure results in the preparation of stoichiometric films at temperatures as low as 50 °C. We demonstrate that in addition to forming high quality ZnO, the optical and electronic properties of ITO can be preserved—even at high temperature—presenting a methodology for preparing highly crystalline ZnO on ITO over a temperature window significantly larger than that of previous literature reports. Furthermore, the low temperature processing opens up the possibility of deposition on a wide range of substrates, especially those unsuitable for exposure to high temperatures.

Journal ArticleDOI
TL;DR: Results on terahertz (THz) spectroscopy on epitaxial vanadium dioxide (VO(2)) films grown on sapphire across the metal-insulator transition demonstrate an 85% reduction in transmission as the thin film completes its phase transition to the conducting phase, which is much greater than the previous observation.
Abstract: We present results on terahertz (THz) spectroscopy on epitaxial vanadium dioxide (VO2) films grown on sapphire across the metal-insulator transition. X-ray diffraction indicates the VO2 film is highly oriented with the crystallographic relationship: (002)film//(0006)sub and [010]film//[21¯1¯0]sub. THz studies measuring the change in transmission as a function of temperature demonstrate an 85% reduction in transmission as the thin film completes its phase transition to the conducting phase, which is much greater than the previous observation on polycrystalline films. This indicates the crucial role of microstructure and phase homogeneity in influencing THz properties.

Journal ArticleDOI
TL;DR: Ferroelectric lead-free thin films were successfully deposited by pulsed laser deposition on PZT substrates using a ceramic BCZT target prepared by conventional solid state reaction.
Abstract: Ferroelectric lead-free thin films of 05(Ba07Ca03TiO3) – 05[Ba(Zr02Ti08)O3] (BCZT) were successfully deposited by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates using a ceramic BCZT target prepared by conventional solid state reaction The in (111) direction orientated 600 nm thick films shows a clamped piezoelectric response of approximately d33,f = 80 pm/V and a dielectric coefficient of about ɛr = 1010; these are close to values obtained for lead zirconate titanate (PZT) films

Journal ArticleDOI
TL;DR: In this article, Hall effect measurements indicate a resistivity of 7.9×10−4 ǫ cm for SZO thin films deposited at 100°C under optimized 1.0-Pa oxygen pressure, in good agreement with optical resistivity simulated from the transmittance spectra.

Journal ArticleDOI
TL;DR: In this article, thermal, optical and structural properties of thin films of Ge 23 Sb 7 S 70 glass were compared with those of the parent bulk glass using micro-Raman spectroscopy.

Journal ArticleDOI
TL;DR: In this paper, the performance of porous La0.6Sr0.4Co0.2Fe0.8O3−−δ (LSCF) cathodes is improved by inserting a dense LSCF layer.

Journal ArticleDOI
TL;DR: In this paper, the structural, optical, and electrical properties of the as-prepared thin films were studied in dependence of substrate temperature and oxygen pressure, and they exhibited high transmittance of 90% and their energy band gap and thickness were in the range 3.26-3.30eV and 256-627nm, respectively.
Abstract: Zinc oxide (ZnO) thin films were deposited on soda lime glass substrates by pulsed laser deposition (PLD) in an oxygen-reactive atmosphere. The structural, optical, and electrical properties of the as-prepared thin films were studied in dependence of substrate temperature and oxygen pressure. High quality polycrystalline ZnO films with hexagonal wurtzite structure were deposited at substrate temperatures of 100 and 300 °C. The RMS roughness of the deposited oxide films was found to be in the range 2–9 nm and was only slightly dependent on substrate temperature and oxygen pressure. Electrical measurements indicated a decrease of film resistivity with the increase of substrate temperature and the decrease of oxygen pressure. The ZnO films exhibited high transmittance of 90% and their energy band gap and thickness were in the range 3.26–3.30 eV and 256–627 nm, respectively.

Journal ArticleDOI
TL;DR: In this paper, a bilayer electrolyte (YSZ ∼330nm) was used for a single cell with NiO-YSZ at 650, 700, and 750°C, respectively.