Showing papers on "Pulsed laser deposition published in 2009"
TL;DR: In this article, photoelectrochemical cells based on traditional and nanostructured ZnO thin films are investigated for hydrogen generation from water splitting using three different deposition geometries: normal pulsed laser, oblique-angle and electron-beam glancing-angle deposition.
Abstract: Photoelectrochemical cells based on traditional and nanostructured ZnO thin films are investigated for hydrogen generation from water splitting. The ZnO thin films are fabricated using three different deposition geometries: normal pulsed laser deposition, pulsed laser oblique-angle deposition, and electron-beam glancing-angle deposition. The nanostructured films are characterized by scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and photoelectrochemical techniques. Normal pulsed laser deposition produces dense thin films with ca. 200 nm grain sizes, while oblique-angle deposition produces nanoplatelets with a fishscale morphology and individual features measuring ca. 900 by 450 nm on average. In contrast, glancing-angle deposition generates a highly porous, interconnected network of spherical nanoparticles of 15–40 nm diameter. Mott-Schottky plots show the flat band potential of pulsed laser deposition, oblique-angle deposition, and glancing-angle deposition samples to be −0.29, −0.28 and +0.20 V, respectively. Generation of photocurrent is observed at anodic potentials and no limiting photocurrents were observed with applied potentials up to 1.3 V for all photoelectrochemical cells. The effective photon-to-hydrogen efficiency is found to be 0.1%, 0.2% and 0.6% for pulsed laser deposition, oblique-angle deposition and glancing-angle deposition samples, respectively. The photoelectrochemical properties of the three types of films are understood to be a function of porosity, crystal defect concentration, charge transport properties and space charge layer characteristics.
421 citations
TL;DR: In this article, the physical processes of pulsed laser deposition (PLD) change strongly from the initial light absorption in a target to the final deposition and growth of a film, and the importance of these processes during the entire PLD process is discussed.
223 citations
TL;DR: In this paper, the influence of substrate temperature and oxygen pressure on the structural properties of copper oxide films were discussed and X-ray diffraction results showed that the structure of the films changes from Cu2O to CuO phase with the increasing of the oxygen pressure.
221 citations
TL;DR: A Nb-doped TiO2 (NTO) thin film was deposited on a fluorinedoped tin oxide (FTO) electrode by pulsed laser deposition (PLD) and its application as a new compact layer material for dye-sensitized s...
Abstract: A Nb-doped TiO2 (NTO) thin film was deposited on a fluorine-doped tin oxide (FTO) electrode by pulsed laser deposition (PLD) and its application as a new compact layer material for dye-sensitized s...
208 citations
TL;DR: In this paper, the leakage current behavior in those ion-doped BFO films indicated the dominance of space-charge-limited current in the high electric field region, and well saturated P-E hysteresis curves were observed.
Abstract: Polycrystalline BiFeO3 (BFO), Ti-doped BFO, Mn-doped BFO, and (Mn, Ti)-codoped BFO (BFMT) thin films were fabricated on Pt/SrTiO3 (100) substrate by pulsed laser deposition. Observed leakage current behavior in those ion-doped BFO films indicated the dominance of space-charge-limited current in the high electric field region. The leakage current of the BFMT film was much reduced in relation to the other films due to the formation of deep traps. In the BFMT film, well saturated P-E hysteresis curves were observed. Remanent polarization and coercive field for maximum electric field of 2100 kV/cm were 75 μC/cm2 and 310 kV/cm, respectively.
208 citations
TL;DR: In this article, the structural, electrical, and optical properties of transparent conductive al-doped zinc oxide (AZO) thin films were investigated by X-ray diffraction, Hall measurement and optical transmission spectroscopy, and the results made the possibility for light emitting diodes and solar cells with AZO films as transparent electrodes, especially using lift-off process to achieve the transparent electrode pattern transfer.
202 citations
TL;DR: The observed presence of an in-plane polarization component in nominally (001) oriented PZT suggests the existence of a significant deviation from the regular tetragonal structure that allows the formation of complex core-polarization states.
Abstract: Two-dimensional arrays of ferroelectric lead zirconate titanate (PZT) nanodots were fabricated using pulsed laser deposition through ultrathin anodic aluminum oxide membrane stencil masks. The static distribution of polarization configurations was investigated using in- and out-of-plane piezoresponse force microscopy (PFM). The observed presence of an in-plane polarization component in nominally (001) oriented PZT suggests the existence of a significant deviation from the regular tetragonal structure that allows the formation of complex core-polarization states. Core-polarization states may indicate the presence of quasi-toroidal polarization ordering. The experimental results are compared with a theoretical model to determine the fingerprint of a vortex polarization state in PFM.
185 citations
TL;DR: In this article, Nanocrystalline MnO thin film has been prepared by a pulsed laser deposition (PLD) method and the reversible lithium storage capacity at 0.125C is over 472 mAh g(-1) (3484 mAh cm(-3)).
173 citations
TL;DR: In this paper, the performance of anhydrous proton conducting yttria-doped barium zirconate (BYZ) membranes was investigated in a fuel cell.
Abstract: Structural and microstructural properties as well as the fuel cell performance of anhydrous proton conducting yttria-doped barium zirconate (BYZ) membranes were investigated. The membranes were nominally about 100 nm thick and were fabricated by both atomic layer deposition (ALD) and pulsed laser deposition (PLD) techniques on micromachined Si substrates. Electrochemical cells (H2, Pt/BYZ/Pt, air) were fabricated using porous platinum electrodes deposited by sputtering. The cells were tested in the temperature regime 200−450 °C. Power densities of 136 mW/cm2 at 400 °C employing a BYZ membrane fabricated by ALD and 120 mW/cm2 at 450 °C employing a BYZ fabricated by PLD clearly represent the highest reported values in the literature at these temperatures. The difference in the cell performances for the ALD BYZ versus PLD BYZ membranes is attributed to differences in their surface morphology and interfacial microstructure.
145 citations
TL;DR: In this article, the authors show that the decrease of the film crystallinity, occurring when the deposition temperature is lowered, is accompanied by a strong increase of the electrochemical oxygen exchange rate of thin-film electrodes.
Abstract: La0.6Sr0.4CoO3–δ (LSC) thin-film electrodes are prepared on yttria-stabilized zirconia (YSZ) substrates by pulsed laser deposition at different deposition temperatures. The decrease of the film crystallinity, occurring when the deposition temperature is lowered, is accompanied by a strong increase of the electrochemical oxygen exchange rate of LSC. For more or less X-ray diffraction (XRD)-amorphous electrodes deposited between ca. 340 and 510 °C polarization resistances as low as 0.1 Ω cm2 can be obtained at 600 °C. Such films also exhibit the best stability of the polarization resistance while electrodes deposited at higher temperatures show a strong and fast degradation of the electrochemical kinetics (thermal deactivation). Possible reasons for this behavior and consequences with respect to the preparation of high-performance solid oxide fuel cell (SOFC) cathodes are discussed.
139 citations
TL;DR: In this paper, superconducting thin films have been grown epitaxially without buffer layers on single crystal substrates by pulsed laser deposition and the onset Tc of the films is observed to increase from 16.2 K to 24.5 K with increasing c/a, mainly due to a slight distortion of the AsFe4 tetrahedron.
Abstract: Ba(Fe1-xCox)2As2 superconducting thin films have been grown on SrTiO3, (La,Sr)(Al,Ta)O3, LaAlO3 and YAlO3 (YAO) single crystal substrates by pulsed laser deposition. All the films, except on YAO, have been grown epitaxially without buffer layers. The films deposited on YAO contained 45 degree in-plane rotated grains and showed a broad superconducting transition. The onset Tc of the films is observed to increase from 16.2 K to 24.5 K with increasing c/a, mainly due to a slight distortion of the AsFe4 tetrahedron. From this correlation, we expect that higher superconducting transition temperatures than 24.5 K in a strained epitaxial film may be possible.
TL;DR: In this article, a template-free process for the synthesis of nanocrystalline TiO2 hierarchical microstructures by reactive pulsed laser deposition (PLD) is presented, where a proper choice of deposition parameters is demonstrated, going from classical compact/columnar films to a dense forest of distinct hierarchical assemblies of ultrafine nanoparticles (<10nm), up to a more disordered, aerogel-type structure.
Abstract: A template-free process for the synthesis of nanocrystalline TiO2 hierarchical microstructures by reactive pulsed laser deposition (PLD) is here presented. By a proper choice of deposition parameters a fine control over the morphology of TiO2 microstructures is demonstrated, going from classical compact/columnar films to a dense forest of distinct hierarchical assemblies of ultrafine nanoparticles (<10 nm), up to a more disordered, aerogel-type structure. Correspondingly, the film density varies with respect to bulk TiO2 anatase, with a degree of porosity going from 48% to over 90%. These structures are stable with respect to heat treatment at 400 °C, which results in crystalline ordering but not in morphological changes down to the nanoscale. Both as deposited and annealed films exhibit very promising photocatalytic properties, even superior to standard Degussa-P25 powder, as demonstrated by the degradation of stearic acid as a model molecule. The observed kinetics are correlated to the peculiar morphology of the PLD grown material. We show that the 3D multiscale hierarchical morphology enhances reaction kinetics and creates an ideal environment for mass transport and photon absorption, maximizing the surface area-to-volume ratio while at the same time providing readily accessible porosity through the large inter-tree spaces that act as distributing channels. The reported strategy provides a versatile technique to fabricate high aspect ratio 3D titania microstructures through a hierarchical assembly of ultrafine nanoparticles. Beyond photocatalytic and catalytic applications, this kind of material could be of interest for those applications where high surface-to-volume and efficient mass transport are required at the same time.
Journal Article•
TL;DR: In this article, superconducting thin films have been grown epitaxially without buffer layers on single crystal substrates by pulsed laser deposition and the onset Tc of the films is observed to increase from 16.2 to 24.5 K with increasing c/a, mainly due to a slight distortion of the AsFe4 tetrahedron.
Abstract: Ba(Fe1−xCox)2As2 superconducting thin films have been grown on SrTiO3, (La,Sr)(Al,Ta)O3, LaAlO3, and YAlO3 (YAO) single crystal substrates by pulsed laser deposition. All the films, except on YAO, have been grown epitaxially without buffer layers. The films deposited on YAO contained 45° in-plane rotated grains and showed a broad superconducting transition. The onset Tc of the films is observed to increase from 16.2 to 24.5 K with increasing c/a, mainly due to a slight distortion of the AsFe4 tetrahedron. From this correlation, we expect that higher superconducting transition temperatures than 24.5 K in a strained epitaxial film may be possible.
TL;DR: In this article, the electrocaloric effect of PMN-PT relaxor relaxor ferroelectric thin film near morphotropic phase boundary composition has been calculated for a thin film of thickness, ∼240 nm, using pulsed laser deposition technique on a highly oriented platinized silicon substrate at 700°C and at 100 mtorr oxygen partial pressure.
Abstract: The electrocaloric effect is calculated for PMN-PT relaxor ferroelectric thin film near morphotropic phase boundary composition. Thin film of thickness, ∼240 nm, has been deposited using pulsed laser deposition technique on a highly (111) oriented platinized silicon substrate at 700°C and at 100 mtorr oxygen partial pressure. Prior to the deposition of PMN-PT, a template layer of LSCO of thickness, ∼60 nm, is deposited on the platinized silicon substrate to hinder the pyrochlore phase formation. The temperature dependent P-E loops were measured at 200 Hz triangular wave operating at the virtual ground mode. Maximum reversible adiabatic temperature change, ΔT = 31 K, was calculated at 140°C for an external applied voltage of 18 V.
TL;DR: This study reveals that the combination of pulsed laser deposition and post-deposition annealing at 300 degrees C have the potential to produce pure, adherent, crystalline HA coatings, which show no dissolution in a simulated body fluid.
TL;DR: In this article, the authors reported that a liquid droplet on these surfaces can be rapidly and reversibly switched between hydrophobicity and superhydrophilicity by alternating UV illumination and dark storage or thermal heating.
Abstract: Control over the wettability of solids as well as the manufacturing of functional surfaces with special wetting properties has aroused much interest because of great advantages given to various applications in daily life, industry, and agriculture. We report here the dynamic optical control of the wetting behavior of liquids on hierarchically structured ZnO surfaces produced by irradiating silicon (Si) wafers with femtosecond laser pulses and subsequently coating them with ZnO by pulsed laser deposition. The final surface exhibits roughness at two length scales, comprising micrometer-sized Si spikes decorated with ZnO nanoprotrusions. It is shown that a liquid droplet on these surfaces can be rapidly and reversibly switched between hydrophobicity and superhydrophilicity by alternating UV illumination and dark storage or thermal heating. By studying the magnitude and the rate of the photoinduced transitions, we investigated the contribution of roughness at different scales in the framework of two theoretic...
TL;DR: In this paper, the oxygen isotope profile is analyzed by secondary ion mass spectrometry to extract tracer diffusion coefficients D∗ and effective surface exchange constants k∗ for high temperature oxygen permeation membranes and solid oxide fuel cell cathodes.
Abstract: Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is an interesting material for high temperature oxygen permeation membranes and solid oxide fuel cell cathodes, applications for which oxygen transport properties are crucial. Here oxygen isotope exchange is performed on dense BSCF films prepared by pulsed laser deposition on MgO single crystal substrates. The oxygen isotope profile is analyzed by secondary ion mass spectrometry to extract tracer diffusion coefficients D∗ and effective surface exchange constants k∗. Tracer diffusion has a low activation energy of 0.5 eV. At moderate temperatures, the related oxygen vacancy diffusion coefficient DVO is significantly larger than that for (La,Sr)(Fe,Co)O3−δ perovskites.
TL;DR: The observed results show promising application of the nanoporous CeO(2) thin film for glucose sensing application without any surface functionalization or mediator.
TL;DR: In this article, Nanocrystalline indium oxide (INO) films are characterized using GIXRD, XPS, AFM and UV-visible spectroscopy to study the effect of substrate temperature on the structural and optical properties of films.
TL;DR: In this paper, magnetoresistive and structural measurements of superconducting FeSe0.5Te 0.5 epitaxial thin films grown by pulsed laser deposition are reported.
Abstract: We report magnetoresistive and structural measurements of superconducting FeSe0.5Te0.5 epitaxial thin films grown by pulsed laser deposition. Enhanced onset superconducting transition temperature (∼17 K) is observed in some of these films. Structural analysis by x-ray diffraction and high resolution transmission electron microscopy reveal that these films generally have significantly shorter out-of-plane lattice constant c than the bulk value, suggesting that the out-of-plane changes have a dominating impact on the superconducting transition in iron-based superconductors. Our data also indicate that the upper critical field Hc2(0) of those films may reach as high as 50 T.
TL;DR: In this article, the junction parameters such as ideality factor, barrier height, and series resistance are determined using conventional forward bias I-V characteristics, the Cheung method, and Norde's function.
Abstract: Transparent and conducting ZnO and NiO films were used for fabrication of p–n junction by pulsed laser deposition. These films were characterized by X-ray diffraction (XRD), atomic force microscopy, UV–visible spectroscopy, and electrical techniques. XRD shows that ZnO films are highly orientated along the (0 0 2) direction, while NiO films have preferred orientation along the (1 1 1) direction. These films are very smooth with surface roughness of ∼1.2 nm. The optical transmittances of ZnO and NiO films are 87% and 64%, respectively. I–V characteristics of the ZnO–NiO junction show rectification. The junction parameters such as ideality factor, barrier height, and series resistance are determined using conventional forward bias I–V characteristics, the Cheung method, and Norde's function. There is a good agreement between the diode parameters obtained from these methods. The ideality factor of ∼4.1 and barrier height of ∼0.33 eV are estimated using current–voltage characteristics.
TL;DR: In this paper, the growth of Zn 1− x Mg x O (ZMO) thin films on quartz substrate using pulsed laser deposition (PLD) technique is reported.
TL;DR: In this article, the sequential pulsed laser deposition technique was used to grow highly transparent and c-axis oriented thin films of Si doped ZnO on sapphire substrates.
Abstract: The sequential pulsed laser deposition technique was used to grow highly transparent and c-axis oriented thin films of Si doped ZnO on sapphire substrates. On doping with Si, the resistivity of the virgin ZnO thin films was found to decrease from ~3.0 ? 10?2 to 6.2 ? 10?4???cm and its bandgap increased from about 3.28 to 3.44?eV at different doping concentrations. XPES measurements revealed that Si predominantly occupies the Zn lattice sites in the Si+3 state. The increase in the bandgap of the ZnO films with increasing Si concentration was found to be due to the collective effects of high carrier concentration induced Burstein?Moss blue shift and bandgap narrowing. Efficient photoluminescence (PL) was observed at room temperature from these Si doped ZnO films. The bandgaps obtained from the PL measurements were found to be Stokes shifted as compared with those obtained from the transmission spectra. Si doping of ZnO offers the possibility of developing superior transparent conducting electrodes for applications such as in display panels, solar cells and transparent resistive non-volatile memories.
TL;DR: In this paper, the growth kinetics study of structures of nano-diamonds embedded in sp2 carbon synthetized by this method is discussed, and the presence of nanodiamonds has been confirmed by Raman spectroscopy as well as TEM analysis.
TL;DR: In this paper, the physical properties of single phase AgO thin films with varying oxygen pressure during growth were reported, and the x-ray diffraction (XRD) analysis showed that all the films were polycrystalline.
Abstract: Silver oxide thin films have potential applications in ultra-high density optical non-volatile memories and in fluorescence imaging. In this paper, the physical properties of silver oxide thin films prepared at room temperature by the pulsed laser deposition (PLD) technique with varying oxygen pressure during growth are reported. The oxygen pressure in the growth chamber is varied between 9 and 50 Pa. The x-ray diffraction (XRD) analysis showed that all the films were polycrystalline. With increasing oxygen pressure in the growth chamber, it is observed that (i) the hexagonal Ag2O transforms to monoclinic AgO, (ii) the grain size in the film increases from 59 to 200 nm, (iii) the surface roughness of the film increases from 9 to 42 nm, (iv) the resistivity of the films increases from 1 to 4 × 104 Ω m, (v) the surface work function of the films increases from 5.47 to 5.61 eV and (vi) the optical band gap of AgO thin films decreases from 1.01 to 0.93 eV. Raman spectroscopy on AgO thin films shows low wave number peaks corresponding to the stretching vibration of Ag–O bonds. This study shows that single phase AgO thin films, a requirement for plasmonic devices, can be prepared at room temperature by the PLD technique with an oxygen pressure of 20 Pa.
TL;DR: In this paper, a defect-dipole complex model is proposed to explain the difference in the electrical properties and domain structures for multiferroic thin films grown under different oxygen partial pressures.
Abstract: The growth window of multiferroic ${\text{BiFeO}}_{3}$ thin films is very small. Both temperature and oxygen pressure will affect the film quality and phase purity significantly. We demonstrate here that even within the window where phase pure ${\text{BiFeO}}_{3}$ thin films can be obtained, different oxygen partial pressures still lead to substantial variation in Bi/Fe ratio in the film, which closely link with the corresponding ferroelectric properties. Piezoelectric force microscopy also reveals significant difference in the domain structures of these films. A defect-dipole complex model is proposed to explain the difference in the electrical properties and domain structures for films grown under different oxygen pressures.
TL;DR: In this paper, the authors employed the Tauc-Lorentz and Cody-Lorenz models for the evaluation of optical functions of thin films in as-deposited (amorphous) and crystalline (cubic) phases.
Abstract: Pulsed laser (532 nm) deposited Ge2Sb2Te5 thin films were investigated by means of spectroscopic ellipsometry and Raman scattering spectroscopy. Tauc–Lorentz and Cody–Lorentz models were employed for the evaluation of optical functions of thin films in as-deposited (amorphous) and crystalline (cubic) phases. The models’ parameters (Lorentz oscillator amplitude, resonance energy, oscillator width, optical band gap, and Urbach energy) calculated for amorphous and crystalline states are discussed. The vibrational modes observed in Raman spectra of amorphous layers are attributed to GeTe4−nGen (n=1, 2, eventually 0) tetrahedra connected by corners (partly by edges) and SbTe3 units. The Raman spectra of crystalline thin films suggest that the local bonding arrangement around Ge atoms changes; GeTe component is thus mainly responsible for the phase transition in Ge2Sb2Te5 alloys.
TL;DR: In this article, a study of the thermoelectric transport properties of Bi-Te thin films with different structures and morphologies is presented, showing the potential of PLD to produce n-type bi-te thin films for peculiar applications.
Abstract: A study of the thermoelectric transport properties of Bi–Te thin films with different structures and morphologies is here presented. Films were grown by pulsed laser deposition (PLD), which permits to control the composition, phase and crystallinity of the deposited material, and the morphology at the micrometer/nanometer scale. The carrier density and mobility at room temperature and the in plane electrical resistivity and Seebeck coefficient in the temperature range 300–400 K have been measured both for films characterized by a compact morphology and by the presence of different phases (Bi2Te3, BiTe, and Bi4Te3) and for Bi2Te3 films with different morphologies at the micrometer/nanometer scale (from a compact structure to a less connected assembly of randomly oriented crystalline grains). The correlation among thermoelectric and structural properties has been investigated, showing the potential of PLD to produce n-type Bi–Te thin films with desired properties for peculiar applications. Films with a layered Bi2Te3 structure show the best properties, with Seebeck coefficient in the range from −175 to −250 μV/K and power factor in the range 20–45 μW/cm K2, with expected ZT values greater than 1.5. Also films composed by partially randomly oriented submicrometer crystals look promising, since the smaller power factor (∼10 μW/cm K2) can in principle be compensated by a strong reduction of the phonon thermal conductivity via proper engineering of grain boundaries.