Pulsed Laser Deposition Setup Research Articles

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Development of UHV pulsed laser deposition set-up for in-situ photoelectron spectroscopic study at ARPES beamline, Indus-1 synchrotron radiation source, India

We have developed an Ultra-High Vacuum (UHV) compatible Pulsed Laser Deposition (PLD) set-up at Angle Resolved Photo Electron Spectroscopy (ARPES) beamline (BL-3) at Indus-1 synchrotron radiation source, Raja Ramanna Centre for Advanced Technology, Indore, India. The set-up is successfully tested and integrated at beamline for in-situ photoelectron spectroscopic (PES) studies of thin films. In present PLD set-up, quick in-situ transfer of deposited thin films to analysis chamber enables the surface sensitive PES measurements on atomically cleaned surfaces without the requirement of any sputtering. This set-up has the capability of thin film depositions using six number of one-inch targets with precise control of various deposition parameters at a base pressure of ∼1x10−9 mbar. To explore the capability of the system, a set of thin films of HfO2, 5 % Ga2O3 doped ZnO (GZO) and GZO/HfO2 are deposited and the band offset of GZO/HfO2 heterostructure is investigated by in-situ PES measurements using synchrotron radiation. The film surface is found to be contamination free, which demonstrates the capability of the set-up for in-situ PES studies. The Hf 4f and Zn 3d core level peaks along with valence band maxima positions are used to determine the valence band offset. The valence band offset is found to be 0.31 ± 0.08 eV, which is the first result reported on this heterostructure system.

Structure and morphology of Pt3Sc alloy thin film prepared by pulsed laser deposition

Pulsed laser deposition (PLD) was used to prepare substitutionaly disordered Pt3Sc. Deposition was performed by using a crossed-beam PLD setup and the laser intensity on the Pt and Sc targets was adjusted to reach the desired composition (Pt:Sc 3:1). Deposition was performed in vacuum, 133Pa He and 133Pa Ar, on both Cu and Si substrates. It was shown that a homogeneous and substitutionaly disordered Pt3Sc alloy is formed when deposition is performed in vacuum and 133Pa Ar on a Cu substrate. Alternatively, a non-homogeneous and multilayered deposit is formed when deposition is performed in vacuum on a Si substrate. This is believed to arise as a consequence of re-sputtering (and decomposition) of the native silicon oxide when highly energetic ablated species impinge on the substrate. The kinetic energy of the ablated species is reduced by increasing the pressure of Ar in the deposition chamber, yielding to an increased stability of the native silicon oxide layer and the formation of a porous deposit made of substitutionaly disordered Pt3Sc. The same phenomenon is observed when deposition is performed on a Ti substrate.

Pulsed laser deposition using diffractively shaped excimer-laser beams

Controlling laser-pulse parameters is an important issue in pulsed laser deposition (PLD). In particular, homogenization of laser beams improves the reproducibility of the PLD process by guaranteeing a uniform intensity distribution and a well-defined energy density of the laser spot on the target. We have integrated a beam-homogenization system into our PLD setup, and here we discuss the results and advantages of using such a system. The optical setup is based on diffractive beam-splitter gratings, which produce a 2×2-mm2 flat-top distribution with fluences of the order of 3 J/cm2 on the target. We demonstrate the applicability of this technique by depositing thin films of ferromagnetic Ni–Mn–Ga shape-memory alloys. Magnetic and structural characterization, including secondary ion mass spectrometry (SIMS), indicate that nearly stoichiometric composition and crystallization in the desired martensitic phase is obtained for films deposited on Al2O3 under optimal conditions. In contrast, the formation of silicide compounds at temperatures above 500 ∘C is detrimental in the deposition of Ni–Mn–Ga films directly on silicon.

Correlation between electrical and ellipsometric properties on high-quality epitaxial thin films of the conductive oxide LaNiO3 on STO (001)

Direct current (dc) electrical transport properties (resistivity and Hall) and spectroscopic ellipsometric measurements have been combined to study high-quality epitaxial thin films of LaNiO3 (LNO) on SrTiO3 (001) substrates. Stoichiometry of LaNiO3 films was changed by varying the oxygen partial pressure between 240 and 420 μbar during the growth in a pulsed laser deposition setup. Structural and temperature-dependent transport properties conform to epitaxial LaNiO3. The ellipsometric data, measured in the 350–850 nm spectral range, are adjusted with a dispersion relation of Drude-Lorentz (DL) type. In addition to the Drude term, only one Lorentz oscillator was used in the modeling for consistency with existing density of states calculations. Increasing oxygen pressure does not induce significant variations of the electronic density, the Hall mobility, or the Drude plasma energy. Neither are the pseudo-cubic lattice parameter and the Lorentz oscillator resonance energy significantly modified. Resistivity from dc transport and “optical” resistivity from the DL dispersion relation are found to be in good agreement in the case of epitaxial LNO films, giving an elegant way to control the electrical properties of the LaNiO3 conductive oxide thin films in situ by the spectroscopic ellipsometry technique during growth.

Thin films of Co–B prepared by pulsed laser deposition as efficient catalysts in hydrogen producing reactions

Abstract Hydrogen generation by catalytic hydrolysis of sodium borohydride (NaBH 4 ) is studied by using Co–B-based thin film catalyst synthesized by pulsed laser deposition (PLD) technique. Co–B nanoparticles, produced in the catalyst film after the laser ablation process, act as active centers producing significantly higher H 2 generation rate than Co–B bulk powder. Surface morphology was studied by using scanning electron microscopy and compositional analysis was established by using X-photoelectron and infrared spectroscopies. Films were deposited at different PLD set-up parameters in order to understand the possible role of size and density of the nanoparticles in the catalytic process. Cobalt has been found here to act as an efficient catalyst only when alloyed with boron which partially prevents cobalt oxidation. In particular we report that when used as suitable thin films, Co–B produces H 2 with a maximum generation rate of about 3300 ml/min per gram of catalyst.

Crystal structure and microwave resistance of YBa2Cu3O7−δ films prepared by cross-beam pulsed-laser deposition

High-Tc superconducting YBa2Cu3O7−δ (YBCO) films were prepared by a unique pulsed-laser deposition using crossed-laser-beam technique onto LaAlO3 substrates in order to develop a basic technology for microwave-device application. The pulsed-laser deposition set-up uses two Nd–YAG lasers with 1064 nm wavelength and 0.3 J/pulse power. The unique feature of this method is a possibility to get a plasma plume with a low level of ‘droplet’, which essentially improves the film-surface quality. Transmission-electron microscopy and x-ray data show that YBCO films deposited at substrate temperature (Ts) of 780 °C exhibit a minimal density of dislocations in the crystal. YBCO films deposited at Ts = 780 °C with a cooling rate of V = 3 K min−1 have the smallest surface resistance below the transition temperature.

Pulsed laser deposition and characterization of perovskite thin films on various substrates

Pulsed laser deposition (PLD) is a unique tool to grow high quality thin films of complex composition. In recent years it was demonstrated by several groups that PLD is capable of depositing material over application relevant substrate sizes with good uniformity. In this contribution YBCO thin films and buffer layers were deposited by a special PLD setup on substrates as large as 7cm×20cm. For this purpose the UV laser light is focussed to an 8cm line on cylindrical targets while the substrate is scanned perpendicular to the line focus. Different kinds of substrates (SrTiO3, MgO, LaAlO3 and Sapphire) were coated with YBCO. Two important points of the presented PLD-setup will be discussed in detail: the way of substrate heating and the variation of the angle between the incident laser beam and the target surface (‘wobbling’). The structural and electrical properties of the deposited YBCO thin films were investigated by X-ray diffraction (XRD) and inductive measurements of the critical current density jc. Furthermore, PLD was used to deposit ferroelectric (Pb,La)(Zr,Ti)O3 (PLZT) thin films on high-grade steel Hastelloy. This polycrystalline alloy is suitable as substrate and electrode material as well. The deposited films were characterized with respect to their structural, topological and ferroelectric properties.