Reactive Laser Deposition Research Articles

Laser‐Induced Reactive Deposition of Nanostructured CoS2‐ and Co2CuS4‐Based Films with Fenton Catalytic Properties

Highly polymorphic cobalt sulfide represents attractive material because of its unique electronic, optical, magnetic, mechanical and catalytic properties. Pulsed laser irradiation of a solid CoS2 target results in ablation and deposition of thin films on Ta and Cu substrate, which were analyzed using scanning electron microscopy, Raman and FTIR spectroscopy, X‐ray photoelectron spectroscopy, high resolution electron microscopy and electron diffraction. These complementary analyses revealed that the film on Ta consists of the parent cubic CoS2 whereas the film on Cu exhibits a multiphase structure containing the cubic CoS2 and cubic Co2CuS4. The ternary species is known as an active electrode material with relatively high energy density for electrochemical capacitors and proves interdiffusion events at the interface of copper and colliding CoS2 particles. Such facile and one‐step process represents the first example of the Co2CuS4 formation through ablative reactive deposition on unheated substrate and adds to very rare examples of reactive laser deposition of ablated metal sulfides on unheated surfaces. The CoS2‐based films deposited on Ta and the Co2CuS4‐based films deposited on Cu were examined for their catalytic effect in Fenton degradation of methylene blue (MB). Their efficiency to degrade MB is compared and discussed.

Laser initiated Ti3SiC2 powder and coating synthesis

In the work the SHS synthesis of MAX phases from Ti-Si-C system were carried and initiated with use of 30 W laser beam with 40 µm spot. That kind of initiation allows locally and rapidly start the SHS synthesis and avoid the contamination coming from heating wire present during conventional method. The reaction was monitored by high-accuracy radiation pyrometer and high quality optical camera. The recorded data, together with reaction bed thermal conductivity measurements allowed to correlate to obtained powders composition and reaction speed. The reaction bed morphology was investigated by scanning electron microscopy with element distribution (EDS). The second part of the paper concerns laser reactive deposition of SHS in-situ synthetized MAX phases layer on silicon carbide substrate. The paths of deposited layer were formed under argon overpressure of 2 bar using 120 W of laser power.

Pulsed laser deposition of the porous nickel oxide thin film at room temperature for high-rate pseudocapacitive energy storage

This work reports the pulsed laser reactive deposition of the NiO thin film by ablating nickel targets in low-pressure O2 atmosphere at room temperature. The electrode exhibits a porous structure, which facilitates ion transport in the electrode/electrolyte. When applied as an electrode, the porous NiO film exhibits the high specific capacitance (835F g−1 at 1A g−1). Meanwhile, the film exhibits a superb rate capability. At a very high current density of 40A g−1 there is more than 59% retention in the capacitance relative to 1A g−1. Furthermore, the excellent cycling performance (94% capacitance retention after 1000 cycles) is achieved for the film electrode. These results demonstrate that pulsed laser deposition (PLD) is a very promising technique for making the film electrodes for applications in electrochemical energy storage.

Ferromagnetic Semiconductors and Half-Metal Compounds Obtained by Laser Deposition

Laser deposition method was used for growing ferromagnetic semiconductor and half-metal compound layers. GaMnAs and InMnAs layers were grown by alternating laser ablation of solid targets (semiconductor and Mn) in hydrogen and arsine flow. The layers exhibited ferromagnetic properties (detected by Hall effect measurements) from 10 K to room temperature (for InMnAs). Half-metal compound layers were deposited by the techniques of reactive laser deposition (MnAs, MnP) and alternating laser deposition (MnSb). The half-metal layers exhibit ferromagnetism at temperatures up to 300 K.

Innovative, Laser-Based Process for Development and Manufacturing of Solid Oxide Fuel Cells

A novel, versatile, scalable and economical laser-pyrolysis based process for high performance solid oxide fuel cells (SOFCs), interconnects and seals is described. The Laser Reactive Deposition (LRD ) process converts low cost metal precursors into SOFC layers; thus eliminating the need to undertake powder synthesis, calcining, ball milling, batch formulation, slurry preparation, tape formation, and binder burnout steps required in conventional SOFC cell fabrication. By simplifying the manufacturing process, the LRD route achieves low SOFC stack manufacturing cost at low volumes, simplifies footprint and throughput scale-up, and dramatically compresses materials and components development cycles, thus accelerating commercialization and market growth. Results from initial efforts to synthesize conventional SOFC layers (Ni-8YSZ anode, 8YSZ electrolyte, and Sr-doped LaMnO 3 cathode) by the LRD route from mixtures of the respective metal nitrates are described. The layers fabricated on 8YSZ substrates using the LRD approach are of the desired phase with crystallite sizes in the nanoscale region, even after sintering at high temperatures.

High-Rate Deposition Of Rare-Earth Doped Silicate Nanoparticles For Porous & Dense Optical Films

AbstractA novel deposition process has been developed for manufacturing of high quality rare-earth doped glass films with complex composition. This process, Laser Reactive Deposition (LRDTM), comprises photothermal laser pyrolysis using an aerosol feedstock coupled with deposition of the resulting nanoparticle product onto Si substrates with our without an underlying glass film. This paper describes this novel process as well as the structure, properties and performance of the Erdoped, multicomponent silicate glass films produced to date with this process.

Characterization and preparation of NiO-V2O5 composite film cathodes

NiO-V 2 O 5 composite films have been fabricated by 355 nm pulsed laser reactive deposition using mixed metallic Ni and V targets with different molar ratios. The optimal deposition conditions of NiO-V 2 O 5 composite films are found to be the substrate temperature of 300 °C and 100 mTorr O 2 ambient. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed that the crystallinity of the NiO-V 2 O 5 composite films gradually decreased with increasing the amount of nickel oxide and transformed to amorphous phase as the molar ratio of NiO/V 2 O 5 ( x ) approaches 0.5. The amorphous (NiO) 0.5 V 2 O 5 composite film electrode exhibited a specific capacity of 340 mAh/g at a discharge rate of 2 C upon cycling with no obvious fading up to 500 cycles. XRD and X-ray photo-electron spectroscopy (XPS) measurements of NiO-V 2 O 5 composite film electrodes revealed that there exists two electrochemical processes upon cycling. During the first discharge, the Li ions insertion process is accompanied by the reduction of NiO into metallic Ni. Then, the reversible processes involving Li ions insertion/extraction in V 2 O 5 matrix and oxidation/reduction of Ni and Li 2 O take place upon the subsequent cycling.

Fabrication and Characterization of Silver−V2O5 Composite Thin Films as Lithium-Ion Insertion Materials

Silver−vanadium pentoxide composite films have been fabricated by 355-nm pulsed laser reactive deposition on stainless steel substrates. XRD and SEM analyses showed that the composite films AgxV2O5 (x = 0.1−0.5) deposited at a substrate temperature of 300 °C in the presence of ambient 100 mTorr O2 for 0.5 h were amorphous and became a polycrystalline structure after 2 h of deposition. The valence states of Ag and V for AgxV2O5 composite film were examined by XPS measurement. The amorphous Ag0.5 V2O5 composite film electrode exhibited a specific capacity as high as 396 mA·h/g in the range of 4.0−1.0 V at a 2 C rate and remained at a capacity of 260 mA·h/g at a high rate of 20 C with no obvious fading upon cycling more than 1000 cycles. In addition, the electronic conductivities of AgxV2O5 composite films were 2−3 orders of magnitude higher than that of pure V2O5 film. The dramatically improved rate and cycling performance might be related to the changes in microstructure of the AgxV2O5 composite films.

P-Type conduction in transparent semiconductor ZnO thin films induced by electron cyclotron resonance N2O plasma

p-Type conduction in transparent ZnO films grown by electron cyclotron resonance (ECR) N2O plasma-enhanced pulsed laser reactive deposition has been induced by incorporating active N radical species created in N2O plasma within the ZnO films. N impurity has been shown experimentally to be an effective acceptor for producing shallow ptype dopant in ZnO films, which is consistent with previously published conclusions [1]. The room-temperature resistivity and carrier density of the as-grown p-type ZnO films are in the range 2–5 X cm and 4–6 � 10 18 cm � 3 , respectively. These properties provide the practical basis for potential applications of ZnO films in LEDs. The p-type conduction properties may be improved by further increasing the emitting proportion of active N radical species from a plasma source. 2002 Elsevier Science B.V. All rights reserved.

Epitaxial growth and optoelectronic properties of nitrogen-doped ZnO films on [formula omitted] Al 2O 3 substrate

Epitaxial ZnO films with high crystallinity and smooth surface were fabricated on a (1 1 2 ̄ 0) Al 2O 3 substrate using a technique of electron cyclotron resonance (ECR) N 2O plasma-enhanced pulsed laser reactive deposition. The electric properties were measured by four-probe Van der Pauw method. The results indicate that the doped N created in ECR N 2O plasma strongly influence the electrical properties and the ZnO film shows a trend toward p-type conduction under optimized deposition condition. A sharp band-edge emission at 3.3 eV irradiated using a 325 nm He–Cd laser at 77 K on ZnO films was clearly observed.

Excimer laser reactive deposition of vanadium nitride thin films

We report on the deposition of thin vanadium nitride films by ablating vanadium targets in low-pressure N 2 atmosphere, and on their characterization. The targets were vanadium foils (purity 99.8%). 3 in. Si(1 1 1) wafers were used as substrates. Film characteristics (composition and crystalline structure) were studied as a function of N 2 pressure (0.5–200 Pa), KrF laser fluence (4.5–19 J/cm 2), substrate temperature (20–750 °C) and target-to-substrate distance (30–70 mm). Vanadium nitride is already formed at low N 2 ambient pressures (1 Pa) and laser fluences (6 J/cm 2) on substrates at room temperature. At the N 2 pressures of 1–10 Pa, the prevalent phase is VN. At higher pressures (100 Pa) and at relatively high laser fluences (16–19 J/cm 2), the dominant phase is V 2N. The crystallinity of the films improves by increasing the substrate temperature. Well-crystallized films are obtained on substrates heated at 500 °C.

Electron spectroscopic identification of carbon species on CN x films

Carbon species produced during reactive laser deposition of carbon nitride (CN x ) films were characterized with Auger, X-ray photoelectron and electron energy-loss spectroscopies. The π→π* and σ+π plasmons show that the carbon atoms are in sp 2 configuration, and the absence of losses in the 26–30 eV is indicative of the non-existence of sp 3-hybridized carbon. When the π loss is applied to N 1s or C 1s photoelectrons, the asymmetric tail in the XPS spectra is satisfactorily reproduced. With this analysis, the minor peaks are assigned to the inelastic losses, and the two main peaks to nitrogen, in substitution on sp 2-hybridized carbon rings, developing pyridine and pyrrole-like configurations.

Pulsed laser reactive deposition of p-type ZnO film enhanced by an electron cyclotron resonance source

P-type ZnO films with carrier density 3–6×10 18 cm −3, resistivity 2–5 Ω cm and Hall mobility=0.1–0.4 cm 2 V −1 s −1 have been grown on fused silica and glass substrate by pulsed laser reactive deposition using a pure metal Zn target in N 2O plasma. The N acceptor doping was effectively enhanced using the active N formed by N 2O gas passing through an electron resonance source during the pulsed laser reactive deposition process. P-type conduction was achieved by optimizing the microwave-input power ( E) and deposition pressure ( P N 2O ). These electrical properties are sufficient for some practical applications. We expect this result to facilitate the fabrication of transparent p–n homojunctions suitable for light-emitting diodes.

Tin‐Based Composite Oxide Thin‐Film Electrodes Prepared by Pulsed Laser Deposition

Tin‐based composite oxide (TCO) thin films with a reversible capacity of 460 mAh/g and good stability were fabricated by pulsed laser reactive deposition in an oxygen ambient. X‐ray diffraction and atomic force microscopy show that nanocrystallinne is dispersed in an amorphous oxide matrix. The lithium ion insertion and extraction processes in a nonaqueous electrolyte are examined. Cyclic voltammetry shows an irreversible reduction process in the first cycle. X‐ray photospectroscopy spectra unambiguously revealed a conversion of Sn(IV) to metallic Sn. In situ spectroelectrochemical measurements demonstrate significant transmittance drops with the discharge of the Li/TCO cells. Our results show that the alloying of tin with lithium occurs reversibly following the irreversible reduction of tin oxide in the TCO film, which is consistent with the electrochemical mechanism proposed by Courtney and Dahn. © 1999 The Electrochemical Society. All rights reserved.

The effects of substrate properties on metal coatings from liquid medium by reactive laser deposition

Laser processing of materials in a liquid medium was examined in this study. A gold solution was used to coat gold onto aluminum, silicon, alumina, and diamond substrates using a 500 mW Ar ion laser and a 3.5 W Nd-YAG laser. The Ar ion laser was found suitable for gold reactive laser deposition. It was observed that the substrate electrical conductivity plays a dominant role in the deposition process. Substrates with a higher thermal conductivity required more laser power for deposition. Laser processing in a liquid medium was shown to be effective and could be used to fabricate electrode and interconnects.

Electrochromic Properties of ZnO Thin Films Prepared by Pulsed Laser Deposition

Thin solid films were prepared on indium‐tin oxide coated glass substrates by reactive laser deposition in an oxygen ambient. The nanocrystalline and high quality c‐axis oriented films were characterized by X‐ray diffraction and atomic force microscopy. Cyclic voltammetry and in situ visible spectroelectrochemical measurements revealed that the thin film electrode is stable during cycling with a charge capacity of , and the efficiency of coloration ranges from 16 to in the visible region. Our results show that thin films may be a new and cheap electrode material for electrochromic devices. ©1999 The Electrochemical Society

Slow laser deposition of high quality ErBa2Cu3O7−x thin films

High quality ErBa2Cu3O7−x thin films were grown by reactive laser deposition on yttria-stabilized zirconia substrate. The structural and electrical properties of the samples were investigated by x-ray double-crystal diffractometry, texture analysis and reciprocal space mapping, and resistivity measurements, respectively. The best films were obtained by using high substrate temperature combined with a low fluence and low laser repetition rate. In these conditions the deposition rate results were very low, namely <0.25 Å/s. We found that in this case we can grow films with a very high degree of crystalline perfection. Preliminary results show that this process promotes the fabrication of very thick films (thickness ≳500 nm) which are highly c-axis oriented.

Reactive laser deposition of high quality YBaCuO and ErBaCuO films

RE1Ba2Cu3O7−δ (RE=Er or Y) superconducting films were fabricated by reactive laser deposition, in situ, on YSZ(100), SrTiO3(100) and Si(001), under various conditions. A complete XRD investigation showed that the films grown with high substrate temperatures (Ts740°C) combined with low fluences (1.5J/cm2 < 2 J/cm2) and laser repetition rate (4 Hz) have the best structural characteristics, very good electrical and magnetic properties.

Activated reactive laser deposition of GeO2 films

Amorphous GeO2 optical thin films were grown in an oxygen ambient on heated Si substrates using the technique of pulsed laser deposition. The application of a partially ionized oxygen plasma generated by passing the plume through a ring electrode facilitated stoichiometric film growth in low O2 partial pressures. Emission spectroscopy of the plume revealed an enhancement in the ionic and neutral excited Ge species. The concentration of excited neutral and ionic oxygen atoms also significantly increased when the ring electrode was activated at P(O2)≳10 mTorr. Coupling the results of the film property measurements with the emission studies suggested that the presence of O atoms near the substrate surface during film growth was more critical in promoting oxidation than the gas phase process in the plume. The low-pressure conditions that were utilized to deposit stoichiometric film growth identified the appropriate conditions to produce uniform films over a large area that may be suitable for waveguide fabrication.