Laser Ablation Deposition Technique Research Articles

Electrochemical behaviour and analytical applications of a manganese porphyrin – silica hybrid film prepared by pulsed laser deposition

Hybrid nanomaterials can have superior properties in comparison with individual components, sometimes greatly improving their optoelectronic activity. For this reason, modified carbon electrodes were obtained using a hybrid material composed of 5,10,15,20-tetra(4-tolyl)porphyrinato manganese (III) chloride (MnTTP) embedded in a silica matrix. The laser ablation deposition technique (PLD) has been used to immobilize the manganese porphyrin–silica hybrid on the surface of the carbon electrodes. The successful transfer of the manganese-porphyrin was evidenced by UV–Vis absorption spectroscopy. The PLD-deposited hybrid film was characterized using AFM and electrochemical methods (cyclic voltammetry and square wave voltammetry). The viability of this hybrid nanomaterial film as a redox mediator for the anodic oxidation and sensitive voltammetric determination of ascorbic acid in buffer solution (pH = 6.5) is described. The recorded anodic process is attributed to its oxidation to dehydroascorbic acid, with satisfactory catalytic current response and low non-Faradaic current.

Synthesis and Deposition of Ag Nanoparticles by Combining Laser Ablation and Electrophoretic Deposition Techniques

Silver nanostructured thin films have been fabricated on silicon substrate by combining simultaneously pulsed laser ablation in liquid (PLAL) and electrophoretic deposition (ED) techniques. The composition, topography, crystalline structure, surface topography, and optical properties of the obtained films have been studied by energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-visible spectrophotometry. The coatings were composed of Ag nanoparticles ranging from a few to hundred nm. The films exhibited homogenous morphology, uniform appearance, and a clear localized surface plasmon resonance (LSPR) around 400 nm.

Utilizing alternate target deposition to increase the magnetoelectric effect at room temperature in a single phase M-type hexaferrite

Abstract

Deposition of Magnetoelectric Ferrite Thin Films Using Multiple Targets Technique

The magnetoelectric (ME) effect has been detected in cobalt-doped M-type hexaferrite bulk. We have demonstrated that the hexaferrite films of the M-type exhibiting the ME effect can be deposited from single targets as well as multiple targets as in the alternating target laser ablation deposition technique. The corresponding ME coupling is sufficiently high at room temperature to allow for potential device applications $\alpha =5.2\times 10^{-9}$ m/s. The saturation magnetization value ( $4\pi M_{s})$ of the film was measured to be 2000 G, consistent with a vibrating sample magnetometer and the ferromagnetic resonance measurement.

Overview and development of metallic photocathodes prepared by laser ablation

The development of photocathodes materials has become an important task for X-ray free electron laser and new generation of particle accelerator. The choice of the op- timum cathode type and its further improvement is a funda- mental issue for the progress in radio-frequency photoinjec- tors. Metallic photocathodes offer several advantages over the semiconductor ones, e.g. long lifetime and prompt re- sponse time on the photoemission. This paper reviews the requirements and the current status of metallic photocath- odes prepared by pulsed laser ablation deposition technique. Magnesium, yttrium and lead are proposed as good alterna- tive to copper photocathode which is generally used in radio- frequency photoinjectors. Parametric studies of the irradia- tion conditions are demanded to optimize the metallic thin film deposition. The main achievements on the morphology and structure characterization as well as photoemission test- ing of metallic photocathodes are presented and discussed.

SnO2/Pt Thin Film Laser Ablated Gas Sensor Array

A gas sensor array was developed in a 10 × 10 mm2 space using Screen Printing and Pulse Laser Ablation Deposition (PLAD) techniques. Heater, electrode, and an insulator interlayer were printed using the screen printing method on an alumina substrate, while tin oxide and platinum films, as sensing and catalyst layers, were deposited on the electrode at room temperature using the PLAD method, respectively. To ablate SnO2 and Pt targets, depositions were achieved by using a 1,064 nm Nd-YAG laser, with a power of 0.7 J/s, at different deposition times of 2, 5 and 10 min, in an atmosphere containing 0.04 mbar (4 kPa) of O2. A range of spectroscopic diffraction and real space imaging techniques, SEM, EDX, XRD, and AFM were used in order to characterize the surface morphology, structure, and composition of the films. Measurement on the array shows sensitivity to some solvent and wood smoke can be achieved with short response and recovery times.

Metallic photocathodes prepared by pulsed laser ablation deposition for application to bright electron sources

AbstractWe present the results of our investigation on metallic films as suitable photocathodes for the production of intense electron beams in radio frequency (RF) photoinjector guns. Pulsed laser ablation deposition (PLAD) technique was used for growing Mg and Y thin films onto Si and Cu substrates in high vacuum of 10−5 Pa and at room temperature. The morphology, the structure, the thickness and the contamination level of thin films surface deposited on Si were deduced by using different diagnostic techniques. Thin films deposited on Cu have been tested as photocathodes in an ultrahigh vacuum photodiode chamber at 10−7 Pa. Relatively high‐quantum efficiencies have been obtained for the deposited films, comparable to those of corresponding bulks. Samples could stay for several months in open air before being tested in a photodiode cell.The deposition process and the role of the gas absorption on the photocathode surface and its influence on the photoelectron performances are also presented and discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Realization of Far From Equilibrium Cation Distributions in Ferrites

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The deposition and characterization of high quality ferrite thin films by the alternating target laser ablation deposition (ATLAD) technique is discussed with the emphasis on the unique magnetic properties induced in these materials by stabilizing far from equilibrium cation distributions. Two spinel systems and three hexagonal ferrite systems are studied. In the case of manganese spinel ferrite a large in-plane uniaxial anisotropy field (<formula formulatype="inline"> <tex Notation="TeX">$&gt;5$</tex></formula> kOe) is induced in ATLAD deposited films. In the case of copper spinel ferrite a 65% enhancement in the saturation magnetization is observed over the bulk value. In the case of manganese substituted barium ferrite a 12–22% enhancement in low temperature saturation magnetization and 40–60 K increase in the NÉel temperature is observed. The unique magnetic properties of the films are correlated with the cation distributions stabilized by the application of the ATLAD technique as determined by the extended X-ray absorption fine structure (EXAFS) analysis. </para>

Atomic Scale Design and Control of Cation Distribution in Hexagonal Ferrites

Using a novel alternating target laser ablation deposition technique, Mn cations were placed in specific interstitial sites of BaFe12O19 thin films as opposed to being distributed throughout the unit cell as in conventional bulk materials. The distribution of Mn cations has been confirmed experimentally and predicted theoretically. As a result of site selection, the saturation magnetization increased 12%-22%, and the Néel temperature increased by 40-60 K compared to bulk materials. This technique implies a new methodology to design and process a new generation of ferrite, oxide, and alloy materials.

Synthesis and control of size and structure of porous carbon films

Nanoporous carbon films are directly synthesized using a pulsed KrF excimer laser ablation deposition technique. Variations of the laser power density, substrate temperature, angle and distance between the substrate and target yield different sizes (0.2–2 μm) of porous structures of carbon films. Optical microscope was used to examine the surfaces of the samples. Raman scattering was used to characterize the samples, and the typical G- and D-bands have been identified. Intensities and profiles of the G- and D-bands strongly depend on the angle of deposition. The relationship between the deposition rate and the power density was also studied.

Alternating target laser ablation deposition of high quality barium hexaferrite thin films from barium monoferrite and hematite targets

An optimized alternating target laser ablation deposition (ATLAD) technique has been developed to grow high quality barium hexaferrite (BaFe12O19) thin films on basal plane oriented sapphire (Al2O3) substrates from barium monoferrite (BaFe2O4) and hematite (α-Fe2O3) targets. Crystallographic and structural characterization results show that the films possess low c-axis dispersion of Δω=0.259° and hexagonal terraced surface morphology. Saturation magnetization and uniaxial magnetic anisotropy field were determined to be consistent with reference data on high quality barium hexaferrite films and bulk single crystals grown by other techniques. Ferromagnetic resonance linewidth of 42Oe was measured at 52GHz by the shorted waveguide technique. We conclude that the ATLAD technique is capable of growing high quality barium hexaferrite films while providing unique opportunities to control the ionic distribution in the hexagonal unit cell by allowing different species of ions to be introduced from the respective targets in any order and at any time during film growth.

Electronic transport in oxygen deficient ferromagnetic semiconductingTiO2−δ

TiO2−δ films were deposited on (100) lanthanum aluminate,LaAlO3, substrates at a low oxygen chamber pressure,P≈0.3 mTorr, employing a pulsed laser ablation deposition technique. In previous work, it wasestablished that the oxygen deficiency in these films induced ferromagnetism. In this work it isdemonstrated that this same oxygen deficiency also gives rise to semiconductor titaniumion impurity donor energy levels. Measurements of the transport resistivity of thin films ofTiO2−δ are presented, as a function of temperature and magnetic field. The magnetoresistivity andHall resistivity are explained in terms of electronic excitations from the titanium ion donorlevels into the conduction band.

Epitaxial growth of PbFe12O19 thin films by alternating target laser ablation deposition of Fe2O3 and PbO

Oriented M-type hexaferrite thin films are deposited using the alternating target laser ablation deposition (ATLAD) technique utilizing PbO and Fe2O3 targets. Crystallographic, dc magnetic, and microwave characterization results confirming the presence of a hexagonal PbFe12O19 phase are presented. We conclude that the ATLAD technique holds great promise for layer by layer deposition of various hexaferrite materials, the properties of which can be adjusted by varying the composition of the targets as well as the number of laser shots from each target during the deposition process. This would provide control over the uniaxial anisotropy fields and saturation magnetization values that was not possible in the conventional single target LAD technique.

Structural properties of single and multilayer ITO and TiO 2 films deposited by reactive pulsed laser ablation deposition technique

Indium tin oxide (ITO) and titanium dioxide (TiO 2) single layer and double layer ITO/TiO 2 films were prepared using reactive pulsed laser ablation deposition (RPLAD) with an ArF excimer laser. The films were deposited on SiO 2 substrates heated at 200 and 400 °C. ITO and TiO 2 films with uniform thicknesses of about 400 and 800 nm, respectively, over large areas were prepared. X-ray diffraction (XRD) analysis revealed that the ITO films are formed of highly orientated nanocrystals with an average particle size of 10–15 nm. Atomic force microscopy (AFM) observations indicate rough ITO films surfaces with average roughness of 26–30 nm. Pores were also observed. TiO 2 films deposited on the prepared ITO films result less crystalline. Annealing at 300 and 500 °C for three consecutive hours promoted formation of TiO 2 anatase phase, with crystal size of ∼6–7 nm. From the scanning transmission electron microscope (STEM) images, it can be seen that the TiO 2 films deposited onto the prepared ITO films present a relatively high pore sizes with an average pore diameter of ∼40 nm and excellent uniformity. In addition, STEM cross-sectional analysis of our films showed a columnar structure but no evidence of voids in the structure. Therefore, films exhibited large surface area, well suited for dye-sensitized solar cells (DSSC) applications.

Magnetism, Structure, and Cation Distribution in MnFeOFilms Processed by Conventional and Alternating Target Laser Ablation Deposition

A series of manganese ferrite thin film samples were prepared by alternating target laser ablation deposition and conventional pulsed laser deposition techniques on (111) MgO substrates. By extended X-ray absorption fine structure (EXAFS) analysis, we have discovered that the cation distribution was sensitive to the processing oxygen pressure and the preparation technique. Correspondingly, the saturation magnetization and uniaxial anisotropy fields change. Saturation magnetization was found to decrease while the percentage of Mn ions on the octahedral site increased, as a function of oxygen processing pressure. The highest magnetization (~4.5 kG) and anisotropy field (~0.5 kOe) corresponded to the sample grown at the lowest oxygen pressure

Enhanced Cathodoluminescent Properties of Nanoencapsulated Zinc Sulfide Phosphors

In this paper we show that nanoencapsulated oxygen deficient aluminum doped zinc oxide (ZAO) coatings can significantly reduce the electron beam degradation of sulfide-based phosphors. The nanoencapsulated coatings on particles were synthesized using a modified pulsed laser ablation deposition technique. Microstructural studies indicate that an oxygen deficient ZAO film acts as both a diffusion barrier and an oxygen getter during the electron beam irradiation process. Under optimized deposition conditions, the degradation lifetime of nanoencapsulated zinc sulfide phosphors increased by more than an order of magnitude, compared to noncoated material.

Synthesis and control of micro to noanscale porous structures of diamond like carbon films

ABSTRACTDiamond like carbon (DLC) films are synthesized on various substrates using a pulsed KrF excimer laser ablation deposition technique. Variations of laser power density, substrate temperature, angle and distance between the substrate and target yield different sizes of porous surfaces of DLC films. Microscope is used to examine the surfaces. Raman scattering is used to characterize the samples, and the typical G and D bands have been identified. Intensities and profiles of the G and D bands closely depend on laser power density. The relationship between the deposition rate and the power density is also studied.

Effect of deposition parameters on morphology and size of FeCo nanoparticles synthesized by pulsed laser ablation deposition

The experimental parameters that control the surface morphology and size of iron cobalt nanoparticles synthesized at room temperature by pulsed laser ablation deposition (PLAD) technique have been systematically investigated. The nanoparticle synthesis has been achieved at higher operating gas pressures of argon. It was found that nanoparticles upon deposition formed small clusters, the size of which increases with decreasing pressure, increasing laser-energy density, and decreasing target-to-substrate distance. This trend could be attributed to change in the kinetic energy of deposited nanoparticles with varying argon pressure, laser-energy, and target-to-substrate distance. The nanoparticles size and size distribution showed strong dependence on argon pressure and weak dependence on laser-energy density and target-to-substrate distance.

Spatial and chemical interface asymmetry in Fe/MgO/Fe(001) heterostructures

The chemical nature of the different interfaces and possible segregation effects are studied in fully epitaxial Fe/MgO/Fe (001) oriented heterostructures fabricated by combined sputtering plus laser ablation deposition techniques. Auger electron spectroscopy depth profiling experiments showed that the interfaces of the MgO spacer with the Fe layers are different, the inner MgO/Fe being spatially broader and with an FeO interlayer, while that of the outer Fe/MgO is spatially narrower with no evidence of FeO formation. This spatial and chemical asymmetry is interpreted in terms of the different deposition procedures, which affect the formation of both interfaces. No Fe segregation in the MgO layers or MgO segregation in the Fe films is observed.

Ar 플라즈마 상태에서 PLAD법에 의한 탄소 입자의 운동 모델링

고본 논문에서는 시뮬레이션 기법을 통하여 PLAD법을 Ar 플라즈마 상태에서 구동하도록 설정하였다. 이것은 플라즈마를 구성하는 요소들이 PLAD법에 의해 방출된 각 입자들에 어떠한 영향을 미치는가를 확인하고자 하였으며, 특히 방출된 입자들의 운동 에너지 및 밀도를 제어할 수 있을 것으로 기대되어지기 때문이다. Ar 플라즈마의 방전 공간내에서, PLAD법에 의한 전자, 탄소 이온(C<SUP>+</SUP>) 및 탄소 원자(C)의 운동 과정을 보다 정확히 계산하기 위해서 입자 및 유체 모델을 융합한 1차원 하이브리드 모델을 계발하였다.<br/> 그 결과 쉬스 내에 형성되는 전위를 제어함으로써 기판에 도달하는 C<SUP>+</SUP>의 밀도 및 에너지를 제어할 수 있는 것으로 기대되어졌다.