Pulsed Laser Ablation Method Research Articles

New Seeding Methodology for Gas Concentration Measurements

This paper presents the first demonstration of the pulsed laser ablation technique to seed a laminar non-reacting gaseous jet at atmospheric pressure. The focused, second harmonic from a pulsed Nd : YAG laser is used to ablate a neutral indium rod at atmospheric pressure and temperature. The ablation products generated with the new seeding method are used to seed the jet, as a marker of the scalar field. The neutral indium atoms so generated are found to be stable and survive a convection time of the order of tens of seconds before entering the interrogation region. The measurements of planar laser-induced fluorescence (PLIF) with indium and laser nephelometry measurements with the ablation products are both reported. The resulting average and root mean square (RMS) of the measurements are found to agree reasonably well although some differences are found. The results show that the pulsed laser ablation method has potential to provide scalar measurement for mixing studies.

Pd2+ reduction and gasochromic properties of colloidal tungsten oxide nanoparticles synthesized by pulsed laser ablation

Tungsten oxide nanoparticles were fabricated by a pulsed laser ablation method in deionized water using the first harmonic of a Nd:YAG laser (λ=1064 nm) at three different laser pulse energies (E1 =160, E2 =370 and E3 =500 mJ/pulse), respectively. The aim is to investigate the effect of laser pulse energy on the size distribution and gasochromic property of colloidal nanoparticles. The products were characterized by dynamic light scattering (DLS), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. The results indicated that WO3 nanoparticles were formed. After ablation, a 0.2 g/l PdCl2 solution was added to activate the solution against hydrogen gas. In this process Pd2+ ions were reduced to deposit fine metallic Pd particles on the surface of tungsten oxide nanoparticles. The gasochromic response was measured by H2 and O2 gases bubbling into the produced colloidal Pd–WO3. The results indicate that the number of unreduced ions (Pd2+) decreases with increasing laser pulse energy; therefore, for colloidal nanoparticles synthesized at the highest laser pulse energy approximately all Pd2+ ions have been reduced. Hence, the gasochromic response for this sample is nearly reversible in all cycles, whereas those due to other samples are not reversible in the first cycle.

Photoluminescence characteristics of Er doped Ge nanocrystals embedded in alumina matrix

Er3+ doped Ge nanocrystals embedded in high-k Al2O3 matrix were prepared by pulsed laser ablation method. X-ray spectra and transmission electron micrographs have confirmed the formation of Ge nanocrystals and the increase in crystallite size with increasing annealing temperature from 750°C to 950°C. An enhanced photoluminescence intensity at 1.54μm is attained by optimizing the Er concentration. Temperature dependent photoluminescence from samples annealed at different temperatures has shown the existence of thermally activated energy transfer process between Er3+ and Ge nanocrystals.

Thin Film Deposition of Tb3Al5O12:Ce by Pulsed Laser Ablation and Effects of Low-temperature Post-annealing

Tb3Al5O312:Ce (TAG:Ce) thin films were successfully deposited by a pulsed laser ablation method on a quartz substrate, and low-temperature post-annealing effects on luminescent properties were investigated in detail. TAG:Ce thin films were analyzed by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The as-deposited films were amorphous, and post-annealing above 700°C was required for crystallization. The post-annealed TAG:Ce thin films showed strong and broad emission bands around 542 nm and excitations at 451 nm, which all corresponded to transitions between the 4f ground level to the 5d1 excited levels of Ce ion.

Pressure-Induced Growth Evolution of Different ZnO Nanostructures by a Pulsed Laser Ablation Method

Pressure-Induced Growth Evolution of Different ZnO Nanostructures by a Pulsed Laser Ablation Method

Ring like self assembled Ni nanoparticles based biosensor for food toxin detection

The self-assembled ring like nickel (RnNi ∼ 10-20 nm) nanoparticles have been prepared by pulsed laser ablation method and confirmed by transmission electron microscopy. These RnNi nanoparticles electrophoretically deposited onto the indium-tin-oxide (ITO) glass substrate have been functionalized with dimethyl sulfoxide (DMSO) for covalent immobilization of anti-aflatoxin (a-AfB1) monoclonal antibodies and bovine serum albumin as blocking agent. The electrochemical response studies of a-AfB1/DMSO/RnNi-film/ITO bioelectrode reveal linearity as 5-100 ngdL−1, detection limit of 32.7 ngdL−1, sensitivity of 0.59 μA/ng dL−1, and shelf-life of 60 days. The low value (1.3 × 1014 molL−1) of association constant (Ka) shows high affinity towards aflatoxin.

In vivo optical imaging with rare earth doped Ca_2Si_5N_8 persistent luminescence nanoparticles

Ca2Si5N8:Eu2+,Tm3+ presents outstanding long lasting luminescence at about 610 nm. However, to be useful for in vivo optical imaging, persistent luminescence materials should possess high optical performance combined with sizes in the nanoscale. With this aim, we investigated two different techniques for the preparation of nanoparticles from Ca2Si5N8:Eu2+,Tm3+ bulk powder. First, nanoparticles were successfully prepared with the pulsed laser ablation method in liquid (abbreviated as PLAL). Secondly, nanoparticles obtained by selective sedimentation from the bulk compound resulted in satisfactory yield and allowed to perform the first real-time in vivo imaging with Ca2Si5N8:Eu2+,Tm3+ host. Finally the influence of surface functionalization on the biodistribution of the probe after systemic injection is discussed.

Graphene Supported Platinum Nanoparticle Counter-Electrode for Enhanced Performance of Dye-Sensitized Solar Cells

Composites of few layered graphene (G) and platinum (Pt) nanoparticles (NP) with different loadings of Pt were used as counter electrode (CE) in dye-sensitized solar cell (DSSC). NPs were deposited directly on to G using pulsed laser ablation method (PLD). DSSCs formed using the composite CEs show improved performance compared to conventional Pt thin film electrode (Std Pt) and unsupported Pt NPs. Composite with 27% loading of Pt shows 45% higher efficiency (η = 2.9%), greater short circuit current (J(sc) = 6.67 mA cm(-2)), and open circuit voltage (V(oc) = 0.74 V) without any loss of the fill factor (FF = 58%) as compared to the cells fabricated using Std Pt electrodes. Values of η, J(sc) and V(oc) for DSSC using Std Pt CE were 2%, 5.05 mA cm(-2) and 0.68 V, respectively. Electrochemical impedance spectroscopy using I(-)(3)/I(-) redox couple confirm lower values of charge transfer resistance for the composite electrodes, e.g., 2.36 Ω cm(2) as opposed to 7.73 Ω cm(2) of Std Pt. The better catalytic activity of these composite materials is also reflected in the stronger I(-)(3) reduction peaks in cyclic voltammetry scans.

Influences of Target and Liquid Media on Morphologies and Optical Properties of ZnO Nanoparticles Prepared by Laser Ablation in Solution

This article reports the target and liquid media influences on the microstructures and optical properties of ZnO nanoparticles synthesized using pulsed laser ablation (PLA) method. Zinc and ZnO target were ablated with laser in pure water and surfactant solution, respectively. The obtained nanoparticles were characterized using X‐ray diffraction spectrometer, transmission electron microscopy, X‐ray photoelectron spectroscopy, optical absorption spectrum, and photoluminescence spectrum. The nanoparticles synthesized in surfactant solution were of spherical shapes, but with different microstructures and optical properties. The nanoparticles synthesized in water using zinc target showed rod shapes and both UV and visible emissions. When ZnO target was ablated in water, flake‐shaped nanoparticles were synthesized and strong UV, but weak violet emissions were observed. At last, the influences of PLA growth condition on the nanoparticles microstructures and the relationship between the optical properties and their stoichiometries were discussed.

Ablation particles parameters influences on VLS oxide nanowire growing

MgO nanowires were grown using vapor–liquid–solid technique by using the Pulsed Laser Ablation method in special shadow-mask system geometry. We compared the MgO nanowires morphology below and outside the shadow-mask areas obtained by using two different laser beams (193nm—ArF excimer, and 266 Nd:YAG fourth harmonic) for target ablation. If for the first laser beam, an MgO nanowire grows outside the mask's shadow area and the growing morphology below the mask tends to change to island growing, in the second case, the nanowire tends rather to form below the shadow-mask. Our results interpretation is based on the ablation plume particles' flux and size. In the first case, results are interpreted based on the ablated particle flux variation in the ablation plume interaction with a plane mask. In the second case, we base our interpretation on 'big' particles filtering by the ablation plume interaction with a plane mask.

Elastic behaviour and internal friction studies on nanocrystalline Mn–Zn ferrite films prepared by the method of pulsed laser ablation

A laser ablation method was used for the preparation of nanocrystalline Mn–Zn ferrite thin films. Films were characterized using X-rays and TEM. The magnetic properties were measured using the vibrating sample magnetometer (VSM). The elastic behaviour and internal friction studies were carried out using composite piezoelectric oscillator method in the temperature range of 300–600 K. It was found that the value of Young's modulus decreases with an increase of temperature and shows anomalous behaviour in the vicinity of the Curie temperature. The internal friction for the present ferrites increases continuously with temperature up to the Curie point and a narrow peak was observed just below the Curie temperature. It was found that the anomalous behaviour observed in the temperature dependence of Young's modulus and internal friction disappears with the application of a magnetic field equal to the saturation field (900 mT) of the specimen under investigation. The observed anomalous behaviour in the vicinity of the Curie temperature was understood with the help of Landau's theory.

In Situ Laser Synthesis of Si Nanowires in the Dynamic TEM

The dynamic transmission electron microscope (DTEM) is introduced as a novel tool for in situ nanowire (NW) synthesis and characterization. Initial results show crystalline Si NW production by a root-based growth mechanism using a pulsed laser ablation (PLA) method inside the microscope column (see image). The potential of the DTEM to characterize the evolution of nanostructures by PLA methods is demonstrated.

Fabrication of conical shape-Si particle by pulsed laser ablation

Abstract We have studied the effects of the laser energy density and vacuum pressure in fabricating Si particles using the PLA (pulsed laser ablation) method. Si particles were formed with different shapes depending on the laser energy density and vacuum pressure. We fabricated a conical shape-Si particle at a He gas pressure of 200 mTorr with a laser energy density of 5∼7 J/cm 2 . We also fabricated the hexagonal shape-Si particles and the ring shape-Si particles at the same pressure with a lower energy density and a higher energy density than that of conical shape-Si particles. Furthermore, we have known that the conical shape-Si particles had step structure with a height of 1.5 μm from FE-SEM and AFM investigations and had a single crystalline from an analysis of the Raman scattering spectroscopy. The laser energy density and the He gas pressure of the chamber affected the shape and the size of the Si particles.

Biaxially textured YBa2Cu3O7−x films deposited on polycrystalline flexible yttria-stabilized zirconia ceramic substrates

Biaxially textured YBa2Cu3O7−x (YBCO) films were grown on polycrystalline flexible yttria-stabilized zirconia (YSZ) ceramic substrates (Ceraflex) buffered with MgO and LaMnO3 layers. These substrates were initially coated with silica glass to obtain a smooth surface and then biaxially textured MgO buffer layers were deposited by ion beam assisted deposition (IBAD-MgO). Lanthanum manganate (LMO) cap layers and YBCO layers were then deposited by the pulsed laser ablation method. Highly textured YBCO films with a full width half maximum (FWHM) of 6.75° in (110) phi scans and a FWHM∼5° in (200) omega scans were obtained. An initial deposition yielded samples with a Tc>88K and a self-field magnetization Jc of 2×105A/cm2 at 77K. A secondary ion mass spectrometry (SIMS) depth profile of the samples indicated that with the present deposition condition, some La, Mn and Mg diffusion into the YBCO layers is possible and this may reduce the Jc in the self-field. The yield strength (YS) of uncoated Ceraflex substrates was compared with that of metallic substrates and it was found that Ceraflex substrates can have a YS at least 4–5 times higher than the YS of biaxially textured Ni–5 at.%W substrates and ∼1.5 times that of HastelloyTM substrates.

Fabrication and characterization of carbon nanotube based high sensitive gas sensors operable at room temperature

Multi-walled carbon nanotubes (MWCNTs) were prepared using both dc sputtering method and thermal CVD method. Single-walled carbon nanotubes (SWCNTs) were prepared by pulsed laser ablation (PLA) method. CNT based NO x gas sensors which can operate at low temperature were fabricated. Both MWCNT thin films and SWCNT thin films were grown on Al 2O 3 substrate with interdigitated Pt-electrodes to make a gas sensor. Gas sensing properties to NO and NO 2 gases were measured. Resistance of the prepared CNT-based gas sensor decreased with increase of NO and NO 2 gas concentration. The SWCNT-based gas sensor showed higher sensitivity and rapid-response to the test gas.

Origin of giant graphite balls including in the carbon nanohorns prepared by pulsed arc-discharge and their removal method

Large sized spherical graphitic particles with the diameter as large as several micrometers, so called giant graphite balls (GGBs), are more or less included in the sample of carbon nanohorns (CNHs) which are prepared by the method of pulsed arc-discharge or laser ablation. For the use of CNHs in the application, it is needed to decrease such impurity from the sample. In order to find a way to decrease the GGBs content, we investigate the origin of GGBs and find a simple method for increasing the sample purity. The origin of GGBs is the exfoliated materials from the carbon rod, and such an exfoliation can be nearly avoided by the preheat treatment of the carbon rod up to 1000°C just in advance of the arc vaporization. According to this preheat, the quantity of GGBs in the sample can be reduced from 30 to 0.01 % (100 ppm) by weight. In addition, it was found that the simple two-staged purification which is combined with the centrifugation and filtration effectively works for removing such a small quantity of GGBs.

Observation of Local Crystal Structure and Electronic States of Laser-Ablated Ge-Sb-Te Nanoparticles for Non-Volatile Memories

Phase-change Ge-Sb-Te (GST) nanoparticles have been synthesized in situ by a pulsed laser ablation method. Crystal formation of the GST nanoparticles was confirmed [H. R. Yoon et al., J. Non-Cryst. Solids, 351, 3430 (2005)]. Scanning and transmission electron microscopy were used to study microstructure and phase formation of the nanoparticles. Fourier transform analysis of electron micrographs exhibits the crystal structure of the GST-225. We have also measured the extended X-ray absorption fine structure of the Ge K edge in the GST nanoparticles with synchrotron radiation. Core-level spectra of Te3d, 4d, Sb3d, 4d and Ge3d of GST nanoparticles were obtained by using X-ray photoelectron spectroscopy. Our results suggest that such X-raybased spectroscopy can be used to study the GST nanoparticles through electronic states and local structural information, these being developed for low-power non-volatile-memory applications.

Fabrication and characterization of a granular film consisting of size-selected silver nanoparticles: application to a SERS substrate

Uniform-sized silver nanoparticles with average diameter of 13.7 nm have been prepared in the gas-phase by combining a pulsed laser ablation method with a low pressure-differential mobility analyzer (LP-DMA). By depositing the silver nanoparticles onto a silicon substrate, a granular film consisting of size-selected silver nanoparticles has been fabricated and its morphology and electronic properties have been examined using transmission electron microscopy (TEM) and UV-visible absorption spectroscopy. This granular silver film serves as a highly active substrate for surface-enhanced Raman scattering (SERS).

Optical and magneto‐optical properties of ZnMnO and ZnMnFeO single crystals and thin films

AbstractSingle crystals of oxide diluted magnetic semiconductor Zn1–x Mnx O have been grown by chemical vapour transport and thin films of Zn1–x Mnx O, Zn1–x –y Mnx Fey O have been deposited by pulsed laser ablation and rf magnetron sputtering methods. Optical absorption spectra of the obtained crystals and films have features associated with band‐to‐band direct type transitions and d–d crystal‐field transitions due to presence of Mn2+ ions. The observed peculiarities of the Faraday rotation for Zn1–x Mnx O crystals and films suggest of paramagnetic behaviour. In contrast, Zn1–x –y Mnx Fey O film samples exhibit ferromagnetic‐like behaviour which is confirmed on typical magnetic field dependence of the Faraday rotation at room temperature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural and optical properties of as‐deposited and annealed SrTiO3 films prepared by laser ablation

AbstractIn order to clarify the large band gap energy reported for thin SrTiO3 film (of which thickness is smaller than 200 nm) and to examine the optical properties reported for bulk SrTiO3 crystals, different thick SrTiO3 films were prepared by a pulsed laser ablation method. The morphology and structure of the as‐deposited and annealed films were studied with the optical‐ and scanning electron microscopes and with an x‐ray diffraction method. The optical absorption and photoluminescence properties of the films are then measured at temperatures between 6.5 and 300 K. A large band gap energy (about 4.0 eV) has been observed even for thick amorphous SrTiO3 films (of which thicknesses are approximately 1.3 μm). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)