Nanosecond Pulsed Laser Deposition Research Articles

Piezoelectric, dielectric and ferromagnetic properties in epitaxial multiferroic Pb(Zr0.45,Ti0.55)O3/Co0.8Fe2.2O4 thin film treatment by nanosecond pulsed laser deposition

Recent years have seen a considerable research interest in multiferroic materials for their potential application as sensors and actuators. However, the scarcity of these materials in a single phase and the weak coupling of their ferroic components have directed research toward multiferroic heterostructures. These systems operate by coupling the magnetic and electric properties of two materials, generally ferromagnetic and ferroelectric, via strain. In this paper, thin films have been grown by chemical solution deposition (CSD) using spin coating technique using rotations peed of 4500 rpm and time of 50 s and dried at 120○C for 20 min. The optical, dielectric, magnetic, ferroelectric, ferromagnetic, and piezoelectric properties of thin films have been investigated by Uv- Visible spectrophotometer (300-2500) nm, X-Ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM), Transmission Electron Microscope (TEM), and Scanning Electron Microscope (SEM) respectively. PZT/CFO thin films deposited at different temperatures from 400 °C, 500 °C and 600 °C. The as-deposited PZT/CFO show week piezoelectricity and the effective piezoelectric coefficient d33 because the materials deposited on the films not only the PZT layer but also the CFO layer, which decreases the piezoelectricity of these films. PZT/CFO Films were then recorded to enhance all physical properties (dielectric, optical, structural, surface morphology, and magnetic properties) as the sintering temperature increased. The images of a thin film before and after treatment with Nd-YAG, which have Power from 10 mw to 5300 mw, Pulse width: 7 ns pulsed laser, Repetition Rate: 10 HZ, and wavelength spectrum in (IR, Vis) laser beam indicate that sample prepared before treated has a lot of porous and agglomeration which decreases after treatment.

Synthesis of smooth amorphous thin films of silicon carbide with controlled properties through pulsed laser deposition

Thin films of silicon carbide (SiC) on Si (100) and SrTiO3 (100) substrates have been grown by nanosecond pulsed laser deposition (PLD) with a Q-switched Nd:YAG laser operating at the wavelengths of 1064, 532 and 266 nm. The deposits obtained consisted of smooth and uniform layers of amorphous SiC, free of holes and cracks, with thicknesses in the range of 30–100 nm and average roughness substantially lower than 1 nm. The role of laser wavelength and of substrate temperature (300 K vs. 1025 K) on morphology, crystallinity and composition of the deposits was assessed. The films were analyzed by X-ray diffraction, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. In addition, optical emission spectroscopy was employed to evaluate the characteristics of the ablation plasma and its correlation with the film growth.

Modification of a silicon surface visible light reflectivity by the carbon nanofilm

Crystalline silicon substrate visible light reflectivity is finely modified by a discrete growth of carbon nanofilm (CNF) on it by nanosecond pulsed laser deposition (PLD) technique. It is established that 71 nm thick CNF effectively reduces the high reflection of the substrate on average to 5% in the visible light wave range. The exact values of the thickness and refractive index of the carbon nanofilm are also determined via an analysis of reflection spectra.

Substituted Hydroxyapatite, Glass, and Glass-Ceramic Thin Films Deposited by Nanosecond Pulsed Laser Deposition (PLD) for Biomedical Applications: A Systematic Review

The deposition of thin films of bioactive materials is the most common approach to improve the bone bonding ability of an implant surface. With this purpose, several wet and plasma assisted deposition methods were proposed in the scientific literature. In this review, we considered films obtained by nanosecond Pulsed Laser Deposition (PLD). Since hydroxyapatite (HA) has composition and structure similar to that of the mineral component of the bone, the initial studies focused on the selection of experimental conditions that would allow the deposition of films that retain HA stoichiometry and crystallinity. However, biological apatite was found to be a poorly crystalline and multi-substituted mineral; consequently, the attention of researchers was oriented towards the deposition of substituted HA, glass (BG), and glass-ceramic (BGC) bioactive materials to exploit the biological relevance of foreign ions and crystallinity. In this work, after a description of the nanosecond ablation and film growth of ceramic materials, we reported studies on the mechanism of HA ablation and deposition, evidencing the peculiarities of PLD. The literature concerning the PLD of ion substituted HA, BG, and BGC was then reviewed and the performances of the coatings were discussed. We concluded by describing the advantages, limitations, and perspectives of PLD for biomedical applications.

Borate and Silicate Bioactive Glass Coatings Prepared by Nanosecond Pulsed Laser Deposition

Silicate (13-93) and borate (13-93-B3) bioactive glass coatings were successfully deposited on titanium using the nanosecond Pulsed Laser Deposition technique. The coatings’ microstructural characteristics, compositions and morphologies were examined by a number of physico-chemical techniques. The deposited coatings retain the same functional groups of the targets, are a few microns thick, amorphous, compact and crack free. Their surface is characterized by the presence of micrometric and nanometric particles. The surface topography, investigated by Atomic Force Microscopy, is characterized by spherical or ellipsoidal particles of the 0.2–3 μm size range for the 13-93 silicate bioactive glass film and of the 0.1–1 µm range for the 13-93-B3 borate bioactive glass coating. Equine adipose tissue-derived mesenchymal stem cells (ADMSCs) were applied for biological tests and the osteogenic differentiation activity of cells on the deposited coatings was studied after ADMSCs growth in osteogenic medium and staining with Alizarin Red. Cytocompatibility and osteogenic differentiation tests have shown that thin films retain the biocompatibility properties of the target silicate and borate glass, respectively. On the other hand, no antibacterial activity of the borate glass films was observed, suggesting that ion doping is advisable to inhibit bacterial growth on the surface of borate glass thin films.

Pulsed laser deposition of Pt-WO3 of hydrogen sensors under atmospheric conditions

Here we report on a hydrogen gas sensor comprised of Pt-WO3 nano-/micro- powder films, which were produced using nanosecond pulsed laser ablation and deposition on a silica glass substrate under atmospheric conditions. An all- optical non-contact method of probing its electromagnetic radiation transmittance in the near-IR 1.3 μm telecommunications frequency band was employed for rapid ~10 s timescale detection of low-concentration (below 4% by volume) hydrogen gas admixtures. Discussion on optimizing the composition of the Pt- WO3 alloy and its processing conditions and temperatures for best performance is provided.

Wavelength, fluence and substrate-dependent room temperature pulsed laser deposited B-enriched thick films

Boron carbide (B4C) has outstanding properties making it particularly interesting in the field of neutron detection. In this study we exploit nanosecond pulsed laser deposition (PLD) for the synthesis of B-enriched films with micrometer-scale thickness for future realization of a neutron converter layer. B-enriched B4C layers were deposited by PLD at room temperature under different wavelength conditions (λP = 266, 248,193 nm), fluence (from 2 to 10 J/cm2) and substrate (silica, Si (100), kapton (polyamide), PMMA and AZ 1512 resist).The measured elemental composition of boron (B), carbon (C) and oxygen (O) as well as the structural properties of the deposited films highlighted: i) wavelength- and fluence-dependent B sub-stoichiometry with respect to the ablated target, ii) formation of polycrystalline grains despite the room temperature growth in the case of λP = 266 nm, and iii) deposition rates higher for λP = 266 than for the other investigated wavelengths.The film deposited at a wavelength of λP = 266 nm and F = 2 J/cm2 yielded the best B/C ratio, negligible O-contaminations, and a very smooth surface with low density of surface particulates.Moreover, the possibility of depositing well adherent films on soft substrates with thicknesses > 1 μm is demonstrated, due to ability to accommodate tensile stress at the substrate-B4C film interface.

Surface edge states and enhanced emission on topological insulator of silicon oxide

The stable form of silicon takes on the structure of diamond (cF8, d-Si) which is an indirect bandgap semiconductor. Its emission efficiency is very lower (about 10−5) that prevents it from being considered as an ext-generation platform for semiconductor technologies [1–5]. Here, we report the formation of a new topological insulator of silicon oxide produced by nanosecond pulsed laser, using a novel two-step preparation methodology, which has a good emission. First, the amorphous silicon layer was fabricated by nanosecond pulsed laser etching and deposition at oxygen environment, then the topological insulator of silicon oxide was prepared by annealing at 1000 °C for suitable time. The stronger emission in visual region was observed in photoluminescence (PL) measurement on the topological insulator doped with lower oxygen density, where its external quantum efficiency in emission rises over 20% by four orders than that on pure silicon. It is interesting that the quantum platform of emission has been founded in the evolution curve of PL intensity with change of excitation power. The physical model shows that the higher emission efficiency is originated from the special electronic properties in the new topological insulator of silicon oxide, which is fundamentally responsible for creating extended edge states. The topological insulator of silicon oxide will become a new potential material for emission on silicon chip.

Laser synthesis of iron nanoparticle for Fe doped hydroxyapatite coatings

Abstract Thin films of iron doped hydroxyapatite have been prepared by nanosecond Pulsed Laser Deposition (PLD). The composite target used for the deposition has been obtained by mixing commercial hydroxyapatite powder with iron-based nanoparticles produced by femtosecond laser ablation in liquid (LAL) (4% of iron nanoparticles). In fact, LAL technique allows to obtain metallic nanostructures without any toxic chemicals and reagents, with a green approach that is crucial for application in biological and medical technologies. Films have been prepared with substrate temperature growing from room temperature (RT) to 500 °C. The effect of deposition temperature on morphology, composition and structural properties of coatings has been investigated. Films deposited at higher temperature result dense and crystalline, they present microscale and nanoscale structures, an average surface roughness of 0.3 μm and magnetic properties suitable for biomedical applications.

Bulk and surface characterisation of micrometer-thick cobalt ferrite films grown by IR PLD

We have studied micrometer-thick cobalt ferrite films deposited on Si (1 0 0) single crystal substrates by nanosecond pulsed laser deposition at 1064 nm.The thickness of the deposited films (1.3 μm) was monitored by AFM. The chemical and structural characterisation of the films was carried out by Raman spectroscopy and transmission Mössbauer spectroscopy at 300 and 26 K. For comparison purposes, transmission Mössbauer data at these two temperatures were also recorded from a commercial cobalt ferrite powder and the home-made target used to grow the films. The surface characterisation was performed by X-ray Photoelectron Spectroscopy (XPS) and Integral Low Energy Electron Spectroscopy (ILEEMS). XPS showed Co and Fe to be present as Co2+ and Fe3+, as expected for cobalt ferrite. The Raman spectra showed the lines characteristic of cobalt ferrite. The Mössbauer spectra, both in the transmission and backscattering modes, were fitted to two sextets whose hyperfine parameters are in good agreement with those expected from Fe3+ cations occupying the tetrahedral and octahedral sites in the spinel-related structure. No significant differences were observed in the relative areas of the two sextets in the transmission and ILEEMS spectra, suggesting that the cation distribution at the surface and the bulk are not too different. However, the relative areas of the two components changed drastically with temperature both in the spectra of the films as in those recorded from the cobalt ferrite standards. We discuss the possible origin of the evolution with temperature of those relative areas.

Magnetic-field-assisted formation of oriented nanowires produced by pld in open air

A laser-based technology is presented for fabrication of oriented nanowires composed by nanoparticles. The nanowires were produced by nanosecond pulsed laser deposition in air at atmospheric pressure in the presence of an external magnetic field. The technology described is relevant to the preparation of nanowires of magnetic materials. Applying an external magnetic field during the deposition resulted in the formation of nanowires with lengths of a few microns oriented longitudinally to the magnetic field lines. The influence was investigated of the process parameters, namely, laser fluence, target-substrate distance, and wavelength used for ablation, on the morphology of the deposited samples. It was found that the degree of the nanowires’ orientation increased with the increase of the target-substrate distance. Also, the density of the deposited material was influenced by the laser fluence applied and by the wavelength used.

Toward a comprehensive UV laser ablation modeling of multicomponent materials—A non-equilibrium investigation on titanium carbide

Titanium carbide (TiC) coatings of great quality can be produced using nanosecond pulsed laser deposition (PLD). Because the deposition rate and the transfer of the target stoichiometry depend strongly on the laser-target/laser-plasma interaction as well as the composition of the laser induced plume, investigating the ruling fundamental mechanisms behind the material ablation and the plasma evolution in the background environment under PLD conditions is essential. This work, which extends previous investigations dedicated to the study of nanosecond laser ablation of pure target materials, is a first step toward a comprehensive non-equilibrium model of multicomponent ones. A laser-material interaction model coupled to a laser-plasma interaction one is presented. A UV 20 ns KrF (248 nm) laser pulse is considered. Ablation depths, plasma ignition thresholds, and shielding rates have been calculated for a wide range of laser beam fluences. A comparison of TiC behavior with pure titanium material under the same conditions is made. Plasma characteristics such as temperature and composition have been investigated. An overall correlation between the various results is presented.

Thermoelectric Analysis of ZnSb Thin Films Prepared by ns-Pulsed Laser Deposition.

Zinc antimonide (ZnSb) is a promising thermoelectric material for the temperature range 300– 600 K. ZnSb thin films were prepared by nanosecond Pulsed Laser Deposition (PLD) to evaluate the performance of nanostructured films for thermoelectric conversion by the determination of the Power Factor. A study of the influence of structural, compositional and thermoelectric properties of thin films is reported as a function of different deposition parameters, such as repetition rate, pulse energy, and substrate temperature. The evaluation of a thin film ZnSb compound with excess Sb has been performed to verify the variation of the thermoelectric properties. The obtained results are reported and discussed in the 300–600 K temperature range.

Pulsed laser-deposited composite carbon–glass–ceramic films with improved hardness

A composite material obtained by mixing a glass–ceramic powder and C60 has been used to obtain thin films by nanosecond pulsed laser deposition technique, with the aim to improve the mechanical properties of the potentially bioactive coatings. Films have been deposited by using a Nd:YAG laser source (λ = 532, τ = 7 ns, 10 Hz) on titanium substrates heated at different temperatures. The deposited coatings present a sub-micron homogeneous texture completely covering the substrate with micrometric inclusions distributed on the whole surface, as observed by AFM and SEM. IR and XRD spectra of films are characteristic of amorphous calcium silicate materials, suggesting that the carbonaceous component inhibits the glass matrix crystallization, also at high deposition temperatures. Micro-Raman measurements evidence that fullerene transforms into amorphous carbon and reduced graphene oxide (RGO)-like domains in films deposited at room temperature and 500 °C, respectively. The presence of the RGO-like domains embedded in the amorphous glassy matrix has been related to the observed improved Vickers microhardness.

Comparison of Vanadium Oxide Thin Films Prepared Using Femtosecond and Nanosecond Pulsed Laser Deposition

ABSTRACTPulsed laser deposition (PLD) is a technique which utilizes a high energy pulsed laser ablation of targets to deposit thin films on substrates in a vacuum chamber. The high-intensity laser pulses create a plasma plume from the target material which is projected towards the substrate whereupon it condenses to deposit a thin film. Here we investigate the properties of vanadium oxide thin films prepared utilizing two variations of the pulsed laser deposition (PLD) technique: femtosecond PLD and nanosecond PLD. Femtosecond PLD (f-PLD) has a significantly higher peak intensity and shorter duration laser pulse compared to that of the excimer-based nanosecond PLD (n-PLD). Experiments have been conducted on the growth of thin films prepared from V2O5 targets on glass substrates using f-PLD and n-PLD. Characterization using SEM, XRD and Raman spectroscopy shows that the f-PLD films have significantly rougher texture prior to annealing and exhibit with an amorphous nano-crystalline character whereas the thin films grown using n-PLD are much smoother and highly predominantly amorphous. The surface morphology, structural, vibrational, and chemical- and electronic-state elemental properties of the vanadium oxide thin films, both prior to and after annealing to 450 °C, will be discussed.

Pulsed laser deposition of metal oxide nanostructures for highly sensitive gas sensor applications

Nanosecond and picosecond pulsed laser deposition (PLD) was used to prepare metal oxide nanostructures with different morphologies as gas sensing materials on top of oxidized silicon substrates and commercial SGX Sensortech SA MEMS microheater platforms. The layers were formed of different types of nanostructures including nanoparticles, agglomerates, and nanotrees with fractal-like growth. Clear dependencies between the deposition parameters, structural morphology, and gas sensing performance were found. Also, some differences in the morphologies of the layers were seen when picosecond PLD was used instead of nanosecond PLD. Many of the sensing materials were found to be highly sensitive to different types of gaseous species. We investigated inorganic gases in the ppm range (2–400ppm) including NO, CO, and NH3, and the selectivity and sensitivity were shown to be dependent, not only on layer morphology, but also on the measurement temperature. Moreover, an investigation with volatile organic compound gases in the ppb range demonstrated that WO3 layers are highly sensitive and selective towards naphthalene at least down to 2.5ppb.

A Comparative Characterization Study of Molybdenum Oxide Thin Films Grown Using Femtosecond and Nanosecond Pulsed Laser Deposition

ABSTRACTGroup 6 transition metal oxide thin films are in large demand for photocatalysis, heterogeneous catalysis, fuel cell, battery and electronic applications. Pulsed laser deposition offers an inexpensive method for the preparation of nanostructured thin films that may be suitable for heterogeneous catalysis. We have synthesized molybdenum oxide thin films using two types of pulsed laser deposition (PLD). The first method utilizes femtosecond laser-based PLD (f-PLD) while the second method uses an excimer (nanosecond) laser-based PLD (n-PLD). The PLD films have been deposited using f-PLD and, separately, n-PLD on glass and silicon substrates and subsequently annealed to 450 °C for up to 20 hours in air using a Linkam stage. SEM, XRD and Raman spectroscopic characterization shows that the f-PLD films are substantially more textured and partially crystalline prior to annealing whereas the n-PLD-grown thin films are much smoother and predominantly amorphous. A 3-dimensional nano-crystalline structure is evident in the post-annealed f-PLD synthesized thin films, which is desirable for catalytic applications. XPS elemental analysis shows that the stoichiometry of the f-PLD and n-PLD thin films is consistent with the presence of MoO2 and MoO3. Our results are discussed in terms of thin film growth models suitable for f-PLD vs n-PLD.

RBP1 bioactive glass-ceramic films obtained by Pulsed Laser Deposition

The deposition of thin films of bioactive materials is an issue of scientific and technological interest due to the possibility to combine mechanical strength of the implants and the bioactive properties of their surface. In this contest, we have deposited thin films of a bioactive glass-ceramics target of innovative composition by using the Pulsed Laser Deposition (PLD) technique. The deposition mechanism and the obtained films have been fully characterized by microscopic and spectroscopic techniques. It has been showed that films produced by nanosecond PLD are formed by the coalescence of nanometric droplets and films surface roughness can be suitable for the cell adhesion.

Carbon-atom wires produced by nanosecond pulsed laser deposition in a background gas

Wires of sp-hybridized carbon atoms are attracting interest for both fundamental aspects of carbon science and for their appealing functional properties. The synthesis by physical vapor deposition has been reported to provide sp-rich carbon films but still needs to be further developed and understood in detail. Here the synthesis of carbon-atom wires (CAWs) has been achieved by nanosecond pulsed laser deposition (PLD) expoliting the strong out-of-equilibrium conditions occurring when the ablation plasma is confined in a background gas. Surface Enhanced Raman Spectroscopy (SERS) spectra of deposited films indicate that CAWs are mixed with a mainly sp2 amorphous carbon in a sp-sp2 hybrid material. Optimal conditions for the deposition of sp-carbon phase have been investigated by changing deposition parameters thus suggesting basic mechanisms of carbon wires formation. Our proof-of-concept may open new perspectives for the targeted fabrication of CAWs and sp-sp2 structures.

Laser nanostructuring of ZnO thin films

In this work, results on laser processing of thin zinc oxide films deposited on metal substrate are presented. ZnO films are obtained by classical nanosecond pulsed laser deposition method in oxygen atmosphere on tantalum substrate. The produced films are then processed by nanosecond laser pulses at wavelength of 355nm. The laser processing parameters and the film thickness are varied and their influence on the fabricated structures is estimated. The film morphology after the laser treatment is found to depend strongly on the laser fluence as two regimes are defined. It is shown that at certain conditions (high fluence regime) the laser treatment of the film leads to formation of a discrete nanostructure, composed of spherical like nanoparticles with narrow size distribution. The dynamics of the melt film on the substrate and fast cooling are found to be the main mechanisms for fabrication of the observed structures. The demonstrated method is an alternative way for direct fabrication of ZnO nanostructures on metal which can be easy implemented in applications as resistive sensor devices, electroluminescent elements, solar cell technology.