CO2 Laser Deposition Research Articles

Facile synthesis of Cu-Sn nanoparticle film and its bonding mechanism for power electronic packaging

The Cu-Sn full intermetallic compound is a promising high-temperature electronic packaging material, while its preparation is usually time-consuming. In this work, a novel dual-beam laser co-deposition method was proposed to prepare Cu-Sn nanoparticle film for power electronic packaging with high bonding efficiency. Various Cu-Sn contents were prepared to reveal the bonding mechanism of the full intermetallic compound structure. The results show that joints with a Cu content ranging from 20 wt% to 80 wt% could form full intermetallic compounds within 2 min with the shear strength reaching 120 MPa. Specifically, Cu6Sn5, 'island-like' Cu3Sn, and sintered Cu generated successively in the bondline center with the increasing Cu content. All failures occurred within the bondline indicating a higher interface bonding quality, while the 'island-like' Cu3Sn enhanced the shear strength. This die attach process is compatible with current commercial SiC die attach process with lower material cost as well as high efficiency, enabling the Cu-Sn nanoparticle film to be a promising material for high-reliability power electronic packaging.

Structural engineering of vertically aligned nanocomposite films fabricated via magnetron and pulsed laser co-deposition for microwave application

Microwaves are often used in communication engineering, including in microwave relays as well as multichannel, mobile, and satellite communications. To meet the demand for a “small, light, thin, and precise” modern electronic machine, developing highly tunable microwave materials to manufacture miniaturized microwave devices has become a top priority. Ferroelectric materials are excellent microwave materials, showing outstanding dielectric properties and tunability. Introducing low dielectric loss oxides in the construction of vertical self-assembly nanocomposites (VSNs) effectively improves their tunability and reduces dielectric loss. However, the optimal doping content of simple VSN films limits further improvement of tunability. Herein, we propose a strategy-gradient VSN to achieve combined improvement in tunability and dielectric constant by designing a sputtering and pulsed laser co-deposition. The resulting VSN composite film has a dielectric constant of 428.08, a dielectric loss of 0.0212, and a tunability of 78.69 %. Our results contribute to the development of filters and have broad application prospects in the microwave industry.

FePt: LaSrFeO4 nanocomposite film prepared by magnetron and pulsed laser co-deposition method

The extensive application of a multifunctional composite film of metal nanoparticles embedded in a dielectric matrix is remarkable. Due to the oxidation susceptibility of atomic iron, it is difficult to directly fabricate embedded Fe nanoparticles in an oxide dielectric matrix with a Fe target. Because La0.5Sr0.5FeO3 can be decomposed into LaSrFeO4 and α-Fe, ferromagnetic and optical absorption FePt:LaSrFeO4 composite films were successfully fabricated at room temperature using Pt and La0.5Sr0.5FeO3 as targets via magnetron and pulsed laser co-deposition. Further annealing was performed on the FePt:LaSrFeO4 composite films. FePt is chemically disordered face-centered cubic phase (A1 structure) below 600 oC annealing and chemically ordered face-centered tetragonal phase (L10 structure) above 600 oC annealing. With increasing the annealing temperature, a redshift of the absorption peak from 256 to 285 nm is seen, which can be attributed to the size growth of the LaSrFeO4 and FePt nanoparticles in the composite films. The strongest absorption peak at around 269 nm for the 600 oC annealed sample can be attributed to the high crystallographic quality and relatively tiny grain size of FePt particles with uniform distribution. FePt:LaSrFeO4 composite films are ferromagnetic and optically absorbent, making them suited for multifunctional applications. Furthermore, magnetron and pulsed laser co-deposition techniques have the potential to produce multiferroic oxides, in which the coupling of different ordering processes e. g. ferroelectricity and ferromagnetism provides the potential for a new breed of multifunctional devices.

Pulsed laser co-deposition in air: a way of fabricating composite nanostructures

This work presents results of applying a method based on pulses laser co-deposition of a noble metal and a magnetic iron oxide for fabrication of ordered composite nanostructures. The experimental scheme includes two nanosecond laser beams with a wavelength of 1064 nm that ablate simultaneously two targets – Au and Fe2O3. The process is implemented in air – a condition that leads to a fast condensation of the ablated material into nanoparticles. By choosing different positioning of the ablation plumes and the substrate, composites of iron oxide nanoparticles decorated by noble metal ones can be fabricated. An external magnetic field applied close to the substrate orients and aligns the nanoparticles into chains. The effects of the processing parameters that define the geometry of the experiment are studied and presented. The method can be optimized for fabrication of complex composite nanostructures with applications in sensorics, optics and magneto-optics.

Specific Features of Reactive Pulsed Laser Deposition of Solid Lubricating Nanocomposite Mo-S-C-H Thin-Film Coatings.

This work investigates the structure and chemical states of thin-film coatings obtained by pulsed laser codeposition of Mo and C in a reactive gas (H2S). The coatings were analysed for their prospective use as solid lubricating coatings for friction units operating in extreme conditions. Pulsed laser ablation of molybdenum and graphite targets was accompanied by the effective interaction of the deposited Mo and C layers with the reactive gas and the chemical states of Mo- and C-containing nanophases were interdependent. This had a negative effect on the tribological properties of Mo–S–C–H nanocomposite coatings obtained at H2S pressures of 9 and 18 Pa, which were optimal for obtaining MoS2 and MoS3 coatings, respectively. The best tribological properties were found for the Mo–S–C–H_5.5 coating formed at an H2S pressure of 5.5 Pa. At this pressure, the x = S/Mo ratio in the MoSx nanophase was slightly less than 2, and the a-C(S,H) nanophase contained ~8 at.% S and ~16 at.% H. The a-C(S,H) nanophase with this composition provided a low coefficient of friction (~0.03) at low ambient humidity and 22 °C. The nanophase composition in Mo–S–C–H_5.5 coating demonstrated fairly good antifriction properties and increased wear resistance even at −100 °C. For wet friction conditions, Mo–S–C–H nanocomposite coatings did not have significant advantages in reducing friction compared to the MoS2 and MoS3 coatings formed by reactive pulsed laser deposition.

Microstructure and Properties of Inconel 625 Fabricated Using Two Types of Laser Metal Deposition Methods.

The effect of using two different deposition systems on the microstructure and mechanical properties was studied in this paper. For this purpose, laser-engineered net shaping (LENS) and high-power CO2 laser deposition processes were applied to fabricate Inconel 625 samples. The microstructure of the Inconel 625 produced by both additive techniques was characterized using light microscopy (LM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The mechanical properties were characterized by tensile tests and microhardness measurements. High-power laser application resulted in a strong <100> build texture, while, at low powers, the {011} <100> Goss component increased. Both types of deposited materials showed dendritic microstructures with Ti-, Mo-, and Nb-rich zones at the cell boundaries, where numerous precipitates (Nb2C, NbC, titanium carbides, Nb3Ni, and NbNiCr) were also observed. It was also noted that both variants were characterized by the same slope with a proportional length, but the Inconel 625 fabricated via LENS showed a higher average yield strength (YS; 524 MPa vs. 472 MPa) and ultimate tensile strength (UTS; 944 MPa vs. 868 MPa) and lower elongation (35% vs. 42%) than samples obtained with the high-power CO2 laser deposition process.

Boron-doped graphene synthesis by pulsed laser co-deposition of carbon and boron

Incorporating dopants, such as boron, in graphene, is crucial for many applications in electrochemistry, sensors, photovoltaics, and catalysis. Many routes have been investigated for the preparation of B-doped graphene (BG) films, including chemical processes. A different way to obtain boron-doped layers to better control the concentration of boron in the doped graphene film, is pulsed laser co-ablation of C and B solid sources followed by rapid thermal heating of the B-doped carbon film deposited on a metal catalyst. Amorphous a-C:B films, containing 2 at. % boron, are synthetized by pulse laser deposition onto a nickel film catalyst. Rapid thermal annealing at 1100 °C leads to the formation of boron-doped graphene films, characterized by Raman, XPS, FEG-SEM, HRTEM and AFM. The results confirm the production of 1–4 layer boron doped graphene films, with a similar 2 at. % boron concentration to that of the a-C:B used as the graphene solid precursor. Boron doping does not modify the nano-architecture of graphene, but increases the concentration of defects in the films. Our results pave a new way for boron doped graphene synthesis using laser processing in a controlled and reproducible way, in particular to achieve designed electrical and chemical properties in various electronic and electrochemical applications.

Features of Sliding Friction on Thin-Film Mo–S–C Coatings Prepared by Pulsed Laser Deposition

To obtain Mo–S–C thin-film coatings on steel substrates with varying structural and chemical states, pulsed laser codeposition method was used at room temperature, including the first ever use of reactive codeposition of Mo and C in H2S. The conditions are determined for obtaining sufficiently smooth layers with optimal local packing of atoms in amorphous MoSx and diamond-like carbon nanophases, which yielded relatively high wear resistance and a low sliding friction coefficient (~0.1) in air without a long running-in phase.

INVESTIGATION OF Pt:MgO COMPOSITE FILMS PREPARED BY MAGNETRON SPUTTERING AND PULSED LASER CO-DEPOSITION METHOD

Pt:MgO composite films are prepared on quartz substrates at room temperature by magnetron sputtering and pulsed laser co-deposition (MSPLC) method, in which the volume ratio of the composite film can be easily controlled by MSPLC method. The sample with Pt volume percents of 40%, 50%, 60% and 70% are prepared, and all the samples are further annealed at 800∘C for 30[Formula: see text]min. Impacts of Pt content on the structural and physical properties have been investigated. Pt (111), (002) and (220) peaks can be observed, and the peak intensity increases with the increase of Pt content, as can be seen from the X-ray diffraction (XRD) pattern. Scanning electron microscope (SEM) results show that the size and density of grains increase and the distance between grains is decreased with the volume fraction increase. Significant absorption peaks were observed for different volume percentage of Pt:MgO composite film. Absorption peaks can be observed at 200, 220, 250 and 275[Formula: see text]nm, corresponding to Pt volume percents of 40%, 50%, 60% and 70%, respectively. The observed red shift of the absorption peak can be mainly related to the increase of Pt grain sizes.

Influence of nanosecond laser irradiation on the structure and conductivity of BCx films

Thin-film precursors of BCx were formed by pulsed laser codeposition of boron and carbon. Targets made of pressed boron and carbon powders with an equal element content (B/C = 1/1) and an increased carbon content (B/C = 1/3) were used. The films were deposited on sapphire substrates at elevated temperature (700°C) which determined the initial properties of the precursor BCx films. Irradiation of the films was carried out by laser pulses of nanosecond duration with varying intensity. The films obtained by laser annealing of BCx (Q-BCx) were studied by scanning electron microscopy and micro-Raman spectroscopy. Irradiation under optimal conditions made allowed to realize pulsed melting of the films and partial preservation of their continuity on the substrate. The local structure of Q-BCx films and the nature of the changes in their electrophysical properties depended on the composition of the precursor films and the laser irradiation regimes.

Features of Pulsed Laser Annealing of BC3 Films on a Sapphire Substrate

The morphology, chemical composition, microstructure, and electrical properties of BC3 thin films subjected to melting by a nanosecond laser pulse are investigated. The original films have been created by pulsed laser codeposition of B and C onto a sapphire substrate at 150 and 350°C. Morphological changes in the films depended on their initial structural state. However, a “frozen” structure of both films after irradiation corresponded to the B-saturated graphite-like phase, the local composition of which varied due to the formation of inclusions of amorphous boron carbide. Before and after irradiation, the films exhibited a slightly decreasing dependence of the surface resistance with increasing temperature from 4.2 to 330 K. After laser irradiation, the films resistance has decreased by a factor of ~2.6.

Preliminary Study of Ge-DLC Nanocomposite Biomaterials Prepared by Laser Codeposition.

This paper deals with the synthesis and study of the properties of germanium-doped diamond-like carbon (DLC) films. For deposition of doped DLC films, hybrid laser technology was used. Using two deposition lasers, it was possible to arrange the dopant concentrations by varying the laser repetition rate. Doped films of Ge concentrations from 0 at.% to 12 at.% were prepared on Si (100) and fused silica (FS) substrates at room temperature. Film properties, such as growth rate, roughness, scanning electron microscopy (SEM) morphology, wavelength dependent X-ray spectroscopy (WDS) composition, VIS-near infrared (IR) transmittance, and biological properties (cytotoxicity, effects on cellular morphology, and ability to produce reactive oxygen species (ROS)) were studied in relation to codeposition conditions and dopant concentrations. The analysis showed that Ge-DLC films exhibit cytotoxicity for higher Ge doping.

Особенности импульсного лазерного отжига пленок ВС-=SUB=-3-=/SUB=- на сапфировой подложке

The morphology, chemical composition, microstructure and electrical properties of BC3 thin films subjected to melting by a nanosecond laser pulse were investigated. The original films were formed by pulsed laser co-deposition of B and C on a sapphire substrate at 150 and 350 °C. Morphological changes in the films depended on their initial structure. However, the structure “frozen” after irradiation in both films was attributed to the B-saturated graphite-like phase, the local composition of which varied due to the formation of inclusions of amorphous boron carbide. Before and after irradiation, the films showed a weakly decreasing dependence of the sheet resistance with increasing temperature from 4.2 to 330 K. After pulsed laser irradiation, the sheet resistance of the films decreased by ~ 2.6 times.

Integration of plasmonic Au nanoparticles in TiO2 hierarchical structures in a single-step pulsed laser co-deposition

The plasmonic resonance of noble metal nanoparticles (NPs) can be exploited to enhance the photoresponse of wide band gap oxides in view of several solar energy applications. Here, we demonstrate single-step synthesis of plasmonic Au nanoparticles integrated in TiO2 hierarchical nanoporous layers through a vapor phase pulsed laser co-deposition approach. Specifically, we report the fabrication and characterization of Au NPs-decorated TiO2 forest-like systems with tunable porosity and density as well as the morphological/structural evolution as a function of Au content and we discuss the corresponding optical properties. The effect of post-deposition thermal treatment has been investigated as well in order to control TiO2 crystallization and Au NPs nucleation and growth. Optical analyses show the onset of characteristic plasmonic resonance of Au NPs with the increase of film absorption in the visible range. Preliminary tests of photodegradation of methyl orange dye indicate that the integration of Au NPs leads to a significant increase of the catalytic activity of nanoporous TiO2. Our results suggest the potentiality of this approach for the synthesis and the integration of metallic NPs within wide band gap semiconductors, while paving the way toward novel plasmonic-based devices.

Activation of electrocatalytic properties of a-C films by doping with MoSex clusters

Nanocomposite a-C(Mo/MoSex) thin films containing amorphous carbon matrix a-C, nano-Mo and MoSex ≥2 clusters were obtained by pulsed laser co-deposition of carbon and MoSe2. The deposition was carried out at room temperature onto a graphite substrate. Atomic content of the MoSex≥2 phase did not exceed 25%. The use of a buffer gas at a pressure of 10 Pa allowed to obtain the maximum Se/Mo ratio in the films and to increase the concentration of sp2-hybridized C atoms for high conductivity realization. The formation of MoSex≥2 cluster inclusions was the essential factor for activation of hydrogen evolution reaction (HER) in 0.5 M H2SO4 aqueous solution. These clusters also promoted cathodic deposition of Pt nanoparticles on the surface of a-C(Mo/MoSex) in a H2SO4/KCl solution when a Pt anode was used as a source of Pt. Hybrid Pt/a-C(Mo/MoSex) thin-film coatings with a low Pt loading (~6 μg/cm2) exhibit excellent HER property, which noticeably exceeds that of relatively thick Pt coating prepared on a graphite substrate by pulsed laser deposition.

Synthesis micro-scale boron nitride nanotubes at low substrate temperature

High temperature synthesis methods produce defects in 1D nanomaterials, which ultimately limit their applications. We report here the synthesis of micro-scale boron nitride nanotubes (BNNT) at low substrate temperature (300 oC) using a pulsed CO2 laser deposition technique in the presence of catalyst. The electron microscopic analyses have shown the nanotubes distributed randomly on the surface of the substrate. The average diameter (∼0.25 μm) of a nanotube, which is the highest reported value to date, is estimated by SEM data and confirmed by TEM measurements. These nanotubes are promising for high response deep-UV photo-luminescent devices. A detailed synthesis mechanism is presented and correlated with the experimental results.

Ag–Al2O3 optical nanocomposites with narrow particle size distribution prepared by pulsed laser deposition

Ag nanoparticles with a narrow size distribution down to 3–4nm have been embedded in an Al2O3 matrix by a single step pulsed laser co-deposition. A two-beam laser setup and a single target which is composed of Ag and Al2O3 are used for achieving a controlled deposition. This approach allows the control of the laser fluency on each target independently. The resulting Ag/Al2O3 nanocomposite thin films exhibit a specific plasmon absorption. This easy-to-apply single step method allows precise particle size and distribution control at room temperature. Therefore the approach can be used for synthesis of various nanocomposite thin films of more complex materials on various substrates.

Structure and mechanical properties of W–Se–C/diamond-like carbon and W–Se/diamond-like carbon bi-layer coatings prepared by pulsed laser deposition

Bi-layer W–Se–C/diamond-like carbon (DLC) and WSex/DLC coatings were obtained by standard and shadow-masked pulsed laser co-deposition from WSe2 and graphite targets. W–Se–C coatings appeared as nanocomposites containing quasi-amorphous WSe2, WC, spherical β-W nanocrystalline particles encapsulated in WSe2 amorphous shell, and amorphous carbon phases. In WSex/DLC coatings, the formation of chemical bonds between W and C atoms was noticed at the interface. An increase of the C concentration over 40at.% increases hardness and elasticity (up to 2 times at ~60at.%C), and the Se/W ratio was always close to 1.4. The use of shadow-masked configuration avoids the deposition of micro- and nanoparticles. However, this method leads to a substantial increase of the Se content (Se/W≥4), and the coatings became softer.

Pulsed laser deposition of composite Mo–Se–Ni–C coatings using standard and shadow mask configuration

Thin film Mo–Se–Ni–C coatings for tribologycal applications were prepared by pulsed laser co-deposition from two targets — MoSe2(Ni) and graphite. Two methods of deposition from the MoSe2(Ni) target were used: deposition with unhindered expansion of the laser plume (standard PLD) and deposition of a plume scattered in collisions with Ar gas (pressure 2Pa) in the shadow of a mask (shadow-masked PLD — SMPLD). Doping with carbon by PLD was used in all cases, and carbon content in the composite Mo–Se–Ni–C coatings was varied in the range 35–85.5at.%. Pure MoSex(Ni) coatings were also prepared by PLD and SMPLD. Rutherford backscattering spectroscopy of helium ions, scanning electron and atomic force microscopy, electron probe microanalysis, transmission electron microscopy and micro-diffraction, micro-Raman spectroscopy, X-ray photoelectron spectroscopy and hardness evaluation were all used for comparative studies of the coatings obtained by PLD and SMPLD/PLD. In the PLD coatings, micron-sized particles were found, consisting of pure Ni or MoSe2, as well as nanometre-sized particles of monocrystalline Mo. The nanoparticles were distributed on the surface and in an amorphous matrix in all PLD coatings. Within the amorphous matrix of the Mo–Se–Ni–C coatings, local ordering of atoms was detected, causing the formation of a mixture of amorphous carbon, Mo–C, and Mo–Se phases. Increasing the carbon content caused an increase in the content of sp3 bonds in the carbon phase, and an increase in the hardness of the coatings. SMPLD/PLD coatings had no micro- and nanoparticles, but these coatings were characterized by high selenium content and reduced density. Doping with carbon in the SMPLD/PLD configuration caused the formation of composite coatings containing Mo–Se and amorphous carbon phases as in the PLD coatings, but the hardness of the composite SMPLD/PLD coatings was significantly lower than even the hardness of the pure PLD MoSex(Ni) coatings.

Effect of the pulsed laser deposition conditions on the tribological properties of thin-film nanostructured coatings based on molybdenum diselenide and carbon

The structural state and tribological properties of gradient and composite antifriction coatings produced by pulsed laser codeposition from MoSe2(Ni) and graphite targets are studied. The coatings are deposited onto steel substrates in vacuum and an inert gas, and an antidrop shield is used to prevent the deposition of micron-size particles from a laser jet onto the coating. The deposition of a laser jet from the graphite target and the application of a negative potential to the substrate ensure additional high-energy atom bombardment of growing coatings. Comparative tribological tests performed at a relative air humidity of ∼50% demonstrate that the “drop-free” deposition of a laser-induced atomic flux in the shield shadow significantly improves the antifriction properties of MoSe x coatings, decreasing the friction coefficient from 0.07 to 0.04. The best tribological properties, which combine a low friction coefficient and high wear resistance, are detected in drop-free MoSe x coatings additionally alloyed with carbon (up to ∼55 at %) and subjected to effective bombardment by high-energy atoms during growth. Under these conditions, a dense nanocomposite structure containing the self-lubricating MoSe2 phase and an amorphous carbon phase with a rather high concentration of diamond bonds forms.