Laser Deposition Technology Research Articles

Variations of the elemental composition distribution over the thickness of YBa2Cu3O7-δ thin films obtained by pulsed laser deposition from one target

Epitaxial YBa2Cu3O7‒δ (YBCO) films 150-200 and 300 nm thick, respectively, were deposited on SrTiO3 (100) substrates by pulsed laser deposition at different conditions: with and without using the velocity filtration technique. The films have T(R=0) in the range of 77.4 - 87 R(T) depending on the conditions of deposition from one target with YBa2Cu3O6.8 composition. The films contain Zn, Sr, Pd, Ag and Ti impurity elements obtained from the target (a total of no more than 2 at. % ). Data of the film resistance temperature dependences, X-ray phase analysis, analysis of X-ray fluorescence (XRF) spectra and study of the surface relief by SEM methods revealed the nonuniform distributions of impurity and matrix Y, Ba, Cu elements over the film depth. Impurity concentrations near the surface lead to the formation of faceted spiral pyramids on the surface, which probably evolve into large elongated particles according to the Ostwald mechanism. This knowledge is practically important for optimizing pulsed laser deposition technologies and creating 2D instruments and devices for studying physical phenomena.

Effect of mechanical vibration on microstructure and performance of Fe-based composite coatings fabricated by underwater laser deposition technology

To solve the problem of the uneven composition and poor performance caused by water environment during the underwater laser deposition process, the mechanical vibration assisted underwater laser deposition technology was innovatively proposed, and Fe-based composite layer was successfully prepared. The microstructure, grain type and properties of Fe-based composite layer with and without mechanical vibration were studied and compared. The results showed that the mechanical vibration broke the grain and promoted the formation of more nuclei, which reduced the average grain size by 13.48 %. The solute located in the grain gap was transferred to the liquid molten pool by mechanical vibration, which reduced the Ti content in the intergranular precipitated phase Fe2Ti and made the Fe2Ti from coarse continuous distribution to fine discontinuous distribution. Additionally, the mechanisms of mechanical vibration promoting the performance of the composite were analyzed comprehensively. Compared with the composite without mechanical vibration, the composite with mechanical vibration had good corrosion resistance after 30 days of immersion, and the tribo-corrosion resistance was also improved. With the aid of mechanical vibration, the ultimate tensile strength and elongation of the composite were increased by 11.30 % and 22.08 %, respectively, due to the formation of recrystallized grains, high density high-angle grain boundaries, and fine intergranular precipitate. This study was expected to provide a new way to regulate the microstructure and properties of the underwater laser deposition layer, and promote the application of underwater laser deposition technology in marine engineering equipment.

High responsivity and detectivity β-Ga2O3 solar-blind photodetectors optimized by oxygen vacancy engineering

Solar-blind photodetectors (SBPDs) are core essential components for many critical applications such as precision guidance, fire warning, and space communications. Ultra-wide bandgap semiconductor β-Ga2O3 is considered to be an ideal material for the fabrication of SBPDs. However, synthetizing β-Ga2O3 with high quality factor while simultaneously in situ modulation of electronic and optoelectronic properties to enhance performance has been challenging. Here, pulsed laser deposition (PLD) technology is used to synthesize high-quality β-Ga2O3 thin films on a sapphire substrate. The oxygen vacancy engineered β-Ga2O3 films can achieve in situ precise control of their surface morphology, optical parameters, and optoelectronic properties by simply adjusting the oxygen pressure. Meanwhile, the optimal thickness of the β-Ga2O3 film for the developing high-performance SBPD is ∼221 nm, determined by fitting and analyzing the optical parameters measured by the ellipsometry. Subsequently, the influence of oxygen pressure on the performance of β-Ga2O3 SBPD is thoroughly explored, considering the optimization of electrode size and deposition time. When the oxygen pressure is set to 15 Pa, the β-Ga2O3-based SBPD achieves highly competitive responsivity (R) and detectivity (D*) at 250 nm, with values of 1080 A·W−1 and 1.4 × 1016 cm·W−1·Hz1/2, respectively. Additionally, the noise component of the β-Ga2O3 SBPD is further studied to calibrated the traditional device performance results. This work introduces a simple and straightforward approach to in situ tuning of the optoelectronic properties of β-Ga2O3, which is important for advancing β-Ga2O3 film growth technology and fabricating high-performance photodetectors.

A novel photoelectrochemical based water splitting and uric acid biosensing using PLD grown In2Se3 thin films

By altering the deposition pressure during the film growth process using the pulsed laser deposition (PLD) technology, indium selenide (In2Se3) thin films have been optimized to produce their distinct phases. The phase purity, optical and morphological studies were carried out using XRD, Raman spectroscopy, XPS, UV–visible spectroscopy, AFM and FESEM measurements. A high absorption in the visible region is observed for In2Se3 thin films with suitable band edges for hydrogen evolution. Photoelectrochemical (PEC) activity for In2Se3 photoelectrodes having various phases was analyzed based on CV and I-t response. A good charge transport characteristics were observed using the EIS measurements on PLD grown In2Se3 thin films. The Mott–Schottky analysis for the charge carrier density, flat band potential, and depletion layer width was performed for the deposition pressure dependent phase formation and high performance for PEC water splitting conversion efficiency of 0.48 %, 0.57 % and 0.98 % corresponding to α-In2Se3, β-In2Se3 and γ-In2Se3 were observed, respectively. The as prepared In2Se3 thin films were employed for the detection of Uric Acid (UA) using the cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry. The high sensitivity (0.38 mA/mM), selectivity and repeatability of the prepared biosensor demonstrates In2Se3 as potential candidate for the PEC based water splitting and biosensing application without the presence of an external mediator and can work in the self-powered mode.

Brushy C-Decorated BiTe-Based Thermoelectric Film for Efficient Photodetection and Photoimaging.

Current strategies for simultaneously achieving high thermoelectric performance and high light absorption efficiency still suffer from complex steps and high costs. Herein, two kinds of amorphous thermoelectric films of n-type Bi2Te3 and p-type Bi0.5Sb1.5Te3 with high Seebeck coefficients were prepared by pulsed laser deposition (PLD) technology. In addition, C-decorated films with excellent light absorption efficiency at the junction of the thermoelectric legs were prepared by simple drop coating and reactive ion etching (RIE) method. The TE/C-RIE composite device exhibits excellent photodetection performance under the conditions of simulated natural light, monochromatic light, and high-frequency chopping. The maximum responsivity and specific detectivity of the device can reach 153.58 mV W-1 and 6.97 × 106 cm Hz1/2 W-1 (under simulated natural light), respectively. This represents an improvement rate of 85.91% compared to that of the pure TE device. Benefiting from the excellent photodetection efficiency of the device and integration advantage of PLD technology, the composite structure can be expanded into integrated photoimaging devices. The accurate identification of patterned light sources with letters (T, J, and U) and digitals (0-9) was successfully realized by associating the response electrical signals of each electrode with the position coordinates. This work provides valuable guidance for the design and fabrication of wide-spectrum photodetectors and complex optical imaging devices.

Wafer-scale mesoporous GaN distributed bragg reflectors with enhanced luminescence for Eu doped β-Ga2O3 thin films

Wafer-scale Mesoporous GaN (MP-GaN) distributed Bragg reflectors (DBRs) with high reflectivity (>99 %) are prepared by electrochemical etching, and then are used as the substrate in growth of large-area europium (Eu) doped Ga2O3 thin films via the pulsed laser deposition (PLD) technology. X-ray diffraction analysis shows that all Ga2O3 thin films with different doping concentration have monoclinic β-Ga2O3 structures with [−201] orientation. The angle of β-Ga2O3 (−201) peak decreases as Eu contents increases, which is due to the fact that Eu3+ substituting for Ga3+ rises the lattice constant of β-Ga2O3. With the increase of Eu doping, the photoluminescence (PL) of the Ga2O3 thin film is enhanced. The epitaxial relationship is β-Ga2O3 (−201) || GaN (0001) with β-Ga2O3 [010] || GaN [-12-10]. Compared to the sample without DBRs, wafer-scale Ga2O3 thin films with MP-GaN DBRs exhibit a markedly increased PL intensity, which is attributed to improved internal quantum efficiency (IQE) of Ga2O3 thin films and enhanced light extraction efficiency (LEE) related to the light reflection effect of MP-GaN DBRs.

Impact of laser energy density on the structure and properties of laser-deposited Fe‒Ni‒Ti composite coatings

To utilise laser deposition for the preparation of high-strength, wear-resistant components, the service life of components in rail transportation equipment should be improved. Laser deposition technology is used to fabricate Fe‒Ni‒Ti coatings on the surface of AISI 1045 steel substrates. By varying the laser power to adjust the laser energy density, Fe‒Ni‒Ti composite coatings are prepared at various energy densities. The morphology, microstructure, phase composition, tensile strength, microhardness, and friction-wear characteristics of the composite coatings are observed and tested. The influence patterns and mechanisms of laser energy density on the organisational variation and friction-wear performance of composite coatings is investigated. When the laser energy density is 97.2 J/mm2 (1400 W), the residual stresses in the deposition layer are minimised, resulting in fewer cracks and gas pore defects, with a porosity rate reaching its lowest value of 1.2% and a density of 99.1%. With the increase in energy density, both the tensile strength and elongation of the deposited layer exhibited an initial increase followed by a decrease. The hardness and wear resistance of Fe‒Ni‒Ti deposition layers is effectively controlled by regulating the laser energy density.

Energy Storage Performance of (Na0.5Bi0.5)TiO3 Relaxor Ferroelectric Film

The (Na0.5Bi0.5)TiO3 relaxor ferroelectric materials have great potential in high energy storage capacitors due to their small hysteresis, low remanent polarization and high breakdown electric field. In this work, (Na0.5Bi0.5)TiO3 thin films with ~400 nm were prepared on (001) SrTiO3 substrate by pulsed laser deposition technology. The (Na0.5Bi0.5)TiO3 films have good crystallization quality with a dense microstructure and relaxor ferroelectric properties, as confirmed by the elongated hysteresis loops and the relation of <A>∝Eα. A high Eb of up to 1400 kV/cm is obtained, which contributes to a good Wrec of 24.6 J/cm3 and η of 72% in (Na0.5Bi0.5)TiO3 film. In addition, the variations of Wrec and η are less than 4% and 10% in the temperature range of 20–120°C. In the frequency range of 103 Hz–2 × 104 Hz, the variations of Wrec and η are less than 10%. All those reveal the great potential of NBT film for energy storage.

Effect of laser energy density on microstructure and critical current of YGBCO and HGBCO films fabricated by PLD

Y0.5Gd0.5Ba2Cu3O7-σ (YGBCO) and Ho0.5Gd0.5Ba2Cu3O7-σ (HGBCO) targets with similar densities were prepared by solid-phase reaction. Pulsed laser deposition (PLD) technology was used to fabricate superconducting films with these targets. During the experiments in this paper, we varied the laser energy by adjusting the optical lens. The structure and texture of RE0.5Gd0.5Ba2Cu3O7-σ (REGBCO, where RE = Y, Ho) thin films were analyzed by X-ray diffraction (XRD). The surface morphology was observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the superconducting critical current was measured at 77 K using the standard four-probe method. The laser energy density and different doping elements can affect the properties of REGBCO films. This may be related to the ejection process of target particles and the size of rare earth atoms. Additionally, we prepared a 510-meter long second-generation high-temperature superconducting tape with the optimized parameters. The critical current of the tape is 350 A, and the current density is 3.9 × 106 A/cm2.

Emergent high-temperature insulating ferromagnetism in Sr4Fe5CoO13- δ epitaxial thin films

High-temperature ferromagnetic insulators play a crucial role in a wide range of emerging magnetoelectricity phenomena and hold the potential to become fundamental components of upcoming spintronic devices. However, the strong interaction between ferromagnetism and metallic properties presents a challenge, impeding the development of high-temperature ferromagnetic insulators based on oxides. Heterostructures or superlattice materials, especially those containing perovskite layers, offer a forward-looking solution. In this work, high-quality Sr4Fe6O13 (SFO) and cobalt-doped SFO (Sr4Fe5CoO13-δ, SFCO) thin films were grown on Nb-SrTiO3(001) substrates using pulsed laser deposition technology. The grown SFO films exhibit paramagnetism, possibly due to the transition of their film structure from the orthorhombic to the tetragonal phase. In contrast to SFO films, high-quality SFCO thin films exhibit significant ferromagnetism at room temperature, with Curie transition temperature as high as 800 K. This phenomenon is mainly attributed to the formed Dzyaloshinskii–Moriya interactions between Fe–O–Co and increased lattice distortions caused by Co-doping. In contrast, the Curie transition temperature of the SFCO film is slightly higher than that of the SFCO ceramics. This enhancement is likely due to surface effects, where an increase in surface energy introduces additional energy barriers at the film surface and interface, thereby enhancing the thermal stability of the film. These characteristics advance the research of high-temperature magnetic insulators and broaden the operating temperature range of spintronic devices based on ferromagnetic insulators.

High‐Throughput Exploration of Phase Evolution in (Pb1−XBaX)ZrO3 Thin Films

AbstractAntiferroelectric thin films hold significant potential for bringing novel physics phenomena and fascinating properties. Their applications are often intertwined with the antiferroelectric‐ferroelectric phase transition, which is contingent on the chemical compositions of the constituent material. Nevertheless, the prevailing trial‐and‐error‐based research methodology is ill‐suited for the exploration of the relationship between chemical compositions and the antiferroelectric‐ferroelectric phase transition. To address this challenge, a high‐throughput synthesis strategy for antiferroelectric thin films is presented, which is enabled by an advanced high‐throughput pulsed laser deposition technology. The effectiveness of this synthesis strategy using (Pb1−XBaX)ZrO3 and achieving precise control over the parameter X is showcased. This approach allows for the deposition of (Pb1−XBaX)ZrO3 thin films encompassing nine chemical compositions ranging from X = 0 to X = 0.08. Based on this high‐throughput method, the composition that corresponds to the phase transition of (Pb1−XBaX)ZrO3, falling within the range of X = 0.04 to X = 0.06 is pinpointed. Furthermore, a temperature‐dependent correlation between the phase transition and chemical composition is established. This work not only presents a practical routine for establishing a comprehensive map of material chemical composition in relation to the properties of antiferroelectric thin films but also offers a method for the high‐throughput exploration of complex oxide thin films.

Effects of film thickness on crystal structure, surface topography, optical, and photoelectric properties of Ga2O3 thin film based solar blind photodetectors

β-Ga2O3 epitaxial thin films with different thicknesses were grown on Al2O3 (0001) substrates by the pulse laser deposition technology. The full width at half maximum of XRD rocking curve, grain size, surface roughness, and optical absorbance (200–300 nm) of the β-Ga2O3 films increase with increasing film thickness. In addition, with increasing film thickness, the adsorption edge presents a red-shift phenomenon, which is accompanied by a slight decrease in the optical band gap (). The metal-semiconductor-metal type photodetector made with the 401-nm β-Ga2O3 film shows the maximal photocurrent (1.06 μA @ 10 V), photo-to-dark current ratio (6.96 × 104), responsivity (90 mA W−1), and detectivity (0.5 × 1011 Jones) under 254-nm UV light illumination with a light intensity of 98.4 μW/cm2. Moreover, the 401-nm photodetector displays a small rise time of 0.111/0.561 s and a decay time of 0.046/0.047 s as well as a good stability and repeatability. These findings provide useful reference for the fabrication of β-Ga2O3 film based solar blind ultraviolet photodetectors.

Relaxor Ferroelectric AgNbO3 Film Fabricated on (110) SrTiO3 Substrates via Pulsed Laser Deposition

AgNbO3-based materials have attracted extensive attention in energy storage due to their double hysteresis loops, but they suffer from low breakdown strength (Eb). AgNbO3 films with few defects and small thickness exhibit high Eb, which helps to improve the energy storage performance. In this work, we successfully prepared AgNbO3 thin films on (110) SrTiO3 substrate using pulsed laser deposition technology. The AgNbO3 film shows good crystalline and relaxor ferroelectric behavior. A high Eb up to 1200 kV/cm is obtained in AgNbO3 film, which contributes to good recoverable energy storage density Wrec up to 10.9 J/cm3 and energy efficiency η of 75.3%. Furthermore, the Wrec remains above 2.9 J/cm3 and the η varies between 72.5% and 82.5% in a wide temperature range of 30–150 °C. This work reveals the great potential of relaxor ferroelectric AgNbO3 film for energy storage.

Effect of Sc on the microstructure and mechanical properties of direct laser-deposited/Al-Cu-Mg-Sc composite coatings

In order to improve the poor plasticity and uneven distribution of ceramic phases in ceramic-reinforced aluminum-based composites, 40 wt% TiC/Al-Cu-Mg-Sc composite depositional layers with different Sc additions were prepared by direct laser deposition (DLD) technology. The microstructure of the deposition layers was characterized by Optical Microscopy (OM), X-ray diffractometer (XRD), Scanning Electron Microscopy (SEM) with Energy Spectrometer (EDS), Electron Backscatter Diffractometer (EBSD), and its mechanical properties were characterized by Bush hardness and room temperature tensile test, respectively. The results showed that the deposition layer was well formed with few macroscopic defects, and an appropriate amount addition of Sc could not only effectively improve the fluidity of the molten pool and promote grain refinement, but also make the distribution of TiC particles more uniform, The composite deposition layer with 0.2 wt% Sc addition showed the best combination of plasticity and strength among all the samples. Meanwhile, the yield strength, tensile strength and elongation reached 126 MPa, 229 MPa and 3.1 %, respectively, which were 4.1 %, 5.5 % and 34.6 % higher than that of deposition layer without Sc addition.

Development of Direct Laser Deposition Technology for Large-Scale Products of Nuclear Power Engineering

Development of Direct Laser Deposition Technology for Large-Scale Products of Nuclear Power Engineering

Preparation and tribological properties of NiCr–Mo–Ag–O/Mo–V–Ag–O bilayer film at RT-1000 °C

The primary objective of this research is to investigate the structure and tribological properties of NiCr–Mo–Ag–O/Mo–V–Ag–O bilayer films in a wide temperature range (RT-1000 °C). The bilayer films were prepared by pulsed laser deposition (PLD) technology, so as to provide the theoretical basis and experimental guidance for the study of the synergistic lubricating effect of Mo and V bimetallic lubricating oxides. The NiCr–Mo–Ag–O composite target was fabricated by the hot-press sintering technique. Subsequently, a NiCr–Mo–Ag–O/Mo–V–Ag–O bilayer film was deposited on Inconel 718 by pulsed laser deposition (PLD). The tribological properties of the film were evaluated by HRT-1000 high-temperature ball-on-disc configuration at RT-1000 °C. The obtained results reveal that the NiCr–Mo–Ag–O target is marked by a compact structure and homogeneous composition. Furthermore, the composite film exhibits a smooth surface and dense structure, comprised of polycrystalline and amorphous phases. The measured hardness and elastic modulus of the film approximated 4.9 GPa and 153.5 GPa, respectively. Additionally, the lowest friction coefficient of the film is about 0.28 at 800 °C. Upon reaching this temperature, the cooperative lubrication resulting from NiMoO4, Ag2Mo2O7, and AgVO3 contributed effectively towards reducing the film's friction coefficient.

Remarkable average thermoelectric performance of the highly oriented Bi(Te, Se)-based thin films and devices

Bi(Te, Se)-based compounds have attracted lots of attention for nearly two centuries as one of the most successful commercial thermoelectric (TE) materials due to their high performance at near room temperature. Compared with 3D bulks, 2D thin films are more compatible with modern semiconductor technology and have unique advantages in the construction of micro- and nano-devices. For device applications, high average TE performance over the entire operating temperature range is critical. Herein, highly c-axis-oriented N-type Bi(Te, Se) epitaxial thin films have been successfully prepared using the pulsed laser deposition technology by adjusting the deposition temperature. The film deposited at ∼260 °C demonstrate a remarkable average power factor (PFave) of ∼24.4 μW·cm−1·K−2 over the temperature range of 305–470 K, higher than most of the state-of-the-art Bi(Te, Se)-based films. Moreover, the estimated average zT value of the film is as high as ∼0.81. We then constructed thin-film TE devices by using the above oriented Bi(Te, Se) films, and the maximum output power density of the device can reach up to ∼30.1 W/m2 under the temperature difference of 40 K. Predictably, the outstanding average TE performance of the highly oriented Bi(Te, Se) thin films will have an excellent panorama of applications in semiconductor cooling and power generation.

Preparation of Novel Heterodimensional Structured Chalcogenide Semiconductor Nano‐Film by Pulsed Laser Deposition Technology

AbstractChalcogenide based nano‐films have attracted considerable attention as a new type of semiconductor material in the fields of optical waveguides, laser devices, and solar cells. However, it remains challenging to use them effectively in a variety of fields, mainly due to their intricate fabrication procedures and limited electrical characteristics. In this study, zinc selenide (ZnSe) is doped with molybdenum (Mo) and gallium (Ga). The heterodimensional structured chalcogenide semiconductor nano‐film is obtained by pulsed laser deposition (PLD). The results of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirm that the structure of the nano‐film is compact and the composition is uniformly distributed. The transmittance of all samples is close to 100% in the 400–2000 nm range shown. The P/N type of the film can be controlled by changing the preparation conditions. All the results indicate that the novel heterodimensional structured chalcogenide semiconductor nano‐film in this study has a simple and efficient preparation method, controllable composition, and unique optical/electrical properties. These properties can be used in integrated circuits and photovoltaic power generation.

Tribological Behavior of Ti-Coated Diamond/Copper Composite Coating Fabricated via Supersonic Laser Deposition

Diamond/copper composite coating is promising for wear-resistant applications, owing to the extreme hardness of the diamond reinforcement. Ti-coated diamond/copper composite coatings with various laser powers were successfully fabricated employing the novel manufacturing technology of supersonic laser deposition (SLD). Ti-coated diamond, which was able to enhance the wettability between diamond and copper, was prepared at the optimal parameters via salt bath. Nano-spherical titanium carbides were uniformly distributed on the diamond’s surface to generate a favorable interface bonding with a copper matrix though mechanical interlocking and metallurgical bonding during impact. Furthermore, the results showed that the transition layer acted as a buffer, preventing the breakage of the diamond in the coating. SLD can prevent the graphitization of the diamonds in the coating due to its low processing temperature. The coordination of laser and diamond metallization significantly improved the tribological properties of the diamond/copper composite coatings with the SLD technique. The microhardness of the diamond/copper composite coating at a laser power of 1000 W reached about 172.58 HV0.1, which was clearly harder than that of the cold sprayed copper. The wear test illustrated that the diamond/copper composite coating at a laser power of 1000 W exhibited a low friction coefficient of 0.44 and a minimal wear rate of 11.85 μm3·N−1·mm−1. SLD technology shows great potential in the field of preparing wear-resistant hard reinforced phase composite coatings.

Analysis of the influence of LMD laser surfacing parameters on selected propertiesof the surfacings produced from HS6-5-2c powder on 1.4923 steel

This paper presents the results of testing surfacings produced by LMD (Laser MetalDeposition) laser deposition technology at different laser beam parameters. On the surface layer ofrectangular-shaped samples made of 1.4923 steel, multiwall surfacing was produced from HS6-5-2cpowder with different degrees of coverage. As part of the laser deposition verification and testing,surface topography, microstructure and hardness tests were carried out in the deposition zone, heataffectedzone and the zone of the parent material. The surface of the surfacing and the microstructurein cross-section were observed on an optical microscope with fibre-optic image transmission. Hardnessmeasurements were made in the cross-section of the sample using a Vickers FLC-50A hardness tester.Based on the observations, it was found that the obtained surfacings have a regular and repeatableshape. There were no welding defects on the surfaces of the produced surfacings and in the zoneof fusion of the surfacing material with the substrate material. The hardness of the surfacings wasobtained in the range of 500-700 HV0.1. The produced surfacings by LMD technology were subjectedto erosion resistance tests, which showed significantly higher (about 5. times) resistance to erosionwear of the produced surface layers (surfacings based on HS6-5-2c powder) in comparison with thesubstrate material, i.e. steel 1.4923.Keywords: steel 1.4923, HS6-5-2c alloy powder, LMD laser deposition, surface layer, depositiongeometry, chemical composition, microstructure, hardness, erosion