Pulsed Excimer Laser Deposition Research Articles

Tuning the tribological property of PLD deposited DLC-Au nanocomposite thin films

Nonhydrogenated Diamond-like Carbon-gold (DLC-Au) nanocomposite thin films with various Au contents and cluster size (<10 nm) have been engineered using Excimer Pulsed Laser Deposition (PLD) on silicon (100) substrates with an aim to achieve reduced coefficient of friction (CoF). Structure, microstructure, chemical bonding and chemical composition of these films were comprehensively investigated using X-ray diffraction (XRD), High resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron spectroscopy (XPS), respectively. It is observed that the DLC matrix with lowest Au content sustained higher sp3 content due to enhanced interaction of carbon and smaller Au nano-cluster formed in these films. DLC-Au Nanocomposite formation takes place due to the low compatibility between carbon and gold which resulted in ultra-smaller Au crystallites in DLC matrix at lowest Au content. This enhanced the sp3 content in DLC films and induces tribofilm nucleation on the ball counter body with large amount of sp2 phase fraction which significantly reduced the CoF.

Microstructure and nanomechanical properties of pulsed excimer laser deposited DLC:Ag films: Enhanced nanotribological response

Diamond-like carbon:silver (DLC:Ag) thin films, with metal contents as high as 16.8at.%, have been deposited on silicon substrates using pulsed excimer laser deposition; the produced DLC:Ag films sustain a substantial sp3 content (36%) in the DLC matrix even for the highest Ag content (~16.8at.%), in contrast to previous reports. The morphological, topographical, crystallographic, compositional and mechanical/tribological characteristics of the films have been studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nanoindentation/nanoscratch tests, respectively. The low miscibility between carbon and silver leads to a nanocomposite material that exhibits a reduced elastic modulus and hardness that scale inversely with the silver content. The mechanical capacity reduction is attributed to the incorporation of the soft/compliant silver phase and the subsequent graphitization of the amorphous carbon matrix, as quantified through XPS. This mechanical softening response, however, is coupled with an increased ductility and an enhanced tribomechanical response (70% increase in the critical load to film failure), making this class of DLC-metal nanocomposites of great interest for protective coatings and other functional applications.

Laser-induced thermoelectric voltage effect of La0.9Sr0.1NiO3 films

Laser-induced thermoelectric voltage effect signal was observed in the La0.9Sr0.1NiO3 (LSNO) thin films grown on LaAlO3 single crystal substrate which is cut with 5° tilting angle along the 〈100〉 direction by excimer pulsed laser deposition. The results of the LITV measurement demonstrated that the peak voltage of LSNO thin films was strong and could reach as large as 700mV when laser energy density is 2mJ/mm2. The rising time of LITV signal was less than 20ns. Moreover, the peak voltage increased linearly with the single-pulse laser energy density. Above characteristics indicate LSNO thin films are a potential candidate for laser energy/power detectors is an excellent choice.

Hybrid Perovskite Films by a New Variant of Pulsed Excimer Laser Deposition: A Room-Temperature Dry Process

A new variant of the classic pulsed laser deposition (PLD) process is introduced as a room-temperature dry process for the growth and stoichiometry control of hybrid perovskite films through the use of nonstoichiometric single target ablation and off-axis growth. Mixed halide hybrid perovskite films nominally represented by CH3NH3PbI3–xAx (A = Cl or F) are also grown and are shown to reveal interesting trends in the optical properties and photoresponse. Growth of good quality lead-free CH3NH3SnI3 films is also demonstrated, and the corresponding optical properties are presented. Finally, perovskite solar cells fabricated at room temperature (which makes the process adaptable to flexible substrates) are shown to yield a conversion efficiency of about 7.7%.

Probing on Growth and Characterizations of SnFe2O4 Epitaxial Thin Films on MgAl2O4 Substrate

Epitaxial tin ferrite (SnFe2O4) thin films were grown using KrF excimer (248 nm) pulsed laser deposition technique under different growth conditions. Highly epitaxial thin films were obtained at growth temperature of 650 ˚C. The quality and epitaxial nature of the films were examined by X-ray diffraction technique. Furthermore, the phi scans of the film and substrate exhibit four folds symmetry which indicates a cube-on-cube epitaxial growth of the film on MgAl2O4 substrate. Moreover, the magnetic force microscopy measurement shows domains with cluster-like structure which is associated with ferromagnetic phase at room temperature. The coercive field and remnant magnetization of the films decrease with increase in temperature. These high quality ingenious magnetic films could be potentially used in data storage devices.

Electrical and optical properties of ITO and ITO/Cr-doped ITO films

In this paper we report on the effects of the insertion of Cr atoms on the electrical and optical properties of indium tin oxide (ITO) films to be used as electrodes in spin-polarized light-emitting devices. ITO films and ITO(80 nm)/Cr-doped ITO(20 nm) bilayers and Cr-doped ITO films with a thickness of 20 nm were grown by pulsed ArF excimer laser deposition. The optical, structural, morphological and electrical properties of ITO films and ITO/Cr-doped structures were characterized by UV–Visible transmission and reflection spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Hall-effect analysis. For the different investigations, the samples were deposited on different substrates like silica and carbon coated Cu grids. ITO films with a thickness of 100 nm, a resistivity as low as ∼4×10−4 Ω cm, an energy gap of ∼4.3 eV and an atomic scale roughness were deposited at room temperature without any post-deposition process. The insertion of Cr into the ITO matrix in the upper 20 nm of the ITO matrix induced variations in the physical properties of the structure like an increase of average roughness (∼0.4–0.5 nm) and resistivity (up to ∼8×10−4 Ω cm). These variations were correlated to the microstructure of the Cr-doped ITO films with particular attention to the upper 20 nm.

A trial of Fe(Se1−xTex) thin film fabrication by pulsed laser deposition using ArF excimer laser

We fabricated Fe(Se1−xTex) thin films on LSAT(100), MgO(001), R-Al2O3 substrates by ArF excimer pulsed laser deposition (ArF-PLD) and investigated pulse repetition rate dependence on film growth of Fe(Se1−xTex) thin films in ArF-PLD. Through x-ray diffraction measurements of Fe(Se1−xTex) thin films grown by ArF-PLD, 00l peaks of Fe(Se1−xTex) were confirmed in Fe(Se1−xTex) thin films grown by pulse repetition rate of 10 Hz but the 00l peaks were not confirmed in Fe(Se1−xTex) thin films grown at 5 Hz. Atomic force microscopy (AFM) revealed that 100 ~ 250 nm sized grains were formed on surface of the thin films grown at 10 Hz. It was found that the thin films grown at 5 Hz were formed thinner than those grown at 10 Hz, in spite of the same pulses. Energy dispersive x-ray spectroscopy (EDX) analysis revealed that composition elements of the thin films grown at 5 Hz were re-evaporated from them more than those grown at 10Hz. In ρ-T measurements of the thin films grown at 10 Hz, it was confirmed that the thin films has TConset = 6.5 ~ 10.5 K and TC0 of the Fe(Se1−xTex) thin film on an MgO substrate is 3.9 K.

Preparation of C-axis textured LiNbO 3 thin films on SiO 2/Si substrates with a ZnO buffer layer by pulsed laser deposition process

Highly C-axis textured LiNbO 3 thin films were grown on SiO 2/Si substrates with a ZnO buffer layer by XeCl excimer pulsed laser deposition technique. We fixed the target–substrate spacing at 40 mm, oxygen flow rate of 20 sccm and the repetition rate of 5 Hz, and then changed the substrate temperature, energy density and oxygen pressure to obtain the optimum deposition conditions. The effect of post-annealing process on improving the structural properties of the as-deposited LiNbO 3 thin films was also studied. The ZnO buffer layers and LiNbO 3 films were characterized by X-ray diffraction (XRD), atomic force microscopy and scanning electron microscopy to analyze their crystalline structure, surface roughness and surface morphology, respectively. For the optimum deposition parameters such as substrate temperature of 700 °C, energy density of 4.6 J/cm 2 and oxygen pressure of 150 Pa, the full width at half maximum intensity (FWHM) of LiNbO 3(0 0 6) peak was 0.22°. The FWHM of LiNbO 3(0 0 6) peak was further reduced to 0.19° via. in-situ post-treatment at 750 °C for 30 min. The results could be useful for integrating the surface acoustic wave device, optical waveguide and semiconductor device on the same Si substrate.

Preparation of c-axis textured SrTiO3 thin films on Si(100) substrates by pulsed laser deposition process

Abstract Highly c-axis textured SrTiO3 (STO) thin films were directly grown on Si(1 0 0) substrates by XeCl excimer pulsed laser deposition technique without the utilization of buffer layer. Among the important deposition parameters, the substrate temperature, oxygen pressure, and target-to-substrate distance imposed most significant effect on the c-axis preferred orientation characteristics of the STO thin films. For the optimum deposition parameters such as substrate temperature of 700 °C, oxygen pressure of 6.67×10−2 mbar and target-to-substrate distance of 35 mm, the full width at half maximum intensity (FWHM) of STO(0 0 2) XRD peak was 0.42°. The FWHM of STO(0 0 2) peak was further reduced to 0.35° and 0.32° via. post-treatment with rapid thermal annealing (RTA at 800 °C for 30 s) and furnace annealing process (at 1000 °C for 1.5 h), respectively. The STO/Si films thus obtained are suitable for the synthesis of perovskite ferroelectric thin films.

Effects of annealing temperature on amorphous GaN films formed on Si(1 1 1) by pulsed laser deposition

GaN thin films were grown on Si(1 1 1) substrates using a pulsed KrF excimer laser-deposition system, and post-annealing was examined to improve the films' quality. In order to investigate the effect of thermal annealing temperature on the crystalline quality, optical properties and surface morphology of the samples, after deposition, the samples were subsequently annealed at different temperatures in ammonia (NH3) ambience for 15 min. The annealed films were characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), Raman spectra and photoluminescence spectra. The measured results show that annealing temperature plays an important role in improving the quality of GaN films, polycrystalline wurtzite structure GaN thin films with c-axis preferred orientation were successfully obtained by annealing, and the optimum annealing temperature is 1100 °C.

Growth of C-Axis Oriented LiNbO3 Film on Sapphire by Pulsed Laser Deposition for Surface Acoustic Wave Applications

Highly c-axis oriented LiNbO3(006) thin films have been successfully grown on sapphire substrates by XeCl excimer pulsed laser deposition (PLD). The as-deposited films were characterized by X-ray diffraction, scanning electron microscope and atomic force microscopy to analyze their crystalline structure and surface morphology. The results show that highly c-axis oriented LiNbO3 thin films of 1 μm thickness were successfully grown on sapphire substrates by PLD. The full width at half maximum intensity of LiNbO3(006) peak of the sample fabricated under the optimum deposition parameters is only 0.15°. The center frequency of the LiNbO3/sapphire substrate with electrode width of 10 μm is 137 MHz, and phase velocities is 5480 m/s, which is much larger than that of the 36° Y-X LiNbO3 substrate (3632 m/s).

Effects of Temperature on Microstructure and Tribological Performance of a-CN&lt;sub&gt;x&lt;/sub&gt; Films Prepared by Pulsed Laser Deposition

a-CNx films were deposited onto silicon wafers at temperatures from RT up to 600 °C by using pulsed KrF excimer laser deposition. The composition, morphology and microstructure of the CNx films were characterized by X-ray photoelectron spectrum (XPS), scanning electron microscopy (SEM) and Raman spectrum. The tribological performance of the films was investigated using a ball-on-disk tribometer. With increasing the deposition temperature ranging from RT to 400 °C, the N content of films dropped from 36 at.% to 22 at.%, the ratio of N-sp3 C bonds, hardness and friction coefficient of the film decreased. Further increase of deposition temperature led to the lack of nitrogen and the increasing degree of order in ringed sp2 C=C bonds of the amorphous carbon film. The mechanical and tribological performances became worse. The film deposited at 300°C showed a low friction coefficient of 0.11 and a preferable wear resistance of 1.65×10–7 mm3 Nm–1 in humid air.

Pulsed excimer laser deposition of Permalloy thin films: structural and electrical properties

We report on the effect of thickness on the structural and electrical properties of permalloy thin films Ni 8i Fe 19 (Py). Permalloy films were deposited onto Si(100) substrates at room temperature using a KrF (wavelength of 248 nm, pulse duration of 30 ns) excimer laser at a fluence of 3 J/cm 2 . The thickness ranges from 25 nm to 250 nm. The micrographs reveal the formation of irregular droplets with dimensions between 4.6 μm and 0.24 μm. We show that all samples presented a strong (100) texture. The lattice constant (a) monotonously increases with increasing thickness. Also, we note that for thickness below 127 nm, the lattice constant (a) is lower than the bulk value, however, for thickness more than 127 nm, (a) is higher than a bulk . The grain size increases from 30 nm to 54 nm as the thickness increases from 45 nm to 250 nm. The different contributions to the electrical resistivity are investigated as a function of the Py thickness.

Growth of c-Axis-Oriented LiNbO3 Films on ZnO/SiO2/Si Substrate by Pulsed Laser Deposition for Surface Acoustic Wave Applications

Highly c-axis-oriented LiNbO3(006) thin films were successfully grown on SiO2/Si substrates with a ZnO buffer layer by XeCl excimer pulsed laser deposition (PLD). The as-deposited films were characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy to analyze their crystalline structure and surface morphology. The results show that the highly c-axis-oriented LiNbO3 thin films of 2.5 µm thickness were successfully grown on SiO2/Si substrates with a ZnO buffer layer by PLD. The full width at half maximum intensity of the LiNbO3(006) peak of the sample fabricated under the optimum deposition conditions is only 0.18°. The center frequency of the LiNbO3/ZnO/SiO2/Si substrate with line width of 4 µm is 188 MHz, and the phase velocity is 3010 m/s, which is slightly lower than that of the 36° Y–X LiNbO3 substrate.

Structural and gasochromic properties of epitaxial WO3 films prepared by pulsed laser deposition

The structural and gasochromic properties of epitaxial tungsten trioxide (WO3) thin films, prepared by ArF excimer pulsed laser deposition under the controlled oxygen atmosphere, have been investigated. The WO3 films were grown on the α-Al2O3(011¯2) substrates, as the oxygen pressure ranged from 0.57 to 1.20Pa and the substrate temperature ranged from 432 to 538°C. The deposited films were characterized by Rutherford backscattering spectroscopy (RBS)/channeling, X-ray diffraction, X-ray pole figures and Raman spectroscopy. RBS and XRD results demonstrated that monoclinic WO3 (001) films were successfully grown on the α-Al2O3(011¯2) substrates. The crystal quality was improved by increasing both the oxygen pressure and the substrate temperature. Gasochromic coloration in the WO3 films by exposure to diluted hydrogen gas was found to correlate with the crystal quality of the films. The gasochromic coloration was suppressed by the epitaxial growth of the films.

Polymeric semiconducting carbon from fullerene by pulsed laser ablation

The polymeric semiconducting carbon films are grown on silicon and quartz substrates by excimer (XeCl) pulsed laser deposition (PLD) technique using fullerene C 60 precursor. The substrate temperature is varied up to 300 °C. The structure and optical properties of the films strongly depend on the substrate temperature. The grain size is increased and uniform polymeric film with improved morphology at higher temperature is observed. The Tauc gap is about 1.35 eV for the film deposited at 100°C and with temperature the gap is decreased upto 1.1 eV for the film deposited at 250 °C and increased to about 1.4 eV for the film deposited at 300 °C. The optical absorption properties are improved with substrate temperature. Raman spectra show the presence of both G peak and D peak and are peaked at about 1590 cm − 1 and 1360 cm − 1 , respectively for the film deposited at 100 °C. The G peak position remains almost unchanged while D peak has changed only a little with temperature might be due to its better crystalline structure compared to the typical amorphous carbon films and might show interesting in device such as, optoelectronic applications.

Effect of incident fluence on the growth of ZnO nanorods by pulsed excimer laser deposition

The incident fluence is shown to be an effective parameter in controlling the diameters of ZnO nanorods grown by pulsed excimer laser deposition following ablation of a ZnO target in low background pressures of oxygen. The evolution in nanorod diameter and the overall sample morphology with incident fluence is rationalised by considering the bombardment effect of high energy species in the plume formed in the ablation event.

Pulsed-laser deposition of nanostructured Pd/C thin films: A new entry into metal-supported catalysts for hydrogen producing reactions

Carbon-supported palladium thin films were synthesized at room temperature by KrF excimer pulsed laser deposition by using oriented pyrolytic graphite and Pd target. By changing the experimental conditions, a range of structures, from smooth to porous cluster-assembled carbon films were obtained prior to deposition of the Pd films. High amount of sp 2 coordinated graphitic carbon embedded with large degree of disorder is observed in these carbon films. Surface morphology was studied by using scanning electron microscopy, while compositional analysis was performed by using energy dispersive spectroscopy. Structural analysis was performed using Raman spectroscopy and Fourier transform infrared spectroscopy. The importance of morphology and chemical structure of carbon films on their catalytic activity was investigated by using the hydrolysis of aqueous NaBH 4 as a reference process. Pd/C film produced by pulsed laser deposition are here demonstrated to be a better catalyst than Pd/C powder because of the high content of sp 2 bonding carbon atoms arranged into the porous and irregular surface of the carbon film.

Preparation and Characterization of SnO&lt;sub&gt;2&lt;/sub&gt; Thin Film Gas Sensor for NO&lt;sub&gt;x&lt;/sub&gt; Gas for Environmental Monitoring

SnO2 thin films have been grown on Si3N4 substrates and also on Al2O3 sensor substrates with Pt interdigitated electrodes by the pulsed excimer laser deposition (PLD). Palladium doped SnO2 thin film was also prepared by the PLD method combined with the DC sputtering process. The substrate temperature and the oxygen gas pressure were changed from 300 to 500°C and from 100 to 300 mTorr, respectively during deposition. The morphology and structural properties of the prepared thin films have been studied by AFM and XRD. The gas sensing properties of the SnO2 sensor to NO gas was evaluated by measuring electrical resistance between interdigitated electrodes. The highest sensitivity of the undoped SnO2 and Pd doped sensor was found to be around 9.5 and 42, respectively.

Crystallization of β-FeSi 2 droplets on silicon substrates by room-temperature pulsed laser deposition

This paper reports the fabrication process of β-FeSi 2 droplets on silicon substrates at room temperature by ArF excimer pulsed laser deposition (PLD). The chemical treatment of substrate could compensate the thermal treatment of the deposited droplets. Observations with the transmission electron microscopy revealed that the crystallization of droplet began from the surface of droplet rather than from the interface between the melt and the substrate.