YAG Laser Deposition Research Articles

Properties of palladium doped tin oxide thin films for gas sensors grown by PLD method combined with sputtering process

The gas sensors based on tin dioxide (SnO 2) thin films and doped with different amount of palladium (Pd) were synthesized by a new developed preparation system using the pulsed Nd:YAG (532 nm) laser deposition method combined with d.c. sputtering. The Pd-doped SnO 2 (SnO 2–Pd) thin films have been grown on Si (1 0 0) and alumina (Al 2O 3) substrates using SnO 2 targets. The composition ratio and the bonding states of SnO 2–Pd thin films were characterized by an X-ray photoelectron spectroscopy. Surface morphology and structure of the films have been obtained by atomic force microscope and glancing-angle X-ray diffraction measurement. The effects of the sputtering discharge power of Pd on the properties of the SnO 2–Pd thin films are discussed. The gas sensing properties of SnO 2–Pd thin films prepared by this new pulsed laser deposition (PLD) method are also investigated over the temperature range 200–600 °C, using 0.31 vol.%H 2 as a test gas. Experimental results suggest that SnO 2–Pd thin films can be prepared using this new PLD method. Atomic concentration ratio of Pd in the SnO 2–Pd film depends on the sputtering discharge power of Pd and varies from 1 to 6%. The maximum sensitivity of SnO 2–Pd thin film gas sensor synthesized by this new PLD method is approximately 3 times higher than that of pure SnO 2 thin film gas sensor grown by the conventional PLD method.

Development of New Preparation System for Highly Sensitive Flammable Gas Sensor

A new deposition system for preparing a highly sensitive flammable gas sensor has been developed. In this method, tin oxide (SnO2) thin films were deposited on Si(100) and Al2O3 substrates using the pulsed Nd:YAG (532 nm) laser deposition (PLD) method and palladium (Pd) thin films were deposited on the same substrate using d.c. sputtering simultaneously. Experimental results suggest that Pd-doped SnO2 thin films can be prepared using this new method. The sensitivity of the Pd-doped SnO2 film sensor prepared using this new deposition system is about 3.2 times higher than that of a pure SnO2 film sensor prepared by the conventional PLD method.

Preparation of crystalline TiC thin films grown by pulsed Nd:YAG laser deposition using Ti target in methane gas

Titanium carbide (TiC) thin films that are smooth and pinhole-free have been synthesized on Si(100) substrates by a pulsed neodymium:yttrium–aluminum–garnet (Nd:YAG) laser deposition method using titanium and TiC targets in methane gas. Glancing angle X-ray diffraction (GXRD) showed that polycrystalline films with components of TiC and Ti can be prepared using a Ti target. Single-phase TiC films can be synthesized using a TiC target. It was found that the methane gas pressure can control the crystallinity and composition. The root-mean-square (RMS) roughness of the film, as measured by an atomic force microscope (AFM), was lower than 2 nm in all the deposition areas. The film thickness, measured by α-step, was about 92 nm and the growth rate was approximately 3.1 nm/min. Measurements of optical emission spectra were performed to estimate the processing plasma state.

Formation and Investigation of Photosensitive Structures Based on Laser-Deposited CuInSe2-2ZnSe Films

Thin (CuInSe2)1—x(2ZnSe)x (0.0 ≤ x ≤ 0.42) p-type films were synthesised on glass substrates by pulsed Nd : YAG laser deposition at 1064 nm with a repetition rate of 3 × 10—2 Hz and a pulse width of 1.1 μs. The applied laser energy was kept in the range 160–190 J per pulse. The target materials and films were characterised by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and hot-point probe technique for electrical characterisation. The as-grown layers were single phase and polycrystalline. The films showed a phase transition from chalcopyrite to sphalerite in the region 0.3 ≤ x ≤ 0.4. Photosensitive structure of In/p-(CuInSe2–2ZnSe) and n-InSe/p-(CuInSe2–2ZnSe) types were obtained. Spectral dependences of the photoconversion relative quantum efficiency in relation to the type of energy barrier and chemical composition of thin films were studied. Analyses of the results showed that the structures based on CuInSe2–2ZnSe films could be used as wide-band photodetectors.

Characterization of Tantalum Nitride Thin Films Fabricated by Pulsed Nd:YAG Laser Deposition Method

Growth mechanisms of crystalline tantalum nitride (TaN) films have been studied on silicon substrates using a pulsed Nd:YAG laser deposition method. Experimental results show that the properties of the TaN films strongly depend on the substrate temperatures and nitrogen gas pressures. This suggests that both the phase reaction in the plasma plume and the surface reaction on the substrate are important for preparing crystalline TaN films.

Formation and Properties of Carbon Nitride Thin Films by Pulsed Nd:YAG Laser Deposition

Carbon nitride thin films were synthesized on Si(100) substrates by pulsed Nd:YAG laser deposition. Several spectral lines originating from the neutral and ionic species, such as carbon atoms, carbon ions, carbon molecules and carbon nitride molecules were identified in the plasma plume. The surface morphology of the carbon nitride thin films reveals numerous droplets on the films out of which several are spiral shaped. The N/C composition ratio is increased from 0.18 to 0.25 with increasing substrate bias voltage. Fourier transform infrared spectroscope absorption spectra show two characteristic bands: a broad band composed of the graphite G-band and disordered D-band of carbon, and another associated with the CN triple bond. Raman spectra have also been used to characterize the films.

Evaluation for Compositional Deviation between PZT Bulk Target and Its Thin Film Synthesized by YAG Laser Deposition.

Evaluation for Compositional Deviation between PZT Bulk Target and Its Thin Film Synthesized by YAG Laser Deposition.

Synthesis of Tin Oxide Thin Films by Pulsed Laser Deposition Using SnO2Targets

ABSTRACTTin oxide (SnO2) thin films have been grown on Si (100) and Al2O3 substrates by pulsed Nd:YAG (532nm) and KrF excimer (248 nm) laser deposition methods using SnO2 targets. X-ray diffraction measurement showed that the almost amorphous microstructure transformed into a crystalline SnO2 phase and preferred orientation varied from (101) to (110) on Si (100) with increasing oxygen gas pressure. This result suggests that oxygen gas pressure affects the phase formation, crystalline structure and preferred orientation of the films. Gas sensing properties of SnO2 thin films by PLD method were also investigated over the temperature range 300 – 600°C, using 0.31vol%H2 as a test gas. The oxygen gas pressure results in a notable change in gas sensing properties of SnO2 thin films.

Synthesis and dielectric properties of Sr Ba1–Nb2O6 formed by YAG laser ablation

Abstract Tungsten-bronze type tetragonal SrxBa1–xNb2O6 (SBN) ceramics have been synthesized by pressure-less sintering at 1250°C through a mixed-oxide route. With increasing x value in the range from 0.3 to 0.6, the Curie temperature shifted to lower temperature, but the corresponding maximum dielectric constant increased. Further, Sr0.3Ba0.7Nb2O6 thin films have been formed by pulsed YAG laser deposition (PLD) technique using a selected SBN bulk target with various choices of the deposition parameters. When Pt-coated Si substrates were used for PLD, a preferential c-axis-ordered structure was observed in the films deposited using an energy density above 2.0 J/cm2, at a substrate temperature above 650°C, and in oxygen partial pressure below 7 Pa. The thin film yielded a rhomboidal P–E hysteresis loop, and showing a remanent polarization (Pr) of 3.1 μ C/cm2 and coercive field (Ec) of 1.28 kV/cm.

Structure and transport properties of polycrystalline Bi films

Polycrystalline bismuth thin films were deposited on glass substrates at room temperature by pulsed Nd:YAG laser deposition. Some relevant aspects of the microstructure of the Bi films as a function of film thickness are reported. In addition, the electrical resistivity, the Hall coefficient and the thermoelectric power were measured between 80 and 380K in films ranging from 25 to 450nm in thickness. The transport properties are discussed and compared to previous studies.

Effects of Ion Beam Energy on the Formation of Cubic Boron Nitride Thin Films by Pulsed Nd:YAG Laser Deposition

Cubic boron nitride (cBN) thin films are synthesized on Si(100) substrates by a pulsed neodymium: yttrium-aluminum-garnet (Nd:YAG) laser deposition method using an ion beam in order to enhance the synthesis of the cBN phase. The deposited films were characterized by a Fourier transform infrared (FT-IR) measurement method. When a pure N2 ion beam is used, some absorption peaks for hexagonal boron nitride (hBN) are visible, but the peak for cBN cannot be observed. When argon(Ar) gas is mixed with the reactant nitrogen(N2) gas, the peak at 1050 cm-1 for cBN appears, in addition to those of hBN. When the ion-beam current and voltage is increased to 20 mA and 400 V, the absorption peak intensity for cBN increases, and that of hBN disappears. These results suggest that nitrogen and argon ion bombardment plays an important role in the formation of cBN films.

Characterization of Crystalline TiC Films Grown by Pulsed Nd:YAG Laser Deposition

Titanium carbide (TiC) thin films have been grown on Si (100) substrates using a pulsed neodymium: yttrium-aluminum-garnet (Nd:YAG) laser deposition method. X-ray diffraction (XRD) pattern of the TiC film shows that substrate temperature is one of the most important parameters in the fabrication of crystalline TiC film. Crystalline TiC films can be prepared at substrate temperatures above 500°C. Field emission scanning electron microscope (FE-SEM) indicates that the surface of the film is very smooth and pinhole-free.

Pulsed Laser Deposition of Doped Lanthanum Gallate and In Situ Analysis by Mass Spectrometry of the Laser Ablation Plume

Sr- and Mg-doped LaGaO3 powders with various dopant concentrations (La1-xSrxGa1-yMgyO3-(x+y)/2 where 0.02 ≤ x ≤ 0.2 and 0.02 ≤ y ≤ 0.2) were synthesized through a novel solution combustion route. X-ray diffraction patterns indicate orthorhombic structure for compositions 0 ≤ x ≤ 0.075 and 0 ≤ y ≤ 0.075 and primitive − cubic for 0.1 ≤ x ≤ 0.2 and 0.1 ≤ y ≤ 0.2. Thin films of La1-xSrxGa1-yMgyO3-(x+y)/2 (0.1 ≤ x ≤ 0.2 and 0.1 ≤ y ≤ 0.2) were deposited using both Nd:YAG (532 nm) and excimer (248 nm) lasers. The as-deposited films at room temperature were amorphous, which on annealing at 973 K exhibited single-phase cubic structure. Films deposited with excimer laser were smooth and particulate free compared to Nd:YAG laser deposition. The LSGM films on Si[111] and sapphire[0001] substrates showed good surface morphology compared to films on MgO[001] and amorphous quartz. Films were found to be slightly rich in Sr/La ratio compared to target composition. O+, O, Ga+, Ga, and La+ were the major species in the la...

Preparation Of Crystalline Chromium Carbide Thin Films Synthesized By Pulsed Nd:YAG Laser Deposition

AbstractChromium carbide thin films are synthesized on Si(100) substrates by a pulsed Nd:YAG laser deposition (PLD) method as parameters of methane gas pressure. Glancing-angle X-ray diffraction patterns show that the film prepared by PLD method is a polycrystalline thin film composed of Cr3C2and Cr7C3, even in the base pressure. Diffraction patterns, however, are depended on the methane gas pressure. Grain size of the prepared film increases with increasing methane gas pressure. One of the reasons of these phenomena may be considered to the phase reaction between the ablated species, such as Cr, CrCx and CH4gas in the plasma plume.

Tantalum Nitride Thin Films Synthesized by Pulsed Nd:YAG Laser Deposition Method

AbstractTantalum nitride (TAN) films have been deposited on silicon substrates by using a pulsed Nd:YAG laser deposition method. Experimental results suggest that the substrate temperature is one of the most important parameters to prepare crystalline tantalum nitride thin films. Glancing-angle X-ray diffraction patterns show that the films deposited at Ts ≤ 300 °C are almost amorphous. and crystalline Ta6N2.57 films are obtained at Ts ≥ 500 °C. Grain size of the film increases with increasing substrate temperature.

Chromium Carbide Thin Films Synthesized by Pulsed Nd:YAG Laser Deposition

Chromium carbide thin films are synthesized on Si(100) substrates by a pulsed Nd:YAG laser deposition method at different substrate temperatures. Glancing-angle X-ray diffraction shows that a crystalline chromium carbide film can be prepared at the substrate temperature of 700°C. Grain size of the films, examined with a field-emission secondary electron microscope, increases with increasing substrate temperature.

Crystalline silicon nitride thin films grown by pulsed YAG laser deposition

Silicon nitride (SiN) and silicon (Si) thin films have been prepared on Si (100) substrates using pulsed Nd: YAG laser (λ-532 nm) deposition. The laser beam is incident on the Si 3N 4 and Si targets. The films are grown using the energy density 3.8 J/cm 2 at a laser repetition rate of 10 Hz. The nitrogen gas pressure in the chamber is 10.0 Pa. The experiments have been done at different substrate temperatures. The films have been characterized by field-emission secondary electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-1R) and glancing angle X-ray diffraction (GXRD). FE-SEM shows that the SiN film consists of many particles whose sizes are about 200 –800 nm. GXRD indicates that crystalline Si 3N 4 and Si thin films are obtained using Si 3N 4 and Si targets, respectively.

Properties of WC films synthesized by pulsed YAG laser deposition

Tungsten carbide (WC) films are synthesized by a pulsed YAG laser deposition. WC films are deposited on heated Si(100) substrates using WC and WC-5% Co alloy targets. The films are grown using a laser repetition rate of 10 Hz at energy density 3.8 J cm −2. Auger electron spectroscopy shows that the almost stoichiometric WC films are deposited at the methane gas pressure of 10.0 Pa. Morphology features of the films have been obtained by employing the technique of scanning electron microscopy. Glancing angle X-ray diffraction shows that the peak signal of W 2C appears for the film deposited at a substrate temperature of 650 °C and the peak signal of WC is observed for the sample prepared at a substrate temperature of 710 °C. Measurements of the optical emission spectrum are performed to estimate the processing plasma state.

In situ growth of ferroelectric lead zirconate–titanate thin films on Si substrates by pulsed Nd:YAG laser deposition

The growth of oriented crystalline PZT films on (111) Si substrates at different substrate temperatures is reported. By varying the laser fluence and other deposition parameters we have been able to produce, in a single-step process, highly oriented PZT films with good piezoelectric properties at much lower temperatures than reported in other PLD experiments. X-ray measurements and secondary ion mass spectroscopy, as well as piezoelectric measurements, are used to characterize the different samples. Experimental evidence is presented that at high laser fluence (25 J/cm 2) better properties for PLD films are obtained with lower substrate temperatures.

Pulsed laser deposition of carbon nitride thin films from graphite targets

Carbon nitride thin films were synthesized on Si(100) substrates by a pulsed Nd:YAG laser deposition. The laser beam is incident on the high-purity graphite targets. The films are grown using an energy density 3.8 J cm −2 at a laser repetition rate of 10 Hz. The nitrogen gas pressure in the chamber is 10.0 Pa. Morphology features of the films have been obtained by employing the technique of scanning electron microscopy. Auger electron spectroscopy has been used to obtain compositional information about the films. The N C composition ratio was found to vary from zero to 0.32 depending on deposition conditions. IR absorption spectra show two characteristic bands: a broad band composed of the graphite G-band and disordered D-band of carbon, and another associated with CN triple bonds. Raman spectra have also been used to characterize the films.