Laser-induced voltage effects in Ca_3Co_4O_9 thin films on tilted LaAlO_3(001) substrates grown by chemical solution deposition

Laser-induced voltage effects in c-axis oriented Ca3Co4O9 thin films have been studied with samples fabricated on 10°tilted LaAIO3 （001） substrates by a simple chemical solution deposition method. An open-circuit voltage with a rise time of about 10 ns and full width at half maximum of about 28 ns is detected when the film surface is irradiated by a 308-nm laser pulse with a duration of 25 ns. Besides, opemcircuit voltage signals are also observed when the film surface is irradiated separately by the laser pulses of 532 nm and 1064 nm. The results indicate that Ca3Co4O9 thin films have a great potential application in the wide range photodetctor from the ultraviolet to near infrared regions.

A novel absorptive thin film for laser welding in optoelectronic device capsulation

A kind of absorptive thin film was designed and used in laser welding of SiO2, Si and LiNbO3. This absorptive thin film of three-layer metal-dielectric-metal structure is designed for further reducing the high reflectance of the Nd:YAG laser beam on the surface of the tin layer that is utilized as solder between the transparent parent materials. The actual absorption of laser energy in experiment exceeds 99%. This combination of absorber and solder transformed the laser energy into heat efficiently and decreased the minimum necessary incident laser power transmitting through the transparent parent materials. As a result, the damage of the parent materials, which is suffered from laser transmission, was avoided; On the other hand, mechanical stability of the welded materials had been improved. Experiment had been made to show the difference between welding with and without the absorptive thin film.

Structural and electrical characterization of Bi2VO5.5 / Bi4Ti3O12 bilayer thin films deposited by pulsed laser ablation technique

The pulsed laser ablation technique has been employed to fabricate bilayer thin films con-sisting of layered structure ferroelectric bismuth vanadate (Bi2VO5.5) and bismuth titanate (Bi4Ti3O12) on platinized silicon substrate. The phase formation of these films was confirmed by X-ray diffraction (XRD) studies and the crystallites in these bilayers were randomly oriented as indicated by diffraction pattern consisting of the peaks corresponding to both the materials. The homogeneous distribution of grains (~300 nm) in these films was confirmed by atomic force microscopy. The cross-sectional scanning electron microscopy indicated the thickness of these films to be around 350 nm. The film exhi-bited P-E hysteresis loops with Pr ~ 11 ?C/cm2 and Ec ~ 115 kV/cm at room temperature. The dielectric constant of the bilayer was ~ 225 at 100 kHz which was higher than that of homogeneous Bi2VO5.5 film.

Optimization of Laser Ablation Technology for PDPhSM Matrix Nanocomposite Thin Film by Artificial Neural Networks-particle Swarm Algorithm

A new thermal ring-opening polymerization technique for 1, 1, 3, 3-tetra-ph enyl-1, 3-disilacyclobutane （TPDC） based on the use of metal nanoparticles produced by pulsed laser ablation was investigated. This method facilitates the synthesis of polydiphenysilylenemethyle （PDPhSM） thin film, which is difficult to make by conventional methods because of its insolubility and high melting point. TPDC was first evaporated on silicon substrates and then exposed to metal nanoparticles deposition by pulsed laser ablation prior to heat treatment.The TPDC films with metal nanoparticles were heated in an electric furnace in air atmosphere to induce ring-opening polymerization of TPDC. The film thicknesses before and after polymerization were measured by a stylus profilometer. Since the polymerization process competes with re-evaporation of TPDC during the heating, the thickness ratio of the polymer to the monomer was defined as the polymerization efficiency, which depends greatly on the technology conditions. Therefore, a well trained radial base function neural network model was constructed to approach the complex nonlinear relationship. Moreover, a particle swarm algorithm was firstly introduced to search for an optimum technology directly from RBF neural network model. This ensures that the fabrication of thin film with appropriate properties using pulsed laser ablation requires no in-depth understanding of the entire behavior of the technology conditions.

Poly-Si Thin Film Grown by Excimer Laser Crystallization and Its Ellipsometric Analysis

A novel approach of two-step laser crystallization for the growth of poly-Si thin film on glass substrate is investigated.Using this approach,we fabricated poly-Si thin film transistors with electron mobility of 103 cm^2/V·s and on/off current ration of 1×10^7,They are better than those of the poly-Si TFTs fabricated by conventional single-step excimer laser crystallization.We also analyzed the structure of the laser crysallized poly-Si thin film and calculated the ellipsometric spectra.The calculated results are in good agreement with the measured results.

Laser Ablated Superconducting and Related Thin Films:A Microscopical Investigation

Laser ablated high temperature superconducting and related thin films are investigated with a microscopical point of view.The microstructure and microchemistry of three thin films(Y-Ba-Cu-O, Bi-Pb-Sr-Ca-Cu-O and Sr-Ca-Cu-O)are demonstrated as examples of laser ablation products.

Epitaxial Growth of Gd_(0.67)Ca_(0.33)MnO_3 Thin Films by Laser Ablation

Gd_(0.67)Ca_(0.33)MnO_3(GCMO)thin films grown by laser ablation on SrTiO_3(100)(STO)substrates was studied. Films are highly crystallized, very well epitaxial and single-phased. The ordering magnetic temperature(T_c)of the films is much higher than the value of bulk samples of similar composition. It is found that the GCMO film exhibits a reversal of its magnetization at low temperature when cooled under a magnetic field. The negative magnetization is a consequence of the rapid increase(～1/T)with decreasing temperature of the magnetization of a sublattice aligned antiparallel to the local field, relative to the magnetic contribution of a second sublattice which is aligned parallel to the applied field.

Characterization of zirconium thin films deposited by pulsed laser deposition

Zirconium （Zr） thin films deposited on Si （100） by pulsed laser deposition （PLD） at different pulse repetition rates are investigated. The deposited Zr films exhibit a polycrystalline structure, and the X-ray diffraction （XRD） patterns of the films show the α Zr phase. Due to the morphology variation of the target and the laser-plasma interaction, the deposition rate significantly decreases from 0.0431 A/pulse at 2 Hz to 0.0189A/pulse at 20 Hz. The presence of droplets on the surface of the deposited film, which is one of the main disadvantages of the PLD, is observed at various pulse repetition rates. Statistical results show that the dimension and the density of the droplets increase with an increasing pulse repetition rate. We find that the source of droplets is the liquid layer formed under the target surface. The dense nanoparticles covered on the film surface are observed through atomic force microscopy （AFM）. The root mean square （RMS） roughness caused by valleys and islands on the film surface initially increases and then decreases with the increasing pulse repetition rate. The results of our investigation will be useful to optimize the synthesis conditions of the Zr films.

Kinetic Monte Carlo simulation of growth of BaTiO_3 thin film via pulsed laser deposition

Considering the characteristics of perovskite structure, a kinetic Monte Carlo(KMC) model, in which Born-Mayer- Huggins(BMH) potential was introduced to calculate the interatomic interactions and the bonding ratio was defined to reflect the crystallinity, was developed to simulate the growth of BaTiO3 thin film via pulsed laser deposition(PLD). Not only the atoms deposition and adatoms diffusion, but also the bonding of adatoms were considered distinguishing with the traditional algorithm. The effects of substrate temperature, laser pulse repetition rate and incident kinetic energy on BaTiO3 thin film growth were investigated at submonolayer regime. The results show that the island density decreases and the bonding ratio increases with the increase of substrate temperature from 700 to 850 K. With the laser pulse repetition rate increasing, the island density decreases while the bonding ratio increases. With the incident kinetic energy increasing, the island density decreases except 6.2 eV<Ek<9.6 eV, and the bonding ratio increases at Ek<9.6 eV. The simulation results were discussed compared with the previous experimental results.

High temperature thermoelectric properties of highly c-axis oriented Bi_2Sr_2Co_2O_y thin films fabricated by pulsed laser deposition

High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices,

Experimental study on microdeposition of the copper thin film by femtosecond laser-induced forward transfer

The morphologies of the deposited dots on the 40 nm-thick copper film by the femtosecond laser-induced forward transfer that depend on the irradiated laser fluence have been studied, and the variations of orderliness of the diameter of deposited dots on the quartz substrate and forward ablated dot on the donor substrate with increasing pulse fluence have been obtained experimentally. The experimental results show that a thinner copper film would generate larger-sized ablated dot and deposited dot at the threshold fluence for transfer. By x-ray diffraction measurement, it is demonstrated that the crystal form of the transferred copper films is unaltered and the size of the crystallites is diminished.

Development of a Low Cost Pulsed Laser Deposition System for Thin Films Growth

.Pulsed Laser Deposition (PLD) is a powerful technique to grow thin films. Oxides, Magnetics and superconducting materials have been obtained by PLD and theirs properties are strongly dependent of deposition parameters. The construction of a simple and cheap PLD system that is suitable for growing various thin films, including magnetic materials, controlling some deposition parameters is presented. The design characteristics and construction are presented for each one of the devices that compose this PLD system. The equipment has the possibility of carrying out films deposition using up to five targets under controlled atmosphere and substrate temperature. The system also allows controlling the cool off sample time after growing up films at high temperatures. A wide range of relative speeds between target and substrate axial rotation can be externally controlled. With the configuration and the dimensions adopted in their construction, a PLD system of great experimental flexibility is achieved, at a very low cost regarding the commercial systems. To evaluate their performance and effectiveness, the deposition characteristics of a BaFe12O19 film on (0001) sapphire substrate is presented.

Preparation and Properties of IrO_2 Thin Films Grown by Pulsed Laser Deposition Technique

Highly conductive IrO2 thin films were prepared on Si （100） substrates by means of pulsed laser deposition technique from an iridium metal target in an oxygen ambient atmosphere. Emphasis was put on the effect of oxygen pressure and substrate temperature on the structure, morphology and resistivity of IrO2 films. It was found that the above properties were strongly dependent on the oxygen pressure and substrate temperature. At 20 Pa oxygen ambient pressure, pure polycrystalline IrO2 thin films were obtained at substrate temperature in the 300-500℃ range with the preferential growth orientation of IrO2 films changed with the substrate temperature. IrO2 films exhibited a uniform and densely packed granular morphology with an average feature size increasing with the substrate temperature. The room-temperature resistivity variations of IrO2 films correlated well with the corresponding film morphology changes. IrO2 films with the minimum resistivity of （42 ±6）μΩ·cm was obtained at 500℃.

Preparation and Characterization of Cu-Zn Nano-Structural Ferrite Thin Films Produced by Pulsed Laser Deposition (PLD)

Cu-Zn ferrite nano thin films were deposited from a target of Cu-Zn ferrite onto a sapphire substrate using XeCl excimer laser operating 308 nm with an energy of 225 mJ and a frequency of 30 Hz. Films were deposited from the target onto sapphire (001) substrates heated to 650℃ in an oxygen atmosphere of 100 mTorr. The laser beam was incident On the target face at an angle of 45°. Studies on crystal structure were done by X-ray diffactometry (XRD). The surface texture, cross-section morphology and grain size was observed by JEOL-JSM-6400 scanning electron microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM) [Model DI 3000, Digital instruments].

XPS study of BZT thin film deposited on Pt/Ti/SiO_2/Si substrate by pulsed laser deposition

Ferroelectric materials were widely applied for actuators and sensors. Barium zirconate titanate Ba(Zr0.25Ti0.75)O3 thin film was grown on Pt/Ti/SiO2/Si(100) substrates by pulsed laser deposition. Structure and surface morphology of the thin film were studied by X-ray diffractometry(XRD) and scan electronic microscopy(SEM). The composition and chemical state near the film surface were obtained by X-ray photoelectron spectroscopy(XPS). On the sample surface,O 1s spectra can be assigned to those from the lattice and surface adsorbed oxygen ions,while C1s only result from surface contamination. The result shows that only one chemical state is found for each spectrum of Ba 3d,Zr 3d and Ti 2p photoelectron in the BZT thin film.

Pulsed-Laser Annealing of NiTi Shape Memory Alloy Thin Film

Local annealing of amorphous NiTi thin films was performed by using an Nd：YAG 1064 nm wavelength pulsed laser beam. Raw samples produced by simultaneous sputter deposition from elemental Ni and Ti targets onto unheated Si （100） and Silica （111） substrates were used for annealing. Delicate treatment with 15.92 W/mm^2 power density resulted in crystallization of small spots; while 16.52 and 17.51 W/mm^2 power densities caused ablation of the amorphous layer. Optical microscopy, scanning electron microscopy, X-ray diffraction and atomic force microscopy were performed to characterize the microstructure and surface morphology of the amorphous/crystallized spot patterns.

Preparation and Characterization of P-Type Bi_0.45Sb_1.55Te₃Thin Film Using Pulsed CO₂Laser

P-type Bi0.45Sb1.55Te3 thermoelectric material was synthesized using cold pressing process. The obtained sample was prepared in the form of pellet with a diameter of 10 mm and 2 mm thick and used as a target for laser ablation. The laser source was a pulsed CO2 laser working at a wavelength of 10.6 μm with a laser energy density of 2 J/cm2 per pulse. P-type Bi0.45Sb1.55Te3 thermoelectric thin films were deposited on Si substrates for different ablation times of 1, 2 and 3 h. The cross-section and surface morphologies of the thermoelectric films were investigated using field emission scanning electron microscopy (FE-SEM). The results show that the thickness and average particle size of the films increased from 35 to 58 nm, and 28 to 35 nm, respectively, when the ablation time was increased from 1 to 3 h. The crystalline structure of the TE films was investigated by X-ray diffraction (XRD).