Bi2Se3 thin films were deposited on the (100) oriented Si substrates by pulsed laser deposition technique at different substrate temperatures (room temperature – 400 ºC). The effects of the substrate temperature on the structural and electrical properties of the Bi2Se3 films were studied. The film prepared at room temperature showed a very poor polycrystalline structure with the mainly orthorhombic phase. The crystallinity of the films was improved by heating the substrate during the deposition and the crystal phase of the film changed to the rhombohedral phase as the substrate temperature was higher than 200 ºC. The stoichiometry of the films and the chemical state of Bi and Se elements in the films were studied by fitting the Se 3d and the Bi 4d5/2 peaks of the X-ray photoelectron spectra. The hexagonal structure was seen clearly for the film prepared at the substrate temperature of 400 ºC. The surface roughness of the film increased as the substrate temperature was increased. The electrical resistivity of the film decreased from 1x10-3 to 3 x 10-4 Ω cm as the substrate temperature was increased from room temperature to 400 ºC.; Shenyang National Laboratory for Material Science (SYNL), China
In this work we investigated ZnO films grown on semi-insulating (100) GaAs substrates by pulsed laser deposition. Samples were studied using techniques including X-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, Raman spectroscopy, temperature dependent photoluminescence, C-V profiling and temperature dependent Hall measurements. The Hall measurements showed a clear p-type response with a relatively high mobility (∼260 cm 2/Vs) and a carrier concentration of ∼1.8 × 1019 cm-3. C-V profiling confirmed a p-type response. XRD and Raman spectroscopy indicated the presence of (0002) oriented wurtzite ZnO plus secondary phase(s) including (101) oriented Zn2As2O 7. The results suggest that significant atomic mixing was occurring at the film/substrate interface for films grown at substrate temperatures of 450°C (without post-annealing).; FCT/FEDER (POCTI/CTM/45236/02)
GaN thin films grown by cyclic pulsed laser deposition were characterised by X-ray diffraction (XRD), photoluminescence (PL), and atomic force microscopy. Films were grown on pre-nitridated c-plane sapphire at two substrate temperatures (600 and 650 °C). Films deposited at 650 °C exhibit a higher growth rate which is reflected in the XRD intensity along the GaN (0002) direction. At this substrate temperature, the quality of the PL spectrum was the best. The typical yellow luminescence, YL (2.2 eV) was dominant at the lower deposition temperature. For this substrate temperature change, the near band edge emission (NBE) to YL ratio increased from 0.3 to a value of 17. This NBE emission was peaked at 3.47 eV with a FWHM of 200 meV at 14 K. Optimisation of deposition parameters is suggested to further improve the quality of binary films.; PRAXIS/P/FIS/10178/1998; COPERNICUS project IC15-CT98-0819
Thin films of bioactive glass-ceramic have been deposited on titanium substrates by the Pulsed Laser Deposition (PLD) technique under different experimental conditions. The effect of parameters such as deposition pressure and temperature of heat treatments was studied. The microstructure and the crystalline phases of the coatings were characterized using SEM, EDX and XRD analysis; the phases present were titanium oxides, calcium magnesium silicates and phosphates. The adhesion of the as-deposited films has been examined by scratch tests. The interfacial adhesion of the coatings was better when the deposition was performed at low pressure. Samples were immersed in simulated body fluid (SBF), and a calcium-phosphate precipitate was observed on the surface of less crystallized samples, suggesting that there is some relationship between surface reactivity and crystallinity.
The Yttria stabilized Zirconia (YSZ) is a standard electrolyte for solid oxide fuel cells (SOFCs), which are potential candidates for next generation portable and mobile power sources. YSZ electrolyte thin films having a cubic single phase allow reducing the SOFC operating temperature without diminishing the electrochemical power density. Films of 8 mol% Yttria stabilized Zirconia (8YSZ) and films with addition of 4 weight% Ceria (8YSZ + 4CeO2) were grown by pulsed laser deposition (PLD) technique using 8YSZ and 8YSZ + 4CeO2 targets and a Nd-YAG laser (355 nm). Films have been deposited on Soda-Calcia-Silica glass and Si(100) substrates at room temperature. The morphology and structural characteristics of the samples have been studied by means of X-ray diffraction and scanning electron microscopy. Films of a cubic-YSZ single phase with thickness in the range of 1-3 µm were grown on different substrates.
Ag films were grown by pulsed laser deposition on insulating SiO2 and mica substrates and exhibited a morphological progression beginning with nucleation of three-dimensional islands and culminating in a continuous, electrically conducting film. The rate of advancement through this progression with increasing pulse frequency was studied with experiments and with kinetic Monte Carlo (KMC) simulations. Experiments at 93 and 135 °C give exponents of −0.34 and −0.31, respectively, for the scaling of the electrical percolation thickness with pulse frequency. Simulations predicted an exponent of −0.34, in excellent agreement with the experiments. Both of these values agree well with the previously reported analytic value of −0.33 for the scaling of the morphology transition thickness with average flux in continuous deposition. Simulations also predicted that data collapse for island density vs amount deposited would be observed for experiments run at the same value of the parameter B/f at constant amount deposited per pulse, where B is the kinetic rate constant for coalescence and f is the pulse frequency. Measurements of the percolation transition were consistent with this prediction. These findings indicate that the elementary processes included in the KMC simulation—substrate terrace diffusion...
We report an experimental comparison of Volmer-Weber metal-on-insulator growth morphology in pulsed laser deposition (PLD) and thermal deposition under identical thermal, background, and surface preparation conditions for Ag on SiO2 and mica. Films exhibit a characteristic morphological progression from isolated three-dimensional islands to elongated clusters to a percolating, electrically conducting film to a pinhole-free film. We observed this same progression for films deposited by PLD. Kinetic Monte Carlo (KMC) simulations that take into account only the pulsed nature of the flux predict that PLD films should advance to percolation with less deposition than thermally deposited films under otherwise identical conditions. At low substrate temperatures, this prediction is confirmed. However, in situ resistance measurements and ex situ atomic force microscopy measurements demonstrate that at high substrate temperatures, PLD films require more deposition to reach percolation. PLD experiments performed at varying kinetic energy of the depositing Ag species suggest a regime in which increasing kinetic energy can delay the percolation transition. Comparison was made with KMC simulations of two-island coalescence in the presence of adatom-vacancy pair creation...
Pulsed laser deposition method was employed to grow MgO thin films with preferred orientation on bare Si(100) and SiO₂/Si(100) substrates. The orientation of MgO thin films was systematically investigated by varying deposition parameters. XRD analysis showed that the preferred orientation of MgO thin films would change from (111) to (100) when laser fluence decreased and oxygen pressure increased to certain extend. But it was difficult to fabricate completely (100)-oriented MgO films. Substrate temperature seemed to have little influence on the orientation of MgO thin films at high laser fluence. SEM images of the MgO thin films on Si(100) deposited at 400°C and the laser fluence of 5J/cm² in the oxygen ambient of 200mTorr demonstrated that there was no presence of interfacial reactions or cracks and the film surface was very smooth. Such film is suitable as buffer layers for the growth of high-quality ferroelectric and superconducting overlayers.; Singapore-MIT Alliance (SMA)
LiNi₀.₅Mn₁.₅O₄ thin films have been grown by pulsed laser deposition (PLD) on stainless steel (SS) substrates. The crystallinity and structure of thin films were investigated by X-ray diffraction (XRD). Microstructure and surface morphology of the thin films were examined using a field-emission scanning electron microscope (FESEM). The electrochemical properties of the thin films were studied with cyclic voltammetry (CV) and galvanostatic charge-discharge in the potential range between 3.0 and 4.9 V. The electrochemical behavior of LiNi₀.₅Mn₁.₅O₄ thin films showed reversible capacity above 4.7 V and good cycle performance up to 50 cycles.; Singapore-MIT Alliance (SMA)
The process of depositing thin films by the use of pulsed laser deposition (PLD) has
become a more widely used technique for the growth of substances in a thin film form.
Pulsed laser deposition allows for the stoichiometric film growth of the target which
is of great significance in the deposition of High Temperature Superconducting materials.
We will describe a system designed using an excimer laser and vaccum chamber in
which thin films and superlattices of YBa2Cuj07_i, PrBa2Cu307_i, and YBajCujOr-j/
PrBajCusOr-^ were deposited on SrTiOs. Results of resistivity measurements using the
four probe technique will be shown.
SrMg^Rui-iOa thin films were made by using pulsed laser deposition on
SrTiOa (100) substrates in either O2 or Ar atmosphere. The thin films
were characterized by x-ray diffraction, energy dispersive x-ray microanalysis,
dc resistivity measurement, and dc magnetization measurement. The
effect of Mg doping was observed. As soon as the amount of Mg increased in
SrMg-cRui-iOa thin films, the magnetization decreased, and the resistivity
increased. It had little effect on the Curie temperature (transition temperature).
The magnetization states of SrMgiRui-iOa thin films, for x < 0.15,
are similar to SrRuOs films. X-ray diffraction results for SrMga-Rui-iOa
thin films made in oxygen showed that the films are epitaxial. The thin films
could not be well made in Ar atmosphere during laser ablation as there was
no clear peak of SrMg^Rui-iOa in x-ray diffraction results. Substrate temperatures
had an effect on the resistivity of the films. The residual resistivity
ratios were increased by increasing substrate temperature. It was observed
that the thickness of thin films are another factor for film quality: Thin films
were epitaxial, but thicker films were not epitaxial.
Thin films of Ge33As12Se55 were produced using two deposition techniques, ultra-fast pulsed laser deposition (UFPLD) and thermal evaporation (TE), and their properties have been investigated. The chemical composition of the UFPLD films was virtually ident
We have successfully fabricated highly oriented GaN films on ZnO-buffered quartz by Nd:YAG pulsed laser deposition to develop large area and low cost optoelectronic devices. The quality of the films was investigated as functions of deposition temperature
[ES] La técnica de depósito mediante ablación con láser es particularmente adecuada para la formación de láminas delgadas de óxidos con varios cationes, por ello se ha aplicado a la preparación de óxidos superconductores, ferroeléctricos y electroópticos. En este trabajo se señalan las ventajas de la técnica y simultáneamente se enfatizan algunos mecanismos secundarios que conducen a diferencias en la composición entre el blanco y la lámina. Específicamente se comentan las modificaciones del blanco, los procesos de dispersión en la fase vapor, la interdifusión entre la lámina y el substrato y la evaporación de especies de la lámina. Estos fenómenos se ilustran mediente el depósito de óxidos de niobio y titanatos de plomo. La compresión de los mecanismos relevantes para cada material permite optimizar las condiciones depósito hasta obtener láminas con la composición y cristalinidad para algunas aplicaciones microeléctricas y ópticas.; [EN] Pulsed laser deposition technique is very well suited for thin film preparation of multicomponent oxides. It has been applied
to the deposition of superconductor, ferroelectric and electrooptics oxides. The main advantages of the technique are briefly
summarised in this review...
We present a detailed study on the morphology and magnetic properties of Co nanostructures deposited onto oxidized Si substrates by femtosecond pulsed laser deposition. Generally, Co disks of nanometric dimensions are obtained just above the ablation threshold, with a size distribution characterized by an increasingly larger number of disks as their size diminishes, and with a maximum disk size that depends on the laser power
density. In Au/Co/Au structures, in-plane magnetic anisotropy is observed in all cases, with no indication of superparamagnetism regardless of the amount of material or the laser power density. Magnetic force microscopy observations show coexistence of single-domain and vortex states for the magnetic domain structure of
the disks. Superconducting quantum interference device magnetometry and x-ray magnetic circular dichroism measurements point to saturation magnetization values lower than the bulk, probably due to partial oxidation of the Co resulting from incomplete coverage by the Au capping layer.; Work was supported in part by the U.S. Department of Energy, Basic Energy Sciences (Grant No. DE-FG02-06ER46273), NSF FOCUS Center, the Spanish Ministerio de
Educación y Ciencia (References No. PR2005-0017 and No.MAT2005-05524-C02)...
An explosion in the growth of organic materials used for optoelectronic devices is linked to the promise that they have demonstrated in several ways: workable carrier mobilities, ease of processing, design flexibility to tailor their optical and electrical characteristics, structural flexibility, and fabrication scalability. However, challenges remain before they are ready for prime time. Deposition of these materials into ordered thin films requires that they be cast from solutions of organic solvents. Drawbacks of solution-casting include the difficulty of producing layered films without utilizing orthogonal solvents (or even with orthogonal solvents), the difficulty in controlling domain sizes in films of mixed materials, and the lack of parameter options used to control the final properties of thin films. Emulsion-based, resonant infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a thin film deposition technique that is demonstrated to provide solutions to these problems.
This work presents fundamental research into the RIR-MAPLE process. An investigation of the molecular weight of deposited materials demonstrates that emulsion-based RIR-MAPLE is capable of depositing polymers with their native molecular weights intact...
Ultra-fast pulsed laser deposition using high-repetition-rate short-pulse lasers has been shown to provide high optical quality, super smooth thin films free of scattering centres. The optimized process conditions require short ps or sub-ps pulses with repetition rate in the range 1-100 MHz, depending on the target material. Ultra-fast pulsed laser deposition was used to successfully deposit atomicaliy-smooth, Smicron thick As2S3 films. The as-deposited films were photosensitive at wavelengths close to the band edge (≈520 nm) and waveguides could be directly patterned into them by photo-darkening using an Argon ion or frequency doubled Nd:YAG laser. The linear and nonlinear optical properties of the films were measured as well as the photosensitivity of the material. The optical losses in photo-darkened waveguides were <0.2 dB/cm at wavelengths beyond 1200nm and <0.1 dB/cm in as-deposited films. The third order nonlinearity, n2,As2S3, was measured using both four-wave mixing and the z-scan technique and varied with wavelength from 100 to 200 times fused silica (n2,Silica ≈3×10-16 cm2/W) between 1100nm and 1100nm with low nonlinear absorption. Encouraged by the Ultrafast laser deposition results, we have built a new specialized mode-locked picosecond laser system for deposition of optical films and for laser formation of nanoclusters. The newly developed "state of the art" powerful Nd:YVO laser can operate over a wide range of wavelengths...
Amorphous carbon films were grown using ultrafast pulsed laser deposition from Q-switched and mode-locked Nd:YAG lasers. High repetition rate laser ablation resulted into very high film deposition rates on the graphite targets. The ultrafast laser ablation gave amorphous films of high surface quality and of excellent thickness uniformity.