Papers by Keyword: Thin Film

Abstract: In-doped ZnO thin film has been found as one of the most promising materials in the optoelectronics, but its optical properties are rarely reported. We calculated optical band gaps and optical properties of Zn_1-xIn_xO with different In doping by using first-principle. The results reveal that the lattice constants of Zn_1-xIn_xO increase linearly with the doping increasing and Zn_1-xIn_xO (x=0.125, x=0.25) crystal comes to be degenerate semiconductor with band gap reduced. The imaginary part of dielectric function has an increasing trend and the absorption capacity significantly increases in ultraviolet (UV) range after doping. Also there is an obvious red-shift in the absorption spectrum. The reflectivity and energy loss spectrum were investigated, too. The results can provide a theoretical reference for finding appropriate UV protective material.

Abstract: The Ion Beam Enhanced Deposited (IBED) lithium tantalate (LiTaO₃) thin film samples with Al/LiTaO₃/Pt electrode structure were prepared on the Pt/Ti/SiO₂/Si(100) and SiO₂/Si(100) substrate respectively. The crystallization, surface morphology, ferroelectric property, and fatigue property of the prepared samples with the different annealed processes were investigated. The XRD measured results show that the prepared samples have the polycrystal structure of LiTaO₃ with the preferred orientation of <012> and <104> located at the 2θ of 23.6⁰ and 32.7⁰ respectively. The SEM morphology analysis reveals the prepared film annealed at 550°C is uniform, smooth and crack-free on the surface and cross section. The ferroelectric property measured results show that the remanent polarization Pr of the samples annealed at different temperature almost increase with the electric field intensity stronger. The leakage current makes the hysteresis loop of the samples subjected to a strong measured electric filed difficult to appear the same saturation hysteresis loop as the single-crystal LiTaO₃. The prepared samples annealed at 550°C have a Pr value of 11.5μC/cm² when subjected to the electrical field of 400kV/cm. The breakdown voltage of the 587nm thick thin film sample is high as to 680 kV/cm. The fatigue property measured results show only 15.17% Pr drop of the prepared films annealed at 550°C appear after 5×1010 cycles polarized by the 10MHz sinusoidal signal with the peak-to-peak amplitude of 10 Volt. The ferroelectric properties of the prepared films meet the practical application requirements of charge response measurement of the LiTaO₃ infrared detector owe to the Pr of the prepared films annealed at different temperature large beyond 10μC/cm² when the prepared films subjected to a strong electric filed larger than 400 kV/cm. The experimental results also show that the surface morphology, the ferroelectric and fatigue properties of the IBED LiTaO₃ thin films are significant better than those of the Sol-Gel derived LiTaO₃ thin films.

Abstract: In this paper, we study the effects of a magnet, located in the cathode, on barium hexaferrite thin films deposited by RF magnetron sputtering technique. During the process, these effects can modify thickness, roughness and stress of coatings. The characteristics of the deposited layers depend on the substrate position that is located opposite of magnetron cathode. In the "magnetron area", one can observe that the high stress can produce cracks or detachment of layers and the increasing of both depositing rate and surface roughness. After sputtering elaboration, barium hexaferrite films are in a compressive stress mode. But, after the post-deposition heat treatment these films are in a tensile stress mode. To improve the quality of BaM films, the subsrtate has to be set outside the magnetron area.

Abstract: In this work the capability of the proton induced X-ray emission (PIXE) technique to monitor a rapid, non-destructive and accurate quantification of Al on or inside SiC is discussed. Optimization of PIXE acquisition parameters was performed using as reference, a thin Al film (2.5 nm) thermally evaporated onto silicon carbide substrate. In order to improve the sensitivity for Al detection and quantitative determination, a systematic study was undertaken using proton ion beam at different energies (from 0.2 to 3 MeV) with a different tilting angle (0°, 60°, and 80°). The limit of detection (LOD) was found to be lower than 0.02 nm. The optimum PIXE conditions (energy, angle) were applied for determining the Al doping concentration in thin (1 µm) 4H-SiC homoepitaxial layer. The Al concentration as determined by PIXE was found to be 3.9x1020 at/cm3 in good agreement with SIMS measurements, and the LOD was estimated to be 6x1018 at/cm3.

Abstract: Abstract. A new technique of inductive measure to determine the initial magnetic permeability (r) of Yttrium Iron Garnet (YIG) thin films has been conceived and developed in our laboratory. The magnetic material is deposited by radio-frequency sputtering between two copper thin layers on alumina substrate. Because the as-deposited films are amorphous and non magnetic, thermal annealing is necessary to make the films crystallize and to obtain satisfactory magnetic properties. After different tests considering the geometrical, morphological and magnetic properties, we have established a protocol permitting to manufacture a prototype in an original design. The performance of the fabricated micro-inductor has been checked using a physical-chemistry characterization. To obtain accurate measurements, we have used a four-point probe test bench and a precision LCR meter. The current sheet method has been validated with thick layers of commercial YIG. The results obtained for thick and thin films of YIG have been compared to the simulation and theoretical ones. Several tests, made for different thickness and different number of loops, have permitted us to evaluate the magnetic permeability of YIG thin films to 32 ± 4.

Abstract: Thin coatings of Tungsten were deposited on substrates fabricated by pre-depositing graphite thin layers on Si(100) wafers. We ablate pure W target using a 20 ns KrF excimer laser (248 nm) in an Ar ambient. The effect of background gas pressure, substrate temperature, and laser fluence, on the properties of the deposited W layers is studied using several techniques including X-Ray Diffraction, Atomic Force Microscopy, surface profilometry, and Rutherford Back-Scattering spectrometry. Our results indicate that the deposited layers consist of the well-crystallized body-centered-cubic α-W phase with bulk-like properties, particularly for films deposited at a substrate temperature of 450°C, laser fluence greater than 400mJ, and pressure of about 10mTorr.

Abstract: This study focus on the nature of different Si-based sensitizers for Er³⁺ ions in Silicon- Rich Silicon oxide thin films. The samples were first analyzed by Cathodoluminescence technique to probe all emitting centers in the films. Some of these centers were found to be potential sensitizers for Er³⁺ ions, such as Silicon Oxygen Deficient Center and Non-Bridging Oxygen Hole Center, in addition to the well-known Silicon-nanoclusters (Si-nc). The influence of the thickness was subsequently examined, revealing that the formation of Si-nc is inhibited for films thinner than 100 nm and this led to less sensitization of the Er³⁺ ions. We demonstrate that the introduction of a SiO₂ buffer layer can overcome this issue and increase the luminescence of Er³⁺ ions by a factor of five for films thinner than 50 nm that are usually used for electrically-driven photonic devices.

Abstract: The effect of corona electric field on the surface of Pr-doped ZnTe thin film was studied. The device which can produce the high-voltage corona electric field is developed and used. The V-A characteristics of positive and negative corona discharge between the adjacent needle plates were measured. Whether positive or negative corona discharge, the corona discharge current of the plate is increased with the applied voltage increasing; the voltage range of negative corona discharge is wider than that of the positive corona discharge, meanwhile under the same applied voltage, the negative corona discharge current is bigger, not only its curve is smooth, but also its discharge is stable. The thermal effect of electric field is small. The electric field strength is 7.0 kV•cm-1. By atomic force microscope, it is found that the size of particles becomes large and uniform, and the surface becomes rough with electric field treatment. The measurement results reveal that the average radius of particles is 108.70nm before the effect and 227.27nm after the effect. By UV-Vis Spectrophotometer, it is found that a strong optical absorption peak appears at the region of 220 - 250nm with electric field treatment. This means that the stronger light absorption peak turn out a blue shift under the effect of electric field. The phenomenon of the blue shift proves that the high-voltage corona electric field has an impact on the band gap of the film. The voltage range of the negative corona discharge is wide and stable. The thermal effect produced by the high-voltage corona electric field on the sample is very small, so usually it can be ignored. The high-voltage corona electric field can change the surface morphology of some films, makes the current density of the sample location increase in a small cross section. The negative high-voltage corona discharge should well be used to research in biophysics such as the transgenic plants. High-voltage corona discharge mutagenesis has become a new physical mutation technique. Introduction

Abstract: In this paper, the growth process of Ni deposited on the Cu() surface at 300K and 700K was simulated by molecular dynamics. The impact of the substrate temperature on the growth pattern and structure of thin film was investigated. The simulation results show that, at the higher substrate temperature, the surface of thin film is smoother and the growth pattern of thin film is two-dimensional layer, however, at the lower temperature, the growth mode of thin film is three-dimensional island.

Abstract: This study used molecular dynamics simulations with an embedded-atom method (EAM) potential to investigate the effect of surface roughness on the surface activated bonding (SAB) of aluminium thin films. The simulations started with the bonding process and followed by the tensile test for estimating bonding strength. By averaging the atomic stresses over the entire system, the stress-time curves for the bonded films under a tensile condition were predicted. Moreover, the evolution of the crystal structure in the local atomic order was examined by the common neighbour analysis. The simulated results show that the decrease in the surface roughness of thin film improves the bonding strength. The observed recrystallization processes inside the bonded thin films also reveal that the plastic deformation of the aluminium surface due to atomic attracting force compensates surface roughness.