Narrow Results

To improve the adhesive strength between the film and substrate, ion bombardment is frequently performed before the deposition of thin film coatings. In this study scratch tests were carried out on aluminum alloy protected with CrN film coated by arc ion plating method. In order to investigate the influence of ion bombardment conditions on the adhesive strength between the aluminum alloy substrate and the CrN coating, the ion bombardment process was performed before CrN coating under several different bias voltages. The properties near the interface were analyzed using SIMS. As a result, the ion bombardment process had an optimum condition and excessive bias voltage reduced the critical load. A Cr rich layer forms near the substrate surface by implantation of Cr ions due to the high incident energy ions. The Cr rich layer is shallow for the high critical load sample, while the low critical load sample has a deep Cr rich layer. It appears that the adhesion strength between the substrate and the film will depend on the depth or intensity of this Cr rich layer.

Amorphous polymer-derived Si-C-N ceramics can be doped with different elements (Al, B etc.) through various pre-ceramic polymer routes. Thus, controlling of the high temperature oxidation resistance can be achieved on an atomic level. An important factor for silica layer growth is oxygen diffusion in protective thermally grown layers. In order to get insight of the oxygen diffusion mechanism, analysis should include both, bulk and short-circuit diffusion. XRD measurements of oxidized Si-C-N and SiC revealed the possibility that oxide layers were fully crystallized and are composed of nano-sized cristobalite-like grains. Secondary ion mass spectrometry depth profile analysis after ¹⁸O₂-¹⁶O₂ isotope exchange experiments on oxidized SiC indicated that short-circuit diffusion is probably grain boundary diffusion of molecular oxygen.

In this paper, we present a comparative study of structural and optical properties of polycrystalline p-type 6H-SiC and thin SiC layer growth onto Si. The thin SiC layer was grown on a p-type Si(100) substrate by pulsed laser deposition (PLD) using KrF excimer laser from a 6H-SiC hot pressed target. The properties of polycrystalline 6H-SiC and thin SiC layer were investigated by scanning electronic microscopy (SEM), high resolution X-Ray Diffraction (XRD), secondary ion mass spectrometry (SIMS), FT-IR spectroscopy and photoluminescence spectrometry. XRD analysis showed that the two materials have the same hexagonal structure (6H-SiC) as identified by ASTM 72-0018. In addition, a SIMS analysis gives a ratio Si/C of the thin SiC layer around 1.15 but the ratio Si/C of the target was found equal to 1.06, whereas one should have 1.0. This is due to the higher ionization efficiency of Si by the report of C atoms and in photoluminescence, the two materials exhibit the same emission bands (blue and green). Finally, a crystalline thin SiC layer of 1.6 μm was elaborated using the PLD method at low-temperature indicating that the technique reproduces the same macroscopic property (optical, structural, mechanical, etc.) of the target.

Hydrogenated amorphous SiC films (a-Si_1-xC_x:H) were prepared by DC magnetron sputtering technique on p type Si(100) and corning 9075 substrates at low temperature, by using 32 sprigs of silicon carbide (6H-SiC). The deposited film a-Si_1-xC_x:H was realized under a mixture of argon and hydrogen gases. The (a-Si_1-xC_x:H) films have been investigated by scanning electronic microscopy equipped with EDS system (SEM-EDS), X-rays diffraction (XRD), secondary ions mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR), UV-visible-IR spectrophotometry, and photoluminescence (PL). XRD results showed that the deposited film was amorphous with a structure of a-Si_0.81C_0.19:H corresponding to 19 at.% carbon. The photoluminescence response of the samples was observed in the visible range at room temperature with two peaks centered at 463 nm (2.68 eV) and 542 nm (2.29 eV). The structural properties and the origin of the luminescence were discussed.

With the current explosion of data, retrieving and integrating information from various sources is a critical problem. Work in multidatabase systems has begun to address this problem, but it has primarily focused on methods for communicating between databases and requires significant effort for each new database added to the system. This paper describes a more general approach that exploits a semantic model of a problem domain to integrate the information from various information sources. The information sources handled include both databases and knowledge bases, and other information sources (e.g. programs) could potentially be incorporated into the system. This paper describes how both the domain and the information sources are modeled, shows how a query at the domain level is mapped into a set of queries to individual information sources, and presents algorithms for automatically improving the efficiency of queries using knowledge about both the domain and the information sources. This work is implemented in a system called SIMS and has been tested in a transportation planning domain using nine Oracle databases and a Loom knowledge base.

Chlorine is one of the most used species to produce n-type ZnSe epilayers. In this paper, we present Secondary Ion Mass Spectrometry (SIMS) profiles of a series of Cl-doped ZnSe samples, which were grown by Molecular Beam Epitaxy (MBE) technique on GaAs substrates. These profiles have been used to examine the limitation of SIMS analysis of narrow Cl-delta layers. In order to convert SIMS raw data to quantified data, the depth profile from a Cl-implanted standard sample has been used to estimate the "useful ion yield" of chlorine and thus the instrumental sensitivity for chlorine in a ZnSe matrix. The "useful ion yield" and detection limit of chlorine in the ZnSe host matrix were calculated to be 4.7 × 10^-7 and 5 × 10¹⁷ atoms/cm³, respectively.

Al_xGa${}_{1-x}$N films were grown on Si/N-treated sapphire substrate by atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) in a home-made vertical reactor. This process can be considered as randomly in situ epitaxial lateral overgrowth (ELO) technology. The growth firstly begins by three-dimensional (3D) mode and is completed in two-dimensional (2D) growth mode as shown by real time in situ laser $(\lambda =632.8$nm$)$ reflectometry measurements and confirmed by scanning electron microscopy (SEM) images. Secondary ion mass spectroscopy (SIMS) measurements evidence Al composition pulling effect in the Al_xGa${}_{1-x}$N layer. The Si/N treatment technique is compared to conventional Al_xGa${}_{1-x}$N growth techniques. The results of high-resolution X-ray diffraction (HRXRD), photoluminescence (PL) measurements and SEM images agree well on the fact that the Si/N treatment produces Al_xGa${}_{1-x}$N layers with comparable qualities of Al_xGa${}_{1-x}$N layers grown on high temperature GaN template but with much higher qualities than Al_xGa${}_{1-x}$N layers grown on low temperature AlN nucleation layer. Moreover, the Si/N treatment technique permits the growth of high quality Al_xGa${}_{1-x}$N layers with appreciable thicknesses with respect to the others techniques.

This paper reviews research works carried out on silicon quantum dots (Si-QDs) embedded in the silicon nitride (SiN_x) dielectric matrix films with different fabrication techniques and different characteristics. The advantages of SiN_x as a dielectric compared to silicon dioxide (SiO₂) for Si-QDs from a device point of view are discussed. Various fabrication techniques along with different optimized deposition conditions are summarized. The typical results of structural characteristics of the films with Raman spectroscopy and Transmission Electron Microscopy (TEM) are discussed. The origin of photoluminescence (PL) from the films and the chemical compositional analysis such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Secondary Ion Mass Spectroscopy (SIMS) analysis of the films are also made available in brief. The charge conduction mechanism in the films with metal–insulator–semiconductor (MIS) structure, with their electrical characterization like capacitance–voltage (C–V) and current–voltage (I–V) measurements are presented.

Analysis using MeV ion beams is a thin film characterisation technique invented some 50 years ago which has recently had the benefit of a number of important advances. This review will cover damage profiling in crystals including studies of defects in semiconductors, surface studies, and depth profiling with sputtering. But it will concentrate on thin film depth profiling using Rutherford backscattering, particle induced X-ray emission and related techniques in the deliberately synergistic way that has only recently become possible. In this review of these new developments, we will show how this integrated approach, which we might call "total IBA", has given the technique great analytical power.

Analysis using MeV ion beams is a thin film characterisation technique invented some 50 years ago which has recently had the benefit of a number of important advances. This review will cover damage profiling in crystals including studies of defects in semiconductors, surface studies, and depth profiling with sputtering. But it will concentrate on thin film depth profiling using Rutherford backscattering, particle induced X-ray emission and related techniques in the deliberately synergistic way that has only recently become possible. In this review of these new developments, we will show how this integrated approach, which we might call “total IBA”, has given the technique great analytical power.