Showing papers on "Evaporation (deposition) published in 2000"

Growth Mechanism of MoS2 Fullerene-like Nanoparticles by Gas-Phase Synthesis

Abstract: Inorganic fullerene-like (hollow onionlike) nanoparticles (IF) and nanotubes have attracted considerable interest in recent years, due to their unusual crystallographic morphology and their interesting physical properties. IF-MoS2 and nanotubes were first synthesized by a gas-phase reaction from MoO3 powder. This process consists of three steps: (1) evaporation of the MoO3 powder as molecular clusters; (2) condensation of the oxide clusters to give MoO3-x nanosize particles; (3) sulfidization of the suboxide nanoparticles to generate IF nanoparticles. The evaporation of MoO3 (step 1) and the IF particle formation from the oxide nanoparticles (step 3) have been investigated already, while the mechanism for the suboxide nanoparticles formation (step 2) has not been studied before and is reported here. According to the present model, a partial reduction of the trioxide molecular clusters (3−5 molecules) leads to the formation of MoO3-x nanoparticles (5−300-nm particles size)the precursor for IF-MoS2. A math...

Film Formation Apparatus and Method for Forming a Film

Abstract: An apparatus for forming a film having high uniformity in its film thickness distribution is provided. An evaporation source is used in which an evaporation cell, or a plurality of evaporation cells, having a longitudinal direction is formed, and by moving the evaporation source in a direction perpendicular to the longitudinal direction of the evaporation source, a thin film is deposited on a substrate. By making the evaporation source longer, the uniformity of the film thickness distribution in the longitudinal direction is increased. The evaporation source is moved, film formation is performed over the entire substrate, and therefore the uniformity of the film thickness distribution over the entire substrate can be increased.

Germanium/carbon core–sheath nanostructures

Abstract: Germanium/carbon core–sheath nanostructures and junctions are produced when Ge nanowires are subject to a thermal treatment in an organic vapor doped vacuum. The organic molecules pyrolyze on the surface of the Ge nanowires and form a continuous graphitic coating. The carbon-sheathed Ge nanowires undergo melting and evaporation at high temperature, which results in the formation of germanium/carbon junctions. These core–sheath nanostructures and junctions generally have diameters of 5–100 nm, sheath thickness of 1–5 nm, and lengths up to several micrometers. This process may prove to be an effective approach to prevent the nanowire surface oxidation and create nanowires with chemically inert surface.

Structure, morphology, and optical properties of highly ordered films of para -sexiphenyl

Abstract: We have investigated the properties of highly textured films of para-sexiphenyl $(6P).$ The films are obtained by evaporation in high vacuum with different deposition rates and substrate temperatures. The crystal structure is analyzed by x-ray and elastic electron diffraction. Depending on the evaporation conditions and on the substrate pretreatment we find a marked texturing of the films. To better understand the growth conditions of $6P$ we have analyzed the film morphology by atomic force microscopy. The optical properties in the ultraviolet and infrared range are studied as a function of the orientation of the molecules. This enables us to show a strong anisotropy of absorption, luminescence, and luminescence excitation spectra. In order to gain a better understanding of the optical-absorption spectrum of the $6P$ molecular crystals we have analyzed the properties of films with chains oriented parallel and perpendicular to the substrate surface at low temperatures using a He cryostat. Both orientation and temperature-dependent absorption experiments clearly show the very complex nature of the low-energy absorption spectrum of $6P.$ To distinguish between intrinsic molecular properties and the effects of the three-dimensional crystal structure we have compared the experimental results to highly correlated post Hartree-Fock and to density functional theory (DFT) calculations for isolated $6P$ molecules as well as to angular dependent absorption spectra derived from DFT band structures.

Single‐fibre surface‐enhanced Raman sensors with angled tips

Abstract: Single-fibre surface-enhanced Raman sensors were prepared by depositing rough metal films at the tips of optical fibres. Different deposition techniques such as slow evaporation of metal island films and vacuum deposition of metal films over nanoparticles or on pre-roughened surfaces were applied and compared. The superposition of surface Raman spectra from the tips with Raman spectra of the fibre core made maximum enhancements necessary for the construction of long fibre sensors. The enhancement was improved significantly by altering the tip geometry. Angled polishing has enhanced the SERS intensity by up to a factor of 6. The intensity increases monotonically with increase in the angle, reaching its maximum value at the largest prepared angle of 40°. Copyright © 2000 John Wiley & Sons, Ltd.

System and method for film deposition

Abstract: PROBLEM TO BE SOLVED: To provide a film deposition system increased in the uniformity of film thickness distribution. SOLUTION: A thin film is deposition on a substrate by using an evaporation source provided with a vapor deposition cell having a longitudinal direction or a plurality of vapor deposition cells and moving the evaporation source in a direction perpendicular to the longitudinal direction of the evaporation cell. Because the uniformity of film thickness distribution in the longitudinal direction is improved by lengthening the evaporation source and film deposition is applied to the whole of the substrate by moving the evaporation source, the uniformity of the film thickness distribution over the whole of the substrate can be improved. COPYRIGHT: (C)2001,JPO

Method for improving electrical properties of high dielectric constant films

Abstract: A method of improving the electrical properties of high dielectric constant films by depositing an initial film and implanting oxygen ions to modify the film by decreasing the oxygen deficiency of the film while reducing or eliminating formation of an interfacial silicon dioxide layer. An initial high dielectric constant material is deposited over a silicon substrate by means of CVD, reactive sputtering or evaporation. Oxygen ions are preferably implanted using plasma ion immersion (PIII), although other methods are also provided. Following implantation the substrate is annealed to condition the high dielectric constant film.

The composite and film hardness of TiN coatings prepared by cathodic arc evaporation

Abstract: On the basis of the relative volume deformation of film and substrate, a new model of the composite hardness equation is presented for thin surface coatings. A solution is applied to arc evaporated TiN films with 0.5–3.0 μm thickness on stainless steel 304 and tool steel M2. The model shows that the hardness of deposited films and of the substrate materials can simultaneously be obtained from the experimental composite hardness as a function of indentation diagonal length.

Plasma and ion beam assisted metallization of polymers and their application

Abstract: Various high-temperature polymeric materials were preconditioned and metallized by using ion-assisted processes for adhesion improvement. The surface of the polymers was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and stylus profilometry. The adhesion of the coatings was controlled by pull-off and peel tests. The measurement of the specific electrical conductivity, the helium gas tightness and soldering experiments give valuable information concerning possible applications. In comparison to the pure copper evaporation onto polyphenylensulfid (PPS) the ion beam assisted deposition (IBAD) of copper films results in a distinct increase of the pull-off force. At ion energies around 2.5 keV and at low ion-to-deposited-atom ratio of 0.01 the film adhesion was enhanced from a pull-off strength of 10 N mm−2 up to 25 N mm−2. Plasma processes at a low pressure provide a high polymer etching rate by a plasmachemical attack and ion sputtering effects in a synergistic manner. The plasma etching process attack the polymer material preferentially. Therefore, mineral particles must still adhere strongly to the polymer to provide mechanical adhesion sites for the metal layers. An peel strength of about 1 N mm−1 was obtained on different substrate materials.

Evaporation and ion assisted deposition of HfO2 coatings: Some key points for high power laser applications

Abstract: Optical interference filters made by layers of optical coatings are used to shape and transport laser beams. If a defect is present in the stack (cosmetic defect, stoichiometry defect, absorption band…), and high laser power density is reached, a strong energy into the material can be deposited involving the destruction of the coatings (either by melting or mechanical failure). One of the key methods to achieve high performance coatings is to reduce such defects as much as possible. Hafnia (HfO2) coatings are undoubtedly one of the most successful materials for high power laser applications. Associated with a low index material such as silica, high laser induced damage threshold (LIDT) interference filters can be achieved. Hafnia is often the LIDT limiting factor. During the evaporation HfO2 particles create buried defects in the deposited material. These defects are sources of the coating damage during laser irradiation. To avoid this phenomenon we have evaporated metallic hafnium that was oxidized by oxygen inlet into the vacuum chamber or use an oxygen ion beam bombardment during the film growth. Argon or, better, xenon ions in the beam produced densities as high as 99% of the bulk, with low water content, and an improved optical transmission in the mid infrared window. This article deals with the optimization of such a deposition process regarding coating density, mechanical stresses, and optical properties (optical absorption). Films deposited by HfO2 evaporation are compared especially using photothermal mapping. The stoichiometry of the defects determined thanks to localized Auger spectroscopy clearly indicates how injurious such defects could be for high laser flux applications. Finally, laser damage thresholds of the films at 1.06 μm are measured and possible damage mechanism discussed.

Organic el element

Abstract: PROBLEM TO BE SOLVED: To prevent the occurrence of recrystallization and coagulation by enabling an organic layer to mainly exhibit a hole transport function or a light emitting function, and providing an evaporation polymerization film of a high molecular compound having a specific repeating unit. SOLUTION: An organic EL element is constituted by laminating an anode, an organic layer and a cathode in order on a substrate. First of all, an anode- formed substrate is prepared to be arranged in a vacuum deposition device. A tetracarboxy compound and a tetraamine compound are simultaneously evaporated on a deposition of the substrate in a vacuum, and a temperature is controlled so as to be evaporated in the (1:1) relationship. After evaporation, heat treatment is performed at a prescribed temperature for a prescribed time while holding a vacuum state in the device to form an evaporation polymerization film having a prescribed thickness. This evaporation polymerization film is a compound having a repeating unit expressed by the formula. (n) in the formula is an integer not less than 1. Afterwards, for example, an Mg-Ag alloy is deposited as a film by vacuum evaporation to obtain the organic EL element.

Investigation of PVD arc coatings on polyamide fabrics

Abstract: In contrast to conventional metallisation procedures for textile fibres and fabrics, physical vapour deposition (PVD) technologies allow the production of a defined structure of thin films on most fabric surfaces. This permits many new applications, especially for so-called technical textiles. The generation of properties such as supreme anti-static; electrical conductivity; shielding against electromagnetic radiation, protection against heat rays, chemical resistance, bacterial contamination, increased thermal stability and so on are only some examples. In the paper, initial results for coatings on polyamide fabrics are described. The experimental basis was an industrial PVD coating device of the HTC 1000/4 ABS™-type. Coating was performed in the arc deposition mode. Titanium and zirconium cathodes served as deposition materials. Nitrogen and acetylene were chosen for reactive processing. The aim of the study was to investigate some relevant correlations between the surface structures and functionalities of PVD-coated fabrics and the main process parameters. In particular, tribological and electrical properties were considered. Depending on the evaporation conditions, reactive metal deposition induces chemical and textural changes at the substrate surface due to an etching process. Higher reactive gas concentration leads to a more drastic recombination of the polymer surface and results in a fibroid fibre structure. Furthermore, reactive metal deposition leads to a better layer adhesion than a non-reactive metal deposition.

Vapour deposited Zn–Cr Alloy coatings for enhanced manufacturing and corrosion resistance of steel sheets

Abstract: In the present work, various Zn–Cr alloy coatings were deposited on automobilistic steels by a vacuum process, in which Zn and Cr are evaporated from resistance heated sources. After ion etching, different Zn:Cr evaporation rates were applied to produce several compositions in the films until a final coating thickness of 4 μm was obtained. The coatings were characterized with respect to morphology (SEM), structure (XRD) and hardness (by nanoindentation). The structure changed from the hexagonal Zn–Cr solid solution to a cubic (bcc) phase as the amount of Cr in the coating increased. Nanoindentation tests showed that the presence of Cr can significantly change coating hardness: this effect can be correlated with compositional and microstructural changes. To optimise the adhesion, the necessity of a multistage pre-treatment of the steel substrates was recognized. Further to Ar + sputter cleaning of the substrates, the deposition of a thin Cr interlayer is necessary. It was observed that, without suitable pre-treatments, the coatings are poorly adherent. Salt spray corrosion tests revealed that even small Cr additions are able to significantly improve the corrosion resistance of Zn coatings. The time for red rust to appear is very long (at least four times) when compared to pure Zn vapour deposited, or steel sheet electroplated with Zn (reference specimens). The generation of protective corrosion products which can suppress cathodic reaction is considered an important factor for that improvement.

Oxygen transportation during Czochralski silicon crystal growth

Abstract: Oxygen transportation processes concerning CZSi crystal growth have been investigated, including dissolution from silica crucible to silicon melt, evaporation from silicon melt to ambient Ar atmosphere and incorporation (segregation) from silicon melt to silicon crystal. It is found that almost all of the dissolved oxygen evaporates as the form of SiO from the surface of the silicon melt to the atmosphere of Ar gas in a conventional CZSi crystal growth. The quantity of the oxygen incorporated into the silicon crystal is only a very small amount compared to the dissolved oxygen or evaporated oxygen. The equilibrium segregation coefficient of oxygen was obtained by comparing the oxygen concentration in the silicon crystal to the oxygen saturation concentration in the silicon melt and the result is suggested to be 0.8±0.1. It is confirmed experimentally that the oxygen distribution in the CZSi crystal becomes much uniform and the oxygen concentration decreases gradually with increasing the cusp magnetic field, which indicates that the application of a cusp magnetic field is an effective method to control the convection in the silicon melt.

Spectroscopic ellipsometry measurements of thin metal films

Abstract: Optical methods are used to determine the thickness of thin metal films, with emphasis on spectroscopic ellipsometry and transmission. We discuss the conditions where this is possible and how to determine the optical constants for the material. The determination of the thickness of each of two metals in a bimetallic stack is discussed. Finally, by measuring thickness with these methods and measuring weight gain, we determine the density of platinum deposited by evaporation and deposited by a simple sputter deposition method. Explicitly, one of the results is that the determined optical constants depend on the deposition method. This implies that, with only a few exceptions, one must determine the optical constants of the material of interest, and that it is inappropriate to use values from another source such as a handbook or from another investigator. The resulting optical constants in this work suggest that the microstructure of the platinum films from the two different methods will not be the same, and x-ray diffraction and sheet resistance measurements verify that this is the case. Specifically, the significantly lower extinction coefficient of the sputter-deposited films correlates with a higher sheet resistance.