Metallic films vacuum deposited

Three techniques have been described in the literature to prepare combinatorial libraries of fuel cell electrocatalysts solution-based methods [8, 10-14], electrodeposition methods [15-17] and thin film, vacuum deposition methods [18-21]. Vacuum deposition methods were chosen herein for electrocatalyst libraries in order to focus on the intrinsic activity of the materials, e.g., for ordered or disordered single-phase, metal alloys. 

Apparatus and Procedure. The metal films were deposited and adsorption thereon was carried out in a high-vacuum apparatus, as shown in Figure 1. The mica window was supported between two chambers that were evacuated simultaneously to prevent breakage the window was coated by evaporating metal from a heated filament in the upper chamber. The gas was then admitted to both chambers until the pressure was 1 atm. Valve 3 was closed to isolate the upper chamber, the bottom plate was removed, and the coxmter tube was positioned mder the window. After the film had been exposed 15 minutes to the gas, the solution was admitted and counting was started with an automatic coxmter-printer system. 

Thin films of (2,5-DM-DCNQI)2M (M=Cu, Ag) were prepared by the vacuum deposition and thermal treatment technique employed previously for analogous TCNQ-based materials (16,17). Thus, succesive layers of acceptor and metal were vacuum-deposited on the appropriate substrate to achieve a 2 1 DCNQI rmetal molar ratio. The so-obtained thin films were heat-treated at ca 150 C for a few minutes, to result in light-blue films for M=Ag and goldish films for M=Cu. Various substrates, such as quartz, KBr or CaF2 were used for transmission spectroscopic measurements covering the mid-infrared to uv spectral range. 

The need for extrapolation may be avoided by measuring the reflectance and transmittance through a metal film simultaneously (SchOler, 1966). The ellip-sometry method offers by far the best way to determine the complex dielectric function. A metal film is deposited in high vacuum onto the base of a silica... 

Most other metal films are deposited by physical vapor deposition, usually evaporation or sputtering. Both processes require a high vacuum and are relatively expensive. Sputtering is the most expensive method, but it allows a much better control of the film composition. As a result of mechanization of physical vapor deposition, the deposition price of metal films is now so low that application for general purpose resistors is possible. 

Fluoroplastic films such as FEP can be metallized by vacuum deposition. Metal adhesion is enhanced if the surface has been treated for adhesion by sodium etching or other procedures. Untreated general purpose FEP film may be vacuum-metallized for some applications depending upon the specific metal and deposition process. Copper, aluminum, silver, gold, and some metallic oxides have been applied to FEP film by vacuum metallization.f ]... 

Glass and copper substrates for anthrax detection and glucose detection respectively were pretreated as described previously (10, II). Approximately 2 pL of the nanosphere suspension (4% solids) was drop-coated onto each glass substrate and 10 pL of the nanosphere suspension was drop-coated onto each copper substrate and allowed to dry in ambient conditions. The metal films were deposited in a modified Consolidated Vacuum Corporation vapor deposition system with a base pressure of 10" Ton. The deposition rates for each film (10 A/sec) were measured as described previously (10). AgFON surfaces were stored in the dark at room temperature prior to use. 

Metall ic fibers are defined as fibers composed of metal, plastic-coated metal, or metal-coated plastic. Single-component metall ic fibers for textile usage are fine drawn filaments of metal which can be spun and woven on normal textile machinery. These metallic fibers possess the properties of the metal from which they are formed. Multicomponent metallic fibers are more commonly used in textiles and are usually made from flat aluminum filaments surrounded with or bonded between clear layers of polyester, cellophane, or cellulose ester or from polyester film which has been metallized through vacuum deposition of aluminum and then encapsulated in polyester. In general, the properties of these fibers resemble the properties of the plastic film used to form the multicomponent fiber. The fibers are generally weak and easily stretched but can be used for decorative purposes and for applications where electrical conductivity and heat resistance are important. Trade names for metallic fibers include Brunsmet and Lurex. 

Arc vaporization has a long history.An early use of vacuum arc deposition of thin film was to deposit carbon " and metal films. Arc-deposited carbon has long been used as a replication film in electron microscopy. Exploding wires (Sec. 6.3.5) are a type of arc discharge. 

Acoustic Wave Sensors. Another emerging physical transduction technique involves the use of acoustic waves to detect the accumulation of species in or on a chemically sensitive film. This technique originated with the use of quartz resonators excited into thickness-shear resonance to monitor vacuum deposition of metals (11). The device is operated in an oscillator configuration. Changes in resonant frequency are simply related to the areal mass density accumulated on the crystal face. These sensors, often referred to as quartz crystal microbalances (QCMs), have been coated with chemically sensitive films to produce gas and vapor detectors (12), and have been operated in solution as Hquid-phase microbalances (13). A dual QCM that has one smooth surface and one textured surface can be used to measure both the density and viscosity of many Hquids in real time (14). 

In order that the possibility of contamination of catalysts with traces of oxides could be eliminated Campbell and Emmett (51) studied the catalytic activity of metallic films of nickel and its alloys with copper or gold. They were deposited under a high vacuum and then sintered (alloys also homogenized) in hydrogen at 5 cm Hg pressure at 350°C or 500°C. The films were subsequently allowed to cool to room temperature and only... 

Soft metals such as In, Ag, Sn, Pb, and Au can lead to reasonably low friction coefficients, when used as solid lubricants, due to their low shear strength. The metals were generally applied as thin films prepared by the vacuum deposition process. Especially, in applications to the high temperature conditions where liquid lubricants fail due to the evaporation, the thin films of soft metals can provide effective protection to the surfaces in sliding. 

A quantitative analysis of the kinetics of CdSe deposition from selenosulfate, Cd(II)-EDTA baths in terms of a mechanism involving nucleation and electrode kinetics has been given by Kutzmutz et al. [65], Note also that selenosulfate-containing baths have been used for the anodic selenization of vacuum-deposited metal films in order to synthesize CdSe and other binary selenide semiconductor thin films such as CuSe and InSe [66],... 

The optical properties of electrodeposited, polycrystalline CdTe have been found to be similar to those of single-crystal CdTe [257]. In 1982, Fulop et al. [258] reported the development of metal junction solar cells of high efficiency using thin film (4 p,m) n-type CdTe as absorber, electrodeposited from a typical acidic aqueous solution on metallic substrate (Cu, steel, Ni) and annealed in air at 300 °C. The cells were constructed using a Schottky barrier rectifying junction at the front surface (vacuum-deposited Au, Ni) and a (electrodeposited) Cd ohmic contact at the back. Passivation of the top surface (treatment with KOH and hydrazine) was seen to improve the photovoltaic properties of the rectifying junction. The best fabricated cell comprised an efficiency of 8.6% (AMI), open-circuit voltage of 0.723 V, short-circuit current of 18.7 mA cm, and a fill factor of 0.64. 

Metallic thin-film media almost always are composed of Co alloys. Cobalt is chosen because of its high moment, but pure Co (either plated or vacuum-deposited) has a... 

To date, most small molecule-based OLEDs are prepared by vapor deposition of the metal-organic light-emitting molecules. Such molecules must, therefore, be thermally stable, highly fluorescent (in the solid state), form thin films on vacuum deposition, and be capable of transporting electrons. These properties limit the number of metal coordination compounds that can be used in OLED fabrication. 

Holland, L., Vacuum Deposition of Thin Films. Chapman Hall, London, 1960. 4B. Smithells, C. J., (Ed.) Metals Reference Book, 4th Ed., Vol. 1. Butterworth, London, 1967. 

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