Vacuum Deposition Techniques Research Articles

Electrochemical reactions by tunnel current through thin insulating anodic oxide films on tantalum

Tantalum electrodes covered with oxide films, the thickness of which ranged from 40–90 A, were investigated. Indium or gold was deposited on the oxide film by the vacuum deposition technique to prevent any change of oxide film properties by polarization. Polarization curves of In¦oxide film¦Ta diodes in a chloride buffer solution of pH 2.3 almost coincided with theI/V curves of them in the solid state. A redox reaction of a ferricyanide/ferrocyanide couple at Au ¦oxide film¦Ta was also perfectly controlled by electron transfer through the insulating oxide layer. Electron conduction with anodic polarization was mainly brought about by the electron tunnelling, while the Schottky emission possibly predominated in the conduction with cathodic polarization. Actual rates of corrosion of indium deposited on the films did not accord with those predicted by extrapolation of polarization curves to the open circuit potential, owing to the high electric resistance of the oxide films.

A Vacuum Coating Technique for the Development of Latent Fingerprints on Polythene

The development of latent fingerprints on low density polyethylene (polythene) packaging film by powdering has been hitherto unsatisfactory other than for fresh or heavy prints. Laboratory experiments and operational trials are described here of a vacuum deposition technique which has a considerably higher success rate. Ridge detail has been developed in 70% of operational cases and useful marks found in approximately 35% of cases.

A new GaAs, GaP, and GaAs xP 1−x vacuum deposition technique using arsine and phosphine gas. : F J Morris and H Fukui, J Vac Sci Technol, 11 (2), 1974, 506–510.

A new GaAs, GaP, and GaAs xP 1−x vacuum deposition technique using arsine and phosphine gas. : F J Morris and H Fukui, J Vac Sci Technol, 11 (2), 1974, 506–510.

Ovonic type switching in tin selenide thin films

Amorphous tin selenide thin films which possess Ovonic type switching properties are fabricated using vacuum deposition techniques. The devices are fabricated in a planar configuration and consist of amorphous tin selenide deposited over silver contacts. Results obtained indicate that Ovonic type memory switching does occur in these films with the energy density required for switching from a high impedance to a low impedance state being dependent on the spacing between the electrodes of the device. There is also a strong implication that the switching is a function of the magnitude of the applied voltage pulse.

Preparation and thermomagnetic properties of Ti-doped MnBi thin films

Ti-substituted MnBi thin films have been prepared on glass substrates by a vacuum deposition technique, and studies of magnetic, magnetooptic, and thermomagnetic properties of the films have been made. The nominal composition range of Mn 1-x Ti x Bi was x=0.1 to 0.4. The films were well oriented with the c-axis perpendicular to the film plane. The Curie point of the quenched high temperature phase (qhtp) decreased with increasing Ti-concentration, but that of the low temperature phase (ltp) was not altered by Ti-doping. The best Kerr rotation obtained for the qhtp films with x=0.4 was 0.5 deg at 6328 A. Both the Faraday and the Kerr rotation of the ltp and qhtp films decreased with increasing the Ti concentration. The time constant associated with the qhtp to ltp transformation was 103sec at 180°C for x=0.4. Curie point writing experiments with a helium-neon gas laser showed that the writing threshold of the qhtp film was about one third of that of the ltp film.

A new capacitive probe for the measurement of high-field domains in Gunn-effect devices

A new capacitive probe for Gunn-effect domain measurements is reported. The probe was constructed by a vacuum deposition technique rather than the use of thin foils. This results in greatly improved resolution and easier construction.

A new GaAs, GaP, and GaAsxP1−x vacuum deposition technique using arsine and phosphine gas

A new vacuum deposition process for depositing thin films of GaAs, GaP, and GaAsxP1−x is described. This process is similar to the standard molecular beam technique except that the arsenic and phosphorus are supplied from the decomposition of arsine and phosphine gas. The advantages of this process over the more conventional one-source and two-source molecular beam techniques are that the new gas-source process is more easily controlled and more reproducible and the deposition source materials are essentially inexhaustible, permitting a large number of samples to be coated during a single run. The process has been optimized for depositing polycrystalline films 800–1000-Å thick with sheet resistivities exceeding 1013 Ω/square for use as a resistive sea for silicon-diode-array camera tube targets. Variations in the deposition parameters, such as gallium temperature, the ratio of gallium to arsenic or phosphorus flux incident on the substrates, deposition time, and substrate temperature, were made to determine their effects on the film properties. A standard process was developed which permitted reproducible deposition of films which satisfactorily met the requirements of the camera tube application.

A New Cubic Iron Sulphide prepared by Vacuum Deposition

A FLASH evaporation technique of vacuum deposition has recently been developed to prepare the low-temperature phases of iron sulphides such as greigite (Fe3S4) and marcasite (FeS2), which are difficult to synthesize by the usual dry method1–3. Applying this technique, we have succeeded for the first time in synthesizing a nickel-free form of pentlandite (Fe,Ni)9S8.

A Thin-Film Intracochlear Multimicroelectrode

A flexible, intracochlear multimicroelectrode array is being developed for differential electrical stimulation of the cochlear nerve in human sensory deafness [M. Sonn, Proc. 25th Annual Conf. Eng. Med. Biol. 14, 159 (1972)]. The conductor elements, 0.3 μm thick, are formed on both sides of a thin-film plastic substrate using vacuum deposition and photolithographic etching techniques. In the present configuration, the array consists of 33 platinum conductors, 12.7 μm wide, each terminating at an electrode surface, 250 μm wide. The electrodes are spaced on 700 μm centers. Substrates investigated include Mylar, Parylene-C, and FEP and TFE Teflon films, 50 to 130 μm thick. Of these, Mylar was found best for electrode fabrication. Insulation of the array is accomplished by dip coating in Silastic. The electrode tips are exposed by mechanical scribing techniques. Short-term body tolerance studies in guinea pigs show good compatibility with the electrode materials. Bipolar sinusoidal stimulation of the electrodes in normal saline shows a decrease in complex impedance proportional to the −0.99 power of the frequency: 23.8 MΩ at 100 Hz to 250 kΩ at 10 kHz. Stimulation studies in vitro and in vivo (scalae tympani of cats) are planned to determine behavioral responses to electrical stimuli and long-term tissue reaction and electrolytic dissolution effects. [This work was supported in part by Raytheon Company.]

蒸着法で製造したCu-C合金の組織

By applying vacuum-deposition techniques, it may be possible to prepare solid solution alloys made up of constituent elements which are mutually insoluble in the liquid state. From this point of view, Cu-C alloys up to 0.25%Cu were succesfully produced, and their structures and the changes by annealing were investigated. The following results were obtained: (1) By using a substrate held at −196°C, ultra-fine polycrystals having grains of 100∼300 Å in diameter were prepared. (2) These foils held at −196°C recovered. The process of recovery in copper foil may be a type of 1st order reaction, but those in Cu-C alloy foils were analysed to be of 2nd order reaction. (3) The ultra-fine polycrystalline foils were recrystallized at 50∼110°C. The activation energies were 20∼25 kcal/mol and the values increased with carbon content. (4) The recrystallization in foils was considered to progress by two-dimensional growth. (5) The 0.2%-proof stress of Cu-C alloys after anealed at 800°C was about 30 kg/mm2.

Vacuum deposition of tin-selenium films

Films of tin and the volatile element selenium, composed in an arbitrary ratio, are produced with high reproducibility by the vacuum deposition technique which has been newly developed. This method comprises a two stepped-evaporation from the mother alloy containing selenium dissolved in tin. The mechanism of this method is investigated experimentally and theoretically, and the process of the first and second step of evaporation is discussed.

A barrier coating on tungsten fibers for nickel-base reinforced composites

1. The compound WAl12 applied to tungsten fibers by the vacuum deposition technique ensures that interfaces in nickel-base composites remain stable for not less than 100 h at temperatures of up to 1200°C and not less than 300 h at 1100°C. 2. In the course of the investigation, suitable heat treatment conditions were established for coated fibers, the condition of coatings was determined by x-ray diffraction, and the distribution of tungsten at the interface after various periods of heat treatment was examined by electron probe microanalysis.

Studies on the Structural and Optical Properties of AgIn<sub>1-X</sub>Ga<sub>X</sub>Se<sub>2</sub> (0 ≤ x ≤ 1.0) thin Films

Polycrystalline thin films of AgIn1-XGaXSe2 (AIGS) with varying x (0 ≤ x ≤ 1.0) have been grown onto glass substrates by stacked elemental layer (SEL) deposition technique in vacuum (~10-6 mbar). The thickness of the films was kept constant at 500 nm measured on line by frequency shift of quartz crystal. The films were annealed in situ at 300°C for 15 minutes. Structural and optical properties of the films were ascertained by X-ray diffraction (XRD) and UV-VIS-NIR spectrophotometry (photon wavelength ranging between 300 and 2500 nm) respectively. The diffractogram indicates that these films are polycrystalline in nature. The optical transmittance spectra reveal a maximum transmission of 85.91% around 1100 nm of wavelength for x = 0.2. A sharp absorption region is evident from the transmittance spectra that indicate a standard semiconducting nature of the films. The abruptness at the fundamental edge is more distinct in the film with x = 0.2. Optical transmittance, reflectance and thickness of the films were utilized to compute the absorption coefficient, band gap energy and refractive index of the films. The optical band gap is found to be direct-allowed. The band gap energy value, found from this study ranging between 2.3 to 2.4 eV, is very close for different gallium content films. The refractive indices increase almost linearly with photon wavelength range between 1300 and 1500 nm. DOI: 10.3329/jbas.v33i2.4098 Journal of Bangladesh Academy of Sciences, Vol. 33, No. 2, 151-157, 2009

Effects of Temperature on the Structural and Optical Preperties of AgGaSe<sub>2</sub> Thin Films

In this study, AgGaSe2 (AGS) thin films were formed onto cleaned glass substrates by using the stacked elemental layer (SEL) deposition technique in vacuum. The films were prepared at the post-deposition annealing temperature from 100 to 350°C for 15 min duration. The atomic composition of the films was measured by energy dispersive analysis of X-ray (EDAX) method. The films ascertain the compositional uniformity. The X-ray diffraction (XRD) has been employed to study the structure of the films. The structures of the films are found to be polycrystalline in nature. The lattice parameters, grain size, strain and dislocation densities of the films were calculated. Optical characteristics of the films were ascertained by spectrophotometer in the photon wavelength ranging between 300 and 2500 nm. The transmittance was found to increase with the increase of annealing temperature. The transmittance falls steeply with decreasing wavelength. It revealed that AGS films have considerable absorption throughout the wavelength region from 400 to 800 nm. The optical band gap energy has been evaluated. Two possible direct allowed and direct forbidden transitions have been observed for all the AGS films in visible region. The former varied from 1.67 to 1.75 eV and the later from 2.05 to 2.08 eV, depending on the post-deposition annealing temperature of the films. DOI: 10.3329/jbas.v33i2.4101 Journal of Bangladesh Academy of Sciences, Vol. 33, No. 2, 179-188, 2009

Preparation and Optical Properties of Evaporated β‐HgS Films

AbstractA modified vacuum deposition technique has been developed for producing thin films of HgS with cubic structure. Transmission and reflection measurements near the fundamental absorption edge have been carried out at various temperatures. The room temperature energy gap is determined to be 0.54 eV. The temperature shift of the optical absorption edge in β‐HgS is +7.7 × 10−4 eV/°K. With increasing carrier concentration, the absorption edge exhibits a shift to higher energies. The electron effective mass has been determined from reflectivity measurements. Its dependence on carrier concentration indicates nonparabolic behaviour of the conduction band. The temperature dependence of the electrical resistivity, Hall coefficient, and mobility between 4.2 and 300 °K has been measured. These studies reveal semimetallic behaviour of β‐HgS.

Development of a Closed-Flux Magnetic Memory Element

The fabrication and basic magnetic characteristics of a closed-flux memory element will be described. The element is made entirely by vacuum deposition and photoetching techniques. The element, which uses oxidized silicon as a substrate, consists of two 0.5-μ cobalt-Permalloy films deposited so that they overlap the bit line and provide flux closure in the easy direction. Partial flux closure in the hard direction is obtained by using a 1-μ ``keeper'' film. Tabs are included on the memory films to help reduce the reluctance through the SiO layer, which insulates the word lines from the bit lines. The problems involved in this development include: obtaining satisfactory insulation from the silicon, raising the Hc of the first magnetic film by a suitable undercoat, keeping the dispersion of the second magnetic layer and keeper film low by use of a smoothing coat, keeping the crystal size of the word and bit lines small during subsequent processing by using 95:5 Al–Cu alloy, and interlayer adherence, particularly the keeper layer.

A review of high vacuum deposition apparatus and techniques : J. Holden and D. Haynes, Lab. Equip. Digest, 5 (8), August (1967), p. 53

A review of high vacuum deposition apparatus and techniques : J. Holden and D. Haynes, Lab. Equip. Digest, 5 (8), August (1967), p. 53

Preparation and Properties of Chromium Films

A study was made of the properties of chromium films formed by vacuum deposition techniques. It was found possible to obtain films that had nearly bulk characteristics by using specific deposition conditions. The resistivity was determined as a function of film thickness. The orientation of the films was determined using x-ray diffraction. The film orientation was found to be dependent upon the particular glassy material used as a substrate. The resistance anomaly associated with the antiferromagnetic-paramagnetic transition in bulk chromium was observed. The experimentally determined resistance-temperature relationships for the Cr films were explained in terms of the effects of stress on the magnetic transition temperature.

Multilayer processing for magnetic film memory devices

Planar processing techniques for producing coupled film storage devices are presented. The discussion centers around a process sequence for a coupled easy-axis structure built on a metal substrate, largely by vacuum deposition techniques. The process results in packing density of about 8000 bits/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Included is a test of one such element displaying useful memory device characteristics under conditions of a worst case pulse test program.

A review of high vacuum deposition apparatus and techniques: J Holden and D Haynes,Lab Equipment Digest, 5 (8), Aug 1967, 53–74

A review of high vacuum deposition apparatus and techniques: J Holden and D Haynes,Lab Equipment Digest, 5 (8), Aug 1967, 53–74