642. Apparatus for vacuum-depositing coatings on ferromagnetic parts

Classified

abstracts

633-642

calculation of desorption saturation density data.

and migration

activation

energies from

D J Packer and S J Hruska, J Vat Sci Technol, 8 (6), Nov-Dee 708-713. 633. Two-layer thick

approach

in making

insulating

1971,

30 films less than 100 A

The merit of making very thin insulating layers less than 100 A thick, by successively forming two layers of different dielectric films, was evaluated. The basic test structure was a capacitor with its insulating layer made up of different thickness combinations of thermally grown AlaO and vacuum-evaporated SiO. The two-layer dielectric films always give superior yields. In general, the result seems to indicate that a thinner insulating layer can be made from two layers of different dielectric films than from a single layer of either material. E J Hsieh, J l’uc Sci Technol, 8 (6), Nov-Dee 1971, 714-717. 30 634. Deposition and detection of Ag and Au films below 0.01 monolayer. (USA)

The controlled deposition of extremely small amounts of Ag andp is described. A shutter arrangement was developed which permits the deposition of metals from 10ms monolayer upwards, in conjunction with a rate-controlled evaporation source. Either continuous or stepwise variation of film thickness was attained. Deposits below about 1 monolayer consisted of particles which were invisible in the electron microscope. Their presence was detected by subsequent amplification of their size such that a visible deposit was formed. This was accomplished either by physical development, as known in photographic chemistry, or by vacuum deposition of zinc which was nucleated by these particles. The detection sensitivity of the methods is compared. M E Behmdt, J Vuc Sci Technol, 8 (6), Nov-Dee 1971, 724-732. 30 635. Model

for calculating the deposit physical-vapour-deposition. (USA)

temperature

in high-rate

A model is proposed for calculating the temperature of the substrate during vacuum deposition. It is based on an energy balance in the substrate-deposit combination. The energy input is from thermal radiation from the evaporation source and from the condensation of metal vapours. It is proposed that with this model one can set up evaporation experiments whereby measuring the substrate temperature and other experimental parameters, the total hemispherical emittance of liquid metals can be obtained. R Chow and R F Bunshah, Proc Vat Metallurgy Conf, J Vat Sci Technol. f3(6), Nov-Dee 1971, VM73-VM78. 30 636. Effect of deposition temperature on condensed phases in sputtered Ni-Cr thick films. (USA) A modified triode sputteiing technique was used to deposit nickelchrome alloys on pure nickel substrates maintained at temperatures varying from 550 to 1050°C by controlled, low energy electron bombardment heating. The coatings (110-200 P thick), deposited at rates between 960 and 1400 A/min, were evaluated utilizing metallographic, chemical analysis, electron micro-probe, x-ray diffraction, and electron diffraction techniques. A new phase, designated + was found when Ni-22 at. per cent Cr was deposited at temperatures above 750°C. The volume fraction of the new phase increased from 10 per cent at 750°C to 13 per cent at 1050°C. Heat treatment for 200 h at 1050°C showed no change in volume fraction of q previously deposited at that temperature, indicating that rl is the equilibrium phase. C Panzera et al, Proc Vat Metallurgy Conf, J Vat Sci Technol, 8 (6), Nov-Dee 1971, VM80-VM85. 30 637. Temperature and thickness distribution on the substrate during high-rate physical vapour deposition of materials. (USA) In high-rate physical-vapour-deposition processes, the thickness

of the deposit and the temperature vary along the substrate. The deposition temperature has a strong effect on grain size and density of the deposit. The deposition rate, thickness variation, and temperature variation depend on the 15 experimental variables, viz., evaporation temperature, source to substrate distance, source diameter, etc. This paper illustrates a method of calculating the temperature and thickness distribution of the deposit. The deposition of yttrium and yttria are used as examples to illustrate the actual range of experi-

mental conditions to be explored. An estimate of probable errors in calculated temperatures due to errors in the emittance data used is made. Radiation from the evaporating source, condensation of vapours, and the reaction of the elements are the sources of heat input to the substrate and the relative contributions of these are calculated for various experimental conditions. R Nhnmagadda and R F Bunshah, Proc Vat Metallurgy ConA J Vat Sci Technol, 8 (6), Nov-Dee 1971, VM85-VM94. 30 638. High-rate physical vapour deposition of hafnium foil-a feasibility study. (USA) The-high-ratelphysical vapour-deposition process has been used to uroduce hiah-nuritv ductile hafnium foil. The ductility of the foils in ihe O.OOl-&~Z &.-thickness range is excellent. Tge thinner foils (tO.001 in. thick) are considerably less ductile. There appears to be an inverse correlation between the ductility of the foil and the number of pinholes. Elimination of these should improve the ductility of the thinner foils. R F Bunshah, and R ‘I Webster, Proc Vat Metallurgy ConA J Vat Sci Technol, 8 (6), Nov-Dee 1971, VM95-VM98. 639. Investigation of hot-filament and hollow-cathode techniques for ion plating. (USA)

30 electron-beam

Several electron-beam melting techniques have been investigated which provide methods for melting various high-melting-point materials within a glow discharge atmosphere. The magnetically focused hot-filament and the cold-hollow-cathode electron sources have been experimentally studied to evaluate their operational and evaporation-deposition characteristics for the ion plating process. The hollow-cathode electron source emits an intense electron beam and is capable of delivering very high beam power. The gun is made of high melting-point sheets or screens formed into a hollow cylinder or sphere having an aperture to allow the emittance of electrons. It operates in an inert-gas, glow discharge environment such as that of ion plating. Gas pressure is a key processing variable in controlling the mode of operation; the hot-cathode mode operates at high pressures with excellent stability and the cold-cathode mode operates at low pressure and is sensitive to gas pressure variation. C T Wan et al, Proc Vat Metallurgy ConA J Vat Sci Technol, 8 (6), Nov-Dee 1971, VM99-VM104. 30 (USSR) 640. An evaporator for the vacuum deposition of coatings. A new type of evaporator for depositing metal and other coatings in vacua is described; it incorporates a reservoir with an electric heater and a dosing device at the bottom, a specially-shaped top being provided to support the heater supply system, together with a cooling spiral. When the heater is switched on, the reservoir is filled with the liquid to be evaporated and kept at the desired level by means of the dosing system, this being controlled by an electrical signal, which is automatically transmitted through a set of contacts when the level of the liquid falls. Evaporation takes place from the open surface only, and the rate of evaporation is controlled by special projections provided in the feed channels. Yu K Vishchakas et al, USSR Patent No 289148, appl2nd June 1969, publd 4th Feb 1971. 30 (USSR) 641. Feeding system for the dosing of powdered materials. A feeding system for use in the field of vacuum metallization is pro-

posed. Whereas conventional dosing devices employed for powdered materials incorporate a bunker connected to a tubular conduit and electromagnet, the new system is distinguished by having a tubular conduit furnished with a special type of piston, the plunger of the latter being made in the form of a plate passing through an opening in the throat of the bunker. This prevents caking of the powdered materials. Z Yu Gotra, USSR Patent, No 299572, appl 17th Nov 1969, publd 28th April 1971. 30 642. Apparatus for vacuum-depositing coatings on ferromagnetic parts. (USSR) A new form of apparatus for vacuum-depositing coatings on ferromagnetic parts is described; it differs from conventional devices of this kind in that the exposure system is made in the form of parallel hollow cylinders containing electromagnets with poles set in alternating directions, the side of the cylinders opposite to the evaporators 207

Classified

abstracts

643-652

being embraced by the yoke of a magnetic conductor, while the magnetic axes of contiguous electromagnets are set at a constant angle to one another in a sense opposite to that of the rotation of the cylinders. Mechanisms for loading and unloading the parts to be treated are attached to the end cylinders. This arrangement gives even coatings and eliminates wastage of the coating material. A G Zeberin, USSR Patent, No 301380, appl 19th Dee 1969, publd 1st June 1971. 30 643. Apparatus for the vacuum deposition of coatings. (USSR) An improved apparatus for the vacuum deposition of coatings is described. The system incorporates a horizontal vacuum chamber, a drum with a system of guiding rods, a motor for rotating the drum, several evaporators, and a pumping system; it is distinguished from others used in the same connection in that, in order to strengthen the whole structure and reduce operating losses, one group of evaporators is situated inside the drum and another over the top of the latter, while the rods are arranged in two rows, forming a rectangular configuration. M S Tsubin et al, USSR Patent No 285441, appl 13th March 1969, publd 26th April 1971.

pdld

31. EVACUATION

649. Material for cathodes.

31

31 645. Apparatus for measuring temperature in multiposition automatic systems used for the sealing of electrical vacuum apparatus. (USSR)

A modification to a standard 24-position automatic machine used in the sealing of electrical vacuum apparatus is described; in effect, one of the positions is converted into a temperature-measuring device for successively monitoring the temperature in all the working zones. As the machine rotates, the sensitive element passes from one zone to another, and the corresponding temperatures are recorded. The sensitive element is made from a material with a minimum thermal inertia and residual deformation, the temperature being determined by reference to its expansion. The apparatus may conveniently be calibrated by means of thermocouples. Examples of working models are described. E Ya Sterkin et al, USSR Patent No 279107, appl 21st July 1967, publd 4th Nov 1970. 31 646. Apparatus

for the vacuum

treatment

31 648. A heating element. (USSR) An invention relating to a heating element (of the kind used in electronic apparatus) designed to reduce the rate of evaporation and increase the specific electrical resistance is described. As a protective layer on the surface of the proposed heating element, the carbide of a refractory metal is empIoyed. Heating elements of a wide variety of shapes (discs, rings, cylinders, spheres) may be made in this way. B N Veretennikov et al, USSR Patent No 294268, appll2th Sept 1969, 12th March

1971. 31

AND SEALING

644. Method of processing electrical vacuum and gas-discharge devices. (USSR) A method of preparing electrical vacuum and gas-discharge devices for service is described. The devices are first connected to a vacuum system and the pressure is reduced at 0.001-10 Iitres/sec, depending on the geometry of the device. A gas-discharge is initiated on reaching a pressure of lW.01 mm Hg, again depending on the nature of the device, the voltage being maintained at 100-3000 V, and evacuation continues. Grease and saltxcontaminants are eliminated by the resultant ion bombardment. In order to prevent the condensation of contaminants after their initial removal, the outside of the device is irradiated with ultrasound at the same time as the gas discharge is ignited, the intensity of the ultrasound being sufficient to remove adsorbed particles. E P Gel’ and Yu S Spiridonov, USSR Patent, No 290343, appl 12th Nov 1968, pub/d 15fh Feb 1971.

magnetrons.

example) are considered, and an improved method which eliminates many of these difficulties is described. In the new method, the integral parts of the cathode unit are first joined loosely by firmly compressing the core of the cathode in a clamp along its whole perimeter, then the unit is mounted as a whole in the envelope. The outer parts are made of a material with a thermal expansion coefficient smaller than that of the inner parts at 606900°C. During the activation of the cathode the heating involved causes diffusion to take place between the contiguous parts, and these automatically become-welded together. N A Iofis, USSR Patent No 285118. , am1 uubld 12th Jan __ 31st Ott 1968. __ 1971.

of the cathode

units

of

(USSR) Existing devices used for the vacuum treatment of the cathode units of magnetrons provide no facilities for verifying the thermionic emission and secondary-emission characteristics of the units without conveying these to a separate installation. In the invention here described such provision is in fact made. This is done by incorporating a measuring device comprising an insulated anode with an annular slot in the middle and an annular tungsten cathode surrounding the anode at the level of the slot ; the inner surface of the anode collects secondary and reflected electrons. A I Pipko et al, USSR Patent No 277119, appl27th Dee 1967, publd 29th March 1971. 31 647. Method of making cathode units. (USSR) Difficulties arising in the ordinary method of preparing the cathode units of electronic apparatus (in the spot-welding of the parts, for

(USSR) A new material for the manufacture of thermionic cathodes is proposed; it differs from many conventional materials in that it comprises a solid solution of the borides of rare-earth and alkaline-earth metals in the proportions 60-95:50-5 molecular per cent. These solid solutions have a lower vapour tension than individual borides and thus evaporate less than the latter during preparation of the cathodes. A typical example is that of BaB, dissolved in LaBB; the solid solution has a metallic type of conductivity and better emission characteristics than LaB, by itself. For cathodes working at 140& 1550°C the current density is twice as great in the solid solution. G A Meerson et al, USSR Patent No 299887, appl2nd Ott 1968, publd 7th June 1971. 31 650. Anti-emission material for coating the grids of electronic valves. (USSR) A new anti-emission material for coating electronic valve grids is described; it differs from existing materials used for this purpose in that it incorporates 20-70 per cent of germanium, as a result of which it evaporates more slowly than its predecessors. The alloy also contains lo-40 wt. per cent of nickel, the balance being tin; it may be prepared by simple fusion of the constituents, and has a melting point between 750 and 82O”C, depending on the precise composition. Different versions of the alloy are thus suitable for valves working at different temperatures. A typical thickness of the coating so applied is l-4 pm. The nickel may be replaced by other metals of the iron group if this should prove more convenient. The alloy is more versatile than the corresponding binary materials. Yu S Pipipkov, USSR Patent No 272998, appl22nd July, 1968 publd 11th May 1971. 31 651. A nickel-base alloy. (USSR) A nickel-base alloy for use in the cathodes of electrical vacuum apparatus is described. The alloy contains 2-10 wt. per cent tungsten and 2-8 wt. per cent rhenium; it is produced by melting the constituents in an induction vacuum furnace, and subsequently remelted in an electron-beam refining installation. The ultimate tensile stress of the alloy is ~18 kg/cm9 at 8OO”C, almost double that of the corresponding alloy in the absence of rhenium. The alloy has excellent activating properties and its working parameters remain stable for 12,000 h; it is most suitable for the manufacture of elongated valve cathodes. N A 106s et al, USSR Patent No 290062, appl 14th Jan 1969, pubId 11th June 1971. 31 652. Grids of high-power electronic apparatus. (USSR) Disadvantages of existing models of grids used in high-power electronic apparatus are pointed out. Thus grids consisting, for example, of a copper framework with tungsten wire wound around it tend to undergo serious distortion as a result of the difference between the thermal expansion coefficients of the constituent metals. This situation may be ameliorated by provided longitudinal grooves in the