A B S T R A C T S ON M I C R O E L E C T R O N I C S AND R E L I A B I L I T Y
A static capacitor m e t h o d for the m e a s u r e m e n t o f the surface potential o f gases on evaporated m e t a l films. T. DELCHAR,.7. Sci. Instrura. 40, 3 (1963), pp. 105-107. A static capacitor is described for the measurement of potential change during the adsorption of gases on evaporated metal films. The method eliminates the need for vibrating or rotating parts in the cell structure, and enables rapid surface potential changes to be followed. The margin of error for all measurements is less than 1 per cent. The preparation and use of a new reference surface is also described. Studies of the exo-electron emission accompanying surface potential changes during chemisorption can be made using the same apparatus. Vapour sources for v a c u u m deposition o f s u p e r c o n d u c t i v e thin-film circuitry. A. J. LEARN and R. S. SPruces, Rev. Sci. Instrum. 34, 2 (1963), pp. 179-182. Radiatively-heated ovens have been used as vapour sources for vacuum deposition of superconductive films, primarily tin and lead. They delivered uniform deposition rates in the entire range tested from tenths of angstroms per second to ~--100 A/sec. For the experimental arrangement employed, a deposition rate of 1 A/sec is found by calculation to correspond to an effusion rate from the oven of 2× 10-; moles/cmO-/sec. By effectively reducing the length of the oven opening to zero and increasing the ratio of oven diameter to opening diameter to about four, an emission characteristic of a surface source was obtained for the same range of deposition rates. For one such oven of typical dimensions, a chart is included by use of which compromise may be made between effective source enlargement, due to self-scattering effects at the source, and deposition rate. Thin film cold cathodes. W. HAAS and R. JOHANNES, Brit. y. Appl. Phys. 14, 5 (1963), pp. 287, 288. Electron emission in vacuum has been observed from thin-film capacitor-like devices, prepared mainly by evaporation techniques and anodization. Continuous emission and destructive processes which depend on the insulating film and counter-electrode material are described. Transfer ratios up to 2 per cent were obtained. Metallic thin films and their properties. C. A. NEUGEBAUER, International Electronics, November (1963), p. 30. It is often found that the physical properties of thin films cannot be explained simply on the assumption that they are thin slices of the bulk materials and differ from them in no other respect. In such cases, the structure of the film differs from that of the bulk. More and more effort is therefore being spent on determining and controlling film structure. Since this structure is largely determined by the processes involved ill its formation and growth, an understanding of these is basic to an understanding of film properties. The articles discusses the physics of evaporation and nucleation, highly disordered, tectured and single-crystal films. Electrodeposited N i - F e thin films.* Y. UEHARa, Japan..7. Appl. Phys. 2, 8 (1963), pp. 451-462. The magnetic properties of nickel-iron thin films electrodeposited on to copper substrates have been experimentally studied with the following results. (1) The coercive force He takes the minimum value at the film composition about 81.5 Ni-18-5 Fe. The squareness ratio Br/Bs of Fe-rich films is very close to 1, while that of Ni-rich films decreases with an increase of nickel concentration. (2) The coercive force, He, is proportional to d -n for the 71--~88 per cent Ni-Fe films, 1200-1400 A thick. The exponent n takes a constant value in Fe-rich regions, while the value gradually decreases with an increase of nickel concentration passing through 81.5 Ni-18.5 Fe. (3) The uniaxial anisotropy is remarkably affected by the geometrical states of the surface of the substrates. M a g n e t i z a t i o n reversal in thin films 82 per cent Ni, 18 per cent Fe. G. R. HOFFMa.X, J. A. TURNER and H. LACHOWlCZ,Archiwum Elektrotechniki XII, 3 (1963), pp. 583-589. During investigations of the shape variation of hysteresis loop of the magnetic materials with rate of rise changes of the driving field, carried out recently by the authors, some results interesting from the point of view of flux reversal in thin films were obtained. These investigations were continued for anisotropic thin permalloy films, using pulse technique. The results of pulse experiments are presented in this paper. The experiments show that even under conditions when coherent rotations is expected to occur domain wall motion or non-coherent rotation is the resulting motion by which a magnetization change takes place. This suggests that the maximum possible operating speed for digital storage system using thin magnetic films will only be achieved by eliminating impurities so that formation of domains is prevented.