Single Crystal Foils Research Articles

Electron-Induced Atomic Displacements near Threshold in Thin Single-Crystal Foils

The cross section for atomic displacement produced by energetic electron beams is obtained in an approximate manner under the following conditions: (a) The electron beam is centered about a major crystallographic direction coinciding with a minimum in the threshold energy surface. (b) The electron beam has angular dispersion due to finite collimation and/or multiple scattering. (c) Energy degradation of the electron beam is accounted for. The displacement cross section is found to be a sensitive function of the angular beam spread and the crystal parameter describing the threshold-energy surface valley. An average cross section is computed for a number of cases and compared with available experimental data for copper.

Growth of Face-Centered-Cubic Metals on Sodium Chloride Substrates

Films of gold, silver, copper, nickel, palladium, and platinum were prepared by evaporation of the metals in ultrahigh vacuum onto hot, vacuum cleaved, sodium chloride substrates. Nickel, palladium, and platinum films that completely covered the surface were single crystals in the orientation of the substrate. Complete gold, silver, and copper films were polycrystals in which there was a tendency for the (111) metal plane to be parallel to the (001) salt surface. Later, it was found that single crystal foils of gold, silver, and copper were obtained if the salt substrate was exposed to air prior to the deposition of metal upon it. Careful comparison of the growth of gold on clean and on air-contaminated salt surfaces has shown that the effect of air is not to improve the alignment of the initial gold nuclei, but is to increase the number of nuclei generated per unit area. This increase causes nuclei to coalesce earlier in film growth. The stage in film growth at which coalescence occurs influences the orientation changes that accompany coalescence, and thereby influences the orientation of the complete film.

The structure of gold films grown in ultra-high vacuum on sodium chloride substrates

Abstract Sodium chloride crystals were cleaved in ultra-high vacuum while the evaporation of gold was in progress. The films that grew on the freshly exposed (001) surfaces were examined in a transmission electron microscope, and in a reflection electron diffraction camera. A film grown at a deposition rate of about 2000 A. per second on sodium chloride at 360°C was a single crystal in the orientation of the substrate. Films grown more slowly on sodium chloride at 20, 150, 250, 320, 360, 420 and 460°C were polycrystals with nine preferrred orientations. One of these was parallel to the substrate lattice. Four had (111) parallel to the deposit plane, and a direction parallel to one of the two directions in the salt surface. The remaining four had (111) parallel to the deposit plane, and parallel to a direction in the surface of the salt. The relative concentration of the preferred orientations varied greatly with deposit thickness. Later experiments showed that single-crystal foils ...

351. A continuous pumped ultrahigh vacuum sorption system for the preparation of highly ordered single crystal metal foils

351. A continuous pumped ultrahigh vacuum sorption system for the preparation of highly ordered single crystal metal foils

A continuously pumped ultra-high vacuum-sorption system for the preparation of highly ordered single-crystal metal foils

A simple sorption-type ultra-high vacuum system has been devised in which thin metal foils can be prepared quickly, with perfection and measurable reproducibility. Ultimate vacuum of 3 × 10-10 torr had been obtained using liquid nitrogen around the sorption, and evaporation chambers. Ultimate vacuum of 3 × 10-9 torr has been routine prior to evaporation of gold, silver, copper, and nickel foils which ranged in thickness from 500-2000 A. High purity single crystal silver foils have been repeatedly prepared in this system which are suitable for direct analysis of deformations by transmission electron microscopy. A comparison is made between the order and quality of these ultra-high vacuum prepared foils with foils prepared using commercially available high vacuum equipment.

Dislocations and Chemical Etch Pits in Copper

The relation between chemical etch pits and dislocations has been studied in thin single-crystal foils of copper. Both deformed and as-grown crystals in {111} orientations were employed. A procedure was developed for etching thin foils so that both the etch pits and dislocations were simultaneously revealed by transmission electron microscopy methods. Results are also presented from companion studies of unetched foils and replica studies of etched surfaces. Although a relation was found between etch pits and dislocation emergent points, a one-to-one correspondence did not exist. A discussion is presented of other defects which may nucleate etch pits, including some experimental results on deformation-produced prismatic dislocation loops. The relation of the present results to dislocation studies by etching methods alone is discussed.

A Method of Preparing Thin Gold and Silver Foils of Uniform Thickness by Electrolysis

Gold and silver single-crystal foils of uniform thickness have been produced by electrolysis. The preparation of gold foils involves three steps: the evaporation of silver onto cleaved mica, the electrodeposition of gold on silver, and, lastly, the stripping of the gold foil by dissolving the intermediate layer of silver. Silverfoils are prepared by (1) evaporating silver onto cleaved mica, (2) electrodepositing silver on silver, and (3)mechanically stripping the silver foil.

A study of growth defects in face-centred cubic metal foils prepared by evaporation

Abstract Single crystal foils of copper, silver and gold were prepared by evaporation of the metal onto the cleavage face of a hot rock salt crystal. Examination of the foils in a transmission electron microscope showed the presence of dislocations and stacking faults. Many of the stacking faults had part of their area on one {111} plane and the remainder on another. A number of defects which involved three faulted planes were also observed. In addition, the foils contained dislocation loops and tetrahedral stacking faults similar to those discovered recently in quenched metals. The formation of defects during film growth has been considered. Stacking faults result from the coalescence of ' out of phase ' metal nuclei. Experimental evidence for this is presented.

On Producing Thin Single Crystal Foils of Aluminium which have any Desired Crystallographic Orientations

By using Prof. T. Fujiwara's method, we have succeeded in producing the aluminium single crystal foils (0.06×5×100 mm 3 , 99.53% in purity) having their definite crystallographic orientations; for example, they are orientated in [110]–(110) or [110]–(100) or D s or D d , etc. It was found that the easiness with which a single crystal foil was produced was remarkably different according to its crystallographic orientation. For the specimens D s and D d , it was also found that the bending behaviors caused by some mechanical shock were different from each other.