W. C. Ellis

Study of the Filamentary Growth of Silicon Crystals from the Vapor

The preparation from vapor and the structure of filamentary crystals of silicon have been studied in detail. It was found by chemical etching, by examination for a twist associated with a screw dislocation, and by observations in the electron microscope, that both ribbons and needles of small dimensions are free of dislocations and imperfections. Certain impurities such as gold, nickel, or platinum, however, are essential for the growth of filamentary crystals.The growth of micron size and larger whisker crystals from the vapor takes place in two stages. The first is a rapid extension in length of a leader‐like crystal of small cross section; the second, a slow thickening of the leader through deposition on lateral faces. Initial growth is associated with impurities and does not require an axial screw dislocation. Subsequent growth may be explained by classical nucleation at a step and lateral translation of the step.

Whisker Crystals of Gallium Arsenide and Gallium Phosphide Grown by the Vapor—Liquid—Solid Mechanism

GaAs and GaP whisker crystals have been grown by the vapor—liquid—solid mechanism of crystal growth. Gold, palladium, platinum, and gallium have been used to produce the required liquid layer. The system employing wet hydrogen developed by Frosch and Thurmond was used for most of the crystal growing. p‐ and n‐type crystals were produced. GaAs crystals were found to have three morphologies: a twinned ribbon with a 〈112〉 growth direction and {111}, {110}, and {113} lateral faces; a single‐crystal hexagonal needle with a 〈111〉 growth direction and {110} lateral faces; and a newly found habit, a single‐crystal blade which grows in an 〈001〉 direction with {110} lateral faces. The largest GaAs blades were about 8×0.3 ×0.010 mm and grew at a rate of about 1 mm/h. The twinned ribbon and the 〈001〉, {110} morphologies were found in GaP.

Preparation and Morphology of Boron Filamentary Crystals Grown by the Vapor‐Liquid‐Solid Mechanism

α‐rhombohedral boron has been grown by the vapor‐liquid‐solid mechanism using the reduction of BCl3 with hydrogen for transport and platinum as the liquid‐forming agent. Both straight and kinked whisker crystals were produced with 〈4401〉 growth directions.

Transitions in Chromium

Discontinuous changes of Young’s modulus, internal friction, coefficient of expansion, electrical resistivity, and thermoelectric power are evidence for a transition in chromium near 37°C. Although the X-ray diffraction pattern gives no clue, a difference between the thermal expansivity and the temperature dependence of the lattice parameter suggests a crystallographic change. Young’s modulus data disclosed another transition near—152°C.

Atomic Relationships in the Cubic Twinned State

The twinned state is characterized by a lattice of coincidence sites. Imperfections are required at stable lateral twin interfaces. Twinned regions can occur with relative ease in the diamond cubic structure.

Growth of MnBi Crystals and Evidence for Subgrains from Domain Patterns

MnBi crystals have been prepared by crystallization in a temperature gradient from a liquid solution of bismuth saturated with manganese. Informative domain patterns have been developed on surfaces of a crystal by the normal Kerr magneto‐optic effect and by the Bitter technique. Block patterns, obtained in some instances, have been interpreted as evidence for subgrain structure.

Effects of compression and annealing on the structure and electrical properties of germanium

Germanium has been compressed under various conditions and has subsequently been annealed. These studies give direct evidence of the operation of the dislocation mechanism of plastic flow. No evidence of recrystallization has been found, but a domain structure composed of small angle boundaries is formed by large deformations at high temperatures. Annealable acceptor centers apparently due to point defects have been found and studied.

Thermal Variation of Young’s Modulus in Some Fe-Ni-Mo Alloys

Young’s modulus and its temperature coefficient were investigated in low coefficient Fe-Ni-Mo alloys under varying conditions of working and annealing. In the, ternary as well as the binary Fe-Ni alloys, the temperature interval of nearly constant Young’s modulus is greatly extended by work hardening. A stress-relief anneal is necessary to stabilize the alloys. Addition of 9 or 10 pct Mo decreases, the sensitivity of the thermal coefficient to variations in nickel by approximately a factor of two. In these, alloys the mean thermal coefficient of modulus for the temperature range —50° to 100°C varies from + 50 to —50 × l0−6 degree C−1 as the nickel varies from 36.5 to 41.5 pct. An alloy containing 9 pct Mo, 38 to 41.5 pct Ni, and balance Fe in the cold-worked condition has a low temperature coefficient of Young’s modulus, substantial magnetic permeability reasonably constant over a limited temperature range, and high strength. The coefficient of modulus can be controlled by controlling the Fe-Ni ratio. A further measure of control can be exercised by varying the straining-annealing procedure. The principal effects of molybdenum on the temperature dependence of modulus are explained by assuming that molybdenum decreases the modification in the interatomic energy-interatomic distance relation from the energy of magnetization.

Young’s modulus and its temperature dependence in 36 to 52 pct nickel-iron alloys

Young’s modulus and its temperature coefficient in 36 to 52 pct Ni-Fe alloys depend upon composition and also the straining-annealing history. Alloys near 42.5 pct Ni, when worked cold and then annealed at 400° or 600°C, have nearly zero mean thermoelastic coefficients between −50° and 100°C. A discussion of the theory is given.