Ribbon Edges Research Articles

High speed EFG of wide silicon ribbon

A system for high speed EFG of silicon ribbon is described which is capable of growing ribbon up to 7.5 cm in width and 7.5 cm/min in speed. A technique for achieving constant width growth has been developed through the utilization of temperature gradients along the ribbon width to stabilize and control the ribbon edge. Problems which have to be solved with respect to maintaining growth stability and eliminating buckling of the ribbon at higher growth speeds are examined in detail.

Imperfections and impurities in EFG silicon ribbons

The structure, morphology, and distribution of crystallographic defects in silicon ribbons grown by the edge defined film-fed growth (EFG) process are found to be functions of crystal growth rate. Two distinct types of defect distributions are observed in these crystals when grown at different rates. At growth rates below about 2.5 cm/min, the structure consists of parallel arrays of dislocations, twins and stacking faults parallel to the ribbon edges and extending through the thickness of the crystal. At growth rates in excess of 2.5 cm/min, a subsurface structure composed of large angle grain boundaries and, sometimes, equiaxed grains develops. An examination of the structure of these crystals is followed by the presentation of a model to account for the particular defect structure developed. The model is based on the proposition that defect generation is a consequence of the association of native point defects in the form of silicon self-interstitials and dissolved carbon which is a major impurity in EFG silicon. The electrical consequences of the development of the particular defect structure are examined, and it is postulated that imperfections in shaped crystals can function as intrinsic gettering agents for impurities, thus causing an improvement in the electrical properties of the crystals.

Automatic signalling of the position of glass ribbon edges in edge-holders

Automatic signalling of the position of glass ribbon edges in edge-holders

Surface Morphology and Shape Stability in Silicon Ribbons Grown by the Edge‐Defined, Film‐Fed Growth Process

The morphology and shape stability of silicon ribbons grown by the edge‐defined, film‐fed growth (EFG) technique are described. A theoretical analysis of shape stability is presented for controlled‐shape growth (where the ribbon shape is determined by the shape of the meniscus); experimental evidence is introduced to show the inherent stability of the ribbon side and the relative instability of the ribbon edges, in agreement with the theory. The characteristic meniscus angle for constant‐dimension growth is shown to depend on the crystallographic orientation of the ribbon surface; the anisotropy is associated with the anisotropy in the crystal‐vapor surface free energy in silicon. Growth features which result from faceted growth on peripheral octahedral planes are described, and the competition between faceted growth and controlled‐shape growth is analyzed. Various morphological features associated with variations and fluctuations in the EFG process variables are described.

Dielectrophoretic liquid expulsion.

In a dielectrophoretic, zero-gravity liquid expulsion system, the polarization forces serve to 1) define a portion of the tank volume where the liquid is preferentially oriented and 2) provide a channeling mechanism by which the liquid can be withdrawn from that region through the agency of external pressure sources. In the relatively lightweight concept described, high-voltage ribbon electrodes deployed along the tank wall form conduits with the wall through which liquid contacting the ribbon at any point is communicated to the drain. The side walls of these conduits are electromechanical and depend for their rigidity on the electrohydrodynamic bang-bang interaction between the liquid interfaces and the strong fringing field gradient at the ribbon edges. A steady-flow design model relates electrode geometry and voltage to fluid properties and withdrawal rate. A dynamic model describes flow criticality effects and the consequences of perturbations in pressure. Electrohydrodynamic surface waves, which play a role in dielectrophoretic pipes similar to that of gravity waves in ordinary free-channel flows, are described and verified experimentally. Experiments demonstrate the significance of the steady-flow and dynamic models, and an example illustrates the design of typical expulsion systems for cryogenic hydrogen and oxygen.

Direct-Positive Variable-Area Recording with the Light Valve

By reflecting light from the back surface of the light-valve ribbons and focusing the ribbon edges at the film plane a bilateral or unilateral type of direct-positive variable-area track is obtained. By relocating the recording lamp so that light is transmitted through the space between the ribbons a normal variable-area negative may be obtained.

Variable-Area Light-Valve Modulator<!--<xref ref-type="fn" rid="fn1-10.5594_J11723">*</xref>-->

A variable-area modulator is described which employs a ribbon light valve as the basic modulating element. Double-width push-pull, variable-area sound track or standard width dulateral sound track may be recorded at will by inserting the appropriate light valve into the modulator. The light valve is registered in place in the modulator by indexing dowels and securely locked by means of lever-controlled clamping springs. — The light-valve ribbons are oriented so as to be parallel to the direction of motion of the film. The ribbon edges are projected at ten times magnification onto the film to define the amplitude co-ordinate of the recording image while the image height is determined by a narrow rectangular stop which is imaged onto the film at a 70:1 reduction in height by a cylindrical lens system. — The modulator is a completely self-contained unit embodying the basic components for the recording optical system, an optical system for rear projecting an enlarged image of the ribbon aperture onto a viewing screen, a photoelectric monitoring system, and an exposure meter.