The gelatin-dichromate photosensitive system has been shown to be very efficient as a recording medium for both two- and three-dimensional holographic gratings. Upon development, as much as 33% of incident reading light is diffracted into the first order for the unmodulated thin phase gratings and 95% for the thick holograms. The material can record a grating spacing at least as small as 2600 A, and gives reconstructions comparable with those obtained in 649F film. The air-gelatin index differential of 0.54 is considered responsible for the high diffracted powers found. Exposures vary from 3 mJ to 150 mJ at 4880 A. Certain films have speeds within two orders of magnitude of 649F holographic film.

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In the selective oxidation scheme for processing Si MOS devices, Si3N4 is used to mask gate oxide areas against the isolation oxidation. After removing the Si3N4 , gate oxide is grown. This scheme produces three topographical features which have ramifications in subsequent processing and in device properties: a notch in the isolation oxide, penetration of the isolation oxide under the masking Si3N4 , and thinning of the gate oxide at the isolation oxide edge; the first two features form the bird's beak configuration. The transmission electron microscope was applied to thin film (<1 μm) cross sections through the bird's beak in order to obtain an accurate description of these features. The bird's beak extended typically 1.5 and 0.8 μm in the n‐ and p‐channel structures, respectively, leading to a corresponding decrease in the active device length of 3.8 and 2.3 μm for the 1.4 μm thick isolation oxide. Gate oxide at the edge of the bird's beak was thinned 35–100% in the n‐channel samples and 20–50% in the p‐channel samples. It was found that oxidation subsequent to the isolation oxidation and Si3N4 removal destroys the oxidation barrier (wet oxidation seemingly more effective than dry and more convenient). Thus, a method which incorporates an additional, short, sacrificial wet oxidation step between isolation and gate oxidations, in order to overcome the thinning phenomenon, is described.

Experiments have been performed which lead to the conclusion that dichromated gelatin holograms arise as a result of the formation of an air-gelatin interface, with the observed high diffraction efficiencies resulting from the air-gelatin refractive index differential of 0.52 found at the interface. It is postulated that rapid removal of water by isopropanol in the development process creates strains in the gelatin film which are relieved by splitting. The resultant cracks in the hologram manifest themselves in an obvious location, between the highly exposed planes of cross-linked gelatin. Photomicrographic evidence on Bragg-Lippmann and on plane gratings, liquid gate data, lack of thickness reciprocity for the gratings, and observations of grating thickness employing bandpass measurements comprise the bulk of the experimental work. From these data, a model is proposed that is consistent with all the experimental results for both Bragg-Lippmann and plane gratings.

with higher state densities near the silicon (2), structures with a metal doped insulator-insulator interface (25) or with a third layer [consisting of a lower bandgap insulator (26)] may be expected to yield charge storage devices with optimized properties.