Thin layers of insulators, from 100 A to 20 000 A thick, have a number of interesting electrical properties. These properties include forming, which is a profound and essentially permanent change produced by an electrical field, and, after forming, differential negative resistance together with switching and memory phenomena. Electroluminescence and electron emission also occur. These features are shown by most amorphous or microcrystalline insulators of the appropriate thickness, and are particularly clearly shown by the oxides, such as Al2O3, Ta2O5 and SiO. In our review we survey the observed properties of metal-insulator-metal devices involving such insulating layers, and discuss the mechanisms which have been proposed for their operation. Further, since the unusual properties may be technologically important, we outline some of the possible uses of these devices and the relevance of the phenomena to the mechanism of corrosion of certain metals.

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Electrical phenomena in amorphous oxide films

Inter-impurity recombinations in semiconductors

The electrical characteristics of ion implanted compound semiconductors

Single‐crystal substrates of ZnO prepared from a large boule of hydrothermally grown material were implanted with ions of Li, Na, N, P, and Ne using energies in the range 30 keV–1 MeV and doses of 1×1011–1×1016 ions/cm2 using substrates maintained at either room temperature or 475 °C. These implanted layers were studied using depth‐resolved cathodoluminescence. The spectra obtained agreed well with those expected based on a comparison of theoretical electron‐hole pair profiles and computer‐generated ion implantation profiles. The spectra of all samples implanted at 475 °C exhibited a peak near 6500 A, and a series of previously unreported phonon‐coupled peaks analogous to the well‐known CdS ’’edge’’ emission was observed to some extent in all the implanted samples, independent of implant species. The luminescence could be quenched by annealing above 600 °C and is probably a result of the formation of damage centers.

Depth-resolved cathodoluminescence of ion-implanted layers in zinc oxide

Development, fabrication and applications of CdS solar cells are reviewed in detail. The suitability of CdS cells for large solar panels and microcircuitry, and their low cost, are emphasized. Developments are reviewed by manufacturer-developer. Vapor phase deposition of thin-film solar cells, doping and co-evaporation, sputtering, chemical spray, and sintered layers are reviewed, in addition to spray deposition, monograin layer structures, and silk screening. Formation of junctions by electroplating, evaporation, brushing, CuCl dip, and chemiplating are discussed, along with counterelectrode fabrication, VPD film structures, the Cu2S barrier layer, and various photovoltaic effects (contact photovoltage, light intensity variation, optical enhancement), and various other CdS topics.

Cadmium sulfide solar cells

The photoelectronic properties of CdS successively implanted with 1.0‐, 0.5‐, and 0.3‐MeV P+ ions versus annealing cycles were studied. Diodes thus formed were highly photosensitive, with photoconductive gains between 102 and 104. Yellow electroluminescence was observed at 77°K. Short annealing creates centers with a sheet resistance thermal activation energy of 0.13 eV. Prolonged annealing creates states 0.75–0.8 eV below the band edge.

J. A. Marley

Papers

PHOTOELECTRONIC PROPERTIES OF ION-IMPLANTED CdS.