A CDSE BISTABLE SWITCH.

Under certain conditions of synthesis, cadmium selenide CdSe shows a hysteresis effect in its current-voltage relationship. The material, therefore, has been of interest for use as a switch to control the electroluminescent EL emission of a solid state display device. Some of the major problems associated with this hysteresis effect were the poor reproducibility of the CdSe synthesis and the non-uniformity of the electrical characteristics. The purpose of this program was to study the procedure for synthesizing hysteretic CdSe powder with the goal of achieving the required uniformity during electrical operation. The synthesis of CdSe powder with hysteresis is an extremely complex process consisting of three firing steps. Each of the firing steps was studied in detail to determine which parameters were most important in the synthesis. It was found that an oxygen-containing atmosphere was necessary during a high temperature firing to produce the hysteresis effect. Without this firing step, the conductivity could be reduced upon subsequent lower temperature firings in oxygen or selenium atmospheres, but the hysteresis would be absent. The second and third firing steps were found not to be as critical as the first step. As a result of these studies, modifications were made in the firing procedures which permitted the syntheses of hysteretic materials with relatively good reproducibility. The quality of hysteresis of many selected CdSe samples was approximately equivalent but the ranges in threshold and cutoff voltages were not sufficiently narrow to attain the required electrical uniformity. Models with 1024 elements in a 32 x 32 array were constructed during the program. Author