ULTRASONIC STRESS WAVES IN CADMIUM SULFIDE,
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OHIO SCHOOL OF ENGINEERING
Pagination or Media Count:
The copper and silver doped cadmium sulfide crystals observed in the experiment exhibited essentially the same ultrasonic amplification characteristics as crystals grown from undoped, high-purity, cadmium sulfide powder. The relaxation time of electron trapping is not affected by the presence of the impurity elements copper and silver, at least if the impurity-element concentrations are restricted to those used in this experiment. The calculated value of .3 for the trapping factor in crystal 4 CdSCu-30ppm, as compared to .5 calculated for all other crystals, is a possible indication that the impurity atoms formed trapping centers not present in the other, less heavily doped, crystals. If the restrictions imposed by the linear small signal approximation are not violated, the modified amplification equation of Uchida et al. correctly describes the experimentally observed ultrasonic amplification in cadmium sulfide. The disadvantage of the modified equation, in the experimental situation, is that it is possible to obtain apparent agreement between theory and experiment when nonlinear conditions are actually present in the crystal. This situation is made possible by the dependence of the theoretically predicted gain values on the experimentally observed values of maximum and minimum gain. For example, the effects of acoustic gain saturation can reduce the observed maximum gain which in turn will result in the ratio of the theoretically predicted maximum gain to minimum gain being reduced as well.
- Solid State Physics