Effects of transient ultrasonic switch for amorphous semiconductor superlattices

We found the effects of transient ultrasonic switch due to optical absorption in periodic compositional amorphous semi-conductor superlattice a-Si:H/a-SiNx:H films (samples). The effects were observed from the amplitude drop of surface acoustic wave (SAW) while the optic light illumining the surface of the samples. For the samples, the thickness of the a-Si:H sublayer is varied from 10 Angstrom to 200 Angstrom, and that of the a-SiNx:H sublayer is fixed at 30 Angstrom respectively. Two interdigital transducers with center frequency of 136 MHz are used as exciting and receiving transducers of SAW. Investigated results show that, the influence of optical radiation on decreasing of SAW amplitude is transient, but on the velocity change of SAW often has some delay. The effects of transient ultrasonic switch depend on the thickness of a-Si:H sublayer and the power of optic tight. The optimum thickness equal to 60 Angstrom. The detail idea, experimental results, analyses and discussions are presented.