Abstract

Thin CdS_xSe_1−x films are easily fabricated by thermal evaporation. Their band edge can be tuned in the visible region by varying the composition allowing to realize optically bistable devices for different operating wavelengths. Investigation on the nonlinear optical response of such films have been done up to now mainly on mechanisms of thermal origin.^[1] To increase the speed of the optical response, we have studied electronic nonlinearities in pico-, nano- and microsecond time scale. Thin films of CdS_xSe_1−x were thermally evaporated on glass substrates at 200 °C. The size of microcrystallites was 30 nm in fresh samples and increased up to 300 nm after annealing at 500 °C in argon atmosphere. The optical and electrical measurements were carried out on given films with different composition using for excitation the second harmonic of Nd-YAG laser (λ. = 530 nm, pulse energy 1 to 5 mJ and duration of 10 ns or 30 ps).

© 1992 IQEC