Synthesis, electrical and ultrafast nonlinear optical properties of Sn–ZnO composite film

Tin (Sn)- zinc oxide (TZO) composite films were successfully synthesized by the magnetron sputtering. Structure and morphology of the TZO composite films with different sputtering conditions (growth time, direct current sputtering powers and substrate temperature) were characterized. X-ray diffraction (XRD) patterns confirmed characteristic peaks of ZnO and SnO2 without any alloys distinct phases. The scanning electron microscope (SEM) micrographs revealed that the average grain size of crystallites was found to increase with increasing growth time and sputtering powers, respectively. The optical, electrical and ultrafast nonlinear optical characterizations of the TZO composite films with different growth time were studied. The effect of Sn content on the optical and electrical properties of the TZO composite films was analyzed. As growth time increasing, the optical gap of TZO composite films increased and then decreased. The Hall test results showed that Sn enhanced the carrier concentration of ZnO film. The carriers of TZO composite films range from 10−15 to 10−19/cm3 in concentration. Meanwhile, from the femtosecond Z-scan experimental results, the samples showed the change from reverse saturable absorption to saturable absorption with increasing growth time. The values of the nonlinear absorption coefficient for the TZO composite films with four growth time were 4.628 × 10−7 m/W, 6.016 × 10−8 m/W, 5.245 × 10−8 m/W and 4.407 × 10−8 m/W, respectively. The ease of the synthesis route and the remarkable electrical and ultrafast nonlinear optical properties offer TZO films as a promising electron source for high current density and nonlinear optical applications.