Nanosecond Response Found in Photoexcited Surface Carriers Generated by CoSi_x Nanoparticles on Si Substrate

Abstract

We have found photovoltaic carriers generated by CoSix nanoparticles (about 10 nm in radius) fabricated on a Si substrate when the illuminated spot was separated by 1 mm from the anode. The CoSix/Si system provided a sensitivity of 420 mA/W under CW laser excitation at 635 nm with an incident power of 1.8 mW. The carrier's response time of <10 ns was observed under pulsed (picosecond) laser excitation. These high-speed carriers were isolated from the Si substrate, as observed from the ∼15 ns delayed peak. These results suggest that the carriers photoinduced from the CoSix nanoparticles are surface conductive and have high mobility comparable to that of thermal emission electrons.