RESPONSE TIME OF PHOTOEMISSION OF ULTRAFINE PARTICLE THIN FILM

The response time of photoemissive materials is required for detecting ultrashort duration laser pulses. In this paper, the response time of photoemission in ultrafine particle thin film is studied, and the transit time spread (TTS) and response time of peak value (t_M) are discussed. The photoelectron's response time will increase with increasing energy of photons. If the surface potential barrier of thin film declines, the photoemissive sensitivity or quantum yield will rise, however the response time will also increase, which means that response-time characteristic gets worse. As an example, the response time for Ag-O-Cs thin film is calculated for different cases when photoelectrons, excited in Ag ultrafine particles, travel through Cs₂O semiconductor layer to the surface and escape into vacuum. The calculated response time is about 50 fs if this thin film is irradiated by infrared rays of wavelength 1.06μm.