Evolution of photocurrent during coadsorption of Cs and O on GaAs (100)

he photocurrent and spectral response curves of gallium arsenide (GaAs) photocathodes have been obtained by a multi-information measurement system, and the evolution of the photocurrent has been investigated as a function of the Cs:O flux ratio. The experimental results show that the photocurrent increases approximately exponentially after the first exposure to Cs until a maximum sensitivity is reached, the detailed evolution process and the ultimate photocurrent being different for different samples. These differences are analyzed in this study, and according to the process of coadsorption of Cs and oxygen on GaAs, an equation is presented to explain the increase of photocurrent.