Analytical study on TPD measurements during NEA activation process

We have investigated the desorption of absorbed Cs-related species on the sample surface by temperature programed desorption (TPD). After forming the negative electron affinity (NEA) surface by alternating supply of Cs and O₂ onto the clean p-GaAs (100) surface in an ultra-high vacuum condition. It was found that Cs had several forms of adsorption states on the NEA surface from TPD measurements. The quantum efficiency under 826 nm illumination drops to zero over 300degC, while that with 367 nm drops to zero at about 500degC. It is considered that Cs desorbed about 100 to 300degC was deeply involved in the formation of the NEA surface. (author)