The preparation process of GaAs photocathodes is very complicated, in order to prepare the high performance cathodes, it is crucial to obtain information enough to evaluate the preparation process in real time. Based on a particular transfer light setup and a flexible communication network, we develop an on-line measurement system for GaAs cathode preparation, which is used to measure the pressure of activation chamber, sample temperature, photocurrent, spectral response curves, and currents heating Cs and oxygen dispensers during the heat-cleaning or activation processes of cathodes. According to these signals, we present some simple and real-time evaluation techniques for cathode preparation. Several peaks of pressure are observed in the pressure variations measured during heat cleaning. These peaks corresponding to the desorption of AsO, As₂O₃, Ga₂O and Ga₂O₃ from the sample surface at different temperatures, respectively, are used to evaluate the effect of heat cleaning very well, while the signals measured during activation can be used to analyze and optimize the activation technique. Based on a revised quantum efficiency equation, many performance parameters of cathodes are obtained from the fitting of spectral response curves. According to these parameters, the performance of cathode material and the effect of activation can be evaluated.

Date Published: 12 December 2007
PDF: 8 pages
Proc. SPIE 6782, Optoelectronic Materials and Devices II, 67823D (12 December 2007); doi: 10.1117/12.745945

Published in SPIE Proceedings Vol. 6782:
Optoelectronic Materials and Devices II
Yoshiaki Nakano, Editor(s)