GaAs光电阴极制备过程中多信息量测试技术研究

Multi-Information Measurement Technology for GaAs Photocathode Preparation

研制了一套基于现场总线技术的GaAs光电阴极多信息量测试系统，该系统可在线测试和保存阴极制备过程中的大部分信息量，如激活系统的真空度、阴极光电流、光谱响应曲线、Cs源和O源电流等。实验测试了GaAs光电阴极加热净化过程中真空度随温度的变化曲线，分析发现，高温净化时有几个真空度下降较快的区域，为160℃～280℃、400℃～500℃、570℃～600℃，分别是由于．AsO的脱附和水分的蒸发、As2O3分解和Ga2O脱附、GaAs和Ga2O3的分解所致，低温净化真空度在370℃后下降较快，这是由于吸附在阴极表面的Cs脱附速度加快造成的。实验还测试了激活过程中多种信息量的变化，发现了真空度和光电流随Cs源和O源电流的变化规律，这些大大方便了对激活工艺进行深入细致的分析研究。

A dedicated,computer-automated multi-information measurement system has been successfully developed,based on field bus, which is capable of on-line measuring, acquiring, saving and processing most information involved in GaAs photocathede preparation, including the pressure of the activation vacuum chamber, photocurrent of the photocathode, spectral response, current of both Cs and O sources. Temperature dependent pressure in the activation chamber was measured and plotted during cleaning of the photocathode by resistive heating. In high temperature cleaning, three specific factors, including AsO desorption and water evaporation, As203 decomposition and Ga20 desorption, GaAs and Ga203 decompositions, have been identified to be responsible for the abrupt pressure rise at the temperature intervals： 160 ℃ - 280℃ ,400 ℃ - 500℃, and 570 ℃- 600 ℃, respectively. Whereas in low temperature cleaning, the pressure rises very fast at 370 ℃because of higher desorption rate of the Cs. Quite a few information involved in the activation can be studied with the system. For instance, influence of Cs and O source currents on the pressure and photocurrent is one example.