GaAs光电阴极激活时Cs的吸附效率研究

Adsorption efficiency of cesium in activation process for GaAs photocathode

从NEAGaAs光电阴极的激活光电流曲线发现,当系统真空度不很高时,在首次Cs激活阶段,表面掺杂浓度较低的阴极材料,其光电流产生需要的时间也较长.同时,随着系统真空度的提高,这种时间上的差异又变得不再明显.该现象表明,Cs原子在阴极表面的吸附效率同表面层掺杂浓度以及系统真空度之间有直接的联系.为定量分析这种关系,本文根据实验数据建立了Cs在阴极表面吸附效率的数学模型,利用该模型仿真的结果同实验现象非常符合.该研究对进一步开展变掺杂阴极结构设计和制备工艺研究具有重要的价值和意义.

Photocathode materials with the lower surface doping density need a longer time to raise photocurrent in the first Cesium activation process when the system vacuum level is not high enough,which can be found from the photocurrent curves during the activation of negative-electron-affinity（NEA） GaAs photocathodes.At the same time,with the enhancement of system vacuum level,these differences in time will become unobvious.It is indicated that the adsorption efficiency of Cesium on cathode surface has the direct relationships with the surface doping density and system vacuum level.In order to analyze these relationships quantitively,in this paper,a mathematical model of the adsorption efficiency of Cesium on cathode surface is established according to the experimental data.The simulation results by the model are in good accordance with the experimental phenomenon.This study is of very important value and significance for the further investigation of structure design and preparation techniques for varying doping GaAs photocathode materials.