负电子亲和势GaN光电阴极激活机理研究

Activation mechanism of negative electron affinity GaN photocathode

利用自行研制的光电阴极激活评估实验系统,给出了GaN光电阴极Cs激活及Cs/O激活的光电流曲线.针对GaN光电阴极的负电子亲和势(NEA)特性的成因,结合激活过程中光电流变化规律和成功激活后的阴极表面模型,研究了NEAGaN光电阴极激活机理.实验表明:GaN光电阴极在单独导入Cs激活时就可获得明显的NEA特性,Cs/O激活时引入O后光电流的增长幅度不大.用双偶极层模型[GaN(Mg):Cs]:O—Cs较好地解释了激活成功后GaN光电阴极NEA特性的成因.

The photocurrent curves during either Cs or Cs/O activation of GaN photocathode were tested by using dedicated experimental system for activation and evaluation of negative electron affinity （NEA） photocathode. Aiming at explaining the formation of NEA property of GaN photocathode and according to the rule of photocurrent change during activation period and the surface model of a fully activated photocathode, the activation mechanism for NEA GaN photocathode was studied. The experiment results show that：the obvious NEA property is be induced in GaN photocathode mainly due to the activation by Cs. The increase extent of photocurrent is not large after introducing O during Cs/O activation process for GaN photocathode. The NEA property formation reasons of GaN photocathode after being activated successfully can be well explained using the double dipole layer model [ GaN（Mg） ： Cs] ： O--Cs.