反射式负电子亲和势GaN光电阴极的光电发射及稳定性研究

利用在线多信息紫外光电阴极激活评估系统,测试了真空室内两个GaN 光电阴极Cs,O激活后及衰减6 h和18 h后补Cs的光谱响应特性曲线和量子效率曲线;并绘制了光纤光源波长为300 nm的光电阴极响应电流衰减变化曲线.实验结果证明,GaN 光电阴极较GaAs阴极具有更好的稳定性,量子效率可保持相对稳定达10 h,然后缓慢衰减,衰减速率较窄禁带半导体材料低得多.补Cs后光电流最大值较刚激活完有16.8%的增长,这充分证明阴极表面量子效率衰减的原因是Cs的脱附,而不是O的吸附.这些现象可由双偶极层模型来解释, 关键词： 光学 光电阴极 量子效率 稳定性

Photoemission stability of negative electron affinity GaN phtocathode

The spectral response and quantum yield curve of reflection mode GaN photocathode just after Cs, O activation and Cs reactivation was achieved by using the online multi-information measurement and evaluation system. Also the attenuation in photocurrent under the radiation of 300 nm light is measured every hour.The result indicates that GaN photcathdoe are much more stable than narrow band material. The photocurrent peak increased by 16.8% after Cs reactivation which demonstrates the reason of the QE attenuation is the Cs desorption on the Cs, O adlayer of surface. This can be explained by a double dipole layer model :Cs-O whose stability determines the stability of GaN photocathode.