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采用Cs源持续、O源断续的交替方法成功激活了GaN光电阴极,原位测试了透射模式下的光谱响应曲线,获得了透射模式下高达13%的量子效率.从一维定态薛定谔方程入手,得到了GaN真空面电子源材料的电子透射系数的表达式.对于一定形状的阴极表面势垒,电子透射系数决定于入射电子能量、表面势垒的高度和宽度.根据具有负电子亲和势(NEA)特性的透射式GaN光电阴极的能带及Cs,O覆盖过程中阴极表面势垒的变化情况,结合双偶极层[GaN(Mg):Cs]:O-Cs表面模型,分析了GaN真空面电子源材料NEA特性的形成原因.研究表明:Cs,O激活过程中形成的双偶极层对电子逸出起促进作用,双偶极层的形成是材料表面真空能级下降的原因.
The GaN photocathode was successfully activated by the alternating source method of Cs source and O source, and the spectral response curve of the transmission mode was tested in situ to obtain the quantum efficiency up to 13% in the transmission mode.From the one-dimensional Schrödinger equation The electron transmission coefficient of the electron source material of GaN vacuum surface is obtained. For a certain shape of the surface potential barrier of the cathode, the electron transmission coefficient is determined by the incident electron energy and the height and width of the surface potential barrier. According to the electron- (NEA), and the potential barrier of the cathode surface during Cs and O overlay, combined with the dual-dipole layer [GaN (Mg): Cs]: O-Cs surface model, The formation reason of the NEA characteristic of GaN vacuum surface electron source materials is studied.The results show that the double dipole layer formed during the activation of Cs and O promotes the electron emission and the double dipole layer formation is the decrease of the vacuum energy level of the surface of the material the reason.