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利用XPS分析了GaAs光阴极高温退火、激活前后表面组分的变化,结合光阴极退火过程中通过四级质谱仪获取的CO2、H2O、O、As、Cs等分压曲线,比较、讨论了两次退火机理的差异。提出第二次加热的目的不仅在于清洁光阴极表面,更重要的是促使第一次激活在光阴极表面形成的偶极层向更稳定的结构转化,Cs2O偶极子在高温下与GaAs本底反应生成了可在光阴极表面稳定存在的GaAs-O-Cs偶极子,形成主要由键合强的GaAs(Zn)--Cs+、GaAs-O-Cs偶极子及靠范德瓦尔斯力附着在光阴极表面的Cs2O偶极子构成的偶极层。根据这一结论,解释了光阴极两次激活过程中光电流变化规律的差异。对理解光阴极激活及表面光电发射模型具有重要意义。
The variation of surface composition before and after activation of GaAs photocathode was analyzed by XPS, and the partial pressure curves of CO2, H2O, O, As, Cs obtained by four-stage mass spectrometer during photocathode annealing were compared. Differences in Secondary Annealing Mechanisms. The purpose of the second heating is not only to clean the photocathode surface, but more importantly to promote the first activation of the dipole layer formed on the photocathode surface to a more stable structure. The Cs2O dipole and GaAs background The reaction results in the stable GaAs-O-Cs dipole at the photocathode surface and the formation of a GaAs-O-Cs dipole mainly composed of strongly bonded GaAs (Zn) -Cs +, GaAs-O-Cs dipoles and van der Waals forces The dipole layer of Cs2O dipole attached to the photocathode surface. According to this conclusion, the difference of the photocurrent variation during the two activations of photocathode is explained. It is of great significance to understand the photo-cathode activation and the surface photoemission model.