Open AccessThe distribution of oxide species in the Cs∕O activation layer on InP(100) negative electron affinity photocathodes
Author(s) -
Dong-Ick Lee,
Yun Sun,
Zhi Liu,
Shiyu Sun,
Samuel Peterson,
P. Pianetta
Publication year - 2007
Publication title -
journal of applied physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.699
H-Index - 319
eISSN - 1089-7550
pISSN - 0021-8979
DOI - 10.1063/1.2786885
Subject(s) - peroxide , x ray photoelectron spectroscopy , chemistry , oxide , photocathode , oxygen , analytical chemistry (journal) , spectral line , photoemission spectroscopy , valence (chemistry) , photochemistry , inorganic chemistry , electron , chemical engineering , physics , organic chemistry , chromatography , quantum mechanics , astronomy , engineering
The atomic arrangement of Cs oxides in the activation layer of an InP photocathode is investigated using Angle Dependent Photoemission Spectroscopy (ADPES). Two distinct peaks in the O1s core level and in valence band spectra have led to the discovery of two molecular oxygen species incorporated in the thin activation layer: Cs peroxide (Cs2O2) and Cs superoxide (CsO2). The different angular dependences of these oxides observed in the photoemission spectra are caused by different vertical locations of the oxygen molecules in each Cs oxide in the activation layer. The thickness of the activation layer, which is about 7Å, suggests lateral distribution of Cs peroxide and Cs superoxide. The quantum efficiency (QE) of InP photocathodes in our Ultra High Vacuum (UHV) system decreases with time due to the chemical transformation of the Cs oxides and subsequent substrate oxidation, as deduced from an
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