Analysis of Cs/GaAs NEA surface by XAFS
Abstract
By exposing a GaAs surface to Cs and O2, a surface which is called negative electron affinity (NEA) surface can be obtained where the vacuum level shifts lower than the bottom of GaAs conduction band. The Cs/GaAs NEA surface has been attracting great attention in recent years, because of its availability for a highly functional electron source which can be controlled by excitation light. In this work, XAFS and X-ray fluorescence measurements were conducted for Cs/GaAs NEA surface prepared on GaAs (001) and (110) substrates. As the result, As and O were considered as near neighbor atoms of center Cs for both of the samples. Most of Cs formed some kind of Cs-oxide and the Cs atoms at interface between Cs-oxide and GaAs were observed as forming Cs-As bond. Taking account of the ratios of coordination numbers and the fluorescence X-ray yield, the Cs-oxide on GaAs (001) surface forms island like structure in which the body/interface ratio is large, and the Cs-oxide on GaAs (110) surface forms layer like structure in which the body/interface ratio is small.
- Publication:
-
Journal of Physics Conference Series
- Pub Date:
- April 2013
- DOI:
- 10.1088/1742-6596/430/1/012079
- Bibcode:
- 2013JPhCS.430a2079T