title: Surface EXAFS via differential electron yield.
abstract: Surface-sensitive analysis via extended X-ray absorption fine-structure (EXAFS) spectroscopy is demonstrated using a thickness-defined SiO2(12.4 nm)/Si sample. The proposed method exploits the differential electron yield (DEY) method wherein Auger electrons escaping from a sample surface are detected by an electron analyzer. The DEY method removes local intensity changes in the EXAFS spectra caused by photoelectrons crossing the Auger peak during X-ray energy sweeps, enabling EXAFS analysis through Fourier transformation of wide-energy-range spectral oscillations. The Si K-edge DEY X-ray absorption near-edge structure (XANES) spectrum appears to comprise high amounts of SiO2and low Si content, suggesting an analysis depth, as expressed using the inelastic mean free path of electrons in general electron spectroscopy, of approximately 4.2 nm. The first nearest neighbor (Si-O) distance derived from the Fourier transform of the Si K-edge DEY-EXAFS oscillation is 1.63 Å. This value is within the reported values of bulk SiO2, showing that DEY can be used to detect a surface layer of 12.4 nm thickness with an analysis depth of approximately 4.2 nm and enable `surface EXAFS' analysis using Fourier transformation.
authors.affiliation: Toyota Central R&D Labs Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192, Japan.
authors.forename: Noritake
authors.initials: N
authors.lastname: Isomura
authors.affiliation: Aichi Synchrotron Radiation Center, 250-3 Minamiyamaguchi-cho, Seto, Aichi 489-0965, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Murai
authors.affiliation: Aichi Synchrotron Radiation Center, 250-3 Minamiyamaguchi-cho, Seto, Aichi 489-0965, Japan.
authors.forename: Toyokazu
authors.initials: T
authors.lastname: Nomoto
authors.affiliation: Toyota Central R&D Labs Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192, Japan.
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Kimoto
keywords: EXAFS; XAS; partial electron yield; silicon dioxide; surface-sensitive