A new EXAFS method for the local structure analysis of low-Z elements

Abstract

A unique analytical method is proposed for local structure analysis via extended X-ray absorption fine structure (EXAFS) spectroscopy. The measurement of electron energy distribution curves at various excitation photon energies using an electron energy analyzer is applied to determine a specific elemental Auger spectrum. To demonstrate the method, the N K-edge EXAFS spectra for a silicon nitride film were obtained via simultaneous measurement of the N KLL Auger and background spectra using dual-energy windows. The background spectrum was then used to remove the photoelectrons and secondary electron mixing in the energy distribution curves. The spectrum obtained following this subtraction procedure represents the `true' N K-edge EXAFS spectrum without the other absorptions that are observed in total electron yield N K-edge EXAFS spectra. The first nearest-neighbor distance (N-Si) derived from the extracted N K-edge EXAFS oscillation was in good agreement with the value derived from Si K-edge analysis. This result confirmed that the present method, referred to as differential electron yield (DEY)-EXAFS, is valid for deriving local surface structure information for low-Z elements.

X-ray Absorption Fine Structural Study of Atomic Structures and Chemical States of Dopants in 4H-SiC(0001)

“…The takeoff angle was set to 90°(surface normal). 16 For the EXAFS measurements, the total electron yield (TEY) was employed. The energy range for the EXAFS measurements was 1500 to 1806 eV.…”

“…The angle between the incident X-ray photon and the electron analyzer was 45°. The takeoff angle was set to 90° (surface normal) . For the EXAFS measurements, the total electron yield (TEY) was employed.…”

X-ray absorption spectroscopy study on SiC-side interface structure of SiO2–SiC formed by thermal oxidation in dry oxygen

“…The SiC-selective EXAFS spectra for the m-face and Si-face were obtained via differential electron yield EXAFS analysis, where the intensities of the SiC-assigned peaks and the background (at 1633 eV) in the AES spectra were mon-itored. 28) These spectra are shown along with the spectrum for bulk SiC in Fig. 2.…”

Local atomic structure analysis of SiC interface with oxide using chemical-state-selective X-ray absorption spectroscopy

“…For SiO 2 =SiC, photoelectron peaks such as C 1s and O 1s cross within the EXAFS oscillation. The differential electron yield (DEY) mode, which is a PEY mode, 19) can remove this photoelectron peak crossing. By using the DEY mode, chemical-stateselective EXAFS becomes feasible, which separates multiple chemical states at the time of the measurement instead of during post-measurement analysis.…”

“…The subtraction was performed after shifting the background EXAFS spectrum by 20 eV to lower energies, following the procedure for DEY-EXAFS analysis. 19) The peaks caused by the photoelectron crossing of C 1s and O 1s were removed in the DEY-EXAFS spectrum. Figure 4 presents the EXAFS oscillations extracted from each EXAFS spectrum, shown in Fig.…”