The Scanning–Tunneling Microscopy, the X-Ray Photoelectron Spectroscopy, the Inner-Shell-Electron Energy-Loss Spectroscopy Studies ofMTe2andM3SiTe6(M=Nb and Ta)
✍ Scribed by Youichi Ohno
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 477 KB
- Volume
- 142
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The Ta N 6,7 and Te N 4,5 inner-shell-electron energy-loss spectroscopy (ISEELS) spectra and the X-ray photoelectron spectroscopy (XPS) spectra in layered transition-metal ditellurides MTe 2 (M ؍ Ta, Nb) for which metal d-derived conduction bands overlap Te 5p valence bands significantly, have been measured to study the effects of band structure on the final states and the valences of constituent atoms. For comparison we have obtained the ISEELS and XPS spectra of M 3 SiTe 6 , which crystallizes in a layer structure akin to that of MTe 2 . The atomically resolved scanning-tunneling microscopy (STM) images of NbTe 2 and Ta 3 SiTe 6 have been obatined to investigate a surface atomic structure as well as a surface electronic structure. It is found that the Ta 4f and Te 4d XPS spectra in MTe 2 reveal a dominant peak for each spin orbit (s.o.) component although two-thirds of M atoms shift from undistorted octahedral sites to form double zigzag chains along the b axis and the STM images indicate the existence of three different kinds of Te sites. The Ta N 6,7 and Te N 4,5 ISEELS spectra reveal a doublet for each (s.o.) component. It arises from two different final states, that is, Ta 3؉ * 4f 13 5d 2 and Ta 4؉ * 4f 13 5d 1 for the Ta N 6,7 spectrum and Te 2؊ * 4d 9 5p 6 and Te ؊ * 4d 9 5p 5 for the Te N 4,5 spectrum. The final-state valence fluctuation model is proposed to explain the experimental result.