Core-Level Shift of Si Nanocrystals Embedded in a SiO2 Matrix

Tu Pei Chen, Yang Liu, Chang Qing Sun, Man Siu Tse, Jang-Hsing Hsieh, Yong Qing Fu, Y. C. Liu, Steve Fung

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)

Abstract

It is expected from existing theories that the core level of Si nanocrystals (nc-Si) embedded in a SiO2 matrix should shift toward a higher binding energy as compared to that of bulk crystalline Si due to quantum size effect. Indeed, it is observed in X-ray photoemission experiments that the Si 2p core level shifts to a higher apparent binding energy by 1−2 eV for all five oxidation states of Sin+ (n = 0, 1, 2, 3, and 4) in the material system of SiO2 containing nc-Si. However, it is found that the core-level shift is due to a charging effect in the material system. After correction for the charging effect by using C 1s binding energy due to contamination on the SiO2 surface, the core level of the oxidation state Si4+ is the same as that of pure SiO2, whereas the core level of the isolated nc-Si with an average size of about 3 nm shifts by ∼ 0.6 eV to a lower binding energy as compared to that of bulk crystalline Si. It is suspected that the core-level shift of the nc-Si toward a lower binding energy is due to the influence of the differential charging between the SiO2 surface layer and the nc-Si underneath.
Original languageEnglish
Pages (from-to)16609-16612
JournalThe Journal of Physical Chemistry B
Volume108
Issue number43
DOIs
Publication statusPublished - 2004

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