4.4 Article

Local valence electronic states of silicon (sub)oxides on HfO2/Si-(sub)oxide/Si(110) and HfSi2/Si(sub)oxide/Si(110) Islands

期刊

SURFACE SCIENCE
卷 681, 期 -, 页码 9-17

出版社

ELSEVIER SCIENCE BV
DOI: 10.1016/j.susc.2018.10.024

关键词

Metal-insulator-semiconductor structure; High-dielectric-constant material; Local valence electronic states at surface and interface; Auger photoelectron coincidence spectroscopy; X-ray photoelectron spectroscopy; Synchrotron radiation

资金

  1. Ministry of Education, Culture, Sports, Science and Technology-Japan [26870416, 23760035]
  2. Grant Program of the Sumitomo Foundation
  3. JGC-S Scholarship Foundation (Saneyoshi Scholarship Foundation)
  4. Photon Factory Program Advisory Committee (PF-PAC) [2013G019, 2015G011]
  5. Grants-in-Aid for Scientific Research [26870416, 23760035] Funding Source: KAKEN

向作者/读者索取更多资源

The effect on the local valence electronic states of Sin+ suboxide components (n = 2, 3, and 4) of hafnium deposited on a low-index Si(110) substrate is investigated by Si-L23VV Auger electron Sin+-2p photoelectron coincidence spectroscopy (Si-L23VV-Sin+-2p APECS), and the chemical states and stabilities are discussed. Hafnium-covered Si(110) is immediately oxidized to HfO2 and SiO2 because hafnium serves as an effective catalyst for Si oxidation. Therefore, a HfO2/Sin+-(sub)oxide/Si(110) [HfO2/Sin+/Si(110)] structure is easily formed (n = 1, 2, 3, and 4). Oxygen diffusion from HfO2 layers toward the Si(110) substrate is promoted by annealing at 923 K. Oxygen atom desorption from the HfO2/Sin+/Si(110) surface occurs after annealing at 1073 K, and HfSi2 islands (i-HfSi2) are formed with a partly exposed Si(110)-16 x 2 double domain (DD) surface. i-HfSi2 shows low reactivity toward O-2 molecules, whereas the exposed Si(110)-16 x 2 DD surface is immediately oxidized. Here, a i-HfSi2/Sin+-(sub)oxide/Si(110) (i-HfSi2/Sin+/Si(110)) structure is formed. Furthermore, we measure the Si-L23VV-Sin+-2p APECS spectra of Sin+ in the HfO2/Sin+/Si(110) and the i-HfSi2/Sin+/Si(110) structures (n = 2, 3, and 4) to evaluate the local valence electronic states of the Sin+ (sub)oxide components. The binding energy at the valence band maximum (BEVBM) of Sin+ in the i-HfSi2/Sin+/Si(110) structure is lower than 1.5 +/- 0.7 eV as compared to that in the HfO2/Sin+/Si(110) structure (n = 2, 3, and 4). The local valence electric states of the nearest neighbors and the second neighbors through oxygen of Sin+ are determined to affect those of the Sin+ atom (n = 2, 3, and 4). The Sin+ atoms in the i-HfSi2/Sin+/Si(110) structure can directly bond to hafnium atoms as the nearest neighbors and most commonly have Sin+ atoms in lower ionic valence states as second neighbors (m < 4), whereas the Sin+ atoms in the HfO2/Sin+/Si(110) structure cannot form this bond. In addition, the existence of Hf silicide and Si in lower ionic valence states can reduce the band gap of the HfO2/Si(110) structure.

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