大学院理工学研究科(理)
理工学専攻(分子科学)
垣内 拓大
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1
ハフニウムが吸着したSi(111)-7×7表面の初期酸化段階における膜厚依存性
2024/07/29
垣内拓大、穴井亮太、佐伯大殊、津田泰孝、吉越章隆
Journal of Physical Chemistry C
128/ 31, 13052-13063
研究論文(学術雑誌)
10.1021/acs.jpcc.4c02368
アメリカ化学会
Coverage dependence on the early oxidation stages of hafnium–adsorbed silicon (111) [Hf–Si(111)] was investigated by synchrotron radiation X-ray photoelectron spectroscopy. The Hf–Si(111) surface with a 0.5 monolayer (ML) comprised Hf tetrasilicide (HfSi4) and Hf monosilicide (HfSi). HfSi4 is inferred to be single Hf adsorption around the Si rest-atoms/corner-holes on the 7 × 7 reconstructed surface, while HfSi is inferred to be a unit of six Hf atoms adsorbed on the top of the Si center adatoms/rest-atoms on the same surface. HfSi was oxidized by exposure to thermal oxygen molecules (O2) with a translational energy (Et) of 0.03 eV; subsequently, a surface passivation behavior was observed. HfSi4 was oxidized by supersonic O2 beam (SOMB) irradiation at Et = 0.39 eV. In Hf–Si(111) with six MLs, Si migration into the Hf overlayers and segregation on the surface were observed by depth profiling. The segregated Si atoms were oxidized by SOMB irradiation with Et = 2.2 eV. The interfacial compounds of metallic Hf, HfSi, and HfSi4 remained regardless of the Et of the impinging O2 because no oxygen reached near the Si substrate. The oxide composition and distribution near the surface were completely different depending on the Hf coverage.
2
Oxidation Mechanisms of Hafnium Overlayers Deposited on an Si(111) Substrate
2022/02/16
Takuhiro Kakiuchi, Tomoki Matoba, Daisuke Koyama, Yuki Yamamoto, Akitaka Yoshigoe
Langmuir
38/ 8, 2642-2650
研究論文(学術雑誌)
10.1021/acs.langmuir.1c02711
ACS publications
The oxidation mechanism of hafnium overlayers on an Si(111) substrate [Hf−Si(111), including the outermost
metallic Hf overlayers and interfacial Hf silicides (HfSi and HfSi_4)] was investigated via high-resolution synchrotron radiation
X-ray photoelectron spectroscopy (SR-XPS) of Hf 4f_(5/2,7/2), Si 2p_(1/2,3/2), and O 1s core levels. The atomic-scale interaction of O_2 molecules with Hf−Si(111) is discussed by comparing the results
obtained following thermal O_2 exposures [translational energy (E_t) ≈ 0.03 eV] with those obtained following supersonic O_2 molecular beam (SOMB) irradiation (E_t ≈ 2.2 eV). Metallic Hf and interfacial HfSi were immediately oxidized to HfO_2 and Hf
(sub)silicates (Hf−O−Si configurations) via trapping-mediated dissociative adsorption. Upon excessive SOMB irradiation, the
other interfacial HfSi_4 was oxidized via direct dissociation. When oxidation proceeded at the Si(111) substrate via excess SOMB irradiation, volatile Si atoms were emitted from the interfacial SiO_2/Si-strained layers. When the volatile Si atoms were trapped in the overlayers, the HfO_2 overlayers were converted into completely oxidized Hf silicate layers. However, when the volatile Si atoms passed through the HfO_2 overlayers, they reacted with the impinging O_2, and the outermost SiO_2 deposition layers were formed on HfO_2 (or Hf silicate) layers.
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