MEDSI2020 - List of Authors (Ozawa, K.)

Paper	Title	Page
TUPA01	Oxygen-Free Titanium Thin Film as a New Nonevaporable Getter with an Activation Temperature as Low as 185 °C	119
	M. Ono, I. Yoshikawa, K. Yoshioka University of Tokyo, Kashiwa, Japan T. Kikuchi, K. Mase KEK, Tsukuba, Japan K. Mase Sokendai, The Graduate University for Advanced Studies, Tsukuba, Japan Y. Masuda, Y. Nakayama Tokyo University of Science, Noda, Japan S. Ohno Yokohama National University, Yokohama, Japan K. Ozawa TIT, Tokyo, Japan Y. Sato Yokohama National University, Graduate School of Engineering Science, Yokohama, Japan
	Funding: This work was partly supported by JSPS KAKENHI (17K05067, 19K05280) and TIA-Kakehashi (TK19-035, TK20-026). The XPS measurements were performed under the Photon Factory proposal (2018S2-005). Although nonevaporable getter (NEG) pumps are widely used in synchrotron radiation facilities, pure metal Titanium (Ti) has not been used as a NEG because the activation temperature of a Ti thin film deposited by DC magnetron sputtering was reported to be 350-400 °C. Recently Miyazawa et al. found that high-purity Ti deposited under ultra-high vacuum (UHV) followed by N₂ introduction works as a NEG with an activation temperature of 185 °C,*. Since the concentration of impurities such as O, C, and N in the Ti thin film prepared by this method is 0.05% or less, we named this as oxygen-free Ti. In this study, we evaluated the pumping properties of oxygen-free Ti thin films after high-purity N₂ introduction by total and partial pressure measurements. A vacuum vessel with oxygen-free Ti deposited on the inner walls was found to pump H₂, H₂O, O₂, CO and CO₂ even after 30 cycles of high purity N₂ introduction, air exposure, pumping, and baking at 185 °C. Furthermore, we analyzed the oxygen-free Ti thin films after high-purity N₂ or air introduction by synchrotron radiation X-ray photoelectron spectroscopy. The results show that more TiN was formed when high-purity N₂ was introduced after oxygen-free Ti deposition. High purity of the Ti thin film and TiN formation on the surface seem to be responsible for the reduced activation temperature as low as 185 °C. C. Benvenuti et al., J. Vac. Sci. Technol. A 16, 148 (1998). T. Miyazawa et al., Vac. Surf. Sci. 61, 227 (2018). *KEK, patent pending, WO2018097325 (Nov. 28, 2017).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-MEDSI2020-TUPA01
About •	paper received ※ 30 July 2021 paper accepted ※ 14 October 2021 issue date ※ 01 November 2021
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Paper

Title

Page

Oxygen-Free Titanium Thin Film as a New Nonevaporable Getter with an Activation Temperature as Low as 185 °C

119

M. Ono, I. Yoshikawa, K. Yoshioka
University of Tokyo, Kashiwa, Japan
T. Kikuchi, K. Mase
KEK, Tsukuba, Japan
K. Mase
Sokendai, The Graduate University for Advanced Studies, Tsukuba, Japan
Y. Masuda, Y. Nakayama
Tokyo University of Science, Noda, Japan
S. Ohno
Yokohama National University, Yokohama, Japan
K. Ozawa
TIT, Tokyo, Japan
Y. Sato
Yokohama National University, Graduate School of Engineering Science, Yokohama, Japan

Funding: This work was partly supported by JSPS KAKENHI (17K05067, 19K05280) and TIA-Kakehashi (TK19-035, TK20-026). The XPS measurements were performed under the Photon Factory proposal (2018S2-005).
Although nonevaporable getter (NEG) pumps are widely used in synchrotron radiation facilities, pure metal Titanium (Ti) has not been used as a NEG because the activation temperature of a Ti thin film deposited by DC magnetron sputtering was reported to be 350-400 °C*. Recently Miyazawa et al. found that high-purity Ti deposited under ultra-high vacuum (UHV) followed by N₂ introduction works as a NEG with an activation temperature of 185 °C**,***. Since the concentration of impurities such as O, C, and N in the Ti thin film prepared by this method is 0.05% or less, we named this as oxygen-free Ti. In this study, we evaluated the pumping properties of oxygen-free Ti thin films after high-purity N₂ introduction by total and partial pressure measurements. A vacuum vessel with oxygen-free Ti deposited on the inner walls was found to pump H₂, H₂O, O₂, CO and CO₂ even after 30 cycles of high purity N₂ introduction, air exposure, pumping, and baking at 185 °C. Furthermore, we analyzed the oxygen-free Ti thin films after high-purity N₂ or air introduction by synchrotron radiation X-ray photoelectron spectroscopy. The results show that more TiN was formed when high-purity N₂ was introduced after oxygen-free Ti deposition. High purity of the Ti thin film and TiN formation on the surface seem to be responsible for the reduced activation temperature as low as 185 °C.
*C. Benvenuti et al., J. Vac. Sci. Technol. A 16, 148 (1998).
**T. Miyazawa et al., Vac. Surf. Sci. 61, 227 (2018).
***KEK, patent pending, WO2018097325 (Nov. 28, 2017).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-MEDSI2020-TUPA01

About •

paper received ※ 30 July 2021 paper accepted ※ 14 October 2021 issue date ※ 01 November 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)