Evaluation of band offset at amorphous-Si/BaSi2 interfaces by hard x-ray photoelectron spectroscopy

Ryota Takabe; Hiroki Takeuchi; Weijie Du; Keita Ito; Kaoru Toko; Shigenori Ueda; Akio Kimura; Takashi Suemasu

doi:10.1063/1.4947501

Evaluation of band offset at amorphous-Si/BaSi₂ interfaces by hard x-ray photoelectron spectroscopy

Ryota Takabe, Hiroki Takeuchi, Weijie Du, Keita Ito, Kaoru Toko, Shigenori Ueda, Akio Kimura, Takashi Suemasu

Materials Development Division

Research output: Contribution to journal › Article › peer-review

22 Citations (Scopus)

Abstract

The 730 nm-thick undoped BaSi₂ films capped with 5 nm-thick amorphous Si (a-Si) intended for solar cell applications were grown on Si(111) by molecular beam epitaxy. The valence band (VB) offset at the interface between the BaSi₂ and the a-Si was measured by hard x-ray photoelectron spectroscopy to understand the carrier transport properties by the determination of the band offset at this heterointerface. We performed the depth-analysis by varying the take-off angle of photoelectrons as 15°, 30°, and 90° with respect to the sample surface to obtain the VB spectra of the BaSi₂ and the a-Si separately. It was found that the barrier height of the a-Si for holes in the BaSi₂ is approximately -0.2 eV, whereas the barrier height for electrons is approximately 0.6 eV. This result means that the holes generated in the BaSi₂ layer under solar radiation could be selectively extracted through the a-Si/BaSi₂ interface, promoting the carrier separation in the BaSi₂ layer. We therefore conclude that the a-Si/BaSi₂ interface is beneficial for BaSi₂ solar cells.

Original language	English
Article number	165304
Journal	Journal of Applied Physics
Volume	119
Issue number	16
DOIs	https://doi.org/10.1063/1.4947501
Publication status	Published - 2016 Apr 28

ASJC Scopus subject areas

Physics and Astronomy(all)

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@article{70ee2ca38cef4f5d9bea92768fa77030,

title = "Evaluation of band offset at amorphous-Si/BaSi2 interfaces by hard x-ray photoelectron spectroscopy",

abstract = "The 730 nm-thick undoped BaSi2 films capped with 5 nm-thick amorphous Si (a-Si) intended for solar cell applications were grown on Si(111) by molecular beam epitaxy. The valence band (VB) offset at the interface between the BaSi2 and the a-Si was measured by hard x-ray photoelectron spectroscopy to understand the carrier transport properties by the determination of the band offset at this heterointerface. We performed the depth-analysis by varying the take-off angle of photoelectrons as 15°, 30°, and 90° with respect to the sample surface to obtain the VB spectra of the BaSi2 and the a-Si separately. It was found that the barrier height of the a-Si for holes in the BaSi2 is approximately -0.2 eV, whereas the barrier height for electrons is approximately 0.6 eV. This result means that the holes generated in the BaSi2 layer under solar radiation could be selectively extracted through the a-Si/BaSi2 interface, promoting the carrier separation in the BaSi2 layer. We therefore conclude that the a-Si/BaSi2 interface is beneficial for BaSi2 solar cells.",

author = "Ryota Takabe and Hiroki Takeuchi and Weijie Du and Keita Ito and Kaoru Toko and Shigenori Ueda and Akio Kimura and Takashi Suemasu",

note = "Funding Information: The HAXPES measurements were conducted at Synchrotron X-ray station of BL15XU, at SPring-8, and were supported by NIMS microstructural characterization platform as a program of Nanotechnology platform (Proposal Nos. 2014A4902, 2015A4907, and 2015B4906) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. S.U. and A.K. are grateful to HiSOR, Hiroshima University, and JAEA at SPring-8 for the development of HAXPES at BL15XU. The authors thank Dr. N. Yoshizawa and Mr. N. Saito in AIST, Japan, for their help in TEM observations. This work was financially supported by the Japan Science and Technology Agency (JST/CREST) and by a Grant-in-Aid for Scientific Research (A) (No. 15H02237) from the JSPS. R.T. was financially supported by a Grant-in-aid for JSPS Fellows (No. 15J02139). Publisher Copyright: {\textcopyright} 2016 Author(s).",

year = "2016",

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day = "28",

doi = "10.1063/1.4947501",

language = "English",

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T1 - Evaluation of band offset at amorphous-Si/BaSi2 interfaces by hard x-ray photoelectron spectroscopy

AU - Takabe, Ryota

AU - Takeuchi, Hiroki

AU - Du, Weijie

AU - Ito, Keita

AU - Toko, Kaoru

AU - Ueda, Shigenori

AU - Kimura, Akio

AU - Suemasu, Takashi

N1 - Funding Information: The HAXPES measurements were conducted at Synchrotron X-ray station of BL15XU, at SPring-8, and were supported by NIMS microstructural characterization platform as a program of Nanotechnology platform (Proposal Nos. 2014A4902, 2015A4907, and 2015B4906) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. S.U. and A.K. are grateful to HiSOR, Hiroshima University, and JAEA at SPring-8 for the development of HAXPES at BL15XU. The authors thank Dr. N. Yoshizawa and Mr. N. Saito in AIST, Japan, for their help in TEM observations. This work was financially supported by the Japan Science and Technology Agency (JST/CREST) and by a Grant-in-Aid for Scientific Research (A) (No. 15H02237) from the JSPS. R.T. was financially supported by a Grant-in-aid for JSPS Fellows (No. 15J02139). Publisher Copyright: © 2016 Author(s).

PY - 2016/4/28

Y1 - 2016/4/28

N2 - The 730 nm-thick undoped BaSi2 films capped with 5 nm-thick amorphous Si (a-Si) intended for solar cell applications were grown on Si(111) by molecular beam epitaxy. The valence band (VB) offset at the interface between the BaSi2 and the a-Si was measured by hard x-ray photoelectron spectroscopy to understand the carrier transport properties by the determination of the band offset at this heterointerface. We performed the depth-analysis by varying the take-off angle of photoelectrons as 15°, 30°, and 90° with respect to the sample surface to obtain the VB spectra of the BaSi2 and the a-Si separately. It was found that the barrier height of the a-Si for holes in the BaSi2 is approximately -0.2 eV, whereas the barrier height for electrons is approximately 0.6 eV. This result means that the holes generated in the BaSi2 layer under solar radiation could be selectively extracted through the a-Si/BaSi2 interface, promoting the carrier separation in the BaSi2 layer. We therefore conclude that the a-Si/BaSi2 interface is beneficial for BaSi2 solar cells.

AB - The 730 nm-thick undoped BaSi2 films capped with 5 nm-thick amorphous Si (a-Si) intended for solar cell applications were grown on Si(111) by molecular beam epitaxy. The valence band (VB) offset at the interface between the BaSi2 and the a-Si was measured by hard x-ray photoelectron spectroscopy to understand the carrier transport properties by the determination of the band offset at this heterointerface. We performed the depth-analysis by varying the take-off angle of photoelectrons as 15°, 30°, and 90° with respect to the sample surface to obtain the VB spectra of the BaSi2 and the a-Si separately. It was found that the barrier height of the a-Si for holes in the BaSi2 is approximately -0.2 eV, whereas the barrier height for electrons is approximately 0.6 eV. This result means that the holes generated in the BaSi2 layer under solar radiation could be selectively extracted through the a-Si/BaSi2 interface, promoting the carrier separation in the BaSi2 layer. We therefore conclude that the a-Si/BaSi2 interface is beneficial for BaSi2 solar cells.

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