Skip to main content
SpringerLink
Log in

Diffusion process in BaSi2 film formation by thermal evaporation and its relation to electrical properties

  • Invited Feature Paper
  • Published:
Journal of Materials Research Aims and scope Submit manuscript

Abstract

For fabricating photovoltaic BaSi2 films with controlled carrier density and suppressed oxidation by thermal evaporation, the mechanism determining the film composition from incongruently evaporated BaSi2 must be elucidated. We investigated the effects of source premelting, substrate temperature, and thickness on the structural and electrical properties of evaporated BaSi2 films. It is found by room-temperature deposition that the vapor composition continuously changes from being Ba-rich to being Si-rich. Source premelting suppresses the deposition of Ba-rich vapor. Deposition at 600–700 °C shows that BaSi2 forms through the mutual diffusion of Ba and Si, followed by surface oxidation by residual gas. Surface oxidation can be suppressed by a-axis-oriented growth. By changing the film thickness, the optimum thickness to obtain homogeneous films with suppressed oxidation is revealed. Sufficient diffusion leads to high film resistivities and low electron densities, which demonstrates a close relationship between the film composition and the electrical properties.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

FIG. 1
FIG. 2
FIG. 3
FIG. 4
FIG. 5
FIG. 6
FIG. 7
FIG. 8

Similar content being viewed by others

References

  1. T. Suemasu and N. Usami: Exploring the potential of semiconducting BaSi2 for thin-film solar cell applications. J. Phys. D: Appl. Phys. 50, 023001 (2016).

    Article  Google Scholar 

  2. K. Toh, T. Saito, and T. Suemasu: Optical absorption properties of BaSi2 epitaxial films grown on a transparent silicon-on-insulator substrate using molecular beam epitaxy. Jpn. J. Appl. Phys. 50, 068001 (2011).

    Article  Google Scholar 

  3. N.A.A. Latiff, T. Yoneyama, T. Shibutami, K. Matsumaru, K. Toko, and T. Suemasu: Fabrication and characterization of polycrystalline BaSi2 by RF sputtering. Phys. Status Solidi C 10, 1759–1761 (2013).

    Article  Google Scholar 

  4. M. Kumar, N. Umezawa, and M. Imai: BaSi2 as a promising low-cost, earth-abundant material with large optical activity for thin-film solar cells: A hybrid density functional study. Appl. Phys. Express 7, 071203 (2014).

    Article  Google Scholar 

  5. C.T. Trinh, Y. Nakagawa, K.O. Hara, R. Takabe, T. Suemasu, and N. Usami: Photoresponse properties of BaSi2 film grown on Si(100) by vacuum evaporation. Mater. Res. Express 3, 076204 (2016).

    Article  Google Scholar 

  6. K.O. Hara, N. Usami, K. Nakamura, R. Takabe, M. Baba, K. Toko, and T. Suemasu: Determination of bulk minority-carrier lifetime in BaSi2 earth-abundant absorber films by utilizing a drastic enhancement of carrier lifetime by post-growth annealing. Appl. Phys. Express 6, 112302 (2013).

    Article  Google Scholar 

  7. R. Takabe, K.O. Hara, M. Baba, W. Du, N. Shimada, K. Toko, N. Usami, and T. Suemasu: Influence of grain size and surface condition on minority-carrier lifetime in undoped n-BaSi2 on Si(111). J. Appl. Phys. 115, 193510 (2014).

    Article  Google Scholar 

  8. T. Suhara, K. Murata, A. Navabi, K.O. Hara, Y. Nakagawa, C.T. Trinh, Y. Kurokawa, T. Suemasu, K.L. Wang, and N. Usami: Postannealing effects on undoped BaSi2 evaporated films grown on Si substrates. Jpn. J. Appl. Phys. 56, 05DB05 (2017).

    Article  Google Scholar 

  9. N.M. Shaalan, K.O. Hara, C.T. Trinh, Y. Nakagawa, and N. Usami: Simple method for significant improvement of minority-carrier lifetime of evaporated BaSi2 thin film by sputtered-AlOx passivation. Mater. Sci. Semicond. Process. 76, 37–41 (2018).

    Article  CAS  Google Scholar 

  10. M. Baba, K. Toh, K. Toko, N. Saito, N. Yoshizawa, K. Jiptner, T. Sekiguchi, K.O. Hara, N. Usami, and T. Suemasu: Investigation of grain boundaries in BaSi2 epitaxial films on Si(111) substrates using transmission electron microscopy and electron-beam-induced current technique. J. Cryst. Growth 348, 75–79 (2012).

    Article  CAS  Google Scholar 

  11. T. Suemasu: Exploring the possibility of semiconducting BaSi2 for thin-film solar cell applications. Jpn. J. Appl. Phys. 54, 07JA01 (2015).

    Article  Google Scholar 

  12. M. Kumar, N. Umezawa, W. Zhou, and M. Imai: Barium disilicide as a promising thin film photovoltaic absorber: Structural, electronic, and defect properties. J. Mater. Chem. A 5, 25293–25302 (2017).

    Article  CAS  Google Scholar 

  13. R. Takabe, T. Deng, K. Kodama, Y. Yamashita, T. Sato, K. Toko, and T. Suemasu: Impact of Ba to Si deposition rate ratios during molecular beam epitaxy on carrier concentration and spectral response of BaSi2 epitaxial films. J. Appl. Phys. 123, 045703 (2018).

    Article  Google Scholar 

  14. M. Kobayashi, Y. Matsumoto, Y. Ichikawa, D. Tsukada, and T. Suemasu: Control of electron and hole concentrations in semiconducting silicide BaSi2 with impurities grown by molecular beam epitaxy. Appl. Phys. Express 1, 051403 (2008).

    Article  Google Scholar 

  15. M.A. Khan, T. Saito, K. Nakamura, M. Baba, W. Du, K. Toh, K. Toko, and T. Suemasu: Electrical characterization and conduction mechanism of impurity-doped BaSi2 films grown on Si(111) by molecular beam epitaxy. Thin Solid Films 522, 95–99 (2012).

    Article  CAS  Google Scholar 

  16. M.A. Khan, K.O. Hara, K. Nakamura, W. Du, M. Baba, K. Toh, M. Suzuno, K. Toko, N. Usami, and T. Suemasu: Molecular beam epitaxy of boron doped p-type BaSi2 epitaxial films on Si(111) substrates for thin-film solar cells. J. Cryst. Growth 378, 201–204 (2013).

    Article  Google Scholar 

  17. M.A. Khan, K.O. Hara, W. Du, M. Baba, K. Nakamura, M. Suzuno, K. Toko, N. Usami, and T. Suemasu: In situ heavily p-type doping of over 1020 cm−3 in semiconducting BaSi2 thin films for solar cells applications. Appl. Phys. Lett. 102, 112107 (2013).

    Article  Google Scholar 

  18. R. Takabe, M. Baba, K. Nakamura, W. Du, M.A. Khan, S. Koike, K. Toko, K.O. Hara, N. Usami, and T. Suemasu: Fabrication and characterizations of phosphorus-doped n-type BaSi2 epitaxial films grown by molecular beam epitaxy. Phys. Status Solidi C 10, 1753–1755 (2013).

    Article  CAS  Google Scholar 

  19. K.O. Hara, Y. Hoshi, N. Usami, Y. Shiraki, K. Nakamura, K. Toko, and T. Suemasu: N-type doping of BaSi2 epitaxial films by phosphorus ion implantation and thermal annealing. Thin Solid Films 557, 90–93 (2014).

    Article  CAS  Google Scholar 

  20. K.O. Hara, N. Usami, M. Baba, K. Toko, and T. Suemasu: N-type doping of BaSi2 epitaxial films by arsenic ion implantation through a dose-dependent carrier generation mechanism. Thin Solid Films 567, 105–108 (2014).

    Article  CAS  Google Scholar 

  21. M. Ajmal Khan and T. Suemasu: Donor and acceptor levels in impurity-doped semiconducting BaSi2 thin films for solar-cell application. Phys. Status Solidi A 214, 1700019 (2017).

    Article  Google Scholar 

  22. K.O. Hara, C.T. Trinh, K. Arimoto, J. Yamanaka, K. Nakagawa, Y. Kurokawa, T. Suemasu, and N. Usami: Effects of deposition rate on the structure and electron density of evaporated BaSi2 films. J. Appl. Phys. 120, 045103 (2016).

    Article  Google Scholar 

  23. D. Tsukahara, S. Yachi, H. Takeuchi, R. Takabe, W. Du, M. Baba, Y. Li, K. Toko, N. Usami, and T. Suemasu: p-BaSi2/n-Si heterojunction solar cells with conversion efficiency reaching 9.0%. Appl. Phys. Lett. 108, 152101 (2016).

    Article  Google Scholar 

  24. S. Yachi, R. Takabe, H. Takeuchi, K. Toko, and T. Suemasu: Effect of amorphous Si capping layer on the hole transport properties of BaSi2 and improved conversion efficiency approaching 10% in p-BaSi2/n-Si solar cells. Appl. Phys. Lett. 109, 072103 (2016).

    Article  Google Scholar 

  25. Y. Nakagawa, K.O. Hara, T. Suemasu, and N. Usami: Fabrication of single-phase polycrystalline BaSi2 thin films on silicon substrates by vacuum evaporation for solar cell applications. Jpn. J. Appl. Phys. 54, 08KC03 (2015).

    Article  Google Scholar 

  26. R. Takabe, W. Du, K. Ito, H. Takeuchi, K. Toko, S. Ueda, A. Kimura, and T. Suemasu: Measurement of valence-band offset at native oxide/BaSi2 interfaces by hard X-ray photoelectron spectroscopy. J. Appl. Phys. 119, 025306 (2016).

    Article  Google Scholar 

  27. K.O. Hara, C. Yamamoto, J. Yamanaka, K. Arimoto, K. Nakagawa, and N. Usami: Investigation on the origin of preferred a-axis orientation of BaSi2 films deposited on Si(100) by thermal evaporation. Mater. Sci. Semicond. Process. 72, 93–98 (2017).

    Article  CAS  Google Scholar 

  28. K.O. Hara, C.T. Trinh, Y. Kurokawa, K. Arimoto, J. Yamanaka, K. Nakagawa, and N. Usami: Post-annealing effects on the surface structure and carrier lifetime of evaporated BaSi2 films. Jpn. J. Appl. Phys. 56, 04CS07 (2017).

    Article  Google Scholar 

  29. K.O. Hara, C. Yamamoto, J. Yamanaka, K. Arimoto, K. Nakagawa, and N. Usami: BaSi2 formation mechanism in thermally evaporated films and its application to reducing oxygen impurity concentration. Jpn. J. Appl. Phys. 57, 04FS01 (2018).

    Article  Google Scholar 

  30. K.O. Hara, K. Arimoto, J. Yamanaka, K. Nakagawa, and N. Usami: Suppression of near-interface oxidation in thermally-evaporated BaSi2 films and its effects on preferred orientation and the rectification behavior of n-BaSi2/p+-Si diodes. MRS Adv. 3, 1387–1392 (2018).

    Article  CAS  Google Scholar 

  31. G. Balducci, S. Brutti, A. Ciccioli, G. Trionfetti, A. Palenzona, and M. Pani: Thermodynamic properties of barium silicides from vapor pressure measurements and density functional calculations. Intermetallics 16, 1006–1012 (2008).

    Article  CAS  Google Scholar 

  32. K.O. Hara, Y. Nakagawa, T. Suemasu, and N. Usami: Realization of single-phase BaSi2 films by vacuum evaporation with suitable optical properties and carrier lifetime for solar cell applications. Jpn. J. Appl. Phys. 54, 07JE02 (2015).

    Article  Google Scholar 

  33. M. Pani and A. Palenzona: The phase diagram of the Ba–Si system. J. Alloys Compd. 454, L1–L2 (2008).

    Article  CAS  Google Scholar 

  34. M. Somer: Vibrational spectra of the cluster anions [E4]4− in the metallic sodium and barium compounds Na4E4 and Ba2E4 (E = Si, Ge). Z. Anorg. Allg. Chem. 626, 2478–2480 (2000).

    Article  CAS  Google Scholar 

  35. Y. Terai, H. Yamaguchi, H. Tsukamoto, N. Murakoso, M. Iinuma, and T. Suemasu: Polarized Raman spectra of BaSi2 epitaxial film grown by molecular beam epitaxy. Jpn. J. Appl. Phys. 56, 05DD02 (2017).

    Article  Google Scholar 

  36. K.O. Hara, C.T. Trinh, Y. Nakagawa, Y. Kurokawa, K. Arimoto, J. Yamanaka, K. Nakagawa, and N. Usami: Preferred orientation of BaSi2 thin films fabricated by thermal evaporation. JJAP Conf. Proc. 5, 011202 (2017).

    Google Scholar 

  37. A. Chandra, C.E.C. Wood, D.W. Woodard, and L.F. Eastman: Surface and interface depletion corrections to free carrier-density determinations by Hall measurements. Solid-State Electron. 22, 645–650 (1979).

    Article  CAS  Google Scholar 

  38. Y. Liu, Y. Sun, and A. Rockett: A new simulation software of solar cells—wxAMPS. Sol. Energy Mater. Sol. Cells 98, 124–128 (2012).

    Article  CAS  Google Scholar 

  39. W. Du, M. Baba, K. Toko, K.O. Hara, K. Watanabe, T. Sekiguchi, N. Usami, and T. Suemasu: Analysis of the electrical properties of Cr/n-BaSi2 Schottky junction and n-BaSi2/p-Si heterojunction diodes for solar cell applications. J. Appl. Phys. 115, 223701 (2014).

    Article  Google Scholar 

  40. K. Morita, Y. Inomata, and T. Suemasu: Optical and electrical properties of semiconducting BaSi2 thin films on Si substrates grown by molecular beam epitaxy. Thin Solid Films 508, 363–366 (2006).

    Article  CAS  Google Scholar 

Download references

ACKNOWLEDGMENT

This work was partly supported by JSPS KAKENHI Grant Nos. JP16H03856 and JP17K14657.

Author information

Authors and Affiliations

  1. Center for Crystal Science and Technology, University of Yamanashi, Kofu, Yamanashi, 400-8511, Japan

    Kosuke O. Hara, Keisuke Arimoto & Kiyokazu Nakagawa

  2. Center for Instrumental Analysis, University of Yamanashi, Kofu, Yamanashi, 400-8510, Japan

    Junji Yamanaka

Authors
  1. Kosuke O. Hara
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Keisuke Arimoto
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Junji Yamanaka
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Kiyokazu Nakagawa
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Kosuke O. Hara.

Additional information

This paper has been selected as an Invited Feature Paper.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hara, K.O., Arimoto, K., Yamanaka, J. et al. Diffusion process in BaSi2 film formation by thermal evaporation and its relation to electrical properties. Journal of Materials Research 33, 2297–2305 (2018). https://doi.org/10.1557/jmr.2018.181

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1557/jmr.2018.181

Search

Navigation