The improvement of optical reactivity for TiO2 thin films by N2-H2 plasma surface-treatment

Lei Miao, Sakae Tanemura, Hiroshige Watanabe, Yukimasa Mori, Kenji Kaneko, Shoichi Toh

Research output: Contribution to journalArticle

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Abstract

To improve the optical reactivity of TiO2 thin film in visible-light region, sputter-deposited anatase film on slide glass substrate with 1200Å film thickness was surface-treated by N2-H 2 mixed gases plasma and additionally anneal-treated in N 2 gases at 400°C for 2h. The absorption edges of plasma-treated sample and plasma plus anneal-treated one shifted from 363nm (3.4eV) to 428nm (2.9eV), and 354nm (3.5eV) to 428nm (2.9eV), while the absorptance for the two corresponding samples increased by 16% and 26%, respectively, in comparison with the as-deposited sample. Spectral absorption is well explained by Tauc-plot extrapolated band-gap using extinction coefficient k obtained from spectroscopic ellipsometry for the surface layers of the three samples, even though in the case of plasma plus anneal-treated sample showed only nominal band-gap value (2.65eV) due to the metallic behavior of extinction coefficient k in lower energy range (2.5eV). X-ray photoemission spectroscopy reveals the formation of TiO2-xNx and TiN deep into about 120Å thickness from the film surface for both plasma-treated and plasma plus anneal-treated samples. Secondary ion mass spectrography also detected high concentration of N element at the surface of the two corresponding samples. From the fact of formation of TiN and TiO2-xNx, N-doping in this work was proved as N substituted O in TiO2 lattice. We confirmed this substitutional N-doping causes the narrowing of band-gap that resulted in the observed significant red shift of the absorption edge to the visible-light region.

Original languageEnglish
Pages (from-to)118-124
Number of pages7
JournalJournal of Crystal Growth
Volume260
Issue number1-2
DOIs
Publication statusPublished - Jan 2 2004

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surface treatment
Surface treatment
reactivity
Plasmas
Thin films
thin films
Energy gap
Doping (additives)
Plasma Gases
Spectroscopic ellipsometry
extinction
Photoelectron spectroscopy
X ray spectroscopy
absorptance
Film thickness
Gases
Titanium dioxide
coefficients
Ions
gases

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Materials Chemistry

Cite this

The improvement of optical reactivity for TiO2 thin films by N2-H2 plasma surface-treatment. / Miao, Lei; Tanemura, Sakae; Watanabe, Hiroshige; Mori, Yukimasa; Kaneko, Kenji; Toh, Shoichi.

In: Journal of Crystal Growth, Vol. 260, No. 1-2, 02.01.2004, p. 118-124.

Research output: Contribution to journalArticle

Miao, Lei ; Tanemura, Sakae ; Watanabe, Hiroshige ; Mori, Yukimasa ; Kaneko, Kenji ; Toh, Shoichi. / The improvement of optical reactivity for TiO2 thin films by N2-H2 plasma surface-treatment. In: Journal of Crystal Growth. 2004 ; Vol. 260, No. 1-2. pp. 118-124.
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