Phase Transitions in TiO
2
Ind
uced by Laser Radiation
Artur Medvid`
1
, Pavels Onufrijevs
1
, Edvins Dauksta
1,2
, Kenji Murakami
2
, Masaru
Shimomura
2
1
Institute of Technical Physics, Faculty of Material science and Applied Chemistry,
Riga Technical University, Paula Valdena str. 7, Riga, LV-1086 Latvia
2
Graduate school of Science and Technology, Shizuoka University
3-5-1 Johoku, Naka-ku, Hamamatsu, 432-8561 Japan
Titanium dioxide (TiO
2
) is a wide band gap metal oxide semiconductor with numerous
applications in science and technology [1]. The main fields are photovoltaic and photo
catalytic for water purification. TiO
2
is known to form many polymorph phases, but the most
studied TiO
2
polymorph phases are anatase, rutile and brookite. It is known that the anatase is
more favorable for photo catalytic applications, while the rutile exhibits better optical and
electrical performance [2]. In recent years, researchers started to focus on anatase/rutile
heterostructures, which showed improved photo catalytic efficiency. In this study, the effects
of laser radiation on TiO
2
thin films were investigated with aim to show the possibility of
phase transitions rutile – anatase and anatase - brookite.
100
200
300
400
500
600
700
800
900
100
1000
10000
100000
1000000
610.1 cm
-1
636.2 cm
-1
200.1 cm
-1
610.2 cm
-1
516 cm
-1
445 cm
-1
397 cm
-1
241 cm
-1
144.3 cm
-1
Intensity, arb.units
Raman shift, cm
-1
Non-Irradiated
Irradiated 100 pulses
Irradiated 1000 pulses
Irradiated 10000 pulses
144.1 cm
-1
238.2 cm
-1
446.5 cm
-1
Fig. Raman spectra of TiO
2
thin films
before and after irradiation by the
fourth harmonic of Nd:YAG laser.
Nb:0.05wt% doped TiO
2
crystal was used in experiments. The crystal was irradiated by
fourth harmonic of Nd:YAG laser with following parameters: λ=266 nm, τ=3 ns, intensity
I=56.0 MW/cm
2
. The sample was irradiated in one spot with 10000 laser pulse. From
Raman scattering spectra, it can be seen that the crystal consists of rutile phase before
the irradiation. However, after irradiation the crystal is transformed in to the anatase
phase, as can be seen in Raman scattering spectra [3].
References
[1] M. Grätzel, Nature 414, 338 (2001).
[2] H. Cheng and A. Selloni, Phys. Rev. B 79, 092101 (2009).
[3] H.L.Ma, J.Y.Yang et al. Appl.Surf. Sc. 253, 7497(2007)
O 52
-118-
