Growth and characteristics of laser deposited anatase and rutile TiO2 films on Si substrates

doi:10.1016/j.tsf.2008.08.179

Thin Solid Films

Volume 517, Issue 2, 28 November 2008, Pages 745-749

https://doi.org/10.1016/j.tsf.2008.08.179 Get rights and content

Abstract

Titanium dioxide thin films have been synthesized on Si (100) substrates using pulsed laser deposition method (KrF: 248 nm, 20 ns, 5 Hz). The emission spectra of the plasma induced by ablating TiO₂ target in the oxygen or argon ambient gas were analyzed. The influences of substrate temperature and ambient gas pressure on the structural properties of TiO₂ films were discussed. The X-ray diffraction results show that the films deposited at 750 °C are (004)-oriented anatase phase and (110)-oriented rutile phase under the oxygen and argon pressure of 5 Pa, respectively. The scanning electron microscopy images indicate that the TiO₂ films have a uniform and smooth surface and are composed of nanocrystal grains. The pure anatase and rutile phase TiO₂ films are further proved by Raman spectromicroscopy. In addition, the optical transmission spectra and Fourier Transform infrared spectroscopy of the films were also studied.

Introduction

Titanium dioxide, TiO₂, has attracted much attention in recent years due to its great potential for applications in optical elements, electrical insulation, capacitors or gates in microelectronic devices and photovoltaic solar cells. It is well known that TiO₂ exists in three crystalline structures: rutile, anatase and brookite. Anatase and rutile have properties of interest for photocatalyst applications so that they have been widely investigated. TiO₂ films with specific crystal structure, orientation or morphology exhibit specific characteristics, which makes it important to control the phase structure of TiO₂ films during the growth. The methods of sol–gel spin-coating, anodization, oxygen plasma assisted molecular beam epitaxy and pulsed laser deposition (PLD) [1], [2], [3], [4] have been used to fabricate TiO₂ films. Among these methods, PLD technique has been widely used for growing oxide films because it allows for stoichiometry of the synthesized material. And because Si substrate is widely used in semiconductor industry the growth of TiO₂ films on Si substrates using PLD attracted much attention. For example, Roy et al. have reported the effects of oxygen pressure and laser fluence on the dielectric properties of TiO₂ films on Si substrate [5], [6], [7]. However, there are few reports on the deposition of anatase and rutile films with preferred orientation on Si under different ambient gases using PLD method.

In this work we report the growth of single anatase phase and rutile phase TiO₂ thin films with preferred orientation on Si(100) substrates prepared by PLD technique. The effects of substrate temperature and gas pressure on the crystallinity and structural properties of TiO₂ films were discussed in detail. Furthermore, the optical transmission spectra, Fourier Transform infrared (FTIR) spectroscopy and micro-Raman spectroscopy were used to investigate the optical properties of the films.

Section snippets

Experimental details

The target for the deposition was prepared from TiO₂ powder with purity of 99.999%. The powder was compacted into pellet, which was then sintered at 1250 °C for 2 h by the conventional ceramic sintering process. The X-ray diffraction (XRD) results showed that the target has a rutile structure. The film-growth experiments were carried out in a typical PLD configuration mentioned in other reports [8]. The beam of a Lambda Physik KrF excimer laser (248 nm, 20 ns full width at half maximum, 5 Hz)

Emission spectra of the plume

The optical emission spectra of the plume produced by ablating TiO₂ target under oxygen or argon of 5 Pa are shown in Fig. 1(a) and (b). In the figure, it is found that the spectra are dominated by Ti I and Ti II emission spectra, which indicate the neutral titanium atom and the single ionized titanium ions, respectively. There were no spectra contributions to the molecular species such as TiO, TiO₂, O₂ or molecular oxygen ions. The results are well in agreement with the optical spectroscopic

Conclusion

In summary, TiO₂ thin films were grown on Si(100) substrates in oxygen or argon ambient gas by PLD technique. The effects of substrate temperature and the pressure of ambient gas on the crystal structure and optical properties were discussed in detail. The XRD, FTIR spectroscopy and Raman spectra indicate that the pure anatase and rutile TiO₂ films can be obtained by adjusting the substrate temperature and pressure of ambient gas. C-axes oriented anatase and (110)-oriented rutile TiO₂ films

Acknowledgement

The authors acknowledge the Analytical and Testing Center in Huazhong University of Science and Technology for XRD, SEM and spectra measurements. The finance support from the National Natural Science Foundation of China (10604018) and Specialized Research Fund for the Doctoral Program of Higher Education (20060487006) are also acknowledged.

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Growth and characteristics of laser deposited anatase and rutile TiO2 films on Si substrates

Abstract

Introduction

Section snippets

Experimental details

Emission spectra of the plume

Conclusion

Acknowledgement

Microelectron. J.

Thin Solid Films

Appl. Surf. Sci.

Phys. Lett. A

Thin Solid Films

Vacuum

Appl. Surf. Sci.

Appl. Surf. Sci.

J. Non-Cryst. Solids

Surf. Sci.

J. Phys., D, Appl. Phys.

J. Phys. Chem. C

Growth and characteristics of laser deposited anatase and rutile TiO₂ films on Si substrates