Conductivity of nanometer TiO2 thin films by magnetron sputtering

doi:10.1016/S0042-207X(02)00618-8

Vacuum

Volume 70, Issue 1, 21 February 2003, Pages 17-20

https://doi.org/10.1016/S0042-207X(02)00618-8 Get rights and content

Abstract

The conductivity of nanometer TiO₂ thin films was presented in this paper. The dependence of the conductivity of TiO₂ thin films on the thickness of the film and the substrate material were educed. The TiO₂ films were deposited by reactive magnetron sputtering of a Ti targets in an Ar+O₂ mixture in a conventional sputtering reactor. The thickness of the films deposited on Ti varied in the range from 15 to 225 nm. The resistivity of the films was measured at room temperature in the air. It was found that the conductivity of TiO₂ thin films varies in the range from conductor, semiconductor to nonconductor. This was attributed to electrons transfer at the interface between the TiO₂ and substrates, and the depth of electrons transfer was determined by the difference of work function.

Introduction

The dependence of the electrical conductivity on the concentration of different gases and on humidity is the basic mechanism of many sensing devices, developed on the basis of TiO₂ ceramics [1], [2], [3], [4]. Recently, much attention has been paid for the studies on nanometer materials as there are many different properties between nanometer materials and block materials. Some properties change obviously for same kind of materials under nanometer conditions. Nanometer materials will be used broadly because of their special characters. The fantastic characters of electricity have been investigated and applied for thin films [5], [6], [7]. If two kinds of materials contact each other, electrons can transfer from one with low work function to another with high work function. The depth of the transfer of electrons is determined by the difference of work function and is about nanometer thickness [8].

The dependence of the conductivity of TiO₂ thin films on the thickness of the film and the substrate material was investigated in this paper.

Section snippets

Experiment

The TiO₂ thin films were prepared on different substrates by RF magnetic sputtering PVD [9] using Ti target in an Ar+O₂ mixture at a total pressure of 1.2 Pa. The deposition conditions of the TiO₂ thin films are summarized in Table 1. The conduction type (p or n) of Si-substrate was n-type (ρ∼5–8 Ω cm). Titanium of 300 nm thick deposited on glass in 100% Ar under the conditions given in Table 1 was used for deposition substrates. Before Si-substrate is put into sputter chamber, it is socked by 10%

Results and discussion

AFM image of the around 100-nm-thick TiO₂ film prepared on Ti is shown in Fig. 1. The sample exhibits the consecutive surface morphology, and had flat surfaces as smooth as 10 nm. It is found that the film consisted of nanosize grains with a dimension of about 10–50 nm. Raman spectra of the TiO₂ thin films prepared on Ti are shown in Fig. 2. There are two strong Raman peaks of rutile at about 448 and 609 cm⁻¹ and three weak peaks of brookite at about 150, 247, and 318 cm⁻¹. The sample with 15 nm

Conclusion

The resistivity of the TiO₂ thin films enhances with the increase of the thickness of the films. The thin films vary in the range from conductor or semiconductor to nonconductor. Electrons can transfer from substrates to TiO₂ thin films through the interface. It is attributed to the different work function for TiO₂ and substrates. The depth of electrons transfer is determined by the difference between TiO₂ and substrates.

Acknowledgements

The author would like to acknowledge assistance in sample measurement from Y.B. Bai of the College of Chemistry of Jilin University.

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Conductivity of nanometer TiO2 thin films by magnetron sputtering

Abstract

Introduction

Section snippets

Experiment

Results and discussion

Conclusion

Acknowledgements

Sensors Actuators A

J Am Ceramic Soc

J Ceram Soc

J Ceram Soc

Conductivity of nanometer TiO₂ thin films by magnetron sputtering