Thermal properties of TiO2 films grown by atomic layer deposition |
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Authors: | MR Saleem P SilfstenS Honkanen J Turunen |
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Affiliation: | a University of Eastern Finland, Department of Physics and Mathematics, P.O. Box 111, FI-80101 Joensuu, Finlandb National University of Sciences and Technology (NUST), School of Chemical and Materials Engineering (SCME), Sector H-12, Islamabad, Pakistanc Aalto University, Department of Micro and Nano-sciences, P.O. Box 13500, FI-00760 Aalto, Finland |
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Abstract: | We study the thermal properties of amorphous TiO2 thin films of various thicknesses t, grown by atomic layer deposition. The thermo-optic coefficient dn/dT and the temperature coefficient dρ/dT of film density ρ are determined from ellipsometric data in wavelength range 380 < λ < 1800 nm with the Cauchy model and the Lorentz-Lorenz relation. It is found that dn/dT exhibits negative values for films with t < 150 nm and positive values for thicker films, while no significant changes in the two coefficients take place if t < 200 nm. A qualitative physical explanation based on porosity of the thin films is suggested. Films with t = 60 nm are illustrated in detail at λ = 640 nm: the room-temperature values of the coefficients are found to be dn/dT = − 3.1 × 10− 5 °C− 1 and dρ/dT = − 4.8 × 10− 5g cm− 3° C− 1. |
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Keywords: | Atomic layer deposition Thermo-optic coefficient Titanium oxide Thin films Optical materials |
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