Next Article in Journal
Phosphorothioate DNA Stabilized Fluorescent Gold and Silver Nanoclusters
Next Article in Special Issue
Electronic Structure and Magnetism of Mn-Doped ZnO Nanowires
Previous Article in Journal
Modeling the Dispersibility of Single Walled Carbon Nanotubes in Organic Solvents by Quantitative Structure-Activity Relationship Approach
Previous Article in Special Issue
Optical and Structural Properties of Si Nanocrystals in SiO2 Films
Open AccessArticle

Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition

1
Institute of Photonics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
2
Center for Advance Studies in Energy (CAS-EN), National University of Sciences and Technology (NUST), Sector H-12, 44000 Islamabad, Pakistan
*
Authors to whom correspondence should be addressed.
Academic Editor: Thomas Nann
Nanomaterials 2015, 5(2), 792-803; https://doi.org/10.3390/nano5020792
Received: 28 February 2015 / Revised: 10 May 2015 / Accepted: 13 May 2015 / Published: 18 May 2015
(This article belongs to the Special Issue Nanophotonic Materials)
We investigate the optical and thermo-optical properties of amorphous TiO\(_2\)–Al\(_2\)O\(_3\) thin-film bilayers fabricated by atomic layer deposition (ALD). Seven samples of TiO\(_2\)–Al\(_2\)O\(_3\) bilayers are fabricated by growing Al\(_2\)O\(_3\) films of different thicknesses on the surface of TiO\(_2\) films of constant thickness (100 nm). Temperature-induced changes in the optical refractive indices of these thin-film bilayers are measured by a variable angle spectroscopic ellipsometer VASE\textsuperscript{\textregistered}. The optical data and the thermo-optic coefficients of the films are retrieved and calculated by applying the Cauchy model and the linear fitting regression algorithm, in order to evaluate the surface porosity model of TiO\(_2\) films. The effects of TiO\(_2\) surface defects on the films' thermo-optic properties are reduced and modified by depositing ultra-thin ALD-Al\(_2\)O\(_3\) diffusion barrier layers. Increasing the ALD-Al\(_2\)O\(_3\) thickness from 20 nm to 30 nm results in a sign change of the thermo-optic coefficient of the ALD-TiO\(_2\). The thermo-optic coefficients of the 100 nm-thick ALD-TiO\(_2\) film and 30 nm-thick ALD-Al\(_2\)O\(_3\) film in a bilayer are (0.048 \(\pm\) 0.134) \(\times 10 ^{-4} {^\circ}\mathrm {C}^{-1}\) and (0.680 \(\pm\) 0.313) \(\times 10^{-4} {^\circ} \mathrm {C}^{-1}\), respectively, at a temperature \(T = 62 ^\circ \mathrm{C}\). View Full-Text
Keywords: atomic layer deposition (ALD); thin barrier films; thermo-optic coefficient; titanium dioxide; aluminum oxide; optical materials atomic layer deposition (ALD); thin barrier films; thermo-optic coefficient; titanium dioxide; aluminum oxide; optical materials
MDPI and ACS Style

Ali, R.; Saleem, M.R.; Pääkkönen, P.; Honkanen, S. Thermo-Optical Properties of Thin-Film TiO2–Al2O3 Bilayers Fabricated by Atomic Layer Deposition. Nanomaterials 2015, 5, 792-803.

Show more citation formats Show less citations formats

Article Access Map by Country/Region

1
Only visits after 24 November 2015 are recorded.
Back to TopTop