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Article

Optimization of Photogenerated Charge Carrier Lifetimes in ALD Grown TiO2 for Photonic Applications

1
Photonic Compounds and Nanomaterials Group, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, 33014 Tampere, Finland
2
Surface Science Group, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, 33014 Tampere, Finland
3
Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, 33014 Tampere, Finland
*
Authors to whom correspondence should be addressed.
Nanomaterials 2020, 10(8), 1567; https://doi.org/10.3390/nano10081567
Received: 25 June 2020 / Revised: 3 August 2020 / Accepted: 7 August 2020 / Published: 10 August 2020
(This article belongs to the Special Issue Characterization of Nanocrystalline Materials)
Titanium dioxide (TiO2) thin films are widely employed for photocatalytic and photovoltaic applications where the long lifetime of charge carriers is a paramount requirement for the device efficiency. To ensure the long lifetime, a high temperature treatment is used which restricts the applicability of TiO2 in devices incorporating organic or polymer components. In this study, we exploited low temperature (100–150 °C) atomic layer deposition (ALD) of 30 nm TiO2 thin films from tetrakis(dimethylamido)titanium. The deposition was followed by a heat treatment in air to find the minimum temperature requirements for the film fabrication without compromising the carrier lifetime. Femto-to nanosecond transient absorption spectroscopy was used to determine the lifetimes, and grazing incidence X-ray diffraction was employed for structural analysis. The optimal result was obtained for the TiO2 thin films grown at 150 °C and heat-treated at as low as 300 °C. The deposited thin films were amorphous and crystallized into anatase phase upon heat treatment at 300–500 °C. The average carrier lifetime for amorphous TiO2 is few picoseconds but increases to >400 ps upon crystallization at 500 °C. The samples deposited at 100 °C were also crystallized as anatase but the carrier lifetime was <100 ps. View Full-Text
Keywords: titanium dioxide; atomic layer deposition; transient absorption spectroscopy; thin films; lifetime of charge carriers titanium dioxide; atomic layer deposition; transient absorption spectroscopy; thin films; lifetime of charge carriers
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MDPI and ACS Style

Khan, R.; Ali-Löytty, H.; Saari, J.; Valden, M.; Tukiainen, A.; Lahtonen, K.; Tkachenko, N.V. Optimization of Photogenerated Charge Carrier Lifetimes in ALD Grown TiO2 for Photonic Applications. Nanomaterials 2020, 10, 1567. https://doi.org/10.3390/nano10081567

AMA Style

Khan R, Ali-Löytty H, Saari J, Valden M, Tukiainen A, Lahtonen K, Tkachenko NV. Optimization of Photogenerated Charge Carrier Lifetimes in ALD Grown TiO2 for Photonic Applications. Nanomaterials. 2020; 10(8):1567. https://doi.org/10.3390/nano10081567

Chicago/Turabian Style

Khan, Ramsha, Harri Ali-Löytty, Jesse Saari, Mika Valden, Antti Tukiainen, Kimmo Lahtonen, and Nikolai V. Tkachenko. 2020. "Optimization of Photogenerated Charge Carrier Lifetimes in ALD Grown TiO2 for Photonic Applications" Nanomaterials 10, no. 8: 1567. https://doi.org/10.3390/nano10081567

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