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

Khan, Ramsha; Ali-Löytty, Harri; Saari, Jesse; Valden, Mika; Tukiainen, Antti; Lahtonen, Kimmo; Tkachenko, Nikolai V.

doi:10.3390/nano10081567

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

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Photonic Compounds and Nanomaterials Group, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, 33014 Tampere, Finland

Surface Science Group, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, 33014 Tampere, Finland

Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, 33014 Tampere, Finland

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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)

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Abstract

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

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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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