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

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. ; Peer reviewed

Topics

• impedance spectroscopy
• polymer
• amorphous
• phase
• x-ray diffraction
• thin film
• titanium
• crystallization
• atomic layer deposition