Distinguishing between Deep Trapping Transients of Electrons and Holes in TiO2 Nanotube Arrays Using Planar Microwave Resonator Sensor
- Mohammad H. Zarifi* ,
- Benjamin D. WiltshireBenjamin D. WiltshireDepartment of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, CanadaMore by Benjamin D. Wiltshire,
- Najia MahdiNajia MahdiDepartment of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, CanadaMore by Najia Mahdi,
- Karthik Shankar* , and
- Mojgan Daneshmand*
A large signal direct current (DC) bias and a small signal microwave bias were simultaneously applied to TiO2 nanotube membranes mounted on a planar microwave resonator. The DC bias modulated the electron concentration in the TiO2 nanotubes and was varied between 0 and 120 V in this study. Transients immediately following the application and removal of DC bias were measured by monitoring the S-parameters of the resonator as a function of time. The DC bias stimulated Poole–Frenkel-type trap-mediated electrical injection of excess carriers into TiO2 nanotubes, which resulted in a near-constant resonant frequency but a pronounced decrease in the microwave amplitude due to free electron absorption. When ultraviolet illumination and DC bias were both present and then stepwise removed, the resonant frequency shifted due to trapping-mediated change in the dielectric constant of the nanotube membranes. Characteristic lifetimes of 60–80, 300–800, and ∼3000 s were present regardless of whether light or bias was applied and were also observed in the presence of a hole scavenger, which we attributed to oxygen adsorption and deep electron traps, whereas another characteristic lifetime >8000 s was only present when illumination was applied, and is attributed to the presence of hole traps.
This article is cited by 6 publications.
- Ryan Kozak, Benjamin Daniel Wiltshire, Md. Arifur Rahman Khandoker, Kevin Golovin, Mohammad H. Zarifi. Modified Microwave Sensor with a Patterned Ground Heater for Detection and Prevention of Ice Accumulation. ACS Applied Materials & Interfaces 2020, 12 (49) , 55483-55492. https://doi.org/10.1021/acsami.0c17173
- Vivek Kale, Chetan Chavan, Chetan Bhongale, K.G. Girija, S.N. Kale. Resonance-based detection of perilous sulphur dioxide using TiO2 nanoparticles and unit-cell ring resonator. Sensors and Actuators A: Physical 2021, 331 , 112898. https://doi.org/10.1016/j.sna.2021.112898
- Benjamin D. Wiltshire, Mohammad Hossein Zarifi. TiO2 nanotube-integrated microwave planar resonator sensor for ultraviolet transmission-based liquid characterization. Sensors and Actuators B: Chemical 2021, 341 , 130014. https://doi.org/10.1016/j.snb.2021.130014
- Benjamin D. Wiltshire, Kiana Mirshahidi, Anupama Vijaya Nadaraja, Sadaf Shabanian, Roozbeh Hajiraissi, Mohammad Hossein Zarifi, Kevin Golovin. Oleophobic textiles with embedded liquid and vapor hazard detection using differential planar microwave resonators. Journal of Hazardous Materials 2021, 409 , 124945. https://doi.org/10.1016/j.jhazmat.2020.124945
- Min Huang, Shuxu Zhu, Yue Wu, Jianli Yu, Qingyao Wang. Hydrothermal deposition of AgCl/AgBr co-sensitizers to modify TiO2 NTs for enhanced photocatalytic performance. Ceramics International 2020, 46 (15) , 24008-24017. https://doi.org/10.1016/j.ceramint.2020.06.178
- Yudong Xue, Yunting Wang. A review of the α-Fe 2 O 3 (hematite) nanotube structure: recent advances in synthesis, characterization, and applications. Nanoscale 2020, 12 (20) , 10912-10932. https://doi.org/10.1039/D0NR02705G