Zinc tin oxide thin film transistors produced by a high rate reactive sputtering: Effect of tin composition and annealing temperatures
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Publication Date
2017-02-01Journal Title
Physica Status Solidi (A) Applications and Materials Science
ISSN
1862-6300
Publisher
Wiley
Volume
214
Language
English
Type
Article
This Version
AM
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Niang, K. M., Cho, J., Sadhanala, A., Milne, W., Friend, R., & Flewitt, A. (2017). Zinc tin oxide thin film transistors produced by a high rate reactive sputtering: Effect of tin composition and annealing temperatures. Physica Status Solidi (A) Applications and Materials Science, 214 https://doi.org/10.1002/pssa.201600470
Abstract
Amorphous zinc tin oxides (a-ZTO), which are stoichiometrically close to the Zn$_2$SnO$_4$ and ZnSnO$_3$ phases, have been deposited using remote-plasma reactive sputtering, and incorporated as the channel layers in thin film transistors (TFTs). The influence of tin composition and annealing temperatures on the structural and phase evolutions of the thin films, and the electrical performances of the TFTs are investigated. Zn$_2$SnO$_4$ exhibited randomly oriented polycrystalline peaks at annealing temperatures ≥700 °C, while ZnSnO$_3$ decomposed into Zn$_2$SnO$_4$ and SnO$_2$ at 950 °C. TFTs employing a Zn$_2$SnO$_4$ channel, after a post-deposition annealing at 500 °C, exhibited a field effect mobility ~14 cm$^2$ V$^{−1}$ s$^{−1}$ and a sub-threshold slope ~0.6 V dec$^{−1}$. When the tin content was increased in the channel, as in ZnSnO$_3$, TFTs exhibited an increase in field effect mobility ~20 cm$^2$ V$^{−1}$ s$^{−1}$, but with a slight deterioration of sub-threshold slope to ~0.8 V dec$^{−1}$. When the post-deposition annealing temperature was reduced to 300 °C, a mobility as high as ~10 cm$^2$ V$^{−1}$ s$^{−1}$ was still achieved, however, a significant shoulder in the IDS–VGS curve, together with a higher off-state current was observed. TFT characteristics are explained by the sub-bandgap defect states measured by photothermal deflection spectroscopy and the extracted Urbach energies.
Sponsorship
The support of this work by the Engineering and Physical Sciences Research Council (EPSRC) through project EP/M013650/1 is acknowledged. A.S. and R.H.F. would like to acknowledge funding and active support from EPSRC and India-UK APEX project. K.M.N. thanks Dr. S. Thornley of PlasmaQuest for providing the metallic tin target.
Funder references
EPSRC (EP/M013650/1)
Identifiers
External DOI: https://doi.org/10.1002/pssa.201600470
This record's URL: https://www.repository.cam.ac.uk/handle/1810/263328
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