Solution processed aluminium titanate dielectrics for their applications in high mobility ZnO based thin film transistors

Afouxenidis, Dimitrios and Bin Esro, Mazran and Vourlias, G. and Adamopoulos, George (2014) Solution processed aluminium titanate dielectrics for their applications in high mobility ZnO based thin film transistors. In: EMRS 2014, Spring Meeting, 2014-05-262014-05-30, France.

Abstract

Metal oxide semiconductors are very attractive candidates for implementation into TFTs mainly because of their high charge carrier mobility, high optical transparency and excellent chemical stability. Recent work has also been focusing on the development of variable-voltage oxide transistors using mainly high-k dielectrics i.e. ZrO2, HfO2, Y2O3 and Al2O3. Oxide transistors based on high-k dielectrics have received the most attention and variable-voltage devices have been demonstrated. Here, we report solution-processed, variable-voltage ZnO transistors based on aluminium and titanium oxide composite films as the gate dielectrics. The films were deposited on ITO-coated glass substrates from Ti and Al soluble precursors using the spray pyrolysis technique at 400 oC. The dielectric films were characterised by AFM, UV-Vis absorption spectroscopy, admittance spectroscopy, X-ray diffraction and spectroscopic ellipsometry. Data analysis showed amorphous Al2O3 and stoichiometric (in the solution) Al2O3.TiO2 films with dielectric constants in the range between 9 and 14 and optical band gaps between 6.1 eV and 4.4 eV respectively. Similarly, stoichiometric Al2O3.TiO2 showed improved leakage currents by 2 orders of magnitude (compared to Al2O3) in the order of 1 nA/cm2. BG-TC ZnO-based TFTs that also manufactured by spray pyrolysis on Al2O3.TiO2 gate dielectrics showed enhanced electron mobilities from 9 cm2 V−1 s−1 to 23 cm2 V−1 s−1 and current on/off ratios from 10^4 to 10^6.