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ZnO-based thin film transistors employing aluminum titanate gate dielectrics deposited by spray pyrolysis at ambient air

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<mark>Journal publication date</mark>8/04/2015
<mark>Journal</mark>ACS Applied Materials and Interfaces
Issue number13
Number of pages8
Pages (from-to)7334-7341
Publication StatusPublished
Early online date16/03/15
<mark>Original language</mark>English


The replacement of SiO2 gate dielectrics with metal oxides of higher dielectric constant has led to the investigation of a wide range of materials with superior properties compared with SiO2. Despite their attractive properties, these high-k dielectrics are usually manufactured using costly vacuum-based techniques. To overcome this bottleneck, research has focused on the development of alternative deposition methods based on solution-processable metal oxides. Here we report the application of spray pyrolysis for the deposition and investigation of Al2x-1•TixOy dielectrics as a function of the [Ti+4]/[Ti+4+2•Al+3] ratio and their implementation in thin film transistors (TFTs) employing spray-coated ZnO as the active semiconducting channels. The films are studied by UV-visible absorption spectroscopy, spectroscopic ellipsometry, impedance spectroscopy, atomic force microscopy, x-ray diffraction and field-effect measurements. Analyses reveal amorphous Al2x-1•TixOy dielectrics that exhibit a wide band gap (~4.5 eV), low roughness (~0.9 nm), high dielectric constant (k~13), Schottky pinning factor S of ~0.44 and very low leakage currents (<5 nA/cm2). TFTs employing stoichiometric Al2O3•TiO2 gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with low operating voltages (~10 V), negligible hysteresis, high on/off current modulation ratio of ~106, subthreshold swing (SS) of ~550 mV/dec and electron mobility of ~10 cm2 V-1 s-1.