Sol–gel-based solution-processed metal oxides have emerged as a key
fabrication method for applications in thin film transistors both as a
semiconducting and a dielectric layer. Here, a low-temperature, green
solvent-based, non-toxic, and cost-effective solution shearing approach for the
fabrication of thin aluminum oxide (AlOx) dielectrics is reported. Optimization
of sustainability aspects like energy demand, and selection of chemicals used
allows to reduce the environmental impact of the life cycle of the resulting
product already in the design phase. Using this approach, ultra-thin,
device-grade AlOx films of 7 nm are coated—the thinnest films to be reported
for any solution-fabrication method. The metal oxide formation is achieved by
both thermal annealing and deep ultra-violet (UV) light exposure techniques,
resulting in capacitances of 750 and 600 nF cm−2, respectively. The structural
analysis using microscopy and x-ray spectroscopy techniques confirmed the
formation of smooth, ultra-thin AlOx films. These thin films are employed in
organic field-effect transistors (OFETs) resulting in stable, low hysteresis
devices leading to high mobilities (6.1 ± 0.9 cm2 V−1 s−1), near zero threshold
voltage (−0.14 ± 0.07 V) and a low subthreshold swing (96 ± 16 mV dec−1),
enabling device operation at only ±0.5 V with a good Ion/Ioff ratio (3.7 × 105).