Frequency-Agile Low-Temperature Solution-Processed Alumina Dielectrics for Inorganic and Organic Electronics Enhanced by Fluoride Doping

The frequency-dependent capacitance of low-temperature solution-processed metal oxide (MO) dielectrics typically yields unreliable and unstable thin-film transistor (TFT) performance metrics, which hinders the development of next-generation roll-to-roll MO electronics and obscures intercomparisons between processing methodologies. Here, capacitance values stable over a wide frequency range are achieved in low-temperature combustion-synthesized aluminum oxide (AlOx) dielectric films by fluoride doping. For an optimal F incorporation of similar to 3.7 atomic % F, the F:AlOx film capacitance of 166 +/- 11 nF/cm(2) is stable over a 10(-1)-10(4) Hz frequency range, far more stable than that of neat AlOx films (capacitance = 336 +/- 201 nF/cm(2)) which falls from 781 +/- 85 nF/cm(2) to 104 +/- 4 nF/cm(2) over this frequency range. Importantly, both n-type/inorganic and p-type/organic TFTs exhibit reliable electrical characteristics with minimum hysteresis when employing the F:AlOx dielectric with similar to 3.7 atomic % F. Systematic characterization of film microstructural/compositional and electronic/dielectric properties by X-ray photoelectron spectroscopy, time-of-fight secondary ion mass spectrometry, cross-section transmission electron microscopy, solid-state nuclear magnetic resonance, and UV-vis absorption spectroscopy reveal that fluoride doping generates AlOF, which strongly reduces the mobile hydrogen content, suppressing polarization mechanisms at low frequencies. Thus, this work provides a broadly applicable anion doping strategy for the realization of high-performance solution-processed metal oxide dielectrics for both organic and inorganic electronics applications.