Kiazadeh, A., D. Salgueiro, R. Branquinho, J. Pinto, H. L. Gomes, P. Barquinha, R. Martins, and E. Fortunato,
"{Operational stability of solution based zinc tin oxide/SiO2 thin film transistors under gate bias stress}",
APL Materials, vol. 3, no. 6: AIP Publishing, pp. 062804, jun, 2015.
AbstractIn this study, we report solution-processed amorphous zinc tin oxide transistors exhibiting high operational stability under positive gate bias stress, translated by a recoverable threshold voltage shift of about 20{%} of total applied stress voltage. Under vacuum condition, the threshold voltage shift saturates showing that the gate-bias stress is limited by trap exhaustion or balance between trap filling and emptying mechanism. In ambient atmosphere, the threshold voltage shift no longer saturates, stability is degraded and the recovering process is impeded. We suggest that the trapping time during the stress and detrapping time in recovering are affected by oxygen adsorption/desorption processes. The time constants extracted from stretched exponential fitting curves are ≈106 s and 105 s in vacuum and air, respectively.
Kololuoma, T., J. Leppäniemi, H. Majumdar, R. Branquinho, E. Herbei-Valcu, V. Musat, R. Martins, E. Fortunato, and A. Alastalo,
"{Gravure printed sol–gel derived AlOOH hybrid nanocomposite thin films for printed electronics}",
J. Mater. Chem. C, vol. 3, no. 8, pp. 1776–1786, 2015.
AbstractWe report a sol-gel approach to fabricate aluminum-oxy-hydroxide (AlOOH) -based inks for gravure printing of high-dielectric-constant nanocomposite films. By reacting 3-glycidoxypropyl- trimethoxysilane (GPTS) with aluminum-oxide-hydroxide (AlOOH) nanoparticles under constant bead milling, inks suitable for gravure printing were obtained. The calculated relative dielectric constant based on measured capacitances and film thicknesses for the gravure-printed GPTS:AlOOH nanocomposite varied between 7 and 11 at a 10 kHz frequency. The dielectric constant depended on the mixing ratio of the composite and was found to follow the Maxwell-Garnett ternary-system mixing rule indicating presence of micro/nanopores that affect the electrical properties of the fabricated films. Increasing leakage current with increasing AlOOH content was observed. High leakage current was reduced by printing two-layer films. The double-layered gravure-coated films exhibited similar capacitance density but clearly lower leakage current and less electrical breakdowns in comparison to single-layered films having comparable film compositions and film thicknesses. The best composite yielded a capacitance density of 109 ± 2 pF/mm2 at the 10 kHz frequency and a leakage current density of 60 ± 20 µA/cm2 at 0.5 MV/cm electric field as a single layer. The calculated relative dielectric constant at the 10 kHz frequency for this composition was 11.2 ± 0.5. Introduction
] 
