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We report on low voltage and high frequency vertical organic field-effect transistors (VOFETs) using silver nanowires (AgNWs) as intermediate grid electrode (source) deposited through Mayer rod-coating. The optimized AgNWs electrodes deposited on insulator surface followed by low thermal annealing have sheet resistance of~30 U/sq and surface roughness of 70 ± 20 nm. Crosslinked poly(vinyl alcohol) is used as gate insulator and C 60 fullerene as n-type channel semiconductor. Our VOFETs have high output current density of 2.5 mA/cm 2 and on/off ratio of 5 Â 10 3 with supply voltages up to 2 V. A fast switching performance of sub-1 ms at frequency gate modulation of 0.13 MHz is demonstrated. Moreover, our devices are produced based on low-cost methods compatible with industrial-scale production of organic electronics.

Sol-gel spin-coating SnO 2 thin films were deposited and processed through positive photolithography (liftoff), avoiding surface interaction with gaseous oxygen species and leading to samples with higher stability and data reproducibility, when submitted to electrical characterization. Processing includes: (1) a narrow conduction channel, (2) the assembly of electric contacts by ultrasound soldering, (3) deposition of an insulating layer, preventing the surface contact with atmospheric oxygen, which contributes for reliable measurements and the possibility of measuring SnO 2 matrix properties without influence of adsorbed oxygen. Lightly Er-doped SnO 2 sample (0.05 at.%), processed by this manner, has allowed the observation of a maximum about 50 K, in the temperaturedependent resistivity curve, which has not been found previously. This result is probably related to the combination of free electron concentration, which grows with temperature, and the grain boundary scattering, which decreases with temperature, and is the dominant mechanism for sol-gel SnO 2 . The processing also assures a remarkable reproducibility in the decay of photo-induced conductivity, yielding reliability to apply a modeling for the determination of important decay parameters, such as capture energy and grain boundary potential barrier.

Alternative materials for use in electronic devices have grown interest in the past recent years. In this paper, the heterojunction SnO 2 /Al 2 O 3 is tested concerning its use as a transparent insulating layer for use in FETs. The alumina layer is obtained by thermal annealing of metallic Al layer, deposited by resistive evaporation technique. Combination of undoped SnO 2 , deposited by sol-gel-dip-coating technique, and Al thermally annealed in O 2 -rich atmosphere, leads to fair insulation when the number of aluminum oxide layers is 4, with 0.3% of the current lost through the gate terminal as leakage current. This insulation is not obtained for devices with alumina layer treated for long time, under room atmosphere, due to degradation of the insulating film and interfusion with the conduction channel even using Sb-doped SnO 2 . The annealing of Al deposited on soda-lime glass substrate leads also to the formation of a Si layer, crystallized at Substrate/Al 2 O 3 interface. The conclusion is that for an efficient insulation the thermal annealing must be short and then, O 2 -rich atmospheres are preferred.

Natural Rubber Latex (NRL) obtained from Hevea brasiliensis is a biocompatible electrically insulating material with exceptional mechanical properties. Poly(3,4-ethylene dioxythiophene) poly(styrene sulfonate), PEDOT:PSS, on the other hand, is a biocompatible highly conductive organic material with poor flexibility. We hereby introduce a blend of NRL/PEDOT:PSS (N/P). This study involved different N/P volume ratios and temperatures of curing aiming at an optimal combination of good flexibility and conductivity. Low-temperature annealing, at 60 °C, dries and cures the blend in a few minutes and improves its tensile strength and conductivity. The blend can stretch more than 700% of its initial length and presents a good gauge factor and small resistance variation (R/R0) for ΔL/L0 of up to 100%. Among the different N/P concentrations, the membranes of an N/P ratio of 1/4 and those thermally cured have the most promising conductive flexible properties for bioelectronic applications.

Titanium dioxide (TiO 2 ) in the form of pellets (pressed powder) and thin films are investigated, revealing the presence of distinct phases: mainly anatase and rutile. Characterization of optical, structural and electrical properties were carried out on samples submitted to different sort of thermal annealing (TA), at distinct temperatures, 500 and 1000 o C, due to their influence on the obtained phases. TA temperature along with pressure application for sample conformation, determine the bands present in the photoluminescence (PL) spectra, being about 550nm, characteristic of anatase phase and 800nm, related to the presence of rutile phase. The bandgap of thin films is determined from optical absorbance data, yielding 3.4eV for anatase phase (indirect transition), and 2.9eV for rutile phase (direct transition). Besides, irradiation with monochromatic light strongly affects the thin film conductivity, but the energy range (above or below the bandgap energy) does not seem to affect the behavior, which is associated with the excitation of intrabandgap states or crystallites belonging to phases with distinct bandgaps.

A study of zirconium oxide (ZrO 2) thin films obtained by the non-alkoxide sol-gel method at different annealing temperatures, up to 450°C, is presented. Morphological, compositional, and optical characterizations of zirconia thin films show high transparency and high bandgap, besides homogeneous and non-porous surface. Metalinsulating-metal (MIM) devices were assembled from this zirconia material for electrical characterizations and have shown high electric resistivity and high specific capacitance. A study of the thin film composition shows residues of S and Cl elements from the precursor solution that contributes for reduction of the dielectric constant of the zirconia thin films, even though they still present higher values when compared to SiO 2 , which is a positive alternative to replace this oxide in electronic devices. A parallel study of MIM assembled on polymeric substrate and annealed at 100°C also leads to positive results concerning high electrical insulating and capacitance. This study aims the understanding of the relations between annealing temperature and impurities found in sol-gel based thin films, as well as their relations to dielectric characteristics of zirconia thin films that impact the final properties of electronic devices, such as in field effect transistors.