AC-conductance and capacitance measurements for ethanol vapor detection using carbon nanotube-polyvinyl alcohol composite based devices.

We report the preparation of inexpensive ethanol sensor devices using multiwalled carbon nanotube-polyvinyl alcohol composite films deposited onto interdigitated electrodes patterned on phenolite substrates. We investigate the frequency dependent response of the device conductance and capacitance showing that higher sensitivity is obtained at higher frequency if the conductance is used as sensing parameter. In the case of capacitance measurements, higher sensitivity is obtained at low frequency. Ethanol detection at a concentration of 300 ppm in air is demonstrated. More than 80% of the sensor conductance and capacitance variation response occurs in less than 20 s.

Hybrid vertical architecture transistor with 2,6-diphenylindenofluorene based emitter and base permeability controlled by polystyrene spheres lithography.

We report on vertical architecture hybrid transistor devices using p-type silicon as collector terminal and 2,6-diphenylindenofluorene as organic semiconductor in the emitter layer. Polystyrene spheres were used as shadow masks in order to control the diameter and density of the openings in the Al metallic base. Two processes of sphere deposition were used: electrospray and dip-coating. The electrospray deposition leads to a smaller density of sphere agglomerates, but for the used sphere diameter, approximately 200 nm, the transistor performance is similar for devices prepared with sphere deposition by both techniques. The so constructed permeable-base transistors show common-emitter current gain of the order of 10(2).