Electrolyte gated transistors modified by polypyrrole nanoparticles

Properties of electrolyte gated transistors were studied on example of a system, where both carbon nanotubes semiconducting channel and modified gold gate were contacting an electrolyte solution, and response mechanisms of such transistors were discussed. Modification of the gate by polypyrrole nanoparticles, particularly those dispersed in poly (vinyl chloride) ion-selective membrane, resulted in significant improvement of transistor output. One of advantageous effects was around tenfold increase of source-drain current and apparent transconductance, compared to non-modified gold gate. This effect was explained in terms of electrochemical behavior of the system, taking into account reduction of polypyrrole at negative gate voltage and accompanying positive charging of carbon nanotubes resulting in increasing source-drain current. This process is coupled with selective ion transfer across the membrane resulting in exposed ionic sensitivity, demonstrated in linear dependence of the transconductance on the logarithm of ions concentration. Thus, transistors with the gate modified by ion-selective membrane with dispersed polypyrrole nanoparticles offer both very good electrical parameters (high apparent transconductance and on/off ratio) and analytical properties as ion-selective sensors. This work shows a new technique to achieve an order of magnitude higher currents for electrolyte gated transistor. It gives chance to increase device performance without increase the physical size of the device, this saves area and helps miniaturization.