Effect of measurement temperature on the charge transport behavior in temperature sensitive ferroelectric dielectric-based organic field-effect transistors

This paper emphasized the charge transport mechanism of a low-powered OFET fabricated using barium titanate (BaTi03) nanocrystal as the dielectric material. These OFET -based devices are highly stable in the air and exhibited significantly much higher carrier mobility. In general, the high temperature processing of BaTi03 proclaims excellent ferro electricity due to the AB03-type perovskite structure. However, the approach towards the very low temperature synthesis of BaTi03 displayed a hexagonal phase in an amorphous matrix. The inclusion of hexagonal barium titanate nanocrystals significantly lowered the surface roughness of the entire bi-Iayer dielectric system. An extensive temperature- dependent study ranging from 50 K to 350 K has been carried out, and the variation of carrier mobility follows the Arrhenius behavior over the temperature range, supporting the hopping assisted charge carrier transport. Interestingly, two distinct regions are seen over the Arrhenius plot. This phenomenon has been explained by the structural phase change of hexagonal barium titanate at around 138 K, reflected in the large threshold voltage shift with temperature. Furthermore, we have calculated the activation energies for the temperature ranging from 150 K to 300 K and obtained the value of 9.47 meV, which reduces to 3.44 meV for the temperature ranging from 25 K to 125 K. Such observation has been explained in terms of different charge transport mechanism at the grain boundaries.