Effect of organic electroactive crystallites in a dielectric matrix on the electrical properties of a polymer dielectric

The effects of inserting chargeable α-quaterthiophene (α4T) crystallites in polystyrene (PS) multilayers used as a transistor gate and capacitor dielectric were investigated. X-ray diffraction, scanning electron microscopy with energy-dispersive x-ray spectroscopy, and confocal microscopy indicated the formation of α4T crystallites in the PS matrix. A modified saturation-regime current-voltage relationship was used to estimate organic field-effect transistor (OFET) threshold voltage VTH shifting, and in turn the quantities of stored charge that were observed as a result of dielectric charging. The crystallites increased the maximum charge-storage capacity as well as the charge-retention capability of the dielectrics. Kelvin probe force microscopy showed that charges were localized near the α4T crystallites upon charging. Trilayer experiments validated the charge-retention improvement of α4T crystallite-embedded PS dielectrics. The crystallites also improved breakdown characteristics in PS used as a capacitor dielectric, suggesting their application to storage capacitors in addition to OFET logic.