Electrical Transport Properties of Polydiacetylene Films during Thermochromic Process

Using the top-contact field-effect transistor (FET) model, the electrical transport properties of polymerized 10,12-tricosadiynoic acid (PTDA) films in the blue and red phases were investigated in detail. The current–voltage ( I – V ) characteristics of the PTDA films during thermochromic transition were examined. The typical FET characteristics were observed for the PTDA films in the blue phase, but not in the red phase. To clarify carrier injection, the succeeding carrier accumulation and carrier transport from the source electrode to the drain electrode across the PTDA films, the capacitance–frequency ( C – F ) characteristics of the top-contact PTDA FETs and the surface potential built across the PTDA films on a Au electrode were also measured during thermochromic transition. An explanation based on charge trapping was presented. Atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy were used to clarify the transition of the surface morphology, molecular orientation and pendant side chain conformation of such films during thermochromic transition. The explanation based on conformation change was presented. It was interpreted in terms of molecular packing in PTDA films.