Effect of amide bond in gate dielectric polymers on memory performance of organic field-effect transistors

We demonstrated organic field-effect transistors (OFETs) using nylon 11, poly(gamma-methyl-L-glutamate) (PMLG), and poly(epsilon-benzyloxycarbonyl-Llysine) [Plys(z)]as gate dielectrics. By a Fourier-transform IR (FT-IR) measurement, the secondary structure of nylon 11 was determined to be a beta-sheet, and those of PMLG and Plys(z) have an alpha-helix. The orientation of the alpha-helix of PMLG and Plys(z) and its crystallinity were determined by FT-IR and X-ray diffraction (XRD) measurements, respectively. The OFET using nylon 11 showed no hysteresis in the transfer characteristic (on/off ratio is 1.2). In contrast, OFETs using PMLG and PLys(z) showed hysteresis and it operated as ferroelectric memories (on/off ratios are 2.2 x 10(4) and 53, respectively). This difference is attributed to the difference in the secondary structure and the crystal system. The memory retention property in OFETs using PMLG and PLys(z) suggested that high crystallinity of the film and highly ordered dipoles are not necessary for the memory retention. (C) 2014 The Japan Society of Applied Physics