Indication of formation of charge density waves in silver nanoparticles dispersed poly(methyl methacrylate) thin films

Silver nanoparticles of various sizes have been prepared through the chemical synthesis and dispersed into poly(methyl methacrylate) (PMMA) matrix resulting in solution cast nanocomposite thin films. For characterization of the films, UV–vis absorption spectroscopy and FESEM were used. Observed blue shift of the surface plasmon absorption band position of the nanocomposite films is an indication of gradually smaller size of the silver nanoparticles that have been dispersed into the PMMA matrix. Dark current (I_d) vs. time profiles and the fluctuations in current–voltage characteristics for the PMMA films with dispersed silver nanoparticles were found to depend on the position of surface plasmon absorption band. Results of electrical studies have been found to be temperature- and voltage-dependent manifesting nonlinear nature of the I_d which may be an indication of formation of charge density waves in the silver nanoparticles–PMMA nanocomposite films. The increase in the standard deviation in I_d (calculated from the I_d vs. time profiles) for the silver nanoparticles–PMMA nanocomposite films may be due to the increase in the plasmon oscillations. Thermal hysteresis has been observed in the PMMA films and in the silver nanoparticles–PMMA nanocomposite films. Results on the observed electrical properties have been discussed in the light of interaction of silver nanoparticles with PMMA matrix, structural reorientation of PMMA, role of electric field in the manipulation of silver nanoparticles in the polymer matrix etc.