Comparisons on Different Liquid Crystals Doped with Various Sized Gold Nanoparticles for Nonvolatile Memory Effects

The demand for ever more efficient non-volatile memory deviceshas triggered intense research into new materials and novel devicearchitectures. In this context, nano-composite materials obtained bydispersing metallic nano-particles in liquid crystal materials, seemsto be particularly promising. In this work we investigated non-volatilememory effects in two different orthoconic smectic liquid crystalmixtures with and without the addition of two different kind ofpolymer capped gold nanoparticles by means of broadband dielectricspectroscopy, which is a powerful method to study molecular dynamicsand molecular mobility of various materials reflected in the relaxationprocesses over a wide frequency range. The dielectric measurementshave been performed by applying bias during spectra aquisition or byapplying the condition potential before the start of spectra aquisition,in order to confirm how the electric field induces charge transferfrom the liquid crystal molecules to the polymeric capping of the goldnanoparticles acting as a trap for ionic charges. The results underlinethe importance of the structure of the host liquid crystal, the size ofthe nanoparticles but, above all, the kind of the polymer coating onthe gold nanoparticles. The observed memory effect is of paramountimportance in development of digital nonvolatile memory devices.