Electric field induced structural change for poly(vinylidene fluoride-co-trifluoroethylene) ultrathin films studied by scanning Maxwell stress microscope

Poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF/TrFE), VDF 75 mol %] ultrathin films of 10 nm thickness were prepared on gold coated silicon wafer substrates by a spin-coating method and their aggregation states were investigated by Fourier transform infrared reflection absorption spectroscopic measurement. It was found that P(VDF/TrFE) formed a ferroelectric phase even in a confined state such as an ultrathin film. The electric field was locally imposed on the ultrathin film through a gold coated cantilever tip. The change of dipole moment orientation of P(VDF/TrFE) was evaluated by measuring surface potential change, performed by scanning Maxwell stress microscopy (SMM). The SMM images revealed that the local dipole moment orientation of P(VDF/TrFE) in ultrathin films could be changed by an application of electric field through an atomic force microscope tip.