Transformation of (BEDT-TTF)2I3 networks in polymer films into superconducting βt phase as studied by resonant Raman spectroscopy

Reticulate doped polymer composites containing polyiodide of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) in polycarbonate (PC) films were investigated by resonant Raman spectroscopy (RRS). We found that RRS spectra of non-annealed composites are similar to the spectra of single crystals of the α-ET2I3 phase but show also an unexpected additional band at 108 cm−1 due to vibration of the I3Poststeggerd− molecule. The RRS spectra of annealed composites are nearly identical to the spectrum of single crystals of the βt-ET2I3 phase. The reproducibility of the RRS spectra taken at different spots on the surface of the composites is very good. Raman microscopy indicated that the surface of the composites is homogeneous.