Three-step molecular beam deposition of crystalline polydiacetylene films on semiconductor substrates with large crystal domains

We have developed a three-step molecular beam deposition method to obtain c rystalline polymer films directly on semiconductor substrates. This is exem plified by alkyluretane-substituted polydiacetylene (PDA-4U4) films compose d of lateral crystal domains of one hundred square microns or larger on GaA s(100) substrates. Polarization dependence of Raman scattering confirms eac h domain is formed by well-aligned crystalline polymers. The blue-to-red th ermochromic phase transition occurs at around 70 degrees C, which is lower than that reported for the PDA-4U4 bulk crystal (T-c = 125 degrees C).