Crystal-to-crystal phase transition in α-quaterthiophene:: An optical and structural study

At 191 degrees C the organic semiconductor alpha-quaterthiophene is demonstrated to undergo a phase transition from the low temperature to the high temperature polymorph. Calorimetry, x-ray diffraction, optical reflectivity, and ellipsometry measurements were employed to analyze this transition and to show that this can be thermally induced on single crystals preserving the single crystalline nature of the sample over large domains. (c) 2007 American Institute of Physics.