Growth of pseudomorphic structures through organic epitaxy

• Published in: The Journal of chemical physics 2012-12, Vol.137 (22), p.224703-224703
• Main Authors: Kaviyil, Sreejith Embekkat, Campione, Marcello, Sassella, Adele, Su, Genbo, He, Youping, Chen, Chenjia, Borghesi, Alessandro
• Format: Article
• Language: English
• Subjects: CARRIER MOBILITY; CHARGE CARRIERS; COMPARATIVE EVALUATIONS; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTALS; FABRICATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LAYERS; MATERIALS SCIENCE; MOLECULAR BEAM EPITAXY; OPTICAL PROPERTIES; ORGANIC SEMICONDUCTORS; ORIENTATION; SURFACES; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; ULTRAVIOLET SPECTRA
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.4770001

The control of molecular orientation in thin solid film phases of organic semiconductors is a basic factor for the exploitation of their physical properties for optoelectronic devices. We compare structural and optical properties of thin films of the organic semiconductor α-quarterthiophene grown by molecular beam epitaxy on different organic substrates. We show how epitactic interactions, characteristic of the surface of organic crystals, can drive the orientation of the crystalline overlayer and the selection of specific polymorphs and new pseudomorphic phases. We identify a key role in this phenomenon played by the marked groove-like corrugations present in some organic crystal surfaces. Since different polymorphs possess rather different performance in terms of, e.g., charge carrier mobility, this strategy is demonstrated to allow for the growth of oriented phases with enhanced physical properties, while keeping the substrate at room temperature. These results provide useful guidelines for the design of technological substrates for organic epitaxy and they substantiate the adoption of an organic epitaxy approach for the fabrication of optoelectronic devices based on thin films of organic semiconductors.