View Generic Document: Correlating HMDS (hexamethyldisilazane) Modified Silica Substrate Surface Characteristics to Thin Film Morphology of Poly(3-hexylthiophene)
Fisher, Nathan (2005). Correlating HMDS (hexamethyldisilazane) Modified Silica Substrate Surface Characteristics to Thin Film Morphology of Poly(3-hexylthiophene). National Institute of Standards and Technology, Technology Administration, U.S. Department of Commerce..
Poly(3-hexylthiophene), also P3HT, a promising organic semiconductor, is known to have a self-ordering, semi-crystalline structure, which results in high field-effect mobilities in
thin film transistor applications. A correlation between the surface characteristics of the substrate and thin film morphology was explored. Oxidized silicon wafers were chemically grafted with
1,1,1,3,3,3-Hexamethyldisilazane to provide substrates with a wide range of hydrophobicity quantified by contact angle analysis with DI water. Controlling the kinetics of the grafting process
proved difficult because of short reaction times. To control the hydrophobicity of the substrate, a near fully grafted surface (hydrophobic) was exposed to UV-generated ozone to destroy the
hydrophobic methyl groups. The exposure time to ozone and the water contact angle of the substrate followed a linear trend. Chloroform and Chlorobenzene were used as solvents for regioregular P3HT.
The polymer was deposited on the surface energy-controlled substrates by spin-coating. Atomic Force Microscopy, confirmed by X-ray reflectivity, was used to measure the surface roughness of the
thin films, which proved to be quite constant and independent of the degree of hydrophobicity of the substrate. Both solvents were unable to wet extremely hydrophobic substrates. Annealing was used
to study direct interactions between the surface of the substrate and the polymer. The surface energy-controlled surfaces were employed in follow-up experiments utilizing the alternative deposition
techniques of dip-coating and drop-casting, which are expected to be more greatly surface energy directed than spin-coating.
National Institute of Standards and Technology, Technology Administration, U.S. Department of Commerce.