Layer-by-Layer Self-Assembly of Large Response Molecular Electro-Optic Materials by a Desilylation Strategy (20010)
A new efficient "one-pot" synthesis of organic self-assembled superlattices having excellent electrooptic response properties. The method provides thermally and photochemically robust thin films that adhere to glass, silicon and ITO coated substrates. The technology is suited for the assembly of photonic and electronic components employed in modulators and non-linear optical (NLO) systems.
ADVANTAGES: A single reactor self-assembly process affording polar superlattices of large response molecular electrooptic materials. The direct deposition permits device/substrate integration. The technology eliminates the need for electric field poling and spin coating and is suitable for automated operation.
SUMMARY: Molecule based optical components such as electrooptic (EO) modulators promise greatly increased rates of information transfer. Organic based devices offer greater EO coefficients and lower dielectric constants than those of established inorganic materials (e.g., LiNbO3).
Of the current technologies employed to create molecular EO / second order NLO materials, self-assembly (SA) appears most amenable to simple manufacture. SA permits deposition of intrinsically polar arrays of covalently bound high hyperpolarizable (β) chromophores directly on silicon or related substrates for direct integration into EO devices. This approach also eliminates the need for electric field poling, spin coating and related equipment.
The present invention involves iterative combination of (i) polar chemisorption of high-β chromophore monolayers, (ii) selective removal of chromophore tertbutyldimethylsilyl (TBDMS) protecting groups to generate a large density of reactive hydroxyl sites and (iii) capping of each deprotected chromophore layer with octachlorotrisiloxane. The latter step deposits a thin (~ 8 Å) polysiloxane film that provides a stable conformal acentric microstructure. Repetition of the process affords a uniform multilayer superlattice. The layer-by-layer construction can be efficiently performed in a single reactor and is suited for automation.
The iterative chemisorptive SA process and resulting multilayer structural regularity have been fully characterized. The superlattices exhibit very large EO responses (χ2~220 pm/V), adhere strongly to glass, silicon, or indium tin oxide (ITO) coated substrates, and are insoluble in common organic solvents.
STATUS: The process has been implemented with a variety of high-β chromophore materials and their EO properties established. A patent has issued.
Tobin J. Marks and Milko E. van der Boom
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