Tunable optical properties of hybrid inorganic-organic [(TiO2)(m)(Ti-O-C6H4-O-)(k)](n) superlattice thin films

A combined atomic layer deposition (ALD) and molecular layer deposition (MLD) process was developed to fabricate inorganic-organic [(TiO2)(m)(Ti-O-C6H4-O-)(k)](n) thin films from TiCl4, water and hydroquinone (HQ) precursors, and in particular, superlattice structures where single-molecular organic layers (k = 1) are periodically sandwiched between thicker TiO2 layers (m > 1). The incorporation of organic layers was found to systematically blue-shift the optical band gap of TiO2 with decreasing superlattice period and - most importantly - to sensitize the TiO2 layers to visible light over a considerable part of the visible range below 700 nm, a fact that could be of substantial interest for photocatalysis and solar cell applications.