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

Abstract

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.