title: Nonaqueous sol-gel chemistry applied to atomic layer deposition: tuning of photonic band gap properties of silica opals.
abstract: Combining both electromagnetic simulations and experiments, it is shown that the photonic pseudo band gap (PPBG) exhibited by a silica opal can be fully controlled by Atomic Layer Deposition (ALD) of titania into the pores of the silica spheres constituting the opal. Different types of opals were assembled by the Langmuir-Blodgett technique: homogeneous closed packed structures set up of, respectively, 260 and 285 nm silica spheres, as well as opal heterostructures consisting of a monolayer of 430 nm silica spheres embedded within 10 layers of 280 nm silica spheres. For the stepwise infiltration of the opals with titania, titanium isopropoxide and acetic acid were used as metal and oxygen sources, in accordance with a recently published non-aqueous approach to ALD. A shift of the direct PPBG, its disappearance, and the subsequent appearance and shifting of the inverse PPBG are observed as the opal is progressively filled. The close agreement between simulated and experimental results is striking, and promising in terms of predicting the properties of advanced photonic materials. Moreover, this work demonstrates that the ALD process is rather robust and can be applied to the coating of complex nanostructures.
authors.affiliation: Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Catherine
authors.initials: C
authors.lastname: Marichy
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Dechézelles
authors.forename: Marc-Georg
authors.initials: MG
authors.lastname: Willinger
authors.forename: Nicola
authors.initials: N
authors.lastname: Pinna
authors.forename: Serge
authors.initials: S
authors.lastname: Ravaine
authors.forename: Renaud
authors.initials: R
authors.lastname: Vallée
mesh_terms: D005782:Gels / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D012822:Silicon Dioxide / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry
chemical_list: D005782:Gels; C009495:titanium dioxide; D012822:Silicon Dioxide; D014025:Titanium