The assembly of nanoscale building blocks in engineered mesostructures is one of the fundamental goals of nanotechnology. Among the various processes developed to date, self-assembly emerges as one of the most promising, since it relays solely on basic physico-chemical forces. Our research is focused on a new type of self-assembly strategy from the gas-phase: Scattered Ballistic Deposition (SBD). SBD arises from the interaction of a supersonic molecular beam with a static gas and enables the growth of quasi-1D hierarchical mesostructures. Overall, they resemble a forest composed of individual, high aspect-ratio, tree-like structures, assembled from amorphous or crystalline nanoparticles. SBD is a general occurring phenomenon and can be obtained with different vapour or cluster sources. In particular, SBD by Pulsed Laser Deposition is a convenient physical vapor technique that allows the generation of supersonic plasma jets from any inorganic material irrespective of melting temperature, preserving even the most complex stoichiometries. One of the advantages of PLD over other vapour deposition techniques is extremely wide operational pressure range, from UHV to ambient pressure. These characteristics allowed us to develop quasi-1D hierarchical nanostructures from different transition metal oxides, semiconductors and metals. The precise control offered by the SBD-PLD technique over material properties at the nanoscale allowed us to fabricate ultra-thin, high efficiency hierarchical porous photonic crystals with Bragg reflectivity up to 85%.
In this communication we will discuss the application of these materials to solar energy harvesting and storage, stimuli responsive photonic crystals and smart surfaces with digital control of their wettability behaviour.
We report the realization and characterization of porous nanostructures where a periodic refractive index modulation is
achieved by stacking layers with different nano-architectures. One multilayer photonic crystal has been fabricated
starting from colloidal dispersion of silicon dioxide and zirconium dioxide using spin coating technique. Improved
efficiency of Bragg reflectivity (up to 85%) has been obtained by a new bottom-up fabrication technique of photonic
hierarchical nanostructures based on self-assembly from the gas-phase at low temperature whit a very thin (≈ 1 μm)
photonic crystal devices. Due to the high porosity, these systems can be infiltrated with nematic liquid crystals leading to
tuning of the Bragg reflection band by applying low voltages to the structure.