Highly ordered self-assembled mesostructured hafnia thin films: An example of rewritable mesostructure

Self-assembly of supramolecular templates is a fascinating route that mimics natural processes to obtain porous organized materials. We have synthesized hafnia mesostructured films with a high degree of order, and the structure has been indexed as rhombohedral (R3̄m space group). The films have been revealed to be particularly interesting in their tunable state, immediately after solvent evaporation. We were able to modulate self-assembly under different conditions by changing the relative humidity in the deposition room and the intensity of the incident X-ray on the as-deposited film. The material has been shown to respond quickly and reversibly to changes in humidity in the deposition room, and the highly tunable state of hafnia films, before drying, has been used to "write" the structure through a high flux X-ray beam. The X-ray controlled reorganization path differs from those that have been traditionally observed because self-assembly can be achieved even in the absence of evaporation. Self-ordering, in this case, can be explained as an entropy-driven process, a general principle that is typical of biological systems.