Structural aspects of TiO2 and TiO2-Al2O3 ALD nanostructures

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Benjamin Rich




Atomic Layer Deposition (ALD) has become an increasingly significant deposition method. This is due to its self-limiting growth, which enables the formation of top-quality, highly conformal, and uniform films with nanometer precision even on surfaces with complex surface topography and high aspect ratios.
We drew inspiration from biomineralization and, in particular, the utilization of amorphous precursors with controlled short-range order and their crystallization which allows control over the morphology, composition, and shape of biominerals. We applied three different ALD approaches in order to study similar aspects in synthetic amorphous thin films and amorphous-to-crystalline transformations: 1. A typical binary approach to deposit thin layers of TiO2 and study size effects on the short-range order. 2. A ternary super-cycle approach to deposit Al2O3-TiO2 nanolaminates to study supersaturation in crystalline Al2O3. 3. A ternary co-dosing technique to deposit high surface area complex nanostructures.
The samples were characterized by GIXRD, XRR, XPS, EELS, GI-XANES, HR-TEM, and HR-SEM. Size effects were shown to significantly affect the structure of the TiO2 films leading to the formation of lower destiny films. By utilizing the nanolaminate technique to disperse low-soluble dopants into an amorphous matrix and a very fast annealing treatment we were able to supersaturate crystalline Al2O3 with Ti. Lastly, we were able to create complex structures with an extremely high surface area that after coating with fluorinated self-assembled monolayers, exhibit super-omniphobic wetting characteristics.

PhD advisor: Professor Boaz Pokroy

Link to ZOOM