4D-STEM Determination of Atomic Structure of Amorphous Materials for Renewable Energy Applications

Hydrogen production using photoelectrochemical (PEC) water splitting is a promising method to sustain a renewable energy source In a PEC a photoelectrode, such as a nanostructured solar energy generates charge carriers to hydrogen reduction It has been found that ultrathin amorphous TiO 2 (a-TiO 2 ) films grown by atomic layer deposition (ALD) on Si photoanode can protect Si from corrosion as well as providing proper charge conductivity Moreover, it has been hypothesized that local nanoscale atomic ordering in a-TiO 2 plays a key role in determining the film properties. In this work, we present the fluctuation electron microscopy (FEM) and angular correlation (AC) analyses of nano-diffraction patterns acquired via four-dimensional scanning transmission electron microscopy (4D-STEM) that provide information about the type and symmetry of medium range orderings (MRO) in a-TiO 2 . The experimental results are then used as an input to the StructOpt optimization [4] to determine the possible structures of MRO that may be critical to film properties. nano-diffraction