The Challenge: Identify precise orientation texture between ZnO substrate - sexipephenyl (6P) - ZnO deposited layer at nm scale The Solution: ASTAR technique couple with precession electron diffraction
Nanocrystalline ZnO is provided in an inorganic/organic system of ZnO deposited on sexiphenyl (6P). Initially, 6P was deposited on aplane ZnO substrate at room temperature forming mesoscopic 1-dimensional islands of 6P. In a second step, the islands were capped with ZnO via molecular beam epitaxy at 373 K. Information on the nanostructure of ZnO grown atop 6P was provided by high-resolution TEM. Imaging was performed along the [00.1] direction of the ZnO exhibits a perfect crystal structure when directly grown on the substrate. This was confirmed by Fourier transformation (FT) which also confirmed that ZnO grown atop 6P undergoes an imperfect growth. Identification of the orientation of the nanocrystals and indexing of the lattice planes only based on FT is rather ambiguous and must be handled with care.
For this reason, ASTAR was used to uncover any specifics of the overgrowth regime of ZnO on 6P at nm scale.
Optical properties of hybrid systems depend on the nm level structural properties
Flexible organic semiconductors With ASTAR scanning the electron beam in nanobeam diffraction mode (probe diameter 1 nm) across an area of 100 nm in width and 80 nm in height provides the orientation maps depicted below. The maps were derived by comparing the diffraction pattern recorded at each position with a set of about 1000 calculated diffraction patterns of hexagonal ZnO. Focussing on ZnO atop 6P, columnar grains are identified that extend even up to the surface as signified by green and red areas.