Studies of bonding defects, and defect state suppression in HfO2 by soft X-ray absorption and photoelectron spectroscopies

This paper identifies two-different regimes of nano-crystallinity: (i) thin films with nano-crystallites >3 nm, that display coherent well-defined grain-boundaries, and (ii) thin films with nano-crystallites less than ∼2 nm, that display neither will-defined grain-boundaries nor lattice planes in high resolution transmission electron microscopy images, but yield an image indicative of clusters of small nano-crystallites with a length scale order of ∼2 nm. Near edge X-ray absorption spectroscopy, and soft-X-ray photoelectron spectroscopy, combined with visible and UV spectroscopic ellipsometry, provide an unambiguous way to distinguish between these two technologically important regimes of nano-crystalline order, yielding significant information on electronic structure of intrinsic band edge states and intrinsic electronically-active defects.