HfO 2 -based unconventional ferroelectric materials were recently discovered and have attracted a great deal of attention in both academia and industry. The growth of epitaxial Si-doped HfO 2 films has opened up a route to understand the mechanism of ferroelectricity. Here, we used pulsed laser deposition to grow epitaxial Si-doped HfO 2 films in different orientations of N-type SrTiO 3 substrates. Polar nanodomains can be written and read using piezoforce microscopy, and these domains are reversibly switched with a phase change of 180°. Films with different thicknesses displayed a coercive field E c and a remnant polarization P r of approximately 4−5 MV/ cm and 8−32 μC/cm 2 , respectively. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) results identified that the as-grown Si-doped HfO 2 films have strained fluorite structures. The ABAB stacking mode of the Hf atomic grid observed by HRTEM clearly demonstrates that the ferroelectricity originates from the noncentrosymmetric Pca2 1 polar structure. Combined with soft X-ray absorption spectra, the results showed that the Pca2 1 ferroelectric crystal structure manifested as an O sublattice distortion by the effect of the interface strain and Si dopant interactions, resulting in a nanoscaled ferroelectric ordered state because of further crystal splitting.

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Films also displayed high transmission greater than 95 % in some cases, in the 400 -800 nm wavelength range. The low temperature photoluminescence spectra of all the ZnO and AZO films showed intense near band edge emission. A considerable spread from semi-insulating to ntype conductive was observed for the films, with resistivity ~10 3 Ω cm and Hall mobility in 4 -14 cm 2 /V-s range, showing marked dependences on film thickness and oxygen pressure.Applications in the fields of microfluidic devices and flexible electronics for these ZnO and AZO films are suggested.3

We have used pulsed-laser deposition, following a specific sequence of heating and cooling phases, to grow ZnO nanorods on ZnO buffer/Si (100) substrates, in a 600 mT oxygen ambient, without catalyst. In these conditions, the nanorods preferentially self-organize in the form of vertically aligned, core/shell structures. X-ray diffraction analyses, obtained from 2θ-ω and pole figure scans, shows a crystalline (wurtzite) ZnO deposit with uniform c-axis orientation normal to the substrate. Field emission SEM, TEM, HR-TEM and selective area electron diffraction (SAED) studies revealed that the nanorods have a crystalline core and an amorphous shell. The low-temperature (13 K) photoluminescence featured a strong I 6 (3.36 eV) line emission, structured green band emission and a hitherto unreported broad emission at 3.331 eV. Further studies on the 3.331 eV band showed the involvement of deeply-bound excitonic constituents in a single electron-hole recombination. The body of structural data suggests that the 3.331 eV emission can be linked to the range of defects associated with the unique crystalline ZnO/amorphous ZnO core/shell structure of the nanorods. The relevance of the work is discussed in the context of the current production methods of core/shell nanorods and their domains of application.