Nanolaminates consisting of Al2O3 and TiO2 oxide sublayers were synthesized by using atomic layer deposition to produce individual layers with atomic scale thickness control. The sublayer thicknesses were kept constant for each multilayer structure, and were changed from 50 to 0.2 nm for a series of different samples. Giant dielectric constant (∼1000) was observed when the sublayer thickness is less than 0.5 nm, which is significantly larger than that of Al2O3 and TiO2 dielectrics. Detailed investigation revealed that the observed giant dielectric constant is originated from the Maxwell–Wagner type dielectric relaxation.

Dielectric materials exhibiting high dielectric constants play critical roles in a wide range of applications from microchip energy storage embedded capacitors for implantable biomedical devices to energy storage capacitors for a new generation of renewable energy generation/storage systems. Instead of searching for new materials, we demonstrate that giant dielectric constants can be achieved by integrating two simple oxides with low dielectric constants into nanolaminate structures. In addition, the obtained dielectric constant values are highly tunable by manipulating the sub-layer thicknesses of the component oxides to control the number of interfaces and oxygen redistribution. The work reported here opens a new pathway for the design and development of high dielectric constant materials based on the nanolaminate concept.

A high speed variation of Scanning Probe Microscopy with continuous image rates on the order of 1 frame per second is applied to investigate the nucleation and growth of individual ferroelectric domains. Movies of consecutive images directly identify nascent domains and their nucleation times, while tracking their development with time and voltage reveals linear domain growth at lateral velocities near 1 mm/s, even faster for nascent domains. Nanoscale maps of nucleation times and growth velocities indicate that domain nucleation and growth are uncorrelated, varying extensively with position. Domain switching dynamics do strongly couple to film defects; for instance, grain boundaries can profoundly pin domain walls, and polarization reversal kinetics are influenced by strain fields near microcracks or in asymmetric specimens. The influence of the onset of switching fatigue is observed as well. These results highlight the importance of updating classical interpretations of ferroelectric switching for truly rigorous models of polarization dynamics. Coupling high speed SPM imaging with in situ activation by voltage or other parameters therefore provides an important methodology to research dynamic surface properties with nanoscale resolution, extendable to a range of materials such as photovoltaics,

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We report an elastic relaxation and increase in local strain variation correlated with ferroelectric domains within epitaxial BiFeO 3 thin film nanostructures fabricated by combined electron-beam and focused ion-beam nanolithography. Nano-focused x-ray diffraction microscopy provided new insights into the relationship between film strain and ferroelectric domains in nanostructures, namely: (i) an out-of-plane (C-axis) elastic relaxation of as much as À1.8% Dc/c in a BFO film-based nanostructure relative to the planar film lattice constant; (ii) an out-of-plane rotation trending from the center towards all released edges of the nanostructure; and (iii) an increase of inter-domain strain variation within the nanostructure of approximately 10 times the inter-domain variation found within the planar film, correlated with ferroelectric domain boundaries as confirmed by piezoresponse-force microscopy. These results indicate that the release of in-plane BFO/SRO mismatch strain in a planar film is taken up by the local ferroelectric domain structure after patterning, resulting in greatly increased mechanical strain gradients within the structure.

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