A nanoindentation technique has been applied to demonstrate the mechanical actuation of thin films fabricated by glancing angle deposition. The films were comprised of a porous layer whose microstructures consisted of helical columns that resembled springs. Surmounting the porous layer was a dense capping layer which served to redistribute the force of the nanoindenter tip and prevent it from penetrating the microstructured film. Atomic force microscope images and force versus displacement curves confirmed that there was an elastic regime to the displacements in the films when low forces were applied. The loading behavior of the porous films was compared with that of dense, unstructured films and revealed a marked difference between the two. A study of the measurements and results enabled such properties as the spring constant and resonant frequencies to be estimated, establishing a basis for future developments and applications in wave-type devices or resonators constructed from these microstructured thin films.
Environmentally benign lead-free ferroelectric (K0.5,Na0.5)(Mn0.005,Nb0.995)O3 (KNMN) thin film capacitors with a small concentration of a BiFeO3 (BF) dopant were prepared by a cost effective chemical solution deposition method for high energy density storage device applications. 6 mol. % BF-doped KNMN thin films showed very slim hysteresis loops with high maximum and near-zero remanent polarization values due to a phase transition from the orthorhombic structure to the pseudo-cubic structure. Increasing the electric field up to 2 MV/cm, the total energy storage density (Jtotal), the effective recoverable energy density (Jeff), and the energy conversion efficiency (η) of lead-free KNMN-BF thin film capacitors were 31.0 J/cm3, 28.0 J/cm3, and 90.3%, respectively. In addition, these thin film capacitors exhibited a fast discharge time of a few μs and a high temperature stability up to 200 °C, proving their strong potential for high energy density storage and conversion applications.
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