2 research outputs found
<i>In Situ</i> Determination of the Pore Opening Point during Wet-Chemical Etching of the Barrier Layer of Porous Anodic Aluminum Oxide: Nonuniform Impurity Distribution in Anodic Oxide
Wet-chemical etching of the barrier
oxide layer of anodic aluminum oxide (AAO) was systematically investigated
by using scanning electron microscopy (SEM), secondary ion mass spectrometry
(SIMS), and a newly devised experimental setup that allows accurate <i>in situ</i> determination of the pore opening point during chemical
etching of the barrier oxide layer. We found that opening of the barrier
oxide layer by wet-chemical etching can be significantly influenced
by anodization time (<i>t</i><sub>anodi</sub>). According
to secondary ion mass spectrometry (SIMS) analysis, porous anodic
aluminum oxide (AAO) samples formed by long-term anodization contained
a lower level of anionic impurity in the barrier oxide layer compared
to the short-term anodized one and consequently exhibited retarded
opening of the barrier oxide layer during the wet-chemical etching.
The observed compositional dependence on the anodization time (<i>t</i><sub>anodi</sub>) in the barrier oxide layer is attributed
to the progressive decrease of the electrolyte concentration upon
anodization. The etching rate of the outer pore wall at the bottom
part is lower than that of the one at the top part due to the lower
level of impurity content in that region. This indicates that a concentration
gradient of anionic impurity in the outer pore wall oxide may be established
along both the vertical and radial directions of cylindrical pores.
Apart from the effect of electrolyte concentration on the chemical
composition of the barrier oxide layer, significantly decreased current
density arising from the lowered concentration of electrolyte during
the long-term anodization (∼120 h) was found to cause disordering
of pores. The results of the present work are expected to provide
viable information not only for practical applications of nanoporous
AAO in nanotechnology but also for thorough understanding of the self-organized
formation of oxide nanopores during anodization
First-Order Reversal Curve Probing of Spatially Resolved Polarization Switching Dynamics in Ferroelectric Nanocapacitors
Spatially resolved polarization switching in ferroelectric nanocapacitors was studied on the sub-25 nm scale using the first-order reversal curve (FORC) method. The chosen capacitor geometry allows both high-veracity observation of the domain structure and mapping of polarization switching in a uniform field, synergistically combining microstructural observations and probing of uniform-field polarization responses as relevant to device operation. A classical Kolmogorov–Avrami–Ishibashi model has been adapted to the voltage domain, and the individual switching dynamics of the FORC response curves are well approximated by the adapted model. The comparison with microstructures suggests a strong spatial variability of the switching dynamics inside the nanocapacitors