Porous silicon, obtained by electrochemical etching, has been used as a substrate for the growth of nanoperforated Nb thin films. The films, deposited by UHV magnetron sputtering on the porous Si substrates, inherited their structure made of holes of 5 or 10 nm diameter and of 10 to 40 nm spacing, which provide an artificial pinning structure. The superconducting properties were investigated by transport measurements performed in the presence of magnetic field for different film thickness and substrates with different interpore spacing. Perpendicular upper critical fields measurements present peculiar features such as a change in the H c2⊥ (T ) curvature and oscillations in the field dependence of the superconducting resistive transition width at H ≈ 1 Tesla. This field value is much higher than typical matching fields in perforated superconductors, as a consequence of the small interpore distance.
Luminescent Er-doped Al2O3 films have been fabricated at room temperature by a technique including magnetron deposition of Er-doped Al film on a silicon substrate and its subsequent electrochemical anodization. The films demonstrate strong Er-related photoluminescence at about 1.53 μm as recorded in the temperature range of 4.2–300 K. The effect is not influenced by annealing of the samples up to 200 °C. Upon annealing at 300–500 °C the luminescence intensity decreases, while above 600 °C it starts to recover. Annealing at 1000 °C restores the photoluminescence spectra to the initial level. The annealing peculiarities observed have been explained by dominant hydrogen outdiffusion at 300–500 °C, rearrangement of point defects at 600–800 °C, and recrystallization processes above 850 °C in the alumina film. Activation energies of these processes have been estimated to be 0.76 eV (for parabolic rate), 0.58 eV (for linear rate), and 0.46 eV (for linear rate), respectively.
Planarity and control of the configuration of the cross-sectional area are important parameters to be considered for high density VLSI devices. The anodization process seems best to fulfill such conditions, but anisotropy (i.e., difference in vertical and lateral anodization rates), must be increased to obtain a competitive technique. In this work factors affecting the anisotropy of the aluminum anodization process were investigated. By varying the electrochemical process parameters, a degree of anisotropy of about 0.6 was obtained. The dimensions of the aluminum porous oxide were determined by scanning electron microscopy. At high forming voltages, the electric field across the barrier layer of the porous oxide cells were calculated and plotted.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.