(a) Scanning electron microscope image and EBSD orientation map of an -type silicon wafer. The scanned area crosses the interface between the etched (porous) and unetched (nonporous) part of the silicon wafer. The thick solid lines in the blue area indicate the boundaries between different regions. The color uniformity in the orientation map (blue area) reveals that all of the crystalline components in this region have the same orientation. From the color key (b), it emerges that the crystal orientation of the analyzed area has the  direction parallel to the wafer normal direction, as schematically shown in (c).
(a) FESEM image of the top of Si20 substrate covered with a conductive Pd/Au layer, 8 nm thick. Histogram of the pore diameter (b) and pore spacing (c) distributions.
Low resolution FESEM image of the edge of the Si20 substrate.
FESEM image of a Nb film 9 nm thick deposited on the PS Si20.
Normalized transition curves of Nb thin films of different thickness grown on the same porous Si10 substrate, namely samples Si10-Nb8.5 and Si10-Nb12. For comparison, the resistive transitions of nonporous reference Nb films of the same thickness are shown. Also, the curve is presented for the sample Si40-Nb8.5. is the resistance value at .
Perpendicular upper critical field vs temperature of nonporous reference Nb films with (circles) and (squares). The solid lines represent the linear fit to the data.
(a) Superconducting phase diagram of Nb thin films of different thickness grown on the porous Si10 substrate, namely samples Si10-Nb8.5 and Si10-Nb12. The linear fits of the data of the samples Si10-Nb8.5 and Si10-Nb12 are shown in figure, near for the sample Si10-Nb8.5 and on whole temperature range for the second one. (b) dependence of two samples of different thickness grown on the porous Si20 template, namely samples Si20-Nb12 and Si20-Nb15. The linear fits of the data of the samples Si20-Nb12 and Si20-Nb15, near are shown in figure. The inset shows the comparison among two samples of the same thickness, grown on the porous template Si20 and on the nonporous template.
(a) Left scale: superconducting phase diagram of the sample Si40-Nb10. Right scale: vs temperature is presented. The inset shows resistive transitions of the same sample, measured for different values of the magnetic fields, from 0 to 2 T. (b) Left scale: phase diagram of the sample Si40-Nb12. The solid line represents the linear fit to the data near . Right scale: vs temperature is shown. The inset presents the transition width, , as a function of the field. The first matching field is indicated.
Characteristics of porous Si templates and properties of Nb thin films deposited on such substrates. indicates the interpore spacing, is the pore diameter, is the Nb thickness, and is the critical temperature of the samples. The interpore spacing and the pore diameter are and , respectively, for -type silicon wafers, and up to 40 nm and for -type silicon wafers.
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