Recently, geometry-induced quantum effects in periodic nanostructures were introduced and observed. Nanograting has been shown to dramatically improve thermoelectric and electron emission properties, and originate a geometry induced doping or G-doping. Here, we concentrate on experimental investigation of G-doping. We fabricate nanograting (NG) layers and measure their electron transport properties. The grating was fabricated on the surface of a silicon on insulator (SOI) wafer device layer using laser interference lithography followed by reactive ion etching. Next, large square islands were shaped in the device layer.The characteristics of NG and plain islands were compared to investigate G-doping. Resistivity temperature dependences were recorded in the range of 4-300 K. For all 21 samples, the NG layers show a 2-3 order of magnitude reduction in resistivity with respect to the plain layer. Hall coefficient and thermopower measurements demonstrate that the NG layers are n-type. Obtained G-doping level corresponded to an "effective impurity" concentration of 10 18 cm À3 . The dependence of the resistivity and Hall coefficient on temperature and magnetic field were recorded in the ranges of 2-300 K and 0-3 T, respectively.

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In this study, we electroplate Cu electrode on Si substrate to realize a large-area vacuum nanogap for electron tunneling. We used cathode coating, cathode rotation, asymmetric current regime, and electrolyte temperature stabilization to obtain the regular geometry of the Cu electrode and reduce its internal tension. Subsequently, internal tension was altered to achieve the predefined surface curvature (concave or convex). For 12-mm diameter Ag/Cu electrode, we achieve the curvature of 40 nm/mm from the Ag side. Reduction of the electrode diameter to 3 mm allowed curvature as low as of 2.5 nm/mm. It also allowed fabrication of two conformal electrodes having a nanogap of less than 5 nm wide, over the area of 7 mm 2 . Such electrodes can be used for efficient energy conversion and cooling in the mixed thermionic and thermotunneling regime.

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