Lateral metallic devices made by a multiangle shadow evaporation technique
(Color online) Suspended mask. (a) Mask features seen from above. A contact between two materials is achieved by using a mask with a small suspended bridge. (b) Material deposition resulting from double angle evaporation through a conventional mask. (c) Material deposition using a thick mask. The features (nearly) parallel to the sample rotation axis do not project a shadow in the substrate and the evaporated material deposits on the mask lateral walls (d) and is later removed by lift-off.
(Color online) Nonsuspended mask. (a) Mask features seen from above. A contact between two materials is achieved by using a mask with a cross shape. (b) The sample rotates about an axis perpendicular to the sample plane and the evaporation directions do not form a plane perpendicular to the mask.
(Color online) Asymmetric single electron transistor. (a) Design of the suspended MMA/PMMA mask for shadow evaporation. The dashed line represents the rotation axis for shadow evaporation. (b) The device is fabricated by three sequential depositions as indicated by the arrows. Such a process results in a threefold projection of the mask.
(Color online) (a) SEM image of a finished device. The bar is 100 nm. (b) Experimental conductance dI/dV as a function of dc voltage V across the SET and gate voltage Vg in a logarithmic scale to highlight the SET subgap transport at a temperature of 25 mK and at a magnetic field B = 1.5 T, where the conditions for spin pumping/spin ratchet are fulfilled (see Ref. 15). The dI/dV amplitude is represented by a color scale from black (zero) to yellow (15 μS).
(Color online) Fabrication of a thermopile and transport characterization. (a) A partial view of the design of the shadow mask made with e-beam lithography using a PMMA/MMA bilayer on a SiO2/Si substrate. The metal deposition sequence is shown. (b) Scanning electron microscope image of a finished device. The central part of the device is formed by 20 Py wire-pairs connected at both ends with Ag wires. The dc voltage generated between the end electrodes is measured as a function of a temperature gradient created with an on-chip Pt heater (bright vertical strip) in close proximity to the Py wires. (c) MR at 295 K (top curves) and at room temperature (bottom curves). The B swept direction is from B > 0 to B < 0 (red) and from B < 0 to B > 0 (blue). The arrows indicate the parallel/antiparallel magnetization configuration of Py wires. The measurements were displaced vertically for clarity.
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