We investigate a wafer scale tunnel junction fabrication method, where a plasma etched via through a dielectric layer covering bottom Al electrode defines the tunnel junction area. The ex-situ tunnel barrier is formed by oxidation of the bottom elect
rode in the junction area. Room temperature resistance mapping over a 150 mm wafer give local deviation values of the tunnel junction resistance that fall below 7.5 % with an average of 1.3 %. The deviation is further investigated by sub-1 K measurements of a device, which has one tunnel junction connected to four arrays consisting of N junctions (N = 41, junction diameter 700 nm). The differential conductance is measured in single-junction and array Coulomb blockade thermometer operation modes. By fitting the experimental data to the theoretical models we found an upper limit for the local tunnel junction resistance deviation of ~5 % for the array of 2N+1 junctions. This value is of the same order as the minimum detectable deviation defined by the accuracy of our experimental setup.
The authors describe how acoustic phonons can directly tunnel through vacuum and, therefore, transmit energy and conduct heat between bodies that are separated by a vacuum gap. This effect is enabled by introducing a coupling mechanism, such as piezo
electricity, that strongly couples electric field and lattice deformation. The electric field leaks into the vacuum as an evanescent field, which leads to finite solid-vacuum-solid transmission probability. Due to strong resonances in the system some phonons can go through the vacuum gap with (or close to) unity transmission, which leads to significant thermal conductance and heat flux.
We investigate carrier transport in a single 22 nm-thick double-gated Si quantum well device, which has independent contacts to electrons and holes. Conductance, Hall density and Hall mobility are mapped in a broad double-gate voltage window. When th
e gate voltage asymmetry is not too large only either electrons or holes occupy the Si well and the Hall mobility shows the fingerprints of volume inversion/accumulation. At strongly asymmetric double-gate voltage an electric field induced electron-hole (EH) bi-layer is formed inside the well. The EH drag resistance R_{he} is explored at balanced carrier densities: R_{he} decreases monotonically from 860 to 37 Ohms when the electron and hole density is varied between ~0.4-1.7x10^{16} m^{-2}.
