Transport Measurements of Surface Electrons in 200 nm Deep Helium-Filled Microchannels Above Amorphous Metallic Electrodes

Abstract

We report transport measurements of electrons on helium in a microchannel device where the channels are 200 nm deep and 3 $\mu$m wide. The channels are fabricated above amorphous metallic Ta${}_{40}$W${}_{40}$Si${}_{20}$, which has surface roughness below 1 nm and minimal variations in work function across the surface due to the absence of polycrystalline grains. We are able to set the electron density in the channels using a ground plane. We estimate a mobility of 300 cm${}^2$/V$\cdot$s and electron densities as high as 2.56$\times$10${}^9$ cm${}^{-2}$. We demonstrate control of the transport using a barrier which enables pinchoff at a central microchannel connecting two reservoirs. The conductance through the central microchannel is measured to be 10 nS for an electron density of 1.58$\times$10${}^9$ cm${}^{-2}$. Our work extends transport measurements of surface electrons to thin helium films in microchannel devices above metallic substrates.

4 pages, 4 figures