Control of polarity in multilayer MoTe field-effect transistors by channel thickness.

In this study, electronic properties of field-effect transistors (FETs) fabricated from exfoliated MoTe single crystals are investigated as a function of channel thickness. The conductivity type in FETs gradually changes from n-type for thick MoTe layers (above ≈ 65 nm) to ambipolar behavior for intermediate MoTe thickness (between ≈ 60 and 15 nm) to p- type for thin layers (below ≈ 10 nm). The n-type behavior in quasi-bulk MoTe is attributed to doping with chlorine atoms from the TeCl transport agent used for the chemical vapor transport (CVT) growth of MoTe.

Faster-than-anticipated Na(+)/Cl(-) diffusion across lipid bilayers in vesicles.

Maintenance of electrochemical potential gradients across lipid membranes is critical for signal transduction and energy generation in biological systems. However, because ions with widely varying membrane permeabilities all contribute to the electrostatic potential, it can be difficult to measure the influence of diffusion of a single ion type across the bilayer. To understand the electrodiffusion of H(+) across lipid bilayers, we used a pH-sensitive fluorophore to monitor the lumenal pH in vesicles after a stepwise change in the bulk pH.

Nanopore-spanning lipid bilayers on silicon nitride membranes that seal and selectively transport ions.

We report the formation of POPC lipid bilayers that span 130 nm pores in a freestanding silicon nitride film supported on a silicon substrate. These solvent-free lipid membranes self-assemble on organosilane-treated Si3N4 via the fusion of 200 nm unilamellar vesicles. Membrane fluidity is verified by fluorescence recovery after photobleaching (FRAP), and membrane resistance in excess of 1 GΩ is demonstrated using electrical impedance spectroscopy (EIS).