Computational design of NDR tunnel diodes with high peak-to-valley current ratio based on two-dimensional cold metals: The case of NbSi2_2N4_4/HfSi2_2N4_4/NbSi2_2N4_4 lateral heterojunction diode

Cold metals have recently gained attention as a promising platform for innovative devices, such as tunnel diodes with negative differential resistance (NDR) and field-effect transistors with subthreshold swings below the thermionic limit. Recently discovered two-dimensional (2D) MA$_2$Z$_4$ (M = Ti, Zr, Hf, Nb, Ta; A = Si, Ge; Z = N, P) compounds exhibit both cold metallic and semiconducting behavior. In this work, we present a computational study of lateral heterojunction tunnel diodes based on 2D NbSi$_2$N$_4$ and HfSi$_2$N$_4$ compounds. Employing density functional theory combined with a nonequilibrium Green function method, we investigate the current-voltage ($I$-$V$) characteristics of lateral tunnel diodes with varying barrier thicknesses in both zigzag and armchair orientations. We find that tunnel diodes in the zigzag orientation exhibit significantly higher peak current densities, while those in the armchair orientation display larger peak-to-valley current ratios (PVCRs) compared to the zigzag orientation. Our findings suggest that MA$_2$Z$_4$ materials are promising candidates for realizing NDR tunnel diodes with high PVCR values, which could have potential applications in memory, logic circuits, and other electronic devices.Comment: ver3.0 with supplemental materia

Effects of mexiletine on ATP sensitive K(+) channel of rat skeletal muscle fibres: a state dependent mechanism of action

1. The effects of mexiletine were evaluated on the ATP-sensitive K(+) channel (K(ATP)) of rat skeletal muscle fibres using patch clamp techniques. The effects of mexiletine were studied on macropatch currents 20 s (maximally activated), 8 min (early stage of rundown) and 15 min (late stage of rundown) after excision in the absence or in the presence of internal ADP (50–100 μM) or UDP (500 μM). In addition, the effects of mexiletine were tested on single channel. 2. In the absence of ADP and UDP, mexiletine inhibited the current through maximally activated channels with an IC(50) of −5.58±0.3 M. Nucleoside diphosphates shifted the current versus mexiletine concentration relationship to the right on the log concentration axis. UDP (500 μM) was more efficacious than ADP (50–100 μM) in this effect. 3. At the early stage of rundown, the sensitivity of the channel to mexiletine was reduced and nucleoside diphosphates, particularly UDP, antagonized the effect of mexiletine. At the late stage of rundown, mexiletine did not affect the currents. 4. At the single channel level, 1 μM mexiletine reduced the mean burst duration by 63% and prolonged the arithmetic mean closed time intervals between the bursts of openings without altering the open time and closed time distributions. Mexiletine did not affect the single channel conductance. 5. These results show that in skeletal muscle, mexiletine is a state-dependent K(ATP) channel inhibitor which either acts through the nucleotide binding site or a site allosterically coupled to it