Origins of Negative Differential Resistance in N-doped ZnO Nano-ribbons: Ab-initio Investigation

Abstract

The electronic transport in low-dimensional materials is controlled by quantum coherence and non-equilibrium statistics. The scope of the present investigation is to search for the origins of negative-differential resistance (NDR) behavior in N-doped ultra-narrow zigzag-edge ZnO nano-ribbons (ZnO-NRs). A state-of-the-art technique, based on a combination of density-functional theory (DFT) and non-equilibrium Green’s function (NEGF) formalism, is employed to probe the electronic and transport properties. The effect of location of N dopant, with respect to the NR edges, on IV-curve and NDR is tested and three different positions for N-atom are considered: (i) at the oxygen-rich edge; (ii) at the center; and (iii) at the Zn-rich edge. The results show that both resistance and top-to-valley current ratio (TVCR) reduce when N-atom is displaced from O-rich edge to center to Zn-rich edge, respectively. After an analysis based on the calculations of transmission coefficient versus bias, band structures, and charge-density plots of HOMO/LUMO states, one is able to draw a conclusion about the origins of NDR. The unpaired electron of N dopant is causing the curdling/localization of wave-function, which in turn causes strong back-scattering and suppression of conductive channels. These effects manifest themselves in the drawback of electric current (or so called NDR). The relevance of NDR for applications in nano-electronic devices (e.g., switches, rectifiers, amplifiers, gas sensing) is further discussed.

Nitrogen-doped zinc oxide nanoribbons for potential resonant tunneling diode applications

“…For the D N -ZnO, an increase in N concentration causes a further shift of the E F down to −4.01 eV. 17…”

“…9 Nanoribbons with a zigzag edge are magnetic while armchair nanoribbons are semiconducting and non-magnetic. 16 Different methods such as doping, 17,18 passivation, 19 defects, 20 external fields, 21,22 and straining 23 are reported to tune the electronic properties of ZnONRs for various applications such as sensors, 24 diodes, 18 spintronics, 16 etc. Zigzag ZnONRs are studied for sensor design to detect heavy metal atoms, gases, and uric acid.…”

“…Doping and passivation approaches are used to develop the NDR mechanism in the ZnONRs. 17,38 Previously, the NDR phenomenon has been reported with nitrogen doping in zigzag nanoribbons. 17 This motivated us to explore the ZnONRs with nitrogen doping to induce the NDR characteristics for improved performance.…”

“…17,38 Previously, the NDR phenomenon has been reported with nitrogen doping in zigzag nanoribbons. 17 This motivated us to explore the ZnONRs with nitrogen doping to induce the NDR characteristics for improved performance. Nitrogen-doped armchair nanoribbons are expected to exhibit NDR behavior with improved results.…”

Electron Transport through Nanoconfined Ferrocene Solution: Density Functional Theory─Nonequilibrium Green Function Approach

“…The I – V relation for the Pt/W + Fc also describes a nonlinear variation of current as a function of the applied bias potential, showing negative differential resistance (NDR) within the negative bias potential with the NDR peak located at −1.21 V (blue arrow in Figure c). The NDR behavior has been observed in various quantum transport systems through individual molecules or low-dimensional solid systems. , In the Pt/W + Fc system, the appearance of NDR seems to be triggered by the ferrocene molecule and its interaction with surroundings, where the distribution of T normalV ( E , V b ) peaks and their shift direction are correlated with the magnitude of electric current as shown in Figure b. For example, when electric currents are compared between −1.21 V (NDR peak) and −2.39 V (NDR valley) for the Pt/W + Fc system, we can confirm that the electrical currents in Figure c are directly correlated with T normalV ( E , V b ) in Figure b in the bias potential window (blue shaded area) of E F – 0.61 eV < E < E F + 0.61 eV and E F – 1.20 eV < E < E F + 1.20 eV, respectively.…”