High selectivity of N-doped ZnO nano-ribbons in detecting H2, O2 and CO2 molecules: Effect of negative-differential resistance on gas-sensing

Abstract

Adsorption and transport properties of ZnO nano-ribbons (ZnO-NRs) are investigated using density-functional theory (DFT) combined with non-equilibrium Green’s-function (NEGF) formalism. Total-energy minimization shows the evidence for a selective chemisorption of three gases H2, O2 and CO2 to take place when ZnO-NR is N-doped. The calculated IV characteristics of ZnO-NR:N based device shows a trend of negative differential resistance (NDR). The NDR behavior persists to exist in the ZnO-NR:N device after the chemisorption of oxidizing-gases O2 and CO2, as causing more charge depletion of N-site, more impedance, and a broadening of NDR range. However, the NDR trend disappears in the case of chemisorption of reduced-gas H2, which donates charge to surface to rectify and enhance the conductance. The sensor responses, due to these three gases, are enormously large but yet with higher selectivity toward H2 gas. Consequently, NDR-based devices are proposed for high sensitivity and selectivity toward, likely, a reduced-gas, such as H2 in our present case. Our findings would be useful in exploring NDR to develop highly sensitive solid-state gas (ZnO-based) sensors of hydrogen and its related storage applications.