First-principles investigation of the asymmetric contact effect on current-voltage characteristics of a molecular device

Abstract

The properties of electronic transport in an electronic device composed of a spatially symmetric phenyldithiolate molecule sandwiched between two gold electrodes with asymmetric contact are investigated by the first-principles study. It is found that the I-V and G-V characteristics of a device show significant asymmetry and the magnitudes of current and conductance depend remarkably on the variation of molecule-metal distance at one of the two contacts. Namely, an asymmetric contact would lead to the weak rectifying effects on the current-voltage characteristics of a molecular device. We also calculate self-consistently other microscopic quantities such as the local density of states, the total density of states, and the distribution of charges in the asymmetric molecular models under the applied bias. The results show that the highest-occupied molecular orbital (HOMO) is responsible for the resonant tunneling and the shifting of the HOMO due to the charging of the device under the bias voltage is the intrinsic origin of asymmetric I(G)-V characteristics.

High rectification ratios of Fe–porphyrin molecules on Au facets

“…In parallel, intense theoretical transport calculations using non-equilibrium Green function and/or first principles density functional calculations have been carried out on simpler single chains of molecules sandwiched between the same electrode materials including s bridge [12], p bridge [13,14], various end-groups [15], and different types of asymmetric molecules [4,16,17], biased-induced orbital hybridization [18], asymmetric electrode coupling [19,20] as well as different metals for two electrodes including Au, Li, Pb, Al, Ag and Pt [6,7,21] in order to better understand the "metal/molecule" junction [2] and search for the optimized rectification.…”

Molecular Electronics Devices: A Short Review

“…[87][88][89] The current-voltage feature shown asymmetry and the values of current as well conductance are dependent of phenyldithiolate-Gold distance at one of the two contacts. 90 This case provides weak rectification and HOMO is responsible for the resonant tunneling provoked by charge shifting of the molecular structure for the applied voltage stressing out through the asymmetric I-V suggesting the importance of the interface for the electronic transport.…”

Enhanced rectifying performance by asymmetrical gate voltage for BDC20 molecular devices

“…In recent years, various molecular devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14] with interesting physical properties such as single-electron characteristic, negative differential resistance, molecular rectication, eldeffect characteristics, and electronic switching have attracted considerable attention owing to their great potential practical applications in atomic-scale circuits. In particular, rectifying behavior [7][8][9][10][11][12][13][14] is the fascinating aspect of the modern quantum transport phenomena because it is one of the most important electronic elements used for logic circuits and memory elements.…”