Negative Differential Resistance of Oligo (Phenylene Ethynylene) Self-Assembled Monolayer Systems: The Electric Field Induced Conformational Change Mechanism
We investigate here a possible mechanism for the room temperature Negative Differential Resistance (NDR) in the Au/AN-OPE/RS/Hg self-assembled monolayer (SAM) system, where AN-OPE = 2’-amino, 5’-nitro oligo (phenylene ethynylene) and RS is a C14 alkyl thiolate. Kiehl and co-workers showed that this molecular system leads to NDR with hysteresis and sweep-rate-dependent position and amplitude in the NDR peak. To investigate a molecular basis for this interesting behavior, we combine first principles quantum mechanics (QM) and meso-scale lattice Monte Carlo (MC) methods to simulate the switching as a function of voltage and voltage rate, leading to results consistent with experimental observations. This simulation shows how the structural changes at the microscopic level lead to the NDR and sweep-rate dependent macroscopic I-V curve observed experimentally, suggesting a microscopic model that might aid in designing improved NDR systems.
KeywordsHexagonal Phenylene Thiol Thiolate Ethynylene
The computational work was initiated with support by the National Science Foundation (NIRT, WAG). The collaboration was supported by the Microelectronics Advanced Research Corporation (MARCO, WAG and RAK) and its Focus Centers on Functional Engineered NanoArchitectonics (FENA). The facilities of the MSC (WAG) were supported by ONR-DURIP, ARO-DURIP and the facilities of the CNBT lab (SSJ) were supported by the start-up from the MSE in Georgia Tech.
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