A Molecular Half-Wave Rectifier

作者：Nijhuis Christian A^*; Reus William F; Siegel Adam C; Whitesides George M

来源：Journal of the American Chemical Society, 2011, 133(39): 15397-15411.

DOI：10.1021/ja201223n

This paper describes the performance of junctions based on self-assembled monolayers (SAMs) as the functional element of a half-wave rectifier (a simple circuit that converts, or rectifies, an alternating current (AC) signal to a direct current (DC) signal). Junctions with SAMs of 11-(ferrocenyl)-1-undecanethiol or 11-(biferrocenyl)-1-undecanethiol on ultraflat, template-stripped Ag (Ag-TS) bottom electrodes, and contacted by top electrodes of eutectic indium-gallium (EGaIn), rectified AC signals, while similar junctions based on SAMs of 1-undecanethiol-SAMs lacking the ferrocenyl terminal group-did not. SAMs in these AC circuits (operating at 50 Hz) remain stable over a larger window of applied bias than in DC circuits. AC measurements, therefore, can investigate charge transport in SAM-based junctions at magnitudes of bias inaccessible to DC measurements. For junctions with SAMs of alkanethiols, combining the results from AC and DC measurements identifies two regimes of bias with different mechanisms of charge transport: (i) low bias (vertical bar V vertical bar < 1.3 V), at which direct tunneling dominates, and (ii) high bias (vertical bar V vertical bar > 1.3 V), at which Fowler-Nordheim (FN) tunneling dominates. For junctions with SAMs terminated by Fc moieties, the transition to FN tunneling occurs at vertical bar V vertical bar approximate to 2.0 V. Furthermore, at sufficient forward bias (v > 0.5 V), hopping makes a significant contribution to charge transport and occurs in series with direct tunneling (V less than or similar to 2.0 V) until FN tunneling activates (V greater than or similar to 2.0 V). Thus, for Fc-terminated SAMs at forward bias, three regimes are apparent: (i) direct tunneling (V = 0-0.5 V), (ii) hopping plus direct tunneling (V approximate to 0.5-2.0 V), and (iii) FN tunneling (V greater than or similar to 2.0 V). Since hopping does not occur at reverse bias, only two regimes are present over the measured range of reverse bias. This difference in the mechanisms of charge transport at forward and reverse bias for junctions with Fc moieties resulted in large rectification ratios (R > 100) and enabled half-wave rectification.

• 出版日期2011-10-5