Improving the Charge Transport in Self-Assembled Monolayer Field-Effect Transistors: From Theory to Devices

Abstract

A three-pronged approach has been used to design rational improvements in self-assembled monolayer field-effect transistors: classical molecular dynamics (MD) simulations to investigate atomistic structure, large-scale quantum mechanical (QM) calculations for electronic properties, and device fabrication and characterization as the ultimate goal. The MD simulations reveal the effect of using two-component monolayers to achieve intact dielectric insulating layers and a well-defined semiconductor channel. The QM calculations identify improved conduction paths in the monolayers that consist of an optimum mixing ratio of the components. These results have been used both to confirm the predictions of the calculations and to optimize real devices. Monolayers were characterized with X-ray reflectivity measurements and by electronic characterization of complete devices.

Modeling charge transport in C60-based self-assembled monolayers for applications in field-effect transistors

“…11 In agreement with experimental results, 12,13 the study revealed the crucial influence of the morphology of the SAM on the transport properties. In the present paper, we extend the previous study using a fully quantum mechanical description of transport.…”

“…16 Lithographically patterned gold (30 nm) is placed on top of the SAM, serving as source and drain electrodes. 11 The semiconducting C 60 head groups of the functionalized PA in the SAM form the active transistor channel in the device. In this paper, we focus on the modeling of charge transport within the SAM.…”

“…11 Here, the SAM-forming molecules were initially aligned on a clean (0001) aluminum-oxide surface that was equilibrated prior to depositing phosphonic acids using an interatomic potential model parameterized by Sun et al. Following the MD simulations, an ensemble of snapshots was extracted and the AlO x substrate was removed for further processing.…”

“…Previous investigations using Monte Carlo path searches based on a local electron affinity potential in the mixed SAM have suggested that there are specific pathways for efficient electron transport across the fullerenes. 11 In the following we will extend this analysis based on the quantum mechanical transport theory employed here using the theory of local currents and transmissions outlined in Sec. II D.…”

Tuning the molecular order of C60-based self-assembled monolayers in field-effect transistors

“…SAMs of functionalized fullerenes have been used in organic photovoltaics, 13,21,22 memory transistors, 9 light sensors 23 and SAMFETs. 18,24,25 In all of these devices the order of the SAM is of crucial importance for electronic properties. Therefore, ways to access information about and actually control the morphology of these films can enhance the device performance.…”