Molecular Electronics with Large-area Molecular Junctions
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1091-AA02-05
Molecular Electronics with Large-area Molecular Junctions Hylke B. Akkerman1, Auke J. Kronemeijer1, Paul W. M. Blom1, Paul van Hal2, Dago M. de Leeuw1,2, and Bert de Boer1 1 Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, NL-9747AG, Netherlands 2 Philips Research, Eindhoven, 5656 AE, Netherlands ABSTRACT A technology is demonstrated to fabricate reliable metal-molecule-metal junctions with unprecedented device diameters up to 100 µm. The yield of these molecular junctions is close to unity. Preliminary stability investigations have shown a shelf life of years and no deterioration upon cycling. Key ingredients are the use of a conducting polymer layer (PEDOT:PSS) sandwiched between a bottom electrode with a self-assembled monolayer (SAM) and the top electrode to prevent electrical shorts, and processing in lithographically defined vertical interconnects (vias) to prevent both parasitic currents and interaction between the environment and the SAM [1]. Modeling the current–voltage (I–V) characteristics of alkanedithiols with the Simmons model showed that the low dielectric constant of the molecules in the junction results in a strong image potential that should be included in the tunneling model. Including image force effects, the tunneling model consistently describes the current-voltage characteristics of the molecular junctions up to 1 V bias for different molecule lengths [2]. Furthermore, we demonstrate a dependence of the I–V characteristics on the monolayer quality. A too low concentration of long alkanedithiols leads to the formation of looped molecules, resulting in a 50-fold increase of the current through the SAM. To obtain an almost full standingup phase of 1,14-tetradecanedithiol (C14) a 30 mM concentration is required, whereas a 0.3 mM concentration leads to a highly looped monolayer. The conduction through the full standing-up phase of C14 and C16 is in accordance with the exponential dependence on molecular length as obtained from shorter alkanedithiols [3]. Finally, a fully functional solid-state molecular electronic switch is manufactured by conventional processing techniques. The molecular switch is based on a monolayer of photochromic diarylethene molecular switches. The monolayer reversibly switches the conductance by more than one order of magnitude between the two conductance states via optical addressing. This reversible conductance switch operates as an electronic ON/OFF switch (or a reprogrammable data storage unit) that can be optically written and electronically read [4].
INTRODUCTION In 1960 Herwald and Angello published an article in Science stating that ‘The trend in electronics circuit construction is toward microminiaturization and molecular electronics.’ [5]. In this article they envisioned that ‘the boundaries between materials and devices and between devices and circuits are being removed, and we shall see an integration of disciplines in the future development of molecular electronics.’ Although the t
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