A new approach for high-yield metal–molecule–metal junctions by direct metal transfer method

Abstract

The realization of high-yield, stable molecular junctions has been a long-standing challenge in the field of molecular electronics research, and it is an essential prerequisite for characterizing and understanding the charge transport properties of molecular junctions prior to their device applications. Here, we introduce a new approach for obtaining high-yield, vertically structured metal-molecule-metal junctions in which the top metal electrodes are formed on alkanethiolate self-assembled monolayers by a direct metal transfer method without the use of any additional protecting interlayers in the junctions. The fabricated alkanethiolate molecular devices exhibited considerably improved device yields (∼70%) in comparison to the typical low device yields (less than a few %) of molecular junctions in which the top metal electrodes are fabricated using the conventional evaporation method. We compared our method with other molecular device fabrication methods in terms of charge transport parameters. This study suggests a potential new device platform for realizing robust, high-yield molecular junctions and investigating the electronic properties of devices.

Ultrasmooth and Photoresist‐Free Micropore‐Based EGaIn Molecular Junctions: Fabrication and How Roughness Determines Voltage Response

“…Figure A shows the 〈log 10 | J |〉 G versus V curves and Figure B shows the histograms of the measured values of log 10 | J | at −0.50 V for all types of junctions. The values of the log standard deviations σ log G are small (average of 0.26), similar to other state‐of‐the‐art techniques . The average yield of working junctions of 81% is similar to that reported for other types of micropore‐based large‐area and EGaIn junctions .…”

Metallic nanoparticle contacts for high-yield, ambient-stable molecular-monolayer devices

“…1 b, the third is omitted for clarity. Both devices show a slight temperature dependence with a tendency to higher current at lower temperature for higher bias, similar to the trend observed by Jeong et al [11], and consistent in magnitude with other work [24], [13], [7].…”

“…As alkane-thiol SAMs are often implemented in large-area molecular junctions, literature is available on the temperature dependent transport properties of these devices. For metal-molecule-metal junctions, no significant temperature was found for three different manufacturing approaches: nanopores [24], direct evaporation on larger pores [13] and direct metal transfer [11]. Similar results where obtained for PEDOT devices [7], with the notable exception of Neuhausen et al, which attributed the dependence to the different polymer used [14].…”

“…This step should maintain film integrity as well as intrinsic functionality, while being mass-fabrication compatible and scalable in terms of active area. Various strategies have been proposed, ranging from direct evaporation onto cooled films in nanopores [6] over PEDOT:PSS [7] and graphene [8] contact layers to EGaIn liquid-metal top electrodes [9], micro-contact printing [10], and metal-transfer methods [11]. Each strategy has drawbacks, for example, low yield due to metal-filament penetration of the SAM [12], [13] or high series resistance [14], that prevent any of those strategies from concurrently fulfilling the above-mentioned requirements.…”

Revealing the Nature of Molecule–Electrode Contact in Tunneling Junctions Using Raw Data Heat Maps

“…9 The EGaIn technique, as an alternative to Hg, has been widely adopted for its stability, high yield, and reproducibility. 9,21,25 EGaIn is a non-Newtonian liquid metal at room temperature and can be shaped into a conical probe that can be used as the top electrode, forming a metal−SAM//Ga 2 O 3 −EGaIn junction (Figure 1a,b). 4,6,26,27 The current EGaIn technique also has its own challenges, for example, the inability to make uniformly configured top electrodes and the difficulty in defining the influence of morphology of the tip on measurements.…”