Upscaling, integration and electrical characterization of molecular junctions

Abstract

The ultimate target of molecular electronics is to combine different types of functional molecules into integrated circuits, preferably through an autonomous self-assembly process. Charge transport through self-assembled monolayers has been investigated previously, but problems remain with reliability, stability and yield, preventing further progress in the integration of discrete molecular junctions. Here we present a technology to simultaneously fabricate over 20,000 molecular junctions-each consisting of a gold bottom electrode, a self-assembled alkanethiol monolayer, a conducting polymer layer and a gold top electrode-on a single 150-mm wafer. Their integration is demonstrated in strings where up to 200 junctions are connected in series with a yield of unity. The statistical analysis on these molecular junctions, for which the processing parameters were varied and the influence on the junction resistance was measured, allows for the tentative interpretation that the perpendicular electrical transport through these monolayer junctions is factorized.

Electrical characteristics of conjugated self-assembled monolayers in large-area molecular junctions

“…The PEDOT:PSS protects the SAM when an auxiliary gold electrode is thermally evaporated and, thereby, prevents short circuit formation. 21,22 Using this technique, over 20 000 stable molecular junctions have been fabricated on a 150 mm wafer with a yield of almost unity. This allows for a statistical analysis of the electronic properties.…”

“…21,22 Complete current density versus voltage ͑J-V͒ scans were performed on a subset of junctions. Figure 1͑a͒ shows the average J-V characteristics of P4DT.…”

Organic π-type thermoelectric module supported by photolithographic mold: a working hypothesis of sticky thermoelectric materials

“…During the vacuum deposition, in principle, atomic Au vapor reaches the surface of the TE materials and condenses into small droplets to build up the electrodes from the atoms. Thus, we can expect a good electrical contact as confirmed in a molecular electronics example of Au/PEDOT:PSS/Au [17]. According to the reported results, the contact resistance should be less than 0.02 Ω for this module design.…”

“…To finalize the organic π-type TE module, we first attempted to form Au electrodes by electron beam physical vapor deposition because we can estimate low contact resistance less than 0.02 Ω for this module design based on the experimental data reported in the literature [17]. However, we realized that the p-type TE legs of the DMSO-mixed dedoped PEDOT:PSS were peeled off in the vacuum chamber of deposition system.…”

Extending the voltage window in the characterization of electrical transport of large-area molecular junctions

“…15 More than 20 000 molecular junctions were fabricated simultaneously on a single 6-in wafer according to a previously reported semi-automated procedure. 16 On a 6-in Si monitor wafer with a 500 nm SiO 2 passivation layer, a 60 nm Au bottom electrode was sputtered onto a Ti adhesion layer and structured by standard photolithography. Vertical interconnects ranging from 1 lm to 50 lm in diameter were defined in insulating photoresist by conventional spin coating and UV lithography.…”