Fabrication of ultra-smooth and oxide-free molecule-ferromagnetic metal interfaces for applications in molecular electronics under ordinary laboratory conditions

Abstract

Direct self-assembly of n-alkanethiolate SAMs on ferromagnetic metal surface was fabricated. The stability and tunnelling characteristics of SAMs were investigated.

The Drive Force of Electrical Breakdown of Large‐Area Molecular Tunnel Junctions

“…To characterize the SAMs, we performed angle‐dependent XPS to examine the structure of SC 10 formed on different metal surfaces (Figure and Table 2 ; Ag TS and Ni TS spectra are given in refs. and ) and compared our results against reported XPS results; see for a detailed review reference . The relative surface coverage and the thickness of the SAMs were determined with respect to the SC 10 SAM on Ag by examining the attenuation of the S 2p peaks recorded at emission angles of 90° and 30° (see Figure , see ref.…”

“…Indeed, we did not observe any dependence of the BVD on the surface morphology. Our X‐ray photoelectron spectroscopy (XPS) results (see below) indicate that our surfaces were not contaminated by metal oxides in agreement with previous studies . The metal surface of interest is in contact with the template and therefore protected from the environment except during transfer (≈5 s) from the template to the solution containing the thiols.…”

“…Since defect‐induced electron scattering inside the metal electrode also may cause heating effects which could lead to electrical breakdown, we used ultraflat surfaces to minimize defects in our junctions. We used previously reported methods and deposited the corresponding metal on a Si/SiO 2 template against which we glued glass supports using a photocurable adhesive . When needed, we template stripped the glass/glue/metal stacks from the template and immediately immersed them into an ethanolic solution of the n ‐alkanethiol.…”

“…The values of β for all junctions fall in the range of 0.90–1.0 per CH 2 unit which is within the consensus value of β for junctions with aliphatic SAMs. [25,26b,29,30,36] The characteristics of the junctions with SAMs supported by the different surfaces are statistically indistinguishable, and thus from these data we conclude that well‐defined junctions were formed on all types of bottom electrodes and that through‐bond tunneling dominates the mechanism of charge transport.…”

“…The metal surface of interest is in contact with the template and therefore protected from the environment except during transfer (≈5 s) from the template to the solution containing the thiols. [28a] We have previously shown that the SAM prevents oxidation of the Ni surface for 24 h, well over the time scales of our experiments …”