Are Asymmetric SAM‐Induced Work Function Modifications Relevant for Real Molecular Rectifiers?

Due to the fabrication architecture employed—flat s(ubstrate) versus sharp t(ip), chemisorption physisorption, etc–, self assembled monolayers (SAMs) break forward-backward invariance even in case of homometal molecular junctions; they induce changes electrodes' work function different from each other ( Δ Φ s ≠ t $ \Delta \Phi _{\text{s}} \ne _{\text{t}}$ ). Because differences > translate into internal (Volta) electric fields often exceeding those created by highest applied biases that real junctions can withstand, one may expect effects relevant for current rectification (RR). Here, theoretically analyze asymmetric raw I-V data benchmark junctions. Notwithstanding large values | − ≈ 1 |\Delta - _{\text{t}}|\approx 1$ eV, found impact on is completely negligible. So, present theoretical results conveys a word caution: not any effect strongly breaks inversion symmetry necessarily leads rectification. While their analysis indicates per se unequal SAM-induced $\Delta \Phi$ 's hardly affect RR-values general, it does rule out an indirect where charge transfer between metal layer at interface and bulk. From this perspective, using interposed narrow-band adlayers be appealing route toward improving via engineering.