Silicon-based molecular electronics

TL;DR

This paper presents a theoretical framework for silicon-based molecular electronics, demonstrating how semiconductor band-edges can enable molecular resonant tunneling diodes with negative differential resistance, supported by experimental evidence.

Contribution

It introduces a combined semi-empirical and first-principles formalism for transport in silicon-molecule heterostructures, revealing novel RTD behavior influenced by semiconductor band-edges.

Findings

Identification of NDR in silicon-molecule devices due to band-edge effects

Charging behavior affected by RTD action, aiding molecular level identification

Experimental results support the theoretical predictions

Abstract

Molecular electronics on silicon has distinct advantages over its metallic counterpart. We describe a theoretical formalism for transport through semiconductor-molecule heterostructures, combining a semi-empirical treatment of the bulk silicon bandstructure with a first-principles description of the molecular chemistry and its bonding with silicon. Using this method, we demonstrate that the presence of a semiconducting band-edge can lead to a novel molecular resonant tunneling diode (RTD) that shows negative differential resistance (NDR) when the molecular levels are driven by an STM potential into the semiconducting band-gap. The peaks appear for positive bias on a p-doped and negative for an n-doped substrate. Charging in these devices is compromised by the RTD action, allowing possible identification of several molecular highest occupied (HOMO) and lowest unoccupied (LUMO) levels. Recent experiments by Hersam et al. [1] support our theoretical predictions.