An On‐Chip Break Junction System for Combined Single‐Molecule Conductance and Raman Spectroscopies

Abstract

Systems that are capable of robustly reproducing single-molecule junctions are an essential prerequisite for enabling the wide-spread testing of molecular electronic properties, the eventual application of molecular electronic devices, and the development of single-molecule based electrical and optical diagnostics. Here, a new approach is proposed for achieving a reliable single-molecule break junction system by using a microelectromechanical system device on a chip. It is demonstrated that the platform can (i) provide subnanometer mechanical resolution over a wide temperature range (≈77-300 K), (ii) provide mechanical stability on par with scanning tunneling microscopy and mechanically controllable break junction systems, and (iii) operate in a variety of environmental conditions. Given these fundamental device performance properties, the electrical characteristics of two standard molecules (hexane-dithiol and biphenyl-dithiol) at the singlemolecule level, and their stability in the junction at both room and cryogenic temperatures (≈77 K) are studied. One of the possible distinctive applications of the system is demonstrated, i.e., observing real-time Raman scattering in a single-molecule junction. This approach may pave a way to achieving high-throughput electrical characterization of single-molecule devices and provide a reliable platform for the convenient characterization and practical application of single-molecule electronic systems in the future.

RNA BioMolecular Electronics: towards new tools for biophysics and biomedicine

“…Some present roadblocks for these new applications are the lack of single-molecule conductance measurements for RNA from human origin and the challenges in miniaturizing these single-molecule devices, despite recent advances in miniaturization and microfabrication of electromechanical molecular break-junctions systems. 80,81 See the last section for more details.…”

Recent Advances in Single-Molecule Sensors Based on STM Break Junction Measurements

“…To solve the above-mentioned issues, we can use the combination of advanced nanofabrication techniques to efficiently construct a molecular device with high stability, such as developing novel molecular devices using carbon electrodes of SWNTs and graphene [ 15 , 101 , 102 ]. The combination of various characterization techniques, such as vibrational spectroscopies can help to in situ monitor the molecular structures in the junctions, such as integrating the surface-enhanced Raman spectroscopy in the STM-BJ and MCBJ [ 19 , 103 , 104 , 105 , 106 ]. Therefore, we believe that the break junction measurements toward molecular electronics have a bright future through a good collaboration between chemists, physicists, materials scientists and engineers, and it can greatly complement traditional electronic devices and applications in various fields, including sensing.…”

Nearfield trapping increases lifetime of single-molecule junction by one order of magnitude

“…To improve our understanding of single-molecule electronic properties, ME research fundamentally relies upon the development of novel techniques to reliably and reproducibly study the diverse properties of individual molecules that are inaccessible in conventional ensemble experiments. 2 Robust tools have been developed for high-precision single-molecule trapping and detection to characterize individual molecules, enabling, for example, molecular sensing, 3 recognition, 4 Raman characterisation 5,6 or single-molecule reactors. 7 Most of these approaches rely on the detection of individual molecular binding events in an electrode-electrode gap of a fixed size as a function of time.…”

“…7 Most of these approaches rely on the detection of individual molecular binding events in an electrode-electrode gap of a fixed size as a function of time. 4,[6][7][8][9][10] One of the most promising approaches to trap and study single molecules bridged in precisely sized, motionless nanogaps is the blinking approach, 11 a scanning tunnelling microscope (STM)-based break-junction technique (STM-BJ). 12 In the blinking approach, a sub-nm precise inter-electrode distance is kept between the STM-tip and substrate electrodes to create a molecular-scale metal-metal gap in which an individual target species can be trapped to form a single-molecule electronic junction.…”

“…11 Typical τ are rather short in the order of tens to hundreds of ms, thus hindering elaborate junction characterization over longer time periods. 6,7,10,14 Immobilising target molecules for longer timescales, i.e. increasing τ, has remained one of ME's central challenges.…”