Hybrid Approach to Fabricate Uniform and Active Molecular Junctions

Abstract

Molecules can serve as ultimate building blocks for extreme nanoscale devices. This requires their precise integration into functional heterojunctions, most commonly in the form of metal–molecule–metal architectures. Structural damage and nonuniformities caused by current fabrication techniques, however, limit their effective incorporation. Here, we present a hybrid fabrication approach enabling uniform and active molecular junctions. A template-stripping technique is developed to form electrodes with sub-nanometer smooth surfaces. Combined with dielectrophoretic trapping of colloidal nanorods, uniform sub-5 nm junctions are achieved. Uniquely, in our design, the top contact is mechanically free to move under an applied stimulus. Using this, we investigate the electromechanical tuning of the junction and its tunneling conduction. Here, the molecules help control sub-nanometer mechanical modulation, which is conventionally challenging due to instabilities caused by surface adhesive forces. Our versatile approach provides a platform to develop and study active molecular junctions for emerging applications in electronics, plasmonics, and electromechanical devices.

Molecular Platform for Fast Low-Voltage Nanoelectromechanical Switching

“…We have implemented a bottom-up approach 20 with nanometer-scale precision for assembly of this NEM switch (Figure 2a). Gold (Au) bottom electrodes are first patterned on a silicon substrate by a standard lift-off process involving electron-beam lithography (EBL) and thermal evaporation.…”

Switching on Versatility: Recent Advances in Switchable Plasmonic Nanostructures

“…In contrast to the use of temperature change in the surrounding medium, induction of thermal effect via irradiating light or applying AC voltage was proposed, [199][200][201] for example, with light irradiation to induce a photothermal effect on DNA-conjugated plasmonic NPs. Wang et al [200] incorporated plasmonic nanostructures into hydrogels to create versatile materials with controllable mechanical properties.…”

“…TEM cross-sectional image (lower) of a nonuniform molecular junction formed between thermally evaporated gold contacts. b) Reproduced with permission [201]. Copyright 2021, American Chemical Society.…”

Directed Assembly of Nanomaterials for Making Nanoscale Devices and Structures: Mechanisms and Applications

“…The continuous miniaturization of CMOS field-effect transistors (FETs) faces challenges related to off-state current leakage and power dissipation . NEM switches have attracted attention in recent years due to their merits of near zero off-state current, steep subthreshold slopes, and robustness in extreme environments. − Han et al fabricated NEM switches using DEP assembled gold nanorods as active components (Figure a). Single gold nanorods were bridged between a pair of gold electrodes with self-assembled molecular spacers between the nanorod and electrodes.…”