Interference-based molecular transistors

Molecular transistors have the potential for switching with lower gate voltages than conventional field-effect transistors. We have calculated the performance of a single-molecule device in which there is interference between electron transport through the highest occupied molecular orbital and the lowest unoccupied molecular orbital of a single molecule. Quantum interference results in a subthreshold slope that is independent of temperature. For realistic parameters the change in gate potential required for a change in source-drain current of two decades is 20 mV, which is a factor of six smaller than the theoretical limit for a metal-oxide-semiconductor field-effect transistor

Three-terminal graphene single-electron transistor fabricated using feedbackcontrolled electroburning

We report room-temperature Coulomb blockade in a single layer graphene three-terminal single-electron transistor fabricated using feedback-controlled electroburning. The small separation between the side gate electrode and the graphene quantum dot results in a gate coupling up to 3 times larger compared to the value found for the back gate electrode. This allows for an effective tuning between the conductive and Coulomb blocked state using a small side gate voltage of about 1V. The technique can potentially be used in the future to fabricate all-graphene based room temperature single-electron transistors or three terminal single molecule transistors with enhanced gate coupling

Graphene nanoelectrodes for biomolecular sensing

Nanoscale biosensor technology has attracted considerable attention with its promise of revolutionizing techniques ranging from biological interfaces to rapid pathogen detection to enabling DNA data storage. Many approaches, such as nanopore sequencing, have been explored and are al ready achieving tremendous success; however, new sensing modalities and architectures are emerging that are envisioned for the next generation of ever more capable biosensors. These novel devices, combined with advances in machine learning, are moving concepts from simulation to experimentation and demonstration. In recent years, rapid advances have been made and many architectures have been put forward for novel approaches to biomolecular sensing using nanoelectronics, including the advent of tunnel junctions as a sensing platform. With high accuracy, sensitivity, and affordability, these sensors are predicted to drive a shift to personalized medicine and rapid diagnostics in real-time anywhere in the world. Here we give an overview of tunneling sequencing and its application in biomolecular sensing and provide a perspective on the use of scalable tunneling sequencing methods utilizing graphene as the active component

Low-frequency noise in graphene tunnel junctions

Graphene tunnel junctions are a promising experimental platform for single molecule electronics and biosensing. Ultimately their noise properties will play a critical role in developing these applications. Here we report a study of electrical noise in graphene tunnel junctions fabricated through feedback-controlled electroburning. We observe random telegraph signals characterized by a Lorentzian noise spectrum at cryogenic temperatures (77 K) and a 1/f noise spectrum at room temperature. To gain insight into the origin of these noise features, we introduce a theoretical model that couples a quantum mechanical tunnel barrier to one or more classical fluctuators. The fluctuators are identified as charge traps in the underlying dielectric, which through random fluctuations in their occupation introduce time-dependent modulations in the electrostatic environment that shift the potential barrier of the junction. Analysis of the experimental results and the tight-binding model indicate that the random trap occupation is governed by Poisson statistics. In the 35 devices measured at room temperature, we observe a 20–60% time-dependent variance of the current, which can be attributed to a relative potential barrier shift of between 6% and 10%. In 10 devices measured at 77 K, we observe a 10% time-dependent variance of the current, which can be attributed to a relative potential barrier shift of between 3% and 4%. Our measurements reveal a high sensitivity of the graphene tunnel junctions to their local electrostatic environment, with observable features of intertrap Coulomb interactions in the distribution of current switching amplitudes

Solid-state nanopore sensors

Nanopore-based sensors have established themselves as a prominent tool for solution-based, single-molecule analysis of the key building blocks of life, including nucleic acids, proteins, glycans and a large pool of biomolecules that have an essential role in life and healthcare. The predominant molecular readout method is based on measuring the temporal fluctuations in the ionic current through the pore. Recent advances in materials science and surface chemistries have not only enabled more robust and sensitive devices but also facilitated alternative detection modalities based on field-effect transistors, quantum tunnelling and optical methods such as fluorescence and plasmonic sensing. In this Review, we discuss recent advances in nanopore fabrication and sensing strategies that endow nanopores not only with sensitivity but also with selectivity and high throughput, and highlight some of the challenges that still need to be addressed