nanojunctions

A nanojunction is a junction formed at nanometer length scales, typically connecting two conducting or semiconducting regions or bridging a nanoscale electrode. Electron transport through a nanojunction is strongly influenced by quantum confinement, discrete energy levels, and reduced dimensions, making nanojunctions central to nanoelectronics and molecular electronics research.

Realizations of nanojunctions include molecular junctions where a single molecule or a molecular layer forms the bridge between metal or semiconductor electrodes; semiconductor nanowire or carbon nanotube junctions; graphene p–n junctions; and quantum dot junctions where a small island acts as a controllable contact. Transport phenomena in nanojunctions often involve quantum tunneling, Coulomb blockade in isolated islands, quantum interference, and, in some cases, conductance quantization. Asymmetry, contact chemistry, and the environment can produce rectification or negative differential resistance.

Fabrication and measurement approaches vary. Common methods include assembling molecules or nanoparticles between nanoscale electrodes, break-junction techniques such as mechanically or electromigrationally creating a nano-gap, and lithographic patterning to define sub-10 nanometer gaps. Electrical characterization uses current–voltage curves, differential conductance (dI/dV), and sometimes spectroscopic tools to probe inelastic processes and energy level alignment.

Applications and challenges: nanojunctions have potential in molecular switches, diodes, sensors, and components for quantum devices, but face issues of reproducibility, stable and well-defined contacts, and sensitivity to the environment. Integrating nanojunctions with larger circuits and achieving consistent performance remain active areas of research.