Nanowire

Nanowires are quasi-one-dimensional nanostructures with diameters on the order of nanometers and lengths extending to micrometers. They exhibit high aspect ratios and crystalline structure, often with well-defined crystallographic orientation along their axis. Their reduced diameter leads to quantum confinement effects in some materials and large surface-to-volume ratios, which influence electrical, optical, and mechanical properties.

Nanowires can be made from a variety of materials, including semiconductors such as silicon, germanium, and gallium arsenide; metals such as gold, silver, and copper; and oxides such as zinc oxide and titanium dioxide. Core-shell and doped variants exist to tailor electronic or optical properties. The small diameter and elongated shape enable unique transport and waveguiding behavior, and the surface chemistry can be engineered for functional interfaces.

Synthesis methods are broadly categorized as bottom-up and top-down approaches. Bottom-up methods build nanowires from atomic or molecular precursors, for example through vapor-liquid-solid growth in which a catalyst particle directs anisotropic crystal growth, solution-based synthesis, or template-assisted electrodeposition. Top-down approaches pattern and etch bulk materials to define nanowire geometries. Post-synthesis treatments can modify surface passivation and doping.

Nanowires have potential in nanoelectronics, photonics, and sensing, with uses in field-effect transistors, optical waveguides, photodetectors, chemical and biological sensors, and energy devices such as solar cells and batteries. Key challenges include precise diameter and length control, uniformity, surface states and contamination, reliable contacting, scalability, and integration into devices.