Semiconductors are the active parts of transistors, integrated circuits, sensors, and LEDs. These materials, mostly based on silicon, are at the heart of today’s electronics industry. Metals, on the other hand, wire the active electronic components and are the framework for the devices.
Researchers analyzed the crystals at the surface of semiconductor materials. They applied a method called colloidal synthesis to lead sulphide nanowires, showing that the lead and sulphur atoms making up the crystals could be arranged in different ways. Crucially, this affected the material’s properties.
In most configurations, the two types of atoms are mixed and the whole structure shows semiconducting behavior as expected; however, the team found that one particular “cut” through the crystal, which contains only lead atoms, shows metallic character. This means that the nanowires carry much higher currents, their transistor behavior is suppressed, they do not respond to illumination as semiconductors would, and they show inverse temperature dependency, which is typical for metals.
After discovering that lead sulphide nanowires can be synthesized with different facets, which makes them look like straight or zigzag wires, the team determined that there must be interesting consequences for electronic properties. The team then made a second discovery: at low temperatures, the skin of the nano-structures even behaves like a superconductor. This means that the electrons are transported through the structures with significantly lower resistance.
This behavior provides insights into how the same material can possess different fundamental physical properties, depending on its structure. One potential application is lossless energy transport, which means that no energy is wasted.