Semiconductors are at the heart of modern technology, powering everything from smartphones and computers to solar panels and electric vehicles.
However, the range of materials that can be used as semiconductors is surprisingly limited.
Now, researchers have developed a new way to turn a normally insulating material into a high-performance semiconductor, opening the door to more durable and energy-efficient electronic devices.
The breakthrough was made by scientists from Carnegie Mellon University and Penn State University and published in the journal Communications Materials.
Many metal oxides are attractive for use in electronics because they are inexpensive, stable and can withstand harsh environments. Unfortunately, most of them are poor electrical conductors, making them unsuitable for semiconductor applications.
The research team found a way to overcome this limitation using a technique known as high-entropy mixing. Instead of building a material from just one or two metals, they combined six different metals—manganese, iron, cobalt, nickel, copper and zinc—inside a tungsten oxide crystal structure known as wolframite.
At first glance, mixing so many different elements together might seem like it would create disorder. In fact, that is exactly what the researchers wanted. This intentional atomic-level “chaos,” known as high configurational entropy, dramatically changed the material’s behavior.
Normally, tungsten oxide acts as an electrical insulator, meaning electricity cannot flow through it easily. But after the researchers introduced the mixture of six metals, the material’s electronic structure changed. The energy barrier that normally blocks the movement of electrons became much smaller, allowing electricity to flow more readily. As a result, the once-insulating material behaved like a semiconductor.
The researchers also discovered another important advantage. The new material has extremely low thermal conductivity, meaning heat moves through it very slowly.
This combination is unusual because materials that conduct electricity well often conduct heat well too. Achieving good electrical performance while blocking heat is difficult, but it is exactly what engineers want for certain energy technologies.
One promising application is thermoelectric devices, which generate electricity by capturing waste heat. These devices work best when electricity flows easily while heat does not. The newly developed material appears to offer both characteristics at the same time.
The team believes the unusually low heat conduction comes from the chemical disorder created by the many different metal atoms. This disorder interrupts the movement of tiny vibrations, known as phonons, that normally carry heat through a solid.
Another advantage is durability. Metal oxides are generally much more resistant to heat, corrosion and harsh environmental conditions than many traditional semiconductor materials. This could make them useful for electronics designed to operate in demanding environments, such as industrial equipment, vehicles or space technologies.
Perhaps most importantly, the study demonstrates a completely new strategy for designing advanced materials. Instead of searching for rare compounds with the perfect properties, scientists may be able to engineer common, abundant materials into high-performance semiconductors simply by carefully mixing multiple elements together.
The researchers say this high-entropy approach provides a new set of design principles for future materials science.
In the years ahead, it could help create a new generation of resilient semiconductors that are more efficient, more environmentally durable and better suited for converting wasted heat into useful electricity.
