Scientists make cheap heat-dissipating crystals to keep computers cool

American researchers have created a potential solution to cool down the circuitry of a computer, according to their study published Thursday in the journal Science.

As consumers demand smaller, faster and more powerful electronic devices that generate more heat, the issue of heat management is reaching a bottleneck.

The researchers have produced crystals of a semiconducting material called boron arsenide that has an extremely high thermal conductivity, a property that describes a material's ability to transport heat.

"For high-powered, small electronics, we cannot use metal to dissipate heat because metal can cause a short circuit. We cannot apply cooling fans because those take up space. What we need is an inexpensive semiconductor that also disperses a lot of heat," said Lv Bing, assistant professor of physics at the University of Texas at Dallas and a corresponding author of the study.

He stressed that "heat management is very important for industries that rely on computer chips and transistors."

Diamond has the highest known thermal conductivity, around 2,200 watts per meter-kelvin, compared to about 150 watts per meter-kelvin for silicon.

But the cost of natural diamonds and structural defects in man-made diamond films make the material impractical for widespread use in electronics, according to Lv.

Lv and his colleagues worked to optimize the crystal-growing process of boron arsenide to boost the material's performance.

They used a technique called chemical vapor transport in which the elements boron and arsenic are placed in a chamber that is hot on one end and cold on the other.

Inside the chamber, another chemical transports the boron and arsenic from the hot end to the cooler end, where the elements combine to form crystals, according to the study.

The way heat is dissipated in boron arsenide and other crystals is linked to the vibrations of the material. As the crystal vibrates, the motion creates packets of energy called phonons, which can be thought of as quasiparticles carrying heat.

Lv said the unique features of boron arsenide crystals, including the mass difference between the boron and arsenic atoms, contribute to the ability of the phonons to travel more efficiently away from the crystals.

While the element arsenic by itself can be toxic to humans, once it is incorporated into a compound like boron arsenide, the material becomes very stable and nontoxic, according to Lv.