Heat is always an issue with electronics and as the devices get smaller and smaller, it becomes a more pressing problem. From the March 13, 2012 news item on Nanowerk,

For decades, engineers have sought to build more efficient electronic devices by reducing the size of their components. In the process of doing so, however, researchers have reached a “thermal bottleneck,” said Argonne [US Dept. of Energy, Argonne Laboratory] nanoscientist Anirudha Sumant.

In a thermal bottleneck, the excess heat generated in the device causes undesirable effects that affect its performance. “Unless we come-up with innovative ways to suck the heat off of our electronics, we are pretty much stuck with this bottleneck,” Sumant explained.

Diamond films have excited interest in the scientific community as a solution to thermal bottlenecks, from the news item,

The unusually attractive thermal properties of diamond thin films have led scientists to suggest using this material as a heat sink that could be integrated with a number of different semiconducting materials. However, the deposition temperatures for the diamond films typically exceed 800 degrees Celsius—roughly 1500 degrees Fahrenheit, which limits the feasibility of this approach.

Reducing the deposition temperature to 400 degrees Celsius would allow for integration of diamond materials with a whole range of semiconductor materials.  A new technique that allows just that thing has been developed (from the news item),

By using a new technique that altered the deposition process of the diamond films, Sumant and his colleagues at Argonne’s Center for Nanoscale Materials were able to both reduce the temperature to close to 400 degrees Celsius and to tune the thermal properties of the diamond films by controlling their grain size. This permitted the eventual combination of the diamond with two other important materials: graphene and gallium nitride.

According to Sumant, diamond has much better heat conduction properties than silicon or silicon oxide, which were traditionally used for fabrication of graphene devices. As a result of better heat removal, graphene devices fabricated on diamond can sustain much higher current densities.

In the other study, Sumant used the same technology to combine diamond thin films with gallium nitride, which is used extensively in high-power light emitting devices (LED). After depositing a 300 nm-thick diamond film on a gallium nitride substrate, Sumant and his colleagues noticed a considerable improvement in the thermal performance. Because a difference within an integrated circuit of just a few degrees can cause a noticeable change in performance, he called this result “remarkable.”

There are two published papers on the technique, one focusing on the graphene application and the other on the gallium nitride application. The first is in Nano Letters, 2012, 12 (3), pp 1603–1608, DOI: 10.1021/nl204545q, (“Graphene-on-Diamond Devices with Increased Current-Carrying Capacity: Carbon sp²-on-sp³Technology”, and the other is in Advanced Functional Materials, first published online: 1 FEB 2012, DOI: 10.1002/adfm.201102786,  (“Direct Low-Temperature Integration of Nanocrystalline Diamond with GaN Substrates for Improved Thermal Management of High-Power Electronics”).