Electron Beams Used To Create Diamonds

Researchers at the University of Tokyo have developed a new method for creating synthetic diamonds using electron radiation. This technique, they suggest, could pave the way for powerful new forms of imaging and analytical techniques.

Currently, diamonds are typically formed under extreme conditions of heat and pressure, such as those deep inside the Earth, or through a controlled growth process called chemical vapor deposition.

However, the Japanese team, led by Professor Eiichi Nakamura, discovered a way to create tiny diamonds (nanodiamonds) at relatively low pressures using an electron beam.

Their starting material was adamantane, a cage-shaped hydrocarbon molecule with the same basic tetrahedral carbon skeleton as diamond.

In adamantane, the carbon atoms are in the right diamond-like arrangement, but each carbon is capped with hydrogen atoms. As the team explains, to turn adamantane into diamond, you need to remove the hydrogens (break carbon–hydrogen bonds).

You also need to link the carbons together (form new carbon–carbon bonds). To achieve this, the team used electron beams inside a transmission electron microscope (TEM), and they carefully "zapped" adamantane crystals.

"Computational data gives you 'virtual' reaction paths, but I wanted to see it with my eyes," Nakamura said.

"However, the common wisdom among TEM specialists was that organic molecules decompose quickly as you shine an electron beam on them. My research since 2004 has been a constant battle to show otherwise," he added.

Instead of destroying the molecules (which is what most people thought would happen), the beam caused the hydrogens to detach and the carbons to link up, thereby slowly building up a diamond lattice.