Russian physicists developed a technique for making thin graphitized layers inside a diamond. These layers, combined with technology of diamond photolithography, open wide perspectives of using diamond-graphite structures in electronics and optical electronics.

Modern electronics is based upon following materials – silicon, germanium, gallium arsenide and etc. However, diamond is one of promising materials for electronics, since its properties are ideal for electronic components, designed to work in harsh environments (high temperatures, high radiation levels, aggressive chemical environments, and etc). Russian physicists developed a technique for synthesizing diamond-graphite structures for advanced application in electronics and optical electronics. This technique is a possible application of long-term studies of diamond graphitization microphysics – first-order phase transition in solid state.

Diamond and graphite are simple substances, containing only carbon, but with different crystal lattice and different chemical bonds between atoms. Diamond is hard, transparent and shows insulating properties, while graphite is soft, black and conducts electric current. Everything points that diamond and graphite are total antagonists.

 

 

However, diamond graphitization is almost never a spontaneous process, since turning diamond into graphite requires a lot of energy. This energy barrier can be broken by radiation, and most effective technology is known as ion-implantation doping. During this process ions, possessing energy of tens and hundreds of kiloelectronvolts, knock atoms out of the crystal lattice, and after that, high-temperature annealing helps a body restore its lattice. However, diamonds with highly defective lattice do not restore it, but pass into the state, when carbon atoms are bonded with sp2 bonds, like in graphite. The result is thin graphitized layers, surrounded by diamond, thus protected chemically and mechanically. Ion-implantation doping is a good tool to make micron-thick layers of graphite inside diamonds on given depths, and these layers can serve as a conductor inside an insulator, a conductor strip or an electrode.

There is a serious difficulty in using diamonds for needs of electronics. Main technology of modern microelectronics is called “photolithography”, which uses light to transfer a geometric pattern from a photo mask to a light-sensitive chemical photo resist, or simply "resist," on the substrate. Diamond has a very low adhesion to a resist, but Russian physicists have successfully solved technological difficulties, and now diamond photolithography works. Here is the secret: first researchers spray diamond with metal, which has good contact with carbon. Then photolithography is performed upon metal surface.

Until recently diamonds weren’t considered a good material for electronic needs – natural stones are expensive, usually small and low-quality. Modern technologies of growing synthetic diamonds of extremely high quality, combined with abovementioned techniques of diamond processing, promise this material a good career in microelectronics.

Source: Institute of Physics

Kizilova Anna