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Diamond-Graphite Sandwiches for Electronic Devices
June 24, 2011 13:05


Russian physicists now know how to insert thinnest graphite layers into diamonds in order to later make various parts for electronic and optoelectronic devices.

Silicon, germanium, gallium arsenide and etc are materials, currently used for various tasks of electronics. Science goes further in search for new advanced materials and new technologies. Diamond is not only girl’s best friend, it is also an ideal material for making electronic components, able to work under harsh operation conditions (high temperature and high radiation levels, aggressive environment and etc).

Researchers from Lebedev Institute of Physics (Russian academy of sciences) have developed a technology for making diamond-graphite structures, which open new possibilities in fields of electronics and optoelectronics. This technology is a result of long-term studies of microphysics of diamond graphitization – first order phase transition in solid state of matter.

Diamond and graphite are in fact very simple substances, made of carbon”, one of the authors of the development says, “but their crystal lattices are totally different from each other, and atoms are bound by different chemical bonds”. We all known the results – diamonds are hard, transparent and insulating pieces of matter, non-soluble in acids; and graphite is black, soft and conducting material, easily reacting with weak acids.

However, diamonds can almost never spontaneously turn into graphite, because energy barrier for this process is significant. Researchers know some methods to break this barrier, and one of them is radiation damage with most effective technique being ion implantation. In simple words, ions with high energies (tens or even hundreds kilo electronvolts) kick out atoms from crystal lattice, after that a solid body undergoes high-temperature annealing for recovery of its crystal structure.

However, a diamond with significant defects doesn’t recover its structure during annealing, but transforms into a state, where its atoms become bound with sp2 bonds, like in graphite. The result is thin graphite layers, surrounded by diamond, thus protected from any aggression from outside.
The technique of ion implantation helps make graphite layers as thick as 10-1000 nanometers. However, there’s one tricky thing about using diamonds in electronics. Photolithography, a technique for “drawing” future microchips on a material, is the fundamental technique of modern microelectronics, but diamonds have a very low adhesion to a photo layer. Russian researchers have found a solution to this problem.

“First, we spray a diamond with metal”, the scientists explain, “and this metal should have a very good contact with carbon”. Photolithography is done over metal coating, and the problem with diamond is eliminated. Until now, diamonds weren’t regarded as good materials for electronic applications due to high costs of natural diamonds and their small size, as well as low quality of natural stones. Today, a possibility of growing cheap and high-quality synthetic diamonds, as well as elimination of some technological problems, offer diamonds a good career in electronics.

Source:
the Institute of Physics

Anna Kizilova


Author: Anna Kizilova

Tags: Russian Scientists     

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