Diamonds have a number of physical and mechanical properties that are sought after in electronics: high hardness, thermal conductivity and a high refractive index. In order to be used in these fields, diamonds are usually metalized via a thin layer of transition metal being applied to their surface. However, metalization is hindered in some cases by the diamond’s low adhesion, i.e., its bond with the transition metal.
“Diamonds have two limitations related to the synthesis of large plates and metalization: when we start metalizing a diamond, most contacts don’t stick to it. For instance, when we were applying gold and other materials while working on detectors for ionizing radiation, the adhesion of contacts to diamonds was very poor. At the time, we asked ourselves how we could improve the adhesion of contacts to diamonds,” Stanislav Evlashin, assistant professor at the Center for Materials Technologies, is quoted as saying by Skoltech.
One solution to this problem is sintering diamonds with titanium, chromium, tantalum and zirconium: during interaction with carbon, a layer of metal carbide is formed, which is characterized by good superconductivity, a high melting point and high mechanical strength. The scientists from Skoltech and the Lebedev Physical Institute decided to try solving the problem with niobium, which, like tantalum, is a transition metal.
“We tried to make a superconductor on the surface of a diamond and came to the conclusion that if niobium is applied to the surface and later annealed to obtain niobium carbide, the annealing causes a chemical reaction with the surface, and the following transformations occur: after heating, the niobium film transforms into the compound Nb₂C, and after further heating above 1200 ℃, it transforms into NbC,” Stanislav Evlashin is quoted as saying by Skoltech.
Experiments conducted during the study showed that the resulting niobium carbamide has the property of superconductivity. Due to the high thermal conductivity of the film, its application to the surface of a diamond makes it possible to obtain a supersensitive detector. This discovery will facilitate the use of diamonds in electronics.
