| Since the beginning of time people have been mesmerized by the glitter and beauty of diamond, the most precious stone of all. Even though diamonds were first mined in India as early as the 4th century BC, only during recent centuries has diamond become popular as a gemstone for jewelry. This is because special techniques are required for cutting and polishing diamond since it is a superhard material (the word diamond derives from the Greek'adamas'meaning'invin-cible'). In addition to its natural high hardness, diamond has an extraordinary range of material properties:diamond has the highest thermal conductivity at room temperature with a high Debye temperature. it is an excellent electrical insulator; it is transparent to UV, visible, and IR radiation; it has a high refrac-tive index; and it is physically and chemically stable. Furthermore, as a result diamond exhibits excellent internal reflection and refraction of light, which is the hallmark of the extraordinary brilliance, sparkle, and luster of cut diamonds.In general, good thermal conductors, such as copper, are also good electri-cal conductors because of the available conduction electrons for the transfer of electrical current and heat. Surprisingly, diamond is an electrical insulator, yet exhibits high thermal conductivity. The high thermal conductivity of diamond is attributed to the high Debye temperature, that is, a high phonon frequency. It was speculated that the strong phonon frequency of diamond could be exploited to produce superconductivity; it was from this idea that the current research on superconductivity in diamond originated.It is possible to search for a new superconductor by applying the McMillan relation,Тc≈θe(?), whereλis an electron phonon interaction constant, since this relationship states that the superconducting transition temperature, Tc is proportional to the De-bye temperatureθ. Clearly, it is possible to identify many materials that ex-hibit a high Debye temperature, and thus there are many candidate materials. Among these materials is diamond, the most likely superconductor candidate with the highest Debye temperature. Unfortunately, diamond is an insulator with no charge carriers that can contribute to superconductivity; therefore, how can excess charge carriers be introduced into diamond?Although pure diamond is an insulator with a 5.5 eV band gap, when doped with impurities such as trivalent boron (B) atoms, diamond exhibits p-type con-ductivity; the boron atoms replace the carbon site and form an impurity level with an activation energy of 0.37 eV. The doping process is similar to that used with silicon semiconductors. Blue diamonds, which contain boron impurities, are beautiful, expensive, and naturally occurring p-type semiconductors. When the boron concentration is over 3 x 1020cm-3, diamond goes into the metal region and exhibits superconductivity.In this paper, firstly, we introduce the method of producing Synthetic dia-mond and the changes of structure of boron-doped diamond. Secondly, By tak-ing superconducting polycrystalline diamond films as an example, we analysed the relationship between the superconducting transition temperature and boron concentration and discussed why the superconducting transition temperature of MPCVD superconducting diamond films is higher than that of High-pressure high-temperature (HPHT) synthesized diamond. Lastly, we introduced the en-ergy band structure of boron-doped diamond and discussed the superconductivity of it. |
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