Synthesis of n-type semiconducting diamond films in acetylene flame with nitrogen doping

• Published in: Proceedings of the Combustion Institute 2017, Vol.36 (3), p.4409-4417
• Main Authors: Okumura, Yukihiko, Kanayama, Kouichi, Nishiguchi, Hiroaki
• Format: Article
• Language: English
• Subjects: Doping; Fabrication technology; Novel combustion concept; Semiconducting property; Synthesis
• ISSN: 1540-7489; 1873-2704
• DOI: 10.1016/j.proci.2016.06.158

The purpose of this research is to fabricate an n-type semiconductor through a combustion flame with addition of nitrogen and to determine the optimum conditions for the synthesis. Although p-type diamond semiconductors, in which holes carry positive charges, can be fabricated at present, methods for fabricating n-type diamond semiconductors have not yet been established to such an extent as to yield substantial results. We have shown that nitrogen atoms form covalent bonds with carbon atoms, which have sp3 hybrid orbitals in the films and the synthesized diamond doped with nitrogen exhibits the electronic characteristics of an n-type semiconductor at low temperature range (423–573K), and carbon atoms in the synthesized film have sp3 hybrid orbitals. In addition, we have evaluated the semiconducting properties of diamond films. In the intrinsic semiconductor region, the logarithmic plot of the volume resistivity of the nitrogen-doped diamond films increases almost linearly with decreasing temperature. The volume resistivity of 1.0%-nitrogen-doped synthetic diamond film is shown to be lower than that of 0.5%-nitrogen-doped synthetic diamond film. The optimum synthesis condition for these films for semiconductor applications corresponds to equivalence ratio of 2.55 and nitrogen addition rate of less than 1.0%. Under these conditions the synthesis facilitates the doping of nitrogen and suppresses amorphous carbon generation in the diamond film.