| AVS 63rd International Symposium & Exhibition | |
| Manufacturing Science and Technology | Monday Sessions |
| Session MS-MoA |
| Session: | pb |
| Presenter: | Delroy Green, Howard University |
| Authors: | D.E. Green, Howard University G.L. Harris, Howard University R.D. Vispute, Bluewave Semiconductor Inc. |
| Correspondent: | Click to Email |
Diamond has a wide bandgap of 5.47 eV at room temperature and is the hardest known naturally occurring material with a Knoop hardness of 10,400 kg/mm2 or 10 on the Mohs scale. Due to the structure of the covalent bonding of its carbon atoms, diamond is extremely strong having each carbon bonded to four neighboring carbon atoms. Although diamond is hard, its toughness, when compared to most engineering materials, is poor. However, because of its hardness, it is an efficient cutting and drilling tool. With the exception of naturally occurring blue diamonds, which are semiconductors, diamond is a good electrical insulator. However, unlike most insulators, diamond has the highest thermal conductivity of 22 W/cm-K among naturally occurring materials. Although diamond is a good electrical insulator, it also shows semiconducting properties when doped with impurities. When diamond is heavily doped with boron the resulting material possess excess electron holes and as such it is classified as a p-type material. If excess boron doping is achieved, then the resulting material is found to behave like a superconductor at very low temperatures. In this superconducting state, the doped diamond conducts electricity.
A series of boron-doped diamond films were grown by hot filament chemical vapor deposition (HFCVD) and tested to determine the optimum technique for doping diamond with boron for superconductivity. The first technique involved the insertion of boron powder (B2O3) around the sample holder to dope seeded poly and nano diamond during growth. The second technique involves doping with diborane gas (B2O6).
Various processing parameters were optimized for diamond quality, structure, morphology, and doping. A combined analysis of scanning electron microscope, Raman mapping and Hall measurements at various temperatures were conducted to ascertain the superconductive nature of the material. Preliminary results of the boron solid source doping on diamond show a superconductive transition temperature of 2.3 oKelvin at a doping concentration of
2.3 x 1020 cm-3.
This research is conducted under research grants CIQM NSF DMR# 1231319 and PREM NSF DMR# 0611595