Metal-insulator transition in boron-ion implanted type IIa diamond.

["Metal-insulator transitions.", "Transition metals.", "Ion implantation."]

Tshepe, Tshakane

University of the Witwatersrand

Others  :  http://wiredspace.wits.ac.za/bitstream/10539/26301/1/Tshepe%2c%20Tshakane%2c%202000.pdf

瑞士|英语

来源: University of the Witwatersrand

【 摘 要 】

High purity natural type Il a diamond specimens were used in this study. Conductinglayers in the surfaces of these diamonds were generated using low-ion dose multipleimplantation-annealing steps. The implantation energies and the ion-doses were spreadevenly to intermix the point-defects, thereby increasing the probability of interstitialvacancyrecombinations and promoting dopant-interstitial-vacancy combination resultingin activated dopant sites in the implanted layers. The process used to prepare our samplesis known as cold-implantation-rapid-annealing (CIRA). Carbon-ion and boron-ionimplantation was used to prepare the diamond specimens, and de-conductivity measurementsin the temperature range of 1.5-300 K were made following each CIRA sequence.An electrical conductivity crossover from the Mott variable range hopping (VRH)to the Efros-Shklovskii VRH conduction was observed when the temperature of insulatingsamples was lowered. The conductivity crossover temperature Tcross decreases withincreasing concentration of the boron-ion dose in the implanted layers, indicating the narrowingof the Coulomb gap in the single-particle density of states near the Fermi energy. (Abbreviation abstract)