Analysis of ion implanted diamond

Abstract

Ion implantation allows controlled introduction of impurities into diamond. A basic problem is to determine if the implanted layers are dominated by substitutional doping or radiation damage effects. Optical and electrical measurements on the implanted diamonds revealed (1) a degradation of the band-gap and sample coloration, (2) no optical absorption levels which would be characteristic of hydrogenic ionization levels, (3) resistivity activation energies of 0.2 to 0.3 eV independent of the ion specie, and (4) no measurable Hall Effect. Phosphorous implanted layers in diamond were analyzed by means of the channeling technique. It was shown that (1) the diamond retained the implanted phosphorous atoms during a vacuum anneal at 950°C which restored crystalline order, (2) the implanted phosphorous atoms did not assume either substitutional or tetrahedral interstitial sites, (3) the measured projected range for 70 keV phosphorous in diamond of 450 ± 115 Å was consistent with theoretical range calculations and (4) a stable monolayer of oxygen atoms (5.5 × 10¹⁵/cm²) exists on the {111} surface of implanted and annealed diamond. The results of the crystal analysis show that these electrical and optical properties are dominated by radiation damage and not substitutional doping mechanisms.