Diamond and related materials vol:8 issue:8-9 pages:1480-1484
Constant photocurrent method (CPM), electron paramagnetic resonance (EPR), and infra-red optical absorption (FTIR) techniques are used to study characteristic defects in the gap of free-standing optical-quality CVD diamond. It is shown that the gap density of states (DOS) is very sensitive to oxidation, hydrogenation and annealing treatments. The room-temperature (RT) EPR and CPM measurements reveal a well-defined single substitutional nitrogen defect (P1). The photoionization energy of this defect is E-i = 2.2 eV. The presence of another defect state, denoted previously as D1 (E-i = 1.2 eV) is discussed. This (D1) defect level is stable up to high annealing temperatures. The changes observed in the EPR spectra after oxidation/hydrogenation are discussed. IR absorption in the CH-stretch band and in one-phonon absorption regions is investigated. (C) 1999 Elsevier Science S.A. All rights reserved.