NEXAFS spectroscopy of crystalline and ion beam irradiated diamond surfaces

In the present work we study the sensitivity of the near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to ion-induced defects in polycrystalline diamond films. The ion bombardment of hydrogenated films is performed using 30-keV Xe+ ions at room temperature for doses ranging from 2 x 10(13) ions/cm(2), producing local point defects, to 2 x 10(15) ions/cm(2) which results in almost complete amorphization of diamond. Partial electron yield (PEY) NEXAFS technique, applied in surface and bulk-sensitive modes, using 35, 15 and 8 eV secondary electrons, respectively, reveals the formation of a defective structure and gradual deterioration of diamond in the near-surface region. From PEY NEXAFS spectra measuring 15 eV secondary electrons the position of C(ls) binding energy is precisely measured. As determined from the NEXAFS spectra, C(ls) binding energy in the implanted samples has a positive shift of 0.6-1 eV, which is indicative of transformation of diamond to disordered carbon. The high sensitivity of NEXAFS spectroscopy to point defects induced by low-dose ion implantation is reflected by a sharp reduction in the intensity of the diamond core exciton peak and by the appearance of a new spectral feature in the region, below the C(ls)-pi* resonance. Analysis of the NEXAFS spectra of ion implanted films is performed on the basis of the electronic band structure of diamond. (C) 2000 Elsevier Science S.A. All rights reserved.