NEXAFS spectroscopy of crystalline and ion beam irradiated diamond surfaces

In the present work we study the sensitivity of the near-edge X-ray absorpt ion fine structure (NEXAFS) spectroscopy to ion-induced defects in polycrys talline diamond films. The ion bombardment of hydrogenated films is perform ed 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) whi ch results in almost complete amorphization of diamond. Partial electron yi eld (PEY) NEXAFS technique, applied in surface and bulk-sensitive modes, us ing 35, 15 and 8 eV secondary electrons, respectively, reveals the formatio n of a defective structure and gradual deterioration of diamond in the near -surface region. From PEY NEXAFS spectra measuring 15 eV secondary electron s 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 dia mond to disordered carbon. The high sensitivity of NEXAFS spectroscopy to p oint defects induced by low-dose ion implantation is reflected by a sharp r eduction in the intensity of the diamond core exciton peak and by the appea rance of a new spectral feature in the region, below the C(ls)-pi* resonanc e. Analysis of the NEXAFS spectra of ion implanted films is performed on th e basis of the electronic band structure of diamond. (C) 2000 Elsevier Scie nce S.A. All rights reserved.