Sensitivity of near-edge x-ray absorption fine structure spectroscopy to ion beam damage in diamond films

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 the diamond surface. Auger electron spectroscopy measurements are not sensitive to the modifications induced by the lowest implantation dose. Whereas partial electron yield (PEY) NEXAFS measurements, 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 measured using 15 eV secondary electrons, the position of C(1s) binding energy is measured. The x-ray photoelectron spectra of the samples were measured using an incident photon energy of 450 eV. It is found that the C(1s) 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 the low dose ion implantation was 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 pre-edge region, below the C(1s)-pi* transition. Analysis of the NEXAFS spectra of ion implanted films is performed on the basis of the electronic structure of diamond. (C) 1999 American Institute of Physics. [S0021-8979(99)02220-3].