THE INFLUENCE OF ION IRRADIATION ON THE ABSOLUTE QUANTUM PHOTOYIELD OF DIAMOND FILMS STUDIED BY ELECTRON SPECTROSCOPY AND H+ PHOTODESORPTION

Abstract

In this study we report on absolute quantum photoyield (QPY) measurements from well-defined defective diamond surfaces in the 140–200 nm spectral range. The effect of defects in polycrystalline diamond films on their photoemission properties is studied by intentionally introducing damage using room temperature 30 keV Xe + ion bombardment to doses ranging from 2×1013 to 2×1015 ions/cm 2. Ion bombardment results in a drastic degradation of the QPY, to less than 1% at 140 nm, even at the lowest implantation dose compared to ~11.5% measured for the unimplanted diamond film. Analysis of the ion-damaged diamond films is performed by photon-stimulated ion desorption (PSID) measurements of H +, high resolution C(KLL) Auger electron spectroscopy and X-ray photoelectron spectroscopy. These measurements reveal that the decay in photoemission is due to the gradual formation of nondiamond carbon in the near-surface region. This damage leads to a change of the electron affinity from negative to positive, as determined by secondary electron emission measurements. PSID measurements reveal that the ion-bombarded diamond films remain hydrogen-terminated. MW hydrogen plasma treatment results in complete regeneration of the photoemission properties for diamond films implanted to Xe + doses of up to 2×1014 cm -2; only partial recovery was obtained for films irradiated with a higher ion dose.