The Influence of Ion Irradiation on the Absolute Quantum Photoyield of Diamond Films Studied by Electron Spectroscopy and H+ Photodesorption
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/cm2. 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.