The effect of low energy ion-beam induced amorphization on the thermionic electron emission properties of polycrystalline diamond films

The effect of low energy irradiation on the Thermionic Electron Emission (TEE) properties of polycrystalline diamond (Poly-Di) film is studied by intentionally introducing damage using room temperature, 3 keV Ar-ion bombardment at dose of ~ 4 × 1017 ions/cm2. The ion bombardment results in a strong deterioration of the TEE properties. The decrease in the TEE is associated with a change of the diamond surface and near-surface region electronic structure caused by formation of a near-surface amorphous carbon layer, as supported by electron energy loss (EEL) spectrum derived from X-ray photoelectron spectroscopy (XPS) measurements of the damaged surface, and by high resolution electron energy loss spectroscopy (HR-EELS) results. In situ hydrogenation of the damaged diamond film results in an insignificant improvement of the TEE properties, indicating the important role of the near-surface region, which include the grain boundaries, the diamond grains, and the diamond grain surfaces, on the TEE properties of Poly-Di films.

► Continuous Poly-Di films were grown on B-doped Si substrate by HF-CVD.
► We report on the suppression of the TEE properties of ion-irradiated Poly-Di films.
► TEE properties of ion-irradiated Poly-Di films cannot be recovered.
► The near-surface region has important role on the TEE process from Poly-Di films.