Electron Field Emission of Silicon-Doped Diamond-Like Carbon Thin Films

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In this work we demonstrate that the field emission characteristics of disordered Si-doped diamond-like carbon (DLC) thin films depend not only on properties of the conductive clustered sp2 phase and the insulating sp3 matrix (or sp2/sp3 ratio) but also on the presence of Si–Hn and C–Hn species in the film. The presence of such species reduces the hardness of the film and simultaneously enhances the field emission performance. A turn on electric field ($E_{\text{TOF}}$) of 6.76 V/μm produced a field emission current density of ${\sim}0.2$ mA/cm2, when an electric field of ${\sim}20$ V/μm was applied. The Fowler–Nordheim (FN) tunneling model is appropriate to explain the field emission mechanism only within limited range of the current density. However, it is found that there is an apparent crossover between space charge limited current (SCLC) and the Frenkel effect due to impurities incorporated during the fabrication of Si-DLC films. This combined effect (SCLC + Frenkel) allows for the emission of electrons from the top of the reduced barriers due to the formation of comparatively soft DLC:Si films. The emission also occurs through tunneling from one conductive cluster (sp2 C=C) to another separated by an insulating matrix (sp3 C–C) after reducing the effective depth of a trap on application of high electric field.
2010-11-25