Abstract
Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2–0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.
Highlights
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not
In this study we present results obtained for two diamond needles (Fig. 1) with different dimensions denoted DN1 and DN2 (L = 100 μm, d = 3 μm)
Field electron emission (FE) current I and voltage drops ΔV in the diamond needles as functions of time, extraction voltage V and temperature T were measured in an ultrahigh vacuum (UHV) system equipped with an electron energy analyzer (Fig. 2)
Summary
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. Even if NEA were achieved on a suitable sample, the electrical conductivity of intrinsic wide band gap diamond is too low to allow sustained emission which would need electron transport through the bulk to the emitting sites on the surface. This can be circumvented in principle by doping or by introducing defects into the diamond structure. The electron transport for a microtip cathode can be provided by the surface states in the diamond crystalline structure[10] Such emitter could keep outstanding thermal and mechanical diamond properties in defect-free bulk and, potentially, negative or low positive electron affinity on its apex. The measured FE characteristics were used to examine carrier transport mechanism in the diamond needles and reveal possibilities for their practical applications as a point source of electrons
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