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O: Fachverband Oberflächenphysik
O 76: Nanostructures at surfaces IV
O 76.1: Vortrag
Donnerstag, 29. März 2012, 16:00–16:15, MA 042
Silicon micro-tip arrays for fast-switchable cold electron sources — •Pavel Serbun1, Aliaksandr Navitski1, Benjamin Bornmann1, Stephan Mingels1, Günter Müller1, Florian Dams2, Christian Prommesberger2, and Rupert Schreiner2 — 1FB C Physics Department, University of Wuppertal, 42119, Wuppertal, Germany — 2Faculty of Microsystems Technology, University of Applied Sciences Regensburg, Germany
Silicon-based cathodes with precisely aligned field emitter arrays applicable for miniaturized electron sources were successfully fabricated. The cathode chips contain about 3x10^5 Si tips/cm^2 in a triangular array with a tip height of 1 or 2.5 um, tip radius of about 20 nm, and 20 um pitch. Amazingly homogeneous and well-aligned field emission (FE) from all tips (100% efficiency) and maximum stable currents of about 0.1 uA for p- and 0.6 uA for n-type Si were reproducibly achieved. Additional coating with a bimetallic layer (5 nm Cr and 10 nm Au) resulted in at least 5 times higher average FE current i.e. typically 3 uA but lead, however, to a 30% increase of the onset voltage. I-V characteristics of p-type Si tips exhibit the expected I-V characteristics consisting of a linear FN-like part at low field/current, a current saturation region, and finally a rapid current rise at high field due to secondary charge effects. Moreover, a high photosensitivity of the saturation current was observed which provides a unique possibility to modulate the electron current by ultra-short light pulses. Detailed FE and light-modulation results of p-type arrays of varying size and tip-number will be presented and discussed at the conference.