Ab Initio Calculation of Field Emission from Metal Surfaces with Atomic
PHYSICAL REVIEW B 100, 165421 (2019) Ab initio calculation of field emission from metal surfaces with atomic-scale defects H. Toijala,1 K. Eimre ,2 A. Kyritsakis ,1,* V. Zadin,2 and F. Djurabekova1,3 1Helsinki Institute of Physics and Department of Physics, University of Helsinki, PO Box 43 (Pietari Kalmin katu 2), FIN-00014 Helsinki, Finland 2Intelligent Materials and Systems Lab, Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia 3National Research Nuclear University MEPhI, Kashirskoye sh. 31, 115409 Moscow, Russia (Received 31 July 2019; revised manuscript received 12 September 2019; published 25 October 2019) In this work we combine density functional theory and quantum transport calculations to study the influence of atomic-scale defects on the work function and field emission characteristics of metal surfaces. We develop a general methodology for the calculation of the field emitted current density from nanofeatured surfaces, which is then used to study specific defects on a Cu(111) surface. Our results show that the inclusion of a defect can significantly locally enhance the field emitted current density. However, this increase is attributed solely to the decrease of the work function due to the defect, with the effective field enhancement being minute. Finally, the Fowler-Nordheim equation is found to be valid when the modified value for the work function is used, with only an approximately constant factor separating the computed currents from those predicted by the Fowler-Nordheim equation. DOI: 10.1103/PhysRevB.100.165421 I. INTRODUCTION have never been observed on the studied surfaces, even when high-resolution electron microscopy is utilized [26].
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