Laser-induced Field Emission from Tungsten Tip: Optical Control of Emission Sites and Emission Process

Field-emission patterns from a clean tungsten tip apex induced by femtosecond laser pulses have been investigated. Strongly asymmetric field-emission intensity distributions are observed depending on three parameters: (i) the polarization of the light, (ii) the azimuthal, and (iii) the polar orientation of the tip apex relative to the laser incidence direction. In effect, we have realized an ultrafast pulsed fieldemission source with site selectivity of a few tens of nanometers. Simulations of local fields on the tip apex and of electron emission patterns based on photoexcited nonequilibrium electron distributions explain our observations quantitatively. Electron emission processes are found to depend on laser power and tip voltage. At relatively low laser power and high tip voltage, field-emission after two-photon photoexcitation is the dominant process. At relatively low laser power and low tip voltage, photoemission processes are dominant. As the laser power increases, photoemission from the tip shank becomes noticeable. © 2010 The American Physical Society DOI: https://doi.org/10.1103/PhysRevB.81.115429 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-45677 Accepted Version Originally published at: Yanagisawa, H; Hafner, C; Doná, P; Klöckner, M; Leuenberger, D; Greber, T; Osterwalder, J; Hengsberger, M (2010). Laser-induced field emission from a tungsten tip: Optical control of emission sites and the emission process. Physical Review. B, Condensed Matter and Materials Physics, 81(11):115429. DOI: https://doi.org/10.1103/PhysRevB.81.115429 ar X iv :1 00 1. 53 75 v1 [ co nd -m at .m es -h al l] 2 9 Ja n 20 10 Laser-induced Field Emission from Tungsten Tip: Optical Control of Emission Sites and Emission Process Hirofumi Yanagisawa, Christian Hafner, Patrick Doná, Martin Klöckner, Dominik Leuenberger, Thomas Greber, Jürg Osterwalder, and Matthias Hengsberger Physik Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland Laboratory for Electromagnetic Fields and Microwave Electronics, ETH Zürich, Gloriastrasse 35, CH-8092 Zürich, Swizerland (Dated: February 1, 2010) Field-emission patterns from a clean tungsten tip apex induced by femtosecond laser pulses have been investigated. Strongly asymmetric field-emission intensity distributions are observed depending on three parameters: (1) the polarization of the light, (2) the azimuthal and (3) the polar orientation of the tip apex relative to the laser incidence direction. In effect, we have realized an ultrafast pulsed field-emission source with site selectivity of a few tens of nanometers. Simulations of local fields on the tip apex and of electron emission patterns based on photo-excited nonequilibrium electron distributions explain our observations quantitatively. Electron emission processes are found to depend on laser power and tip voltage. At relatively low laser power and high tip voltage, field-emission after two-photon photo-excitation is the dominant process. At relatively low laser power and low tip voltage, photoemission processes are dominant. As the laser power increases, photoemission from the tip shank becomes noticeable. PACS numbers: 79.70.+q, 73.20.Mf, 78.47.J-, 78.67.Bf