Electron field emission from a gold tip under laser irradiation at the plasmon-resonant wavelength

Electron field emission properties of a sharp gold tip under continuous wave laser irradiation at the plasmon-resonant wavelength are investigated. A gold-coated tungsten emitter with a tip radius of 100 nm is used. The plasmon-resonant wavelength of the tip obtained by a finite-difference time-domain calculation is around 530 nm. Thus, I-V characteristics of the tip under laser irradiations at 442, 532, and 633 nm were measured. The intensity of 10 mW, 532 nm irradiation at the focal point was 13.9 kW/cm(2). TE-polarized 532 nm irradiation shows the maximum current enhancement despite its smaller photon energy and intensity compared with the irradiation at 442 nm. The current enhancement factor ranged from 13.7 to 217. From the energy dispersive x-ray analysis, these results can be attributed to plasmon resonance. The possible mechanisms of plasmon-resonant current enhancement are considered to be the effective photoassisted field emission and thermal field emission. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3523103]