Threshold of ion-induced kinetic electron emission from a clean metal surface

Subsurface excitations in a metal

“…This measurement scheme and representation of the yield are sensitive to the low energy subsurface kinetic excitations that are generated within the metal layer. Prior external measurements of electron emission in this velocity regime 9 indicate a saturated or constant PE signal which should be present within our measured I f values. However, as our measurement was not designed to collect or quantify these external excitations, we make no correction for them in our calculations of ⌫ ie and note that a constant PE contribution would represent a rigid shift in the yield and would not alter the physically relevant KE trend that is observed and discussed below.…”

“…9,10,[17][18][19][20] For our measurements we can rule out the first two mechanisms as the incident energies employed are too low for close-collision-induced promotion and the projectiles are too simple ͑low Z͒ for multielectron effects to arise. Additionally, no Auger transitions analogous to those seen in previous systems exist for our projectiletarget combinations.…”

“…Therefore, the few experimental studies performed in this energy regime have been limited to measurements outside a target where emitted excitations ͑electrons͒ can be collected. 9,10 In particular, the work of Lakits et al used the detection of externally emitted electrons to provide precise statistical information on the yield of electrons emitted per incident ion. 9 Those data showed clear differences in the dependence of the yield on ion velocity, and distinct regimes for the yield were found that could be characterized by either potential emission ͑PE͒ or kinetic emission ͑KE͒.…”

“…9,10 In particular, the work of Lakits et al used the detection of externally emitted electrons to provide precise statistical information on the yield of electrons emitted per incident ion. 9 Those data showed clear differences in the dependence of the yield on ion velocity, and distinct regimes for the yield were found that could be characterized by either potential emission ͑PE͒ or kinetic emission ͑KE͒. For example, in the limit of low velocities, species with ionization energies significantly greater than the surface work function gave a saturated PE yield that corresponded well with values specified by the depth of the ion's ionization level.…”

Observation of self-sputtering in energetic condensation of metal ions

“…KE has an energy threshold and it is safe to neglect KE for the energy range in the present experiment. 10 Hence, Eq. (5) can be simplified to…”