Surface states and resonances in field emission from low-index facets of clean tungsten |
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Authors: | Z A Ibrahim and M J G Lee |
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Institution: | Department of Physics, University of Toronto, 60 St George St., Toronto, Ont., Canada M5S 1A7 |
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Abstract: | The energies, widths, and shapes of features observed in the total energy distributions in field emission from W(1 0 0) and W(1 1 1) are compared with the results of a full-potential LAPW calculation of the surface density of states based on a supercell model of the crystal structure at the metal–vacuum interface. The Swanson hump on W(1 0 0) is attributed to two bands of surface states and surface resonances of dz2 symmetry that are highly localised at
, and a second peak observed at lower energy is attributed to a band of surface resonances, also of dz2 symmetry, centred at
from
along
. The energy scale of the calculated total energy distribution is compressed by about 20% relative to the experimental data. The present calculation yields strong evidence that the broad asymmetric peak observed on W(1 1 1) is due to emission from a band of surface resonances. Further calculations for W(1 1 1) are proposed both to test the accuracy of the band model and to take into account the velocity factor that enters in a calculation of the emission current. |
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Keywords: | Field emission Spin–orbit interaction Surface states Surface resonances Tungsten |
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