Reflection of slow electrons from the (110) face of a tungsten crystal

Abstract

Secondary-electron emission from the (110) face of tungsten was studied at low primaryelectron energies (1–30 eV). The electrons reflected from the target surface were distinguished by analyzing the retardation curves of the secondary particles found in retardation in a spherical capacitor. The reflection coefficient R for an electron energy of about 1 eV is 0.08; it increases with increasing energy, reaching a maximum (0.34) at 3.3 eV; then it decreases; passing through a low maximum near 13 eV. Contamination of the target surface shifts the maximum by 0.7 eV and reduces the maximum reflection coefficient to 0.22. The total secondary-emission yield σ at the clean surface also reaches a maximum at 3.3 eV. Above 13 eV, σ increases, reaching a value of 0.5 at 30 eV. The σ value for a contaminated target is lower than that for a clean target. On a clean target the yield corresponding to true secondaries and inelastically reflected electrons remains at 0.1 for primary energies below 5 eV (down to 1 eV), while the value of this yield for a contaminated surface is nearly 0 for a primary energy of 1 eV.