کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5425837 | 1395867 | 2006 | 8 صفحه PDF | دانلود رایگان |

The electron stimulated desorption (ESD) yield and energy distributions for Cs atoms from cesium layers adsorbed on germanium-covered tungsten have been measured for different Ge film thicknesses, 0.25-4.75Â ML (monolayer), as a function of electron energy and cesium coverage Î. The measurements have been carried out using a time-of-flight method and surface ionization detector. In the majority of measurements Cs is adsorbed at 300Â K. The appearance threshold for Cs atoms is about 30Â eV, which correlates well with the Ge 3d ionization energy. As the electron energy increases the Cs atom ESD yield passes through a wide maximum at an electron energy of about 120Â eV. In the Ge film thickness range from 0.5 to 2Â ML, resonant Cs atom yield peaks are observed at electron energies of 50 and 80Â eV that can be associated with W 5p and W 5s level excitations. As the cesium coverage increases the Cs atom yield passes through a smooth maximum at 1Â ML coverage. The Cs atom ESD energy distributions are bell-shaped; they shift toward higher energies with increasing cesium coverage for thin germanium films and shift toward lower energies with increasing cesium coverage for thick germanium films. The energy distributions for ESD of Cs from a 1Â ML Ge film exhibit a strong temperature dependence; at TÂ =Â 160Â K they consist of two bell-shaped curves: a narrow peak with a maximum at a kinetic energy of 0.35Â eV and a wider peak with a maximum at a kinetic energy of 0.5Â eV. The former is associated with W level excitations and the latter with a Ge 3d level excitation. These results can be interpreted in terms of the Auger stimulated desorption model.
Journal: Surface Science - Volume 600, Issue 10, 15 May 2006, Pages 2163-2170