Interaction of K, Na, Li and Ti with silicon (111) and (100) surfaces; surface ionization and kinetics of desorption

• Published in: Surface science 1982-08, Vol.120 (1), p.103-126
• Main Authors: Greene, E.F., Keeley, J.T., Pickering, M.A.
• Format: Article
• Language: English
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(82)90277-1

Atomic beams of K, Na, Li and Tl are used to determine the work function and desorption energies for Si(111) and (100) surfaces. The (111) surface appears to go through a surface transition at ca. 1100K. Below 1000K, the (111) surface appears stable with a surface ionization work function φ + = 4.80 ± 0.05 eV. The desorption of K and Na from this surface has both a first- and second-order component with activation energies for desorption of E a1 = 3.15 ± 0.15 eV, E a2 = 2.53 ± 0.10 eV for K, and E a1 = 3.47 ± 0.15 eV, E a2 = 2.39 ± 0.13 eV for Na. The second-order part of the desorption is probably due to interactions or collisions of the atoms as they move along the surface. Above 1100 K the work function decreases by 0.03 ± 0.01 eV and the desorption of K and Na from this surface is predominantly first order with E a1 = 2.35±0.07 eV for K and E a1 = 2.45± 0.12 eV for Na. The (100) surface in the temperature range of 800 to 1550 K has φ + = 4.67 ± 0.08 eV and a first order desorption energy E a1 = 2.54 ± 0.14 eV for K. The work functions from the thermionic emission of electrons are φ c − = 4.55 ± 0.1and φ e − =4.53 ± 0.1eVfor the (111) and (100) surfaces, respectively, for T ⩾ 1000 K.