Samarium-atom adsorption and desorption on iridium

Abstract

The adsorption and condensation of samarium on Ir(111) are investigated by thermionic emission spectroscopy and thermal desorption spectroscopy (TDS). During Sm deposition, the work function is found to fall monotonically from 5.8 to 2.7 eV and then to rise slowly to a plateau at 2.9 eV, for any substrate temperature from the range 700–1200 K. The optimal Sm coverage is estimated at 0.51 ± 0.03. The activation energy E⁺ and the preexponential factor C for Sm-ion desorption and those for Sm-atom desorption, E₀ and D, respectively, are determined in the temperature range 1800–2050 K and at a coverage small enough not to alter the work function of the iridium. Their values are as follows: E⁺ = 5.72 ± 0.10 eV, E⁺ = 5.72 ± 0.10 eV, D ∼ 1 × 10¹³s⁻¹, and C ∼ 1.3 × 10¹³ s⁻¹. Several Sm phases are detected in each TDS peak.