Surfaces of rare earth metals

Abstract

The review considers the impact of modern surface science techniques on understanding the properties of rare earth metal surfaces. Methods for obtaining and evaluating clean surfaces are critically assessed, and the geometrical and electronic properties of the surface are compared with those of bulk metals. Low energy electron diffraction is available on only a limited range of single crystals, but electron spectroscopy has been applied extensively to clean polycrystalline materials. The insights gained imply both a continuation of bulk-like phenomena at the surface (strong exchange and correlation of 4f electrons and of core hole-4f interactions) and intrinsic surface effects such as 4f binding energy shifts, modified surface valence and anomalous surface magnetism.

Calculations of electron inelastic mean free paths

“…It is clear from Fig. 19(b) that Z eff ¾ 9 (the value of N v given in Table 1 for Gd, Tb and Dy) when E max reaches 50 eV; the seven 4f electrons 36 in Gd contribute to the monotonic increase of Z eff in Fig. 19(b) with increasing E max until the beginning of the 4d excitations at E max D 141 eV.…”

“…As a result, an IMFP estimated from TPP-2M with N v computed only from the number of valence electrons may be an overestimate of the IMFP. 7 We recommended there that, for the rare-earth elements, N v should be computed from the sum of the number of valence electrons for the solid state, which is either two or three as discussed by Netzer and Matthew, 36 and the six 5p electrons that contribute strongly to the energy-loss function. Although the 5p electrons for the lanthanides have binding energies of 18-27 eV, 37 they have been included in the calculation of N v because of the strong 5p !…”

Hot electron lifetimes in metals probed by time-resolved two-photon photoemission

“…We suspect that surface contaminations (oxygen) account for this behavior, similar to the findings for aluminum discussed in Section 4.2. Due to the high reactivity of La [234,235] oxygen may have accumulated during the time-resolved 2PPE experiments, even though the La sample was cleaned by numerous heating and sputtering cycles prior to the measurements.…”

Low Schottky barrier height for ErSi2−x/n-Si contacts formed with a Ti cap

“…16 In the perspective of RE silicide integration, the question of the removal of the sacrificial protecting layer must be taken into account. 17 Second, Pt was found to mix with RE metals even at 300°C. However, RE silicides are easily removed in a solution containing halogen ions.…”