Field evaporation and field desorption from HTSC single-crystal surfaces

The problems of field evaporation (FE) and field desorption (FD) from surface of oxide high-temperature superconductors (HTSC) of 123, 2212 and 2223 type are discussed. Wide-angle atom probe, usual time-of-flight atom probe and field ionization magnet mass-spectrometer have been used in these experiments. The main purpose of the investigation was to search for effects connected with phase transition. Therefore, the experiments were carried out over a wide range of temperatures: from T of solid nitrogen to room T.

Composition of pure, contaminated and deep corroded surface and typical species of FE and FD spectra have been studied. The bond energies between some atoms (or clusters) and the surface have been estimated on the basis of experimental results and FE theory. From these estimations, and from discovering of correlated ion pairs, it was concluded that the redistribution of local bonds should be taken into consideration in this case. The increase of FE rate was observed at cryogenic temperatures. Various versions are discussed to explain these effects. Some of them are connected with phase transition.

A detailed study of FD of water protonized clusters is performed and the catalytic activity of HTSC crystal surfaces is discussed.