The surface metal-insulator phase transition of MBE (100) magnetite thin film

The (100) surface of the magnetite thin film has been investigated by low-e nergy ion scattering in the small-angle geometry and in the temperature ran ge of 85-300 K. Thin film of Fe3O4 was grown on MgO (100) substrate by the molecular beam epitaxy (MBE) and characterized by low-energy electron diffr action, conversion electron Mossbauer spectroscopy and scanning tunneling m icroscopy. The scattered ion spectra have shown two maxima, in which the in tensity of the maximum at low-energy side increases enormously with increas ing bombarding energy values. The temperature dependence of scattering ion yield, R+(T), for 5.0, 5.5 and 6.0 keV Ne+ bombardments exhibit two minima, around 110 K and around 125 K, related to the metal-insulator phase transi tion of this material. The high-temperature minimum was found to disappear at 6.5 keV Ne+ bombardment, indicating the ion velocity dependence of the c haracter of the R+(T) curve, which has been observed previously for the MBE (111) magnetite thin film. This phenomenon has been explained in the frame work of the resonant and Auger neutralization. (C) 2001 Elsevier Science Lt d. All Iights reserved.