Insights into the (1×1)-to-(2×1) phase transition of the α-Fe2O3() surface using EELS, LEED and water TPD

摘要: Abstract The (1×1)-to-(2×1) surface reconstruction of α-Fe2O3(0 1 2) (also known as the R-cut or ( 0 1 2 ) surface) was examined using low energy electron diffraction (LEED), loss spectroscopy (EELS) and temperature programmed desorption (TPD). (1×1) is generated by heating in 5×10−7 Torr O2 at 750 K, followed cooling O2. prepared this manner exhibits a p(1×1) LEED pattern consistent with bulk-terminated structure. EELS analysis shows eV bandgap that hematite little no evidence for Fe2+ sites. In contrast, (2×1) observed after annealing UHV 950 K. spectrum prominent feature about eV, which K does not possess termination film Fe3O4, has been reported literature (0 0 1) surface, since phonon remains α-Fe2O3. Both detect onset process to be 700 whereas water TPD, distinctively different features those two phases, detects occur 600 appears highly nucleated based on observations spots grow during without streaking coverage-dependent TPD half (1×1)–half simultaneous filling both binding Given accompanied reduction Fe3+ sites sites, preference growth existing domains over initiation new implies kinetics (i.e., formation) are more favorable vicinity other than regions rich Fe3+.