X-ray scattering study of the stoichiometric recovery of the α-Fe2O3(0001) surface

Environmentally dependent stability of low-index hematite surfaces

“…The structures and stability of nonhydroxylated surfaces have been investigated by a vast number of studies in the past. The stoichiometric clean termination has been consistently proposed to be thermodynamically stable with low-pressure background oxygen [4] and may co-exist with magnetite (1 1 1) or wustite (1 1 1) in minute concentrations of oxygen [26,30,40,[82][83][84]. Hematite (0 0 1) surface is coherent with magnetite (1 1 1) and wustite (1 1 1) surfaces.…”

“…As the present study focuses on thermodynamics of the surfaces, we will not go in details about the oxidation states of individual surfaces, but direct Readers to Refs. [30,82,53,26].…”

“…Whereas in anhydrous environments, it appears that the (0 0 1) surface displays several types of terminations depending on the partial pressure of oxygen and temperature [28,38], including the stoichiometric Fe-termination [37,36] and in coexistence with Otermination [39,30,26,31,29,34,32], and exclusively O-terminations [28]. Because of the low P H 2 O to hydroxylate the hematite (0 0 1) surface [16,41], the surface hydroxyl groups may form spontaneously during sample transfer or characterization.…”

The Fe3O4 origin of the “Biphase” reconstruction on α-Fe2O3(0001)

“…Thus a Fe 1Àx O(1 1 1)/a-Fe 2 O 3 (0 0 0 1) interface was assumed. Barbieri to scattering across an interface between Fe 2 O 3 and its reduction products is the study by Kim et al [22]. There it was found that the surface of a post-sputtered sample was non-stoichiometric, but upon annealing at low temperatures and high oxygen pressure the outer-most surface recovered to a-Fe 2 O 3 while a sub-surface region remained as remnant Fe 3 O 4 .…”

“…The (0 0 0 1) surface of a-Fe 2 O 3 has been studied extensively, however the results [9][10][11][12][13][14][15][16][17][18][19][20][21][22] are often contradictory. For example, several groups have observed the presence of hexagonally symmetric satellite spots surrounding the {1 1 0}-type spots in a LEED pattern of the (0 0 0 1) surface following annealing treatment in vacuum.…”