Structure ofO/Fe(001)-p(1×1)studied by surface x-ray diffraction

Abstract

The geometric structure of O / Fe͑001͒-p͑1 ϫ 1͒ is studied by surface x-ray diffraction ͑SXRD͒. After dosing of about 4 L ͑1 L=10 −6 Torr s͒ of oxygen at room temperature we find approximately one monolayer ͑ML͒ of oxygen in an FeO-like structure forming two layer thick islands covering about 40% of a roughened Fe͑001͒ surface. Subsequent annealing up to 500°C results in surface flattening leading to a highly ordered structure. Very precise SXRD data reveal the presence of 1 ML of oxygen atoms located in fourfold hollow sites at d ͑O-Fe͒ = 0.48Ϯ 0.08 Å above the first Fe layer. The first Fe-Fe-interlayer spacing is expanded to d 12 = 1.66Ϯ 0.02 Å corresponding to an increase of 16% relative to the bulk spacing ͑1.43 Å͒. Density-functional calculations confirm our findings and indicate a strong dependence of the ͑local͒ layer expansion on the oxygen coverage. Our results are important for understanding the surface magnetic properties of the O / Fe͑001͒-p͑1 ϫ 1͒ surface in general.

Self-organized chromium oxide monolayers on Fe(001)

“…Indeed, the layer of O atoms protrudes over the Cr one by d O−Cr = 26% [here and in the following interlayer distances are given in terms of percentages of the one of bulk Fe(001), i.e., d = 100% corresponds to 1.43Å]. One further notices a considerable expansion of the Cr-Fe distance, (d Cr−Fe ), similarly to the case of 1 ML of oxygen deposited on either pure Fe(001) 30 or Cr(001). 59 More specifically, we found d Cr−Fe = 125%.…”

“…29 The well-ordered and defect-free Fe(001)-p(1 × 1)O surface is an ideal template to implement this strategy. [30][31][32][33][34][35][36] The surface is characterized by one oxygen atom per surface unit cell, which can be used as a reservoir for the stabilization of two-dimensional transition metal oxides. Furthermore, the atomic structure of the Fe(001)-p(1 × 1)O surface has been suggested to be similar to an ultrathin rocksalt-type FeO film.…”

Oxygen adsorption on Fe(110) surface revisited

“…Investigations of the initial stages of the interaction of oxygen with an Fe(100) surface have shown [24,25] that oxygen atoms adsorb in the fourfold coordinated hollow sites on Fe(100). These findings were confirmed by density-functional calculations [4,25]. On the Fe(110) surface, a sequence of well ordered structures has been identified.…”

Effect of mesoscopic misfit on growth, morphology, electronic properties and magnetism of nanostructures at metallic surfaces

“…Moreover, the adsorption system O/Fe(001) is widely investigated due to its intriguing magnetic properties. Already in 1985 Huang et al [173] discussed the correlation between the oxygen induced expansion of the top iron interlayer spacing ðΔd 12 =d 12 % 16%Þ [46,[174][175][176][177] with the enhancement of the surface iron magnetic moment. In the following years experimental and theoretical studies followed focusing on the enhanced magnetic moment and the increased exchange splitting [178][179][180][181][182], also aiming to employ oxygen covered Fe(001) as a spin analyzer.…”

“…An ordered structure of oxygen on Fe(001) is easily prepared by dosing several Langmuirs ðL; 1L ¼ 10 À 6 Torr s ¼ 1:33 Â 10 À 6 mbar sÞ of oxygen on the atomically clean iron surface [184] followed by annealing up to 500 1C [174,177,182]. Subsequent iron deposition follows the layer-by-layer growth mode calibrated by the oscillatory intensity variation of SXRD reflections collected at the anti-phase position along a CTR [177,181].…”