Translation-related domain boundaries form to relieve strain in a thin alumina film on NiAl (110)

McCarty, K. F.; Pierce, J. P.; Carter, C. Barry

doi:10.1063/1.2191739

Cited by 19 publications

(16 citation statements)

References 21 publications

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“…This wavelike topogra- phy of the surface unit cells is in fact typical for the film 26 and related to stress and commensurability. 27,28 As observed by FM-DFM before, 18 the crests have a distance of 9 Å but the full repeat unit has a length of 18 Å, i.e., that of an oxide unit cell. Each two of the protruding rows differ slightly in apparent structure, height, and contrast making them inequivalent as shown in Fig.…”

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confidence: 86%

Atomically resolved force microscopy images of complex surface unit cells: Ultrathin alumina film on NiAl(110)

et al. 2008

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In this Brief Report we present atomically resolved images of the ultrathin alumina film on NiAl͑110͒. For the first time detailed images of the complex microstructure for both reflection domains have been obtained by frequency modulation dynamic force microscopy using a very stable, custom built, dual mode scanning force and scanning tunneling microscope. Measurements have been performed under ultrahigh vacuum conditions at 5 K with a quartz tuning fork as a force sensor. The high spatial resolution allows to derive 28 atomic positions in real space in the surface unit cell by simple graphical analysis. This has been successful without application of filtering or correlation methods, emphasizing the potential of this force microscopy method on complex oxide surfaces. With respect to topographic height even quantitative agreement with theory could be achieved, here shown for selected structural elements within the unit cell. Furthermore, deeper insight into a wavelike morphological feature could be obtained. Consistency with a published density-functional theory model and connections to other data from the literature are discussed.Ultrathin alumina overlayers on certain low index faces of metal or alloy single crystals, originally developed to mimic properties of bulk aluminum oxide in surface studies, where charging hampered analysis with electron techniques, have long become a research field in their own right. This is still due to the full set of electron analysis techniques applied to them, but besides this the thin films can be linked to technological problems regarding interfaces and insulating interlayers in miniaturized electronic and magnetic devices as well as protective coatings and heterogeneous catalysis. Of academic interest are fundamental physical and chemical properties of these wide band-gap insulators, in particular the relation between structure and functions such as adsorption as well as transport and interface properties. One example for such a film is the 5 Å thin ordered alumina overlayer which can be grown by selective oxidation on ͑110͒ surfaces ͑CsCl structure͒ of the ordered intermetallic NiAl. 1 Despite its large band gap of about 6.7 eV 2 it allows electron flow due to its limited thickness. Thorough low-energy electron diffraction ͑LEED͒, photoemission spectroscopy, Auger electron spectroscopy, electron-energy-loss spectroscopy, angle-resolved ultraviolet photoelectron spectroscopy, ion scattering spectroscopy, and scanning tunneling microscopy ͑STM͒ and scanning tunneling spectroscopy studies 1-10 have been performed in the framework of model catalysis over the last two decades. Together with a recent STM and density-functional theory ͑DFT͒ study this led to an atomistic model of the film that matches many of the experimental findings. 11 The accumulated data on this film in the literature give so far evidence for a two double-layer structure free of nickel with alternating aluminum and oxygen layers. It is oxygen terminated toward the vacuum with the next lower aluminum layer bein...

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confidence: 86%

Atomically resolved force microscopy images of complex surface unit cells: Ultrathin alumina film on NiAl(110)

et al. 2008

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“…This means a very dynamic interaction between the substrate and the surface during the film preparation is confirmed. It may be assumed that the substrate step edges restructure during the film crystallization at high temperature, 12 which is the second step during film preparation. Due to the increase of the total length of the individual step edges which accompanies the restructuring, it might be that step edges are not energetically unfavorable.…”

Section: F Interpretation: the Structure Of The Step Edgementioning

confidence: 99%

“…7,8 In the aluminum oxide film, linear dislocations between two domains of the same orientations are known as antiphase domain boundaries ͑APDBs͒. [9][10][11][12] Other frequent structural defects are step edges. In this work we investigate the nature of the step edges in the aluminum oxide by means of atomic force and scanning tunneling microscopy.…”

Section: Introductionmentioning

confidence: 99%

Structure and electronic properties of step edges in the aluminum oxide film on NiAl(110)

et al. 2010

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Thin film aluminum oxide has been investigated at step edges of the NiAl͑110͒ substrate by means of low temperature scanning tunneling microscopy and atomic force microscopy. A preference of the step edges for certain orientations and a restructuring of the substrate step edges during the oxidation were shown. The surface unit cell of the oxide film at the step edge is similarly extended as at the antiphase domain boundaries ͑APDBs͒, which are oxygen deficient defects with F 2+ -like centers. The local electronic structure and the local work function at the step edges resemble that of the APDBs. Therefore, an oxide film structure at the step edge which is similar to the APDB as well as a carpetlike coverage of the substrate steps is concluded. This means there are F 2+ -like centers at step edges.

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“…When NiAl͑110͒ is exposed to small O 2 doses at 800-1350 K, discrete structures of two different aluminum-oxide phases form on the surface. 10,11 One phase is the well-studied Al 10 O 13 phase, 6,9 whose complex structure is distinct from all bulk forms of alumina. 6 This surface oxide has two O layers, with an Al layer in between, and another Al layer next to the substrate.…”

Section: Introductionmentioning

confidence: 99%

Stability of ultrathin alumina layers on NiAl(110)

et al. 2008

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By observing with low-energy electron microscopy whether individual alumina islands grow or shrink for different substrate temperatures and O 2 pressures, we determine the stability of thin oxide layers on the NiAl͑110͒ surface. At each temperature, a well-defined O 2 pressure exists where islands do not change in size. Yet we conclude that the oxide cannot be in thermodynamic equilibrium with O 2 gas and NiAl bulk, because the O 2 pressures needed to attain this state are 20 orders of magnitude higher than expected. We discuss what kinetic processes can lead to the observed steady state, where the O 2 pressure needed for stability differs greatly from thermodynamic predictions.

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Translation-related domain boundaries form to relieve strain in a thin alumina film on NiAl (110)

Cited by 19 publications

References 21 publications

Atomically resolved force microscopy images of complex surface unit cells: Ultrathin alumina film on NiAl(110)

Atomically resolved force microscopy images of complex surface unit cells: Ultrathin alumina film on NiAl(110)

Structure and electronic properties of step edges in the aluminum oxide film on NiAl(110)

Stability of ultrathin alumina layers on NiAl(110)

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