Strain relief through stair-rod dislocations in ultrathin epitaxial metal films: Defect geometry and energetics

Klein, Andreas; Meyer, Wolfgang; Schmidt, A.; Gumler, B.; Müller, Stefan; Hammer, Lutz; Heinz, K.

doi:10.1103/physrevb.78.045422

Cited by 8 publications

(14 citation statements)

References 31 publications

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“…We note that such dark lines (depressions) are reminiscent of stair-rod dislocations (a common form of surface misfit partial dislocations) previously found in heteroepitaxial thin films. 39 It is also worth noting that in our case the partial dislocations are formed in the surface layers of the bulk substrate (Cu) instead of the overlayer (graphene). Indeed the graphene lattice appears to be intact with no signs of reconstruction in our STM images ( Figures 1b,d, 2a,c, and S2).…”

mentioning

confidence: 82%

Graphene Induced Surface Reconstruction of Cu

Tian

Cao

et al. 2012

Nano Lett.

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An atomic-scale study utilizing scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV) is performed on large single crystalline graphene grains synthesized on Cu foil by a chemical vapor deposition (CVD) method. After thermal annealing, we observe the presence of periodic surface depressions (stripe patterns) that exhibit long-range order formed in the area of Cu covered by graphene. We suggest that the observed stripe pattern is a Cu surface reconstruction formed by partial dislocations (which appeared to be stair-rod-like) resulting from the strain induced by the graphene overlayer. In addition, these graphene grains are shown to be more decoupled from the Cu substrate compared to previously studied grains that exhibited Moirépatterns.

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confidence: 82%

Graphene Induced Surface Reconstruction of Cu

Tian

Cao

et al. 2012

Nano Lett.

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“…11 We observed narrow and sunk-in wedges in completed layers for n =3-5. Consistently, DFT calculations revealed that flat Ni layers pseudomorphic with Ir͑100͒-͑1 ϫ 1͒ are unstable for n Ն 3 and that the tensile stress buildup in the films is ͑at least partly͒ released by the formation of stair-rod-like dislocations.…”

Section: Discussionmentioning

confidence: 70%

“…1͑c͒ ͑all ball models result from quantitative LEED͒. [10][11][12] Neglecting the slight buckling of the full layers all films suffer from a 9.0% tensile strain due to the different in-plane lattice parameters of Ir and Ni ͑a Ir = 2.715 Å , a Ni = 2.490 Å͒.…”

Section: A Nanowires On Ir(100)-(5 ã 1)-hmentioning

confidence: 99%

Growth of metal nanowires of tunable width

et al. 2010

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Using scanning tunneling microscopy and low-energy electron diffraction it is demonstrated that the deposition of nickel on the hydrogen-stabilized ͑5 ϫ 1͒-H phase of Ir͑100͒ leads to the formation of nickel nanowires of tunable widths and of lengths up to the order of 0.1 m. The tuning parameter is the number n of full monolayers deposited on the substrate: with that layer completed the next layer starts to grow by forming nanowires of n-atomic width whereby n is in the range 2 Յ n Յ 5. The formation of the wires is interpreted as decoration or induction of stair rod dislocations which-as we reported earlier-develop to release the 9.0% pseudomorphic tensile strain of the full nickel layers. They lead to long sunk-in wedges at the surface whose width grows linearly with the number of layers deposited and so, by their decoration, nanowires of corresponding width develop. The wedges, and so the Ni wires, appear above single-atomic and macroscopically long Ir wires of the Ir͑100͒-͑5 ϫ 1͒-H substrate which pin the dislocations. Above n = 6, however, the films become rough and develop a squarelike patterning. It is speculated that the deposition of other metals with the same order of pseudomorphic strain should develop similar nanowires.

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“…Possible candidates that can form without long-range mass transfer are either interface dislocations with out-of-plane Burgers vectors revealing themselves by crystallographically aligned step edges on the surface 36 or stacking fault wedges. 37,38 The latter are structurally similar to bulk stair-rod dislocations 38 with the partial dislocations replaced by pairs of 1/3-or 2/3-height surface steps ͑about 60 or 120 pm high͒ laterally separated by a few nanometer causing tell-tale bright or dark stripes. Both steps or stripes are completely absent in our STM images ͓cf.…”

Section: E Closed Films Up To 20 ML Thicknessmentioning

confidence: 97%

Ultrathin Mn layers on Rh(001): Investigations using scanning tunneling microscopy and density functional calculations

et al. 2010

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The structural and magnetic properties of ultrathin layers of Mn grown on Rh͑001͒ surfaces have been investigated using scanning tunneling microscopy ͑STM͒ and ab initio density-functional calculations. STM shows perfect wetting of the Rh substrate by the first Mn monolayer ͑ML͒ accompanied by a high mobility of the Mn atoms and only little film-substrate intermixing. By way of contrast, the second monolayer is unstable against formation of multilayer islands at 300 K. However, this is only a transient effect and growth approaches a layer-by-layer mode in thicker films. At 170 K growth proceeds layer-by-layer throughout. The structure of the films is face-centered tetragonal ͑fct͒ without any indication of lateral lattice mismatch up to 20 ML thickness. The apparent height differences between terraces of different local thickness are consistent with an average axial ratio close to unity ͑near fcc͒ for 2-3-ML-thick films that decreases continuously to Ϸ0.94 in thicker films. Detailed spin-polarized density-functional calculations have been performed for the bulk and the ͑001͒ surface of strained fct Mn, as well as for free-standing and supported Mn/Rh͑001͒. The results demonstrate that structure and stability of surface and thin films are strongly influenced by antiferromagnetic ͑AFM͒ ordering. In-plane c͑2 ϫ 2͒ AFM is found at the surface while bulk and the deeper layers prefer layered AFM. The calculations reproduce and explain the growth instability of 2 ML films and reproduce qualitatively the thickness-dependent variation in the film structure while the tetragonal distortion imposed by the size mismatch is overestimated because with all known exchange-correlation functionals the size ratio of bulk Rh and Mn crystals is overestimated. The calculations show that interface alloying is slightly exothermic but kinetically hindered because of a high activation energy for exchange processes.

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Strain relief through stair-rod dislocations in ultrathin epitaxial metal films: Defect geometry and energetics

Cited by 8 publications

References 31 publications

Graphene Induced Surface Reconstruction of Cu

Graphene Induced Surface Reconstruction of Cu

Growth of metal nanowires of tunable width

Ultrathin Mn layers on Rh(001): Investigations using scanning tunneling microscopy and density functional calculations

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