Scanning tunneling microscopy of reconstructions on the SrTiO3() surface

Castell, Martin R.

doi:10.1016/s0039-6028(02)01393-6

Cited by 207 publications

(209 citation statements)

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“…The template patterns and molecular ordering are investigated through UHV scanning tunneling microscopy (STM) at room temperature. Etched W tips are used for imaging the sample surfaces at room temperature with a bias voltage applied to the sample.Close-packed surface ordering of fullerenes is achieved on a c(4 × 2) surface reconstruction, 22,23 as shown in the STM images of Figure 1b,c. The c(4 × 2) surface was formed by annealing at 1090°C for 30 min after sputtering.…”

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Template Ordered Open-Grid Arrays of Paired Endohedral Fullerenes

et al. 2006

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Developing useful molecular systems, such as planar networks of molecules for novel molecular-electronic architectures, 1-4 requires the ability to control the way molecules assemble at surfaces. Many techniques exploit non-covalent directional bonding interactions between molecules, such as hydrogen bonding, to facilitate the molecular assembly process. [5][6][7][8][9] However, if the molecules lack such directional bonding attributes then it becomes difficult to develop novel molecular architectures using this approach. Fullerenes 10 are molecules that do lack these directional bonds but are otherwise very attractive candidates for molecular based nanotechnologies. Endohedral fullerenes 11 are of particular interest in this area, because the atomic species bounded within the fullerenes could be manipulated for storing and processing bits of information. For example, the magneto-optical activity 12 of the Er 3 N@C 80 molecule 13 ( Figure 1a) may prove useful in solid-state quantum information processing systems. [2][3][4]14 Overcoming the challenge of coercing endohedral fullerenes to order into useful spatial configurations can be achieved through template-assisted assembly. A successful template requires the surface to be made up of patterned arrays of bonding sites for the fullerenes to adsorb onto. Impressive demonstrations of this have been achieved using pre-assembled molecular templates on metal or metal-terminated substrates. [15][16][17][18] Here we report how oxide crystal surfaces can be used as a template to controllably order endohedral fullerenes into two-dimensional (2D) open-grid arrays. This is compared to the ordinary close-packed ordering of endohedral fullerenes. The template is a nanostructured surface phase of (001) strontium titanate, 19 and the endohedral fullerenes are Er 3 N@C 80 molecules 13 (Figure 1a).The surfaces are prepared through an Ar + sputtering and annealing procedure, described in earlier work, 19 on 0.5%-weight Nb-doped SrTiO 3 (001) single crystals in ultrahigh vacuum (UHV) conditions. Er 3 N@C 80 molecules, or fullerenes, were deposited onto the surfaces from the vapor phase. Createc Knudsen cells, heated at 480°C, were used to evaporate Er 3 N@C 80 molecules for 20-30 min, allowing 0.15-0.20 monolayer coverage for each deposition. Er 3 N@C 80 has advantages over other endohedral fullerenes 3,4 (e.g. N@C 60 ) in that M 3 N@C 80 species (M ) metal forming a planar M 3 N species) are thermally stable 20,21 and can be readily evaporated onto heated substrates in UHV. The template patterns and molecular ordering are investigated through UHV scanning tunneling microscopy (STM) at room temperature. Etched W tips are used for imaging the sample surfaces at room temperature with a bias voltage applied to the sample.Close-packed surface ordering of fullerenes is achieved on a c(4 × 2) surface reconstruction, 22,23 as shown in the STM images of Figure 1b,c. The c(4 × 2) surface was formed by annealing at 1090°C for 30 min after sputtering. Er 3 N@C 80 is deposited on the c(4 × 2)...

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“…Close-packed surface ordering of fullerenes is achieved on a c(4 × 2) surface reconstruction, 22,23 The open-grid ordering of fullerenes is achieved on a template made of 2D arrays of trenches with highly ordered crosslike structures along them (Figure 2a). These trench arrays, termed waffles, 19 have an associated (6 × 8) surface periodicity.…”

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Template Ordered Open-Grid Arrays of Paired Endohedral Fullerenes

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“…Many spatially resolved tools for determining chemical structure at an interface exist 8 . Scanning probe techniques have been applied to a wide range of oxide materials [9][10][11][12][13][14] . However, and particularly with SrTiO 3 , these techniques have been utilized to investigate the surface morphology and resulting surface reconstructions following various sample preparation techniques that involve chemical and thermal processing [15][16][17][18][19] .…”

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Nanometer-Scale Striped Surface Terminations on Fractured SrTiO₃ Surfaces

et al. 2009

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Using cross-sectional scanning tunneling microscopy on in situ fractured SrTiO 3 , one of the most commonly used substrates for the growth of complex oxide thin films and superlattices, atomically smooth terraces have been observed on (001) surfaces. Furthermore, it was discovered that fracturing this material at room temperature results in the formation of stripe patterned domains having characteristic widths (~10 nm to ~20 nm) of alternating surface terminations that extend over a longrange. Spatial characterization utilizing spectroscopy techniques revealed a strong contrast in the electronic structure of the two domains. Combining these results with topographic data, we are able to assign both TiO 2 and SrO terminations to their respective domains. The results of this proof-of-principle experiment reveal that fracturing this material leads to reproducibly flat surfaces that can be characterized at the atomic-scale and suggests that this technique can be utilized for the study of technologically relevant complex oxide interfaces.

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“…The SrTiO 3 (001)−c(4 × 2) surface [32] is used for cobalt deposition. The c(4 × 2) reconstruction was verified by STM and low-energy electron diffraction before deposition.…”

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Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: Tight-binding and first-principles studies

Barreteau

Castell

et al. 2014

Phys. Rev. B

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We report tight-binding and density functional theory calculations of magnetocrystalline anisotropy energy (MAE) of free Fe (body-centered-cubic) and Co (face-centered-cubic) slabs and nanocrystals. The nanocrystals are truncated square pyramids which can be grown experimentally by deposition of metal on a SrTiO 3 (001) substrate. For both elements our local analysis shows that the total MAE of the nanocrystals is largely dominated by the contribution of (001) facets. However, while the easy axis of Fe (001) is out-of-plane, it is in-plane for Co(001). This has direct consequences on the magnetic reversal mechanism of the nanocrystals. Indeed, the very high uniaxial anisotropy of Fe nanocrystals makes them a much better potential candidate for magnetic storage devices.

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Scanning tunneling microscopy of reconstructions on the SrTiO3() surface

Cited by 207 publications

References 36 publications

Template Ordered Open-Grid Arrays of Paired Endohedral Fullerenes

Template Ordered Open-Grid Arrays of Paired Endohedral Fullerenes

Nanometer-Scale Striped Surface Terminations on Fractured SrTiO₃ Surfaces

Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: Tight-binding and first-principles studies

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Scanning tunneling microscopy of reconstructions on the SrTiO3() surface

Cited by 207 publications

References 36 publications

Template Ordered Open-Grid Arrays of Paired Endohedral Fullerenes

Template Ordered Open-Grid Arrays of Paired Endohedral Fullerenes

Nanometer-Scale Striped Surface Terminations on Fractured SrTiO3 Surfaces

Out- versus in-plane magnetic anisotropy of free Fe and Co nanocrystals: Tight-binding and first-principles studies

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Nanometer-Scale Striped Surface Terminations on Fractured SrTiO₃ Surfaces