Long-range surface faceting induced by chemisorption of PTCDA on stepped Ag(111) surfaces

Schmitt, Stefan; Schöll, A.; Umbach, E.

doi:10.1016/j.susc.2015.07.017

Cited by 12 publications

(33 citation statements)

References 44 publications

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“…These PTCDAcovered step bundles develop and grow in width with increasing PTCDA coverage and availability of 'free' steps until all steps are bundled and covered [25]. Since the step bundles form ordered arrays they become facets and new vicinal surfaces, respectively [25]. A documentation and assignment of all observed facets is given in [25] and in the supporting information.…”

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“…Since the step bundles form ordered arrays they become facets and new vicinal surfaces, respectively [25]. A documentation and assignment of all observed facets is given in [25] and in the supporting information. The multitude of observed superstructures will be discussed in an upcoming publication.…”

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“…The labeling of the facets was derived from a careful analysis of STM and LEED data using energy-dependent reciprocal space maps for the latter [25]. More details like tilt angles and superstructure data can be found in [25,26]. The question that remains to be answered, however, is why do regular patterns of PTCDA covered vicinal faces develop?…”

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“…The matching geometric parameters of the [102] plane of PTCDA single crystals in the β-modification and those of the Ag(111) plane allow epitaxial growth of PTCDA multilayers under certain, well-defined preparation conditions [21][22][23][24]. In previous studies [25,26] we have investigated adsorption on vicinal Ag surfaces with high step densities, i.e. surfaces the normal of which is a few degrees off the [111] direction.…”

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“…The STM images of the clean Ag surfaces confirm that the selected angle of inclination of 8.5°of the (global) surface normal with respect to the [111] direction had led to equally spaced monoatomic steps between (111) terraces of about 1.6 nm. The almost constant terrace width is ascribed to repulsive elastic interactions between the steps [25]. The STM image of figure 1(a) had been taken after deposition of 0.3 ML (1 ML defines a saturated monolayer) PTCDA onto Ag(775) at 200 K and annealing at 350 K. The STM image reveals a pattern of linear stripes consisting of PTCDA monolayers on high-index faces ('step bunches'), separated by uncovered Ag(111) terraces.…”

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Nanoscale patterning, macroscopic reconstruction, and enhanced surface stress by organic adsorption on vicinal surfaces

et al. 2017

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Self-organization is a promising method within the framework of bottom-up architectures to generate nanostructures in an efficient way. The present work demonstrates that self-organization on the length scale of a few to several tens of nanometers can be achieved by a proper combination of a large (organic) molecule and a vicinal metal surface if the local bonding of the molecule on steps is significantly stronger than that on low-index surfaces. In this case thermal annealing may lead to large mass transport of the subjacent substrate atoms such that nanometer-wide and micrometer-long molecular stripes or other patterns are being formed on high-index planes. The formation of these patterns can be controlled by the initial surface orientation and adsorbate coverage. The patterns arrange self-organized in regular arrays by repulsive mechanical interactions over long distances accompanied by a significant enhancement of surface stress. We demonstrate this effect using the planar organic molecule PTCDA as adsorbate and Ag (10 8 7) and Ag(775) surfaces as substrate. The patterns are directly observed by STM, the formation of vicinal surfaces is monitored by highresolution electron diffraction, the microscopic surface morphology changes are followed by spectromicroscopy, and the macroscopic changes of surface stress are measured by a cantilever bending method. The in situ combination of these complementary techniques provides compelling evidence for elastic interaction and a significant stress contribution to long-range order and nanopattern formation.It is well established that the formation of interfaces, e.g. by adsorption of atoms or small molecules on a metal or semiconductor surface, can lead to (changes of) reconstructions of the surface on atomic scales and hence to new geometric and electronic interface structures [1]. In some cases it has been argued that such reconstructions lead to regular nanoscopic patterns, which may be used to align molecules [2][3][4][5] or as templates for the subsequent buildup of three-dimensional (3D) nanostructures [6-10]. It is less well established, however, that such reconstructions can occur on large (mesoscopic) scales [11][12][13][14]. And it is hardly known that such reconstructions involving considerable mass transport of several substrate layers can even be induced by adsorption of large organic molecules, which are also used in organic devices.In the present work we present experimental evidence for this phenomenon. Several complementary in situ methods are employed to investigate the possible changes as function of preparation parameters and to understand the underlying mechanisms for microscopic and mesoscopic reconstructions. It is particularly shown that the adsorption of a large organic molecule on vicinal metal surfaces can lead to very significant

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