To tilt or not to tilt: Correction of the distortion caused by inclined sample surfaces in low-energy electron diffraction

Helgert, Christian; Meißner, Matthias; Zwick, Christian; Forker, Roman; Vyshnepolsky, Michael; Klein, C.; Hoegen, M. Horn‐von; Fritz, Torsten

doi:10.1016/j.ultramic.2013.04.005

Cited by 28 publications

(22 citation statements)

References 21 publications

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“…LEED patterns measured at three sample temperatures between 350 and 250 K are presented in Figure . All LEED images are distortion‐corrected, calibrated using LEEDCal and analyzed using LEEDLab (overlayed simulations) . The uniformity and sufficient quality of the crystal surfaces for ARUPS measurements were confirmed in advance by varying the sample position and beam‐energy of LEED (Figure S2, Supporting Information).…”

Section: Summarized Parameters Of Various Experimental and Calculatedsupporting

confidence: 87%

Band Dispersion and Hole Effective Mass of Methylammonium Lead Iodide Perovskite

et al. 2018

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Solar cells incorporating organic–inorganic perovskites, especially methylammonium lead iodide (CH3NH3PbI3), have recently shown remarkable performances and therefore attracted wide interest. For understanding the origin of the high performance, the effective charge carrier masses of CH3NH3PbI3 are critical. However, reliable experimental data on its electronic band structure, which determines the effective mass, is yet to be provided. Here, the electronic structure of CH3NH3PbI3 single crystals is studied by using angle‐resolved photoelectron spectroscopy on cleaved crystal surfaces after characterizing the surface structure by low‐energy electron diffraction. Coexisting cubic and tetragonal phases of CH3NH3PbI3 are found in diffraction patterns. Moreover, a clear band dispersion of the top valence band is observed along directions parallel to different high‐symmetry points of the cubic structure, in consistence with theoretical calculations. Based on these values, the effective hole mass is then estimated to be 0.24(±0.10)m0 around the M point and 0.35(±0.15)m0 around the X point, which are significantly lower than in organic semiconductors. These results reveal the physical origin of the high performance of solar cells incorporating perovskite materials compared to pure organic semiconductors.

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Section: Summarized Parameters Of Various Experimental and Calculatedsupporting

confidence: 87%

Band Dispersion and Hole Effective Mass of Methylammonium Lead Iodide Perovskite

et al. 2018

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“…Figure 1 a shows a LEED image of a monolayer of HBC on a tilted EG sample at room temperature that was corrected for imaging 38 and tilt distortions. 39 The beam energy was chosen such that both the specular beam near the left screen edge and a first diffraction order of graphite near the right edge are visible. Additional bright spots mainly in the left part of the image can be attributed to the HBC lattice (turquoise circles).…”

Section: Resultsmentioning

confidence: 99%

“… (a) Room temperature LEED image (incident electron energy 38.0 eV, sample tilted by 15°, logarithmic contrast) of one HBC monolayer on epitaxial graphene (EG), corrected for imaging 38 and tilt distortions. 39 Dark blue zoom: the (1̅,6) HBC spot (turquoise) and its equivalents do not coincide with first order substrate spots (magenta), rendering the structure not commensurate. EG reconstruction spots (magenta as well) and multiple scattering between HBC and EG (blue) are needed to explain all spots ( cf.…”

Section: Resultsmentioning

confidence: 99%

Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves

et al. 2016

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The epitaxy of many organic films on inorganic substrates can be classified within the framework of rigid lattices which helps to understand the origin of energy gain driving the epitaxy of the films. Yet, there are adsorbate–substrate combinations with distinct mutual orientations for which this classification fails and epitaxy cannot be explained within a rigid lattice concept. It has been proposed that tiny shifts in atomic positions away from ideal lattice points, so-called static distortion waves (SDWs), are responsible for the observed orientational epitaxy in such cases. Using low-energy electron diffraction and scanning tunneling microscopy, we provide direct experimental evidence for SDWs in organic adsorbate films, namely hexa-peri-hexabenzocoronene on graphite. They manifest as wave-like sub-Ångström molecular displacements away from an ideal adsorbate lattice which is incommensurate with graphite. By means of a density-functional-theory based model, we show that, due to the flexibility in the adsorbate layer, molecule–substrate energy is gained by straining the intermolecular bonds and that the resulting total energy is minimal for the observed domain orientation, constituting the orientational epitaxy. While structural relaxation at an interface is a common assumption, the combination of the precise determination of the incommensurate epitaxial relation, the direct observation of SDWs in real space, and their identification as the sole source of epitaxial energy gain constitutes a comprehensive proof of this effect.

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“…Following this procedure, the reciprocal space dimensions were calibrated with well-known Si(111)-(7 × 7) and commensurate PTCDA/Ag(111) superstructures as reference samples [19,20], yielding highly precise results for the unit cell parameters and epitaxial relations. A high precision analysis of the LEED images measured was performed via LEEDLab by numerical fitting a simulated structure to the spots found [21]. All observable spots of one structure are simultaneously used leading to higher accuracy than usual (cf.…”

Section: Methodsmentioning

confidence: 99%

Growth of coronene on (100)- and (111)-surfaces of fcc-crystals

et al. 2015

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To tilt or not to tilt: Correction of the distortion caused by inclined sample surfaces in low-energy electron diffraction

Cited by 28 publications

References 21 publications

Band Dispersion and Hole Effective Mass of Methylammonium Lead Iodide Perovskite

Band Dispersion and Hole Effective Mass of Methylammonium Lead Iodide Perovskite

Flexible 2D Crystals of Polycyclic Aromatics Stabilized by Static Distortion Waves

Growth of coronene on (100)- and (111)-surfaces of fcc-crystals

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