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See detailRoute Toward High-Efficiency Single-Phase Cu2ZnSn(S,Se)4 Thin-Film Solar Cells: Model Experiments and Literature Review
Redinger, Alex UL; Berg, Dominik M.; Dale, Phillip UL et al

in IEEE Journal of Photovoltaics (2011)

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See detailSputtering at grazing ion incidence: Influence of adatom islands
Rosandi, Yudi; Redinger, Alex UL; Michely, Thomas et al

in PHYSICAL REVIEW B (2010), 82(12),

When energetic ions impinge at grazing incidence onto an atomically flat terrace, they will not sputter. However, when adatom islands (containing N atoms) are deposited on the surface, they induce ... [more ▼]

When energetic ions impinge at grazing incidence onto an atomically flat terrace, they will not sputter. However, when adatom islands (containing N atoms) are deposited on the surface, they induce sputtering. We investigate this effect for the specific case of 83 degrees-incident 5 keV Ar ions on a Pt (111) surface by means of molecular-dynamics simulation and experiment. We find that-for constant coverage Theta-the sputter yield has a maximum at island sizes of N congruent to 10-20. A detailed picture explaining the decline of the sputter yield toward larger and smaller island sizes is worked out. Our simulation results are compared with dedicated sputtering experiments, in which a coverage 0.09 of Pt adatoms are deposited onto the Pt (111) surface and form islands with a broad distribution around a most probable size of N congruent to 20. [less ▲]

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See detailCoevaporation of Cu2ZnSnSe4 thin films
Redinger, Alex UL; Siebentritt, Susanne UL

in Applied Physics Letters (2010), 97(9), 092111-1

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See detailMolecular structure of the H2O wetting layer on Pt(111)
Standop, Sebastian; Redinger, Alex UL; Morgenstern, Markus et al

in PHYSICAL REVIEW B (2010), 82(16),

The molecular structure of the wetting layer of ice on Pt(111) is resolved using scanning tunneling microscopy. Two structures observed previously by diffraction techniques are imaged for coverages at or ... [more ▼]

The molecular structure of the wetting layer of ice on Pt(111) is resolved using scanning tunneling microscopy. Two structures observed previously by diffraction techniques are imaged for coverages at or close to completion of the wetting layer. At 140 K only a root 37 x root 37R25.3 degrees superstructure can be established while at 130 K also a root 39 x root 39R16.1 degrees superstructure with slightly higher molecular density is formed. In the temperature range under concern the superstructures reversibly transform into each other by slight changes in coverage through adsorption or desorption. The superstructures exhibit a complex pattern of molecules in different geometries. [less ▲]

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See detailTrails of Kilovolt Ions Created by Subsurface Channeling
Redinger, Alex UL; Standop, Sebastian; Michely, Thomas et al

in PHYSICAL REVIEW LETTERS (2010), 104(7),

Using scanning tunneling microscopy, we observe the damage trails produced by keV noble-gas ions incident at glancing angles onto Pt(111). Surface vacancies and adatoms aligned along the ion trajectory ... [more ▼]

Using scanning tunneling microscopy, we observe the damage trails produced by keV noble-gas ions incident at glancing angles onto Pt(111). Surface vacancies and adatoms aligned along the ion trajectory constitute the ion trails. Atomistic simulations reveal that these straight trails are produced by nuclear (elastic) collisions with surface layer atoms during subsurface channeling of the projectiles. In a small energy window around 5 keV, Xe(+) ions create vacancy grooves that mark the ion trajectory with atomic precision. The asymmetry of the adatom production on the two sides of the projectile path is traced back to the asymmetry of the ion's subsurface channel. [less ▲]

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See detailDesorption of H2O from Flat and Stepped Pt(111)
Picolin, Alexander; Busse, Carsten; Redinger, Alex UL et al

in JOURNAL OF PHYSICAL CHEMISTRY C (2009), 113(2), 691-697

To investigate the effect of steps on H2O binding on a nominal Pt(111) surface, we used thermal desorption spectroscopy of water adsorbed on purposefully nanostructured surfaces: a rippled surface ... [more ▼]

To investigate the effect of steps on H2O binding on a nominal Pt(111) surface, we used thermal desorption spectroscopy of water adsorbed on purposefully nanostructured surfaces: a rippled surface containing densely packed (100)-microfaceted and (111)-microfaceted steps was created using grazing incidence ion bombardment, and a surface with triangular mounds mainly consisting of (111)-microfaceted steps was fabricated through hornoepitaxial growth. These morphologies are determined by scanning tunneling microscopy. We find two additional high -temperature H2O desorption peaks using the rippled surface, whereas only the peak with the highest desorption temperature is present on the (111)-microfaceted mound. Thus, water preferentially binds to steps and especially favors (111)-microfaceted ones. Furthermore, the large step concentration on our nanostructured surfaces precludes the coexistence of a condensed and a diluted phase in a monolayer of water and suppresses the formation of crystalline ice multilayers during heating. [less ▲]

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See detailCompetition of terrace and step-edge sputtering under oblique-incidence ion impact on a stepped Pt(111) surface
Rosandi, Yudi; Redinger, Alex UL; Michely, Thomas et al

in NUCLEAR INSTRUMENTS METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS (2009), 267(16), 2769-2773

Using molecular-dynamics simulation, we study the sputtering of a Pt(111) surface under oblique and glancing incidence 5 keV Ar ions. For incidence angles larger than a critical angle theta(c), the ... [more ▼]

Using molecular-dynamics simulation, we study the sputtering of a Pt(111) surface under oblique and glancing incidence 5 keV Ar ions. For incidence angles larger than a critical angle theta(c), the projectile is reflected off the surface and the sputter yield is zero. We discuss the azimuth dependence of the critical angle theta(c) with the help of the surface corrugation felt by the impinging ion. If a step exists on the surface, sputtering occurs also for glancing incidence theta > theta(c). We demonstrate that for realistic step densities, the total sputtering of a stepped surface may be sizable even at glancing incidence. (C) 2009 Elsevier B.V. All rights reserved. [less ▲]

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See detailRapid Coarsening of Ion Beam Ripple Patterns by Defect Annihilation
Hansen, Henri; Redinger, Alex UL; Messlinger, Sebastian et al

in PHYSICAL REVIEW LETTERS (2009), 102(14),

Ripple patterns formed on Pt(111) through grazing incidence ion beam erosion coarsen rapidly. At and below 450 K coarsening of the patterns is athermal and kinetic, unrelated to diffusion and surface free ... [more ▼]

Ripple patterns formed on Pt(111) through grazing incidence ion beam erosion coarsen rapidly. At and below 450 K coarsening of the patterns is athermal and kinetic, unrelated to diffusion and surface free energy. Similar to the situation for sand dunes, coarsening takes place through annihilation reactions of mobile defects in the pattern. The defect velocity derived on the basis of a simple model agrees quantitatively with the velocity of monatomic steps illuminated by the ion beam. [less ▲]

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See detailInfluence of a single adatom on sputtering at grazing incidence - A molecular-dynamics case study of 5 keV Ar impact on Pt (111)
Rosandi, Yudi; Redinger, Alex UL; Michely, Thomas et al

in SURFACE SCIENCE (2009), 603(2), 320-325

Grazing incidence ion impact on a flat terrace lets the projectile reflect specularly off the surface, leading to little or no damage production or sputtering. The presence of isolated surface defects may ... [more ▼]

Grazing incidence ion impact on a flat terrace lets the projectile reflect specularly off the surface, leading to little or no damage production or sputtering. The presence of isolated surface defects may change this behaviour drastically. We investigate this phenomenon for the specific case of 5 keV Ar ions impinging at 83 degrees towards the surface normal onto the Pt (111) surface. Molecular-dynamics simulations allow to study the influence of isolated adatoms in detail. The scattering of the projectile from the adatom can redirect the projectile, or let the adatom recoil, such that either of them deposits considerable energy in the target surface, leading to abundant damage production and sputtering. Two distinct collision zones are identified: (i) When the projectile hits the surface in front of the adatom, it may collide with the adatom indirectly (after being specularly reflected off the surface); (ii) alternatively, it may hit the adatom directly. We quantify our results by measuring the zone of influence (congruent to 13 angstrom(2)) around the adatom, into which the projectile must hit in order to collide with the adatom, and by the sputter cross section of roughly 110 angstrom(2). The data compare well with previous simulation results of sputtering from an atomically rough surface. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailStep-edge sputtering through grazing incidence ions investigated by scanning tunneling microscopy and molecular dynamics simulations
Redinger, Alex UL; Rosandi, Yudi; Urbassek, Herbert M. et al

in PHYSICAL REVIEW B (2008), 77(19),

Scanning tunneling microscopy is used to quantify step-edge sputtering of Pt(111) at 550 K by grazing incidence ion bombardment with 5 keV Ar(+) ions. For bombardment conditions causing negligible erosion ... [more ▼]

Scanning tunneling microscopy is used to quantify step-edge sputtering of Pt(111) at 550 K by grazing incidence ion bombardment with 5 keV Ar(+) ions. For bombardment conditions causing negligible erosion on terraces, damage features associated with step bombardment allow us to visualize step retraction and thus to quantify the step-edge sputtering yield. An alternative method for step-edge yield determination, which is applicable under more general conditions, is the analysis of the concentration of ascending steps together with the removed amount as a function of ion fluence. Interestingly, the azimuthal direction of the impinging ions with respect to the surface significantly changes the sputtering yield at step edges. This change is attributed to the orientation dependence of subsurface channeling. Atomistic insight into step-edge sputtering and its azimuthal dependence is given by molecular dynamics simulations of ion impacts at 0 and 550 K. The simulations also demonstrate a strong dependence of the step-edge sputtering yield on temperature. [less ▲]

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See detailSpiral growth and step edge barriers
Redinger, Alex UL; Ricken, Oliver; Kuhn, Philipp et al

in PHYSICAL REVIEW LETTERS (2008), 100(3),

The growth of spiral mounds containing a screw dislocation is compared to the growth of wedding cakes by two-dimensional nucleation. Using phase field simulations and homoepitaxial growth experiments on ... [more ▼]

The growth of spiral mounds containing a screw dislocation is compared to the growth of wedding cakes by two-dimensional nucleation. Using phase field simulations and homoepitaxial growth experiments on the Pt(111) surface we show that both structures attain the same large scale shape when a significant step-edge barrier suppresses interlayer transport. The higher vertical growth rate of the spiral mounds on Pt(111) reflects the different incorporation mechanisms for atoms in the top region and can be formally represented by an enhanced apparent step-edge barrier. [less ▲]

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See detailMechanisms of pattern formation in grazing-incidence ion bombardment of Pt(111)
Hansen, Henri; Redinger, Alex UL; Messlinger, Sebastian et al

in PHYSICAL REVIEW B (2006), 73(23),

Ripple patterns forming on Pt(111) due to 5 keV Ar(+) grazing-incidence ion bombardment were investigated by scanning tunneling microscopy in a broad temperature range from 100 to 720 K and for ion ... [more ▼]

Ripple patterns forming on Pt(111) due to 5 keV Ar(+) grazing-incidence ion bombardment were investigated by scanning tunneling microscopy in a broad temperature range from 100 to 720 K and for ion fluences up to 3x10(20) ions/m(2). A detailed morphological analysis together with molecular dynamics simulations of single ion impacts allow us to develop atomic scale models for the formation of these patterns. The large difference in step edge versus terrace damage is shown to be crucial for ripple formation under grazing incidence. The importance of distinct diffusion processes-step adatom generation at kinks and adatom lattice gas formation-for temperature dependent transitions in the surface morphology is highlighted. Surprisingly, ion bombardment effects like thermal spike induced adatom production and planar subsurface channeling are important for pattern ordering. [less ▲]

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