Article
Chemistry, Physical
Tom Ruediger, Martin Mitzschke, Andrea Prager, Ying Liu, Bernd Abel, Agnes Schulze, Frank Frost
Summary: Interactions between ion beams and polymers can tailor the properties of the polymer surface by modifying morphology and chemical composition. Research shows that varying ion incidence angles and erosion time leads to the evolution of different nanopatterns, with changes in polymer surface composition detectable by X-ray photoelectron spectroscopy.
APPLIED SURFACE SCIENCE
(2022)
Article
Physics, Condensed Matter
J. Seo, D. A. Pearson, R. M. Bradley, J-S Kim
Summary: The nanoscale patterns produced by bombardment of the (100) surface of silicon with a 2 keV Kr ion beam are investigated both experimentally and theoretically. The experimental results show that the observed patterns depend sensitively on the angle of incidence Theta, and five distinct morphologies are observed for Theta values between 74 degrees and 85 degrees. Simulation results indicate that the inclusion of a linearly dispersive term and a conserved Kuramoto-Sivashinsky nonlinearity can reproduce the triangular nanostructures observed in experiments, while the Harrison-Pearson-Bradley equation can generate ridges traversed by ripples. The simulations of the anisotropic Edwards-Wilkinson equation match the experimental results for Theta = 85 degrees. However, explanation for the other two patterns observed in experiments remains a challenge for future theoretical work.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Physics, Applied
R. Mark Bradley, Tejas Sharath
Summary: Surface ripples can spontaneously emerge during the growth of an amorphous thin film by oblique-incidence sputter deposition. Over time, the ripples become increasingly faceted, with facet slopes and the form of the ripple crests and troughs being analytically determined at long times. Ultimately, the ripples become highly ordered in the transverse direction, but variations in wavelength and amplitude lead to imperfect ordering in the longitudinal direction even at long times.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Physical
Byung-Hyun Kim, Sang-Pil Kim, Joonhee Kang, Yong-Chae Chung, Kyung-Suk Kim, Kwang-Ryeol Lee
Summary: The study investigated the composition modulation by Ar bombardment on the Co0.5Cu0.5 alloy and the CoAl B2 phase using molecular dynamics simulation. The results showed that Ar bombardment induces surface composition modulation in a layer-by-layer mode and the rearrangement of substrate atoms plays a significant role in the observed modulation.
APPLIED SURFACE SCIENCE
(2021)
Article
Physics, Fluids & Plasmas
R. Mark Bradley, Tejas Sharath
Summary: The study shows that nearly defect-free ripples with a sawtooth profile can form on the surface under low-energy ion bombardment, and the ripples coarsen with time passing.
Article
Physics, Applied
Haonan Yang, Shuhang Shen, Ruoyu Xu, Mingyu Zhou, Joseph Yan, Zhongdong Wang
Summary: A three-dimensional model based on molecular dynamics is developed to study the formation of a single cathode spot in vacuum arcs. The simulation shows that the formation of the cathode spot is controlled by plasma ions through ion bombardment. The size of the crater formed by ion bombardment is determined by the spatial distribution of injected ions. The study also investigates the electron emission and evaporated atoms during the cathode spot development process.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Review
Biochemistry & Molecular Biology
Jan Rombouts, Jenna Elliott, Anna Erzberger
Summary: Biological pattern formation is crucial for generating and maintaining spatial structures in the biological context. In addition to biochemical interactions, mechanical and geometrical features also play a significant role in pattern generation.
Article
Chemistry, Multidisciplinary
Lucien Eisenburger, Valentin Weippert, Carsten Paulmann, Dirk Johrendt, Oliver Oeckler, Wolfgang Schnick
Summary: TiP4N8 was synthesized from TiN and P3N5 using NH4F as a mineralizer, resulting in two polymorphs with different structures and prism shapes. The measured band gaps were confirmed by DFT calculations, which also predicted the thermochemistry of the polymorphs.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Geochemistry & Geophysics
Jose M. Carcione, Davide Gei, Boris Gurevich, Jing Ba
Summary: The study compares the exact normal-incidence PP reflection coefficient with approximations reported by several authors based on open-pore boundary conditions between two porous media. It is found that there are significant differences at low frequencies, and further differences are shown at high frequencies when extending the Geertsma-Smit equations to include the high-frequency viscodynamic operator. The use of the correct expression is crucial to accurately describe the physics across the frequency range.
SURVEYS IN GEOPHYSICS
(2021)
Article
Chemistry, Physical
Parand R. Riley, Pratik Joshi, Nayna Khosla, Roger J. Narayan, Jagdish Narayan
Summary: In this study, highly uniform Q-carbon layers were formed through PECVD and ion bombardment, enabling wafer-scale integration. The conversion of Si-DLC films into Q-carbon was achieved by low-energy ion bombardment, resulting in the formation of diamond nucleation sites. If an epitaxial template is provided by the underlying substrate, wafer-scale growth of diamond epitaxial films can be realized.
Article
Nanoscience & Nanotechnology
Matthias Lorenz, Alison A. Pawlicki, Holland E. Hysmith, Kerry Cogen, Hitesh Thaker, Olga S. Ovchinnikova
Summary: Understanding the formation mechanism of antiwear tribofilms and controlling their functionality through surface chemistry is crucial for the development of next-generation oil lubricants. This study investigates the early formation of antiwear films on steel surfaces using in-situ multimodal chemical imaging. The results show a direct correlation between changes in friction and local surface chemistry, providing insights into the formation and modification of these films.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Min Gi Choi, Alex Belianinov, Alison Pawlicki, Seonha Park, Habeom Lee, Olga S. Ovchinnikova, Songkil Kim
Summary: Two-dimensional layered nanomaterials like MoS2 were studied for their frictional effects of defects, where controlled irradiation of helium ions was used to pattern defects into the material. The research found that friction in MoS2 depends on defect formation controlled by helium ion irradiation, providing insights into the correlation between surface topography, defects, and friction. Understanding the relative friction of MoS2 in the presence of different levels of defects is crucial for studying its tribological properties at both nanoscales and macroscales.
SURFACES AND INTERFACES
(2021)
Article
Chemistry, Multidisciplinary
Adam Juhasz, Laszlo Seres, Norbert Varga, Ditta Ungor, Marek Wojnicki, Edit Csapo
Summary: This study quantitatively investigated the thermodynamic parameters of mixed surfactants, revealing that some mixed micelles have critical micelle concentration lower than predicted by the ideal mixing model, and they exhibit higher solubilization ability for poorly water-soluble model drugs.
Article
Chemistry, Physical
Tuan T. Tran, Christian Lavoie, Zhen Zhang, Daniel Primetzhofer
Summary: The study characterizes the composition and structure of ultrathin nickel silicide formed from 3 nm nickel films on silicon (100) through in-situ high-resolution ion scattering and high-resolution transmission electron microscopy. It shows a transition occurring in discrete steps, with an intermediate phase observed between 230 degrees C and 290 degrees C. The film composition of the intermediate phase is found to be 50% Ni:50% Si, while the final phase resembles cubic disilicide NiSi2 with a slightly off-stoichiometric composition of 38% Ni and 62% Si. The epitaxial growth of the silicide results in a contraction of the film's c lattice constant by 0.7-1%.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Physical
Eric Sivonxay, Kristin A. Persson
Summary: The development of alloy-based anodes has the potential to increase the energy storage capacity of Li-ion technology. Si-based anodes, in particular, have a high theoretical capacity but suffer from poor cycle and calendar life. Adding amorphous components can improve the stability of Si anodes during the lithiation process.
ENERGY STORAGE MATERIALS
(2022)
Article
Physics, Condensed Matter
Kevin M. Loew, R. Mark Bradley
Summary: A deep learning model has been developed to estimate all five parameters in the anisotropic Kuramoto-Sivashinsky equation using a single image of the surface, with root-mean-square errors under 3% of the parameter ranges used for training. This provides a tool for experimentalists to quickly determine the parameters for a given sputtering experiment and can serve as an independent check on other methods of estimating parameters.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Physics, Applied
R. Mark Bradley, Tejas Sharath
Summary: Surface ripples can spontaneously emerge during the growth of an amorphous thin film by oblique-incidence sputter deposition. Over time, the ripples become increasingly faceted, with facet slopes and the form of the ripple crests and troughs being analytically determined at long times. Ultimately, the ripples become highly ordered in the transverse direction, but variations in wavelength and amplitude lead to imperfect ordering in the longitudinal direction even at long times.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
R. Mark Bradley, Gerhard Hobler
Summary: This study investigates the effects of curvature on the sputter yield of a surface struck by ions, showing that the mean curvature and Gaussian curvature impact the yield. Analytically, two second order corrections to the yield are identified, with simulations confirming the importance of these corrections in extending the applicability of the approximate formula for a wider range of radii of curvature. The implications of this theory on nanoscale pattern formation under ion bombardment on flat surfaces are highlighted.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Condensed Matter
J. Seo, D. A. Pearson, R. M. Bradley, J-S Kim
Summary: The nanoscale patterns produced by bombardment of the (100) surface of silicon with a 2 keV Kr ion beam are investigated both experimentally and theoretically. The experimental results show that the observed patterns depend sensitively on the angle of incidence Theta, and five distinct morphologies are observed for Theta values between 74 degrees and 85 degrees. Simulation results indicate that the inclusion of a linearly dispersive term and a conserved Kuramoto-Sivashinsky nonlinearity can reproduce the triangular nanostructures observed in experiments, while the Harrison-Pearson-Bradley equation can generate ridges traversed by ripples. The simulations of the anisotropic Edwards-Wilkinson equation match the experimental results for Theta = 85 degrees. However, explanation for the other two patterns observed in experiments remains a challenge for future theoretical work.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Physics, Applied
R. Mark Bradley, Gerhard Hobler
Summary: In this study, we analytically determine the average sputter yield Y for non-planar surfaces with slowly varying heights. We neglect nonlocal effects such as redeposition of sputtered material and secondary sputtering. Our analysis reveals that the leading order corrections to Y depend on the spatial averages of the square of the height gradients in the x and y directions. The constants of proportionality can be expressed in terms of the derivatives of the sputter yield for a flat surface with respect to the ion incidence angle.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
Patrick D. Shipman, Tejas Sharath, R. Mark Bradley
Summary: Motivated by patterns with defects, this study develops two quantitative measures of order for imperfect Bravais lattices in the plane. Persistent homology and the sliced Wasserstein distance are used to define these measures. These measures generalize previous measures of order and are sensitive to the degree of perturbation in various lattice types and pattern-forming partial differential equations.
Article
Physics, Fluids & Plasmas
Brenden Balch, Patrick D. Shipman, R. Mark Bradley
Summary: Motivated by previous results, we studied the Swift-Hohenberg equation with an added linear dispersive term, called the dispersive Swift-Hohenberg equation (DSHE). The DSHE produces stripe patterns with spatially extended defects known as seams. These seams correspond to spiral waves in the anisotropic complex Ginzburg-Landau equation (ACGLE) and tend to organize themselves into chains. analytical and numerical results confirm these findings.
Article
Physics, Fluids & Plasmas
R. Mark Bradley, Patrick D. Shipman
Summary: In this study, the patterns created by scanning an atomic force microscope tip over a polymer surface were investigated using a mesoscopic model. The research discovered that the steady-state solution is only stable below a critical value, beyond which periodic stick-slip motion occurs.
Article
Physics, Fluids & Plasmas
Tejas Sharath, R. Mark Bradley
Summary: We study the surface ripples formed on a (001) GaAs surface with a small miscut along the [110] direction under near-normal incidence ion bombardment. When the ion beam is normally incident and there is no miscut, highly ordered, faceted ripples with their wave vector aligned with the [110] direction are formed. Linearly dispersive and nonlinearly dispersive terms appear in the equation of motion when the beam is obliquely incident and/or there is a miscut. Strong linear dispersion leads to ripples with increased degree of order, while strong nonlinear dispersion disrupts the exceptionally high degree of order. However, appropriately choosing the angle of ion incidence can produce highly ordered ripples.