587 research outputs found
Projection optics for extreme ultraviolet lithography (EUVL) micro-field exposure tools (METs) with a numerical aperture of 0.5
Abstract not provide
Combined SIMS-SPM Instrument For High Sensitivity And High Resolution Elemental 3D Analysis
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 - August 2, 201
Advanced atomic force microscopy techniques
Cataloged from PDF version of article.Although its conceptual approach is as simple as the technique used in record players already introduced in the 19th century, the invention of the atomic force microscope (AFM) in 1986 by Binnig, Quate, and Gerber was a milestone for nanotechnology. The scanning tunneling microscope (STM), introduced some years earlier, had already achieved atomic resolution, but is limited to conductive surfaces. Since its operational principle is based on the detection of the forces acting between tip and sample, this restriction does not exist for the AFM. Consequently, atomic force microscopy quickly became the standard tool for nanometer-scale imaging of all types of surfaces in all environments. True atomic resolution was first achieved in the 1990s. The most convincing results, however, were restricted to the so-called noncontact mode in vacuum for a long time, but recent technical developments overcame this limitation, and atomic-resolution imaging is now also a standard in liquids.
Beyond pushing the resolution limit to the picometer range, the invention of the AFM triggered the development of a growing number of new scanning probe methods and approaches, ranging from an expansion of the properties that can be mapped to the active manipulation of surfaces and small particles. Practically every month, reports on the growing capabilities of AFMs appear. Nearly every physical effect that influences the tip–sample interaction has been used to improve existing modes and to develop new ones. For example, many recently presented techniques include the excitation of higher cantilever oscillation modes; it is amazing in how many ways the shaking of a simple cantilever can improve our knowledge about the tip–sample interaction. Another direction is high-speed atomic force microscopy, which is one of the eminent challenges that need to be solved in order to allow the in situ observation of biological processes. Data acquisition times have already reached the millisecond range, enabling the visualization of the dynamic behavior of biological molecules and cells. Other recent accomplishments include imaging of organic molecules with unprecedented resolution, full three-dimensional mapping of surface force fields, and the imaging and discrimination of individual chemical bonds.
The development of advanced techniques is the focus of this Thematic Series, following the Thematic Series “Scanning probe microscopy and related techniques” edited by Ernst Meyer and the Thematic Series “Noncontact atomic force microscopy” edited by Udo Schwarz. The articles that are part of the series demonstrate that, despite its 25 years of history, the AFM is still far from reaching its limits, and today’s developments are far-reaching. As the number of research groups utilizing advanced atomic force microscopy techniques increases with each passing year, the technical improvements, data-acquisition approaches, analysis procedures, user friendliness, and application areas of the technique further diversify. With this Thematic Series, it is our intention to stimulate these improvements.
We thank all authors for contributing their excellent work to this series. Furthermore, we acknowledge all referees for their promptly provided reports keeping the publication times short and attractive for contributors. Finally, we are grateful to the open access policy of the Beilstein Journal of Nanotechnology providing the ground for unrestricted discussions on advanced atomic force microscopy techniques.
Thilo Glatzel, Hendrik Hölscher, Thomas Schimmel, Mehmet Z. Baykara, Udo D. Schwarz and Ricardo Garcia
December 201
Galactic Twins of the Ring Nebula Around SN1987A and a Possible LBV-like Phase for Sk-69 202
Some core-collapse supernovae show clear signs of interaction with dense
circumstellar material that often appears to be non-spherical. Circumstellar
nebulae around supernova progenitors provide clues to the origin of that
asymmetry in immediate pre-supernova evolution. Here I discuss outstanding
questions about the formation of the ring nebula around SN1987A and some
implications of similar ring nebulae around Galactic B supergiants. Several
clues hint that SN1987A's nebula may have been ejected in an LBV-like event,
rather than through interacting winds in a transition from a red supergiant to
a blue supergiant.Comment: 2 pages, to appear in procedings of "Massive stars: fundamental
parameters and circumstellar interactions", conference in honor of Virpi
Niemela's 70th birthda
Long-range interactions in the effective low energy Hamiltonian of Sr2IrO4: a core level resonant inelastic x-ray scattering study
We have investigated the electronic structure of Sr2IrO4 using core level
resonant inelastic x-ray scattering. The experimental spectra can be well
reproduced using ab initio density functional theory based multiplet ligand
field theory calculations, thereby validating these calculations. We found that
the low-energy, effective Ir t2g orbitals are practically degenerate in energy.
We uncovered that covalency in Sr2IrO4, and generally in iridates, is very
large with substantial oxygen ligand hole character in the Ir t2g Wannier
orbitals. This has far reaching consequences, as not only the onsite
crystal-field energies are determined by the long range crystal-structure, but,
more significantly, magnetic exchange interactions will have long range
distance dependent anisotropies in the spin direction. These findings set
constraints and show pathways for the design of d^5 materials that can host
compass-like magnetic interactions
New Constraints on the Origin of the Short-Term Cyclical Variability of the Wolf-Rayet Star WR 46
The Wolf-Rayet star WR 46 is known to exhibit a very complex variability
pattern on relatively short time scales of a few hours. Periodic but
intermittent radial velocity shifts of optical lines as well as multiple
photometric periods have been found in the past. Non-radial pulsations, rapid
rotational modulation or the presence of a putative low-mass companion have
been proposed to explain the short-term behaviour. In an effort to unveil its
true nature, we observed WR 46 with FUSE (Far Ultraviolet Spectroscopic
Explorer) over several short-term variability cycles. We found significant
variations on a time scale of ~8 hours in the far-ultraviolet (FUV) continuum,
in the blue edge of the absorption trough of the OVI {\lambda}{\lambda}1032,
1038 doublet P Cygni profile and in the SVI {\lambda}{\lambda}933, 944 P Cygni
absorption profile. We complemented these observations with X-ray and UV
light-curves and an X-ray spectrum from archival XMM-Newton (X-ray Multi-Mirror
Mission - Newton Space Telescope) data. The X-ray and UV light-curves show
variations on a time scale similar to the variability found in the FUV. We
discuss our results in the context of the different scenarios suggested to
explain the short-term variability of this object and reiterate that non-radial
pulsations is the most likely to occur.Comment: 36 pages, 11 figures. Accepted for publication in Ap
A Chandra X-ray Study of NGC 1068: II. The Luminous X-ray Source Population
We present an analysis of the compact X-ray source population in the
Seyfert~2 galaxy NGC 1068, imaged with Chandra. We find a total of 84 compact
sources, of which 66 are projected onto the galactic disk of NGC 1068. Spectra
of the brightest sources have been modeled with both multi-color disk blackbody
and power-law models. The power-law model provides the better description of
the spectrum for most of these sources. Five sources have 0.4-8 keV intrinsic
luminosities greater than 10^{39} erg/s, assuming that their emission is
isotropic and that they are associated with NGC 1068. We refer to these sources
as Intermediate Luminosity X-ray Objects (IXOs). If these five sources are
X-ray binaries accreting with luminosities that are both sub-Eddington and
isotropic, then the implied source masses are >7 solar masses, and so they are
inferred to be black holes. The brightest source has a much harder spectrum
(Gamma = 0.9\pm0.1) than that found in Galactic black hole candidates and other
IXOs. It also shows large-amplitude variability on both short-term and
long-term timescales. The ratio of the number of sources with luminosities
greater than 2.1 x 10^{38} erg/s in the 0.4-8 keV band to the rate of massive
star formation is the same, to within a factor of two, for NGC 1068, the
Antennae, NGC 5194 (the main galaxy in M51), and the Circinus galaxy. This
suggests that the rate of production of X-ray binaries per massive star is
approximately the same for galaxies with currently active star formation,
including ``starbursts''.Comment: 33 pages, 10 figures. To appear in The Astrophysical Journal, v591
n1, July 1, 2003 issu
The Structure of the Homunculus. III. Forming a Disk and Bipolar Lobes in a Rotating Surface Explosion
We present a semi-analytic model for shaping the nebula around eta Carinae
that accounts for the simultaneous production of bipolar lobes and an
equatorial disk through a rotating surface explosion. Material is launched
normal to the surface of an oblate rotating star with an initial kick velocity
that scales approximately with the local escape speed. Thereafter, ejecta
follow ballistic orbital trajectories, feeling only a central force
corresponding to a radiatively reduced gravity. Our model is conceptually
similar to the wind-compressed disk model of Bjorkman & Cassinelli, but we
modify it to an explosion instead of a steady line-driven wind, we include a
rotationally-distorted star, and we treat the dynamics somewhat differently.
Continuum-driving avoids the disk inhibition that normally operates in
line-driven winds. Our model provides a simple method by which rotating hot
stars can simultaneously produce intrinsically bipolar and equatorial mass
ejections, without an aspherical environment or magnetic fields. Although
motivated by eta Carinae, the model may have generic application to other LBVs,
B[e] stars, or SN1987A's nebula. When near-Eddington radiative driving is less
influential, our model generalizes to produce bipolar morphologies without
disks, as seen in many PNe.Comment: ApJ accepted, 9 page
Altering the properties of graphene on Cu(111) by intercalation of potassium bromide
The catalytic growth on transition metal surfaces provides a clean and controllable route to obtain defect-free, monocrystalline graphene. However, graphene's optical and electronic properties are diminished by the interaction with the metal substrate. One way to overcome this obstacle is the intercalation of atoms and molecules decoupling the graphene and restoring its electronic structure. We applied noncontact atomic force microscopy to study the structural and electric properties of graphene on clean Cu(111) and after the adsorption of KBr or NaCl. By means of Kelvin probe force microscopy, a change in graphene's work function has been observed after the deposition of KBr, indicating a changed graphene-substrate interaction. Further measurements of single-electron charging events as well as X-ray photoelectron spectroscopy confirmed an electronic decoupling of the graphene islands by KBr intercalation. The results have been compared with density functional theory calculations, supporting our experimental findings
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