Huge Images? - GIT Verlag

Lasers Fabricated by Nanoimprint
Lithography
The team of V. Reboud at the Tyndall National Institute,
Cork, Ireland, report on the fabrication and
characterization of two-dimensional polymer photonic
crystal band-edge lasers operating in the visible
range. The components have been fabricated in
a dye chromophore-loaded polymer matrix by nanoimprint
lithography and high-symmetry bandedge
modes are used to generate laser emission.
Their work demonstrates the potential of nanoimprint
lithography for the fabrication of two-dimensional
planar photonic crystal structures in an active
medium in a one-step process.
» Appl. Phys. Lett. 91, 151101
» doi:10.1063/1.2798250
Optical Coherence Computed
Tomography
L. Li and L.V. Wang from the Washington University
in St Louis, Missouri, USA, propose a device to
bridge the gap between diffuse optical tomography
and optical coherence tomography. Both ballistic
and multiple-scattered photons are measured at
multiple source-detection positions by low-coherence
interferometry providing a temporal resolution
smaller than 100 fs. A light-tissue interaction
model was established using the time-resolved
Monte Carlo method. The optical properties were
then reconstructed by solving the inverse transient
radiative transport problem under the first Born approximation.
Absorbing inclusions of 100 µm diameter
were imaged through a 2.6-mm-thick (~ 30
scattering mean-free-paths) scattering medium.
» Appl. Phys. Lett. 91, 141107
» doi:10.1063/1.2793625
Frequency Response of an AFM:
Magnetic Versus Acoustic Excitation
E.T. Herruzo and R. Garcia from the CSIC, Madrid,
Spain, discuss the dynamics of an amplitude modulation
AFM in different environments such as water
and air, and show that the resonance curves depend
on the excitation method used to drive the
cantilever, either mechanical or magnetic. This dependence
is magnified for small force constants
and quality factors, i.e., below 1 N/m and 10, respectively.
They also show that the equation for the
observable, the cantilever deflection, depends on
the excitation method. Under mechanical excitation,
the deflection involves the base and tip displacements,
while in magnetic excitation, the cantilever
deflection and tip displacement coincide.
» Appl. Phys. Lett. 91, 143113
» doi:10.1063/1.2794426
• G.I.T. Imaging & Microscopy 4/2007
NEwS TICkER
Influence of Sample Conductivity on
Oxidation by the Tip of AFM
V. Cambel and J. Soltys at the Slovak Academy of
Sciences, Bratislava, Slovakia analyzed the role of
the electric field distribution in the nano-oxidation
process realized by the tip of AFM experimentally
and theoretically. Authors show the importance of
the sample conductivity and the water bridge in the
process applied to bulk GaAs and Ga[Al]As heterostructures
in both contact and noncontact AFM
modes and the consequences for the lines witten.
They show that the electric field distribution in the
system tip-sample is controlled by the sample conductivity.
In the case of low-conductive samples,
maximum field is located apart from the tip apex
for both contact and noncontact AFM modes.
» J. Appl. Phys. 102, 074315
» doi:10.1063/1.2794374
High-resolution Microscope for Tipenhanced
Optical Processes in UHV
J. Steidtner and B. Pettinger in Berlin, Germany
present an optical microscope based on tip-enhanced
optical processes that can be used for studies
on adsorbates as well as thin layers and nanostructures.
It provides chemical and topographic
informations with a resolution of a few nanometers
and can be employed in ultrahigh vacuum as well
as gas phase. The central idea is to mount, within
an UHV system, an optical platform with all necessary
optical elements to a rigid frame that also carries
the scanning tunneling microscope unit and to
integrate a high numerical aperture parabolic mirror
between the scanning probe microscope head
and the sample. Authors present the first results of
Raman measurements using the device and the experimentally
determined requirements of the parabolic
mirror in terms of alignment accuracy.
» Rev. Sci. Instrum. 78, 103104
» doi:10.1063/1.2794227
An UHV Fast-scanning and Variable
Temperature STM for Large Scale
Imaging
B. Diaconescu and co-workers from the University
of New Hampshire, USA describe the design and
performance of a fast-scanning, variable temperature
scanning tunneling microscope (STM) operating
from 80 to 700 K in ultrahigh vacuum (UHV),
which routinely achieves large scale atomically resolved
imaging of compact metallic surfaces. The
vertical resolution of the instrument was found to
be about 2 pm at room temperature. The total
scanning area is about 8 × 8 µm 2 . The sample tem-
perature can be adjusted by a few tens of degrees
while scanning over the same sample area.
» Rev. Sci. Instrum. 78, 103701
» doi:10.1063/1.2789655
Suppression of Spurious Vibration of
Cantilever in AFM
T. Tsuji and colleagues from Tohoku University, Japan,
developed a simple but effective method for
suppressing spurious response (SR) to improve the
precision of dynamic AFM using cantilever vibration
spectra. The dominant origin of SR was identified
to be the bending vibration of the cantilever
substrate, but while a rigid cover pressing the
whole surface of the substrate suppressed SR, the
utility was insufficient. Then, a method of enhancing
the bending rigidity of the substrate by gluing a
rigid plate (clamping plate, CP) to the substrate
was developed. The CP method will particularly
contribute to improving dynamic-mode AFM, in
which resonance spectra with a low quality factor
are used, such as noncontact mode AFM in liquid or
contact resonance mode AFM.
» Rev. Sci. Instrum. 78, 103703
» doi:10.1063/1.2793498
High Resolution Gamma Ray
Tomography Scanner
U. Hampel and co-workers at Forschungszentrum
Dresden-Rossendorf e.V., Dresden, Germany, report
on the development of a high resolution gamma
ray tomography scanner that is operated with a Cs-
137 isotopic source at 662 keV gamma photon energy
and achieves a spatial image resolution of 0.2
line pairs/mm at 10 % modulation transfer function
for noncollimated detectors. It is primarily intended
for the scientific study of flow regimes and phase
fraction distributions in fuel element assemblies,
chemical reactors, pipelines, and hydrodynamic machines,
but it is applicable to nondestructive testing
of larger radiologically dense objects. They also
built a computed tomography scanner gantry for
measurements at fixed vessels or plant components.
» Rev. Sci. Instrum. 78, 103704
» doi:10.1063/1.2795648
Correction of Axial Geometrical Distortion
in Microscopic Images
H.J. Van Elburg and colleagues from the University
of Antwerp, Belgium, discuss the extraction of
quantitative data from microscopic volume images
when imperfectly matched immersion and mounting
media result in axial geometrical distortion. Linear
correction of the axial distortion using the