10 research outputs found
Ptychographic hyperspectral spectromicroscopy with an extreme ultraviolet high harmonic comb
We demonstrate a new scheme of spectromicroscopy in the extreme ultraviolet
(EUV) spectral range, where the spectral response of the sample at different
wavelengths is imaged simultaneously. It is enabled by applying ptychographical
information multiplexing (PIM) to a tabletop EUV source based on high harmonic
generation, where four spectrally narrow harmonics near 30 nm form a spectral
comb structure. Extending PIM from previously demonstrated visible wavelengths
to the EUV/X-ray wavelengths promises much higher spatial resolution and more
powerful spectral contrast mechanism, making PIM an attractive
spectromicroscopy method in both the microscopy and the spectroscopy aspects.
Besides the sample, the multicolor EUV beam is also imaged in situ, making our
method a powerful beam characterization technique. No hardware is used to
separate or narrow down the wavelengths, leading to efficient use of the EUV
radiation
Quantitative Chemically-Specific Coherent Diffractive Imaging of Buried Interfaces using a Tabletop EUV Nanoscope
Characterizing buried layers and interfaces is critical for a host of
applications in nanoscience and nano-manufacturing. Here we demonstrate
non-invasive, non-destructive imaging of buried interfaces using a tabletop,
extreme ultraviolet (EUV), coherent diffractive imaging (CDI) nanoscope. Copper
nanostructures inlaid in SiO2 are coated with 100 nm of aluminum, which is
opaque to visible light and thick enough that neither optical microscopy nor
atomic force microscopy can image the buried interfaces. Short wavelength (29
nm) high harmonic light can penetrate the aluminum layer, yielding
high-contrast images of the buried structures. Moreover, differences in the
absolute reflectivity of the interfaces before and after coating reveal the
formation of interstitial diffusion and oxidation layers at the Al-Cu and
Al-SiO2 boundaries. Finally, we show that EUV CDI provides a unique capability
for quantitative, chemically-specific imaging of buried structures, and the
material evolution that occurs at these buried interfaces, compared with all
other approaches.Comment: 12 pages, 8 figure
Supplement 1: Tabletop nanometer extreme ultraviolet imaging in an extended reflection mode using coherent Fresnel ptychography
Originally published in Optica on 22 July 2014 (optica-1-1-39
Quantitative Chemically Specific Coherent Diffractive Imaging of Reactions at Buried Interfaces with Few Nanometer Precision
We
demonstrate quantitative, chemically specific imaging of buried nanostructures,
including oxidation and diffusion reactions at buried interfaces,
using nondestructive tabletop extreme ultraviolet (EUV) coherent diffractive
imaging (CDI). Copper nanostructures inlaid in SiO<sub>2</sub> are
coated with 100 nm of aluminum, which is opaque to visible light and
thick enough that neither visible microscopy nor atomic force microscopy
can image the buried interface. Short wavelength high harmonic beams
can penetrate the aluminum layer, yielding high-contrast images of
the buried structures. Quantitative analysis shows that the reflected
EUV light is extremely sensitive to the formation of multiple oxide
layers, as well as interdiffusion of materials occurring at the metal–metal
and metal–insulator boundaries deep within the nanostructure
with few nanometers precision
Subwavelength coherent imaging of periodic samples using a 13.5 nm tabletop high-harmonic light source
Coherent diffractive imaging is unique, being the only route for achieving high spatial resolution in the extreme ultraviolet and X-ray regions, limited only by the wavelength of the light. Recently, advances in coherent short-wavelength light sources, coupled with progress in algorithm development, have significantly enhanced the power of X-ray imaging. However, so far, high-fidelity diffraction imaging of periodic objects has been a challenge because the scattered light is concentrated in isolated peaks. Here, we use tabletop 13.5 nm high-harmonic beams to make two significant advances. First, we demonstrate high-quality imaging of an extended, nearly periodic sample for the first time. Second, we achieve subwavelength spatial resolution (12.6 nm) imaging at short wavelengths, also for the first time. The key to both advances is a novel technique called 'modulus enforced probe', which enables robust and quantitative reconstructions of periodic objects. This work is important for imaging next-generation nano-engineered devices
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Colloidal crystal order and structure revealed by tabletop extreme ultraviolet scattering and coherent diffractive imaging
Colloidal crystals with specific electronic, optical, magnetic, vibrational properties, can be rationally designed by controlling fundamental parameters such as chemical composition, scale, periodicity and lattice symmetry. In particular, silica nanospheres -which assemble to form colloidal crystals- are ideal for this purpose, because of the ability to infiltrate their templates with semiconductors or metals. However characterization of these crystals is often limited to techniques such as grazing incidence small-angle scattering that provide only global structural information and also often require synchrotron sources. Here we demonstrate small-angle Bragg scattering from nanostructured materials using a tabletop-scale setup based on high-harmonic generation, to reveal important information about the local order of nanosphere grains, separated by grain boundaries and discontinuities. We also apply full-field quantitative ptychographic imaging to visualize the extended structure of a silica close-packed nanosphere multilayer, with thickness information encoded in the phase. These combined techniques allow us to simultaneously characterize the silica nanospheres size, their symmetry and distribution within single colloidal crystal grains, the local arrangement of nearest-neighbor grains, as well as to quantitatively determine the number of layers within the sample. Key to this advance is the good match between the high harmonic wavelength used (13.5nm) and the high transmission, high scattering efficiency, and low sample damage of the silica colloidal crystal at this wavelength. As a result, the relevant distances in the sample - namely, the interparticle distance (≈124nm) and the colloidal grains local arrangement (≈1μm) - can be investigated with Bragg coherent EUV scatterometry and ptychographic imaging within the same experiment simply by tuning the EUV spot size at the sample plane (5μm and 15μm respectively). In addition, the high spatial coherence of high harmonics light, combined with advances in imaging techniques, makes it possible to image near-periodic structures quantitatively and nondestructively, and enables the observation of the extended order of quasi-periodic colloidal crystals, with a spatial resolution better than 20nm. In the future, by harnessing the high time-resolution of tabletop high harmonics, this technique can be extended to dynamically image the three-dimensional electronic, magnetic, and transport properties of functional nanosystems