487 research outputs found
Wideband multilayer mirrors with minimal layer thicknesses variation
Wideband multilayers designed for various applications in hard
X-ray to Extreme UV spectral regions are based on a layered system with
layer thicknesses varying largely in depth. However, because the internal
structure of a thin film depends on its thickness, this will result in
multilayers in which material properties such as density, crystallinity,
dielectric constant and effective thickness vary from layer to layer. This
variation causes the fabricated multilayers to deviate from the model and
negatively influences the reflectivity of the multilayers. In this work we
solve this problem by developing designs of wideband multilayers with
strongly reduced layer thickness variations in depth, without essential
degradation of their optical characteristics
Active multilayer mirrors for reflectance tuning at extreme ultraviolet (EUV) wavelengths
We propose an active multilayer mirror structure for EUV wavelengths
which can be adjusted to compensate for reflectance changes. The multilayer structure tunes the reflectance via an integrated piezoelectric layer that can change its dimension due to an externally applied voltage. Here, we present design and optimization of the mirror structure for maximum reflectance tuning. In addition, we present preliminary results showing that the deposition of piezoelectric thin films with the requisite layer smoothness and crystal structure are possible. Finally, polarization switching of the smoothest piezoelectric film is presented
Characterization of carbon contamination under ion and hot atom bombardment in a tin-plasma extreme ultraviolet light source
Molecular contamination of a grazing incidence collector for extreme
ultraviolet (EUV) lithography was experimentally studied. A carbon film was
found to have grown under irradiation from a pulsed tin plasma discharge. Our
studies show that the film is chemically inert and has characteristics that are
typical for a hydrogenated amorphous carbon film. It was experimentally
observed that the film consists of carbon (~70 at. %), oxygen (~20 at. %) and
hydrogen (bound to oxygen and carbon), along with a few at. % of tin. Most of
the oxygen and hydrogen are most likely present as OH groups, chemically bound
to carbon, indicating an important role for adsorbed water during the film
formation process. It was observed that the film is predominantly sp3
hybridized carbon, as is typical for diamond-like carbon. The Raman spectra of
the film, under 514 and 264 nm excitation, are typical for hydrogenated
diamond-like carbon. Additionally, the lower etch rate and higher energy
threshold in chemical ion sputtering in H2 plasma, compared to
magnetron-sputtered carbon films, suggests that the film exhibits diamond-like
carbon properties.Comment: 18 pages, 10 figure
Graphene defect formation by extreme ultraviolet generated photoelectrons
We have studied the effect of photoelectrons on defect formation in graphene
during extreme ultraviolet (EUV) irradiation. Assuming the major role of these
low energy electrons, we have mimicked the process by using low energy primary
electrons. Graphene is irradiated by an electron beam with energy lower than 80
eV. After e-beam irradiation, it is found that the D peak, I(D), appears in the
Raman spectrum, indicating defect formation in graphene. The evolution of
I(D)/I(G) follows the amorphization trajectory with increasing irradiation
dose, indicating that graphene goes through a transformation from
microcrystalline to nanocrystalline and then further to amorphous carbon.
Further, irradiation of graphene with increased water partial pressure does not
significantly change the Raman spectra, which suggests that, in the extremely
low energy range, e-beam induced chemical reactions between residual water and
graphene is not the dominant mechanism driving defect formation in graphene.
Single layer graphene, partially suspended over holes was irradiated with EUV
radiation. By comparing with the Raman results from e-beam irradiation, it is
concluded that the photoelectrons, especially those from the valence band,
contribute to defect formation in graphene during irradiation.Comment: appears in Journal of Applied Physics 201
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