Secondary electron deposition mechanism of carbon contamination

Leontowich, Adam F. G.; Hitchcock, Adam P.

doi:10.1116/1.3698602

Cited by 21 publications

(15 citation statements)

References 26 publications

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“…The relatively high carbon content is attributed to a comparably low base pressure within the gas cell resulting in deposition from residual gas and the CO ligands of the precursor molecule. The detected C K-edge NEXAFS spectra are in accordance with spectra from "dead-end"-products of long-time illuminated carbon containing material that has reached a state that cannot be further altered solely by X-ray illumination [89,99]. Due to the relatively high contamination level it was not surprising that XMCD imaging of the respective deposit did not yield any contrast indicating magnetic properties from pure Co or respective pure oxides.…”

Section: What We Have Already Learned About Fxbidsupporting

confidence: 63%

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

Späth

2019

Micromachines

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Focused soft X-ray beam induced deposition (FXBID) is a novel technique for direct-write nanofabrication of metallic nanostructures from metal organic precursor gases. It combines the established concepts of focused electron beam induced processing (FEBIP) and X-ray lithography (XRL). The present setup is based on a scanning transmission X-ray microscope (STXM) equipped with a gas flow cell to provide metal organic precursor molecules towards the intended deposition zone. Fundamentals of X-ray microscopy instrumentation and X-ray radiation chemistry relevant for FXBID development are presented in a comprehensive form. Recently published proof-of-concept studies on initial experiments on FXBID nanolithography are reviewed for an overview on current progress and proposed advances of nanofabrication performance. Potential applications and advantages of FXBID are discussed with respect to competing electron/ion based techniques. polymer resulting in 3D patterning by radiation chemistry [33,34]. The approach is limited to materials with significantly different absorption cross-sections at the chosen incident photon energies, as in transmission geometry, all layers are exposed to the beam at different degrees of focusing. However, such experiments open a completely novel perspective for complex direct-write nanofabrication. It should be mentioned that during the late 1980s and early 1990s several groups attempted to exploit broad-band synchrotron light [38][39][40][41] as well as the monochromatic X-ray beam of a photon-induced scanning Auger microscope [42,43] for additive manufacturing of metal deposits from metal organic precursors. However, due to limited instrumental capabilities, only spatially extended thin films with an optimum of some 10 µm resolution could be produced [43].FXBID exploits the photon energy-selectivity of synchrotron-based XRL and extends it by the idea of depositing metal nanostructures from suitable precursor gases [21,22]. The use of a STXM setup for these experiments offers several advantages. STXM is a raster-scanning technique which avoids the necessity of shadow masks. According to comparable results from polymer lithography the theoretical minimum feature size of the deposited metal structures is mainly determined by the spot size of the incident beam [36,37]. Recent developments in X-ray optics have pushed this parameter below 10 nm [44,45]. Finally, STXM can be employed for an in-situ analysis of the metallic deposits directly after fabrication by means of resonant imaging and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to evaluate confinement, growth rates, oxidation state and chemical purity [21,22,46,47]. X-ray magnetic circular dichroism (XMCD) can be used to characterize magnetic deposits with respect to their magnetization and coercivity [48].This review presents some basic principles of X-ray optics and X-ray microscopy as well as X-ray beam dosimetry that are relevant for FXBID experiments. In accordance, limitations, challenges and opportunities of additiv...

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Section: What We Have Already Learned About Fxbidsupporting

confidence: 63%

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

Späth

2019

Micromachines

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“…These chemical modifications are likely due to the dissociation of Cu-O, C-H [26,27], and C-O bonds and to the recombination of volatile molecules as O 2 and H 2 O that easily desorb under the action of the impinging electrons. In this reaction, a possible role of secondary electrons coming from the bulk of the sample cannot be excluded [36]. The loss of O-containing molecules reduces the oxidized components in the contaminated surface and results in a SEY decrease.…”

Section: Resultsmentioning

confidence: 99%

Secondary electron yield of Cu technical surfaces: Dependence on electron irradiation

Larciprete

Grosso

Commisso

et al. 2013

Phys. Rev. ST Accel. Beams

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The secondary emission yield (SEY) properties of colaminated Cu samples for LHC beam screens are correlated to the surface chemical composition determined by x-ray photoelectron spectroscopy. The surface of the as-received samples is characterized by the presence of significant quantities of contaminating adsorbates and by the maximum of the SEY curve ( max ) being as high as 2.1. After extended electron scrubbing at kinetic energy of 10 and 500 eV, the max value drops to the ultimate values of 1.35 and 1.1, respectively. In both cases the surface oxidized phases are significantly reduced, whereas only in the sample scrubbed at 500 eV the formation of a graphitic-like C layer is observed. We find that the electron scrubbing of technical Cu surfaces can be described as occurring in two steps: the first step consists in the electron-induced desorption of weakly bound contaminants that occurs indifferently at 10 and at 500 eV and corresponds to a partial decrease of max ; the second step, activated by more energetic electrons and becoming evident at high doses, increases the number of graphitic-like C-C bonds via the dissociation of adsorbates already contaminating the as-received surface or accumulating on this surface during irradiation. Our results demonstrate how the kinetic energy of impinging electrons is a crucial parameter when conditioning the surfaces of Cu and other metals by means of electron-induced chemical processing.

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“…It is imperative to image the structures in the proper order to avoid introducing artefacts. Both SEM and STXM involve ionizing radiation which can induce mass loss, chemical changes, and deposit carbon, 17 permanently altering the sample. [4][5][6] Tapping mode AFM imaging did not noticeably alter the sample and therefore was always performed before SEM or STXM imaging.…”

Section: Imagingmentioning

confidence: 99%

Zone plate focused soft x-ray lithography for fabrication of nanofluidic devices

Leontowich

Hitchcock

2012

Alternative Lithographic Technologies IV

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Sealed nanofluidic channels with cross sections of sub-100 nm * 100 nm were created in a polymer bilayer using the focused soft X-rays of a scanning transmission X-ray microscope and the direct write method. The width of the nanochannels can be controlled by the area patterned in X and Y, while the height can be controlled by tuning the layer thicknesses. Formation of the desired structures has been confirmed by near edge X-ray absorption fine structure spectromicroscopy and scanning electron microscopy. The maximum length of the nanochannels fabricated by this method was found to be limited by the efficiency of excavation of patterned material out of the channel, as well as the stability of the polymer over-layer which seals it. Schemes toward interfacing these nanochannels with conventional microfluidics are discussed.

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Secondary electron deposition mechanism of carbon contamination

Cited by 21 publications

References 26 publications

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

Secondary electron yield of Cu technical surfaces: Dependence on electron irradiation

Zone plate focused soft x-ray lithography for fabrication of nanofluidic devices

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