Prevention of electron field emission from molybdenum substrates for photocathodes by the native oxide layer

Lagotzky, Stefan; Barday, R.; Jankowiak, Andreas; Kamps, T.; Klimm, C.; Knobloch, Jens; Müller, Günter; Senkovskiy, Boris V.; Siewert, Frank

doi:10.1051/epjap/2015150167

Cited by 3 publications

(2 citation statements)

References 23 publications

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“…All samples were grown on polished Mo substrates, as this is the intended plug material for photoinjector operation. Mo has also been studied in terms of unwanted field emission [21]. Mo sheets of size 10 × 10 mm 2 have been used for the sample P006 and so-called Mo plugs, with a diameter of 10 mm in the final photoinjector design, have been used for the other samples.…”

Section: A Substrate Preparationmentioning

confidence: 99%

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Schmeißer

Mistry

Kirschner

et al. 2018

Phys. Rev. Accel. Beams

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High quantum efficiency photocathodes are mandatory for the operation of photoinjector driven electron accelerators with high average current and high brightness beams. Photocathodes based on bi-alkali antimonides, e.g., CsK 2 Sb, exhibit high quantum efficiencies for visible light and can be operated close to the photoemission threshold, thus they are suitable candidates to provide high current and low emittance electron beams. In this paper, a codeposition procedure of K and Cs on Sb resulting in high quantum efficiency photocathodes is presented and compared to the sequential growth procedure that was established for photomultiplier and accelerator applications. In-situ x-ray photoelectron spectroscopy is applied to gain insights into the reaction pathway of antimony with alkali metals, and to optimize the growth process of CsK 2 Sb on Mo. It has been found that the average stoichiometry of the samples is similar after both procedures. The study also presents the behavior of the photocurrent at cryogenic temperatures, the influence of cooling and warmup cycles on the photocathode lifetime and our experience with storage and transport. This work demonstrates that our codeposition growth procedure reproducibly delivers high quantum efficiency photocathodes, and that their quantum efficiency, when excited with green photons, is not influenced by cryogenic temperatures.

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Section: A Substrate Preparationmentioning

confidence: 99%

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Schmeißer

Mistry

Kirschner

et al. 2018

Phys. Rev. Accel. Beams

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“…In the case of Mo, a deeper understanding of the field emission from its surfaces, naturally-oxidized and/or heated, is required. Recently, Lagotzky et al [36] showed that well-polished Mo samples did not show parasitic field emission up to a field level of 50 MV/m, while in situ heat treatments above 400 • C activated the field emission at lower field strength. However, oxygen loading into the Mo surface partially weakens the emitters revealing the suppression of field emission by native Mo oxides.…”

Section: Discussionmentioning

confidence: 99%

Materials and Breakdown Phenomena: Heterogeneous Molybdenum Metallic Films

et al. 2017

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Technological activities to design, manufacture, and test new accelerating devices using different materials and methods is under way all over the world. The main goal of these studies is to increase the accelerating gradients and reduce the probability of radio-frequency (RF) breakdown. Indeed, it is still not clear why, by increasing the intensity of the applied field, intense surface damage is observed in copper structures, limiting the lifetime and, therefore, the practical applications. A possible solution is represented by a coating of a relatively thick layer of molybdenum in order to improve the breakdown rate. molybdenum can be reliably grown on different substrates with a negligible strain and, for thicknesses up to 600 nm, with a resistivity <100-150·µΩ cm. Moreover, Mo coatings with controlled composition, internal stress, and roughness may allow improving thermo-mechanical properties reaching values not attainable by uncoated copper. Although the Mo conductivity remains lower compared to Cu, a Mo coating represents a very interesting option for high gradient accelerator components manufactured in copper.

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MoO3 films grown on polycrystalline Cu: Morphological, structural, and electronic properties

Macis

Aramo

Bonavolontà

et al. 2019

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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In this work, the authors investigated MoO3 films with thickness between 30 nm and 1 μm grown at room temperature by solid phase deposition on polycrystalline Cu substrates. Atomic force microscopy, scanning electron microscopy, and scanning tunneling microscopy revealed the presence of a homogenous MoO3 film with a “grainlike” morphology, while Raman spectroscopy showed an amorphous character of the film. Nanoindentation measurements evidenced a coating hardness and stiffness comparable with the copper substrate ones, while Auger electron spectroscopy, x-ray absorption spectroscopy, and secondary electron spectroscopy displayed a pure MoO3 stoichiometry and a work function ΦMoO3 = 6.5 eV, 1.8 eV higher than that of the Cu substrate. MoO3 films of thickness between 30 and 300 nm evidenced a metallic behavior, whereas for higher thickness, the resistance–temperature curves showed a semiconducting character.

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Prevention of electron field emission from molybdenum substrates for photocathodes by the native oxide layer

Cited by 3 publications

References 23 publications

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Towards the operation of Cs-K-Sb photocathodes in superconducting rf photoinjectors

Materials and Breakdown Phenomena: Heterogeneous Molybdenum Metallic Films

MoO3 films grown on polycrystalline Cu: Morphological, structural, and electronic properties

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