Multipactor suppression by micro-structured gold/silver coatings for space applications

Nistor, V.; Gonzalez, L.; Aguilera, Lydya; Montero, I.; Galán, L.; Wochner, Ulrich; Raboso, D.

doi:10.1016/j.apsusc.2014.05.049

Cited by 78 publications

(44 citation statements)

References 16 publications

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“…It is clear that the porous Ag/TiO 2 /Au coatings show pronounced SEY suppression effect when compared with smooth Ag/Au coatings. The range that an electron of a given primary energy below 2000 eV can penetrate through Au material is lower than 50 nm1633, and thus much smaller than the Au layer thickness on either porous Ag/TiO 2 surface or smooth Ag surface. Therefore, the structure of coatings plays a significant role in SEY suppression.…”

Section: Resultsmentioning

confidence: 99%

Fabrication of Porous Ag/TiO2/Au Coatings with Excellent Multipactor Suppression

Bao

et al. 2017

Sci Rep

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Porous Ag/TiO2/Au coatings with excellent multipactor suppression were prepared by fabrication of porous Ag surface through two-step wet chemical etching, synthesis of TiO2 coatings by electroless-plating-like solution deposition and deposition of Au coatings via electroless plating. Porous structure of Ag surface, TiO2 coatings on porous Ag surface and Au coatings on porous Ag/TiO2 surface were verified by field-emission scanning electron microscopy, the composition and crystal type of TiO2 coatings was characterized by X-ray photoelectron spectroscopy and X-ray diffraction. Secondary electron yield (SEY) measurement was used to monitor the SEY coefficient of the porous Ag coatings and Ag/TiO2/Au coatings. The as-obtained porous Ag coatings were proved exhibiting low SEY below 1.2, and the process was highly reproducible. In addition, the porous Ag/TiO2/Au coatings showed excellent multipactor suppression with the SEY 1.23 and good environmental stability. It is worth mentioning that the whole preparation process is simple and feasible, which would provide a promising application in RF devices.

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Section: Resultsmentioning

confidence: 99%

Fabrication of Porous Ag/TiO2/Au Coatings with Excellent Multipactor Suppression

Bao

et al. 2017

Sci Rep

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“…Recently, a new wall concept based nano-architected surfaces has been proposed to mitigate surface erosion and SEE [22][23][24][25]. Demonstration designs based on high-Z refractory materials have been developed, including architectures based on metal nanowires and nanofoams [26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the energy imparted by the sheath to the ions within the discharge determines the impact energy and incident angle of ions upon the surface, thus affecting the amount of material sputtered and consequently the wall erosion rate [20,21]. Thus, understanding how SEE affects sheath stability is crucial to make predictions of channel wall lifetime.Recently, a new wall concept based nano-architected surfaces has been proposed to mitigate surface erosion and SEE [22][23][24][25]. Demonstration designs based on high-Z refractory materials have been developed, including architectures based on metal nanowires and nanofoams [26][27][28][29][30].…”

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confidence: 99%

Calculation of secondary electron emission yields from low-energy electron deposition in tungsten surfaces

Chang

Alvarado

Marian

2018

Applied Surface Science

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We present calculations of secondary electron emission (SEE) yields in tungsten as a function of primary electron energies between 50 eV and 1 keV and incidence angles between 0 and 90 • . We conduct a review of the established Monte Carlo methods to simulate multiple electron scattering in solids and select the best suited to study SEE in high-Z metals. We generate secondary electron yield and emission energy functions of the incident energy and angle and fit them to bivariate fitting functions using symbolic regression. We compare the numerical results with experimental data, with good agreement found. Our calculations are the first step towards studying SEE in nanoarchitected surfaces for electric propulsion chamber walls. IntroductionSecondary electron emission (SEE) is the emission of free electrons from a solid surface, which occurs when these surfaces are irradiated with external (also known as primary) electrons. SEE is an important process in surface physics with applications in numerous fields, such as electric propulsion [1-5], particle accelerators [6], plasma-walls in fusion reactors [7][8][9][10][11], electron microscopy and spectroscopy [12,13], radio frequency devices [14-16], etc. In Hall thrusters for electric propulsion, a key component is the channel wall lining protecting the magnetic circuits from the discharge plasma. These channel walls are a significant factor in Hall thruster performance and lifetime through its interactions with the discharge plasma. These interactions are governed by the sheath formed along the walls, and so the properties of the sheath determine the amount of electron energy absorbed by the wall, which in turn affects the electron dynamics within the bulk discharge [1,[17][18][19]. Furthermore, the energy imparted by the sheath to the ions within the discharge determines the impact energy and incident angle of ions upon the surface, thus affecting the amount of material sputtered and consequently the wall erosion rate [20,21]. Thus, understanding how SEE affects sheath stability is crucial to make predictions of channel wall lifetime.Recently, a new wall concept based nano-architected surfaces has been proposed to mitigate surface erosion and SEE [22][23][24][25]. Demonstration designs based on high-Z refractory materials have been developed, including architectures based on metal nanowires and nanofoams [26][27][28][29][30]. The idea behind these designs is to take advantage of very-high surface-to-volume ratios to reduce SEE and ion erosion by internal trapping and redeposition. Preliminary designs are based on W, W/Mo, and W/Re structures, known to have intrinsically low sputtering yields secondary

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“…20,21 However, Bruining notes the greatest reduction in SEY for carbonized nickel occurs when the carbon granules have diameters of about 30 Å, implying that smaller surface structures will be more efficient for controlling a material's SEY. Figure 3 shows two different micron-sized surface structures resulting from two common fabrication processes.…”

Section: Secondary Electron Emission Controlmentioning

confidence: 99%

Surface feature engineering through nanosphere lithography

Laurvick

Coutu

Sattler

et al. 2016

J. Micro/Nanolith. MEMS MOEMS

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Abstract. How surface geometries can be selectively manipulated through nanosphere lithography (NSL) is discussed. Self-assembled monolayers and multilayers of nanospheres have been studied for decades and have been applied to lithography for almost as long. When compared to the most modern, state-of-the-art techniques, NSL offers comparable feature resolution with many advantages over competing technologies. Several high-resolution alternatives require scan-based implementation (i.e., focused ion beams and e-beam lithography) while NSL is much more of a batch operation, allowing for full wafer or possibly even multiple wafer processing, potentially saving time and increasing throughput in a manufacturing environment. Additionally, NSL has continued to be of interest because it does not require expensive, complex equipment to be researched and realized, which continues to fuel interest in this approach. In spite of these advantages, applying NSL to specific, realizable devices is limited in the literature. The reason for this lack of application is not only unreliability in the self-assembly process, but also control of these patterned nanospheres within larger, multistep processes often required to fabricate most devices. Both of these items are addressed in this paper. The first issue was addressed through the development of a series of custom-designed nanosphere application vessels. These were designed based on the best published results from the literature, utilizing an alternate method of dip-coating but performed through draining the carrier fluid over the substrate rather than moving the substrate across the liquid-air boundary layer. This method is in the easier to perform, but arguably less-reliable spin-coating method also commonly employed. The key enabler in this effort lies in commercially available three-dimensional (3-D) printing technology, and how it was applied to rapidly prototype-improved deposition vessels. This was accomplished primarily with a single day turn-around between each 3-D printed design iteration. Each vessel design was incrementally improved, built, and tested to optimize the best performance in achieving the most reliable, repeatable self-aligned nanosphere layer formation. With an optimized design of this vessel in hand, the second challenge was addressed by using this vessel and the patterned nanosphere layers it produced with a patterned photoresist design to capture single layers of nanospheres in specifically designed locations and orientations. The hybrid mask produced from this approach can be integrated within virtually any multistep fabrication process. Additionally, other processing steps will be discussed, such as reactive ion etching (RIE), plasma ashing, and photoresist reflowing, and how they might be combined with these hybrid masks. Various results from combinations of these steps are presented. Finally, two potential applications which could benefit greatly from the resulting, engineered surface structures are discussed. These include a small-scale device appl...

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Multipactor suppression by micro-structured gold/silver coatings for space applications

Cited by 78 publications

References 16 publications

Fabrication of Porous Ag/TiO2/Au Coatings with Excellent Multipactor Suppression

Fabrication of Porous Ag/TiO2/Au Coatings with Excellent Multipactor Suppression

Calculation of secondary electron emission yields from low-energy electron deposition in tungsten surfaces

Surface feature engineering through nanosphere lithography

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