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Akan, Rabia
Publications (2 of 2) Show all publications
Akan, R., Parfeniukas, K., Vogt, C., Toprak, M. S. & Vogt, U. (2018). Reaction control of metal-assisted chemical etching for silicon-based zone plate nanostructures. RSC Advances, 8(23), 12628-12634
Open this publication in new window or tab >>Reaction control of metal-assisted chemical etching for silicon-based zone plate nanostructures
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2018 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, no 23, p. 12628-12634Article in journal (Refereed) Published
Abstract [en]

Metal-assisted chemical etching (MACE) reaction parameters were investigated for the fabrication of specially designed silicon-based X-ray zone plate nanostructures using a gold catalyst pattern and etching solutions composed of HF and H2O2. Etching depth, zone verticality and zone roughness were studied as a function of etching solution composition, temperature and processing time. Homogeneous, vertical etching with increasing depth is observed at increasing H2O2 concentrations and elevated processing temperatures, implying a balance in the hole injection and silica dissolution kinetics at the gold-silicon interface. The etching depth decreases and zone roughness increases at the highest investigated H2O2 concentration and temperature. Possible reasons for these observations are discussed based on reaction chemistry and zone plate design. Optimum MACE conditions are found at HFH2O2 concentrations of 4.7 M:0.68 M and room temperature with an etching rate of ≈0.7 μm min-1, which is about an order of magnitude higher than previous reports. Moreover, our results show that a grid catalyst design is important for successful fabrication of vertical high aspect ratio silicon nanostructures. 

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
Keywords
Aspect ratio, Charge injection, Hydrofluoric acid, Nanocatalysts, Nanostructures, Plate metal, Processing, Silica, Silicon, X ray diffraction, Etching solutions, Metal-assisted chemical etching, Processing temperature, Reaction chemistry, Reaction parameters, Silica dissolution, Silicon interface, Silicon nano structures, Etching
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-227483 (URN)10.1039/c8ra01627e (DOI)2-s2.0-85045188242 (Scopus ID)
Funder
Swedish Research Council
Note

Export Date: 9 May 2018; Article; CODEN: RSCAC; Correspondence Address: Vogt, U.; KTH Royal Institute of Technology, Department of Applied Physics, Biomedical and X-ray Physics, Albanova University CenterSweden; email: uvogt@kth.se; Funding details: VR, Vetenskapsrådet; Funding text: This work was supported by the Swedish Research Council. We thank Adem B. Ergul for help with the cross-section images and Jussi Rahomäki for starting with MACE in our group. QC 20180516

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2019-10-18Bibliographically approved
Parfeniukas, K., Giakoumidis, S., Akan, R. & Vogt, U. (2017). High-aspect ratio zone plate fabrication for hard x-ray nanoimaging. In: Morawe, C Khounsary, AM Goto, S (Ed.), Advances in X-Ray/EUV Optics and Components XII: . Paper presented at Conference on Advances in XRay/ EUV Optics and Components XII held as part of the SPIE Optics + Photonics Symposium, AUG 08-09, 2017, San Diego, CA. SPIE - International Society for Optical Engineering, 10386, Article ID UNSP 103860S.
Open this publication in new window or tab >>High-aspect ratio zone plate fabrication for hard x-ray nanoimaging
2017 (English)In: Advances in X-Ray/EUV Optics and Components XII / [ed] Morawe, C Khounsary, AM Goto, S, SPIE - International Society for Optical Engineering, 2017, Vol. 10386, article id UNSP 103860SConference paper (Refereed)
Abstract [en]

We present our results in fabricating Fresnel zone plate optics for the NanoMAX beamline at the fourth-generation synchrotron radiation facility MAX IV, to be used in the energy range of 6-10 keV. The results and challenges of tungsten nanofabrication are discussed, and an alternative approach using metal-assisted chemical etching (MACE) of silicon is showcased. We successfully manufactured diffraction-limited zone plates in tungsten with 30 nm outermost zone width and an aspect ratio of 21:1. These optics were used for nanoimaging experiments at NanoMAX. However, we found it challenging to further improve resolution and diffraction efficiency using tungsten. High efficiency is desirable to fully utilize the advantage of increased coherence on the optics at MAX IV. Therefore, we started to investigate MACE of silicon for the nanofabrication of high-resolution and high-efficiency zone plates. The first type of structures we propose use the silicon directly as the phase-shifting material. We have achieved 6 mu m deep dense vertical structures with 100 nm linewidth. The second type of optics use iridium as the phase material. The structures in the silicon substrate act as a mold for iridium coating via atomic layer deposition (ALD). A semi-dense pattern is used with line-to-space ratio of 1:3 for a so-called frequency-doubled zone plate. This way, it is possible to produce smaller structures with the tradeoff of the additional ALD step. We have fabricated 45 nm-wide and 3.6 mu m-tall silicon/iridium structures.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2017
Series
Proceedings of SPIE, ISSN 0277-786X ; 10386
Keywords
zone plate, high-aspect ratio, etching, RIE, MACE, tungsten, silicon, gold
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-220503 (URN)10.1117/12.2272695 (DOI)000417334200016 ()2-s2.0-85038958242 (Scopus ID)978-1-5106-1230-3 (ISBN)978-1-5106-1229-7 (ISBN)
Conference
Conference on Advances in XRay/ EUV Optics and Components XII held as part of the SPIE Optics + Photonics Symposium, AUG 08-09, 2017, San Diego, CA
Funder
Swedish Research Council, C0242401Knut and Alice Wallenberg Foundation
Note

QC 20171222

Available from: 2017-12-22 Created: 2017-12-22 Last updated: 2018-03-09Bibliographically approved
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