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  • 1.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Toprak, M. S.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Reaction control of metal-assisted chemical etching for silicon-based zone plate nanostructures2018In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, no 23, p. 12628-12634Article in journal (Refereed)
    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. 

  • 2.
    Akan, Rabia
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Carmen
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Toprak, Muhammet S.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Reaction control of metal-assisted chemical etching for silicon-based zone plate nanostructuresManuscript (preprint) (Other academic)
    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 HF:H2O2 concentrations of 4.7 M:0.68 M and room temperature with an etching rate of 0.7 micrometers per minute, 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.

  • 3.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    High-Aspect Ratio Nanofabrication for Hard X-Ray Zone Plates2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hard x-ray nanoimaging enables structural investigations of new materials for many applications. For high-resolution experiments, zone plate x-ray optics are commonly chosen.Two methods of zone plate nanofabrication are presented in this thesis.

    Zone plates are circular diffraction gratings with radially decreasing grating period. Their optical resolution depends on the width of the smallest zone, which nowadays can be around 10 nanometers. However, the efficiency of a zone plate depends on its thickness and its material. For hard x-rays, the optimal zone plate thickness is in the order of micrometers. Therefore, high aspect ratio nanofabrication processes are needed.Two such methods are investigated in this study.

    First, an existing tungsten nanofabrication process based on reactive ion etching (RIE) was extended to 22:1 aspect ratio structures at 30~nm line width. The core improvement was a resist curing step that enhanced pattern transfer during RIE. Such a zone plate with 200 micrometer diameter and 2.2% efficiency was used in the commissioning experiment of NanoMAX, the nanoimaging beamline at the Swedish synchrotron facility MAX IV. Transmission imaging with 40 nm resolution, as well as the fluorescence imaging modality were demonstrated.

    Second, metal-assisted chemical etching (MACE) of silicon using gold catalyst patterns was investigated. MACE dependence on gold pattern geometry, etching solution composition, temperature, and substrate doping is described. The process is characterized in terms of etching rate, directionality, and nanostructure surface roughness.

    Finally, the Ronchi test is presented as a way to quickly judge the performance of x-ray optics in terms of present aberrations and x-ray sources in terms of coherence.

  • 4.
    Parfeniukas, Karolis
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Giakoumidis, Stylianos
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Akan, Rabia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    High-aspect ratio zone plate fabrication for hard x-ray nanoimaging2017In: 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.

  • 5.
    Parfeniukas, Karolis
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Rahomäki, Jussi
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Giakoumidis, Stylianos
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Seiboth, F.
    Wittwer, F.
    Schroer, C. G.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Improved tungsten nanofabrication for hard X-ray zone plates2016In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 152, p. 6-9Article in journal (Refereed)
    Abstract [en]

    We present an improved nanofabrication method of high aspect ratio tungsten structures for use in high efficiency nanofocusing hard X-ray zone plates. A ZEP 7000 electron beam resist layer used for patterning is cured by a second, much larger electron dose after development. The curing step improves pattern transfer fidelity into a chromium hard mask by reactive ion etching using Cl2/O2 chemistry. The pattern can then be transferred into an underlying tungsten layer by another reactive ion etching step using SF6/O2. A 630 nm-thick tungsten zone plate with smallest line width of 30 nm was fabricated using this method and characterized. At 8.2 keV photon energy the device showed an efficiency of 2.2% with a focal spot size at the diffraction limit, measured at Diamond Light Source I-13-1 beamline.

  • 6. Seiboth, Frank
    et al.
    Schropp, Andreas
    Scholz, Maria
    Wittwer, Felix
    Roedel, Christian
    Wuensche, Martin
    Ullsperger, Tobias
    Nolte, Stefan
    Rahomäki, Jussi
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Giakoumidis, Stylianos
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Wagner, Ulrich
    Rau, Christoph
    Boesenberg, Ulrike
    Garrevoet, Jan
    Falkenberg, Gerald
    Galtier, Eric C.
    Lee, Hae Ja
    Nagler, Bob
    Schroer, Christian G.
    Aberration Correction for Hard X-ray Focusing at the Nanoscale2017In: Advances in X-Ray/EUV Optics and Components XII / [ed] Morawe, C Khounsary, AM Goto, S, SPIE - International Society for Optical Engineering, 2017, article id UNSP 103860AConference paper (Refereed)
    Abstract [en]

    We developed a corrective phase plate that enables the correction of residual aberration in reflective, diffractive, and refractive X-ray optics. The principle is demonstrated on a stack of beryllium compound refractive lenses with a numerical aperture of 0.49 x 10(-3) at three different synchrotron radiation and x-ray free-electron laser facilities. By introducing this phase plate into the beam path, we were able to correct the spherical aberration of the optical system and improve the Strehl ratio of the optics from 0.29(7) to 0.87(5), creating a diffraction-limited, large aperture, nanofocusing optics that is radiation resistant and very compact.

  • 7. Seiboth, Frank
    et al.
    Schropp, Andreas
    Scholz, Maria
    Wittwer, Felix
    Rödel, Christian
    Wünsche, Martin
    Ullsperger, Tobias
    Nolte, Stefan
    Rahomäki, Jussi
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Giakoumidis, Stylianos
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Vogt, Ulrich
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Wagner, Ulrich
    Rau, Christoph
    Boesenberg, Ulrike
    Garrevoet, Jan
    Falkenberg, Gerald
    Galtier, Eric C.
    Ja Lee, Hae
    Nagler, Bob
    Schroer, Christian G.
    Perfect X-ray focusing via fitting corrective glasses to aberrated optics2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8Article in journal (Refereed)
    Abstract [en]

    Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and below. At the same time, it is this short wavelength that puts stringent requirements on X-ray optics and their metrology. Both are limited by today’s technology. In this work, we present accurate at wavelength measurements of residual aberrations of a refractive X-ray lens using ptychography to manufacture a corrective phase plate. Together with the fitted phase plate the optics shows diffraction-limited performance, generating a nearly Gaussian beam profile with a Strehl ratio above 0.8. This scheme can be applied to any other focusing optics, thus solving the X-ray optical problem at synchrotron radiation sources and X-ray free-electron lasers.

  • 8.
    Vogt, Ulrich
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Parfeniukas, Karolis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Stankevic, Tomas
    Kalbfleisch, Sebastian
    Liebi, Marianne
    Matej, Zdenek
    Björling, Alexander
    Carbone, Gerardina
    Mikkelsen, Anders
    Johansson, Ulf
    First x-ray nanoimaging experiments at NanoMAX2017In: X-Ray Nanoimaging: Instruments and Methods III 2017 / [ed] Lai, B Somogyi, A, SPIE - International Society for Optical Engineering, 2017, Vol. 10389, article id 103890KConference paper (Refereed)
    Abstract [en]

    NanoMAX is a hard x-ray nanoimaging beamline at the new Swedish synchrotron radiation source MAX IV that became operational in 2016. Being a beamline dedicated to x-ray nanoimaging in both 2D and 3D, NanoMAX is the first to take full advantage of MAX IVs exceptional low emittance and resulting coherent properties. We present results from the first experiments at NanoMAX that took place in December 2016. These did not use the final experimental stations that will become available to users, but a temporary arrangement including zone plate and order-sorting aperture stages and a piezo-driven sample scanner. We used zone plates with outermost zone widths of 100 nm and 30 nm and performed experiments at 8 keV photon energy for x-ray absorption and fluorescence imaging and ptychography. Moreover, we investigated stability and coherence with a Ronchi test method. Despite the rather simple setup, we could demonstrate spatial resolution below 50 nm after only a few hours of beamtime. The results showed that the beamline is working as expected and experiments approaching the 10 nm resolution level or below should be possible in the future.

1 - 8 of 8
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