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Dive into the research topics where Jiří Spousta is active.

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Featured researches published by Jiří Spousta.


Nature Nanotechnology | 2013

Dynamic switching of the spin circulation in tapered magnetic nanodisks

V. Uhlíř; Michal Urbánek; L. Hladík; Jiří Spousta; M-Y. Im; Peter Fischer; Nasim Eibagi; Jimmy J. Kan; Eric E. Fullerton; Tomáš Šikola

Magnetic vortices are characterized by the sense of in-plane magnetization circulation and by the polarity of the vortex core. With each having two possible states, there are four possible stable magnetization configurations that can be utilized for a multibit memory cell. Dynamic control of vortex core polarity has been demonstrated using both alternating and pulsed magnetic fields and currents. Here, we show controlled dynamic switching of spin circulation in vortices using nanosecond field pulses by imaging the process with full-field soft X-ray transmission microscopy. The dynamic reversal process is controlled by far-from-equilibrium gyrotropic precession of the vortex core, and the reversal is achieved at significantly reduced field amplitudes when compared with static switching. We further show that both the field pulse amplitude and duration required for efficient circulation reversal can be controlled by appropriate selection of the disk geometry.


Nanotechnology | 2010

Focused ion beam fabrication of spintronic nanostructures: an optimization of the milling process

Michal Urbánek; V. Uhlíř; Petr Bábor; E Kolíbalová; T Hrnčíř; Jiří Spousta; Tomáš Šikola

Focused ion beam (FIB) milling has been used to fabricate magnetic nanostructures (wires, squares, discs) from single magnetic layers (Co, permalloy) and spin-valve (permalloy/Cu/Co) multilayers (thicknesses 5-50 nm) prepared by ion beam sputtering deposition. Milled surfaces of metallic thin films typically exhibit residual roughness, which is also transferred onto the edges of the milled patterns. This can lead to domain wall pinning and influence the magnetization behaviour of the nanostructures. We have investigated the milling process and the influence of the FIB parameters (incidence angle, dwell time, overlap and ion beam current) on the roughness of the milled surface. It has been found that the main reasons for increased roughness are different sputter yields for various crystallographic orientations of the grains in polycrystalline magnetic thin films. We have found that the oblique ion beam angle, long dwell time and overlap < 1 are favourable parameters for suppression of this intrinsic roughness. Finally, we have shown how to determine the ion dose necessary to mill through the whole thin film up to the silicon substrate from scanning electron microscopy (SEM) images only.


Journal of Physics: Conference Series | 2007

The influence of humidity on the kinetics of local anodic oxidation

Miroslav Bartošík; David Škoda; O. Tomanec; Radek Kalousek; P Jánský; Jakub Zlámal; Jiří Spousta; Tomáš Šikola

In this paper the influence of relative humidity on fabrication of nanostructures at GaAs (100) surfaces by local anodic oxidation (LAO) is reported. The attention was paid both to the dimensions of oxide nanolines prepared at different relative humidities for tip-surface voltages of 6 - 9 V and tip speeds of 10 - 200 nm/s, and to the profiles corresponding to line trenches (etched in HCl after the nanoxidation). Contrary to the expectations the height and the half-width of oxide nanolines did not increase with relative humidity in the whole interval from 35% to 90%, but for lower relative humidities (< 50%) the lines were comparable in size to those prepared at 90%. However, this was accompanied with instabilities in the oxidation process resulting most probably from enhanced size variations of the water meniscus between the tip and the surface at these low humidities.


Review of Scientific Instruments | 2011

An ultra-low energy (30-200 eV) ion-atomic beam source for ion-beam-assisted deposition in ultrahigh vacuum.

Jindřich Mach; Tomáš Šamořil; Stanislav Voborný; Miroslav Kolíbal; Jakub Zlámal; Jiří Spousta; L. Dittrichová; Tomáš Šikola

The paper describes the design and construction of an ion-atomic beam source with an optimized generation of ions for ion-beam-assisted deposition under ultrahigh vacuum (UHV) conditions. The source combines an effusion cell and an electron impact ion source and produces ion beams with ultra-low energies in the range from 30 eV to 200 eV. Decreasing ion beam energy to hyperthermal values (≈10(1) eV) without loosing optimum ionization conditions has been mainly achieved by the incorporation of an ionization chamber with a grid transparent enough for electron and ion beams. In this way the energy and current density of nitrogen ion beams in the order of 10(1) eV and 10(1) nA/cm(2), respectively, have been achieved. The source is capable of growing ultrathin layers or nanostructures at ultra-low energies with a growth rate of several MLs/h. The ion-atomic beam source will be preferentially applied for the synthesis of GaN under UHV conditions.


Optics Express | 2017

Imaging of near-field interference patterns by aperture-type SNOM – influence of illumination wavelength and polarization state

Petr Dvořák; Zoltán Édes; Michal Kvapil; Tomáš Šamořil; Filip Ligmajer; Martin Hrtoň; Radek Kalousek; Vlastimil Křápek; Petr Dub; Jiří Spousta; Peter Varga; Tomáš Šikola

Scanning near-field optical microscopy (SNOM) in combination with interference structures is a powerful tool for imaging and analysis of surface plasmon polaritons (SPPs). However, the correct interpretation of SNOM images requires profound understanding of principles behind their formation. To study fundamental principles of SNOM imaging in detail, we performed spectroscopic measurements by an aperture-type SNOM setup equipped with a supercontinuum laser and a polarizer, which gave us all the degrees of freedom necessary for our investigation. The series of wavelength- and polarization-resolved measurements, together with results of numerical simulations, then allowed us to identify the role of individual near-field components in formation of SNOM images, and to show that the out-of-plane component generally dominates within a broad range of parameters explored in our study. Our results challenge the widespread notion that this component does not couple to the aperture-type SNOM probe and indicate that the issue of SNOM probe sensitivity towards the in-plane and out-of-plane near-field components - one of the most challenging tasks of near field interference SNOM measurements - is not yet fully resolved.


Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 1997

CLEANING OF METAL SURFACES BY A BROAD BEAM ION SOURCE

Tomáš Šikola; L. Dittrichová; Jiří Spousta; Jakub Zlámal; Jan Štefka

Abstract To describe and analyse a process of the surface cleaning by ion beams, a simple model based on the static TRIM92 code is presented and compared with the dynamic T-Dyn code. Although we have found a systematic shift between values based on TRIM92 and T-Dyn calculations, a combination of both methods made possible to analyse a process of removing ultra-thin carbon films from a copper surface. The simulation confirmed that to increase the efficiency of the cleaning process, the sputtering should be carried out at higher angles of incidence (60°–70°). The energy of the ion beam should be kept as low as possible to reduce a penetration of recoil carbon atoms into copper (at least during the final phase of the sputtering process). On the other hand, the sputtering yield corresponding to low ion energies may not be high enough to keep the etching process going on. Thus, the energy of 500–2000 eV seems to be a reasonable compromise between these two opposite requirements.


Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology | 2015

Experimental optimization of power-function-shaped drive pulse for stick-slip piezo actuators

J. Neuman; Z. Nováček; M. Pavera; Jakub Zlámal; Radek Kalousek; Jiří Spousta; L. Dittrichová; Tomáš Šikola


Thin Solid Films | 2004

Deposition and in-situ characterization of ultra-thin films

Stanislav Voborný; Miroslav Kolíbal; Jindřich Mach; Jan Čechal; Petr Bábor; Stanislav Průša; Jiří Spousta; Tomáš Šikola


Surface and Interface Analysis | 2002

In situ measurements of surface homogeneity of optical parameters of weakly absorbing thin films

Jiří Spousta; Michal Urbánek; Radim Chmelik; J. Jiruše; Jakub Zlámal; Karel Navrátil; A. Nebojsa; Tomáš Šikola


Surface and Interface Analysis | 2004

Instrument for thin film diagnostics by UV spectroscopic reflectometry

Michal Urbánek; Jiří Spousta; Karel Navrátil; R. Szotkowski; Radim Chmelik; M. Buček; Tomáš Šikola

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Tomáš Šikola

Brno University of Technology

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Jakub Zlámal

Brno University of Technology

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Michal Urbánek

Brno University of Technology

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Radek Kalousek

Brno University of Technology

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L. Dittrichová

Brno University of Technology

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Petr Dub

Brno University of Technology

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Jan Čechal

Central European Institute of Technology

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Jindřich Mach

Brno University of Technology

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Miroslav Kolíbal

Brno University of Technology

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