Michal Bodik

Last Name

Bodik

First Name

Michal

ORCID

0000-0002-6518-7617

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Publications 1 - 6 of 6

The effect of work function during electron spectroscopy measurements in Scanning Field-Emission Microscopy
Bodik, Michal; Walker, Christopher; Demydenko, Maksym; et al. (2022)
Ultramicroscopy
Electron spectroscopy proves to be a handy tool in material science. Combination of electron spectroscopy and scanning probe microscopy is possible through Scanning Field Emission Microscopy (SFEM), where a metallic probe positioned close to the surface is used as an electron source. However, using this not too much technologically demanding technique, it looks like the compromise between the lateral resolution and spectroscopic clarity must be considered. Here, we demonstrate, using experimental and simulation data, that the spectroscopic information can be understood without the need to grossly deteriorate the potential spatial resolution of the microscope. We prepared a three-section sample with clean W(110), sub-monolayer Cs on W(110) and monolayer of Cs on W(110) on which electron energy loss spectra are obtained via Scanning Probe Energy Loss Spectroscopy (SPELS) measurements. To explain the detected spectra a new model describing SPELS measurements in a SFEM is developed which aids to uncover the origin of spectral features typically detected during experiments. Experimental and simulation data are in a mutual agreement and observed spectral features on different surfaces could be explained. This novel understanding of SPELS can solve the main issue previously related to this technique, and good spatial resolution can be accompanied by the understanding of the measured spectra.
Multilayer Langmuir Film of Monodisperse Au Nanoclusters: Unusual Growth via Bilayers
Mičky, Simon; Bodik, Michal; Mičetić, Maja; et al. (2022)
Langmuir
The assembly of nanomaterials into thin films is an important area in the nanofabrication of novel devices. The monodispersity of nanoparticles plays an essential role in the resulting quality of the assembled mono- and multilayers. Larger polydispersity leads to smaller lateral correlation lengths and smaller domains of aligned nanoparticles, thus resulting in more point and line defects. Perfectly monodisperse nanoparticles should therefore minimize the number of defects in the assembled films. Despite tremendous progress in reducing the polydispersity of nanoparticles, there has been limited research on the assembly of thin films out of perfectly monodisperse nanoclusters. Here, we show a formation of Langmuir films using perfectly monodisperse gold nanoclusters with composition Au32(nBu3P)12Cl8 exhibiting a diameter of 1.8 nm. Using both in situ and ex situ small-angle X-ray scattering, we show that the monolayer formed on a Langmuir-Blodgett trough exhibits long-range order. Moreover, after compressing the monolayer, we found that the stress accumulated prior to the monolayer collapse triggers a transition to a short-range order not previously reported. If such monolayer is compressed further, the second layer is not formed as in the case of standard nanoparticles. Instead, a growth of islands by an odd number of layers is observed, leading to a thin film with a structure consisting of two different orientations of the hexagonal lattice. Such anomalous behavior may have implications for the possibilities of thin-film formation.
Tunable Subnanometer Gaps in Self-Assembled Monolayer Gold Nanoparticle Superlattices Enabling Strong Plasmonic Field Confinement
Lu, Bin; Vegso, Karol; Micky, Simon; et al. (2023)
ACS Nano
Nanoparticle superlattices produced with controllableinterparticlegap distances down to the subnanometer range are of superior significancefor applications in electronic and plasmonic devices as well as inoptical metasurfaces. In this work, a method to fabricate large-area(& SIM;1 cm(2)) gold nanoparticle (GNP) superlattices witha typical size of single domains at several micrometers and high-densitynanogaps of tunable distances (from 2.3 to 0.1 nm) as well as variableconstituents (from organothiols to inorganic S2-) is demonstrated. Our approach is based on the combination of interfacialnanoparticle self-assembly, subphase exchange, and free-floating ligandexchange. Electrical transport measurements on our GNP superlatticesreveal variations in the nanogap conductance of more than 6 ordersof magnitude. Meanwhile, nanoscopic modifications in the surface potentiallandscape of active GNP devices have been observed following engineerednanogaps. In situ optical reflectance measurementsduring free-floating ligand exchange show a gradual enhancement ofplasmonic capacitive coupling with a diminishing average interparticlegap distance down to 0.1 nm, as continuously red-shifted localizedsurface plasmon resonances with increasing intensity have been observed.Optical metasurfaces consisting of such GNP superlattices exhibittunable effective refractive index over a broad wavelength range.Maximal real part of the effective refractive index, n (max), reaching 5.4 is obtained as a result of the extremefield confinement in the high-density subnanometer plasmonic gaps.
Electron energy analysis in Scanning Field Emission Microscopy using a Bessel box energy analyzer
Bodik, Michal; Demydenko, Maksym; Walker, Chris G.H.; et al. (2021)
In this study, we use Scanning Field Emission Microscopy (SFEM) combined with a miniature electron energy analyzer known as a Bessel box to measure electron energy spectra emitted from a sample. Previous studies using SFEM have revealed that the work function (ϕ) of the material under study has a significant role to play in the formation of the signal intensity. Hence, in order to understand the role of ϕ in greater detail, a sample of W(110) (ϕ = 5.25 eV) and a sample of Cs deposited on W(110) (ϕ ≈ 1.7 eV) were investigated. STM images show that the Cs covered surface has a speckled appearance indicating small Cs islands. The electron energy loss spectra obtained (which are the first using the Bessel box in SFEM) show differing structure in the elastic peak region. Monte Carlo (MC) simulations including quantum mechanical "bouncing" have been carried out. The results are consistent with MC simulations of the electrons escaping from the tip-sample junction.
Scanning Field Emission Microscopy using a miniature Bessel box electron energy analyser
Bodik, Michal; Demydenko, Maksym; Walker, Christopher; et al. (2021)
Proceedings of the Microscience Microscopy Congress 2021 incorporating EMAG 2021
Aligned Bilayer of Single-Walled Carbon Nanotubes Suppresses the Polysulfide Shuttle in Li-S Batteries
Ashraf, Muhammad Adeel; Vegso, Karol; Shaji, Ashin; et al. (2022)
ACS Applied Energy Materials
Lithium-sulfur (Li-S) batteries have attracted much attention due to their high energy density and cost efficiency. However, the drawbacks such as the polysulfide shuttle effect and low electrical conductivity of active sulfur material result in poor cycling performance. In this work, we endeavored to overcome these problems by applying a highly engineered bilayer of single-walled carbon nanotubes (SWCNTs). Two monolayers of aligned SWCNTs were deposited on a glass fiber separator using a modified Langmuir-Schaefer method. The deposited bilayer forms a mesh pattern that acts as a spatial filter to mitigate the polysulfide shuttle effect. To confirm the improvement, we assembled cells with modified glass fiber separators coated by SWCNT bilayers and compared their electrochemical performance with unprotected cells with pristine glass fiber separators. The electrochemical results revealed that the discharge capacity increased significantly for the battery with the modified separator. After 50 cycles (0.5 C), the battery with the coated separator had the same discharge capacity as the battery with the pristine separator after only 20 cycles (600 mA h/g), indicating a significant difference of 30 cycles in capacity retention. This implies that an ultrathin bilayer of SWCNTs on the conventional glass fiber separator significantly suppresses the polysulfide shuttle effect.

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Michal Bodik

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