Příprava a charakterizace nanostruktur

Browse

Now showing 1 - 5 of 86

Singular and Nonsingular Transitions in the Infrared Plasmons of Nearly Touching Nanocube Dimers
(AMER CHEMICAL SOC, 2024-05-28) Wu, Yina; Konečná, Andrea; Cho, Shin Hum; Milliron, Delia J.; Hachtel, Jordan A.; de Abajo, F. Javier García
Narrow gaps between plasmon-supporting materials can confine infrared electromagnetic energy at the nanoscale, thus enabling applications in areas such as optical sensing. However, in nanoparticle dimers, the nature of the transition between touching (zero gap) and nearly nontouching (nonzero gap less than or similar to 15 nm) regimes is still a subject of debate. Here, we observe both singular and nonsingular transitions in infrared plasmons confined to dimers of fluorine-doped indium oxide nanocubes when moving from touching to nontouching configurations depending on the dimensionality of the contact region. Through spatially resolved electron energy-loss spectroscopy, we find a continuous spectral evolution of the lowest-order plasmon mode across the transition for finite touching areas, in excellent agreement with the simulations. This behavior challenges the widely accepted idea that a singular transition always emerges in the near-touching regime of plasmonic particle dimers. The apparent contradiction is resolved by theoretically examining different types of gap morphologies, revealing that the presence of a finite touching area renders the transition nonsingular, while one-dimensional and point-like contacts produce a singular behavior in which the lowest-order dipolar mode in the touching configuration, characterized by a net induced charge in each of the particles, becomes unphysical as soon as they are separated. Our results provide valuable insights into the nature of dimer plasmons in highly doped semiconductors.
Terahertz magnetic response of plasmonic metasurface resonators: origin and orientation dependence
(NATURE PORTFOLIO, 2024-07-03) Tesi, Lorenzo; Hrtoň, Martin; Bloos, Dominik; Hentschel, Mario; Šikola, Tomáš; van Slageren, Joris
The increasing miniaturization of everyday devices necessitates advancements in surface-sensitive techniques to access phenomena more effectively. Magnetic resonance methods, such as nuclear or electron paramagnetic resonance, play a crucial role due to their unique analytical capabilities. Recently, the development of a novel plasmonic metasurface resonator aimed at boosting the THz electron magnetic response in 2D materials resulted in a significant magnetic field enhancement, confirmed by both numerical simulations and experimental data. Yet, the mechanisms driving this resonance were not explored in detail. In this study, we elucidate these mechanisms using two semi-analytical models: one addressing the resonant behaviour and the other examining the orientation-dependent response, considering the anisotropy of the antennas and experimental framework. Our findings contribute to advancing magnetic spectroscopic techniques, broadening their applicability to 2D systems.
Electrical and optical characterization of Os-substituted rare-earth orthoferrite YbFeO3-gamma powders
(Springer Nature, 2021-01-02) Polat, Özgür; Coskun, Mustafa; Sobola, Dinara; Kurt, B. Zengin; Caglar, Mujdat; Turut, Abduelmecit
The electrical properties of Os-doped YbFeO3 (YbFO) powders prepared by solid-state reaction have been studied by Impedance Spectrometer/Impedance Spectrometer. SEM, XPS and Raman spectroscopy were utilized for understanding chemical and structured analysis of the synthesized compounds. SEM images have revealed the void nature of the pellets. Furthermore, XPS studies have exhibited that Yb has 3+valance state. It is also revealed that the oxygen vacancies concentration drops as the Os doping level raises by XPS analysis. The frequency dependency of loss-tan(delta) examination has demonstrated that the 5 mol% Os-substituted sample has the lowest loss-tan(delta) values at high frequency regions at 100 degrees C. It has been also realized that the 5 mol% Os-doped compound exhibits the highest resistivity among the samples. Raman spectroscopy examination has unveiled that the samples have similar space group. In addition, the optical band gap of the synthesized powders was also extracted via utilizing the Kubelka-Munk technique. It was realized that the band gap of YbFO slightly increases as the Os dopant ratio advances.
Correlative Imaging of Individual CsPbBr3 Nanocrystals: Role of Isolated Grains in Photoluminescence of Perovskite Polycrystalline Thin Films
(AMER CHEMICAL SOC, 2023-06-20) Liška, Petr; Musálek, Tomáš; Šamořil, Tomáš; Kratochvíl, Matouš; Matula, Radovan; Horák, Michal; Nedvěd, Matěj; Urban, Jakub; Planer, Jakub; Rovenská, Katarína; Viewegh, Petr; Kolíbal, Miroslav; Křápek, Vlastimil; Kalousek, Radek; Šikola, Tomáš
We report on the optical properties of a CsPbBr3 polycrystallinethin film on a single grain level. A sample composed of isolated nanocrystals(NCs) mimicking the properties of the polycrystalline thin film grainsthat can be individually probed by photoluminescence spectroscopywas prepared. These NCs were analyzed using correlative microscopyallowing the examination of structural, chemical, and optical propertiesfrom identical sites. Our results show that the stoichiometry of theCsPbBr(3) NCs is uniform and independent of the NCs'morphology. The photoluminescence (PL) peak emission wavelength isslightly dependent on the dimensions of NCs, with a blue shift upto 9 nm for the smallest analyzed NCs. The magnitude of theblueshift is smaller than the emission line width, thus detectableonly by high-resolution PL mapping. By comparing the emission energiesobtained from the experiment and a rigorous effective mass model,we can fully attribute the observed variations to the size-dependentquantum confinement effect.
A Versatile Setup for Fourier-Transform Infrared Magneto-Spectroscopy
(IEEE, 2023-06-09) Dubnická Midlíková, Jana; Šedivý, Matúš; Sojka, Antonín; Santana, Vinicius Tadeu; Dubroka, Adam; Neugebauer, Petr
Fourier-transform infrared (FTIR) magneto-spectroscopy is a powerful spectroscopic technique used to investigate many important effects in materials, e.g., electron spin resonance (ESR), cyclotron resonance, and transitions between Landau levels (LLs). Despite their enormous potential in material science, infrared (IR) magneto-spectrometers are still relatively rare and custom-made since such systems generally require complex infrastructure. This article presents a versatile broadband setup for FTIR magneto-spectroscopy spanning the range from THz/far-IR (FIR) to near-IR (NIR), high magnetic field up to 16 T, and cryogenic temperatures down to 2 K. It consists of a commercial FTIR spectrometer and 16 T cryogen-free superconducting magnet coupled with custom-designed optical coupling and transmission probes for experiments with various detectors. The functionality of the FTIR magneto-spectroscopic setup is demonstrated by the magneto-optical measurements on a cobalt-based single-molecule magnet (SMM) in the FIR region and germanium (Ge) in the NIR region.

Browse

Recent Submissions