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We report on the formation of silver nanoparticles by gas aggregation in a reaction chamber at room temperature. The size distribution of nanoparticles deposited on a silicon substrate for various lengths of an aggregation (high-pressure) chamber was investigated by atomic force microscopy. Nanoparticles were characterized by scanning and transmission electron microscopy and spectral ellipsometry. The physical shape of the nanoparticles and its distribution was correlated with their optical properties. Metal–dielectric nanocomposites were deposited employing simultaneous deposition of Ag NPs via high-pressure magnetron sputtering and the dielectric matrix was deposited via thermal evaporation. Pure and Eu-, Er-, and Yb-doped lithium fluoride was used as the dielectric host matrix. Optical transmittance of lithium fluoride containing silver nanoparticles was measured and their theoretical absorption cross-section calculated. The nanoparticles were also embedded in Eu3+-doped downshifting and Er3+- and Yb3+-doped up-conversion materials to study their influence on emission spectra. Spectra of identical layers with and without nanoparticles were compared. Their transmittance at various annealing temperatures is also presented.

Various copper oxide stoichiometries have been grown by Pulsed Laser Deposition (PLD) on MgO (100). The role of oxygen pressure on the structural and physical properties of the films was investigated in the 1·10 –5 Pa – 1 Pa range. Positron annihilation spectroscopy revealed positrons trapped at vacancies and large vacancy clusters with lifetimes ranging from 400 ps to 500 ps. Different stoichiometries were found to be dominated by characteristic vacancies. Single copper vacancies V Cu are found for CuO phase with good indication for p-type applications while for the Cu 2 O complexes of copper vacancies coupled with oxygen vacancies (V Cu + V O and V Cu + 2V O ) are seen. Particular O 2 atmosphere conditions induce a mixture of copper oxide phases with the CuO crystals growing on top of Cu 2 O films. The deposition process was monitored with in situ diagnostic techniques based on optical emission spectroscopy and Langmuir probe method. The kinetics of the plasma during the deposition process are well correlated with the properties of the deposited films. The monitoring tools define clear energetic threshold for the formation of CuO or Cu 2 O phases.

The influence of Mo on the electronic states and crystalline structure, as well as morphology, phase composition, luminescence, and defects in ZnO rods grown as free-standing nanoparticles, was studied using a variety of experimental techniques. Mo has almost no influence on the luminescence of the grown ZnO particles, whereas shallow donors are strongly affected in ZnO rods. Annealing in air causes exciton and defect-related bands to drop upon Mo doping level. The increase of the Mo doping level from 20 to 30% leads to the creation of dominating molybdates. This leads to a concomitant drop in the number of formed ZnO nanorods.

The efficiency of green hydrogen production through photo- or electrochemical splitting of water depends strongly on the catalyst used. Several 2D materials have recently been proposed as effective catalysts or co-catalysts, and among them, oxygen-terminated MXenes deserve significant attention for both electro- and photo-induced water splitting. In this work, we described a hybrid photo-electrochemical approach based on the coupling of Ti3C2Tx MXene flakes on a plasmon-supported Au grating and light triggering of the electrocatalytic activity of the generated hybrid structure in a water splitting half reaction, namely, the hydrogen evolution reaction (HER). In particular, MXene flakes with both fluor and oxygen surface terminations were deposited on a periodic patterned gold surface that was capable of supporting surface plasmon-polariton (SPP) excitation under visible and near-infrared (NIR) light illumination. SPP excitation allows sub-diffraction focusing of light energy and effective enhancement of the electrocatalytic performance of Ti3C2Tx flakes. Under illumination, a significant enhancement of the HER kinetics was observed, as well as tuning of the HER rate-determining step from the Volmer step to the Heyrovsky step. In turn, we observed several-fold enhanced hydrogen evolution, which was attributed to plasmon-assisted hot charge carrier injection, with an additional contribution from the plasmon heating effect. The proposed Au grating/Ti3C2Tx hybrid structure allows utilization of the NIR part of the solar spectrum, which is commonly not used in water photolysis but achieves better efficiency in renewable energy-assisted green hydrogen production.

Detonation of explosives was used to synthesize silicon carbide nanoparticles. Polycarbosilane was added to a mixture of 1,3,5-Trinitro-1,3,5-triazinane and 2,4,6-trinitrotoluene, which was subsequently detonated in an enclosed chamber backfilled with inert gas. X-ray diffraction analysis of the detonation soot was consistent with the presence of crystalline silicon with a diamond cubic structure and cubic silicon carbide, along with amorphous material. Further analysis by transmission electron microscopy revealed the presence of crystalline angular particles. High resolution imaging showed that the particles contained numerous stacking faults along the [111] direction and had an interplanar spacing of 2.5 A, both of which are characteristic of beta (cubic) silicon carbide. This is the first report of the detonation synthesis of silicon carbide by dissolving a silicon-containing precursor into an explosive composition.

Cationic doping of ZnO nanorods has gained increased interest as it can lead to the production of materials with improved luminescent properties, electrical conductivity and stability. We report on various Mo-doped ZnO powders of nanorods synthesized by the hydrothermal growth method. Further annealing or/and cold hydrogen or oxygen plasma modification was applied. The atomic structure of the as-grown and plasma-modified rods was characterized by X-ray diffraction. To identify any possible changes in morphology, scanning electron microscopy was used. Paramagnetic point defects were investigated by electron paramagnetic resonance. In particular, two new types of defects were initiated by the plasma treatment. Their appearance was explained, and corresponding mechanisms were proposed. The changes in the luminescence and scintillation properties were characterized by photo- and radioluminescence, respectively. Charge trapping phenomena were studied by thermally stimulated luminescence. Cold plasma treatment influenced the luminescence properties of ZnO:Mo structures. The contact with hydrogen lead to an approximately threefold increase in intensity of the ultraviolet exciton-related band peaking at ~3.24 eV, whereas the red band attributed to zinc vacancies (~1.97 eV) was suppressed compared to the as-grown samples. The exciton- and defect-related emission subsided after the treatment in oxygen plasma.

Eu3+-doped oxide thin films possess a great potential for several emerging applications in optics, optoelectronics, and sensors. The applications demand maximizing Eu3+ photoluminescence response. Eu-doped ZnO, TiO2, and Lu2O3 thin films were deposited by Pulsed Laser Deposition (PLD). Pulsed UV Laser Annealing (PLA) was utilized to modify the properties of the films. In situ monitoring of the evolution of optical properties (photoluminescence and transmittance) at PLA was realized to optimize efficiently PLA conditions. The changes in optical properties were related to structural, microstructural, and surface properties characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The substantial increase of Eu3+ emission was observed for all annealed materials. PLA induces crystallization of TiO2 and Lu2O3 amorphous matrix, while in the case of already nanocrystalline ZnO, rather surface smoothening0related grains’ coalescence was observed.

The dynamics of transient plasma generated by UV ns-laser ablation of selected metals (Co, Cu, Ag, Bi) were investigated by the Langmuir Probe method in angle- and time-resolved modes. Multiple ionic and electronic structures were seen for all plasmas with some corresponding to anions or nanoparticle-dominated structures. The addition of an Ar atmosphere energetically confined the plasma and increased the charge density by several orders of magnitude. For pressure ranges exceeding 0.5 Pa fast ions were generated in the plasma as a result of Ar ionization and acceleration in the double layer defining the front of the plasma plume. Several correlations between the target nature plasma properties were attempted. The individual plasma structure expansion velocity increases with the melting point and decreases with the atomic mass while the corresponding charged particle densities decrease with the melting point, evidencing the relationship between the volatility of the sample and the overall abated mass.

The history of pulsed laser deposition (PLD) and transient plasmas generated by laser ablation is intertwined with the development of various techniques for its fundamental understanding. Some diagnostic tools have been developed to better suit the rapid transient nature of the plasma (space and time dependence of all parameters, fast decay and complex chemistry inside the plasma), whereas others have been adapted from basic plasma physics studies. Langmuir probe method has been used as a real-time in situ diagnostic tool for laser ablation and later for PLD. It remains a useful tool for the PLD community arsenal, which can easily be adapted to the development of new lasers and ablation regimes and new deposition configuration, being one of the most versatile techniques for plasma diagnostics. It is the cornerstone on which charge particles are analyzed and has led to several important discoveries, such as multiple peak distribution, selective acceleration during expansion, plume splitting, plasma turbulences and fluctuations. However, because the Langmuir probe theory adaptation from classical plasma physics is not straightforward, it might lead to misinterpretation and often incorrect analysis of data. This review analyzes the limits and understanding of the technique as a foundation for attaining its full potential, which can impact the way PLD is used. This is especially useful for the pressing need of real-time, in-situ diagnostics and feedback loops for systematic semi-industrial implementation of the PLD technique.

The recent advancements in pulsed laser deposition (PLD) control via plasma diagnostics techniques have been positive and raised questions on the limitation of some techniques, such as the Langmuir probe (LP). The particularities of laser-produced plasma can lead to incorrect interpretation of collected electrical signal. In this paper, we explored the limitations of LP as a technique for in situ PLD control by performing investigations on several metallic plasmas, expanding in various Ar atmosphere conditions. Sub-microsecond modulation was seen in the reconstructed IV characteristics attributed to non-equilibrium dynamics of the ejected charges. A perturbative regime was recorded for Ar pressures higher than 2 Pa, where ionic bursts were observed in the electron saturation region. This perturbation was identified as a plasma fireball. A non-linear multifractal model was developed here to explore these new regimes of the LP. The strange attractors characterizing each fireball were reconstructed, and their evolution with the Ar pressure is discussed. Both short- and long-time non-linear behavior were correlated via probe bias, and the pressure effect on the strange attractor’s defining the fireball-like behavior was investigated. A good correlation was noticed between the simulated data and experimental findings.

The continuous effort for transitioning pulsed laser deposition technique from an experimental tool into an industrial one is sustained by the use of complex technologies for in situ real-time monitoring of the deposition process. Floating Langmuir Probe (LP) and optical emission spectroscopy (OES) measurements were used for plasma monitoring during the pulsed laser deposition of Ag films under various Ar pressure conditions. The electrical measurements revealed a complex multi-structured distribution of the ions, which was strongly influenced by the increase of Ar pressure. The generation of highly energetic ions with the addition of Ar and the degree of Ar gas ionization was also explored. OES measurements confirmed the presence of highly ionized Ar species in the plasma. A peculiar effect was seen under pressures higher than 10 Pa, where the presence of high electronic charges lead to a perturbative behavior of plasma in the vicinity of the LP. The effect of these complex dynamics on the structure and quality of the deposited thin film was also investigated revealing a strong correlation between the electronic distribution in plasma and thin film thickness profile.

The effect of hydrogen and oxygen plasma treatment has been studied in erbium doped zinc oxide (ZnO:Er) nano- and microrods synthesized by the hydrothermal growth. It has been found that hydrogen plasma does not affect the phase purity of the samples whereas the oxygen plasma created the Er2O3 crystalline phase and led to partial powder amorphization only in the ZnO:Er(1%) sample. According to the X-ray photoelectron spectroscopy the modification/improvement of the ZnO surface structure can be expected after the oxygen plasma treatment. The exciton-related luminescence band was improved by the hydrogen plasma treatment whereas the VZn-related red luminescence band was moderated with the dependence on the Er content. The existence of energy transfer between the VZn and Zni was assumed. Correlated experiments of electron paramagnetic resonance and photoluminescence allowed to infer that hydrogen plasma also affects the Er3+ distribution and incorporation into ZnO rods. The red band appeared suppressed after oxygen plasma treatment while the exciton-related emission remained unchanged. The luminescence mechanism was proposed. Shallow donors also appeared affected by the plasma treatment in the low-level Er doped ZnO while the increased Er content seemed to protect them from the plasma influence. Moreover, plasma treatment resulted in the creation of new point defects.

A large family of two-dimensional transition metal carbides and nitrides (MXenes) has increasingly raised interest for electronic and optoelectronic applications due to their high electrical conductivity, potentially tunable electronic structure, nonlinear optical properties, and ability to be manufactured in the thin film state. During delamination and storage in ambient air environment, spontaneous oxidation of MXene flakes leads to formation of titanium oxide, a process that, as we demonstrate here, can be harnessed for manufacturing MXene–titania composites for optoelectronics, sensing, and other applications. We show that partially oxidized MXene thin films containing the in situ formed phase of titanium oxide have a significant photoresponse in the UV region of the spectrum. The relaxation process of photoexcited charge carriers takes a long time (∼24 h) but can be accelerated in the presence of oxygen and water vapor in the atmosphere. These properties of spontaneously formed MXene–titania thin fil...

The continuous effort for transitioning pulsed laser deposition (PLD) technique from an experimental tool into an industrial one can be sustained by the use of complex tools for in situ real-time monitoring of the deposition process. Langmuir Probe (LP) and optical emission spectroscopy (OES) measurements were used for plasma monitoring during PLD of silver films under various Ar pressure conditions. The LP measurements revealed a multi-structured distribution of the ions, which was strongly influenced by the increase of Ar pressure. The generation of highly energetic ions with the addition of Ar and the degree of Ar gas ionization was confirmed by OES measurements. A perturbative effect was seen under pressures higher than 10 Pa, where the presence of high electronic charges leads to an unstable behavior of plasma in the vicinity of the LP. The effect of these complex dynamics on the structure and quality of the deposited thin film was investigated revealing a strong correlation between the electronic distribution in plasma and thin film thickness profile.

The properties of MXenes, new generation of 2D materials, are determined by the surface terminations, which depends on flake preparation method. Changing the surface termination chemical groups can significantly modify the MXene flake properties and functionality. However, the common methods of MXene flake surface chemistry tuning require high-energy treatments and often lead to flake damage. In this work, we propose a plasmon-assisted chemical transformation for tuning the surface chemistry and termination of MXene flakes. The plasmon resonance was directly excited on MXene flakes and induced the generation of highly reactive radicals from electrostatically absorbed iodonium salt cations, leading to immediate grafting of the created radicals to the flake edges and basal planes. We used bis-CF3-substituted iodonium salts, and subsequent analysis of the Ti3C2Tx MXene flake surface composition indicated decreases in the total oxygen concentration and oxidized titanium with a simultaneous increase in the fluorine surface concentration, which was related to –C6H3(CF3)2 moiety attachment. The ability to substitute the hydrophilic oxygen-containing groups with hydrophobic and oleophilic –CF3 groups containing functional groups allows us to create a stable suspension of a MXene in nonpolar organic solvents and prepare a superhydrophobic, water-repellent and oxidation-stable conductive MXene coating.

Ultra-thin silver films of thicknesses of the order of 10 nm and less were prepared in different ambient conditions (vacuum, Ar, and N2) by pulsed laser deposition on glass and fused silica substrates. The in situ monitoring of electrical resistance of deposited films and optical emission spectroscopy of plasma were implemented as real-time analysis techniques. Change in the growth mechanism of the Ag layer in N2 ambient is expressed by an acceleration of the coalescence process, which shifts the percolation point toward lower mass thicknesses. The films prepared in vacuum and Ar ambient were found to be unstable for a final resistance in the range from 1 to 100 MΩ while the films deposited in N2 revealed stable electrical resistance. The percolation point was further lowered by introducing a sublayer of AgxOy for the film deposited in N2 gas. Based on data provided by AFM, SEM, and spectroscopic ellipsometry, different film formation mechanisms are discussed in relation to surface morphology and optical properties. Optical emission spectroscopy was used to monitor the deposition process and identify the species presented during the deposition process. The energy of the ejected particle is affected by the addition of ambient gas and depends on the properties of the working gas.

In this work, we deal with a study of the electron-transport behavior of zirconium nitride RF magnetron sputtered films using Zr target in reactive nitrogen ambient. The films were grown on silica-coated silicon substrates at a substrate temperature of 300°C. The growth process was monitored using an in-situ spectral ellipsometer in a spectral range from 245 to 1690 nm. The ellipsometric data were analyzed using a dispersion model based on Drude-Lorentz oscillators. We estimated electron-transport properties at each stage of the deposition process by analysis of the model parameters. The mechanism of the thickness-dependent electron-transport phenomenon of the ZrN films is discussed in this work.

ZnO:Mo powders of nano- and microrods were fabricated by the hydrothermal growth method. ZnO:Mo thin films deposited on a fused silica glass substrate were synthesized for comparison as well. X-ray diffraction and fluorescence (XRD, XRF), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), photo- and radioluminescence (PL, RL) were applied to characterize these materials. The samples were also annealed in air at elevated temperatures to study the defects and luminescence modification. In particular, EPR spectra in the powder and thin film samples were composed of the signals originating from shallow donors before any treatment. The Mo5+ signal appeared after the annealing at 350 °C in the powder spectra. It existed prior to the treatment in the thin film samples. New EPR signal appears after X-ray irradiation in the powder samples. Red luminescence occurs in all powder samples. The intensity of this band demonstrated different dependences on the annealing temperatures in the samples with different Mo content. The exciton-related band at 380 nm never observed in the powder samples before the annealing, appears after the annealing at 350 °C. The strongest it was in the ZnO:Mo powder with low Mo content.

We use time-resolved THz spectroscopy to study the effects of photoexcitation on conductivity and ultrafast carrier in 2D layered materials with different electronic properties: metallic transition metal carbides (MXenes) [1] and semiconducting germanium sulfide (GeS) [2].

The growth of organic single crystals of naphthalene (C10H8) and anthracene (С14H10) at the liquid‒air interface from a mixture of solvents has been investigated. The growth technique used in the study makes it possible to obtain single-crystal sheets up to 10 mm in size for 24 h. The surface morphology and structure of the crystals have been analyzed by optical microscopy and X-ray diffraction. C10H8 and С14H10 single crystals grow coplanarly along the (001) plane. A thermodynamic model of the flat-crystal nucleus formation at the liquid‒air interface, based on the analysis of the change in the free Gibbs energy, is considered.

MXenes comprise a new class of 2D transition metal carbides, nitrides, and carbonitrides that exhibit unique light-matter interactions. Recently, 2D Ti

Colloidal CdS nanoparticles measuring 1.9-2.3 nm and stabilized by guanidine-containing dendrimers were produced. It was established that such nanoparticles are characterized by photoluminescence in a wide spectral range (2.1-3.2 eV) with an average radiative lifetime of 55-85 ns depending on the energy of the emitted quanta and also by electroluminescence in the visible region of the spectrum (1.8-2.8 eV).

MXenes is an emerging class of 2D transition metal carbides, nitrides and carbonitrides which exhibit large conductivity, ultrahigh volumetric capacitance, high threshold for light-induced damage and nonlinear optical transmittance, making them attractive candidates for a variety of optoelectronic and electrochemical applications. Here, we report on equilibrium and non-equilibrium free carrier dynamics of Ti3C2T x gleaned from THz spectroscopic studies for the first time. Ti3C2T x showed high (~2 × 1021 cm−3) intrinsic charge carrier density and relatively high (~34 cm2 V−1 s−1) mobility of carriers with an exceptionally large, ~46 000 cm−1 absorption in the THz range, which suggests that Ti3C2T x is well suited for THz detection. We also demonstrate that Ti3C2T x conductivity and THz transmission can be manipulated by photoexcitation, as absorption of near-infrared, 800 nm pulses is found to cause transient suppression of the conductivity that recovers over hundreds of picoseconds. The possibility of control over THz transmission and conductivity by photoexcitation suggests the promise for application of Ti3C2T x Mxenes in THz modulation devices and variable electromagnetic shielding.

MXenes comprise a new class of 2D transition metal carbides, nitrides, and carbonitrides that exhibit unique light-matter interactions. Recently, 2D Ti3 CNTx (Tx represents functional groups such as OH and F) was found to exhibit nonlinear saturable absorption (SA) or increased transmittance at higher light fluences, which is useful for mode locking in fiber-based femtosecond lasers. However, the fundamental origin and thickness dependence of SA behavior in MXenes remain to be understood. 2D Ti3 C2 Tx thin films of different thicknesses are fabricated using an interfacial film formation technique to systematically study their nonlinear optical properties. Using the open aperture Z-scan method, it is found that the SA behavior in Ti3 C2 Tx MXene arises from plasmon-induced increase in the ground state absorption at photon energies above the threshold for free carrier oscillations. The saturation fluence and modulation depth of Ti3 C2 Tx MXene is observed to be dependent on the film thickness. Unlike other 2D materials, Ti3 C2 Tx is found to show higher threshold for light-induced damage with up to 50% increase in nonlinear transmittance. Lastly, building on the SA behavior of Ti3 C2 Tx MXenes, a Ti3 C2 Tx MXene-based photonic diode that breaks time-reversal symmetry to achieve nonreciprocal transmission of nanosecond laser pulses is demonstrated.