arXiv subjects

Marianna Sledzinska

Publications and source records attributed to Marianna Sledzinska.

12 recordsLinked to original sources

arXiv2026

Comparative Evaluation of Encapsulation Methods for Endohedral Doping of Single-Wall Carbon Nanotubes

Single wall carbon nanotubes (SWCNTs) are promising building blocks for nanoelectronic and optoelectronic devices, yet reliable and stable doping, particularly n type, remains challenging due to strong environmental sensitivity and competing extrinsic effects. Encapsulation of charge transfer molecules within the SWCNT cavity offers a promising route to stable doping while preserving the nanotubes outer surface for subsequent processing. Here, we systematically investigate the filling of arc discharge SWCNTs with the electron donor tetrathiafulvalene and electron acceptor tetracyanoquinodimethane, comparing different methods for filling, including melt filling, solution reflux, and vacuum phase sublimation. We follow the entire processing workflow from raw, unfilled powders to aqueous dispersions and employ density gradient ultracentrifugation to separate filled from empty nanotubes as well as metallic from semiconducting ones. Encapsulation efficiency and electronic modification are assessed using absorption spectroscopy, resonant Raman scattering, thermogravimetric analysis, X-ray photoelectron spectroscopy and electron paramagnetic resonance. Finally, we introduce a complementary vacuum-phase method that removes externally adsorbed molecules without extensive solvent washing, enabling cleaner encapsulated systems.

cond-mat.mes-hall↗

arXiv2026

Fluctuation-Controlled Asymmetric Kinetics in Metal-Insulator Transitions

We report asymmetric kinetics in thermally driven metal-insulator transitions (MITs) in 1T-TaS$_2$. Using combined transport, calorimetric, and Raman measurements, we show that the transition proceeds via burst-like avalanches during cooling, while remaining continuous during heating. Although bulk transport is masked by percolative conduction, local probes and thermal measurements reveal intrinsic asymmetry in the transformation pathways. Using controlled nonequilibrium thermal perturbations generated by pulsed Joule heating, we demonstrate that the phase-ordering dynamics remains strongly athermal during cooling, whereas during heating fluctuations progressively overcome nucleation barriers, leading to a smooth transformation. The distinct responses to thermal perturbations indicate different degrees of athermality of the two hysteresis branches, which govern the transformation pathways and give rise to the observed kinetic asymmetry. These results establish a general framework in which the degree of athermality controls pathway selection in first-order phase transitions.

cond-mat.stat-mech↗

arXiv2026

From Amorphous to Amorphous-Crystalline Mixed-Phase Boron Nitride: Evolution of the Thermal and Elastic Properties

Amorphous boron nitride (aBN) is a promising dielectric and protective coating, yet its nanoscale heat dissipation and elastic response remain poorly quantified. Here we synthesize a variety of BN thin films by borazine-based chemical vapor deposition (800-1000 C) and study the temperature-driven structural transition from fully amorphous networks to mixed amorphous-crystalline films with embedded BN nanocrystallites.Frequency-domain thermoreflectance data show an ultralow, thickness-dependent cross-plane thermal conductivity for aBN (kout < 0.5 W m-1 K-1 for 10-40 nm), which increases systematically with crystalline order up to 1.5 W m-1 K-1. Micro-Brillouin light scattering and finite-element modelling reveal a concomitant stiffening, with Young's modulus rising from 7.5 +/- 0.7 GPa (800 C) to 53 +/- 5 GPa (1000 C). Green-Kubo molecular dynamics simulations rationalize these trends via bonding topology and vibrational transport, and highlight how oxygen, hydrogen and carbon impurities and composition provide practical knobs to further tune the thermal and mechanical responses in BN films for improving nano-electronics, interconnects and coating applications.

cond-mat.mtrl-sci↗

arXiv2026

Evanescent absorption spectroscopy of transition metal dichalcogenide materials using guided photoluminescence in Si$_3$N$_4$ photonic waveguides

On-chip integration of two-dimensional transition metal dichalcogenides (TMDs) with photonic waveguides underpins a growing class of compact optoelectronic and sensing devices, whose performance depends on the optical absorption of the 2D material in this integrated environment. We demonstrate source-free, on-chip evanescent absorption spectroscopy of MoS$_2$ and WS$_2$ flakes integrated on Si$_3$N$_4$ waveguides, in which the broadband defect-related photoluminescence of the Si$_3$N$_4$ core itself acts as the internal probe. Light generated inside the core propagates under the TMD flake and is spectrally attenuated by evanescent interaction with the 2D material, and normalizing the transmitted spectrum to a reference waveguide without TMD yields the energy-dependent absorption response without any external illumination. The extracted guided absorption agrees with Raman and local micro-photoluminescence characterization and resolves differences between spatially uniform and non-uniform flakes. A complementary top-pumping scheme recovers guided WS$_2$ photoluminescence, whose spectral reshaping during propagation is quantitatively reproduced by the measured absorption. This source-free platform qualifies 2D materials in their integrated photonic environment and provides a direct route toward waveguide-integrated TMD photodetectors and sensors.

physics.optics↗

arXiv2022

Thermal insulation and heat guiding using nanopatterned MoS2

In the modern electronics overheating is one of the major reasons for device failure. Overheating causes irreversible damage to circuit components and can also lead to fire, explosions, and injuries. Accordingly, in the advent of 2D material-based electronics, an understanding of their thermal properties in addition to their electric ones is crucial to enable efficient transfer of excess heat away from the electronic components. In this work we propose structures based on free-standing, few-layer, nanopatterned MoS2 that insulate and guide heat in the in-plane direction. We arrive at these designs via a thorough study of the in-plane thermal conductivity as a function of thickness, porosity, and temperature in both pristine and nanopatterned MoS2 membranes. Two-laser Raman thermometry was employed to measure the thermal conductivities of a set of free-standing MoS2 flakes with diameters greater than 20 um and thicknesses from 5 to 40 nm, resulting in values from 30 to 85 W/mK, respectively. After nanopatterning a square lattice of 100-nm diameter holes with a focused ion beam we have obtained a greater than 10-fold reduction of the thermal conductivities for the period of 500 nm and values below 1 W/mK for the period of 300 nm. The results were supported by equilibrium molecular dynamic simulations for both pristine and nanopatterned MoS2. The selective patterning of certain areas results in extremely large difference in thermal conductivities within the same material. Exploitation of this effect enabled for the first time thermal insulation and heat guiding in the few-layer MoS2. The patterned regions act as high thermal resistors: we obtained a thermal resistance of 4x10-6 m2K/W with only four patterned lattice periods of 300 nm, highlighting the significant potential of MoS2 for thermal management applications.

cond-mat.mes-hall↗

arXiv2022

Excitation and detection of acoustic phonons in nanoscale systems

Phonons play a key role in the physical properties of materials, and have long been a topic of study in physics. While the effects of phonons had historically been considered to be a hindrance, modern research has shown that phonons can be exploited due to their ability to couple to other excitations and consequently affect the thermal, dielectric, and electronic properties of solid state systems, greatly motivating the engineering of phononic structures. Advances in nanofabrication have allowed for structuring and phonon confinement even down to the nanoscale, drastically changing material properties. Despite developments in fabricating such nanoscale devices, the proper manipulation and characterization of phonons continues to be challenging. However, a fundamental understanding of these processes could enable the realization of key applications in diverse fields such as topological phononics, information technologies, sensing, and quantum electrodynamics, especially when integrated with existing electronic and photonic devices. Here, we highlight seven of the available methods for the excitation and detection of acoustic phonons and vibrations in solid materials, as well as advantages, disadvantages, and additional considerations related to their application. We then provide perspectives towards open challenges in nanophononics and how the additional understanding granted by these techniques could serve to enable the next generation of phononic technological applications.

cond-mat.mtrl-sci↗

arXiv2021

Phonon dynamics and thermal conductivity of PtSe2 thin films: Impact of crystallinity and film thickness on heat dissipation

We present a comparative investigation of the influence of crystallinity and film thickness on the acoustic and thermal properties of 2D layered PtSe2 thin films of varying thickness (0.6-24 nm) by combining a set of experimental techniques, namely, frequency domain thermo-reflectance, low-frequency Raman and pump-probe coherent phonon spectroscopy. We find a 35% reduction in the cross-plane thermal conductivity of polycrystalline films with thickness larger than 12 nm compared to the crystalline films of the same thickness due to phonon grain boundary scattering. Density functional theory calculations are in good agreement with the experiments and further reveal the ballistic nature of cross-plane heat transport in PtSe2 up to a certain thickness (~20 nm). In addition, our experiments revealed strong interlayer interactions in PtSe2, short acoustic phonon lifetimes in the range of picoseconds, out-of-plane elastic constant C33=31.8 GPa and layer-dependent group velocity ranging from 1340 m/s in bilayer PtSe2 to 1873 m/s in 8 layers of PtSe2. The potential of tuning the lattice cross-plane thermal conductivity of layered 2D materials with the level of crystallinity and the real-time observation of coherent phonon dynamics, which have direct implications on the cooling and transport of electrons, open a new playground for research in 2D thermoelectric devices and provide guidelines for thermal management in 2D electronics.

cond-mat.mtrl-sci↗

arXiv2021

Heat dissipation in few-layer MoS2 and MoS2/hBN heterostructure

State-of-the-art fabrication and characterization techniques have been employed to measure the thermal conductivity of suspended, single-crystalline MoS2 and MoS2/hBN heterostructures. Two-laser Raman scattering thermometry was used combined with real time measurements of the absorbed laser power, which allowed us to determine the thermal conductivities without any assumptions. Measurements on MoS2 layers with thicknesses of 5 and 14 exhibit thermal conductivity in the range between 12 and 24 Wm-1K-1. Additionally, after determining the thermal conductivity of a selected MoS2 sample, an hBN flake was transferred onto it and the effective thermal conductivity of the heterostructure was subsequently measured. Remarkably, despite that the thickness of the hBN layer was less than a third of the thickness of the MoS2 layer, the heterostructure showed an almost eight-fold increase in the thermal conductivity, being able to dissipate more than 10 times the laser power without any visible sign of damage. These results are consistent with a high thermal interface conductance between MoS2 and hBN and an efficient in-plane heat spreading driven by hBN. Indeed, we estimate G 70 MWm-2K-1 which is significantly higher than previously reported values. Our work therefore demonstrates that the insertion of hBN layers in potential MoS2 based devices holds the promise for efficient thermal management.

cond-mat.mes-hall↗

arXiv2020

Thermal transport in nanoporous holey silicon membranes investigated with optically-induced transient thermal gratings

In this study, we use the transient thermal grating optical technique \textemdash a non-contact, laser-based thermal metrology technique with intrinsically high accuracy \textemdash to investigate room-temperature phonon-mediated thermal transport in two nanoporous holey silicon membranes with limiting dimensions of 100 nm and 250 nm respectively. We compare the experimental results to ab initio calculations of phonon-mediated thermal transport according to the phonon Boltzmann transport equation (BTE) using two different computational techniques. We find that the calculations conducted within the Casimir framework, i.e. based on the BTE with the bulk phonon dispersion and diffuse scattering from surfaces, are in quantitative agreement with the experimental data, and thus conclude that this framework is adequate for describing phonon-mediated thermal transport through holey silicon membranes with feature sizes on the order of 100 nm.

cond-mat.mes-hall↗

arXiv2018

Thermal conductivity of disordered porous membranes

We report measurements and Monte Carlo simulations of thermal conductivity of porous 100nm- thick silicon membranes, in which size, shape and position of the pores were varied randomly. Measurements using 2-laser Raman thermometry on both plain membrane and porous membranes revealed more than 10-fold reduction of thermal conductivity compared to bulk silicon and six-fold reduction compared to non-patterned membrane for the sample with 37% filling fraction. Using Monte Carlo solution of the Boltzmann transport equation for phonons we compared different possibilities of pore organization and its influence on the thermal conductivity of the samples. The simulations confirmed that the strongest reduction of thermal conductivity is achieved for a distribution of pores with arbitrary shapes that partly overlap. Up to 15% reduction of thermal conductivity with respect to the purely circular pores was predicted for a porous membrane with 37% filling fraction. The effect of pore shape, distribution and surface roughness is further discussed.

physics.app-ph↗

arXiv2016

Thermal transport in suspended silicon membranes measured by laser-induced transient gratings

Studying thermal transport at the nanoscale poses formidable experimental challenges due both to the physics of the measurement process and to the issues of accuracy and reproducibility. The laser-induced transient thermal grating (TTG) technique permits non-contact measurements on nanostructured samples without a need for metal heaters or any other extraneous structures, offering the advantage of inherently high absolute accuracy. We present a review of recent studies of thermal transport in nanoscale silicon membranes using the TTG technique. An overview of the methodology, including an analysis of measurements errors, is followed by a discussion of new findings obtained from measurements on both solid and nanopatterned membranes. The most important results have been a direct observation of non-diffusive phonon-mediated transport at room temperature and measurements of thickness-dependent thermal conductivity of suspended membranes across a wide thickness range, showing good agreement with first-principles-based theory assuming diffuse scattering at the boundaries. Measurements on a membrane with a periodic pattern of nanosized holes indicated fully diffusive transport and yielded thermal diffusivity values in agreement with Monte Carlo simulations. Based on the results obtained to-date, we conclude that room-temperature thermal transport in membranebased silicon nanostructures is now reasonably well understood.

cond-mat.mes-hall↗

arXiv2016

Two-Dimensional Phononic Crystals: Disorder Matters

The design and fabrication of phononic crystals (PnCs) hold the key to control the propagation of heat and sound at the nanoscale. However, there is a lack of experimental studies addressing the impact of order/disorder on the phononic properties of PnCs. Here, we present a comparative investigation of the influence of disorder on the hypersonic and thermal properties of two-dimensional PnCs. PnCs of ordered and disordered lattices are fabricated of circular holes with equal filling fractions in free-standing Si membranes. Ultrafast pump and probe spectroscopy (asynchronous optical sampling) and Raman thermometry based on a novel two-laser approach are used to study the phononic properties in the gigahertz (GHz) and terahertz (THz) regime, respectively. Finite element method simulations of the phonon dispersion relation and three-dimensional displacement fields furthermore enable the unique identification of the different hypersonic vibrations. The increase of surface roughness and the introduction of short-range disorder are shown to modify the phonon dispersion and phonon coherence in the hypersonic (GHz) range without affecting the room-temperature thermal conductivity. On the basis of these findings, we suggest a criteria for predicting phonon coherence as a function of roughness and disorder.

cond-mat.mtrl-sci↗