arXiv subjects

Dorota A. Pawlak

Publications and source records attributed to Dorota A. Pawlak.

4 recordsLinked to original sources

arXiv2026

Photo-thermoelectrics of a distributed Schottky junction system: Delineating the photo and thermal currents

Hybrid materials, consisting of diverse materials combined in various configurations, exhibit intriguing opto-electronic properties and are a focal point of research in functional materials. However, achieving precise predictability and tunability of their macroscopic properties in terms of the control parameters remains a challenge. One promising approach involves leveraging self-organization through eutectic growth and subsequent engineering via annealing to engineer niche properties. Here, the electronic properties of eutectic NiTiO$_3$-TiO$_2$ samples and their H$_2$-reduced counterpart Ni-TiO$_2$ are investigated, where the latter features high aspect ratio TiO$_2$ nanostructures decorated with nodular Ni globules. By exploiting this unique architecture and capitalizing on the nanostructuring processes alongside material properties, performance enhancement of photoactive devices is shown. Further, the competing mechanisms of photo-driven and photo-thermal-driven transport is delineated to characterize the overall photo-response of the system. The ability for self-powered functionality further showcases this approach as a promising strategy for developing efficient self-powered devices.

physics.app-ph↗

arXiv2023

Anisotropic transport and Negative Resistance in a polycrystalline metal-semiconductor (Ni-TiO2) hybrid

We investigate anomalous electrical transport properties of a Ni-TiO2 hybrid system displaying a unique nanostructured morphology. The system undergoes an insulator to metal transition below 150 K with a low temperature metallic phase that shows negative resistance in a four-probe configuration. Temperature dependent transport measurements and numerical modelling show that the anomalies originate from the dendritic architecture of the TiO2 backbone interspersed with Ni nanoparticles that paradoxically renders this polycrystalline, heterogeneous system highly anisotropic. The study critiques inferences that may be drawn from four-probe transport measurements and offers valuable insights into modelling conductivity of anisotropic hybrid materials.

cond-mat.mtrl-sci↗

arXiv2023

Spontaneous off-stoichiometry as the knob to control dielectric properties of gapped metals

Using the first-principles calculations and La3Te4 as an example of an n-type gapped metal, we demonstrate that gapped metals can develop spontaneous defect formation resulting in off-stoichiometric compounds. Importantly, these compounds have different free carrier concentrations and can be realized by optimizing synthesis conditions. The ability to manipulate the free carrier concentration allows to tailor intraband and interband transitions, thus controlling the optoelectronic properties of materials in general. Specifically, by realizing different off-stochiometric La3-xTe4 compounds, it is possible to reach specific crossings of the real part of the dielectric function with the zero line, reduce plasma frequency contribution to absorption spectra, or, more generally, induce metal-to-insulator transition. This is particularly important in the context of optoelectronic, plasmonic, and epsilon-near-zero materials, as it enables materials design with a target functionality. While this work is limited to the specific gapped metal, we demonstrate that the fundamental physics is transferable to other gapped metals and can be generally used to design a wide class of new optoelectronic/plasmonic materials.

cond-mat.mtrl-sci↗

arXiv2010

Self-Organized V - Mo Oxide Fibers by the Micro-Pulling Down Method

The V2O5-MoO3 mixtures offer a whole range of materials where properties can be adjusted by simple modification of experimental parameters, which may be utilized in manufacturing of metamaterials with on-demand properties. The V2O5-MoO3 system contains an intermediate phase V9Mo6O40, with a small fraction of V4+ instead of V5+. Consequently, this system should rather be considered as pseudobinary. The V4+ content depends on the oxygen partial pressure in the atmosphere. Thus, by changing the oxygen partial pressure one can tailor the electric properties of the system, and by changing the supercooling, the morphologic structure of crystallized bodies as well. For better understanding of this system differential thermal analysis and thermodynamic modeling was performed. Fibers of eutectic composition between V9Mo6O40 and MoO3 were grown by the micro-pulling-down technique. X-ray diffraction confirmed the existence of the V9Mo6O40 intermediate phase.

cond-mat.mtrl-sci↗