Oleg Korotchenkov

The performance and reliability of thermoelectric materials and devices based on low-dimensional materials are strongly influenced by heat dissipation and thermal stability, which are directly linked to the thermal conductivity of the materials. Therefore, accurate determination of the thermal properties remains a critical aspect of material development efforts, which requires the continuous advancement and refinement of the measurement techniques. In recent years, substantial progress has been achieved in theoretical and experimental approaches for the characterization of thermal conductivity in low-dimensional materials. This article reviews these advances, focusing on recent developments in the measurement of thermal conductivity in thin films, two-dimensional materials, and other nanostructures. The fundamental concepts underlying a range of experimental and theoretical techniques are presented together with their theoretical framework, underscoring the critical role of selecting a measurement approach appropriate to the sample thickness, thermal conductivity regime, and material characteristics. Special attention is paid to the thermal conductivity of emerging materials relevant for thermal management, including carbon-based materials, black phosphorus, MXenes, and boron nitride. Furthermore, the advantages and limitations of the different measurement techniques are discussed, in relation to the type and structure of the material under study. Finally, the review summarizes the key findings and outlines future research opportunities, highlighting promising directions across different classes of low-dimensional materials.

Emerging evidence suggests that doped ZnO is one of the serious candidates for next-generation electronic devices because of its abundance in Earth, its nontoxicity, biocompatibility, and affordability, thus motivating many research efforts. Progress includes yet-undiscovered potential in simultaneous codoping ZnO with two or even more elements. Multidoping ZnO with rare-earth (RE) elements and Hf can induce synergistic effects that exceed individual dopant contributions. The concurrent presence of RE3+ and Hf4+ likely establishes a self-compensating defect equilibrium that suppresses oxygen vacancies and zinc interstitials, improving crystallinity and minimizing nonradiative recombination. Using this approach, new pathways for exploration of novel optoelectronic properties and applications can be provided. Meanwhile, most existing studies focus on singly doped or codoped ZnO systems, suggesting that the broader potential of multidoping remains largely unexplored. Although codoping has demonstrated notable improvements in carrier mobility, optical transparency, and defect control through compensating mechanisms between donor and acceptor ions, multidoping introduces an additional degree of freedom in tailoring material properties. Therefore, a deeper investigation of multidoped ZnO could uncover new pathways to optimize its electronic, optical, and catalytic functionalities. In this study, we show that hafnium and multi-rare earth ion implantation and post-annealing of ZnO thin films deposited on Si by magnetron sputtering enables control over the photo-transport properties of the films. Thus, their electrical resistivity can be reduced by about 50 times by multidoping. Moreover, the photoluminescence (PL) and surface photovoltage (SPV) measurements of the films revealed that multiply ion-implanted doping using Hf and different rare-earth elements, such as Nd, Ho, Er, Sm, and Tm, is beneficial for enhancing the PL intensity, slowing down the SPV rise, and speeding up the SPV decay. The signatures of the oxygen and zinc vacancies as well as an ionized local energy level formed by Hf in the modified photo-transport properties of ZnO films are observed. These results are relevant for the development of advanced optoelectronic and photonic devices that utilize zinc and hafnium oxides. Particular emphasis was placed on exploring the potential of the multidoped ZnO layers for ultraviolet photodetection applications.

The thermal conductivity of epoxy nanocomposites filled with self-assembled hybrid nanoparticles composed of multilayered graphene nanoplatelets and anatase nanoparticles was described using an analytical model based on the effective medium approximation with a reasonable amount of input data. The proposed effective thickness approach allowed for the simplification of the thermal conductivity simulations in hybrid graphene@anatase TiO₂ nanosheets by including the phenomenological thermal boundary resistance. The sensitivity of the modeled thermal conductivity to the geometrical and material parameters of filling particles and the host polymer matrix, filler’s mass concentration, self-assembling degree, and Kapitza thermal boundary resistances at emerging interfaces was numerically evaluated. A fair agreement of the calculated and measured room-temperature thermal conductivity was obtained.

Aims: To activate Si and SiGe surfaces by employing the sonochemical treatment at different operating frequencies in dichloromethane to improve the surface photovoltage signal. Background: To produce integrated electronic devices, one needs to achieve low surface and interface trap densities. In this respect, placing a passivating thin layer on Si and Ge surfaces, which saturates the electronic levels of traps and therefore affects the carrier recombination velocities at the surface, is of great interest. Objective: To demonstrate that the effectiveness of the treatment of Si and SiGe surfaces depends on the ultrasonic frequency used. Methods: Photovoltaic transients, electron microscopy, EDX spectroscopy. Result: The surface photovoltage (SPV) decay curves can be divided into rapid (τ_1) and slow (τ_2) components. The sonication effect on the SPV is different for the treatment done at about 25 and 400 kHz. The SPV signal in Si gradually increases with increasing lower-frequency sonication time, whereas the SPV enhancement on SiGe is somewhat smaller. Increasing the sonication time increases the amplitude of the τ_2 component in Si. In SiGe, the lower-frequency sonication quenches the τ_2 component yielding a nearly single-exponential decay form. This trend is even more pronounced at the higher-frequency sonication. Conclusion: The sonochemical treatments greatly intensify the formation of CxHy–Si and CxHy–Ge bonds on Si and Si1-xGex surfaces, resulting in increased SPV signals and prolonged SPV decay times. These results demonstrate that sonochemical treatment is a more effective technique to obtain stable highly passivated Si and Si1-xGex surfaces in comparison with wet chemical treatments in hydrocarbon solutions.