Physica E-low-dimensional Systems & Nanostructures最新文献

By means of the Monte-Carlo/Molecular Dynamics and the non-equilibrium Molecular Dynamics methods we investigate the cross- and in-plane thermal conductivities of the (001)-, (110)- and (111)-oriented Si/Ge films (2 − 20 nm) and bulk superlattices with an intermixing at interfaces in comparison with the corresponding alloy structures at 300 K. For the first time the anomalous conductivity reduction of the in-plane thermal transport with respect to the film thickness has been revealed. This effect can be caused by interplay of three phonon scattering mechanisms: the phonon-alloy scattering mechanism, which is dominant, and competing phonon-phonon and phonon-surface scatterings due to the phonon depletion and the surface phonon localization, respectively. In general, the estimated minimal in-plane thermal conductivity values are found to be of 1.7 W/(m∙K) for the SiGe alloy thin films. It is established that the cross-plane thermal conductivity in the Si/Ge film superlattices crucially depends on intermixing at interfaces displaying even smaller values (less 1.5 W/(m∙K)) than in the corresponding SiGe alloy structures. We also show Si/SiGe superlattices in comparison with Ge/SiGe ones to provide up to 9 % gain in decreasing of both cross and in-plane thermal conductivities due to specific redistribution of peak weights in phonon density of states, which affect the thermal transport. These results reveal the insights into the application of SiGe-based superlattices and alloys for the cross- and in-plane thermoelectrics from the thermal transport minimization viewpoint.

We have theoretically investigated the enhancement of superluminal birefringence modes of surface plasmon polaritons (SPPs) at the interface of a chiral quantum dot (QD) nanostructure and a metallic nanoparticle (MNP) hybrid system. This configuration facilitates the generation of SPP birefringence modes when illuminated by incident light. The resonances of SPPs within the hybrid nanostructure are determined through analytical calculations using Maxwell’s equations under specific boundary conditions. Additionally, we model the dynamics of the chiral quantum dots system using the density matrix approach, considering it as a four-level configuration interacting with weak probe, magnetic, and strong coupling fields. Our findings indicate that electron tunneling strength and the intensity of the control field significantly influence the birefringence modes of superluminal SPPs. Furthermore, the observation of negative group index and advanced time in the birefringence beams of SPPs provides evidence for the enhanced superluminal birefringence modes. This research has substantial implications across diverse areas such as optical information processing, temporal cloaking, quantum communication, and the advancement of computer chip speed.

In the presented work, 321 Stainless Steel + B₄C + Al₂O₃ compounds were synthesized by atmospheric plasma technique, with 167 MeV energy swift heavy Xe²⁶⁺ ions were irradiated with different flux and structure, defect formation and Raman spectroscopic analyzes were performed. The total number of displacements was determined based on the DPA and NRT model of interacting ions with SRIM/TRIM calculations. Depending on the concentration of B₄C crystal, phase space groups, lattice parameters, surface morphology and their changes were determined in non-irradiated and SHI-irradiated compounds by structural analysis. Raman shift analyzes were performed depending on the change of Al₂O₃ concentration on the surface of the compound after SHI irradiation. It has been established that SHI radiation causes the formation of defect centers on the surface and volume of the 321 Stainless Steel + B₄C + Al₂O₃ compound, amorphization of the surface, and reduction of the lattice parameters in the existing structural phases.

In the present work, a comprehensive study is carried out to investigate the memristive behaviour of reduced graphene oxide (rGO) conjugated cadmium sulphide quantum dot (CdS QD) nanocomposites (rGO-CdS), offering insights into their dynamic response under varying thermal conditions. The study integrates experimental analysis with MATLAB simulation to provide a detailed understanding of the complex interplay between different operating temperature (300K, 350K, 400K, and 450K) and memristive behavior in rGO-CdS nanocomposites. Different structural and chemical characterizations were carried out which confirms the formation of rGO-CdS nanocomposites. A sandwich structured device was fabricated with the synthesized rGO-CdS nanocomposites using Aluminum (Al) as top and Fluorine doped tin oxide (FTO) as bottom electrode. The influence of operating temperature on hysteresis behaviour of the fabricated Al/rGO-CdS/FTO device was investigated using Keithley 2450 source meter by sweeping a direct current (dc) voltage (−5 V → 5 V → −5 V). Notably, we observe a positive temperature coefficient in the device current, with maximum and minimum recorded current of $\left|1.29mA\right|$ and $\left|0.66mA\right|$ at 450K and 300K respectively. The current-voltage (I-V) behavior observed in the device reveals that in the low resistance state (LRS), conduction is dominated by bulk-limited mechanisms. However, in the high resistance state (HRS), conduction involves contributions from both Schottky barriers and the Pool-Frenkel effect. A MATLAB based linear drift model was used to simulate the device responses at different temperatures using the experimental data. The study provides first comprehensive analysis of temperature dependent hysteresis behaviour of Al/rGO-CdS/FTO device, integrating MATLAB simulation to glean valuable insights into its operation and possible applications as memristive material across different temperature regimes.

The advancement of novel energy materials, encompassing photovoltaic and thermoelectric materials, assumes paramount significance in ameliorating the energy crisis and proactively combating climate change. The BAs/BlueP van der Waals heterostructure (vdWH), characterized by its outstanding optical absorption properties, high power conversion efficiency (PCE), and excellent thermoelectric performance, offers novel insights into the advancement of materials for photonic and thermoelectric applications. We have engineered a vdWH by combining BAs and BlueP, and conducted a comprehensive investigation of its electronic, optical, and thermoelectric properties. The BAs/BlueP vdWH demonstrates excellent thermodynamic and kinetic stability with type I band alignment, facilitating rapid interlayer electron-hole recombination. The remarkable optical absorption capability within the visible and ultraviolet (UV) spectral regions, coupled with an outstanding power conversion efficiency reaching up to 22.35 % under strain, firmly establishes the potential for utilization in photovoltaic conversion applications. At 1000 K, the significant ZT value (1.25) and high thermoelectric conversion efficiency (19.45 %) provide the theoretical foundation for its application in the field of thermoelectrics.

Modern-era energy crises have arisen as a result of industry's quick expansion. There must be a proliferation of autonomous, renewable-energy-powered, high-capacity storage systems. The high specific capacitance (C_s) is a result of the Electric Double Layered Capacitors (EDLC's) stellar cathode characteristics. The remarkable conductivity and storage capacity of transition metal nitride-based oxides (TMOs) have made them an attractive option for use as cathode materials in SC devices. The present study successfully synthesized the TiN-CuO composite for electrode material by employing the straightforward wet-chemical method. But the fact that the TiN-CuO combination is crystalline suggests it could be used as an electrode in SCs. The electrochemical performance of the TiN-CuO electrode was also highlighted by its excellent C_s of 843.5 F g⁻¹. Furthermore, the TiN-CuO‖MnO₂-KOH electrode displays a power density (P_d) of 17595 W/kg and an energy density (E_d) of 44.88 Wh kg⁻¹. In addition, the TiN-CuO‖MnO₂-KOH electrode has shown remarkable cyclic stability of 97.3 % up to 10,000 cycles, at 10 A g⁻¹. The electrochemical characteristics of fabricated TiN-CuO electrode material are superior to those of pure materials, rendering it an attractive candidate for use in energy storage devices such as SCs.

This study investigates the structural, optical, and electrical properties of tin disulfide (SnS₂) and SnS₂-graphene oxide (GO) nanosheets synthesized via chemical bath deposition method (CBD). Structural characterization confirms the formation of hexagonal crystal phases with nanosheet morphology. It shows a well distribution of nanosheet average square sizes of 10 nm for SnS₂ and 6 nm for SnS₂-GO. Optical analysis shows blue shifts in absorption edges compared to bulk SnS₂, attributed to quantum confinement effects. Photoluminescence emission peaks exhibit different energy levels in SnS₂-GO originated to native defects. The composites show a sharp reduced of PL intensity due to enhanced charge carrier separation. Electrical measurements on SnS₂-GO thin films demonstrate negative differential resistance (NDR) behavior in both planar and sandwich contact configurations, suggesting electron injection/extraction mechanisms. The NDR phenomenon exhibits a dependence on voltage scan rate, indicating the involvement of electronic and ionic elements in charge transport mechanisms. Overall, this study provides insights into the NDR properties of SnS₂-GO nanocomposite, laying the groundwork for their potential applications in optoelectronics and nanoelectronics.

Two-dimensional ferromagnetic nanodot structures exhibit intriguing magnetization dynamics and hold promise for future magnonic devices. In this study, we present a comparative experimental investigation into the reconfigurable magnetization dynamics of non-ellipsoidal diamond and triangular-shaped nanodot structures, employing broadband ferromagnetic resonance spectroscopy. Our findings reveal substantial variations in the spin wave (SW) spectra of these structures under different bias field strengths (H) and angles (φ). Notably, the diamond nanodot structure exhibits a variation from nearly symmetric W-shaped dispersion to a skewed dispersion and subsequent transition to a discontinuous dispersion with subtle variation in bias field angle. On the other hand, in the triangular nanodot array a SW mode anti-crossing appears at φ = 15° which is starkly modified with the increase in φ to 30°. By analyzing the static magnetic configurations, we unveil the nature of the SW spectra in these two shapes. We reinforce our observations with simulated spatial power and phase maps. This study underscores the critical impact of dot shape and inversion symmetry on SW dynamical response, highlighting the significance of selecting appropriate structures and bias field strength and orientation for required functionalities. The remarkable tunability demonstrated by the magnonic crystals underscores their potential suitability for future magnonic devices.