Journal of Physics D: Applied Physics

Kim, Kyunho; Bong, Cheolwoo; Bak, Moon Soo

doi: 10.1088/1361-6463/ad6878pmid: N/A

Laser absorption measurements were conducted on a high-density, laser-induced plasma produced in atmospheric-pressure air to investigate the spatiotemporal evolution of its electron number density. Measurements taken both along and perpendicular to the plasma’s symmetric axis showed that, upon formation, the plasma propagates in the direction opposite to the laser beam used for plasma generation, while expanding rapidly radially. The spatiotemporal evolution of the electron density was further analyzed from the measurements taken perpendicular to the plasma’s symmetric axis through tomographic reconstruction. Notably, the reconstruction was achieved using a genetic algorithm, as a probe laser beam used for absorption measurement is non-negligible in size compared to the plasma. Importantly, our measurements could reveal that the electron density reaches 4.99 × 1019 cm−3 immediately after the plasma formation at the center; moreover, there is a development of a pressure wave with high electron density, propagating outward radially due to the rapid expansion of the produced plasma.

Du, Bo Xue; Chen, Ke; Liu, Haoliang; Xiao, Meng

doi: 10.1088/1361-6463/ad6610pmid: N/A

In this paper, a method of significantly increasing the energy density of biaxially oriented polypropylene (BOPP) film by cryogenic environment has been proposed. The notable enhancements in the dielectric and energy storage performance can be attributed to precise microstructure manipulation, aimed at controlling charge injection limitations and optimizing molecular chain dynamics. The experimental results show that the maximum discharged energy density of BOPP film with thicknesses of 3.4 μwm has reached 11.83 J cm−3 at −196 °C (2.9 times that at 25 °C) with a charge-discharge efficiency of 92.74%. The direct current breakdown strength as high as 1120.4 kV mm−1 is obtained at −196 °C, exhibiting a substantial 63.7% augmentation compared to the measurement at 25 °C. Furthermore, reductions in conductance loss and capacitance loss (post self-healing testing) are realized. Mechanistic insights into the observed enhancements are investigated through computational simulations. This research provides a pivotal advancement and valuable perspective towards the development of film capacitors boasting the excellent energy storage characteristics.

Wang, An; Tian, Zunyi; Peng, Yang; Wang, Haitao; Zhang, Mengmeng; Sun, Shuobei; Hou, Zhongyu

doi: 10.1088/1361-6463/ad632epmid: N/A

The degradation of the dielectric layer is a common issue in dielectric barrier discharge (DBD). The performance of DBD devices may suffer from instability due to potential corrosion of the dielectric layer caused by discharge, which could even result in structural failure. To gain a comprehensive understanding of the degradation of DBD devices during discharge, the evolution of the performance of DBD devices with various dielectric materials over time is studied. Periodic patterns are found to form on the dielectric surface along the edge of the high-voltage electrode. The electrical data, emission spectra, and surface morphologies of DBD devices with three different dielectric materials, namely ceramics, glass, and PCB, are obtained during an eight-hour discharge. The electrical and thermodynamic characteristics of DBD devices with the three dielectric materials are found to initially decrease by about 20%∼40%. Subsequently, they remain stable in devices with ceramics and PCB dielectric layers but increase in devices with glass dielectric layers until the end. Surface morphologies reveal that periodic patterns consisting of metal accumulations, etching pits, and metal depositions form on the surfaces of ceramics, glass, and PCBs, respectively. Some organic compounds vaporize from the surface of PCBs. The deposition, etching, and vaporization could be reasons for changes in the electrical and thermodynamic characteristics. It shows that degradation occurs not only in organic dielectrics like polymers but also in inorganic dielectrics such as ceramics and glass. To enhance stability and prevent potential failures and overestimations, electrical and optical measurements could be utilized as diagnostic methods in applications involving DBD devices.

Babori, Chaimae; Barati, Mahmoud; Segouin, Valentin; Corcolle, Romain; Daniel, Laurent

doi: 10.1088/1361-6463/ad6a22pmid: N/A

This study investigates anhysteretic strains in PZT ceramics. The anhysteretic curves are associated with a stable balanced state of polarization in the domain structure, excluding dissipative effects related to mechanisms such as domain wall pinning. Anhysteretic measurements are representative of an -ideal- scenario in which the material would undergo no energy loss due to dissipative processes, focusing on the stable and reversible aspects of the domain configuration. The different methodologies employed to measure deformations under electromechanical loading are presented, leading to the introduction of digital image correlation (DIC) as the chosen technique, recognized for its ability to capture detailed information on transverse and longitudinal strain. The article then describes a procedure developed to obtain anhysteretic strain and anhysteretic polarisation for different levels of compressive loadings. The subsequent presentation of the results of the transverse and longitudinal strain analyses provides valuable insights into the reversible and irreversible behavior of the material. They can be used as a basis for the thermodynamical modelling approaches grounded on separating reversible and irreversible contributions or as a validation of existing models describing anhysteretic behavior. The compressive stress affects both the shape of hysteretic and anhysteretic curves. The anhysteretic curve represents a stable equilibrium in the domain structure. Compressive stress reduces strain by affecting the pinning of domain walls. These points justify the interest in studying the effect of compressive stress on the anhysteretic behavior of ferroelectrics.

Liu, Liu; Li, Anding; Chen, Yukun; Liu, Ruirui; Xu, Jiayue; Zhai, Jiwei; Song, Zhitang; Song, Sannian

doi: 10.1088/1361-6463/ad6a25pmid: N/A

This study investigates the phase-change properties of [Ge8Sb92 (25 nm)-Ge2Sb2Te5 (25 nm)]1 multilayer thin films, elucidating three distinct resistance states originating from two structural transitions: initial Sb precipitation and Ge2Sb2Te5-FCC crystallization, followed by Ge2Sb2Te5-FCC to Ge2Sb2Te5-HEX transformation with additional Sb precipitation. The phase transitions induce two abrupt changes in resistance at temperatures of 169.8 °C and 197.7 °C, respectively, with corresponding data retention temperatures of 97 °C and 129 °C, indicating robust thermal stability. The [Ge8Sb92 (25 nm)-Ge2Sb2Te5 (25 nm)]1-based phase change random access memory (PCRAM) device demonstrates reversible switching characteristics and multi-level storage capabilities within 20 ns, showcasing enhanced phase-change speed and storage density. In summary, [Ge8Sb92(25 nm)-Ge2Sb2Te5(25 nm)]1 demonstrates enhanced thermal stability, swift phase transition, and increased storage density relative to conventional Ge2Sb2Te5, establishing it as a promising new phase-change material for PCRAM applications.

Yao, Huanmin; Mu, Haibao; Li, He; Qian, Zhiyuan; Liu, Chengshan; Li, Wendong; Zhang, Daning; Zhang, Guanjun

doi: 10.1088/1361-6463/ad699apmid: N/A

Using the AC electric field to induce the orientation of nonlinear conductive fillers in composites is an effective solution for alleviating electric field distortion in power modules. However, the mechanism by which the electric field affects the filler dynamic characteristics and the composites’ electrical properties remains unclear. In this paper, the correlation between the microscopic dynamic processes of fillers and the macroscopic current amplitude was analyzed. The results show that the current increases rapidly (0 ∼ 173 s) and then slowly (173 ∼ 869 s) at 600 V mm−1, influenced by the rotation and attraction processes of the fillers. This demonstrates that the orientation stops at about 869 s and the filler orientation state is a key factor in determining the dielectric properties. Secondly, the global orientation evaluation index D for the filler network was proposed, which can also derive the minimum time and energy loss required for preparation. Finally, the impact of different filler orientations on the composites’ conductivity was investigated. In the low electric field stress region, with the average carrier jump distance decreasing from 150.23 to 109.71 nm as the D increases from −0.93 to −0.05. On this basis, materials with nonlinear conductivity gradient distribution can be easily prepared. Before optimization, the electric field stress of the power module at the triple point was 35.79 kV. This composite can reduce the value to 15.42 kV, a decrease of 56.9%, while maintaining good electric field uniformity.

Xiao, Na; Khandelwal, Vishal; Yuvaraja, Saravanan; Chettri, Dhanu; Mainali, Genesh; Liu, Zhiyuan; Hassine, Mohamed Ben; Tang, Xiao; Li, Xiaohang

doi: 10.1088/1361-6463/ad6a23pmid: N/A

Here, we demonstrate a high-mobility indium oxide (In2O3) thin-film transistor (TFT) with a sputtered alumina (Al2O3) passivation layer (PVL) with a low thermal budget (200 °C). The sputtering process of the Al2O3 PVL plays a positive role in improving the field-effect mobility (µFE) and current on/off ratio (ION/IOFF) performance of the In2O3 TFTs. However, these enhancements are limited due to the high density of intrinsic trap defects in the In2O3 channels, as reflected in their large hysteresis and poor bias stability. Treating the In2O3 channel with oxygen (O2) plasma prior to sputtering the Al2O3 PVL results in notable improvements. Specifically, a high µFE of 128.3 cm2V−1 s−1, a high ION/IOFF over 106 at VDS of 0.1 V, a small hysteresis of 0.03 V, and a negligible threshold voltage shift under negative bias stress are achieved in the passivated In2O3 TFT (with O2 plasma pretreatment), representing a significant improvement compared to the passivated In2O3 TFT (without O2 plasma pretreatment) and the unpassivated In2O3 TFT. The remarkable reduction of intrinsic trap defects in the passivated In2O3 TFT compensated by O2 plasma is the primary mechanism underlying the improvement in µFE and bias stability, as validated by x-ray photoelectron spectra, hysteresis analysis, and temperature-stress electrical characterizations. Plasma treatment effectively compensates for intrinsic trap defects in oxide semiconductor (OS) channels, when combined with sputter passivation, resulting in a significant enhancement of the overall performance of OS TFTs under low thermal budgets. This approach offers valuable insights into advancing OS TFTs with satisfactory driving capability and wide applicability.

Gautam, Vidushi; Verma, Sandeep Kumar; Singh, Roshani; Ashraf, Zaid; Kandpal, Kavindra; Kumar, Pramod

doi: 10.1088/1361-6463/ad6a20pmid: N/A

The structure and versatile interfacial properties of heterostructures of two-dimensional (2D) materials have drawn a lot of attention. The fundamental curiosity and efficient possibilities encourage the fabrication of 2D materials. 2D materials offer a variety of key elements with distinct optical, electrical, and optoelectronic characteristics. Recently, topological insulators became fascinating for the future of spintronics due to strongspin–orbit coupling and dissipation-less counter-propagating conduction channels in the surface state. When topological traits and magnetic order come together, they may result in new quantum states, leading to the quantum anomalous Hall effect. Here, an overview of 2D fabrication techniques, device applications, magnetic—topological coupling and interfacial effects in heterostructures is discussed, offering a flexible platform for engineering magnetic and topological properties, additionally providing perspectives on emerging research opportunities.

Pandey, Anand; Kumar, Tarun; Mondal, Arnab; Bag, Ankush

doi: 10.1088/1361-6463/ad6999pmid: N/A

Carrier selective contacts are a primary requirement for fabricating silicon heterojunction solar cells (SHSCs). TiO2 is a prominent carrier selective contact in SHSCs owing to its excellent optoelectronic features such as suitable band offset, work function, and cost-effectiveness. Herein, we fabricated simple SHSCs in an Al/TiO2/p-Si/Ti/Au device configuration. Ultrathin 3 nm TiO2 layers were deposited onto a p-type silicon substrate using the atomic layer deposition method. The deposition temperature of TiO2 layers varied from 100 °C to 250 °C. X-ray photoelectron spectroscopic studies suggest that deposition temperature highly affects the chemical states of TiO2 and reduces the formation of defective state densities at the Fermi energy. The optical band gap values of TiO2 layers are also altered from 3.13 eV to 3.27 eV when the deposition temperature increases. The work function tuning from −5.13 eV to −4.83 eV has also been observed in TiO2 layers, suggesting the variation in Fermi level tuning, which arises due to changes in carrier concentrations at higher temperatures. Several device parameters, such as ideality factor, trap density, reverse saturation current density, barrier height, etc, have been quantified to comprehend the effects of deposition temperature on photovoltaic device performance. The results suggest that the deposition temperature significantly influences the charge transport and device performance. At an optimum temperature, a significant reduction in charge carrier recombination and trap state density has been observed, which helps to improve power conversion efficiency.

Rout, Sushree Nibedita; Das, Tupan; Shukla, Anant; Kar, Manoranjan

doi: 10.1088/1361-6463/ad626fpmid: N/A

(100-x) Sr0.7La0.3Fe11.75Co0.25O19–(x) CoFe2O4 composites were synthesized by the one pot sol–gel auto-combustion method. The individual phase purity, morphology, and magnetic hysteresis loop of the composite magnet were analyzed by x-ray powder diffraction, field emission scanning electron microscopy and vibrating sample magnetometer, respectively. The apparent observation of the room temperature hysteresis loop indicates the existence of interfacial exchange interactions. Nevertheless, saturation magnetization (Ms) follows the trend of Vegard’s law. The nature of magnetic interaction and its dependency on the amount of each phase were analyzed by employing the Thamm–Hesse plot. The critical size of the soft phase particle did not corroborate with the results of ΔM vs Hplot. However, this synthesis method is found to be successful in obtaining single-step magnetization reversal in hard–soft composite magnets. The deviation from ideal non-interacting Stoner–Wohlfarth particles puts the single hard phase into the limelight. The (BH)max in the range of 1.07–0.98 MGOe has been obtained for the synthesized composite magnet.