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Phase-change materials (PCMs) can switch between amorphous and crystalline states permanently yet reversibly. However, the change in their mechanical properties has largely gone unexploited. The most practical configuration using suspended thin-films suffer from filamentation and melt-quenching. Here, we overcome these limitations using nanowires as active nanoelectromechanical systems (NEMS). We achieve active modulation of the Young’s modulus in GeTe nanowires by exploiting a unique dislocation-based route for amorphization. These nanowire NEMS enable power-free tuning of the resonance frequency over a range of 30%. Furthermore, their high quality factors ( Q  > 10 4 ) are retained after phase transformation. We utilize their intrinsic piezoresistivity with unprecedented gauge factors (up to 1100) to facilitate monolithic integration. Our NEMS demonstrate real-time frequency tuning in a frequency-hopping spread spectrum radio prototype. This work not only opens up an entirely new area of phase-change NEMS but also provides a novel framework for utilizing functional nanowires in active mechanical systems. Direct modulation of Young‟s Modulus to affect mechanical resonances in real-time has not been achieved before. Here, the authors leverage the dislocation migration phenomenon in GeTe nanowires to develop nanoelectromechanical systems with powerfree tuning of mechanical resonances within a range of 30%, high and stable quality and gauge factors.

Background: Across the globe, people are seeking integrative and holistic measures to prevent coronavirus (COVID-19) infection in the form of complementary and alternative medicines (CAM) with or without conventional medicines. This study was done to know the extent of CAM use for COVID-19 prophylaxis and to know beliefs and attitudes of people related to CAM use in India. Methodology: A pretested and prevalidated questionnaire was circulated on social media. Participants, who completed the online form and gave voluntary consent, were included. The questionnaire included demographic details and questions related to CAM use, preferences with reasons, preparations used, perceived role of CAM in prevention, immunity boosting and side effects, sources of information, etc. Results: Out of 514 responses, 495 were analyzed. 47.07% of respondents were males and 52.93% were females. 66.9% were using CAM for COVID-19 prophylaxis. The association between age, gender, and profession with CAM use was statistically significant (P < 0.05). 41.1% reported CAM use in the past. 36.6% of CAM users were taking \"Kadha\" and 33% were using ayurvedic medicines. Other frequently used CAM preparations were chyavanprash, giloy, tulsi, ginger, pepper, cloves, honey, sudarshanghanvati, arsenic-30, lemon juice, cinnamon, steam inhalation, ashwagandha, swasarivati, coronil, and warm saline water gargles. 46.9% of the CAM users were on self-medication and 52.3% preferred CAM over allopathy. Conclusion: Complementary and alternative medicine utilization for COVID-19 prophylaxis is widespread and self-medication is prevalent. As no specific cure is available in conventional systems, people believe in traditional medicines more than conventional, yet confusion exists. There is a need of increasing awareness regarding side effects, drug-drug interactions, and self-medication.

Attractive attributes of carbon nanotubes (CNTs),, which include high aspect ratio, excellent electrical and thermal conductivity, high melting point, and longer lifetime, have made this one-dimensional material a promising candidate for next-generation field emitters. In the present work, CNTs were grown directly on copper foil, copper foam, nickel foil and nickel foam through chemical vapor deposition. A comparison between CNT-based two-dimensional emitters, i.e. CNTs synthesized on copper and nickel foils, CNT-based three-dimensional (3D) emitters, i.e. CNTs developed on foams of copper and nickel, have been demonstrated. We observed that CNTs on foams exhibited better field emission compared to CNTs synthesized on foils. This is due to the multistage structure of the 3D foams which provides high surface area for CNT growth and hence enhanced field emission response. In the present work, a CNT sample prepared on nickel foam was observed to exhibit better field emission response compared to the other samples synthesized in the present study. This particular sample demonstrateda very low turn-on field of 0.93 V/µm, excellent field enhancement factor of 13,343 and good stability of electron emission. Graphic Abstract

Solar energy conversion system (SECS) operation becomes strenuous when it is integrated into a weak distribution AC grid and feeds local nonlinear loads. Distorted/unbalanced point of common coupling (PCC) voltages create challenges in SECS, such as loss of synchronism and inferior power quality. These power quality issues are intensified if power drawn by local loads from SECS contains harmonics components. This work confronts these issues in SECS and introduces a control algorithm to revamp its performance. Presented SECS adjusts its generated currents to maintain power quality in AC network. A variable step-size (VSS)-least mean square (LMS) adaptive algorithm is presented to deal with challenges confronted in SECS due to distorted AC voltages and load currents. It filters distorted PCC voltages and load currents and evaluates their fundamental components. Then, obtained fundamental voltages and generalized integrator are utilized to resolve synchronization issues. This arrangement eliminates phase-locked loop (PLL) requisite to synchronize SECS with AC grid, simplifying designed control structure. A thorough analysis of developed control algorithm is done here on designed simulation model and experimental setup for SECS.

Studies of moiré systems have explained the effect of superlattice modulations on their properties, demonstrating new correlated phases 1 . However, most experimental studies have focused on a few layers in two-dimensional systems. Extending twistronics to three dimensions, in which the twist extends into the third dimension, remains underexplored because of the challenges associated with the manual stacking of layers. Here we study three-dimensional twistronics using a self-assembled twisted spiral superlattice of multilayered WS 2 . Our findings show an opto-twistronic Hall effect driven by structural chirality and coherence length, modulated by the moiré potential of the spiral superlattice. This is an experimental manifestation of the noncommutative geometry of the system. We observe enhanced light–matter interactions and an altered dependence of the Hall coefficient on photon momentum. Our model suggests contributions from higher-order quantum geometric quantities to this observation, providing opportunities for designing quantum-materials-based optoelectronic lattices with large nonlinearities. Opto-twistronic Hall effect driven by structural chirality and coherence length is observed in a three-dimensional self-assembled twisted spiral superlattice of WS 2 .

Electrically induced amorphization is uncommon and has so far been realized by pulsed electrical current in only a few material systems, which are mostly based on the melt–quench process 1 . However, if the melting step can be avoided and solid-state amorphization can be realized electrically, it opens up the possibility for low-power device applications 2 – 5 . Here we report an energy-efficient, unconventional long-range solid-state amorphization in a new ferroic β″-phase of indium selenide nanowires through the application of a direct-current bias rather than a pulsed electrical stimulus. The complex interplay of the applied electric field perpendicular to the polarization, current flow parallel to the van der Waals layer and piezoelectric stress results in the formation of interlayer sliding defects and coupled disorder induced by in-plane polarization rotation in this layered material. On reaching a critical limit of the electrically induced disorder, the structure becomes frustrated and locally collapses into an amorphous phase 6 , and this phenomenon is replicated over a much larger microscopic-length scale through acoustic jerks 7 , 8 . Our work uncovers previously unknown multimodal coupling mechanisms of the ferroic order in materials to the externally applied electric field, current and internally generated stress, and can be useful to design new materials and devices for low-power electronic and photonic applications. Energy-efficient, solid-state amorphization of indium selenide nanowires is achieved using direct current, avoiding the melt–quench process.

Studies of moiré systems have explained the effect of superlattice modulations on their properties, demonstrating new correlated phases1. However, most experimental studies have focused on a few layers in two-dimensional systems. Extending twistronics to three dimensions, in which the twist extends into the third dimension, remains underexplored because of the challenges associated with the manual stacking of layers. Here we study three-dimensional twistronics using a self-assembled twisted spiral superlattice of multilayered WS2. Our findings show an opto-twistronic Hall effect driven by structural chirality and coherence length, modulated by the moiré potential of the spiral superlattice. This is an experimental manifestation of the noncommutative geometry of the system. We observe enhanced light-matter interactions and an altered dependence of the Hall coefficient on photon momentum. Our model suggests contributions from higher-order quantum geometric quantities to this observation, providing opportunities for designing quantum-materials-based optoelectronic lattices with large nonlinearities.

Phase change memory (PCM) can reversibly transform between the amorphous and crystalline phase within nanoseconds, making it a promising candidate for non-volatile memory (NVM) applications. The conventional method to realize the crystal−amorphous transformation in PCM is to heat the material above its melting point by an electrical pulse, after which it is quenched by sudden removal of the pulse. However, such a method requires very large current densities, which results in massive parasitic heat losses and also accelerated failure of the device. On the other hand, it has been recently shown that resistance switching in PCM systems such as superlattices and nanowires can occur at much lower current densities, where the temperature of the material always stays below its melting point. In-situ transmission electron microscopy (TEM) studies on nanowires, with a growth direction aligned with the dislocation slip system, have shown that the resistance change occurs by a dislocation-templated amorphization process. However, the resistance switching mechanism in superlattices, which consist of periodically alternating layers of two different PCM materials, has been much debated with many studies claiming it to be an order-to-order transition.In this study, we attempt to further lower the current density for the crystal-amorphous transformation by multiple strategies: pre-inducing defects in the nanowire by a size-mismatched dopant, synthesizing self-assembled compositionally modulated superlattice nanowires, and lastly by utilizing an unconventional flat phonon mode based amorphization mechanism in In2Se3 nanowires. Furthermore, we utilize TEM extensively to correlate the structural and electrical resistance changes in these nanowires, which reveal several interesting characteristics. The resistance switching mechanism in the superlattice nanowires is found to be an order-disorder transition, contrary to what is proposed in literature. Ab-initio simulations indicate that such an amorphization occurs with the aid of large concentration of vacancies in this material. On the other hand, In2Se3 PCM are found to undergo a collapse of long-range order by a d.c. voltage, but at intermediate voltage range, nucleation of topological dislocation occurs suggesting a possible charge density wave in this material. Overall, in this work, synthesis of novel nanowires is combined with ex-situ TEM experiments to uncover the structure-property correlations in the PCM materials, which is otherwise difficult to perform in thin-film PCM devices.

Electrically induced amorphization is uncommon and has so far been realized by pulsed electrical current in only a few material systems, which are mostly based on the melt-quench process . However, if the melting step can be avoided and solid-state amorphization can be realized electrically, it opens up the possibility for low-power device applications . Here we report an energy-efficient, unconventional long-range solid-state amorphization in a new ferroic β″-phase of indium selenide nanowires through the application of a direct-current bias rather than a pulsed electrical stimulus. The complex interplay of the applied electric field perpendicular to the polarization, current flow parallel to the van der Waals layer and piezoelectric stress results in the formation of interlayer sliding defects and coupled disorder induced by in-plane polarization rotation in this layered material. On reaching a critical limit of the electrically induced disorder, the structure becomes frustrated and locally collapses into an amorphous phase , and this phenomenon is replicated over a much larger microscopic-length scale through acoustic jerks . Our work uncovers previously unknown multimodal coupling mechanisms of the ferroic order in materials to the externally applied electric field, current and internally generated stress, and can be useful to design new materials and devices for low-power electronic and photonic applications.

Studies of moire systems have elucidated the exquisite effect of quantum geometry on the electronic bands and their properties, leading to the discovery of new correlated phases. However, most experimental studies have been confined to a few layers in the 2D limit. The extension of twistronics to its 3D limit, where the twist is extended into the third dimension between adjacent layers, remains underexplored due to the challenges in precisely stacking layers. Here, we focus on 3D twistronics on a platform of self-assembled spiral superlattice of multilayered WS2. Our findings reveal an opto-twistronic Hall effect in the spiral superlattice. This mesoscopic response is an experimental manifestation of the noncommutative geometry that arises when translational symmetry is replaced by a non-symmorphic screw operation. We also discover signatures of altered laws of optical excitation, manifested as an unconventional photon momentum-lattice interaction owing to moire of moire modulations in the 3D twistronic system. Crucially, our findings mark the initial identification of higher-order quantum geometrical tensors in light-matter interactions. This breakthrough opens new avenues for designing quantum materials-based optical lattices with large nonlinearities, paving the way for the development of advanced quantum nanophotonic devices.