Organic semiconductors exhibit unique semiconducting behaviour due to π-electron delocalization along their molecular chains, making them attractive for various optoelectronic applications. However, their low optical damage thresholds have limited their use in nonlinear optics, particularly in stimulated Raman scattering. Here we demonstrate a general method to significantly amplify molecular vibrations in organic semiconductors by utilizing spectrally tailored gain from stimulated emission, bypassing the necessity for traditional optical cavities. This method achieves Raman thresholds as low as ~10-50 μJ cm-2 or ~2-10 kW cm-2, outperforming current Raman lasers by four orders of magnitude. The resulting nonlinear Raman response leads to cascaded Raman emission characterized by pump-dependent emission efficiency, a nonlinearity factor of 3.8, a signal-to-noise ratio of 30.9 dB and a bandwidth of 110 nm. Our study opens exciting prospects for the development of compact, efficient Raman amplifiers and lasers, leveraging the unique properties of organic semiconductors for advanced photonic applications, including high-sensitivity spectroscopy and versatile frequency conversion technologies.

Due to the COVID-19 pandemic, distance learning is inevitable, and technology is greatly incorporated in education. However, it is challenging for science educators as there are more physical and instrumental constraints in laboratory learning than usual. A real-time web-based remote laboratory platform provides more experimental opportunities for high school students anywhere/anytime. The current project is to develop an online laboratory platform, Borderless-Lab-365 (BL365). Through the server, the experiment setups residing in the university receive commands from users and make responses. The new designed platform is more engaging with live streaming and interactive interface adjusting parameters instantly. It stands out from virtual lab using computer simulations, randomness and errors arisen in real experiments can be investigated and experimental skills are needed. The platform was successfully implemented. One hundred and one participants aged 13-19 from five secondary schools completed a user survey after performing experiments on BL365. Students were encouraged to learn new things and gained better understanding.

Rare-earth ion garnets (ReIG) with magnetization compensation are being extensively studied, such as in the ferrimagnetic insulator (FMI)/heavy metal (HM) heterostructures, with primary focus on the interface effect between single -layer garnets and HM. Here, we study the anomalous Hall behavior of bilayer garnet in Tb3Fe5O12 (TbIG)/Eu3Fe5O12 (EuIG)/Pt system. TbIG (30 nm)/EuIG (t nm) films with strong perpendicular magnetic anisotropy (PMA) were deposited on single -crystal Gd3Ga5O12 (GGG) (1 1 1) substrates using pulsed laser deposition. Subsequently, a 5-nm Pt layer was sputtered and patterned into Hall bars. Tunable compensation temperature (Tcomp) was achieved in the system by changing the thickness of EuIG, which is ascribed to the ferromagnetic coupling of Fe sublattices in the two different garnets. This study provides guidance for designing garnet spintronic devices with controllable compensation behavior.

Abstract The superior electronic, optical and magnetic properties of the one-dimensional carbyne are of high technological relevance for the development of future optoelectronic and magnetoelectronic applications. However, the production of a monoatomic chain with more than 6000 carbon atoms is an enormous technological challenge. To predict the exact growth conditions and in particular the optimal chain length of a carbyne fibre in different molecular environments, we have developed a Monte Carlo model in which a finite-length carbyne with a size of 4000-15000 atoms is encapsulated by a carbon nanotube at finite temperature. Our simulation shows that the stability of the carbyne-nanotube is strongly influenced by the nature and porosity of the carbon nanotube, the external pressure, the temperature and the chain length. When the exact geometric structure of the carbon nanotube and the environmental parameters are provided as input, our simulation can predict the optimal length of the encapsulated carbyne. We have found four mechanisms of triggering chain breakage and have predicted the probable size of the carbyne fragments in excited states. Our work provides much needed input for optimising the carbyne length to produce carbon chains much longer than 6000 atoms at room temperature.

Armchair graphene nanoribbons (AGNRs) with sub-nanometer width are potential materials for the fabrication of novel nanodevices thanks to their moderate direct band gaps. AGNRs are usually synthesized by polymerizing precursor molecules on substrate surface. However, it is time-consuming and not suitable for large-scale production. AGNRs can also be grown by transforming precursor molecules inside single-walled carbon nanotubes (SWCNTs) via furnace annealing, but the obtained AGNRs are normally twisted. In this work, microwave heating is applied for transforming precursor molecules into AGNRs. The fast heating process allows synthesizing the AGNRs in seconds. Several different molecules were successfully transformed into AGNRs, suggesting that it is a universal method. More importantly, as demonstrated by Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy and theoretical calculations, less twisted AGNRs are synthesized by the microwave heating than the furnace annealing. Our results reveal a route for rapid production of AGNRs in large scale, which would benefit future applications in novel AGNRs-based semiconductor devices.

Electric‐field regulation of magnetic properties in perovskite manganites has attracted much attention for its potential in spintronics. For antiferromagnetic perovskite manganites, fewer studies are reported due to technological difficulties in probing their magnetic properties. Here, negative exchange bias (EB) is realized in epitaxial antiferromagnetic/ferromagnetic manganite bilayers with atomically flat interfaces. The low‐voltage pulse modulation of EB is demonstrated using the field‐effect device geometry with the ferroelectric copolymer, polyvinylidene fluoride with trifluoroethylene as a dielectric gating layer, antiferromagnetic La 0.35 Sr 0.65 MnO 3 (AF‐LSMO) as pinning layer, and ferromagnetic La 0.7 Sr 0.3 MnO 3 (FM‐LSMO) as conduction channel. Instead of using non‐volatile polarizations to control the EB, volatile polarizations in ferroelectric field effect transistors are suggested to be capable of modulating the EB. With high‐resolution electron microscopy and spectroscopy, the non‐volatile regulation of EB is attributed to the creation/annihilation of oxygen vacancies in the AF‐LSMO layer via low‐voltage pulses. This study reveals the effect of volatile electric polarizations in ferroelectric field effect devices and highlights the potential for low‐voltage pulse control of the physical properties in antiferromagnetic perovskite oxide insulators.

Various trilayers (ITO-Au-ITO) of a constant total thickness of 43 nm, with different bottom and top ITO film thicknesses, have been prepared by magnetron sputtering. The effects of the relative position of the inserted gold layer on the trilayers' plasmonic properties have been systemically investigated. To study their optical reflectance changes caused by the surface plasmon resonance, total internal reflection ellipsometry (TIRE) has been employed. Two reflectance minima, corresponding to the pseudo-Brewster (PB) and bulk plasmon polariton (BPP), are observed from the reflectance spectra. The impacts of the light incident angles on the behaviors of these modes have been monitored. The measured reflectivity spectra match well with the simulated reflectivity spectra based on the Fresnel formalism. For the ITOt/Au/ITOb = 5/3/35 sample, where the Au layer is positioned closest to the sampling liquid, the BPP mode becomes the sharpest (based on the amplitude and half-width) as compared to other samples, indicating that the closer the ITOt/Au interface is to the sampling liquid, the stronger the observable plasmonic resonance effect is. Furthermore, it is found that the dip position of this BPP mode is independent of the angle of incidence but is sensitive to the refractive index of the sampling liquid. Our results show that the dip position shifts to a shorter wavelength with increasing refractive index of the sampling liquid. This means that the trilayer can act as a refractive index sensor. By linear regression, the obtained sensing accuracy is up to 552 nm/RIU. This facilitates the potential application of this trilayer structure as a surface plasmon-enhanced refractive index sensor.

Transistors made up of carbon nanotube CNT have demonstrated excellent current–voltage characteristics which outperform some high-grade silicon-based transistors. A continuously tunable energy barrier across semiconductor interfaces is desired to make the CNT-based transistors more robust. Despite that the direct band gap of the carbyne inside a CNT can be widely tuned by strain, the size of the carbyne cannot be controlled easily. The production of a monoatomic chain with more than 6000 carbon atoms is an enormous technological challenge. To predict the optimal chain length of a carbyne in different molecular environments, we have developed a Monte Carlo model in which a finite-length carbyne with a size of 4000–15,000 atoms is encapsulated by a CNT at finite temperatures. Our simulation shows that the stability of the carbyne@nanotube is strongly influenced by the nature and porosity of the CNT, the external pressure, the temperature, and the chain length. We have observed an initiation of the chain-breaking process in a compressed carbyne@nanotube. Our work provides much-needed input for optimizing the carbyne length to produce carbon chains much longer than 6000 atoms at ~300 K. Design rules are proposed for synthesizing ~1% strained carbyne@(6,5)CNT as a component in CNT-based transistors to tune the energy barriers continuously.

The interlayer antiferromagnetic (AFM) coupling between thin films plays a significant role in the application of spintronics and magnetic memory devices. Previously, we observed AFM coupling phenomenon at low temperatures in rare-earth iron garnet bilayers epitaxially grown on Y3Al5O12 substrates. Here, we report a detailed study on the impacts of various factors, including temperature, crystallographic orientation, and layer thickness, on the AMF coupling and magnetization reversal behavior of such a bilayer system. A simple energy model qualitatively described the coupling behavior of the two layers during the magnetization reversal process. The interlayer coupling strength was calculated by measuring the minor magnetic hysteresis loops. The current results can serve as a reminder for future research on interlayer AFM coupling phenomena and highlight the potential of manipulating the magnetic properties in rare-earth garnet bilayers for spintronics studies and other applications.

Transistors made up of carbon nanotubes CNT have demonstrated excellent current-voltage characteristics which outperform some high-grade silicon-based transistors. A continuously tunable energy barrier across semiconductor interfaces is desired to make the CNT-based transistors more robust. Despite the direct band gap of carbyne inside a CNT can be widely tuned by strain, the size of carbyne cannot be controlled easily. The production of a monoatomic chain with more than 6000 carbon atoms is an enormous technological challenge. To predict the optimal chain length of a carbyne in different molecular environments, we have developed a Monte Carlo model in which a finite-length carbyne with a size of 4000-15000 atoms is encapsulated by a CNT at finite temperatures. Our simulation shows that the stability of the carbyne@nanotube is strongly influenced by the nature and porosity of the CNT, the external pressure, the temperature and the chain length. We have observed an initiation of chain-breaking process in a compressed carbyne@nanotube. Our work provides much needed input for optimising the carbyne length to produce carbon chains much longer than 6000 atoms at ~300K. Design rules are proposed for synthesizing ~1% strained carbyne@(6,5)CNT as a component in CNT-based transistors to tune the energy barriers continuously.

The anomalous Hall effect measurements are used to probe the magnetization reversal of terbium iron garnet (TbIG) thin films at different temperatures. The compensation temperature (Tcomp) of TbIG thin films is revealed, and the film thickness effect on the Tcomp is studied. The results indicate a rise of Tcomp along with decreasing film thickness. We postulate two possible origins for the observed behavior, namely interfacial element diffusion and strain effects between TbIG films and Gd3Ga5O12 substrates. The results have implications for the study of spintronic devices based on ultrathin rare-earth iron garnet thin films.

Mechanisms of nucleation have been debated for more than a century, despite successes of classical nucleation theory. The nucleation process has been recently argued as involving a nonclassical mechanism (the "two-step" mechanism) in which an intermediate step occurs before the formation of a nascent ordered phase. However, a thorough understanding of this mechanism, in terms of both microscopic kinetics and thermodynamics, remains experimentally challenging. Here, in situ observations using transmission electron microscopy on a solid-state nucleation case indicate that early-stage crystallization can follow the non-classical pathway, yet proceed via a more complex manner in which multiple metastable states precede the emergence of a stable nucleus. The intermediate steps were sequentially isolated as spinodal decomposition of amorphous precursor, mass transport and structural oscillations between crystalline and amorphous states. Our experimental and theoretical analyses support the idea that the energetic favorability is the driving force for the observed sequence of events. Due to the broad applicability of solid-state crystallization, the findings of this study offer new insights into modern nucleation theory and a potential avenue for materials design.

Electric-field-based modulation is a promising way for realizing ultrafast and high-density antiferromagnetic spintronics. Here, we investigate a low-voltage pulse modulation of antiferromagnetic La1-xSrxMnO3 ( $x =0.65$ ) (AF-LSMO) thin films. Positive voltage pulses can increase the resistance at low temperatures, which is ascribed to the oxygen vacancies induced by positive voltage pulses. This effect is supported by X-ray photoelectron spectroscopy (XPS) results. Using low-voltage pulses, we demonstrate exchange bias modulation in ferromagnetic La0.7Sr0.3MnO3 (FM-LSMO)/AF-LSMO bilayer structure. Temperature-dependent resistance, exchange bias field and coercivity all show voltage-polarity dependence. While positive pulses can induce significant changes in the AF-LSMO, negative pulsing has little impact and is consistent with oxygen vacancy related process observed in various electrochemical reaction systems. Our findings can find potential for exploring electric-field modification of antiferromagnetic spintronics.

We report a study on the interfacial antiferromagnetic coupling between ferrimagnetic TbIG/YIG thin films. TbIG/YIG bilayers are grown on YAG (110) substrates. The crystal structure and magnetic properties of the films are characterized. The temperature and directional dependences of the antiferromagnetic coupling effect are observed at low temperatures. This work enriches the magnetic research of ferrimagnetic oxide films with complex structures, providing new ideas for the design of antiferromagnetically coupled spintronics devices.

The magnetic ground state of LaMnO3 (LMO) thin film is still a controversial issue, even though various mechanisms, such as cation/anion non-stoichiometry, epitaxial strain, interfacial charge reconstruction, and orbital ordering, have been proposed. Here, exchange bias (EB) was introduced into a high-quality epitaxial LMO thin film via relatively low oxygen growth pressure. The EB in LMO was modulated by +2 V gating via ionic liquid method with increased EB field (HEB), coercivity (HC), blocking temperature (TB), and reduced ferromagnetic (FM) magnetization. However, the −2 V gating has a much weaker tunability. By investigating the change of structure, surface morphology, and Mn oxidation state in LMO thin films, the modulation of magnetic properties is attributed to the creation/annihilation of oxygen vacancy in an LMO thin film. The suppressed FM phase in LMO can be ascribed to reduced Mn valence, structure disorders, and structure transition. However, the enriched antiferromagnetic phase results from the transition of the pseudocubic structure to the distorted orthorhombic structure. This work not only highlights the importance of functional defects in perovskite oxides but also sheds light on the potential of electric-field modulation of magnetism in spintronic devices.

Nucleation and Growth of Bubbles In article number 2103301, Yongming Hu, Chee Leung Mak, Linfeng Fei, and co-workers present the nucleation and growth mechanisms of bubbles extracted in TEM by monitoring the decomposition of a solid precursor. Under electron-beam irradiation, the 2D Ni(OH)2 flake emits gaseous species within the solid matrix, leading to nanoscale bubbling processes via a three-step pathway.

We systematically investigate the strain-dependent microstructure and anomalous Hall effect in Pt/Tb3Fe5O12 (TbIG) grown on (1 1 1)-oriented Y3Al5O12 (YAG) substrates with different thickness of Ga3Gd5O12 (GGG) buffer layer. Structural measurements indicated that the out-of-plane lattice spacing of TbIG layers firstly increased with the rising thickness of GGG (t(G)) and then decreased, which was attributed to the impact of the buffer layer on strain relaxation of the epitaxial films. A variation of compensation temperature was found at t(G) about 30 nm. Furthermore, both the anomalous Hall resistance and its sign change temperature increased and then kept constant with increasing t(G). Our results indicated that strain played a key role to tune the physical properties of Pt/TbIG/GGG heterostructures, providing a possible approach to tune the spin-orbital coupling in heavy metal/ferromagnetic insulator system by strain engineering.

The nucleation and growth of bubbles within a solid matrix is a ubiquitous phenomenon that affects many natural and synthetic processes. However, such a bubbling process is almost "invisible" to common characterization methods because it has an intrinsically multiphased nature and occurs on very short time/length scales. Using in situ transmission electron microscopy to explore the decomposition of a solid precursor that emits gaseous byproducts, the direct observation of a complete nanoscale bubbling process confined in ultrathin 2D flakes is presented here. This result suggests a three-step pathway for bubble formation in the confined environment: void formation via spinodal decomposition, bubble nucleation from the spherization of voids, and bubble growth by coalescence. Furthermore, the systematic kinetics analysis based on COMSOL simulations shows that bubble growth is actually achieved by developing metastable or unstable necks between neighboring bubbles before coalescing into one. This thorough understanding of the bubbling mechanism in a confined geometry has implications for refining modern nucleation theories and controlling bubble-related processes in the fabrication of advanced materials (i.e., topological porous materials).

Most previous attempts on achieving electric-field manipulation of ferromagnetism in complex oxides, such as La0.66Sr0.33MnO3 (LSMO), are based on electrostatically induced charge carrier changes through high-k dielectrics or ferroelectrics. Here, the use of a ferroelectric copolymer, polyvinylidene fluoride with trifluoroethylene [P(VDF-TrFE)], as a gate dielectric to successfully modulate the ferromagnetism of the LSMO thin film in a field-effect device geometry is demonstrated. Specifically, through the application of low-voltage pulse chains inadequate to switch the electric dipoles of the copolymer, enhanced tunability of the oxide magnetic response is obtained, compared to that induced by ferroelectric polarization. Such observations have been attributed to electric field-induced oxygen vacancy accumulation/ depletion in the LSMO layer upon the application of pulse chains, which is supported by surface-sensitive-characterization techniques, including X-ray photoelectron spectroscopy and X-ray magnetic circular dichroism. These techniques not only unveil the electrochemical nature of the mechanism but also establish a direct correlation between the oxygen vacancies created and subsequent changes to the valence states of Mn ions in LSMO. These demonstrations based on the pulsing strategy can be a viable route equally applicable to other functional oxides for the construction of electric field-controlled magnetic devices.

Tin-doped indium oxide (ITO)/Au/ITO sandwich structures with varying top and bottom ITO film thicknesses were deposited by magnetron sputtering. The effects of varying thickness of the two ITO films on the structural, electrical, and optical properties of the sandwich structures were investigated. X-ray diffraction spectra showed that by inserting an ultrathin Au film, the average grain size of the top ITO layer was significantly increased, but not for the bottom one. The optical properties of the sandwich structures were measured by transmittance measurement and spectroscopic ellipsometry. In the symmetric structure, where the top and the bottom ITO layers had the same thickness, we demonstrated that the crossover wavelength can be changed from the visible range (830 nm) to the near-infrared range (1490 nm) by increasing the top as well as bottom ITO thickness, corresponding to a plasmonic tuning ability of over 600 nm. The evaluation of this trilayer structure as a plasmonic device was asserted based on three quality factors. A comparison of the performance of this trilayer structure with conventional materials was also discussed.