Advanced Physics Research最新文献

Transparent conducting oxides, like indium tin oxide, enable lateral charge carrier transport in silicon heterojunction solar cells. However, their deposition can damage the passivation quality in the solar cell. This damage during the sputter deposition is a complex issue that has not been fully understood, particularly in various silicon-based materials like amorphous silicon, polycrystalline silicon, or nanocrystalline silicon carbide. The degradation in passivation quality observed in, for example, amorphous silicon is not only explainable by UV light degradation. This study explores the origin of this degradation based on the example of hydrogenated nanocrystalline silicon carbide by combining simulations with experimental analyses. It delves into potential sources of damage during the sputtering process and determines that neither primary nor secondary effects from plasma luminescence or electron bombardment are likely contributors to the damage. Similarly, the implantation of ions, as well as the creation of vacancies and ionization of lattice atoms, are also considered improbable causes. It is, however, proposed that the transfer of energy to the crystalline silicon interface via phonons can factor into the degradation of the passivation quality. This transfer might be a plausible explanation for the damage observed in the passivation layers during the sputtering process.

The precise shaping of optical waveguides is crucial for advancing photonic circuit technologies. In this study, the first fabrication of a resonator is introduced with coiled circular geometry(CCG) using pseudo-plastic microcrystals of 6,6′-((1E,1′E)-hydrazine-1,2-diylidenebis(methaneylylidene))bis(2,4-dibromophenol), HDBP. The molecular packing supported by type-II inter-molecular halogen bonding and hydrogen bonding provides an exceptional strain-holding capacity for HDBP crystals. This property enables the creation of compact CCGs with three interconnected turns utilizing an atomic force microscopy cantilever tip-based mechanophotonics technique. This CCG acts as a concentric ring-resonator (CRR) that splits and routes light in clockwise and anticlockwise directions along circular turns, providing optical interference. Subsequently, an HDBP optical waveguide is integrated with the CRR, resulting in the development of the organic crystal-based optical filter. The modulation observed in optical modes’ wavelengths and their intensities in the waveguide when coupled with CRR shows optical filter functionality. This fabricated device holds promise for applications in high-fidelity sensing, precision micro-measurements, and optical quantum processing technologies, showcasing the potential of organic crystals in advancing photonics.

Metasurfaces, as 2D artificial electromagnetic materials, play a pivotal role in manipulating electromagnetic waves by controlling their amplitude, phase, and polarization. Achieving this control involves designing subwavelength meta-molecules with specific geometries and periodicities. In the context of microfluidic metasurfaces, optical properties can be dynamically modulated by altering either the geometric structure of liquid meta-molecules or the refractive index of the liquid medium. Leveraging the fluidity of liquid materials, microfluidic metasurfaces exhibit remarkable performance in terms of reconfigurability and flexibility. These properties not only establish a cutting-edge research area but also broaden the scope of applications for active metasurface devices. Additionally, the integration of metasurfaces within microfluidic systems has led to novel functionalities, including enhanced particle manipulation and sensor technologies. Compared to conventional solid-material-based metasurfaces, microfluidic metasurfaces offer greater design freedom, making them advantageous for diverse fields such as electromagnetic absorption, optical sensing, holographic displays, and tunable optical meta-devices like flat lenses and polarizers. This review provides insights into the characteristics, modulation techniques, and potential applications of microfluidic metasurfaces, illuminating both the current research landscape and promising avenues for further explorations.

A straightforward analytical approach is proposed for the design of minimally thin metal absorbers. Unlike traditional resonant design principles, where shape, size, and periodicity of a nanostructured film determine the absorption properties, this study uses only the thickness and permittivity (i.e., sheet conductivity) of the material at hand to demonstrate maximal absorption in the minimal possible thickness at any given wavelength in planar layers – guided by only the derived material-agnostic equations. An alternative mechanism is further proposed and experimentally demonstrated to obtain precise control over the sheet conductivity of metal films necessary for such designs using metal dilution, enabling the tuning of both the amplitude and the phase of reflected waves. Finally, the concept of “phase doping” is proposed and experimentally demonstrated, wherein an ultrathin metal layer is placed within the spacer of the absorber cavity, which spectrally tunes the absorption feature without changing the spacer thickness or participating in the absorption. By judiciously combining the dilution of the absorbing and phase layers, a multifunctional ultrathin absorber architecture is demonstrated with customizable amplitude, spectral position, and selectivity, all leveraging the same vertical stack. These findings are promising for the design of ultrasensitive detectors, thermal emitters, and nonlinear optical components.

The linear magnetoelectric (ME) characteristics of a quasi-1D spin-chain compound, FePbBiO₄, are reported. Two distinct antiferromagnetic (AFM) orders occurring at ≈23 K (T_N1) and 12 K (T_N2) are verified using magnetization, specific heat, and conspicuous dielectric (ε′) anomalies. A striking observation is that no pyrocurrent (I_py) is detected in the absence of magnetic field (H); however, H-induced ferroelectric polarization (P) at T_N1 and P unexpectedly partially switches or reverses below T_N2 as reproduced by applying positive and negative electric fields (E). The resulting magnetic field and temperature (H-T) phase diagram illustrates T-dependent H-induced spin reorientation and electric P. The interaction between T, H, spin dynamics, and lattice structures is pivotal and is qualitatively discussed and proposed as an explanation for the observed ME nature.

Materials featuring touching points, localized states, and flat bands are of great interest in condensed matter and artificial systems due to their implications in topology, quantum geometry, superconductivity, and interactions. In this theoretical study, the experimental realization of the dice lattice with adjustable parameters is proposed by arranging carbon monoxide molecules on a two-dimensional (2D) electron system at a (111) copper surface. First, a theoretical framework is developed to obtain the spectral properties within a nearly free electron approximation and then compare them with tight-binding calculations. This investigation reveals that the high mobility of Shockley state electrons enables an accurate theoretical description of the artificial lattice using a next-nearest-neighbor tight-binding model, resulting in the emergence of a touching point, a quasi-flat band, and localized lattice site behavior in the local density of states. Additionally, theoretical results for a long-wavelength low-energy model that accounts for next-nearest-neighbor hopping terms are presented. Furthermore, the model's behavior under an external magnetic field is theoretically examined by employing Peierl's substitution, a commonly used technique in theoretical physics to incorporate magnetic fields into lattice models. The theoretical findings suggest that, owing to the exceptional electron mobility, the highly degenerate eigenenergy associated with the Aharonov-Bohm caging mechanism may not manifest in the proposed experiment.

The magnetic phase transition is explored in CrSBr flakes through non-magnetic ion irradiation, revealing a novel method for magnetic control in two-dimensional (2D) materials. The rise and fall of the ferromagnetic phase is observed in antiferromagnetic CrSBr with increasing the irradiation fluence. The irradiated CrSBr shows ferromagnetic critical temperature ranging from 110 to 84 K, well above liquid N₂ temperature. Raman spectroscopy reveals phonon softening, suggesting the formation of defects. These findings not only highlight CrSBr's potential in spintronics, but also present ion irradiation as an effective tool for tuning magnetic properties in 2D materials, opening new avenues for the development of spintronic devices based on air-stable van der Waals semiconductors.

Geometrically perfect S = ½ kagome lattices with frustrated magnetism are typically electrical insulators. Electron or hole doping is predicted to induce an exotic conducting state including superconductivity. Herein, an unconventional strategy of doping an S = ½ kagome lattice CoCu₃(OH)₆Cl₂ is adopted – a structural analogue of a well-known quantum spin liquid (QSL) candidate herbertsmithite (ZnCu₃(OH)₆Cl₂) – by integrating it with reduced graphene oxide (rGO) via in situ redox chemistry. Such an integration drastically enhances the electrical conductivity, resulting in the transformation of an insulator to a semiconductor, corroborating the respective density of states obtained from the density functional theory calculations. Estimation of the magnetic moments, data on the Hall-effect measurements, Bader charge analysis, and photoemission signals, altogether provide a bold signature of remote hole doping in CoCu₃(OH)₆Cl₂ by rGO. The remote doping provides an alternative to the site doping approach to impart exotic electronic properties in spin liquid candidates, specifically, the generation of topological states like Dirac metal is envisioned.

Oblique angle deposition (OAD) of inclined thin films is mainly performed using electron beam evaporation due to its accurate point source control over the incoming evaporated flux angle α, leading to thin films with a nanocolumnar inclination angle β. However, the utilization of magnetron sputtering (MS) with an extended source for OAD is not extensively studied and reported. This work presents a thorough analysis of ZnO inclined thin films deposited by a novel restricted DC-reactive MS-OAD technique. OAD-inclined films are deposited at α ranged 60°-88°, where incoming flux is restricted using a patented masking configuration enabling tunable control of deposited nanocolumn angular range. The described technique provides accurate control over the resulting β (99.5% reproducibility), allowing demonstrated β_max of 47.3°, close to theoretical limits predicted for ZnO. The approach discussed here probes enhanced control of β comparable to that observed in evaporation, however using an extended source, resulting in high-quality reproducible nanocolumnar-inclined films. The mentioned improvements result from the exploration of operational parameters such as magnetron power, working pressure, and chamber temperature, as well as the design of the restricting configuration and substrate holders and their influence on the resulting inclined thin film crystallinity, and morphology.