物理最新文献

This study investigated the dependence of irradiation fluence and pulse duration on the non–thermal alloying of Cu and Sn through laser irradiation. Femtosecond and picosecond laser irradiation were applied to the GaN part of a bilayer of Cu and Sn deposited on GaN. The laser beam operated at a wavelength and repetition rate of 1030 nm and 1 MHz, respectively, with pulse durations of 0.65 and 38 ps. Subsequently, the irradiated samples were thinned using a focused ion beam, and the cross-sections were examined with transmission electron microscopy. The lattice constants of the resultant phases were identified from selected area diffraction patterns. In data analysis, we identified the phases as β-Sn and ε-phases first, if discernible within a 5% error margin, employing high-temperature phases when identification was not possible. In the irradiated area, only Cu and Sn were detected under a lower fluence and shorter pulse duration. However, δ-phases, which are alloys of Cu and Sn, formed at relatively higher fluences and longer pulse durations. This high-temperature phase, unique to picosecond laser irradiation, cannot be obtained through conventional thermodynamic processes, highlighting the unique capabilities of laser-induced processing in creating novel alloy phases. These findings advance our understanding of laser-material interactions and provides a foundation for developing advanced materials with tailored properties for various applications.

In this work, a new design of flexible photodetectors based on ZnO/ZnS/PVC composite films was realized using polyvinyl chloride as the polymer substrate. ZnO/ZnS composites were successfully synthesized by a hydrothermal method using a mixture of zinc acetate and thiourea, resulting in the formation of microspheres with a core- shell structure. The effect of thiourea concentration as sulfur source (0.2, 0.4, and 0.6 M) on the physical properties of ZnO/ZnS composites was investigated. XRD patterns and FTIR spectra demonstrated a successful fabrication of ZnO and ZnS composites. In addition, the particle size, morphology, elemental composition and the bandgap energy of ZnO/ZnS were studied through the utilization of SEM, EDS and UV-visible spectrophotometer. Finally, the effect of thiourea on the performance of UV photodetectors based on ZnO/ZnS/PVC composite films was investigated using I–V characteristics under dark and UV light conditions. The results showed that the photodetection of the samples improved with increasing thiourea concentration. In particular, the UV photodetector based on PVC-ZSO-3 exhibits a higher photocurrent (2.55 nA), responsivity (0.187 µA/W) and detectivity (5.18 × 10⁶ Jones) than other samples. This gives the impression that the polymer as an insulating material has a promising future as a flexible photodetector worth exploiting.

External cavity diode laser (ECDL) can continuously alter its output optical frequency by tuning the external cavity. Wide mode-hop-free (MHF) range and linear optical frequency tuning are two critical characteristics of the ECDL. However, using an uncoated laser diode (LD) limits the MHF range due to the influence of internal cavity formed by the LD. To obtain linear optical frequency, a triangular wave voltage is generally used to scan the external cavity. Nevertheless, the inherent hysteresis characteristic of piezoelectric transducer (PZT) in the external cavity introduces nonlinearity in the optical frequency. The limited MHF range and nonlinear optical frequency can greatly affect the performance and accuracy of applications with uncoated ECDL as the light source. Therefore, it is crucial to address these two issues of uncoated ECDL. This study introduces a hybrid method incorporating synchronous tuning with proportional-integral-derivative (PID) feedback control. Synchronous tuning facilitates simultaneous changes in both the internal and external cavities output modes, thereby extending the MHF range. PID feedback control utilizes the displacement signal of prism in the external cavity to establish a closed-loop control system, compensating for the PZT’s hysteresis. Through PID feedback control, the uncoated ECDL’s optical frequency tuning nonlinearity is effectively suppressed while its MHF range is extended. Experimental results validate the efficacy of this hybrid method within the triangular wave scanning frequency of 50 Hz.

Dynamics of a polar diatomic molecule (represented as the oscillating rotator model) under external fields is the most fundamental problem and the testbed in molecular physics—analogously to the dynamics of hydrogenic atom (represented as the model of an electron in the Coulomb field) under external fields being the most fundamental problem and the testbed in atomic physics. We present the classical analytical study of the dynamical Stark effect in the oscillating rotator under a high-frequency laser field. We obtain the analytical results by using the method of effective potentials. We demonstrate that under the laser field, the rotation frequency increases, while the oscillation frequency decreases, and the amplitude of the oscillations increases. More significantly, the laser field causes the generation of the second harmonic in the oscillations of this system. This is an important, counterintuitive result in studying this fundamental physical system. We also drew attention to some flaws in the literature on this subject.

In this study, Al-doped ZnO/Ag/WO₃ (AZO/Ag/WO₃)multilayer films were fabricated on polyethylene terephthalate (PET) substrates using the magnetron sputtering technique. A two-step magnetron sputtering process was employed to deposit WO₃, effectively preventing insulation in the AZO/Ag/WO₃ multilayer film caused by silver oxidation. The optical properties of the AZO/Ag/WO₃ multilayer films can be adjusted by varying the thickness of AZO and WO₃ layers. The optimal AZO/Ag/WO₃ multilayer film demonstrates a maximum figure-of-merit of 1.74 × 10^− 2 Ω⁻¹, with an average visible light transmittance of 81.1% and a sheet resistance of 7.04 Ω sq^− 1. When applied in transparent flexible heaters, the AZO/Ag/WO₃ multilayer films exhibit rapid thermal response, stable and controllable heating performance at low operating voltage, indicating exceptional thermal properties and high conductivity. The two-step magnetron sputtering deposition of external oxide layers to prevent the oxidation of silver is cost-effective and can be utilized to create high-performance oxide/metal/oxide transparent electrodes.

The decay of the D meson into multibody final states is a complex process that provides valuable insights into the fundamental interactions within the Standard Model of particle physics. This study focuses on the decay cascade (D^{+}rightarrow K^{*}_{J} ell ^{+}nu rightarrow K^{pm }pi ^{mp } ell ^{+}nu ) where the (K^*_J) resonance encompasses the (K^*(892),K^{*}(1410),K^{*}_0(1430)) states. We employ the helicity amplitude technique to derive the angular distributions for the decay chain, enabling the extraction of one-dimensional and two-dimensional distributions. Utilizing form factors for the (Drightarrow K^*) transition derived from the quark model, we calculate the differential and integrated partial decay widths, explicitly considering the electron and muon masses. Decay branching fractions are calculated, the ratios of the branching fractions are found to be (frac{mathcal {B}r(D^{+}rightarrow K^{*}(892)(rightarrow K ^{-}pi ^{+}) , mu ^{+}nu _{mu })}{mathcal {B}r(D^{+}rightarrow K^{*}(892)(rightarrow K ^{-}pi ^{+}) , e^{+}nu _{e})} = 0.975), (frac{mathcal {B}r(D^{+}rightarrow K^{*}(1410)(rightarrow K ^{-}pi ^{+}) , mu ^{+}nu _{mu })}{mathcal {B}r(D^{+}rightarrow K^{*}(1410)(rightarrow K ^{-}pi ^{+}) , e^{+}nu _{e})} = 0.714) and (frac{mathcal {B}r(D^{+}rightarrow K^{*}_{0}(1430)(rightarrow K ^{+}pi ^{-}) , mu ^{+}nu _{mu })}{mathcal {B}r(D^{+}rightarrow K^{*}_{0}(1430)(rightarrow K ^{+}pi ^{-}) , e^{+}nu _{e})} = 0.774). Results in this work will serve a calibration for the study of (c rightarrow s ) in D meson decays in future and provide useful information towards the understanding of the properties of the (K^{*}) meson, as well as (K pi ) system.

In a dimensionless multi-scalar extension of the Standard Model, Gildener and Weinberg assumed that along a flat direction, there is only one classically massless scalar, known as the scalon, which acquires mass through radiative corrections à la Coleman–Weinberg, while all other scalars remain heavy. In this paper, by introducing a toy model with four scalar degrees of freedom we demonstrate the existence of two scalons along a specific flat direction that we construct. We present the effective potential for the model and provide the masses of the heavy scalars and two radiatively light pseudo-Goldstone bosons.

In this paper, we explore cosmological bouncing solutions to investigate the cosmic evolution in the framework of energy-momentum squared gravity. We consider flat Friedmann–Robertson–Walker spacetime with a perfect matter distribution. We assume two different functional forms of (f(mathcal {R},T^2)) gravity model to examine the impact of this modified framework in the evolution of the universe. Furthermore, we consider a specific scale factor to investigate different cosmological parameters, analyzing the evolutionary behavior of the universe in this gravity. We also perform stability analysis using the perturbation technique. Our findings indicate that the null energy condition violates at the bounce point and equation of state parameter exhibits characteristics of a quintessence era or phantom regimes. These aspects highlight the complex interplay between energy conditions and stability in bouncing cosmological model. We conclude that the (f(mathcal {R},T^2)) theory successfully provides viable alternatives to the standard cosmological scenarios, offering insights into the early universe and the nature of gravity.

The present study provides new solid-phase absorption data of different Polycyclic Aromatic Hydrocarbon (PAHs) molecules in the Far Ultraviolet (FUV) and UV/Visible regions. Two features of interstellar extinction curves fall in this region: the FUV rise and the UV bump. Here, thin films of PAHs were prepared by means of the spin coating method onto a transparent substrate, and their solid phase absorption spectra were recorded. Spectra of isolated molecules simulated by Time-Dependent Density Functional Theory (TD-DFT) calculations were also produced for comparison. The results fit quite well with the FUV rise but not with the UV bump. Given the scarcity of FUV experimental absorption data of PAHs in the literature and especially in solid phase, these results are also interesting for reference for other studies ranging from thin films applications to interstellar medium models.