Current Applied Physics最新文献

Infrared spectroscopy is a powerful and versatile experimental technique for studying the electronic response of condensed matter. Infrared spectroscopy measurements in a broad energy region provide invaluable insights on the electronic excitations and collective modes in condensed matter and thus play pivotal roles in establishing current understandings of various classes of condensed matter. Here we discuss the usefulness and importance of infrared spectroscopy to study the physics of quantum materials, which were formerly known as strongly correlated materials. We will describe the basic principles and experimental methods of infrared spectroscopy and discuss how infrared spectroscopy can be utilized to extract quantitative information on the charge dynamics and electronic band structures of quantum materials.

Flexible electronics, such as wearable devices and biosensors, require materials that maintain their properties under mechanical stress. A recent study addresses this by focusing on SrRuO₃ (SRO) thin films, which typically suffer reduced coercivity under strain. Herein, we introduce a novel approach by using CoFe₂O₄ (CFO) as a buffer layer in SRO/CFO/F-mica heterostructures to address this issue. When subjected to a strain of up to ±0.553 %, these heterostructures displayed a mere 11 % variation in saturation magnetic moment and coercive field, significantly outperforming SRO/BaTiO₃ configurations, which showed a 95 % reduction in coercivity at only −0.3 % strain. This result demonstrates the effectiveness of the CFO layer in stabilizing the magnetic properties of SRO films against external mechanical deformations. These findings mark a significant advancement in the development of mechanically robust thin films for complex oxide heterostructures in flexible device applications.

Magnesium diboride (MgB₂) is a two-band superconductor with a high superconducting critical temperature (T_c) of approximately 39 K. Owing to the lack of vortex pinning centers, MgB₂ exhibits an abrupt decline in the critical current density (J_c) in an applied magnetic field. Here, we prepared 1 MeV Nb ion-irradiated MgB₂ thin-film samples with doses of $3\times {10}^{13}$, $7\times {10}^{13}$, and $9\times {10}^{13}$ ions/cm². Temperature-dependent magnetization and x-ray diffraction (XRD) measurements were performed to determine the T_c and c-axis lattice constant of each sample. Furthermore, a Fourier transform infrared (FTIR) spectroscopy was performed to obtain the infrared properties of the Nb-ion-irradiated MgB₂ thin-film samples. The optical conductivity of each sample in the low-energy region was fitted with two (narrow and broad) Drude modes. We found that the spectral weight redistribution from the low-to high-frequency regions and the broadening of the narrow Drude mode caused by irradiation are closely related to the reduction in T_c.

This study investigates the interfacial thermal resistance effect, primarily associated with the bottom-gate stack, in self-aligned top-gate amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). We analyze self-heating and heat transfer characteristics across three different a-IGZO TFT configurations: single-gate, dual-gate type 1, and dual-gate type 2. Temperature maps, corresponding to various bias conditions, are acquired using infrared thermal microscopy. The extracted values of thermal resistance reveal a significant disparity between single- and dual-gate configurations. This suggests that the bottom-gate stack in a-IGZO TFTs, including the interfaces, notably impedes heat dissipation. These findings offer crucial insights into the power dissipation aspects of TFT technology, highlighting the importance of interfacial design for thermal management in advanced electronic devices.

Materials that produce electric charges in response to a mechanical load are known as piezoelectric materials. Materials with a lattice structure devoid of centosymmetry exhibit piezoelectric activity. These days, non-centrosymmetric 2D nanomaterials have been used in many possible applications and have attracted a lot of attention as piezoelectric materials. The crystal structure, crystal nonsymmetry, and nonzero electronic bandgap energy values of two-dimensional nanomaterials have a significant influence on their piezoelectric capabilities. For example, it was discovered that the symmetry of certain mono- or few-layered 2D nanomaterials differed from that of their bulk counterparts. Piezoelectricity is found at the atomic thickness level in many 2D monolayer materials with structurally broken symmetry, but it gradually vanishes with increasing thickness. Secondly, there is a strong correlation between this piezoelectric action and the polarization direction. In this sense, improving the piezoelectric capabilities in 2D mono, few, and multilayer nanomaterials requires a deeper comprehension of the crystal structure and direction of polarization. Based on theoretical and experimental findings, the crystal structure and direction of polarization of various 2D nanomaterials will be the main topics of this review. We will also discuss recent developments and applications of various 2D nanomaterials.

We developed a geometry of metal-insulated-semiconductor field-effect-transistor for the formation of two-dimensional electron gas (2DEG) in dopant-free GaAs/AlGaAs heterostructures in which the conduction band can be modulated by external electric field. We showed two different kinds of device processes: for simple device fabrication and for the uniform 2DEG. We optimized the process of ohmic contacts and the gate geometry for the high quality 2DEG in a triangular quantum well formed at the GaAs/AlGaAs heterointerface. We use these two types of devices to perform a direct comparison of the magneto-transport properties at a low temperature (1.2 K) to get a relationship between the induced carrier density and external electric field. By using our developed fabrication process, the tunability of a high-quality 2DEG was obtained with a carrier density ranging from 0.8 to 2.3 × 10¹¹ cm⁻², for which the corresponding mobility ranged 1.5 to 3.3 × 10⁶ cm² V⁻¹ s⁻¹. Also, we demonstrated that the 2DEG is well established with a suitable depth, 120 nm below the surface (near the GaAs/AlGaAs heterointerface) which is calculated by the capacitance model.

The enhancement of the wettability characteristics in stainless steel holds substantial significance for the application of inhibitor coatings. Investigating a s surface design along with assessing the influences of roughness, surface topography, and chemical heterogeneity on wettability has been a primary focus. In this context, the manipulation of stainless steel surface properties has gained significant attention, specifically for the purpose of fine-tuning wettability. Despite this, uncomplicated surface treatment techniques for stainless steels remain insufficiently established. This study presents a simple etching and oxidation approach for tuning the wettability of stainless steel (STS316L). Through etching and oxidation of STS316L, a superhydrophilic wetting state was achieved (contact angle ∼ 2°). Subsequent application of a monolayer coating led to the reversal of wettability from superhydrophilic to superhydrophobic (contact angle ∼ 168°). Additionally, the proposed methodology for STS316L surface treatment opens up broad expansion possibilities for the applications of superhydrophobic surfaces.

Er³⁺/Nd³⁺ co-doped tellurate glass was prepared by melt quenching method. The relationship between the energy levels of two rare earth ions was studied by absorption spectra and excitation spectra. At 379/407/488 nm excitation, visible light, near-infrared (NIR) emission spectra, and fluorescence attenuation curves were measured. The NIR emission spectrum and fluorescence lifetime show that Er³⁺ can transfer energy to Nd³⁺, thus enhancing the NIR emission of Nd³⁺ in tellurate glass. In the co-doped sample, under excitation of 379/407/488 nm, the NIR emission of Nd³⁺ has a concentration quenching point related to Er³⁺, and the optimal co-doped concentration is 1mol% ErF₃. At 365/451 nm excitation, NIR emission was not enhanced and no energy transfer occurred. In contrast to the energy transfer between conventional Er³⁺-Nd³⁺ co-doped glasses, this paper investigates the effect of matching the higher Er³⁺ energy levels with adjacent Nd³⁺ levels on the energy transfer. The energy transfer process of Er³⁺-Nd³⁺ co-doped glasses is studied in the energy level diagram.

In this article, we introduce our custom-built back-focal plane (BFP) scanning spectroscopy to explore an angle-resolved optical dispersion in two-dimensional (2D) photonic crystal (PhC) constructed with hexagonal lattice of nano-scaled dielectric rods. We fabricated a uniformly large-area photonic crystal measuring 1 cm by 0.5 cm, featuring a polymer-based hexagonal lattice on a gold layer, using capillary force lithography. This precision enables the effective confinement of photonic modes, leading to enhanced optical interactions. We successfully map out the angle-resolved reflectance spectra by directly scanning BFP, revealing the structure's angle dependent optical response and providing insights into its iso-frequency contours. Our approach simplifies the exploration of advanced optical materials, highlighting the role of precise fabrication and measurement techniques in understanding and utilizing the optical properties of structured materials for various technological applications.

In this study, we developed an inductively coupled plasma ion source that can be applied to implanters in semiconductor production. We employed an infrared camera and thermocouples to assess the temperature properties of the ion source operated at temperatures below 500 °C. This reduced temperature is expected to facilitate the adoption of various materials as the ion source. Ion densities of the direct current ion source measured using a double Langmuir probe were found to range from 1.66 × 10¹⁶ to 5.06 × 10¹⁶ m⁻³ within an input power range of 682–895 W. In contrast, the ion densities of a radio-frequency ion source ranged from 7.86 × 10¹⁶–9.58 × 10¹⁶ m⁻³ within an input power range of 700–900 W. This proposed ion source can serve as a next-generation solution because of its low operating temperature and high ion density.