Current Applied Physics最新文献

Spin-coating stands out as one of the fastest and simplest processes for material solidification. While it is commonly employed for producing polycrystalline thin films, recent endeavors have explored its potential for epitaxial growth, albeit primarily limited to inorganic materials. In this study, we demonstrate the spin-coating method enabling the rapid growth of large-sized organic single crystals (OSCs). Within 2 h, we successfully obtained OSCs with controlled lateral sizes of up to 2 mm, which conventionally takes several weeks using slow solvent evaporation. Raman mapping and UV–Vis absorption measurements confirmed the growths of the OSCs. We propose the growth mechanism by using the supersaturated dynamic fluid model. Furthermore, we demonstrate the device integration of these OSCs for charge-transfer complex channel, revealing ambipolar behavior during gate sweep. This innovative OSCs production method has the potential to advance the various field of science and electronics, traditionally hindered by the scarcity of adequately sized OSCs.

Herein, the rotary triboelectric nanogenerator (R-TENG) with a modified structure is simulated and fabricated to investigate the effect of changes on the geometric structure experimentally. The R-TENGs were fabricated using cost-effective and easily accessible dry-film lithography based on the PCB approach. This process which is explained step-by-step in detail in this paper, provides uniform electrode layers without using high-tech instruments, resulting in enhanced fabrication speed and electrical performance. R-TENGs with varying electrode and PTFE sector counts (32/16, 16/8, and 8/4) were fabricated and analyzed. At 1000 rpm, the output power of R-TENGs with 8, 16, and 32 electrodes demonstrated escalating output power with increasing electrode numbers: 6.82, 19.52, and 30.64 Wm^-2, respectively. Simulation results corroborated the experimental findings, confirming that more electrodes and freestanding sectors yield superior power density and electrical generation. The 32-electrode, 16-sector R-TENG outperformed its counterparts, suggesting that strategic design alterations can significantly optimize energy harvesting in R-TENGs.

Ge₂Sb₂Te₅ (GST225) thin films are used as a functional element in multilayer cells of phase change random access memory (PCRAM, PCM) and have good prospects in electrically driven tunable reflective metasurfaces and on-chip waveguide devices, including those implemented on a flexible substrate. Knowledge of the mechanical properties of GST225 thin films, their adhesion to conductive layers, and the correct choice of conductive material is critical to the reliable operation of these devices. The present work focuses on the effect of phase change on mechanical parameters such as hardness, Young's modulus and stiffness, as well as on the adhesion of GST225 thin films to various metal sublayers (Al, Ti, TiN, W, Ni). The formation of GST225 films was carried out by vacuum thermal evaporation and DC magnetron sputtering, which made it possible to study layers with different distributions of elements over the thickness.

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.