ACS Applied Electronic Materials最新文献

Epitaxial cuprous oxide (Cu₂O) thin films were deposited from aqueous alkaline solutions within confined microsquares in micropatterned GaAs. Raman spectroscopy and transmission electron microscopy analysis revealed the presence of single-phase Cu₂O, with no detectable CuO impurity. In contrast to (110) textured polycrystalline Cu₂O films obtained on unpatterned substrates, monocrystalline Cu₂O (100) films were obtained within the GaAs microsquares. It was found that a 45° in-plane rotation of the prefabricated microsquares with respect to the [01̅1] GaAs axis promotes Cu₂O (100) monocrystalline growth by minimizing lattice mismatch and providing optimal substrate/film orientation for growth. The thickness of the Cu₂O film and the growth rate within the confined squares emerge as dominant parameters affecting crystal quality and controlling photoluminescence emission, as evidenced by formation of point defects, primarily oxygen vacancies.

Using density functional theory (DFT), the structural, electronic, magnetic, and optical properties of 3d transition metals (TMs) adsorbed on a porphyrin sheet (PS) made up of a 2-D covalent organic framework (COF) have been investigated. All the systems show good adsorption behavior with the PS, and the Bader charge reveals the electron transfer from TMs to PS. The spin-polarized density of states (DOS) shows a major contribution of spin in both states in all the systems, except Cu-adsorbed PS, because it has symmetry in the spin state due to the fully filled d-orbital. The COHP, ELF, CDD, and spin analyses further explain the change in crystal orbitals, charge transfer, and magnetization of the TMs on the PS. The cohesive energy is calculated for the stability of the material, and the magnetic coupling between two TMs on the PS has been analyzed. The system obtains an FM state for Sc, Cr, Fe, Co, and Cu atoms, and for Ti, Mn, and Ni atoms, it obtains an AFM state. Furthermore, the light-induced properties of the material have been studied, and it suggests that the materials are capable of conducting higher energies in the UV region. Therefore, this work reinforces existing findings of TMs on the PS and offers new insights into optimizing material selection for future spintronics and optoelectronic devices.

Terahertz emission from spintronic systems has been extensively studied in bilayer structures composed of ferromagnets and heavy metals, where the former functions as the spin source and the latter serves as the spin-to-charge converter through key mechanisms like the inverse spin Hall effect and inverse Rashba-Edelstein effect. Here, we report THz emission from various ferromagnet-only bilayers, including CoFeB/Ni, CoFeB/NiFe, NiFe/Ni, and Fe/Ni, with a particular focus on CoFeB/Ni structures. By systematically varying the pumping power and layer thickness, we were able to isolate the contributions from the individual layers and interfaces. It is found that both anomalous Hall-like conversion at the substrate/CoFeB interface and inverse spin Hall-like conversion in the Ni layer play important roles in terahertz generation. Although the overall emission efficiency is lower than conventional ferromagnet/heavy metal bilayers, the results obtained provide new insights into spin transport across all-ferromagnet interfaces, a topic that has so far been underexplored compared to other types of spintronic systems.

Visible light communication (VLC) represents a forefront technology that integrates illumination and data transmission using light-emitting diodes (LEDs). However, conventional phosphor-based LEDs are limited by their narrow bandwidth due to slow photoluminescence (PL) lifetimes and resistive-capacitive (RC) delays, hindering their data transmission capabilities. In this study, we address these limitations by incorporating a highly emissive fluorescent organic green emitter, CC-MP4, which achieves a modulation bandwidth of 185 MHz─approximately 35 times greater than that of traditional phosphors. A commercial orange-red emitter, MEH-PPV, is also employed as a color-conversion material in the VLC system. The Förster resonance energy transfer from CC-MP4 to MEH-PPV decreases the PL lifetimes in the composite blend. When excited by a semipolar (20–21) blue micro-LED with a bandwidth of 1233 MHz, the composite system forms a high-bandwidth white-light source with a correlated color temperature (CCT) of 5249 K, a color rendering index (CRI) of ∼90, and a total bandwidth of 1027 MHz. This white-light system successfully achieves a data rate of 1.62 Gbps using nonreturn-to-zero on–off keying (NRZ-OOK) modulation. Notably, the stability of the CC-MP4 film is confirmed after three months of storage, maintaining robust optical and frequency response performance, which underscores its potential for practical applications in VLC and solid-state lighting (SSL).

In recent years, perylene diimides (PDIs) have attracted significant research attention in energy storage systems. To expand on these uses, we report here the design, synthesis, and characterization of halo phenoxy-based bay-substituted perylene diimides (PDIs). The performance of these materials having extended π-conjugation is evaluated as an active electrode material in supercapacitors. The introduction of the different halo phenoxy groups viz. 2,4-difluoro phenoxy (DFP), 2,4-dichloro phenoxy (DCP), and 2,6-dichloro-4-fluoro phenoxy (DCFP) at the 1,7- and 1,6-positions of perylene diimides significantly modulate the structural, optoelectronic, and thermal properties of PDIs. Additionally, the density functional theory calculations showed that the type and location of halogen substituents profoundly impact the molecular planarity, dihedral angles, and electron-withdrawing ability, leading to tunable absorption and emission spectra. Cyclic voltammetry (CV), UV–vis spectroscopy, and fluorescence spectroscopy are used to precisely examine the optoelectronic characteristics of these materials. Furthermore, these synthesized PDIs demonstrated, the potential use as an electrode material for symmetric supercapacitors by achieving impressive specific capacitance values of approximately 221 F g⁻¹ (CV) and 163 F g⁻¹ (GCD) using a three-electrode system and 176 F g⁻¹ (electrochemical impedance spectroscopy), 127 F g⁻¹ (CV), and 116 F g⁻¹ (GCD) using a two-electrode system when 2,6-dichloro 4-fluoro phenoxy-based PDI (FCh1) was used as electrode material. Our findings provide valuable insights into the structure–property relationships of bay-substituted PDIs and pave the way for the development of high-performance optoelectronic materials.

Achieving high mobility and stability in IGO-based thin film transistors is vital for practical applications in relevant display fields. In this work, we report the heterojunction-channel InGaO/AlInGaO (IGO/AIGO) TFT by a solution process that effectively enhances stability while maintaining high mobility. The large conduction band offset causes electron accumulation at the heterojunction interface, resulting in implementation of the quantum trap, which cooperates with the main electron path to form a double conductive path, as demonstrated by a combination of theoretical and experimental research studies. The IGO/AIGO TFT exhibits a high overall performance, the characteristic parameter including a high mobility of 43 cm²/(V s) that is nearly 4 times higher than the mobility of AIGO TFT (11 cm²/(V s)), and a threshold voltage shift of less than 0.2 V under illumination bias stress after 3600 s. The research results indicate that the oxide thin film transistor we studied, which combines a solution process and heterojunction structure, exhibits significant advantages in the next generation of printed electronic products.

Tin dioxide (SnO₂)-based sensors have been widely used to monitor various gases in the environment. However, they suffer from several inherent drawbacks, such as high operating temperatures, low sensitivity and selectivity, and unreliable performance under high-humidity conditions, significantly limiting their practical applications. Additionally, current technologies for designing and fabricating SnO₂-based gas sensors typically involve organic solvents and additional steps for dispersion and deposition, leading to increased energy and time consumption, as well as concerns over solvent waste. To address these challenges, we present a simple one-step thermal annealing approach to develop a tin aminoclay (SnAC) nanoparticle-based chemical sensor with high performance for detecting NH₃ gas at room temperature. Through structural investigations and characterizations, p–n SnO/SnO₂ heterojunctions within the SnAC nanoparticles were achieved and optimized by varying annealing temperatures from 200 to 400 °C. The SnAC nanoparticles annealed at 350 °C demonstrated the highest sensing performance for NH₃ gas, attributed to the synergistic effects of morphological, structural, and electrical properties of the p–n SnO/SnO₂ heterojunction. The sensor exhibits high sensitivity (∼37.3%/ppm), selectivity, and good long-term stability at room temperature and under various relative humidity conditions. This study provides a facile, environmentally friendly, and cost-effective approach for developing and designing commercial tin oxide-based gas sensors that overcome many existing limitations.

Deoxyribonucleic acid (DNA) testing is a key step in personalized medical treatments. The technique often involves hybridization between complementary single DNA strands to identify the target gene. However, the formation of a hybrid DNA is slow. To capture the target quickly, we present a label-free hybrid-free DNA detection by surface-enhanced Raman spectroscopy (SERS), whose performances are boosted by InGaN quantum wells (QWs) and machine learning. This is realized by tuning the energy states of QWs, within which the confined electrons resonate with those vibrating on the oligonucleotide and the roughened aluminum (Al) surface. The QW-Al-DNA resonance promotes many minor SERS signals to the detectable level, allowing the machine to identify four distinct circulating tumor DNAs responsible for pancreatic, thyroid, lung, and breast cancers in 1 h.

Organic electronic devices are increasingly linked to energy generation, storage, and transduction mechanisms that emphasize ecological and sustainable principles. Consequently, device fabrication must align with these goals to minimize carbon footprints throughout the manufacturing process and product lifecycle. Chitosan, a biopolymer derived from the chemical processing of chitin found in crustacean shells and fish, offers notable advantages, including unique chemical properties, accessibility, low cost, and biodegradability. When combined with polysulfone, it provides enhanced durability and mechanical stability, enabling improved processability. This study explores the use of membranes synthesized from these materials as potential thermoplastic substrate replacements in the organic electronic device. We present two examples: the first device is an organic photovoltaic that exhibits rectifier diode characteristics, with a short-circuit current of 1.1 mA/cm² and an open-circuit voltage of 0.45 V under illumination. The second device is a vapor sensor demonstrating ammonia sensing activity, achieving 4% efficiency. The membranes were fabricated using the casting method and slot-die printing technology and were characterized by their mechanical and optical properties under different solvent exposures and temperature conditions. In both membranes, a thin film of PEDOT:PSS was used as an electrical conductor in two different chitosan-based substrates for organic devices.

The tuning of magnetic anisotropy in magnetic thin films is the key aspect in the condensed matter physics research field to develop materials useful for practical applications. In the present work, we have investigated the microscopic origin of magnetic anisotropy evolution in W-buffered (CoFeB)_100–xNb_x (x = 0, 3, 5, 10) alloy films induced by a 4d transition metal (Nb). All films were prepared at an elevated growth temperature of 500 °C using the magnetron sputtering technique. Nb-free films (x = 0) exhibit a polycrystalline structure, magnetically isotropic nature, and soft magnetism (coercive field ∼30 Oe). Systematic addition of Nb (from x = 0 to 10) leads to microstructural transformation from polycrystalline to nearly amorphous structure, with a reduction in grain size (from ∼9 to ∼3 nm), surface smoothening, enhanced soft magnetism (coercive field decreases from ∼30 to ∼6 Oe), and more importantly, the emergence of magnetic anisotropy in CoFeB films. In the anisotropic state, angular variation of coercivity reveals that the magnetization reversal process is consistent with a two-phase model. Remarkably, the orbital and spin magnetic moments of Fe and Co atoms were quantified using an element-specific technique of X-ray magnetic circular dichroism. The correlation between the orbital-to-spin moment ratio and observed magnetic anisotropy provides insight into the role of Nb 4d transition metal in inducing the magnetic anisotropy in amorphous/polycrystalline CoFeB thin films, which is vital for advancing their application in spintronics devices.