ACS Applied Electronic Materials最新文献

Piezoelectric pressure sensors have attracted considerable interest owing to their high sensitivity, dynamic pressure detection capability, and self-powered operation, enabling broad applications in healthcare monitoring, soft robotics, and human-machine interaction (HMI). However, current piezoelectric sensors fall short in spanning the multiscale pressures generated by human motion. Here, we report a self-powered piezoelectric pressure sensor constructed by integrating the molecule-based piezoelectric compound [(CH₃)₃NCH₂CH₂Br]GaBr₄ (1) into a three-dimensional porous PDMS sponge fabricated via a sucrose-templating strategy. The synergistic interplay between compound 1 and the porous elastomeric framework endows the sensor with high sensitivity (0.64 V·kPa^–1 below 50 kPa), ranking third among molecule-based piezoelectric sensors, and the broadest monitoring range reported to date for such sensors, extending up to 300 kPa. As a result, the device enables precise detection of subtle motions such as gripping and joint bending (below 100 kPa), as well as dynamic activities including walking, running, and jumping (above 100 kPa). These findings highlight its strong potential for practical applications in wearable electronics and human-machine interaction systems.

High-mobility p-type transparent conductive films (TCFs) are crucial for transparent optoelectronic devices. This work addresses this gap by growing high-quality γ-CuI films on c-Al₂O₃ substrates via physical vapor transport (PVT), with a focus on the role of deposition temperature. The temperature significantly influences the structural, morphological, optical, and electrical properties of the films. The method delivers an ultrahigh deposition rate of 371 nm/min at 490 °C. The films exhibit (111) out-of-plane orientation and >85% average transmittance (400–800 nm). Structural and morphological analyses reveal temperature-driven growth mode from porous polycrystalline islands to step-flow triangular domains and merged hexagonal structures, which is governed by domain epitaxy. The φ-scan and transmission electron microscopy (TEM) results established the epitaxial relationship as γ-CuI <112̅> (111) // Al₂O₃ [1̅1̅20] (0001). Electron backscatter diffraction (EBSD) revealed two crystallographic domains that were rotated by 60° relative to each other. The hole mobility increased with deposition temperature, yielding a high hole mobility of 19 cm²/V·s at 490 °C with a carrier concentration of 1.86 × 10¹⁷/cm³. These findings indicate that the deposition temperature is critical for achieving high-mobility films. Furthermore, PVT affords a scalable and efficient epitaxy route to p-type transparent conductors, thereby enabling high-performance transparent optoelectronic devices.

Bulk-heterojunction (BHJ) based organic photodetectors (OPDs) are promising candidates for next-generation flexible photodetectors, owing to their solution processability, mechanical flexibility, and low-cost fabrication. However, the BHJ OPD often suffers from high dark currents, leading to high noise and low detectivity. Here, we report low-noise and highly sensitive binary and ternary blends of OPDs using PM6, Y6, and perylene diimide (PDI). By optimizing the thickness and morphology of the photoactive layer, we reduced the dark current while maintaining light absorption across the range of 300 to 950 nm. The best-performing binary-blend OPD exhibited a dark current density of 14.9 pA/cm², responsivity of 0.50 A/W, noise-equivalent power (NEP) of 1.96 × 10^–13 W, and detectivity (D*) of 3.19 × 10¹³ Jones. The devices are fast, featuring a −3 dB cutoff frequency of 1.72 MHz and a turn-on response time of 330 ns. The lowest detectable light intensity is ∼798 fW, with a dynamic range of 132 dB. The inclusion of a morphologically and energetically compatible third component with complementary absorption reduced the dark current density by a factor of 10 to 1.72 pA/cm². This led to improved specific detectivity of 9.65 × 10¹³ Jones, which is comparable to that of conventional silicon photodetectors, although silicon possesses other superior properties. This work presents a comprehensive strategy designed to significantly enhance the performance of the near-IR OPDs.

Understanding the regulation mechanism of GaN lattice orientation and hexagonal boron nitride (h-BN) layer thickness on the electrical and interfacial physical properties of single-layer graphene (SLG)/GaN heterojunctions is crucial for enhancing photoelectric performance of heterojunction devices. Here, we report the role of h-BN insertion layers (1–5 layers) and GaN lattice orientations (polar Ga-plane and N-plane, semipolar r-plane and nonpolar a-plane) in modulating the electrical and interfacial physical properties of SLG/GaN heterojunctions, including barrier height and charge transfer. The structure and electrical properties of the heterojunction were characterized using Raman spectrometer, scanning electron microscopy, and probe station. Increasing the h-BN thickness can enhance 10 interface-related parameters (e.g., barrier height) while suppressing current and reducing 4 charge transfer-related parameters (e.g., Fermi level shift) in heterojunctions. Initial h-BN insertion significantly boosts threshold voltage while suppressing current. The SLG/GaN heterojunction on r-plane GaN exhibits the highest current response at fixed voltage among all orientations, whereas the a-plane configuration shows the lowest response, with current enhancement ranging from 2.278× (minimum, r-plane) to 7.536× (maximum, N-plane). Heterojunctions on semipolar r-plane and nonpolar a-plane GaN exhibit markedly distinct current responses and physical properties compared to those on polar GaN surfaces (Ga- and N-planes), which show relatively minor variations in interface states, electrical properties, and certain physical properties such as barrier height. Contact potential difference (CPD) variation partially reflects charge transfer efficiency. These insights advance the development of interface engineering strategies for graphene/GaN heterojunctions and facilitate the fabrication of heterojunction-based devices.

Quantum dots (QDs), which exhibit strong absorption in the visible light spectrum, can be used as photoactive materials to enhance visible light detection by phototransistors. In this study, CdSe/ZnS QDs were spin-coated onto indium–tin–zinc oxide (ITZO) thin-film transistors to form QD-coated phototransistors with enhanced photoresponsivity. To ensure compatibility with the photolithography process for the QD films, a ZnO layer was applied by atomic layer deposition (ALD) as a passivation layer to provide solvent orthogonality. Notably, beyond this protective function, the ALD ZnO treatment enhanced the interfacial charge transport. This is attributed to the partial replacement of the insulating oleic acid ligands on the QD surfaces via vapor-phase ligand exchange and reduction in the conduction band barrier between the QD shell and the ITZO channel. Under low-light conditions (0.02 mW/cm²), the devices achieved a responsivity of 266.7 A/W at V_G = 10 V and detectivity of 9.3 × 10¹⁰ jones at V_G = 10 V, both higher than those of the untreated device (200 A/W, 5.6 × 10¹⁰ jones). Furthermore, scanning photocurrent microscopy mapping analysis revealed that the ALD ZnO-treated device exhibited a maximum photocurrent of 286 μA, while the untreated device showed only 192 nA under 532 nm illumination at 1.58 mW/cm². This represents an approximately 1000-fold enhancement in the photocurrent, thereby indicating the synergistic contributions of photoconductive and photogating effects.

Ferroelectric (FE) oxides are key design parameters for developing Negative Capacitance Field-Effect Transistors (NCFETs). The properties of FE oxides, such as remnant polarization (P_r) and coercive field (E_c), are greatly affected by the thickness of the FE film. However, most existing analyses of NCFETs assume constant ferroelectric parameters (CFP) independent of thickness, which can lead to an overestimation of device performance. In this study, we develop, for the first time, a comprehensive analytical and simulation framework that incorporates the influence of thickness-dependent ferroelectric parameters (TDFP) on the negative capacitance (NC) in Forksheet FETs (FSFET). To accurately capture device performance, the NCFSFET is modeled using a Landau–Khalatnikov approach. The analytical model and simulation approach highlight device-level metrics, including surface potential, ON current, OFF current, transfer characteristics, and output characteristics, for ferroelectric thickness variations ranging from 2 to 5 nm. By integrating experimentally validated thickness-polarization field correlations, the model reveals a significant deviation between CFP and thickness-dependent approaches, with up to 100% overestimation of ON current and 93% underestimation of leakage current when constant parameters are used. The findings highlight that realistic modeling of ferroelectric thickness is crucial for predicting electrostatic stability, DIBL, and capacitance behavior in scaled NCFETs. This study establishes a pathway toward more reliable and physically consistent modeling of negative capacitance devices for future neuromorphic and unconventional computing systems.

Wearable biomedical devices have attracted increasing attention because they can detect various physiological data from the human body by their intimate contact with the body. Particularly, in ophthalmology, smart contact lenses provide a unique platform for ocular theranostics by directly interfacing with the eye surface as a wearable device, enabling applications ranging from glaucoma monitoring to targeted phototherapy. However, the operation of integrated devices on the smart lens, such as interocular pressure (IOP) sensors and a light source for treatment, demands considerable power that scales with the device functionality. Nevertheless, antenna-based wireless power transfer (WPT) suffers from low efficiency in confined areas and is further constrained by limitations in fabrication, such as photolithography. Here, we present a flexible helically stacked antenna (HSA) fabricated by using a blocker-assisted deposition method in which antenna lines are helically stacked to enhance efficiency within a compact footprint. The stacking method was verified by optical microscopy (OM), surface profilometry (SP), and scanning electron microscopy (SEM). We characterized the antenna performance across different numbers of stacked turns and analyzed the effects of the alignment and mechanical deformation. The three-turn stacked antenna has the greatest efficiency of 20.9%. Furthermore, we demonstrated the capability of the HSA to wirelessly power light-emitting diodes (LEDs) and organic light-emitting diodes (OLEDs), highlighting its suitability for ocular applications such as smart contact lenses.

Red perovskite light-emitting diodes (RPeLEDs) prepared by quasi-two-dimensional (quasi-2D) perovskites have attracted extensive attention due to their exceptional electroluminescence efficiency and robust device stability. However, current research on the color regulation mechanism of quasi-2D PeLEDs is still not comprehensive. Most researchers have focused on the transformation from green light to blue light, which has hindered the further application and development of quasi-2D PeLEDs in color adjustment. In this paper, we achieve color control from deep red light to orange-yellow light by adjusting the preparation process of quasi-2D films. While improving the color control mechanism of quasi-2D PeLEDs, the preparation method is provided to obtain quasi-2D perovskite structures. We successfully prepared quasi-2D perovskite structures by directly introducing 2D (4-BA)₂PbI₄ (4-BA = 4-benzylaniline) perovskite into the 3D CsPbI₃ perovskite system. RPeLEDs were successfully fabricated by proportional control, additive doping, device structure control, and so on. When the EL of this device is 688 nm, the maximum EQE reaches 7.74%. Subsequently, we optimized the color control of the quasi-2D perovskite device based on this structure by using the halogen doping strategy. A series of quasi-2D RPeLEDs of (4-BA)Cs_0.5PbBr_3.5xI_3.5–3.5x light-emitting layer groups were prepared and successfully realized the luminescence regulation from 684 to 596 nm. The luminous color gradually changed from deep red to orange-yellow. This work provides a special preparation method and improves the color control of quasi-2D PeLEDs in the red-light color gamut, offering valuable references for their development in the display field.

The fabrication of ferroelectric multilayer systems based on hafnia represents a promising approach for achieving high-performance ferroelectric devices. Electrical cycling instability is, in this regard, a key barrier to commercialization. Here, we report on the incorporation of La:HfO₂ subnanolayers into an epitaxial Hf_0.5Zr_0.5O₂ film, forming multilayer heterostructures. Ferroelectric properties of multilayers are compared with single-layer structures. We observe that wake-up and fatigue are not present up to 10⁵ cycles in the multilayers. The improved stability is enabled by the ≈25% reduction of coercive field together with the lower leakage resulting from the columnar microstructure throughout the entire thickness without phase discontinuity at interfaces and negligible presence of structural defects. This improvement on endurance response is obtained while the polarization is maintained in comparison with single Hf_0.5Zr_0.5O₂ films; there is negligible loss of the polarization throught time and there is a fast response time lower than 100 ns, limited by the measurement circuit. In addition, dielectric permittivity and large resistive switching up to 10⁸%, not related to the ferroelectric response, are also observed. These findings underscore multilayer architecture as an interesting approach to improve properties while also showing that careful selection of interlayer composition is critical to improve device performance.

This study systematically investigates the influence of TiO₂ interlayer thickness on the electrical and dielectric properties of Al/TiO₂/p-Si metal/insulator/semiconductor (MIS) structures. TiO₂ thin films with precisely controlled thicknesses (29, 40.6, 159, 278.7, and 390 nm) were deposited onto [100]-oriented p-Si substrates via spin-coating, and cross-sectional FE-SEM analysis confirmed the uniformity and exact thickness of each layer. The X-ray diffraction analysis performed on all samples confirmed the prominent formation of the anatase phase of TiO₂ in every sample. Capacitance, conductance, dielectric permittivity, dielectric loss, electrical modulus, and impedance measurements were performed to assess the effect of varying TiO₂ thickness on device performance. The results reveal that increasing TiO₂ thickness systematically modifies the flat-band voltage, interface trap density, and series resistance, while thicker layers introduce complex grain and grain-boundary contributions requiring multielement equivalent circuits for accurate impedance modeling. It has been found that TiO₂ interlayer thicknesses at the nanometer scale are critical for optimizing the performance of Al/TiO₂/p-Si/Al devices. The 40 nm (T2) sample yielded the best results and highlighted the importance of nanoengineered dielectric layers. Notably, films around 40 nm exhibit an optimal balance of high capacitance, balanced dielectric behavior, and favorable conductivity, highlighting the critical role of interlayer thickness in tuning electrical-dielectric behavior. This work provides valuable insights for the design of MIS devices, emphasizing how precise control of TiO₂ thickness can optimize device performance and reliability in electronic applications.