ACS Applied Electronic Materials最新文献

The unique combination of atomically thin layers and well-defined interfaces in two-dimensional (2D) semiconductors holds promise for applications in electronics and optoelectronics. As promising newcomers, p-type InSe and n-type PtS₂ nanosheets present exciting possibilities, with their unique characteristics. Here, we investigate gate-controlled InSe/PtS₂ van der Waals heterostructures (vdWHs), highlighting their potential as candidates for advanced electronic and optoelectronic applications. This work demonstrates the realization of a 2D p-n diode with a precisely defined atomic interface, exhibiting strong interlayer interactions. InSe/PtS₂ vdWHs demonstrate impressive functionalities surpassing previously reported van der Waals counterparts with gate-dependent rectification of 1.5 × 10⁵ at a gate voltage of V_g = −20 V and ideality factor of 1.17, close to an ideal diode. Investigating the photovoltaic response of the InSe/PtS₂ heterostructure under varied light intensities revealed a significant responsivity that varies from 31.85 to 43.2 A/W upon exposure to a light wavelength of 220 nm. Additionally, a substantial external quantum efficiency (EQE) ratio of ∼2.4 × 10⁴ % with high detectivity (D*) of 7.06 × 10⁹ Jones values is achieved. This work demonstrates the development of advanced p-n junctions, paving the way for the realization of high-performance electronics and optoelectronic devices.

The unique electronic properties of amorphous indium gallium zinc oxide (a-IGZO) thin films are closely associated with the complex charge dynamics of the materials. Conventional studies of charge transport in a-IGZO usually involve steady-state or transient measurements on field-effect transistors. Here, we employed microwave impedance microscopy to carry out position-dependent time-of-flight (TOF) experiments on a-IGZO devices, which offer spatial and temporal information on the underlying transport dynamics. The drift mobility calculated from the delay time between carrier injection and onset of TOF response is 2–3 cm²/(V s), consistent with the field-effect mobility from device measurements. The spatiotemporal conductivity data can be nicely fitted to a two-step function, corresponding to two coexisting mechanisms with a typical time scale of milliseconds. The competition between multiple-trap-and-release conduction through band-tail states and hopping conduction through deep trap states is evident from the fitting parameters. The underlying length scale and time scale of charge dynamics in a-IGZO are of fundamental importance for transparent and flexible nanoelectronics and optoelectronics, as well as emerging back-end-of-line applications.

In this work, the back-end of line (BEOL) compatible sub-6 nm Hf_0.5Zr_0.5O₂/ZrO₂/Hf_0.5Zr_0.5O₂ (HZO/ZrO₂/HZO) stack and the corresponding capacitors were fabricated. The capacitor with the sub-6 nm HZO/ZrO₂/HZO stack annealed at 400 °C shows a superior remanent polarization (2P_r) of 26.3 μC/cm² under only ±1.25 V sweeping, while the conventional HZO film presents nonferroelectricity. The enhanced ferroelectricity stems from the increased ferroelectric phase proportion with ZrO₂ insertion. Moreover, the capacitor with a HZO/ZrO₂/HZO stack also achieved an excellent endurance with a 2P_r of 27.1 μC/cm² after 10¹¹ cycles without breakdown and only ∼12% 2P_r degradation at 85 °C. The robust reliability is ascribed to the suppressed generation of defects and domain pinning under the low operating voltage. The sub-6 nm HZO/ZrO₂/HZO stack presents great potential for BEOL compatible nonvolatile memories in advanced process nodes.

Ta-doped h-ZnTiO₃ (h-ZnTiO₃:Ta) films with an atomic ratio of 0–5% are grown on sapphire substrates by pulsed laser deposition. The prepared films exhibit n-type semiconductor behavior with high epitaxial crystalline quality. These films have high transparency, and their optical band gaps exceed 3.72 eV. The Hall mobility and carrier concentration of the 1% Ta-doped film are 4.6 cm²/(V·s) and 4.20 × 10¹⁴ /cm³, respectively. The h-ZnTiO₃:Ta film-based metal–semiconductor–metal (MSM) photodetectors are fabricated, and their characteristics are analyzed in detail. Among them, 1% Ta-doped h-ZnTiO₃ film-based devices show the best detection performance, including responsivity of 4.23 mA/W and detectivity of 1.43 × 10¹¹ Jones, under the wavelength of 308 nm ultraviolet light with an optical density of 140 μW/cm². The detector also has an extremely fast response time (rise time: 0.16 s and fall time: 0.04 s). This work proves that h-ZnTiO₃:Ta epitaxial films have great application prospects in future optoelectronic devices.

Photoferroelectric BiFeO₃ (BFO) has attracted renewed interest to be integrated into thin film photovoltaic (PV) devices as a stable, lead-free, and versatile photoabsorber with simplified architecture. While significant efforts have been dedicated toward the exploration of strategies to tailor the properties of this photoabsorber to improve the device performance, efficiencies still remain low. The modification of the BFO interface by the incorporation of transport-selective layers can offer fresh opportunities to modify the properties of the device. Identifying an optical and electrically suitable selective layer while ensuring easy device processing and controlled film properties is challenging. In this work, we determine the influence of incorporating a ZnO layer on the ferroelectric and photoresponse behavior of an epitaxial BiFe_0.9Co_0.1O₃ (BFCO)-based heterostructure. The device is completed with Sn-doped In₂O₃ (ITO) and La_0.7Sr_0.3MnO₃ (LSMO) electrodes. This all-oxide system is stable under ambient conditions and displays robust ferroelectricity. The coupled ferroelectricity–photoresponse measurements demonstrate that the short circuit current can be modulated by ferroelectric polarization in up to 68% under blue monochromatic light. Also, the responsivity of the system with the ZnO-modified interface is larger than that of the system with no ZnO. Complementary band energy alignment studies reveal that the observed increase in the short circuit current density of the device with ZnO is attributed to lower Fermi level energy at the ZnO/BFCO interface compared to the ITO/BFCO interface, which reduces charge recombination. Therefore, this study provides useful insights into the role of the ZnO interface layer in stable BFO-based devices to further explore their viability for potential optoelectronic applications.

We investigated the mechanism and application of the modulation of terahertz waves using perovskite heterostructures. At the interface between PEDOT:PSS and the perovskite layers under excitation by an external light source, photogenerated carriers transferred from the perovskite layer to the PEDOT:PSS layer, which was accompanied by charge accumulation. A large number of photogenerated carriers scattered terahertz waves, thereby modulating the terahertz signal in the sample. The process of modulation and recovery of the terahertz signal by a perovskite material under external light is analogous to the principle of biological synapses, which are involved in memory and learning in animal brains. This enabled us to develop perovskite-based synaptic devices. The memory properties of perovskite heterojunction materials open up applications of terahertz technology.

Photoferroelectric BiFeO₃ (BFO) has attracted renewed interest to be integrated into thin film photovoltaic (PV) devices as a stable, lead-free, and versatile photoabsorber with simplified architecture. While significant efforts have been dedicated toward the exploration of strategies to tailor the properties of this photoabsorber to improve the device performance, efficiencies still remain low. The modification of the BFO interface by the incorporation of transport-selective layers can offer fresh opportunities to modify the properties of the device. Identifying an optical and electrically suitable selective layer while ensuring easy device processing and controlled film properties is challenging. In this work, we determine the influence of incorporating a ZnO layer on the ferroelectric and photoresponse behavior of an epitaxial BiFe_0.9Co_0.1O₃ (BFCO)-based heterostructure. The device is completed with Sn-doped In₂O₃ (ITO) and La_0.7Sr_0.3MnO₃ (LSMO) electrodes. This all-oxide system is stable under ambient conditions and displays robust ferroelectricity. The coupled ferroelectricity-photoresponse measurements demonstrate that the short circuit current can be modulated by ferroelectric polarization in up to 68% under blue monochromatic light. Also, the responsivity of the system with the ZnO-modified interface is larger than that of the system with no ZnO. Complementary band energy alignment studies reveal that the observed increase in the short circuit current density of the device with ZnO is attributed to lower Fermi level energy at the ZnO/BFCO interface compared to the ITO/BFCO interface, which reduces charge recombination. Therefore, this study provides useful insights into the role of the ZnO interface layer in stable BFO-based devices to further explore their viability for potential optoelectronic applications.

This study proposes a portable, paper-based tactile feedback system interaction device, engineered to serve blind users with an integrated platform for both input and output functionalities. The device comprises six functional units, each measuring 10 × 10 mm, crafted using a sandwiched structure of paper substrate, graphite, and two PLA films via the hot-pressing technique. Utilizing the corona charging method, the PLA electret films exhibit an impressive piezoelectric coefficient peaking at 3578 pC/N, making it highly sensitive for both sensing and actuating. The pressure sensor, used for writing purposes, demonstrates a sensitivity of 1.01 V/N, while the vibration actuator, used for reading, achieves an output force of 60 mN at an applied voltage of 400 V. Notably, both the surface charge density and the performance of the sensor and actuator stabilize post approximately 1000 interactions. Our psychophysical experiments indicate the device has a perceptible threshold voltage as low as 50 V. Subsequent tactile interaction communication tests offer a preliminary validation of the device’s applicability. The proposed tactile interaction device, being flexibly constructed and intrinsically biodegradable, paves the way for cost-effective tactile communication solutions.

Compared to SrTiO₃-based 3d two-dimensional electron gases (2DEGs), KTaO₃-based 5d 2DEGs have much more exceptional physical properties, such as a higher Curie temperature of spin-polarized 2DEG, higher T_c for the 2DEG at superconducting state, and larger spin–orbit coupling. Herein, the CaZrO₃ (CZO) films were deposited on KTaO₃ (001) substrates at the deposition temperature varied from 700 °C to room temperature, and the conductive CZO/KTO interface was obtained at all deposition temperatures. The conductivity of the CZO/KTO heterointerface exhibits critical dependence on the film thickness, where the critical thickness for conduction increases from 3.2 to 6 nm when decreasing the deposition temperature from 700 °C to room temperature. Moreover, the electric properties of the heterointerface grown at room temperature can be modulated strongly by the light illumination. The strength of the spin–orbit coupling exhibits large relative variation with the carrier density. Under the light illumination, the strength of the spin–orbit coupling increases from ∼3.9 × 10^–12 eV m to the maximum of ∼9 × 10^–12 eV m, with the maximal change of the carrier density of only 3 × 10¹² cm^–2. The present work demonstrates an effective tuning of the special 5d-electron-based 2DEGs by light illumination, showing a feasible way for advanced optoelectronic device application.

Micromechanical resonators with very low mass are highly desirable for sensing and transduction applications. Layered materials (LMs) can be used to fabricate single- to few-atom thick suspended membranes, representing the ultimate limit to low mass. Transition-metal dichalcogenides (TMDs), such as WSe₂, are particularly compelling because they can host spatially confined excitons in single layer (1L), potentially enabling the creation of nonclassical mechanical states and interconnects between quantum networks and processors. However, these exciting prospects have been tempered by low device yields, invasive methods for detecting resonator motion, and high mechanical damping. Here, we report the creation of mechanical resonators by suspending 1L-WSe₂ across a 90 × 90 array of 2.5-μm diameter holes with a > 75% success rate. We detect the resonator room-temperature (RT) Brownian motion and measure resonator mass to quantify contamination, using below-bandgap laser interferometry. We investigate the relation between frequency, diameter, and mechanical quality factor, which can exceed 1000 in our devices. We find the dependence agrees with the effect of dissipation dilution, highlighting the importance of reducing mechanical mode-bending. Key to this is the large-scale, high-quality arrays that make it possible to access a frequency range that surpasses previous works. Further, the ability to fabricate large numbers of 1L resonators, and the simplicity of probing their motion without electrodes or an underlying reflective substrate, facilitates previously hard-to-reach configurations, such as resonators in phononic crystals or within optical cavities.