ACS Applied Electronic Materials最新文献

Strain engineering is a powerful technique to enhance the carrier mobility of silicon in semiconductor technology. Similarly, introducing tensile strain can increase the mobility of MoS₂ and other transition metal dichalcogenides. Although bending a flexible substrate is a simple and effective method to introduce tensile strain into MoS₂, the application of tensile strain to MoS₂ on a rigid substrate, such as surface-oxidized silicon (SiO₂/Si), is highly desirable. In this study, tensile and compressive strains were introduced into monolayer MoS₂ on SiO₂/Si by adjusting the transfer process. By increasing the thermal treatment temperature during the transfer process, the biaxial strain of approximately 0.5% was introduced into MoS₂, as confirmed by Raman spectroscopy. Consequently, we found that the carrier mobility of MoS₂ with a thermal treatment temperature of 130 °C was higher than MoS₂ with a 50 °C thermal treatment. Therefore, tuning the transfer process can control the properties of two-dimensional (2D) materials and achieve performance-controlled 2D material-based devices.

With the rise of big data and artificial intelligence, the von Neumann architecture’s limitations in computing power and energy efficiency are becoming increasingly evident. Neuromorphic computing, an innovative approach inspired by simulating the workings of the human brain, aims to achieve high computational capabilities with low energy consumption. Two-dimensional (2D) van der Waals ferroelectric semiconductor α-In₂Se₃ exhibits a unique combination of ferroelectricity, semiconductor properties, and the advantages of 2D materials, demonstrating significant potential as an ideal platform for information processing. This work reports a 2D ferroelectric semiconductor synaptic transistor based on α-In₂Se₃, which exhibits nonvolatile characteristics and synaptic plasticity due to the ferroelectric remanent polarization of α-In₂Se₃. The tight coupling between ferroelectric polarization and semiconducting nature allowed the α-In₂Se₃ ferroelectric semiconductor field-effect transistor to achieve a high current on/off ratio of 10⁵, a wide memory window of 81 V, and retention time greater than 600 s. Furthermore, the device demonstrated tunable synaptic plasticity, exhibiting paired-pulse facilitation, long-term potentiation/depression, the transition from short-term to long-term plasticity, as well as learning-experience behavior. Electrically modulated synaptic plasticity enabled an artificial neural network to achieve a peak accuracy of 94.8% on the MNIST handwritten digit data set, maintaining over 80% accuracy under background noise (standard deviation up to 50%), highlighting the robust fault tolerance of the conductance states. These results demonstrate that the 2D ferroelectric semiconductor α-In₂Se₃ holds significant potential for applications in high-performance information storage, processing, and neuromorphic computing.

This paper presents integrated sensing and computing memory (ISCM) devices based on V₂O₅/WO₃ heterostructures using wafer-scalable semiconductor microfabrication processes. The impact of the V₂O₅/WO₃ heterostructure-based ISCM devices was tested and compared with the V₂O₅- and WO₃-based ISCM structures. The heterostructured devices have broadband sensing capability with improved performance metrics as compared to the single-material-based ISCM devices. The heterostructured device has shown responsivity (1.5 A/W) and detectivity (1.2 × 10¹¹ Jones) at 950 nm. All fabricated devices were stimulated using AC and DC stimuli under various illumination conditions. The heterostructured ISCM device offers a high current switching ratio (30.6), and this value is 2 times and 17 times higher than WO₃ and V₂O₅, respectively. In addition, all devices have ultrafast resistive switching capability and long-term stability of >10² cycles. The heterostructured device has shown the set and reset times of 88.6/35.7 μs, respectively, at 950 nm. In addition, the AND gate logic circuit is realized using electrical and optical stimuli. These test results have proven that the fabricated devices can be deployed as sensing/storage devices for future broadband sensing and memory technology.

Well-defined heterojunctions inside nanostructured device structures are a basic requirement for any nanoscale device design with advanced electrical properties. For the evaluation of the desired functionalities on the nanoscale, a study of the electrical behavior with appropriate spatial resolution is highly revealing. We specifically address GaN-based core–shell heterostructures and perform multiprobe measurements with ultrahigh spatial resolution. The n⁺-GaN nanowire core exhibits favorable electrical conductivity, and the behavior of charge carrier transport at a n⁺-nonintentionally doped -n⁺-doped core–shell double heterojunction is demonstrated when applying an electron beam-induced current mode. This investigation offers direct insights into the selective charge carrier transport, and therefore into the rectifying junction within the core–shell GaN nanowire, and contributes to a model of the conductivity channels. This experimental approach is crucial for any future advancement of device structures that incorporate bottom-up-grown, heterostructure core–shell GaN nanowires on conductive Si(111) substrates.

Broadband photodetectors (i.e., sensing units) within the sensor node are a crucial component that plays a critical role in efficiently embedding cutting-edge technologies like the Internet of Things. Compared to other fabrication techniques, 2D layered material’s hybrid structure-based broadband photodetectors (PDs) may be more helpful in effectively deploying these technologies, as they can eliminate fabrication challenges such as complex device fabrication, low operating temperature requirements, and the toxic fabrication environment. Despite the above fabrication eases, the issue of nonuniform spectral response across the operating wavelength, adversely impacting PD efficacy, still needs to be addressed. The present work demonstrates a cost-effective and facile approach for achieving a substantially uniform spectral response across the broadband. The comparative investigation of WS₂-QDs-based PD fabricated with and without CuO NPs blending revealed that by blending WS₂-QDs with CuO NPs, the spectral response’s uniformity has been improved in addition to the quantitative improvement in the responsivity. The blended heterojunction PD structure demonstrated a broadband response between 365 and 950 nm at a low operating voltage of −1.5 V, with a peak responsivity of 111.84 A/W, EQE of 37993.74%, and detectivity of 2.13 × 10¹⁴ Jones. The PD’s temporal response was similarly found to be sufficiently fast, with rise and fall times of 40.83 and 39.76 ms, respectively.

Copper (Cu) is an indispensable conductive material widely utilized in applications such as integrated electronic circuits and the growth of two-dimensional materials. Single-crystalline Cu exhibits superior performance over polycrystalline Cu; however, the synthesis of single-crystalline Cu typically requires relatively high temperatures. Therefore, the realization of room-temperature epitaxy for Cu films is crucial for advancing both fundamental science and practical applications. Here, we synthesized high-quality wafer-scale Cu films at room temperature by homemade high-pressure magnetron sputtering. The measurements of the crystal and electronic structures confirmed the high quality of the films. Atomic force microscopy characterized a smooth and uniform surface of the films. Remarkably, the unexpectedly high carrier density (10²³ cm^–3) and exceptional optical properties of the Cu films were revealed through electrical transport and spectroscopic ellipsometry measurements, comparable to those of bulk crystals. Our results demonstrate the successful achievement of high-quality single-crystalline Cu films grown at room temperature, offering significant potential for integrating the films into advanced electronic, photonic, and flexible applications.

Tb-doped SnO₂ (represented as Tb–SnO₂) was prepared by calcining Tb-doped Sn MOF synthesized by a solvothermal method. 5% Tb–SnO₂ exhibits excellent selectivity, high response (28.2), and fast response/recovery time (28 s/135 s) toward 50 ppb (volume concentration in parts per billion) formaldehyde (HCHO) at low operating temperature (200 °C). The low detection limit of the HCHO gas sensor is mainly due to the large number of oxygen vacancies in Tb–SnO₂ caused by the charge imbalance between Tb ions and Sn ions during the high-temperature calcination process of Tb-doped Sn MOF. Oxygen vacancies promote the conversion of oxygen molecules into active adsorbed oxygen species, narrow the band gap of semiconductor oxides, and reduce the activation energy of formaldehyde gas-sensing reactions, thereby improving the performance of gas sensors. 5% Tb–SnO₂ gas sensor has strong moisture resistance, with a response value of 209.3 to 10 ppm of HCHO at a high relative humidity of 80%. The moisture resistance mechanism of the material is explained as Tb³⁺/Tb⁴⁺ redox pairs acting as water molecule capture agents, which reduce the occupation of gas-sensing reaction active sites by water molecules on the material surface.

The substantial exciton binding energy in two-dimensional transition metal dichalcogenide (TMDC) monolayers offers a prime platform for investigating many-body effects and realizing excitonic devices at room temperature. In these monolayers, exciton behaviors can be efficiently modulated by external stimuli, such as temperature, mechanical stress, and electric fields. Particularly, in-plane electrical modulation of exciton emission and distribution has been achieved recently; however, the modulation depth is still too small to support practice application. Here, by combining in-plane electric field with a local strain, we have prominently elevated the modulation depth of exciton emission in monolayer tungsten disulfide (WS₂) by ∼3 times. Such modulation relies on both the electric field modulated exciton emission via trap states at the Au-WS₂ interface and the strain field-induced exciton funneling effect at the localized strained area. This work sheds light on the cooperative multifield control of excitonic devices based on monolayer TMDCs.

Resistive random-access memory (RRAM) has emerged as a promising alternative to conventional memory components, offering nonvolatility, high density, low power consumption, and fast read/write speeds. This study investigates the integration of 2D cadmium selenide nanoplates (CdSe NPLs) into an organic semiconductor to enhance the RRAM performance. Utilizing poly(vinylcarbazole) (PVK) as the organic semiconductor, we systematically evaluate the impact of CdSe NPLs on memory properties. Our findings demonstrate that CdSe NPL integration enhances both charge entrapment and release, resulting in nonvolatile memory attributes and rewritability. The synergistic interplay between CdSe NPLs and the energy barrier of PVK defines distinct memory properties. Fabricated CdSe-PVK RRAM devices exhibit impressive performance characteristics, including a current ON/OFF ratio exceeding 10⁵, a retention time exceeding 10⁵ seconds, and an operational voltage below +3 V. These results surpass those reported in similar studies, highlighting the efficacy of integrating CdSe NPLs into RRAM materials. Overall, this study provides insights into the enhanced performance of RRAM through nanostructure integration, paving the way for further research in this promising area.

As ionic crystals, halide perovskite materials have a low defect formation energy, resulting in serious ion migration. Research has shown that the density of deep-level defects near the surface of perovskites is much higher than that in the bulk. Nevertheless, up to now, many studies have focused on the top surface of perovskites, and it is rather difficult to study and passivate the buried interface defects. Here, we report an effective method for passivating the buried interface, that is, introducing potassium hypophosphite (KH₂PO₂) at the buried interface of perovskite, which can simultaneously regulate the crystallization of perovskite and the passivation of ionic defects. Through this strategy, the grain size of CH₃NH₃PbI₃ can be precisely controlled, high-quality thin films can be formed, and the defect density in the crystals can be reduced. By taking advantage of the reducibility of the hypophosphite ion, we can inhibit the generation of iodine and reduce metal Pb-related defects in the CH₃NH₃PbI₃ thin films. Consequently, the ionic interface charge density of the device is significantly decreased, the formation energy of ionic defects is obviously increased, and ionic migration is effectively suppressed. Finally, the performance and stability of perovskite optoelectronic devices are significantly improved.