To address the demands of emerging data-centric computing applications, ferroelectric field-effect transistors (Fe-FETs) are considered the forefront of semiconductor electronics owing to their energy and area efficiency and merged logic-memory functionalities. Herein, the fabrication and application of an Fe-FET, which is integrated with a van der Waals ferroelectrics heterostructure (CuInP 2 S 6 /𝜶-In 2 Se 3 ), is reported. Leveraging enhanced polarization originating from the dipole coupling of CIPS and 𝜶-In 2 Se 3 , the fabricated Fe-FET exhibits a large memory window of 14.5 V at V GS = ±10 V, reaching a memory window to sweep range of ≈72%. Piezoelectric force microscopy measurements confirm the enhanced polarization-induced wider hysteresis loop of the double-stacked ferroelectrics compared to single ferroelectric layers. The Landau-Khalatnikov theory is extended to analyze the ferroelectric characteristics of a ferroelectric heterostructure, providing detailed explanations of the hysteresis behaviors and enhanced memory window formation. The fabricated Fe-FET shows nonvolatile memory characteristics, with a high on/off current ratio of over 10 6 , long retention time (>10 4 s), and stable cyclic endurance (>10 4 cycles). Furthermore, the applicability of the ferroelectrics heterostructure is investigated for artificial synapses and for hardware neural networks through training and inference simulation. These results provide a promising pathway for exploring low-dimensional ferroelectronics.

Atomic switches, also known as conductive bridging random access memory devices, are resistive-switching devices that utilize the electrochemical reactions within a solid electrolyte between metal electrodes, and are considered essential components of future information storage and logic building blocks. In spite of their advantages as next generation switching components such as high density, large scalability, and low power consumption, the large deviations in their electrical properties and the instability of their switching behaviors hinder their application in information processing systems. Here, we report the fabrication of a uniform, low-power atomic switch with a bi-layer structure consisting of TaO as the main switching layer (SL) and a relatively oxygen-deficient TaO as an oxygen vacancy control layer (VCL). The depth profiles of the filaments in the bi-layer device were obtained by performing conductive atomic force microscopy to assess the improvements in uniformity, reliability, and electrical performance that result from the insertion of the VCL. The coefficient of variation of the high resistance state of the bi-layer device was found to be drastically reduced from 60.92% to 2.77% in the cycle-to-cycle measurements and from 82.73% to 4.85% in the device-to-device measurements when compared with the values obtained for a single-layer device. The bi-layer device also exhibits a forming-free low operation voltage of ∼0.4 V, a high on/off ratio of ∼10, and high reliability with 10 years data retention at 85 °C.

Ferroelectric Field‐Effect‐Transistors In article number 2200566 , Sungjoo Lee and co‐workers report on the fabrication and application of a ferroelectric transistor integrated with a van der Waals ferroelectrics heterostructure (CuInP 2 S 6 /α‐In 2 Se 3 ). Leveraging enhanced polarization originating from the dipole coupling, the fabricated device exhibits a large memory window and nonvolatile memory characteristics with a long retention time and stable cyclic endurance, providing a promising pathway for exploring low‐dimensional ferroelectronics.

formula M n+1 X n T x (n = 1-3) has been studied all over the world, since the discovery of Ti 3 C 2 T x in 2011. [10][11][12][13] These 2D MXenes exhibit many fascinating properties, such as metallic conductivity, [14] high transparency, [15] water dispersibility, [16] thermal stability, [17] good mechanical properties, [18] and antibacterial activity, [19] which are required for functional electronic and optoelectronic devices. Recently, resistive switching properties required to mimic the dynamics of biological synapses, including short-term and long-term plasticity, [8,20] have been demonstrated in MXenes. This indicates the applicability of these 2D materials to artificial synapses required for brain-inspired neuromorphic computing. [8,[21][22][23] To date, only a few studies on MXene synapse electronics have been reported. In 2019, Yan et al. used Ti 3 C 2 T x MXene as an active layer of artificial synapses. [24] Here, Ti and oxygen vacancies acted as trap sites for hopping carriers, which enabled fundamental synaptic operations such as "update" and "memorize" of an internal conductivity in response to external electrical stimuli. [8] In 2020, Wei et al. coupled Ti 3 C 2 MXene with a solid lithium-polymer-electrolyte layer to implement the synaptic functionalities. [25] The inherently large interlayer spacing, good conductivity, and fast ion diffusion facilitated the migration of lithium ions in the MXene layer, which enabled multistate conductivity control. Although resistive switching phenomenon in the MXene layer has been reported in a few studies, desirable synaptic characteristics, including linear long-term potentiation (LTP)/long-term depression (LTD) characteristics, a large number of conductance states, large conductance on/off ratio (dynamic range), and so on, have not been demonstrated yet. Furthermore, the applicability of 2D MXene synapses for neural networks (NNs) have not been demonstrated (see also Table S1, Supporting Information).Here, we report an artificial 2D MXene synapse fabricated with Ti 3 C 2 T x MXene nanosheets, which successfully mimics the dynamics of biological synapses, such as excitatory/inhibitory postsynaptic currents (EPSC/IPSC), paired-pulse facilitation (PPF), and LTP/LTD characteristics. Through in-depth analyses such as X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (EDS), we reveal that such synaptic functionalities originated from the gradual formation and annihilation of the conductive metallic filaments on the MXene surface with distributed functional groups. We also discuss the synaptic MXenes, an emerging class of two-dimensional (2D) transition metal carbides and nitrides, have attracted wide attention because of their fascinating properties required in functional electronics. Here, an atomic-switch-type artificial synapse fabricated on Ti 3 C 2 T x MXene nanosheets with lots of surface functional groups, which successfully mimics the dynamics of biological synapses, is reported. Through ...

In this study, we propose a hybrid black phosphorus (BP)/Au nanoparticle (NP)-based photodetector, which greatly enhances the performance of photodetectors compared to BP-only photodetectors. By integrating Au NPs onto the BP surface, the light absorption was greatly enhanced owing to the localized surface plasmon resonance induced by the Au NPs, and the dark current of the photodetector was suppressed because the holes were withdrawn from the BP to the Au NPs due to the difference in the work function. After optimizing the density of the Au NPs, the responsivity of the BP/Au-NP photodetector reached 6000 and 500 A/W for 655 and 980 nm wavelengths, respectively, which are 60 and 500 times higher than those of BP photodetectors, respectively. The proposed hybrid photodetector, a two-dimensional (2D) semiconductor with noble metal NPs, opens up the possibility of realizing highly sensitive optoelectronic devices in the future.