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Flexible electronic devices have been extensively studied for their advantages of distinguished portability, conformal contact characteristics, and human‐friendly interfaces compared with conventional bulk Si technology. Flexible electronics can be attached to various surfaces like skin and internal organs for human–machine interaction, which has made significant advances in electronics, medicine, neuromorphic computing, etc. Owing to the innovation and maturation of the thin film preparation process, which have promoted the successful preparation of high‐quality flexible ferroelectric films. Herein, the preparation of flexible ferroelectric devices and the progress of their applications in recent years are reviewed. Prevailing methods for preparing flexible ferroelectric films including the van der Waals heteroepitaxy on flexible substrate, delamination of the ferroelectric films on rigid substrate by chemical etching techniques, and direct use of novel 2D ferroelectric materials etc. are summarized. The research progress of flexible ferroelectric devices applied to memories, sensors, photovoltaic devices, and energy harvesters are also be discussed in detail. Moreover, the potential applications of flexible ferroelectric devices in the field of neuromorphic computing are studied, a new trend which contributes to the further development of brain‐like chip systems. Finally, the challenges and prospects of flexible ferroelectric devices in the future advanced electronics are briefly proposed. [ABSTRACT FROM AUTHOR]

Ferroelectric Hf0.5Zr0.5O2 (HZO) thin films have attracted wide attention in terms of potential applications of nonvolatile ferroelectric memories. However, the effect of strain on the resistance switching characteristics of the ferroelectric HZO thin‐film memristors has not been fully studied so far. In this work, the strain effects on the HZO thin‐film memristors are investigated. HZO films with different resistance properties are also prepared by controlling the value of oxygen pressure. Based on the testing results, it is proposed that the resistance switching behavior of HZO films may be caused by the joint participation between ferroelectricity and oxygen vacancy migration. The study also found that HZO films can successfully simulate learning behavior similar to the human brain. The applied pulses with a width of tens of nanoseconds timescale are beneficial to realize fast learning and computing. These results provide a fundamental and deep insight on HZO‐based ferroelectric semiconductor oxide thin‐film memristors and their potential applications in next‐generation artificial electronic synaptic devices. [ABSTRACT FROM AUTHOR]

Quantum conductance, known as Sharvin point contact, has been extensively investigated in many electronic devices, including diodes, transistors, and switches, especially in conductive filaments-based memristors. Quantum conductance with one or multiple atoms point connection can overcome the limitations of scaling and operating speed of nonvolatile multiple memory, logic device, and brain-inspired computing systems. However, because of the instability of the atomic arrangement in the one/multiple atoms connection in a conductive filaments-based memristor, it is a great challenge to maintain quantum conductance states for a long time. Here, we demonstrate that the stable long-time retention of multi-level quantum conductance states can be realized in Mott insulator vanadium dioxide with a highly oriented crystalline texture. According to in situ transmission electron microscope, conductive atomic force microscope, and detailed energy band analysis results, it is proposed that the grain boundaries act as reservoirs for oxygen vacancies and confine the oxygen vacancy diffusion in the narrow grain boundaries due to the higher bulk diffusion barrier. Our approach is extremely crucial for realizing quantum conductance-based electronic devices, such as multi-level and high-density storage and neuromorphic computing. [ABSTRACT FROM AUTHOR]

With the advancement of artificial intelligence technology, more and more biological functions need to be imitated to complete more complex tasks and adapt to a complex external work environment. Memristors, as an excellent candidate for neuromorphic artificial electronic devices with many biological functions, have inspired the interest of researchers because of the advantages of scalability, good retention, and high operating speed. In this work, wide band gap semiconductor materials silicon carbide (SiC) films are prepared as a memristor medium. By adjusting the current compliance, both threshold character and bipolar resistive switching phenomenon are realized in one device with both lower powers for set operation. For the threshold characteristic, this device has mimicked the "threshold," "inadaptation," and "relaxation" features of a nociceptor, which will protect the artificial intelligence system to have stronger adaptability to the external environment. For the bipolar resistive switching characteristics, this device demonstrates good stability and retention time, with a switching speed of 18 ns. These bipolar resistance switching characteristics have simulated many synaptic functions. Pulses with hundreds of nanosecond time scale widths are conducive to fast learning and calculation. This device‐based third‐generation SiC semiconductor material will find a broad application in neuromorphic chip systems. [ABSTRACT FROM AUTHOR]

Designing suitable material systems to construct artificial synapses and exploring novel synaptic functions is a crucial step toward the realization of efficient large‐scale bioinspired neuromorphic systems. In this work, flexible and insoluble bio‐memristor devices are fabricated by precisely engineering the molecular structures of wool keratin. This flexible Ag/keratin/indium tin oxide‐polyethylene naphthalate synaptic device possesses enhanced mechanical resistance, which is achieved by photo‐cross‐linking keratin molecules, and can withstand a bending radius of up to 1.2 mm. This device is promising for implantable applications because it is water‐resistant. When modulated by triangle‐wave DC voltages and pulsed voltages, this flexible electronic device emulates typical memristor characteristics and synaptic functions, including potentiation/depression, spike timing dependent plasticity, and long‐term/short‐term plasticity. Simulation results indicate that a memristor network made by this wool‐keratin based device has ≈95.8% memory learning accuracy and capability for pattern learning. Combined, these features prove that the cross‐linked wool‐keratin based device has potential in wearable and flexible neuron computing systems. [ABSTRACT FROM AUTHOR]

With accelerating the miniaturization process of electronic devices, multifunctional optoelectronic devices that increases the compactness between the integrated devices have attracted much attention. In this work, we prepared a 1.0 cm2 two-dimensional Bi2Te2.7Se0.3 material by pulsed laser deposition technology, and fabricated Pd/Bi2Te2.7Se0.3/SiO2/Si multifunctional optoelectronic devices. Under the light illumination, the electron separation and aggregation at the Bi2Te2.7Se0.3/SiO2 interface lead to reducing a lower interface barrier. Meanwhile, electrons in the narrow-bandgap Bi2Te2.7Se0.3 photosensitive material easily escape from shackles and are trapped at the Pd/Bi2Te2.7Se0.3 surface, resulting in the resistance switching for monolithic devices. In addition, the capture of electrons at the interface enables the device to achieve long-term storage of information. The device can perform single functions of logical sum calculation (“OR” gate), multilevel information storage, photodetection and optical information demodulation. Meanwhile, the device might simultaneously implement photodetection and demodulation, logical calculation and memory, and demodulation and storage functions, which will increase the compactness of integrated circuits and reduce power consumption. [ABSTRACT FROM AUTHOR]

Flexoelectricity induced by the strain gradient is attracting much attention due to its potential applications in electronic devices. Here, by combining a tunable flexoelectric effect and the ferroelectric photovoltaic effect, we demonstrate the continuous tunability of photoconductance in BiFeO3 films. The BiFeO3 film epitaxially grown on SrTiO3 is transferred to a flexible substrate by dissolving a sacrificing layer. The tunable flexoelectricity is achieved by bending the flexible substrate which induces a nonuniform lattice distortion in BiFeO3 and thus influences the inversion asymmetry of the film. Multilevel conductance is thus realized through the coupling between flexoelectric and ferroelectric photovoltaic effect in freestanding BiFeO3. The strain gradient induced multilevel photoconductance shows very good reproducibility by bending the flexible BiFeO3 device. This control strategy offers an alternative degree of freedom to tailor the physical properties of flexible devices and thus provides a compelling toolbox for flexible materials in a wide range of applications. Previous methods to generate strain gradient and flexoelectricity are limited to a localized effect or cannot be tuned continuously. Here, the authors achieve macroscale continuously controllable strain gradient in freestanding ferroelectric thin film. Multilevel photoconductance in BiFeO3 films can be achieved by coupling between the flexoelectric and ferroelectric photovoltaic effect. [ABSTRACT FROM AUTHOR]

Resistive random-access memory plays a key role in non-volatile and neuromorphic artificial electronic devices. In this work, we fabricated Ta/TaOx/AlN/Pt resistive memory devices with the inserted AlN layer to improve the performance. The devices have better stability, lower threshold voltage (≈0.37 V), longer retention time (>104 s), and faster switching speed (9 ns) than those without the AlN film layer. More importantly, when different pulse parameters were applied, two phenomena, abrupt jumps in conductance and gradual change in conductance, were obtained. Furthermore, the biological synaptic functions were simulated, including the spiking-time-dependent plasticity and the paired-pulse facilitation. The Ta/TaOx/AlN/Pt resistive memory devices offer promising features; hence, they are good candidates for next-generation electronic devices for chip systems. [ABSTRACT FROM AUTHOR]