Photoinduced Nonvolatile Resistive Switching Behavior in Oxygen-Doped MoS2 for a Neuromorphic Vision System.

Controlling resistance by external fields provides fascinating opportunities for the development of novel devices and circuits, such as temperature-field-induced superconductors, magnetic-field-triggered giant magnetoresistance devices, and electric-field-operated flash memories. In this work, we demonstrate a light-triggered nonvolatile resistive switching behavior in oxygen-doped MoS2. The two-terminal devices exhibit stable light-modulated resistive switching characteristics and optically tunable synaptic properties with an on/off ratio of up to 104. The integrated device with crossbar architecture enables simultaneous image sensing, preprocessing, and storage in a single device, thereby increasing the training efficiency and recognition rate of image recognition tasks. This work presents a novel pathway to develop the next generation of light-controlled memory and artificial vision systems for neuromorphic computing.

Heterojunction interface-induced enhancement of position-sensitive photodetection in the nano-film of Ti/SrTiO3 based on the p-type silicon.

Complex oxide perovskites exhibit a range of novel, to the best of our knowledge, physical phenomena and have gained popularity as a material system in the past decades. Strontium titanate (SrTiO3) is an iconic material among oxide perovskite due to its unusual electronic transport behavior and has been investigated in many electronic devices. In this Letter, a type of SrTiO3 nano-film-induced enhancement of lateral photovoltaic effect (LPE) is observed in the heterojunction of Ti/SrTiO3/p-type Si. Optimizing the thickness of SrTiO3, the LPE sensitivity can reach 123.2 mV/mm, which is much higher than the sensitivity in the control samples of Ti/Si (55.3 mV/mm) and SrTiO3/Si (∼0mV/mm). These findings offer an effective way to improve the sensitivity and will be helpful in the development of oxide-based photodetection devices.

Improved uniformity in resistive switching behaviors by embedding Cu nanodots.

An improvement in the uniformity of resistive switching behaviors by embedding Cu nanodots is observed in Ta2O5 memory cells. In the conventional device structure, the growth of conductive filaments tends to be random and uncontrollable, which is the major obstacle for memory cell fabrication. By using a bottom electrode covered in metal nanodots, the field distribution in the electrolyte layer is modified and the conductive filaments prefer to grow along the direction of the Cu nanodots. Such controlled growth of conductive filaments leads to a reduced variation of switching parameters, as well as the disappearance of an unpredictable multistep resistive switching phenomenon, which is helpful for improving the device stability. Meanwhile, scaling relations are used to reveal the relationship between switching parameters and the microstructure of conductive filaments. By overlapping the scaling relations and electric field simulation, a model is proposed to explain the improvement in resistive switching performance caused by the presence of embedded Cu nanodots.

High sensitivity Si-based photodetection with nanoscale protective layer based on interface states.

A large lateral photovoltaic effect has been observed at the interface of SiO2/p-Si/SiO2 structure. Different from the traditional Schottky junction or PN junction device, this photovoltage is mainly dominated by the interface states existing at SiO2/p-Si interface, where the covered nanoscale SiO2 layer brings this device a stable and high photoelectric performance. These interface states can be explained as built-in field caused by the band bending at interface, which regulates the generation and diffusion of photo induced carriers. In this study, we discuss clearly the factors that impact greatly on the photovoltage output and sensitivity, including the oxide thickness, resistivity and tunneling effect. We believe this simple but efficient device will be beneficial for the exploring in photoelectric detection.

Laser tuned large position-dependent tunneling detection dominated by interface states in silicon based oxide-semiconductor structure.

A laser tuned tunneling detection is observed in SiO2(50nm)/p-Si/SiO2 structure. In comparison of dark condition, the tunneling current get amplified considerably over 250 times when irradiated with a low intensity laser (5mW) directly on the oxide layers. This huge amplified tunneling is unusual and rarely seen. Interestingly, this amplified tunneling effect is of position-dependent, and has a wide adjustment scope (centimeter level). Different from the traditional tunneling effect, where tremendous research efforts were directed only towards the influence of applied voltage or magnetic field, we demonstrate that this laser tuned amplifying process strongly associates with the interface states existing at SiO2/p-Si interface. These interface states can largely collect the light-induced careers and regulate its diffusion in a controllable manner. This work, for the first time, unambiguously demonstrate a novel tunneling detection based on the interface states, suggesting a new approach for light and position sensitive tunneling devices.

Magnetically tuned photoelectric response observed in nanoscale Co-SiO2-Si structures.

We report a large magnetically tuned lateral photovoltaic effect (LPE) observed in nanoscale Co-SiO2-Si structures. This tunable effect strongly depends on the location of two electrodes. The change ratio of lateral photovoltage (LPV) can reach a considerable value of 94.15% under an external magnetic field of 1.77 Teslas. This phenomenon is mainly ascribed to the asymmetric Lorentz force acting on the photo-current in the region of the edge area of the nanostructure. It adds a new functionality to traditional LPE-based devices, and provides a potential prospect for the development of multifunctional high-sensitive photoelectric devices or sensors.