Neurodegenerative disorders are challenging issues for initial diagnosis and cure. False signals from neurons that make up the brain must be corrected. To treat neurodegenerative diseases, neuromorphic devices are inserted into the body and connected to nerves. However, there are major concerns regarding implanting these devices into living bodies, that is, toxicity caused by the materials and the need for an additional operation to remove the device after treatment. In this research, a neuromorphic device is fabricated based on hyaluronic acid (HA), which is biocompatible and biodegradable, that meets the requirements for implantable bioelectronics. The fabricated device have a paired-pulse facilitation index of ≈121.00% and short term-tolong term memory transition behavior that resembled human learning-experience behavior. It is confirmed that the synaptic behavior mechanism of the device is due to an Mg oxide layer formed at the Mg/HA interface. Biodegradability and cell cytotoxicity tests confirmed the suitability of HA-based neuromorphic devices as implantable bioelectronics. Based on the results, it is believed that such implantable devices will lead to better healthcare.

P-type copper oxide (Cu x O) thin-film transistors (TFTs) with enhanced switching characteristics were fabricated by introducing a sputter-processed capping layer capable of controlling the back-channel phase (labeled as phase-controlling layer, PCL). By optimizing the processing conditions (the deposition power and postdeposition annealing parameters), the switching characteristics of the TFTs achieved a subthreshold swing of 0.11 V dec–1, an on/off current ratio (I on/I off) of 2.81 × 108, and a field-effect mobility (μFET) of 0.75 cm2 V–1 s–1, a considerable enhancement in performance compared to that of Cu x O TFTs without the PCL. Through optical/electrical analyses and technology computer-aided design simulations, we determined that the performance improvements were because of the Cu x O back-channel phase reconstruction through PCL deposition and subsequent annealing. The two factors that occurred during the process, sputtering damage and heat treatment, played key roles in creating the phase reconstruction by inducing a local phase transition that sharply reduced the off-current via controlling back-channel hole conduction. As a sample application, we fabricated a complementary metal oxide semiconductor inverter based on our optimized Cu x O TFT and an InGaZnO TFT that demonstrated a large inverter voltage gain of >14. The proposed approach opens up advancements in low-power circuit design by expanding the utilization range of oxide TFTs.

possible due to the parallel computing that efficiently processes and memorizes the information at the same time through neural network that consists of ≈10 12 neurons and ≈10 15 synapses. [6][7][8][9] This allows the brain to be efficient in handling cognitive operations such as think, read, learn, remember, and reason. [10][11][12][13] Therefore, in order to mimic the brain, neuromorphic computing that simulates the neural network has been developed and in considerable attention ever since. As one of the neuromorphic applications, neuromorphic visual system, i.e., optical synapse, that mimics the biological visual system is one of the most researched due to its importance as the development of artificial eyes would benefit humans greatly. However, this neuromorphic visual system consists of a separate photosensor and a neuromorphic synapse that are connected via a circuitry, leading to a low efficiency and a complex circuitry. Although the neuromorphic device enables processing and memorizing in one device, the signal itself should be converted to electric signal by the photodetector and transported through the circuit to the neuromorphic device. This extra transportation of the signal requires extra energy consumption and also could cause the bottleneck effect similar to von-Neumann computing system, diminishing the advantages of using neuromorphic devices. [14][15][16][17] Therefore, in order to improve the visual information processing efficiency, optical synapses are also developed where it has both the synaptic functions and the photo-sensing abilities. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Different types of devices, such as memristors, field-effect transistors, and phase change memories, have been studied for the application of artificial synapses. [16,18,19,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]44] Additionally, numerous materials including but not limited to low-dimensional materials, perovskites, oxide semiconductors, and organic materials have been applied to artificial synapses. [16,18,19,[24][25][26][27][28][29][30][31][32][41][42][43][44] Among these, oxide semiconductor thin-film transistors show promising properties for optical synapses. [18,19,24,[27][28][29][30][31][32] Oxide semiconductors, in terms of light detection, have wavelength-and intensity-selectivity as the current increases when intensity increases and wavelength decreases. This property is crucial to optical neuromorphic synapses for learning property.

We introduced an organic interlayer into the Schottky contact interface to control the contact property. After inserting an 11-nm-thick polyethylenimine (PEI) interlayer between the aluminum (Al) source/drain electrode and the cuprous oxide (Cu2O) channel layer, the Cu2O thin-film transistors (TFTs) exhibited improved electrical characteristics compared with Cu2O TFTs without a PEI interlayer; the field-effect mobility improved from 0.02 to 0.12 cm2/V s, the subthreshold swing decreased from 14.82 to 7.34 V/dec, and the on/off current ratio increased from 2.43 × 102 to 1.47 × 103, respectively. Careful investigation of the contact interface between the source/drain electrode and the channel layer established that the performance improvements were caused by the formation of electric dipoles in the PEI interlayer. These electric dipoles reduced the Schottky barrier height by neutralizing the charges at the metal/oxide semiconductor interface, and the holes passed the reduced Schottky barrier by means of tunneling or thermionic injection. In this way, p-type oxide TFTs, which generally need a noble metal having a high work function as an electrode, were demonstrated with a low-work-function metal. As a basic application for logic circuits, a complementary inverter based on n-type indium–gallium–zinc oxide and p-type Cu2O TFTs was fabricated using only Al source/drain electrodes. This research achieved advances in low-cost circuit design by broadening the electrode metals available for the manufacture of p-type oxide semiconductor-based electronics.

The principal causes of the poor picture quality on active matrix organic light-emitting diode (AMOLED) displays, operating under extremely low brightness and gray-scale conditions, were analyzed and verified by measuring and modelling of the electrical simulations. Through the analysis, it was found that the deteriorated picture quality was induced by a delayed saturation voltage, which means the electric potential difference between the initial voltage applied to the anode of the OLED (V init ) and the OLED saturated voltage (V sat ) for emission. This is because the deviations of pico-ampere-level currents and delayed OLED charging prior to light emission increased the saturation voltage when there were low driving currents. Thus, we optimized the voltage by increasing V init from −4.5 to −2.7 V, effectively eliminating image deterioration by reducing the OLED charging delay. Thus, the proposed approach opens up advancements of obtaining superior picture quality with ultra-low luminance, even in the dark illuminance environments. We discuss how OLED picture quality may be enhanced under low brightness, including the driving methods, design considerations, and processes involved.