Abstract
Memristors are promising building blocks for the next-generation memory and neuromorphic computing systems. Most memristors use materials that are incompatible with the silicon dominant ...complementary metal-oxide-semiconductor technology, and require external selectors in order for large memristor arrays to function properly. Here we demonstrate a fully foundry-compatible, all-silicon-based and self-rectifying memristor that negates the need for external selectors in large arrays. With a p-Si/SiO
2
/n-Si structure, our memristor exhibits repeatable unipolar resistance switching behaviour (10
5
rectifying ratio, 10
4
ON/OFF) and excellent retention at 300 °C. We further build three-dimensinal crossbar arrays (up to five layers of 100 nm memristors) using fluid-supported silicon membranes, and experimentally confirm the successful suppression of both intra- and inter-layer sneak path currents through the built-in diodes. The current work opens up opportunities for low-cost mass production of three-dimensional memristor arrays on large silicon and flexible substrates without increasing circuit complexity.
Interests in group IV-VI compound semiconductors for MWIR applications have undergone multiple resurgences over the last 70 years due to the high IR responsivity. Many research groups have shown they ...can achieve high IR response by making modification of the sensitization process; however, nearly all are using traditional deposition methods (Chemical Bath Deposition or Chemical/Physical Vapor Deposition) involving complex chemical processing or vacuum-based equipment. This work introduces a flexible alternative method for producing ultrapure polycrystalline thin films with exceptional morphological control. The process utilizes a planetary ball-mill to wet-mill ultra-pure crystalline ingot into colloidal nanocrystals (NC), followed by rapid deposition in a centrifuge to form a compact, thin film across a silicon substrate. Laser sintering is then used to rapidly form a continuous denser film with excellent substrate adhesion and unique control of the morphological properties. This work demonstrates a new method using laser sintering that can form a 1.5 μm thin film of PbSe with equivalent physical and electrical (p-type with a carrier concentration of 4.5 × 1017/cm3 and resistivity value of 0.17 Ωcm) properties to CBD/PVD. The results are presented for the process development, film morphology, crystal structure, and electrical properties. Lastly, unlike traditional deposition methods, this alternative process is environmentally responsible by producing zero hazardous waste by allowing recovery of all unused PbSe for reuse. The reported method is applicable for achieving thin films from a variety of high purity bulk materials.
•New methods for reducing hazardous materials in microelectronics and sensors.•Rapid and tailorable way to deposit polycrystalline thin films.•Performance of infrared sensors has room to improve.•Combine deposition and patterning in one laser sintering step.•Insitu-doping of thin films.
Memristive devices are promising candidates for the next generation non-volatile memory and neuromorphic computing. It has been widely accepted that the motion of oxygen anions leads to the ...resistance changes for valence-change-memory (VCM) type of materials. Only very recently it was speculated that metal cations could also play an important role, but no direct physical characterizations have been reported yet. Here we report a Ta/HfO2/Pt memristor with fast switching speed, record high endurance (120 billion cycles) and reliable retention. We programmed the device to 24 discrete resistance levels, and also demonstrated over a million (2(20)) epochs of potentiation and depression, suggesting that our devices can be used for both multi-level non-volatile memory and neuromorphic computing applications. More importantly, we directly observed a sub-10 nm Ta-rich and O-deficient conduction channel within the HfO2 layer that is responsible for the switching. This work deepens our understanding of the resistance switching mechanism behind oxide-based memristive devices and paves the way for further device performance optimization for a broad spectrum of applications.
Oxygen vacancy formation, migration, and subsequent agglomeration into conductive filaments in transition metal oxides under applied electric field is widely believed to be responsible for ...electroforming in resistive memory devices, although direct evidence of such a pathway is lacking. Here, by utilizing strong metal–support interaction (SMSI) between Pt and TiO2, we observe via transmission electron microscopy the electroforming event in lateral Pt/TiO2/Pt devices where the atomic Pt from the electrode itself acts as a tracer for the propagating oxygen vacancy front. SMSI, which originates from the d-orbital overlap between Pt atom and the reduced cation of the insulating oxide in the vicinity of oxygen vacancies, was optimized by fabricating nanoscale devices causing Pt atom migration tracking the moving oxygen vacancy front from the anode to cathode during electroforming. Experiments performed in different oxidizing and reducing conditions, which tune SMSI in the Pt-TiO2 system, further confirmed the role of oxygen vacancies during electroforming. These observations also demonstrate that the noble metal electrode may not be as inert as previously assumed.
A novel self-powered wearable triboelectric biosensor concept is proposed in this paper, which consists of Scotch tape and a metalized polyester sheet (Al/PET). The Scotch tape is the sensing element ...by exploring the interaction between the tape polypropylene backing material and the acrylic adhesive layer when pressing and releasing. The polypropylene surface only has partial positive charges because of a nonpolar surface, while the acrylic adhesive has a polar surface with positively and negatively charged and neutral regions. Atomic size gaps are formed because of the attractive and repulsive areas at the interface due to van der Waals forces. These density depleted regions act as 'geometric' gaps to produce triboelectric charges
contact and separation on a microscopic scale. This leads to our wearable biosensor design for measuring human body motion. Associated skin contraction and relaxation during body motion will activate the contact and separation between the polypropylene and acrylic adhesive layer when the sensor assembly is adhered to the skin. Various demonstrations were conducted to detect different body motions, including elbow flexion at a low angle, forearm protonation, forearm supination, knee flexion/extension, proximal interphalangeal flexion/extension, temple motion due to eye blinking, and temporomandibular opening. Unique features can be identified which are associated with different body motions. Moreover, the measurements from our triboelectric sensor correlate well with the results from a commercial electromyography (EMG) sensor in an isokinetic leg extension test, which leads to a new method of measuring human muscle activation.
Although plane wave imaging (PWI) has been extensively employed for ultrafast ultrasound imaging, its potential for sectorial B-mode imaging with a convex array transducer has not yet been widely ...recognized. Recently, we reported an optimized PWI approach for sector scanning that exploits the dynamic transmit focusing capability. In this paper, we first report the clinical applicability of the optimized PWI for abdominal ultrasonography by in vivo image and video evaluations and compare it with conventional focusing (CF) and diverging wave imaging (DWI), which is another dynamic transmit focusing technique generally used for sectorial imaging. In vivo images and videos of the liver, kidney, and gallbladder were obtained from 30 healthy volunteers using PWI, DWI, and CF. Three radiologists assessed the phantom images, 156 in vivo images, and 66 in vivo videos. PWI showed significantly enhanced (
< 0.05) spatial resolution, contrast, and noise and artifact reduction, and a 4-fold higher acquisition rate compared to CF and provided similar performances compared to DWI. Because the computations required for PWI are considerably lower than that for DWI, PWI may represent a promising technique for sectorial imaging in abdominal ultrasonography that provides better image quality and eliminates the need for focal depth adjustment.
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