Mechanism Of Resistance Change Research Articles

CNTs@fabric/Ni@PU piezoresistive sensor with enhanced interfacial contact resistance variation for motion detection and deep-learning-assisted recognition

Abstract Flexible piezoresistive sensors based on the mechanism of interfacial contact resistance change are receiving increasing attention in the fields of human-computer interaction, health monitoring, and behavior tracking. However, the high cost and complex manufacturing process limit the wide application and development of these flexible piezoresistive sensors. Here, a novel carbon nanotubes@fabric (CNTs@fabric)/Ni@polyurethane (Ni@PU) piezoresistive sensor (CNPS) with low-cost, simple-preparation and high-sensitivity was proposed. The effective contact area is obtained by synergizing the woven micro-convex structure of the fabric, the large specific surface area of the CNTs and the porous three dimensional electrodes. Within the small pressure (0–9.52 kPa) effect, the area of connection with the electrodes to the active layer plays a dominant role, resulting in a sensitivity of up to 6.39 kPa−1 for CNPS. In the high pressure region (9.52–44.92 kPa), where internal mechanism of change in the sensitive material dominants, the CNPS has a response time of 85 ms at a constant pressure of 28.31 kPa. Considering the excellent output electrical performances, a variety of body movements could be detected by fixing the CNPS to different joints. Significantly, the designed intelligent object recognition system implemented by the combination of matrix stress detection module and residual neural network (ResNet) algorithm has a recognition accuracy of 99.26%. Enhancing the interfacial contact resistance change mechanism using a simple fabrication process offers a promising strategy for the rapid development of flexible piezoresistive sensors.

Monitoring bridge bearings based on rubber-based composite materials

To improve the real-time monitoring capability of bridge structure safety, intelligent bridge bearings were prepared based on rubber based composite materials. The study selected T4/3-5 intelligent rubber bearings and conducted a systematic experimental analysis on their response characteristics under different loading speeds and holding states. By measuring the displacement and resistance changes of the intelligent bearings under various load conditions, their sensitivity and stability were evaluated. These experiments confirmed that the T4/3-5 intelligent rubber bearings exhibited a total creep deformation of approximately 1 mm and 1.5 mm under loads of 60 kN and 45 kN, respectively. This suggests that the molecular chains reach a relatively stable configuration under high loads and are not prone to further changes. Moreover, the resistance reduction ratio under a load of 60 kN is approximately 0.57, while under a load of 45 kN it is approximately 0.62, indicating that nickel powder particles in the composite material form a more stable conductive network after molecular rearrangement. At different loading rates, the displacement-load and load-resistance curves of the bearings show consistent trends, and the creep and resistance relaxation behaviors exhibit certain regularity with the concentration of load size. Through the analysis of these data, the study elucidated the resistance change mechanism in the bearings and validated the feasibility of intelligent bearings as a real-time load monitoring tool.

Highly Sensitive, Wide-Range Pressure Sensor Based on Negative Poisson’s Ratio for Human Motion Detection

Flexible wearable materials can be attached to human skin to collect a range of health information, such as wrist rotation, finger joint movement, knee flexion, and so on. Moreover, facial muscle-based signal monitoring can infer people’s emotional expressions, which has a wide range of applications. At present, it is difficult for one sensor to realize the interactive information monitoring of multiple parts of the human body, which is caused by the contradiction between sensitivity and range. In this work, an innovative method of mechanical structure is proposed. A PDMS elastomer with negative Poisson’s ratio (NPR) is embedded in the graphene–silicon rubber foam composite (rGO-PDMS/SR) in a simple and low-cost process, which improves the mechanical performance and resistance variation range effectively. The performance test results show that compared with ordinary graphene–silicon rubber composites (rGO-SR), the resistance variation range of the rGO-PDMS/SR has expanded by six times, which has high linear sensitivities of 7.0838 kPa−1 at 0–50 kPa and 0.0168 kPa−1 at 50–250 kPa. In addition, the composite shows reliable stability during cyclic compression. By analyzing the resistance change mechanism of the sensor, the explicit expression between the composite material performance parameters and the resistance is obtained. The results of human interaction experiments show that the sensor can meet the requirements of signal detection at nine different positions of the human body, including facial expression judgment, motion state monitoring, and other fields, which indicates good human interaction performance.

Directly revealing the electrical annealing of nanoscale conductive networks with solid spins

Complex electrical structures composed of nanomaterials are widely studied in the research of nanoelectronics. Characterizing the current distribution is important to understand the current conducting mechanism and optimize the device's design. In this work, we employed the nitrogen vacancy centers in diamond as quantum sensors to directly and noninvasively monitor currents in nanowire networks. The sub-micrometer magnetic field imaging was achieved by injecting microwave current into networks and detecting the magnetic resonate spins' population, revealing the internal current paths involved in electrical conduction during electrical annealing. The establishment, breakdown, and reform of current paths were imaged in detail, which are difficult to realize through conventional methods. The mechanism of resistance change and relocating of current pathways was subsequently analyzed. This work demonstrates that a diamond-based quantum microscope is a useful tool to unveil the nanoscale conducting properties of complex conductive networks and guide the design for potential applications.

Lithium-ion-Based Resistive Devices of LiCoO2/LiPON/Cu With Ultrathin Interlayers of Titanium Oxide for Neuromorphic Computing

Lithium (Li)-ion materials such as LiCoO2 and (Li3PO4)-N (LiPON) are used in Li-ion all-solid-state batteries, and are now expected to be used as ion-electron hybrid materials to create a new degree of freedom in future integrated circuits. We fabricated thin-film devices on the basis of LiCoO2/LiPON/Cu and ultrathin titanium oxide (TiOx) to demonstrate their new type of resistance change mechanism and characteristics. Multi-level resistance changes promising as synaptic plasticity were obtained, and the resistance properties enable neuromorphic computing to enter a new era.

Model and simulation of bilayered tantalum-oxide (Pt/Ta2O5/TaOx/Pt) memristor

As a new type of microelectronic device with a special resistance change mechanism, the memerists based on the novel resistive materials have been an emerging hot-spot in the area of electronics. Among tremendous memerists, the bilayered tantalum-oxide (Pt/Ta2O5/TaOx/Pt) devices are believed to one of the typical device structures, its peculiar current-voltage (I-V) feature makes it distinct from other traditional devices, like resistor, capacitor or metal-oxide-semiconductor (MOS) transistor. It has been accepted as an alternative candidate of the traditional silicon-based memories. There have been lots of experimental works in this field, however, the theoretical works about its physical model and simulation are relatively few. In this work, its working principle is illustrated firstly, according to the thermionic emission theory of Schottky barrier in semiconductor physics. Then a quantitative physical model is presented and simulated, the calculated results are compared with the reported data to evaluate the effectiveness of the proposed model. The established physical model is constructed and calculated mathematically by using MATLAB, the computed results are compared with the experimental data to verify the proposed arithmetic model.

In situ observations of topotactic phase transitions in a ferrite memristor

Oxide-based memristive devices have recently been proposed for various applications, such as next-generation memory and neuromorphic devices. Microstructural alterations depending on the oxygen ion concentration, such as the formation of conductive filaments and interface reactions, have been posited as the operating mechanism. Accordingly, it is important to explore the role of oxygen ion mobility in the behavior of memristive devices. In this study, memristive devices fabricated with brownmillerite SrFeO2.5 in the (111) and (001) orientations were studied via high-resolution transmission electron microscopy and in situ current–voltage measurements. The resistance of the devices was changed by a reversible topotactic phase change between the insulating brownmillerite SrFeO2.5 and the conductive perovskite SrFeO3−δ. Importantly, the oxygen vacancy channel was designed so that the phase change occurred across the electrodes in (111), where the channel was directly connected to both electrodes, whereas in (001) the channel is ordered along the in-plane direction and a phase change occurs only near the electrode. This work provides direct evidence of a brownmillerite-based mechanism of resistance change and a better understanding of routes to performance improvement.

Novel Graphene Planar Architecture with Ultrahigh Stretchability and Sensitivity.

Graphene has attracted increasing attention for strain sensing due to its unique electrical and mechanical properties by tailoring and assembling functional macrostructures with a well-defined configuration. Here a novel graphene-based planar network (GPN) with highly stretchable strain sensing is developed by direct ink writing. The integrated and regulated structure of GPN indicates an excellent response sensitivity and cyclic stability to various strain modes compared with the traditional graphene-based woven fabric (GWF) structure. An equivalent resistance network is introduced to analyze the resistance change mechanism and fracture failure mode of the network structures, in which the difference can be mainly attributed to the interfacial resistance at the crosspoints of the crossed ribbons. The tunable and interconnected GPN shows a significant difference in the response sensitivity under stretching strain in different directions, and the relative resistance change is up to 20 and 3 in horizontal and vertical directions after 1000 cycles for a 20% stretching strain, respectively, which can be explained by the transformation of the stretching mode from macro-structural stretching to micromaterial stretching. The controllable fabrication of GPN can be utilized not only for the detection of full-range human activities but monitoring external stress distribution in real-time by integration.

Resistance Change Mechanism of Electronic Component Mounting through Contact Pressure Using Elastic Adhesive.

For mounting electronic components through contact pressure using elastic adhesives, a high contact resistance is an inevitable issue in achieving solderless wiring in a low-temperature and low-cost process. To decrease the contact resistance, we investigated the resistance change mechanism by measuring the contact resistance with various contact pressures and copper layer thicknesses. The contact resistivity decreased to 4.2 × 10−8 Ω·m2 as the contact pressure increased to 800 kPa and the copper layer thickness decreased to 5 µm. In addition, we measured the change in the total resistance with various copper layer thicknesses, including the contact and wiring resistance, and obtained the minimum combined resistance of 123 mΩ with a copper-layer thickness of 30 µm using our mounting method. In this measurement, a low contact resistance was obtained with a 5-µm-thick copper layer and a contact pressure of 200 kPa or more; however, there is a trade-off with respect to the copper layer thickness in obtaining the minimum combined resistance because of the increasing wiring resistance. Subsequently, based on these measurements, we developed a sandwich structure to decrease the contact resistance, and a contact resistivity of 8.0 × 10−8 Ω·m2 was obtained with the proposed structure.

Increased Resistance of Salmonella enterica Serovar Typhimurium and Escherichia coli O157:H7 to 222-Nanometer Krypton-Chlorine Excilamp Treatment by Acid Adaptation.

In this study, we examined the change in resistance of Salmonella enterica serovar Typhimurium and Escherichia coli O157:H7 to 222-nm krypton-chlorine (KrCl) excilamp treatment as influenced by acid adaptation and identified a mechanism of resistance change. In addition, we measured changes in apple juice quality indicators, such as color, total phenols, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, during treatment. Non-acid-adapted and acid-adapted pathogens were induced by growing the cells in tryptic soy broth without dextrose (TSB w/o D) at pH 7.3 and in TSB w/o D at pH 5.0 (adjusted with HCl), respectively. For the KrCl excilamp treatment, acid-adapted pathogens exhibited significantly (P < 0.05) higher D5d values, which indicate dosages required to achieve a 5-log reduction, than those for non-acid-adapted pathogens in both commercially clarified apple juice and phosphate-buffered saline (PBS), and the pathogens in the juice showed significantly (P < 0.05) higher D5d values than those for pathogens in PBS because of the UV-absorbing characteristics of apple juice. Through mechanism identification, it was found that the generation of lipid peroxidation in the cell membrane, inducing cell membrane destruction, was significantly (P < 0.05) lower in acid-adapted cells than in non-acid-adapted cells for the same amount of reactive oxygen species (ROS) generated at the same dose because the ratio of unsaturated to saturated fatty acids (USFA/SFA) in the cell membrane was significantly (P < 0.05) decreased as a result of acid adaptation. Treated apple juice showed no significant (P > 0.05) difference in quality indicators compared to those of untreated controls during treatment at 1,773 mJ/cm2IMPORTANCE There is a need for novel, mercury-free UV lamp technology to replace germicidal lamps containing harmful mercury, which are routinely utilized for UV pasteurization of apple juice. In addition, consideration of the changes in response to antimicrobial treatments that may occur when pathogens are adapted to the acid in an apple juice matrix is critical to the practical application of this technology. Based on this, an investigation using 222-nm KrCl excilamp technology, an attractive alternative to mercury lamps, was conducted. Our study demonstrated increased resistance to 222-nm KrCl excilamp treatment as pathogens adapted to acids, and this was due to changes in reactivity to ROS with changes in the fatty acid composition of the cell membrane. Despite increased resistance, the 222-nm KrCl excilamp achieved pathogen reductions of 5 log or more at laboratory scale without affecting apple juice quality. These results provide valuable baseline data for application of 222-nm KrCl excilamps in the apple juice industry.

Resistance change mechanism of conductive track printed on textile under stretching deformation

Resistance change mechanism of conductive track printed on textile under stretching deformation

Enhanced Ammonia Adsorption on Directly Deposited Nanofibrous Carbon Films

The ammonia adsorption on the nanostructured carbon thin film was significantly influenced by the choice of deposition temperature and deposition time of thin film synthesis. The thin films were prepared on Si/SiO2 substrates by chemical vapour deposition in Ar/C2H2 gas mixture using iron catalytic nanoparticles. The analysis of the grown layer by the scanning and transmission electron microscopy showed the transition from long multiwalled nanotubes (MWCNTs) to bamboo-like hollow carbon nanofiber structure with the decrease of the deposition temperature from 700 to 600°C. Further, the material was analyzed by energy-dispersive X-ray spectroscopy and Raman spectroscopy confirmed the transition from graphitic sp2 structure to highly defective structure at lower deposition temperature. The resistance of the prepared layer strongly depends on deposition temperature (Td) and deposition time (td). High resistance layer, 38.6 kΩ, was formed at Td 600°C and td 10 min, while at Td 700°C and td 60 min, the resistance decreased to 860 ohms. Such behaviour is consistent with MWCNTs being responsible for the formation of the conductive network. Such system was studied using chemiresistor ammonia gas sensor configuration. The sensor resistance increased when exposed to ammonia in all the cases, but their response varied considerably. A decrease in deposition time, from 60 to 10 min, and the deposition temperature, from 700 to 600°C, led to the 10-fold increase in the sensor response. The measurements carried out at room temperature showed the higher sensor response than the measurements carried out at 200°C. This behaviour can be explained by the change in adsorption-desorption equilibrium at different temperatures. Analysis of dependence of the sensor response on the ammonia concentration proved that the underlying resistance change mechanism is chemisorption of ammonia molecules on the carbon network corresponding to the Langmuir isotherm.

Investigation of Single Event Induced Soft Errors in Programmable Metallization Cell Memory

Programmable metallization cell (PMC) devices belong to a class of non-volatile ionic resistive memory devices that have already demonstrated tolerance to high total doses of ionizing radiation. In this work, the susceptibility of integrated 1T-1R PMC memory array to ion strike induced single event upsets is analyzed. Circuit simulations that model single event transients in 1T-1R elements are performed using a PMC compact model which captures the voltage driven resistance change mechanism experimentally observed in such devices. The relationship between incident ion LET and change in PMC resistance and its consequent susceptibility to an upset is investigated through both simulation and experiment.

Effect of Nanotube Aspect Ratio on Chemical Vapour Sensing Properties of Polymer/MWCNT Composites

The main topic of this paper is the study of polyisoprene-multi wall carbon nanotubes (PiMWCNT) composites electrical conductivity and volatile organic compound sensing properties with respect to type of multi wall carbon nanotubes used. Electrical percolation parameters like percolation threshold and critical exponent of produced composites are determined and analyzed. PiMWCNT composites exhibit a promising sensitivity to the presence of volatile organic compounds. Therefore the composites sensing mechanism of volatile organic compounds are analyzed in more detail by applying an original measuring technique which enables simultaneous measurement of an electrical resistance, mass and length change measurement of the sample in the presence and subsequent absence of a vapour. Measurement results enabled the evaluation of both vapour diffusion behavior in the composite and electrical resistance change mechanism.

Analysis on Resistance Change Mechanism of NiO-ReRAM Using Visualization Technique of Data Storage Area With Secondary Electron Image

AbstractBoth a low resistance state and a high resistance state which were written by the voltage application in a local region of NiO/Pt films by using conducting atomic force microscopy (C-AFM) were observed by using scanning electron microscope (SEM) and electron probe micro analysis (EPMA). The writing regions are distinguishable as dark areas in a secondary electron image and thus can be specified without using complicated sample fabrication process to narrow down the writing regions such as the photolithography technique. In addition, the writing regions were analyzed by using energy dispersive X-ray spectroscopy (EDS) mapping. No difference between the inside and outside of the writing regions is observed for all the mapped elements including C and Rh. Here, C and Rh are the most probable candidates for contamination which affect the secondary electron image. Therefore, our results suggested that the observed change in the contrast of the second electron image is related to the intrinsic change in the electronic state of the NiO film and a secondary electron yield is correlated to the physical properties of the film.

Conductive polymer switching mechanism for high power current-limiting applications

Various thermoplastic and thermo-set based polymers, blended with acetylene carbon blacks and graphite fillers to form electrically conductive polymers, were investigated to determine the switching mechanism under high power short-circuit fault conditions. Presently, a positive temperature coefficient (PTC) effect is the accepted switching mechanism for low power overcurrent devices. However, for high power, distribution level devices, this mechanism has been assumed to be the same under high fault conditions. This work proposes another possible switching mechanism responsible for a steep change in resistance under high power faults. The proposed mechanism of resistance change comes, not from the PTC change in the material, but rather from the vaporization of the conducting polymer contact areas at the polymer/electrode interface. A comparison between low power polypropylene based devices with a positive temperature coefficient (PTC) effect (thermal expansion of the polymer bulk) and high power devices was done to support this theory. A model was developed along with numerous short-circuit tests to support this theory. Modifications with e-beam irradiation were made to alter the PTC characteristics of thermoplastics but had little effect on high fault short-circuit switching. Also, numerous short-circuit testing on thermo-set based materials without any PTC transition still switched under high fault currents. These all supported the proposed theory that switching, under high fault currents, was from vaporization of the contact areas at the polymer surface rather than thermal expansion in the bulk of the conductive polymer as previously accepted.

Nanoscale formation mechanism of conducting filaments in NiO thin films

We have studied the nanoscale electrical properties of NiO thin films by using conducting atomic force microscopy (CAFM) to understand the mechanism of resistance change of the NiO thin films as we changed the applied voltage. We observed that inhomogeneous conducting filaments were generated by external voltage bias; in addition, some of the inhomogeneous conducting filaments were durable while some of them were not, and they disappeared. We deduced that the resistance change of the NiO thin films was related to inhomogeneous filamentary conducting paths generated by both Ni ions in thermodynamically unstable NiO and the existence of conducting filament segments generated by high voltage bias.

Electric Resistance Change Mechanism of Indium-Tin Oxide Film During Deposition of Dielectric Oxide Films by RF Magnetron Sputtering

Electric resistance change of indium-tin oxide (ITO) film was investigated when dielectric oxide films such as Sr(Zr0.2Ti0.8)O3 and Y2O3 for an electroluminescent device were deposited on the ITO by the rf magnetron sputtering method using oxide ceramic targets. In order to understand the mechanism of the resistance change, a dc voltage of -70∼+70 V was biased to an ITO film during the sputtering of dielectric oxide films. The resistance of the ITO film became higher in the positive bias region. The cause of the increase in resistance of the ITO films was confirmed to be oxidation by the oxide targets and the sputtering gas. The amount of the resistance change could be qualitatively explained by the ratio of the oxygen introduced into the ITO film and the combined oxygen forming O2 gas at the ITO surface incident to the ITO film at the sputtering of the dielectric oxide films.

High-Frequency-Discharge Trimming of RuO&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;-Based Thick-Film Resistors-Part II: Mechanism of Resistance Change

Mechanism of resistance change by high-frequency-discharge trimming has been investigated for RuO2 glaze resistors. As a result, it is found that the resistance of RuO2 glaze resistors eventually increases when subjected to the discharging over an extended period because of structural damage of the resistor films. As for RuO2 · glass resistors, the resistance increases with the increasing discharge time, but as for Ag- or Nb-doped RuO2 · glass resistors, the resistance decreases during the initial stage of the discharging. The main cause for the resistance reduction is the increasing concentration of Ag atoms in the trimmed area in the case of Ag-dopad resistors, and in the case of Nb-doped resistors the change in valence value of Ru, i.e., Ru4+ -> Ru3+.

Mechanism of resistance change by high‐frequency discharge trimming

Mechanism of resistance change by high‐frequency discharge trimming