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While acupuncture has been used for thousands of years, modern technology to develop new needle materials has rarely been discussed. We aim to explore a new acupuncture needle material and compare the differences in the needling sensations between the acupuncture needle surface treated with nitrogen applied supercritical fluid (SCF-N) and conventional stainless steel needles.This was a double-blind cohort study. The acupuncture needles were randomly used in this experiment, including the SCF-N-treated needles and the control stainless steel needles. LI 4 (Hegu) and LI 11 (Quchi) acupuncture points in the Yangming Large Intestine Meridian of Hand were treated. Physical electrical resistance, scanning electron microscopy, energy dispersive spectrometry, and visual analog scale (VAS) score including the sensations of soreness, numbness, distention, and heaviness were assessed.The proportion of nitrogen (N) was significantly higher in the SCF-N-treated needles than in the stainless steel needles group (2.3 ± 0.2% vs 0.0 ± 0.0%, P 0.01). The cumulative de-qi sensation score at the LI 4 Hegu acupoint (1.87 ± 1.88 vs 1.54 ± 1.62, P = 0.014), especially the sensation of soreness score (2.76 ± 2.06 vs 2.13 ± 1.85, P = 0.045), revealed statistically significant differences between both groups. SCF-N surface treatment of acupuncture needles may lower the electrical resistance more than the control stainless steel needles (24.67 ± 0.88 kW vs 26.45 ± 0.75 kW, p 0.01).Acupuncture needles modified with SCF-N surface treatment can enhance de-qi sensations to improve electrical conductivity of the meridian and therapeutic effects on the Yangming Large Intestine Meridian of Hand. SCF-N surface treated needles can be as a new acupuncture needle material in the future.

The quality and stability of thin-film transistors (TFTs) applied to large-scale displays are crucial to their successful manufacture and commercial applicability. This article introduces a TFT manufacturing process in which the source/drain system is defined by hydrogen doping in the dielectric layer of the top-gate amorphous indium gallium zinc oxide (a-IGZO). A size effect related to this system exists where longer channels allow a greater amount of hydrogen to diffuse into the center of the channel. For shorter channels, this results in a lower energy barrier and a shift in the threshold voltage. A physical mechanism model is proposed to verify the abnormal electrical characteristics caused by hydrogen diffusion into the top-gate a-IGZO. The insights provided by these results can be used to further develop TFTs for use in large-scale display applications.

In this experiment, the electrical performance of zinc oxide based-resistive random access memory (RRAM) is successfully improved by using annealing in ammonia hydroxide solution at low-temperature and high pressure to complete ammonium-doped ZnO based-RRAM. The results of material analysis indicate that using CO2 as ammonia hydroxide carrier during the annealing process leads to the reduction in dangling bond density. This can be clearly observed in the decrease in breakdown voltage during the forming process and a lower operating current during operation. Furthermore, in this ammonium-doped ZnO based-RRAM, we study the molecular doping of NH3 in ZnO, where the endurance and retention properties are improved as well. These improvements can be attributed to the higher concentration of nitrogen in the switching layer, which can effectively control the active oxygen ions during the operation process.

In this paper, vanadium oxide (VO x ) was chosen for the resistive switching layer in a typical resistive random access memory (RRAM) structure. During negative forming bias, we found an initial selector property. This indicates the presence of metal–insulator-transition characteristics in the VO x layer even without an annealing process. In order to study this phenomenon, material analyses were conducted, with results indicating that there are V-O stretching bonds and an oxide/vanadium ratio of nearly 2.2 ( ${O}/{V} = {2.2}$ ). In addition, the experimental results of the dc sweeping test indicated that off-state current gradually decreased after each cycle, meaning that the selectivity characteristics in the VO x selector could be improved. Endurance performance of our experimental devices reached 108, sufficient for integration with RRAM devices in a 1S1R array. To further investigate this special phenomenon, current fitting analysis and simulation analyses were conducted. The results of the fitting analysis indicated that the conduction mechanism for off-state current was Schottky emission and the Schottky distance increased with increasing numbers of cycles. In other words, oxide ions migrate toward the filament at low negative voltage during dc sweeping, causing the formation of VO x . Furthermore, the results of thermal field simulation analysis indicated that there is a thermal concentration effect in and around the filament. Thus, oxide ions more easily migrate toward the vanadium filament when a stronger electrical field is present around the filament during dc sweeping cycles. Finally, stable vanadium selector characteristics are obtained and a conduction filament behavior model is proposed.

In this letter, we determine the importance of the electrical field distribution and strength during the switching process by demonstrating different trends in the degree of reset and the reset pulse time. In general, a longer reset pulse time results in a higher reset energy; a higher reset energy leads to a higher degree of reset, which we obtained by applying different width square waves. But quite notably, the opposite result was obtained using triangle waves, where a higher degree of reset occurred with a shorter rising time and lower reset energy. We believe that this is due to the electric field effect: if the voltage rises faster than the filament oxidation, the device can produce a larger effective electric field and a higher resistance in the reset process. To further investigate the mechanism, the procedure of the reset process was analyzed in detail, and COMSOL simulation is also carried out for confirmation.

This letter introduces a method of using bipolarity bias voltages in the forming process to effectively reduce the forming voltage of a one-transistor and one-resistance random access memory device. A bipolar incremental-step-pulse programming process is applied, and a complete operation pulse for the forming process is described. This method reduces forming voltage without any cost to the device performance, and the device maintains good reliability. The likely physical mechanism of this bipolar operation is also presented based on the measured electrical characteristics.

In conventional HfO2-based resistive random access memory (RRAM), SiO2 is usually adopted as side wall spacer (low-k spacer) to define the device feature size. It is found that the forming voltage of the conventional HfO2 RRAM with SiO2 spacer rises when the device size is scaling down from 16.0 μm2 to 0.16 μm2, which is detrimental for application of high density HfO2-based RRAM. In this study, a high permittivity side wall spacer (high-k spacer) Ta2O5 is introduced to replace SiO2 spacer. The Ta2O5 side wall effectively suppress the forming voltage rising issues during RRAM device scaling without introducing costly processing steps. Moreover, compared to the conventional HfO2-based RRAM, the side wall enhanced device exhibits faster switching speed, smaller operation voltage, and higher reliabilities, including endurance and retention. As a result, the use of Ta2O5 side wall significantly enhances the overall switching characteristics of the HfO2-based RRAM device.

In this study, we demonstrate a complementary metal–oxide–semiconductor (CMOS) backside-illuminated photovoltaic (PV) module. Fabrication of the module involves localized substrate removal from a CMOS PV chip, the application of antireflective silicon nanowires, and supercritical carbon dioxide fluid treatment. The resulting PV module achieved open-circuit voltage of 1.76–2.05 V and electrical power of 0.061–3.44 mW under an illumination intensity of 0.1–4 mW/mm2, which is sufficient for the direct powering of implantable temperature sensors without the need for a voltage-boosting circuit. The proposed PV module is applicable to remote self-powered systems in a wide variety of applications.

Enlargement of memory window through forming compliance current was demonstrated in Gd:SiO2 resistive random access memory (RRAM) with a gadolinium (Gd) electrode. Lower forming compliance current for Gd:SiO2 RRAM with a Gd electrode results in larger memory window as compared with the RRAM with a Pt electrode. Through analyses on the current conduction mechanism, we demonstrate that a lower forming compliance current leads to a thinner conductive filament forming and less oxygen ions penetrating into Gd electrode, which caused higher on current and lower off current. Furthermore, a possible resistive switching model was proposed to explain the effect of Gd electrode on RRAM device.

In this paper, we implement a post-oxidation method to modify surface characteristics of indium tin oxide (ITO) films by using an O2 inductively coupled plasma (ICP) treatment. Based on field emission-scanning electron microscope (FE-SEM) and atomic force microscope (AFM) analysis, we found that the surface morphologies of the ITO films become slightly flatter after the O2 plasma treatment. The optical characteristics and X-ray diffraction (XRD) experiments of either pure ITO or O2 plasma treated ITO films were also verified. Even though the XRD results showed no difference from bulk crystallizations, the oxygen concentrations increased at the film surface after O2 plasma treatment, according to the XPS inspection results. Moreover, this study investigated the effects of two different plasma treatment times on oxygen concentration in the ITO films. The surface sheet resistance of the plasma treated ITO films became nearly non-conductive when measured with a 4-point probe. Finally, we applied the O2 plasma treated ITO films as the insulator in resistive random access memory (RRAM) to examine their potential for use in resistive switching storage applications. Stable resistance switching characteristics were obtained by applying the O2 plasma treatment to the ITO-based RRAM. We also confirmed the relationship between plasma treatment time and RRAM performance. These material analyses and electrical measurements suggest possible advantages in using this plasma treatment technique in device fabrication processes for RRAM applications.

This letter investigates the influence of ammonia on amorphous carbon resistance random access memory by sputtering the carbon target with argon and ammonia mixed gas. The device fabricated with ammonia (C (NH3)-RRAM) showed remarkable improvement in memory window and high resistance state as compared to the device deposited without ammonia. Material analysis confirmed the absorption signal of amine. Current fitting indicated the conduction mechanism changes from hopping conduction to Schottky conduction with the addition of ammonia. Finally, we propose a model to explain the influence of ammonia on the resistive switching behaviors of the amorphous carbon RRAM.

This paper investigates the characteristics of applying indium–tin oxide (ITO) with and without nitride gas (N2) as the insulator in resistive random access memory (RRAM). After cosputtering an ITO target with N2 as the insulator and capping the same ITO material as the top electrode, the device exhibits rectifier and resistance switching characteristics before and after the forming process, respectively. The Schottky diodelike rectifier mechanism was also verified by various temperature measurements. Furthermore, robust resistance switching at a positive forming voltage, smaller than that required during negative bias forming, can be achieved. Both positive and negative forming processes are examined with current fitting results, which show different dominant mechanisms when using positive or negative biases. All these mechanisms have also been verified by temperature effect experiments, which confirmed the dominant conduction mechanisms. This, in combination with the fact that the positive forming voltage itself is smaller than the negative forming voltage, and decreases with device scale down, provides two highly beneficial results. This good performance achieved by using ITO with N2 suggests significant progress of RRAM and remarkable potential applications.

A lower switching voltage of indium–tin–oxide (ITO)-based resistance random access memory (RRAM) with an inserted SiO2 thin film was presented. The amplitude of switching voltage of device was below 0.2 V whether measured by direct current or alternating current sweep operation. Notably, the observed reset voltage increased with temperature. To clarify the switching mechanism, conduction current fitting and switching voltage statistics were applied to explore the regular voltage variation dependent on temperature. In addition, a reaction model was proposed to explain the oxygen concentration gradient induced between the inserted SiO2 and ITO electrode on the ITO-based RRAM device.

We presented the galvanic effect of Au–Ag electrode in a conductive bridging resistive switching memory. Because of the different chemical activities between Au and Ag metals, the Ag element in the Au–Ag electrode will drift into silicon oxide easily to achieve the resistive switching properties during device operation. In this letter, we found that the forming voltage of the device will be reduced, and the switching speed will be improved due to the galvanic effect. We demonstrate the galvanic effect of Au–Ag electrode by two different metal composition ratios through the material and electrical analyses.

The manipulation of temperature coefficient of resistance (TCR) in TaN thin-film resistor (TFR) was demonstrated by electrical measurement and analysis through supercritical carbon dioxide (SCCO 2 ) fluid treatment for the first time. The negative TCR value of TaN TFR changes to positive TCR value through annealing process due to the growth and merge of TaN x grain. After SCCO 2 treatment, the positive TCR value was changed back to negative TCR value in TaN TFR. The TaN grain boundary isolated by dehydroxyl effect of SCCO 2 fluid treatment causes the current conduction mechanism changed to hopping conduction from ohmic conduction.

In this letter, we propose a novel low-temperature nitridation technology on a tantalum nitride (TaN) thin film resistor (TFR) through supercritical carbon dioxide (SCCO2) treatment for temperature sensor applications. We also found that the sensitivity of temperature of the TaN TFR was improved about 10.2 %, which can be demonstrated from measurement of temperature coefficient of resistance (TCR). In order to understand the mechanism of SCCO2 nitridation on the TaN TFR, the carrier conduction mechanism of the device was analyzed through current fitting. The current conduction mechanism of the TaN TFR changes from hopping to a Schottky emission after the low-temperature SCCO2 nitridation treatment. A model of vacancy passivation in TaN grains with nitrogen and by SCCO2 nitridation treatment is eventually proposed to increase the isolation ability in TaN TFR, which causes the transfer of current conduction mechanisms.

In this study, an Ag-Cu alloy was chosen as the electrode in conductive bridging random access memory (CBRAM), with results indicating a significant decrease in forming voltage. In addition, resistive switching characteristics as well as a retention test indicated better stability and a resistive switching window of at least an order. The switching time of the Ag-Cu alloy CBRAM is shorter than that of both Ag and Cu electrode CBRAMs under fast current-voltage (fast I-V). The experimental result indicated that the mechanism was dominated by the galvanic effect. Active atoms (Ag) captured electrons of inactive atoms (Cu) and generated metallic ions (Cu ions) in the alloy electrode. Cu ions drifted into the insulator and generated a conductive path when applying voltage bias. The use of this alloy as an electrode in CBRAM can significantly decrease forming voltage and enhance CBRAM characteristics.In this study, an Ag-Cu alloy was chosen as the electrode in conductive bridging random access memory (CBRAM), with results indicating a significant decrease in forming voltage. In addition, resistive switching characteristics as well as a retention test indicated better stability and a resistive switching window of at least an order. The switching time of the Ag-Cu alloy CBRAM is shorter than that of both Ag and Cu electrode CBRAMs under fast current-voltage (fast I-V). The experimental result indicated that the mechanism was dominated by the galvanic effect. Active atoms (Ag) captured electrons of inactive atoms (Cu) and generated metallic ions (Cu ions) in the alloy electrode. Cu ions drifted into the insulator and generated a conductive path when applying voltage bias. The use of this alloy as an electrode in CBRAM can significantly decrease forming voltage and enhance CBRAM characteristics.

Nitrogen atoms were introduced into a Pt/HfO2/TiN resistance random-access memory (RRAM) device to improve the resistive switching characteristics induced by a high-pressure nitridation treatment. Compared with a similar untreated HfO2 device, it exhibited superior performance, including a lower forming voltage, a higher on/off ratio, and high-endurance cycle operations. Current–voltage curve-fitting results confirmed the difference of the carrier transport mechanisms after the nitridation treatment. Finally, a reaction model was proposed to explain the improvement of RRAM switching due to the introduction of nitrogen atoms.

In this review, we provide an overview of our work in resistive switching mechanisms on oxide-based resistance random access memory (RRAM) devices. Based on the investigation of physical and chemical mechanisms, we focus on its materials, device structures, and treatment methods so as to provide an in-depth perspective of state-of-the-art oxide-based RRAM. The critical voltage and constant reaction energy properties were found, which can be used to prospectively modulate voltage and operation time to control RRAM device working performance and forecast material composition. The quantized switching phenomena in RRAM devices were demonstrated at ultra-cryogenic temperature (4K), which is attributed to the atomic-level reaction in metallic filament. In the aspect of chemical mechanisms, we use the Coulomb Faraday theorem to investigate the chemical reaction equations of RRAM for the first time. We can clearly observe that the first-order reaction series is the basis for chemical reaction during reset process in the study. Furthermore, the activation energy of chemical reactions can be extracted by changing temperature during the reset process, from which the oxygen ion reaction process can be found in the RRAM device. As for its materials, silicon oxide is compatible to semiconductor fabrication lines. It is especially promising for the silicon oxide-doped metal technology to be introduced into the industry. Based on that, double-ended graphene oxide-doped silicon oxide based via-structure RRAM with filament self-aligning formation, and self-current limiting operation ability is demonstrated. The outstanding device characteristics are attributed to the oxidation and reduction of graphene oxide flakes formed during the sputter process. Besides, we have also adopted a new concept of supercritical CO2 fluid treatment to efficiently reduce the operation current of RRAM devices for portable electronic applications.

In this study, we demonstrate a forming technique that enables us to control whether the switching layer of a Pt/In2O3/TiN device is near the Pt electrode or the TiN electrode. This means that In2O3-based resistive random access memory (RRAM) can be switched at either the active or inert electrode. The resistive switching current–voltage (I–V) curves for both electrodes exhibit stable memory windows. Through material and electrical analyses, we found that the reason for switching at the inert electrode is the oxygen-vacancy-rich characteristic of In2O3. Finally, a physical model is proposed to explain this phenomenon.

In this study, a structure of Pt/Cu18Si12O70/TiN has been investigated. By co-sputtering the Cu and SiO2 targets in the switching layer, we can measure the operation mechanism of complementary resistive switching (CRS). This differs from conventional conductive bridge random access memory (CBRAM) that tends to use Cu electrodes rather than Cu18Si12O70. By changing the voltage and compliance current, we can control device operating characteristics. Because Cu distributes differently in the device depending on this setting, the operating end can be located at either the top or bottom electrode. Device current–voltage (I–V) curves are used to demonstrate that the CRS in the CBRAM device is a double-electrode operation.

In this study of resistance random access memory in a resistive switching film, the breakdown degree was controlled by varying forming current compliance. A SiOx layer was introduced into the ZnO layer of the structure to induce both typical bipolar resistive switching (RS) and complementary resistive switching (CRS). In addition, the SiOx layer-generated vacuum spaces in typical bipolar RS can be verified by electrical characteristics. Changing forming current compliance strikingly modifies the oxygen storage capacity of the inserted SiOx layer. CRS can be achieved, therefore, by tuning the oxygen ion storage behavior made possible by the SiOx layer.