Effect of Fluoride Ions on Wet Etching of Copper/ Molybdenum in Hydrogen Peroxide Solution.

Copper metallization is a key issue for high performance thin film transistor technology. Hydrogen peroxide-based copper etchants are widely used in copper metallization. Recently, a hydrogen peroxide-based copper etchant for a copper/molybdenum double layer was investigated for its versatile use in both amorphous silicon TFTs and in metal-oxide TFTs. However, little is known about the etching mechanism for molybdenum and copper in a hydrogen peroxide solution containing fluorine ions. In this paper, it is shown that the amount of fluorine ions in the hydrogen peroxide-based copper etchant plays an important role in controlling the galvanic reaction between the copper and the molybdenum. A new mechanism of molybdenum dissolution in the presence of fluoride ions in 1.5 M hydrogen peroxide solution is suggested. The concentration of the fluoride ions is also important in eliminating the residue of molybdenum after wet patterning.

Ultrahigh Tensile Strength Nanowires with a Ni/Ni-Au Multilayer Nanocrystalline Structure.

Superior mechanical properties of nanolayered structures have attracted great interest recently. However, previously fabricated multilayer metallic nanostructures have high strength under compressive load but never reached such high strength under tensile loads. Here, we report that our microalloying-based electrodeposition method creates a strong and stable Ni/Ni-Au multilayer nanocrystalline structure by incorporating Au atoms that makes nickel nanowires (NWs) strongest ever under tensile loads even with diameters exceeding 200 nm. When the layer thickness is reduced to 10 nm, the tensile strength reaches the unprecedentedly high 7.4 GPa, approximately 10 times that of metal NWs with similar diameters, and exceeding that of most metal nanostructures previously reported at any scale.

Origin of size dependency in coherent-twin-propagation-mediated tensile deformation of noble metal nanowires.

Researchers have recently discovered ultrastrong and ductile behavior of Au nanowires (NWs) through long-ranged coherent-twin-propagation. An elusive but fundamentally important question arises whether the size and surface effects impact the twin propagation behavior with a decreasing diameter. In this work, we demonstrate size-dependent strength behavior of ultrastrong and ductile metallic NWs. For Au, Pd, and AuPd NWs, high ductility of about 50% is observed through coherent twin propagation, which occurs by a concurrent reorientation of the bounding surfaces from {111} to {100}. Importantly, the ductility is not reduced with an increase in strength, while the twin propagation stress dramatically increases with decreasing NW diameter from 250 to 40 nm. Furthermore, we find that the power-law exponent describing the twin propagation stress is fundamentally different from the exponent describing the size-dependence of the yield strength. Specifically, the inverse diameter-dependence of the twin propagation stress is directly attributed to surface reorientation, which can be captured by a surface energy differential model. Our work further highlights the fundamental role that surface reorientations play in enhancing the size-dependent mechanical behavior and properties of metal NWs that imply the feasibility of high efficiency mechanical energy storage devices suggested before.

Negative gate bias and light illumination-induced hump in amorphous InGaZnO thin film transistor.

While observing the transfer characteristics of a-IGZO TFTs, it was noticed that a hump occurred in the subthreshold regime after light and bias stress. This study analyzes the mechanism of the hump occurrence. It was determined that hump characteristics were related with parasitic TFTs which formed at the peripheral edges parallel with the channel direction. It seems that the negative shift of the transfer characteristics of parasitic TFTs was larger than that of the main TFT under light and bias stress. Therefore, the difference in the negative shift between the main TFT and the parasitic TFT was the origin of the hump occurrence. We investigated the instability of a-IGZO TFTs under negative gate bias with light illumination for various channel structures in order to verify the above mechanism.

In situ heating transmission electron microscopy observation of nanoeutectic lamellar structure in Sn-Ag-Cu alloy on Au under-bump metallization.

We investigated the microstructural evolution of Sn(96.4)Ag(2.8)Cu(0.8) solder through in situ heating transmission electron microscopy observations. As-soldered bump consisted of seven layers, containing the nanoeutectic lamella structure of AuSn and Au5Sn phases, and the polygonal grains of AuSn2 and AuSn4, on Au-plated Cu bond pads. Here, we found that there are two nanoeutectic lamellar layers with lamella spacing of 40 and 250 nm. By in situ heating above 140°C, the nanoeutectic lamella of AuSn and Au5Sn was decomposed with structural degradation by sphering and coarsening processes of the lamellar interface. At the third layer neighboring to the lamella layer, on the other hand, Au5Sn particles with a zig-zag shape in AuSn matrix became spherical and were finally dissipated in order to minimize the interface energy between two phases. In the other layers except both lamella layers, polycrystal grains of AuSn2 and AuSn4 grew by normal grain growth during in situ heating. The high interface energy of nanoeutectic lamella and polygonal nanograins, which are formed by rapid solidification, acted as a principal driving force on the microstructural change during the in situ heating.

Metabolomic profiling in kidney cells treated with a sodium glucose-cotransporter 2 inhibitor.

We aimed to determine the metabolomic profile of kidney cells under high glucose conditions and following sodium-glucose cotransporter 2 (SGLT2) inhibitor treatment. Targeted metabolomics using the Absolute IDQ-p180 kit was applied to quantify metabolites in kidney cells stimulated with high glucose (25 and 50 mM) and treated with SGLT2 inhibitor, dapagliflozin (2 µM). Primary cultured human tubular epithelial cells and podocytes were used to identify the metabolomic profile in high glucose conditions following dapagliflozin treatment. The levels of asparagine, PC ae C34:1, and PC ae C36:2 were elevated in tubular epithelial cells stimulated with 50 mM glucose and were significantly decreased after 2 µM dapagliflozin treatment. The level of PC aa C32:0 was significantly decreased after 50 mM glucose treatment compared with the control, and its level was significantly increased after dapagliflozin treatment in podocytes. The metabolism of glutathione, asparagine and proline was significantly changed in tubular epithelial cells under high-glucose stimulation. And the pathway analysis showed that aminoacyl-tRNA biosynthesis, arginine and proline metabolism, glutathione metabolism, valine, leucine and isoleucine biosynthesis, phenylalanine, tyrosine, and tryptophan biosynthesis, beta-alanine metabolism, phenylalanine metabolism, arginine biosynthesis, alanine, aspartate and glutamate metabolism, glycine, serine and threonine metabolism were altered in tubular epithelial cells after dapagliflozin treatment following 50 mM glucose compared to those treated with 50 mM glucose.

Effects of Pt junction on electrical transport of individual ZnO nanorod device fabricated by focused ion beam.

The electrical transport of individual ZnO nanorod devices manufactured by focused ion beam (FIB) was investigated by the direct measurement of electrical resistance at electrode junctions of cross-sectioned devices using two nanoprobes. The cathodoluminescence (CL) measurements were also performed to evaluate the crystallinity at the center and edge of the cross-sectioned ZnO nanorods. The electrical transport of the individual ZnO nanorod device depends strongly on the crystallinity of the ZnO nanorod itself and the carbon contents at Pt junctions. The ZnO-Au junction of the device acted as the fastest path for electrical transport.

The effects of nitrogen bonding on hardness of AIN/CrN multilayer hard coatings.

AIN/CrN multilayer hard coatings with various bilayer thicknesses were fabricated by a reactive sputtering process. The microstructural and mechanical characterizations of multilayer coatings were investigated through transmission electron microscope (TEM) observations and the hardness measurements by nano indentation. In particular, the variation of chemical bonding states of the bilayer nitrides was elucidated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Many broken nitrogen bonds were formed by decreasing the bilayer thickness of AIN/CrN multilayer coatings. Existence of optimum AIN/CrN multilayer coatings thickness for maximum hardness could be explained by the competition of softening by the formation of broken nitrogen bonds and strengthening induced by decreasing bilayer thickness.

Hardness and nitrogen bonding structure of AlxTi1-xN/CrN multilayer hard coating.

AlxTi1-xN/CrN multilayer coatings were fabricated by magnetron sputtering and those hardness variations were studied by observing the crack propagation and measuring the chemical bonding state of nitrides by Ti addition. While AlN/CrN multilayer shown stair-like crack propagation, AlxTi1-xN/CrN multilayer illustrated straight crack propagation. Most interestingly, Ti addition induced more broken nitrogen bonds in the nitride multilayers, leading to the reduction of hardness. However, the hardness of Al0.25Ti0.75N/CrN multilayer, having high Ti contents, increased by the formation of many Ti-N bond again instead of Al-N bond. From these results, we found that linear crack propagation behavior was dominated by broken nitrogen bonds in the AlxTi1-xN/CrN multilayer coatings.

Superplastic deformation of defect-free Au nanowires via coherent twin propagation.

We report that defect-free Au nanowires show superplasticity on tensile deformation. Evidences from high-resolution electron microscopes indicated that the plastic deformation proceeds layer-by-layer in an atomically coherent fashion to a long distance. Furthermore, the stress-strain curve provides full interpretation of the deformation. After initial superelastic deformation, the nanowire shows superplastic deformation induced by coherent twin propagation, completely reorientating the crystal from <110> to <100>. Uniquely well-disciplined and long-propagating atomic movements deduced here are ascribed to the superb crystallinity as well as the radial confinement of the Au nanowires.

Synaptic Current Response of a Liquid Ga Electrode via a Surface Electrochemical Redox Reaction in a NaOH Solution.

An ionic device using a liquid Ga electrode in a 1 M NaOH solution is proposed to generate artificial neural spike signals. The oxidation and reduction at the liquid Ga surface were investigated for different bias voltages at 50 °C. When the positive sweep voltage from the starting voltage (V S) of 1 V was applied to the Ga electrode, the oxidation current flowed immediately and decreased exponentially with time. The spike and decay current behavior resembled the polarization and depolarization at the influx and extrusion of Ca2+ in biological synapses. Different average decay times of ∼81 and ∼310 ms were implemented for V S of -2 and -5 V, respectively, to mimic the synaptic responses to short- and long-term plasticity; these decay states can be exploited for application in binary electrochemical memory devices. The oxidation mechanism of liquid Ga was studied. The differences in Ga ion concentration due to V S led to differences in oxidation behavior. Our device is beneficial for the organ cell-machine interface system because liquid Ga is biocompatible and flexible; thus, it can be applied in biocompatible and flexible neuromorphic device development for neuroprosthetics, human cell-machine interface formation, and personal health care monitoring.

Exploiting elastic buckling of high-strength gold nanowire toward stable electrical probing.

Buckling is a loss of structural stability. It occurs in long slender structures or thin plate structures which is subjected to compressive forces. For the structural materials, such a sudden change in shape has been considered to be avoided. In this study, we utilize the Au nanowire's buckling instability for the electrical measurement. We confirmed that the high-strength single crystalline Au nanowire with an aspect ratio of 150 and 230-nm-diameter shows classical Euler buckling under constant compressive force without failure. The buckling instability enables stable contact between the Au nanowire and the substrate without any damage. Clearly, the in situ electrical measurement shows a transition of the contact resistance between the nanowire and the substrate from the Sharvin (ballistic limit) mode to the Holm (Ohmic) mode during deformation, enabling reliable electrical measurements. This study suggests Au nanowire probes exhibiting structural instability to ensure stable and precise electrical measurements at the nanoscale.

Usefulness of videofluoroscopic swallow study with mixed consistency food for patients with stroke or other brain injuries.

This study evaluated the feasibility of mixed consistency foods test in patients with dysphagia which developed after stroke or other brain injuries. The findings of a videofluoroscopic swallow study (VFSS) were compared using single versus mixed consistency foods. Forty-nine patients with stroke or other brain injuries who had no significant abnormal findings in the single consistency food VFSS and started regular hospital diet were recruited for this study. Twenty-five (51%) of the 49 patients showed normal findings whereas 24 (49%) patients showed abnormal findings in the mixed consistency food VFSS. Abnormal findings included posterior spillage of liquid prematurely to pyriform sinus (n = 23), laryngeal penetration (n = 6), subglottic aspiration in the oral preparatory phase of swallowing (chewing), solid components (n = 2), and significant (more than 10%) residue in valleculae or pyriform sinus (n = 2). There was an increased risk of abnormal findings in mixed consistency food VFSS such as aspiration and penetration when a patient showed delayed pharyngeal delay time in single consistency food using liquids. In conclusion, VFSS protocols using mixed consistency foods would be useful before starting regular diet for patients after stroke or other brain injuries.

Closed atraumatic complete rupture of the flexor halluces longus tendon during forward lunge exercise: A case report.

RATIONALE: Acute rupture of the flexor halluces longus (FHL) tendon due to trauma or laceration is a well-known phenomenon. Partial rupture of the FHL tendon caused by tendinitis or stenosing tenosynovitis is common in ballet dancers and athletes. However, atraumatic complete rupture of the FHL is rare: as of 2018, only 7 cases of closed atraumatic complete rupture of the FHL tendon have been reported in the literature. Here, we report on a patient who presented with a closed atraumatic complete rupture of the FHL tendon during a forward lunge exercise. PATIENT CONCERNS: A 35-year-old female visited the clinic with pain in the plantar medial aspect of the left foot, along with weakness and loss of great toe flexion. The patient had a normal foot structure and no history of trauma or systemic disease. She performed a forward lunge exercise more than 50 times on 1 leg per day, more than once a week to strengthen her leg muscles. She reported that she felt a slight pain in her left, great toe while exercising for 3 weeks prior to her visit. One week prior to presentation, severe pain occurred suddenly when her left hallux dorsiflexed strongly during an anterior lunge exercise motion. DIAGNOSIS: Magnetic resonance imaging revealed complete rupture of the FHL tendon near the level of the metatarsal head and neck junction. The lesion was prolonged, with the proximal end displaced to the metatarsal shaft region. INTERVENTIONS: Complete rupture of the FHL tendon was treated with a primary suture. OUTCOMES: At the 1-year follow-up, active plantar flexion of the interphalangeal joint was possible but joint function had a range of 0° to 25°. Flexion strength was reduced slightly, measuring about 70% when compared to the contralateral side, but flexion strength of the metatarsophalangeal joint was normal. LESSONS: We describe an extremely rare case of complete rupture of the FHL tendon at the level of metatarsal head and neck junction. It should be understood that this injury can occur not only in professional athletes but also in the general public, and we recommend educating personal trainers on how to prevent it.

Ultrafast Sodiation of Single-Crystalline Sn Anodes.

Sodiation was performed on crystalline Sn cylinders using an in situ electron microscope to evaluate the rate performance of the Sn anode by directly measuring the sodiation rate. We observed that the sodiation rate of the Sn anode is more than 2 orders of magnitude higher than the lithiation rate of the Si anode under the same conditions. This unprecedented rate displayed by the Na-Sn system is attributed to the bond characteristics and crystalline-to-amorphous transformation of the Sn crystal at the thin interface of the Na-Sn diffusion couple. Here, using atomic simulations, we explain how and why the Sn anode exhibits this high rate performance by resolving the diffusion process of Na ions in the Na-Sn interfacial region and the electron structure of the crystalline Sn. This work provides a useful insight into the use of Sn as an attractive anode material for realizing ultrafast-charging batteries for electric vehicles and mobile devices.

Investigation of Blood Flow During Intermittent Pneumatic Compression and Proposal of a New Compression Protocol.

INTRODUCTION: Intermittent pneumatic compression (IPC) is now a widely used therapy for the prophylaxis of deep vein thrombosis and pulmonary embolism. In general, the IPC sequence is composed of sequential compression and simultaneous deflation. Typically, veins are considered to be squeezed and emptied during the compression phase and to be refilled during the deflation phase. However, because the stop or sudden increase in blood flow can be dangerous, a further investigation is needed with respect to the blood flow. MATERIALS AND METHODS: We demonstrated a new compression protocol based on the investigation results of venous blood flow during IPC. This new compression protocol involves successive compression without the deflation phase; thus, the expelled blood volume flow during a given period can be maximized. To investigate the blood flow during IPC, sonography movie clips and in-laboratory developed blood flow analysis software was used. RESULTS: The increases in the peak volume flow during IPC were 49% (±24%) and 25% (±29%) with the conventional protocol and the new protocol, respectively, whereas the total volume flow (TVF) was not significantly changed (-1.0% and -13.0%, respectively). With the new protocol, the peak velocity (PV) was 49% lower than that with the conventional protocol. Thus, the new protocol has an effect of maintaining TVF without resulting in a sudden large increase or decrease in PV. CONCLUSION: The new suggested protocol might improve safety because it can maintain the stability of blood flow by reducing the risk of blood stasis and a rapid change in blood flow.

Natural orifice transluminal endoscopic surgery with a snake-mechanism using a movable pulley.

BACKGROUND: Natural orifice transluminal endoscopic surgery is an emerging technique. We aimed to develop an advanced surgical robot mechanism for natural orifice surgery. METHODS: We propose the active-controlled overtube-type platform with multiple channels for an endoscopic camera and surgical tools. To make such a platform, we suggest an advanced snake mechanism comprising movable pulleys to make a snake mechanism with multiple degrees of freedom and high operating force. RESULTS: The stiffness and maneuverability of the active-controlled platform appeared satisfactory. Using prototypes and ex vivo experiments, we confirmed that the mechanism was suitable for a snake-like robotic platform for natural orifice surgery. CONCLUSIONS: The suggested snake mechanism using movable pulleys has the advantages of stiffness and maneuverability. This new mechanism can be an alternative platform for natural orifice surgery.

Development of a control algorithm for the ultrasound scanning robot (NCCUSR) using ultrasound image and force feedback.

BACKGROUND: Clinicians who frequently perform ultrasound scanning procedures often suffer from musculoskeletal disorders, arthritis, and myalgias. To minimize their occurrence and to assist clinicians, ultrasound scanning robots have been developed worldwide. Although, to date, there is still no commercially available ultrasound scanning robot, many control methods have been suggested and researched. These control algorithms are either image based or force based. If the ultrasound scanning robot control algorithm was a combination of the two algorithms, it could benefit from the advantage of each one. However, there are no existing control methods for ultrasound scanning robots that combine force control and image analysis. Therefore, in this work, a control algorithm is developed for an ultrasound scanning robot using force feedback and ultrasound image analysis. METHODS: A manipulator-type ultrasound scanning robot named 'NCCUSR' is developed and a control algorithm for this robot is suggested and verified. First, conventional hybrid position-force control is implemented for the robot and the hybrid position-force control algorithm is combined with ultrasound image analysis to fully control the robot. The control method is verified using a thyroid phantom. RESULTS: It was found that the proposed algorithm can be applied to control the ultrasound scanning robot and experimental outcomes suggest that the images acquired using the proposed control method can yield a rating score that is equivalent to images acquired directly by the clinicians. CONCLUSIONS: The proposed control method can be applied to control the ultrasound scanning robot. However, more work must be completed to verify the proposed control method in order to become clinically feasible. Copyright © 2016 John Wiley & Sons, Ltd.

Impedance and admittance control for respiratory-motion compensation during robotic needle insertion - a preliminary test.

BACKGROUND: Many robotic needle-biopsy systems have been developed to enhance the accuracy of needle-biopsy intervention. These systems can reduce the intervention time and the radiation exposure of clinicians. However, respiratory-motion compensation is needed to ensure the accuracy and efficiency of needle biopsy intervention. METHODS: Human respiratory-motion data were acquired using three inertial measurement units (IMUs), and respiratory motion was simulated using the Stewart-Gough platform. Robotic needle intervention was performed using impedance and admittance control algorithms for respiratory-motion compensation using the Stewart-Gough platform and a gelatin phantom. RESULTS: The impedance and admittance control algorithms can be used to compensate for respiratory motion during robotic needle insertion. The admittance control algorithm exhibits better performance than the impedance control algorithm. CONCLUSIONS: The impedance and admittance control algorithms can be applied for respiratory-motion compensation during robotic needle insertion. However, further study is needed for them to become clinically feasible.

An Investigation of Gate Pulse Induced Degradation in a-InGaZnO Thin Film Transistors.

We investigated the effects of pulsed gate bias on degradation of amorphous indium gallium zinc oxide (a-InGaZnO) thin film transistors (TFTs). The waveform composed of 0 V and 20 V produced little degradation, but the waveform composed of -20 V and 0 V produced a considerable degradation on the turn-on current in the transfer characteristics. Those instabilities were found mostly in TFTs of which the concentration of Zn is higher than the other metallic components (In, Ga). In order to explain the anomalous degradation behaviors, we propose a possible degradation model which is different from the conventional model of charge trapping. Our proposed model is related to an increase of acceptor-like states in a-InGaZnO near the source and drain electrodes. More electrons can be trapped there, and the increased potential barrier hinders current flow in the channel. The proposed model can also account for the increased frequency dispersion in C-V characteristics of our a-InGaZnO TFTs after the waveform stress.