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Congenital cytomegalovirus (cCMV) infection is the most common congenital viral infection and is the leading non-genetic cause of sensorineural hearing loss and an important cause of neurodevelopmental disabilities. Auto auditory brainstem response (AABR) is a simple hearing test and used for the purpose of neonatal hearing screening, but can use it for early detection hard of hearing within the study age of the model. We experienced two case of asymptomatic CMV infection in which congenital and late-onset hearing loss were diagnosed early with AABR, and hearing loss improved with valganciclovir.

Objective Acoustic therapies including hearing aids and tinnitus control instruments are widely used in Japan but without high levels of evidence. The outpatient hearing aid clinic at our institution fits patients with hearing aids and instructs patients on how to use them to control tinnitus if present. In this study, we examined the effects of this approach on tinnitus. Methods One hundred and eleven of 138 patients who visited our hearing aid clinic from April 2016 to September 2018 purchased hearing aids after fitting. Sixty-six of these patients (31 men, 35 women; mean age 78.0 ± 8.0 years) had both hearing loss and tinnitus and were enrolled. The tinnitus was bilateral in 41 patients and unilateral in 25 (poor hearing ear, n = 16, good hearing ear, n = 9). Hearing aids were worn bilaterally by 23 patients and unilaterally by 43 (89 devices). Seventeen of the 23 patients wearing bilateral hearing aids had bilateral tinnitus and 6 had unilateral tinnitus, i.e., in 40 ears, the tinnitus side matched the hearing aid side (40 devices) and in 6 ears did not (6 devices). Twenty-four of 43 patients wearing unilateral hearing aids had bilateral tinnitus, meaning that in 24 ears the tinnitus side matched the hearing aid side (24 devices). In six of the remaining 19 cases with unilateral tinnitus, the hearing aid and tinnitus were on the same side (6 devices) and in 13 were on opposite sides (13 devices). Changes in the Tinnitus Handicap Inventory (THI), visual analog scale (VAS, for tinnitus discomfort, severity, and persistence), and Hospital Anxiety and Depression Scale scores were measured immediately before using a hearing aid and 12 months later. Results Significant effects of hearing aids on tinnitus were observed in all subjects (THI, p = 0.0000030), VAS (severity, p = 0.000000066; discomfort, p = 0.0000013). Significant effects were observed with bilateral hearing aids (THI, p = 0.0012; VAS for severity, p = 0.00069; VAS for discomfort, p = 0.00052) and with unilateral hearing aids (THI, p = 0.00055; VAS for severity, p = 0.000034; VAS for discomfort, p = 0.00007). Spearman's rank correlation coefficient showed a significant positive correlation between the THI and VAS scores (p = 0.0033). In cases of bilateral tinnitus, significant differences were observed with bilateral hearing aids (THI, p = 0.011; VAS for severity, p = 0.0019; VAS for discomfort; p = 0.020) and with unilateral hearing aids (THI, p = 0.00069; VAS for severity, p = 0.00071; VAS for discomfort, p = 0.000093). Conclusion Acoustic therapy using hearing aids was effective for tinnitus. Even when bilateral, a unilateral hearing aid is able to improve tinnitus. When unilateral, the ipsilateral hearing aid is able to improve tinnitus.

The purpose of this study was to evaluate the functional duration and survival rate of tympanostomy ventilation tubes and the complications associated with their use in pediatric patients who underwent tube insertion for otitis media with effusion (OME). Complications were analyzed including recurrence and tympanic membrane perforation after the tube removal or extrusion.Altogether, 447 ears from 234 pediatric patients younger than 15 years of age were studied retrospectively. All patients had undergone long-term tympanostomy ventilation tube: the Goode T-tube insertion for OME at the Osaka Women's and Children's Hospital, which is the pediatrics specialty hospital between April 2014 and March 2016. They were typically followed up every 3-4 months or more frequently if necessary due to otorrhea or tube infection. Subsequently, the tube duration, survival rates of the tube especially at 22 months after insertion defined as "full-term placement", and the rates of recurrence and perforation were calculated and statistically evaluated.Of 447 ears, 335 ears from 184 patients underwent their first tube insertion, and 112 ears from 64 patients underwent their second or subsequent tube insertion within the targeted period. Two hundred ears from 106 patients were associated with a cleft palate. The survival rate at full-term placement was 51.7%. The recurrence rate was 56.3%, and the rate of the tympanic perforation was 8.5%.Approximately half of the tubes survived for 22 months. The perforation rate was relatively low; however, recurrence of OME was seen in more than half the ears.

Synthetic excitatory synaptic organizer The human brain contains trillions of synapses within a vast network of neurons. Synapse remodeling is essential to ensure the efficient reception and integration of external stimuli and to store and retrieve information. Building and remodeling of synapses occurs throughout life under the control of synaptic organizer proteins. Errors in this process can lead to neuropsychiatric or neurological disorders. Suzuki et al. combined structural elements of natural synaptic organizers to develop an artificial version called CPTX, which has different binding properties (see the Perspective by Salinas). CPTX could act as a molecular bridge to reconnect neurons and restore excitatory synaptic function in animal models of cerebellar ataxia, familial Alzheimer's disease, and spinal cord injury. The findings illustrate how structure-guided approaches can help to repair neuronal circuits. Science , this issue p. eabb4853 ; see also p. 1052

We have demonstrated that sub-10 nm-thick heteroepitaxial Ge films on Si (001) having smooth surfaces can be obtained by DC magnetron sputtering. Ge films grown at 350 °C preserve the smooth surfaces with a roughness root mean square (RMS) of 0.39 nm, whereas, the Ge films grown at 500 °C show significant roughness with an island-like morphology. In samples grown at 350 °C, it is confirmed that the Ge films are grown epitaxially by cross-section transmission electron microscopy (TEM) and X-ray diffraction (XRD) rocking curve measurements. Rapid thermal annealing (RTA) at 720 °C is effective in improving the crystalline quality and the degradation in the roughness is negligible. Raman spectra and an XRD reciprocal space map reveal that the epitaxial Ge grown at 350 °C show an in-plane compressive strain and that the strain continues to remain after a 720 °C RTA.

The influence of extension doping on parasitic resistance and its variability has been investigated for FinFETs. Electrical characterization of FinFETs and crystallinity evaluation of the doped fin structure are carried out for different fin thicknesses and different donor species for ion implantation, i.e., As and P. Reducing the fin thickness and the use of donor species with a larger mass cause serious degradation in the variability and median value of the parasitic resistance. Crystallinity evaluation by transmission electron microscope reveals that significant crystal defects remain after dopant activation annealing for the cases of smaller fin thickness and the implanted dopant with a larger mass. The unrecovered defects cause serious degradation in the parasitic resistance and its variability.

A mouse model of epilepsy was generated by inducing status epilepticus (SE) for either 1.5 or 4.5h with pilocarpine to study anxiety-related behaviors, changes in the electroencephalogram of the cerebral cortex and hippocampus, and expression of hippocampal proteins. The viability and rate of success of SE induction were high in C57BL/6N mice but not in C57BL/6J mice. C57BL/6N mice were immotile during the first 2days after SE; however, by the third day, most mice were recovered and exhibited strong anxiety-related behaviors in response to the light/dark preference test and open field test. There was a striking difference in the temporal appearance of anxiety-related behavior between the two SE durations: 1.5h SE mice exhibited strong anxiety-related behavior 3days after SE that gradually attenuated over the next few weeks, whereas 4.5h SE mice exhibited strong anxiety-related behavior 3days after SE that persisted even at nearly 1year after SE. Mice receiving both SE durations exhibited generalized seizures (GS) after SE; however, there was a marked difference in the timing and duration of GS appearance. Mice in the 4.5h SE group exhibited spontaneous GS from 4days to at least 96days after SE. In contrast, mice in the 1.5h SE group exhibited GS only within the first several days after SE; however, epileptic spike clusters continuously appeared in the cerebral cortex and hippocampus for up to twelve days after SE. Among the hippocampal proteins tested, only brain derived-neurotrophic factor (BDNF) exhibited altered expression in parallel with anxiety-related behavior. These results showed the possibility that BDNF expression in the hippocampus might cause anxiety-related behavior in adulthood.

A linearly polarized hard X-ray photoemission system has been developed for studying the ground-state symmetry of strongly correlated materials., An angle-resolved linearly polarized hard X-ray photoemission spectroscopy (HAXPES) system has been developed to study the ground-state symmetry of strongly correlated materials. The linear polarization of the incoming X-ray beam is switched by a transmission-type phase retarder composed of two diamond (100) crystals. The best value of the degree of linear polarization was found to be −0.96, containing a vertical polarization component of 98%. A newly developed low-temperature two-axis manipulator enables easy polar and azimuthal rotations to select the detection direction of photoelectrons. The lowest temperature achieved was 9 K, offering the chance to access the ground state even for strongly correlated electron systems in cubic symmetry. A co-axial sample monitoring system with long-working-distance microscope enables the same region on the sample surface to be measured before and after rotation. Combining this sample monitoring system with a micro-focused X-ray beam by means of an ellipsoidal Kirkpatrick–Baez mirror (25 µm × 25 µm FWHM), polarized valence-band HAXPES has been performed on NiO for voltage application as resistive random access memory to demonstrate the micro-positioning technique and polarization switching.

Objectives Hearing loss is a serious problem in infants and children because it may interfere with the development of typical speech, verbal language, and auditory and communication skills. By measuring hearing ability (thresholds) as early as possible, even as early as during infancy, effective treatment can be administered. These treatments may significantly reduce the handicap associated with hearing loss. However, at times during behavioral auditory tests, observers cannot determine whether or not an accurate threshold was obtained. To support the use of infant audiometry for accurate diagnosis, audiologic behavioral responses may be obtained by selecting stimuli that interest infants, e.g., their mothers’ voices. Methods We evaluated 30 infants who were presented to our hospital for behavioral auditory assessment in 2016. The infants' ages ranged from 4 months to 3 years and 6 months. The mean age was 1 year and 10 months ±10 months (±standard deviation). The infants' hearing thresholds for their mothers' voices and warble tones at 250–4000 Hz were measured. Auditory brainstem response (ABR) had already been evaluated in 24 infants. Relationships between mother's voice and warble tone or ABR thresholds as well as responses to the initial stimuli and stimuli at the threshold were investigated. These responses were classified into four grades (no response, uncertain response, possible positive response, and positive response), and the response to mother's voice and warble tone were subsequently compared. Results Mother's voice thresholds significantly correlated with all warble tone thresholds. In the relationship between the mother's voice threshold and average hearing levels of 500, 1000, and 2000 Hz, two infants were outliers. In these infants, the average hearing levels were relatively higher than the mother's voice thresholds. Judging from their ABR thresholds, the mother's voice thresholds were valid and the average hearing levels were worse than their original assessed hearing ability. The responses to mothers' voices were more distinct than those to warble tones, both for initial stimuli presentation and the determined threshold. Conclusions Audiologic behavioral responses to mothers' voices were clearer than those for warble tones. Evaluations that use the mother's voice threshold are useful for estimating hearing levels in infants.

At the second postoperative year, there were no significant differences between results for vertigo and hearing after endolymphatic sac drainage with steroid instillation surgery (EDSS) and EDSS with posterior tympanotomy with steroids at the round window (EDRW). In particular, as regards hearing recovery to the preoperative level, the periods after EDRW were shorter than those after the second EDSS.Patients sometimes faces recurrent problems years after EDSS due to endolymphatic sac closure and/or disease progression. In the present study, we examined the effects of EDRW on vertigo and hearing after revision surgery for intractable relapsed Meniere's disease.Sixteen patients with Meniere's disease had revision surgery due to intractable recurrence of disease, and were followed up regularly at least for 2 years. As revision surgery, EDSS was performed repeated in eight cases and EDRW was performed in the other eight. There were no significant differences between the patients' backgrounds in the two groups.Periods of hearing recovery to the preoperative level were 11.5 ± 4.4 months after the first EDSS, although it took 16.4 ± 2.6 months longer after revision surgery with the second EDSS (p = 0.0380.05: first EDSS vs second EDSS) and was 10.0 ± 3.3 months shorter after revision surgery with EDRW (p = 0.0100.05: second EDSS vs EDRW).

There is a question whether the conductive filament (CF) formed in the oxide layer of a resistive-switching random access memory is made of oxygen vacancies or metallic atoms. We investigated the CF of Ni/TiO2/Pt device using temperature coefficient of resistance (TCR), anisotropic magnetoresistance (AMR), and cross-sectional transmission electron microscopy with energy dispersive X-ray analysis (TEM-EDX). The low resistance state (LRS) of the device showed metallic property by TCR measurement. Furthermore, the device in the LRS showed AMR, which was a direct evidence of the formation of ferromagnetic CF. The cross-sectional TEM-EDX observation revealed that a nano-sized Ni precipitation existed in the area nearby a conductive spot. It is intensively suggested that Ni atoms migrated from the adjacent Ni electrode to TiO2 layer to form the nano-sized ferromagnetic CF.

A resistance random access memory (ReRAM) is expected to be a next-generation nonvolatile memory because of its fast switching speed, and low power consumption. The device structure is composed of an oxide layer sandwiched with two metal electrodes. ReRAM exhibits repetitive transition between high resistance state (HRS) and low resistance state (LRS). It is considered that resistive switching phenomenon is caused by the formation and rupture of the conductive filament formed in the oxide layer. In this study, we investigated HfOx thickness dependence of current-voltage characteristics for Ni/HfOx/Pt ReRAM device. We fabricated Ni/HfOx/Pt devices with a simple crossbar structure. HfOx layer was deposited on the Pt bottom electrode by DC reactive sputtering. The I-Vcharacteristics were measured by two-probe method at room temperature. Red line in Figure 1 shows I-V characteristics of the Ni/ HfOx/Pt device with oxide thickness of 5.6 nm. Initial state of resistance is HRS. SET process (from HRS to LRS) took place at 2.4 V with a current compliance of 0.1 mA. RESET process (from LRS to HRS) occurred at -1.6 V. The resistance ratio of HRS to LRS is about 107 with 0.1 V readout bias. On the other hand, blue line shows the I-V characteristics of the Ni/ HfO2/Pt device with oxide thickness of 4.0 nm. Initial state of resistance is LRS. Forming process was not observed in this device. SET process took place at 1.0 V. RESET process was observed at -0.6 V. Switching voltage of this device is smaller than the former device with the thicker oxide layer. The resistance ratio of HRS/LRS is about 101 with 0.1 V readout bias. There was a significant difference in switching properties between these devices whose oxide thicknesses differ only 1.6 nm. It is suggested that leakage current increases when the oxide thickness decreases, thereby the on-state occurred initially for the device with 4.0 nm oxide. It should be noted that I-V characteristic is symmetrical for the device with 4.0 nm oxide, while it is asymmetrical for the device with 5.6 nm oxide. This suggests the mechanism of conductive filament formation and rupture is completely different between these devices. Further discussions and analysis will be presented in the symposium.

A resistive switching (RS) memory has been expected to be a next-generation memory owing to its high density, low power consumption, and high switching speed. The mechanism of the reversible RS phenomenon has been considered in terms of the formation and rupture of conductive filaments (CF). Recently, it has been reported that a ferromagnetic CF was formed in NiO-based RS memory. This suggested the possibility of the new device that has both RS memory and spintronics device functions. The presence of a ferromagnetic CF in the NiO layer was confirmed by measuring the magnetization of the large number of CFs at room temperature using a SQUID magnetometer. Although, it is not yet confirmed that a single ferromagnetic CF is formed by the SET process. The purpose of this study is to understand the physical properties of a single ferromagnetic CF by focusing on magnetoresistance (MR). We prepared Ni/HfO2/Pt memory device, having ferromagnetic Ni electrode and the oxide of a non-magnetic metal. The fabricated RS memory devices have a cross-bar structure. The crossed electrode size is 1×1 mm2. RS characteristic was measured with the bipolar operation mode. When current limit is 5 mA, the anisotropic magnetoresistance (AMR) was observed in the low resistance state. The direction of the external magnetic field is in-plane to the substrate, and the current is perpendicular to the magnetic field. The AMR showed a convex behavior with magnetic field, and the MR ratio was approximately 0.15%. It is strongly suggested that AMR came from a ferromagnetic CF formed in the oxide layer. Further discussions will be shown in the workshop.

We investigated resistive switching (RS) characteristics and temperature dependences of a resistance of the Ni/TiO2/Pt resistive switching memory. The device was operated in a unipolar mode. From the temperature dependence of resistance, it is shown that the conductive filament in the low resistance state (LRS) is metallic. Fabricated Pt/NiO/Pt RS memory to compare the RS characteristics showed similar RS phenomenon. The conductive mechanism of the Pt/NiO/Pt RS memory is also metallic. Temperature coefficients of resistance of various RS memory were compared.

The morphological changes of etched Si surfaces on the concentration of AgNO3 using single-step metal assisted etching and their reflectance were investigated. We used aqueous mixture solution containing silver nitrate (AgNO3) and hydrofluoric acid (HF) as single-step metal assisted etching solution. With changing concentration of silver ions in the etching solution, three types of Si surface morphologies (“nanowire”, “wall”, “polished”) were prepared. Then, phase diagram is developed for these morphologies obtained as a function of AgNO3 concentration and resistivity of silicon substrates. The measurement of reflectance for etched surface indicates that the nanowire is the lowest reflectance of three types of morphologies.

The electric conduction mechanism of electrochemically treated anodic porous alumina (APA) resistance switching (RS) memory is investigated. The current-voltage characteristics of the APA were measured for both of high resistance state and low resistant state at room temperature. The conduction mechanism of a high resistance state can be explained by separating into three regions of Ohm's law, space charge limited current (SCLC), and Fowler-Nordheim (F-N) tunneling. It was suggested that the F-N tunneling decreases the reproducibility of switching voltages.

We improved the performance of a complementary circuit comprising Si-based tunnel field-effect transistors (TFETs) by using isoelectronic trap (IET) technology. IET technology was found to increase the ON current (I ON ) 5 times in P-TFETs and 2 times in N-TFETs. The ION enhancement improved the inverter performance. In addition, ring oscillator (RO) circuit operation with the complementary TFET inverters was experimentally demonstrated for the first time. The RO circuit with IET-TFETs exhibited a higher operation frequency than that with conventional TFETs. IET technology provides a breakthrough towards realizing complementary circuits with Si-TFETs.

The cerebellum is thought to be involved in cognitive functions in addition to its well established role in motor coordination and motor learning in humans. Cerebellin 1 (Cbln1) is predominantly expressed in cerebellar granule cells and plays a crucial role in the formation and function of parallel fiber–Purkinje cell synapses. Although genes encoding Cbln1 and its postsynaptic receptor, the delta2 glutamate receptor (GluD2), are suggested to be associated with autistic-like traits and many psychiatric disorders, whether such cognitive impairments are caused by cerebellar dysfunction remains unclear. In the present study, we investigated whether and how Cbln1 signaling is involved in non-motor functions in adult mice. We show that acquisition and retention/retrieval of cued and contextual fear memory were impaired inCbln1-null mice.In situhybridization and immunohistochemical analyses revealed that Cbln1 is expressed in various extracerebellar regions, including the retrosplenial granular cortex and the hippocampus. In the hippocampus, Cbln1 immunoreactivity was present at the molecular layer of the dentate gyrus and the stratum lacunosum-moleculare without overt mRNA expression, suggesting that Cbln1 is provided by perforant path fibers. Retention/retrieval, but not acquisition, of cued and contextual fear memory was impaired in forebrain-predominantCbln1-null mice. Spatial learning in the radial arm water maze was also abrogated. In contrast, acquisition of fear memory was affected in cerebellum-predominantCbln1-null mice. These results indicate that Cbln1 in the forebrain and cerebellum mediates specific aspects of fear conditioning and spatial memory differentially and that Cbln1 signaling likely regulates motor and non-motor functions in multiple brain regions.SIGNIFICANCE STATEMENTDespites its well known role in motor coordination and motor learning, whether and how the cerebellum is involved in cognitive functions remains less clear. Cerebellin 1 (Cbln1) is highly expressed in the cerebellum and serves as an essential synaptic organizer. Although genes encoding Cbln1 and its receptor are associated with many psychiatric disorders, it remains unknown whether such cognitive impairments are caused by cerebellar dysfunction. Here, we show that Cbln1 is also expressed in the forebrain, including the hippocampus and retrosplenial granular cortex. Using forebrain- and cerebellum-predominant conditionalCbln1-null mice, we show that Cbln1 in the forebrain and cerebellum mediates specific aspects of fear conditioning and spatial memory differentially, indicating that Cbln1 signaling regulates both motor and non-motor functions in multiple brain regions.

We have studied variation of switching voltage of resistive random access memory (ReRAM). Basically, the switching voltage at every switching has a different value because there are many conduction paths, which are randomly chosen at every switching with different conductivity in an oxide insulator between top and bottom electrodes. Limitation of the number of conductive paths is expected to lead the suppression of the variation of switching voltage. In this study, Ni nanorods buried into the nanoholes of an anodic aluminum oxide (AAO) film have been fabricated to restrict the formation of many filaments and the switching behaviors of the In/NiO/Ni nanorods has been investigated.

We have investigated the precise crystal structure and their temperature dependences of oxyarsenides (LaO)TAs; T = Mn, Fe, Co, as the Fe based superconductor’s parent material family using high energy synchrotron radiation x-ray powder diffraction. Lattice constants a and c decrease with decreasing temperature. Focusing the ratios of the changes normalized by room temperature lattice constants, we have found anisotropic shrinks for the superconductor’s parent material of (LaO)FeAs and the ferromagnetic metal (LaO)CoAs. The shrinkage of the lattice constant c along the stacking direction will be discussed by the temperature dependence of the divided three components of the LaO layer, TAs layer, and the interlayer distance.

Study of temperature dependence of magnetoresistance and I–V characteristics for the resistive random access memory with ferromagnetic electrode was carried out. The device exhibited bipolar operation mode. From temperature dependence of magnetoresistance of on-state, it is suggested that a very fine ferromagnetic conductive filament is formed.

We have demonstrated the operation of a CMOS inverter consisting of Si tunnel FinFETs. Both p- and n-type tunnel FinFETs are successfully fabricated and operated on the same SOI wafer. The current mismatch between p- and n-type tunnel FETs is compensated by tuning the number of fin channels. Very low short-circuit current and clear voltage input–output characteristics are obtained. The thin epitaxial channel in the tunnel FinFETs effectively increases the drain current and accordingly reduces the drain capacitance, which could help high-performance tunnel FET CMOS inverter operation.

We structurally and electrically characterize sub-10-nm-thick heteroepitaxial Ge films on Si(001), formed by heated sputtering and subsequent rapid thermal annealing (RTA). After RTA treatment at 720 °C, we find the heteroepitaxial Ge films to have smooth surfaces with a roughness root mean square value of 0.54 nm. Raman measurement reveals that the 720 °C RTA improves the crystallinity of Ge films while maintaining abrupt Ge/Si interfaces. Cross-sectional transmission electron microscopy confirms that the 720 °C RTA step effectively reduces stacking faults and dislocations in the Ge films. The Richardson plot of the TaN/Ge/n-Si diode indicates a Schottky barrier height (SBH) of 0.33 V, which is close to the height of 0.37 V measured from the capacitance–voltage measurement. These values are reasonable compared with the reported SBH of the TaN/bulk Ge Schottky barrier diode, indicating that the method involving heated sputtering and subsequent RTA provides adequate thin Ge films for Ge/Si heterostructures.

This paper discusses the impact of the tunneling probability on the variability of tunnel field-effect transistors (TFETs). Isoelectronic trap (IET) technology, which enhances the tunneling current in TFETs, is used to suppress the variability of the ON current and threshold voltage. The simulation results show that suppressing the tunneling rate fluctuations results in suppression of the variability. In addition, a formula describing the relationship between the tunneling rate fluctuations and the electric field strength is derived based on Kane's band-to-band tunneling model. This formula indicates that the magnitude of the tunneling rate fluctuations is proportional to the magnitude of the fluctuations in the electric field strength and a higher tunneling probability results in a lower variability. The derived relationship is universally valid for any technologies that exploit enhancement of the tunneling probability, including IET technology, channel material engineering, heterojunctions, strain engineering, etc.

The influence of the extension doping conditions on gate-induced drain leakage (GIDL) has been investigated to optimize fin field-effect transistors (FinFETs) for ultralow-power (ULP) applications. An increased GIDL for a smaller fin thickness and a dependence on the implanted ion species, i.e., a larger GIDL for As than for P, are recognized. These results suggest that the residual defects due to extension doping increase the GIDL, and the suppression of the defects by the optimization of the doping process is the key to the optimization of FinFETs for ULP applications.

Hydrogen anneal effects on reproducibility of the switching voltages for a resistive switching memory using anodic porous alumina have been investigated. The hydrogen anneal made the reproducibility worse.

Huge magnetoresistance switching phenomenon, whose MR ratio exceeded 300%, was observed in a nano-conduction path (NCP). The ferromagnetic NCP was formed by the use of dielectric breakdown of insulator (SiO 2 ) concomitant with an introduction of ferromagnetic atoms into NCP by electromigration.

The switching process of the conductive filament formed in Ni/HfOx/Pt resistive random access memory (ReRAM) devices were studied. We evaluated the oxide thickness dependence and temperature dependence of voltage for the Forming, Set and Reset operations for HfOx layers whose thickness are between 3.3 and 6.5 nm. The resistance of conductive filaments showed typical metallic behavior, which suggests Ni filament formation in the HfOx layer. There is a clear dependence of switching voltages for the Set and Reset processes on oxide thickness, which implies that the formation and rupture of conductive filaments occur in the entire thickness range of the HfOx layer. This finding differs from that of a previous study by Yang, which suggests the existence of a constant-thickness switching region. It is suggested that the thickness of the switching region in HfOx may be larger than 6.5 nm.

Resistive change memory has been expected to be a next generation memory due to high-speed response. However, wide variations of switching voltages are often found in the current–voltage (I–V) characteristics and hinder the practical applications. We have tried suppressing the variation by three tactics based on the filament model; confinement of conductive filaments, concentration of electric field, and preparation of many routes for conductive filaments with the same electrical properties. In this study, we have investigated the combination of concentration of electric field method and preparation of many routes for conductive filaments in the insulator by electrochemical treatment (ET) using sulfuric acid. The I–V curves depend on the ET time. The best result is obtained in the long ET time. With regards to switching voltage distribution, the combination of two methods provide better switching characters than those of single method.

Ferromagnetic conductive filaments (CFs) were formed in a conductive-bridge random access memory (CBRAM) with a Ni electrode using high current compliances during a set process. We investigated CFs in a Ni/HfO2/Pt CBRAM using the current compliance dependences of the set process, low-temperature characteristics, and anisotropic magnetoresistance (AMR). Set processes occurred when a positive bias was applied to the Ni electrode only; therefore, the switching phenomena showed polarity. The resistance of the ON state (low resistance state) was dependent on the current compliance between 2 and 5 mA. The ON state of the device showed a metallic conduction property, suggested by the temperature dependence of resistance. When a high current compliance (5 mA) was used for programming, the ON state showed AMR, which was direct evidence of ferromagnetic CF formation. This suggests that the formation of a ferromagnetic CF is associated with the accumulation of Ni ions that diffused from the Ni electrode. The OFF-state (high resistance state) resistance slightly increased with decreasing temperature and AMR was not observed.

An attempt to reduce the SET voltage and RESET current of resistive switching (RS) memory was made using a geometric array of nanopeak (NP) structures. Bottoms of anodic porous alumina were used to form the NP structures that act as guides for the formation of conductive filaments that effectively concentrate the electric field. Samples were fabricated with flat surfaces (FS) and with two types of NP structure with different NP pitch. The NP samples provided SET voltages less than 2 V with narrow distributions and the RESET current was lower than that with the FS sample.

We have tried suppressing variation of switching voltages which hinder the practical application of resistive switching random access memory. On the basis of a filament model, fabrication of the top electrode with small enough size against the filament size and confining the filament are thought to be the solutions. In this study, we have investigated the confinement effects on the switching voltage variations using anodic porous alumina with ordered nano holes. Variation of the voltage has a trend to reduce with enlarging the diameters of nano holes by chemical etching. The confinement is very effective to improve the reproducibility of the switching voltages.

We investigated the resistive switching characteristics and temperature dependence of resistance of a Ni/NiOx/Pt resistive switching memory. The device was operated in a unipolar operation mode. From the temperature dependence of resistance, it is suggested that the conduction mechanism of the low-resistance state is metallic. Moreover, a deformed site that may correspond to the conductive filament appeared after the forming process. Cross-sectional transmission electron microscopy with energy dispersive X-ray analysis showed that the Ni atomic content at the NiOx of the deformed area was larger than those of other areas. It is strongly suggested that the conductive filament formed in the NiOx layer is composed of Ni atoms.

The control of the crystal orientation and diameter of vertically grown epitaxial Si nanowires was demonstrated using a combination of a vapor–liquid–solid (VLS) growth technique and the use of an anodic aluminum oxide (AAO) template on a single-crystal Si substrate. The [100], [110], and [111] nanowires were selectively obtained by choosing the Si substrate with appropriate crystal orientation. The diameter of a Si nanowire in the AAO template could be controlled by the modification of the pore size of the AAO template with anodic voltage during anodization.

An investigation of current–voltage (I–V) characteristics and the temperature dependence of resistance in a resistive switching (RS) memory with a Cu/SiO2/Au device was performed. Moreover, conductive spots were observed by scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (TEM). Both unipolar and bipolar operation modes were obtained. From the temperature dependence of resistance, it is suggested that the conduction mechanism of the low resistance state (LRS) is metallic conduction and that of the high resistance state (HRS) is variable-range hopping (VRH) conduction. The results of observing the device support this suggestion. We propose the switching mechanism in the Cu/SiO2/Au device from these results.

Resistance change random access memory (ReRAM) has been expected to be a next generation non-volatile memory. However, poor reproducibility of threshold voltage at which the dramatic change of the resistivity occurs hinders the practical application. We have attempted to improve the reproducibility of switching voltages using anodic porous alumina whose nanoholes are quite useful to restrict the filament forming area on the basis of the filament model. In this study, we have reported the pore size and film properties dependences of the variation width of the switching voltages. Two kinds of oxide films prepared by oxalic and sulfuric acids with two different anodic times were used as the insulating layer. Contrary to our expectation, just the sulfuric samples indicate good improvement about the switching voltages. Considering that the size of the effective contact area is not enough small against the filament size, the changing the film properties seems to be important for the suppressing the variation of switching voltages.