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SiOx-based resistive random access memory devices with metal-insulator-metal structure are compared to metal-insulator-semiconductor structures, and the effects of external resistance on device performance are characterized. The different reset behaviors are explained as a positive feedback mechanism involving a sudden voltage decrease across the external series resistance when the reset process commences. By varying external resistance, we observe a constant threshold voltage (2.46 V) for the reset process that is possibly due to a voltage-triggered switching mechanism. Our experimental results not only clarify the reset mechanism but also provide insights on optimization of external resistance for programing reliability and operating speed. [ABSTRACT FROM AUTHOR]

In this paper, we show the simulation of a plasmonic band-pass filter which consists of two surface plasmon polaritons (SPPs) waveguides and a resonator in metal-insulator-metal (MIM) structure. The resonator is formed by two square rings and a patch between them. The patch is a tiny rectangle cavity in order to transfer the SPPs from one ring to the other. The finite element method (FEM) method is employed in simulation. The results show that the dual-ring resonator performs better than a single ring does. The 3 dB bandwidth near the peak wavelength λ = 1054 nm is merely 31.7 nm. The resonant wavelength can be shifted by changing the side length of the square ring. This narrow band-pass filter is easy to fabricate and has potential applications in future integrated optical circuits. [ABSTRACT FROM AUTHOR]

The effects of gamma irradiation on electrical parameters of Au/Si3N4/n-Si (MIS) structure were investigated by using the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The MIS structure was irradiated using gamma-radiation source at a dose rate of 0.69 kGy/h. TheC–VandG/ω–Vmeasurements were carried out at a total dose range of 0–100 kGy for five different frequencies (1, 10, 100, 500 and 1000 kHz). The obtained results showed that theCandG/ωvalues decrease with the increasing radiation dose due to the irradiation-induced defects at the interface. Also, the observed decrease in theCandG/ωvalues with the increasing frequency was explained on the basis of interface states (Nss). The values of series resistance (Rs) increase with the increasing radiation dose. To obtain the real capacitance and conductance of the capacitor, the measured values ofCandG/ωwere corrected to eliminate the effect of series resistance. The values ofNsswere determined by using the conductance method and were decreased with the increasing radiation dose. [ABSTRACT FROM PUBLISHER]

A plasmonic filter based on metal-insulator-metal (MIM) waveguide with phase shifts is proposed, and the corresponding transmission characteristics are investigated. Since the insulator layer in the MIM waveguide is structured by alternately stacking two insulators with different refractive indices, an inverse arrangement of the two insulators leads to the generation of a π phase shift, and multiple π phase shifts can be formed in the insulator layer in this way. Due to the introduction of π phase shifts into MIM waveguides, novel transmission characteristics can be obtained, like these in one-dimensional photonic crystals or fiber gratings. Such transmission responses of the plasmonic filter with phase shifts are then investigated using the finite-difference time-domain (FDTD) method. When a π phase shift is inserted into the insulator layer, a transmission channel in the plasmonic band gap is excited, owing to the resultant resonant defect mode. Next, multiple transmission channels can also be obtained by inserting multiple π phase shifts into the insulator layer, of which the wavelengths are associated with the distribution of these phase shifts. Further, when the spacing of multiple phase shifts is increased, the transmission channels converge together, and then a single narrow transmission channel is formed. On the other hand, as the spacing is reduced, the transmission channels move far from each other and the total loss of multiple channels can be reduced and flattened, leading to the generation of multiple high-uniformity transmission channels in the plasmonic band gap. [ABSTRACT FROM AUTHOR]

An ultra-narrow band absorber consisting of continuous silver and alumina films is investigated. Owing to Fabry-Pérot resonance and silver's inherent loss, an ultra-narrow spectral range of light can be entirely trapped in the structure. By varying thicknesses of metallic and dielectric films, absorption peak shifts in visible and near-infrared regions. When two such metal-insulator-metal stacks are cascaded, experimental results show that an ultra-narrow absorption bandwidth of 7 nm is achieved, though theoretical results give that of 2 nm. Features of high-efficiency and ultra-narrow band absorption have huge potential in optical filtering, thermal emitter design, etc. [ABSTRACT FROM AUTHOR]

A subwavelength intersection structure with wavelength filtering functionality is proposed by using an open loop which consists of four slot cavities and four metal-insulator-metal (MIM) drop waveguides. The slot cavities are used as the resonators while the MIM waveguides serve as the input/output ports. The SPPs propagations and the transmission wavelengths in two pairs of matched input/output ports are immune to each other, which satisfy the intersection characters. The results based on finite difference time domain (FDTD) method demonstrate that high transmittance for the expected output port and high isolation for other ports have been achieved. Specifically, the transmittance and isolation is larger than 0.64 and 14 dB, respectively. In addition, a transmission peak, whose wavelength can be modulated by adjusting the length of the slot cavities, is available for the output port. Such a device can find applications in various optical systems, such as the wavelength filtering area and the optical intersection area. [ABSTRACT FROM AUTHOR]

Through ab initio calculations, we propose that the conductive filaments in Pt/HfO2/Pt resistive random access memories are due to HfOx suboxides, possibly tetragonal, where x\leq 1.5 . The electroforming process is initiated by a continuous supply of oxygen Frenkel defect pairs through an electrochemical process. The accumulation of oxygen vacancies leads to metallic suboxide phases, which remain conductive even as ultranarrow 1- {\rm nm}^{2} filaments embedded in an insulating {\rm HfO}_{2}$ matrix. Our experiments further show that the filaments remain as major leakage paths even in the OFF-state. Moreover, thermal heating may increase the OFF-state resistance, implying that there are oxygen interstitials left in the oxide layer, which may recombine with the oxygen vacancies in the filaments at high temperature. [ABSTRACT FROM PUBLISHER]

Metal-Insulator-Metal (MIM) structures have raised as the most promising configuration for next generation information storage, leading to great performance and fabrication-friendly Resistive Random Access Memories (RRAM). In these cells, the memory concept is no more based on the charge storage, but on tuning the electrical resistance of the insulating layer by applying electrical stresses to reach a high resistive state (HRS or "0") and a low resistive state (LRS or "1"), which makes the memory point. Some high-k dielectrics show this unusual property and in the last years high-k based RRAM have been extensively analyzed, especially at the device level. However, as resistance switching (in the most promising cells) is a local phenomenon that takes place in areas of ~100 nm2, the use of characterization tools with high lateral spatial resolution is necessary. In this paper the status of resistive switching in high-k materials is reviewed from a nanoscale point of view by means of conductive atomic force microscope analyses. [ABSTRACT FROM AUTHOR]

Structural properties of YBa2Cu3O7-δ/PrBa2Cu3O7-δ heterointerfaces have been investigated by aberration-corrected electron microscopy. Experimental evidence shows that c-axis-oriented YBa2Cu3O7-δ/PrBa2Cu3O7-δ heterostructures with atomically sharp interface epitaxially grow on SrTiO3(001) substrates. In terms of the contrast analysis, no apparent interdiffusion between YBa2Cu3O7-δ and PrBa2Cu3O7-δ occurs at the interface. In addition, stand-off misfit dislocations and planar faults appear within PrBa2Cu3O7-δ layer near the interface. Both misfit dislocations and interfacial dislocations resulting from the termination of planar faults contribute to misfit relaxation at the YBa2Cu3O7-δ/PrBa2Cu3O7-δ interface. The defect configuration of planar faults and stand-off misfit dislocations is explored. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The influence of the growth temperature on structure and the electrical properties of TiO2 thin films deposited from TiCl4 and H2O and from TiCl4 and O3 was investigated in the temperature range of 150-500 °C. The high-permittivity rutile phase of TiO2 was obtained on RuO2 in both processes at 225 °C and higher substrate temperatures. The films deposited on Si contained rutile only when were deposited from TiCl4 and H2O at temperatures above 425 °C. Comparison of the films grown on RuO2 revealed superior electrical performance of those deposited from TiCl4 and O3. Although the k values ranging from 100 to 130 in the Pt/TiO2/RuO2 structures were somewhat lower for these films than for the films deposited from TiCl4 and H2O, the former process resulted in lower leakage current densities at similar capacitance effective thicknesses (CET). The leakage current density as low as 6.6 × 10−8 A cm−2 at 0.8 V and CET = 0.41 nm was obtained for films deposited from TiCl4 and O3 at 350 °C. [ABSTRACT FROM AUTHOR]

We present a bistable device consisting of a Bragg grating resonator with a Kerr medium sandwiched between two dielectric slab waveguides. The resonator is situated in a nanometer-scaled metal–insulator–metal plasmonic waveguide. Due to the dimensional confinement from the dielectric waveguide to the nanoscaled plasmonic waveguide, electric fields are enhanced greatly, which will further reduce the threshold value. Moreover, a semi-analytic method, based on the impedance theory and the transfer matrix method, is developed to study the transmission and reflection spectra as well as the bistability loop of such a switch. Our method is fast and accurate, as confirmed by the finite-difference time-domain simulation. [ABSTRACT FROM AUTHOR]

Two-element tapered slot antenna (TSA) array for terahertz (THz) resonant tunneling diode (RTD) oscillators is proposed in this paper. The proposed TSA array has the advantages of both the high directivity and high gain at the horizontal direction and hence can facilitate the horizontal communication between the RTD oscillators and other integrated circuit chips. A MIM (metal-insulator-metal) stub with a T-shaped slot is used to reduce the mutual coupling between the TSA elements. The validity and feasibility of the proposed TSA array have been simulated and analyzed by the ANSYS/ANSOFT's High Frequency Structure Simulator (HFSS). Detailed modeling approaches and theoretical analysis of the proposed TSA array have been fully addressed. The simulation results show that the mutual coupling between the TSA elements is reduced below -40 dB. Furthermore, at 500 GHz, the directivity, the gain, and the half power beam width (HPBW) at the E-plane of the proposed TSA array are 12.18 dB, 13.09 dB, and 61°, respectively. The proposed analytical method and achieved performance are very promising for the antenna array integrated with the RTD oscillators at the THz frequency and could pave the way to the design of the THz antenna array for the RTD oscillators. [ABSTRACT FROM AUTHOR]

We describe abnormal dual bipolar resistive switching events in simple Pt/Ta2O5-x/TiOxNy and Pt/Ta2O5-x/TiN matrices in which the typical switching directions (SD) are initially clockwise (CW). The negative difference region in a high resistance state before reaching the typical 'CW set' process enables the SD transition to a counterclockwise direction. It thereby emphasizes the occurrence of a highly stable secondary bipolar resistive switching curve. The origin of two different switching modes is described by adapting a bias-dependent oxygen ion accumulation and depletion process at TiOxNy and TiN electrode interfaces and by performing various structural analyses. [ABSTRACT FROM AUTHOR]

Plasmonic waveguides that allow deeply subwavelength confinement of light provide an effective platform for the design of ultra-compact photonic devices. As an important plasmonic waveguide, metal-insulator-metal (MIM) structure supports the propagation of light in the nanoscale regime at the visible and near-infrared ranges. Here, we focus on our work in MIM plasmonic waveguide devices for manipulating light, and review some of the recent development of this topic. We introduce MIM plasmonic wavelength filtering and demultiplexing devices, and present the electromagnetic induced transparency (EIT)-like and Fano resonance effects in MIM waveguide systems. The slow-light and rainbow trapping effects are demonstrated theoretically. These results pave a way toward dynamic control of the special and useful optical responses, which actualize some new plasmonic waveguide-integrated devices such as nanoscale filters, demultiplexers, sensors, slow light waveguides, and buffers. [ABSTRACT FROM AUTHOR]

A tunable narrow band filter based on a Bragg grating with surface plasmon polaritons is developed and investigated numerically by using the finite-difference time-domain method. A defect state with narrow transmission peak (about 15 nm) is shown to appear in the bandgap by introduction of a defect into the Bragg grating, which can thus be used as filtering device. We also show that double-channel filtering can be realized by introducing two defects into the Bragg grating. The resonant wavelengths in the bandgap are related to the position of defects and the refractive index of the insulator. Our results may provide useful information in the design of tunable narrow band filters in nano-circuits. [ABSTRACT FROM PUBLISHER]

We demonstrate controlled optical critical coupling into highly confining metal-insulator-metal grating-based resonators. We achieve the coupling-and hence the absorption-of more than 95% of the incoming photons in a gallium arsenide based system confined between a metallic ground plane and a metallic grating. The demonstration is given in the terahertz range of the electromagnetic spectrum, at 75 μm ≤ λ ≤ 120 μm, for a semiconductor core thickness of only 10 μm. It is valid, however, at any wavelength, upon linear scaling. The critical coupling regime is judiciously tuned by precise etching of the semiconductor material in between the metallic fingers. The experimental results are in accordance with the universal behaviour predicted by temporal coupled mode theory. [ABSTRACT FROM AUTHOR]

Resistive switching and conductance quantization are systematically studied in a Ag/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester/indium-tin oxide sandwich structure. The observed bipolar switching behavior can be attributed to the formation and dissolution of Ag filaments during positive and negative voltage sweeps, respectively. More importantly, conductance quantization with both integer and half integer multiples of single atomic point contact can be realized by slowing down the voltage sweep speed as well as by pulse measurement. The former may reflect the formed Ag filaments with different atomic point contacts, while the latter probably originates from the interaction between the Ag filaments and the elemental hydrogen provided by the organic storage medium. With appropriate current compliances, low resistance states with desired quantized conductance values are successfully achieved, thus showing the potential for ultrahigh density memory applications. Besides, 100 successive switching cycles with densely distributed resistance values of each resistance state and extrapolated retention properties over ten years are also demonstrated. [ABSTRACT FROM AUTHOR]

Complex impedance spectra of the low- and high-resistance states of Au/NiO/Pt and ITO/TiO2/ITO heterostructures were studied to probe the characteristics of conducting filaments (CFs). Different types of CFs were compared both qualitatively and quantitatively. It was demonstrated that important information of CFs, including the conducting behavior as well as the position and degree of rupture, can be obtained by analysis of the complex impedance data. We further employed this tool to explore resistive switching effect in HfO2 based heterostructures fabricated by different methods, and revealed the switching mechanisms and the effect of growth process on the properties of CFs. [ABSTRACT FROM AUTHOR]

A simple plasmonic filter with symmetrical tooth-shaped waveguides is proposed and investigated by using finite element method. It is found that the structure with a single symmetrical tooth-shaped waveguide couple can realize a tunable band-stop filter. Attributed to cascaded symmetrical tooth-shaped waveguide couples, the structure can achieve a flat band-stop response with no intensity variation over the transmission spectrum. And the central wavelength of the stopband linearly increases with the simultaneous increasing of depths of waveguides. Moreover, reduced structure size can be achieved by controlling the dielectric constant of the medium. [ABSTRACT FROM AUTHOR]

In this paper, we explore the potential of the plasmonic metal-insulator-metal (MIM) periodically graded structure. Based on the coupled modes approach, an analytical model has been observed for the surface plasmon polariton (SPP) propagation. The band modes of SPP can be also supported by the MIM structure and we have analyzed the strong dependence of band width on structure parameters. The obtained analytical expressions allow one to easily choose the structure parameters for the desired band width. [ABSTRACT FROM AUTHOR]

The filter function of the metal-insulator-metal (MIM) waveguide with a gear-shaped nanocavity is investigated using the finite-difference time-domain method. Since the gear breaks the symmetric distribution of the resonance, Fano resonance occurs in the gear-shaped nanocavity. Fano resonance strongly depends on the structural parameters of the gear. Compared to the MIM waveguide with a disk-shaped nanocavity, the MIM waveguide with a gear-shaped nanocavity allows for a much more sensitive detection of small refractive index changes of the filled media inside the nanocavity, which reveals a potential sensor application of the MIM waveguide with a gear-shaped nanocavity. [ABSTRACT FROM AUTHOR]

An easy-to-design single-stub nano-coupler is proposed to increase the direct coupling efficiency between metal-insulator-metal (MIM) plasmonic and high-index dielectric waveguides. The modal reflection and transmission from the junction are exploited to provide a circuit description for the structure. The return loss of direct coupling is then minimized by loading the MIM waveguide with a single stub. Numerical examples are given, and the accuracy of the model is examined via finite-difference time-domain method. [ABSTRACT FROM AUTHOR]

The Ag-Cu nanoparticle arrays, prepared using the electrochemical deposition method, were assembled into the metal-insulator-metal (MIM) structure with polyvinyl alcohol acting as insulating layer, the transmission spectrum of the MIM structure was observed to support the multiple surface plasmon resonances in the wavelength range 1,000 to 2,600 nm. The multiple peaks were formed due to the superposition and coupling of the surface plasmon resonance of nanoparticles with various sizes in the metal layers. The newly found MIM structure in which multiple resonances exist has a potential application in multiband-pass filters and optical magnetic metamaterials at the resonance wavelength. [ABSTRACT FROM AUTHOR]

A subwavelength plasmonic comb-like filter is proposed by using dual symmetric slot cavities which are placed between two parallel metal-insulator-metal (MIM) structure waveguides. The structure can be considered as a resonance loop which consists of slot cavity resonators and MIM waveguide resonators. The reflective wavelength range and channel spacing are determined by the lengths of slot cavities and MIM waveguides, respectively. Three, four, and five reflective channels with high reflection are achieved in a small wavelength range. Higher channel count can be available by increasing the length or the real part of effective index of MIM waveguides. Such a device can find applications in various optical systems such as wavelength demultiplexing components. [ABSTRACT FROM AUTHOR]

In this paper, a novel plasmonic filter with very high extinction ratio and low insertion loss is proposed based on the coherent coupled nano-cavity array in a metal-insulator-metal (MIM) waveguide. The coherent coupling interactions among nano-cavities are investigated with an analytical model which is derived based on the temporal coupled-mode theory and transfer-matrix method. The destructive interference of the surface plasmon polaritons coupled from the nano-cavities at the resonant wavelength is achieved by suitably designing the period of the cavity array, which may be used for increasing the extinction ratio of the filter based on the nano-cavity array in the MIM waveguide. A plasmonic filter with an extinction ratio higher than 60 dB and an insertion loss less than 1.0 dB is obtained by applying the destructive interference in the design of a six-rectangular-cavity array in an Ag-air-Ag waveguide. And the correctness of the design for the filter is verified by the results obtained with the finite-difference time-domain simulation technique. This work may provide useful schemes and approaches for realization of various wavelength-sensitive devices in plasmonic integrated circuits. [ABSTRACT FROM AUTHOR]

This paper presents a precision mismatch measurement method to characterize an integrated capacitor array. Conventional mismatch measurement methods using floating gate capacitance measurement (FGCM) have measurement error due to the large input-referred noise and the small input signal range of the source follower. In order to improve the measurement accuracy, we propose a new measurement method using a parasitic-insensitive switched capacitor amplifier and the correlated double sampling (CDS) technique. The CDS technique eliminates the measurement error from parasitic capacitances, switching errors, and the offset voltage of the amplifier. In order to verify the proposed method, a test chip was fabricated using a 0.18-\mmb\mum CMOS process. The chip consists of a 4\,\times\,16 metal–insulator–metal capacitor array and a measurement circuit. The measured standard deviation of the capacitance mismatch, \sigma(\DeltaCn{{<}C{>}}), ranges from 0.0067% to 0.0130%, and the measured standard deviation of the short-term repeatability, \sigma(\Delta (\DeltaCn/{<}C{>})), is 0.0025%. These results show that the measurement accuracy of the proposed method is improved by ten times over that of the FGCM method. [ABSTRACT FROM PUBLISHER]

A novel symmetric plasmonic structure consisting of a metal-insulator-metal waveguide and a rectangular cavity is proposed to investigate Fano resonance performance by adjusting the size of the structure. The Fano resonance originates from the interference between a local quadrupolar and a broad spectral line in the rectangular cavity. The tuning of the Fano profile is realized by changing the size of the rectangular cavity. The nanostructure is expected to work as an excellent plasmonic sensor with a high sensitivity of about 530nm/RIU and a figure of merit of about 650. [ABSTRACT FROM AUTHOR]

We propose a specially designed plasmonic lens structure to succeed in realizing sub-diffraction phase-contrast imaging of transparent nano-objects. The nano-objects are embedded inside the insulator layer of the metal-insulator-metal (MIM) plasmonic structure and have a small refractive index difference with respect to the transparent insulator layer. The excited surface plasmons in the MIM structure help to greatly enhance scattered light from the nano-objects and effectively suppress the transmitted illumination light. A spatial resolution of about 64 nm and a minimum distinguishable refractive index difference down to 0.05 are numerically demonstrated. For sub-diffraction phase-contrast imaging of irregular three-dimensional (3D) nanowires and nanocylinders, the optimized MIM structure shows much better performance in comparison with that of a superlens. [ABSTRACT FROM AUTHOR]

This paper presents a film transfer process to integrate barium strontium titanate (BST) metal-insulator-metal (MIM) structures with surface acoustic wave (SAW) devices on a lithium niobate (LN) substrate. A high-quality BST film grown on a Si substrate above 650 °C was patterned into the MIM structures, and transferred to a LN substrate below 130 °C by Ar-plasma-activated Au-Au bonding and the Si lost wafer process. Simple test SAW devices with the transferred BST variable capacitors (VCs) were fabricated and characterized. The resonance frequency of a one-port SAW resonator with the VC connected in series changed from 999 to 1018 MHz, when a dc bias voltage of 3 V was applied to the VC. Although the observed frequency tuning range was smaller than expected due to the degradation of BST in the process, the experimental result demonstrated that a tunable SAW filter with the transferred BST VCs was feasible. [ABSTRACT FROM AUTHOR]

The structural and electrical properties of Lu2O3 dielectric films deposited by radio frequency (RF) magnetron sputtering on TaN electrode have been studied for metal-insulator-metal (MIM) capacitor in analog/RF applications. From X-ray diffraction study, it is observed that the deposited films remain amorphous within the thermal budget (400°C) of back-end-of-line process. The root mean square value of surface roughness of the Lu2O3 film decreases after annealing at 400°C using atomic force microscopy. The chemical composition of the Lu2O3 film was characterized by X-ray photoelectron spectroscopy. The MIM capacitor using a Lu2O3 dielectric film exhibited better electrical characteristics, such as a low leakage current of 5 × 10-8 A/cm2 at −1 V and a high capacitance density of 7.5 fF/µm2 with a low quadratic voltage coefficient of capacitance of 75 ppm/V2. The current conduction mechanism was found to be dominated by Schottky emission mechanism in low electric field (<1 MV/cm) region and hence further improvement in the leakage characteristics can be realized by employing a high work-function electrode or a large bandgap oxide as a barrier layer. [ABSTRACT FROM AUTHOR]

Metal–insulator–metal (MIM) structures have been proposed for infrared photodetectors, optical rectennas, and alternative choices to conventional solar cells. Generally, if two dissimilar electrodes are separated by a sufficiently thin insulator, electrons can travel through the insulating gap region due to the quantum tunneling effect. This tunneling through the insulating gap can be driven by an electromagnetic field or an external bias voltage. In our work, we incorporate the contributions of the Poole–Frenkel (PF) effect on the energy barrier of the MIM junction and the effect of Coulomb interaction between the electron charge and its virtual image charges. Using this modified PF-Coulombic barrier, we perform quantum calculations for electron tunneling using the transfer matrix method and Wentzel–Kramers–Brillouin approximations. This, along with the density of states, the Fermi occupation probability, and the quantum confinement effect is used to derive the dark current density for the MIM diode. To test the theory, MIM Au-TiO2-Ti diodes are designed and fabricated in-house using photolithography, along with electron beam evaporation and sputter depositions. The dark current–voltage (I − V) characteristics of the fabricated MIM photodiodes are measured and show good agreement with theoretical predictions. [ABSTRACT FROM AUTHOR]

These phase change oxide-based switches will enable highspeed electronics for memory devices, neural computation, and radio frequency communication. B Ultra-Fast Switches b In article number 2100428, Sumaiya Kabir, Madhu Bhaskaran, and colleagues demonstrate metal-insulator-metal structures needed for high-speed switching of vanadium dioxide thin-films using a low electrical input. Device Geometry Insights for Efficient Electrically Driven Insulator-to-Metal Transition in Vanadium Dioxide Thin-Films (Adv. [Extracted from the article]

This paper describes a new low-pass filter topology based on tapered periodic structures. These filters exhibit interesting characteristics in terms of compactness, return loss, insertion loss, selectivity, and the suppression of spurious frequency bands. Hybrid prototypes with a 1-GHz cutoff frequency, based on a coplanar-waveguide technology, and using both low-cost and high-performance substrates, have been fabricated and measured. Spurious frequency bands can be suppressed to below -22 dB at frequencies up to 20 GHz. Passband ripples are negligible, and the return loss is better than 20 dB. A two-section filter has a length of 0.2 lambda and exhibits a -120-dB/dec selectivity, while a six-section filter is 0.51 lambda long and has a -560-dB/dec selectivity. A design procedure has been established. These filters are compatible with monolithic microwave integrated circuit technologies in which the capacitors can be realized as metal-insulator-metal structures [ABSTRACT FROM PUBLISHER]

Magnetostatic ferromagnetic coupling in magnetic tunnel junctions was selectively analyzed. We have shown that in samples involving polycrystalline magnetic films, beyond the orange-peel coupling, an important class of interaction is related to the dispersion fields associated to magnetic inhomogeneities. These magnetization fluctuations were described in terms of magnetic roughness arising from the local anisotropy fluctuations. Therefore, using roughness data extracted from atomic/ magnetic force microscopy analysis, the amplitude and the variation with distance of the magnetostatic interactions were selectively quantified. [ABSTRACT FROM AUTHOR]

We study the linear conductance of single electron devices showing Coulomb blockade phenomena. Our approach is based on a formally exact path integral representation describing electron tunneling nonperturbatively. The electromagnetic environment of the device is treated in terms of the Caldeira-Leggett model. We obtain the linear conductance from the Kubo formula leading to a formally exact expression which is evaluated in the semiclassical limit. Specifically we consider three models. First, the influence of an electromagnetic environment of arbitrary impedance on a single tunnel junction is studied focusing on the limits of large tunneling conductance and high to moderately low temperatures. The predictions are compared with recent experimental data. Second, the conductance of an array of N tunnel junctions is determined in dependence on the length N of the array and the environmental impedance. Finally, we consider a single electron transistor and compare our results for large tunneling conductance with experimental findings. [ABSTRACT FROM AUTHOR]

Tiny spatial fluctuations of tunnel barrier parameters are shown to have dramatic consequences on the statistical properties of quantum tunneling. A direct experimental evidence is provided that the tunnel current through metal-oxide junctions, imaged at a nanometric scale, exhibits broad statistical distributions extending over more than 4 orders of magnitude. Striking effects of broad current distributions are shown: the total tunnel transmission is dominated by few highly transmitting sites and the typical current density varies strongly with the size of the junction. Moreover, self-averaging of the tunnel current fluctuations occurs only for unexpectedly large junction areas. [ABSTRACT FROM AUTHOR]

To reduce the loss of the metal–insulator–metal waveguide structure in the near-infrared region, a plasmonic nanosensor structure based on a racetrack resonant cavity is proposed herein. Through finite element simulation, the transmission spectra of the sensor under different size parameters were analyzed, and its influence on the sensing characteristics of the system was examined. The analysis results show that the structure can excite the double Fano resonance, which has a distinctive dependence on the size parameters of the sensor. The position and line shape of the resonance peak can be adjusted by changing the key parameters. In addition, the sensor has a higher sensitivity, which can reach 1503.7 nm/RIU when being used in refractive index sensing; the figure of merit is 26.8, and it can reach 0.75 nm/°C when it is used in temperature sensing. This structure can be used in optical integrated circuits, especially high-sensitivity nanosensors. [ABSTRACT FROM AUTHOR]

A single electron transistor based on Al-AlOx-Nb tunnel junctions was fabricated by shadow evaporation and in situ barrier formation. Its output current noise was measured, using a transimpedance amplifier setup, as a function of bias voltage, gain, and temperature, in the frequency range (1-300) Hz. The spot noise at 10 Hz is dominated by a gain dependent component, indicating that the main noise contribution comes from fluctuations at the input of the transistor. Deviations from ideal input charge noise behaviour are found in the form of a bias dependence of the differential charge equivalent noise, i.e. the derivative of current noise with respect to gain. The temperature dependence of this effect could indicate that heating is activating the noise sources, and that they are located inside or in the near vicinity of the junctions. [ABSTRACT FROM AUTHOR]

A microwire technique has been developed for fabricating three-dimensional (3-D) structures for use in ultra-compact GaAs monolithic microwave/millimeter wave integrated circuits (MMIC). By folding metal into a U-shapedl wall and burying it in a relatively thick polyimide insulator, vertical microwires can be made with greatly reduced process complexity. This technique also offers process compatibility with multilevel interconnects. In this paper, the fundamental characteristics of the proposed Ushaped microwire are dkcussed and its applications to 3-D passive elements and circuits are demonstrated. The characteristics of the U-shaped microwires are almost the same as those of I-shaped microwires and can be accurately estimated and designed by using numerical analysis. The fabricated and designed transmission lines are one-half to one-third the size of conventional lines with the same transmission loss, and if the microwire is also used as a shielding wall, the occupied area can be made much smaller. Miniature inductors made of vertical U-shaped microwires exhibit a self-resonance freqnency as high as that of conventional inductors, with one-half the size and offer a great advantage in L- or S-band applications. A fabricated miniature wideband 3-D balun had an insertion loss of 1.5 + 1 dB at frequencies from 10 to 30 GHz, and an amplitude and phase balance of 2 dB and 5/spl deg/, respectively. [ABSTRACT FROM AUTHOR]

Leakage currents as low as \(10^{\mathrm {\mathbf {-7}}}\) A/cm \(^{\mathrm {\mathbf {2}}}\) at both 1 V and −1 V top electrode bias in the sub-0.4-nm equivalent SiO2 thickness range are demonstrated in Ru/SrTiOx/Ru metal-insulator–metal capacitors in which the 8.5-nm SrTiOx layer is deposited by atomic layer deposition. The top electrode material and deposition technique as well as the postdeposition anneal are crucial parameters to control the leakage, not only at negative, but also at positive top electrode bias. [ABSTRACT FROM AUTHOR]

Current overshoot has severe effects on the reliability of resistive random access memory (RRAM). It is well known that the current overshoot during the SET process is caused by parasitic capacitance. In this letter, we observed a different type of current overshoot during the RESET process. The RESET current overshoot was confirmed to have severe effects on the endurance of RRAM. We also demonstrated the relation between the current overshoot and the intrinsic capacitive elements of each state of RRAM. Finally, an optimized pulse shape was proposed to minimize the current overshoot and was experimentally verified to significantly improve the variability and endurance in a typical RRAM device with a W/Zr/ HfO2 /TiN structure. [ABSTRACT FROM AUTHOR]

TaN/ZrTiOx/Pt metal-insulator-metal structure was employed as the platform to evaluate the eligibility for antifuse one-time programmable (OTP) memory applications, and the impact of O2 plasma on device performance was also discussed. Owing to the oxygen radicals that enhance the dielectric integrity, the voltage for state switching increases with O2 plasma treatment. Memory cells without plasma treatment demonstrate promising characteristics for OTP memory applications in terms of a low dc switching voltage of 2 V, high programming speed of 60 ns, high read endurance up to 10^6 reading cycles, and desirable retention time and low switching power density of 6.4 mW/cm^2. The memory cell technology not only exhibits the prominent performance which is advantageous over other dielectrics reported in the literature, but it also possesses the capability to from stackable 3-D architecture. [ABSTRACT FROM PUBLISHER]

A metallic nano-trench is a unique optical structure capable of ultrasensitive detection of molecules, active modulation as well as potential electrochemical applications. Recently, wet-etching the dielectrics of metal–insulator–metal structures has emerged as a reliable method of creating optically active metallic nano-trenches with a gap width of 10 nm or less, opening a new venue for studying the dynamics of nanoconfined molecules. Yet, the high surface tension of water in the process of drying leaves the nano-trenches vulnerable to collapsing, limiting the achievable width to no less than 5 nm. In this work, we overcome the technical limit and realize metallic nano-trenches with widths as small as 1.5 nm. The critical point drying technique significantly alleviates the stress applied to the gap in the drying process, keeping the ultra-narrow gap from collapsing. Terahertz spectroscopy of the trenches clearly reveals the signature of successful wet etching of the dielectrics without apparent damage to the gap. We expect that our work will enable various optical and electrochemical studies at a few-molecules-thick level. [ABSTRACT FROM AUTHOR]

Colloidal cubic silicon-carbide nanocrystals have been fabricated, characterized, and introduced into metal–insulator–semiconductor and metal–insulator–metal structures based on hafnium oxide layers. The fabricated structures were characterized through the stress-and-sense measurements in terms of device capacitance, flat-band voltage shift, switching characteristics, and retention time. The examined electrical performance of the sample structures has demonstrated the feasibility of the application of both types of structures based on SiC nanoparticles in memory devices. [ABSTRACT FROM AUTHOR]

Presents the cover/table of contents for this issue of the periodical. [ABSTRACT FROM PUBLISHER]

We propose a wide-band metamaterial perfect absorber (MPA), using the coupling in the near-field of a quadruple split-ring resonator concentric with crossed ellipses. We designed the MPA with a metal–insulator-metal (MIM) structure for use in thermal energy harvesting. A gradient-based optimization approach was carried out to maximize the absorption of infrared (IR) radiation around 10 μm. Owing to the near-field coupling of resonators with optimal design parameters, the peaks of the absorption responses approach each other, thus broadening the overall bandwidth with almost unity absorptivity. The proposed design has a resonance at 10 μm resulting from magnetic polaritons (MPs) and thus maintains high absorption above 99% up to a range of incident-angles greater than 60° and exhibits a polarization-free behavior due to symmetry. When the optimal design was numerically examined to fabrication tolerances, it showed negligible sensitivities in the absorptivity with respect to design parameters. The strong electric field enhancement inside the split-ring gaps and between the ends of the cross arms and the surrounding ring enables designing MIM diodes to rectify the harvested thermal radiations at 288 K. MIM diodes can be built by the deposition of thin insulators to sit in these gaps. The MIM diode and MPA work together to harvest and rectify the incident IR radiation in a manner similar to the operation of rectennas. The MPA outperforms the traditional nano-antennas in impedance matching efficiency because of its higher resistance. Also, its dual-polarization reception capability doubles the rectenna efficiency. Our proposed MPA retained absorptivity more than 99% when coupled with MIM diodes whose resistances are in the range of 500 Ω–1 MΩ. [ABSTRACT FROM AUTHOR]

Medical interventions increasingly rely on biosensors that can provide reliable quantitative information. A longstanding bottleneck in realizing this, is various non-idealities that generate offsets and variable responses across sensors. Current mitigation strategies involve the calibration of sensors, performed in software or via auxiliary compensation circuitry thus constraining real-time operation and integration efforts. Here, we show that bio-functionalized metal-oxide memristors can be utilized for directly transducing biomarker concentration levels to discrete memory states. The introduced chemical state-variable is found to be dependent on the devices' initial resistance, with its response to chemical stimuli being more pronounced for higher resistive states. We leverage this attribute along with memristors' inherent state programmability for calibrating a biosensing array to render a homogeneous response across all cells. Finally, we demonstrate the application of this technology in detecting Prostate Specific Antigen in clinically relevant levels (ng/ml), paving the way towards applications in large multi-panel assays. [ABSTRACT FROM AUTHOR]

In this paper, a reconfigurable sensing platform based on an asymmetrical metal-insulator-metal stacked structure integrating an indium tin oxide (ITO) ultrathin film is proposed and investigated numerically. The epsilon-near-zero (ENZ) mode and antisymmetric mode can be resonantly excited, generating near-perfect absorption of over 99.7% at 1144 and 1404 nm, respectively. The absorptivity for the ENZ mode can be modulated from 90.2% to 98.0% by varying the ENZ wavelength of ITO by applying different voltages. To obtain a highly sensitive biosensor, we show that the proposed structure has a full-width at half-maximum (FWHM) of 8.65 nm and a figure-of-merit (FOM) of 24.7 with a sensitivity of 213.3 nm/RI (refractive index) for the glucose solution. Our proposed device has potential for developing tunable biosensors for real-time health monitoring. [ABSTRACT FROM AUTHOR]