Planar Metal Insulator Research Articles

Fabry–Pérot Resonances in Planar Metal–Insulator–Metal Structures for Optical Data Processing: A Review

Fabry–Pérot Resonances in Planar Metal–Insulator–Metal Structures for Optical Data Processing: A Review

Engineering the directionality of hot carrier tunneling in plasmonic tunneling structures

Tunneling metal–insulator–metal (MIM) junctions can exhibit an open-circuit photovoltage (OCPV) response under illumination that may be useful for photodetection. One mechanism for photovoltage generation is hot carrier tunneling, in which photoexcited carriers generate a net photocurrent that must be balanced by a drift current in the open-circuit configuration. We present experiments in electromigrated planar MIM structures, designed with asymmetric plasmonic properties using Au and Pt electrodes. Decay of optically excited local plasmonic modes preferentially creates hot carriers on the Au side of the junction, leading to a clear preferred directionality of the hot electron photocurrent and hence a preferred polarity of the resulting OCPV. In contrast, in an ensemble of symmetric devices constructed from only Au, polarity of the OCPV has no preferred direction.

Low Leakage Current Metal–Insulator–Metal Device Based on a Beryllium Oxide Insulator Created by a Two-Step Spin-Coating Method as a Novel Type of Modified Pechini Synthesis

Beryllium oxide (BeO) is considered to be an attractive alternative material for use in future industries in areas such as semiconductors, spacecraft, aircraft, and rocket technologies due to its high bandgap energy, useful melting point, good thermal conductivity, and dielectric constants. In this context, our approach is a novel method to produce BeO thin films based on a two-step spin-coating innovation of the conventional powder synthesis method. The surface morphology and the crystal structure of BeO thin films were observed to be dependent on the citric acid/beryllium sulfate ratio and the sintering temperature, respectively. To characterize the BeO films, X-ray photoelectron spectroscopy was conducted for an elemental analysis. Furthermore, the bandgap of the BeO thin films was determined by reflection electron energy loss spectroscopy. Finally, the leakage current of a planar metal–insulator–metal device consisting of Au/Ti/BeO thin film/Ti/Au electrodes was determined to be below the nA range over the linear voltage sweeping range of −20 V to +20 V. These results can assist researchers in the areas of morphology control strategies, phase transfer theories, and applications that utilize BeO thin film manufactured by a solution process.

Effects of post metallization annealing on Al2O3 atomic layer deposition on n-GaN

The chemical, physical and electrical properties and the robustness of post metallization annealed Al2O3 atomic layers deposited on n-type GaN are investigated in this work. Planar metal insulator capacitors are used to demonstrate a gate-first with following ohmic contacts formation at elevated temperature up to 600 °C process flow. X-ray photoelectron spectroscopy indicates that no new bonds in the Al2O3 layer are formed due to exposure to the elevated annealing temperature. X-ray diffraction measurements show no crystallization of the oxide layer. Atomic force microscopy shows signs of degradation of the sample annealed at 600 °C. Electrical measurements indicate that the elevated annealing temperature results in an increase of the oxide depletion and the deep depletion capacitances simultaneously, that results in a reduction of the flat band voltage to zero, which is explained by fixed oxide charges curing. A forward bias step stress capacitance measurement shows that the total number of induced trapped charges are not strongly affected by the elevated annealing temperatures. Interface trap density of states analysis shows the lowest trapping concentration for the capacitor annealed at 500 °C. Above this temperature, the interface trap density of states increases. When all results are taken into consideration, we have found that the process thermal budget allows for an overlap between the gate oxide post metallization annealing and the ohmic contact formation at 500 °C.

Magnetic Field-Assisted Self-Wound 3-D Nanomembrane Capacitors Bridge the Gap Between MLCC and Trench Capacitor Technologies

This letter reports the transformation of large-area planar metal–insulator–metal (MIM) nanomembrane capacitors into compact tubular 3-D architectures. By combining the powerful approach of strain-induced nanomembrane self-assembly with an external magnetic field, a stable winding process over a large distance in the range of centimeters is demonstrated. A wet release platform based on encapsulated methyl cellulose allows to release the planar structures with rates of several $100~\mu \text{m}$ /s from their substrate. Footprint shrinkage factors up to 230 are shown by assembling 24-mm long planar structures into 3-D architectures having 82- $\mu \text{m}$ diameter and ~120 windings. The fabricated capacitors feature a capacitance per footprint up to $1.3~\mu \text{F}$ /mm2 for a 15-nm Al2O3 dielectric with less than 100-nA/ $\mu \text{F}$ leakage at 6 V and improved frequency characteristics. This technology is a promising candidate for bridging the gap between discrete multilayer ceramic capacitor (MLCC) and ON-chip trench capacitor technologies.

Analytical plasmon dispersion in subwavelength closely spaced Au nanorod arrays from planar metal–insulator–metal waveguides

The Fabry–Perot-like cavity modes in subwavelength closely spaced Au nanorod arrays can be determined from an analytical model for the plasmon dispersion in planar metal–insulator–metal (MIM) waveguides of equivalent widths.

3-D Integrated Track-and-Hold Circuit Using InAs Nanowire MOSFETs and Capacitors

This letter presents a vertical integration scheme where track-and-hold circuits, consisting of a MOSFET in series with a metal-insulator-metal (MIM) capacitor, are successfully fabricated along vertical InAs nanowires. The nanowire MOSFET is used as a switch with varying switch resistance, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sw</sub> , as the gate-source voltage, V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> , is varied. The track-andhold circuit operation is verified by a sine wave that is properly evaluated by the circuit. In addition, calculations show that the three-dimensional integration reduces the track-and-hold area a factor of 2, as compared with planar MIM capacitor only. With further nanowire pitch reduction, about ten times area saving is projected.

Three-dimensional concentration of light in deeply sub-wavelength, laterally tapered gap-plasmon nanocavities

Gap-plasmons (GP) in metal-insulator-metal (MIM) structures have shown exceptional performance in guiding and concentrating light within deep subwavelength layers. Reported designs to date exploit tapered thicknesses of the insulating layer in order to confine and focus the GP mode. Here, we propose a mechanism for the three dimensional concentration of light in planar MIM structures which exploits exclusively the lateral tapering of the front metallic layer while keeping a constant thickness of the insulating layer. We demonstrate that an array of tapered planar GP nanocavities can efficiently concentrate light in all three dimensions. A semi-analytical, one-dimensional model provides understanding of the underlying physics and approximately predicts the behavior of the structure. Three-dimensional simulations are then used to precisely calculate the optical behavior. Cavities with effective volumes as small as 10−5 λ3 are achieved in an ultrathin MIM configuration. Our design is inherently capable of efficiently coupling with free-space radiation. In addition, being composed of two electrically continuous layers separated by an ultrathin dielectric spacer, it could find interesting applications in the area of active metamaterials or plasmonic photocatalysis where both electrical access and light concentration are required.

Planar metal–insulator–metal diodes based on the Nb/Nb2O5/X material system

The authors report the performance of various planar metal–insulator–metal (MIM) tunneling diodes, which are being investigated for use in rectenna devices for energy harvesting applications. Six cathode materials (M2): Nb, Ag, Cu, Ni, Au, and Pt are studied in conjunction with Nb as the anode (M1) and Nb2O5 (I) as the dielectric. The cathode materials selections were based on results from a prior rapid-screening study that employed a bent-wire metal cathode point-contact method. Planar devices, to enable analysis using standard MIM diode models, were fabricated with the resultant current density–voltage data obtained at both room temperature and 77 K. The tunnel barrier heights and dielectric properties for these systems were extracted from the modeling results. Nb/Nb2O5/Pt MIM diodes showed the best performance with an asymmetry ratio greater than 7700, a nonlinearity value of 4.7, and a responsivity of 16.9, all at 0.5 V and 300 K. These results confirm prior rapid-screening efforts and further validate the Nb/Nb2O5/Pt system in particular as a promising MIM architecture due to the low barrier height of the junction.

Loss measurement of plasmonic modes in planar metal–insulator–metal waveguides by an attenuated total reflection method

We report experimental excitation and characterization of surface plasmon modes in planar metal-insulator-metal (MIM) waveguides. Our approach is based on determining the width of the reflection angular spectrum in the attenuated total reflection (ATR) configuration. Owing to its transverse character, the ATR configuration provides a more straightforward and simpler way to determine the loss of plasmonic modes in MIM structures, compared to using tapered end couplers with multiple waveguide samples or scanning near-field optical microscopy. In this Letter, two waveguide structures with Au claddings and 50/200 nm SiO(2) cores are investigated. The propagation lengths measured at λ = 1.55 μm are 5.7 and 18 μm, respectively, in agreement with the theoretical predictions.

Bacteriorhodopsin‐Monolayer‐Based Planar Metal–Insulator–Metal Junctions via Biomimetic Vesicle Fusion: Preparation, Characterization, and Bio‐optoelectronic Characteristics

AbstractA reliable and reproducible method for preparing bacteriorhodopsin (bR)‐containing metal–biomolecule–monolayer‐metal planar junctions via vesicle fusion tactics and soft deposition of Au top electrodes is reported. Optimum monolayer and junction preparations, including contact effects, are discussed. The electron‐transport characteristics of bR‐containing membranes are studied systematically by incorporating native bR or artificial bR pigments derived from synthetic retinal analogues, into single solid‐supported lipid bilayers. Current–voltage (I–V) measurements at ambient conditions show that a single layer of such bR‐containing artificial lipid bilayers pass current in solid electrode/bilayer/solid electrode structures. The current is passed only if retinal or its analogue is present in the protein. Furthermore, the preparations show photoconductivity as long as the retinal can isomerize following light absorption. Optical characterization suggests that the junction photocurrents might be associated with a photochemically induced M‐like intermediate of bR. I–V measurements along with theoretical estimates reveal that electron transfer through the protein is over four orders of magnitude more efficient than what would be estimated for direct tunneling through 5 nm of water‐free peptides. Our results furthermore suggest that the light‐driven proton‐pumping activity of the sandwiched solid‐state bR monolayer contributes negligibly to the steady‐state light currents that are observed, and that the orientation of bR does not significantly affect the observed I–V characteristics.

Modeling and optimization of series resistance of planar MIM capacitors

Integrated circuits for analog and telecom applications require metal insulator metal (MIM) capacitors with not only a high capacitance value (typically 5nF/mm2), but also a low series resistance Rs. The optimization of this latter parameter is investigated in this paper, by means of a simple analytical model, taking into account both the impact of material parameters and device architectures, suggesting possible strategies for Rs minimization. Such a model is also suitable for MIM circuit simulation, and can be also extended to other devices, such as to the gate series resistance modeling of RF MOSFET. Results are in good agreement with numerical simulations and HF measurements, performed on state of the art planar MIM devices. Moreover, discussion on via placement to access the top electrode has been held, in order to optimize the series resistance of the capacitor.

The Umbrella Cell: A High-Density 2T Cell for SOC Applications

To realize a high-density on-chip memory, the authors have proposed a novel logic-process-compatible memory cell. This cell consists of two logic transistors, and placing a planar MIM (metal insulator metal) capacitor on a copper wire above the transistors produces a memory area of 26 F 2 , which is approximately 60% smaller than a 6T SRAM cell. A suitable cell-bias design and a dual precharge scheme solve the coupling problem inherent in the cell and allow standard logic transistors to be used. This cell-applying the proposed schemes-can handle 10-ns cycle time at a hit-line voltage of 0.7 V. The random cycle is about three times faster than that of a conventional V BL precharge scheme. These results indicate that the umbrella cell is a strong candidate for providing a high-density memory for SOC applications.

Planar metal–insulator–semiconductor type field emitter fabricated on an epitaxial Al/Al2O3/Si (111) structure

A planar metal–insulator–semiconductor (MIS)-type field emitter using epitaxial γ-Al2O3 (111)/Si (111) structure was successively fabricated and field-emission phenomena were observed. Planar MIS-type field emitters using epitaxially grown Al2O3 were fabricated by molecular beam epitaxy (MBE) method and characteristics of these emitters were evaluated. It was confirmed that the Al2O3 possessed good crystalline quality and surface morphology. The breakdown field of the epitaxial Al2O3 layer was able to increase in situ annealing at the substrate temperature of 750 °C. From experimental measurements of diode current, conduction band offset (ΔEc) value between the epitaxial γ-Al2O3 and Si (111) substrate was calculated to be 2.5 eV. Fowler–Nordheim (F–N) tunneling was observed from the 8-nm-thick epitaxial Al2O3 film. Emission characteristics were obtained from the 10-nm-thick epitaxial Al2O3 insulator with a 20-nm-thick Al gate electrode. The maximum transfer ratio of emission current was confirmed to be 1%.

Path Integral Analysis of Local and Nonlocal Effects in Electron Tunneling

We analyze the origin and character of dynamical effects in electron tunneling in planar metal–insulator–metal systems evaluating semiclassically a path integral expression for the tunneling amplitude. A transparent connection between the interaction of the tunneling electron with the quantized charge fluctuations and the effective one-electron potential is made. For the first time a comparison between the local and nonlocal parts of the effective potential for the electron tunneling for zero and finite temperatures is explicitly analyzed in a single approach. The situations when local and nonlocal parts, always of opposite sign, are comparable in strength are found and discussed.

Properties of native ultrathin aluminium oxide tunnel barriers

We have investigated planar metal–insulator–metal tunnel junctions withaluminium oxide as the dielectricum. These oxide barriers were grownon an aluminium electrode in pure oxygen at room temperature tillsaturation. By applying the Simmons model we derived discrete widths ofthe tunnelling barrier, separated by Δs ≈ 0.38 nm.This corresponds to the addition of single layers of oxygenatoms. The minimum thickness of s0 ≈ 0.54 nm isthen due to a double layer of oxygen. We found a strong and systematic dependenceof the barrier height on the barrier thickness. Breakdown fields up to 5 GV m−1were reached. They decreased strongly with increasing barrier thickness. Electricalbreakdown could be described by a metal–insulator like transition of thedielectric barrier due to the large density of tunnelling electrons.

Observation of inversion behavior in n-type GaN planar metal–insulator–semiconductor capacitor

Electrical characterization of SiO 2/n-type GaN planar metal–insulator–semiconductor (MIS) capacitors fabricated on sapphire substrates was carried out with a capacitance–time ( C– t) technique. C– t measurements after applying strong reversed voltages showed capacitance transients, corresponding to the generation of minority carriers in the MIS structure. This result indicates the formation of inversion mode at the SiO 2/GaN interface in the deep depletion state. From the temperature dependence of the capacitance transient, thermal activation energy for the generation of minority hole carriers is estimated to be ∼0.46 eV, which is much smaller than the GaN band gap. This implies that the observed inversion behavior originates in defects inside the GaN layer.

Local modification of HF-treated silicon (100) surface and its characterization by scanning tunneling microscopy and spectroscopy

The modification of silicon (100) surfaces on samples etched with HF and without rinsing in de-ionized H2O is produced and studied by scanning tunneling microscopy and spectroscopy. The dependence of the size of the modification with the tunnel current and the voltage between tip and sample is explained from the evaluation of the electrical field between the tip and the silicon surface, starting from the planar metal–insulator–semiconductor theory. Current image tunneling spectroscopy data allow to clarify the nature of the modification, concluding that an electrochemical change on the surface of the sample has been produced.

High resolution potentiometry of planar electroformed MIM structures

Abstract Many attempts have been made to detect the current carrying filaments in electroformed metal-insulator-metal (MIM) structures (Pagnia and Sotnik 1988, Pagnia 1990). Transmission and scanning electron microscopes have been used without real success. Even experiments with the scanning tunnelling microscope (STM) could not definitely detect the filaments. We have mapped the potential distribution on an electroformed planar MIM diode (gold on quartz glass) with an STM and found usually only one (sometimes a few) sharp potential drop(s) in the microslit.

New reusable optoelectronic storage medium

An investigation was made of the characteristics of switching and photosensitivity of a reusable optoelectronic storage medium based on planar metal–insulator–semiconductor–insulator–metal structures. Estimates indicate that data can be stored in such a medium with a density in excess of 107 bit/cm2 and the energy needed to record one bit is about 2×10−13 J.