The electrical characterization of metal–insulator–semiconductor device with β-naphthol orange interface

Journal of Materials Science: Materials in Electronics - This study was formed by the β-naphthol orange/p-Si metal–insulator–semiconductor (MIS) structure by obtaining...     

Dual wavelength demultiplexer based on metal–insulator–metal plasmonic circular ring resonators

Abstract

In this paper, we investigated a plasmonic demultiplexer structure based on Metal–Insulator–Metal (MIM) waveguides and circular ring resonators. In order to achieve the structure of demultiplexer, two improved ring resonators have been used, which input and outputs MIM waveguides coupled by the ring resonators. To improve the transmission efficiency, a reflector was introduced at the right end of the input and output waveguides. By substituting the ring core with dielectric, the possibility of tuning the resonance wavelength of the proposed structure is illustrated, and the effect of various parameters such as radius and refractive index in transmission efficiency is studied in detail. This is useful for the design of integrated circuits in which it is not possible to extend the dimension of the ring resonator to attain a longer resonance wavelength. Transmission efficiency and quality factor of the single ring are 84% and 110, respectively. The simulation results using finite difference time domain method shows that in the proposed demultiplexer, which is composed of two rings with different core refractive indexes, the average power efficiency, bandwidth for each output channel, and the mean value of crosstalk are estimated 80%, 17 nm, and ?26.95 dB, respectively. It is revealed that the significant features of the device are high transmission efficiency, low crosstalk, high-quality factor, and tunability for desired wavelengths. Therefore, the proposed structure has the potential to be applied in plasmonic integrated circuits.     

Nanostructures bilayer ZnO/MgO dielectrics for metal–insulator–metal capacitor applications

Bilayer ZnO/MgO dielectrics for metal–insulator–metal (MIM) capacitor application were successfully deposited using simple chemical technique which is sol–gel spin coating method with different annealing temperatures. Important criteria in determining good dielectric layer have been investigated which include structural, electrical and dielectric properties. Cubic-like grain was observed for films annealed at 400 and 425 °C which enhance the carrier density and polarization that resulted in high k value produced. Bilayer film annealed at 475 °C improved in small surface roughness (17.629 nm), minimum leakage current density (~10^?8 A cm^?2) and high resistivity (3.14 × 10⁵ Ω cm). Dielectric constant, k was varied with frequency and k value was found to be 5.09 at 10 kHz. The results obtained in this study indicated that film annealed at temperature of 475 °C is suitable to be used as dielectrics for MIM capacitor application.     

Tunable narrow band filter based on a surface plasmon polaritons Bragg grating with a metal–insulator–metal waveguide

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.     

Synthesis,growth mechanism,photoluminescence and field emission properties of metal–semiconductor Zn–ZnO core–shell microcactuses

Metal–semiconductor Zn–ZnO core–shell microcactuses have been synthesized on Si substrate by simple thermal evaporation and condensation route using NH₃ as carrier gas at 600 °C under ambient pressure. Microcactuses with average size of 65–75 μm are composed of hollow microspheres with high density single crystalline ZnO rods. The structure, composition and morphology of the product were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A vapor–liquid–solid (VLS) based growth mechanism was proposed for the formation of Zn–ZnO core–shell microcactuses. Room temperature photoluminescence (PL) investigations revealed a strong and broad blue emission band at 441 nm associated with a weak ultraviolet (UV) peak at 374 nm. This blue emission (BE) is different from usually reported green/yellow-green emission from Zn–ZnO or ZnO structures. The field emission (FE) measurements exhibited moderate values of turn-on and threshold fields compared with reported large field emissions for other materials. These studies indicate the promise of Zn–ZnO core–shell microcactuses for the applications in UV-blue light display and field emission microelectronic devices.     

Impact of insulator layer thickness on the performance of metal–MgO–ZnO tunneling diodes

The performance of metal–insulator–semiconductor (MIS) type tunneling diodes based on ZnO nanostructures is investigated through modeling. The framework used in this work is the Schrödinger equation with an effective-mass approximation. The working mechanism of the MIS type tunneling diode is investigated by examining the electron density, electric field, electrostatic potential, and conduction band edge of the device. We show that a valley in the electrostatic potential is formed at the ZnO/MgO interface, which induces an energy barrier at the ZnO side of this interface. Therefore, electrons need to overcome two barriers: the high and narrow MgO barrier, and the barrier from the depletion region induced at the ZnO side of the ZnO/MgO interface. As the MgO layer becomes thicker, the valley in electrostatic potential becomes deeper. At the same time, the barrier induced at the ZnO/MgO interface becomes higher and wider. This leads to a fast decrease in the current passing through the MIS diode. We optimize the thickness of the MgO insulating layer, sandwiched between a ZnO film (in this work we use a single ZnO nanowire) and a metal contact, to achieve maximum performance of the diode, in terms of rectification ratio. An optimal MgO layer thickness of 1.5 nm is found to yield the highest rectification ratio, of approximately 169 times that of a conventional metal–semiconductor–metal Schottky diode. These simulated results can be useful in the design and optimization of ZnO nanodevices, such as light emitting diodes and UV photodetectors.

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Structural properties and sensing characteristics of high-k Ho2O3 sensing film-based electrolyte–insulator–semiconductor

In this study, we report a Ho₂O₃ electrolyte–insulator–semiconductor (EIS) device films deposited on Si substrates through reactive sputtering. The effect of thermal annealing (700, 800, and 900 °C) on the structural and surface properties of Ho₂O₃ sensing film was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. We found that the EIS device with a Ho₂O₃ sensing film annealed at 800 °C exhibited a higher sensitivity of ∼57 mV/pH, a lower hysteresis voltage of 2.68 mV, and a smaller drift rate of 2.83 mV h⁻¹ compared to those at other annealing conditions. This improvement can be attributed to the well-crystallized Ho₂O₃ structure and the large surface roughness.     

Preparation of rare earth CeO<Subscript>2</Subscript> thin films using metal organic decomposition method for metal-oxide–semiconductor capacitors

Investigation of metal organic decomposed rare earth cerium oxide thin films deposited on Si substrate by sol–gel spin coating technique was carried out. The structural properties have been examined by using XRD, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The XRD confirms the cubic phase of CeO₂ thin films with (111) plane observed at 28.54°. The FTIR and EDAX spectra confirm the formation of CeO₂ films with atomic percentage of 19.39 and 54.82% of Ce and O₂, respectively. Thickness of 60.11 nm of CeO₂ film measured by cross sectional FESEM image, the average roughness of ~0.6 nm of 400?°C annealed CeO₂ films were observed from AFM micrograph. The MOS capacitors were fabricated by using Ti/Au bilayer metal contact depositing by E-beam evaporator on CeO₂/Si thin film for electrical measurements. Capacitance and conductance voltage measurement was carried out to determine the effective oxide charges (Q_eff), interface trap density (D_it) and dielectric constant (k) and are 2.48?×?10¹² cm^?2, 1.26?×?10¹² eV^?1cm^?2 and ~39, respectively. The effective metal work function of 5.68 for Ti/Au bilayer is observed to be higher than the work function of Ti or Au metals in vacuum.     

Synthesis and processing of ceramic–metal composites by reactive metal penetration

Molten aluminum reduces and penetrates silicate ceramics to produce a metal–ceramic composite which yields an Al₂O₃ skeleton infiltrated with a solidified Al–Si alloy. Penetration experiments have been used to study the influence of p(O₂), temperature and substrate composition on penetration kinetics and composite microstructure. The limiting kinetic step for Al penetration is the chemical reaction between Al and the ceramic. For dense substrates the maximum reaction rates are observed between 1000–1200°C and are independent of p(O₂). For porous substrates it is necessary to reach a critical temperature or p(O₂), before infiltration starts. Increasing the Si concentration in the molten Al results in the reduction of the reaction rates.     

Synthesis of nanoparticles composed of silver and copper for metal–metal bonding

A metal–metal bonding technique is described that uses nanoparticles composed of silver and copper. Colloid solutions of nanoparticles with an Ag content of 0–100?mol% were prepared by simultaneous reduction of Ag⁺ and Cu²⁺ using hydrazine with polyvinylpyrrolidone and citric acid as stabilisers. The nanoparticles ranged in size from 34 to 149?nm depending on the Ag content. Copper discs were strongly bonded at 400°C for 5?min under 1.2?MPa pressure in hydrogen gas; the maximum shear strength was as high as 23.9?MPa. The dependence of shear strength on the Ag content was explained by a mismatch between the d-spacings of Cu metal and Ag metal.     

On the triggering mechanism for the metal–insulator transition in thin film VO<Subscript>2</Subscript> devices: electric field versus thermal effects

Vanadium dioxide (VO₂) has been shown to undergo an abrupt electronic phase transition near 70 °C from a semiconductor to a metal, with an increase in dc conductivity of over three orders of magnitude, making it an interesting candidate for advanced electronics as well as fundamental research in understanding correlated electron systems. Recent experiments suggest that this transition can be manifested independent of a structural phase transition in the system, and that it can be triggered by the application of an electric field across the VO₂ thin film. Several experiments that have studied this behavior, however, also involve a heating of the VO₂ channel by leakage currents, raising doubts about the underlying mechanism behind the transition. To address the important question of thermal effects due to the applied field, we report the results of electro-thermal simulations on a number of experimentally realized device geometries, showing the extent of heating caused by the leakage current in the “off” state of the VO₂ device. The simulations suggest that in a majority of the cases considered, Joule heating is insufficient to trigger the transition by itself, resulting in a typical temperature rise of less than 10 K. However, the heating following a field-induced transition often also induces the structural transition. Nevertheless, for certain devices, we identify the possibility of maintaining the field-induced high conductivity phase without causing the structural phase transition: an important requirement for the prospect of making high-speed switching devices based on VO₂ thin film structures. Such electronically driven transitions may also lead to novel device functionalities including ultra-fast sensors or gated switches incorporating ferroelectrics.     

Fabrication and comparative study of top-gate and bottom-gate ZnO–TFTs with various insulator layers

Transparent ZnO thin film transistors (ZnO–TFTs) with different structures and dielectric layers were fabricated by rf magnetron sputtering. The PbTiO₃, AlO _x , SiN _x and SiO _x films were attempted to serve as the gate dielectric layers in the devices, respectively, and XRD was employed to investigate the crystal structure of ZnO films deposited on these dielectric layers. The optical properties of transparent TFTs were measured and revealed the average transmittance ranged from 60 to 80% in the visible part of the spectrum. Electrical measurement shows the properties of the ZnO–TFTs have great relations with the device structure. The bottom-gate TFTs have better behaviors than top-gate ones with the mobility, threshold voltage and the current on/off ratio of 18.4 cm² V⁻¹ s⁻¹, −0.7 V and 10⁴, respectively. The electrical difference of the devices may be due to different character of the interface between the channel and dielectric layers.     

Resonant tunnelling leakage in planar metal–oxide–metal nanojunctions

The leakage–current in planar nanojunctions, usually employed to realize molecular field-effect devices, is investigated. Resonances are observed on p-doped substrates when the voltage drop between drain and gate electrodes is around 1.1 V. These resonances are related to resonant tunneling via impurity atoms and are otherwise not observed on n-type substrates.     

Preparation and optical properties of TPPS-doped metal–carboxylate-salts glasses

Li and Na carboxylate salts glasses with different number chains containing molecules of Tetraphenyl-porphine-tetrasulfonic acid (TPPS) were prepared by the melting method. TPPS doped in the glasses had the same form as the TPPS in the aqueous solutions. However the form of TPPS in the glasses changed because TPPS reacted with matrix glass during the melting process. Tetraphenyl-porphine (TPP) could no be incorporated into the Li and Na carboxylate salts glasses by the present melting method. The free base TPPS is important for photochemical hole burning (PHB) properties, and a mixed metal–carboxylate salts glasses containing free-base TPPS, which is the active form for PHB, were prepared by controlling the melting condition. It was found that a preparation condition such as holding time of the melts affects the formation of the complex of the TPPS and that in the mixed metal–carboxylate salts melts the TPPS formed a complex with Li but did not form a complex with Na.     

Preparation and optical properties of TPPS-doped metal–carboxylate-salts glasses

Li and Na carboxylate salts glasses with different number chains containing molecules of Tetraphenyl-porphine-tetrasulfonic acid (TPPS) were prepared by the melting method. TPPS doped in the glasses had the same form as the TPPS in the aqueous solutions. However the form of TPPS in the glasses changed because TPPS reacted with matrix glass during the melting process. Tetraphenyl-porphine (TPP) could no be incorporated into the Li and Na carboxylate salts glasses by the present melting method. The free base TPPS is important for photochemical hole burning (PHB) properties, and a mixed metal–carboxylate salts glasses containing free-base TPPS, which is the active form for PHB, were prepared by controlling the melting condition. It was found that a preparation condition such as holding time of the melts affects the formation of the complex of the TPPS and that in the mixed metal–carboxylate salts melts the TPPS formed a complex with Li but did not form a complex with Na.     

Ceramic–metal and ceramic–polymer composites prepared by a biomimetic process

A biomimetic process was developed to prepare apatite–metal and apatite–polymer composites. A variety of metals and organic polymers incorporated surface functional groups such as Si–OH, Ti–OH or Ta–OH to induce formation of a biologically active bonelike apatite by chemical treatment or physical adsorption. Subsequent immersion in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma or 1.5 SBF led to the formation of a dense and uniform bonelike apatite layer on the surface. Apatite–metal and apatite–polymer composites prepared in this way are believed to be very useful as artificial bone substitutes.