Performance Improvement and Analysis of PtSi Schottky Barrier p-MOSFET Based on Charge Plasma Concept for Low Power Applications

This work reports a platinum silicide (PtSi) Schottky Barrier (SB) p-MOSFET (SB p-MOSFET) using charge plasma concept for low power applications. Here, we use two different materials to form source of the device. The source consists of two parts as primary source and extension. To consist source, PtSi and for extension, platinum metal is used. The proposed device is named as charge plasma (CP) SB p-MOSFET (CP SB p-MOSFET). The use of platinum extension induces the hole plasma near the source end. As a result, increased band bending reduces the SB width. This enhances the DC performance of the device. In addition, we have compared the DC and analog/RF performance of both the proposed device and the conventional SB p-MOSFET. It is observed that the proposed device exhibits improvement in on-state current (I_on), on- to off current ratio (I_ON/I_OFF), transconductance (g_m), cut-off frequency (f_t), product of gain and bandwidth (f_a) and transconductance generation factor (g_m/I_ds). We also optimized the performance of the device by modulating the work function and length of metal employed for extension. Moreover, the proposed device eliminated the doping, lowers the thermal budget requirement and unaffected from fluctuations due to randomly distributed dopant.

     

Influence of Annealing Temperature on Structural and dc Electrical Properties of SnO2 Thin Films for Schottky Barrier Diodes

This paper reports about the influence of annealing temperature on the structural, morphological, optical and electrical properties of SnO₂ thin films prepared by the spin-coating method. The structural analysis reveals the presence of rutile SnO₂ with tetragonal structure and its defects are reduced in higher annealing temperatures. SEM images show that the size of the grains was improved due to increase in annealing temperature. From UV-visible analysis, band gap energy (E_g), refractive index (n), and extinction coefficient (k) are estimated. The band gap energy increases from 3.46 to 3.54 eV with annealing temperatures. dc analysis shows that the Arrhenius conduction mechanism has a profound influence on the electrical conductivity and varies in the range 1.08–6.80 × 10^− 8(Ω cm)^− 1 with annealing temperature. The Al/n-SnO₂/p-Si Schottky barrier diode parameters such as ideality factor (n), barrier height (4Φ_B), leakage current (I₀) and series resistance (R_s) were studied by the I-V method as a function of annealing temperature as per the Thermionic Emission method (TE). The barrier height varies from 0.84 to 0.73 eV and the device ideality has improved at higher annealing temperature.

     

Properties of metal-polyaniline schottky barriers

In the present paper we report studies on metal-polyaniline (PAn) Schottky junctions where PAn is doped with various dopants such as hydrochloric acid (HCl), formic acid (HCOOH), iodine (I₂) and methylene blue (C₁₆H₁₈N₃SCl). The I-V characteristics for the different Schottky junctions have been reported. Electronic parameters such as Richardson constant, ideality factor, barrier height etc., have been calculated. © 1996 John Wiley & Sons, Inc.     

Investigation of electronic properties of graphene/Si field-effect transistor

We report a high-performance graphene/Si field-effect transistor fabricated via rapid chemical vapor deposition. Oligolayered graphene with a large uniform surface acts as the local gate of the graphene transistors. The scaled transconductance, g_m, of the graphene transistors exceeds 3 mS/μm, and the ratio of the current switch, I_on/I_off, is up to 100. Moreover, the output properties of the graphene transistor show significant current saturation, and the graphene transistor can be modulated using the local graphene gate. These results clearly show that the device is well suited for analog applications.     

Characterization of capacitance–voltage features of Ni/diamond Schottky diodes on oxidized boron-doped homoepitaxial diamond film

The electrical properties of Ni/diamond Schottky diodes fabricated on oxidized boron-doped homoepitaxial diamond film have been studied in order to investigate the electrical behavior of diamond-based electronic devices. The current–voltage (I–V) characteristics of the Ni–Schottky contacts to the boron-doped homoepitaxial diamond film show excellent rectification properties. The capacitance–voltage (C–V) features of the Ni/diamond Schottky diodes were characterized in the frequency range from 10⁻³ to 2×10⁵ Hz. The C–V measurements indicate that the space charge density (N_I) and built-in potential (V_d) values are approximately 6.0×10¹⁶ cm⁻³ and 1.25 V, respectively, and show weak frequency dependence in the range from 10⁻³ to 10⁴ Hz. Capacitance–frequency measurement at zero bias indicated that the degrading capacitance at high frequency (>10⁴ Hz) is primarily due to the high series resistance of the homoepitaxial diamond film.     

Scaling of Dopant Segregation Schottky Barrier Using Metal Strip Buried Oxide MOSFET and its Comparison with Conventional Device

In this paper, a Schottky barrier silicon-on-insulator (SOI) MOSFET with asymmetric doping (dopant segregated) at the source/drain side and a metal strip in the BOX (Buried oxide) layer has been proposed. The asymmetric doping reduces the off-state leakage (I_OFF) and improves the on-state drive current (I_ON) in comparison to the conventional structure. The metal strip inside the BOX improves the subthreshold swing and I_ON/I_OFF current ratio. The simulation study of a conventional device using an image force barrier lowering model and without image force barrier lowering is presented. The channel length scaling leads to a high on-current in the conventional device. The thermionic emission and tunneling current are increased with barrier lowering and hence a high leakage current in the off-state region. Moreover, the proposed device is compared with the conventional device. The proposed device shows high I_ON/I_OFF ratio of 10⁷-10⁸ at V_DS = 0.1 V and Subthreshold Swing (SS) of 66 mV/dec.     

Novolac epoxy resins and positron annihilation

Four kinds of epoxy resins: cresol novolac, tris-hydroxyphenylmethane, tetramethylbiphenol, and bisphenol A, were cured with phenol novolac epoxy resins. Characteristics of these epoxy compounds were studied by the positron annihilation lifetime (PAL) technique. Glass transition temperatures, thermal expansion coefficients, and volume of intermolecularspace holes among polymer chains were obtained from the lifetime, τ₃, of the long-lived component of ortho-positronium. It was revealed that, at the glass transition temperature, T_g, the volume of the hole created among polymer chains expanded 1.4 times the volume at room temperature. The smaller flexural modulus of tris-hydroxyphenylmethane than that of the other samples was explained by the volume of intermolecular-space holes obtained from τ₃. Aging effects were seen in the data of the intensities, I₃, of ortho-positronium, which became smaller after heating the samples above T_g. I₃ and τ₃ were strongly affected by the density of cross-linkings, and their chemical structures. The larger the density of cross-linkings, the smaller I₃ and higher T_g were obtained. Epoxy compounds with the higher water-absorption rates had larger intermolecular-space holes. © 1993 John Wiley & Sons, Inc.     

Iodide/triiodide electrochemistry in ionic liquids: Effect of viscosity on mass transport, voltammetry and scanning electrochemical microscopy

The electrochemistry of I⁻/I₃⁻ was studied in ionic liquids using a combination of cyclic voltammetry, chronoamperometry and scanning electrochemical microscopy (SECM). The electrolytes were 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C_nC₁Im][Tf₂N], ionic liquids (where n = 2, 4 and 8) and I⁻ was typically added at a concentration of approximately 11 mM. During cyclic voltammetry, two sets of peaks were observed in each ionic liquid due to oxidation and reduction of the I⁻/I₃⁻ redox couple and oxidation/reduction of the I₃⁻/I₂ redox couple. The diffusion coefficients of I⁻ and I₃⁻, as determined using chronoamperometry, increased with increasing temperature and decreased with increasing ionic liquid viscosity. The effect of ionic liquid viscosity on ultramicroelectrode (UME) voltammetry was also determined using the I⁻/I₃⁻ redox couple. Steady-state behaviour was observed at 1.3 μm UMEs at slow voltammetric scan rates and steady-state SECM feedback approach curves were also obtained at a 1.3 μm Pt SECM tips, provided that the tip approach speed was sufficiently low.     

Magnetic properties of Co3O4 polycrystal powder

The results of investigations of magnetic properties of Co₃O₄ polycrystals in powder morphology with average crystallite size of 10 µm are presented. The temperature dependence of the magnetic susceptibility, measured in a wide temperature interval (1.5≤T≤400 K) using SQUID magnetometer, as well as electron spin resonance (ESR) spectra measured at X-band and Q-band frequency ranges have been studied. Antiferromagnetism with a Néel temperature T_N at about 39 K was observed from the analysis of evolution of molar magnetic susceptibility and ESR intensity as a function of temperature. ESR parameters namely g-factor, intensity (I_ESR), g-value, and linewidth ΔH for powder Co₃O₄ have been obtained. Some deviations from the expected values of some magnetic properties were determined and discussed.     

Fabrication of single-walled carbon nanotube Schottky diode with gold contacts modified by asymmetric thiolate molecules

We have fabricated single-walled carbon nanotube (SWCNT) Schottky diodes by asymmetrically modifying the two Au/SWCNT contacts using different thiolate molecules, methanethiol (CH₃SH) and trifluoroethanethiol (CF₃CH₂SH). Characterization has revealed that highly asymmetrical contacts with Schottky barrier heights of ∼190 and ∼40 meV (increased by over 70% and decreased by over 60%, respectively with respect to that of pristine Au/SWCNT contact of ∼110 meV) were achieved for the Au/SWCNT contacts modified by CH₃SH and CF₃CH₂SH, respectively. The performance of our SWCNT Schottky diodes is as follows: the forward and reverse current ratio (I_forward/I_reverse) higher than 10⁴, a forward current as high as ∼5 μA, a reverse leakage current as low as ∼100 pA, and a current ideality factor as low as ∼1.42. This is at least comparable to, if not better than SWCNT Schottky diodes fabricated with asymmetrical metals, where one contact is a metal with a work function lower than that of SWCNTs to yield a Schottky contact, while the other has a work function higher than that of SWCNTs to achieve an ohmic (more near ohmic) contact.     

Improvement of Subthreshold Characteristics of Dopingless Tunnel FET Using Hetero Gate Dielectric Material: Analytical Modeling and Simulation

An improved subthreshold analytical model of Dual Material Double Gate Junctionless Tunnel FET (DMDG JLTFET) with stacked / hetero-dielectric gate oxide structure is proposed. The stacked gate oxide structure comprises of Silicon-dioxide (SiO₂) and Titanium Oxide (TiO₂). The high-K gate stack engineered device overcomes the Short Channel Effects (SCEs) caused by the ultrathin silicon devices. The subthreshold analysis is carried out by solving a two-dimensional Poisson’s equation using Parabolic approximation method. These characteristics are analyzed against various device parameters. Also, the impact of different high-K gate oxide materials with SiO₂ is also studied. A comparative analysis of short channel effects for DMDG TFET and DMDG JLTFET has been carried out. The results reveal that the proposed device provides better I_ON current, low leakage current and improved Transconductance-to-drain current ratio. Using TCAD Sentaurus device simulator, the subthreshold analytical model results have been simulated and verified with other TFET models.

     

Vitrification effect on the curing reaction of epoxy resin

Summary The curing reaction of diglycidyl ether of Bisphenol A(DGEBA) with triethylene tetramine(TETA) was studied by the differential scanning calorimetry(DSC). The reaction was affected as the vitrification occurred when the glass transition temperature(T_g) of the reaction mixture exceeded the curing temperature. In order to describe the curing reaction in the rubbery state as well as in the glassy state, the reaction kinetic equation containing the generalized WLF equation term was proposed and the parameters were determined from the DSC data.Nomenclature a_T time temperature shift factor, dimensionless - A_T temperature dependent frequency factor, /sec - A_Tg temperature dependent frequency factor at T_g, /sec - A_To temperature dependent frequency factor at T_g, /sec - A empirical parameter in temperature dependent frequency factor, dimensionless - B empirical parameter in temperature dependent frequency factor, K - C₁ empirical parameter in the generalized WLF equation, dimensionless - C₂ empirical parameter in the generalized WLF equation, K - D correction parameter in temperature dependent frequency factor, K - E activation energy, cal/mole - E_x/E_m ratio of lattice energies for crosslinked and uncrosslinked polymer, dimensionless - F_x/F_m ratio of segmental mobilities for crosslinked and uncrosslinked polymer, dimensionless - H_t cumulative heat generated up to time t, cal/g - H_RXN heat of reaction under complete conversion, cal/g - n reaction order, dimensionless - S _r scan rate of the DSC experiment, °C/sec - t time, second - T temperature, K - T_g glass transition temperature of the partially cured reaction mixture, K - T_go glass transition temperature of uncured reactant, 253 K - X conversion, dimensionless     

High crystalline tungsten trioxide thin layer obtained by SPD technique

A nanostructured layer of tungsten oxide, WO₃, was prepared by a spray pyrolysis deposition (SPD) method using (NH₄)₂WO₄ precursor. The films were investigated in order to determine the electrical behaviour (impedance, Mott–Schottky and I–V) and the morphological characteristics (SEM). The XRD analysis reveals that tungsten oxide is present in monoclinic phase but the orthorhombic phase is also expected to be present in the structure of WO₃ crystals. Changes in conductivity of the WO₃ films have been observed after immersion in water.     

Near‐Infrared and Upconversion Luminescence in Er:Y2O3 Ceramics under 1.5 μm Excitation

Results of the spectroscopic characteristics and upconversion luminescence in Er³⁺ doped yttria (Y₂O₃) transparent ceramics prepared by a modified two‐step sintering method are presented. The near‐infrared (1.5 μm) luminescence properties were evaluated as a function of Er³⁺ concentration. Judd–Ofelt intensity parameters, radiative rates, branching ratios, and emission lifetimes were determined and compared with results reported for Er³⁺‐doped Y₂O₃ single crystal and nanocrystals. Following pumping at 1.532 μm, weak blue (~0.41 μm, ²H_9/2 → ⁴I_15/2), strong green (~0.56 μm, ²H_11/2, ⁴S_3/2 → ⁴I_15/2), and red (~0.67 μm, ⁴F_9/2 → ⁴I_15/2) emission bands were observed as well as weak near‐infrared emissions at 0.8 μm (⁴I_9/2 → ⁴I_15/2) and 0.85 μm (⁴S_3/2 → ⁴I_13/2) at room temperature. The upconversion luminescence properties under ~1.5 μm pumping were further investigated through pump power dependence and decay time studies. Sequential two‐photon absorption leads to the ⁴I_9/2 upconversion emission, whereas energy‐transfer upconversion is responsible for the emission from the higher excited states ²H_9/2, ²H_11/2, ⁴S_3/2, and ⁴F_9/2. The enhanced red emission with increasing Er³⁺ concentration most likely occurred via the cross‐relaxation process between (⁴F_7/2 → ⁴F_9/2) and (⁴I_11/2 → ⁴F_9/2) transitions, which increased the population of the ⁴F_9/2 level.     

Dynamic study of free volume properties in polyethylene/styrene butadiene rubber blends by positron annihilation lifetime method

Positronium (Ps) formation in low and high‐density polyethylene (LDPE and HDPE) and styrene butadiene rubber (SBR), as well as in their blends (LDPE/SBR: 50/50 and HDPE/SBR: 50/50) has been investigated by positron annihilation lifetime (PAL) measurements as a function of low temperature (100–300 K). The glass transition temperature (T_g) for the initial polymers and their blends are determined by ortho‐positronium (o‐Ps) lifetime, τ₃ versus temperature as well as by differential scanning calorimetry (DSC) measurements. The temperature dependence of nanoscale free volume size shows similar trend for all the investigated samples indicating an abrupt change at T_g, which is found to be higher for SBR sample characterized by its high chain mobility. In addition, The T_g values deduced from PAL measurements are compared with the corresponding data deduced from DSC. The variation of o‐Ps formation probability I₃ versus temperature for polyethylene and their blends were interpreted in the frame work of spur reaction model of Ps formation. On the other hand, the lifetime coefficient below and above T_g is found to be one order of magnitude larger than the linear expansion coefficient. This constitutes evidence that Ps is only probing free volumes. The results obtained from change in free volume–hole distribution with temperature reflect both thermal expansion and increase in free volume–hole size with the rise in temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrical properties of conductive rubber blends subjected to solvent penetration

Abstract

The influence of solvent uptake (%) on the electrical resistivity S of ethylene propylene diene monomer rubber (EPDM)/acrylonitrile butadiene rubber (NBR) blends filled with different concentrations of high abrasion furnace carbon black has been studied. The effects of the EPDM/NBR weight ratio and carbon black content on the room temperature resistivity of the composites were elucidated in detail. The performance of these sensors depends on a number of parameters, including the geometry and concentration of the conductive component dispersed in the polymer. Direct current current–voltage I–V characteristics of the filled rubber blends were studied at room temperature. The current–voltage relationship can be expressed as I?=?AV^B, where A and B are constants that show capability and property of electrical conduction respectively. The I–V curve can be divided into ohmic and non-ohmic regions. A number of important parameters, namely, Schottky and Poole–Frenkel effects, have been determined.     

A wide temperature insensitive piezoceramics for high-temperature energy harvesting

One of the key challenges in the development of high-temperature energy harvesting (HTEH) technology is to clarify the relationship between temperature-dependent material parameters and device power generation capabilities. However, at present, the research on temperature stability of piezoceramics mainly relies on thermal annealing technology, which cannot follow the actual temperature dependence of the piezoelectricity, and it is even more difficult to predict the temperature stability of HTEH. To shed light on this field, here, (1−x)BiScO₃–xPbTiO₃ system was chosen for building HTEH material, and the temperature-dependent electrical parameters, such as d₃₃, ε_r, and g₃₃, have been measured by multiple in situ techniques. It was found that the synergistic effect of d₃₃ and ε_r with temperature helps to obtain a stable g₃₃ value in a wide temperature range. Moreover, in the mode of the cantilever-type energy harvester, a stable output voltage was obtained at x = 0.64 harvester with <20% change over a broad temperature range of 100-250°C, and it was verified that the temperature stability of g₃₃ is crucial to the operation stability of HTEH devices.     

Green and red upconversion luminescence of Er-doped K0.5Na0.5NbO3 ceramics

Er³⁺ doped K_0.5Na_0.5NbO₃ (KNN) lead-free piezoelectric ceramics were synthesized by the solid-state reaction method. The upconversion emission properties of Er³⁺ doped KNN ceramics were investigated as a function of Er³⁺ concentration and incident pumping power intensity. Bright green (~555 nm) and red (670 nm) upconversion emission bands were obtained under 980 nm excitation at room temperature, which are attributed to (²H_11/2, ⁴S_3/2)→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions, respectively. The upconversion emission intensity can be adjusted by changing Er³⁺ concentration, and the mechanism of upconversion processes involve not only a two-photon absorption but also a three-photon absorption. In addition to the admirable intrinsic piezoelectric properties of KNN, this kind of material may have potential application as a multifunctional device by integrating its upconversion and piezoelectric property.     

AN ELECTROCHEMICAL STUDY OF SOLUBLE COPOLYMER OF ETHYL CARBAZOLE WITH N-METHYL PYRROLE AND 3-METHYL THIOPHENE

Copolymers of N-ethyl Carbazole (ECZ) with N-Methyl Pyrrole (N-MPy) and 3-Methyl Thiophene (3-MTh) were synthesized on platinum substrate and electrochemical investigation of polymeric films was performed. The characterization of homopolymer and copolymer films was performed by electrochemical methods (i.e. polarization curves and cyclovoltammetric measurements), solid-state conductivity measurements and spectrophotometric methods comparatively. A possible scheme for the copolymerization has been suggested. Solid state conductivity of PECz can be improved by inclusion of 3MTh and NMPy into chain. The ionization potentials, I_p, electron affinity, E_a, optical band gap, E_g, peak potentials, E_p, and doping degrees, y, of copolymer electrodes were calculated from these measurements. Copolymer electrodes have lower I_p, E_g, E_p values and better switching properties in accordance with homopolymer electrodes. Presence of alkyl group gives solubility to copolymers obtained both chemically and electrochemically.