Electrical parameters of Schottky contacts in CaCu3Ti4O12 thin film capacitors

CaCu₃T_i4O₁₂ (CCTO) thin films were grown by pulsed laser deposition on Pt and La_0.9Sr_1.1NiO₄ (LSNO) bottom electrodes. The electrical characteristics of the CCTO/Pt and CCTO/LSNO Schottky junctions have been analyzed by impedance spectroscopy, capacitance–voltage (C–V) and current–voltage (I–V) measurements as a function of frequency (40 Hz–1 MHz) and temperature (300–475 K). Similar results were obtained for the two Schottky diodes. The conduction mechanism through the Schottky junctions was described using a thermionic emission model and the electrical parameters were determined. The strong deviation from the ideal I–V characteristics and the increase in capacitance at low frequency for ?0.5 V bias are in agreement with the presence of traps near the interfaces. Results point toward the important effect of defects generated at the interface by deposition of CCTO.     

The effect of thermomechanical treatment regimes on microstructure and mechanical properties of V–Me(Cr,W)–Zr–C alloys

The regularities of the formation of a heterophase structure in dispersion-strengthened vanadium V–Me(Cr, W)–Zr–C alloys are studied as a function of the regimes of their thermomechanical treatment. The regimes of treatment providing a substantial increase in the dispersity and homogeneity of spatial distribution of ZrC particles, temperature of recrystallization, and high-temperature (at T = 800°C) short-time strength are found in comparison to conventional treatment regimes.     

Defect density reduction of the Al2O3/GaAs(001) interface by using H2S molecular beam passivation

The integration of higher carrier mobility materials to increase drive current capability in the next CMOS generations is required for device scaling. But a fundamental issue regarding the introduction of high-mobility III–V in CMOS is the electrical passivation of the interface with the high-κ gate dielectric. In this work, we show that in situ H₂S surface treatment on GaAs(001) leads to a stable and reorganized oxide/III–V interface. The exposition of the GaAs surface is monitored in situ by RHEED and the interface is characterized by XPS analyses. Finally, MOS capacitors are fabricated to extract interface state density over the band gap. These results highlight a promising re-interest in chalcogenide passivation of III–V surfaces for CMOS applications.     

Effect of 100 MeV Si7+ ions’ irradiation on Pd/n-GaAs Schottky diodes

Pd/n-GaAs realized devices (junction made on a virgin substrate prior to irradiation) and Pd/n-GaAs fabricated devices (junction realized after the virgin substrate irradiation) have been irradiated with 100?MeV Si⁷⁺ ions for the varying fluence of 10¹²–10^13?ions/cm². The devices have been characterized by I–V and C–V techniques for an electrical response. The electrical characterization of these devices shows the presence of interfacial layer. Moreover, the C–V characteristics show strong frequency dependence behavior, which indicates the involvement of interfacial charge layer with deep electron states. The hydrogenation of these devices has not caused any significant change in the electrical (I–V and C–V) characteristics. The observed results have been discussed in the realm of radiation-induced defects, which cause the carrier removal and compensation phenomena to cause the observed high resistivity and filling and unfilling of these traps’ level to cause strong frequency dependence behavior.     

Study of radiation damage induced by 12 keV X‐rays in MOS structures built on high‐resistivity n‐type silicon

Imaging experiments at the European X‐ray Free Electron Laser (XFEL) require silicon pixel sensors with extraordinary performance specifications: doses of up to 1 GGy of 12 keV photons, up to 10⁵ 12 keV photons per 200 µm × 200 µm pixel arriving within less than 100 fs, and a time interval between XFEL pulses of 220 ns. To address these challenges, in particular the question of radiation damage, the properties of the SiO₂ layer and of the Si–SiO₂ interface, using MOS (metal‐oxide‐semiconductor) capacitors manufactured on high‐resistivity n‐type silicon irradiated to X‐ray doses between 10 kGy and 1 GGy, have been studied. Measurements of capacitance/conductance–voltage (C/G–V) at different frequencies, as well as of thermal dielectric relaxation current (TDRC), have been performed. The data can be described by a dose‐dependent oxide charge density and three dominant radiation‐induced interface states with Gaussian‐like energy distributions in the silicon band gap. It is found that the densities of the fixed oxide charges and of the three interface states increase up to dose values of approximately 10 MGy and then saturate or even decrease. The shapes and the frequency dependences of the C/G–V measurements can be quantitatively described by a simple model using the parameters extracted from the TDRC measurements.     

Electrical conduction mechanism of polyvinylidenefluoride (PVDF) – polysulfone (PSF) blend film

The electrical conductivity of polyvinylidenefluoride (PVDF) – polysulfone (PSF) blend films have been measured by studying the I–V characteristics in the temperature range of 298–398 K. The results are shown by measuring the dependence of current on field, temperature, and blending compositions in the form of I–V characteristics and analysis has been made by interpretation of Poole–Frenkel, Schottky ln (J) vs. T plots, Richardson and Arrhenius plots. For individual polymers, the conduction mechanism observed to be a Poole–Frenkel type. On blending, the charge conduction appears to be the Schottky emission at lower temperature while Poole–Frenkel mechanism at higher temperature. The analysis of these results suggests that Pool–Frenkel mechanism is mainly responsible for the observed conduction. The conductivity was found to increase with an increase in the polysulfone concentration in the blend; it could be justified in terms of mobility of charge carriers. It is found that mobility of charge carriers increases with the increase in polysulfone concentration in the blend.     

Effect of dimethyl sulfoxide on the electrical properties of PEDOT:PSS/n-Si heterojunction diodes

Effect of dimethyl sulfoxide (DMSO) on the electrical properties of PEDOT:PSS/n-Si heterojunction diodes has been studied. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) was deposited on n-type Si wafer using facile process of spin coating. The DMSO content was varied from 0 to 8 vol%. Electrical characterization of these heterojunction diodes as performed using both current–voltage (I–V) and capacitance–voltage (C–V) measurements. All diodes showed rectifying behavior. AFM measurement revealed that the surface became more rough after the DMSO treatment of PEDOT:PSS films. The RMS values were found in the range of 4–6 nm. The resistivity of the PEDOT:PSS films decreased with increase in temperature. The addition of DMSO into PEDOT:PSS solution results in a decrease in resistivity of films by approximately two orders of magnitude. PEDOT:PSS films showed high transmission more than 85% in the entire visible region. Raman spectroscopy indicated effect of the DMSO treatment on the chemical structure of PEDOT chains, suggesting a conformational change of PEDOT chain in the film. An optimal value of DMSO was obtained with 5 vol% content, and it showed the best PEDOT:PSS films properties and good quality heterojunction diodes characteristics with ideality factor of 2.4 and barrier height 0.80 eV.     

Thickness dependent supercapacitor behaviour of sol-gel spin coated nanostructured vanadium pentoxide thin films

Vanadium pentoxide thin films of various thicknesses have been prepared by sol-gel spin coating method on glass and conducting substrates. X-ray diffraction analysis reveals crystalline nature for the 6–12 layered films (170–310?nm). The crystalline films indicate a preferential orientation of the crystallites along the (200) plane. FTIR studies of the V₂O₅ xerogel show the presence of V–O–V and V=?O bond confirming the formation of V₂O_5. The scanning electron microscope images reveal formation of nanostructures in the 6–12 layered films. Optical absorption studies indicate a band gap of 2.2–2.5?eV. Pseudocapacitance behaviour of the V₂O₅ films was studied using cyclic voltammetric technique and impedance analysis. V₂O₅ films of thickness 202?nm (8 layers) exhibit a specific capacitance of 346?F/g at a scan rate of 5?mV/s.     

Microstructure and mechanical properties of V–4Ti–4Cr alloy as a function of the chemical heat treatment regimes

The regularities of the formation of a heterophase structure and mechanical properties of V–4Ti–4Cr alloy as a function of thermomechanical and chemical heat treatments are studied. The regimes of thermomechanical treatment which provide the formation of a heterophase structure with a homogeneous volume distribution of oxycarbonitride nanoparticles with a size of about 10 nm and an increase in the volume content and thermal stability of this phase and which provide an increase in the temperature of alloy recrystallization are developed. The formation of the heterophase structure results in a substantial (up to 70%) increase in the short-term high-temperature strength of the alloy at T = 800°C. The increase in the strength is achieved while keeping a rather high level of plasticity.     

High-rate erosion of Ti–6Al–4V ultrafine-grained titanium alloy obtained via intensive plastic torsional deformation

Testing results for Ti–6Al–4V ultrafine-grained titanium alloy obtained via intensive plastic torsional deformation (IPTD) are presented. To estimate the effect of IPTD treatment on the behavior of this material under erosion conditions, special experimental techniques were developed. The ultrafine-grained alloy was tested alongside with the traditional coarse-grained titanium alloy in an erosion wind tunnel in an air flow with corundum particles as an abrasive material. The erosion resistance of the material was estimated from the mass loss of specimens. Despite a considerable increase in the static strength characteristics, the nanostructured material did not demonstrate any increase in its erosion resistance in comparison with the initial alloy.     

Effects of Cr and V impurities on cohesion properties of Pd/TiAl interfaces

First principles calculations reveal that for Pd/TiAl interfaces the substitution of interface Ti atoms with Cr or V atoms is energetically favorable with negative heat of formation, and could bring about a very small increase of interface bond strength, while the interstitial Cr and V atoms should be unfeasible with highly positive heat of formation and would increase the bond lengths of interface Pd–Al and Pd–Ti bonds. Calculations also demonstrate that both Cr and V would induce an increase of interface energy, suggesting that the impurity atoms of Cr or V should be reduced to a minimum level, in order to get a thermally stable Pd/TiAl interface with a longer lifetime. In addition, it is found that the substitution of V at the Pd/TiAl interfaces should be much easier than that of Cr, which is in good agreement with similar experimental observations in the literature.     

Analysis of electrical characteristics of Er/p-InP Schottky diode at high temperature range

We report on the temperature-dependent electrical characteristics of Er/p-InP Schottky barrier diodes. The current–voltage (I–V) and capacitance–voltage (C–V) measurements have been carried out in the temperature range of 300–400 K. Using thermionic emission (TE) theory, the zero-bias barrier height (Φ_bo) and ideality factor (n) are estimated from I–V characteristics. It is observed that there is a decrease in n and an increase in the Φ_bo with an increase in temperature. The barrier height inhomogenity at the metal/semiconductor (MS) interface resulted in Gaussian distribution of Φ_bo and n. The laterally homogeneous Schottky barrier height value of approximately 1.008 eV for the Er/p-InP Schottky barrier diodes is extracted from the linear relationship between the experimental zero-bias barrier heights and ideality factors. The series resistance (R_s) is calculated by Chenug's method and it is found that it increases with the decrease in temperature. The reverse-bias leakage current mechanism of Er/p-InP Schottky diode is investigated. Both Poole–Frenkel and Schottky emissions are described and discussed. Furthermore, capacitance–voltage (C–V) measurements of the Er/p-InP Schottky contacts are also carried out at room temperature in dark at different frequencies of 10, 100 and 1000 kHz. Using Terman's method, the interface state density is calculated for Er/p-InP Schottky diode at different temperatures.     

Mössbauer studies of a martensitic transformation and of cryogenic treatments of a D2 tool steel

A D2 tool steel X153CrVMo12 with composition C1.53 Cr12 V0.95 Mo0.80 Mn0.40(wt% Fe balanced) was studied by use of Mössbauer spectroscopy and X-ray diffraction. It was observed that the study of carbides by X-ray diffraction was difficult while Mössbauer spectroscopy gives some light on the process occurring during cryogenic treatment. With the increase of the martensitic phase the carbides decrease and are dissolved in solid solution of martensite as well as the chromium element.     

Decontamination Effectiveness of Ferrocyanides in Irradiated Rats Contaminated Internally with Radiocesium

The experiment was performed on 192 Wistar rats irradiated with 154.5 mC kg^?1. Therefore, the animals were divided into 5 groups and were treated as follows: group I, controls, with Cs-137; groups II and III with Cs-137 followed by 2-fold administration of ferric ferrocyanide (FF) and ammonium ferric-cyanoferrate (AFCF), respectively; groups IV and V with Cs-137 followed by 6-fold and 10-fold administration of FF and AFCF, respectively. Organ and muscle (16 samples) concentrations of Cs-137 in groups I–III were measured on days 1, 3, 5 and 7, and those of groups IV – V on day 7 after the contamination. The results indicated that in rats contaminated internally with Cs-137 one day post irradiation 2-fold treatment with FF and AFCF in the day resulted in a similar and significant decrease of Cs-137, whereas manyfold treatment (6× or 10×) with these agents did not increase their decontamination effectiveness.     

Bias temperature instability analysis on memory properties improved by hydrogen annealing treatment in Ti/HfOx /Pt capacitors

The influence of the hydrogen annealing treatment on the reliability of Ti/HfO_x /Pt capacitors is investigated by analyzing bias temperature instability (BTI). As compared to the N₂‐annealed sample, in the case of hydrogen‐annealed samples, both the set/reset voltages and currents are reduced from 6.5 V/–1.6 V to 3.8 V/–1.2 V and from 4 mA/170 nA to 800 µA/30 nA at 0.1 V, respectively. Of particular interest is the dramatic reduction in the set voltage variation from 3.3 V to 1.8 V. In addition, in BTI experiments, the current shift at the high resistance state (HRS) is reduced from 1.5 µA to 40 nA under a bias stress of –1 V/1000 s and from 40 µA to 0.5 µA under a temperature stress of 120 °C/1000 s. These results show that the hydrogen annealing treatment is very effective in improving the reliability of RRAM cells because it reduces the leakage current under bias temperature stress. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Improved characteristics for MOHOS memory with oxygen-rich GdO as charge storage layer annealed by NH3

Characteristics of metal–oxide–high-k–oxide–silicon (MOHOS) memories with oxygen-rich or oxygen-deficient GdO as charge storage layer annealed by NH₃ or N₂ are investigated. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used to analyze the cross-sectional quality, composition and crystallinity, respectively, of the stacked gate dielectric with a structure of Al/Al₂O₃/GdO/SiO₂/Si. The MOHOS capacitor with oxygen-rich GdO annealed in NH₃ exhibits a good trade-off among its memory properties: large memory window (4.8 V at ±12 V, 1 s), high programming speed (2.6 V at ±12 V/100 μs), good endurance and retention properties (window degradation of 5 % after 10⁵ program/erase cycles and charge loss of 18.6 % at 85 °C after 10 years, respectively) due to passivation of oxygen vacancies, generation of deep-level traps in the grain boundaries of the GdO layer and suppression of the interlayer between GdO and SiO₂ by the NH₃ annealing.     

Effects of ultrasonic and graft treatments on grafting degree,structure, functionality,and digestibility of rapeseed protein isolate-dextran conjugates

Rapeseed protein isolate (RPI) and dextran conjugates were prepared by traditional and ultrasonic assisted wet-heating. The effects on the grafting degree (GD), structure, functionality, and digestibility of conjugates were studied. Ultrasonic frequency, temperature, and time all significantly affected the GD. Under the optimum conditions (temperature of 90 °C and time of 60 min), compared to traditional wet-heating, ultrasonic treatment at 28 kHz significantly increased the GD by 2.12 times. Compared to RPI, surface hydrophobicities of conjugates were significantly decreased by graft and ultrasonic treatments. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and amino acid composition results confirmed that traditional graft reaction involved cysteine (Cys) and lysine (Lys) whereas the ultrasonic assisted one involved only Cys. Both were from the 12S globulin subunit and cruciferin. Fourier transform infrared spectrum (FT-IR) and circular dichroism (CD) results showed that graft treatment significantly changed secondary structure and ultrasonic treatment had the greatest impact on the decrease in the β-sheet (19.1%) and the increase in the random coil (49.6%). Graft and ultrasonic treatments both made surface structure looser and more porous. The two treatments also caused molecular weight to become bigger, and ultrasonic treatment had the greatest effect on the increase (68.2%) in 110–20.5 kDa. Structural modifications of RPI by grafting to dextran caused improvements of solubility (at pH 5–6), emulsifying activity (at pH 4–10), emulsion stability (at pH 4–5 and 9–10), and thermal stability (at temperature 90–100 °C). The digestibility of conjugates was decreased by graft and ultrasonic treatments and the conjugates were mainly digested in the intestinal phase. The ultrasonic assisted wet-heating was an efficient and safe method for producing RPI-dextran conjugates and improving the utilization value of rapeseed meal.     

Resistive switching in a negative temperature coefficient metal oxide memristive one-port

A current-controlled memristive one-port was constructed from cobalt monoxide (CoO) using a traditional solid reaction method at 1150 °C in argon atmosphere. Hysteretic current–voltage (I–V) characteristics and resistance switching were investigated in the as-obtained Ag/CoO/Ag cell. Dependences of the I–V loop on voltage range (0 to 10, 11, and 12 V), voltage scan rate (0.1, 1, and 10 V/s), and temperature (323, 373, and 423 K) were reported. A thermistor model for materials with negative temperature coefficient (NTC) was proposed for explanation of the mechanism. An ideal NTC thermistor-based memristive one-port would broaden the applications of memristors and memristive devices.     

The metals chemical states in hydrated vanadium oxides

The X-ray photoelectron spectroscopy (XPS) spectra of hydrated vanadium oxides (VO)Mo(x)V(12-x).nH(2)O (x=0, 1, 2, 3) were studied to provide the vanadium ions reduction ratio (RR)=V(4+)/(V(4+)+V(5+)) dependence on the molybdenum ions concentration and thermal treatment. The vanadium valence does not depend on Mo doping (x相似文献   

Crystallographic features of the approximant H (Mn7Si2V) phase in the Mn–Si–V alloy system

The intermetallic compound H (Mn₇Si₂V) phase in the Mn–Si–V alloy system can be regarded as an approximant phase of the dodecagonal quasicrystal as one of the two-dimensional quasicrystals. To understand the features of the approximant H phase, in this study, the crystallographic features of both the H phase and the (σ → H) reaction in Mn–Si–V alloy samples were investigated, mainly by transmission electron microscopy. It was found that, in the H phase, there were characteristic structural disorders with respect to an array of a dodecagonal structural unit consisting of 19 dodecagonal atomic columns. Concretely, penetrated structural units consisting of two dodecagonal structural units were presumed to be typical of such disorders. An interesting feature of the (σ → H) reaction was that regions with a rectangular arrangement of penetrated structural units (RAPU) first appeared in the σ matrix as the initial state, and H regions were then nucleated in contact with RAPU regions. The subsequent conversion of RAPU regions into H regions eventually resulted in the formation of the approximant H state as the final state. Furthermore, atomic positions in both the H structure and the dodecagonal quasicrystal were examined using a simple plane-wave model with 12 plane waves.