Responses of Pt/n-InP Schottky diode to electron irradiation in different temperature conditions

Different radiation and temperature effects on Schottky diodes are technologically important from radiation to sensing applications. We discussed irradiation and temperature dependent electronic properties of Pt/n-InP Schottky contact. Firstly we fabricated Pt/n-InP Schottky diode by magnetron sputtering technique. Then sample was exposed to 12 MeV electron irradiation. We measured I–V characteristics in 20, 160, 300 and 400 K before and after irradiation. Changes in forward currents for 160, 300 and 400 K were not remarkable but irradiation was effective only in 20 K slightly. Reverse currents of Pt/n-InP Schottky diode were increased in 20, 160, 300 and 400 K by irradiation.     

Polyaniline/gallium doped ZnO heterostructure device via plasma enhanced polymerization technique: Preparation, characterization and electrical properties

The ZnO and gallium-doped ZnO nanoparticles (NPs) were synthesized by simple chemical method and used for the fabrication of p-polyaniline/n-ZnO heterostructures devices in which polyaniline was deposited by plasma-enhanced polymerization. The increment in the crystallite sizes of gallium doped ZnO nanoparticles from ~21.85 nm to ~32.39 nm indicated the incorporation of gallium ion into the ZnO nanoparticles. The surface and structural studies investigated the participation of protonated N atom for the bond formation between polyaniline and gallium-ZnO through partial hydrogen bonding. Compared to a Pt/polyaniline/ZnO diode, the fabricated Pt/polyaniline/gallium-ZnO heterostructure diode exhibited good rectifying behavior with Current–Voltage characteristics of improved saturation current, low ideality factor, and a high barrier height might due to the efficient charge conduction via gallium ion at the junction of the polyaniline/gallium doped-ZnO interface.

<Superscript>63</Superscript>Ni schottky barrier nuclear battery of 4H-SiC

The design, fabrication, and testing of a 4H-SiC Schottky betavoltaic nuclear battery based on MEMS fabrication technology are presented in this paper. It uses a Schottky diode with an active area of 3.14 mm² to collect the charge from a 4 mCi/cm^{2 63}Ni source. Some of the critical steps in process integration for fabricating silicon carbide-based Schottky diode were addressed. A prototype of this battery was fabricated and tested under the illumination of the ⁶³Ni source with an activity of 0.12 mCi. An open circuit voltage (V _OC) of 0.27 V and a short circuit current density (J _SC) of 25.57 nA/cm² are measured. The maximum output power density (P _max) of 4.08 nW/cm² and power conversion efficiency (η) of 1.01% is obtained. The performance of this battery is expected to be significantly improved by using larger activity and optimizing the design and processing technology of the battery. By achieving comparable performance with previously constructed p–n or p–i–n junction energy conversion structures, the Schottky barrier diode proves to be a feasible approach to achieve practical betavoltaics.     

RECTIFYING EFFECT OF POLYANILINE(PANI)/N-TYPE POROUS SILICONE HETEROJUNCTION*

Heterojunctions between polyaniline (PANI) and n-type porous silicon (PS), Al/PS-PANI/Au cell,were fabricated, and the rectifying parameters of this heterojunction diode were measured as a function of thepreparation conditions of PANI and PS, the electronic structure of PANI as well as cell structure. Therectifying parameters of Al/PS-PANI/Au cell were determined to be γ= 1 .8×10~1～ 1 .0×10~5 for the rectifyingratio at 3V, n = 3 ～12 for the ideal factor,j_0 = 8.0×10~(-5)～5.6×10~(-2) mA/cm~2 for the reversed saturated currentdensity, and φ_b = 0.67～ 0.83 V for the barrier height, respectively. The best rectifying heterojunction diodemade between PANI and n-type PS with higher rectifying factor (γ= 1 .0×10~5 at 3V ), output current (>1500mA/cm~2 at 3V) and lower ideal factor (n = 3.3) was obtained by preventing the oxidation of PS beforeevaporating Al electrode.     

Studies of nanocomposite of Polyaniline with gold nanoparticles and Schottky junction with aluminium for electrical and CO2 gas sensing properties

Gold nanocomposite of Polyaniline was prepared by chemical synthesis method and its thin film was made by drop casting. The Schottky junction of thin film was fabricated with aluminium metal. TGA analysis of the sample showed good stability. Current density-voltage characteristics of the junction showed good rectifying nature. The diode ideality factor is greater than unity. The junction showed good sensitivity to CO₂ gas with decrease of forward current. The response time of the junction to CO₂ showed good repeatability and recovery time is about 52 s.     

Application of polysulfone (PSf)– and polyether ether ketone (PEEK)–tungstophosphoric acid (TPA) composite membranes for water electrolysis

The ion exchange membrane using polysulfone (PSf) and polyether ether ketone (PEEK) as a basic material was prepared to apply in the polymer electrolyte membrane electrolysis (PEME). The sulfonated block copolymer of PSf and poly(phenylene sulfide sulfone) (SPSf-co-PPSS) and the sulfonated PEEK (SPEEK) were blended with tungstophosphoric acid (TPA) to avoid water swelling at elevated temperatures led to decrease in mechanical strength. These prepared ion exchange membranes showed some interesting characteristics including physicochemical stabilities, mechanical and membrane properties.The prepared ion exchange membrane was utilized to prepare the membrane electrode assembly (MEA). MEA consisted of Pt/PEM/Pt was prepared by equilibrium and non-equilibrium impregnation–reduction (I–R) methods. The prepared MEA by non-equilibrium I–R method was used in the PEME unit cell. The cell voltages of the MEA using SPSf-co-PPSS/TPA and SPEEK/TPA membranes were 1.83 V and 1.90 V at 1 A/cm² and 80 °C, with platinum loadings of 1.12 and 1.01 mg/cm², respectively.     

ZnO:Al thin films used in ZnO: Al/p-Si heterojunctions

Al-doped n-ZnO/p-Si heterojunctions were fabricated using a sol–gel dip coating technique at 700 °C, in a nitrogen ambient. The structural, optical, and electrical properties of ZnO:Al thin films, and the heterojunction properties of ZnO:Al/p-Si were investigated with respect to the effects of Al doping concentration. Hexagonal nano-structured ZnO: Al thin films with a 1.2% and a 1.6 at.% Al concentration exhibited high optical transmittance in visible ranges. Electrical resistivity changed with respect to Al doping concentration, and minimum resistivity was detected at a 1.2 at.% Al concentration. The ZnO:Al/p-Si heterojunction properties were analysed using current–voltage (I–V) measurements at four different Al concentrations, ranging from 0.8 to 1.6 (at.%). The ZnO:Al/p-Si heterojunctions exhibited diode-like rectifying behaviour. Under UV illumination, the photoelectric behaviour observed for the ZnO:Al/p-Si heterojunctions was diode.     

Direct control of electron transfer to the surface-CO bond on a Pt/TiO2 catalytic diode

We study CO adsorption on a multilayer catalytic diode in which electron transfer at the metal-semiconductor (Pt/TiO(2)) junction is controlled by an applied external voltage. The multilayer diode structure enhances infrared absorption signals from CO molecules adsorbed on the small area Pt surface. We find that the diode behaves like a Schottky junction and that changes in electron transfer at the junction are directly correlated with reversible shifts in the vibrational frequency of adsorbed CO. Infrared polarization and incidence angle dependent studies show that the magnitude of vibrational frequency shift varies with orientation of the molecules being probed and increases with proximity to the Pt/TiO(2) interface. The results demonstrate the ability to control the metal-adsorbate bond through external electronic modifications of a metal-support junction. The catalytic diode can potentially provide control of the surface chemical bond by an external voltage, providing a new approach for investigations in heterogeneous catalysis, sensors, and plasmonic devices.     

Pt and Pt–Ru nanoparticles decorated polypyrrole/multiwalled carbon nanotubes and their catalytic activity towards methanol oxidation

Conducting polymer composite films comprised of polypyrrole (PPy) and multiwalled carbon nanotubes (MWCNTs) [PPy–CNT] were synthesized by in situ polymerization of pyrrole on carbon nanotubes in 0.1 M HCl containing (NH₄)S₂O₈ as oxidizing agent over a temperature range of 0–5 °C. Pt nanoparticles are deposited on PPy–CNT composite films by chemical reduction of H₂PtCl₆ using HCHO as reducing agent at pH = 11 [Pt/PPy–CNT]. The presence of MWCNTs leads to higher activity, which might be due to the increase of electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces allowing higher dispersion and utilization of the deposited Pt nanoparticles. A comparative investigation was carried out using Pt–Ru nanoparticles decorated PPy–CNT composites. Cyclic voltammetry demonstrated that the synthesized Pt–Ru/PPy–CNT catalysts exhibited higher catalytic activity for methanol oxidation than Pt/PPy–CNT catalyst. Such kinds of Pt and Pt–Ru particles deposited on PPy–CNT composite polymer films exhibit excellent catalytic activity and stability towards methanol oxidation, which indicates that the composite films is more promising support material for fuel cell applications.     

Fabrication and conduction mechanism evaluation of polyfluorene polymeric Schottky diode

A thin film of polyflourene polymer was sandwiched between a conductive polymer deposited on silver nanowire and metal electrode to form a multilayer polymer‐based diode device. The electrical properties of fabricated polymeric diode have been studied by current–voltage method. The current–voltage characteristics of the fabricated device exhibited non‐ideal, asymmetrical, and rectifying behavior. Ohmic current conduction mechanism was observed in the device at low voltage. At higher voltage values, the space‐charge‐limited current conduction mechanism was found to be dominated. The values of the Schottky barrier height, ideality factor, and saturation current density were extracted according to the standard thermionic emission model and discussed. The barrier height and ideality factor were calculated as 0.72 eV and 2.53, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Gate-controlled rectifying behavior in C70@SWNT networks

We report the gate-controlled rectification behavior in C(70)@SWNT networks at room temperature in air. The electrical transport characteristics can be fitted well with the conventional Schottky diode model. The origin of the rectifying behavior in fullerene peapod networks device is qualitatively discussed. This paper demonstrates a strategy for diode fabrication based on peapod networks.     

Hydrogen sensing properties of a Pd/SiO2/AlGaN-based MOS diode

Hydrogen sensing properties of a Pd/AlGaN-based Schottky diode are improved by the deposition of SiO₂ at the metal/semiconductor (MS) interface. The wide Schottky barrier height variation of the MOS diode could be attributed to the large electric field across the SiO₂ layer. This leads to the presence of more hydrogen dipoles caused by the polarization effect. The sensing response of the MOS diode at room temperature (1.3 × 10⁵) is comparable to that of the MS one at 150 °C (2.04 × 10⁵). Thus, the MOS-type sensing device shows the benefit of low-temperature operation. Kinetic analyses confirm that the short response times of the MOS diode are attributed to high reaction rate at the Pd/SiO₂ interface.     

HETEROJUNCTION DIODES OF POROUS SILICON WITH SOLUBLE POLYANILINE*

Two kinds of heterojunction diodes of porous silicon (PS) with soluble polyaniline (PANI) werefabricated. One is a heterojunction diode of PS with water-soluble copolymer of polyaniline (PAOABSA),Al/PS-PAOABSA/Au cell as rectifying diode. Another is a heterojunction diode of PS with solublepolyaniline doped with DBSA, Al/PS-PANI (DBSA)/Au cell as light emitting diode (LED). The rectifyingcharacteristics of the rectifying diodes were measured as a function of the degree of sulfonation and thicknessof the copolymers, as well as oxidation of PS. The rectifying ratio of the heterojunction can reach 5.0×10~4 at±3 V bias. For the LED, the photoluminescence (PL) and electroluminescence (EL) spectra were measuredand discussed.     

MgZnO/ZnO p–n junction UV photodetector fabricated on sapphire substrate by plasma-assisted molecular beam epitaxy

We have investigated the spectral response of back- and front-surface-illumination MgZnO/ZnO p–n ultraviolet photodetector fabricated by plasma-assisted molecular beam epitaxy on sapphire substrate. The current–voltage measurements show that the device has a rectifying behavior with a turn-on voltage of 4.5 V. The detector exhibits a broad spectral response which covers the visible and UV spectra regions (from 275 to 375 nm) and has a maximum peak response at the wavelength of 330 nm. At a reverse bias of 5 V, the visible rejection (R330 nm/R500 nm) was more than two orders of magnitude. The peak responsivity at 330 nm for the device under back-illumination is about four times larger than that of the device under front-illumination under the same reverse bias. The response mechanisms of the device under back- and front-illumination are discussed.     

CO tolerant Pt/WC methanol electro-oxidation catalyst

Platinum supported on WC (Pt/WC) catalyst (20 wt.% Pt) was synthesized as a new methanol electro-oxidation catalyst. Particle size of 7.5 nm was obtained from X-ray diffraction results and a uniform distribution of particles was observed by transmission electron microscopy. In cyclic voltammetry (CV) measurement, the reduction peak potential of PtO increased from 0.72 V in commercial Pt/C to 0.76 V in Pt/WC. By combining the CV and CO stripping results, spill-over of H⁺ from Pt to WC was observed. Electrochemically active surface area calculated from the desorption area of H⁺ were 11.2 and 5.74 m²/g catalyst for Pt/WC and Pt/C, while those obtained from the desorption area of CO were 4.42 and 6.40 m²/g catalyst, respectively. CO electro-oxidation peak potential greatly decreased from 0.80 V in Pt/C to 0.68 V in Pt/WC. The reaction of WC with water to produce WC–OH could lower to CO electro-oxidation peak potential. Specific activity for methanol electro-oxidation increased from 144 mA/m² in Pt/C to 188 mA/m² in Pt/WC.     

Electrical and structural properties of Pd/V/n‐type InP (111) Schottky structure as a function of annealing temperature

Palladium/Vanadium (Pd/V) Schottky structures are fabricated on n‐type InP (100) and the electrical, structural and surface morphological characteristics have been studied at different annealing temperatures. The extracted barrier height of as‐deposited Pd/V/n‐InP Schottky diode is 0.59 eV (I–V) and 0.79 eV (C–V), respectively. However, the Schottky barrier height of the Pd/V Schottky contact slightly increases to 0.61 eV (I–V) and 0.84 eV (C–V) when the contact is annealed at 200 °C for 1 min. It is observed that the Schottky barrier height of the contact slightly decreases after annealing at 300, 400 and 500 °C for 1 min in N₂ atmosphere. From the above observations, it is clear that the electrical characteristics of Pd/V Schottky contacts improve after annealing at 200 °C. This indicates that the optimum annealing temperature for the Pd/V Schottky contact is 200 °C. Basing on the auger electron spectroscopy and X‐ray diffraction results, the formation of Pd‐In intermetallic compound at the interface may be the reason for the increase of barrier height upon annealing at 200 °C. The formation of phosphide phases at the Pd/V/n‐InP interface could be the reason for the degradation in the barrier heights after annealing at 300, 400 and 500 °C. From the AFM results, it is evident that the overall surface morphology of the Pd/V Schottky contacts is fairly smooth. Copyright © 2011 John Wiley & Sons, Ltd.     

Zinc oxide/polypyrrole nanocomposite as a novel solid phase microextraction coating for extraction of aliphatic hydrocarbons from water and soil samples

In this work, ZnO/PPy nanocomposite coating was fabricated on stainless steel and evaluated as a novel headspace solid phase microextraction (HS-SPME) fiber coating for extraction of ultra-trace amounts of environmental pollutants; namely, aliphatic hydrocarbons in water and soil samples. The ZnO/PPy nanocomposite were prepared by a two-step process including the electrochemical deposition of PPy on the surface of stainless steel in the first step, and the synthesis of ZnO nanorods by hydrothermal process in the pores of PPy matrix in the second step. Porous structure together with ZnO nanorods with the average diameter of 70 nm were observed on the surface by using scanning electron microscopy (SEM). The effective parameters on HS-SPME of hydrocarbons (i.e., extraction temperature, extraction time, desorption temperature, desorption time, salt concentration, and stirring rate) were investigated and optimized by one-variable-at-a-time method. Under optimized conditions (extraction temperature, 65 ± 1 °C; extraction time, 15 min; desorption temperature, 250 °C; desorption time, 3 min; salt concentration, 10% w/v; and stirring rate, 1200 rpm), the limits of detection (LODs) were found in the range of 0.08–0.5 μg L⁻¹, whereas the repeatability and fiber-to-fiber reproducibility were in the range 5.4–7.6% and 8.6–10.4%, respectively. Also, the accuracies obtained for the spiked n-alkanes were in the range of 85–108%; indicating the absence of matrix effects in the proposed HS-SPME method. The results obtained in this work suggest that ZnO/PPy can be promising coating materials for future applications of SPME and related sample preparation techniques.     

Effect of Electropolymerization Condition on Polypyrrole Schottky Barrier

Schottky barriers of some polypyrrole(PPy) nitrate film, which was prepared electro-chemically from ethyl alcohol solution, and poly(N-methylpyrrole) (PNMP) films were observed and investigated by means of measuring the current density (J)-voltage(V) characteristics of Al/PPy/ITO and Al/PNMP/ITO. A strong effect of the film thickness on the rectification ratios was recognized for the PPy films. The Schottky barrier parameters were evaluated from J-V plots.     

Electrical and photoconducting properties of nanorod in based spinel compound/p-Si photodiode by sol–gel spin coating technique

A new Schottky diode (InFe₂O₄/p-Si/Al) was fabricated using the sol–gel spin coating technique. The current–voltage (I–V) characteristics of the Schottky diode were investigated under various illumination intensities. The value of ideality factor (n) and zero-bias barrier height (Φ_B0) for all illuminations was determined by using the forward-bias I–V measurements, and were found to be about 4.20 and 0.72 eV, respectively. The reverse current of the diode in the reverse bias increases with the increasing illumination intensities. Also, the photocurrent under illumination is higher than the dark current. In addition, the capacitance–voltage (C–V) and conductance–voltage (G–V) measurements of the diode were studied in the frequency range of 10 kHz–1 MHz. The measured values of the C decrease with the increasing frequency. The decrease in capacitance was explained on the basis of interface states. To obtain the real C and G of the diode, the measured values of C and G were corrected to eliminate the effect of series resistance. The obtained results suggest that the diode can be used as a photodiode in optoelectronic applications.     

Ultraviolet electroluminescence from n-ZnO:Ga/p-ZnO:N homojunction device on sapphire substrate with p-type ZnO:N layer formed by annealing in N2O plasma ambient

ZnO homojunction light emitting device (LED) with n-ZnO:Ga/p-ZnO:N structure was fabricated on sapphire substrate by metal organic chemical vapor deposition. The reproducible p-type ZnO:N layer with hole concentration of 1.29 × 10¹⁷ cm⁻³ was formed with NH₃ as N doping source followed by thermal annealing in N₂O plasma protective ambient. The device exhibited desirable rectifying behavior. Distinct electroluminescence emission centered at 3.2 eV and 2.4 eV were detected from this device under forward bias at room temperature. The intensive ultraviolet emission was comparable to the visible emission in the electroluminescence spectrum, which represent remarkable progress in the performance of ZnO homojunction LED.