Cr Electrodes Research Articles

Mass-to-charge composition of high-current vacuum arc plasmas with Cu–Cr cathodes

Copper–chromium composite electrodes are widely used in high-current vacuum interrupters. Current interruption may trigger a vacuum arc between such electrodes. The operational dynamics of interrupters is determined by the vacuum arc parameters. We have employed a time-of-flight spectrometer to study the mass-to-charge composition of plasma ions in the arc discharge with Cu–Cr electrodes at a current density of 1 kA cm−2 as is typical for the arc in interrupters. We find that the average charge states of copper and chromium ions depend on their fractional content in the cathode material. With the percentage of chromium ions increasing from 0% to 50%, the average charge state of chromium ions 〈Q〉Cr increases from 1.98 to 2.13, while that of copper ions 〈Q〉Cu decreases from 2.15 to 1.95. We observe a decrease in the average charge states of both copper and chromium ions over the duration of the arc pulse. The results of our investigations of arc plasma composition may be useful for analysis of mass and charge transport in interrupters.

Oxide Layer Enhances Photocurrent Gain of the Planar MAPbI3 Photodetector

AbstractEven though the current development of hybrid perovskite photodetectors makes them competitive with their inorganic analogs, a detailed fundamental understanding of their operating principles is still lacking. Here, the performance of planar polycrystalline perovskite photodetectors fabricated on interdigitated comb electrodes made from various metals is studied. It is demonstrated that the oxide layer on Cr and Pt electrodes increases the photo current gain by an order of magnitude. It is suggested that the gain enhancement originates from the hindered extraction of photogenerated holes and the migration of ions, which creates additional hole‐traps at interfaces. These effects reduce the barrier for electron injection and enable the passage of a larger number of electrons during the prolonged lifetime of photogenerated holes.

Studies on Cr electrode of CdZnTe detector for high energy radiation detection

Electrode with proper contact properties is of vital importance to CdZnTe detector for high energy radiation detection. In this work, Au and Cr electrodes are prepared on CdZnTe surface using magnetron sputtering method. The surface morphology and the interface structure are analyzed using atomic force microscopy and X-ray photoelectron spectroscopy (XPS). No reaction is found at Au/CZT interface. But for Cr/CdZnTe, interface layers of CrO and Te were found, which forms a structure of Cr/Cr–O/Te/CdZnTe with a metal-insulator-metal tunnel junction. Due to this interface structure, Schottky Barrier height was tuned, which enhanced the collection efficiency and energy resolution for high energy irradiation. The energy resolution of CdZnTe detector with Cr electrode for 137Cs isotope with the energy of 662 keV reaches about 1.3%. The adhesive force of Cr is also enhanced because of the interface reaction. The results prove Cr to be a proper electrode material for CdZnTe detectors.

N-Type Ohmic contact and p-type Schottky contact of monolayer InSe transistors.

Owing to their few lateral dangling bonds and enhanced gate electrostatics, two-dimensional semiconductors have attracted much attention for the fabrication of channels in next-generation field-effect transistors (FETs). Herein, combining first-principle band structure calculations with more precise quantum transport simulations, we systematically explore the interface properties between monolayer (ML) indium selenide (InSe) and a sequence of common electrodes in an FET. The ML InSe band structure is damaged by Sc, Au, Cr, Pt, and Pd electrodes but identifiable in contact with Ag, Cu, In, graphene and ML O-terminated Cr2C electrodes. A lateral n-type Schottky contact is generated with Sc, Au, Cr, Pt, Pd, and ML graphene electrodes owing to Fermi level pinning originating from the metal-induced gap states, which feature a pinning factor of 0.32. Luckily, a highly desirable lateral n-type Ohmic contact is generated with the Ag, Cu, and In electrodes. The calculated contact polarity is in agreement with the available experimental results using Au, Cr, ML graphene, Ag, and In as electrodes. Remarkably, a lateral p-type Schottky contact is generated with ML O-terminated Cr2C despite the very high work function of ML InSe. Therefore, this study offers a deeper understanding of ML InSe device interfaces and instructions for the design of ML InSe transistors.

SPOT WELDING COPPER - 1% Cr ELECTRODE TIPS PRODUCED VIA EQUAL CHAN NEL ANGULAR PRESSING

A sharp 120o Equal channel angular pressing (ECAP) was applied at room temperature to refine the grains sizes of pure copper and copper - 1% Chromium alloy for spot welding electrode tips application. Initially deformation behavior was investigated with the position using colorful plasticine as work piece followed by copper alloy. It was found the deformation at the central part of the work piece is heavily sheared than the outer part. Optical and Scanning electron microscopy were used to study the progress of grain refining under the influence of rotation and number of passes during pressing. The influence of elongated fibrous nano graines on electrical conductivity and hardness were discussed. Shear test of spot welded 303 stainless steel indicated that nano structural Cu-1% Cr electrode tips used showed superior results compared to commercial electrodes.

Single walled carbon nanotube-based stochastic resonance device with molecular self-noise source

Stochastic resonance (SR) is an intrinsic noise usage system for small-signal sensing found in various living creatures. The noise-enhanced signal transmission and detection system, which is probabilistic but consumes low power, has not been used in modern electronics. We demonstrated SR in a summing network based on a single-walled carbon nanotube (SWNT) device that detects small subthreshold signals with very low current flow. The nonlinear current-voltage characteristics of this SWNT device, which incorporated Cr electrodes, were used as the threshold level of signal detection. The adsorption of redox-active polyoxometalate molecules on SWNTs generated additional noise, which was utilized as a self-noise source. To form a summing network SR device, a large number of SWNTs were aligned parallel to each other between the electrodes, which increased the signal detection ability. The functional capabilities of the present small-size summing network SR device, which rely on dense nanomaterials and exploit intrinsic spontaneous noise at room temperature, offer a glimpse of future bio-inspired electronic devices.

Large-Area CVD-Grown Sub-2 V ReS2 Transistors and Logic Gates.

We demonstrated the fabrication of large-area ReS2 transistors and logic gates composed of a chemical vapor deposition (CVD)-grown multilayer ReS2 semiconductor channel and graphene electrodes. Single-layer graphene was used as the source/drain and coplanar gate electrodes. An ion gel with an ultrahigh capacitance effectively gated the ReS2 channel at a low voltage, below 2 V, through a coplanar gate. The contact resistance of the ion gel-gated ReS2 transistors with graphene electrodes decreased dramatically compared with the SiO2-devices prepared with Cr electrodes. The resulting transistors exhibited good device performances, including a maximum electron mobility of 0.9 cm2/(V s) and an on/off current ratio exceeding 104. NMOS logic devices, such as NOT, NAND, and NOR gates, were assembled using the resulting transistors as a proof of concept demonstration of the applicability of the devices to complex logic circuits. The large-area synthesis of ReS2 semiconductors and graphene electrodes and their applications in logic devices open up new opportunities for realizing future flexible electronics based on 2D nanomaterials.

Various and Tunable Transport Properties of WSe2 Transistor Formed by Metal Contacts.

The abundant electronic and optical properties of 2D materials that are just one-atom thick pave the way for many novel electronic applications. One important application is to explore the band-to-band tunneling in the heterojunction built by different 2D materials. Here, a gate-controlled WSe2 transistor is constructed by using different work function metals to form the drain (Pt) and source (Cr) electrodes. The device can be gate-modulated to exhibit three modes of operation, i.e., the tunneling mode with remarkable negative differential resistance, the transition mode with a second electron tunneling phenomenon for backward bias, and finally the conventional diode mode with rectifying characteristics. In contrast to the heterojunctions built by different 2D materials, these devices show significantly enhanced tunneling current by two orders of magnitude, which may largely benefit from the clean interfaces. These results pave the way toward design of novel electronic devices using the modulation of metal work functions.

Multilayer graphene electrodes for one-port surface acoustic wave resonator mass sensor

A one-port surface acoustic wave (SAW) resonator mass sensor composed of multilayer graphene (MLG) electrodes was investigated by the finite element method (FEM) and analyses were carried out to study the enhancement of sensitivity and the secondary effects caused by MLG electrodes on the performance of the resonator. Unlike metal electrodes, MLG electrode offers elastic loading to the contact surface, as evidenced by the increase in the surface velocity of the SAW device. In terms of the sensitivity of the mass sensor, MLG electrode showed the largest center frequency shift in response to a change in mass loading, as well as when used as a gas sensor to detect volatile organic compounds (VOCs). Also, MLG electrodes offered the least triple transit signal (TTS) and bulk acoustic wave (BAW) generations compared with Al and Au–Cr electrodes. Thus, the one-port SAW resonator with graphene electrodes not only possesses excellent performance characteristics but also gives rise to new opportunities in the development of highly sensitive mass sensors.

Integration of ZnO nanowires in gated field emitter arrays for large-area vacuum microelectronics applications

Addressable field emitter arrays (FEAs) have important applications in vacuum electronic devices. However, it is important to integrate nanowire emitters into a gated structure without influencing the device structure and maintain the excellent field emission properties of nanowire emitters in the FEAs after the fabrication process. In this study, gate-structure ZnO nanowire FEAs were fabricated by a microfabrication process. The structure combines a planar gate and an under-gate, which is compatible with the preparation of ZnO nanowire emitters. The effect of electrode materials on the field emission properties of ZnO nanowires was studied using a diode structure, and it was found that ZnO nanowire pads on indium-tin-oxide (ITO) electrode showed better field emission performance compared with chromium (Cr) electrode. In addition, effective emission current modulation by the gate voltage was achieved and the addressing capability was demonstrated by integrating the ZnO nanowire FEAs in a vacuum-encapsulated field emission display. The reported technique could be a promising route to achieve large area addressable FEAs.

Moderately-doped Schottky barriers: a description using thermionic emission over a wide temperature range

We report on a low temperature study of Schottky barriers between Au, Cr or Al electrodes deposited directly onto moderately-doped Si or GaAs substrates with doping densities in the range cm−3 and find the unexpected result that for temperatures 150 K both the zero-voltage Schottky barrier height, and the reciprocal ideality factor, , have linear temperature dependences that extrapolate to zero at T = 0. Accordingly, the thermionic emission equation with these modified temperature-dependent parameters gives a good description of the current–voltage (I–V) characteristics at temperatures where thermionic field emission and field emission (direct tunneling) in addition to thermionic emission are known to be important. Our analysis utilizes a barrier inhomogeneity model to show that the temperature-independent product determined from forward bias characteristics defines a flat band voltage which is shown to be equivalent to the built-in voltage separately determined by extrapolation of capacitance versus voltage measurements made in the reverse bias region.

Stark effect and photoconductivity of fullerene С70 measured on samples with a submicron electrode grating and sandwich geometry

The electroabsorption (Stark effect) and photoconductivity of polycrystalline fullerene C70 in thinfilm samples with radically different geometries (sample 1 with interdigital Cr electrodes and sandwichlike sample 2 with SnO2 and Al electrodes) have been investigated. It is noteworthy that sample 1 is a submicron grating with 0.88-µm gaps between electrodes. When measuring electroabsorption and photoconductivity, the external voltage does not exceed 4 V. It was assumed that the small gap size may significantly affect the polycrystalline film morphology and surface effects and, as a consequence, the electroabsorption and charge carrier mobility. However, the results of the Stark effect measurements on samples with different geometries differ by only 25%, whereas the spectral photoconductivity values differ by factors of 1–2.5. The increase in photoconductivity may be related to the decrease in the carrier mobility in the sandwich sample or the increase in the number of carriers under the influence of atmospheric oxygen in the surface layer of C70 sample with interdigital electrodes.

Experimental Investigations of Surface Modification of AISI 1045 Die Steel by Electro Discharge Machining Process

In the present work Electric discharge machining process has been used for surface modification of AISI 1045 Die steel with copper chromium (Cu Cr) electrodes (made through powder metallurgy technique) by varying different machining parameters such as peak current, pulse on-time, pulse off-time and compaction pressure. Parametric optimization of Surface Deposition Rate, Surface Roughness and Micro Hardness was carried out by using Central Composite Design technique. Material characterization was also performed using X-Ray Diffraction and Scanning Electron Microscope to study the structure of the modified surface layer. It has been found that hardness increases by two times as compared to the base material. By the use of copper-chromium composite electrode, chromium particles gets collected on the surface which modified the work piece surface by increasing its corrosion and wear resistance The input process parameter pulse off-time has greater effect on surface deposition rate followed by peak current, pulse on-time and compaction pressure respectively.

Light emission from electrodes under dielectrophoresis conditions

The use of fluorescence in microfluidic optical biodetection requires materials with low-background fluorescence to avoid influencing the desired optical signal with spurious light emission. For the same reason, spurious light emission from galvanoluminescence (GL) should be avoided when fluorescence is used in dielectrophoresis (DEP)-based biosensors. Use of non-noble metal electrodes such as indium tin oxide (ITO) in DEP devices is therefore a concern. We evaluate GL in the context of conditions typical of DEP devices. We experimentally show that use of ITO can result in GL. We also show that GL can be avoided, even with metals that demonstrate strong GL such as Al, by proper selection of operating frequency, which can be determined by measuring the impedance spectrum of the DEP device. In addition, we demonstrate that GL results in broadband emission for all of the salt solutions tested. Broadband emission implies that at least some of the light will pass through typical fluorescence filters if a device exhibits GL. We also show that Ni and Cr electrodes do not exhibit GL and may therefore be suitable as low-cost DEP electrodes.

Monolayer Phosphorene–Metal Contacts

Recently, phosphorene electronic and optoelectronic prototype devices have been fabricated with various metal electrodes. We systematically explore for the first time the contact properties of monolayer (ML) phosphorene with a series of commonly used metals in a transistor by using both ab initio electronic structure calculations and more reliable quantum transport simulations. ML phosphorene undergoes a metallization under the checked metals, and the metallized ML phosphorenes have an unnegligible coupling with channel ML phosphorene. ML phosphorene forms an n-type Schottky contact with Au, Cu, Cr, Al, and Ag electrodes and a p-type Schottky contact with Ti, Ni, and Pd electrodes upon inclusion of such a coupling. The calculated Schottky barrier heights are in good agreement with the available experimental data with Ni and Ti as electrodes. Our findings not only provide an insight into the ML phosphorene–metal interfaces but also help in ML phosphorene based device design.

Metal electrode dependent field effect transistors made of lanthanide ion-doped DNA crystals

We fabricated lanthanide ion (Ln3+, e.g. Dy3+, Er3+, Eu3+, and Gd3+)-doped self-assembled double-crossover (DX) DNA crystals grown on the surface of field effect transistors (FETs) containing either a Cr, Au, or Ni electrode. Here we demonstrate the metal electrode dependent FET characteristics as a function of various Ln3+. The drain–source current (Ids), controlled by the drain–source voltage (Vds) of Ln3+-doped DX DNA crystals with a Cr electrode on an FET, changed significantly under various gate voltages (Vg) due to the relative closeness of the work function of Cr to the energy band gap of Ln3+-DNA crystals compared to those of Au and Ni. For Ln3+-DNA crystals on an FET with either a Cr or Ni electrode at a fixed Vds, Ids decreased with increasing Vg ranging from −2 to 0 V and from 0 to +3 V in the positive and negative regions, respectively. By contrast, Ids for Ln3+-DNA crystals on an FET with Au decreased with increasing Vg in only the positive region due to the greater electronegativity of Au. Furthermore, Ln3+-DNA crystals on an FET exhibited behaviour sensitive to Vg due to the appreciable charge carriers generated from Ln3+. Finally, we address the resistivity and the mobility of Ln3+-DNA crystals on an FET with different metal electrodes obtained from Ids–Vds and Ids–Vg curves. The resistivities of Ln3+-DNA crystals on FETs with Cr and Au electrodes were smaller than those of pristine DNA crystals on an FET, and the mobility of Ln3+-DNA crystals on an FET with Cr was relatively higher than that associated with other electrodes.

On-chip fabrication of lateral growth ZnO nanowire array UV sensor

In this paper, we integrate nano technology into traditional microelectronic processing, and develop an on-chip UV sensor based on lateral growth ZnO nanowire arrays. Traditional procedures are used to fabricate the interdigital electrodes, and ZnO nanowires are self-organized and grown between electrodes laterally by hydrothermal method. Additional inclined nanowires are removed during the post-processing procedures, such as ultrasound cleansing and electrode reinforcement. Two kinds of electrode structures are applied, i.e., Cr and Au. For the Cr electrode device structure, because Cr will restrain nanowires from growing vertically on its top, the laterally grown nanowire is long enough to reach the other side of the electrode. The corresponding photoelectric response mechanism is photoconduction controlled by surface oxide ion adsorption. Although the photocurrent is large, the gain is low, and the response speed is slow. Under the UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 2.210-4 A with 1 V bias voltage, the gain is up to 64, the photocurrent cannot reach saturation after 25 s, and the recovery time is 51.9 s. A secondary electrode can be fabricated after growing the nanowire arrays to reinforce the connection between the electrode and the ends of the nanowires. However, the direct contact between metal and semiconductor will form a Schottky contact. The photoelectric response mechanism is then changed to photovoltaic effect, which can greatly improve the gain and response speed. Under UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 4.310-8 A with 1 V bias voltage, the gain is up to 1300, the respond time is 3.8 s, and the recovery time is 5.7 s. For the Au electrode device structure, because Au is catalysis for ZnO nanowire growth, nanowires grown in lateral direction will compete with those grown in vertical direction, and hence the laterally grown nanowires are not long enough to reach the other side of the electrode. Nanowires grown from two sides of the electrodes will meet each other and form a bridging junction, however, this will turn the photoconduction mechanism from surface ion controlled into a bridging junction controlled, which yields the best device performance. Before removing the inclined nanowires by ultrasound cleansing, under UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 8.310-3 A with 1 V bias voltage, the gain is up to 1350, the respond time is 3.3 s, and the recovery time is 3.4 s. After removing the inclined nanowires, under UV radiations of 20 mW/cm2 and of 365 nm in wavelength, the dark current is 10-9 A with 1 V bias voltage, the gain is up to 8105, the respond time is 1.1 s, and the recovery time is 1.3 s.

Metal-based bracken-like single-sided dye-sensitized solar cells with horizontal separation.

One of the drawbacks of typical dye-sensitized solar cells (DSCs) is their high cost and the high electrical resistance of the transparent conducting substrate. In conventional sandwich-type DSCs, only one of the FTO substrates can be replaced by a metal substrate. We investigated an all-metal-electrode single-sided DSC in which interpenetrated bracken-like Cr electrodes were created using photolithography; mesoporous TiO2 and Pt films were deposited on the laterally separated electrodes. Thermal Pt deposition and electrodeposition methods were investigated and it was found that a cyclic electrodeposition method resulted in selective Pt deposition at room temperature with a higher device performance. Cu or ZnO sacrificial layers and TiO2 or TiO2/SiO2 porous layers were used for the spacer layer that keeps the Pt electrode away from the TiO2 mesoporous layer and the optimum results were obtained when a TiO2/SiO2 layer was used. The best device had a current density of 8.47 mA cm(-2), an open circuit voltage of 0.685 V and an efficiency of 2.44%. The results of open circuit voltage decay and electrochemical impedance spectrometry showed the formation of a high-resistivity blocking layer, which was attributed to the Cr oxide formed during thermal treatment. The efficiency may be improved further by developing low-temperature fabrication processes.

Spectroscopic Data of W I, Mo I and Cr I Spectral Lines: Selection and Analysis

Plasma of electric arc discharges between composite Cu–W, Cu–Mo and Cu–Cr electrodes in argon flow and their spectra were studied by optical emission spectroscopy. Since values of oscillator strengths for W I, Mo I and Cr I presented in various sources are significantly different, selection of spectroscopic data for these elements (particularly oscillator strength) was expected to be useful for plasma diagnostics. The Boltzmann plot method was used as a tool for the selection of appropriate spectral lines and their spectroscopic data. The main result of the paper is W I, Mo I and Cr I spectral lines and spectroscopic data recommended for diagnostics of plasma with such metal impurities.

Influence of Incorporated Pt–Fe<SUB>2</SUB>O<SUB>3</SUB> Core–Shell Nanoparticles on the Resistive Switching Characteristics of ZnO Thin Film

The resistance-switching characteristics of metal oxides have attracted great interest for the non-volatile memory applications such as resistive random access memory. A basic resistive random access memory device has a metal/insulator/metal structure, and its memory effect is achieved by applying voltage to change the resistance of the insulating layer. One of the promising candidates for explaining the resistance-switching mechanism is the formation and rupture of nanoscale conductive filaments. However, this model has an issue that needs to be addressed: the wide distribution of switching voltage due to randomly formed filaments. Therefore, some researchers have reported a decrease in switching voltage distribution and an increase in switching stability by incorporating nanoparticles into the insulating layer. In this study, we investigated influence of incorporated Pt-Fe2O3 core-shell nanoparticles on the resistive switching characteristics of ZnO thin films. Devices were fabricated on SiO2 wafers. A 100-nm-thick Cr layer was used as the bottom electrode. A 50-nm-thick ZnO layer was deposited using the sputtering method, and Pt-Fe2O3 nanoparticles were deposited on it by the dip coating method. A 50-nm-thick ZnO layer was then deposited again. A top Cr electrode (size: 100 μm x 100 μm) was deposited using a shadow mask and sputtering system. All the devices showed bipolar resistance-switching behavior that is observed in Cr/ZnO/Cr structures. However, the on/off voltage was dramatically lowered by incorporating nanoparticles into the insulating layer when compared with that of the devices without nanoparticles. In addition, the switching stability of the devices was improved upon the incorporation of nanoparticles. On the basis of these results, we can conclude that Pt-Fe2O3 nanoparticles may be used to enhance the resistance switching properties of ZnO thin films by incorporating them into the films.