Cr Electrodes Research Articles

Improvement of N-type carbon nanotube field effect transistor performance using the combination of yttrium diffusion layer in HfO2 dielectrics and metal contacts

In this paper, we obtained n-type top-gate carbon nanotube (CNT) thin film field effect transistors (FET) with source/drain extensions structure through dielectrics optimization strategy, combining the yttrium layer with HfO2dielectric argon annealing process, and metal contacts. The mechanism for enhanced n-type conduction was explained as being due to the vertical diffusion of yttrium to the HfO2dielectric during argon annealing. This diffusion causes a bending of the energy band, which results in more positive fixed charges, and a reduction in the electron injection barrier between the low work function source/drain Cr electrode and CNT thin film. The optimized technology has great prospects for the low cost, large scale and high performance n-type CNT thin film FET to be used in integrated electronic devices.

Transformation Dynamics of Nanosized Bi Films into Semiconductor Films of Bismuth Oxide in the Cold Plasma Device

This work proposes an original method that reveals the transformation dynamics of nanosized Bi films into semiconductor films of bismuth oxide (Bi2O3) and the factors affecting the low‐energy cold plasma on the electro‐optical properties of Bi2O3. In the plasma microreactor with a photosensitive GaAs:Cr electrode, the transformed Bi films 400–1100 nm thick are analyzed by X‐ray diffraction to determine the crystal structure of Bi2O3 and by an electron probe microanalyzer to explore the evolution of the composition. The morphological properties of the Bi films exposed to electron–ion flow are examined by processing the scanning electron microscope images. It is found that as a result of the combined effect of photoactive illumination, charged particles, and active plasma components: 1) an absorption spectrum of a new substance is formed in the range λ = 330–1100 nm; 2) the optical width of the bandgap of the resulting substance is Eg ≈ 3 eV, which satisfactorily coincides with the width of the bandgap of Bi2O3; and 3) to overcome the potential barrier and formation of semiconducting Bi2O3 film energy is required, which is provided by the combined kinetic energy of electrons and negatively charged oxygen ions bombarding on the Bi film.

Anomalous deformation behavior of Ag nanowires on Au electrode in low-temperature environments

We discovered that Ag nanowires (AgNWs) on an Au electrode exhibited an anomalous deformation behavior despite a low-temperature environment of 65 °C. Most AgNWs on the Au electrode were deformed after heating. In contrast, AgNWs on the Cr and Ag electrodes exhibited a few changes and maintained their initial shape. The deformation behavior of AgNWs on metal electrodes has not yet been reported and is currently difficult to explain using known processes such as diffusion and alloying. Nonetheless, they evidently depend on the electrode material. The findings of this study are crucial for the design of AgNW-based electronic devices.

Efficient and stable self-powered PbSe photodetectors via doping-induced asymmetric Cr electrodes modulation of surface work function

Conventional PbSe infrared photodetectors typically demands a substantial external electric field, posing challenges in energy-constrained environments. Self-powered photodetectors present a promising avenue for addressing such electricity-related challenges. Nevertheless, the inherent limitations of symmetric Schottky contacts in metal-semiconductor-metal (MSM) photodetectors constrain their self-powered performance, resulting in opposing photocurrents. Constructing asymmetric MSM structures usually requires intricate design or sustained external fields. In this study, we propose a novel contact engineering strategy based on iodine doping to modulate surface work functions of PbSe film. Utilizing Cr electrodes, we achieve Ohmic contact on the iodine-doped top surface of PbSe film and Schottky contact on the as-grown bottom surface. This approach establishes a self-powered PbSe infrared photodetector with an asymmetric top-bottom MSM structure. We comprehensively investigate contact engineering by investigating surface chemical states, elemental variations, and surface work functions variation. Remarkably, the photodetector demonstrates an exceptional zero-bias detectivity of 1.13 × 109 Jones, with an extremely low dark current of 3.67 pA, high Ilight/Idark ratio exceeding 104, and extremely short response times of less than 1 ms, respectively. Our work introduces a new strategy for modifying the band structure, contributing to the fabrication of high-performance self-powered photodetectors.

Unravelling the Factors Influencing Halide Perovskite Based Switchable Photovoltaics

AbstractLead halide perovskites have revolutionized the field of optoelectronics (such as photovoltaics and light emitting diodes) demonstrating extraordinary material properties despite being formed at low temperatures. However, ion migration in the bulk or at the interfaces results in stability issues especially in devices where metal electrodes directly interface with the perovskite film. Utilizing the switchable photovoltaic phenomenon (SPV) in halide perovskites as a measure of ion migration and electrochemical reactions within them, Cs0.05MA0.15FA0.70PbI2.5Br0.5 triple cation perovskite, widely used in photovoltaics is evaluated. The various factors determining the SPV, including electric field magnitudes, type of metal contacts, Illumination conditions, and temperature is systematically measured. This study reveals the roles of electrode work functions and reactivities on ion migration and local electronic structure modulation. ITO electrodes demonstrated the highest open‐circuit voltage (Voc) about 0.85 V while Ag electrodes developed conductive filaments. However, the Voc distribution for Ti and Cr electrodes shows a more pronounced linear correlation with the poling electric field strength. Insights from this lateral design are directly relevant to transistor and memristor architectures and offer inputs into the design of perovskite‐based photovoltaic/optoelectronic devices.

Enhancing electrocatalytic activity in metallic thin films through surface segregation of carbon.

Thin layers of commonly used adhesion metals i.e., Cr and Ti were annealed to investigate and estimate their impact on the electrochemical properties of the carbon nanomaterials grown on top of them. The microstructure, surface chemistry, and electrochemical activities of these materials were evaluated and compared with those of as-deposited thin films. The results from X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, grazing incidence X-ray diffraction (GIXRD), time-of-flight elastic recoil detection analysis (TOF-ERDA), and conductive atomic force microscopy (C-AFM) indicated the formation of a catalytic graphite layer on Cr following annealing, while no such layer was formed on Ti. This is attributed to the formation of the Cr2O3 layer on annealed Cr, which acts as a barrier to carbon diffusion into the underlying Cr. Conversely, Ti exhibits a high solubility for both carbon and oxygen, preventing the formation of the graphite layer. Cyclic voltammetry results showed that annealed Cr electrodes are electrochemically active towards both dopamine (DA) and ascorbic acid (AA) while no electrochemical activity is exhibited by annealed Ti. Quantum chemical calculations suggested that the presence of carbon as graphene or an amorphous form is critical for the oxidation reaction of probes. These results are significant for comprehending how the distinct solubilities of typical interstitial solutes influence the microstructure of adhesion metal layers and consequently yield diverse electrochemical properties.

Enhancing performance of electrical discharge machining by ultrafine-grained Cu-0.5%Cr electrode

Enhancing performance of electrical discharge machining by ultrafine-grained Cu-0.5%Cr electrode

Tuned Transport Path of Perovskite MAPbI3-based Memristor Structure.

In this study, the features of resistive random access memory (RRAM) employing a straightforward Cr/MAPbI3/FTO three-layer structure have been examined and clarified. The device displays various resistance switching (RS) behavior at various sweep voltages between 0.5 and 5 V. The RS effect has a conversion in the direction of the SET and RESET processes during sweeping for a number of cycles at a specific voltage. The directional change of the RS processes corresponds to the dominant transition between the generation/recombination of iodide ion and vacancy in the MAPbI3 perovskite layer and the electrochemical metallization of the Cr electrode under the influence of an electric field, which results in the conductive filament (CF) formation/rupture. At each stage, these processes are controlled by specific charge conduction mechanisms, including Ohmic conduction, space-charge-limited conduction (SCLC), and variable-range hopping (VRH). By identifying the biased voltage and the quantity of voltage sweep cycles, one can take a new approach to control or modulate the pathways for effective charge transport. This new approach is made possible by an understanding of the RS characteristics and the corresponding mechanisms causing the variation of RS behavior in the structure.

An In Situ, multi-electrode electrochemical method to assess the open circuit potential corrosion of Cr in unpurified molten FLiNaK

An in situ electrochemical method to investigate the time-dependent spontaneous corrosion of pure Cr in an unpurified LiF-NaF-KF eutectic salt at 600 °C was developed. A multi-electrode electrochemical cell and a dual-electrode method were utilized to detect Cr(II) and Cr(III) ions on a platinum working electrode using cyclic voltammetry as a function of exposure time and compensating for the distance from the Cr electrode. XRD was performed to characterize the crystalline composition of the exposed FLiNaK and the salt films formed on the working electrodes. The fate of all electro-oxidized Cr must be accounted for to quantify corrosion rates. The concentrations of Cr(II) and Cr(III) species obtained were compared with the gravimetric mass change and ICP-OES analysis of the residual salt. Outcomes, difficulties, and limitations are discussed.

Comparative of MIL101(Cr) and nano‐MIL101(Cr) Electrode as an Electrochemical Hydrogen Peroxide Sensor

AbstractHerein, an electrochemical sensor for the detection of H2O2 based on nafion glassy carbon electrode modified with MIL101(Cr) and nano‐MIL101(Cr) are developed and its electrochemical characterizations analyzed by CV and CA. In comparison with the NGCE, MIL101/NGCE and nano‐MIL101/NGCE, the nano‐MIL101/NGCE showed a sharp redox peak specific to H2O2 was obtained in the phosphate‐calibrated solution. nano‐MIL101/NGCE exhibited good linear response in terms of the relationship between peak currents and concentrations as from 0 to 650 μM (R2=0.99), with a low limit of detection 3.8 μM, high sensitivity 986 μA mM−1 cm−2 and nano‐MIL101/NGCE exhibited ideal repeatability, reproducibility, stability and the interference‐free perception of H2O2.

Comparative study on effect of Mo–Cr bilayer and Mo back electrodes on performance of Cu2ZnSn(S, Se)4 solar cell

In the present work, Mo–Cr bilayer back electrode is prepared and used in Cu2ZnSn(S, Se)4 (CZTSSe) solar cells, to enhance adhesion of Mo to soda lime glass (SLG) substrate and so improve power conversion efficiency (PCE) of CZTSSe solar cell. It is found that the Mo–Cr bilayer electrode has smaller resistivity and stronger adhesion to SLG than conventional Mo electrode. CZTSSe film grown on the Mo–Cr electrode has better crystal quality and closer contact with back electrode than that grown on Mo electrode. Compared to Mo electrode, Mo–Cr bilayer electrode can improve open-circuit voltage; short-circuit current density and filling factor and so PCE of CZTSSe solar cell. By optimizing process, the PCE of CZTSSe solar cell is increased from 8.4% (7.9% for total area) with Mo as electrode to 9.6% (9.0% for total area) with Mo–Cr as electrode. The increment of the PCE is mainly attributed to increase in open circuit voltage (Voc) and filling factor (FF). The increased FF and Voc are due to decrease in series resistance and reverse saturation current density induced by substitution of Mo–Cr for Mo, respectively.

Near‐Infrared Electroluminescent Light‐Emitting Transistors Based on CVD‐Synthesized Ambipolar ReSe2 Nanosheets

AbstractNear‐infrared light‐emitting technology is ideal for noncontact diagnostic medical imaging and high‐speed data communications. High‐quality ReSe2 nanosheets of anisotropic single‐crystal structure with a bandgap of 1.26 eV (≈984 nm) are synthesized with an atmospheric pressure chemical vapor deposition (APCVD) method. The as‐synthesized ReSe2 nanosheets‐fabricated light‐emitting transistors (LETs) exhibit nearly symmetric ambipolar characteristics in electrical transport. Judicious selection of asymmetric platinum (Pt)/chromium (Cr) electrodes, with their work functions matching respectively the conduction‐ and valence‐band edges of ambipolar ReSe2, generates a low turn‐on voltage ReSe2‐LET with the balanced number density and field‐effect mobility of bipolar carriers (i.e., electrons and holes). Room‐temperature near‐infrared electroluminescence (NIR EL) from the frequency‐modulated ReSe2‐LET has been observed unprecedentedly with the assistance of a lock‐in detection system. The NIR EL intensity is tested by varying the bias voltage applied to the ReSe2‐LET devices with different channel lengths. The wavelength of the NIR EL from ReSe2‐LET is differentiated with optical bandpass filters. Room‐temperature angle‐dependent two lobe‐shaped EL pattern manifests the inherent anisotropic in‐plane excitonic polarization of the ReSe2 crystal. The highly stable NIR EL from ReSe2‐LETs provides prospective 2D material‐based ultrathin scalable data communication electronics for future development.

Characterization of Schottky-diode X/[formula omitted]-ray detectors based on CdTe crystals with different uncompensated impurity concentrations

The Schottky-diode X/ γ-ray detectors based on semi-insulating p-like CdTe single crystals with four values of uncompensated impurity concentration (N≈ 2 × 1012 cm−3, 2 × 1011 cm−3, 1 × 1011 cm−3, 4 × 1010 cm−3) were developed and characterized by I-V measurements at low reverse bias (0.005–100 V) and detection of 137Cs and 241Am radioisotope emission spectra. All the detectors were fabricated by the same technique using vacuum evaporation of a Cr electrode (rectifying contact) and chemical deposition of an Au electrode (Ohmic contact) onto the B- and A-face of CdTe(111) crystals, respectively, pre-treated with Ar-ion bombardment. The change of the charge transport mechanism from over-barrier (thermionic) to generation current along with the analysis of the temperature dependence of the differential resistivity evidenced a high concentration of deep level impurities near the middle of the semiconductor bandgap. The detection efficiency η of the detectors was calculated using the corrected expressions for the coordinate dependence of the electrical field strength in a diode which took into account the fact that the depletion region width exceeded the CdTe crystal thickness at higher bias voltages. It was shown that the dependence η(N) decreased with increasing N without a maximum corresponding to an optimal value Nopt as reported earlier. The Cr/CdTe/Au Schottky-diode detectors, fabricated using CdTe with the lowest N, demonstrated the highest energy resolution (0.6% @662 keV and 7.5% @59.5 keV) and it degraded when crystals with higher N were used.

Unraveling the hysteretic behavior at double cations-double halides perovskite - electrode interfaces

Despite over a decade of research on metal halide perovskites (MHPs) in the context of photovoltaic applications, understanding the nature of electronic and ionic processes associated with current-voltage (I-V) hysteretic behavior has been limited. Here, we explore the hysteretic behavior in (FAPbI3)0.85(MAPbBr3)0.15 perovskite devices with lateral Cr electrodes by applying first order reversal curve (FORC) bias waveform in I-V, Kelvin probe force microscopy (KPFM) measurements, and in-situ chemical imaging by time-resolved time-of-flight secondary ion mass spectrometry (tr-ToF-SIMS). In dark, we reveal pronounced hysteretic behaviors of charge dynamics in the off-field by probing time-dependent current and contact potential difference (CPD). Under illumination, transient and hysteretic behaviors are significantly reduced. The tr-ToF-SIMS results reveal that the hysteretic behaviors are strongly associated with accumulation of Br- ions at the interfaces. In addition, the low mobility MA+ ions result in transient behavior and contribute to the hysteretic phenomena. It was shown that Pb2+ ions can be reduced at the interfaces due to electrochemical reactions with the electrode in the presence of charge injection and photogenerated charges. These hysteretic behaviors associated with charge dynamics, ion migration, and interfacial electrochemical reaction are critical to further improve the performance and stability of MHPs photovoltaics and optoelectronics.

Novel Cr and Sn co-doped Co3O4 polygon-based electrode material for supercapacitor application

Novel Cr and Sn co-doped Co3O4 polygon-based electrode material for supercapacitor application

A scalable molecule-based magnetic thin film for spin-thermoelectric energy conversion

Spin thermoelectrics, an emerging thermoelectric technology, offers energy harvesting from waste heat with potential advantages of scalability and energy conversion efficiency, thanks to orthogonal paths for heat and charge flow. However, magnetic insulators previously used for spin thermoelectrics pose challenges for scale-up due to high temperature processing and difficulty in large-area deposition. Here, we introduce a molecule-based magnetic film for spin thermoelectric applications because it entails versatile synthetic routes in addition to weak spin-lattice interaction and low thermal conductivity. Thin films of CrII[CrIII(CN)6], Prussian blue analogue, electrochemically deposited on Cr electrodes at room temperature show effective spin thermoelectricity. Moreover, the ferromagnetic resonance studies exhibit an extremely low Gilbert damping constant ~(2.4 ± 0.67) × 10−4, indicating low loss of heat-generated magnons. The demonstrated STE applications of a new class of magnet will pave the way for versatile recycling of ubiquitous waste heat.

Novel Pd–Cr electrocatalyst with low Pd content for coal electrolysis for hydrogen production

Highly efficient Pd–Cr alloy electrocatalyst with various Cr/Pd ratios supported on carbon fibers (CFs) is prepared by an impregnation and hydrogen-reduction method, and used for hydrogen production from coal electrolysis for the first time. The catalyst is characterized using X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) with Energy Dispersive X-Ray Spectroscopy (EDS). The results show that the Pd–Cr nanoparticles are evenly distributed on the carbon fibers surface. Electrochemical tests determine that the catalytic performance of the Pd–Cr electrodes is higher than that of pure Pd, and PdCr/CFs (3:7) exhibits the best performance, improving the activity for coal electrolysis by 37.1% compared to Pd. The electronic structure modulation of Pd–Cr alloy is important for coal electrooxidation, with the added benefit that Cr is corrosion resistant in acidic solution.

X (metal: Al, Cu, Sn, Ti)-functionalized tunable 2D-MoS2 nanostructure assembled biosensor arrays for qualitative and quantitative analysis of vital neurological drugs.

In this work we report for the first time surface functionalization of 2D MoS2 with X (metals: Al, Cu, Sn, Ti) to develop a low-cost, ultra-selective biosensor array based Electronic Tongue (E-Tongue) for the detection of 4 vital neurological drugs in human saliva. The hydrothermally grown surface functionalized X-MoS2 was integrated onto a single 1 × 1 cm aluminium foil and contacts were defined using Cr electrodes. Detailed characterization revealed the formation of 2-H MoS2 and metal-X (Al, Cu, Sn, Ti)-functionalized MoS2 nanoflower like morphology decorated with nanoflake, nanorod, nanocube and nanostick structures, respectively. The response of the sensor array was recorded for aspirin, nicotine, caffeine and tramadol. Principal Component Analysis (PCA) was performed to reduce the dimension of numerous response data sets from all sensors and predict the likely possible response from various neurological drugs towards each sensor. Pattern-recognition analysis confirmed a definite pattern in response to respective functionalization and could efficiently differentiate neurological drugs from one another. Real-time analysis was performed using saliva samples for monitoring the therapeutic neurological drug concentration in the human body. Furthermore, the biosensor array was exposed to respective neurological drugs to study their sensitivity, selectivity, stability, reproducibility and adhesion onto the device. The strategy outlined can be used to develop lab-on-a-chip devices for the real-time detection of numerous bioanalytes in body fluids.

Effect of CdTe crystal thickness on the efficiency of Cr/CdTe/Au Schottky-diode detectors

The effect of CdTe crystal thickness on the detection efficiency and energy resolution of Cr/CdTe/Au diode X/γ-ray detectors has been studied. The Schottky (Cr electrode) and near Ohmic (Au electrode) contacts were created using Ar plasma treatment of the B- and A-faces of CdTe(111) single crystals at different regimes, respectively. Detector-grade CdTe wafers with an area of 5 × 5 mm2 and thicknesses d of 0.5 mm, 0.75 mm, 1.0 mm and 2.0 mm were used. High energy resolution (FWHM) in the 137Cs spectra (662 keV peak) was achieved: from 0.5 % for thin detectors to 3.0 % for thick ones. From the comparison of the detection efficiency dependences on the CdTe crystal thickness with the corresponding calculated dependences, the uncompensated impurity concentration in CdTe was obtained as N ≈ 4 × 1010 cm−3. N determines the space–charge region width W in Schottky diodes, therefore the effect of this value on the detection efficiency was analyzed. A key feature of the efficiency calculation was the correct evaluation of the electric field strength in the crystals and also using the integration limit d rather than W when W >d (in contrast to the earlier works).

Design of metal contacts for monolayer Fe3GeTe2 based devices

Using ab initio density functional calculations, we study the interfacial properties of the Fe3GeTe2 monolayer in contact with the Au, Cu, In, Cr, Ti, and Ni metal substrates. It is found that Cr, Ti, and Ni bind strongly with Fe3GeTe2, in contrast to Au, Cu, and In. By analyzing the density of states, charge redistribution, and tunneling barrier, it is suggested that the commonly used Au, Cu, In, and Cr electrodes are insufficient for the electron and spin injection. Ti and Ni metal substrates are proposed to have good electronic transparency to the Fe3GeTe2 monolayer. The Ni substrate is found to have a large spin injection to the Fe3GeTe2 monolayer in addition to its excellent electron injection. Our results indicate that Ni is a promising electrode for the Fe3GeTe2 monolayer to form current in-plane devices, thus shedding light on the optimal selection of metal electrodes for the development of next generation spintronic devices based on atomically thin nanomaterials.