CoO3 Thin Films Research Articles

Retraction Note to: Sol–gel derived Co3O4 thin films: effect of annealing on structural, morphological and optoelectronic properties

Retraction Note to: Sol–gel derived Co3O4 thin films: effect of annealing on structural, morphological and optoelectronic properties

Deposition of nanostructured Sn doped Co3O4 films by a facile nebulizer spray pyrolysis method and fabrication of p-Sn doped Co3O4/n-Si junction diodes for opto-nanoelectronics

In this work, we have prepared Co3O4 thin films for different doping level including 0, 2, 4, and 6 wt% by JNSP method and analyzed their structural, morphological, optical, and electrical properties by XRD, FE-SEM, EDX, UV-Vis, and current-voltage (I-V) characteristics. The XRD profiles confirm the cubic crystal structures of Sn doped Co3O4 films. Spherical-like grains are observed from the FE-SEM images and were suppressed due to Sn doping. Also, the elements like Sn, Co, and O were confirmed by EDX analysis. The optical band gap of Co3O4 film is noticed to be increased after adding Sn ions, which has been studied through UV-Vis spectroscopy. Most importantly, we have fabricated an undoped and Sn doped p-Co3O4/n-Si junction diode for various concentrations. The determined ideality factor of the p-Sn doped Co3O4/n-Si diodes were reduced for both under dark and light conditions. In addition, the calculated responsivity, quantum efficiency, and specific detectivity of the diodes were enhanced with forwarded voltage. The p-Sn@Co3O4/n-Si diode fabricated with 2 wt% was achieved maximum responsivity and quantum efficiency of R = 247.03 mA/W, QE = 95.7%, and D* = 2.84 ×1010 at 3 V. We observed that the p-Sn doped Co3O4/n-Si diodes are highly sensitive and appropriate for photo-detection applications.

Physical and electrochemical properties of spray-deposited Co3O4 thin films

ABSTRACT Nanostructured cobalt oxide films have been prepared by a simple and cost-effective chemical spray pyrolysis. The effect of the quantity of the spraying solution for various film properties has been studied. The X-ray diffraction analysis shows that Co3O4 thin films are cubic in nature with strong (311) orientation. SEM images show a porous morphology. Optical band gap energies are between 1.41 and 1.48 eV in the lower and 1.84–2.02 eV in the higher energy regions, respectively. Specific capacitance is 565 Fg−1 at a scan rate of 5 mVs−1. Specific energy 57.50 Whkg−1, specific power 1.8 kWkg−1 and columbic efficiency 89.15% are found from galvanostatic charge/discharge studies. Such unique nanostructures delivered adequate active sites for redox reaction resulting in enhanced electrochemical behaviour. These findings suggest a favourable route towards the fabrication of electrodes for high-performance supercapacitors.

LiOx-modification of Ni and Co3O4 surfaces: An XPS, LEIS and LEED study

LiOx was deposited at room temperature by physical vapor deposition (PVD) on polycrystalline Ni foil and Co3O4(111) thin film, creating uniform model systems well-suited for surface-sensitive characterization by X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) or low energy electron diffraction (LEED). In the case of Ni, about 15 layers of LiOx film were grown under the current conditions either stepwise or continuously, with XPS analysis indicating a deposition rate of 0.16 and 0.24 ML/min, respectively. Li 1s and O 1s spectra revealed that Li2O and to a lesser extent LiOH were preferentially formed. The stability of the LiOx films was examined in UHV, upon annealing at 573 K and upon hydrogen reduction at 723 K. On the more reactive Co3O4(111) film grown on Ir(100), the Li accommodation rate was about twice as high, at least within the first minutes of deposition. Post-deposition LEED showed an obscured cobalt oxide diffraction pattern, not unexpected in light of the LiOx deposited. On both substrates, LEIS characterization of Li (≈ 103 eV) was prevented by the high background in this kinetic energy region, due to surface roughness and unspecific scattering. Still, LiOx deposition was evident from the vanished LEIS signals of Ni or Co. The prepared LiOx-modified surfaces may serve as starting point for the future growth of epitaxial LixCoO2 model systems.

Anode‐supported solid oxide fuel cells with multilayer LSC/CGO/LSC cathode

AbstractThe multilayer La0.6Sr0.4CoO3/Ce0.9Gd0.1O2/La0.6Sr0.4CoO3 (LSC/CGO/LSC) thin film cathode of the solid oxide fuel cell (SOFC) with the different thickness of the LSC and CGO layers are obtained by magnetron sputtering. Cathodes are deposited onto the NiO/8YSZ anode‐supported 8YSZ/CGO bilayer electrolyte. The influence of the deposited multilayer cathode on the SOFC performance is investigated in the temperature range between 800 and 600°C. It is shown that the thin‐film multilayer cathode allows increasing the SOFC efficiency, and the obtained optimum thickness of the LSC and CGO layers provides the maximum power density for SOFCs. The maximum power density of 2430, 1170, and 290 mW cm–2 is obtained respectively at 800, 700, and 600°C for the SOFCs with the LSC/CGO/LSC layer 50/50/50 nm thick. The polarization resistance measured at 800 and 750°C on the symmetric SOFC with the CGO electrolyte and LSC/CGO/LSC cathode is 0.17 and 0.3 Ω cm2, respectively.

Investigation of structure, dielectrical, optical, and electronic properties for Y0.225Sr0.775CoO3 thin films deposited on different single crystal substrates using pulsed laser deposition (PLD) method

Investigation of structure, dielectrical, optical, and electronic properties for Y0.225Sr0.775CoO3 thin films deposited on different single crystal substrates using pulsed laser deposition (PLD) method

Novel (CH6N3+, NH3+)-functionalized and nitrogen doped Co3O4 thin film electrochemical sensor for nanomolar detection of nitrite in neutral pH

The present work provides a soft chemical route for simultaneous nitrogen doping and (CH6N3+, NH3+)-functionalization of pre-deposited Co3O4 thin film. The Co3O4 thin film was prepared by metal-organic decomposition (MOD) on fluorine-doped tin oxide (FTO) substrate and hydrothermally treated in the presence of amino acid, L-Arginine. The L-Arginine-treated Co3O4 thin film (L-Arginine/Co3O4/FTO) was used for the electrochemical detection of nitrite under neutral pH condition. Various physical (i.e. XRD, XPS, SEM, and Raman spectroscopy) and electrochemical characterization (i.e. CV, CA, EIS, and Tafel slope) was conducted to elucidate the role and effect of L-Arginine on Co3O4 film and determine the sensor performance characteristics. L-Arginine/Co3O4/FTO electrode exhibited a low limit of detection of 1.95 nM, an ultrafast response time of <2 s, and a wide linear range of up to 16 mM in neutral pH. The sensor was nitrite selective in the presence of common interferants and showed chemical stability and reproducibility. The practical application of the proposed sensor was demonstrated using real samples for nitrite detection.

Study and synthesis of polymer-blend PVA-PEG doped with 5wt% MgO and different wt% of Co3O4 Thin Film

In this study, Poly (vinyl alcohol) - Poly (ethylene glycol) (PVA-PEG) poly-blend and its composite with 5wt.% and different wt.% (2, 4, and 6) of Co3O4 films were synthesized using blend casting method. The characterization was considered such as; Fourier transforms infrared (FT-IR), electrical properties, and its application for gamma ray shielding. The electrical properties showed that the dielectric constant and dielectric loss for all different rates of Co3O4 particles decreases with the increase of the electric field frequency, and that its values increase with the increasing of the wt.% of Co3O4 particles. The (PVA-PEG) poly-blend and its composite with and different wt.% of Co3O4 films have good linear attenuation coefficients for gamma ray radiation.

Study of resistive switching, photoresponse, and magnetism modulation in the Pt/Co3O4/Nb:SrTiO3 heterostructure

Co3O4 thin films are epitaxially grown on an Nb-doped (001) SrTiO3 (NSTO) single-crystal substrate using pulsed laser deposition to form Pt/Co3O4/NSTO heterostructures. These devices display stable bipolar resistive switching (RS) with multilevel memory, good endurance, and a maximum ON/OFF ratio of up to 104. The high resistance state of the device exhibits significant photoresponse characteristics with an open-circuit voltage of 0.47 V, under the illumination of a 405 nm laser. Moreover, the saturation magnetization of the Co3O4 film shows reversible switching associated with different resistance states. The RS and related photoelectricity could be attributed to the modulation of the potential barrier via the oxygen vacancy migration coupled with electron trapping/detrapping and light illumination at the Co3O4/NSTO interface; meanwhile, the change in magnetism might be due to the redistribution of the oxygen vacancies. These results provide a promising pathway for developing multifunctional, multilevel memory devices with RS, photoresponse, and magnetism.

Model Studies on the Formation of the Solid Electrolyte Interphase: Reaction of Li with Ultrathin Adsorbed Ionic-Liquid Films and Co3 O4 (111) Thin Films.

In this work we aim towards the molecular understanding of the solid electrolyte interphase (SEI) formation at the electrode electrolyte interface (EEI). Herein, we investigated the interaction between the battery‐relevant ionic liquid (IL) 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP‐TFSI), Li and a Co3O4(111) thin film model anode grown on Ir(100) as a model study of the SEI formation in Li‐ion batteries (LIBs). We employed mostly X‐ray photoelectron spectroscopy (XPS) in combination with dispersion‐corrected density functional theory calculations (DFT‐D3). If the surface is pre‐covered by BMP‐TFSI species (model electrolyte), post‐deposition of Li (Li+ ion shuttle) reveals thermodynamically favorable TFSI decomposition products such as LiCN, Li2NSO2CF3, LiF, Li2S, Li2O2, Li2O, but also kinetic products like Li2NCH3C4H9 or LiNCH3C4H9 of BMP. Simultaneously, Li adsorption and/or lithiation of Co3O4(111) to LinCo3O4 takes place due to insertion via step edges or defects; a partial transformation to CoO cannot be excluded. Formation of Co0 could not be observed in the experiment indicating that surface reaction products and inserted/adsorbed Li at the step edges may inhibit or slow down further Li diffusion into the bulk. This study provides detailed insights of the SEI formation at the EEI, which might be crucial for the improvement of future batteries.

Temperature and pH effect on reaction mechanism and particle size of nanostructured Co3O4 thin films obtained by sol-gel/dip-coating

This article reports the preparation of Co3O4 phase films by sol-gel. Initially, the precursor solution was prepared by the reaction of cobalt acetate tetrahydrate with methanol. Clean glass substrates were dipped into the solution for 4 times with a speed of dipping of 2 cm per minute. Afterwards, the films deposited were thermally treated at 500 °C to produce the Co3O4 phase. FTIR, UV-Vis and XRD techniques were used to analyze the effects of temperature and pH on reaction carried out on the precursor solution. While the microstructural characterization of thermally treated films was performed through XRD and SEM techniques. In parallel, were studied the thermal decompositions of both Co(CH3COO)2 phase as precursor solution S2 powders using TGA-DTA techniques. The results show that Co3(CH3COO)5OH phase was identified as the precursor to the Co3O4 phase. It was observed that the synthesis temperature promotes the formation reaction of Co(CH3COO)5OH. While the decrease in pH by addition of citric acid had 2 effects. The first was to delay the formation reaction, and the second was to decrease the particle size of phase Co3O4 < 10 nm.

Study of some Physical Properties and the Effect of Gamma Irradiation on Optical Properties of Electrochromic Co&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Thin Film

Cobalt oxide thin film (Co3O4) has been prepared from cobalt chloride with distilled water on conducting glass substrates Fluorine doped Tin Oxide (FTO) at (400ºC) by depositing chemical spray pyrolysis, with thickness (200 nm). The structural properties are studied by XRD. Also, optical properties and electrical properties of Co3O4 thin film are studied by UV spectroscopy and Cyclic voltammetry (CV) respectively. The effects of gamma irradiation on optical properties are also examined. XRD results showed that the film was polycrystalline with cubic structure having preferred orientation (111). The as-prepared Co3O4 film exhibits a noticeable EC behaviour with reversible colour which changes from dark grey to pale yellow with bleaching time (55 s) and colouring time (40 s). After irradiation, the optical properties showed that as the transmittance decrease leads to decrease the direct optical band gap from (3.68eV) to (3.55eV)

Elevated performance of binder-free Co3O4 electrode for the supercapacitor applications

In the present work, we have designed a symmetric supercapacitor (SS) device by synthesizing a pseudocapacitive binder-free cobalt oxide (Co3O4) thin film based electrode using reactive DC magnetron sputtering technique. The thin film electrodes were characterized by x-ray diffraction, Raman spectroscopy and x-ray photoelectron spectroscopy to reveal the crystallographic details, stoichiometry, and electronic configuration, respectively. Furthermore, Co3O4 thin film electrode is used for pseudocapacitor and electrochemically tested in 1M aqueous KOH electrolyte solution, in addition, a symmetric supercapacitor (SS) device was fabricated. It was found that the SS device exhibits tremendous electrochemical stability in terms of high capacitance and good cycling stability. The value of specific capacitance for Co3O4 thin film electrodes and the SS device was calculated to be 392 Fg−1 and 95 Fg−1, respectively, at a scan rate of 2 mAcm−2. The SS device exhibits high specific energy (29 W-hkg−1) along with comparable good specific power (4745 Wkg−1). In this work, the fabricated SS device demonstrates 91.40% cyclic and capacitance retention at 8 mAcm−2 beyond 10 000 cycles. The excellent electrochemical stability and capacitive performance of the SS device suggest that it would be an ideal and potential candidate for energy storage applications in the future.

Electronic interactions between graphene and cobaltite thin film La0.7Sr0.3CoO3 and its magnetic consequences

We have successfully synthesized and transferred graphene (Gr) monolayers on top of epitaxial mixed valence La0.7Sr0.3CoO3 (LSCO) thin films. Raman spectroscopy reveals that Jahn-Teller (JT) modes associated with the oxygen octahedral distortions usually unobserved for bare LSCO are activated by the deposited graphene. The appearance of these JT modes in the Gr/LSCO heterostructure is attributed to the electronic interactions at the interface between the graphene and the LSCO thin film promoting intermediate spin states of the Co ions. As a result, the magnetic properties of LSCO are affected. Indeed, magnetization measurements show a phase transition at ~135 K which is due to the presence of the graphene while the ferromagnetic transition of bare LSCO films is observed at~200 K. This magnetic phase is confirmed by Raman spectroscopy measurements as a function of temperature revealing a vibrational transition around the same temperature.

Facile preparation of a cobalt diamine diketonate adduct as a potential vapor phase precursor for Co3O4films.

Co3O4 thin films and nanosystems are implemented in a broad range of functional systems, including gas sensors, (photo)catalysts, and electrochemical devices for energy applications. In this regard, chemical vapor deposition (CVD) is a promising route for the fabrication of high-quality films in which the precursor choice plays a key role in the process development. In this work, a heteroleptic cobalt complex bearing fluorinated diketonate ligands along with a diamine moiety [Co(tfa)2·TMEDA; tfa = 1,1,1-trifluoro-2,4-pentanedionate and TMEDA = N,N,N',N'-tetramethylethylenediamine] is investigated as a potential Co molecular precursor for the CVD of Co3O4 systems. For the first time, the compound is characterized by crystal structure determination and comprehensive analytical studies, focusing also on its thermal properties and fragmentation patterns, important figures of merit for a CVD precursor. The outcomes of this investigation, accompanied by detailed theoretical studies, highlight its very favorable properties for CVD applications. In fact, growth experiments under oxygen atmospheres containing water vapor revealed the suitability of Co(tfa)2·TMEDA for the fabrication of high-quality, phase-pure Co3O4 thin films. The versatility of the proposed strategy in tailoring Co3O4 structural/morphological features highlights its potential to obtain multi-functional films with controllable properties for a variety of eventual technological end-uses.

Microplotter-Printed On-Chip Combinatorial Library of Ink-Derived Multiple Metal Oxides as an "Electronic Olfaction" Unit.

Information about the surrounding atmosphere at a real timescale significantly relies on available gas sensors to be efficiently combined into multisensor arrays as electronic olfaction units. However, the array's performance is challenged by the ability to provide orthogonal responses from the employed sensors at a reasonable cost. This issue becomes more demanded when the arrays are designed under an on-chip paradigm to meet a number of emerging calls either in the internet-of-things industry or in situ noninvasive diagnostics of human breath, to name a few, for small-sized low-powered detectors. The recent advances in additive manufacturing provide a solid top-down background to develop such chip-based gas-analytical systems under low-cost technology protocols. Here, we employ hydrolytically active heteroligand complexes of metals as ink components for microplotter patterning a multioxide combinatorial library of chemiresistive type at a single chip equipped with multiple electrodes. To primarily test the performance of such a multisensor array, various semiconducting oxides of the p- and n-conductance origins based on pristine and mixed nanocrystalline MnOx, TiO2, ZrO2, CeO2, ZnO, Cr2O3, Co3O4, and SnO2 thin films, of up to 70 nm thick, have been printed over hundred μm areas and their micronanostructure and fabrication conditions are thoroughly assessed. The developed multioxide library is shown to deliver at a range of operating temperatures, up to 400 °C, highly sensitive and highly selective vector signals to different, but chemically akin, alcohol vapors (methanol, ethanol, isopropanol, and n-butanol) as examples at low ppm concentrations when mixed with air. The suggested approach provides us a promising way to achieve cost-effective and well-performed electronic olfaction devices matured from the diverse chemiresistive responses of the printed nanocrystalline oxides.

Laser Irradiation Effect on The Optical Properties of CoO2 Thin Films deposited via Semi-Computerized Spraying System

In this paper deals with the effect laser irradiation on the optical properties of cobalt oxide (CoO2) thin films and that was prepared using semi computerized spray pyrolysis technique. The films deposited on glass substrate using such as an ideal value concentration of (0.02)M with a total volume of 100 ml. With substrate temperature was (350 C), spray rate (15 ml/min).The XRD diffraction given polycrystalline nature with Crystal system trigonal (hexagonal axes). The obtained films were irradiated by continuous green laser (532.8 nm) with power 140 mW for different time periods is 10 min,20min and 30min. The result was that the optical properties of cobalt oxide thin films affected by laser irradiation where the absorbance, absorbance coefficient, extinction coefficient and the real ε 1 and imaginary ε 2 part of the dielectric constant of the films increases after laser irradiation. While the Transmittance and refractive index decrease with laser irradiation. The optical energy gap was decreased from (1.89 eV to 1.6 eV) after laser irradiation, and this is a good variation of bandgap values for photovoltaic applications.

Cobalt Oxide-Supported Pt Electrocatalysts: Intimate Correlation between Particle Size, Electronic Metal-Support Interaction and Stability.

Oxide supports can modify and stabilize platinum nanoparticles (NPs) in electrocatalytic materials. We studied related phenomena on model systems consisting of Pt NPs on atomically defined Co3O4(111) thin films. Chemical states and dissolution behavior of model catalysts were investigated as a function of the particle size and the electrochemical potential by ex situ emersion synchrotron radiation photoelectron spectroscopy and by online inductively coupled plasma mass spectrometry. Electronic metal-support interaction (EMSI) yields partially oxidized Ptδ+ species at the metal/support interface of metallic nanometer-sized Pt NPs. In contrast, subnanometer particles form Ptδ+ aggregates that are exclusively accompanied by subsurface Pt4+ species. Dissolution of Cox+ ions is strongly coupled to the presence of Ptδ+ and the reduction of subsurface Pt4+ species. Our findings suggest that EMSI directly affects the integrity of oxide-based electrocatalysts and may be employed to stabilize Pt NPs against sintering and dissolution.

A Highly Sensitive and Selective Non‐enzymatic Hydrogen Peroxide Sensor Based on Nanostructured Co3O4 Thin Films Using the Sol‐gel Method

AbstractIn this work we report an easy and efficient way to fabricate nanostructured cobalt oxide (Co3O4) thin films as a non‐enzymatic sensor for H2O2 detection. Co3O4 thin films were grown on ITO glass substrates via the sol‐gel method and characterized with several techniques including X‐ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorbance. The Co3O4 thin films’ performance regarding hydrogen peroxide detection was studied in a 0.1 M NaOH solution using two techniques, cyclic voltammetry (CV) and amperometry. The films exhibited a high sensitivity of 1450 μA.mM−1.cm−2, a wide linear range from 0.05 μM to 1.1 mM, and a very low detection limit of 18 nM. Likewise, the Co3O4 thin films produced showed an exceptional stability and a high selectivity.

Interaction between Li, Ultrathin Adsorbed Ethylene Carbonate Films, and CoO(111) Thin Films: A Model Study of the Solid Electrolyte Interphase Formation at CoO Anodes

Aiming at a detailed understanding of the formation of the solid electrolyte interphase (SEI) at the electrode–electrolyte interface, which plays a critical role in the performance of Li-ion batteries (LIBs), we studied the interaction between Li, ultrathin films of ethylene carbonate (EC, main electrolyte component in LIBs), and CoO(111) thin films grown on Ru(0001), where the latter serves as a model for a conversion electrode, under ultrahigh vacuum conditions. Employing X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Fourier transform infrared spectroscopy, we found that vapor deposition of EC on CoO(111) at 80 K results in partial decomposition of EC for films in the monolayer range, most likely because of interaction with defect sites, while it adsorbs molecularly in the multilayer regime. In both cases, desorption sets in at 170 K. Between 220 and 240 K, competing desorption and decomposition take place. To mimic the electrolyte, 0.5–2 ML of Li was stepwise postdeposited on a preadsorbed EC adlayer at 80 K and at 300 K, which leads to EC decomposition, most likely into Li-containing −C═O, −C–O–C–, −C–H, −C–C– species, and Li2O2 or LiOH. This can be considered as the initial stage of the chemical SEI formation (open-circuit conditions). CoO conversion, which is essential for Li storage in the electrode, is observed after postdeposition of Li onto a surface precovered with EC decomposition products at 300 K. In these measurements, we could resolve molecular details on the SEI formation on a CoO model anode and on the conversion of CoO, both of which are important processes in conversion-based LIBs.