Effect Of Co-doping Research Articles

B2O3- and Y2O3-doped ZnO varistor ceramics: Enhanced voltage gradient and nonlinear properties for UHV

In this paper, the effects of boron and yttrium co-doping on the electrical properties of ZnO varistors were determined. The presence of both B3+ and Y3+ co-dopant improved the electrical performance of varistor ceramics. The nonlinearity coefficient α and potential barrier ϕb were increased noticeably. The nonlinearity coefficient α was 73 and ϕb was 2.75 eV, at the same time, a voltage gradient of 425 V/mm and leakage current of 0.9 μA/cm2 were obtained. This work provided a way to enhance the protective effects of ZnO varistor arresters for ultra-high voltage power transmission systems.

Sub-nm Near-Surface Activation Profiling for Highly Doped Si and Ge Using Differential Hall Effect Metrology (DHEM)

Contact resistivity at the metal-semiconductor interface is a strong function of the carrier concentration in the near surface. For next generation 2D/3D MOSFET transistors, industry has been investigating very highly doped materials (>1x1021cm-3) approaching alloy concentrations in Silicon and various Silicon-Germanium materials. All the while, contact development in Ge NMOS has favored co-doping approaches. Regardless of the material system, it is very important to accurately measure near-surface dopant activation. In this paper, we use Differential Hall Effect Metrology (DHEM) implemented on the ALPro™ tool to characterize the activation profiles in both materials. The method employs electrochemical means of reducing the electrically active thickness of a semiconductor film and determining the sheet resistance and mobility of the thinned down layer using Van der Pauw/Hall effect type measurements. By repeating this process and using differential equations, depth profiles of mobility and carrier concentration are obtained [1] at sub-nm resolutions.It is difficult to achieve high n-type dopant activation in Ge. Point defects in Ge are known to behave as acceptor sites and reduce the overall free electron density, particularly near the surface. Minimization of these defects is essential to achieving high performance Ge NMOS. Accurate analysis of dopant activation within 5 nm of the surface is critical to understanding effectiveness of various process steps on improving contact resistance. We have previously published a study on the effect of Ge co-doping with Sb and P on near-surface dopant activation. In Ge with only P-doping it was found that only ~5x1018cm-3 or 5% of the total surface dopants (~1x1020cm-3) were electrically active. With Sb as a co-dopant, the active electron concentration increased to ~2x1019cm-3 with a similar P chemical concentration. Prior work has shown similar increases in activation with co-doping but did not capture the significant decrease in electron concentration by 4x within 10 nm of the surface. Here, we further study the effects of the implantation and annealing processes on near-surface dopant activation in n-type Ge. Samples were prepared by growing 3 µm thick epi-Ge layers on Si substrates. Sample 1 was capped with 20 nm SiO2 and Sample 2 was capped with 20 nm Al2O3 to minimize implant damage and control implant depth. Both samples were implanted first with Sb (dose: 6x1014cm-2, energy: 65 keV) followed by P (dose: 6x1014cm-2, energy: 90 keV). Post-implant anneal was done at 500°C for 10 s in N2 to activate the dopants. ALProTM and SIMS measurements were done to characterize active dopant concentration and total chemical dopant concentration, respectively. The Al2O3 capped sample (Sample 2) showed significantly lower carrier concentration than the SiO2 capped sample (Sample 1) throughout the depth of the profile (Figure 1). Carrier concentration at the surface was lower by nearly an order of magnitude, decreasing from ~2x1019cm-3 to ~2x1018cm-3. Additionally, the peak concentration decreased from 1x1020cm-3 to 5x1019cm-3 at a depth of ~30 nm in both cases. The variations in the carrier profile for the Al2O3 capped sample also indicate greater process variation. SIMS profiles show that there is significant diffusion of Al into the Ge matrix after implant and anneal. Al chemical concentration is 1x1020cm-3 at the Ge surface and steadily decays up to a depth of more than 300 nm. This indicates that there is significant damage caused during the implantation process and the activation anneal is not enough to remove these defects. Al atoms then diffuse from the Al2O3 capping layer into the highly defective Ge substrate. Al is a p-type dopant in Ge and counter-dopes the Sb and P implants to reduce overall electron concentration in Sample 2. It is important to note the high resolution DHEM technique was able to resolve this important phenomenon right near the surface of the material.Additionally, we present early data on very highly phosphorus-doped (~1x1021cm-3) epitaxial silicon thin films grown on Si substrates. In very highly doped Silicon materials, the effect of near-alloy levels of dopant in the matrix on dopant deactivation is not well-known. Samples were obtained with different levels of dopant concentration above ~1x1021cm-3and different anneal temperatures. It was found that near-surface activation in these un-capped samples led to a lowering of activation in the <20nm region from the surface. Extensive post-DHEM metrology (using TEM and SIMS analysis) will also be presented demonstrating control and precision of DHEM data.

(Invited) Effects of Cobalt Co-Doping on Mixed Ion Conductivity in La(Sr)Ga(Fe)O3 for Oxygen Separation

Mixed ion conductor shows oxide ion and electronic conduction simultaneously and expecting for application to oxygen separation membrane from air. Because of significant volume change depending on oxygen partial pressure, oxygen separation membrane using mixed ion conductor has disadvantage of narrow range of oxygen partial pressure resulting in the limited permeation rate. Therefore, increased oxide ion conductivity and mechanical strength have been required for mixed ion conducting membrane for oxygen separator. In our previous study, we found that Fe doped LaGaO3 shows reasonably high oxide ion conductivity and chemical stability. In particular, La0.7Sr0.3Ga0.6Fe0.4O3 (LSGF) shows largest oxide permeation rate from air to He. In this study, for further increase in oxygen permeation rate, effects of dopant to Ga site in LSGF was investigated. Application to CH4 partial oxidation was also studied. All LSGF sample was prepared with conventional solid state reaction method using oxide as source materials. Partial substitution was performed for Ga site in LSGF and dense sample without impurity phase was confirmed by XRD measurement. For oxygen permeation measurement, La0.6Sr0.4CoO3 catalyst was coated on the surface of LSGF disk (Φ17mm diameter, 0.5mm thickness) It was found that the oxygen permeation from air to He was sensitively influenced by dopant and the oxygen permeation rate was increased as the following order, Co>Al>In>Ni>Mn at 1273 K. On the other hand, in case of Ru and Ir which is easily reduced to metallic state decreased the oxygen permeation rate significantly. Therefore, it was found that addition of 10 mol % of Co or Al is effective for increasing oxygen permeation rate of LSGF. Effects of Co in LSGF was further studied from oxygen permeation rate and the highest oxygen permeation rate was achieved at 3 mol% in Ga site of LSGC. On this optimized composition, La0.7Sr0.3Ga0.57Fe0.4Co0.03O3, shows 225 μmol min-1 cm-2 at 1273 K and this value is almost 2.5 times larger than that of LSGF. Effects of small amount of Co on electrical conductivity in LSGF were also studied. Although LSGF shows high hole conduction like log(σ/Scm-1)=0.6, the conductivity was increased by Co doping, in particular, at lower temperature. In contrast, Al doping decreases total conductivity and so, increase in oxygen permeation rate could be assigned to the increased mobility of oxide ion in LSGF. Application of Co doped LSGF to CH4 partial oxidation was further studied. Although optimized amount of Co doped for Ga site in LSGF is 3 mol%, the membrane was broken when 3 mol% doped LSGF was used for oxygen membrane. 1% Co doped LSGF was applied for oxygen permeation membrane and it was found that amount of oxygen permeation rate was 1.5 times increased comparing with LSGF. In addition, no crack was formed in membrane. The amount of oxygen permeation was achieved 364μmol cm2 min-1 which is corresponded to 8.9ml/min cm2 at 1273K. In summary, this study reveals that doping small amount of Co to Ga site of LSGF is highly effective for increasing oxygen permeation rate without decreasing chemical stability.

Synthesis of M-Hexaferrites Material Based on Natural Iron Sand with Metal Co Doping Using the Coprecipitation Method

The synthesis of M-hexaferrite with metal doping Co (BaFe12-3xCoxO19 ) based on natural iron sand at Ketapang beach in Pringgabaya Subdistrict, East Lombok using the coprecipitation method has been successful. The basic ingredients used in this study were natural iron sand and BariumCarbonate (BaCO3) powder, while the doping material used was Cobalt (II) Chloride Hexahydrate (CoCl2.6H2O) powder with a variety of mole fraction (X = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0). The solvent uses 37% hydrochloric acid (HCl), 25% NH4OH solution, and distilled water. The sample formed was then calcined at 200 0C, 400 0C, 600 0C, 800 0C and 1000 0C. The resulting sample shows that there is an effect of Co doping and calcination temperature in the formation of barium M-hexaferrite. The higher the mole fraction of Co doping ions and the calcination temperature, the darker the color of the powder produced.

Co-doping effect of lead or erbium upon the spectroscopic properties of bismuth doped optical fibres

The effect of the lead or erbium co-doping upon the spectroscopic properties has been systematically investigated through the analysis of the absorption and emission spectra of Bi doped fibre (BDF), Bi/Pb and Bi/Er co-doped fibre (BPDF and BEDF). All these BDFs have a broadband emission from 1000 nm to 1600 nm. The Pb or Er co-doping in BDFs will evidently reduce the formation of bismuth related active centres (BACs) due to the formation of other types’ centres and then restrain the emission of BAC through their competition of the pump consumption and the cross energy transfer among these active centres. Further analysis indicates that the co-doping effect of Pb to restrain the formation of BAC and its emission is stronger than that of Er to some degree, possibly due to the analogy property between Bin+ and Pbn+ with isoelectronic configures. In addition, the analysis of the BAC concentration indicates that the atom concentration measured by energy dispersive X-ray (EDX) analyser has a large gap with the effective content reflected from the absorption and emission. All these results point out a way to design and fabricate bismuth doped/co-doped fibre with high performance in future.

Influence of Eu3+ on the Structure and Photophysical Properties in (Y,Gd)F3 Nanophosphors.

The scientific community has shown a growing interest in relating to the lanthanide based luminescent materials and it has made an effort to develop them. Among these several luminescent materials, we have proposed to developed (Y,Gd)F3 nanophosphors doped with distinct of Eu3+ concentrations using modified hydrothermal process. The effect of co-doping of rare earth activators to the host lattice structure and morphology are investigated using different analytical techniques. The diffuse reflectance spectra reveal a tuning of optical band gap due to substitutions. From the extensive XPS analysis, Gd and Eu are found to be in a stable ionic state of +3 which is replacing Y3+ in YF3 host. Photoluminescence emission spectra of the nanophosphors are excited by near ultraviolet (UV, 393nm) excitation. From photoluminescence study, the intensity variation is observed for emission peak at 591nm and fluorescence quenching occurs at higher doping level. This effect subsequently explained on the frame work of local symmetry and nonradiative transfer among multipole-multipole interaction. At 393nm excitation Eu3+ (2, 3, 5, 7, 10 at %) doped (Y, Gd) F3 show CIE chromaticity coordinates shifted to red regions with increase in Eu doping levels. Because of the longer decay time these phosphors can be used for bio-labeling and other similar applications.

Co-doping effect of Hf and Y on improving cyclic oxidation behavior of (Ni,Pt)Al coating at 1150 °C

Hf and/or Y doped (Ni,Pt)Al coatings were prepared to investigate their initial oxidation behavior and cyclic oxidation performance at 1150 °C. Finer grain sizes were observed in Hf and/or Y doped (Ni,Pt)Al coatings in as-received state, wherein the best oxidation resistance was achieved in the co-doped coating. In oxidation, Hf and Y were observed synchronously segregating at grain boundaries of alumina scale, which more effectively retarded the phase transformations of θ-Al2O3 to α-Al2O3 for the oxide scale and from β to γ′ for the coating. Mechanisms responsible for the merits of Hf-Y co-doping in (Ni,Pt)Al coating are discussed.

Effect of Nd2O3 and CeO2 co-doping on the Dielectric Properties of Ba0.94Ca0.06Ti0.90Sn0.10O3 Lead-Free Ceramics

Effect of Nd2O3 and CeO2 co-doping on the Dielectric Properties of Ba0.94Ca0.06Ti0.90Sn0.10O3 Lead-Free Ceramics

Nitrogen and sulfur co-doped reduced graphene oxide-gold nanoparticle composites for electrochemical sensing of rutin

The extraordinary biological and physiological properties of rutin have been used in the preparation of therapeutical drugs. So it is very significant to develop a simple and sensitive method for rutin determaination in pharmaceutical samples. Herein, nitrogen and sulfur co-doped reduced graphene oxide attached with gold nanoparticles (NS-rGO/AuNPs) was developed for electrochemical determination of rutin. The NS-rGO was first prepared by a simple one-step thermal annealing method, and AuNPs were embedded onto NS-rGO through the interaction force of Au with N and S atoms. Detailed characterizations showed that the AuNPs are well dispersed and the presence of nitrogen and sulfur are significant. The NS-rGO/AuNPs modified electrode exhibited a significantly enhanced electrocatalytic activity towards rutin compared with NS-rGO, N-rGO and S-rGO modified electrodes. The excellent performance was achieved by the synergistic effect of AuNPs and heteroatoms co-doping. As a consequence, the NS-rGO/AuNPs based sensor showed a wide linear range of 0.2–1400 nM with a nanomolar detection limit of 0.067 nM (S/N = 3). Also the sensor exhibited satisfying selectivity, reproducibility, and stability. Finally, the sensor was successfully used to determine rutin in pharmaceutical tablets.

Effect of Al and Mg Co-doping on the Microstructural and Gas-Sensing Characteristics of ZnO Nanoparticles

Al and Mg co-doped ZnO nanoparticles were synthesized via the sol-gel technique to detect carbon oxides. The impact of Al and Mg on the structural, morphological and optical properties was discussed. XRD patterns revealed that Al and Mg ions successfully incorporate within the hexagonal crystalline structure of ZnO. The crystallites sizes of the samples heated at 400 °C ranges between 23 and 27 nm. TEM characterizations showed prismatic-like shape crystallites. Optical characterizations were carried out by UV-VIS-NIR spectroscopy and photoluminescence, showing high absorbance in the UV region and a slight decrease in energy band-gap compared to undoped ZnO. The PL spectra of all samples illustrated two major emissions including a broad visible band and a narrow ultraviolet (UV) band. Finally, it was confirmed that Al-Mg co-doping ZnO films promote carbon oxides sensing properties in terms of higher response, low detection limit and lower response/recovery time in comparison with undoped ZnO film.

Modulating broadband near infrared emission from Bi doped borate laser glass by codoping nonactive rare earth ions

Bismuth (Bi) doped glasses and fibers, as a new generation of gain media, have been drawing wide attention for the super broad and long lived near infrared (NIR) emission. Yet, great challenge exists for modulating the Bi NIR emission in multi-component glasses. Codoping rare earth ions is a feasible way to modulate the NIR emission properties of Bi, yet limited success have been achieved. Here, to provide deeper understanding on Bi-RE codoped glass, we prepared a series of Bi and nonactive rare earth (RE) codoped aluminoborate glasses and systematically investigated the optical and structure properties. Evidenced by detailed structural and optical characterizations, it is found that the addition of nonactive RE ions changes the glass structure and optical basicity, so as to alter the optical properties of Bi. These results indicate that one should consider the effect of codopant on glass structure and optical basicity when modulating the optical spectra of active ions based on energy transfer, especially for those with multiple valences.

A new perspective of co-doping and Nd segregation effect on proton stability and transportation in Y and Nd co-doped BaCeO3

Bulk and surface properties of proton stability and transportation in Y and Nd co-doped BaCeO3 (BCYN), especially the effect of Nd segregation, were investigated by first-principles calculations. Since the structure of doped BaCeO3 at the operating temperature of proton-conducting has been unclear for a long time, we have summarized the latest experimental results and calculated the structure of the asymmetric BCYN for the first time. The results show that compared with Y, Nd doping promotes oxygen vacancy formation, however reduces proton stability. Our calculation can also provide a possible explanation for the formation of space charge layer at the grain boundary of doped BaCeO3 in experiment. Unlike the stable Y in BCYN, Nd is calculated to be easily segregated, which can facilitate both proton hydration and proton transportation near the surface. Moreover, Nd segregation at the grain boundary is predicted to be beneficial for proton transportation between grains.

Effect of (Sm, Co) co-doping on the structure and electrical conductivity of ZnO nanoparticles

(Sm, Co) co-doped ZnO nanoparticles (Zn1−2xSmxCoxO), have been prepared by the co-precipitation technique. The effect of the dopant ions Sm3+ and Co2+ on the structural, morphological, and electrical conductivity of ZnO has been studied. XRD analysis shows the substitution of Zn2+ ions by the co-doping Sm3+ and Co2+ ions with the formation of secondary phases as Sm2O3 and Co3O4 upon 0.005 co-doping and above. Raman spectra showed the characteristic mode of the wurtzite structure of ZnO nanoparticles with a vibration assigned to the bound of Co with the donor defects at high doping level of (Sm, Co). The spherical morphology of pure ZnO is transformed into nanorods as the concentration of Sm3+ and Co2+ increases. From EDX spectra, it was shown that all samples exhibit an excellent compositional homogeneity that verifies the Sm and Co presence as real dopants in ZnO crystalline structure. FTIR spectra show one discrete peak at 417 cm−1 with another broad peak at 568 cm−1corresponding to Zn–O stretching, which confirms the formation of the wurtzite structure of the samples. Photoluminescence studies reveal the existence of minor defects in the co-doped samples. The study proposes the suitable use of the samples in the high-efficiency UV light-emitting devices due to the intense UV peaks compared with the lower visible peaks. The excitation dependent PL spectra demonstrated a redshift with increasing the excitation wavelength accounting for the distribution of energetic species in the ground state. The DC electrical conductivity is enhanced with (Sm, Co) co-doping of x = 0.1 due to the formation of thermally activated donor levels.

Metal–organic frameworks derived C/TiO2 for visible light photocatalysis: Simple synthesis and contribution of carbon species

A series of in-situ carbon-doped TiO2 (Cx/TiO2) composites with a porous and crystalline structure were successfully synthesized via one-step and low-temperature calcination of titanium metal–organic framework (MOF), MIL-125(Ti). The resultant materials were comprehensively investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption measurements, UV–vis diffuse reflectance spectrum (DRS), photoluminescence (PL) spectra and photoelectrochemical measurements, and their photocatalytic activities for bisphenol A (BPA) degradation were assessed. Compared with the benchmark TiO2 photocatalyst (P25), the Cx/TiO2 composite material with high specific surface, lower band gap, and reduced photogenerated electron hole ratio exhibited outstanding photodegradation activity and durability for BPA, which could be attributed to the combined effect of co-doping of multiple carbon species (substituent carbon and carbonate) and porous structure. During BPA degradation, the holes and superoxide radicals were the primary role oxidative species in the reaction process. Therefore, this new efficient photocatalyst is promising candidate for photodegradation of organic pollutants.

Tailoring of Optical and Physical Properties of ZnO Films by Co-Doping Concentration

The modification and tailoring characteristic of nanostructured materials are of great interest due to controllable and unusual inherent properties in such materials. Cobalt-doped zinc oxide (Co:ZnO) thin films were prepared using the sol-gel technique with the spin coating method. The optical and physical properties of Co:ZnO films were tailored by the adjustment of Co concentration, which was realised by varying the ratio. The morphology and structure properties were characterised, and the effects of Co doping and post-annealing were investigated. Similar with undoped ZnO, the synthesised Co:ZnO films have a hexagonal wurtzite structure with the crystallinity deteriorated, and present high visible transparency with the absorption edge redshifted. Debye–Scherrer analysis of XRD pattern reveals an increase of the crystallite size with doping concentration. The bandgap, calculated using a Tauc Plot method, reveals a decrease in the absorption onset with an increase in the doping level.

Effect of Mn and Ba Codoping on a Magnetic Spin Cycloid of Multiferroic Bismuth Ferrite Nanoparticles

Bismuth ferrite (BFO) is the drosophila of research in multiferroic materials due to its simultaneous magnetic and electric ordering at room temperature. The unfortunate detail is its antiferromagn...

Co-doping effects of Ba2+ and Ta5+ on the microstructure and ionic conductivity of garnet-type solid state electrolytes

A series of garnet-type electrolytes with the compositions of Li6.6+yLa3–yBayZr1.6Ta0.4O12 (0 ≤ y ≤ 0.08) and Li6.4+yLa3–yBayZr1.4Ta0.6O12 (0 ≤ y ≤ 0.08) were obtained through pressureless sintering method at 1230 °C for 1 h successfully. The microstructure and electr0.4O12performance of the electrolytes were characterized and the co-doping effects of Ba2+ and Ta5+ were investigated. The substantially promoted ionic conductivity was achieved by doping Ba2+ into the Li6.4La3Zr1.4Ta0.6O12 ceramic. Ba2+ dopant made the LLZTO electrolyte a higher Li+ concentration ascribed to the valence gap between Ba2+ and La3+. This facilitated the grain growth so that the electrolytes could be sintered densely in a relatively short sintering time. Meanwhile. The Li+ transportation channel would be enlarged due to the larger ion radius of Ba2+ compared to that of La3+. The higher Li+ concentration and the broader Li+ transportation channel contributed primarily to the improvement of the electrical performance of LLZTO electrolytes. The specimen with the constituent of Li6.46La2.94Ba0.06Zr1.4Ta0.6O12 exhibited the highest conductivity of 6.04 × 10−4 S cm−1 and the lowest activation energy of 0.27 eV.

Al/F codoping effect on the structural, electrical, and optical properties of ZnO films grown via atomic layer deposition

Aluminum/fluorine-codoped zinc oxide (AFZO) thin films were prepared on silicon and glass substrates through atomic layer deposition at 150 °C. Their structural, electrical, and optical properties were investigated as functions of the F/Al codoping ratio. The X-ray diffraction analysis revealed that the preferred growth orientation changed depending on the codoping with F, that is, from (0002) for Al-doped ZnO (AZO) films to (1010) for the AFZO ones. The electrical resistivity of the AFZO films (around 5.0 × 10–4 Ω∙cm) was lower than that of the AZO ones; this was mainly attributed to an increase in the n-type carrier concentration (from 4.11 × 1020 cm3 for AZO to 5.86 × 1020 cm3 for AFZO) due to the substitution of the Zn and O sublattice sites by, respectively, the Al and F atoms. The enhanced carrier concentration affected also the optical property of the AFZO films according to the Moss–Burstein shift. The carrier mobility was similarly improved (from 6.96 cm2/V∙s for AZO to 21.2 cm2/V∙s for AFZO) by the passivation of the oxygen vacancies via the F-doping.

Magnetic homogeneity in Fe-Mn co-doped NiO nanoparticles

The effect of Fe and Mn co-doping on the magnetic properties of the antiferromagnetic (AFM) NiO nanoparticles which offer large potential for different magnetic applications have been studied. The Rietveld refinement fitting of powder x-ray diffractometry (XRD) patterns confirmed the phase formation of face-centred cubic crystal structure of NiO and average crystallite size lies in the short range of 32–38 nm. The cavity and broadband ferromagnetic resonance (FMR) measurements taken at room temperature demonstrate the smaller local magnetic inhomogeneity for 4%Mn-4%Fe co-doped NiO nanoparticles as compared to undoped, single doped and co-doped with different concentration NiO nanoparticles. The M-H loops revealed the room temperature ferromagnetism-like behaviour for higher Fe doping concentration and lower Mn doping concentration. This can be attributed to the double exchange interaction. The zero field cooled (ZFC) and field cooled (FC) dc magnetization curves showed a small surface freezing peak (at at low temperatures and a blocking peak (at at higher temperatures. For samples with 4%Mn-4%Fe and 2%Mn-6%Fe, the blocking peak was found at a relatively high temperature in comparison to other samples. This can be attributed to the presence of magnetic exchange interactions which block the magnetic spins against a thermal increase. The ZFC AC-susceptibility showed three peaks; a surface freezing peak at Tf, a blocking peak at TB peak and an anomalous peak at Tx in between and , which was found to be most prominent for the 4%Mn-4%Fe co-doped nanoparticles. The neutron diffraction pattern confirmed the AFM order of the core of the 4%Mn-4%Fe co-doped nanoparticles, which indicates an AFM coupling between the Fe2+ and Mn2+ ions and the Ni2+ ions through super-exchange interaction. Therefore, the origin of TX peak can be attributed to the ferromagnetic coupling between the Fe2+ and Mn2+ ions which has a maximum strength at equal concentration. Thus, small and equal doping concentration of Fe and Mn in NiO nanoparticles increase the magnetic homogeneity which makes them attractive for magnetic applications.

Effect of the N/P/S and transition-metal co-doping on the quantum capacitance of supercapacitor electrodes based on mono- and multilayer graphene

The effect of co-dopants (N, P, and S) and transition metals (TMs = Ti, V, Cr, Mn, Co, Ni) presence in mono- and multilayer graphene on the final material geometry, stability, electrical and magnetic properties, and quantum capacitance was systematically investigated using density functional theory (DFT) calculations. The simultaneous presence of dopants and vacancies is more effective than doping alone in enlarging the quantum capacitance of graphene. Incorporation of N, P, and S co-dopants and TMs -dopants significantly improved the quantum capacitance and surface charge storage of graphene. The co-doping of Ti and N/P/S systems are the most outstanding, with the highest quantum capacitance of 239.84 μF/cm2. However, due to the interaction between layers, the quantum capacitance of multilayered co-doped graphene is lower than the capacitance of similarly-doped monolayered graphene. The results demonstrated in this work provide insights on the effective approach of the quantum capacitance enhancement of graphene-based supercapacitor.