Effect Of Nitrogen Doping Research Articles

Effect of Nitrogen Doping on the Photoluminescence of Amorphous Silicon Oxycarbide Films

The effect of nitrogen doping on the photoluminescence (PL) of amorphous SiCxOy films was investigated. An increase in the content of nitrogen in the films from 1.07% to 25.6% resulted in red, orange-yellow, white, and blue switching PL. Luminescence decay measurements showed an ultrafast decay dynamic with a lifetime of ~1 ns for all the nitrogen-doped SiCxOy films. Nitrogen doping could also widen the bandgap of SiCxOy films. The microstructure and the elemental compositions of the films were studied by obtaining their Raman spectra and their X-ray photoelectron spectroscopy, respectively. The PL characteristics combined with an analysis of the chemical bonds configurations present in the films suggested that the switching PL was attributed to the change in defect luminescent centers resulting from the chemical bond reconstruction as a function of nitrogen doping. Nitrogen doping provides an alternative route for designing and fabricating tunable and efficient SiCxOy-based luminescent films for the development of Si-based optoelectronic devices.

Nitrogen-Doped Cu2O Thin Films for Photovoltaic Applications

Cuprous oxide (Cu2O) is a p-type semiconductor with high optical absorption and a direct bandgap of about 2.1 eV, making it an attractive material for photovoltaic applications. For a high-performance photovoltaic device, the formation of low-resistivity contacts on Cu2O thin films is a prerequisite, which can be achieved by, for instance, nitrogen doping of Cu2O in order to increase the carrier concentration. In this work, nitrogen-doped p-type Cu2O thin films were prepared on quartz substrates by magnetron sputter deposition. By adding N2 gas during the deposition process, a nitrogen concentration of up to 2.3 × 1021 atoms/cm3 in the Cu2O thin films was achieved, as determined from secondary ion mass spectroscopy measurements. The effect of nitrogen doping on the structural, optical, and electrical properties of the Cu2O thin films was investigated. X-ray diffraction measurements suggest a preservation of the Cu2O phase for the nitrogen doped thin films, whereas spectrophotometric measurements show that the optical properties were not significantly altered by incorporation of nitrogen into the Cu2O matrix. A significant conductivity enhancement was achieved for the nitrogen-doped Cu2O thin films, based on Hall effect measurements, i.e., the hole concentration was increased from 4 × 1015 to 3 × 1019 cm−3 and the resistivity was reduced from 190 to 1.9 Ω⋅cm by adding nitrogen to the Cu2O thin films.

Effect of nitrogen doping on the catalytic activity of carbon nano-onions for the oxygen reduction reaction in microbial fuel cells

In this study, highly graphitic nitrogen-doped carbon nano-onions (N-CNOs) were prepared by a one-step, direct, in situ flame synthesis technique and their potential applications as catalysts for oxygen reduction reaction (ORR) in a microbial fuel cell (MFC) were evaluated for the first time. The ORR activity of the CNO, N-CNO, and the commercial Pt/C were measured using a rotating ring-disk electrode (RRDE). The reaction mechanism for the N-CNO was found to follow a four-electron transfer pathway and possess a higher onset potential in RRDE measurement than CNOs. The ORR activity of N-CNO was 5.4 times better than that of CNO, which was attributed to the introduction of nitrogen to the carbon faramework. The MFC fabricated with the N-CNO cathode produced a maximum power density of 49.6mWm–2, which was approximately double the performance of the CNO-based MFC. The performance of N-CNO was low compared to Pt/C but the cost per power was only 1/310th. These results confirmed that N-CNOs could be used as a low-cost alternative and an energy-efficient metal-free ORR catalyst for practical MFC applications.

Synergistic Effects of Nitrogen Doping on MXene for Enhancement of Hydrogen Evolution Reaction

Earth-abundant, nonprecious, and efficient electrocatalysts for effective hydrogen evolution reaction (HER) are crucial for future large-scale green energy production. Low-cost two-dimensional MXen...

Investigation of nitrogen doping effects on light-induced oxygen vacancy ionization and oxygen desorption in c-IGO TFTs

In this study, crystalized indium–gallium oxide (c-IGO) thin-film transistors (TFTs) were fabricated. By applying illumination with three wavelengths and conducting recovery tests, we thoroughly investigated the mechanism for light-induced instability. Results showed that the ionization of oxygen vacancy (VO) had the greatest impact. Through nitrogen doping during channel deposition, the VO-ionization was considerably suppressed. The XPS results also revealed that the incorporated nitrogen filled oxygen vacancies and enhanced the binding energy. This approach was evident to decrease the proability of VO-ionization and improve the recovery performance simultaneously. The c-IGO TFT with N-doping channel layer was proven to have better ambient stability under light stress.

Effect of Nitrogen Doping on Oxygen Reduction Activity of TiO2 in Acidic Media

In order to develop low-cost nonprecious metal cathodes that have both high activity of oxygen reduction reaction (ORR) and high durability as alternatives to Pt-based electrocatalysts for practical fuel cell vehicle application, we have focused on group 4 and 5 oxide-based compounds because they are insoluble in acidic media and are much less expensive than platinum. We already demonstrated that titanium and zirconium oxide-based compounds prepared from these oxy-phthalocyanines showed definite ORR activities [1,2]. However, these types of the catalysts used multi-walled carbon nano-tubes as a support and deposited carbon derived from phthalocyanine as a local electron conduction path. Carbons are fundamentally oxidized at high potential and temperature. Therefore, carbon-free nonprecious ORR catalysts are required for fuel cell vehicle application. An arc-plasma deposition method is useful to control the oxidation state of the oxides without heat-treatment. We prepared zirconium oxide-based cathode using tin-oxide based electroconductive support by arc-plasma deposition as a carbon-free nonprecious metal cathode. Fig. 1 shows the potential-ORR current density curves of the ZrOx/SnO2-based support prepared by arc-plasma deposition method, the SnO2-based support, and the TixNbyOz+Ti4O7 [3] in 0.1 M H2SO4 at 30 oC. The ZrOx/SnO2-based support had superior ORR activity. Fig. 2 shows comparison of the onset potential of the ZrOx/SnO2-based support and the TixNbyOz+Ti4O7 in 0.1 M H2SO4 at 30 oC. Both onset potentials are above 1.1 V vs. RHE, indicating that these active sites are superior in quality. Figs. 1 and 2 suggested the great potential of carbon-free nonprecious metal oxide-based cathodes. Acknowledgment The authors thank the New Energy and Industrial Technology Development Organization (NEDO) for financial support. This work was conducted under the auspices of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Program for Promoting the Reform of National Universities.

Electronic and transport characteristics of vacancy and nitrogen-doped graphene nanoribbon rotational switch

The effect of nitrogen (N) doping and single vacancy defect is investigated on the electromechanical properties of twisted armchair graphene nanoribbon (TAGNR). Five different twist angles were investigated for the perfect model, N doping and single vacancy defect which are located in three different positions and in three different widths of AGNR. In general, 105 models were produced with this specification. The results show that among the above models, eight devices with suitable switching behavior can be selected as the first graphene-based nanoribbon rotational switch (GRS) with defect and doping. The combination of density function theory (DFT) and the non-equilibrium Green's function methods were utilized in the computation. Having applied the twist, the bond length structure of the atoms, the charge density distribution, and transmission pathways vary leading to the different strain energies and change in the electronic behavior of the device. The change in the twist angle causes the maximum and minimum currents of the device able to increase or decrease in the value of these changes through creating defect and doping in the structure which, also, relies on the defect or doping and their position. Based on the above results, applying electromechanical changes therein can control the electronic properties of the device.

Effect of nitrogen doping in the few layer graphene cathode of an aluminum ion battery

We examine the effect of nitrogen dopants in Few-layer graphene (FLG) cathodes on anion intercalation. Different nitrogen dopant configurations within the FLG were achieved by varying the synthesis parameters and their effects are compared. The dopant configurations of the samples were determined via X-ray photoelectron spectroscopy (XPS) and formation energies were calculated using density functional theory, allowing correlation between cell performance and dopant configuration. The reduced ion intercalation within the nitrogen doped FLG, and thus poor charge/discharge characteristics of nitrogen doped FLG cathodes, is attributed to the reduced mobility of the chloroaluminate ions in the presence of nitrogen dopants.

Nitrogen-doped carbon black supported Pt–M (M = Pd, Fe, Ni) alloy catalysts for oxygen reduction reaction in proton exchange membrane fuel cell

Platinum (Pt) alloy catalysts on nitrogen doped carbon black was prepared and applied to a proton exchange membrane fuel cell, and the effects of nitrogen doping on the electrochemical properties were investigated. Pt was alloyed with 3d transition metals (Fe, Ni and Pd) in 3:1 atomic ratio and deposited onto nitrogen-doped carbon black (NCB). Alloying 3d transition metal causes an electron transfer from the Pt atom to the alloying element, depending on the work function and electronegativity of the element. The cell performances of Pt3Fe1 before and after N doping are almost the same due to the facilitation of electron transfer from Fe to Pt. It is attributed to the smallest work function of Fe, increasing the number of electron in the Pt 5d orbital. However, N doping for Pt–Pd and Pt–Ni alloys increases the total number of electrons per Pt atom, enhancing the oxygen reduction reaction (ORR) and the dispersion of Pt nanoparticles. The rotating disk electrode clearly shows an increase of onset potential upon nitrogen doping, suggesting the enhancement of the ORR. The accelerated durability test demonstrates the enhancement in durability and less agglomeration after 1200 cycles of operation upon nitrogen doping.

Doped graphene and Ag(1 1 1) hybrid material as fuel cell electrode: New insights on interfacial features and oxygen adsorption from dispersion-corrected density functional theory

Graphene nanostructures are among the most interesting materials investigated in recent years for several different applications. Their activity towards Oxygen Reduction Reaction (ORR) has attracted a lot of attention for application in fuel cells and lithium-air batteries. In this, and many other applications, a graphene-metal interface is involved. In this work, we investigated the interaction between graphene and Ag(1 1 1), the effect of boron and nitrogen doping on graphene, and the combination of both factors. We applied a dispersion-corrected DFT method derived from a recent reparameterization of DFT-D2, purposely tuned for silver-molecule interfaces. With this approach, we analyse the adsorption of an oxygen molecule (the first key step of ORR) on the pristine/doped and metal-supported graphene systems. Our results highlight the role of specific dopant-substrate interactions that are key to enhance the adsorption of molecular oxygen.

Adsorption capacity of oxidized nitrogen-doped bamboo-like carbon nanotubes

Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) were synthetized by catalytic chemical vapor deposition (CCVD) and characterized by electron microscopy. The produced nanotubes were oxidized in different degree by using of various oxidizing agents (H2O2, HClO4 and HNO3) in order to change their adsorption potential by creating dissociable functional groups (e.g. -OH) on their surface. The appearance of oxygen containing groups was confirmed by spectroscopic analysis and the zeta potential (ζ of the samples was measured. The HNO3 treatment has led to the emergence of the most polar groups on the nanotube surface (ζ = −27.1 mV), while the other two oxidizing agents were less effective (H2O2 and HClO4, ζ = −18.3 and −19.8 mV, respectively). The adsorption potential of the oxidized N-BCNT samples were tested with copper(II)-ion. Despite the difference in their surface properties, the oxidized nanotubes adsorbed copper to the same extent. The contribution of the oxidized surface for the adsorption capacity is smaller than the effects of nitrogen doping. Thus, more things involved in the adsorption mechanism not only electrostatic attraction, but sorption-precipitation, and complex formation between copper and heteroatoms of the nanotubes. Thus, it is not enough to discuss the effect of dissociable functional groups, but the contribution of e.g. heteroatoms must also be taken into account to fully understand metal ion adsorption on oxidized carbon materials.

Effect of Nitrogen Doping on Oxygen Reduction Activity of TiO2 in Acidic Media

In order to investigate the effect of the nitriation of TiO2 on the ORR activity, TiO2 powders with three different kinds of crystalline structure (rutile, anatase, and brookite) were heat-treated under NH3 containing gas atmosphere to dope the nitrogen. We found that the increase in the ORR activity by nitrogen doping depended on the crystalline structure of TiO2 and the apparent relationship was observed for rutile type TiO2. We found that the increase in the ORR activity of the rutile TiO2 with nitrogen content of 0.7wt% was responsible for the production of the oxygen vacancies in the rutile TiO2 as active sites and the formation of the electron supply path by formation of the electronic conductive Ti4O7 on the surface by nitridation.

A Facile and Effective Method for Patching Sulfur Vacancies of WS2 via Nitrogen Plasma Treatment.

Although transition metal dichalcogenides (TMDs) are attractive for the next-generation nanoelectronic era due to their unique optoelectronic and electronic properties, carrier scattering during the transmission of electronic devices, and the distinct contact barrier between the metal and the semiconductors, which is caused by inevitable defects in TMDs, remain formidable challenges. To address these issues, a facile, effective, and universal patching defect approach that uses a nitrogen plasma doping protocol is developed, via which the intrinsic vacancies are repaired effectively. To reveal sulfur vacancies and the nature of the nitrogen doping effects, a high-resolution spherical aberration corrected scanning transmission electron microscopy is used, which confirms the N atoms doping in sulfur vacancies. In this study, a typical TMD material, namely tungsten disulfide, is employed to fabricate field-effect transistors (FETs) as a preliminary paradigm to demonstrate the patching defects method. This doping method endows FETs with high electrical performance and excellent contact interface properties. As a result, an electron mobility of up to 184.2 cm2 V-1 s-1 and a threshold voltage of as low as 3.8 V are realized. This study provides a valuable approach to improve the performance of electronic devices that are based on TMDs in practical electronic applications.

Nitrogen‐Doped Nickel Oxide as Hole Transport Layer for High‐Efficiency Inverted Planar Perovskite Solar Cells

Nickel oxide (NiOx) is commonly used as a hole transport layer (HTL) in inverted‐structure (p‐i‐n) planar perovskite solar cells (PSCs), playing a critical role in the device performance. However, a solution‐processed NiOx HTL usually suffers from low electrical conductivity, consequently resulting in an inefficient interfacial charge transport. Herein, a facile method is developed to prepare nitrogen‐doped NiOx (N:NiOx), which is applied as a novel HTL in inverted PSCs for the first time, achieving a decent improvement in average power conversion efficiency (PCE) from 15.28% to 17.02%. The effects of nitrogen doping on the electrical conductivity and the energy band structure of NiOx as well as the quality of CH3NH3PbI3 perovskite layer atop are studied by a series of characterizations, revealing that nitrogen doping leads to increased electrical conductivity and lowered valence band energy of the NiOx film, which are beneficial to interfacial hole transport. In addition, the trap density of the CH3NH3PbI3 perovskite film atop N:NiOx layer is reduced, prohibiting unfavorable charge recombination.

Understanding the improved electrochemical performance of nitrogen-doped hard carbons as an anode for sodium ion battery

To understand the effect of nitrogen doping in hard carbon as anode for sodium ion battery, experimental and theoretical study have been done. To also see the size effect along with nitrogen doping, four varieties of carbon spheres are synthesized of two different size ranges viz. micron and nano-sized. Two of these spheres are nitrogen-doped, while the other two are un-doped. Nitrogen doping enhances the electrochemical performance of carbon spheres and increases the active storage sites by enhancing the number of defects and porosity. It further improves electrochemical performance by increasing electrical conductivity and controlling volume expansion. The density functional theory (DFT) study shows significant reduction in expansion associated with sodiation, i.e., from 21.7% to 7.9% because of nitrogen doping. After nitrogen doping, micron and nano-sized carbon spheres show an increase in capacity by 38.6% and 39.5%, respectively. Among these four electrodes, nitrogen-doped nano carbon spheres (NNCS) give the best performance. NNCS shows first reversible capacity of 286 mAh g−1, retains 85% of the capacity till 200 cycles at a current density of 30 mAg−1. This increase in electrical conductivity, defects, porosity, and reduction in volume expansion in nitrogen-doped carbon samples makes them an excellent material for sodium ion batteries.

Effects of nitrogen doping in amorphous carbon layers on the diffusion of fluorine atoms: A first-principles study

We investigated the effects of nitrogen doping in amorphous carbon layers on the diffusion of fluorine atoms based on density functional theory calculations. For N doping at both substitutional and interstitial sites, the F atom binds to the surrounding C atoms rather than the N atom during structural relaxation due to the electrostatic repulsion between N and F atoms. Furthermore, the diffusion barriers associated with the F atom passing by the N atom are extremely large (5.19 eV for substitutional N doping and 4.77 eV for interstitial N doping), primarily due to the electrostatic repulsion originating from the strong electronegativities of both atoms. The results clearly show that N doping increases the diffusion barrier of the F atom, thereby suppressing the diffusion of the F atom. The findings provide information about the role of N doping in amorphous carbon layers and yield insights for improving the fabrication processes of future integrated semiconductor devices.

The effect of nitrogen doping of TiO2 compact blocking layers on perovskite solar cell performance

In this paper, nitrogen-doped titanium oxide (N-TiO2) with different dopant concentrations (0, 0.25, 0.5, and 1 at.%) were grown on FTO substrates by spray pyrolysis and applied in perovskite solar cells (PVSC) as a compact blocking layer. Morphology, chemical and physical properties of the samples were investigated by SEM, XRD, XPS, UV–Visible, and PL characterization techniques. Measurements indicate that the device based on N-TiO2 with a nitrogen content of 0.25% exhibits higher PCE (17.83%) than the device based on un-doped TiO2 (17.04%). Results show that the lowest series resistance is obtained in the device based on 0.25% N-TiO2, leading to an increase in the fill factor (FF) parameter. Also, higher VOC of this device results from lower e-h recombination due to longer electron lifetime than the un-doped sample. In addition, a slight increase in JSC is related to the small decrease in the band gap of TiO2 with nitrogen doping. Enhanced FF, VOC, and JSC are the main reasons for the improved performance of the PVSC devices by using the optimal level of nitrogen in TiO2.

Effects of nitrogen doping on vacancy-oxygen complexes in neutron irradiated Czochralski silicon

We have investigated the effect of nitrogen doping on the evolution of vacancy-oxygen (V-O) complexes in neutron irradiated Czochralski (CZ) silicon. During isothermal anneals in the temperature range of 290–330 °C, it is found that both the annihilation rate of VO and generation rate of VO2 are obviously modified with nitrogen doping. Correspondingly, the activation energies for VO annihilation and VO2 generation are 1.84 and 1.23 eV, both smaller (∼ 0.24 eV) than those of the conventional CZ silicon. Moreover, the critical temperatures for total disappearance of VO and VO2 peaks decrease in nitrogen doped CZ silicon, which means that the conversion processes of VO to VO2 and VO2 to VO3 are promoted, respectively. It is suggested that the nitrogen doping in CZ silicon which introduces a tensile stress enhances the diffusion of vacancy and VO complex, promoting the conversion of V-O complexes.

Effects of nitrogen doping on Si/carbon composite anode derived from Si wastes as potential active materials for Li ion batteries

In this study, we propose a one-step method for synthesizing nitrogen-doped silicon/carbon composite as an anode material for lithium-ion batteries. The electrochemical results indicate that the carbon and doped nitrogen content in Si considerably influence its electronic conductivity and structural stability. The X-ray photoelectron spectroscopy results indicate that approximately 0.73–3.67 mol.% of nitrogen atoms were successfully doped in Si/C composite. Nitrogen-doped Si/C composite exhibited a high reversible capacity of 1238 mAhg−1 after 100 cycles at 0.5 C, which is considerably higher than that of bare Si/C (690 mAhg−1). Moreover, nitrogen-doped Si/C composite exhibited a higher rate capability than bare Si/C. The N-doped sample had a charge capacity of approximately 877 mAhg−1 at a current rate of 1 C. Furthermore, by using four-point probe tests, the electronic conductivity of nitrogen-doped Si/C composite and bare electrodes were obtained as 19100 and 14298 Scm−1, respectively. The obtained results indicate that the electrochemical performance of a silicon electrode can be considerably improved through the combination of N doping and pitch coating.

The remarkable morphology regulatory effect of NH4+ ions on TiO2 nanorod arrays and their application in dye-sensitized solar cells

Nitrogen doping is often used to expand the response range of wide-bandgap semiconductors to improve their photoelectrical properties. Unique morphology regulatory effect of NH4+ ions on one-dimensional TiO2 nanorod arrays (TNAs) is proved in this research for the first time, but nitrogen-doping effect is hardly detected. Once NH4Cl is added, the growth of TNAs is greatly promoted especially in radial direction, but little amount of nitrogen from NH4+ ions can enter the modified TNAs (N-TNAs). Furthermore, the bandgap energy of N-TNAs is almost unchanged compared with TNAs, meaning that trace nitrogen doping does not affect response ability to irradiation. When fabricated into dye-sensitized solar cells (DSSCs) with N-TNAs, the optimal photoelectrical conversion efficiency (3.16%) is nearly twice that with TNAs (1.62%). It is worth noting that the increased efficiency mainly results from the photoinduced current but not voltage. Second, the change of conversion efficiency is related to nanorod length. In summary, the improvement of photoelectrical property is caused by the directional growth of nanorods, which results from the addition of NH4+ ions as an effective structure regulatory agent.