Doping Methods Research Articles

In Situ Doping System To Improve the Electric-Field-Induced Fluorescence Properties of CdZnS/ZnS Quantum Rods for Light-Emitting Devices

One-dimensional quantum rods (QRs) have the properties of the electron and hole are separated under the electric field, the overlap of the wave function decreases, and photoluminescence quenching occurs. Because of these properties, QRs can be used in optical switching and future display applications. The CdZnS/ZnS QR is a material capable of emitting blue light. CdZnS/ZnS can easily separate carriers because the difference between the valence band of the core and the shell is small. However, CdS and ZnS have very low hole conductivity and cannot easily be separated. To solve this problem, we developed an in situ doping system and demonstrated nitrogen doping. The in situ doping system not only coats ZnS onto CdZnS QR but also proceeds with nitrogen doping. Previously studied doping methods additionally doped the synthesized nanomaterials and had no effect of doping because the dopant was not dispersed without subsequent heat treatment. However, the in situ doping system grows the ZnS shell and uniformly ...

Спортивное уголовное право: основания и пределы криминализации деяний, связанных с допингом

The article has been based on the theses of speeches of the author at the International Scientific and Practical Conference Sports in the National Law and International Law Dimension: Relevant Issues (April 4, 2018, the Institute of Legislation and Comparative Law under the Government of the Russian Federation) and is dedicated to the issues of sports criminal law related to the detection and investigation of basis of criminal activities connected with doping. It is concluded that criminalization of activities related to doping shall be based on their social hazard connected with the serious hazard of doping for the health of sportsmen. Within the context of establishment of criminalization limits for activities related to doping, articles of the Criminal Code of the Russian Federation are analyzed, which set responsibility for inducement of sportsmen to use doping (substances or methods forbidden in sports) and the use of doping in relation to a sportsman (articles 230. and 230. of the Criminal Code of the Russian Federation).

Electrospun nitrogen-doped carbon nanofibers with tuned microstructure and enhanced lithium storage properties

Nitrogen-doped carbon materials hold great potential for high-performance lithium storage. However, the excess defects introduced by dominated nitrogen doping methods may lead to a thickened solid electrolyte interphase (SEI), resulting in a higher Li+ diffusion resistance and inferior rate performance. Herein, composite carbon nanofibers (CNFs) with tuned microstructure and relatively high nitrogen content were fabricated by co-electrospinning the mixture of nitrogen-rich pitch, a soft carbon precursor, with polyacrylonitrile (PAN) in controlled mass ratio. The result shows that the SEI formed on the composite CNFs with less surface defects is much thinner yet tighter than that formed on the PAN-based CNFs. As such, the composite CNFs present a double capacity retention of 37.3% to that of the PAN-based CNFs at 10 A g−1. More importantly, the cycle retention of the composite CNFs anode is 88.0% after 1000 cycles at 2 A g−1, much higher than that of PAN-based CNFs (61.5%). It is believed that the improved rate and cycle performance are due to the superior structure and chemical composition of the SEI, which can be attributed to the modified microstructure by addition of nitrogen-rich pitch to a great extent.

Iron isotopic analyses of geological reference materials on MC-ICP-MS with instrumental mass bias corrected by three independent methods

Here we report iron (Fe) isotopic data of three pure Fe solution standards (IRMM-014, GSB Fe, and NIST 3126a) and five widely used geological reference materials (RMs) from the United States Geological Survey and Geological Survey of Japan obtained on a Neptune Plus multi-collector–inductively coupled plasma–mass spectrometer (MC-ICP-MS) in our laboratory over the past 3 years. The instrumental mass bias was corrected by three independent methods: sample-standard bracketing (SSB), Ni doping + SSB, and 57Fe–58Fe double spike + SSB. Measurements reveal that both the Ni doping and double spike methods helped calibrate short-term fluctuations in mass bias. Collectively, almost all measurements of RMs yielded δ56Fe within ± 0.05 of recommended values, provided that each sample was measured four times on MC-ICP-MS. For the first time, new recommended values for NIST SRM3126a are reported (δ56Fe = 0.363 ± 0.006, 2SE, 95% CI; and δ57Fe = 0.534 ± 0.010, 2SE).

Surface Photocatalytic Research of Fe -doped TiO2 (001) Based On the First-principles

In this paper, the first-principles based on density functional theory was used to study the Fe/TiO2(001) band gap width and adsorption energy of C6H6 molecules at different positions on the surface of the molecule with different doping methods and different Fe content. Calculation of the band structure and density of states of Fe-doped TiO2 nanoparticles shows that, the surface gap doping is more favorable than the substitution doping to reduce the band gap of TiO2, and when the doping concentration is 6.122%, the maximum reduction of the band gap width is 59.3% higher than that of pure TiO2. According to the comparement of adsorption energy, it works out that the benzene molecule is mainly about horizontal adsorption on the surface of TiO2(001). Within the scope of the study, with the increase of Fe doping concentration, The adsorption energy does not decrease as the band gap, when the Fe atoms doping concentration is 4.167%, the maximum increase of adsorption energy is 63.2%.

Dopant Diffusion in Sequentially Doped Poly(3-hexylthiophene) Studied by Infrared and Photoelectron Spectroscopy

The diffusivity of dopants in semiconducting polymers is of high interest as it enables methods of sequential doping but also affects device stability. In this study, we investigate the diffusion of a bulky sequentially deposited p-dopant in poly(3-hexylthiophene) (P3HT) thin films using nondestructive in situ infrared (IR) spectroscopy and photoelectron spectroscopy (PES). We probe dopant diffusion into the polymer film at varying coverage by differentially evaluating electron transfer in the bulk and at the surface. Thereby it is possible to determine dopant coverages at which both electron transfer and incorporation of dopants are saturated. By use of PES, neutral and charged dopants can be distinguished, revealing that charged dopants are less mobile in the diffusion process than neutral molecules. We further compare the diffusivity in semicrystalline and fully amorphous P3HT. We find that at high coverage semicrystalline P3HT seems to yield a higher capacity for dopants than fully amorphous P3HT. A t...

An efficient strategy for sensing pyrophosphate based on nitrogen-rich quantum dots combined with graphene oxide

A facile approach was developed to prepare fluorescent nitrogen-rich quantum dots (NCQDs) using 2-azidoimidazole and ammonium hydroxide as reactants. The nitrogen and carbon elements of NCQDs form the frameworks of their nanostructures together and bear multiple active sites. By using NCQDs as fluorophores and graphene oxide (GO) as controllers, a hydrogen binding-based nanosensor was constructed for the detection of pyrophosphate (PPi). In NCQDs-GO sensing assemblies, the binding of GO to NCQDs results in the fluorescence quenching by FRET mechanism; while the addition of PPi leads to the fluorescence recovery of NCQDs because of the competitive binding between NCQDs and PPi to GO. The fluorescence intensity showed linearity with the added PPi concentration ranging from 0 to 400 μM with the detection limit of 8.3 nM (σ = 3). This procedure for the fabrication of amino-functionalized carbon quantum dots is simpler and more efficient compared to conventional doping and surface modification methods. The proposed NCQDs-GO sensing assemblies showed high selectivity and sensitivity to PPi over the competing anions in aqueous solution.

Effects of photocatalytic activity of metal and non-metal doped Tio2 for Hydrogen production enhancement - A Review

Titanium dioxide TiO2 is well-known materials that has become an efficient photocatalyst for environmental sustainability. Known as solar driven catalysis, TiO2 is considered as the most promising way to alleviate environmental issues caused by the combustion of fossil fuels and to meet worldwide demands for energy. Much effort has been concerned on TiO2 band gap modification to become a visible-light-activated photocatalysts of TiO2 because it can only be excited by UV light irradiation due to its large band gap. Modifications like metals and nonmetals doping has been proposed in the past decades. This reviews survey recent advanced preparation methods of doped-TiO2 including various types of doping methods for various types of dopants and provides general review on further modifications. The characterizations techniques used in order to determine the structural, morphological and optical properties of modified TiO2 is also discussed. Further, a new method of TiO2 modification is proposed in this mini review paper.

Defect-Mediated In-Plane Electrical Conduction in Few-Layer sp2-Hybridized Boron Nitrides.

In-plane electrical conduction in sp2-hybridized boron nitride (sp2-BN) is presented to explore a huge potential of sp2-BN as an active material for electronics and ultraviolet optoelectronics. Systematic investigation on temperature-dependent current-voltage ( I- V) characteristics of a few-layer sp2-BN grown by metal-organic vapor-phase epitaxyreveals two types of predominant conduction mechanisms that are Ohmic conduction at the low bias region and space-charge-limited conduction at the high bias region. From the temperature-dependent I- V characteristics, two shallow traps with activation energies of approximately 25 and 185 meV are observed. On the basis of the near-edge X-ray absorption fine-structure spectroscopy, boron-boron (B-B) homoelemental bonding which can be related to grain boundary and nitrogen vacancy (VN) are proposed as the origin of the shallow traps mediating the in-plane conduction in the sp2-BN layer. In addition, a drastic enhancement in the electrical conductivity is observed with the increasing amount of VN that acts as a donor, implying that controlled generation of VN can be an alternative and better approach for the n-type doping of the sp2-BN film rather than ineffective conventional substitutional doping methods.

Effect of [6,6]-phenyl C61-butyric acid methyl ester phase on the charge generation of poly(3-hexylthiophene)-based polymer solar cells

In this work, we have studied the effect of [6,6]-phenyl C61-butyric acid methyl ester (PC61BM) phase on the performance and charge photogeneration processes of poly (3-hexylthiophene) (P3HT) polymer solar cells (PSCs) using photoluminescence, electrochemical doping and transient absorption methods. The results show that the PC61BM phase facilitates the dissociation of photogenerated excitons and increases the charge photogeneration yield. The PC61BM phase blend in the active layer is able to increase the yield of the delocalized polarons (DP) in the P3HT donor phase using electrochemical doping methods. Furthermore, PC61BM phase facilitates the formation of bipolarons (BP) from polarons (P). These results aid in better understanding the charge photogeneration processes of PC61BM blended PSCs.

Comprehensive growth and characterization study on highly n-doped InGaAs as a contact layer for quantum cascade laser applications

We present growth and characterization studies of highly n-doped InGaAs epilayers on InP substrate by metal organic vapor phase epitaxy to use as an n-contact layer in quantum cascade laser applications. We have introduced quasi two-dimensional electrons between 10 s pulsed growth n-doped InGaAs epilayers to improve both carrier concentration and mobility of structure by applying pulsed growth and doping methods towards increasing the Si dopant concentration in InGaAs. Additionally, the V/III ratio optimization under fixed group III source flow has been investigated with this new method to understand the effects on both crystalline quality and electrical properties of n-InGaAs epilayers. Finally, we have obtained high crystalline quality of n-InGaAs epilayers grown by 10 s pulsed as a contact layer with 2.8 × 1019 cm−3 carrier concentration and 1530 cm2 V−1 s−1 mobility.

Effect of surface states on monolayer doping: Crystal orientations, crystallinities, and surface defects

Monolayer doping (MLD) has been regarded as the most suitable doping method for future semiconductor devices. MLD based on surface functionalization can be seriously affected by the surface states, including the orientations, crystallinities, and defects. We report for the first time the effect of surface states on boron-MLD (B-MLD) process and discuss the applicability of MLD for a fin structures. Depending on the surface states, the monolayer formation reaction is restricted, which causes more than five-fold differences in the doping level. Therefore, the surface states should be gravely considered before applying MLD and are crucial constraints in the MLD process on non-planar structures that have different surface states depending on its structural position. The B-MLD process on as-cleaned (100) and (110) silicon surfaces provides doping levels of 4.69 × 1020 and 2.48 × 1020 atoms/cm3, respectively. The MLD efficiency on the (110) orientation is degraded by insufficient reaction sites for the hydrosilylation reaction on the monohydride-terminated (110) silicon surface. Additionally, the surface damage interrupts the formation of a dopant-containing monolayer, causing a poor doping level and dose uniformity. Our research provides new insights into the development of wet-chemical doping methods for non-planar devices by studying the effect of surface states on MLD efficiency.

8.2: Invited Paper: Research on the Effects of Different Doping Methods on Top-Gate IGZO TFT

By N2O/N2/O2 doped the active layer and He/Ar/Al/SiNx doped the S/D of Top-Gate IGZO TFT, we have summarized the effects of different doping modes on the properties of Top-Gate IGZO TFT, including doping the active layer of Top-Gate IGZO TFT with N2O can obviously improve the electrical uniformity of devices , and doping the S/D of Top-Gate IGZO TFT with aluminum(Al) can significantly improve the NBTIS/ PBTIS of devices, etc. By optimizing the doping method, we have fabricated a device with both good electrical uniformity and good electrical properties, with threshold voltage shift (ΔVth) of 18 points less than 1V, Mobility=8.6 cm2/V.S,Subthreshold Swing(SS) =0.26 V/dec ,Threshold Voltage （Vth） =2.9V ,ΔVth=1.54 V (NBTIS, Bias=-30V,T=80 ℃ ,Backlight=4500Nit,2000S,W/L=6/12), ΔVth= 5.28V(PBTIS,Bias=+30V ， T=80 ℃ ,Backlight=4500Nit, 2000S， W/L=6/12).

Surface modified polypyrrole for the efficient removal of phenolic compounds from aqueous medium

In this study, we have reported the effect of acid doping on the adsorption of phenolic compounds on polypyrrole (PPy) particles. Both the in-situ doping and post-doping methods were adopted for the preparation of acid doped PPy particles. It is observed that acid doped PPy showed a higher adsorption capacity than the pristine PPy. It has also been observed that both in-situ doped and post-doped PPy have similar effect on adsorption. Electrostatic interaction, hydrogen bonding and ππ interactions are assumed to be responsible for the adsorption. The adsorbents were characterized by FTIR, XRD, SEM and TGA. Batch adsorption experiments were performed under different experimental conditions. Thermodynamic and kinetic parameters were determined from the adsorption experiments. The Langmuir, Freundlich and Temkin isotherm models have been utilized to fit the experimental data. The experimental data fits best in Langmuir model. The Langmuir adsorption capacity of pristine PPy and post-doped PPy were found to be 21.3 and 31.6 mg/g for phenol and 29.3 and 43.6 mg/g for resorcinol respectively. The thermodynamic studies show negative ΔG and positive ΔH values for both phenol and resorcinol. The adsorption data fit best with pseudo first order kinetic model.

Influence of morphology and structure on hydrophilicity of TiO2NTs

The TiO2NTs with special three-dimensional tubular morphology was prepared by anodic oxidation method, the methods of nonmetal doping, Ti3+ self-doping and semiconductor recombination were used as the modification of TiO2NTs. The contact angles of different samples after modification were measured. The structure and morphology of the samples were characterized by SEM, EDS and XPS, and the influence of different factors on the contact angle of TiO2NTs was investigated. The results show that the hydrophilicity is closely related to the morphology and structure of the material. The special tubular structure of TiO2NTs has a smaller contact angle, and the semiconductor composite will block the nozzle and increase the contact angle to a certain extent. Under the premise of not changing the morphology, doping modification can make TiO2NTs achieve hydrophilicity under visible light.

Band-gap narrowing and electrochemical properties in N-doped and reduced anodic TiO2 nanotube arrays

Electrochemical activity of TiO2 nanotube arrays (NTAs) is restricted by a wide band gap of TiO2. To overcome this restriction, we considered systematic research on two effective methods of doping of TiO2 NTAs such as the N-doping and electrochemical reductive doping and predicting the proper application of them. Band gap narrowing was occurred from 3.16 eV for undoped TiO2 NTAs to 2.9 and 2.7 eV at N-doped and self-doped TiO2 ones respectively. The electrochemical responses of the TiO2 NTAs before and after doping were examined by cyclic Voltammetry (CV) curve. To understand the electrochemical behavior of the undoped and doped TiO2 NTAs, electrochemical impedance spectroscopy (EIS) was used and three equivalent circuit models were also built. The results showed that the undoped TiO2 NTAs is not strictly capacitive but a small quantity of N in TiO2 remarkably decreases the surface resistance of TiO2 electrode. In contrast, self-doped TiO2 NTAs resistance is reduced to very negligible contents of 0.0001322 Ωcm−2, that not only self-doped sample becomes to completely capacitive but also, it leads to the semiconductor nature of TiO2 NTAs transforms to semi-metallic one, and the two orders of enhancement in capacitance of blue TiO2 NTAs are very astonishing and it has outstanding potential for applications like supercapacitors as the electrochemical response of the self-doped TiO2 NTA sample was found to be a content of about 7 mF cm−2 that it is improved about 20 times compared with undoped one. Furthermore, it was found that doping of TiO2 NTAs with nitrogen atoms increases the carrier density about 2.82 × 1021 and self-doped TiO2 NTAs show the higher carrier density about 1.14 × 1025 compared with N-doped NTAs. These finding help to understand the mechanism of doping in two different methods and select the best one in relevant applications.

Effects of preparation methods on the structure and property of Al-stabilized CaO-based sorbents for CO2 capture

CaO-based sorbents are promising candidates for CO2 capture at high temperatures via Ca looping systems. This work aims to examine the effects of preparation methods on the microstructure and performance of Al-stabilized CaO-based sorbents for capturing CO2. Different preparation techniques including wet mixing, co-precipitation and sol-gel auto-combustion synthesis were employed to prepare the Al2O3-stabilized Ca-based sorbents with various mass ratios of components. Changes in CO2 absorbing capacity and stability were clearly observed for the sorbents prepared with different methods. Field scanning electron microscope and N2 adsorption and desorption isotherms analyses showed that the preparation methods tended to impact the morphology and porosity of the sorbents, hence affecting the adsorption capacity. The 27Al magic angle spinning nuclear magnetic resonance spectra of the mixed oxides revealed that the sorbents prepared from different methods all contained the same structural units of tetrahedral Al site (AlO4), but with obviously different intensity and broad shoulder peak. This demonstrated that the micro domain environment of 27Al atoms residing in the lattice could be effectively modified by the doping methods.

Heavy doping of ceria by wet impregnation: a viable alternative to bulk doping approaches.

To avoid the deleterious effects of dopant segregation, synthesis methods that facilitate a homogenous dopant distribution in the ceria lattice were employed. Though doping ceria by wet impregnation was also credited to induce a homogeneous solid solution even in the heavy regime (concentration ≥20%, A. Corma, P. Atienzar, H. Garcia and J. Chane-Ching, Nat. Mater., 2004, 3, 394-397), no follow up investigation has been reported. Herein, we investigated ceria nanoparticles (1%Tm-CeO2 and 1%Eu-CeO2) wet-impregnated with trivalent rare-earth (Yb, 20%), bivalent (Ca, 20%) and isovalent (Zr, 30%) metals, followed by annealing in air. Homogeneity of the solid solutions of Yb-impregnated ceria was confirmed by a two-feature characterization toolbox that included X-ray diffraction, Raman spectroscopy, transmission electron microscopy, as well as up-conversion emission as a probe tool. Since the up-conversion emission of Tm was not detectable in the absence of Yb while its efficiency depends on the average distance between Yb and Tm ions, the Yb incorporation and its migration from the surface to the lattice bulk sites in wet-impregnated ceria can be "visualized" and compared with that of the Yb bulk-doped counterpart. The use of Eu luminescence as a local probe confirmed the homogeneity of solid solutions of Ca and Zr-impregnated ceria and also sustained the opposite roles of Ca and Zr as the repeller and the scavenger of oxygen vacancies, respectively. All these results suggested that heavy doping of ceria by wet impregnation with metals with +2, +3 and +4 valencies represent a facile alternative to conventional doping approaches. Therefore, the effects of the amount and the type of metal dopant on the structural properties of CeO2 could be investigated in a more systematic and probably a more reproducible manner, which would significantly increase the potential of ceria in catalysis and other applications.

High Seebeck Coefficient and Power Factor in n‐Type Organic Thermoelectrics

AbstractThe n‐type thermoelectric properties of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) are investigated for different solution‐based doping methods. A novel inverse‐sequential doping method where the semiconductor (PCBM) is deposited on a previously cast dopant 4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)‐N,N‐diphenylaniline film to achieve a very high power factor PF ≈ 35 µW m−1 K−2 with a conductivity σ ≈ 40 S m−1 is introduced. It is also shown that n‐type organic semiconductors obey the −1/4 power law relation between Seebeck coefficient S and σ that are previously found for p‐type materials. An analytical model on basis of variable range hopping unifies these results. The power law for n‐type materials is shifted toward higher conductivities by two orders of magnitude with respect to that of p‐type, suggesting strongly that n‐type organic semiconductors can eventually become superior to their p‐type counterparts. Adding a small fraction lower lowest unoccupied molecular orbital material (core‐cyanated naphthalene diimide) into PCBM leads to a higher S for inverse‐sequential doping but not for bulk doping due to different morphologies.

Enhancement of photocatalytic activity of titanium dioxide using non-metal doping methods under visible light: a review

Titanium dioxide (TiO2) is an efficient photocatalyst for removing organics in photocatalytic wastewater treatment, but its low photoactivity limits its practical applications in a visible-light-driven chemical reaction. Many efforts have been made in the activation of the visible light absorption property on TiO2 photocatalyst. In this paper, a thorough review of current non-metal doping methods of TiO2 to improve photocatalyst activation under visible light is presented. The focus of this study is on doping non-metals onto TiO2 by several methods to enhance its visible light photoactivity. Besides, the resultant characteristics of the chemical structure, physical structure, and optical properties of the doped photocatalysts are discussed. This review enables a better understanding of current advantages and disadvantages that can arise during the production of non-metal-doped TiO2 and its applications. The annealing and hydrothermal methods are found to be more efficient in preparing doped photocatalysts with respect to time and costs. When choosing between these two approaches, the hydrothermal method can be applied using a variety of precursors, whereas the annealing methods are restricted only to solid form precursors. Thus, the hydrothermal method is a more favorable method of non-metal doping of TiO2. However, studies should focus on the effects of different factors involved in each synthesis/preparation method to determine optimal preparation conditions.