Doping Behavior Research Articles

Regulating the dopant clustering in LiZnAs-based diluted magnetic semiconductor

Tuning of the magnetic interaction plays the vital role in reducing the clustering of magnetic dopant in diluted magnetic semiconductors (DMS). Due to the not well understood magnetic mechanism and the interplay between different magnetic mechanisms, no efficient and universal tuning strategy is proposed at present. Here, the magnetic interactions and formation energies of isovalent-doped (Mn) and aliovalent (Cr)-doped LiZnAs are studied based on density functional theory (DFT). It is found that the dopant–dopant distance-dependent magnetic interaction is highly sensitive to the carrier concentration and carrier type and can only be explained by the interplay between two magnetic mechanisms, i.e., super-exchange and Zener’s p–d exchange model. Thus, the magnetic behavior and clustering of magnetic dopant can be tuned by the interplay between two magnetic mechanisms. The insensitivity of the tuning effect to U parameter suggests that our strategy could be universal to other DMS.

From non‐doped to dopable: The impact of methoxy functionalization on doping and thermoelectric properties of conjugated polymers

AbstractThe introduction of alkoxy side chains into the backbone of conjugated polymers is an effective way to change their properties. While the impact on the structure and optoelectronic properties of polymer thin films was well‐studied in organic solar cells and transistors, limited research has been conducted on their effects on doping and thermoelectric properties. In this study, the effects of methoxy functionalization of conjugated backbones on the doping and thermoelectric properties are investigated through a comparative study of diketopyrrolopyrrole‐based conjugated polymers with and without methoxy groups (P29DPP‐BTOM and P29DPP‐BT, respectively). Methoxy‐functionalization significantly enhances doping efficiency, converting undopable pairs to dopable ones. This dramatic change is attributed to the structural changes in the polymer film caused by the methoxy groups, which increases the lamellar spacing and facilitates the incorporation of dopants within the polymer crystals. Moreover, methoxy‐functionalization is advantageous in improving the Seebeck coefficient and power factor of the doped polymers, because it induces a bimodal orientational distribution in the polymer, which contributes to the increased splitting of Fermi and charge transport levels. This study demonstrates the impact of methoxy‐functionalization of a conjugated polymer on doping behavior and thermoelectric properties, providing a guideline for designing high‐performance conjugated polymers for thermoelectric applications.image

The meta-cognitive role of thought morality in attitude change and behavioural intentions related to doping

ABSTRACT Prior research has examined the relationships between morality, attitudes, and intentions related to doping predominantly via correlational studies based on the theoretical frameworks provided by extensions to the theory of planned behaviour, and the social cognitive theory of moral thought and action. In contrast, the present study experimentally analysed a psychological process (i.e., self-validation) through which thought morality can influence attitudes and intentions. Two hundred and forty-two participants (122 males and 120 females) were randomly assigned to read a message either against or in favour of legalising several doping behaviours in sports, then listed their thoughts regarding that proposal. Next, they were randomly assigned to perceive their thoughts as either moral or immoral, then indicated the extent to which they considered their thoughts as valid. Finally, participants reported their attitudes and intentions regarding the legalisation proposal. As hypothesised, the anti-legalisation (vs. pro-legalisation) message produced more unfavourable thoughts and attitudes, as well as lower intentions to support the legalisation proposal and engage in banned behaviours if legalised in sport. Most importantly, the effects of message direction on attitudes and intentions were greater for participants in the moral (vs. immoral) thought condition. Furthermore, changes in attitudes were consistent with a self-validation process.

Redistribution of dopants between amorphous and crystalline phases in ZrO2–SiO2 nanoceramics

AbstractExtensive efforts have been devoted to investigate the distribution of dopants in ceramics. However, one critical question remained barely explored, which is the redistribution of dopants between amorphous and crystalline phases during fast sintering of ceramics. Here we address this gap by observing the redistribution of five selected dopants (Y, Ce, Yb, Hf, and Ta) in ZrO2–SiO2 nanoceramics during sintering. We designed two groups of experiments: In group one, dual‐phase amorphous particles were sintered with multicomponent crystalline ones. The former particles were ZrO2–SiO2 glass, whereas the latter ones consisted of ZrO2 solid‐solution nanocrystallites (SSNCs) embedded in an oxide glass containing Zr, Si, Y, Ce, Hf, Yb, and Ta. In group two, dual‐phase crystalline particles were sintered with multicomponent amorphous ones. The former particles were composed of ZrO2 nanocrystallites (NCs) embedded in an amorphous SiO2 matrix, whereas the latter ones were oxide glass containing Zr, Si, Y, Ce, Hf, Yb, and Ta. Redistribution of the dopants from the glass to ZrO2 NCs occurred in the two groups, that is, the five dopants migrated from the glass matrix into the ZrO2 NCs, forming ZrO2 SSNCs. The redistribution of the dopants not only increased the configuration entropy of the ZrO2 NCs but also benefited the network structure integrity of SiO2 glass. The dopant redistribution process was driven by the minimization of the studied material's free energy. The reported results are important for understanding the redistribution behaviors of dopants and are expected to provide new insights to design new ceramics via the multielement co‐doping strategy.

The effect of cerium, neodymium, and ytterbium doping on UO2 dissolution

The dissolution rate of spent nuclear fuel under environmental conditions has been studied heavily to understand the impacts of a failed waste package on potential radionuclide release from a geologic repository. Multiple countries have evaluated these scenarios in oxidizing and reducing environments respective to their relevant repository conditions. The repository environment (e.g., water chemistry, temperature, oxygen content) and the fuel itself (i.e., chemical composition of the fuel) both heavily impact the dissolution rate of the spent fuel. This work examined the impact that rare earth element dopants (Ce, Nd, Yb) have on the fuel dissolution under repository relevant conditions with decreasing oxidizing conditions using a single pass flowthrough system. UO2 samples were doped with Ce, Nd, or Yb with concentrations between 1 and 5 at%. The addition of dopants to the samples reduced the dissolution rates on most samples relative to pure UO2 samples. Preliminary experiments that occurred in a less oxidizing environment showed a reduction in dissolution rate compared to fully oxidizing conditions. The results within highlight the importance of dopant behavior in used fuel dissolution modeling.

Effect of plumbum on the solidification tendency in ordinary Portland cement clinker and its liquid phase properties

Using industrial solid waste as raw materials to produce cement clinker is an effective way to reduce environmental impact and disposal costs, however, industrial solid waste may have an impact on the sintering and mineral properties of cement clinker. This paper reports on the tendency of plumbum (Pb) ions to solidify within ordinary Portland cement (OPC) clinker and the effect on liquid phase properties. The results of elemental distributions, phase analysis, and density functional theory (DFT) indicate that Pb ions are most likely to enter C4AF by displacing Fe ions. The further analysis of bond order and bond length (BO-BL) and partial density of states (PDOS) showed that the solid solution tendency of Pb in C4AF can be ascribed to the new bond formation efficiency after Pb ions doping. The effect of Pb ions on the liquid phase properties during the calcination of OPC clinker was investigated experimentally. It was found that an increase in the amount of Pb ions doping lead to an earlier generation of the liquid phase, and the reason for this phenomenon can be attributed to the decrease in the elasticity constant of the mixture of Pb-rich and clinker phases formed by Pb ions doping, which leads to a decrease in the melting temperature. These insights into the doping behaviour of Pb ions will provide meaningful information to guide the use of Pb-containing solid waste as an alternative raw material for the synthesis of OPC clinker.

Investigation on doping behavior of Ho ions in Lu2SiO5 lattice by XRD Rietveld refinement and first-principles calculations

The effect of Ho doping on Lu2SiO5 lattice parameters and its occupation preference were investigated by experimentally and theoretically. A series of (Lu1-xHox)2SiO5 precursors were synthesized by a Sol-gel processing, the phase evolution behaviors were explored by XRD characterization after being calcined under temperatures ranging from 975 °C to 1300 °C. It was discovered that the crystallization temperature of synthetic precursors from amorphous to X1-(Lu1-xHox)2SiO5 phase was about 975 °C, and the temperatures of phase transformation from X1-(Lu1-xHox)2SiO5 to X2-(Lu1-xHox)2SiO5 varied from 1100–1300 °C. The defect formation energies of Ho substituted in X2- Lu2SiO5 were obtained by first-principles calculations, which indicated that the Ho3+ was prone to occupy the coordination polyhedral of [LuO7]. Furthermore, it was found that the introduction of Ho into X2- Lu2SiO5 caused the increasing of lattice parameters and the distortion of [LuO7] coordination polyhedron, which contributed to regulate and control the physical and chemical properties.

Dynamic behaviour of platinum and copper dopants in gold nanoclusters supported on ceria catalysts

Understanding the behaviour of active catalyst sites at the atomic level is crucial for optimizing catalytic performance. Here, the evolution of Pt and Cu dopants in Au25 clusters on CeO2 supports is investigated in the water-gas shift (WGS) reaction, using operando XAFS and DRIFTS. Different behaviour is observed for the Cu and Pt dopants during the pretreatment and reaction. The Cu migrates and builds clusters on the support, whereas the Pt creates single-atom active sites on the surface of the cluster, leading to better performance. Doping with both metals induces strong interactions and pretreatment and reaction conditions lead to the growth of the Au clusters, thereby affecting their catalytic behaviour. This highlights importance of understanding the behaviour of atoms at different stages of catalyst evolution. These insights into the atomic dynamics at the different stages are crucial for the precise optimisation of catalysts, which ultimately enables improved catalytic performance.

Revealing the mechanism of manganese doping in sulphoaluminate cement clinker

The production of cement clinker from solid waste generated by industrial development is a valid way to reduce the exploitation of natural resources and protect the environment. This paper reports the doping behavior of manganese (Mn) ions in sulphoaluminate cement (SAC) clinker. Results from energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and density functional theory (DFT) simulations indicate that Mn ions enter C4AF by replacing Fe ions, and rarely incorporate into the other two minerals, C4A3S‾ and C2S. Further analysis of the partial density of states (PDOS) and electron density difference (EDD) indicates that the Mn doping mechanism can be ascribed to the comparable electronic contributions of the host and guest ions. These insights into the doping behavior of Mn ions will provide meaningful information to guide the utilization of Mn-containing solid waste as an alternative raw material for the synthesis of SAC clinker.

Perspective on defect control in semiconductors for photovoltaics

Harnessing the boundless solar energy, photovoltaic cells emerge as pivotal players in the world’s sustainable energy landscape. The efficiency of solar cells is intimately tied to the carrier properties influenced by defects and impurities within the sunlight-absorbing semiconductors. In this Perspective, we offer a brief overview of recent advances in exploring doping properties with a focus on three vital thin-film photovoltaic semiconductors: CdTe, CIGS, and halide perovskites. Our discourse encompasses their electronic band structure, intrinsic and extrinsic doping behaviors, defect-assisted nonradiative recombination losses, as well as promising strategies poised to enhance solar cell efficiency. Additionally, we discuss several lingering challenges associated with defects in the advancement of photovoltaic technologies.

Significant enhancement of electrical conductivity in boron-doped diamond through HPHT post-annealing treatment

Boron-doped diamond (BDD) is expected as a promising semiconductor candidate for potential application in next-generation high-power and high-voltage electronics. Unfortunately, a feasible strategy that focuses on the improvement of the semiconducting performance of BDD materials is still lacking and remains a fundamental challenge in material science. Thus, we aim to study the stability and adjustment behaviors of boron dopants in BDD single crystals through post-annealing treatment under high pressure and high temperature (HPHT) conditions. In this work, our study demonstrates that boron dopants show high structural stability, and no extra complex defects were observed during the HPHT annealing process, a superior advantage for the device application in extreme environments. Our work further reveals that the HPHT post-annealing process is effective to eliminate the intrinsic stress and local lattice strain that were inherently formed during the diamond growth process. This process is accompanied by the enhancement of ionization ratio of boron dopants. The carrier content of one 〈111〉-GS BDD increases by more than ten times after post-annealing at 1000 °C and 5.5 GPa, resulting in significant improvement of conductivity by a factor of 2. This result provides an effective strategy to improve the semiconducting performance of BDD materials through HPHT annealing approach and promote their practical device applications.

The effect of the isoelectronic traps on the luminescence properties of Zn1-XCdXO thin films

In this report, Zn1-xCdxO ceramic thin films were deposited by the sol-gel method on an n-type Si (100) substrate. The structure, morphology, and luminescence properties of the thin films were studied. To elucidate the structure and the optical properties of Zn1-xCdxO thin films, our study focuses on the roles of changing the content of the doped Cd and the annealing temperature in Cd-doped ZnO thin films. The Cd doping behavior was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The research concentrates on the effects of doping concentration, annealing temperature, and isoelectronic trapping on the crystallization quality and luminescence properties of the thin films. On the basis of the different electronegativity of the doping elements, Cd substitution for Zn forms isoelectronic traps, which influence the intensity of luminescence and change the luminous peaks. By raising the annealing temperature further, the intensity of each diffraction peak of ZnO is gradually increasing, improving the quantity of Cd entering the ZnO crystal lattice. The PL spectra display that the ZnO thin films only appear in yellow-green emission bands, which appear redshift through the incorporation of Cd. With the increase in Cd doping amount, the yellow light luminous center keeps moving in the low energy direction. When the Cd doping amount reaches 20 %, the luminescence intensity reaches its maximum, which holds great promise for its application in light devices.

Magnesium Mitigation Behavior in P2-Layered Sodium-Ion Battery Cathode.

Heteroatom incorporation can effectively suppress the phase transition of layered sodium-ion battery cathode, but heteroatom behaviors during operating conditions are not completely understood at the atomic scale. Here, density functional theory calculations are combined with experiments to explore the mitigation behavior of Mg dopant and its mechanisms under operating conditions in P2-Na0.67Ni0.33Mn0.67O2. The void formed by Na extraction will pump some Mg dopants into Na layers from TM layers, and the collective diffusion of more than one Mg ion most likely occurs when the Mg content is relatively high in the TM layer, finally aggregating to form Mg-enrich regions (i.e., Mg segregation) apart from Ni vacancies. The void-pump-effect-induced Mg segregation effectively suppresses the P2-O2 phase transition owing to the stronger Mg-O electrostatic attraction that enhances the integrate of two adjacent oxygen layers and prevents the crack growth by mitigating the lattice volume variation under high-voltage cycling. Our work provides a fundamental understanding of heteroatom mitigation behavior in layered cathodes at the atomic level for next-generation energy storage technologies.

Impact of Molecular Weight on the Ionic and Electronic Transport of Self‐Doped Conjugated Polyelectrolytes Relevant to Organic Electrochemical Transistors

AbstractOrganic electrochemical transistors (OECTs) have gained considerable attention due to their potential applications in emerging biosensor platforms. The use of conjugated polyelectrolytes (CPEs) as active materials in OECTs is particularly advantageous owing to their functional, water‐processable, and biocompatible nature, as well as their tunable electronic and ionic transport properties. However, there exists a lack of systematic studies of the structure‐property relationships of these materials with respect to OECT performance. This study shows how by tuning the molecular weight of self‐doped CPE (CPE‐K) it is possible to fabricate OECTs with a µC* value of 14.7 F cm−1 V−1 s−1, one order of magnitude higher than previously reported CPE‐based devices. Furthermore, OECTs with a transconductance of 120 mS are demonstrated via device engineering. While CPE‐K batches with different molecular weights show good doping behavior and high volumetric capacitance, as confirmed by spectroelectrochemistry and electrochemical impedance spectroscopy, the medium molecular weight possesses the highest carrier mobility of ≈0.1 cm2 V−1 s−1 leading to the highest transconductance. The enhanced charge transport is due to a favorable charge percolation pathway, as revealed by the combination of X‐ray analysis and conductive atomic force microscope. These insights provide guidelines for further improving the performance of CPE‐based OECTs.

Reduced Defect Density in MOCVD-Grown MoS2 by Manipulating the Precursor Phase.

Advancements in the synthesis of large-area, high-quality two-dimensional transition metal dichalcogenides such as MoS2 play a crucial role in the development of future electronic and optoelectronic devices. The presence of defects formed by sulfur vacancies in MoS2 results in low photoluminescence emission and imparts high n-type doping behavior, thus substantially affecting material quality. Herein, we report a new method in which single-phase (liquid) precursors are used for the metal-organic chemical vapor deposition (MOCVD) growth of a MoS2 film. Furthermore, we fabricated a high-performance photodetector (PD) and achieved improved photoresponsivity and faster photoresponse in the spectral range 405-637 nm compared to those of PDs fabricated by the conventional MOCVD method. In addition, the fabricated MoS2 thin film showed a threshold voltage shift in the positive gate bias direction owing to the reduced number of S vacancy defects in the MoS2 lattice. Thus, our method significantly improved the synthesis of monolayer MoS2 and can expand the application scope of high-quality, atomically thin materials in large-scale electronic and optoelectronic devices.

The atomic and electronic band structures in Ca/Si-doped and Ca/Si/Ti-doped Al2O3 grain boundaries

Grain boundary (GB) segregation plays a crucial role in determining structures, chemistries and resultant properties of polycrystalline ceramic materials. Although GB segregation behaviors of single-element dopants have been extensively investigated, GB segregation in practical polycrystalline ceramics often involves multiple elements. In this study, we conducted experimental investigations to explore the atomic and electronic band structures of Ca/Si-doped and Ca/Si/Ti-doped Al2O3 Σ745̅10 GBs. By employing atomic-resolution scanning transmission electron microscopy combined with density functional theory calculations, we elucidated the interactions between different elements at the GBs. Our findings reveal that Ca and Si were synergistically co-segregated in both GBs, maintaining charge neutrality within the GB core, while the site competition between Ca and Ti occurred in the Ca/Si/Ti-doped GB. Furthermore, valence electron energy loss spectroscopy measurements provided insights into the band gaps of doped GBs, demonstrating that they are dependent on doping species but independent of interactions between different elements.

Direct synthesis of nitrogen-doped narrow-diameter carbon nanotubes through floating-catalyst chemical vapor deposition with high hydrogen flow rate

The precise control of substitutional nitrogen (N) doping into a carbon nanotube (CNT) lattice is key to tuning their unique one-dimensional electronic properties. Here we report a direct synthesis of high-quality N-doped single-wall CNTs (N-SWCNTs) with ∼1 nm in diameter using a floating-catalyst chemical vapor deposition under a high flow rate of hydrogen as a carrier gas. The high hydrogen flow rate enhances the total N content in the CNT lattice. The N-SWCNTs exhibit an n-type doping behavior induced by enriched graphitic-N as confirmed by Raman analysis. Our finding will be beneficial to tailoring the doping state of N-SWCNTs.

Enhanced charge transport behaviors of single-walled carbon nanotube transistors by phenylphosphonic acid doping

Inkjet printing technology holds promise as a cost-effective method for fabricating large-area electronics, with high compatibility with various substrates. In this paper, we investigate the electrical doping behaviors of p-type transistors based on single-walled carbon nanotubes (SWCNTs), where semiconducting channels and electrodes are patterned using inkjet printing. We demonstrate improved charge transport properties by encapsulating SWCNTs with phenylphosphonic acid (PPA) without annealing. The PPA-coated SWCNT transistors exhibit significantly enhanced hole mobility, reaching approximately 8.25 cm2 V−1 s−1. The presence of the benzene ring in PPA facilitates hole injection and induces a p-doping effect, resulting in a 4.3-fold increase in the on-current level of the transistors.

Structural and Mechanical Properties of Doped Tobermorite.

As calcium silicate hydrate (C-S-H) is the main binding phase in concrete, understanding the doping behavior of impurity elements in it is important for optimizing the structure of cementitious materials. However, most of the current studies focus on cement clinker, and the doping mechanism of impurity elements in hydrated calcium silicate is not yet fully understood. The hydrated calcium silicate component is complex, and its structure is very similar to that of the tobermorite mineral family. In this study, the effects of three different dopants (Mg, Sr and Ba) on a representing structure of C-S-H-tobermorite-was systematically explored using densify functional theory (DFT) calculations. The calculations show that Mg doping leads to a decrease in lattice volume and causes obvious structure and coordination changes of magnesium-oxygen polyhedra. This may be the reason why high formation energy is required for the Mg-doped tobermorite. Meanwhile, doping only increases the volume of the Sr- and Ba-centered oxygen polyhedra. Specifically, the Mg-doped structure exhibits higher chemical stability and shorter interatomic bonding. In addition, although Mg doping distorts the structure, the stronger chemical bonding between Mg-O atoms also improves the compressive (~1.99% on average) and shear resistance (~2.74% on average) of tobermorillonite according to the elastic modulus and has less effect on the anisotropy of the Young's modulus. Our results suggest that Mg doping is a promising strategy for the optimized structural design of C-S-H.

Overcoming the compensation of acceptors in GaN:Mg by defect complex formation

In GaN:Mg, the MgGa acceptor is compensated extensively by the formation of nitrogen vacancies (VN) and Mg interstitials (Mgi). However, we show that such compensation can be overcome by forming two kinds of Mg-rich complexes: one that contains VN and the other that contains only MgGa and Mgi. Such complexing not only neutralizes VN and Mgi but also forms better complex acceptors that have lower formation energies and smaller hole localization energies than isolated MgGa. Our results help explain the different doping behaviors in samples grown by different methods.