Uniform Doping Research Articles

Performance Analysis of JL-FinFET with Varied Non-Uniform Doping Concentrations, Fin Height and Fin Width using Device Simulator

With the growth of the MOSFET technology, the size of the transistor becomes smaller which can lead to Short-Channel Effects (SCEs). In order to address the SCEs, multi-gate transistor such as Fin Field-Effect Transistor (FinFET) has been invented. Meanwhile, it is found that the conventional transistor with junctions also has its drawbacks and limitations due to the decrease in the gate length. The SCEs can occur and affect the overall performance of the device with lower switching times and lower current density . In order to address these limitations, new structure of transistor without junction known as a junctionless (JL) transistor has been proposed. In this work, the impact of uniform versus non-uniform doping concentrations, fin height (Hfin) and fin width (Wfin) in JL-FinFET were investigated by using Technology Computer Aided Design (TCAD) Tools. It was found that non-uniform doping concentration of 4 x1018 cm-3 for the source/drain and of 4 x1017 cm-3 for the channel, together with Hfin of 20 nm and Wfin of 4 nm provide the best electrical performance of Ioff = 6.45 x10-17 A, Ion = 6.14 x10-6 A, Ion/Ioff = 9.52 x1010 and DIBL = 11 mV/V. The outcome of this research work can be used as a basis to understand JL-FinFET biosensors for medical applications and more complex JL structures.

Uniform Sb doping of ZnO films with controllable morphology and enhanced optical property

In order to provide an effective and reliable approach to solving the difficulties in p-type modification of ZnO nanomaterials, in this work, we successfully synthesized ZnO films with uniform antimony distribution through low temperature aqueous growth method. The growth quality and dopant distribution of Sb-doped ZnO (SZO) films were evaluated by high-resolution micro-structural characterizations, and the growth mechanism for SZO films with various doping concentrations was discussed and revealed. Uniform and dispersive Sb distribution within SZO films contributed to the light transmittance of SZO films. The blue-shifted UV emission accompanied with weak visible light emission of SZO films were observed in room-temperature photoluminescent (PL) spectra, the rare yellow-red light emission and XPS results confirmed the existence of SbZn-related complex defects. This type of SZO films is competitive and promising for serving as the highly photo-conductive and photo-sensitive ZnO-based nanomaterials. And SZO films could be served as the basis for realizing the purpose of p-type modification with high efficiency and excellent stability.

High-Volume SiC Epitaxial Layer Manufacturing-Maintaining High Materials Quality of Lab Results in Production

Typically, research and development (R&D) results of epitaxial layer growth show superior properties of the grown layers compared to high volume results. Layer uniformities are excellent and achieved defect densities are low compared to typical results. In particular, the conversion of basal plane dislocations (BPD) from the silicon carbide (SiC) substrate is in focus to reduce bipolar degradation of p-n-junctions. It is a great challenge to maintain those excellent results in high-volume manufacturing considering all the factors that impact the properties of the epilayer. Thus, quality of the layers, high throughput and low cost have to be assessed to find a compromise between these key factors. In this paper we present results on the growth of epitaxial layers on 150 mm and 200 mm 4° off-oriented 4H-SiC substrates using warm-wall multi-wafer chemical vapor deposition (CVD) systems. Single wafer data of the key epitaxial layer parameters, thickness, doping and defect densities, are compared to batch and lot results, as well as to statistical data of several hundreds of wafers produced. Improvements in wafer-to-wafer (w-t-w) doping uniformity could be achieved for instance by implementation of an on-wafer temperature measurement. Substrate impact on defect levels is shown comparing X-ray topography (XRT) results of bare substrate wafers and defect analysis of epilayers on sister wafers from the same crystal. Statistical defect data and resulting predicted yield loss also show a dependence on substrate suppliers. For the first time we show w-t-w and run-to-run (r-t-r) results of doping and thickness measurements on 200 mm substrates. Also, defect results of epilayers on 200 mm wafers are compared to results on 150 mm.

Local Charge Modulation Induced the Formation of High‐Valent Nickel Sites for Enhanced Urea Electrolysis

AbstractNi‐based electrocatalysts are considered to be significantly promising candidates for electrocatalytic urea oxidation reaction (UOR). However, their UOR activity and stability are severely enslaved by the inevitable Ni group self‐oxidation phenomenon. In this study, the glassy state NiFe LDH with uniform Cu dopant (Cu‐NiFe LDH) by a simple sol–gel strategy is successfully synthesized. When served as the UOR catalyst, Cu‐NiFe LDH required a 123 mV lower potential for UOR at both 10 and 100 mA cm−2 in comparison with the conventional anodic OER. It can also operate steadily for more than 300 h at 10 mA cm−2. The in‐depth investigation reveals that Cu incorporation can optimize the local electronic structure of Ni species to induce high‐valent Ni sites. The high‐valent Ni sites would act as the active center during the proposed energetically favorable UOR route, which directly reacts on the high‐valent Ni sites without self‐oxidation inducing the formation of NiOOH species, resulting in a boosted electrocatalytic UOR activity and stability.

Mechanism study of trimetallic single-cluster catalysts loaded on graphdiyne for highly efficient oxygen-reduction reactions

Single-cluster catalysts (SCCs) have become a research hotspot due to their abundant active sites and tunable interatomic electronic structure, demonstrating excellent catalytic properties. However, the diversity of metal species in SCCs leads to unclear intrinsic activity toward metals and interaction between different metal species. In this manuscript, the impact of a series of precious metal-based (Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au) trimetallic SCCs loaded on graphdiyne (UxVyWz@GDY) on the performance of the oxygen reduction reaction (ORR) is investigated using first-principles. The results show that the 18 holes of graphdiyne (GDY) efficiently achieve uniform doping of trimetallic clusters. In the UxVyWz@GDY structure, Pt3@GDY, Pt2Pd@GDY, and AuPdPt@GDY displayed high thermodynamic limit potentials near the top of the volcano plot at 0.79 eV, 0.80 eV, and 0.82 eV, respectively. These catalysts also show low overpotentials of 0.44 V, 0.43 V and 0.50 V, respectively. Deeper scrutiny of the interaction mechanism between *OH and the catalytic sites on Pt3@GDY, Pt2Pd@GDY, and AuPdPt@GDY unveils the pivotal role of electron transfer and intermetallic interactions in modulating the d-band center. Notably, the observed left shift of the d-band center in these catalysts, leading to the generation of more electron-deficient centers, effectively mitigates the issue of over-absorption between *OH and metal active sites, thereby significantly enhancing *OH desorption. This work provides inspiration for the efficient design of trimetallic SCCs.

Optimizing phosphorus-doped polysilicon in TOPCon structures using silicon oxide layers to improve silicon solar cell performance

Tunnel Oxide Passivated Contact (TOPCon) technology is one of the most influential and industrially viable solar cell technologies available today. Improving the quality of passivation contact has become a central focus of current research. Although the conventional monolayer polycrystalline silicon method is highly effective in TOPCon solar cells, it is limited by doping inhomogeneity, which impairs the passivation and electrical properties, and the cell's photovoltaic conversion efficiency remains suboptimal. To address this issue, this study investigates the deposition of two layers of silicon oxide and two layers of in-situ doped phosphorus amorphous silicon, termed double poly-Si/SiOx structures, on n-type silicon wafers using plasma-enhanced chemical vapor deposition (PECVD). The effectiveness of the structure was confirmed through various characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Key findings indicate that the double-polysilicon structure significantly enhances the uniformity of phosphorus doping, improving the carrier lifetime of the cell and reducing the contact resistance. As a result, the average efficiency in the final production stage has a conversion efficiency gain of 0.23 % over the baseline group. This study underscores the potential of this PECVD methodology to advance the fabrication of high-efficiency solar cells by providing significant improvements in passivation, doping uniformity, and overall cell performance.

In-situ construction of ionic liquid salt-derived graphene-like dual-heteroatoms doping engineering as efficient metal-free electrocatalyst for oxygen reduction reaction

Metal-free heteroatom-doped carbon catalysts can effectively eliminate the degradation and pollution problems caused by metal dissolution. However, single heteroatom doping often restricts the regulation of geometric and electronic structures for oxygen reduction reaction (ORR) electrocatalysts. Herein, a dual atomic doping engineering to optimize the electronic structure and local coordination environment of ionic liquid salt-derived graphene-like host material as an efficient metal-free electrocatalyst for ORR. The resultant PNG catalyst with a typical nanosheets morphology with a high specific surface area and unique hierarchical porous structure. Benefiting from the uniform doping of P, N heteroatoms, graphene-like structure, optimized electronic structure and coordination environment, thus-prepared PNG-2 exhibits outstanding ORR activity, which the onset potential and half-potential are negatively shifted by around 70 mV and 46 mV, respectively, as compared to the commercial Pt/C (20 wt.%) for ORR. Furthermore, the PNG-2 exhibits the higher diffusion limiting current density, superior long-term stability as well as excellent resistance to methanol oxidation than Pt/C. Experimental studies and density functional theory (DFT) calculations reveal that the enhanced chemisorption of oxygen species (*OOH, *O and *OH) onto the P and N sites of the PNG catalysts can effectively accelerate the charge transfer kinetics and promote a favorable ORR performance.

High-Quality 4H-SiC Homogeneous Epitaxy via Homemade Horizontal Hot-Wall Reactor

In this paper, using a self-developed silicon carbide epitaxial reactor, we obtained high-quality 6-inch epitaxial wafers with doping concentration uniformity less than 2%, thickness uniformity less than 1% and roughness less than 0.2 nm on domestic substrates, which meets the application requirements of high-quality Schottky Barrier Diode (SBD) and Metal–Oxide–Semiconductor Field-Effect Transistor (MOSFET) devices. We found that increasing the carrier gas flow rate can minimize source gas depletion and optimize the doping uniformity of the 6-inch epitaxial wafer from over 5% to less than 2%. Moreover, reducing the C/Si ratio significantly can suppress the “two-dimensional nucleation growth mode” and improve the wafer surface roughness Ra from 1.82 nm to 0.16 nm.

Enhanced green hydrogen production via CdS/Cu-doped TiO2 nanotubes: Advancements in photoanode performance

Cadmium Sulfide (CdS) deposited Copper (Cu) doped TiO2 nanotube hybrid photoanode (CdS/Cu-TNT) is developed via electrochemical anodization and subsequent electrochemical deposition for efficient green hydrogen production. Cu-doping of TiO2 Nanotube (TNT) is achieved in one-step anodization, which is more energy efficient than conventional arc melting. Results indicate that CdS/Cu-TNT photoanodes increased carrier density by 9 times and achieved a low bandgap of 2.46 eV which enhancing their suitability as photoanodes. Particle size distribution analysis has shown that Cu doping causes thicker nanotube walls with decreased surface area. CdS is coated over the Cu-doped TNT to enhance the photoelectrochemical properties further. The photocurrent of CdS-deposited TNT is 7.8 times higher than bare TNTs. Raman Spectral Mapping indicates the uniformity of CdS deposition and Cu doping. Photostability experiments reveal excellent performance and switching characteristics for Cu-doped, CdS-deposited, and CdS/Cu-TNT hybrid samples. The hybrid electrode with larger diameter nanotubes shows a 52.39 % increase in the Fill Factor of photocurrent response for CdS/Cu-TNT. Moreover, hydrogen production is significantly enhanced, with CdS/TNT demonstrating a 3.8-fold increase and CdS/Cu-TNT demonstrating a 4.1-fold increase. This research highlights the potential of Cu doping in TiO2 nanotubes for hydrogen generation, offering improvements over the limitations of TiO2 as a photoanode.

Enhanced Li storage of pure crystalline-C60 and TiNb2O7-nanostructure composite for Li-ion battery anodes

We propose a method for producing composite materials (hTNO@C60) comprising crystalline C60 particles and hollow-structured TiNb2O7 (hTNO) nanofibers via facile liquid–liquid interface precipitation followed by low-temperature annealing. This allows the systematic design of crystalline C60 as an active material for Li-ion battery anodes. The hTNO@C60 composite demonstrates outstanding cyclic stability, retaining a capacity of 465 mA h g−1 after 1,000 cycles at 1 A g−1. It maintains a capacity of 98 mA h g−1 even after 16,000 ultralong cycles at 8 A g−1. The enhancement in electrochemical properties is attributed to the successful growth and uniform doping of crystalline C60, resulting in improved electrical conductivity. The excellent electrochemical stability and properties of these composites make them promising anode materials.

Metal-free solid base catalysis: Boron-doped graphitic carbon nitride for the efficient synthesis of ethyl coumarin-3-carboxylate

In this work, boron doped graphitic carbon nitride materials (BgCN-x) were successfully prepared by thermal copolymerization of melamine and boric acid. The comprehensive characterization using various techniques, including powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), UV-Visible spectroscopy (UV-Vis), Field emission scanning electron microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDS), Field emission transmission electron microscopy (FETEM), and X-ray photoelectron spectroscopy (XPS) revealed the uniform doping of boron in the tri-s-triazine rings of g-C3N4 by substituting the carbon or nitrogen atoms. Furthermore, the basic site concentrations of the catalysts were evaluated using CO2-TPD technique. The BgCN catalysts exhibited significantly enhanced catalytic activity in the base-catalyzed Knoevenagel condensation between salicylaldehyde and diethyl malonate for coumarin synthesis. This work underscores the potential of boron-doped or two-dimensional boron-dominant materials as promising candidates for metal-free heterogeneous base catalysis, paving the way for further advancements in the field.

Enhancing Orbital Interaction in Spinel LiNi0.5Mn1.5O4 Cathode for High-Voltage and High-Rate Li-Ion Batteries.

High voltage cobalt-free spinel LiNi0.5Mn1.5O4 (LNMO) is well organized as a high-power cathode material for lithium (Li)-ion batteries, however, the weak interaction between the 3d orbital of the transition metal (TM) ions and the 2p orbital of oxygen (O) leads to the instability of crystal structural, hindering the long-term stable cycling of LNMO cathode especially at high temperatures. Here, a design strategy of orbital interaction is initiated to strengthen TM 3d-O 2p framework in P-doped LNMO (P-LNMO) by choosing phytic acid as P dopant, which can realize more uniform doping compared to regular phosphate. The results show that the enhancement of TM 3d-O 2p orbital interaction in P-LNMO can suppress the Jahn-Teller effect and subsequent dissolution of Mn, as well as lowers the energy barrier for Li ion insertion/extraction kinetics. As a result, superior electrochemical performances including high discharge capacity, stable cycling behavior and enhanced rate capability of P-LNMO are obtained. Significantly, the P-LNMO pouch cell shows great cycling stability with 97.4% capacity retention after 100 cycles.

Hydrothermal preparation of N and O-rich porous carbon microspheres and their capacitance properties

In this paper, N and O-rich porous activated carbon (N-O/AC) microsphere with various pore sizes was prepared by thermal and KOH activation of g-C3N4@graphene oxide (CN@GO) microsphere. CN@GO microsphere was pre-prepared through a hydrothermal method directly from glucose and melamine, which resulted into high content and uniform doping of O and N in the final product. CN@GO microsphere was composed of GO/CN/GO sandwich nanochips, forming a porous structure with various pore sizes. The obtained N-O/AC has high energy density (33.19 Wh/kg) and high power density (499.93 W/kg), in company with excellent cyclic stability (remaining 98.64 % after 1000 cycles). The N-O/AC derived from the hydrothermal method provides a low-cost way of constructing porous carbon matrix composites with pseudo-capacitance.

Effect of TCS gas flow and pre-etching on homopitaxial growth of 4H-SiC.

In this study, the epitaxial growth of 6-inch n-type 4° off-axis Si-face substrates using a horizontal hot-wall LPCVD system was investigated. The study explored the epitaxial growth under different source gas flow rates, growth pressures, and pre-etching times, with particular emphasis on their effects on epitaxial growth rate, epitaxial layer thickness uniformity, doping concentration and uniformity, and epitaxial layer surface roughness. The observation was made that the increase in source gas flow rate led to variations in dopant concentration due to different transport models between nitrogen gas and source gas. Additionally, with the increase in etching time, overetching phenomena occurred, resulting in changes in both dopant concentration and uniformity. Furthermore, the relationships between these three factors and their corresponding indicators were explained by combining the CVD growth process with the laminar flow model. These observed patterns are beneficial for further optimizing growth conditions in industrial settings, ultimately enhancing the quality of the growth process.

Electrochemical aptasensors based on porous carbon derived from graphene oxide/ZIF-8 composites for the detection of Erwinia cypripedii

In this research, self-screening aptamer and MOFs-derived nanomaterial have been combined to construct electrochemical aptasensor for environmental detection. By utilizing the large specific surface area of reduced graphene oxide (rGO), ZIF-8 was grown in situ on surface of rGO, and the composites was pyrolyzed to obtain MOFs-derived porous carbon materials (rGO-NCZIF). Thanks to the synergistic effect between rGO and NCZIF, the complex exhibits remarkable characteristics, including a high electron transfer rate and electrocatalytic activity. In addition, the orderly arrangement of imidazole ligands within ZIF-8 facilitated the uniform doping of nitrogen elements into the porous carbon, thereby significantly enhancing its electrochemical performance. After carboxylation, rGO-NCZIF was functionalized with self-screening aptamer for fabricating electrochemical aptasensor, which can be used to detect Erwinia cypripedii, a kind of quarantine plant bacteria, with detection limit of 4.92 × 103 cfu/mL. Due to the simplicity and speed, the aptasensor is suitable for rapid customs inspection and quarantine. Additionally, the universality of this sensing strategy was verified through exosomes detection by changing the aptamer. The results indicated that the rGO-NCZIF-based electrochemical aptasensor had practical value in the environmental and medical fields.

Enhanced ethanol gas detection using TiO2 nanorods dispersed in cholesteric liquid crystal: Synthesis, characterization, and sensing performance

This research presents an innovative approach for ethanol gas detection by utilizing a cholesteric liquid crystal (CLC) dispersed with titanium dioxide nanorods (TiO2 NRs). Titanium dioxide nanorods (TiO2 NRs) are synthesized using a hydrothermal method, ensuring uniform and effective doping process in the CLC matrix. The morphological and structural properties of the synthesized TiO2 nanorods are thoroughly analyzed using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), revealing the successful formation of rod-like structures. Brunauer-Emmett-Teller (BET) analysis confirms the porous nature of these nanorods, with a surface area of 3.158 m²/g and a mesoporous distribution featuring an average pore size of 14.0 nm. The CLC/TiO2 NRs sensor shows high sensitivity and rapid detection, with a response time of 21 sec. It also exhibits excellent selectivity against various gases, maintaining consistent performance over multiple cycles. The enhanced sensing performance is attributed to the interaction between ethanol gas molecules and TiO2 NRs, leading to a change in resistance within the CLC matrix. This work demonstrates the potential of TiO2 NRs in enhancing the capabilities of CLCs for environmental sensing and provides a promising direction for future research in developing highly sensitive and selective gas sensors.

In-situ rapid nondestructive characterization of multiple irregular three-dimensional grain boundary structures and electrical properties by nanorobot with SEM in ZnO

To address the problem of spatial quantification of irregular grain boundaries, a unique approach for the nondestructive characterization of multiple irregular three-dimensional grain boundaries is proposed using nanorobots with scanning electron microscopy (SEM) to accomplish in-situ rapid synchronized quantification of structures and electrical properties. By constructing a three-dimensional trigonometric geometric mapping relationship, multiple irregular three-dimensional grain boundary structures and electrical properties can be rapidly quantified. Experimental results demonstrate that it is feasible to accomplish in-situ rapid nondestructive characterizations. The two-dimensional profile shapes of the targeted grain boundaries at each layer exhibit irregular and non-uniform features in the Y-Z plane. The hypotenuse length between the virtual space tilting lines presents a three-dimensional characteristic in the X-Z plane. The spatial tilt angle of the virtual space tilting line can be calculated using the right-triangle relation. The unequal numbers of grains along the same tilted hypotenuse direction with equal lengths directly illustrate the existence of irregular and nonlinear grain boundaries in bulk ZnO ceramics. The relatively uniform spatial sizes of the grain boundary illustrate the coupled spatial characteristics existing in the irregular micro-structures. The relatively uniform equivalent circuit fitting parameters confirm the existence of relatively uniform doping components in bulk ZnO ceramics. Furthermore, this method provides a unique approach for the rapid nondestructive quantitative analysis of multiple three-dimensional irregular grain boundaries in bulk polycrystalline materials.

Sulfur and nitrogen co-doping of peanut shell-derived biochar for sustainable supercapacitor applications

To enhance the biochar produced from biomass and utilize it in the development of electrodes for applications in supercapacitors, doping the biochar with multiple or double heteroatom elements could be more beneficial than single-element doping. The search for the right heteroatom doping sources and synthesis techniques is difficult but necessary. This study exhibited the synthesis of peanut shell-derived biochar doped with sulfur (S) and nitrogen (N) through carbonization, activation, and ex-situ doping with affordable melamine and thiourea as S and S/N sources. Characterizations such as XPS, XRD, TEM, Raman, EDS mapping revealed that the S and N co-doped biochar has multilayered nanosheet-like morphology, uniform heteroatom doping, and hierarchical pore structure. Electrochemical characterization showed that the S and N co-doped electrode material has a specific capacitance of 224 F/g, higher than those of 200 F/g and 178.94 F/g of N-doped and pristine biochar at 1 A/g, respectively. The supercapacitor fabricated by the developed electrodes at 1 A/g has a specific capacitance of 80.25 F/g with a density of energy of 11.15 Wh/Kg. It is considered that S and N co-doping can enhance the active regions and pore arrangement of peanut shell-derived biochar to improve the passage of ions of the electrolyte and transfer of charge to the electrode surface in supercapacitor applications.

Multi-microscopy characterization of threading dislocations in CVD-grown diamond films

We present site-coincident imaging of a high dislocation density boron-doped chemical vapor deposition-grown homoepitaxial (001) diamond film using electron channeling contrast imaging (ECCI), cathodoluminescence, transmission electron microscopy (TEM), and scanning secondary ion mass spectroscopy (SIMS). With growing interest in large area heteroepitaxial substrates, we show that ECCI is a promising technique to accurately evaluate dislocations in diamond films. We find the electron backscatter yield is sufficient to distinguish individual threading dislocations in ECCI despite the low atomic number of carbon, and we have generally good agreement between dislocations observed in ECCI and TEM of the same region. Importantly, relying on luminescence in the 430 nm dislocation-related A-band alone results in an underestimation of the defect density as we find only 20%–40% of the threading dislocations luminesce. We further show that dislocations do not perturb the spatial uniformity of boron doping measured by SIMS, even when the dislocations are clustered with high density, and we can tentatively rule out strong segregation effects at the dislocations. Our results establish the complementary use of microscopy and microanalysis methods to rapidly characterize and understand the impact of dislocations in diamond thin films.

Impact of Mo doping on photo-sensing properties of ZnO thin films for advanced photodetection applications

This work explored the impact of Mo-doping on the structural, optical, photophysical, and electrical characteristics of ZnO thin films and their potential application to the UV light detection properties was investigated. The hexagonal structure of the films without any impurities or extra phases was confirmed by X-ray diffraction and FT-Raman spectroscopy. The crystallite size reduced from 36 nm to 25 nm with the addition of 3 wt% of Mo in ZnO. The EDX/SEM e-mapping verified the elemental composition and uniform Mo doping throughout the films. The FESEM images revealed spherical nanoparticles with smaller grains size for higher Mo-doping levels. The absorption spectra were recorded from UV to NIR range, and the bandgap was observed to increase from 3.25 eV for pure ZnO to 3.42 for 3% Mo-doped ZnO sample. The Mo-doped ZnO film showed PL quenching, which indicates charge transfer and suppression of defect sates in the ZnO films via Mo-doping. The time-resolved fluorescence spectra (TRFS) of these films revealed that the carrier lifetime increased from 80 ps for pure ZnO to 144 ps for 3% Mo-doped ZnO thin film. The electrical parameters including resistivity, carrier mobility, concentrations, and sheet resistance of fabricated films were evaluated by Hall-effect measurement. The resistivity and mobility were observed to decrease from 9.33×104 Ω.cm, 55.1 cm2/V.s to 2.03×103 Ω.cm 15.4 cm2/V.s for 3% Mo-doped ZnO thin film, while carrier density increased. The photodetection study demonstrated that the responsivity, detectivity, external quantum efficiency and response time of devices were significantly enhanced with Mo idoping.