Doped Nanowires Research Articles

Unveiling the Mn3+/ Mn4+ and Ni2+ potential as a high-capacity material for next-generation energy storage devices

In this study, we synthesized MnOx nanowires via hydrothermal methods and explored the impact of nickel (Ni) doping on their morphology and electrochemical properties. We investigated the structural and chemical changes induced by Ni incorporation by utilizing TEM and XPS analyses. Our results revealed that Ni doping influenced the distribution of manganese oxidation states, with 1.6 wt% Ni-doped nanowires exhibiting the optimized condition. Also, we observed a balance between the Mn3+/Mn4+ ratio with the Ni doping. Electrochemical characterization demonstrated enhanced capacity in Ni-MnOx nanowires at the 1.6 wt% Ni doping level. Galvanostatic charge-discharge measurements confirmed the superior performance of this level of Ni doping; moreover, the fabrication of asymmetric supercapacitor cells using these nanowires showed improved energy storage capabilities. The main results showed exceptionally high capacity (955.55 and 383.33 mAh g−1 at 1 and 20 A g−1, respectively) and an excellent rate capability. Cycling stability tests over 8500 cycles demonstrated excellent retention of capacity, underscoring the durability of the optimized Ni-MnOx nanowires, with a retention of 85 % of its initial capacity. Thus, this study emphasizes the significance of Ni doping in MnOx nanowires for enhancing electrochemical performance when the synthetic process is controlled, offering valuable insights for high-performance energy storage device development.

Urea adsorption and detection using silicon nanowires doped with B, Al, C, Ge, N, and P: A DFT investigation

Urea can serve as a biomarker for the detection of various illnesses, including renal and hepatic failure. Consequently, the development of novel devices and materials capable of adsorbing and identifying urea is a crucial objective for the scientific community. This study theoretically investigates the adsorption and detection capabilities of doped silicon nanowires (SiNWs) for urea using Density Functional Theory (DFT). Doping involves substituting a silicon atom on the surface with a dopant atom; B, Al, C, Ge, N, and P were employed for this purpose. This study presents an innovative method for enhancing urea adsorption and detection by doping SiNWs with group XIII elements, specifically aluminum and boron atoms. The results indicate that this doping significantly improves urea adsorption on SiNWs compared to undoped SiNWs. Notable changes in the bandgaps and work functions of the doped nanowires following urea adsorption suggest their potential use as diagnostic tools for uremia.

Ultra-long Al doped core-shell nanowires: Relationship between structural defect and optical property

The defects in nanomaterials can greatly affect their photoluminescence (PL) properties. To investigate the role of defects in the PL properties of SiCnw and improve their properties, Al doping and core-shell structure design are employed. Based on the above purpose, ultra-long Al-SiCnw@SiO2 with a length of hundreds of micrometers are prepared via one-step thermal evaporation process. The Al exists in the lattice of SiC and SiO2 in the form of substitutional and interstitial atoms, respectively, causing more defects in the nanowires. These defects can enhance the phonon scattering and phonon energy. After doping Al, the PL property of nanowires is improved by 36% and 244%, respectively, compared with SiCnw@SiO2 and SiCnw. The enhanced Fröhlich electron-phonon interaction caused by defects and the decreased band gap accelerating the transition of electrons are the main mechanisms of the property improvement. With the help of phonons, the electrons will be easier excited to conduction band. When they back to the ground state, more energy will be released, thereby improving the PL property. This work is helpful for the design of nanowires by doping elements to improve the PL property, and the preparation of large scale ultra-long doped nanowires applied in the optoelectronics.

Photoelectrochemical properties of doped TiO2 nanowires grown by seed-assisted thermal oxidation

Titanium dioxide Nanowires (NWs) are particularly interesting because of their very high surface/volume ratio and their photocatalytic activity allows them to be used in a myriad of applications. This manuscript presents a study of nanowires grown on a conductive substrate making use of a seed-assisted thermal oxidation process. To obtain doped NWs, before the oxidation, metallic titanium was doped with Fe (or Cr) by ion implantation technology. Analyses showed good quality Rutile phase and light absorption in the visible range. Transport properties of the NWs/electrolyte junction were investigated by using linear sweep voltammetry and electrochemical impedance spectroscopy. They allowed us to measure the photovoltage and the barrier height of the junction. We also evaluated the density of hole trap states at the interface during illumination. Electrical results indicate that the formation of deep levels, induced by doping, influences the electron concentration in the TiO2 and the transport properties.Graphical abstract

Application of Ultrasonic Power in Forming Sn58Bi/Cu Solder Joints with Trace Si3N4 Nanowire Doping

Application of Ultrasonic Power in Forming Sn58Bi/Cu Solder Joints with Trace Si3N4 Nanowire Doping

Parameter modulation on p-type doping of AlGaN nanowires

The p-type doping process during the growth of AlGaN nanowires directly influences the optoelectronic properties of the related devices. However, research on the p-type ionization mechanism in AlxGa1-xN nanowires remains limited. In this work, we utilize first principles calculations to investigate p-type doping in AlxGa1-xN nanowires under different structural variables (Al component, doping element, doping site, and doping concentration). Our results demonstrate that p-type doping in AlxGa1-xN nanowires is an endothermic process, and increased dopant concentration leads to a decrease in system stability. Moreover, we found that dopant atoms are easier to substitute for Ga atoms than Al atoms. Among the three doping elements (Zn, Be and Mg), Zn exhibits the most challenging doping difficulty, while Be shows the easiest doping process, with Mg falling in between. Crystal Orbital Hamilton Population (COHP) and bond population calculations reveal the mechanism for the variation in doping structure stability. Doping induces a rearrangement of energy level orbitals, resulting in changes in the band gap. Specifically, the valence band exhibits an overall upward trend crossing the Fermi level, showing the p-type conductive properties. Notably, a significant decrease in electron density near Mg and Be leads to the formation of p-type conductive properties. The changes in hole density and effective mass further confirm the formation of p-type conductivity after doping. Additionally, structures with lower Al composition exhibit higher doping ionization degrees. This study is expected to provide a theoretical basis for the growth, preparation, and application of optoelectronic devices based on p-type AlGaN nanowires.

Highly-doped MBE-grown GaP nanowires: Synthesis, electrical study and modeling

Efficient doping of semiconductor nanowires remains a major challenge towards the commercialization of nanowire-based devices. In this work we investigate the growth regimes and electrical properties of MBE-grown p- and n-type gallium phosphide nanowires doped with Be and Si, respectively. Electrical conductivity of individual nanowires is quantitatively studied via atomic force microscopy supported with numerical analysis. Based on conductivity measurements, we provide growth strategies for achieving the doping level up to ND=5⋅1018 cm-3 and NA=2⋅1019 cm-3 for GaP:Si and GaP:Be nanowires respectively, which is high enough for technological applications.

Design and Analysis of Junctionless-Based Gate All Around N+ Doped Layer Nanowire TFET Biosensor

This work is based on the analysis and designing of Gate All Around N+ doped layer Nanowire Tunnel Field Effect Transistors (NTFET) without junctions for application in biosensor by considering the various bio molecules like uricase, proteins, biotin, streptavidin, Aminopropyl-triethoxy-silane (ATS) and many more with dielectric modulation technique and gate-all-around (GAA) environment. Device sensitivity and tunneling probability is further improved by N+ doped layer (1 × 1020 cm−3). The change in the subthreshold-slope (SS), drain current (ID), transconductance(gm), and ratio of ION/IOFF has been examined to detect the sensitivity of the proposed device by confining various biomolecules in the area of nanocavity. The nanocavity area creates a shield in the source gate of oxide layer and electrodes metal. The Junctionless Gate All Around Nanowire Tunnel-Field-Effect-Transistor (JLGAA-NTFET) shows less leakage current and large control on the channel. The design of JLGAA-NTFET is with high doping concentration and observed higher sensitivity for ATS biomolecule which is suitable for sensor design application.

Eu3+ doped hydroxyapatite nanowires enabling solid-state electrolytes with enhanced ion transport

The polymer-based solid-state electrolytes (PSEs) are promising for solid-state batteries but they have deficiencies such as low ionic conductivity, low lithium-ion transference number, and unstable electrode/electrolyte interface. Herein, we designed a hydroxyapatite nanowire doped with high-valence cations in anticipation of the formation of positively charged active sites on the nanowire surface. The higher surface activity can reduce the reaction activation energy on the nanowire surface and adsorb the anions in the PSEs as a way to improve the ionic conductivity and Li+ transference number of the PSEs. The active sites on the surface of the nanowires anchor the anions, thus increasing the Li+ transference number to 0.38, which effectively improves the ionic conductivity of the PSE to 1.58 × 10−4 S cm−1 at room temperature. At the same time, the composite polymer electrolyte has a wide electrochemical window. The lithium symmetric cell stably cycles for 800 h at a current density of 0.1 mA cm−2, and the LiFePO4||Li full cell steadily cycles for 180 cycles at a rate of 0.5 C with a capacity retention of 94.2 %. The ion doping strategy to change the surface electrical behavior of nanowires provides an idea to improve the ionic conductivity of solid-state electrolytes.

Exciton-to-Dopant Energy Transfer Dynamics in Mn2+ Doped CsPbBr3 Nanowires Synthesized by Diffusion Doping.

Mn2+ doped perovskite nanocrystals have garnered significant attention in optoelectronic applications. However, the synthesis of Mn2+ doped perovskite nanowires (NWs) poses challenges, and the dynamics of energy transfer from the exciton to Mn2+ remains unexplored, which is crucial for optimizing Mn2+ luminescence efficiency. Herein, we present a method to synthesize Mn2+ doped CsPbBr3 NWs with a photoluminescence quantum yield of 52% by diffusing Mn2+ into seed CsPbBr3 NWs grown via a hot injection method. We control the solution and lattice chemical potentials of Pb2+ and Mn2+ to enable Mn2+ to diffuse into the CsPbBr3 NWs while minimizing Ostwald ripening. Variable temperature photoluminescence spectroscopy reveals that the energy transfer from the exciton to Mn2+ in Mn2+ doped CsPbBr3 NWs is temperature dependent. A dynamic competition is observed between energy transfer and backward energy transfer, resulting in stronger Mn2+ photoluminescence at 80 K. This work provides a specific synthesis pathway for Mn2+ doped CsPbBr3 NWs and sheds light on their exciton-to-Mn2+ energy transfer dynamics.

Iron-doped nickel–cobalt bimetallic phosphide nanowire hybrids for solid-state supercapacitors with excellent electromagnetic interference shielding

The development of flexible and wearable electronics subjects to the limited energy density and accompanying electromagnetic pollution. With a high theoretical specific capacity, nickel–cobalt bimetallic phosphide (NiCoP) is considered to be potential cathode materials for supercapacitor. However, the pristine NiCoP fails to display excellent electrochemical performance due to its inferior rate performance and cycling stability. Herein, we design Fe doped NiCoP nanowire arrays on carbon cloth (Fe-NiCoP/CC) as the cathode for supercapacitors. The introduced Fe doping enable to increase in the electronic conductivity and enhance the adsorption of OH−, supported by the density functional theory (DFT) analysis. As a result, Fe-NiCoP/CC electrode displays a high areal capacity of 3.18 F cm−2 at 1 mA cm−2, superb rate capability (86.3 % capacity retention at 20 mA cm−2) and outstanding structure stability, superior to the NiCo/CC, FeNiCo/CC, and NiCoP/CC counterparts. Moreover, the assembled Fe-NiCoP/CC||VN/CNT/CC hybrid supercapacitor (HSC) device delivers a high energy density of 176.9 μWh cm−2 at the power density of 750 μW cm−2. More importantly, the designed electrodes and assembled HSC device exhibits excellent electromagnetic interference (EMI) shielding performance. This design concept presented in this paper can provide insights into the construction of multifunctional and high-performance flexible electronic devices.

Modulation Doping of Silicon Nanowires to Tune the Contact Properties of Nano‐Scale Schottky Barriers

AbstractDoping silicon on the nanoscale by the intentional introduction of impurities into the intrinsic semiconductor suffers from effects such as dopant deactivation, random dopant fluctuations, out‐diffusion, and mobility degradation. This paper presents the first experimental proof that doping of silicon nanowires can also be achieved via the purposeful addition of aluminium‐induced acceptor states to the SiO2 shell around a silicon nanowire channel. It is shown that modulation doping lowers the overall resistance of silicon nanowires with nickel silicide Schottky contacts by up to six orders of magnitude. The effect is consistently observed for various channel geometries and systematically studied as a function of Al2O3 content during fabrication. The transfer length method is used to separate the effects on the channel conductivity from that on the barriers. A silicon resistivity is achieved as low as 0.04–0.06 Ω ·cm in the nominal undoped material. In addition, the specific contact resistivity is also strongly influenced by the modulation doping and reduced down to 3.5E‐7 Ω · cm2, which relates to lowering the effective Schottky barrier to 0.09 eV. This alternative doping method has the potential to overcome the issues associated with doping and contact formation on the nanoscale.

Confirmation of spontaneous doping of GaN nanowires grown on vicinal SiC/Si substrate by electron beam induced current mapping

This study is devoted to the confirmation of spontaneous doping of GaN nanowires grown on vicinal SiC/Si hybrid substrates by electron beam induced current mapping. GaN nanowires (NWs) were grown on singular and vicinal SiC/Si substrates by molecular beam epitaxy with nitrogen plasma activation. The morphological properties of the NWs were studied by scanning electron microscopy. The electrophysical properties of the obtained nanostructures were studied by electron beam induced current mapping. By electron beam induced current mapping, we confirmed the spontaneous doping of the GaN NWs grown on vicinal SiC/Si wafers. It was also shown that the GaN NWs grown on singular SiC/Si substrates did not exhibit an induced current signal, indicating that they were not doped

Detection of Be dopant pairing in VLS grown GaAs nanowires with twinning superlattices

Control over the distribution of dopants in nanowires is essential for regulating their electronic properties, but perturbations in nanowire microstructure may affect doping. Conversely, dopants may be used to control nanowire microstructure including the generation of twinning superlattices (TSLs)—periodic arrays of twin planes. Here the spatial distribution of Be dopants in a GaAs nanowire with a TSL is investigated using atom probe tomography. Homogeneous dopant distributions in both the radial and axial directions are observed, indicating a decoupling of the dopant distribution from the nanowire microstructure. Although the dopant distribution is microscopically homogenous, radial distribution function analysis discovered that 1% of the Be atoms occur in substitutional-interstitial pairs. The pairing confirms theoretical predictions based on the low defect formation energy. These findings indicate that using dopants to engineer microstructure does not necessarily imply that the dopant distribution is non-uniform.

Surface metal ion doped TiO2 nanowire arrays by low energy ion implantation for enhanced photoelectrochemical performance

Various metal ions, including Mg, Co, Nb, and W, were chfosen for ion implantation to modify TiO2 nanowire arrays. The introduction of metal ions was confirmed by both simulations and transmission electron microscopy (TEM) morphology characterization. A doped TiO2 shell on the surface was formed by the ion implantation process. Furthermore, the unbonded metal W was found in the doped TiO2 nanowires. The XPS results implied a special mechanism of heavy ions chosen for low-energy ion implantation. The presence of non-bonded metal restricted water splitting ability evidently. PEC results provided brief evidence that Nb doped TiO2 nanowire arrays is a promising choice with a 60% improvement in current density. The charge transfer resistance and the flat band potential are more benefit to water splitting than other doped metal ions. The theoretical calculation also supported efficient band gap narrowing of TiO2 caused by Nb dopant.

Boosting the piezoelectric coefficients of flexible dynamic strain sensors made of chemically-deposited ZnO nanowires using compensatory Sb doping

The piezoelectric devices made of ZnO nanowires have received a great interest in the past decade as potential nanogenerators and sensors. However, their characteristics are still limited significantly by the screening of the piezoelectric potential generated under mechanical solicitations, originating from the high density of free electrons in ZnO nanowires. In order to tackle that issue, we develop the compensatory Sb doping of ZnO nanowires grown by chemical bath deposition, both in the low- and high-pH regions using Sb glycolate and ammonia as chemical additives. The adsorption process of Sb(III) species on the positively charged surfaces of ZnO nanowires proceeds through attractive electrostatic forces, resulting in the significant incorporation of Sb dopants with an atomic ratio in the range of 0.11–0.45%. The optical properties of Sb-doped ZnO nanowires exhibit additional phonon modes related to Sb dopants in the range of 500–750 cm-1 in the Raman spectra, and some specific characteristics in the nature and intensity of radiative recombination in the cathodoluminescence spectra. Importantly, the integration of Sb-doped ZnO nanowires encapsulated in PMMA and grown on PDMS into flexible piezoelectric dynamic strain sensors is shown to drastically boost the piezoelectric charge and voltage coefficients by a factor of 2.65 and 1.91, following the significant incorporation of Sb dopants. A subsequent thermal annealing under oxygen atmosphere is revealed to further increase the piezoelectric charge and voltage coefficients by an additional factor of 1.38 and 1.49, following the activation of Sb doping and engineering of hydrogen-related defects. Two figures-of-merit are eventually derived from the piezoelectric charge and voltage coefficients and their values for flexible piezoelectric composites made of annealed Sb-doped ZnO nanowires are compared to more conventional piezoelectric materials, showing their high potential for medical devices. The present findings highlight the strategy consisting in simultaneously introducing compensatory acceptors and engineering hydrogen-related defects to reduce the screening effect, representing an additional powerful way to enhance the characteristics of the piezoelectric devices integrating ZnO nanowires.

Sacrificial Doping as an Approach to Controlling the Energy Properties of Adsorption Sites in Gas-Sensitive ZnO Nanowires

Currently, devices for environmental gas analyses are required in many areas of application. Among such devices, semiconductor-resistive gas sensors differ advantageously. However, their characteristics need further improvement. The development of methods for controlling the surface properties of nanostructured metal oxides for their use as gas sensors is of great interest. In this paper, a method involving the sacrificial doping of ZnO nanowires to control the content of their surface defects (oxygen vacancies) was proposed. Zinc oxide nanowires were synthesized using the hydrothermal method with sodium iodide or bromide as an additional precursor. The surface composition was studied using X-ray photoelectron spectroscopy. The sensor properties of the isopropyl alcohol vapors at 150 °C were studied. It was shown that a higher concentration of oxygen vacancies/hydroxyl groups was observed on the surfaces of the samples synthesized with the addition of iodine and bromine precursors compared to the pure zinc oxide nanowires. It was also found out that these samples were more sensitive to isopropyl alcohol vapors. A model was proposed to explain the appearance of additional oxygen vacancies in the subsurface layer of the zinc oxide nanowires when sodium iodide or sodium bromide was added to the initial solution. The roles of oxygen vacancies and surface hydroxyl groups in providing the samples with an increased sensitivity were explained. Thus, a method involving the sacrificial doping of zinc oxide nanowires has been developed, which led to an improvement in their gas sensor characteristics due to an increase in the concentration of oxygen vacancies on their surface. The results are promising for percolation gas sensors equipped with additional water vapor traps that work stably in a high humidity.

Ternary transition metal of Fe/Co/Ni doping on MoSx nanowires for highly efficient electrochemical oxygen evolution

The crucial step for splitting water is the oxygen evolution reaction. The key to promote this reaction lies in the catalyst. Molybdenum disulfide, as a two-dimensional material with molybdenum and sulfur atoms stacked, is especially suitable as a doping platform to develop high-performance OER catalysts. Fe/Co/Ni ternary transition metal combination has always been a highly active catalytic site for OER. Heteroelement of Fe/Co/Ni doping is expected to effectively modify the local electronic configuration of matrix materials and thus enhances their electrocatalytic OER capability. With this in mind, we report a simple in-situ hydrothermal doping of MoSx nanowires on iron‑nickel alloy foam with ternary transition metal of Fe/Co/Ni. This ternary transition metal of Fe/Co/Ni doped f self-supported electrode (denoted Fe/Co/Ni-MoSx/INF) displays outstanding OER performance in terms of small overpotentials of 214 and 263 mV at current densities of 10 and 100 mA/cm2, respectively, in alkaline solution. It was far better than the commercial Ir/C catalysts (253 and 434 mV@10 and 100 mA/cm2). The Tafel slope is about 48.1 mV/dec. Moreover, Fe/Co/Ni-MoSx/INF also has an excellent catalytic stability without any obvious performance decay after 20 h operation. This work contributes to the investigation of high-efficiency OER catalysts based on transition metal-doped MoSx and offers a substitute for noble metal catalysts.

Estimation of the Depletion Layer Thickness in Silicon Nanowire-Based Biosensors from Attomolar-Level Biomolecular Detection.

Silicon nanowire (SiNW) biosensors have attracted a lot of attention due to their superior sensitivity. Recently, the dependence of biomolecule detection sensitivity on the nanowire (NW) width, number, and doping density has been partially investigated. However, the primary reason for achieving ultrahigh sensitivity has not been elucidated thus far. In this study, we designed and fabricated SiNW biosensors with different widths (10.8-155 nm) by integrating a complementary metal-oxide-semiconductor process and electron beam lithography. We aimed to investigate the detection limit of SiNW biosensors and reveal the critical effect of the 10-nm-scaled SiNW width on the detection sensitivity. The sensing performance was evaluated by detecting antiovalbumin immunoglobulin G (IgG) with various concentrations (from 6 aM to 600 nM). The initial thickness of the depletion region of the SiNW and the changes in the depletion region due to biomolecule binding were calculated. The basis of this calculation are the resistance change ratios as functions of IgG concentrations using SiNWs with different widths. The calculation results reveal that the proportion of the depletion region over the entire SiNW channel is the essential reason for high-sensitivity detection. Therefore, this study is crucial for an indepth understanding on how to maximize the sensitivity of SiNW biosensors.

Controlled Synthesis and Enhanced Gas Sensing Performance of Zinc-Doped Indium Oxide Nanowires.

Indium oxide (In2O3) is a widely used n-type semiconductor for detection of pollutant gases; however, its gas selectivity and sensitivity have been suboptimal in previous studies. In this work, zinc-doped indium oxide nanowires with appropriate morphologies and high crystallinity were synthesized using chemical vapor deposition (CVD). An accurate method for electrical measurement was attained using a single nanowire microdevice, showing that electrical resistivity increased after doping with zinc. This is attributed to the lower valence of the dopant, which acts as an acceptor, leading to the decrease in electrical conductivity. X-ray photoelectron spectroscopy (XPS) analysis confirms the increased oxygen vacancies due to doping a suitable number of atoms, which altered oxygen adsorption on the nanowires and contributed to improved gas sensing performance. The sensing performance was evaluated using reducing gases, including carbon monoxide, acetone, and ethanol. Overall, the response of the doped nanowires was found to be higher than that of undoped nanowires at a low concentration (5 ppm) and low operating temperatures. At 300 °C, the gas sensing response of zinc-doped In2O3 nanowires was 13 times higher than that of undoped In2O3 nanowires. The study concludes that higher zinc doping concentration in In2O3 nanowires improves gas sensing properties by increasing oxygen vacancies after doping and enhancing gas molecule adsorption. With better response to reducing gases, zinc-doped In2O3 nanowires will be applicable in environmental detection and life science.