Defective Nanostructures Research Articles

Quasi-visualizable detection of deep sub-wavelength defects in patterned wafers by breaking the optical form birefringence

Abstract In integrated circuit (IC) manufacturing, fast, nondestructive, and precise detection of defects in patterned wafers, realized by bright-field microscopy, is one of the critical factors for ensuring the final performance and yields of chips. With the critical dimensions of IC nanostructures continuing to shrink, directly imaging or classifying deep-subwavelength defects by bright-field microscopy is challenging due to the well-known diffraction barrier, the weak scattering effect, and the faint correlation between the scattering cross-section and the defect morphology. Herein, we propose an optical far-field inspection method based on the form-birefringence scattering imaging of the defective nanostructure, which can identify and classify various defects without requiring optical super-resolution. The technique is built upon the principle of breaking the optical form birefringence of the original periodic nanostructures by the defect perturbation under the anisotropic illumination modes, such as the orthogonally polarized plane waves, then combined with the high-order difference of far-field images. We validated the feasibility and effectiveness of the proposed method in detecting deep subwavelength defects through rigid vector imaging modeling and optical detection experiments of various defective nanostructures based on polarization microscopy. On this basis, an intelligent classification algorithm for typical patterned defects based on a dual-channel AlexNet neural network has been proposed, stabilizing the classification accuracy of λ/16-sized defects with highly similar features at more than 90%. The strong classification capability of the two-channel network on typical patterned defects can be attributed to the high-order difference image and its transverse gradient being used as the network’s input, which highlights the polarization modulation difference between different patterned defects more significantly than conventional bright-field microscopy results. This work will provide a new but easy-to-operate method for detecting and classifying deep-subwavelength defects in patterned wafers or photomasks, which thus endows current online inspection equipment with more missions in advanced IC manufacturing.

Selective adsorption of coalbed methane on multilayer defective graphene nanostructures and their Mn-modified nanostructures: A DFT study

Coalbed methane (CBM) is an unconventional natural gas with CH4 as the main component. It is found in coal seams and surrounding rocks. The development and exploitation of CBM is a promising approach to ensure the safety of coal mine production, reduce greenhouse effects, and increase clean energy resources. Based on the first-principles calculations in conjunction with a grand canonical Monte Carlo (GCMC) simulation, this paper aims to examine the effects of interlayer spacing and Mn modification on CBM and CO2 adsorption. We assess the CH4 storage performance in multilayered defective graphene nanostructures (MDGNs). Using density functional theory in conjunction with the Grimm correction method (DFT-D approach), both the adsorption energy and charge distribution between CBM components and extended line defects (ELD) are appropriately evaluated in the presence or lack of Mn modification (Mn-ELD). The GCMC simulation is implemented to investigate CH4 adsorption isotherms of MDGN and Mn-MDGN configurations at 298.15 K. The selective adsorption capabilities of MDGNs and Mn-MDGNs for CO2, N2, and CH4 are also systematically analyzed. The obtained results reveal that an Mn-MDGN configuration with an interlayer spacing of dGL=1.02 nm is effective in sequestering CO2 from CBM. In contrast, MDGN configurations with interlayer spacings of dGL=0.68 and 1.02 nm are more effective for the storage of purified CBM. In continuing, the CH4 purification mechanism in Mn-MDGNs and the CH4 storage mechanism in MDGNs are also methodically explored at the molecular level. The research work reported here can serve as a crucial guide for the future development and utilization of CBM.

Molybdenum induced defective WO3 multifunctional nanostructure as an electrochromic energy storage device: Novel assembled photovoltaic-electrochromic Mo–WO3 film

In this work, a self-powered electrochromic device incorporating molybdenum-doped tungsten oxide (WO3) is developed for enhanced performances, offering a potential solution for energy efficient technologies. Defective nanostructure of WO3, enabled with molybdenum doping, is achieved through an electrochemical co-deposition method. A film of Mo–WO3 is investigated for multifunctional purposes, acting as both an electrochromic (EC) and energy storage device (ESD). As an EC film, it exhibits an optimal optical contrast of 84.5 %, minimum coloration time of 0.4 s, high coloration efficiency of 90.4 cm2/C, and excellent optical stability. In ESD applications, Mo–WO3 displays charge-transfer resistance of 7.6 Ω, a commendable capacitance of 39.1 mF/cm2, and excellent capacitance retention of 80.4 %. The integration of Mo ions into the WO3 nanostructure results in the formation of oxygen defect sites, which enhances the mobility of Li+ ions over the amorphous and deagglomerated morphology of Mo–WO3. Furthermore, the EC activity of Mo–WO3 film does not require an external power source as the film is powered by an integrated quantum dot-sensitized solar cell (QDSSCs). The open circuit voltage of 0.62 V, resulting from the QDSSCs power source, successfully facilitates the switching operation of the Mo–WO3 EC film.

Engineering defective MOF-801 nanostructures on the surface of a calcium alginate aerogel for efficient and stable atmospheric water harvesting

A calcium alginate surface-loaded nano-defective MOF-801-G (PMC) aerogel for efficient atmospheric water harvesting applications.

Tuning defects in Cu2O nanostructures via room temperature mechanical pressing: impacts on defect-dependent optical and photoelectrochemical sensing performances

Room temperature mechanical pressing is applied to specifically remediate oxygen vacancies in a defective Cu2O nanostructure, which provides information on the sensing performances of Cu2O through various defect-dependent mechanisms.

Dynamics of Plasma‐Assisted Epitaxial Silicon Growth Driven by a Hydrogen‐Incorporated Nanostructure for Novel Applications

Plasma‐assisted epitaxially grown silicon (plasma‐epi Si) is a new silicon‐based material with a tailorable nanostructure. Nanovoids can be introduced into plasma‐epi Si during growth, enabling the bottom‐up fabrication of porous Si for applications such as batteries, hydrogen storage, and even explosives. To fully control the nanostructure of plasma‐epi Si, its growth dynamics must be studied. In this study, the correlation between hydrogen incorporation and defect nanostructures in plasma‐epi Si grown under various process conditions is investigated, and the experimental results are supported by molecular dynamics simulations. The nanostructural evolution during growth suggests a model in which plasma‐epi Si shows two growth stages distinguished by different dominant defect nanostructures. In the initial growth stage, the nanostructure can be controlled by the deposition conditions, whereas the nanostructure is dominated by interconnected voids, forming a porous structure. In the subsequent bulk growth stage, the material growth is less sensitive to the deposition conditions, whereas the nanostructure becomes prevalent isolated defects. In the results of this study, different strategies for the plasma‐epi Si growth process for different applications are suggested. In these results, a better understanding of this new material may be provided and the discovery of various applications for bottom‐up‐grown porous Si is facilitated.

A high improvement of tensile properties and interfacial interaction of calcium silicate hydrate/hexagonal boron nitride layered nanostructures via defect field

Previous studies have shown that the increase in Young's modulus of cement-based materials by h-BN (about 20%) is lower than that of graphene and graphene oxide (an increase of 35.8%−78.6%). In order to further improve the interfacial interaction between calcium silicate hydrate (CSH) and hBN nanostructures, a series of defective hBN nanostructures were inserted between CSH layers to form defective hBN-CSH layered nanostructures. The interfacial interaction and tensile properties of hBN-CSH layered nanostructures were investigated, in considering the effect of internal (defect sizes in hBN) and external field (strain rate and temperature). The results show that the failure strain and stress of CSH models are enhanced by 18.18% and 14.74% with the incorporation of pure hBN while an increase of 35.53% and 31.58% in failure strain and stress is achieved by incorporating defective hBN (R3), attributed to high interfacial interaction. In addition, the tensile strain of defective hBN-CSH nanostructures (with a decrease of 33.49%) is more sensitive to temperature than that of free-defect hBN-CSH (with a decrease of 29.71%). Also, the tensile strain of defective hBN-CSH (R3) nanostructure (with an increase of 6.49%) is more sensitive to strain rate than that of free-defect hBN-CSH (with an increase of 4.38%). By constructing different interface interactions, a parameterized scheme is provided for the optimization and regulation of the spatial structure of the cement matrix.

Nanostructured Ti–Ni–Co Alloys Showing Shape‐Memory Actuation of Large Work Output at Low Temperature

In the present study, by combining the effect of point defect doping and nanostructure, low‐temperature shape‐memory alloys (SMAs) are developed showing good actuation property. The doping of Co into Ti–Ni host alloy suppresses the martensitic transformation to lower temperature. By post‐deformation annealing, the partially recrystallized state containing dense dislocations and nanoprecipitates is achieved. And, this remarkably strengthens the matrix to avoid irreversible strain under large external load. A alloy thereby exhibits a recoverable actuation strain of 4.5% under biased tensile stress of 800 MPa at temperatures below −50 °C. The work output up to outperforms most SMAs, showing a promise for low‐temperature actuator applications.

Evolution of point defects in pulsed-laser-melted Ge1-x Sn x probed by positron annihilation lifetime spectroscopy

Direct-band-gap Germanium-Tin alloys (Ge1-x Sn x ) with high carrier mobilities are promising materials for nano- and optoelectronics. The concentration of open volume defects in the alloy, such as Sn and Ge vacancies, influences the final device performance. In this article, we present an evaluation of the point defects in molecular-beam-epitaxy grown Ge1-x Sn x films treated by post-growth nanosecond-range pulsed laser melting (PLM). Doppler broadening – variable energy positron annihilation spectroscopy and variable energy positron annihilation lifetime spectroscopy are used to investigate the defect nanostructure in the Ge1-x Sn x films exposed to increasing laser energy density. The experimental results, supported with ATomic SUPerposition calculations, evidence that after PLM, the average size of the open volume defects increases, which represents a raise in concentration of vacancy agglomerations, but the overall defect density is reduced as a function of the PLM fluence. At the same time, the positron annihilation spectroscopy analysis provides information about dislocations and Ge vacancies decorated by Sn atoms. Moreover, it is shown that the PLM reduces the strain in the layer, while dislocations are responsible for trapping of Sn and formation of small Sn-rich-clusters.

Facile four-electrode electrolytic synthesis of defective PtPd/graphene with low Pt content for hydrogen evolution reaction and ethanol oxidation reaction

The fabrication of low-Pt loading and cost-efficient electrocatalysts still remains a challenge. In this work, a defective PtPd alloy with ultralow Pt content loaded on graphene (PtPd/G-40) is prepared by electrolytic synthesis method. During electrolysis, the formation of PtPd precursors and the exfoliation of graphite are achieved at the anode and cathode of the cell, respectively. The as-prepared PtPd/G-40 shows excellent electrocatalytic activity and stability toward hydrogen evolution reaction (HER) and ethanol oxidation reaction (EOR). Its mass activity is 29.7 times (at −100 mV) and 1.5 times higher than that of commercial Pt/C for HER and EOR, respectively. The ligand effect generated by formation of PtPd alloy and strain effect caused by abundant defects optimize the electronic structure of active Pt, which enhances its intrinsic activity and reduces the activation energy for HER and EOR. This facile synthetic approach generates a new type of graphene supporting defective metal alloy nanostructures as potential electrocatalysts for advanced energy conversion applications.

Microwave-Assisted Synthesis as a Promising Tool for the Preparation of Materials Containing Defective Carbon Nanostructures: Implications on Properties and Applications.

In this review, we focus on a small section of the literature that deals with the materials containing pristine defective carbon nanostructures (CNs) and those incorporated into the larger systems containing carbon atoms, heteroatoms, and inorganic components.. Briefly, we discuss only those topics that focus on structural defects related to introducing perturbation into the surface topology of the ideal lattice structure. The disorder in the crystal structure may vary in character, size, and location, which significantly modifies the physical and chemical properties of CNs or their hybrid combination. We focus mainly on the method using microwave (MW) irradiation, which is a powerful tool for synthesizing and modifying carbon-based solid materials due to its simplicity, the possibility of conducting the reaction in solvents and solid phases, and the presence of components of different chemical natures. Herein, we will emphasize the advantages of synthesis using MW-assisted heating and indicate the influence of the structure of the obtained materials on their physical and chemical properties. It is the first review paper that comprehensively summarizes research in the context of using MW-assisted heating to modify the structure of CNs, paying attention to its remarkable universality and simplicity. In the final part, we emphasize the role of MW-assisted heating in creating defects in CNs and the implications in designing their properties and applications. The presented review is a valuable source summarizing the achievements of scientists in this area of research.

Design of platinum nanoflower catalyst exhibiting near-ideal local coordination in a complex shape

Here, we investigate the oxygen reduction reaction activity of near-monocrystalline platinum nanoflowers presenting a low microstrain to decorrelate the contribution of (i) distorted lattice and (ii) high coordination active sites found within the platinum nanoflower pores to the specific activity enhancement. The results are discussed within the framework of previous investigations onto various catalytic nanostructures. We evidenced that the microstrain of the platinum nanoflowers stands out of the trends previously established for defective platinum-based nanostructures, where the activity is driven by lattice distortion. This indicates that (i) ‘defective’ structures with low lattice distortion, but high variation in coordination number, can be synthesized and (ii) that their specific activity improvement is comparable to the surface distortion approach in liquid electrolyte.

Engineering of Defective MOF-801 Nanostructures within Macroporous Spheres for Highly Efficient and Stable Water Harvesting.

Water harvesting using the metal-organic framework (MOF)-801 is restricted by limited working capacity, powder structuring, and finite stability. To overcome these issues, wecrystallized MOF-801 on the surface of macroporous poly(N-isopropylacrylamide-glycidyl methacrylate) spheres, called P(NIPAM-GMA), through an in situ confined growth strategy, forming spherical MOF-801@P(NIPAM-GMA) composite with temperature-responsive function. By lowering the nucleation energy barrier, the average size of the MOF-801 crystals decreased by 20 times. Thus, abundant defects as adsorption sites for water couldbe installed in the crystals lattices. As a consequence, the composite provides an unprecedented high water harvesting efficiency. The composite wasproduced in the kilogram-scale and can capture 1.60kg H2 O/kg composite/day from 20% RH between 25°C and 85°C. This work provides an effective methodology for improving the adsorption capacity through controlled defects formation as adsorption sites and to improve the kinetics through the design of a composite with macroporous transport channel network. This article is protected by copyright. All rights reserved.

Two-Dimensional Ti3C2Tx-Patched-GO heterojunctionas charge booster and defect passivator for Stable, Carbon-Based inorganic perovskite solar cell

Simultaneously manipulating the interfacial energetics to boost charge extraction and passivate defective nanostructure to suppress unwanted non-radiative recombination is of great importance to increase the power conversion efficiency and long-term stability of carbon-based perovskite solar cells (C-PSCs), which requires rational design of interfacial regulator. Herein, a novel two-dimensional (2D) Ti3C2Tx MXene patched graphene oxide (GO) heterojunction is fabricated as perovskite film plaster to improve the overall photovoltaic performance of C-PSCs. Arising from the nucleophilic substitution and dehydration reaction between MXene (Ti-O-) and GO (-C=OH+), the negative-charge-centered GO induced by the oxygen-containing functional groups is healed. As a result, this heterojunction not only aligns the perovskite/carbon energy-level and provides a channel for carrier transport, but also effectively solidifies the soft perovskite lattice, universally promoting the efficiencies up to 11.07% for inorganic CsPbIBr2 C-PSC and 15.04% for CsPbI2Br C-PSC with significantly improved stability.

High efficacy of substrate dimensionality control in optimizing the specific capacitance and phase stability of hybridized nanostructures

The hybridization with conductive nanostructures has attracted intense research interest because of its high efficiency in the exploration of efficient energy-functional materials. In this study, we reported a high efficacy of substrate dimensionality control in optimizing the specific capacitance and phase stability of hybridized nanostructures. Employing defective holey TiN nanostructures as substrates was found to enhance the interfacial interactions with a hybridized layered double hydroxide (LDH). A comparative investigation of two-dimensional TiN-LDH nanohybrids with zero-dimensional/one-dimensional TiN-LDH homologs demonstrated that hybridization with holey two-dimensional TiN nanosheets led to a much greater specific capacitance of 2127 F g−1, which is one of the best performances among LDH-based electrodes ever-reported. In situ Raman analysis during electrochemical cycling clearly demonstrated that holey nanosheet morphology of TiN substrate is quite crucial in promoting the phase transition of hybridized Ni-Fe-LDH to NiOOH/FeOOH with the maximization of cation redox activities. These advantages of atomically thin holey TiN nanosheets could be ascribed to intimate electronic coupling at the bilateral interfaces of the two-dimensional LDH nanosheets, in addition to optimized porosity and improved mass transport.

Microwave surface resistance in nanostructured high-Tc superconductor films

The impact of artificially created defects nanostructure, formed by implanted dielectric nanoparticles or irradiation defects, on microwave properties of high-Tc superconductor films is analyzed in the framework of phenomenological theory for microwave response of type-II superconductors. We have calculated the surface resistance for such a kind of nanostructured type-II superconductor film and investigated conditions for the emergence of nonlinear response caused by the entrance of microwave-induced vortices in the film's interior through its edges. The obtained results indicate that artificial defect nanostructure in the film's interior formed by point-like or columnar structural defects can significantly improve its microwave characteristics in both the Meissner and mixed states and also increase the threshold for the onset of nonlinear response.

Surface oxygen vacancy defects induced CoTiO3-x perovskite nanostructures for highly efficient catalytic activity from acidic and seawater electrolysis

Efficient electrocatalysts have great demand for improved hydrogen evolution (HE) from natural seawater splitting. In this work, a new type of oxygen (O2) vacancies and Ti3+ defective perovskite nanostructures (DPNSs) of D-CoTiO3-x were prepared by using eco-friendly sonochemical assisted laser irradiation technique (SCA-LIT) for the first time. These DPNSs were thoroughly characterized, and HE activity was evaluated to determine their electrocatalytic potential and efficiency improvement. The existence of abundantly available active sites in the prepared D-CoTiO3-x electrocatalyst composed of defective D-TiO2-x was confirmed through various physicochemical measurements. The designed DPNSs-based working electrode exhibited excellent electrochemical performance due to its low over-potential (0.352 V), reduced Tafel slope (94.7 mV/dec), high double layer capacitance (235.3 µF/cm2), large electrochemically active surface area (6.72 cm2) and exceptional long-term stability. The attained improvement in the HE efficiency was ascribed to the induced synergistic strong metal-support interaction (SMSI) effect of the surface O2 vacancies and Ti3+ defects in DPNSs that yielded high conductivity, high exposure of abundant active sites, wide active surface area, improved kinetics, and fast charge transport. Furthermore, Volmer-Heyrovsky (V-H) reaction mechanism was responsible for the generation of hydrogen (H2) by the proposed DPNSs-based electrode. In addition to the natural seawater, the D-CoTiO3-x DPNSs outperformed in terms of the electrocatalytic hydrogen activity and stability. Thus, our systematic approach for the fabrication of surface O2 vacancy and Ti3+ defect engineering DPNSs-based electrodes to produce H2 from natural seawater splitting may be beneficial for green energy generation, solving future environmental problems and energy demand crises.

Electrochemical charge/discharge cycling and morphological effects in MnO2/PANC nanostructures for supercapacitors

The improvement of electrochemical properties of MnO2 has been an attractive topic for a long time. Here, MnO2/polyacrylonitrile carbon (MnO2/PANC) nanostructures with well-modified morphology are required by chemical direct synthesis. The cycling stability and specific capacitance performance of MnO2/PANC electrode are enhanced during electrochemical cycling and explored to be closely related to the internal morphologies and crystal form of the various MnO2/PANC nanostructures. The Na+ ion and PANC are forced to interact with increased active sites of the MnO2/PANC surface by cycling protocol. The resulting electrode exhibits the defective nanostructure, in which the MnOC bond is introduced and comprehensive Mn valence occurred in the untrathin MnO2/PANC nanostructure; such unique core-shell nanostructure, providing more structural defects, increased surface area and rich functional groups, and subsequently, enhanced electrochemical capacitance performance. Therefore, this work suggests a new concept for the development of manganese-based electrode materials with enhanced performance and may have broad application in high-energy storage devices.

Unusual Luminescence of Quartz from La Sassa, Tuscany: Insights on the Crystal and Defect Nanostructure of Quartz Further Developments

Quartz luminescence finds applications on many fields, but much work still needs to be done to precisely characterize it. In this work, we made further developments on the study of luminescence of quartz from La Sassa, Tuscany: a sample with unique properties in this regard. Photoluminescence (PL) measurements allowed study of the excitation profile of the previously reported luminescence, showing an excitation maximum at around 4.3 eV, among other minor ones. This kind of luminescence has also been studied as a function of X-ray irradiation, showing that ionizing radiation desensitizes the photoluminescence emissions. New radioluminescence (RL) measurements have been done to study the effect of thermal annealing at 1000 °C, showing a more complex emission picture in the red region (1.8–2.0 eV), with multiple emissions. The data presented here allow more precise assumptions regarding the assignment of the centers responsible for each emission. The assignment has been confirmed by chemical profiles measured by laser-ablation inductively coupled plasma (ICP) mass spectrometry. The previously tentative assignment of non-bridging oxygen hole centers (NBOHCs) has been disproved for the PL and LIF emissions and confirmed for the RL ones.

Defect Nanostructure and its Impact on Magnetism of α-Cr2 O3 Thin Films.

Thin films of the magnetoelectric insulator α-Cr2 O3 are technologically relevant for energy-efficient magnetic memory devices controlled by electric fields. In contrast to single crystals, the quality of thin Cr2 O3 films is usually compromised by the presence of point defects and their agglomerations at grain boundaries, putting into question their application potential. Here, the impact of the defect nanostructure, including sparse small-volume defects and their complexes is studied on the magnetic properties of Cr2 O3 thin films. By tuning the deposition temperature, the type, size, and relative concentration of defects is tailored, which is analyzed using the positron annihilation spectroscopy complemented with electron microscopy studies. The structural characterization is correlated with magnetotransport measurements and nitrogen-vacancy microscopy of antiferromagnetic domain patterns. Defects pin antiferromagnetic domain walls and stabilize complex multidomain states with a domain size in the sub-micrometer range. Despite their influence on the domain configuration, neither small open-volume defects nor grain boundaries in Cr2 O3 thin films affect the Néel temperature in a broad range of deposition parameters. The results pave the way toward the realization of spin-orbitronic devices where magnetic domain patterns can be tailored based on defect nanostructures without affecting their operation temperature.