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Lithium metal batteries (LMBs) are considered the most promising energy storage devices for applications such as electrical vehicles owing to its tremendous theoretical capacity (3860 mAh g−1). However, the serious safety issues and poor cycling performance caused by the dendritic crystal growth during deposition are concerned for any rechargeable batteries with a lithium metal anode. To make widespread adoption a possibility, considerable efforts have been devoted to suppressing lithium (Li) dendrite growth. In this review, the recent strategies to developing dendrite free Li anode, including constructing an artificial solid electrolyte interface, current collector modification, separator film improvement, and electrolyte additive, are summarized. The merits and shortcomings for different strategies are reviewed and a general summary and perspective on the next generation rechargeable batteries are presented.

The combination of conductivity, optical transparency, and wide anodic potential window has driven significant interest in indium tin oxide (ITO) as an electrode material for electrochemical measurements. More recently, ITO has been applied to the detection of trace metals using cathodic stripping voltammetry (CSV), specifically manganese (Mn). However, the optimization of ITO fabrication for a voltammetric method such as CSV is yet to be reported, nor have the microstructural properties of ITO been investigated for CSV. Furthermore, CSV does not require optical transparency, thereby allowing nontransparent substrates to be used for deposition. This enables microfabrication procedures to be expanded and simplified compared to glass or quartz. Combining this with the profound importance of sensitive, selective detection of toxic metal ions in environmentally and biologically relevant samples makes ITO especially attractive. In this work, we report a thorough investigation of ITO deposition and processing on silicon (Si) substrates for CSV analysis using Mn as the model analyte. Several ITO process parameters were examined such as heated deposition and post-process annealing. Each ITO film was characterized using a variety of surface, bulk (X-ray diffraction), and electrochemical measurements. Although each ITO film type showed electrochemical activity, the heated and annealed (HA) ITO fabrication process yielded superior results for Mn CSV; a limit of detection (LOD) of 0.1 ppb (1.8 nM) was obtained. This work exemplifies new applications of ITO as an electrode material while providing a baseline for trace detection of toxic metals and other contaminants amenable to detection by CSV.

Sub-micron-size light sources are currently extremely dim, achieving nanowatt output powers due to the current density and temperature droop. Recently, we reported a droop-free fin light-emitting diode (LED) pixel that at high current densities becomes a laser with record output power in the microwatt range. Here, we show a scalable method for selectively metallizing fins via their nonpolar side facet that allows electrical injection to sub-200 nm wide n-ZnO fins on p-GaN with at least 0.8 μm2 active area. Electrically addressable fin LEDs are fabricated in a linear array format using standard 2 μm resolution photolithography. Electroluminescence analysis across different pixels shows that the fin acts as the active region of the LED and generates a narrow-band ultraviolet emission between ≈368 and ≈390 nm. Investigating fins at high current densities, ranging from 100 to 2000 kA/cm2, shows that their emission increases without any decline even as the junction temperature reaches a range of 200-340 °C. The absence of electron leakage to p-GaN at high injection levels and an undetectable electron-hole escape from the fin at high temperatures indicate that the fin shape is highly efficient in controlling the nonradiative recombination pathways such as Auger recombination. The fin LED geometry is expected to enable the realization of high-brightness arrays of light sources at sub-micron-size regimes suitable for operation at high temperatures and high current densities.

MXene has been considered as a promising electrode materials for energy storage devices. This work reports using an electrophoresis effect to efficiently deposit Ti3C2Tx/rGO composite on flexible substrates, which are subsequently used as the electrodes of all-solid-state supercapacitors. The electrophoresis deposition does not require a binder in the fabrication of the Ti3C2Tx/rGO electrodes. The structures and properties of the MXene/graphene electrode materials are characterized using Zeta potential, scanning electronic microscope, X-ray powder diffraction, Fourier-transform infrared and X-ray photoelectron spectroscopy. The performance of the all-solid-state flexible supercapacitors are evaluated using cyclic voltammetry, galvanostatic charge/discharge, electrochemical impedance spectroscopy, and cycle life tests. The devices show high areal specific capacitance of ~12 mF cm−2, small resistance, and excellent cycling stability at different current densities for over 4,000 cycles. Moreover, the all-solid-state flexible supercapacitors exhibit superior mechanical flexibility under different deformations.

This work details a polyolefin-elastomer-based binder system to prepare fused filament fabrication (FFF) filaments and print cores for coils for electrical engines. The processability, homogeneity, and thermal properties of the polyolefin-elastomer-based filaments are explored. A two-step debinding and sintering process was established for manufacturing dense iron parts. Results indicate the developed filaments possess superior printing and sintering (at 900°C) performance, yielding only 20% weight loss by polymer decomposition and 14 vol.% shrinkage. This indicates that the FFF technique potentially enables printing of innovative electric motor designs. The designed FFF filaments could be loaded with 80 wt.% Fe powder while keeping a decent melt-viscosity for the printing process. Due to the high metal loading, dense iron parts could be sintered without bending or deformation.

The electronic properties of carbon nanotubes depend on several factors such as diameter, chirality, and defects. Defects such as vacancies can drastically modify the electronic properties of these nanostructures. The introduction of defects by irradiation processes can not only lead to interesting defective nanomaterials but also tailor its intrinsic properties for specific electronic applications. The ability to accurately identify and quantify defects in carbon nanotubes is of major importance for their incorporation into electronic devices. We report on a newly developed quantitative method which combines a known fluence or pulse of ions from a focused beam source with Raman spectroscopy for characterization of defects enabling the detection of systematic variations in defect concentration emerging at 0.5% from different single-wall carbon nanotube (SWCNT) types, semiconducting and metallic. It was also demonstrated that this result is independent from the selected ion species and its energy for thin ...

High-volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultrathin films will require deposition techniques that are capable of reproducible wafer-scale growth with monolayer control. To date, TMD growth efforts have largely relied upon sublimation and transport of solid precursors with minimal control over vapor-phase flux and gas-phase chemistry, which are critical for scaling up laboratory processes to manufacturing settings. To address these issues, we report a new pulsed metal–organic chemical vapor deposition (MOCVD) route for MoS2 film growth in a research-grade single-wafer reactor. Using bis(tert-butylimido)bis(dimethylamido)molybdenum and diethyl disulfide, we deposit MoS2 films from ∼1 nm to ∼25 nm in thickness on SiO2/Si substrates. We show that layered 2H-MoS2 can be produced at comparatively low reaction temperatures of 591 °C at short deposition times, approximately 90 s for few-layer films. In addition to the growth studies performed on SiO2/Si, films with wafer-...

In metal additive manufacturing, microstructural inhomogeneities, like anisotropic mechanical strength and geometric limitations in directed energy deposition, electron beam melting, or selective laser sintering, have led to the exploration of alternative techniques in recent years. Among these techniques, fused filament fabrication is an attractive alternative due to its successes in producing dense parts, approaching traditional manufacturing specifications. Despite this success, many challenges remain to produce reliable parts with reproducible properties using FFF, particularly in the thermal treatment for part densification. Here are presented results of using a polyolefin-based binder system loaded with 55-59 vol. % Ti-6Al-4V powder to create a printable filament. Printed Ti-6Al-4V parts using these filaments were sintered at temperatures ranging from 900 to 1340 °C and evaluated by x-ray diffraction, scanning electron microscopy and optical microscopy. The sintered samples demonstrated a linear decrease in v-phase from 15 to 11 vol. % with increasing temperature, while residual stress and Young's modulus increased. Additionally, the density of printed and sintered Ti-6Al-4V parts could be increased up to 91 % of the theoretical density of Ti-6Al-4V by increasing the sintering temperature up to 1340 °C. Samples that were sintered at 1340 °C showed a higher Young's modulus compared to SLM samples, likely due to the increased a-phase in samples sintered at 1340 °C.

High volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultra-thin films will require deposition techniques that are capable of reproducible wafer-scale growth with monolayer control. To date, TMD growth efforts have largely relied upon sublimation and transport of solid precursors with minimal control over vapor phase flux and gas-phase chemistry, which are critical for scaling up laboratory processes to manufacturing settings. To address these issues, we report a new pulsed metalorganic chemical vapor deposition (MOCVD) route for MoS2 film growth in a research-grade single-wafer reactor. Using bis(tert-butylimido)-bis(dimethylamido)molybdenum and diethyl disulfide we deposit MoS2 films from ≈ 1 nm to ≈ 25 nm in thickness on SiO2/Si substrates. We show that layered 2H-MoS2 can be produced at comparatively low reaction temperatures of 591 °C at short deposition times, approximately 90 s for few-layer films. In addition to the growth studies performed on SiO2/Si, films with wafer-level uniformity are demonstrated on 50 mm quartz wafers. Process chemistry and impurity incorporation from precursors are also discussed. This low-temperature and fast process highlights the opportunities presented by metalorganic reagents in the controlled synthesis of TMDs.

We investigate the impact of a quasi-crystalline two-dimensional (2D) surface on the lateral epitaxy of one-dimensional (1D) nanocrystals. The quasi-2D surface was formed by locally conditioning a GaN crystalline lattice at and below surface using a low-dose focused Ga ion beam ranging from 9 to 354 ions/pulse. Short ion pulses/site are used to create the 2D arrays of sub-10-nm circular disks modulating the GaN lattice to a depth of about 30 nm. Impact of this localized lattice modulation was investigated on lateral epitaxy of 1D ZnO nanocrystal and electronic structure of formed hetero-junctions. High resolution transmission electron microscopy (HRTEM) below the GaN surface reveals direct evidence of a "skin effect" that influences the surface epitaxy of low dimensional nanocrystals. We define this effect as the crystallinity of the top 10 nm of the substrate that is found, to be a key factor in occurrence of lateral epitaxy. HRTEM shows that lateral epitaxy stops, if the thin skin layer is disrupted. However, if the lattice structure of this layer rebounds, the lateral epitaxy occurs. Results indicate; that, beyond the skin depth of about 10 nm, the disorder of the subsurface lattice does not impact the structure of the overgrown nanocrystals. These findings suggest the possibility of surface engineering for enabling spatially controlled modulation of the electronic structure of low-dimensional nanocrystals on a scalable fashion.

Amorphous carbon films have been deposited with various levels of negative substrate bias and hydrogen flow rates using argon and argon + nitrogen as sputtering gas. The effect of hydrogenation and substrate bias on the final concentration of trapped elements is studied using ion beam analysis (IBA) techniques. The elemental concentrations were measured in the films deposited on silicon substrates with a 2.5 MeV H+ beam and 16 MeV O5+ beam. Argon was found trapped in the non-hydrogenated films to a level of up to ~ 4.6 %. The concentration of argon increased for the films deposited under higher negative bias. With the introduction of hydrogen, argon trapping was first minimized and later completely eliminated, even at higher bias conditions. This suggests the softness of the films brought on by hydrogenation. Moreover, the effect of bias on the thermal stability of trapped hydrogen in the films was also studied. As the films were heated in-situ in vacuum using a non-gassy button heater, hydrogen was found to be decreasing around 400 °C.

Recent breakthroughs in deterministic approaches to the fabrication of nanowire arrays have demonstrated the possibility of fabricating such networks using low-cost scalable methods. In this regard, we have developed a scalable growth platform for lateral fabrication of nanocrystals with high precision utilizing lattice match and symmetry. Using this planar architecture, a number of homo- and heterostructures have been demonstrated including ZnO nanowires grown over GaN. The latter combination produces horizontal, epitaxially formed crystals aligned in the plane of the substrate containing a very low number of intrinsic defects. We use such ordered structures as model systems in the interests of gauging the interfacial structural dynamics in relation to external stimuli. Nanosecond pulses of focused ion beams are used to slightly modify the substrate surface and selectively form lattice disorders in the path of nanowire growth to examine the nanocrystal, namely: its directionality and lattice defects. High resolution electron microscopies are used to reveal some interesting structural effects; for instance, a minimum threshold of surface defects that can divert nanowires. We also discuss data indicating formation of surface strains and show their mitigation during the growth process.

Deterministic control over the location and number of donors is crucial to donor spin quantum bits (qubits) in semiconductor based quantum computing. In this work, a focused ion beam is used to implant antimony donors in 100 nm × 150 nm windows straddling quantum dots. Ion detectors are integrated next to the quantum dots to sense the implants. The numbers of donors implanted can be counted to a precision of a single ion. In low-temperature transport measurements, regular Coulomb blockade is observed from the quantum dots. Charge offsets indicative of donor ionization are also observed in devices with counted donor implants.

Understanding and developing metrics on how nanocrystals respond to local external surface stimuli at their interfaces during growth or operation is a key step in advancing scalable and deterministic approaches for fabricating functional one- and two-dimensional (1D and 2D) nanoscale networks. Here, we present early results on a general approach for surface-directed nanocrystal epitaxy on a surface with an irregular lattice constant. We show that patches of lattice matched areas as small as 7 nm in a background of surface lattice disorder could satisfy the condition for epitaxial growth of a crawling nanocrystal over the disordered region. Threshold of failure in nanocrystal epitaxy is found to depend on the spacing between the patches and their total surface area. Results indicate nanoepitaxy on a disordered surface occurs if it contains patches of lattice matched regions with at least 20% of surface coverage, illustrating the remarkable tolerance of this type of growth to surface lattice disorder. By adjusting this threshold, it is possible to scalably restrict nanocrystal growth, filter out single nanowires and partition nanowire heterojunctions into segments with different orientations or modulate their electronic structures. This approach is expected to impact epitaxy of highly-mismatched semiconductors and lead to realization of ultrathin heterojunctions of 1D-2D materials.

Nano-Crystalline Diamond (NCD) thin films are a topic of recent interest due to their excellent mechanical and electrical properties. The inclusion of nitrogen is a specific interest as its presence within NCD modifies its conductive properties. The methodology adopted for the characterization of nitrogen incorporated NCD films grown on a chromium underlayer determined a correlation between the chromium and nitrogen concentrations as well as a variation in the concentration profile of elements. Additionally, the concentration of nitrogen was found to be more than three times greater for these films versus those grown on a silicon substrate.

This paper investigated the effect of chromium underlayer on the structure, microstructure, and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on single crystal silicon substrate with a thin film of chromium as an underlayer. Characterization of the film was implemented using non-Rutherford backscattering spectrometry, Raman spectroscopy, near-edge x-ray absorption fine structure, x-ray diffraction, and atomic force microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analyses determined consistency between the sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.

Unbalanced magnetron sputtering deposition of C-H films has been performed with various levels of negative substrate bias and with a fixed flow rate of hydrogen. Argon was used as a sputtering gas and formed the majority of the gas in the plasma. The effect of hydrogenation on the final concentration of trapped elements and their thermal stability with respect to hydrogen content is studied using ion beam analysis (IBA) techniques. The elemental concentrations of the films were measured in samples deposited on silicon substrates with a 3.3 MeV of He++ beam used to perform Rutherford Backscattering Spectroscopy (RBS), Non-Rutherford backscattering Spectroscopy (NRBS) and Elastic Recoil Detection Analysis (ERDA). Thermal stability with respect to trapped hydrogen in the film has been studied. As the films were heated in-situ in the vacuum using a o non-gassy button heater, hydrogen was found to be decreasing around 400° C.

Determination of the elemental composition is important to correlate the electrical and the optical properties of ultrananocrystalline diamond (UNCD) films, doped with and without nitrogen. To obtain the complete picture of impurities in the UNCD thin films, Rutherford backscattering spectroscopy (RBS), Non-Rutherford backscattering spectroscopy (NRBS), Elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA) were performed on UNCD films on Si substrate and on free standing films. Helium beam was used for RBS and ERDA and protons were used for NRBS measurements. Exploiting the nuclear reaction of deuterons with C, O and N, 1.1 MeV D+ beam was used to quantitatively measure the concentration of these elements. Our results show that UNCD films contain less than 3% of Hydrogen while Nitrogen content incorporated in the film was estimated to be lower than 1%. The intermixing region between the substrate and the film was found to be negligible.

The requirements of low cost and high-temperature corrosion resistance for bipolar interconnect plates in solid oxide fuel cell stacks has directed attention to the use of metal plates with oxidation resistant coatings. We have investigated the performance of steel plates with homogenous coatings of CrAlON (oxynitrides). The coatings were deposited using RF magnetron sputtering, with Ar as a sputtering gas. Oxygen in these coatings was not intentionally added. Oxygen might have come through contaminated nitrogen gas bottle, leak in the chamber or from the partial pressure of water vapors. Nitrogen was added during the growth process to get oxynitride coating. The Cr/Al composition ratio in the coatings was varied in a combinatorial approach. The coatings were subsequently annealed in air for up to 25 hours at 800 oC. The composition of the coated plates and the rate of oxidation were characterized using Rutherford backscattering (RBS) and nuclear reaction analysis (NRA). Surface characterization was carried out using Atomic Force Microscopy (AFM) and surfaces of the coatings were found smooth on submicron scale. From our results, we conclude that Al rich coatings are more susceptible to oxidation than Cr rich coatings.