Low-temperature Technique Research Articles

On the Ion Implantation Synthesis of Ag-Embedded Over Sr-Substituted Hydroxyapatite on a Nano-Topography Patterned Ti for Application in Acetabular Fracture Sites.

There is an ongoing need for improved healing response and expedited osseointegration on the Ti implants in acetabular fracture sites. To achieve adequate bonding and mechanical stability between the implant surface and the acetabular fracture, a new coating technology must be developed to promote bone integration and prevent bacterial growth. A cylindrical Ti substrate mounted on a rotating specimen holder was used to implant Ca2+, P2+, and Sr2+ ions at energies of 100 KeV, 75 KeV and 180 KeV, respectively, using a low-energy accelerator to synthesize strontium-substituted hydroxyapatite at varying conditions. Ag2+ ions of energy 100 KeV were subsequently implanted on the as-formed surface at the near-surface region to provide anti-bacterial properties to the as-formed specimen. The properties of the as-formed ion-implanted specimen were compared with the SrHA-Ag synthesized specimens by cathodic deposition and low-temperature high-speed collision technique. The adhesion strength of the ion-implanted specimen was 43 ± 2.3 MPa, which is well above the ASTM standard for Ca-P coating on Ti. Live/dead cell analysis showed higher osteoblast activity on the ion-implanted specimen than the other two. Ag in the SrHA implanted Ti by ion implantation process showed superior antibacterial activity. In the ion implantation technique, nano-topography patterned surfaces are not concealed after implantation, and their efficacy in interacting with the osteoblasts is retained. Although all three studies examined the antibacterial effects of Ag2+ ions and the ability to promote bone tissue formation by MC3T3-E1 cells on SrHA-Ag/Ti surfaces, ion implantation techniques demonstrated superior ability. The synthesized specimen can be used as an effective implant in acetabular fracture sites based on their mechanical and biological properties.

Epitaxial Growth of GaN Films on Chemical-Vapor-Deposited 2D MoS2 Layers by Plasma-Assisted Molecular Beam Epitaxy.

The van der Waals epitaxy of wafer-scale GaN on 2D MoS2 and the integration of GaN/MoS2 heterostructures were investigated in this report. GaN films have been successfully grown on 2D MoS2 layers using three different Ga fluxes via a plasma-assisted molecular beam epitaxy (PA-MBE) system. The substrate for the growth was a few-layer 2D MoS2 deposited on sapphire using chemical vapor deposition (CVD). Three different Ga fluxes were provided by the gallium source of the K-cell at temperatures of 825, 875, and 925 °C, respectively. After the growth, RHEED, HR-XRD, and TEM were conducted to study the crystal structure of GaN films. The surface morphology was obtained using FE-SEM and AFM. Chemical composition was confirmed by XPS and EDS. Raman and PL spectra were carried out to investigate the optical properties of GaN films. According to the characterizations of GaN films, the van der Waals epitaxial growth mechanism of GaN films changed from 3D to 2D with the increase in Ga flux, provided by higher temperatures of the K-cell. GaN films grown at 750 °C for 3 h with a K-cell temperature of 925 °C demonstrated the greatest crystal quality, chemical composition, and optical properties. The heterostructure of 3D GaN on 2D MoS2 was integrated successfully using the low-temperature PA-MBE technique, which could be applied to novel electronics and optoelectronics.

The growth aspects and experimental techniques for the characterization of amino acid L-histidine hybrid crystals for nonlinear optical device applications

The development of crystal growth and measurement methods opens new possibilities for studying materials with remarkable nonlinear optical features. The development of bulk crystals is a constant concern to be beneficial for device applications. This study focuses on the development of nonlinear optical crystals of l-histidine complexes, characterization approaches, and prospective applications. The solution growth approach, a straightforward, inexpensive, and low-temperature growth technique, was adopted broadly. Recent studies show that l-histidine derivatives have potential optical, SHG, thermal, dielectric, and mechanical properties, making them an excellent choice for nonlinear optical devices. In this work, structural, spectroscopic, chemical composition, linear and nonlinear optical analyses, thermal, and dielectric characterizations of l-histidine derivatives were conducted. Most of the l-histidine complexes were found to be crystallized in orthorhombic and monoclinic crystal systems with P212121 and P21 space groups. The crystalline perfections of the samples were analyzed by the HR-XRD method. The energy-dispersive X-ray (EDX) spectroscopic technique was applied to evaluate the chemical content of the compounds. FT-IR and FT-Raman techniques were used to recognize the molecular vibrations and functional groups of the l-histidine derivatives. The UV-visible and photoconductivity studies were done to examine the optical behaviors of the developed crystals. Most of the crystals were found to have excellent optical transparency and wide bandgaps. It has been observed that l-histidine hydro-fluoride dehydrate and l-histidine tetrafluoroborate are found to have the highest second harmonic generation (SHG) efficiencies. The dielectric analyses were utilized to study the dielectric constant and dielectric loss variations with the applied frequency. According to the thermal analyses, most of the crystals were found to have substantial thermal stabilities suitable for device applications.

Low-Temperature Deposition of Diamond Films by MPCVD with Graphite Paste Additive

Modern integrated circuits (ICs) take advantage of three-dimensional (3D) nanostructures in devices and interconnects to achieve high-speed and ultra-low-power performance. The choice of electrical insulation materials with excellent dielectric strength, electrical resistivity, strong mechanical strength, and high thermal conductivity becomes critical. Diamond possesses these properties and is recently recognized as a promising dielectric material for the fabrication of advanced ICs, which are sensitive to detrimental high-temperature processes. Therefore, a high-rate low-temperature deposition technique for large-grain, high-quality diamond films of the thickness of a few tens to a few hundred nanometers is desirable. The diamond growth rate by microwave plasma chemical vapor deposition (MPCVD) decreases rapidly with lowering substrate temperature. In addition, the thermal conductivity of non-diamond carbon is much lower than that of diamond. Furthermore, a small-grain diamond film suffers from poor thermal conductivity due to frequent phonon scattering at grain boundaries. This paper reports a novel MPCVD process aiming at high growth rate, large grain size, and high sp3/sp2 ratio for diamond films deposited on silicon. Graphite paste containing nanoscale graphite and oxy-hydrocarbon binder and solvent vaporizes and mixes with gas feeds of hydrogen, methane, and carbon dioxide to form plasma. Rapid diamond growth of diamond seeds at 450 °C by the plasma results in large-grained diamond films on silicon at a high deposition rate of 200 nm/h.

Wood-Derived Graphite: A Sustainable and Cost-Effective Material for the Wide Range of Industrial Applications

The study explored the graphitization of wood through two distinct methods: a high-temperature approach at 2400 °C and a low-temperature technique at 1400 °C using a catalyst. The graphitization properties were assessed by conducting thermal experiments at various temperatures (1100 °C, 1400 °C, 1800 °C, 2000 °C, and 2400 °C), both with and without a catalyst. The development of graphite lattices was quantitatively analyzed using an array of techniques: X-ray diffractometer (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared spectroscopy (FTIR). The XRD analysis highlighted temperature-dependent changes in lattice parameters (d002, La, and Lc), while Raman spectroscopy tracked alterations in the D to G peak ratio (D/G) with temperature. An increase in temperature is correlated with a rise in the number of graphene layers and the degree of graphitization. Notably, the process of graphite lattice formation varied across the experimental temperature spectrum. The use of a catalyst resulted in a reduced d002 spacing, signifying an enhanced degree of graphitization. Moreover, the catalyst promoted a consistent and smooth graphitization process throughout the heating stages. In contrast, graphitization without a catalyst occurred at higher temperatures, specifically between 1800 °C and 2000 °C, with the d002 value stabilizing around 0.338 nm. The catalyst proved instrumental in transforming the initial structure into well-ordered graphite at lower temperatures. This investigation underscores the potential and benefits of employing a catalyst to generate high-quality graphite from wood at reduced temperatures, paving the way for sustainable and economically viable applications of this material.

Mitigating Crack Propagation in Hybrid Composites: An Experimental and Computational Study

The exceptional properties of carbon nanotubes (CNTs) make them ideal nanofillers for various composite materials. In carbon fiber-reinforced polymer (CFRP) composites. CNTs can be grown on the carbon fiber surface to act as a third interface between the fiber and the matrix. However, it was established that the uncontrolled random growth of CNTs could exacerbate delamination in composite structures. Thick nanofiller films could hinder the epoxy from seeping into the carbon fiber, resulting in insufficient interlaminar strength. Hence, the density and distribution of nanofillers play a crucial role in determining the hybrid composite fracture mechanisms. In this investigation, CNTs were grown using the low-temperature technique into specific patterns over carbon fibers to discern their derived composites’ fracture properties. The composite fracture energy release was probed using a double cantilever beam (DCB) test setup and digital image correlation (DIC) to monitor interlaminar crack propagation. A standard finite element simulation model based on the cohesive zone method (CZM) was also utilized to delineate fracture behaviors of the various composite configurations. Results conclude that a coarser pattern of CNT growth enhances resistance to crack propagation, thus improving the interlaminar fracture toughness of a composite structure.

Optimization of a Solution-Processed TiOx/(n)c-Si Electron-Selective Interface by Pre- and Postdeposition Treatments.

Developing a vacuum-free and low-temperature deposition technique for dopant-free carrier-selective materials without sacrificing their performance can reduce the fabrication cost and CO2 footprint of silicon heterojunction (SHJ) solar cells. In this contribution, to activate the full capacity of the solution-processed TiOx as an electron-selective passivation contact, the effects of various pre- and postdeposition treatments on the passivation quality and contact resistivity are investigated simultaneously. It is demonstrated that the electrical properties of a thin TiOx layer spin-coated on an n-type silicon substrate can be remarkably improved through tailor-made pre- and postdeposition treatments. A notable low surface recombination velocity (SRV) of 6.54 cm/s and a high implied open-circuit voltage (iVoc) of 706 mV are achieved. In addition, by inserting a 1 nm LiFx buffer layer between TiOx and Al metal contact, a low contact resistivity (ρc) of 15.4 mΩ·cm2 is extracted at the n-Si/SiOx/TiOx heterojunction. Our results bring the solution-processed TiOx electrical properties to a level on par with those of state-of-the-art pure TiOx layers deposited by other techniques. Chemical and electrical characterizations elucidate that the improved electrical properties of the investigated Si/SiOx/TiOx heterojunction are mediated by the concomitant involvement of chemical and field-effect passivation.

Efficacy of mosquito repellent finishes on polyester fabrics using four essential oils against the vector of the West Nile virus, Culex pipiens (Diptera: Culicidae)

One of the most common ways to prevent mosquito bites is to use treated textiles, which can be used to repel mosquitoes in the form of nets, clothing, uniforms, and other items. Four eco-friendly essential oils: lemongrass (Cymbopogon citratus), eucalyptus (Eucalyptus camaldulensis), clove (Dianthus caryophyllus), and marjoram (Origanum vulgare), were evaluated and used to finish polyester fabrics (PE) to give them a pleasant odor and antibacterial properties, as well as mosquito repellent as medical textiles. A low-temperature drying process and thermal stabilization technique were used to bond the polyester to the fragrance-containing compounds. The effect of essential oil finishes on polyester textile properties has been studied using various techniques such as mechanical measurements, contact angle, ultraviolet tests, infrared spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, GC-MS analysis, etc. Scanning electron microscopy showed the physical adsorption of oil on PE surfaces and the penetration of oil droplets between PE fibers. The ability of polyester textiles treated with essential oils of lemongrass, eucalyptus, clove, and marjoram to kill Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger was also tested. Polyester fabrics treated with clove showed the strongest antibacterial effect, surpassing that of eucalyptus oil. 12 essential oils were screened to determine their superiority in repelling mosquitoes at a concentration of 1% through the CDC bottle and WHO cone tests. Cymbopogon citratus (LT50 = 60.03 min) oil was the most effective against Cx. pipiens, followed by Eucalyptus camaldulensis (LT50 = 61.65 min) and Dianthus caryophyllus (LT50 = 64.73 min) with CDC tests. It was found that finishing PE with clove and eucalyptus oils provided 76 and 68% protection from Culex pipiens mosquitoes, even after 6 cycles of washing. This approach is innovative because it meets the goal of having antibacterial, mosquito-repellent, and pleasant-smelling fabrics as requirements for economically viable medical textiles. There is an urgent need to engineer textiles, with or without insecticides, to effectively repel mosquitoes. Our data showed the efficiency of polyester fabric treated with clove and eucalyptus oils in repelling mosquitoes after 6 washings.

Elimination of Low-Angle Grain Boundary Networks in FeCrAl Alloys with the Electron Wind Force at a Low Temperature

Low-angle grain boundaries (LAGBs) accommodate residual stress through the rearrangement and accumulation of dislocations during cold rolling. This study presents an electron wind force-based annealing approach to recover cold-rolling induced residual stress in FeCrAl alloy below 100 °C in 1 min. This is significantly lower than conventional thermal annealing, which typically requires temperatures around 750 °C for about 1.5 h. A key feature of our approach is the athermal electron wind force effect, which promotes dislocation movement and stress relief at significantly lower temperatures. The electron backscattered diffraction (EBSD) analysis reveals that the concentration of low-angle grain boundaries (LAGBs) is reduced from 82.4% in the cold-rolled state to a mere 47.5% following electropulsing. This level of defect recovery even surpasses the pristine material’s initial state, which exhibited 54.8% LAGBs. This reduction in LAGB concentration was complemented by kernel average misorientation (KAM) maps and X-ray diffraction (XRD) Full Width at Half Maximum (FWHM) measurements, which further validated the microstructural enhancements. Nanoindentation tests revealed a slight increase in hardness despite the reduction in dislocation density, suggesting a balance between grain boundary refinement and dislocation dynamics. This proposed low-temperature technique, driven by athermal electron wind forces, presents a promising avenue for residual stress mitigation while minimizing undesirable thermal effects, paving the way for advancements in various material processing applications.

Highly conductive and flexible transparent hybrid superlattices with gas-barrier properties: Implications in optoelectronics

Transparent electrodes and passivation layers find extensive application in optoelectronic devices such as light-emitting diodes, solar cell. Integrating transparent conductive and gas diffusion barrier layers into a unified component holds promise for enhancing device performance and cost-effectiveness. However, research on these dual-function materials remains relatively scarce. Here, we introduce an innovative hybrid superlattice composed of ZnO and self-assembled monolayers, designed to function simultaneously as transparent conductive and gas diffusion barrier. Fabricated using low-temperature atomic layer deposition and molecular layer deposition techniques, the hybrid superlattice exhibited robust electric conductivity (surpassing 1400 S cm-1), exceptional moisture barrier characteristics (water vapor transmission rate < 4 × 10-7 g m-2 day-1), and remarkable flexibility. We systematically investigated the significant electrical improvement, attributing it to the formation of a well-defined amorphous/crystalline phase-composite structure in the ZnO nanolayer. Moreover, the organic layers in the superlattice enhance resilience against environmental degradation and mechanical deformation by forming a multilayered structure that effectively decouples defects in the underlying layers. These compelling features position the hybrid superlattice as a promising candidate for transparent conductive gas diffusion barriers, with diverse applications in emerging optoelectronics.

High mechanical strength superhydrophobic colored sand prepared by a low-temperature strategy

The desert aeolian sand is one of the most abundant resources worldwide, and the utilization of sand with superhydrophobic function has become a heated research field. However, same as other superhydrophobic materials, the abrasion of the surface will lead to the loss of hydrophobic performance. Therefore, we prepared high-performance and mechanically stable superhydrophobic colored sand with a maximum water contact angle of 155° by low-temperature layered chaining technique (80 °C). The technical property of the co-existence of superhydrophobicity and mechanical stability was achieved on the surface of our high mechanical strength superhydrophobic colored sand. The interaction between the grafted particles and water molecules was revealed by molecular adsorption dynamics simulation to investigate the factors that affect hydrophobicity performance. The prepared superhydrophobic colored sand presented stable superhydrophobic performance after 40 min continuous abrasion tests. Moreover, the superhydrophobic sand had excellent chemical stability and liquid impact resistance with the composition stability under 240 °C. This work presents an environment-friendly, and resource-utilization surface modification method on inert materials like sand under a low-temperature condition. It provides framework surfaces like road ground and architectures with high mechanical strength and functional “layer” through a long-term performance and stable method.

Realization of low specific-contact-resistance on N-polar GaN surfaces using heavily-Ge-doped n-type GaN films deposited by low-temperature reactive sputtering technique

We developed a low-temperature ohmic contact formation process for N-polar GaN surfaces. Specific-contact-resistances of 9.4 × 10−5 and 2.0 × 10−5 Ω cm2 were obtained using Ti/Al metal stacks on heavily-germanium-doped GaN films, which were deposited at 500 °C and 600 °C using a radical-assisted reactive sputtering method, respectively. The electrode sintering temperature was as low as 475 °C. Carrier concentrations for the 500 °C and 600 °C samples were 2.6 × 1020 and 1.8 × 1020 cm−3, respectively. These results suggest that this method is highly effective in reducing the contact resistance of GaN devices with low thermal budgets.

Hydrothermal Synthesis, Phase Analysis, and Magneto-Electronic Characterizations of Lead-Free Ferroelectric BM2+(Zn, Ca, Mg)T-BFO System.

In this study, lead-free BiM2+(Zn, Ca, Mg)Ti-BiFeO3 ceramics are fabricated under eco-friendly hydrothermal reaction conditions at 250 °C. XRD patterns show that all the synthesized compounds exhibit a phase coexistence of monoclinic and tetragonal perovskite-type structures with a morphotropic phase boundary at x = 0.4, with minimum impurity. The calculated average crystallite/grain size of the samples was close to 50 nm at full width at half-maximum of the main peak. The corresponding bonds of the constituent elements were observed by FTIR analysis, which further supports the formation of the local structure. EDS analyses detect all of the elements, their quantities, and compositional homogeneity. SEM data show agglomerated and nearly spherical morphology with an average particle size of about 128 nm. All synthesized ceramic powders revealed thermal stability with trivial mass loss up to investigated high temperatures (1000 οC). The dielectric constant reached its maximum at 38.7 MHz and finally remained constant after 80 MHz for all nanoceramics. Because of the complementary impact of different compositions, the most effective piezoelectric characteristics of d33 = 136 pCN-1, Pr = 8.6 pCN-1 cm-2, and kp = 11% at 30 °C were attained at x = 0.4 content for 0.4BiCaTi-0.6BiFeO3 ceramic. The measured magnetic hysteresis data (M-H curve) showed a weak ferromagnetic nature with the highest moment of ∼0.23 emu/g for 0.4BiCaTi-0.6BiFeO3, and other samples exhibited negligible ferromagnetic to diamagnetic transition. The optical response study shows that the 0.4BiMgTi-0.6BiFeO3 sample yielded the maximal transmittance (50%), whereas the 0.4BiCaTi-0.6BiFeO3 compound exhibited the highest refractive index. The calculated large band gap shows a high insulating or dielectric nature. Our findings demonstrate that the BiM2+Ti-BiFeO3 system, which was fabricated using a low-temperature hydrothermal technique, is an excellent lead-free piezoelectric and multiferroic nanoceramic.

An investigation into low-temperature HFCVD and derivative techniques for the enhancement of diamond-coated cemented carbide tool performance

The performance of diamond-coated cemented carbide tools manufactured via the conventional hot filament chemical vapor deposition (HFCVD) technique exhibits certain limitations, including issues with poor toughness and reduced adhesive strength of film-substrate systems, primarily attributed to the cobalt diffusion at elevated temperatures (> 800 °C). In this study, a pioneering exploration of a low-temperature diamond film deposition technique on cemented carbide is developed, and a comprehensive evaluation of the film properties is conducted. The results indicate that owing to constraints related to growth rate and diamond film purity, it may not serve as an effective approach for enhancing the performance of conventional coated tools. Nonetheless, the inherent capability of this technique in inhibiting cobalt diffusion is strategically harnessed to pioneer the development of a derivative technique referred to as the “low-temperature to high-temperature HFCVD (LT-HT-HFCVD)”. This innovative method leverages a low-temperature deposited diamond layer as an intermediate layer to impede cobalt diffusion while serving as a densely nucleated layer for subsequent diamond growth. Subsequently, the conventional technique is employed to facilitate an effective growth rate and maintain high growth purity. The diamond-coated tools generated by this technique are subject to a comprehensive comparative analysis against those generated by low-temperature HFCVD (LT-HFCVD) and conventional HFCVD (CT-HFCVD) techniques. The results reveal that tools fabricated using the LT-HT-HFCVD combine the advantages inherent to both the LT-HFCVD and CT-HFCVD techniques, thereby manifesting superior toughness, enhanced film-substrate adhesive strength, and outstanding cutting performance.

Cathodized Stainless Steel Mesh for Binder-Free NiFe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/NiFe Layer Double Hydroxides Oxygen Evolution Reaction Electrode

Oxygen evolution reaction (OER) is an essential reaction commonly applied in various energy storage and conversion technologies. One of the common issues of OER lies in its low kinetic activity. Therefore, developing durable, low-cost, and high-performance OER catalysts is critical. Recently, many attempts have used stainless steel mesh (SSM) as the substrate for OER electrodes because SSM is abundant, cheap, and durable. Nickel/iron-based materials, i.e., NiFe2O4/NiFe layer double hydroxides (LDHs), are regarded as one of the most excellent OER catalysts in alkaline electrolytes, making them attractive low-cost materials for OER catalysts. However, synthesizing NiFe2O4/NiFe LDHs directly on the surface of SSM is challenging. Modifying the SSM surface through cathodization has proved to enhance the adhesion and OER activity. Moreover, the cathodization technique is facile and cost-effective. In this work, the surface of SSM is modified by cathodization treatment. Subsequently, NiFe2O4/NiFe LDHs are deposited onto the surface of treated SSM via a low-temperature one-step chemical bath deposition technique. This synthesis is a binder-free method; the resulted electrodes show excellent OER performance without the binder effects. The as-prepared electrodes have a small Tafel slope of 125.4 mV/dec (1 M KOH) and high durability (10 mA/cm2 for 50 hours).

Realizing a Superior Conversion Efficiency of ≈11.3% in the Group IV-VI Thermoelectric Module.

GeTe-based materials exhibit superior thermoelectric performance, while the development of power generation devices has mainly been limited by the challenge of designing the interface due to the phase transition in GeTe. In this work, via utilizing the low-temperature nano-Ag sintering technique and screening suitable Ti-Al alloys, a reliable interface with excellent connection performance has been realized. The Ti-Al intermetallic compounds effectively inhibit the diffusion process at Ti-34Al/Ge0.9Sb0.1Te interface. Thus, the thickness of the interfacial reaction layer only increases by ≈2.08µm, and the interfacial electrical contact resistivity remains as low as ≈15.2 µΩ cm2 even after 30 days of isothermal aging at 773 K. A high conversion efficiency of ≈11.3% has been achieved in the GeTe/PbTe module at a hot-side temperature of 773 K and a cold-side temperature of 300 K. More importantly, the module's performance and the reliability of the interface remain consistently stable throughout 50 thermal cycles and long-term aging. This work promotes the application of high-performance GeTe materials for thermoelectric power generation.

The study of Correlated Barrier Hopping (CBH) conduction mechanism and modulus spectroscopy of YFe0.5Co0.5O3 compound

This research paper studied the electrical properties of Yttrium orthoferrite by substituting 50-mol percent of Co into the Fe-site. The crystalline morphology of the obtained compound, YFe0.5Co0.5O3, was studied using XRD and Rietveld refinement with FullProf software. A low-temperature solid-state reaction technique was used to make this compound. X-ray diffraction results indicate that the obtained compound has an orthorhombic structure with space group Pbnm. X-ray peak broadening analysis was used to evaluate crystallite size and strain using Williamson-Hall plots (W–H plot). FESEM with EDX data revealed the phase purity of the obtained compound. XPS studies showed the presence of multiple oxidation states of Fe and Co in the compound. The Nyquist plots show non-Debye-type behavior in all samples. The CBH (Correlated Barrier Hopping) Model was adopted to explain the conduction mechanism.

Low-temperature aluminum doped and induced polysilicon and its application as partial rear contacts on p-type silicon solar cells

Low-temperature contact techniques offer benefits for various solar cells, including tandem solar cells, which risk degradation from high-temperature contact fabrication for top cell materials, such as in III-V/Si multijunction cells. This paper presents aluminum (Al) doped and induced poly-Si (formed through annealing at 190 °C for 5 min) as localized contacts on p-type silicon absorbers. This approach avoids the high-temperature processes required for poly-Si formation and the toxic gases involved in in-situ doping through chemical vapor deposition. Raman spectroscopy confirms poly-Si formation due to Al-induced recrystallization of a-Si:H(i), with electrochemical capacitance-voltage (ECV) measurements validating Al doping in the newly-formed poly-Si. The contact stack of p-Si/a-Si:H(i)/Al exhibits ohmic behavior after annealing at 190 °C for 5 min, achieving a contact resistivity of ∼13.2 mΩ⋅cm2. Finally, a cell featuring a localized Al-doped poly-Si contact structure is fabricated, realizing a 3% absolute efficiency improvement compared to a full-area Al back contact cell.

A sustainable bio-based char as emerging electrode material for energy storage applications

In the last few years, extensive research efforts have been made to develop novel bio-char-based electrodes using different strategies starting from a variety of biomass precursors as well as applying different thermochemical conversion paths. In this regard, hydrothermal carbonization method is becoming a more prevalent option among conversion procedures even if pyrolysis remains crucial in converting biomass into carbonaceous materials. The main aim of this study is to develop an innovative supercapacitor electrode from spruce bark waste through a unique low-temperature technique approach, which proved to effectively eliminate the pyrolysis step. Consequently, a hybrid spruce-bark-graphene oxide compound (HySB) was obtained as electrode material for supercapacitors. When compared to a regularly used commercial electrode material, SLC1512P graphite (reference) with 150.3 µF cm−2 capacitance, the HySB has a substantially higher capacitive performance of 530.5 µF cm−2. In contrast to the reference, the HySB polarization resistance increases by two orders of magnitude at the stationary potential and by three orders of magnitude at the optimum potential, underlying that the superior performances of HySB extend beyond static conditions. The synthesis strategy provides an appropriate energy-efficient option for converting biomass into carbonaceous materials with meaningful properties suitable for energy storage applications.

Development of a low-temperature immersion microscopy technique for ice research

Abstract Perennial ice can be studied for many purposes, including paleoclimate records or rheological properties. For most of those purposes, the ice microstructure must be studied, often through optical microscopy. The aim of this work is to assess the viability of immersion microscopy for the study of ice microstructures. It consists of using an oil between the objective lens and the specimen, to increase image resolution. Immersion microscopy is a technique well-developed for the investigation of diverse materials, but it has so far not been explored for ice research. Here we investigate the challenges and advantages of that technique. The main challenge is related to the selection of the immersion oil itself, which must satisfy a number of criteria, ranging from refractive index and viscosity to toxicity and reactivity. We identify pure silicone oil (dimethicone) as a simple and safe option for immersion microscopy of inner ice structures. Among its advantages, it provides higher resolution (compared to standard ‘dry’ microscopy) and it can be simultaneously used as a long-term coating to prevent undesired sublimation of the ice-sample surfaces. For the observation of surface structures, however, another type of oil with higher refractive index should be used.