Electrodeposition of reactive aluminum-nickel coatings in an AlCl3:[EMIm]Cl ionic liquid containing nickel nanoparticles. - In: Journal of the Electrochemical Society, ISSN 1945-7111, Bd. 170 (2023), 7, 072504
The electrodeposition of aluminum-nickel coatings was performed by pulsed direct current in the ionic liquid (IL) 1.5:1 AlCl3:EMIm]Cl containing nickel nanoparticles (Ni NPs), for reactive dispersion coating application. Several electrochemical and characterization techniques were used to shed more light on the mechanism of Ni particle incorporation into the Al matrix. Thus, particle incorporation at the early stage of the deposition would mainly take place via particle adsorption at the substrate. However, as the thickness of the coating increases, it seems that the main mechanism for particle incorporation is via the reduction of ions adsorbed at the particles surface. Although a considerable high incorporation of Ni NPs has been achieved from the IL containing the highest concentration of Ni NPs (i.e. ∼33 wt% from a 20 g/L of Ni NPs bath), a high concentration of NPs in the IL resulted having a negative effect in terms of quality of the coatings, due to solidification of the electrolyte in a poorly conductive compound. Moreover, almost equivalent amounts of Ni and Al (Ni ∼45 wt.%and Al ∼44 wt.%) have been detected in some areas of the coatings. Such a layer composition would be desired for the targeted application.
Ruthenium and rhodium vertical interconnect formation using gas phase electrodeposition. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), insges. 3 S.
This paper presents localized gas phase electrodeposition of ruthenium (Ru) and rhodium (Rh) species into vertical interconnects. A spark discharge generates gas ions and charged species of the desired metal, which are transported by a gas flow and form a plasma jet. Prior lateral nano-bridge growth is further developed and enables the localized metal species deposition into vertical interconnect openings. This approach is additive and saves rare materials during processing. The process allows precise adjustment of the diameter, airgap size, and top finishing bump of the vertical interconnect.
Novel gas phase route toward patterned deposition of sputter-free Pt/Al nanofoils. - In: Advanced Materials Technologies, ISSN 2365-709X, Bd. 0 (2023), 0, 2300448, S. 1-8
This article reports a new approach toward fabrication and directed assembly of nanoparticulate reactive system (Nanofoils) on patterned substrates. Different from current state-of-the-art, gas phase electrodeposition uses nanoparticles instead of atoms to form densely packed multilayered thin films at room temperature-pressure. On ignition, the multilayer system undergoes an exothermic self-propagating reaction. The numerous contact points between two metallic nanoparticulate layers aid in high heat release. Sub-10-nm Platinum (Pt) and Aluminum (Al) particles are synthesized through cathode erosion of metal electrodes in a flow of pure nitrogen gas (spark ablation). Pt/Al bilayer stacks with total thickness of 3-8 µm undergo self-propagating reaction with a 10.3 mm s^−1 wavefront velocity on local ignition. The reaction wavefront is captured using high speed videography. Calorimetry studies reveal two exothermic peaks suggesting Pt/Al alloy formation. The peak at 135 ˚C has a higher calorific value of 150 mW g^−1 while the peak at 400 ˚C has a 12 mW g^−1 exothermic peak. X-ray diffraction study shows reaction-products are cubic Al2Pt with small quantities of orthorhombic Al6Pt and orthorhombic AlPt2. Electron microscopy studies help draw a correlation between film morphology, bimetallic interface, nanoparticle oxidation, and self-propagating reaction kinetics that is significant in broadening our understanding towards nanoparticulate reactive systems.
Evaluation of hysteresis response in achiral edges of graphene nanoribbons on semi-insulating SiC. - In: Materials science forum, ISSN 1662-9752, Bd. 1089 (2023), S. 15-22
Hysteresis response of epitaxially grown graphene nanoribbons devices on semi-insulating 4H-SiC in the armchair and zigzag directions is evaluated and studied. The influence of the orientation of fabrication and dimensions of graphene nanoribbons on the hysteresis effect reveals the metallic and semiconducting nature graphene nanoribbons. The hysteresis response of armchair based graphene nanoribbon side gate and top gated devices implies the influence of gate field electric strength and the contribution of surface traps, adsorbents, and initial defects on graphene as the primary sources of hysteresis. Additionally, passivation with AlOx and top gate modulation decreased the hysteresis and improved the current-voltage characteristics.
Three-dimensional MoS2 nanosheet structures: CVD synthesis, characterization, and electrical properties. - In: Crystals, ISSN 2073-4352, Bd. 13 (2023), 3, 448, S. 1-14
The proposed study demonstrates a single-step CVD method for synthesizing three-dimensional vertical MoS2 nanosheets. The postulated synthesizing approach employs a temperature ramp with a continuous N2 gas flow during the deposition process. The distinctive signals of MoS2 were revealed via Raman spectroscopy study, and the substantial frequency difference in the characteristic signals supported the bulk nature of the synthesized material. Additionally, XRD measurements sustained the material’s crystallinity and its 2H-MoS2 nature. The FIB cross-sectional analysis provided information on the origin and evolution of the vertical MoS2 structures and their growth mechanisms. The strain energy produced by the compression between MoS2 islands is assumed to primarily drive the formation of vertical MoS2 nanosheets. In addition, vertical MoS2 structures that emerge from micro fissures (cracks) on individual MoS2 islands were observed and examined. For the evaluation of electrical properties, field-effect transistor structures were fabricated on the synthesized material employing standard semiconductor technology. The lateral back-gated field-effect transistors fabricated on the synthesized material showed an n-type behavior with field-effect mobility of 1.46 cm2 V^-1 s^-1 and an estimated carrier concentration of 4.5 × 10^12 cm^-2. Furthermore, the effects of a back-gate voltage bias and channel dimensions on the hysteresis effect of FET devices were investigated and quantified.
Phase formation of cubic silicon carbide from reactive silicon-carbon multilayers. - In: MRS advances, ISSN 2059-8521, Bd. 8 (2023), 9, S. 494-498
Silicon carbide layers were fabricated using self-propagating high-temperature synthesis of binary silicon-carbon based reactive multilayers. The silicon and carbon bilayers were fabricated with two different bilayer thicknesses. They are deposited by magnetron sputtering in an alternating layer system with a total thickness of 1 μm. The entire system is annealed by rapid thermal annealing at different temperatures ranging from 500 to 1100 ˚C. From XRD analysis we could find that the formation of the silicon carbide phase was initiated from 700 ˚C. With increasing bilayer thickness the silicon carbide phase formation was partially suppressed by the silicon recrystallization due to resulting lower carbon diffusion into silicon. The transformation process proceeds in a four-step process: densification/recrystallization, interdiffusion, nucleation and transformation. From this, it was noted that when compared to low bilayer thickness samples, the formation of the silicon carbide phase is delayed with increasing bilayer thickness and needs higher reaction initiation temperatures.
Energy-efficient operation conditions of MoS2-based memristors. - In: Physica status solidi, ISSN 1862-6319, Bd. 220 (2023), 13, 2200893, S. 1-12
Sufficient energy consumption for conventional information processing makes it necessary to look for new computational methods. One of the possible solutions to this problem is neuromorphic computations using memristive devices. Memristors based on molybdenum disulfide (MoS2) are a promising way to provide a sizeable amount of hysteresis at low energy costs. Herein, different configurations of MoS2 memristors as well as the mechanisms involved in hysteresis formation are shown. Bottom gated configuration is beneficial in terms of hysteresis area and energy efficiency. The impact of device channel dimensions on the hysteresis area and energy consumption is discussed. Different operation conditions with triangular, rectangular, sinusoidal, and sawtooth drain-to-source pulses are simulated, and rectangular pulses demonstrate the highest energy efficiency. The study shows the potential to realize low-power neuromorphic systems using MoS2 memristive devices.
Influence of environment on self-propagating reactions in Al/Ni multilayer foils. - In: MRS advances, ISSN 2059-8521, Bd. 8 (2023), 9, S. 477-483
Reactive aluminum-nickel multilayer system shows exothermic energetic materials which act as a heat source for packaging and bonding of microsystems. The main challenge is controlling the self-propagation reaction velocity and temperature generated by thermal management through different thermal conductive substrate materials. The current work investigates the heat distribution of Al/Ni multilayer foils from different thermal conductive substrates which act as heat sink materials during the self-propagating reaction. A two-dimensional numerical model was developed to study thermal conductive heat loss and substrate thermal properties on the self-propagating reaction in Al/Ni multilayer foils. The self-propagating reaction was introduced on the surface of the foils by an electrical spark. Here we investigate the minimum critical thickness of Al/Ni multilayer foils which shows the self-propagation reaction on different substrates and verified from the two-dimensional numerical model. The outcomes of this investigation will facilitate the integration of Al/Ni multilayer foils on different substrates as intrinsic heat sources for different applications of micro/nanodevices.
Self-aligning metallic vertical interconnect access formation through microlensing gas phase electrodeposition controlling airgap and morphology. - In: Advanced electronic materials, ISSN 2199-160X, Bd. 9 (2023), 1, 2200838, S. 1-8
This publication reports self-aligning metallic via microlensing gas phase electrodeposition formation. Key operational parameters to fabricate vertical ruthenium and rhodium interconnects (via) with a diameter of 100 nm are discussed. Moreover, airgaps are implemented during the deposition process, which utilizes spark discharge to generate a flux of charged nanoparticles. An inert gas flow transports the nanoparticles through a reactor chamber close to the target substrate. The substrate uses a pre-patterned resist with openings to a silicon/silicon dioxide/metal stack to direct the deposition of the nanoparticles to form localized self-aligning vertical interconnects. Five process parameters were identified, which impact the morphology and conductance of the resulting interconnects: spark discharge power, gas flow rate, microlens via dimensions, substrate surface potential, and in situ flash lamp power. This parameter set enables a controlled adjustment of the via interconnect morphology and its minimum feature size. Gas flow rate in combination with spark discharge power contribute significantly to the morphology of the interconnect. Spark power and microlens via dimensions have the largest influence on the surface potential of the insulating resist cover, which enables a localized microlensing gas phase electrodeposition of a via with a controlled ratio between conducting diameter and airgap.
Large single domain iron oxide nanoparticles as thermal markers for lateral flow assays. - In: Biomedical engineering, ISSN 1862-278X, Bd. 67 (2022), S. 63