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• Scalable method to fabricate high-performance flexible LIG-based microsupercapacitor. • NiCo2S4 improves pseudocapacitive behaviour and wettability. • LIG/NiCo 2 S 4 MSC is suitable for use in flexible and miniaturized portable devices. • Remarkable cycling stability of 122 % after 5000 charge/discharge cycles. The next generation of energy storage technologies requires enhanced fabrication techniques such as the use of CO 2 infrared lasers to pattern micro-supercapacitor (MSC) electrodoes. This study reports direct-writen laser-induced graphene (LIG) micro-supercapacitors with electrodepositated NiCo 2 S 4 - nanoparticles on commercial polyimide sheets. X-ray photoelectron spectroscopy (XPS) combined with transmission electron microscopy (TEM) showed NiCo 2 S 4 nanoparticles decorating the graphene, within a highly porous carbon-based electrode. The LIG/NiCo 2 S 4 exhibited outstanding properties with a specific capacitance of 30.4 mF cm−2 at 0.75 mA cm−2 and an energy density of 16.9 µWh cm−2 at a power density of 367.5 µW cm−2. High capacitance retention of 1.22-fold was measured after 5000 cycles of charge/discharge, and of ∼90% when bent to 120˚ angle. Here, it is demonstrated that surface decoration is an effective route in improving LIG MSC storage properties, and that the LIG/NiCo 2 S 4 MSC is suitable for use in next generation of flexible and miniaturized portable devices. Flexible micro-supercapacitors based on LIG/NiCo 2 S 4 to be applied in the field of microelectronics and micro energy storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

SnO 2 -based varistors have been considered promising technological devices. However their practical application is usually stated as limited to high voltage circuits based on the high breakdown electric field exhibited by these ceramics. Recently, authors have shown that the insertion of one-dimensional (1D) SnO 2 belts allows overcoming this limitation. In this work, we present a detailed study of the growth mechanism of the belts inside varistors using electron microscopy techniques. We were able to show that mass transport has an intrinsic dependence on the sintering time and requires similar crystalline structure between the belts and the matrix. Dual beam and high-resolution transmission electron microscopy techniques permitted determining that 3D growth of belts occurs by coalescence. [ABSTRACT FROM AUTHOR]

This paper presents the results of a thorough study conducted on the action mechanism of one-dimensional single-crystalline SnO 2 nanobelts in decreasing the breakdown electric field (E b ) in SnO 2 -based varistors. The proposed method has general validity in that our investigation was focused on the traditional varistor composition SnO 2 -CoO-Cr 2 O 3 -Nb 2 O 5 . To accomplish our study objective, two methods of decreasing E b value were compared; one involving the increase in average grain size of the varistor through the sintering time and the other one related to the addition of nanobelts. The morphological results show that the method involving the increase in average grain size is limited by the formation of intragranular pores. Furthermore, despite contributing successfully towards decreasing the E b value (which underwent a decline from 3990 V cm −1 to 1133 V cm −1 with an increase in sintering time from 1 h to 2 h), the reduction obtained by this method is found to be much lower compared to that obtained via the nanobelts insertion method (E b = 270 V cm −1 ). Impedance spectroscopy results showed that the insertion of nanobelts caused a decline in the grain boundary resistance while surface potential measurements proved that this decline in resistance is attributed to the absence of potential barriers along the belts which leads to the formation of a lower resistance percolation path in the varistor. [ABSTRACT FROM AUTHOR]

Semiconducting metal oxides have many practical applications, including varistors. Varistors based on SnO 2 exhibit both high nonlinear coefficients and high breakdown electric fields. In this work we present a facile means for controlling the breakdown electric field in the SnO 2 -CoO-Cr 2 O 3 -Nb 2 O 5 varistor system by the introduction of 1D SnO 2 nanobelts. The materials were prepared by a solid state reaction method with Nb 2 O 5 doping levels at 0.10 and 0.20, mole percent. The materials were studied in detail by dual beam microscopy, direct current and impedance measurements. Exaggerated three-dimensional growth of the tin dioxide belts was observed, which was attributed to Ostwald ripening. The breakdown electric field was observed to decrease from 2510 V/cm to 2280 V/cm and from 1700 V/cm to 804 V/cm after nanobelt insertion, into the systems with 0.10 and 0.20, mole percent Nb 2 O 5 respectively. A model for the observed results was proposed based on the percolation of electrons through the belts, decreasing the number of effective potential barriers at the grain boundaries. The simulations of the impedance data showed one order of magnitude decrease in the grain boundary resistance due to the nanobelt insertion for both studied systems. [ABSTRACT FROM AUTHOR]

The material and electrical properties of silicon dioxide derived insulators formed with a focused electron beam in the presence of a TEOS or TMCTS precursor are presented. Raman and energy dispersive X-ray spectroscopy were used to analyse the chemical structure and composition of the deposited dielectric. It was found that the TEOS precursor induced a purer dielectric with a reduced carbon percentage (∼ 3 %) which was independent of the electron beam energy. An investigation with TMCTS showed the importance of using an additional water vapour supply as an in-situ oxidising co-reactant, suppressing the deposited carbon content by up to a factor of six. Leakage current and voltage breakdown measurements were used to calculate the effective resistance and the dielectric strength of the insulator. The two precursors formed insulators with similar electrical properties with effective resistances on the order of G Ω for < 100 nm thick depositions and dielectric strengths of 7 MV cm−1, equivalent to those found in sputtered silicon dioxides, but allowing high-resolution maskless lithography. [ABSTRACT FROM AUTHOR]

CNTs can have the ability to act as compliant small-scale springs or as shock resistance micro-contactors. This work investigates the performance of vertically-aligned CNTs (VA-CNTs) as micro-contactors in electromechanical testing applications for testing at wafer-level chip-scale-packaging (WLCSP) and wafer-level-packaging (WLP). Fabricated on ohmic substrates, 500-μm-tall CNT-metal composite contact structures are electromechanically characterized. The probe design and architecture are scalable, allowing for the assembly of thousands of probes in short manufacturing times, with easy pitch control. We discuss the effects of the metallization morphology and thickness on the compliance and electromechanical response of the metal-CNT composite contacts. Pd-metallized CNT contactors show up to 25 μm of compliance, with contact resistance as low as 460 mΩ (3.6 kΩ/μm) and network resistivity of 1.8 × 10−5 Ω cm, after 2500 touchdowns, with 50 μm of over-travel; they form reproducible and repeatable contacts, with less than 5% contact resistance degradation. Failure mechanisms are studied in-situ and after cyclic testing and show that, for top-cap-and-side metallized contacts, the CNT-metal shell provides stiffness to the probe structure in the elastic region, whilst reducing the contact resistance. The stable low resistance achieved, the high repeatability and endurance of the manufactured probes make CNT micro-contacts a viable candidate for WLP and WLCSP testing. Image 1 [ABSTRACT FROM AUTHOR]