On-chip Energy Storage Devices Research Articles

Recent Advancements in Light-responsive Supercapacitors

Abstract: With so many of our daily activities related to electricity, from telecommunication to laptops and computers, the use of electric energy has skyrocketed in today's technology-based world. Energy output must rise to meet rising energy demand. Still, as fossil fuels are running out, we must turn to more renewable energy sources, particularly solar energy, which can be harnessed and converted to electricity by solar-powered cells. The issues, however, are brought about by the sunlight's unpredictable energy output. The energy produced by solar cells should therefore be stored using energy storage technologies. This notion led to the development of the photo-supercapacitor, a device that combines a solar cell with a supercapacitor to store the energy generated by the solar cells. However, recently researchers developed light-responsive materials for supercapacitors that could be used directly as electrode materials and deposited on various transparent and conductive substrates. Such light-responsive supercapacitors could be operated directly by shining solar light without using any solar cell. A light-responsive supercapacitor's efficiency is primarily influenced by the active materials used in its electrode fabrication. The main components of high-energy conversion, which improves a light-responsive supercapacitor's performance and shelf life, are photoactive materials, counter electrodes, compatible electrolytes, and transparent substrate performances. Furthermore, light-responsive supercapacitors are cutting-edge and promising energy storage devices that can self-charge under light illumination by converting light to electrical energy and storing it for later use. They are considered a novel approach to energy issues in electrical transportation, electronic equipment, and on-chip energy storage devices. Thus, this review paper opens up an avenue for the direct utilization of photoactive nanomaterials for electrochemical energy storage and demonstrates the substantial potential for the fabrication of advanced light-responsive supercapacitors. This study also covers the fundamentals of how this exciting field works, the historical trajectory of how far it has come, and the promising prospects for its future.

In Situ and Ex Situ diagnostics of ALD-Ultrathin Lithium-Ion Films

All solid-state ion layers has an ever-growing interest in order to accomplish on-chip energy storage devices. As such, lithium-ion synaptic transistor to build artificial neural networks, integrated area-enhanced capacitors and lithium-ion microbatteries for energy supply are suitable candidates fulfilling energy-efficient devices. Atomic layer deposition (ALD) is one of the most promising techniques for manufacturing ultrathin layers for lithium-ion devices with exceptional capabilities to enable conformal growth at atomic scale. In this area, in situ diagnostics has become of vital importance for the growth process understanding especially on view of the air-sensitivity character of lithium ultra-thin layers.The purpose of this work is to present an in situ spectroscopic ellipsometry (SE) study of ALD thin films used on the fabrication of lithium-ion devices. We will consider several aspects of ALD ultrathin films growth, such as film thickness, saturation curves and initial films nucleation. We shall compare in situ SE results with those of ex situ diagnostics such as XRR (x-ray reflectometry) and XPS (x-ray photoelectron spectroscopy).We focus on the characterization of 10-100 nm thin lithium phosphate electrolyte with and without nitrogen doping deposited at ALD temperature range 300-350°C using LiHMDS-TMPO and LiHMDS-DEPA precursors, respectively. On the other hand, the realization of silicon integrated lithium ionic devices requires the implementation of essential barrier films to prevent Li-ion into the Si substrate. We will explore here the ability of titanium nitride depositions to act as lithium-ion diffusion barriers. TiN deposition (10-20 nm thin) by ALD process (350°C-400°C) uses TiCl4 and NH3 precursors.First, we investigate the growth process of LiPO, LiPON and TiN intrinsic layers deposited using thermal ALD. Secondly, we apply in situ and ex situ diagnostics on exemplary LiPO/LiPON deposited on top of the 10 nm ALD TiN film (Figure 1: Monitoring of LiPON thickness vs deposition time using in-situ Ellipsometry). The film thickness deduced from in situ SE measurements was corroborated by thickness measurements with XRR technique (Figure 2: Evolution of LiPON thickness vs ALD cycles using Ellipsometry and SE characterization techniques). Ex situ SE was used most often for WiW uniformity evaluating (Figure 3: 8” Wafer thickness mapping of ALD LiPON layers (a: 10nm TiN film; b: 17nm LiPON film). The preliminary results underline the fact that ALD growth rate and nucleation of lithium electrolyte and titanium nitride obviously depends on the ALD process parameters (temperature, pulse and purge times, number of cycles) but on the substrate nature (silicon, thermal oxide, and metallic). In situ and ex situ diagnostics highlight that initial film growth of lithium electrolytes and TiN layers strongly depends on the precursors kind used in the ALD process and the substrate material employed. Figure 1

Thermal stress-induced fabrication of carbon micro/nanostructures and the application in high-performance enzyme-free glucose sensors

Enzyme-free glucose sensors are of great significance for monitoring patients’ blood glucose, but the fabrication of high performance sensors is still challenging. Carbon micro/nanostructures are good candidates for enzyme-free glucose sensors due to good biocompatibility and conductivity, and highly active surface area. In this study, the formation of flower-like carbon micro/nanostructure arrays by the thermal stress from pyrolysis of suspended micro/nanostructures was studied. The modified carbon microelectromechanical system (C-MEMS) technology involved overexposure of photoresist structures, oxygen plasma etching and pyrolysis processes with stainless steel as substrate. The effects of fabrication parameters like exposure time and width of suspended part to the formation of carbon micro/nanostructures were discussed. The novel carbon micro/nanostructures were integrated with copper oxide (CuO) nanofilm for the application of enzyme-free glucose sensors. The electrochemical performances of CuO nanofilm/carbon micro/nanostructures were characterized, and the results showed that the enzymeless glucose sensors demonstrated excellent specificity, good stability, high sensitivity of (1.09 ± 0.05)×103 μA mM−1 cm−2 and low detection limit of 4.51 ± 0.03 μM. The obtained micro/nanostructures have great potential for high performance micro sensors and on-chip energy storage devices, and the presented approach is promising for large-scale manufacturing of carbon micro/nanostructures.

Fully Three-Dimensional Silicon-Integrated Dielectric Capacitor at 1 µFmm-2 for on-Chip Energy Storage

The increasing request of on-chip energy storage devices is driven by the augmented connectivity between people and things for IoT, portable, and wearable electronic applications. These systems require high performance components with low power consumption, compact size, and high energy storage capability. Supercapacitors (SCs) achieve capacitance density in the order of 0.1–1 mF/mm2. Nonetheless, their poor performance in terms of operation frequency (from Hz to tens of Hz, rarely beyond 1 kHz) and voltage (rarely exceeding 2 V), together with their low compatibility with standard integrated circuit (IC) technologies, have inhibited their integration to date.Dielectric capacitors (DCs) make use of solid-state dielectrics sandwiched between two conductive electrodes. These capacitors operate at high frequency (up to a several MHz) and voltages (exceeding tens of Volt). However, the areal capacitance of DCs is order of magnitude smaller than that of SCs. The use of high dielectric constant materials (k>10) and the exploitation of the third dimension (3D capacitor) to increase the effective surface area of the capacitor per unit volume have been proposed.In this work, we successfully address the challenge of achieving a 3D silicon-based dielectric capacitor with high capacitance density and large operation voltage and frequency range, using a fabrication process that is compatible with silicon ICs technology.Specifically, we report on 3D DCs fully integrated in a silicon chip with areal capacitance up to 1 μF/mm2 by atomic layer deposition of conductive (TiN) and high-k dielectric (Al2O3 and HfAlOX) nanocoatings (20 and 40 nm) into trenches electrochemically etched in silicon with aspect ratio up to 100 [1]. The 3D DCs operate up to 70kHz with an excellent stability with voltage (up to 16V) and temperature (up to 100°C), over 100 h of continuous operation (>108charge/discharge cycles). The 3D DCs exhibit power and energy densities of 566 W/cm2 and 1.7 μWh/cm2, respectively, greater that those of most state-of-the-art dielectric capacitors and supercapacitors.[1] L. M Strambini, A. Paghi, S. Mariani, A. Sood, J. Kalliomäki, P. Järvinen, F. Toia, M. Scurati, M. Morelli, A. Lamperti, G. Barillaro, Three-dimensional silicon-integrated capacitor with unprecedented areal capacitance for on-chip energy storage, Nano Energy, 68, 104281 (2020)

3D printing of high-performance micro-supercapacitors with patterned exfoliated graphene/carbon nanotube/silver nanowire electrodes

Micro-supercapacitors (MSCs) show great potential as on-chip energy storage devices for portable electronics. The major flaw of thin-film MSCs is their low energy density. To improve the energy density, thicker electrodes are required. However, the fabrication of MSCs with thick electrodes remains a challenge. In this work, a novel 3D printing method is employed to fabricate high-performance MSCs with interdigitated exfoliated graphene (EG)/carbon nanotube (CNT)/silver nanowire (AgNW) electrodes. The nanowelding of AgNW junction plays a critical role in the realization of 3D printing. To enhance the electrochemical performances of EG, phosphorus atoms are incorporated into the carbon framework with 1.7 at%. The areal capacitance of the 3D printed MSC is 21.6 mF cm−2 at a scan rate of 0.01 V s−1. The areal energy density of the MSC ranges from 0.5 to 2 μWh cm−2 with a maximum power density of 2.5 mW cm−2.

Wafer-Scale Fabrication of Solid-State on-Chip Microsupercapacitors Based on Silicon-Processing Techniques

Conventional silicon-based fabrication techniques, ranging from photolithography to various etching processes, are well-established approaches for achieving high-resolution patterns for microelectronics in the semiconductor industry. Although the use of microfabrication methods in the production of electrochemical energy storage (EES) devices has not really been considered, the adaption of these silicon processing techniques can open up new fabrication routes especially for integrated on-chip energy storage devices. One important consideration for the development of on-chip EES devices is to fabricate a mechanically rigid solid electrolyte with spatial and thickness control, which can be achieved using photopatterning functionality.1 This presentation will review our results on the synthesis and characterization of a photopatternable, ionically conducting solid electrolyte for on-chip micro-supercapacitors (MSC). Our approach was to create ‘quasi-solid’ electrolytes in which the photopatternable epoxy-based polymer matrix (SU-8) confines charge-carrying ions to provide measurable ionic conductivity. The resulting ion modified electrolyte is a promising gel polymer electrolyte with excellent thermal and physical properties and a room temperature ionic conductivity of 10-4 S cm-1. In addition, we demonstrate wafer-scale fabrication of all-photopatterned solid-state MSC devices. Electrochemical testing of tandem MSC devices validated that the potential range and total current output of MSC devices can easily be tailored through modifying the device arrangements in series or parallel configurations. The proposed fabrication strategy, based on magnetron sputtering of electrode materials in conjunction with a photopatternable solid electrolyte, provides a unique opportunity for the development of robust solid-state MSC that can be integrated with microelectronics in a single chip.Reference 1. Choi, J. Lau, J. Hur, L. Smith, C. Wang, B. Dunn, Advanced Materials. 30 (2017) 1703772.

Scalable, and low-cost treating-cutting-coating manufacture platform for MXene-based on-chip micro-supercapacitors

The rapid development of silicon-based microelectronic devices urgently demand for compatibly silicon-based micro-supercapacitors (MSCs) with smaller size, higher power density, and higher integration density. However, there are still some challenges in fabricating silicon-based MSCs, such as weakly-connected interface and expensively-manufactured process. Here we demonstrate a scalable and low-cost treating-cutting-coating (TCC) manufacture platform for Ti3C2Tx MXene-based on-chip MSCs. The hydrophilical treating of silicon/silicon dioxide (Si/SiO2) surface can effectively enforce MXene-silicon interface adhesion, resulting in the improved integrity and uniformity of MXene films. Subsequently, cold laser-cutting followed by spin-coating can rapidly prepare the MXene-based electrodes on the kapton-masked Si/SiO2 substrates. This as-obtained MSC displays a high areal and volumetric capacitance of 472 μF cm−2 and 21.4 F cm−3, incorporating with outstanding cycling stability of over 87.6% capacitance retention after 10 000 cycles. Evidently, this treating-cutting-coating manufacture process will support a general platform toward scalable on-chip energy storage devices based on 2D materials.

Laser-induced conductive nanofibers for microsupercapacitors

The rapid development of portable and miniaturized electronic devices has promoted the demand for on-chip energy storage devices. Because of the long cyclic lifetime and high power density, microsupercapacitors have great potential to be the alternative of microbatteries in various applications. Conductive nanofibers with large surface area and excellent electron conductive matrix render itself a feasible electrode material for microsupercapacitors. However, the conventional preparation process is energy consumption and time-consuming. Herein, we demonstrate a new method to fabricate conductive nanofibers-based microsupercapacitors (CNFs-MSCs) by employing the electrospinning of nanofibers on Au-coated glass substrate followed by direct laser writing. The fabricated CNFs-MSCs have an initial areal capacitance of 4 mF cm−2 and outstanding cycling stability with a retention of 180% after 7600 cycles. This superior electrochemical performance indicates that the fabricated devices have greatly promising potential for smart energy storage devices.

Marker Pen Lithography for Flexible and Curvilinear on-Chip Energy Storage

On-Chip energy storage is currently on high demand as its potentiality for compatible integration with flexible and miniaturized functional electronic devices. Conventional microfabrication has been the widely employed technique in fabricating interdigitated microsupercapacitor devices in a reliable manner. However, developing unconventional lithography techniques can be attractive interms of simplicity with minimal sophistication while not compromising the performance. Here, we propose a simple and versatile strategy to fabricate on-chip microsupercapacitors (MSCs) employing hand-written sacrificial marker ink patterns, both in lift-off and etching modes. As a prototype, this technique is demonstrated for the fabrication of conducting polymer MSCs involving poly(3,4-ethylenedioxythiophene), polyaniline and metal oxide electrode materials. Typical values of energy density in the range of 5-11 mWh/cm3 at power densities of 1-6 W/cm3 are achieved, that are comparable to thin film batteries and superior to the carbon and metal oxide based microsupercapacitors reported in the literature. Fabrication of microsupercapacitor devices on curved surfaces and multi-stack designs are additional assets of this technique. This innovative strategy may be broadened for scalable fabrication of a wide variety of on-chip energy storage devices.

On-chip interdigitated supercapacitor based on nano-porous gold/manganese oxide nanowires hybrid electrode

The rapid development of micro-sized electronics has aroused demand for on-chip energy storage devices of high reliability, stability and performance. Micro fabrication technology has now enabled planar supercapacitors (SCs), based on various electrode materials, to be prepared onto a chip for a variety of applications. Nano-porous metal/manganese oxide hybrid electrode with enhanced conductivity and capacitive performance has been proven to be a promising candidate for SCs but has not yet been utilized for interdigitated on-chip energy storage. Herein, we demonstrate a scalable preparation of nano-porous gold/manganese oxide nanowires thin film electrode material, which can be further fabricated to on-chip interdigitated all-solid-state supercapacitors on silicon wafers so that they can be integrated with MEMS or CMOS. Also the nucleation and growth mechanism of manganese oxide nanowires on nano-porous gold has been investigated. Remarkably, the miniaturized SCs based on the nano-porous gold/manganese oxide nanowires hybrid material exhibits excellent cycle stability and superior frequency response (4ms) and demonstrates energy density of 55μWhcm−3 and power density of 3.4Wcm−3, which is relatively high compared with other manganese oxide based supercapacitors.

Fabrication of a 3D micro/nano dual-scale carbon array and its demonstration as the microelectrodes for supercapacitors

An easily accessible method is proposed for the fabrication of a 3D micro/nano dual-scale carbon array with a large surface area. The process mainly consists of three critical steps. Firstly, a hemispherical photoresist micro-array was obtained by the cost-effective nanoimprint lithography process. Then the micro-array was transformed into hierarchical structures with longitudinal nanowires on the microstructure surface by oxygen plasma etching. Finally, the micro/nano dual-scale carbon array was fabricated by carbonizing these hierarchical photoresist structures. It has also been demonstrated that the micro/nano dual-scale carbon array can be used as the microelectrodes for supercapacitors by the electrodeposition of a manganese dioxide (MnO2) film onto the hierarchical carbon structures with greatly enhanced electrochemical performance. The specific gravimetric capacitance of the deposited micro/nano dual-scale microelectrodes is estimated to be 337 F g−1 at the scan rate of 5 mV s−1. This proposed approach of fabricating a micro/nano dual-scale carbon array provides a facile way in large-scale microstructures’ manufacturing for a wide variety of applications, including sensors and on-chip energy storage devices.