| 1. |
- Li, Qi, 1990, et al.
(författare)
-
Compact and low loss electrochemical capacitors using a graphite / carbon nanotube hybrid material for miniaturized systems
- 2019
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 412, s. 374-383
-
Tidskriftsartikel (refereegranskat)abstract
- With the establishment of the internet of things (IoT) and the rapid development of advanced microsystems, there is a growing demand to develop electrochemical capacitors (ECs) to replace bulky electrolytic capacitors on circuit boards for AC line filtering, and as a storage unit in energy autonomous systems. For this purpose, ECs must be capable of handling sufficiently high signal frequencies, display minimum energy loss through self-discharge and leakage current as well as maintaining an adequate capacitance. Here, we demonstrate ECs based on mechanically flexible, covalently bonded graphite/vertically aligned carbon nanotubes (graphite/VACNTs) hybrid materials. The ECs employing a KOH electrolyte exhibit a phase angle of −84.8°, an areal capacitance of 1.38 mF cm−2 and a volumetric capacitance (device level) of 345 mF cm−3 at 120 Hz, which is among the highest values for carbon based high frequency ECs. Additionally, the performance as a storage EC for miniaturized systems is evaluated. We demonstrate capacitive charging/discharging at μA current with a gel electrolyte, and sub-μA leakage current reached within 50 s, and 100 nA level equilibrium leakage within 100 s at 2.0 V floating with an ionic liquid electrolyte.
|
|
| 2. |
- Smith, Anderson David, 1985, et al.
(författare)
-
Carbon-Based Electrode Materials for Microsupercapacitors in Self-Powering Sensor Networks : Present and Future Development
- 2019
-
Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 19:19
-
Tidskriftsartikel (refereegranskat)abstract
- There is an urgent need to fulfill future energy demands for micro and nanoelectronics. This work outlines a number of important design features for carbon-based microsupercapacitors, which enhance both their performance and integration potential and are critical for complimentary metal oxide semiconductor (CMOS) compatibility. Based on these design features, we present CMOS-compatible, graphene-based microsupercapacitors that can be integrated at the back end of the line of the integrated circuit fabrication. Electrode materials and their interfaces play a crucial role for the device characteristics. As such, different carbon-based materials are discussed and the importance of careful design of current collector/electrode interfaces is emphasized. Electrode adhesion is an important factor to improve device performance and uniformity. Additionally, doping of the electrodes can greatly improve the energy density of the devices. As microsupercapacitors are engineered for targeted applications, device scaling is critically important, and we present the first steps toward general scaling trends. Last, we outline a potential future integration scheme for a complete microsystem on a chip, containing sensors, logic, power generation, power management, and power storage. Such a system would be self-powering.
|
|
| 3. |
- Vyas, Agin, 1992, et al.
(författare)
-
Investigation of palladium current collectors for vertical graphene-based microsupercapacitors
- 2019
-
Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1319:1
-
Konferensbidrag (refereegranskat)abstract
- As microsystems are reduced in size and become integrated in the Internet of Things (IoT), they require an adequate power supply which can be integrated at the same size scale. Microsupercapacitors (MSCs), if coupled with on-chip harvesters, can offer solutions for a self-sustaining, on-chip power supply. However, the implementation of reliable MSC wafer-scale production compatible with CMOS technology remains a challenge. Palladium (Pd) is known as a CMOS compatible metal and, in this paper, we investigate the use of Pd as a contact material for vertical graphene (VG) electrodes in wafer-scale MSC fabrication. We show that a Ti diffusion barrier is required to prevent short-circuiting for the successful employment of Pd contacts. The fabricated MSCs demonstrate a capacitance of 1.3 μF/cm2 with an energy density of 0.42 μJ/cm2. Thus, utilization of a Ti diffusion barrier with a CMOS compatible Pd metal electrode is a step towards integrating MSCs in semiconductor microsystems.
|
|
| 4. |
- Vyas, Agin, 1992, et al.
(författare)
-
Surface Roughening with Iron Nanoparticles for Promoted Adhesion of Spin Coated Microsupercapacitor Electrodes
- 2019
-
Ingår i: MRS Advances. - : Springer Science and Business Media LLC. - 2059-8521. ; 4:23, s. 1335-1340
-
Konferensbidrag (refereegranskat)abstract
- Microsupercapacitors (MSCs) are miniaturized energy storage devices that can be integrated in an on-chip platform as a component of a power supply for Internet of things' sensors. Integration of these on-chip MSCs require them to be fabricated through CMOS compatible fabrication techniques such as spin coating. One of the biggest challenges in spin coated MSCs is the poor surface adhesion. In this work, we present a CMOS compatible electrode deposition process with enhanced adhesion and retention for reduced graphene oxide (rGO) using spin coating. In order to improve the adhesion and surface uniformity of the deposited electrode material, the surface of Si/SiO 2 wafers was subjected to roughening through Fe nanoparticle formation. A 4 nm thick Fe layer deposition substantially magnified the average mean surface roughness of the substrates. In comparison with substrates without the Fe deposition, the treated ones have more than 300% improvement in surface coverage and rGO mass retention after sonication testing. These results suggest that the surface roughening has a positive influence on electrode deposition via a spin-coating method.
|
|
