Enhanced Electrode Deposition for On-Chip Integrated Micro-Supercapacitors by Controlled Surface Roughening.

Agin Vyas,Per Lundgren,Peter Enoksson,Kejian Wang,Anderson Smith,Alec Anderson,Ruben Van den Eeckhoudt,Andres Velasco,Qi Li,Mohammad Mazharul Haque

doi:10.1021/acsomega.9b04266

Abstract

On-chip micro-supercapacitors (MSCs), integrated with energy harvesters, hold substantial promise for developing self-powered wireless sensor systems. However, MSCs have conventionally been manufactured through techniques incompatible with semiconductor fabrication technology, the most significant bottleneck being the electrode deposition technique. Utilization of spin-coating for electrode deposition has shown potential to deliver several complementary metal–oxide–semiconductor (CMOS)-compatible MSCs on a silicon substrate. Yet, their limited electrochemical performance and yield over the substrate have remained challenges obstructing their subsequent integration. We report a facile surface roughening technique for improving the wafer yield and the electrochemical performance of CMOS-compatible MSCs, specifically for reduced graphene oxide as an electrode material. A 4 nm iron layer is deposited and annealed on the wafer substrate to increase the roughness of the surface. In comparison to standard nonroughened MSCs, the increase in surface roughness leads to a 78% increased electrode thickness, 21% improvement in mass retention, 57% improvement in the uniformity of the spin-coated electrodes, and a high yield of 87% working devices on a 2″ silicon substrate. Furthermore, these improvements directly translate to higher capacitive performance with enhanced rate capability, energy, and power density. This technique brings us one step closer to fully integrable CMOS-compatible MSCs in self-powered systems for on-chip wireless sensor electronics.

Highlights

Intelligent wireless sensors are currently being used in several domains such as structural health monitoring through motion, strain, and temperature sensors;[1] physical and chemical sensing of biosignals;[2] damage detection in food and agriculture;[3] and in smartphones.[4]
We have demonstrated that a substrate with an increased surface roughness due to a 4 nm annealed Fe layer enhances the performance of the MSCs fabricated through spin-coated graphene oxide (GO) electrode deposition
The electrode layers deposited on C and SE substrates demonstrate that the latter has a 78% increased thickness and a 21% improved mass retention

Summary

Introduction

Intelligent wireless sensors are currently being used in several domains such as structural health monitoring through motion, strain, and temperature sensors;[1] physical and chemical sensing of biosignals;[2] damage detection in food and agriculture;[3] and in smartphones.[4] These sensors comprise four functional units sensing, processing, communications, and a power unit. Powering these sensors is a critical issue that influences their application and architecture. Batteries could potentially be replaced by pairing on-chip supercapacitors called micro-supercapacitors (MSCs) with energy harvesters that convert energy from sources present in an ambient environment, such as thermal, vibrational, or acoustic energy.[7]

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Discussion

Conclusion