Development of high-performance silicon carbide based temperature and humidity sensors using low cost, industry ready materials and fabrications techniques

Abstract

Printed physical sensors have been successfully deployed in industry and academic research over the past two decades. Although most printed sensors suffice for general purpose applications, most sensing and supplementary materials used are susceptible to limiting environmental factors. For printed sensors to perform at elevated environmental conditions such a temperature and humidity, often ceramic materials are employed. Silicon carbide ( SiC ) traditionally performs exceptionally well towards temperature, humidity, gas and photodetection applications, however its use in printed physical sensors has severely been limited. Silicon carbide offers significant properties such as high temperature and corrosive chemical tolerance along with being inert and bio-compatible. Nanoparticle based silicon carbide printed films pose a unique opportunity towards sensing applications where dense networks of SiC nanopaticles facilitate the movement of charge. Some attempts have been made towards fabricating fully printed physical sensors based on SiC nanoparticles with a majority of research still under theoretical and experimental investigation leading to a scarcity of commercial fabricated SiC printed sensors. This doctoral thesis aims to investigate and advance fully printed SiC temperature and humidity sensors. Owing to its high temperature tolerance, SiC based printed devices are potential candidates for deployment in harsh environments such as ultra high temperatures. In order to facilitate these devices the printed silver interconnects must be robust and sustainable under these conditions. To achieve this, we need to investigate the failure mechanism of commercial silver inks at high temperatures and implement modifications to enhance the inks stability at said conditions. After an extensive literature review we first establish the key properties, fabrication techniques and applications of silicon carbide as a sensing material and conventional printed sensors and interconnect technologies. Next, we formulate and fabricate SiC nanoparticle based temperature and humidity sensors using industry ready, low cost additive technique; screen printing. This allows us to fabricate reliable and repeatable devices which are further investigated. The simple architecture of printing the sensing material atop printed interdigitated electrodes allows these sensors to be incorporated into large scale sensing applications with ease and insignificant cost addition. Following the device fabrication, the performance of both the temperature and humidity sensors are evaluated. We report highly sensitive and flexible SiC humidity sensors adsorption and desperation times far superior to those recently reported in literature. We also demonstrate the implementation of these devices into medical diagnostic and prevention tools. The printed SiC temperature sensors are highly sensitive to changes in temperature with in a large range. We also investigate the impact of bending and humidity on these sensors with repeatable and adequate response. Lastly, we achieve significant operational temperature enhancement of commercial silver ink using silicon additives. The Zener pinning mechanism helps stabilize the inks morphology and electrical conductivity at ultra high temperature making it an excellent low cost alternatives to precious metal inks. Overall, this doctoral thesis successfully delivers all printed, low cost SiC temperature and humidity sensors along with the understanding and means to modify commercial interconnect silver inks for high temperature applications.

Date	16 Feb 2025
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Sylvain G. Cloutier (Supervisor) & Martin Bolduc (Co-supervisor)