Reliability, power dissipation, sensing, and thermal transport in carbon nanomaterials and devices

Carbon Nanotubes;Graphene;Hysteresis;Thermal Transport;Power Dissipation;Chemical Sensors

Estrada, David

关键词: Carbon Nanotubes;    Graphene;    Hysteresis;    Thermal Transport;    Power Dissipation;    Chemical Sensors;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/44405/David_Estrada.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Energy consumption is a significant challenge across the globe ranging from power consumption in large-scale buildings to nanoscale devices. A fundamental examination of energy dissipation in such contexts can lead to orders of magnitude improvements in energy efficiency. Emerging classes of nanomaterials, such as carbon nanotubes and 2-dimensional crystals (e.g. graphene), have presented new opportunities to improve energy use at the macro and nanoscale. However, much work remains to be done to fully understand the high-field reliability and fundamental properties of these nanomaterials in order to promote their widespread use in energy applications. In this work, we investigate the reliability of carbon nanotube transistors by developing a pulsed measurement technique to suppress hysteresis for carbon nanotube (CNT) mobility measurements in air, in vacuum, and over a wide (80 – 453 K) temperature range. The use of this pulsed measurement technique provides a route towards measuring the device mobility without the effects of charge screening as well as the interface quality of low-dimensional systems and their surrounding bulk environments. We then use infrared thermometry to investigate power dissipation in carbon nanotube network (CNN) transistors and find the formation of distinct hot spots during operation. However, the average CNN temperature at breakdown is significantly lower than expected from the breakdown of individual nanotubes, which we attribute to extremely high regions of power dissipation at the nanotube junctions.We then turn our attention to the fundamental properties of large-scale polycrystalline graphene films grown by chemical vapor deposition (CVD). We elucidate the chemical sensing mechanisms of such films, and find that linear defects or continuous lines of point defects are needed to enhance the chemical sensitivity of graphene. Therefore, simple chemiresistors made from CVD polycrystalline graphene could be used as highly sensitive pollutant detectors in “smart” climate control systems to reduce energy consumption by residential and commercial buildings. Lastly, we develop an electrical thermometry platform to investigate the practical tuning of thermal transport in layer-by-layer assembled graphene van der Waals (vdW) solids. We find thermal transport in a single layer of transferred CVD graphene is limited by substrate phonon and grain boundary scattering, but can be significantly enhanced by transferring subsequent layers of CVD graphene. Overall, the research summarized in this dissertation represents a significant advancement in the understanding of the reliability and fundamental physical properties of emerging nanomaterials, which are increasingly finding their way to commercial applications.