Heat dissipation in current carrying multiwalled carbon nanotubes

Abstract

Understanding thermal transport is of great interest in combatting the excess heat generated in current electronic circuits. In this dissertation we provide insight and progress in thermal transport in current carrying MWCNT. Chapter 1 gives an overview of the work presented in this dissertation, quickly discusses the motivation for studying heat dissipation in current carrying carbon nanotubes, and outlines the key findings. The chapter outlines the unique remote heating phenomena observed in Joule heated MWCNTs, as well as, the process in which the research led to the discovery of a detection method for near-field heat transfer. The physical properties of carbon nanotubes are discussed in Chapter 2 and the relevant heat transfer mechanisms are introduced. Chapter 3 outlines some of the previous experimental work in studying thermal properties of nanotubes. The results presented in this dissertation rely on previously measured thermal conductivity and thermal contact resistance for nanotubes and thus a discussion of these results is critical. The fabrication process for the measured devices is presenter in Chapter 4. In addition, chapter 4 provides a detailed discussion of the measurement technique employed to probe the thermal properties of the devices presented in Chapter 5 and 6. Chapter 5 discusses the findings in regard to heat dissipation for a current carrying MWCNT supported on a SiN substrate. The results provide definitive proof of substrate heating via hot electrons; a process which can not be explained using traditional Joule heating model and requires the presence of an additional remote heating mechanism. Analysis of the results indicate a reduction in remote Joule heating which led to a series of controlled experiments presented in Chapter 6 in an effort to study substrate thermal conductivity, kSiN, variations as a function of voltage. In this chapter we outline the experimental and simulated results which indicate the remarkable ability of our technique to detect near-field thermal radiation. The enhanced thermal transport via near-field radiation is of great interest for scientific and engineering purposes but its detection has proven difficult. This thesis provides evidence of the sensitivity of the electron thermal microscopy technique to measure near-field radiation.