Thermal dissipation and variability in electrical breakdown of carbon nanotube devices

Abstract

We study high-field electrical breakdown and heat dissipation from carbon nanotube (CNT) devices on ${\text{SiO}}_{2}$ substrates. The thermal ``footprint'' of a CNT caused by van der Waals interactions with the substrate is revealed through molecular dynamics simulations. Experiments and modeling find the CNT-substrate thermal coupling scales proportionally with CNT diameter and inversely with ${\text{SiO}}_{2}$ surface roughness $(\ensuremath{\sim}d/\ensuremath{\Delta})$. Comparison of diffuse mismatch modeling and data reveals the upper limit of thermal coupling $\ensuremath{\sim}0.4\text{ }\text{W}\text{ }{\text{K}}^{\ensuremath{-}1}\text{ }{\text{m}}^{\ensuremath{-}1}$ per unit CNT length at room temperature, ($130\text{ }\text{MW}\text{ }{\text{K}}^{\ensuremath{-}1}\text{ }{\text{m}}^{\ensuremath{-}2}$ per unit area), and $\ensuremath{\sim}0.7\text{ }\text{W}\text{ }{\text{K}}^{\ensuremath{-}1}\text{ }{\text{m}}^{\ensuremath{-}1}$ at $600\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ for the largest diameter ($\ensuremath{\sim}$3.2 nm) CNTs. We also find semiconducting CNTs can break down prematurely and display more variability due to dynamic shifts in threshold voltage, which metallic CNTs are immune to; this poses a fundamental challenge for selective electrical breakdowns in CNT electronics.