Thermal dissipation and variability in electrical breakdown of carbon nanotube devices

We study high-field electrical breakdown and heat dissipation from carbon nanotube (CNT) devices on SiO₂ 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 SiO₂ surface roughness (∼d/Δ). Comparison of diffuse mismatch modeling and data reveals the upper limit of thermal coupling ∼0.4 W K^-1 m^-1 per unit CNT length at room temperature, (130 MW K^-1 m^-2 per unit area), and ∼0.7 W K^-1 m^-1 at 600°C for the largest diameter (∼ 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.