Mechanism of the negative linear temperature coefficient of resistance in defective nanocarbon materials

This paper presents the evidential results of the negative linear temperature coefficient mechanism commonly observed in defect-containing nanocarbon materials. Single-walled carbon nanotubes (CNTs) were annealed at high temperatures ranging from 1200 to 3000 °C. These samples exhibited a general hopping conduction-like behavior between the CNTs in the pristine state. However, the high-temperature annealed samples exhibited a resistance change with a negative temperature coefficient. Recently, we proposed that the origin of this negative linear temperature dependence of resistance behavior is a scattering phenomenon due to Friedel oscillations occurring in a flat graphene sheet containing defects. In fact, from the cross-sectional high-resolution transmission electron microscopy images, we found that the tube structure of the CNTs collapsed and fused with each other in the high-temperature annealed samples, revealing a stacked, flat graphite structure. These results show that the Friedel scattering phenomenon originates from the negative linear temperature coefficient widely observed in defect-containing nanocarbon materials. This negative linear temperature coefficient provides important information on the application of nanocarbon materials to thermistors, which have recently attracted significant attention, and on the optimal design guidelines for such thermistors. Moreover, the nonzero current and nondivergent resistance behavior based on the Friedel scattering phenomenon provide more stable measurement conditions for the quantum research field, including quantum computing, cryptography, and communications.