In Situ Resistance Measurements of Strained Carbon Nanotubes

Since the advent of atomic force microscopy, mechanical resonators have been used to study a wide variety of phenomena, such as the dynamics of individual electron spins, persistent currents in normal metal rings, and the Casimir force. Key to these experiments is the ability to measure weak forces. Here, we report on force sensing experiments with a sensitivity of 12 zN Hz^(-1/2) at a temperature of 1.2 K using a resonator made of a carbon nanotube. An ultra-sensitive method...

The nonlinear mechanical response of carbon nanotubes, referred to as their "buckling" behavior, is a major topic in the nanotube research community. Buckling means a deformation process in which a large strain beyond a threshold causes an abrupt change in the strain energy vs. deformation profile. Thus far, much effort has been devoted to analysis of the buckling of nanotubes under various loading conditions: compression, bending, torsion, and their certain combinations. Suc...

A mechanically bistable single-walled carbon nanotube can act as a variable-shaped capacitor with a voltage-controlled transition between collapsed and inflated states. This external control parameter provides a means to tune the system so that collapsed and inflated states are degenerate, at which point the tube's susceptibility to diverse external stimuli-- temperature, voltage, trapped atoms -- diverges following a universal curve, yielding an exceptionally sensitive senso...

The mechanical stability of open single wall carbon nanotubes (SWCNT) under axial stress (compression and tension) and twist has been re-examined in a search of specific tube-length and load scaling. SWCNT with different chiralities and lengths have been simulated with a classical molecular dynamics method employing the many-body empirical Tersoff-Brenner potential. Stress has been achieved by enforcing constant linear velocity on the edge atoms from both sides of the SWCNT a...

Brittle fracture is one of the important failure modes of Single-Walled Carbon Nanotube (SWNT) due to mechanical loading. In this paper, the fracture resistance of zigzag SWNTs with preexisting defects is calculated using fracture mechanics concepts based on atomistic simulations. The problem of unstable crack growth at finite temperature, presumably caused by lattice trapping effect, is circumvented by computing the strain energy release rate through a series of displacement...

We report electrical transport experiments using the phenomenon of electrical breakdown to perform thermometry that probe the thermal properties of individual multi-walled nanotubes. Our results show that nanotubes can readily conduct heat by ballistic phonon propagation, reaching a quantum-mechanical limit to thermal conductance. We determine the thermal conductance quantum, the ultimate limit to thermal conductance for a single phonon channel, and find good agreement with t...

We investigate the piezoresistive effect of carbon nanotubes (CNTs) within density functional theory (DFT) aiming at application-relevant CNTs. CNTs are excellent candidates for the usage in nano-electromechanical sensors (NEMS) due to their small band gap at zero strain leading to a finite resistivity at room temperature. The application of strain induces a band gap-opening leading to a tremendous change in the resistivity. DFT with the LDA approximation yields reasonable re...

The intrinsic mechanical strength of single-walled carbon nanotubes (SWNTs) within the diameter range of 0.3-0.8 nm has been studied based on ab initio density functional theory calculations. In contrast to predicting "smaller is stronger and more elastic" in nanomaterials, the strength of the SWNTs is significantly reduced when decreasing the tube diameter. The results obtained show that the Young`s modulus E significantly reduced in the ultra-small SWNTs with the diameter l...

The failure stresses and strains of nanotubes given by theoretical or numerical predictions are much higher than observed in experiments. We show that defects can explain part of this discrepancy: for an n-atom defect with 2<=n<=8, the range of failure stresses for a molecular mechanics calculation is found to be 36GPa to 64GPa. This compares quite well with upper end of the experimental failure stresses, 11GPa to 63GPa. The computed failure strains are 4% to 8%, whereas the ...

Atomic Force Microscopy (AFM) allows to probe matter at atomic scale by measuring the perturbation of a nanomechanical oscillator induced by near-field interaction forces. The quest to improve sensitivity and resolution of AFM has forced the introduction of a new class of resonators with dimensions well below the micrometer scale. In this context, nanotube resonators are the ultimate mechanical oscillators because of their one dimensional nature, small mass and almost perfect...