We investigated a carbon nanotube (CNT) oscillator controlled by the thermal gas expansion using classical molecular
dynamics simulations. When the temperature rapidly increased, the force on the CNT oscillator induced by the thermal
gas expansion rapidly increased and pushed out the CNT oscillator. As the CNT oscillator extruded from the outer
nanotube, the suction force on the CNT oscillator increased by the excess van der Waals <i>vdW</i> energy. When the CNT
oscillator reached at the maximum extrusion point, the CNT oscillator was encapsulated into the outer nanotube by the
suction force. Therefore, the CNT oscillator could be oscillated by both the gas expansion and the excess <i>vdW</i> interaction.
As the temperature increased, the amplitude of the CNT oscillator increased. At the high temperatures, the CNT
oscillator escaped from the outer nanotube, because the force on the CNT oscillator due to the thermal gas expansion was
higher than the suction force due to the excess <i>vdW</i> energy. By the appropriate temperature controls, such as the
maximum temperature, the heating rate, and the cooling rate, the CNT oscillator could be operated.
The coupled oscillation of multi-walled CNT oscillators consisting of (5n,5n) CNTs was investigated by molecular
dynamics simulations. The oscillation feature of the CNT oscillators can not be described by a continuum theory. All
walls of the multi-walled CNT are oscillated due to the interwall coupling. The frequencies of the multi-walled CNT oscillators are higher than those of the double-walled CNT oscillators. In spire of the different core CNT, the frequency peaks due to the interwall coupling are similar to each other as the number of walls increases. This reason is that the interwall coupling effects increase as the number of walls increases.
We investigated a linear carbon nanotube motor serving as the key building block for nanoscale motion control by
using molecular dynamics simulations. This linear nanomotor, is based on the electrostatically telescoping multi-walled
carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback
sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency.
The temperature is very important factor to operate this nanomotor.
We propose a novel carbon-nanotube (CNT)-based nonvolatile memory, which can serve as a key building block for
molecular-scale computers and perform molecular dynamics simulations to investigate the dynamic operation of a
double-walled CNT memory. We find that the most important physical characteristics of the proposed nanometer-scale
memory device are the bi-stability achieved by using the CNT inter-wall van der Waals interaction, the CNT-metal
binding energies and the reversibility caused by the electrostatic attractive forces. Since the CNT shuttle can have a high
kinetic energy during the transition, the dynamical collisions between the CNT and the metal electrodes are very
important factors to be considered for design of an electrostatically telescoping CNT memory. The long collision time
and the several rebounds cause a delay in the state transition.
A nanoelectromechanical model based on atomistic simulations including charge transfer was investigated. Classical molecular dynamics method combined with continuum electric models could be applied to a carbon-nanotube nanoelectromechanical memory device that could be characterized by carbon-nanotube bending performance by
atomistic capacitive and interatomic forces. The capacitance of the carbon atom was changed with the height of the carbon atom. We performed MD simulations for a suspended (5,5) carbon-nanotube-bridge with the length of 11.567 nm (<i>L<sub>CNT</sub></i>) and the depth of the trench of 0.9 ~ 1.5 nm (<i>H</i>). After the carbon-nanotube collided on the gold surface, the carbon-nanotube-bridge oscillated on the gold surface with amplitude of ~1 Å, and the amplitude gradually decreased. When <i>H</i> ≤ 1.3 nm, the carbon-nanotube-bridge continually contacted with the gold surface after the first collision. When <i>H</i> ≥ 1.4 nm, the carbon-nanotube-bridge stably contacted with the gold surface after several rebounds. As <i>H</i> increased, the threshold voltage linearly increased. As the applied bias increased, the transition time exponentially decreased at each trench depth. When <i>H</i> / <i>L<sub>CNT</sub></i> was below 0.13, the carbon-nanotube nanoelectromechanical memories were permanent nonvolatile memory devices, whereas the carbon-nanotube nanoelectromechanical memories were volatile memory or switching devices when <i>H / L<sub>CNT</sub></i> was above 0.14. The turn-on voltages and tunneling resistances obtained from our simulations are compatible to those obtained from previous experimental and theoretical results.