Nanoelectromechanical carbon nanotube memory analysis

We have performed static and dynamic analyses of nanoelectromechanical (NEM) carbon nanotube (CNT) memory devices called nanotube random access memory (NRAM). In static analyses, the current–voltage (I–V) curves showed the hysteresis characteristics. For CNT, diameters (Dcnt) were below 2 nm, turn-on voltages almost linearly increased with the increasing of the depth (H) of the trench for the separation between the suspended CNT and the gate surface. As Dcnt increased above 2 nm, turn-on and turn-off voltages nonlinearly increased with the increasing of H. For Dcnt ⩾2 nm, as H increased, the ranges of the hysteresis regions in the I–V curves decreased. Nonvolatility of the NRAMs could be increased by small Dcnt and small H. Dcnt, the suspended length (Lcnt), and H of the CNT should be carefully considered to operate NRAMs as the nonvolatile memory devices. Structural conditions for the nonvolatile NRAMs were summarized by Dcnt:H:Lcnt=1–2:5–15:100. Dynamic analyses showed that CNTs with small diameters were effective to operate the NRAMs with low turn-on voltages and high throughput rates. Although the static analyses of the NRAMs showed the nonvolatility, the dynamic analyses of the NRAMs did not show the nonvolatility because of the thermal fluctuation and the CNT–gate binding energy when the magnitudes of the turn-off voltage were less then 0.2 V.