Controlled deposition of nanotubes on opposing electrodes

Abstract

We report a method of depositing individual 'templated carbon nanotubes' (T-CNTs) on opposing electrodes so that they are suspended across 100 mu m deep trenches, and in separate experiments across low profile (70 nm thick) opposing electrodes. The geometry of the electrodes with deep trenches was chosen to be essentially identical to that in a micro-electromechanical system (MEMS) testing stage used for mechanical loading of nanostructures. An electric field was used to attract the T-CNTs dispersed in a solvent and critical point drying was employed to protect them from breaking or deforming. The real-time potential change in the circuit was monitored as a means of characterizing the deposition of an individual T-CNT across this deep trench. For the case of sequential deposition on electrodes that are 70 nm above the substrate surface, a method was developed for counting the number of sequentially deposited T-CNTs. Simultaneous video recording of the deposition of T-CNTs confirmed the measured real-time potential changes for both cases. It was found that the resistance of the circuit changed as each new T-CNT was deposited for the sequential deposition; up to five T-CNTs were sequentially detected. This approach allows for controlled deposition of one-dimensional nanostructures for their potential use in NEMS devices, and may be useful for large-scale integration.