Fabrication and Characterization of NEMS-Based Single Nanotube Emitter Arrays

Abstract

Arrays of individual carbon nanotube (CNT) emitters for nanoelectromechanical systems (NEMS) are constructed and characterized. Vertically aligned single multi-walled carbon nanotubes (MWNTs) are realized using a combination of e-beam lithography and plasma-enhanced chemical vapour deposition (PECVD) growth. Field emission properties of the arrays are investigated inside a scanning electron microscope (SEM) using scanning anode field emission microscopy (SAFEM) realized from a scanning anode actuated by a 3-DOF nanorobotic manipulator with sub-nanometer resolution. With the SA-FEM and the arrays of single MWNTs, a linear nano encoder is proposed. Vertical position is detected by the change in emission current, whereas the horizontal position of the scanning anode is sensed from the emission distribution. A resolution of 98.3 nm in the vertical direction and 38.0 nm (best: 12.9 nm) in the lateral direction has been achieved. Failure mechanisms of the emitters are systematically investigated in theory and experiment. Failure modes include opening, shortening, breaking, eradicating, and telescoping, which can be identified/monitored with I-V curves and Fowler-Nordheim plots of field emission. Controlled “failures” can find applications in length modification of individual tubes in an array. As an example, selective eradication for fabricating a patterned emitter array is demonstrated. Such techniques will in turn enable applications in NEMS such as field emission based sensor and actuator arrays, nanoelectronics such as wiring or in situ construction of functional elements.