Single nanotube array based nano encoders

Linear encoders for nanoscale position sensing based on single carbon nanotube (CNT) arrays are presented. 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. Electron beam lithography is used to define 50-150 nm nickel catalyst dots at precise locations on a silicon chip. Precise control of the position, density and alignment of the tubes has been achieved. Aligned nanotube arrays with spacing varying from 250 nm to 25 /spl mu/m are realized. Field emission properties of the array are investigated inside a scanning electron microscope (SEM) equipped with a 3-DOF nanorobotic manipulator with nanometer resolution functioning as a scanning anode. With this scanning anode and the single MWNT array, a nano encoder is investigated experimentally. 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.