Nano encoders based on vertical arrays of individual carbon nanotubes

Linear encoders for nanoscale position sensing based on vertical arrays of individual carbon nanotubes are presented. Vertical arrays of single multi-walled carbon nanotubes (MWNTs) are realized using a combination of electron beam lithography (EBL) and plasma-enhanced chemical vapour deposition growth. EBL is used to define 50- to 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 μm are realized. Field emission properties of the array are investigated inside a scanning electron microscope equipped with a 3-d.o.f. 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.