Femtosecond laser machining: A new technique to fabricate carbon nanotube based emitters

Abstract

A convenient and facile method to fabricate cathodes for efficient field-electron emission, which consists of columns of vertically aligned carbon nanotubes (VACNTs), is presented. The new top-down approach that uses femtosecond laser pulses to make a VACNT-column array starting from a mat of VACNTs is versatile in making diverse cathode architecture because the synthesis and sculpturing processes are completely decoupled. Moreover, this laser-machining process is scalable for the fabrication of large size cathodes. Test of field-electron emission from a typical laser-machined cathode showed a promising result. Emission currents of 0.10 mu A and 0.57 mA were measured at the respective applied fields of 0.76 and 1.47 V/mu m from a cathode that consisted of a 5x5 array of VACNT columns. The total cathode area occupied by the 5x5 VACNT columns was 0.80x0.80 mm(2) while the net area of 25 VACNT columns' top surfaces was 1.00x10(-2) mm(2). The stability of the 5x5 VACNT-column array was proved by the continuous operation at the current level of 0.3 mA for 30 h without catastrophic failure