Fabrication of pyrolyzed carbon nanowire array and its application to field emission

Abstract

The alignment and assembly is essential process to integrate nanowire within nanosystems. One of methods is vertically aligned nanowire fabrication which synthesis and alignment of nanowire are integrated. In this thesis, a novel fabrication method of vertically aligned high aspect ratio carbon nanowire array using a conventional photolithography with a modification and pyrolysis is proposed as a top down approach having the advantage of controlling their position and shape. In chapter 2, high aspect ratio (~30) SU-8 micro/nano tip array whose shape is defined by concentration of intensity of exposed UV by diffraction was fabricated by single UV photolithography on backside and its exposed dose control. The fabrication result of the tip agrees well with the Rayleigh-Sommerfeld solution of the Huygens-Fresnel principle at a wide observation distance. In a very near field below the distance 2㎛ (only several times of wavelength), ‘necking points’ also agree with the solution although it is assumed that the distance is much larger than wavelength. In chapter 3, well aligned pyrolyzed carbon nanowire is fabricated by photolithography and pyrolysis. High aspect ratio SU-8 tip array fabricated in chapter 2 is transformed to carbon structure with shrinkage. Finally, carbon nanowire which width is 300 ㎚and aspect ratio is 6 is obtained by proposed fabrication method. The occasional results shows that the width can be reduced to lower than 50 ㎚ with 2 ㎛ height. The EDX, XRD, and Raman spectroscopy show that the fabricated carbon nanowire is amorphous carbon mixed with sp2 (G-band) and sp3 (D-band) bonding. In chapter 4, pyrolyzed carbon as a field emitter array was investigated. Vertically carbon nanowires is fabricated by photo lithography and pyrolysis developed in previous chapters. The field emission experiment was examined in cryogenic vacuum chamber with tungsten tip as a counter electrode. The turn-on electric field of pyrolyzed carbon nanowires and t...