We report an effective procedure for fabricating carbon microcoils and nanocoils with three-dimensional spiral structures in high yield by nickel (Ni)-catalyzed thermal decomposition of acetylene. The Ni catalyst particles used in this preparation were electrochemically deposited onto tungsten substrates. Springlike coils having low pitch and micrometer-scale diameters and ropelike coils having higher pitch and nanometer-scale diameters were observed. Electrical and optical properties were investigated by employing a field-emission probe system equipped with an optical spectrometer. In an applied field above 1.5 V/μm, significant electron emission was observed from individual ropelike nanocoils. The approximately linear slope of the corresponding Fowler-Nordheim plot denotes predominately field-emission behavior. During measurement, individual carbon coils aligned themselves along the electric field, exhibiting a natural resonance on some occasions. As the field strength increased above 2.5 V/μm, the emission-current density for a single nanocoil was measured to be on the order of 104 A/cm2. This high-current density caused Joule heating, resulting in strong photon emission by incandescence.
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