Electron emission from randomly-oriented and vertically-aligned carbon nanotubes synthesized directly on conducting surface*

Field emission properties of carbon nanotubes (CNTs) have been intensively studied for various applications. It is desirable to synthesize CNTs directly on conducting substrates to develop field emission displays capable of operating at low voltages and at room temperature. As compared to the randomly-oriented CNTs, vertically-aligned CNTs demonstrate improved field emission properties with greater electric field enhancement and lower turn-on/threshold electric fields. In this work, we compare the electron emission between randomly-oriented and vertically-aligned CNT emitters synthesized directly on stainless steel substrates. The surface morphology of these CNTs has been studied with electron microscopy and the defects are analyzed by the Raman spectroscopy. The vertical alignment of the CNT emitters benefits the emission process by reducing the screening effect and by streamlining the path of ejected electrons directly onto the anode.