The synthesis of vertically oriented carbon nanosheet–carbon nanotube hybrid films and their excellent field emission properties

Vertically oriented carbon nanosheet (VCNS)–carbon nanotube (CNT) hybrid films with a large area (∼4 cm2) were fabricated on Mo layers by using microwave plasma-assisted chemical vapor deposition technique. The Mo layers, which were deposited on Al2O3 ceramic substrates through electron beam evaporation deposition, were pretreated by a laser-grooving technology (4 lines/mm). The films were characterized by scanning electron microscopy, Raman spectroscopy and field emission I–V measurements. A pure VCNS film was found in the laser-etched area, while in the un-etched area a hybrid film of VCNS–CNT was formed. The growth mechanisms of the films were discussed. Effects of laser-grooving pretreatment on surface morphologies and microstructure of the hybrid films were investigated. Field electron emission results showed a turn on field as low as 1.0 V/μm and a high current density of 3.2 mA/cm2 at an electric field of 5.8 V/μm. The low threshold field and high emission current density were attributed primarily to the unique shape and small resistivity of the films.