Photo-enhanced field emission study of TiO2 nanotubes array

Aligned TiO(2) nanotubes were synthesized by simple anodization of the Ti foil surface. The as-anodized product is further characterized by SEM, XRD, and PL. The tube inner diameter is found to be ≈ 60-80 nm with the average wall thickness ≈ 30 nm and areal density ≈ 15 × 10(6)/cm(2). FE studies of the aligned TiO(2) nanotubes are carried out at base pressure of ≈ 1 × 10(-8) mbar. The turn-on field observed for an emission current density of ≈ 10 μA/cm(2) is found to be ≈ 1.7V/μm and current density of ≈ 44 μA/cm(2) is obtained at an applied field of ≈ 2.3 V/μm. Photo-enhanced FE study is carried out by shining visible and UV light on the cathode. The aligned TiO(2) nanotubes show sensitivity to both the light sources. The FE current shows fast switching response to the visible light. The increment in the preset current upon UV illumination can be attributed to the band edge excitation of the electrons. The free excitons associated with band gap of the TiO(2) nanotubes array may be responsible for the visible light sensitivity. TiO(2) nanotubes are also grown on the Ti wire and exhibit similar photo-enhanced behavior. The FE and photo-enhanced FE properties demonstrate the applicability of the aligned TiO(2) nanotubes in the FE based micro/nanoelectronic devices.