Enhanced field emission from chemically synthesized cadmium sulphide-polyaniline (CdS-PANI) nanotube composite

Cadmium sulphide-polyaniline (CdS-PANI) nanotube composite was synthesized in two steps. Simple chemical oxidative polymerization has been used to synthesize PANI nanotubes in the first step, which are used further to form nanocomposite with CdS nanoparticles in the second step. The structural, optical and chemical properties of the CdS-PANI nanotube composite are revealed using XRD, UV-visible TEM, EDAX, FTIR, and PL spectroscopy. The TEM image shows that the PANI nanotubes with cavity diameter ~ 10-20 nm are decorated with CdS nanoparticles of size 5-10 nm. The XRD spectrum indicates formation of hcp phase of CdS, which is supported by the SAED pattern obtained during the TEM analysis. The UV-visible, FTIR and PL spectra confirm formation of conducting state of PANI. The field electron emission (FE) studies carried out at base pressure of ~ 1×10^-8 torr exhibit low turn on field of ~ 0.6 V/μm, corresponding to emission current of 1 nA and emission current density of 5.5 mA/cm² has been at an applied field of 3.8 V/μm. The lower value of the turn on field is attributed to the nanometric dimensions of the PANI nanotubes as well CdS nanoparticles. The emission current is observed to be stable over long duration, around 7h. The low value of turn on field, ability to deliver very high current density at moderate applied field, and good stability of emission current propose the CdS-PANI nanotube composite as a promising material for field emission based devices.