Effect of electron-phonon interaction and valence band edge shift for carrier-type reversal in layered ZnS/rGO nanocomposites.

ABSTRACT

The artificial stacking of nanohybrid films helps to enhance their properties and thus intrigues researchers to explore this possibility in emerging technologies. The layer-by-layer approach was used to fabricate samples of zinc sulfide/reduced graphene oxide (ZnS/rGO) by using spin coating technique. The structure and optoelectronic properties has been extensively studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-VIS-NIR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Hall measurements. Raman spectrum elucidates the phonon contribution of ZnS and breathing mode of κ-point phonons and sp2 bonds of carbon atoms of rGO. The electron-phonon interactions reveal reduction in electron mobility and enhancement in holes contribution with rGO content leading to surface charge transfer doping (SCTD). XPS results explain the valence band edge and conduction band edge to form type-I band alignment to reconfirm carrier-type reversal. A change in the dispersion of refractive indices along with a small rise in the value of absorption coefficient in terahertz (THz) region for ZnS/rGO nanocomposite films has been observed. These results will open up new opportunities to furthering the science of this technologically important class of materials for future electronics.