Electronic property enhancement of zinc oxide by surface decoration with carbon nanotubes: experimental and theoretical studies

Abstract

Experimental and theoretical investigations are performed to study the electronic property enhancement of zinc oxide (ZnO) thin films when their surfaces are decorated with carbon nanotubes (CNTs). Sample preparations have been achieved using the spray pyrolysis method to obtain ZnO (0001) surfaces decorated with carbon nanotubes. Atomic force microscopy and scanning electron microscopy studies allow for the elucidation of surface roughness and morphology. In the current–voltage (I–V) curves, conductivity has improved as induced by surface decoration of ZnO with CNTs. When the thin films are irradiated with visible light, they present an increased current from 3.8 to 100 nA, but when irradiated with UV light, a greater increase from 4.5 to 100 nA is observed. To explain these experimental measurements, first-principles total energy calculations have been performed to determine the electronic properties of the ZnO (0001) surface decorated with carbon nanotubes. Results indicate that the density of states of the ZnO (0001) surface is modified when carbon nanotubes are adsorbed. Electron states emerge at proximities of the Fermi level as a consequence of the nanotube presence. This may help to explain the current increase in the sample as decorated by the carbon nanotubes.