An original way to obtain porous Zn(1–x)MgxO thin films by spray pyrolysis technique

Zn (1-x) Mg x O thin films with various concentrations of magnesium were deposited using the spray pyrolysis method.The transmittance spectra recorded for all films exhibit maxima exceeding 90%.The band gap energy of the films with wurtzite structure increases from 3.22 up to 3.60 eV by incorporating Mg into ZnO.However, when the atomic ratio of Mg exceeded 0.4, a second crystalline phase (assigned to cubic MgO) became discernable in XRD patterns, a compressive strain was observed in the wurtzite lattice, and crystallite sizes decreased significantly.In accordance with these observations, finer grains with a pronounced columnar growth were observed in 3D AFM representations and the surface roughness decreases significantly.Finally, selective etching in water yields to porous films with a great surface-to-volume ratio, a lower refractive index and a better light transmission.These porous films with tunable band gap seem to be excellent candidates to various interesting applications.