Abstract:
Copper oxide (CuO) thin films are deposited onto glass substrates at various substrate
temperatures (Ts) 300, 350, 370 and 400 °C by spray pyrolysis technique (SPT).Zinc
doped copper oxide (CuO: Zn)thin films are deposited at the Ts of 350 °C with various
concentrations of Zn, varied from 1 to 6 at%. The effect ofTs and Zn doping on
structure, morphology, optical and electrical properties ofCuO andCuO: Zn thin films
has been investigated in the present work. In field emission scanning electron
microscope images, nanoparticles are observed around the nucleation center. Energy
dispersive X-ray analysis reveals thatCuO andCuO: Zn thin films are stoichiometric
and typically comprised of Cu, O and Zn. X-ray diffraction analysis ofCuO andCuO:
Zn thin films indicates that the thin films have monoclinic structure with the preferred
orientation along (1 1 1) plane. Maximum value of crystallite size is found about
28.24 nm for 5 at% CuO: Zn thin film. UV-Vis-NIR spectroscopic investigation
shows thatCuO andCuO: Zn thin films are highly transparent in NIR region. The
maximum transmittance is about 87% for CuO thin films deposited at Ts= 350 °C
with 5 at% of Zn concentration.The direct band gap ofCuOthin films are found to be
from 1.81 to 2.64 eV. The direct band gapCuO: Zn thin films are found to be from
2.50 to 2.88eV.Refractive index ofCuO varies between 1.33 and 2.60 and that of CuO:
Zn thin films varies between 1.19 and 2.62. Dielectric constant of CuO thin films
decreases with increasing Ts up to 350 °C and that of CuO: Zn decreases with Zn
concentration up to 5 at%. The highest optical conductivity is found for 5 at% CuO:
Zn thin filmprepared at Ts = 350 °C. The lowest electrical resistivity at room
temperature is about1.51x103 ohm-m for 5 at% CuO: Zn thin films prepared at Ts =
350 °C. For CuO thin films the activation energy (ΔE) decreases as the Ts
increases.The value of ΔE is varied from 0.12 to 0.26 eV for CuO thin films.In lower
temperature region, Zn concentration has no significant effect on ΔE for CuO: Zn thin
films. In higher temperature region, ΔE decreases at 2 at% Zn concentration and then
it is increased slowly with increasing Zn concentrations. The value of ΔE varies from
0.06 to 0.39 eV for CuO: Zn thin films in both lower and highertemperature regions.
