  Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films
on amorphous and conducting glass substrates. The doped amount of Cu in ZnO was
varied up to 5% in atomic percentage. Speed of spin coating system, coating
time, initial chemical solution and annealing conditions were varied to
optimize the properties of samples. Transmittance of samples was measured for
ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive
index were derived from the measured transmittance. Film thickness of each film
was calculated using the graphs of refractive index versus wavelength. Film
thickness varies in a random manner depending on the amount of ZnO or Cu doped
ZnO solutions spread on the substrate. The energy gap of each film was
calculated using the graph of square of absorption coefficient time photon
energy versus photon energy. The calculated energy gap values of Cu doped ZnO
film samples decrease with the Cu concentration in ZnO. This means that the
conductivity of ZnO can be increased by adding a trace amount of conducting
material such as Cu.
