Concentration
Dependent Structural, Morphological and Optoelectronic Properties of
Sprayed Cadmium Based Transparent Conducting Oxide by Av Moholkar in BJSTR
Abstract
The effect of precursor concentration on the physico-chemical
properties of cadmium oxide (CdO] thin films deposited using simple and
effective chemical spray pyrolysis technique (SPTJ is studied for the
first time. The X-ray diffraction study shows polycrystalline, face
centered cubic structure of CdO films. Field emission scanning electron
micrographs and cross-sectional images of CdO thin films shows that
morphology of films changes from rough to smooth and thickness of the
films increases from 794 nm to 1523 nm, as cadmium content increased in
spraying solution. X-ray photoelectron spectroscopy confirms presence of
4d, 4s, 3d5/2, 3d3/2, 3p3/2, 3p1/2
fine structural states of cadmium and 1s fine structure state of
oxygen. The optical study shows that the direct band gap energy values
decreases from 2.58 to 2.42 eV with increase in precursor concentration
which is attributed to B-M effect. The Hall Effect measurement indicates
that all the films exhibit n-type semiconducting behavior, the
electrical resistivity decreases from 34.5 x 10-4 to 2.7 x 10-4 Ωcm for 0.025M to 0.1 M solution concentration and further increase to 12.5 x 10-4
Ωcm for 0.125 M concentration. The CdO thin film deposited with 0.1 M
precursor concentration exhibits the best optoelectronics properties
amongst the all other CdO films. It shows transmittance of 74 %, high
figure of merit of 25.3 x 10-3 (Ω)-1, carrier concentration of 5.87 x 1020 /cm3 and mobility of 40 cm2/Vs.
Photoluminescence spectra of CdO thin film gives two significant
photoemission peaks at 434 and 539.80 nm (green) when they are excited
at 400 nm wavelengths
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