| Effect of Annealing Temperature on Excitonic Binding
Energy and Other Optical Properties of Mn-Ni Co-Doped
Transparent ZnO Thin Films
|
Shital Prasad,a, b Sonia Bansal,a
Amir Mansoori,c
Manju Balad
and Preeti Sharmad,*
Pages : 31-39
DOI : 10.1080/0371750X.2022.2160376 |
| Abstract |
| In this work, low cost sol-gel spin coating technique was successfully employed to
deposit Mn-Ni co-doped ZnO (MNZO) thin films on glass substrates. Structural,
topographical and optical properties of MNZO thin films were studied in the light of
XRD spectra, Raman spectroscopy, SEM, AFM, UV-visible spectroscopy and
photoluminescence spectroscopy. XRD study revealed that all annealed ZnO thin films
have hexagonal wurtzite structure with (002) preferred orientation along c-axis.
Hexagonal wurtzite structure for all films has been confirmed by Raman spectra which
show ELow and EHigh optical phonon modes. Grain size, micropores and RMS surface
roughness showed an increasing trend with the rise in annealing temperature as
revealed by SEM and AFM images. The experimental data of absorption coefficient
was analysed in the light of hydrogenic excitonic model to estimate excitonic binding
energy (R) and other optical parameters of the prepared thin films. The excitonic
binding energy decreased from 71.55 to 49.2 meV on increasing annealing temperature
from 200o
to 500oC. Peaks corresponding to UV, violet, green, yellow and orange were
clearly observed in photoluminescence spectra for all annealed thin films. The
ultraviolet peak shifted towards lower wavelength (blue-shifted) as the annealing
temperature was increased. All the peaks in visible region were attributed to transition
between complex intrinsic and extrinsic defects. Such films can be a potential
candidate for efficient lasers and LEDs and for variety of optoelectronic device
applications.
[Keywords: ZnO thin film, Urbach energy, Photoluminescence, Raman spectroscopy,
Hydrogenic excitonic model] |
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