Uddhao N. Ingle1,
Milind S. Kale2
1Depatment of Electronics,
Smt. G.G. Khadse College ,Muktainagar Dist. Jalgaon
2Department of Electronics,
D.N.C.V.P.S. Shirish MadhukarraoChaudhari College, Jalgaon
Corresponding Author: uddhaoingle@gmail.com
ABSTRACT:
Cu
doped ZnTethinfilmswere depositedontoglasssubstratesby using thermal
evaporation technique. The structure analysis of the film was performed by XRD
technique. The surface morphological analysis was carried out by using optical
microscope. The optical band gap were calculated by UV-VIS spectrometry
analysis. The XRD revels that, the thin films arepolycrystalline in nature. The
crystal structure is found to be hexagonal shape. The microscopic images revels
that films are homogenous and particles are uniformly deposited on the substrate.
Optical band gap, was calculated from the absorption spectra is situated in the
range of 2eV.
Keywords:Cu
doped ZnTeThinfilms, XRD, UV-VIS.
1. INTRODUCTION
The II-VI compound group semiconductor
materials isanimportantsemiconductormaterialbecause of its extensive potentials
applicationsforthe development ofvariousmodern technologies of solid-state
devices like blue light emitting diodes, laser diodes, solar cells, microwave
devices, etc. ZnTe is one of the interesting materialsfor potential
photovoltaic applications in different opto-electronics devices such asphotodiodes,
solar cells, and LED[1-4]. The ZnTecan be used as awindow material in solar
cells. In addition, it reduces the toxic nature of CdS thin films in currentlydevelopedthin
film solar cells[5].
A variety of methods have been developed
for the preparation of Cu doped ZnTethin films such as physical vapor
deposition under vacuum, molecular beam epitaxy, CBD, Sillar, Chemical vapor
deposition, Solution growth, spraypyrolysis, molecular beam epitaxyetc [2, 6, 7].
In this paper, structural, morphological
and optical properties of Cu doped ZnTe thin film grown by thermal evaporation
technique, are investigate.
2. EXPERIMENTAL
First of all, the Cu doped ZnTe powder
were prepared by using Cu(NO3)2,ZnCl2 and
Telluride (Te) metal powder by reflux method in chemical synthesis technique. After chemical
synthesis process, filter the precipitateand washed the solid with distilled
water and ethanol to remove byproducts and un-reacted materials. Finally, dry
the powder under IR lamp for 2-3 hours .Then black or gray precipitate was
formed which indicate the formation of ZnTe:Cu powder. Then the prepared powder
compound of ZnTe:Cuwas used for the deposition and were placed in a Mo boat by
using Thermal Evaporation Technique .
The prepared powder compound of Cu doped ZnTewas used for
the deposition.
During the deposition, the pressure was keepabout
10−5 torr. The substrate tosource distance was keeping about 13 cm.
The samples of differentthicknesses were deposit under similar conditions.
Thethickness of the films was monitored by quartz crystal digital thickness
monitor (Model No. DTM-101), provided by Hind-Hi Vac. The deposition rate was
maintained 5 - 10 Ã…/sec throughoutsample preparation.
Before thermal evaporation, the glass
substrateswere clean thoroughly using detergent, chromic acid,isopropyl
alcohol, pure distilled water and finally acetone.
3. RESULTSAND DISCUSSION
3.1.X-raydiffraction (XRD) Analysis:
To study the structural properties, the
grown samplewas characterized by XRD technique. The XRD patterns of grown Cu
doped ZnTethin film having thickness of 1000 Ã… is shownin figure 1.
Figure
1: The XRD patterns of Cu doped ZnTethin film.
The XRD patterns shows the samples is polycrystalline
with orthorhombic crystal structure.The 2θ peak observed at 24.8°, 33.5°, 47.35°,
49.5° and 65°exhibit the formation ofthe hexagonal structurephase of Cu doped
Zn Te which correspond to the(0 1 10), (1 411), (022),(202) and (041) planes of
reflections. Thepresence of number of peaks indicates that the films
arepolycrystalline in nature. The values of lattice parameters are found a =
5.379, b = 5.9471 and c = 5.01. The crystal size was calculated by Scherrer
equitation.
Crystallite
size = (0.94 x λ) / (β x CosΘ)
Where, λ =wavelength of incident X-Ray,β = Full width at
half maxima in radian andΘ =
Bragg angle/diffracted angle. The crystal size was found to be 346.60.
3.2.Morphological Analysis:
The surface morphological properties, the
grown sample was observed under optical microscope. The figure 2 shows the optical microscopic
image of grown Cu doped ZnTethin film having thickness of 1000 Ã….
Figure
2:Optical microscopic images of Cu doped ZnTethin film.
From the micrograph images, it is
observed that thefilm is uniform. The nano size grainswere uniformly
distributed over smooth homogeneousbackground and well cover on substrate. The sample
is free from any microscopy defect like cracks or peeling. Similarly it is
observed that the particles forms the cluster with random shape.
3.3.UV-VIS Analysis:
To study the optical properties were
studied with UV-VIS spectrometry. The figure 3 shows the optical properties of
grown Cu doped ZnTe thin film having thickness of 1000 Ã….
The optical absorption spectra were
obtain in 350nm to 900 nm wavelength range by employing a Shimadzu2450
UV-Visible model of the spectrophotometer. According to absorbance and
transmittance it is found that the film has high absorbance. The optical band
gap of these films has been calculatedusing the relation (Tauc 1974).
αhν =
A (hν – Eg)n
where, hν is the photon energy, α is the absorption coefficient,Eg the band gap, A is
constant and, n = 0.5 for direct bandgap material and n = 2 for indirect band
gap material.
Figure
3: Optical properties of grown Cu doped ZnTe thin film
Figure
4: Band gap of grown Cu doped ZnTe Thin Film.
The plot of (αhν)2 versus hν for
Cu doped ZnTe films is presented in Fig. 4.Thestraight line portion is
extrapolated to cut the x-axis, whichgives the energy gap. This figure clearly
shows the the optical band gap is 2 eV [8],which is in good agreement for solar
cell and other optical devices.Hence, the Cu doped ZnTe, can be used in development
of efficient photovoltaic application.
Conclusions
The study of Cu doped ZnTe thin films
deposited by vacuum thermal evaporation technique revealed the sample is a
polycrystalline structure. The grown sample is homogenous and free from any
defects. The optical band gap is 2 eV allowing it toefficiently capture
high-energy. Materials with this band gap has enhanced stability and
high-performance, due to which is in good agreement for solar cell
manufacturing.
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