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Influence of Cerium (Ce) Doping on the Optical Properties of Silver
Telluride (Ag
2
Te) Thin Films Deposited by Electrodeposition
Method.
Okafor Lois Ugomma
1*
, Okafor Anthony Amaechi
2
, Abonyi Sylvester Emeka
3
1
Department of Physics and industrial physics, Nnamdi Azikiwe University, Awka Anambra State,
Nigeria
2
Department of Mechanical Engineering, Nnamdi Azikiwe University, Awka AnambraState, Nigeria
3
Department of Electrical Engineering, Nnamdi Azikiwe University, Awka Anambra State, Nigeria
*
Corresponding Author
DOI:
https://doi.org/10.51583/IJLTEMAS.2026.150600246
Received: 12 July 2026; Accepted: 17 July 2026; Published: 01 August 2026
ABSTRACT
In this investigation, Silver telluride (Ag
2
Te) thin films have been successfully deposited onto FTO glass
substrate using electro deposition method to investigate the influence of Ce doping on optical properties of Ag
2
Te
films. Silver trioxonitrate (V) and tellurium (iv) oxide were the precursors used for silver and tellurium ions.
Depositions of films made from cerium-doped silver telluride were conducted at room temperature. The
percentages concentration of cerium dopant used in this investigation are 2.5%, 5.0%, 7.5% and10.0%. The
optical properties of the thin films were characterized using Uv-Vis spectrometry. Absorbance results confirm
that increasing Ce concentration significantly increases the absorbance of Ag
2
T films across the UV, VIS, and
NIR regions. The 10.0% Ce-doped sample demonstrates the highest absorbance across all regions, with values
of 43.36% at 365 nm, 42.68% at 400 nm, 34.00% at 700 nm, and 35.16% at 1100 nm, indicating the strong
influence of cerium in enhancing light absorption. This trend reflects that as Ce concentration increases,
absorbance improves significantly in all spectral regions, suggesting that Ce doping introduces additional
localized states that facilitate electronic transitions, thereby enhancing the films' optical properties. The
transmittance of Ag
2
Te and Ce-doped Ag
2
Te films decreases notably with increasing cerium concentration
across the UV, VIS, and NIR regions. This decline in transmittance with increasing Ce concentration is consistent
with the corresponding increase in absorbance suggesting that Ce doping enhances light absorption, thus
reducing the amount of light transmitted through the films. Cerium doping enhances reflectance slightly,
particularly in the NIR regions, likely due to increased surface roughness and scattering effects introduced by
Ce incorporation. The extinction coefficient (k) of silver telluride and cerium-doped silver telluride films
generally increases with wavelength, indicating higher optical absorption at longer wavelengths. Other optical
results were also presented.
Keywords: Silver Telluride, optical properties, Electrodeposition. Cerium doping Spectrophotometer
INTRODUCTION
Silver telluride (Ag
2
Te) is a chalcogenide semiconductor composed of silver (Ag) and tellurium (Te), belonging
to group iv-vi compounds on the periodic table [1] which exhibit semiconductor properties. In bulk form, it
crystallizes in a monoclinic at room temperature and undergoes a phase transition to a cubic
at elevated temperatures, approximately 423k [2], with associated changes in electrical behavior. Ag
2
Te
exhibits n-type conductivity and has been studied for magneto resistance and thermo electric applications [2].
Nanostructured forms of silver telluride, such as quantum dots or nanorods , show enhanced properties due to
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quantum confinement effects, including increased band gaps and strong photoluminescence within infrared
range, which differs greatly from bulk materials [3]. These nanostructures are synthesized by different methods
such as hydrothermal processes or chemical deposition, using precursors such as AgNO
3
and TeCl
4
[4]. Recently,
Ag
2
Te quantum dots have emerged as heavy metal-free alternatives to traditional chalcogenide nano materials,
giving tunable optoelectronic properties for near-infrared (NR) and shortwave infrared (SWIR) photodetectors
with competitive responsivity and detectivity [3]. Besides optoelectronics, the compound finds application in
non linear optical devices, ion-selective electrodes, electrochemical storage cells, solar cells and biological
sensors, stating its versatility in energy, environmental and sensing technologies [2]. Reports from literature [6,
7, 8, 9] showed no information on the influence of dopant concentration on the optical properties of cerium
doped silver telluride films. The purpose of this research is to address the literature gap by investigating the
influence of concentration of cerium doping on the optical properties of silver telluride films synthesized via
electrodeposition. Specifically, we aim to elucidate how different dopant concentration influences the optical
properties of electrodeposited Ag
2
Te films.
Experimental
Reagents
Reagents used for electrodeposition of cerium doped silver telluride
were; Silver trioxonitrate (V):
used as precursor for silver ion., Cerium tetraoxosulphate (VI) tetrahydrate: used as precursor for cerium ion
(dopant ion), Tellurium (IV) oxide: used as precursor for tellurium ion, ethylene diamine tetra acetic acid
(EDTA): used as a complexing agent, distilled water was used as solvent.
Apparatus
The experimental arrangement shown in section 4, Figure 1 [5] illustrates the setup for electrodeposition,
comprising the electrolyte, power supply unit, and electrodes. It adopts a three-electrode configuration for
depositing thin films onto conducting substrates. The conducting substrate, specifically FTO, was used as the
cathode or working electrode. A platinum electrode functioned as the anode or counter electrode, while a
silver/silver chloride (Ag/AgCl) electrode served as the reference electrode. The energy supply for the
electrodeposition setup is provided by a Dazheng digital DC-power supply unit, specifically the PS-1502A
model. Two digital multimeters, the DT9201A CE and the highly sensitive Mastech: MY60 were employed for
measuring voltage and current, respectively. The Mastech: MY60 multimeter is capable of measuring currents
within the range of
A.
Material preparation
Molar solutions of the reagents prepared for the deposition include:
Silver trioxonitrate (V)
Silver trioxonitrate (V) is an inorganic compound with chemical formula AgNO
3
. It is a versatile precursor to
many other silver compounds. It is a colorless salt with molar mass of 169.87 g/mol. About 256 g of the salt is
soluble in 100 mL at 25 °C. In this work, silver trioxonitrate (V) served as precursor for Ag ion and various
concentrations (0.10 M and 0.01 M) of silver trioxonitrate (V) was prepared by dissolving particular amount of
the compound in 100 ml of distilled water.
Cerium tetraoxosulphate (VI) tetrahydrate
Cerium (IV) tetraoxosulphatetetrahydrate, also called ceric sulfate, is an inorganic compound with chemical
formula (Ce (SO
4
)
2
. 4H
2
O). The salt is a yellow solids that are moderately soluble in water and dilute acids.
Solutions of ceric sulfate have a strong yellow color. It has a molar mass of 404.30 g/mol. In this work, 0.01 M
of the salt was prepared by dissolving 0.40 g in 100 mlof distilled water
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Tellurium (IV) oxide
Tellurium (IV) oxide, also known as tellurium dioxide (TeO
2
) is a white crystalline solid with molecular weight
of 159.60 g/mol and it is negligible soluble in water. Tellurium (IV) oxide served as precursor for tellurium ion.
In this work, 0.20 mole solution of TeO
2
was prepared by dissolving 7.98 g in 250 ml of distilled water.
Diluted tetraoxosulphate (VI) acid solution
H
2
SO
4
has a molar mass of 98.079 g/mol. 1.0 M of H
2
SO
4
was prepared by adding 55.60 ml of 96 % concentrated
H
2
SO
4
to 1000 ml of distilled water. The 55.60 ml of H
2
SO
4
was obtained by using the percentage concentration
of the H
2
SO
4
(96%), molar mass of H
2
SO
4
(98.079 g/mol) and specific density of (1.84 g/ml). The diluted H
2
SO
4
served as pH adjuster
Substrate pre-treatment
Prior to electrodeposition of the films, the FTO substrates were subjected to distinct pre – treatment to ensure
the presence of catalytic surface to improve the adhesion of the films to the substrates most especially when
there is possibility of increase in film thickness as deposition proceeds. This pre – treatment of FTO glass
substrates was achieved through the following six steps;
(i) We cleaned the FTO glass substrates with detergents.
(ii) We soaked the substrates in acetone for 10 minutes for degreasing.
(iii) We ultrasonicated the substrates for 20 minutes in an ultrasonic bath using ethanol as a solvent.
(iv) We ultrasonicated the substrates for 10 minutes in an ultrasonic bath using distilled as a solvent.
(v) We rinsed the substrates twice with distilled water.
(vi) We dried the substrates in an electronic oven for 10 minutes at a temperature of about 100.
Electrodeposition
Figure 1: Schematic diagram of the electrodeposition experimental set – up [5]
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Depositions of thin films made from cerium-doped silver chalcogenide ( Ce:Ag
2
Te) were conducted at room
temperature. Molar concentration bath parameter of the cerium precursor was adjusted to optimize their impact
on the optical characteristics of these films.
Electrodeposition of silver telluride and cerium doped silver telluride
thin films
For electrodeposition of silver telluride thin film on FTO substrate, aqueous electrolytic bath composed of 20ml
of 0.10 M of silver trioxonitrate (V) and 5 ml of 1.0 M of H
2
SO
4
were poured into the electrolytic bath. The
mixture was stirred for 5 minutes. This was followed by addition of 15 ml of 0.1 M of tellurium (IV) oxide
solution to the mixture. This followed with another stirring for 5 minutes. After stirring, the three electrodes
were immersed into the bath containing the electrolytic solution and 2 volts was allowed to pass through the
setup for 15 seconds. After the allowed time, grey film of Ag
2
Te was found to be deposited on the conductive
surface of the FTO substrate. The deposited Ag
2
Te thin film was heat-treated at 100 for 10 minute to remove
water and improve the crystallinity of the deposited thin films. The mechanism of the formation of silver telluride
and cerium doped silver telluride is shown in equation (1) and (2).
1
Optimization of Ce ion concentration for
thin films
For the deposition of Ce doped Ag
2
Te thin films, 0.05 M of cerium (IV) tetraoxo sulphate tetrahydrate was used
as dopant source. Similar procedure used for deposition of silver telluride thin film was adopted but with addition
of different volume concentrations of 0.05 M of cerium (IV) tetraoxosulphate tetra hydrate as shown in Table 1.
Four samples with different dopant volume concentrations of 1 ml, 2 ml, 3 ml and 4 ml were fabricated.
2
Table 1: Bath parameter for deposition of Ag
2
Te and Ce doped Ag
2
Te thin films
0.10 M of
AgNO
3
0.10 M of
TeO
2
0.05 M of CeSO
4
·4H
2
O
1.0 M of H
2
SO
4
Applied Voltage
Time
Vol. (ml)
Vol. (ml)
Vol. (ml)
Vol. (ml)
(volts)
(sec.)
20.00
15.00
-
5.00
2.00
15
20.00
15.00
1.00
5.00
2.00
15
20.00
15.00
2.00
5.00
2.00
15
20.00
15.00
3.00
5.00
2.00
15
20.00
15.00
4.00
5.00
2.00
15
Characterization of deposited thin films
The fabricated thin films were characterized to determine their optical properties using spectrophotom
eter, Thickness measurements of the films were carried out using gravimetric method
Film thickness measurement
The deposited film thicknesses (t) were evaluated using the gravimetric method given by [10]; [11]; [12].
3
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In equation (3), is the mass of the film. A is the surface area of the deposited film and is the bulk density
of the material film. The masses of the deposited films were obtained by finding the difference in mass between
the mass of the glass substrate with the film after deposited and the mass of glass substrate before deposition.
These differences in mass of the films were measured using analytical weighing balance with sensitivity of
0.0001 g.
Bulk density of Ag
2
Te is 8.32 g/cm
3
. Bulk density of cerium is 8.16 g/cm
3
. Because of small amount of cerium
impurity used and possibility of cerium ions to substitute silver in the crystal structure, density of Ce:Ag
2
Te was
approximated to bulk density of Ag
2
Te.
Optical characterization
The optical absorbance of the films deposited was obtained using spectrophotometer (model: 756S UV – VIS)
at Nano Research Laboratory, Department of Physics and Astronomy, University of Nigeria Nsukka, Enugu
State, Nigeria. Other optical properties of the films such as transmittance, reflectance, refractive index, extinction
coefficient, real dielectric constant, imaginary dielectric constant and energy band gap were evaluated using the
formulae below;
Transmittance of the film was evaluated using equation (4) given by [13; 14]
4
Reflectance was obtained using the expression in equation (5) as given by [15; 16].
5
The absorption coefficient
was calculated from the transmittance values using the equation (6) as given by
[17; 18; 19].
6
Where is the thickness of the film obtained using equation (3) above.
Extinction coefficient was obtained using equation (7) as given by [20; 21; 22].
7
Refractive indices of the films were calculated using equation (8) as given by [23;24; 25].
8
Optical conductivity was estimated using equation (9) as given by [26].
9
Where c is the speed of light.
The energy band gap was estimated using Tauc’s model of equation (10) as given by [ 20]
10 Where
is a constant, for direct band gap. The energy band gaps of the films were obtained by extrapolating
the straight portion of the plot of
against the photon energy
at
.
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RESULTS AND DISCUSSIONS
Optical Properties of Ag
2
Te and cerium doped Ag
2
Te thin films
Variation of optical properties Ag
2
Te with percentage concentration of cerium dopant
400 500 600 700 800 900 1000 1100
0
10
20
30
40
50
60
Absorbance (%)
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 2: Plot of absorbance against wavelength for silver telluride and cerium doped silver telluride thin
films deposited at different concentration of cerium ion precursor
As shown in Figure 2, the absorbance of Ag
2
Te and Ce-doped Ag
2
Te thin films varies significantly across the
UV, VIS, and NIR regions, with notable differences among the samples. For pure Ag
2
Te, the absorbance starts
at 18.85% at 365 nm, slightly increases to 18.92% at 400 nm, and continues to decline to 15.22% at 700 nm and
14.45% at 1100 nm, indicating a gradual reduction in photon absorption as wavelength increases. With 2.5% Ce
doping, absorbance increases to 26.04% at 365 nm, 25.92% at 400 nm, 21.47% at 700 nm, and 21.62% at 1100
nm, showing enhanced absorption compared to pure Ag
2
Te, particularly in the UV and VIS regions. The 5.0%
Ce-doped sample exhibits further improvement, with absorbance reaching 30.52% at 365 nm, 30.12% at 400
nm, 25.46% at 700 nm, and 26.88% at 1100 nm, highlighting the effect of increased Ce concentration on optical
activity. At 7.5% Ce doping, absorbance rises to 38.73% at 365 nm, 38.33% at 400 nm, 34.04% at 700 nm, and
31.87% at 1100 nm, showing a substantial increase, especially in the VIS and NIR regions. The 10.0% Ce-doped
sample demonstrates the highest absorbance across all regions, with values of 43.36% at 365 nm, 42.68% at 400
nm, 34.00% at 700 nm, and 35.16% at 1100 nm, indicating the strong influence of cerium in enhancing light
absorption. This trend reflects that as Ce concentration increases, absorbance improves significantly in all
spectral regions, suggesting that Ce doping introduces additional localized states that facilitate electronic
transitions, thereby enhancing the films' optical properties.
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400 500 600 700 800 900 1000 1100
0
10
20
30
40
50
60
70
80
Transmittance (%)
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 3: Plot of transmittance against wavelength for silver telluride and cerium doped silver telluride
thin films deposited at different concentration of cerium ion precursor
As illustrated in Figure 3, the transmittance of Ag
2
Te and Ce-doped Ag
2
Te thin films decreases notably with
increasing cerium concentration across the UV, VIS, and NIR regions. For pure Ag
2
Te, the transmittance is
highest, starting at 64.79% at 365 nm, slightly decreasing to 64.69% at 400 nm, and increasing to 70.44% at 700
nm and 71.69% at 1100 nm which indicate higher transparency in the longer wavelength regions. When doped
with 2.5% Ce, the transmittance drops to 54.90% at 365 nm, 55.05% at 400 nm, 61.00% at 700 nm, and 60.79%
at 1100 nm, reflecting reduced transparency compared to pure Ag
2
Te. At 5.0% Ce doping, transmittance further
decreases to 49.52% at 365 nm, 49.97% at 400 nm, 56.93% at 700 nm, and 53.38% at 1100 nm. This trend
continues with 7.5% Ce doping, where transmittance values are 40.99% at 365 nm, 41.37% at 400 nm, 48.93%
at 700 nm, and 44.00% at 1100 nm, showing significant reduction, especially in the NIR region. The 10.0% Ce-
doped sample exhibits the lowest transmittance across all wavelengths, with 36.85% at 365 nm, 37.43% at 400
nm, 45.71% at 700 nm, and 44.51% at 1100 nm. This decline in transmittance with increasing Ce concentration
is consistent with the corresponding increase in absorbance suggesting that Ce doping enhances light absorption,
thus reducing the amount of light transmitted through the films.
As shown in Figure 4, the reflectance of Ag
2
Te and Ce-doped Ag
2
Te thin films varies moderately with both
wavelength and cerium concentration. For pure Ag
2
Te, the reflectance decreases slightly from 16.39% at 365
nm to 16.25% at 400 nm, then reduces further to 14.34% at 700 nm and 13.86% at 1100 nm, indicating lower
reflection at longer wavelengths. Upon doping with 2.5% Ce, reflectance increases to 19.06% at 365 nm, 19.03%
at 400 nm, 17.53% at 700 nm, and 17.59% at 1100 nm, showing an overall increase compared to pure Ag
2
Te.
With 5.0% Ce doping, the reflectance values are 19.96% at 365 nm, 19.90% at 400 nm, 18.60% at 700 nm, and
18.73% at 1100 nm, indicating a slight rise across the spectrum. For the 7.5% Ce-doped film, reflectance
continues to increase, reaching 20.28% at 365 nm, 20.30% at 400 nm, 20.03% at 700 nm, and 20.12% at 1100
nm. At the highest doping level of 10.0% Ce, reflectance stabilizes around 19.79% at 365 nm, 19.89% at 400
nm, 20.29% at 700 nm, and 20.34% at 1100 nm. This trend suggests that cerium doping enhances reflectance
slightly, particularly in the NIR regions, likely due to increased surface roughness and scattering effects
introduced by Ce incorporation.
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400 500 600 700 800 900 1000 1100
10
12
14
16
18
20
Reflectance (%)
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 4: Plot of reflectance against wavelength for silver telluride and cerium doped silver telluride thin
films deposited at different concentration of cerium ion precursor
400 500 600 700 800 900 1000 1100
0
1
2
3
4
5
6
Extinction coefficient x 10
-1
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 5: Plot of extinction coefficient against wavelength for silver telluride and cerium doped silver
telluride thin films deposited at different concentration of cerium ion precursor
The extinction coefficient commonly denoted as k in the context of optics and electromagnetism is a measure of
how strongly a material absorbs light at a given wavelength. The extinction coefficient (k) of silver telluride and
cerium-doped silver telluride thin films, as shown in Figure 5, generally increases with wavelength, indicating
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higher optical absorption at longer wavelengths. For pure Ag
2
Te, k increases from 2.16×
at 365 nm to
4.99×
at 1100 nm, showing a strong wavelength-dependent absorption. At 2.5% cerium doping, k starts
lower at 1.72×
but rises to 4.30×
at 1100 nm, suggesting reduced absorption at shorter wavelengths
but a comparable response at higher wavelengths. Similarly, the 5.0% doped film exhibits a lower extinction
coefficient of 1.73×
at 365 nm, which increases to 4.26×
at 1100 nm. The 7.5% doped sample
follows a slightly different trend, starting at 2.17×
at 365 nm and reaching a peak of 5.37×
at 1100
nm, the highest among the samples, indicating enhanced light absorption in the infrared region. The 10.0% doped
film shows an intermediate response with k values of 2.04×
at 365 nm and 4.99×
at 1100 nm, similar
to pure Ag
2
Te. The trend suggests that doping influences optical absorption by modifying carrier concentration
and defect states. The lower extinction coefficient at shorter wavelengths for doped films indicates improved
transparency in the UV region.
400 500 600 700 800 900 1000 1100
1.8
2.0
2.2
2.4
2.6
2.8
Refractive Index
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 6: Plot of refractive index against wavelength for silver telluride and cerium doped silver telluride
thin films deposited at different concentration of cerium ion precursor
Cerium doping significantly increases the refractive index of silver telluride thin films across all wavelengths,
with higher doping concentrations resulting in progressively higher values, as shown in Figure 6. Pure Ag
2
Te
exhibits a decreasing refractive index from 2.33 in the UV region to 2.15 in the visible region and 2.03 in the
NIR region, while doped films maintain higher values. At 2.5% cerium doping, the refractive index is 2.53 in
the UV, 2.40 in the visible, and 2.35 in the NIR, while at 5.0% doping, it is 2.60 in the UV, 2.58 in the visible,
and 2.43 in the NIR. For 7.5% doping, the refractive index values are 2.61, 2.57, and 2.52 in the UV, visible,
and NIR regions, respectively, whereas at the highest doping level of 10.0%, the values reach 2.58, 2.60, and
2.58. The reduced wavelength dependence of the refractive index in doped films suggests improved optical
uniformity and minimized free carrier absorption. Higher refractive indices enhance light confinement, making
these films suitable for optical coatings and photonic applications.
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1.0 1.5 2.0 2.5 3.0 3.5
0.0
0.1
0.2
E
g
= 1.85 eV
(ahv)
2
x 10
15
(eV/m)
2
Photon Energy (eV)
Ag
2
Te
1.0 1.5 2.0 2.5 3.0 3.5
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
(ahv)
2
x 10
15
(eV/m)
2
Photon Energy (eV)
Ce: 2.5%
E
g
= 1.80 eV
1.0 1.5 2.0 2.5 3.0 3.5
0.0
0.1
0.2
0.3
E
g
= 1.80 eV
E
g
= 1.80 eV
E
g
= 1.80 eV
(ahv)
2
x 10
15
(eV/m)
2
Photon Energy (eV)
Ce: 5.0%
1.0 1.5 2.0 2.5 3.0 3.5
0.0
0.1
0.2
0.3
0.4
(ahv)
2
x 10
15
(eV/m)
2
Photon Energy (eV)
Ce: 7.5%
1.0 1.5 2.0 2.5 3.0 3.5
0.0
0.1
0.2
0.3
0.4
0.5
(ahv)
2
x 10
15
(eV/m)
2
Photon Energy (eV)
Ce: 10.0%
Figure 7: Plot of
against photon energy for silver telluride and cerium doped silver telluride thin
films deposited at different concentration of cerium ion precursor
Figure 7 shows the plot of
against photon energy for silver telluride and cerium doped silver telluride
thin films deposited at different concentration of cerium ion precursor. The energy band gap (
) of silver
telluride and cerium-doped silver telluride thin films decreases slightly with cerium doping. Pure Ag
2
Te has the
highest band gap of 1.85 eV, indicating a wider energy range required for electron excitation. With cerium
doping at 2.5%, the band gap reduces to 1.80 eV, showing a shift towards lower energy levels, which remains
consistent for higher doping levels of 5.0%, 7.5%, and 10.0%, all exhibiting an
of 1.80 eV. This reduction
suggests that cerium incorporation introduces localized states within the band structure, enhancing light
absorption in lower energy regions. The narrowing of the band gap in doped films improves optical absorption
in the visible and near-infrared regions, making them more efficient for optoelectronic applications. A lower
band gap generally enhances the material’s photoconductivity, making cerium-doped films suitable for
photodetector and solar cell applications. The nearly constant
at higher doping levels suggests a saturation
effect, where additional cerium does not significantly alter the electronic band structure. Overall, the controlled
tuning of the band gap with cerium doping makes these films promising for applications requiring specific optical
absorption properties.
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400 500 600 700 800 900 1000 1100
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
Real Dielectric Constant
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 8: Plot of real dielectric constant against wavelength for silver telluride and cerium doped silver
telluride thin films deposited at different concentration of cerium ion precursor
The real dielectric constant (
) of silver telluride and cerium-doped silver telluride thin films, as shown in Figure
8, increases with cerium doping and decreases with increasing wavelength. Pure Ag
2
Te exhibits a dielectric
constant of 5.40 at 365 nm, which gradually declines to 3.86 at 1100 nm, indicating reduced polarization response
at longer wavelengths. Cerium doping significantly enhances
with the 2.5% doped sample showing values of
6.40 at 365 nm and 5.34 at 1100 nm. Higher doping levels of 5.0%, 7.5%, and 10.0% further increase
, reaching
maximum values of 6.74, 6.80, and 6.64 at 365 nm, respectively. The higher dielectric constant in doped films
suggests increased charge carrier density and stronger optical interaction. The observed trend of increasing
with decrease in wavelength aligns with the behavior of refractive index, reinforcing the correlation between
optical dispersion and dielectric response. The stabilization of
at higher doping concentrations indicates a
saturation effect in polarization enhancement. A higher dielectric constant improves optical confinement, making
these films suitable for applications in photonic and optoelectronic devices.
400 500 600 700 800 900 1000 1100
0.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
Imaginary Dielectric Constant
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 9: Plot of imaginary dielectric against wavelength for silver telluride and cerium doped silver
telluride thin films deposited at different concentration of cerium ion precursor
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INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
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The imaginary dielectric constant (
) of silver telluride and cerium-doped silver telluride thin films, as shown
in Figure 9, increases with wavelength, indicating enhanced optical losses at longer wavelengths. For pure
Ag
2
Te,
increases from 1.01 at 365 nm to 2.02 at 1100 nm, reflecting stronger absorption in the infrared region.
At 2.5% cerium doping,
is lower at 0.87 at 365 nm but reaches 2.02 at 1100 nm, suggesting reduced absorption
in the UV but similar losses in the infrared. The 5.0% doped sample follows a similar trend, with
increasing
from 0.90 at 365 nm to 2.08 at 1100 nm. The 7.5% doped film exhibits the highest absorption enhancement, with
values of 1.13 at 365 nm and 2.67 at 1100 nm, indicating significant influence of cerium doping on absorption
behavior. The 10.0% doped sample shows
values of 1.06 at 365 nm and 2.52 at 1100 nm, slightly lower than
the 7.5% sample but still higher than undoped Ag
2
Te. The increased
at longer wavelengths for doped films
suggests enhanced free carrier absorption due to doping-induced charge carriers. The tunability of
with doping
concentration makes these films suitable for optoelectronic applications where controlled absorption is essential.
400 500 600 700 800 900 1000 1100
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
s
0
x 10
14
s
-1
Wavelength (nm)
Ag
2
Te
Ce: 2.5%
Ce: 5.0%
Ce: 7.5%
Ce: 10.0%
Figure 10: Plot of optical conductivity against wavelength for cerium doped silver telluride thin films
deposited at different concentration of cerium ion precursor
The optical conductivity (
) of silver telluride and cerium-doped silver telluride thin films, as shown in Figure
10, decreases with increasing wavelength, indicating a decline in charge carrier excitation at longer wavelengths.
For pure Ag
2
Te,
is 4.14 × 10
14
s⁻¹ at 365 nm and reduces to 2.76 × 10
14
s⁻¹ at 1100 nm, showing significant
optical response in the UV region. At 2.5% cerium doping,
starts at 3.58 × 10
14
s⁻¹ at 365 nm and slightly
decreases to 2.76 × 10
14
s⁻¹ at 1100 nm, indicating reduced conductivity compared to pure Ag₂Te. The 5.0%
doped sample follows a similar trend, with values of 3.71 × 10
14
s⁻¹ at 365 nm and 2.83 × 10
14
s⁻¹ at 1100 nm,
suggesting a minor improvement in charge transport. The 7.5% doped film exhibits the highest conductivity
enhancement, with
increasing to 4.66 × 10
14
s⁻¹ at 365 nm and maintaining a higher value of 4.65 × 10
14
s⁻¹
at 1100 nm, demonstrating significant doping influence. The 10.0% doped sample shows
values of 4.34 ×
10
14
s⁻¹ at 365 nm and 4.21 × 10
14
s⁻¹ at 1100 nm, slightly lower than the 7.5% sample but still higher than
undoped Ag
2
Te. The higher optical conductivity in doped films, particularly at 7.5%, suggests enhanced free
carrier generation due to cerium incorporation. The declining trend with wavelength indicates that the films are
more optically active in the UV-visible region. The improved conductivity at higher doping levels enhances the
potential of these materials for optoelectronic applications, such as photodetectors and transparent conductive
coatings
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INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
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ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XV, Issue VI, June 2026
CONCLUSION
Thin films of silver telluride (Ag
2
Te), and cerium-doped silver telluride (Ce: Ag
2
Te) were successfully deposited
on fluorine-doped tin oxide (FTO) glass substrates using the electrodeposition technique. The precursors used
for the deposition included aqueous solutions of silver trioxonitrate (V), cerium tetraoxosulphate (VI)
tetrahydrate, and tellurium (IV) oxide, which served as sources of Ag, Ce, and Te, respectively. Ethylene diamine
tetra acetic acid (EDTA) was employed as a complexing agent, while tetraoxosulphate (VI) acid was used to
adjust the pH of the electrolyte bath. Cerium ions were incorporated as dopants into Ag
2
Te matrices. Deposition
parameter such as dopant concentration (0–10%),was systematically optimized to study their effects on the film
optical properties.
Optical characterization using UV-Vis-NIR spectroscopy showed that absorbance improved significantly with
cerium doping. For example, absorbance at 365 nm increased from 33.46% to 39.35% in Ag
2
Te. Corresponding
transmittance values decreased, indicating enhanced optical density. Reflectance increased slightly, reaching a
maximum of approximately 20.3%. Extinction coefficients ranged between 1.26 × 10⁻¹ and 1.83 × 10⁻¹, while
refractive indices varied from 2.42 to 2.63. Dielectric constants (real and imaginary), optical conductivity, and
other derived optical functions also showed enhancements with doping. The optical band gaps narrowed with
increasing cerium content from 1.61 to 1.34 eV in Ag
2
Te, indicating improved light absorption in the visible to
near-infrared region.
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