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Materials Research Express
ACCEPTED MANUSCRIPT
Novel optical Properties of CdS:Zn Rocksalt system (A theoretical study)
To cite this article before publication: Junaid Iqbal Khan et al 2017 Mater. Res. Express in press https://doi.org/10.1088/2053-1591/aa93c4
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Page 1 of 15
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Novel Optical Properties of CdS:Zn Rocksalt system (A theoretical study)
M. Junaid Iqbal Khan*, M. Nauman Usmani*, Zarfishan Kanwal*
Laboratory of theoretical and experimental physics, Department of Physics, Bahauddin Zakariya
University, Multan, Pakistan. (60800)
.
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*
Email: drjunaid.iqbalkhan@bzu.edu.pk
Tel: +923006889132
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Abstract
In present computational study, we focus on optical properties of Zn doped CdS for 1x1x2 and
2x2x2 supercell configurations. Cd atoms are substituted with Zn atoms and results for optical
properties demonstrate different trends due to interaction of Zn with S atoms. The study has been
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performed by PBE-GGA approach using Wien2K within framework of DFT. TDOS and PDOS
represent that S-3p states are responsible for conduction. For large supercell configuration, a
tremendous change in optical properties has been observed due to different bonding. Optical
absorption tends to increase in visible range which supports candidacy of Zn doped CdS for
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enhanced optoelectronic and nanotechnology applications.
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Keywords: Cadmium Sulfide, Zn-doping, Density of States, DFT calculations, Optical
Properties
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1. Introduction
Semiconductors with large band gap belonging to II-VI class carry large mandate due to its
potential applications in field of light applications including solar cells, X-ray detection, light
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probe, photovoltaic and optoelectronic devices. Research based on experimental and theoretical
study revealed a technological thrust in this field of study. Cadmium Sulfide (CdS) is II-VI
semiconductor with appreciable applications in field of light or energy applications. It is an ntype semiconductor with direct band gap and is very important in technological sense due to its
applications in much electronic instrumentation. It is window material for heterojunction solar
cells. Few of its applications are in field of non-linear optics [1], thin film transistors [2], photo
voltaic cells [3], photoelectrochemical solar cells [4] and gas detectors [5]. Nonlinear optical,
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electroluminescent displays photoconductors, biosensing devices are other extending
applications of CdS which make its uses for fabrication.
Zinc blend, Wurtzite and rocksalt structures are natural structural forms of CdS. Zinc blend and
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Wurtzite structures are both polymorphous and found energetically degenerate. The first one
structure is a face centered cubic (fcc) lattice with diatomic basis while second one is
symmetrically hexagonal with four atomic basis and is more stable. Wurtzite structures exist in
bulk and nanocrystallite forms while rocksalt structures (cubic) are observable in nanocrystallite
form. Also rocksalt phase is observed under high pressure roughly above 2.5-3.5 GPa [6].
Nanocyrstalline study of CdS is significant in predicting electronic properties by both theoretical
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and experimental methods. Doping CdS with certain dopants may enhance its optical, electronic,
magnetic, electrical and piezoelectric properties [7, 8]. Currently numerous studies have been
conducted in order to investigate the optical, electronic and related properties by using
experimental and theoretical methods [9-11]. Due to astonishing and reasonable properties of
CdS involving low cost, efficiency and enhanced optoelectronic properties, this material is still a
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matter of subject for theoretical and experimental physicists.
While investigating the physical properties of doped CdS, numerous studies have been carried
out experimentally [12-14] but a few research remarks have been presented theoretically [15, 16]
which support experimental predictions. Doping CdS with transition metals [14, 17-19] have
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Page 2 of 15
been a subject of study since years but theoretical studies are not very much encouraging by
certain simulation packages within the framework of Density Functional theory (DFT) [20-22].
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Experimental study on doping CdS with Zinc (Zn) exhibited that Zn enhances its optical
properties considerably. Zinc is worthy element among transition metals with ionic radius 0.074
nm while for Cd is 0.097 nm which is much smaller than Cd+2 and henceforth Zn+2 can easily
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penetrate in lattice or crystal of CdS upon substitution [23]. Agbo et al. have studied the effect of
concentrations of Zn doped CdS and reported its structural analysis with conclusion that optical
properties are enhanced [13]. Foaad et al. in 2013 have studied the effect of zinc on structural
and optical properties with interpretations that blue shift occurs in absorption edge with increase
in Zn contents [24]. In [25], Anbarasi et al. have reported experimental study of Zn doped CdS
including structural, morphological, optical and electrical properties by spray technique. Their
findings nominate CdS:Zn as a best candidate for optoelectronic devices and supports its
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candidacy as window material in photovoltaic energy cells. Lakshmy et al. [26] have focused
research on CdS thin films by chemical bath deposition and pointed that change in optical
properties related to absorption and transmittance depends on concentrations and pH value. F.
Yang et al have studied Zn doped CdS nanostructures prepared by hydrothermal synthesis and
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reported results including XRD, SEM, XPS and absorption with noticeable remarks that Zn
contents in CdS bring an appreciable change in optical properties [27]. Moreover their
experimental findings also match with the theoretical DFT study by VASP while considering
wurtzite structure of CdS as reported in same study. Their study directs the high oxidative ability
of CdS and shows enhanced photocatalytic activity with stability under visible light. Theoretical
studies based on Wien2K package particularly with rocksalt structure of CdS are not yet done in
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this context and hence does not provide any situational background with experimental analysis.
2. Computational Method
Natural occurrence of CdS is in different forms which are prescribed with various structure
constants but for current DFT calculations, we have chosen rocksalt structure. In this connection,
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we selected two supercells with
and
configurations in order to observe a
possible change in optical properties. For both supercell configurations, we calculated partial
density of states (PDOS), total density of states (TDOS) and optical properties using DFT
simulations. The entire calculations have been calculated by varying two supercell configurations
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AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
at Zn concentrations of 6.25 % and 1.56%. The computational approach is accomplished within
the framework of Wien2K code. We simulated supercell symmetrically with space group Fm-3m
AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
. Various optical properties including optical absorption, reflectivity,
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and
conductivity, dielectric constant, extinction coefficient and index of refraction have been
calculated. Computationally, we employed PBE-GGA (Perdew, Burke and Ernzerhof,
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Generalized Gradient approximation) scheme for exchange correlation potentials. Atomic
position relaxations were carried out using self-consistency criterion involving minimum charge
and energy convergence at
and
respectively. All calculations for both supercell
configurations are performed for 1000 k-point using Monkhorst-pack [28] scheme. Several
interesting and unprecedented properties are explored in present study which emphasize that Zn
doping may enhance optoelectronic properties.
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3. Results and Discussion
3.1 Density of States
CdS is a semiconductor having interesting applications in recent technological advancements.
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Doped CdS may stretch attention in nanomaterials applications because of the reason that
dopants may adjust physical, optical and chemical properties which in turn dictate it a material
suitable for nano and micro applications. CdS when doped with Zn exhibits surprising results as
it may enhance its optical properties which explore its astonishing applications in electronics,
energy and optoelectronic devices. Details of PDOS and TDOS analysis exhibit that resulting
properties of CdS:Zn appear due to hybridization of host and transition metal orbitals. In
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addition, the most contributing orbitals of Zn dopant are s and p while for sulfur it is p-orbital.
In current DFT study, we present PDOS of pure and Zn doped CdS (rocksalt structure) illustrated
in Fig. 1(a), which are related to fact involving declaration of those states which participate in
hybridization. The states are more pronounced in case of
supercell configuration. A
comparison is also made between undoped and Zn doped CdS (for 1x1x2 and 2x2x2 supercell)
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which may explain how optical properties change during doping and by increasing supercell size.
PDOS of pure CdS depicts the contributions of Cd-s orbitals in conduction band and those of S-p
orbitals in both conduction and valence bands. This signifies the dominant role of p orbitals of
sulfur in CdS as obvious from plots of TDOS (fig. 1(b)). However, energy peak at about -4.9 eV
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related to d-orbitals of Cd can also contribute to conduction to improve conductivity. As clear
from fig. 1(a), transitions of electrons from valence to conduction band evidently take place.
Page 5 of 15
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Density of states (DOS) explains the role of dopant (Zn) which may provide sufficient number of
conduction holes adjacent to the Fermi surface. So variations in doping concentrations and
substitutional positions may affect intraband transitions which may create a considerable impact
(a)
EF
9
s
------ p
7
-1
-15
-10
-5
0
5
0.4
0.3
0.2
0.1
0.0
10
s
------ p
------ d
(b )
8
T D O (Se V )
PDOS (Arbitrary Units)
0.4
0.3
0.2
0.1
0.0
6
5
4
3
2
1
-10
-5
0
Energy (eV)
5
10
0
-1 5
E
F
TD O S C d
TD O S S
-1 0
-5
0
E n e rg y (e V )
5
10
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on optical and related properties.
Fig. 1(a) Plot for PDOS and 1(b) Plot for TDOS of pure CdS.
Moreover there is creation of localized states in band gap region due to addition of impurity
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atoms. This results in shift of band gap energy upon adding Zn concentration. From PDOS and
TDOS plots (figs. 2 & 3) for Zn-doped CdS, it is observed that contribution of various orbitals to
DOS in valence band involves three regions where density of states is somewhere maximum
with wide and narrow distributions. First peak lies in energy range between -12.6 to -11.6 eV due
to Zn d-states and S s-states with considerable impact of Cd d-states. The second peak observed
in range -8.1 to -6.0 eV includes contributions of Zn d-states, S p-states with dominant role of Cd
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d-states. The third peak which is quite wide, ranges between -5.04 to -0.01 eV in valence band
depicting key role of S p-states and least impact of Zn and Cd s-states. All such states may
contribute to conduction process to enhance conductivity of Zn-doped CdS system. On other
side, conduction band demonstrates contributions of states mainly from Cd s-states, S p-states
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and Zn s-states (orbitals). However in case of 2x2x2 supercell configuration, region adjacent to
conduction band is more extending (-5.89 to -0.25 eV) and sulfur is more dominant as in case of
1x1x2 supercell. Moreover, there is creation of localized states in region between conduction and
valence band caused by impurity (Zn) addition.
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EF
____Zn-s
____ Zn-p
____ Zn-d
0.2
0.0
0.8-15
-10
-5
0
5
10
____S-s
------ S-p
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0.8-15
-10
-5
0
5
0.6
0.4
10
____Cd-s
____Cd-p
____Cd-d
0.2
(b)
0.4
CdS: Zn (2x2x2)
0.2
0.0
0.8-15
____ Zn-s
EF
0.6
-10
-5
pt
PDOS (Arbitrary Units)
0.4
0.8
(a)
CdS: Zn (1x1x2)
____
____
0
Zn-p
Zn-d
5
10
____ S-s
____ S-p
0.6
0.4
0.2
0.0
0.8-15
-10
-5
0
5
10
____ Cd-s
0.6
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0.6
PDOS (Arbitrary Units)
0.8
____ Cd-p
____ Cd-d
0.4
0.2
0.0
0.0
-15
-10
-5
0
Energy (eV)
5
-15
10
-10
-5
0
Energy (eV)
5
10
Fig. 2(a) PDOS of 1x1x2 and 2(b) PDOS of 2x2x2 Zn doped Supercell configurations.
Total density of states (TDOS) usually represents energies obtained by solving Kohn-Sham
equations related to occupied and unoccupied energy levels [29]. TDOS plots demonstrated in
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fig. 3 illustrate that sulfur (s-orbital) is playing vital role in conduction band and states
corresponding to various subshells of cadmium, sulfur and zinc. In valence band, states of S and
Zn are prominent close to valence band edge which can be transferred to conduction band. The
region between -5.1 to -0.1 eV is dominated by S states while the region in energy range -8.1 to -
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5.9 eV is occupied with Zn and Cd states as discussed in Refs. [30, 31]. The region in range 12.89 to -11.50 eV mostly dominated by sulfur states. The inner occupied levels which
participate in state occupancy of valence band are Cd-4d, Zn-3d and S-3p as expressed in fig. 3.
Moreover top of valence band is occupied with S-3p states which dictate that in process of
electron transfer during doping, charge carriers mostly coming from sulfur atoms and causes
conduction. TDOS graphical trend matches with those presented by Wu et al. [32] but difference
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between these plots may be due to fact that our calculations are based on rocksalt structure
simulated by Wien2K with PBE-GGA approach. Fig. 3(b) demonstrates prominent role of Zn in
2x2x2 supercell configuration involving more atomic correlations due to large supercell volume.
(a)
8
EF
Total
7
CdS:Zn (1x1x2)
6
Zn
TDOS (eV-1)
TDOS (eV-1)
5
4
3
5
4
3
2
2
1
1
0
-15
-10
-5
0
Energy (eV)
5
EF
TDOS
Cd
S
S
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(b)
7
Cd
10
CdS:Zn (2X2X2)
8
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Page 6 of 15
0
-15
Zn
-10
-5
0
Energy (eV)
5
10
Fig 3(a) TDOS of 1x1x2 and (b) TDOS of 2x2x2 Zn doped CdS supercell configurations.
3.2 Optical properties
CdS nanoparticles exhibit unexpected optical properties due to quantum effects. Doping effects
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on CdS have higher expectancy to bring significant changes in structural and optical properties.
Henceforth, on increasing Zn contents in pure CdS, more Zn atoms will substitute Cd atoms and
as a result, material exhibit exceptional optoelectronic properties due to excess of holes in
valence band [27]. Current PDOS and TDOS calculations translate primary investigations as
discussed above. It is obvious that Zn substituted CdS is sensitive to absorption of
electromagnetic radiations. Sekhar et al. in 2015 have studied optical properties of Zn doped CdS
nanopowders and pointed that absorption peak at 462 nm appears due to surface states of
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accumulative effects of particles [33].
Optical properties of Zn-doped CdS rocksalt structure for both supercell configurations including
pure CdS as a function of energy have been studied in this work and observations are marked
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graphically as optical absorbance, optical reflectivity, index of refraction, dielectric constant and
optical conductivity etc. Optical properties based on DFT calculations are plotted in figs. 4-6,
which depict reasonable agreement with experimental work presented by Abgo et al. [13]. Fig.
4(a) illustrates absorption of Zn-doped CdS, where graphical trend shows a gradual increase and
then sudden rise in absorption with increase in energy up to 4.6 eV where absorption becomes
maximum. After this energy value, absorption decreases slightly while for high energy values it
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becomes almost constant. Fig. 4(a) demonstrates graphical trends of photon energy and
absorption for two supercells configurations exhibiting different behaviors in case of both 1x1x2
and 2x2x2 supercells, which may be due to formation of ZnS when Zn substitutes Cd atoms in
the rocksalt CdS lattice. Experimental XRD studies suggested that Zn+2 ions substitute Cd+2 ions
in the lattice in a well-mannered way so chances of Zn bonding to S increase which may result in
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formation of ZnS as described in Refs. [34, 35]. Also in the conduction band of DOS plots,
hybridization of Zn and S orbitals are clear which may leads chances of formation of ZnS phases
in the system of Zn-doped CdS. The narrow peak in case of 1x1x2 supercell configurations is
269 nm (4.60 eV) may be reasoned as the exciton peak of CdS. Which may have physical
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AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
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Page 7 of 15
interpretation that energies of exciton peaks are distributed over a wide range resembling with
the experimental findings as discussed in [24, 33]. The graph in case of 2x2x2 supercell
AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
the peak at
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configuration differs from the 1x1x2 supercell due to possible bonding between Zn and S since
4.2 eV may be identified as the ZnS absorption spectrum as discussed in [36, 37].
Shifting of peaks for two supercell configuration may be related to the nanocrystalline and bulk
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form of CdS along with formation of ZnS bonding as has been discussed in experimental
findings in [35]. However, if we extrapolate trends (before and after maximum absorption
4.2
eV) for 2x2x2 supercell configuration up to zero absorption then we has two energy intercepts at
2.5 eV and 3.3 eV as shown in fig. 4(a). The value of 2.5 eV is close to the band gap of pure CdS
(2.4 eV) and the value of 3.3 eV is close to band gap of pure ZnS (3.64 eV) which indicates that
these absorptions are related with intraband transitions [38]. It means addition of Zn impurities in
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(a)
450
400
350
Undoped CdS
1x1x2
2x2x2
300
250
200
150
100
50
0
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
4.0
3.5
3.0
2.5
2.0
1.5
2.0
2.5
0.9
(b)
Pure CdS
1x1x2
2x2x2
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
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
Energy (eV)
80
60
(d)
Pure CdS
1x1x2
2x2x2
50
40
30
20
10
1.5
1.0
1.0
1.0
70
Dielectric Constant
4.5
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5.0
Pure CdS
1x1x2
2x2x2
ce
Index of Refraction (Arbitrary Units)
Energy (eV)
5.5 (c)
Optical Reflectivity (Arbitrary Units)
500
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Optical Absorption (Arbitrary Units)
CdS lattice indicate the interaction of Zn with sulfur atoms.
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Page 8 of 15
3.0
3.5
Energy (eV)
4.0
4.5
5.0
0
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
Energy (eV)
Fig. 4(a) Optical Absorption, 4(b) Optical Reflectivity, 4(c) Index of refraction, and 4(d)
dielectric constant of pure CdS and two supercell configurations
Page 9 of 15
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In fig. 4(b), we have a plot of optical reflectivity with variation in energy in range between 0-6
eV along energy axis. The plot expresses two ascending curves in different manner due to the
reason that supercell configuration is different for both. In case of 1x1x2 supercell configuration,
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the plot shows a gradual increase in reflectivity up to 4.79 eV and then falling in the range 4.795.6 eV. The trait becomes almost constant as energy is further increased and matches with the
experimental work presented in [13]. While the second curve for 2x2x2 supercell configuration
exhibits sudden increase in reflectivity in two steps first up to 3 eV and then beyond 3.65 eV.
The reflectivity remains constant up to 1.4 eV. This trend is different from 1x1x2 supercell
configuration due to involvement of interactions and correlations terms which significantly
increases due to many body interactions. These peaks may be referred due to the interaction of
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Zn with S atoms as we have substituted Cd with Zn and has been discussed in [39]. The
graphical trend for both supercell configurations differs due to DFT calculations based on
rocksalt CdS structure doped with Zn. As experimental findings are based on calculations fitting
with certain models while DFT calculations are obtained for many body system with theoretical
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equations containing more interaction terms and type of crystal structure. Hence theoretical
calculations may differ considerably from experimental one.
In plot represented in fig. 4(c), we exhibited index of refraction with increase in photon energy.
Two plots for 1x1x2 and 2x2x2 supercell configurations have different behaviors in the same
range of energy up to 5 eV. For 1x1x2 supercell configuration, there is slight increase of index
when energy is increased up to 3.76 eV and after it decreases. This trend matches with the
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experimental findings as reported in [13] where graphical trend steep fall after energies greater
than 3.5 eV. The values of n in low energy region increases from 3 to maximum value of index
of refraction
.0 at energy value 3.71 eV (334 nm). Similar behavior is observed by M.
Kamruzzaman et al. in [38]. The experimental value of index of refraction for pure CdS is 2.38 at
ce
632.8 nm (i.e 1.96 eV) [24, 40]. Other trait for 2x2x2 supercell is different enough than 1x1x2
supercell due to interaction of Zn and S ions. The maximum value of index of refraction for
2x2x2 supercell is
5.6 at energy 4.11 eV (301 nm) while experimental values of n lie between
5-9 at this wavelength (energy) with increasing concentrations of Zn. Such type of variation may
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AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
emerge because of dispersion of light as it moves deeper inside material and interact with
different atoms in different configurations of supercell. As a result successive internal reflections
may occur which contribute to variations of n. This may also be caused by trapping of photons
AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
pt
by the grain boundaries as observed experimentally [38]. The rise of n in high energy region (> 3
eV) might be due to loss of energy in various processes such as free carrier absorption, scattering
with impurity atoms (Zn) and phonon generation etc.
us
cri
In fig. 4(d), we plotted dielectric constant for pure and Zn doped CdS for two supercell
configurations 1x1x2 and 2x2x2. The plot expresses two different trends which are uniquely
defined in the range of energy 0-6 eV. For 1x1x2 supercell the graphical trend shows increase
upto 3.7 eV and then it decreases suddenly upto energy value 4.46 eV. The graph then continues
until another peak at value 4.81 eV is obtained which further becomes almost constant. On the
other hand, the trait for 2x2x2 supercell apparently seems to be divided in two parts where
energy increases upto 4.28 eV. Then during the interval 4.28-5.12 eV, graph is almost constant
an
and after it suddenly rises. The increase in dielectric constant physically means that speed of
light in material is slowed down. The dielectric losses for both supercell configurations increases
as energy increases (wavelength decreases) and the results are in accordance with already
dM
reported work [38]. However, graphical trend for presented calculations matches with the results
reported in [19] where primarily dielectric constant increases to maximum value and then it
decreases and further rises with energy. The difference may be due to fact that our dopant is
changed which changes the entire optical properties of CdS. Also 2x2x2 supercell for Zn doped
CdS shows different behavior which may be interpreted as possibility of formation of ZnS with
time as energy increases.
pte
Extinction coefficient is an optical characteristic of any material and related to the complex index
of refraction where it is its imaginary part. However it is related to absorption of light by
ce
equation,
Where
is absorption coefficient and k is extinction coefficient. In fig. 5, variation in extinction
coefficient has been shown with increase in energy (eV) obtained from solution of many body
wave function by method of DFT. Plots are sketched for two different supercell configurations
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Page 10 of 15
1x1x2 and 2x2x2 including pure CdS. Two curves for both supercells are different from each
other but graphical trend is almost same where extinction coefficient first increases until
maximum value is achieved for specific energy value and then it decreases further. From figs.
Page 11 of 15
pt
4(a) and 6, it is concluded that they resemble to each other as supported by above equation. The
rise in values of k may be reasoned with quantum mechanical phenomenon where we have
quantum confinement effect which is further connected to experimental observation related to
us
cri
crystallite size as stated in [41]. The increase in graph for both supercell configurations is similar
up to energy value 2.82 eV and after that the curve shows slight displacement from each other till
3.89 eV while after this value both graphs have obvious difference. The difference in traits may
be due to possibility of the formation of ZnS in case of larger supercell and also due to our
atomic correlation effects which are enhanced in case of 2x2x2 supercell. The peaks at different
values of energy for two supercells may be nominated as caused by density of states created near
edge of the Fermi level and by addition of Zn impurities. The rapid rise of extinction coefficient
2.7 eV can be
an
k is related with rise of photon energy exceeding band gap. The first rise of k at
associated with CdS bandgap whereas second rapid rise of k beyond 3.8 eV could be attributed to
ZnS bandgap. Moreover, rise of k with energy is an indication of the probability of increasing
electron transfer across mobility gap. Therefore maximum value of k leads to maximum
dM
attenuation or light absorption at defect sides such as impurities and grain boundaries.
Extinction Coefficient (Arbitrary Units)
8
Pure Cds
1x1x2
2x2x2
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4
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AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
0
0
1
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5
6
Energy (eV)
Fig. 5. Extinction Coefficient of Zn doped CdS
Fig. 6 illustrates graph of optical conductivity of two supercells 1x1x2 and 2x2x2 including pure
CdS with increase in energy (eV) for Zn doped CdS. The increase in conductivity for both
AUTHOR SUBMITTED MANUSCRIPT - MRX-105480.R1
pt
supercells is same up to energy value 3.84 eV and after that trend is different such that for 1x1x2
supercell the conductivity peak is broader while 2x2x2 supercell peak is sharp which decreases
further in both cases. Wider absorption peak for 1x1x2 supercell is at 4.40 eV and for 2x2x2
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supercell is at 4.10 eV. This red shift of peak value might be attributed to the interaction of Zn
35000
Pure CdS
1x1x2
2x2x2
30000
25000
an
20000
15000
10000
5000
dM
Optical Conductivity (Arbitrary Units)
and S atoms which is more prominent in the 2x2x2 supercell.
0
0
1
2
3
Energy (eV)
4
5
6
Fig. 6. Optical Conductivity of Zn doped CdS
pte
Conclusion
Theoretical study has been performed on Zn doped CdS rocksalt structure using Wien2K code
through DFT calculations employing PBE-GGA approximation. Optical properties, DOS and
PDOS are focused. Graphical trends presented in this theoretical study are in close agreement
with experimental findings reported in literature. Optical properties exhibit distinct graphical
ce
behavior for two supercell configurations (1x1x2 and 2x2x2) due to bonding effects. In
conduction process, most contributing orbitals are Cu-4d, S-3p and Zn-3d. Doping Zn in CdS
lattice bring significant variations in optical and electronic properties which supports its wide
applications in optoelectronics, optical sensors and similar devices.
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