In this paper we report the preparation of Hg- and Mg-doped nanostructured CdS thin films deposited on commercial glass slide substrate by chemical bath deposition technique at room temperature. The asdeposited doped CdS nanostructured thin films were characterized using X-ray diffractometer, SEM and UV-VIS spectrophotometer. The SEM micrographs confirmed the formation of doped CdS thin film with
nano-structured morphologies. The EDX studies confirm chemical composition of Hg- and Mg-doped nanostructured CdS thin films.The XRD studies confirmed the crystalline nature of thin films and nanostructured behavior. The optical studies reveal the optical energy bandgap of 3.82eV(12hrs) & 3.74eV(24hrs) and 3.59 (12hrs) & 3.22eV (24hrs) for Mg-doped CdS and Hg-doped CdS nanostructured thin films respectively. Blue shift was observed in both the doped CdS nanostructured thin films

Kumar, S.

Kundu, V.

Vohra, A.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 4 No 1, 01NTF03(4pp) (2015)   2304-1862/2015/4(1)01NTF03(4) 01NTF03-1  2015 Sumy State University Fabrication and Characterization of Mg- and Hg-doped CdS Nanostructured Thin Films  Deposited by Chemical Bath Deposition  Suresh Kumar*, Virender Kundu, Anil Vohra  Department of Electronic Science, Kurukshetra University, Kurukshetra 136119, India  (Received 31 May 2015; published online 28 August 2015)  In this paper we report the preparation of Hg- and Mg-doped nanostructured CdS thin films deposited on commercial glass slide substrate by chemical bath deposition technique at room temperature. The as-deposited doped CdS nanostructured thin films were characterized using X-ray diffractometer, SEM and UV-VIS spectrophotometer. The SEM micrographs confirmed the formation of doped CdS thin film with nano-structured morphologies. The EDX studies confirm chemical composition of Hg- and Mg-doped nanostructured CdS thin films.The XRD studies confirmed the crystalline nature of thin films and nanostructured behavior. The optical studies reveal the optical energy bandgap of 3.82eV(12hrs) & 3.74eV(24hrs) and 3.59 (12hrs) & 3.22eV (24hrs) for Mg-doped CdS and Hg-doped CdS nanostructured thin films respectively. Blue shift was observed in both the doped CdS nanostructured thin films.  Keywords: Chemical Bath Déposition; Nanostructured Thin Films; Mg-CdS; Hg-CdS; Characterization    PACS numbers: 68.55.J – , 81.07.Bc                                                      * sawan2k2@yahoo.co.in 1. INTRODUCTION  II-VI compound semiconductors are very im-portant class of materials for their potential applica-tions in various electronic devices such as solar cell, light emitting diodes, photo detectors, lasers etc. due to their wide energy band gap (1-4). Among them, cadmium sulphide (CdS) is the most studied chalco-genide semiconductor due to its wide band-gap (2.4eV) and better optical transmitting properties [5]. It is commonly used materials as window layer for CdTe, CdSe and Cu(In,Ga)Se2 thin films and nanostructured solar cells [6-8 ]. The study of nanostructured materials is of great interest among scientific community owing to their remarkable prop-erties as compared to their bulk counterparts. Nanostructures and nanostructured thin films plays very important role in designing future nanoscale electronic devices with remarkable properties. In re-cent years, CdS nanostructures have greatly received much attention as a candidate for various optoelec-tronic devices due to their promising physical and chemical properties [9-10]. Singh et al. [11] fabricat-ed nanostructured CdTe, CdS, TiO2 thin films and demonstrated solar cell based on them. Deng et al. [10] presented CdS nanostructures based photo de-tectors. The research on CdS is still under investiga-tion to see the effect of doping to it and is therefore a current topic of research. Ixtlilco et al. [12], Shah et al. [13] and Oliva et al. [14] fabricated Ag-, Zn- & Cu-doped CdS thin films/nanostructures via thermal evaporation and chemical bath deposition methods and presented their various physical properties. In this paper, Mg-and Hg-doped CdS nanostructured thin films have been fabricated via a simple & low cost chemical bath deposition method and their struc-tural, morphological and optical properties are pre-sented.  2. EXPERIMENTAL DETAILS   Mg-and Hg-doped CdS nanostructured thin films have been grown on cleaned commercially available glass slides at room temperature via chemical bath deposition. Commercial glass slides were first cleaned with soap solution in de-ionized water then boiled in concentrated chromic acid for 30 minutes.  The slides were then rinsed with acetone and ultrasonically cleaned in de-ionized water for 15 minutes and then dried in air for further use. The clean surface of glass slides provides good nucleation growth of the film with uniform deposition and best yield. All the chemicals were of analytical grade and used without purification.  2.1 Preparation of Mg-doped CdS Nanostruc-tured Thin Film  Mg-doped CdS nanostructured thin films were grown on glass slides via chemical bath deposition at room temperature. The bath composition for Mg-doped CdS nanostructured thin films was consist of 0.1M magnesium sulphate (MgSO4), 0.2 M cadmium sul-phate (CdSO4), 0.5 M thiourea (CH4N2S), 2 ml tri-ethanolamine (TEA) and  5ml ammonia (NH3).   2.2 Preparation of Hg-doped CdS Nanostruc-tured Thin Film  Hg-doped CdS nanostructured thin films were also grown on glass slides via chemical bath deposition at room temperature. The bath composition for Hg-doped CdS nanostructured thin films was consist of 0.1M mercury sulphate (HgSO4), 0.2 M cadmium sulphate (CdSO4), 0.5 M thiourea (CH4N2S), 2 ml tri-ethanolamine (TEA) and  5ml ammonia (NH3). A common procedure was followed in growing both Mg- and Hg-doped CdS nanostructured thin films. 20ml of 0.1M MgSO4 is mixed with 20 ml 0.2 M CdSO4 in a beaker A under constant stirring and a clear solution  SURESH KUMAR, VIRENDER KUNDU, ANIL VOHRA PROC. NAP 4, 01NTF03 (2015)   01NTF03-2 was obtained. Then 10 ml of 0.5 M CH4N2S was added to it with constant stirring and the color of the solu-tion was turned milky white and upon addition of 2ml of TEA to this solution, the color of the solution changed to light yellow. The final volume solution was made 50ml. The pH of the solution was kept 9 by the addition of NH3. Similar procedure was followed in the preparation solution for deposition of Hg-doped CdS nanostructured thin films. The final color of this solu-tion was dark brown with pH 10. The clean glass sub-strates were immersed vertically in beaker for 12 and 24 hrs at room temperature to deposit Mg- and Hg-doped CdS nanostructured thin films. The as-grown samples were then characterized with different char-acterization techniques and studied.  3. RESULTS AND DISCUSSION  The color of the Mg-doped CdS thin film was brown-ish yellow and that of Hg-doped CdS thin film was dark brown. The as-obtained thin films were characterized via scanning electron microscopy, Energy dispersive X-ray spectroscopy, X-ray diffractometer and Uv-vis spec-trophotometer to study their structural, morphological and optical properties.  3.1 Morphological Studies  The morphological studies of chemical bath depos-ited Mg- and Hg-doped nanostructured CdS thin films have been studied by scanning electron microscope. The as-obtained samples were first coated by thin layer of gold in Polaron SC7640 Sputter Coater and then viewed under scanning electron microscope (Zeiss EVO 40) an accelerating voltage of 20kV at high vacuum.  The Fig. 1 and 2 shows the SEM mi-crographs of as-prepared Mg- and Hg-doped CdS nanostructured thin films. The SEM micrographs of Mg-doped CdS thin films are composed of leaves type nanostructures.     Fig. 1 – SEM Micrographs of Mg-doped CdS Nanostruc-tured Thin films (a) 12 hrs (b) 24 hrs  The Mg-doped CdS nanostructured thin film grown for 24 hours has fewer defects as compared to the thin film grown for 12 hours. The white spot as defect is clearly visible in Mg-doped CdS nanostructured thin film grown for 12 hours. The SEM micrographs of as-prepared Hg-doped CdS thin films are composed of seeds type nanostructures. The Hg-doped CdS nanostructured thin film grown for 24 hours has fewer defects as compared to the thin film grown for 12 hours. The white spots as defects are clearly visible in Hg-doped CdS nanostructured thin film grown for 12 hours. SEM analysis reveal the nanostructured morpholo-gies of Mg- and Hg-doped CdS nanostructured thin films and confirm the deposition via chemical bath deposition.    Fig. 2 – SEM micrographs of Hg-doped CdS thin nanostruc-tured films (a) 12 hrs (b) 24 hrs)  3.2 Chemical Studies  The chemical studies were carried out to study the stoichiometric behaviour of Hg- and Mg-doped CdS nanostructured thin films by a BRUKER EDX system in conjunction with a Zeiss EVO 40 scanning electron microscope. The Fig. 3 shows the EDX spectrum of Mg- doped nanostructured CdS thin film that reveal the grown thin film is constituted of elements Cd, S and Mg with stoichiometric ratio (in At.%) of 79.02:10.13:6.54. Other elements such as O, Sn and Si are also present in the system but their percentage is very less and their presence can be attributed to impuri-ties present in the sample that arises from chemicals and substrate material.    Fig. 3 – EDX spectrum of Mg-doped CdS nanostructured thin films   The Fig. 4 shows the EDX spectrum of Hg-doped nanostructured CdS thin films. The EDX spectrum reveals the chemical composition mainly consists of elements Cd, S and Hg with stoichiometric ratio (in at.%) of 80.73:9.68:4.09. Other EDX peaks arise from impurities present in chemical used and substrate material. The sulphur contents in both the films are found moderate as compared to cadmium compound.    FABRICATION AND CHARACTERIZATION OF MG- AND HG-DOPED CDS… PROC. NAP 4, 01NTF03 (2015)   01NTF03-3   Fig. 4 – EDX spectrum of Hg-doped CdS nanostructured thin films  3.3 Structural Studies  The structural studies of as-prepared Mg- and Hg-doped nanostructured CdS thin films was performed by X-ray Diffraction system (PANalytical X’PERT-PRO X-ray powder diffractometer) using wavelength (Cu-Kα) 1.54060Å at 40 mA, 45 keV. The X-ray dif-fraction pattern was recorded using a step size of 0.0170 from 0-80° of 2θ angle. Fig. 5 shows the dif-fraction pattern of Mg-doped nanostructured CdS thin films for 12 and 24 hrs. In both the spectrum, the highest peak was observed at 2θ angle of 29.2130° and is indexed as (111) and the other minor peak was observed at 2θ angle of 51.7936° and is indexed as (311). The preferential direction of growth of Mg-doped nanostructured CdS thin films was found at 29.2130° and the spectrum matches with diffraction data file JCPDS (10-454) that confirms the formation of Mg-doped nanostructured CdS thin films.  Fig. 6 shows the diffraction pattern of Hg-doped nanostructured CdS thin films for 12 and 24 hrs. In both the spectrum, the highest peak was observed at 2θ angle of 29.0352° and is indexed as (111) and the other minor peak was also observed at 2θ angle of 51.4094° and is indexed as (311). The preferential direction of growth of Hg-doped nanostructured CdS thin films was also found at 29.2130° and the spec-trum matches with diffraction data file JCPDS (10-454) that confirms the formation of Mg-doped nanostructured CdS thin films. The broad diffraction peaks in the XRD pattern shows the nanostructured behavior of the thin films. The films deposited for 24hrs is found more crystalline in nature as compared to thin films of 12hrs formation. The XRD studies con-firm the crystallinity in both the films grown by chem-ical bath deposition method. The major (111) and the other complimentary (311) diffraction peaks reveal the  cubic structure of the doped CdS films.The aver-age crystal size as calculated by Scherrer formula from XRD measurements was estimated in the range of 16-22nm.    Fig. 5 – XRD patterns of Mg-doped nanostructured CdS thin films (a) 12 hrs (b) 24 hrs)    Fig. 6 – XRD patterns of Hg-doped nanostructured CdS  thin films (a) 12 hrs (b) 24 hrs)  3.4 Optical Studies   The optical properties of Mg- and Hg-doped CdS nanostructured thin films were studied using Shimad-zu 2550 UV-Vis spectrometer. Fig.7 shows the absorp-tion spectra of both of the Mg- and Hg-doped nanostructured CdS thin films. Blue shifts was ob-served in all the doped CdS thin films as the absorption edge moves to lower wavelength region (324-385nm) in doped CdS thin films in comparison with un-doped CdS thin film (512nm) thus blue shifted. Fig.8 shows the Tauc’s plot for both of the Mg- and Hg-doped nanostructured CdS thin films to determine their optical energy band gaps. The optical energy band gap of Mg- and Hg-doped nanostructured CdS thin films is calculated from absorption coefficient data as a func-tion of wavelength using Tauc relationship [15] given by   SURESH KUMAR, VIRENDER KUNDU, ANIL VOHRA PROC. NAP 4, 01NTF03 (2015)   01NTF03-4   Fig. 7 – Plot of absorbance vs wavelength    Fig. 8 – Tauc`s Plot for Energy Band Gap Calculation         ngh B h E  (1)  where  the absorption coefficient, hν photon energy, Eg the optical energy band gap, B (a constant term) the band tailing parameter  and ‘n’ an  index and can have  different values i.e. 2, 3, 1/2 and 1/3 depending on band to band transitions. It is observed that  equation (1) gives the best linear fit (n=2 ) for the Tauc plot shown in Fig. 7 and that corresponds to the direct band to band transition. The energy band gaps are found to be 3.82 (12hrs) & 3.74eV (24hrs) and 3.22 (12hrs) & 3.59eV (24hrs) for Mg- and Hg-doped nanostructured CdS thin films respectively. The “blue shift” occurred as the energy band gaps increases for doped nanostruc-tured CdS thin films from 2.4eV (pure CdS thin film) thus can be due to doping and the quantum size effect as well. It is also observed that mmagnesium has great effect on optical band gap compared to mercury.  4. CONCLUSIONS  The Mg- and Hg-doped nanostructured CdS thin films have been fabricated successfully from a low cost chemical bath deposition method at room temperature. The SEM studies reveal the  leaf and seed type mor-phologies of the Mg- and Hg-doped nanostructured CdS thin films. The XRD study confirms the crystalline na-ture with cubic structure. The optical studies observed increased band gap of doped nanostructured CdS thin films in comparison with pure CdS thin film. The above studies reveal that Mg- and Hg-doped nanostructured CdS thin films with higher energy band gaps can be useful in future nanostructured solar cell and other optoelectronic devices.  ACKNOWLEDGEMENTS   The authors intend to thank Science and Engineer-ing Research Board, Department of Science & Technolo-gy (DST), Govt. of India (Grant No. SERB/F/2139/2013-14) for providing financial support toward this work.    REFERENCES  1. J. Schrier, D. Demchenko, L. Wang, A. Alivisatos, Nano Lett. 7, 2377 (2007). 2. U. Gangopadhyay, K. Kim, D. Mangalaraj, J. Yi, Appl. Surf. Sci. 230, 364 (2004). 3. Q. Shen, J. Kobayashi, L. Diguna, T. Toyoda, J. Appl. Phys. 103, 084304 (2008). 4. S.J. Jiao, Z.Z. Zhang, Y.M. Lu, D.Z. Shen, B. Yao, J. Y. Zhang, B.H. Li, D.X. Zhao, X.W. Fan, Z.K. Tang, Appl. Phys. Lett. 88, 031911 (2006). 5. P. Roy, S.K. Srivastava, J. Phys. D: Appl. Phys. 39, 4771 (2006). 6. A.M. Acevedo, Solar Energ. 80, 675 (2006). 7. Z. Zhu, J.Qiu, K. Yan, S. Yan, ACS Appl. Mater. Interfac-es 5, 4000 (2013). 8. Y.D. Chung, D.H. Cho, N.M. Park, K.S. Lee, J. Kim, Curr. Appl. Phys. 11, S65 (2011). 9. H. Li, X. Wang, J. Xu, Q. Zhang, Y. Bando, D. Golberg,  Y. Ma, T. Zhai, Adv. Mater. 25, 3017 (2013).  10. K. Deng, L. Li, Adv. Mater. 26, 2619 (2014). 11. R.S. Singh, V.K. Rangra, S. Sanagapalli, V. Jayaraman,  S. Mehandra, V.P. Singh, Solar Energ. Mater.Sol. Cell. 82, 315 (2004). 12. L. Ixtlilco, P.J. Sebastian, D. Eapen, J. Pantoja, J. New Mater. Electrochem. Sys. 13, 22 (2010). 13. N.A. Shah, A. Nazir, W. Mahmood, W.A.A. Syed, S. Butt, Z. Ali, A. Maqsood, J. Alloy. Compnd. 512, 27 (2012). 14. A.I. Oliva, J.E. Corona, R. Patiño, A.I.O. Avilés, Bull. Ma-ter. Sci. 37, 247 (2014). 15. E.A. Davis, N.F. Mott, Phil. Magn. 22, 903 (1970).   

Fabrication and Characterization of Mg- and Hg-doped CdS Nanostructured Thin Films Deposited by Chemical Bath Deposition

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 4 No 1, 01NTF03(4pp) (2015) 
 
 
2304-1862/2015/4(1)01NTF03(4) 01NTF03-1  2015 Sumy State University 
Fabrication and Characterization of Mg- and Hg-doped CdS Nanostructured Thin Films  
Deposited by Chemical Bath Deposition 
 
Suresh Kumar*, Virender Kundu, Anil Vohra 
 
Department of Electronic Science, Kurukshetra University, Kurukshetra 136119, India 
 
(Received 31 May 2015; published online 28 August 2015) 
 
In this paper we report the preparation of Hg- and Mg-doped nanostructured CdS thin films deposited 
on commercial glass slide substrate by chemical bath deposition technique at room temperature. The as-
deposited doped CdS nanostructured thin films were characterized using X-ray diffractometer, SEM and 
UV-VIS spectrophotometer. The SEM micrographs confirmed the formation of doped CdS thin film with 
nano-structured morphologies. The EDX studies confirm chemical composition of Hg- and Mg-doped 
nanostructured CdS thin films.The XRD studies confirmed the crystalline nature of thin films and 
nanostructured behavior. The optical studies reveal the optical energy bandgap of 3.82eV(12hrs) & 
3.74eV(24hrs) and 3.59 (12hrs) & 3.22eV (24hrs) for Mg-doped CdS and Hg-doped CdS nanostructured thin 
films respectively. Blue shift was observed in both the doped CdS nanostructured thin films. 
 
Keywords: Chemical Bath Déposition; Nanostructured Thin Films; Mg-CdS; Hg-CdS; Characterization  
 
 PACS numbers: 68.55.J – , 81.07.Bc 
 
 
                                                   
*
 sawan2k2@yahoo.co.in 
1. INTRODUCTION 
 
II-VI compound semiconductors are very im-
portant class of materials for their potential applica-
tions in various electronic devices such as solar cell, 
light emitting diodes, photo detectors, lasers etc. due 
to their wide energy band gap (1-4). Among them, 
cadmium sulphide (CdS) is the most studied chalco-
genide semiconductor due to its wide band-gap 
(2.4eV) and better optical transmitting properties [5]. 
It is commonly used materials as window layer for 
CdTe, CdSe and Cu(In,Ga)Se2 thin films and 
nanostructured solar cells [6-8 ]. The study of 
nanostructured materials is of great interest among 
scientific community owing to their remarkable prop-
erties as compared to their bulk counterparts. 
Nanostructures and nanostructured thin films plays 
very important role in designing future nanoscale 
electronic devices with remarkable properties. In re-
cent years, CdS nanostructures have greatly received 
much attention as a candidate for various optoelec-
tronic devices due to their promising physical and 
chemical properties [9-10]. Singh et al. [11] fabricat-
ed nanostructured CdTe, CdS, TiO2 thin films and 
demonstrated solar cell based on them. Deng et al. 
[10] presented CdS nanostructures based photo de-
tectors. The research on CdS is still under investiga-
tion to see the effect of doping to it and is therefore a 
current topic of research. Ixtlilco et al. [12], Shah et 
al. [13] and Oliva et al. [14] fabricated Ag-, Zn- & Cu-
doped CdS thin films/nanostructures via thermal 
evaporation and chemical bath deposition methods 
and presented their various physical properties. In 
this paper, Mg-and Hg-doped CdS nanostructured 
thin films have been fabricated via a simple & low 
cost chemical bath deposition method and their struc-
tural, morphological and optical properties are pre-
sented. 
 
2. EXPERIMENTAL DETAILS  
 
Mg-and Hg-doped CdS nanostructured thin films 
have been grown on cleaned commercially available 
glass slides at room temperature via chemical bath 
deposition. Commercial glass slides were first cleaned 
with soap solution in de-ionized water then boiled in 
concentrated chromic acid for 30 minutes.  The slides 
were then rinsed with acetone and ultrasonically 
cleaned in de-ionized water for 15 minutes and then 
dried in air for further use. The clean surface of glass 
slides provides good nucleation growth of the film with 
uniform deposition and best yield. All the chemicals 
were of analytical grade and used without purification. 
 
2.1 Preparation of Mg-doped CdS Nanostruc-
tured Thin Film 
 
Mg-doped CdS nanostructured thin films were 
grown on glass slides via chemical bath deposition at 
room temperature. The bath composition for Mg-doped 
CdS nanostructured thin films was consist of 0.1M 
magnesium sulphate (MgSO4), 0.2 M cadmium sul-
phate (CdSO4), 0.5 M thiourea (CH4N2S), 2 ml tri-
ethanolamine (TEA) and  5ml ammonia (NH3).  
 
2.2 Preparation of Hg-doped CdS Nanostruc-
tured Thin Film 
 
Hg-doped CdS nanostructured thin films were also 
grown on glass slides via chemical bath deposition at 
room temperature. The bath composition for Hg-doped 
CdS nanostructured thin films was consist of 0.1M 
mercury sulphate (HgSO4), 0.2 M cadmium sulphate 
(CdSO4), 0.5 M thiourea (CH4N2S), 2 ml tri-
ethanolamine (TEA) and  5ml ammonia (NH3). A 
common procedure was followed in growing both Mg- 
and Hg-doped CdS nanostructured thin films. 20ml of 
0.1M MgSO4 is mixed with 20 ml 0.2 M CdSO4 in a 
beaker A under constant stirring and a clear solution 
 SURESH KUMAR, VIRENDER KUNDU, ANIL VOHRA PROC. NAP 4, 01NTF03 (2015) 
 
 
01NTF03-2 
was obtained. Then 10 ml of 0.5 M CH4N2S was added 
to it with constant stirring and the color of the solu-
tion was turned milky white and upon addition of 2ml 
of TEA to this solution, the color of the solution 
changed to light yellow. The final volume solution was 
made 50ml. The pH of the solution was kept 9 by the 
addition of NH3. Similar procedure was followed in the 
preparation solution for deposition of Hg-doped CdS 
nanostructured thin films. The final color of this solu-
tion was dark brown with pH 10. The clean glass sub-
strates were immersed vertically in beaker for 12 and 
24 hrs at room temperature to deposit Mg- and Hg-
doped CdS nanostructured thin films. The as-grown 
samples were then characterized with different char-
acterization techniques and studied. 
 
3. RESULTS AND DISCUSSION 
 
The color of the Mg-doped CdS thin film was brown-
ish yellow and that of Hg-doped CdS thin film was dark 
brown. The as-obtained thin films were characterized 
via scanning electron microscopy, Energy dispersive X-
ray spectroscopy, X-ray diffractometer and Uv-vis spec-
trophotometer to study their structural, morphological 
and optical properties. 
 
3.1 Morphological Studies 
 
The morphological studies of chemical bath depos-
ited Mg- and Hg-doped nanostructured CdS thin films 
have been studied by scanning electron microscope. 
The as-obtained samples were first coated by thin 
layer of gold in Polaron SC7640 Sputter Coater and 
then viewed under scanning electron microscope 
(Zeiss EVO 40) an accelerating voltage of 20kV at 
high vacuum.  The Fig. 1 and 2 shows the SEM mi-
crographs of as-prepared Mg- and Hg-doped CdS 
nanostructured thin films. The SEM micrographs of 
Mg-doped CdS thin films are composed of leaves type 
nanostructures.  
 
 
 
Fig. 1 – SEM Micrographs of Mg-doped CdS Nanostruc-
tured Thin films (a) 12 hrs (b) 24 hrs 
 
The Mg-doped CdS nanostructured thin film grown for 
24 hours has fewer defects as compared to the thin film 
grown for 12 hours. The white spot as defect is clearly 
visible in Mg-doped CdS nanostructured thin film 
grown for 12 hours. 
The SEM micrographs of as-prepared Hg-doped 
CdS thin films are composed of seeds type 
nanostructures. The Hg-doped CdS nanostructured 
thin film grown for 24 hours has fewer defects as 
compared to the thin film grown for 12 hours. The 
white spots as defects are clearly visible in Hg-doped 
CdS nanostructured thin film grown for 12 hours. 
SEM analysis reveal the nanostructured morpholo-
gies of Mg- and Hg-doped CdS nanostructured thin 
films and confirm the deposition via chemical bath 
deposition. 
 
 
 
Fig. 2 – SEM micrographs of Hg-doped CdS thin nanostruc-
tured films (a) 12 hrs (b) 24 hrs) 
 
3.2 Chemical Studies 
 
The chemical studies were carried out to study the 
stoichiometric behaviour of Hg- and Mg-doped CdS 
nanostructured thin films by a BRUKER EDX system 
in conjunction with a Zeiss EVO 40 scanning electron 
microscope. The Fig. 3 shows the EDX spectrum of 
Mg- doped nanostructured CdS thin film that reveal 
the grown thin film is constituted of elements Cd, S 
and Mg with stoichiometric ratio (in At.%) of 
79.02:10.13:6.54. Other elements such as O, Sn and Si 
are also present in the system but their percentage is 
very less and their presence can be attributed to impuri-
ties present in the sample that arises from chemicals and 
substrate material. 
 
 
 
Fig. 3 – EDX spectrum of Mg-doped CdS nanostructured thin 
films  
 
The Fig. 4 shows the EDX spectrum of Hg-doped 
nanostructured CdS thin films. The EDX spectrum 
reveals the chemical composition mainly consists of 
elements Cd, S and Hg with stoichiometric ratio (in 
at.%) of 80.73:9.68:4.09. Other EDX peaks arise from 
impurities present in chemical used and substrate 
material. The sulphur contents in both the films are 
found moderate as compared to cadmium compound. 
 
 
 FABRICATION AND CHARACTERIZATION OF MG- AND HG-DOPED CDS… PROC. NAP 4, 01NTF03 (2015) 
 
 
01NTF03-3 
 
 
Fig. 4 – EDX spectrum of Hg-doped CdS nanostructured thin 
films 
 
3.3 Structural Studies 
 
The structural studies of as-prepared Mg- and Hg-
doped nanostructured CdS thin films was performed 
by X-ray Diffraction system (PANalytical X’PERT-
PRO X-ray powder diffractometer) using wavelength 
(Cu-Kα) 1.54060Å at 40 mA, 45 keV. The X-ray dif-
fraction pattern was recorded using a step size of 
0.0170 from 0-80° of 2θ angle. Fig. 5 shows the dif-
fraction pattern of Mg-doped nanostructured CdS thin 
films for 12 and 24 hrs. In both the spectrum, the 
highest peak was observed at 2θ angle of 29.2130° 
and is indexed as (111) and the other minor peak was 
observed at 2θ angle of 51.7936° and is indexed as 
(311). The preferential direction of growth of Mg-
doped nanostructured CdS thin films was found at 
29.2130° and the spectrum matches with diffraction 
data file JCPDS (10-454) that confirms the formation 
of Mg-doped nanostructured CdS thin films.  
Fig. 6 shows the diffraction pattern of Hg-doped 
nanostructured CdS thin films for 12 and 24 hrs. In 
both the spectrum, the highest peak was observed at 
2θ angle of 29.0352° and is indexed as (111) and the 
other minor peak was also observed at 2θ angle of 
51.4094° and is indexed as (311). The preferential 
direction of growth of Hg-doped nanostructured CdS 
thin films was also found at 29.2130° and the spec-
trum matches with diffraction data file JCPDS (10-
454) that confirms the formation of Mg-doped 
nanostructured CdS thin films. The broad diffraction 
peaks in the XRD pattern shows the nanostructured 
behavior of the thin films. The films deposited for 
24hrs is found more crystalline in nature as compared 
to thin films of 12hrs formation. The XRD studies con-
firm the crystallinity in both the films grown by chem-
ical bath deposition method. The major (111) and the 
other complimentary (311) diffraction peaks reveal 
the  cubic structure of the doped CdS films.The aver-
age crystal size as calculated by Scherrer formula 
from XRD measurements was estimated in the range 
of 16-22nm. 
 
 
 
Fig. 5 – XRD patterns of Mg-doped nanostructured CdS thin 
films (a) 12 hrs (b) 24 hrs) 
 
 
 
Fig. 6 – XRD patterns of Hg-doped nanostructured CdS  
thin films (a) 12 hrs (b) 24 hrs) 
 
3.4 Optical Studies 
 
 The optical properties of Mg- and Hg-doped CdS 
nanostructured thin films were studied using Shimad-
zu 2550 UV-Vis spectrometer. Fig.7 shows the absorp-
tion spectra of both of the Mg- and Hg-doped 
nanostructured CdS thin films. Blue shifts was ob-
served in all the doped CdS thin films as the absorption 
edge moves to lower wavelength region (324-385nm) in 
doped CdS thin films in comparison with un-doped CdS 
thin film (512nm) thus blue shifted. 
Fig.8 shows the Tauc’s plot for both of the Mg- and 
Hg-doped nanostructured CdS thin films to determine 
their optical energy band gaps. The optical energy band 
gap of Mg- and Hg-doped nanostructured CdS thin films 
is calculated from absorption coefficient data as a func-
tion of wavelength using Tauc relationship [15] given by 
 
 SURESH KUMAR, VIRENDER KUNDU, ANIL VOHRA PROC. NAP 4, 01NTF03 (2015) 
 
 
01NTF03-4 
 
 
Fig. 7 – Plot of absorbance vs wavelength 
 
 
 
Fig. 8 – Tauc`s Plot for Energy Band Gap Calculation 
 
       
n
g
h B h E  (1) 
 
where  the absorption coefficient, hν photon energy, Eg 
the optical energy band gap, B (a constant term) the 
band tailing parameter  and ‘n’ an  index and can have  
different values i.e. 2, 3, 1/2 and 1/3 depending on band 
to band transitions. It is observed that  equation (1) 
gives the best linear fit (n=2 ) for the Tauc plot shown 
in Fig. 7 and that corresponds to the direct band to 
band transition. The energy band gaps are found to be 
3.82 (12hrs) & 3.74eV (24hrs) and 3.22 (12hrs) & 
3.59eV (24hrs) for Mg- and Hg-doped nanostructured 
CdS thin films respectively. The “blue shift” occurred 
as the energy band gaps increases for doped nanostruc-
tured CdS thin films from 2.4eV (pure CdS thin film) 
thus can be due to doping and the quantum size effect 
as well. It is also observed that mmagnesium has great 
effect on optical band gap compared to mercury. 
 
4. CONCLUSIONS 
 
The Mg- and Hg-doped nanostructured CdS thin 
films have been fabricated successfully from a low cost 
chemical bath deposition method at room temperature. 
The SEM studies reveal the  leaf and seed type mor-
phologies of the Mg- and Hg-doped nanostructured CdS 
thin films. The XRD study confirms the crystalline na-
ture with cubic structure. The optical studies observed 
increased band gap of doped nanostructured CdS thin 
films in comparison with pure CdS thin film. The above 
studies reveal that Mg- and Hg-doped nanostructured 
CdS thin films with higher energy band gaps can be 
useful in future nanostructured solar cell and other 
optoelectronic devices. 
 
ACKNOWLEDGEMENTS  
 
The authors intend to thank Science and Engineer-
ing Research Board, Department of Science & Technolo-
gy (DST), Govt. of India (Grant No. SERB/F/2139/2013-
14) for providing financial support toward this work. 
 
 
 
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Fabrication and Characterization of Mg- and Hg-doped CdS Nanostructured Thin Films Deposited by Chemical Bath Deposition

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