Zinc oxide thin films have been deposited onto glass substrates from zinc sulfate, ammonia and thiourea aqueous solution by chemical bath deposition. In the work there were specified solution preparation procedure and optimized the composition of the solution and content of component in it. X-ray diffraction and high-resolution scanning electron microscopy were used to characterize structure formation of obtaining ZnO films. As a result of investigation the effect of time deposition on the structural and substructural properties such as lattice parameters, texture quality, coherent scattering domain size was determined.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3095

Berestok, T.O.

Danilchenko, S.M.

Kurbatov, Denys Ihorovych

Manzhos, Oleksii Pavlovych

Opanasiuk, Nadiia Mykolaivna

Pohrebniak, Oleksandr Dmytrovych

Курбатов, Денис Игоревич

Курбатов, Денис Ігорович

Манжос, Алексей Павлович

Манжос, Олексій Павлович

Опанасюк, Надежда Николаевна

Опанасюк, Надія Миколаївна

Погребняк, Александр Дмитриевич

Погребняк, Олександр Дмитрович

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 5 No 1, 01009(4pp) (2013) Том 5 № 1, 01009(4cc) (2013)   2077-6772/2013/5(1)01009(4) 01009-1  2013 Sumy State University Structural Properties of ZnO Thin Films Obtained by Chemical Bath Deposition Technique  T.O. Berestok1, D.I. Kurbatov1, N.M. Opanasyuk1, A.D. Pogrebnjak1,*,  O.P. Manzhos1, S.M. Danilchenko2  1 Sumy State University, 2, Rimsky-Korsakov Str., 40007 Sumy, Ukraine  2 Institute of Applied Physics NAS of Ukraine, 58, Petropavliska Str., Sumy, 40030 Ukraine   (Received 11 November 2012; published online 28 March 2013)  Zinc oxide thin films have been deposited onto glass substrates from zinc sulfate, ammonia and thiou-rea aqueous solution by chemical bath deposition. In the work there were specified solution preparation procedure and optimized the composition of the solution and content of component in it. X-ray diffraction and high-resolution scanning electron microscopy were used to characterize structure formation of obtain-ing ZnO films. As a result of investigation the effect of time deposition on the structural and substructural properties such as lattice parameters, texture quality, coherent scattering domain size was determined.  Keywords: Zinc Oxide, Chemical bath deposition, Morphology, Structure, Substructure.   PACS number: 81.05.Dz                                                           * alexp@i.ua The article was reported at the 2nd International Conference «Nanomaterials: Applications  Properties-2012» 1. INTRODUCTION  Zinc oxide thin films have attracted special atten-tion of researchers due to its wide range of applications. It is used as a key material for light-emitting diodes [1], cathode-ray tubes [2], thin film electroluminescence [3], gas sensors and etc. [1-3]. ZnO thin films are widely used as conductive and optical cover layers of large area solar cells [4-5]. Recently much attention of researchers has been at-tracted to fabrication the semiconductor thin layer by chemical method [6-12]. Along with this chemical bath deposition (CBD) technique is the most promising method of thin films deposition [6-10]. Compared to the vapor deposition method, the chemical deposition method is generally economical, simpler, doesn’t re-quire high temperature and pressure and convenient for large-area deposition. Moreover, this method can also be used to obtain thin films with contolable struc-tural properties such as nanocrystalline layers, nan-owires and nanobelts [7-8]. Along with this, the CBD method is suitable for making films of any shape, such as flat-panel, spherical, and porous structures. Main feature of this method is that for the deposition of thin films there can be used a solution with different chemi-cal compounds. By the authors of works [6-8] ZnO films were obtained from zinc nitrate and hexamethylene tetramine (HMTA) solution [7], hexamethylene tetra-mine and ammonia solution [8], ethylenediamine and triethanolamine [6] solution. In contrast to that, for deposition films, we have used more available solutions of zinc sulphate (ZnSO4) and thiourea (CS(NH2)2). In the work was specified solution preparation procedure and optimized the composition of the solution and con-tent of component in it, investigated structural features of obtained from this solution thin films.  2. EXPERIMENTAL DETAILS  The details of the procedure are: appropriate amounts of zinc sulfate ZnSO4 solution and ammonia solution (NH4OH) were separately prepared. Formed mixture is thoroughly stirring for several minutes in order to dissolve the formed precipitate and solution to become homogeneous. Then in obtaining solution was added thiourea CS(NH2)2. These solutions were mixed in a beaker and stirred well for a few minutes. Thor-oughly cleaned substrates were maintained in a glass reaction vessel. Substrate mounted in a solution within a specified time (usually 15-120 minutes) in order to obtain the required film thickness.  Two series of samples have been investigated in this work. In the first case the solution was maintained at room temperature, in the second case the solution was heated to 85 С after placing the substrate. A schematic diagram of the deposition set up is shown in Fig 1.  substratethin filmsolutionheater  Fig. 1 – Schematic diagram of the chemical deposition system  Structural investigations were carried out with using X-ray diffractometer DRON 4-07 (Ni-filtered Kα – radiation of Cu-anode). The spectra were registered in the angle range 2 from 20  to 80 , where 2 is the Bragg angle. X-ray radiation was focused according to the Bragg-Brentano method. The phase analysis was carried out by comparing interplane distances and specific intensities of diffraction patterns from the investigated samples and JCPDS etalon [13].  The quality of the film texture had been estimated by the Harris method. It is especially convenient when plane specimens with the axis of the texture that is oriented normal to the surface tested [14-15]. The pole density was calculated as:    T.O. BERESTOK, D.I. KURBATOV, N.M. OPANASYUK, ET AL. J. NANO.-ELECTRON. PHYS. 5, 01009 (2013)   01009-2    0011i ii Ni iiI IPI IN , (1)  Thereafter the dependencies Pi – φ (where φ – is an angle between chosen direction and the normal to differ-ent crystallographic planes corresponding to the reflexes in the XRD patterns) and Pi – (hkl)i (where (hkl)i – Miller indexes ) were built on the base of the calculation. The angle φ was calculated for triclinic and hexagonal lattices according to expressions given in [14]. The axis of the texture has values corresponding to the maximum Pi. The orientation factor was calculated as:   211( 1) .Niif PN    (2)  The interplane distances for wurtzite phases of the ZnO were carried out by position of Kα1 component of all the most intensive lines registered in XRD-patterns.  Lattice parameters a and c of the hexagonal phase for ZnO were calculated according to the next expres-sions:   22 2 24 ( )2sin 3aa h hk k lc       , (3)   22 2 24 ( ) ,2sin 3cc h hk k la       (4)  where  is X-ray wavelength. Further we have applied the Nelson-Riley extrapo-lation method for more precise determination of the parameters a and c for both phases [14-16]. Least-squares method has enabled to linearly approximate the obtained numerical values. The XRD results were also used for the description of the coherent scattering domain (CSD) size in the films. The values of CSD size (L) in the films can be calculated using the Scherrer’s relation [14]:   ,cosKL   (5)  where K is a coefficient weekly depending on the grain shape (K = 0,94);  is a physical broadening of the X-ray line.   3. INTERPRETATION OF EXPERIMENTAL RESULTS  Chemical composition of solutions, concentration and other process variables that were used for ZnO films deposition are presented in Table 1. It was noted that in this work two series of samples have been studied. However, the results of X-ray analy-sis showed that in contrast to the expected results ob-taining ZnO thin films, we have obtained Zn4SO4(OH)6 films. It was found that obtaining condensates had tri-clinic structure (Fig. 2a).  Litreview proves that [18], layers annealing in vac-uum leads to decomposition of compound Zn4SO4(OH)6 and formation of ZnO or ZnS thin films that depend on the annealing temperature. Table 1 – The content of reagents in solution and technologi-cal parameters of obtaining films  № First series of samples ZnSO4 (0,1 mol), ml CS(NH2)2 (1 mol),  ml NH4OH, ml pH Тr, 0С τ, min 1 20 4 2 9-10 85 20 2 10 1 1 20 3 20 20 2 20 4 10 1 1 85  Second series of samples 1 50 5 7 10 85 20 2 30 3 60 4 90 5 120      Fig. 2 – X-ray patterns of films: first series (Table 1, 1-4 sam-ples) (a) and second series (Table 1, 1-5 samples) (b) of samples  Initial layers annealing in air leads to their oxida-tion and the formation of ZnSxO1 – x solid solution films. Therefore, we have carried out further annealing in vacuum at 500 С for 60 min and in the air - at 200 С for 20 min. In this case we have obtained low quality ZnO films.  The second series of samples was obtained from a solution of zinc sulfate, thiourea and ammonia in order to control pH value. pH was raised at 10. On X-Ray diffraction patterns of this series of samples we have registered reflexes with dominant intensity on degrees 34.410-34.420. Experimentally revealed diffraction peaks may be interpreted as reflexes from the plane (002) of the hexagonal phase ZnO (Fig. 2b). Along with the peaks mentioned above we have registered reflexes on degrees 31.750-31.760 and 36.240-36.250 which can be interpreted as reflexes from the planes (100) and (101) respectively. Consequently there took place for-mation ZnO thin films with hexagonal structure.   b а  STRUCTURAL PROPERTIES OF ZNO THIN FILMS OBTAINED… J. NANO.-ELECTRON. PHYS. 5, 01009 (2013)   01009-3        Fig. 3 – SEM images of ZnO films obtained under deposition time: 90 min (a, b); 120 min (c, d)    Fig. 4 – Pole density Pi and orientation factor f as a function of the incidence angle φ between the direction and the normal to the reflection plane for films: first series (Table 1, 1-4 samples) (a) and second series (Table 1, 1-5 samples) (b) of  samples  Fig. 3 displays images of the surface for ZnO. It is found that density of crystallites increases with the increase of time deposition. Accordingly there took place formation of the continuous film at a thickness more than 1 µm. When create heterojunctions based on ZnO thin films it is important that layers coupling occurred in the same crystallographic plane in different crystallites [17]. This is due to the fact that the density of interfa-cial defects depends on the plane contact type of hetero pair materials. Consequently condition interfacial area determines the transport mechanism of charge carriers through heterojunction. Therefore it determines the efficiency of its use in such devices as solar cells and photodetectors. This caused the urgency of determining of the effect on the time deposition on texture quality.  Reverse pole figures from ZnO are shown in Fig. 4a. As it seen, the samples are well textured. Along with this, the dominated orientation of crystallites is [002]. The quality of texture depends on technological condi-tions. In the obtained ZnO films increasing deposition time  from 20 to 60 minutes leads to improvement, and then (from 90 to 120 min) to a significant deterio-ration of the texture quality (inset in Fig. 4a). This is associated with growth features of obtained layer.  It is found that condensates deposited for  = 20 min have nanorods form as hexagonal prisms. These struc-tures grew with dimension: d = (0.25-1.00) µm in  diameter and l = (2.50-3.00) µm on length. It should be noted that nanorods grew at different angles (in most cases – perpendicular) to the substrate and oriented perpendicular to the substrate by crystal-lographic axis с, which coincides with the texture axis. And this makes high quality of texture at the early stages of the film growth. With the increasing conden-sation time due to the secondary nucleation there took place growth of plate crystallites between nanorods intervals. Finally this fact leads to the formation of a continuous film and decrease texture quality.  Along with this, Zn4SO4 (OH)6 thin films had tex-ture on plane [0-13]. These kinds of exotic textures quite often take place in films obtained by chemical bath deposition [18]. The results of lattice constants estimation are presented in Table 2.     а b b а b c d  T.O. BERESTOK, D.I. KURBATOV, N.M. OPANASYUK, ET AL. J. NANO.-ELECTRON. PHYS. 5, 01009 (2013)   01009-4 Table 2 – Lattice parameters of ZnO with hexagonal structure   τ, (min) Lattice parameters, (nm) CSD size, L (nm) hkl а с с/a (100) (002) 20 0.37645 0.57117 1.517 40.1 45.0 30 0.33407 0.50727 1.518 35.9 46.4 60 0.33895 0.51446 1.517 92.9 43.1 90 0.32168 0.48838 1.518 49.1 54.3 120 0.33425 0.50696 1.516 35.5 40.8 Ref. [13] 0.34298 0.52066 1.520    From Table 2, lattice parameters of films with low thickness (  20 min) are a  0.37602 nm, c  0.57081 nm. These values are more than reference ones (a  0.34298 nm, c  0.52066 nm) [13]. This effect     Fig. 5 – Effect of the time deposition on the CSD size in ZnO thin films. The CSD sizes in directions normal to the crystallographic planes (100) (1) and (002) (2)  are determined  may be due to a small size of crystallites in conden-sates, which has nanorods form as already mentioned. With the increase of time deposition and film thickness corresponding lattice constants value is approaching to the reference one. Fig. 5 depicts the effect of the time deposition on the CSD in directions normal to the crystallographic planes (100) and (002) in ZnO thin films. These values correspond to the size of CSD in perpendicular directions to а and с axes of ZnO lattice. The values of CSD were equal to L(100)  (35-93) nm, L(002)  (40-54) nm. These data are much smaller than electron-defined (d  (0.25-1.00) µm, l  (2.50-3.00) µm). This indicates that crystallites consist of several CSD.   4. CONCLUSIONS  ZnO thin films with different thickness have been obtained from zinc sulfate, ammonia and thiourea aqueous solution with the help of chemical bath deposi-tion technique. It is found that growth of thin layers took place by the formation of nanorods as hexagonal prisms and grew perpendicular to the substrate with further growth of plate crystallites between nanorods intervals. It is shown that the films have a hexagonal structure with lattice constant, varying with increasing thickness from а  0.37601 nm, с  0.57079 to а  0.33408 nm and с  0.50714 nm.  In addition it was studied the effect of the time dep-osition on texture quality of ZnO thin films. Further-more it is shown that the quality of texture was wors-ened with increasing deposition time. CSD estimating allowed us to evaluate that crystallites which formed at the initial stage of film growth consist of several sub-grain.  AKNOWLEDGEMENTS  This work is supported by the Ukraine State Agency for the Science, Innovation and Informatization and by the NRF grant funded by the MEST of Korea (2011-0019204) within the project «Advanced materials for low-cost high-efficiency polycrystalline heterojunction thin films solar cells» and by the Ministry of Education and Science, Youth and Sport of Ukraine (Grant №. 0112U000772).   REFERENCES  1. C. Klingshirn, phys. status solidi b 244, 3027 (2007). 2. I.I. Shpetelyuk, G.V. Lashkar, V.Y. Lazorenko, FHTT 11 No2, 277 (2010). (In Ukrainian). 3. А.І. Evtushenko, G.V. Lashkar, V.Y. Lazorenko, FHTT 9 No4, 869 (2008). (In Ukrainian). 4. J.A. Nikolaev, V.J. Rud’, J.V. Rud’, FTP 36 No9, 1128 (2002). (In Russian).  5. D. Hariskos, S. Spiering, M. Powalla, Thin Solid Films 480-481, 99 (2005).  6. M.O. Lopez, A. Avila-Garcıa, M.L. Albor-Aguilera, V.M. Sanchez Resendiz, Mater. Res. Bull. 38, 1241 (2003). 7. M.E. Fragalà, Y. Aleeva, G. Malandrino, Superlattice Mi-crost. 48, 408 (2010). 8. H. Wang, C. Xie, J. Cryst. Growth 291, 187 (2006). 9. R. Ebrahimifard, H. Abdizadeh, M.R. Golobostanfard, J. Nano- Electron. Phys. 4 No1, 01018 (2012). 10. V. Kumari, V. Kumar, B.P.Malik, D. Mohan, R.M. Mehra, J. Nano- Electron. Phys. 3 No 1, 601 (2011). 11. T.P. Rao, M.C.S. Kumar, A. Safarulla, Physica B 405, 2226 (2010). 12. A. Bougrine, A. Hichou, M. Addou, Mat. Chem. Phys. 80, 438 (2003). 13. Selected powder diffraction data for education and train-ing (Search manual and data cards). USA (1988). 14. Ya.S. Umanskii, Kristallografiya, rentgenografiya i el-ektronnaya mikroskopiya (Moskva: Metallurgiya: 1982) (In Russian). 15. X-Ray Metrology in Semiconductor Manufacturing (Ed. D.K. Bowen) (Oxford: Taylor&Francis Group: 2006). 16. D. Kurbatov, H. Khlyap, A. Оpanasyuk, phys. status solidi a 206, 1549 (2009). 17. B.L. Sharma, R.K. Purohit, Semiconductor Heterojunc-tions (Moscow: Soviet Radio: 1979). 18. F. Long, W.-M. Wang, Zh. Cui, L. Fan, Zh. Zou, T. Jia, Chem. Phys. Lett. 462, 84 (2008).   

Structural Properties of ZnO Thin Films Obtained by Chemical Bath Deposition Technique

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 5 No 1, 01009(4pp) (2013) Том 5 № 1, 01009(4cc) (2013) 
 
 
2077-6772/2013/5(1)01009(4) 01009-1  2013 Sumy State University 
Structural Properties of ZnO Thin Films Obtained by Chemical Bath Deposition Technique 
 
T.O. Berestok1, D.I. Kurbatov1, N.M. Opanasyuk1, A.D. Pogrebnjak1,*,  
O.P. Manzhos1, S.M. Danilchenko2 
 
1 Sumy State University, 2, Rimsky-Korsakov Str., 40007 Sumy, Ukraine  
2 Institute of Applied Physics NAS of Ukraine, 58, Petropavliska Str., Sumy, 40030 Ukraine  
 
(Received 11 November 2012; published online 28 March 2013) 
 
Zinc oxide thin films have been deposited onto glass substrates from zinc sulfate, ammonia and thiou-
rea aqueous solution by chemical bath deposition. In the work there were specified solution preparation 
procedure and optimized the composition of the solution and content of component in it. X-ray diffraction 
and high-resolution scanning electron microscopy were used to characterize structure formation of obtain-
ing ZnO films. As a result of investigation the effect of time deposition on the structural and substructural 
properties such as lattice parameters, texture quality, coherent scattering domain size was determined. 
 
Keywords: Zinc Oxide, Chemical bath deposition, Morphology, Structure, Substructure. 
 
 PACS number: 81.05.Dz 
 
 
                                                        
* alexp@i.ua 

The article was reported at the 2nd International Conference «Nanomaterials: Applications  Properties-2012» 
1. INTRODUCTION 
 
Zinc oxide thin films have attracted special atten-
tion of researchers due to its wide range of applications. 
It is used as a key material for light-emitting diodes [1], 
cathode-ray tubes [2], thin film electroluminescence [3], 
gas sensors and etc. [1-3]. ZnO thin films are widely 
used as conductive and optical cover layers of large 
area solar cells [4-5]. 
Recently much attention of researchers has been at-
tracted to fabrication the semiconductor thin layer by 
chemical method [6-12]. Along with this chemical bath 
deposition (CBD) technique is the most promising 
method of thin films deposition [6-10]. Compared to the 
vapor deposition method, the chemical deposition 
method is generally economical, simpler, doesn’t re-
quire high temperature and pressure and convenient 
for large-area deposition. Moreover, this method can 
also be used to obtain thin films with contolable struc-
tural properties such as nanocrystalline layers, nan-
owires and nanobelts [7-8]. Along with this, the CBD 
method is suitable for making films of any shape, such 
as flat-panel, spherical, and porous structures. Main 
feature of this method is that for the deposition of thin 
films there can be used a solution with different chemi-
cal compounds. By the authors of works [6-8] ZnO films 
were obtained from zinc nitrate and hexamethylene 
tetramine (HMTA) solution [7], hexamethylene tetra-
mine and ammonia solution [8], ethylenediamine and 
triethanolamine [6] solution. In contrast to that, for 
deposition films, we have used more available solutions 
of zinc sulphate (ZnSO4) and thiourea (CS(NH2)2). In 
the work was specified solution preparation procedure 
and optimized the composition of the solution and con-
tent of component in it, investigated structural features 
of obtained from this solution thin films. 
 
2. EXPERIMENTAL DETAILS 
 
The details of the procedure are: appropriate 
amounts of zinc sulfate ZnSO4 solution and ammonia 
solution (NH4OH) were separately prepared. Formed 
mixture is thoroughly stirring for several minutes in 
order to dissolve the formed precipitate and solution to 
become homogeneous. Then in obtaining solution was 
added thiourea CS(NH2)2. These solutions were mixed 
in a beaker and stirred well for a few minutes. Thor-
oughly cleaned substrates were maintained in a glass 
reaction vessel. Substrate mounted in a solution within 
a specified time (usually 15-120 minutes) in order to 
obtain the required film thickness.  
Two series of samples have been investigated in this 
work. In the first case the solution was maintained at 
room temperature, in the second case the solution was 
heated to 85 С after placing the substrate. A schematic 
diagram of the deposition set up is shown in Fig 1. 
 
substrate
thin film
solution
heater  
Fig. 1 – Schematic diagram of the chemical deposition system 
 
Structural investigations were carried out with 
using X-ray diffractometer DRON 4-07 (Ni-filtered Kα – 
radiation of Cu-anode). The spectra were registered in 
the angle range 2 from 20  to 80 , where 2 is the 
Bragg angle. X-ray radiation was focused according to 
the Bragg-Brentano method. The phase analysis was 
carried out by comparing interplane distances and 
specific intensities of diffraction patterns from the 
investigated samples and JCPDS etalon [13].  
The quality of the film texture had been estimated 
by the Harris method. It is especially convenient when 
plane specimens with the axis of the texture that is 
oriented normal to the surface tested [14-15]. The pole 
density was calculated as:  
 
 T.O. BERESTOK, D.I. KURBATOV, N.M. OPANASYUK, ET AL. J. NANO.-ELECTRON. PHYS. 5, 01009 (2013) 
 
 
01009-2 
 
 
 
0
0
1
1
i i
i N
i i
i
I I
P
I I
N 


, (1) 
 
Thereafter the dependencies Pi – φ (where φ – is an 
angle between chosen direction and the normal to differ-
ent crystallographic planes corresponding to the reflexes 
in the XRD patterns) and Pi – (hkl)i (where (hkl)i –
 Miller indexes ) were built on the base of the calculation. 
The angle φ was calculated for triclinic and hexagonal 
lattices according to expressions given in [14]. 
The axis of the texture has values corresponding to the 
maximum Pi. The orientation factor was calculated as: 
 
 2
1
1
( 1) .
N
i
i
f P
N 
   (2) 
 
The interplane distances for wurtzite phases of the 
ZnO were carried out by position of Kα1 component of 
all the most intensive lines registered in XRD-patterns.  
Lattice parameters a and c of the hexagonal phase 
for ZnO were calculated according to the next expres-
sions: 
 
 
2
2 2 24 ( )
2sin 3
a
a h hk k l
c


 
     
 
, (3) 
 
 
2
2 2 24 ( ) ,
2sin 3
c
c h hk k l
a


 
    
 
 (4) 
 
where  is X-ray wavelength. 
Further we have applied the Nelson-Riley extrapo-
lation method for more precise determination of the 
parameters a and c for both phases [14-16]. Least-
squares method has enabled to linearly approximate 
the obtained numerical values. 
The XRD results were also used for the description 
of the coherent scattering domain (CSD) size in the 
films. The values of CSD size (L) in the films can be 
calculated using the Scherrer’s relation [14]: 
 
 ,
cos
K
L

 
  (5) 
 
where K is a coefficient weekly depending on the 
grain shape (K = 0,94);  is a physical broadening of the 
X-ray line.  
 
3. INTERPRETATION OF EXPERIMENTAL 
RESULTS 
 
Chemical composition of solutions, concentration 
and other process variables that were used for ZnO 
films deposition are presented in Table 1. 
It was noted that in this work two series of samples 
have been studied. However, the results of X-ray analy-
sis showed that in contrast to the expected results ob-
taining ZnO thin films, we have obtained Zn4SO4(OH)6 
films. It was found that obtaining condensates had tri-
clinic structure (Fig. 2a).  
Litreview proves that [18], layers annealing in vac-
uum leads to decomposition of compound Zn4SO4(OH)6 
and formation of ZnO or ZnS thin films that depend on 
the annealing temperature. 
Table 1 – The content of reagents in solution and technologi-
cal parameters of obtaining films 
 
№ 
First series of samples 
ZnSO4 
(0,1 mol), 
ml 
CS(NH2)2 
(1 mol),  
ml 
NH4
OH, 
ml 
pH Тr, 
0С 
τ, 
min 
1 20 4 2 9-10 85 20 
2 10 1 1 20 
3 20 20 2 20 
4 10 1 1 85 
 Second series of samples 
1 
50 5 7 10 85 
20 
2 30 
3 60 
4 90 
5 120 
 
 
  
 
Fig. 2 – X-ray patterns of films: first series (Table 1, 1-4 sam-
ples) (a) and second series (Table 1, 1-5 samples) (b) of samples 
 
Initial layers annealing in air leads to their oxida-
tion and the formation of ZnSxO1 – x solid solution films. 
Therefore, we have carried out further annealing in 
vacuum at 500 С for 60 min and in the air - at 200 С 
for 20 min. In this case we have obtained low quality 
ZnO films.  
The second series of samples was obtained from a 
solution of zinc sulfate, thiourea and ammonia in order 
to control pH value. pH was raised at 10. On X-Ray 
diffraction patterns of this series of samples we have 
registered reflexes with dominant intensity on degrees 
34.410-34.420. Experimentally revealed diffraction 
peaks may be interpreted as reflexes from the plane 
(002) of the hexagonal phase ZnO (Fig. 2b). Along with 
the peaks mentioned above we have registered reflexes 
on degrees 31.750-31.760 and 36.240-36.250 which can 
be interpreted as reflexes from the planes (100) and 
(101) respectively. Consequently there took place for-
mation ZnO thin films with hexagonal structure.  
 
b 
а 
 STRUCTURAL PROPERTIES OF ZNO THIN FILMS OBTAINED… J. NANO.-ELECTRON. PHYS. 5, 01009 (2013) 
 
 
01009-3 
  
 
  
 
 
Fig. 3 – SEM images of ZnO films obtained under deposition time: 90 min (a, b); 120 min (c, d)
 
   
Fig. 4 – Pole density Pi and orientation factor f as a function of the incidence angle φ between the direction and the normal to the 
reflection plane for films: first series (Table 1, 1-4 samples) (a) and second series (Table 1, 1-5 samples) (b) of  samples 
 
Fig. 3 displays images of the surface for ZnO. It is 
found that density of crystallites increases with the 
increase of time deposition. Accordingly there took 
place formation of the continuous film at a thickness 
more than 1 µm. 
When create heterojunctions based on ZnO thin 
films it is important that layers coupling occurred in 
the same crystallographic plane in different crystallites 
[17]. This is due to the fact that the density of interfa-
cial defects depends on the plane contact type of hetero 
pair materials. Consequently condition interfacial area 
determines the transport mechanism of charge carriers 
through heterojunction. Therefore it determines the 
efficiency of its use in such devices as solar cells and 
photodetectors. This caused the urgency of determining 
of the effect on the time deposition on texture quality.  
Reverse pole figures from ZnO are shown in Fig. 4a. 
As it seen, the samples are well textured. Along with 
this, the dominated orientation of crystallites is [002]. 
The quality of texture depends on technological condi-
tions. In the obtained ZnO films increasing deposition 
time  from 20 to 60 minutes leads to improvement, 
and then (from 90 to 120 min) to a significant deterio-
ration of the texture quality (inset in Fig. 4a). This is 
associated with growth features of obtained layer.  
It is found that condensates deposited for  = 20 min 
have nanorods form as hexagonal prisms. These struc-
tures grew with dimension: d = (0.25-1.00) µm in  
diameter and l = (2.50-3.00) µm on length. 
It should be noted that nanorods grew at different 
angles (in most cases – perpendicular) to the substrate 
and oriented perpendicular to the substrate by crystal-
lographic axis с, which coincides with the texture axis. 
And this makes high quality of texture at the early 
stages of the film growth. With the increasing conden-
sation time due to the secondary nucleation there took 
place growth of plate crystallites between nanorods 
intervals. Finally this fact leads to the formation of a 
continuous film and decrease texture quality.  
Along with this, Zn4SO4 (OH)6 thin films had tex-
ture on plane [0-13]. These kinds of exotic textures 
quite often take place in films obtained by chemical 
bath deposition [18]. The results of lattice constants 
estimation are presented in Table 2.  
 
 
 
а 
b 
b 
а b 
c d 
 T.O. BERESTOK, D.I. KURBATOV, N.M. OPANASYUK, ET AL. J. NANO.-ELECTRON. PHYS. 5, 01009 (2013) 
 
 
01009-4 
Table 2 – Lattice parameters of ZnO with hexagonal structure  
 
τ, 
(min) 
Lattice parameters, 
(nm) 
CSD size, L 
(nm) 
hkl 
а с с/a (100) (002) 
20 0.37645 0.57117 1.517 40.1 45.0 
30 0.33407 0.50727 1.518 35.9 46.4 
60 0.33895 0.51446 1.517 92.9 43.1 
90 0.32168 0.48838 1.518 49.1 54.3 
120 0.33425 0.50696 1.516 35.5 40.8 
Ref. [13] 0.34298 0.52066 1.520   
 
From Table 2, lattice parameters of films with low 
thickness (  20 min) are a  0.37602 nm, 
c  0.57081 nm. These values are more than reference 
ones (a  0.34298 nm, c  0.52066 nm) [13]. This effect  
 
 
 
Fig. 5 – Effect of the time deposition on the CSD size in ZnO 
thin films. The CSD sizes in directions normal to the 
crystallographic planes (100) (1) and (002) (2)  are determined 
 
may be due to a small size of crystallites in conden-
sates, which has nanorods form as already mentioned. 
With the increase of time deposition and film thickness 
corresponding lattice constants value is approaching to 
the reference one. 
Fig. 5 depicts the effect of the time deposition on the 
CSD in directions normal to the crystallographic planes 
(100) and (002) in ZnO thin films. These values 
correspond to the size of CSD in perpendicular directions 
to а and с axes of ZnO lattice. 
The values of CSD were equal to L(100)  (35-93) nm, 
L(002)  (40-54) nm. These data are much smaller than 
electron-defined (d  (0.25-1.00) µm, l  (2.50-3.00) µm). 
This indicates that crystallites consist of several CSD.  
 
4. CONCLUSIONS 
 
ZnO thin films with different thickness have been 
obtained from zinc sulfate, ammonia and thiourea 
aqueous solution with the help of chemical bath deposi-
tion technique. It is found that growth of thin layers 
took place by the formation of nanorods as hexagonal 
prisms and grew perpendicular to the substrate with 
further growth of plate crystallites between nanorods 
intervals. It is shown that the films have a hexagonal 
structure with lattice constant, varying with increasing 
thickness from а  0.37601 nm, с  0.57079 to 
а  0.33408 nm and с  0.50714 nm.  
In addition it was studied the effect of the time dep-
osition on texture quality of ZnO thin films. Further-
more it is shown that the quality of texture was wors-
ened with increasing deposition time. CSD estimating 
allowed us to evaluate that crystallites which formed at 
the initial stage of film growth consist of several sub-
grain. 
 
AKNOWLEDGEMENTS 
 
This work is supported by the Ukraine State Agency 
for the Science, Innovation and Informatization and by 
the NRF grant funded by the MEST of Korea (2011-
0019204) within the project «Advanced materials for 
low-cost high-efficiency polycrystalline heterojunction 
thin films solar cells» and by the Ministry of Education 
and Science, Youth and Sport of Ukraine (Grant №. 
0112U000772). 
 
 
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Structural Properties of ZnO Thin Films Obtained by Chemical Bath Deposition Technique

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