In this work by energy dispersive analysis of X-rays, scanning electron microscopy and X-ray diffraction methods films of CdxZn1-xTe solid solution, obtained by a close-spaced vacuum sublimation technique under different temperatures of glass substrate, has been studied. Films were deposited by the co sublimation of Cadmium Telluride (CdTe) and Zinc Telluride (ZnTe) chunks, mixed in the ratio of 2:1. The effect of substrate temperature on the surface morphology, elemental and phase composition, lattice parameter, scattering domain sizes has been studied. The results of these studies can be used for obtaining absorber layers of tandem solar cells, basic layers of X-ray and gamma detectors

Gnatenko, Yu.P.

Kosyak, V.V.

Kuznetsov, V.

Opanasiuk, Anatolii Serhiiovych

Stanislavov, A.

Znamenshchykov, Y.V.

Опанасюк, Анатолий Сергеевич

Опанасюк, Анатолій Сергійович

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 3 No 1, 01NTF24(4pp) (2014) 
 
  
2304-1862/2014/3(1)01NTF24(4) 01NTF24-1  2014 Sumy State University 
Effect of Substrate Temperature on the Structural Properties of CdxZn1 – xTe Films Grown 
by Close-Spaced Sublimation Method 
 
Y.V. Znamenshchykov1,*, V.V. Kosyak1, A.S. Opanasyuk1, 
A. Stanislavov2, V. Kuznetsov2, Yu.P. Gnatenko3 
 
1 Sumy State University, 2, Rymsky Korsakov Str., 40007 Sumy, Ukraine 
2 Institute of Applied Physics, NAS of Ukraine, 58, Petropavlivska Str., 40030 Sumy, Ukraine 
3 Institute of Physics of National Academy of Sciences of Ukraine, 03028 Kyiv, Ukraine 
 
(Received 01 August 2014; published online 29 August 2014) 
 
In this work by energy dispersive analysis of X-rays, scanning electron microscopy and X-ray diffrac-
tion methods films of CdxZn1-xTe solid solution, obtained by a close-spaced vacuum sublimation technique 
under different temperatures of glass substrate, has been studied. Films were deposited by the co sublima-
tion of Cadmium Telluride (CdTe) and Zinc Telluride (ZnTe) chunks, mixed in the ratio of 2:1. The effect of 
substrate temperature on the surface morphology, elemental and phase composition, lattice parameter, 
scattering domain sizes has been studied. The results of these studies can be used for obtaining absorber 
layers of tandem solar cells, basic layers of X-ray and gamma detectors.  
 
Keywords: CdZnTe, Closed space sublimation, XRD, Bandgap, Film. 
 
 PACS numbers: 68.37.Hk, 71.55.Gs, 81.40. – z 
 
 
                                                 
*
 yaroslav.znamenshchykov@gmail.com 
1. INTRODUCTION 
 
Chlorine doped Cadmium Telluride CdTe:Cl single 
crystals were used as basic material for X-ray and 
gamma-ray detectors during a long period [3]. Howev-
er, recent time a trend of replacing this material by 
solid three-component solutions, especially of Zn-
containing, has observed. This is due to a number of 
significant advantages of CdxZn1-xTe solid solutions 
over the two-component compound, namely: higher 
resistivity of the material, higher atomic binding ener-
gy, tunable band gap of semiconductor by adjusting the 
film composition [11].  
Last time mono- and polycrystalline films of three-
component solution with high-quality crystal structure 
are used as a detector material [5]. Wherein adjusting 
of Zn constitution allows to vary band gap of the mate-
rial in the range from Eg1 = 1.50 eV (CdTe) to Eg2 = 
2.26 eV (ZnTe). The films of CdxZn1-xTe with band gap 
in the range of 1.65-1.75 eV are perspective material 
for absorber layers of X-ray and gamma-ray detectors 
and tandem solar cells that can operate at room tem-
perature [6]. 
There are several techniques for preparation of 
CdxZn1-xTe films, such as  electrodeposition [24], molec-
ular beam epitaxy [19], metal-organic chemical vapor 
desposition [20], sputtering [2], thermal vacuum evapo-
ration [20].We used close-spaced vacuum sublimation 
(CSVS) method for the deposition of solid solutions. In 
comparison with other techniques, close spaced subli-
mation is quite simple and cheap method, which allows 
to obtain films in conditions close to thermodynamically 
equilibrium, where structurally perfect layers of chal-
cogenides are grown [6]. In case of using CSVS method, 
properties of the films depend on physical and techno-
logical conditions of their growing. According to the 
analysis of published data [6], substrate temperature 
has the greatest effect on structural, optical and elec-
trophysical properties of obtained layers. Thus the aim 
of this work is to investigate effect of substrate temper-
ature on structural and substructural properties of 
CdxZn1-xTe films obtained by close-spaced vacuum sub-
limation.  
 
2. EXPERIMENTAL DETAILS 
 
Films of CdxZn1-xTe solid solutions were deposited 
on non-oriented glass substrates by close spaced vacu-
um sublimation in vacuum equipment VUP-5M. Resid-
ual gas pressure in the chamber did not exceed of 5×10-3 
Pa. Evaporator temperature was Te = 923 K, substrate 
temperature was varied in the range of Ts = 673-823 K. 
Two different sources (CdTe and ZnTe mixed in the 
ratio 2:1) were co-evaporated to form films.  
The surface morphology of the films has been inves-
tigated by optical and scanning electron microscopy 
(SEM). The average grain size (D) in the layers was 
estimated by Jeffries method [16]. 
Elementary composition of the films was deter-
mined by X-ray energodispersive spectroscopy (EDAX) 
using the console to the electron microscope. Determi-
nation of the mass concentration of the elements, that 
are included in film (СCd, СZn, CTe), was carried out at 
least in 3 points on the surface of samples, following  
averaging of result was performed.  
Structural investigations of the films were per-
formed with an X-ray diffractometer, DRON 4-07 
(λ = 0.15406 nm, U = 40 kV, I = 40 uA), with Cu Kα ra-
diation over the range 20° ≤ 2θ ≤ 80° (where 2θ is the 
Bragg angle) at room temperature.  
The diffraction patterns obtained under study were 
normalized to the intensity of (111) peak of the cubic 
phase. Phase analysis was done by comparison of in-
terplanar distances and relative intensities from the 
 Y.V. ZNAMENSHCHYKOV, V.V. KOSYAK, ET AL. PROC. NAP 3, 01NTF24 (2014) 
 
 
01NTF24-2 
investigated samples and references according to Joint 
Committee on Powder Diffraction Standards (JCPDS 
card № 01-089-1397).  
Lattice constants a of cubic phase were found by the 
position of the K 1 component of the diffraction pattern 
observed at large angles from the following equation  
 
2 2 2( )
2sin
a h k l
.   (2) 
Subsequently, the values of these constants was clari-
fied using the the Nelson–Riley extrapolation method 
[15]. Thus plots were built in a(c) – 1/2cos2θ(1/sin(θ)+1/θ)) 
coordinates. Linear approximation of obtained points 
was conducted using the method of least squares using 
the software package OriginPro.  
Average coherent scattering regions (CSR) size was 
determined from the Debye-Scherrer formula: 
 
,
cos
k
L
   (4) 
Where λ is the x-ray wavelength, β is the line width 
of the “pure” diffraction profile resulting from small 
crystallite size, and k is a constant approximately equal 
to unity and related to crystallite shape (k = 0.9).  
Detailed methodology for determining the structur-
al characteristics of the films is described in [15].  
 
3. RESULTS AND DISCUSSION 
 
In figure 1 surface morphology of the films grown 
under different substrate temperatures is shown.  
As it is seen from figure, average grain sizes in 
films depends on technological conditions of growing 
and increases with increasing the substrate 
temperature Ts. At Ts = 673 K it is D = 4.1 microns, 
while at Ts = 823 K - D = 14.5 microns. Particularly 
significant increase of grain size of CdxZn1-xTe films is 
observed at Ts > 700 K (figure 1). This can be explained 
by changing of their deposition regime from the molecu-
lar to the gas-dynamic and approaching of growth con-
ditions close to thermodynamically equilibrium [15]. 
 
  
  
Fig. 1 – SEM images of surface morphology of the CdxZn1-xTe 
films, obtained on non-oriented glass substrates under differ-
ent substrate temperatures Ts, K: 673 (а), 723 (b), 773 (c) and 
823 (d). 
In figure 2 typical EDAX spectras of syntezed layers 
are shown. The analysis shows that the film includes 
only components of a solid solution - Cd, Zn, Te. 
According to EDAX, films contain 7-13 at. % of Zinc. 
Extraneous components that belong to substrate or 
residual atmosphere of the vacuum chamber, were not 
identified. 
 
 
 
Рис.2.  - Typical EDAX spectra of films obtained under differ-
ent substrate temperature Ts, K: 723 (a) and 823 (b).  
 
The XRD patterns of the CdxZn1-xTe films obtained 
at different substrate temperatures are presented in 
Figure 2. In these patterns positions of diffraction 
peaks from CdTe (solid black line) and ZnTe (dashed 
red line) compounds are shown. As it is seen on figure 
2, reflection from planes of solid solution locates 
between reflections from clear materials. This indicates 
that we invistigated CdxZn1-xTe films. 
 
 
 
Fig. 3 – Diffraction patterns of CdxZn1-xTe films obtained un-
der different substrate temperature Ts, K: 673 (1), 723 (2), 773 
(3), 823 (4). Vertical lines correspond to JCPDS reference data 
of CdTe (solid line) and ZnTe (dashed line) compounds.  
 
Phase analysis of samples was performed using 
JCPDS directory  (card № 01-089-1397). As it is seen 
a b 
c d 
a 
b 
 STRUCTURAL PROPERTIES OF CHEMICALLY-DEPOSITED… PROC. NAP 3, 01NTF24 (2014) 
 
 
01NTF24-3 
from figure, peak at angles 24.10°-24.60° dominates, 
which corresponds to the reflection from the (111) plane 
of the cubic phase CdxZn1-xTe. In some cases, there was 
a double peak, indicating the formation of two solid 
solutions with different concentrations of zinc. But 
basically, the samples were single-phase and contained 
cubic phase. Oxide and other extraneous phases in the 
condensates were found. 
The lattice parameters of A2B6 compound 
semiconductors are very sensitive to changes in the 
material stoichiometry, impurity inclusions, oxidation, 
etc., what is why precise measurement of this quantity 
makes it possible to study these processes. We carried 
out X-ray diffraction (XRD) determination of the lattice 
parameter for the material of films obtained under 
different regimes of condensation. As studies have 
shown, the lattice parameter of the material film was a 
= 0.63166 - 0.64144 nm.  
In Figure 4 the dependence of the lattice parameter 
a under the substrate temperature is shown. As it is 
shown in Fig. 4, as the substrate temperature Ts 
increases from 673 K to 823 K, the calculated values of 
lattice parameter a of film material decreases from a = 
0.64144 nm to a = 0.63166 nm. This may indicate an 
increase of zinc content in a high-temperature 
condensates because atomic radius of zinc atom (142 
pm) is smaller than cadmium (161 pm). 
 
 
Fig. 4 – Dependence of the lattice parameter a of  CdxZn1-xTe 
films on substrate temperature.  
 
Results of calculation of CSD sizes in CdxZn1-xTe 
films in directions perpendicular to (111), (220) and 
(311) crystallographic planes are shown in Figure 5. It 
is found that these dimensions take the following 
values: L(111) = 17-31 nm, L(220) = 16-32 nm, L(311) = 12-
27 nm. As it is seen in figure, with the increase of 
substrate temperature from 673K to 723K CSR size, for 
example in direction (111), increases slightly from 26 to 
31 nm, but with further increase of Ts it desreases to 
17-21 nm. A similar trend is observed for the CSR size 
in all other crystallographic directions.  Similar L - Ts 
dependence with a maximum at temperatures 600-700 
K was observed earlier in A2B6 compounds films [16]. 
Deterioration of structure of the films after increase of 
substrate temperature above 673 K can be explained by 
re-evaporation of components of solid solution 
(especially of cadmium) from the surface of the 
condensate, which leads to occurrence of additional 
dislocations in their volume and leads to a reduction in 
the CSR sizes.  
 
 
 
Fig. 5 – Dependence of CSR sizes (L) of CdxZn1-xTe films on 
substrate temperature. Values for the crystallographic direc-
tions  [111], [220] and [311] are presented.  
 
According to the results of the studies, due to its 
structural and substructural features, obtained CdxZn1-
xTe films can be used as an absorbing layers of tandem 
solar cells and as basic layers of X-ray detectors and 
gamma-ray detectors. Thus films grown at substrate 
temperatures close to 723 K have optimal for instru-
mental usage properties. Such films have single-phase 
structure with sufficiently large grain size and high 
crystalline quality.  
 
4. CONCLUSION 
 
In this work by energy dispersive analysis of X-rays, 
scanning electron microscopy and X-ray diffraction 
methods films of CdxZn1-xTe solid solution, obtained 
by a close-spaced vacuum sublimation technique under 
different temperatures of glass substrate, has been 
studied. The effect of substrate temperature on the sur-
face morphology, elementary and phase composition, 
lattice parameter, scattering domain sizes has been 
studied.  
It is shown that obtained films have a polycrystal-
line structure with a grain size of 4-15 microns, which 
increases with increasing of the substrate temperature. 
Films were mostly single-phase and contained a cubic 
phase of CdxZn1-xTe. 
It was determined that the experimental values of 
the lattice parameter of the material of the films de-
creases  from а = 0.64144 nm to а = 0.63166 nm as sub-
strate temterature Ts increases from 673K to 823K, 
which may indicate an increase of zinc content in a 
high-temperature condensates. CSR sizes in films take 
following values: L(111) = 17-31 nm, L(220) = 16-32 nm, 
L(311) = 12-27 nm, thus L-Ts  dependences have form of 
the curve with a maximum at substrate temperature Ts 
= 673K. 
Obtained CdxZn1-xTe films can be used as an absorb-
ing layers of tandem solar cells and as basic layers of X-
ray detectors and gamma-ray detectors. 
 
 Y.V. ZNAMENSHCHYKOV, V.V. KOSYAK, ET AL. PROC. NAP 3, 01NTF24 (2014) 
 
 
01NTF24-4 
REFERENCES 
 
1. K.H. Kim, K.N. Oh, and S.U. Kim, J. Korean Phys. Soc. 41 
No4, 471 (2002). 
2. Dongmei Zeng, Wanqi Jie, Hai Zhou, Adv. Mater. Res.  
194-196, 2312 (2011).  
3. H. Shirinzadeh, K. Ahmadi, Int. J. Fund. Phys. Sci. 1, No 
2, 37 (2011). 
4. Rekha G. Solanki, Ind. J. Pure Appl. Phys. 48, 133 (2010). 
5. Monisha Chakraborty, Int. J. Eng. Res. Appl. 2 No2, 994 
(2012). 
6. J. Huang, L. J. Wang, K. Tang, Run Xu, Phys. Procedia 32, 
161 (2012). 
7. R. Dhere, T.Gessert, J. Zhou, S. Asher, J. Pankow, and H. 
Moutinho, Materials Research Society Spring Meeting (San 
Francisco, California, April 21-25, 2003). 
8. Bulent M. Basol, Vijay K. Kapur, and Michael L. Ferris,  
J. Appl. Phys. 66, 1816 (1989). 
9. G.E. Hallani, A. Ryah, N. Hassanain, Progress in Electro-
magnetics Research Symposium Proceedings (Marrakesh, 
Morocco 1897, 2011). 
10. Monisha Chakraborty, Int. J. Eng. Sci. Tech. 3 No5, 3798 
(2011). 
11. Satoshi Tokuda, Hiroyuki Kishihara, Susumu Adachi, 
Toshiyuki Sato, J. Mater. Sci. Mat. Electron. 15, 1 (2004). 
12. S. Stolyarova, F. Edelman, A. Chack, A. Berner, P. Wer-
ner, J. Phys. D: Appl. Phys. 41 065402 (2008). 
13. I.P. Kalinkin, V.B. Aleskovskiy Epitaksial'nyye plenki 
soyedineniy A2B6 (Leningrad: Izd-vo LGU, 1978). 
14. B.E. Warren, X-ray Diffraction (New York: Dover, 1990). 
15. D. Kurbatov, V. Kosyak, M. Kolesnyk, A. Оpanasyuk, 
S. Danilchenko, Integr. Ferroelectrics 103 No1, 32 (2009). 
16. V.V. Kosyak, D.I. Kurbatov, M.M. Kolesnyk, A.S. 
Opanasyuk,  S.N. Danilchenko, Yu.P. Gnatenko, J. Mater. 
Chem. Phys. 138, 731 (2013). 
17. D. Kurbatov, S. Kshnyakina, S. Danilchenko, XIII Interna-
tional Conference on Physics and Technology of Thin Films 
and Nanostructures (ICPTTFN-XIII), 152 (Ivano-
Frankivsk, Ukraine, 2011). 
18. Anu Bansal, P. Rajaram, J. Mater. Lett. 59, 3666 (2005). 
19. K. Zanio, Semiconductors and Semimetals, Vol. 13, Cad-
mium Telluride (Academic Press: 1978). 
20. Robert K. Willardson, Albert C. Beer, Contacts, Junctions, 
Emitters, Vol. 15, Semiconductors and Semimetals (Aca-
demic Press, 1981). 
21. A.J. Bard, L.R. Faulkner, Electro-chemical Methods, 
Eighteenth edition (John Wiley, New York: 1980). 
22. M. Singh, E. Mumcuoglu, IEEE Trans. Nucl. Sci. 45, 153 
(1998). 
23. B.M. Basol, V.K. Kapur, R.L. Mitchell, Thin Solid Films, 
67, 509 (1990). 
24. A. Brenner, Electrodeposition of Alloys: Principles and 
Practice, Vol. 12 (Academic Press, New York: 1963). 
25. T. Mahalingham, V.S. John, S. Rajendran, P.J. Sebastain, 
J. Semicond. Sci. Technol. 17, 465 (2002). 
26. A. Lopez-Otero, Thin Solid Films 49, 3 (1978). 
 


English

Effect of Substrate Temperature on the Structural Properties of CdxZn1-xTe Films Grown by Close-Spaced Sublimation Method

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 3 No 1, 01NTF24(4pp) (2014)    2304-1862/2014/3(1)01NTF24(4) 01NTF24-1  2014 Sumy State University Effect of Substrate Temperature on the Structural Properties of CdxZn1 – xTe Films Grown by Close-Spaced Sublimation Method  Y.V. Znamenshchykov1,*, V.V. Kosyak1, A.S. Opanasyuk1, A. Stanislavov2, V. Kuznetsov2, Yu.P. Gnatenko3  1 Sumy State University, 2, Rymsky Korsakov Str., 40007 Sumy, Ukraine 2 Institute of Applied Physics, NAS of Ukraine, 58, Petropavlivska Str., 40030 Sumy, Ukraine 3 Institute of Physics of National Academy of Sciences of Ukraine, 03028 Kyiv, Ukraine  (Received 01 August 2014; published online 29 August 2014)  In this work by energy dispersive analysis of X-rays, scanning electron microscopy and X-ray diffrac-tion methods films of CdxZn1-xTe solid solution, obtained by a close-spaced vacuum sublimation technique under different temperatures of glass substrate, has been studied. Films were deposited by the co sublima-tion of Cadmium Telluride (CdTe) and Zinc Telluride (ZnTe) chunks, mixed in the ratio of 2:1. The effect of substrate temperature on the surface morphology, elemental and phase composition, lattice parameter, scattering domain sizes has been studied. The results of these studies can be used for obtaining absorber layers of tandem solar cells, basic layers of X-ray and gamma detectors.   Keywords: CdZnTe, Closed space sublimation, XRD, Bandgap, Film.   PACS numbers: 68.37.Hk, 71.55.Gs, 81.40. – z                                                    * yaroslav.znamenshchykov@gmail.com 1. INTRODUCTION  Chlorine doped Cadmium Telluride CdTe:Cl single crystals were used as basic material for X-ray and gamma-ray detectors during a long period [3]. Howev-er, recent time a trend of replacing this material by solid three-component solutions, especially of Zn-containing, has observed. This is due to a number of significant advantages of CdxZn1-xTe solid solutions over the two-component compound, namely: higher resistivity of the material, higher atomic binding ener-gy, tunable band gap of semiconductor by adjusting the film composition [11].  Last time mono- and polycrystalline films of three-component solution with high-quality crystal structure are used as a detector material [5]. Wherein adjusting of Zn constitution allows to vary band gap of the mate-rial in the range from Eg1 = 1.50 eV (CdTe) to Eg2 = 2.26 eV (ZnTe). The films of CdxZn1-xTe with band gap in the range of 1.65-1.75 eV are perspective material for absorber layers of X-ray and gamma-ray detectors and tandem solar cells that can operate at room tem-perature [6]. There are several techniques for preparation of CdxZn1-xTe films, such as  electrodeposition [24], molec-ular beam epitaxy [19], metal-organic chemical vapor desposition [20], sputtering [2], thermal vacuum evapo-ration [20].We used close-spaced vacuum sublimation (CSVS) method for the deposition of solid solutions. In comparison with other techniques, close spaced subli-mation is quite simple and cheap method, which allows to obtain films in conditions close to thermodynamically equilibrium, where structurally perfect layers of chal-cogenides are grown [6]. In case of using CSVS method, properties of the films depend on physical and techno-logical conditions of their growing. According to the analysis of published data [6], substrate temperature has the greatest effect on structural, optical and elec-trophysical properties of obtained layers. Thus the aim of this work is to investigate effect of substrate temper-ature on structural and substructural properties of CdxZn1-xTe films obtained by close-spaced vacuum sub-limation.   2. EXPERIMENTAL DETAILS  Films of CdxZn1-xTe solid solutions were deposited on non-oriented glass substrates by close spaced vacu-um sublimation in vacuum equipment VUP-5M. Resid-ual gas pressure in the chamber did not exceed of 5×10-3 Pa. Evaporator temperature was Te = 923 K, substrate temperature was varied in the range of Ts = 673-823 K. Two different sources (CdTe and ZnTe mixed in the ratio 2:1) were co-evaporated to form films.  The surface morphology of the films has been inves-tigated by optical and scanning electron microscopy (SEM). The average grain size (D) in the layers was estimated by Jeffries method [16]. Elementary composition of the films was deter-mined by X-ray energodispersive spectroscopy (EDAX) using the console to the electron microscope. Determi-nation of the mass concentration of the elements, that are included in film (СCd, СZn, CTe), was carried out at least in 3 points on the surface of samples, following  averaging of result was performed.  Structural investigations of the films were per-formed with an X-ray diffractometer, DRON 4-07 (λ = 0.15406 nm, U = 40 kV, I = 40 uA), with Cu Kα ra-diation over the range 20° ≤ 2θ ≤ 80° (where 2θ is the Bragg angle) at room temperature.  The diffraction patterns obtained under study were normalized to the intensity of (111) peak of the cubic phase. Phase analysis was done by comparison of in-terplanar distances and relative intensities from the  Y.V. ZNAMENSHCHYKOV, V.V. KOSYAK, ET AL. PROC. NAP 3, 01NTF24 (2014)   01NTF24-2 investigated samples and references according to Joint Committee on Powder Diffraction Standards (JCPDS card № 01-089-1397).  Lattice constants a of cubic phase were found by the position of the K 1 component of the diffraction pattern observed at large angles from the following equation   2 2 2( )2sina h k l.   (2) Subsequently, the values of these constants was clari-fied using the the Nelson–Riley extrapolation method [15]. Thus plots were built in a(c) – 1/2cos2θ(1/sin(θ)+1/θ)) coordinates. Linear approximation of obtained points was conducted using the method of least squares using the software package OriginPro.  Average coherent scattering regions (CSR) size was determined from the Debye-Scherrer formula:  ,coskL   (4) Where λ is the x-ray wavelength, β is the line width of the “pure” diffraction profile resulting from small crystallite size, and k is a constant approximately equal to unity and related to crystallite shape (k = 0.9).  Detailed methodology for determining the structur-al characteristics of the films is described in [15].   3. RESULTS AND DISCUSSION  In figure 1 surface morphology of the films grown under different substrate temperatures is shown.  As it is seen from figure, average grain sizes in films depends on technological conditions of growing and increases with increasing the substrate temperature Ts. At Ts = 673 K it is D = 4.1 microns, while at Ts = 823 K - D = 14.5 microns. Particularly significant increase of grain size of CdxZn1-xTe films is observed at Ts > 700 K (figure 1). This can be explained by changing of their deposition regime from the molecu-lar to the gas-dynamic and approaching of growth con-ditions close to thermodynamically equilibrium [15].      Fig. 1 – SEM images of surface morphology of the CdxZn1-xTe films, obtained on non-oriented glass substrates under differ-ent substrate temperatures Ts, K: 673 (а), 723 (b), 773 (c) and 823 (d). In figure 2 typical EDAX spectras of syntezed layers are shown. The analysis shows that the film includes only components of a solid solution - Cd, Zn, Te. According to EDAX, films contain 7-13 at. % of Zinc. Extraneous components that belong to substrate or residual atmosphere of the vacuum chamber, were not identified.    Рис.2.  - Typical EDAX spectra of films obtained under differ-ent substrate temperature Ts, K: 723 (a) and 823 (b).   The XRD patterns of the CdxZn1-xTe films obtained at different substrate temperatures are presented in Figure 2. In these patterns positions of diffraction peaks from CdTe (solid black line) and ZnTe (dashed red line) compounds are shown. As it is seen on figure 2, reflection from planes of solid solution locates between reflections from clear materials. This indicates that we invistigated CdxZn1-xTe films.    Fig. 3 – Diffraction patterns of CdxZn1-xTe films obtained un-der different substrate temperature Ts, K: 673 (1), 723 (2), 773 (3), 823 (4). Vertical lines correspond to JCPDS reference data of CdTe (solid line) and ZnTe (dashed line) compounds.   Phase analysis of samples was performed using JCPDS directory  (card № 01-089-1397). As it is seen a b c d a b  STRUCTURAL PROPERTIES OF CHEMICALLY-DEPOSITED… PROC. NAP 3, 01NTF24 (2014)   01NTF24-3 from figure, peak at angles 24.10°-24.60° dominates, which corresponds to the reflection from the (111) plane of the cubic phase CdxZn1-xTe. In some cases, there was a double peak, indicating the formation of two solid solutions with different concentrations of zinc. But basically, the samples were single-phase and contained cubic phase. Oxide and other extraneous phases in the condensates were found. The lattice parameters of A2B6 compound semiconductors are very sensitive to changes in the material stoichiometry, impurity inclusions, oxidation, etc., what is why precise measurement of this quantity makes it possible to study these processes. We carried out X-ray diffraction (XRD) determination of the lattice parameter for the material of films obtained under different regimes of condensation. As studies have shown, the lattice parameter of the material film was a = 0.63166 - 0.64144 nm.  In Figure 4 the dependence of the lattice parameter a under the substrate temperature is shown. As it is shown in Fig. 4, as the substrate temperature Ts increases from 673 K to 823 K, the calculated values of lattice parameter a of film material decreases from a = 0.64144 nm to a = 0.63166 nm. This may indicate an increase of zinc content in a high-temperature condensates because atomic radius of zinc atom (142 pm) is smaller than cadmium (161 pm).   Fig. 4 – Dependence of the lattice parameter a of  CdxZn1-xTe films on substrate temperature.   Results of calculation of CSD sizes in CdxZn1-xTe films in directions perpendicular to (111), (220) and (311) crystallographic planes are shown in Figure 5. It is found that these dimensions take the following values: L(111) = 17-31 nm, L(220) = 16-32 nm, L(311) = 12-27 nm. As it is seen in figure, with the increase of substrate temperature from 673K to 723K CSR size, for example in direction (111), increases slightly from 26 to 31 nm, but with further increase of Ts it desreases to 17-21 nm. A similar trend is observed for the CSR size in all other crystallographic directions.  Similar L - Ts dependence with a maximum at temperatures 600-700 K was observed earlier in A2B6 compounds films [16]. Deterioration of structure of the films after increase of substrate temperature above 673 K can be explained by re-evaporation of components of solid solution (especially of cadmium) from the surface of the condensate, which leads to occurrence of additional dislocations in their volume and leads to a reduction in the CSR sizes.     Fig. 5 – Dependence of CSR sizes (L) of CdxZn1-xTe films on substrate temperature. Values for the crystallographic direc-tions  [111], [220] and [311] are presented.   According to the results of the studies, due to its structural and substructural features, obtained CdxZn1-xTe films can be used as an absorbing layers of tandem solar cells and as basic layers of X-ray detectors and gamma-ray detectors. Thus films grown at substrate temperatures close to 723 K have optimal for instru-mental usage properties. Such films have single-phase structure with sufficiently large grain size and high crystalline quality.   4. CONCLUSION  In this work by energy dispersive analysis of X-rays, scanning electron microscopy and X-ray diffraction methods films of CdxZn1-xTe solid solution, obtained by a close-spaced vacuum sublimation technique under different temperatures of glass substrate, has been studied. The effect of substrate temperature on the sur-face morphology, elementary and phase composition, lattice parameter, scattering domain sizes has been studied.  It is shown that obtained films have a polycrystal-line structure with a grain size of 4-15 microns, which increases with increasing of the substrate temperature. Films were mostly single-phase and contained a cubic phase of CdxZn1-xTe. It was determined that the experimental values of the lattice parameter of the material of the films de-creases  from а = 0.64144 nm to а = 0.63166 nm as sub-strate temterature Ts increases from 673K to 823K, which may indicate an increase of zinc content in a high-temperature condensates. CSR sizes in films take following values: L(111) = 17-31 nm, L(220) = 16-32 nm, L(311) = 12-27 nm, thus L-Ts  dependences have form of the curve with a maximum at substrate temperature Ts = 673K. Obtained CdxZn1-xTe films can be used as an absorb-ing layers of tandem solar cells and as basic layers of X-ray detectors and gamma-ray detectors.   Y.V. ZNAMENSHCHYKOV, V.V. KOSYAK, ET AL. PROC. NAP 3, 01NTF24 (2014)   01NTF24-4 REFERENCES  1. K.H. Kim, K.N. Oh, and S.U. Kim, J. Korean Phys. Soc. 41 No4, 471 (2002). 2. Dongmei Zeng, Wanqi Jie, Hai Zhou, Adv. Mater. Res.  194-196, 2312 (2011).  3. H. Shirinzadeh, K. Ahmadi, Int. J. Fund. Phys. Sci. 1, No 2, 37 (2011). 4. Rekha G. Solanki, Ind. J. Pure Appl. Phys. 48, 133 (2010). 5. Monisha Chakraborty, Int. J. Eng. Res. Appl. 2 No2, 994 (2012). 6. J. Huang, L. J. Wang, K. Tang, Run Xu, Phys. Procedia 32, 161 (2012). 7. R. Dhere, T.Gessert, J. Zhou, S. Asher, J. Pankow, and H. Moutinho, Materials Research Society Spring Meeting (San Francisco, California, April 21-25, 2003). 8. Bulent M. Basol, Vijay K. Kapur, and Michael L. Ferris,  J. Appl. Phys. 66, 1816 (1989). 9. G.E. Hallani, A. Ryah, N. Hassanain, Progress in Electro-magnetics Research Symposium Proceedings (Marrakesh, Morocco 1897, 2011). 10. Monisha Chakraborty, Int. J. Eng. Sci. Tech. 3 No5, 3798 (2011). 11. Satoshi Tokuda, Hiroyuki Kishihara, Susumu Adachi, Toshiyuki Sato, J. Mater. Sci. Mat. Electron. 15, 1 (2004). 12. S. Stolyarova, F. Edelman, A. Chack, A. Berner, P. Wer-ner, J. Phys. D: Appl. Phys. 41 065402 (2008). 13. I.P. Kalinkin, V.B. Aleskovskiy Epitaksial'nyye plenki soyedineniy A2B6 (Leningrad: Izd-vo LGU, 1978). 14. B.E. Warren, X-ray Diffraction (New York: Dover, 1990). 15. D. Kurbatov, V. Kosyak, M. Kolesnyk, A. Оpanasyuk, S. Danilchenko, Integr. Ferroelectrics 103 No1, 32 (2009). 16. V.V. Kosyak, D.I. Kurbatov, M.M. Kolesnyk, A.S. Opanasyuk,  S.N. Danilchenko, Yu.P. Gnatenko, J. Mater. Chem. Phys. 138, 731 (2013). 17. D. Kurbatov, S. Kshnyakina, S. Danilchenko, XIII Interna-tional Conference on Physics and Technology of Thin Films and Nanostructures (ICPTTFN-XIII), 152 (Ivano-Frankivsk, Ukraine, 2011). 18. Anu Bansal, P. Rajaram, J. Mater. Lett. 59, 3666 (2005). 19. K. Zanio, Semiconductors and Semimetals, Vol. 13, Cad-mium Telluride (Academic Press: 1978). 20. Robert K. Willardson, Albert C. Beer, Contacts, Junctions, Emitters, Vol. 15, Semiconductors and Semimetals (Aca-demic Press, 1981). 21. A.J. Bard, L.R. Faulkner, Electro-chemical Methods, Eighteenth edition (John Wiley, New York: 1980). 22. M. Singh, E. Mumcuoglu, IEEE Trans. Nucl. Sci. 45, 153 (1998). 23. B.M. Basol, V.K. Kapur, R.L. Mitchell, Thin Solid Films, 67, 509 (1990). 24. A. Brenner, Electrodeposition of Alloys: Principles and Practice, Vol. 12 (Academic Press, New York: 1963). 25. T. Mahalingham, V.S. John, S. Rajendran, P.J. Sebastain, J. Semicond. Sci. Technol. 17, 465 (2002). 26. A. Lopez-Otero, Thin Solid Films 49, 3 (1978).  

https://essuir.sumdu.edu.ua/bitstream/123456789/37188/1/Znamenshchykov_Kosyak_Opanasyuk_%20Stanislavov_Kuznetsov_Gnatenko.pdf

Effect of Substrate Temperature on the Structural Properties of CdxZn1-xTe Films Grown by Close-Spaced Sublimation Method

Abstract

Similar works

Full text

Available Versions

SocioEconomic Challenges Journal (Sumy State University)

Electronic Sumy State University Institutional Repository