In the present study, investigations of dielectric parameters viz dielectric constant (), dielectric loss () and AC conductivity measurements have been made for bulk chalcogenide Ge15Se85 glass in the frequency range 10 to 500 kHz within the temperature range from 300 to 390 K. The variation of dielectric constant and dielectric loss with frequency at room temperature is reported and discussed in the investigated glassy binary alloy.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3101

Kumar, Rajesh

Neha

Patial, Balbir Singh

Prakash, Jai

Thakur, Nagesh

Tripathi, S.K.

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 5 No 2, 02019(4pp) (2013) Том 5 № 2, 02019(4cc) (2013)   2077-6772/2013/5(2)02019(4) 02019-1  2013 Sumy State University Dielectric Properties and AC Conductivity Measurements of Amorphous Ge15Se85 Glass   Balbir Singh Patial1,*, Neha2, Jai Prakash2, Rajesh Kumar3, S.K. Tripathi4,†, Nagesh Thakur2,‡   1 Department of Physics, Rajiv Gandhi Govt. College Chaura Maidan (Kotshera) Shimla, 171 004, H.P., India 2 Department of Physics, H.P. University Summer Hill Shimla, 171 005 H.P., India  3 Department of Physics, Jaypee University of Information Technology, Waknaghat 173215 H.P., India 4 Centre of Advanced Study in Physics, Panjab University Chandigarh, 160 014, India  (Received 15 February 2013; revised manuscript received 28 April 2013; published online 04 May 2013)  In the present study, investigations of dielectric parameters viz dielectric constant ( ), dielectric loss ( ) and AC conductivity measurements have been made for bulk chalcogenide Ge15Se85 glass in the fre-quency range 10 to 500 kHz within the temperature range from 300 to 390 K. The variation of dielectric constant and dielectric loss with frequency at room temperature is reported and discussed in the investi-gated glassy binary alloy.  Keywords: Chalcogenide semiconductors, Dielectric constant, Dielectric loss, AC conductivity.   PACS numbers: 78.20.Ci, 77.22.Gm, 73.61.Jc                                                                   * bspatial@gmail.com † surya@pu.ac.in ‡ ntb668@yahoo.com 1. INTRODUCTION  Great consideration has been given to chalcogenide glasses in last two decades because of their potential applications in various solid state devices both in scien-tific and technological fields. Among the amorphous chalcogenide alloys, mostly selenium (Se) based mate-rials are preferred due to its commercial use and tech-nological importance. But in pure state it has disad-vantages because of its short life time and low sensitiv-ity [1]. The problem can be overcome by alloying sele-nium with some impurities such as Ge, Te etc which in terms gives high sensitivity, greater hardness, high crystallization temperature and small ageing effects as compared to pure Se glass [2]. Ge-Se glasses have been widely studied due to their extended amorphization composition range [3]. The fact that bulk glasses are easily obtained, makes Ge-Se sys-tem an ideal one to investigate a great variety of prop-erties and their correlation with structure and compo-sition. This system is extensively studied and glass formation in this system occurs predominantly in alloys enriched with Se and containing 0 to 25 at. % of Ge [4]. Furthermore, addition of Ge into the polymeric Se ma-trix produces a cross linking of selenium chain, mediat-ed by the formation of Ge(Se1/2)4 tetrahedral units [5]. At low doping (x  15 at. %), the tetrahedral units are sparsely distributed in the background matrix, with rather flexible interconnections. By x  15 at. %, the amount of Ge becomes sufficient to join some of the tetrahedral pairs by corner sharing [6]. Chalcogenide glasses in Ge-Se system are used as switching, memory elements and optoelectronic devices and are interesting material for infrared optics too. It has been observed that the addition of the third ele-ment to Ge-Se system effectively controls its electrical, optical, thermal, dielectric and physical properties. Moreover, Ge-Se system has drawn more attention as some metallic additives have been found [7-9] to change the conduction type from p to n in these glasses. Structural studies of these glasses are very im-portant for better understanding of transport mecha-nisms. The study of dielectric properties of chalcogenide glasses is predictable to reveal structural information, which in fact, can be useful for the understanding of conduction mechanism in these materials. In addition, study of temperature and frequency dependence of die-lectric parameters, particularly in the range of high fre-quency where the dielectric dispersion occurs can be of utmost importance for the understanding of the nature as well as the origin of the various losses happening in these materials. In the present work, we have reported and discussed the temperature and frequency dependence of dielectric properties as well as AC conductivity measurements of glassy Ge15Se85 alloy. Studies of AC conductivity and dielectric properties of Ge-Se system are rare and have not attracted much interest. Therefore, the aim of this work is to analyze the frequency and temperature de-pendence of the AC conductivity ac( ), the dielectric constant ( ) and the dielectric loss ( ) for the amor-phous Ge15Se85 chalcogenide glass.  2. EXPERIMENTAL DETAILS  Glassy alloy of Ge15Se85 has been prepared using the melt quenching technique. 5N highly pure materials (99.999 %) are weighed according to their atomic per-centages and sealed in a quartz ampoule (length ~ 5 cm, diameter ~ 12 mm) under a vacuum of ~ 2  10 – 5 mbar. The sealed ampoule has been kept inside a furnace where the temperature is raised to 1000 °C at a rate of 3-4 ºC/min. The ampoules are rocked frequently for 24 h at maximum temperature to make the melt homoge-nous. The quenching is done in the ice cooled water very rapidly to prevent crystallization. The amorphous nature of the glassy alloy has been verified by X-ray diffraction. Fig. 1 shows the XRD pattern for Ge15Se85.  BALBIR SINGH PATIAL, NEHA, JAI PRAKASH, ET AL. J. NANO- ELECTRON. PHYS. 5, 02019 (2013)   02019-2   Fig. 1 – XRD pattern of Ge15Se85 glassy alloy  For the dielectric measurements, the pallets of pow-der are prepared by a die using a hydraulic machine at a load of 5 tons. The pallets are made of different thick-nesses; 1.622 mm, 1.673 mm and 1.677 mm and diame-ter 9.957 mm, 10.058 mm and 10.042 mm respectively, to study the conduction process in the investigated sys-tem. The reproducibility of the results has been checked by making many runs at different times over the entire temperature and frequency ranges for the three thick-nesses. However, only the results of the thickness 1.622 mm are reported here. The dielectric parameters viz dielectric constant  and the dielectric loss  are determined using the Impedance Analyzer (Wayne Kerr 6500 B). The dielectric constant  (the real part of the dielectric constant) is calculated using the relation:   0CdA (1)  where C is the capacitance of the sample, d is the pallet thickness, A is the cross-sectional area and 0 is the free space permittivity. The dielectric loss  (imaginary part of the dielectric constant) is calculated from the equation:   tan  (2)  where (   90- ) and  is the phase angle. Moreover, tan  is known as the dissipation factor or loss factor ob-tained from the impedance analyzer.  3. RESULTS AND DISCUSSION  The frequency and temperature dependence of the dielectric constant , the dielectric loss  and AC con-ductivity ac( ), are investigated for bulk sample of the glassy Ge15Se85 alloy in the frequency range 10 to 500 kHz and in the temperature range 300-390 K, to study the dielectric behavior in the investigated system.  3.1 Dielectric Properties of Ge15Se85 Glass  3.1.1 Temperature and Frequency Dependence of the Dielectric Constant ( )  The variation of dielectric constant ( ) with fre-quency ( ) at room temperature is shown in Fig. 2. It is observed that the dielectric constant decreases with the frequency. This decrease is fast at low frequency as compared to higher frequency that may be due to the electrode polarization effects [10, 11]. The decrease of  with frequency can be attributed to the fact that at low frequency,  for polar material is explained by the con-tribution of multi-component of polarization viz elec-tronic, ionic, dipolar or orientation and space charge [12]. Thus, the total polarization (P) of the dielectric material can be represented as the sum of these four polarizations [13]:   e i d sP P P P P  (3)  Dielectric materials exhibit at least one of these po-larization types. This depends on the bonding and structure of the material and frequency [14].    Fig. 2 – Frequency dependence of dielectric constant at room temperature for Ge15Se85 chalcogenide glass.  Fig. 3 shows the temperature dependence of the die-lectric constant ( ) at different frequencies. It indicates that there is an increase in the dielectric constant with temperature. The increase in the dielectric constant of the sample may be attributed to the electric field which is accompanied by the applied frequencies. Such field will cause some ordering inside the sample as well as the formation of an electric moment in the entire volume of the dielectric and in each separate polarizing molecule. The molecular dipoles in polar material cannot orient themselves at low temperature. When the temperature rises, the dipoles orientation is facilitated and the dielec-tric constant increases. As the frequency is increased, the variation in the field become too rapid for the molec-ular dipoles to follow, so that their contribution to polar-ization becomes less with a measurable lag because of internal frictional forces [15].  3.1.2 Temperature and Frequency Dependence of the Dielectric Loss ( )  The variation of dielectric loss ( ) with frequency at room temperature is shown in Fig. 4. It is obvious from Fig. 4 that the dielectric loss also follows the same trend as followed by the dielectric constant ( ). The decrease in the dielectric loss with frequency in the investigated system may be attributed to the fact that  DIELECTRIC PROPERTIES AND AC CONDUCTIVITY MEASUREMENTS … J. NANO- ELECTRON. PHYS. 5, 02019 (2013)   02019-3 the migration of the ions in the glass is the main source of the dielectric loss at low frequencies. Therefore, die-lectric loss at low and moderate frequencies is charac-terized by the higher values of ( ) due to the contri-bution of ion jump and conduction loss of ion migration in addition to the ion polarization. However, at higher frequencies, the ion vibrations may be the only source of dielectric loss. So, ( ) decreases at higher values of frequency [16].     Fig. 3 – Variation of the dielectric constant ( ) with temper-ature at different frequencies for Ge15Se85  The variation in the dielectric loss ( ) as a func-tion of temperature at different frequencies is also shown in Fig. 4 which illustrates that ( ) exhibits temperature dependence and is found to be more at low frequencies. The origins of dielectric loss are conduc-tion losses, dipole losses and vibration losses [17]. As the temperature increases, the electrical conduction losses increase with further increasing of the dielectric loss ( ). The dielectric loss is also given by the following em-pirical relation [16]:   mB  (4)  where B is a constant and m  is a power of angular fre-quency. The plot between ln( ) and ln( ) should be a straight line and the slope of the plot enables us to ob-tain the value of m (Fig. 6). The value of the exponent m obtained from the negative slope of Fig. 6 is found to be negative (m  0.55691 at T  298 K) in the studied sample which is consistent with earlier values of m obtained for the other chalcogenide glasses [18]. According to Guintini et al. [19] model for dielectric dispersion in chalcogenide glasses based on the Elliot’s idea [20], the dielectric loss at a particular frequency is given by:   4mkTmW (6)  where Wm is the maximum barrier height i.e. the ener-gy required to move the electron from a site to infinity and is found equal to 0.18 eV for the present investi-gated Ge15Se85 glassy alloy.   Fig. 4 – Frequency dependence of dielectric loss at room tem-perature for Ge15Se85 chalcogenide glass    Fig. 5 – Variation of the dielectric loss ( ) with temperature at different frequencies for Ge15Se85    Fig. 6 – Plot of ln( ) versus ln( ) for chalcogenide Ge15Se85 glass at room temperature  3.2 Temperature and Frequency Dependence of AC Conductivity  The AC conductivity of the studied sample has been deduced from the data of dielectric constant ( ) and loss factor tan  using the following relation:  BALBIR SINGH PATIAL, NEHA, JAI PRAKASH, ET AL. J. NANO- ELECTRON. PHYS. 5, 02019 (2013)   02019-4  tanac o , (7)  where symbols have their usual meaning. A common feature to all the amorphous semicon-ductors is that AC conductivity ac( ) changes with frequency according to the following relation [21]:   ( ) sac oA , (8)    Fig. 7 – Variation of AC conductivity ac( ) with temperature at different frequencies for chalcogenide Ge15Se85 glass where Ao is a constant dependent on temperature,  is the angular frequency and the exponent s denotes the frequency dependence of ac and it is generally less than or equal to unity and is found equal to 0.45 in the stud-ied glass. Fig. 7 shows the frequency dependence of ac( ). Fig. 7 shows the variation of AC conductivity as a function of reciprocal temperature at different frequen-cies. This figure depicts the temperature independence and the frequency dependence of ac( ) in the investi-gated temperature and frequencies ranges for the stud-ied chalcogenide alloy. It indicates that ac( ) is not thermally activated in this range of temperature.  4. CONCLUSIONS  Dielectric properties and conductivity measure-ments have been made for Ge15Se85 glassy alloy at dif-ferent frequencies and temperature. Dielectric constant and dielectric loss are found to decrease with frequency at room temperatures in the studied system. The AC conductivity measurements shows that ac( ) is inde-pendent of temperature. However, it is found to vary with different frequencies in the temperature and fre-quency range of the investigated binary alloy.   REFERENCES  1. S.A. Khan, M. Zulfequar, M. Hussain, Solid State Comm. 123, 463 (2002).  2. B.S. Patial, N. Thakur, S.K. Tripathi, Phys. Scripta 85, 045603 (2012).  3. X. Fang, W.J. Bresser, P. Boolchand, Phys. Rev. Lett. 78, 4423 (1997). 4. E.A. Kislitskaya, V.B. Nosob, V.F. Kokorina, Fiz. Khim. Stekla 6, 624 (1997). 5. S. Susman, D.L. Price, K.J. Volin, R.J. Dejus, D.G. Montague, J. Non-Cryst. Solids 106, 26 (1988).  6. B.E. Warren, H. Krutter, O. Morningstar, J. Am Ceram. Soc. 19, 202 (1936). 7. N. Tohge, T. Minami, M. Tanaka, J. Non-Cryst. Solids 37, 23 (1980). 8. P. Nagel, H. Ticha, L. Tichy, A. Triska, J. Non-Cryst. Sol-ids 59-60, 1015 (1983). 9. N. Tohge, M. Hideaki, T. Minami, J. Non-Cryst. Solids 95-96, 809 (1987) 10. J.R. Macdonald, J. Non- Cryst. Solids 197, 83 (1996). 11. M. Cutroni, A. Mandanici, A. Piccols, C. Tomasi, Philos. Mag. B 71, 843 (1995). 12. N.A. Hegab, M.A. Afify, H.E. Atiya, A.S. Farid, J. Alloy. Compd. 477, 925 (2009).  13. M. Barsoum, Fundamentals of Ceramics (McGraw-Hill: New York: 1997). 14. V.Q. Nguyen, J.S. Sanghera, I.K. Lloyd, I.D. Aggarwal, D. Gershon, J. Non-Cryst. Solids 276, 151 (2000).  15. M.M. El-Nahass, A.F. El-Deeb, H.E.A. El-Sayed, A.M. Hassanien, Physica B 388, 26 (2007).  16. S.C. Agarawal, S. Guha, K.L. Narasimhan, J. Non-Cryst. Solids 18, 429 (1975).  17. J.M. Stevels, Handbuch der Physik (Ed.: S. Flugge) (Springer: Berlin 1957). 18. A. Sharma, N. Mehta, A. Kumar, J. Mater. Sci. 46, 4509 (2011). 19. J.C. Guintini, J.V. Zancheha, J. Non-Cryst. Solids 34, 419 (1979).  20. S.R. Elliot, Adv. Phys. 36, 135 (1987). 21. S.R. Elliot, Physics of Amorphous Materials (Wiley: New York: 1983).  

Dielectric Properties and AC Conductivity Measurements of Amorphous Ge15Se85 Glass

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 5 No 2, 02019(4pp) (2013) Том 5 № 2, 02019(4cc) (2013) 
 
 
2077-6772/2013/5(2)02019(4) 02019-1  2013 Sumy State University 
Dielectric Properties and AC Conductivity Measurements of Amorphous Ge15Se85 Glass  
 
Balbir Singh Patial1,*, Neha2, Jai Prakash2, Rajesh Kumar3, S.K. Tripathi4,†, Nagesh Thakur2,‡  
 
1 Department of Physics, Rajiv Gandhi Govt. College Chaura Maidan (Kotshera) Shimla, 171 004, H.P., India 
2 Department of Physics, H.P. University Summer Hill Shimla, 171 005 H.P., India 
 3 Department of Physics, Jaypee University of Information Technology, Waknaghat 173215 H.P., India 
4 Centre of Advanced Study in Physics, Panjab University Chandigarh, 160 014, India 
 
(Received 15 February 2013; revised manuscript received 28 April 2013; published online 04 May 2013) 
 
In the present study, investigations of dielectric parameters viz dielectric constant ( ), dielectric loss 
( ) and AC conductivity measurements have been made for bulk chalcogenide Ge15Se85 glass in the fre-
quency range 10 to 500 kHz within the temperature range from 300 to 390 K. The variation of dielectric 
constant and dielectric loss with frequency at room temperature is reported and discussed in the investi-
gated glassy binary alloy. 
 
Keywords: Chalcogenide semiconductors, Dielectric constant, Dielectric loss, AC conductivity. 
 
 PACS numbers: 78.20.Ci, 77.22.Gm, 73.61.Jc 
 
 
                                                                
* bspatial@gmail.com 
†
 surya@pu.ac.in 
‡
 ntb668@yahoo.com 
1. INTRODUCTION 
 
Great consideration has been given to chalcogenide 
glasses in last two decades because of their potential 
applications in various solid state devices both in scien-
tific and technological fields. Among the amorphous 
chalcogenide alloys, mostly selenium (Se) based mate-
rials are preferred due to its commercial use and tech-
nological importance. But in pure state it has disad-
vantages because of its short life time and low sensitiv-
ity [1]. The problem can be overcome by alloying sele-
nium with some impurities such as Ge, Te etc which in 
terms gives high sensitivity, greater hardness, high 
crystallization temperature and small ageing effects as 
compared to pure Se glass [2]. 
Ge-Se glasses have been widely studied due to their 
extended amorphization composition range [3]. The fact 
that bulk glasses are easily obtained, makes Ge-Se sys-
tem an ideal one to investigate a great variety of prop-
erties and their correlation with structure and compo-
sition. This system is extensively studied and glass 
formation in this system occurs predominantly in alloys 
enriched with Se and containing 0 to 25 at. % of Ge [4]. 
Furthermore, addition of Ge into the polymeric Se ma-
trix produces a cross linking of selenium chain, mediat-
ed by the formation of Ge(Se1/2)4 tetrahedral units [5]. 
At low doping (x  15 at. %), the tetrahedral units are 
sparsely distributed in the background matrix, with 
rather flexible interconnections. By x  15 at. %, the 
amount of Ge becomes sufficient to join some of the 
tetrahedral pairs by corner sharing [6]. 
Chalcogenide glasses in Ge-Se system are used as 
switching, memory elements and optoelectronic devices 
and are interesting material for infrared optics too. It 
has been observed that the addition of the third ele-
ment to Ge-Se system effectively controls its electrical, 
optical, thermal, dielectric and physical properties. 
Moreover, Ge-Se system has drawn more attention as 
some metallic additives have been found [7-9] to change 
the conduction type from p to n in these glasses. 
Structural studies of these glasses are very im-
portant for better understanding of transport mecha-
nisms. The study of dielectric properties of chalcogenide 
glasses is predictable to reveal structural information, 
which in fact, can be useful for the understanding of 
conduction mechanism in these materials. In addition, 
study of temperature and frequency dependence of die-
lectric parameters, particularly in the range of high fre-
quency where the dielectric dispersion occurs can be of 
utmost importance for the understanding of the nature 
as well as the origin of the various losses happening in 
these materials. 
In the present work, we have reported and discussed 
the temperature and frequency dependence of dielectric 
properties as well as AC conductivity measurements of 
glassy Ge15Se85 alloy. Studies of AC conductivity and 
dielectric properties of Ge-Se system are rare and have 
not attracted much interest. Therefore, the aim of this 
work is to analyze the frequency and temperature de-
pendence of the AC conductivity ac( ), the dielectric 
constant ( ) and the dielectric loss ( ) for the amor-
phous Ge15Se85 chalcogenide glass. 
 
2. EXPERIMENTAL DETAILS 
 
Glassy alloy of Ge15Se85 has been prepared using the 
melt quenching technique. 5N highly pure materials 
(99.999 %) are weighed according to their atomic per-
centages and sealed in a quartz ampoule (length ~ 5 cm, 
diameter ~ 12 mm) under a vacuum of ~ 2  10 – 5 mbar. 
The sealed ampoule has been kept inside a furnace 
where the temperature is raised to 1000 °C at a rate of 
3-4 ºC/min. The ampoules are rocked frequently for 24 h 
at maximum temperature to make the melt homoge-
nous. The quenching is done in the ice cooled water very 
rapidly to prevent crystallization. The amorphous nature 
of the glassy alloy has been verified by X-ray diffraction. 
Fig. 1 shows the XRD pattern for Ge15Se85. 
 BALBIR SINGH PATIAL, NEHA, JAI PRAKASH, ET AL. J. NANO- ELECTRON. PHYS. 5, 02019 (2013) 
 
 
02019-2 
 
 
Fig. 1 – XRD pattern of Ge15Se85 glassy alloy 
 
For the dielectric measurements, the pallets of pow-
der are prepared by a die using a hydraulic machine at a 
load of 5 tons. The pallets are made of different thick-
nesses; 1.622 mm, 1.673 mm and 1.677 mm and diame-
ter 9.957 mm, 10.058 mm and 10.042 mm respectively, 
to study the conduction process in the investigated sys-
tem. The reproducibility of the results has been checked 
by making many runs at different times over the entire 
temperature and frequency ranges for the three thick-
nesses. However, only the results of the thickness 
1.622 mm are reported here. The dielectric parameters 
viz dielectric constant  and the dielectric loss  are 
determined using the Impedance Analyzer (Wayne Kerr 
6500 B). The dielectric constant  (the real part of the 
dielectric constant) is calculated using the relation: 
 
 
0
Cd
A
 (1) 
 
where C is the capacitance of the sample, d is the pallet 
thickness, A is the cross-sectional area and 0 is the free 
space permittivity. The dielectric loss  (imaginary part 
of the dielectric constant) is calculated from the equation: 
 
 tan  (2) 
 
where (   90- ) and  is the phase angle. Moreover, 
tan  is known as the dissipation factor or loss factor ob-
tained from the impedance analyzer. 
 
3. RESULTS AND DISCUSSION 
 
The frequency and temperature dependence of the 
dielectric constant , the dielectric loss  and AC con-
ductivity ac( ), are investigated for bulk sample of the 
glassy Ge15Se85 alloy in the frequency range 10 to 
500 kHz and in the temperature range 300-390 K, to 
study the dielectric behavior in the investigated system. 
 
3.1 Dielectric Properties of Ge15Se85 Glass 
 
3.1.1 Temperature and Frequency Dependence of 
the Dielectric Constant ( ) 
 
The variation of dielectric constant ( ) with fre-
quency ( ) at room temperature is shown in Fig. 2. It is 
observed that the dielectric constant decreases with the 
frequency. This decrease is fast at low frequency as 
compared to higher frequency that may be due to the 
electrode polarization effects [10, 11]. The decrease of  
with frequency can be attributed to the fact that at low 
frequency,  for polar material is explained by the con-
tribution of multi-component of polarization viz elec-
tronic, ionic, dipolar or orientation and space charge 
[12]. Thus, the total polarization (P) of the dielectric 
material can be represented as the sum of these four 
polarizations [13]: 
 
 
e i d sP P P P P  (3) 
 
Dielectric materials exhibit at least one of these po-
larization types. This depends on the bonding and 
structure of the material and frequency [14]. 
 
 
 
Fig. 2 – Frequency dependence of dielectric constant at room 
temperature for Ge15Se85 chalcogenide glass. 
 
Fig. 3 shows the temperature dependence of the die-
lectric constant ( ) at different frequencies. It indicates 
that there is an increase in the dielectric constant with 
temperature. The increase in the dielectric constant of 
the sample may be attributed to the electric field which 
is accompanied by the applied frequencies. Such field 
will cause some ordering inside the sample as well as the 
formation of an electric moment in the entire volume of 
the dielectric and in each separate polarizing molecule. 
The molecular dipoles in polar material cannot orient 
themselves at low temperature. When the temperature 
rises, the dipoles orientation is facilitated and the dielec-
tric constant increases. As the frequency is increased, 
the variation in the field become too rapid for the molec-
ular dipoles to follow, so that their contribution to polar-
ization becomes less with a measurable lag because of 
internal frictional forces [15]. 
 
3.1.2 Temperature and Frequency Dependence 
of the Dielectric Loss ( ) 
 
The variation of dielectric loss ( ) with frequency 
at room temperature is shown in Fig. 4. It is obvious 
from Fig. 4 that the dielectric loss also follows the same 
trend as followed by the dielectric constant ( ). The 
decrease in the dielectric loss with frequency in the 
investigated system may be attributed to the fact that 
 DIELECTRIC PROPERTIES AND AC CONDUCTIVITY MEASUREMENTS … J. NANO- ELECTRON. PHYS. 5, 02019 (2013) 
 
 
02019-3 
the migration of the ions in the glass is the main source 
of the dielectric loss at low frequencies. Therefore, die-
lectric loss at low and moderate frequencies is charac-
terized by the higher values of ( ) due to the contri-
bution of ion jump and conduction loss of ion migration 
in addition to the ion polarization. However, at higher 
frequencies, the ion vibrations may be the only source 
of dielectric loss. So, ( ) decreases at higher values of 
frequency [16].  
 
 
 
Fig. 3 – Variation of the dielectric constant ( ) with temper-
ature at different frequencies for Ge15Se85 
 
The variation in the dielectric loss ( ) as a func-
tion of temperature at different frequencies is also 
shown in Fig. 4 which illustrates that ( ) exhibits 
temperature dependence and is found to be more at low 
frequencies. The origins of dielectric loss are conduc-
tion losses, dipole losses and vibration losses [17]. As 
the temperature increases, the electrical conduction 
losses increase with further increasing of the dielectric 
loss ( ). 
The dielectric loss is also given by the following em-
pirical relation [16]: 
 
 mB  (4) 
 
where B is a constant and m  is a power of angular fre-
quency. The plot between ln( ) and ln( ) should be a 
straight line and the slope of the plot enables us to ob-
tain the value of m (Fig. 6). The value of the exponent 
m obtained from the negative slope of Fig. 6 is found to 
be negative (m  0.55691 at T  298 K) in the studied 
sample which is consistent with earlier values of m 
obtained for the other chalcogenide glasses [18]. 
According to Guintini et al. [19] model for dielectric 
dispersion in chalcogenide glasses based on the Elliot’s 
idea [20], the dielectric loss at a particular frequency is 
given by: 
 
 
4
m
kT
m
W
 (6) 
 
where Wm is the maximum barrier height i.e. the ener-
gy required to move the electron from a site to infinity 
and is found equal to 0.18 eV for the present investi-
gated Ge15Se85 glassy alloy. 
 
 
Fig. 4 – Frequency dependence of dielectric loss at room tem-
perature for Ge15Se85 chalcogenide glass 
 
 
 
Fig. 5 – Variation of the dielectric loss ( ) with temperature 
at different frequencies for Ge15Se85 
 
 
 
Fig. 6 – Plot of ln( ) versus ln( ) for chalcogenide Ge15Se85 
glass at room temperature 
 
3.2 Temperature and Frequency Dependence of 
AC Conductivity 
 
The AC conductivity of the studied sample has been 
deduced from the data of dielectric constant ( ) and 
loss factor tan  using the following relation: 
 BALBIR SINGH PATIAL, NEHA, JAI PRAKASH, ET AL. J. NANO- ELECTRON. PHYS. 5, 02019 (2013) 
 
 
02019-4 
 tanac o , (7) 
 
where symbols have their usual meaning. 
A common feature to all the amorphous semicon-
ductors is that AC conductivity ac( ) changes with 
frequency according to the following relation [21]: 
 
 ( ) sac oA , (8) 
 
 
 
Fig. 7 – Variation of AC conductivity ac( ) with temperature 
at different frequencies for chalcogenide Ge15Se85 glass 
where Ao is a constant dependent on temperature,  is 
the angular frequency and the exponent s denotes the 
frequency dependence of ac and it is generally less than 
or equal to unity and is found equal to 0.45 in the stud-
ied glass. Fig. 7 shows the frequency dependence of 
ac( ). 
Fig. 7 shows the variation of AC conductivity as a 
function of reciprocal temperature at different frequen-
cies. This figure depicts the temperature independence 
and the frequency dependence of ac( ) in the investi-
gated temperature and frequencies ranges for the stud-
ied chalcogenide alloy. It indicates that ac( ) is not 
thermally activated in this range of temperature. 
 
4. CONCLUSIONS 
 
Dielectric properties and conductivity measure-
ments have been made for Ge15Se85 glassy alloy at dif-
ferent frequencies and temperature. Dielectric constant 
and dielectric loss are found to decrease with frequency 
at room temperatures in the studied system. The AC 
conductivity measurements shows that ac( ) is inde-
pendent of temperature. However, it is found to vary 
with different frequencies in the temperature and fre-
quency range of the investigated binary alloy. 
 
 
REFERENCES 
 
1. S.A. Khan, M. Zulfequar, M. Hussain, Solid State Comm. 
123, 463 (2002).  
2. B.S. Patial, N. Thakur, S.K. Tripathi, Phys. Scripta 85, 
045603 (2012).  
3. X. Fang, W.J. Bresser, P. Boolchand, Phys. Rev. Lett. 78, 
4423 (1997). 
4. E.A. Kislitskaya, V.B. Nosob, V.F. Kokorina, Fiz. Khim. 
Stekla 6, 624 (1997). 
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Dielectric Properties and AC Conductivity Measurements of Amorphous Ge15Se85 Glass

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