Optical, dielectric & ferroelectric studies on amino acids doped TGS single crystals

Article abstract of DOI:10.1039/c5ra25700j

Pure TGS and amino acids (L-arginine, L-histidine and L-alanine) doped TGS crystals were grown by slow evaporation solution growth technique at room temperature. The optical transmission window and optical band gap of the crystals were found by UV-Vis studies. The cut off wavelengths of the grown crystals were observed between 220 nm and 290 nm. The dielectric behaviour was investigated at different frequencies and temperatures. AC conductivity was determined. Photoconductivity study reveals that the grown crystals exhibit negative photoconductivity. The ferroelectric nature of the crystals was identified by P-E hysteresis loop analysis. The piezoelectric d₃₃ coefficient has been measured for the doped TGS crystals. Two close emission bands in the luminescence spectra in the near UV region reveal their application in developing new coherent sources of radiation in this region. Among the three dopants, l-arginine doped TGS possesses low dielectric constant and high piezo electric coefficient, suggesting that this can be a potential material for infrared detectors.

Full text of DOI:10.1039/c5ra25700j

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: D. P R and S. J,
RSC Adv., 2016, DOI: 10.1039/C5RA25700J.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Please do not adjust margins
RSC Advances
Page 1 of 23
View Article Online
DOI: 10.1039/C5RA25700J
Journal Name
ARTICLE
Optical, Dielectric & Ferroelectric Studies on Amino acids Doped
TGS Single Crystals.
P. R. Deepthia and J. Shanthib
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Pure TGS and amino acids (L-Arginine, L-Histidine and L-Alanine) doped TGS crystals were grown by slow evaporation
solution growth technique at room temperature. The optical transmission window and optical band gap of the crystals
were found by UV-vis studies. The cut off wavelength of the grown crystals were observed between 220nm and 290 nm.
The dielectric behaviour was investigated at different frequencies and temperatures. AC conductivity was determined.
Photoconductivity study reveals that the grown crystals exhibit negative photoconductivity. Ferro electric nature of the
crystals was identified by P-E hysteresis loop analysis. Piezoelectric d33 coefficient has been measured for the doped TGS
crystals. Two close emission bands in the luminescence spectra in near UV region reveals their application in developing
new coherent sources of radiations in this region. . Among the three dopants, L-Arginine doped TGS possesses low
dielectric constant and high piezo electric coefficient suggesting that this can be a potential material for infrared detectors.
www.rsc.org/
Keywords: Crystal growth, Optical properties, Ferroelectric properties, Photoluminescence spectrum, Dielectric properties
devices. Crystals of pure TGS with different additives have
been used for the construction of the most sensitive detectors,
because of their high value of figure of merit [5]. However, TGS
Introduction
crystals are found to depolarize by thermal, electrical or
mechanical means [6]. An efficient way to stabilize the single
domain state is practiced by doping an optically active
molecule into TGS. The partial substitution of an optically
active molecule in the place of glycine molecule causes an
internal bias field, resulting in a permanent polarization [7].
Many efforts have been made to improve the optical,
ferroelectric, pyroelectric and other properties of the TGS
family crystals by doping with various amino acids [8–12].
Triglycinesulphate (TGS) is one of the extensively studied
ferroelectric materials, which finds wide applications due to
low cost, low power requirement and wide operating range of
temperature and frequency, as room temperature infrared (IR)
detectors, pyroelectric vidicon tubes, transducers and sensors
[1, 2]. TGS shows second order phase transition at the Curie
point Tc =49◦C. In ferroelectric phase below the Curie point the
symmetry is monoclinic with space group P21. Above Tc, the
structure gains an additional set of mirror planes in the space
group P21/m [3]. According to the structural analysis of
ferroelectric triglycinesulphate, there are two kinds of glycine
group, glycinium ions and zwitter ions. Such configuration of
glycine ions interconnected by short O–H· · ·O hydrogen bonds
are regarded as particularly important for the ferroelectric
behavior of this crystal [4]. A disadvantage of these crystals is
the tendency of their polarization to spontaneous reversal.
Therefore, studies dealing with the influence of doping TGS
crystals on their physical properties are of particular interest.
In the present paper, the effect of L-amino acids on the growth
of TGS by slow evaporation method at room temperature has
been studied. The grown crystals were characterized by UV-
VIS, ferroelectric analysis, photoconductivity, dielectric and
photoluminescence.
A comparative study on the results
obtained for pure TGS, L- Arginine, L-Histidine and L-Alanine
doped TGS crystals (Pure TGS, L-Ar TGS, L-H TGS and L-Al TGS)
are detailed below.
In recent years, the interest in studying pure and doped TGS
crystals has increased because of their application in various
Materials and Methods
Synthesis and crystal growth: Analar grade reagents Glycine
and concentrated sulphuric acid (H2SO4) were dissolved in
deionized water in the molar ratio of 3:1, and the solution was
heated at 500C to obtain synthesized TGS salt. Glycine reacts
with sulphuric acid as follows.
a.Department of Physics, School of Engineering, Presidency University, Bengaluru,
Karnataka, India-560 089
b.Department of Physics, Avinashilingam University for Women, Coimbatore,
Tamilnadu, India- 641038.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 2 of 23
View Article Online
DOI: 10.1039/C5RA25700J
ARTICLE
Journal Name
3(NH2CH2COOH) +H2SO4 → (NH2CH2COOH)3.H2SO4
The cut off wavelength is 289 nm and band gap is found to be
4.29 eV for L-Ar TGS crystal. From the UV-Visible spectrum, it is
found that the L-Ar TGS crystal is transparent in the visible region
with around 90% of transmittance. The cut off wavelength is
262 nm and band gap is found to be 4.74 eV for L-H TGS crystal. It is
found that L-H TGS crystal is conveniently transparent from 380 to
900 nm with around 80% of transmittance. The cut off wavelength
is 271 nm and band gap is found to be 4.58 eV for L-Al TGS crystal.
It is found that the L-Al TGS crystal is transparent in the visible
region with about 85% of transmittance.
The synthesized salt was again dissolved in double distilled
water and then recrystallized by natural evaporation process.
This process was repeated two times to improve the purity of
the material. Well defined and transparent crystals of
dimension up to 9 × 11 × 5 mm3 were formed within 15 days.
In the case of amino acids doped TGS crystals, the saturated
solution of TGS was first prepared. To this solution,
appropriate mole of L-Arginine, L-Histidine and L-Alanine was
added as dopant. The seed crystals were obtained over a
period of five days and suspended in the parent solution to get
good quality crystals. Transparent crystals of L-Arginine doped
TGS crystals of dimension 15 × 14 × 8 mm3 and L-Alanine
doped TGS crystals of dimension 9 × 10 × 8 mm3 were
obtained over a period of three weeks whereas on doping with
L-Histidine full faced crystals of dimension 9 × 11 × 6 mm3
were obtained within two weeks. The photographs of the
grown crystals of pure and doped TGS crystals are shown in
Figure 1.
The optical absorption coefficient (α) was calculated from
transmittance using the relation α= ꢁꢀ ꢂꢃꢄ ꢅꢀ, where ‘T’ is the
transmittance, and ‘d’ is the thickness of the crystal. Owing to the
direct band gap, the crystal under study has an absorption
coefficient (α) obeying the relation for high photon energies (ν),
ꢍ
)
ꢆ = ꢇ(ꢈꢉꢊꢋ where Eg is the optical band gap of the crystal and A
ꢌ
ꢈꢉ
is a constant. The variation of (αhν)2 vs (hν) is plotted and is shown
in Figure 3. From the plot Eg is evaluated by the extrapolation of the
linear part. The measured band gap is found to be 5.51 eV for pure
TGS, 4.31 eV for L-Ar TGS, 4.74 eV for L-HTGS and 4.69eV for L-Al
TGS.
Figure 1. The photograph of the grown crystals of (a) pure TGS (b) L-
Ar TGS (c) L-H TGS and (d) L-Al TGS.
Figure 3. (αhν)2 vs hν spectra of Pure and doped TGS crystals.
Ferroelectric Measurements
Results and discussion
The properties of ferroelectrics are governed by their
crystallographic structure [15-17] and strongly influenced by the
lattice defects, presence of which in crystals leads to appearing and
existence of internal bias field [18]. Ferro electricity of the material
is ascertained by P – E hysteresis loop. The polarization and electric
field (P–E) curve was traced in L-Ar TGS, L-H TGS and L-Al TGS
crystals using a standard computer controlled Sawyer–Tower P–E
hysteresis analyser. A good quality crystal of size 10 mm × 10 mm ×
1 mm was used for the study. The opposite faces were electroded
with conducting silver paste.
UV-Visible Analysis
The optical properties of materials provide information on the
electronic band structures, localized states and types of optical
transitions. The desired lower cut off in the transmittance analysis is
to be between 200 and 400 nm for effective optical applications:
lower the value of cut off wider is the optical window [13]. UV–
Visible studies also give important structural information because
the absorption of UV and visible light involves promotion of the
electrons in p and s orbital from the ground state to high energy
states. To determine the optical transmittance range and hence to
know the suitability of pure and amino acids doped TGS single
crystals for optical applications, the UV–VIS transmittance spectrum
were recorded using SHIMADZU UV-Spectrometer 1601 in the
range of 200 to 1000 nm and is as shown in Figure.2.
Observed hysteresis loops in present investigation are in elliptical
shape which shows the ferroelectric nature of the materials. Area of
the hysteresis curve increases along with the remnant polarization
and coercive field with increase of applied electric field. The
squareness of hysteresis loop was determined. For an ideal
hysteresis loop the squareness parameter (Rsq) is equal to 2. The
value of squareness close to 2 in the case of grown doped TGS
crystals indicates a very good switching behaviour of the crystal.
The ferroelectric parameters were calculated and presented in
Table 1.
Figure 2. UV- Visible Transmission spectra of Pure and doped TGS
crystals.
The lower cut off region for pure TGS is obtained at 224 nm and
band gap is found to be 5.54 eV, which is in good agreement with
the reported values [14]. Almost there is a steady transmittance in
the visible region. From the UV-Visible spectrum, it is found that the
pure triglycine sulphate crystal is conveniently transparent from
380 to 1000 nm with around 80% of transmittance for pure TGS.
The coercive field (Ec) value will be large in the case of specimens
having a single domain compared to the multi domain specimen
[19]. The coercive field (Ec) value and spontaneous polarization (PS)
for pure TGS has been reported in literature [20, 21]. The reported
coercive field value for pure TGS is 2.58 kV/cm and the spontaneous
polarization is 3.4 μC /cm2. The coercive field (Ec) value of the
L-Arginine, L-Histidine and L-Alanine crystals is more than the pure
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 3 of 23
Journal Name
View Article Online
DOI: 10.1039/C5RA25700J
ARTICLE
one, implying that the crystals are in the single-domain state. A
similar effect was observed in literature when L-Cysteine was used
as the dopant [8]. Polarization reversal in TGS occurs very easily
(low Ec) if many domains are present, but with great difficulty (large
Ec) in single-domain crystals. The mono domain state of the
specimen is the one in which the dipolar moments are
unswitchable. Owing to the high dipole moment of the substituted
amino acid, a bias field is created, which results in the shift of the
entire loop.
Table 2. The d33 coefficient for pure and doped TGS crystals.
CRYSTAL
Pure TGS
L-Ar TGS
L-H TGS
L-Al TGS
d33(pC/N)
10.22
5
2
2
Table 1.The ferroelectric parameters for pure and doped TGS
crystals.
Photoconductivity Measurement
Rsq
Crystal PS(μC
/cm2)
Pr(μC
/cm2)
EC(kV/cm)
12.46
Area
Enclosed
Photoconductivity measurements were carried out on a cut and
well-polished sample of the grown single crystal by fixing it onto a
microscope slide. Two electrodes of thin copper wire of 0.3 mm
thickness were fixed using silver paint and the sample was
connected in series with a dc power supply and KEITHLEY 485 pico
ammeter. The dark current was recorded by keeping the sample
unexposed to any radiation. The sample was covered with a black
cloth and the voltage applied was increased from 0 to 300 volts in
steps of 20 volts and the dark current was recorded. The sample
was illuminated by the radiation from 100 W halogen lamp
containing iodine vapour and tungsten filament. The photocurrent
was recorded for the same values of the applied voltage. Field
dependence of dark and photo currents is depicted in Figure 4 for
pure TGS, L-Ar TGS, L-H TGS and L-Al TGS crystals. It is observed that
the dark current (Id) and the photocurrent (Ip) show linear response
for all the crystals with respect to applied field.
L-Ar
TGS
0.94
0.46
2.16
2.14
49.57
L-H
TGS
0.71
2.26
0.50
1.73
15.53
16.92
46.20
L-Al
TGS
1.93
137.01
Piezoelectric (d33) measurements
The piezoelectric applications, such as ultrasonic transducers and
piezoelectric actuators demand high electromechanical coupling
coefficients and relatively large dielectric constants in addition to a
large piezoelectric d33 coefficient. The piezoelectric property is
related to the polarity of the material [22]. Piezoelectric behaviour
of the pure and doped TGS crystals was confirmed by determining
the piezoelectric co-efficient (d33) using PM-300 piezometer system.
A piezoelectric substance is one that produces an electric charge
when a mechanical stress is applied and the piezoelectric property
is related to the polarity of the crystalline material. A precision
force generator applied a calibrated force (0.25 N) that generated a
charge on the piezoelectric material under test. The output was
measured directly from oscilloscope, which gives the d33 coefficient
in units of pC/N. The reported d33 coefficient value for pure TGS is
10.22 pC/N [20]. The obtained d33 coefficient value for doped TGS
crystals is given in Table 2.
Figure 4. Field dependence of dark and photo currents for (a) Pure
TGS (b) L-ArTGS (c) L-HTGS and (d) L-AlTGS.
It is seen from the plots that both dark current and photo current of
the samples increase linearly with applied field. The dark current is
always higher than the photo current, thus confirming negative
photoconductivity. The phenomenon of negative photoconductivity
is explained by Stockmann model [25]. The negative
photoconductivity in a solid is due to the decrease in the number of
charge carriers or their lifetime, in the presence of radiation [26].
Table 3 gives a comparison of cross analysis of percentage of
depression at two different applied field namely 60V/cm and
100V/cm. The depression is maximum in L-Alanine doped TGS and
minimum in L-Histidine doped TGS. A probable mechanism is
sought through the literature and found from reported works on L-
Arginine [27] and L-amino acids [28] that there is a probable
correlation of this photoconductive action to the dopants. The
carbon length and the planarity of the molecules appear to have
relevance with the percentage of depression. In L-Arginine the
guanidyl group falls in plane with carbon back bone though there is
angular variation till the C4 position (Figure 5 and 6) which provides
the possibility of the electron transfer when photo electrons are
The obtained low value of d33 coefficient (2pC/N) in L-H TGS and
L-Al TGS crystals could be due to the higher density of dislocations
present in both crystals when compared with L-Ar TGS crystal
whose d33 coefficient is 5 pC/N. It has been already reported that
the piezoelectric properties are largely affected by the dislocations
[23]. Any defects irrespective of their origin may cause slowing
down of the domain wall mobility and tends to reduce the d33
coefficient [24].
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 4 of 23
View Article Online
DOI: 10.1039/C5RA25700J
ARTICLE
Journal Name
generated. (The L-Histidine does not have such coplanar carbon increase with temperature. This is a normal behaviour of polar
back bone to transfer the photo electrons in the system).
Figure 5.Bond lengths for L-Arginine molecule.
Figure 6. Bond angles for L-Arginine molecule.
(non-centro symmetric) dielectric and it obeys Debye equation. The
behaviour is due to the fact that at low frequency, dipoles follow
the applied field whereas at high frequency they do not. The
dielectric constant of the materials is due to the contribution of
electronic, ionic, dipolar, space charge polarizations, which depend
on frequencies. At low frequencies, space charge polarization is
more predominant and hence the dielectric constant increases
abnormally. As frequency increases to a point where space charge
cannot sustain and comply with the external field and hence
polarization decreases, giving rise to diminishing values of dielectric
constant. A similar effect was observed in literature [28] when TGS
crystals were doped with amino acids. However, the values
obtained are still lower in comparison to those for other TGS-doped
crystals [29,30].The low value of dielectric constant at high
frequencies are important for the materials in the construction of
photonic and NLO devices.
Table 3.Comparison of cross analysis of percentage of depression
and polarization.
Photoconductivity Analysis
Slope
Calculation
based on
Hysteresis
curve
Sample
Depression
at 60 V/cm
Depression
at 100V/cm
Figure 7(a). Dielectric constant versus log f for Pure and doped TGS
crystals and 7(b). Dielectric loss versus log f for Pure and doped TGS
crystals.
L-Ar TGS
L-H TGS
L-Al TGS
52%
34%
87%
49%
37%
86%
140×10-6
Usually the dielectric losses fall into two categories, intrinsic and
extrinsic. Intrinsic losses are dependent on the crystal structure and
can be described by the interaction of the phonon system with the
varying electric field. The applied electric field alters the equilibrium
of the phonon system and the subsequent relaxation is associated
with energy dissipation. These intrinsic losses set the lower limit of
losses found in pure “defect free” single crystals. Extrinsic losses are
associated with imperfections in the crystal such as impurities,
micro structural defects, porosity, micro cracks and random
crystallite orientation. The decrease in dielectric loss with increasing
frequency accounts for good chemical homogeneity of the grown
crystal with lesser defects and this parameter is important for the
fabrication of materials for photonic and electro optic devices. An
essential property of NLO material is its ability to support an
electrostatic field while dissipating minimal energy in the form of
heat. The lower is the dielectric loss (the proportion of energy lost
as heat), the more effective is a dielectric material [31].
37.75×10-6
127.5×10-6
In contrary L-Alanine [28] possess a short chain thus providing
possibility of interlock to a greater extent packing it stronger. The
shorter chain brings the molecules more packed and forms a bond
parallel to itself forming an interlocking layer. Hence the
photoelectron does not have possibility of draining and leads to
severe polarization. Hence it is very obvious that lighter the
polarization more would be the depression in photocurrent (Table
3).
AC conductivity
Dielectric Studies
The AC conductivity was calculated using the formula.
ꢎꢏꢐ = ꢍꢑꢒꢓꢔꢓꢕꢖꢏꢗꢘ
The measurement of dielectric constant as a function of frequency
and temperature is of considerable interest. The dielectric
measurements were carried out using an LCR meter. The dielectric
constants were determined at different frequencies viz., 50 Hz to 50
MHz at room temperature. Crystals with high transparency and
defect free were used for study. The extended portions of the
crystals were removed completely and the opposite faces were
polished and coated with graphite to get a good conductive surface
layer. The dimensions of the crystals were measured using a
travelling microscope. The readings were taken when the sample
was cooled. The air capacitance was also measured.
where Ԑ0 is the vacuum dielectric constant, Ԑr is the relative
dielectric constant and f is the frequency of the applied field. The
variation of ac conductivity with frequency at different
temperatures is shown in Figure 8. It is seen that at a given
temperature, the magnitude of conductivity is high at high
frequencies which is a normal dielectric behaviour. The electrical
conduction in dielectric is mainly a defect controlled process in the
low temperature region. At any particular temperature, Gibb's free
energy of a crystal is minimum when certain fractions of which in
turn increase the conductivity [32].
The variation of dielectric constant and dielectric loss with
frequency for pure and doped TGS crystals is shown in Figure 7(a)
and 7 (b) respectively .It is seen that the value of dielectric constant
and dielectric loss decrease exponentially with frequency and
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 5 of 23
View Article Online
DOI: 10.1039/C5RA25700J
Journal Name
ARTICLE
Figure 8. Ac conductivity versus log f for (a) pure TGS, (b) L-ArTGS,
(c) L-HTGS and (d) L-AlTGS
crystals are in the single-domain state. It is seen that the value of
dielectric constant and dielectric loss decreases exponentially with
frequency. Further, low dielectric loss of the crystals at high
frequency range, is an ideal condition for NLO materials. In
summary, a decrease in the dielectric constant, low dielectric loss,
increased uniform figure of merit and coercive field suggests that
amino acids doped TGS crystals are potential material for IR
sensors. Photoconduction studies reveal that the grown crystals
have negative photoconductivity. Two close emission bands in the
luminescence spectra in near UV region reveals their application in
developing new coherent sources of radiation in this region.
AC conductivity values are fitted in equation
−ꢋꢏ
ꢜꢅ
ꢎꢏꢐ = ꢎꢔ ꢙꢚꢛ(
)
where σ0 is a constant which depends on the type of the sample, Ea
is the activation energy, k is the Boltzmann constant and T is the
absolute temperature. The Arrhenius plot between 1000/T and ln
σac gives a straight line (Figure. 9), and the slope of the straight line
is equal to (Ea/k), from which the activation energy (Ea = - slope × k
× 1000) is calculated to be 0.34 eV for pure TGS, 0.213 eV for
L-H TGS, 0.204 eV for L-Ar TGS and 0.65 eV for L-Al TGS. The
activation energy is the energy required for the charge carriers to
take part in the conduction process. As the value of Ea is less than
0.5 eV, it is concluded that the material possesses ionic conductivity
[33].
Acknowledgements
The authors thank Dr Binay Kumar, Crystal Growth Centre,
Delhi University for Ferroelectric studies and also place on
record the support given by SAIF, Kochi, where the analyses
were done.
Figure 9. Plot of 1000/T versus ln σac
References
1
2
3
4
5
H.V. Alexandru, C. Berbecaru, L. Ion, A. Dutu, F. Ion, L.
Pintilie, R.C. Radulescu., Appl. Surf. Sci. 2006,253, 358.
Nidhi Sinha, NeetiGoel , B.K. Singh, M.K. Gupta, Binay Kumar,
Journal of Solid State Chemistry, 2012,190, 180.
N. Kartheeswari and K. Viswanathan, Journal of
Spectroscopy, 2013, 2013,1.
V. Lhotska, J. Fousek, N. Neumann, Physica Status Solidi
A,1990,120, 273.
R. Muralidharan, R. Mohankumar, R. Dhanasekaran, A.K.
Tirupathi, R. Jayavel, P. Ramasamy, Material Letters,
2003,57 3291.
N. Nakatani, Japaneese Journal of Applied Physics, 1973, 12
1723–1728.
J. Stankowska, A. Czarrecka, B.D. Gemi, Acta Physica
Polonica, 1993, 83, 485.
K. Meera, R. Muralidharan, P. Santhanaraghavan, R.
Gopalakrishnan, P. Ramasamy, Journal of Crystal Growth,
2001, 226, 303.; K. Meera, S. Aravazhi, P.S. Raghavan, P.
Ramasamy, Journal of Crystal Growth, 2000, 211, 220.
R.M. Kumar, R.Muralidharan, D.R. Babu, K.V. Rajendran, R.
Jayavel, D. Jayaraman, P. Ramasamy, Journal of Crystal
Growth, 2001, 229, 568.; R.M. Kumar, R.Muralidharan, D.R.
Babu, K.V. Rajendran, R. Jayavel, D. Jayaraman, P.
Ramasamy, Journal of Crystal Growth, 1993, 133, 212.
Photoluminescence studies
The photoluminescence spectrum of pure and amino acids doped
TGS crystals were recorded at 310 K and 340 K and the spectrum is
shown in Figure 10(a) and 10 (b) respectively. All crystals were
excited at 240nm.A sharp emission band was clearly observed near
361nm for pure TGS crystal with a small peak at 389 nm. A similar
effect was observed very recently upon doping TGS crystals with
crystal violet and amaranth dye [34, 2]. These two close emission
bands appearing in the near UV region in TGS crystal is strongly
related to the electronic structure of the material and is termed as
hyper- luminescence [35,36]. The observed luminescence spectrum
6
7
8
can be interpreted as
a
manifestation of electron–hole
recombination and de-excitation of exciton terms, accompanied by
transitions to vibrational sub levels of the ground state of the
crystal. This type of luminescence in TGS crystal is termed as hyper-
luminescence in which two closely placed equal intensity peaks are
observed and the relative intensity of these peaks is changed by the
excitation wavelength as discussed by Gorelik et al. [36].
9
10 R. Malekfar, A. Daraei, ActaPhysicaPolonica A, 2008, 114
859.
11 J. Novotny, L. Prokopova, Z. Micka, Journal of Crystal
Growth,2001, 226, 333.
,
Figure 10. The photoluminescence spectrum of pure and amino
acids doped TGS crystals at (a) 310 K and (b) 340 K.
12 A.P.Levanyuk, V.V.Osipov, A.S.Sigov, A.A.Sobyanin, ZheTP 76
(1979) 345.
13 K.Balasubramanian, and P.Selvarajan, Recent Research in
Conclusions
Science and Technology, 2010,2, 6.
14 X.Zhao, C.Sun, Y.Si, M.Liu,D.Xue, Modern Physics Letters B,
2009, 23, 3809.
15 D.Xue, and K.Kitamura, Ferroelectrics, 2003, 297, 19.
16 X.Zhang, and D. Xue, Journal of Physical Chemistry B, 2007,
111, 2587.
Crystals of pure TGS, L-Arginine, L-Histidine and L-Alanine doped
TGS have been grown by slow solvent evaporation technique at
room temperature. The crystals were found to show good
transparency in the UV-visible region with increased band gap and
enhanced optical constants making them useful for photonic device
applications. P-E Hysteresis loop measurements reveals that the
grown crystals are Ferro electric in nature. The coercive field value
of the doped crystals is more than the pure one, implying that the
17 O. V Rogazinskaya, S. DMilovidova, A. S Sidorkin, A.
BPlaksizkii, A. ASidorkin,T. V.Vorobzhanskaya, Ferroelectrics,
2004, 307, 255.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 6 of 23
View Article Online
DOI: 10.1039/C5RA25700J
ARTICLE
Journal Name
18 J.Stankowska, Ferroelectrics, 1978,22, 753.
19 M. Senthil Pandian, P. Ramasamy, and Binay Kumar,
Materials Research Bulletin, 2012, 47, 1587.
20 T. Bharthasarathi, V. Siva Shankar, R. Jayavel, P.
Murugakoothan, Journal of Crystal Growth, 2009, 311, 1147.
21 Wenwei Ge, Hong Liu, Xiangyong Zhao, Xiaoming Pan,
Tianhou He, Di Lin, Haiqing Xu, Haosu Luo., Journal of Alloys
and Compounds, 2008, 456, 503.
22 X. Guisheng, L. Haosu, W.Pingchu, X. Haiqing, Y. Zhiwen,
ChineseScience Bulletin, 2000,45, 491.
23 A. Saxena, V. Gupta, K. Sreenivas, Journal of Crystal Growth,
2004, 263, 192.
24 V. N Joshi, “Photoconductivity”, 1990, Marcel Dekker, New
York.
25 Bube,R. H., (1981), “Photoconductivity of solids”, Wiley, New
York.
26 I.L. Karle, and J. Karle, (1964), ACTA Crystallographica, 1964,
17, 835.
27 P.R Tulip, and S.J. Clark, Physical Review B, 2005, 71, 195117.
28 J. Mary Linet, S. Mary NavisPriya, S. Dinakaran, and S. Jerome
Das, Crystal Research Technology, 2008, 43, 806.
29 R. Parimaladevi, C. Sekar and V. Krishnakumar,
Spectrochim.Acta, Part A, 2010, 75, 617.
30 P. K. Bajpai, D. Shah and R. Kumar, Nucl. Instrum. Methods
Phys. Res., Sect. B, 2012, 270, 93.
31 Zhihua Sun, Tianliang Chen, Ning-ningCai, Jing-wei Chen, Lina
Li, Yan Wang, Junhua Luo, Maochun Hong, New. J.
Chem.,2011,35,2804.
32 B.D. Hatton, K. Landskron, W.J. Hunks, M.R. Bennett, D.
Shukaris, D.D. Pervoic,G.A. Ozin, Mater. Today.,2006, 9, 22.
33 A. Cyrac Peter, M. Vimalan, P. Sagayaraj, J. Madhavan, Phys.
B Condens. Matter.2010,405, 65.
34 Nidhi Sinha, Sonia Bhandari, Harsh Yadav, Geeta Ray, Sanjay
Godara, Nidhi Tyagi, JyotiDalal, Sonu Kumar and Binay
Kumar, CrystEngComm., 2015, 17,5757.
35 V.S. Gorelik, E.V. Zhabotinskii, J. Russ. Laser Res. 1995,16
287.
36 V.S. Gorelik, E.V. Zhabotinskii, Quantum Electron. 1993,23
1053–1054.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J
1(a)
1(b)
1(c)

RSC Advances
Page 8 of 23
View Article Online
DOI: 10.1039/C5RA25700J
1(d)
Figure 1. The photograph of the grown crystals of (a) pure TGS (b) L-Ar TGS (c) L-H TGS and (d) L-Al TGS.
Figure 2. UV- Visible Transmission spectra of Pure and doped TGS crystals.

Page 9 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J
Figure 3. (αhν)2 vs hν spectra of Pure and doped TGS crystals.

RSC Advances
Page 10 of 23
View Article Online
DOI: 10.1039/C5RA25700J

Page 11 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J

RSC Advances
Page 12 of 23
View Article Online
DOI: 10.1039/C5RA25700J

Page 13 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J
Figure 4. Field dependence of dark and photo currents for (a) Pure TGS (b) L-Ar TGS (c) L-H TGS and (d) L-Al TGS.
Figure 5.Bond lengths for L-Arginine molecule.

RSC Advances
Page 14 of 23
View Article Online
DOI: 10.1039/C5RA25700J
Figure 6. Bond angles for L-Arginine molecule.

Page 15 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J

RSC Advances
Page 16 of 23
View Article Online
DOI: 10.1039/C5RA25700J
Figure 7(a). Dielectric constant versus log f for Pure and doped TGS crystals and 7(b). Dielectric loss versus log f for Pure and
doped TGS crystals.

Page 17 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J

RSC Advances
Page 18 of 23
View Article Online
DOI: 10.1039/C5RA25700J

Page 19 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J

RSC Advances
Page 20 of 23
View Article Online
DOI: 10.1039/C5RA25700J
Figure 8. Ac conductivity versus log f for (a) pure TGS, (b) L-Ar TGS, (c) L-H TGS and (d) L-Al TGS

Page 21 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J
Figure 9. Plot of 1000/T versus ln σac

RSC Advances
Page 22 of 23
View Article Online
DOI: 10.1039/C5RA25700J

Page 23 of 23
RSC Advances
View Article Online
DOI: 10.1039/C5RA25700J
Figure 10. The photoluminescence spectrum of pure and amino acids doped TGS crystals at (a) 310 K and (b) 340 K.