World Jour nal of Condensed Matter Physics, 2011, 1, 24-32
doi:10.4236/wjcmp.2011.12005 Published Online May 2011 (
Copyright © 2011 SciRes. WJCMP
Growth and Characteriz ation of Novel System of
Nanoparticles Embedded in Phosphate Glass
Wageh Swelm1, Anwar Higazy2, Mohammed Algradee2,3
1Physics and Engineering Mathematics Department, Faculty of Electronic Engineering, Menufiya University, Menouf, Egypt;
2Department of Physics, Faculty of Science, Menoufia University, Shebin El-Koom, Egypt; 3Department of Physics, Faculty of
Science, Ibb University, Ibb, Yemen.
Received March 7th, 2011; revised March 22nd, 2011; accepted March 25th, 2011.
We present a study of growth of a novel system of CdTe nanoparticles embedded in sodium/lithium-mixed phosphate
glass matrix in a strong quantum confinement regime. The prepared systems are characterized by differential thermal
analysis, X-ray diffraction, TEM, optical absorption, infrared and Raman Spectroscopy. We have investigated the effect
of glass matrix composition and annealing time on the growth mechanism of the CdTe semiconductor nanoparticles. We
found that the decrease in Na2O content and addition of ZnO to the glass composition is strongly affecting the nanopar-
ticles formation and capping surface of the nanoparticls. On the other hand, we have calculated the size of nanopar-
ticles by effective mass approximation (EMA ) and empirical method based on tight binding approximation and found
that the calculation based on tight binding approximation are very plausible than that one calculated by EMA.
Keywords: Semiconductor Nanoparticles, CdTe, Infrared and optical Spectroscopy
1. Introduction
Semiconductor nanoparticles have received considerable
attention in the field of material science research due to
their unique optical and electronic properties. These
unique properties like the enhancement in the lumines-
cence properties of semiconductor nanoparticles, with
high spectral purity and excellent fluorescence efficien-
cies. Another advantage comes from the size-tunability
of their emission and absorption. The colour of absorp-
tion and emission can be tuned just by changing the size
of the nanocrystals, without any changes in composition
or stoichiometry. These properties make nanoparticles a
very attractive material for many applications.
The unique in optical properties of the nanoparticles
comes from the quantum confinement effects w hich ari se
when the size of the semiconductor have dimensions of
10 nanometers or less [1-3]. In this framework a number
of researches have been dedicated to the fabrication of
small semiconductor nanocrystals in different type of
dielectric matrices either solids or liquid s [4-8].
Specifically, II-VI semiconductor nanoparticles have
attracted much attention due to both their unique proper-
ties brought by the three dimensional quantum confine-
ments and their potential for photonic applications as
optical devices [9-11]. CdTe is one of the II-VI semi-
conductor nanocrystals which have a large exciton Bohr
15 nm, and therefore it offers the possibility
of studying quantum confinement effects in higher clus-
ter size regimes. Up to now very rare work are published
about the glass matrices doped with CdTe nanocrystals
Therefore, it is desired to develop new glasses with
semiconducting nanocrystals of will controlled size, size
distribution and content, which may extended the appli-
cation of these composite to the new era of optical func-
tion devices. In view of this, we have prepared a novel
system of nanoparticles embedded in glass. To the best
of our knowledge, CdTe nanocrystal embedded in so-
dium/lithium-mixed phosphate glass matrix has not been
reported yet. Our nanoparticles doped sodium/lithium-
mixed phosphate glass matrix begun in 2008 [19] and
2009 [20], and we have studied the growth of CdSe and
PbSe nanocrystals in this glass matrix through optical
absorption, X-ray diffraction and infrared spectroscopy
Growth and Characterization of Novel System of Nanoparticles Embedded in Phosphate Glass Matrix
Copyright © 2011 SciRes. WJCMP
techniques. In this work, it is intended to study the
growth of CdTe quantum dots in P2O5Na2O–Li2O and
P2O5–Na2O–ZnO–Li2O glass matrices. We have studied
the effect of glass composition and annealing time on the
growth of nanoparticles. The prepared samples characte-
rized by differential thermal analysis, X-ray diffraction,
TEM, optical absorption spectroscopy, Infrared spec-
troscopy and Raman Spectroscopy.
2. Preparation
In this work we have prepared a new system of CdTe
nanoparticles embedded in phosphate glass matrix. There
are some problems for the preparation of nanoparticles
embedded in glass. Among these problems the low solu-
bility of semiconductor in the melted glass matrix which
lead to low concentration of the nanoparticles in the glass
matrix. The melting point of the glass also is very im-
portant for reducing the loss of semiconductor elements.
As the melting point is dependent on the component of
glass matrices so the choices of these elements are very
important. To avoid these problems we have chosen a
glass matrix with melting temperature 1100˚C, which
is less than about 500˚C in analogies with silicate glass
matrices. We have prepared two systems with different
compositions of glass matrix. These two systems are
P2O5–Na2O–Li2O-2wt% CdO-2wt%Te and P2O5–Na2O–
ZnO–Li2O-2wt% CdO-2wt%Te. On the preparation of
the second system P2O5Na2O–ZnO–Li2O-2wt% CdO
-2wt%Te, we have added 7 % of ZnO on the expense of
Na2O. We have calculated the amounts of consisting
components (P2O5, Na2O, ZnO and Li2O) using the mo-
lecular formula of glass. Hereafter, we call the two sys-
tems P2O5–Na2O–Li2O-2wt% CdO-2wt%Te and P2O5
Na2O–ZnO–Li2O-2wt% CdO-2wt %Te as S1 and S2,
respectively. The raw materials used in preparation are
Li2CO3, Na2CO3, ZnO, P2O5, CdO and Te reagent grades.
The raw materials were weighted, mixed and stirred me-
chanically many times to obtain homogeneous mixture.
The mixture has put in porcelain crucibles and inserted in
an electric furnace held at 250˚C for 1 h. This process of
heat treatment allows the P2O5 decompose and react with
other raw materials before melting. Then the mixtures
have transferred to a second furnace which held at
1100˚C for 15 min for melting (the melting temperature
is depending on the composition of the base glass). Then
the melt has poured into two mild steel split mould pre-
viously heated to 210˚C. Then the samples immediately
transferred to an annealing furnace held at 210˚C, only
for 1 min then the composite was allowed to cool gr adu-
ally to room temperature to relieve excess internal stress
in the glass base and to initiate the nucleation and growth
of the nanoparticles. This adopted method allows pro-
ducing samples with small nanoparticles and narrow size
distribution embedded in the glass matrix, hereafter we
call these samples as quenched.
In view of a study of thermal anne aling of our samples,
we have also performed a prior analysis of the composite
versus temperature. A deferential thermal analysis mea-
surement (DTA) for as quenched S2 sample is shown in
Figure 1. DTA allow us to identify the glass transition
temperature (Tg), onset crystallization temperature (Tx)
and crystallization peak temperature (Tp). We have found
the values of Tg, Tx, and Tp are 270, 499 and 511˚C, re-
spectively. According to these result we have treated the
produced samples at 350˚C for different time periods to
grow different size of nanoparticles. The samples have
been kept in desiccator to prevent possible attack by
moisture. Some samples were polished to optical quality
for optical measurements. For this purpose, ethylengly-
cole have been used to avoid the selective removal of any
components from the surface layer.
3. Characterization
The obtained composites were characterized by different
techniques. Thermal properties were studied using Shi-
madzu DTA-50 in a platinum crucible and nitrogen flux
with flow rate of 10 ml/min1 to determine glass transi-
tion temperature, (Tg), crystallization onset temperature,
(Tx), and crystallization peak temperature, (Tp). The
X-ray analysis was performed on a Philips Pw1373
X-ray diffractometer with Cu radiation (λ = 1.542 ºA)
and Ni filter operated at 36 kV and 20 mA with a scan-
ning rate of 2 deg min1 in the angular range 20 to 70˚.
The optical absorption spectra were recorded using a
UV-VIS spectrophotometer (Unico UV-VIS double
beam model 4862, USA) in the spectral range 200 - 1000
nm at room temperature. The morphology of the samples
and particle distribution were characterized by JEOL
Figure 1. DTA curve of the as quenched S2 sample. The
large difference between the onset crystallization tempera-
ture and glass transition (241˚C) will be promise for further
annealing attempts as future work.
26 Growth and Characterization of Novel System of Nanoparticles Embedded in Phosphate Glass Matrix
Copyright © 2011 SciRes. WJCMP
JEM 1230 transmission electron microscopy (TEM) op-
erated at 200 kV accelerating voltage. The samples were
prepared by making a suspension from the glass powder
in Ethylene Glycol. The suspension was centrifuged to
collimate the large size particles. Then a drop of the sus-
pension was put into the copper grid (400 mesh) in each
solution of nanoparticles. The IR transmission spectra of
the glass samples were measured for each glass sample
over the range, 4000 - 400 cm1 of wave numbers. A
JASCO 460 FTIR (made in Japan) Infrared Spectrometer
was used in conjunction with the potassium bromide,
KBr, disc technique. For this, powdered glass samples
were thoroughly mixed with dry KBr in the ratio 1:20 by
weight and the pellets were formed using a pellet press.
Raman scattering spectra were recorded at room temper-
ature using a Jasco FT/IR 6300-RFT and Raman At-
tachment with a single monochromator and a filter. The
excitation was provided by Nd: YVO4 laser at 1064 nm
(power 200 mW). All measurements were carried out on
bulk vit re o us sample s at room temperature.
4. Results and Discussions
We have investigated the effect of adding ZnO to the
components of glass matrix on the structure configura-
tion through density calculation. Density is affected by
structural softening/compactness, changes in geometrical
configuration, coordination number, cross-link density
and the dimensions of interstitial spaces in the structure.
We have determined the density ρ of S1 and S2 compo-
sites using Archimedes method, in this method toluene is
used as an immersion liquid. The density calculated ac-
cording to the following equation:
()() ()
1 11ta aa tta
=−−+ −
is the density of toluene and equal 0.653
gm/cm3 at 20˚C, Wa is the weight of the glass in air ,
is the weight of the glass in toluene and
, 1t
weights of suspended thread in air and toluene, respec-
tively. Repeated density measurements were agreed
within ±0.01%. The calculated density for S1 and S2
samples are 2.49 and 2.58 gm/cm3, respectively. We
have attributed the increase in the density of S2 compo-
site contain ZnO to the difference in molecular weight
between Na2O (61.98) and ZnO (81.38), i.e. , introducing
heavier molecule into the structure of glass instead of
lighter one increase the density.
To completely explain the difference in density for the
two composities S1 and S2, we have calculated the molar
volume, Vm, of each composite using: Vm = M / ρ, where,
M is the molecular weight of glass components.
The calculated molar volume of S1 and S2 composites
are 42.35 and 41.41 cm3, respectively. This result can be
explained that the addition of ZnO to P2O5 glass in the
expense of Na2O can increase the cross-links between
phosphate chains [21]. As alkali ions (Li+, Na+) can lead
to the breaking of P-O-P linkages and the creation of
non-bridging oxygen atoms in the glass [22], then, add-
ing zinc oxide in the expense of Na2O or Li2O can in-
crease the cross-links between phosphate chains and can
reduce the number non-bridging oxygen. The decrease of
non-bridging oxygen bonds may be lead to a decrease in
the probability of formation of Te-O bond at the surface
of the nanopartic les.
Figure 2 shows the X-ray diffraction pattern (XRD)
for as quenched S1 sample. The XRD pattern shows a
diffraction lines at 2θ = 23.58˚, 25.78˚, 29.75˚, 35.41˚,
41.033˚, 45.53˚, 50.27˚, 52.93˚, 56.95˚, 59.88˚ and 61.33˚
corresponding to (100), (101), (102), (103) , (110), (112),
(015), (022 ), (023), (106) and (204) planes of Hexagonal
CdTe, respectively (JCPDS data file: 80-0089-Hexagon-
al). Besides the planes of the Hexagonal CdTe there are
some diffraction peaks at 31.2˚, 38.79˚ and 44.26˚ which
corresponding TeO2 at the surface of the nanoparticles
(JCPDS data file: 74-1131). This result indicates that our
quenching method leads to formation and crystallization
of CdTe nanoparticles which covered by Te-O bonds at
the surface of the nanoparticles.
Figure 3 presents the XRD of as quenched S2 sample;
here we have added 7% ZnO on the expense of Na2O.
The XRD pattern shows a diffraction lines at 2θ = 23.58˚,
25.0˚, 26.15˚, 30.66˚, 35.41˚, 39.40 ˚, 41.94˚, 48.8˚, 52.56 ˚,
and 59.51˚ corresponding to(100), (101), (003), (102),
(103), (220) C, (110), (200), (022) and (106) planes of
Hexagonal CdTe (JCPDS data file: 80-0089- Hexagonal)
and the peak appeared at 39.40˚ corresponding to (220)
cubic phase. In addition to, the diffraction lines appeared
at 2θ = 31.75˚ and 37.37˚ which related to TeO2 at the
surface of the nanoparticles. Clearly, there is a remarkable
difference between the two diffraction patterns of S1 and
S2 glass composite. The most important change is highly
increasing in the intensity of the peak at 2θ = 23.58˚
which corresponding to (100) plane. In addition, the
Figure 2. X-ray diffraction pattern of as quenched S1 sam-
ple. The CdTe nanoparticles embedded in glass have Hex-
agonal structure and the diameter of the nanoparticles is
2.04 nm as calculated by Debye–Sherrer equation.
Growth and Characterization of Novel System of Nanoparticles Embedded in Phosphate Glass Matrix
Copyright © 2011 SciRes. WJCMP
Figure 3. X-ray diffraction pattern of as quenched S2 sam-
ple. The CdTe nanoparticles embedded in glass have Hex-
agonal structure and the diameter of the nanoparticles is
2.76 nm as calculated by Deby–Sherrer equation.
relative intensity of TeO2 to (1 00) lin e is decreased for S2
sample. These result revealed that the decrease in Na2O
content and addition of ZnO to the glass composition is
strongly affecting the nanoparticles formation and cap-
ping surface of the nanoparticls which confirmed by the
result of molar volume calculation.
We have calculated the mean sizes for the nanopar-
ticles embedded in glass for as quenched S1 and S2 sam-
ples using the (101) and (100) reflections, respectively.
The half width of these two peaks has been used to cal-
culate size of CdTe nanoparticles using DebyeSherrer
equatio n [23],
L is the coherence length, B is the full width at half
maximum of the peak,
is the wavelength of X-ray
radiation, and
is the angle of diffraction. In case of
a small crystallites L = 3/4 d, where d is diameter of na-
noparticles. The calculated nanoparticles diameters for
the as quenched S1and S2 samples are 2.04 and 2.76 nm,
Figure 4(a) and (b) shows TEM images for the as
quenched S1 and S2 samples. Obviously, we can see the
glass matrix contains crystalline CdTe particles d ispersed
and well separated in the glass matrix. The figures re-
veals that mean size of the nanoparticles are 3.22 and 3.6
nm for S1 and S2, respectively.
Cadmium telluride have relatively larg e Bohr radius of
approximately 7.5 nm which is three times the diameter
of the nanoparticles, consequently the prepared nanopar-
ticles in strong confinement regime. We have used the
optical absorption spectroscopy to analyze the influence
of heat treatment duration and change in glass composi-
tion on the light absorption mechanisms in CdTe nano-
particles embedded in glass. From the position of the first
absorption maximum and the fundamental absorption
edge we have obtained some information on the growing
of the nanoparticles and deduced some important proper-
ties of the material, like the optical band gap, and size of
the nanoparticles. All the absorption spectra applied at
room temperatures for all samples.
Figure 5 shows the comparison between the absorp-
tion spectra for the as quenched S1 and S2 samples.
The absorption spectra for S1 sample show an initial
step at 2.42 eV. This unresolved peak at 2.42 eV is blue
shifted by 0.99 eV from the bulk band gap of CdTe.
While the absorption spectra for the as quenched S2
sample is clearly different as shown in Figure 5. A dis-
tinct peak appear s at 2.34 eV and is b lue shifted by 0.91
eV from the bulk band gap of CdTe. These results indi-
cate a coexistence of nucleation and growth of nanopa-
ticles during the quenching process due to the low rate
of cooling around the transition temperature. The dif-
ference between the absorption spectra of the S1 and S2
samples means that the size of the nanoparticles formed
in glass contains ZnO is greater than the particles
formed in Zn free glass. These results indicated that the
presence of ZnO in the host glass matrix leads to an in-
crease in the number of CdTe nanoparticles nucleated
during the quenching of the melt to room temperatures
which confirm the obtained results from X-ray analysis.
It’s worth mention that there is a difference of the opti-
cal band gap of the two bases of glass. The optical band
gap for the base glass of S1 and S2 s amples are 3.71 and
4.04 eV respectively. This difference of the optical band
gap of base glass leads to a change in the degree of con-
finement of the two composites which in turn affect on
the oscillator strength and energy of the absorption
spectra. Also, the shift of the absorption maximum for
S2 sample to lower energy indicates that the Zn ions
don’t replaced the Cd ions in the core of the nanopar-
ticles, if Zn replaced Cd will lead to shift of the absorp-
tion band to higher energy. We have calculated the sizes
of nanoparticles embedded in glass for S1 and S2 sam-
ples from the position of the first absorption maximum
using effective mass approximation model for spherical
particles. In this model the ground electron hole pair
state energy (E1s1s) can be approximately calculated us-
ing the expression [1 ] :
1.786 0.248
ss gyyy
∗ ∗∗
= +π−−
is the energy of the first absorption maximum,
is the bulk band gap energy, a is the nanoparticle ra-
is the exciton Bohr radius (
nm), and
is the exciton Rydberg energy (
meV). The
nanoparticle diameters (d) calculated using above equa-
tion are 4. 5 8 nm a nd 4.78 nm for S1 and S2, respectively.
These values are extremely higher than the sizes esti-
mated using Debye-Scher rer equation and measured by
TEM. On the other hand, the di fference between the sizes
Growth and Characterization of Novel System of Nanoparticles Embedded in Phosphate Glass Matr i x
Copyright © 2011 SciRes. WJCMP
Figure 4. (a) TEM image for as quenched S1 sample (the mean diameter 3.22 nm) and (b) TEM image for as quenched S2
sample (the mean diameter 3.6 nm).
Growth and Characterization of Novel System of Nanoparticles Embedded in Phosphate Glass Matr i x
Copyright © 2011 SciRes. WJCMP
Figure 5. Absorption spectra of as quenched S1 and S2
of the naoparticles for med in the two matrices is n ot com-
patible wi th the X-ray and TEM results. In addition to, the
two bases of glass have different optical band gap. In view
of all of these information we can attribute the overestim a-
tion obtained from the calculations based on the effective
mass approximation due to the uses of infinite barrier po-
tential with vanishing wave functions at the boundary.
These results ind icate that the value of th e potential barri er
is the crucial parameter for the effective mass calculation
to adapt the real sizes of the nanoparticles embedded in
glass matrix. This result compatible with the previously
reported theoretical result by Laheld and Einevoll which
showed that the application of finite barrier will gave rea-
sonable fit s to exper im ental resul t [24] .
On the other hand, we have calculated the size of na-
noparticles by the formula based on tight binding ap-
proximation. This formula is [25]
( )()
Ed Eadbd c
= ∞+++
(4 )
where Eg(d) and Eg() are the band gap for the nanopar-
ticle with diameter d and the bulk state, respectively. a, b
and c are constants which were determined by fitting
Equation (4) with experimental data [26], the value of a,
b and c are 0.137, 0.0 and 0.26, respectively. The calcu-
lated sizes for S1 and S2 are 2.45 and 2.65 nm, respec-
tively. These sizes are lied between the estimated values
using Deb ye -Scherrer equation and that one measured by
TEM for S1 sample and very close to the estimated val-
ues using Debye-Scherrer equation for S2 sample.
Figure 6 shows the effect of annealing time on the
absorption spectra of S1 sample. The absorption spectra
for the sample annealed for 30 minutes shows a feature-
less relatively sharp absorption spectrum. With increas-
ing annealing time the sharpness of the absorption spec-
tra increases which indicates a decrease in size distribu-
tion. In addition the energy of the absorption edge shifts
to lower energy with increasing annealing time.
Figure 7 shows the effect of annealing time on the
Figure 6. The effect of annealing duration on the absorption
for S1 system at constant annealing temperature 350˚C.
absorption spectra of S2 sample. Clearly, for annealing
with short duration the absorption spectra grows with a
will defined structure peak at 2.34 eV, after one hour the
absorption spectra shows a shoulder at 2.3 eV. With fur-
ther increasing of annealing time the absorption spectra
consists of steep featureless absorption edge.
Due to the appearance of featureless nonstructural ab-
sorption spectra for the annealed samples, we have cal-
culated the size of the nanoparticles from the energy de-
pendence of the absorption coefficient near the band
edge. The effective band gap of the CdTe nanoparticles
calculated from the energy dependence of the absorption
coefficient near the band edge using the following rela-
tion [27]
()( )
= −
where α is the absorption coefficient, E = ħ
is the pho-
ton energy and Eg(d) is the effective band gap energy of
the nanoparticles. Figure 8 shows as an example of the
relation between
( )
as a function of photon ener-
gy and the linear fitting to this relation for as quenched
S1 samples annealed for (60 min). The value of band
gaps Eg(d) for the nanoparticles were determined by
extrapolating the straight line of the linear fit to the
energy axis at
( )
= 0. We have used these calculated
band gaps to calculate the nanoparticle diameters by ap-
plying equation 4 for the two composites S1 and S2 an-
nealed at different times. Figure 9 shows the effect of
annealing time on the size of nanoparticles in diameters
for S1 and S2 systems. Clearly, the nanoparticle diameter
increases with increasing annealing time. In addition to,
the rate of increasing the diameter for S2 system is rela-
tively higher than that one for S1 system. This result in-
dicates that the addition of ZnO on the expense of Na2O
will affect on the diffusion of the semiconductor ions.
In order to investigate the effects of adding ZnO to the
base glass matrix we have studied IR transmission spec-
tra for as quenched S1 and S2 samples. Figure 10 shows
the IR transmission spectra recorded over the range
30 Growth and Characterization of Novel System of Nanoparticles Embedded in Phosphate Glass Matrix
Copyright © 2011 SciRes. WJCMP
Figure 7. The effect of annealing duration on the absorption
spectra for S2 system at constant annealing temperature
Figure 8. Variation of
( )
as a function of photon
energy and the linear fitting to this relation for as quenched
S2 sample annealed for 60 min at 350˚C.
Figure 9. Nanoparticle diameters calculated by Equation (4)
which is based on tight binding approximation against the
heat treatment time for S1 and S2 samples at constant an-
nealing temperature (350˚C). Solid lines and equations s how
a least-squares fit to the data.
400 - 4000 cm1 for S1 and S2 composities. The features
appeared for S1 and S2 samples, can be explained as
Figure 10. Inf rared spectr a for as quenched S1 and S2 sam-
follows. The absorption bands around 3438 cm-1 is due to
the symmetric stretching of O-H, and the signal at aroun d
1648 cm1 is due to the deformation modes of O-H
groups and absorbed water molecules, δ(H-O-H) [28].
The two bands appeared at 2922 and 2372 cm1 are re-
lated to ethylene glycol which adsorbed on the surface of
samples during the smoothing process. The absorption
band appeared at 1269 cm1 corresponding to a P = O
vibration b and [29], the עas (PO2)- asymmetric stretching
vibrations at 1170 cm1 [30], the νas(PO3) asymmetric
stretching mode at 1079 cm1, the νs(PO3) symmetric
stretching mode at 974 cm1 [31], the νas(P–O–P) groups
at 906 cm-1, the νs(P–O–P) groups at 775 cm1 and 731
cm1 [32] and the band at 506 cm1 due to the deforma-
tion mode of (P-O-) groups [33] overlapped with the third
longitudinal optical phonon (3LO) of CdTe. There are
some differences between the infrared absorption bands
for S1 and S2 samples which reflect some important in-
formation about the effect of adding ZnO to the glass
1) The position of δ(H-O-H) band is little shifted to
lower frequency for S2 sample (i.e., it weakened) which
has ZnO in the base glass matrix. In addition to, the de-
crease in the intensity of stretching mode of O-H. These
differences reflect that the adding of ZnO to the glass
decrease the hygroscopicity of the composite.
2) The increase in the symmetry on the high energy
side of the observed band at 1269 cm1 which is attri-
buted to P = O for S2 sample. Also the increase in asy-
metery of νas (PO2)-band for S2 sample due to P-O-Zn
linkage formation. On the other hand, the absorption
band associated with νas (PO3) shifts from 1076 cm1 for
S1 sample to 1087 cm1 for S2 sample. We attributed
these result to the reticulation effect appeared by adding
ZnO to the composite, where Zinc oxide tend to increase
the cross-link in the glass matrix and also increase the
Growth and Characterization of Novel System of Nanoparticles Embedded in Phosphate Glass Matrix
Copyright © 2011 SciRes. WJCMP
linkage with the surface of the nanoparticles through
P-O- Zn-Te bonds.
We have determined the phonon modes using Raman
scattering experiments. Figure 11 shows Raman spec-
trum for S1 and S2 samples. For Zn free glass sample S1
the Raman peaks at 143.14 and 162.14 cm1 are due to
the fundamental transverse optical mode (1TO) and lon-
gitudinal optical mode (1LO) of CdTe, respectively [16].
The peak at 120.17 cm1 corresponds to Te-O bond [34]
located at the surface of the nanoparticle. On the other
hand, for the sample S2 which contain Zn in the base
glass the vibration due to 1LO mode and Te-O bond are
little shifted to higher energy. This blue shift may be due
to lattice contraction or zinc incorporation into the nano-
particle core. Optical absorption spectroscopy showed
that there is no incorporation of Zn into the nanoparticles
core. So, we attributed this shift to the lattice contraction.
This lattice contraction may be due to local strain in in-
dividual crystallites by the increase in density of the S2
base glass and the increase of crystallite size in this ma-
trix. Also its worth to mention that, the relative intensity
of the peak due to Te-O bond to 1LO peak vibration is
decreased for the S2 sample, which confirms the ob-
tained result from X-ray analysis. The decrease in inten-
sity of TeO2 vibration mode indicates that the decrease in
the number of Te-O bonds at the surface of the nanopar-
ticles. The decrease of number of Te-O bonds may be
due to the formation of some Te-Zn-O bonds at the sur-
face of the nanoparticles which is the extension of
P-O-Zn in the glass structure.
5. Conclusion
We have presented a preparation of a novel system of
CdTe embedded in phosphate glass matrix. The prepared
samples characterized by differential thermal analysis
(DTA), X-ray diffraction, TEM, infrared, Raman and
optical absorption spectroscopy. The X-ray diffraction
Figure 11. Raman spectra for as quenched S1 and S2 sam-
study showed the prepared nanoparticles are crystallized
in hexagonal structure and presence of diffraction peak
related to TeO2 which cover the surface of the nanopar-
ticles. And Raman spectroscopy showed that a decrease
of Te-O bonds at the surface of the nanoparticles em-
bedded in the glass matrix which has ZnO in the compo-
sition of the base glass. On the other hand, we have stu-
died the effect of annealing duration on sizes of the na-
noparticles through the optical absorption spectroscopy.
We have determined the size of the nanoparticles by
XRD and TEM. In addition to, the size of the nanopar-
ticles calculated from the absorption spectra by effective
mass approximation and empirical method based on tight
binding approximation. These calculations revealed that
the sizes of the nanoparticles based on the tight binding
approximation are very close to TEM and XRD results.
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