Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics
Undoped as well as Li-, Ag-, Cu- and Zn-doped MgxZn₁₋xO ceramics with x = 0–0.20 were sintered at 1000 °C. Defect-related photoluminescence (PL) and PL excitation spectra were measured at room temperature in 400–800 nm and 250–400 nm spectral ranges, accordingly. Two types of PL bands were observed:...
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| Cite this: | Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics / I.V. Markevich, T.R. Stara, V.O. Bondarenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 3. — С. 344-348. — Бібліогр.: 17 назв. — англ. |
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Markevich, I.V. Stara, T.R. Bondarenko, V.O. 2017-06-13T17:43:33Z 2017-06-13T17:43:33Z 2015 Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics / I.V. Markevich, T.R. Stara, V.O. Bondarenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 3. — С. 344-348. — Бібліогр.: 17 назв. — англ. 1560-8034 DOI: 10.15407/spqeo18.03.344 PACS 81.05.Dz, 81.05.Je https://nasplib.isofts.kiev.ua/handle/123456789/121244 Undoped as well as Li-, Ag-, Cu- and Zn-doped MgxZn₁₋xO ceramics with x = 0–0.20 were sintered at 1000 °C. Defect-related photoluminescence (PL) and PL excitation spectra were measured at room temperature in 400–800 nm and 250–400 nm spectral ranges, accordingly. Two types of PL bands were observed: i) the bands, spectral positions of which were not influenced by the Mg content (Cu-related as well as selfactivated orange and red ones); ii) the bands, spectral positions of which exhibited some blueshift with increasing Mg content (Li- and Ag-related and self-activated green ones). It has been shown that used doping gives the possibility to obtain the phosphor with intense visible emission within the blue-yellow spectral range. This research has been financially supported by National Academy of Sciences of Ukraine (project III-4-11). en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics Article published earlier |
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Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics |
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Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics Markevich, I.V. Stara, T.R. Bondarenko, V.O. |
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Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics |
| title_full |
Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics |
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Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics |
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Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics |
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influence of mg content on defect-related luminescence of undoped and doped wurtzite mgzno ceramics |
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Markevich, I.V. Stara, T.R. Bondarenko, V.O. |
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Markevich, I.V. Stara, T.R. Bondarenko, V.O. |
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2015 |
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Semiconductor Physics Quantum Electronics & Optoelectronics |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Undoped as well as Li-, Ag-, Cu- and Zn-doped MgxZn₁₋xO ceramics with x = 0–0.20 were sintered at 1000 °C. Defect-related photoluminescence (PL) and PL excitation spectra were measured at room temperature in 400–800 nm and 250–400 nm spectral ranges, accordingly. Two types of PL bands were observed: i) the bands, spectral positions of which were not influenced by the Mg content (Cu-related as well as selfactivated orange and red ones); ii) the bands, spectral positions of which exhibited some blueshift with increasing Mg content (Li- and Ag-related and self-activated green ones). It has been shown that used doping gives the possibility to obtain the phosphor with intense visible emission within the blue-yellow spectral range.
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1560-8034 |
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Influence of Mg content on defect-related luminescence of undoped and doped wurtzite MgZnO ceramics / I.V. Markevich, T.R. Stara, V.O. Bondarenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 3. — С. 344-348. — Бібліогр.: 17 назв. — англ. |
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2025-11-24T02:25:07Z |
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1850838075225145344 |
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 344-348.
doi: 10.15407/spqeo18.03.344
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
344
PACS 81.05.Dz, 81.05.Je
Influence of Mg content on defect-related luminescence
of undoped and doped wurtzite MgZnO ceramics
I.V. Markevich, T.R. Stara, V.O. Bondarenko
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, prospect Nauky, 03028 Kyiv, Ukraine;
Phone: +38(044)525-7234; e-mail: stara_t@ukr.net
Abstract. Undoped as well as Li-, Ag-, Cu- and Zn-doped MgxZn1–xO ceramics with x =
0–0.20 were sintered at 1000 °C. Defect-related photoluminescence (PL) and PL
excitation spectra were measured at room temperature in 400–800 nm and 250–400 nm
spectral ranges, accordingly. Two types of PL bands were observed: i) the bands, spectral
positions of which were not influenced by the Mg content (Cu-related as well as self-
activated orange and red ones); ii) the bands, spectral positions of which exhibited some
blueshift with increasing Mg content (Li- and Ag-related and self-activated green ones).
It has been shown that used doping gives the possibility to obtain the phosphor with
intense visible emission within the blue-yellow spectral range.
Keywords: MgZnO alloy, doping, photoluminescence.
Manuscript received 25.03.15; revised version received 30.07.15; accepted for
publication 03.09.15; published online 30.09.15.
1. Introduction
In recent years, the MgZnO ternary system attracts much
attention as a promising material for UV light emitters.
Alloying with MgO results in essential broadening the
ZnO bandgap and gives the possibility to shift near-
band-edge emission into deep ultraviolet, which calls
forth the extensive investigation of UV emission in these
solid solutions. On the other hand, MgZnO composition
can be considered as a potential candidate for fabricating
white-light phosphors. In fact, zinc oxide is known to
demonstrate visible emission in a comparatively broad
spectral range [1, 2]. One can expect that alloying with
MgO will affect ZnO defect-related emission and will
enable to modify its intensity and spectrum. Up to now,
however, the reported data on the influence of Mg
content on defect-related emission in MgZnO alloys are
rather scarce and controversial. With increasing the Mg
content, both the enhancement [3-5] and weakening
[6, 7] of the visible emission intensity were observed. In
[3-6, 8], the shift of defect-related emission band toward
the short wavelength side as a result of alloying ZnO
with MgO was found, whereas in [9, 10] any change of
emission band shape or peak position was not observed.
In [11], it was shown that self-activated defect-related
emission in sol-gel MgZnO phosphors can be shifted
from the orange to green-blue spectral region by
changing the annealing temperature and gas ambient.
The data on impurity-related emission in MgZnO alloys
are, in fact, absent in the available literature.
It was earlier shown that, in MgZnO ceramics, a
blueshift of self-activated green emission took place
with increasing Mg content [12]. In the present paper,
this effect has been considered in more detail, and
investigation of photoluminescence (PL) in MgZnO
ceramics undoped as well as doped with lithium, silver
and copper has been performed.
2. Experimental procedure
The samples were formed of the mixture of ZnO
(99.99% purity) and MgO (99.99% purity) powders with
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 344-348.
doi: 10.15407/spqeo18.03.344
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
345
distillate water as well as LiNO3, AgNO3 or CuCl2
aqueous solutions, the concentration of impurity being
about 1018 cm–3. The Mg content x was changed from 0
up to 0.20, which was found to be the solubility limit of
Mg in hexagonal-structure MgxZn1–xO ceramics [13].
After drying at room temperature, the samples were
sintered in air at 1050 °C for 3 hours and cooled with the
furnace. A number of undoped samples were also
sintered in Zn vapor. In this case, the samples were
located in a closed crucible with metallic zinc scraps and
annealed in N2 flow. In all cases, firm and dense
hexagonal phase ceramics were obtained (X-ray
diffraction patterns were shown in [13]). Prepared
samples were cut transversally and defect-related PL
spectra in 400–800 nm range as well as PL excitation
(PLE) spectra in 250–400 nm range were measured from
cleft surface at room temperature. Xe-lamp light passing
through grating monochromator was used as exciting
source. The wavelength of 320 nm that produced band-
to-band transitions in all the investigated samples was
used for PL excitation. PLE spectra were measured at
the fixed wavelength corresponding to the maximum of
PL band under investigation. The broadening of ZnO
bandgap due to adding MgO was monitored by the shift
of PLE peak, the position of which was known to
coincide with that of the free exciton emission band [13].
3. Results and discussion
PLE spectra of undoped ceramics with different x values
are shown in Fig. 1. One can see that increasing the Mg
content from x = 0 up to 0.20 results in the shift of PLE
maximum from 380 nm (3.26 eV) to 340 nm (3.64 eV).
The influence of doping on PLE spectra was not
observed: in all the samples, independently of used
impurity, PLE peak positions were the same for the same
x values.
3.1. Photoluminescence of doped MgZnO ceramics
The ceramics sintered in Zn vapor demonstrated
extremely intense blue-green PL band, the peak position
of which was shifted toward the shorter wavelength side
from 515 down to 485 nm with the increasing x value
(Fig. 2).
Doping with Li and Ag caused appearance of
orange bands peaking at 600 and 580 nm, accordingly, at
x = 0. Increasing x resulted in the shift of these bands
toward shorter wavelengths (Figs. 3 and 4).
The samples doped with Cu demonstrated the green
PL band peaking at 540 nm, which did not change its
position with increasing x (Fig. 5).
3.2. Photoluminescence of undoped MgZnO ceramics
Defect-related emission in intentionally undoped ZnO is
known to demonstrate itself as a broad band consisting
of green, orange and red ones, relative intensities of
these bands depending on preparation conditions [1,2].
Green emission, in its turn, includes self-activated
250 300 350 400
1.0
0.0
0.6
0.2
0.4
0.8
1.2
4 3 2 1
PL
E
in
te
ns
ity
, a
.u
.
λ, nm
Fig. 1. PLE spectra of undoped MgxZn1–xO ceramics with
different x: 0 (1), 0.10 (2), 0.20 (3).
500 600 700 800
1.2
1.0
0.8
0.6
0.4
0.2
0.0
3
2
1
PL
in
te
ns
ity
, a
.u
.
λ, nm
Fig. 2. PL spectra of sintered in Zn vapor MgxZn1–xO ceramics
different x: 0 (1), 0.10 (2), 0.20 (3).
500 600 700 800 900
0.0
0.2
0.4
0.6
0.8
1.0
3
2
1
PL
in
te
ns
ity
, a
.u
.
λ, nm
Fig. 3. PL spectra of Li-doped MgxZn1–xO ceramics with
different x: 0 (1), 0.10 (2), 0.20 (3).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 344-348.
doi: 10.15407/spqeo18.03.344
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
346
500 600 700 800 900
0.0
0.2
0.4
0.8
0.6
1.0
3
2
1
PL
in
te
ns
ity
, a
.u
.
λ, nm
Fig. 4. PL spectra of Ag-doped MgxZn1–xO ceramics with
different x: 0 (1), 0.10 (2), 0.20 (3).
500 600 700 800 900
1.0
0.0
0.2
0.4
0.8
0.6
32
1
PL
in
te
ns
ity
, a
.u
.
λ, nm
Fig. 5. PL spectra of Cu-doped MgxZn1–xO ceramics with
different x: 0 (1), 0.10 (2), 0.20 (3).
and Cu-related bands [1, 2, 14]. Red emission is often
concealed in the tail of the orange one but sometimes
displays itself as a distinct band at about 700 nm
[1, 15, 16].
PL spectra of undoped ZnMgO ceramics are shown
in Figs. 6a-6c. The intensity of defect-related emission in
undoped samples was noticeably weaker than that in the
doped ones. It was also found that PL intensity
remained, in fact, the same at x = 0.10 but increased
markedly at x = 20 with respect to the samples with
x = 0. With increasing the Mg content, PL band showed
at first red shift (Fig. 6b) and then blue shift (Fig. 6c). To
clarify the origin of this behavior, Gaussian
deconvolution of the obtained PL spectra was
performed. Before this procedure, the samples with
different x values exhibiting distinct red PL band were
chosen and their PL spectra were compared. It was
found that the peak of self-activated red band was
located at 720 nm, and its position was independent of
the Mg content (Fig. 7).
500 600 700 800
b
PL
in
te
ns
ity
, a
.u
.
a
c
λ, nm
Fig. 6. PL spectra of undoped MgxZn1–xO ceramics with
different x: 0 (1), 0.10 (2), 0.20 (3).
500 600 700 800 900
0
10
20
30
40
3
2
PL
in
te
ns
ity
, a
.u
.
λ, nm
1
Fig. 7. PL spectra of undoped MgxZn1–xO ceramics with diffe-
rent x exhibiting distinct red band: 0 (1), 0.10 (2), 0.20 (3).
Gaussian deconvolution of PL spectra obtained for
undoped samples was performed using the determined
above peak positions of self-activated and Cu-related
green bands as well as that of red one (Fig. 6). As a
result, the orange emission band with the same peak
position at 610 nm was separated for all the used x
values. From the data displayed in Fig. 6, one can
conclude that, with increasing the Mg content, at first
formation of “orange”emission centers and then appe-
arance of “green” ones takes place. The enhancement of
orange emission due to Mg introduction was also
observed for MgxZn1–xO ceramics with x < 0.15 in [17].
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 3. P. 344-348.
doi: 10.15407/spqeo18.03.344
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
347
Thus, there are two types of emission centers in
MgZnO alloys with different behavior of corresponding
energy levels: i) the centers, which PL band peak
position is not influenced by the Mg content (Cu-related
as well as self-activated orange and red centers); ii) the
centers, which PL band position demonstrates the blue
shift with increasing the Mg content (Li- and Ag-related
as well as self-activated blue-green centers). For the
first-type centers, two possibilities should be considered:
i) center energy level is pinned to the involved allowed
band from which carrier recombination on the center
occurs; ii) this emission is caused by the intra-defect
transition, excited and ground states of the center being
weakly coupled to the band properties of the host lattice.
The latter has been stated for CuZn acceptor in ZnO
[1, 2]. For orange and red self-activated centers, the
former possibility seems to be more probable. The
related emission bands were shown to appear due to
stoichiometric oxygen excess, and electron transitions
from c-band or shallow donor to deep acceptor are
supposed to be responsible for these bands [1, 2]. The
second-type centers show the shift of their energy level
position with respect to the involved allowed band under
bandgap broadening. This shift is about 0.2 eV at
x = 0.20 for all the second-type centers, which is twice
as little as that of free exciton (Fig. 1) and, hence, of
bandgap broadening (0.4 eV). One can think, therefore,
that energy levels of these centers shift equally with
respect to both c- and v-bands. It should be noted,
however, that electron-hole transitions responsible for
specific emission bands in ZnO still remain highly
disputable throughout the literature, and further
investigations in this field are required.
The obtained results show that defect-related
emission in undoped MgZnO ceramics is rather weak.
At the same time, phosphors with bright blue and green-
yellow emissions can be prepared by doping this
material with Zn, Li and Ag. To obtain white-light
phosphor based on MgZnO alloy, the impurity, which
will produce intense emission in orange-red spectral
region, should be found.
4. Conclusion
To reveal the influence of alloying ZnO with MgO on
impurity-related and self-activated emissions of material,
PL spectra of doped with Li-, Ag-, Cu- and Zn as well as
of undoped MgxZn1–xO ceramics with x = 0–0.20 were
investigated. It was found that the doped samples
demonstrated more intense PL than the undoped ones
and that used doping enabled to prepare MgZnO
phosphors with bright emission in the blue-yellow
spectral range. It was shown that spectral positions of
some PL bands, namely, of green Cu-related as well as
the self-activated orange and red ones, were not
influenced by the Mg content. At the same time, Li-, Ag-
and Zn-related PL bands showed some blue shift with
increasing Mg content, this blue shift being the same for
all the mentioned bands and reaches about 0.20 eV at
x = 0.20. Based on these facts, it should be stated that
there are two types of emission centers, which different
reaction to ZnO bandgap broadening by alloying with
MgO indicates their different interaction with the host
lattice.
Acknowledgments
This research has been financially supported by National
Academy of Sciences of Ukraine (project III-4-11).
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