Evidence for photochemical transformations in porous silicon
The dynamics of the variation of photoluminescence intensity (PLI) of porous silicon (PS) samples subjected to laser irradiation (337 nm, 3.7 mW) during their ageing in air has been studied. The PLI turned out to increase rapidly under UV irradiation and to flatten out in several hours. The subseque...
Збережено в:
| Опубліковано в: : | Semiconductor Physics Quantum Electronics & Optoelectronics |
|---|---|
| Дата: | 1999 |
| Автори: | , , , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
1999
|
| Онлайн доступ: | https://nasplib.isofts.kiev.ua/handle/123456789/119859 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Evidence for photochemical transformations in porous silicon / V.B. Shevchenko, V.A. Makara, O.V. Vakulenko, O.I. Dacenko, O.V. Rudenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 1999. — Т. 2, № 2. — С. 50-53. — Бібліогр.: 17 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
nasplib_isofts_kiev_ua-123456789-119859 |
|---|---|
| record_format |
dspace |
| spelling |
Shevchenko, V.B. Makara, V.A. Vakulenko, O.V. Dacenko, O.I. Rudenko, O.V. 2017-06-10T07:45:00Z 2017-06-10T07:45:00Z 1999 Evidence for photochemical transformations in porous silicon / V.B. Shevchenko, V.A. Makara, O.V. Vakulenko, O.I. Dacenko, O.V. Rudenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 1999. — Т. 2, № 2. — С. 50-53. — Бібліогр.: 17 назв. — англ. 1560-8034 PACS 78.55.Mb, S5.11 https://nasplib.isofts.kiev.ua/handle/123456789/119859 The dynamics of the variation of photoluminescence intensity (PLI) of porous silicon (PS) samples subjected to laser irradiation (337 nm, 3.7 mW) during their ageing in air has been studied. The PLI turned out to increase rapidly under UV irradiation and to flatten out in several hours. The subsequent irradiation leads to intensity degradation, which may be explained by the luminescence fatigue effect. At the same time, the PLI of the unilluminated sample almost does not change during the experiment. It turned out that the anomaly as a small surge down is observed on the PLI evolution curve at the stage of the initial monotonous increase of PLI after a short-time (1 to 2 minutes) interruption of the laser illumination of the sample, whereas this anomaly is a surge up at the stage of the monotonous fall of the PLI curve. In the case of a long-time (tens of hours) discontinuation of illumination, the anomaly was similar for all the portions of the PLI curve. The described results are explained by effect of two competing factors which are the luminescence fatigue and light-induced formation of unstable (molecular) chemical bonds that can transform to the stable atomic ones. en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Evidence for photochemical transformations in porous silicon Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Evidence for photochemical transformations in porous silicon |
| spellingShingle |
Evidence for photochemical transformations in porous silicon Shevchenko, V.B. Makara, V.A. Vakulenko, O.V. Dacenko, O.I. Rudenko, O.V. |
| title_short |
Evidence for photochemical transformations in porous silicon |
| title_full |
Evidence for photochemical transformations in porous silicon |
| title_fullStr |
Evidence for photochemical transformations in porous silicon |
| title_full_unstemmed |
Evidence for photochemical transformations in porous silicon |
| title_sort |
evidence for photochemical transformations in porous silicon |
| author |
Shevchenko, V.B. Makara, V.A. Vakulenko, O.V. Dacenko, O.I. Rudenko, O.V. |
| author_facet |
Shevchenko, V.B. Makara, V.A. Vakulenko, O.V. Dacenko, O.I. Rudenko, O.V. |
| publishDate |
1999 |
| language |
English |
| container_title |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| format |
Article |
| description |
The dynamics of the variation of photoluminescence intensity (PLI) of porous silicon (PS) samples subjected to laser irradiation (337 nm, 3.7 mW) during their ageing in air has been studied. The PLI turned out to increase rapidly under UV irradiation and to flatten out in several hours. The subsequent irradiation leads to intensity degradation, which may be explained by the luminescence fatigue effect. At the same time, the PLI of the unilluminated sample almost does not change during the experiment. It turned out that the anomaly as a small surge down is observed on the PLI evolution curve at the stage of the initial monotonous increase of PLI after a short-time (1 to 2 minutes) interruption of the laser illumination of the sample, whereas this anomaly is a surge up at the stage of the monotonous fall of the PLI curve. In the case of a long-time (tens of hours) discontinuation of illumination, the anomaly was similar for all the portions of the PLI curve. The described results are explained by effect of two competing factors which are the luminescence fatigue and light-induced formation of unstable (molecular) chemical bonds that can transform to the stable atomic ones.
|
| issn |
1560-8034 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/119859 |
| citation_txt |
Evidence for photochemical transformations in porous silicon / V.B. Shevchenko, V.A. Makara, O.V. Vakulenko, O.I. Dacenko, O.V. Rudenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 1999. — Т. 2, № 2. — С. 50-53. — Бібліогр.: 17 назв. — англ. |
| work_keys_str_mv |
AT shevchenkovb evidenceforphotochemicaltransformationsinporoussilicon AT makarava evidenceforphotochemicaltransformationsinporoussilicon AT vakulenkoov evidenceforphotochemicaltransformationsinporoussilicon AT dacenkooi evidenceforphotochemicaltransformationsinporoussilicon AT rudenkoov evidenceforphotochemicaltransformationsinporoussilicon |
| first_indexed |
2025-11-25T23:28:33Z |
| last_indexed |
2025-11-25T23:28:33Z |
| _version_ |
1850581053741203456 |
| fulltext |
50 © 1999, Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
Semiconductor Physics, Quantum Electronics & Optoelectronics. 1999. V. 2, N 2. P. 50-53.
1. Introduction
Porous silicon (PS) has been known to researchers for a
rather long time. The interest in it has sharply risen in
1990 due to the discovery of its ability to emit an intense
visible luminescence [1]. However, the nature of the PS
red luminescence has not been exactly established despite
the intensive investigations.
The extreme sensitivity of luminescence to ambient is
one of the most distinguished properties of PS. On the
one hand, such a property complicates the practical use
of PS in technology due to its instability in the air [2-6].
On the other hand, this property allows one to control
the PS luminescent parameters [7,8]. Studies in this direc-
tion can also be useful for elucidation of the luminescence
mechanism.
This work is devoted to the study of PS photolumi-
nescence (PL) intensity evolution in the air under UV
laser irradiation.
PACS 78.55.Mb, S5.11
Evidence for photochemical transformations
in porous silicon
V. B. Shevchenko, V. A. Makara, O. V. Vakulenko, O. I. Dacenko, O. V. Rudenko
Taras Shevchenko Kyiv Univ., 6, prospect Glushkova, 252127 Kyiv, Ukraine,
tel. 38 044 5134058, fax: 38 044 2662326, e-mail: doce@hq.ups.kiev.ua
Abstract. The dynamics of the variation of photoluminescence intensity (PLI) of porous silicon
(PS) samples subjected to laser irradiation (337 nm, 3.7 mW) during their ageing in air has been
studied. The PLI turned out to increase rapidly under UV irradiation and to flatten out in several
hours. The subsequent irradiation leads to intensity degradation, which may be explained by the
luminescence fatigue effect. At the same time, the PLI of the unilluminated sample almost does not
change during the experiment. It turned out that the anomaly as a small surge down is observed on
the PLI evolution curve at the stage of the initial monotonous increase of PLI after a short-time (1
to 2 minutes) interruption of the laser illumination of the sample, whereas this anomaly is a surge
up at the stage of the monotonous fall of the PLI curve. In the case of a long-time (tens of hours)
discontinuation of illumination, the anomaly was similar for all the portions of the PLI curve. The
described results are explained by effect of two competing factors which are the luminescence
fatigue and light-induced formation of unstable (molecular) chemical bonds that can transform to
the stable atomic ones.
Keywords: porous silicon, nanostructure, laser irradiation, luminescence fatigue.
Paper received 21.06.99; revised manuscript received 29.06.99; accepted for publication 12.07.99.
2. Experiment
The PS layers were obtained by electrochemical anodiz-
ing of (111) p-Si wafers in the 1:1 mixture of 48 % HF
and isopropyl alcohol at a current density of 10 mA/cm2
for 5 min. As-prepared PS displayed a weak PL signal
comparable to the noise level of the experimental setup.
After anodizing, the samples were kept in the air for 3
months. Their luminescence intensities essentially in-
creased during that period of time, which occurred, prob-
ably, due to effects of porous layer oxidation [9,10]. Im-
mediately before the experiment, the samples were chem-
ically etched in HF for 3 seconds. Such a treatment re-
turned the nanostructure surface to the initial state, that
is, removed the surface oxide and saturated the external
silicon bonds by hydrogen. Furthermore, the porous layer
surface cracks as a result of the HF treatment, which
promotes the penetration of oxygen into the depth of
porous layer and accelerates the PS ageing process
[10,11].
V. B. Shevchenko et al.: Evidence for photochemical transformations...
51SQO, 2(2), 1999
The integral intensity of PL was measured at room temper-
ature in the visible, the luminescence was excited by unfo-
cused beam of ILGI-503 laser (337 nm, 3.7 mW). The beam
diameter was close to 2.5 mm in the sample plane. A photo-
diode with spectral sensitivity in the range of 365 to 750 nm
was used as a light detector. The UV excitation light scattered
from the sample was cut off by the GS-4 absorptive filter placed
before the emission detector.
During the experiments for the study of the laser
emission effect on the PS PL, the laser was periodically
switched on for a few hours during a week. All the rest
time it was switched off. The duration of the laser con-
tinuous operation did not exceed 4 to 5 hours, after which
the sample was not illuminated for tens of hours. Dur-
ing the laser operation, the beam was intercepted by a
screen several times. By this means we studied the effect
of the UV irradiation on the sample PL and also ob-
served the effect of a short- and long-time interruption
of irradiation action on the evolution of PL intensity.
For comparison, we used a sample which was stored
in the dark and illuminated by laser only episodically
during the scheduled measurements of its PL intensity.
3. Results and discussion
The results of the study of the PL intensity of the sample
irradiated by the laser are shown in Fig.1. The time when
the laser was switched on is plotted along the X-axis.
The breaks in the laser irradiation of the sample are
marked by the arrows, their durations are indicated.
As it is shown in Fig.1, the chemical treatment of sam-
ples in concentrated HF at the beginning of experiment
has led to PL intensity increase by a factor of 2. At the
surface of silicon nanostructure, dissolution of the oxygen-
containing compounds of Si formed in anodizing and stor-
ing the prepared PS in the air, evidently occurs during such
a treatment. These compounds are the PL sensitizers in PS
[12,13]. According to the supposition of [10], the interaction
of PS with oxygen takes place preferentially near the surface
of porous layer when storing the sample in the air. After a
prolonged contact with the atmosphere, an emitting layer is
formed in the near-surface region. This layer is SiOx sensi-
tizer with embedded Si nanocrystals, in which the radiative
recombination occurs. At the sample surface, however, a
rather thick oxide layer, where the complete oxidation of the
nanostructure has happened, i.e. oxide layer without residu-
als of nanocrystalline silicon can be formed under certain
conditions. This layer would not participate in the lumines-
cence. On the contrary, its presence would negatively affect
the quantum yield of the sample because the layer absorbs
the excitation light. Therefore, its removal by a short-time
treatment in HF would increase the intensity of sample emis-
sion.
Not taking into account the short-time intensity drop
for the first minutes of the experiment (Fig.1) and the
meaningful anomalies related to breaks of laser beam
action, one can conclude that the luminescence quan-
tum yield monotonously rises and flattens out during
the experiment. In principle, this correlates with the most
of data for the PL intensity behaviour when ageing a PS
sample in the air (see, e.g., [3,4,6,9,11]). The causes for
the rise of PS PL intensity in the air are associated with
the atmospheric oxidation of the nanostructure [10]: in-
crease of the sensitizer mass (which is the Si oxide for
UV region of excitation [12]), effective saturation of the
silicon dangling bonds (nonradiative recombination cen-
0 5 10 15
0
200
400
600
800
1000
1200
3 s in HF
2
0
h
9
0
h
2
1
h
1
8
h
5
m
in
1
.2
5
m
in
1
.5
m
in
1
.5
m
in
1
.5
m
in
1
m
in
1
m
in
2
m
in
2
m
in
2
m
in
2
m
in
I P
L
,
a
rb
.u
n
.
Exposition time, h
Fig. 1. Evolution of PL intensity of the PS sample exposed to the air under the laser illumination. Breaks in irradiating the sample are marked
as the jumps on the curve, their durations are indicated nearby.
V. B. Shevchenko et al.: Evidence for photochemical transformations...
52 SQO, 2(2), 1999
ters [2]) by oxygen, and the nanostructure modification due
to the oxidation.
For the reference sample which was stored in the dark, a
monotonous increase of PL intensity is documented as well,
but it was significantly slower than that for the laser-illumi-
nated sample. This indicates the effect of laser irradiation on
the processes happening in porous layer.
It should be noted that the pattern of PL intensity evolu-
tion in Fig.1 is somewhat distorted due to the luminescence
fatigue effect [14,15]. The presence of this phenomenon
manifests itself most evidently at the final stage of our ex-
periments (the portion of flattened intensity in the curve).
At the stage of continuous illumination of the sample, the
PL intensity decreases monotonously rather than reaches a
steady-state value, which would be expected in the case of
episodic illumination of the sample by excitation light while
it is exposed to the air [11]. This effect is obscured on the
background of the total rise of intensity at the outset of
experiment.
The luminescence fatigue should apparently be consid-
ered as a reason of the fast drop of the intensity for the first
minutes of experiment (Fig.1). However, this is unlikely to be
the main reason because we observed a similar intensity
drop for as-prepared samples and the samples as-etched in
HF without continuous laser illumination. The authors of
Ref. [16] also observed the fast degradation of PS PL at the
outset of experiment when exposing the samples in the pure
oxygen atmosphere. They concluded that the intensity de-
crease is conditioned by formation of Si dangling bonds at
the PS surface. Taking into account the suggestion that the
hydrogen coating of the nanostructure is changed by oxy-
gen in as-prepared or HF-etched sample as a reason of in-
crease of the PL intensity of aged PS [12,17], one can con-
clude that the hydrogen escape from PS surface runs more
rapidly than the surface saturation by oxygen. The PL inten-
sity decreases as a result of the temporary formation of Si
dangling bonds being the centers of nonradiative recombi-
nation [2].
The anomalies related to temporal break of irradiation for
the short (1 to 5 minutes) and long (tens of hours) terms
attract the greatest interest on the PL evolution curve (Fig.1).
The long-term break of sample illumination by the laser
light leads to significant drop of PL intensity. As a result of
the further irradiation of sample, the complete restoration of
the PL intensity occurs for the first 20 minutes, the magni-
tude of the shading-induced intensity drop relative to that
of the intensity measured before switching off the illumina-
tion constantly decreasing. The noted anomalies related to
the illumination interruption are not observed at all for sta-
ble samples stored in the air under illumination for a long
time.
The PL intensity jumps as a consequence of temporary
interruption of laser irradiation of the PS may be explained
by formation of unstable molecular bonds on the Si surface
of nanocrystallites with air atomic groups during photochem-
ical transformations, the silicon skeleton surface turns out
to be passivated due to this.
An illumination interruption causes the reverse trans-
formations at the nanostructure surface, i.e. decaying the
unstable passivating coating. As a result, the sample PL
quantum yield after repeated switching on the light turned
out to be lower than that before the shading, although the
intensity rapidly restores under light due to saturation of
dangling bonds. One can see that not only does the intensity
rapidly restore (Fig.1), but it also exceeds the magnitude be-
fore the shading. In our opinion, the PL fatigue effect mani-
fests itself here. Due to this, the intensity magnitude before
switching off the light is lower than that after several hours of
the sample being in the dark.
The stability of the surface coating evidently rises irre-
versibly with time. This is confirmed by absence of the anom-
alies related to the illumination termination in stable samples
being in the air for a long time.
The effect of a short-time interception of the laser beam
on the PL intensity of the irradiated sample is given in Fig.2
in more detail. The time intervals while the laser beam did
not impinge on the sample surface are marked by the dashed
line. Fig.2a illustrates the case of the laser beam interception
at the stage of the total rise of PL quantum yield of the
sample. Fig.2b shows the laser interruption effect at the stage
of the flattened curve of the PL intensity evolution or, more
precisely, during fatigue-induced PL efficiency degradation
Fig. 2. Behaviour of PS sample PL intensity in short-time interception of laser irradiation at the stage of the PL efficiency total rise (a) and
in the flattened part of the plot (b).
1,6 1,8 2,0 2,2 2,4
440
460
480
500
520
540
(a)
1
.2
5
m
in
I P
L,
a
rb
.u
n
.
Exposition tim e, h
1.6 1.8 2.0 2.2 2.4 13,8 14,0 14,2 14,4 14,6
820
840
860
880
900
920
(b)
2
m
in
I P
L
,
a
rb
.u
n
.
Exposition time, h
13.8 14.0 14.2 14.4 14.6
V. B. Shevchenko et al.: Evidence for photochemical transformations...
53SQO, 2(2), 1999
while continuous irradiation. In the former case (Fig.2a), the
PL intensity just after restoration of the laser action turns
out to be lower that that before the laser beam interception;
the PL efficiency of the sample increases for the first min-
utes of illumination. In the latter case (Fig.2b), the PL inten-
sity of sample noticeably increases while the laser beam
does not illuminate the sample surface. It decreases in the
course of the further illumination.
The reasons of the PL intensity jump down (Fig.2a) after
the short-time interception of laser beam are obviously the
same as in the case of the long-time switching the light off
(Fig.1). The instability level of the surface silicon compounds
is the highest at the first stage of nanostructure surface
formation (saturation of the dangling bonds) and, therefore,
destruction of the unstable bonds would be essential even
during the short-time illumination interruption and, as a re-
sult, degradation of the PL yield would be observed. The
surface coating of nanostructure becomes more stable with
time, hence degradation of the PL efficiency is not observed
after the short-time shading of the sample (Fig.2b). At this
stage, another effect affects the PL intensity instead. This is
the luminescence fatigue. Therefore, just after illumination
restoration, the intensity has a higher value than that before
shading.
4. Conclusions
The luminescence efficiency of PS sample rises monoto-
nously when exposing the sample to the air and flattens out
some time after. The increase of PL quantum yield is signif-
icantly accelerated while illuminating the sample by UV la-
ser radiation. As a result of restoration of sample illumina-
tion after its temporary interruption, the PL intensity value
appears to be unequal to that after the interception of laser
beam. According to this supposition, two competing fac-
tors affect the PL intensity behaviour: 1) luminescence fa-
tigue and 2) light-induced formation of unstable (molecular)
chemical bonds, which can transform to the stable ones with
time.
References
1. L. T. Canham. Silicon quantum wire array fabrication by electro-
chemical and chemical dissolution of wafers // Appl. Phys. Lett.
57, p. 1046-1048 (1990).
2. M. A. Tischler, R. T. Collins, J. H. Stathis, and J. C. Tsang. Lu-
minescence degradation in porous silicon // Appl. Phys. Lett. 60,
p. 639-641 (1992).
3. T. Maruyama and S. Ohtani. Photoluminescence of porous sili-
con exposed to ambient air // Appl. Phys. Lett. 65, p. 1346-1348
(1994).
4. C.-H. Lin, S.-C. Lee, and Y.-F. Chen. Morfologies and photolu-
minescence of porous silicon under different etching and oxida-
tion conditions // J. Appl. Phys. 75, p. 7728-7736 (1994).
5. R. Sabet-Dariani, N. S. McAlpine, and D. Haneman. Electrolu-
minescence in porous silicon // J. Appl. Phys. 75, p. 8008-8011
(1994).
6. S. Banerjee, K. L. Narasimhan, and A. Sardesai. Role of hydro-
gen- and oxygen-terminated surfaces in the luminescence of po-
rous silicon // Phys. Rev. B. 49, p 2915-2918 (1994).
7. A. Bsiesy, J. C. Vial, F. Gaspard, R. Herino, V. Ligeon, F. Muller,
R. Romestain, A. Wasiela, A. Halimaoui, and G. Bomchil. Pho-
toluminescence of high porosity and of electrochemically oxidized
porous silicon layers // Surf. Sci. 254, p. 195-200 (1991).
8. V. P. Bondarenko, A. M. Dorofeev, V. I. Levchenko, A. I. Luko-
mskiy, L. I. Postnova. Method of control of porous silicon lumi-
nescence parameters in the visible // Pisjma v Zhurn. Tekh. Fiz.
(Russ. Tech. Phys. Lett.) 20, p. 61-65 (1994).
9. V. A. Makara, V. A. Odarych, O. V. Vakulenko, and O. I. Dacen-
ko. Ellipsometric studies of porous silicon // Thin Solid Films 342,
p. 230-237 (1999).
10. O. I. Dacenko, V. A. Makara, S. M. Naumenko, T. V. Ostapchuk,
O. V. Rudenko, V. B. Shevchenko, O. V. Vakulenko, and M. S.
Boltovets. Evolution of the porous silicon sample properties in
the atmospheric ambient // J. Luminescence 81, p. 263-270
(1999).
11. V. A. Makara, M. S. Boltovets, O. V. Vakulenko, O. I. Dacenko,
S. M. Naumenko, T. V. Ostapchuk, and O. V. Rudenko. Pecu-
liarities of porous silicon photoluminescence after chemical etch-
ing in HF // Zurn. Prikl. Spetrosc. (Belorus. J. Appl. Spectrosc.)
66, p. 423-427 (1999).
12. I. A. Buyanova, I. Ya. Gorodetsky, N. E. Korsunskaya, T. N.
Mel�nik, I. M. Rarenko, A. U. Savchuk, and M. K. Sheynkman.
Sensitized luminescence of porous silicon and its polarization
characteristics // Fiz. Tekh. Polupr. (Russ. Phys. and Tech. of
Semicond.) 30, p. 1516-1524 (1996).
13. V. A. Makara, O. V. Vakulenko, O. I. Dacenko, V. M. Kravchen-
ko, T. V. Ostapchuk, O. V. Rudenko, M. S. Boltovets, V. O. Fe-
sunenko. Effect of boron diffusion doping of silicon on the mi-
cromechanical and luminescence properties of porous layers // Thin
Solid Films 312, p. 202-206 (1998).
14. I. M. Chang, S. C. Pan, and Y. F. Chen. Light-induced degrada-
tion on porous silicon, Phys.Rev.B. 48, p. 8747-8750 (1993).
15. K. S. Zhuravlev, N. P. Stepina, T. S. Shamirzaev, E. Yu. Buchin,
N. E. Mokrous. Decay and rise kinetics of porous silicon photo-
luminescence under continuous laser radiation // Fiz. Tekh. Polu-
pr. (Russ. Phys. and Tech. of Semicond.) 28, p. 482-487 (1994).
16. P. K. Kashkarov, E. A. Konstantinova, and V. Yu. Timoshen-
ko. Mechanisms of molecule adsorbtion effect on the recombina-
tion processes in porous silicon // Fiz. Tekh. Polupr. (Russ. Phys.
and Tech. of Semicond.) 30, p. 1479-1489 (1996).
17. V. G. Golubev, A. V. Zherzdev, G. K. Moroz, A. V. Patsekin,
and D. T. Yan. Strong photoinduced increase of photolumines-
cence intensity of anodically oxidized porous silicon // Fiz. Tekh.
Polupr. (Russ. Phys. and Tech. of Semicond.) 30, p. 852-863
(1996).
|