Dynamic electrophysical characterization of porous silicon humidity sensing
The results of the investigation of changes of parameters of bipolar and unipolar dynamic current-voltage characteristics and transient currents as well as dynamic bipolar charge-voltage loops connected with the pulse change of humidity for the samples of por-Si are presented. The hysteresis view of...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2006
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| Цитувати: | Dynamic electrophysical characterization of porous silicon humidity sensing / S. Bravina, N. Morozovsky, R. Boukroub // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 1. — С. 79-83. — Бібліогр.: 10 назв. — англ. |
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irk-123456789-1215972017-06-15T03:04:48Z Dynamic electrophysical characterization of porous silicon humidity sensing Bravina, S. Morozovsky, N. Boukroub, R. The results of the investigation of changes of parameters of bipolar and unipolar dynamic current-voltage characteristics and transient currents as well as dynamic bipolar charge-voltage loops connected with the pulse change of humidity for the samples of por-Si are presented. The hysteresis view of charge-voltage and current-voltage curves is characteristic for poling processes in the space charge region similar to that observed in the case of typical ionic conductors. Observed phases of transformation of investigated electrophysical characteristics reflect the time sсale of processes in the consequence “adsorption – dissociation and transfer – desorption”. The efficiency of using the methods of dynamic electrophysical characterization for studying characteristics of porous materials under fast humidity changes was demonstrated. 2006 Article Dynamic electrophysical characterization of porous silicon humidity sensing / S. Bravina, N. Morozovsky, R. Boukroub // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 1. — С. 79-83. — Бібліогр.: 10 назв. — англ. 1560-8034 PACS 07.07.DF http://dspace.nbuv.gov.ua/handle/123456789/121597 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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The results of the investigation of changes of parameters of bipolar and unipolar dynamic current-voltage characteristics and transient currents as well as dynamic bipolar charge-voltage loops connected with the pulse change of humidity for the samples of por-Si are presented. The hysteresis view of charge-voltage and current-voltage curves is characteristic for poling processes in the space charge region similar to that observed in the case of typical ionic conductors. Observed phases of transformation of investigated electrophysical characteristics reflect the time sсale of processes in the consequence “adsorption – dissociation and transfer – desorption”. The efficiency of using the methods of dynamic electrophysical characterization for studying characteristics of porous materials under fast humidity changes was demonstrated. |
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Article |
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Bravina, S. Morozovsky, N. Boukroub, R. |
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Bravina, S. Morozovsky, N. Boukroub, R. Dynamic electrophysical characterization of porous silicon humidity sensing Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Bravina, S. Morozovsky, N. Boukroub, R. |
| author_sort |
Bravina, S. |
| title |
Dynamic electrophysical characterization of porous silicon humidity sensing |
| title_short |
Dynamic electrophysical characterization of porous silicon humidity sensing |
| title_full |
Dynamic electrophysical characterization of porous silicon humidity sensing |
| title_fullStr |
Dynamic electrophysical characterization of porous silicon humidity sensing |
| title_full_unstemmed |
Dynamic electrophysical characterization of porous silicon humidity sensing |
| title_sort |
dynamic electrophysical characterization of porous silicon humidity sensing |
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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2006 |
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http://dspace.nbuv.gov.ua/handle/123456789/121597 |
| citation_txt |
Dynamic electrophysical characterization of porous silicon humidity sensing / S. Bravina, N. Morozovsky, R. Boukroub // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2006. — Т. 9, № 1. — С. 79-83. — Бібліогр.: 10 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
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AT bravinas dynamicelectrophysicalcharacterizationofporoussiliconhumiditysensing AT morozovskyn dynamicelectrophysicalcharacterizationofporoussiliconhumiditysensing AT boukroubr dynamicelectrophysicalcharacterizationofporoussiliconhumiditysensing |
| first_indexed |
2025-07-08T20:11:42Z |
| last_indexed |
2025-07-08T20:11:42Z |
| _version_ |
1837110922637737984 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 79-83.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
79
PACS 07.07.DF
Dynamic electrophysical characterization
of porous silicon humidity sensing
S. Bravina1, N. Morozovsky1, R. Boukroub2
1Institute of Physics, NAS of Ukraine, 46, prospect Nauky, 03028 Kyiv, Ukraine
E-mail: bravina@iop.kiev.ua
2Interdisciplinary Research Institute, IRI, IEMN-IRI, Avenue Poincaré - BP 69
59652 Villeneuve d'Ascq, France
Abstract. The results of the investigation of changes of parameters of bipolar and
unipolar dynamic current-voltage characteristics and transient currents as well as
dynamic bipolar charge-voltage loops connected with the pulse change of humidity for
the samples of por-Si are presented. The hysteresis view of charge-voltage and current-
voltage curves is characteristic for poling processes in the space charge region similar to
that observed in the case of typical ionic conductors. Observed phases of transformation
of investigated electrophysical characteristics reflect the time sсale of processes in the
consequence “adsorption – dissociation and transfer – desorption”. The efficiency of
using the methods of dynamic electrophysical characterization for studying
characteristics of porous materials under fast humidity changes was demonstrated.
Keywords: porous silicon, humidity, bipolar and unipolar dynamic current-voltage
characteristics, transient currents.
Manuscript received 21.11.05; accepted for publication 15.12.05.
1. Introduction
The problem of environment parameters monitoring
demands from the modern sensorics many efforts
directed to development of sensitive, high speed and
stable humidity sensors integrated in the modern silicon
(Si) base.
Electrophysical and thermal characteristics of
systems based on porous materials with open pores are
rather sensitive to the nature of molecules penetrated
into the pores [1]. That is the base of using porous
materials in sensors of environmental control, in
particular for humidity sensors.
In this way, many humidity sensitive media with
open pores were examined. As promising materials
selected are the following: polymers as the cheapest,
porous ceramics as more flexible, and zeolite-like
systems and also mezo-porous phases as thermo-stable.
Recently we have investigated the humidity-electric
activity in some of porous ceramics and zeolite-like
systems as well as mezo-porous phases [2,3].
Taking into account a stable tendency of integrating
environmental sensors into Si-based modern
microelectronics it is reasonable to perform the
investigations of humidity-electric activity in porous
silicon (PSi) [4]. This material is considered as a
promising one due to its photo- and electroluminescence
properties as well as due to its thermal properties,
namely our thermowave-probing investigations
confirmed the prospects of using of PSi in thermal
sensorics as a buffer insulating substrate material of
integrated thermal detectors [5]. We also marked in [5]
that the application of por-Si is also possible for design of
elements of heat-insulating surrounding for temperature-
controlled units of electronic devices based on Si-
technology.
On account of the well known humidity sensing of
PSi [6] and the criticality of humidity level on electronic
components operation the investigations of humidity
impact on electrophysical characteristics of PSi in pulse
mode under environmental conditions similar to those of
operating Si-based devices are desirable.
In this paper, we present the results of investigating
the changes of parameters of bipolar and unipolar
dynamic current-voltage characteristics, bipolar charge-
voltage loops and transient currents connected with the
pulse change of humidity for the samples of porous Si.
2. Experiment
2.1. Samples
The samples of PSi were prepared on 500 μm of
thickness Si(111) B-doped p-type wafers with the
resistivity ρ = 6…10 Ohm⋅cm. Anodic electrochemical
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 79-83.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
80
-1,5 -1,0 -0,5 0,0 0,5 1,0 1,5
-100
-80
-60
-40
-20
0
20
40
60
80
100
10-20 s
after
Hr pulse
Just after
90%-
Hr pulse
Voltage in mV
on the Current
Resistor 105 Ω
Drive Voltage, V
up
down
-6 -4 -2 0 2 4 6
-100
-80
-60
-40
-20
0
20
40
60
80
100
Just
after
90%-
Hr pulse
10-20 s
after
Hr pulse
Initial:
Hr=50%
Voltage in mV
on the Current
Resistor 105 Ω
Drive Voltage, V
up
down
Fig. 1. Current-voltage loops before, under and after humidity pulse impact at different amplitudes and frequencies of the drive
voltage (left: 1 V, 1 kHz and right: 4 V, 1 Hz).
etching was performed in electrolyte HF/EtOH=1/1 with
current density of anodization 5…20 mA/cm2 for 5 to
8 min. Then the samples were aged in the same
electrolyte for 30 min. As the electrodes, the In clamped
ones and those from Ag-paste with the area of 0.3 up to
1 mm2 were used.
2.2. Measurements
We investigated the variations of parameters of dynamic
current-voltage bipolar (I-V loops) and unipolar (I-V
curves) characteristics, charge-voltage (Q-V) loops, and
also dynamic transient currents (I-t curves) induced by
continuous and pulse (with 1-3 s duration) relative
humidity Hr changes.
When measuring I-V loops, I-V curves and I-t curves
as a load used was the reference resistor and during the
measurements of Q-V loops used was the reference
capacitor, as it was done under investigations of
corresponding characteristics of ferroelectric capacitors
[2-4, 7].
The corresponding measurements were performed in
the multicycle regime under the applied a.c. triangular
drive voltage Vd and meander voltage V0 in the
frequency range 0.1 Hz ≤ f ≤ 1 kHz and applied voltage
range of ±10 mV ≤ V ≤ ±10 V.
For minimization of the contribution of polarization
reversal currents under I-V curves examination, the
unipolar saw-tooth drive voltage Vd was applied.
The temporal changes of investigated characteristics
of Ag-PSi-Ag system during and just after wet air pulse
and also under restoration of the initial state were also
under registration.
3. Results and comments
Figs 1 and 2 present the current-voltage loops and
transient current-time curves before, under and after
humidity pulse impact.
The shape of low-voltage I-V loops at 1 kHz (Fig. 1,
left) and low-voltage I-t curves (Fig. 2, left) under low
Hr value corresponds to equivalent linear sequence-
parallel R-C circuit.
Transformation of I-V loops and I-t curves under
action of wet air pulse corresponds to decrease of R
value and increase of C value under occurrence of
apparent voltage R-C non-linearity. This state with high
C and low R values remains for 5 to 20 s depending on
duration of Hr-pulse. Returning to the initial state is
accompanied by decrease of degree of R and C non-
linearity to the initial value.
Under decreasing frequency, R and C voltage non-
linearity becomes apparent, and at infra-low frequencies
the I-V loops show high R and C non-linearity (Fig. 1,
right). Under increasing Hr, one can observe appearance
and broadening of hysteresis regions on the positive and
negative branches of I-V loops (Fig. 1, right) with
corresponding appearance of characteristic “hump” on
I-t curves (Fig. 2, right). The height of this “hump” is
maximal at high Hr and decreases under drying the PSi
sample in the course of returning to the initial state.
The Q-V loops obtained under low and high Hr are
presented in Fig. 3. The increase of Hr leads to the
increase of the loop vertical size which corresponds to
the increase of the value of electrical charge transferred
and to the vertical shift of the loop (see the low part of
Fig. 3).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 79-83.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
81
0 1 2 3 4 5 6
- 5 0
- 4 0
- 3 0
- 2 0
- 1 0
0
1 0
2 0
3 0
4 0
5 0
just after Hr-pulse
Initial:
H
r
=50%
Vo
lta
ge
in
m
V
on
c
ur
re
nt
re
si
st
or
1
05
W
Time scale:
2 ms/div.
with time
10-20 s
after Hr pulse
Under 90%
2 s Hr-pulse
0 1 2 3 4 5 6
- 1 0 0
- 8 0
- 6 0
- 4 0
- 2 0
0
2 0
4 0
6 0
8 0
1 0 0
just after H
r
-pulse
Initial:
Hr=50%
Vo
lta
ge
in
m
V
on
c
ur
re
nt
re
si
st
or
1
05
W
Time scale:
2 ms/div.
with the time
10-20 s
after Hr pulse
Under 90%
2 s Hr-pulse
Fig. 2. Transient current-time curves before, under and after humidity pulse impact at different amplitudes of 10 Hz meander
voltage (left: 1 V and right: 4 V).
-1,5 -1,0 -0,5 0,0 0,5 1,0 1,5
-20
-10
0
10
20
10 ηF
100 ηF
Voltage in mV
on the
charge
capacitor
Drive Voltage, V
up
down
0 5 10 15 20 25
-4
-2
0
2
4
"0
" s
hi
ft,
m
V
Time, s
-6 -4 -2 0 2 4 6
-20
-10
0
10
20
30
10 ηF
100 ηF
Voltage in mV
on the
charge
capacitor
Drive Voltage, V
up
down
0 5 10 15 20
-4
-2
0
2
4
6
"0
" s
hi
ft,
m
V
Time, s
Fig. 3. Charge-voltage loops obtained under low and high humidity at different amplitudes of 10 Hz drive voltage (left: 1 V and
right: 4 V) (upper part) and changes of the position of the centre of the loop after humidity pulse impact (lower part).
Unipolar I-V curves are presented in Fig. 4. Low-
voltage I-V curves under increasing humidity are
changed from almost linear to weakly non-linear. Under
high Vd, the increase of Hr leads to the increase of non-
linearity degree and I-V curves acquire exponential
character.
4. Discussion
The change of the shape of low-voltage I-V loops under
humidity variation can be characterized by series-
parallel R-C circuit with pronounced R(V) and C(V)
dependences.
The main observed peculiarities of I-V loops can be
explained by simplifying to the parallel R-C circuit and
neglecting the effect of the series resistor. Since for this
R-C circuit I(V) = d(CV)/dt+V/R, under V = V0(1±bt)
with b = const and C = const, the current value is I(V) =
±V0(bC+V/V0R). So, any deviation of I(V) from linearity
is related with the existence of some R(V) and C(V)
dependences.
The existence of a “hump” on I-V curves is
characteristic for both ferroelectric systems under pulse
switching of polarization [7] and semiconductor systems
under transfer of injected charge carriers [8]. The
unipolar I-V curves near to exponential ones in the case
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2006. V. 9, N 1. P. 79-83.
© 2006, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
82
0,0 0,5 1,0 1,5
0
10
20
30
40
50
60
70
Just
after
90%-
Hr pulse
10-20 s
after
Hr pulse
Initial:
Hr=50%
Current
Resistor
106 Ω
Vo
lta
ge
in
th
e
cu
rre
nt
re
si
st
or
, m
V
Drive Voltage, V
0 2 4 6
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
1 0 0
Ju s t
a fte r
9 0 % -
H r p u lse
1 0 -2 0 s
a fte r
H r p u lse
In it ia l:
H r= 5 0 %
C u rre n t
R e s is to r
1 0 5 Ω
Vo
lta
ge
in
th
e
cu
rr
en
t r
es
is
to
r,
m
V
D r ive V o lta g e , V
Fig. 4. Unipolar current-voltage curves before, just after and after humidity pulse impact at different amplitudes of 1 Hz drive
voltage (left: 1 V and right: 4 V).
of injection correspond to a wide spectrum of
distribution of capture centers on the energy in the
forbidden band of semiconductor material [8].
The vertical shift of Q-V loops is connected with the
rectification effect and corresponds to the observed
asymmetry of I-V loops.
The results obtained for the PSi samples are
comparable with those obtained for porous metal-oxide
ceramics and zeolite-like (of Na-Y type) and silica
mezo-porous systems (of MCM-41 type) [2, 3].
It should be pointed out the similarity of the look of
observed I-V loops for PSi and I-V loops for the model
ionic semiconductors Ag3AsS3 and Ag3SbS3 [9], for
which it is characteristic the availability of the
electrolytic reactions of Ag++e-=Ag0 type in under-
surface regions.
For the investigated systems, the observed
peculiarities of I-V loops and I-t curves are related with
adsorption of H2O vapor, post-dissociation of water
molecules, H2O → H++OH- and ion-electron transfer in
porous conglomerate of PSi and desorption of H2O as
the source of ionic charge carriers. The mechanism of
charge transfer in the PSi is associated with the hopping
transport of H+ ions by means of switching OH- dangling
bonds [10]. Kinetics of these processes determines the
shape of corresponding characteristics and peculiarities
of their time transformation.
With a certain degree of approximation, it can be
considered that the observed times in the consequence
“transformation of I-V loops (I-t curves and Q-V loops) –
their stabilization in time – restoration” correspond to
the characteristic ones in the consequence “adsorption -
dissociation and transfer – desorption”.
5. Conclusion
For PSi, as for an example, shown was the efficiency of
using the methods of dynamic electrophysical charac-
terization for studying the changing characteristics of
porous materials under fast humidity changes.
The hysteresis view of high voltage current-voltage
curves is characteristic for poling processes in the space
charge region similar to that observed in the case of
typical ionic conductors.
Observed phases of transformation of investigated
electrophysical characteristics reflect the time sсale of
processes in the consequence “adsorption – dissociation
and transfer – desorption”.
Acknowledgements
Authors gratefully acknowledge Conseil Regional of
Nord-Pas-de-Calais for financial support (grant
no04140209).
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