For the rst time current quantization is reported for antimony sulfoiodide (SbSI) nanowires. It has been registered in current responses on electric eld switching as well as on illumination on and o. Current steps determined in all experiments have been equal to each other within the experimental error. It has been explained by the quantized change of free carrier concentration in nanowire. Lateral dimensions of SbSI nanowires estimated from quantum steps are comparable with geometrical data reported for the same technology of material preparation

A Guiseppi-Elie

K Mistewicz

M Jesionek

M Nowak

P Szperlich

R Paszkiewicz

R Wrzalik

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Vol. 124 (2013) ACTA PHYSICA POLONICA A No. 5
Proceedings of the 42th Jaszowiec International School and Conference on the Physics of Semiconductors, Wisªa 2013
Quantum Eects in Electrical Conductivity
and Photoconductivity of Single SbSI Nanowire
K. Mistewicza,∗, M. Nowaka, R. Wrzalikb, M. Jesioneka, P. Szperlicha,
R. Paszkiewiczc and A. Guiseppi-Elied
aInstitute of Physics, Silesian University of Technology, Z. Krasi«skiego 8, 40-019 Katowice, Poland
bInstitute of Physics, University of Silesia, Bankowa 14, 40-007 Katowice, Poland
cDivision of Microelectronics and Nanotechnology, Wrocªaw University of Technology
Dªuga 65, 53-633 Wrocªaw, Poland
dCenter for Bioelectronics, Biosensors and Biochips, Clemson University, 132 Earle Hall, Clemson, USA
For the rst time current quantization is reported for antimony sulfoiodide (SbSI) nanowires. It has been
registered in current responses on electric eld switching as well as on illumination on and o. Current steps
determined in all experiments have been equal to each other within the experimental error. It has been explained
by the quantized change of free carrier concentration in nanowire. Lateral dimensions of SbSI nanowires estimated
from quantum steps are comparable with geometrical data reported for the same technology of material preparation.
DOI: 10.12693/APhysPolA.124.827
PACS: 81.07.Vb, 81.07.Bc, 73.63.Bd
1. Introduction
All around the world a great deal of attention is focused
on one-dimensional nanostructures because of their prop-
erties related to quantum eects, which may be promising
for various electronics and optoelectronics applications.
To the best of our knowledge, the quantum eects in
antimony sulfoiodide (SbSI) nanowires have never been
reported before. Simultaneously, the SbSI (being a semi-
conducting ferroelectric [1]) is a promising material due
to a large number of interesting properties, e.g., pyroelec-
tric, pyrooptic, piezoelectric, and electrooptic. Measure-
ments of current quantization in current responses on the
switch on of voltages and illumination of SbSI nanowires
have been the aim of this paper.
2. Experiment
The route of preparing single SbSI nanowires on
Si/SiO2 substrates as well as glass substrates (model
IAME-co-IME2-1AU made by Abtech Scientic Inc.)
equipped with interdigitated gold electrodes (with l =
1 µm spacing) can be summarized as follows. First of
all, SbSI gel was prepared sonically from the constituents
(the elements Sb, S and I) in ethanol. This gel consisted
of large number of crystalline nanowires with average lat-
eral dimensions of 1050 nm and average lengths up to
several micrometers. The used experimental setup, the
applied procedure, and characterization of the product
were the same as described in [2]. After this ethanol was
replaced with toluene and the product (in ratio: 0.7 mg
SbSI gel/1 ml toluene) was again sonicated to disperse
∗corresponding author; e-mail: krystian.mistewicz@polsl.pl
the solidied gel. As prepared SbSI sol was dropped
upon substrates in very small volume using insulin sy-
ringe equipped with 31G needle. In the case of IAME-
-co-IME2-1AU substrates, dc electric eld of 5×105 V/m
was applied between electrodes during the deposition of
SbSI sol to align the nanowires perpendicularly to the
electrodes. Then the sample was dried in a glove box, in
room temperature, in order to evaporate the toluene. In
next stage SbSI nanowires deposited on the Si/SiO2 sub-
strate were ultrasonically welded to the metal electrodes
applying technique similar to the reported in [3]. We used
ultrasonic generator ADG70-100P-230-NO (Rinco Ultra-
sonics) with working frequency 70 kHz and max power
120 W, transducer C 70-2 (Rinco Ultrasonics) and a spe-
cial sonotrode made by ourselves with SiC single crystal
end. Ultrasonic nanowelding was carried out by applying
one ultrasonic impulse of duration 90 ms and amplitude
0.05 µm. Press force of the welding head on the sample
was equal to 0.96 N. Energy realized during the welding
process amounted to 2.3 J.
Fig. 1. AFM image of a single SbSI nanowire ultrason-
ically welded to interdigitated electrodes on the Si/SiO2
substrate.
(827)
828 K. Mistewicz et al.
Figure 1 presents a single SbSI nanowire ultrasoni-
cally welded to interdigitated electrodes on the Si/SiO2
substrate. The atomic force microscopy (AFM) investi-
gations were carried out using atomic force microscope
Solver P47H-PRO (NT-MDT).
The electrical connections between gold electrodes and
the measurement board were made using HB05 ther-
mosonic wire bonder (TPT Wire Bonder). All electric
measurements were done using the Keithley 6517A elec-
trometer in normal atmosphere at 298 K temperature.
Acquisition of the data and control of the applied volt-
age were realized using a PC computer with IEEE 488
bus and appropriate programs in LabView 7.5 (National
Instruments).
Fig. 2. Current response ( ) on electric eld (solid
curve) applied to SbSI single nanowire. Inset in g-
ure shows the magnication of area indicated by dashed
rectangle.
Fig. 3. Kinetics of photoconductivity current for sin-
gle SbSI nanowire. Dashed vertical lines indicate the
illumination switch on and switch o.
Figure 2 presents current response on electric eld ap-
plied to the unilluminated SbSI single nanowire. After
quick response the current decreases in step-like form (see
inset in Fig. 2). Magnitudes of the 32 observed current
steps are practically the same. The averaged value of the
current step was ∆ID = 66(4) fA.
Figure 3 shows kinetics of photoconductivity current
for a single SbSI nanowire illuminated with visible light.
Intensity of the bias electric eld was 2.5 × 106 V/m.
The observed photoconductivity current steps had the
average value ∆IPC = 60(7) fA.
3. Discussion
The quick increase followed by a slow decrease of a
current after electric eld switch on is characteristic for
the trapping of carriers at boarders of electric domains in
SbSI [1]. Authors of [4] reported that SbSI in paraelectric
phase (i.e. in T = 298 K) consists of irregular positively
or negatively polarized nanodomains. The nanodomains
about 0.5 nm thick, 2.0 nm broad and a few nm long are
elongated in the [001] direction, i.e. along SbSI nanowire.
Therefore the observed quantization eect (Fig. 2) can be
explained as a result of the change of free carrier concen-
tration with time after polarization of the nanodomains.
Also in the case of illumination of SbSI nanowire the
change of free carrier concentration with time (Fig. 3)
can explain the observed quantization of photoconduc-
tivity current. It should be noticed that the current steps
∆ID and ∆IPC are equal to each other within the exper-
imental error. It seems to be a proof of the same nature
of quantization eects observed in electrical conductivity
(Fig. 2) and photoconductivity (Fig. 3).
Let us assume that the observed changes of electrical
conductivity and photoconductivity in SbSI nanowire are
represented by the elementary unit of conductance
∆σ = e2/h, (1)
where e is electron charge, h is Planck's constant. Then,
applying the determined value of current step into simple
formula describing electrical conductivity of a nanowire
with square cross-section, one can estimate the nanowire
lateral dimension
d =
1
e
√
h∆IA
E
, (2)
where ∆IA = ∆ID for the measurements on electrical
conductivity in darkness or ∆IA = ∆IPC for the mea-
surements on photoconductivity. Hence, lateral dimen-
sion of SbSI nanowire determined from the time depen-
dence of dark current (Fig. 2) and photoconductivity
current (Fig. 3) have been estimated as 26.1(8) nm and
25(2) nm, respectively. These values are very compara-
ble to the lateral dimensions of SbSI nanowires fabricated
with the applied sonochemical technique and reported in
[2, 5, 6].
4. Conclusions
For the rst time the quantum eects in conductiv-
ity and photoconductivity of single SbSI nanowires have
been observed. Lateral dimensions of SbSI nanowires cal-
culated from quantum steps in two dierent experiments
(electrical conductivity and photoconductivity measure-
ments) are very close to each other. In addition, they
are comparable with values of lateral dimensions of SbSI
Quantum Eects in Electrical Conductivity and Photoconductivity . . . 829
nanowires reported in literature for the same technology
of material preparation.
Acknowledgments
This paper was partially supported by the National
Science Centre (Poland) under contract No. 2011/01/B/
ST5/06273.
References
[1] V.M. Fridkin, Ferroelectric Semiconductors, Consul-
tants Bureau, New York 1980.
[2] M. Nowak, . Bober, B. Borkowski, M. K¦pi«ska,
P. Szperlich, D. Stró», M. Soza«ska, Opt. Mater.
35, 2208 (2013).
[3] C. Chen, L. Liu, Y. Lu, E. Siu-Wai Kong, Y. Zhang,
X. Sheng, H. Ding, Carbon 45, 436 (2007).
[4] K. ukasiewicz, A. Pietraszko, M. Kucharska, Ferro-
electrics 375, 170 (2008).
[5] M. Nowak, P. Szperlich, . Bober, J. Szala, G. Moskal,
D. Stró», Ultrason. Sonochem. 15, 709 (2008).
[6] M. Nowak, in: Nanowires Science and Technology,
Ed. N. Lupu, Intech, Croatia 2010, p. 269.


Quantum Eects in Electrical Conductivity and Photoconductivity of Single SbSI Nanowire

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Quantum Eects in Electrical Conductivity and Photoconductivity of Single SbSI Nanowire

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