Preparation of MoSe2 nano-islands array embedded in a TiO2 matrix for photo-regulated resistive switching memory

Article abstract of DOI:10.1016/j.jallcom.2015.12.238

The electrically driven resistance change of a material, called memristive switching, is a fascinating phenomenon in the development of next generation nonvolatile memory alternatives to flash technology. Herein, the composite of MoSe₂ nano-islands array inserted into TiO₂ matrix grown on fluorine-doped tin oxide (FTO) substrate was prepared by anodic aluminum oxide (AAO) template assisted radio frequency magnetron sputtering. Further, a photo-controlled resistive switching memory device with Ag/[MoSe₂/TiO₂]/FTO structure is demonstrated. The device presents stable resistive switching memory behaviors in dark and under illumination respectively. Finally, the mechanism for the photo-controlled memory behaviors is discussed in detail. This implication provides a foundation for exploring the multifunctional composites and their applications in photo-controlled nonvolatile memory devices.

Full text of DOI:10.1016/j.jallcom.2015.12.238

Journal of Alloys and Compounds 664 (2016) 619e625
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: http://www.elsevier.com/locate/jalcom
Preparation of MoSe nano-islands array embedded in a TiO matrix
2
2
for photo-regulated resistive switching memory
a
,
*
b
a
a
a
a
Pengde Han , Bai Sun , Sen Cheng , Fangli Yu , Baoxiang Jiao , Qisheng Wu
a
School of Materials Engineering, Yancheng Institute of Technology, Yancheng 224051, China
School of Physics Science and Technology, Southwest University, Chongqing 400715, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 November 2015
Received in revised form
The electrically driven resistance change of a material, called memristive switching, is a fascinating
phenomenon in the development of next generation nonvolatile memory alternatives to flash technol-
ogy. Herein, the composite of MoSe nano-islands array inserted into TiO matrix grown on fluorine-
2 2
doped tin oxide (FTO) substrate was prepared by anodic aluminum oxide (AAO) template assisted ra-
dio frequency magnetron sputtering. Further, a photo-controlled resistive switching memory device with
6
December 2015
Accepted 15 December 2015
Available online 31 December 2015
2 2
Ag/[MoSe /TiO ]/FTO structure is demonstrated. The device presents stable resistive switching memory
behaviors in dark and under illumination respectively. Finally, the mechanism for the photo-controlled
memory behaviors is discussed in detail. This implication provides a foundation for exploring the
multifunctional composites and their applications in photo-controlled nonvolatile memory devices.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
Resistive switching
Photo-controlled memory
MoSe
TiO matrix
Anodic aluminum oxide (AAO) template
2
nano-islands
2
1. Introduction
attractive because optical signals are easier to apply over long
distances than electrical signals, and optical signals can efficiently
Memristive switching phenomena at simple metal/oxide/metal
junctions have attracted much attention due to not only funda-
mental interest in the mechanisms but also the potential uses in
high-density universal memory devices, which has stimulated
extensive research for exploring new functional materials and their
applications in non-volatile memory devices [1e5]. Recently,
resistive switching in many transition metal oxides has been
observed and becomes the basis for the development of novel non-
volatile resistive random access memory (RRAM) [6]. In the
exploration of mechanism, the resistive switching effect is
interface-related and takes place at the interface between metal
electrode and the oxide materials. The interface plays a key role in
the presence of oxygen vacancies that modulate the interface
resistance [7e10]. However, the nanoscale physical and chemical
origins of resistive switching are still under debate.
manage the interactions between circuit devices without disrup-
tion by signal interference.
During the last decade, as graphene and its related applications
have stimulated many studies, numerous other two-dimensional
materials have attracted great interest due to their unique prop-
erties and different energy band gaps compared to bulk material
[15,16]. In recent investigations, new two-dimensional materials,
such as MoSe
cations [15e20]. It is truly worthy of note that MoSe
2
, have been utilized in a variety of important appli-
is an indirect
2
semiconductor with a band gap of 1.7e1.9 eV [21e23]. The layers of
SeeMoeSe interact with each other through van der Waals forces.
In addition, the typical synthesis routes, such as chemical vapor
deposition, electro deposition, spray pyrolysis, physical vapor
deposition and hydrothermal method, have been used widely for
the preparation of MoSe
Although the preparation of individual MoSe
intensively investigated, the resistive switching memory properties
of MoSe /TiO composite have not been reported yet. In order to
explore new developments and applications of the MoSe material,
in this work, MoSe and TiO powder were firstly synthesized by
hydrothermal method, then the self-assembly MoSe nano-islands
array inserted into TiO matrix grown on fluorine-doped tin oxide
FTO) substrate was prepared by anodic aluminum oxide (AAO)
2
nanostructures [24e29].
Recently, photo as new control method in the resistive switching
has been reported [11e14]. The extra control parameter (photo-
control) in the resistive switching can greatly broaden its applica-
tions. Indeed, the light-illumination conditions are particularly
2
and TiO
2
has been
2
2
2
2
2
2
2
*
Corresponding author.
(
E-mail address: hanpengde@163.com (P. Han).
http://dx.doi.org/10.1016/j.jallcom.2015.12.238
925-8388/© 2015 Elsevier B.V. All rights reserved.
0

620
P. Han et al. / Journal of Alloys and Compounds 664 (2016) 619e625
template assisted radio frequency magnetron sputtering, and the
electrodes of Ag were made by vacuum deposition. The preparation
sheets. The first anodization of Al sheet in 0.3 M H
was conducted for 12 h at 5 C. The anodized Al sheet was
2
C
2
O
4
solution
ꢀ
process is shown in Fig. 1. In addition, Ag/[MoSe
ture device displays an excellent photo-controlled bipolar resistive
switching behaviors, indicating the MoSe /TiO composite holds
2
/TiO
2
]/FTO struc-
completely removed in an aqueous acid mixture of H
3
PO
4
and CrO
3
ꢀ
(6 wt% and 1.8 wt%) at 60 C for 12 h. The second anodization was
ꢀ
2
2
carried out for 3 min at 5 C. The etching process in HgCl
2
at room
promise for practical applications of photo-controlled RRAM
devices.
temperature detached the alumina layer from the Al sheet. In
sequence, the barrier layer was removed by the pore widening
ꢀ
process with 5 wt% H
3
PO
4
at 30 C for 20 min. Finally, we obtained
2
. Experimental procedure
500 nm-thick AAO membranes that provided excellent contacts
with substrates.
2
.1. Preparation of MoSe and TiO
2
2
powder
MoSe
AAO nano-template by radio frequency magnetron sputtering
method. The MoSe nano-islands were deposited at room tem-
perature and the power of the radio frequency was set at 80 W. The
2
nano-islands were fabricated on FTO substrates through
In this work, MoSe
2
powder was synthesized by a hydrothermal
MoO $2H O) and sele-
2
method. Analytical sodium molybdate (Na
nium (Se) of analytical grade were used as precursor reagents
without any further purification. A stoichiometric amount of
Na
autoclave with a 50 ml capacity with stirring until completely
dissolved. Then an appropriate amount of hydrazine hydrate
2
4
2
ꢁ
1
deposition rate of MoSe
pressure for the deposition was 5.0 ꢂ 10 Pa and the Ar working
chamber pressure was 1.0 Pa. After MoSe deposition, extended
arrays of MoSe nano-islands were obtained by mechanically lifting
off the AAO mask. Then TiO film with the thickness of ~200 nm was
deposited on interspace of MoSe nano-islands at
2
was 0.02 nm s . The typical base chamber
ꢁ
5
2
MoO
4
$2H
2
O and Se powder was put into a stainless steel
2
2
2
(
N
H
2 4
2
$H O) was added into the tank under stirring. Distilled water
2
2
was added to fill the autoclave up to 80% of the total volume under
vigorous stirring for 30 min, and then the pH value was adjusted to
about 12 with the addition of solid NaOH. The autoclave was sealed
roomtemperature. Finally, the electrodes with the area of ~1 mm
and the thickness of ~200 nm were deposited on the same side for
the electric measurement by vacuum deposition.
ꢀ
and maintained at 180 C for 48 h, and then cooled to room tem-
perature naturally. A black precipitate was collected. After being
2.3. Material characteristics
washed with absolute ethanol and distilled water, the final product
ꢀ
was dried in a vacuum box at 60 C for overnight. Finally, we made a
Microstructure of MoSe
X-ray diffraction (XRD, Shimadzu XRD-7000 X-ray diffractometer)
with Cu K radiation. Surface morphology and energy dispersive X-
ray spectroscopy (EDX) spectra of MoSe /TiO compound grown on
FTO substrate was characterized using scanning electron micro-
scopy (SEM, JSM-6510). The microstructure characterization of the
2 2
/TiO compound was characterized by
target of magnetron sputtering using as-prepared MoSe
The TiO powder was prepared using the solegel method. TiO
powder was synthesized using titanium(IV) isopropoxide (TIP)
Aldrich Chemical, SigmaeAldrich Corporation, St. Louis, MO, USA),
nitric acid, ethyl alcohol, and distilled water. The TIP was mixed
with ethanol, and distilled water was added drop by drop under
vigorous stirring for 1 h. This solution was then peptized using
2
powders.
2
2
a
2
2
(
2 2
MoSe /TiO compound was tested by transmission electron mi-
croscopy (JEM-2100) at an acceleration voltage of 200 kV. The
chemical state was analyzed by X-ray photoelectron spectroscopy
(XPSESCALAB250).
ꢀ
nitric acid and heated under reflux at 80 C for 8 h. After this period,
a TiO
powder. The TiO
2
sol was prepared. The prepared sol was dried to yield a TiO
2
ꢀ
2
particles were annealed in air at 450 C for 1 h
using a programmable furnace to obtain the desired TiO
ometry and crystallinity. Similarly, we made a target of magnetron
sputtering using as-prepared TiO powders.
2
stoichi-
2.4. Device characteristics
2
In the test of resistive switching characteristics, Ag and FTO is
the top electrode and bottom electrode respectively. All the electric
measurements were measured using the electrochemical work-
station CHI-660D at room temperature. An ordinary filament lamp
with various power densities was used as light source. The spec-
trum of the light is shown in Fig. 2, which shows two peaks at
2 2
2.2. Preparation of Ag/[MoSe /TiO ]/FTO structure device
Anodic aluminum oxide (AAO) membranes with ~200 nm pore
size were fabricated by a two-step anodization of electropolished Al
Fig. 1. Schematics fabrication of Ag/[MoSe
2 2 2
/TiO ]/FTO structure device with MoSe
nano-island array inserted into TiO matrix grown on FTO substrate.
2
Fig. 2. The light spectra used as the light source in our experiment process.

P. Han et al. / Journal of Alloys and Compounds 664 (2016) 619e625
621
~445 nm and ~555 nm, and the wavelength range of the light is
other impurities.
4
00e760 nm.
Chemical compositions of MoSe
2
/TiO
2
composite were investi-
gated by X-ray photoelectron spectroscopy (XPS) analysis (Fig. 4).
Mo 3d5/2 and Mo 3d3/2 ware found at 229 and 232 eV confirming
that molybdenum is in its Mo (IV) state; and the 3d peak of Se
element is split into well-defined 3d5/2 and 3d3/2 peaks at 54.4 and
3
. Results and discussion
Fig. 3(a) exhibits the scanning electron microscope (SEM) image
55.3 eV respectively. The residual carbon content in the matter was
2
of self-assembly MoSe nano-islands array grown on FTO substrate.
also a little higher although still in trace amount from Fig. 4(a). We
can see that there were two peaks in the Ti 2p region, the peak
located at 464.2 eV corresponded to Ti 2p1/2 and another one
located at 458.6 eV was assigned to Ti 2p3/2. The splitting between
We can see that as-prepared sample consists of nano-islands array
with the diameter of ~200 nm. The SEM image of anodic aluminum
oxide (AAO) template is shown in the inset of Fig. 3(a). It is obvious
that MoSe
2 2
nano-islands array inserted into TiO matrix from
4
þ
Ti 2p1/2 and Ti 2p3/2 was 5.7 eV, indicating a normal state of Ti in
the as-prepared MoSe /TiO composite. The one peak of O 1s was
related to TieO bonds (530.1 eV). The above XRD and XPS results
transmission electron microscope (TEM) image in Fig. 3(b).
The crystalline compositions of as-prepared samples were
characterized by XRD patterns. In order to make diffraction peaks of
2
2
confirmed the coexistence of MoSe
2
and TiO
2
in the MoSe
2
/TiO
2
MoSe
the pure FTO substrate without MoSe
that the crystallizations of TiO and MoSe
any other impurity phase from Fig. 3(c). Fig. 3(c) shows the X-ray
powder diffraction (XRD) pattern of MoSe /TiO compound at room
temperature. The XRD profile of MoSe powder matches very well
with that in the reported work [30,31]. Obviously, all XRD peaks can
be indexed to 2HeMoSe structure. In addition, TiO exhibits rutile
phase (JCPDS: 211276). No other impurity peaks are detected. The
low background and sharp peaks suggest that the MoSe and TiO
retain their crystallinity. Moreover, the MoSe /TiO composite were
2
/TiO
2
composite clearer, we also present the XRD pattern of
/TiO composite. We can see
are sufficiently without
composite.
2
2
To check the capacitive performance of Ag/[MoSe
2
/TiO
2
]/FTO
2
2
structure device, a typical currentevoltage (IeV) response of het-
erostructure was investigated. Fig. 5(a) shows the experimental
setup, in which Ag and FTO are the top and bottom electrode
2
2
2
respectively, and an ordinary filament lamps with power density
2
6
0 mW/cm is used as light source, where the wavelength range of
2
2
white-light is 400e760 nm. The typical IeV characteristics curves
of Ag/[MoSe /TiO ]/FTO structure in dark and under light irradia-
tion exhibit an asymmetric behavior with significant hysteresis
Fig. 5(b)). The arrows in the figure denote the sweeping directions
2
2
2
2
2
2
(
further confirmed by elemental analysis carried out from energy-
dispersive X-ray (EDX) spectra, the EDX data in Fig. 3(d) confirms
that the elements of composite are Mo, Se, Ti and O without any
of the applied voltage. An obvious bipolar resistive switching
behavior with rapid conversion and good reproducibility in Ag/
Fig. 3. (a) SEM image of MoSe
MoSe /TiO composite. (c) X-ray powder diffraction (XRD) patterns of MoSe
composite.
2
nano-islands array with a diameter of ~200 nm, the inset shows SEM image of anodic aluminum oxide (AAO) nano-template. (b) TEM image of
2
2
2
/TiO composite at room temperature. (d) Energy-dispersive X-ray (EDX) spectra of MoSe /TiO
2
2
2

622
P. Han et al. / Journal of Alloys and Compounds 664 (2016) 619e625
Fig. 4. (a) XPS survey spectra of MoSe
2
/TiO
2
composite. (b) High resolution C 1s spectra. (c) High resolution Mo 3d spectra. (d) High resolution Se 3d spectra. (e) High resolution Ti
2p spectra. (f) High resolution O 1s spectra.
[
MoSe
2
/TiO
2
]/FTO device is observed. To avoid electrical permanent
LRS in dark and 65 kU at LRS under white-light illumination, which
breakdown for the devices, the compliance current (CC) of 25
used during the set and reset process.
Fig. 5(c) displays a prominent resistance switching effect in
logarithmic scale. We can see that the device exhibits two stable
resistance states when applying a positive electric field. It is
m
A is
indicate the white-light illumination can reduce the resistance
value for LRS. More importantly, the resistances of HRS and LRS in
dark and under light irradiation are nearly unchanged after 50
successive cycles, illustrating that the resistive switching effects in
dark and under light irradiation are highly stable. According to the
above results, the steady photo-controlled bistable resistive
obvious that a sudden current increase occurs at about 2.22 V (VSet
)
in dark and 2.02 V (V1Set) under white-light illumination, indicating
a “Set” process from a high resistance state (HRS) or “OFF” state to a
low resistance state (LRS) or “ON” state happens. When the applied
2 2
switching behavior in Ag/[MoSe /TiO ]/FTO device provides the
potential for photo-controlled non-volatile memory applications.
It is well known that the non-volatile resistive switching
random access memory (RRAM) is based the hysteresis IeV curves
of a material. Fig. 6 display the memory application of IeV response
voltage sweeps from zero to a negative voltage of about ꢁ1.98 V
1
(V
Reset) in dark and ꢁ1.79 V (V Reset) under illumination, a “Reset”
process from a low resistance state (LRS) or “ON” state to high
resistance state (HRS) or “OFF” state occurs. The two well-resolved
states provide a clear memory window of the device. More
importantly, it is highly obvious that white-light illumination can
regulate the resistive switching effect and magnify the memory
2 2
curves of Ag/[MoSe /TiO ]/FTO device, which is corresponding well
to memristive switching behavior, indicating that the device could
be reliably written, read, and erased during each step in dark
(Fig. 6(aed)) and under illumination with power density of 60 mW/
2
0
0
cm (Fig. 6(a ed )) respectively. In dark, the device display a well
resistive switching behavior with an abrupt written voltage Vwrite of
windows, demonstrating the great potential of Ag/[MoSe
2 2
/TiO ]/
FTO device for photo-controlled memory applications.
2.22 V under the compliance current (CC) of 25 mA. Then it displays
To evaluate the practical application of the resistive switching
characteristics of Ag/[MoSe /TiO ]/FTO device, the resistance-cycle
number curves with a positive bias voltage of 1.0 V were tested and
shown in Fig. 5(d). It is obvious that the resistance is about
a single LRS state with read behavior with operating voltage range
from 1.45 V to ꢁ1.33 V. Next, the device can erase the storage in-
formation with an obvious erase voltage of ꢁ1.33 V, which is called
2
2
V
erase. Finally, this device exhibit a correspondent HRS state with
1
500 k
mination, suggesting the white-light illumination can change the
resistance value for HRS. However, the resistance is about 142 k at
U
at HRS in dark and 640 k
U
at HRS under white-light illu-
read behavior with operating voltage range from ꢁ1.95 V to 2.17 V
again. If we call the LRS is logic “0”, then HRS is logic “1” for this
device. Thus the device exhibit memristive switching. During the
U

P. Han et al. / Journal of Alloys and Compounds 664 (2016) 619e625
623
Fig. 5. (a) The experimental test circuit, Ag and FTO is top and bottom electrode respectively. (b) The typical currentevoltage (IeV) characteristics curve of Ag/[MoSe
2
/TiO
2
]/FTO
structure. (c) The corresponding resistance switching effects in logarithmic scale. (d) The resistance-cycles curve with a positive bias voltage of 1.0 V.
2 2
Fig. 6. The sequential write-read-erase-read operations yielded the corresponding IeV behaviors of the Ag/[MoSe /TiO ]/FTO device containing in dark and under white-light
illumination respectively.

624
P. Han et al. / Journal of Alloys and Compounds 664 (2016) 619e625
2 2
superior resistive switching characteristics of Ag/[MoSe /TiO ]/FTO
hold great promise for next-generation photo-controlled nonvola-
tile memory applications.
Acknowledgments
This work was supported by Natural Science Foundation of
Jiangsu Province (No. BK20150431), Research Foundation of Yan-
cheng Institute of Technology (No. KJC2014004) and National
Natural Science Foundation of China (No. 51202211).
References
[1] D.S. Jeong, R. Thomas, R.S. Katiyar, J.F. Scott, H. Kohlstedt, A. Petraru,
C.S. Hwang, Rep. Prog. Phys. 75 (2012) 076502.
2 2
Fig. 7. A schematic of the electronehole generation process of MoSe /TiO composite
under light illumination.
[
[
[
2] C. Jin, J. Lee, E. Lee, E. Hwang, H. Lee, Chem. Commun. 48 (2012) 4235.
3] R. Waser, R. Dittmann, G. Staikov, K. Szot, Adv. Mater. 21 (2009) 2632.
4] H.J. Kim, Y.J. Baek, Y.J. Choi, C.J. Kang, H.H. Lee, H.M. Kim, K.B. Kim, T.S. Yoon,
RSC Adv. 3 (2013) 20978.
white-light illumination, it is greatly obvious that the Vwrite is
become 1.98 V nearly, and the read behavior at LRS with operating
voltage range from 1.22 V to ꢁ1.23 V. Moreover, the Verase is also
become ꢁ1.23 V. Further, the operating voltage of HRS state with
read behavior range from ꢁ1.71 V to 1.98 V accordingly. Therefore,
[5] H.G. Yoo, S. Kim, K.J. Lee, RSC Adv. 4 (2014) 20017.
[6] J. Kolar, J.M. Macak, K. Terabe, T. Wagner, J. Mater. Chem. C 2 (2014) 349.
[7] B. Sun, W. Zhao, L. Wei, H. Li, P. Chen, Chem. Commun. 50 (2014) 13142.
[8] H. Borkar, A. Thakre, S.S. Kushvaha, R.P. Aloysius, A. Kumar, RSC Adv. 5 (2015)
35046.
[9] B. Sun, Y. Liu, W. Zhao, J. Wu, P. Chen, Nano-Micro Lett. 7 (2015) 80.
10] B. Sun, C.M. Li, Phys. Chem. Chem. Phys. 17 (2015) 6718.
11] M. Ungureanu, R. Zazpe, F. Golmar, P. Stoliar, R. Llopis, F. Casanova, L.E. Hueso,
Adv. Mater. 24 (2012) 2496.
[12] M. Adachi, K. Yoshida, T. Kurata, J. Adachi, K. Tsuchiya, Y. Mori, F. Uchida,
J. Mater. Res. 27 (2011) 440.
[
[
2 2
the resistive switching memory behaviors of Ag/[MoSe /TiO ]/FTO
device are useful in data storage technologies because they allow
information to be written to the device once, and the data may not
be subsequently erased or deleted from the device.
The mechanisms for resistive switching in metal/oxides/oxides
structure have been extensively investigated [32]. It is generally
believed that the electrically driven migration of the oxygen ions/
vacancies plays a critical role in the operation of these devices
[
[
13] J. Park, S. Lee, J. Lee, K. Yong, Adv. Mater. 25 (2013) 6423.
14] J. Park, S. Lee, K. Yong, Nanotechnology 23 (2012) 385707.
[15] Q.H. Wang, K.K. Zadeh, A. Kls, J.N. Coleman, M.S. Strano, Nat. Nanotechnol. 7
2012) 699.
(
[
[
16] C. Fan, Z. Wei, S. Yang, J. Li, RSC Adv. 4 (2014) 775.
17] D. Duphil, S. Bastide, J.C. Rouchaud, J.L. Pastol, B. Legendre, C.L. Clemen,
Nanotechnology 15 (2004) 828.
[
33e37]. In our works, the hysteresis loop IeV curve of Ag/[MoSe
TiO ]/FTO device might be attributed to FTO as an oxygen guttering
material to induce the oxygen vacancies at the [MoSe /TiO ]/FTO
2
/
[
18] Y.D. Ma, Y. Dai, C.W. Niu, L. Yu, B.B. Huang, J. Phys. Chem. C 115 (2011)
2
202371.
2
2
[
19] S. Larents, B. Fallahazad, E. Tutuc, Appl. Phys. Lett. 101 (2012) 223104.
interface with a Schottky-like barrier [38e51], which would modify
the oxygen vacancies distribution within the device to result in the
resistive switching characteristics [52e54]. Therefore, this bipolar
resistive switching behavior should be result from the trapped and
detrapped charge in the Schottky-like depletion layer [55]. The
white-light illumination can modulate the resistive switching
behavior by a large number of photogenerated charges, as shown in
Fig. 7, which shows a schematic of the photogenerated charges
transition between the valence band and the conduction band
under light illumination. At room temperature, some of the elec-
[20] H.S. Lee, S.W. Min, Y.G. Chang, M.K. Park, T. Nam, H. Kim, J.H. Kim, S. Ryu, S. Im,
Nano Lett. 12 (2012) 3695.
[21] A. Ramasubramaniam, Phys. Rev. B Condens. Matter Mater. Phys. 86 (2012)
115409.
[22] S.M. Delphine, M. Jayachandran, C. Sanjeeviraja, Crystallogr. Rev. 17 (2011)
281.
[
[
[
[
23] P.P. Hankare, A.A. Patil, K.M. Garadkar, D.J. Sathe, A.H. Manikshete, I.S. Mulla,
J. Cryst. Growth 311 (2008) 15.
24] S.Y. Hu, Y.C. Lee, J.L. Shen, K.W. Chen, K.K. Tiong, Y.S. Huang, Solid State
Commun. 139 (2006) 176.
25] D.A. Ras, G. Kostorz, D. Bremaud, M. Kalin, F.V. Kurdesau, A.N. Tiwari,
M. Dobeli, Thin Solid Films 480 (2005) 433.
26] J.H. Zhan, Z.D. Zhang, X.F. Qian, C. Wang, Y. Xie, Y.T. Qian, Mater. Res. Bull. 34
(1999) 497.
2 2
trons exist in the conductive band of MoSe and TiO due to ther-
[
[
[
27] K. Tang, Y. Qian, J.H. Zeng, X.G. Yang, Adv. Mater. 15 (2003) 448.
28] X.H. Chen, R. Fan, Chem. Mater. 13 (2001) 802.
29] G.G. Tang, J.R. Sun, C. Wei, K.Q. Wu, X.R. Ji, S.S. Liu, H. Tang, C.S. Li, Mater. Lett.
86 (2012) 9.
mal energy, which leads to good conductivity. When the light was
turned on, the electrons in the valence band transit to the con-
duction band with the assistance of the phonons, and holes were
generated in the valence band at the same time. Then the electrons
will shift under the bias voltage, which leads to the photocurrent
seen under light illumination. Due to the increasing of the photon
densities, the probability of a transition between the valence band
and the conduction band in the same part of the MoSe and TiO is
2 2
increased. More electrons will shift under the bias voltage to form a
current. Therefore, we observed a photo-controlled resistive
[30] H. Shi, X. Zhou, Y. Lin, X. Fu, Mater. Lett. 62 (2008) 3649.
[31] H. Tang, K. Dou, C.-C. Kaun, Q. Kuang, S. Yang, J. Mater. Chem. A 2 (2014) 360.
[32] B. Sun, L. Wei, H. Li, X. Jia, J. Wu, P. Chen, J. Mater. Chem. C 3 (2015) 12149.
[33] B. Sun, C.M. Li, Chem. Phys. Lett. 604 (2014) 127.
[34] K. Nagashima, T. Yanagida, K. Oka, M. Kanai, A. Klamchuen, J.-S. Kim, B.H. Park,
T. Kawai, Nano Lett. 11 (2011) 2114.
[35] D.B. Strukov, G.S. Snider, D.R. Stewart, R.S. Williams, Nature 453 (2008) 80.
[36] M.K. Yang, J.W. Park, T.K. Ko, J.K. Lee, Appl. Phys. Lett. 95 (2009) 042105.
[37] P. Erhart, K. Albe, Appl. Phys. Lett. 88 (2006) 201918.
[
[
38] A. Sawa, T. Fujii, M. Kawasaki, Y. Tokurad, Appl. Phys. Lett. 85 (2004) 1.
39] X.G. Chen, X.B. Ma, Y.B. Yang, L.P. Chen, G.C. Xiong, G.J. Lian, Y.C. Yang,
J.B. Yang, Appl. Phys. Lett. 98 (2011) 122102.
2 2
switching memory effect in the [MoSe /TiO ]/FTO device.
[
[
[
40] J.K. Hyung, Y.J. Baek, Y.J. Choi, C.J. Kang, H.H. Lee, H.M. Kim, K.B. Kim, T.S. Yoon,
RSC Adv. 3 (2013) 20978.
41] A. Shih, W. Zhou, J. Qiu, H.J. Yang, S. Chen, Z. Mi, I. Shih, Nanotechnology 21
4
. Conclusions
(2010) 125201.
2 2
In conclusion, the MoSe /TiO composite was prepared on FTO
42] S. Hong, T. Choi, J.H. Jeon, Y. Kim, H. Lee, H.Y. Joo, I. Hwang, J.S. Kim, S.O. Kang,
S.V. Kalinin, B.H. Park, Adv. Mater. 25 (2013) 2339.
substrate, and a photo-controlled bipolar resistive switching
memory characteristic based on Ag/[MoSe /TiO ]/FTO device was
observed. Our data indicates that the resistive switching effect in
the Ag/[MoSe /TiO ]/FTO structure results from the trapping-
assisted carrier tunneling at the [MoSe /TiO ]/FTO interface. The
[43] B. Sun, J. Wu, X. Jia, F. Lou, P. Chen, J. Sol-Gel Sci. Technol. 16 (2015) 1573.
2
2
[
[
[
44] A. Sawa, T. Fujii, M. Kawasaki, Y. Tokura, Appl. Phys. Lett. 88 (2006) 232112.
45] B. Sun, Y. Liu, W. Zhao, P. Chen, RSC Adv. 5 (2015) 13513.
46] H. Sim, D.J. Seong, M. Chang, H. Hwang, J. Appl. Phys. 100 (2006) 88.
2
2
2
2
[47] X.L. Deng, S. Hong, I. Hwang, J.S. Kim, J.H. Jeon, Y.C. Park, J. Lee, S.O. Kang,

P. Han et al. / Journal of Alloys and Compounds 664 (2016) 619e625
625
T. Kawai, B.H. Park, Nanoscale 4 (2012) 2029.
48] X.G. Chen, J.B. Fu, S.Q. Liu, Y.B. Yang, C.S. Wang, H.L. Du, G.C. Xiong, G.J. Lian,
[52] C.Y. Lin, C.Y. Wu, C.Y. Wu, T.C. Lee, F.L. Yang, C.M. Hu, T.Y. Tseng, IEEE Electron
Device Lett. 28 (2007) 5.
[
J.B. Yang, Appl. Phys. Lett. 101 (2012) 153509.
49] G. Chen, C. Song, C. Chen, S. Gao, F. Zeng, F. Pan, Adv. Mater. 24 (2012) 3515.
50] D. Rubi, F. Gomez-Marlasca, P. Bonville, D. Colson, P. Levy, Phys. B 407 (2012)
[53] R. Zazpe, M. Ungureanu, F. Golmar, P. Stoliar, R. Llopis, F. Casanova,
D.F. Pickup, C. Rogerofh, L.E. Hueso, J. Mater. Chem. C 2 (2014) 2013.
[54] B. Sun, Y. Liu, F. Lou, P. Chen, Chem. Phys. 457 (2015) 28.
[55] C.Y. Lin, D.Y. Lee, S.Y. Wang, C.C. Lin, T.Y. Tseng, Surf. Coat. Technol. 203 (2008)
628.
[
[
3144.
[
51] A. Sawa, T. Fujii, M. Kawasaki, Y. Tokura, Appl. Phys. Lett. 85 (2004) 18.