Novel computing technologies that imitate the principles of biological neural systems may offer low power consumption along with distinct cognitive and learning advantages [1], [2]. The development of reliable memristive devices capable of storing multiple states of information has opened up new applications such as neuromorphic circuits and adaptive systems [3], [4]. At the same time, the explosive growth of the printed electronics industry has expedited the search for advanced memory materials suitable for manufacturing flexible devices [5].

1. SUPPLEMENTARY INFORMATION
DOI: 10.1038/NMAT4135
NATURE MATERIALS | www.nature.com/naturematerials 1
1
Layered memristive and memcapacitive switches for printable electronics
Alexander A. Bessonov1
, Marina N. Kirikova1
, Dmitrii I. Petukhov1,2
, Mark Allen3
, Tapani Ryhänen3
, Marc J.A. Bailey1
1 Nokia Labs Skolkovo, Nokia Technologies, Moscow region 143025, Russia
2
Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia
3 Sensor Systems, Nokia Technologies, Cambridge CB3 0FA, United Kingdom
Figure S1. Solution-processed MoOx/MoS2 memristors.
Figure S2. XPS analysis of MoOx/MoS2 heterostructures.
Figure S3. Photonic flash oxidation of transition metal dichalcohenides (TMDs).
Figure S4. I-V characteristics of layered switching devices.
Figure S5. Memristive and memcapacitive effects.
Figure S6. Multilevel operation and endurance test.
© 2014 Macmillan Publishers Limited. All rights reserved.

2. 2 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135
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Figure S1 | Solution-processed MoOx/MoS2 memristors. a, Top-view optical image of a cross-point
area (~130×170 m2
) with inkjet printed bottom electrode (BE) and screen printed top electrode (TE).
b, Cross-section SEM image of the AgNW/MoOx/MoS2 switching device with both BE and TE
fabricated by screen printing; insets show a top-view image of the MoOx/MoS2 film on printed silver
(top) and a cross-section of the MoOx/MoS2 film conformally covering the Ag BE (bottom). c, UV-vis
transmittance spectra of MoOx/MoS2 and WOx/WS2 films on the 50 m thick PEN substrate. Thermal
oxidation is performed at 200°C for 3 h. The transmittance at 565 nm is 51% for MoS2 and 68% for
WS2.
400 500 600 700 800
Wavelength (nm)
0
20
40
60
80
100
Transmittance(%)
MoOx
/MoS2
WOx
/WS2
1 m
500 nm
MoOx/MoS2
Ag BE
AgNW
PEN
1 m
b
Inkjet-printed
silver BE
Screen-printed
silver TE
100 m
MoOx/MoS2 filma
c
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SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4135
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Figure S2 | XPS analysis of MoOx/MoS2 heterostructures. a, Evolution of Mo 3d core levels with
depth profiling for layered MoOx/MoS2 films obtained by 200°C / 3 h oxidation. The intensities are
normalized for visual clarity. The features at 228.8 and 231.9 eV are associated with Mo4+
3d5/2 and
3d3/2 core levels in MoS2, respectively, while S 2s appears at 225.9 eV. The peak at 229.7 and
232.8 eV could be attributed to the Mo5+
3d core level in MoOxSy. The features at 232.4 and 235.5 eV
indicate the presence of Mo6+
(MoO3) on the surface of the film. With oxidation progression the oxide
components are seen to increase in intensity. The MoOx thickness of < 3 nm is confirmed, which is
consistent with previous data1,2
. In addition, we observe a shift of the Mo 3d peaks from the inner
disulfide to the top oxide layer towards the higher binding energy values that can be attributed to a
stronger n-doping process at the MoOx/MoS2 interface due to more electronegative oxygen, indicating
a relative shift of the Fermi level towards the conductive band edge3
. However, it should be noted that
the interfacial MoOx layer is assumed to reveal p-type semiconductivity because of heavily
chemisorbed oxygen, as discussed in the main text of paper. b, Mo6+
and Mo5+
oxidation-state XPS
profiles of the MoOx/MoS2 sample oxidized at various conditions; the sputtering rate is approximately
0.1 nm/s. We note that the oxidation at 150°C for 3 h reveals a larger Mo5+
/Mo6+
ratio and thus a more
pronounced MoOxSy content with depth showing a less distinct MoOx/MoS2 interface compared to
annealing at higher temperatures (180°C and 200°C for 3 h) and photonic flash oxidation for 600 s,
which is probably caused by a greater oxygen diffusion through the poorly oxidized top layers.
0 30 60 90 120 150
0
20
40
Sputtering time (s)
Relativepeakarea(%)
Mo5+
(MoOx
Sy
)
10
20
30
150o
C
180o
C
200o
C
xenon flash lamp
Mo6+
(MoO3
)
224226228230232234236238240242
Mo5+
3d (MoOx
Sy
)
S 2s
Mo6+
3d (MoO3
)
Mo4+
3d3/2
(MoS2
)
Mo4+
3d5/2
(MoS2
)
Normalizedintensity
10 nm depth
3 nm depth
surface
Binding energy (eV)
ba
© 2014 Macmillan Publishers Limited. All rights reserved.

4. 4 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135
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Figure S3 | Photonic flash oxidation of transition metal dichalcohenides (TMDs). a, Schematics
of the oxidation of TMD film on PEN using a xenon flash lamp tool (UIS-100, Aeromed LLC). As a
result, an ultrathin transition metal oxide (TMO) layer forms on the top of TMD film. The technique is
fast and works at low bulk temperatures making it preferable in high-volume roll-to-roll
manufacturing4,5,6
. The apparatus consists of a power supply, discharge unit, controller, and lamp
housing. A linear xenon flash lamp with an emission spectrum ranging from 200 to 900 nm is placed
in the elliptical reflector (reflectivity of > 98%). A forced air cooling of the lamp and the sample can be
applied in the case of high power operation. The reflector projects an image on the substrate with an
illumination area of 20 × 250 mm. An adjustable table for samples allows tuning the focus line width
and thus changing the light intensity. The setup has an average electric power consumption of
~1000 W with a pulsed peak power of approximately 2.2 MW. A pulse energy is adjustable in the
range of 12 – 108 J, a pulse frequency can be varied from 1 to 50 Hz, and a pulse duration is 50 s.
b, Few-layer MoS2 and WS2 materials absorb the light in the UV-visual range where the xenon flash
lamp emits. The photonic exposure in air causes a local heating of the TMD film facilitating rapid
oxidation of the topmost layers and finally resulting in TMO/TMD heterostructures.
200 400 600 800 1000
MoS2
WS2
Xenon flash lamp
Normalizedabsorbance/emittance
Wavelength (nm)
PEN
TMD
PEN
TMO
Xenon flash lamp
Elliptic reflector
Focus line
ba
© 2014 Macmillan Publishers Limited. All rights reserved.

5. NATURE MATERIALS | www.nature.com/naturematerials 5
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4135
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Figure S4 | I-V characteristics of layered switching devices. a, b, The MoOx/MoS2 and WOx/WS2
heterostructures sandwiched between two screen-printed silver electrodes show a typical bipolar
resistive switching in contrast to a linear I-V curve of non-oxidized MoS2 device (in forward direction
the TE is negatively charged, the sweep rate is 16.5 mV/s, the compliance current is 1 mA). Being
structural analogues and having similar electronic properties, MoOx/MoS2 and WOx/WS2 exhibit an
almost identical I-V behavior. Thus, we show that few-layer TMD-based systems can be used as a
viable way for active materials to enable printable resistive switches. An observed rectifying I-V
orientation suggests an important role of a Schottky junction at the interface of TMO and Ag TE, which
blocks the current in the OFF state (IOFF). A compositional gradient (Mo6+
to Mo4+
) built into the
switching layer supports a resistance memory effect via oxygen vacancy migration under applied
voltage, similar to that previously observed in WO3 devices7,8
. Pre-electroforming is not required since
the insulating oxygen-saturated MoOx interfacial layer with the thickness of less than 3 nm is located
on the oxygen-deficient area with anion vacancies ready to move towards the negatively biased TE.
When a large fraction of applied voltage drops on the resistive Ag/MoOx interface, a virtual anode
naturally propagates towards the cathode along defects and structural imperfections supported by the
low-dimensional nature9
. c, Temperature effect on the AgNW/MoOx/MoS2 resistive switching
performance. The activation energy (EA) of 0.36 ± 0.04 eV extracted from temperature-dependent
measurements of the reverse IOFF at -0.2 V appears to be slightly higher than EA = 0.30 ± 0.02 eV
obtained for MoOx/MoS2 memristors lacking an intermediate AgNW layer (Fig. 2e).
-0.2 -0.1 0.0 0.1 0.2
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
25o
C
40o
C
60o
C
80o
C
Current(A)
Voltage (V)
32 34 36 38 40
-28
-27
-26
-25
ln(IR
/T2
)
1/kT (eV-1
)
EA=0.36 eV
-0.1 0.1-0.2 0.0 0.2
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
Current(A)
Voltage (V)
WOx
/WS2
-0.2 -0.1 0.0 0.1 0.2
-1.0
-0.5
0.0
0.5
1.0
Reset
Set
OFF
Current(mA)
Voltage (V)
MoS2
MoOx
/MoS2
WOx
/WS2
ON
c
a b
© 2014 Macmillan Publishers Limited. All rights reserved.

6. 6 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135
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Figure S5 | Memristive and memcapacitive effects. a, Resistive (RM) and capacitive (CM)
components of the MoOx/MoS2 as a function of AC 10 mV signal frequency in the ON (after +0.2 V
bias) and OFF (after -0.2 V bias) states. Inset shows the Nyquist plot in the OFF state. The equivalent
circuit is represented as a parallel combination of a resistor and a capacitor. b, AgNW/MoOx/MoS2
switches concurrently support memristive and memcapacitive behavior with the same state variables,
which is consistent with previous observations10
. The CM-V and RM-V profiles are extracted from the
impedance measurements with 10 mV 0.5 kHz AC signal superimposed on a continuous DC bias
sweep. Capacitive and resistive switching ratios appear to be 103
and 106
, respectively.
1 10 100 1k 10k 100k 1M
100
1k
10k
100k
1M
10M MoOx
/MoS2
RM
(ON)
Resistance()
Frequency (Hz)
RM
(OFF)
CM
(OFF)
CM
(ON)
1p
10p
100p
1n
10n
Capacitance(F)
0 1 2 3
0
1
2
3-Z"(M)
Z' (M)
1p
10p
100p
1n
10n
-0.1 0.1-0.2 0.0 0.2
10
1k
100k
10M
dwewdwed
deeededed
dedede de xd
CM
(F)
AgNW/MoOx
/MoS2
CM
RM
RM
()
Voltage (V)
ba
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SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4135
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Figure S6 | Multilevel operation and endurance test. a, Multiple states of the resistance recorded
after three pulses of 0.3 V for 10 s with varied compliance currents (IC). The read voltage is 0.01 V.
The resistance values are calculated by Ohm’s law at 1000 s. The AgNW/MoOx/MoS2 device under
investigation is obtained by heat-assisted oxidation at 200⁰C for 10 h. The range of possible resistance
states depends on the Schottky junction height; when the depletion width becomes narrow electron
tunneling occurs reducing the contact resistance. b, Cycling endurance of the AgNW/MoOx/MoS2
switch. ON/OFF switching is programmed by alternating pulses of +0.3 V for 0.6 s and -0.1 V for 1.8 s
(IC = 1 mA).
0 200 400 600 800 1000
10-9
10-8
10-5
10-4
10-3
Ic
=10 mA
Ic
=1 mA
Ic
=100 A
Ic
=10 A
Ic
=5 A
Ic
=1 A
Current(A)
Time (s)
25.5 
123 
614 
1.51 k
3.09 M
13.1 M
0 10000 20000 30000
10-11
10-9
10-7
10-5
10-3
10-1
OFF
ON
Current(A)
Number of cycles
-0.1 V
+0.3 V
0
ba
© 2014 Macmillan Publishers Limited. All rights reserved.

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SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135
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