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j.matlet.2018.08.091

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Accepted Manuscript
Organic non-volatile memory device based on cellulose fibers
Anuja P. Rananavare, Sunil J. Kadam, Subodh V. Prabhu, Sachin S. Chavan,
Prashant V. Anbhule, Tukaram D. Dongale
PII:
DOI:
Reference:
S0167-577X(18)31294-1
https://doi.org/10.1016/j.matlet.2018.08.091
MLBLUE 24802
To appear in:
Materials Letters
Received Date:
Revised Date:
Accepted Date:
16 July 2018
16 August 2018
17 August 2018
Please cite this article as: A.P. Rananavare, S.J. Kadam, S.V. Prabhu, S.S. Chavan, P.V. Anbhule, T.D. Dongale,
Organic non-volatile memory device based on cellulose fibers, Materials Letters (2018), doi: https://doi.org/
10.1016/j.matlet.2018.08.091
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
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Organic non-volatile memory device based on
cellulose fibers
Anuja P. Rananavare a, Sunil J. Kadam b, Subodh V. Prabhu a,
Sachin S. Chavan c, Prashant V. Anbhule d, Tukaram D. Dongale a, †
a Computational
Electronics and Nanoscience Research Laboratory,
School of Nanoscience and Biotechnology, Shivaji University, Kolhapur, India
b
Department of Mechanical Engineering, Bharati Vidyapeeth’s College of Engineering,
Kolhapur, India
c
Department of Mechanical Engineering, Bharati Vidyapeeth’s College of Engineering,
Pune, India
d
Department of Chemistry, Shivaji University, Kolhapur, India
† Corresponding Author's E-mail: [email protected] (T. D. Dongale)
3
Abstract: The present manuscript reports the development of Ag/cellulose fibers/Al
memory
device
using
the
electrospinning
technique.
The
morphological
characterization suggested that the active layer is composed of micro-fibers. The
developed device shows fingerprint pinched hysteresis loop of the memristive device in
I-V plane without any additional electroforming step. An excellent endurance for 6x103
resistive switching cycles with 10x memory window is achieved. Furthermore, the data
retention capability of the developed device is extended for the 3x102 seconds without
any observable degradation in the resistance states. The statistical results suggested
that the high resistance state loosely distributed whereas tight distribution is observed
for low resistance state. The electrical characterization results suggested that the
formation and breaking of Ag conductive filament in the active cellulose fiber layer are
responsible for the bipolar resistive switching effect. Our results suggested that the
cellulose fibers based memristive device is a potential candidate for the organic nonvolatile memory application.
Keywords: Organic memory; Biomaterials; Electrical properties; Cellulose fibers;
Resistive switching; Memristive device.
4
1. Introduction
The memristor is popularly conceived as a fourth fundamental circuit element,
which was predicted by L. Chua in 1971 [1] and experimentally realized by HP
researchers in 2008 [2]. In the recent years, significant attention is given towards the
development of memristor/memristive devices for different applications such as
resistive memory, brain-inspired computing, sensors, analog circuits and nonlinear
dynamics [3]. The functional properties of the memristive devices can be achieved by
properly engineering the active material and interface between the active layer and
electrodes. For the non-volatile resistive random access memory (RRAM) application,
different types of materials were investigated such as oxides, polymers and
biomaterials. In the recent years, biomaterial-based memristive and resistive switching
devices are developed due to its natural advantages such as biodegradability,
biocompatibility and environment-friendliness [4]. One of the biomaterial which
actively investigated for electronic application is the cellulose fiber. The cellulose fibers
are abundant in nature hence end product will be cost-effective. In addition to this,
cellulose fibers have high tensile strength, low thermal expansion coefficient and
excellent flexibility [4]. In the present report, we have developed cellulose fibers based
memristive device and demonstrated the excellent non-volatile resistive switching
properties without additional metal decoration and doping. The reported device works
on low resistive switching voltage (± 1V) and does not require additional
electroforming step. Furthermore, excellent endurance cycles and good data retention
stability is achieved for the present device.
2. Experimental
Cellulose acetate phthalate (CAP), isopropyl alcohol (IPA) and ethyl acetate (EA)
were obtained from Sigma-Aldrich. All chemicals used in the experiment were of
analytical grade and used without purification. The CAP was mixed with the IPA and EA
and the resultant solution was stirred for the 90 minutes. The cellulose fibers were
developed using electrospinning system (Holmarc HO-NFES-040). At the outset, the
prepared solution was loaded into the 30 ml glass syringe and aluminum (Al) foil was
wrapped around the rotating mandrel. The distance between the needle and collector
was kept 15 cm. An approximately 17.5 kV high-voltage direct current was applied
between the needle and drum. Furthermore, the flow rate of the solution was fixed at
5
1.5 mL/h and collector was rotated at a speed of 500 rpm for 4 hours. The developed
cellulose fibers were collected carefully from the collector and dried at room
temperature for 48 h. The Ag paste was carefully applied to the cellulose fibers/Al foil
structure to form the top electrode. The surface morphology of cellulose fibers was
examined by Scanning Electron Microscope (SEM) (JEOL-JSM 6360 A). The electrical
measurements of Ag/cellulose fibers/Al device were recorded using memristor
characterization platform (ArC ONE).
3. Result and discussions
The morphological characterization of cellulose fiber was examined by SEM, as
shown in Fig. 1 (a). The bead with micro-fiber like morphology is observed for the
developed active layer. The bead-like morphology is observed due to the variation in an
electric field, insufficient chain entanglements and surface tension [5]. The average fiber
diameter was calculated using ImageJ software and it was found to be 3.34 µm. The
interconnected micro-fibers provides the excellent charge transport pathways and
support to form the conductive filament for the bipolar resistive switching operation.
The typical device structure and pinched hysteresis current-voltage (I-V) loop are
shown in Fig. 1 (b and c), respectively. The result clearly indicates that the Ag/cellulose
fibers/Al memristive device shows bipolar resistive switching characteristics with low
resistive switching voltage (± 1V). This characteristic is achieved without additional
electroforming step. It is observed that the developed device required symmetric
resistive switching voltage and resultant I-V characteristics possess quasi-symmetric
pinched hysteresis I-V loop. The direction of resistive switching is indicated by arrows
and voltage sweeping was changed as 0V⟶ +1V⟶ 0V⟶ -1V⟶ 0V. Initially, the device
is in the high resistance state (HRS) and the flow of the current through the device is
very low. The current reaches to its maximum value at a SET voltage (+ 1V) and this
state is generally known as low resistance state (LRS). The current of the device is
gradually decreased as the sweeping direction changed to +1V to 0V. Similar behavior is
also observed in the negative bias and corresponding state-changing voltage is termed
as RESET voltage (- 1V).
The non-volatile memory properties of Ag/cellulose fibers/Ag memristive device
was investigated by the endurance and retention tests, as shown in Fig. 2 (a and b). The
developed memory device shows excellent switching endurance for 6x103 cycles
6
without any observable degradation in the resistances states at 0.25 V read voltage. The
memory window is a ratio of HRS and LRS and it decides the resolution between two
resistance states. In the present case, 10x memory window is observed which can be
useful for the practical applications [6]. The data retention capability of the memory
device can be understood by the measuring the LRS and HRS states at every second for
an extended period of time. In the present case, the developed device shows data
retention capability for 3x102 seconds without any observable degradation in the
resistance states. In view of this, cellulose fibers based memristive device shows good
reliability in terms of endurance and retention.
It is observed that the LRS and HRS do not show the same resistance during the
cycle to cycle operation. In order to quantify the variation in the resistance during
resistive switching, we have calculated the cumulative probability of LRS and HRS, as
shown in Fig. 3 (a). It is observed that the LRS is tightly distributed whereas, HRS shows
the quite loose distribution of the measured resistance during the cycle to cycle
operations. The statistical analysis suggested that the mean values (µ) of LRS and HRS
are 13.26 KΩ and 144.46 KΩ, respectively. The standard deviation () of LRS and HRS
are found to be 76.96 Ω and 6.45 KΩ, respectively. Furthermore, the coefficient of
variation (/µ) is found to be 0.58 % and 4.46 % for LRS and HRS, respectively. The
descriptive statistics results clearly suggested that the HRS is loosely distributed
whereas, tight distribution is observed for LRS during the cycle to cycle operations. The
observed non-uniformity in the HRS values is may be due to the stochastic breaking of
the conductive filament and interface effects [7].
It is observed that the current of the device abruptly increases and decreases at
SET and RESET voltages, respectively. Furthermore, two distinct resistive switching
states are clearly observed during endurance and retention measurements. It is wellknown fact that the formation and breaking of the conductive filament are responsible
for the abrupt transition between two resistive switching states. By considering the
above facts and electrical measurements results, the possible bipolar resistive
mechanism of the Ag/cellulose fibers/Al memristive device is shown in Fig. 3 (b). The
developed device is composed of Ag/cellulose fibers/Al layered structure. During the
electrical measurements, the top electrode was biased and the bottom electrode was
grounded. When a positive voltage is applied to the top electrode with respect to the
bottom electrode, Ag atoms are ionized near the top electrode and they are a drift
7
towards the bottom electrode. When the magnitude of the applied voltage (VSET)
reaches to its sufficient value, Ag ions are reduced to neutral Ag atoms and form a
conducting Ag filament in the active layer (Ag⟶ Ag+ + e-). During the negative bias,
reset voltage break the conductive filament electrochemically and device undergoes in
the HRS (Ag+ + e- ⟶ Ag). In view of this, formation and breaking of Ag conductive
filament responsible for the bipolar resistive switching effect in the Ag/cellulose
fibers/Al memristive device.
4. Conclusions
In conclusion, we have successfully developed Ag/cellulose fibers/Al memory
device using electrospinning system. The bead with micro-fiber like morphology is
observed for the cellulose fibers layer. The typical pinched hysteresis I-V loop is clearly
observed for the developed device, which is fingerprint characteristics of the
memristive device. The result clearly indicates that the Ag/cellulose fibers/Al
memristive device shows bipolar resistive switching characteristics with low resistive
switching voltage (± 1V). The developed memory device shows excellent switching
endurance for 6x103 cycles with 10x memory window at 0.25 V read voltage.
Furthermore, the developed device shows data retention capability for 3x102 seconds
without any observable degradation in the resistance states. The descriptive statistics
such as mean, standard deviation and coefficient of variation suggested the HRS is
loosely distributed whereas tight distribution is observed for LRS during the cycle to
cycle operations. The electrical results suggested that the formation and breaking of Ag
conductive filament in the active cellulose fiber layer are responsible for the bipolar
resistive switching effect. In view of this, cellulose fibers based memristive device
shows good reliability in terms of endurance and retention and can be useful for the
development of organic non-volatile memory devices for RRAM application.
Acknowledgments: One of the author T. D. Dongale would like to thank the Shivaji
University, Kolhapur for the financial assistance under the 'Research Initiation Scheme'.
8
References
(1) Chua L. Memristor-the missing circuit element. IEEE Trans. Circuit Theory
1971; 18:507-519.
(2) Strukov DB, Snider GS, Stewart DR, Williams RS. The missing memristor found.
Nature 2008; 453:80-83.
(3) Pershin YV & Di Ventra M. Memory effects in complex materials and nanoscale
systems. Adv. Phys. 2011; 60:145-227.
(4) Nagashima K, Koga H, Celano U, Zhuge F, Kanai M, Rahong S, Meng G, He Y, De
Boeck J, Jurczak M, Vandervorst W. Cellulose nanofiber paper as an ultra flexible
nonvolatile memory. Sci. Rep. 2014; 4: 5532.
(5) Pillay V, Dott C, Choonara YE, Tyagi C, Tomar L, Kumar P, du Toit LC, Ndesendo VM.
A Review of the Effect of Processing Variables on the Fabrication of Electrospun
Nanofibers for Drug Delivery Applications. J. Nanomater. 2013; 2013:1-22.
(6) Dongale TD, Khot KV, Mohite SV, Desai ND, Shinde SS, Patil VL, Vanalkar SA,
Moholkar AV, Rajpure KY, Bhosale PN, Patil PS. Effect of write voltage and
frequency on the reliability aspects of Memristor-based RRAM, Int. Nano Lett. 2017;
7:209-216.
(7) Raghavan N. Performance and reliability trade-offs for high-κ RRAM. Microelectron.
Reliab. 2014; 54:2253-2257.
9
+ V -
A
Ag
Cellulose Fibers
Al
10 um
-8
Current (A)
4.0x10
-8
2.0x10
0.0
-8
-2.0x10
-8
-4.0x10
-8
-6.0x10
-1.2 -0.8 -0.4
0.0
0.4
0.8
1.2
Voltage (V)
Fig. 1 (a) SEM micrograph of the cellulose fibers prepared using Electrospinning system. (b)
Typical device structure of developed organic memory device. (c) I-V characteristics of the
Ag/cellulose fibers/Al memory device.
10
5
10
Read @ 0.25 V
~ 10x Memory Window
4
10
0
2000
4000
6000
Resistance ()
Resistance ()
LRS
HRS
HRS
5
10
4
10
LRS
0
Endurance Cycles (#)
50 100 150 200 250 300
Retention Time (s)
Cumulative Probability (%)
Fig. 2 (a) Endurance and (b) retention memory properties of Ag/cellulose fibers/Al memory
device.
100
Bipolar Resistive
Switching Mechanism
ON/SET State OFF/RESET State
Ag (-)
Ag (+)
LRS
HRS
80
60
40
20
Oxidized
Reduced
0
12.0k
14.0k
140.0k
160.0k
Resistance ()
Al (-)
Al (+)
Fig. 3 (a) Cumulative probability plot of LRS and HRS. (b) The possible bipolar resistive
switching mechanism of the Ag/cellulose fibers/Al memory device.
Graphical Abstract
11
ON/SET State
Ag (+)
-8
Reduced
-8
2.0x10
Al (-)
0.0
-8
-2.0x10
Resistance ()
Current (A)
4.0x10
OFF/RESET State
Ag (-)
-8
-4.0x10
Oxidized
LRS
HRS
5
10
Read @ 0.25 V
~ 10x Memory Window
4
10
0
-8
-6.0x10
2000
4000
6000
Endurance Cycles (#)
Al (+)
-1.2 -0.8 -0.4
0.0
0.4
0.8
Voltage (V)
Highlights

Demonstration of low-cost organic (cellulose fiber) non-volatile memory device

Excellent endurance for 6x103 resistive switching cycles with 10x memory window

Data retention is extended for the 3x102 seconds without any degradation

Resistive switching is due to the formation and breaking of Ag filament
12
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