The majority of the research work in the area of resistive switching has been carried out with the help of organic, inorganic and hybrid materials. Only a few reports investigate resistive switching properties of ionic liquid and soft materials. In this report, we have synthesized ZnO nanorods (NRs) and Bmim(Br) ionic liquid using simple and low-temperature chemical route i.e., hydrothermal and reflux method, respectively. The structural study of ZnO NRs indicates that the formation of hexagonal crystal structure,
evident from the XRD pattern. The FESEM image suggested the formation of nanorods like morphology. The effect of dispersed ZnO NRs on the resistive switching behavior of Bmim(Br) ionic liquid was studied. The study explains the change in switching behavior by dispersing the different concentrations of ZnO NRs in ionic liquid. The results demonstrated that the dispersed ZnO NRs in ionic liquid plays a vital role and will be a potential active switching material for resistive switching applications

Dongale, Tukaram D.

Kamat, Rajanish K.

Khairnar, Nikita A.

Kim, Deok-kee

Nirmale, Sunil S.

Patil, Aditya A.

Rane, Shreeya H.

Shinde, Sandeep P.

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 12 No 2, 02003(4pp) (2020) Том 12 № 2, 02003(4cc) (2020)   2077-6772/2020/12(2)02003(4) 02003-1  2020 Sumy State University Resistive Switching Property of Bmim(Br) Ionic Liquid  under the Influence of ZnO Nanorods  Nikita A. Khairnar1, Aditya A. Patil1, Shreeya H. Rane1, Sunil S. Nirmale1, Sandeep P. Shinde2,  Rajanish K. Kamat3, Tukaram D. Dongale1,*, Deok-kee Kim4,†  1 Computational Electronics and Nanoscience Research Laboratory, School of Nanoscience and Biotechnology, Shivaji University, 416004 Kolhapur, India 2 Department of Chemistry, Sathaye College, 400057 Mumbai, India 3 Department of Electronics, Shivaji University, 416004 Kolhapur, India 4 Department of Electrical Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, 05006  Seoul, Republic of Korea  (Received 15 February 2020; revised manuscript received 11 April 2020; published online 25 April 2020)  The majority of the research work in the area of resistive switching has been carried out with the help of organic, inorganic and hybrid materials. Only a few reports investigate resistive switching properties of ionic liquid and soft materials. In this report, we have synthesized ZnO nanorods (NRs) and Bmim(Br)  ionic liquid using simple and low-temperature chemical route i.e., hydrothermal and reflux method,  respectively. The structural study of ZnO NRs indicates that the formation of hexagonal crystal structure, evident from the XRD pattern. The FESEM image suggested the formation of nanorods like morphology. The effect of dispersed ZnO NRs on the resistive switching behavior of Bmim(Br) ionic liquid was studied. The study explains the change in switching behavior by dispersing the different concentrations of ZnO NRs in ionic liquid. The results demonstrated that the dispersed ZnO NRs in ionic liquid plays a vital role and will be a potential active switching material for resistive switching applications.  Keywords: ZnO, Nanorods, Ionic liquid, Chemical route, Resistive switching, Memristive effect.  DOI: 10.21272/jnep.12(2).02003 PACS numbers: 61.46.Km, 78.30.cd                                                                   * tdd.snst@unishivaji.ac.in † deokkeekim@sejong.ac.kr 1. INTRODUCTION  The search for an excellent non-volatile memory de-vice is currently pursued by academia and industry. Many potential candidates are being researched and developed in recent years that included but not limited to the phase change memory, flash memory, magneto-resistive memory, ferroelectric memory, and resistive memory. Among them, resistive memory is one of the preferred candidates for future memory storage appli-cations. The resistive memory depends on the re-sistance change under the influence of electric stress; therefore, it promises many advantages over other counterparts such as low power consumption, high speed, and high density [1-2]. One of the device level artifacts of the resistive memory is a memristor or memristive device [3-4]. Apart from non-volatile memory, memristive devices also used for the develop-ment of synaptic devices [5] and sensors [6]. Given this, much research is currently underway to explore the memristive nature of various materials.  In order to find efficient memristive devices, various kinds of solid-state materials are being tested such as oxide [7], ferrite [8], biomaterials [9], and polymers [10]. On the other hand, few liquid-based systems also showed the memristive properties [11]. In the case of solid-state materials, zinc oxide (ZnO) is a propitious material for the memristive device due to its unique physical and chemical features. ZnO possesses excel-lent mechanical and thermal properties; therefore, it is an attractive material for electronic devices [12]. On account of the liquid system, the ionic liquid (IL) is an exciting material and possess active electrical property, owing to inherent ions and ephemeral ion pairs [13]. Furthermore, ILs are regarded as a ‘green solvent’ and find many applications in the industry due to the excel-lent chemical and thermal stability [13]. In this contribution, we have synthesized ZnO na-norods (NRs) using the hydrothermal method, and the reflux method was employed for the synthesis of Bmim (Br) IL. The X-ray diffraction data (XRD) suggested the formation of a hexagonal crystal structure of the ZnO. We have dispersed the ZnO NRs in the Bmim(Br) IL and studied the resistive switching behavior of the ZnO NRs-Bmim(Br) IL system. For this, different concentra-tions of ZnO NRs dispersed in IL. The results indicate that the dispersed ZnO NRs in IL play an important role and show the memristive properties.  2. EXPERIMENTAL DETAILS  2.1 Materials  All the chemicals utilized in this work are analytical grade with high purity. Toluene, n-bromobutane,  1-methylimidazole, ethyl acetate, zinc acetate, ammo-nia solution, and deionized water were used for the synthesis of Bmim(Br) ionic liquid and ZnO NRs. All chemicals were used as it is, without any purification.  2.2 Synthesis of 1-butyl-3-methylimidazolium Bromide [Bmim][Br]  The synthesis of Bmim(Br) IL was carried out by a  NIKITA A. KHAIRNAR, ADITYA A. PATIL, SHREEYA H. RANE, ET AL. J. NANO- ELECTRON. PHYS. 12, 02003 (2020)   02003-2 simple chemical route, as reported in the ref. [11]. In the typical process, an equimolar 1-methylimidazole and n-bromobutane were taken and mixed with tolu-ene. The blend was refluxed at 80 °C for 48 h, freeze for 3 h and decanted the supernatant liquid from mixture. In addition to this, toluene traces from IL was removed by washing with ethyl acetate. The prepared Bmim(Br) IL was kept in the oven (low temperature) for 48 h to remove traces of ethyl acetate.   2.3 Synthesis of ZnO NRs  The hydrothermal method was used for the synthesis of ZnO NRs by varying growth temperature. At the out-set, 1.09 g of zinc acetate was liquefied in 50 ml of dis-tilled water, and ammonia was added dropwise under constant stirring until the formation of a precipitate. The beaker containing the end solution was kept in the auto-clave at 90 for 2 h. After the reaction, a white solid product was collected and centrifuged at 9000 rpm for 15 min. Finally, it was annealed at 400 for 2 h. On a similar line, ZnO NRs were developed at various synthe-sis temperatures such as 100, 110 and 120.  2.4 Dispersions of ZnO NRs in Ionic Liquid and Development of Devices  Dispersion of ZnO NRs in the Bmim(Br) IL was car-ried out by using an ultrasonic treatment. For the pre-sent study, different concentrations of ZnO NRs such as 0.05, 0.1, 0.5 and 1 wt. % were used. In the typical dis-persion process, the desired amount of ZnO NRs and ionic liquid were inserted in a laboratory-grade tube. Furthermore, tubes suspended in the ultrasonic bath and treated for 1 hour at 80 W. Fig. 1 depicts the device assembly and experimental setup. We have followed the methodology reported in the ref. [11]. Here we have used symmetric thick copper electrodes as an anode and cathode (diameter: ~2 mm). The ArC ONE system was employed for the electrical measurements of the ZnO NRs-Bmim(Br) IL devices.     Fig. 1 – Device structure and measurement setup of the ZnO NRs-Bmim(Br) IL memristive devices  3. RESULTS AND DISCUSSION  The FESEM (MIRA3, TESCAN) was employed to investigate the morphology of the synthesized ZnO at 110 temperature. The low and high magnified FESEM images suggested that the well-ordered ZnO NRs were produced by the hydrothermal synthesis technique, as shown in Fig. 2a-b. The structural properties of the ZnO NRs were confirmed by XRD (D2 phaser, Bruker). Fig. 3a-d represents the XRD spectra of the synthesized ZnO NRs. All characteristic peaks can be indexed to  (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0), (1 0 3) and (1 1 2) diffraction planes and assigned to the 31.75, 34.40, 36.23, 47.53, 56.57, 62.85 and 67.94 two theta an-gle. The intense peak of (1 0 1) suggested the formation of the hexagonal wurtzite structure. The ZnO NRs syn-thesized at 90, 100, 110 and 120 shows average crys-tallite size equals to the 38.56, 34.87, 54.79 and 48.64 nm, respectively. The results suggested that the ZnO NRs synthesized at 110 °C temperature shows better morphological and structural properties.    Fig. 2 – Low (a) and high magnification (b) FESEM images of the synthesized ZnO at 110 C temperature  10 20 30 40 50 60 70 80 90   2(degree) 90 C Intensity (a.u.)  100 C   110 C    120 C(110)(100)(101)(002)(102)(112)(103)10 20 30 40 50 60 70 80 90   2(degree) 90 C Intensity (a.u.)  100 C   110 C    120 C(110)(100)(101)(002)(102)(112)(103)   Intensity (a.u.)     (101)10 20 30 40 50 60 70 8 90   2(degree) 90 C Intensity (a.u.)  100 C   110 C    120 C(110)(100)(101)(002)(102)(112)(103)10 20 30 40 50 60 70 80 90   2(degree) 90 C Intensity (a.u.)  100 C   11    120 C(110)(100)(101)(002)(102)(112)(103)10 20 30 40 50 60 70 80 90   2(degree) 9   Intensity (a.u.)  10    1    2  (110)(100)(101)(002)(102)(112)(103)(a) (b)(c)(d)(100)(002)(101)(102)(110)(103)(112) (100)(002)(101)(102)(110)(103)(112)(100)(002)(101)(102)(110)(103)(112)Intensity (a.u.)  Fig. 3 – XRD spectra of the synthesized ZnO NRs at different temperature such as 90 (a), 100 (b), 110 (c), and 120 (d)   To understand the memristive switching effect within the device, the hysteresis loop in the current-voltage (I-V) plane is one of the critical criteria. In the present case, we have developed ZnO NRs-Bmim(Br) IL devices in the dis-crete form and investigated their memristive switching effects. In order to examine the ZnO NRs concentration effect on the memristive property of the Bmim(Br) IL, we have dispersed different concentrations of ZnO NRs in the Bmim(Br) IL such as 0.05, 0.1, 0.5 and 1 wt. %. Fig. 4a-d represents the ZnO NRs concentration-dependent I-V characteristics of the Bmim(Br) IL devic-es. For each concentration study, four types of ZnO NRs, synthesized at different temperatures such as 90, 100, 110, and 120 were used. All devices show a hysteresis loop in the I-V plane along with non-zero crossing prop-erty. This suggested that the developed ZnO NRs-Bmim(Br) IL devices display the memristive switching effect [11, 14-15]. For all concentrations, the IL device based on 90 synthesized ZnO NRs shows poor memris-tive switching property than other devices. In the pre-sent case, the IL device based on 110 synthesized ZnO NRs shows good memristive switching property than other devices. On the other hand, the IL device based on 100 and 120 synthesized ZnO NRs shows moderate memristive switching property than other counterparts. RESISTIVE SWITCHING PROPERTY OF BMIM(BR) IONIC LIQUID… J. NANO- ELECTRON. PHYS. 12, 02003 (2020)   02003-3 -1.0 -0.5 0.0 0.5 1.0-1.0x10-3-5.0x10-40.05.0x10-41.0x10-3Current (A)Voltage (V) 90C 100C 110C 120C  -1.0 -0.5 0.0 0.5 1.0-1.0x10-3-5.0x10-40.05.0x10-41.0x10-3Voltage (V) 90C 100C 110C 120CCurrent (A)  -1.0 -0.5 0.0 0.5 1.0-1.0x10-3-5.0x10-40.05.0x10-41.0x10-3Current (A)Voltage (V) 90C 100C 110C 120C  -1.0 -0.5 0.0 0.5 1.0-1.0x10-3-5.0x10-40.05.0x10-41.0x10-3Current (A)Voltage (V) 90C 100C 110C 120C  (a) (b)(c) (d)  Fig. 4 – I-V characteristics of the ZnO NRs-Bmim(Br) IL devices. Various concentrations of ZnO NRs dispersed in the Bmim(Br) IL such as 0.05 wt. % (a), 0.1 wt. % (b), 0.5 wt. % (c), and 1 wt. % (d)  The hysteresis area is one of the crucial properties the memristive devices. Fig. 5a represents the concen-tration and synthesis temperature-dependent hystere-sis area of ZnO NRs-Bmim(Br) IL memristive devices. It is noticed that, as the concentration of the dispersed ZnO NRs in the IL increases, the hysteresis area tends to increases for 90 synthesized ZnO NRs. For other cases, the correlation of concentration of the dispersed ZnO NRs in the IL and the hysteresis area was not observed. However, ZnO NRs synthesized at 100, 110 and 120 show higher memristive hysteresis than 90 synthesized ZnO NRs. The 110 synthesized ZnO NRs show a good memristive hysteresis area than other devices. In particular, 0.1 wt. % (at 110) ZnO NRs shows a good memristive hysteresis area than other devices. The endurance was measured to understand cyclic switching of the ZnO NRs-Bmim(Br) IL memris-tive devices (Fig. 5b). The bi-level switching from low resistance state (LRS) to high resistance state (HRS) and vice versa were detected for all devices. Further-more, good endurance switching over 103 cycles were observed for all devices, suggesting the good reliability of the device. Because of this, developed ZnO NRs-Bmim(Br) IL-based discrete memristive devices can be useful for the various applications.  0 200 400 600 800 10006008001000120014001600180020002200 HRS-0.05 wt.%  LRS-0.05 wt.% HRS-0.1 wt.%    LRS-0.1 wt.% HRS-0.5 wt.%    LRS-0.5 wt.% HRS-1 wt.%       LRS-1 wt.%Resistance ()Switching Cycles (#)0.0 0.2 0.4 0.6 0.8 1.08.0x10-41.0x10-31.2x10-31.4x10-31.6x10-3Hysteresis Area (W)Concentration of ZnO dispersed in IL (wt. %) 90 C 100 C 110 C 120 C  (a) (b)  Fig. 5 – Concentration of ZnO NRs dependent a memristive hysteresis area (a) and endurance property (b) of 110 synthe-sized ZnO NRs-Bmim(Br) IL memristive devices  4. CONCLUSION  The ZnO NRs and Bmim(Br) ionic liquid were syn-thesized by using simple chemical routes i.e. hydro-thermal and reflux method, respectively. In this work, ZnO NRs were developed at various synthesis tempera-tures such as 90, 100, 110 and 120 C. Furthermore, different concentration ZnO NRs such as 0.05, 0.1, 0.5 and 1 wt. % were dispersed in the IL and investigated their memristive switching property. The XRD spectra suggested the formation of a hexagonal crystal struc-ture. The FESEM image suggested the formation of nanorods like morphology. The effect of dispersed ZnO NRs on the resistive switching behavior of Bmim(Br) ionic liquid was studied. The hysteresis loop along with non-zero crossing property, was observed for all the memristive devices. In the present case, 110 C synthe-sized ZnO NRs with 0.1 wt. % shows good memristive switching property than other devices. The endurance test suggested that all devices show bi-level switching from LRS to HRS and vice versa. Furthermore, good endurance switching over 103 cycles were observed for all devices, suggesting the good reliability of the devel-oped devices.  ACKNOWLEDGMENTS  This study was supported by the Basic research program (2016R1D1A1B01009537) through the Na-tional Research Foundation (NRF) of Korea and by the MOTIE (Ministry of Trade, Industry & Energy (10080581) and KSRC (Korea Semiconductor Research  Consortium) support program for the development of the future semiconductor device.    NIKITA A. KHAIRNAR, ADITYA A. PATIL, SHREEYA H. RANE, ET AL. J. NANO- ELECTRON. PHYS. 12, 02003 (2020)   02003-4 REFERENCES  1. S.H. Jo, K.H. Kim, W. Lu, Nano Lett. 9, 870 (2009). 2. M.D. Pickett, D.B. Strukov, J.L. Borghetti, J.J. Yang, G.S. Snider, D.R. Stewart, R.S. Williams, J. Appl. Phys. 106, 074508 (2009). 3. V.L. Patil, A.A. Patil, S.V. Patil, N.A. Khairnar, N.L. Tarwal, S.A. Vanalakar, R.N. Bulakhe, I. In, P.S. Patil, T.D. Dongale, Mater. Sci. Semicond. Process. 106, 104769 (2020). 4. K.K. Pawar, D.V. Desai, S.M. Bodake, H.S. Patil, S.M. More, A.S. Nimbalkar, S.S. Mali, C.K. Hong, S. Kim, P.S. Patil, T.D. Dongale, J. Phys. D: Appl. Phys. 52, 175306 (2019). 5. S.S. More, P.A. Patil, K.D. Kadam, H.S. Patil, S.L. Patil, A.V. Pawar, S.S. Kanapally, D.V. Desai, S.M. Bodake, R.K. Kamat, S. Kim, Result. Phys. 12, 1946 (2019). 6. A.V. Pawar, S.S. Kanapally, K.D. Kadam, S.L. Patil, V.S. Dongle, S.A. Jadhav, S. Kim, T.D. Dongale, J. Mater. Sci.: Mater. Electron. 30, 11383 (2019). 7. S. Pi, C. Li, H. Jiang, W. Xia, H. Xin, J.J. Yang, Q. Xia, Nat. Nanotechnol. 14, 35 (2019). 8. N.M. Samardžić, B. Bajac, J. Bajić, E. Đurđić, B. Miljević, V.V. Srdić, G.M. Stojanović, Microelectron. Eng. 187, 139 (2018). 9. A.P. Rananavare, S.J. Kadam, S.V. Prabhu, S.S. Chavan, P.V. Anbhule, T.D. Dongale, Mater. Lett. 232, 99 (2018). 10. Y. Chen, G. Liu, C. Wang, W. Zhang, R.W. Li, L. Wang, Mater. Horiz. 1, 489 (2014). 11. M.Y. Chougale, S.R. Patil, S.P. Shinde, S.S. Khot, A.A. Patil, A.C. Khot, S.S. Chougule, C.K. Volos, S. Kim, T.D. Dongale, Ionics 25, 5575 (2019). 12. C.B. Ong, L.Y. Ng, A.W. Mohammad, Renew. Sustainable Energ. Rev. 81, 536 (2018). 13. A. Abo-Hamad, M.A. AlSaadi, M. Hayyan, I. Juneidi, M.A. Hashim, Electrochim. Acta 193, 321 (2016). 14. S. Patil, M. Chougale, T. Rane, S. Khot, A. Patil, O. Bagal, S. Jadhav, A. Sheikh, S. Kim, T. Dongale, Electronics 7, 445 (2018). 15. T.S. Bhat, A.S. Kalekar, D.S. Dalavi, C.C. Revadekar, A.C. Khot, T.D. Dongale, P.S. Patil, J. Mater. Sci.: Mater. Electron. 30, 17725 (2019).  

Resistive Switching Property of Bmim(Br) Ionic Liquid under the Influence of ZnO Nanorods

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 12 No 2, 02003(4pp) (2020) Том 12 № 2, 02003(4cc) (2020) 
 
 
2077-6772/2020/12(2)02003(4) 02003-1  2020 Sumy State University 
Resistive Switching Property of Bmim(Br) Ionic Liquid  
under the Influence of ZnO Nanorods 
 
Nikita A. Khairnar1, Aditya A. Patil1, Shreeya H. Rane1, Sunil S. Nirmale1, Sandeep P. Shinde2,  
Rajanish K. Kamat3, Tukaram D. Dongale1,*, Deok-kee Kim4,† 
 
1 Computational Electronics and Nanoscience Research Laboratory, School of Nanoscience and Biotechnology, 
Shivaji University, 416004 Kolhapur, India 
2 Department of Chemistry, Sathaye College, 400057 Mumbai, India 
3 Department of Electronics, Shivaji University, 416004 Kolhapur, India 
4 Department of Electrical Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, 05006  
Seoul, Republic of Korea 
 
(Received 15 February 2020; revised manuscript received 11 April 2020; published online 25 April 2020) 
 
The majority of the research work in the area of resistive switching has been carried out with the help 
of organic, inorganic and hybrid materials. Only a few reports investigate resistive switching properties of 
ionic liquid and soft materials. In this report, we have synthesized ZnO nanorods (NRs) and Bmim(Br)  
ionic liquid using simple and low-temperature chemical route i.e., hydrothermal and reflux method,  
respectively. The structural study of ZnO NRs indicates that the formation of hexagonal crystal structure, 
evident from the XRD pattern. The FESEM image suggested the formation of nanorods like morphology. 
The effect of dispersed ZnO NRs on the resistive switching behavior of Bmim(Br) ionic liquid was studied. 
The study explains the change in switching behavior by dispersing the different concentrations of ZnO NRs 
in ionic liquid. The results demonstrated that the dispersed ZnO NRs in ionic liquid plays a vital role and 
will be a potential active switching material for resistive switching applications. 
 
Keywords: ZnO, Nanorods, Ionic liquid, Chemical route, Resistive switching, Memristive effect. 
 
DOI: 10.21272/jnep.12(2).02003 PACS numbers: 61.46.Km, 78.30.cd 
 
 
                                                                
* tdd.snst@unishivaji.ac.in 
† deokkeekim@sejong.ac.kr 
1. INTRODUCTION 
 
The search for an excellent non-volatile memory de-
vice is currently pursued by academia and industry. 
Many potential candidates are being researched and 
developed in recent years that included but not limited 
to the phase change memory, flash memory, magneto-
resistive memory, ferroelectric memory, and resistive 
memory. Among them, resistive memory is one of the 
preferred candidates for future memory storage appli-
cations. The resistive memory depends on the re-
sistance change under the influence of electric stress; 
therefore, it promises many advantages over other 
counterparts such as low power consumption, high 
speed, and high density [1-2]. One of the device level 
artifacts of the resistive memory is a memristor or 
memristive device [3-4]. Apart from non-volatile 
memory, memristive devices also used for the develop-
ment of synaptic devices [5] and sensors [6]. Given this, 
much research is currently underway to explore the 
memristive nature of various materials.  
In order to find efficient memristive devices, various 
kinds of solid-state materials are being tested such as 
oxide [7], ferrite [8], biomaterials [9], and polymers 
[10]. On the other hand, few liquid-based systems also 
showed the memristive properties [11]. In the case of 
solid-state materials, zinc oxide (ZnO) is a propitious 
material for the memristive device due to its unique 
physical and chemical features. ZnO possesses excel-
lent mechanical and thermal properties; therefore, it is 
an attractive material for electronic devices [12]. On 
account of the liquid system, the ionic liquid (IL) is an 
exciting material and possess active electrical property, 
owing to inherent ions and ephemeral ion pairs [13]. 
Furthermore, ILs are regarded as a ‘green solvent’ and 
find many applications in the industry due to the excel-
lent chemical and thermal stability [13]. 
In this contribution, we have synthesized ZnO na-
norods (NRs) using the hydrothermal method, and the 
reflux method was employed for the synthesis of Bmim 
(Br) IL. The X-ray diffraction data (XRD) suggested the 
formation of a hexagonal crystal structure of the ZnO. 
We have dispersed the ZnO NRs in the Bmim(Br) IL 
and studied the resistive switching behavior of the ZnO 
NRs-Bmim(Br) IL system. For this, different concentra-
tions of ZnO NRs dispersed in IL. The results indicate 
that the dispersed ZnO NRs in IL play an important 
role and show the memristive properties. 
 
2. EXPERIMENTAL DETAILS 
 
2.1 Materials 
 
All the chemicals utilized in this work are analytical 
grade with high purity. Toluene, n-bromobutane,  
1-methylimidazole, ethyl acetate, zinc acetate, ammo-
nia solution, and deionized water were used for the 
synthesis of Bmim(Br) ionic liquid and ZnO NRs. All 
chemicals were used as it is, without any purification. 
 
2.2 Synthesis of 1-butyl-3-methylimidazolium 
Bromide [Bmim][Br] 
 
The synthesis of Bmim(Br) IL was carried out by a 
 NIKITA A. KHAIRNAR, ADITYA A. PATIL, SHREEYA H. RANE, ET AL. J. NANO- ELECTRON. PHYS. 12, 02003 (2020) 
 
 
02003-2 
simple chemical route, as reported in the ref. [11]. In 
the typical process, an equimolar 1-methylimidazole 
and n-bromobutane were taken and mixed with tolu-
ene. The blend was refluxed at 80 °C for 48 h, freeze for 
3 h and decanted the supernatant liquid from mixture. 
In addition to this, toluene traces from IL was removed 
by washing with ethyl acetate. The prepared Bmim(Br) 
IL was kept in the oven (low temperature) for 48 h to 
remove traces of ethyl acetate.  
 
2.3 Synthesis of ZnO NRs 
 
The hydrothermal method was used for the synthesis 
of ZnO NRs by varying growth temperature. At the out-
set, 1.09 g of zinc acetate was liquefied in 50 ml of dis-
tilled water, and ammonia was added dropwise under 
constant stirring until the formation of a precipitate. The 
beaker containing the end solution was kept in the auto-
clave at 90 for 2 h. After the reaction, a white solid 
product was collected and centrifuged at 9000 rpm for 
15 min. Finally, it was annealed at 400 for 2 h. On a 
similar line, ZnO NRs were developed at various synthe-
sis temperatures such as 100, 110 and 120. 
 
2.4 Dispersions of ZnO NRs in Ionic Liquid and 
Development of Devices 
 
Dispersion of ZnO NRs in the Bmim(Br) IL was car-
ried out by using an ultrasonic treatment. For the pre-
sent study, different concentrations of ZnO NRs such as 
0.05, 0.1, 0.5 and 1 wt. % were used. In the typical dis-
persion process, the desired amount of ZnO NRs and 
ionic liquid were inserted in a laboratory-grade tube. 
Furthermore, tubes suspended in the ultrasonic bath 
and treated for 1 hour at 80 W. Fig. 1 depicts the device 
assembly and experimental setup. We have followed 
the methodology reported in the ref. [11]. Here we have 
used symmetric thick copper electrodes as an anode 
and cathode (diameter: ~2 mm). The ArC ONE system 
was employed for the electrical measurements of the 
ZnO NRs-Bmim(Br) IL devices.  
 
 
 
Fig. 1 – Device structure and measurement setup of the ZnO 
NRs-Bmim(Br) IL memristive devices 
 
3. RESULTS AND DISCUSSION 
 
The FESEM (MIRA3, TESCAN) was employed to 
investigate the morphology of the synthesized ZnO at 
110 temperature. The low and high magnified FESEM 
images suggested that the well-ordered ZnO NRs were 
produced by the hydrothermal synthesis technique, as 
shown in Fig. 2a-b. The structural properties of the 
ZnO NRs were confirmed by XRD (D2 phaser, Bruker). 
Fig. 3a-d represents the XRD spectra of the synthesized 
ZnO NRs. All characteristic peaks can be indexed to  
(1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0), (1 0 3) and (1 1 2) 
diffraction planes and assigned to the 31.75, 34.40, 
36.23, 47.53, 56.57, 62.85 and 67.94 two theta an-
gle. The intense peak of (1 0 1) suggested the formation 
of the hexagonal wurtzite structure. The ZnO NRs syn-
thesized at 90, 100, 110 and 120 shows average crys-
tallite size equals to the 38.56, 34.87, 54.79 and 48.64 
nm, respectively. The results suggested that the ZnO 
NRs synthesized at 110 °C temperature shows better 
morphological and structural properties. 
 
 
 
Fig. 2 – Low (a) and high magnification (b) FESEM images of 
the synthesized ZnO at 110 C temperature 
 
10 20 30 40 50 60 70 80 90
  
 2(degree)
 90 C
 In
te
n
s
it
y
 (
a
.u
.)
 
 100 C
  
 110 C
 
 
 
 120 C
(1
1
0
)
(1
0
0
)
(1
0
1
)
(0
0
2
)
(1
0
2
)
(1
1
2
)
(1
0
3
)
10 20 30 40 50 60 70 80 90
  
 2(degree)
 90 C
 In
te
n
s
it
y
 (
a
.u
.)
 
 100 C
  
 110 C
 
 
 
 120 C
(1
1
0
)
(1
0
0
)
(1
0
1
)
(0
0
2
)
(1
0
2
)
(1
1
2
)
(1
0
3
)
  
 In
te
n
s
it
y
 (
a
.u
.)
 
  
  
(1
0
1
)
10 20 30 40 50 60 70 8 90
  
 2(degree)
 90 C
 In
te
n
s
it
y
 (
a
.u
.)
 
 100 C
  
 110 C
 
 
 
 120 C
(1
1
0
)
(1
0
0
)
(1
0
1
)
(0
0
2
)
(1
0
2
)
(1
1
2
)
(1
0
3
)
10 20 30 40 50 60 70 80 90
  
 2(degree)
 90 C
 In
te
n
s
it
y
 (
a
.u
.)
 
 100 C
  
 11
 
 
 
 120 C
(1
1
0
)
(1
0
0
)
(1
0
1
)
(0
0
2
)
(1
0
2
)
(1
1
2
)
(1
0
3
)
10 20 30 40 50 60 70 80 90
  
 2(degree)
 9  
 In
te
n
s
it
y
 (
a
.u
.)
 
 10  
  
1
 
 
 
 2  
(1
1
0
)
(1
0
0
)
(1
0
1
)
(0
0
2
)
(1
0
2
)
(1
1
2
)
(1
0
3
)
(a) (b)
(c)(d)
(1
0
0
)
(0
0
2
)
(1
0
1
)
(1
0
2
)
(1
1
0
)
(1
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)
(1
1
2
) (1
0
0
)
(0
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2
)
(1
0
1
)
(1
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2
)
(1
1
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)
(1
0
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)
(1
1
2
)
(1
0
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)
(0
0
2
)
(1
0
1
)
(1
0
2
)
(1
1
0
)
(1
0
3
)
(1
1
2
)
In
te
n
s
it
y
 (
a
.u
.)
 
 
Fig. 3 – XRD spectra of the synthesized ZnO NRs at different 
temperature such as 90 (a), 100 (b), 110 (c), and 120 (d)  
 
To understand the memristive switching effect within 
the device, the hysteresis loop in the current-voltage (I-V) 
plane is one of the critical criteria. In the present case, we 
have developed ZnO NRs-Bmim(Br) IL devices in the dis-
crete form and investigated their memristive switching 
effects. In order to examine the ZnO NRs concentration 
effect on the memristive property of the Bmim(Br) IL, we 
have dispersed different concentrations of ZnO NRs in the 
Bmim(Br) IL such as 0.05, 0.1, 0.5 and 1 wt. %. 
Fig. 4a-d represents the ZnO NRs concentration-
dependent I-V characteristics of the Bmim(Br) IL devic-
es. For each concentration study, four types of ZnO NRs, 
synthesized at different temperatures such as 90, 100, 
110, and 120 were used. All devices show a hysteresis 
loop in the I-V plane along with non-zero crossing prop-
erty. This suggested that the developed ZnO NRs-
Bmim(Br) IL devices display the memristive switching 
effect [11, 14-15]. For all concentrations, the IL device 
based on 90 synthesized ZnO NRs shows poor memris-
tive switching property than other devices. In the pre-
sent case, the IL device based on 110 synthesized ZnO 
NRs shows good memristive switching property than 
other devices. On the other hand, the IL device based on 
100 and 120 synthesized ZnO NRs shows moderate 
memristive switching property than other counterparts.
 RESISTIVE SWITCHING PROPERTY OF BMIM(BR) IONIC LIQUID… J. NANO- ELECTRON. PHYS. 12, 02003 (2020) 
 
 
02003-3 
-1.0 -0.5 0.0 0.5 1.0
-1.0x10
-3
-5.0x10
-4
0.0
5.0x10
-4
1.0x10
-3
C
u
rr
e
n
t 
(A
)
Voltage (V)
 90C
 100C
 110C
 120C
 
 
-1.0 -0.5 0.0 0.5 1.0
-1.0x10
-3
-5.0x10
-4
0.0
5.0x10
-4
1.0x10
-3
Voltage (V)
 90C
 100C
 110C
 120C
C
u
rr
e
n
t 
(A
)
 
 
-1.0 -0.5 0.0 0.5 1.0
-1.0x10
-3
-5.0x10
-4
0.0
5.0x10
-4
1.0x10
-3
C
u
rr
e
n
t 
(A
)
Voltage (V)
 90C
 100C
 110C
 120C
 
 
-1.0 -0.5 0.0 0.5 1.0
-1.0x10
-3
-5.0x10
-4
0.0
5.0x10
-4
1.0x10
-3
C
u
rr
e
n
t 
(A
)
Voltage (V)
 90C
 100C
 110C
 120C
 
 
(a) (b)
(c) (d)
 
 
Fig. 4 – I-V characteristics of the ZnO NRs-Bmim(Br) IL devices. Various concentrations of ZnO NRs dispersed in the Bmim(Br) 
IL such as 0.05 wt. % (a), 0.1 wt. % (b), 0.5 wt. % (c), and 1 wt. % (d) 
 
The hysteresis area is one of the crucial properties 
the memristive devices. Fig. 5a represents the concen-
tration and synthesis temperature-dependent hystere-
sis area of ZnO NRs-Bmim(Br) IL memristive devices. 
It is noticed that, as the concentration of the dispersed 
ZnO NRs in the IL increases, the hysteresis area tends 
to increases for 90 synthesized ZnO NRs. For other 
cases, the correlation of concentration of the dispersed 
ZnO NRs in the IL and the hysteresis area was not 
observed. However, ZnO NRs synthesized at 100, 110 
and 120 show higher memristive hysteresis than 90 
synthesized ZnO NRs. The 110 synthesized ZnO NRs 
show a good memristive hysteresis area than other 
devices. In particular, 0.1 wt. % (at 110) ZnO NRs 
shows a good memristive hysteresis area than other 
devices. The endurance was measured to understand 
cyclic switching of the ZnO NRs-Bmim(Br) IL memris-
tive devices (Fig. 5b). The bi-level switching from low 
resistance state (LRS) to high resistance state (HRS) 
and vice versa were detected for all devices. Further-
more, good endurance switching over 103 cycles were 
observed for all devices, suggesting the good reliability 
of the device. Because of this, developed ZnO NRs-
Bmim(Br) IL-based discrete memristive devices can be 
useful for the various applications. 
 
0 200 400 600 800 1000
600
800
1000
1200
1400
1600
1800
2000
2200
 HRS-0.05 wt.%  LRS-0.05 wt.%
 HRS-0.1 wt.%    LRS-0.1 wt.%
 HRS-0.5 wt.%    LRS-0.5 wt.%
 HRS-1 wt.%       LRS-1 wt.%
R
e
s
is
ta
n
c
e
 (

)
Switching Cycles (#)
0.0 0.2 0.4 0.6 0.8 1.0
8.0x10
-4
1.0x10
-3
1.2x10
-3
1.4x10
-3
1.6x10
-3
H
y
s
te
re
s
is
 A
re
a
 (
W
)
Concentration of ZnO dispersed in IL (wt. %)
 90 C
 100 C
 110 C
 120 C
 
 
(a) (b)
 
 
Fig. 5 – Concentration of ZnO NRs dependent a memristive 
hysteresis area (a) and endurance property (b) of 110 synthe-
sized ZnO NRs-Bmim(Br) IL memristive devices  
4. CONCLUSION 
 
The ZnO NRs and Bmim(Br) ionic liquid were syn-
thesized by using simple chemical routes i.e. hydro-
thermal and reflux method, respectively. In this work, 
ZnO NRs were developed at various synthesis tempera-
tures such as 90, 100, 110 and 120 C. Furthermore, 
different concentration ZnO NRs such as 0.05, 0.1, 0.5 
and 1 wt. % were dispersed in the IL and investigated 
their memristive switching property. The XRD spectra 
suggested the formation of a hexagonal crystal struc-
ture. The FESEM image suggested the formation of 
nanorods like morphology. The effect of dispersed ZnO 
NRs on the resistive switching behavior of Bmim(Br) 
ionic liquid was studied. The hysteresis loop along with 
non-zero crossing property, was observed for all the 
memristive devices. In the present case, 110 C synthe-
sized ZnO NRs with 0.1 wt. % shows good memristive 
switching property than other devices. The endurance 
test suggested that all devices show bi-level switching 
from LRS to HRS and vice versa. Furthermore, good 
endurance switching over 103 cycles were observed for 
all devices, suggesting the good reliability of the devel-
oped devices. 
 
ACKNOWLEDGMENTS 
 
This study was supported by the Basic research 
program (2016R1D1A1B01009537) through the Na-
tional Research Foundation (NRF) of Korea and by the 
MOTIE (Ministry of Trade, Industry & Energy 
(10080581) and KSRC (Korea Semiconductor Research  
Consortium) support program for the development of 
the future semiconductor device. 
 
 
 NIKITA A. KHAIRNAR, ADITYA A. PATIL, SHREEYA H. RANE, ET AL. J. NANO- ELECTRON. PHYS. 12, 02003 (2020) 
 
 
02003-4 
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Resistive Switching Property of Bmim(Br) Ionic Liquid under the Influence of ZnO Nanorods

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