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Evaluation of Flexible Resistive Random Access Memory Devices Fabricated with Nanocomposites of 2D Materials

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Abstract
In this study, 2D materials and their nanocomposites have been explored as the functional layer of resistive random access memory (RRAM) devices. 2D materials and their nanocomposites such as molybdenum disulfide-polyvinyl alcohol (MoS_2-PVA), hexagonal boron nitride flakes-MoS2 quantum dots (hBN-MoS_2QDs), flakes of tungsten disulfide (WS_2) and hBN flakes-graphene quantum dots (hBN-GQDs) have been sandwiched between two metallic electrodes to complete the simple structure of RRAM devices. All-Printed technology was used to fabricate each RRAM device on a flexible and transparent substrate. All the devices displayed highly stable, repeatable and bipolar resistive switching characteristics. The least switching ratio was shown by the active layer of MoS2-PVA (1.28x10^2) while hBN-MoS_2QDs, WS_2 and hBN-GQDs exhibited a superior value of 10^3 each. Lowest retention time of 10^4 s was exhibited by the WS_2 flakes while MoS_2-PVA, hBN-MoS_2QDs, and hBN-GQDs showed a higher value of 10^5 s each. All 2D materials based flexible RRAM devices were tested for their bendability in the bending diameter range of 500 mm to 2 mm. Functional layer of MoS_2-PVA showed maximum number of bending cycles (2000 cycles) without any prominent decay in the device performance while hBN-MoS_2QDs, WS_2 flakes and hBN-GQDs exhibited mechanical robustness upto 1500 cycles each respectively. Conduction mechanism shown by active layers of MoS_2-PVA and WS_2 flakes was space charge limited current (SCLC) while conductive filaments were formed in the active layer of hBN-GQDs and hBN-MoS_2QDs. Furthermore, functional thin films of hBN-GQDs and WS_2 flakes were also encapsulated with atomically thin film of aluminum oxide (Al_2O_3) through spatial atmospheric atomic layer deposition (SAALD) system to enhance their lifetime. These obtained results clearly illustrate that functional layers based on 2D materials have a huge potential to replace the existing nanomaterials used as active layers of RRAM devices.
Author(s)
레흐만무하마드무키트
Issued Date
2018
Awarded Date
2018. 2
Type
Dissertation
URI
http://dcoll.jejunu.ac.kr/jsp/common/DcLoOrgPer.jsp?sItemId=000000008489
Alternative Author(s)
Rehman, Muhammad Muqeet
Affiliation
제주대학교 일반대학원
Department
대학원 메카트로닉스공학과
Advisor
최경현
Table Of Contents
Abstract xiii
1. Introduction 1
1.1 Two Dimensional Materials 1
1.2 Role of 2D Materials in RRAM Devices 3
1.2.1 Graphene and its Nanocomposites 3
1.2.2 MoS_2 and its Nanocomposites 4
1.2.3 Other 2D Materials and their Nanocomposites 4
1.3 Printing Technologies 5
1.3.1 Reverse Offset Electrode Patterning 5
1.3.2 Electrohydrodynamic Patterning and Atomization 7
1.3.3 Reciprocating Inkjet Head for Electrode Patterning 8
1.3.4 Electrohydrodynamic Atomization for Thin Film Deposition 10
2 Experimental 11
2.1 Synthesis of functional materials 11
2.1.1 Synthesis of WS_2 flakes 11
2.1.2 Synthesis of MoS_2 flakes blended with PVA 13
2.1.3 Synthesis of hBN flakes blended with GQDs 14
2.1.4 Synthesis of hBN flakes blended with MoS_2QDs 17
2.2 Surface Characterizations 18
2.2.1 Surface Morphology 18
2.2.2 Compositional Characterization 22
2.2.3 Optical Characterization 25
2.2 Fabrication of flexible RRAM devices 27
2.2.1 Fabrication of Ag/WS_2/Ag RRAM 27
2.2.2 Fabrication of Ag/hBN-GQDs/Ag RRAM 31
2.2.3 Fabrication of ITO/hBN-MoS_2QDs/Ag RRAM 36
2.2.4 Fabrication of Ag/MoS_2-PVA/Ag RRAM 39
3 Resistive switching in as synthesized 2D materials and their nanocomposites 43
3.1 Flexible Ag/WS_2/Ag RRAM 43
3.1.1 Electrical Characterization 43
3.1.2 Conduction Mechanism 46
3.1.3 Mechanical Characterization 48
3.2 Flexible Ag/hBN-GQDs/Ag RRAM 49
3.2.1 Electrical Characterization 49
3.2.2 Conduction Mechanism 52
3.2.3 Mechanical Characterization 55
3.3 Flexible ITO/hBN-MoS_2QDs/Ag RRAM 57
3.3.1 Electrical Characterization 57
3.3.2 Conduction Mechanism 60
3.3.3 Mechanical Characterization 63
3.4 Flexible Ag/MoS_2-PVA/Ag RRAM 66
3.4.1 Electrical Characterization 66
3.4.2 Conduction Mechanism 68
3.4.3 Mechanical Characterization 72
4. Conclusions and Future work 75
4.1 Conclusions 75
4.2 Future work 75
References 77
Degree
Doctor
Publisher
제주대학교 일반대학원
Citation
레흐만무하마드무키트. (2018). Evaluation of Flexible Resistive Random Access Memory Devices Fabricated with Nanocomposites of 2D Materials
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Faculty of Applied Energy System > Mechatronics Engineering
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