Resistive Switching in Bigraphene/Diamane Nanostructures Formed on a La3Ga5SiO14 Substrate Using Electron Beam Irradiation

At a Glance

Metadata	Details
Publication Date	2023-11-20
Journal	Nanomaterials
Authors	E. V. Emelin, Hak Dong Cho, Vitaly I. Korepanov, Liubov A. Varlamova, Darya O. Klimchuk
Institutions	Dongguk University, National University of Science and Technology
Citations	2
Analysis	Full AI Review Included

Executive Summary

This study successfully demonstrates resistive switching (memristor behavior) in a novel lateral composite structure formed by locally converting bilayer graphene (bigraphene) into 2D diamond (diamane) using focused electron beam irradiation (EBI).

Core Achievement: Direct “writing” of a bigraphene/diamane/bigraphene lateral nanostructure on a La₃Ga₅SiO₁₄ (LGS) substrate, resulting in a functional memristor device.
Switching Performance: The device exhibits non-volatile resistive switching with an On/Off ratio of approximately 40, transitioning between a High Resistance State (HRS, ~20 kΩ) and a Low Resistance State (LRS, ~0.5 kΩ).
Low-Voltage Operation: Switching is achieved at low bias voltages (±0.9 V), making the device highly suitable for energy-efficient computing applications.
Mechanism of Switching: Density Functional Theory (DFT) modeling confirms that the resistive transition is governed by the migration and desorption of oxygen-related functional groups under an applied electric field. This process breaks the stabilizing sp³ carbon bonds, restoring the high conductivity of bigraphene (sp²).
Fabrication Advantage: The EBI-assisted chemically induced phase transition offers a CMOS-compatible technology for the localized fabrication of 2D layered memristors, enabling integration into built-in integral circuits.

Technical Specifications

Parameter	Value	Unit	Context
Substrate Material	La₃Ga₅SiO₁₄ (LGS)	N/A	Used for bilayer graphene transfer.
Initial Resistance (Bigraphene)	360	Ohms (Ω)	Linear I-V characteristic prior to EBI.
High Resistance State (HRS)	~20	kΩ	Resistance of the diamane structure.
Low Resistance State (LRS)	~0.5	kΩ	Resistance after switching (restored bigraphene).
On/Off Ratio	~40	N/A	Ratio of HRS/LRS during voltage sweep.
Switching Voltage	±0.9	V	Voltage required to induce resistive transition.
E-Beam Accelerating Voltage	25	kV	Used for localized sp² to sp³ conversion.
E-Beam Dose	1	mC/cm²	Used to define the diamane stripe region.
Diamane sp³ Defect Density	10¹²	cm^-2	Estimated concentration of sp³ carbon in irradiated region.
CVD Growth Temperature	1020	°C	Temperature for graphene synthesis on Cu foil.
CVD Growth Pressure	600	mTorr	Pressure maintained during graphene growth.
Theoretical Cleavage Barrier Reduction	~50%	N/A	Reduction achieved by applying 1.0 eV/Angstrom electric field.
Raman D Peak Shift (Irradiated)	1335	cm^-1	Indicates increased sp³ hybridization (diamane formation).

Key Methodologies

The fabrication of the lateral bigraphene/diamane nanostructure involved a multi-step process combining chemical vapor deposition (CVD), wet transfer, and focused electron beam irradiation (EBI).

Graphene Synthesis (CVD):
- Graphene monolayers were grown on 99.999% pure copper foil using a horizontal quartz tube furnace.
- Process gases: Methane (CH₄), Hydrogen (H₂), and Argon (Ar) carrier gas.
- Growth conditions: 1020 °C, 600 mTorr pressure, 30 min duration.
Bilayer Graphene Transfer:
- A two-step wet transfer process was used, supported by a poly(methyl methacrylate) (PMMA) layer.
- The copper foil was etched away, and the PMMA/graphene stack was transferred onto the polished La₃Ga₅SiO₁₄ (LGS) substrate.
- PMMA was removed using solvents, followed by a 30% HCl rinse at 60 °C to eliminate residual Fe³⁺ ions, ensuring high-quality bilayer stacking.
Diamane Nanostructure Formation (EBI):
- A 300 nm layer of PMMA-950 resist was deposited over the bilayer graphene/LGS structure.
- Focused EBI (25 kV, 1 mC/cm²) was applied along a specific line (vertical stripe).
- EBI induces a chemically driven phase transition (sp² to sp³) by releasing hydrogen (from PMMA) and oxygen (from LGS), locally converting bigraphene into high-resistivity diamane.
Structural and Electrical Characterization:
- Raman spectroscopy (532 nm laser) was used to map the intensity ratio of the D and G bands, confirming the elevated density of sp³-hybridized carbon in the irradiated region.
- Al/Cr side electrodes were deposited laterally across the bigraphene/diamane/bigraphene structure.
- Current-voltage (I-V) characteristics and resistive switching behavior were measured using a microprobe station and SMU instrument.
Theoretical Modeling (DFT):
- DFT calculations (SIESTA code) were performed on a simplified graphene/diamane heterostructure model (passivated by H and peroxide groups).
- A periodic sawtooth-type potential was applied to simulate the external electric field, investigating its effect on the C-O and C-H bond cleavage barriers and structural stability.

Commercial Applications

The development of localized, low-voltage resistive switching elements based on 2D carbon materials offers significant potential for next-generation electronics and computing architectures.

Neuromorphic Hardware: The ability to mimic synaptic plasticity (adaptive behavior influenced by previous states) makes this technology ideal for developing energy-efficient artificial neural networks and neuromorphic processors.
Non-Volatile Memory (NVM): The high On/Off ratio (~40) and low operating voltage (±0.9 V) position these devices as promising candidates for ultra-thin, high-density resistive random-access memory (RRAM).
CMOS-Compatible Fabrication: The use of electron beam lithography for direct “writing” of functional elements allows for seamless integration of these 2D memristors into existing silicon-based CMOS manufacturing processes.
Advanced Computing: Utilization in specialized computing systems requiring high endurance, sub-nanoscale switching speeds, and low power consumption, such as edge AI devices and advanced data centers.
2D Material Heterostructure Engineering: The technique provides a controlled method for localized chemical modification (sp² to sp³ phase transition) of 2D materials, opening pathways for fabricating complex lateral heterostructures with tailored electronic properties.

View Original Abstract

Memristors, resistive switching memory devices, play a crucial role in the energy-efficient implementation of artificial intelligence. This study investigates resistive switching behavior in a lateral 2D composite structure composed of bilayer graphene and 2D diamond (diamane) nanostructures formed using electron beam irradiation. The resulting bigraphene/diamane structure exhibits nonlinear charge carrier transport behavior and a significant increase in resistance. It is shown that the resistive switching of the nanostructure is well controlled using bias voltage. The impact of an electrical field on the bonding of diamane-stabilizing functional groups is investigated. By subjecting the lateral bigraphene/diamane/bigraphene nanostructure to a sufficiently strong electric field, the migration of hydrogen ions and/or oxygen-related groups located on one or both sides of the nanostructure can occur. This process leads to the disruption of sp3 carbon bonds, restoring the high conductivity of bigraphene.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano13222978

References

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2011 - Resistive Switching in Al/Graphene Oxide/Al Structure [Crossref]