Name: Optimized Fabrication Procedure for High-Quality Graphene-based Moiré Superlattice Devices (Video) | JoVE Journal
Uploaded: 2025-07-11T13:10:00.000+00:00
Duration: 11 min 24 s
Description: Learn an optimized fabrication protocol for high-quality graphene-based moiré superlattice devices with precise twist angles. This method improves uniformity, yield, and reproducibility in quantum materials research.

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The authors deeply thank all of the current and former Jarillo-Herrero Group members for developing and optimizing the fabrication protocol. This work has been primarily supported by the Army Research Office MURI W911NF2120147; with support also by the 2DMAGIC MURI FA9550-19-1-0390, the MIT/Microsystems Technology Laboratories Samsung Semiconductor Research Fund, the Sagol WIS-MIT Bridge Program, the National Science Foundation (DMR-1809802), the Gordon and Betty Moore Foundation&#39;s EPiQS Initiative through grant GBMF9463, and the Ramon Areces Foundation. This work made use of Harvard&#39;s Center for Nanoscale Systems, supported by the NSF (ECS-0335765).

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The authors declare no conflict of interest.

Imposing a small twist angle between graphene layers can introduce significant disorder within the heterostructure. Therefore, to maximize the success rate in fabricating high-quality graphene moir&#233; superlattice devices, a highly tunable transfer setup with precise control over position, angle, and temperature is essential. Additionally, several critical aspects during the fabrication process are identified: rigorous flake selection criteria, pre-cleaned bubble-free bottom gates, graphene laser ablation, and, most i...

A key driving force of modern condensed matter physics is the combination of strong correlations and topology into a single tunable physical system. Since the discovery of correlated insulator states1 and superconductivity2 in magic-angle twisted bilayer graphene (MATBG), its remarkable properties have stimulated a growing number of studies on moir&#233; materials3. In recent years, a variety of graphene-based moir&#233; superlattices have been constructed and investigated. This rapidly growing field has revealed a wealth of emergent phenomena, including but not limited to exotic correlated insulators4,5,6,7,8,9, unconventional superconductivity10,11,12,13,14, nematicity15, and orbital ferromagnetism16,17,18.
The rich physics unveiled in these graphene moir&#233; superlattices benefits from the unprecedented in situ tunability offered by the small twist angles between graphene layers. Meanwhile, it is also impacted by the uncertainties arising from this additional twist angle degree of freedom. The twist angle is created by overlaying two graphene flakes with a relative rotation of their crystal axes. To achieve the magic-angle regime (1&#176;-1.2&#176;), where correlations play a dominant role, it is imperative to precisely control the twist angle with sub-0.1&#176; accuracy. However, during the fabrication procedure, various detrimental factors can be introduced, such as heterostrain19,20, twist angle disorder21,22,23, and lattice relaxation24,25, among others. Using imperfect flakes or failing to control the pickup speed of graphene can result in excessive strain and angular disorder. As the small twist angle configuration is not the thermodynamic ground state, incorporating unnecessary high-temperature transfer processes increases the risk of undesired lattice relaxation. These factors reduce the success rate of graphene moir&#233; superlattice device fabrication and are especially prominent in the magic-angle regime. They pose significant experimental challenges26 for researchers in this field, making it difficult to obtain devices with the desired twist angle or even reproducing previous measurement results.
In this article, with the objective of alleviating the above challenges, an optimized, experience-informed, and step-by-step protocol for fabricating high-quality graphene-based moir&#233; superlattice devices is presented. Based on a modified dry transfer technique27,28, the transfer process is performed using a highly tunable, custom-built transfer setup with precise position, angle, and temperature control. At the heart of this protocol are rigorous flake selection criteria, pre-cleaned bubble-free bottom gates, graphene laser ablation, and, most importantly, smooth pickup of the pre-cut graphene flakes at a submicron speed at room temperature. Apart from these crucial aspects, minor factors that possibly affect the experimental outcomes are also discussed. Even though the presented protocol uses twisted bilayer graphene as an example, it is applicable to all kinds of graphene-based moir&#233; superlattice structures. The detailed workflow aims to enhance accessibility to the fabrication of high-quality graphene moir&#233; superlattice devices for the broader research community.

<table><tbody><tr><td>Bench Top Vibration Isolation Platform</td><td>Minus K Technology, Inc</td><td>100BM-8</td><td>Vibration isolation for the custom-built transfer setup</td></tr><tr><td>Color camera</td><td>Teledyne FLIR LLC</td><td>BFS-U3-200S6C-C</td><td>CMOS camera for the custom-built transfer setup</td></tr><tr><td>Diaphragm pump</td><td>Pfeiffer Vacuum</td><td>MVP 015-2</td><td>Provide vacuum suction power to secure the wafer on the sample stage</td></tr><tr><td>Direct drive rotation stage</td><td>Thorlabs, Inc</td><td>DDR 100</td><td>Rotation stage for the custom-built transfer setup</td></tr><tr><td>Ergonomic high-power microscope</td><td>Mitutoyo&amp;nbsp;</td><td>FS70</td><td>Microscope body for the custom-built transfer setup</td></tr><tr><td>Goniometer stage</td><td>Thorlabs, Inc</td><td>GNL 18 and GNL 10</td><td>Control the tilt angle of the glass slide</td></tr><tr><td>Graphite crystals</td><td>NGS Trading &amp;amp; Consulting GmbH</td><td>Flaggy Flakes</td><td>Flat and shiny graphite crystals for graphene exfoliation</td></tr><tr><td>High power supercontinuum fiber laser</td><td>Fianium, Inc</td><td>SC-400&amp;nbsp;</td><td>For graphene laser ablation</td></tr><tr><td>Micro linear actuators with built-in controllers</td><td>Zaber Technologies</td><td>X-NA08A25</td><td>Control the X-Y sample stage</td></tr><tr><td>Mitutoyo 10x M Plan APO Objective</td><td>Mitutoyo&amp;nbsp;</td><td>378-803-3</td><td>10x objective used on the transfer stage</td></tr><tr><td>Mitutoyo 2x M Plan APO Objective</td><td>Mitutoyo&amp;nbsp;</td><td>378-801-12</td><td>2x objective used on the transfer stage</td></tr><tr><td>Mitutoyo 50x M Plan APO Objective</td><td>Mitutoyo&amp;nbsp;</td><td>378-805-3</td><td>50x objective used on the transfer stage</td></tr><tr><td>Motorized actuator</td><td>Zaber Technologies</td><td>TRB12CC&amp;nbsp;</td><td>Control the X-Y-Z glass slide holder stage</td></tr><tr><td>Poly(Bisphenol A carbonate)</td><td>MilliporeSigma</td><td>181641-25G</td><td>PC particles for making glass slides with PC/PDMS stamps</td></tr><tr><td>Prime Grade Si wafers</td><td>NOVA Electronic Materials</td><td>FP02-61160-DO</td><td>P-doped Si wafer for 2D material exfoliation. Detailed description: 6&quot; P &amp;lt;100&gt; .001-.005 ohm-cm 650-700&amp;mu;m Thick Prime Grade SSP Si wafers w/Primary Flat Only &amp;amp; 2850 A&amp;deg;&amp;plusmn;5% Dry Thermal Oxide</td></tr><tr><td>Silicone-free blue adhesive plastic film</td><td>Ultron Systems, Inc</td><td>1005R/1009R</td><td>Blue tape for exfoliating 2D materials</td></tr><tr><td>SYLGARD 184 Silicone Encapsulant Clear</td><td>Dow Inc.</td><td>4019862</td><td>Make PDMS stamp</td></tr><tr><td>Tapping Mode AFM Probe with Aluminum Reflective Coating</td><td>Innovative Solutions Bulgaria Ltd</td><td>Tap300Al-G</td><td>Tapping mode tip used for tip-cleaning</td></tr><tr><td>XY manual linear stage</td><td>Newport Corporation</td><td>M-462-XY</td><td>X-Y sample stage for the custom-built transfer setup</td></tr><tr><td>XYZ manual linear stage</td><td>Newport Corporation</td><td>M-562-XYZ</td><td>X-Y-Z glass slide holder stage for the custom-built transfer setup</td></tr></tbody></table>

optimized fabrication procedure for high-quality graphene-based moir&#233; superlattice devices

Optimized Fabrication Procedure for High-Quality Graphene-based Moir&#233; Superlattice Devices

Moir&#233; superlattices constitute a versatile platform to investigate emergent phenomena arising from the interplay of strong correlations and topology, while offering flexible in situ tunability. However, the fabrication of such moir&#233; superlattices is challenging. It is difficult to achieve highly uniform devices with a precise twist angle because of the unintentional introduction of heterostrain, twist angle disorder, and angle/lattice relaxation during the nanofabrication process. This article introduces an optimized, experience-informed protocol for fabricating high-quality graphene-based moir&#233; superlattice devices, focusing on a modified dry transfer technique. The transfer process is performed in a highly tunable, custom-built transfer setup that enables precise position, angle, and temperature control. By combining rigorous flake selection criteria, pre-cleaned bubble-free bottom gates, and graphene laser ablation, the moir&#233; superlattice is constructed by deliberately overlaying twisted graphene flakes at a submicron speed at room temperature. Through precise control of the transfer process, the resulting graphene moir&#233; superlattice devices exhibit high uniformity and desired twist angles. This optimized protocol addresses existing challenges in the fabrication of graphene-based moir&#233; superlattice devices and paves the way for further advances in the rapidly evolving field of moir&#233; materials.

Low temperature transport measurements were performed to characterize the graphene moiré superlattice devices. Starting with MATBG as an example, the typical Landau fan diagram of a high-quality magic-angle device is shown in Figure 8A22. The filling factor of the flat bands ν = 4n/ns describes the carrier density of the system, where n is the carrier density and ns = <img alt="Equation: \(8\theta^2/\sqrt{3a^2}\); mathe...

This article presents an optimized, experience-informed protocol for fabricating high-quality graphene-based moir&#233; superlattice devices with precise twist angles, utilizing a modified dry transfer technique based on a highly tunable, custom-built transfer setup.

Moir&#233; superlattices constitute a versatile platform to investigate emergent phenomena arising from the interplay of strong correlations and topology, ...

optimized-fabrication-procedure-for-high-quality-graphene-based-moir

Research

JoVE Journal

Engineering

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Learn an optimized fabrication protocol for high-quality graphene-based moiré superlattice devices with precise twist angles. This method improves uniformity, yield, and reproducibility in quantum materials research.

Optimized Fabrication Procedure for High-Quality Graphene-based Moiré Superlattice Devices

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