Electrostatic actuation of 2D-materials-based heterostructures for in situ twistronics

Informazioni relative al progetto

2DTWIST

ID dell’accordo di sovvenzione: 101109662

DOI

10.3030/101109662

Progetto concluso il 30 Settembre 2025

Data della firma CE 7 Aprile 2023

Data di avvio 1 Luglio 2023

Data di completamento 30 Giugno 2026

Finanziato da

• Marie Skłodowska-Curie Actions (MSCA)

Costo totale

Nessun dato

Contributo UE

€ 297 164,16

Coordinato da

POLITECNICO DI TORINO
Italy

Periodic Reporting for period 2 - 2DTWIST (Electrostatic actuation of 2D-materials-based heterostructures for in situ twistronics)

Periodo di rendicontazione: 2025-07-01 al 2026-06-30

Sintesi del contesto e degli obiettivi generali del progetto

The development of advanced, energy-efficient, and miniaturized electronic devices is driving the need for new materials and innovative engineering solutions. Among these, two-dimensional (2D) materials, such as graphene and hexagonal boron nitride (hBN), stand out due to their extraordinary properties and the possibility of stacking them into van der Waals (vdW) heterostructures with tailored functionalities. In particular, the concept of “twistronics,” where the electronic and optical properties of 2D heterostructures can be tuned by controlling the relative twist angle between layers, has opened a new frontier in material science and quantum technology. However, current fabrication methods allow only static control of the twist angle, limiting both the scientific exploration of emergent phenomena and the development of practical devices.

The 2DTWIST project aims to overcome these limitations by developing a platform for dynamic, in situ control of the twist angle in 2D heterostructures. The main objectives are:
(1) the design and fabrication of electrostatic actuators based on 2D materials, capable of inducing controlled angular motion between stacked layers;
(2) the implementation and optical/electrical characterization of dynamically twistable graphene/hBN heterostructures;
(3) the demonstration of operando modulation of moiré patterns and their associated quantum phenomena.

These advances are expected to lay the foundation for new classes of reconfigurable quantum devices, sensors, and optoelectronic components, thus addressing key scientific and technological challenges identified at the European and international levels.

Lavoro eseguito dall’inizio del progetto fino alla fine del periodo coperto dalla relazione e principali risultati finora ottenuti

Significant progress has been made in the fabrication, assembly, and characterization of 2D material-based heterostructures.

1. Fabrication and Assembly of 2D Heterostructures:
Robust protocols were established for the mechanical exfoliation of large-area, high-quality monolayers of graphene and hexagonal boron nitride. The process was optimized by incorporating gold-assisted exfoliation and APTES-based surface functionalization, leading to improved yield, adhesion, and transfer uniformity. These methods allowed the reproducible assembly of van der Waals heterostructures with clean interfaces and minimal defect density. The workflow is compatible with standard microfabrication techniques, demonstrating scalability and adaptability.

2. Device Microfabrication:
Lithographic techniques, including electron beam lithography (EBL) and reactive ion etching (RIE), were employed to pattern graphene stators and define the device geometry. Gold electrodes were deposited via thermal evaporation to enable precise electrical interfacing of each heterostructure.

3. Development and Demonstration of Contactless Electrostatic Actuation:
A major scientific achievement was the proof-of-concept demonstration of contactless electrostatic actuation in graphene/hBN heterostructures, realized through electron-beam-induced charge injection. By locally charging the hBN layer with a focused scanning electron beam, an in-plane electrostatic field and lateral torque were generated, resulting in controlled angular displacement of the hBN flake relative to the underlying graphene. This approach offers a non-invasive and versatile method to modulate the twist angle directly in situ, without the need for mechanical contact or external actuators.

4. Characterization:
The induced angular displacement and interlayer reconfiguration were monitored and quantified using a combination of techniques:

-In situ SEM imaging provided real-time visualization of the rotational motion, with angular displacements of typically 2–3 degrees measured between pre- and post-actuation states.
-Spatially resolved Raman spectroscopy was employed to independently verify twist modulation by mapping changes in the full width at half maximum (FWHM) and position of the graphene 2D Raman band in the overlap region, providing a spectroscopic fingerprint of moiré pattern evolution.

Progressi oltre lo stato dell’arte e potenziale impatto previsto (incluso l’impatto socioeconomico e le implicazioni sociali più ampie del progetto fino ad ora)

The 2DTWIST project has established a contactless approach for the dynamic modulation of the twist angle in 2D van der Waals heterostructures, exploiting electron-beam-induced electrostatic actuation. This proof-of-concept method enables in situ control of angular displacement between stacked layers through local charge injection, providing a versatile platform for investigating twist-dependent physical phenomena.

Compared to previous techniques, which often require mechanical contact, external manipulation, or complex micro-electromechanical architectures, this strategy simplifies device fabrication and opens up new possibilities for scalable, reconfigurable 2D material-based systems. The actuation principle is validated by combining real-time SEM imaging with Raman spectroscopy, offering complementary and non-destructive insight into interlayer dynamics and moiré pattern evolution.

The results pave the way for next-generation applications in optoelectronics, sensing, and quantum technologies, where precise control over the twist angle can be used to engineer electronic, optical, and quantum properties on demand. The methodology demonstrated here can be extended to other material systems and integrated into advanced device architectures, offering broad versatility and compatibility with established microfabrication processes.

To ensure further uptake and success, ongoing efforts focus on developing integrated actuation schemes, refining angular precision and reversibility, and exploring scalable device concepts suitable for industrial application and technology transfer. These advances will facilitate the transition from proof-of-concept experiments to robust, practical platforms for dynamically reconfigurable 2D material devices.