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Laser EnAbled TransFer of 2D Materials

Periodic Reporting for period 2 - LEAF-2D (Laser EnAbled TransFer of 2D Materials)

Reporting period: 2019-11-01 to 2022-04-30

LEAF-2D aims to introduce Laser Direct Transfer (LDT) processes LIBT and LIFT, as a novel nano-manufacturing platform for the controllable and deterministic transfer of 2D materials onto different substrates including rigid (Si) and flexible substrates. Using LDT processes, the project envisages to exploit the unique properties of 2D materials towards a transformative breakthrough in diverse technological fields namely embedded NIR light sources and flexible graphene-based touch sensors. These unique properties involve the direct and on demand transfer of highly resolved 2D material pixels that can provide a substantial advantage in device fabrication in terms of printing speed and throughput, device miniaturization and elimination of additional fabrication and processing steps.
The importance for society both in societal and economic terms involves advancements in diverse fields including environmental monitoring, communications, healthcare, sensors and displays. The proposed innovative technologies will enable graphene and other 2D materials to change their application status from research to the industrial market stage. LEAF-2D’s low cost printable emitter technology will disrupt the photonics industry and will enable new devices and applications that will provide added-value to the European technological ecosystem. Technological fields that are also expected to be benefited from the project’s outcome include consumer electronics with the integration of high-speed transceivers onto flexible platforms and infrared LEDs for applications including portable spectroscopy systems and gas sensors through the shifting of the operational wavelengths at 1.3 μm in respect of the IEC 60825-1 directive for relaxed eye safety limits.
LEAF-2D’s primary objectives are:
Objective 1: Controllable transfer and intact and defect-free 2D material monolayer pixels by means of LDT processes starting from 2D material films. Lateral resolution down to micron scale.
Objective 2: High quality 2D films growth (Graphene, h-BN, and direct bandgap 2D semiconductors).
Objective 3: Apply LEAF-2D’s technology for the fabrication of 2D materials enabled Si emitters integrated on Si and touch sensors on flexible substrates.
WP1. 2D Material Growth and investigation of substrates
During the reporting period, BIU grew new 2D materials (Bi2Se(3-x)Sx)for expanding the variety of available layered materials processed by CVD growth. BIU also aimed at bandgap engineering of 2D materials alloys.
GS has a series of CVD grown Graphene or Graphene/hBN substrates samples.
NTUA, carried on with the DFT studies on the physical properties of 2D materials with a special focus on the electronic and topological properties of Bi2Se3-xSex alloys.

WP2. Laser Direct Transfer (LDT) process: LIBT and LIFT
The LIBT process for graphene transfer on glass has been developed and the resulting samples have been characterized using optical microscopy, Raman spectroscopy and SEM microscopy. Similarly, the LIFT process for the transfer of graphene, graphene/hBN and MoS2 on SiO2/Si substrates has been demonstrated and validated. Finite-temperature Ab Initio Molecular Dynamics (AIMD) DFT-based simulations were employed to identify a range of initial conditions for the atomic velocities in the substrate that can lead to detachment of the 2D overlayer.

WP3. Application 1: 2D SC enabled emitter integrated on Si photonic chip.
The final targets of the LEAF-2D project are split into three prototypes. All three prototypes have been designed, fabricated and evaluated at material and device level by the involved partners. I Diode behavior was observed, validating the successful transfer of the 2D material via LIFT. Record modulation speed was achieved using the 2nd generation of silicon photonics. Ultra-high bandwidth transmission lines (CPWs) were implemented using laser patterning and laser sintering of Ag nanoparticle inks. LIFT-based interconnection of the CPWs to the VCSELs was demonstrated. High-speed operation of the LIFT-interconnected VCSELs was verified by optical measurements.

WP4. Application 2: Graphene enabled touch sensor
The specifications for the performance and the design of the touch sensor have been defined and associated with KPIs. The fabrications processes involve laser based, conventional material processing and hybrid approaches comprising both. The resulting capacitors are characterized morphologically using optical microscopy, SEM, Raman to validate the presence of Graphene. At the device level, the capacitors are fully characterized by carrying out capacitance over voltage measurements and finally the most promising configurations are evaluated as touch sensors by applying controllable loads in cycles of CV measurements.

WP5. Dissemination and Exploitation
During the second reporting period, partner EXEL in close cooperation with the coordinator and the rest of the consortium, continued to implement consistently the project’s dissemination plan and making use of the already established tools and mechanisms for the dissemination of the project results to the relevant stakeholders and wider society. The consortium partners have already filed the following two patent applications.

WP6. Project management and coordination
The overall project management, including the administrative and scientific/technical management have been undertaken by the coordinator according to the provisions of GA art. 41.2b. The timely submission of project deliverables has been ensured and in the cases that this was not feasible, adequate justification has been provided. All milestones have been achieved, and overall the implementation of the project fulfilled the initially envisioned objectives, with some deviations for which mitigation strategies were successfully employed yielding scientifically and technologically interesting outcomes.
LEAF-2D’s underlying concepts and outcomes hold tremendous potential for the advancement of the field of 2D materials and the 2D-related applications in optoelectronics and sensors. The results obtained within the project have validated that the controllable and digital transfer of 2D materials is feasible using LIFT and LIBT and demonstrated at TRL4 two applications enabled by these materials. This will have a huge impact on the innovation capacity of the academic and research parties involved in the consortium. The project results have been already published in four high impact peer-reviewed journals and at least five more publications are currently being prepared or have already been submitted. The innovation potential of LEAF-2D’s outcomes, is not only restricted to the already obtained results, but has laid the foundation for a self-sustainable chain of innovations.
Therefore, the involved academic partners will benefit from their participation in LEAF-2D over a long-lasting period offering increased opportunities for innovation and fruitful scientific collaborations, including the Horizon Europe - EIC transition projects. Three patents have already been filed and two more are currently being prepared, comprising exclusively findings related to LEAF-2D’s activities. The two companies which are involved in the consortium, GS and MELL will fully benefit from this potential and have developed dedicated exploitation plans which are built on the leverage offered by LEAF-2D.
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