Ryoichi Ishihara

Associate Professor, Group leader

Qutech, Dep. Quantum and Computer Engineering, Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology

Ishihara-lab focuses on the integration technologies for unconventional electronic systems; quantum computers, quantum sensors, neuromorphic computers, and biodegradable sensors. Our work involves new materials, scalable fabrication of electronic and photonic devices, and 3D heterogeneous integration, aiming to realize unconventional electronic systems.

Graphene on Diamond – Growth Process Development and Property Testing

Introduction and Background:

Graphene is renowned for its exceptional electrical, optical, and thermal properties, while diamond offers unmatched thermal conductivity, wide bandgap, and mechanical robustness. Integrating graphene with diamond can create a hybrid platform with significant potential for advanced optoelectronic and quantum devices, including photonic memristors, tunable diamond photonic cavities for quantum applications, scalable MASERs for sensing/time-keeping, and devices suited for harsh environments.

Graphene can be grown on diamond using various techniques. Two promising approaches are ultrafast laser-induced graphitization and chemical vapor deposition (CVD). Laser processing—using femtosecond pulses—directly converts the diamond’s sp³-bonded surface into a graphene-like (sp²) layer, while CVD offers an alternative route that may yield larger-area, higher-quality films under controlled conditions. A comparative study of these methods is essential to understand their relative advantages and limitations for fabricating continuous graphene films on diamond. Although advanced applications are a strong motivation, this project will focus primarily on optimizing the growth processes and comprehensively testing the properties of the resulting hybrid system.

Project Objectives:

Growth Optimization and Comparison:

• Explore ultrafast laser techniques (e.g., varying fluence, pulse duration, scanning strategies such as controlled pulse overlap, beam shaping, and defocusing) to promote the lateral growth of high-quality graphene-like films on diamond.
• Test CVD methods (through adjustments in temperature, precursor gases, and deposition time) for direct graphene deposition on diamond.
• Compare both approaches in terms of film quality, continuity, and scalability.

Material Characterization:

• Use Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) to assess crystallinity, defect density, and sp²/sp³ bonding ratios.
• Employ scanning electron microscopy (SEM) and atomic force microscopy (AFM) to analyze surface morphology and uniformity.

Property Testing:

• Measure electrical properties (conductivity, carrier mobility) using I–V characterization.
• Evaluate optical properties (transmittance and photoluminescence) and mechanical properties (hardness and adhesion) relevant to device integration.

Expected Outcomes:

Optimized Growth Protocols:

• Establish/initiate recipes for both laser-induced graphitization and CVD processes which have potential for yielding high-quality continuous graphene-like films on diamond.

Comprehensive Characterization Data:

• Provide detailed insights into the structural, chemical, electrical, optical, and mechanical properties of the hybrid material.

Foundation for Future Applications:

• Develop a promising process platform and outlook that underpins future integration into advanced optoelectronic and quantum devices.

Key References:

1. Khomich, A. A., Kononenko, V., Kudryavtsev, O., Zavedeev, E., & Khomich, A. V. (2023). Raman study of the diamond to graphite transition induced by the single femtosecond laser pulse on the (111) face. Nanomaterials, 13(1), 162.
2. Ali, B., Xu, H., Chetty, D., Sang, R. T., Litvinyuk, I. V., & Rybachuk, M. (2022). Laser-induced graphitization of diamond under 30 fs laser pulse irradiation. The Journal of Physical Chemistry Letters, 13(12), 2679–2685.
3. Saeed, M., Alshammari, Y., Majeed, S. A. & Al-Nasrallah, E. (2020). Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: A Review. Molecules 25, 3856.
4. Kononenko, V. V. (2023). Modification of Diamond Surface by Femtosecond Laser Pulses. Photonics 10, 1077.

Interested? Please contact Ryoichi Ishihara r.ishihara@tudelft.nl or Salahuddin Nur <S.Nur@tudelft.nl>