Aisuluu Aitkulova: Graphene on Diamond: Device Fabrication and Characterization for Electronics Applications

Abstract

Diamond and graphene are two unique carbon allotropes whose exceptional properties, extensively investigated separately, make them attractive for next-generation electronics. Diamond combines ultra-high thermal conductivity, a wide bandgap, excellent mechanical robustness, and chemical inertness, enabling efficient heat dissipation and high breakdown fields. Graphene, by contrast, is a two-dimensional material with extremely high carrier mobility and outstanding electrical conductivity arising from its Dirac-cone band structure. These attributes have sparked strong interest in integrating graphene with diamond to realize high-power, high-frequency, and quantum-compatible devices.

However, reproducible fabrication of graphene-based devices and a comprehensive understanding of the physical and chemical properties of the graphene/diamond interface are still lacking. Furthermore, the physical and chemical properties of the graphene/diamond heterostructure remain incompletely explored.

This thesis investigates two routes for forming graphene/diamond interface —rapid direct growth on (100) single-crystalline diamond (SCD) using a Nickel (Ni) catalyst at high temperature (1073 K), and wet transfer of commercial CVD graphene— and evaluates their electrical and quantum-sensing performance. Direct growth yields predominantly multilayer graphene with only ~20% monolayer coverage due to high carbon solubility in Ni, resulting in a room-temperature Hall mobility of ~79 cm2V−1s−1, underscoring challenges such as Ni dewetting and non-uniform precipitation. In contrast, transferred graphene on electronic-grade SCD with low Nitrogen concentration(< 5 ppb) attains derived hole Hall mobilities up to 2750 cm2V−1s−1 and exhibits weak temperature dependence from 80 K to 300 K, indicating that charged-impurity scattering is strongly suppressed.

Surface-termination engineering, such as plasma O-termination and thermal H-termination, further improves low-temperature mobility, increasing from 1238 to 1640 cm2V−1s−1 and reveals distinct remote-interfacial-phonon energies, ~60 meV and ~114 meV, for O- and H-termination types respectively. Electrical robustness is demonstrated by current densities exceeding 1×109 A/cm2, surpassing limits on conventional substrates such as SiO2.

Photoelectric detection of magnetic resonance (PDMR) of NV ensembles operates reliably from 77 K to 395 K, yielding a zero-field-splitting temperature coefficient dD/dT ~73 kHz/K and magnetic-field sensitivities comparable to conventional ODMR, thereby providing an on-chip electrical readout pathway for quantum sensing.

The goal is to develop a fabrication process and investigate its properties. Ultimately, this study aims to explore the potential of graphene-on-diamond for electronic devices and to identify factors that can optimize their performance.