Towards on-chip integration of diamond quantum sensors

Abstract

Diamond, is an excellent material for electronic and photonic applications due to its extremely high carrier mobility, thermal conductivity, dielectric breakdown strength, and an ultrawide bandgap and optical transparency that range from the infrared to the deep-ultraviolet. Additionally, it enables excellent quantum performance by hosting some quantum defects that are known as color centers, which are atomic defects in the crystal lattice of a material that can exhibit unique optical and electronic properties. Nowadays, integration development plays a crucial role in various industries and technologies. The ongoing advancements in microelectronics, nanotechnology, material science have led to the development of increasingly sophisticated integration strategies. Therefore, developing smaller, more powerful, energy-efficient, and cost-effective on-chip integrated devices is crucial in various industries and technologies.

Although some integrated strategies have been proposed in sensing applications such as fiber-optic devices, miniature MEMS devices, Lab-on-a-chip devices, and nanomaterials and nanostructures, they are still suffering separated sensing components such as signal source and detector, making them hard to realize a true on-chip integration. To tackle this problem, a Gallium Nitride (GaN)-based optoelectronic chip is demonstrated in this thesis. This monolithic GaN chip integrates light emitter and light detector in a single chip, realizing simultaneously light emission and detection without external assistances. As demonstrations, this micro-sized GaN chip has been successfully used in pressure sensing, salinity content sensing, and cell activities monitoring, indicating its diverse potential applications.

Compared with classical sensing, development of diamond-based quantum sensing is an effective way to achieve higher sensitivity, faster response, better precision and more versatility. However, due to the large thickness and low flexibility of bulk diamond, diamond-based on-chip integration is still hindered. In this thesis, mechanical exfoliation is demonstrated as a simple way to massively produce ultrathin and transferable diamond membrane at wafer-scale. The demonstrated transferability, ultraflat surface (Ra < 1 nm) and flexibility (~ 4.08 % strain) of exfoliated membrane enable it develop diamond-based optical metasurfaces and flexible electronic sensors. This new-found approach will undoubtedly boost the development of diamond in diverse heterogeneous integration applications.

Compared with bulk diamond, nanodiamonds show obvious advantages in quantum-based biosensing and bioimaging due to their manipulated small sizes. However, nanodiamond-based on-chip integration is also hindered due to the lack of efficient methods for scalably and precisely positioning nanodiamonds in target substrates. In this thesis, a novel method, based on electrostatic trapping, is demonstrated effective to pattern single nanodiamond in wafer-scale, which breaks the area limitation of millimeter at maximum achieved by other strategies. This will extremely promote the development of nanodiamond-based on-chip integrations.