Characterization of Single Photon Avalanche Diodes and Integration with Diamond for Quantum Bio-sensing
G.D. Aliberti (TU Delft - Applied Sciences)
Ryoichi Ishihara – Graduation committee member (TU Delft - QID/Ishihara Lab)
S. Goswami – Graduation committee member (TU Delft - QRD/Goswami Lab)
S. Nur – Graduation committee member (TU Delft - Quantum Circuit Architectures and Technology)
Ioannis Varveris – Graduation committee member (TU Delft - Quantum Circuit Architectures and Technology)
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Abstract
The quantum diamond microscope (QDM) is a device that uses nitrogen-vacancy (NV) color centers in diamond to detect magnetic fields using a technique called optically detected magnetic resonance (ODMR). NV centers are suitable for biological measurements because they can operate at room temperature and diamond is bio-compatible. This thesis works towards integrating this technology in a compact portable quantum bio-sensor, for which a chip with single photon detectors is a promising integration platform. Before this thesis started, a CMOS chip had been fabricated with single photon avalanche diodes (SPAD) on it including circuitry for digital communication.
During this thesis, first, software was improved for an existing confocal ODMR setup, adding all necessary features for 2D scanning routines. Then, a new widefield setup was designed and established for testing the CMOS SPADs. Afterwards, the SPADs were electrically characterized and optically tested, the latter by using the widefield setup. The SPADs dit not function correctly and thus could only be partially characterized, leading to the CMOS design needing to be checked for errors. Finally, an attempt at bio-sensing was made. A sample was prepared by cultivating human embryonic kidney (HEK) cells on diamond, submersed in a 40 $\mu$g/mL solution of magnetic nanoparticles (MNP). During incubation the cells absorbed the MNPs, making them responsive to magnetism. This diamond has been scanned with the confocal setup while applying an external magnetic field of 1.07 mT. No HEK cells were found this way, even though the photo-luminescence intensity map hints at their presence within the scanning area, indicating that the external magnetic field and/or the concentration of the MNPs may be too low. More research is needed to confirm this.