Diamond is a material host of more than 100 different color centers. Of particular interest is the Nitrogen-Vacancy (NV) defect, where nitrogen substitutes a carbon atom and lies next to a vacancy site in the diamond lattice. This defect luminesces in the visible regime, its spin state can be optically read out and initialized, and it can also be coherently manipulated, which makes it a leading candidate for solid-state quantum information processing . Our group focuses on changing the material properties, such as the structure of the diamond, to enhance the emission properties and manipulate these defect properties.
We have developed a process to fabricate high quality single-crystal diamond membranes. Diamond membranes are lifted off from an ion implanted bulk diamond sample using an aqueous electrochemical etching process . A high quality diamond thin film is grown on top of the lifted-off membranes . The diamond membranes are then mechanically stamped onto a dielectric substrate and the lifted-off membranes are etched using an inductively coupled plasma- reactive ion etching (ICP-RIE) process leaving the high quality overgrown diamond membranes on top of a dielectric substrate. Optical micro-cavities and photonic crystal cavities can be subsequently fabricated on the high quality diamond membranes [4, 5].
In addition, we characterize and study the chemistry of diamond surfaces. In particular, we're interested in understanding how to manipulate shallow NV properties, such as charge and lifetime, with surface chemistry. We functionalize the surface of bulk and nanodiamonds with biomolecules and organic ligands, for applications in biotagging and spin sensing.
Nanofabrication of photonic devices
To better study properties of the defect centers in diamond, we pattern optical micro-cavities on our single crystal diamond membranes. Using both photolithography and electron beam lithography, we have patterned microdisks, micro-ring resonators, and both one- and two-dimensional photonic crystals. We study the coupling of defect emission to our optical cavities. Such coupling allows for resonant enhancement of the defect emission, an effect which we can observe using photoluminescence spectroscopy.
In a similar vein, a set of near IR, spin defects has recently been detected in silicon carbide (SiC) . As in diamond, we wish to couple the emission of these defects to micro-cavities. We can fabricate devices in a thin epilayer of doped SiC grown on a thicker layer of different doping. Therefore, one possible advantage of working with SiC is the ability to fabricate photonic devices without needing to first produce thin membranes, as in diamond. Moreover, the defects are of interest because they lie in a different part of the EM spectrum than does the NV center in diamond.
- Awschalom, D. D., Bassett, L. C., Dzurak, A. S., Hu, E. L. & Petta, J. R. Quantum Spintronics: Engineering and Manipulating Atom-Like Spins in Semiconductors. Science 339, 1174–1179 (2013).
- Magyar, A. P. et al. Fabrication of thin, luminescent, single-crystal diamond membranes. Appl. Phys. Lett. 99, 081913–081913–3 (2011).
- Aharonovich, I. et al. Homoepitaxial Growth of Single Crystal Diamond Membranes for Quantum Information Processing. Advanced Materials 24, OP54–OP59 (2012)
- Lee, J. C., Magyar, A. P., Bracher, D. O., Aharonovich, I. & Hu, E. L. Fabrication of thin diamond membranes for photonic applications. Diamond and Related Materials 33, 45–48 (2013).
- Lee, J. C., Aharononvich, I., Magyar, A. P., Rol, F. & Hu, E. L. Coupling of silicon-vacancy centers to a single crystal diamond cavity. Optics Express 20, 8891–8897 (2012).
- Koehl, William F., et al. "Room temperature coherent control of defect spin qubits in silicon carbide." Nature 479.7371 (2011): 84-87.