Graphene Quantum Dot Bolometers and their Applications for the Characterization of Single Molecule Magnets
St Marie, Luke Riley
Graphene’s unique and extraordinary electronic, thermal, mechanical, and chemical properties give it incredible potential for nanotechnology applications. The electronic properties in particular are very sensitive to the graphene’s geometry and size, providing nanostructured graphene with great potential for device applications. This study explores how epitaxial graphene can be patterned into quantum dot devices that function as highly responsive bolometers. By utilizing quantum confinement effects to create an energy barrier requiring thermal activation to conduct across the device, nanostructured graphene gains massively temperature-dependent resistance. Graphene’s nature as a broadband absorber allows for these bolometers to function for regions of the electromagnetic spectrum that are ordinarily difficult to work with. These properties give graphene quantum dot bolometers the potential to be used in combination with another fascinating nanomaterial: single molecule magnets.Single molecule magnets are versatile nanomagnets with potential applications in quantum computing, spintronics, and high-density data storage, but these applications require the molecules to be isolated in monolayers, which are difficult to characterize. This study investigates how graphene quantum dot devices can be used to measure properties of single molecule magnets, even in thin layers. We take advantage of nanostructured graphene bolometers’ high responsivity to create devices that could be used for electron paramagnetic resonance spectroscopy of monolayer single molecule magnets. The interactions between single molecule magnets and graphene also creates spin valve interactions that could be used to read the spins of a single molecule magnet qubit in a quantum computer. This spin valve effect was observed at temperatures in excess of 50 K, much higher than has been observed for other molecular spin valve devices. This work also includes investigations of other phenomena that arise in graphene quantum dot devices, such as the effects of graphene defects on electron cooling processes and negative magnetoresistance based on Dirac Landau level formation. These results provide insights into the fundamental physics of graphene and promote the development of nanostructured graphene devices.
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