Members: Omer Beeri-Shani

Supervisor: Dr. Jonah Waissman

"The growing family of two-dimensional materials has been highly studied in recent years as many of these materials exhibit unique properties. For future applications, thermal properties are critical for circuit design. However, thermal measurements on 2D materials remain challenging due to their atomic thickness and microscale lateral dimensions. In our group, we use 2D Graphene sheets as thermometers, enabling direct thermal contact and sensitive thermometry for 2D materials. Graphene possesses low energy loss to phonons, chemical compatibility with other 2D materials, and high sensitivity due to its 2D nature. We measure their electronic Johnson noise to accurately measure electronic temperature over a wide temperature range. Our graphene thermometers use metal contacts, but these introduce a contact resistance and diminish the accuracy of our measurement. The resistance arises from the fabrication process itself and is affected by various fabrication parameters. To improve our thermometer's accuracy, we are fabricating two different measurement devices, the first is 2 terminal probing of graphene in its ballistic electron regime, and the second is a special design combining 2 terminal probing and 4 terminal Current vs Voltage (I-V) sensing, commonly used for contact resistance measurements. We employ a dry transfer methodology involving the exfoliation of hBN and graphene, and construction of hBN-encapsulated graphene heterostructures using the Poly a Carbonate (PC) pick-up method. Subsequently, we utilize Electron-Beam lithography, Reactive Ion Etching, and Metal Evaporation to shape and fabricate our two terminal and four terminal devices. Finally, we conduct I-V sweep and frequency depended measurements using a multi-channel Lock In."