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▲ [20p-C304-5] Suspension of large, electrically contacted graphene for sub-15-nm phononic crystal patterning
Keywords:graphene, large area, helium ion beam milling
Phononic crystals (PnCs), periodic structures where the period is of similar dimension as the phonon wavelength, promise the opening of phononic band gaps (PnBGs) that could improve thermoelectric conversion efficiency and allow thermal rectification, as shown in Figure 1a [1]. Graphene, the atomic layer of carbon atoms in a hexagonal lattice, has a high Young’s modulus of ~1000 GPa and Debye termperature of ~2800 K. Thus, the wavelength of phonons at a given temperature is greatly increased compared to other materials such as silicon. This reduces the requirements for PnC patterning with PnBGs at room temperature.
Recently, we have demonstrated sub-10-nm milling of a 3x3 pore array into suspended graphene by helium ion beam milling, where a tightly focused beam of ions (beam diameter <0.5 nm) interacts with the graphene and carbon atoms are ejected through collisions [2]. Up to 300 nm long PnCs with pitch of 18 nm were demonstrated, as well. However, to allow optical probing and increase the change of thermal conductivity by the PnCs formation above the noise level, larger PnCs with smaller pitch are required.
In this work, we will report the successful suspension of up to 9.6 µm long and 16 µm wide, electrically contacted, monolayer graphene with an air gap of 300 nm, as shown in Figure 1b and c. We show that the HIM milling approach for PnCs formation can be applied for µm-scaled suspended graphene with pore pitch below 15 nm by adjustment of the point dose.
Acknowledgment: The authors acknowledge T. Iijima and Y. Morita for the usage of the helium ion microscope at the AIST SCR station for the helium ion irradiations. This research was supported through the Grant-in-Aid for Scientific Research (S) No. 25220904 from Japan Society for the Promotion of Science and the Center Of Innovation (COI) program of the Japan Science Technology Agency.
References:
[1] M. M. Haque, M. E. Schmidt, T. Iwasaki, M. Muruganathan, and H. Mizuta, presented at the The 77th JSAP Autumn Meeting 2017, Fukuoka, Japan, 2017.
[2] T. Kanzaki, M. E. Schmidt, M. Muruganathan, S. Ogawa, and H. Mizuta, presented at the The 64th JSAP Spring Meeting 2017, 2017.
Recently, we have demonstrated sub-10-nm milling of a 3x3 pore array into suspended graphene by helium ion beam milling, where a tightly focused beam of ions (beam diameter <0.5 nm) interacts with the graphene and carbon atoms are ejected through collisions [2]. Up to 300 nm long PnCs with pitch of 18 nm were demonstrated, as well. However, to allow optical probing and increase the change of thermal conductivity by the PnCs formation above the noise level, larger PnCs with smaller pitch are required.
In this work, we will report the successful suspension of up to 9.6 µm long and 16 µm wide, electrically contacted, monolayer graphene with an air gap of 300 nm, as shown in Figure 1b and c. We show that the HIM milling approach for PnCs formation can be applied for µm-scaled suspended graphene with pore pitch below 15 nm by adjustment of the point dose.
Acknowledgment: The authors acknowledge T. Iijima and Y. Morita for the usage of the helium ion microscope at the AIST SCR station for the helium ion irradiations. This research was supported through the Grant-in-Aid for Scientific Research (S) No. 25220904 from Japan Society for the Promotion of Science and the Center Of Innovation (COI) program of the Japan Science Technology Agency.
References:
[1] M. M. Haque, M. E. Schmidt, T. Iwasaki, M. Muruganathan, and H. Mizuta, presented at the The 77th JSAP Autumn Meeting 2017, Fukuoka, Japan, 2017.
[2] T. Kanzaki, M. E. Schmidt, M. Muruganathan, S. Ogawa, and H. Mizuta, presented at the The 64th JSAP Spring Meeting 2017, 2017.