17:30 〜 17:45
▼ [16p-Z32-15] Thermal rectification based on asymmetric nanomesh formed on suspended graphene
キーワード：graphene nanomesh, thermal rectification, helium ion microscope
The thermal rectifier is one of the basic units for thermal engineering, in which the heat transfer from the preferred direction is much larger than that from the opposite direction. The conventional mechanism is based on the combination of two different materials with opposite κ-T dependence (κ: thermal conductivity, T: temperature). However, there are many critical obstacles on the way forward to the practical applications for thermal information processing. One is that most of the reported thermal rectifier has a low recertification ratio just around 10-20%. Another is that it is quite difficult to measure the κ separately for two different nanomaterials. The last but the most is that both the diffusion and ballistic transport of the phonons should be considered if the device scale is smaller than the phonon main free path. In this case, the κ-T dependence method is losing efficacy to explain and guide the thermal rectifier development in advanced nanomaterials. In this work, we use suspended graphene and graphene-nanomesh (GNM) combined structure as a simplified 2D platform to investigate the mechanism of thermal transport. We report that the thermal rectification phenomenon is observed with up to 60% thermal rectification ratio at 150 K. The GNM was patterned by the helium ion beam milling (HIBM) technique with sub-10 nm diameter periodical nanopores. The thermal transport properties from the two directions were characterized by the “differential thermal leakage” method. Both the neck (nanopore edge to edge) dependence and the environmental temperature dependence of the thermal rectification ratio are investigated. Based on the results, the “nanomesh phonon filter model” is proposed, which may provide a new way to design and improve the thermal rectifier beyond the conventional thermal conductivity method.