Ethanol Assisted Transfer Method And Heat Transfer Property Of Two-Dimensional Materials

As two-dimensional materials（2D materials）demonstrate unique and diverse properties,they have received widespread attention in basic science and practical applications.However,the research on the thermal properties of two-dimensional materials is few.One of the reasons is the technical difficulty in the sample preparation,transfer,and testing of thermal devices.For example,the transfer process of suspended micro-bridge device demands complete cleanliness and precise positioning.In the field of two-dimensional materials research,clean transferring methods could serve a cornerstone for creative assembly of these two-dimensional building blocks for both fundamental explorations and versatile applications.One of the major challenges for preserving the pristine property of 2D materials during transferring and construction is to de-bond 2D materials from original substrates without inducing structural damage and external contamination.Traditional transfer methods like polymer-assisted transfer and van der Waals force assisted transfer,either have the polymer contamination,or cannot be positioned precisely.We found that ethanol,a common and environmentally friendly solution,can be used to effectively reduce the adhesion energy between 2D materials and substrates,and therefore enable a clean transfer method for 2D materials.Through both molecular dynamic study and experimental demonstration,we demonstrate the effect of ethanol.The cleanness of transfer has been proved by atom force microscopy,Raman spectrum,and photoluminance.Various assembled structures based on 2D building blocks,such as van der Waals hetero-structures,2D materials on suspended devices have all been demonstrated.Thermal conductivity measurements of5-layer Mo S₂ nanosheets on a suspended micro-bridge device also confirm the successful application of suspended 2D transfer.The thermal conductivity first increases and then decreases with a peak at 140 K.The room temperature thermal conductivity of 52 W m^-1 K^-1 is higher than those in previous studies measured with the same micro-bridge method,confirming that the crystal quality of the 2D material is well preserved during the transfer process.It can be expected that this clean,feasible,and precise ethanol assisted transfer method can serve as a powerful tool for constructing novel materials and structures based on 2D building blocks,and exploring their intrinsic properties and functionalities onto suspended devices.