| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 107 === Graphene is a novel two-dimensional material, which has excellent properties in mechanical, optical fields, including high mechanical strength (~1100 GPa), thermal conductivity (5300 Wm-1k-1), transparency (>97%) and charge carrier mobility (200,000 cm2V-1s-1). One of the current methods for preparing graphene is that growing graphene on a copper foil by using chemical vapor deposition (CVD) and transferring graphene from the copper to a target substrate. Therefore, how to efficiently transfer graphene to the target substrate is one of the important issues. At present, transferring high-quality graphene with large area as well as without polymer or metal ion residues is the main problems to solve.
In this study, in order to achieve a large area of high-quality graphene transferring, as well as high cleanliness and integrity of graphene to the substrate, several methods were studied to optimize the transfer process of graphene. First, we discussed the roll-to-roll dry transfer through different release methods: (1) direct exfoliation (2) heated exfoliation. As much as 92 % of surface integrity can be obtained by the method of heat exfoliation in transfer graphene. Then, we discussed using rosin to replace PMMA as a buffer layer in roll-to-roll dry transfer, and the high surface cleanliness of 97% with the large-area graphene could be obtained.
In addition, electrochemical delamination combined with the roll-to-roll dry transfer was further carried out for reducing the etching steps of the copper substrate to improve the cleanliness of transferred graphene. Moreover, after tearing the copper foil with the top of graphene, the copper foil could be used repeatedly to grow graphene, and the cost of using copper foil to grow graphene could be greatly reduced. This method of graphene transferring will greatly reduce the cost of copper foil.
In electrochemical assisted delamination, using PMMA could obtain graphene with a surface cleanliness of up to 99%. We studied the mechanism of this transferring process with the high cleanliness. The intercalation of Na ions could weaken the adhesion between graphene and PMMA layer by electrochemical assisted delamination, as the result, PMMA on top of graphene could be easily washed away, which results in the high cleanliness of transferred graphene.
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