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Caption : fig. s1 (a) the real image of the coating chamber and rotatable table; (b) the schematic diagram of coating au and pd film via magnetron sputtering. 

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Caption : fig. s2 (a) scanning electron microscopy (sem) image of the graphene-au-pd film; (b) enlarged sem image of the film, and the thickness of the film is ~130 nm; (c) the height profiles of the au-pd films on the glass slide.

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Caption : fig. s3 the spectra of (a) sample-1, (b) sample-2 and (c) sample-3. the fabrication parameters of the three samples were same