Low Energy Electron Point Projection Microscopy of Suspended Graphene, the Ultimate “Microscope Slide”

Point Projection Microscopy (PPM) is used to image suspended graphene using low-energy electrons (100-200eV). Because of the low energies used, the graphene is neither damaged or contaminated by the electron beam. The transparency of graphene is measured to be 74%, equivalent to electron transmission through a sheet as thick as twice the covalent radius of sp2-bonded carbon. Also observed is rip-pling in the structure of the suspended graphene, with a wavelength of approximately 26 nm. The interference of the electron beam due to the diffraction off the edge of a graphene knife edge is observed and used to calculate a virtual source size of 4.7 ± 0.6A ̊ for the electron emitter. It is demonstrated that graphene can serve as both anode and substrate in PPM, thereby avoiding distortions due to strong field gradients around nano-scale objects. Graphene can be used to image objects suspended on the sheet using PPM, and in the future, electron holography. 1 a