Heat treatment effect of field emission from carbon inverse opals

Carbon inverse opals (CIOs) are fabricated by a replica method using synthetic opals formed by the sedimentation of SiO2 spheres as a template. The pore size of the CIOs is determined by the diameter of the SiO2 spheres. These periodic structures of carbon exhibit field emission (FE) characteristics. The main emission sites of CIOs are interpreted to be the sharp edge of triangular prisms formed along the boundary of the neighbouring pores. The FE characteristics improved upon heat treatment at high temperature, in cases where the pore structure was not deformed. The graphitization of the carbon and the shrinking of the pore structure led to an improvement of the FE characteristics. On the other hand, the deformation of the pore structure prevents the FE characteristics from improving.