▎ 摘　　要

NOVELTY - Device using the side surface of at least one thin-film graphene film as a field emission source. USE - The device is useful in field emission (claimed) X-ray source and terahertz oscillator for self-diagnosis and disease diagnosis in health and medical fields including non-destructive testing and bio-imaging. ADVANTAGE - The device has high current density, practical output current and long-term stable field emission. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for producing field emission device, comprising (a) placing the graphene oxide solution drops on the primary glass plate, and covering the secondary glass plate on the primary glass plate to prepare a specimen; (b) putting the prepared specimen in a thermal vacuum chamber, applying heat to evaporate the water of the graphene oxide solution to form a graphene thin film; and (c) reducing the formed graphene thin film to prepare a field emission source using a side surface of the reduced graphene thin film. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the producing graphene used as field emission source for producing field emission device.