A robust and scalable electron transparent multi-stacked graphene gate for effective electron-beam convergence in field emission digital X-ray sources

Recently, carbon nanotube (CNT)-based field emission digital X-ray sources have received enormous attention in medical and industrial imaging systems. For high-resolution X-ray images, the field-emitted electron-beam (e -beam) must create a small focal spot size onto an anode by properly converging and focusing of e-beam. Here, multi-stacked graphene by using a layer-by-layer (LBL) stacking method was fabricated as an electron trans-parent graphene gate (ETGG) for effective e-beam convergence. The ETGG that was completely made on molybdenum (Mo) apertures with scalable diameters of 300 mu m extracted and then effectively converged e-beams onto the anode in a triode structure. From the current-voltage measurements, the ETGG reduced turn-on voltage of CNT paste emitters by approximately 24%, as compared with an aperture-gate. The e-beam area originating from the CNT paste emitters with the ETGG was largely converged (almost 77%) compared to the aperture-gate, and scattering of the primary e-beams was eliminated with an optimized collimation module. Long-term durability of the ETGG was confirmed, as the graphene on the apertures robustly remained without any deterioration even upon the 140,000 shots of several-keV-electron bombardment in pulse operation mode. These results demonstrate the potential and suitability of the ETGG for application in field emission digital X-ray sources.