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

• Published in: Applied surface science Vol. 604; p. 154524
• Main Authors: Ahn, Yujung, Kim, Seong Jun, Go, Eunsol, Lee, Jeong-Woong, Park, Sora, Jeong, Jin-Woo, Kim, Jae-Woo, Kang, Jun-Tae, Yun, Ki Nam, Choi, Sunghoon, Kim, Sunghee, Yeon, Ji-Hwan, Song, Yoon-Ho
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2022
• Subjects: CNT emitter; E-beam convergence; Field emissions; Graphene; Micro-lens; Triode structure; scanning electron microscopy; carbon nanotube; layer-by-layer; Field emissions; Poly(methyl methacrylate); multi-layer graphene; 3-dimensional finite element method; active-current control; atomic force microscopy; ammonium persulfate; electron transparent graphene gate; single-layer graphene; Graphene; Fowler-Nordheim; e-beam; FWHM; E-beam convergence; Triode structure; multi-stacked graphene; CNT emitter; Micro-lens; molybdenum
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2022.154524

Effectively converged field emission electron beams were achieved using the electron transparent graphene gate (ETGG) of multi-stacked graphene (MSG). The MSG-ETGG was prepared by a layer-by-layer stacking, showing robust and scalable to diameters of 300 µm on the apertures. The 7L-ETGG showed good durability upon the prolonged high-energy electron collision over 140,000 times without any deterioration of the MSG suitable for high-resolution X-ray sources. [Display omitted] •Electron transparent graphene gate (ETGG) for effective e-beam convergence.•Robustly suspended multi-stacked graphene of ETGG with scalable diameters of 300 µm.•E-beam convergence with the ETGG by almost 77% compared to the aperture-gate.•Stability of the ETGG upon the 140,000 shots of electron emissions in pulse operation.•The potential of the ETGG for application 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 transparent graphene gate (ETGG) for effective e-beam convergence. The ETGG that was completely made on molybdenum (Mo) apertures with scalable diameters of 300 µm 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.