Kyu Chang Park's research while affiliated with Kyung Hee University and other places

... In various applications, VEDs [14][15][16], including travelling wave tubes, X-ray tubes, electron microscopes, etc., all require a high current and high current density electron source to achieve optimal device performance. They also require a low energy distribution to improve electron beam control, such as focus, diffusion, laminar flow, etc. ...

... There are several ways to fabricate field emitters, such as electrochemical etching of tungsten wires, 6 metal cones deposited on a surface, 7 silicon tips etched with DRIE or wet etching processes, 8,9 and deposition of CNT emission on a surface. [10][11][12] Research on new techniques of fabrication of electron emitters as well as research on their application is still widely conducted. [13][14][15][16][17] However, research usually deals with fabrication and testing of the emitters in laboratory setup, and when the emitters are applied to a final device, the conditions change and the emission properties of the emitters are worse than before its integration. ...

... Field emitter array has important applications in field emission display [1][2][3][4][5], parallel electron-beam lithography [6][7][8][9], and X-ray source [10][11][12][13][14][15]. Until now, only CNT [16], Si nanotip [17], and ZnO nanowire [18] have been active in studies of field emitter array applications. Among them, ZnO nanowire has advantages in terms of its simple synthesis method, low cost, high uniformity, and compatibility with microfabrication techniques, which makes it outstanding in large-area gated field emitter arrays [18]. ...

... The functional groups at the SAM endpoints can anchor to the ceramic film surface and significantly affect its properties and deposition. Using this method, compact and uniform TiO 2 , SnO 2 , V 2 O 5 ·nH 2 O, and other oxides have been successfully deposited [9][10][11]. Research has also found that SAMs promote the formation of oxide films and can facilitate solid heteronucleation because they decrease surface energy relative to the bare substrate surface. ...

... The X-ray has been widely used in medical diagnosis, security checks, and drug testing since Roentgen discovered it in 1895 [1]. It has made remarkable progress in communication, material analysis, high-resolution imaging, and other fields [2][3][4][5]. X-ray sources can be roughly classified into two types: thermal cathodes and cold cathodes. Traditional thermal cathode X-ray sources exhibit limitations such as low current densities, high operating temperatures, and long response times, which render them unsuitable for miniaturization. ...

... Carbon nanotubes (CNTs) present numerous advantages as field emission cathode (FEC), such as their ultralow turn-on voltage (~0.4 V μm −1 ) 1 resulting from the low work function (~5 eV) 2 , exceptional chemical and physical stabilities 3 , as well as high electrical and thermal conductivity 4,5 attributed to the C-C covalent bond, seamless hexagonal network architecture and one-dimension carbon nanostructures 6,7 . These unique characteristics render FEC an ideal electron source for various applications, including field emission scanning electron microscopy (FESEM) 8 , field emission display (FED) 9 , electron beam (E-beam) lithography (EBL) 10 , and X-ray tube 11 . In modern space technologies 12 , FEC often serves as the cathode for electric propulsion (EP) system, providing electrons to neutralize the positive ions or positively charged droplets to avoid charging of the spacecraft 13 . ...

... The FSS is divided into two parts: horizontal FSS (H FSS ) for the beam's short axis and vertical FSS (V FSS ) for the beam's long axis. Using the EN-12543-5 standard, we measured the blurriness of tungsten (W) wire, [22][23][24][25] and we achieved an FSS H FSS of 0.58 and V FSS of 0.76 mm, respectively, as shown in Figs. 7(a) and 7(b). ...