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Effective radius of adatoms/single atom of polycrystalline W nanotip in gas field ion source
Bishwa Chandra Adhikari,김주성,Sohail Mumtaz,Ramhari Paneru,Pradeep Lamichhane,민부기,장정현,최은하 한국물리학회 2020 Current Applied Physics Vol.20 No.5
A gas field ion source (GFIS) has several advantages such as high current density, low energy spread, and high brightness. In this study, Helium gas was used in a GFIS, generated using the field ionization and field evaporation processes. The (110) oriented three adatoms tip (TAT) and single atom tip (SAT) were prepared with its ion emission stability 9.8% and 10.1% by the nitrogen field-assisted etching, respectively. The TAT and SAT were reproduced throughout the field evaporation and nitrogen field-assisted etching along the same crystal axis with its brightness 2.6 × 107 A/(m2 sr) and 1.6 × 108 A/(m2 sr), respectively. The field emission electron beam effective radii for three adatoms and single atom were calculated to be 2.90 Å and 1.47 Å, respectively, by Fowler-Nordheim plot, in which the single atom size was especially shown to be quite in good consistency with an atomic radius of tungsten.
Effect of electrolyte solution in the morphology control of polycrystalline W nanotip
Bishwa Chandra Adhikari,Jun Sung Kim,Pradeep Lamichhane,Ramhari Paneru,Eun Ha Choi 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
The consistency in the shape and reproducibility of the ultra-sharp nanotips are important for both commercial application and research. In this study, a polycrystalline tungsten wire of diameter 150 ㎛ was used to fabricate the nanotip below the 10 nm by static process of electrochemical etching. The static electrochemical etching process was a common process in which electrolyte solution of NaOH, and KOH varied from 2N to 8N. The taper length, a radius of curvature, and the etching current of nanotips were observed and compared between 4N of NaOH and KOH, respectively. The drop off process quickly occurred in the aqueous solution of 4N of NaOH than in the KOH solution because of high conductivity. The field emission electron beam stability, I-V curve, Fowler-Nordheim (FN) plot are compared between 4N of NaOH and KOH, respectively. Furthermore, the scanning electron microscopy (SEM), field ion microscopy (FIM), field emission microscopy (FEM) image was compared between two nanotips prepared by 4N of NaOH and KOH, respectively.
Biodegradable polymer film modification for food packaging application
Ramhari Paneru,Se Hoon Ki,Bishwa Chandra Adhikari,Eun Ha Choi 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
The surface of biodegradable polymer composite film made up of polyvinyl alcohol and chitosan was modified by dielectric barrier discharge argon plasma. The surface physical and chemical properties of the films were investigated by scanning electron microscope, water contact angle, X-ray photoelectron spectroscopy, and atomic force microscope. The surface hydrophilicity was evaluated by measuring the water contact angle and corresponding surface energy were calculated using Owens-Wendt method. Moreover, the antibacterial properties of samples were studied using the plate counting method.