Evaluating Angular Ion Current Density for Atomically Defined Nanotips

2014 ◽  
Vol 20 (5) ◽  
pp. 1514-1520 ◽  
Author(s):  
Radovan Urban ◽  
Robert A. Wolkow ◽  
Jason L. Pitters
Keyword(s):  
Current Density ◽  
Ion Beam ◽  
Beam Profile ◽  
Ion Current ◽  
Beam Diameter ◽  
Gas Field ◽  
Gaussian Shape ◽  
Gaussian Profile ◽  
Ion Current Density

AbstractIn this paper we investigate methods to characterize angular current density from atomically defined gas field ion sources. We show that the ion beam emitted from a single apex atom is described by a two-dimensional Gaussian profile. Owing to the Gaussian shape of the beam and the requirement to collect the majority of the ion current, fixed apertures have inhomogeneous illumination. Therefore, angular current density measurements through a fixed aperture record averaged angular current density. This makes comparison of data difficult as averaged angular current density depends on aperture size. For the same reasons, voltage normalization cannot be performed for fixed aperture measurements except for aperture sizes that are infinitely small. Consistent determination of angular current density and voltage normalization, however, can be achieved if the beam diameter as well as total ion current are known. In cases where beam profile cannot be directly imaged with a field ion microscope, the beam profile could be extracted from measurements taken at multiple acceleration voltages and/or with multiple aperture sizes.

Influence of Ion Current Density on the Surface Morphology of AZ31 Magnesium Alloy Irradiated by High-Intensity Pulsed Ion Beam

2011 ◽  
Vol 391-392 ◽  
pp. 868-871
Author(s):  
Peng Li ◽  
Y.X. Wang ◽  
L. Xue
Keyword(s):  
Magnesium Alloy ◽  
Current Density ◽  
Ion Beam ◽  
Surface Profile ◽  
Ion Current ◽  
Az31 Magnesium Alloy ◽  
Horizontal Wave ◽  
Surface Profiles ◽  
Surface Morphologies ◽  
Ion Current Density

HIPIB irradiation into AZ31 magnesium alloy is performed at ion current density of 100-300 A/cm2 with 1 shot. The surface morphologies and surface profiles of the irradiated AZ31 magnesium alloy samples are characterized by scanning electron microscopy (SEM) and profilometer, respectively. It is found that HIPIB irradiation leads to the formation of crater in local region of irradiated samples, and crater density increases with increasing ion current density. Both the surface roughness that reflects the vertical wave of surface profile and the mean spacing of surface profile irregularities that reflects the horizontal wave of surface profile increase as ion current density increases. These results are in agreement with the SEM observation on the irradiated surface.

scholarly journals Two-dimensional focusing of self-magnetically insulated “Plasma Focus Diode”

1989 ◽  
Vol 7 (2) ◽  
pp. 287-303 ◽  
Author(s):  
Katsumi Masugata ◽  
Hironobu Isobe ◽  
Keigo Aga ◽  
Masami Matsumoto ◽  
Shigeo Kawata ◽  
...  
Keyword(s):  
Current Density ◽  
Plasma Focus ◽  
Ion Beam ◽  
Ion Current ◽  
Anode Surface ◽  
Beam Power ◽  
Simple Type ◽  
Experimental Conditions ◽  
Simulation Code ◽  
Ion Current Density

A new and simple type of self-magnetically insulated, vacuum ion diode named “Plasma Focus Diode” has been successfully developed with a large solid angle of irradiation and low divergence angle. The diode has a pair of coaxial cylindrical electrodes similar to a Mather-type plasma focus device. Ion-current density of 1·9 kA/cm2 has been obtained on the anode surface under the experimental conditions of diode voltage ∼1·4 MV, diode current ∼180 kA, and pulse width ∼75 ns. The generated ion beam has been two-dimensionally focused (line focusing) with a focusing radius of ∼0·18 mm, giving a maximum ion current density and beam power density at the axis of ∼0·14 MA/cm2 and ∼0·18 TW/cm2, respectively. The motion of electrons in the gap has been numerically simulated by use of a newly developed particle-in-cell computer simulation code, and good agreement has been obtained between the simulation and the experiment.

Time Resolved Studies of Focused Ion Beam Induced Tungsten Deposition

2002 ◽  
Vol 749 ◽  
Author(s):  
H. Langfischer ◽  
S. Harasek ◽  
H. D. Wanzenboeck ◽  
B. Basnar ◽  
E. Bertagnolli
Keyword(s):  
Current Density ◽  
Focused Ion Beam ◽  
Metal Layer ◽  
Ion Beam ◽  
Ion Current ◽  
Transformation Rate ◽  
Average Current Density ◽  
Time Resolved ◽  
Tungsten Hexacarbonyl ◽  
Ion Current Density

ABSTRACTIn this study we investigate the nucleation and growth mechanisms of tungsten films processed by focused ion beam (FIB) induced chemical vapor deposition. For our investigation we use a 50 keV Ga+ ion beam focused on the substrate target and tungsten hexacarbonyl (W(CO)6) as precursor gas. Mediated by the substrate the energy of the impinging ions leads to the decomposition of the tungsten hexacarbonyl molecules adsorbed on the substrate into volatile parts and nonvolatile residues forming a metal deposit. Time resolved FIB secondary electron microscope imaging in combination with atomic force microscopy reveal first the formation of isolated nuclei and further their coalescence finally resulting in the formation of a contiguous metal layer. Despite the local impacts of the ion beam within the irradiated area of the substrate the localization of the nucleation spots is neither correlated to the spot centers nor to the scan path of the ion beam. After formation, the nanoscale tungsten nuclei preserve their positions and typical shapes during further deposition. Only after merging the nuclei to a contiguous tungsten layer, a further regime of growth sets on which is characterized by deposition of tungsten on a tungsten surface. In this regime the deposition process is determined by the total ion dose and the average current density the samples are subjected to. In this regime, deposition yields up to 3.5 atoms per incident gallium ion are achieved. The contiguous layer quality is determined by Auger electron analysis. The measured growth data were interpreted by adopting the analytic Ruedenauer Steiger approach mainly incorporating ion current density, precursor gas transformation rate, and ion induced sputtering. As a result, the critical ion current density, where ion sputtering exceeds deposition, was identified by the model. Because the model shows excellent agreement with the measurement it should be suitable for further survey concerning focused ion beam process development.

Study of Oxygen-Ion-Beam-Assisted Evaporated Aluminum Oxide Films

1992 ◽  
Vol 279 ◽  
Author(s):  
W. Franzen ◽  
T. Tetreault ◽  
W. Kosik ◽  
W. Croft ◽  
J. K. Hirvonen
Keyword(s):  
Aluminum Oxide ◽  
Current Density ◽  
Crystalline Silicon ◽  
Ion Beam ◽  
Oxide Films ◽  
Electron Beam Evaporation ◽  
Index Of Refraction ◽  
Ion Current ◽  
Oxygen Ion ◽  
Ion Current Density

ABSTRACTAluminum oxide films have been deposited by electron-beam evaporation on heated substrates under oxygen ion bombardment. Substrates were crystalline silicon, grafoil and glass. Both substrat temperature and ion current density were changed for each deposition The films deposited on silicon were examined by spectroscopie ellipsometry which showed that for substrate temperatures between 70°C and 250°C the index of refraction, and therefore the film density, first rose and then decreased with increasing ion current density. Ai 400°C the index reached a plateau under these conditions. Study by Rutherford backscattering of films deposited on grafoil showed no significant correlation between oxygen-aluminum stoichiometry and fi; density, suggesting that the decrease in density for large ion currei is not due to oxygen-ion incorporation, as has been suggested in the past. The films deposited on glass at 400°C showed some evidence of crystallization.

High Damage Threshold Optical Films for Excimer Lasers

1991 ◽  
Vol 236 ◽  
Author(s):  
H. Ito ◽  
N. Kajita ◽  
Y. Minowa ◽  
H. Yoshida ◽  
T. Ina
Keyword(s):  
Current Density ◽  
Film Growth ◽  
Laser Energy ◽  
Ion Beam ◽  
Damage Threshold ◽  
High Energy ◽  
Sio2 Film ◽  
Ion Current ◽  
Optical Films ◽  
Ion Current Density

AbstractHigh damage threshold coating for high energy KrF excimer laser has been developed by the multiple ion beam deposition system, which contains a couple of the ionized cluster beam (ICB) sources and the ionized gas beam source. The damage threshold of low refractive SiO2, high refractive A12O3 and SiO2/A12O3 multilayer coatings is found to be more than 105 shots at 8J/cm2 laser energy. Oxidation is enhanced by ion bombardment during the film growth.The refractive indices of SiO2 and A1203 films were 1.46 and 1.62 at the ion current density of 0.8μA/cm2. The film density of SiOx approaches to the bulk SiO2 of 2.3Og/cm3 with increasing ion current density. The stress-free SiO2 film can be obtained at the ion current density of around 0.5 μA/cm2.

Radiation-induced change of polyimide properties under high-fluence and high ion current density implantation

2004 ◽  
Vol 78 (7) ◽  
pp. 1067-1072 ◽  
Author(s):  
V.N. Popok ◽  
I.I. Azarko ◽  
R.I. Khaibullin ◽  
A.L. Stepanov ◽  
V. Hnatowicz ◽  
...  
Keyword(s):  
Current Density ◽  
Ion Current ◽  
High Fluence ◽  
Radiation Induced ◽  
Ion Current Density
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