Beam-current density

The sample was analysed with a primary ion beam of extracted from an oxygen cold cathode discharge type source. A well-focussed 200 nA spot was attained at 4keV per molecular ion. The beam was scanned over a square of side 400 pm to produce a uniform primary beam current density and thus a flat-bottomed crater. In order to eliminate crater-edge effects, the counting system was only enabled when the centre of deflection of the beam was in a central area 125 x 125 pm. 

Figure 7. Efficiency of green-emitting (Zn,Cd)S Cu,Al relative to LasO S.-Tb " as a function of electron beam current density (O) 30 kV, 25 kV, (A) 20 kV. Electron beam dwell is 0.5 fis and pulse repetition rate is 60 pps.

Next, consider the time required to expose a pattern with a focused electron beam. The electron beam with current density J(A/cm2) must strike a pixel for time r(sec) to produce exposure Q (coulombs/cm2) = J t. The beam current density is... 

The luminescence can be of the donor acceptor type. This is the case for ZnS Ag,Cl and ZnS Cu,Al used for the blue and green components of TV screens. At low electron beam current density, the intensity of the green phosphor is maximinn for Cu concentrations of about 10 mole % ... 

Recently there has been a report of the use of Ar+ ion milling (500 eV) to open the bottom cap in the anodized alumina using a normal ion milling machine. The rate of milling can be controlled by the ion beam current density (generally <1 mA cm ) and also the incident angle. The nominal milling rate is 100 A min at normal incidence for a current density of 1 mA cm [12]. 

In the ion beam experiments, the beam-current density is measured and converted to a flux, ion/cm s. The fluence (in ions/cm experienced by the specimen is the flux multiplied by time. In many papers, the measured fluence is converted to an ion dose in units of displacements per atom (dpa). This is essentially a measure of the actual amount of damage (i.e. number of atomic displacements) that results from cascade formation, but it does not consider subsequent relaxation or recrystallization events. The fluence-to-dose... 

Silica glasses from Heraeus were implanted with Cu ions at 50 keV, to a dose of S.OxlO ion/cm at a beam current density of 10 pA/cm. A crucial condition of the implants is that they are thermally bonded to a water cooled sample holder and maintained at a constant substrate temperature of 20°C during the implantation. 

Numerically, this ionization rate coefficient is about 10 -10 cm /s. The total rate of ionization by relativistic electron beams can be expressed in this case as a function of the electron beam concentration Ub or the electron beam current density p (c is the speed of light) ... 

Electron beam energy Electron beam current density (Flux), cm s Concentration of F atoms, cm" F atom production per one EB/F2 collision... 

Figure 11-56. Energy cost of SO2 oxidation as a function of electron beam current density. Dashed line shows energy cost decrease by the cluster effect dotted line shows energy cost decrease by the effect of droplets.

In these relations, is the steady-state ion density generated in atmospheric air (density no) by, for example, a relativistic electron beam (current density j, electron velocity c, electron charge e), which can be calculated as... 

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