Ion beam Current density

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]. 

Ion beam processing provides an alternative and non-equilibrium method of introducing dopant atoms into the lattice. In typical applications, a beam of dopant ions is accelerated through a potential of 10-100 kV. The implantation system shown in Fig. 1.1 illustrates the basic elements required in this technique ion source, acceleration column, mass-separator, and target chamber. With different types of ion sources available, a wide variety of beams may be produced with sufficient intensity for implantation purposes for integrated circuit technology 10 " -10 ions cm (less than a monolayer see Sect. 1.4) is a representative ion dose. Ion dose is defined as the number of ions cm implanted into the sample. Alternatively, the term fluence is used instead of dose. The ion beam current density is expressed in units of A cm . The dose rate or flux is given in units of ions s cm . ... 

The passivation was done using a Kaufman ion source [6]. Such ion sources provide the ability to vary the ion beam energy (up to 2 keV) and ion beam current density (up to several mA/cm ) scmiewhat independently. 

N+-N" /cm at 75 keV (Fig. 2) (Ref 5). The high ion-beam current densities employed during the processing (up to 500 )xA/cm versus <50 pA/cm for conventional ion implantation) results in short-time beam exposures of only a few minutes at the elevated temperatures (Ref 29), which would not degrade bulk material properties. 

Oriented PE foils, 10 [am thick with a molecular weight of 1.8 x 10 and a density of 945 kg/m, were irradiated with 10 and 63 keV Ar " ions at fluences from 10 to 3 x 10 7m. The ion beam current density was below 50 nA/cm and the pressure in the implanter chamber was 10 -10 Pa. The irradiated specimens were exposed to solutions of 2 wt% alanine [CH3CH(NH2)COOH] in water, at room temperature, for 12 hours [59]. The adhesion of 3T3 rat fibroblasts on the modified PE was studied in vitro. The radiation damages to the polymer chain, such as free radicals and... 

Concerning implantation parameters, three values are essential the ion beam current density (generally contained between 0.1 and 1 fxAlcm ), the fluence D (or the dose, the number of ions deposited on a unit surface), and the energy of the implanted ions. 

In a more recent study," PC substrates were irradiated with Ar ions in an oxygen environment. The acceleration voltage of the ions was 0.8 kV. A cold cathode hollow ion source was used for generating the ions. Argon ions are the dominant species under these conditions oxygen ions are seldom seen. The vacuum chamber was evacuated to 2 x 10 Torr with rotary and turbo pumps. Working pressure was approximately 1 X 10 " Torr, with the Ar and O2 flow rates of 3 and 12 seem, respectively. The ion-beam current density was measured by a Faraday cup and was fixed at 14.4 xA/cm. The ion doses varied from 1 x 10 ions/cm toSxlO ions/cm. A detailed description of the setup has been presented in a previous article. 

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. 

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. 

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... 

We used commercially available chitosan (Wako Chemical Co., Inc.). Kr-ion bombardment was carried out at energy of 150 keV with fluences of 1.0 x 10 1.0X 10 ionscm in the base pressure of less than 4.0 x 10 Pa at room temperature using a RTKF.N 200 kV low current implanter. The beam current density used was about 0.2 p,A cm to prevent the specimen from heating. 

The studies of influence produced by basic parameters of the IBAD process (ion energy and beam current density) on tribological characteristics of the CrN coating showed that the coefficient of friction is not very much dependent on both parameters [13], However, the wear resistance of coated steel increases essentially. The current density range of 8-32 pA/cm and the energy density range of 4-12 keV have been studied. Maximum values of energy equal to 12 keV and minimum values of the current density equal to 8 pA/cm turned out to be the most optimal. 

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