A Novel Rectilinear Negative Carbon Ion Beam Source for Large-Area Amorphous Diamond Like Carbon Coatings
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ABSTRACT A novel rectilinear negative carbon ion beam source for large-area coatings has been developed, based on SKION's Solid State Ion Beam Technology. The negative carbon ion beam is effectively produced by a primary cesium ion bombardment and the secondary negative carbon ion yield has been observed to be about 0.5. The ion source produces a negative carbon ion current density of 0.25 mA/cm 2 at the extraction voltage of 4 kV. The ion beam energy can be independently controlled from 0 eV to 300 eV. Due to the rectilinear geometry for the production of ion beams, the scale-up of the ion beam in length direction can be easily obtained with no limit. Furthermore, the ion source uses no gas discharge to generate ion beams and does not use any hydrogen gas. The ion source can be operated in a high vacuum ( 50 GPa), atomically smooth (< I nm Ra), and hydrogen-free amorphous diamond-like-carbon (DLC) films over large areas.
INTRODUCTION In the last two decades, Diamond Like Carbon (DLC) has been investigated intensively because its properties are very similar to crystalline diamond. The DLC films have an extreme hardness, very low friction coefficient, high electrical resistivity, chemical inertness, and optical transparency. These films have been deposited by various techniques, such as rf plasma-assisted chemical vapor deposition[l], laser arc[2], rf or dc plasma decomposition of a hydrocarbon gas[3-6], and dual ion beam sputtering[7-8]. Recently, it has been suggested that much better defined growth conditions of thin films can be achieved by direct ion beam deposition[9-1 1] since in this technique, deposition parameters, such as ion-beam energy and ion flux, can be controlled independently. It is well known that DLC film properties strongly depend on the carbon ion energy for deposition. Cuomo et al.[12] suggested that DLC films deposited by laser vaporization exhibit more diamond-like properties for all substrates than sputtered films. Since the laser vaporized particles have a relatively higher energy than the sputtered particles, a greater fraction of these atoms initially achieve a tetrahedral bond, resulting in more diamond-like final films. However, the laser vaporization, including all the conventional deposition techniques, cannot control the energy of the deposited particles. Direct ion beam deposition is the only technique that can control ion beam energy independently to optimize the properties of DLC films.
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Mat. Res. Soc. Symp. Proc. Vol. 396 01996 Materials Research Society
In this paper, we are presenting a novel design of a negative carbon ion beam source which can produce DLC films over large areas. This source generates the negative carbon ion beam taking advantage of a high negative secondary carbon ion yield of cesium ions (0.20.5)[13]. Since this source is a sputter type without any gas discharge, it can produce negative ion beams in a high vacuum range (10--10-7 Torr). This source is also suitable to operate in a low energy range (0-300 eV). Moreover, this ion beam source has distin
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