METHOD FOR PRODUCING AMORPHOUS CARBON COATINGS ON EXTERNAL SURFACES USING DIAMONDOID PRECURSORS
The invention relates to a method for forming high sp 3 content amorphous carbon coatings deposited by plasma enhanced chemical vapor deposition on external surfaces. This method allows adjustment of tribological properties, such as hardness, Young's modulus, wear resistance and coefficient of friction as well as optical properties, such as refractive index. In addition the resulting coatings are uniform and have high corrosion resistance. By controlling pressure, type of diamondoid precursor and bias voltage, the new method prevents the diamondoid precursor from fully breaking upon impact with the substrate. The diamondoid retains sp 3 bonds which yields a high sp 3 content film at higher pressure. This enables a faster deposition rate than would be possible without the use of a diamondoid precursor.
1 . A method of forming a diamond-like carbon coating by plasma enhanced chemical vapor deposition comprising the steps of:
(a) creating a reduced atmospheric pressure adjacent a surface to be treated;
(b) introducing a diamondoid precursor gas to said surface;
(c) establishing a bias voltage between a first electrode and a second electrode with a power source; and
(d) establishing a plasma region adjacent said surface;
wherein said diamondoid precursor gas contains diamondoids of the adamantane series and said pressure and bias voltage are selected such as to cause the deposition of diamond-like carbon on said surface.
2 . The method of claim 1 wherein said pressure and bias voltage are above 20 m Torr and 600V respectively.
3 . The method of claim 1 wherein the pressure is between 20 m Torr and 200 m Torr and the bias voltage is between 600V and 3000V.
4 . The method of claim 1 wherein said precursor is selected from the group consisting of adamantane, diamantane, triamantane and combinations thereof.
5 . The method of claim 1 wherein said precursor is alkylated.
6 . The method of claim 1 wherein said diamondoid precursor is 1,3 dimethyl-adamantane.
7 . The method of claim 1 wherein said adamantane is present as a percentage of between 10% and 100% in another reactive gas.
8 . The method of claim 1 wherein magnets are used to increase ionization and allow low pressure operation of between 20 m Torr and 50 m Torr, with high deposition rate
9 . The method of claim 1 further comprising the step of introducing a hydrocarbon with the diamondoid precursor.
10 . The method of claim 9 wherein the hydrocarbon is in the form of C 2 H 2 or C 4 H 8 .
11 . The method of claim 1 further comprising the step of adding a metal to the precursor.
12 . The method of claim 11 wherein the metal is tetrakisdimethylamino-titanium (TDMAT).
13 . The method of claim 1 further comprising the step of layering diamondoid without any other reactive gas, and other reactive gases with or without diaomondoid, to form composite coatings.
14 . The method of claim 1 further comprising the step of adding a dopant to said diamondoid precursor.
15 . The method of claim 1 wherein the dopant is selected from the group consisting of: N 2 , silicon, germanium, TDMAT, other metals containing MOCVD precursor, and combinations thereof.
16 . The method of claim 1 wherein a second power source establishes a plasma adjacent to said surface.
17 . The method of claim 16 wherein said pressure and bias voltage are above 20 m Torr and 50 V respectively and a deposition rate is greater than 4 μm/hr.
18 . The method of claim 16 wherein the pressure is between 10 m Torr and 200 m Torr and the bias voltage is between 50 V and 500 V to produce a subset of said DLC coating including high sp 3 content polymers.
19 . The method of claim 16 wherein both said power source and second power source are in electrical contact with said first electrode, said first electrode is in electrical contact with said surface, and wherein said power source and second power source have separate return electrodes.
20 . The method of claim 16 wherein said power source is a DC pulse supply and said second power source is an RF supply.
21 . A product coated by the method of claim 1