Recording media having protective overcoats of highly tetrahedral amorphous carbon and methods for their production
View Patent ↗The invention provides systems and methods for the deposition of an improved diamond-like carbon material, particularly for the production of magnetic recording media. The diamond-like carbon material of the present invention is highly tetrahedral, that is, it features a large number of the sp 3 carbon-carbon bonds which are found within a diamond crystal lattice. The material is also amorphous, providing a combination of short-range order with long-range disorder, and can be deposited as films which are ultrasmooth and continuous at thicknesses substantially lower than known amorphous carbon coating materials. The carbon protective coatings of the present invention will often be hydrogenated. In a preferred method for depositing of these materials, capacitive coupling forms a highly uniform, selectively energized stream of ions from a dense, inductively ionized plasma. Such inductive ionization is enhanced by a relatively slow moving (or “quasi-static”) magnetic field, which promotes resonant ionization and ion beam homogenization.
1. A method for formation of an ion beam that provides carbon deposition over a substrate, the ion beam produced by inductively ionizing an acetylene plasma within a plasma volume and capacitatively coupling the plasma so as to form a stream of ions from within the plasma volume, the method comprising:
moving a magnetic field through the plasma volume to promote even resonant inductive ionization and homogenize the ion beam which deposits carbon over the substrate, wherein the magnetic field rotates with a frequency of less than 10,000 Hz.
2. A method as claimed in claim 1 , wherein moving the magnetic field comprises selectively energizing magnetic coils disposed about the plasma volume.
3. A method as claimed in claim 1 , wherein the magnetic field rotates through the plasma volume with a frequency which is much less than the frequency of an alternating induction potential within the plasma volume.
4. A method as claimed in claim 1 , wherein the magnetic field is transverse and rotates about an axis which is substantially normal to a capacitatively coupled extraction grid within the plasma volume.
5. A method as claimed in claim 1 , wherein the magnetic field rotates with a frequency of less than 100 Hz.
6. A method as in claim 1 , wherein the carbon is deposited on the substrate at a rate in a range from 20 Å per second to 100 Å per second.
7. A method as in claim 1 , wherein the substrate includes a magnetic recording medium.
8. A method as in claim 1 , wherein the substrate includes a semiconductor material.