Carbon usually exists in several forms; graphite, diamond, and the new form of fullerines. All three of these forms are crystalline in structure but have varying properties based on the bonding order of the carbon atoms. Diamond-like carbon (DLC), on the other hand, is amorphous in structure, containing both SP2 and SP3 bonded carbon. As such, DLC has both diamond-like and graphitic properties. Hence the name diamond-like carbon (DLC).
An AFM scan of DLC Thin-film
DLC thin-film is produced in the high-vacumn environment inside the
Nanocoat 1000
machine chamber by a physical vapor deposition (PVD) process. During the
PVD process, benzene is disassociated and ionized by a DC arc discharge
(plasma). The resulting ions migrate towards the substrate to be coated
which is negatively biased relative to the plasma. Collisions between ions
in the gas phase result in the formation of both SP2 and SP3 bonded carbon
structures which are then deposited on the substrate surface. As this is
a PVD process, no chemistry takes place on the substrate surface and, thus,
the substrate temperature can be less than 200° C.
DLC Ion Gun Diagram
DLC thin-film has an amorphous structure which is lacking in crystal grains. DLC has a much smoother surface than TiN. Nanotec's DLC has an average roughness of 7 angstroms whereas a typical TiN film has an average roughness of 110 angstroms. This exceptional smoothness, along with hardness, results in DLC's superior tribological properties as well as other properties such as wear-resistance, chemical inertness, build-up resistance, and low friction coefficient.
Check out comparison AST scans of DLC and Tin (100K image).
The results of a ball-on-disk tribology test is shown below. This test
measures the friction coefficient between the ball and coated disk as well
as the diameter of the wear spot on the ball. The test consists of rotating
a disk which has been coated with the thin-film to be tested under a stationary
ball with a given load applied. An aluminum ball was used in this test.
The materials tested included WC-Co (uncoated), DLC, TiN, CrN, TiCN, TiAlN
thin-films. As shown below, the DLC thin-film out-performed the other materials
for both friction coefficient and ball wear.
Diagram of tribology test
In addition to our regular DLC thin-film, we now offer ion implanted DLC (such as Si:DLC or N:DLC) as well as metal-doped DLC (MDLC). All of these DLC thin-films can be produced by our Nanocoat 1000 machine by use of our modular ion-implant and magnetron sputter units. These modular units can be retrofitted to any existing Nanocoat 1000 machine.
Regular DLC Thin-film
Ion Implant DLC Thin-film
MDLC Thin-film
