For protecting against damage, computer hard disks have to be coated by hard films. The increasing data density requires reducing the film thickness down to few nano-meters due to the decreasing distance between the write-read head and the disk. This can only be realized using ultra-thin films of enhanced performance for wear and corrosion protecting. The excellent properties of amorphous carbon films termed diamond-like carbon (DLC) have turned to be suitable for this application. The mechanical testing of these ultra-thin and super-hard films is a challenge for the available test methods. Efforts have been done to adapt the laser-acoustic method to the requirements of testing ultra-thin films. The laser-acoustic method yields the Young's modulus, revealing the effect of varying bonding structure of the material, porosity and other micro-defects, including insufficient adhesion. For diamond-like carbon material, Young's modulus correlates with the fraction of tetrahedral sp{sup}3-bonds causing its high hardness and excellent wear behavior. The films were deposited by high current pulsed vacuum arc discharges. The effects of the substrate temperature during the deposition and the film thickness were studied. The minimum film thickness was less than 3 nm.
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