Laser-induced deformation on hard disk surface

Laser-induced deformation on hard disk surface has been studied. A diode-pumped Q-switched Nd:YVO4 laser was used in the experiment. The sample is a commercial hard disk. Atomic force microscope AFM.was employed to analyze the surface morphology after laser irradiation. Depending on the laser fluence used, a radial structure with or without a circular protruding center could be obtained. Auger electron spectroscopy AES. analyses on different sputtered level were performed to analyze the compositions at irradiated and unirradiated areas. The mechanisms of surface deformation are proposed qualitatively based on the results. Since the upper three layers, the carbon, magnetic and chromium layers, are quite thin and have higher melting points than that of the underlying nickel–phosphorous layer, the radial structure is possibly due to the interfacial stress developed during the localized sub-surface melting of the nickel–phosphorous layer. The circular protruding center is probably resulted by the whole surface melting due to higher local laser fluence. q1999 Published by Elsevier Science B.V. All rights reserved.