KINETIC ROUGHENING OF AMORPHOUS ZR65AL7.5CU27.5 FILMS INVESTIGATED IN-SITU WITH SCANNING-TUNNELING-MICROSCOPY

The isotropic nature of metallic glasses, lacking in long-range struct ural order, suggests an advantage for surface growth studies. In the p resent work the surface topography of vapor quenched amorphous Zr65Al7 .5Cu27.5 films is investigated in situ with scanning tunneling microsc opy. The development of surface morphology on mesoscopic length scales is analyzed with respect to an increasing film thickness. Vertical ro ughness and in-plane correlation are statistically analyzed by a heigh t-height correlation function. With film thickness less than 30 nm, th e surface roughness evolves with a growth exponent beta of approximate ly 0.2. Above a film thickness of 30 nm we find strong deviations from a self-affine scaling behavior. A roughening transition is observed, at which the lateral size of the characteristic surface structures con verges to a maximum value. Moreover, the size of the uniform surface s tructures is increased with elevated substrate temperature during film deposition. We show that the in-plane size of these structures is gov erned by surface diffusion. In an approximation, neglecting nonlinear corrections, the experimental results are analyzed with respect to a g rowth model proposed by Wolf and Villain.