Early growth stages of sputter deposited Ag on native SiO 2 S. Banerjee * , S. Kundu Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064, India Received 26 November 2002; accepted for publication 24 April 2003 Abstract We have presented the kinetic study of the very initial growth stages of an ultrathin film (40–150  A) of Ag sputter deposited on a Si(0 0 1) substrate, covered by native oxide, using grazing incidence X-ray reflectivity (GIXR) technique and atomic force microscopy (AFM). We observe that the films consist of mounds with the presence of voids. The thickness Ôd xray Õ and the packing fraction ÔgÕ of the film as a function of growth time ÔtÕ follow a simple power law, d xray  t m and g  t n with the exponent m ¼ 0:58 and n ¼ 0:4 respectively. We have quantitatively determined that the voids between the mounds decrease at the initial growth stages with the increase in mound size. The mound size in- creases mainly by coalescence. The mound size increases radially as  t z as a function of time. The radial growth ex- ponent z crosses over from z > 0:5 to 0.25 indicating two growth regimes. GIXR measurements reveal sublinear dependence of g on d and the AFM measurements show a cross over of the radial growth exponent. Both these indicate that at the initial stages, the lateral growth of the mound is dominant over the vertical growth hence reducing the voids. Ó 2003 Published by Elsevier Science B.V. Keywords: X-ray scattering, diffraction, and reflection; Atomic force microscopy; Growth; Sputtering 1. Introduction The study on the growth of ultrathin metallic films are of great importance not only for under- standing the growth kinetics at its fundamental level but also for its technological application in the fabrication of nanodevices. In the semicon- ductor industries, sputtering is commonly used for depositing ultrathin films for metallization. Here we report a study on the growth kinetics of the initial growth stages of Ag films using grazing in- cidence X-ray reflectivity (GIXR) and atomic force microscope (AFM). In recent years, GIXR has been successfully used in a non-destructive manner to obtain the structure and chemical profile of a film as a function of its depth [1–3]. AFM is used for obtaining topographic images of hard and soft surfaces with Angstrom resolution. Recently we have reported that when Ag is deposited using dc magnetron sputtering, the initial growth of the film is carpet-like and above a critical thickness 40  A the film structure changes to form mounds [4]. Below the critical thickness one can easily modify the ultrathin film of Ag intentionally by the tip of AFM to fabricate periodic pattern of nanoscale order [4,5] and above the critical thickness, one observes the onset of mound formation. These mounds are significantly stable and cannot be * Corresponding author. Tel.: +91-33-3375346; fax: +91-33- 3374637. E-mail address: sangam@hpl.saha.ernet.in (S. Banerjee). 0039-6028/03/$ - see front matter Ó 2003 Published by Elsevier Science B.V. doi:10.1016/S0039-6028(03)00612-5 Surface Science 537 (2003) 153–160 www.elsevier.com/locate/susc