Thin film growth is a very complicated stochastic process, and for investigation of growth condition, one of the important parameter is roughness of interface width, of film surfaces. Roughness has various applications and impact on many phenomena, and also can effect different characteristics of thin film, (optical, electrical, mechanical, diffusion, friction). Recently by help of atomic force microscopy and using various scaling and models for growth conditions, knowledge about statistical characteristics of surface growth have been understood, [1 and 2].
In this experimental work, pure Aluminum and Copper (F.C.C metals), have been sputtered on glass substrate. Atomic force microscopy (AFM) of these samples have been carried out, and surface roughness, (w), structure function, S2 (l), correlation length, l0 growth and roughness exponent (α and β respectively) have been calculated for different deposition rates.
A vacuum system was employed, and for plasma formation pure research grade Argon was used. By changing discharge current, voltage, and gas pressure (Ar), deposition rate was varied in range of 3-15, 4-25 A0/S for Al and Cu films respectively. By use of crystal thickness monitor and also exact balance (10-4 gr) coating rate and film thickness was measured, and Al film with 100 nm and copper film with 250 nm thickness were studied. For both of these metals roughness increases with rise of deposition rate, and by help of computer curve fitting, an empirical relationship has been fitted, and good agreement with experimental results has been obtained. Structure function S2 (l) against l (in logarithmic scale) is very similar for both materials (Al, Cu). Changes of l0 versus R0 (deposition rate) also has been investigated, and l0 depends on coating rate R0 differences and similarities between results are discussed.
References:
[1] Hao, Schwarzacher, W., Anomalous Scaling of the Surface Width during Cu Electrodeposition Phys.Rev.Lett. 86, 2001
[2] Irajizad, A. Ahadian, M.M. Vashaei, Z. J. Phys.D. Room temperature diffusion of Cu in vanadium pentoxide thin films. Appl.Phys. 35, 2002.
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