Aspects of thin film deposition on granulates by physical vapor deposition

Abstract

Abstract: Thin film and coating technology has entered fields which may show significant deviationsfrom classical coating applications where films are deposited on plane, sometimes largesubstrates. Often surfaces of small and irregularly shaped bodies have to be improved inrespect to electrical, thermal or mechanical properties. Film deposition andcharacterization on such small substrates is not a trivial task. This specially holds formethods based on Physical Vapor Deposition (PVD) processes such as sputter deposition andits ion- and plasma assisted varieties. Due to their line of sight nature a key issue forhomogenous films is efficient intermixing. If this problem is mastered, another task isthe prediction and determination of the film thickness on single particles as well as onlarge scale ensembles thereof. In this work a mechanism capable of uniformly coating up to1000 cm3 ofgranulate with particle sizes ranging from approx. 10 μm to 150 μm by magnetron sputteringis thoroughly described. A method for predicting the average film thickness on theparticles is presented and tested for several differently shaped objects likemicrospheres, irregular grains of sinter powder or micro diamonds. For assessing the filmthickness on single particles as well as on particle ensembles several complementarymethods based on optics, X-ray analysis and gravimetry are employed. Their respectivemerits and limitations are discussed. Finally an outlook on adapting the describedtechnology for surface modification by plasma based reactive and non-reactive processes isgiven. Graphical abstract: [Figure not available: see fulltext.]