Influence of surface topography on the multilayer film formation
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ACE AND THIN FILMS
Influence of Surface Topography on the Multilayer Film Formation Yu. V. Grishchenkoa, b, M. L. Zanaveskinb, and A. L. Tolstikhinaa a
Shubnikov Institute of Crystallography, Russian Academy of Sciences, LeninskiŃ– pr. 59, Moscow, 119333 Russia b Russian Research Centre Kurchatov Institute, pl. Akademika Kurchatova 1, Moscow, 123182 Russia email: [email protected] Received June 18, 2009
Abstract—The relationship between the topography of substrates and multilayer films deposited on these substrates (which are used in ring laser gyroscopes) has been investigated. The surfaces were studied by atomicforce microscopy. The statistical properties of the surface topography are analyzed within the approach based on a comparative analysis of the power spectral density functions of roughness calculated for the substrate and film. The degree of correlation between the substrate nanotopography and multilayer film is determined, and the influence of the substrate roughness on the optical characteristics of the deposited mir rors is established. DOI: 10.1134/S1063774510010207
INTRODUCTION Progress in various fields of research and technol ogy is determined by the development of film deposi tion technology. Film coatings are currently widely used, for example, in ring laser gyroscopes (RLGs) (multilayer interference mirror coatings). One of the critical parameters that negatively affect the working characteristics of gyroscopes is the radiation scattering from mirror elements which occurs in the roughness of interfaces in multilayer coatings [1]. Therefore, to optimize coating deposition, it is necessary to establish the relationship between the substrate roughness, the roughness of the mirror coating on the substrate, and the RLG optical characteristics. A complex study of RLG mirror elements by atomicforce microscopy (AFM), Xray scattering, and integral light scattering [2] revealed that an increase in the substrate roughness leads a higher roughness of the mirror coating external boundary and a total light loss of mirrors. The study was performed within an approach based on a comparative analysis of the power spectral density (PSD) functions of the film and substrate surfaces. This method was previously applied to investigate the UV and Xray multilayer mirrors [3, 4]. This study is a continuation of our previous investi gations. The main analytical method is AFM, which makes it possible to obtain 3D topography images with a resolution of about several nanometers in the lateral direction and about an angstrom in height. The calcu lation and comparative analysis of the roughness PSD functions made it possible to trace the evolution of surface nanotopography during the formation of mul tilayer optical mirrors. A PSD function describes the
statistical properties of surface topography, thus allow ing one to compare the corresponding properties of the substrate and multilayer coating topographies on different linear size scales. CALCULATION METHOD AFM data form a 2D function of surface topogra
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