0030-400X/01/9105- $21.00 © 2001 MAIK “Nauka/Interperiodica” 0779 Optics and Spectroscopy, Vol. 91, No. 5, 2001, pp. 779–785. Translated from Optika i Spektroskopiya, Vol. 91, No. 5, 2001, pp. 830–836. Original Russian Text Copyright © 2001 by Bonch-Bruevich, Vartanyan, Leonov, Przhibel’skiœ, Khromov. INTRODUCTION Investigations of the structure of island films run into a number of complicated technical problems. The methods of investigation that have been developed up to the present are very laborious and either are accom- panied by the destruction of the subject being investi- gated (electron microscopy) or require a direct combi- nation of the evaporation chamber with the measuring equipment (atomic force microscopy). The monitoring of the kinetics of film growth or variations in structural film parameters under a certain external action is partic- ularly difficult using these methods. In addition, both these high-resolution methods have another essential disadvantage. They give information only about small film areas (of the order of 1 μm 2 ), and the data obtained require subsequent processing. To solve the above- mentioned problems, we have proposed and realized the optical method of noncontact determination of structural film parameters [1]. In this paper, we have demonstrated the possibility of determining parameters of island films such as the density of nanometer islands, their size, and the size dispersion. In the present study, we monitored variations in the structural parameters of island metal sodium films on the quartz surface during heating of the substrate and exposure of the films to an intense optical radiation. Recall briefly the idea of the proposed method. In this method, the reflection and transmission of the light beam focused on a film and scanned over it are mea- sured. Since the sizes and the number of islands falling within the focal spot are random quantities, the mea- sured local optical characteristics of the film are also random quantities. By using the measurement data of these random characteristics of the film, one can suc- ceed in determining the statistical characteristics of the islands, such as the density, the mean size, and the size dispersion. It has been shown that it is possible to obtain the island size distribution function from the measurement data of the evolution of the film parame- ters under heating of the substrate or under the action of intense optical radiation, if the law of decrease of their sizes in time is known. In this case, it is possible to reconstruct the distribution function at any instant of action on the film. RELATION BETWEEN THE STRUCTURE OF THE FILM AND ITS OPTICAL PROPERTIES Let us describe the technique for determining the structural parameters from the measured data of optical reflection and transmission coefficients for the films deposited on the surface of a transparent dielectric. Ini- tially note the specific features of implementation of the proposed method. The first feature is connected with the fact that no intrinsic optical characteristics of a film are measured experimentally, because it is always located on a dielectric surface. The second feature is caused by the focus of the beam scanned over the film. Both circumstances complicate the determination of the inherent optical characteristics of a film based on the measurement data. For purposes of simplification Comparative Investigation of the Effect of Heat and Optical Radiation on the Structure of Island Metal Films by Optical Fluctuation Microscopy A. M. Bonch-Bruevich, T. A. Vartanyan, N. B. Leonov, S. G. Przhibel’skiœ, and V. V. Khromov Vavilov State Optical Institute, All-Russia Scientific Center, St. Petersburg, 199034 Russia e-mail: tigran@jamnet.spb.su Received April 12, 2001 Abstract—Variations in the structural parameters of island sodium films on the quartz surface, caused by heat- ing or exposure to optical radiation, are investigated by the optical method proposed earlier. A correct scheme of processing the measured data is developed. It is shown that to determine the structure parameters, the mea- surements of both the mean values and fluctuations of transmission and reflection coefficients of the film and of their correlator are required. It is also demonstrated that under a number of assumptions, it is possible to determine the character of the process of evaporation of islands and to reveal the evolution of the distribution function by using the data of measurements. It was found experimentally that variations in the structural param- eters of a film during its evaporation caused by heating of the substrate or irradiation by light can noticeably differ. This fact is explained by a difference in the mechanisms of action of heating and irradiation on an island. © 2001 MAIK “Nauka/Interperiodica”. PHYSICAL AND QUANTUM OPTICS