The analysis and further development of the experimental-analytical approach for determining the values of the optical parameters of nanosized particles for a system with a statistically inhomogeneous structure is presented. An improved experimental-analytical method for determining the complex specific electric polarizability of nanosized particles in systems with a statistically inhomogeneous structure is based on spectrophotometric and electron-microscopic measurements on two-dimensional structures and application of analytical solution of Rosenberg's spectrophotometric equations with the consideration of analysis of particle size distribution.Experimental spectrophotometric and electron-microscopic studies of nickel islet films with weight thickness from 0.3 nm to 2.0 nm deposited by high-vacuum sputtering on quartz substrates in the range of the spectrum 0.2 ÷ 1, 1 μm are performed. Islands nickel film presented morphological microstructure in the form of monolayers isolated from each other nanoislands spherical surface nickel concentration (0.8 ÷ 2.0) • 10 12 cm -2 and an average particle diameter 2.5 ÷ 7 nm.The optical characteristics, namely, the complex specific electric polarizability, optical electric conductivity of nanosized nickel particles are determined in the spectral range 0.2 ÷ 1.1 μm with the help of the improved experimental-analytical method. A significant increase to one order of magnitude of the absolute values of complex specific electric polarizability of nickel particles with a decrease in their size and in comparison with absolute values of complex specific electric polarizability of model spheres with refractive index and absorption index of nickel in macroscopic volumes was revealed. It is established that in the spectral dependences of optical electric conductivity of nickel nanoparticles in the range 0.2 ÷ 1.1 μm there is a band that diminishing size is shifted to a high-frequency region. In this case, the value of optical electric conductivity of nickel nanoparticles monotonically decreases with a decrease in the size by 1-2 orders of magnitude. Comparison of the obtained values of optical electric conductivity of particles in the range of the considered interval with the values of optical electric conductivity of macroscopic samples of nickel in the studied range of the spectrum shows that in particles the value of optical electric conductivity is 2-3 orders of magnitude smaller than that of bulk metals. It is shown that in the nanoparticles of nickel absorption of "Drude" type in the near infrared region the spectrum is suppressed. The reason for this phenomenon may be the change of the mechanism of low-frequency electromagnetic response in nanosized metal particles in comparison with macroscopic metals.The research results are of interest for the development and optimization of nanostructured systems with the inclusion of nanosized nickel particles and functional devices based on them with given electromagnetic characteristics.Ref. 22, fig. 4.
Work is devoted to a research of dimensional changes in optical properties of nanosized copper particles with sizes less than 10 nm in statistically inhomogeneous systems. Experimental spectral and dimensional dependences of the complex specific electric polarizability of nanosized copper particles with experimental-analytical method are determined in the optical spectral range from 0.2 to 1.1 μm. The values of the complex specific electric polarizability were determined by analytical solution of Rosenberg's spectrophotometric equations with the use of experimental results of spectrophotometric measurements of transmission and reflection coefficients of copper islet films and the results of electron microscopic studies of their morphological microstructure, taking into account the statistical analysis of the particle size distribution. Nanosized copper particles with a statistically inhomogeneous structure in the system of islet films on quartz substrates were obtained by vacuum-magnetron sputtering. An analysis of function of copper nanoparticles distribution in size in a system with a statistically inhomogeneous structure was carried out using the Pearson's consensus criterion.To find out the features of optical absorption of nanosized copper particles, their experimental spectral and dimensional dependences of the complex specific electric polarizability are compared with the corresponding characteristics for model particles with properties characteristic for macroscopic volumes of copper. It was found that the optical properties of nanosized copper particles differ from optical properties of copper in a macroscopic volume. An increase in the absolute values of the components of the complex specific electric polarizability of spherical nanosized copper particles with decreasing their diameter within the range from 8 nm to 3.2 nm for wavelengths of 0.2 -1.1 μm is established.The spectral dependences of optical parameters of nanosized copper particles according to well-known theories of classical and quantum dimensional effects are calculated. In order to study the nature of dimensional dependences of optical parameters of copper nanoparticles, a comparative analysis of calculated and experimental spectral and dimensional dependences of their optical parameters was carried out. It is shown that the experimental dimensional changes in the complex specific electric polarizability of copper particles in the investigated range of sizes not be due to the classical or quantum dimensional effect in the dipole approximation.Ref. 36, fig. 3.
In the dipole approximation for the spherical nickel nanoparticle with a diameter D0 = 2.5 ÷ 7 nm in the spectral range from 0.2 to 1.1 μm at T = 300 K, efficiency factors of the absorption Κa and scattering Κs were determined with the help of the experimental values of the complex specific electrical polarizability. Numerical calculations of the Κa and Κs of the nickel nanoparticles were carried out in accordance with the theories of classical and quantum dimensional effects. It was shown that it is impossible to explain the photoabsorption of nickel nanoparticles by the intraband (Drude) type of absorption even taking into account classical or quantum dimensional effects.
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