Refractive index and extinction coefficient dependence of thin Al and Ir films on deposition technique and thickness

Abstract

We show that the optical properties of thin metallic films depend on the thickness of the film as well as on the deposition technique. Several thicknesses of electron-beam-gun-evaporated aluminium films were measured and the refractive index and the extinction coefficient defined using ellipsometry. In addition, the refractive indexes and the extinction coefficients of atomic-layer-deposited iridium were compared with those of evaporated iridium samples.

General approach to reliable characterization of thin metal films

“…In the case of metal films, this approach may lead to unstable characterization results for the following reason. It is known from a number of publications (see, for example, [5,8,11,13,14,[19][20][21]36]) that wavelength dependencies of the optical constants of bulk metals and thin metal films in the visible and infrared spectral ranges are quite complicated and cannot be described by simple parametric models. By using multiparametric models, it is possible to provide an excellent fitting of measurement data but it is not guaranteed that the obtained parameters have physical sense.…”

“…In the last 20 years, the interest in research of thin metal films and metal-dielectric coatings has increased significantly [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Thin metal films possess a potential in design and manufacture of multilayer structures with sophisticated spectral performances over wide wavelength ranges.…”

“…Characterization results related to different types of thin metal films can be found in many publications (see, for example, [5,[12][13][14]16,[26][27][28]). In these publications, different sets of experimental data were used and various characterization approaches were applied.…”

Comparison of two techniques for reliable characterization of thin metal–dielectric films

“…In recent years, a number of papers related to characterization and modeling of metal-dielectric thin films have been published [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The permanently growing interest in the study of thin metal and metal-dielectric films is explained by their specific optical properties, which allow using these films in the design of multilayer structures of special types [4,6,14,15,[17][18][19][20][21].…”

“…The most popular technique is based on a well-known oscillator model [23][24][25]. However, wavelength dependencies of the optical constants of thin metal-dielectric films in the visible and infrared spectral ranges are quite complicated [1,[7][8][9]13,[26][27][28], and multiple oscillator models have to be used. Because each oscillator is defined by several parameters, a large number of parameters has to be determined in the course of the characterization process using a multiple oscillator model [23][24][25]29].…”