Effects of interface roughness on the spectral properties of thin films and multilayers

Abstract

We introduce two parameters, large-scale and small-scale rms roughness, to take into account the interface properties of thin films and multilayers in the calculation of their specular reflectance and transmittance. A theoretical motivation for the introduction of these two parameters instead of a standard single rms roughness is provided. Experimental power spectral density functions of several samples are used to illustrate ways in which the parameters introduced can be evaluated.

Spectroscopic ellipsometry and reflectometry of statistically rough surfaces exhibiting wide intervals of spatial frequencies

“…It is caused by the fact that the RRT includes correctly the roughness components corresponding to the higher and medium spatial frequencies whereas the EMT only includes the components with the highest spatial frequencies [11]. In spite of this conclusion there is a good agreement between the total rms values of the heights determined using AFM and both the opti- [11,15].…”

Reflectance and transmittance model for multilayer optical coatings with roughness at oblique incidence

“…We can expand it to the situation of multilayer system by mathematical induction, according to transfer relation between layers, we obtain the expression as follows [9]:…”

“…According to the relationship between surface spatial wavelength and incident light wavelength, surface roughness can be divided into large-scale roughness and small-scale roughness [9]. When surface spatial wavelength is bigger than incident light wavelength, we define surface roughness as large-scale roughness; when surface spatial wavelength is smaller than incident light wavelength, we define it as small-scale roughness.…”

“…The former ignores the characteristic of surface spatial wavelength, and the latter is difficult for recurrent computation to be expanded to multilayer system. Considering these, based on the different scattering effect mechanism between surface roughness of different spatial wavelength, Tikhonravov [9] proposed the concept of large and small scale RMS roughness, expanded rough surface single-layer optical characteristics calculation model to multilayer system, and had the model embedded in Optilayer software. There is a possibility in Optilayer software to use "interlayers" instead of interface roughness.…”

Self-Organized Nanoscale Roughness Engineering for Broadband Light Trapping in Thin Film Solar Cells

“…In order to further enhance the vertical amplification of transferred nanostructures, we developed an upgraded version of the process where the metal stencil mask lifetime is prolonged by co-evaporation of metallic atoms during ion irradiation (assisted-ion projection lithography, A-IPL) [18]. The high aspect ratio features confer broadband anti-reflection functionality to the textured glass substrate and at the same time ensure a high efficiency for diffuse scattering (high haze) [19,20].…”