UV-induced in-plane anisotropy in layers of mixture of the azo-dyes SD-1/SDA-2 characterized by spectroscopic ellipsometry

• The optical properties of the azo-dyes SD-1/SDA-2, which are used for photoaligning of liquid crystals (LCs), are investigated with Variable Angle Spectroscopic Ellipsometry (VASE). Films of mixture of SD-1/SDA-2 are deposited by spin coating on silicon wafers. The estimated thickness is approximately 10 nm. To achieve photo-induced anisotropy, one of the samples is illuminated during 15 minutes with linearly polarized UV light followed by thermal stabilization during 1 hour at 150 °C. VASE measurements are performed in the wavelength range 200–1350 nm at several angles of incidence and at different sample orientations. Dielectric functions of azo-dye films without/with polarized UV light illumination were modelled using an ensemble of Lorentz oscillators. The results confirm the diffusion model proposed recently for explanation of the formation of the photo-induced order in azo-dye films under the action of polarized light. Refractive indices, their wavelength dispersion and thicknesses of films of SD-1/SDA-2 are reported here.

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TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Annan materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Other Materials Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

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