The determination of infrared optical constants of rare earth fluorides by classical Lorentz oscillator model

Abstract

Rare earth fluoride (REF3, RE = La, Ce, Pr, Sm, Er, Yb, Y) films were deposited on Ge(1 1 1) and silicon wafers in order to determine optical constants from the near infrared up to the high frequency tail of the reststrahlen band. The FT-IR transmission spectrum and the reflection spectrum were used to examine the infrared optical properties of the fluorides. The optical constants of the films in the infrared spectrum from 2 to 20 µm were calculated using the classical Lorentz oscillator model by fitting the transmission spectrum. The reflective spectrum of the fluorides on silicon was used to demonstrate the absorption difference in this region. It is found that the extinction coefficients of rare earth fluorides films with Pnma structure (REF3, RE = Y, Yb, Er) are larger than the other fluorides films with structure (REF3, RE = La, Ce, Pr, Sm) from 15 to 20 µm.

Combinatorial synthesis of BaClF-ReF3 (Re = La, Pr, Er, Sm) layers with graded-index as antireflection coatings in the thermal infrared

“…The profile of refractive index is in good agreement with the result for depth profiles of Ba and Pr presented in Fig. 6, since BaClF has a greater refractive than that of rareearth fluorides [20,22]. It has been reported that the Gaussian index profile and quintic-index profile are near the optimum profile to minimalize the Fresnel reflections [23], therefore, in our investigation, an extraordinarily lower reflection and effective refractive index can be attributed to an appropriate refractive index gradient existing in the layer.…”

“…The effective indices of refraction n and extinction coefficient k was derived by using Lorentz oscillator as a dispersion model, as described in details in our previous studies [19,20]. The profile of refractive index was also investigated using OptiChar (version 8.85), which is one of the modules of OptiLayer thin film software (OptiLayer GmbH, Russia) [21].…”

ALD of YF3 Thin Films from TiF4 and Y(thd)3 Precursors

“…[6] The most often used techniques have been physical vapor deposition (PVD) methods, e.g., electron beam evaporation (EBE), [4,5,[7][8][9][10] and thermal evaporation. [9,[11][12][13][14][15] Evaporation has also been applied to the fabrication of epitaxial Y x La 1-x F 3 (x ¼ 0-0.8) thin films onto GaAs substrates, [16] as well as YF 3 /ZnS/Ge/ ZnS multilayer structures on germanium substrates. [17] Because the evaporation distribution is not geometrically (and perhaps compositionally) uniform, the properties of the coating can vary spatially over the substrate holder.…”

The structure and optical properties of evaporated Samarium fluoride films

“…Crystal structure of SmF 3 films SmF 3 films have two types of crystal structure according to the deposition temperature, which are Pnma and P3C1. The SmF 3 films deposited in our experiment belong to P3C1 structure according to the far infrared reflective spectrum that is published in the previous work [11]. The SmF 3 films deposited at different temperature from 100 8C to 250 8C are all polycrystalline films, which are shown in Fig.…”