Optical and structural properties of LaF_3 thin films

Abstract

LaF(3) thin films of different thicknesses were deposited on CaF(2) (111) and silicon substrates at a relatively low substrate temperature of 150 degrees C. Optical (transmittance, reflectance, refractive index, and extinction coefficient) and mechanical (morphology and crystalline structure) properties have been investigated and are discussed. It is shown that LaF(3) thin films deposited on CaF(2) (111) substrates are monocrystalline and have a bulklike dense structure. Furthermore, it is presented that low-loss LaF(3) thin films can be deposited not only by boat evaporation but also by electron beam evaporation.

Electron beam evaporated LaF3 thin films prepared by different temperatures and deposition rates

“…LaF 3 is a very important optical material widely used for UV-DUV-VUV coatings region due to its wide band gap and relative high refractive index [1][2][3][4][5][6]. Traditionally, LaF 3 thin films were always prepared by resistive heating (RH) boat method and excellent films with low optical loss and high LIDT were produced by this method [1][2][3], But impurities are always introduced because of the reaction between the original material and boat material (Mo, Ta, W, etc.)…”

“…Traditionally, LaF 3 thin films were always prepared by resistive heating (RH) boat method and excellent films with low optical loss and high LIDT were produced by this method [1][2][3], But impurities are always introduced because of the reaction between the original material and boat material (Mo, Ta, W, etc.) [4], the impurities are always the inclusion of absorption, and so the LIDT of the films decrease. Additionally, huge stress and relative low packing density make the RH gotten films fragile and easy to absorb water which limits their application in optical system.…”

“…Microstructure and optical properties of films are decided by the deposition process [4,7]. In this paper, LaF 3 thin films were deposited by EB evaporation method with different deposition temperatures and rates, aiming to get an optimized parameter to produce LaF 3 thin films.…”

Optimal design and fabrication method for antireflection coatings for P-polarized 193 nm laser beam at large angles of incidence (68°–74°)

“…Figure 1(b) shows that the refractive index varies with the thicknesses of LaF 3 single layer; different thicknesses of LaF 3 single layer give different optical constant results. This is because the surface mobility of LaF 3 molecules is particularly sensitive to the temperature, deposition rate, substrate surface quality, and so on [11,12]. The LaF 3 film becomes inhomogeneous with increasing thickness, so the refractive index of LaF 3 was carefully chosen and modified according to the required coating thickness during the deposition process.…”

Non-stabilized europium-doped lanthanum oxyfluoride and fluoride nanoparticles well dispersed in thin silica films

“…The most common host matrixes are fluorides and oxyfluorides, mainly LaF 3 and LaOF, due to their low phonon energy, high chemical stability, high refractive index and high transparence in the UV-Vis-NIR region. Bischoff et al 10 prepared and studied the optical properties of LaF 3 thin films in CaF 2 substrates and demonstrated the high refractive index and low extinction coefficient of the samples, being suitable for optical applications. Buchal et al 11 studied Er(III)-doped thin films of LaF 3 , LuF 3 and YF 3 for photoluminescence and found LaF 3 as the most appropriate host matrix for the Er(III) ion, being largely used in up-conversion applications.…”