The structural, optical and morphological properties of CaF2 thin films by using Thermionic Vacuum Arc (TVA)

Abstract

a b s t r a c tIn this study, calcium fluoride (CaF 2 ) thin films have been prepared by Thermionic Vacuum Arc (TVA) technique on glass substrates. In this technique CaF 2 thin films are produced by condensing the plasma of anode material generated in the TVA setup under high vacuum conditions on glass substrates. Crystal structures as well as optical and surface properties of CaF 2 antireflective (AR) coated thin films were investigated. X-ray diffraction (XRD) measurements showed that amorphous CaF 2 thin films were formed. Optical and surface properties of CaF 2 films have been studied based on optical transmittance, reflectance, refractive index and atomic force microscopy imaging (AFM). Our results also show that CaF 2 coated samples exhibit lower reflectance (R). From our optical studies, we have observed that CaF 2 thin films have high AR properties.

Optical Properties of CaF2 Thin Film Deposited on Borosilicate Glass and Its Electrical Performance in PV Module Applications

“…The Un CG shows an average transmittance and reflectance of~91% and 8.1%, respectively, across the wide spectrum from~350 to 1100 nm (Figure 2a), whereas CaF 2 -CG shows improved an transmittance and reflectance of~95.7% and 4.3%, respectively, in the broad spectrum of~350-1100 nm as shown in Figure 2b. The observed results are in good agreement with the results reported by Hahn et al [29] and exhibit an improvement in the result, as discussed by Cetin et al in their study on vacuum-evaporated CaF 2 [24]. The observed absorbance is the minimum (~0.015%) at 600 nm, which is quite low as expected.…”

“…The measured refractive index of ~1.39 at 600 nm indicated the excellent transparency of ~95% of CaF2-CG. There was good improvement in the refractive index, as a result of the vacuum thermal evaporation process, when compared to that presented in the literature and that of bulk material [24].…”

“…It is important to note that the excellent surface uniformity of ARC is highly dependent on the deposition technique. Numerous techniques have been introduced for depositing CaF 2 thin films on substrates for various purposes such as electron beam evaporation [16][17][18][19], radio frequency magnetron sputtering [20], molecular beam epitaxial [21], pulsed laser deposition [22,23] and thermionic vacuum arc [24]. Of these techniques, thermal evaporation has been found to be the most suitable because of its advantages of large-area deposition, low-temperature, and simple process, and it has been proven to be a cheap fabrication process [25].…”

Thermionic Vacuum Arc—A Versatile Technology for Thin Film Deposition and Its Applications

“…The films were uniform, smooth, with a low roughness and had a rather high refractive index 2.07. Antireflective coatings based on MgF 2 are discussed also in [141]; those based on CaF 2 in [142]. The BaF 2 films with high transparency and low reflections values were produced in [143].…”

Ion beam effects of 26.0 MeV Cu 7+ ions in thin metallic and insulating films during Heavy Ion ERDA measurements

“…As another example, thin film alkali-earth fluorides and multilayer structures that include such layers are known to be prospective materials for optics, photonics and chemical sensors. Calcium Fluoride (CaF 2 ) films in particular have been used for a long time in many optical components due to its exceptional transparency in the ultra violet (UV) as well as in the infra-red (IR) spectral domain [4].…”