Growth and characterization of hydrophobic anti-reflection CaF 2 films
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Growth and characterization of hydrophobic anti-reflection CaF2 films Ravish K. Jain1 · Jatinder Kaur1 · Atul Khanna1 · Amit K. Chawla2 Received: 2 May 2020 / Revised: 24 June 2020 / Accepted: 8 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract CaF2 films of thicknesses in the range of 50–200 nm were deposited by thermal evaporation on glass substrates. A series of CaF2 films were also grown by oblique angle deposition in which the orientation of the substrate with the horizontal direction was varied from 0° to 75°. C aF2 films are crystalline and show X-ray reflections corresponding to (111), (220), and (311) crystal planes of the cubic phase. The surface morphology of the films was analyzed by atomic force microscopy and it is found that surface roughness increases with an increase in the deposition angle. The water contact angle studies on C aF2 films show that the wettability properties of the films depend on the film thickness and hydrophobicity enhances with the angled deposition. Optical studies found that CaF2 films have high transmittance (> 85%) and good anti-reflection properties in the wavelength range of 400–1000 nm. The study shows that the anti-reflection and hydrophobic properties of C aF2 films can be modified by the oblique angle thermal evaporation.
1 Introduction Hydrophobic anti-reflection coatings with high chemical, thermal, and mechanical stability can play an important role in solar panels, outdoor display devices, windshields of vehicles, and other optical and opto-electronic components [1–8]. Such coatings protect them against unavoidable environmental conditions such as dust, wind, rain, humidity etc. and aid in maintaining the high light transmittance [1–8]. The efficiency of the optical devices such as solar panels, display devices, and vehicles’ windshields is adversely affected by the accumulation of the dust particles and moisture on the surface that obstructs the transmission of light [1, 5]. Hydrophobicity imparts a self-cleaning property to the surface as the water droplets readily roll on the hydrophobic surface and carry away the dust particles [1]. Quan et al. have reported the growth and characterization of hydrophobic SiO2-based coatings that have lesser adhesion to dust particles and possess self-cleaning features [1]. Transparent and protective top coatings on solar cells and other devices * Atul Khanna [email protected] 1
Sensors and Glass Physics Laboratory, Department of Physics, Guru Nanak Dev University, Amirtsar, Punjab 143005, India
Department of Physics, University of Petroleum and Energy Studies, Dehradun, Uttarakhand 248007, India
2
should have wide wavelength range of transparency, wide band gap, low refractive index, low optical loss, and high chemical and thermal durability [8]. Alkaline earth metal fluorides meet these requirements and are already being used in optical components and devices such as optical windows, polarizers, and lenses [9–14]. Most commonly used material with anti-reflecting p
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