Influences of Oxygen Ion Beam on the Properties of Magnesium Fluoride Thin Film Deposited Using Electron Beam Evaporation Deposition

Abstract

Magnesium fluoride (MgF2) materials are commonly used for near/medium infrared anti-reflection optical coatings due to their low refractive index and wide-range transparency. Ion assistant deposition is an important technique to increase the density of MgF2 and reduce absorption around 2.94 µm caused by high porosity and moisture adsorption. However, the excessive energy of Argon ion will induce a color center and; therefore, lead to UV/Visible absorption. In this paper, oxygen ion was introduced to reduce the color center effect in MgF2 thin film deposited using electron beam evaporation with ion assistant. The films were deposited on Bk7 and single crystal silicon substrates under various oxygen ion beam currents. The microstructure, optical constant, film density, stress, and adhesion are investigated, including the absorption properties at the infrared hydroxyl (–OH) vibration peak. The results show that as the oxygen ion beam current increases, the absorption value at the position of the infrared OH vibration, defects, and stress of the film decrease, while the refractive index increases. However, MgF2 has poor adhesion using oxygen ion-assisted deposition. Thin MgF2 film without ion beam assistant was used as adhesive layer, high density, and low absorption MgF2 film with good adhesion was obtained.

Exploration of Long-Range Surface Plasmon Resonance on Multilayer Single Mode Optical Fiber With Function of MgF2

“…As a dielectric, MgF2 has grabbed wide attention with its less refractive index and larger range of transparency [13], metallic purities and high surface area for better sensitivity [14]. Evaporating conditions can slightly influence the MgF2 because of their stability.…”

Special Issue: Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation

“…Zhang et al [31] investigated the use of an oxygen ion beam to improve the performance of magnesium fluoride (MgF 2 ) as an optical coating layer in the visible, near infrared (NIR) and mid-wavelength infrared (MWIR) spectral regions. They report that as oxygen flow increases, the film density and refractive index increases; an MgO phase is formed within the MgF 2 matrix, with oxygen filling F − ionic vacancies.…”