Fabrication of amorphous Al2O3 optical film with various refractive index and low surface roughness

Abstract

Alumina(Al _2 O _3 ) thin film has been widely used in many applications due to its excellent properties, especially in optical films and semiconductor industries. Refractive index, amorphous property and surface roughness are essential parameters related to its applications. In this study, the fabrication method of preparing various refractive index Al _2 O _3 optical films was proposed. The Al _2 O _3 optical films were deposited at room temperature by electron beam evaporation(EBE) technique. The effects of deposition rate and post-annealed temperature on refractive index, vibration peak of molecular and atom, amorphous property and surface roughness were investigated. Refractive index ranging from 1.519 to 1.627 was realized by EBE method at different deposition rates and different post-annealed temperatures. The variable refractive index was very important in adjusting half-width of reflector band. Meanwhile, analysis showed that the suitable post-annealed temperature could not exceed 400 °C. In short, this work provided an effective approach to fabricate amorphous Al _2 O _3 optical film, which was pretty important in its applications in UV antireflection films and blue light reflection films.

Keywords

• amorphous Al2O3 optical films
• deposition rate
• post-annealed temperature
• various refractive index
• low surface roughness