Preparation and optical properties of holmium oxide thin films

Holmium oxide films were prepared by an electron beam deposition method in vacuum. Films exhibited b.c.c. type structure of holmium sesquioxide as determined from electron diffraction studies. Optical properties of Ho2O3 films deposited onto quartz substrates were examined for the wavelength range of 0.2–2.5 μm. Films are characterized by a high transparency between 0.3 and 2.5 μm. The complex refractive index, n*=n−jk, and the complex dielectric function, ε*=ε′−jε′′, for optical frequencies were evaluated. The dispersion characteristics for n(λ), k(λ), ε′(ω) and ε′′(ω) were presented. At λ=0.55 μm the refractive index was n=1.80. Ho2O3 films exhibited low absorption in the whole visible spectral range (k<0.002). The high frequency relative permittivity of Ho2O3 was also determined: ε′∞=3.24.