Room temperature deposition of GeO₂ thin film using dielectric barrier discharge driven excimer lamps

Abstract
We discuss the fabrication of GeO₂ and GeO₂/SiO₂ films at room temperature by photo-chemical vapor deposition. Excimer lamps were used for the light source, and tetraethoxyorthogermanate (TEOG) and tetraethoxyorthosilicate (TEOS), as raw materials. First, we fabricated GeO₂ films from single-precursor TEOG. The surface of the films obtained with Ar₂*, Kr₂*, and Xe₂* lamps was extremely smooth (R_rms ~0.3 nm). Second, we fabricated GeO₂/SiO₂ composite films from a mixed vapor of TEOS and TEOG. In this instance, we used a Xe₂* lamp, which was able to produce films of good quality for both SiO₂ and GeO₂ individually. The refractive indices of the obtained films showed intermediate values between those of SiO₂ (n = 1.46) and GeO₂ (n = 1.60). The relationship between the Ge concentration in these films and the refractive indices was examined. We successfully obtained a GeO₂/SiO₂ composite material of higher refractive index than that of similar composites produced by conventional methods.