Effect of thickness affecting optical properties of Ge thin film preparing by Ultra Vacuum Ion Beam Sputtering

The different thicknesses of Germanium(Ge) films are prepared by Ultra Vacuum Ion Beam Sputtering(UBIS). When the thickness is larger than 100nm, the value of loss function increases by thickness and the peak of loss function appears near 450 nm. Owing to the perpendicular direction of the incident light through the film, it has high loss and phase transform as the high incident angle at 780. The loss value of violet-blue (wavelength 400-500nm) area is higher than red-orange (wavelength 650-700nm) area which has less 10% loss. As the wavelength 700 nm increase, the loss of Ge film will near 0 when the film is thicker than 100nm. Oppositely, the loss of Ge films has the linear relation with the wavelength when the film thickness is thinner than 100nm. As the wavelength decrease, the loss will increase linearly, which can increase optical and photo detector sensitivity.