In situ film diagnostics during plasma polymerisation using waveguide mode spectroscopy

An in situ determination of the optical properties of films deposited during plasma polymerisation processes with nanometer accuracy has been realised using waveguide mode spectroscopy. The detection method relies on a bi-diffractive grating coupler with two grating constants and allows the background free detection of the propagation constants in a reflected mode geometry. It enables separate determination of the refractive index (n) and the thickness (d) as the plasma polymer film grows. The method has been applied in a preliminary study of the plasma assisted deposition mechanism of allylamine and maleic anhydride.