Optical energy gap measurement of plasma chemical vapor deposition very thin films using evanescent wave

We propose the use of an evanescent field of waveguided light transmitted along a portion of an optical fiber with the cladding removed (a cladless optical fiber) to obtain the optical energy gap (E₀) of a semiconductor. Through our study of this new method of measurement, it is clarified that E₀ of hydrogenated amorphous silicon (a-Si:H) semiconductor can be determined using a longer fabricated film which is thinner than ordinarily used. While ordinary methods of measurement require a film thickness on the order of 1 μm, this new method of measurement requires a film thickness on the order of 4 nm, with the cladless part of 50 mm in length.