Research about the method of measuring the ultra thin film and the plasma reaction under film growth using optical waveguides

利用CVD设备在裸露铁芯的结构的多模光纤传感器上沉积了约10 nm厚的薄膜，随着时间的推移，685~800 nm波长的透射光强度逐渐变小，并在约600秒内饱和，此外，为了提高传感器的灵敏度，需要加长传感器部分或使其变薄。然后，采用芯层厚度比前者薄7微米×6微米的嵌入式三维波导作为传感器，测量了a-Si：H薄膜的光学物理性能。从而得到了与常规光纤和常规平板光波导作为传感器时具有相同趋势的吸收光谱。在得到吸收光谱的基础上，当被问及在波导上沉积的a-Si：H薄膜的光能带隙时，得到了约1.70-1.72[eV]的值，而与波导长度无关。这与传统的测量方法得到的值基本一致。此外，当在直径为110im的光纤中将传感器长度设置为50[mm]时，由于吸收量变得不足而导致的测量极限为a-Si：H厚度50[nm]。通过所介绍的测量系统，当传感器长度设置为50[mm]时，由于a-Si：H厚度为3[nm]，因此能够达到提高大灵敏度的目的。由于它不同于平板波导，它是三维波导，所以用有限元方法进行了高精度的分析。

The thin film of about 10 nm of thickness was made to deposit on the multimode optical fiber sensor of the structure which exposed the core using CVD equipment, and with time progress, transmitted light intensity with a wavelength of 685-800 nm became small, and was saturated in about about 600 seconds.Moreover, in order to raise the sensitivity of a sensor, it is necessary to lengthen a sensor part or to make it thin. Then, the embedded type 3-dimensional waveguide with a 7micrometerx6micrometer core thinner than the former is used as a sensor and the optical physical-properties value of an a-Si : H film was measured. Consequently, the absorption spectrum with the same tendency as the case where a conventional optical fiber and conventional slab waveguide are used as a sensor was obtained. It carried out based on the absorption spectrum obtained here, and when asked for the optical energy band gap of the a-Si : H film made to deposit on a waveguide, the value about 1.70-1.72 [eV] was acquired irrespective of waveguide length. This is mostly in agreement with the value acquired by the conventional measuring method. Moreover, the measurement limit resulting from the amount of absorption becoming inadequate was a-Si : H thickness 50 [nm], when sensor length was set to 50 [mm] in the optical fiber of the diameter 110 im of a core. By the introduced measurement system, since it was a-Si : H thickness 3 [nm] when sensor length set to 50 [mm], improvement in large sensitivity is able to be aimed at. Since it is the 3-dimensional waveguide unlike slab waveguide, analysis by the finite element method with high accuracy is performed.