Research on resolution improving the method of film thickness measurement through THz wave based on fitting the...

Thermal barrier coatings generate very thin thermally grown oxide (TGO) during service life. The thickness detection of (TGO) using terahertz time-domain spectroscopy combined with the time of flight (TOF) method causes the problem of the position of the front pulse signal peak not being recognized due to the overlapping of the succeeding pulse. This greatly limits the detection accuracy. In this paper, a novel fitting-waveform method is proposed. The complete front pulse signal is fitted by the constant localized signal belonging to the front pulse in the overlapped signal to determine its peak position. The article verifies the method's feasibility through experiments on polyimide (PI) films and applies it to the thickness detection of TGO. The results show that the method can measure the thickness of 4 µm TGO relatively accurately with an error of about 0.8 µm.