Effect of trimethylsilane flow rate on the growth of SiC thin-films for fiber-optic temperature sensors

We have investigated the effect of trimethylsilane ([(CH₃)₃SiH] or 3MS) flow rate on the growth of SiC thin-film on single-crystal sapphire substrate for fiber-optic temperature sensor. The SiC film thickness was in the range of 2-3 μm. The variation of the 3MS flow rate affected the structural properties of the SiC films. This, in turn, changed the optical properties and temperature sensing performance of the sensors. Optical reflection from the SiC thin-film Fabry-Pe´rot interferometers showed one-way phase shifts in resonant minima on all measured samples. Linear fits to the resonant minima (at 660 to 710 nm) versus temperature provide the corresponding thermal expansion coefficient, κ_φ, of 1.7-1.9×10^-5/°C. With the optimized 3MS flow rate, the SiC temperature sensor exhibits a temperature accuracy of ±2.8°C from 22 to 540°C. The short-term SiC sensor stability at 532°C for two weeks shows a very small standard deviation of 0.97°C.