Microstructure and physical properties of iron carbide films formed by plasma enhanced chemical vapor deposition

We report the structure and properties of iron-containing films deposited on glass substrates maintained at temperatures between 200 and 500 °C. The films investigated were Fe 3 O 4 , Fe 7 C 3 , Fe 3 C 1 and α-Fe, deposited at substrate temperatures of 200, 300, 400 and 500 °C, respectively. The measured SEM grain sizes from these 200–700 nm thick films were in the 50–350 nm range. X-ray diffraction and scanning electron microscopy show larger grains and increased crystallinity in the films deposited at higher substrate temperatures. The larger grain sizes and increased crystallinity are consequences of bulk diffusion and surface recrystallization. The sheet conductivities of the films increase with increasing film deposition temperature, due to coarser grain structures and higher iron to carbon ratios in the higher temperature films. The phases remain unchanged after annealing at 400 °C for 4 h. X-ray diffraction and scanning electron microscopy show evidence of bulk rearrangement and a reduction of thickness in the annealed films.