Silicon carbonitride nanolayers — Synthesis and chemical characterization

SiCxNy thin films were produced by plasma-enhanced chemical vapor deposition and characterized by ellipsometry, Fourier transform infrared and Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, as well as, by near-edge X-ray absorption fine structure measurements in total-reflection X-ray fluorescence geometry. The temperature of synthesis was varied between 100 °C and 800 °C, the precursors hexamethyldisilazane or hexamethylcyclotrisilazane were used with an addition of N2, He, and NH3, respectively. The composition of the products was determined to be constant in Si with about 20 at.%, whereas the sum of C and N results in 80 at.% (each varying between 20 and 60 at.%). Consequently, it can be stated, that in the produced silicon carbonitride a network of Si is built with SiCSi, SiCCSi, and SiNSi bridges. The comparison of the chemical composition and of the physical properties shows for the samples produced with He or N2, respectively (without NH3) that the refractive index and the absorption coefficient are increasing with an increasing content of carbon in the final formula SiC4 − nNn (with n = 1, 2, or 3).

► Silicon carbonitride nanolayers were produced by chemical vapor deposition.
► The chemical bonds SiC, SiN, and CC were identified.
► The tetragonal structure contains cross-linking SiCSi, SiNSi, and SiCCSi.
► The elemental composition can be given as SiC4 − nNn (n = 1, 2, 3)