Relief of the internal stress in ternary boron carbonitride thin films

Ternary boron carbonitride (BCN) thin films were deposited by radio frequency reactive sputtering. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) absorption measurements suggested that the films are atomic-level hybrids composed of B, C and N atoms. The structure of the samples is graphitic BC2N. High compressive stresses were observed in the films deposited on silicon and fused silica substrates. When the films were peeled off the substrates, the absorption bands in the FT-IR spectra shift to lower wavenumbers due to the stress relief. The compressive stresses caused buckling of the films, and the buckling patterns were related to the used substrates. For the samples deposited on Si wafer, a branching type buckling pattern was observed, while a telephone-cord morphology was noted for the samples deposited on fused silica plate. The telephone-cord morphology can be explained based on the buckling-driven delamination theory proposed by Oritiz and Gioia [J. Mech. Phys. Solids 42 (1994) 531].