Residual stress measurement in DLC films deposited by PBIID method using Raman microprobe spectroscopy

Diamond-like carbon (DLC) films were prepared and their residual stresses were measured nondestructively using Raman microprobe spectroscopy. The plasma-based ion implantation and deposition (PBIID) method was used to coat the DLC films on thin glass substrates using acetylene, a mixture of acetylene and toluene, or only toluene gas at 1.0 Pa. Peaks in the Raman spectra of the DLC films were assigned as the D'(disordered) or C-C bonding peaks at 1150 cm(-1). The phonon deformation potentials (a') of the films were estimated from data for the phonon deformation potentials for pure graphite and diamond and calculated using the sp(3)/sp(2) bonding ratio and the hydrogen content of the films. Thus, a relation was observed between the Raman shift of the G peak (omega(G)) and the residual stress (sigma(c)) in each film. The Raman shifts (omega(0)) of the G peak for the films with no deformation were 1554, 1556, and 1562 cm(-1) for the films deposited using acetylene, a mixture gas and toluene gas. Moreover, only toluene had stress constants of -0.378, -0.384, and -0.391 GPa/cm(-1). The residual stresses constant in each film using (8.2 x 10(-4).a')(-1) omega(-1)(0) were estimated as -0.379, -0.384, and -0.391 GPa/cm(-1). The Raman shift of the D peak remained stationary as the compressive sigma(c) in the films increased but changed when the deposition gas was varied. The distance the D peak moved from 1420 cm(-1) corresponded to that of the G peak from 1560 cm(-1) in the Raman spectra of the films in the stress-free state. In addition, the compressive residual stress in the DLC film had a major impact on the hardness. (C) 2015 Elsevier B.V. All rights reserved.