Investigation of the coefficient of thermal expansion in nanocrystalline diamond films

Temperature dependence of stress in CVD diamond films studied by Raman spectroscopy

“…The stress for temperatures over 80°C was converted into tensile stress, and at the highest temperature the residual stress for both samples achieved values above 5 GPa. In fact, Woehrl et al [10] observed exactly the opposite trend for CVD diamond films (deposited on silicon (1 0 0)) of thicknesses ranging from 7 to about 14 µm. They reported that at room temperature all samples had tensile residual stress which changed with increasing temperature to comprehensive one, independently of the deposition conditions.…”

“…Many of recent publications [5,[10][11][12] have concerned the measurement and calculation of stress in CVD diamond films by combining one of residual stress measurement techniques, like substrate curvature, X-ray diffraction or Raman spectroscopy with bi-metal plate-bending theory, however, most of them have neglected the temperature dependence of thermal expansion coefficients (CTE) [6].…”

A Critical Review of Measures for an Effective Application of Nano-Structured Coatings in Milling

“…The residual stresses in diamond films are associated with numerous reasons such as epitaxial crystal differences as well as the significantly smaller thermal expansion coefficient of the diamond coating compared to its cemented carbide substrate [9,10]. The employed deposition parameters affect significantly the level of residual stress in diamond film structure.…”

“…Moreover, nano multi-layer PVD structures has to be applied for restricting the film brittleness [7,8]. Furthermore, diamond coatings deposited on cemented carbide tools are characterized by high residual stresses in their structure mainly due to epitaxial crystal differences and thermal expansion coefficients mismatch of the diamond coating and its cemented-carbide substrate [9][10][11]. Multilayered diamond coating systems, with successive nano-and micro-structured layers, can absorb a part of the residual stresses because of the more deformable microstructured layers compared to nanocomposite ones.…”

Ultrananocrystalline Diamond as Material for Surface Acoustic Wave Devices

“…By combining soft matrix properties with the hard diamond crystals on the nanoscale it is possible to combine hard with elastic properties and get a material that is hard and tough at the same time. With tailoring the mechanical stress in the films or the coefficient of thermal expansion it was possible to tailor yet other very important mechanical properties for the application of UNCD films by adjusting the overall matrix fraction to the film volume (in the case of a 3D matrix surrounding the nanocrystals) (Woehrl & Buck, 2007) (Woehrl et. al., 2009).…”