Preparation of flat adherent diamond films on thin copper substrates using a nickel interlayer

Flat adherent diamond films on copper substrates have been prepared using a nickel interlayer. The structure of the interface between the substrate and the diamond film has been investigated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD shows that a Cu–Ni alloy is formed on the substrate surface after a hydrogen plasma annealing treatment. XPS demonstrates that some chemical bonds such as CO, CC and C-metal appear on the surface of the substrate. The adhesion of the diamond film on the copper substrate is improved due to the formation of Cu–Ni alloy and C–Ni bonds at the interface. The optimum thickness of the nickel interlayer for the adhesion improvement is 5∼10 μm. To minimize the deformation of the specimen owing to the largely thermally-induced stress, a new three-step-method has been adopted to relax this stress. In the three-step-method, the intrinsic stress of the diamond film characterized by micro-Raman spectroscopy is controlled and adjusted by the deposition conditions. By balancing the tensile intrinsic stress and compressive thermal stress, a flat diamond film/copper substrate composite is obtained when the substrate temperature falls from the deposition temperature to room temperature.