Solid-phase reaction of tungsten thin films with polycrystalline diamond

The thermally induced solid-phase reaction of 135 nm thick sputter-deposited W films with polycrystalline CVD-grown diamond substrates is investigated. The samples are annealed in vacuum (5×10^-7 torr) at temperatures between 700 °C and 1100 °C for 1 hour and examined by 2 MeV ⁴He⁺⁺ backscattering spectrometry, x-ray diffraction, and scanning electron microscopy. The as-deposited W films contain roughly 5 at.% oxygen. After annealing the samples at 800 °C this oxygen concentration falls below the detection limit of less than 1%. Incipient W₂C phase formation occurs during annealing at 900 °C. The final state, the WC phase, is reached after annealing at 1100 °C.