Low-temperature growth of boron carbide coatings by direct current magnetron sputtering and high-power impulse magnetron sputtering

B4C coatings for 10B-based neutron detector applications were deposited using high-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) processes. The coatings were deposited on Si(001) as well as on flat and macrostructured (grooved) Al blades in an industrial coating unit using B4C compound targets in Ar. The HiPIMS and DCMS processes were conducted at substrate temperatures of 100 and 400 °C and the Ar pressure was varied between 300 and 800 mPa. Neutron detector-relevant coating characterization was performed and the coating properties were evaluated with regard to their growth rate, density, level of impurities, and residual coating stress. The coating properties are mainly influenced by general process parameters such as the Ar pressure and substrate temperature. The deposition mode shows only minor effects on the coating quality and no effects on the step coverage. At a substrate temperature of 100 °C and an Ar pressure of 800 mPa, well-adhering and functional coatings were deposited in both deposition modes; the coatings showed a density of 2.2 g/cm3, a B/C ratio of ~3.9, and the lowest compressive residual stresses of 180 MPa. The best coating quality was obtained in DCMS mode using an Ar pressure of 300 mPa and a substrate temperature of 400 °C. Such process parameters yielded coatings with a slightly higher density of 2.3 g/cm3, a B/C ratio of ~4, and the compressive residual stresses limited to 220 MPa.