High lateral resolution 2D mapping of the B/C ratio in a boron carbide film formed by femtosecond pulsed laser deposition

Boron carbide films with a thickness of up to 550 nm and deposit size of 40 mm × 30 mm were prepared by ablating a B4C target in high vacuum by pulses of 700 fs duration at 248 nm. Layer thickness and lateral distribution of the constituting elements along the symmetry axes of a deposit were investigated with Rutherford backscattering spectrometry (RBS) with a focussed 2.5 MeV He+ ion beam. RBS spectra were fitted with the DataFurnace computer code. The results of 2D mapping proved that both the elemental composition and the film thickness of the deposit were non-uniform. The B/C ∼ 1 ratio measured at the edge of the deposit increased up to about three toward the centre, with both the B content and the B/C ratio varying linearly with the film thickness.