Wavelength, fluence and substrate-dependent room temperature pulsed laser deposited B-enriched thick films

Abstract

Boron carbide (B4C) has outstanding properties making it particularly interesting in the field of neutron detection. In this study we exploit nanosecond pulsed laser deposition (PLD) for the synthesis of B-enriched films with micrometer-scale thickness for future realization of a neutron converter layer. B-enriched B4C layers were deposited by PLD at room temperature under different wavelength conditions (λP = 266, 248,193 nm), fluence (from 2 to 10 J/cm2) and substrate (silica, Si (100), kapton (polyamide), PMMA and AZ 1512 resist).The measured elemental composition of boron (B), carbon (C) and oxygen (O) as well as the structural properties of the deposited films highlighted: i) wavelength- and fluence-dependent B sub-stoichiometry with respect to the ablated target, ii) formation of polycrystalline grains despite the room temperature growth in the case of λP = 266 nm, and iii) deposition rates higher for λP = 266 than for the other investigated wavelengths.The film deposited at a wavelength of λP = 266 nm and F = 2 J/cm2 yielded the best B/C ratio, negligible O-contaminations, and a very smooth surface with low density of surface particulates.Moreover, the possibility of depositing well adherent films on soft substrates with thicknesses > 1 μm is demonstrated, due to ability to accommodate tensile stress at the substrate-B4C film interface.